Morphodynamics of barjanoid and longitudinal dune systems in an arid coastal desert (Atacama, Chile)

Coastal dune systems in (hyper)arid environments provide exceptional natural laboratories for studying aeolian morphodynamics and sediment routing. In the southern Atacama Desert (Chile), a barjanoid dune field and two longitudinal dunes located in close proximity form a highly dynamic inland‑migrating system sourced from coastal sands redistributed by persistent SW winds. In this study, we digitized these dune types from multitemporal satellite imagery from 2005 to 2023 and analysed their 18-year spatio-temporal evolution, focusing on migration rates, morphometric characteristics and the geomorphic controls that govern their trajectories. The barjanoid dune field consists of 4–5 sinuous crests perpendicular to the prevailing winds whose migration rates vary significantly according to their position relative to a Late Pleistocene marine terrace. Crests located on the terrace slope exhibit low net migration (Net Shoreline Movement [NSM]: 3–36 m; Linear Regression Rate [LRR]: 1.14–2.35 m/yr), whereas those that have surpassed the topographic break show markedly higher displacement (NSM: 49–59 m; LRR: 3.80–4.21 m/yr). This sharp contrast demonstrates that terrace gradients act as temporary sediment traps, delaying crest propagation until the accumulation threshold is overcome. To the east of the barjanoid dune field, both longitudinal dunes, parallel and approximately 75 m apart, emanate from a sediment source just landward of the marine terrace, and show sinuous crests that reflect a slightly bi-directional wind regime. However, the first one displays significantly shorter length and faster migration rates than its counterpart to the east (630 and 1275 m and 6.75 and 4.7 m/yr, respectively). These differences, which need further investigation, may reflect variations in proximity to the barjanoid dune field acting as a dynamic sediment supplier, as well as pronounced disparities in dune dimensions, likely reflecting distinct formation times. Additionally, it was observed that both longitudinal dunes could originate from the barjanoid dune crests surpassing the marine terrace and rotating to be aligned with the prevailing wind direction. Together, these results reveal a morphodynamic system strongly conditioned by sediment supply pathways, topographic barriers and inherited deposits. The contrasting behaviours observed suggest sequential formation phases and spatial reorganization of the aeolian system. Integrating migration rates, sediment pathways and terrace-controlled dynamics offers new insights. These findings improve our understanding of coastal dune evolution in tectonically active, sediment-limited arid coasts. The authors thank project PID2021-127268NB-I00 funded by MCIN/AEI /10.13039/501100011033 and by FEDER/UE.