© I.Sasgen, GFZ
Floating icebergs from Greenland’s largest glacier, Jakobshavn Isbrae. The smooth side indicates part of the iceberg that has already tipped over as sub-marine melting brought it out of balance.

Ice Melt on Steroids: Greenland's Ice Sheet Being Cooked From Above and Below

ICTMN Staff
8/13/13

Is Mother Earth melting from the inside out?

A new study has brought to light yet another factor that must be added into the complex set of data that is chronicling the melting of the Arctic: The Earth’s molten core may be heating things up from below.

In a paper published on August 11 in the online journal Nature Geosciences, scientists working on an international research initiative called IceGeoHeat at the GFZ German Research Centre for Geosciences in Potsdam, Germany, said they had found a distinct difference in the melt depending on the thickness of the Earth’s crust and upper mantle. Together those two elements form the lithosphere, and in some places on Greenland this has proven to be exceptionally thin, the researchers found. And the thinner the lithosphere, the greater the melt right above it.

"The temperature at the base of the ice, and therefore the current dynamics of the Greenland ice sheet is the result of the interaction between the heat flow from the earth's interior and the temperature changes associated with glacial cycles," said study co-author Irina Rogozhina, who initiated IceGeoHeat, in a statement from the research center. "We found areas where the ice melts at the base next to other areas where the base is extremely cold."

Previous models have assumed that the Greenland ice sheet, which loses 227 gigatonnes of ice annually—contributing 0.7 millimeters to the average 3-mm-per-year sea level change that has been observed worldwide—was melting solely because of air and water temperatures, as well as other surface phenomena, the center’s statement said. The lithosphere was thought to play a minimal role, if any. The new research disputes that notion, the scientists said.

"We have run the model over a simulated period of three million years, and taken into account measurements from ice cores and independent magnetic and seismic data," said Alexey Petrunin, another lead researcher, in the statement. "Our model calculations are in good agreement with the measurements. Both the thickness of the ice sheet as well as the temperature at its base are depicted very accurately."

It is just one more factor to be added in when analyzing climate, said the research center, Germany’s main Earth science institute, which studies “the history of the Earth and its characteristics, as well as the processes which occur on its surface and within is interior,” according to its website.

“This effect cannot be neglected when modeling the ice sheet as part of a climate study,” the institute said. “The current climate is influenced by processes that go far back into the history of Earth: The Greenland lithosphere is 2.8 to 1.7 billion years old and is only about 70 to 80 kilometers thick under Central Greenland. It remains to be explored why it is so exceptionally thin. It turns out, however, that the coupling of models of ice dynamics with thermo-mechanical models of the solid earth allows a more accurate view of the processes that are melting the Greenland ice.”

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