Cutting-edge radar technology developed at the Center for Remote Sensing of Ice Sheets, based at the University of Kansas, has cast new light on the field of glaciology, compelling scientists to reassess the role of melt water beneath miles-thick ice sheets in Antarctica and Greenland.
The startling findings, to be published in Science magazine, show that water underneath Antarctic ice sheets — by repeatedly freezing, melting and refreezing — changes the basic structure of a glacier all the way up to the surface of the ice.
“This project was centered in east Antarctica over a high point in the ice called ‘Dome A’ in a very remote area close to the pole of inaccessibility,” said David Braaten, professor of geography at KU and co-author of the Science paper. “The data set was generated by an airborne geophysical survey with a CReSIS radar on board that was flown in a grid pattern to try and understand what was below the ice.”
In conjunction with a team from Columbia University, researchers at CReSIS analyzed the data, finding that liquid water formed by friction and pressure at the bottom of the glacier changed the contour and elevation at the top of the ice sheet. Although water at the bedrock had been known to act as a lubricant in the movement of ice sheets, never before has it been understood to deform the visible topography of a glacier. In some places, water from below contributed to as much as half of the ice sheet’s overall depth.
“It was an observation made from the radar data of a formation below the ice,” Braaten said. “The premise of this formation is that it developed because of freeze-on at the bed of the ice. So liquid water was produced, it froze on to the bed of the ice and it changed the structure of the ice, essentially pushing up the ice from below.”
The researchers focused on a dome of ice where seismic work by Russian scientists in the 1950s revealed the possibility of a large mountain range underneath the ice, dubbed the Gamburtsev Mountains, which cover an area roughly the size of New York. “But basically, nobody knew what was down there,” said Braaten. “This work confirmed that it’s a mountain range the same size as the Alps.”
The investigation was performed as part of Antarctica’s Gamburtsev Province project, conducted during the International Polar Year, which began in 2007 and continued until 2009. The Office of Polar Programs at the National Science Foundation supported the research.
The radar system developed at CReSIS is called the Multichannel Coherent Radar Depth Sounder. The MCoRDS system mapped the jagged mountain range by sending out energy pulses from antennas fixed to the wings of a dual-engine propeller aircraft. The radar penetrated the thick glacier, reflecting off the bedrock at the bottom of the ice, and then returned a signal to the aircraft that let researchers chart both the bedrock contour and the layers that comprise the ice sheet.
“The radar was developed by CReSIS and tested in Greenland and Antarctica over the years,” Braaten said. “It was offered to this group at Columbia University to duplicate. So the radar was a clone of a radar system developed at KU. It was a state-of-the-art radar for ice sounding, it was the best available, and that’s why they were very interested in obtaining it.”
CReSIS is a Science and Technology Center established by the National Science Foundation in 2005, with the mission of developing new technologies and computer models to measure and predict the response of sea level change to the mass balance of ice sheets in Greenland and Antarctica.