Evaluation and intercomparison of three-dimensional marine carbon cycle models, OGCM/OCMIP-Najjar, 2005 (U.S. JGOFS Synthesis & Modeling Phase project results)

<p>The main objective of the proposed work is to accelerate the development of global three-dimensional&nbsp; (3-D) models of the pre-industrial marine carbon cycle and its anthropogenic perturbation.&nbsp; We propose&nbsp; to achieve this objective through a coordinated evaluation and intercomparison of four existing models of this type in the United States.&nbsp; Global observational data sets-such as those provided by the Joint Global Ocean Flux Study (JGOFS), satellite ocean color measurements (such as the Sea-viewing Wide Field of View Sensor, SeaWiFS), and historical compilations-will provide and unprecedented opportunity for model evaluation and improvement.&nbsp; The proposed project will capitalize on this opportunity through the direct involvement of observationalists and data synthesists in the model evaluation process.&nbsp; By intercomparing controlled and carefully designed simulations by the four models, which have profound differences in their treatment of biogeochemical and physical aspects of the marine carbon cycle, we expect to improve the models at a rate much greater than would be achieved by individual modelers working in isolation.</p>

<p>Three distinct evaluation/intercomparison activities will be undertaken.&nbsp; First, recognizing that ocean circulation plays a key role in the marine carbon cycle, aspects of the models' circulation fields that are relevant to the marine carbon cycle will be evaluated by conducting simulations of chlorofluorocarbons, natural radiocarbon and bomb radiocarbon.&nbsp; Second, simulations of the uptake of anthropogenic CO₂ will be conducted and then evaluated with observed distributions of surface pCO₂ and observationally-based estimates of marine anthropogenic inorganic carbon.&nbsp; Third, the natural marine carbon cycle will be simulated using a variety of approaches, the simplest of which will be common to all of the circulation models.&nbsp; These simulations will be evaluated using observed distributions of surface ocean color, phosphate, oxygen, dissolved inorganic carbon, surface pCO₂.</p>

<p>The above set of controlled simulations is based on a framework proposed by the Ocean Carbon-cycle Model Intercomparison Project (OCMIP), an international project initiated in 1995 by the Global Analysis, Interpretation and Modeling (GAIM) Task Force of the International Geosphere-Biosphere Program (IGBP). We are seeking support for the U.S. participation in the next phase of OCMIP, bringing to it three more modeling groups, closer collaboration with those conducting and synthesizing observations, and a more structured evaluation/intercomparison of natural carbon cycle simulations. We will coordinate with a related European effort consisting of seven individual marine carbon cycle modeling groups. Model results and data analyses will be submitted to central analysis facilities (established by OCMIP) in Europe and the U.S. for processing and posting on an Internet site accessible to all participants immediately, and soon after to the general scientific community.&nbsp; We expect this interchange of model output and data syntheses on an international level to greatly accelerate the development of global 3-D marine carbon cycle models and therefore contribute to two of the major elements of the JGOFS Synthesis and Modeling Project: (1) extrapolation and prediction and (2) global and regional balances of carbon and related biologically-active substances.</p>

本研究的核心目标是加速工业化前海洋碳循环及其人为扰动的全球三维（3-D）模型研发。我们提出通过对美国现有4个同类模型开展协同评估与相互比较来实现这一目标。联合全球海洋通量研究（Joint Global Ocean Flux Study, JGOFS）、卫星海洋颜色测量（如宽视场海洋观测传感器（Sea-viewing Wide Field of View Sensor, SeaWiFS））以及历史汇编数据等全球观测数据集，将为模型评估与改进提供前所未有的契机。本项目将借助观测学家与数据合成人员直接参与模型评估流程来把握这一契机。通过对4个模型开展受控且精心设计的模拟对比——这4个模型在海洋碳循环的生物地球化学与物理过程处理上存在显著差异——我们预期模型的改进速度将远高于单个建模者独立开展工作所能达成的效果。

本次研究将开展三项独立的评估/相互比较工作。其一，鉴于海洋环流在海洋碳循环中发挥关键作用，我们将通过模拟氯氟烃、天然放射性碳以及核爆放射性碳，对模型中与海洋碳循环相关的环流场特征展开评估。其二，将开展人为二氧化碳吸收的模拟工作，并结合观测得到的表层二氧化碳分压（pCO₂）分布以及基于观测估算的海洋人为无机碳数据进行评估。其三，将采用多种方法模拟天然海洋碳循环，其中所有环流模型通用的最简单方案将被纳入考量。这些模拟将通过观测得到的表层海洋颜色、磷酸盐、溶解氧、溶解无机碳以及表层pCO₂的分布情况进行验证。

上述受控模拟集基于海洋碳循环模型相互比较计划（Ocean Carbon-cycle Model Intercomparison Project, OCMIP）提出的框架，该国际计划于1995年由国际地圈-生物圈计划（International Geosphere-Biosphere Program, IGBP）的全球分析、解释与建模（Global Analysis, Interpretation and Modeling, GAIM）工作组发起。我们正寻求支持美国参与OCMIP下一阶段的工作，届时将新增3个建模小组，进一步加强与观测数据收集及合成团队的协作，并对天然碳循环模拟开展更具结构化的评估与相互比较。我们将与由7个独立海洋碳循环建模小组组成的欧洲相关研究团队开展协作。模型结果与数据分析将被提交至欧洲与美国由OCMIP建立的中央分析机构，用于处理并即刻发布至所有参与者均可访问的互联网站点，随后将尽快面向全体科研群体开放。我们预期，这种国际层面的模型输出与数据合成交流将极大加速全球三维海洋碳循环模型的研发进程，从而为JGOFS合成与建模项目的两大核心内容作出贡献：（1）外推与预测；（2）碳及相关生物活性物质的全球与区域平衡。