2026-04-29 ハーバード大学
Above Artist’s rendition of a fully-frozen snowball Ear
＜関連情報＞
- https://seas.harvard.edu/news/new-explanation-snowball-earth
- https://www.pnas.org/doi/10.1073/pnas.2525919123
新原生代スターティアン氷河期における繰り返されるスノーボール・ホットハウスサイクル Repeated snowball–hothouse cycles within the Neoproterozoic Sturtian glaciation
Charlotte Minsky, Robin Wordsworth, David T. Johnston, and Andrew H. Knoll
Proceedings of the National Academy of Sciences Published:April 27, 2026
DOI:https://doi.org/10.1073/pnas.2525919123
Significance
Earth experienced extreme climate swings during the Neoproterozoic epoch, including the Sturtian glaciation, when ice likely covered the planet. Explaining aspects of the geologic record and the survival of life through this event has been a longstanding puzzle. Additionally, geochronology indicates that the Sturtian lasted for 56 My—far longer than can be accommodated by standard models of climate evolution. Here, we use a model of the carbon cycle and climate to show that Earth may have alternated between ice-covered and ice-free states for the duration of the Sturtian. This “limit cycle” regime resolves the discrepancy between modeled and observed duration, is consistent with the sedimentary record, and explains how oxygen could have persisted in the atmosphere.
Abstract
The Neoproterozoic Era was a pivotal era of Earth’s history in which multiple severe glaciations profoundly influenced the biosphere, but explaining the duration and nature of these events remains a major challenge. Notably, geochronology indicates that the Sturtian glaciation lasted for ∼56 Myr—far longer than can be accommodated by canonical “Snowball” or “Slushball” models. Here we use a coupled box model of the Neoproterozoic climate and carbon cycle to develop a hypothesis for Sturtian climate evolution. We show that weathering of the Franklin igneous province would have caused Earth to enter a limit cycle regime, alternating between Snowball and hothouse states for the duration of the Sturtian. This scenario resolves the duration problem, is allowable given currently observed patterns of sedimentation, and predicts syn-Sturtian oxygen stability.
