Abstract
We report sedimentological evidence for a tsunami from a coastal lake at Innaarsuit, Disko Bugt (west Greenland), which was most likely generated by a rolling iceberg. The tsunami invaded the lake c. 6000 years ago, during a period of time when relative sea level (RSL) was falling quickly because of isostatic rebound. We use the background rate of RSL fall, together with an age model for the sediment sequence, to infer a minimum wave run-up during the event of c. 3.3 m. The stratigraphic signature of the event bears similarities to that described from studies of the early-Holocene Storegga slide tsunami in Norwegian coastal basins. Conditions conducive to iceberg tsunami include a supply of icebergs, deep water close to the shore, a depositional setting protected from storms or landslide tsunami, and a coastal configuration that has the potential to amplify the height of tsunami waves as water depths shallow and the waves approach and impact the coast. Future warming of polar regions will lead to increased calving and iceberg production, at a time when human use of polar coasts will also grow. We predict, therefore, that iceberg-generated tsunami will become a growing hazard in polar coastal waters, especially in areas adjacent to large, fast-flowing, marine-terminating ice streams that are close to human populations or infrastructure.
Highlights
Most tsunamis are generated on active plate boundaries, triggered by earthquake-generated rapid vertical seabed movement (e.g. [47, 56])
We report sedimentological evidence for a tsunami from a coastal lake at Innaarsuit, Disko Bugt, which was most likely generated by a rolling iceberg
Conditions conducive to iceberg tsunami include a supply of icebergs, deep water close to the shore, a depositional setting protected from storms or landslide tsunami, and a coastal configuration that has the potential to amplify the height of tsunami waves as water depths shallow and the waves approach and impact the coast
Summary
Most tsunamis are generated on active plate boundaries, triggered by earthquake-generated rapid vertical seabed movement (e.g. [47, 56]). Icebergs provide a further potential source of tsunami in polar regions. We use the term ‘‘iceberg-generated tsunami’’ to capture the range of potential iceberg motions (e.g. rocking, capsizing, rolling, collapsing) that can generate waves. Tsunamis generated by icebergs are frequently observed in parts of Antarctica and Greenland, where they routinely have wave heights of 2 m or so [1, 2, 40]. Their occurrence and geomorphic significance over longer (Holocene) timescales have not previously been studied
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