Scientists Warn Of Growing Tsunami Threat Lurking In Greenland's Fjords

Scientists have warned of a growing tsunami threat in Greenland's fjords, after finding two large unstable slopes that could collapse and send waves towards nearby settlements. 

Research published in Communications Earth & Environment says the slopes are in the Uummannaq Fjord system in central West Greenland. Both were discovered after the catastrophic landslide and tsunami in 2017 that left a village abandoned.

The 2017 disaster began with a massive landslide in Karrat Fjord. Scientists estimate up to 58 million cubic metres of rock fell from an unstable slope on Ummiammakku Mountain. The tsunami that followed hit the village of Nuugaatsiaq with a run-up of about 10 metres. Four people were killed, and nine were injured. The village still sits abandoned.

The new study, led by geologist Marie Keiding and colleagues from the Geological Survey of Denmark and Greenland and the Norwegian Geotechnical Institute, analysed two newly identified unstable slopes in the same fjord system.

One large slope in Karrat Fjord, just 3 kilometres west of the 2017 landslide, spans 2.65 million square metres above sea level. The researchers estimate it holds about 400 million cubic metres of material waiting to fall.

The second slope is smaller but poses the most immediate threat. It is in Kangerluarsuk Fjord. A landslide from this slope would displace around 30 million cubic metres of mountain, according to the team.

The researchers say this slope was barely noticeable until 2015, but it has developed rapidly since then and may have been accelerating.

"It is likely to fail in whole or in parts within the next few years or decades as a translational rockslide, although the timing of this remains very uncertain," the authors wrote.

If this slope falls, it could generate a run-up of 3 to 7 metres at the settlement of Ukkusissat, about 25 kilometres away. The wave would arrive just 6 minutes after the landslide.

If the entire Karrat Fjord slope were to fail, the impact could be far larger. Simulations suggest tsunamis as tall as telephone poles could ricochet across the entire Uummannaq Fjord system. A full collapse could generate a tsunami with a run-up exceeding 10 metres more than 100 kilometres away.

Landslides are a normal process in fjords, but scientists think climate change may be playing a part in the growing risk. Melting permafrost may be loosening the slopes.

"These slopes and the tsunamis they may cause illustrate an emerging hazard in Arctic and high mountain areas, where progressive permafrost degradation associated with global warming will increase the frequency and magnitude of such events," the authors wrote.

The findings underline the need for monitoring and risk mitigation by local authorities in these rapidly changing high-latitude environments.