Australasian Southern Ocean frontal stucture during summer 1976-77

Abstract

Fourteen north-south expendable bathythermograph temperature sections are used to define the positions of the Subtropical Convergence, the Subantarctic Front and the Polar Front in the Australasian sector of the Southern Ocean. The data were collected by supply vessels sailing to the Antarctic mainland during the austral summer of 1976-77. Frontal features are identified on the basis of both temperature structure and observations of surface salinity. The Polar Front is found to be more convoluted than the other fronts, leading to wide and narrow sections of the Antarctic Polar Frontal Zone between it and the Subantarctic Front. South-west of Australia the Subantarctic Front shifts north along with the Subtropical Convergence, and the Antarctic Polar Frontal Zone is at its widest. East of a southward shift of all three fronts, south of eastern Australia, they separate to give almost equal separations of about 700 km between fronts south-east of New Zealand. The homogeneous Subantarctic Mode Water between the Subantarctic Front and the Subtropical Convergence is found to be progressively warmer towards the west. Though the data is not truly synoptic, being spread over 3½ months, it does reflect the frontal structure during the period of observation.