A UH researcher solves the mystery of glacial floods


University of Hawaiʻi

ice cap
Aerial image of subsidence and crevasses on the Vatnajókull ice sheet on the western Skaftákatlar subglacial lake. (Photo credit: Benedikt Gunnar Ófeigsson, Icelandic Meteorological Office)

A long-standing mystery involving floods or “jökulhlaup” emerging suddenly and unpredictably from glaciers or ice caps was fortuitously solved by a team led by the University Hawaii from Mānoa astrobiologist and Earth scientist Eric Gaidos. The results were published in Geophysical Research Letters.

This mystery occurs in Iceland, where volcanic heat melts glacial ice and water builds up in lakes under glaciers. Scientists have long studied the development of these floods, which are among the largest on Earth.

machine drilling into ice
The hot water drill used to drill the glacier to subglacial lakes. (Photo credit: Eric Gaidos)
team standing on the ice
The team used hot water to melt a hole through a thick layer of ice to sample a lake under a glacier. (Photo credit: Gaidos)
water motion graphic
Illustration of the water movement that may have triggered the June 2015 flood. (Photo credit: Gaidos et al 2020)

“These floods can affect the movement of some glaciers and represent a significant danger in Iceland,” said Gaidos, a professor at UH Mānoa’s School of Ocean and Earth Science and Technology (SOEST). “But the mechanism and timing of the onset of these floods were not understood.”

Then, in June 2015, an unexpected series of events revealed how these floods begin.

That summer, Gaidos and colleagues 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, like a bathtub drain, in the hole.

“The flow was so strong that we almost lost our 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 few days later, after the team left the glacier, the lake dried up in flood. Fortunately, the flood was small and Icelanders have an elaborate early warning system that monitors their rivers so that no people were injured, nor infrastructure damaged in this event.

The researchers 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.

“We found that the glacier may contain smaller bodies of water above the lakes fed by the summer melt,” Gaidos said. “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.”

For more information, see the SOEST website.

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