Soil organic carbon (SOC) and sediment contents and fluxes for terrain units along the Yukon Coastal Plain, Canada, including corrections for volumetric ground ice contents

Narrowing uncertainties about carbon cycling is important in the Arctic where rapid environmental changes contribute to enhanced mobilization of carbon. Here we quantify soil organic carbon (SOC) contents of permafrost soils along the Yukon Coastal Plain and determine the annual fluxes from erosion. Different terrain units are assessed based on surficial geology, morphology, and ground ice conditions. To account for the volume of wedge ice and massive ice in a unit, sample SOC contents are reduced by 19% and sediment contents by 16%. The SOC content in a 1 m**2 column of soil varies according to the height of the bluff, ranging from 30 to 662 kg, with a mean value of 183 kg. Forty-four per cent of the SOC is within the top 1 m of soil and values vary based on surficial materials, ranging from 30 to 53 kg C/m**3, with a mean of 41 kg. Eighty per cent of the shoreline is erosive with a mean annual rate of change is 0.7 m/a. This results in a SOC flux per meter of shoreline of 131 kg C/m/a, and a total flux for the entire Yukon coast of 35.5 10**6 kg C/a (0.036 Tg C/a). The mean flux of sediment per meter of shoreline is 5.3 10**3 kg/m/a, with a total flux of 1,832.0 10**6 kg/a (1.832 Tg/a). Sedimentation rates indicate that approximately 13% of the eroded carbon is sequestered in nearshore sediments, where the overwhelming majority of organic carbon is of terrestrial origin.

厘清碳循环相关的不确定性，在北极地区尤为关键——该区域的快速环境变化加剧了碳的活化迁移。本研究针对育空沿海平原的多年冻土土壤，量化其土壤有机碳（Soil Organic Carbon, SOC）含量，并估算侵蚀作用引发的年碳通量。研究依据表层地质、地貌及地下冰条件，对不同地形单元展开评估。为计入某一地形单元内的楔状冰与块状冰体积，样品的SOC含量需校正扣除19%，沉积物含量则校正扣除16%。每1平方米土壤柱体的SOC含量随海岸断崖高度变化，区间为30~662 kg，平均值为183 kg。44%的SOC储存在土壤表层1米范围内，其含量随表层物质类型有所差异，区间为30~53 kg C/m³，平均值为41 kg。育空沿海80%的岸线为侵蚀性岸线，年均岸线变化速率为0.7 m/a。据此可得，每米岸线的SOC通量为131 kg C/m/a，育空沿海整体的总SOC通量为35.5×10^6 kg C/a（即0.036 Tg C/a）。每米岸线的沉积物年均通量为5.3×10^3 kg/m/a，总沉积物通量为1832.0×10^6 kg/a（即1.832 Tg/a）。沉积速率数据表明，约13%的侵蚀碳被固存于近岸沉积物中，且其中绝大多数有机碳为陆源成因。