A recent investigation detailed in the Proceedings of the National Academy of Sciences reveals that the profound ice accumulation at Camp Century in northwestern Greenland underwent complete thawing on at least one occasion within the last million years, and during that period, it was adorned with flora, including bryophytes and potentially arboreal species.
Understanding the history of the Greenland Ice Sheet is critical for predicting its response to future climate warming and contribution to sea-level rise. Image credit: Rolf Johansson.
“Typically, ice sheets obliterate and decimate all in their trajectory, yet our findings uncovered exquisitely preserved, delicate botanical structures,” stated Dr. Andrew Christ, an investigator affiliated with the Department of Geology and the Gund Institute for Environment at the University of Vermont.
“These are fossils, but their condition suggests they perished only recently. They serve as an unearthed chronicle of Greenland’s past inhabitants, providing insights unobtainable elsewhere.”
Dr. Christ and his associates undertook an analysis of sedimentary material extracted from the base of the Camp Century ice core, which was retrieved 120 kilometers (75 miles) from the coast in the northwestern sector of Greenland.
“The subglacial sediment originating from the Camp Century ice core was first collected in 1966,” the researchers elaborated.
“This sediment was maintained in a frozen state, initially housed at the University at Buffalo from 1966, before its transfer to the Niels Bohr Institute in 1994 and subsequently in 1996.”
The sediment, situated beneath approximately 1.4 kilometers (0.9 miles) of frozen ice, yielded well-preserved fossilized plant matter and biomolecular evidence indicating at least two ice-free, warmer intervals occurring within the last few million years.
Micrographs of fossils (A-J); leaf wax concentrations of n-alkanoic acids and alkanes (K), multiple columns correspond to replicate analyses. Image credit: Christ et al., doi: 10.1073/pnas.2021442118.
“Employing a battery of sophisticated analytical methodologies—techniques that were unavailable to researchers half a century ago—we meticulously examined the sediment, the fossilized remains, and the lipid-rich cuticular coatings found within the detritus at the foundation of the Camp Century ice core,” the scientific team reported.
“For instance, we quantified the isotopic ratios of aluminum and beryllium, rare elements that are synthesized in quartz solely when geological surfaces are exposed to atmospheric conditions and consequently subjected to cosmic radiation.”
“An additional diagnostic technique involved the analysis of scarce oxygen isotopes present in the ice interspersed within the sediment. This evidence indicated that precipitation must have historically descended at considerably lower elevations than the summit of the contemporary ice sheet, thereby substantiating periods of ice sheet absence.”
The study’s authors deduced that although the Greenland Ice Sheet remained largely intact throughout a significant portion of the Pleistocene epoch, it did indeed melt and subsequently re-form on at least one occasion subsequent to 1.1 million years ago.
“Our research demonstrates that Greenland exhibits a far greater susceptibility to natural climatic warming than previously surmised—and we are already cognizant that the unchecked global warming driven by human activity vastly surpasses the pace of these natural fluctuations,” Dr. Christ commented.
“While Greenland may appear geographically remote, its ice mass is capable of rapid diminution, leading to substantial influxes into the oceans that would imperil coastal metropolises such as New York, Miami, or Dhaka, submerging them,” added Dr. Paul Bierman, a faculty member in the Department of Geology, the Gund Institute for Environment, and the Rubenstein School of the Environment and Natural Resources at the University of Vermont.
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Andrew J. Christ et al. 2021. A multimillion-year-old record of Greenland 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
