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Can shearing of Thwaites glacier slow or stop if humans control greenhouse gas emissions?

Posted on 23 November 2020 by greenman3610

This is a re-post from Yale Climate Connections

Here’s the take-home message from this month’s original video by independent videographer Peter Sinclair for Yale Climate Connections:

Let’s hope Thwaites in Antarctica waits. Waits patiently, quietly, and long-term, perhaps even indefinitely.

And here’s a moral of this Thwaites video, adapted freely from Las Vegas tourism interests: What happens in Antarctica, and in particular in this instance at Thwaites, doesn’t stay in Antarctica. Not by a long shot.

The video addresses fairly widespread concerns and misunderstandings not about ongoing loss of Antarctic ice at Thwaites and Pine Island, but rather about whether that loss has become unstoppable, is rapidly accelerating, and is reaching the proverbial doomsday point of no return.

Let’s face it: Thwaites has the makings of being the lead role in an upcoming cli-fi thriller, one strong on emotion and drama but lacking something when it comes to hard science. The Sinclair video strives to set things straight.

Runaway feedback ‘not very likely’

It does so through quick and concise interviews with scientists most familiar with the issue. None of them takes a “What? Me worry?” Mad magazine/Alfred E. Neuman approach, nor that of Bobby McFerrin’s popular “Don’t Worry. Be Happy.” Rather, each points to the empirical evidence that human actions still could help determine the eventual prospects for Thwaites.

Scripps Institution of Oceanography scientist Jeffrey Severinghaus opens the video pointing to someone’s gradually rolling a large round boulder down a hill: Stop pushing a few moments, and the boulder may pause, may sit in place. But in time, the pushing gets to the point that the boulder sets apace on its own. Severinghaus calls that a “runaway positive feedback,” something to be avoided. Is that runaway prospect inevitable? he asks rhetorically. “We are possibly in a collapse right now,” he says. “but I would say it’s not very likely.” There’s a “but” coming, as Severinghaus adds “but we can’t completely rule it out either.”

Susheel Adusumilli of Scripps says the problem with Thwaites comes in large part from the increased ocean heat delivered to the ice shelves, primarily as a result of greenhouse gas emissions.

It all comes down to what humans know … and do

Severinghaus shares with climate scientist Eric Rignot, of the University of California, Irvine, a concern that so little is known about the underlying topography of the Antarctic ice sheets. “We know more about the topography of Mars than we know about the topography beneath Antarctic Ice,” he says. Rignot agrees, pointing to “not enough observations.”

“The accident of where it is, is that Thwaites can cause tremendously more sea-level rise by itself than these others can,” says Penn State climate scientist Richard Alley. He notes that some models show the unending shearing and collapse of Thwaites ice “keeps going,” but says other models hold that the shearing can be constrained – and the resulting sea-level rise kept “small, slow, and expected” – if greenhouse emissions can be substantially reduced, and soon.

That’s a point Twila Moon, scientist with the National Snow and Ice Data Center, fully buys into. “All of these different elements of the cryosphere” in the future will look “dramatically different if we are taking very strong action to reduce GHG emissions, versus if we are following a path like today.”

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