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The abrupt weakening of the East Asian summer monsoon (EASM) during Younger Dryas (YD) has been attributed to freshwater discharge into the North Atlantic ocean and resultant Northern Hemisphere cooling. Recent studies have found that sea ice variability in the Nordic Sea during the YD exerted a great influence upon the northern high-latitude climate. However, the influence of sea ice upon EASM evolution during YD event remains unclear. In this paper, we report two precisely-dated speleothem oxygen isotope records from the EASM-dominated region of central China. Our records archive abrupt changes in EASM variability during the YD event. Initially, there was a significant strengthening of the EASM during the mid-YD following the gradually increased Atlantic meridional overturning circulation (AMOC). Later this trend reversed at ∼12.15 ka due to northern high-latitude sea ice fluctuations and a consequent reduction of AMOC. At the YD termination, abrupt intensification of the EASM was synchronous with the rapid decline of sea-ice and recovery of the AMOC indicating that sea ice variability was a significant influence on high latitude climate and EASM variation during the YD. • A new speleothem δ18O record show significant EASM strengthening during mid-YD. • Mid-YD oscillation in EASM linked with NH sea ice variability. • Abrupt EASM intensification at YD termination synchronous with the rapid decline of sea ice. • Drier interval following the YD termination in central China. [ABSTRACT FROM AUTHOR]

Abstract The Eocene was an interval of climate evolution, when the extreme high temperatures of the earliest Cenozoic gave way to a global cooling trend. Fine-grained lacustrine sediments of Eocene age from northeastern China represent an excellent archive to study long-term environmental and climatic changes at high-resolution. The Huadian Basin is a Cenozoic, fault-bounded basin in Jilin Province, northeastern China. Though small in area, it contains numerous oil shale- and coal-bearing layers, which provide an abundant Middle to Late Eocene palynoflora. Eighty-five palynomorph genera and one hundred palynomorph species were identified in the Huadian Formation, allowing to distinguish 4 palynozones. The nearest living relatives of the recovered palynomorph taxa suggest the presence of subtropical evergreen and deciduous broad-leaved forests during deposition of the Huadian Formation. Using the coexistence approach (CA), we calculated seven paleoclimatic parameters, which indicate a subtropical warm and humid climate with a mean annual temperature above 13.6 °C and a mean annual precipitation of at least 887 mm. However, the climate became cooler and drier during the transition from the lower Oil Shale Member to the upper Carbonaceous Shale Member. Palaeoclimatic data from the various Middle and Late Eocene basins of northeastern China (i.e., the Huadian, Fushun, Yilan, Hunchun and Jishu basins) were compared with data from North American and European basins. Middle Eocene climate in the Northern Hemisphere was generally warm and humid, and the mean annual temperature and precipitation in northeastern China were similar to those in North America, though slightly lower than those of Europe. Similar trends in temperature and precipitation on different continents support the existence of a global Mid-Eocene cooling event. This paper is the first systematic study of Middle to Late Eocene seasonality in the Huadian Basin. Our results show an apparent differentiation in both temperature and precipitation between summer and winter, supporting the view that the East Asian Monsoon was established in northeastern China already during the Middle to Late Eocene. This Middle and Late Eocene monsoon was likely driven by the development of Pacific trade winds and an alternating, seasonal high- and low-pressure system over Siberia. The climatic changes observed in our dataset, especially the precipitation changes, appear to have played an important role in controlling oil shale formation in the Huadian Basin. A warmer and more humid climate, with abundant precipitation and high subsidence rates, formed a deeper Huadian depositional lake. High productivity and stable stratification provided the abundant organic matter and favorable preservation conditions necessary for oil shale accumulation. Highlights • The Middle-Late Eocene palynoflora were firstly systematically studied in Huadian Basin. • We quantitatively estimated the Middle-Late Eocene climate based on CA method. • A globally cooler phase was recognized in the Middle Eocene. • Climate seasonality in the Middle-Late Eocene supports the EAM was already prevalent in NE China. • Changes in climate, especially precipitation, play an important role in oil shale formation. [ABSTRACT FROM AUTHOR]

Understanding environmental conditions faced by hunter-fisher-gatherers during the Pleistocene and Holocene, and interpretation of subsistence strategies, social organisation and settlement patterns, are key topics for the study of past human societies. In this respect, oxygen isotope values (δ 18 O) of mollusc shell calcium carbonate can provide important information on palaeoclimate and the seasonality of shell collection at archaeological sites. In this paper, we tested P. vulgata shells from northern Iberia as a paleoclimate archive through the study of shell oxygen isotope values and sclerochronology of modern samples. Results showed that limpets formed their shells close to isotopic equilibrium, with an average offset between measured and predicted values of 0.36‰. This offset is significantly reduced with respect to those reported in previous studies, probably due to the use of highly resolved data on the isotopic composition of the water when calculating predicted values. Despite large intra-specific variability, shell growth patterns of P. vulgata revealed a common pattern of higher growth in spring and a growth cessation/slowdown in summer and winter. The seasonal growth cessation/slowdown did not exceed three months. Therefore, a correct interpretation of the season of shell collection is still possible. Reconstructed seawater temperature exhibited a high correlation with instrumental temperature (R 2 = 0.68 to 0.93; p < 0.0001). Despite periods of growth cessation/slowdown, mean seawater temperatures and annual ranges were reconstructed accurately. As demonstrated here, seawater temperature can be reconstructed with a maximum uncertainty of ± 2.7 °C. Therefore, our study shows that oxygen isotope values from P. vulgata can be used for the reconstruction of paleoclimate and the season of shell collection. [ABSTRACT FROM AUTHOR]

Understanding environmental conditions faced by hunter-fisher-gatherers during the Pleistocene and Holocene, and interpretation of subsistence strategies, social organisation and settlement patterns, are key topics for the study of past human societies. In this respect, oxygen isotope values (δ 18 O) of mollusc shell calcium carbonate can provide important information on palaeoclimate and the seasonality of shell collection at archaeological sites. In this paper, we tested P. vulgata shells from northern Iberia as a paleoclimate archive through the study of shell oxygen isotope values and sclerochronology of modern samples. Results showed that limpets formed their shells close to isotopic equilibrium, with an average offset between measured and predicted values of 0.36‰. This offset is significantly reduced with respect to those reported in previous studies, probably due to the use of highly resolved data on the isotopic composition of the water when calculating predicted values. Despite large intra-specific variability, shell growth patterns of P. vulgata revealed a common pattern of higher growth in spring and a growth cessation/slowdown in summer and winter. The seasonal growth cessation/slowdown did not exceed three months. Therefore, a correct interpretation of the season of shell collection is still possible. Reconstructed seawater temperature exhibited a high correlation with instrumental temperature (R 2 = 0.68 to 0.93; p < 0.0001). Despite periods of growth cessation/slowdown, mean seawater temperatures and annual ranges were reconstructed accurately. As demonstrated here, seawater temperature can be reconstructed with a maximum uncertainty of ± 2.7 °C. Therefore, our study shows that oxygen isotope values from P. vulgata can be used for the reconstruction of paleoclimate and the season of shell collection. [ABSTRACT FROM AUTHOR]

• The potential of Spisula sachalinensis as a high resolution temperature indicator • δ 18O inversely correlates to seasonal ocean temperature but δ 13C is less cyclical • Annual growth lines are formed during the warmest part of the year • Annual and non-annual growth lines are distinguishable via stable isotope analysis • Archaeological S. sachalinensis offer a valuable regional palaeoclimate record This paper presents a four year subannual isotope marine temperature record using modern Spisula sachalinensis specimens from Tomakomai (Hokkaido's Pacific coast, Japan). This species is commonly found in pre- and protohistoric shell middens and faunal assemblages from around the Seas of Japan and Okhotsk, so has significant potential as an indicator of past marine and, by inference, climatic conditions. However, previous sclerochronological research on the species' growth has shown significant geographical variation in growth pattern, rendering palaeoclimatic interpretation difficult. To address this issue, this study applied sequential isotopic analysis to two sectioned modern valves, providing a proxy for sea surface temperature (SST) and allowing the direct identification of seasonality during shell growth. The sequences span four years of growth, as confirmed by visually identified growth patterns and the oxygen stable isotope results, which show clear annual cycles in δ 18O. δ 13C seasonality is less clear, but shows a weak inverse correlation with temperature potentially relating to primary productivity. Annual growth lines show that shell growth occurs during both warmer and cooler SSTs, but is more rapid during the cooler seasons. This is consistent with warm-season growth minima seen in shells from Hakodate Bay by Kato and Hamai (1975) , but not with their suggestion that it is associated with shells growing at the southern limits of their distribution. Comparison to average local SST shows that δ 18O-derived temperature falls within the expected range, but, contrary to expectations given preferential cool-season shell growth, appears biased towards warmer temperatures. Factors that could contribute to this are discussed. Overall, stable isotope analysis of Spisula sachalinensis is considered a useful complement to macro/microscopic sclerochronological research in building a holistic picture of shell growth, and has significant potential as a high resolution proxy for palaeoenvironmental studies of past SST. [ABSTRACT FROM AUTHOR]

Abstract: The Lodève basin, which contains an exceptional long and nearly uninterrupted profile of Early to Late Permian continental red beds, is well correlated to the other European Permocarboniferous basins. Together they cover the time span from the Late Pennsylvanian to the Permian–Triassic boundary. Although these basins were placed within the equatorial belt for the whole Permian, several climatic changes are recorded in the sediments. Terrestrial sedimentation is governed by the interaction of climate and tectonics as well as by volcanism to a variable degree. Therefore, small scale climatic variations of the Milankovitch band are hardly discernable and if so, they could not be correlated between different basins. Indeed, larger scale climatic shifts could be identified. It is shown, that the shift from the Carboniferous icehouse to the Mesozoic warmhouse was a multi-stage process. This global warming resulted in a general aridisation of northern Pangea, indicated by outspreading playa and sabkha red beds, aeolianites and evaporites. Several short phases of increased humidity interrupted this trend, indicated by wet red beds, lake sediments and coal deposits. In central and southern Europe, these wet periods are traceable within the Late Stephanian/Lower Rotliegend (Gzhelian/Asselian), topmost Lower Rotliegend (Asselian/Sakmarian), Upper Rotliegend I (late Artinskian/early Kungurian) and Upper Rotliegend II/Zechstein (Wuchiapingian). The aridisation of the northern Pangea which accelerated near the Sakmarian/Artinskian transition is attributed to a reorganisation of the major ocean currents. Cold water currents along the western flank of the Pangea, indicated by the Permian chert event, blocks moisture transport from West onto the continent. During Roadian and Wordian the onset of an additional cold water current along the Cimmerian continents, blocks moisture transport from the East. Both phenomena together are responsible for the maximum of aridity at the Early to Middle Permian transition. Additionally, the equatorial climate has been affected by an increasing seasonality within the Late Pennsylvanian and Permian, caused by the wide shifting of the Zone of Inter-tropical Convergence (ITC) over the equator. Based on a new reconstruction of the Pangean assembly in this paper, climatic changes in the Permian are interpreted and causes of the arid-humid-arid shifts are examined. Phases of higher humidity are often related to events of global impact, like the waxing and waning of the Gondwanan glaciation, obtained in the South African Karoo Basin (Dwyka Group). But also regional events had strong climatic influence. The Zechstein transgression in the Northern and Southern Permian Basin as well as the Bellerophon transgression of the Southern Alps caused the wet phase in the Wuchiapingian. [Copyright &y& Elsevier]