Deep currents of the northern Tasman Sea Basin

Abstract

Off the southeast Australian cost in the Tasman Basin, north of 40°S, the deeper structure obtained from hydrological data is highly correlated with the surface flow, especially in the region east of Sydney where the East Australian Current forms southwards meanders that often break off to form large, warm-core rings. This indicates that the East Australian Current and its warm-core rings have a dominant influence on the baroclinic flow down to abyssal depths. Typical current shears below 2000 m are estimated to be of order 4 cm s−1 km−1. Further north, between 30 and 32.5°S, the correlation between deep and shallow structure is of similar magnitude and there is a definite correlation between parameters of the deep flow and distance offshore. It is concluded that the correlation is due to an east-west tilt of the surface of no motion. Still further north, no significant correlations exist between the deep structure and either distance offshore or shallow structure parameters. No evidence has been found for a swift, narrow, western boundary undercurrent in the Tasman Sea north of 40°S.