Spatiotemporal variability of permafrost degradation on the Qinghai-Tibet Plateau

Based on data from six meteorological stations in the permafrost regions, 60 boreholes for long-term monitoring of permafrost temperatures, and 710 hand-dug pits and shallow boreholes on the Qinghai-Tibet Plateau (QTP), the spatiotemporal variability of permafrost degradation was closely examined in relation to the rates of changes in air, surface, and ground temperatures. The decadal averages and increases in the mean annual air temperatures (MAATs) from 1961-2010 were the largest and most persistent during the last century. MAATs rose by 1.3.degrees C, with an average increase rate of 0.03.degrees C/yr. The average of mean annual ground surface temperatures (MAGSTs) increased by 1.3.degrees C at an average rate of 0.03.degrees C/yr. The rates of changes in ground temperatures were -0.01 to 0.07. C/yr. The rates of changes in the depths of the permafrost table were -1 to + 10 cm/yr. The areal extent of permafrost on the QTP shrank from about 1.50x106 km2 in 1975 to about 1.26x106 km2 in 2006. About 60% of the shrinkage in area of permafrost occurred during the period from 1996 to 2006. Due to increasing air temperature since the late 1980s, warm (>-1.degrees C) permafrost has started to degrade, and the degradation has gradually expanded to the zones of transitory (-1 to -2.degrees C) and cold (<-2.degrees C) permafrost. Permafrost on the southern and southeastern plateau degrades more markedly. It is projected that the degradation of permafrost is likely to accelerate, and substantial changes in the distributive features and thermal regimes of permafrost should be anticipated. However, regarding the relationships between degrading permafrost and the degradation of rangelands, it is still too early to draw reliable conclusions due to inadequate scientific criteria and evidence.