The coupled moisture-heat process of permafrost around a thermokarst pond in Qinghai-Tibet Plateau under global warming

Due to environmental disturbances such as local human activity and global warming, melting of massive ground ice has resulted in thermokarst ponds, which are extensively distributed in the Qinghai-Tibet Plateau (QTP). Besides the global warming, the thermokarst pond, as a major heat source, speeds up the moisture change and degradation of its surrounding permafrost. To analyze the long-term coupled moisture-heat process near a representative nonpenetrative thermokarst pond in a permafrost region, abundant temperature data over multiple years at different depths and horizontal distances from the center of the thermokarst pond have been collected at a field experimental station in QTP. A numerical model is built to analyze this thermokarst pond. The temperature and moisture processes of surrounding permafrost are simulated by this model and compared with measured temperature data. Our results show that if the rate of air temperature rise is 0.048 degrees C/yr, which refers to a 2.4 degrees C temperature rise over 50years, the thawing fronts underneath the thermokarst pond move downward at a linear rate of 0.18m/yr and the permafrost beneath the pond center would disappear after the year of 2281. Beyond that time, the impact range of the pond on the natural ground increases to about 50m in horizontal direction. So a dish-shape thawing zone occurs around the thermokarst pond. Simultaneously, the moisture state is greatly changed in 2281 and becomes completely different from that in 2013. All of these would inevitably deteriorate the ecological and environmental system in QTP.