The paleoclimatic environment reconstruction of Lop Nur in NW China in UAV spectroscopy

The change in the ecological environment in the arid core area is a critical issue in the context of global warming. To study the paleoclimate evolution, precise identification of minerals deposited in Asia's arid hinterland, Lop Nur Salt Lake, NW China was conducted. The hyperspectral data of the salt crust was sampled to identify the species and content of sedimentary minerals, and the multispectral photos were used to reconstruct the salt crust morphology using the unmanned aerial vehicles platform. The SUnSAL (sparse unmixing by variable splitting and augmented Lagrangian) method was employed to inverse the sedimentary mineral components along the shoreline. The heterogeneity of salt and clay minerals in bright and dark ear-shaped strips was evaluated. The paleoclimatic environment associated with salt lake extinction was reconstructed by analyzing paleoclimate records of sediments, spectral reflectance and morphology of the salt crust. Results show that: (1) the variations in the micro-geomorphology of the salt crust are obviously the reason for the formation of bright and dark ear-shaped strips and the differences in the species and relative content of the sedimentary minerals are the microscopic reason. The high ratio of sedimentary salt minerals to clay minerals (R-S/C) contributes to the high reflectivity, and the salt crust presents a bright texture. The low R-S/C results in the low reflectivity, salt crust presents a dark texture; (2) the bright and dark ear-shaped strips represent warm-arid and cold-humid climates. The shape of the Lop Nur Lake shoreline evolved due to alternating warm-dry and cold-humid paleoclimate changes.