A long-standing mystery about glacial lakes involves floods or “jokulhlaups” that appear suddenly and unpredictably from glaciers or ice caps. Scientists have long studied the development of these floods, which are some of the biggest floods on Earth.
These floods affect the movement of some glaciers and pose a significant danger in Iceland. And the mechanism and the timing of these floods are not well understood.
A new study by aerospace biologist and earth scientist Eric Gaidos of the University of Hawai’i in Mānoa has solved this mystery.
In June 2015, a series of surprise events revealed how these floods started. That summer, scientists drilled a hole in one of the lakes in Iceland to study its microbial life. While collecting samples through the borehole, the team found that there was an electrical current going down in the hole.
The flow was so strong that the scientists almost lost their sensors and sampling equipment into the pit.
Gaidos says, “We surmised that we accidentally connected a water mass inside a glacier to the lake below. That volume of water is rapidly receding into the lake. “
A few days later, after the team left the glacier, the lake flooded with floods. Fortunately, the small floods and the Icelandics had a complicated early warning system on their rivers, so no people were harmed or infrastructure was damaged during the event.
The scientists used a computer model of the drainage of the flow through the hole and its impact on the lake, to show that this could cause flooding.
Gaidos says, “We have found that glaciers can store smaller bodies of water above lakes powered by summer melting. If this body of water is hydraulically connected to the lake, then the pressure in the lake will increase and that allows water to begin to escape below the glacier. “
While the team performed an artificial bond with the lake in 2015, natural connections could form when rainwater or melted snow accumulates in the openings. The pressure eventually cracks the glacier to the lake. This discovery provides a new understanding of how these floods can begin and how this depends on the weather and the season.
Collaborators in Iceland are continuing to study this phenomenon by using radio echo measurement to look for bodies of water within the ice and study the larger lake below it.
- E. Gaidos et al, Après Nous, le Déluge: A man-activated Jökulhlaup from Lake Subglacial, Geophysical Research Letter (2020). DOI: 10.1029 / 2020GL089876