A pacific equatorial temperature section from 172°E to 110°W during winter and spring 1979

Abstract

A composite zonal-depth temperature section was occupied along the equator between 172°E and 110°W, nearly 8.6 × 10 3 km, by combining temperature profiles recorded at about 1- degree intervals on 28 February 1979 between 172°E and 158°W with profiles recorded at 1 4 - degree interval from 23 April to 2 May 1979 between 153°W and 110°W. Coincident with the zonal temperature section, which combined with salinity data produced dynamic height anomalies, were moored current measurements in the upper ocean at three equator sites (166°E, 152°W, and 110°W). The thickness of the mixed layer decreased from about 100 m near 180° to 10 m near 110°W. The depth of the thermocline was about 125 m near 180° and approximately 50 m east of 120°W. At 166°E the velocity core of the Cromwell Current was near the bottom of the thermocline; at 152°W and 110°W it was within the central region of the thermocline. East of about 140°W a 100-m-thick 13°C thermostad occurred below about 175 m. At 110°W the bulk Richardson number encompassing the 150- to 200-m interval was virtually always less than unity from 20 January to 2 May, suggesting that the thermostad was formed by shear-induced dynamic instabilities below the velocity core of the Cromwell Current. The surface dynamic height anomaly relative to 27 dbar tilted upward toward the west between 172°E and 120°W, with the maximum inclination from 153°W to 133°W. East of 120°W the zonal gradient of the 0/270 dbar steric sea level was indistinguishable from a horizontal surface. East of 132°W the directions of the 270/400 dbar pressure force and of the zonal wind field were both westward, indicating that the influence of the prevailing westward wind stress was confined to the region above the thermocline.