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

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 x 10(19) J and -8.1 +/- 1.5 x 10(11) kg relative to the surrounding Subantarctic waters of one such eddy. Despite the importance of this process, eddy heat transport remains one of the most poorly observed quantities in the Southern Ocean.