Origin of Interannual Variability in Global Mean Sea Level

The two dominant drivers of the GMSL variability at interannual to decadal timescales are steric changes due to changes in ocean heat content and barystatic changes due to the exchange of water mass between land and ocean. With GRACE satellites and Argo profiling floats, it has been possible to measure the relative steric and barystatic contributions to GMSL since 2004. While efforts to “close the budget” with satellite altimetry have been largely successful with regards to trends, the short time period covered by these records prohibits a full understanding of the drivers of interannual to decadal variability in GMSL. One particular area of focus is the link between variations in the El Nino-Southern Oscillation (ENSO) and GMSL, with recent literature disagreeing on the relative importance of steric and barystatic contributions to interannual to decadal variability in GMSL. Here, we use a novel multivariate data analysis technique to estimate variability in barystatic and steric contributions to GMSL back to 1982. These independent estimates explain the observed interannual and decadal variability in satellite altimeter-measured GMSL. Both processes, which are highly correlated with ENSO variations, contribute about equally to observed interannual and decadal GMSL variability. A theoretical scaling analysis corroborates the observational results. The improved understanding of the origins of interannual to decadal variability in GMSL established here has important implications for our understanding of long-term trends in sea level, the hydrological cycle, and the planet’s radiation imbalance.