If you were heading to Antarctica 40 million or so years ago it probably would have been a good idea to bring your swimsuit along to enjoy the Florida-like water temperatures. Two studies appearing in the Proceedings of the National Academy of Science (PNAS) used new measurement techniques that can help scientists better understand climate change, and one finds that waters off of Antarctica were once as warm as those along the Florida coast.
The first study, led by Yale scientists, measured the amount of carbon-13 and oxygen-18 in fossil shells dating from the Eocene epoch 40-50 million years ago and combined the results with other geo-thermometers and model simulations. The new measurement technique, called carbonate clumped isotope thermometry, found that the continent's temperature then averaged 14 degrees Celsius (63F) Fahrenheit, and went as high as 17 degrees (63F). The waters in the surrounding southern Pacific Ocean, now about 0 degrees Celsius, were a balmy 22 degrees Celsius (72F).
The paper's lead author, Peter M.J. Douglas, said "By measuring past temperatures in different parts of Antarctica, this study gives us a clearer perspective of just how warm Antarctica was when the Earth's atmosphere contained much more CO2 than it does today." During the Eocene epoch, Antarctica had a greenhouse climate, demonstrating the consequences that increasing C02 levels can have today. The findings also help in the understanding of how global warming is amplified in the polar regions.
In the second study, funded by the National Science Foundation, a new radiometric-Krypton dating technique that greatly extends how far back ice can be dated, was used on ice from Antarctica's Taylor Glacier. It will help to provide insights into causes of climate change today because it extends the ability to date ice back to 1.5 million years.
During the past 800,000 years it's believed that the Earth went in and out of ice ages about every 100,000 years, but before that there is evidence that the changes occurred only every 40,000 years. Being able to date and study ice older than 800,000 years will allow scientists to test the hypothesis that changes in levels of CO2 in the atmosphere played a role in these shifts and help them to better understand the process of global warming today.
Christo Buizert of Oregon State University and the PNAS article's lead author said, "The oldest ice found in drilled cores is around 800,000 years old and with this new technique we think we can look back in other regions and successfully date polar ice back as far as 1.5 million years. That is very exciting because a lot of interesting things happened with the Earth's climate prior to 800,000 years ago that we currently cannot study in the ice-core record."
Krypton dating is similar to carbon-14 dating, but can reach much further back in time since the half life of krypton is 230,000 years - about 5x that of carbon. Scientists have been interested in Krypton dating since 1969 when researchers at the University of Bern first detected the decay of Krypton-81 in Krypton gas. But, Krypton-81 atoms are very scarce and difficult to count. A new type of atom counter, Atom Trap Trace Analysis (ATTA) was the breakthrough that made Krypton-81 dating practical. It was first demonstrated in 1999, but it was not until the development of the ATTA-3 instrument in 2011 that Krypton-81 dating could be widely used by earth scientists.
It's likely that these and other innovative test methods will lead to more hard data on climate change and its causes, furthering debate on this contentious issue.