Past and future changes in the North Sea extreme waves

Past and future changes in the North Sea extreme waves are investigated in this article. Estimates obtained from non-stationary extreme value analyses, expressing the extreme value distribution parameters as functions of time and wind speed related covariates, are given. The results show that there is a significant trend of about 9 mm/yr in the current climate extremes of significant wave height and a trend of 1 mm/yr in the projections from 2001 to 2100. The characteristics of the extremes of wave period depend on whether swell or wind-sea events are considered. If both types of events are considered, the extremes are dominated by swell events and no present or future changes are identified. Considering wind-sea events only, a trend of less than 0.01s/yr in the present climate wave periods and a trend an order of magnitude smaller in the projections from 2001 to 2001 were detected.