Abstract In this study we used fluorescence excitation and emission matrix spectroscopy, hydrographic data, and a self‐organizing map (SOM) analysis to assess the spatial distribution of labile and refractory fluorescent dissolved organic matter (FDOM) for the Chukchi and Beaufort Seas at the time of a massive under‐ice phytoplankton bloom during early summer 2011. Biogeochemical properties were assessed through decomposition of water property classes and sample classification that employed a SOM neural network‐based analysis which classified 10 clusters from 269 samples and 17 variables. The terrestrial, humic‐like component FDOM (ArC1, 4.98 ± 1.54 Quinine Sulfate Units (QSU)) and protein‐like component FDOM (ArC3, 1.63 ± 0.88 QSU) were found to have elevated fluorescence in the Lower Polar Mixed Layer (LPML) (salinity ~29.56 ± 0.76). In the LPML water mass, the observed contribution of meteoric water fraction was 17%, relative to a 12% contribution from the sea ice melt fraction. The labile ArC3‐protein‐like component (2.01 ± 1.92 QSU) was also observed to be elevated in the Pacific Winter Waters mass, where the under‐ice algal bloom was observed (~40–50 m). We interpreted these relationships to indicate that the accumulation and variable distribution of the protein‐like component on the shelf could be influenced directly by sea ice melt, transport, and mixing processes and indirectly by the in situ algal bloom and microbial activity. ArC5, corresponding to what is commonly considered marine humic FDOM, indicated a bimodal distribution with high values in both the freshest and saltiest waters. The association of ArC5 with deep, dense salty water is consistent with this component as refractory humic‐like FDOM, whereas our evidence of a terrestrial origin challenges this classic paradigm for this component.

中文翻译：

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北冰洋西部冰下藻华期间荧光溶解有机物分布的控制

摘要 在这项研究中，我们使用荧光激发和发射矩阵光谱、水文数据和自组织图 (SOM) 分析来评估楚科奇海和波弗特海不稳定和难熔荧光溶解有机物 (FDOM) 的空间分布。 2011 年初夏大规模冰下浮游植物爆发的时间。通过分解水属性类别和样本分类来评估生物地球化学特性，使用基于 SOM 神经网络的分析对 269 个样本和 17 个变量中的 10 个集群进行分类。发现陆生类腐殖质成分 FDOM（ArC1，4.98 ± 1.54 硫酸奎宁单位（QSU））和类蛋白质成分 FDOM（ArC3，1.63 ± 0.88 QSU）在下极混合层 (LPML) 中具有增强的荧光（盐度 ~29.56 ± 0.76）。在 LPML 水团中，观测到的大气水部分的贡献为 17%，而海冰融化部分的贡献为 12%。还观察到不稳定的 ArC3 蛋白样成分（2.01 ± 1.92 QSU）在太平洋冬季水域质量升高，在那里观察到冰下藻华（~40-50 m）。我们解释了这些关系，表明陆架上蛋白质样成分的积累和可变分布可能直接受到海冰融化、运输和混合过程的影响，并间接受到原位藻华和微生物活动的影响。ArC5 对应于通常认为的海洋腐殖质 FDOM，表明在最新鲜和最咸的水域中具有高值的双峰分布。ArC5 与深度的关联，