Arctic Climate Change

雪儿 · 发表于: 2011-7-8 12:36:55

Arctic Circle Ice

Photograph by Paul Nicklen

The Arctic Ocean's sea ice is in a "death spiral" due to rising temperatures, scientists said in 2008. Many marine species, such as these narwhals swimming through a bay in Nunavut, Canada, depend on the ice throughout their life cycles. Experts predict that summer Arctic ice may completely disappear within a few decades.

雪儿 · 发表于: 2011-7-8 12:37:13

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Polar Bear in Svalbard

Photograph by Ralph Lee Hopkins

Polar bears—like this one leaping between ice floes in Svalbard, Norway's Hinlopen Strait—live on the Arctic ice, hunting seals and other fatty marine mammals. But as the ice vanishes, some experts predict this predator will also disappear from the Arctic by 2050.

雪儿 · 发表于: 2011-7-8 12:37:27

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Alaska Permafrost Meltwater

Photograph courtesy Goddard Space Flight Center

Permafrost—the frozen soil that forms the backbone of the Arctic tundra—is melting due to climbing global temperatures. In Alaska, the mercury may rise by 1 to 5 degrees Celsius (1.8 to 9 degrees Fahrenheit) by 2100. In this false-color image of Alaska's North Slope, taken by NASA's Terra satellite, the blue-black color shows the many ponds of meltwater that collected on the coast in July 2007.

雪儿 · 发表于: 2011-7-8 12:37:49

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Alaska Permafrost Collapse

Photograph by Christine Dell'Amore

Thermokarst failures occur when permafrost—a layer of frozen soil in Earth's polar regions—thaws and becomes unstable, possibly releasing greenhouse gases into the atmosphere. Though the features occur naturally in some parts of the Arctic, many scientists suspect that rising temperatures are causing more to form. Until 2003, thermokarsts—such as this one, located about 155 miles (about 250 kilometers) north of the Arctic Circle—were unheard of in northern Alaska.

雪儿 · 发表于: 2011-7-8 12:38:00

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Canada River

Photograph by Bernhard Edmaier

Freezing water from beneath Earth's surface forces the ground upward in Canada's Mackenzie River delta. Much of the basin is made up of permafrost, a layer of frozen soil in Earth's polar regions. Loss of permafrost due to climate change in Canada's Northern Territories may increase runoff and sediment flowing into rivers and make some slopes more unstable and vulnerable to landslides.

雪儿 · 发表于: 2011-7-8 12:38:16

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Caribou and Northern Lights

Photograph by Alaska Stock Images

Caribou—such as this large-antlered specimen silhouetted by Alaska's northern lights—are being affected as global warming accelerates in the Arctic. In Greenland, caribou time their births to coincide with the blooming of tundra vegetation. But as climate change causes plants to peak earlier, caribou newborns that eat the plants face tougher odds for survival.

雪儿 · 发表于: 2011-7-8 12:38:28

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Alaska Spruce Trees

Photograph courtesy Peter Essick/Getty Images

A forest of dead spruce trees near Homer, Alaska, is the victim of a tiny beetle that has boomed in the state's milder winters. Since the mid-1970s, about 50 percent, or 1 million acres (400,000 hectares), of the Kenai Peninsula's adult spruce trees have succumbed to the spruce bark beetle. The swaths of downed trees may actually turn forests from carbon sinks to sources, according to an April 2008 study. For instance, when dead trees decompose, they release the greenhouse gas carbon dioxide into the atmosphere.

雪儿 · 发表于: 2011-7-8 12:38:44

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Burned Alaskan Tundra

Photograph by Jason Stuckey

Fires are rare in the tundra, where "fuel"—in the form of tall plants or trees—is scarce. But as temperatures rise, thicker, taller shrubs are spreading throughout the region, raising the likelihood for more fires in coming years. Tundra burning may also release more organic carbon, a greenhouse gas currently stored in the soil, into the atmosphere.

雪儿 · 发表于: 2011-7-8 12:38:54

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Alaska Inuit Child

Photograph by Joel Sartore

The Inuit, a group of indigenous people living in the Arctic, are finding their land and cultures rapidly changing as climate change deepens its grip. As ice declines, so does the number of days available for Inuit to hunt for animals such as seals and walrus. Shifting winds are also reshaping ice formations used as landmarks for generations, making navigation more difficult. But, as Theo Ikummaq of Canada's Nunavut Province said, "We have lived in this region for centuries and we will continue to. As the climate changes, we will adapt."

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[其他] Arctic Climate Change

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