Uncertainties in the Projection of Sterodynamic Sea Level in CMIP6 Models

Sterodynamic sea level (SdynSL) is an essential component of sea level that climate models can simulate directly. Here, we disentangle the impacts of intermodel uncertainty, internal variability, and scenario uncertainty on SdynSL projections from Coupled Model Intercomparison Project Phase 6 (CMIP6) models. Regarding the global mean, intermodel (scenario) uncertainty dominates before (after) similar to 2070, while internal variability is negligible. At the regional scale, intermodel uncertainty is the largest contributor, whereas internal variability plays a secondary role mainly in the tropical Indo-Pacific Ocean. Scenario uncertainty becomes significant in certain regions toward the end of this century. The anthropogenic signal of global mean SdynSL emerges at the beginning of this century relative to 1971-2000. In contrast, the anthropogenic signals of regional SdynSL are likely to emerge over 70% of the global ocean by the 2090s, which could be advanced to the 2040s if model differences can be totally eliminated.