An ice cap is a dome-shaped ice mass that covers an area less than 19,305 square miles (50,000 km2) in size. Ice caps are very responsive to the effects of albedo. Normally, they act as "reflectors," redirecting the Sun's energy back out into space and keeping Earth cool. If the ice caps begin to melt, however, and darker surfaces are exposed, a negative feedback occurs, and Earth's surface begins to absorb the Sun's energy (heat) and accelerate the melting process.
The Arctic ice cap has been under great scrutiny the past several years. In 2007, for a time, the Northwest Passage shipping route over Canada and the Northern Sea Route over Russia was opened. During this time span, floating ice melted more than it had in more than 100 years. The results surprised scientists. No models predicted that the rate of melting and change would be as rapid as it has been. Scientists believe the response is tied directly to the rising concentration of greenhouse
(opposite page) This map depicts the extent of the melting of the Arctic polar ice cap from 1979 to 2007. Because of the extensive melting that has recently occurred, the Northwest Passage has been opened up to shipping traffic.
St. Lawrence I.
East Siberian Sea
Beaufort r' Sea
New ', Siberian
North Magnetic Pole
Severnaya Zemlya i Cape Columbia "Cape Sheridan *,Lincoln Sea
Foxe Basin ¿C
Cape Morris Jesup
I CE LAI
G Infobase Publishing
Northwest passage Arctic sea ice boundary, 1979 Polar ice cap in 2007
200 km gases in the atmosphere. Some scientists believe the ice melt is completely accounted for by global warming. Others disagree, saying that while global warming is contributing a great deal, there could be other factors at play that scientists do not yet fully understand.
According to Jay Zwally, for example, a NASA climate scientist, "At this rate, the Arctic Ocean could be nearly ice free at the end of summer by 2012, much faster than previous predictions. The Arctic is often cited as the canary in the coal mine for climate warming. Now as a sign of climate warming, the canary has died. It is time to start getting out of the coal mines." He says it is the burning of coal, oil, and other fossil fuels that produces carbon dioxide and other greenhouse gases, responsible for human-made global warming.
According to Professor Wieslaw Maslowski, from the Department of Oceanography in the School of Engineering and Applied Sciences at Monterey, California, he believes that most models have seriously underestimated some key melting processes. He believes that models need to incorporate more realistic representations of the way warm water is moving into the Arctic Basin from the Pacific and Atlantic Oceans. According to Maslowski, "global climate models underestimate the amount of heat delivered to the sea ice by oceanic advection. The reason is that their low spatial resolution actually limits them from seeing important detailed factors. We use a high-resolution regional model for the Arctic Ocean and sea ice forced with realistic atmospheric data. This way, we get much more realistic forcing, from above by the atmosphere and from the bottom by the ocean."
Professor Peter Wadhams from Cambridge University used sonar data collected by Royal Navy submarines and says that the ice-albedo
Arctic sea ice has decreased about 14 percent since the 1970s. In this illustration, the extent of ice melt that has occurred on the Greenland Ice Cap from 1992 to 2005 covers an enormous area. By 2080, sea ice is expected to completely disappear during the summer months. The summer melting trend in Greenland has increased each year since 1979. Water flows through cracks to the base of the ice, lubricating it and causing it to flow toward the ocean. (Modeled after Steffen/Huff, CIRES, University of Colorado, Boulder)
Extent of Surface Melt, Greenland Ice Cap
1992 I I 2005
Extent of Surface Melt, Greenland Ice Cap
1992 I I 2005
Infobase Publishing feedback effect in which open water receives more solar radiation, which in turn leads to additional warming and further melting, is another process that needs to be considered. He believes this feedback effect is setting up the Arctic for further ice loss in the coming years. According to him, "The implication is that this is not a cycle, not just a fluctuation. The loss this year will precondition the ice for the same thing to happen again next year, only worse."
People see good and bad in recent developments of melting sea ice. With ice melting and opening up major shipping routes, it represents a boon for shipping, fishing, and oil exploration industries. The other side of the scenario is far from positive, however. The repeated melting and freezing cycles have extremely negative effects on the natural wildlife in the Arctic, such as the polar bear and walrus. It could destroy their fragile habitat and the delicate ecosystem.
A significant rise in carbon dioxide would trigger accelerated melting of the Arctic Ocean and Greenland ice caps, releasing large quantities of water into the oceans, in turn, triggering huge rises in sea level. It is projected that if the CO2 level rose to 550 parts per million (ppm) by the year 2100, it could make the seas rise 8-37 inches (20-94 cm). If this were to happen, it would severely affect the coastal areas of continents and submerge areas such as New Orleans, in Louisiana, and Venice, Italy.
Through the analysis of satellite imagery and ground-based data, scientists at NASA have determined the Arctic has been steadily warming, causing the ice caps to shrink. In fact, over the past 30 years, the Arctic ice cap has both thinned and lost ice at its margins. NASA scientists expect the Arctic ice cap will shrink 40 percent by 2050 in most regions.
Was this article helpful?