Marine Biogeochemical Cycles Deep Time: An Improved Reservoir Model

本文提出了一种改进的中等复杂度箱模型，用于研究深海时期的海洋地球化学循环。在深时古海洋学中，快速改进的数据集和新假设的产生了对更通用和更灵活的模型的需求，这些模型可以测试各种各样的假设。该模式是一个对流-扩散-反应型箱模式，用于模拟海洋生物地球化学循环，重点是发展氮循环的机械表示。目前，海洋环流是在一个1.5维模式，有三个区域;分层的“环流”区，“上升流”区，和“高纬度”区。环流区和上升流区有34个垂直高度，分辨率从近海面的50米到深海的400米不等，以提供地球化学相关成分的真实垂直剖面图。该模型的设计是为了模拟CNPOS系统中的主要地球化学过程。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代表性。我们将根据现代海洋化学数据集对它进行校准，以获得海洋地球化学函数和适当的水交换系数。我们将扩展其功能，包括C，N和S的稳定同位素比的计算，使预测是可测试的对日益增长的数据库的同位素数据从沉积archives.We计划测试三种类型的假设：1）减少O2供应到深海的结果，通过反硝化和厌氧氨氧化，这是补偿到一个未知的程度增加N固定。我们将计算预期的d15 N值为N-充满和N-有限的情况下，并期望它们将产生可分辨的不同的同位素签名，可以对沉积记录进行测试。2)我们将研究新元古代富含DOC的海洋的动力学。我们将模拟垂直梯度的P，H2S和d13 C在这样的海洋，和必要的时间尺度和通量，以消除这个大的拟议DOC水库在非稳态的方式。3)我们将与应用于二叠纪-三叠纪的GENIE EMIC模型进行模型-模型比较。我们将使用GENIE模拟的结果来初始化我们的模型中的完全耦合的CNPOS系统，并测试的N系统的响应建议透光区硫化物fluxs.Scientific优点：拟议的模型开发将导致一个强大的，但易于使用的工具，用于测试假设的古海洋生物地球化学循环的功能。虽然模型不能证明一个特定的假设，但它们在理解地球化学系统的动力学方面非常有用。特别是，研究深时的工作者已经开始提出关于古代耦合地球化学循环的功能的复杂假设，并且需要适当的模型来探索这些想法的后果。我们将能够测试深时工作人员提出的一系列假设，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，特别是专注于N系统的响应，到目前为止，在深时研究中相对较少。更广泛的影响：我们计划遵循“开源”方法，并向科学界提供模型和适当的文档。该模型结构是故意模块化的，以使生物化学功能的容易修改，而不必修改核心结构。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，开发类似模型的障碍会很高。我们还希望，当一个社区，而不是一个单独的研究小组，可以很容易地进行开发和模拟模型的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.