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New Study Suggests Antarctic Cooling - 2002-01-27

A new study says Antarctica - the southernmost continent - has cooled measurably in recent years. The findings are a departure from global trends that show significant warming during the last century.

University of Illinois at Chicago Professor Peter Doran monitors the pulse of Antarctica. He and other researchers have plotted climate trends in the region. They are working with data from weather stations in Antarctica's Dry Valleys, a perpetually snow free, mountainous zone, and from stations across the continent. "We built a map of the trends, where it is warming and where it is cooling. That's for the continent," he says. "And, for the Dry Valleys, many of the authors of our paper go down and visit and run automatic stations there that sampled temperature every thirty seconds for the last 14 years."

Their records show a decrease by 0.7 degrees Celsius per decade in the Dry Valleys since 1986 and a similar cooling trend across the continent since 1978. That stands in sharp contrast to the planet-wide average increase in air temperature of 0.06 degrees Celsius during the 20th century.

Lead author Peter Doran says one explanation could be the unique climate system of the polar region.

Doran: "Antarctica is somewhat isolated because there is a big ocean current that constantly circles around the continent and actually sort of isolates it, and that's what makes it cold. And, that may be a factor in why we are seeing Antarctica cooling is that slight disconnect from the rest of the globe, and it's not behaving in the same way."
Skirble: "But, what do you think is causing it?"
Doran: "In the Dry Valleys, the (14-year) record, we see decreasing wind speeds, and that's very interesting. The Antarctic is a very high continent. It is a big dome of ice that reaches up to 2.5 kilometers high. And, so what is happening as air flows off the continent it descends and compresses and it warms. And, when it is windy it is warm along the coast. And, when it is less windy it is cool. So, something is causing the wind speeds to decrease (or) the wind flow to decrease. And, that is largely responsible for our decreasing temperatures."

As wind speeds decrease, lake levels decrease, the ice thickens and the ecology changes. "All of these factors together tend to start to slow the ecosystem, to reduce the numbers of individuals in the ecosystems and over time it will be dramatically reduced and perhaps even go into like a freeze dried state," says Mr. Doran. "We don't expect it to go extinct because there have been cold periods in the past like this, where the lakes have dried up all together. Twelve hundred years ago may have been the last (time) and the ecosystem is still there. So, it is a pretty hardy ecosystem. You can dry up this ecosystem and not kill it and make it go into a deep, deep sleep and when water comes back it will spring back to life, but it will be dramatically altered because of the cooling."

Peter Doran says the biggest uncertainty in Antarctica is not the local impact of cooling, but the consequences of potential global warming and melting of the West Antarctic ice sheet. That, he says, would dramatically raise sea levels, cause vast flooding in low-lying countries and change weather patterns.

But, he says, if current cooling trends continue in Antarctica, as climate models predict, that scenario won't be a problem anytime soon. "In the next 100 years the models (have said) that sea level (was) not going to be affected by Antarctica," he says. "It wasn't going to get warm enough. There was going to be sea-level rise, but that won't be from the thermal expansion of the oceans. Antarctica wasn't (according to climate models) going to start kicking in (getting warmer) until beyond 100 years. So, we need to get Antarctica figured out before it becomes important in the whole sea-level change scenario."

Peter Doran says that can be done with more research to help verify and adjust climate models for Antarctica. That, he says, can lead to a greater understanding of the continent's complex climate and any potential change.