ANDRILL research indicates remarkably warm period in Antarctica 15.7 million years ago
Released on 10/01/2009, at 12:25 PM
Office of University Communications
University of Nebraska–Lincoln
BATON ROUGE, La., USA, Oct. 1, 2009 -- Researchers with the Antarctic Geological Drilling Program (ANDRILL) found unexpected evidence of a remarkably warm period in Antarctica 15.7 million years ago.
The evidence includes fossils of marine algae and pollen of woody plants indicating that land temperatures reached a January (austral summer) average of 10 degrees Celsius (50 degrees Fahrenheit) while estimated sea surface temperatures ranged between zero and 11.5 degrees Celsius (32 to 53 degrees Fahrenheit). The algae and pollen were found in sedimentary rock cores drilled in the austral spring of 2007 from beneath the sea floor of Antarctica's McMurdo Sound during ANDRILL's Southern McMurdo Sound Project.
Sophie Warny of Louisiana State University, USA, found the first indication of the warm period while studying samples from the SMS Project last year. One sample, she said, stood out as a complete anomaly.
"First I thought it was a mistake, that it was a sample from another location, not Antarctica, because of the unusual abundance in microscopic fossil cysts of marine algae called dinoflagellates. But it turned out not to be a mistake, it was just an amazingly rich layer," said Warny, assistant professor of geology and geophysics at LSU and curator of the LSU Museum of Natural Science.
Warny immediately notified her colleagues in the ANDRILL Program, a multinational collaboration between the Antarctic programs of the United States, Germany, Italy and New Zealand, about what she had found. Some had noted an increase in pollen grains of woody plants in the samples immediately above, but none of the other samples had such a unique abundance in marine algae, which at first gave Warny some doubts about potential contamination.
"But the two co-chief scientists in charge of the drilling project, David Harwood of the University of Nebraska-Lincoln and Fabio Florindo of the National Institute of Geophysics and Volcanology in Italy, were equally excited about the discovery," Warny said. "They had noticed that this thin layer had a unique consistency that had been characterized by the science team as a diatomite, which is a layer extremely rich in fossils of another microscopic algae called diatoms."
All research parties involved met at the Antarctic Research Facility at Florida State University, USA. Together, they sampled this zone of interest in great detail and processed new samples in various labs. One month later, the unusual abundance in microfossils was confirmed and the findings were published as the cover story in the October issue of Geology, the journal of the Geological Society of America.
Warny's co-authors on the Geology paper are Rosemary Askin of LSU; Michael Hannah of the School of Geography, Environment and Earth Sciences and the Antarctic Research Centre at Victoria University in Wellington, New Zealand; Barbara Mohr at the Museum of Natural History in Berlin, Germany; Ian Raine of GNS Science in Lower Hutt, New Zealand; Harwood, professor of geosciences and research director for ANDRILL's Science Management Office at UNL; Florindo of the National Institute of Geophysics and Volcanology in Rome; and the Southern McMurdo Sound Project Science Team.
Among the 1,107 meters of sediment core recovered and analyzed for microfossil content, a 2-meter thick layer in the core contained an abundance of these marine and terrestrial microfossils. This is unusual, Warny said, because the Antarctic ice sheet was formed about 35 million years ago, and the frigid temperatures there impede the presence of woody plants and blooms of dinoflagellate algae.
"We all analyzed the new samples and saw a 2,000-fold increase in two species of fossil dinoflagellate cysts, a five-fold increase in freshwater algae and up to an 80-fold increase in terrestrial pollen," said Warny. "Together, these shifts in the microfossil assemblages represent a relatively short period of time during which Antarctica became abruptly much warmer."
This event occurs during a generally warm time referred to as the Mid-Miocene Climatic Optimum, a time when global temperatures were warmer than at present, and a time which many scientists are looking toward as an analogue to study future ice sheet and climate behavior.
"This event will lead to a better understanding of global connections and climate forcing, in other words, it will provide a better understanding of how external factors imposed fluctuations in Earth's climate system," Harwood said. "The Mid-Miocene Climate Optimum has long been recognized in global proxy records outside of the Antarctic region. Direct information from a setting proximal to the dynamic Antarctic ice sheets responsible for driving many of these changes is vital to the correct calibration and interpretation of these proxy records."
These startling results will offer new insights into Antarctica's climate past -- insights that could potentially help climate scientists better understand the current climate change scenario.
"In the case of these results, the microfossils provide us with quantitative data of what the environment was actually like in Antarctica at the time, showing how this continent reacted when climatic conditions were warmer than they are today," Warny said.
The presence of freshwater algae in the sediments suggests to researchers that an increase in melt-water and perhaps also in rainfall produced ponds and lakes adjacent to the Ross Sea during this warm period, which would obviously have resulted in reduction in sea ice. These findings corroborate and expand evidence for lakes and vegetation further inland in the Dry Valley region of the adjacent Transantarctic Mountains.
While the results are certainly impressive, the work isn't yet complete.
"The SMS Project Science Team is looking at the stratigraphic sequence and timing of climate events evident throughout the ANDRILL AND-2A drill core, including those that enclose this event," Florindo said. "A clear understanding of what has happened in the past, and the integration of these data into ice sheet and climate models, are important steps in advancing the ability of these computer models to reproduce past conditions, and with improved models be able to better predict future climate responses."
ANDRILL is a multinational collaboration involving 150 scientists from Germany, Italy, New Zealand and the United States. Its purpose is to recover sediment core samples from the McMurdo Sound region of Antarctica to develop a detailed history of the Antarctic climate and the expansion and contraction of the Ross Sea area's ice sheets and ice shelves over the past 20 million years.
Operations and logistics for ANDRILL are managed by Antarctica New Zealand. Scientific research is administered and coordinated through the ANDRILL Science Management Office located at the University of Nebraska-Lincoln.
Funding Support for ANDRILL comes from the U.S. National Science Foundation, New Zealand Foundation of Research, Science, and Technology, Royal Society of New Zealand Marsden Fund, Antarctica New Zealand, the Italian National Program for Research in Antarctica-PNRA; The German Science Foundation and the Alfred Wegener Institute for Polar and Marine Research Science.
News Release Contacts:
- David Harwood, Professor, Earth and Atmospheric Sciences
phone: 402 472 2648
- Sophie Warny, Louisiana State University
phone: (225) 578-5089
- Fabio Florindo, National Institute of Geophysics and Volcanology, Italy