Tsunami propagation over a wide, shallow continental shelf caused by the Storegga slide, southeastern North Sea, Denmark

The large Storegga slide, which occurred on the Norwegian Atlantic shelf ~8150 yr ago, triggered a tsunami that has been identified in sediment deposits along the coasts of Greenland, Norway, the Faroe Islands, the Shetland Islands, Scotland, and the northernmost coasts of England, but hitherto not along the southeastern shores of the North Sea. It has generally been assumed that the shallow continental shelf of the North Sea attenuated and dissipated the energy of the tsunami before it reached those coastlines. We used radiocarbon and optically stimulated luminescence dating as well as stratigraphic, lithologic, chemical, and palynological analyses of sediment cores to identify tsunami deposits on the barrier island of Rømø located on the southwestern North Sea coast of Denmark. We show that tsunami sediments were deposited in a freshwater paleolake that is located ~16 m below present-day mean sea level. The tsunami sediment run-up was between 1.5 m and 5.5 m above the contemporaneous sea level. Our results demonstrate that the Storegga slide tsunami propagated across the wide (>500 km) and relatively shallow (depth <95 m) continental shelf of the North Sea and resulted in run-up along adjacent coastlines. In contradiction to earlier theoretical studies, the coastline of the southeastern North Sea cannot be regarded as being sheltered from impacts of North Atlantic tsunami incidents.