Growth of Ice Sheets on Antarctica: Climate Change 40 million years ago

A talk and public discussion by Dr. Ellen Martin
Friday, September 5th at 8:00 p.m. in the Museum Space Gallery

During a dramatic climate transition 33.6 million years ago, Antarctica changed from a continent characterized by boreal forests to a continent covered by ice sheets miles thick. Scientists have long argued that this transition coincided with the tectonic separation of Antarctica from South America and Australia, and the subsequent development of a circumpolar current, isolating the new continent from warmer subtropical ocean waters.

Computer modeling studies challenged this theory, saying that the change in heat transported to the pole due to this new circumpolar current was insufficient to account for the dramatic ice growth.

New data derived from tiny fossil fish teeth show that the circumpolar current did develop prior to the ice sheets. However, geologic evidence suggests that the dramatic growth and expansion of the ice sheets was probably related not just to changes in heat transfer, but to changes in ocean circulation that brought higher levels of nutrients to the surface of the Southern Ocean, leading to more phytoplankton and associated marine life. This increase in productivity resulted in the absorption of more atmospheric carbon dioxide by the ocean, leading to a decrease in atmosphere carbon dioxide, causing rapid cooling.

The dynamics revealed by this past evidence of climate change may have important lessons for present day concerns, in which increasing levels of atmospheric carbon dioxide are prompting concerns about the rapid decay of giant ice sheets, and the resulting sea level rise.



About Dr. Martin

Dr. Ellen Martin is a member of the faculty in Geological Sciences at the University of Florida, where she teaches courses in oceanography and climate change. Her research focuses on paleoclimate change through the study of fossils preserved in marine sediments. In particular, she has developed a technique using the chemistry of tiny fossil fish teeth to reconstruct past patterns of ocean circulation. The goal of her research is to understand the relationship between ocean circulation and climate change over the past 100 million years. Ellen received an M.S. from Duke University and a Ph.D. from Scripps Institution of Oceanography. She has served on panels for the Ocean Drilling Program and the National Science Foundation, and is currently completing a year as a Distinguished Lecturer for the Consortium for Ocean Leadership.

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