The signal of La Niña in wave transport

La Niña phenomena have significant impact on extreme weather and marine disasters in China. Large-scale water transport is one of the primary factors affecting the development of La Niña events; however, the contribution of swell transport from the Southern Ocean to the sea surface temperature anomaly (SSTA) in the eastern equatorial Pacific (EEP) has been ignored in previous studies. Through various statistical techniques, this study used seven sets of satellite altimeter and reanalysis data to reveal the relationship between swell transport and La Niña. Based on the characteristics of significant SSTA changes in the Niño 3 region (5°S-5°N, 90°-150°W) following an El Niño event, two cases of La Niña and non-La-Niña were defined. Wave transport in the first case presents an anomaly to the north of the 30°S section, i.e., cold water carried by swell transport to the EEP increases prior to the onset of a La Niña event. However, the characteristics of swell transport in the non-La-Niña scenario are contrary to the first case. Wave transport anomalies in the two considered cases produce sufficient and necessary conditions for the development of La Niña and non-La-Niña events. In addition, the impact of swell transport from the westerlies on La Niña events is confirmed further based on heat flux calculations. Wave transport has considerable effect on SSTA variability in the EEP; therefore, it should not be neglected in future studies.