Antarctica Once had Tropical Climate and Trees

A team of international scientists have discovered an intense warming phase around 52 million years ago in drill cores obtained from the seafloor near Antarctica a region that has been important in climate research.

The study was led by scientists from the Goethe University and the Biodiversity and Climate Research Centre in Frankfurt, Germany.

The study that was published in the Journal Nature came up with a remarkable finding. Hey claim that the tropical vegetation, including palms and relatives of today's tropical Baobab trees, was growing on the coast of Antarctica 52 million years ago. 

The study highlights the extreme contrast between modern and past climatic conditions that existed in Antarctica. Also the extent of global warming, during the period of elevated atmospheric carbon dioxide levels.  

The researchers estimated that concentration of the greenhouse gas carbon dioxide (CO2) in the atmosphere was two times more than what it is today.

"If the current CO₂emissions continue unabated due to the burning of fossil fuels, CO₂concentrations in the atmosphere, as they existed in the distant past, are likely to be achieved within a few hundred years", explained Prof. Jorg Pross, a paleoclimatologist at the Goethe University and member of the Biodiversity and Climate Research Centre (BiK-F) in Frankfurt, Germany. "By studying naturally occurring climate warming periods in the geological past, our knowledge of the mechanisms and processes in the climate system increases. This contributes enormously to improving our understanding of current human-induced global warming."

He computer models shows that future climate warming will be pronounced in high latitude regions near the poles. Though it still remains a mystery as, how Antarctic terrestrial ecosystems responded in the geological past to a greenhouse climate with high atmospheric CO2 concentrations.

The scientists working with Prof. Pross analysed rock samples from drill cores on the seabed, which were obtained off the coast of Wilkes Land, Antarctica, as part of the Integrated Ocean Drilling Program (IODP). The rock samples are between 53 and 46 million years old and contain fossil pollen and spores that are known to originate from the Antarctic coastal region. The researchers were thus able to reconstruct the local vegetation on Antarctica and, accordingly, interpret the presence of tropical and subtropical rainforests covering the coastal region 52 million years ago.

Palms and the ancestors of today's baobab trees flourished 52 million years ago. The scientists' evaluations show that the winter temperatures on the Wilkes Land coast of Antarctica were warmer than 10 degrees Celsius at that time, despite three months of polar night.

"The CO₂ content of the atmosphere as assumed for that time interval is not enough on its own to explain the almost tropical conditions in the Antarctic", says Pross. "Another important factor was the transfer of heat via warm ocean currents that reached Antarctica."

When the warm ocean current collapsed and the Antarctic coast came under the influence of cooler ocean currents, the tropical rainforests including palms and Baobab relatives also disappeared.