Hiroshi Matsuura, Kyozo Ueyoshi, Junichi Kimura, Kentaro Ando and Yoshifumi Kuroda
Japan Marine Science and Technology Center
Strong eastward currents near the surface (SENS) caused by strong westerly wind burst (WWB) occurred frequently from late 1996 through 1997 in this region. The first such event in December 1996 caused the strongest current ever observed at 142E and at 147E, and it penetrated to, at least, 150m. TOGA/TAO data showed that striking deepening of mixed layer occurred during this event. The third SENS event in March 1997 caused weaker acceleration of zonal current and lesser deepening of the mixed layer at 142E and 147E than those during the first SENS while a very strong northward current occurred near the bottom of the mixed layer at 147E-0S. The NSCAT data shows that the WWB during the first SENS was centered almost at the equator while it was centered few degrees south of the equator during the third SENS. These data suggest the importance of symmetry of forcing at the equator on the local acceleration of zonal current and deepening of the mixed layer.
The secondary core of the equatorial undercurrent (EUC) started developing at 142E-0S and at 147E-0S while the main body of the EUC shoaled at 156E-0S and at 165E-0S in the boreal summer of 1997. After this period, main body of EUC gradually shoaled to the shallowest depth ever observed at 142E-0S and at 147E-0S. This shoaling of EUC coincided with but not parallel to the shoaling of isotherms in the upper ocean.
