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We used a combination of buoy the temperature and salinity gradients are largely tracking, intensive hydrography, satellite thermal offsetting in their effect on density. The imagery, and moored current meters to resolve the resulting density difference across the front in structure of eddies at the shelfbreak front in the at is only about 0.5 kg/m s, while the temperature Middle Atlantic Bight south of New England. difference is typically 50C and the salinity Eddylike features were always present at the front difference about 2 g/kg. in our study area throughout the 15-day period of The mean and low-frequency structure of the observations in June 1984. We found that hydrographic and current fields at the front are hydrographic features in our across-shelf relatively well known. We omit an account of them hydrographic transects that appeared to represent here and refer the interested reader to the recent the detached parcels of shelf water often reported papers of Beardsley and Flagg [1976], Voorhis et in the literature were, in fact

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Near bottom water temperatures were mapped along 400 km of the strike of the Juan de Fuca Ridge as part of a combined Sea MARC/Seabeam experiment to image the variability of morphology and structure along a spreading center segment. The water temperature data collected by a continuously towed thermistor chain, in addition to salinity data, indicate that there are four geothermal areas spaced at distances of 100 km from each other south of the Cobb propagator and one field just to the north of the propagator on the Endeavor Ridge segment. Each thermal region is located above a morphological dome on the spreading center. These domes are an average of 100–200 m shallower than the rest of the axis. The structure of bottom water suggests that the geothermal regions are on average 20 km long and that the heat from these fields raises the temperature in the water column by a minimum of 0.06°C up to 300 m above the bottom. Two simple models are used to estimate the heat flux associated with these features.

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Abstract-A CTD-O2 and ADCP section across the African Atlantic continental margin near 275, obtained during R.R.S. Discovery cruise 165B in May 1987, reveals the water mass structure and associated velocity field of the shelf and upper slope of the Benguela upwelling system. Continental shelf water upwelling within the Benguela Current is drawn from the 12°C (about 200 m) level. The upwelling water is drawn from oxygen depleted, tropical South Atlantic thermocline water that is advected along the shelf floor by a southward flowing subsurface current. Lower thermocline and intermediate water from the tropical South Atlantic are also observed flowing southward over the continental slope. Tropical Atlantic water generally resides north of the Angola-Benguela Front at 165. A narrow band of upwelled water is observed well seaward of the shelf, along the western edge of a large Agulhas eddy, indicating that Agulhas eddies play a role in stirring eastern boundary upwelled water into the ocean interior. These eddies also draw into the interior tropical Atlantic water found over the upper continental slope. The net transport between the 120 and 350 isobaths as measured by the ship-mounted ADCP, referenced to the sea floor, is 0.9 x lob m3 s-' to the south, with 1.6 x lob m3 SK' of southward flowing tropical Atlantic water and 0.7 x lob m3 s-l of northward flowing upwelled surface water. The tropical thermocline water mass advected to the south is not observed offshore within the northward flowing Benguela Current, in an unaltered state, thus the 0.9 x lob m3 s-' must feed shelf upwelling south of 27"s. implying a net offshore flux of upwelled water between Liideritz (26") and Cape Columbine (33"s).

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