Polar Ice Melt Sped Up Six-Fold from 1990s to 2010s
Polar ice caps in Greenland and Antarctica are melting six times faster than they were in the 1990s, putting them on track with the worst-case scenarios laid out by the Intergovernmental Panel on Climate Change (IPCC), according to new analysis led by the University of Leeds and NASA’s Jet Propulsion Laboratory and published last week.
The two locations combined for average annual ice loss of 475 billion tonnes in the 2010s, up from 81 billion in the 1990s, The Guardian reports. “In total the two ice caps lost 6.4 trillion tonnes of ice from 1992 to 2017, with melting in Greenland responsible for 60% of that figure.”
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The analysis predicts that 2019 will stand out as a record year for ice mass loss. “Without rapid cuts to carbon emissions the analysis indicates there could be a rise in sea levels that would leave 400 million people exposed to coastal flooding each year by the end of the century,” The Guardian says.
That projection puts ice loss at the poles on track with the most pessimistic of the IPCC’s past projection. “The IPCC’s most recent mid-range prediction for global sea level rise in 2100 is 53 centimetres,” the news story notes. “But the new analysis suggests that if current trends continue the oceans will rise by an additional 17 centimetres.”
The difference matters, because “every centimetre of sea level rise leads to coastal flooding and coastal erosion, disrupting people’s lives around the planet,” said University of Leeds professor and study co-author Andrew Shepherd. The additional 17 centimetres of sea level rise would boost the number of people exposed to coastal flooding each year from 360 to 400 million, and “these are not unlikely events with small impacts,” he added. “They are already under way and will be devastating for coastal communities.”
The study, conducted by 89 scientists from 50 international institutions, brought together the findings of 26 difference ice surveys, including 11 satellite missions that tracked changes in the ice sheets’ volume, mass, and speed of flow. It found that almost all the ice loss in Antarctica and half of it in Greenland “arose from warming oceans melting the glaciers that flow from the ice caps,” The Guardian says. “This causes glacial flow to speed up, dumping more icebergs into the ocean. The remainder of Greenland’s ice losses are caused by hotter air temperatures that melt the surface of the ice sheet.”
The UK-based paper says about one-third of sea level rise now comes from ice loss, just under half from thermal expansion of ocean water as it warms, and one-fifth from other glaciers—but of the three sources, only ice loss is accelerating.
“Shepherd said the ice caps had been slow to respond to human-caused global heating,” The Guardian adds, taking about 30 years to react. But “now that they had, a further 30 years of melting was inevitable, even if emissions were halted today. Nonetheless, he said, urgent carbon emissions cuts were vital.”
“We can offset some of that [sea level rise] if we stop heating the planet,” Shepherd said.