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idealized channel model

Subpolar gyres and overturning circulation in the Southern Ocean

The Southern Ocean is arguably the central cog in the global ocean overturning circulation. In addition to connecting all the major ocean basins, the Southern Ocean facilitates the upwelling of deep, carbon-rich waters as well as the production of the dense bottom water that fills most of the abyssal ocean. While deep water upwelling generally occurs within Antarctic Circumpolar Current (ACC), bottom water is formed almost exclusively along the continental margins of Antarctica. In between these two regions lie the subpolar gyres—the most prominent of which are located in the Ross and Weddell Seas. We aim to better understand the dynamical coupling between the ACC, subpolar gyres and the Antarctic margin.

map of sea surface temperature anomaly

Marine heatwaves and surface variability in the Southern Ocean

In contrast to the Arctic region, the Southern Ocean has experienced sea ice expansion and surface cooling over much of the past four decades. These trends came to an abrupt halt in late 2016 when Antarctic sea ice extent (SIE) plummeted to record low levels and summertime sea surface temperature (SST) soared record highs. A similar event occurred during austral summer of 2019-2020, albeit with less dramatic sea ice loss. These recent spikes in summertime SST may be described as marine heatwaves. Our work seeks to uncover the underlying drivers of these recent surface warming events and what they bode for the future. 

 

glacier-cross-section

Subglacial discharge and seawater intrusions

Marine-terminating glaciers, such as those along the coastline of Greenland, often release meltwater into the ocean via subglacial discharge plumes. Though the existence of these plumes can dramatically alter the ice loss along the front of a glacier, the conditions surrounding their genesis remain poorly constrained. In particular, little is known about the geometry of subglacial outlets and the extent to which seawater may intrude into them. To explore this problem, we have developed a theory that describes the steady-state dynamics of subglacial seawater intrusion. We are interested in carrying out further refinements of this theory, validating its predictions with observations, and exploring the impacts of subglacial seawater intrusions on ice sheet stability. 

weddell sea polynya

Open-ocean polynyas and sea ice-ocean feedbacks

A key feature of the sea-ice-covered Southern Ocean is the vertical arrangement of cold, fresh surface water over warmer, saltier deep water. When sea ice grows in the winter, it releases dense brine that entrains warm deep into the mixed layer. Under special circumstances, the entrained heat may melt the overlying sea ice cover leading to what are known as open-ocean polynyas, which may support deep convection into the otherwise sequestered ocean interior. We aim to better characterize the coupling between sea ice growth and deep ocean ventilation, especially in the presence of extreme weather events.