Understanding saline lake sand dunes dynamics: Coupling remote sensing techniques and field studies

Abstract

Large saline lakes, a benchmark for natural and anthropogenic fluctuations in the Earth's climate system, are drying up worldwide at accelerated rates. This study focuses on Lake Urmia, the world's second-largest hypersaline lake that indicates significant environmental challenges as it approaches near-complete dryness. Over the last decade, new aeolian features, including sand dunes, have emerged due to anthropogenic and natural factors. The present study documents the dynamics of recent aeolian processes on exposed dried-up lakebeds of saline lakes environments by investigating their mineralogy, geochemistry, and sedimentology to understand better dune morphology, evolution and migration rate. Quantitative analyses are performed on the dunes of Lake Urmia's western shores using ancillary data (meteorological and climate), field data, X-Ray Diffraction, Scanning Electron Microscopy and Energy Dispersive X-rays Spectroscopy (SEM - EDX), petrographic analysis, and supervised classification and change detection of satellite imagery from 2003 to 2019. The migration rates yielded high values, approximately above 20 m yr−1 on average, mostly related to (1) the rising drift potential (DP), (2) the percentage of wind speeds that are above the threshold velocity (V > Vt%), (3) decline in precipitation and unidirectional wind regime and (4) atmospheric circulations over the Mediterranean Sea. The results infer that local and global-scale factors significantly impact the migration rate of Lake Urmia dunes. The study outcomes are widely applicable to drying up saline lakes worldwide, enhancing the understanding of current aeolian processes and the evolution of dune fields/sand seas, building towards sustainable land management and policy-making.