@article {douglass_distributed_2023, title = {Distributed acoustic sensing for detecting near surface hydroacoustic signals}, journal = {JASA Express Letters}, volume = {3}, number = {6}, year = {2023}, month = {jun}, pages = {066005}, abstract = {Distributed acoustic sensing (DAS) is a technology that turns a fiber-optic cable into an acoustic sensor by measuring the phase change of backscattered light caused by changes in strain from an acoustic field. In October 2022, 9 days of DAS and co-located hydrophone data were collected in the Puget Sound near Seattle, WA. Passive data were continuously recorded for the duration and a broadband source was fired from several locations and depths on the first and last days. This dataset provides comparisons between DAS and hydrophone measurements and demonstrates the ability of DAS to measure acoustics signals up to \~{}700 Hz.}, issn = {2691-1191}, doi = {10.1121/10.0019703}, url = {https://doi.org/10.1121/10.0019703}, author = {Douglass, Alexander S. and Abadi, Shima and Lipovsky, Bradley P.} } @inbook {lubchenco_technology_2023, title = {Technology, Data and New Models for Sustainably Managing Ocean Resources}, booktitle = {The Blue Compendium: From Knowledge to Action for a Sustainable Ocean Economy}, year = {2023}, pages = {185{\textendash}211}, publisher = {Springer International Publishing}, organization = {Springer International Publishing}, address = {Cham}, abstract = {We are in the middle of an explosion in new data on the ocean, creating enormous potential for advances in our understanding and stewardship of ocean resources. An exponential increase in the number and variety of ocean observing systems and other new data sources has created the prospect of a digital ocean ecosystem. Advances in processing techniques and visualisation are rapidly expanding our ability to extract information from those data, and are enabling a wide array of tools to provide real-time information in actionable form to decision-makers, such as policymakers, resource managers, resource users, consumers and citizens.}, isbn = {978-3-031-16277-0}, doi = {10.1007/978-3-031-16277-0_6}, url = {https://doi.org/10.1007/978-3-031-16277-0_6}, author = {Lubchenco, Jane and Haugan, Peter M.}, editor = {Lubchenco, Jane and Haugan, Peter M.} } @article {lee_detection_2022, title = {Detection of Magma Beneath the Northern and Southern Rift Zones of Axial Seamount at the Juan de Fuca Ridge}, journal = {Geochemistry, Geophysics, Geosystems}, volume = {23}, number = {8}, year = {2022}, note = {_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2022GC010426}, pages = {e2022GC010426}, abstract = {Axial Seamount is an active hotspot-related volcanic system located along the Juan de Fuca Ridge (JdFR) that includes a central volcano and bounding northern and southern rift zones (NRZ and SRZ). Three documented volcanic eruptions in 1998, 2011, and 2015 included dike propagation into and eruptions within the rift zones that are believed to have been sourced from the well-imaged large magma reservoir found beneath the central volcano. However, areas beyond the central volcano have not been explored for potential magma sources that could have contributed to these events, and geochemical studies of older rift zone lavas indicate differences in compositions suggestive of magma reservoirs fed by more mid-ocean ridge-dominated mantle sources. In this study, we analyze multichannel seismic data acquired in 2002 to characterize the internal crustal structure of the rift zones. The new reflectivity images reveal small (<5 km wide) and discontinuous crustal magma bodies at depths of \~{}1.5 to 4 km beneath and in the vicinity of the rift zone lava flows from the three eruptions. We also image wide magma bodies within the overlap regions between the rift zones and neighboring segments of JdFR including a 6.4 km wide body under the east flank of NRZ and a 1-km wide, \~{}400 to 500 m, thick body near the base of the crust under the SRZ-Vance overlap basin. Collectively the new observations indicate that multiple small crustal magma bodies underlie Axial segment, in addition to the main reservoir, and likely contribute to rift zone magmatism with implications for interpretations of seismicity patterns and lava flow compositions.}, issn = {1525-2027}, doi = {10.1029/2022GC010426}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2022GC010426}, author = {Lee, Michelle K. and Carbotte, Suzanne M. and Arnulf, Adrien F.} } @article {chadwick_geodetic_2022, title = {Geodetic Monitoring at Axial Seamount Since Its 2015 Eruption Reveals a Waning Magma Supply and Tightly Linked Rates of Deformation and Seismicity}, journal = {Geochemistry Geophysics Geosystems}, volume = {23}, number = {1}, year = {2022}, note = {Place: Washington Publisher: Amer Geophysical Union WOS:000751308100015}, pages = {e2021GC010153}, abstract = {Axial Seamount is a basaltic hot spot volcano with a summit caldera at a depth of similar to 1,500 m below sea level, superimposed on the Juan de Fuca spreading ridge, giving it a robust and continuous magma supply. Axial erupted in 1998, 2011, and 2015, and is monitored by a cabled network of instruments including bottom pressure recorders and seismometers. Since its last eruption, Axial has re-inflated to 85\%-90\% of its pre-eruption level. During that time, we have identified eight discrete, short-term deflation events of 1-4 cm over 1-3 weeks that occurred quasi-periodically, about every 4-6 months between August 2016 and May 2019. During each short-term deflation event, the rate of earthquakes dropped abruptly to low levels, and then did not return to higher levels until reinflation had resumed and returned near its previous high. The long-term geodetic monitoring record suggests that the rate of magma supply has varied by an order of magnitude over decadal time scales. There was a surge in magma supply between 2011 and 2015, causing those two eruptions to be closely spaced in time and the supply rate has been waning since then. This waning supply has implications for eruption forecasting and the next eruption at Axial still appears to be 4-9 years away. We also show that the number of earthquakes per unit of uplift has increased exponentially with total uplift since the 2015 eruption, a pattern consistent with a mechanical model of cumulative rock damage leading to bulk failure during magma accumulation between eruptions.}, keywords = {bottom pressure recorders, de-fuca ridge, eruption forecasting, galapagos, ground deformation, high-resolution, inflation, kilauea volcano, lava flows, midocean ridge, ocean bottom seismometers, OOI cabled observatory, precursors, seafloor geodesy, sierra-negra-volcano, submarine volcano monitoring}, doi = {10.1029/2021GC010153}, url = {https://www.webofscience.com/api/gateway?GWVersion=2\&SrcAuth=DOISource\&SrcApp=WOS\&KeyAID=10.1029\%2F2021gc010153\&DestApp=DOI\&SrcAppSID=USW2EC0AF0FhQ3gq3aJ9tUIgn6Kiy\&SrcJTitle=GEOCHEMISTRY+GEOPHYSICS+GEOSYSTEMS\&DestDOIRegistrantName=American+Geophysical+Uni}, author = {Chadwick, William W. and Wilcock, William S. D. and Nooner, Scott L. and Beeson, Jeffrey W. and Sawyer, Audra M. and Lau, T.-k} } @article {268, title = {Integrating Multidisciplinary Observations in Vent Environments (IMOVE): Decadal Progress in Deep-Sea Observatories at Hydrothermal Vents}, journal = {Frontiers in Marine Science}, volume = {9}, year = {2022}, month = {2022/05/13/}, abstract = {The unique ecosystems and biodiversity associated with mid-ocean ridge (MOR) hydrothermal vent systems contrast sharply with surrounding deep-sea habitats, however both may be increasingly threatened by anthropogenic activity (e.g., mining activities at massive sulphide deposits). Climate change can alter the deep-sea through increased bottom temperatures, loss of oxygen, and modifications to deep water circulation. Despite the potential of these profound impacts, the mechanisms enabling these systems and their ecosystems to persist, function and respond to oceanic, crustal, and anthropogenic forces remain poorly understood. This is due primarily to technological challenges and difficulties in accessing, observing and monitoring the deep-sea. In this context, the development of deep-sea observatories in the 2000s focused on understanding the coupling between sub-surface flow and oceanic and crustal conditions, and how they influence biological processes. Deep-sea observatories provide long-term, multidisciplinary time-series data comprising repeated observations and sampling at temporal resolutions from seconds to decades, through a combination of cabled, wireless, remotely controlled, and autonomous measurement systems. The three existing vent observatories are located on the Juan de Fuca and Mid-Atlantic Ridges (Ocean Observing Initiative, Ocean Networks Canada and the European Multidisciplinary Seafloor and water column Observatory). These observatories promote stewardship by defining effective environmental monitoring including characterizing biological and environmental baseline states, discriminating changes from natural variations versus those from anthropogenic activities, and assessing degradation, resilience and recovery after disturbance. This highlights the potential of observatories as valuable tools for environmental impact assessment (EIA) in the context of climate change and other anthropogenic activities, primarily ocean mining. This paper provides a synthesis on scientific advancements enabled by the three observatories this last decade, and recommendations to support future studies through international collaboration and coordination. The proposed recommendations include: i) establishing common global scientific questions and identification of Essential Ocean Variables (EOVs) specific to MORs, ii) guidance towards the effective use of observatories to support and inform policies that can impact society, iii) strategies for observatory infrastructure development that will help standardize sensors, data formats and capabilities, and iv) future technology needs and common sampling approaches to answer today{\textquoteright}s most urgent and timely questions.}, keywords = {COMMUNITY DYNAMICS}, doi = {10.3389/fmars.2022.866422}, author = {Matabos, Marjolaine and Barreyre, Thibaut and Juniper, S. Kim and Cannat, Mathilde and Kelley, Deborah and Alfaro-Lucas, Joan M. and Chavagnac, Valerie and Cola{\c c}o, Ana and Escartin, Javier and Escobar, Elva and Fornari, Daniel and Hasenclever, Jorg and Huber, Julie A. and Laes-Huon, Agathe and Lanteri, Nadine and Levin, Lisa Ann and Mihaly, Steve and Mittelstaedt, Eric and Pradillon, Florence and Sarradin, Pierre-Marie and Sarrazin, Jozee and Tomasi, Beatrice and Venkatesan, Ramasamy and Vic, Clement} } @article {275, title = {Long-term noise interferometry analysis in the northeast Pacific Ocean}, journal = {The Journal of the Acoustical Society of America}, volume = {151}, year = {2022}, month = {2022/01//}, pages = {194 - 204}, abstract = {Long-term noise interferometry analysis is conducted over six years of data using two hydrophones on the Ocean Observatories Initiative Cabled Array. The two hydrophones are separated by 3.2 km and are bottom-mounted at 1500 m. We demonstrate the ability of ambient noise interferometry to reliably detect multi-path arrivals in the deep ocean from bottom-mounted hydrophones. An analysis of the multi-path arrival peak emergence is presented, as well as long-term trends of the signal-to-noise ratio of the arrival peaks. Last, we show that long-term ambient noise interferometry provides the opportunity for monitoring directional, coherent ambient sound such as the fin whale chorus.}, isbn = {0001-4966}, doi = {10.1121/10.0009232}, url = {https://asa.scitation.org/doi/full/10.1121/10.0009232}, author = {Ragland, John and Abadi, Shima and Sabra, Karim} } @article {fluegel_magnetization_2022, title = {The Magnetization of an Underwater Caldera: A Time-Lapse Magnetic Anomaly Study of Axial Seamount}, journal = {Geophysical Research Letters}, volume = {49}, number = {17}, year = {2022}, note = {_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2022GL100008}, pages = {e2022GL100008}, abstract = {Axial Seamount in the northeast Pacific erupted in 2015, 2011, and 1998. Although monitored by the Regional Cabled Array of the Ocean Observatory Initiative, few magnetic surveys have been conducted over the region. This study uses high-resolution magnetic data over the seamount collected by autonomous underwater vehicle Sentry during three years (2015, 2017, and 2020). The goal is to investigate whether there are temporal changes in the near-surface magnetic field observable over the time scale of one volcanic cycle. We compare magnetic maps from repeated tracklines from each year. We find maps of the yearly difference in magnetization show coherent patterns that are not random. The central region of the caldera has become more magnetic during recent years, suggesting cooling of the surficial lava flows since 2015. Sentry data are more sensitive to shallow crustal structure compared to sea surface data which show longer wavelength anomalies extending deeper into the crust.}, keywords = {magnetism, monitoring, seamounts, volcanic hazards, volcanology}, issn = {1944-8007}, doi = {10.1029/2022GL100008}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2022GL100008}, author = {Fluegel, Bailey and Tivey, Maurice and Biasi, Joseph and Chadwick Jr., William W. and Nooner, Scott L.} } @article {283, title = {Management and Sustainable Exploitation of Marine Environments through Smart Monitoring and Automation}, journal = {Journal of Marine Science and Engineering}, volume = {10}, year = {2022}, month = {2022/02//}, pages = {297}, abstract = {Monitoring of aquatic ecosystems has been historically accomplished by intensive campaigns of direct measurements (by probes and other boat instruments) and indirect extensive methods such as aero-photogrammetry and satellite detection. These measurements characterized the research in the last century, with significant but limited improvements within those technological boundaries. The newest advances in the field of smart devices and increased networking capabilities provided by emerging tools, such as the Internet of Things (IoT), offer increasing opportunities to provide accurate and precise measurements over larger areas. These perspectives also correspond to an increasing need to promptly respond to frequent catastrophic impacts produced by drilling stations and intense transportation activities of dangerous materials over ocean routes. The shape of coastal ecosystems continuously varies due to increasing anthropic activities and climatic changes, aside from touristic activities, industrial impacts, and conservation practices. Smart buoy networks (SBNs), autonomous underwater vehicles (AUVs), and multi-sensor microsystems (MSMs) such as smart cable water (SCW) are able to learn specific patterns of ecological conditions, along with electronic {\textquotedblleft}noses{\textquotedblright}, permitting them to set innovative low-cost monitoring stations reacting in real time to the signals of marine environments by autonomously adapting their monitoring programs and eventually sending alarm messages to prompt human intervention. These opportunities, according to multimodal scenarios, are dramatically changing both the coastal monitoring operations and the investigations over large oceanic areas by yielding huge amounts of information and partially computing them in order to provide intelligent responses. However, the major effects of these tools on the management of marine environments are still to be realized, and they are likely to become evident in the next decade. In this review, we examined from an ecological perspective the most striking innovations applied by various research groups around the world and analyzed their advantages and limits to depict scenarios of monitoring activities made possible for the next decade.}, keywords = {aquaculture, buoy, coastal, connectivity, IoT, network, real time, transmission}, isbn = {2077-1312}, doi = {10.3390/jmse10020297}, url = {https://www.mdpi.com/2077-1312/10/2/297}, author = {Glaviano, Francesca and Esposito, Roberta and Di Cosmo, Anna and Esposito, Francesco and Gerevini, Luca and Ria, Andrea and Molinara, Mario and Bruschi, Paolo and Costantini, Maria and Zupo, Valerio} } @article {278, title = {An overview of ambient sound using Ocean Observatories Initiative hydrophones}, journal = {The Journal of the Acoustical Society of America}, volume = {151}, year = {2022}, month = {2022/03//}, pages = {2085 - 2100}, abstract = {The Ocean Observatories Initiative (OOI) sensor network provides a unique opportunity to study ambient sound in the north-east Pacific Ocean. The OOI sensor network has five low frequency (Fs = 200 Hz) and six broadband (Fs = 64 kHz) hydrophones that have been recording ambient sound since 2015. In this paper, we analyze acoustic data from 2015 to 2020 to identify prominent features that are present in the OOI acoustic dataset. Notable features in the acoustic dataset that are highlighted in this paper include volcanic and seismic activity, rain and wind noise, marine mammal vocalizations, and anthropogenic sound, such as shipping noise. For all low frequency hydrophones and four of the six broadband hydrophones, we will present long-term spectrograms, median time-series trends for different spectral bands, and different statistical metrics about the acoustic environment. We find that 6-yr acoustic trends vary, depending on the location of the hydrophone and the spectral band that is observed. Over the course of six years, increases in spectral levels are seen in some locations and spectral bands, while decreases are seen in other locations and spectral bands. Last, we discuss future areas of research to which the OOI dataset lends itself.}, isbn = {0001-4966}, doi = {10.1121/10.0009836}, url = {https://asa.scitation.org/doi/full/10.1121/10.0009836}, author = {Ragland, John and Schwock, Felix and Munson, Matthew and Abadi, Shima} } @article {farghal_potential_2022, title = {The Potential of Using Fiber Optic Distributed Acoustic Sensing (DAS) in Earthquake Early Warning Applications}, journal = {Bulletin of the Seismological Society of America}, volume = {112}, number = {3}, year = {2022}, month = {apr}, pages = {1416{\textendash}1435}, abstract = {As the seismological community embraces fiber optic distributed acoustic sensing (DAS), DAS arrays are becoming a logical, scalable option to obtain strain and ground-motion data for which the installation of seismometers is not easy or cheap, such as in dense offshore arrays. The potential of strain data in earthquake early warning (EEW) applications has been recently demonstrated using records from borehole strainmeters (BSMs). However, current BSM networks are sparse, installing more BSMs is expensive and often impractical, and BSMs have the same limitations in offshore environments as other traditional seismic instruments. Here, we aim to provide a road map about how DAS data could be used in existing EEW applications, using the ShakeAlert EEW System for the West Coast of the United States as an example. We review the data requirements for EEW systems, examine ways in which strain-derived ground-motion data can be incorporated into such systems without significant modifications, and determine what is still needed for full utilization of DAS data in these applications. Importantly, EEW algorithms require ground-motion amplitude information for rapid earthquake source characterization; thus, accurate strain amplitude observations, not only phase information, are necessary for deriving these ground-motion metrics from DAS data. To obtain high-quality ground-motion observations, EEW-compatible DAS arrays need to be multicomponent, well coupled, and low noise. We suggest ways to achieve such data requirements using existing DAS technology and discuss areas in which further research is needed to optimize DAS array performance for EEW.}, issn = {0037-1106}, doi = {10.1785/0120210214}, url = {https://doi.org/10.1785/0120210214}, author = {Farghal, Noha S. and Saunders, Jessie K. and Parker, Grace A.} } @article {nomikou_santory_2022, title = {SANTORY: SANTORini{\textquoteright}s Seafloor Volcanic ObservatorY}, journal = {Frontiers in Marine Science}, volume = {9}, year = {2022}, abstract = {Submarine hydrothermal systems along active volcanic ridges and arcs are highly dynamic, responding to both oceanographic (e.g., currents, tides) and deep-seated geological forcing (e.g., magma eruption, seismicity, hydrothermalism, and crustal deformation, etc.). In particular, volcanic and hydrothermal activity may also pose profoundly negative societal impacts (tsunamis, the release of climate-relevant gases and toxic metal(loid)s). These risks are particularly significant in shallow (<1000m) coastal environments, as demonstrated by the January 2022 submarine paroxysmal eruption by the Hunga Tonga-Hunga Ha{\textquoteright}apai Volcano that destroyed part of the island, and the October 2011 submarine eruption of El Hierro (Canary Islands) that caused vigorous upwelling, floating lava bombs, and natural seawater acidification. Volcanic hazards may be posed by the Kolumbo submarine volcano, which is part of the subduction-related Hellenic Volcanic Arc at the intersection between the Eurasian and African tectonic plates. There, the Kolumbo submarine volcano, 7 km NE of Santorini and part of Santorini{\textquoteright}s volcanic complex, hosts an active hydrothermal vent field (HVF) on its crater floor (\textasciitilde500m b.s.l.), which degasses boiling CO2{\textendash}dominated fluids at high temperatures (\textasciitilde265{\textdegree}C) with a clear mantle signature. Kolumbo{\textquoteright}s HVF hosts actively forming seafloor massive sulfide deposits with high contents of potentially toxic, volatile metal(loid)s (As, Sb, Pb, Ag, Hg, and Tl). The proximity to highly populated/tourist areas at Santorini poses significant risks. However, we have limited knowledge of the potential impacts of this type of magmatic and hydrothermal activity, including those from magmatic gases and seismicity. To better evaluate such risks the activity of the submarine system must be continuously monitored with multidisciplinary and high resolution instrumentation as part of an in-situ observatory supported by discrete sampling and measurements. This paper is a design study that describes a new long-term seafloor observatory that will be installed within the Kolumbo volcano, including cutting-edge and innovative marine-technology that integrates hyperspectral imaging, temperature sensors, a radiation spectrometer, fluid/gas samplers, and pressure gauges. These instruments will be integrated into a hazard monitoring platform aimed at identifying the precursors of potentially disastrous explosive volcanic eruptions, earthquakes, landslides of the hydrothermally weakened volcanic edifice and the release of potentially toxic elements into the water column.}, issn = {2296-7745}, doi = {10.3389/fmars.2022.796376}, url = {https://www.frontiersin.org/articles/10.3389/fmars.2022.796376}, author = {Nomikou, Paraskevi and Polymenakou, Paraskevi N. and Rizzo, Andrea Luca and Petersen, Sven and Hannington, Mark and Kilias, Stephanos Pantelis and Papanikolaou, Dimitris and Escartin, Javier and Karantzalos, Konstantinos and Mertzimekis, Theodoros J. and Antoniou, Varvara and Krokos, Mel and Grammatikopoulos, Lazaros and Italiano, Francesco and Caruso, Cinzia Giuseppina and Lazzaro, Gianluca and Longo, Manfredi and Scir{\'e} Scappuzzo, Sergio and D{\textquoteright}Alessandro, Walter and Grassa, Fausto and Bejelou, Konstantina and Lampridou, Danai and Katsigera, Anna and Dura, Anne} } @article {jackson_sonar_2022, title = {Sonar Observation of Heat Flux of Diffuse Hydrothermal Flows}, journal = {Earth and Space Science}, volume = {9}, number = {n/a}, year = {2022}, note = {_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2021EA001974}, pages = {e2021EA001974}, abstract = {Previous work using multibeam sonar to map diffuse hydrothermal flows is extended to estimate the heat output of diffuse flows. In the first step toward inversion, temperature statistics are obtained from sonar data and compared to thermistor data in order to set the value of an empirical constant. Finally, a simple model is used to obtain heat-flux density from sonar-derived temperature statistics. The method is applied to data from the Cabled Observatory Vent Imaging Sonar (COVIS) deployed on the Ocean Observatories Initiative{\textquoteright}s Regional Cabled Array at the ASHES vent field on Axial Seamount. Inversion results are presented as maps of heat-flux density in MW/m2 and as time series of heat-flux density averaged over COVIS{\textquoteright} field of view.}, keywords = {Deep-Sea Hydrothermal, Heat flux, sonar}, issn = {2333-5084}, doi = {10.1029/2021EA001974}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2021EA001974}, author = {Jackson, Darrell and Bemis, Karen and Xu, Guangyu and Ivakin, Anatoliy} } @mastersthesis {carlson_is_2022, title = {Is the tidal triggering of earthquakes at Axial Seamount predictive of eruptions?}, year = {2022}, note = {Accepted: 2022-04-19T21:27:49Z}, school = {University of Washington}, type = {Senior Thesis}, address = {Seattle, WA, USA}, abstract = {Scientists have long hypothesized that tidal forces can trigger earthquakes due to the change in stress along a fault. This phenomenon is called tidal triggering of earthquakes. My study investigated the tidal triggering of earthquakes at Axial Seamount, Juan de Fuca Ridge from the time of the last eruption in 2015, to the present. This study tests the validity of the correlation between tidal triggering and volcanic cycles. My hypothesis is that the fraction of earthquakes is highest at low tidal heights / phases, and that tidal triggering increases in strength over time, therefore a potential sign during the onset of an eruption. Using data from the Ocean Observatories Initiative Regional Cabled Array, and the Oregon State University Tidal Model, I interpolated the time of earthquakes with the tidal cycle. Data from an earthquake catalog was plotted against the tidal model. Results prove my hypothesis to be valid. On an annual basis, the highest percentage of earthquakes occur within 30{\textdegree} of lowest tide (180{\textdegree}), and the highest rate of earthquakes per hour occur between -2m to -1m tidal height. On average, the percentage of earthquakes between 150{\textdegree} to 210{\textdegree} increases annually with a slope 1.88 \%/y. Additionally, the relative rate of earthquakes at -2m to -1m increases by 0.24 per year. I propose that the Axial Seamount will erupt soon, given tidal triggering has increased in strength and current data reflects similar data to what was seen prior to the 2015 eruption.}, url = {https://digital.lib.washington.edu:443/researchworks/handle/1773/48372}, author = {Carlson, Anders} } @article {279, title = {On using nonlinear wave interactions in multi-directional seas for energy conversion on the ocean floor}, journal = {Applied Ocean Research}, volume = {124}, year = {2022}, month = {2022/07/01/}, pages = {103193}, abstract = {This paper investigates possible utilization of energy in interacting surface waves on the seafloor. Theory suggests that resonant wave interactions in confused open seas can cause energetic downward traveling second-order pressure waves, which during stormy conditions can be large enough to excite seafloor microseisms (Longuet-Higgins, 1950). Our analysis of contemporaneous data from seafloor pressure and velocity sensors from an Ocean Observatories Initiative (OOI) installation in the Northern Pacific and collocated surface-wave hindcasts showed evidence of the theoretically predicted vertical resonances (Longuet-Higgins, 1950). We observed that area-averaged predicted dynamic pressures and particle velocities 200~m below the water surface and their measured counterparts 2.6~km below at the seafloor were well correlated at the predicted resonance frequencies. Our results further revealed occurrence of net vertical power transfer at resonance from surface to seafloor by means of the predicted double-frequency pressure waves. Motivated by these findings, we estimated year-long seafloor power availability at five selected deep-sea locations. Next, we evaluated upper bounds on potentially convertible area averaged yearly-mean power amounts by a small flexible sphere type device at the seafloor. At \~{}400 mW m-2 to \~{}15 Wm-2, these power levels could assist sensor operations on and from the deep ocean floor.}, keywords = {Deep ocean sensing, Interacting surface waves, Ocean Observatories Initiative, Seafloor energy, Wave energy}, isbn = {0141-1187}, doi = {10.1016/j.apor.2022.103193}, url = {https://www.sciencedirect.com/science/article/pii/S0141118722001353}, author = {Korde, Umesh A. and McBeth, Michael S.} } @article {RN203, title = {Don{\textquoteright}t catch me if you can {\textendash} Using cabled observatories as multidisciplinary platforms for marine fish community monitoring: an in situ case study combining Underwater Video and environmental DNA data}, journal = {The Science of The Total Environment}, year = {2021}, pages = {145351}, type = {Journal Article}, abstract = {Cabled observatories are marine infrastructures equipped with biogeochemical and oceanographic sensors as well as High-Definition video and audio equipment, hence providing unprecedented opportunities to study marine biotic and abiotic components. Additionally, non-invasive monitoring approaches such as environmental DNA (eDNA) metabarcoding have further enhanced the ability to characterize marine life. Although the use of non-invasive tools beholds great potential for the sustainable monitoring of biodiversity and declining natural resources, such techniques are rarely used in parallel and understanding their limitations is challenging. Thus, this study combined Underwater Video (UV) with eDNA metabarcoding data to produce marine fish community profiles over a 2 months period in situ at a cabled observatory in the northeast Atlantic (SmartBay Ireland). By combining both approaches, an increased number of fish could be identified to the species level (total of 22 species), including ecologically and economically important species such as Atlantic cod, whiting, mackerel and monkfish. The eDNA approach alone successfully identified a higher number of species (59\%) compared to the UV approach (18\%), whereby 23\% of species were detected by both methods. The parallel implementation of point collection eDNA and time series UV data not only confirmed expectations of the corroborative effect of using multiple disciplines in fish community composition, but also enabled the assessment of limitations intrinsic to each technique including the identification of false-negative detections in one sampling technology relative to the other. This work showcased the usefulness of cabled observatories as key platforms for in situ empirical assessment of both challenges and prospects of novel technologies in aid to future monitoring of marine life. }, keywords = {Cabled observatory, Environmental DNA, Marine fish, Metabarcoding, Non-invasive monitoring, Underwater Video}, doi = {10.1016/j.scitotenv.2021.145351}, url = {https://app.dimensions.ai/details/publication/pub.1135067559}, author = {Mirimin, Luca and Desmet, Sam and Romero, David L{\'o}pez and Fernandez, Sara Fernandez and Miller, Dulaney L. and Mynott, Sebastian and Brincau, Alejandro Gonzalez and Stefanni, Sergio and Berry, Alan and Gaughan, Paul and Aguzzi, Jacopo} } @article {RN210, title = {Seafloor Geodetic Pressure Measurements to Detect Shallow Slow Slip Events: Methods to Remove Contributions from Ocean Water}, journal = {Journal of Geophysical Research: Solid Earth}, year = {2021}, type = {Journal Article}, abstract = {Shallow slow slip events (SSEs) provide a mechanism for strain release in the shallow part of subduction zones, with fundamental implications for fault mechanics and tsunami hazards. Despite their importance, SSEs are challenging to monitor. They occur under the ocean far from land-based GPS stations, and while seafloor pressure sensors can detect SSE vertical seafloor movements, the measured bottom pressure includes {\textquotedblleft}ocean noise{\textquotedblright} signals from pressure variations within the water column. Seeking to improve techniques to remove ocean noise, a pilot study offshore Oregon collected seafloor pressure and near-bottom current measurements at four sites from April to November 2017. Three methods were applied to reduce ocean noise: 1) subtract a reference pressure, 2) apply complex empirical orthogonal function analysis to pressure measurements, and 3) combine pressure and current measurements with optimal interpolation (OI). All three methods are established techniques from either geodesy or oceanography. Each method produced residual standard deviation, σ < 1 hPa. No SSE was detected during this study. For illustration purposes synthetic SSEs of 2 cm amplitude and 7-days duration were added and detected, one at a time at different spots. Because currents are unaffected by a SSE, the combination of currents and pressures with the dynamical constraint of geostrophy in OI reduced the false interpretation of the synthetic SSEs as oceanic. OI produced the most reliable detection. Future seafloor geodesy field projects should consider adding current sensors and using OI methods to reduce ocean noise and to reveal tectonic signals.}, doi = {10.1029/2020jb020065}, url = {https://app.dimensions.ai/details/publication/pub.1136480068}, author = {Watts, D. Randolph and Wei, Meng and Tracey, Karen L. and Donohue, Kathleen A. and He, Bing} } @article {RN209, title = {The Seismo-acoustics of Submarine Volcanic Eruptions}, journal = {Journal of Geophysical Research: Solid Earth}, year = {2021}, type = {Journal Article}, abstract = {Many of the world{\textquoteright}s volcanoes are hidden beneath the ocean{\textquoteright}s surface where eruptions are difficult to observe. However, seismo-acoustic signals produced by these eruptions provide a useful means of identifying active submarine volcanism. A literature survey revealed reports of 119 seismo-acoustically recorded submarine eruptions since 1939. Submarine eruptions have been recorded in all major tectonic settings, with a range of geochemistries, and at a variety of water depths, but the reports are dominated by eruptions in the Pacific and at only a few locations. Many of the reports offer little detail, with over half of the observations made from distances >500 km, and only about half were confirmed as eruptions by non-seismo-acoustic evidence. The reported seismo-acoustic signals cover a wide variety of processes, including earthquakes, explosions, various types of tremor, signals related to lava extrusion, and landslides. Recorded signals can sometimes be difficult to classify or confidently associate with an eruption, although there has been progress in this regard. Real-time monitoring of submarine eruptions has been on-going for several decades on regional and global scales with growing interest and effort in local networks. Real-time networks are complemented by short-term instrument deployments that often give more detailed insights into the dynamics and processes of submarine eruptions. Thorough seismo-acoustic monitoring and study has increased our understanding of submarine eruptions, especially of deep-sea volcanoes and spreading centers. Despite this, there are still many outstanding questions that need to be addressed for submarine volcanoes to be as well understood and monitored as their terrestrial counterparts.}, doi = {10.1029/2020jb020912}, url = {https://app.dimensions.ai/details/publication/pub.1136472734}, author = {Tepp, Gabrielle and Dziak, Robert P.} } @article {RN243, title = {Trends in low-frequency underwater noise off the Oregon coast and impacts of COVID-19 pandemica)}, journal = {Journal of the Acoustical Society of America}, volume = {149}, number = {6}, year = {2021}, pages = {4073-4077}, type = {Journal Article}, abstract = {Approximately six years of underwater noise data recorded from the Regional Cabled Array network are examined to study long-term trends. The data originate from station HYS14 located 87 km offshore of Newport, OR. The results indicate that the third-octave band level centered at 63 Hz and attributable to shipping activity is reduced in the spring of 2020 by about 1.6 dB relative to the mean of the prior five years, owing to the reduced economic activity initiated by the COVID-19 pandemic. The results are subtle, as the noise reduction is less than the typical seasonal fluctuation associated with warming ocean surface temperatures in the summer that reduces mode excitation support at typical ship source depths, causing a repeated annual level change on the order of 4 dB at shipping frequencies. Seasonality of the noise contribution near 20 Hz from fin whales is also discussed. Corroboration of a COVID-19 effect on shipping noise is offered by an analysis of automatic identification system shipping data and shipping container activity for Puget Sound, over the same six-year period, which shows a reduction in the second quarter of 2020 by \~{}19\% and \~{}17\%, respectively, relative to the mean of the prior five years. }, issn = {0001-4966}, doi = {10.1121/10.0005192}, author = {Dahl, P. H. and Dall{\textquoteright}Osto, D. R. and Harrington, M. J.} } @article {RN197, title = {Wintertime particulate organic matter distributions in surface waters of the northern California current system}, journal = {Continental Shelf Research}, volume = {213}, year = {2021}, pages = {104312}, type = {Journal Article}, abstract = {Semi-automated sampling via the surface underway systems of research vessels was used to explore the distribution and composition of particulate organic matter in surface waters of the northern California Current ecosystem during winter, a poorly studied period that is characterized by downwelling favorable winds and elevated discharge by coastal rivers. New wintertime observations were compared to those measured during a summer cruise characterized by strong upwelling and highly reduced coastal river flows. Particulate organic carbon (POC) concentrations in surface waters along the Oregon shelf during winter periods were significantly lower (7.0 {\textpm} 5.0 μM) than those measured in the same region during summer (21 {\textpm} 25 μM) with similar seasonal contrasts in chlorophyll (Chl) concentrations (1.7 {\textpm} 1.7 mg Chl m-3 in winter and 8.7 {\textpm} 3.8 mg Chl m-3 in summer). The combination of POC, Chl, and particle beam attenuation (cp) measurements revealed spatial and temporal distributions that confirm the importance of physical drivers such as wind, waves and river discharge in influencing the biogeochemistry of eastern boundary current systems during non-upwelling conditions. Elevated contributions of allocthonous particulate materials with distinct compositional characteristics, including low Chl:POC and POC:cp ratios, were measured during winter in low-density, low-salinity surface waters influenced by coastal river discharge. In contrast, mid-salinity, intermediate-density surface waters exhibited higher concentrations of POM with elevated Chl:POC and POC:cp ratios, which approached those measured during highly productive summer upwelling periods. These results are solid evidence for wintertime phytoplankton productivity along this margin under elevated buoyancy and nutrient contributions from the discharge of coastal rivers.}, keywords = {California current, Oregon margin, Particulate organic matter}, doi = {10.1016/j.csr.2020.104312}, url = {https://app.dimensions.ai/details/publication/pub.1132922324}, author = {Go{\~n}i, Miguel A. and Welch, Kylie A. and Alegria, Emmanuel and Alleau, Yvan and Watkins-Brandt, Katie and White, Angelicque E.} } @article {RN192, title = {Acoustic and In-situ Observations of Deep Seafloor Hydrothermal Discharge: an OOI Cabled Array ASHES Vent Field Case Study}, journal = {Earth and Space Science}, year = {2020}, type = {Journal Article}, abstract = {The Cabled Observatory Vent Imaging Sonar (COVIS) was installed on the Ocean Observatories Initiative{\textquoteright}s Regional Cabled Array observatory at ASHES hydrothermal vent field on Axial Seamount in July 2018. The acoustic backscatter data recorded by COVIS in August{\textendash}September 2018, in conjunction with in situ temperature measurements, are used to showcase and verify the use of COVIS for long-term, quantitative monitoring of hydrothermal discharge. Specifically, sonar data processing generates three-dimensional backscatter images of the buoyant plumes above major sulfide structures and two-dimensional maps of diffuse flows within COVIS{\textquoteright}s field-of-view. The backscatter images show substantial changes of plume appearance and orientation that mostly reflect plume bending in the presence of ambient currents and potentially the variations of outflow fluxes. The intensity of acoustic backscatter decreases significantly for highly bent plumes as compared to nearly vertical plumes, reflecting enhanced mixing of plume fluids with seawater driven by ambient currents. A forward model of acoustic backscatter from a buoyancy-driven plume developed in this study yields a reasonable match with the observation, which paves the way for inversely estimating the source heat flux of a hydrothermal plume from acoustic backscatter measurements. The acoustic observations of diffuse flows show large temporal variations on time scales of hours to days, especially at tidal frequencies, but no apparent long-term trend. These findings demonstrate COVIS{\textquoteright}s ability to quantitatively monitor hydrothermal discharge from both focused and diffuse sources to provide the research community with key observational data for studying the linkage of hydrothermal activity with oceanic and geological processes.}, keywords = {acoustic, axial seamount, hydrothermal, imaging, observatory, sonar}, doi = {10.1029/2020ea001269}, url = {https://app.dimensions.ai/details/publication/pub.1133310442}, author = {Xu, Guangyu and Bemis, Karen and Jackson, Darrell and Ivakin, Anatoliy} } @article {RN190, title = {Compact representation of temporal processes in echosounder time series via matrix decompositiona)}, journal = {Journal of the Acoustical Society of America}, volume = {148}, number = {6}, year = {2020}, pages = {3429-3442}, type = {Journal Article}, abstract = {The recent explosion in the availability of echosounder data from diverse ocean platforms has created unprecedented opportunities to observe the marine ecosystems at broad scales. However, the critical lack of methods capable of automatically discovering and summarizing prominent spatio-temporal echogram structures has limited the effective and wider use of these rich datasets. To address this challenge, a data-driven methodology is developed based on matrix decomposition that builds compact representation of long-term echosounder time series using intrinsic features in the data. In a two-stage approach, noisy outliers are first removed from the data by principal component pursuit, then a temporally smooth nonnegative matrix factorization is employed to automatically discover a small number of distinct daily echogram patterns, whose time-varying linear combination (activation) reconstructs the dominant echogram structures. This low-rank representation provides biological information that is more tractable and interpretable than the original data, and is suitable for visualization and systematic analysis with other ocean variables. Unlike existing methods that rely on fixed, handcrafted rules, this unsupervised machine learning approach is well-suited for extracting information from data collected from unfamiliar or rapidly changing ecosystems. This work forms the basis for constructing robust time series analytics for large-scale, acoustics-based biological observation in the ocean. }, issn = {0001-4966}, doi = {10.1121/10.0002670}, author = {Lee, W. J. and Staneva, V.} } @article {RN215, title = {Continuous evolution of oceanic crustal structure following an eruption at Axial Seamount, Juan de Fuca Ridge}, journal = {Geology}, volume = {48}, number = {5}, year = {2020}, pages = {452-456}, type = {Journal Article}, abstract = {We present the first continuous observations of the temporal evolution of oceanic crustal shear velocity beneath Axial Seamount, a submarine volcano on the Juan de Fuca Ridge (offshore northwestern North America). Weekly values of seafloor compliance, the periodic deformation of the seafloor under ocean waves, were estimated over the time period between December 2014 and May 2018 using data from two cabled broadband ocean-bottom seismometers with collocated absolute pressure sensors. We inverted these measurements for shear-wave velocity within the volcano beneath the two stations as a function of depth and time. Our results, combined with estimates of seismic compressional wave velocity, suggest that the shallow melt reservoir and the lower crust beneath the central caldera contain melt fractions of 14\% and at least 4\%, respectively. The eruption of April 2015 induced a dramatic drop in shear velocities beneath the central station, primarily in the lower crust, which could have been caused by an increase in melt fraction, a change in small-scale melt geometry, or both. The absence of such a change beneath the eastern flank of the caldera indicates that there is a lower-crustal conduit beneath the caldera center, which is much narrower in cross section (<1 km2) than the overlying melt reservoir (>=42 km2). Our study demonstrates the promise of using continuous data to understand submarine volcanism and crustal accretionary processes.}, issn = {0091-7613}, doi = {10.1130/G46831.1}, url = {https://doi.org/10.1130/G46831.1}, author = {Doran, Adrian K. and Crawford, Wayne C.} } @article {RN179, title = {Crustal Strength Variations Inferred from Earthquake Stress Drop at Axial Seamount Surrounding the 2015 Eruption}, journal = {Geophysical Research Letters}, year = {2020}, type = {Journal Article}, abstract = {Variations in stress drops of earthquakes associated with the April and May 2015 eruption of Axial Seamount, on the Juan de Fuca Ridge, suggest a reduction in crustal strength as a result of the eruption. Seismicity during the inflation and deflation periods was well recorded by ocean bottom seismometers located within and along the caldera. We use these nearby recordings and an empirical Green{\textquoteright}s function spectral ratio method to obtain corner frequencies for stress drops of earthquakes on caldera ring faults. We find stress drops from 0.6 to 43 MPa for 423 ring fault earthquakes (1.6 <= MW <= 3.6) and an average stress drop two times higher during the inflation period (6.4 MPa) prior to the eruption, than during the subsequent deflation (3.2 MPa). Stress drops also correlate with spatially varying shear wave speed, possibly reflecting a region of pervasive cracking in the northern caldera.}, doi = {10.1029/2020gl088447}, url = {https://app.dimensions.ai/details/publication/pub.1129927688}, author = {Moyer, Pamela A. and Boettcher, Margaret S. and Bohnenstiehl, Del Wayne R. and Abercrombie, Rachel E.} } @article {RN173, title = {Learning features from georeferenced seafloor imagery with location guided autoencoders}, journal = {Journal of Field Robotics}, year = {2020}, type = {Journal Article}, abstract = {The Cabled Observatory Vent Imaging Sonar (COVIS) was installed on the Ocean Observatories Initiative{\textquoteright}s Regional Cabled Array observatory at ASHES hydrothermal vent field on Axial Seamount in July 2018. The acoustic backscatter data recorded by COVIS in August{\textendash}September 2018, in conjunction with in situ temperature measurements, are used to showcase and verify the use of COVIS for long-term, quantitative monitoring of hydrothermal discharge. Specifically, sonar data processing generates three-dimensional backscatter images of the buoyant plumes above major sulfide structures and two-dimensional maps of diffuse flows within COVIS{\textquoteright}s field-of-view. The backscatter images show substantial changes of plume appearance and orientation that mostly reflect plume bending in the presence of ambient currents and potentially the variations of outflow fluxes. The intensity of acoustic backscatter decreases significantly for highly bent plumes as compared to nearly vertical plumes, reflecting enhanced mixing of plume fluids with seawater driven by ambient currents. A forward model of acoustic backscatter from a buoyancy-driven plume developed in this study yields a reasonable match with the observation, which paves the way for inversely estimating the source heat flux of a hydrothermal plume from acoustic backscatter measurements. The acoustic observations of diffuse flows show large temporal variations on time scales of hours to days, especially at tidal frequencies, but no apparent long-term trend. These findings demonstrate COVIS{\textquoteright}s ability to quantitatively monitor hydrothermal discharge from both focused and diffuse sources to provide the research community with key observational data for studying the linkage of hydrothermal activity with oceanic and geological processes.}, keywords = {acoustic, axial seamount, hydrothermal, imaging, observatory, sonar}, doi = {10.1002/rob.21961}, url = {https://app.dimensions.ai/details/publication/pub.1127976526}, author = {Yamada, Takaki and Pr{\"u}gel-Bennett, Adam and Thornton, Blair} } @article {RN165, title = {Measurement and Quality Control of MIROS Wave Radar Data at Dokdo}, journal = {Journal of Korean Society of Coastal and Ocean Engineers}, volume = {32}, number = {2}, year = {2020}, pages = {135-145}, type = {Journal Article}, abstract = {Wave observation is widely used to direct observation method for observing the water surface elevation using wave buoy or pressure gauge and remote-sensing wave observation method. The wave buoy and pressure gauge can produce high-quality wave data but have disadvantages of the high risk of damage and loss of the instrument, and high maintenance cost in the offshore area. On the other hand, remote observation method such as radar is easy to maintain by installing the equipment on the land, but the accuracy is somewhat lower than the direct observation method. This study investigates the data quality of MIROS Wave and Current Radar (MWR) installed at Dokdo and improve the data quality of remote wave observation data using the wave buoy (CWB) observation data operated by the Korea Meteorological Administration. We applied and developed the three types of wave data quality control; 1) the combined use (Optimal Filter) of the filter designed by MIROS (Reduce Noise Frequency, Phillips Check, Energy Level Check), 2) Spike Test Algorithm (Spike Test) developed by OOI (Ocean Observatories Initiative) and 3) a new filter (H-Ts QC) using the significant wave height-period relationship. As a result, the wave observation data of MWR using three quality control have some reliability about the significant wave height. On the other hand, there are still some errors in the significant wave period, so improvements are required. Also, since the wave observation data of MWR is different somewhat from the CWB data in high waves of over 3 m, further research such as collection and analysis of long-term remote wave observation data and filter development is necessary.}, keywords = {data processing, Dokdo, quality control, quality enhancement of wave data, wave and current radar}, doi = {10.9765/kscoe.2020.32.2.135}, url = {https://app.dimensions.ai/details/publication/pub.1127450425 http://jkscoe.or.kr/upload/pdf/jkscoe-32-2-135.pdf}, author = {Jun, Hyunjung and Min, Yongchim and Jeong, Jin-Yong and Do, Kideok} } @article {RN159, title = {New insights into the structural elements of the upper mantle beneath the contiguous United States from S-to-P converted seismic waves}, journal = {Geophysical Journal International}, volume = {222}, number = {1}, year = {2020}, pages = {646-659}, type = {Journal Article}, abstract = {The S-receiver function (SRF) technique is an effective tool to study seismic discontinuities in the upper mantle such as the mid-lithospheric discontinuity (MLD) and the lithosphere{\textendash}asthenosphere boundary (LAB). This technique uses deconvolution and aligns traces along the maximum of the deconvolved SV signal. Both of these steps lead to acausal signals, which may cause interference with real signals from below the Moho. Here we go back to the origin of the SRF method and process S-to-P converted waves using S-onset times as the reference time and waveform summation without any filter like deconvolution or bandpass. We apply this {\textquoteleft}causal{\textquoteright} SRF (C-SRF) method to data of the USArray and obtain partially different results in comparison with previous studies using the traditional acausal SRF method. The new method does not confirm the existence of an MLD beneath large regions of the cratonic US. The shallow LAB in the western US is, however, confirmed with the new method. The elimination of the MLD signal below much of the cratonic US reveals lower amplitude but highly significant phases that previously had been overwhelmed by the apparent MLD signals. Along the northern part of the area with data coverage we see relics of Archean or younger northwest directed low-angle subduction below the entire Superior Craton. In the cratonic part of the US we see indications of the cratonic LAB near 200 km depth. In the Gulf Coast of the southern US, we image relics of southeast directed shallow subduction, likely of mid-Palaeozoic age.}, issn = {0956-540X}, doi = {10.1093/gji/ggaa203}, author = {Kind, R. and Mooney, W. D. and Yuan, X. H.} } @article {RN143, title = {A Novel Fault Location Approach for Scientific Cabled Seafloor Observatories}, journal = {Journal of Marine Science and Engineering}, volume = {8}, number = {3}, year = {2020}, pages = {190}, type = {Journal Article}, abstract = {The maintenance of scientific cabled seafloor observatories (CSOs) is not only extremely difficult but also of high cost for their subsea location. Therefore, the cable fault detection and location are essential and must be carried out accurately. For this purpose, a novel on-line fault location approach based on robust state estimation is proposed, considering state data gross errors in sensor measurements and the influence of temperature on system parameter variation. The circuit theory is used to build state estimation equations and identify the power system topology of faulty CSOs. This method can increase the accuracy of fault location, and reduce the lose form shutting down a faulty CSO in traditional fault location methods. It is verified by computer simulation and the laboratory prototype of a planned CSO in the East China Sea, and the fault location error is proved to be less than 1 km.}, keywords = {cabled seafloor observatories, on-line fault location, robust state estimation, topology identification}, doi = {10.3390/jmse8030190}, url = {https://app.dimensions.ai/details/publication/pub.1125648256}, author = {Yang, Fan and Lyu, Feng} } @article {RN169, title = {Optimal sensors placement for detecting CO2 discharges from unknown locations on the seafloor}, journal = {International Journal of Greenhouse Gas Control}, volume = {95}, year = {2020}, pages = {102951}, type = {Journal Article}, abstract = {Assurance monitoring of the marine environment is a required and intrinsic part of CO2 storage project. To reduce the costs related to the monitoring effort, the monitoring program must be designed with optimal use of instrumentation. Here we use solution of a classical set cover problem to design placement of an array of fixed chemical sensors with the purpose of detecting a seep of CO2 through the seafloor from an unknown location. The solution of the problem is not unique and different aspects, such as cost or existing infrastructure, can be added to define an optimal solution. We formulate an optimization problem and propose a method to generate footprints of potential seeps using an advection{\textendash}diffusion model and a stoichiometric method for detection of small seepage CO2 signals. We provide some numerical experiments to illustrate the concepts.}, keywords = {Chemical sensors, Monitoring design, Offshore, Optimal sensor placement, Subsea CO2 seepage}, doi = {10.1016/j.ijggc.2019.102951}, url = {https://app.dimensions.ai/details/publication/pub.1124683604 https://doi.org/10.1016/j.ijggc.2019.102951}, author = {Oleynik, Anna and Garc{\'\i}a-Ib{\'a}{\~n}ez, Maribel I. and Blaser, Nello and Omar, Abdirahman and Alendal, Guttorm} } @article {RN185, title = {Physical Sources of High-Frequency Seismic Noise on Cascadia Initiative Ocean Bottom Seismometers}, journal = {Geochemistry Geophysics Geosystems}, year = {2020}, type = {Journal Article}, abstract = {Physical sources of high-frequency seismic noise in the ocean are investigated using data from the Cascadia Initiative (CI) ocean bottom seismometer (OBS) network, hindcasts of wind speed, waves, and the bottom currents predicted by a regional ocean circulation model and observed at sites on cabled observatories. Seismic data in the 5{\textendash}12 Hz band are considered because it is best for detecting regional earthquakes and lies between the frequencies of local microseisms and the seasonal whale calls. Median noise levels in this range vary by ~20 dB between sites at a given depth but on average decrease with increasing depth. On the continental shelf, the orbital motions of ocean waves are a major source of noise while at the quietest sites in the deep ocean, noise increases when wind speeds exceed ~10 m/s. On the continental slope and abyssal plain within about 100 km of the slope, seismic noise is not predicted at specific sites by the bottom currents in the ocean circulation model. In these regions, ocean currents are inferred to be the primary source of noise, because noise varies on tidal periods, is low on buried seismometers, and has spatial variations broadly consistent with those of median absolute currents. Comparisons between OBSs suggest that high-frequency noise is reduced by low-profile hydrodynamic designs but not by shielding. Many OBSs also record numerous short duration events on and near the continental shelf that have been attributed elsewhere to animals bumping into the sensor or gas bubbles moving through sediments.}, doi = {10.1029/2020gc009085}, url = {https://app.dimensions.ai/details/publication/pub.1131195022}, author = {Hilmo, Rose and Wilcock, William S. D.} } @article {RN183, title = {Precision Seismic Monitoring and Analysis at Axial Seamount Using a Real-Time Double-Difference System}, journal = {Journal of Geophysical Research-Solid Earth}, volume = {125}, number = {5}, year = {2020}, type = {Journal Article}, abstract = {Seven three-component ocean bottom seismometers (OBS) of the Ocean Observatories Initiative (OOI) Cabled Array on top of Axial Seamount are continuously streaming data in real time to the Incorporated Research Institutions for Seismology (IRIS). The OBS array records earthquakes from the submarine volcano which last erupted on 24 April 2015, about 4 months after the array came online. The OBS data have proven crucial in providing insight into the volcano structure and dynamics (Wilcock et al., 2016, https://doi.org/10.1126/science.aah5563). We implemented a real-time double-difference (RT-DD) monitoring system that automatically computes high-precision (tens of meters) locations of new earthquakes. The system{\textquoteright}s underlying double-difference base catalog includes nearly 100,000 earthquakes and was computed using kurtosis phase onset picks, cross-correlation phase delay times, and 3-D P and S velocity models to predict the data. The relocations reveal the fine-scale structures of long-lived, narrow (<200 m wide), outward dipping, convex faults on the east and west walls of the caldera that appear to form a figure 8-shaped ring fault system. These faults accommodate stresses caused by the inflation of magma prior to and deflation during eruptions. The east fault is segmented and pulled apart in east-west direction due to its interaction with the Juan de Fuca Ridge, which at this location forms an overlapping spreading center. The RT-DD system enables the monitoring and rapid analysis of variations in fine-scale seismic and fault properties and has the potential to improve prediction of timing and location of the next Axial eruption expected to occur in the 2022{\textendash}2023 time frame. }, issn = {2169-9313}, doi = {10.1029/2019JB018796}, author = {Waldhauser, F. and Wilcock, W. S. D. and Tolstoy, M. and Baillard, C. and Tan, Y. J. and Schaff, D. P.} } @article {RN176, title = {Quantification of eruption dynamics on the north rift at Axial Seamount, Juan de Fuca Ridge}, journal = {Geochemistry Geophysics Geosystems}, year = {2020}, type = {Journal Article}, abstract = {Quantifying eruption dynamics in submarine environments is challenging. During the 2015 eruption of Axial Seamount, the formation of hummocky mounds along the north rift was accompanied by tens of thousands of impulsive acoustic signals generated by the interaction of lava and seawater. A catalog of these sounds was integrated with detailed seafloor mapping to better understand eruptive processes in time and space. Mounds grew over a period of 28 days with average extrusion rates of 22 to 45 m3 s-1. The most distant mounds, ~9.5 to 15.5 km down rift from the caldera, grew primarily over the first few days of the eruption. The focus of eruptive activity then retreated ~5 km toward the caldera where it was sustained. Mounds are constructed as a series of superimposed lobes formed through alternating periods of flow inflation, generating up to 30-m-thick hummocks, and periods of flow advancement, with <0.02 m s-1 average speeds typically observed.}, doi = {10.1029/2020gc009136}, url = {https://app.dimensions.ai/details/publication/pub.1129829964}, author = {Le Saout, M. and Bohnenstiehl, D. R. and Paduan, J. B. and Clague, D. A.} } @article {RN131, title = {Revised Magmatic Source Models for the 2015 Eruption at Axial Seamount Including Estimates of Fault-Induced Deformation}, journal = {Journal of Geophysical Research: Solid Earth}, volume = {125}, number = {4}, year = {2020}, type = {Journal Article}, abstract = {Axial Seamount is an active submarine volcano located at the intersection of the Cobb hot spot and the Juan de Fuca Ridge (45{\textdegree}57'N, 130{\textdegree}01'W). Bottom pressure recorders captured co-eruption subsidence of 2.4{\textendash}3.2 m in 1998, 2011, and 2015, and campaign-style pressure surveys every 1{\textendash}2 years have provided a long-term time series of inter-eruption re-inflation. The 2015 eruption occurred shortly after the Ocean Observatories Initiative (OOI) Cabled Array came online providing real-time seismic and deformation observations for the first time. Nooner and Chadwick (2016, https://doi.org/10.1126/science.aah4666) used the available vertical deformation data to model the 2015 eruption deformation source as a steeply dipping prolate-spheroid, approximating a high-melt zone or conduit beneath the eastern caldera wall. More recently, Levy et al. (2018, https://doi.org/10.1130/G39978.1) used OOI seismic data to estimate dip-slip motion along a pair of outward-dipping caldera ring faults. This fault motion complicates the deformation field by contributing up to several centimeters of vertical seafloor motion. In this study, fault-induced surface deformation was calculated from the slip estimates of Levy et al. (2018, https://doi.org/10.1130/G39978.1) then removed from vertical deformation data prior to model inversions. Removing fault motion resulted in an improved model fit with a new best-fitting deformation source located 2.11 km S64{\textdegree}W of the source of Nooner and Chadwick (2016, https://doi.org/10.1126/science.aah4666) with similar geometry. This result shows that ring fault motion can have a significant impact on surface deformation, and future modeling efforts need to consider the contribution of fault motion when estimating the location and geometry of subsurface magma movement at Axial Seamount.}, doi = {10.1029/2020jb019356}, url = {https://app.dimensions.ai/details/publication/pub.1125839587}, author = {Hefner, William L. and Nooner, Scott L. and Chadwick, William W. and Bohnenstiehl, DelWayne R.} } @article {RN163, title = {Toward a Universal Frequency of Occurrence Distribution for Tsunamis: Statistical Analysis of a 32-Year Bottom Pressure Record at Axial Seamount}, journal = {Geophysical Research Letters}, volume = {47}, number = {10}, year = {2020}, type = {Journal Article}, abstract = {The Atlantic Meridional Overturning Circulation (AMOC) is a key mechanism of heat, freshwater, and carbon redistribution in the climate system. The precept that the AMOC has changed abruptly in the past, notably during and at the end of the last ice age, and that it is {\textquotedblleft}very likely{\textquotedblright} to weaken in the coming century due to anthropogenic climate change is a key motivation for sustained observations of the AMOC. This paper reviews the methodology and technology used to observe the AMOC and assesses these ideas and systems for accuracy, shortcomings, potential improvements, and sustainability. We review hydrographic techniques and look at how these traditional techniques can meet modern requirements. Transport mooring arrays (TMAs) provide the {\textquotedblleft}gold standard{\textquotedblright} for sustained AMOC observing, utilizing dynamic height, current meter, and other instrumentation and techniques to produce continuous observations of the AMOC. We consider the principle of these systems and how they can be sustained and improved into the future. Techniques utilizing indirect measurements, such as satellite altimetry, coupled with in situ measurements, such as the Argo float array, are also discussed. Existing technologies that perhaps have not been fully exploited for estimating AMOC are reviewed and considered for this purpose. Technology is constantly evolving, and we look to the future of technology and how it can be deployed for sustained and expanded AMOC measurements. Finally, all of these methodologies and technologies are considered with a view to a sustained and sustainable future for AMOC observation.}, doi = {10.1029/2020gl087372}, url = {https://app.dimensions.ai/details/publication/pub.1126751179}, author = {Fine, Isaac V. and Thomson, Richard E. and Chadwick, William W. and Fox, Christopher G.} } @article {RN160, title = {Towards Naples Ecological REsearch for Augmented Observatories (NEREA): The NEREA-Fix Module, a Stand-Alone Platform for Long-Term Deep-Sea Ecosystem Monitoring}, journal = {Sensors}, volume = {20}, number = {10}, year = {2020}, type = {Journal Article}, abstract = {Deep-sea ecological monitoring is increasingly recognized as indispensable for the comprehension of the largest biome on Earth, but at the same time it is subjected to growing human impacts for the exploitation of biotic and abiotic resources. Here, we present the Naples Ecological REsearch (NEREA) stand-alone observatory concept (NEREA-fix), an integrated observatory with a modular, adaptive structure, characterized by a multiparametric video-platform to be deployed in the Dohrn canyon (Gulf of Naples, Tyrrhenian Sea) at ca. 650 m depth. The observatory integrates a seabed platform with optoacoustic and oceanographic/geochemical sensors connected to a surface transmission buoy, plus a mooring line (also equipped with depth-staged environmental sensors). This reinforced high-frequency and long-lasting ecological monitoring will integrate the historical data conducted over 40 years for the Long-Term Ecological Research (LTER) at the station {\textquotedblleft}Mare Chiara{\textquotedblright}, and ongoing vessel-assisted plankton (and future environmental DNA-eDNA) sampling. NEREA aims at expanding the observational capacity in a key area of the Mediterranean Sea, representing a first step towards the establishment of a bentho-pelagic network to enforce an end-to-end transdisciplinary approach for the monitoring of marine ecosystems across a wide range of animal sizes (from bacteria to megafauna).}, keywords = {stand-alone observatory; optoacoustic imaging; ecological monitoring; remote data transmission; Artificial Intelligence}, doi = {10.3390/s20102911}, author = {Fanelli, E. and Aguzzi, J. and Marini, S. and del Rio, J. and Nogueras, M. and Canese, S. and Stefanni, S. and Danovaro, R. and Conversano, F.} } @article {RN161, title = {Triggering of eruptions at Axial Seamount, Juan de Fuca Ridge}, journal = {Scientific Reports}, volume = {10}, number = {1}, year = {2020}, pages = {10219}, type = {Journal Article}, abstract = {The submarine volcano Axial Seamount has exhibited an inflation predictable eruption cycle, which allowed for the successful forecast of its 2015 eruption. However, the exact triggering mechanism of its eruptions remains ambiguous. The inflation predictable eruption pattern suggests a magma reservoir pressure threshold at which eruptions occur, and as such, an overpressure eruption triggering mechanism. However, recent models of volcano unrest suggest that eruptions are triggered when conditions of critical stress are achieved in the host rock surrounding a magma reservoir. We test hypotheses of eruption triggering using 3-dimensional finite element models which track stress evolution and mechanical failure in the host rock surrounding the Axial magma reservoir. In addition, we provide an assessment of model sensitivity to various temperature and non-temperature-dependent rheologies and external tectonic stresses. In this way, we assess the contribution of these conditions to volcanic deformation, crustal stress evolution, and eruption forecasts. We conclude that model rheology significantly impacts the predicted timing of through-going failure and eruption. Models consistently predict eruption at a reservoir pressure threshold of 12{\textendash}14 MPa regardless of assumed model rheology, lending support to the interpretation that eruptions at Axial Seamount are triggered by reservoir overpressurization. }, doi = {10.1038/s41598-020-67043-0}, url = {https://app.dimensions.ai/details/publication/pub.1128680799 https://www.nature.com/articles/s41598-020-67043-0.pdf}, author = {Cabaniss, Haley E. and Gregg, Patricia M. and Nooner, Scott L. and Chadwick, William W.} } @article {RN66, title = {Axial Seamount: Periodic tidal loading reveals stress dependence of the earthquake size distribution (b value)}, journal = {Earth and Planetary Science Letters}, volume = {512}, year = {2019}, pages = {39-45}, type = {Journal Article}, abstract = {Earthquake size-frequency distributions commonly follow a power law, with the b value often used to quantify the relative proportion of small and large events. Laboratory experi13 ments have found that the b value of microfractures decreases with increasing stress. Stud14 ies have inferred that this relationship also holds for earthquakes based on observations of earthquake b values varying systematically with faulting style, depth, and for subduction zone earthquakes, plate age. However, these studies are limited by small sample sizes de17 spite aggregating events over large regions, which precludes the ability to control for other variables that might also affect earthquake b values such as rock heterogeneity and fault roughness. Our natural experiment in a unique seafloor laboratory on Axial Seamount involves analyzing the size-frequency distribution of \~{}60,000 microearthquakes which delineate a ring-fault system in a 25 km3 21 block of crust that experiences periodic tidal loading of {\textpm}20 kPa. We find that above a threshold stress amplitude, b value is inversely correlated with tidal stress. The earthquake b value varies by \~{}0.09 per kPa change in Coulomb stress. Our results support the potential use of b values to estimate small stress variations in the Earth{\textquoteright}s crust.}, issn = {0012-821X}, doi = {10.1016/j.epsl.2019.01.047}, url = {http://www.sciencedirect.com/science/article/pii/S0012821X19300731}, author = {Tan, Yen Joe and Waldhauser, Felix and Tolstoy, Maya and Wilcock, William S. D.} } @article {RN67, title = {Better Regional Ocean Observing Through Cross-National Cooperation: A Case Study From the Northeast Pacific}, journal = {Frontiers in Marine Science}, volume = {6}, year = {2019}, pages = {93}, type = {Journal Article}, abstract = {The ocean knows no political borders. Ocean processes, like summertime wind-driven upwelling, stretch thousands of kilometers along the Northeast Pacific (NEP) coast. This upwelling drives marine ecosystem productivity and is modulated by weather systems and seasonal to interdecadal ocean-atmosphere variability. Major ocean currents in the NEP transport water properties such as heat, fresh water, nutrients, dissolved oxygen, pCO2, and pH close to the shore. The eastward North Pacific Current bifurcates offshore in the NEP, delivering open-ocean signals south into the California Current and north into the Gulf of Alaska. There is a large and growing number of NEP ocean observing elements operated by government agencies, Native American Tribes, First Nations groups, not-for-profit organizations, and private entities. Observing elements include moored and mobile platforms, shipboard repeat cruises, as well as land-based and estuarine stations. A wide range of multidisciplinary ocean sensors are deployed to track, for example, upwelling, downwelling, ocean productivity, harmful algal blooms, ocean acidification and hypoxia, seismic activity and tsunami wave propagation. Data delivery to shore and observatory controls are done through satellite and cell phone communication, and via seafloor cables. Remote sensing from satellites and land-based coastal radar provide broader spatial coverage, while numerical circulation and biogeochemical modeling complement ocean observing efforts. Models span from the deep ocean into the inland Salish Sea and estuaries. NEP ocean observing systems are used to understand regional processes and, together with numerical models, provide ocean forecasts. By sharing data, experiences and lessons learned, the regional ocean observatory is better than the sum of its parts. }, keywords = {coastal oceanography, data delivery, marine eco system, ocean model and observations comparison, Ocean observation}, issn = {2296-7745}, doi = {10.3389/fmars.2019.00093}, url = {https://www.frontiersin.org/article/10.3389/fmars.2019.00093}, author = {Barth, John A. and Allen, Susan E. and Dever, Edward P. and Dewey, Richard K. and Evans, Wiley and Feely, Richard A. and Fisher, Jennifer L. and Fram, Jonathan P. and Hales, Burke and Ianson, Debby and Jackson, Jennifer and Juniper, Kim and Kawka, Orest and Kelley, Deborah and Klymak, Jody M. and Konovsky, John and Kosro, P. Michael and Kurapov, Alexander and Mayorga, Emilio and MacCready, Parker and Newton, Jan and Perry, R. Ian and Risien, Craig M. and Robert, Marie and Ross, Tetjana and Shearman, R. Kipp and Schumacker, Joe and Siedlecki, Samantha and Trainer, Vera L. and Waterman, Stephanie and Wingard, Christopher E.} } @article {RN73, title = {Development of physical modelling tools in support of risk scenarios: A new framework focused on deep-sea mining}, journal = {Science of The Total Environment}, volume = {650}, year = {2019}, pages = {2294-2306}, type = {Journal Article}, abstract = {Deep-sea mining has gained international interest to provide materials for the worldwide industry. European oceans and, particularly, the Portuguese Exclusive Economic Zone present a recognized number of areas with polymetallic sulphides rich in metals used in high technology developments. A large part of these resources are in the vicinity of sensitive ecosystems, where the mineral extraction can potentially damage deep-ocean life services. In this context, technological research must be intensified, towards the implementation of environmental friendly solutions that mitigate the associated impacts. To reproduce deep-sea dynamics and evaluate the effects of the mining activities, reliable numerical modelling tools should be developed. The present work highlights the usefulness of a new framework for risk and impact assessment based on oceanographic numerical models to support the adoption of good management practices for deep-sea sustainable exploitation. This tool integrates the oceanic circulation model ROMS-Agrif with the semi-Lagrangian model ICHTHYOP, allowing the representation of deep-sea dynamics and particles trajectories considering the sediments physical properties. Numerical simulations for the North Mid-Atlantic Ridge region, revealed the ability of ROMS-Agrif to simulate real deep-sea dynamics through validation with in situ data. Results showed a strong diversity in the particle residence time, with a dependency on their density and size but also on local ocean conditions and bottom topography. The highest distances are obtained for the smaller and less dense particles, although they tend to be confined by bathymetric constrains and deposited in deepest regions. This work highlights the potential of this modelling tool to forecast laden plume trajectories, allowing the definition of risk assessment scenarios for deep-sea mining activities and the implementation of sustainable exploitation plans. Furthermore, the coupling of this numerical solution with models of biota inhabiting deep-sea vent fields into ecosystem models is discussed and outlined as cost-effective tools for the management of these remote ecosystems.}, keywords = {Adaptive management, Biological communities, Deep-sea technologies, Hazard assessment, Numerical modelling, Precautionary principles}, issn = {0048-9697}, doi = {10.1016/j.scitotenv.2018.09.351}, url = {http://www.sciencedirect.com/science/article/pii/S004896971833852X}, author = {Lopes, Carina L. and Bastos, Lu{\'\i}sa and Caetano, Miguel and Martins, Irene and Santos, Miguel M. and Iglesias, Isabel} } @article {RN113, title = {Global Observing Needs in the Deep Ocean}, journal = {Frontiers in Marine Science}, volume = {6}, year = {2019}, pages = {241}, type = {Journal Article}, abstract = {The deep ocean below 200 m water depth is the least observed, but largest habitat on our planet by volume and area. Over 150 years of exploration has revealed that this dynamic system provides critical climate regulation, houses a wealth of energy, mineral, and biological resources, and represents a vast repository of biological diversity. A long history of deep-ocean exploration and observation led to the initial concept for the Deep-Ocean Observing Strategy (DOOS), under the auspices of the Global Ocean Observing System (GOOS). Here we discuss the scientific need for globally integrated deep-ocean observing, its status, and the key scientific questions and societal mandates driving observing requirements over the next decade. We consider the Essential Ocean Variables (EOVs) needed to address deep-ocean challenges within the physical, biogeochemical, and biological/ecosystem sciences according to the Framework for Ocean Observing (FOO), and map these onto scientific questions. Opportunities for new and expanded synergies among deep-ocean stakeholders are discussed, including academic-industry partnerships with the oil and gas, mining, cable and fishing industries, the ocean exploration and mapping community, and biodiversity conservation initiatives. Future deep-ocean observing will benefit from the greater integration across traditional disciplines and sectors, achieved through demonstration projects and facilitated reuse and repurposing of existing deep-sea data efforts. We highlight examples of existing and emerging deep-sea methods and technologies, noting key challenges associated with data volume, preservation, standardization, and accessibility. Emerging technologies relevant to deep-ocean sustainability and the blue economy include novel genomics approaches, imaging technologies, and ultra-deep hydrographic measurements. Capacity building will be necessary to integrate capabilities into programs and projects at a global scale. Progress can be facilitated by Open Science and Findable, Accessible, Interoperable, Reusable (FAIR) data principles and converge on agreed to data standards, practices, vocabularies, and registries. We envision expansion of the deep-ocean observing community to embrace the participation of academia, industry, NGOs, national governments, international governmental organizations, and the public at large in order to unlock critical knowledge contained in the deep ocean over coming decades, and to realize the mutual benefits of thoughtful deep-ocean observing for all elements of a sustainable ocean. }, keywords = {biodiversity, blue economy, deep sea, essential ocean variables, Ocean observation, ocean sensors}, issn = {2296-7745}, doi = {10.3389/fmars.2019.00241}, url = {https://www.frontiersin.org/article/10.3389/fmars.2019.00241}, author = {Levin, Lisa A. and Bett, Brian J. and Gates, Andrew R. and Heimbach, Patrick and Howe, Bruce M. and Janssen, Felix and McCurdy, Andrea and Ruhl, Henry A. and Snelgrove, Paul and Stocks, Karen I. and Bailey, David and Baumann-Pickering, Simone and Beaverson, Chris and Benfield, Mark C. and Booth, David J. and Carreiro-Silva, Marina and Cola{\c c}o, Ana and Ebl{\'e}, Marie C. and Fowler, Ashley M. and Gjerde, Kristina M. and Jones, Daniel O. B. and Katsumata, K. and Kelley, Deborah and Le Bris, Nadine and Leonardi, Alan P. and Lejzerowicz, Franck and Macreadie, Peter I. and McLean, Dianne and Meitz, Fred and Morato, Telmo and Netburn, Amanda and Pawlowski, Jan and Smith, Craig R. and Sun, Song and Uchida, Hiroshi and Vardaro, Michael F. and Venkatesan, R. and Weller, Robert A.} } @article {RN140, title = {Interpretation of detections of volcanic activity at Ioto Island obtained from in situ seismometers and remote hydrophones of the International Monitoring System}, journal = {Scientific Reports}, volume = {9}, number = {1}, year = {2019}, pages = {19519}, type = {Journal Article}, abstract = {In-situ seismic observations identified that volcanic activity of Ioto (formerly Iwojima), a volcanic island offshore Japan, increased in early September 2018. Observations of discolored nearshore waters and a splash reported by a local flyover provided evidence for a connection between undersea eruptions and recorded seismic activity. However there remain uncertainties as to when the undersea eruption series commenced and how much of the in-situ seismic activity recorded on the island was associated with volcanic earthquakes versus undersea eruptions. During this period, a large number of underwater acoustic (hydroacoustic) signals were recorded by the Comprehensive Nuclear-Test-Ban Treaty (CTBT) International Monitoring System (IMS) hydroacoustic station HA11, at Wake Island (U.S. Territory), in the northwestern Pacific Ocean with signals with directions of arrival consistent with sources located at Ioto. The analysis presented here interprets signal features of the remote hydroacoustic recordings provided by HA11 in order to attempt to distinguish between volcanic earthquake signals and undersea eruption signals originating from Ioto. Histograms of hydroacoustic events interpreted as originating from Ioto correlate well with the in-situ seismic observations at Ioto in the early stage of volcanic activity. The results presented suggest that around 75\% of the signals detected at HA11 with directions of arrival consistent with Ioto as their origin could be associated with undersea eruptions, supporting the conclusion that the IMS hydroacoustic stations can contribute to volcanic event remote monitoring. }, doi = {10.1038/s41598-019-55918-w}, url = {https://app.dimensions.ai/details/publication/pub.1123547312 https://www.nature.com/articles/s41598-019-55918-w.pdf}, author = {Matsumoto, Hiroyuki and Zampolli, Mario and Haralabus, Georgios and Stanley, Jerry and Mattila, James and Meral {\"O}zel, Nurcan} } @article {RN122, title = {A Joint Inversion for Three-dimensional P and S Wave Velocity Structure and Earthquake Locations Beneath Axial Seamount}, journal = {Journal of Geophysical Research: Solid Earth}, volume = {n/a}, number = {n/a}, year = {2019}, type = {Journal Article}, abstract = {Axial Seamount is a prominent volcano located at the intersection of the Juan de Fuca Ridge and the Cobb-Eickelberg hot spot in the northeast Pacific Ocean that has erupted in 1998, 2011, and 2015. The 2015 eruption was recorded by a seven-station seismic network in the southern part of the summit caldera that forms part of the Ocean Observatories Initiative Cabled Array. We utilize a data set of ~3,900 well-recorded earthquakes from January 2015 to February 2017 and a three-dimensional P wave velocity model obtained previously from active source data to conduct a joint inversion for three-dimensional P and S wave velocities and hypocentral parameters. The resulting velocity models are used to relocate >76,000 earthquakes with >=10 arrival times. The velocity models reveal a low-velocity anomaly in the center of the southern caldera at depths less than ~2 km, which corresponds to the top of the magma chamber and is interpreted as a region that is intensely fractured by the cyclical deformation of the caldera. High velocities around the caldera rim are likely due to consolidated undeformed lava flows. Low VP/VS in the southern caldera is consistent with the presence of hydrothermal vapor. Low S wave velocities and high VP/VS in the northern caldera may indicate a region dominated by thin cracks caused by dike injection. The relocated earthquakes delineate outward-dipping ring faults more clearly than previous studies and image a subvertical inward-dipping fault within the network that connects to the east caldera wall and eruptive fissures.}, keywords = {axial seamount, Earthquakes location, Hydrothermal systems, Joint inversion, Tomography, volcano}, issn = {2169-9313}, doi = {10.1029/2019JB017970}, author = {Baillard, Christian and Wilcock, William S. D. and Arnulf, Adrien F. and Tolstoy, Maya and Waldhauser, Felix} } @article {RN117, title = {Large-Signal Stability Analysis of the Undersea Direct Current Power System for Scientific Cabled Seafloor Observatories}, journal = {Applied Sciences}, volume = {9}, number = {15}, year = {2019}, type = {Journal Article}, abstract = {A large number of power electronic converters and long-distance submarine cables are an important part of the undersea direct current (DC) power system of the scientific cabled seafloor observatories (CSOs). However, the constant power load (CPL) characteristics of the converters and the distributed parameter characteristics of long-distance submarine cables greatly affect the stability of the CSO DC power system. This paper analyzes the large-signal stability of the CSO DC power system, and the equivalent circuits of long-distance submarine cables are established by theoretical analysis and computer simulation. A simplified computer simulation model and an equivalent experimental prototype model of a single-node CSO DC power system was built in the laboratory to study this issue. The mixed potential function method is used to analyze the large-signal stability of the CSO DC power system, and the large-signal stability criterion is obtained theoretically. The validity of the large-signal stability criterion is proved by simulations and experiments. The conclusion is that reducing the inductance of the submarine cable, increasing the capacitance of the submarine cable, increasing the output voltage of the shore station power feeding equipment (PFE) or reducing the power consumption of the undersea station, are beneficial to improve the large-signal stability of the CSO DC power system.}, keywords = {cabled seafloor observatories, direct current power systems, large-signal stability, mixed potential function}, issn = {2076-3417}, doi = {10.3390/app9153149}, author = {Jiang, Yamei and Lyu, Feng} } @article {RN68, title = {Location of Seismic {\textquotedblleft}Hum{\textquotedblright} Sources Following Storms in the North Pacific Ocean}, journal = {Geochemistry, Geophysics, Geosystems}, year = {2019}, type = {Journal Article}, abstract = {We investigate the spatially and temporally varying distributions of sources of the Earth{\textquoteright}s low-frequency seismic hum at high space-time resolution during a seismically quiet 7-day period in December 2015, when two large storms with different reaches propagate across the North Pacific Ocean. We integrate information from a variety of data from ocean wave height, infragravity wave prediction model, and broadband seismic data. We analyze seismic data to understand the seismic hum better: power spectral density at stations for detection and location of sources using array beamforming and backprojection methods, with a ~3-hr temporal and ~5{\textdegree} spatial resolution. For storms propagating west to east across the northern Pacific hitting the west coast of North America broadscale, we show that the distribution of hum sources is consistent with a model of seismic energy generated via infragravity waves, produced near the impact location of the storm, and propagating along the coast as well as toward the open ocean. The generation of seismic hum depends strongly on the reach of the storm and is very weak for a storm with more northerly propagation toward Alaska. At shorter periods (e.g., ~70 s), the seismic hum is generated in a narrow band that follows the coast, reaching progressively further to the north, while at longer periods (e.g. 150 s), it covers a broader area reaching far into the deep ocean. It may thus be possible to predict the distribution of the strongest {\textquotedblleft}hum{\textquotedblright} sources, to first order, from the knowledge of the direction of propagation and strength of northern Pacific storms. }, issn = {1525-2027}, doi = {10.1029/2018GC008112}, url = {https://doi.org/10.1029/2018GC008112}, author = {Maurya, Satish and Taira, Taka{\textquoteright}aki and Romanowicz, Barbara} } @article {RN217, title = {The mechanism of tidal triggering of earthquakes at mid-ocean ridges}, journal = {Nature Communications}, volume = {10}, number = {1}, year = {2019}, pages = {2526}, type = {Journal Article}, abstract = {The strong tidal triggering of mid-ocean ridge earthquakes has remained unexplained because the earthquakes occur preferentially during low tide, when normal faulting earthquakes should be inhibited. Using Axial Volcano on the Juan de Fuca ridge as an example, we show that the axial magma chamber inflates/deflates in response to tidal stresses, producing Coulomb stresses on the faults that are opposite in sign to those produced by the tides. When the magma chamber{\textquoteright}s bulk modulus is sufficiently low, the phase of tidal triggering is inverted. We find that the stress dependence of seismicity rate conforms to triggering theory over the entire tidal stress range. There is no triggering stress threshold and stress shadowing is just a continuous function of stress decrease. We find the viscous friction parameter A to be an order of magnitude smaller than laboratory measurements. The high tidal sensitivity at Axial Volcano results from the shallow earthquake depths.}, issn = {2041-1723}, doi = {10.1038/s41467-019-10605-2}, url = {https://doi.org/10.1038/s41467-019-10605-2}, author = {Scholz, Christopher H. and Tan, Yen Joe and Albino, Fabien} } @article {RN121, title = {Ocean Observatories as a Tool to Advance Gas Hydrate Research}, journal = {Earth and Space Science}, year = {2019}, type = {Journal Article}, abstract = {Since 2009, unprecedented comprehensive long-term gas hydrate observations have become available from Ocean Networks Canada{\textquoteright}s NEPTUNE cabled ocean observatory at the northern Cascadia margin. Several experiments demonstrate the scientific importance of permanent power and Internet connectivity to the ocean floor as they have advanced the field of gas hydrate related research. One example is the cabled crawler Wally at Barkley Canyon, enabling live in situ exploration of the hydrate mounds and its associated benthic communities through the crawler{\textquoteright}s mobility and permanent accessibility throughout the year. Another example is a bubble-imaging sonar at Clayoquot Slope, revealing the strong relationship between ebullition of natural gas and tidal pressure, without apparent correlation to earthquakes, storms, or temperature fluctuations, in year-long continuous recordings. Finally, regular observatory maintenance cruises allow additional science sampling including echo-sounder surveys to extend the observatory footprint. Long-term trends in the data are not yet apparent but can also become evident from continuous measurements, as ocean observatories such as NEPTUNE are built for a 25-year lifetime, and expansion of the observatory networks makes these findings comparable and testable.}, doi = {10.1029/2019EA000762}, author = {Scherwath, M. and Thomsen, L. and Riedel, M. and Romer, M. and Chatzievangelou, D. and Schwendner, J. and Duda, A. and Heesemann, M.} } @article {RN125, title = {Optimizing Sensor Configurations for the Detection of Slow-Slip Earthquakes in Seafloor Pressure Records, Using the Cascadia Subduction Zone as a Case Study}, journal = {Journal of Geophysical Research-Solid Earth}, year = {2019}, type = {Journal Article}, abstract = {We present seafloor pressure records from the Cascadia Subduction Zone, alongside oceanographic and geophysical models, to evaluate the spatial uniformity of bottom pressure and optimize the geometry of sensor networks for resolving offshore slow-slip transients. Seafloor pressure records from 2011 to 2015 show that signal amplitudes are depth-dependent, with tidally filtered and detrended root-mean-squares of <2 cm on the abyssal plain and >6 cm on the continental shelf. This is consistent with bottom pressure predictions from circulation models and comparable to deformation amplitudes from offshore slow slip observed in other subduction zones. We show that the oceanographic component of seafloor pressure can be reduced to <=1-cm root-mean-square by differencing against a reference record from a similar depth, under restrictions that vary with depth. Instruments at 100{\textendash}250 m require depths matched within 10 m at separations of <100 km, while locations deeper than 1,400 m are broadly comparable over separations of at least 300 km. Despite the significant noise reduction from this method, no slow slip was identified in the dataset, possibly due to poor spatiotemporal instrument coverage, nonideal deployment geometry, and limited depth-matched instruments. We use forward predictions of deformation from elastic half-space models and hindcast pressure from circulation models to generate synthetic slow-slip observational records and show that a range of slip scenarios produce resolvable signals under depth-matched differencing. For future detection of offshore slow slip in Cascadia, we recommend a geometry in which instruments are deployed along isobaths to optimize corrections for oceanographic signals.}, issn = {2169-9313}, doi = {10.1029/2019JB018053}, author = {Fredrickson, E. K. and Wilcock, W. S. D. and Schmidt, D. A. and MacCready, P. and Roland, E. and Kurapov, A. L. and Zumberge, M. A. and Sasagawa, G. S.} } @article {RN72, title = {Posteruption Enhancement of Hydrothermal Activity: A 33-Year, Multieruption Time Series at Axial Seamount (Juan de Fuca Ridge)}, journal = {Geochemistry, Geophysics, Geosystems}, volume = {20}, number = {2}, year = {2019}, pages = {814-828}, type = {Journal Article}, abstract = {Mid-ocean ridge eruptions, initiating or revitalizing hydrothermal discharge and disrupting seafloor ecosystems, occur regularly as a consequence of plate spreading. Evaluating their impact on long-term hydrothermal discharge requires information on the scale and duration of any posteruption enhancement. Here we describe a unique hydrothermal plume time series of annual (or more frequent) observations at Axial Seamount vent fields from 1985 through 2017, missing only 7 years. Axial, a hot spot volcano astride the Juan de Fuca Ridge, experienced eruptions in 1998, 2011, and 2015. In 1998 and 2011 lava flooded the SE caldera and south rift zone, but in 2015 most lava was extruded in a series of flows extending ~20 km down the north rift zone. Response cruises occurred within 18 days (1998) to about 4 months, followed by regular posteruption observations. All 30 cruises measured plume rise height (a proxy for heat flux) and turbidity (indicative of chemical changes in vent discharge) at several vent sites, yielding an integrated view of vent field activity. Venting in the SE caldera area persisted throughout the time series, consistent with the imaged location of the shallowest portion of the melt-rich magma reservoir. Eruptions produced substantial and diagnostic increases in plume rise and turbidity, and posteruption enhancements lasted 2{\textendash}5 years, totaling ~10 years over the course of the time series. Estimates of the relative heat flux indicate a sixfold increase during eruption-enhanced periods, implying that generalizations about mid-ocean ridge hydrothermal fluxes may be underestimates if based on non{\textendash}eruption-enhanced hydrothermal activity alone.}, issn = {1525-2027}, doi = {10.1029/2018GC007802}, url = {https://doi.org/10.1029/2018GC007802}, author = {Baker, Edward T. and Walker, Sharon L. and Chadwick Jr, William W. and Butterfield, David A. and Buck, Nathaniel J. and Resing, Joseph A.} } @article {RN123, title = {A Sensor Web Prototype for Cabled Seafloor Observatories in the East China Sea}, journal = {Journal of Marine Science and Engineering}, volume = {7}, number = {11}, year = {2019}, pages = {414}, type = {Journal Article}, abstract = {Seafloor observatories enable continuous power supply and real-time bidirectional data transmission, which marks a new way for marine environment monitoring. As in situ observation produces massive data in a constant way, the research involved with data acquisition, data transmission, data analysis, and user-oriented data application is vital to the close-loop operations of seafloor observatories. In this paper, we design and implement a sensor web prototype (ESOSW) to resolve seafloor observatory information processing in a plug-and-play way. A sensor web architecture is first introduced, which is information-oriented and structured into four layers enabling bidirectional information flow of observation data and control commands. Based on the layered architecture, the GOE Control Method and the Hot Swapping Interpretation Method are proposed as the plug-and-play mechanism for sensor control and data processing of seafloor observatory networks. ESOSW was thus implemented with the remote-control system, the data management system, and the real-time monitoring system, supporting managed sensor control and on-demand measurement. ESOSW was tested for plug-and-play enablement through a series of trials and was put into service for the East China Sea Seafloor Observation System. The experiment shows that the sensor web prototype design and implementation are feasible and could be a general reference to related seafloor observatory networks.}, keywords = {control systems, data processing, plug-and-play, seafloor observatories, sensor web}, issn = {2077-1312}, doi = {10.3390/jmse7110414}, url = {https://www.mdpi.com/2077-1312/7/11/414}, author = {Yu, Yang and Xu, Huiping and Xu, Changwei} } @article {RN110, title = {SMART Cables for Observing the Global Ocean: Science and Implementation}, journal = {Frontiers in Marine Science}, volume = {6}, year = {2019}, pages = {424}, type = {Journal Article}, abstract = {The ocean is key to understanding societal threats including climate change, sea level rise, ocean warming, tsunamis, and earthquakes. Because the ocean is difficult and costly to monitor, we lack fundamental data needed to adequately model, understand, and address these threats. One solution is to integrate sensors into future undersea telecommunications cables. This is the mission of the SMART subsea cables initiative (Science Monitoring And Reliable Telecommunications). SMART sensors would {\textquotedblleft}piggyback{\textquotedblright} on the power and communications infrastructure of a million kilometers of undersea fiber optic cable and thousands of repeaters, creating the potential for seafloor-based global ocean observing at a modest incremental cost. Initial sensors would measure temperature, pressure, and seismic acceleration. The resulting data would address two critical scientific and societal issues: the long-term need for sustained climate-quality data from the under-sampled ocean (e.g., deep ocean temperature, sea level, and circulation), and the near-term need for improvements to global tsunami warning networks. A Joint Task Force (JTF) led by three UN agencies (ITU/WMO/UNESCO-IOC) is working to bring this initiative to fruition. This paper explores the ocean science and early warning improvements available from SMART cable data, and the societal, technological, and financial elements of realizing such a global network. Simulations show that deep ocean temperature and pressure measurements can improve estimates of ocean circulation and heat content, and cable-based pressure and seismic-acceleration sensors can improve tsunami warning times and earthquake parameters. The technology of integrating these sensors into fiber optic cables is discussed, addressing sea and land-based elements plus delivery of real-time open data products to end users. The science and business case for SMART cables is evaluated. SMART cables have been endorsed by major ocean science organizations, and JTF is working with cable suppliers and sponsors, multilateral development banks and end users to incorporate SMART capabilities into future cable projects. By investing now, we can build up a global ocean network of long-lived SMART cable sensors, creating a transformative addition to the Global Ocean Observing System. }, keywords = {ocean cabled observatories, ocean circulation, ocean observing, SMART subsea cables, submarine telecommunications cables, tsunami early warning, UN Joint Task Force}, issn = {2296-7745}, doi = {10.3389/fmars.2019.00424}, url = {https://www.frontiersin.org/article/10.3389/fmars.2019.00424}, author = {Howe, Bruce M. and Arbic, Brian K. and Aucan, J{\'e}rome and Barnes, Christopher R. and Bayliff, Nigel and Becker, Nathan and Butler, Rhett and Doyle, Laurie and Elipot, Shane and Johnson, Gregory C. and Landerer, Felix and Lentz, Stephen and Luther, Douglas S. and M{\"u}ller, Malte and Mariano, John and Panayotou, Kate and Rowe, Charlotte and Ota, Hiroshi and Song, Y. Tony and Thomas, Maik and Thomas, Preston N. and Thompson, Philip and Tilmann, Frederik and Weber, Tobias and Weinstein, Stuart} } @article {RN150, title = {Stress Drops on the Blanco Oceanic Transform Fault from Interstation Phase CoherenceStress Drops on the Blanco Oceanic Transform Fault from Interstation Phase Coherence}, journal = {Bulletin of the Seismological Society of America}, volume = {109}, number = {3}, year = {2019}, pages = {929-943}, type = {Journal Article}, abstract = { Oceanic transform faults display a wide range of earthquake stress drops, large aseismic slip, and along-strike variation in seismic coupling. We use and further develop a phase coherence-based method to calculate and analyze stress drops of 61 M>=5.0 events between 2000 and 2016 on the Blanco fault, off the coast of Oregon. With this method, we estimate earthquake rupture extents by examining how apparent source time functions (ASTFs) vary between stations. The variation is caused by the generation of seismic waves at different locations along the rupture, which arrive at different times depending on station location. We isolate ASTFs at a range of stations by comparing seismograms of collocated earthquakes and then use the interstation ASTF coherence to infer rupture extent and stress drop. We examine how our analysis is influenced by various factors, including poor trace alignment, relative earthquake locations, focal mechanism variation, azimuthal distribution of stations, and depth phase arrivals. We find that as alignment accuracy decreases or distance between earthquakes increases, coherence is reduced, but coherence is unaffected by focal mechanism variation or depth phase arrivals for our dataset. We calibrate the coherence{\textendash}rupture extent relationship based on the azimuthal distribution of stations. We find the phase coherence method can be used to estimate stress drops for offshore earthquakes, but is limited to M>=5.0 earthquakes for the Blanco fault due to poor trace alignment accuracy. The median stress drop on the Blanco fault is 8 MPa (with 95\% confidence limits of 6{\textendash}12 MPa) for 61 earthquakes. Stress drops are a factor of 1.7 (95\% confidence limits 0.8{\textendash}3.5) lower on the more aseismic northwest segment of the Blanco fault. These lower stress drops could be linked to reduced healing time due to higher temperatures, which reduce the depth of the seismogenic zone and shorten the seismic cycle.}, doi = {10.1785/0120180319}, url = {https://app.dimensions.ai/details/publication/pub.1113957538 http://eprints.whiterose.ac.uk/145490/1/manuscriptrevised2.pdf}, author = {Williams, Joshua R. and Hawthorne, Jessica C. and Rost, Sebastian and Wright, Tim J.} } @article {RN74, title = {Tsunami Wavefield Reconstruction and Forecasting Using the Ensemble Kalman Filter}, journal = {Geophysical Research Letters}, volume = {46}, number = {2}, year = {2019}, pages = {853-860}, type = {Journal Article}, abstract = {Offshore sensor networks like DONET and S-NET, providing real-time estimates of wave height through measurements of pressure changes along the seafloor, are revolutionizing local tsunami early warning. Data assimilation techniques, in particular, optimal interpolation (OI), provide real-time wavefield reconstructions and forecasts. Here we explore an alternative assimilation method, the ensemble Kalman filter (EnKF), and compare it to OI. The methods are tested on a scenario tsunami in the Cascadia subduction zone, obtained from a 2-D coupled dynamic earthquake and tsunami simulation. Data assimilation uses a 1-D linear long-wave model. We find that EnKF achieves more accurate and stable forecasts than OI, both at the coast and across the entire domain, especially for large station spacing. Although EnKF is more computationally expensive than OI, with development in high-performance computing, it is a promising candidate for real-time local tsunami early warning.}, issn = {0094-8276}, doi = {10.1029/2018GL080644}, url = {https://doi.org/10.1029/2018GL080644}, author = {Yang, Yuyun and Dunham, Eric M. and Barnier, Guillaume and Almquist, Martin} } @article {RN97, title = {Volcanic Tremor of Mt. Etna (Italy) Recorded by NEMO-SN1 Seafloor Observatory: A New Perspective on Volcanic Eruptions Monitoring}, journal = {Geosciences}, volume = {9}, number = {3}, year = {2019}, pages = {115}, type = {Journal Article}, abstract = {The NEMO-SN1 seafloor observatory, located 2100 m below sea level and about 40 km from Mt. Etna volcano, normally records a background seismic signal called oceanographic noise. This signal is characterized by high amplitude increases, lasting up to a few days, and by two typical 0.1 and 0.3 Hz frequencies in its spectrum. Particle motion analysis shows a strong E-W directivity, coinciding with the direction of sea waves; gravity waves induced by local winds are considered the main source of oceanographic noise. During the deployment of NEMO-SN1, the vigorous 2002{\textendash}2003 Mt. Etna eruption occurred. High-amplitude background signals were recorded during the explosive episodes accompanying the eruption. The spectral content of this signal ranges from 0.1 to 4 Hz, with the most powerful signal in the 0.5{\textendash}2 Hz band, typical of an Etna volcanic tremor. The tremor recorded by NEMO-SN1 shows a strong NW-SE directivity towards the volcano. Since the receiver is underwater, we inferred the presence of a circulation of magmatic fluids extended under the seafloor. This process is able to generate a signal strong enough to be recorded by the NEMO-SN1 seafloor observatory that hides frequencies linked to the oceanographic noise, permitting the offshore monitoring of the volcanic activity of Mt. Etna.}, keywords = {Mt. Etna volcano, oceanographic noise, volcanic monitoring by seafloor observatories, volcanic tremor}, doi = {10.3390/geosciences9030115}, url = {https://app.dimensions.ai/details/publication/pub.1112570519 https://www.mdpi.com/2076-3263/9/3/115/pdf}, author = {Sgroi, Tiziana and Di Grazia, Giuseppe and Favali, Paolo} } @article {RN89, title = {Augmenting Onshore GNSS Displacements With Offshore Observations to Improve Slip Characterization for Cascadia Subduction Zone Earthquakes}, journal = {Geophysical Research Letters}, volume = {45}, number = {12}, year = {2018}, pages = {6008-6017}, type = {Journal Article}, abstract = {For the Cascadia subduction zone, Mw~8 megathrust earthquake hazard is of particular interest because uncertainties in the predicted tsunami size affect evacuation alerts. To reduce these uncertainties, we examine how augmenting the current Global Navigation Satellite Systems (GNSS) network in Cascadia with offshore stations improves static slip inversions for Mw~8 megathrust earthquakes at different rupture depths. We test two offshore coseismic data types: vertical-only bottom pressure sensors and pressure sensors combined with GNSS-Acoustic aided horizontal positions. We find that amphibious networks best constrain slip for a shallow earthquake compared to onshore-only networks when offshore stations are located above the rupture. However, inversions using vertical-only offshore data underestimate shallow slip and tsunami impact. Including offshore horizontal observations improves slip estimates, particularly maximum slip. This suggests that while real-time GNSS-Acoustic sensors may have a long development timeline, they will have more impact for static inversion-based tsunami early warning systems than bottom pressure sensors.}, issn = {0094-8276}, doi = {10.1029/2018GL078233}, url = {https://doi.org/10.1029/2018GL078233}, author = {Saunders, Jessie K. and Haase, Jennifer S.} } @article {RN90, title = {Automated Large-Scale Full Seismic Waveform Inversion for North America and the North Atlantic}, journal = {Journal of Geophysical Research: Solid Earth}, volume = {123}, number = {7}, year = {2018}, pages = {5902-5928}, type = {Journal Article}, abstract = {We present a new anisotropic seismic tomography model based on a multiscale full seismic waveform inversion for crustal and upper-mantle structure from the western edge of North America across the North Atlantic and into Europe. The gradient-based inversion strategy utilizes the adjoint state method coupled with an L-BFGS quasi-Newton optimization scheme. To improve the handling of large data quantities in the context of full seismic waveform inversions, we developed a workflow framework automating the procedure across all stages, enabling us to confidently invert for waveforms from 72 events recorded at 7,737 unique stations, resulting in a total of 144,693 raypaths, most of them with three-component recordings. The final model after 20 iterations is able to explain complete waveforms including body as well as surface waves of earthquakes that were not used in the inversion down to periods of around 30 s. The model is complemented by a detailed resolution analysis in the form of 3-D distributions of direction-dependent resolution lengths.}, issn = {2169-9313}, doi = {10.1029/2017JB015289}, url = {https://doi.org/10.1029/2017JB015289}, author = {Krischer, Lion and Fichtner, Andreas and Boehm, Christian and Igel, Heiner} } @article {RN3, title = {Deep-Sea Volcanic Eruptions Create Unique Chemical and Biological Linkages Between the Subsurface Lithosphere and the Oceanic Hydrosphere}, journal = {Oceanography}, volume = {31}, number = {1}, year = {2018}, pages = {128-135}, type = {Journal Article}, abstract = {In April 2015, pressure recorders, seismometers, and hydrophones attached to the Ocean Observatories Initiative (OOI) Cabled Array on Axial Seamount detected, in real time, a volcanic eruption predominantly located along the north rift zone (NRZ). Real-time detection enabled a rapid response cruise to augment OOI data with ship-based physical, chemical, and biological sampling of the eruption and the new lava flows. The combined data set demonstrates the synergistic value of real-time monitoring combined with rapid response efforts that sample beyond the boundaries of a fixed cabled array. These combined data show that the 2015 eruption gave rise to chemically and microbiologically variable hydrothermal plumes over new NRZ lava flows, reflecting chemical and biological linkages between the subsurface lithosphere and the oceanic hydrosphere. The warmest and least diluted plume near the new lava flows was 0.119{\textdegree}C above background seawater and hosted thermophilic and hyperthermophilic taxa that are typically identified in hydrothermal fluids emanating from the warm subsurface. Cooler and more diluted hydrothermal plumes farther from a hydrothermal fluid source were 0.072{\textdegree}{\textendash}0.078{\textdegree}C above background seawater and hosted mesophilic and psychrophilic taxa that are typically identified in neutrally buoyant plumes at persistent hydrothermal venting sites. Potentially chemosynthetic microbial lineages, including Epsilonproteobacteria, Gammaproteobacteria, and Methanococcales, were positively correlated with elevated temperature anomalies. These data suggest that hydrothermal fluid flow through new lava flows on the NRZ supported diverse microbial communities for several months following the 2015 eruption and that subsurface heterogeneity contributed to the structure of unique hydrothermal-plume-hosted microbial communities.}, issn = {1042-8275}, doi = {10.5670/oceanog.2018.120}, url = {://WOS:000427367300020}, author = {Spietz, R. L. and Butterfield, D. A. and Buck, N. J. and Larson, B. I. and Chadwick, W. W. and Walker, S. L. and Kelley, D. S. and Morris, R. M.} } @article {RN79, title = {Distributed natural gas venting offshore along the Cascadia margin}, journal = {Nature Communications}, volume = {9}, number = {1}, year = {2018}, pages = {3264}, type = {Journal Article}, abstract = {Widespread gas venting along the Cascadia margin is investigated from acoustic water column data and reveals a nonuniform regional distribution of over 1100 mapped acoustic flares. The highest number of flares occurs on the shelf, and the highest flare density is seen around the nutrition-rich outflow of the Juan de Fuca Strait. We determine \~{}430 flow-rates at \~{}340 individual flare locations along the margin with instantaneous in situ values ranging from \~{}6 mL min-1 to \~{}18 L min-1. Applying a tidal-modulation model, a depth-dependent methane density, and extrapolating these results across the margin using two normalization techniques yields a combined average in situ flow-rate of \~{}88 {\texttimes} 106 kg y-1. The average methane flux-rate for the Cascadia margin is thus estimated to \~{}0.9 g y-1m-2. Combined uncertainties result in a range of these values between 4.5 and 1800\% of the estimated mean values.}, issn = {2041-1723}, doi = {10.1038/s41467-018-05736-x}, url = {https://doi.org/10.1038/s41467-018-05736-x}, author = {Riedel, M. and Scherwath, M. and Romer, M. and Veloso, M. and Heesemann, M. and Spence, G. D.} } @article {RN88, title = {Measuring Seafloor Strain With an Optical Fiber Interferometer}, journal = {Earth and Space Science}, volume = {5}, number = {8}, year = {2018}, pages = {371-379}, type = {Journal Article}, abstract = {We monitored the length of an optical fiber cable stretched between two seafloor anchors separated by 200 m at a depth of 1900 m, 90 km west of Newport, OR, near the toe of the accretionary prism of the Cascadia subduction zone. We continuously recorded length changes using an equal arm Michelson interferometer formed by the sensing cable fiber and a mandrel-wound reference fiber. A second, nearly identical fiber interferometer (sharing the same cable and housing), differing only in its fiber{\textquoteright}s temperature coefficient, was recorded simultaneously, allowing the separation of optical path length change due to temperature from that due to strain. Data were collected for 100 days following deployment on 18 October 2015, and showed an overall strain (length change) of -10.7 με (shorter by 2.14 mm). At seismic periods, the sensitivity was a few nε; at tidal periods the noise level was a few tens of nε. The RMS variation after removal of a -79 nε/day drift over the final 30 days was 36 nε. No strain transients were observed. An unexpected response to the varying hydrostatic load from ocean tides was observed with a coefficient of -101 nε per meter of ocean tide height.}, issn = {2333-5084}, doi = {10.1029/2018EA000418}, url = {https://doi.org/10.1029/2018EA000418}, author = {Zumberge, Mark A. and Hatfield, William and Wyatt, Frank K.} } @article {RN1, title = {Mechanics of fault reactivation before, during, and after the 2015 eruption of Axial Seamount}, journal = {Geology}, volume = {46}, number = {5}, year = {2018}, pages = {447-450}, type = {Journal Article}, abstract = {Ocean-bottom seismic and seafloor pressure data from the Ocean Observatories Initiative{\textquoteright}s Cabled Array were used to study fault reactivation within Axial Seamount (offshore Oregon, USA). Microearthquakes that occurred during 2015{\textendash}2016 were located on portions of an outward-dipping ring fault system that was reactivated in response to the inflation and deflation of the underlying magma chamber. Prior to an eruption in April 2015, focal mechanisms showed a pattern of normal slip consistent with the differential vertical uplift of the caldera floor relative to the rim. During the eruption, seismic activity remained localized along these outward-dipping structures; however, the slip direction was reversed as the caldera floor subsided. After the eruption, as the volcano reinflated and the caldera floor uplifted, these faults exhibited sparser seismicity with a more heterogeneous pattern of slip. Monitoring the evolution of ring fault behavior through time may have utility as a metric in future eruption forecasts.}, issn = {0091-7613}, doi = {10.1130/G39978.1}, url = {://WOS:000431359800019}, author = {Levy, S. and Bohnenstiehl, D. R. and Sprinkle, P. and Boettcher, M. S. and Wilcock, W. S. D. and Tolstoy, M. and Waldhauser, F.} } @article {RN80, title = {Newly detected earthquakes in the Cascadia subduction zone linked to seamount subduction and deformed upper plate}, journal = {Geology}, volume = {46}, number = {11}, year = {2018}, pages = {943-946}, type = {Journal Article}, abstract = {Data from an amphibious seismic network in Cascadia (northwest North America) provide unique near-source observations to assess the influence of subducting topography on seismicity. Using subspace detection, we detect and locate 222 events in two separate clusters, near a subducted seamount and a possibly accreted seamount. Seismicity in both clusters is largely shallower than the plate interface and exhibits occasional swarm-like behavior. This implies that the seamount is subducting aseismically via weak coupling with the overriding plate, while earthquakes in the upper plate arise from a high degree of fracturing due to seamount interaction, and the accreted seamount induced similar fracturing before off-scraping. }, issn = {0091-7613}, doi = {10.1130/G45354.1}, url = {https://doi.org/10.1130/G45354.1}, author = {Morton, Emily A. and Bilek, Susan L. and Rowe, Charlotte A.} } @article {RN10, title = {Observation and Modeling of Hydrothermal Response to the 2015 Eruption at Axial Seamount, Northeast Pacific}, journal = {Geochemistry, Geophysics, Geosystems}, number = {ja}, year = {2018}, type = {Journal Article}, abstract = {The 2015 eruption at Axial Seamount, an active volcano at a depth of 1500 m in the Northeast Pacific, marked the first time a seafloor eruption was detected and monitored by an in situ cabled observatory{\textemdash}the Cabled Array, which is part of the Ocean Observatories Initiative. After the onset of the eruption, eight cabled and noncabled instruments on the seafloor recorded unusual, nearly synchronous and spatially uniform temperature increases of 0.6{\textendash}0.7{\textdegree}C across the southern half of the caldera and neighboring areas. These temperature signals were substantially different from those observed after the 2011 and 1998 eruptions at Axial and hence cannot be explained by emplacement of the 2015 lava flows on the seafloor. In this study, we investigate several possible explanations for the 2015 temperature anomalies and use a numerical model to test our preferred hypothesis that the temperature increases were caused by the release of a warm, dense brine that had previously been stored in the crust. If our interpretation is correct, this is the first time that the release of a hydrothermal brine has been observed due to a submarine eruption. This observation would have important implications for the salt balance of hydrothermal systems and the fate of brines stored in the subsurface. The observation of the 2015 temperature anomalies and the modeling presented in this study also demonstrate the importance of contemporaneous water column observations to better understand hydrothermal impacts of submarine eruptions.}, issn = {15252027}, doi = {10.1029/2018gc007607}, url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018GC007607}, author = {Xu, Guangyu and Chadwick, William W. and Wilcock, William S. D. and Bemis, Karen G. and Delaney, John} } @article {RN87, title = {Passive acoustic records of seafloor methane bubble streams on the Oregon continental margin}, journal = {Deep Sea Research Part II: Topical Studies in Oceanography}, volume = {150}, year = {2018}, pages = {210-217}, type = {Journal Article}, abstract = {We present acoustic records of methane bubble streams recorded ~10 km southwest of Heceta Bank on the Oregon continental margin using an autonomous hydrophone. The hydrophone was deployed at 1228 m water depth via a Remotely Operated Vehicle (ROV) during the E/V Nautilus expedition (NA072) in June 2016. Bubble sound is produced by detachment of the gas bubble from the end of a tube or conduit which causes the bubble to oscillate, producing a sound signal. Despite persistent ship propeller and ROV noise, the acoustic signature of the overall bubble seep site can be seen in the hydrophone record as a broadband (1.0 {\textendash} 45 kHz) series of short duration (~10{\textendash}20 ms) oscillatory signals that occur in clusters lasting 2{\textendash}3 s. The frequency of an individual bubble{\textquoteright}s oscillation is proportional to the bubble{\textquoteright}s radius; estimates here of bubble radii are consistent with bubble sizes observed in ROV still images. Acoustic signal loss models imply bubble sounds might be recorded over an area of seafloor from ~300 {\textendash} 3.2 {\texttimes} 104 m2. This study represents a first-step in attempting to identify and quantify deep-ocean bubble stream sounds using passive acoustic techniques.}, keywords = {Bubble streams, E/V Nautilus Cruise ID NA072, Gas flux, Methane seep, Passive acoustics}, issn = {0967-0645}, doi = {10.1016/j.dsr2.2018.04.001}, url = {http://www.sciencedirect.com/science/article/pii/S096706451730084X}, author = {Dziak, R. P. and Matsumoto, H. and Embley, R. W. and Merle, S. G. and Lau, T. K. and Baumberger, T. and Hammond, S. R. and Raineault, N.} } @article {RN45, title = {Power from Benthic Microbial Fuel Cells Drives Autonomous Sensors and Acoustic Modems}, journal = {Oceanography}, volume = {31}, number = {1}, year = {2018}, pages = {98-103}, type = {Journal Article}, abstract = {Autonomous platforms that support low-power sensors represent one approach to expanding ocean observing. This paper describes a unique autonomous platform designed to deliver long-term sensor measurements from the benthic boundary layer at low cost. The platform, called a Benthic Observer (BeOb), is powered by energy harvested with a benthic microbial fuel cell (BMFC), and it uses an acoustic modem to both store and transmit data organized in daily reports of hourly measurements. A BeOb equipped with sensors to measure dissolved oxygen, temperature, and conductivity ~1 m above the seabed has been active for over 14 months on the Oregon slope at a location within the core of the oxygen minimum zone. During this observation period, the system{\textquoteright}s battery reserves have been kept fully charged by the BMFC. A 90-day time series of sensor data are compared to simultaneous high-frequency measurements at a neighboring Ocean Observatories Initiative cabled Benthic Experiment Package to examine the expected quality and confidence levels for seasonal or annual means of continued measurements. An ocean observing system incorporating arrays of BMFCpowered platforms transmitting to central gateway modems is proposed for future ocean-property monitoring programs. Such arrays may be especially helpful for tracking expansions of ocean oxygen minimum zones.}, issn = {1042-8275}, doi = {10.5670/oceanog.2018.115}, url = {://WOS:000427367300015}, author = {Reimers, C. E. and Wolf, M.} } @article {RN92, title = {Probabilistic Cable Damage Risk Assessment Method for Seafloor Cabled Observatory and Its Application to Hydrothermal Fields}, journal = {Ohki, Takeshi}, volume = {52}, number = {3}, year = {2018}, pages = {138-149(12)}, type = {Journal Article}, abstract = {As part of a recent Japanese governmental project, the government has planned and begun a program to develop a seafloor cabled observatory that facilitates the long-term monitoring of hydrothermal vents and the ecological changes surrounding them. Because commercial cables are typically laid to avoid rough terrain and hydrothermal fields, there is no established method to assess system damage risk for a cabled observatory installed on a hydrothermal field. In this article, we propose a probabilistic cable damage risk assessment method for a seafloor cabled observatory installed on a hydrothermal field. The core concept of our method is the use of probability functions to estimate the system damage risk for the system of a seafloor cabled observatory laid on a defined route. The considered damage factors are potential heat damage risks to the cabled system and damage risks caused by frequent contact between the cable and seafloor. The product of each risk probability represents the total survivability of the system on the route. The proposed method was applied to the Oomuro-hole hydrothermal field on the active submarine Oomuro-dashi volcano, where remotely operated vehicle (ROV) surveys have been performed. The discovered risk factors are organized into a geographic database, and risk value fields are generated. We planned and evaluated several candidate routes that connect a target site for observation to the cabled system terminal unit. Finally, the proposed method derives quantitative system survivability values for the candidate routes and facilitates planning of the layout for a seafloor cabled observatory installed on a hydrothermal field.}, keywords = {Cabled observatory, hydrothermal field, remotely operated vehicle (ROV)}, doi = {10.4031/mtsj.52.3.4}, url = {https://app.dimensions.ai/details/publication/pub.1111829968}, author = {Ohki, Takeshi and Yokobiki, Takashi and Nishida, Shuhei and Tani, Kenichiro and Araki, Eiichiro and Kawaguchi, Katsuyoshi} } @article {RN2, title = {THE RECENT VOLCANIC HISTORY OF AXIAL SEAMOUNT Geophysical Insights into Past Eruption Dynamics with an Eye Toward Enhanced Observations of Future Eruptions}, journal = {Oceanography}, volume = {31}, number = {1}, year = {2018}, pages = {114-123}, type = {Journal Article}, abstract = {To understand the processes that form oceanic crust as well as the role of submarine volcanoes in exchanging heat and chemicals with the ocean and in supporting chemosynthetic biological communities, it is essential to study underwater eruptions. The world{\textquoteright}s most advanced underwater volcano observatory{\textemdash}the Ocean Observatories Initiative Cabled Array at Axial Seamount{\textemdash}builds upon ~30 years of sustained geophysical monitoring at this site with autonomous and remote systems. In April 2015, only months after the Cabled Array{\textquoteright}s installation, it recorded an eruption at Axial Seamount, adding to the records of two prior eruptions in 1998 and 2011. Between eruptions, magma recharge is focused beneath the southeast part of the summit caldera, leading to steady inflation and increasing rates of seismicity. During each eruption, the volcano deflates over days to weeks, coincident with high levels of seismicity as a dike is emplaced along one of the volcano{\textquoteright}s rifts and lava erupts on the seafloor. Cabled Array seismic data show that motions on an outward-dipping ring fault beneath the caldera accommodate the inflation and deflation. Eruptions appear to occur at a predictable level of inflation; hence, it should be possible to time deployments of additional cabled and autonomous instrumentation to further enhance observations of the next eruption.}, issn = {1042-8275}, doi = {10.5670/oceanog.2018.117}, url = {://WOS:000427367300017}, author = {Wilcock, W. S. D. and Dziak, R. P. and Tolstoy, M. and Chadwick, W. W. and Nooner, S. L. and Bohnenstiehl, D. R. and Caplan-Auerbach, J. and Waldhauser, F. and Arnulf, A. F. and Baillard, C. and Lau, T. K. and Haxel, J. H. and Tan, Y. J. and Garcia, C. and Levy, S. and Mann, M. E.} } @article {RN46, title = {The Role of the Ocean Observatories Initiative in Monitoring the Offshore Earthquake Activity of the Cascadia Subduction Zone}, journal = {Oceanography}, volume = {31}, number = {1}, year = {2018}, pages = {104-113}, type = {Journal Article}, abstract = {Geological and historical data indicate that the Cascadia subduction zone last ruptured in a major earthquake in 1700. The timing of the next event is currently impossible to predict, but recent studies of several large subduction zone earthquakes provide tantalizing hints of precursory activity. The seismometers at the Ocean Observatories Initiative (OOI) Slope Base and Southern Hydrate Ridge nodes are well placed to provide new insights into interplate coupling because they are located over a segment of the subduction zone that is nominally locked but that has been relatively active for more than a decade. Since their installation in 2014, 18 earthquakes with magnitudes up to 3.8 have been located by the Pacific Northwest Seismic Network between 44{\textdegree}N and 45{\textdegree}N in the region of the plate boundary thought to be accumulating strain. The OOI seismometers have also detected events that were not reported by the onshore seismic network. Noting that OOI data are available in real time, which is a necessary criterion for routine earthquake monitoring, and that the OOI seismometers generally have lower noise levels than campaign-style ocean bottom seismometers, there would be significant benefit to adding seismometers to existing nodes that are not yet instrumented with seismometers. }, issn = {1042-8275}, doi = {10.5670/oceanog.2018.116}, url = {://WOS:000427367300016}, author = {Trehu, A. M. and Wilcock, W. S. D. and Hilmo, R. and Bodin, P. and Connolly, J. and Roland, E. C. and Braunmiller, J.} } @article {RN8, title = {Structure, Seismicity, and Accretionary Processes at the Hot Spot-Influenced Axial Seamount on the Juan de Fuca Ridge}, journal = {Journal of Geophysical Research: Solid Earth}, volume = {123}, number = {6}, year = {2018}, pages = {4618-4646}, type = {Journal Article}, abstract = {Axial Seamount is the most volcanically active site of the northeast Pacific, and it has been monitored with a growing set of observations and sensors during the last two decades. Accurate imaging of the internal structure of volcanic systems is critical to better understand magma storage processes and to quantify mass and energy transport mechanisms in the crust. To improve the three-dimensional velocity structure of Axial Seamount, we combined 469,891 new traveltime arrivals, from 12 downward extrapolated seismic profiles, with 3,962 existing ocean-bottom-seismometers traveltime arrivals, into a joint tomographic inversion. Our approach reveals two elongated magma reservoirs, with melt fraction up to 65\%, representing an unusually large volume of melt (26{\textendash}60 km3), which is likely the result of enhanced magma supply from the juxtaposition of the Cobb hot spot plume (0.26{\textendash}0.53 m3/s) and the Axial spreading segment (0.79{\textendash}1.06 m3/s). The tomographic model also resolves a subsided caldera floor that provides an effective trap for ponding lava flows, via a {\textquotedblleft}trapdoor{\textquotedblright} mechanism. Our model also shows that Axial{\textquoteright}s extrusive section is thinnest beneath the elevated volcano, where anomalously thick (11 km) oceanic crust is present. We therefore suggest that focused and enhanced melt supply predominantly thickens the crust beneath Axial Seamount through diking accretion and gabbro crystallization. Lastly, we demonstrate that our three-dimensional velocity model provides a more realistic starting point for relocating the local seismicity, better resolving a network of conjugate outward and inward dipping faults beneath the caldera walls.}, keywords = {axial seamount, hot spot, Juan de Fuca ridge, magmatic system, traveltime tomography, volcano}, issn = {21699313}, doi = {10.1029/2017jb015131}, author = {Arnulf, A. F. and Harding, A. J. and Kent, G. M. and Wilcock, W. S. D.} } @article {RN219, title = {A Tale of Two Eruptions HOW DATA FROM AXIAL SEAMOUNT LED TO A DISCOVERY ON THE EAST PACIFIC RISE}, journal = {Oceanography}, volume = {31}, number = {1}, year = {2018}, pages = {124-126}, type = {Journal Article}, issn = {1042-8275}, doi = {10.5670/oceanog.2018.118}, author = {Tolstoy, M. and Wilcock, W. S. D. and Tan, Y. J. and Waldhauser, F.} } @article {RN34, title = {Warm Blobs, Low-Oxygen Events, and an Eclipse THE OCEAN OBSERVATORIES INITIATIVE ENDURANCE ARRAY CAPTURES THEM ALL}, journal = {Oceanography}, volume = {31}, number = {1}, year = {2018}, pages = {90-97}, type = {Journal Article}, abstract = {The Ocean Observatories Initiative (OOI) Endurance Array in the Northeast Pacific off the coasts of Oregon and Washington is designed to measure changes in the ocean on timescales from hours to decades. The Endurance Array is located halfway between the pole and the equator in one of the major coastal upwelling systems on our planet, the California Current System. This area is forced locally by winds, waves, tides, and freshwater inputs from rivers and, more broadly, by large-scale ocean-atmosphere phenomena from both the south, for example, the El Ni{\~n}o-Southern Oscillation, and the north, for example, changes originating in the subarctic Gulf of Alaska. The Endurance Array spans the continental shelf and slope and hosts a variety of platforms and sensors for measuring physical-biogeochemical oceanographic processes. After briefly introducing the unique OOI platforms and range of sensors that make up the Endurance Array, we describe three phenomena with durations spanning hours to years. These include an ocean response to the total eclipse of the Sun on August 21, 2017, the devastating effects of a low-oxygen event off central Oregon, and the appearance of an anomalously warm upper-ocean feature off the Pacific Northwest in recent years.}, issn = {1042-8275}, doi = {10.5670/oceanog.2018.114}, url = {://WOS:000427367300014}, author = {Barth, J. A. and Fram, J. P. and Dever, E. P. and Risien, C. M. and Wingard, C. E. and Collier, R. W. and Kearney, T. D.} } @article {RN4, title = {Circulation, hydrography, and transport over the summit of Axial Seamount, a deep volcano in the Northeast Pacific}, journal = {Journal of Geophysical Research-Oceans}, volume = {122}, number = {7}, year = {2017}, pages = {5404-5422}, type = {Journal Article}, abstract = {A numerical model of ocean flow, hydrography, and transport is used to extrapolate observations of currents and hydrography and infer patterns of material flux in the deep ocean around Axial Seamount, a destination node of NSF{\textquoteright}s Ocean Observatories Initiative{\textquoteright}s Cabled Array. Using an inverse method, the model is made to approximate measured deep ocean flow around this site during a 35 day time period in the year 2002. The model is then used to extract month-long mean patterns and examine smaller-scale spatial and temporal variability around Axial. Like prior observations, model month-long mean currents flow anticyclonically around the seamount{\textquoteright}s summit in toroidal form with maximum speeds at 1500 m depth of 10{\textendash}11 cm/s. As a time mean, the temperature (salinity) anomaly distribution takes the form of a cold (briny) dome above the summit. Passive tracer material continually released at the location of the ASHES vent field exits the caldera primarily through its southern open end before filling the caldera. Once outside the caldera, the tracer circles the summit in clockwise fashion, fractionally reentering the caldera over lower walls at its north end, while gradually bleeding southwestward during the modeled time period into the ambient ocean. A second tracer release experiment using a source of only 2 day duration inside and near the CASM vent field at the northern end of the caldera suggests a residence time of the fluid at that locale of 8{\textendash}9 days.}, issn = {2169-9275}, doi = {10.1002/2016jc012464}, url = {://WOS:000409893600012}, author = {Xu, G. and Lavelle, J. W.} } @article {RN225, title = {An ecosystem-based deep-ocean strategy}, journal = {Science}, volume = {355}, number = {6324}, year = {2017}, pages = {452-454}, type = {Journal Article}, abstract = {Increasing exploration and industrial exploitation of the vast and fragile deep-ocean environment for a wide range of resources (e.g., oil, gas, fisheries, new molecules, and soon, minerals) raises global concerns about potential ecological impacts (1{\textendash}3). Multiple impacts on deep-sea ecosystems (>200 m below sea level; \~{}65\% of the Earth{\textquoteright}s surface is covered by deep ocean) caused by human activities may act synergistically and span extensive areas. Cumulative impacts could eventually cause regime shifts and alter deep-ocean life-support services, such as the biological pump or nutrient recycling (2, 4, 5). Although international law and national legislation largely ignore the deep sea{\textquoteright}s critical role in the functioning and buffering of planetary systems, there are promising developments in support of deep-sea protection at the United Nations and the International Seabed Authority (ISA). We propose a strategy that builds from existing infrastructures to address research and monitoring needs to inform governments and regulators.}, issn = {0036-8075}, doi = {10.1126/science.aah7178}, author = {Danovaro, R. and Aguzzi, J. and Fanelli, E. and Billett, D. and Gjerde, K. and Jamieson, A. and Ramirez-Llodra, E. and Smith, C. R. and Snelgrove, P. V. R. and Thomsen, L. and Van Dover, C. L.} } @article {RN5, title = {Explosive processes during the 2015 eruption of Axial Seamount, as recorded by seafloor hydrophones}, journal = {Geochemistry Geophysics Geosystems}, volume = {18}, number = {4}, year = {2017}, pages = {1761-1774}, type = {Journal Article}, abstract = {Following the installation of the Ocean Observatories Initiative cabled array, the 2015 eruption of Axial Seamount, Juan de Fuca ridge, became the first submarine eruption to be captured in real time by seafloor seismic and acoustic instruments. This eruption also marked the first instance where the entire eruption cycle of a submarine volcano, from the previous eruption in 2011 to the end of the month-long 2015 event, was monitored continuously using autonomous ocean bottom hydrophones. Impulsive sounds associated with explosive lava-water interactions are identified within hydrophone records during both eruptions. Explosions within the caldera are acoustically distinguishable from those occurring in association with north rift lava flows erupting in 2015. Acoustic data also record a series of broadband diffuse events, occurring in the waning phase of the eruption, and are interpreted as submarine Hawaiian explosions. This transition from gas-poor to gas-rich eruptive activity coincides with an increase in water temperature within the caldera and with a decrease in the rate of deflation. The last recorded diffuse events coincide with the end of the eruption, represented by the onset of inflation. All the observed explosion signals couple strongly into the water column, and only weakly into the solid Earth, demonstrating the importance of hydroacoustic observations as a complement to seismic and geodetic studies of submarine eruptions.}, issn = {1525-2027}, doi = {10.1002/2016gc006734}, url = {://WOS:000403478500025}, author = {Caplan-Auerbach, J. and Dziak, R. P. and Haxel, J. and Bohnenstiehl, D. R. and Garcia, C.} } @article {RN223, title = {High-Resolution AUV Mapping and Targeted ROV Observations of Three Historic Lava Flows at Axial Seamount}, journal = {Oceanography}, volume = {30}, number = {4}, year = {2017}, pages = {82-99}, type = {Journal Article}, abstract = {The lava flows produced by eruptions at Axial Seamount in 1998, 2011, and 2015 were mapped at 1 m resolution from autonomous underwater vehicles (AUVs) developed at the Monterey Bay Aquarium Research Institute (MBARI). A portion of the flows erupted in 2011 and 2015 are defined by pre- and post-eruption AUV surveys. Data processing software, also developed at MBARI, precisely coregisters pre- and post-eruption surveys to allow construction of difference maps by subtracting a pre-eruption grid from a post-eruption grid. Such difference maps are key to extracting detailed information about eruptive processes and emplacement of the lava flows. All three eruptions began on the east side of the caldera, and each produced ~25 {\texttimes} 106 m3 of thin channelized flows (with sheet lava channels, lobate lava interiors with pillars, and distal inflated pillow lobes) in the caldera and on the upper south or north rifts. The 1998 and 2011 eruptions propagated down the south rift, and the 2015 eruption propagated down the north rift. The 2011 and 2015 eruptions formed shallow grabens surrounding new non-eruptive open fissures on the east rim of the caldera and produced thick hummocky flows on upper to mid rifts, and the 2011 eruption also produced a thick hummocky flow on the lower south rift. Future eruptions at Axial Seamount will likely follow this pattern, regardless of which rift is the locus of the eruption.}, issn = {1042-8275}, doi = {10.5670/oceanog.2017.426}, author = {Clague, D. A. and Paduan, J. B. and Caress, D. W. and Chadwick, W. W. and Le Saout, M. and Dreyer, B. M. and Portner, R. A.} } @article {RN19, title = {Thirty-Three Years of Ocean Benthic Warming Along the U.S. Northeast Continental Shelf and Slope: Patterns, Drivers, and Ecological Consequences}, journal = {J Geophys Res Oceans}, volume = {122}, number = {12}, year = {2017}, pages = {9399-9414}, type = {Journal Article}, abstract = {The U.S. Northeast Continental Shelf is experiencing rapid warming, with potentially profound consequences to marine ecosystems. While satellites document multiple scales of spatial and temporal variability on the surface, our understanding of the status, trends, and drivers of the benthic environmental change remains limited. We interpolated sparse benthic temperature data along the New England Shelf and upper Slope using a seasonally dynamic, regionally specific multiple linear regression model that merged in situ and remote sensing data. The statistical model predicted nearly 90\% of the variability of the data, resulting in a synoptic time series spanning over three decades from 1982 to 2014. Benthic temperatures increased throughout the domain, including in the Gulf of Maine. Rates of benthic warming ranged from 0.1 to 0.4{\textdegree}C per decade, with fastest rates occurring in shallow, nearshore regions and on Georges Bank, the latter exceeding rates observed in the surface. Rates of benthic warming were up to 1.6 times faster in winter than the rest of the year in many regions, with important implications for disease occurrence and energetics of overwintering species. Drivers of warming varied over the domain. In southern New England and the mid-Atlantic shallow Shelf regions, benthic warming was tightly coupled to changes in SST, whereas both regional and basin-scale changes in ocean circulation affect temperatures in the Gulf of Maine, the Continental Shelf, and Georges Banks. These results highlight data gaps, the current feasibility of prediction from remotely sensed variables, and the need for improved understanding on how climate may affect seasonally specific ecological processes.}, issn = {2169-9275 (Print) 2169-9275 (Linking)}, doi = {10.1002/2017JC012953}, url = {https://www.ncbi.nlm.nih.gov/pubmed/29497591}, author = {Kavanaugh, M. T. and Rheuban, J. E. and Luis, K. M. A. and Doney, S. C.} } @article {RN224, title = {VOLCANOLOGY Vulcan rule beneath the sea}, journal = {Nature Geoscience}, volume = {10}, number = {4}, year = {2017}, pages = {251-252}, type = {Journal Article}, abstract = {Over 70\% of the volcanism on Earth occurs beneath an ocean veil. Now, robotic- and fibre-optic-based technologies are beginning to reveal this deep environment and identify subaqueous volcanoes as rich sources of sulfur, carbon dioxide and life.}, issn = {1752-0894}, doi = {10.1038/ngeo2929}, author = {Kelley, D.} } @article {RN51, title = {Diffuse venting at the ASHES hydrothermal field: Heat flux and tidally modulated flow variability derived from in situ time-series measurements}, journal = {Geochemistry Geophysics Geosystems}, volume = {17}, number = {4}, year = {2016}, pages = {1435-1453}, type = {Journal Article}, abstract = {Time-series measurements of diffuse exit-fluid temperature and velocity collected with a new, deep-sea camera, and temperature measurement system, the Diffuse Effluent Measurement System (DEMS), were examined from a fracture network within the ASHES hydrothermal field located in the caldera of Axial Seamount, Juan de Fuca Ridge. The DEMS was installed using the HOV Alvin above a fracture near the Phoenix vent. The system collected 20 s of 20 Hz video imagery and 24 s of 1 Hz temperature measurements each hour between 22 July and 2 August 2014. Fluid velocities were calculated using the Diffuse Fluid Velocimetry (DFV) technique. Over the \~{}12 day deployment, median upwelling rates and mean fluid temperature anomalies ranged from 0.5 to 6 cm/s and 0{\textdegree}C to \~{}6.5{\textdegree}C above ambient, yielding a heat flux of 0.29 {\textpm} 0.22 MW m-2 and heat output of 3.1{\textpm} 2.5 kW. Using a photo mosaic to measure fracture dimensions, the total diffuse heat output from cracks across ASHES field is estimated to be 2.05 {\textpm} 1.95 MW. Variability in temperatures and velocities are strongest at semidiurnal periods and show significant coherence with tidal height variations. These data indicate that periodic variability near Phoenix vent is modulated both by tidally controlled bottom currents and seafloor pressure, with seafloor pressures being the dominant influence. These results emphasize the importance of local permeability on diffuse hydrothermal venting at mid-ocean ridges and the need to better quantify heat flux associated with young oceanic crust.}, issn = {1525-2027}, doi = {10.1002/2015gc006144}, url = {://WOS:000379523900012}, author = {Mittelstaedt, E. and Fornari, D. J. and Crone, T. J. and Kinsey, J. and Kelley, D. and Elend, M.} } @article {RN228, title = {Drift-corrected seafloor pressure observations of vertical deformation at Axial Seamount 2013{\textendash}2014}, journal = {Earth and Space Science}, volume = {3}, number = {9}, year = {2016}, pages = {381-385}, type = {Journal Article}, abstract = {Axial Seamount on the Juan de Fuca Ridge is a site of ongoing volcanic activity. The vertical component of the deformation can be observed with ambient seawater pressure gauges, which have excellent short-term resolution. However, pressure gauge drift adds additional and significant uncertainty in estimates of long-period deformation; drift rates equivalent to 20{\textendash}30 cm/yr have been observed. One way to circumvent gauge drift is to make differential pressure measurements relative to a distant and presumably stable seafloor reference site. Such measurements require a remotely operated vehicle and can only be made infrequently. Another approach is to incorporate a piston gauge calibrator in the seafloor pressure recorder to generate an in situ reference pressure that, when periodically applied to the drift-susceptible gauge, can be used to determine and remove gauge drift from the time series. We constructed a self-calibrating pressure recorder and deployed it at Axial Seamount in September 2013. The drift-corrected record from that deployment revealed an uplift of the volcano summit of 60 cm over 17 months.}, issn = {2333-5084}, doi = {https://doi.org/10.1002/2016EA000190}, url = {https://doi.org/10.1002/2016EA000190}, author = {Sasagawa, G. and Cook, M. J. and Zumberge, M. A.} } @article {RN7, title = {Inflation-predictable behavior and co-eruption deformation at Axial Seamount}, journal = {Science}, volume = {354}, number = {6318}, year = {2016}, pages = {1399-1403}, type = {Journal Article}, abstract = {Deformation of the ground surface at active volcanoes provides information about magma movements at depth. Improved seafloor deformation measurements between 2011 and 2015 documented a fourfold increase in magma supply and confirmed that Axial Seamount{\textquoteright}s eruptive behavior is inflation-predictable, probably triggered by a critical level of magmatic pressure. A 2015 eruption was successfully forecast on the basis of this deformation pattern and marked the first time that deflation and tilt were captured in real time by a new seafloor cabled observatory, revealing the timing, location, and volume of eruption-related magma movements. Improved modeling of the deformation suggests a steeply dipping prolate-spheroid pressure source beneath the eastern caldera that is consistent with the location of the zone of highest melt within the subcaldera magma reservoir determined from multichannel seismic results.}, issn = {1095-9203 (Electronic) 0036-8075 (Linking)}, doi = {10.1126/science.aah4666}, url = {https://www.ncbi.nlm.nih.gov/pubmed/27980205}, author = {Nooner, S. L. and Chadwick, W. W., Jr.} } @article {RN11, title = {New insights into magma plumbing along rift systems from detailed observations of eruptive behavior at Axial volcano}, journal = {Geophysical Research Letters}, volume = {43}, number = {24}, year = {2016}, pages = {12423-12427}, type = {Journal Article}, abstract = {The magma reservoir in geophysical volcano plumbing models is often modeled as a simple geometric volume, filled with magma of uniform properties. However, the constraints on reservoir size and magma properties in volcano roots are typically indirect and poor. Axial Seamount, a volcano at a depth of about 1500 m on the Juan de Fuca mid-oceanic ridge in the Pacific Ocean, has both high-resolution seismic images of its subsurface magma and detailed results from monitoring of its most recent eruption and associated seismicity and ground deformation. The 2015 eruption at Axial Seamount is the best monitored submarine eruption so far because of observations made possible by the Ocean Observatories Initiative, and seismic imaging of magma at this volcano is better than in most other environments because of advanced analysis of extensive seismic reflection profiling at sea and the relatively simple volcano structure. This allows new understanding compared to findings from earlier observations from monitored rifting episodes on land. Geophysical magma plumbing models, in general, may need to allow for more complexities, namely, spatial heterogeneities in magma composition, melt content, and location of major volume changes within a single magma dominated crustal volume during eruptions.}, issn = {0094-8276}, doi = {10.1002/2016gl071884}, url = {://WOS:000392741900015}, author = {Sigmundsson, F.} } @article {RN6, title = {Seismic constraints on caldera dynamics from the 2015 Axial Seamount eruption}, journal = {Science}, volume = {354}, number = {6318}, year = {2016}, pages = {1395-1399}, type = {Journal Article}, abstract = {Seismic observations in volcanically active calderas are challenging. A new cabled observatory atop Axial Seamount on the Juan de Fuca ridge allows unprecedented real-time monitoring of a submarine caldera. Beginning on 24 April 2015, the seismic network captured an eruption that culminated in explosive acoustic signals where lava erupted on the seafloor. Extensive seismic activity preceding the eruption shows that inflation is accommodated by the reactivation of an outward-dipping caldera ring fault, with strong tidal triggering indicating a critically stressed system. The ring fault accommodated deflation during the eruption and provided a pathway for a dike that propagated south and north beneath the caldera{\textquoteright}s east wall. Once north of the caldera, the eruption stepped westward, and a dike propagated along the extensional north rift.}, issn = {1095-9203 (Electronic) 0036-8075 (Linking)}, doi = {10.1126/science.aah5563}, url = {https://www.ncbi.nlm.nih.gov/pubmed/27980204}, author = {Wilcock, W. S. and Tolstoy, M. and Waldhauser, F. and Garcia, C. and Tan, Y. J. and Bohnenstiehl, D. R. and Caplan-Auerbach, J. and Dziak, R. P. and Arnulf, A. F. and Mann, M. E.} } @article {RN227, title = {Time-series measurements of bubble plume variability and water column methane distribution above Southern Hydrate Ridge, Oregon}, journal = {Geochemistry, Geophysics, Geosystems}, volume = {17}, number = {3}, year = {2016}, pages = {1182-1196}, type = {Journal Article}, abstract = {An estimated 500{\textendash}2500 gigatons of methane carbon is sequestered in gas hydrate at continental margins and some of these deposits are associated with overlying methane seeps. To constrain the impact that seeps have on methane concentrations in overlying ocean waters and to characterize the bubble plumes that transport methane vertically into the ocean, water samples and time-series acoustic images were collected above Southern Hydrate Ridge (SHR), a well-studied hydrate-bearing seep site \~{}90 km west of Newport, Oregon. These data were coregistered with robotic vehicle observations to determine the origin of the seeps, the plume rise heights above the seafloor, and the temporal variability in bubble emissions. Results show that the locations of seep activity and bubble release remained unchanged over the 3 year time-series investigation, however, the magnitude of gas release was highly variable on hourly time scales. Bubble plumes were detected to depths of 320{\textendash}620 m below sea level (mbsl), in several cases exceeding the upper limit of hydrate stability by \~{}190 m. For the first time, sustained gas release was imaged at the Pinnacle site and in-between the Pinnacle and the Summit area of venting, indicating that the subseafloor transport of fluid and gas is not restricted to the Summit at SHR, requiring a revision of fluid-flow models. Dissolved methane concentrations above background levels from 100 to 300 mbsl are consistent with long-term seep gas transport into the upper water column, which may lead to the build-up of seep-derived carbon in regional subsurface waters and to increases in associated biological activity.}, issn = {1525-2027}, doi = {https://doi.org/10.1002/2016GC006250}, url = {https://doi.org/10.1002/2016GC006250}, author = {Philip, Brendan T. and Denny, Alden R. and Solomon, Evan A. and Kelley, Deborah S.} } @article {RN226, title = {Voluminous eruption from a zoned magma body after an increase in supply rate at Axial Seamount}, journal = {Geophysical Research Letters}, volume = {43}, number = {23}, year = {2016}, pages = {12,063-12,070}, type = {Journal Article}, abstract = {Axial Seamount is the best monitored submarine volcano in the world, providing an exceptional window into the dynamic interactions between magma storage, transport, and eruption processes in a mid-ocean ridge setting. An eruption in April 2015 produced the largest volume of erupted lava since monitoring and mapping began in the mid-1980s after the shortest repose time, due to a recent increase in magma supply. The higher rate of magma replenishment since 2011 resulted in the eruption of the most mafic lava in the last 500{\textendash}600 years. Eruptive fissures at the volcano summit produced pyroclastic ash that was deposited over an area of at least 8 km2. A systematic spatial distribution of compositions is consistent with a single dike tapping different parts of a thermally and chemically zoned magma reservoir that can be directly related to previous multichannel seismic-imaging results.}, issn = {0094-8276}, doi = {https://doi.org/10.1002/2016GL071327}, url = {https://doi.org/10.1002/2016GL071327}, author = {Chadwick Jr, W. W. and Paduan, J. B. and Clague, D. A. and Dreyer, B. M. and Merle, S. G. and Bobbitt, A. M. and Caress, D. W. and Philip, B. T. and Kelley, D. S. and Nooner, S. L.} } @article {RN12, title = {An Inductive Charging and Real-Time Communications System for Profiling Moorings}, journal = {Journal of Atmospheric and Oceanic Technology}, volume = {32}, number = {12}, year = {2015}, pages = {2243-2252}, type = {Journal Article}, abstract = {This paper describes a system for providing power and communications to moored profiling vehicles. A McLane Moored Profiler (MP) was equipped with a rechargeable battery pack and an inductive charging system to allow it to move periodically to a charging dock at the top of a subsurface mooring. Power was provided from a large bank of alkaline batteries housed in two 0.94-m steel spheres. Data were transferred inductively from the profiler to a mooring controller, and from there back to shore via radio and Iridium satellite modems housed in a small surface communications float on an {\textquotedblleft}L{\textquotedblright} tether. An acoustic modem provided backup communications to a nearby ship in the event of loss or damage to the surface float. The system was tested in a 180-m-deep fjord (Puget Sound, Washington) and at Station ALOHA (A Long-Term Oligotrophic Habitat Assessment), a 4748-m-deep open-ocean location north of Hawaii. Basic functionality of the system was demonstrated, with the profiler repeatedly recharging at about 225 W (with an overall efficiency of about 70\%). Data were relayed back to shore via Iridium and to a nearby ship via the radio and acoustic modems. The system profiled flawlessly for the entire 6-week test in Puget Sound, but charging at the deep site stopped after only 9 days in the deep-ocean deployment owing to damage to the charging station, possibly by surface wave action.}, keywords = {Observational techniques and algorithms, Profilers; oceanic}, issn = {0739-0572}, doi = {10.1175/Jtech-D-15-0103.1}, author = {Alford, M. H. and McGinnis, T. and Howe, B. M.} } @article {RN231, title = {THE CASCADIA INITIATIVE A Sea Change In Seismological Studies of Subduction Zones}, journal = {Oceanography}, volume = {27}, number = {2}, year = {2014}, pages = {138-150}, type = {Journal Article}, abstract = {Increasing public awareness that the Cascadia subduction zone in the Pacific Northwest is capable of great earthquakes (magnitude 9 and greater) motivates the Cascadia Initiative, an ambitious onshore/offshore seismic and geodetic experiment that takes advantage of an amphibious array to study questions ranging from megathrust earthquakes, to volcanic arc structure, to the formation, deformation and hydration of the Juan De Fuca and Gorda Plates. Here, we provide an overview of the Cascadia Initiative, including its primary science objectives, its experimental design and implementation, and a preview of how the resulting data are being used by a diverse and growing scientific community. The Cascadia Initiative also exemplifies how new technology and community-based experiments are opening up frontiers for marine science. The new technology{\textemdash}shielded ocean bottom seismometers{\textemdash}is allowing more routine investigation of the source zone of megathrust earthquakes, which almost exclusively lies offshore and in shallow water. The Cascadia Initiative offers opportunities and accompanying challenges to a rapidly expanding community of those who use ocean bottom seismic data.}, issn = {1042-8275}, doi = {10.5670/oceanog.2014.49}, author = {Toomey, D. R. and Allen, R. M. and Barclay, A. H. and Bell, S. W. and Bromirski, P. D. and Carlson, R. L. and Chen, X. W. and Collins, J. A. and Dziak, R. P. and Evers, B. and Forsyth, D. W. and Gerstoft, P. and Hooft, E. E. E. and Livelybrooks, D. and Lodewyk, J. A. and Luther, D. S. and McGuire, J. J. and Schwartz, S. Y. and Tolstoy, M. and Trehu, A. M. and Weirathmueller, M. and Wilcock, W. S. D.} } @article {RN229, title = {Establishing a new era of submarine volcanic observatories: Cabling Axial Seamount and the Endeavour Segment of the Juan de Fuca Ridge}, journal = {Marine Geology}, volume = {352}, year = {2014}, pages = {426-450}, type = {Journal Article}, abstract = {At least 70\% of the volcanism on Earth occurs along the 65,000 km network of mid-ocean ridge (MOR) spreading centers. Within these dynamic environments, the highest fluxes of heat, chemicals, and biological material from the lithosphere to the hydrosphere occur during volcanic eruptions. However, because underwater volcanoes are difficult and expensive to access, researchers are rarely, if ever, in the right place at the right time to characterize these events. Therefore, our knowledge is limited about the linkages among hydrothermal, chemical and biological processes during seafloor formation and crustal evolution. To make significant advancements in understanding the evolution of MOR environments, the United States and Canada have invested in the first plate-scale submarine cabled observatory linked through the global Internet. Spanning the Juan de Fuca tectonic plate, these two networks include > 1700 km of cable and 14 subsea terminals that provide 8{\textendash}10 kW power and 10 Gbs communications to hundreds of instruments on the seafloor and throughout the overlying water column {\textemdash} resulting in a 24/7/365 presence in the oceans. Data and imagery are available in real- to near-real time. The initial experimental sites for monitoring volcanic processes include the MOR volcanoes called Axial Seamount and the Endeavour Segment that are located on the Juan de Fuca Ridge. Axial, a hot-spot influenced seamount, is the most robust volcano along the ridge rising nearly 1400 m above the surrounding seafloor and it has erupted twice in the last 15 years. In contrast, the Endeavour Segment is characterized by more subdued topography with a well defined axial rift and it hosts one of the most intensely venting hydrothermal systems known. A non-eruptive spreading event lasting 6 years was documented at Endeavour between 1999 and 2005. Hydrothermal venting intensity, chemistry, and temperature, as well as associated biological communities at both sites were significantly perturbed by the magmatic and intrusive events. This paper presents the similarities and differences between the Axial and Endeavour volcanic systems and identifies reasons why they are ideal candidates for comparative studies. The U.S. has made a 25-year commitment for sustained observations using the cabled infrastructure. The highly expandable nature of submarine optical networking will allow for the future addition of novel experiments that utilize ever evolving advancements in computer sciences, robotics, genomics and sensor miniaturization. Comprehensive modeling of the myriad processes involved will continue to assimilate and integrate growing databases yielding a new understanding of integrated processes that create the seafloor in the global ocean basins. }, keywords = {axial seamount, cabled observatories, Endeavour Segment, hydrothermal vents, Juan de Fuca ridge, submarine volcanoes}, issn = {0025-3227}, doi = {https://doi.org/10.1016/j.margeo.2014.03.010}, url = {https://www.sciencedirect.com/science/article/pii/S0025322714000723}, author = {Kelley, Deborah S. and Delaney, John R. and Juniper, S. Kim} } @article {RN230, title = {Sulfur oxidizers dominate carbon fixation at a biogeochemical hot spot in the dark ocean}, journal = {The ISME Journal}, volume = {7}, number = {12}, year = {2013}, pages = {2349-2360}, type = {Journal Article}, abstract = {Bacteria and archaea in the dark ocean (>200 m) comprise 0.3-1.3 billion tons of actively cycled marine carbon. Many of these microorganisms have the genetic potential to fix inorganic carbon (autotrophs) or assimilate single-carbon compounds (methylotrophs). We identified the functions of autotrophic and methylotrophic microorganisms in a vent plume at Axial Seamount, where hydrothermal activity provides a biogeochemical hot spot for carbon fixation in the dark ocean. Free-living members of the SUP05/Arctic96BD-19 clade of marine gamma-proteobacterial sulfur oxidizers (GSOs) are distributed throughout the northeastern Pacific Ocean and dominated hydrothermal plume waters at Axial Seamount. Marine GSOs expressed proteins for sulfur oxidation (adenosine phosphosulfate reductase, sox (sulfur oxidizing system), dissimilatory sulfite reductase and ATP sulfurylase), carbon fixation (ribulose-1,5-bisphosphate carboxylase oxygenase (RuBisCO)), aerobic respiration (cytochrome c oxidase) and nitrogen regulation (PII). Methylotrophs and iron oxidizers were also active in plume waters and expressed key proteins for methane oxidation and inorganic carbon fixation (particulate methane monooxygenase/methanol dehydrogenase and RuBisCO, respectively). Proteomic data suggest that free-living sulfur oxidizers and methylotrophs are among the dominant primary producers in vent plume waters in the northeastern Pacific Ocean. }, issn = {1751-7370}, doi = {10.1038/ismej.2013.113}, url = {https://doi.org/10.1038/ismej.2013.113}, author = {Mattes, Timothy E. and Nunn, Brook L. and Marshall, Katharine T. and Proskurowski, Giora and Kelley, Deborah S. and Kawka, Orest E. and Goodlett, David R. and Hansell, Dennis A. and Morris, Robert M.} } @article {RN234, title = {Design and Application of a Junction Box for Cabled Ocean Observatories}, journal = {Marine Technology Society Journal}, volume = {46}, number = {3}, year = {2012}, pages = {50-63}, type = {Journal Article}, abstract = {Cabled ocean observatories enabling large amounts of power and two-way communication bandwidth for underwater experiments are a future approach for studying the oceans. On April 21, 2011, at Monterey Bay, California, USA, a network node composed of a junction box (JBox) and three scientific instruments was deployed at the Monterey Accelerated Research System (MARS) site for a 6-month uninterrupted sea trial. The JBox is a facility that can provide multiple wet-mateable connections for various instruments. Each connection can draw 500 W of power and has 10/100 Mbit/s network communication. The current study presents the design and construction of the JBox with focus on the following aspects: a power distribution system with high reliability; a flexible springloaded mechanical structure for heat dissipation; communication that incorporates various data protocols; and self-protection against faults like over-current, short fault, ground fault, and flooding. The deployment and operation of the JBox is described. The sea trial results show that the technologies and methods applied on the JBox and the deploying approach are applicable and worthy of consideration for long-term cabled ocean observatories.}, issn = {0025-3324}, doi = {10.4031/MTSJ.46.3.4}, author = {Chen, Y. H. and Yang, C. J. and Li, D. J. and Jin, B. and Chen, Y.} }