Radar Probing of Subsurface Moisture in Barchan Dunes

Sand sheets and barchan dunes are a dominant landscape feature of the hyper-arid deserts of North Africa and the Arabian Peninsula. The ability to characterize their morphology, moisture content, internal layering and structure provides unique insights into both the local and regional paleoclimatic conditions that prevailed during their formation and development. We constrain the moisture content inside barchan dunes and its association to the dune geomorphology, internal structure and evolution by performing a radar attenuation study at the frequency band from 40 to 150 MHz carried on six barchan dunes in Qatar. Our results suggest that the measured average loss across the dune is *10% higher than the expected attenuation for dry sand. The inner parts of the dune show higher losses than its outer parts. When compared to laboratory dielectric losses of desiccated sand, our observations suggest that despite the harsh and arid conditions, these aeolian landforms are capable of maintaining a significant amount of moisture arising from the sparse precipitations, several meters deep under their surface. We examine how such moisture content impacts the dunes’ dynamics and implications for understanding precipitation variability through the Holocene.