New 3-D map sheds light on how Greenland Ice Sheet evolved

A team of scientists using ice-penetrating radar data collected by NASA's Operation IceBridge and earlier airborne campaigns have built the first comprehensive map of layers deep inside the Greenland Ice Sheet, opening a window on past climate conditions and the ice sheet's potentially perilous future.

This new map allows scientists at The University of Texas to determine the age of large swaths of the second largest mass of ice on Earth, an area containing enough water to raise ocean levels by about 20 feet.

Lead author Joe MacGregor said that this new, huge data volume records how the ice sheet evolved and how it's flowing today.

Ice-penetrating radar works by sending radar signals into the ice and recording the strength and return time of reflected signals. From those signals, scientists can detect the ice surface, sub-ice bedrock and layers within the ice.

New techniques used in this study allowed scientists to efficiently pick out these layers in radar data. Prior studies had mapped internal layers, but not at the scale made possible by these newer, faster methods.

Another major factor in this study was the scope of Operation IceBridge's measurements across Greenland, which included flights that covered distances of tens of thousands of kilometers across the ice sheet.

Comparing this age volume to simple computer models helped the study's team better understand the ice sheet's history. Differences in the mapped and modeled age volumes point to past changes in ice flow or processes such as melting at the ice sheet's base. This information will be helpful for evaluating the more sophisticated ice sheet models that are crucial for projecting Greenland's future contribution to sea-level rise.

MacGregor added that prior to this study, a good ice-sheet model was one that got its present thickness and surface speed right. Now, they'll also be able to work on getting its history right, which is important because ice sheets have very long memories.

This study is published online in Journal of Geophysical Research: Earth Surface.