BRICS: Biology's Role In ocean Carbon Storage - a gap analysis

海洋是一个巨大的碳储存库，其碳含量是大气中的50倍。在与气候相关的时间尺度上（数百年至数千年），生物过程有助于海洋中的碳储存。海洋浮游植物是一种漂浮的微小植物，它们利用海洋上层的阳光和二氧化碳来形成它们的生物量，也被称为有机物。当浮游植物死亡时，它们会沉入海洋内部，将有机碳带到更深的水柱中；它潜得越深，与大气隔绝的时间就越长。这一过程通常被称为生物碳泵，它有助于调节我们的气候。研究表明，如果海洋中没有生物，大气中的二氧化碳水平可能是现在的近两倍。在这个项目中，我们将研究生物过程影响全球海洋碳储量的三种方式，以及知识差距阻碍未来海洋碳储量预测进展的地方。首先，了解海水的缓冲能力是如何在浮游植物的驱动下发生变化的，浮游植物产生白垩壳，最终影响二氧化碳的吸收。二是了解浮游植物初级生产有机物的效率和变异性。第三，了解有多少有机物质到达海洋内部，这就告诉我们有多少碳在从上层海洋运输的过程中被呼吸。由于在遥远的未来运行全球模型的计算成本，地球系统模型对生物碳泵有不同的简化表示。为政府间气候变化专门委员会（IPCC）报告做出贡献的一系列模型在未来气候情景下海洋碳储量变化的幅度和方向上并不一致。这意味着我们对未来预测的信心很低，而模型与观测之间越来越大的差异又进一步阻碍了我们的预测。本项目将确定我们在理解上的差距，并强调上述三个领域的模型限制。我们将通过回顾当前文献来确定关键过程来实现这一目标。我们将评估当前气候模式如何表现缓冲能力、有机物初级生产和内部呼吸量变化的差异，以及这些差异如何影响未来海洋碳储量预测。这将有助于确定所需的观察结果，以提高我们对控制生物碳泵过程的掌握，这将反过来允许改进模型表示和预测。我们的目标是确定对生物碳储存有重要贡献的优先过程，这些过程有可能被广泛测量以允许稳健的模型表示，可以可行地包括在模型中，并且在长时间尺度和全球范围内具有相关性。我们将进行专家评估，请国际科学界对哪些过程对海洋碳储存和气候反馈最重要进行排名。我们的分析和调查结果将根据观察关键过程的可追踪性以及能够将其纳入模型的可能性，为今后的实地方案提供建议。

The ocean is a large carbon reservoir which contains fifty times the amount of carbon in the atmosphere. Biological processes contribute to carbon storage in the ocean on climate-relevant timescales (hundreds to thousands of years). Marine phytoplankton, which are drifting microscopic plants, use sunlight and carbon dioxide in the upper ocean to form their biomass, also called organic matter. When phytoplankton die they sink into the ocean interior, moving organic carbon deeper in the water column; the deeper it goes the longer it will remain out of contact with the atmosphere. This process, often called the biological carbon pump, helps to regulate our climate and without biology in the ocean it has been shown that atmospheric carbon dioxide levels could be nearly double what they are today. In this project we will examine three ways in which biological processes influence global ocean carbon storage, and where knowledge gaps are hindering progress on predicting ocean carbon storage in the future. First, is understanding how the buffering capacity of seawater changes, driven by phytoplankton that produce chalk shells, which ultimately affects CO2 uptake. Second, is understanding the efficiency and variability of the primary production of organic matter by phytoplankton. Third, is understanding how much of this organic matter reaches the interior ocean, which tells us how much carbon has been respired during the transit from the upper ocean. Earth system models have differing simplistic representations of the biological carbon pump due to the computational costs of running global models far into the future. The suite of models that contribute to the Intergovernmental Panel on Climate Change (IPCC) reports do not agree on the magnitude or direction of change for ocean carbon storage under future climate scenarios. This means we have low confidence for our future projections, which is further impeded by a growing discrepancy between models and observations. This project will identify the gaps in our understanding and highlight model limitations for each of the three areas outlined above. We will achieve this by reviewing the current literature to identify key processes. We will assess the differences in how current climate models represent changes in the buffering capacity, primary production of organic matter and the amount of interior respiration, and how these differences may affect future ocean carbon storage projections. This will aid in identifying the observations that are needed to improve our grasp of the processes controlling the biological carbon pump, which will in turn allow for improved model representations and predictions. We aim to identify the priority processes that are significant contributors to biological carbon storage, have the potential to be widely measured to allow robust model representations, can be feasibly included into models, and are relevant over long timescales and globally. We will carry out an expert assessment by asking the international scientific community to rank which processes are the most significant for ocean carbon storage and climate feedbacks. Our analysis and the survey results will inform recommendations for future field programmes based on the tractability of observing key processes, and the likelihood of being able to include them in models.