COLLABORATIVE RESEARCH: Modeling Permain Ocean Stagnation and Anoxia

重要的生物和气候变化的间隔，如发生在新元古代、晚奥陶纪、晚二叠纪和白垩纪/第三纪边界的生物和气候变化，通常与海洋化学和同位素组成的显著偏移有关。对这些事件的一些解释在很大程度上是基于直觉推理，即引起热盐环流速率的急剧下降。“海洋停滞。”很少有海洋学的物理限制，如热、盐和动量平衡对这些问题产生影响。因此，我们要求资助进行一套动态海洋环流/生物地球化学模型模拟，以定量评估这些“海洋停滞”假设的有效性。虽然我们的工作重点是晚二叠纪事件，但结果也将广泛适用于地球历史的其他间隔。GFDL模块化海洋模型将用于研究晚二叠纪海洋的三维环流，大气边界条件由我们与威斯康星大学和芝加哥大学的同事合作提供。这些边界条件预计会产生强烈和缓慢的温盐环流状态。少量的生物地球化学成分将被添加到这个模型中，使我们能够评估缺氧的空间分布。由三维模型生成的环流场将被纬向平均，并用于二维多组分生物地球化学模型，以研究缓慢环流的生物地球化学后果。除了磷酸盐和氧外，二维模型还将计算溶解无机碳、硫和锶同位素组成的分布。因此，我们将能够调查海洋活跃的假设，向大气释放有毒的二氧化碳，并比较预测和观测到的同位素记录。将进行若干敏感性分析，包括模型对河流和热液输入变化的响应，对各种动力学和同位素参数的响应，以及对盘古大陆离开南极漂移的响应。

805139KumpIntervals of significant biotic and climatic change, such as those occurring in the Neoproterozoic, the late Ordovician, the latest Permian, and the Cretaceous/Tertiary boundary, are commonly associated with marked excursions in the chemical and isotopic composition of the ocean. Some explanations of these events have been based largely on intuitive reasoning that invokes dramatic decreases in the rate of thermohaline circulation, i.e. "ocean stagnation." Rarely have physical oceanographic constraints, such as heat, salt and momentum balance been brought to bear on such problems. We therefore request funding to conduct a suite of dynamic ocean circulation/biogeochemical model simulations to quantitatively assess the efficacy of these "ocean stagnation" hypotheses. Although we focus our efforts on the Late Permian event, the results will be broadly applicable to other intervals of Earth history as well.The GFDL Modular Ocean Model will be used to study the three-dimensional general circulation of the Late Permian ocean, with atmospheric boundary conditions being provided through collaboration with our colleagues at the University of Wisconsin and University of Chicago. These boundary conditions are expected to yield both vigorous and sluggish thermohaline circulation states. A small number of biogeochemical constituents will be added to this model, allowing us to assess the spatial distribution of anoxia. The circulation fields generated by the 3-D model will then be zonally averaged and used in a 2-D, multi-constituent biogeochemical model to study the biogeochemical consequences of sluggish circulation. In addition to phosphate and oxygen, the 2-D model will calculate distributions of dissolved inorganic carbon, sulfur and strontium isotopic compositions. Thus we will be able to investigate the hypothesis that an invigoration of ocean, releasing toxic amounts of carbon dioxide to the atmosphere, and to compare the predicted and observed isotopic records of such an event. A number of sensitivity analyses will be performed, including the model response to variations in riverine and hydrothermal input, to various kinetic and isotopic parameters, and to the drift of Pangea off the South Pole.