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Ice Sheet: definition.
An ice sheet is the layer of ice covering extensive regions of the world, notably
Antarctica and Greenland. The ice sheets form from the accumulation of thousands
or millions of years of snowfall, followed by compression of the snow as the weight
of new snow presses down on previous years’ fall.
Who cares? Climate scientists are interested in ice sheets because they
lock away fresh water that would otherwise be added to the oceans and raise global
sea level. If all the ice in Antarctica melted, sea level would rise by about
200 feet, flooding large inhabited regions of the world. Even a small change in
the volume of ice sheets would have catastrophic consequences for low-lying areas.
Ice sheets also can be used to look at past climate. As new snow is added each
year, signals of present climate are locked away in the ice. For example, scientists
can look through ice cores from Greenland (see Greenland
Ice Sheet Project 2 website) and Antarctica (see WAISCORES
project and Vostok project
websites) for the history of atmospheric CO2 concentration over several hundred
thousand years, and can also see the dust spikes corresponding to large volcanic
eruptions.