Why is Arctic ice melting 50 years too fast?

This satellite image shows that Arctic ice levels in 2007 (left) were less than even the record low levels of 2005 (right). See more global warming images.
Image courtesy

On Aug. 19, 2007, a joint survey by the Japan Agency for Marine-Earth Science and Technology and the Japan Aerospace Exploration Agency revealed that Arctic ice was melting at a far quicker rate than anticipated. What's particularly alarming about this discovery is that the United Nations' scientific models anticipated that the ice levels measured by the Japanese team would not be reached until after 2040 -- and possibly not until 2050.

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A researcher at the Colorado Center for Astrodynamics said that Arctic ice is melting at previously unseen rates [source: Science Daily]. The melting has caused coastal ice in parts of Canada and Alaska to become quite brittle. That ice easily breaks away in large chunks (a process known as calving) and melts in the open ocean. There's also less sea ice in the Arctic Ocean

because ice has floated into the Atlantic Ocean. The previous record low for Arctic sea ice was recorded on Aug. 15, 2005, though scientists said there was a high probability that the record would be breached in 2007.

The Arctic saw another milestone in the summer of 2007. In August, the Northwest Passage had almost no floating ice. It was the first time the Passage had been completely open to shipping since people started keeping records in 1972. Scientists say that the lack of ice represents clear proof that the planet is warming. The now-open sea lane means that someone could sail from New York to Korea without encountering any ice, though bad weather is always possible. In comparison, the first explorer to navigate the Northwest Passage successfully, Roald Amundsen, took three years to get through the waterway's thick ice.

Sea ice is measured primarily through three methods: microwave scanners on orbiting satellites, buoys and observation platforms. The latter two are generally equipped with several types of measuring devices. Scientists focus their measurements on the extent of sea ice, rather than the thickness, since it's easier for satellites to measure extent. When examining sea ice, scientists look at the minimum and maximum extent, thickness, environmental conditions and changes in the melting season. The Arctic sea ice melting season usually lasts from March to the middle of September.

This record pace of Arctic ice melt has scientists concerned about rising sea levels, diminished habitats for polar bears and other animals and an impending rush for fossil fuels in the region. Increased traffic through the Northwest Passage and the Northeast Passage (which runs by Siberia) may increase pollution in the area.

Ice re-forms during winter, but due to warmer waters the amount of re-formed ice appears to be decreasing. Ice that was previously considered "permanent" is now melting. That leaves an ever-decreasing base of ice at the beginning of each melting season.

Sea ice plays an important role in keeping temperatures down around the world. Whereas sea ice reflects 80 percent of sunlight back into the atmosphere, ocean water absorbs 90 percent of sunlight [source: National Snow and Ice Data Center]. As melting ice exposes more ocean to direct sunlight, scientists expect water temperatures to rise, accelerating the ice melt.

On the next page, we'll take a look at more consequences of melting Arctic ice, including the rush to claim the seabed and the valuable energy stores underneath it.