Permafrost

temperature variability throughout the year and high precipitation. Simple air temperature
modelling and continuous ground temperature measurements in four boreholes (up to 22 m
depth) combined with DC resistivity tomography document warm, thin, but wide-spread
mountain permafrost at altitudes above 850 to 900 m a.s.l., at least in wind-blown areas.
Numerical modelling of ground temperatures indicates that the permafrost is highly sensitive to
climate variations, and modelled permafrost variations based on empirical derived time series
back to the 1950ies are presented.
At Banak airport (5 m a.s.l.) close to our field area in Gaissane mountains, Finnmark,
northern Norway, MAAT is 0.6°C, annual range of temperature 22°C and mean annual
precipitation 345 mm. The field area constitutes a range of periglacial landforms, which
includes rock glaciers, palsas, fossile ice wedge polygons, patterned ground, ploughing
boulders and solifluction lobes. Bottom Tempereature of Snow cover (BTS) measurements, a
network of ground surface temperature data loggers and extensive geophysical soundings
indicate lower permafrost limit of nearly 400 m a.s.l. in north facing slopes, and permafrost
distribution seems to be more dependent on incoming solar radiation than what is known from
southern Norway.
In both areas, the investigations indicate more wide-spread permafrost than anticipated
earlier, which has wider implications on geomorphological processes, landscape development
and responses to present climate change.
Keywords: Permafrost; Thermal regime; Periglacial geomorphology; DC resistivity
tomography; Iceland; Norway
Degradation of Permafrost in the Da- and Xiao-Xing’anling Mountains,
Northeastern China and Assessment of Its Trends
172
Hui-jun Jin, Shao-peng Yu, Rui-xia He, Yan-jun Ji, Si-zhong Yang, Zhi Wei, Dong-xin Guo, and
Ying-wu Li
(State Key Laboratory of Frozen Soils Engineering, Cold and Arid Regions Environmental and
Engineering Research Institute, Chinese Academy of Sciences, 326 West Donggang Road, Lanzhou,
China 730000)
Abstract: Permafrost in the Xing’anling Mountains in northeastern China is warm, thin,
thermally unstable and subsequently sensitive to climatic warming. During the past 40 years,
permafrost has been degrading as evidenced by the deepening active layer, thinning of
permafrost, rising ground temperatures, expansion of taliks, and disappearance of permafrost
islands. Detailed analyses indicate that climatic warming and sharp reduction of forest coverage
during the past century are the general and basic reasons for the degradation of permafrost, and
increasing human activities have been accelerating the retreat of permafrost. Based on the close
correlations between the southern limit of permafrost (SLP) and multi-year average air
temperatures (MYAAT), present positions of the SLP are delineated using the MYAAT
isotherms of -1.0 to +1.0ºC during the 1999-2000 decade. The SLP would shift northwards
upon a warming of 1.0 to 1.5ºC during the next 40~50 years, but with significant uneven