Interannual to multidecadal climate oscillations in the Cryogenian

The two Cryogenian ‘snowball Earth’ glaciations, the Sturtian (~717-658 Ma) and Marinoan (~654-635 Ma), represent extreme climate states when ice reached equatorial latitudes and persisted for millions of years. Varve-like laminites deposited before and after the Sturtian glaciation reflect high-frequency climate cycles linked to solar, ocean and atmospheric dynamics. However, to date, no evidence of such cycles has been documented during the snowball Earth interval. Here, we analyze a ~5.5 m thick bed of laminites within the Port Askaig Formation, Scotland—a Sturtian glaciogenic succession—to reconstruct short-term climate variability on snowball Earth. Petrographic analysis indicates the laminites represent annual varves, reflecting freeze-thaw cycles and seasonal sediment contributions to a glacio-lacustrine environment. Spectral analysis of laminar set thickness reveals statistically significant periodicities of similar length to the present-day Quasi-Biennial Oscillation, Schwabe cycle, and Gleissberg cycle. This finding supports linkages between solar forcing, dynamic ocean circulation and regional climatic variability, which modulated glaciogenic sedimentation during the Sturtian. The preservation of multiannual to multidecadal cycles within the laminites provides important new insight into the persistence of solar-ocean-atmospheric interactions during the Cryogenian.