Description: 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 accurately1 and reconstruct on Quaternary timescales. This is partly because regional hydroclimate records that cover multiple glacial-interglacial cycles2,3 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.

Description: Published

Description: 256–260

Description: 5A. Ricerche polari e paleoclima

Description: JCR Journal

Description: 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 584m 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 460m of this sequence. Tephrochronology and tuning biogeochemical proxy data to orbital parameters revealed that the upper 247.8m represent the last 637 kyr. The multi-proxy data set covering these 637 kyr indicates longterm 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.

Description: Published

Description: 2033–2054

Description: 1A. Geomagnetismo e Paleomagnetismo

Description: JCR Journal

Description: Archaeological investigations carried out at Case Bastione (Enna, central Sicily) provide a key insight into the cultural and environmental changes that occurred during the transition from the Copper Age to the Bronze Age. Preliminary data of an ongoing paleoenvironmental reconstruction through archaeobotanical analyses are here presented. The selective exploitation of vegetation, the adaptation of lifestyle to local resources, and changing climatic conditions are analysed using different on-site and off-site environmental and archaeological proxies. The environment around the site was constituted by mixed oak woodland. Dietary preferences were reconstructed through the analysis of carpo-remains. Isotopic values provide new data on the 4.2 ka BP event and its effects on vegetation in central Sicily. In a whole, first results from Case Bastione give new light to human choices of vegetal resources exploitation. Comparison of the local results with the regional pollen data support the hypothesis that the growth in population and settlement in the inland part of the island since the Late Copper Age may reflect changing climatic conditions in coastal areas.

Description: Published

Description: 102332

Description: 7SR AMBIENTE – Servizi e ricerca per la società

Description: JCR Journal

Description: Sediment samples from the Ocean Drilling Program Site 976 (36°12.3'N, 4°18.8'W) were used to derive high temporal resolution δ¹⁸O G. bulloides, palynological (pollen and spores) and calcareous plankton (coccolithophores and foraminifera) records. This data set was used to trace the climate variability within late Marine Isotope Stage (MIS) 20 and MIS 19 in the area surrounding the Alboran Sea (western Mediterranean Sea).

Description: Here we present the pollen data obtained for the DEEP core of Lake Ohrid located at the border between Albania and F.Y.R. of Macedonia. The very long sequence covers the last 500 ka BP in ca. 200 m. The study has been carried out by 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. The original paper, published by Sadori et al. 2016 (https://doi.org/10.5194/bg-13-1423-2016), has been followed by a corrigendum due to chemical procedure problems that affected 104 samples. The record shows a progressive change from cooler and wetter to slightly warmer and drier interglacial conditions. This shift in temperature and moisture availability is visible also in vegetation during glacial periods. Pollen results support the notion that Lake Ohrid has been a refugium area for both temperate and montane trees during glacials.

Description: We present a new mid-latitude speleothem record of millennial-scale climatic variability during OIS3 from the Villars Cave that, combined with former published contemporaneous samples from the same cave, gives a coherent image of the climate variability in SW-France between ~55 ka and ~30 ka. The 0.82 m long stalagmite Vil-stm27 was dated with 26 TIMS U-Th analyses and its growth curve displays variations that are linked with the stable isotopes, both controlled by the climatic conditions. It consists in a higher resolved replicate of the previously published Vil-stm9 and Vil-stm14 stalagmites where Dansgaard-Oeschger (DO) events have been observed. The good consistency between these three stalagmites and the comparison with other palaoeclimatic reconstructions, especially high resolution pollen records (ODP 976 from the Alboran Sea, Monticchio Lake record from southern Italy) and the nearby MD04-2845 Atlantic Ocean record, permits to draw a specific climatic pattern in SW-France during the OIS3 and to see regional differences between these sites. Main features of this period are: 1) warm events corresponding to Greenland Interstadials (GIS) that are characterized by low speleothem d13C, high temperate pollen percentages, warm temperatures and high humidity; among these events, GIS#12 is the most pronounced one at Villars characterized by an abrupt onset at ~46.6 ka and a duration of about 2.5 ka. The other well individualized warm event coincides with GIS#8 which is however much less pronounced and occurred during a cooler period as shown by a lower growth rate and a higher d13C; 2) cold events corresponding to Greenland Stadials (GS) that are clearly characterized by high speleothem d13C, low temperate pollen abundance, low temperature and enhanced dryness, particularly well expressed during GS coinciding with Heinrich events H5 and H4. The main feature of the Villars record is a general cooling trend between the DO#12 event ~45.5 ka and the synchronous stop of the three stalagmites at ~30 ka ±1, with a first well marked climatic threshold at ~41 ka after which the growth rate and the diameter of all stalagmites slows down significantly. This climatic evolution differs from that shown at southern Mediterranean sites where this trend is not observed. The ~30 ka age marks the second climatic threshold after which low temperatures and low rainfalls prevent speleothem growth in the Villars area until the Lateglacial warming that occurred at ~16.5 ± 0.5 ka. This 15 ka long hiatus, as the older Villars growth hiatus that occurred between 67.4 and 61 ka, are linked to low sea levels, reduced ocean circulation and a southward shift of the Polar Front that likely provoked local permafrost formation. These cold periods coincide with both low summer 65°N insolation, low atmospheric CO2 concentration and large ice sheets development (especially the Fennoscandian).