Variability of Subsurface and Intermediate Currents in the Western Equatorial Pacific Ocean and Their Impacting Factors

Based on direct current measurements by ADCP moorings conducted during 2014-2018, seasonal-to-interannual variabilities of the Western Equatorial Pacific currents in different depth layers are analyzed. GODAS, Tropflux and NCEP reanalysis2 data are used to study the climatological factors influencing the current variabilities. The results show that both Equatorial Under Current (EUC) and Equatorial Intermediate Current (EIC) have significant seasonal-to-interannual variabilities. Both are closely related to the ENSO cycle, but through different mechanisms. Variations of the zonal velocity of Western Pacific EUC have noticeable correlations with subtropical SST, SLP and wind velocity, suggesting an influence of the Pacific meridional mode. The EIC, however, changes basically in corresponding to the Pacific zonal mode (ie. canonical ENSO mode). ENSO signals of the Eastern Equatorial Pacific might impact the Western Pacific EIC through vertical propagation of Rossby wave. This study gives an example on how atmospheric signals influence the subsurface ocean currents up to 800m depth.