FY 1990

Thermohaline structure and zonal pressure gradient in the western equatorial Pacific

Mangum, L.J., S.P. Hayes, J.M. Toole, Z. Wang, S. Pu, and D. Hu

J. Geophys. Res., 95(C5), doi: 10.1029/JC095iC05p07279, 7279–7288 (1990)

Two recent sections of temperature and salinity along the equator in the western Pacific were examined in the context of the historical hydrographic data. Both sections occurred during the December-February period when climatological mean winds are northwesterly. The historical data indicate that the zonal sea surface slope responds to the seasonal change in wind stress. During the southeasterly monsoon the historical mean surface relative to 500 dbar dynamic height slopes upwards from east to west; during the northwesterly monsoon this slope reverses. Vertical profiles of the mean zonal pressure gradient relative to 500 dbar suggest that the wind influence may extend quite deep in the water column. The two quasi-synoptic sections both indicated that the sea level sloped downward towards the west between 155°E and 140°E. The sign of this slope agrees with the historical seasonal mean; however, the zonally averaged sea level in this westernmost region changed by nearly 0.1 dyn m between sections. Upper ocean water properties and stratification confirmed the importance of salinity in determining mixed layer depth. Comparisons of repeat stations collected during a 16-day period indicated relatively rapid changes in near surface properties and the importance of lateral advection.