Connections of the western tropical Pacific-North Pacific across the 1998/99 regime shift

In this study we examined the role of the western tropical Pacific in changing SST variability in the western North Pacific across the 1998/99 regime shift during boreal winter (December-January-February). It was found that the western North Pacific SST variability is associated differently with the SST variability in the western tropical Pacific before and after 1998/99, in the North Equatorial Current (NEC) bifurcation region (8°N-18°N, 125°E-160°E) in particular. The NEC bifurcation region experiences a regime shift from a cooling to a warming across the 1998/99. Consequently, the Kuroshio current, which originates in the NEC bifurcation region, could transport the anomalous warm water into the North Pacific. Before 1998/99, the SST variability in the western North Pacific including the Kuroshio current and its extension was negatively correlated with the SST variability in the NEC bifurcation region. Conversely, there was no systematic relationship between the western North Pacific and the NEC bifurcation region after 1998/99. We speculate that an alteration in the atmospheric teleconnections from the tropics to the North Pacific after 1998/99, which might have been associated with the regime shift in the Pacific across the 1998/99, caused the changes in the relationship between the western tropical Pacific and North Pacific SST variability.