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Spatially contrasted response of Devonian anoxia to astronomical forcing
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DOI：10.5194/cp-22-1003-2026.png)
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Abstract
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Abstract. The Devonian period; spanning from 419 to 359 million years ago; was marked by a warmer-than-present climate and recurring ocean anoxic events; with evidence increasingly suggesting a link between these events and astronomical forcing. Here; we explore how astronomical forcing influences ocean oxygenation by modulating the continental weathering flux of phosphate within a Late Devonian climate framework. To investigate this; we performed transient simulations spanning 1.1 Myr; crossing a 2.4 Myr eccentricity node using the cGENIE Earth system model. These simulations were driven by spatially resolved fluxes of reactive phosphorus from continents; computed using the emulator developed by Sablon et al. (2025); trained on GEOCLIM and HadSM3 outputs. Our results provide new evidence supporting eccentricity maxima as a driver of Late Devonian anoxic events. Additionally; global analysis reveals that obliquity variations can leave an imprint on global ocean oxygen levels via their influence on biological productivity; suggesting a potential pathway for obliquity-driven anoxia under greenhouse conditions. Regional analysis revealed pronounced spatial heterogeneity in the biogeochemical response to astronomical forcing. Local ocean circulation emerged as a critical factor in shaping these patterns. The simulations indicate that astronomical forcing can; through its impact on continental weathering fluxes; exert a dominant influence on ocean oxygenation; with regional oxygen concentrations varying by up to 35 % and driving changes in regional anoxic volume of up to 19 %. Finally; these findings help explain why proxy records from different locations may show divergent expressions of astronomical signals; potentially leading to contrasting interpretations of their role in driving ocean anoxia.
Keywords:
Astronomical forcing
Ocean anoxia
Continental weathering
Phosphate flux
Climate modeling
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