The Nanwenghe Wetlands Reserve in the Yile'huli Mountains is a representative region of the Xing'an permafrost. The response of permafrost to climate change remains unclear due to limited field investigations. Thus, longer-term responses of the ground thermal state to climate change since 2011 have been monitored at four sites with varied surface characteristics: Carex tato wetland (P1) and shrub-C. tato wetland (P2) with a multi-year average temperatures at the depth of zero annual amplitude (T-ZAA) of -0.52 and -1.19 degrees C, respectively; Betula platyphylla-Larix gmelinii (Rupr.) Kuzen mixed forest (P3) with T-ZAA of 0.17 degrees C, and; the forest of L. gmelinii (Rupr.) Kuzen (P4) with T-ZAA of 1.65 degrees C. Continuous observations demonstrate that the ecosystem-protected Xing'an permafrost experienced a cooling under a warming climate. The temperature at the top of permafrost (TTOP) rose (1.8 degrees C per decade) but the T-ZAA declined (-0.14 degrees C per decade), while the active layer thickness (ALT) thinned from 0.9 m in 2012 to 0.8 m in 2014 at P1. Both the TTOP and T-ZAA increased (0.89 and 0.06 degrees C per decade, respectively), but the ALT thinned from 1.4 m in 2012 to 0.7 m in 2016 at P2. Vertically detached permafrost at P3 disappeared in summer 2012, with warming rates of +0.42 and + 0.17 degrees C per decade for TTOP and T-ZAA, respectively. However, up to date, the ground thermal state has remained stable at P4. We conclude that the thermal offset is crucial for the preservation and persistence of the Xing'an permafrost at the southern fringe.

The Cryosphere has been undergoing a worldwide retreat, as seen in the decrease in the areal extent and volume of glaciers and in the areal extent of permafrost. This paper presents a systematic examination of the inherent stability changes of glaciers and permafrost caused by warming. Various study results suggest that over the past 30 years, the internal temperature of glaciers and permafrost exhibits an overall accelerating warming trend. The warming rate peaked in the mid-2000s and slowed slightly for several years afterward. In recent years, however, the warming rate has seemed to pick up again. The warming of glaciers and permafrost has exerted great impact on their stability, displayed as intensified melting, increased glacier surging, enlargement of supraglacial lakes, and increased permafrost degradation. Even without a future temperature increase, some glaciers will continue to shrink, and the number of surging glaciers will increase. The transition from low-temperature to high-temperature permafrost is a noticeable warning sign of a comprehensive degradation of permafrost. These results indicate that warming glaciers and permafrost will exert significant impacts on the hydrology, ecology, and stability of engineering in cold regions. (C) 2019 Science China Press. Published by Elsevier B.V. and Science China Press. All rights reserved.

Beiluhe basin is underlain by warm and ice-rich permafrost, and covered by vegetation and soils characteristic of the Qinghai-Tibet Plateau. A field monitoring network was established to investigate permafrost conditions and to assess potential impacts of local factors and climate change. This paper describes the spatial variations in permafrost conditions from instrumented boreholes, controlling environmental factors, and recent thermal evolution of permafrost in the basin. The study area was divided into 10 ecotypes using satellite imagery based classification. The field investigations and cluster analysis of ground temperatures indicated that permafrost underlies most of the ground in swamp meadow, undisturbed alpine meadow, degrading alpine meadow, and desert alpine grassland, but is absent in other cover types. Permafrost-ecotope relations examined over a 2-year (2014-2016) period indicated that: (i) ground surface temperatures varied largely among ecotopes; (ii) annual mean ground temperatures ranged from 1.5 to 0 degrees C in permafrost, indicating sensitive permafrost conditions; (iii) active-layer thicknesses ranged from 1.4 m to 3.4 m; (iv) ground ice content at the top of permafrost is high, but the active-layer soil is relatively dry. Long-term climate warming has driven thermal changes to permafrost, but ground surface characteristics and soil moisture content strongly influence the ground thermal state. These factors control local-scale spatial variations in permafrost conditions. The warm permafrost in the basin is commonly in thermal disequilibrium, and is sensitive to future climate change. Active-layer thicknesses have increased by at least 42 cm and the mean annual ground temperatures have increased by up to 0.2 degrees C in the past 10 years over the basin. A permafrost distribution map was produced based on ecotypes, suggesting that permafrost underlies 64% of the study region.

Alpine permafrost is particularly sensitive to climate change, since it's temperature is often close to the melting point of ice. In summer 1987, several hundred debris flows caused considerable damage and several victims in the Swiss Alps. Analysis showed that one out of three debris flows started at the lower boundary of mountain permafrost. A 58m deep borehole through creeping permafrost was drilled in 1987 near Piz Corvatsch (Upper Engadine, Swiss Alps). Temperatures have been measured regularly since then. Comparisons of two permafrost boreholes some 20km apart, where temperatures were measured once a year, indicated at least the regional character of the signal. Between 1987 and 1994, the uppermost 25m warmed rapidly. Surface temperature is estimated to have increased from -3.3 degreesC (1988) to -2.3 degreesC (1994), thereby probably exceeding previous peak temperatures during the 20th century. In the two-year period from 1994 to 1996, when winter snowfall was low, intensive cooling of the ground occurred, the temperatures reaching values similar to those in 1987. Since 1996, permafrost temperatures have once again been raising, followed by a cooling last winter. The variability of the observed permafrost temperatures is caused by several processes, including: (1) a reduced period of negative temperatures within the active layer due to long-lasting zero-curtains in autumn; (2) global radiation and air temperature changes influencing ground temperatures mainly in summer; and (3) variations in the duration of winter snow-cover. If the observed warming trend in alpine mountain permafrost temperatures continues into the foreseeable future, widespread permafrost degradation is likely, with potentially serious consequences with regard to mountain slope instability.