Research published today in the journal Nature gives a detailed picture of how scientists are looking to the much warmer Antarctic climate of the distant past to learn more about how the planet could look in the future if climate change continues unchecked.
The University of Glasgow’s James Bendle is one of the authors of the paper, which is part of a major international research project to examine the Earth’s climate during the ‘Greenhouse world’ of the early Eocene epoch, between 48 and 55 million years ago.
Bendle joined 36 other scientists and more than 100 crew members for the 2010 Integrated Ocean Drilling Research Program, on a ship bound for Wilkes Land on the eastern coast of Antarctica.
There the scientists dropped a string of drill-pipe through four kilometres of water, to bore one kilometre deep into the ocean floor to collect samples of sediment.
Analysis of the sediment samples has created for the first time a detailed picture of the Antarctic climate during the peak of the Eocene Greenhouse world. This level of detail was previously impossible because any Eocene sediments remaining on land were destroyed by the glaciation of Antarctica 34 million years ago or covered with thousands of metres of ice.
The sediments, collected continuously and undisturbed over millions of years, contain tiny fossils and chemicals that yield information on the climate at the time the sediments were deposited. They show that the Eocene Antarctic was vastly different than it is today.
Bendle, of the University’s School of Geographical and Earth Sciences, said: “The Eocene sediment samples are the first detailed evidence we have of what was happening on the Antarctic during this vitally important time.
“We conducted the drilling expedition against a backdrop of freezing temperatures, huge ocean swells, calving glaciers, snow-covered mountains and icebergs. It’s amazing to imagine a time-traveller, arriving at the same coastline in the early Eocene, could paddle in pleasantly warm waters lapping at a lush forest.”
The scientists found fossilised pollen in the sediments, from plants that live in two different environments.
The findings show that one plant environment was a lowland, warm rainforest dominated by tree-ferns, palms and trees belonging to the bombacaceae family. Modern bombacaceae include baobab trees found on Madagascar – also known as the ‘tree of life’ as they hold water in their thick trunks. The other was an upland, mountain forest region with beech trees and conifers.
Pollen from both environments would have been washed, blown or transported by insects into the shallow coastal shelf, where it settled in the mud and was preserved for 50 million years.
The pollen indicates that temperatures on the Antarctic coast were around 16°C and summers reached a balmy 21°C, while winters were warmer than 10°C even during the coldest and darkest months of the year. Antarctica was in nearly the same position it currently is, over the south pole. The winter months would have been dark, like today, but it was far warmer. Organic molecules preserved from Eocene soil bacteria confirm that the temperature at least was at warm as the pollen indicate.
Bendle added: “Our work carries a sobering message. Carbon dioxide levels were naturally high in the early Eocene, but today CO2 levels are rising rapidly through human combustion of fossil fuels and deforestation. We haven’t reached Eocene levels yet, but we are increasing at a rate faster than anytime in Earth’s history.
“Atmospherically speaking we are heading rapidly back in time towards the Eocene. Already CO2 levels are at a peak not seen since the Pliocene warm period 3.5 million years ago. The biggest threat lies in the fact that Antarctica today is covered with ice, enough to potentially raise global sea-levels by 60 metres if the continent once again reaches Eocene temperatures, which would have devastating effects all over the world.”
Lead author Professor Jörg Pross, paleoclimatologist at the Goethe University, Frankfurt, said: "If the current CO2 emissions continue unabated due to the burning of fossil fuels, CO2 concentrations in the atmosphere, as they existed in the distant past, are likely to be achieved within a few hundred years.
"By studying naturally occurring climate warming periods in the geological past, our knowledge of the mechanisms and processes in the climate system increases. This contributes enormously to improving our understanding of current human-induced global warming."
The Integrated Ocean Drilling Program is one of the world’s most successful and long-running international scientific collaborations. Founded in 1961, the IODP has contributed to major scientific discoveries including plate tectonics and the cyclical nature of ice ages.
Bendle is funded by the Natural Environment Research Council (NERC). He is co-author on the new paper, entitled ’Persistent near-tropical warmth on the Antarctic continent during the early Eocene epoch’, published in the journal Nature and is available from http://bit.ly/M5qGKZ