Preprints
https://doi.org/10.5194/esd-2023-32
https://doi.org/10.5194/esd-2023-32
11 Dec 2023
 | 11 Dec 2023
Status: a revised version of this preprint is currently under review for the journal ESD.

Linkage of tropical glaciation to supercontinents: a thermodynamic closure model

Hsien-Wang Ou

Abstract. Precambrian tropical glaciations pose a significant challenge to our understanding of Earth’s climate. A popular explanation invokes runaway ice-albedo feedback leading to “iceball earth”, an extreme state conflicting however with the sedimentary evidence of an open ocean and active hydrological cycle. We point out flawed physics of the runaway scenario, which overlooks potency of the ocean heat transport in deterring the perennial sea ice. Nor is frozen ocean needed for tropical glaciation as the latter requires only that the tropical land be cooled to below the marking temperature of the glacial margin, which is necessarily above the freezing point to counter the yearly accumulation. Since tropical glaciations generally coincide with Precambrian supercontinents, we posit that it is their blockage of the brighter tropical sun that causes the required cooling. To test this hypothesis, we formulate a minimal two-box model, which is nonetheless thermodynamically closed and yields lowering tropical/polar temperatures with increasing tropical land, whose crossings of the glacial marking temperature would divide non/polar/pan-glacial regimes—the last being characterized by tropical glaciation abutting an open ocean. Given the observed chronology of paleogeography, our theory may provide a unified account of the faint-young-sun paradox, Precambrian tropical glaciations and glacio-epochs through Earth’s history.

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Hsien-Wang Ou

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-2023-32', Christoph Braun, 29 Feb 2024
  • RC2: 'Comment on esd-2023-32', Anonymous Referee #2, 01 Mar 2024
Hsien-Wang Ou
Hsien-Wang Ou

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Short summary

We postulate that a tropical supercontinent, by blocking the brighter sun, may cool the tropics to below the marking temperature of the glacial margin, enabling the tropical glaciation. Since this marking temperature is above the freezing point to counter the accumulation, glacial margin is abutting an open ocean, contrary to the snowball-earth hypothesis. The theory provides a unified account of faint-young-sun paradox, Precambrian tropical glaciations and glacio-epochs through Earth’s history.

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