NASA scientists are flying a suite of instruments on two planes as part of Operation IceBridge, which is now on the third year of its critical study of the changing ice of Antarctica.

Antarctica is 98 percent covered with ice, and researchers want to know how fast climate change is melting key features like the Pine Island Glacier, which rests on a bedrock below sea level.

From their operations base in Punta Arenas, Chile, researchers are flying a DC-8 operated by NASA and a Gulfstream V (G-V) operated by the National Science Foundation and the National Center for Atmospheric Research.

The planes will carry a variety of remote-sensing instruments above Antarctica's land and sea ice, and in some regions, above the ocean floor. The G-V will carry a laser-ranging topography mapper, while the DC-8 will bring seven instruments, including a laser altimeter to continue the crucial ice sheet elevation record begun by the Ice, Cloud and land Elevation Satellite mission that ended in 2009.

The flying laboratory also will carry radars that will monitor how much snow sits on top of sea ice and map the terrain of bedrock below thick ice cover. The topography of the rocky surface beneath the ice sheets has remained relatively unknown, and without this information, it will be impossible to know exactly how much ice sits on top of Antarctica.

According to Michael Studinger, IceBridge project scientist at NASA's Goddard Space Flight Center in Greenbelt, Md., they will be resurveying previous flight lines to observe changes in the glaciers and ice sheets while establishing a baseline for future years and for a new satellite mission in 2016.

"With IceBridge, our aim is to understand what the world's major ice sheets could contribute to sea-level rise. To understand that you have to record how ice sheets and glaciers are changing over time," Studinger said.