SOUTHERN-OCEAN FRONTS FROM THE GREENWICH MERIDIAN TO TASMANIA

All available meridional sections have been analyzed to investigate th e evolution of main fronts between 0 degrees and 150 degrees E. The ce ntral South Atlantic is featured by the Subtropical Frontal Zone (STFZ ), bordered by the North and South Subtropical Fronts (NSTF and SSTF, respectively), and by the Polar Frontal Zone (PFZ), bordered by the Su bantarctic and Polar Fronts (SAF and PF, respectively). This structure becomes more complex in the African sector as the Agulhas Retroflecti on and the bottom topography force a more convoluted pattern. The Retr oflection and associated Agulhas Front (AF) press the SSTF from 38 deg rees to 42 degrees-43 degrees S. Strong interactions of the AF, SSTF, and SAF with topography shift the fronts but do not obliterate them. T he AF can be traced reliably up to 52 degrees E, sometimes up to 75 de grees E. The SAF is deflected from 45 degrees to 43 degrees S by the M id-Ocean Ridge and converges with the SSTF north of the Prince Edward Islands to form a combined SSTF/SAF, This front intensifies east of 50 degrees-52 degrees E as a result of the confluence with the AF, and b etween 52 degrees and 65 degrees E a triple AF/SSTF/SAF (''the Crozet Front'') is observed. The PF continues along 49 degrees and 50 degrees S between the Crozet Plateau and the Ob-Lena (Conrad) Rise, passing n orth of Kerguelen,; nearly joining the triple Crozet Front. Downstream of the Kerguelen-Amsterdam Passage the canonical structure is being r estored (SSTF, SAF, PF); however, the front parameters in the Australi an sector are different from the African sector, largely because of st rong air-sea interaction and cross-frontal exchanges in the Crozet-Ker guelen region. The SSTF, squeezed between the AF and SAF, loses charac teristics to both. The SSTF/SAF interaction results in the Australian SAF being warmer and saltier downstream, while the SSTF becomes shallo wer and weaker. The Australian STF derives its characteristics mostly from the AF, thus bringing the modified Agulhas waters' to the Pacific Ocean. The newly defined North Subtropical Front (NSTF) was distingui shed in the Indian Ocean between 31 degrees and 38 degrees S. The fron t marks the southern boundary of the subtropical salty, warm water poo l of the central South Indian Ocean. The NSTF location is coincident w ith the position of the wind convergence between westerlies and easter lies, suggesting the possible wind-driven frontogenesis.