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

Abstract

Abstract. Annual and decadal-scale hydroclimatic variability describes key characteristics that are embedded into climate in situ and is of prime importance in subtropical regions. The study of hydroclimatic variability is therefore crucial to understand its manifestation and implications for climate derivatives such as hydrological phenomena and water 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 annual 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 intervals (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 shifting centennial-scale climate regimes, which are particularly pronounced during wetter conditions. The combined application of multiple time series analyses suggests that the studied episodes are characterized by weak and non-significant cyclical components of sub-decadal frequencies. The interpretation of these observations using modern synoptic-scale hydroclimatology suggests that Pleistocene climate changes resulted in shifts in the dominance of the key synoptic systems that govern rainfall, annual inflow and flood frequency in the eastern Mediterranean Sea over centennial timescales.

Phases of stability during major hydroclimate change ending the Last Glacial in the Levant

“…In both sites, the two oscillations of higher aragonite sublayer thickness lasting between ~ 110 and ~ 200 years (Fig. 4 b,d; Supplementary Discussion 2) suggest centennial-scale intervals of increased freshwater inflow that could have supported aragonite precipitation 16 , 42 , although other mechanisms, like calcite-rich dust or sulfate-reducing bacteria, could have contributed bicarbonate as well 41 .…”

Fluvial palaeohydrology in the 21st century and beyond

“…Lacustrine environments are commonly used for reconstructing mean decadal to millennial hydroclimatology using direct indicators, such as lake levels, and indirect sedimentological, geochemical, palynological, and faunal proxies (e.g. Anderson, 1993; Ben Dor, Flax et al, 2021; Ben Dor, Marra et al, 2021; Brauer et al, 1999; Litt & Anselmetti, 2014; Müller et al, 2021; Torfstein & Enzel, 2017; Valero‐Garcés & Moreno, 2011). Nevertheless, lake sediments also record discrete hydroclimatic events such as debris flows and floods (e.g.…”

Implications of submonthly oxygen and carbon isotope variations in late Pleistocene Melanopsis shells for regional and local hydroclimate in the upper Jordan River valley

“…However, few existing paleoclimate records can be correlated with human activity at archaeological sites (Rambeau, 2010; Enzel and Bar-Yosef, 2017). In addition, very few studies of pre-Holocene paleoseasonality have been performed in this region (Ben Dor et al, 2018, 2021; Langgut et al, 2021; Müller et al, 2022). During the final Pleistocene, archeologically known as the Epipaleolithic (EP; 25–11.7 ka), human communities in the Levant shifted from small bands of nomadic hunter-gatherers into the earliest sedentary settlements (Belfer-Cohen and Goring-Morris, 2020).…”