Premium
Asymmetry of Interannual Sea Level Variability in the Western Tropical Pacific: Responses to El Niño and La Niña
Author(s) -
Ren Qiuping,
Li Yuanlong,
Zheng Fei,
Wang Fan,
Duan Jing,
Li Rui
Publication year - 2020
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1029/2020jc016616
Subject(s) - upwelling , climatology , anomaly (physics) , el niño southern oscillation , asymmetry , environmental science , sea surface temperature , longitude , sea level , oceanography , boundary current , geology , trade wind , tropical eastern pacific , atmospheric sciences , pacific ocean , latitude , ocean current , physics , geodesy , quantum mechanics , condensed matter physics
The western tropical Pacific (WTP) exhibits pronounced large‐scale sea level anomalies (SLAs) during El Niño‐Southern Oscillation (ENSO) events with amplitudes of ~0.1 m, exerting potential threats to many low‐lying islands. It is found that the sea level falling in El Niño condition is evidently stronger than the rising in La Niña condition. This SLA asymmetry in the WTP associated with ENSO is investigated in this study, and the underlying dynamic processes are explored. Such asymmetry is most prominent at around 160°E with the SLA response to El Niño being three times stronger than to La Niña, but it is much inconspicuous near the western boundary. Sensitivity experiments of a simplified ocean model suggest that the different structures of surface wind anomalies between El Niño and La Niña conditions are critical in generating asymmetric SLA responses of the WTP. The El Niño's westerly wind anomaly patch locates more to the east than the La Niña's easterly wind patch during the mature stage, and its upwelling effects are accumulated over a wider longitude range and cause stronger negative SLAs in the WTP. Near the western boundary, however, upwelling effects are attenuated by easterly wind anomalies during the mature stage of El Niño. Further analysis reveals that eastern Pacific‐type El Niño events are more favorable for generating asymmetric SLAs in the WTP than the central Pacific‐type events.