An ‘inland tsunami’: 15 million people are at risk from catastrophic glacial lake outbursts, researchers find 

Glaciers around the world are melting at an alarming rate, and are leaving massive pools of water in their wake. The meltwater fills the depression left behind by the glacier, forming what’s known as a glacial lake.

As temperatures get warmer and more pieces of the glacier melt away, the lake rises — and living downstream from one could be incredibly dangerous. If the lake rises too high or the surrounding land or ice gives way, the lake could burst, sending water and debris rushing down mountains.

This phenomenon is called a glacial lake outburst, and according to a study published Tuesday in the journal Nature Communications, the roughly 15 million people around the globe that live within 30 miles of a glacial lake are at risk. More than half of them are concentrated in just four countries — India, Pakistan, Peru and China.

It’s the first study that looks specifically at the potential impact of glacial lake outbursts, which experts say cannot be overstated.

Tom Robinson, a co-author of the study and a senior lecturer at the University of Canterbury in New Zealand, said a glacial lake outburst is like an “inland tsunami.” He compared its impact to a sudden dam collapse.

“These glacial dams are no different to constructed dams,” Robinson told CNN. “If you take the Hoover Dam, for instance, you’ve got a massive lake behind it, but if you suddenly remove the Hoover Dam, that water has to go somewhere, and it’s going to come cascading down a valley in massive flood waves.”

These floods happen with little to no warning. Previous glacial lake outbursts have killed thousands of people and destroyed property and critical infrastructure. The Cordillera Blanca in Peru is one hot spot for this dangerous phenomenon. Since 1941, the mountain range has experienced more than 30 glacier disasters from avalanches to glacial lake outbursts that have claimed more than 15,000 lives, researchers found.

While it’s not yet clear how much of Pakistan’s flooding last year was linked to glacial melt, the country is home to more glaciers than anywhere in the world outside the polar regions. In 2022 alone, there were at least 16 glacial lake outburst incidents in the country’s northern Gilgit-Baltistan region – significantly more than the five or six events seen in previous years, scientists said.We, as a global community, only have limited resources — and some of us have access to more resources than others,” he said. “We want to be making sure those resources are put to good use in the areas where impacts could potentially be quite severe.” 

Robinson added that once there is investment in the most vulnerable countries like India, Pakistan, Peru and China, “we can work our way down that list and keep working down,” to save even more lives from these bursting glacial lakes.