The deep ice at Camp Century in northwestern Greenland has completely melted at least once in the last million years and was covered with vegetation, including moss and perhaps trees, according to an article published in the United States. Proceedings of the National Academy of Sciences
Understanding the history of the Greenland ice sheet is critical to predicting the response to future global warming and contribution to sea level rise. Image credit: Rolf Johansson.
“Ice sheets usually pulverize and destroy everything in their path, but what we found was delicate plant structures – perfectly preserved,” said Dr. Andrew Christ, a researcher in the Department of Geology and the Gund Institute for Environment at the University of Vermont.
‘They are fossils, but they look like they died yesterday. It’s a time capsule of what used to be in Greenland that we wouldn’t be able to find anywhere else. “
Dr. Christ and colleagues analyzed sediment collected at the bottom of the Camp Century ice core, 120 km (75 miles) off the coast in northwestern Greenland.
“The subglacial sediment from the Camp Century ice core was collected in 1966,” they explained.
“The sediment was stored frozen, initially from 1966 at the University of Buffalo, until it was transferred to the Niels Bohr Institute in 1994 and 1996.”
The sediment, frozen under nearly 1.4 km of ice, contained well-preserved fossil plants and biomolecules from at least two ice-free warm periods over the past few million years.
Photomicrographs of fossils (AJ); leaf washing concentrations 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 range of advanced analytical techniques – none of which were available to researchers 50 years ago – to examine the sediment, fossils and waxy layer of leaves at the bottom of the Camp Century ice core,” the scientists said.
“For example, we measured ratios of rare isotopes of both aluminum and the element beryllium that only form in quartz when the soil is exposed to air and can be hit by cosmic rays.”
“Another test used rare forms of oxygen found in the ice in the sediment to show that the precipitation must have fallen at altitudes much lower than the height of the current ice sheet, demonstrating the absence of ice sheets.”
The authors concluded that the Greenland ice sheet persisted for much of the Pleistocene, but melted and reformed at least once since 1.1 million years ago.
“Our study shows that Greenland is much more sensitive to natural global warming than we used to think – and we already know that humanity’s uncontrolled warming is vastly outpacing the natural rate,” said Dr. Christ.
“Greenland may seem distant, but it could melt quickly and pour into the oceans enough that New York, Miami, Dhaka – choose your city – will go under water,” added Dr. Paul Bierman, a researcher in the Department of Geology. Gund Institute for Environment and the Rubenstein School of the Environment and Natural Resources at the University of Vermont.
Andrew J. Christ et al2021. A million-year record of Greenlandic vegetation and glacial history preserved in sediment beneath 1.4 km of ice at Camp Century. PNAS 118 (13): e2021442118; doi: 10.1073 / pnas.2021442118