A17 sampled the southern subpolar, subtropical, and subequatorial wind-driven regimes, and the northern subequatorial regime.

Figure 4: Volume transport streamfunction deduced from Sverdrup dynamics, with the track of A17 superimposed (adapted from Onken, 1994).

The four regimes are recognized in the full-depth alongshore transports between A17 and the coast (Fig 5a) by an alternance of northward and southward flows. In figures (5b) and (5c), the warm and cold waters of the thermohaline overturning cell are distinguished. The modifications brought on the wind-driven boundary flow of the upper ocean by the thermohaline mode vary from 20+/-10 Sv southward in the Argentine Basin to 40+/-10 Sv northward in the northern subequatorial domain. In this region, the dominating thermohaline contribution leads to an upper ocean boundary transport that is in opposite direction to the one predicted by the wind-driven theory.

Figure 5: Meridional distribution of the alongshore transport between A17 and the continental slope, positive southward, in the whole water column (a), in the warm waters of the ovreturning thermohaline cell (b), and in the cold waters of the thermohaline cell (c). Sensitivity studies suggest uncertainties of about 5 Sv for these curves, increasing to 10 Sv to the north of the equator and south of 30°S in (a) and (b).