TOPOGRAPHIC EFFECTS OF THE MAUD RISE ON THE STRATIFICATION AND CIRCULATION OF THE WEDDELL GYRE

Hydrographic data indicate that due to the Maud Rise (65-degrees-S, 3-degrees-E) the upwelling of relatively warm and more saline Lower Circumpolar Deep Water (LCDW) in the Weddell Gyre and the entrainment of LCDW into the upper layer are enhanced, which increase the ocean heat loss and enrich the salinity of the upper layer. By these processes the water column is preconditioned for deep convection. An anomalous water column with a diameter of about 150-200 km, notable for its relatively cold deep water and its relatively saline upper layer, is situated above the crest of the Maud Rise. Water from its main pycnocline spreads laterally within the upper 500 m and compensates for the entrainment of LCDW into the upper layer. Current meter data from the Winter Weddell Sea Project 1986 show a marked temporal and spatial variability of the southward transport of LCDW in the lee of the Maud Rise. An anticyclone of LCDW, which had cut off from the main body of LCDW cast of the Maud Rise, migrated southward along the western stope with a velocity of about 3 cm s-1. It was followed by a cyclone. which had probably formed at the front of the anomaly due to a strengthened flow, undergoing an enhanced meandering. The wavelength of the entire disturbance is estimated to be about 380 km, one-third of the circumference of the Maud Rise anomaly. If the disturbance repeats continuously, about two to three anticyclones detach per year.