A Climatological Interpretation of the Circulation in the Western South Pacific

Abstract

Time-averaged circulation is examined using historical hydrographic data near the Australia and Papua New Guinea coast in the Pacific. By averaging the data along isopycnal surfaces in a 0.5° ? 0.5° grid, the authors are able to show many detailed phenomena associated with the narrow western boundary currents, including the vertical structure of the bifurcation latitude of the South Equatorial Current (SEC) and the connection between the Solomon and Coral Seas. The bifurcation latitude of the SEC is found to move southward from about 15°S near the surface to south of 22°S in the intermediate layers. The origin of the Great Barrier Reef Undercurrent (GBRUC) is identified to be at about 22°S. Farther to the north, the GBRUC intensifies underlying the surface East Australian Current, and merges with the North Queensland Current (NQC) at about 15°S. The NQC turns eastward to flow along the Papua New Guinea coast and feeds into the New Guinea Coastal Undercurrent (NGCUC) through the Louisiade Archipelago. Further analysis shows that there is a strong water property connection between the Coral and Solomon Seas, confirming the earlier speculation on the water mass origins of the NGCUC.