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Greenland's Ice Anomaly -
Heat Flow From The Mantle Intensifies Ice Melting

12 August, 2013

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MessageToEagle.com - The Greenland ice sheet - playing a central role in climate - is systematically melting from below, because of a high heat flow from the mantle into the thin lithosphere, researchers say.

It loses about 227 gigatonnes of ice per year and contributes about 0.7 millimeters to the currently observed mean sea level change of about 3 mm per year.

The process has its origin in an exceptionally thin lithosphere. Consequently, there is an increased heat flow from the mantle and a complex interplay between this geothermal heating and the Greenland ice sheet.



Click on image to enlarge

Modeled basal ice temperatures of the present-day Greenland Ice Shield across the Summit region, GRIP and GISP2 indicate borehole locations. Credit: A. Petrunin/GFZ


Existing model calculations, however, were based on a consideration of the ice cap and considered the effect of the lithosphere, i.e. the earth's crust and upper mantle, too simplistic and primarily mechanical: the ice presses the crust down due to its weight.

Scientists Alexey Petrunin and Irina Rogozhina from the GFZ German Research Centre for Geosciences have now coupled an ice/climate model with a thermo-mechanical model for the Greenland lithosphere.

"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", says Petrunin.

"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."

The model can even explain the difference in temperature measured at two adjacent drill holes: the thickness of the Greenland lithosphere and thus the geothermal heat flow varies greatly in narrow confines.

What does this mean for climate modeling?

"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," explains corresponding author Irina Rogozhina (GFZ) who initiated IceGeoHeat.



A NASA study of Greenlandís ice sheet reveals that it is rapidly thinning.


"We found areas where the ice melts at the base next to other areas where the base is extremely cold."

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.

Paper.

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See also:
Earth's Clouds Are Dropping - Something Important Is Happening

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