Original version With this story appeared in Quanta Magazine.
In May 2014, NASA announced at a press conference it was stated that part of the West Antarctic Ice Sheet had reached the point of irreversible retreat. Glaciers flowing seaward at the edges of the two-kilometer ice sheet were losing ice faster than snowfall could replenish it, causing their edges to retreat inland. Therefore, the question was no longer whether the West Antarctic Ice Sheet would disappear, but when. When these glaciers disappear, sea levels will rise by more than a meter, flooding currently inhabited areas 230 million people. And that would be just the first act before the entire ice sheet collapses, which could raise sea levels 5 meters and redraw the coastlines of the world.
Scientists then assumed that the disappearance of these glaciers would continue over the centuries. But in 2016, a bombshell study was conducted in Nature he concluded that crumbling ice cliffs could trigger a rapid retreat process, dramatically accelerating the timeline. The Intergovernmental Panel on Climate Change (IPCC) has taken notice, setting a sobering novel worst-case scenario: by 2100, meltwater from Antarctica, Greenland and mountain glaciers, combined with the thermal expansion of seawater, could raise global sea levels by more than 2 meters. And that would be just the beginning. If greenhouse gas emissions continues unabated, sea levels would rise to astonishing levels 15 meters to 2300.
However, not all scientists are convinced by this escape scenario. As a result, tension has arisen over how much time we have before the immense glaciers of West Antarctica disappear. If their retreat continues for centuries, humanity may have time to adapt. However, if rapid destabilization begins in the coming decades as a result of a controversial, uncontrolled process, the consequences may exceed our ability to respond. Scientists warn that major population centers – Novel York, Novel Orleans, Miami and Houston – may not be ready for it.
“We definitely do not rule out this possibility,” he said Karen Alleya glaciologist from the University of Manitoba, whose research confirms the possibility of an uncontrolled process. “But I’m not ready to say it’s going to happen soon. And I’m not going to say it can’t happen.”
For millennia, humanity has flourished along the coast, unaware that we are living in a geological fluke – an extraordinary period of low seas. The oceans will return, but how quickly? What does science say about retreating ice sheets and, therefore, the future of our ports, our homes and the billions of people living near the coast?
Grounded by the sea
In 1978, John Mercer, an eccentric glaciologist at Ohio State University who allegedly conducted field research in the nude, was one of the first to provide that global warming threatens the West Antarctic Ice Sheet. He based his theory on the extremely uncertain relationship between the ice sheet and the sea.
Larger than Alaska and Texas combined, West Antarctica is separated from the eastern part of the continent by the Transantarctic Mountains, whose peaks are buried up to their necks in ice. Unlike East Antarctica (and Greenland), where most of the ice rests on land high above the water, in West Antarctica the ice sheet settles deep below sea level in a bowl-shaped depression, with seawater lapping at its edges. This makes the West Antarctic Ice Sheet most susceptible to collapse.
The ice cap, resembling an ice dome, flows outward under its own weight through tentacle-like glaciers. But glaciers don’t stop at the shoreline; instead, colossal floating slabs of ice hundreds of meters hefty stretch out over the sea. These “ice shelves” float like giant rafts, tethered by drag forces and contact with underwater rises and ridges. They shore up glaciers against their inexorable gravitational pull toward the sea.