Authors: Nelson G Hogg Andreas M Thurnherr
Publish Date: 2005/06/01
Volume: 61, Issue: 3, Pages: 493-507
Abstract
Several large deployments of neutrally buoyant floats took place within the Antarctic Intermediate AAIW North Atlantic Deep Water NADW and the Antarctic Bottom Water AABW of the South Atlantic in the 1990s and a number of hydrographic sections were occupied as well Here we use the spatially and temporally averaged velocities measured by these floats combined with the hydrographic section data and various estimates of regional current transports from moored current meter arrays to determine the circulation of the three major subthermocline water masses in a zonal strip across the South Atlantic between the latitudes of 19°S and 30°S We concentrate on this region because the historical literature suggests that it is where the Deep Western Boundary Current containing NADW bifurcates In support of this notion we find that a net of about 5 Sv of the 15–20 Sv that crosses 19°S does continue zonally eastward at least as far as the MidAtlantic Ridge Once across the ridge it takes a circuit to the north along the ridge flanks before returning to the south in the eastern half of the Angola Basin The data suggest that the NADW then continues on into the Indian Ocean This scheme is discussed in the context of distributions of dissolved oxygen silicate and salinity In spite of the many floatyears of data that were collected in the region a surprising result is that their impact on the computed solutions is quite modest Although the focus is on the NADW we also discuss the circulation for the AAIW and AABW layers
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