Antarctic bottom water
From AMS Glossary
Antarctic Bottom Water
(Abbreviated AABW.) A water mass formed by deep winter convection at the coast of Antarctica, particularly in the Weddell and Ross Seas but also at other shelf locations.
Being the densest water mass of the World Ocean, AABW is found to occupy the depth range below 4000 m of all ocean basins that have a connection to the Southern Ocean at that level. At the time of formation its temperature is close to the freezing point (-1.9°C), but to enter the oceans, AABW has to pass through and mix with the water of the Antarctic Circumpolar Current, which gives it its typical salinity of 34.7 psu and temperature of +0.3°C. Because of this it is also known as Antarctic Circumpolar Water, particularly in the Indian and Pacific Oceans.