The subduction and propagation of subsurface salinity anomalies in the northwestern Pacific

The subsurface ocean signal propagation from subtropics to tropics has been reported to play a vital role in low-frequency climate variability. In this study, monthly gridded temperature and salinity datasets based mainly on Argo profiles for 2003-2012 are used to investigate the subduction and propagation of salinity anomalies along the =24.5-25.4kg.m^-3 isopycnals in the northwestern Pacific. Statistical results as well as case studies suggest that prominent salinity anomalies generated in the northwestern subtropical outcropping area (30-35°N,130-160°E), with their maximum magnitude of about 0.15 PSU, can be subducted in late winter and advected to the eastern Luzon Strait (15°N,130°E) by southwestward subtropical circulation in roughly one year. In contrast to anomalies generated in the northeastern subtropical Pacific that propagate slowly and dissipate strongly, these anomalies have a noticeable signature along their propagation pathway and quickly impact the subsurface thermohaline structure in the western boundary.