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Tuesday, October 19, 1999 Published at 10:49 GMT 11:49 UK


Radar reveals the frozen continent

East Antarctic ice streams pour ice into the oceans

By BBC News Online Science Editor Dr David Whitehouse

The first high-resolution radar map of Antarctica has revealed the frozen continent in such detail that even research huts sat on icebergs can be spotted.

[ image: The radar map covers the whole continent]
The radar map covers the whole continent
"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 at Nasa Headquarters.

Radasat, a Nasa-launched Canadian satellite, spent 18 days in spring 1997 bouncing radar signals from the Earth's surface and analysing the echoes.

Antarctica looks almost featureless with the images from low-resolution satellites that previously mapped the frozen landscape. With the new Radarsat map, however, the continent comes to life.

One can see blocks of broken sea ice that line the coast; sedimentary rock protruding from the rocky walls of Antarctica's Dry Valleys; vast, perplexing ice flows that snake into the sea and volcanoes that poke their heads through the ice sheet.

[ image: A vehicle track over Lake Vostok is visible]
A vehicle track over Lake Vostok is visible
Even the tracks of snow tractors on their way to inland stations are visible, as is the road that runs over the flat ice-cap that overlies Lake Vostok, the largest under-ice sea in the world.

The new map has answered scientists' questions about the icy continent, but it has also left them wondering what to make of strange and fascinating features never seen before.

"We have a new view of the entire southern continent," said Kenneth Jezek, a glaciologist from the Byrd Polar Research Centre at Ohio State University. "It shows us an extraordinary part of our world and how humans may be changing it - on both local and global scales."

Some scientists believe that the most amazing features that can be seen in Radasat's images are twisted patterns of ice flowing from the ice sheet into the ocean.

[ image: Snow dunes captured by satellite camera]
Snow dunes captured by satellite camera
"We were surprised to see a complex network of ice streams reaching deep into the heart of East Antarctica," said Dr Jezek. "There are some extraordinary ice streams that extend almost 500 miles."

Ice streams are vast rivers of ice that flow up to 100 times faster than the ice they channel through, with speeds up to 900 metres (3,000 feet) per year.

It is believed that ice streams form in the most energetic parts of the Antarctic ice sheet, and scientists believe that they are quite susceptible to environmental change. They are important to the long-term stability of the Antarctic ice sheet as they transport most of the snow that falls on the continent's interior back to the ocean.

"We've recently used Radarsat and other satellite data to estimate that one ice stream system sends over 78 cubic kilometres of ice to the sea every year - an amount equivalent to burying Washington DC, in 520 m (1,700 ft) of ice every 12 months," said Dr Jezek.

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