Ancient ice core could help explain mysterious shift in Earth's ice ages: Record-setting Antarctic archive reveals sharp swings in carbon dioxide 1 million years ago.

The article focuses on the Beyond EPICA (European Project for Ice Coring in Antarctica) Antarctic drilling project, which recovered a 1.2-million-year ice core revealing detailed records of atmospheric carbon dioxide (CO2) during the Mid-Pleistocene Transition (MPT). This period marks a shift in Earth's ice age cycles from 40,000-year to 100,000-year intervals, with the ice core showing a significant CO2 spike about 950,000 years ago followed by a drop to a record low of 170 ppm, coinciding with the onset of longer glacial cycles. Isotopic analysis suggests that increased carbon storage in the deep ocean, rather than release, influenced these CO2 changes, challenging alternative hypotheses like the regolith hypothesis related to ice sheet dynamics. The findings underscore the major role of greenhouse gases in past climate shifts and provide new insights into the mechanisms behind the MPT. [Extracted from the article]