| Summary: | Vita. Descriptions of the characteristic relations, vertical structure and lateral spreading of Antarctic Bottom Water within the four major oceanic basins adjacent to Antarctica are presented. Three major layers of Antarctic Bottom Water are identified. Boundaries between these layers occur near the surfaces where the potential densities referenced to 4000 db (σ₄) are 46.08 mg cm⁻³, 46.15 mg cm⁻³ (46.12 mg cm⁻³ in the Macquarie Ridge-Balleny Islands complex and western Southeast Pacific Basin) and 46.21 mg cm⁻³. These isopycnal surfaces are associated with strata of maximum stability and slope changes in the characteristic relations. The densest layer of Antarctic Bottom Water (σ₄ (greater than or equal to) 46.21 mg cm⁻³) occurs in two separate regions. In the central and western Atlantic-Indian Basin, this layer is comprised of Weddell Sea Bottom Water, characterized by low potential temperature (< 0.8 °C), salinity (34.63-34.67 °/ (two lower degree symbols)) and dissolved silicate concentration (<100 μM) and by high dissolved oxygen concentration (>5.7 ml/l). Over the southern Macquarie Ridge, this layer contains Ross Sea Bottom Water, marked by low potential temperature (-0.6 to -0.3 °C) and dissolved oxygen (5.5 to 5.7 ml/l). A part of the Ross Sea Bottom Water flows south of the Balleny Islands and into the South Indian Basin where it mixes with Adelie Coast Bottom Water. East of the Balleny Islands, the other part of the Ross Sea Bottom Water flows northward along the southern Macquarie Ridge and is rapidly mixed with Antarctic Bottom Water flowing eastward from the South Indian Basin.
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