New research has tracked the evolution of a glacier lake dammed by a glacier surge using satellite images, to help better understand its life cycle and the hazard it presents to nearby communities.
During glacier surges, the ice begins moving at speed and the glacier front can advance, in some settings blocking rivers and forming lakes that put communities and infrastructure downstream at risk of flooding.
The study, published in the Journal of Glaciology , monitored the evolution of a lake dammed by a surge of the Shisper Glacier, located in the Karakoram mountain range, which extends across the borders of Pakistan, China, and India.
Life cycle of the Shisper Glacier lake
The glacier began surging in early 2018, blocking a river and forming an ice-dammed lake. Researchers from the University of Portsmouth and International Centre of Integrated Mountain Development analysed this phenomenon using satellite images captured by the European Space Agency. They identified that the lake underwent six phases of filling and drainage, continuing even after the glacier stopped surging in 2020.
Four of the phases led to the formation of a large lake that grew to its maximum size by May each year, threatening the safety of the communities below. It took on average at least 155 days for the lake to fill.
The largest lake phase reached a volume of 33.7 million cubic metres in May 2022 - more than 13,000 Olympic sized swimming pools. Each large lake phase drained rapidly between May and July as glacial lake outburst floods (GLOFs), typically over one to two days.
The GLOF in May 2022 caused the Hassanabad Bridge, a major crossing point on the Karakoram Highway between Pakistan and China, to collapse, and also caused extensive damage to nearby homes, buildings, and hydropower infrastructure.
Sentinel-2 false colour near-infrared images. Credit: ESA and the Sentinel Hub EO Browser.
Protecting nearby communities
Pakistan is home to the largest number of glaciers outside the polar regions. The new study highlights the importance of closely monitoring glacier surges and any lakes that subsequently form, in an effort to reduce potential future damage.
Lead author, Dr. Harold Lovell , Senior Lecturer and glaciologist from the University of Portsmouth, said: "It's hard to predict when glaciers will surge and whether they will dam dangerous lakes, but we know that in some settings this is more likely. Satellite data allows us to identify and track surges, potentially helping to pinpoint locations where lakes may be dammed in the future. This information is crucial for helping to warn communities about periods of increased flood risk."
The findings also revealed that hazards caused by glacier surges - like the formation of large lakes - can continue for many years after the surge has ended.
Co-lead author, Dr. Sher Muhammad from the International Centre of Integrated Mountain Development, said: "Even after the Shisper Glacier stopped surging and advancing, the lake continued to form and drain for two more years, causing damaging floods with estimated losses of over $4 million to private property.
"However, our data suggests that the phases of lake formation resulting from the Shisper Glacier's latest surge have ended, which may offer a period of respite, particularly to residents of Hassanabad village who live in its path."
The risks of glacier-related hazards in the region could be reduced through the implementation of community-based early warning systems, the installation of gabion walls for flood protection, and the building of community and infrastructure resilience.
