@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 {hirzel_high_2023,
	title = {High resolution analysis of plankton distributions at the middle atlantic bight shelf-break front},
	journal = {Continental Shelf Research},
	volume = {267},
	year = {2023},
	pages = {105113},
	abstract = {The Middle Atlantic Bight (MAB) is a highly productive ecosystem, supporting several economically important commercial fisheries. Chlorophyll enhancement at the MAB shelf-break front has been observed only intermittently, despite several studies suggesting persistent upwelling at the front. High resolution cross-frontal transects were conducted during three two-week cruises in April 2018, May 2019, and July 2019. Mesoplankton distributions at the front were measured with a Video Plankton Recorder equipped with hydrographic and bio-optical sensors. Zooplankton were also sampled with a Multiple Opening/Closing Net and Environment Sensing System. Each of the three cruises had distinctly different frontal characteristics, with lower variability in frontal position in April 2018 and higher variability in May and July 2019, primarily due to frontal eddies and a Gulf Stream warm core ring, respectively. Eulerian means of all transect crossings within each cruise did not show mean frontal chlorophyll enhancement in April 2018 or July 2019, despite individual crossings showing chlorophyll enhancement in April 2018. Transformation of the April 2018 data into a cross-frontal coordinate system revealed a weak enhancement of chlorophyll and copepods at the front. Mean frontal chlorophyll enhancement was observed in May and was associated with enhancement in the periphery of a frontal eddy rather than the front itself. None of the planktonic categories observed were enhanced at the front in the cross-shelf mean distribution, though diatom chains and copepods were more abundant inshore of the front, particularly in May and July 2019, as well as within the center of a frontal eddy in May. The high variability of the MAB frontal region obscured the impact of ephemeral frontal enhancement in mean observations of April 2018, while frontal eddies contributed to chlorophyll enhancement in mean observations of May 2019. The influence of both argues for the necessity for 3-D models rather than idealized 2-D models to explain frontal behavior and its effects on biological responses.},
	keywords = {Chlorophyll, Eddies, Fronts, Plankton, Shelf-break, Video plankton recorder},
	issn = {0278-4343},
	doi = {10.1016/j.csr.2023.105113},
	url = {https://www.sciencedirect.com/science/article/pii/S0278434323001905},
	author = {Hirzel, Andrew J. and Alatalo, Philip and Oliver, Hilde and Petitpas, Christian M. and Turner, Jefferson T. and Zhang, Weifeng (Gordon) and McGillicuddy, Dennis J.}
}
@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.}
}
@article {RN187,
	title = {Warm Spiral Streamers over Gulf Stream Warm-Core Rings},
	journal = {Journal of Physical Oceanography},
	year = {2020},
	pages = {1-58},
	type = {Journal Article},
	abstract = {This study examines the generation of warm spiral structures (referred to as spiral streamers here) over Gulf Stream warm-core rings. Satellite sea surface temperature imagery shows spiral streamers forming after warmer water from the Gulf Stream or newly formed warm-core rings impinges onto old warm-core rings and then intrudes into the old rings. Field measurements in April 2018 capture the vertical structure of a warm spiral streamer as a shallow lens of low-density water winding over an old ring. Observations also show subduction on both sides of the spiral streamer, which carries surface waters downward. Idealized numerical model simulations initialized with observed water-mass densities reproduce spiral streamers over warm-core rings and reveal that their formation is a nonlinear submesoscale process forced by mesoscale dynamics. The negative density anomaly of the intruding water causes a density front at the interface between the intruding water and surface ring water, which, through thermal wind balance, drives a local anticyclonic flow. The pressure gradient and momentum advection of the local interfacial flow push the intruding water toward the ring center. The large-scale anticyclonic flow of the ring and the radial motion of the intruding water together form the spiral streamer. The observed subduction on both sides of the spiral streamer is part of the secondary cross-streamer circulation resulting from frontogenesis on the stretching streamer edges. The surface divergence of the secondary circulation pushes the side edges of the streamer away from each other, widens the warm spiral on the surface, and thus enhances its surface signal.},
	keywords = {Buoyancy, Eddies, Frontogenesis/frontolysis, Mesoscale processes, Transport, Vertical motion},
	doi = {10.1175/jpo-d-20-0035.1},
	url = {https://app.dimensions.ai/details/publication/pub.1130879065},
	author = {Zhang, Weifeng and McGillicuddy, Dennis J.}
}
