Recent distribution and accumulation of organic carbon on the continental margin west off Spitsbergen

The study compiles the controlling factors for organic matter sedimentation patterns from a suite of organogeochemical parameters in surface sediments off Spitsbergen and direct seabed observations using a Remotely Operated Vehicle (ROV). In addition we assess its storage rates as well as the potential of carbon sinks on the northwestern margin of the Barents Sea with short sediment cores from a selected fjord environment (Storfjord). While sedimentation in the fjords is mainly controlled by river/meltwater discharge and coastal erosion by sea ice/glaciers resulting in high supply of terrigenous organic matter, Atlantic water inflow, and thus enhanced marine organic matter supply, characterizes the environment on the outer shelf and slope. Local deviations from this pattern, particularly on the shelf, are due to erosion and out washing of fine-grained material by bottom currents. Spots dominated by marine productivity close to the island have been found at the outer Isfjord and west off Prins Karls Forland as well as off the Kongsfjord/Krossfjord area and probably reflect local upwelling of nutrient-rich Atlantic water-derived water masses. Accumulation rates of marine organic carbon as well as reconstructed primary productivities decreased since the middle of the last century. Negative correlation of the Isfjord temperature record with reconstructed productivities in the Storfjord could be explained by a reduced annual duration of the marginal ice zone in the area due to global warming. Extremely high accumulation rates of marine organic carbon between 5.4 and 17.2 g/m**2/yr mark the Storfjord area, and probably high-latitude fjord environments in general, as a sink for carbon dioxide.本研究基于斯匹次卑尔根（Spitsbergen）周边表层沉积物中的一系列有机地球化学参数，以及利用遥控无人潜水器（Remotely Operated Vehicle, ROV）获取的直接海底观测数据，系统梳理了有机质沉积模式的控制因素。此外，本研究借助选定峡湾环境（斯特尔峡湾，Storfjord）的短沉积岩芯，评估了巴伦支海（Barents Sea）西北缘的碳埋藏速率与碳汇潜力。 峡湾内的沉积作用主要受河流/融水径流以及海冰/冰川引发的海岸侵蚀控制，该过程会带来大量陆源有机质供给；而外陆架与陆坡环境则以大西洋水输入为核心特征，伴随海洋有机质供给的显著提升。该沉积模式的局部偏离（尤其在陆架区域），源于底流对细粒物质的侵蚀与冲刷作用。 在伊萨峡湾（Isfjord）外缘、普林斯卡尔斯福兰岛以西，以及孔斯峡湾（Kongsfjord）/克罗斯峡湾（Krossfjord）周边海域，均发现了靠近岛屿、受海洋生产力主导的区域，这些区域大概率反映了营养盐富集的大西洋源水团的局部上升流活动。 自上世纪中叶以来，海洋有机碳的堆积速率以及重建的初级生产力均呈现下降趋势。伊萨峡湾的温度记录与斯特尔峡湾的重建生产力呈负相关，这一现象可归因于全球变暖导致该区域边缘冰带的年持续时间缩短。 斯特尔峡湾海域的海洋有机碳堆积速率达5.4至17.2 g/m²/yr，这一特征将斯特尔峡湾乃至总体上的高纬度峡湾环境，确立为二氧化碳的碳汇。