MELTING MOMENTS IN GEEK HEAVEN

Antarctica is rich in wildlife and natural beauty - and also of unique interest to scientists, especially those studying global warming. But, reports Fred Pearce, the land of the big chill is warming up

In September, Antarctica awakes. The first rays of the southern summer extend across the ice continent - a land the size of the US that is dedicated by the world's major governments to science.

Antarctica makes up a tenth of the planet's land surface. And on it sits 90 per cent of the world's ice. That ice traps unique evidence of our planet's past, and holds vital clues to its future. Each southern summer, some 3,000 scientists head south.

Here they can plumb the planet's past. Earlier this year, British scientists from the Scott Polar Research Institute reported that their radio-echo experiments and seismic tests have revealed a vast biological time capsule. Locked between layers of ice below the Russian research station at Vostok, Gordon Robin and his colleagues have found a freshwater lake which is thought to be roughly the size of Northern Ireland and 100m deep.

Like something out of Jules Verne's Journey to the Centre of the Earth, the lake "has been cut off from the world above for at least half a million years," says Cynan Ellis-Evans of the British Antarctic Survey (BAS). Between it and the world above lies a 4km layer of packed ice, so heavy that its pressure (of perhaps 300 atmospheres) keeps the lake liquid in the sub-zero temperatures.

Ellis-Evans believes there could be living organisms down there, perhaps populating the lake's sediments. They will be bacteria, and perhaps other creatures, that have evolved to live in the cold, at great pressures and with few conventional nutrients on which to feed. He hopes eventually to retrieve for analysis some organisms from the lake, that is now known as Lake Vostok. But devising a way of drilling down to this time capsule without polluting it with organisms from the world above could tax scientists and engineers well into the next century.

In Antarctica, the ice preserves much that could never survive elsewhere. It is the best place on earth to find meteorites. It was here that scientists picked up the fragment of Mars in which NASA researchers recently announced that they had discovered evidence of Martian life forms.

The ice even traps ancient air in tiny bubbles that are now revealing the history of the chemical composition of our atmosphere. Teams of Russian drillers have extracted tubes of ice extending more than two kilometres into the ice. Since the early 1980s, these cores have brought back for analysis bubbles of air, trapped in ice tens and then hundreds of thousands of years ago.

From this analysis French researchers led by Michael Legrand of the Laboratory of Glaciology and Geophysics of the Environment at Grenoble have produced graphs of the temperature (measured by the isotopic composition of the ice) and the chemical make-up of the air over Antarctica through the last ice age and into the warm period before it, 150,000 years ago.

The graphs reveal an almost exact match between changes in temperature and levels of carbon dioxide. These detailed fingerprints of the greenhouse effect in action have become one of the vital elements in the arsenal of scientists calling for action to halt global warming by controlling our emissions of carbon dioxide.

Besides plotting the past, Antarctic science is also presaging the future. Global warming is proceeding here faster than anywhere else on earth. Early this year, David Vaughan of the British Antarctic Survey reported in the journal Nature a warming of 2.5 degrees Celsius in the past 40 years at the BAS's Faraday Research Base in the Antarctic peninsula. British researchers were also the first to announce a stunning increase in the growth of grass around the fringes of Antarctica, including the Signy islands where they have a base, leading in turn to invasions of sea mammals such as fur seals.

As the air and oceans warm, the ice is melting. In the past decade, the map of Antarctica has begun to change as huge sections of floating ice shelves - large slabs of permanent sea ice connected to the continent's main ice sheets - have sheared off. Each southern spring, icebergs the size of English counties float north (every direction is north) towards the Falklands or South Africa or Australasia. The Antarctic peninsula's Wordie and Larsen ice shelves and the ice between the peninsula and James Ross Island are all melting fast. Two-thirds of the Wordie sheet has disappeared in 30 years, says Vaughan. Sometimes the scientists themselves are threatened. One of the first great ice "calvings" from around the Antarctic peninsula, a massive chunk measuring 15,000 square kilometres that broke off in 1986, took Russia's Druzhnaya research station with it.

Vaughan warned in Nature of an "abrupt thermal limit on ice-shield viability". Beyond a critical threshold temperature, the shelves collapse. Melting Antarctic ice matters for the whole planet. If all the ice stored on the Antarctic land surface melted, slipping into the oceans, it would raise worldwide sea levels by 60 metres - flooding all of lowland Britain, for instance.

Something similar has happened before. About 100,000 years ago, the world's sea levels rose by 20 metres within less than a century after large parts of the Antarctic ice sheets became unstable and slid into the ocean. Two million years ago, there were green hills, trees and streams in the Transantarctic Mountains near the South Pole, where now there is three kilometres depth of ice.

Could it happen again? Most scientists say it would take thousands of years for so much ice to melt. But surveys have revealed that parts of the Antarctic ice sheets are unstable. One of the two main sheets, covering West Antarctic, is in fact a vast iceberg grounded on an archipelago of islands the size of the Philippines but with ocean water flowing round and beneath. Three years ago Donald Blankenship of the Institute of Geophysics at the University of Texas at Austin, after an aerial geophysical survey of the region, published a warning that active volcanoes among these West Antarctic islands could melt the ice that tethers the ice sheet to the islands and "trigger a collapse of the ice sheet".

And other researchers warn that changes in sea temperature not much greater than those experienced in recent years could lift the ice sheet free of the islands, forcing it into the open ocean, where it could melt within a few decades. The result in either case could be a global five-metre rise in sea levels.

The first scientist to warn of this threat was John Mercer of the Institute of Polar Studies at the Ohio State University. In 1978 he published a paper predicting that the destruction of the West Antarctic ice sheet would probably begin with the melting of ice shelves on the Antarctic peninsula, the most northerly part of the continent and so the most vulnerable. He warned that "a major disaster" - a rapid five-metre rise in sea level, caused by deglaciation of the West Antarctic - "may be imminent or in progress ... within about 40 years." In the past five years, researchers have charted precisely this process. "So far, Mercer's predictions have been borne out," Vaughan says.

Antarctic ice, and the air and oceans around it, are not just sensitive indicators of the state of the planet; they are very active participants in global changes. The Antarctic ice is the planet's freezer. This vast expanse of white reflects almost all the solar radiation that reaches Earth and hits straight back into space. It helps keep the planet cool. If the area of ice starts to diminish, it will accelerate global warming.

But meanwhile, it has created the largest area of cold air over the planet. Each southern winter, with the sun out of sight for four months and the ice radiating heat into space, the temperature in the lower stratosphere plunges to below minus 90 degrees Celsius, a temperature found nowhere else on the planet.

What moisture remains in this petrified air forms a translucent cloud of supercooled ice crystals. And on the surface of these crystals unique chemistry occurs. Chlorine atoms from man-made chemicals such as chlorofluorocarbons destroy ozone in a series of runaway reactions that are only halted when all the ozone is gone. Result: the ozone hole.

For some, Antarctic science seems the ultimate irrelevance, and the entire continent an absurd giant playground for nerdy scientists, explorers with a faraway look in their eyes and the socially challenged. "Geek heaven," the New Scientist recently called it. Until the 1980s it was also largely a continent for men only, with women kept off most research stations. The only good thing to emerge from its frosty embrace, they said, was the string vest, developed in the 1920s to keep British explorers warm.

The discovery of the ozone hole changed all that. It was one of the great triumphs for the doggedness of the continent's scientists. For more than 20 years, British boffins at the Halley Bay research station on the Antarctic peninsula had pointed a device known as a Dobsonmeter, after its inventor, into the skies to measure the thickness of the ozone layer above the base.

They plotted a regular but small seasonal cycle of such consuming dullness that by the early 1980s, they were about to shut down the equipment and bring it home. But then its minder, veteran Antarctic researcher Joe Farman, spotted that the pattern was changing. And changing drastically as each southern spring, more and more ozone started to disappear.

The data confounded atmospheric chemists. They had known for a decade that man-made chemicals such as CFCs might destroy ozone. But they did not realise that the ice particles could dramatically speed up ozone destruction, creating the "hole".

Farman says: "It was in a way a triumph for routine monitoring, not relying on computer models or dismissing data that does not fit the theories." And that, he says, is one of the great virtues of science in the ice continent - the whole place is a dramatic laboratory for observing the planet at its most raw and simple. The truth is that, without Antarctic science, the world might not know even now that its industrial chemicals were eating away one of the planet's primary defences against cosmic radiation. As it is, we do, and after 10 years of effort to ban the offending chemicals, this year could be the first in which the hole begins to fill again.

Each southern summer, the ice continent becomes less remote. Scientists now fly in rather than taking the slow boat to the bottom of the world. And the numbers of tourists are increasing too. This year as many as 10,000 people will visit by ship or plane, thanks to a growing list of specialist tour operators, including five based in Britain. For the moment, the continent's only permanent settlements are science bases - including the US's McMurdo base which is home for up to 1,200 people. But this summer, as for several summers past, tourists will outnumber the 3,000 or so scientists on the continent. The Antarctic peninsula, easily accessible from the Falklands, Chile and Argentina, will once again resemble a cold-weather French Riviera with Zodiac inflatable boats shuttling between cruise ships and the shore.

On land, most visitors will simply look at the penguins and head back to the boat. But some fly Twin Otters and helicopters or even ride snowmobiles into the interior, go mountaineering or head for the South Pole. What Captain Scott died to accomplish in the first decade of the century, is now the latest tourist fad. !

THE ANTARCTIC'S ROLES

THE MYTH is that the peopling of Antarctica has advanced seamlessly from exploration to permanent science. It is not true. After the great expeditions of the 19th and early 20th centuries - of Scott, Amundsen and Shackleton - the next steps were unambiguously military. Britain laid claim to the Antarctic peninsula south of the Falklands in 1908. In 1939, as World War II got under way, German aviators dropped Swastika flags onto the ice and claimed it for the Third Reich. In 1940 and 1942 Chile and Argentina contested Britain's claim. Then in 1946, the US landed 5,000 soldiers in Operation Highjump to photograph the coastline and declare its own interest. Altogether seven nations - Norway, France, Australia, New Zealand, Chile, Britain and Argentina - have claims, some of them competing.

Science only seriously got under way in 1957, during the International Geophysical Year, when researchers chose Antarctica as the best place to view solar radiation during a year of intense sunspot activity. Some 60 research stations were established, and many have persisted ever since. Whether it was through altruism or because, in truth, nobody could think of another use for the largest untouched landscape on Earth, scientific co-operation became the cornerstone of the 1961 Antarctic Treaty. Initially signed by 12 nations, the treaty froze (but did not expunge) the territorial claims of seven of them. Antarctica became a nuclear-free zone, dedicated to peaceful purposes and with special freedoms for scientists. Today the "club" of members party to the treaty has extended to 42. Any nation can join. The only requirement is that they carry out scientific research there.

There are periodic calls for the UN to assume complete control of the continent. But since any member of the UN can join the Treaty too, this has little force. Some complain that tourism is not effectively overseen by the treaty; and that there is no rule to prevent the extraction of ice for water supply, as rich desert nations such as Saudi Arabia have sometimes proposed. But defenders say the treaty can be adapted to meet the area's changing needs. In 1993, for instance, it adopted an environmental protocol, which prohibits oil or minerals exploration for another 50 years, and has forced a clean-up at several "dirty" research stations. A tourism protocol could one day follow. If it ain't broke, don't fix it, they say.

For now, minor transgressions excepted, the continent is, in effect, a world park. A tenth of the land surface of the planet remains to all intents and purposes protected for the sole and exclusive use of scientists.