Beating the freeze

Abstract

Snowball Earth Despite multiple episodes during the Cryogenian period in which the planet was mostly covered in ice for millions of years—essentially shutting down air–sea exchange and causing widespread ocean anoxia—marine aerobic eukaryotes somehow survived those Snowball Earth conditions. How did they do it? Lechte et al. show that oxygenated glacial meltwater was supplied to the oceans near ice sheet grounding lines, offering a lifeline to microbial communities there. This process may have created glaciomarine oxygen oases that were critical to the survival and evolution of those organisms during episodes of extreme glaciation. Proc. Natl. Acad. Sci. U.S.A. 116 , 25478 (2019).