DANGEROUS floods caused by meltwater from glaciers are happening far more often than initially thought, new research has revealed.
An international team of researchers, including the University of Dundee’s glaciology and geohazards expert, Dr Simon Cook, uncovered more than 200 additional incidents which had not been previously recorded in global data.
And climate change means that more of these incidents – similar to the floods in the Himalayan state of Sikkim in India, in 2023, which killed 55 people – are on their way, warns Dr Cook, from the university’s Division of Energy, Environment and Society.
The research team, led by environmental experts at the Chinese Academy of Sciences, studied countless satellite images and documentary records across a 120-year period to identify 609 incidents of glacial meltwater lakes bursting their dams and causing floods.
Only 400 events had been identified and recorded in previous inventories of glacial lake outburst floods (GLOFs) during the period of 1900-2020.
More than one hundred of the now 609 GLOFs recorded caused damage downstream, and there have been more than 13,000 fatalities globally, with the highest number of damaging floods occurring in High Mountain Asia and in the Tropical Andes.
The research, co-authored by Dr Cook, has been published in Nature Communications.
Dr Cook said: “The concerning thing this research shows is that the number of these incidents remains relatively steady between the 1900s to around 1970.
“Then from the 1970s, when we know climate warming has accelerated, they start to creep up, before a threefold increase between 2011-2020.
“There’s a time delay of around five to 20 years from the warming happening and the flood incidents taking place.
“That means that we know there will be many more glacial floods to come.
“We have time to act to prevent them – but we have to act fast.”
Meltwater from glaciers settles into natural hollows in the landscape that are vacated by glaciers as they recede, and the water becomes dammed by deposits of mud, sand and gravel deposited by the glaciers.
These lakes are known as moraine-dammed lakes, but the “dams” can be unstable and result in a flood downstream when they are weakened or breached, which can have devastating consequences for communities and infrastructure downstream.
The new study documents a marked increase in the frequency of these events since the 1980s, rising from 5.2 GLOFs per year (1981-1990) to 15.2 GLOFs per year (2011-2020).
This same time period has been characterised by rapidly rising global temperatures.
The research found a strong, lagged relationship between GLOF frequency and temperature such that temperature increase leads to an increase in GLOF frequency between five and 20 years later.
The updated GLOF inventory also sheds light on what causes glacial lakes to burst, with approximately 70% of these events having been triggered by ice avalanches and rockfalls landing in a lake and causing a wave of water to then overtop the dam.
Dr Cook added: “As the climate warms, not only are we seeing the shrinkage of glaciers and the ponding of meltwater to form these glacial lakes, but we’re also seeing the stability of mountain slopes being threatened.
“Steep, cold glaciers loosen up and generate ice avalanches, and the rock and sediment in the mountain walls become more prone to failure because the permafrost here is warming and thawing, meaning that we get more landslides into the lakes.
“These factors conspire to make GLOFs more likely to occur in a warming world.
“With global temperatures continuing to rise, and recent progress in tackling climate change stalling at the COP30 meeting, GLOFs will remain a threat to people and infrastructure in the world’s high-mountain regions.”
