The consistency between Na content distribution at the subsurface and the lake body’s movement in Lop Nur

Abstract

Historically, Lop Nur was a large and famous salt lake that acted as an important geographic position along the ancient ‘Silk Road’, and was associated with the surrounding old civilizations, such as Loulan and Haitou. However, it dried up before 1972. It shows a clear ‘Ear’ feature on synthetic aperture radar (SAR) images. The objective of this paper is to interpret Lop Nur's environmental evolution during its drying-up process based on an analysis of its sodium sedimentary feature. The genetic algorithm-partial least squares approach is introduced as a modeling method to retrieve the subsurface sodium content from polarimetric parameters obtained by Cloude decomposition. As a result, the R2 and root-mean-square error can reach 0.7 and 9.1 g/kg. It is suggested that the subsurface salt content was the primary reason for the bright-grey strips textures on SAR images. Furthermore, our results show that the sodium content along the same strip changed, with its distribution exhibiting consistency with the lake body's movement driven by the strong wind. In future, high-precision topographical data will be considered, and should be helpful in the analysis of lake body movement. The method of this paper can also be applied in other similar dried salt lakes.