GCM greenhouse and high-obliquity solutions for early Proterozoic glaciation and middle Proterozoic warmth

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Abstract

The first definitive evidence of low-latitude glaciation occurs in the early Proterozoic approximately 2.3 billion years ago. This period of glaciation occurs near the time for a significant rise in oxygen levels. A reduction in the methane producing population through the oxidation of Earth's atmosphere has been proposed as the cause for generating cold climatic conditions. Another alternative is that cold climatic conditions could have been generated by the migration of a landmass into low latitudes if Earth's obliquity was considerably higher than present. These two hypotheses are tested with global climate model simulations using present-day and high-obliquity (70°) boundary conditions. Further, the solar constant is reduced by 17% and 10 × CO 2 is used. An idealized supercontinent is used and methane mixing ratios vary from 0.1 ppmv to 25 ppmv in the simulations. For the present-day obliquity, low-latitude glaciation occurs when CH 4 concentrations are reduced from 10 to 0.1 ppmv. However, the same result is produced when the oceanic heat transport is turned off. In high obliquity simulations, low-latitude glaciation occurs when the idealized super-continent is moved from middle into low latitudes. Finally, high-obliquity may explain the warm middle Proterozoic, as warm simulated climatic conditions occur even for a low latitude super-continent using a solar constant representative of the Middle Proterozoic and reduced atmospheric methane mixing ratios.

Original languageEnglish (US)
JournalJournal of Geophysical Research D: Atmospheres
Volume108
Issue number3
StatePublished - Feb 16 2003

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greenhouses
obliquity
Greenhouses
Methane
glaciation
tropical regions
general circulation model
Proterozoic
supercontinent
solar constant
methane
Climate models
Earth atmosphere
Carbon Monoxide
continents
mixing ratios
mixing ratio
Earth (planet)
Boundary conditions
Oxygen

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Space and Planetary Science
  • Earth and Planetary Sciences (miscellaneous)
  • Palaeontology

Cite this

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abstract = "The first definitive evidence of low-latitude glaciation occurs in the early Proterozoic approximately 2.3 billion years ago. This period of glaciation occurs near the time for a significant rise in oxygen levels. A reduction in the methane producing population through the oxidation of Earth's atmosphere has been proposed as the cause for generating cold climatic conditions. Another alternative is that cold climatic conditions could have been generated by the migration of a landmass into low latitudes if Earth's obliquity was considerably higher than present. These two hypotheses are tested with global climate model simulations using present-day and high-obliquity (70°) boundary conditions. Further, the solar constant is reduced by 17{\%} and 10 × CO 2 is used. An idealized supercontinent is used and methane mixing ratios vary from 0.1 ppmv to 25 ppmv in the simulations. For the present-day obliquity, low-latitude glaciation occurs when CH 4 concentrations are reduced from 10 to 0.1 ppmv. However, the same result is produced when the oceanic heat transport is turned off. In high obliquity simulations, low-latitude glaciation occurs when the idealized super-continent is moved from middle into low latitudes. Finally, high-obliquity may explain the warm middle Proterozoic, as warm simulated climatic conditions occur even for a low latitude super-continent using a solar constant representative of the Middle Proterozoic and reduced atmospheric methane mixing ratios.",
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N2 - The first definitive evidence of low-latitude glaciation occurs in the early Proterozoic approximately 2.3 billion years ago. This period of glaciation occurs near the time for a significant rise in oxygen levels. A reduction in the methane producing population through the oxidation of Earth's atmosphere has been proposed as the cause for generating cold climatic conditions. Another alternative is that cold climatic conditions could have been generated by the migration of a landmass into low latitudes if Earth's obliquity was considerably higher than present. These two hypotheses are tested with global climate model simulations using present-day and high-obliquity (70°) boundary conditions. Further, the solar constant is reduced by 17% and 10 × CO 2 is used. An idealized supercontinent is used and methane mixing ratios vary from 0.1 ppmv to 25 ppmv in the simulations. For the present-day obliquity, low-latitude glaciation occurs when CH 4 concentrations are reduced from 10 to 0.1 ppmv. However, the same result is produced when the oceanic heat transport is turned off. In high obliquity simulations, low-latitude glaciation occurs when the idealized super-continent is moved from middle into low latitudes. Finally, high-obliquity may explain the warm middle Proterozoic, as warm simulated climatic conditions occur even for a low latitude super-continent using a solar constant representative of the Middle Proterozoic and reduced atmospheric methane mixing ratios.

AB - The first definitive evidence of low-latitude glaciation occurs in the early Proterozoic approximately 2.3 billion years ago. This period of glaciation occurs near the time for a significant rise in oxygen levels. A reduction in the methane producing population through the oxidation of Earth's atmosphere has been proposed as the cause for generating cold climatic conditions. Another alternative is that cold climatic conditions could have been generated by the migration of a landmass into low latitudes if Earth's obliquity was considerably higher than present. These two hypotheses are tested with global climate model simulations using present-day and high-obliquity (70°) boundary conditions. Further, the solar constant is reduced by 17% and 10 × CO 2 is used. An idealized supercontinent is used and methane mixing ratios vary from 0.1 ppmv to 25 ppmv in the simulations. For the present-day obliquity, low-latitude glaciation occurs when CH 4 concentrations are reduced from 10 to 0.1 ppmv. However, the same result is produced when the oceanic heat transport is turned off. In high obliquity simulations, low-latitude glaciation occurs when the idealized super-continent is moved from middle into low latitudes. Finally, high-obliquity may explain the warm middle Proterozoic, as warm simulated climatic conditions occur even for a low latitude super-continent using a solar constant representative of the Middle Proterozoic and reduced atmospheric methane mixing ratios.

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