Journal
GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS
Volume 21, Issue 2, Pages -Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1029/2019GC008464
Keywords
supercontinental assembly and breakup; mantle convective thermal mixing; long-term climate variability; Neoproterozoic snowball Earth; Mesozoic cooling-warming; Precambrian global warming
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Funding
- NSERC
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Supercontinent assembly and breakup can influence the rate and global extent to which insulated and relatively warm subcontinental mantle is mixed globally, potentially introducing lateral oceanic-continental mantle temperature variations that regulate volcanic and weathering controls on Earth's long-term carbon cycle for a few hundred million years. We propose that the relatively warm and unchanging climate of the Nuna supercontinental epoch (1.8-1.3 Ga) is characteristic of thorough mantle thermal mixing. By contrast, the extreme cooling-warming climate variability of the Neoproterozoic Rodinia episode (1-0.63 Ga) and the more modest but similar climate change during the Mesozoic Pangea cycle (0.3-0.05 Ga) are characteristic features of the effects of subcontinental mantle thermal isolation with differing longevity. A tectonically modulated carbon cycle model coupled to a one-dimensional energy balance climate model predicts the qualitative form of Mesozoic climate evolution expressed in tropical sea-surface temperature and ice sheet proxy data. Applied to the Neoproterozoic, this supercontinental control can drive Earth into, as well as out of, a continuous or intermittently panglacial climate, consistent with aspects of proxy data for the Cryogenian-Ediacaran period. The timing and magnitude of this cooling-warming climate variability depends, however, on the detailed character of mantle thermal mixing, which is incompletely constrained. We show also that the predominant modes of chemical weathering and a tectonically paced abiotic methane production at mid-ocean ridges can modulate the intensity of this climate change. For the Nuna epoch, the model predicts a relatively warm and ice-free climate related to mantle dynamics potentially consistent with the intense anorogenic magmatism of this period.
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