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The low-amplitude, large-scale, interannual, and longer-term sea level changes are linked to the variations of ocean heat and freshwater content and strongly controlled by ocean dynamics. Near the coast, especially in low-lying and flood-vulnerable regions, these changes can provide background conditions favorable for the occurrence of extreme sea levels that represent a threat for coastal communities and ecosystems. In this study, we identify a tripole mode of the ocean gyre-scale sea surface height variability in the North Atlantic and show that this mode is responsible for most of the interannual-to-decadal sea surface height changes along the southeast coast of the United States, including the Gulf of Mexico. We also show that these changes are largely driven by the large-scale heat divergence related to the Atlantic Meridional Overturning Circulation and linked to the low-frequency North Atlantic Oscillation.

Plain Language Summary The global mean sea level rise caused by ocean warming and terrestrial glacier melting is one of the most alarming aspects of climate change. However, ocean and atmosphere dynamics make sea level change spatially and temporally nonuniform. In fact, the ocean exhibits certain patterns of sea level change with alternating signs over different time periods. These patterns provide background conditions, on top of which shorter-period and often stronger weather-driven sea level fluctuations are superimposed. In order to improve our capacity to predict regional sea level variability, it is important to identify these patterns and to explore the mechanisms responsible for their evolution. In this study, we identify such a pattern in the North Atlantic Ocean and show that it is largely responsible for year-to-year changes of coastal sea level south of Cape Hatteras and in the Gulf of Mexico. These coastal regions of the United States are particularly vulnerable to extreme weather conditions, such as tropical storms and hurricanes, that can cause catastrophic flooding. We show that the temporal evolution of the identified pattern is due to the basin-scale ocean heat content changes in the North Atlantic, driven by changes in the large-scale ocean and atmosphere circulations.