On the understanding of the North Atlantic storm conditions responsible for coastal flooding along the Western European coast

Water level at the coast integrates several components from different genesis. This study focuses on the climate-related component of extreme coastal water levels, i.e. the variations in water level over time due to the atmospheric and oceanic circulation variability and their interaction. The extreme climatic component of coastal water levels mostly integrates the storm surge, which represents the sea level variations due to atmospheric wind and pressure drivers, and the wave set-up, which represents the coastal water level variations induced by wind waves. Extreme events of the climatic component of coastal water levels under storm conditions are a major hazard in coastal impacts. These extreme events significantly increase coastal total water levels, which may result in coastal damage through catastrophic flooding episodes.

This study assesses the atmospheric storm conditions in the North Atlantic Ocean linked to extreme climate-induced water levels along the Atlantic coast of Europe. A coastal water level indicator that integrates the storm surge and wind wave set-up components is computed first. North Atlantic atmospheric wind-pressure synoptic patterns are classified, identifying the storm-related patterns most probable to cause extreme water level events along the Western European coast. In addition, the track of the storms causing coastal water level extremes are identified and its main characteristics are analyzed (e.g., track orientation, storm intensity, landfall latitude). Results allow to unravel the differences between coastal regions regarding the characteristics of the storms potentially responsible for coastal impacts. For completeness, the projected changes in the storm conditions causing coastal climate-induced water level extremes by the end of the century due to climate change are explored.