Permafrost characteristics and potential influencing factors in the lake regions of Hoh Xil, Qinghai-Tibet Plateau

Abstract

The Qinghai-Tibet Plateau (QTP) is one of the regions in the world where permafrost and lakes are widely developed. Yet, the current understanding of permafrost characteristics surrounding large alpine lakes is still not clear. Based on the observation of permafrost surrounding Zonag Lake and Yanhu Lake (>100 km2) in the Hoh Xil region since 2012, we first investigated the permafrost characteristics and potential influencing factors around large alpine lakes on the QTP. The results indicate that the large alpine lakes have only a marginal thermal effect on the surrounding permafrost. Except for the sites located at the lake bottom and adjacent to the lakeshore, cold permafrost is extensively developed around the lakes, where the mean annual ground temperature is below −1.0℃, and the permafrost thickness is generally more than 40 m. Moreover, significant differences exist in ground temperature between boreholes located in the Yanhu Lake basin and those outside the basin, which the permafrost temperature in the lake basin is remarkably lower. These phenomena are closely related to the high soil water content around lakes. Statistical results show that ground temperature decreases and permafrost thickness increases gradually with increasing soil water content. The latent heat effects play an important role in the thermal dynamics of permafrost, which can buffer the increase of permafrost temperature under climate warming. Meanwhile, the salinity of water can weaken the thermal erosion effect of the lake on the surrounding permafrost to a certain extent. Overall, the permafrost thermal regime in the lake regions is not only controlled by altitude but also affected by soil water content. This study will provide us with a basis for understanding the state and characteristics of the frozen ground around lakes in the permafrost regions of the QTP, as well as for conducting research on the interaction of frozen ground with lakes and even the atmosphere.