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Abstract

A significant consequence of rising sea levels due to climate change is an increase in the frequency of floods and extreme sea level events that cause severe damage to coastal infrastructure and endanger human lives. Sea level data from more than 300 tide gauge stations along the European coasts, with a sampling resolution of 1 second - 20 minutes, were collected to evaluate the contribution of low-frequency (T > 2 h) and high-frequency (T < 2 h) sea level oscillations to extreme sea levels. The data were obtained from: (1) the IOC-SLSMF website and (2) National agencies for the period from 2004. to 2021.Due to numerous data quality issues (i.e., spikes, shifts, drifts) in large portions of the raw dataset, quality control procedure was required. Spurious values were removed using automatic procedures and a week-by-week visual examination. Following quality control, all data series were de-tided, and residuals were split into a low-frequency (T > 2 h) and a high-frequency (T < 2 h) component. Five highest positive sea level extremes per year were extracted from residual series, upon which contribution of low-frequency and high-frequency component to total extremes was assessed. It was shown that contribution of low and high-frequency sea level oscillations to extreme heights is strongly spatially and station dependant and that both components should be considered when estimating flooding levels.