Fixed a longstanding conundrum about glacial lake flooding

A long-standing secret of the glacial lake is the floods or “Jokulhlaups” that arise suddenly and unpredictably from glaciers or ice caps. Scientists have long studied the evolution of these floods, which are among the largest in the world.

These floods affect the movement of some glaciers and pose a significant threat to Iceland. And the mechanism and timing of these floods were not understood.

A new study from the University of Hawaii at Mānoa, astrobiologist and earth scientist Eric Gaidos, has solved this mystery.

In June 2015, an unexpected series of events showed how these floods begin. That summer, scientists drilled a hole in one of Iceland’s lakes to study its microbial life. While collecting samples through the well, the team noticed a downward flow in a hole.

This flow was so strong that the scientists almost lost the sensors and sampling equipment in the hole.

Gaidos said: “We suspected we had accidentally connected a body of water in the glacier to the lake below. This body of water quickly flowed into the lake. “

A few days later, after the team exited the glacier, the lake dried up at high tide. Fortunately, the tide was low and Icelanders have a sophisticated early warning system on the rivers so that no people were injured or infrastructure was damaged in the event.

The scientists used a computer model of the river’s drainage through the hole and its impact on the lake to show that this could have triggered the tide.

Gaidos said: “We found that the glacier can contain smaller bodies of water on lakes that are fed by melt in the summer. When this body of water is hydraulically connected to the lake, the pressure in the lake increases and the water can drain under the glacier. “

While the team created an artificial link to the lake in 2015, natural links can form when water from rain or melting snow builds up in crevasses. The pressure eventually breaks through the glacier to the lake. This discovery provides a new understanding of how these floods can start and how this depends on the weather and time of year.

Staff in Iceland are continuing to search for this phenomenon by using radio echoes to search for bodies of water in the ice and examine the larger lake below.

Journal reference:

1. E. Gaidos et al., Après Nous, le Déluge: A glacial run-off from a subglacial lake, Geophysical Research Letters (2020). DOI: 10.1029 / 2020GL089876