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- PP13C-0897: Seafloor Weathering Explains the Disparate Durations of Neoproterozoic Snowball Earth Glaciations
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Board 0897‚ Hall EFG (Poster Hall)NOLA CC
Author(s):Generic 'disconnected' Message
Trent Thomas, University of Washington (First Author, Presenting Author)
Francis Macdonald, University of California Berkeley
David Catling, University of Washington
The Cryogenian Period (720-635 million years ago) witnessed two global glaciations, known as Snowball Earth events. Recent measurements show that the first glaciation lasted 56 million years, whereas the second glaciation lasted 4 million years. This highlights a major unresolved question: why was there a 14-fold difference in Snowball Earth duration? By applying a geologic carbon cycle model to simulate Snowball Earth events, we show that the mysterious 14-fold duration difference can be explained by changes in seafloor weathering. Seafloor weathering is a CO2 sink that responds to the chemistry of the ocean, so it controls the rate of atmospheric CO2 buildup (and thus, greenhouse warming) during a Snowball Earth event. We found that a relatively small difference in the seafloor weathering rate between Snowball Earth events can modify the rate of CO2 buildup enough to explain the 14-fold duration difference. We propose that the small difference in seafloor weathering was driven by evolving ocean chemistry related to oxygen, sulfate, and anhydrite.
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