Predicting Terrestrial CDOM Fate and Impact on Plankton Productivity in the Rapidly Changing Arctic Ocean

有一个共识：北冰洋面临着海冰减少的未来。因此，更多的阳光照射到地表水域，并对生态系统功能、生产力和生物地球化学产生重大影响。阳光对海洋中的生命是必不可少的。它通过浮游植物驱动生物物质的光合作用，进而推动整个远洋食物网的生产力。准确模拟浮游植物所经历的水下光环境是强有力地预测北冰洋生态系统对气候变化的反应的关键。对于以复杂光学性质为特征的生产性陆架水域来说，情况尤其如此。最近的一项研究预测，由于海冰融化导致的更长时间的阳光照射，北极浮游生物的生产力将大幅增加。然而，这可能不是海洋中所有地方的普遍规则。北极大陆架的淡水和溶解有机物(DOM)排放量是所有海洋中最高的，而且由于北极变暖，这一数字将会增加。这种DOM的很大一部分是有色的(CDOM)，因此强烈地吸收阳光，减少浮游植物生长所需的光照水平。在快速变化的北极，这种强大的阳光吸收器将在多大程度上降低浮游生物的生产力？需要在生物地球化学模型中嵌入河流CDOM，以回答这一紧迫问题，并进一步产生北冰洋强大的气候变化情景。将使用高分辨率海洋-海冰-浮游生物生态系统模型来模拟巴伦支海/喀拉海正常和相对较低的海冰覆盖率(即浮游植物暴露在较高的阳光下)多年的海洋和生物条件。模型中将河流CDOM作为输运变量考虑，以绘制和验证其在近岸水域的时空分布。然后开发一个复杂的生物光学模型，并嵌入到物理-生物耦合模型中，模拟TCDOM对水下光场的遮挡效应及其主要的光中介去除过程(光降解)。这将允许更准确地模拟初级生产力，将其与使用该项目的两个合作者开发的新方法获得的一致的卫星得出的估计值进行比较。这将是对北极水域的第一次比较，因此构成了在这一多产和重要的经济区域进行生物海洋学业务的重要框架。

There is a consensus: the Arctic Ocean faces a future with less sea ice. Therefore more sunlight reaches the surface waters accompanied with major implications for the ecosystem functioning, productivity, and biogeochemistry. Sunlight is essential for life in the ocean. It drives the photosynthesis of biogenic matter by phytoplankton that fuels in turn the productivity of the whole pelagic food web. Long minimized by biogeochemical modellers, simulating accurately the underwater light environment experienced by phytoplankton is pivotal to robustly predict the Arctic Ocean ecosystem response to climate change. It is particularly true for the productive shelf waters characterized by complex optical properties. A recent study predicts a substantial increase of Arctic plankton productivity in response to longer sunlight exposure caused by sea ice melt. However, it might not be a general rule everywhere in the ocean. Arctic shelves experience the highest freshwater and dissolved organic matter (DOM) discharge of any ocean and it this will increase due to Arctic warming. A large fraction of this DOM is coloured (CDOM) and therefore strongly absorbs sunlight, reducing light levels needed for phytoplankton growth. How much would this strong sunlight absorber contribute to lower plankton productivity in the rapidly changing Arctic? Embedding the riverine CDOM in biogeochemical models is required to answer this pressing question and to further produce robust climate change scenarios for the Arctic Ocean. A high-resolution ocean-sea ice-plankton ecosystem model will be used to simulate the ocean and biological conditions for years of normal and relatively low sea ice coverage (i.e. higher sunlight exposure for phytoplankton) in the Barents/Kara Sea. Riverine CDOM will be accounted in the model as a variable subject to transport to map and validate its spatio-temporal distribution in the coastal waters. A complex bio-optical model will be then developed and embedded in the physical-biological coupled model to simulate the TCDOM shading effect on the underwater light field jointly with its main light-mediated removal process (photodegradation). This will allow more accurate simulated primary production rates that will be compared with coincident satellite-derived estimates obtained using a new method developed by two collaborators of this project. This comparison will be the first for the Arctic waters and therefore constitutes an important framework for operational biological oceanography in this productive and economically important area.