Observational-based quantification of physical processes that impact the evolution of global mean sea level

Abstract. The global mean sea level (GMSL) rise budget can be closed by integrating over global density distribution to account for ocean expansion, combined with satellite altimetry and ice sheet mass balances obtained from satellites and models. Such methods are of great importance, but the disadvantage is that they gloss over the individual fundamental physical processes that impact the evolution of GMSL. Such process are for example (but not limited to) the impact of ocean mixing and stirring, neutral physics, shortwave radiation and boundary heat and freshwater fluxes. It is valuable to quantify these processes as it provides understanding in the fundamental processes behind the observed GMSL rise and how these processes may change and in a transient ocean and climate. This study estimates the contribution of individual physical processes contributing to GMSL rise, using observational based products. It is not the intention and neither possible at this stage, to close the GMSL budget by means of this approach. Instead the results allow us to gain insights in the magnitude and uncertainty of processes and their relative importance in shaping GMSL rise, and allows for a comparison of the impact on GMSL by single processes or parameterizations. Results indicate the great uncertainty related to boundary heat, mass and freshwater fluxes, and the importance of ocean mixing for GMSL rise. Unexpected results are the significant impact of shortwave radiation depth penetration parameterizations and the way by which neutral physics is implemented. Many of the results are of importance for observational-based calculations as well as for modelers that have specific choices to make about which method and parameterizations they choose. These choices significantly impact the accuracy of predicted future sea level rise upon which policy will be based.