Spatiotemporal properties of intrinsic sea level variability along the Southeast United States coastline

Abstract. The influence of intrinsic ocean variability on coastal sea level remains largely unexplored but is of potential importance for emerging forecasting efforts. As in weather forecasts, intrinsic variability will amplify uncertainty in initial conditions. However, variability originating from intrinsic processes may be predictable in a forecast system with sufficient resolution and accurate initialization. Here, we examine the spatiotemporal properties of intrinsic sea level variability along the Southeast United States coast using a suite of global ocean/sea-ice simulations at 0.1° horizontal resolution. In model simulations, intrinsic variability is a dominant component of the monthly de-seasonalized and detrended sea level variability in deep waters, but it is damped along continental shelves, where it comprises ~10–30 % of the sea level standard deviation. Our analyses demonstrate that US East Coast and Gulf of Mexico shelves exhibit a common intrinsic mode of sea level variability, with maximal amplitude in the South Atlantic Bight and almost no expression north of Cape Hatteras. This coastal mode is coherent with sea level along the Gulf Stream axis after detachment from Cape Hatteras. Intrinsic sea level variability in the detached Gulf Stream leads the coastal mode by 2–3 months, suggesting that intrinsic coastal sea level variability may exhibit predictability.