In May 2014, NASA announced in a press conference that a portion of the West Antarctic Ice Sheet had reached the point of no return. Seaward-flowing glaciers on the perimeter of the 2-kilometer-thick sheet of ice were losing ice faster than they were flowing, causing their edges to slide inward. With this, the question is no longer whether the West Antarctic Ice Sheet will disappear, but rather when. When those glaciers are gone, sea levels will rise by more than a metre, submerging the land currently populated by 230 million people. And it would be the first act before the entire ice sheet collapses, which could raise seas by 5 meters and redraw the world’s coastlines.
At the time, scientists assumed that the loss of those glaciers would continue for centuries. But a shocking study came out in 2016 Nature Concluded that collapsing ice shelves could trigger a runaway process of retreat, dramatically accelerating the timeline. The Intergovernmental Panel on Climate Change (IPCC) took note of this and established a serious new worst-case scenario: by 2100, meltwater from Antarctica, Greenland and mountain glaciers combined with thermal expansion of seawater could raise global sea levels by more than 2 metres. And that will only be the beginning. If greenhouse gas emissions continue unabated, seas will rise by 15 meters by 2300.
However, not all scientists are convinced by the runaway scenario. Thus, tensions have emerged over how much time we have until the vast glaciers of West Antarctica disappear. If their retreat continues for centuries, humanity may have time to adapt. But if destabilization begins to accelerate through the controversial runaway process in the coming decades, the consequences could outstrip our ability to respond. Scientists warn that major population centers—New York City, New Orleans, Miami and Houston—may not be prepared.
“We certainly haven’t ruled it out,” said glaciologist Karen Alley of the University of Manitoba, whose research supports the possibility of a migration process. “But I’m not ready to say it’s going to happen any time soon. I’m also not going to say it can’t happen.”
For millennia, humanity has flourished along the coast, unaware that we were living in a geological upswing – an unusual spell of the low sea. The oceans will return, but how soon? What does the science say about how the ice sheets retreat, and therefore, about the future of our ports, our homes, and the billions of people who live near the coast?
land by sea
In 1978, John Mercer, an eccentric glaciologist at Ohio State University who reportedly conducted fieldwork while naked, was among the first to predict that global warming threatened the West Antarctic ice sheet. He based his theory on the ice sheet’s uniquely uncertain relationship with the ocean.
Larger than Alaska and Texas combined, Western Antarctica is divided from the eastern half of the continent by the Transantarctic Mountains, whose peaks are buried chin-deep in snow. Unlike East Antarctica (and Greenland), where most of the ice rests on land above water, the ice sheet in West Antarctica has settled into a bowl-shaped depression well below sea level, with seawater lapping at its edges. This makes the West Antarctica ice sheet most vulnerable to collapse.
A towering dome of ice, the ice sheet flows outward through tentacle-like glaciers under its own weight. But glaciers don’t stop at the shoreline; Instead, huge floating plates of ice hundreds of meters thick extend over the ocean. These “ice shelves” float like giant rafts, held together by drag forces and exposed to underwater heights and peaks. They support the glaciers against the harsh gravitational attraction toward the ocean.
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