Ancient Antarctica Was Ringed With Plant Life
Picturing Antarctica brings to mind barren snow-covered icescapes, but new research shows that ancient global warming brought plant life to the remote continent.
Scientists began to suspect that temperatures during the middle Miocene epoch - about 15 to 20 million years ago - were warmer than previously believed when Sophie Warny, co-author of the Nature Geoscience paper, discovered large quantities of pollen and algae in sediment cores taken around Antarctica.
Because of the movement of large ice sheets, plant fossils are often ground away, leaving no evidence of the former vegetation that ringed the continent. So the team from the University of Southern California, Louisiana State University and NASA's Jet Propulsion Laboratory examined deep ice cores that contain layer upon layer of ice and sediment from below Antarctica's Ross Ice Shelf.
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"Deep sea cores are ideal to look for clues of past vegetation as the fossils deposited are protected from ice-sheet advances, but these are technically very difficult to acquire in the Antarctic and require international collaboration," said Sophie Warny, assistant professor of palynology at Louisiana State University.
They found plant leaf wax, which acts as a record of climate change by preserving details about the hydrogen isotope ratios of the water the plant drank while it was alive. They were able to determine that summer temperatures along the ancient Antarctic coast were 20 degrees warmer than they are today, with highs of about 45 degrees and considerably more precipitation.
"Ice cores can only go back about 1 million years," said earth scientist and study leader Sarah Feakins, according to UPI. "Sediment cores allow us to go into 'deep time.'"
"When the planet heats up, the biggest changes are seen toward the poles," said co-author Jung-Eun Lee, a scientist at NASA's Jet Propulsion Laboratory and. "The southward movement of rain bands made the margins of Antarctica less like a polar desert, and more like present-day Iceland."
These warm conditions during the middle Miocene epoch are thought to be associated with carbon dioxide levels, probably around 400 to 600 parts per million (ppm). In 2012, carbon dioxide levels have climbed to 393 ppm, the highest they've been in the past several million years. At the current rate of increase, atmospheric carbon dioxide levels are on track to reach middle Miocene levels by the end of this century.
"Just as history has a lot to teach us about the future, so does past climate," said Feakins, according to MSNBC. "What this record shows us is how much warmer and wetter it can get around the Antarctic ice sheet as the climate system heats up."
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