Greenland and Antarctic ice sheet melting, rate unknownFebruary 17th, 2009 - 12:36 pm ICT by ANI
Washington, Feb 17 (ANI): A scientist has determined that the Greenland and Antarctica ice sheets are melting, but the amounts that will melt and the time it will take are still unknown.
In the past, the Greenland ice sheet has grown when its surroundings cooled, shrunk when its surroundings warmed and even disappeared completely when the temperatures became warm enough.
If the ice sheet on Greenland melts, sea level will rise about 23 feet, which will inundate portions of nearly all continental shores.
However, Antarctica, containing much more water, could add up to another 190 feet to sea level.
According to Richard Alley, Evan Pugh professor of geosciences, Penn State University, We do not think that we will lose all, or even most, of Antarcticas ice sheet.
But, important losses may have already started and could raise sea level as much or more than melting of Greenlands ice over hundreds or thousands of years, he added.
Warming is expected to cause more precipitation on Greenland and Antarctica, adding snow.
Previously, many scientists suggested that this would offset increasing melting. However, recent studies show that the ice sheets on both Greenland and in Antarctica are melting faster than the snow is replacing the mass.
A number of things can contribute to the increased rate of melting in Greenland and Antarctica.
For one, large lakes of water on the ice in Greenland pose a problem. This water, by wedging open a crack or crevasse in the ice, quickly flows through to the bottom, melting the bottom of the ice sheet and causing it to move more rapidly toward the ocean.
Also, observers have seen lakes on the Greenland ice sheet drain at the speed of Niagara Falls.
All ice sheets spread due to their large mass, but friction from the rocks beneath slows the ices motion. Water beneath the ice allows the ice to move more rapidly.
Right now, the center of the Greenland ice sheet is frozen to the rocks, said Alley. If the melt water moves inland as the world warms and gets to the bottom, it will thaw the bottom and unstick the ice from the rocks, he added.
Another contributor to the melting ice sheets is the warming of the ocean. When ice shelves melt, they also cause the ice sheet to flow faster.
Warmer oceans, caused by general global warming or local events can trigger more breakups of ice shelves and faster flow of ice streams in Antarctica.
In Greenland, sustained increase in temperatures of only a few degrees will remove the ice. (ANI)
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Tags: antarctica, crack, crevasse, friction, geosciences, greenland ice sheet, losses, niagara falls, observers, penn state university, precipitation, richard alley, rocks, scientist, scientists, sea level, surroundings, temperatures