Description: Seasonal meridional ocean temperature fluxes were computed in a regional study of the eastern North Atlantic Ocean east of 30°30′W between 12°30′N and 39°30′N for the upper 1500 m of the ocean. Historical oceanographic and meteorological measurements are the data base for the direct method of computing temperature fluxes. Seasonal changes in temperature fluxes caused by the seasonality of Ekman transport and geostrophic transport are strongly dependent on latitude. Between 19N and 25N the meridional temperature flux shows low seasonality. In this area the permanent subtropical gyre and the stable trade-winds result in low seasonal changes. North of 25N the Ekman transport shows large seasonal variations. The latitude of the transition of southward Ekman temperature flux to northward Ekman temperature flux is located at 28N in winter. In summer it is found at 38N. The seasonal variability of the meridional temperature fluxes in the subtropics north of 25N is influenced by this annual cycle in Ekman transport, as well as by the southward displacement in summer and the northward movement of the Azores Current in winter. The tropical eastern Atlantic Ocean shows seasonal changes both in the geostrophic and Ekman transports. South of 17N the total temperature flux is always to the north. The largest meridional temperature fluxes, with more than 0.7 PW, are found in fall at 12°30′N directed northward, and in winter at 33°30′N to the south. In general the subtropical eastern North Atlantic Ocean transports heat to the south all the year round, while in the tropics heat is transported to the north. The seasonality in the eastern Atlantic Ocean is found to be different from seasonal variations in global investigations. The seasonal heat budget computations show a heat gain in the ocean in the area investigated from April to September and a heat loss from October to March. Over the whole year the eastern North Atlantic gains about 0.09 PW from the atmosphere.

Description: Geostrophic transport calculations from historical data of the equatorial South Atlantic are presented for the investigation of the flow field in the South Equatorial Current region. On the basis of water mass distribution, the potential density surface of sigma-1 = 32.15 kg m-3 is used as a reference for geostrophic shears. This reference surface is located at a depth of 1000 to 1200 m and represents the boundary between the upper branch of the Circumpolar Deep Water and the Upper North Atlantic Deep Water. The southern band of the South Equatorial Current (SSEC) is fed by the Benguela Current, which crosses the Greenwich Meridian south of 20S. West of the Greenwich Meridian the subtropical gyre has its northermost current band as the westward flowing SSEC. The SSEC was found to be a broad sluggish flow between 10S and 25S. The transport of the SSEC in the upper 500 m is in the order of 20 Sv, with surface velocities of around 10 cm s-1. At 30W the SSEC turns northward. A small part of the water turns poleward south of 10S to form the Brazil Current, whereas the bulk of the flow contributes to the North Brazil Current and the South Equatorial Countercurrent (SECC). The SECC seems to cross the entire South Atlantic eastward to at least the Greenwich Meridian, but part of the flow might contribute to the middle branch of the South Equatorial Current flowing westward. The northernmost current band sampled is the eastward flowing South Equatorial Undercurrent. From this data no seasonality in the geostrophic field can be proven.

Description: The flow field off the southwest coast of India at 8N was investigated during RV Sonne cruise 89 in August 1993 by direct velocity observations from shipboard- and lowered-ADCP and geostrophic computations from CTD stations. The upper ocean between 75E and 76°52′E near the South Indian shelf was governed by a northward flow with a subsurface velocity maximum of 25 cm s−1 at about 100 m depth. This flow, organized as a poleward undercurrent hugging the continental slope, is typical for the southwest monsoon season. The northward transport in August 1993 was 4.7 Sv (1 Sverdrup = 106 m3 s−1) for the upper 300 m from the shipboard ADCP. Earlier geostrophic observations showed southward surface flow above the poleward undercurrent, but in August 1993 the northward flow reached to the surface and in the geostrophy calculations, i.e. without the southward Ekman flow near the surface, there was even no clear subsurface core. The T-S characteristics show that Bay of Bengal Water (BBW) was carried with this flow, and low wind conditions seemed to be connected to the flow of BBW from the southern tip of Sri Lanka toward the southwest coast of India. Further offshore, two meridional current bands were identified in the upper 300 m of the ocean. West of the coastal undercurrent a band of southward flow existed with velocities up to 35 cm s−1 above and to the east of the Chagos-Laccadive Ridge, from 72°10′E to 75E. The associated geostrophic transport in the upper 500 m was 5.2 Sv. As the T-S relation was different from that of the northward flow, this current band was not a local recirculation of the poleward undercurrent. Further west, the flow was weak, but intensified toward the central Arabian Sea, between 66E and 69°20′E, where another southward current band was found with velocities of up to 20 cm s−1 and a total geostrophic transport for the upper 300 m of −7.2 Sv.