Arctic shelf seas receive greater quantities of river runoff than any other ocean region and are experiencing increased freshwater loads and associated terrestrial matter inputs since recent decades. Amplified terrestrial permafrost thaw and coastal erosion is exposing previously frozen organic matter, enhancing its mobilization and release to nearshore regions. Changing terrestrial dissolved organic matter (terr-DOM) loads and composition may alter shelf primary productivity and respiration, ultimately affecting net regional CO₂ air–sea fluxes. However, the future evolution of Arctic Ocean climate feedbacks are highly dependent upon the biological degradability of terr-DOM in coastal waters, a factor often omitted in modelling studies. Here, we assess the sensitivity of CO₂ air–sea fluxes from East Siberian Arctic Shelf (ESAS) waters to changing terr-DOM supply and degradability using a biogeochemical model explicitly accounting for bacteria dynamics and shifting terr-DOM composition. We find increasing terr-DOM loads and degradability trigger a series of biogeochemical and ecological processes shifting ESAS waters from a net sink to a net source of CO₂, even after accounting for strengthening coastal productivity by additional land-derived nutrients. Our results suggest that future projected inputs of labile terr-DOM from peat and permafrost thaw may strongly increase the CO₂ efflux from the Arctic shelf sea, causing currently unquantified positive feedback to climate change.

与其他任何海洋区域相比，北极大陆架海域的河流径流量更大，并且近几十年来淡水负荷和相关的陆地物质输入正在增加。扩大的陆地永久冻土融化和海岸侵蚀正在暴露以前冻结的有机物质，增强其向近岸地区的流动和释放。改变陆地溶解有机物 (terr-DOM) 负荷和组成可能会改变陆架初级生产力和呼吸作用，最终影响净区域 CO ₂海气通量。然而，北冰洋气候反馈的未来演变高度依赖于沿海水域 terr-DOM 的生物降解性，这是建模研究中经常忽略的一个因素。在这里，我们评估 CO _{2的敏感性}使用明确考虑细菌动力学和变化的 terr-DOM 组成的生物地球化学模型，东西伯利亚北极大陆架 (ESAS) 水域的海气通量到不断变化的 terr-DOM 供应和可降解性。我们发现增加的 terr-DOM 负荷和可降解性引发了一系列生物地球化学和生态过程，将 ESAS 水域从净汇转变为 CO ₂的净源，即使在通过额外的陆源养分提高沿海生产力之后也是如此。我们的研究结果表明，未来预计来自泥炭和永久冻土融化的不稳定 terr-DOM 输入可能会强烈增加北极陆架海的 CO _{2流出量，从而导致目前无法量化的气候变化正反馈。}