Eddy heat fluxes from direct current measurements of the Antarctic Polar Front in Shag Rocks Passage

Abstract

Determining meridional heat flux in the Southern Ocean is critical to the accurate understanding and model simulation of the global ocean. Mesoscale eddies provide a significant but poorly‐defined contribution to this transport. An eighteen‐month deep‐water current meter array deployment in Shag Rocks Passage (53°S, 48°W) between May 2003 and November 2004 provides estimates of the eddy flux of heat across the Polar Front. We calculate a statistically nonzero (99% level), vertically coherent local poleward heat flux of 12.0 ± 5.8 kW m−2 within the eddy frequency band at ∼2750 m depth. Exceeding previous deep‐water estimates by up to an order of magnitude, this highlights the large spatial variation in flux estimates and illustrates that constriction of circumpolar fronts facilitates large eddy transfers of heat southwards.