Ancient Warming Greened Antarctica, Study Finds
A new University-led study that received NASA participation has discovered that Antarctica was warmer and wetter during the Miocene era than had previously been suspected, to the point where the climate was able to sustain substantial vegetation along the edges of the mostly frozen continent.
The team of scientists — led by Sarah J. Feakins of the University of Southern California in Los Angeles, also with researchers from NASA’s Jet Propulsion Laboratory in Pasadena, Calif., and Louisiana State University in Baton Rouge — examined plant leaf wax remnants in sediment core samples taken from beneath the Ross Ice Shelf.
Scientists had begun to suspect that high-latitude temperatures during the middle Miocene epoch were warmer than previously understood when co-author Sophie Warny, assistant professor at LSU, discovered large quantities of pollen and algae in sediment cores taken around Antarctica.
Antarctica is a hard place to find good samples of fossilised plant life, considering that the movement of the massive ice sheets often ends up grinding and scarping the evidence away.
“Marine sediment 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 Warny.
By examining the plant leaf wax remnants, the research team found summer temperatures along the Antarctic coast 15 to 20 million years ago were 20 degrees Fahrenheit (11 degrees Celsius) warmer than today, with temperatures reaching as high as 45 degrees Fahrenheit (7 degrees Celsius). Additionally, precipitation levels were also several times higher than that of today.
“The ultimate goal of the study was to better understand what the future of climate change may look like,” said Feakins, an assistant professor of Earth sciences at the USC Dornsife College of Letters, Arts and Sciences. “Just as history has a lot to teach us about the future, so does past climate. This record shows us how much warmer and wetter it can get around the Antarctic ice sheet as the climate system heats up. This is some of the first evidence of just how much warmer it was.”
“When the planet heats up, the biggest changes are seen toward the poles,” said co-author and JPL scientist Jung-Eun Lee. “The southward movement of rain bands associated with a warmer climate in the high-latitude southern hemisphere made the margins of Antarctica less like a polar desert, and more like present-day Iceland.”
The research found that the peak of this specific Antarctic greening took place during the middle Miocene epoch, somewhere between 16.4 and 15.7 million years ago, when modern-looking animals were plenty, such as the three-toed horses, deer, camel, and various species of apes.
Warm conditions during the middle Miocene are thought to be associated with carbon dioxide levels of around 400 to 600 parts per million (ppm). In 2012, carbon dioxide levels have climbed to over 400 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.