NASA is conducting aerial surveillance missions to monitor a massive crack that cuts across the floating ice shelf of Pine Island Glacier in Antarctica.
The six-year mission - dubbed Operation Ice Bridge - is expected to yield an unprecedented three-dimensional view of Arctic and Antarctic ice sheets, ice shelves and sea ice.
Pine Island Glacier last calved a significant iceberg in 2001, and some scientists recently speculated that it was primed to calve again. But until an October overflight, no one had observed any evidence of the ice shelf beginning to break apart. Since then, a more detailed look back at satellite imagery seems to show the first signs of the crack in early October.
"We are actually now witnessing how it happens and it’s very exciting for us," explained IceBridge project scientist Michael Studinger, Goddard Space Flight Center, Greenbelt, Md.
"It’s part of a natural process but it’s pretty exciting to be here and actually observe it while it happens. To my knowledge, no one has flown a lidar instrument over an actively developing rift such as this."
According to Studinger, the IceBridge team observed the rift running across the ice shelf for approximately 18 miles. The lidar instrument on the DC-8, the Airborne Topographic Mapper, measured the rift's shoulders about 820 feet apart (250 meters) at its widest, although the rift stretched about 260 feet wide along most of the crack. The deepest points from the ice shelf surface ranged 165 to 195 feet (50 to 60 meters).
When the iceberg breaks free it is expected to cover about 340 square miles (880 square kilometers) of surface area.
Radar measurements suggest the ice shelf in the region of the rift is approximately 1,640 feet (500 meters) feet thick, with only about 160 feet of that floating above water and the rest submerged. It is likely that once the iceberg floats away, the leading edge of the ice shelf will have receded farther than at any time since its location was first recorded in the 1940s.