Seasonal thermal regime and climatic trends in lakes of the Tibetan highlands
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 the thermal and stratification regimes of lak...
Main Authors: | , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2017-04-01
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Series: | Hydrology and Earth System Sciences |
Online Access: | http://www.hydrol-earth-syst-sci.net/21/1895/2017/hess-21-1895-2017.pdf |
Summary: | 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 the thermal
and stratification regimes of lakes on the Tibetan Plateau and (ii) tested
the performance of the one-dimensional lake parameterization scheme FLake
for the Tibetan lake system. For this purpose, we combined 3 years of in
situ lake temperature measurements, several decades of 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 4 decades. The model
suggested that Ngoring and Gyaring were ice-covered for about 6 months and
stratified in summer for about 4 months per year with a short spring
overturn and a longer autumn overturn. In summer the surface mixed boundary
layer extended to 6–8 m of depth and was about 20 % shallower in the more
turbid Gyaring. The thermal regime of the transparent Ngoring responded more
strongly to atmospheric forcing than Gyaring, where the higher turbidity
damped the response. According to the reanalysis data, air temperatures and
humidity have increased, whereas solar radiation has decreased, since the 1970s.
Surprisingly, the modeled mean lake temperatures did not change, nor did the
phenology of the ice cover or stratification. Lake surface temperatures in
summer increased 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
shortwave radiation for the thermal regime of high-altitude lakes. |
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ISSN: | 1027-5606 1607-7938 |