The Antarctic Slope Front (ASF) 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. 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, heterogeneous bathymetry, and small-scale/high-frequency sources of variability such as eddies, tides, overflows and topographic waves.

Intellectual Merit: This project facilitated substantial advances in our understanding of ASF processes, and of dynamical interactions between the ocean and the Antarctic ice sheet, using idealized simulation experiments and analysis/development of realistic ocean/sea ice/ice shelf simulations. Major findings include: identification of tides and sea ice as playing key roles in in modulating the strength of the Antarctic Slope Current; identification of changes in the salt content of the ocean over the Antarctic continental shelf in dictating future feedbacks between meltwater input from the ice sheet and heat transport across the ASF; a first quantification of the importance of meltwater feedbacks on circulation and heat transport around the entire Antarctic continent, and a demonstration that this is of comparable importance to changes directly forced by atmospheric climate shifts; and development of a novel theory that accurately predicts Antarctic ice shelf melt rates based on the ocean temperature and salinity in the core of the ASF.

Broader Impacts: The project also supported new educational initiative to engage UCLA undergraduate students in research cruises to the local continental shelf and slope off the coast of California. The UCLA Zodiac education program now routinely takes hundreds of students per year on these cruises, around which the students participate in pre- and post-cruise hypothesis-testing exercises to maximize the impact on their learning. 

This work was supported by the National Science Foundation, grant number OCE-1751386.

A snapshot of ocean (potential) temperature at 230m depth around Antarctica, or at the ocean bed in locations where the ocean is shallower than 230m. This snapshot was taken from a global ocean/sea ice model simulation run at NASA Ames by D. Menemenlis (NASA JPL). For further information, see Stewart et al., Geophys. Res. Lett. 2018 on the Publications page.