Viigand, K.; Eelsalu, M., and Soomere, T., 2024. Evaluating coastal vulnerability by temporal and spatial variation of parameters of the GEV distribution along the Baltic Sea coast. In: Phillips, M.R.; Al-Naemi, S., and Duarte, C.M. (eds.), Coastlines under Global Change: Proceedings from the International Coastal Symposium (ICS) 2024 (Doha, Qatar). Journal of Coastal Research, Special Issue No. 113, pp. 996-1000. Charlotte (North Carolina), ISSN 0749-0208.

Extreme water levels (EWLs) pose significant threats to low-lying coastal communities. In the microtidal Baltic Sea, the EWLs are created by a combination of joint impact of water volume of the sea, storm surge and wave-driven effects. We address variations of EWLs along the coastline of the Baltic Sea using the Generalized Extreme Value (GEV) distribution, characterized by shape, location and scale parameters. A negative shape parameter of a GEV distribution leads to a Weibull distribution indicating limited growth of future extremes. A near-zero parameter means that EWLs are represented by a Gumbel distribution. A positive shape parameter signals that a Fréchet distribution governs EWLs and the growth of extremes can be rapid. In the changing climate, the processes that govern EWLs do not necessarily remain statistically stationary. We evaluate the vulnerability of the coastline of the Baltic Sea in terms of the likelihood of experiencing significantly higher EWLs in the future based on the distributions that govern EWLs and their return periods. We apply the block maxima of water level in 1979–2014 extracted from model runs forced with the Climate Forecast System Reanalysis. While the shape parameter evaluated from the tide gauge data exhibits regime-shift-like changes in the Gulf of Riga in 1975–2005, changes to this parameter evaluated from the General Estuarine Transport Model provided by Leibniz Institute for Baltic Sea Research have a more complicated appearance.