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1 Routine wave observations from buoys in the northeast Pacific now extend up to 35 years. Several recent studies reported long-term trends extracted from these records. However, significant modifications of the wave measurement hardware as well as the analysis procedures since the start of the observations result in inhomogeneities of the records. We analyze significant wave heights from seven offshore wave records. Several step changes of the mean monthly significant wave height of a few decimetres are identified. These changes are induced by buoy modifications and poor data quality rather than changes in the wave climate. After adjusting the data for these step changes the wave heights show positive trends for some of the southern locations and negative trends at the northern buoys, however all trends are much smaller than reported in previous studies. Storm wave heights are extracted from the occurrence rate distributions of the adjusted significant wave heights. No statistically significant trends can be established for storm wave heights.
Gemmrich et al. (Thu,) studied this question.