More than two years after the discovery of the world’s oldest ice core, scientists published what they found about Earth's ancient atmosphere—with one particularly surprising finding. ScienceMagArchives
, scientists have published an analysis of the 2.7-million-year-old sample. One surprising finding: Air bubbles from 1.5 million years ago—from a time before the planet's ice age cycles suddenly doubled in length—contain lower than expected levels of carbon dioxide , a possible clue to the shift in the ice age cycle.levels are"amazingly low," says Yige Zhang, a paleoclimatologist at Texas A&M University in College Station. He adds that the study, published today inSome 2.
To reach further back in time, a team of scientists targeted so-called"blue ice" near Antarctica's surface in the Allan Hills. Here, ancient ice flows have exhumed the oldest ice from the deep. Old ice layers are driven up from below, while wind strips away snow and younger ice.
Given its limitations, including a small amount of material collected by a narrow drill, the Allan Hills core is unlikely to settle debate on the ice age transition. However, its data are helping calibrate other, indirect methods of measuring ancient CO, like using isotopic shifts in single-celled foraminifera fossils. As those methods have improved, their estimates have lined up with the new findings.
Meanwhile, the team hasn't stopped its exploration of the blue ice."It's conceivable that there's ice as old, or even older, out there," Yan says. Next month, a team led by HigginsAn earlier version of this story implied that Clark's hypothesis suggested ice reflecting sunlight into space drove ancient cooling.
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