Quasi-continuous fugacity of CO2 (fCO2) data were collected in the eastern Weddell Gyre and southern Antarctic Circumpolar Current (ACC) of the Southern Ocean during austral autumn 1996. Full depth Total CO2 (TCO2) sections are presented for austral autumn and winter (1992) cruises. Pronounced fCO2 gradients were observed at the Southern Ocean fronts. In the Weddell Gyre, fCO2 regimes appeared to coincide with surface and subsurface hydrographic regimes. The southern ACC was supersaturated with respect to CO2, as was part of the northern Weddell Gyre. The southern Weddell Gyre was markedly undersaturated. The great potential of autumn cooling for generating undersaturation and CO2 uptake from the atmosphere was demonstrated. In the northeastern Weddell Gyre, upwelling of CO2- and salt-rich deep water was shown to play a role as the horizontal fCO2 distribution closely resembled that of the surface salinity. The total uptake of atmospheric CO2 by the Weddell Gyre in autumn (45 days) was calculated to be 7 1012 g C. The deep TCO2 distribution noticeably reflected the different water masses in the region. A new deep TCO2 maximum was detected in the ACC, which apparently characterizes the boundary between the equatorward flowing Antarctic Bottom Water (AABW) and the Circumpolar Deep Water. East of the Weddell Gyre the AABW stratum is much thicker (>2000 m) than more to the west, on the prime meridian (<300 m).