CT scan of sediment core - Antarctic rainforest
https://vimeo.com/402614855
The sediment core revealed that during the mid-Cretaceous, West Antarctica had a mild climate, with an annual mean air temperature of about 54 F (12 C), similar to that of Seattle. Summer temperatures were warmer, with an average of 66 F (19 C). In rivers and swamps, the water would have reached up to 68 F (20 C).
In addition, the rainfall back then was comparable to the rainfall of Wales, England, today, the researchers found.
These temperatures are impressively warm, given that Antarctica had a four-month polar night, meaning that a third of every year had no life-giving sunlight. However, the world was warmer back then, in part, because the carbon dioxide concentration in the atmosphere was high — even higher than previously thought, according to the analysis of the sediment core, the researchers said.
"Before our study, the general assumption was that the global carbon dioxide concentration in the Cretaceous was roughly 1,000 ppm [parts per million]," study co-researcher Gerrit Lohmann, a climate modeler at Alfred Wegener Institute, said in the statement. "But in our model-based experiments, it took concentration levels of 1,120 to 1,680 ppm to reach the average temperatures back then in the Antarctic."
These findings show how potent greenhouse gases like carbon dioxide can cause temperatures to skyrocket, so much so that today's freezing West Antarctica once hosted a rainforest. Moreover, it shows how important the cooling effects of today's ice sheets are, the researchers said