The Bender group examines atmospheric gases trapped in ice cores to understand the history of CO2 and climate. The group is extending the CO2 record back in time by looking for ever-older ice in Antarctica.


Extending the ice core record of climate-CO2 links back in time

The deepest ice cores yet drilled, targeted to encompass the longest possible continuous records, end at ice 800,000 years old. To extend this record, Michael Bender and colleagues have been searching Antarctic sites where, because of complex glacier flows influenced by the Transantarctic Mountains, older ice may be present near the surface. Working with John Higgins (Princeton) and collaborators from the University of Maine, Bender’s group drilled a 126-meter long ice core in the Allan Hills region of Antarctica and dated it to be 1,000,000 years old in the bottom 10 m. This age is 200,000 years older than the previous oldest ice. It takes us back to a time when glacial cycles lasted 40,000 years instead of the 100,000 year period characterizing the past 800,000 years.

Working with Ed Brook (Oregon State), the researchers have begun measuring greenhouse gases in this ice. Previous work has shown that there is a very strong link between atmospheric CO2 and global temperature over the past 800,000 years. The new data show that this link persisted in the earlier world of 40,000 year climate cycles. They also show that interglacials, known to be warmer between 0-400,000 years than between 400,000 and 800,000 years, were once again warmer prior to 800,000 years ago. The work also suggests that glacial periods in the 40,000 year world were not as cold as more recent glacial periods. The team is exploring the implications of these results for the dynamics of climate change. Already their results strengthen the empirical link between CO2 and global temperature.