An international team of researchers led by geoscientists from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, have now provided a new and unprecedented perspective on the climate history of Antarctica.
An international team of researchers led by geoscientists from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, have now provided a new and unprecedented perspective on the climate history of Antarctica. In a sediment core collected in the Amundsen Sea, West Antarctica, in February 2017, the team discovered pristinely preserved forest soil from the Cretaceous, including a wealth of plant pollen and spores and a dense network of roots. These plant remains confirm that, roughly 90 million years ago, the coast of West Antarctica was home to temperate, swampy rainforests where the annual mean temperature was ca. 12 degrees Celsius – an exceptionally warm climate for a location near the South Pole. The researchers surmise that this warmth was only possible because there was no Antarctic ice sheet and because the atmospheric carbon dioxide concentration was significantly higher than indicated by climate models to date. The study, which provides the southernmost directly assessable climate and environmental data from the Cretaceous and poses new challenges for climate modellers around the globe, was released today in the journal NATURE.
The mid-Cretaceous time interval, from ca. 115 million to 80 million years ago, is not only considered the age of the dinosaurs, but was also the warmest period in the past 140 million years. Sea surface temperatures in the tropics at this time were likely as high as ca. 35 degrees Celsius, and sea level was 170 metres higher than today. Yet we still know very little about environmental conditions in the Cretaceous south of the polar circle, since there are virtually no reliable climate archives that extend that far back in time. The new sediment core offers the team of experts the first chance to reconstruct the West Antarctic climate during the warmest interval of the Cretaceous, thanks to the unique evidence it contains.
In the sediment core, which the team collected with the University of Bremen’s seafloor drill rig MARUM-MeBo70 near the Pine Island Glacier on an RV Polarstern expedition, they found pristinely preserved forest soil from the Cretaceous. “During the initial shipboard assessments, the unusual colouration of the sediment layer quickly caught our attention; it clearly differed from the layers above it. Moreover, the first analyses indicated that, at a depth of 27 to 30 metres below the ocean floor, we had found a layer originally formed on land, not in the ocean,” reports first author Dr Johann Klages, a geologist at the AWI.
Read more at Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research
Image: Germany's icebreaking research vessel POLARSTERN, operated by the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI) (Credit: © Alfred-Wegener-Institut/Johann Klages)
