The upper ocean heat content of the western equatorial Pacific: processes controlling its change during the Tropical Ocean-Global Atmosphere Coupled Ocean-Atmosphere Response Experiment

摘要

The processes controlling the upper ocean heat content in the western equatorial Pacific are examined using data collected during the Tropical Ocean-Global Atmosphere Coupled Ocean-Atmosphere Response Experiment. The work centers on a number of meridional sections taken along 156 degrees E from 5 degrees S to 5 degrees N undertaken from December 1992 to February 1993. We compare and contrast the conditions north anti south of the equator. The net change ill the depth-averaged temperature (here taken over the top 40 m of the ocean) over the entire sampling period is found to be very similar over the observed range of latitude; the change being a decrcase of approximately 0.5 degrees C. However, there are periods lasting a few tens of days when there are large differences (by as much as 1 degrees C) in the change to the depth averaged temperature north and south of the equator. By examining the heat balance, these changes are found to be brought about by a combination of the differing surface heat fluxes and ocean currents in the two subregions. The surface heat Bur over the region is estimated using an empirical formula based on winds from the Tropical Ocean Atmosphere array and cloud albedo measurements from the GMS satellite. Intense meridional flows in the ocean in response to high-frequency wind events play a crucial role in the heat balance both north and south of the equator. The timing of such flows varies with latitude. The redistribution of heat caused by the ocean flow produces changes to the meridional gradient of sea surface temperature. These changes in temperature gradient have the potential of feeding back to the atmosphere. [References: 31]