By Philip W. Conkling, Richard Alley, Wallace S. Broecker, George Denton
Specialists talk about how Greenland's warming climate--seen in its melting ice sheets and backing out glaciers--could impact the remainder of the area.
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Extra info for The Fate of Greenland: Lessons from Abrupt Climate Change
Sample text
By June, Earth has moved halfway around the sun, but Earth’s tilt is still the same, so in June the North Pole is sun-tanning while the South Pole gets no sun. Because Earth’s orbit is slightly eccentric rather than round, our distance from the sun varies slightly from year to year. For the last couple of millennia, and for the next couple of millennia, the north has summer and the south has winter when Earth is far from the sun. Thus, for people in the northern hemisphere, summer and winter are not quite as different as they might be.
A cautious person standing by such a river where it emerges from under the glacier can hear boulders knocking together in the current, and an incautious wader risks a crushed ankle, or worse. The glacier-fed rivers often pile gravel benches or terraces along their paths down the valley. Beneath a glacier, the moving ice picks up boulders and smaller rocks and drags them over the bedrock beneath, scratching and polishing the rock in many places. In other places, the glacier breaks chunks loose and shoves them into the bedrock to make beautiful crescent-shaped cracks.
Trapped bubbles of old air contain carbon dioxide, which can be studied for any correlation with the advance and retreat of ice sheets. The bubbles also contain “swamp-gas” methane, which can tell scientists how widespread wetlands were. Scientists were thus able to sample air bubbles trapped in individual layers of ice to measure CO2, methane, and other “greenhouse gases” locked inside to “see” the composition of the atmosphere as the climate changed. After drilling down two miles and extracting the cores, scientists from the United States and Europe could produce a year-by-year climate history extending back for over 100,000 years.