Greenland’s ice sheet and glaciers have an uncertain future. A new study has found that the holes in the ice are larger than previously thought, while separate research suggests the island’s largest glaciers are melting faster than feared.
Greenland’s three largest glaciers hold enough frozen water that if they were to melt completely, the global sea level would increase by about 1.3 meters (4.3 feet). Danish and British scientists reported in Nature Communications that these glaciers have experienced sizable losses since records began. From 1880 to 2012, the Jakobshavn Isbrae glacier lost more than 1.5 trillion tonnes of ice. Between 1900 and 2012, glacier Kangerlussuaq lost 1.4 trillion tons of ice while Helheim glacier lost 31 billion tonnes in the same period.
In late-September, a different study showed that Greenland may lose up to 36 trillion tonnes of ice, 12 times the total loss of the last century, depending on how well we curb greenhouse gas emissions. If that were to happen, it would add 9.9 centimeters (3.9 inches) to the global waterline.
One reason for the increased melting of Greenland’s ice is moulins. A moulin is a hole in the ice sheet that allows meltwater to penetrate deep within the ice, reaching the base. Even a thin layer of water under the base lubricates the ice sheet, making it easier for the sheet to slide towards the ocean.
Published in Geophysical Research Letters, the team’s research shows how moulin volume affects the pressure of the water at the bottom of the ice sheet. To begin the study, it was crucial to establish how big these holes actually were inside the sheet. The team found they are much larger than they appear from the surface and in models.
"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. 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,” lead author Professor Matt Covington, from the University of Arkansas, said in a statement.
“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.
The research coming out from Greenland suggests the changes to our climate and the choices we make now will have a profound effect on the future of this region.