“If there is going to be a climate catastrophe,” says Ohio State glaciologist Ian Howat, “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. When a chunk of ice the size of Pennsylvania falls apart, that’s a big problem. It won’t happen overnight, but if we don’t slow the warming of the planet, it could happen within decades. And its loss will destabilize the rest of the West Antarctic ice, and that will go too. Seas will rise about 10 feet in many parts of the world; in New York and Boston, because of the way gravity pushes water around the planet, the waters will rise even higher, as much as 13 feet. “West Antarctica could do to the coastlines of the world what Hurricane Sandy did in a few hours to New York City,” explains Richard Alley, a geologist at Penn State University and arguably the most respected ice scientist in the world. “Except when the water comes in, it doesn’t go away in a few hours – it stays.”
Antarctica is the size of the United States and Mexico combined, with a permanent population of zero. Seventy percent of the Earth’s fresh water is frozen here in ice sheets that can be nearly three miles thick.
Until recently, most climate scientists didn’t worry too much about Antarctica. It is, after all, the coldest place on Earth, and except for a small part of the Antarctic Peninsula that juts north, it hasn’t been warming much. It was also thought to be isolated from the warming oceans by a current that surrounds the continent, essentially walling it off from the rest of the planet.
But in recent years, things have gotten weird in Antarctica. The first alarming event was the sudden collapse, in 2002, of the Larsen B ice shelf, a vast chunk of ice on the Antarctic Peninsula. An ice shelf is like an enormous fingernail that grows off the end of a glacier where it meets the water. The glaciers behind the Larsen B, like many glaciers in both Antarctica and Greenland, are known as “marine-terminating glaciers,” because large portions of them lie below sea level. The collapse of ice shelves does not in itself contribute to sea-level rise, since they are already floating (just like ice melting in a glass doesn’t raise the level of liquid). But they perform an important role in buttressing, or restraining, the glaciers. After the Larsen B ice shelf vanished, the glaciers that had been behind it started flowing into the sea up to eight times faster than they had before. “It was like, ‘Oh, what is going on here?’ ” says Ted Scambos, lead scientist at the National Snow and Ice Data Center in Boulder, Colorado. “It turns out glaciers are much more responsive than anyone thought.”
Someday soon – possibly even by the time you read this – a chunk of the Larsen C ice shelf will break off and float into the ocean that surrounds Antarctica. The crack in the Larsen C, which is a close cousin to the Larsen B that broke up in 2002, has been developing for several years. But in the past few months, it has increased dramatically. As I write this, the crack is more than 100 miles long. Such a collapse of ice shelves is exactly what Mercer predicted would be the first sign that disaster is imminent. When it breaks, it will likely be front-page news and cited as evidence that Antarctica is rapidly falling apart.
In the end, no one can say exactly how much longer the West Antarctica glaciers will remain stable. “We just don’t know what the upper boundary is for how fast this can happen,” Alley says, sounding a bit spooked. “We are dealing with an event that no human has ever witnessed before. We have no analogue for this.” But it is clear that thanks to our 200-year-long fossil-fuel binge, the collapse of West Antarctica is already underway, and every Miami Beach condo owner and Bangladeshi farmer is living at the mercy of ice physics right now. Alley himself would never put it this way, but in West Antarctica, scientists have discovered the engine of catastrophe.