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。如果没有这个“生物碳泵”，大气中的二氧化碳将比现在高出50%。尽管颗粒有机碳(POC)通量很重要，但我们的理解受到船上观测的限制，特别是颗粒有机碳(POC)通量如何随天和季节的变化。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。滑翔机是无人驾驶的自动飞行器，可以在几周到几个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。在英国的长期观察点之一PAP，我们收集了多个滑翔机任务的数据，包括与NASA的同事合作。这些数据将使重要的悬而未决的问题得以解决：通量如何随季节变化与浮游植物水华有关？这些流量有多大的间歇性？这对表征全球范围的有机碳通量有何影响？(Bol等人，2018年；Henson等人，2015)填补这一空白将使人们能够更好地预测这一重要的全球碳通量如何与生产力有关，以及它如何应对环境的变化。该项目最初将使用过去在太平洋地区执行任务时从滑翔机上获得的数据，如渗透率[1]和出口数据，以确定POC通量的时间模式，它们随深度的衰减，以及这与浮游植物水华的关系。滑翔机衍生的光学后向散射数据将被转换为POC浓度和通量的估计，使用共同主管布里格斯建立的协议[2]。将计算不同的指标来描述到达中层带的POC通量的比例。您的初步分析将侧重于建立浮游植物水华、通量和衰减的时间模式，然后继续评估物理条件的年际变化如何改变初级生产力和通量之间的关系。根据您的兴趣，后续工作可能包括利用其他自主技术来研究特定过程，例如颗粒破碎[2]、更详细的其他位置、卫星数据以将研究扩展到更大的空间和时间尺度，或者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。如果感兴趣，您可以参与为即将到来的两个资助项目(生物碳和叛军)规划和部署更多自主平台，这两个项目都旨在更好地量化亚极地地区的碳封存路径。

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.