Connecting Antarctic Cross-Slope Exchange with Southern Ocean Overturning

• Published in: Journal of Physical Oceanography
• Main Authors: Stewart, Andrew L., Thompson, Andrew F.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: American Meteorological Society 2013
• Subjects: Antarctica; Southern Ocean; Eddies; Meridional overturning circulation; Mesoscale processes; Primitive equations model; Antarctic; The Antarctic; Antarc*
• Online Access: https://doi.org/10.1175/JPO-D-12-0205.1

Previous idealized investigations of Southern Ocean overturning have omitted its connection with the Antarctic continental shelves, leaving the influence of shelf processes on Antarctic Bottom Water (AABW) export unconsidered. In particular, the contribution of mesoscale eddies to setting the stratification and overturning circulation in the Antarctic Circumpolar Current (ACC) is well established, yet their role in cross-shelf exchange of water masses remains unclear. This study proposes a residual-mean theory that elucidates the connection between Antarctic cross-shelf exchange and overturning in the ACC, and the contribution of mesoscale eddies to the export of AABW. The authors motivate and verify this theory using an eddy-resolving process model of a sector of the Southern Ocean. The strength and pattern of the simulated overturning circulation strongly resemble those of the real ocean and are closely captured by the residual-mean theory. Over the continental slope baroclinic instability is suppressed, and so transport by mesoscale eddies is reduced. This suppression of the eddy fluxes also gives rise to the steep "V"-shaped isopycnals that characterize the Antarctic Slope Front in AABW-forming regions of the continental shelf. Furthermore, to produce water on the continental shelf that is dense enough to sink to the deep ocean, the deep overturning cell must be at least comparable in strength to wind-driven mean overturning on the continental slope. This results in a strong sensitivity of the deep overturning strength to changes in the polar easterly winds. © 2013 American Meteorological Society. Manuscript received 14 October 2012, in final form 11 March 2013. A.L.S.'s and A.F.T.'s research was supported by the California Institute of Technology and NSF Award OCE-1235488. The simulations presented herein were conducted using the CITerra computing cluster in the Division of Geological and Planetary Sciences at the California Institute of Technology, and the authors thank the CITerra technicians for ...