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Polar ice cap

2007 Schools Wikipedia Selection. Related subjects: Antarctica

   A polar ice cap or polar ice sheet is a high- latitude region of a
   planet or moon that is covered in ice. This term is somewhat of a
   misnomer since an ice cap is less than 50,000 km² and is always over
   land: a larger area of ice is called an ice sheet. Polar ice caps do
   not have size, composition or geologic requirements of being over land,
   but they must be centered in the polar region.

   The composition of the ice will vary. Earth's polar ice caps are mainly
   water ice, while Mars's polar ice caps are a mixture of carbon dioxide
   ice and water ice.

   Polar ice caps form because high- latitude regions receive less energy
   in the form of solar radiation from the sun than equatorial regions,
   resulting in lower surface temperatures. Seasonal variations of the ice
   caps will take place due to varied solar energy absorption as the
   planet or moon revolves around the sun. Additionally, in geologic time
   scale, the ice caps may grow or shrink due to climate variation. See
   ice age, polar climate.

   The Arctic ice cap is currently shrinking, where as the Anarctic ice
   cap is thickening, possibly as a result of anthropogenic global
   warming.

Earth

   A satellite composite image of Antarctica
   Enlarge
   A satellite composite image of Antarctica

   Earth's north pole is covered by floating pack ice (sea ice) over the
   Arctic Ocean. Portions of the ice that don't melt seasonally can get
   very thick, up to 3–4 meters thick over large areas, with ridges up to
   20 meters thick. One-year ice is usually about a meter thick. The area
   covered by sea ice ranges between 9 and 12 million km².

   The land mass of the Earth's south pole, in Antarctica, is covered by
   the Antarctic ice sheet. It covers an area of almost 14 million km² and
   contains 30 million km³ of ice. Around 90% of the fresh water on the
   Earth's surface is held in this ice sheet. In addition, the West
   Antarctic Ice Sheet covers 3.2 million km² and the Ross Ice Shelf
   covers 0.5 million km². See Climate of Antarctica.

   Extent of the Arctic ice-pack in September, 1978-2002

   Extent of the Arctic ice-pack in February, 1978-2002

   Earth as seen from Apollo 17, with southern polar ice cap visible
   (Courtesy NASA)

Mars

   Mars's north polar region with ice cap, composite of Viking 1 orbiter
   images (Courtesy NASA/JPL-Caltech)
   Enlarge
   Mars's north polar region with ice cap, composite of Viking 1 orbiter
   images (Courtesy NASA/ JPL-Caltech)

   The planet Mars also has polar ice caps, but they consist of frozen
   carbon dioxide as well as water. The ice caps change with the Martian
   seasons-the carbon dioxide ice sublimes in summer, uncovering a surface
   of layered rocks, and forms again in winter.
   Retrieved from " http://en.wikipedia.org/wiki/Polar_ice_cap"
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   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
