Oldest Antarctic ice ever found shows climate of 2.7 million years ago

(credit: NASA/EO)

Antarctic ice cores have recorded an impressive span of climatic history for us, covering the last 800,000 years. But scientists are greedy, always looking to go back just a little further. Climate records based on things like seafloor sediment cores already take us much further back, but ice cores can reveal unique details. Groups are currently searching for locations to drill new ice cores that might provide a contiguous record back to over the million-year mark.

But another group has been cheating, and this has allowed them to take a big leap past everyone else. Instead of looking at places where the ice at the bottom might be oldest, they’ve been looking at places where that oldest ice has been squeezed up to the surface against high points of bedrock. A few years ago, they published data from samples of ice that came back at right about 1 million years old. At a conference on Wednesday, the researchers revealed the fruits of their second attempt—ice as old as 2.7 million years, blowing away their previous record.

The ice is fairly squished up and convoluted, with sections of ice less than 800,000 years old showing up between sections of ice between 1 million and 2.7 million years old—the effort to determine its age requires careful dating based on isotopes of argon. But the researchers are able to measure greenhouse gas concentrations from trapped air bubbles and indicators of past ocean temperature.