Toward a mechanistic model of the ocean biological carbon pump

海洋表面浮游植物的光合作用吸收大气中的二氧化碳以产生有机物。在生命周期结束时，这些海洋生物聚集成快速下沉的大颗粒。这些下沉的有机物反过来又以细菌和浮游动物为食，呼吸二氧化碳，这些二氧化碳可以在深海中溶解数千年。这一系列过程统称为生物碳泵(BCP)，是碳从大气输送到深海的主要途径。了解控制BCP效率的复杂过程，从而控制碳在海洋和大气之间以及最终气候之间的相对分配，是海洋学和气候科学中的主要问题之一，也是NERC资助的COMICS(海洋中远洋内部碳储存控制)项目的主题，该项目支持这项研究。不幸的是，尽管BCP很重要，但嵌入全球气候模型的当前BCP模型并没有BCP的机械表示。因此，它们在很大程度上不能对环境变化做出反应，也不能用来调查BCP未来将如何演变或它过去可能是如何运作的。这个项目的主要目标是从机械上了解BCP及其对环境条件的反应。为了实现这一目标，将开发一个全球模型，代表海洋颗粒粘在一起或分解的过程。从浮游植物在表面的生长开始，该模型将明确考虑影响有机颗粒通过海洋下沉的主要过程。这种颗粒和生物地球化学模型将与UKESM等模型模拟的海洋环流相互作用。具体地说，目标是采用随机方法模拟海洋颗粒的动力学，其中单个颗粒、生物和海洋环流之间的相互作用被显式模拟。这种拉格朗日方法以前没有在3-D中尝试过，因为它的计算成本很高。我们计划通过开发新的计算硬件来解决这个问题，例如可编程图形处理单元GPU，以实现模型的计算加速。学生不仅将领导模型的开发-获得海洋生物地球化学、海洋学以及高性能计算和数值建模方面的培训和技能-而且还将进行实验，从机械上探索BCP对气候变化的反应，特别是环流、大气二氧化碳和海洋化学的变化。这名学生将积极与南安普敦国家海洋学中心的漫画团队成员以及美国、德国和法国的其他观察和建模小组合作。

Photosynthesis by phytoplankton at the surface of the ocean absorb CO2 from the atmosphere to produce organic matter. At the end of their life cycle these marine organisms aggregate into large, rapidly sinking particles. This sinking organic matter is in turn fed on by bacteria and zooplankton, respiring CO2 that can remain dissolved in the deep ocean for thousands of years. This set of processes, collectively known as the "biological carbon pump" (BCP), is a major pathway by which carbon is transported from the atmosphere to the deep sea. Understanding the complex processes that control the efficiency of the BCP and hence the relative partitioning of carbon between the ocean and atmosphere and, ultimately, climate, is one of the leading problems in oceanography and climate science, and the subject of the NERC-funded COMICS (Controls over Ocean Mesopelagic Interior Carbon Storage) project supporting this studentship. Unfortunately, important as it is, current models of the BCP embedded within global climate models do not have a mechanistic representation of the BCP. They are thus largely incapable of responding to environmental changes and cannot be used to investigate how the BCP will evolve in the future or how it may have operated in the past. The primary objective of this project is to obtain a mechanistic understanding of the BCP and it's response to environmental conditions. To achieve this goal, a global model that represents the processes through which marine particles stick together or break apart will be developed. Starting with the growth of phytoplankton at the surface the model will explicitly consider the main processes affecting the sinking of organic particles through the ocean. This model of particles and biogeochemistry will interact with ocean circulation as simulated by models such as UKESM.Specifically, the goal is to take a stochastic approach to modeling the dynamics of marine particles in which the interaction between individual particles, biology and ocean circulation are explicitly simulated. Such a Lagrangian approach has not previously been attempted in 3-d because of its computational expense. We plan to address this by exploiting novel computational hardware such as programmable Graphics Processing Units GPUs to achieve computational speedup of the model. The student will not only lead the development of the model-acquiring training and skills in marine biogeochemistry, oceanography and high performance computing and numerical modeling-but also perform experiments to mechanistically explore the BCP's response to climate change, especially changes in circulation, atmospheric CO2 and ocean chemistry. The student will actively collaborate with COMICS team members at the National Oceanography Centre, Southampton, and other observational and modeling groups in the US, Germany and France.