What is it about?
To investigate and monitor permafrost in the Bayan Har Mountains (BHM), northeastern Qinghai–Tibet Plateau, southwest China, 19 boreholes ranging from 20 to 100 m in depth were drilled along an elevational transect (4,221–4,833 m a.s.l.) from July to September 2010. Measurements from these boreholes demonstrate that ground temperatures at the depth of zero annual amplitude (TZAA) are generally higher than −2.0°C. The lapse rates of TZAA are 4 and 6 °C km−1, and the lower limits of permafrost with TZAA < −1°C are approximately 4,650 and 4,750 m a.s.l. on the northern (near Yeniugou) and southern (near Qingshui'he) slopes, respectively. TZAA changes abruptly within short distances from −0.2 to +1.2°C near the northern lower limits of permafrost and from about +0.5 to +1.5°C near the southern lower limits of permafrost. Thawing and freezing on the ground surface at Qingshui'he (4,413 m a. s. l.) are 13.3 d earlier and 26 d later than that at Chalaping (4,724 m a. s. l.), respectively. The temperature gradient at Qingshui'he is clearly larger than that at Chalaping. The changes of permafrost TZAA ranged from 0.03°C to 0.2°C from 2010 to 2017. A 3.5‐m‐thick permafrost near Qingshui'he was observed to disappear in summer 2013. There is no significant correlation between elevation and permafrost temperature changes in the study area, whereas the changes of very warm (close to 0°C) permafrost seem to be slow in the intermontane basins.
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Why is it important?
The thermal state of permafrost in the mid-latitudinal mountainous regions is quite sensitive to climate change. Yet there is few report about its dynamics in recent decades. In this study, the thermal regime of permafrost in a typical elevational permafrost region, the Bayan Har Mountains with elevations ranging from 4,200 m to 5,000 m has been reported on the basis of the data collected from a comprehensive permafrost-climate monitoring network. We showed that the temperature at the depth of zero annual amplitude increased at an average rate of 0.20 °C·(10a)-1, which is more significant than the rate at high latitudes.
Perspectives
The thermal regime of elevational permafrost on the Qinghai-Tibet Plateau is sensitive to elevation, while there is no significant relationship between elevation and the increasing rate of permafrost; The warm permafrost degrades less drastically than that of cold permafrost, especially for those with temperature close to 0 °C; The field observations showed the disappearing of permafrost at the southern lower limits of permafrost; It may take a relatively long time for thermally unstable permafrost (with TZAA of −0.5°C and 0°C) to combat “disappearance”.
Dr Dongliang Luo
Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences
Read the Original
This page is a summary of: Elevation-dependent thermal regime and dynamics of frozen ground in the Bayan Har Mountains, northeastern Qinghai-Tibet Plateau, southwest China, Permafrost and Periglacial Processes, October 2018, Wiley,
DOI: 10.1002/ppp.1988.
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