@article {xu_acoustic_2021,
	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},
	volume = {8},
	number = {3},
	year = {2021},
	note = {_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2020EA001269},
	pages = {e2020EA001269},
	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},
	issn = {2333-5084},
	doi = {10.1029/2020EA001269},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2020EA001269},
	author = {Xu, Guangyu and Bemis, Karen and Jackson, Darrell and Ivakin, Anatoliy}
}
@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 {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 {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 {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 {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}
}
