NASA's Operation IceBridge landed in Fairbanks last week, when the special P3 "flying laboratory" arrived to use the airport as a base for missions over the Beaufort and Chukchi seas. IceBridge is an airborne science mission that uses a variety of different aircraft to obtain detailed analysis of ice. In Alaska this includes not only the visiting P3 but smaller aircraft operating year-round which have been studying the state's glaciers for more than two decades.
IceBridge serves first and foremost as a continuity mission for the period that began in 2009 when the Ice, Cloud and Land Elevation Satellite (ICESat) reached the end of its operational lifespan. ICESat-2 is scheduled to launch in 2017 and in the meantime, IceBridge will continue to monitor Earth's polar ice -- over both the north and south poles -- so that a data gap will not exist between the two satellite deployments. Between March and May of this year, the Arctic campaign is operating first out of Thule Air Force Base, to monitor ice accumulation on the Greenland Ice Sheet, later out of the more southern Greenland location of Kangerlussuaq and also overflying the Arctic Ocean regions off Alaska in the Beaufort and Chukchi areas.
According to an article in Earthzine by IceBridge Science Outreach Coordinator George Hale, the two main IceBridge aircraft, the P3 and a DC-8, (which is not flying for this mission), are equipped with a variety of instruments "...ranging from laser altimeters and advanced radars, to digital imaging systems and even magnetic, gravity and surface temperature sensors." These instruments are designed to "gather information on ice surface elevation, ice thickness, snow depth, snow accumulation, and the shape of bedrock and water beneath the ice." If successful, the survey flights will provide a solid snapshot of the size and condition of the monitored ice which reveals how the ice has changed over time.
One of the new instruments being tested on this mission is a spectrometer used to measure ice albedo or reflectivity. According to NASA sea ice scientist Nathan Kurtz, quoted on the IceBridge website, "A small change in albedo over the entire Arctic could have a significant effect on how much heat is absorbed by the surface."
In a recent email exchange, Program Manager Jim Yungel, who is with the mission in Greenland and Alaska, said the new albedo instrument is acquiring data as designed.
"It will be a challenge converting the data into accurate albedo due to the exceeding low sun angles encountered on the missions to date," said Yungel. "but that should improve as we continue to fly later into the spring. We look forward to working with scientists to understand the data we're collecting and how to improve the instrument in the future."
When gathering data, the P3 generally flies at 1,500 feet, as permitted by terrain and weather. It may also, according to Yungel, fly as low as 1,000 feet to get under clouds. "One of the reasons we fly low is to increase the accuracy of the Lidar and radar instruments, since accuracy in measuring aircraft attitude (recorded by laser gyro INS instruments) increases with altitude," he wrote. "Fifteen hundred feet has proved to be the best compromise between accuracy of data (keeping the attitude errors low) and obtaining a wide swath of data."
This year Operation IceBridge is also working with the Seasonal Ice Zone Reconnaissance Surveys program -- located in the East Beaufort sea -- and CryoVex Marginal Ice Zone Camp #2 -- near Barrow -- both of which are studying sea ice and thickness from the ground.
In Fairbanks, Geophysical Institute professor Chris Larsen oversees the glacier altimetry program and has been director of Operation IceBridge since 2009. He followed in the footsteps of institute glaciologist Keith Echelmeyer, who started flying routes over the state's glaciers in 1991. Echelmeyer, who died in 2010, set the standard according to Larsen while personally introducing him to aviation. Larsen now flies his own Cessna 180 on Echelmeyer's established flight paths using a specially mounted LiDAR instrument to measure over 200 glaciers. Ultima Thule Lodge pilot Paul Claus also flies the paths in support of the program in one of his De Havilland Otters with similar equipment.
"Paul and I fly over glaciers in several different fields across the state, including the Stikine Icefield, Glacier Bay National Park, Wrangell St. Elias, the Chugach Icefield and the Alaska Range including Denali," Larsen said in a recent phone conversation. "We try to visit 100 of the glaciers a year, spending about 100 to 150 hours annually in the air between the two of us."
Much of the flying is "below the ridgeline" according to Larsen, at 1,500 feet or less, and he relies on Claus in the more remote areas where his extensive back country flying experience comes into play.
For Larsen, the mission is a "dream come true" and he is particularly interested in visiting a few of the glaciers again this year that exhibited some serious changes in 2013.
Glaciology's use of aviation in Alaska carries on in the footsteps of many other modes of transportation dating back to John Muir's journeys by canoe with Tlingit guides at the end of the 19th century through the Lynn Canal area. His naming of glaciers in Southeast and reports on their size and and changes over time, sparked an interest in the region that directly led to the establishment of Glacier Bay National Park. The study of the state's glaciers is in-depth and well-documented with a massive amount of data; the current visit from Operation IceBridge is just another way to study Alaska's ice and learn what it can tell us about the global climate.