Wintertime sea surface temperature front around the Kuroshio Extension and its impact on North Pacific blocking

Abstract

AbstractThe influence of the wintertime sea surface temperature (SST) fronts around the Kuroshio Extension (KE) on North Pacific blocking is analysed using observational and reanalysis data. The dipole pattern of sea surface height anomalies in the KE induces opposite changes in the Kuroshio and Oyashio Extension SST front (KOEF) and the KE SST front. Composite analysis shows that the KOEF may affect the frequency, duration, location, intensity and movement of wintertime North Pacific blocking. A strong (weak) KOEF tends to inhibit (promote) the genesis of atmospheric blocking, which might be due to intensified (weakening) background mid‐latitude zonal wind. In weak‐KOEF years, blocking tends to have a long life cycle, quasi‐stationary state and intensified amplitude. However, when the KOEF is strong, the blocking high tends to move continuously westward with a weakened amplitude. A strong KOEF is conducive to a strengthened anomalous turbulent heat flux release over the front region, localized anchoring of the cut‐off low, and the forcing of a change in the intensity and movement of the blocking dipole. Also investigated are the contributions to cold spells over North America attributable to the North Pacific blockings link with the KOEF.