ALBERT

Description: Knowledge about the timing, amplitude and spatial gradients of Holocene environmental variability in the circum-Baltic region is key to understanding its responses to ongoing climate change. Based on a multi-dating and proxy approach, we reconstruct changes in productivity using total organic carbon (TOC) contents in sediments of Lake Kälksjön (KKJ) from west–central Sweden spanning the last 9612 (+255 − 114) years. An exception is the period from 1878 CE until today, in which sedimentation was dominated by anthropogenic lake level lowering and land use. In-lake productivity was higher during periods of warmer winters with shortened ice cover and prolonged growing seasons. A multi-millennial increase in productivity throughout the last ∼ 9600 years is associated with progressively warmer winters in northwestern Europe, likely triggered by the coinciding increase in Northern Hemisphere winter insolation. Decadal to centennial periods of higher productivity in KKJ tend to correspond to warmer winters during a more positive North Atlantic Oscillation (NAO) polarity, as reconstructed for the last 8000 years. In consequence, we assume our decadal to centennial productivity record from KKJ sediments for the complete ∼ 9600 years to provide a qualitative record of NAO polarity. A shift towards higher productivity variability at ∼ 5450 cal a BP is hypothesized to reect a reinforcement of NAO-like atmospheric circulation variability, possibly driven by more vigorous changes in North Atlantic deep-water formation.

Description: The lake level of the Dead Sea, Southern Levant, has fluctuated with an amplitude of ∼250 m in response to the last glacial-interglacial cycle. This exceptional sensitivity to climate change, and the availability of long sedimentary archives, make the Dead Sea a benchmark for long quantitative paleohydrological reconstructions. However, discontinuities and chronological uncertainties in the marginal sedimentary record have hampered the reconstruction of Dead Sea lake levels beyond the Last Glacial (70–14 ka before present, BP). Here, we apply a two-pronged methodology. First, we measure the lake water density along ICDP deep core 5017-1-A using a new method, Brillouin spectroscopy on two-phase halite fluid inclusions; we combine it with the composition of pore water and the thickness of halite layers in the core to reconstruct lake level, volume, mass balance and subsidence rate. Second, we tune the chronology of lake levels from outcrops by matching it to the chronology of the deep core. The resulting lake level reconstruction, spanning 237–70 ka BP, is validated by the excellent agreement between outcrop- and mass balance-based methodologies. It shows a long-term recession of the lake, its level decreasing from one interglacial to the other, down to a Holocene record low. There are two reasons for this lake level fall. First, with an average rate of 2.65 ± 0.15 m/ka, subsidence has outpaced sedimentation at least over the last ∼130 ka. Second, by reducing the solute inventory of the lake, massive halite precipitation events such as that of 131–116 ka BP have durably increased surface water activity and evaporation, and thus lowered the lake level, up to today. Conversely, our analysis suggests that, during 191–11 ka BP, the dissolution of Mount Sedom salt diapir and freshwater inflows provided to the lake about three times the mass of solute NaCl contained in the modern Dead Sea (in 1985). This massive solute influx, occurring mainly during glacial highstands, strongly contributed to lowering surface water activity and evaporation and, therefore, to increasing the lake volume. Our results suggest that Dead Sea lake levels are more accurately interpreted in terms of climatic change if surface water activity is taken into account.

Description: In-depth understanding of the reorganization of the hydrological cycle in response to global climate change is crucial in highly sensitive regions like the eastern Mediterranean, where water availability is a major factor for socioeconomic and political development. The sediments of Lake Lisan provide a unique record of hydroclimatic change during the last glacial to Holocene transition (ca. 24–11 ka) with its tremendous water level drop of ~ 240 m that finally led to its transition into the present hypersaline water body—the Dead Sea. Here we utilize high-resolution sedimentological analyses from the marginal terraces and deep lake to reconstruct an unprecedented seasonal record of the last millennia of Lake Lisan. Aragonite varve formation in intercalated intervals of our record demonstrates that a stepwise long-term lake level decline was interrupted by almost one millennium of rising or stable water level. Even periods of pronounced water level drops indicated by gypsum deposition were interrupted by decades of positive water budgets. Our results thus highlight that even during major climate change at the end of the last glacial, decadal to millennial periods of relatively stable or positive moisture supply occurred which could have been an important premise for human sedentism.

Description: This dataset provides annually resolved microfacies data from ICDP core 5017-1-A, retrieved from the deep northern Dead Sea basin in 2010/11, for the last glacial-interglacial transition (ca. 14-13 ka BP). Sediments of the Lisan Formation were investigated between ~94.7 and 91.8 m sediment depth below lake floor (lithozone C2) by continuous thin section microscopy. Thin sections were prepared following the standard procedure by Brauer and Casanova (2001) that was adjusted for salty sediments. Thin section analyses were performed on overlapping large-scale thin sections using a Zeiss Axiolab pol microscope at magnifications of 50-400x. Microfacies analyses included varve counting and measurements of varve and sublayer thickness. The amount of varves in erosional gaps was interpolated and the position of mass flow deposits (MFD) is marked.

Description: These datasets provide sedimentological data partly at annual resolution and an age model for the lateglacial part of (1) the ICDP sediment core 5017-1-A retrieved from the deep northern Dead Sea basin in 2010/11, and (2) for the Masada outcrop located at the southwestern shore of the Dead Sea sampled in 2018. The here investigated two sediment sections cover the last glacial-interglacial transition (ca. 17-11.5 ka BP) in the hydroclimatically sensitive Levant, when the water level of Lake Lisan – the precursor of the Dead Sea – dropped dramatically from its glacial high-stand to the Holocene low levels. Here, we analyze the interval between the last two gypsum units – the Upper Gypsum Unit (UGU) and the Additional Gypsum Unit (AGU) – which were also used to correlate the two sites. In the ICDP core this section is located between ~101 and 88.5 m sediment depth below lake floor and at Masada it encompasses the uppermost ~3.8 m sediments of the Lisan Formation, which form the terminal deposit at this site. Due to the lake level decline, the complete transition into the Holocene is only recorded in the ICDP core, while sedimentation at Masada terminates earlier. The microfacies was investigated by continuous thin section microscopy, while additional macroscopic information is provided from over- and underlying sediment sections. A revised chronology using age modelling in OxCal (Ramsey 2008; Ramsey 2009; Ramsey and Lee 2013) was developed for the ICDP core and a floating varve chronology was constructed at Masada. Using these new microfacies data from marginal (Masada) and deep-water (ICDP core) sediments, the hydroclimatic variability during the final stage of Lake Lisan can be reconstructed, which could provide important insights into the development of human sedentism in the region at this time.

Description: This dataset provides annually resolved microfacies data from ICDP core 5017-1-A, retrieved from the deep northern Dead Sea basin in 2010/11, for the last glacial-interglacial transition (ca. 17-11.5 ka BP). Sediments of the Lisan Formation were investigated between ~101 and 88.5 m sediment depth below lake floor by continuous thin section microscopy, while additional macroscopic information is provided from core catchers, as well as from over- and underlying sediment sections. Thin sections were prepared following the standard procedure by Brauer and Casanova (2001) that was adjusted for salty sediments. Thin section analyses were performed on overlapping large-scale thin sections using a Zeiss Axiolab pol microscope at magnifications of 50-400x. Microfacies analyses included varve counting and measurements of varve and sublayer thickness.

Description: This dataset provides the results from Bayesian age depth modelling in OxCal for ICDP core 5017-1-A, retrieved from the deep northern Dead Sea basin in 2010/11, for the last glacial-interglacial transition between ~101 and 88.5 m sediment depth below lake floor (ca. 17-11.5 ka BP). The model was performed in OxCal v.4.4 using a P_Sequence (1,1,C(-2,2)) (Ramsey 2008; Ramsey 2009; Ramsey and Lee 2013) and includes three tephrochronological ages from Neugebauer et al. (2021) and three radiocarbon ages from Kitagawa et al. (2017).

Description: This dataset provides lithological data from ICDP core 5017-1-A, retrieved from the deep northern Dead Sea basin in 2010/11, for the last glacial-interglacial transition (ca. 17-11.5 ka BP). The microfacies of the Lisan Formation was investigated between ~101 and 88.5 m sediment depth below lake floor by continuous thin section microscopy, while additional macroscopic information is provided from core catchers, as well as from over- and underlying sediment sections. Thin sections were prepared following the standard procedure by Brauer and Casanova (2001) that was adjusted for salty sediments. Thin section analyses were performed on overlapping large-scale thin sections using a Zeiss Axiolab pol microscope at magnifications of 50-400x.

Description: This dataset provides microfacies data from the sediment profile at Masada (MAS), located at the southwestern shore of the Dead Sea for the last glacial-interglacial transition (ca. 17-11.5 ka BP). The uppermost ~3.8 m sediments of the Lisan Formation were analyzed, which form the terminal deposit at this site. About 1.37 m from the uppermost UGU to the lowermost AGU were sampled continuously for thin section analyses, while macroscopic information is provided for most of the gypsum units. Sampling was performed in 2018 and followed the subsequent procedure: after smoothing the outcrop surface with a sharp knife, stainless steel boxes (~34 cm x 5 cm) with removable side walls were pressed into the sediment along a vertical profile. The boxes were overlapping by several centimeters and a battery-operated dovetail saw was used to cut the hard gypsum sections. At the GFZ in Potsdam, the sediments were carefully transferred into aluminum boxes and impregnated with epoxy resin. Thin sections (10x2 cm) with 2 cm overlap were prepared subsequently. Thin section analyses were performed using a Zeiss Axiolab pol microscope at magnifications of 50-400x. A floating varve chronology was established between the UGU and AGU and anchored at the bottom of the AGU using the transferred age from the new OxCal age model from the ICDP core. Uncertainties are derived from the age model and varve counting. Microfacies analyses included varve counting and measurements of varve and sublayer thickness.

Description: Well-known for their geological and natural singularity, the Dead Sea brines evolved from a marine ingression of the Mediterranean during the Pliocene. Dead Sea brines are currently almost ten times more concentrated than seawater and have a unique chemical composition with high boron isotope values (δ11Bbrine=∼57). However, little is known on how these values were attained and their underlaying driving processes. Here we use boron isotopes (δ11B) combined with B/Ca and B/Li of lacustrine authigenic aragonites from the deep basin drill-core ICDP 5017-1, and Ein Gedi and Masada profiles to reconstruct past brine conditions. Comparing reconstructed δ11Bbrinefrom two key periods of contrasting hydro-climatic regimes we find that the brines of the late Holocene Dead Sea were enriched in 11B (δ11Bbrine=∼60) relative to its glacial precursor Lake Lisan (∼57). With the aid of boron cycle modelling, we quantify the main boron fluxes in the basin. We show that the post-glacial δ11Bbrineenrichment is best explained by overall reduction of freshwater inflow to the lake and coeval increase in 10B sink through boron co-precipitation in evaporitic deposits and boron loss in atmospheric water vapour, consistent with the onset of warmer and drier climate in the Eastern Mediterranean during the Holocene. On geological time scales, adsorption of 10B on clastic sediments has acted as an important 10B sink and can explain the evolution of the high δ11Bbrinevalues.