A long-held mystery in the study of recent glaciers —- and by chance ̵1; is solved by a team led by astrophysicist and earth scientist Eric Gaidos of the University of Hawai’i in Mānoa head. Their findings were published this week in the journal Geophysical research letter.
Mysteries involving flooding or “jokulhlaups” appear suddenly and unpredictably from glaciers or ice caps like in Iceland, where the heat of volcanoes melts the ice and water accumulates in the lakes below ice River. Scientists have long studied the development of these floods, which are some of the biggest floods on Earth.
“These floods can affect the movement of some glaciers and pose a significant danger in,” said Gaidos, professor at the UH Mānoa School of Earth and Ocean Science and Technology (SOEST). Iceland. “But the mechanism and the timing of these floods are not well understood.”
Then, in June 2015, a series of surprise events revealed how these floods started.
That summer, Gaidos and his colleagues drilled a hole in one of the lakes in Iceland to study its microbiological life. While collecting the sample through the borehole, the team noticed an electric current going down, like a bath drain pipe, in the hole.
“The currents were so strong that we almost lost our sensors and sampler into the pit,” Gaidos said. “We surmised that we accidentally connected a body of water inside a glacier to the lake below. That mass of water is rapidly receding into the lake.”
A few days later, after the team left the glacier, the lake was depleted in a flood. Fortunately, the small floods and the Icelandics had complicated early warning systems on their rivers so no people were injured, as well as the infrastructure was damaged during the event, Gaidos assured.
The researchers 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.
“We found that glaciers can hold smaller bodies of water above lakes powered by summer melting,” said Gaidos. “If this water body 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 created an artificial connection to the lake in 2015, the natural connections could form when water from rain or melted snow accumulates in the gutter and the pressure eventually creates a trace. cracks from glaciers to lakes. 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, as well as studying the larger lake below it.
Consequences of glacial shrinkage
E. Gaidos et al, After Us, The Flood: A Human – Jökulhlaup activated from a Subglacial lake, Geophysical research letter (Year 2020). DOI: 10.1029 / 2020GL089876
Provided by University of Hawaii at Manoa
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