From time immemorial, the poles of the Earth resembled frozen wastelands. Life can and does exist there, but there are good reasons why most other animals prefer a more hospitable climate closer to the equator.
Although the poles were not always frozen deserts. We know that conditions were completely different in the ancient past of our planet. In the middle of the Cretaceous, about 90 million years ago, an increased concentration of CO2 in the atmosphere could have created higher global temperatures, melting polar ice sheets and sea levels 170 meters higher than today.
What would the South Pole look like in such a world? Thanks to a startling scientific discovery, we have the answer.
In 2017, during an expedition aboard the RV Polarstern in the Amundsen Sea, researchers drilled a well under the seabed of West Antarctica, near the location of the Pine and Thwaites Island glaciers, and only 900 kilometers from the South Pole.
A simplified overview map of the South Pole region 90 million years ago. (J. P. Klages, Alfred-Wegener-Institut)
What they got from a depth of about 30 meters was in stark contrast to the composition of the sediments closer to the surface.
“During the initial assessment on board, the unusual coloration of the sediment layer quickly caught our attention,” says geologist Johann Klages of the Alfred Wegener Institute, Center for Polar and Marine Research. Helmholtz in Germany.
“The first analyzes showed that at a depth of 27 to 30 meters below the ocean floor, we found a layer originally formed on land, not in the ocean.”
No one has ever pulled a sample of the Cretaceous period from such a southern point of the globe. However, the researchers could not have been prepared for what a more thorough examination using X-ray computed tomography would reveal.
Back on land, the scans described an intricate network of fossilized plant roots. Microscopic analysis has also revealed signs of pollen and spores that point to preserved remains of an ancient rainforest that existed in Antarctica about 90 million years ago, several years before the landscape turned into a barren ice desert.
“Numerous plant remains indicate that the coast of West Antarctica was a dense, swampy forest at the time, similar to those found in New Zealand today,” says paleoecologist Ulrich Salzmann of the University of Northumbria in the UK.
The results are reported in Nature.
Sources: Photo: Alfred-Wegener-Institut / James McKay / CC-BY-4.0
