The doomsday glacier

The research vessel ‘Nathaniel B. Palmer’ was surrounded overnight by icebergs while exploring the Thwaites Glacier in 2019.

This long piece from Rolling Stone is most interesting, and scary, and you should read it in full.  Some excerpts:

One thing that’s hard to grasp about the climate crisis is that big changes can happen fast. In 2019, I was aboard the Nathaniel B. Palmer, a 308-foot-long scientific research vessel, cruising in front of the Thwaites Glacier in Antarctica. One day, we were sailing in clear seas in front of the glacier. The next day, we were surrounded by icebergs the size of aircraft carriers.

As we later learned from satellite images, in a matter of 48 hours or so, a mélange of ice about 21 miles wide and 15 miles deep had cracked up and scattered into the sea.

It was a spooky moment. Thwaites Glacier is the size of Florida. It is the cork in the bottle of the entire West Antarctic ice sheet, which contains enough ice to raise sea levels by 10 feet. The mélange that disintegrated was not part of the glacier itself, but a mix of icebergs and sea ice that had cozied up next to it. Still, the idea that it could just fall apart overnight was mind-blowing.

As it turns out, the ice breakup I witnessed was not a freak event. A few weeks ago, scientists participating in the International Thwaites Glacier Collaboration, a $25 million five-year-long joint research program between the National Science Foundation in the U.S. and the Natural Environment Research Council in the U.K., presented their latest research. They described the discovery of cracks and fissures in the Thwaites eastern ice shelf, predicting that the ice shelf could fracture like a shattered car window in as little as five years. “It won’t scatter out into sea as quickly as what you saw when you were down there,” Erin Pettit, a glaciologist at Oregon State University and one of the lead principal investigators in the ITGC, later told me. “But the basic process is the same. The ice shelf is breaking up and could be gone in less than a decade.”

If Thwaites Glacier collapses, it opens the door for the rest of the West Antarctic ice sheet to slide into the sea. Globally, 250 million people live within three feet of high tide lines. Ten feet of sea level rise would be a world-bending catastrophe. It’s not only goodbye Miami, but goodbye to virtually every low-lying coastal city in the world.

But predicting the breakup of ice sheets and the implications for future sea level rise is fraught with uncertainty. Depending on various emissions scenarios in the latest Intergovernmental Panel on Climate Change report, we could have as little as one foot of sea level rise by the end of the century, or nearly six feet of sea level rise (of course, rising seas won’t stop in 2100, but that date has become a common benchmark). “The difference between those [models] is a lot of lives and money,” says Richard Alley, a glaciologist at Penn State University and one of the great ice scientists of our time. Alley adds: “The most likely place to generate [the worst scenario] is Thwaites.”

Or to put it more urgently: “If there is going to be a climate catastrophe,” Ohio State glaciologist Ian Howat once told me, “it’s probably going to start at Thwaites.”

The trouble with Thwaites, which is one of the largest glaciers on the planet, is that it’s also what scientists call “a threshold system.” That means instead of melting slowly like an ice cube on a summer day, it is more like a house of cards: It’s stable until it is pushed too far, then it collapses.

Thwaites is very different from other big glaciers, such as those in Greenland. For one thing, it is not melting from above, due to warmer air temperatures. It’s melting from below, due to warmer ocean water eating away at its underbelly. More importantly, the terrain beneath the West Antarctic ice sheet is peculiar. “Think of it as a giant soup bowl filled with ice,” Sridhar Anandakrishnan, an expert in polar glaciology at Penn State University, once told me. In the bowl analogy, the edge of the glacier — the spot where a glacier leaves the land and begins to float — is perched on the lip of the bowl 1,000 feet or more below sea level. Scientists call that lip the “grounding line.” Below the lip, the terrain falls away on a downward slope for hundreds of miles, all the way to the Transantarctic Mountains that divide East and West Antarctica. At the deepest part of the basin, the ice is about two miles thick.

What this means is that once the warm water gets below ice, it can flow down the slope of the bowl, weakening the ice from below. Through a mechanism called “marine ice-cliff Instability,” you can get what amounts to a runaway collapse of the ice sheet that could raise global sea levels very high, very fast.

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