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

Abstract

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°C/yr, which refers to a 2.4°C temperature rise over 50 years, the thawing fronts underneath the thermokarst pond move downward at a linear rate of 0.18 m/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 50 m 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.

Lake Volume Monitoring from Space

“…In general, the magnitude of precipitation changes is too low to explain water level increasing a few decimeters per year as noted by Zhang et al (2011a). The impact of climate change on water resources over the TP is therefore very complex: a mix not only of direct precipitation changes and evaporation increase under a warming climate, but also of glaciers, snow, and thickening of the active layer of the permafrost, which increase surface and underground inflow to the lakes (Ma et al 2010;Liu et al 2009a;Kang et al 2010;Huang et al 2011;Zhang et al 2011a;Li et al 2014;Song et al 2014c;Zhang et al 2015). The decrease in the frozen duration due to warming, which is very pronounced in winter time, also increases the potential contribution of permafrost to lake storage changes (Huang et al 2011;Li et al 2008;Liao et al 2013).…”

“…It could be focused on a specific subregion of the TP concerning an individual or limited number of lakes such as lakes Namco and Ziling that were studied in Wang et al (2013), Li et al (2014), Song et al (2015), Ngoring-co by Lee et al (2011), Liao et al (2013, Ngangze and La'anga from Hwang et al (2005) and many others (along with references in the papers cited before). Since 2010 several authors have studied lake level changes and their connection to climate change using satellite altimetry and/or satellite imagery as a principal source of information for the whole TP (Liu et al 2009a;Zhang et al 2011a;Phan et al 2011;Huang et al 2011;Song et al 2014b;Kleinherenbrink et al 2015).…”

Experimental and numerical investigations on frost damage mechanism of a canal in cold regions

“…In multi-dimension stress state, the viscoplastic strain rate is given by a general expression (Li et al, 2014b;Owen and Hinton, 1980).…”

“…The moisture-heat module of the software has been well used in some references (Li et al, 2014a(Li et al, , 2015. In addition, the moisture, temperature, stress and displacement states of an actual canal were successfully modeled by this software (Li et al, 2014b).…”

“…The following expressions can describe the change of hydraulic conductivity and diffusivity with water content and include an impedance factor to account for the effect of ice at temperature below freezing (Harlan, 1973;Jame and Norum, 1980;Newman and Wilson, 1997). where a 2 , b 2 , a 3 and b 3 are constants and are listed in Table 1 Li et al, 2014b;Xu et al, 2010;Zhong et al, 2012). Because of its direct influence on the amount of unfrozen water and on the strength of intergranular ice in a frozen soil, temperature has a marked effect on all aspects of its mechanical behavior.…”