A major scientific warning has emerged from Alaska after a 2025 mega tsunami in Tracy Arm fjord revealed how rapidly changing glaciers can reshape coastal risk. The event, now under close study, shows how climate driven instability in Arctic landscapes may directly threaten growing cruise tourism in the region.
What happened at the 2025 Mega Tsunami Event
On 10 August 2025, a colossal wave surged through a 48 km-long fjord in south-east Alaska. The tsunami reached an estimated height of 481 metres, making it one of the tallest ever recorded in modern history, second only to the 1958 Lituya Bay wave at 530 metres and no lives were lost, but the scale shocked researchers.
What Triggered the Disaster
Scientists link the event to a massive rockslide that occurred around 5:26am local time with eoughly 1 kilometre of vertical cliff collapsed onto the South Sawyer Glacier and plunged into narrow waters below. The sudden displacement of rock, ice and water generated extreme force, enough to trigger long-period seismic waves comparable to a magnitude 5.4 earthquake.
A Wave on a Historic Scale
The tsunami did not behave like typical ocean waves. It produced a 36-hour seiche, meaning the water continued oscillating long after impact. In some nearby locations, observers recorded wave surges of 2 to 2.5 metres, followed by secondary waves around 1 metre and scientists note that fjord geometry can amplify runup far beyond open-ocean tsunamis.
Cruise Tourism & Rising Exposure
Risk is increasing as tourism expands. Alaska’s cruise traffic has risen from about 1 million passengers in 2016 to roughly 1.6 million in 2025 while aound three cruise ships pass through Tracy Arm daily in peak season. On the day of the collapse, multiple passenger vessels were scheduled within hours of the event, underscoring how close tourism operates to unstable terrain.
What Witnesses Reported
Eyewitness accounts show how far the energy travelled as Kayakers nearly 55 km away reported water rushing through campsites and sweeping away equipment. A motor vessel about 50 km from the source observed waves breaking along shorelines, with visible surges moving rapidly through the fjord system.
Arctic Amplification of Risk
Researchers stress that glacier retreat is not just a background trend but a direct trigger. As ice melts, it removes support from steep valley walls, increasing the likelihood of rock collapses without recent glacier thinning, scientists suggest the landslide may not have generated such an extreme wave or may not have occurred at all.
Scientists Warn of Rising Arctic Tsunami Risks After Alaska Event
Studies published in peer-reviewed research highlight a growing pattern as landslide generated tsunamis are becoming more likely in Arctic fjords. Compared to earthquake driven waves, these events can produce higher localized runups because water is displaced directly and violently in confined spaces.
According to the new research published in Science on Wednesday and led by Dan Shugar, a geomorphologist of the University of Calgary, the sequence began at 5.26am local time on 10 August 2025 with a large landslide collapsed 1km vertically onto the South Sawyer glacier and into the narrow, 48km fjord, producing the huge tsunami.
“With fjord regions increasingly visited by cruise ships and climate change making similar events more likely, this unanticipated, near miss event highlights the growing risk from landslides and tsunamis in coastal environments,” researchers said in their report.
Lessons & Future Preparedness
- Expand real-time monitoring of unstable glacier-adjacent slopes
- Improve tsunami modelling specific to fjord environments
- Adjust cruise ship routing during high-risk seasonal periods
- Increase early-warning systems for remote coastal regions
- Map high-risk landslide zones across Arctic tourism routes
- Strengthen coordination between scientists and maritime operators
