How a Colossal Ice Shelf Collapsed After the Last Ice Age

First Posted: Feb 18, 2016 09:49 AM EST

What happened after the last ice age? Scientists have found that a colossal ice shelf collapse may have occurred with the end of cold weather.

The Ross Ice shelf is the world's largest ice shelf. It's a vast floating extension of the West Antarctic Ice sheet that's about the size of France. At the end of the last ice age, though, it extended much farther north and covered the entire Ross Sea.

Now, researchers have taken a closer look at how this ice shelf shrank during a period of climate warming that followed the ice age. This, in particular, could tell researchers a bit more about how ice shelves may react today.

"At the height of the last ice age, we know that the sheet of ice covering the Antarctic continent was larger and thicker than it is today," said John Anderson, one of the researchers, in a news release. "This continent-enveloping ice sheet extended all the way to the continental shelf, and in western Antarctica it filled the entire Ross Sea basin."

While people typically think of continents as landmasses that rise above the sea, the margins of all continents extend well beyond their shores to include continental shelves. In western Antarctica, the Ross Sea has a continental shelf that extends nearly 1,000 miles from the coast and is as much as 3,500 feet deep. About 18,000 years ago, the entire Ross basin was filled with ice that was so thick and heavy it was grounded on the seafloor all the way to the edge of the continental shelf.

In this case, the researchers found that the ice shelf retreated until the grounding line reached a series of shallow banks that acted as anchors and stabilized the ice shelf for about 5,000 years. On the surface, the ice still covered large portions of the Ross Sea, but there was open water beneath the ice shelf.

"The really big breakup began around 3000 BC," said Anderson. "We believe it was similar, in many respects, to the breakup of the Larsen B Ice Shelf in 2002. The Larsen is far smaller than the Ross Ice Shelf, but satellite imagery that year showed the Larsen dramatically breaking apart in just a few weeks. We believe the large breakup of the Ross Ice Shelf occurred at roughly this same pace, but the area involved was so much larger-about the size of the state of Colorado-that it took several centuries to complete."

The findings reveal a bit more about how ice shelves react to warming temperatures. This, in turn, may tell us a bit more about the changes occurring today.

The findings are published in the journal Proceedings of the National Academy of Sciences.

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