Blocked coastal propagation inhibits model representation of southeast United States coastal sea level variability

Previous studies indicate that climate models misrepresent southeast United States coastal sea level variability but do not propose a definitive mechanistic explanation. Here, by isolating a mode of variability responsible for the majority of observed nonseasonal United States East Coast (USEC) sea level variance and comparing its representation in ocean models of differing horizontal resolution, we identify a critical role for oceanic coastal propagation. At 1º horizontal resolution, southward propagation of energy is almost entirely blocked by deep coastal bathymetry near Cape Hatteras. Simulation of daily-to-monthly USEC sea level at 1º is greatly improved by decreasing the depth of coastal grid cells. It is likely that bathymetry-induced errors influence the representation of coastal sea level in other locations and over longer time scales. Improvements will require either alterations to bathymetry or higher grid resolution near coastlines.