Oxygen pathways into the deep ocean: investigating boundary current ventilation in the western Irminger Sea

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This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).This proposal would fund recovery of deployed oxygen sensors on the OSNAP moorings in the western boundary current of the Irminger Sea, along with deep calibration casts upon recovery, and subsequent processing and analysis of the data. The purpose is to measure O2 that ventilates the deeper boundary current through several pathways leading from the near surface ocean exposed to the atmosphere, into the deeper boundary current, and to investigate the processes responsible. In so doing, the project will also provide information about the pathways of dissolved atmosphere-derived CO2 from the near surface ocean to the deep. Carbon dioxide uptake in the subpolar North Atlantic is thought to significantly mitigate global warming, but as global warming continues, ventilation may decline, potentially weakening this CO2 sink and also reducing oxygen levels throughout the Atlantic. A lack of direct observations of dissolved gases has limited accurate budgeting and hindered understanding of the processes which govern the sequestration of gases into the deep ocean. These results may apply to other ocean regions and inform dissolved gas coupling in ocean and climate models. Broad use of these data will be promoted, to fuel additional advances in the ocean chemistry, ecology, and climate dynamics of this critical region. The project will support an early career female Hispanic/Latina scientist and a graduate student, along with several outreach activities, including documentation of at-sea experience through a blog and interaction with URM student groups.Carbon dioxide uptake in the subpolar North Atlantic is thought to significantly mitigate global warming; moreover, oxygen uptake in this region prevents large scale hypoxia throughout the North Atlantic. As global warming continues, convection is expected to decline, potentially weakening this CO2 sink and reducing oxygen levels throughout the Atlantic. However, a lack of direct observations of dissolved gases, particularly in winter and in boundary current regions, has limited accurate budgeting and has hindered our understanding of the processes which govern the sequestration of gases into the deep ocean. Careful calibration and analysis of these valuable new O2 observations is planned, to emphasize an understanding of the dynamics underlying boundary current ventilation and interior-boundary current exchange. Science question addressed are: 1) How effectively does slantwise convection directly ventilate boundary currents? 2) How much oxygen reaches the Irminger Sea’s boundary current through the draining of Labrador Sea Water (LSW) from the interior? 3) To what extent does LSW entrainment set the high oxygen levels in Denmark Strait Overflow Water (DSOW)? These results may apply to other ocean regions and inform dissolved gas coupling in ocean and climate models.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.