Geopotential Topographies and Associated Circulation in the Western South Pacific Ocean

Abstract

Geopotential topographies of the surface and several subsurface depths are drawn from observations on three cruises of H.M.A.S. Gascoyne in the waters of the western South Pacific Ocean in 1960 and 1961. The associated circulation is discussed. Surface circulation is found to be in agreement with the topographies only in the major current branches, while wind-induced currents do not show in the topographies. The inflow into the region occurs from the east between 25º S. and the Solomon Islands. It is stronger in subsurface layers than at the surface. A comparison with five cruises made by the Institut Franpais d'Oceanie in Noumea into the region between Kew Caledonia and the Solomons shows a permanent inflow in layers between 100 and 700 m, while the geostrophic circulation at the surface is very variable. The outflow from the region is effected by a current in the Tasman Sea between 30º and 36º S. flowing east and leaving the region north of New Zealand. Between Tasmania and New Zealand an outflow to the south occurs, reaching to 1200 m depth. The East Australian Current continues as an eddy system as far south as Tasmania. The calculated current pattern agrees in all parts with the circulation as derived from water mass analysis.