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There is growing concern on the survival of Mediterranean forests under the projected near-future droughts as a result of anthropogenic climate change. Here we determine the resilience of Mediterranean forests across the entire range of climatic boundary conditions realized during the past 500 kyrs based on continuous pollen and geochemical records of (sub)centennial-scale resolution from drillcores from Tenaghi Philippon, Greece. Using convergent cross-mapping we provide empirical confirmation that global atmospheric carbon dioxide (CO 2 ) may affect Mediterranean vegetation through forcing on moisture availability. Our analysis documents two stable vegetation regimes across the wide range of CO 2 and moisture levels realized during the past four glacial-interglacial cycles, with abrupt shifts from forest to steppe biomes occurring when a threshold in precipitation is crossed. Our approach highlights that a CO 2 -driven moisture decrease in the near future may bear an impending risk for abrupt vegetation regime shifts prompting forest loss in the Mediterranean region. A 500 kyr long record of vegetation change from SE Europe demonstrates that forest resilience is lost when precipitation decreases below a threshold limit, and highlights the vulnerability of Mediterranean forests to near-future climate change

Super-eruptions disperse volcanic ash over vast areas, impacting the environment and human health. Fine ash, particularly its respirable fraction (< 4 µm), poses a significant health hazard by inhalation due to its high dispersal potential. Understanding the aerodynamic properties but also composition of ash particles is fundamental to constrain dispersal and deposition mechanisms in both proximal and distal environments. Current atmospheric dispersal models rely on empirical drag equations calibrated with geometric shape descriptors. However, these models often overlook the effects of the actual particle density, as a uniform componentry is typically assumed. In addition, particles have variable shapes but such data from super-eruptions remains limited and no standardized measurement methods exist. Here, we determine the terminal fall velocity ( v t ) of fine ash from the Campanian Ignimbrite super-eruption (~ 40 ka, Campi Flegrei), by evaluating the components and particle shapes from proximal to ultra-distal locations. To verify the attribution of the proximal sample to the CI eruption, a 40 Ar/ 39 Ar dating was performed, allowing its correlation with the ultra-distal deposits. Results show that, due to the influence of shape and density, glass particles exhibit lower v t compared to mineral phases ( v t , feldspar / v t , glass  = 1.05 ± 0.03, v t , SiO2 / v t , glass  = 1.09 ± 0.02), enabling greater travel distances. Drag equations accounting for measured particle shapes differ significantly from spherical approximations. The spherical model overestimation of v t highlights the necessity of shape-specific models to produce more accurate dispersal predictions. Extremely low v t (< 0.1 cm/s) for respirable ash fraction, which indicates prolonged atmospheric suspension and long-time resuspension potential, along with the presence of cristobalite, lead to important implications for health hazards. These findings further enhance our understanding of volcanic ash aerodynamic behaviour and the far-reaching impact of super-eruptions .

The Aegean hosts some of the earliest cultural centers in European antiquity. To reconstruct the evolution of early anthropogenic impact in this region, we have examined lead (Pb) contents and vegetation dynamics on well-dated environmental archives extending to the early Holocene. We show that the impact of agropastoral societies on terrestrial ecosystems was locally confined during the Bronze and Iron Ages (5200–2750 years ago), although we record an onset of Pb pollution already at 5200 cal. years BP and thus about 1200 years earlier than previous archeological evidence. Our data demonstrate a marked increase in Pb pollution at 2150 cal. years BP that left an imprint across terrestrial and marine settings of the Aegean region. This first manifestation of marine pollution coincides with maximum deforestation and agricultural expansion, signaling pervasive human impact on ecosystems connected to the advanced monetized societies during the Hellenistic and Roman periods in Ancient Greece. The increase in lead contamination 2150 years before present affected marine and terrestrial environments of the Aegean region. It coincided with the expansion of monetized societies, as shown by lead pollution, pollen analysis, and radiocarbon dating on terrestrial and marine drillcores.

Mesopelagic fish are integral to ocean food webs and play an important role in carbon transport through their vertical migration behavior. Ocean deoxygenation caused by anthropogenic warming is expected to pose severe threats to mesopelagic fauna by enhancing physical stress and changing predator-prey relationships. In agreement with this expectation, our fish otolith record in a Mediterranean sediment core shows near absence of mesopelagic species during Sapropel deposition between ~7 and ~10 thousand years ago, concurrent with high surface productivity and low oxygenation of mid-depth waters. Instead, the otolith record is dominated by fish species adapted to epipelagic habitats, including European anchovy ( Engraulis encrasicolus ) and silvery lightfish ( Maurolicus muelleri ). Subsequent reoxygenation starting ~7 thousand years ago is accompanied by a three-fold increase in total otolith abundance. The large majority of these are mesopelagic lanternfish (Myctophidae) that dominate the otolith assemblage from the middle-Holocene to the present. Our findings corroborate expectations that future expansion of midwater deoxygenation could severely deplete mesopelagic fish communities over the coming centuries, with major impacts on marine fisheries, marine conservation, ocean food web structure, carbon storage and other marine ecosystem services. Historical phases of ocean oxygen minimum are associated with near extinctions of mesopelagic fish, suggesting risks of future deoxygenation to marine fisheries due to warming, according to an analysis of a fish otolith record from a Mediterranean sediment core.

The sediment record from Lake Ohrid (Southwestern Balkans) represents the longest continuous lake archive in Europe, extending back to 1.36 Ma. We reconstruct the vegetation history based on pollen analysis of the DEEP core to reveal changes in vegetation cover and forest diversity during glacial–interglacial (G–IG) cycles and early basin development. The earliest lake phase saw a significantly different composition rich in relict tree taxa and few herbs. Subsequent establishment of a permanent steppic herb association around 1.2 Ma implies a threshold response to changes in moisture availability and temperature and gradual adjustment of the basin morphology. A change in the character of G–IG cycles during the Early–Middle Pleistocene Transition is reflected in the record by reorganization of the vegetation from obliquity- to eccentricity-paced cycles. Based on a quantitative analysis of tree taxa richness, the first large-scale decline in tree diversity occurred around 0.94 Ma. Subsequent variations in tree richness were largely driven by the amplitude and duration of G–IG cycles. Significant tree richness declines occurred in periods with abundant dry herb associations, pointing to aridity affecting tree population survival. Assessment of long-term legacy effects between global climate and regional vegetation change reveals a significant influence of cool interglacial conditions on subsequent glacial vegetation composition and diversity. This effect is contrary to observations at high latitudes, where glacial intensity is known to control subsequent interglacial vegetation, and the evidence demonstrates that the Lake Ohrid catchment functioned as a refugium for both thermophilous and temperate tree species.

Lake Ohrid is located at the border between FYROM (Former Yugoslavian Republic of Macedonia) and Albania and formed during the latest phases of Alpine orogenesis. It is the deepest, the largest and the oldest tectonic lake in Europe. To better understand the paleoclimatic and paleoenvironmental evolution of Lake Ohrid, deep drilling was carried out in 2013 within the framework of the Scientific Collaboration on Past Speciation Conditions (SCOPSCO) project that was funded by the International Continental Scientific Drilling Program (ICDP). Preliminary results indicate that lacustrine sedimentation of Lake Ohrid started between 1.2 and 1.9 Ma ago. Here we present new pollen data (selected percentage and concentration taxa/groups) of the uppermost  ∼  200 m of the 569 m long DEEP core drilled in the depocentre of Lake Ohrid. The study is the fruit of a cooperative work carried out in several European palynological laboratories. The age model of this part of the core is based on 10 tephra layers and on tuning of biogeochemical proxy data to orbital parameters. According to the age model, the studied sequence covers the last  ∼  500 000 years at a millennial-scale resolution ( ∼  1.6 ka) and records the major vegetation and climate changes that occurred during the last 12 (13 only pro parte) marine isotope stages (MIS). Our results indicate that there is a general good correspondence between forested/non-forested periods and glacial–interglacial cycles of the marine isotope stratigraphy. The record shows a progressive change from cooler and wetter to warmer and drier interglacial conditions. This shift in temperature and moisture availability is visible also in vegetation during glacial periods. The period corresponding to MIS11 (pollen assemblage zone OD-10, 428–368 ka BP) is dominated by montane trees such as conifers. Mesophilous elements such as deciduous and semi-deciduous oaks dominate forest periods of MIS5 (PASZ OD-3, 129–70 ka BP) and MIS1 (PASZ OD-1, 14 ka BP to present). Moreover, MIS7 (PASZ OD-6, 245–190 ka) shows a very high interglacial variability, with alternating expansions of montane and mesophilous arboreal taxa. Grasslands (open vegetation formations requiring relatively humid conditions) characterize the earlier glacial phases of MIS12 (PASZ OD-12, 488–459 ka), MIS10 (corresponding to the central part of PASZ OD-10, 428–366 ka) and MIS8 (PASZ OD-7, 288–245 ka). Steppes (open vegetation formations typical of dry environments) prevail during MIS6 (OD-5 and OD-4, 190–129 ka) and during MIS4-2 (PASZ OD-2, 70–14 ka). Our palynological results support the notion that Lake Ohrid has been a refugium area for both temperate and montane trees during glacials. Closer comparisons with other long southern European and Near Eastern pollen records will be achieved through ongoing high-resolution studies.

Mediterranean climates are characterized by strong seasonal contrasts between dry summers and wet winters. Changes in winter rainfall are critical for regional socioeconomic development, but are difficult to simulate accurately 1 and reconstruct on Quaternary timescales. This is partly because regional hydroclimate records that cover multiple glacial–interglacial cycles 2 , 3 with different orbital geometries, global ice volume and atmospheric greenhouse gas concentrations are scarce. Moreover, the underlying mechanisms of change and their persistence remain unexplored. Here we show that, over the past 1.36 million years, wet winters in the northcentral Mediterranean tend to occur with high contrasts in local, seasonal insolation and a vigorous African summer monsoon. Our proxy time series from Lake Ohrid on the Balkan Peninsula, together with a 784,000-year transient climate model hindcast, suggest that increased sea surface temperatures amplify local cyclone development and refuel North Atlantic low-pressure systems that enter the Mediterranean during phases of low continental ice volume and high concentrations of atmospheric greenhouse gases. A comparison with modern reanalysis data shows that current drivers of the amount of rainfall in the Mediterranean share some similarities to those that drive the reconstructed increases in precipitation. Our data cover multiple insolation maxima and are therefore an important benchmark for testing climate model performance. Comparisons between past regional drivers of precipitation extremes found time series data from Lake Ohrid and modern climate models of the Mediterranean may help to reduce simulation uncertainties in predictions of the Mediterranean climate.

The dominant feature of large-scale mass transfer in the modern ocean is the Atlantic meridional overturning circulation (AMOC). The geometry and vigour of this circulation influences global climate on various timescales. Palaeoceanographic evidence suggests that during glacial periods of the past 1.5 million years the AMOC had markedly different features from today 1 ; in the Atlantic basin, deep waters of Southern Ocean origin increased in volume while above them the core of the North Atlantic Deep Water (NADW) shoaled 2 . An absence of evidence on the origin of this phenomenon means that the sequence of events leading to global glacial conditions remains unclear. Here we present multi-proxy evidence showing that northward shifts in Antarctic iceberg melt in the Indian–Atlantic Southern Ocean (0–50° E) systematically preceded deep-water mass reorganizations by one to two thousand years during Pleistocene-era glaciations. With the aid of iceberg-trajectory model experiments, we demonstrate that such a shift in iceberg trajectories during glacial periods can result in a considerable redistribution of freshwater in the Southern Ocean. We suggest that this, in concert with increased sea-ice cover, enabled positive buoyancy anomalies to ‘escape’ into the upper limb of the AMOC, providing a teleconnection between surface Southern Ocean conditions and the formation of NADW. The magnitude and pacing of this mechanism evolved substantially across the mid-Pleistocene transition, and the coeval increase in magnitude of the ‘southern escape’ and deep circulation perturbations implicate this mechanism as a key feedback in the transition to the ‘100-kyr world’, in which glacial–interglacial cycles occur at roughly 100,000-year periods. Iceberg-trajectory models along with multi-proxy evidence from sediment cores from the Indian Ocean show that northward shifts in Antarctic iceberg melt redistributed freshwater in the Southern Ocean during the Pleistocene.

Cold-water corals (CWCs) constitute important deep-water ecosystems that are under increasing environmental pressure due to ocean acidification and global warming. The sensitivity of these deep-water ecosystems to environmental change is demonstrated by abundant paleorecords drilled through CWC mounds that reveal characteristic alterations between rapid formation and dormant or erosive phases. Previous studies have identified several central parameters for driving or inhibiting CWC growth such as food supply, oxygenation, and the carbon saturation state of bottom water, yet there are still large uncertainties about the relative importance of the different environmental parameters. To advance this debate we have performed a multiproxy study on a sediment core retrieved from the 25 m high Bowie Mound, located at 866 m water depth on the continental slope off southeastern Brazil, a structure built up mainly by the CWC Solenosmilia variabilis. Our results indicate a multifactorial control on CWC growth at Bowie Mound during the past ∼ 160 kyr, which reveals distinct formation pulses during northern high-latitude glacial cold events (Heinrich stadials, HSs) largely associated with anomalously strong monsoonal rainfall over the continent. The ensuing enhanced runoff elevated the terrigenous nutrient and organic-matter supply to the continental margin and likely boosted marine productivity. The dispersal of food particles towards the CWC colonies during HSs was facilitated by the highly dynamic hydraulic conditions along the continental slope that prevailed throughout glacial periods. These conditions caused the emplacement of a pronounced nepheloid layer above Bowie Mound, thereby aiding the concentration and along-slope dispersal of organic matter. Our study thus emphasizes the impact of continental climate variability on a highly vulnerable deep-marine ecosystem.

This study reviews and synthesises existing information generated within the SCOPSCO (Scientific Collaboration on Past Speciation Conditions in Lake Ohrid) deep drilling project. The four main aims of the project are to infer (i) the age and origin of Lake Ohrid (Former Yugoslav Republic of Macedonia/Republic of Albania), (ii) its regional seismotectonic history, (iii) volcanic activity and climate change in the central northern Mediterranean region, and (iv) the influence of major geological events on the evolution of its endemic species. The Ohrid basin formed by transtension during the Miocene, opened during the Pliocene and Pleistocene, and the lake established de novo in the still relatively narrow valley between 1.9 and 1.3 Ma. The lake history is recorded in a 584 m long sediment sequence, which was recovered within the framework of the International Continental Scientific Drilling Program (ICDP) from the central part (DEEP site) of the lake in spring 2013. To date, 54 tephra and cryptotephra horizons have been found in the upper 460 m of this sequence. Tephrochronology and tuning biogeochemical proxy data to orbital parameters revealed that the upper 247.8 m represent the last 637 kyr. The multi-proxy data set covering these 637 kyr indicates long-term variability. Some proxies show a change from generally cooler and wetter to drier and warmer glacial and interglacial periods around 300 ka. Short-term environmental change caused, for example, by tephra deposition or the climatic impact of millennial-scale Dansgaard–Oeschger and Heinrich events are superimposed on the long-term trends. Evolutionary studies on the extant fauna indicate that Lake Ohrid was not a refugial area for regional freshwater animals. This differs from the surrounding catchment, where the mountainous setting with relatively high water availability provided a refuge for temperate and montane trees during the relatively cold and dry glacial periods. Although Lake Ohrid experienced significant environmental change over the last 637 kyr, preliminary molecular data from extant microgastropod species do not indicate significant changes in diversification rate during this period. The reasons for this constant rate remain largely unknown, but a possible lack of environmentally induced extinction events in Lake Ohrid and/or the high resilience of the ecosystems may have played a role.