Cold facts of global warming

By Nicholas Booth Copyright 1999 The Times (UK) March 3, 1999

In Antarctica, you are either too hot or too cold. That's how Dr David Sugden describes living conditions at the South Pole where he moves around in the coruscating cold in layers of clothes and impressive-looking hoods.

He could just as well be describing the enduring controversy about the frozen continent's climate. For years, glaciologists have debated whether the Antarctic climate has undergone periodic warmings or remained freezing cold. As the man who discovered the world's oldest ice, Dr Sugden believes he has solved the mystery.

A professor of geography at Edinburgh University, he believes he has proof that the Antarctic has long been in deep freeze, implying that the Earth's climate as a whole is far more resilient than had been thought. Reports of catastrophic effects to come from global warming may well be exaggerated, he says.

"We've argued that the Antarctic ice has been very stable for a long time. Now we have shown that there is a genuinely large lump of ancient ice in a dry valley. Its survival implies that the climate must have been similar in the past."

Few people thought that ice could survive for eight million years, even in Antarctica. Along with American colleagues, Dr Sugden published his findings in 1995, but there was little reaction from the outside world. Chris McKay, a biologist with Nasa, observes: "They produced a paper called 'Miocene Ice in Antarctica'. That's another way of saying 'This is the world's oldest ice'. Most ice on Earth has only been around for a few hundred thousand years."

Recently, Mr McKay shared a tent with Dr Sugden on the floor of Beacon Valley in Antarctica, where they were equipped with drills and ground-penetrating radars.

The dry valleys are associated with tragedies of earlier expeditions. They were discovered by Robert Falcon Scott on his first visit to the southern continent in 1905. Even by the breathtaking standards of vertiginous landscapes of sculpted ice, the valleys were a revelation. Climatically, they are bizarre - drier than the Gobi desert with little water vapour available to fall as snow. They are cut off from the nearby ice by the towering Transantarctic Mountains and, over the millennia, have been peppered with volcanic ash and dust.

"I've been down to the south a dozen times," Dr Sugden says. "It came as quite a surprise to find old, glacial ice under the rubble of the dry valleys."

The ice in Antarctica plays a fundamental role in modifying climate. Although it covers only about 10 per cent of the total landmass on Earth, Antarctica contains about 90 per cent of the world's ice. Polar icecaps keep the Earth cool, with the ice limiting the exchange of heat between the atmosphere and the ocean in the polar regions. What happens to Antarctic ice is viewed as a marker for global climate change: the first signs of global warming are likely be seen at the South Pole.

The controversy stems from the disputed age of the ice in the dry valleys and hangs on the question of how hot or cold the climate has been in the past. The advocates of periodically warmer climates have examined microscopic flora which could have thrived in warmer times if the surrounding regions were deglaciated. "We think these things blew in from elsewhere at a later date," Dr Sugden says. "They are found so widely in the ice over the rest of the continent."

He and his colleagues have come at the problem from a different angle: volcanic ash. There are active volcanoes in Antarctica today; in the past, they could have spewed untold quantities of ash and dust into the atmosphere which rained down into the dry valleys. By looking at argon isotopes within the ash, Dr Sugden's team has dated the ice to eight million years. After their earlier paper, more recent extensive analyses have bolstered their findings. "When you have nine out of ten grains giving you this age, you can be pretty certain you're right," he says.

But could the ice have been just a few metres deep and a more recent phenomenon, caused by water seeping into the moraines when warmed by sunlight during the austral summer? Samples of the ice, analysed by Belgian researchers, show that their structure is glacial, having the characteristic shape of snowflakes packed together over time. And the ground radar used on the most recent research trip shows that the ice extends for at least 120 metres below the surface.

What does this mean? Dr Sugden believes that it could have a curious outcome on the future of the continent. The Antarctic is bisected by the Transantarctic Mountains. Climatically, it is a continent of two halves, a distinction which informs the debate on global warming.

Western Antarctica is more unstable because most of the land on which the ice rests is below sea level. Ice continues to spread out to the sea, forming ice shelves that are glued to the landmass by the freezing cold. "The ice is like a ship that is aground," Dr Sugden says. "Its weight keeps it moored there." If temperatures rise, the sea level could rise by a few metres, though this has not been measured yet.

But Eastern Antarctica, in which the dry valleys are located, is a different matter. Containing ten times more ice than the western half, the results from Beacon Valley suggest that it is much more stable. Eastern Antarctica is effectively a giant dome of ice that rises some four kilometres above sea level because its underlying rock is higher.

Dr Sugden believes that this larger part of the ice sheet will act as its own thermostat and control the climatic conditions. Increase the temperature and water will go into the atmosphere as vapour, form snow and, paradoxically, increase the snow cover. "To get rid of this ice, you're going to have to do something very, very drastic," he adds. "Our findings show that the climate has been stable in the past and would be expected to remain so."

If all the ice in Antarctica were melted, then global sea levels could rise by 60 metres. But Dr Sugden believes that the curious ice found in the dry valleys is telling us that that is a very unlikely event indeed.

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