UC San Diego

South Pacific Low Latitude Western Boundary Currents (LLWBCs) establish the major connection between the South Pacific subtropical gyre and the Equatorial Pacific. Despite their immense potential in influencing global thermohaline circulation and modulating the El Niño Southern Oscillation, South Pacific LLWBCs are largely undocumented through observations. This study provides a high-resolution investigation of the pathways and properties of the Solomon Sea’s LLWBCs using high-resolution expendable bathythermographs (HR-XBTs), Argo hydrographic surveys, and satellite altimetry. Combined Argo+HR-XBT data was used to calculate near 16-year time-mean conservative temperature, absolute salinity, potential density, dynamic height, and geostrophic velocity. Combined Argo+HR-XBT+Altimetry data was used to investigate monthly and seasonal conservative temperature, absolute salinity, and geostrophic velocity. Key findings include: (1) identification of five water masses within the Solomon Sea; (2) a shallow freshwater pool in the central Solomon Sea moving northward in austral spring; (3) southern/northern cores (~425m and ~250m depth respectively) of the Gulf of Papua Current reaching the surface when strengthened; (4) southern/northern cores of the New Guinea Coastal Undercurrent and New Guinea Coastal Current flowing at speeds 0.26m/s (~230m depth) and 0.2m/s (0-270m depth) respectively; (5) the discovery of a shallow, fast, and persistent (~0.42m/s) eastward flow in the central Solomon Sea; (6) flow speeds near 0.38m/s for the Solomon Strait inflow; (7) the New Britain Coastal Undercurrent (~0.24m/s between 260-450m depth) connects to an eastward surface flow from June-November; (8) a highly variable and indistinct New Ireland Coastal Undercurrent; (9) improved understanding of the flow reversals and subsurface flows from ~3°S-1°S.