A New Map of the Permafrost Distribution on the Tibetan Plateau

Other literature type English OPEN
Zou, Defu ; Zhao, Lin ; Sheng, Yu ; Chen, Ji ; Hu, Guojie ; Wu, Tonghua ; Wu, Jichun ; Xie, Changwei ; Wu, Xiaodong ; Pang, Qiangqiang ; Wang, Wu ; Du, Erji ; Li, Wangping ; Liu, Guangyue ; Li, Jing ; Qin, Yanhui ; Qiao, Yongping ; Wang, Zhiwei ; Shi, Jianzong ; Cheng, Guodong (2016)

The Tibetan Plateau (TP) possesses the largest areas of permafrost terrain in the mid- and low-latitude regions of the world. A detailed database of the distribution and characteristics of permafrost is crucial for engineering planning, water resource management, ecosystem protection, climate modelling, and carbon cycle research. Although some permafrost distribution maps have been compiled in previous studies and have been proven to be very useful, due to the limited data source, ambiguous criteria, little validation, and the deficiency of high-quality spatial datasets, there is high uncertainty in the mapping of the permafrost distribution on the TP. In this paper, a new permafrost map was generated mostly based on freezing and thawing indices from modified Moderate Resolution Imaging Spectroradiometer (MODIS) land surface temperatures (LSTs) and validated by various ground-based datasets. The soil thermal properties of five soil types across the TP were estimated according to an empirical equation and in situ observed soil properties (moisture content and bulk density). The Temperature at the Top of Permafrost (TTOP) model was applied to simulate the permafrost distribution. The results show that permafrost, seasonally frozen ground, and unfrozen ground covered areas of 1.06&times;10<sup>6</sup>&thinsp;km<sup>2</sup> (40&thinsp;%), 1.46&times;10<sup>6</sup>&thinsp;km<sup>2</sup> (56&thinsp;%), and 0.03&times;10<sup>6</sup>&thinsp;km<sup>2</sup> (1&thinsp;%), respectively, excluding glaciers and lakes. The ground-based observations of the permafrost distribution across the five investigated regions (IRs, located in the transition zones of the permafrost and seasonally frozen ground) and three highway transects (across the entire permafrost regions from north to south) have been used to validate the model. The result of the validation shows that the kappa coefficient varies from 0.38 to 0.78 with an average of 0.57 at the five IRs and 0.62 to 0.74 with an average of 0.68 within the three transects. Compared with two maps compiled in 1996 and 2006 (kappa coefficients in average 0.06 and 0.35 in five IRs, 0.34 and 0.50 within three transects, respectively), the result of the TTOP modelling shows greater accuracy, especially in identifying thawing regions. Overall, the results provide much more detailed maps of the permafrost distribution and could be a promising basic data set for further research on permafrost on the Tibetan Plateau.
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