Greenland Melt Contorts Base Of Ice Sheet Into Surreal, Warped Patterns - Climate Central

Melting and refreezing at the bottom of ice sheets warps the layer-cake structure of the ice above, as seen in this radar image from Greenland.
Credit: Mike Wolovick

The flat, glistening, white expanse of the Greenland Ice Sheet, stretching out across hundreds of thousands of square miles, appears placid, unchanging … boring even. But this tranquil surface belies the turmoil taking place below, at the base of the ice sheet. There, scientists have discovered sections of ice up to a kilometer thick and tens of kilometers long where meltwater has refrozen to the base of the ice sheet, setting off a dynamic process that causes the layers of ice to build up over the eons and contort into sinuous folds.

The refreezing and folding heats the surrounding ice, which impacts how it flows on its journey from the ice sheet’s interior out to the ocean. Several of those regions coincide with the place where one glacier dramatically speeds up. Understanding what controls the behavior and flow of ice sheets and the glaciers within them is a key part of improving climate models that project what effects global warming might have on the ice and how that might impact sea level rise.

What this shows is we have to go past just watching the surface,” said Robin Bell, a climate researcher with Columbia University’s Lamont-Doherty Earth Observatory and leader of a new study describing the strange sections of ice in the journal Nature Geoscience.

Sections of refrozen ice were known to exist at the base of the East Antarctic Ice Sheet, which is much thicker, larger and colder than the Greenland Ice Sheet, itself almost incomprehensibly large. Early radar measurements made by flights over Greenland hinted that something similar could be hiding under the surface there, but the data was too coarse and sparse to tell for sure. Some thought the radar signatures were the echoes of mountains trapped below the ice. But her experience in Antarctica had Bell “pretty convinced” that they were showing these “basal units” of refrozen meltwater.

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http://www.climatecentral.org/news/warps-in-greenlands-ice-17554