Accurate prediction of the extreme sea levels (ESLs) that cause coastal-urban flooding requires high horizontal mesh resolution (O(100 m)) in order to resolve the complexities of estuaries and floodplains. The surface gravity wave dynamics of ESLs, which result from the combination of tides and storm surge, are well-described by depth-integrated, barotropic models that can reasonably provide the required resolution due to their two-dimensional nature. However, this level of resolution is infeasible for the ocean general circulation models (OGCMs) used for global Earth system modeling. OGCMs are essential for describing the thermohaline circulation that drives subtidal variations in mean sea level (MSL) and the fluxes from terrestrial and cryospheric sources that contribute to longer-term sea level change. Understanding the interaction of MSL and ESLs in a changing climate is essential for producing actionable science that can assist stakeholders in mitigating the evolving risks of coastal flooding, which affect a significant fraction of the U.S. population. In support of this goal, we are developing a novel, multi-resolution barotropic-baroclinic two-way coupling that will help bridge the global and coastal scales and enable accurate predictions of future coastal water levels within E3SM. This capability is being built to help support E3SM’s long-term objectives related to coastal inundation due to extreme storms and sea level rise.