Publication Abstracts

Wofford et al. 2026, submitted

Wofford, A., N.J. Burls, L. Sohl, S. Domagal-Goldman, E. Wolf, and D. Straus, 2026: From freeze to thaw: Evaluating the CO2 forcing threshold needed to thaw the Paleoproterozoic Snowball Earth. Earth Planet. Sci. Lett., submitted.

With no direct observations currently available to characterize potentially habitable exoplanets, Earth's extreme paleoclimates offer critical analogs and our only window into climates of habitable worlds beyond that of modern Earth. Studying these past climate states help guide upcoming missions by testing and refining our understanding of planetary habitability. One such state is the Paleoproterozoic Snowball Earth (∼2400-2100 Ma), when reduced solar luminosity (∼82-84% of modern) likely triggered global-scale glaciation. Understanding how such a planet deglaciates remains a key scientific challenge. Deglaciation is typically thought to require a buildup of volcanic CO2 to a critical threshold. That threshold is high — energy balance models suggest values ranging from ∼100,000-300,000 ppm, and previous general circulation model (GCM) studies of Neoproterozoic snowball states suggest that high CO2 alone may not suffice. However, those prior studies did not incorporate a dynamic ocean, which could trigger feedback mechanisms that would serve to lower this CO2 threshold. In this study, we use the fully coupled ROCKE-3D GCM with a dynamic ocean and low-latitude supercontinent to constrain the CO2 threshold for deglaciating a Paleoproterozoic hard Snowball state. Our simulations show that full deglaciation is possible at 45,000 ppm CO2, significantly lower than thresholds found in previous Neoproterozoic GCM studies conducted with ∼94% solar luminosity. Intermediate CO2 scenarios (30,000-40,000 ppm) show a more complex response, where initial warming reduces sea ice through the ice-albedo feedback, but a delayed snow-albedo feedback, enhanced by a more vigorous hydrological cycle, leads to increased snowfall that stabilizes and restores remaining ice cover. These results offer new insights into early Earth's climate dynamics and have implications for assessing transient habitability on exoplanets with similar boundary conditions.

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BibTeX Citation

@unpublished{wo07100r,
  author={Wofford, A. and Burls, N. J. and Sohl, L. and Domagal-Goldman, S. and Wolf, E. and Straus, D.},
  title={From freeze to thaw: Evaluating the CO2 forcing threshold needed to thaw the Paleoproterozoic Snowball Earth},
  year={2026},
  journal={Earth and Planetary Science Letters},
  note={Manuscript submitted for publication}
}

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RIS Citation

TY  - UNPB
ID  - wo07100r
AU  - Wofford, A.
AU  - Burls, N. J.
AU  - Sohl, L.
AU  - Domagal-Goldman, S.
AU  - Wolf, E.
AU  - Straus, D.
PY  - 2026
TI  - From freeze to thaw: Evaluating the CO2 forcing threshold needed to thaw the Paleoproterozoic Snowball Earth
JA  - Earth Planet. Sci. Lett.
JO  - Earth and Planetary Science Letters
ER  -

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