Long-standing mystery of glacial lake floods solved

A long-standing mystery of the glacial lake has to do with the floods or “jokulhlaups” that emerge suddenly and unpredictably from glaciers or ice caps. Scientists have long studied the development of these floods, which are among the largest on Earth.

These floods affect the movement of some glaciers and represent a significant danger in Iceland. And the mechanism and timing of the onset of these floods were not understood.

A new study conducted by astrobiologist and earth scientist Eric Gaidos of the University of Hawai’i in Mānoa has solved this mystery.

In June 2015, an unexpected series of events revealed 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 current in a hole.

That flow was so strong that the scientists nearly lost the sensors and sampling equipment in the hole.

Gaidos said, “We hypothesized that we accidentally connected a body of water inside the glacier to the lake below. That body of water was rapidly draining into the lake. “

A couple of days later, after the team left the glacier, the lake completely dried up. Fortunately, the flood was small and Icelanders have an elaborate early warning system on the rivers, so no people were harmed, nor were the infrastructure damaged in this event.

The scientists used a computer model of the drainage of the flow through the hole and its effect on the lake to show that this could have triggered the flood.

Gaidos said, “We found that the glacier could contain smaller bodies of water above the lakes fed by the summer melt. If this body of water is hydraulically connected to the lake, the pressure in the lake increases and this allows the water to start flowing under the glacier. “

While the team established an artificial association with the lake in 2015, natural connections can form when water from rain or melting snow builds up in crevasses. The pressure eventually splits across 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 season.

Collaborators in Iceland are continuing to research this phenomenon by using radio echo to search for bodies of water within the ice and study the larger lake below.

Journal reference:

1. E. Gaidos et al., Après Nous, le Déluge: A Human-Triggered Jökulhlaup from a Subglacial Lake, Geophysical Research Letters (2020). DOI: 10.1029 / 2020GL089876