A study of the wave effects on the current circulation in Galway Bay, using the numerical model COAWST

A model coupling waves and currents is set up for Galway Bay, Ireland, using COAWST. The impact of the coupling on the accuracy of the model is shown to be marginal on the overall statistics. The model is in good agreement with the available in-situ observations that are used for the validation. However a closer look at the data during storms shows a deterioration of the agreement, which is barely improved by the coupling. A special analysis of the different processes ruling the ocean circulation is conducted during Storm Hector (2018/06/14). It shows a strong 7cm wave-induced surge in the back of Galway Bay, and a strong response in terms of currents along the coast of Clare, about 30cms−1. Most of the surge is attributed to the impact of the conservative wave-induced Stokes drift forcing. The response in currents is partly attributed to the Stokes drift forcing terms, but mostly to the wave-enhanced surface roughness. In both cases waves induce an additional transport of mass or momentum, which is then subject to the particular characteristics of the bay. •Wave–current interaction is only strong inside Galway Bay during storm events.•Wave–current interaction is strongly spatially localised.•Main effects are caused by the Stokes drift and enhancement of the surface roughness.•A significant wave-induced surge is observed near Galway City during Storm Hector.•The wind–induced circulation is enhanced by wave effects along the coast of Clare.