Magazine article Science News

Sea Level Rise Forecast Doubles: By 2100, Antarctic Melt Could Boost Oceans by over a Meter

Magazine article Science News

Sea Level Rise Forecast Doubles: By 2100, Antarctic Melt Could Boost Oceans by over a Meter

Article excerpt

Antarctica's meltdown could spur sea level rise well beyond current predictions. New simulations suggest that Antarctic melting alone will raise global sea levels by about 64 to 114 centimeters by 2100, scientists report in the March 31 Nature.

Adding Antarctic melt to other sources of sea level rise, such as the expansion of warming seawater and melting Greenland ice, the scientists predict that sea levels will rise 1.5 to 2.1 meters by the end of the century. That's as much as double previous predictions that didn't incorporate mechanisms that can expedite the Antarctic ice sheet's collapse, though uncertainties remain, says study coauthor David Pollard, a paleoclimatologist at Penn State.

Predicting future sea level rise requires understanding how the oceans rose in the past. Scientists often glean ancient sea level rise by reconstructing the locations of ancient coastlines. But these coastlines can be a slippery target: Forces such as tectonic activity can cause Earth's surface to rise and fall, obscuring the effects of past sea level rise. Depending on how much uplift obfuscated ancient sea level records--ranging from no uplift to massive uplift--the new prediction of 21st century sea level rise can differ by 35 centimeters or more.

"I really would be happier if we had the luxury of doing the research on this without bothering the public until we have 95 percent confidence in an answer," says Penn State glaciologist Richard Alley, who was not involved in the study. "Any single forecast is notably uncertain, but if we continue warming the world rapidly, the most likely outcome is a major event of large and rapid sea level rise."

Two warm periods, one about 125,000 years ago and another about 3 million years ago, were particularly useful for Pollard and geoscientist Robert DeConto of the University of Massachusetts Amherst. …

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