Sea-level rise could nearly double over earlier estimates in next 100 years

http://www.eurekalert.org/pub_releases/2016-03/ps-srf032916.php

Public Release: 30-Mar-2016
Sea-level rise from Antarctic ice sheet could double
Penn State

An ice sheet model that includes previously underappreciated processes indicates that sea level may rise almost 50 feet by 2500 due to Antarctic ice sheet melting if greenhouse gas emissions continue unabated, according to researchers from Penn State and University of Massachusetts, Amherst.

"In this case the atmospheric warming will soon become the dominant driver of ice loss, but prolonged ocean warming will delay the recovery for thousands of years," the researchers report in today's (Mar. 31) issue of Nature.

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Antarctica was the primary contributor to sea level rise in the past and may be the primary contributor in the future because much of its ice sits on ground. Floating ice, like that of the Arctic Ocean, is already in the water and if it melts, does not raise sea level. The Antarctic contribution will also probably dominate melt from the smaller Greenland Ice Sheet. While only parts of Antarctica will melt in the worst case scenario, the melting suggested by the model would be sufficient to double the recent estimates by the Intergovernmental Panel on Climate Change for future sea-level rise over the next 100 years.

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Both of these mechanisms are known, but neither has been applied to this type of ice-sheet model before. The researchers incorporated the physics and tested the model, driven by high-resolution climate models and past climate data. The updated model reproduced ice-sheet retreat consistent with geologic sea-level data for the warm Pliocene and also for the last interglacial period around 125,000 years ago. Then they applied the model to the future, forcing it with various greenhouse-gas emission scenarios.

"Although the future sea-level contribution in our model is greater than previously thought, it is based on credible mechanisms and is consistent with geologic evidence of past sea-level rise," said Pollard. "We regard the results as worst-case envelopes of possible future behavior, and the mechanisms should be considered seriously in future work.