Sensational find: A rainforest grew near the South Pole

According to a new study, the Antarctic was warmer during the Cretaceous period than it is today in Central Europe. Not a sight that would be associated with the Antarctic. But that's how it was supposed to have looked there 90 million years ago. Bremerhaven - It is known that there have always been extended periods in the earth's history in which the global climate was warmer than today. The Cretaceous, the last era of the great dinosaurs, has also been identified as such a period. Nevertheless, the extent of this warming phase has apparently been underestimated so far: This is indicated by a sensational discovery, of which researchers report in the journal "Nature". 

Surprise find

During an expedition in 2017, geologists near the Pine Island and Thwaites glaciers in the coastal area of ​​western Antarctica removed a sediment core, the unexpected colour of which they immediately noticed. When analyzed using computer tomography, it was found that this sample contained a lot of plant material. The researchers discovered remnants of dense root network, pollen, spores from vascular plants and remnants of flowering plants. Even details of cell structures could be identified.

An entire forest has apparently sunk here - more precisely a so-called temperate rainforest, as can be found today mainly on the west coast of North America, but also in New Zealand. Their Cretaceous counterpart, however, grew near the South Pole, at a geographic latitude of 82 degrees and only 900 kilometres from the Pole. Conifers and tree ferns created a dense, swampy forest 90 million years ago and thus a lush habitat. 

"The find surprised us very much," said geologist and student author Johann Klages* from the Alfred Wegener Institute (AWI) in Bremerhaven. His team's analyzes had shown that the Antarctic had an average annual temperature of 12 degrees Celsius during the Middle Cretaceous Period. That is two degrees higher than the current average in Central Europe. And that means even more: "It is certain that Antarctica must have been ice-free," said Klages. There has already been speculation about this, but it has not yet been certain. "We only knew that the Cretaceous was one of the warmest times, but we had no evidence from the area near the South Pole." Instead of wearing an ice cap, the entire continent of Antarctica may have been covered by vegetation at the time. According to the researchers, the same substance was responsible for the greenhouse climate at the time, which drives the temperatures up again today - even if it only came from natural sources at the time: carbon dioxide. At that time, the CO2 concentration in the atmosphere must have been much higher than previously thought.

And that means even more: "It is certain that Antarctica must have been ice-free," said Klages. There has already been speculation about this, but it has not yet been certain. "We only knew that the Cretaceous was one of the warmest times, but we had no evidence from the area near the South Pole." Instead of wearing an ice cap, the entire continent of Antarctica may have been covered by vegetation at the time. According to the researchers, the same substance was responsible for the greenhouse climate at the time, which drives the temperatures up again today - even if it only came from natural sources at the time: carbon dioxide. At that time, the CO2 concentration in the atmosphere must have been much higher than previously thought. "The study illustrates the high potential of the greenhouse gas carbon dioxide as an energy supplier and the cooling properties of today's ice sheets," says Klages. Another number clearly shows the effects: the climate at that time was accompanied by a sea-level that was 170 meters above today's level.

There are still open questions about the growth cycle of plants. Because even though it was snugly warm in the Antarctic at that time, the Cretaceous conditions were not a bit different from today's ones: At a geographic latitude of 82 degrees south, the Antarctic rainforests had to cope with a four-month polar night.

For other Ada blogs article click here.