Heat flux estimates for the western North Atlantic. Part II: the upper-ocean heat balance

Abstract

The assimilation of temperature and altimetric velocity into a numerical model of the upper-ocean mixed layer in Part I allowed an analysis of the upper ocean heat budget for the western North Atlantic Ocean over the 2.5-yr period of the Geosat Exact Repeat Mission (November 1986-April 1989). Within the Gulf Stream and to the north of it, cooling of the upper ocean by advection was as large as 0.15°C/day for periods of several weeks. An analysis of the advection term showed that cooling by Ekman transport was opposed by warming from the geostrophic currents of the Gulf Stream, with cooling typically stronger by a factor of 2 because nonuniform Ekman transport disrupted the normal alignment between isotherms and sea surface height contours. There is a complex ocean-atmosphere coupling in this region: in addition to its increase during strong wind events, warming by geostrophic currents is a function of the strength of the Gulf stream and its recirculation gyres. -from Authors