Polar ice packs

[
NOAA Projected Arctic changes] Polar ice packs are large areas of pack ice formed from seawater in the Earth's polar regions, known as polar ice caps: the Arctic ice pack (or Arctic ice cap) of the Arctic Ocean and the Antarctic ice pack of the Southern Ocean, fringing the Antarctic ice sheet. Polar packs significantly change their size during seasonal changes of the year.

In spring and summer, when melting occurs, the margins of the sea ice retreat. The vast bulk of the world's sea ice forms in the Arctic ocean and the Southern Ocean, around Antarctica. The Antarctic ice cover is highly seasonal, with very little ice in the austral summer, expanding to an area roughly equal to that of Antarctica in winter. Consequently, most Antarctic sea ice is first year ice, up to 1 meter thick. The situation in the Arctic is very different (a polar sea surrounded by land, as opposed to a polar continent surrounded by sea) and the seasonal variation much less] .

The Arctic Ocean has not been ice free for a period of at least one million years, and perhaps much longer. [ [http://atoc.colorado.edu/~dcn/reprints/Overpeck_etal_EOS2005.pdf "Arctic System on Trajectory to New, Seasonally Ice-Free State"] ]

The NSIDC also reported that, for the first time in recorded history, the Northwest Passage opened to ships without the need of icebreakers [http://www.guardian.co.uk/environment/2007/aug/28/climatechange.internationalnews North-West Passage is now plain sailing] ] . The main channel of this passage (Lancaster Sound to M'Clure Strait) has been open since about August 11. As of September 10, the Northeast Passage remained blocked by a narrow band of sea ice around Severnaya Zemlya.

Winter 2007/2008 Arctic ice growth

Extremely cold temperatures for the Northern Hemisphere in the Winter of 2007/2008 helped the Arctic ice pack to grow to more near normal levels "in terms of surface area covered". [ [http://www.cbc.ca/technology/story/2008/02/15/arctic-ice.html Recent cold snap helping Arctic sea ice, scientists find] ] The ice was also found to be 10 to 20 centimeters thicker than the previous year in some areas. "But it's too soon to say what impact this winter will have on the Arctic summer sea ice, which reached its lowest coverage ever recorded in the summer of 2007," according to Gilles Langis, a senior ice forecaster with the Canadian Ice Service in Ottawa. [ [http://www.cbc.ca/technology/story/2008/02/15/arctic-ice.html Recent cold snap helping Arctic sea ice, scientists find] ]

While the cold winter did allow sea ice to re-cover much of the Arctic during the Winter of 2007/2008, conditions were "far from normal" as "this" pair of NASA images (in the cited reference) reveals . The February 2008 ice pack (right) contained much more young ice than the long-term average (left). In the past, more ice survived the summer melt season and had the chance to thicken over the following winter. In the mid- to late 1980s, over 20 percent of Arctic sea ice was at least six years old; in February 2008, just 6 percent of the ice was six years old or older. [ [http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=17975 NASA Earth Observatory "Arctic Sea Ice Younger than Normal"] ]

Critical Arctic sea ice this winter made a tenuous partial recovery from last summer's record melt, U. S. scientists said Tuesday. But that's an illusion, like a Hollywood movie set, The ice is very thin and vulnerable to heavy melting again this summer. - Walter Meier of the National Snow and Ice Data Center [ [http://www.sfgate.com/cgi-bin/article.cgi?f=/n/a/2008/03/18/national/a130311D23.DTL&type=science San Francisco Chronicle, March 18, 2008] ]

"We're in for a world of hurt this summer. Depending on the weather, there could be as much melting this year as last, maybe more." - NSIDC senior scientist Mark Serreze [ [http://www.sfgate.com/cgi-bin/article.cgi?f=/n/a/2008/03/18/national/a130311D23.DTL&type=science San Francisco Chronicle, March 18, 2008] ]

ummer 2008 Arctic ice shrinking

In the summer of 2008, Arctic sea ice shrank again to near-record-breaking lows. By August 26, the sea ice extent fell to 5.26 million square kilometers (2.03 million square miles), making 2008 the second ice-freeest year ever, after 2007. [http://www.nsidc.org/arcticseaicenews/] On August 27, both the Northwest Passage and the Northeast Passage were ice-free. According to US scientist Mark Serreze, this was the first time in history that both passages have been open at the same time. [http://www.spiegel.de/wissenschaft/natur/0,1518,574539,00.html] The North Pole can now be circumnavigated. [ [http://www.independent.co.uk/environment/climate-change/for-the-first-time-in-human-history-the-north-pole-can-be-circumnavigated-913924.html independent.co.uk, For the first time in human history, the North Pole can be circumnavigated] ] The Beluga group of Bremen, Germany, announced plans to send the first ship through the Northern Sea Route in 2009, thereby cutting 4,000 nautical miles off the voyage from Germany to Japan. [ [http://www.dailymail.co.uk/news/article-1050990/The-North-Pole-island-time-history-ice-melts.html dailymail.co.uk, The North Pole becomes an 'island' for the first time in history as ice melts] ]

References

See also

*Arctic Ocean
*Arctic shrinkage
*Global warming
*Marine Modeling and Analysis Branch.
*Sea ice

External links

* [http://www.irbs.com/bowditch/pdf/chapt34.pdf Ice in the Sea] , chapter from Nathaniel Bowditch's "American Practical Navigator".
* [http://arctic.atmos.uiuc.edu/cryosphere/ Cryosphere Today] : current Arctic sea ice conditions.
* [http://www.gfdl.noaa.gov/research/climate/highlights/index.html#seaice The Shrinking Arctic Ice Cap] research summary, graphics and [http://www.gfdl.noaa.gov/research/climate/highlights/images/ani/Sea_Ice_ASO_anim_640x320.mpg animations] from NOAA Geophysical Fluid Dynamics Laboratory
* [http://www.antarctica.ac.uk/met/wmc/misc/seaice/ Data source for sea ice picture] .
* [http://southport.jpl.nasa.gov/polar/iceinfo.html Everything you ever wanted to know about sea ice but were afraid to ask] .
* [http://www.arctic.noaa.gov/detect/animations/halfsize_20030928-20040510.avi Animation of the movement of sea ice, September 2003 through May of 2004] .
* [http://nsidc.org/data/seaice_index/ NSIDC Sea Ice Index] .
* [http://www.arctic.noaa.gov/essay_untersteiner3.html Arctic summer time: The short summer of 2004] . North Pole webcam view.
* [http://nsidc.org/sotc/sea_ice.html Global Sea Ice Extent and Concentration] : what sensors on satellites are telling us about sea ice.
* [http://news.bbc.co.uk/2/hi/science/nature/4290340.stm "Arctic ice 'disappearing quickly'"] , BBC News, 28 September 2005.
* [http://www.guardian.co.uk/environment/2007/sep/05/climatechange.sciencenews "Ice-free Arctic could be here in 23 years"] David Adam, environment correspondent, The Guardian, September 5, 2007, Retrieved September 5 2007
* [http://www.nytimes.com/2007/10/02/science/earth/02arct.html "Arctic Melt Unnerves the Experts"] Andrew C. Revkin, The New York Times, October 2, 2007, Retrieved October 2, 2007.