Climate change is causing sea levels to rise and coastal regions around the world are increasingly suffering from flooding. Storm surges are particularly serious in this context. A new analysis now confirms that storm surges on the European Atlantic and North Sea coasts have increased since 1960 – parallel to the rise in sea level. According to the results, this trend was influenced by both internal climate variability and human influences. The study also points to more frequent storms over Great Britain and Central Europe in the future and thus has important implications for coastal protection planning.
Floods resulting from storm surges cost the global economy billions of dollars each year. Affected regions try to reduce damage with coastal protection measures. So far, however, they have usually assumed that the frequency of storm surges will remain the same. While previous research has suggested that sea-level rise makes flooding more likely, the impact of storms has been unclear.
Designing coastal protection based on science
A team led by Francisco Calafat from the National Oceanography Center in Liverpool has now evaluated sea level measurements taken between 1960 and 2018 by 79 measuring stations along the European Atlantic and North Sea coasts. They focused on extreme events with particularly high water levels. They combined this data with statistical model calculations to derive trends and crystallize the proportion of human influences.
“The success of coastal protection measures depends on a solid understanding of how climate change affects the likelihood of extreme sea level events,” the researchers explain. “On the one hand, changes in storm strength, which affect the occurrence of storm surges, and on the other hand changes in mean sea level, which increase or decrease the initial level for storm surges, play a role.” record the influence of storms, the database was too small, since most studies only focused on individual locations.
storms shift
In their analysis, Calafat and his colleagues come to the conclusion that extreme water levels on Europe’s coasts have increased since 1960. The trend is consistent with sea level rise over the same period. Unlike previous publications, however, the study also shows that changes in storms have a similarly large impact on extreme water levels. The authors determine a differentiated influence: According to the data and model calculations, North Atlantic storms expand eastwards, which could lead to an increase in the risk of storm surges in Great Britain and northern Central Europe in the future. For the south of Europe, on the other hand, the authors identify an opposite trend.
With the help of climate models, the researchers have also calculated the proportion of human influences on the observed and predicted changes and how much is due to natural climate variability. Accordingly, the internal variability, which is influenced among other things by interactions between the oceans and the atmosphere, already has a large influence and is amplified by human activities. Both factors together lead to a spatial shift in the pattern of storm surge extremes. “If this factor is ignored, it can lead to premature failure of flood protection systems – with catastrophic consequences,” the researchers write. They recommend rethinking previous coastal protection measures and supporting them with further research.
Source: Francisco Calafat (National Oceanography Centre, Liverpool) et al., Nature, doi: 10.1038/s41586-022-04426-5