Researchers Investigate Giant Holes in Greenland Ice Sheet

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Matt Covington Drone

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University of Arkansas geosciences associate teacher Matt Covington flies a drone on the Greenland ice sheet. Credit: Jason Gulley

Researchers climbed up into moulins, which drain pipes meltwater from the ice sheet, to much better comprehend how volume connects to ice motion.

Holes that bring surface area meltwater to the base of the Greenland ice sheet, called moulins, are much bigger than formerly believed, according to a brand-new research study based upon observation and first-hand expedition by a group consisting of a geologist from the University of Arkansas.

The additional volume might affect the stability of the Greenland ice sheet and how rapidly it moves towards the sea.

Researchers Inside Moulin Greenland Ice Sheet

Researchers inside a moulin on the Greenland ice sheet. Credit: Jason Gulley

The group studied the relationship in between the size of the moulins and the everyday variation of water depth in them throughout the summertime melt season. Scientists think increased water depth, and for that reason pressure, inside moulins oils the base of the ice sheet and increases the speed of its motion towards the sea, the method an ice slides quickly on a thin movie of water. But previously, little was understood about the real size of moulins and just how much water they can hold.

“We compared our models with in-the-field observations of the water levels and it seemed like we would need really huge volumes inside moulins to produce the relatively smaller water variations that we were seeing,” stated Matt Covington, associate teacher of geosciences and very first author of the research study released in the journal Geophysical Research Letters. “Then when we went back in the following year and explored a moulin, it was giant. It was a case where the model made the prediction, and we went out in the field and it turned out to be right.”

Matt Covington Climbs Moulin

University of Arkansas associate teacher of geosciences Matt Covington climbs up into a moulin on the Greenland ice sheet. Credit: Jason Gulley

The group made 2 journeys to the Greenland ice sheet in October 2018 and October 2019. During each journey, they utilized ropes and other climbing up devices to rappel 100 meters into 2 different moulins, practically reaching the water level.

“It’s intimidating,” stated Covington, a knowledgeable cavern explorer. “You back over the edge and you just see blueish ice going down as far as you can see, and then it’s blackness and there also are occasional sounds of crashing ice, which is pretty unnerving.”

Scientists have actually long observed that Greenland’s ice sheet relocations and thought that warmer summertime melt seasons due to environment modification might accelerate that motion. But scientists have little information to assist them comprehend the interaction in between meltwater and the base of the ice sheet. The group’s findings contribute to the understanding of how water engages with the base of the ice sheet.

Matt Covington Investigates Moulin

University of Arkansas associate teacher of geosciences Matt Covington examines a moulin on the Greenland ice sheet. Credit: Jason Gulley

“We’re trying to understand the way the meltwater is interacting with the ice motion, and the main thing that we found is that the water pressure within these moulins is not as variable as was previously observed, and that this seems to result from really large volumes in the moulins,” Covington stated.

Reference: “Moulin Volumes Regulate Subglacial Water Pressure on the Greenland Ice Sheet” by M. D. Covington, J. D. Gulley, C. Trunz, J. Mejia and W. Gadd, 9 October 2020, Geophysical Research Letters.
DOI: 10.1029/2020GL088901



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