Controls on Wintertime Ventilation in Southern Drake Passage
Drake Passage is a key region for transport between the surface and interior ocean, but a mechanistic understanding of this exchange remains immature. Here, we present wintertime, submesoscale-resolving hydrographic transects spanning the southern boundary of the Antarctic Circumpolar Current and the Polar Front (PF). Despite the strong surface wind and buoyancy forcing, a freshwater lens suppresses surface-interior exchange south of the PF; ventilation is instead localized to the PF. Multiple lines of the analysis suggest submesoscale processes contribute to ventilation at the PF, including small-scale, O(10 km), frontal structure in water mass properties below the mixed layer and modulation of a surface eddy diffusivity at sub-50 km scales. These results show that ventilation is sensitive to both submesoscale properties near fronts and non-local processes, for example, sea-ice melt, that set stratification and mixed layer properties. This highlights the need for adaptive observing strategies to constrain Southern Ocean heat and carbon budgets.
© 2023. The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. LAD was financially supported by the Resnick Sustainability Institute and an NSF graduate research fellowship. GAV and AFT were supported by NSF Award OPP-1246460. MMF was supported by the Internal Research and Technology Development program (Earth 2050 project) through the Jet Propulsion Laboratory, California Institute of Technology. TRC was supported by a Resnick Sustainability Institute WAVE summer research fellowship. JS was supported by NSF Awards OPP-1246160 and OCE-1755529. The authors would like to thank the Antarctic Support Contract staff as well as the captains and crews of the ARSV Laurence M. Gould for their support during the deployment and recovery cruises. LAD thanks Zachary K. Erickson for useful discussions while preparing this manuscript. The authors are grateful for the reviews of four reviewers, whose critiques improved the quality of this manuscript. Data Availability Statement. Seaglider data are archived at the NOAA National Centers for Environmental Information (https://www.ncei.noaa.gov/archive/accession/0276223). Sea level anomaly and surface velocity products were produced and distributed by the Copernicus Marine 360 and Environment Monitoring Service (https://data.marine.copernicus.eu/product/SEALEVEL_GLO_PHY_L4_MY_008_047/description). Estimates of surface forcing fields (wind speed and direction, surface heat fluxes) for Drake Passage were obtained from the ERA5 atmospheric reanalysis from the European Centre for Medium-Range Weather Forecasts (https://cds.climate.copernicus.eu/cdsapp#!/dataset/10.24381/cds.bd0915c6). Lilian A. Dove and Giuliana A. Viglione contributed equally to this work.
Supplemental Material - 2022gl102550-sup-0001-supporting_information_si-s01.pdf
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