The deep ice in Camp Century in northwestern Greenland has melted at least once in the past million years and has been covered with vegetation, including moss and perhaps trees, according to an article in the Proceedings of the National Academy of Sciences.
To understand the history of the Greenland ice sheet, it is critical to predict its response to future global warming and its contribution to sea level rise. Image credit: Rolf Johansson.
“Ice sheets usually wear out and destroy everything in their path, but what we discovered were delicate plant structures – perfectly preserved,” said dr. Andrew Christ, a researcher from the Department of Geology and the Gund Institute for Environment at the University of Vermont, said.
“These are fossils, but they look like they died yesterday. It is a time capsule of what used to live in Greenland that we could not find anywhere else. ”
Dr Christ and colleagues analyzed sediment at the bottom of the Camp Century ice core, which was collected 120 km (75 miles) from the coast in northwest Greenland.
“The subglacial sediment of the Camp Century ice core was collected in 1966,” they explained.
“The sediment was stored frozen, initially at the University of Buffalo from 1966, until it was transferred to the Niels Bohr Institute in 1994 and 1996.”
The sediment, frozen under nearly 1.4 km of ice, contains fossils and well-preserved fossil plants and biomolecules from at least two ice-free warm periods in the past few years.
Fossil (AJ) micrographs; concentrations of leaf wax of n-alkanoic acids and alkanes (K), multiple columns correspond to repeated analyzes. Image Credit: Christ et al., doi: 10.1073 / pnas.2021442118.
“We used a series of advanced analytical techniques – none of which were available to researchers fifty years ago – to investigate the sediment, fossils and waxy cover of leaves found at the bottom of the Camp Century ice core,” scientists said. said.
“For example, we measured the ratios of rare isotopes of both aluminum and the element beryllium that only form in quartz when the soil is exposed to the air and can be hit by cosmic rays.”
“In another test, rare forms of oxygen in the ice in the sediment were used to indicate that precipitation must have fallen at much lower altitudes than the current ice sheet, indicating the absence of ice sheets.”
The authors concluded that the Greenland ice sheet retained much of the Pleistocene, but had melted and reformed at least once since 1.1 million years ago.
“Our study shows that Greenland is much more sensitive to natural climate warming than we previously thought – and we already know that humanity’s out-of-control warming of the planet’s natural rate is much higher,” said Dr. Christ said.
“Greenland may seem far away, but it can melt quickly and plunge into the oceans enough that New York, Miami, Dhaka – choose your city – go under water,” said Dr. Paul Bierman, a researcher at the Department of Geology, the Gund Institute of Environment, and the Rubenstein School of Environment and Natural Resources at the University of Vermont.
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Andrew J. Christus et al. 2021. A million-year-old report of Greenland’s vegetation and ice history preserved in the sediment under 1.4 km of ice in Camp Century. PNAS 118 (13): e2021442118; doi: 10.1073 / pnas.2021442118