Ancient Soil Suggests Antarctica May Have Been A Rainforest 90 Million Years Ago

Illustration of the Antarctic rainforest. The painting is based on plant and environmental information inferred from material from the sediment core sample. Alfred-Wegener-Institut/James McKay

Madison Dapcevich 01 Apr 2020, 16:00

Antarctica may have once been home to warm, swampy ecosystems surrounded by ferns and conifer trees 90 million years ago. 

An analysis of ancient soil extracted from the western region of Antarctica suggests the icy continent may have once been more similar to modern New Zealand than the frigid temperatures that characterize it today, according to findings published in Nature. If Antarctica was warmer, then geoscientists from the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research in Germany and researchers from the Imperial College London argue that the rest of the world’s climate was similarly incredibly warm at the time.

"The preservation of this 90-million-year-old forest is exceptional, but even more surprising is the world it reveals. Even during months of darkness, swampy temperate rainforests were able to grow close to the South Pole, revealing an even warmer climate than we expected,” said co-author Professor Tina van de Flierdt, from the Department of Earth Science and Engineering at Imperial, in a statement.

Marked as the heyday for dinosaurs, the mid-Cretaceous period between 80 and 155 million years ago was one of the warmest periods in Earth’s history. High levels of atmospheric carbon drove warmer temperatures around the planet, resulting in tropical temperature averages as high as 35°C (95°F) and a sea level 170 meters (557 feet) higher than today. But a full picture of life at the South Pole has long eluded scientists.

Map of the drill site and how to continents were arranged 90 million years ago. Alfred-Wegener-Institute

To piece together the ancient puzzle, an international team of researchers extracted sediment samples from the seabed near an area known as the Amundsen Sea Embayment close to Pine Island and Thwaites glaciers in West Antarctica. One section of the core sample – a large cylindrical sample used to maintain layers of soil – was a strange color that made it look as though it belonged on land rather than at the bottom of the ocean. CT-scans of the section revealed fossilized root systems so well-preserved that scientists could see individual cell structures, as well as pollen and spore specimens from some of the first flowering plants ever found at such Antarctic latitudes.

But what type of conditions would have supported such life? The team used simulated climate models of known information about the floral and faunal specimens to determine conditions that might have supported their growth.

The findings suggest that Antarctica saw average temperatures of around 12°C (53°F) – about 2°C warmer than the mean temperature in Germany today. Summer temperatures were likely as high as 19°C (66°F) with swamps and rivers seeing similar temperatures. This warmer climate means there was likely no ice cap at the time, but instead the continent was covered in dense vegetation growth supported by heavy rainfall. Because of its southern location, the continent likely had a four-month polar night, meaning it was void of sunlight for about one-third of the year.

Germany's icebreaking research vessel POLARSTERN, operated by the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI). © Alfred-Wegener-Institut/Johann Klages

 

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