(Calgary) The meltwater from the glaciers then forms enormous lakes that, according to recently published research, could potentially pose a threat from severe flash floods.
Posted August 31, 2020 at 12:48 PM
The Canadian Press
Glaciers around the world are already known to shrink as a result of climate change. On the other hand, we know less where all that meltwater is going.
In an article published Monday in the journal Nature Climate Change, Professor Dan Shugar, a geographer at the University of Calgary, and colleagues give the first estimate of how much water is in these so-called “proglacial” lakes – and how much water there is. is. speed at which these water volumes increase. This assessment was only possible a few years ago, when computers finally became powerful enough to handle a massive amount of data and 250,000 satellite images.
Proglacial lakes are formed when melt water from glaciers cannot flow through the ice itself. They form on the glacier, in front of it, next to it or even below it. These lakes are growing rapidly wherever there are glaciers.
Professor Shugar and his team estimate that the amount of water in these lakes has increased by nearly 50% since 1990. The total volume on the planet would be 158 cubic miles of water – like a huge ice cube of 5.5 km sides. Many proglacial lakes are located in sparsely populated areas such as Greenland, but others can be found in places such as the Himalayas, where they stand next to villages and communities.
And these proglacial lakes are also swelling in Canada. Their volume, including those in the high Arctic, has increased by about 20% and they contain about 37 km3 of water, Professor Shugar estimates. The lakes of British Columbia and the Yukon have grown even faster, almost doubling in size in the last 30 years to 21 km3.
These lakes can pose a risk: since the water is only held by ice, these lakes are prone to flash flooding. “The risks are not that high in the west of North America [que dans l’Himalaya]but they are certainly not non-existent, ”argued Mr. Shugar. And when these events occur, they become “absolutely gigantic.”
In 1996, a massive flash flood in Iceland caused what became the world’s second largest river for a few days. In the 1930s, such an ‘eruptive flood’ from the Chong Khumdan Glacier in the Karakoram Range suddenly threw a wall of water, mud and debris nearly 26 meters high into the Indus River for about 1,500 km.
Professor Shugar is not yet able to say whether these “eruptive floods” are becoming more common. But he warns that water managers should keep a close eye on them as climate change continues to melt glaciers and fill these lakes. “Even here in the Rockies we see an increased development of these lakes. It’s a dangerously changing landscape. ”