CAREER: Circumpolar Variability and Exchanges Across the Antarctic Slope Front

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The Antarctic Slope Front almost completely encircles the Antarctic continent, separating relatively cold shelf waters from warmer waters at mid-depth in the open ocean. It serves as a ``gatekeeper'' for waters intruding onto the Antarctic continental shelf, such as the warm Circumpolar Deep Water that supplies heat to melt the bases of Antarctica's ice shelves, and for waters escaping the continental shelf, such as the dense water outflows that fill more than one-third of the global sub-surface ocean. A series of high-resolution numerical ocean simulations will be conducted to assess whether past and ongoing regional models and observational campaigns are capturing the ``hot spots'' of heat transport toward the continent, and identify which small-scale/high-frequency processes must be resolved to capture this heat transport. The educational component will substantially broaden participation of undergraduates in oceanography by combining field trips and research-based exercises which have been shown to increase student learning and retention compared to conventional teaching methods. The educational initiative will engage hundreds of undergraduate students per year in research cruises to the local continental shelf and slope off the coast of California. A captain/technician will be recruited to facilitate dozens of cruises annually using the UCLA Zodiac research vessel. The project investigator will develop organizational and educational materials to support the research cruises, with students guided to form their own research hypotheses and analyzing their own data using scientific computing tools. By the end of the project period this educational program will become self-sustaining, drawing from a combination of course fees, research/education grants, donations and direct support from UCLA. The project will also provide research training for a graduate student and support for an early-career faculty member.Practical constraints imposed by Antarctica's climate and the small scales of variability have limited previous quantification of cross-slope exchange processes to localized regions. There remains a substantial gap in understanding how continental-scale exchanges of water between the open ocean and the shelf seas are modulated by seasonal variability in atmospheric conditions, hetereogenous bathymetry, and small-scale/high-frequency sources of variability such as eddies, tides, overflows and topographic waves. The project investigator proposes to close this gap in understanding by developing the first ocean/sea ice model simulations of the entire Antarctic margins, including the ocean beneath the floating ice shelves, that can resolve small-scale variability and tides. Using analysis techniques based on multiple separation of time scales, the cross-slope exchanges of mass and properties will be quantified and thereby identify regimes in which the Antarctic Slope Front serves as a ``barrier'' vs. a ``blender''. The same framework will then be used to diagnose the dynamics of the Antarctic Slope Current, for example the energy and vorticity budgets, to distinguish the relative roles of atmospheric forcing, bathymetric steering and small-scale variability in localizing exchanges across the Antarctic Slope Front. Finally, idealized process models will be constructed to explore specific hypotheses derived from the circum-Antarctic model simulation.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.