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Climate Connection?

Antarctic Ice Core Reveals Climate Link with Greenland

By Gerald Traufetter

The ice in the Antarctic is giving German scientists a unique glimpse of the earth's climate history. They have discovered evidence of a global temperature seesaw, connecting the two hemispheres.

Germany's southern-most village consists of a few orange-colored trailer homes. Yet even here German thoroughness reigns. The cleaning service is strictly organized, the garbage is sorted into different bins, and on Sundays everyone gathers for a roast dinner. But in this place the everyday becomes the unusual -- the settlement is located on a three-kilometer thick sheet of ice.

Located in the interior of the Antarctic, the Kohnen Station is right in the middle of the icy desert surrounding the South Pole. Only around a dozen people live in this lonely spot during the short polar summers, researchers from throughout Europe enjoying German hospitality.

And doing climate research. Indeed, the Kohnen Station is responsible for the latest insight into the fate of the world's climate -- and the publication of their findings in the journal Nature could hardly have been better timed. The article appeared just as 6,000 delegates were gathering in the Kenyan capital Nairobi for a United Nations conference focused on how best to grapple with a climate changed by humanity.

The European Project for Ice Coring in Antarctica (EPICA) has managed to look back to the future. Their analysis of the ice core drilled at the Kohnen Station has revealed a significant link between temperature variations in Greenland and Antarctica -- a mechanism that governs the oscillation between warm and cold phases in the Northern and Southern hemispheres. "We call it the bipolar seesaw", says Hubertus Fischer, a researcher at Germanys Alfred Wegener Institute for Polar and Marine Research (AWI) and the main author of the new study.

His main concern was with the evidence of unusual climate change Greenland ice cores had revealed a few years ago. Temperatures during the last Ice Age, the cores revealed, had swung repeatedly up and down -- "by more than 10 degrees within a few decades," Fischer explains.

Scientists have long wondered if these enormous swings in temperature were only a regional phenomenon. This latest research now shows that they weren’t. The 2,774 meter-long ice core the EPICA team finished extracting out of the Antarctic ice in February reveals a mirror image of the temperature changes in the Northern Hemisphere. "When it was warm in the north, the ocean surrounding Antarctica cooled down," says Fischer. "And vice versa: the Southern Hemisphere warmed up when it got colder in the north."

These temperature swings seem to be caused by the system of currents in the Atlantic Ocean. Acting like a giant conveyor belt it carries water from the southern pole to the tropics and from there on to Europe and Greenland. The northern extension is better known as the Gulf Stream.

The current varies in its flow -- sometimes stronger, sometimes weaker. The analysis of the ice core now shows that two factors determine these fluctuations: On the one hand, precipitation and massive amounts of melt-water can weaken the stream. The influx of freshwater makes the water lighter; it doesn’t rush as quickly into the depths in the region between Greenland and the Arctic island of Spitsbergen. "The result is that the conveyor belt slows down," says Fischer.

Some time later, however, it picks up again, and the impulse may come from the south. Initially, the weakened current causes the southern seas to become warmer. Eventually, after a time lag which could last up to a few hundred years, southern waters could increase in temperature by as much as 3 degrees Celsius, Fischer and his team have concluded based on their analysis of the ice core.

This warming could lead to an increase in the salinity of the water on the edges of the Antarctic ice sheets as the less saline ice breaks off and floats away. The heavier, saltier water on the edges sinks and the giant conveyor belt thus regains its speed, the researchers think. "These phases have alternated repeatedly in the history of the earth," Fischer says, explaining the principle of this climatic seesaw.

And the ice core contained another surprise for the researchers. The massive ice masses of the Antarctic are a lot less stable than had been thought up to now. When the team's drillmaster Frank Wilhelms bored deeper into the rock, water surged into the hole. "There is a bubbling brook underneath the ice crust," he reports.

The massive pressure of 250 bar is apparently causing the ice to melt -- even at the temperature of minus 2 degrees Celsius (28.4 degrees Fahrenheit). "We would have to assume that a considerable part of the Antarctic interior ice lies on top of this watery layer," the AWI scientist concludes.

The newly discovered north-south connection could definitely have consequences: "In particular Australia, South America and South Africa could experience even higher temperatures than we had previously thought," Fischer says.

The message contained in the ice will provide little comfort for the climate politicians in Nairobi, says the glaciologist. The climate seesaw does indeed help to distribute the warmth between the north and the south. "But it doesn’t change the fact that, on average, it's going to get warmer."