Thermohaline Structure, Fronts, and Sea-Air Energy Exchange of the Trade Wind Region East of Hawaii

Abstract

The thermohaline structure, fronts, and sea-air energy exchange of the trade wind region east of Hawaii are investigated. The wind stress, heat, salt and buoyancy flux fields at the sea surface are evaluated on a 1° latitude-longitude grid and are related to the main thermohaline features of the upper ocean sampled meridionally at 36-km intervals. It is shown that there exists a close relation between the configuration of the above-mentioned fields and the meridional temperature and salinity structure. Two oceanic fronts occur at the borders of the trade wind region. The southern, or doldrum, front occurs in the zone of strongest net evaporation gradients, between latitudes 11 and 12N, and is characterized by salinity gradients of 1%o per 36 km and strong baroclinity in the upper 50 m. The northern, or subtropical, front is encountered between latitudes 31 and 33N in the region of confluence of the California current with the trade wind drift. During summer and fall, the subtropical front is essentially a salinity front, deepening from east to west, and is marked by horizontal gradients of 0.7%? per 36 km and weak baroclinity in the upper 50?175 m. Numerous salinity and some temperature inversions occur in the vicinity of the subtropical front.