NASA maps layers deep inside Greenland ice sheet

Scientists using ice-penetrating radar data collected by NASA have created the first-ever comprehensive map of layers deep inside the Greenland ice sheet.
The new map, developed using data collected by NASA's Operation IceBridge and earlier airborne campaigns, allows scientists to determine the age of large swaths of Greenland's ice, extending ice core data for a better picture of the ice sheet's history.
"This new, huge data volume records how the ice sheet evolved and how it's flowing today," said Joe MacGregor, a glaciologist at The University of Texas at Austin's Institute for Geophysics and the study's lead author.
Scientists are studying ice from different climate periods in the past to better understand how Greenland's ice sheet might respond in the future. One way of studying this distant past is with ice cores.

These cylinders of ice drilled from the ice sheet hold evidence of past snow accumulation and temperature and contain impurities like dust and volcanic ash that were carried by snow that accumulated and compacted over hundreds of thousands of years.
These layers are visible in ice cores and can be detected with ice-penetrating radar.

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, researchers said.
"IceBridge surveyed previously unexplored parts of the Greenland ice sheet and did it using state-of-the-art CReSIS radars," said study co-author, Mark Fahnestock, a glaciologist from the Geophysical Institute at University of Alaska Fairbanks and IceBridge science team member.
CReSIS is the Center for Remote Sensing of Ice Sheets, a National Science Foundation Science and Technology Center headquartered at the University of Kansas in Lawrence, Kansas.
IceBridge's flight lines often intersect ice core sites where other scientists have analysed the ice's chemical composition to map and date layers in the ice.

These core data provide a reference for radar measurements and provide a way to calculate how much ice from a given climate period exists across the ice sheet, something known as an age volume.
Scientists are interested in knowing more about ice from the Eemian period, a time from 115,000 to 130,000 years ago that was roughly as warm as today.
This new age volume provides the first rough estimate of where Eemian ice may remain.
Comparing this age volume to simple computer models helped the study's team better understand the ice sheet's history.