Earth oblateness changes reveal land ice contribution to interannual sea level variability

A broad consensus has emerged regarding the importance of both ocean mass and heat content changes for global sea level (GSL) rise, but their respective contributions to interannual GSL variability are less certain. Here, we use changes in the Earth's dynamic oblateness (J₂) to infer land ice contributions to GSL variability during a 10.5-year period encompassing the intense 1997-98 ENSO event. By accounting for heat content and water mass distribution changes in the oceans, atmosphere and land hydrology using observational and model results, we isolate unexplained residuals in J ₂ and GSL that are well-correlated with each other and with melt-season temperature and mass balance anomalies in Alaska, a particularly active and well-studied glaciated region. The close agreement between residual GSL and oblateness variations found in our results indicates that the latter can provide a useful proxy for changes in high-latitude land ice when corrections for other sources are applied.