As glaciers retreat, tsunamis may increase
Alaskan case study uncovers how glacial melt causes landslides into deep water bodies. Andrew Masterson reports.
In 2015, ice melting at the leading edge of the Tyndall Glacier in Alaska triggered a landslide which sent 180 million tonnes of rock tumbling into Taan Fiord beneath it, triggering a tsunami that overshot the opposite bank by 193 metres.
The event, say researchers from the University of Washington Tacoma in the US, may well be the first of many.
In a paper published in the journal Scientific Reports, the university’s Bretwood Higman and colleagues report field observations from the Tyndall landslide which show that the tsunami had more impact on the landscape than the rockfall itself.
The landslide affected only two square kilometres of the surrounding environment, while the tsunami’s effect was an order of magnitude larger, with water temporarily covering 20 square kilometres.
Higman’s team found that the tsunami left a distinct sedimentary layer on the land it passed over, providing a clue for geologists looking for evidence of past events.
The researchers say that their detailed modelling of the landslide – which was detected within hours through automated seismographs dotted across Alaska – will provide a benchmark for modelling other landslide and tsunami risks.
“Our results call attention to an indirect effect of climate change that is increasing the frequency and magnitude of natural hazards near glaciated mountains,” they write.
Global warming, they note, is shrinking glaciers around the world, and in many cases exposing unstable hill slopes in the process and increasing the likelihood of catastrophic landslides.
“Along the glacially sculpted coastlines of Alaska, Patagonia, Norway, and Greenland, communities, tourism, and infrastructure are becoming increasingly exposed to such landslides and the tsunamis they may generate,” they note.