Scientists Race to Understand Why Ice Shelves Collapse

By Eric Betz | May 5, 2017 2:02 pm
Scientists are tracking a large crack in the Larsen C Ice Shelf that will soon calve a Delaware-sized iceberg. Other floating ice shelves in the region have collapsed after similar events in recent decades.

Scientists are tracking a large crack in the Larsen C Ice Shelf that will soon calve a Delaware-sized iceberg. Other floating ice shelves in the region have collapsed after similar events in recent decades.(Credit: NASA/John Sonntag)

An 80-mile crack is spreading across the Antarctic Peninsula’s Larsen C ice shelf. And once that crack reaches the ocean, it will calve an iceberg the size of Delaware. The chunk looked like it could break off a few months ago, but it’s still clinging on by a roughly 10-mile thread. Earlier this week, scientists from the MIDAS project, which monitors Larsen C, reported a new branch on that crack.

Icebergs naturally calve from ice shelves all the time. But scientists are concerned that the entire Larsen C Ice Shelf — Antarctica’s fourth largest — could eventually collapse after this iceberg drifts out to sea. The iceberg will take 10 percent of Larsen C’s mass with it, leaving the floating shelf less stable.

There’s good reason to worry. The nearby Larsen A ice shelf collapsed in 1995. Seven years later, the neighboring Larsen B crumbled after a particularly warm summer.

Larsen B spanned more than 1,000 square miles and was some 700 feet thick. Yet it collapsed in about a week. Scientists were shocked at the time. They didn’t realize that could happen to a large ice shelf.

“It constantly blows my mind that these systems can go through that much change so quickly,” says University of Alaska, Fairbanks glaciologist Erin Pettit. “After maybe 100,000 years of ice being there, suddenly there’s no ice.”

And a long-running monitoring effort at a doomed ice shelf not far away could help scientists predict what’s next for Larsen C.

Erin Pettit (left) of the University of Alaska, Fairbanks, and Chucky Stevens of the British Antarctic Survey, look for the best spot to setup a remote camera. Behind them, the Scar Inlet Ice Shelf meets sea ice. (Credit: Christina Carr/University of Alaska, Fairbanks)

Erin Pettit (left) of the University of Alaska, Fairbanks, and Chucky Stevens of the British Antarctic Survey, look for the best spot to setup a remote camera. Behind them, the Scar Inlet Ice Shelf meets sea ice. (Credit: Christina Carr/University of Alaska, Fairbanks)

In recent years, scientists have discovered that warmer ocean waters are washing up under Antarctica’s ice shelves, melting them from below. At the same time, warmer air is melting them from above. That’s especially true in the Antarctic Peninsula, the continent’s northernmost landmass, which is warming at least twice as fast as Earth’s overall average.

These ice shelves form as glaciers slide off the continent onto the sea. And because they float, a collapsed ice shelf won’t add to sea level rise directly. But the ice also serves as blockade. Once gone, the glaciers that feed the ice shelf will retreat much faster.

No one’s ever witnessed a large ice shelf collapse in real time. With Larsen B, scientists had to go back and study satellite images from before and after. And in hindsight, they could see the ice shelf was covered in cracks and topped with meltwater. Pettit calls it forensic glaciology.

Yet, it’s not clear what delivers the deathblow to these thin, weakened ice shelves.

Now Pettit and her colleagues are applying lessons learned from other collapsed ice shelves to their years-long study of the Larsen B’s last remnant. It’s an ice shelf one-third the size of Rhode Island called the Scar Inlet.

The Larsen A and B oce shelves have already collapsed on the Antarctic Peninsula. The final Larsen B remnant, or Scar Inlet, sits just north of Larsen C. (Credit: Scambos et al., 2004)

The Larsen A and B ice shelves have already collapsed on the Antarctic Peninsula. The final Larsen B remnant, or Scar Inlet, sits just north of Larsen C. (Credit: Scambos et al., 2004)

Scientists predict its demise is imminent. Pettit’s team has visited the region repeatedly in recent years. They’ve installed a suite of instruments — cameras, ocean microphones, weather stations — so they’ll have instant replay once the Scar Inlet collapses.

“We have a GPS monitor sitting on top of the ice shelf that’s going to fall into the ocean when the whole thing disintegrates,” Pettit says. That should happen within a year, she expects. The Scar Inlet looked ready to fall just a few weeks ago. Now it looks like the ice shelf will remain through the coming southern winter.

And once Scar Inlet finally crumbles, the data researchers gather could help better predict the future of the much larger Larsen C Ice Shelf.

“(Larsen C) has already shrunk to the size where we know it’s reaching the limit of its stability,” Pettit says. “This might be one of the last big icebergs that goes off this ice shelf before it does do a full collapse.” And even if Larsen C holds steady as the Delaware-sized iceberg drifts away, warmer temperatures on the Antarctic Peninsula don’t bode well for its future.

“It really is down to the last decades of the life of this ice shelf,” Pettit says.

Larsen C is the largest ice shelf on the Antarctic Peninsula, but there are much larger floating ice masses around the continent. As Antarctica warms, they too could be at risk.

“If the fourth largest ice shelf in Antarctica disintegrates, bigger ice shelves with bigger drainage basins could also be in danger,” says Ala Khazendar, a NASA JPL ice shelf scientist.

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  • OWilson

    Interesting.

    They tell us the Arctic is warming at “twice the rate of the rest of the world”, and here we have the Antarctic Peninsula that is “warming at least twice as fast as the world’s average”.

    Wonder where the cooling is occuring to balance the observed slight global warming.

    Ice shelves are a natural phenomena that form as glacial ice flows out from inland precipitation. They flow out until they break off and melt. Others flow down to take their place in a process that has been going on for thousands, if not millions of years.

    But, apparently he scientists are puzzled, “Yet, it’s not clear what delivers the deathblow to these thin, weakened ice shelves”

    Hopefully my comments are of assistance! :)

    • Jochen

      One has to wonder why people want to study glaciers when it’s apparently so simple. Oh, I forgot, these are scientists who have nothing else in mind as spending tax payers money to produce more “ifs” and “coulds” and publish “alarmist pamphlets”.

      Scientist prefer “if” over “when”, because it is not 100% clear that something will happen. There’s always an uncertainty. However, that does not mean that a prognosis is unlikely or even wrong. If, sorry when events occur 9 out of 10 times, then the prognosis was still correct in the one failure. (I had an old starter in my car. Most of the time it worked, but occasionally it wouldn’t. Still, I was right with my assumption that my car will start when I turn the starter.)

      • OWilson

        A poor assumption, if you were suddenly forced to drive your family away, or to a hospital in an emergency! :)

        They are talking about life and death here, the Deadliest Threat to Humankind, the Sixth Great Extinction. :)

        • Jochen

          You might be aware that the subject of global warming has been discussed for decades, and has been OPEN for discussion ever since then.

          You might also be aware that discussions on reaction and pro-action have also been varied, from curbing greenhouse gases to environmental engineering, and also OPEN to discussion.

          It is a myth, repeated over and over again, that dissenting views are oppressed by the scientific community based on their political bias. In fact, these dissenting views are not published based on the lack of scientific evidence. Natural science is not political, because nature is not political. The rocks that I study don’t share a political view, neither do my scientific publications. Science is politicized by those that don’t like the results. The politicization of global warming is a repetition of the fight the tobacco industry waged when cigarettes were proved unhealthy.

          Having said this, the initial story was about the collapse of an ice shield in Antarctica and the scientists who study it. Nowhere in that article is global warming or climate change directly addressed. Do you really read a political undertone in the article? You seem to be disturbed by the fact that people are studying glaciers at all. And THAT’s what I find disturbing.

          • OWilson

            Another nonsensical piece of logic to match your seriously flawed “broken starter” logic’ :)

            Scientists are not rocks. Scientists are human. Humans are political.

            Get it, Einstein?

          • Jochen

            I get it!

            Following your flawless logic, science is political, since scientists are humans. Hence, good or bad science depends on the ideology of the person conducting science. In your case, it has to be conservative or right-wing. Go figure, I never thought there’d be something like liberal or conservative gravity or DNA (since these concepts were discovered by scientists they have to be).

            By the way, Einstein was not a geologist – but that’s probably beyond your knowledge…

            No reason to continue discussions with you. I see you are drifting towards insults.

          • OWilson

            If you are going to publicly lecture me on logic, make sure you have a basic understanding of the subject. :)

  • http://www.mazepath.com/uncleal/qz4.htm Uncle Al

    The pictured crack has a mountain chain of ice on one side. Brittle materials fail in tension, staying flat. Somebody is lying.

    • OWilson

      Not lies, just the usual non-scientific, speculative, alarmist language,

      They string enough “ifs”, “coulds” and “mights” together with their doom and gloom scenarios, that it covers any eventuality.

      They’ll be “right” even if they’re “wrong!

      (listen to an “expert” economist describing next month’s stock market, and you’ll get the idea)

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    • TLongmire

      There isn’t a mountain chain of ice, it’s just the way he photoshopped/increased the contrast of the image. It broke clean from below and pulled other side with it.

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