CURRENT STRUCTURE OF THE SOUTH INDIAN-OCEAN

Using recently published atlas data [Olbers et al., 1992] and the Fine Resolution Antarctic Model (FRAM) [Webb er al., 1991], an investigati on has been conducted into the structure of the frontal jets centered around tile region of the islands of Crozet (46 degrees 27'S, 52 degre es 0'E) and Kerguelen (48 degrees 15'S, 69 degrees 10'E) in the south Indian Ocean. Geostrophic current velocities and transports were calcu lated from the temperature and salinity fields available from the atla s and compared with results from FRAM and previous studies. We have id entified the Agulhas Return Front (ARF) and the Subtropical Front (STF ), as well as the following fronts of the Antarctic Circumpolar Curren t (ACC): the Subantarctic Front (SAF), the Polar Front (PF), and the S outhern ACC Front (SACCF), from temperature and salinity characteristi cs and from geostrophic currents. This analysis of model and atlas dat a indicates that the jets associated with the ARF, STF, and SAF are to pographically steered into a unique frontal system north of the island s, having some of the largest temperature and salinity gradients anywh ere in the world ocean. The frontal jet associated with the ARF is det ectable up to 75 degrees E and has associated with it several northwar d branching jets. The PF bifurcates in the region of the Ob'Lena (Conr ad) seamount; subsurface and surface expressions are identified, separ ated by as much as 8 degrees of latitude immediately west of the Kergu elen Plateau. Tile surface expression, carrying the bulk of the transp ort (similar to 65 Sv), is steered through the col in the Kerguelen Pl ateau at 56 degrees S, 6 degrees south of the latitude normally associ ated with the PF at this meridian. On crossing the plateau it rejoins the subsurface expression. In the south, passing eastward along the ma rgin of the Antarctic continent and through the Princess Elizabeth Tro ugh, a frontal jet is identified transporting up to 35 Sv, believed to be the SACCF [Orsi et al., 1995], placing the southern extent of the ACC in the region at 67 degrees S.