PNAS - Greenland's Vulnerability To Sudden Ice Loss Greater Than Previously Thought
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The findings, published Monday in the Proceedings of the National Academy of Sciences, indicate that the biggest reservoir of ice in the Northern Hemisphere can collapse due to relatively small increases in temperature over a long period of time. That makes it even more vulnerable to human-caused warming, which is causing the Earth to warm faster now than at any other period in its history.
“We know the Greenland ice sheet has this threshold,” Christ said — and humanity is pushing it. The world has just over a decade to get climate change under control, U.N. scientists say. Greenhouse gas emissions from human activities have already raised global average temperatures more than 1 degree Celsius (1.4 degrees Fahrenheit) since 1880. Greenland is losing ice at its fastest rate since humans invented agriculture, causing about 14 millimeters of sea level rise in the past half-century.
If the island’s entire ice sheet were to melt now, global sea levels would rise by more than 20 feet. “We don’t want to see what that looks like,” said Christ, a geologist at the University of Vermont. “It underscores the urgency of needing to change the way things are going right now.” The story of this soil sample is almost as dramatic as the data it contains. It comes from the bottom of an ice core taken during “Project Iceworm,” a failed Cold War effort to hide nuclear missiles beneath Greenland’s ice. Camp Century, in the far northwest of Greenland, was to be a base for the U.S. military project. Housing, dining and medical facilities, all powered by a nuclear reactor, were dug into the ice.
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Meanwhile, the folly of Project Iceworm became apparent when the ice began to shift. Tunnels collapsed. Equipment got crushed. The nuclear reactor was swiftly dismantled, and the camp abandoned. Any scientific materials collected were sent off to laboratories and rarely thought of again. More than a half-century later, glaciologist Jørgen P. Steffensen was conducting an inventory at the University of Copenhagen’s ice core repository when he stumbled upon what looked to be cookie jars full of sand, clay and soil. Curious, he shipped them to a few colleagues for analysis. The samples arrived at the University of Vermont in coolers stuffed with freezer packs. Christ, then a doctoral student, was tasked with sifting through the material, pulling out intriguing fragments and placing them on microscope slides. He leaned in to look, and then his eyes went wide. “It’s twigs and leaves and moss,” he said, “freeze dried for hundreds of thousands of years. They literally look like they could have been alive yesterday.”
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https://www.washingtonpost.com/climate-environment/2021/03/15/greenland-ice-sheet-more-vulnerable/
