How does Antarctic Bottom Water form?

Antarctic Bottom Water (AABW) is a dense, cold water mass that forms primarily along the continental margins of Antarctica, most notably in the Weddell Sea and the Ross Sea, during the southern winter.12

The formation process is driven by the following mechanisms:

• Surface Cooling and Convection: The Antarctic Circumpolar Current brings deep water to the surface, where it is exposed to frigid Antarctic air. This intense cooling increases the water's density, triggering convective overturning.2
• Brine Rejection: As seawater freezes to form sea ice, salt is largely excluded from the ice structure. This process, known as brine rejection, significantly increases the salinity of the remaining water beneath the ice.13
• Sinking: The resulting water is both extremely cold and highly saline, making it dense enough to sink to the deep seafloor. Once it reaches the bottom, this Antarctic Bottom Water flows northward, spreading across the global ocean basins.132