NASA airborne mission maps remote, deteriorating Antarctic glaciers

NASA: NASA's airborne expedition over Antarctica this October and November has measured the change in glaciers vital to sea level rise projections and mapped others rarely traversed by humans. Operation IceBridge, nearing completion of its third year, is the largest airborne campaign ever flown over the world's polar regions. Bridging a gap between two ice elevation mapping satellites, and breaking new scientific ground on its own, IceBridge this fall has charted the continued rapid acceleration and mass loss of Pine Island Glacier.

IceBridge has now generated three years of laser altimetry data over certain locations to continue the record from NASA's Ice Climate and Elevation Satellite (ICESat), which stopped operating in 2009. IceBridge measurements show Pine Island following its rapid deterioration that began around 2006. Combined IceBridge and ICESat data show the glacier is losing more than six times as much mass per year -- mass loss was measured at 7 gigatons a year in 2005 and about 46 gigatons a year in 2010 – making it one of the most significant climate change response trends that scientists see worldwide. For comparison, the Chesapeake Bay holds about 70 gigatons of water.

Satellites still operating, such as NASA's Gravity Recovery and Climate Experiment (GRACE), can provide a large-scale picture of this trend. But it takes a more focused mission such as Operation IceBridge to gather higher-resolution data near the surface to piece together the dynamic interactions of ice, bedrock and ocean currents behind specific changes, and to improve the models that scientists use to predict how much an unstable ice sheet like West Antarctica will contribute to sea level rise.

Two planes make up this year's Antarctica 2011 campaign – NASA's DC-8 flying laboratory, based at Dryden Flight Research Center, Palmdale, Cal., and a Gulfstream-V (G-V) owned by the National Science Foundation and operated by the National Center for Atmospheric Research. The campaign also spotted and flew over a large rift developing across the Pine Island ice shelf on Oct. 14. A natural process, the crack could calve a new iceberg of about 350 square miles of surface area in the coming weeks or months. Pine Island Glacier hasn't calved a major iceberg since 2001.

On a follow-up flight on Oct. 26 to gather data around Pine Island's grounding line, the DC-8 was able to fly along the crack for about 18 miles at an altitude of 3,000 feet, making what are believed to be the first detailed airborne measurements of an active calving rift....

A close-up image of the crack spreading across the ice shelf of Pine Island Glacier shows the details of the boulder-like blocks of ice that fell into the rift when it split. For most of the 18-mile stretch of the crack that NASA’s DC-8 flew over on Oct. 26, 2011, it stretched about 240 feet wide, as roughly seen here. The deepest points ranged from about 165 to 190 feet, roughly equal to the top of the ice shelf down to sea level. Scientists expect the crack to propagate and the ice shelf to calve an iceberg of more than 300 square miles in the coming months. This image was captured by the Digital Mapping System (DMS) aboard the DC-8. Credit: NASA/DMS