Marine Biogeochemical Cycles Deep Time: An Improved Reservoir Model

我们提出了一种改进的中等复杂性盒子模型，用于研究深海海洋生物地球化学循环。深部时间古海洋学数据集的迅速改进和新假说的产生，产生了对能够检验各种假说的更通用和更灵活的模型的需求。该模型是一个用于模拟海洋生物地球化学循环的对流-扩散-反应类型的箱式模型，重点是开发氮循环的机理表示。目前，海洋环流是一个1.5维的模型，有三个区域：分层的“环流”区、“上升流”区和“高纬度”区。环流和上升流带有34个垂直级别，从表面附近的50米分辨率到深海中的400米分辨率不等，以提供真实的生物地球化学相关成分的垂直剖面。该模型用于模拟CNPOS系统中的主要生物地球化学过程。我们建议改进模型的功能，特别是溶解有机碳和底栖生物交换过程的表示。我们将根据现代海洋化学数据集对其进行生物地球化学功能和适当的水交换系数的校准。我们将扩展它的功能，包括计算碳、氮和S的稳定同位素比率，以便能够根据不断增长的沉积档案同位素数据数据库进行可验证的预测。我们计划测试三种类型的假设：1)减少对深海的氧气供应导致通过反硝化和厌氧氨氧化增加氮的损失，这在未知的程度上被增加的氮固定所补偿。我们将计算N全和N有限情况下的预期d15N值，并期望它们将产生可分辨的不同的同位素特征，这些特征可以对照沉积记录进行测试。2)我们将研究新元古代富含DOC海洋的动力学。我们将模拟这样一个海洋中P、H_2S和d13C的垂直梯度，以及以非稳态方式消除这个拟议的大型DOC水库所需的时间尺度和通量。3)与二叠系-三叠系的Genie EMIC模型进行模型-模型对比。我们将使用GENIE模拟的结果来初始化我们模型中的全耦合CNPOS系统，并测试N系统对所建议的光带硫化物通量的响应。科学价值：所提出的模型开发将导致一个强大而易用的工具来检验关于古代海洋生物地球化学循环的功能的假说。虽然模型不能证明特定的假设，但它们在理解生物地球化学系统的动力学方面非常有用。特别是，深部时间的工作人员已经开始提出关于古代耦合生物地球化学循环的功能的复杂假说，需要足够的模型来探索这些想法的后果。我们将能够测试由深度时间工作者提出的一系列假设，并检查它们对耦合的CNPOS系统的预测影响。我们将能够做出可测试的预测，特别是关注N系统的响应，到目前为止，在深度时间研究中对N系统的响应研究相对较少。更广泛的影响：我们计划遵循“开源”的方法，并向科学界提供模型和适当的文档。模型结构故意模块化，以便在不必修改核心结构的情况下轻松修改生物地球化学功能。我们相信，该模型可以很容易地被各种研究人员使用，对他们来说，开发类似的模型的门槛会很高。我们还预计，当一个社区而不是一个单独的研究小组可以随时进行开发和模拟时，模型开发和假设检验可以进行得最快。

We propose to develop an improved intermediate complexity box model for the study of ocean biogeochemical cycles in Deep Time. The rapidly improving data sets and the generation of novel hypotheses in Deep Time paleoceanography have created the need for more general and flexible models that can test a wide variety of hypotheses. The model is an advection-diffusion-reaction type box-model for the simulation of marine biogeochemical cycles, with emphasis on developing a mechanistic representation of the nitrogen cycle. Ocean circulation is currently represented in a 1.5-D model with three zones; a stratified "gyre" zone, an "upwelling" zone, and a "high latitude" zone. The gyre and upwelling zones are constructed with 34 vertical levels, ranging from 50 m resolution near the surface to 400 m resolution in the abyssal ocean, to provide realistic vertical profiles of biogeochemically relevant components. The model is designed to simulate the major biogeochemical processes in the CNPOS system. We propose to improve the functionality of the model, particularly the representation of dissolved organic carbon and of benthic exchange processes. We will calibrate it against modern ocean chemical data sets for both biogeochemical function and appropriate water exchange coefficients. We will extend its capabilities to include the calculation of the stable isotope ratios of C, N and S, to enable predictions that are testable against the growing database of isotopic data from sedimentary archives.We plan to test three types of hypotheses: 1) reduced O2 supply to the deep ocean results in enhanced N losses via denitrification and anammox, which are compensated to an unknown extent by increased N fixation. We will compute the expected d15N values for N-replete and N-limited cases and expect that they will yield resolvably different isotopic signatures that can be tested against the sedimentary record. 2) We will investigate the dynamics of a DOC-rich ocean proposed for the Neoproterozoic. We will simulate vertical gradients of P, H2S and d13C in such an ocean, and the time scales and fluxes necessary to eliminate this large proposed DOC reservoir in a non-steady state fashion. 3) We will perform a model-model comparison with the GENIE EMIC model applied to the Permo-Triassic. We will use the results of the GENIE simulation to initialize the fully coupled CNPOS system in our model, and test the response of the N system to proposed photic zone sulfide fluxes.Scientific merit: The proposed model development will result in a powerful, yet easy to use tool for testing hypotheses about the function of ancient marine biogeochemical cycles. While model cannot prove a particular hypothesis, they can be very useful in understanding the dynamics of biogeochemical systems. In particular, workers in Deep Time have begun to pose sophisticated hypotheses about the function of ancient coupled biogeochemical cycles, and adequate models are necessary to explore the consequences of these ideas. We will be able to test a series of hypotheses posed by Deep Time workers and examine their predicted impact on the coupled CNPOS system. We will be able to make testable predictions, particularly focused on the response of the N system which has been so far relatively little investigated in Deep Time studies. Broader impacts: We plan to follow an "open source" approach, and make the model and appropriate documentation available to the scientific community. The model structure is deliberately modular, to enable easy modification of biogeochemical functions without having to modify the core structure. We believe that the model can readily used by a variety of researchers, for whom the barriers to developing a similar model would be high. We also expect that model development and hypothesis testing can proceed most rapidly when a community, rather than an individual research group, can readily carry out both development and simulations.