The impact of storm surges on ocean tides: insights from numerical simulations

The interaction between tides and storm surges can significantly affect shallow water regions with large tidal ranges. In modelling studies, including the atmospheric forcing, which drives the storm surge estimations within the model, can result in changes to the amplitudes and phases of the major tidal constituents. In certain regions, this can have severe impacts on the tidal predictions. A standard product used to provide the atmospheric forcing is the ERA5 product developed at ECWMF. Previous studies have shown the presence of tidal constituents within the sea level pressure data provided by ERA5 used in various applications. For example, the commonly used Dynamic Atmospheric Correction derived from these data, which is used to correct satellite altimetry measurements for the atmospheric influence on the radar returns, has been shown to significantly impact the estimation of ocean tides from satellite altimetry.  The Global Tide and Surge Model (GTSM), developed at Deltares, allows for the global estimation of ocean tides with and without atmospheric forcings. This presents the possibility of evaluating the influence of storm surges on the estimation of individual tidal constituents and the resultant prediction of tidal heights. In this poster, three model simulations are produced, which are as follows: an ocean tide-only version, a storm surge-only simulation and a tide plus storm surge version. The eight major tidal constituents are evaluated globally to assess the changes in their respective amplitudes and phases. Finally, several case studies are presented in regions with high influence on the individual constituents by evaluating the results of the tidal predictions with respect to in-situ measurements.