Subantarctic Mode Water (SAMW)

Subantarctic Mode Water (SAMW) is a thick, weakly stratified water mass formed by deep wintertime convection on the equatorward side of the Subantarctic Front, where a deep mixed layer homogenizes temperature and density over hundreds of meters. It is subducted into the subtropical gyres of all three Southern Hemisphere oceans as a near-uniform layer, recognized by low potential vorticity. SAMW is the precursor of Antarctic Intermediate Water and the main pathway by which the Southern Ocean ventilates the thermocline, taking up heat, oxygen, and anthropogenic carbon.