Interannual variability of the subtropical countercurrent eddies in the North Pacific associated with the Western-Pacific teleconnection pattern

Abstract

The connection and the relevant dynamical processes between oceanic eddies in the North Pacific Subtropical Countercurrent (STCC) region and the atmospheric Western-Pacific (WP) teleconnection is investigated on interannual timescales. North of the STCC region, the local northerly surface wind anomalies cool the ocean surface during negative phases of the WP teleconnection. The local surface cooling modifies the meridional gradient of sea surface temperature (SST), strengthening the SST front at its south. In the STCC region, we show the meridional gradient of surface-heat-flux forcing caused by the local surface cooling is the same order as the Ekman-convergence forcing. The strengthened SST front then leads to the pycnocline shoaling in the STCC region, which can also enhance the growth of baroclinic instability to produce more oceanic eddies, in addition to the enhanced STCC proposed previously. These dynamics are reversed during the positive phases of WP teleconnection.