Arctic

A similar scenario is taking place in the Arctic regions of the Northern Hemisphere. NASA is currently monitoring the polar ice sheets with the Ice, Cloud, and Land Elevation Satellite (ICESat), which was launched in January 2003. Three times a year this satellite uses a laser beam to measure the elevation of the ice sheets with a high degree of precision. NASA scientists have determined that 9 percent of the mass of Arctic sea ice is melting away each decade.

Meanwhile, a study conducted at the University of Colorado's NSIDC by Josefino Comiso found that most of the Arctic warmed significantly in the 1990s. It was also determined that the season when ice melt occurs (early spring to late fall) has gotten longer and warmer each decade. Climatologists at NSIDC view these trends as early warning signals of a changing global climate. Due to its responsive nature, the Arctic is one of the best places to detect the first serious indications of global warming, and as portrayed in National Geographic's film Arctic

Tale (2007), the Arctic is already undergoing serious changes to its ecosystem, putting the wildlife in jeopardy.

In addition to global warming being the cause, researchers at NASA's GISS have also suggested that the increasing loss of Arctic sea ice may also be partly caused by changing atmospheric pressure and wind patterns over the Arctic that move ice around. This also serves to warm temperatures. It is believed that changes in air pressure and wind patterns may be caused by the high concentrations of greenhouse gases in the atmosphere, aggravated by the burning of fossil fuels.

Scientists at GISS point to several pieces of evidence that the Arctic is warming. The rate of warming since 1981 is eight times greater than the rate over the previous 100 years. The Arctic spring, summer, and autumn have all extended in duration, which has lengthened the prime sea ice melting period by 10 to 17 days per decade. A major problem with this is the positive feedback mechanism it causes. As temperatures climb, more ice is melted, which lowers the albedo, which, in turn, melts more ice. This feedback eventually changes the temperature of the ocean layers and impacts ocean circulation and salinity.

Whereas the melting of ice and consequent opening up of the Northwest Passage might open up new shipping lane access, which some may see as a benefit, it would be detrimental to wildlife habitat (polar bears, walruses, and seals), as it would impact their delicate ecosystems. It would also pose a hardship on the native communities that live in the area, because their culture, their lifestyle, and their survival would be placed at risk.

In addition, if Arctic permafrost is thawed, the soils could release vast amounts of stored carbon dioxide and methane into the atmosphere. If the oceans warm, the frozen natural gases currently stored on the seafloor may also be triggered to release because of the higher temperatures, which will also add more greenhouse gases to the atmosphere.

The Greenland Ice Sheet is another area of intense research today, visited by scientists from the United States, Canada, Britain, Australia, Finland, Norway, Sweden, Russia, Denmark, and Iceland. Like the Arctic ice, this ice sheet begins to melt earlier in the spring than it ever had before. Usually, seasonal melt occurs along the edges at its lowest points. In 2002, the ice sheet melting accelerated. According to GISS, several scientists have been involved in research trying to determine whether the Greenland ice sheet is melting. Various scientists using different sources of data and different raw data processing techniques have generated a range of estimates depicting the mass balance of the Greenland Ice Sheet.

E. Hanna, a member of the Department of Geography at the University of Sheffield, in the United Kingdom; J. Box, of the Byrd Polar Research Center at Ohio State University; and P. Huybrechts, from the Department of Geography at the University of Brussels, Belgium, for example, used a combination of GRACE satellite data to calculate mass volume losses, airborne and satellite laser altimetry data analysis to calculate mass volume loss, and InSAR satellite radar interferometry to reveal widespread acceleration of glaciers. Jay Zwally, from NASA, used ERS radar altimeter data from airborne laser surveys to derive his measurements. The Climate Change Institute, supported by the NSF, NOAA, and NASA used a precision global positioning system (GPS) supplemented with ground survey and ice-core analysis and correlation. Although techniques and estimates varied among these studies, the end results all indicated that the Greenland Ice Sheet has lost hundreds of gigatons of mass in recent years.

These researchers agree that in the early 1990s, Greenland's ice sheet was nearly in balance. Since then, however, the ice sheet has become extremely out of balance, because it is currently losing a significant amount of ice to the ocean. The more they study global warming and how it relates to the equilibrium of the world's ice sheets, the more they try to develop sophisticated models to predict the future. They all acknowledge, too, however, that because the complicated physics of ice sheets are still not completely understood, the current models still are not able to portray all the complexity of nature.

An article appearing in the New York Times on January 8, 2008, titled "Melting Ice-Rising Seas? Easy. How Fast? Hard." expressed sci-entists's worry that Arctic ice melt may cause sea levels to rise more than two feet (0.6 m) this century—an estimate made also by the IPCC in its fourth report in 2007. The Arctic Council—an organization of countries within Arctic territory (Canada, Denmark/Greenland/Faeroe Islands, Finland, Iceland, Norway, Sweden, the Russian Federation, and the United States)—has commissioned a report on Greenland's situation to be completed prior to the climate treaty talks in Copenhagen, scheduled in December 2009.

A special three-day summit was held in Copenhagen beginning on February 10, 2009, by the Arctic Council in order to update the scientific community with the latest climate research information based on their report before the global political negotiations to be held in December (which are to be the formal successor to the Kyoto treaty).

Jonathan Bamber, an ice sheet expert at the University of Bristol, explained to the conference attendees that previous studies had misjudged the so-called Greenland tipping point (the point at which the ice sheet is certain to melt completely). "We're talking about the point at which it is 100 percent doomed. It seems quite an important number to get right. Such catastrophic melting would produce enough water to raise world sea levels by more than 20 feet (6 m).

"We found that the threshold is about double what was previously published. It would take an average global temperature rise of 10°F (6°C) to push Greenland into irreversible melting. I'm not saying that if you have a temperature rise of 3.3°F (2°C) then you're not going to lose mass from Greenland, because you are. You warm the planet, ice melts." At the meeting in December, the world's nations plan to agree on a long-term solution for limiting human-caused global warming.

In August 2005, a 25.5 square mile (66 km2) piece of ice broke off the Ellesmere Island Ice Shelf in the Canadian Arctic near Greenland. This represents the biggest single ice loss in the past 25 years. The collapse even registered on earthquake monitors 155 miles (249 km) away. Scientists believe that the ice reaches some type of threshold, which triggers the fracture. What they wonder now is if the area has reached a critical threshold, and how much more ice may break away.

This ice shelf is only one of six in the Canadian Arctic, and global warming played a key role in its collapse. An expert in Arctic studies, Warwick Vincent of Laval University says that the remaining ice shelves in the area are currently 90 percent smaller than when they were first discovered in the early 1900s. Luke Copland of the University of Ottawa remarks that scientists are surprised at how fast ice shelves are reacting to climate change.

CRYOSPHERiC FACTS

Although most of Earth's ice exists in two remote polar locations, it affects the entire planet. It plays an important role in sea-level rise, storage of freshwater, and Earth's energy balance. The following list summarizes unique facts about Earth's ice:

• The melting of floating sea ice and the calving of glaciers into the ocean do not change sea level, because ice displaces about the same volume of water as it produces when it melts. The thinning and the retreat of glaciers on land do add water to the oceans.

• Antarctic ice is more than 13,780 feet (4,200 m) thick in some areas.

• The Antarctic Ice Sheet has existed for more than 40 million years.

• From 1950 to 2000, average temperatures in the Antarctic Peninsula increased by 4.2°F (2.5°C). This is equal to four times the global average.

• Over the past 100 years, almost 7,720 square miles (20,000 km2) of ice shelf was lost on the Antarctic Peninsula.

• Almost 90 percent of an iceberg lies below the water's surface— only 10 percent is above.

• Antarctic icebergs can calve icebergs more than 50 miles (80 km) long.

• The mass of ice is so heavy on Antarctica that the land underneath it sits 1.6 miles (2.5 km) below sea level.

• If all the ice on land melted, it would make sea levels rise more than 230 feet (70 m) worldwide.

• The mean height of the Greenland ice cap is 7,005 feet (2,135 m).

• Sea ice in the Arctic is getting thinner and covers less area by late summer.

• During the Ice Age, the sea level was about 400 feet (122 m) lower than it is today. Glaciers covered almost one-third of the land's surface.

• During the last warm period, 125,000 years ago, the seas were 18 feet (5.5 m) higher than they are today. Three million years ago, the seas may have been 165 feet (50.3 m) higher.

• If the ice on Antarctica melted, it would raise sea levels by 215 feet (66 m).

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• If the ice on Greenland melted, it would raise sea levels 23 feet (7 m).

• The Greenland Ice Sheet covers 82 percent of the surface of Greenland.

As global warming continues and Earth's energy balance changes, the ice cover will continue to adjust, causing not only local but global effects on ecosystems, such as rising sea level, destruction of polar habitats, changes in the water cycle, and changes in surface albedo.

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