Researchers have uncovered the oldest intact ice core sample dating back 2m years, providing invaluable data on ancient climate change.
When it comes to understanding the onset of the climate crisis, scientists are trying to learn from the past to better prepare for the future. Now, a team of US researchers has uncovered a prized find that reveals the planet’s ancient history of greenhouse gas emissions.
In a paper published to Nature, the team documented the discovery of a 2m-year-old ice core sample from Antarctica, containing air bubbles that can be used to measure the levels of CO2 and methane during that period. This is the first time that scientists have been able to study an ice core of this age as the previous oldest ice core dated back 800,000 years.
Previous studies using this younger ice core showed that atmospheric CO2 was directly linked with Antarctic and global temperature, but this new study has revealed a wealth of new information from before then.
It has been established that over the past 1m years, the cycle of ice ages has been followed by warm periods that occurred every 100,000 years. However, between 2.8m years ago and 1.2m years ago, these cycles shortened substantially to just 40,000 years with less extreme ice ages.
The newly discovered core sample showed that the highest levels of CO2 matched with the warm periods of more recent times. The lowest levels, however, did not reach the very low concentrations found in the ice ages of the last 800,000 years.
The search continues
“One of the important results of this study is to show that CO2 is linked to temperature in this earlier time period,” said Prof Ed Brook of Oregon State University, who was one of the researchers on the team.
This, he said, was based on the chemistry of the ice, which provided an indication of temperature change in Antarctica at the same time as CO2 variations.
“That’s an important baseline for understanding climate science and calibrating models that predict future change,” Brook added.
The ice core was taken from an area known as Allan Hills where ancient meteorites have been discovered, leading researchers to believe that ancient ice could exist beneath the surface. The team drilled down 200 metres to collect the sample, and in the future will look to find even older samples.
“We don’t know the age limit in this area,” Brook said. “It could be much older in some places. That’s why we’re going back. Pushing beyond 2m years would be pretty amazing.”