Antarctica’s Larsen B Ice Shelf Will Likely Disintegrate By Decade's End

Antarctica’s Larsen B Ice Shelf, which has existed for at least 10,000 years, will likely crumble completely away before the end of this decade, according to a new NASA study. “Although it’s fascinating scientifically,” says JPL researcher Khazendar, who led the investigation, “it’s bad news for our planet.”

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As NASA explains, “ice shelves are the gatekeepers for glaciers flowing from Antarctica toward the ocean. Without them, glacial ice enters the ocean faster and accelerates the pace of global sea level rise.” When Larsen B partially collapsed in 2002, the tributary glaciers that remained appeared to be more or less unaffected, “and hence assumed to be buttressed sufficiently by the remnant ice shelf,” Khazendar and his colleagues report in the latest issue of Earth and Planetary Science Letters. But when Khazendar’s team looked into the health of the Larsen B remnant, they found it in surprisingly poor shape:

Khazendar’s team used data on ice surface elevations and bedrock depths from instrumented aircraft participating in NASA’s Operation IceBridge, a multiyear airborne survey campaign that provides unprecedented documentation annually of Antarctica’s glaciers, ice shelves and ice sheets. Data on flow speeds came from spaceborne synthetic aperture radars operating since 1997.

Khazendar noted his estimate of the remnant’s remaining life span was based on the likely scenario that a huge, widening rift that has formed near the ice shelf’s grounding line will eventually crack all the way across. The free-floating remnant will shatter into hundreds of icebergs that will drift away, and the glaciers will rev up for their unhindered move to the sea.

Located on the coast of the Antarctic Peninsula, the Larsen B remnant is about 625 square miles (1,600 square kilometers) in area and about 1,640 feet (500 meters) thick at its thickest point. Its three major tributary glaciers are fed by their own tributaries farther inland.

“What is really surprising about Larsen B is how quickly the changes are taking place,” Khazendar said. “Change has been relentless.”

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From its observations, Khazendar’s team concludes that the ice shelf is likely to fragment into hundreds of icebergs within the decade.

More at NASA. Read the full scientific study at Earth and Planetary Science Letters.


Contact the author at rtgonzalez@io9.com.

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DISCUSSION

To address some talking points and some misunderstandings that somehow aren’t just hiding in the greys where they belong

1) It formed 10,000 years ago? After the last glaciation? During the Holocene Optimum when earth was much warmer than now? And it wasn’t there when earth was much colder?

Ice shelves are extensions of glaciers and ice sheets; they’re land ice that is sitting on top of beach and ocean. So their presence is indicative of a world that is cold enough to preserve glaciers and ice sheets, but warm enough that there is, at least, seasonal variation that promotes glacial movement. Also there is very little evidence that the Holocene Climatic Optimum was globally warmer than now.

2) Perhaps it wasn’t there prior to 10,000 years ago because of the active volcanoes around it, and perhaps the volcanoes (buried under glaciers) are becoming more active again.

That sounds like something that has been looked into. Comparisons of the warming effects from volcanoes and from a warming ocean show that warming oceans are much much of a cause of Antarctic land ice melt than volcanoes.

3) If the Larson B ice shelf is collapsing because of global warming, then why do we have reports like this: “Satellite observations show a new daily record being set for ­Antarctic sea ice every day for the past two weeks. Annual records have also been broken every year for the past three years.”

Because sea ice and land ice are not the same thing. If you want to be taken seriously with your comments about the cryosphere, it helps to be able to have basic understanding of it.

4) If it existed before, then it has collapsed before. The earth didn’t end then.

Non sequitor is non sequitor

.5) Prior to 2.5 million years ago (and for 250 million years prior to that time), the world was so warm there were no polar caps at all. The world didn’t end then.

Non sequitor is non sequitor again.