Ice Sheets

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Ice Sheets


glaciers in which the ice flows from ice divides located in the interior to the periphery; the ice flows in the direction of the surface slope, without a direct dependence on subglacial relief.

Ice sheets form in areas where the snow line descends to the level of the lowlands. Small ice sheets (particularly those having steeply sloped surfaces, the domes) are also encountered on high plateaus. The position of the ice divides and the shape of the surface are caused by the distribution of accumulation and the drainage conditions; that is, both are indirectly dependent on subglacial relief. If subglacial features are small in comparison with ice thickness, then the radial profile of the surface approaches a semi-oval, and convexity of the semi-oval increases as the glacier becomes smaller. To a small degree, the convexity of the profile also increases with a drop in ice temperature and with an acceleration in accumulation. The loss of ice in Antarctica occurs predominantly by the discharge of ice into ice shelves and the breaking off of icebergs, and in warmer regions by melting in the marginal zone.

Of the total area of ice sheets (14.4 million sq km), 85.3 percent is accounted for by the continental ice sheets of Antarctica, which consist of five large contiguous sheets and a number of peripheral small sheets and domes. The ice sheets of Greenland constitute 12.1 percent, and 2.6 percent is constituted by the small ice sheets of the Canadian Arctic Archipelago, Iceland, Spitsbergen, Franz Josef Land, Novaia Zemlia, Severnaia Zemlia, and other polar islands, as well as by the mountain regions of Patagonia and the Scandinavian Peninsula. Ice sheets attained even greater development during periods of the culmination of Pleistocene glaciation.

Continental ice sheets are the world poles of cold: in the center of Antarctica the mean annual temperature reaches — 61°C, and in the center of Greenland it reaches — 32°C. The temperature of the ice is negative to the bottom (in the center of Antarctica the ice temperature on the bottom is as low as — 30°C), but in the narrow marginal zone, in deep basins of the sea floor (to — 2.6 km below sea level), and under outlet glaciers as well as in southern Greenland and the north of the Antarctic Peninsula, the temperature reaches the melting point.

The rate of movement increases from the ice divides to the periphery, where there is a differentiation into inactive areas (above rises in the floor) and outlet glaciers in which the speed reaches several kilometers per year.


References in periodicals archive ?
The findings confirm accelerating ice losses from the West Antarctic Ice Sheet and reveal surprisingly steady rates of flow from its much larger neighbor to the east.
Around 14,000 years ago the Earth started warming, which led to melting of ice caps and thinning of ice sheets.
This phenomenon occurred even though some of the ice sheets were located as far as one thousand miles from the closest eruption.
If you have very good coverage, like an array with separations of about 70 kilometers, we could in principle make a map of the regions that have more melting than others, using this monitoring, and maybe better refine models of how ice sheets respond to climate change," Prieto says.
All three countries have experienced multiple ice ages over the last million years - with one occurring every 100,000 years on average - so an understanding of ice sheet conditions is vital in planning for the long-term management of a deep geological repository for used nuclear fuel.
To do this, NASA Earth is using instruments aboard aircraft, ships, sensors placed in the ocean, and spacecraft in Earth's orbit to collect the data of all of the variables affecting the Greenland ice sheet.
FOR NEARLY 40 years we have known that the West Antarctic Ice Sheet is susceptible to the sudden loss of ice into the ocean, a process termed marine instability.
She has forged a new collaboration with Oxford University scientist Ian Hewitt, who has done extensive work modeling the hydrodynamic plumbing system in the difficult-to-access realm beneath the ice sheets.
Because the way in which water moves beneath ice sheets strongly affects ice flow speeds, improved understanding of these lakes will allow us to predict more accurately how the ice sheet will respond to anticipated future warming," Palme said.
Professor Mike Bentley from the Department of Geography at Durham University will be carrying out the mission as part of a team of British scientists to discover why the Pine Island Glacier on the West Antarctic Ice Sheet has been losing ice.
TEHRAN (FNA)- The results of a research showed that contrary to the popularly held scientific view, an ice sheet on West Antarctica existed 20 million years earlier than previously thought.
Robert Nicholls, professor of coastal engineering at Southampton, said: "Future increases in mass loss from the Greenland and West Antarctic ice sheets are likely to significantly enhance the rate of global sea-level rise, which is currently just over three millimetres per year, as these ice-sheet changes become an increasingly dominant contributor.