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The Holocene is on global multimillenial scale generally regarded as a relative stable in hydroclimate terms, but at the finer scale, it is characterized by frequent changes both in temperature and precipitation. Based on stable isotope (δ13C and δ18O) records of two coeval stalagmites from Nova Grgosova Cave (Croatia), we identified several centennial to millennial hydroclimate oscillations. During the 9.2-8.8 ka period local environmental conditions were improved in terms of vegetation dynamics, while the following 8.2 ka event was characterized by change in seasonal distribution of precipitation with somewhat drier autumn/winter seasons. The most remarkable excursion in δ13C series occurred around 7.4 ka within the Holocene Climate Optimum (HCO), due to reduced vegetation and soil microbial activity in response to enhanced spring/summer aridity, and likely also reduced autumn/winter precipitation. Regional signal of aridity during the 4.2 ka event is relatively small in magnitude, and must be confirmed in other coeval speleothems. Since the lowlands along the rivers further to east were preferred for human settlement over hilly region of Nova Grgosova Cave, Neolithic agricultural revolution and associated anthropogenic deforestation left no trace in studied speleothems, supporting hydroclimate causes of isotopic variations rather than anthropogenic. However, potential record of the short-term (centennial) climatic variability during the last millennium has been overprinted by the human intervention into natural forest landscape related to the mining activity. Namely, increased copper production required more arable land for increased population, mine timber (supporting pillars), as well as wood for smelting, which all lead to intensified deforestation and consequently masked δ13C signal of concurrent rapid climate changes such as those of Medieval Warm Period and Little Ice Age.

The Adriatic Sea, as the northernmost and practically landlocked part of the Mediterranean Sea, is influenced by both Atlantic and Mediterranean air masses, so the isotopic records from coastal cave speleothems are expected to reveal local and regional responses to global climate changes on that bordering region. In this study we present a 365-kyr long composite isotopic record of three speleothems from Modrič Cave located 120 m from the shoreline on the central part of the eastern Adriatic coast. Results of a 4-year monitoring program of the surface and cave microclimate, rain and drip water stable isotope composition and rain and drip intensities, show cave air temperature variations within 1 °C, a relative humidity of 100%, dripwater O and H stable isotopic composition (range 0.4‰) very well buffered against the seasonal rainfall range (6.8‰). Such conditions enable calcite deposition without strong kinetic isotopic disequilibrium effects, as validated by Hendy tests, and give us confidence that the isotopic signal is faithfully recording climate changes. All three speleothems (MOD-31, MOD-32, MOD-33) were active, collected from their growth position, so Holocene signals can be traced in all of them. Within their older parts, U-Th dating reveals the following growth periods: MOD-31 from MIS10 to MIS 7, MOD-32 from MIS 4 to MIS 2, and MOD-33 from MIS 6 to MIS 5. Relatively large 18O and 13C ranges (-8.16‰ – -2.97‰ and -13.11‰ – -1.00‰, respectively) indicate significant environmental changes whose comparison with stable isotope time series of adjacent speleothem records and other regional proxies provides the longest eastern Adriatic speleothem-based record.

The Mediterranean region and the Levant have returned some of the clearest evidence of a climatically dry period occurring around 4200 years ago. However, some regional evidence is controversial and contradictory, and issues remain regarding timing, progression, and regional articulation of this event. In this paper, we review the evidence from selected proxies (sea-surface temperature, precipitation, and temperature reconstructed from pollen, δ18O on speleothems, and δ18O on lacustrine carbonate) over the Mediterranean Basin to infer possible regional climate patterns during the interval between 4.3 and 3.8 ka. The values and limitations of these proxies are discussed, and their potential for furnishing information on seasonality is also explored. Despite the chronological uncertainties, which are the main limitations for disentangling details of the climatic conditions, the data suggest that winter over the Mediterranean involved drier conditions, in addition to already dry summers. However, some exceptions to this prevail – where wetter conditions seem to have persisted – suggesting regional heterogeneity in climate patterns. Temperature data, even if sparse, also suggest a cooling anomaly, even if this is not uniform. The most common paradigm to interpret the precipitation regime in the Mediterranean – a North Atlantic Oscillation-like pattern – is not completely satisfactory to interpret the selected data.

Quaternary environmental changes in Croatia have been subject of an interdisciplinary study with multi-proxy approach, with speleothems being an important archive when it comes to the Upper Pleistocene – Holocene transition. Monitoring of modern environmental settings in three caves (Nova Grgosova, Lokvarka and Modrič) and seven speleothem samples from different parts of Croatia deciphered variable atmospheric influences and specific hydrological behaviour of each drip site (Surić et al., 2017). They both lead to particular isotopic imprint in spelean calcite which is, in case of equilibrium conditions, crucial for the reconstruction of the past natural settings. Progress in speleothem-based palaeoenvironmental studies in Croatia is particularly apparent in extended periods covered by speleothem growth, so at the moment, the oldest record is from Modrič Cave starting from MIS 10 and covering several intervals to the Recent. Another advancement is expected from the Nova Grgosova Cave speleothems which cover only the Holocene, but the quality of the isotopic records provides rather detailed insight into environmental changes in the recent past. On the other hand, constraints are tied to the isotopic disequilibrium during the speleothem growth and to the content of U and Th – either to the low U or to the high initial 232Th. Although the later was evident in speleothems from Lokvarka Cave, the intention is to date the major events by 14C method. Acknowledgement This study was funded by Croatian Science Foundation within the project HRZZ-IP-11-2013- 1623 Reconstruction of the Quaternary environment in Croatia using isotope methods (REQUENCRIM). References: Surić, M., Lončarić, R., Bočić, N., Lončar, N., Buzjak, N. (2017): Monitoring of selected caves as a prerequisite for the speleothem-based reconstruction of the Quaternary environment in Croatia. Quaternary International, https://doi.org/10.1016/j.quaint.2017.06.042

A multi-proxy record was acquired from a Late Pleistocene lacustrine succession in the Sulmona basin, central Italy. Previous and new tephrostratigraphic analyses of six volcanic ash layers constrain the investigated interval to between 92.3 and 115.0 ka. The δ18O composition is interpreted as a proxy for precipitation amount in the high-altitude catchment of the karst recharge system. The oxygen record shows millennial variability that is consistent with Greenland Interstadials GI25–23 and North Atlantic cold events C24–C22, indicating a strong Mediterranean–North Atlantic climate teleconnection. However, while no appreciable isotopic difference between the three interstadials is revealed by the Greenland record, the Sulmona section reveals a wetter climate during GI24 compared with GI23 and GI25. Comparison of our record with speleothem and pollen data from central and southern Italy suggests higher seasonality of the precipitation (wet winter–dry summer) for GI24, which matches a precession minimum. The wettest period recorded at Sulmona is also coincident with the deposition of Sapropel S4 in the Tyrrhenian Sea, suggesting a teleconnection between a higher seasonality in the western Mediterranean and strengthening of the boreal monsoon system.

Relatively few radiometrically dated records are available for the central Mediterranean spanning the marine oxygen isotope stage 6–5 (MIS 6–5) transition and the first part of the Last Interglacial. Two flowstone cores from Tana che Urla Cave (TCU, central Italy), constrained by 19 U/Th ages, preserve an interval of continuous speleothem deposition between ca. 159 and 121 ka. A multiproxy record (δ18O, δ13C, growth rate and petrographic changes) obtained from this flowstone preserves significant regional-scale hydrological changes through the glacial/interglacial transition and multi-centennial variability (interpreted as alternations between wetter and drier periods) within both glacial and interglacial stages. The glacial stage shows a wetter period between ca. 154 and 152 ka, while the early to middle Last Interglacial period shows several drying events at ca. 129, 126 and 122 ka, which can be placed in the wider context of climatic instability emerging from North Atlantic marine and NW European terrestrial records. The TCU record also provides important insights into the evolution of local environmental conditions (i.e. soil development) in response to regional and global-scale climate events.

Many geographically dispersed records from across the globe reveal the occurrence of abrupt climate changes, called interstadial events, during the last glacial period. These events appear to have happened at the same time, but the difficulty of determining absolute dates in many of the records have made that proposition difficult to prove. Corrick et al. present results from 63 precisely dated speleothems that confirm the synchrony of those interstadial events. Their results also provide a tool with which to validate model simulations of abrupt climate change and calibrate other time series such as ice-core chronologies.Science, this issue p. 963Abrupt climate changes during the last glacial period have been detected in a global array of palaeoclimate records, but our understanding of their absolute timing and regional synchrony is incomplete. Our compilation of 63 published, independently dated speleothem records shows that abrupt warmings in Greenland were associated with synchronous climate changes across the Asian Monsoon, South American Monsoon, and European-Mediterranean regions that occurred within decades. Together with the demonstration of bipolar synchrony in atmospheric response, this provides independent evidence of synchronous high-latitude–to-tropical coupling of climate changes during these abrupt warmings. Our results provide a globally coherent framework with which to validate model simulations of abrupt climate change and to constrain ice-core chronologies.

Radiometric dating of glacial terminations over the past 640,000 years suggests pacing by Earth’s climatic precession, with each glacial-interglacial period spanning four or five cycles of ~20,000 years. However, the lack of firm age estimates for older Pleistocene terminations confounds attempts to test the persistence of precession forcing. We combine an Italian speleothem record anchored by a uranium-lead chronology with North Atlantic ocean data to show that the first two deglaciations of the so-called 100,000-year world are separated by two obliquity cycles, with each termination starting at the same high phase of obliquity, but at opposing phases of precession. An assessment of 11 radiometrically dated terminations spanning the past million years suggests that obliquity exerted a persistent influence on not only their initiation but also their duration. We acknowledge financial support from Australian Research Council Discovery Project grants 0664621 (to J.D.W.), 110102185 (to R.N.D., J.D.W., J.C.H., E.W., A.E.F., and S.F.), and 160102969 (to R.N.D., J.D.W., G.Z., E.W., and P.F.). We thank the Gruppo Speleologico Lucchese and the Federazione Speleologica Toscana for logistic and funding support. The SUERC contribution to this study falls within the framework of the Scottish Alliance for Geoscience, Environment and Society (SAGES). P.B. was the recipient of a University of Melbourne International Postgraduate Research Scholarship and Postgraduate Writing-Up Award supported by the Albert Shimmins Fund. J.C.H. was the recipient of an Australian Research Council Future Fellowship (FT130100801). P.F. acknowledges support from the European Union through a Marie-Curie Reintegration grant (PERG-GA-2010-272134 - MILLEVARIABILI). D.H. acknowledges support from the UK Natural Environmental Research Council. E.W. is supported by a Royal Society Professorship. A.H.L.V. and T.R. received financial support from Fundação para a Ciência e a Tecnologia (FCT, Portugal) projects MOWCADYN (PTDC/MAR-PRO/3761/2012), WarmWorld (PTDC/CTA-GEO/29897/2017), and CCMAR (UID/ Multi/04326/2019). Samples from the marine sites were provided by the Integrated Ocean Drilling Program to D.H., A.H.L.V., and T.R. info:eu-repo/semantics/publishedVersion

We present new data on the 4.2 ka event in the central Mediterranean from Corchia Cave (Tuscany, central Italy) stalagmite CC27. The stalagmite was analyzed for stable isotopes (δ13C and δ18O) and trace elements (Mg, U, P, Y), with all proxies showing a coherent phase of reduced cave recharge between ca. 4.5 and 4.1 ka BP. Based on the current climatological data on cyclogenesis, the reduction in cave recharge is considered to be associated with the weakening of the cyclone center located in the Gulf of Genoa in response to reduced advection of air masses from the Atlantic during winter. These conditions, which closely resemble a positive North Atlantic Oscillation (NAO) type of configuration, are associated with cooler and wetter summers with reduced sea warming, which reduced the western Mediterranean evaporation during autumn–early winter, further reducing precipitation.