In physical oceanography, a water mass in the Subantarctic Zone of the Southern Ocean. This is one type of Subpolar Mode Water. The SAMW is the deep surface layer of water with uniform temperature and salinity created by convective processes in the winter. It can by identified by a temperature of around -1.8° C and a salinity of around 34.4 and is separated from the overlying surface water by a halocline at around 50 m in the summer. Although it is not considered to be a water mass, it contributes to the Central Water of the southern hemisphere, and is additionally responsible for the formation of AAIW in the eastern part of the south Pacific Ocean. This has also previously been called Winter Water.