They found that ‘hot ice’ affects the movement of glaciers in Greenland

Concern about the future of glaciers is widespread in the scientific community and Greenland represents a particular center of interest. Several studies have found that there is global warming they wreak proportionally greater havoc than elsewhere.

A recent study by experts in the University of Cambridge revealed that glacier movement in Greenland is more complex than previously thought, with deformation in regions of warmer ice containing small amounts of water. This explains the movement thought to be caused by a landslide where the ice meets the bedrock below.

For their research, the scientists used computer modeling techniques based on previous fiber optic measurements of the ice sheet on Greenland build a more detailed picture the behavior of the second largest ice cap in the world. Their findings, which have been published in the journal Science Advances, could be used to develop more accurate predictions of how the Greenland Ice Sheet will continue to move in response to climate change.

The mass loss of the Greenland Ice Sheet was multiplied of six since the decade of 1980 and is now the largest contributor to sea level rise globally. About half of this mass loss comes from surface meltwater runoff, while the other half is driven by the discharge of ice directly into the ocean from fast-flowing glaciers reaching the sea.

The project Respondentfinanced by the European Research Council, explores the dynamics of the Greenland Ice Sheet through a combination of physical measurements and computer modelling. Specifically, the current research builds on previous observations reported by the Responder team in 2021 using fiber optic cables. In this work, the team found that the temperature of the ice sheets does not vary like a smooth gradient, but rather is much more heterogeneous, with very localized deformation zones heating the ice further.

Measurements from the well also showed that the ice at the base contains small amounts, up to about 2%, of water. In some parts of this surface, this mixed layer of ice and water, called temperate ice, was about eight meters thick, but in other areas it was up to 70 meters thick.

“The addition of even small amounts of water considerably softens the ice, transforming it into a unique material with significantly modified mechanical characteristics. We wanted to know why the thickness of this layer varies so much, because if we don’t fully understand it, our behavioral models won’t fully capture the physical processes that occur in the natureexplained first author tem, who completed the work while working at the Scott Polar Research Institute in Cambridge and now continues his work at the University of Bergen.

What has been taken as a basis so far indicates that glacier movement occurs with a clear separation between basal slip and internal deformation, “and that both are well understood. But that’s not what we see when we carefully analyze wells with new techniques. With less detailed observations in the past, it was difficult to get a really good picture of how the ice sheet is moving and more. difficult reproduce it with computer models,” said Poul Christoffersen, co-author and project leader of the Responder project, who works at the Scott Polar Research Institute (SPRI).

Law, Christoffersen and their colleagues from the UK, US, Switzerland and France have developed a model based on their previous well measurements that can account for any new observations. They took into account the natural variations of the landscape at the base of the sea ice which, in Greenland, is full of rocky hills, basins and deep fjords. Researchers have found that when a glacier moves over a large obstacle or a hill, there is an effect of deformation there heating sometimes extending several hundred meters from the base of the ice sheet. Previously, this effect was omitted from models.

“The stress in the ice base is higher at the top of these hills, resulting in lower slip. But until now, most models have not accounted for all of this variation in the landscape,” Law added. By integrating these deviations, the model developed by the researchers showed that a variable layer of temperate ice as the glacier moves across the landscape, whether the glacier itself is moving fast or slow.

The thickness of this temperate ice sheet is consistent with previous well measurements, but differs significantly from standard modeling methods used to predict sea level rise from ice sheets.

Because of this landscape mountainous, the ice can shift from almost complete sliding along its base to only short distances of a few kilometres. This directly influences the structure thermal: if you have less basal slip, then you have more deformation and internal heating, which can cause the temperate ice sheet to thicken, altering the mechanical properties of the ice over a wide range. This warm basal ice sheet may actually act as a deformation bridge between hills, facilitating the rapid movement of much colder ice directly over it,” Law added.

The researchers hope to use this better understanding to build descriptive more precise of ice movement for ice sheet models used to predict future sea level rise, a task they have just begun in a second phase of their studies.

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