Antarctic ice sheet
hideThe Antarctic ice sheet is one of the two polar ice caps of the Earth. It covers about 98% of the Antarctic continent and is the largest single mass of ice on Earth. It covers an area of almost 14 million square km and contains 30 million cubic km of ice. That is, approximately 61 percent of all fresh water on the Earth is held in the Antarctic ice sheet, an amount equivalent to 70 m of water in the world's oceans. In East Antarctica, the ice sheet rests on a major land mass, but in West Antarctica the bed can extend to more than 2,500 m below sea level. The land in this area would be seabed if the ice sheet were not there.
Ice enters the sheet through precipitation as snow. This snow is then compacted to form glacier ice which moves under gravity towards the coast. Most of it is carried to the coast by fast moving ice streams. The ice then passes into the ocean, often forming vast floating ice shelves. These shelves then melt or calve off to give icebergs that eventually melt.
If the transfer of the ice from the land to the sea is balanced by snow falling back on the land then there will be no net contribution to global sea levels. A 2002 analysis of NASA satellite data from 1979-1999 showed that areas of Antarctica where ice was increasing outnumbered areas of decreasing ice roughly 2:1. The general trend shows that a warming climate in the southern hemisphere would transport more moisture to Antarctica, causing the interior ice sheets to grow, while calving events along the coast will increase, causing these areas to shrink. However more recent satellite data, which measures changes in the gravity of the ice mass, suggests that the total amount of ice in Antarctica has begun decreasing in the past few years. Another recent study compared the ice leaving the ice sheet, by measuring the ice velocity and thickness along the coast, to the amount of snow accumulation over the continent. This found that the East Antarctic Ice Sheet was in balance but the West Antarctic Ice Sheet was losing mass. This was largely due to acceleration of ice streams such as Pine Island Glacier. These results agree closely with the gravity changes.
The continent-wide average surface temperature trend of Antarctica is positive and significant at >0.05°C/decade since 1957. West Antarctica has warmed by more than 0.1°C/decade in the last 50 years, and this warming is strongest in winter and spring. Although this is partly offset by fall cooling in East Antarctica, this effect is restricted to the 1980s and 1990s.
Despite this warming total Antarctic sea ice anomalies have been steadily increasing since 1978 (NSIDC (2006)). 2007 showed the largest positive anomaly of sea ice in the southern hemisphere since records have been kept starting in 1979 and 2008 is currently on pace to surpass last years record. The atmospheric warming cannot be directly linked to the recent mass losses in West Antarctica. This mass loss is more likely to be due to increased melting of the ice shelves because of changes in ocean circulation patterns. This in turn causes the ice streams to speed up. The melting and disappearance of the floating ice shelves will only have a small effect on sea level, which is due to salinity differences. The most important consequence of their increased melting is the speed up of the ice streams on land which are buttressed by these ice shelves.
For more information about Antarctic ice sheet, read the full article at
Wikipedia.
This text uses material from Wikipedia and is available under the GNU Free Documentation License.
News tagged with antarctic ice
LSU gets to the bottom of things -- in Antarctica
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Nov 24, 2009 |
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Antarctica has long held secrets of the earth's history locked in its icy depths, and until recently, there has been very little information on the environments that have been sealed beneath miles of ice for millions of years. ...
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A new study that reconstructed ocean temperatures from millions of years ago could provide new insight into how the Earth responds to climate change.
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(PhysOrg.com) -- A new study of Antarctica's past climate reveals that temperatures during the warm periods between ice ages (interglacials) may have been higher than previously thought. The latest analysis ...
Giant Antarctic iceberg heads towards N.Zealand: experts
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Nov 12, 2009 |
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A giant iceberg twice the length of Beijing's "Bird's Nest" Stadium has been spotted floating off Australia and could be headed for New Zealand, scientists said on Thursday.
West Antarctic ice sheet may not be losing ice as fast as once thought
Space & Earth / Earth Sciences
Oct 19, 2009 |
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New ground measurements made by the West Antarctic GPS Network (WAGN) project, composed of researchers from The University of Texas at Austin, The Ohio State University, and The University of Memphis, suggest ...
NASA flies to Antarctica for largest airborne polar ice survey
Space & Earth / Earth Sciences
Oct 08, 2009 |
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NASA begins a series of flights Oct. 15 to study changes to Antarctica's sea ice, glaciers and ice sheets. The flights are part of Operation Ice Bridge, a six-year campaign that is the largest airborne survey ever made of ...
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The link between declining CO2 levels in the earth's atmosphere and the formation of the Antarctic ice caps some 34 million years ago has been confirmed for the first time in a major research study.
Computer model documents the history of the West Antarctic ice sheet
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(PhysOrg.com) -- One major threat of planetary warming is the melting of the great polar ice sheets, and the resulting rise in global sea level. Particularly worrisome to researchers is the fragility of the ...
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Fossil coral data and temperature records derived from ice-core measurements have been used to place better constraints on future sea level rise, and to test sea level projections.
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Forty miles off the Jersey Shore, an international team of scientists is grappling with a worrisome phenomenon: The oceans are slowly rising. The researchers are not studying the sea itself. Living for weeks at a time on ...
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Southern Elephant seals responded rapidly to climate and habitat change and established a new breeding site thousands of kilometres from existing breeding grounds, according to new research.
Melting threat from West Antarctic Ice Sheet less than previously believed
Space & Earth / Earth Sciences
May 14, 2009 |
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(PhysOrg.com) -- While a total or partial collapse of the West Antarctic Ice Sheet as a result of warming would not raise global sea levels as high as some predict, levels on the U.S. seaboards would rise 25 percent more ...
New Antarctic seabed sonar images reveal clues to sea-level rise
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May 05, 2009 |
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Motorway-sized troughs and channels carved into Antarctica's continental shelves by glaciers thousands of years ago could help scientists to predict future sea-level rise according to a report in the journal ...
Dust may settle unanswered questions on Antarctica
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Dust trapped deep in Antarctic ice sheets is helping scientists unravel details of past climate change.
West Antarctic ice comes and goes, rapidly
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Mar 18, 2009 |
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Researchers today worry about the collapse of West Antarctic ice shelves and loss of the West Antarctic ice sheet, but little is known about the past movements of this ice. Now climatologists from Penn State ...
