Sea state contributions to thermosteric sea-level in high-resolution ocean-wave coupled simulations

Abstract

This study examines the impact of wave-induced processes (WIPs) in modulating thermosteric sea-level changes, highlighting the need to include these processes in future sea-level rise assessments and climate projections. The impact of wave-induced processes on thermosteric sea-level changes is investigated using coupled ocean-wave simulations. These simulations include the effects of Stokes-Coriolis forcing, sea-state dependent surface stress and energy fluxes, and wave-induced mixing. The experiments use a high-resolution configuration of the Geesthacht COAstal Model SysTem (GCOAST), covering the Northeast Atlantic, the North Sea and the Baltic Sea. The GCOAST system uses the Nucleus for European Modelling of the Ocean (NEMO) ocean model to account for wave-ocean interactions and ocean circulation. It is fully coupled with the WAM spectral wind wave model. The aim is to accurately quantify the sea state contribution to thermosteric sea level variability and trends over a 26-year period (1992–2017). The ability of wave-ocean coupled simulations to reveal the contribution of sea state to sea level variability and surge is demonstrated. It is clear that wave-induced processes (WIPs) play a significant role in sea surface dynamics, ocean mixing (mixed layer thickness) and modulation of air-sea fluxes (e.g. heat flux) in both winter (10–20%) and summer (10%), which in turn affect thermosteric sea level variability. The North Atlantic (in summer) and the Norwegian Trench (in winter) show significant contributions (40%) to the thermosteric sea-level variability due to wave-induced processes. The influence of WIPs on thermosteric sea level trends in the North Atlantic is up to the order of 1 mm yr-1 in both winter and summer, in the open ocean and at the shelf break. Smaller contributions are observed over the shelf areas of the North Sea. This study underscores the crucial role of WIPs in modulating sea-level changes and highlights the importance of including these processes in future sea-level rise assessments and climate projections.