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Abstract. Sedimentary records of lipid biomarkers such as leaf wax n-alkanes are influenced by not only ecosystem turnover and physiological changes in plants but also earth surface processes integrating these signals into the sedimentary record, though the effect of these integration processes is not fully understood. To determine the depositional constraints on biomarker records in a high-altitude small catchment system, we collected both soil and stream sediments along a 1000 m altitude transect (1500–2500 m a.s.l.) in the Areguni Mountains, a subrange of the Lesser Caucasus Mountains in Armenia. We utilize a treeline at ∼ 2000 m a.s.l., which separates alpine meadow above from deciduous forest below, to assess the relative contribution of upstream biomarker transport to local vegetation input in the stream. We find that average chain length (ACL), hydrogen isotope (δD) and carbon isotope (δ13C) values of n-alkanes are significantly different in soils collected above and below the treeline. However, samples collected from the stream sediments do not integrate these signals quantitatively. As the stream drops below the treeline, the ACL, δD and δ13C values of n-alkanes preserved in streambed sediments reflect a bias toward n-alkanes sourced from trees. This suggests that either (1) there is minimal transportation of organic matter from the more open vegetation at higher elevations or (2) greater production of target biomarkers by trees and shrubs found at lower elevations results in overprinting of stream signals by local vegetation. Though these observations may preclude using n-alkanes to measure past treeline movement in these mountains, δD values of biomarkers in fluvial deposits in these settings are more likely to record local hydrological changes rather than reflect fractionation changes due to turnover in the upstream vegetation structure. 

The mechanisms underlying the current greenhouse gas (GHG) forced decline in Mediterranean rainfall remain a matter of debate. To inform our understanding of the current and projected drying, we examined extended arid intervals in the late Quaternary, Eastern Mediterranean (EM) Levant indicated by substantial salt deposits in a Dead Sea sediment core covering the past 220 kyr. These arid events occurred during interglacials, when the Earth was at perihelion to the sun in boreal fall and during glacial–interglacial transitions, associated with icesheet melting. Climate models forced with realistic late Quaternary insolation variations show that when the Earth is closest to the Sun in boreal fall, the North Atlantic latitudinal surface temperature gradient in the winter intensifies. In response, the overlying midlatitude North Atlantic jet stream and the extratropical storm track move poleward while sea-level pressure rises in the subtropics. These changes bring about a weakening of the Mediterranean storm track and a decline in rainfall over the entire basin. During glacial–interglacial transitions, meltwater from continental icesheets forced abrupt subpolar North Atlantic cooling. This also strengthened the latitudinal surface temperature gradient, likely causing similar atmospheric response and aridity in the Mediterranean. There is a strong resemblance between this paleoclimate scenario and the climatic changes corresponding to the present and projected GHG drying of the EM. Hence, the late Quaternary palaeohydrology of the Dead Sea indicates an important North Atlantic centered response to external forcing, which leads to Mediterranean drying and is relevant in the present. 

Water availability in the Levant is predicted to decline due to global warming in the upcoming decades and is expected to substantially impact the region. Determining the long-term natural rainfall variability in this region is essential for understanding the regional hydroclimatic response to external climate forcings and for contex- tualizing future hydroclimate changes. The Dead Sea (DS), located in the southern Levant, is a closed-basin lake whose size varies as a function of water availability. Reconstructing DS lake-level variations through time provides a quantitative measure of the natural hydroclimate variability and can inform on the local hydroclimate response to changes in global climate. Here, we constructed an updated lake-level history of the Holocene DS by: 1) studying lake high-stands derived from a series of new cores collected in the DS southern basin, 2) re-dating of the two major Holocene high-stand exposures, and 3) compiling all previously published ages of Holocene DS lake-level markers (n = 296 radiocarbon ages). The results show that the early (10–6.1 kyr cal BP) and late Holocene (3.6–0 kyr cal BP) in the DS were predominantly wet albeit punctuated by dry intervals, whereas the middle Holocene (6.1–3.6 kyr cal BP) was most likely relatively dry. This pattern of two Holocene humid in- tervals is also evident in distillation records derived from Levant speleothem caves (which represent the inte- grated magnitude of rainout from the vapor source to the caves), indicating that rainfall intensity and total water availability were correlated throughout the Holocene. These two humid intervals occurred during high and low summer insolation conditions, suggesting that they were modulated by different climatic mechanisms. The predicted future drying in the Levant is of similar magnitude to the natural hydroclimate variability and thus, it is crucial to assess whether the anthropogenic drying is in- or out-of phase with the natural climate variability.