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Air Temperature Regulates Erodible Landscape, Water, and Sediment Fluxes in the Permafrost‐Dominated Catchment on the Tibetan Plateau
Water Resources Research ( IF 5.4 ) Pub Date : 2021-01-05 , DOI: 10.1029/2020wr028193
Dongfeng Li 1 , Irina Overeem 2 , Albert J. Kettner 2 , Yinjun Zhou 3 , Xixi Lu 1, 4
Affiliation  

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.

中文翻译:

气温调节青藏高原多年冻土为主集水区的可侵蚀景观,水和泥沙通量

大约40%的青藏高原(TP)处于连续多年冻土之下,但是对河流水和沉积物动力学的影响仍然缺乏研究。在这里,根据33年的每日实地观测(1985-2017年),我们显示了TP上以多年冻土为主的Tu河河盆地的水和泥沙动力学受气温和多年冻土融化的驱动。空气温度通过控制活动贡献流域(ACDA,有助于流域内水文地貌过程的未冻结易蚀景观)的变化并控制冰川和雪融等多种热过程来调节排放量和悬浮沉积物浓度(SSC)的季节性模式。和永久冻土融化。暴雨通过加剧斜坡过程和河道侵蚀,还可能通过增强融化塌陷来确定短暂的河流极端事件。此外,秋季(9月至10月)同等排放水平的SSC低于春季(5月至6月)和夏季(7月至8月)。秋季减少的沉积物可利用量可能归因于超多年冻土层地下水径流增加以及地表径流和侵蚀减少。由于气候迅速升温,从1985年到2017年,ACDA显着增加,这意味着水文地貌过程的易蚀景观不断扩大。结果,河流水和沉积物通量大大增加。在TP的温暖潮湿的未来中,随着可蚀性景观的扩大以及热力和河流驱动的地貌过程的加剧,相似的多年冻土层下盆地的河流沉积物通量将继续增加。因此,多年冻土融化应被认为是TP过去和未来水和沉积物变化的重要驱动力。
更新日期:2021-02-02
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