Sensitivity of MPI-ESM Sea Level Projections to Its Ocean Spatial Resolution

The dependence of future regional sea level changes on ocean model resolution is investigated based on Max Planck Institute Earth System Model (MPI-ESM) simulations with varying spatial resolution, ranging from low reso-lution (LR), high resolution (HR), to eddy-rich (ER) resolution. Each run was driven by the shared socioeconomic path-way (SSP) 5-8.5 (fossil-fueled development) forcing. For each run the dynamic sea level (DSL) changes are evaluated by comparing the time mean of the SSP5-8.5 climate change scenario for the years 2080-99 to the time mean of the historical simulation for the years 1995-2014. Respective results indicate that each run reproduces previously identified large-scale DSL change patterns. However, substantial sensitivity of the projected DSL changes can be found on a regional to local scale with respect to model resolution. In comparison to models with parameterized eddies (HR and LR), enhanced sea level changes are found in the North Atlantic subtropical region, the Kuroshio region, and the Arctic Ocean in the model version capturing mesoscale processes (ER). Smaller yet still significant sea level changes can be found in the Southern Ocean and the North Atlantic subpolar region. These sea level changes are associated with changes in the regional circula-tion. Our study suggests that low-resolution sea level projections should be interpreted with care in regions where major differences are revealed here, particularly in eddy active regions such as the Kuroshio, Antarctic Circumpolar Current, Gulf Stream, and East Australian Current.

Automated summary

This study investigates the dependence of future regional sea level changes on ocean model resolution. The results indicate that each run reproduces previously identified large-scale dynamic sea level change patterns, but substantial sensitivity of the projected changes can be found on a regional to local scale with respect to model resolution. Sea level changes are enhanced in regions capturing mesoscale processes, such as the North Atlantic subtropical region, the Kuroshio region, and the Arctic Ocean. Smaller yet significant sea level changes are found in the Southern Ocean and the North Atlantic subpolar region. This study suggests that low-resolution sea level projections should be interpreted with care in regions with major differences revealed here.