Scientists say new U.S. and Canadian satellite images have tracked what they call a stunning reduction in Arctic Sea ice following the northern summer. The shrinkage is far more extensive than normal for the fourth consecutive year. The researchers say the current rate of decline could mean that the Arctic would be free of ice well before the end of the century.
Since 2002, U.S. satellite data have revealed unusual springtime melting in areas north of Siberia and Alaska. Now, the National Snow and Ice Data Center at the University of Colorado says the trend expanded this year to include the entire Arctic ice pack.
"What it's telling us is that the pace of retreat of ice in summer is accelerating," said snow and ice data center researcher Ted Scambos.
He says the record Arctic ice sheet reductions each summer are feeding on themselves, making each subsequent year worse.
"It's sort of a vicious circle. What happens is if you start to melt the sea ice up in the Arctic, it actually starts to get darker. Dry, white snow reflects 85 percent of the sunlight that falls on it. If you start to melt it, though, that brightness goes down to about 60 percent, and so it starts to absorb more energy. Once it gets a little more darker, it starts absorbing more heat, leading to further melting," he added.
Mr. Scambos says the shrinking summer Arctic ice cap means less and less expansion each winter, with less thickness. The new report shows that last winter's recovery was the smallest in a quarter century of satellite monitoring.
The researchers believe the best explanation is a general global warming caused by pollution from burning fossil fuels.
The findings are the latest warning about rising Arctic temperatures. Late last year, an international team of scientists said heat-trapping gases in the atmosphere, such as carbon dioxide, have caused a three to four degree Celsius rise in Arctic temperatures over the last 50 years. The group predicted a continuation of the trend over the next century with an additional average temperature increase of three to five degrees over land and up to seven degrees over the Arctic Ocean.
The chairman of the panel that wrote the report, Robert Correll of the American Meteorological Society, says that as the Arctic ice cover shrinks more, polar bears and some seal species might become extinct and Arctic peoples will suffer severe economic consequences.
"Climate change is really happening in the Arctic and it is having deleterious effects on many systems," said Mr. Correll. "The preponderance of evidence is suggesting that it is creating some very difficult times for the people who live there, for the animals and plants that are residing there."
Ted Scambos at the National Snow and Ice Data Center says Arctic air contributes powerfully to the world's climate. He points out that frigid air at the poles and the heat at the equator create global wind patterns that cause the weather we experience. Arctic warming changes the balance.
"If we start to change that balance in the fundamental way that losing Arctic ice for a few months out of the year would represent, we can expect to see major changes, first in the Arctic, where it will be a lot warmer, and then other changes that would propagate elsewhere in the world as climate adjusts to having a warm and humid patch of air over the Arctic ocean," added Mr. Scambos.
The most pronounced global effect of Arctic warming will be rising sea levels, according to Michael McCracken of the U.S.-based non-profit organization the Climate Institute. He says coastlines and other low-lying areas will be threatened with inundation.
"Once we start this melting going, it has the potential for raising sea level very significantly. We're not talking about sea level rise just in the Arctic," said Mr. McCracken. "We're talking about sea level rise around the globe, so everybody is going to experience it, particularly regions that have low lying areas."
The report from the University of Colorado team says the Arctic spring thaw is coming a little earlier each year. Using a satellite record going back to 1978, the researchers show that this year's melt began two-and-a-half weeks earlier than usual, a new record.