Daily to annual net primary production in the North Sea determined using autonomous underwater gliders and satellite Earth observation

Abstract. Shelf-seas play a key role in both the global carbon cycle and coastal marine ecosystems through the drawn-down and fixing of carbon, as measured through phytoplankton net primary production (NPP). Measuring NPP in situ, and extrapolating this to the local, regional and global scale presents challenges however because of limitations with the techniques utilised (e.g. radiocarbon isotopes), data sparsity and the inherent biogeochemical heterogeneity of coastal and open-shelf waters. Here, we introduce a powerful new technique based on the synergistic use of in situ glider profiles and satellite Earth Observation measurements which can be implemented in a real-time or delayed mode system. We apply this system to a fleet of gliders successively deployed over a 19-month time-frame in the North Sea, generating an unprecedented fine scale time-series of NPP in the region (Loveday and Smyth, 2020). At the large-scale, this time-series gives close agreement with existing satellite-based estimates of NPP for the region and previous in situ estimates. What has not been elucidated before is the high-frequency, small-scale, depth-resolved variability associated with bloom phenology, mesoscale phenomena and mixed layer dynamics.

摘要。通过浮游植物净初级生产（NPP）来衡量，陆架海在全球碳循环和沿海海洋生态系统中都通过碳的吸收和固定发挥着关键作用。然而，由于所使用技术（例如放射性碳同位素）的局限性、数据稀疏以及沿海和开阔陆架水域固有的生物地球化学异质性，原位测量NPP并将其外推到地方、区域和全球范围存在挑战。在此，我们介绍一种基于原位滑翔机剖面和卫星地球观测测量协同使用的强大新技术，该技术可在实时或延迟模式系统中实施。我们将该系统应用于在北海19个月的时间框架内连续部署的一组滑翔机，生成了该地区前所未有的精细尺度NPP时间序列（洛夫戴和史密斯，2020年）。在大尺度上，该时间序列与该地区现有的基于卫星的NPP估计值以及先前的原位估计值非常吻合。以前未曾阐明的是与水华物候、中尺度现象和混合层动力学相关的高频、小尺度、深度分辨的变异性。