Nutrients as the dominant control on the spread of anoxia and euxinia across the Cenomanian-Turonian oceanic anoxic event (OAE2): Model-data comparison
Nutrients as the dominant control on the spread of anoxia and euxinia across the Cenomanian-Turonian oceanic anoxic event (OAE2): Model-data comparison
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营养物质是塞诺曼期-土伦期海洋缺氧事件（OAE2）中缺氧和真氧传播的主要控制因素：模型数据比较
DOI：
10.1029/2012pa002351
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
Monteiro F
中科院分区：
文献类型：
--
作者：
Monteiro F
森诺曼-图伦海洋缺氧事件（OAE 2）的特征是海洋氧和硫循环的大扰动，可能是由于氧供应（通过氧溶解度和海洋环流）和海洋生产力的变化造成的。我们评估这些机制的相对影响，比较模型实验与海底缺氧/缺氧和透光区euxinia的观测新汇编。所采用的模型是一个中等复杂度的地球系统模型，它解释了白垩纪气候的主要海洋动力学和地球化学。由于大气中二氧化碳和海洋营养物浓度较高，在模型中评估了温度升高和海洋生产力提高的影响。该模型表明，温度并不能单独重现观察到的与OAE 2相关的海洋氧化还原变化模式。观测结果在模型中重现，主要是通过提高海洋生产力，由于更高的营养含量（负责85%的变化）。较高的磷酸盐含量可以通过增加化学风化和缺氧沉积物中的磷再生来维持，这反过来又通过固氮引起海洋中氮营养物含量的增加。该模型还表明，海底缺氧的存在，如事件发生前原北大西洋中的黑色页岩沉积所表明的，可能是该盆地在晚白垩世的底床形状和缺乏深水形成的结果。总体而言，我们的模型数据比较显示，OAE 2缺氧是准全球性的，从事件发生前海洋体积的5%到OAE 2期间的至少50%。
The Cenomanian‐Turonian oceanic anoxic event (OAE2) is characterized by large perturbations in the oxygen and sulfur cycles of the ocean, potentially resulting from changes in oxygen supply (via oxygen solubility and ocean circulation) and in marine productivity. We assess the relative impact of these mechanisms, comparing model experiments with a new compilation of observations for seafloor dysoxia/anoxia and photic zone euxinia. The model employed is an intermediate‐complexity Earth system model which accounts for the main ocean dynamics and biogeochemistry of the Cretaceous climate. The impact of higher temperature and marine productivity is evaluated in the model as a result of higher atmospheric carbon dioxide and oceanic nutrient concentrations. The model shows that temperature is not alone able to reproduce the observed patterns of oceanic redox changes associated with OAE2. Observations are reproduced in the model mainly via enhanced marine productivity due to higher nutrient content (responsible for 85% of the change). Higher phosphate content could have been sustained by increased chemical weathering and phosphorus regeneration from anoxic sediments, which in turn induced an enhanced nitrogen nutrient content of the ocean via nitrogen fixation. The model also shows that the presence of seafloor anoxia, as suggested by black‐shale deposition in the proto‐North Atlantic Ocean before the event, might be the result of the silled shape and lack of deep‐water formation of this basin at the Late Cretaceous. Overall our model‐data comparison shows that OAE2 anoxia was quasi‐global spreading from 5% of the ocean volume before the event to at least 50% during OAE2.
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