Bloom and bust: seasonal cycles of phytoplankton and carbon flux

海洋中的生物过程从大气中吸收的二氧化碳主要以下沉颗粒的形式转移到深海。如果没有这种“生物碳泵”，大气中的二氧化碳含量将比现在高出50%。尽管它很重要，但我们的理解受到船上观测的限制，特别是颗粒有机碳（POC）通量随时间和季节的变化。然而，越来越多的水下机器人网络正在为这些下沉粒子的高分辨率观测打开大门。滑翔机是一种无人驾驶的自动驾驶车辆，可以在数周到数月的时间内进行测量，包括可用于估计POC通量的光学后向散射数据。在PAP，英国的一个长期观测站，我们从多个滑翔机任务中收集数据，包括与美国宇航局的同事合作。这些数据将使未解决的重要问题得以解决：与浮游植物大量繁殖有关的通量是如何随季节变化的？这些变化有多短暂？表征全球尺度有机碳通量的意义是什么？（Bol et al., 2018; Henson et al., 2015）填补这一空白将有助于更好地预测这一重要的行星碳通量如何与生产力联系在一起，以及它如何响应环境的变化。该项目最初将使用在PAP过去的任务中从滑翔机获得的数据，如OSMOSIS[1]和EXPORTS，以确定POC通量的时间模式，它们随深度的衰减，以及这与浮游植物大量繁殖的关系。使用联合主管Briggs[2]建立的协议，滑翔机衍生的光学后向散射数据将转换为POC浓度和通量的估计。将计算不同的度量来表征到达中远洋区的POC通量的比例。你们的初步分析将侧重于确定浮游植物繁殖、通量和衰减的时间模式，然后再评估物理条件的年际变化如何改变初级生产和通量之间的关系。根据您的兴趣，后续工作可能包括利用额外的自主技术来研究特定过程，例如，粒子破碎[2]，其他更详细的地点，卫星数据将研究范围扩大到更大的时空尺度，或使用全球生物地球化学模型来探索POC通量变化的机制和模式。如果有兴趣，您可以参与两个即将资助的项目（Bio-carbon和ReBELS）的更自主平台的规划和部署，这两个项目都旨在更好地量化亚极地地区的碳固存途径。

CO2 taken up from the atmosphere by biological processes in the ocean is transferred into the deep ocean mostly in the form of sinking particles. Without this "biological carbon pump", atmospheric CO2 would be 50% higher than it already is. Despite its importance, our understanding is limited by scarce ship-board observations, especially how particulate organic carbon (POC) fluxes vary over days to seasons. However, a growing network of underwater robots are opening the door for high-resolution observations of these sinking particles. Gliders are unmanned autonomous vehicles that make measurements over weeks to months, including optical backscatter data which can be used to estimate POC fluxes. At PAP, one of the UK's long-term observing sites, we have collected data from multiple glider missions, including in collaboration with colleagues at NASA. These data will allow important unresolved questions to be addressed: How do fluxes vary seasonally in relation to phytoplankton blooms? How episodic are the fluxes? What are the implications for characterizing global-scale organic carbon fluxes? (Bol et al., 2018; Henson et al., 2015) Filling this gap will allow better predictions of how this important planetary carbon flux is linked to productivity and how it responds to variability in the environment. The project will initially use data obtained from gliders during past missions at PAP, such as OSMOSIS [1] and EXPORTS to determine the temporal patterns in POC fluxes, their attenuation with depth, and how this relates to phytoplankton blooms. Glider-derived optical backscatter data will be transformed into estimates of POC concentration and flux, using protocols established by co-supervisor Briggs [2]. Different metrics to characterise the fraction of POC flux reaching the mesopelagic zone will be calculated. Your initial analysis will focus on establishing the temporal patterns of phytoplankton blooms, flux and attenuation, before moving on to assessing how interannual variability in physical conditions may alter the relationship between primary production and fluxes. Depending on your interests, subsequent work may include exploiting additional autonomous technologies to study particular processes, e.g. particle fragmentation [2], other locations in more detail, satellite data to broaden the study to larger spatial and temporal scales, or using global biogeochemical models to explore the mechanisms and patterns of variability in POC fluxes. If interested, you may participate in the planning and deployment of more autonomous platforms for 2 upcoming funded projects (Bio-carbon and ReBELS), both aimed at better quantifying the carbon sequestration pathways in subpolar regions.