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 ?
They slow the flow of ice from glaciers and ice sheets into the ocean, where it melts and raises sea levels.
The problem is researchers still don't fully understand the complexities of Earth's major ice sheets, in Greenland and Antarctica.
While studying glacial processes in the summer of 2012, UCLA researchers observed how meltwater from the ice sheet flowed.
Washington, June 16 ( ANI ): A new research has discovered a mysterious blocks of ice as tall as city skyscrapers and as wide as the island of Manhattan at the very bottom of the ice sheet in Greenland.
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.
The robot known as GROVER, which stands for both Greenland Rover and Goddard Remotely Operated Vehicle for Exploration and Research, will roam the frigid landscape collecting measurements to help scientists better understand changes in the massive ice sheet.
And these studies have looked at different regions of the ice sheets over different, usually brief, intervals, says Richard Alley, a glaciologist at Penn State.
So it was only natural that the focus of her research would be someplace cold: the massive West Antarctic Ice Sheet.
The study's findings suggest that the ice sheets are becoming the dominant contributor to global sea-level rise, overtaking ice loss from the Earth's mountain glaciers and ice caps.
Ice sheets are affected by many natural processes besides man-made warming, including atmospheric changes, shifting pressure systems, ocean temperature events.