Author(s): Norman Ier; Christian Schlamko; Peter Frohle
Linked Author(s):
Keywords: Baltic Sea; Climate Change; Cosmo-CLM; Average and Extreme Wave Conditions
Abstract: In this study dynamically downscaled wind data from a regional climate model is used as input data for the calculation of four long-term time series of wave parameters for two of the global emission scenarios A1B, B1 (as compiled from Special Report On Emission Scenarios, IPCC - Intergovernmental Panel on Climate Change) with two realisations each. The long-term time series are calculated for a time period from 1960 to 2100 with the help of wind-wave-correlations and a spectral wave model. To assess the changes of the average wave conditions, we compared the frequency of occurrence and average values of the significant wave heights and mean wave directions for time periods of 30 years. The changes of the future wave conditions (2001 to 2100) are compared to actual conditions (1971 to 2000) and the statistical significance of the changes is shown. Moreover significant wave heights with a return period of 200 years are calculated with the help of extreme value statistics for time periods of 40 years and compared between future (2001 to 2100) and actual conditions (1961-2000). Some of the key findings in this study are, that changes of the future wind conditions, with more westerly winds and increasing average wind velocities (up to 4% ) to the end of the 21st century, can be linked to significant changes of the frequency of occurrence with increasing average significant wave heights (up to 8% ) and more waves coming from westerly directions. Moreover we found a spatial pattern for the changes of the average wave conditions. At westerly wind exposed locations, the average wave heights increase and at easterly wind exposed locations the average wave heights decrease and fewer waves come from northerly to easterly directions. In contrast, we found no significant trend or spatial pattern regarding the changes of the extreme wave heights. Causes of future changes of the extreme wave heights are more complex and cannot directly be linked to the local changes of the average wind conditions. Extreme wave heights with a return period of 200 years can increase/decrease up to/down to 14% depending on the location and the realisation of the future climate.
Year: 2013