During the Cretaceous period, a forest grew less than 1000 kilometers from the South Pole, according to new research that has managed to discover remains of spores and ancient roots in this area.
Millions of years ago, Earth’s atmosphere had several times more carbon dioxide than it does now, making the Cretaceous one of the warmest periods on the planet. But scientists have few records of what Antarctica looked like during this time. A recent expedition to drill below the frozen continent revealed the existence of dozens of different plant species thanks to their fossilized pollen grains and spores, dating back 90 million years ago, in a region that was just 900 kilometers from the South Pole during this period.
“We went there with special drilling equipment for the seabed. It was the first time that anyone had managed to penetrate this layer of the Amundsen Sea, ”the study’s first author, Johann Klages, of the Alfred Wegener Institute for Polar and Marine Research, told Gizmodo. “We knew that it must be ancient and that we could retract into the Cretaceous, but what part and what we would find was something that nobody really knew. We were quite amazed when the first materials appeared. ”
The team traveled on the RV Polarstern research icebreaker in 2017 to a channel in the Amundsen Sea, West Antarctica. Previous glaciers had compacted sediment from this region, making penetration difficult. But they had brought with them the MARUM-MeBo70 seabed drilling rig, a remotely operated portable rig capable of drilling up to 80 meters into the seabed. They needed to monitor the area using satellite imagery and helicopters to search for icebergs that could disrupt drilling sessions, which could last for several days. Fortunately, they found an entire treasure just 30 meters below the sea floor.
Analysis of the drilled samples, including the CT scans, revealed the existence of at least 62 plant species thanks to the pollen, roots and fossilized spores found. Species identified include conifers and ferns from the southern hemisphere, according to Article published in Nature. Although today all of this is in the depths of the ocean off the Antarctic coast, an analysis of tectonic activity in this area suggests that it used to be at a latitude of 82 ° S and part of the continent of Zealandia, which is now submerged, and whose sediments and fossils date back 90 million years.
Taken together, the work demonstrates that a rain forest existed, such as the type of coniferous rain forest that can be found in parts of New Zealand or the Pacific Northwest in the United States, about 900 kilometers from the South Pole during the Cretaceous period. “We found incredible diversity to be at that latitude,” Klages said.
Later, the team built a model to determine what temperatures these plants could allow to live and managed to calculate that the annual average temperature would be around 13 degrees Celsius. However, to withstand these temperatures in a region with four months of uninterrupted night, the Earth should have had extremely high concentrations of carbon dioxide in the atmosphere (perhaps between 1,120 and 1,680 parts per million). Current levels of CO2 in the atmosphere are around 415 ppm.
Dietmar Muller, a professor of geophysics at the University of Sydney in Australia who reviewed the paper, told Gizmodo that it was quite compelling. He thought the most exciting thing about the paper was that there was no Antarctic ice during the Cretaceous. However, he warned that this could be the world’s fate again if humans continue to pump CO2 into the atmosphere uncontrollably. Some models estimate that we could increase the atmospheric CO2 concentration to 1,000 ppm by the year 2100. If so, and if all Antarctic ice melts, the planet could remain in a constant greenhouse effect for a long, long time, perhaps even millions years, he said.
Klages also told Gizmodo that his team hopes to continue working on models of what the Cretaceous climate would have been like to maintain a rain forest that far south.