Marine Biogeochemical Cycles Deep Time: An Improved Reservoir Model

我们提出了一种改进的中间复杂性盒模型，用于研究深海生物地球化学循环。在深时间古海洋学中，快速改进的数据集和新假设的产生产生了对更通用和灵活的模型的需求，这些模型可以测试各种各样的假设。该模型是模拟海洋生物地球化学循环的平流-扩散-反应型箱型模型，重点是建立氮循环的机制表示。海洋环流目前用一个1.5维模型表示，有三个区域；一个分层的“环流”区，一个“上升流”区和一个“高纬度”区。为了提供生物地球化学相关成分的真实垂直剖面，在地表50米分辨率到深海400米分辨率范围内，构建了34个垂直水平的环流和上升流带。该模型旨在模拟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校准。我们将扩展它的能力，包括计算碳、氮和硫的稳定同位素比率，使预测能够根据沉积档案中不断增长的同位素数据数据库进行检验。我们计划测试三种类型的假设：1)深海氧气供应的减少导致反硝化和厌氧氨氧化导致氮损失增加，而氮固定的增加在未知程度上补偿了氮损失。我们将计算富氮和限氮情况下的预期d15N值，并期望它们将产生不同的同位素特征，可以根据沉积记录进行测试。2)研究新元古代富doc海洋的动力学。我们将模拟这样一个海洋中P、H2S和d13C的垂直梯度，以及以非稳态方式消除这个大型DOC水库所需的时间尺度和通量。3)与应用于二叠系-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系统对所提出的光区硫化物通量的响应。科学价值：提出的模型发展将导致一个强大而易于使用的工具，用于测试关于古代海洋生物地球化学循环功能的假设。虽然模型不能证明一个特定的假设，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，深时的工作者已经开始提出关于古代耦合生物地球化学循环功能的复杂假设，并且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Deep Time工作人员提出的一系列假设，并检查它们对耦合CNPOS系统的预测影响。我们将能够做出可测试的预测，特别是专注于N系统的响应，迄今为止在深度时间研究中研究的相对较少。更广泛的影响：我们计划遵循“开放源代码”的方法，并将模型和适当的文档提供给科学界。模型结构特意采用模块化设计，以便无需修改核心结构即可轻松修改生物地球化学功能。我们相信，这个模型可以很容易地被各种各样的研究人员使用，对他们来说，开发一个类似的模型的障碍将是很高的。我们还期望，当一个社区，而不是一个单独的研究小组，可以轻松地进行开发和模拟时，模型开发和假设测试可以进行得最快。

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.