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.
Highlights
Human activity relies on the continuous availability of freshwater, which in turn depends on the interaction of climatic, environmental, and hydrologic processes
Ben Dor et al.: Hydroclimatic variability of opposing Late Pleistocene climates could be affected by climate changes, such as those humanity faces in the upcoming decades (Peleg et al, 2015; Seager et al, 2019; Zappa et al, 2015; IPCC, 2021)
This study focuses on two properties of the varves that are interpreted as hydrological proxies: (a) the number of detrital sub-laminae in each detrital lamina, reflecting the number of flooding events that reached the coring site (Ben Dor et al, 2018), and (b) the thicknesses of aragonite laminae
Summary
Human activity relies on the continuous availability of freshwater, which in turn depends on the interaction of climatic, environmental, and hydrologic processes. Because palaeohydrologic archives often record centennial and millennial intervals at various resolutions (e.g., Allen et al, 2020; Baker, 2008; Brauer et al, 2008; Redmond et al, 2002; Witt et al, 2017), they have the potential to improve our understating of how climate change is manifested locally as short-term hydroclimatic variability (e.g., Ahlborn et al, 2018; Swierczynski et al, 2012) This requires continuous high-resolution archives, which are rare, especially in subtropical terrestrial environments (e.g., Zolitschka et al, 2015)
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