Antarctica is now a harsh land of ice and snow but has not always been that way. Earth's southernmost continent long ago was home to temperate, swampy rainforests teeming with life, scientists said on Wednesday based on pristinely preserved forest soil they retrieved by drilling under the seafloor off Antarctica's coast.
The sediment core obtained by scientists working aboard the research icebreaker RV Polarstern in the Amundsen Sea near the Pine Island Glacier dated to about 90 million years ago during the Cretaceous Period when dinosaurs were the dominant land animals.
The researchers estimated based on the soil content that this location, 900 kilometers from the South Pole, experienced average annual temperatures of about 53-55 degrees Fahrenheit (12-13 Celsius) and average temperatures during the warmest summer months of about 68-77 Fahrenheit (20-25 Celsius).
That is exceptionally warm for a location near the South Pole, where the average annual temperature now is around minus 40 Fahrenheit (minus 40 Celsius).
A modern temperature analogue may be New York City, according to marine geologist Johann Klages of the Alfred Wegener Institute's Helmholtz Centre for Polar and Marine Research in Germany, lead author of the research published in the journal Nature.
The dark-brownish gray soil was composed of fine-grained silt and clay bearing remains of fossil roots in a dense network, pollen and spores spanning 65 types of plants, with individual cell structures clearly visible.
If you would go to a forest near you and drill a hole, it would probably look pretty similar, Klages said.
Klages said the plants included conifers, ferns and flowering plants. While they did not find any animal remains, Klages said there likely were dinosaurs, flying reptiles called pterosaurs and many insects. Dinosaur fossils from Antarctica have been known for years.
The soil came from nearly 27 meters beneath the seafloor under ocean depths of about 1,000 meters. It was obtained using a seafloor drill rig. The research underscores the dramatic climate changes Earth has undergone in the past - and is currently undergoing today.
The soil core sample dated from 93-83 million years ago, Klages said. This dates from the planet's warmest period of the past 140 million years, with sea levels about 170 meters higher than today.
The rainforest environment is all the more remarkable, the researchers said, considering that the region annually experiences a four-month polar night when there is no sunlight to nurture plant life. Klages said no ice sheets were present at the time though seasonal snow fall was likely.