Impacts of climate changes on light-stimulated carbon fluxes in the Arctic Ocean: quantification of primary production and photooxidation using satellite remote sensing

在过去的30年里，北冰洋失去了50%的永久海冰覆盖，使更多的地表水暴露在太阳直接辐射下。这种现象刺激了光驱动碳过程：浮游植物的初级生产和溶解有机物（DOM）的光氧化。虽然最近有文献记载了光供应增加对初级生产者的刺激，但迄今为止，这种辐射强迫对DOM光化学氧化和光驱动碳通量之间净平衡的影响很少受到关注。事实上，北冰洋表面的DOM主要来自北部陆地生态系统，那里储存了全球近三分之一的土壤有机碳。在气候变暖的背景下，这些生态系统正在经历重要的生物地球化学转变，改变了陆源DOM的数量和化学特征，改变了输入北冰洋的有机和无机养分的相对丰度。在这里，我提出了一个框架，使用诊断模型方法来研究北冰洋光刺激碳通量之间的净平衡。因此，将开发一个基于卫星的大气-海洋耦合系统的光谱辐射传输模型，以量化光化学过程并评估初级生产和光氧化之间净平衡的趋势。光化学模式的参数化将基于北冰洋研究巡航期间收集的现场观测资料。为了预测这些光化学参数的变化，将研究它们与可观测或可计算的环境参数的关系。这一建议的新颖之处在于将各种遥感环境参数协同使用，并将其合并到诊断建模方法中，以回答有关气候变化反馈的基本问题。特别是，这项工作将致力于利用自1997年以来卫星提供的连续海洋颜色观测。研究结果将有利于遥感问题、全球生物地球化学循环、气候模拟、海洋光合作用和DOM光化学等方面的研究。

During the last 3 decades, the Arctic Ocean has lost 50% of its permanent sea ice cover, exposing more surface waters to direct solar radiation. This phenomenon stimulates light-driven carbon processes: primary production by phytoplankton and photo-oxidation of dissolved organic matter (DOM). While the stimulation of primary producers by increased light availability has been recently documented, the impacts of this radiative forcing on photochemical oxidation of DOM and the net balance between light-driven carbon fluxes has received little attention thus far. Indeed, DOM in the Arctic Ocean surface originates largely from northern terrestrial ecosystems, which store nearly one third of global soil organic carbon. These ecosystems are currently experiencing important biogeochemical transformations under a warming climate, modifying the quantity and chemical character of terrigenous DOM, and the relative abundance of organic and inorganic nutrient inputs into the Arctic Ocean. Here I propose a framework to study the net balance between light-stimulated carbon fluxes in the Arctic Ocean using a diagnostic modelling approach. Therefore, a satellite-based spectral radiative transfer model for the coupled atmosphere-ocean system will be developed to quantify photochemical processes and assess trends in the net balance between primary production and photoooxidation. The parameterization of the photochemical models will be based on in situ observations gathered during research cruises in the Arctic Ocean. In order to predict variation in these photochemical parameters, their variability will be investigated in relation to observable or calculable environmental parameters. The novelty of this proposal resides in the synergetic use of various remotely sensed parameters of the environment merged within a diagnostic modelling approach to answer fundamental questions regarding climate change feedbacks. In particular, the work will aim to exploit the continuous ocean colour observations provided by satellites since 1997. The results should benefit studies focusing on remote sensing problems, global biogeochemical cycles, climate modeling, marine photosynthesis and DOM photochemistry.