Post by lee on Aug 6th, 2016 at 7:15pm
'Melt at the Base of the Greenland Ice Sheet'
'Though it seems counter-intuitive, Greenland’s thick ice sheet actually insulates the bedrock below from the cold air temperatures at the surface. As a result, the bottom of the ice—slowly warmed by heat coming from Earth’s depths—can be tens of degrees warmer than at the top. Knowing whether Greenland’s ice lies on wet, slippery ground or is anchored to dry, frozen bedrock is essential for understanding how the ice sheet will react to a warming climate and flow in the future.
But the thermal conditions below 3 kilometers (2 miles) of ice are hard to determine. Scientists have very few direct observations beneath the ice sheet, and those were obtained through fewer than two dozen boreholes that have reached the bedrock. Now, a new study synthesizes NASA airborne and satellite data from the past two decades to infer the Greenland Ice Sheet’s basal thermal state—whether the bottom of the ice is melted or not.
The results of that synthesis are represented on the map above. Red areas show where the ice is likely thawed on the bottom (43 percent of the ice sheet), and blue areas show where it is likely frozen (24 percent). Gray areas are where the thermal state is uncertain.'
http://earthobservatory.nasa.gov/IOTD/view.php?id=88505
'Though it seems counter-intuitive, Greenland’s thick ice sheet actually insulates the bedrock below from the cold air temperatures at the surface. As a result, the bottom of the ice—slowly warmed by heat coming from Earth’s depths—can be tens of degrees warmer than at the top. Knowing whether Greenland’s ice lies on wet, slippery ground or is anchored to dry, frozen bedrock is essential for understanding how the ice sheet will react to a warming climate and flow in the future.
But the thermal conditions below 3 kilometers (2 miles) of ice are hard to determine. Scientists have very few direct observations beneath the ice sheet, and those were obtained through fewer than two dozen boreholes that have reached the bedrock. Now, a new study synthesizes NASA airborne and satellite data from the past two decades to infer the Greenland Ice Sheet’s basal thermal state—whether the bottom of the ice is melted or not.
The results of that synthesis are represented on the map above. Red areas show where the ice is likely thawed on the bottom (43 percent of the ice sheet), and blue areas show where it is likely frozen (24 percent). Gray areas are where the thermal state is uncertain.'
http://earthobservatory.nasa.gov/IOTD/view.php?id=88505