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Glacial extent

Lines mark the retreat of ice from Illecillewaet Glacier, Glacier National Park.

CMI, Dan McCarthy, Brock U.

  • Earth's Changing Ice Cover Featured Article Earth's Changing Ice Cover Earth's Changing Ice Cover

    This article, written by Charles W. Schmidt, a freelance writer specializing in science, medicine and technology, appeared first in Environmental Health... More »

  • Arctic sea ice: lowest extent for 2011 Featured News Article Arctic sea ice: lowest extent for 2011 Arctic sea ice: lowest extent for 2011

    As the sun sets over the Arctic Ocean and the air and water cool, sea ice begins its annual freeze-up. Arctic sea ice appears to have reached its minimum extent for the... More »

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Greenland glaciers and rising sea level Last Updated on 2012-05-08 00:00:00 Researchers determine that although glaciers continue to increase in velocity, the rate at which they can dump ice into the ocean is limited. Analysis of Speed of Greenland Glaciers Gives New Insight for Rising Sea Level Changes in the speed that ice travels in more than 200 outlet glaciers indicates that Greenland's contribution to rising sea level in the 21st century could be significantly less than the upper limits some scientists thought possible. The finding comes from a paper funded by the National Science Foundation (NSF) and NASA and published in the May 4, 2012, issue of the journal Science. While the study indicates that a melting Greenland's contributions to rising sea levels could be less than expected, researchers concede that more work needs to be done before any definitive trend can be identified. Studies like this one are designed to examine... More »
Antarctic ice shelf rift: Pine Island Glacier Last Updated on 2011-11-05 00:00:00 Watching the Birth of an Iceberg After discovering an emerging crack that cuts across the floating ice shelf of Pine Island Glacier in Antarctica, NASA's Operation IceBridge flew a follow-up mission and made the first-ever detailed airborne measurements of a major iceberg calving in progress. NASA's Operation Ice Bridge, the largest airborne survey of Earth's polar ice ever flown, is in the midst of its third field campaign from Punta Arenas, Chile. The six-year mission will yield an unprecedented three-dimensional view of Arctic and Antarctic ice sheets, ice shelves and sea ice. Pine Island Glacier last calved a significant iceberg in 2001, and some scientists have speculated recently that it was primed to calve again. But until an Oct. 14 IceBridge flight of NASA's DC-8, no one had seen any evidence of the ice shelf beginning to break apart. Since then, a... More »
Arctic sea ice: lowest extent for 2011 Last Updated on 2011-09-16 00:00:00 As the sun sets over the Arctic Ocean and the air and water cool, sea ice begins its annual freeze-up. Arctic sea ice appears to have reached its minimum extent for the year—it will now continue to expand until March or April. The photograph above was taken over the Arctic Ocean in September, 2008. Media Advisory: Arctic sea ice reaches lowest extent for 2011 The blanket of sea ice that floats on the Arctic Ocean appears to have reached its lowest extent for the year. Arctic sea ice extent fell to 4.33 million square kilometers (1.67 million square miles) on September 9, 2011. This year's minimum was the second lowest in the satellite record, which started in 1979. The lowest extent was recorded in 2007. Over the last thirty years, ice extent, a two-dimensional measure of the ice cover on the Arctic Ocean, has declined in all months, with a more pronounced drop in... More »
Earth's Changing Ice Cover Last Updated on 2011-03-11 00:00:00 This article, written by Charles W. Schmidt, a freelance writer specializing in science, medicine and technology, appeared first in Environmental Health Perspectives—the peer-reviewed, open access journal of the National Institute of Environmental Health Sciences. The article is a verbatim version of the original and is not available for edits or additions by Encyclopedia of Earth editors or authors. Companion articles on the same topic that are editable may exist within the Encyclopedia of Earth.   Out of Equilibrium? The World's Changing Ice Cover In August 2010 an iceberg four times the size of Manhattan broke off Greenland’s northwestern coast and began drifting out to the sea. At nearly 100 square miles, this was the largest iceberg to appear in Arctic waters since 1962 and a fresh indicator that Greenland’s frozen landscape is... More »
Permafrost Last Updated on 2010-05-20 00:00:00 A soil is considered permafrost if its temperature remains permanently below the melting point of water for at least two years. Such permafrost soil is ubiquitous in high latitude (e.g. in Siberia, Alaska and the Antarctic) but can also be found in mountainous areas at lower latitudes. Typically, the below-ground temperature will be less variable from season to season than the air temperature, with temperatures tending to increase with depth. Permafrost typically occurs during glacial periods. The thickness of a permafrost layer can reach from a few decimetres to well over one kilometre, while it may extend in area from small patches of a few tens of square metres to thousands of square kilometres. Since our present glacial period is considered an interglacial within the fifth Ice age there are presently large areas of the Earth that are classified as permafrost. Permafrost... More »