کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
4678217 | 1634832 | 2011 | 10 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Conditions required for oceanic anoxia/euxinia: Constraints from a one-dimensional ocean biogeochemical cycle model Conditions required for oceanic anoxia/euxinia: Constraints from a one-dimensional ocean biogeochemical cycle model](/preview/png/4678217.png)
Widespread black shale depositional intervals termed oceanic anoxic events (OAEs) occurred repeatedly during the Phanerozoic Eon. Here we developed a new vertical one-dimensional ocean biogeochemical cycle model that involves several chemical reactions in an oxic–anoxic–sulfidic water column. To explore the theoretical constraints for global oceanic anoxia/euxinia quantitatively and systematically, we conducted sensitivity analyses of the proposed causal mechanisms, including elevated rates of riverine phosphorus (P) input, ocean stagnation, and lowered oxygen solubility due to climate warming. We gave special attention to the vertical chemical structure of the ocean and also to the characteristic behaviors of the marine P cycle under anoxic conditions, because the relationship between the depth of anoxia and the benthic phosphorus flux could be important for the occurrence of oceanic anoxia/euxinia. Steady-state simulations indicated that (1) a decrease in ocean stagnation or oxygen solubility is not enough by itself to achieve widespread anoxia with the present reactive P river input rate, and (2) shallow water anoxia followed by massive P liberation from surface sediments can lead to widespread eutrophication and anoxia/euxinia. We conclude that elevated riverine flux of reactive P is the most important factor for triggering global anoxic events via a positive feedback loop among ocean anoxia, phosphorus regeneration, and surface biological productivity.
Research Highlights
► New ocean biogeochemical cycle model is developed.
► Necessary conditions for global oceanic anoxia/euxinia are examined.
► Oceanic redox states as functions of P input flux, ocean circulation rate, and SST.
► Elevated riverine flux of P is a most important factor for triggering OAEs.
► Redox-dependent phosphorus cycle greatly affects on the marine environment.
Journal: Earth and Planetary Science Letters - Volume 304, Issues 1–2, 1 April 2011, Pages 270–279