Linking aeolian geomorphology with climate for the Karakum and Kyzylkum Deserts

<p>Much geomorphological research has been conducted on the origin and evolution of sand seas, some of which focused on categorizing dune types, some determining past climatic conditions using Optically Stimulated Luminescence (OSL) dating, and some, understanding dune patterns and stability in relation to the current climate. Sand seas are, in essence, climate archives. Even though the central Asian sand seas, Karakum and Kyzylkum, occupy more than 450.000 km2, relatively little climatic research has been conducted on the formation and evolution of these aeolian deserts. The meteorological data (current & historical) for these regions is scarce and incomplete. Moreover, the area is not extensively recognized in the worldwide available aeolian literature, which has little information about its climatic performances. Using the common method for the examination of wind data—Fyberger’s Drift Erosion equations (1979) and the most recent Copernicus ERA5 wind reanalysis model conducted on 5081 control grid points, we show that both the Karakum and Kyzylkum Deserts are and have been low-energy environments for the statistical period 1950–2019. The data set was transferred into the form of a space-time cube, a multidimensionally-orientated raster, enabling time-series analysis and data mining. Such analysis has revealed that 93% of the desert was under a low-energy wind setting during the past 70 years. The directionality index shows that erosive winds didn’t deviate extensively from their primal directions as observed from the same statistical period. Such performance favors vegetation growth and biogenic crust development, thus, dune stabilization. Alongside, a similar type of procedure was performed for the wind data obtained from NOAA weather stations that are at close distance or within the study area. Both data sets were mutually analyzed with respect to the Resultant Drift Direction (RDD) calculated for the period 2010-2019 and all available portions of time. By comparing dune orientation and characteristics of their current morphology to the wind directions, the results indicate that the morphology of active aeolian features, (e.g. complex barchanoid ridges, star and seif dunes) are in high correlation with current winds and their erosive powers. Simultaneously, stable aeolian formations that overlay most of the observed area (determined as different formations of Vegetated Linear Dunes - VLDs) show disassociation between the dune's orientation and the wind power (RDP), direction (RDD) and variability (UDI), confirming that most of the vegetated aeolian formations were not developed, or presently reworked, by contemporary winds. An analysis of wind parameters in both active and stable aeolian morphologies in these deserts has permitted the discovery of present and paleo-wind interactions, as well as putative paleo-environmental climatic conditions.</p>