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Abstract

In the future, shifts in storms across the North and Baltic Seas are highly unpredictable, challenging the projection of wave conditions for managing coastal hazards. Moreover, regional sea level rise (SLR), with very large uncertainty, complicates the situation for stakeholders seeking recommendations for climate adaptation plans. In this study we examine the change of storm surge and wind wave components of the water level due to climate change in a low tidal range Køge Bay near the entrance of the Baltic Sea. Under a high greenhouse gas emission scenario RCP8.5, we employed a regional climate model (HIRHAM) forced wave model (WAM) and study the wave model results during the “storm surge conditions” (exceeding 20 years storm surge events) and “stormy conditions” (exceeding 90th percentile of wave heights). We find that the change in wave height and wave period in the future is negligible under “stormy conditions”, but noticeable under “storm surge conditions” when considering SLR. Simulated wave heights are projected to double in the near future (mid-century) under RCP 8.5 and wave periods could increase by 1.5 seconds. This is because some high significant wave height events in the future are associated with the storm surge events when considering SLR. The findings suggest that the combined effects of mean sea level rise, storm surge and waves are likely to increase the risk for a bay with similar geography and exposure as Køge Bay. Future plans for climate protection should take into account the wave energy protection associated with storm surges.