Seawater sulfate (SO42−) concentrations have changed by orders of magnitude in response to atmospheric and ocean redox dynamics throughout Earth’s history. A fundamental model that constrains seawater SO42− dynamics based on the principles of mass balance, however, is still lacking. Here, we used a dynamical systems approach to determine the effects of global source and sink strengths on seawater SO42− concentrations. Our stochastic analysis of the SO42− mass balance revealed two most probable seawater SO42− concentration ranges: one under widespread oceanic anoxic conditions with SO42− concentrations <1000 µM, and the other with SO42− concentrations around or above 10,000 µM under widely oxygenated ocean conditions. Swings between these two seawater SO42− concentration ranges are notably evident during the Phanerozoic Eon and developed in response to reoccurring oceanic anoxic events. We also identified a threshold for the extent of oceanic anoxia above which seawater SO42− concentrations collapse to <1000 µM, with corresponding impacts on global biogeochemical cycles, biology, and climate.
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Research Article|
September 25, 2024
Early Publication
Seawater sulfate dynamics and a new tipping point in the Earth system
Mojtaba Fakhraee;
Mojtaba Fakhraee
1
Department of Earth and Planetary Sciences, Yale University, New Haven, Connecticut 06511, USA2
National Aeronautics and Space Administration (NASA) Interdisciplinary Consortia for Astrobiology Research (ICAR), Alternative Earths Team
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Kohen W. Bauer;
Kohen W. Bauer
3
Ocean Networks Canada, University of Victoria, Victoria, British Columbia V8N 1V8, Canada
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Sean A. Crowe
Sean A. Crowe
4
Departments of Microbiology and Immunology and Earth, Ocean, and Atmospheric Sciences, University of British Columbia, Vancouver, British Columbia V6T 2A1, Canada
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Mojtaba Fakhraee
1
Department of Earth and Planetary Sciences, Yale University, New Haven, Connecticut 06511, USA2
National Aeronautics and Space Administration (NASA) Interdisciplinary Consortia for Astrobiology Research (ICAR), Alternative Earths Team
Kohen W. Bauer
3
Ocean Networks Canada, University of Victoria, Victoria, British Columbia V8N 1V8, Canada
Sean A. Crowe
4
Departments of Microbiology and Immunology and Earth, Ocean, and Atmospheric Sciences, University of British Columbia, Vancouver, British Columbia V6T 2A1, Canada
Publisher: Geological Society of America
Received:
15 Mar 2024
Revision Received:
01 Sep 2024
Accepted:
06 Sep 2024
First Online:
25 Sep 2024
Online ISSN: 1943-2682
Print ISSN: 0091-7613
© 2024 Geological Society of America
Geology (2024)
Article history
Received:
15 Mar 2024
Revision Received:
01 Sep 2024
Accepted:
06 Sep 2024
First Online:
25 Sep 2024
Citation
Mojtaba Fakhraee, Kohen W. Bauer, Sean A. Crowe; Seawater sulfate dynamics and a new tipping point in the Earth system. Geology 2024; doi: https://doi.org/10.1130/G52228.1
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