Climate Change

The Doomsday Glacier. In the farthest reaches of Antarctica, a nightmare scenario of crumbling ice – and rapidly rising seas – could spell disaster for a warming planet. Rolling Stone  May 9, 2017 Jeff Goodell interviewed Knut Christianson, a 33-year-old glaciologist at the University of Washington who is one of 28 people to walk on West Antarctica’s Thwaites Glacier. “If there is going to be a climate catastrophe,” says Ohio State glaciologist Ian Howat, “it’s probably going to start at Thwaites.” “We like to think that change happens slowly, especially in a landscape like Antarctica,” Christianson tells me. “But we now know that is wrong.”

“The most recent report by the United Nations’ Intergovernmental Panel on Climate Change, which is the gold standard for climate-change science, projected between less than 1 foot and 3.2 feet of global sea-level rise by 2100, with very little of it coming from Antarctica (although the IPCC did include a caveat suggesting that could change).”

“The IPCC’s sea-level-rise projections have long been controversial, partly because the melting of the Greenland and Antarctica ice sheets is so difficult to predict. A few years ago, James Hansen, the godfather of global-warming science, told me that he believed the IPCC estimates were far too conservative and that the waters could rise as much as 10 feet by 2100. For Hansen, the past is prologue. Three million years ago, during the Pliocene Epoch, when the level of CO₂ in the atmosphere was about the same as it is today, and temperatures were only slightly warmer, the seas were at least 20 feet higher. That suggests there is a lot of melting to come before the ice sheets reach a happy equilibrium. Mountain glaciers could contribute a little bit, as would the thermal expansion of the oceans as they warmed, but to get to more than 20 feet of sea-level rise, Greenland and Antarctica would both have to contribute in a big way….If all of Greenland were to melt, that’s 22 feet of sea-level rise. If Antarctica goes, it’s 200 feet…Then, in 1974, Hans Weertman, a materials scientist at Northwestern University, figured out that these glaciers in West Antarctica were more vulnerable to rapid melting than anyone had previously understood. He coined a term for it: “marine ice-sheet instability.” Weertman pointed out that warm ocean water could penetrate the grounding line, melting the ice from below. If the melting continued at a rate that was faster than the glacier grew – which is currently the case – the glacier would slip off the grounding line and begin retreating backward down the slope, like “a ball rolling downhill,” says Howat, the Ohio State glaciologist.

“In a 1978 paper called “West Antarctic Ice Sheet and the CO₂ Greenhouse Effect: A Threat of Disaster,” Mercer focused on the floating ice shelves that buttress the West Antarctica glaciers. “I contend that a major disaster – a rapid [16-foot] rise in sea level, caused by the deglaciation of West Antarctica – may be imminent,” he wrote, predicting it would lead to the “submergence of low-lying areas such as much of Florida and the Netherlands.” Mercer didn’t know how soon this might happen, but when he made his calculations in the mid-1970s, he predicted that if fossil-fuel consumption continued to accelerate, it could begin in 50 years. That is, right about now.  ”