Estimating contribution of permafrost to lake expansion by SBAS-InSAR: a case study from Hohxil Lake basin in the Tibetan Plateau

Abstract

Due to climate warming and increased precipitation, the permafrost of the Tibet Plateau (TP) has undergone serious degradation along with obvious lake expansion in recent decades. Model simulation is often used to analyze the contribution of permafrost melting to lake expansion, which may have many limitations. Taking Hohxil Lake (HL) basin over north TP as an example, this study makes full use of Sentinel-1 images by an improved small baseline subset interferometric technique (SBAS-InSAR), monitors the permafrost deformation from 2015 to 2020, and estimates its contribution to the lake expansion. The results show that the permafrost settlements mainly occur in the flat terrain around HL. The average line of sight (LOS) de-formation rate of permafrost is -3.59 ± 0.001 cm/yr, where there existed many obvious funnel-shaped thawing areas around the lake, indicating a close relationship between lake expansion and permafrost under-ground ice melting. The long-term linear deformation rate of underground ice is inverted by the traditional linear model, and the melting rate is estimated to be (31.17 ± 0.0054) ×106 m3/yr with 9.3% contribution to the HL expansion. This study takes full advantage of Interferometric Synthetic Aperture Radar (InSAR) to quantitatively analyze the contribution of permafrost to lake expansion, which provides a new insight into the study of permafrost hydrological process and the proposed method can be easily extended to analyze lake water budget for underground ice in other watershed over the TP.