04 Aug 2022
04 Aug 2022
Status: this preprint is currently under review for the journal ESD.

Tracing the Snowball bifurcation of Aquaplanets through time reveals a fundamental shift in critical-state dynamics

Georg Feulner1, Mona Sofie Bukenberger1,2, and Stefan Petri1 Georg Feulner et al.
  • 1Earth System Analysis, Potsdam Institute for Climate Impact Research, Member of the Leibniz Association, Potsdam, Germany
  • 2Institute for Atmospheric and Climate Science, ETH Zürich, Switzerland

Abstract. The instability with respect to global glaciation is a fundamental property of the climate system caused by the positive ice-albedo feedback. The atmospheric concentration of carbon dioxide (CO2) at which this Snowball bifurcation occurs changes through Earth's history, most notably because of the slowly increasing solar luminosity. Quantifying this critical CO2 concentration is not only interesting from a climate dynamics perspective, but also an important prerequisite for understanding past Snowball Earth episodes as well as the conditions for habitability on Earth and other planets. Earlier studies are limited to investigations with very simple climate models for Earth's entire history, or studies of individual time slices carried out with a variety of more complex models and for different boundary conditions, making comparisons and the identification of secular changes difficult. Here we use a coupled climate model of intermediate complexity to trace the Snowball bifurcation of an Aquaplanet through Earth's history in one consistent model framework. We find that the critical CO2 concentration decreases more or less logarithmically with increasing solar luminosity until about 1 billion years ago, but drops faster in more recent times. Furthermore, there is a fundamental shift in the dynamics of the critical state about 1.2 billion years ago, driven by the interplay of wind-driven sea-ice dynamics and the surface energy balance: For critical states at low solar luminosities, the ice line lies in the Ferrel cell, stabilised by the poleward winds despite moderate meridional temperature gradients under strong greenhouse warming. For critical states at high solar luminosities on the other hand, the ice line rests at the Hadley-cell boundary, stabilised against the equatorward winds by steep meridional temperature gradients resulting from the increased solar energy input at lower latitudes.

Georg Feulner et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on esd-2022-36', Aiko Voigt, 22 Aug 2022
  • RC2: 'Comment on esd-2022-36', Yonggang Liu, 23 Oct 2022

Georg Feulner et al.

Data sets

Simulation data for tracing snowball bifurcation on an earth-like aquaplanet over 4 billion years Feulner, Georg; Bukenberger, Mona Sofie; Petri, Stefan

Georg Feulner et al.


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Short summary
One limit of planetary habitability is defined by the threshold of global glaciation: If Earth cools, growing ice cover makes it brighter, leading to further cooling since more sunlight is reflected, eventually leading to global ice cover ("Snowball Earth"). We study how much carbon dioxide is needed to prevent global glaciation in Earth's history given the slow increase in the Sun's brightness. We find an unexpected change in the characteristics of climate states close to the Snowball limit.