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

美国JGOFS综合和建模项目的一个具体目标是确定和量化控制海洋储层之间以及海洋和大气之间在焦点和区域尺度上的碳分配的主要过程，以期在全球范围内进行综合和预测。作为对实现这一目标的贡献，Barber，Peng，Chai和Dugdale博士将为赤道太平洋开发一个生态系统模型，重点是硅酸盐和铁如何影响新的， 出口生产力和碳在大气、表层海洋和深海之间的分配。 这项研究将使用嵌入赤道太平洋最先进的大气环流模型的生态系统模型，调查新的和出口生产力如何对不断变化的物理和化学作用力作出反应。模式的区域在30+S和30+N之间，120+E和70+W之间，具有真实的几何和地形，但分析将集中在从5+N到5+S的赤道区域。北卡罗来纳州超级计算中心（NCSC）（CrayT 90）和北极地区超级计算中心（ARSC）的超级计算机最近升级（Cray-YMP）和授予Peng，Chai和Barber数百小时的CPU时间，使其有可能在高分辨率，三维预测海洋模式中嵌入适度复杂的生态系统模式，并及时有效地对生态系统模型结构和参数进行大量试验。 该项目的第一阶段将修改现有的五室生态系统模型，增加三个隔间（硅酸盐，硅藻和mesozoooacetotonic食草动物）Dugdale等人的方法。这个三维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的大小依赖性生长速率响应和不同的放牧脆弱性，新的硅藻生产调节Si和Fe的作用可以深入研究。 同样在阶段1、2中：将添加CO2和总碱度（ALK），以计算pCO 2。 利用工业化前的大气CO2浓度（280 llatm）反演赤道太平洋地区的CO2海气通量。与使用硝酸盐作为调节营养素相比，对硅酸盐的新生产调节应该提供更准确的CO2计算。在阶段2中，铁的影响被添加到模型中，使得光合作用与辐照度曲线的初始斜率a是铁的函数。 a的值是基于对天然和实验性铁添加物的赤道观测。独立地，Si（OH 4）的Ks是铁的函数，这种效应只涉及硅藻。 “平衡到水华”的过渡将用两种铁效应来模拟，以再现IronEx 1和2浮游植物对瞬时铁添加的响应。这项建模研究将提供新的和出口生产力的估计，并在赤道太平洋的Si和Fe的调节机制的正式描述。当新的和输出的生产力是准确的建模和验证与JGOFS的研究，它将有可能预测更有信心的气候变化可能会改变，通过生物输出，维持海气ApCO 2，从而海洋的吸收和释放的CO2。

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.