Spatio-Directional Extreme Value Analysis of Surface Currents in the Eastern Mediterranean: An Assessment of Uncertainty in the Gulf of Antalya

Sea surface currents are crucial for navigation and the design of coastal and offshore structures. This study presents a spatio-directional extreme value analysis of surface currents in the Gulf of Antalya, Eastern Mediterranean, using 20 years (2000–2019) of hourly reanalysis data at 118 grid points for eight flow directions and the omnidirectional series. Annual maxima were fitted with the Gumbel or generalized extreme value distribution, selected by the Bayesian information criterion, and peaks over the 99.5th percentile with the generalized Pareto distribution (GPD). Uncertainty was quantified with Monte Carlo simulations, and the sensitivity to the threshold and declustering window was evaluated. The omnidirectional 50-year return levels range between 0.5 and 1.5 m/s, increase towards the open sea and vary strongly with direction, being highest for the northward flow. The two approaches agree within ±10% at 89% of the points, with larger differences in the directional series. The median uncertainty is 0.15 m/s for the annual maxima and 0.21 m/s for the GPD. The return levels are more sensitive to the threshold than to the declustering window.