Historic data proves ice sheets can melt fast when climate warms

Scientists estimate the melting of the Cordilleran Ice Sheet at the end of the last ice age caused sea levels to rise by some 20 feet.
By Brooks Hays  |  Nov. 10, 2017 at 12:13 PM
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Nov. 10 (UPI) -- Ice sheets can disappear surprisingly quickly according to a new analysis by researchers at Purdue University.

Scientists determined that the Cordilleran Ice Sheet was halved in size in just 500 years at the end of the last ice age. It's possible the modern Greenland Ice Sheet could suffer a similar fate as global temperatures continue to rise.

During the Pleistocene, the Cordilleran Ice Sheet blanketed much of North America. Previous studies have found evidence of the ice sheet's presence in western Canada as late as 12,500 years ago. More recently, scientists determined much of western Canada was ice-free just 1,500 years prior, proof that ice sheets can dramatically advance and retreat during a relatively short amount of time.

Scientists estimate the melting of the Cordilleran Ice Sheet at the end of the last ice age caused sea levels to rise by some 20 feet. When cold meltwater enters the ocean it sinks to the bottom as a result of its density. The influx of cold, dense water can disrupt the system of global ocean currents known as the conveyer belt.

To better understand how quickly ice sheets can disappear and how rapidly glaciers can advance and retreat, researchers analyzed beryllium isotopes from moraine samples across Canada. Moraines are the deposits of rock left at the terminus of a glacier.

"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, professor of physics in Purdue, said in a news release. "The only way this would happen is if the ice in that area had completely gone away and then advanced."

When the planet started to warm 14,000 years ago, ice receded from the tops of Canada's mountains. But shortly after, the planet began to cool again and the ice returned. The ice again retreated -- for good in most places -- as the ice age ended and the Pleistocene became the Holocene.

Establishing timelines helps scientists tease out the cause and effect of different climate and geologic phenomena. Their latest analysis confirms that the Cordilleran Ice Sheet had disappeared prior to the period of global cooling just before the end of the last ice age, known the Younger Dryras cooling.

Had the Cordilleran Ice Sheet still been present during this brief respite of cooling, researchers wouldn't see evidence of advancing cirque and valley glaciers. Thus, scientists can confirm the ice sheet melting was rapid not gradual.

Researchers detailed their conclusions in a new paper published this week in the journal Science.

Though rapid, the continental ice sheet's disappearance was surely complicated, researchers estimate. More research is needed to better understand how exactly the ice sheet melted so quickly -- and what that might mean for the Greenland Ice Sheet moving forward.

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