Record retreat of Arctic sea ice

Scientists: July extent is most extreme since 1979
University of Colorado

Todd Neff, Camera Staff Writer
Monday, August 7, 2006

This year's melting of Arctic summer sea ice is on track to be the most extreme since satellites began to track the polar ice cap in 1979, scientists at the National Snow and Ice Data Center on the University of Colorado campus say.

Arctic ice spreads and shrinks with the seasons, reaching its maximum in March and its minimum in mid-September. In September 2005, the previous record, there was 20 percent less ice � five Colorados' worth � than the 1979-2000 average minimum of 7 million square kilometers. This summer figures to see more melting yet, National Snow and Ice Data Center data show.

"It's the most irrefutable evidence I can think of that we're in the era where global warming is really having an impact on the environment," said Ted Scambos, the center's lead scientist.

As of the end of July, Arctic sea ice covered 8.7 million square kilometers, down from 9.1 million square kilometers in 2005 and the 1979-2000 average of 10.1 million square kilometers.

"The simplest prediction you can make of the September sea-ice extent is that if it's really low in July, chances are it's going to be really low in September," said Mark Serreze, a National Snow and Ice Data Center scientist.

A positive-feedback loop fuels faster Arctic melting. Ice reflects about 90 percent of incoming sunlight. Exposed ocean water absorbs that amount, accelerating melting.

Serreze said Arctic temperatures have consistently been 4 degrees to 5 degrees warmer this year than the 20-year average.

Last year was the warmest on record, NASA records show. This year, January through June was the sixth-warmest on record, 0.9 degrees above the 20th-century average, the National Climatic Data Center in Asheville, N.C., says.

Serreze says the north pole could have ice-free summers by 2050. It would be the first time that happened in more than a million years.

But the ice-free Arctic could occur faster yet. In a May presentation to the American Meteorological Society, Wieslaw Maslowski, a professor at the Naval Postgraduate School in Monterrey, Calif., said warm Pacific waters pushing through the Bering Strait between Alaska and Russia are accelerating melting. Summer ice could be gone before 2020, he said.
Nearly 400 years after Henry Hudson's ill-fated attempts to discover a northwest passage, the emergence of an alternative to the Panama Canal would introduce commercial opportunity and strategic challenges.
Ecologically, the impacts could extend beyond polar-bear drownings.

Historically, the medieval warm period between about 900 and 1300 A.D., which also saw significant Arctic ice melting, produced extended droughts in the southwestern United States, Scambos said.

Contact Camera Staff Writer Todd Neff at (303) 473-1327 or [email protected].