Sea level anomalies in the northwestern Pacific during 2011 associated with La Niña and negative Indian Ocean Dipole

The sea level anomalies (SLAs) pattern in the northwestern Pacific delineated significant differences between La Nina events occurring with and without negative Indian Ocean Dipole (IOD) events. During the pure La Nina events, positive the sea surface level anomalies (SLAs) appear in the northwestern Pacific, but SLAs are weakened and negative SLAs appear in the northwestern Pacific under the contribution of the negative IOD events in 2010/2011. The negative IOD events can trigger significant westerly wind anomalies in the western tropical Pacific, which lead to the breakdown of the pronounced positive SLAs in the northwestern Pacific. Meanwhile, negative SLAs excited by the positive wind stress curl near the dateline propagated westward in the form of Rossby waves until it approached the western Pacific boundary in mid-2011, which maintained and enhanced the negative phase of SLAs in the northwestern Pacific and eventually, it could significantly influence the bifurcation and transport of the North Equatorial Current (NEC).