New and Export Productivity Regulation by Si and Fe in the Equatorial Pacific Ocean

在焦点和区域尺度上确定和量化控制海洋储层之间以及海洋与大气之间碳分配的主要过程，以期在全球尺度上进行综合和预测，这是美国JGOFS综合和模拟项目的一个具体目标。为了实现这一目标，dr。Barber、Peng、Chai和Dugdale将为赤道太平洋开发一个生态系统模型，重点关注硅酸盐和铁如何影响新的和输出的生产力，以及大气、表层海洋和深海之间的碳分配。该研究将使用嵌入赤道太平洋最先进环流模型中的生态系统模型，以调查新生产力和出口生产力如何响应不断变化的物理和化学强迫。模型的区域在30+S到30+N之间，120+E到70+W之间，具有真实的几何和地形，但分析将集中在5+N到5+S之间的赤道区域。最近北卡罗来纳州超级计算中心（NCSC） （CrayT90）和北极地区超级计算中心（ARSC） （Cray-YMP）的超级计算机升级，以及向Peng， Chai和Barber授予数百小时的CPU时间，使得在高分辨率，三维预测海洋模型中嵌入具有中等复杂性的生态系统模型成为可能。并及时高效地进行大量生态系统模型结构和参数的实验。项目的第一阶段将根据Dugdale等人的方法修改现有的五区系生态系统模型，增加三个区系（硅酸盐、硅藻和中浮游动物食草动物）。该三维Si/N/光模型的初步目标是重现高硝酸盐-低硅酸盐-低叶绿素（HNLSLC）条件。随着小型浮游植物和硅藻生长速率的大小依赖性响应以及放牧脆弱性的变化，可以深入研究新的硅藻生产对Si和Fe的调节作用。同样在第1、2阶段：为了计算pCO2，将添加CO2和总碱度（ALK）。将利用工业化前大气CO2 （2801latm）来预测赤道太平洋的海气CO2通量。与使用硝酸盐作为调节养分相比，以硅酸盐作为调节养分的新生产调节应提供更准确的CO2计算。在第二阶段，铁的影响被添加到模型中，使光合作用与辐照度曲线的初始斜率a成为铁的函数。a的值是根据自然和实验铁添加量的赤道观测得来的。独立地，Si（OH4）的Ks是铁的函数，这种效应只涉及硅藻。“从平衡到开花”的过渡将用两种铁效应来模拟，以重现IronEx 1和2浮游植物对短暂铁添加的反应。该模型研究将提供新生产力和出口生产力的估计，以及Si和Fe作为赤道太平洋调节机制的正式描述。当新的和出口的生产力得到准确的模拟，并得到JGOFS研究的验证时，就有可能更有信心地预测气候变化如何通过生物出口改变海气ApCO2的维持，从而改变海洋对CO2的吸收和释放。

To identify and quantify the principal processes that control the partitioning of carbon among oceanic reservoirs and between the ocean and atmosphere on focal and regional scales, with a view towards synthesis and prediction on a global scale, is a specific goal of the U.S. JGOFS Synthesis and Modeling Project. As a contribution towards achieving this goal, Drs. Barber, Peng, Chai and Dugdale will develop an ecosystem model for the equatorial Pacific Ocean, with a focus on how silicate and iron affect new and export productivity and the partitioning of carbon between the atmosphere, surface ocean and deep ocean. The study will use an ecosystem model embedded in a state-of-the-art general circulation model for the equatorial Pacific Ocean to investigate how new and export productivity responds to changing physical and chemical forcing. The domain of the model is between 30+S and 30+N, 120+E and 70+W, with real geometry and topography, but analysis will focus on the equatorial region from 5+N to 5+S. The recent upgrade of supercomputers at North Carolina Supercomputing Center (NCSC) (CrayT90) and Arctic Region Supercomputing Center (ARSC) (Cray-YMP) and the award of several hundred hours of CPU time to Peng, Chai and Barber make it possible to embed an ecosystem model with modest complexity in a high resolution, three dimensional prognostic ocean model, and to conduct numerous experiments on the ecosystem model structure and parameters in a timely and efficient manner. Phase 1 of the project will modify an existing five-compartment ecosystem model by adding three more compartments (silicate, diatoms and mesozooplanktonic grazers) following the approach of Dugdale et al. The preliminary objective of this three-dimensional Si/N/light model is to reproduce High Nitrate-Low Silicate-Low Chlorophyll (HNLSLC) conditions. With size-dependent growth rate responses in small phytoplankton and diatoms and varying grazing vulnerability, the role of new diatom production regulating on Si and Fe can be thoroughly investigated. Also in Phase 1, 2:CO2 and total alkalinity () ALK) will be added in order to calculate pCO2. The pre-industrial atmospheric CO2 (280 1latm) will be used to hindcast air-sea flux of CO2 in the equatorial Pacific. New production regulating on silicate should provide a more accurate calculation of CO2 compared to using nitrate as a regulating nutrient. In Phase 2 the effect of iron is added to the model making a, the initial slope of the photosynthesis vs. irradiance curve, a function of iron. The values of a are based on equatorial observations of natural and experimental iron additions. Independently, Ks for Si(OH4) is made a function of iron, an effect that involves only diatoms. The `balance to bloom` transition will be simulated with the two iron effects to reproduce the IronEx 1 and 2 phytoplankton responses to a transient iron addition. This modeling study will provide estimates of new and export productivity, and a formal description of Si and Fe as regulating mechanisms in the equatorial Pacific Ocean. When new and export productivity is modeled accurately and validated with JGOFS studies, it will possible to predict with increased confidence how climate change may alter, via biogenic export, maintenance of the air-sea ApCO2 and hence the ocean's uptake and release of CO2.