Biological and Environmental Research - Earth and Environmental System Sciences
Earth and Environmental System Modeling
12 August 2020

The Large-Scale Vorticity Balance of the Antarctic Continental Margin in a Fine-Resolution Global Simulation

Science

The Antarctic Continental Margin (ACM) is a globally important region, particularly due to its role in sea level change through loss of continental ice buttressing caused by melting of floating ice shelves. This melting is known to be in large part associated with the penetration of relatively warm deep-ocean water onto the ACM. Understanding cross-shelf exchange mechanisms over the ACM has therefore received increasing scientific interest over the past decade. This study contributes to this problem by linking the vorticity balance of a 1/10-degree global, coupled ocean-sea ice simulation to potential mechanisms of cross-slope transport over the ACM.

Impact

This study performs a detailed examination of the depth-integrated vorticity balance in a 1/10-degree global, coupled ocean-sea ice simulation (POP/CICE) around the Antarctic Continental Margin (ACM). The results emphasize the need for accurate small-scale bottom topography and surface stress due to both wind and sea ice. The study also suggests a potential mechanism for cross-slope transport (both onshore and offshore) based on the vorticity input of the surface stress curl and shows that this mechanism is more important in certain segments of the ACM than in others. These findings may have relevance for the representation of cross-slope transport in the ACM in next-generation Earth System Models, such as the Energy Exascale Earth System Model (E3SM).

Summary

The depth-integrated vorticity budget of a global, ocean/sea-ice simulation that is eddy-permitting over the Antarctic Continental Margin (ACM) is diagnosed to understand the physical mechanisms implicated in meridional transport. The flow in the Amundsen, Bellingshausen and Weddell Seas and, to a lesser extent, in the western portion of East Antarctica, is closer to an approximate Topographic Sverdrup Balance (a balance between the surface stress curl, bottom stress curl, topographic effects, and meridional advection) compared to other segments of the ACM. Inclusion of the vorticity tendency term in the response increases the correlation with the forcing, and also increases the coherence between forcing and response at high frequencies across the ACM, except for the West Antarctic Peninsula. These findings suggest that the surface-stress curl, imparted by the wind and the sea ice, has the potential to contribute to the meridional, approximately cross-slope, transport to a greater extent in the Amundsen, Bellingshausen, Weddell and part of the East Antarctic continental margin than elsewhere in the ACM.

Contact
Julie McClean
Scripps Institution of Oceanography
Publications
Paloczy, A, J McClean, S Gille, and H Wang.  2020.  "The Large-Scale Vorticity Balance of the Antarctic Continental Margin in a Fine-Resolution Global Simulation."  Journal of Physical Oceanography 50(8): 2173-2188.  https://doi.org/10.1175/jpo-d-19-0307.1.