Description: Characterizing extreme sea levels in coastal areas (i.e., estimates for high return periods) and its regional climate variations is a requirement to better understand coastal hazards. In many coastal regions, however, in-situ data or accurate modeled maxima values are not available. Satellite altimetry provides almost 30 years of global historical sea level data. Nonetheless, analyzing extreme sea levels from satellite data poses challenges, including the contamination of altimeter measurements near the coast and the need to manage along-track and inter-calibrated multi-mission products. To address these challenges, we developed a global statistical approach that involves identifying extreme subsamples of non-tidal-residual data on coastal areas and modeling the extreme behavior using a time-dependent extreme generalized value (GEV) model. The method and results obtained are validated with tide-gauge records.This study presents an assessment of the climate variability of sea level extreme events at time scales ranging from monthly to the long-term all over the world coast. The study quantifies the seasonal variability of extreme sea levels and identifies the periods with the highest probability of experiencing such events. The impact of various climate teleconnection patterns, such as the Arctic Oscillation and ENSO, on the magnitude of extreme events is also investigated. Moreover, the study addresses the modeled trend of sea level extremes, demonstrating a general clear and significant increase over time. Finally, the relative contribution of non-tidal residual sea level component and the astronomical tide in sea level extremes is assessed, identifying the coastal regions predominantly controlled by each component.

Description: The climate-related component of high coastal water levels is mainly composed of the storm surge and the wave set-up. Extreme water levels pose a major hazard to coastal regions, as they can cause flooding episodes with negative consequences.This study examines the atmospheric circulation storm conditions over the North Atlantic Ocean associated with extreme climate-induced water levels along the Atlantic coast of Europe. In addition, the projected changes under climate change scenarios in the Atlantic storms are also evaluated. A coastal water level indicator that integrates storm surge and wind-wave set-up components is computed. Maxima values of storm surge and wave setup are estimated from regional European hindcasts for the last three decades. The study analyzes the characteristics of North Atlantic storm tracks derived from sea level pressure fields, such as the track orientation, storm intensity and landfall latitude. The linkage between the atmospheric storm tracks and coastal sea level dynamics helps to discern the storm characteristics responsible for coastal flooding. Additionally, the different contributions between wind-waves and storm surge to coastal extreme water levels is also examined, as well as the variability of these contributions under different atmospheric conditions. Finally, this study assesses the projected changes in storm conditions causing climate-induced coastal water level extremes, and explores the derived changes in coastal hazards.