Permafrost Deformation Model Establishment And Active Layer Thickness Inversion Based On SBAS-InSAR

Permafrost is an important part of the cryosphere which is one of the five spheres of the earth. With the global warming, the permafrost in Qinghai-Tibet plateau degenerates significantly, such as the permafrost area reduction and active layer thickness increase, which have a profound impact on ecological environment, hydrological environment, economic construction, engineering construction and people’s life, etc. Thus large area, high precision of permafrost monitoring is of great significance to study global climate change and guarantee people’s life and property security in cold area.Although traditional small baseline subset interferometry can be able to monitor permafrost deformation, its linear deformation model is not suitable to describe permafrost deformation, and how to obtain permafrost active layer thickness using InSAR technique is still a hot research topic. Thus we propose a new permafrost deformation model with regard to climate factor influence to get frozen soil deformation, and then develop the algorithm of permafrost active layer thickness inversion based on permafrost deformation. The main research contents and contribution of this paper are as follows:(1) By analyzing the influence that internal factors, such as soil and geological tectonic activities, and external climate factors have on permafrost deformation, we establish permafrost deformation model with regard to climate factors to acquire the deformation time series of permafrost area based on SBAS-InSAR. The annual cycle permafrost deformation in the study area is between4-5.5cm, and along Qinghai-Tibet railway and Qinghai-Tibet highway annual cycle deformation is between3-4cm. And the negative correlation between permafrost deformation and the temperature and precipitation reach0.61and0.91, respectively.(2) Permafrost deformation model with regard to climate factors is applied to acquire the permafrost deformation time series based on SBAS-InSAR. Then simplify the algorithm of deformation of embankment along Qinghai-Tibet Railway to obtain the thawing depths with the hypothesis that permafrost subsidence is due to thawing of ice in the permafrost active layer, and further calculate permafrost tables in the study area. Numerical calculation indicates that, the range of permafrost tables of Ning Zhong basin are0-223cm and0-364cm, respectively in2007and in2010. the range of permafrost tables mean are102-153cm in2007and108-1.58cm, in2010.(3) As a whole, the permafrost tables of Ning Zhong basin decrease from the low-lying central basin to high altitude. And the permafrost tables in August2010increase than that in August2007. According to this result, we can obtain that the permafrost tables go down at the mean speed of1～2cm/a, and the increment of active layer will be about0.9-1.8m after one hundred years, which will influent the ecological environment and engineering construction in the study area, and also threat the safe operation of the Qinghai-Tibet highway.