On the water masses and mean circulation of the South Atlantic Ocean Loth•r $tr•mrn•

schemes •t different depths of the South Atlantic Ocean to propose • l•yered, qualitative representation of the mean distribution of flow in this region. This furthers the simple upper l•yer geostrophic flow estimates of Peterson and $tramma [1991]. In addition, we •ssess how well ocean general circulation models (GCMs) c•pture the overall structure of flow in the South Atlantic in this regard. The South Atlantic Central Water (SACW) is of South Atlantic origin in the subtropical gyre, while the $ACW in the tropical region in p•rt originates from the South Indian Ocean. The Antarctic Intermediate W•ter in the South Atlantic originates from • surface region of the circumpolar l•yer, especially in the northern Drake P•ss•ge •nd the F•lkl•nd Current loop, but •lso receives some w•ter from the Indian Ocean. The subtropical South Atlantic •bove the North Atlantic Deep W•ter •nd north of the Antarctic Circumpolar Current (ACC) is dominated by the •nticyclonic subtropical gyre. In the e•stern tropical South Atlantic the cyclonic Angol • Gyre exists, embedded in • l•rge tropical cyclonic gyre. The equatorial p•rt of the South Atlantic shows several depth-dependent zonal current b•nds besides the Angol • Gyre. Ocean GCMs have difficulty capturing this detailed zonal circulation structure, even at eddy-permitting resolution. The northward extent of the subtropical gyre reduces with increasing depth, located near Brazil at 16øS in the near-surface layer and at 26øS in the Antarctic Intermediate Water layer, while the tropical cyclonic gyre progresses southward. The southward shift of the northern part of the subtropical gyr • is well resolved in global ocean GCMs. However, high horizontal resolution is required to capture the South Atlantic Current north of the ACC. The North Atlantic Deep Water in the South Atlantic progresses mainly southward in the Deep Western Boundary Current, but some water also moves southward at the eastern boundary