The Greenland ice sheet 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. New research from the Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, claims that “The Greenland ice sheet is melting from below, caused by a high heat flow from the mantle into the lithosphere.” See press release here, and an enlargement of the graphic here.
The melting is quite variable spatially and reflects the relatively thin crust under Greenland. “The Greenland lithosphere is 2.8 to 1.7 billion years old and is only about 70 to 80 kilometers thick under Central Greenland.” Climate models fail to take this phenomenon into effect.
The German researchers say, “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. 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 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.”
Citation: Petrunin, A. G., Rogozhina, I., Vaughan, A. P. M., Kukkonen, I. T., Kaban, M. K., Koulakov, I. & Thomas, M., “Heat flux variations beneath central Greenland’s ice due to anomalously thin lithosphere”, Advance Online Publication, Nature Geoscience, 11. 08. 2013, http://dx.doi.org/10.1038/ngeo1898)