Scientists Stunned to Discover Plants Beneath Mile-Deep Greenland Icehttps://www.uvm.edu/uvmnews/news/uvm-scientists-stunned-discover-plants-beneath-mile-deep-greenland-ice
In 1966, US Army scientists drilled down through nearly a mile of ice in northwestern Greenland—and pulled up a fifteen-foot-long tube of dirt from the bottom. Then this frozen sediment was lost in a freezer for decades. It was accidentally rediscovered in 2017.
In 2019, University of Vermont scientist Andrew Christ looked at it through his microscope—and couldn't believe what he was seeing: twigs and leaves instead of just sand and rock. That suggested that the ice was gone in the recent geologic past—and that a vegetated landscape, perhaps a boreal forest, stood where a mile-deep ice sheet as big as Alaska stands today.
Over the last year, Christ and an international team of scientists—led by Paul Bierman at UVM, Joerg Schaefer at Columbia University and Dorthe Dahl-Jensen at the University of Copenhagen—have studied these one-of-a-kind fossil plants and sediment from the bottom of Greenland. Their results show that most, or all, of Greenland must have been ice-free within the last million years, perhaps even the last few hundred-thousand years.
The discovery helps confirm a new and troubling understanding that the Greenland ice has melted off entirely during recent warm periods in Earth's history—periods like the one we are now creating with human-caused climate change.
The new study provides the strongest evidence yet that Greenland is more fragile and sensitive to climate change than previously understood—and at grave risk of irreversibly melting off.
"This is not a twenty-generation problem," says Paul Bierman, a geoscientist at UVM in the College of Arts & Sciences, Rubenstein School of Environment & Natural Resources, and fellow in the Gund Institute for Environment. "This is an urgent problem for the next 50 years."
https://www.uvm.edu/uvmnews/news/secrets-under-iceThe material for the new PNAS study came from Camp Century, a Cold War military base dug inside the ice sheet far above the Arctic Circle in the 1960s. The real purpose of the camp was a super-secret effort, called Project Iceworm, to hide 600 nuclear missiles under the ice close to the Soviet Union. As cover, the Army presented the camp as a polar science station.
The military mission failed, but the science team did complete important research, including drilling a 4560-foot-deep ice core.
They were focused on the ice and, apparently, took less interest in a bit of dirt gathered from beneath the ice core. Then, in a truly cinematic set of strange plot twists, the ice core was moved from an Army freezer to the University of Buffalo in the 1970s, to another freezer in Copenhagen, Denmark, in the 1990s, where it languished for decades—until it surfaced when the cores were being moved to a new freezer.
... The new study makes clear that the deep ice at Camp Century—some 75 miles inland from the coast and only 800 miles from the North Pole—entirely melted at least once within the last million years and was covered with vegetation, including moss and perhaps trees. The new research, supported by the National Science Foundation, lines up with data from two other ice cores from the center of Greenland, collected in 1990s. Sediment from the bottom of these cores also indicate that the ice sheet was gone for some time in the recent geologic past.
And the new study shows that ecosystems of the past were not scoured into oblivion by ages of glaciers and ice sheets bulldozing overtop. Instead, the story of these living landscapes remains captured under the relatively young ice that formed on top of the ground, frozen in place, and holds them still.
Andrew J. Christ el al.,
"A multimillion-year-old record of Greenland vegetation and glacial history preserved in sediment beneath 1.4 km of ice at Camp Century," PNAS (2021).
https://www.pnas.org/content/118/13/e2021442118 ... Cosmogenic 26Al/10Be and luminescence data bracket the burial of the lower-most sediment between <3.2 ± 0.4 Ma and >0.7 to 1.4 Ma. In the upper-most sediment, cosmogenic 26Al/10Be data require exposure within the last 1.0 ± 0.1 My.
The unique subglacial sedimentary record from Camp Century documents at least two episodes of ice-free, vegetated conditions, each followed by glaciation. The lower sediment derives from an Early Pleistocene GrIS advance. 26Al/10Be ratios in the upper-most sediment match those in subglacial bedrock from central Greenland, suggesting similar ice-cover histories across the GrIS. We conclude that the GrIS persisted through much of the Pleistocene but melted and reformed at least once since 1.1 Ma.
