[애니멀피플] ‘Green traces’ found under 1400m ice
Direct evidence that has completely melted more than once in the last million years
If ice melts throughout Greenland, sea level rises by 6m.
Summer landscape in eastern Greenland, with bushes growing behind whale bones. If the ice sheet in the whole Greenland disappears like here, the sea level rises by 6m, and the densely populated metropolitan cities along the coast such as New York, Miami, and Dhaka are submerged. Hannes Grove, courtesy of Wikimedia Commons.
Direct evidence has been found that Greenland, covered with more than 3000 m of ice, was once a green land. In addition, it is revealed that Greenland has completely melted at least once in the past 1 million years, and is drawing attention in relation to the large-scale sea level rise caused by climate change. An international research team, including a geologist at the University of Vermont in the United States, Andrew Christ, analyzed the drilling core obtained by excavating the ice sheet and the sediment below 1.4 km deep in 1966 at the US military base camp Century in northwest Greenland. It was revealed in a paper published in the National Academy of Sciences Bulletin (PNAS).
Deep drilling to build a US Army nuclear base at Camp Century Greenland. Provided by the U.S. Army.
The ice part of the drilling core left as a by-product in the process of the US Army building a nuclear missile base targeting the Soviet Union during the Cold War era has contributed significantly to the Greenland ice sheet research. However, the 3.44m long sedimentary layer excavated under the ice layer and the initial core of the 14m mud ice layer had been moved around the freezer for half a century without knowing its value.
Camp Century location (yellow circle). Andrew Christ et al. (2021) Courtesy of PNAS.
Analysis of this sedimentary core, which was’rediscovered’ in Denmark in 2017, revealed surprisingly well-preserved plant branches and leaves. Geologically, it has become evident that, in the last million or hundreds of thousands of years, Greenland’s ice sheets have melted and tundra areas with moss, grass and small trees have spread. Christ said, “Usually, everything is destroyed and turned into powder on an ice sheet, but here, even the shape of the plant was preserved, so it seemed to have died yesterday rather than a fossil.” In this university press release said.
Plant debris from the time when the Greenland ice sheet melted and the tundra ecosystem unfolded was found in the drilling core. The rhododendron family polar plants such as shiromi (B), cuckoo moss (D), and serrata (I) can be seen. Andrew Christ et al. (2021) Courtesy of PNAS.
In the sediments, the remains of tundra bushes of the Rhododendron family, such as shiromi, cuckoo moss, and ferns were contained. “These plants show that they were tundra ecosystems, but coniferous forests may have spread together,” the researchers wrote in the paper.
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Ice sheet sensitive to climate change
What does it mean to have such a greenery spread out at a distance of only 1280 km from the North Pole and 120 km from the coast? The researchers analyzed oxygen isotopes in the sediment and concluded that the altitude at the time of sedimentation was much lower than the current altitude of Camp Century (1890 m) where ice was deposited. It indicates that the ice sheet has not accumulated. If it is at high latitudes, it can be said that most of Greenland is not covered by ice.
A view of the eastern coast of Greenland where the ice sheet melts. Joshua Brown, Vs Vermont.
The researchers also analyzed the quartz in the sediments to calculate when they were exposed to spacecraft. If it is covered in ice, it is not exposed to spacecraft. The analysis revealed that Greenland, which had always been covered in ice during the Plystoce (2.5 million to 12,500 years ago), had completely melted at least once in the last 1.1 million years. These results have significant implications for Greenland, which suffers the most from climate change. “It’s a painful realization that Greenland has ever completely melted’recently’,” the researchers pointed out. When all the ice sheets that cover Greenland melt, the Earth’s sea level rises by 6 m, and major cities along the coast are known to be submerged. “This study will give us a clue to how quickly the ice sheets in Greenland will melt,” the researchers said. “Greenland is more sensitive to climate change than we understood and can irreversibly melt.”
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Greenland, a name designed to attract immigrants
The name Greenland, meaning green land, was coined by Eric Torbaldsson (aka red-haired Eric), the first Norse settlers here, to attract immigrants from Iceland. The immigrants gathered in this way settled on the southwest coast of Greenland aboard 25 ships in 985, and once flourished with a population of 5,000, but after twists and turns, such as the death of Eric from an infectious disease, it fell during the 15th century ice age.
The construction of a nuclear base in the ice at Camp Century in the 1960s. Provided by the U.S. Army.
In 1966, the US Army Camp Century Base, which has undergone in-depth drilling, began the’Ice Worm Project’ disguised as an polar science base, and began to conceal 600 nuclear missiles in a 3,200 km long tunnel in an ice sheet close to the Soviet Union. However, contrary to expectations, the tunnel was frequently deformed and collapsed due to frequent movements such as a huge ice sheet, and the following year he abandoned the project. The ice drilled for the foundations survived and moved to freezers in several laboratories, and the sedimentary drilling core was moved to the University of Copenhagen, Denmark in 1993, left unattended, and rediscovered in 2018 as contained in a cookie jar. Cited Papers: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.2021442118 By Cho Hong-seop, staff reporter [email protected]