Circumpolar properties of Antarctic intermediate water and Subantarctic Mode Water

Abstract

Antarctic Intermediate Water and Subantarctic Mode Water are studied by examining their modal density and modal salinity characteristics around Antarctic. The study focuses on 15 regions between 40 and 45°S. Circumpolar distributions for the cores of Antarctic Intermediate and Subantarctic Mode Water and potential temperature-salinity diagrams provide a detailed description of the water masses. The modal salinity and density change gradually across each of the three oceans, presumably due to the alteration of a single water mass. Large changes occur in the transition regions in the Drake Passage, south of Africa, and south of New Zealand. These large changes are due to the presence of distinctly different water masses. Thermohaline finestructure is associated with the water mass transitions. The finestructure intensity between the 27.10 and 27.40 σ θ isopycnals is quantified. Although continuous temperature-depth data are not available for the entire region the study indicates that the most intense finestructure occurs in regions of large water mass contrast and decreases by an order of magnitude away from them. Increased vertical temperature gradient variances were observed near a 100-km diameter eddy south of New Zealand.