For 18 days during the Southern Hemisphere spring of 1997, a
NASA-launched Canadian satellite called RADARSAT collected pieces
of a puzzle that will help scientists study the most remote and
inaccessible part of the Earth -- Antarctica. Scientists now have
the puzzle pieces put together, forming the first high-resolution
radar map of the mysterious frozen continent.
With detail to the point of picking out a research bungalow
on an iceberg, the new map has both answered scientists' questions
about the icy continent, and left them scratching their heads
about what to make of strange and fascinating features never seen
before.
"This map is truly a new window on the Antarctic continent,
providing new beginnings in our Earth science studies there," said
Dr. Ghassem Asrar, Associate Administrator for Earth Science, NASA
Headquarters, Washington, DC. The new map was produced as part of
NASA's Antarctic Mapping Project.
The most amazing features scientists now see are twisted
patterns of ice draining from the ice sheet into the ocean. "We
were surprised to see a complex network of ice streams reaching
deep into the heart of East Antarctica," said Kenneth Jezek, a
glaciologist from the Byrd Polar Research Center at Ohio State
University. Ice streams are vast rivers of ice that flow up to
100 times faster than the ice they channel through, with speeds up
to 3000 feet per year. "There are some extraordinary ice streams
in East Antarctica that extend almost 500 miles -- nearly the
distance along the Mississippi River from New Orleans to Cairo,
Illinois," Jezek said.
Ice streams form the most energetic parts of the Antarctic
ice sheet, and scientists believe that they are quite susceptible
to environmental change. Ice streams also transport most of the
snow that falls on the continent's interior and dump it into the
ocean.
"We've recently used RADARSAT and other satellite data to
estimate that one ice stream system sends over 19 cubic miles of
ice to the sea every year -- an amount equivalent to burying
Washington, DC, in 1700 feet of ice every 12 months," said Jezek.
Antarctica looks pure, white and mostly featureless to the
low-resolution satellites that previously mapped the frozen
landscape. With the new RADARSAT map, however, the continent
comes alive. Blocks of broken sea ice line the coast and
sedimentary rock protrudes from the rocky walls of Antarctica's
Dry Valleys. The vast, perplexing Antarctic Ice Sheet flows and
twists into the sea, volcanoes poke through the ice sheet and ice
streams flow like rivers into the Southern Ocean. Even the tracks
of wayward snow tractors on their way to inland stations are
visible. "We have a new view of the entire southern continent.
It shows us something about an extraordinary part of our world and
how humans may be changing it -- on both local and global scales,"
said Jezek.
Jezek and his colleagues have been working to complete the
enormous map since the Canadian Space Agency began the mission
with a complex in-orbit rotation of the satellite. Researchers
chose RADARSAT because its radar collects data day and night,
through cloudy weather or clear. Such capability enabled the
mapping to be completed in just 18 days, compared to the last
satellite map of Antarctica which required images from five
different satellites spanning a 13-year period from 1980 to 1994.
Even at that time, parts of the continent remained obscured by
cloud cover.
The map also depends on accurate ground measurements by
scientists from many of the nations that study Antarctica. "The
entire mission was conducted in a true spirit of international
cooperation, and that is why it succeeded," said Verne Kaupp,
NASA's Alaska SAR Facility Director and Chief Scientist.
RADARSAT-1 is owned and operated by the Canadian Space Agency
(CSA). Its data is distributed and marketed by RADARSAT
International, a Canadian company licensed by the CSA. "We at the
Canadian Space Agency are very pleased to make this significant
contribution to the international science community," said Dr.
Rolf Mamem, Director General, CSA Space Operations Branch. "We
are looking forward to the exploitation of these data for the
benefit of all."
The Antarctic Mapping Mission is only one part of NASA's
study of the frozen continent. NASA's study of the Antarctic is
part of the Agency's Earth Science Enterprise, a dedicated effort
to better understand how natural and human-induced changes affect
our Earth's environmental system.
RADARSAT images of Antarctica are available on the Internet
at:
http://svs.gsfc.nasa.gov/stories/antarctica/index.html
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