Glacial lake floods: a rising, unpredictable local weather threat
By Sara HUSSEIN
Bangkok (AFP) Oct 6, 2023
Indian rescuers are trying to find over 100 individuals lacking in a flash flood brought on by a glacial lake bursting its banks, a threat scientists warn is growing with local weather change.
AFP explains what glacial lake outburst floods are and the dangers they pose, significantly in components of Asia:
What’s a glacial lake outburst flood?
A glacial lake outburst flood (GLOF) is the sudden launch of water that has collected in former glacier beds.
These lakes are fashioned by the retreat of glaciers, a naturally occurring phenomenon that has been turbocharged by the hotter temperatures of human-caused local weather change.
Glacier soften is commonly channelled into rivers, however ice or the build-up of particles can type what’s successfully a pure dam, behind which a glacial lake builds.
If these pure dams are breached, massive portions of water could be launched immediately from the lakes, inflicting devastating flooding.
What causes these breaches?
The pure dams holding again glacial lakes could be breached for quite a lot of causes, defined Lauren Vargo, a glacier skilled and scientist on the Antarctic Analysis Centre in New Zealand.
Causes embody “an avalanche of snow, or a landslide inflicting a wave within the lake, or overfilling of the lake… from rain or the glacier melting”, she instructed AFP.
Typically the dam has been steadily degraded over time, or is ruptured by an occasion like an earthquake.
The breaches are extremely unpredictable, “as a result of they are often brought on by so many alternative components”, she added.
What’s the impression of local weather change?
Local weather change is driving the disappearance of glaciers, with half the Earth’s 215,000 glaciers projected to soften by the tip of the century, even when warming could be capped at 1.5 levels Celsius.
The amount of glacial lakes has jumped by 50 p.c in 30 years, in accordance with a 2020 examine primarily based on satellite tv for pc information.
The extra and bigger lakes type, the higher the danger they pose to populations downstream.
Local weather change shouldn’t be solely driving the creation of glacial lakes, but additionally can produce the circumstances that lead to dam breaches.
“The flooding could be brought on by glaciers melting or these large rainfall occasions, we all know that is taking place extra due to local weather change,” stated Vargo.
How harmful are these floods?
The actual hazard of GLOFs lies of their unpredictability.
“The chance of a lake releasing a GLOF is tough to precisely quantify with out detailed and localised research,” a examine of the issue globally warned this yr.
The examine, printed in Nature Communications, discovered that 15 million individuals reside inside 50 kilometres (31 miles) of a glacial lake and inside one kilometre of potential flooding from a breach.
The chance was biggest in “Excessive Mountains Asia”, an space that covers components of 12 nations, together with India, Pakistan, China and Nepal.
That’s partly as a result of extra individuals reside nearer to glacial lakes within the area than in different components of the world, making warning instances even shorter.
However it additionally displays the vulnerability of these populations, who could also be poorer and fewer ready to take care of the sudden arrival of catastrophic floodwaters.
“Probably the most harmful basins… don’t all the time host essentially the most, or the biggest, glacial lakes,” the authors wrote.
“Fairly it’s the excessive variety of individuals and the decreased capability of these individuals to deal with catastrophe that performs a key function in figuring out total GLOF hazard.”
Hundreds of individuals, for instance, have been killed by glacier lake outburst floods in Excessive Mountains Asia however solely a handful in North America’s Pacific Northwest, though that area has twice as many glacial lakes.
Specialists have known as for extra analysis on the dangers posed by GLOFs, significantly within the Andean area, which stays comparatively understudied, but additionally for higher preparedness.
“However then there’s the bigger a part of what we will do by way of lowering emissions, to attempt to decelerate local weather change and cut back the threats of this from rising much more,” Vargo stated.
Past the Ice Age