Hydroclimatic variability of opposing late Pleistocene climates in the Levant revealed by deep Dead Sea sediments

Annual and decadal-scale hydroclimatic variabil- ity describes key characteristics that are embedded into cli- mate in situ and is of prime importance in subtropical re- gions. The study of hydroclimatic variability is therefore cru- cial to understand its manifestation and implications for cli- mate derivatives such as hydrological phenomena and wa- ter availability. However, the study of this variability from modern records is limited due to their relatively short span, whereas model simulations relying on modern dynamics could misrepresent some of its aspects. Here we study an- nual to decadal hydroclimatic variability in the Levant using two sedimentary sections covering ~ 700 years each, from the depocenter of the Dead Sea, which has been continuously recording environmental conditions since the Pleistocene. We focus on two series of annually deposited laminated in- tervals (i.e., varves) that represent two episodes of opposing mean climates, deposited during MIS2 lake-level rise and fall at ~ 27 and 18 ka, respectively. These two series comprise alternations of authigenic aragonite that precipitated during summer and flood-borne detrital laminae deposited by winter floods. Within this record, aragonite laminae form a proxy of annual inflow and the extent of epilimnion dilution, whereas detrital laminae are comprised of sub-laminae deposited by individual flooding events. The two series depict distinct characteristics with increased mean and variance of annual inflow and flood frequency during "wetter", with respect to the relatively "dryer", conditions, reflected by opposite lake-level changes. In addition, decades of intense flood frequency (clusters) are identified, reflecting the in situ impact of shift- ing centennial-scale climate regimes, which are particularly pronounced during wetter conditions. The combined appli- cation of multiple time series analyses suggests that the stud- ied episodes are characterized by weak and non-significant cyclical components of sub-decadal frequencies. The inter- pretation of these observations using modern synoptic-scale hydroclimatology suggests that Pleistocene climate changes resulted in shifts in the dominance of the key synoptic sys- tems that govern rainfall, annual inflow and flood frequency in the eastern Mediterranean Sea over centennial timescales.