Fronts, transport, and Weddell Gyre at 30°E between Africa and Antarctica

A detailed description of the frontal structure of major currents and estimates of transport between Africa and Antarctica at 30°E were made on the basis of a finely resolved hydrographic section made during the 1996 Civa‐2 cruise. Particular emphasis was put on a refinement of the eastern boundary of the Weddell Gyre by analyzing also supplementary hydrographic data from the 1993 Civa‐1 cruise and the best available historical hydrographic data in the Weddell and Enderby Basins. Contrary to the general belief, our results show that the Weddell Gyre extends far beyond 30°E, reaching at least as far east as the Enderby Land promontory (53°E). From this point, westward currents along the Antarctic continental margin constitute the gyre's southern boundary, thus closing the cyclonic circulation of the gyre at its easternmost end. As the most convincing evidence for this refined circulation scheme, significant westward transport south of 65°S has been identified from the Civa‐1 acoustic Doppler current profiler data. We have shown also, using an inertial jet model, that the blocked feature of the Weddell cold regime (∼57°S) to the west of 25°E is due to the topographic control of flow by local bathymetry. During the Civa‐2 cruise, ∼70% of the Antarctic Circumpolar Current (ACC) was concentrated near the Polar Front (51°S), with surface speeds reaching up to 70 cm s−1. The baroclinic current field in the subpolar area south of the Weddell Front (58°S for Civa‐2 and 57°S for Civa‐1) is featureless (