Understanding Ice Sheet Behavior: How Ice Melts in the Past and Present

A new study may be a leap forward when it comes to understanding ice sheet behavior. Scientists have discovered an alternative narrative of the manner in which an ice sheet can disappear.

In recent years, climate scientists have grown increasingly concerned that massive rivers of ice flowing into the ocean from Greenland and Antarctica could accelerate as the planet warms, leading to a catastrophic collapse of the Earth's ice sheets. Knowing this, the researchers of this latest study decided to take a closer look at the Laurentide Ice Sheet, which covered much of North America until about 10,000 years ago.

In this latest study, the researchers created a historical reconstruction of how ice streams behaved as the ice sheet disintegrated. This revealed that ice loss through these frozen rivers did not increase rapidly as the ice sheet disappeared.

"Their evidence shows that ice streams turned on and off, and shifted from place to place, during the disappearance of the Laurentide Ice Sheet-the Antarctic-sized ice sheet that occupied Canada and the northern United States at that time," wrote Jason Briner, a University at Buffalo geologist not involved in the research, in a news release. "Perhaps most notably, Stokes and colleagues find that ice-stream activity decreased as the planet warmed: the number of ice streams fell, the amount of ice expunged by them decrease and ice streams occupied a progressively smaller percentage of the ice-sheet edge."

This doesn't mean that today's ice sheets will behave exactly like the Laurentide did. For one thing, the Laurentide Ice Sheet was quite different from the Greenland and Antarctic ice sheets. Many of the Laurentide's ice streams ended on land, while Greenland's and Antarctica's flow into the ocean.

"Greenland has three major ice streams-Jakobshavn, Kangerlussuaq and Helheim-and in the early 2000s, they all madly accelerated at the same time," said Briner. "So we had this doomsday scenario for a while, because if they continued to accelerate, their discharges into the ocean would be huge. Then, several years later, they slowed down again. There is still a lot we don't know about how these ice streams behave, and understanding their behavior is crucial for accurate modeling of future ice sheet decline."

The findings are published in the journal Nature.

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