Was our South Pole’s past a prelude to its future? An ancient 90-million-year-old sediment core from the Cretaceous revealed a startling discovery –fossil pollen and spores, indicating a long-lost rain forest from the age of the dinosaurs that was cloaked in perpetual darkness for months at a time.
“We have a really nice X-ray movie through the sediment core,” said Karsten Gohl at the Alfred Wegener Institute Helmholtz Center for Polar and Marine Research (AWI), who spearheaded the expedition on Germany’s Research Vessel Polarstern (image above). “It’s like we’ve drilled into a modern swamp environment and you’re seeing the living root system, small plant particles and pollen – but this is all preserved from 90 million years ago. It’s amazing.”
The picture of this ancient Antarctic rainforest provides first glimpse of Cretaceous ecosystems at bottom of the planet, 500 miles from the South Pole when global sea levels would have been over 100 meters higher than at present that was found by AWI scientists.
Simulations suggests average annual temperatures in this Cretaceous environment would have been in the mid-teens Celsius; summer averages would have been in the 20s.
But, says lead author geologist Johann Klages, the, vegetation must have been pretty special because, being so far south, it would have had to endure three to four months of polar darkness. “Probably these plants, they had a much more effective way of shutting down for a much longer amount of time and then come back successfully,” he speculated. “That was quite an interesting adaptation, which is not present right now on the planet, but which can evolve,” he told BBC News.
Dame Jane Francis, Director of British Antarctic Survey, who’s research focuses on understanding past climate change during both greenhouse and icehouse periods, particularly in the polar regions, the areas on Earth most sensitive to climate change, says there have been several periods in Earth history when Antarctica’s great glaciers were absent.
This seminal study, she says, represents the first evidence for Cretaceous forests so close to the South Pole – just 900 km away. “And, yes, there probably were dinosaurs in the forests,” she adds. “If you go to the tip of the Antarctic Peninsula, you’ll find a whole range of fossils – things like hadrosaurs and sauropods, and primitive bird-like dinosaurs. The whole range of dinosaurs that lived in the rest of the world managed to get down to Antarctica during the Cretaceous.”
To maintain this ecosystem, greenhouse gases in the atmosphere – like carbon dioxide – must have been three or four times current levels. If today the concentration of CO2 in the atmosphere is just above 400 parts per million (ppm), back then the figure was certainly above 1,000ppm and maybe as high as 1,600ppm.
“The world was a different place in other ways that would have contributed to the climate differences at this time,” observed marine geophysicist, BAS co-author Dr Robert Larter. “In particular, the positions of continents and the patterns of ocean currents were different. However, there is no doubt that the biggest factor leading to such a warm climate was the extremely high levels of CO2 in the atmosphere at that time. It is worth noting that if the current rate of CO2 increase continues (44 ppm increase over past 20 years), we will reach a CO2 level greater than 1,000 ppm in less than 300 years.”
Klages and his colleagues obtained the core during a 2017 expedition of the research vessel Polarstern, using specialized drilling machine to pierce the seafloor required several days to pull out each new core, and all it seemed to be reaching was quartzitic sandstone layers bereft of fossils.
During the expedition on the White Continent, reports Becky Ferreira for Motherboard Science, ice sheets from the nearby island began advancing toward the sample site, threatening to slice the cord between the drill and the vessel. Before evacuating the area to prevent the loss of expensive equipment, Klages and his colleagues decided to take one last three-meter core. Unlike the light-colored sandstone, this core was dark, suggesting it was rich in organic materials. “We are quite confident now in saying that there was no ice present, that Antarctica was completely vegetated, and that we had very high CO2 concentrations.”
Klages and his AWI colleagues simulated what would happen if the current version of our Anthropocene Earth had the same CO2 levels, and found that: “The presence of an ice sheet makes a huge difference, even if you have very high CO2 concentrations,” Klages said referring to the ability of the polar ice cover to reflect too much sunlight to result in the same high global temperatures.. “That is really important for us to know, and to think about how we can better preserve ice sheets.”
“We need to look into these extreme climates that happened on the planet already, because they show us what a greenhouse climate looks like,” he concluded. “We are definitely in an interesting time because if we continue what we’re doing right now, then it could lead into something that we can’t control anymore.”