Woods Hole Research Center, The (WHRC)
A melting glacier, and potentially thawing permafrost, have destabilized a massive slope in Alaska’s Barry Arm, raising the risk of a landslide that could generate a tsunami hundreds of feet high, a coalition of scientists has warned. Discovery of the threat has led the scientists to issue a warning in a public letter. The team has also launched an immediate effort to better understand what could trigger a landslide, to model what the impacts of a failure might be, and to detect changes in the slope that might forewarn of a landslide.
Barry Arm, a fjord 60 miles east of Anchorage, is frequently visited by as many as 500 people at a time, including tourists, fishing crews, and hunters. While some slumping has been noted for decades, in recent years Barry Glacier has retreated from the slope’s foot, raising the risk of sudden collapse.
The scientists say that collapse of 650 million cubic yards of the slope, potentially triggered by an earthquake, extreme rain, or heat wave, is plausible within the next year and likely within the next 20 years. In addition to the massive tsunami wave in the immediate vicinity of Barry Arm, the team’s analysis shows that about 20 minutes later the nearby community of Whittier would be in the danger zone for a possible surge of over 30 feet. Smaller ripple effects could be felt throughout Prince William Sound.
Alaska has seen several massive landslide-generated tsunamis, including the 1958 Lituya Bay, 1967 Grewingk and 2015 Taan events. In Greenland, a 2017 landslide-caused tsunami killed four people. However, with the Barry Arm slump both significantly larger and higher in elevation, the team concludes its potential energy is significantly larger than any of those recent incidents.
“We’ve been in the business of studying landslide-generated tsunamis after they happen, but at Barry Arm I hope we can get ahead of the game and give people some warning. I worry that these large landslides into fjords and lakes near retreating glaciers might be getting a lot more likely with climate change. In the past they’ve been rare events, but I’m not sure about the future,” said Dr. Bretwood Higman, co-founder and executive director of Ground Truth Alaska.
“As global warming continues to thaw glaciers and permafrost, landslide-created tsunamis are emerging as a greater threat – not just in Alaska, but in places like British Columbia and Norway. In the short term, we need more scientific study of threats like the one we’ve identified in Barry Arm to provide earlier, more accurate warnings. And in the long term, we need governments to act on climate,” said Woods Hole Research Center scientist Dr. Anna Liljedahl.
“The largest tsunamis we have witnessed in recorded history were generated by landslides in fjords. Luckily, most of these historical landslides have been remote and isolated, with very little impact on coastal communities. Here, with this potential Barry Arm landslide, towns and near-shore infrastructure through Prince William Sound, and in particular Whittier, could see the damaging effects of a major tsunami, with little warning. Monitoring and preparation is necessary – this is how we will save lives,” said Professor Patrick J. Lynett of University of Southern California’s Viterbi School of Engineering.
Funding support for this effort: