The influence of the Antarctic Circumpolar Current on the oceanographic setting of a sub-Antarctic island

Abstract

The circulation in the Southern Ocean is dominated by the Antarctic Circumpolar Current (ACe), which is the only current that flowscompletely around the globe. The ACC is a complex system consisting of narrow regions of sharp horizontal density gradients, whichextend through the entire water column as frontal bands separated by broad zones with less intense gradients. Meridional excursions fromthe otherwise zonaillow in the form of meanders or mesoscale eddies occur in regions of prominent bathymetric features, suggesting a closerelationship between the level of mesoscale sea surface variability and bottom topography, The Prince Edward Islands (Marion Island andPrince Edward Island) lying within the Polar Frontal Zone (PFZ) at approximately 38 DE, 47 os form a very special terrestrial habitat andhave, for this reason, been designated a declared nature reserve. The ecology of the islands is directly dependent on its ocean environment,With the advent of satellite altimetry it has become apparent that the Prince Edward Islands are located on the northern border of a regionof remarkably high mesoscale variability. The source of this variability lies where the current jet associated with the ACC intersects theSouth-West Indian Ridge. From here newly generated eddies are steered by the bottom topography past the Prince Edward Islands. '[hisdiscovery probably explains the high physical and biological variability found at the islands, and warrants further analysis,