At COP21 yesterday, leaders of developed countries expressed an unprecedented commitment to helping preserve indigenous populations and vulnerable island states from extermination. But to understand how we can save Kiribati or the Marshall Islands, we'll need to pay much closer attention to the ice sheets in Greenland and Antarctica.
A panel of the International Cryosphere Climate Initiative drove home that message this morning. The ICCI is a fixture at these annual negotiations: They send scientists and former diplomats to observe the talks and advocate for new solutions to close "the gap between science and policy," as Svante Bodin, director of ICCI Europe, put it this morning in a conversation with reporters.
The precarity of polar glaciers is one of the oldest and most familiar climate concerns—one with which we've become a bit too comfortable. But the mechanisms of melting, in Greenland and Antarctica especially, are both more interesting and more terrifying than most civilians realize. Today's experts laid out the latest research with eloquent urgency.
"Greenland alone is contributing a third of the total sea-level budget."
The ICCI panel, chaired by Bodin, included Dr. Frank Pattyn of the Université Libre de Bruxelles (an ice-sheet modeler), Jonathan Bamber of the University of Bristol (a professor of geography specializing in satellites and glacier erosion), Dr. Ricarda Winkelmann of the Potsdam Institute (a climate systems analyst), and Dr. Julian Gutt (polar ecologist and chief officer of the SCAR biology program). Pattyn gave a four-minute master class in "self-amplifying mass loss," the iterative loop whereby glaciers, disrupted by warming, begin to melt, which raises surface temperatures, which in turn accelerates melting.
Pattyn also illustrated the trends of self-amplifying mass loss that result from precarious grounding lines: As glaciers melt, they become semi-unmoored from their footing in deep bedrock—a pattern that further hastens glacial erosion.
“If increased melting perturbs the contact zone between the ice sheet that is resting on the bedrock, then the bedrock starts dipping toward the interior," Pattyn said. "And then you get a kind of irreversible retreat. Some authors believe we have already reached such a tipping point."
Bamber, an energetic Brit, lamented that he had "only about five minutes to cover what we're seeing in Greenland and western Antarctica," then promptly did so. (He also addressed past inaccuracies among certain glacial models, rejecting any suggestion that scientists had been willfully cooking numbers.) Bamber noted that well over 90 percent of terrestrial ice is located either in Greenland or in western Antarctica, where ice sheets are up to five kilometers in depth.
"Not to belittle the importance of the European Alps," he said with a smile, "but this is where we should be looking. Greenland alone is contributing a third of the total sea-level budget."
Based on current INDCs and the conference's stated objective of limiting warming to two degrees Celsius above pre-industrial levels, Greenland is screwed. "The best estimate for the viability threshold for Greenland is 1.6 degrees Celsius," Bamber said—an almost impossible goal. "After that, the Greenland ice sheet will no longer be viable. In other words, it will be a last relic of the previous ice age." (At a follow-up event this afternoon, Bamber noted that, together, Antarctica and Greenland represent about 65 meters of potential sea-level rise.)*
Winkelmann recapitulated dark forecasts about the "irreversible retreat" of ice in the Antarctic; focusing her remarks on Wilkes Basin and Amundsen Basin, Winkelmann noted that changes in the Amundsen ice pack could contribute five meters of sea-level rise by the close of the century. Winkelmann also brought the most frightening GIFs of the morning—see, for example, this simulation of Antarctic erosion over the next 200 years:
In a brief valedictory plea for sustaining oceanic biodiversity, Gutt discussed marine ecology in the southern oceans, and how emperor penguins aren't the only creatures to suffer as Antarctica thaws—the role of the southern ocean in the carbon cycle is hardly negligible.
"We cannot even discuss global marine biodiversity without discussing biodiversity in the southern ocean," Gutt said.
At the Nordic Pavilion this afternoon, Bamber reiterated these grim realities. But he also made it clear that fatalism is not an option, even once we blow past the 1.6-degree mark.
"What we do now will have an impact, not on the irreversibility, but on the rate of the sea-level rise. And that matters."
*Update — December 03, 2015: This article has been updated to correct a misquote of Jonathan Bamber of the University of Bristol.
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