Wired-Global Warming Protects Antarctic Sea Ice But Not For Long

photo credit: wired.com

(Story reported by Brandon Keim for Wired Magazine)

An Antarctic ice paradox that has puzzled climate scientists and fueled skeptics’ arguments appears to have been resolved, with a dire forecast.

A new study finds that global warming is responsible for snowfall that’s expanded the range of Southern Ocean sea ice, even as western Antarctic glaciers have disintegrated.

That expansion contrasts with the common public perception of a uniformly melting Antarctic. But this fortunate balance between loss and gain likely won’t last. By the end of this century, continued warming will turn extra snow into rain.

“With increased loading of greenhouse gases in the atmosphere through the 21st century, the models show an accelerated warming in the Southern Ocean,” writes Georgia Institute of Technology climatologists Jiping Liu and Judity Curry in an Aug. 16 Proceedings of the National Academy of Sciences study. The ultimate result “is a projected decline of the Antarctic sea ice.”

Unlike the Arctic, where much of the sea ice is — at least for now — year-round, the Southern Ocean’s sea ice is thin and seasonal. And during the latter half of the 20th century, its winter surface area has increased. 

Climatologists say the expansion doesn’t change long-term projections of Antarctic melt, but skeptics have used it to attack their forecasts.

“Ice is expanding in much of Antarctica, contrary to the widespread public belief that global warming is melting the continental ice cap,” read one FoxNews story on the expansion.

Indeed, global warming appears to have been protective. By combining temperature and precipitation records with simulations of Southern Ocean climate, Curry and Liu linked the 20th-century warming of .36 degrees Fahrenheit in the Southern Ocean’s upper waters to increased regional snowfall. The finding makes intuitive sense: Rising temperatures increase the amount of moisture in the air, which eventually becomes snow. And for the last few decades, that snow kept surface waters from warming even more, added bulk to sea ice, and reflected sunlight.

But as the Antarctic continues to warm, Curry and Liu’s models show snow becoming rain (see image below), even as total precipitation rises (see image above). By the century’s end, they predict snowfall retreating to the Antarctic continent’s edge. The Southern Ocean at large will be rainy. Sea ice will contract. 

Continental ice will continue to melt.

(click here to read the full story on the Wired Magazine website)