Observational evidence for a cross frontal heat pump in the Southern Ocean

Abstract

Transient eddies in the Southern Ocean play a central role in the global thermohaline circulation. Meridional exchange of heat and salt is not geographically uniformly distributed, but may be concentrated in a number of specific regions where high levels of mesoscale turbulence are generated. We have identified a powerful example of such a region at the South-West Indian Ridge in which cross-ACC heat transport is dependent on eddy shedding. We show that Antarctic eddies are shed across the APF into the Subantarctic at an average of 3 a year and that they have a longevity of 11 months. Furthermore, we calculate the meridional heat and salt deficit of -5.6 ± 1.5 × 1019 J and -8.1 ± 1.5 × 1011 kg relative to the surrounding Subantarctic waters of one such eddy. Despite the importance of this process, eddy heat transport remains I one of the most poorly observed quantities in the Southern Ocean. Copyright 2006 by the American Geophysical Union.