Multi-Decadal Modulation of Tropical Pacific Instability Wave Activity since the Middle of the Twentieth Century

Abstract

Modulation of the Pacific tropical instability waves (TIWs) is investigated from 1950 to 2007 using high-resolution ocean data assimilation. So far, detecting their multi-decadal variations is difficult due to the lack of a fine-scale observation network. The results of our high-resolution general circulation model indicate that the Pacific TIW activity increased rapidly after the early 1990s, because a precedent intensified subsurface temperature front north of the cold tongue associated with the mid-1970s' climate shift positively influenced the baroclinic source. This intensified subsurface meridional temperature gradient related to a warm phase of the tropical Pacific decadal variability associated with cold anomalies along the subsurface thermocline which contribute to decay of the surface warm phase, characterized by wide-spread meridional warm anomalies and upwelled cold anomalies along the equator.