caa a22 4500 445299312 CHVBK 20180317142552.0 cr unu---uuuuu 170323e20100101xx s 000 0 eng 10.1007/s11430-009-0198-5 doi (NATIONALLICENCE)springer-10.1007/s11430-009-0198-5 Processes and modes of permafrost degradation on the Qinghai-Tibet Plateau [Elektronische Daten] [JiChun Wu, Yu Sheng, QingBai Wu, Zhi Wen] Climate warming must lead the mainly air temperature controlled permafrost to degrade. Based on the numerical simulation, the process of permafrost degradation can be divided into five stages, i.e., starting stage, temperature rising stage, zero geothermal gradient stage, talic layers stage, and disappearing stage, according to the shape of ground temperature profile. Permafrost on the Qinghai-Tibet Plateau (QTP) is generally considered a relic from late Pleistocene, and has been degenerating as a whole during Holocene. According to spatial-temporal compensation, the present thermal state discrepancy of permafrost in different areas on the QTP may correspond with their degradation stages. On the QTP, permafrost in the high and middle mountains belongs to temperature rising stage, the permafrost thermal state is transiting from late rising temperature stage to zero geothermal gradient stage that is distributed in the middle-low-mountains. Permafrost that is in a zero gradient stage mainly appears in the high plateau and valley, whereas the transition from zero gradient stage to talic layers stage of permafrost is located in the vicinity of the lower limit of permafrost, and permafrost is disappearing from margin of perennially frozen ground. There are two modes of perennially frozen ground thawing, thawing from top to bottom and thawing from bottom to top respectively. During the temperature rising stage, when the heat flux in the perennially frozen soil layer is less than that in the unfrozen soil underlying frozen soil layer, the geothermal flux is partly used to thaw the base of permafrost, and permafrost thaws from bottom to top. With the decrease of thermal gradient in the perennially frozen ground, the heat that is used to thaw permafrost base increases, and geothermal heat will be entirely consumed to thaw the base of permafrost until the temperature gradient reaches zero thermal gradient state. On the other hand, the disappearance of permafrost may be delayed by "thermal offset” and "seasonal offset” effects in the upper of permafrost layer. When ground surface temperature rises to the level that can counteract the thermal offset effect, heat accumulation in the active layer would start, and the thickness of the active layer increases until a talic layer to appear. This process can be intensified by the "seasonal anti-offset effect”. Science in China Press and Springer Berlin Heidelberg, 2009 Qinghai-Tibet Plateau nationallicence permafrost nationallicence degradation process nationallicence degradation stage nationallicence degradation mode nationallicence Wu JiChun State Key Laboratory of Frozen Soil Engineering, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, 730000, Lanzhou, China aut Sheng Yu State Key Laboratory of Frozen Soil Engineering, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, 730000, Lanzhou, China aut Wu QingBai State Key Laboratory of Frozen Soil Engineering, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, 730000, Lanzhou, China aut Wen Zhi State Key Laboratory of Frozen Soil Engineering, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, 730000, Lanzhou, China aut Science in China Series D: Earth Sciences SP Science in China Press 53/1(2010-01-01), 150-158 1674-7313 53:1<150 2010 53 11430 https://doi.org/10.1007/s11430-009-0198-5 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s11430-009-0198-5 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Wu JiChun State Key Laboratory of Frozen Soil Engineering, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, 730000, Lanzhou, China aut NATIONALLICENCE 700 1- Sheng Yu State Key Laboratory of Frozen Soil Engineering, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, 730000, Lanzhou, China aut NATIONALLICENCE 700 1- Wu QingBai State Key Laboratory of Frozen Soil Engineering, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, 730000, Lanzhou, China aut NATIONALLICENCE 700 1- Wen Zhi State Key Laboratory of Frozen Soil Engineering, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, 730000, Lanzhou, China aut NATIONALLICENCE 773 0- Science in China Series D: Earth Sciences SP Science in China Press 53/1(2010-01-01), 150-158 1674-7313 53:1<150 2010 53 11430 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer