ON DEEP-CURRENT AND HYDROGRAPHIC OBSERVATIONS FROM A MUDWAVE REGION AND ELSEWHERE IN THE ARGENTINE BASIN

Near-bottom current measurements from both sides of a mudwave, in an e xtensive mudwave region of the mid-Argentine Basin, are examined for e vidence of lee waves. Such waves appear to exist when the across-crest flow exceeds a critical value predicted by FLOOD (1988), Deep-Sea Re search, 35, 973-983! of about 9 cm s-1. The observations agree with th e predictions of BLUMSACK and WEATHERLY (1989, Deep-Sea Research, 36, 155-172) in three of four cases. However, if it is assumed that the fl ow perturbations induced by lee waves are shifted slightly downcurrent from that predicted by the Blumsack and Weatherly model, then there i s agreement in all four cases. The mudwave region is characterized as having a strong (almost-equal-to 10 cm s-1), steady (eddy kinetic ener gy < mean kinetic energy) current. The westward flow is consistent wit h the anticyclonic abyssal gyre centered about the Zapiola Drift infer red by FLOOD and SHOR (1987, Deep-Sea Research, 35, 973-983). Near-bot tom flow measurements made further to the west, in the region of confl uence of the Brazil and Malvinas Current Extensions, reveal relatively energetic fluctuations, and equatorward flowing deep western boundary currents along the continental slope. Along the continental rise a po leward flow is observed, consistent with that inferred by REID (1989, Progress in Oceanography, 23,149-244). Too-cold bottom layers were fou nd to be common only on the lower continental slope (4000 m depth) and at the mid-basin, mudwave site.