基于遥感影像的祁连山区俄博岭热融滑塌发育特征

CHARACTERISTICS OF THAW SLUMPS OVER EBOLING AREAS IN QILIAN MOUNTAINS USING REMOTE SENSING DATA

热融滑塌是山地多年冻土退化最直接的表现形式之一,通过解译祁连山俄博岭地区遥感影像,结合实地考察,对俄博岭热融滑塌的空间分布和时间变化进行了研究,明确了热融滑塌的发育特征。结果表明,俄博岭热融滑塌发育活跃,1997~2015年热融滑塌数量增加(11~13个),面积增大(7765~20605m^2),其中1997~2009年面积增加速率为679.9m^2/a,2009~2015年面积增加速率为780.2m^2/a。通过分析热融滑塌景观分布与地形因子的关系,发现俄博岭热融滑塌在海拔3570~3700m,坡度3°~10°的富冰多年冻土区北向斜坡发育;通过对典型热融滑塌溯源后退速率分析发现,1997~2009年其平均后退速率为2m/a,2009~2015年平均后退速率为5m/a,呈明显增大趋势,且其后退速率主要与坡度、地下冰含量和地表径流相关。

Thaw slumps or thermokarst in general are the most direct manifestations of permafrost degradation in cold regions. Development of thaw slumps and thermokarst terrains has significant impact on surface energy balance, surface and subsurface hydrological processes, vegetation, soil carbon fluxes, geomorphological processes, and engineering constructions. The objective of this study is to investigate the occurrence and development of thaw slumps and thermokarst terrains in northern Tibetan Plateau during the past few decades. Aerial photographs in 1997 and satellite imageries in 2009 and 2015 were used to analyze creation and expansion of thaw slumps and thermokarst terrains. Field survey was conducted during the summers of 2016 and 2017 to validate the results from aerial photographs and satellite imageries. The results show that there were 13 active thaw slumps over Eboling areas in Qilian Mountains of northern Tibetan Plateau in 2015. Thaw slumps are mainly developed at elevation between 3570 m and 3700 m above sea level on north-facing slopes with slope angles varying from 3°~10°.Based on remote sensing data, the total thaw slump covered area increased from 7765 m^2 to 20605 m^2 over a period from 1997 through 2015 with an average rate about 713.3 m^2/a. However, the rate expansion of thaw slump area was about 679.9 m2/a from 1997 through 2009 and increased to 780.2 m^2/a from 2009 through 2015. The retrogressive erosion rate toward the upper slope was about 2 m/a during 1997 through 2009 period and increased about 5 m/a during 2009 to 2015 period. The controlling factors for retrogressive erosion rate were slope angles, ground ice content and surface water runoff.