In the early hours of 20th century, a succession of adventurers and scientists pioneered the exploration of Antarctica. A century later, they are still at it, albeit by means of a different set of tools. This fall, a team of modern explorers will wing over Earth's southern ice-covered regions to study changes to its sea ice, ice sheets along with the glaciers as part of NASA's Operation Ice Bridge.
Starting next month, NASA will take wing its DC-8, a 157-foot-long airborne laboratory that can provide accommodation for many instruments. The fall 2009 campaign is one of few excursions to the remote continent made by the DC-8, the largest aircraft in NASA's fleet.
The plane is programmed to leave NASA's Dryden Flight Research Center in Edwards, Calif., on October 12 and take wing to Punta Arenas, Chile, where the plane, crew and researchers will be based for all the way through mid-November. Around six weeks, the Ice Bridge team will go over the Southern Ocean for up to 17 flights over West Antarctica, the Antarctic Peninsula, and coastal areas where sea ice is prevalent. Each round-trip flight lasts about 11 hours in which two-thirds of that time dedicated to getting to and from Antarctica.
Operation Ice Bridge is a six-year campaign of yearly flights to each and every part of Earth's Polar Regions. The initial flights in March and April carried researchers over Greenland as well as the Arctic Ocean. This fall's Antarctic movement, led by principal investigator Seelye Martin of the University of Washington, will initiate the first sustained airborne research effort of its kind over the continent. Data collected by researchers will definitely help the scientists to bridge the gap between NASA's Ice, Cloud as well as Land Elevation Satellite (ICESat) -- which is operating the very last of its three lasers -- and ICESat-II, scheduled to launch in 2014.
The Ice Bridge flights will help out scientists to keep up the record of changes to sea ice as well as ice sheets that have been collected since 2003 by ICESat. The flights will be deficient in the continent-wide coverage that can be achieved by satellite, so researchers cautiously select key target locations. But the flights will also turn up new information not possible from orbit, such as the shape of the terrain below the ice.
"Space-based instruments like the ICESat lasers are the only way to locate where the change is occurring in remote, continent-sized ice sheets similar to Antarctica," said Tom Wagner, cryosphere program scientist at NASA Headquarters in Washington, D.C. "But aircraft missions like Ice Bridge allow us to follow up with more detailed studies and make other measurements critical to modeling sea level rise."
Lasers and Radars
ICESat launched in January 2003 and since then, its one and only instrument -- a precise laser altimeter which has helped the scientists to map the ice sheet elevation, calculate sea ice thickness and moreover it helps to monitor how both have changed.
"With ICESat, we have seen noteworthy changes, things we would not otherwise know were taking place," alleged Jay Zwally of NASA's Goddard Space Flight Center in Greenbelt, Md., and ICESat investigator on the mission. For instance, shifts in surface elevation have formerly revealed the draining and filling of lakes below Antarctica's ice.
After ICESat, scientists will rely on an airborne laser known as the Airborne Topographic Mapper (ATM), developed at NASA Wallops Flight Facility in Wallops Island, Va. ATM pulses laser light in circular scans on the ground, and those pulses reflect back to the aircraft and are converted into elevation maps of the ice surface. By flying ATM over the same swath of ground covered by ICESat, researchers can compare the two data sets and calibrate them so that aircraft can go on with the record keeping after the satellite data ends. They can also make more detailed elevation studies over dynamic areas, such as the Crane glacier on the Antarctic Peninsula, which sped up following the collapse of the Larsen Ice Shelf in 2002.
In adding together, University of Kansas scientists will take wing the Multichannel Coherent Radar Depth Sounder, which measures ice sheet thickness and it can also map the varied terrain below the ice, which is very much important for computer modeling of the future behavior of the ice.
The Laser Vegetation Imaging Sensor, developed at Goddard, will map large areas of sea ice and glacier zones. And a gravimeter, managed by Columbia University, will evaluate the shape of seawater-filled cavities at the edge of some major fast-moving major glaciers. Lastly, snow radar from University of Kansas will compute the thickness of snow on top of sea ice and glaciers, allowing researchers to differentiate between snow and ice and make more accurate thickness measurements.
Targets
The Antarctic continent may be remote, but it plays a noteworthy role in Earth's climate system. The stretch is home to glaciers ass well as the ice sheets that hold frozen about 90 percent of Earth's freshwater -- a huge potential contribution to sea level rise should all the ice melt.
How and where are Antarctica's ice sheets, glaciers as well as sea ice changing? Compared to the Arctic, where sea ice has long been on the decline, sea ice in Antarctica is budding in some coastal areas. Snow as well as ice has been accumulating in some land regions in the east. West Antarctica and the Peninsula, however, have seen more dramatic warming and rapid ice loss.
"We don't see the parallel sea ice changes in Antarctica that we see in the Arctic, and the reason is that the system is more complex," alleged Thorsten Markus of NASA Goddard, the principal sea ice investigator for the mission. "However the fact that we don't see the similar changes in Antarctica that we see in the Arctic doesn’t make it less imperative to study those changes and it is really important for us to understand the global climate system."
With the DC-8 restricted to just a few hours over Antarctica on each and every flight, mission planners have cautiously selected targets of current and potential rapid change.
One such target is West Antarctica's Pine Island Glacier. "That glacier is one of the huge unknowns because its bed -- where the glacier contacts rock and it is below the sea level," Martin said. "So if there's a surge or dramatic change, seawater might get below the glacier furthermore we could be looking at very rapid change."
Other projected targets all along the Amundsen coast include the Thwaites, Smith, and Kohler glaciers and the Getz Ice Shelf. Researchers also have it in mind to study the myriad glaciers as well as the ice shelves on the Peninsula, which has been undergoing remarkable changes.
"An outstanding change is happening on the Earth, truly one of the major changes in environmental conditions on Earth as the end of the ice age," Wagner said. "It is not a simple thing to observe, let alone predict what might happen next. Studies like this one are key."
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