Collaborative Research: Biogeochemical Modeling of Carbon Partitioning in the Pacific: the Role of Si and Fe in Regulating Production by Siliceous and Calcifying Phytoplankton

物理和生物相互作用在碳在大气、上层海洋、深海和沉积物之间的分配中发挥着复杂的作用。目前，跨学科模型提供了最好的方法来检验假设，即在几年到几个世纪的时间尺度上，不同海洋区域的碳分配是如何受到调节的。一个新的跨学科模型将综合几个领域的进展来检验两个相关的假设：1)硅藻和其他浮游植物(如非硅质微浮游植物和钙化浮游植物)之间群落和生产力优势的转换显著影响碳分配，在空间和时间上都有变化，并受硅和铁的组合调节；2)南大洋中硅捕获的变化影响了提供赤道上升流的“模式”水域中的Si(OH)4浓度，以及赤道浮游植物对硅和碳的吸收改变了赤道二氧化碳的海-气交换。一个由生物和化学海洋学家和模型师组成的跨学科科学小组将通过四种方法解决这些问题。首先，一个钙化的浮游植物成分将被添加到现有的模型中，并用于包括水柱的产生和CaC03的溶解。其次，将设计和进行模型实验，以探索硅质(硅藻)和非硅质(微微和钙化)浮游生物之间的转换规律。第三，为赤道太平洋开发的一个改进的博客化学模型将在空间上扩展到包括南大洋，并用于对将高纬度“模式”水区与赤道上升流的源水连接起来的过程进行一系列模拟实验。最后，模型中对铁敏感的浮游植物生长参数将被操纵，以测试赤道太平洋和南大洋对铁丰富的生态系统的响应。这些目标是为探索海洋生物地球化学过程对气候变化的反应而开发的耦合物理生物地球化学模型的重要一步。

Physical and biological interactions play a complex role in the partitioning of carbon between the atmosphere, upper ocean, deep ocean and sediments. At present, interdisciplinary models offer the best means to test hypotheses about how carbon partitioning is regulated in various oceanic regions on time scales of years to centuries. A new interdisciplinary model will integrate advances in several areas to test two related hypotheses: 1) that switches in community and productivity dominance between diatoms and other phytoplankton groups (e.g. non?siliceous picoplankton and calcifying phytoplankton) significantly affect carbon partitioning, vary spatially and temporally and are regulated by a combination of Si and Fe in combination; 2) that changes in Si trapping in the Southern Ocean affect Si(OH)4 concentrations in the "mode" waters that feed equatorial upwelling, and that Si and C uptake by equatorial phytoplankton alters air?sea exchange of carbon dioxide at the equator.An interdisciplinary science team of biological and chemical oceanographers and modelers will address these issues via four approaches. First, a calcifying phytoplankton component will be added to an existing model and used to incorporate water column production and dissolution of CaC03. Second, model experiments will be designed and executed to explore the regulation of switching between siliceous (diatoms) and non?siliceous (pico and calcifying) plankton. Third, an improved blogeochemical model developed for the equatorial Pacific will be spatially expanded to include the Southern Ocean, and used to conduct a series of simulation experiments on the processes that link high latitude "mode" water regions with the source waters for equatorial upwelling. Finally, iron?sensitive growth parameters of the phytoplankton components of the model will be manipulated to test the ecosystem response to iron enrichment in both the equatorial Pacific Ocean and the Southern Ocean. These objectives represent a significant step in the development of coupled physical biogeochemical models for exploring the response of marine biogeochemical processes to climate change.