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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. 

Abstract Chemical events involving deep carbon- and water-rich fluids impact the continental lithosphere over its history. Diamonds are a by-product of such episodic fluid infiltrations, and entrapment of these fluids as microinclusions in lithospheric diamonds provide unique opportunities to investigate their nature. However, until now, direct constraints on the timing of such events have not been available. Here we report three alteration events in the southwest Kaapvaal lithosphere using U-Th-He geochronology of fluid-bearing diamonds, and constrain the upper limit of He diffusivity (toD ≈ 1.8 × 10⁻¹⁹cm²s⁻¹), thus providing a means to directly place both upper and lower age limits on these alteration episodes. The youngest, during the Cretaceous, involved highly saline fluids, indicating a relationship with late-Mesozoic kimberlite eruptions. Remnants of two preceding events, by a Paleozoic silicic fluid and a Proterozoic carbonatitic fluid, are also encapsulated in Kaapvaal diamonds and are likely coeval with major surface tectonic events (e.g. the Damara and Namaqua–Natal orogenies). 

Abstract Submarine groundwater discharge is increasingly recognized as an important component of the oceanic geochemical budget, but knowledge of the distribution of this phenomenon is limited. To date, reports of meteoric inputs to marine sediments are typically limited to shallow shelf and coastal environments, whereas contributions of freshwater along deeper sections of tectonically active margins have generally been attributed to silicate diagenesis, mineral dehydration, or methane hydrate dissociation. Here, using geochemical fingerprinting of pore water data from Site J1003 recovered from the Chilean Margin during D/V JOIDES Resolution Expedition 379 T, we show that substantial offshore freshening reflects deep and focused contributions of meteorically modified geothermal groundwater, which is likely sourced from a reservoir ~2.8 km deep in the Aysén region of Patagonia and infiltrated marine sediments during or shortly after the last glacial period. Emplacement of fossil groundwaters reflects an apparently ubiquitous phenomenon in margin sediments globally, but our results now identify an unappreciated locus of deep submarine groundwater discharge along active margins with potential implications for coastal biogeochemical processes and tectonic instability.