Wave climate projection in the Persian Gulf: An ensemble of statistically downscaled CMIP6-GCMs

Abstract

Wave climate projection can provide useful information for climate change adaptation and mitigation. This study explores the future variability of wave conditions in the Persian Gulf under three different shared socio-economic pathways (SSP1-2.6, SSP2-4.5, and SSP5-8.5). Near-surface wind speed simulations of the CMIP6 (Coupled Model Intercomparison Project Phase 6) models are evaluated against the ERA5 reanalysis outputs to find the general circulation models (GCMs) with relatively better performance. The outputs related to the selected GCMs are regionalized through a Weibull-based bias-correction technique, applied to the interpolated grid points. A third-generation numerical wave model is employed to simulate wave characteristics over the computational domain using the modified wind field of each CMIP6 GCM. An ensemble model is obtained by applying the arithmetic mean on the wave model's output of the selected GCMs. The ensemble model projects a mild decrease in the future significant wave height, 95th wave height, and peak wave period to the corresponding values in the historical period. The mean wave direction shows partial variations intensifying for the higher emission scenarios in the southern part of the gulf. Projections of extreme waves for the return periods of 2, 5, 10, 50, and 100 years demonstrate insignificant variation in the future extreme conditions. Moreover, the frequency of extreme events under different SSPs is expected to decrease slightly. Finally, wave steepness and wave age calculations for a location in the middle of the gulf show a mixed condition of swells and sea waves with insignificant variability under climate change scenarios.