Synoptic- to meso-scale circulation connects fluvial and coastal gravel conveyors and directional deposition of coastal landforms in the Dead Sea basin

Streams convey coarse-clastic sediments towards coasts, where interactions with deltaic and coastal processes determine the resultant landscape morphology. Although extracting hydroclimatic signals from landscapes is a desired goal, many studies rely on interpreting paleoclimatic proxies and the link between depositional/geomorphic processes and the hydroclimate remains vague. This is a consequence of the challenge to link processes that often are studied separately, span across large spatial and temporal scales including synoptic-scale hydroclimatic forcing, stream flows, water body hydrodynamics, fluvial and coastal sediment transport, and sedimentation. Here, we explore this chain of connected processes in the unique setting of the Dead Sea basin, where present-day hydroclimatology is tied closely with geomorphic evolution and sediment transport of streams and coasts that rapidly respond to lake-level fall. We use a five-years-long (2018-2022) rich dataset of (i) high-resolution synoptic-scale circulation patterns, (ii) continuous wind-wave and rain-floods records, and (iii) storm-scale fluvial and coastal sediment transport of varied-mass, ‘smart’ and marked boulders. We show that Mediterranean cyclones approaching the eastern Mediterranean are the main circulation pattern that can provide sufficient rainfall and winds that concurrently activate two perpendicular sediment conveyors: fluvial (floods) and coastal (wind-waves). The synoptic-scale westerlies (>10 m s^-1) are orographically funneled inside the Dead Sea rift valley, turning into surface southerlies. They generate 10-30 high-amplitude northward propagating storm waves per winter, with <4 m wave height. Such storms transport cobbles for hundreds of meters alongshore, north of the supplying channel mouths. Towards the decay of the storm wave, the high-altitude synoptic westerlies provide moisture to generate 4-9 flash-floods, delivering unsorted coarse gravels into the basin. These gravels are dispersed alongshore by waves only during subsequent storms. As storm waves dominates and are >five times more frequent than flash-floods, coarse-clastic beach berms and fan-deltas are deposited preferentially north of channel mouths. This depositional architecture, controlled by regional hydroclimate, 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 since the Late Pleistocene when Lake Lisan occupied the basin.