[ad_1]
Matt Covington, associate professor of geosciences at the University of Arkansas, flies a drone over the Greenland ice sheet. Credit: Jason Gulley
The researchers climbed the moulins, which drain meltwater from the ice sheet, to better understand how volume correlates with ice movement.
The holes carrying surface meltwater at the base of the Greenland ice sheet, called moulins, are much larger than previously thought, according to a new study based on first-hand observation and exploration by a team that includes a geologist from the University of Arkansas.
The extra volume could affect the stability of the Greenland ice sheet and the speed at which it flows out to sea.
Researchers inside a moulin on the Greenland ice sheet. Credit: Jason Gulley
The team studied the relationship between the size of the moulins and the daily variation in water depth in them during the summer melt season. Scientists believe that greater water depth, and therefore pressure, within the moulins lubricates the base of the ice sheet and increases the speed of its movement towards the sea, as an ice cube slides easily over a thin layer of water. ‘water. But until now, little was known about the actual size of moulins and how much water they can hold.
“We compared our models to field observations of water levels and it looked like we would need really huge volumes within the moulins to produce the relatively smaller water variations we were seeing,” said Matt Covington. , associate professor of geosciences and first author of the study published in the journal Geophysical Research Letters. “Then when we went back the next year and explored a moulin, it was gigantic. It was a case where the model made the prediction, we went out into the field and it turned out it was right. “
Matt Covington, associate professor of geosciences at the University of Arkansas, climbs a moulin on the Greenland ice sheet. Credit: Jason Gulley
The team made two trips to the Greenland ice sheet in October 2018 and October 2019. During each trip, they used ropes and other climbing equipment to abseil 100 meters in two separate moulins, almost reaching level. of water.
“It’s intimidating,” said Covington, an experienced cave explorer. “You go back over the edge and you see the bluish ice coming down as far as you can see, then it’s dark and there are also occasional noises of ice crashing, which is quite unnerving.”
Scientists have long observed that Greenland’s ice sheet is moving and have theorized that warmer summer melt seasons due to climate change could accelerate that movement. But researchers have little data to help them understand the interaction between meltwater and the base of the ice sheet. The team’s findings add to their knowledge of how water interacts with the base of the ice sheet.
Matt Covington, associate professor of geosciences at the University of Arkansas, investigates a moulin on the Greenland ice sheet. Credit: Jason Gulley
“We are trying to understand how meltwater interacts with the movement of ice, and the main thing we have found is that the water pressure within these moulins is not as variable as has been observed in previously, and that this appears to stem from large volumes in the moulins, ”Covington said.
Reference: “Moulin Volumes Regulate Subglacial Water Pressure on the Greenland Ice Sheet” by MD Covington, JD Gulley, C. Trunz, J. Mejia and W. Gadd, 9 October 2020, Geophysical Research Letters.
DOI: 10.1029 / 2020GL088901
[ad_2]
Source link
