ORIGINAL ARTICLE Hydrothermal pattern of frozen soil in Nam Co lake basin, the Tibetan Plateau Keming Tian Æ Jingshi Liu Æ Shichang Kang Æ Iain B. Campbell Æ Fei Zhang Æ Qianggong Zhang Æ Wei Lu Received: 21 January 2008 / Accepted: 24 June 2008 / Published online: 22 July 2008 Ó Springer-Verlag 2008 Abstract Hydrothermal processes and the regimes of frozen soil formed in alpine regions with glaciers and lake area are complex and important for ecological environment but have not been studied in Tibet. Based on soil temper- ature and moisture data from October 2005 to September 2006 collected in the Nam Co lake basin, Tibetan Plateau (TP), those questions were discussed. The mean annual air temperature was -3.4°C with 8 months below 0°C. Air and soil temperature varied between -25.3*13.1°C and -10.3*8.8°C, respectively. Soil moisture variations in the active layer were small with the minimum value of 1.4%, but were influenced greatly by snowmelt, rainfall and evaporation, varying up to 53.8%. The active layer froze later, thawed earlier and was thinner, however, the lower altitude limit of permafrost is higher than that in most areas of TP. The effects of soil moisture (unfrozen water content) on soil temperature, which were estimated through proposed models, were more significant near ground sur- face than the other layers. The surface soil temperature decreased with snowcover, the effect of cold snow melt- water infiltration on soil thermal conditions was negligible, however, the effect of rainfall infiltration was evident causing thermal disruptions. Keywords Active layer  Soil temperature  Soil moisture  Snow meltwater  Rainfall Introduction Frozen soil, which is closely related to climate, hydrological processes and ecological environment in cold regions (French 2003; Qin et al. 1987; Wu et al. 2003), accounts for large land area over the world. Permafrost and seasonally frozen soil account for 24 and 30% of the land area in the northern Hemisphere, respectively (Williams and Smith 1989; Zhang et al. 1999). Permafrost in China includes high latitude permafrost in the northeastern China, alpine per- mafrost in the northwestern China and high plateau permafrost on the Tibetan Plateau (TP) which accounts for 70% of the total permafrost area of China (Cheng 1990). Freezing and thawing in the active layer will release or consume large amount of heat and therefore influence the energy exchange and balance within the soil-atmosphere system (Li et al. 2002). It will also change land surface albedo (ground surface ice, soil color), soil heat capacity, land surface evaporation and the growth of vegetation. Scenarios from numerical simulations showed that varia- tions of soil moisture and vegetation will cause apparent climate change (Dickinson and Henderson-Sellers 1988; Liu et al. 1989; Mintz 1984; Shukla and Mintz 1982). In addition, frozen soil greatly influences hydrological pro- cesses and ecosystems (Niu and Yang 2006; Yamazaki et al. 2006; Yang et al. 1993) and hence affects water K. Tian  J. Liu (&)  S. Kang  F. Zhang  Q. Zhang  W. Lu Institute of Tibetan Plateau Research, CAS, Shuangqing Road 18, Haidian District, Beijing 100085, China e-mail: jsliu@itpcas.ac.cn S. Kang State Key Laboratory of Cryospheric Science, CAREERI, CAS, Lanzhou 730000, China K. Tian  Q. Zhang  W. Lu Graduate University of Chinese Academy of Sciences, Beijing 100039, China I. B. Campbell Land and Soil Consultancy Services, Nelson 7011, New Zealand 123 Environ Geol (2009) 57:1775–1784 DOI 10.1007/s00254-008-1462-2