Paleohydrology and Paleoclimate of Arabian Peninsula
The Arabian Peninsula witnessed alternating wet and dry periods during the previous wet periods, precipitation was much more intense than nowadays, extensive wadi networks developed, groundwater levels rose, natural discharge increased, and paleolakes developed. The paleochannels were mapped using deep-penetrating PALSAR data, whereas the modern channel networks were derived from DEM and from high resolution VNIR data. The configuration of the stream networks was different that observed nowadays, the paleochannel networks were denser and their streams were wider compared to the modern stream networks and channels. The encroachment of the sand sheets and dunes covered the paleochannels and controlled the distribution of the ephemeral valleys. The rise in groundwater levels during the previous wet climatic periods gave rise to excessive groundwater discharge in depressions where the water table exceeded the surface elevation. In these areas paleolakes developed. The distribution of a number of these lakes across the Arabian Peninsula was accomplished by mapping the depressions (from DEM) and identifying the spectral signature of lake deposits (from VNIR bands). One of these paleolakes is found in the eastern parts of the Empty Quarter. Not only did the rising groundwater give rise to paleolakes but to massive sapping features across the Arabian Peninsula. These features correlated with the distribution of faults, cliffs, springs, and the onset of paleochannels. All of these spatial observations support the suggestion that sapping formed by ascending groundwater via deep-seated faults in previous wet periods. The areal distribution of these features was mapped using statistical methods (regression analysis). Finally, our preliminary investigations imply that the morphologic features (e.g., stream network density, stream width, sapping features) that are indicative of wet periods were more pronounced in the northern parts of the Arabian Peninsula compared to the southern parts, perhaps due to the intensification of the northerly wind regimes.