@article {zhang_cross-shelf_2023,
	title = {Cross-shelf exchange associated with a shelf-water streamer at the Mid-Atlantic Bight shelf edge},
	journal = {Progress in Oceanography},
	volume = {210},
	year = {2023},
	month = {jan},
	pages = {102931},
	abstract = {Significant exchanges between the Mid-Atlantic Bight (MAB) continental shelf and the neighboring open ocean can be induced by shelf water streamers, submesoscale filaments of shelf water entrained into the open ocean by Gulf Stream warm-core rings (WCRs) impinging onto the MAB continental shelf. Shelf water streamers have distinctive surface temperature and chlorophyll signals, and are thus visible from space. Satellite-measured sea surface height, temperature and chlorophyll show the evolution of a WCR over its 6-month lifespan in February-August 2019 and the persistent shelf water streamer it generated on its outskirt. In situ measurements from a two-week cruise in July 2019 were analyzed to investigate the physical, biological and biogeochemical characteristics of the shelf water streamer below the surface, and to quantify the associated cross-shelf transport of volume, heat, salt, carbon and oxygen. The analyses demonstrated that offshore transport of shelf water by the streamer, which was presumably balanced by either onshore intrusion of ring water or enhanced transport of shelf water from upstream, represented a major form of exchange between the MAB continental shelf and the open ocean. The streamer caused significant net onshore transport of heat and salt, and a significant net offshore transport of organic carbon and oxygen. Primary productivity in the streamer was higher than the surrounding slope and ring waters on the surface, which likely resulted from subsurface nutrients in the offshore-flowing shelf water being gradually consumed as the overlying water became clearer. WCR-induced shelf water streamers thus enhanced surface biological productivity in the slope sea. Plain Language Summary: Waters of the shallow Mid-Atlantic Bight continental shelf and the neighboring deep slope sea have distinctly different physical, biological and chemical properties. Mixing between them can affect the shelf ecosystem and the dispersal of coastal materials into the deep ocean. One type of cross-shelf-edge mixing process results from strong clockwise-rotating vortices {\textendash} so-called warm-core rings {\textendash} formed from meanders of the Gulf Stream. As a warm-core ring intrudes onto the shelf edge, it often draws shelf water offshore, forming a thin filament in the slope sea. This filament is called a shelf-water streamer and has distinctive surface temperature and chlorophyll signals that are visible from space. Warm-core rings can also push offshore water onto the shallow shelf. This study examines the evolution of a warm-core ring over its 6-month lifespan in 2019 and the shelf-water streamer the ring induced in 5 of the 6~months. Interdisciplinary measurements from a field expedition in July 2019 were examined to assess the subsurface patterns of the streamer and to quantify the induced cross-shelf fluxes of heat, salt, organic carbon and oxygen. The analysis showed that the streamer represented a major form of cross-shelf mixing and caused a substantial onshore transport of heat and salt, as well as a substantial offshore transport of organic carbon and oxygen.},
	keywords = {carbon flux, Cross-shelf exchange, Heat flux, Primary productivity, Salt flux, Shelf-water streamer, Warm-core ring},
	issn = {0079-6611},
	doi = {10.1016/j.pocean.2022.102931},
	url = {https://www.sciencedirect.com/science/article/pii/S0079661122001902},
	author = {Zhang, Weifeng (Gordon) and Alatalo, Philip and Crockford, Taylor and Hirzel, Andrew J. and Meyer, Meredith G. and Oliver, Hilde and Peacock, Emily and Petitpas, Christian M. and Sandwith, Zoe and Smith, Walker O. and Sosik, Heidi M. and Stanley, Rachel H. R. and Stevens, Bethany L. F. and Turner, Jefferson T. and McGillicuddy, Dennis J.}
}
@article {oliver_ephemeral_2022,
	title = {Ephemeral Surface Chlorophyll Enhancement at the New England Shelf Break Driven by Ekman Restratification},
	journal = {JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS},
	volume = {127},
	number = {1},
	year = {2022},
	month = {jan},
	pages = {e2021JC017715},
	abstract = {The Mid-Atlantic Bight (MAB) hosts a large and productive marine ecosystem supported by high phytoplankton concentrations. Enhanced surface chlorophyll concentrations at the MAB shelf-break front have been detected in synoptic measurements, yet this feature is not present in seasonal means. To understand why, we assess the conditions associated with enhanced surface chlorophyll at the shelf break. We employ in-situ and remote sensing data, and a 2-dimensional model to show that Ekman restratification driven by upfront winds drives ephemerally enhanced chlorophyll concentrations at the shelf-break front in spring. Using 8-day composite satellite-measured surface chlorophyll concentration data from 2003{\textendash}2020, we constructed a daily running mean (DRM) climatology of the cross-shelf chlorophyll distribution for the northern MAB region. While the frontal enhancement of chlorophyll is apparent in the DRM climatology, it is not captured in the seasonal climatology due to its short duration of less than a week. In-situ measurements of the frontal chlorophyll enhancement reveal that chlorophyll is highest in spring when the shelf-break front slumps offshore from its steep wintertime position causing restratification in the upper part of the water column. Several restratification mechanisms are possible, but the first day of enhanced chlorophyll at the shelf break corresponds to increasing upfront winds, suggesting that the frontal restratification is driven by offshore Ekman transport of the shelf water over the denser slope water. The 2-dimensional model shows that upfront winds can indeed drive Ekman restratification and alleviate light limitation of phytoplankton growth at the shelf-break front.},
	issn = {2169-9275},
	doi = {10.1029/2021JC017715},
	author = {Oliver, Hilde and Zhang, Weifeng Gordon and Archibald, Kevin M. and Hirzel, Andrew J. and Smith, Walker O. and Sosik, Heidi M. and Stanley, Rachel H. R. and McGillicuddy, Jr., Dennis J.}
}
@article {274,
	title = {Primary Productivity in the Mid-Atlantic Bight: Is the Shelf Break a Location of Enhanced Productivity?},
	journal = {Frontiers in Marine Science},
	volume = {9},
	year = {2022},
	month = {2022///},
	abstract = {Estimates of primary production represent the input of carbon into food webs, as well as the initial step in the biological pump. For the past 60 years, much of the productivity information has been obtained using measurements of 14C-bicarbonate removal during simulated in situ incubations. However, such measurements often do not reflect the complexity of the environment, and also suffer from uncertainties, biases and limitations. A vertically resolved bio-optical model has been used to estimate productivity based on profiles commonly assessed in oceanographic investigations, but comparisons with simultaneous measurements of 14C-uptake are limited. We conducted three cruises off the coast of New England that included sampling continental shelf waters, the shelf-break region, and deeper waters at scales of 7 km, all of which had productivity estimated by a vertically resolved productivity model as well as by traditional 14C-uptake measurements using simulated in situ techniques. We found that the vertically resolved bio-optical model gave results that appear to be more robust and resolved productivity at smaller vertical and horizontal scales, and seem less biased by some of the uncertainties in 14C-uptake measurements. Both estimates suggest that the New England waters are highly productive due to a variety of biological and physical processes occurring at different times of the year, but there was no consistent stimulation at the shelf break over the time scales of these estimates.},
	isbn = {2296-7745},
	doi = {10.3389/fmars.2022.824303},
	url = {https://www.frontiersin.org/article/10.3389/fmars.2022.824303},
	author = {Ma, Jiejie and Smith, Walker O.}
}
@article {RN238,
	title = {Diatom Hotspots Driven by Western Boundary Current Instability},
	journal = {Geophysical Research Letters},
	year = {2021},
	type = {Journal Article},
	abstract = {Climatic changes have decreased the stability of the Gulf Stream (GS), increasing the frequency at which its meanders interact with the Mid-Atlantic Bight (MAB) continental shelf and slope region. These intrusions are thought to suppress biological productivity by transporting low-nutrient water to the otherwise productive shelf edge region. Here we present evidence of widespread, anomalously intense subsurface diatom hotspots in the MAB slope sea that likely resulted from a GS intrusion in July 2019. The hotspots (at \~{}50 m) were associated with water mass properties characteristic of GS water (\~{}100 m); it is probable that the hotspots resulted from the upwelling of GS water during its transport into the slope sea, likely by a GS meander directly intruding onto the continental slope east of where the hotspots were observed. Further work is required to unravel how increasingly frequent direct GS intrusions could influence MAB marine ecosystems.},
	doi = {10.1029/2020gl091943},
	url = {https://app.dimensions.ai/details/publication/pub.1137908537},
	author = {Oliver, Hilde and Zhang, Weifeng G. and Smith, Walker O. and Alatalo, Philip and Chappell, P. Dreux and Hirzel, Andrew J. and Selden, Corday R. and Sosik, Heidi M. and Stanley, Rachel H. R. and Zhu, Yifan and McGillicuddy, Dennis J.}
}
@article {RN274,
	title = {Ephemeral surface chlorophyll enhancement at the New England shelf break driven by Ekman restratification},
	journal = {Journal of Geophysical Research - Oceans},
	year = {2021},
	type = {Journal Article},
	doi = {10.1029/2021jc017715},
	url = {https://app.dimensions.ai/details/publication/pub.1144229542},
	author = {Oliver, Hilde and Zhang, Weifeng Gordon and Archibald, Kevin M. and Hirzel, Andrew J. and Smith, Walker O. and Sosik, Heidi M. and Stanley, Rachel H. R. and McGillicuddy, Dennis J.}
}
@article {RN200,
	title = {A regional, early spring bloom of Phaeocystis pouchetii on the New England continental shelf},
	journal = {Journal of Geophysical Research - Oceans},
	year = {2021},
	type = {Journal Article},
	abstract = {The genus Phaeocystis is distributed globally and has considerable ecological, biogeochemical, and societal impacts. Understanding its distribution, growth and ecological impacts has been limited by lack of extensive observations on appropriate scales. In 2018, we investigated the biological dynamics of the New England continental shelf and encountered a substantial bloom of Phaeocystis pouchetii. Based on satellite imagery during January through April, the bloom extended over broad expanses of the shelf; furthermore, our observations demonstrated that it reached high biomass levels, with maximum chlorophyll concentrations exceeding 16 {\textmu}g L-1 and particulate organic carbon levels > 95 {\textmu}mol L-1. Initially, the bloom was largely confined to waters with temperatures <6{\textdegree}C, which in turn were mostly restricted to shallow areas near the coast. As the bloom progressed, it appeared to sink into the bottom boundary layer; however, enough light and nutrients were available for growth. The bloom was highly productive (net community production integrated through the mixed layer from stations within the bloom averaged 1.16 g C m-2 d-1) and reduced nutrient concentrations considerably. Long-term coastal observations suggest that Phaeocystis blooms occur sporadically in spring on Nantucket Shoals and presumably expand onto the continental shelf. Based on the distribution of Phaeocystis during our study, we suggest that it can have a significant impact on the overall productivity and ecology of the New England shelf during the winter/spring transition.},
	doi = {10.1029/2020jc016856},
	url = {https://app.dimensions.ai/details/publication/pub.1134619519},
	author = {Smith, Walker O. and Zhang, Weifeng and Hirzel, Andrew and Stanley, Rachel M. and Meyer, Meredith G. and Sosik, Heidi and Alatalo, Philip and Oliver, Hilde and Sandwith, Zoe and Crockford, Taylor and Peacock, Emily E. and Mehta, Arshia and McGillicuddy, Dennis J.}
}
