Climate scientists may have significantly underestimated the power of global warming from human-generated heat-trapping gases to shrink the cap of sea ice floating on the Arctic Ocean, according to a new study of polar trends.
The study, published online today in Geophysical Research Letters, concluded that an open-water Arctic in summers could be more likely in this century than had been estimated in the latest international review of climate research released in February by the United Nations Intergovernmental Panel on Climate Change.
"There are huge changes going on," said Julienne Stroeve, a lead author of the new study and a researcher at the National Snow and Ice Data Center in Boulder, Colo. "Just with warm waters entering the Arctic, combined with warming air temperatures, this is wreaking havoc on the sea ice, really."
The intergovernmental panel concluded that if emissions of heat-trapping gases like carbon dioxide were not significantly reduced, the region could be end up bereft of floating ice in summers sometime between 2050 and the early decades of the next century.
For the new study, Dr. Stroeve and others at the ice center reviewed nearly six decades of measurements by ships, airplanes and satellites estimating the maximum and minimum area of Arctic sea ice, which typically expands most in March and shrinks most in September.
With an expert from the National Center for Atmospheric Research, also in Boulder, they then compared the observed trends with the projections made for the climate panel's review using the world's most advanced computer models of climate.
Dr. Stroeve's team found that since 1953 the area of sea ice in September has declined at an average rate of 7.8 percent per decade. Computer climate simulations of the same period had an average rate of ice loss of 2.5 percent per decade.
The finding implies that the Arctic ice may be quicker to respond to warming as concentrations of heat-trapping gases rise in coming decades, said Marika Holland, an author of the new paper and a computer modeler at the Boulder climate center.