May 9, 2021
The Solomon Sea, in the western tropical Pacific, is part of a major oceanic pathway for waters connecting the tropics to the equator via low latitude western boundary currents. Shipboard Acoustic Doppler Current Profiler data from 94 various cruises and transits are used to describe the Solomon Sea mean circulation and its seasonal variability above 300 m depth, providing an unprecedently detailed picture from observations. The circulation in the near-surface (20-100 m) and thermocline (100-300 m) layers were analyzed separately but found to have many similar features. They are compared with circulations inferred from hydrological and satellite data. The New Guinea Coastal Undercurrent enters the Solomon Sea east of the Louisiade Archipelago (15 Sv inflow above 300 m), splits and rejoins around the Woodlark Chain, then divides against the coast of New Britain forming two branches flowing westward and eastward. The westward branch has been previously observed flowing through Vitiaz Strait; in the present SADCP data this transport is found to be 7-8 Sv in the upper 300 m. The eastward branch has been suspected and occurs in some models; it exits the Solomon Sea through St. George’s Channel (1-2 Sv) and Solomon Strait (4-5 Sv) in the thermocline. At the surface, waters enter the Solomon Strait from the north. The seasonal variability can be documented in locations of sufficient data coverage. It is shown that this western boundary system strengthens in June-August. A summary of transport variability in the straits of the Solomon Sea from individual cruises is also presented. Transports in the straits display some stable features, but also high non-seasonal variability.