Polar ice cap
From Wikipedia, the free encyclopedia
A polar ice cap is a high latitude region of a planet or natural satellite that is covered in ice. There are no requirements with respect to size or composition for a body of ice to be termed a polar ice cap, nor any geological requirement for it to be over land; only that it must be a body of solid phase matter in the polar region. This causes the term 'polar ice cap' to be somewhat of a misnomer, as the term ice cap itself is applied with greater scrutiny as such bodies must be found over land, and possess a surface area of less than 50,000 km²: larger bodies are referred to as ice sheets.
The Earth's polar ice caps have changed dramatically over the last 12,000 years. Seasonal variations of the ice caps takes place due to varied solar energy absorption as the planet or moon revolves around the sun. Additionally, in geologic time scales, the ice caps may grow or shrink due to climate variation. See ice age, polar climate.
North pole september ice-pack 1978-2002.png
Extent of the Arctic ice-pack in September, 1978-2002
North pole february ice-pack 1978-2002.png
Extent of the Arctic ice-pack in February, 1978-2002
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. In addition, the Greenland ice sheet covers about 1.71 million km² and contains about 2.6 million km³ of ice.
While the International Panel on Climate Change 2001 report predicted that the North polar ice cap would last to 2100 in spite of global warming caused by climate change, the dramatic reduction in the size of the ice cap during the northern summer of 2007 has led some scientists to estimate that there will be no ice at the North Pole by 2030 with devastating effects on the environment.
Other scientists such as Wieslaw Maslowski, a professor at the Naval Postgraduate School, estimate that there will be no summer ice by as soon as 2013. He argues that this projection is already too conservative as his dataset did not include the minima of 2005 and 2007.
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 25-30 million km³ of ice. Around 70% of the fresh water on the Earth is held in this ice sheet. See Climate of Antarctica.
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 then reforms in winter.
Data collected in 2005 from NASA missions to Mars show that the carbon dioxide "ice caps" are melting. The most widely accepted explanation is that fluctuations in the planet's orbit are causing the changes.
- ^ The National Snow and Ice Data Center Glossary
- ^ "NSIDC Arctic Sea Ice News Fall 2007". nsidc.org. http://nsidc.org/news/press/2007_seaiceminimum/20070810_index.html. Retrieved 2008-03-27.
- ^ "Arctic ice cap to melt faster than feared, scientists say". seattletimes.nwsource.com. http://seattletimes.nwsource.com/html/localnews/2003873003_arcticice07m.html. Retrieved 2008-04-14.
- ^ "Arctic summers ice-free 'by 2013'". bbc.co.uk. http://news.bbc.co.uk/2/hi/science/nature/7139797.stm. Retrieved 2008-04-14.
- ^ Ravilious, Kate (2007-02-28). "Mars Melt Hints at Solar, Not Human, Cause for Warming, Scientist Says". National Geographic News. National Geographic Society. http://news.nationalgeographic.com/news/2007/02/070228-mars-warming.html. Retrieved 2008-10-28.