Projected Changes in Wave Conditions in the Baltic Sea by the end of 21st Century and the Corresponding Shoreline Changes

ABSTRACT Suursaar, Ü.; Tõnisson, H; Alari, V.; Raudsepp, U.; Rästas, H., and Anderson, A., 2016. Projected changes in wave conditions in the Baltic Sea by the end of 21st century and the corresponding shoreline changes. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 1012 - 1016. Coconut Creek (Florida), ISSN 0749-0208. The aim of the study is to analyse possible future changes in the Baltic Sea wave conditions and to project coastal changes in six differently exposed Estonian coastal sections resulting from changing wind climates. In the open parts of the Baltic Sea, the SWAN model with 3 NM spatial resolution was used for simulation of wave fields in 1966–2100. Regional climate projection EUR-11 assuming the RCP4.5 greenhouse gas scenario was used as wind forcing. In addition, using a site-dependently calibrated fetch-based wave model, a set of semi-realistic scenario calculations was obtained by modifying the baseline wind input data in order to investigate the reaction of wave climates and coastal developments. For coastal change, past developments in the shoreline and accumulation-erosion areas were tracked using repeated GPS measurements and GIS-overlaid cartographic and photographic material. The projections showed spatially and temporally varying wave fields and a slight overall increase, which corresponds to increased south-westerly winds. Depending on exposition, the wave climates would change differently even within a single semi-enclosed sea. Using the previously established empirical relationships between wave parameters and shoreline changes, we predict that erosion will probably increase in transitional zones while accumulation increases within bays. Sea-level rise and shortening of the sea-ice duration will probably have a remarkable contribution.