Antarctic bottom water

The Antarctic bottom water (AABW) is a type of water mass in the Southern Ocean surrounding Antarctica with temperatures ranging from −0.8 to 2 °C (35 °F) and absolute salinities from 34.6 to 35.0 g/kg.^[1] As the densest water mass of the oceans, 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.^[2] AABW forms the lower branch of the large-scale movement in the world's oceans through thermohaline circulation.

AABW forms near the surface in coastal polynyas along the coastline of Antarctica,^[3] where high rates of sea ice formation during winter leads to the densification of the surface waters through brine rejection.^[4] Since the water mass forms near the surface, it is responsible for the exchange of large quantities of heat and gases with the atmosphere.^[5] AABW has a high oxygen content relative to the rest of the oceans' deep waters, but this depletes over time. This water sinks at four distinct regions around the margins of the continent and forms the AABW; this process leads to ventilation of the deep ocean, or abyssal ventilation.^[6]