In physical oceanography, a water mass in the Antarctic Zone of the Southern Ocean AASW is found in the upper 200 m south of the Polar Front (PF) and is cold, fresh, and high in oxygen and nutrients relative to the subantarctic surface waters, although it is high in nutrients compared to underyling waters. The most easily distinguishable characteristics of AASW in summer sections is a intense temperature minimum at about 200 m that marks the base of the winter mixed layer. The water around this minimum is also commonly known as Winter Water, and ranges from 50 m deep in the Weddell Gyre to nearly 1000 m just north of the PF. It is characterized by very low temperatures ranging down to the freezing point of -1. 9° C and low salinities as the result of ice melting in the summer in the upper 100-250 m of the water column.