carbon, and other climatically important tracers in the Southern Ocean. In this presentation we determine the rate of meridional mixing across the Antarctic Circumpolar Current by combining hydrographic sections of temperature and salinity with altimetric measurements of geostrophic velocity. We show that mixing rates are very variable, even though the intensity of the geostrophic eddy field is quite uniform. In particular we find that mixing is strongly suppressed across the strong jets that characterize the Antarctic Circumpolar Current. These results are interpreted with simple kinematic models of eddy mixing across jets. We conclude by discussing the implications of our results for tracer transport in the Southern Ocean.