South Atlantic mass transports obtained from subsurface float and hydrographic data
Abstract:Mean total (barotropic + baroclinic) mass transports of the oceanic top 1000 dbar are estimated for two regions of the South Atlantic between 18°S and 47°S. These transports are obtained by using Gravest Empirical Mode (GEM) fields calculated from historical hydrography with temperature and position data from quasi-isobaric subsurface floats deployed from 1992 through 2001. The float-GEM-estimated total mass transports reveal a Brazil Current with a southward flow of 20.9 Sv at 30°S and 46 Sv at 35°S (1 Sverdrup, Sv = 106 m3 s–1). Two recirculation cells are identified in the southwest corner of the subtropical gyre north of 40°S, one centered at 48°W, 37°S recirculating 28.5 Sv and another centered at 40°W, 38°S recirculating 13.9 Sv. The South Atlantic Current (SAC) flows eastward with 50 Sv at 30°W and splits into two branches in the east, one north of 38°S transporting 19 Sv and one south of 41°S transporting 31 Sv. Of the 39.7 Sv of SAC transport that comes from the Malvinas Current/Antarctic Circumpolar Current (ACC) system in the western basin, only 8.7 Sv flow with the northern branch and the remaining 31 Sv flow as the southern branch out of the South Atlantic rejoining the ACC directly (20.6 Sv) or interacting with the Agulhas Current Retroflection (10.4 Sv). From the northern branch, only 4.7 Sv of Malvinas Current/ACC origin and 10.3 Sv of Brazil Current origin (a total of 15 Sv) stays in the South Atlantic forming the Benguela Current, recirculating within the subtropical gyre. The Agulhas Current Retroflection reaches westward as far as 10°E with a transport of 48 Sv. In terms of mean total transport, the cold-water route carries 4.7 Sv in the upper 1000 dbar whereas the warm-water route carries 8.5 Sv. However, considering the interaction between waters from both origins, there is a total of 19.1 Sv of waters entering the Cape Basin from the Pacific Ocean and 18.5 Sv from the Indian Ocean.
Document Type: Research Article
Publication date: 2010-11-01
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