Journal cover Journal topic
Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
doi:10.5194/hess-2016-632
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
23 Dec 2016
Review status
A revision of this discussion paper is under review for the journal Hydrology and Earth System Sciences (HESS).
Seasonal thermal regime and climatic trends in lakes of Tibetan Highlands
Georgiy Kirillin1, Lijuan Wen2, and Tom Shatwell1 1Department of Ecohydrology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB). Berlin, 12587 Germany
2Key Laboratory of Land Surface Process and Climate Change in Cold and Arid regions, Northwest Institute of Eco- Environment and Resources, Chinese Academy of Sciences, Lanzhou , 73000 China
Abstract. The hydrology of the lake-rich Tibetan Plateau is important for the global climate yet little is known about the thermal regime of Tibetan lakes due to scant data. We (i) investigated the characteristic seasonal temperature patterns and recent trends in thermal and stratification regime of lakes on the Tibetan Plateau and (ii) tested theperformance of the one-dimensional lake parameterization scheme FLake for the Tibetan lake system. For this purpose we combined three years of in situ lake temperature measurements, several decadesof satellite observations and the global reanalysis data. We chose the two largest freshwater Tibetan lakes – Ngoring and Gyaring – as study sites. The lake model FLake faithfully reproduced the specific features of the high-altitude lakes and was subsequently applied to reconstruct the vertically resolved heat transport in both lakes during the last four decades. The modelsuggested Ngoring and Gyaring were ice-covered forabout 6 months and stratified in summer for about 4 months per year with a short spring overturn and longer autumn overturn. In summer the surface mixed boundary layer extended to 6–8 m depth and was about 20 % shallower in the more turbid Gyaring. The thermal regime of transparent Ngoring responded more strongly to atmospheric forcing than Gyaring, where the higher turbidity dampened the response. According to reanalysis data, air temperatures and humidity increased, whereas solar radiation decreased since the 1970s. Surprisingly, mean lake temperatures did not change, nor did the phenology of ice cover or stratification. Lake surface temperatures in summerincreased only marginally. The reason is that the increase in air temperature was offset by the decrease in radiation, probably due to increasing humidity. This study demonstrates that air temperature trends are not directly coupled to lake temperatures and underscores the importance of short-wave radiation for the thermal regime of high-altitude lakes.

Citation: Kirillin, G., Wen, L., and Shatwell, T.: Seasonal thermal regime and climatic trends in lakes of Tibetan Highlands, Hydrol. Earth Syst. Sci. Discuss., doi:10.5194/hess-2016-632, in review, 2016.
Georgiy Kirillin et al.
Georgiy Kirillin et al.
Georgiy Kirillin et al.

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Short summary
We report first descritpion of the seasonal temperature, mixing, and ice regime in the two largest freshwater lakes of the Tibetan Plateau, perform validation of the lake model FLake for parameterization of the Tibetan lake system in regional climate models, and present an evidence of the absent warming trend in the Tibetan lakes despite significant atmospheric warming. The reason for this unexpected behavior is the significant decrease in the solar radiation at the surface.
We report first descritpion of the seasonal temperature, mixing, and ice regime in the two...
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