In a statement issued several weeks ago, scientists reported Arctic sea ice coverage has shrunk to its lowest level in more than 30 years, alarming researchers that global warming might be occurring at an even faster rate than expected.
Recent images from the European Space Agency's (ESA) Envisat satellite and the U.S. National Snow and Ice Data Center's (NSIDC) satellites reveal how Arctic sea ice has been declining in coverage at an accelerating pace. The latest images show the previously hidden Northwest Passage between Europe and Asia has been exposed.
The Northwest Passage is a sea path located in the Arctic Ocean between Europe and Asia. None of the satellite images before this year have revealed the passage as being ice-free. NSIDC, researchers, however, assert that ice is beginning to form over the Northwest Passage again.
Sea ice is frozen ocean water that helps to maintain global climate. Sea ice coverage follows a seasonal pattern, in which the ice coverage recedes in the summer and increases in the winter.
The ESA reports ice coverage in the Arctic dropped to approximately three million square kilometers, a loss of one million square kilometers from the previous minima in 2005 and 2006. NSIDC researchers yield similar observations, noting that in this year's melting season, satellite images indicate that 1.19 million square kilometers of ice have been lost.
The 2007 sea ice record is meaningful because it is an accentuation of a steadily downward trend in ice cover that is very apparent over the past several years,"" said Stephen Vavrus, UW-Madison associate scientist in the Center for Climatic Research. ""This year's ice behavior is therefore an exclamation point on the current trend, which is very much in line with climate model simulations of how the ice pack should respond to rising concentrations of greenhouse gases.""
According to Eric DeWeaver, UW-Madison assistant professor of atmospheric and oceanic sciences, this year's extreme low in ice cover follows at least two decades of sea ice decline.
""[Computer simulations of sea ice decline] suggest that late summer sea ice is likely to disappear entirely at some point within this century, maybe during the next 50 years,"" DeWeaver said. ""The observations of summer sea ice reductions seem to confirm this prediction.""
One consequence of the loss of Arctic sea ice is increasing solar radiation, which will act as another source of global warming. Because sea water is darker in color, it absorbs more solar radiation than sea ice. According to Dr. Galen McKinley, UW-Madison assistant professor of atmospheric and oceanic sciences, the loss of arctic ice can lead to climatic changes outside of the Arctic.
""A loss of sea ice enhances absorption of solar radiation, warming of the surface ocean, and thus the surface climate,"" McKinley said.
Animals, such as polar bears, and marine organisms that depend on sea ice for survival are in vulnerable positions because their habitat is rapidly shrinking. As a result, conservationists are considering placing polar bears on a threatened species list under the U.S. Endangered Species Act.
According to Vavrus, circumstantial evidence suggests the decline of Arctic sea ice appears to be a result of high carbon emission levels.
""If [high carbon emissions are] the cause, then the only way we can slow down or stop this ice loss is by reducing the buildup of greenhouse gases, such as carbon dioxide and methane, in our atmosphere,"" Vavrus said. ""We know the sources of this pollution, but we continue to increase the emissions rates for a variety of economic and cultural reasons.
