Pathways and Water Mass Properties of the Thermocline and Intermediate Waters in the Solomon Sea

Abstract

he semienclosed Solomon Sea is the final passage in the equatorward transit of the South Pacific western boundary currents (WBCs) that play a key role in heat and mass budgets of the equatorial Pacific. The Solomon WBCs and their associated water properties are examined using data from two oceanographic cruises undertaken during the contrasting trade wind seasons: July 2012 and March 2014. The mean circulation and associated transports with uncertainties is determined from the cruise data using a unique configuration of an inverse box model formulated based on measured shipboard acoustic Doppler current profiler velocities. An intense inflow of 36 Sv is found entering the Solomon Sea in July?August 2012 that falls by 70% to 11 Sv in March 2014. Large differences are also found in the total transport partitioning through each of the major exit passages during each season. Different water masses are found in the WBC stream northeast of the Solomon Islands that are likely related to a northern stream of the South Equatorial Current. Within the Solomon Sea, isopycnal salinity gradients are gradually stronger than within the subtropical Pacific, likely induced by stronger diapycnal mixing processes. WBC pathways exhibit distinct water mass signatures in salinity, oxygen, and nutrients that can be traced across the Solomon Sea, associated with significant water mass modifications at the northern exit straits and south of the Woodlark Island.