Sensitivity of SSP585 sea-level projections to ocean model resolution in the MPI-ESM climate model

The existence of reliable coastal sea-level projections is essential for identifying necessary adaptation and mitigation strategies of policymakers and coastal communities over the following decades. However, today only a few ocean components of climate projections can resolve the small-scale processes that affect the Dynamic Sea Level (DSL) change in the open ocean and in coastal areas, predominantly in the eddy rich regions such as Antarctic Circumpolar Current (ACC) and the western boundary currents. Therefore, we investigate the dependence of regional sea-level projections on ocean model resolution using the recent Max Planck Institute Earth System Model (MPI-ESM) for the shared socioeconomic pathway 585 (SSP585, fossil-fuel development). By comparing the climate change scenario from 2080 to 2099 to a historical simulation from 1995 to 2014, our results indicate that the models, from eddy-rich (ER), eddy-permitting (HR) to coarser resolution (LR), successfully produce the previously identified global DSL patterns. However, the magnitude of the DSL increase in the North Atlantic subpolar gyre and the decrease in the subtropical gyre is significantly larger in the ER ocean in contrast to HR and LR; the same holds for the magnitude of the opposite dipole pattern in the North Pacific. In the southern ocean, the DSL increases north of ACC but decreases further to the south, projecting much smaller changes in the ER. We note that the meridional shift of ACC, associated with sea-level change, is smaller in ER than in HR and LR, indicating an accelerated ACC compared to HR simulation, which shows no acceleration at the end of the 21st century.