Ice core evidence for atmospheric oxygen decline since the Mid-Pleistocene transition.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 34910502.
- Also identified by DOI 10.1126/sciadv.abj9341 and PMC identifier 8673763.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
The history of atmospheric oxygen (<i>P</i>O<sub>2</sub>) and the processes that act to regulate it remain enigmatic because of difficulties in quantitative reconstructions using indirect proxies. Here, we extend the ice-core record of <i>P</i>O<sub>2</sub> using 1.5-million-year-old (Ma) discontinuous ice samples drilled from Allan Hills Blue Ice Area, East Antarctica. No statistically significant difference exists in <i>P</i>O<sub>2</sub> between samples at 1.5 Ma and 810 thousand years (ka), suggesting that the Late-Pleistocene imbalance in O<sub>2</sub> sources and sinks began around the time of the transition from 40- to 100-ka glacial cycles in the Mid-Pleistocene between ~1.2 Ma and 700 ka. The absence of a coeval secular increase in atmospheric CO<sub>2</sub> over the past ~1 Ma requires negative feedback mechanisms such as <i>P</i>co<sub>2</sub>-dependent silicate weathering. Fast processes must also act to suppress the immediate <i>P</i>co<sub>2</sub> increase because of the imbalance in O<sub>2</sub> sinks over sources beginning in the Mid-Pleistocene.