Objective assessment of storm surge risk in the German Bight – historical events and future climate change

Abstract

Storm surges in the German Bight can have great destructive potential. This includes devastating floods, structural damage to infrastructure, and even loss of life. The most important driver of storm surge events in the German Bight is strong winds from north-westerly directions, often related to intense extra-tropical cyclones travelling from the North Atlantic into the North Sea region.Making use of an objective, impact-oriented identification and tracking scheme, we analyse storm events related to storm surges in the German Bight. This particular version of the tracking algorithm includes the so-called Storm Surge Severity Index (SSSI) and is used as a complementary tool in operational forecasting by the German Federal Maritime and Hydrographic Agency (BSH). The SSSI takes wind speed and direction into account and intends to quantify storm surge risk in the German Bight. However, to date, the SSSI has never been systematically evaluated for past storm surge events. To fill this gap and to prove that the SSSI can be used as a proxy for storm surge risk, we analyse the relationship between SSSI values of past storm events and the associated water levels recorded in the German Bight using ERA5 atmospheric reanalysis data. Moreover, we analyse potentially storm surge-relevant storms in a multi-model ensemble of global climate model simulations to assess potential future changes in storm surge risk in the German Bight.