Antarctic Bottom Water
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The Antarctic Bottom Water (AABW) is a type of water mass 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. AABW is formed in the Weddell and Ross Seas from surface water cooling in Polynyas and below the ice shelf. Surface water is enriched in salt from sea ice formation. Due to its increased density, the water is flowing down the Antarctic continental margin and on the bottom further north. It is the densest water in the free ocean and 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.
About one-third of the northward flowing AABW enters the Guiana Basin, mainly through the southern half of the Equatorial Channel at 35°W. 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. At 44°W, north of the Ceara Rise, AABW flows west in the interior of the basin. A large fraction of the AABW enters the eastern Atlantic through the Vema Fracture Zone.
