February 9, 2009
Some unknown day in the future, ongoing climate change virtually assures the West Antarctic Ice Sheet will melt away. This ice sheet sits on a bit of land that rests below sea level. Some of the water will fill up this hole and the rest will spread out over the globe. Models that assume the world is something like a bathtub in which the water rises evenly worldwide predict that sea level will rise about five meters.
But, of course, the world is not a bathtub; it’s a bit more complicated than that. And a new study from Science shows that some places, such as North America, would be even worse off than previously thought.
The researchers cite three complicating factors to the bathtub model:
1. Because of its mass, an ice sheet has a gravitational pull that attracts water. As the ice sheet melts, its gravitational pull lessens and water moves away from it. Counterintuitively, sea level within 2,000 kilometers of an ice sheet will fall as the ice sheet melts. But that means that sea level farther away will rise; the water has to go somewhere.
2. The ice sheet is so heavy that it depresses the ground beneath it. Remove the ice and the ground will rise. The models of sea level rise depend on a certain amount of water filling up the hole in Antarctica beneath the West Antarctic Ice Sheet. But under the new model less water will fill up the hole and more will end up in the ocean.
3. The melting of the West Antarctic Ice Sheet would be dramatic enough to cause a change in the earth’s rotation axis, ultimately moving water northward in the Atlantic, Pacific and Indian Oceans.
These factors add another 1.3 meters to the total sea level rise (6.3 meters total, or 20.7 feet) in Washington, DC, more than enough to put the National Mall—and much of the Smithsonian Institution—underwater.
But the West Antarctic Ice Sheet is not the only one vulnerable to climate change, the scientists warn in a National Science Foundation video. To get the whole picture, researchers will need to add Greenland, Alaska and mountain glaciers to the models. How much would it take to put your hometown underwater?
See the world under six meters of sea level rise in a CReSIS animation.
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