Abstract
The Qinghai–Tibet Plateau (QTP) is characterized by its extreme climate and dominated by periglacial processes. Permafrost conditions vary greatly, and the recent changes on the QTP are not well known in the hinterland. Here, we examine the changes in climate and permafrost temperatures in several different regions. Climate data were obtained from three weather stations from 1957 to 2019. Annual mean air temperature (Ta) has gradually increased at .031°C/yr–.039°C/yr. Climate warming has been more rapid in the past two decades, particularly during the cold season (November to February). Precipitation has also been slowly increasing during the instrumental record. However, there is pronounced heterogeneity in the seasonal distribution of precipitation, with very little falling between October and April. Ground temperatures and active-layer thickness (ALT) have been investigated over ∼20 years at five sites representative of the hinterland of the QTP. These sites are located along the Qinghai–Tibet Highway, which crosses the permafrost zone and traverses the mountainous area and basin areas. Annual mean ground temperatures within the active layer (Tal ∼ 1 m depth) indicate recent ground warming at all sites, at rates near .05°C/yr. The ALT at five sites has been increasing steadily by 2–9 cm/yr, with an average of 4.6 cm/yr. The temperature near the permafrost table (Tps) has been increasing at .01°C/yr and .06°C/yr, with an average of .03°C/yr. Permafrost temperatures at 15 m depth (Tg) have been increasing by about .01°C/yr–.02°C/yr. The southern boundary (AD site) of the permafrost has warmed the least among the five locations. In high mountainous areas where permafrost temperatures are low (e.g., KLS site), the annual mean Tg has increased by nearly .02°C/yr. The rate of permafrost warming at a basin site (BLH), with relatively high ground temperatures, was approximately .01°C/yr. The GIPL2.0 model simulation results indicate that the annual mean permafrost temperature at 1 m depth at these sites will increase by .6°C–1.8°C in the next 100 years (to 2100) and that ALT will increase by ∼40–100 cm. We also discuss the impacts of permafrost changes on the environment and infrastructure on the QTP. This study provides useful information to understand observed and anticipated permafrost changes in this region, under different shared socioeconomic pathways, which will allow engineers to develop adaptation measures.
Highlights
Permafrost is ground that remains at or below 0°C for at least 2 years and is primarily a consequence of climate (Henry and Smith, 2001; Smith and Riseborough, 2002)
The mean monthly air temperatures were above 0°C from June to September at three weather stations in most years over the last 60 years
Over 90% of the annual precipitation arrives between May and September, so the hinterland of the Qinghai–Tibet Plateau (QTP) is cold and dry in the winter (Figure 2)
Summary
Permafrost is ground that remains at or below 0°C for at least 2 years and is primarily a consequence of climate (Henry and Smith, 2001; Smith and Riseborough, 2002). Permafrost terrain comprises a seasonally thawed active layer underlain by perennially frozen ground. Climate warming increases the active-layer thickness and ground temperature (Wolfe et al, 2000; Smith and Burgess, 2004). Changes in permafrost conditions associated with climate warming have resulted in widespread thermokarst development (Lin et al, 2010; Niu et al, 2011; Luo et al, 2015), thaw slump (Niu et al, 2014b; 2016), and increased rates of solifluction. During the 20th century, permafrost warming was documented in the mountains of Eurasia (Harris et al, 2003; Isaksen et al, 2007), Northern Canada (Mackay, 1975; Kwong and Gan, 1994; Burn and Zhang, 2009), and Alaska, USA (Lachenbruch and Marshall, 1986; Osterkamp, 2007; Osterkamp and Romanovsky, 2015)
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