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Water 2019, 11(4), 706; https://doi.org/10.3390/w11040706

Quantifying Impacts of Mean Annual Lake Bottom Temperature on Talik Development and Permafrost Degradation below Expanding Thermokarst Lakes on the Qinghai–Tibet Plateau

1,2,* and 2
1
School of Mathematics and Statistics, Zhaoqing University, Zhaoqing 526061, Guangdong, China
2
Department of Geography and the Environment, University of North Texas, Denton, TX 76203, USA
*
Author to whom correspondence should be addressed.
Received: 17 March 2019 / Revised: 27 March 2019 / Accepted: 29 March 2019 / Published: 5 April 2019
(This article belongs to the Section Hydrology)
PDF [578 KB, uploaded 5 April 2019]
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Abstract

Variations in thermokarst lake area, lake water depth, lake age, air temperature,
permafrost condition, and other environmental variables could have important influences on the
mean annual lake bottom temperature (MALBT) and thus affect the ground thermal regime and
talik development beneath the lakes through their direct impacts on the MALBT. A lake expanding
model was employed for examining the impacts of variations in the MALBT on talik development
and permafrost degradation beneath expanding thermokarst lakes in the Beiluhe Basin on the
Qinghai–Tibetan Plateau (QTP). All required boundary and initial conditions and model parameters
were determined based on field measurements. Four simulation cases were conducted with
different respective fitting sinusoidal functions of the MALBTs at 3.75 °C, 4.5 °C, 5.25 °C, and 6.0 °C.
The simulated results show that for lakes with MALBTs of 3.75 °C, 4.5 °C, 5.25 °C, and 6.0 °C, the
maximum thicknesses of bowl-shaped talik below the lakes at year 300 were 27.2 m, 29.6 m, 32.0 m,
and 34.4 m; funnel-shaped open taliks formed beneath the lakes at years 451, 411, 382, and 356 after
the formation of thermokarst lakes, with mean downward thaw rates of 9.1 m/year, 10.2 m/year,
11.2 m/year, and 12.0 m/year, respectively. Increases in the MALBT from 3.75 °C to 4.52 °C, 4.25 °C
to 5.25 °C, and 5.25 °C to 6.0 °C respectively resulted in the permafrost with a horizontal distance to
lake centerline less than or equal to 45 m thawing completely 36 years, 32 years, and 24 years in
advance, and the maximum ground temperature increases at a depth of 40 m below the lakes at year
600 ranged from 2.16 °C to 2.80 °C, 3.57 °C, and 4.09 °C, depending on the MALBT. The ground
temperature increases of more than 0.5 °C at a depth of 40 m in year 600 occurred as far as 74.9 m,
87.2 m, 97.8 m, and 106.6 m from the lake centerlines. The simulation results also show that changes
in the MALBT almost have no impact on the open talik lateral progress rate, although the minimum
distances from the open talik profile to lake centerlines below the lakes with different MALBTs
exhibited substantial differences.
Keywords: mean annual lake bottom temperature (MALBT); open talik; permafrost degradation; numerical simulation; Qinghai–Tibetan Plateau (QTP) mean annual lake bottom temperature (MALBT); open talik; permafrost degradation; numerical simulation; Qinghai–Tibetan Plateau (QTP)
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Ling, F.; Pan, F. Quantifying Impacts of Mean Annual Lake Bottom Temperature on Talik Development and Permafrost Degradation below Expanding Thermokarst Lakes on the Qinghai–Tibet Plateau. Water 2019, 11, 706.

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