Modulation of decadal oscillation on surface chlorophyll in the Kuroshio Extension

Abstract

In the study, the responses of chlorophyll to decadal oscillations of Kuroshio Extension (KE) between two dynamical states are investigated using satellite data. Associated with the KE stable and unstable states, the surface chlorophyll south of 35°N also undergoes two different contrast patterns: low (high) chlorophyll (∼12% relative to multiyear mean) corresponding to strengthened (weakened) KE jet, i.e., stable (unstable) KE. Two distinct seesaw patterns exist on the north and south side of 35°N for both chlorophyll and sea level anomaly and on the east and west side of 153°E for both chlorophyll and eddy kinetic energy. Similarly, the magnitude of spring bloom was also modulated by decadal variations of KE. The spring bloom was suppressed (enhanced) relative to the magnitude of climatological spring bloom south of 35°N during the KE stable (unstable) period. This change is significant and can reach 35% in extreme years of 2006 and 2009. The decadal variation of chlorophyll in the KE is likely modulated by vertical nutrient supply induced by divergences (convergences) associated with the westward propagation of wind‐induced Rossby waves in the central and eastern North Pacific Ocean, which are dynamically modulated by the North Pacific Gyre Oscillations (NPGO) or PDO (Pacific Decadal Oscillations).