T210 Advances in Arid Lands Geomorphology

Tuesday, 24 September 2024
1:30 PM - 5:30 PM
210B

SYNOPTIC-SCALE TO MESOSCALE ATMOSPHERIC CIRCULATION CONNECTS FLUVIAL AND COASTAL GRAVEL CONVEYORS AND DIRECTIONAL DEPOSITION OF COASTAL LANDFORMS IN THE DEAD SEA BASIN

Paper number: T210-11
Program: Technical Sessions
Time: 4:15 PM – 4:30 PM

Authors

Abstract

Streams convey coarse-clastic sediments towards coasts, where interactions with deltaic and coastal processes determine their resultant sedimentology and geomorphology. Extracting hydroclimatic signals from such environments is a desired goal, and therefore, studies commonly rely on interpreting available paleoclimatic proxy data, but the direct linking of depositional/geomorphic processes with the hydroclimate remains obscure. This is a consequence of the challenge to link processes that often are studied separately, span across large spatiotemporal scales including synoptic-scale hydroclimatic forcing, stream flows, water body hydrodynamics, fluvial and coastal sediment transport, and sedimentation. Here, we explore this chain of processes in the unique setting of the Dead Sea basin, where present-day hydroclimatology is tied closely with geomorphic evolution of streams and coasts that rapidly respond to lake-level fall. We use a five-years-long rich dataset of (i) synoptic-scale circulation patterns, (ii) wind-wave and rain-floods records, and (iii) storm-scale fluvial and coastal sediment transport of ‘smart’ and marked boulders. We show the significance of Mediterranean cyclones in the concurrent activation of fluvial and coastal sediment conveyors. These synoptic-scale patterns drive the westerlies necessary for (i) delivering the moisture across the Judean desert, which is transformed into floods, and at the same time, (ii) the coeval, topographically funneled winds that turn into surface southerlies (>10 m s-1), along the Dead Sea rift valley. During winter, these meso-scale southerlies generate 10-30 high-amplitude, northward propagating storm waves, with <4 m wave heights. Four to nine times per winter the rainfall generated by these atmospheric patterns is capable of generating floods that reach the stream mouths, delivering poorly sorted, coarse gravels. As storm waves dominate, coarse-clastic beach berms and fan-deltas are deposited preferentially north of the delivering channel mouths. This asymmetric depositional architecture, controlled by the regional hydroclimatology, is identified for both the modern and Late Pleistocene coast and delta environments, implying that the dominance of present-day Mediterranean cyclones has persisted in the region also during the Late Pleistocene when Lake Lisan occupied the basin.

Geological Society of America Abstracts with Programs. Vol. 56, No. 5

doi: 10.1130/abs/2024AM-402664

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