OBSERVATIONS OF A STREET OF CYCLONIC EDDIES IN THE INDIAN-OCEAN SECTOR OF THE ANTARCTIC DIVERGENCE

Hydrographic and drifting buoy data from Japanese cruises show that th e Antarctic Divergence in the Indian Ocean sector is composed of a str eet of cyclonic eddies. These eddies measure about 500 km in the zonal direction and 200 km in the meridional. Part of the eastward flowing Antarctic Circumpolar Current (ACC) meanders southward in the regions between the eddies. In the eddy regions, warm, saline Circumpolar Deep Water is upwelled into the shallow layers, while cold, dense coastal water advects into the deep layers; the advection occurs along the iso baths of ridges which extend north from the coast. The combination of the advection with the upwelling produces a water column denser than t he surrounding water and leads to the formation and maintenance of the cyclonic eddies. Presence of the northward extending ridges approxima tely governs the location of eddy formation. The eddy formation recurs year after year, although eddy locations can vary somewhat. A polynya was observed to persistently occur and corresponded with one of the e ddies in location, size, and form. The oceanographic observations also suggest that the primary meridional exchanges of heat and salt in the Antarctic are caused through the eddies and ACC meanders within the A ntarctic Divergence.