Research Shines Some Light On Mysteries of Antarctica
Two Studies Give Clues About Warming, Continent's Future

By Marc Kaufman
Washington Post Staff Writer
Sunday, February 18, 2007

When researchers think about the effects of global warming, and especially about how much ocean levels will rise along with temperatures, they inevitably turn their attention to Antarctica. Almost 90 percent of the planet's ice is frozen in the glaciers and ice sheets of the continent, so conditions there will in large part determine whether sea level rise will be manageable -- or catastrophic.

Unfortunately, Antarctica's climate has proven very difficult to understand or predict, and it has given off seemingly contradictory signals. Both temperatures and snowfall have remained relatively constant for the continent as a whole over the past 50 years, but the Antarctic Peninsula -- which reaches northward toward South America -- has been losing ice rapidly and is among the most quickly warming places on Earth.

Now, two new research efforts have tackled the subject -- producing new insights into the systems that control and change Antarctica, as well into the worrisome limits to our knowledge about the suddenly crucial continent.

The first project revealed that a previously unknown system of seemingly connected lakes lies under the massive streams of ice that move Antarctica's frozen water from the center of the continent to its coasts. It is a system that might work to moderate climate change, the researchers said, or alternatively might speed it up if a tipping point is reached.

"The big question in climate change for the next decade is what happens to the sea level, how much ice melts into the oceans," said Robert Bindschadler, a senior fellow at the NASA Goddard Space Flight Center in Greenbelt and co-author of the paper on the continent's subglacial "plumbing."

Because so much of Earth's ice is in Antarctica, he said, that plumbing may be the key to whether coastlines far away will someday be submerged. "Yet at this point, we know very little about the physics of how it works," he said.

The other new research found that while temperatures have remained relatively constant for much of Antarctica, westerly winds have been growing significantly more powerful around the continent. Those stronger winds, the researchers suggest, may be keeping temperatures in check but also causing the ice shelves along the Antarctic Peninsula to collapse.

And while it is uncertain why the winds have increased, one explanation involves another change wrought by humans -- depletion of the stratospheric polar ozone layer.

Reflecting the urgency of the issue, Bindschadler said the Intergovernmental Panel on Climate Change -- the panel of top climate scientists that earlier this month issued its most definitive warning on the buildup of man-made greenhouse gases -- has specifically asked researchers to speed their studies of the dynamics of Antarctic climate and how its ice is formed, moved and melted. While much remains to be learned, researchers have an inexact but clearer understanding of what would happen if some of the more vulnerable Antarctic ice melts. Disappearance of the west Antarctic ice sheet, for instance, could raise worldwide sea levels by about 20 feet.

David Bromwich, a professor at Ohio State University and researcher at its Byrd Polar Research Center, has been recording Antarctic temperatures and snowfall for some time, and his newest results do not conform to the predictions of most climate models. With global temperatures on the rise, he said, those models predict a warmer -- rather than an overall colder -- Antarctica, as his data found.

"The best we can say right now is that the climate models are somewhat inconsistent with the evidence that we have for the last 50 years from continental Antarctica," he said last week at the annual meeting of the American Association for the Advancement of Science.

That finding is itself a cause for concern, he said, because it means that scientists' ability to understand the Antarctic climate, and so to predict how it may change, appears limited. What is more, it has become increasingly clear that Antarctica -- which is about the size of the United States and Mexico combined -- is not a frozen and static wasteland but a dynamic and sometimes fast-changing system.

For instance, the research into the Antarctic ice streams and the melted lakes a half-mile and more below their surface found that the ice is moving as fast as two yards a day. "We thought these changes took place over years and decades, but we are seeing large changes over months," said lead author Helen Fricker of the University of California at San Diego's Scripps Institution of Oceanography. Their findings appeared in Friday's edition of the journal Science.

It remains unclear whether the newly found subglacial lakes have anything to do with climate change. They might be caused by underground geothermal heat or by the heat-producing friction of the glaciers' motion. But Fricker and Bindschadler said the presence of the lakes has alerted scientists to the fact that the ice streams are, to some extent, sitting on top of water -- a situation that could allow them to move even faster.

"Water is critical because it's essentially the grease on the wheel," said Bindschadler, whose research was based on first-of-their-kind measurements by NASA satellites.

For Bromwich, the changeability of the Antarctic climate can be seen in effects seemingly caused by the thinning ozone layer, a process set in motion by the release of chlorofluorocarbon (CFC) molecules from man-made aerosols. Even though consumer products containing CFCs were taken off the market almost 20 years ago, they linger in the atmosphere for decades and continue to cause harm.

Bromwich said the Antarctic ozone layer was depleted in 2006 to an extent never seen before.

As the ozone diminishes, he said, warming ultraviolet light from the sun is not absorbed as readily and the atmosphere stays cooler. That in turns leads to longer periods of winter-like conditions, which might offset any warming from greenhouse gases. In addition, he said, the loss of ozone is believed by some researchers to cause the intensifying westerly winds.

Under these hypotheses, a return to more normal ozone levels would allow built-up greenhouse gases to rapidly warm -- and perhaps dramatically change -- the continent.

Bindschadler said the continent remains essentially mysterious. "Every time we think we understand something, we find that conditions are more complicated, more dynamic than we appreciated. Things are changing fast, and probably a whole lot faster than we know."