Icesheets as large as Greenland can disappear dramatically fast when climate warms: researchers

Source: Xinhua| 2017-11-13 11:25:27|Editor: liuxin
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LOS ANGELES, Nov. 12 (Xinhua) -- The Cordilleran Ice Sheet was halved in size in just 500 years at the end of the last ice age caused by climate warming, indicating the modern Greenland Ice Sheet could have a similar fate, according to a new research published this week in Science.

During the Pleistocene, or Last Ice Age, the Cordilleran Ice Sheet, similar in mass to the Greenland Ice Sheet, blanketed large parts of North America.

According to the study, the Cordilleran Ice Sheet's melting likely caused about 20 feet of sea level rise and big changes in ocean temperature and circulation. Because cold water is denser than warm water, the water contained by ice sheets sinks when it melts, disrupting the "global conveyor belt" of ocean circulation and changing climate.

Previous studies have found evidence of the ice sheet's presence in western Canada as late as 12,500 years ago, but new data shows that large areas in the region were ice-free just 1,500 years prior, which reveals that ice sheets can advance and retreat during a relatively short period of time.

Using geologic evidence and ice sheet models, researchers constructed a timeline of the Cordilleran's advance and retreat. In Purdue University's PRIME Lab, a research facility dedicated to accelerator mass spectrometry, they mapped and dated moraines throughout western Canada using beryllium-10, a rare isotope of beryllium that is often used as a proxy for solar intensity.

"We have one group of beryllium-10 measurements, which is 14,000 years old, and another group, which is 11,500 years old, and the difference in these ages is statistically significant," Marc Caffee, a professor of physics in Purdue's College of Science and director of PRIME Lab, was quoted as saying in a news release. "The only way this would happen is if the ice in that area had completely gone away and then advanced."

Reconstructing precise chronologies of past climate helps researchers establish cause and effect. Creating a timeline of glacial retreat also provides insight into how the first people got to North America.

"This paper should serve as motivation for further studies," said Caffee. "Continental ice sheets don't disappear in a simple, monolithic way, it's an extremely complicated process. The more we know about the retreat of the Cordilleran Ice Sheet, the better we'll be able to predict what's to come for the Greenland Ice Sheet."