THE MASSIVE Greenland ice sheet is being melted as a result of heat emitted from within the Earth, rather than rising atmospheric temperatures, a new NASA study has claimed.
But they also said it was heat coming out of the bedrock itself which was causing the melting.
This means the ice sheet would melt from below anyway even if global warming was not taking place.
A NASA spokesman said: “Greenland’s thick ice sheet insulates the bedrock below from the cold temperatures at the surface, so the bottom of the ice is often tens of degrees warmer than at the top, because the ice bottom is slowly warmed by heat coming from the Earth’s depths.
“Knowing whether Greenland’s ice lies on wet, slippery ground or is anchored to dry, frozen bedrock is essential for predicting how this ice will flow in the future, but scientists have very few direct observations of the thermal conditions beneath the ice sheet, obtained through fewer than two dozen boreholes that have reached the bottom.
“Now, a new study synthesises several methods to infer the Greenland Ice Sheet’s basal thermal state – whether the bottom of the ice is melted or not – leading to the first map that identifies frozen and thawed areas across the whole ice sheet.”
But the news does not mean NASA has ruled out the fear of the effects of a warming climate, as this would likely speed up the overall melting.
It will use the new map to better predict how the ice sheet will react to a warming climate.
Joe MacGregor, lead author of the study and a glaciologist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said: “We’re ultimately interested in understanding how the ice sheet flows and how it will behave in the future.
“If the ice at its bottom is at the melting point temperature, or thawed, then there could be enough liquid water there for the ice to flow faster and affect how quickly it responds to climate change.”
For the study, published in the Journal of Geophysical Research – Earth Surface, Mr MacGregor’s team combined four different approaches to investigate the basal thermal state.
First, they examined results from eight recent computer models of the ice sheet, which predict bottom temperatures.
Secondly, they studied the layers that compose the ice sheet itself, which are detected by radars onboard NASA’s Operation IceBridge aircraft and suggest where the bottom of the ice is melting rapidly.
For each method, the team looked for areas where the technique confidently inferred that the bed of Greenland’s ice sheet was thawed or frozen.
They then looked at the places where these methods agreed and classified these areas as likely thawed or likely frozen.
The zones where there was insufficient data or the methods disagreed, they classified as uncertain.
From this synthesis, Mr MacGregor and his colleagues determined the bed is likely thawed under Greenland’s southwestern and northeastern ice drainages, while it’s frozen in the interior and west of the ice sheet’s central ice divide.
For a third of the Greenland ice sheet, there’s not enough data available to determine its basal thermal state.
Mr MacGregor said the team’s map is just one step in fully assessing the thermal state of the bottom of Greenland’s ice sheet.
He said: “I call this the piñata, because it’s a first assessment that is bound to get beat up by other groups as techniques improve or new data are introduced.
“But that still makes our effort essential, because prior to our study, we had little to pick on.”
Climate change campaigners remain concerned and insist summer melting of the ice sheet is increasing year on year.
In July 2012 a large ice sheet twice the size of Manhattan (46 square miles) broke free from the Petermann glacier in northern Greenland.