Century-Old Antarctic Station Shows Warming

THE GIST:

• More than 100 years of weather data are showing a warming pattern.
• An ozone hole and climate change is behind this trend.

Records of more than a century of weather data from the southern hemisphere's oldest, coldest weather station have revealed an extraordinary burst of warming since 1950 -- but it's not all caused by global warming.

The base at the Islas Orcadas, a remote band of land that looks as if it's been whipped off the tip of the Antarctic Peninsula, was founded by Scots in 1903, and has been manned by Argentines ever since, all of whom collected daily weather data.

That longevity is paying off in terms of getting a better grasp of southern climate changes, explains NOAA climate researcher Susan Solomon and her colleagues in the Jan. 2010 issue of the Journal of Climate.

The Orcadas weather data were the culmination of years of searching for old records that contained daily weather information from the Antarctic. Such records are especially useful because they reveal extreme warm and cold weather days, all of which are lost in the easier to locate monthly mean records, she explained.

"It turns out to be a fascinating record," Solomon told Discovery News. "What it shows is that there have been changes in the extremes and changes in the actual cycles."

The Orcadas record shows that summers at the base have been warming up since the 1950s. However the warming is probably not primarily caused by global warming, Solomon said.

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"A big chunk of that is how the way ozone changed the circulation patterns," she said. A gigantic ozone hole has been forming over Antarctica every southern spring since the 1970s.

The ozone hole has cooled the stratosphere over Antarctica. That cooling has filtered down to the lower, much thicker part of the atmosphere where all the weather happens: the troposphere.

That extra bit of cooling tends to reinforce the circular cold airmass that can form atop Antarctica called the polar vortex.

"The region outside of the vortex, like Orcadas, is much warmer," Solomon said. "So Orcadas is in a special situation where it's getting much less of the cold waves."

"There was a little bit of that effect before the ozone," she added, which can be attributed to global warming.

"It's quite difficult to tease these out," said climatologist Gareth Marshall of the British Antarctic Survey. One of the things that supports the ozone hole scenario is computer modeling, which reproduces the effect, he said.

Whatever the cause, said Marshall, "Orcadas has probably warmed more than any other area in the last 50 years." And that alone makes it worth a closer look.