Terrestrial Water Storage Anomalies Emphasize Interannual Variations in Global Mean Sea Level During 1997-1998 and 2015-2016 El Nino Events

Interannual variations in global mean sea level (GMSL) closely correlate with the evolution of El Nino-Southern Oscillation. However, GMSL differences occur in extreme El Ninos; for example, in the 2015-2016 and 1997-1998 El Ninos, the peak GMSL during the mature stage of the former (9.00 mm) is almost 2.5 times higher than the latter (3.72 mm). Analyses from satellite and reanalysis data sets show that the disparity in GMSL is primarily due to barystatic (ocean mass) changes. We find that the 2015-2016 event developed not purely as an Eastern Pacific El Nino event but with Central Pacific (CP) El Nino forcing. CP El Ninos contribute to a stronger negative anomaly of global terrestrial water storage and subsequent higher barystatic heights. Our results suggest that the mechanism of hydrology-related interannual variations of GMSL should be further emphasized, as more CP El Nino events are projected to occur.

Automated summary

Interannual variations in global mean sea level are closely correlated with the evolution of El Nino-Southern Oscillation, but differences occur in extreme El Ninos, primarily due to changes in barystatic heights. The 2015-2016 event developed with Central Pacific El Nino forcing, which contributed to a stronger negative anomaly of global terrestrial water storage. It is suggested that hydrology-related mechanisms of interannual variations in GMSL should be emphasized further.