A type of water in the seas surrounding Antarctica with temperatures ranging from 0 to -0. 8° C, salinities from 34. 6 to 34. 7, and a density near 27. 88. ABW is formed in the Weddell and Ross Seas. This is the densest water in the free ocean, with the only denser waters being found in regional sill basins such as the Norwegian Sea or the Mediterranean. It is overlain by Antarctic Circumpolar Water (AACW) at a depth of 1000 to 2000 m and overlies Weddell Sea Bottom Water (WSBW) in some locations.

The flow of AABW in the tropical Atlantic is described by Rhein et al. (1998) as:

About one-third of the northward flowing AABW at 10°S (4. 8 Sv) and at 5°S (4. 7 Sv) west of about 31°30'W enters the Guiana Basin, mainly through the southern half of the Equatorial Channel at 35°W (1. 5-1. 8 Sv). The other part recirculates and some of it flows through the Romanche Fracture Zone into the eastern Atlantic. In the Guiana Basin, west of 40°W, the sloping topography and the strong, eastward flowing deep western boundary current might prevent the AABW from flowing west: thus it has to turn north at the eastern slope of the Ceara Rise (2. 2 Sv). At 44°W, north of the Ceara Rise, AABW flows west in the interior of the basin in a main core near 7°15'N (1. 9 Sv). A net return flow of about 0. 5 Sv was found north of 8°43'N. A large fraction of the AABW (1. 1 Sv) enters the eastern Atlantic through the Vema Fracture Zone, leaving only 0. 3 Sv of AABW for the western Atlantic basins.