GEOSPATIAL ANALYSIS OF CLIMATIC BOUNDARY CONDITIONS GOVERNING DUNE ACTIVITY

Inland sand dunes occur in a wide spectrum of states, from un-vegetated “active” dunes to vegetation-stabilized “inactive” dunes. Understanding the climatic and geomorphic boundary conditions that govern dune “activity” has until now been hampered by the lack of pertinent observational data on boundary conditions and dune status for most dune areas.

We have combined the results of digital mapping of dune field and sand sea extent (Hesse et al., 2015) with: (1) systematic observations of dune activity at 0.2° intervals from high resolution satellite image data, grouped into four categories to produce global, regional, and intra-dunefield maps of dune activity status; (2) global gridded datasets for precipitation and the aridity index (AI) (Trabucco and Zomer, 2009), satellite-derived percent vegetation cover (Broxton et al., 2014), and (3) estimates of sand transport potential (DP) (Ashkenazy et al., 2011) in a GIS based approach that analyzes boundary conditions at a range of spatial scales from dunefield to global. In addition, we have developed a revised climatic index of sand mobility based on the gridded DP and AI datasets.

Our results indicate that at a regional scale, observed dunefield-average activity state is negatively correlated with the revised climatic index of sand mobility. On an intra-dunefield scale, local (individual grid cell) dune activity state is negatively correlated with local interpolated mobility index, which also correlates well with local vegetation cover percentage.

Our analyses so far indicate the potential of this approach for understanding dune activity and relationships to boundary conditions that can be used to assess responses to climate change and variability past, present, and future.

References

Ashkenazy, Y., Yizhaq, H., Tsoar, H., 2011. Climate Change, 112(3-4), 901-923.

Broxton, P.D., Zeng, X., Scheftic, W., Troch, P.A., 2014. Journal of Applied Meteorology and Climatology, 53(8), 1996-2004.

Hesse, P., Lancaster, N., Telfer, M.W., 2015. Geophysical Research Abstracts, 17(EGU General Assembly 2015), EGU2015-3638.

Trabucco, A., Zomer, R.J., 2009. Global Aridity Index (Global-Aridity) and Global Potential Evapo-Transpiration (Global-PET) Geospatial Database. CGIAR Consortium for Spatial Information, CGIAR-CSI GeoPortal - http://www.csi.cgiar.org/.