North Sea Storm Surges Amplified by Oscillations Triggered by Preceding Storms

Abstract Storm surges are often treated as independent extremes, yet extratropical cyclones and associated coastal water‐level extremes frequently occur in clustered sequences. Although clustering can increase flood hazard by shortening recovery time, it remains unclear whether preceding storms amplify subsequent surges. We investigate this for the North Sea along the NW European Shelf using long‐term tide gauge records and idealized hydrodynamic modeling. Observations show a pronounced excess of surge events separated by 1–3 days; events occurring about 2 days after a preceding surge have median peak heights 17.5% (6.8 cm) higher than more isolated events. Sequential‐storm experiments reproduce this timing dependence. Amplification arises from lingering post‐surge basin oscillations that constructively interact with subsequent storms, while nonlinear tide–surge interactions modulate but do not remove the effect. Storm clustering can therefore influence not only the frequency, but also the magnitude, of extreme coastal water levels.