Air Temperature Regulates Erodible Landscape, Water, and Sediment Fluxes in the Permafrost‐Dominated Catchment on the Tibetan Plateau
Air Temperature Regulates Erodible Landscape, Water, and Sediment Fluxes in the Permafrost‐Dominated Catchment on the Tibetan Plateau
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DOI：
10.1029/2020wr028193
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发表时间：
2021-02
影响因子：
5.4
通讯作者：
Dongfeng Li;I. Overeem;A. Kettner;Yin-jun Zhou;Xixi Lu
中科院分区：
文献类型：
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作者：
Dongfeng Li;I. Overeem;A. Kettner;Yin-jun Zhou;Xixi Lu
青藏高原 (TP) 约 40% 的面积位于连续的多年冻土之下，但其对河流水和沉积物动态的影响仍鲜有研究。在这里，我们根据 33 年的每日现场观测（1985-2017）表明，青藏高原上以多年冻土为主的沱沱河盆地的水和沉积物动态是由气温和多年冻土融化驱动的。气温通过控制活跃排水面积（ACDA，在流域内促进水文地貌过程的未冻侵蚀景观）的变化并控制冰川雪融化和永久冻土融化等多种热过程，来调节排放和悬浮沉积物浓度（SSC）的季节性模式。暴雨通过加剧斜坡过程和河道侵蚀，也可能通过增强解冻滑落来决定短暂的河流极端事件。此外，同等排放水平下，秋季（9 月至 10 月）的SSC 低于春季（5 月至6 月）和夏季（7 月至8 月）。秋季沉积物可用性的减少可能归因于永久冻土层上地下水径流的增加以及地表径流和侵蚀的减少。由于气候迅速变暖，ACDA 从 1985 年到 2017 年显着增加，这意味着水文地貌过程的侵蚀景观不断扩大。结果，河流水量和沉积物通量大幅增加。在青藏高原更加温暖和湿润的未来，随着侵蚀景观的扩大以及热力和洪水驱动的地貌过程的加剧，类似的永久冻土盆地的河流沉积通量将继续增加。因此，多年冻土融化应被视为青藏高原过去和未来水和沉积物变化的重要驱动因素。
Approximately 40% of the Tibetan Plateau (TP) is underlain by continuous permafrost, yet its impact on fluvial water and sediment dynamics remains poorly investigated. Here we show that water and sediment dynamics in the permafrost‐dominated Tuotuohe basin on the TP are driven by air temperature and permafrost thaw, based on 33‐year daily in situ observations (1985–2017). Air temperature regulates the seasonal patterns of discharge and suspended sediment concentration (SSC) by controlling the changes in active contributing drainage area (ACDA, the unfrozen erodible landscape that contributes hydrogeomorphic processes within a catchment) and governing multiple thermal processes such as glacier‐snow melt and permafrost thaw. Rainstorms determine the short‐lived fluvial extreme events by intensifying slope processes and channel erosion and likely also by enhancing thaw slumps. Furthermore, the SSCs at equal levels of discharges are lower in autumn (September–October) than in spring (May–June) and summer (July–August). This reduced sediment availability in autumn can possibly be attributed to the increased supra‐permafrost groundwater runoff and the reduced surface runoff and erosion. Due to rapid climate warming, the ACDA has increased significantly from 1985 to 2017, implying expanding erodible landscapes for hydrogeomorphic processes. As a result, the fluvial water and sediment fluxes have substantially increased. In a warmer and wetter future for the TP, the fluvial sediment fluxes of similar permafrost‐underlain basins will continue to increase with expanding erodible landscapes and intensifying thermal and pluvial‐driven geomorphic processes. Thus, permafrost thaw should be considered as an important driver of past and future water and sediment changes for the TP.