The researchers led by Irina Rogozhina and Alexey Petrunin from GFZ German Research Centre for Geosciences had to go far back into the Earth's history to explain the reason for the melting base of the world's second largest ice sheet.
Their observations from radar and ice core drilling data indicated the melt from below and the rapid ice flow over a distance of 750 kilometres from the summit area of the Greenland ice sheet to the North Atlantic Ocean.
"The geothermal anomaly which resulted from the Icelandic mantle-plume tens of millions of years ago is an important motor for today's hydrology under the ice sheet and for the high flow-rate of the ice," Rogozhina said.
"This, in turn, broadly influences the dynamic behaviour of ice masses and must be included in studies of the future response to climate change," she added.
The North Atlantic Ocean is an area of active plate tectonics. Between 80 and 35 million years ago, tectonic processes moved Greenland over an area where the mantle material heated and thinned Greenland at depth producing a strong geothermal anomaly that spans a quarter of the land area of Greenland.
The researchers used an innovative combination of computer models and data sets from seismology, gravity measurements, ice core drilling campaigns, radar sounding, as well as both airborne, satellite and ground-based measurements to reveal the secrets of Greenland's past hidden beneath a three-km thick ice sheet.