An Interhemispheric Tropical Sea Level Seesaw due to El Nino Taimasa

During strong El Nino events, sea level drops around some tropical western Pacific islands by up to 20-30 cm. Such events (referred to as taimasa in Samoa) expose shallow reefs, thereby causing severe damage to associated coral ecosystems and contributing to the formation of microatolls. During the termination of strong El Nino events, a southward movement of weak trade winds and the development of an anomalous anticyclone in the Philippine Sea are shown to force an interhemispheric sea level seesaw in the tropical Pacific that enhances and prolongs extreme low sea levels in the southwestern Pacific. Spectral features, in addition to wind-forced linear shallow water ocean model experiments, identify a nonlinear interaction between El Nino and the annual cycle as the main cause of these sea level anomalies.