Impacts of the East Atlantic pattern on the interannual sea level variability along the U.S. eastern seaboard

Understanding the causes of coastal sea level variations at different time scales is necessary for predicting future coastal impacts and improving coastal resilience, especially in regions such as the U.S. East Coast, which currently experiences sea level rise at rates larger than the global mean, and is also prone to frequent nuisance flooding and extreme weather events. At interannual time scales, sea level variations along the United States (U.S.) East Coast north of Cape Hatteras have been shown to be largely driven by local changes in atmospheric pressure and alongshore wind patterns (Piecuch et al., 2019). While atmospheric conditions also play a role south of Cape Hatteras, sea level changes along the southeast U.S. coast have been primarily linked to the gyre-scale oceanic heat divergence modulated by the low-frequency North Atlantic Oscillation (NAO) (Volkov et al., 2019), which is the large-scale leading mode of atmospheric variability in the North Atlantic. In this study, we highlight the role of the East Atlantic (EA) pattern, the second leading mode of surface atmospheric variation over the North Atlantic, in driving significant interannual coastal sea level fluctuations. Based on satellite altimetry data, here we show that the interannual sea level variability attributable to the EA during 1993-2017 can explain a significant amount of the total sea level variance that is, to a good extent, comparable to the variance explained by the NAO-induced sea level changes. Our results further suggest that the EA-modulated changes in wind stress curl and associated Sverdrup dynamics are largely responsible for the relevant interannual coastal sea level fluctuations. Comparisons between observed interannual sea level variations from discrete monthly tide gauge records along the U.S East Coast and the EA-induced sea level changes will be also presented.