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| NASA's DC-8 over the Pacific during transit to Chile [PHOTO: NASA/Jim Yungel] |
Washington: Scientists and flight crew members with Operation IceBridge,
NASA's airborne mission to study Earth's changing polar ice, are beginning
another campaign over Antarctica. Now in its fourth year, IceBridge's return to
the Antarctic comes almost a year after the discovery of a large rift in the
continent's Pine Island Glacier.
The first science flight of the campaign began Friday at 8
a.m. EDT when NASA's DC-8 research aircraft left Punta Arenas, Chile, for an
11-hour flight that will take it over the Thwaites Glacier in west Antarctica.
This year, IceBridge will survey previously unmeasured areas of land and sea
ice and gather further data on rapidly changing areas like Pine Island Glacier.
The IceBridge Antarctic campaign will operate out of Punta Arenas through
mid-November.
Several of IceBridge's planned flights focus on previously
unmeasured ice streams feeding into the Weddell Sea. These flights will gather data
on what lies beneath these ice streams, something vital for understanding how
changing conditions might affect the flow of ice into the ocean and sea-level
rise.
"We have added surveys of ice streams flowing into the
Ronne and Filchner ice shelves," said IceBridge project scientist Michael
Studinger at NASA's Goddard Spaceflight Center in Greenbelt, Md. "This is
something we haven't done before."
The large crack in Pine Island Glacier's floating ice shelf
has been the focus of worldwide attention as it has grown. The ice shelf now
threatens to calve, or break off, a large iceberg into Pine Island Bay in the
Amundsen Sea. Researchers have been using imagery from NASA's Aqua and Terra
spacecraft and synthetic aperture radar data from the German Aerospace Center's
TerraSAR-X satellite to monitor the rift since its discovery last year.
IceBridge also will gather data on sea ice in the Weddell
and Bellingshausen seas. Because of geographical differences, Antarctic sea ice
behaves differently from ice in the Arctic and presents unique challenges.
"Sea ice in the Antarctic is a very different physical
system," Goddard sea ice researcher Nathan Kurtz said.
Ocean currents, precipitation patterns and the shape of land
masses are just a few of the differences. Instead of compacting ice against
land like in the Arctic basin, currents in the Southern Ocean push much of it
farther out to sea. Also, the Antarctic averages more snowfall, which weighs
sea ice down and allows ocean water into the bottom layer of the snow on top of
the sea ice. The Antarctic has more frequent strong wind events and large
temperature swings than the Arctic, which causes layers of ice to form in snow
cover. Both of these factors make getting accurate readings of snow on top of sea
ice challenging.
Arctic sea ice extent and volume reached record lows this
year, but Antarctic sea ice volume has been holding steady and the extent has
been increasing. Predictive models have a hard time pinpointing what Antarctic
sea ice might do under a warming global climate. Having more data to work with
could make these models more useful. Further observations will give researchers
more data on how Antarctic sea ice changes over time.
"This is why having observations is really
important," Kurtz said. "We want to make sure these models are
getting the physics right.
IceBridge will gather information on many different aspects
of land and sea ice using a variety of scientific sensors onboard the DC-8.
These instruments include a laser altimeter to measure surface elevation
changes, various radar instruments for determining snow depth and ice
thickness, a gravimeter that will gather data on the size and shape of water
cavities under ice shelves, and a digital camera instrument that takes high-resolution
images useful for building maps and digital elevation models of the ice.
By flying previously surveyed tracks in rapidly changing
areas like Pine Island Glacier, IceBridge is building on a legacy of
measurements started by NASA's ICESat satellite that will continue with the
launch of ICESat-2 in 2016.
"This area is changing so rapidly we need to survey
every year," Studinger said.
In addition, IceBridge will fly along tracks for the
European Space Agency's ice-monitoring satellite, CryoSat-2.
This year's campaign also will see visits to IceBridge by
school teachers. Two English-speaking Chilean science teachers will meet with
IceBridge scientists and instrument operators this month and ride on a survey
flight to learn more about polar science research with the goal of using their
new knowledge to better engage and teach students.