Signature of changing wave climate in the North Sea

In the central North Sea we observed in the recent four decades a increase in the frequency of eastward wave direction. To asses the significance of this change we reconstructed the wave statistic for this century using a statistical model. With a linear multivariate technique (redundancy analysis) we downscaled the sea level pressure over the North Atlantic and Western Europe on the wave parameters. We found that the observed change is significant on the 5% level. In order to investigate the reason for this local climatic change we compared the reconstruction with the downscaled results of a transient GCM scenario (ECHAM4-OPYC3) and a high resolution time slice experiment under increasing concentrations of greenhouse gases and aerosols. Both downscaled runs produced the same qualitative characteristic as were observed in the last decades. Therefore the recent increase of eastward waves, seems to be a local effect of anthropogenic global climate change.