Glacial erosion likely caused atmospheric oxygen levels to dip over past 800,000 years.
© Photo by Yuzhen YanResearchers studied Earth’s ancient atmosphere by capturing tiny bubbles of air that were preserved in Antarctic ice for up to 1.5 million years.
Houston - An unknown culprit has been removing oxygen from our atmosphere for at least 800,000 years, and an analysis of air bubbles preserved in Antarctic ice for up to 1.5 million years has revealed the likely suspect.
"We know atmospheric oxygen levels began declining slightly in the late Pleistocene, and it looks like glaciers might have something to do with that," said Rice University's
Yuzhen Yan, corresponding author of the
geochemistry study published in
Science Advances.
"Glaciation became more expansive and more intense about the same time, and the simple fact that there is glacial grinding increases weathering."Weathering refers to the physical and chemical processes that break down rocks and minerals, and the oxidation of metals is among the most important. The rusting of iron is an example. Reddish iron oxide forms quickly on iron surfaces exposed to atmospheric oxygen, or O2.
"When you expose fresh crystalline surfaces from the sedimentary reservoir to O2, you get weathering that consumes oxygen," said Yan, a postdoctoral research associate in Rice's Department of Earth, Environmental and Planetary Sciences.
Another way glaciers could promote the consumption of atmospheric oxygen is by exposing organic carbon that had been buried for millions of years, Yan said.
During Yan's Ph.D. studies in the labs of Princeton University's Michael Bender and
John Higgins, Yan worked on a 2016 study led by
Daniel Stolper, now an assistant professor at the University of California, Berkeley, that used
air bubbles in ice cores to show the proportion of oxygen in Earth's atmosphere had declined by about 0.2% in the past 800,000 years.
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