Ice shelf
From Wikipedia, the free encyclopedia
An ice shelf is a thick, floating platform of ice that forms where a glacier or ice sheet flows down to a coastline and onto the ocean surface. Ice shelves are found in Antarctica, Greenland and Canada only. The boundary between floating ice shelf and the grounded (resting on bedrock) ice that feeds it is called the grounding line. When the grounding line retreats inland, water is added to the ocean and sea level rises.
In contrast, sea ice is formed on water, is much thinner, and forms throughout the Arctic Ocean. It also is found in the Southern Ocean around the continent of Antarctica.
Ice shelves flow by gravity-driven horizontal spreading on the ocean surface. That flow continually moves ice from the grounding line to seaward front of the shelf. The primary mechanism of mass loss from ice shelves is iceberg calving, in which a chunk of ice breaks off from the seaward front of the shelf. Typically, a shelf front will extend forward for years or decades between major calving events. Snow accumulation on the upper surface and melting from the lower surface are also important to the mass balance of an ice shelf.
The thickness of modern-day ice shelves ranges from about 100 to 1000 meters. The density contrast between solid ice and liquid water means that only about 1/9 of the floating ice is above the ocean surface. The world's largest ice shelves are the Ross Ice Shelf and the Filchner-Ronne Ice Shelf in Antarctica.
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[edit] Greenlandic ice shelves
[edit] Canadian ice shelves
All Canadian ice shelves are attached to Ellesmere Island and lie north of 82°N:
- Milne Ice Shelf
- Ayles Ice Shelf
- M'Clintock Ice Shelf
- Ward Hunt Ice Shelf
[edit] Antarctic ice shelves
44 percent of the Antarctic coastline has ice shelves attached. The individual ice shelf areas are listed below, in a clockwise manner, starting in the west of Eastern Antarctica:
- Filchner Ice Shelf
- Brunt Ice Shelf
- Riiser-Larsen Ice Shelf
- Quar Ice Shelf
- Ekstrom Ice Shelf
- Jelbart Ice Shelf
- Fimbul Ice Shelf
- Lazarev Ice Shelf
- Hannan Ice Shelf
- Zubchatyy Ice Shelf
- Wyers Ice Shelf
- Edward VIII Ice Shelf
- Amery Ice Shelf
- Publications Ice Shelf
- West Ice Shelf
- Shackleton Ice Shelf
- Moscow University Ice Shelf
- Voyeykov Ice Shelf
- Cook Ice Shelf
- Slava Ice Shelf
- Gillett Ice Shelf
- Nansen Ice Sheet
- McMurdo Ice Shelf
- Ross Ice Shelf
- Swinburne Ice Shelf
- Sulzberger Ice Shelf
- Nickerson Ice Shelf
- Getz Ice Shelf
- Dotson Ice Shelf
- Crosson Ice Shelf
- Cosgrove Ice Shelf
- Abbot Ice Shelf
- Venable Ice Shelf
- Stange Ice Shelf
- Bach Ice Shelf
- George VI Ice Shelf
- Wilkins Ice Shelf
- Wordie Ice Shelf
- Jones Ice Shelf
- Müller Ice Shelf
- Prince Gustav Ice Shelf
- Larsen Ice Shelf
- Ronne Ice Shelf
Recently, glaciologists have observed unexpected ice-shelf events, such as complete disintegration of some small ice shelves. For example, two sections of Antarctica's Larsen Ice Shelf broke apart into hundreds of unusually small fragments (100's of meters wide or less) in 1995 and 2002. The breakup events are linked to climate change in the region, although there is not complete agreement about the most important causative process. The leading ideas involve enhanced ice fracturing due to surface meltwater and enhanced bottom melting due to warmer ocean water circulating under the floating ice.
The cold, fresh water produced by melting underneath the Ross and Flichner-Ronne ice shelves is a component of Antarctic Bottom Water.
[edit] External links
- http://www.antdiv.gov.au/default.asp?casid=1547 - from the Australian Antarctic Division
- http://nsidc.org/iceshelves - from the U.S. National Snow and Ice Data Center
