Glacial Climate Changes Research Articles

Phytolith based paleoecological reconstruction from a loess-paleosol sequence in the Kashmir Himalaya, India

The temporal vegetation development provides vital information for understanding past climatic changes. In this study, we reconstruct vegetation dynamics from the last glacial period using phytoliths as a proxy from the Wanihama loess-paleosol sequence (LPS) near Srinagar in Kashmir Himalaya, India. Different phytolith assemblages and indices (Ic and Iw) revealed a series of warm and cold events documented in the LPS. The data indicate the predominance of broad-leaved and sparse conifer vegetation from ca. 42 ka to 39 ka, suggesting a comparatively warm and humid climate. After ca. 39 ka, conifers and grasses increased, indicating a transition to a cold climate. The cold climate, intervened by a short stadial, continued until ca. 31 ka with the predominance of conifers, grasses, and sedges. Subsequently, three other cold events were noted until ca. 14 ka, which resulted in vegetation disappearance and a substantial decrease in phytolith count. These cold events roughly coincide with the climatic instability in the Atlantic Ocean that caused severe cooling at high northern latitudes and likely impacted the Asian climate. Phytolith assemblages showed an overall increasing proportion of C4 grasses towards the top of the LPS, suggesting warm and dry climatic conditions. We also correlated the phytolith-based vegetation reconstruction with other paleoenvironmental proxies recorded from the same section, as well as with the last glacial climatic changes documented in different regions, to determine the reliability of phytoliths in LPSs as a proxy for past vegetation and climate reconstruction in the Kashmir Himalaya.

Evidence for Admixture and Rapid Evolution During Glacial Climate Change in an Alpine Specialist.

The pace of current climate change is expected to be problematic for alpine flora and fauna, as their adaptive capacity may be limited by small population size. Yet, despite substantial genetic drift following post-glacial recolonization of alpine habitats, alpine species are notable for their success surviving in highly heterogeneous environments. Population genomic analyses demonstrating how alpine species have adapted to novel environments with limited genetic diversity remain rare, yet are important in understanding the potential for species to respond to contemporary climate change. In this study, we explored the evolutionary history of alpine ground beetles in the Nebria ingens complex, including the demographic and adaptive changes that followed the last glacier retreat. We first tested alternative models of evolutionary divergence in the species complex. Using millions of genome-wide SNP markers from hundreds of beetles, we found evidence that the N. ingens complex has been formed by past admixture of lineages responding to glacial cycles. Recolonization of alpine sites involved a distributional range shift to higher elevation, which was accompanied by a reduction in suitable habitat and the emergence of complex spatial genetic structure. We tested several possible genetic pathways involved in adaptation to heterogeneous local environments using genome scan and genotype-environment association approaches. From the identified genes, we found enriched functions associated with abiotic stress responses, with strong evidence for adaptation to hypoxia-related pathways. The results demonstrate that despite rapid demographic change, alpine beetles in the N. ingens complex underwent rapid physiological evolution.

Solutrean macrofauna from Cova de les Cendres (Alicante, Spain): zooarchaeological and taphonomic analysis

Zooarchaeological and taphonomic analysis were performed on the macrofaunal remains from Solutrean levels XIII and XIV (ca. 17 and 20 ka cal BP) of Cova de les Cendres. The faunal assemblage shows predominance of red deer, followed by Spanish ibex and equids, among which wild ass (Equus hydruntinus) was identified. Carnivores are well represented in level XIII, especially the lynx, whereas they are very rare in level XIV. Different activities of the butchery process were documented in the main taxa, showing an intensive exploitation of different animal resources, such as meat, fur, and raw material for tools and ornaments. Our results provide new zooarchaeological data on the Solutrean hunting system and shed light on the human subsistence variations in response to late glacial climate changes in the central area of the Mediterranean Iberia.

Genomic analysis reveals a cryptic pangolin species

Eight extant species of pangolins are currently recognized. Recent studies found that two mitochondrial haplotypes identified in confiscations in Hong Kong could not be assigned to any known pangolin species, implying the existence of a species. Here, we report that two additional mitochondrial haplotypes identified in independent confiscations from Yunnan align with the putative species haplotypes supporting the existence of this mysterious species/population. To verify the new species scenario we performed a comprehensive analysis of scale characteristics and 138 whole genomes representing all recognized pangolin species and the cryptic new species, 98 of which were generated here. Our morphometric results clearly attributed this cryptic species to Asian pangolins (Manis sp.) and the genomic data provide robust and compelling evidence that it is a pangolin species distinct from those recognized previously, which separated from the Philippine pangolin and Malayan pangolin over 5 Mya. Our study provides a solid genomic basis for its formal recognition as the ninth pangolin species or the fifth Asian one, supporting a new taxonomic classification of pangolins. The effects of glacial climate changes and recent anthropogenic activities driven by illegal trade are inferred to have caused its population decline with the genomic signatures showing low genetic diversity, a high level of inbreeding, and high genetic load. Our finding greatly expands current knowledge of pangolin diversity and evolution and has vital implications for conservation efforts to prevent the extinction of this enigmatic and endangered species from the wild.

Millennial-timescale quantitative estimates of climate dynamics in central Europe from earthworm calcite granules in loess deposits

Ice core and marine archives provide detailed quantitative records of last glacial climate changes, whereas comparable terrestrial records from the mid-latitudes remain scarce. Here we quantify warm season land-surface temperatures and precipitation over millennial timescales for central Europe for the period spanning 45,000–22,000 years before present that derive from two temporally overlapping loess-palaeosol-sequences, dated at high resolution by radiocarbon on earthworm calcite granules. Interstadial temperatures were 1–4 °C warmer than stadial climate, a temperature difference which is strongly attenuated compared to Greenland records. We show that climate in the Rhine Valley was significantly cooler during the warm season and overall drier with annual precipitation values reduced by up to 70% compared to the present day. We combine quantitative estimates with mesoscale wind and moisture transport modelling demonstrating that this region was dominated by westerlies and thereby inextricably linked to North Atlantic climate forcing, although ameliorated.

Genetic Diversity, Population Structure, and Conservation Units of Castanopsis sclerophylla (Fagaceae)

Castanopsis sclerophylla (Lindl.) Schott. is a canopy tree species of evergreen broad-leaved forests in subtropical China. In this study, the genetic diversity and population structure of C. sclerophylla were investigated by using chloroplast DNA sequences and nuclear microsatellite markers. Permutation tests with chloroplast DNA sequences indicated the presence of phylogeographic structure in C. sclerophylla. Based on nuclear microsatellite markers, Bayesian clustering analysis revealed eastern-to-western differentiation in C. sclerophylla, and the analysis of molecular variance suggested population divergence has arisen along the Xuefeng, Luoxiao, and Wuyi mountain ranges. The approximate Bayesian computation demonstrated that the genetic diversity pattern of C. sclerophylla could be explained by geographic isolation followed by secondary contact. Ecological niche modelling showed that distribution of C. sclerophylla shrank southward at the Last Glacial Maximum and expanded northward at the Mid Holocene. These results suggested that the uplift of the Xuefeng, Luoxiao, and Wuyi mountain ranges and the interglacial–glacial climate change shaped the genetic diversity of C. sclerophylla. The Luoxiao mountain range should be considered as a key conservation unit of C. sclerophylla due to its higher level of genetic diversity. Our study supplies important information for prioritizing the conservation and sustainable utilization of C. sclerophylla, and provides insight on the dynamics of evergreen broad-leaved forests in subtropical China.

Hysteresis of the Glacial Atlantic Meridional Overturning Circulation Controlled by Thermal Feedbacks

AbstractThe multiple equilibrium behavior of the Atlantic meridional overturning circulation (AMOC) is related to the mode transition of the AMOC, which played an important role in abrupt glacial climate changes. However, the difference between modern and glacial climates is not well understood. Here, we examined the structure of the multiple equilibria of the AMOC under the modern and glacial climates through hysteresis experiments using an earth system model of intermediate complexity. The glacial AMOC exhibited a shallower AMOC mode but not the off mode, and a narrower range of multiple equilibria than the modern AMOC. This glacial hysteresis behavior occurred associated with a shift of deep water formation due to changes in surface air temperature and sea ice, whereas that of the modern AMOC is attributed to the basin‐scale salinity feedback. These features were commonly found in two glacial simulations with different strengths of the AMOC at the Last Glacial Maximum.

Rapid reductions and millennial-scale variability in Nordic Seas sea ice cover during abrupt glacial climate changes

Constraining the past sea ice variability in the Nordic Seas is critical for a comprehensive understanding of the abrupt Dansgaard-Oeschger (D-O) climate changes during the last glacial. Here we present unprecedentedly detailed sea ice proxy evidence from two Norwegian Sea sediment cores and an East Greenland ice core to resolve and constrain sea ice variations during four D-O events between 32 and 41 ka. Our independent sea ice records consistently reveal a millennial-scale variability and threshold response between an extensive seasonal sea ice cover in the Nordic Seas during cold stadials and reduced seasonal sea ice conditions during warmer interstadials. They document substantial and rapid sea ice reductions that may have happened within 250 y or less, concomitant with reinvigoration of deep convection in the Nordic Seas and the abrupt warming transitions in Greenland. Our empirical evidence thus underpins the cardinal role of rapid sea ice decline and related feedbacks to trigger abrupt and large-amplitude climate change of the glacial D-O events.

Coupling of the Subpolar Gyre and the Overturning Circulation During Abrupt Glacial Climate Transitions

AbstractWe present a mechanism for self‐sustained ocean circulation changes that cause abrupt temperature changes over Greenland in a multimillennial climate model simulation with glacial CO2 concentrations representative of Marine Isotope Stage 3. The Atlantic meridional overturning circulation (AMOC) and the subpolar gyre (SPG) oscillate on millennial time scales. When the AMOC is strong, the SPG is weak and contracted; when the AMOC is weak, the SPG is strong and extensive. The coupling between the two systems via wind‐driven and density‐driven feedbacks is key to maintaining the oscillations. The SPG controls the transport of heat and salt into the deep‐water formation sites and thus controls the AMOC strength. The strength and location of the deep‐water formation affect the density‐driven part of the SPG and thus control the mean strength and extent of the SPG. This mechanism supports the hypothesis that coupled ocean‐ice‐atmosphere interactions could have triggered abrupt glacial climate change.

Towards understanding potential atmospheric contributions to abrupt climate changes: characterizing changes to the North Atlantic eddy-driven jet over the last deglaciation

Abstract. Abrupt climate shifts of large amplitudes were common features of the Earth's climate as it transitioned into and out of the last full glacial state approximately 20 000 years ago, but their causes are not yet established. Midlatitude atmospheric dynamics may have played an important role in these climate variations through their effects on heat and precipitation distributions, sea ice extent, and wind-driven ocean circulation patterns. This study characterizes deglacial winter wind changes over the North Atlantic (NAtl) in a suite of transient deglacial simulations using the PlaSim Earth system model (run at T42 resolution) and the TraCE-21ka (T31) simulation. Though driven with yearly updates in surface elevation, we detect multiple instances of NAtl jet transitions in the PlaSim simulations that occur within 10 simulation years and a sensitivity of the jet to background climate conditions. Thus, we suggest that changes to the NAtl jet may play an important role in abrupt glacial climate changes. We identify two types of simulated wind changes over the last deglaciation. Firstly, the latitude of the NAtl eddy-driven jet shifts northward over the deglaciation in a sequence of distinct steps. Secondly, the variability in the NAtl jet gradually shifts from a Last Glacial Maximum (LGM) state with a strongly preferred jet latitude and a restricted latitudinal range to one with no single preferred latitude and a range that is at least 11∘ broader. These changes can significantly affect ocean circulation. Changes to the position of the NAtl jet alter the location of the wind forcing driving oceanic surface gyres and the limits of sea ice extent, whereas a shift to a more variable jet reduces the effectiveness of the wind forcing at driving surface ocean transports. The processes controlling these two types of changes differ on the upstream and downstream ends of the NAtl eddy-driven jet. On the upstream side over eastern North America, the elevated ice sheet margin acts as a barrier to the winds in both the PlaSim simulations and the TraCE-21ka experiment. This constrains both the position and the latitudinal variability in the jet at LGM, so the jet shifts in sync with ice sheet margin changes. In contrast, the downstream side over the eastern NAtl is more sensitive to the thermal state of the background climate. Our results suggest that the presence of an elevated ice sheet margin in the south-eastern sector of the North American ice complex strongly constrains the deglacial position of the jet over eastern North America and the western North Atlantic as well as its variability.

The presence of a cryptic barrier in the West Pacific Ocean suggests the effect of glacial climate changes on a widespread sea-dispersed plant, Vigna marina (Fabaceae).

Ocean currents are an important driver of evolution for sea‐dispersed plants, enabling them to maintain reciprocal gene flow via sea‐dispersed diaspores and obtain wide distribution ranges. Although geographic barriers are known to be the primary factors shaping present genetic structure of sea‐dispersed plants, cryptic barriers which form clear genetic structure within oceanic regions are poorly understood. To test the presence of a cryptic barrier, we conducted a phylogeographic study together with past demographic inference for a widespread sea‐dispersed plant, Vigna marina, using 308 individuals collected from the entire Indo‐West Pacific (IWP) region. Chloroplast DNA variation showed strong genetic structure that separated populations into three groups: North Pacific (NP), South Pacific (SP) and Indian Ocean (IN) (F′CT among groups = 0.954–1.000). According to the Approximate Bayesian computation inference, splitting time between NP and SP was approximately 20,200 years (95%HPD, 4,530–95,400) before present. Moreover, a signal of recent population expansion was detected in the NP group. This study clearly showed the presence of a cryptic barrier in the West Pacific region of the distributional range of V. marina. The locations of the cryptic barrier observed in V. marina corresponded to the genetic breaks found in other plants, suggesting the presence of a common cryptic barrier for sea‐dispersed plants. Demographic inference suggested that genetic structure related to this cryptic barrier has been present since the last glacial maximum and may reflect patterns of past population expansion from refugia.

Phylogeography and ecological niche modeling unravel the evolutionary history of the Yarkand hare, Lepus yarkandensis (Mammalia: Leporidae), through the Quaternary

BackgroundThe Taklimakan Desert in China is characterized by unique geological and historical dynamics and endemic flora and fauna, but the influence of historical climate oscillations on the evolutionary history of endemic animals is poorly understood. Lepus yarkandensis is an oases-dependent Near Threatened species that lives in fragmented oasis habitats in the Taklimakan Desert, China. We investigated the geological and climatic impacts on its geographical differentiation, demographic history and influence of Pleistocene glacial-interglacial cycles on the evolutionary history of L. yarkandensis. Further, studied the impact of climatic oscillation based modification on phylogeography, distribution and diversification pattern of Yarkand hare by using Cytb (1140 bp), MGF (592 bp) and SPTBN1 (619 bp) markers. Ecological niche modeling (ENM) revealed the evolutionary history of this species in response to climate change during the Quaternary. Paleodistribution modeling was used to identify putative refugia and estimate their historical distributions.ResultsBoth historical demographic analyses and climatic niche modeling revealed strong effects of glacial climate changes, suggesting recurrent range contractions and expansions. The EBSP results indicated clear population expansion of L. yarkandensis since the Pleistocene. In the “early Pleistocene”, the demographic expansion continued from 0.83 MYA to the last glacial period. The ENM analysis supported a wide distribution of Lepus yarkandensis at high altitudes during the last interglacial (LIG) period. During the last glacial maximum (LGM), the suitable climate was reduced and restricted to the western part of the Taklimakan Desert.ConclusionsInland aridification, oasis evolution and river flow played major roles in the population differentiation and demographic history of Yarkand hares. Historically, the large, continuous oases in the Taklimakan Desert contained a viable and unique population of L. yarkandensis. The fragmented desert environment might have caused low gene flow between individuals or groups, thus leading to predominant genetic differentiation. The Pleistocene climatic cycles triggered the diversification and expansion of this species during cold and warm periods, respectively, leading to multiple colonization events within the Taklimakan Desert. These events might be due to the expansion of the Taklimakan Desert during the Middle Pleistocene. Yarkand hare previously occupied vast areas at low and intermediate altitudes in Xinjiang, Gansu, Shanxi, Henan and Shaanxi Provinces in China. The past aridification, climate change-induced oasis modifications, changes in river volumes and flow directions, and human activities all affected the population demography and phylogeography of the Yarkand hare.

A consistent statistical model selection for abrupt glacial climate changes

The most pronounced mode of climate variability during the last glacial period are the so-called Dansgaard–Oeschger events. There is no consensus of the underlying dynamical mechanism of these abrupt climate changes and they are elusive in most simulations of state-of-the-art coupled climate models. There has been significant debate over whether the climate system is exhibiting self-sustained oscillations with vastly varying periods across these events, or rather noise-induced jumps in between two quasi-stable regimes. In previous studies, statistical model comparison has been employed to the NGRIP ice core record from Greenland in order to compare different classes of stochastic dynamical systems, representing different dynamical paradigms. Such model comparison studies typically rely on accurately reproducing the observed records. We aim to avoid this due to the large amount of stochasticity and uncertainty both on long and short time scales in the record. Instead, we focus on the most important qualitative features of the data, as captured by summary statistics. These are computed from the distributions of waiting times in between events and residence times in warm and cold regimes, as well as the stationary density and the autocorrelation function. We perform Bayesian inference and model comparison experiments based solely on these summary statistics via Approximate Bayesian Computation. This yields an alternative approach to existing studies that helps to reconcile and synthesize insights from Bayesian model comparison and qualitative statistical analysis.

Mitochondrial phylogeography of the Iberian endemic frog Rana iberica, with implications for its conservation.

Genetic characterization of species using phylogeographic approaches represents a basic reference to understand their evolutionary history as well as to identify conservation priorities to protect areas of particular interest regarding evolutionary potential. Even in well-studied regions such information is lacking for the majority of species, including many endemic species with reduced distribution ranges. We investigate the phylogeographic pattern of the Iberian frog Rana iberica, an endemic amphibian restricted to Central and North-Western Iberian Peninsula. Using mitochondrial sequences, we reconstruct the phylogeographic history of the species to test the effect of Quaternary climate changes on the evolutionary diversification of lineages, that is, the differentiation of mitochondrial lineages and the formation of genetic diversity melting pots, and integrate phylogeographic evidence for future conservation planning. Our results indicate the existence of 3 main mitochondrial lineages differentiated during the Upper Pleistocene. Both historical demographic analyses and climatic niche modeling show a strong effect of glacial climate changes, suggesting recurrent range contractions and expansions. Under such circumstances, differentiation took place most likely by isolation in allopatric interglacial refugia. Secondary lineage admixture in northern Portugal generated a broad mixed zone with highest nucleotide diversity. Given its particular evolutionary potential, its reduced distribution and eventual threats under current climate change scenario, conservation priorities should focus on the isolated lineage from Sierra de Guadalupe.

The Last Glacial aeolian record of the Island of Susak (Croatia) as seen from a high-resolution grain–size and rock magnetic analysis

The loess-palaeosol record on the island of Susak in Croatia is a unique archive of Late Glacial climate changes in the Adriatic region, possibly even in the wider area. On Susak up to 90 m of thick Quaternary sediments were deposited, and are accessible for detailed palaeoclimate reconstructions. In this paper, the results of a high-resolution grain-size and rock magnetic investigation on the Last Glacial (Upper Pleniglacial) Sand Pit section from Susak are presented. In spite of its significant thickness, the Sand Pit section does not represent a continuous record; it is a result of a very dynamic environment. There, the deposition of dust and formation of loess has been interrupted by pedogenesis, periods of increased sand accumulation, erosion due to slope wash and water activity, redeposition and wildfires, and all in the time period of about 10.000 years of the Upper Pleniglacial, as seen from the IRSL dating results. The grain-size data clearly show a shift towards coarser grain sizes which differs from typical loess regions. Such predominance of the coarser-grained over the fine-grained fraction, very likely resulted from the predominance of deposition over pedogenesis, increased wind activity and proximal source of material. The rock magnetic signal preserved in the sediment also differs compared to loess-palaeosol records from other regions. The susceptibility values are several times higher than in the records from the Pannonian basin and from typical Eurasian loess. Both the increased susceptibility values and the grain-size are very likely the result of a significant proximal material input from the Po River plain.

A new high-resolution pollen sequence at Lake Van, Turkey: insights into penultimate interglacial–glacial climate change on vegetation history

Abstract. A new detailed pollen and oxygen isotope record of the penultimate interglacial–glacial cycle, corresponding to the marine isotope stage (MIS) 7–6, has been generated from the Ahlat Ridge (AR) sediment core at Lake Van, Turkey. The presented Lake Van pollen record (ca. 250.2–128.8 ka) displays the highest temporal resolution in this region with a mean sampling interval of ∼ 540 years.The integration of all available proxies shows three temperate intervals of high effective soil moisture availability. This is evidenced by the predominance of steppe-forested landscapes (oak steppe-forest) similar to the present interglacial vegetation in this sensitive semiarid region between the Black Sea, the Caspian Sea, and the Mediterranean Sea.The wettest and warmest stage, as indicated by highest temperate tree percentages, can be broadly correlated with MIS 7c, while the amplitude of the tree population maximum during the oldest penultimate interglacial (MIS 7e) appears to be reduced due to warm but drier climatic conditions. The detailed comparison of the penultimate interglacial complex (MIS 7) to the last interglacial (Eemian, MIS 5e) and the current interglacial (Holocene, MIS 1) provides a vivid illustration of possible differences in the successive climatic cycles. Intervening periods of treeless vegetation can be correlated with MIS 7d and 7a, in which open landscapes favor local erosion and detrital sedimentation. The predominance of steppe elements (e.g., Artemisia, Chenopodiaceae) during MIS 7d indicates very dry and cold climatic conditions. In contrast, the occurrence of higher temperate tree percentages (mainly deciduous Quercus) throughout MIS 7b points to relatively humid and mild conditions, which is in agreement with other pollen sequences in southern Europe.Despite the general dominance of dry and cold desert-steppe vegetation during the penultimate glacial (broadly equivalent to MIS 6), this period can be divided into two parts: an early stage (ca. 193–157 ka) with higher oscillations in tree percentages and a later stage (ca. 157–131 ka) with lower tree percentages and subdued oscillations. This subdivision of the penultimate glacial is also seen in other pollen records from southern Europe (e.g., MD01-2444 and I-284; Margari et al., 2010; Roucoux et al., 2011). The occurring vegetation pattern is analogous to the division of MIS 3 and MIS 2 during the last glacial in the same sediment sequence. Furthermore, we are able to identify the MIS 6e event (ca. 179–159 ka) as described in marine pollen records, which reveals clear climate variability due to rapid alternation in the vegetation cover.In comparison with long European pollen archives, speleothem isotope records from the Near East, and global climate parameters (e.g., insolation, atmospheric CO2 content), the new high-resolution Lake Van record presents an improved insight into regional vegetation dynamics and climate variability in the eastern Mediterranean region.

The impact of Last Glacial climate variability in west-European loess revealed by radiocarbon dating of fossil earthworm granules

The characterization of Last Glacial millennial-timescale warming phases, known as interstadials or Dansgaard-Oeschger events, requires precise chronologies for the study of paleoclimate records. On the European continent, such chronologies are only available for several Last Glacial pollen and rare speleothem archives principally located in the Mediterranean domain. Farther north, in continental lowlands, numerous high-resolution records of loess and paleosols sequences show a consistent environmental response to stadial-interstadial cycles. However, the limited precision and accuracy of luminescence dating methods commonly used in loess deposits preclude exact correlations of paleosol horizons with Greenland interstadials. To overcome this problem, a radiocarbon dating protocol has been developed to date earthworm calcite granules from the reference loess sequence of Nussloch (Germany). Its application yields a consistent radiocarbon chronology of all soil horizons formed between 47 and 20 ka and unambiguously shows the correlation of every Greenland interstadial identified in isotope records with specific soil horizons. Furthermore, eight additional minor soil horizons dated between 27.5 and 21 ka only correlate with minor decreases in Greenland dust records. This dating strategy reveals the high sensitivity of loess paleoenvironments to Northern Hemisphere climate changes. A connection between loess sedimentation rate, Fennoscandian ice sheet dynamics, and sea level changes is proposed. The chronological improvements enabled by the radiocarbon "earthworm clock" thus strongly enhance our understanding of loess records to a better perception of the impact of Last Glacial climate changes on European paleoenvironments.

Success of a flexible behavior. Considerations on the manufacture of Late Epigravettian lithic projectile implements according to experimental tests

It is generally recognized that the function and modality of hafting are the main factors influencing mental templates, and consequently, stone tool standardization. But what role do technical knowledge and traditions play? In this study, we investigate the interaction between mental templates and technological choices in the manufacture of Late Epigravettian projectile implements. The examined specimens come from different dwelling phases of the Dalmeri rock shelter (Italian Alps). Technological analyses suggest that lithic production systems gradually simplified their structure over time, implying a shift in technical investment from shaping on the core to a subsequent shaping on the derived flake blank. However, correlations between the dimensions and morphological features among the armatures from the different units suggest that mental templates remained unchanged throughout the Allerod. Experimentation attests to the frequent combined application of different retouching techniques. Further, the variability in their arrangement denotes the absence of strict rules and the Epigravettian capability to recognize the most situationally suitable method. In the Dalmeri rock shelter, the standardization of lithic projectile implements is therefore a result of flexibility in retouching, framed in a production system characterized by a progressive simplification. A such rapidly produced and responsive technology must have been encouraged by Late Glacial climatic and environmental changes and the occupation of alpine territories previously inaccessible. Thus, the flexibility of technical behaviors turns out to be a key element in the transformation of Late Epigravettian societies during this period, enabling them to adapt and evolve in response to environmental, social, and economic changes.

Global atmospheric teleconnections during Dansgaard–Oeschger events

During the last glacial period, the North Atlantic region experienced a series of Dansgaard–Oeschger cycles in which climate abruptly alternated between warm and cold periods. Corresponding variations in Antarctic surface temperature were out of phase with their Northern Hemisphere counterparts. The temperature relationship between the hemispheres is commonly attributed to an interhemispheric redistribution of heat by the ocean overturning circulation. Changes in ocean heat transport should be accompanied by changes in atmospheric circulation to satisfy global energy budget constraints. Although changes in tropical atmospheric circulation linked to abrupt events in the Northern Hemisphere are well documented, evidence for predicted changes in the Southern Hemisphere’s atmospheric circulation during Dansgaard–Oeschger cycles is lacking. Here we use a high-resolution deuterium-excess record from West Antarctica to show that the latitude of the mean moisture source for Antarctic precipitation changed in phase with abrupt shifts in Northern Hemisphere climate, and significantly before Antarctic temperature change. This provides direct evidence that Southern Hemisphere mid-latitude storm tracks shifted within decades of abrupt changes in the North Atlantic, in parallel with meridional migrations of the intertropical convergence zone. We conclude that both oceanic and atmospheric processes, operating on different timescales, link the hemispheres during abrupt climate change. Abrupt glacial climate changes were slowly communicated between hemispheres by oceanic heat transport. Ice core data point to more rapid atmospheric teleconnections linking the North Atlantic, tropics, and southern storm track.

Vegetation history and climate change recorded by stomata evidence during the late glacial in the Great Khingan Mountain Region, Northeastern China

The research on the evolution of larch forest is significant to understand the vegetation and climate change in mid-high latitude region of the Northern Hemisphere. However, the pollen records to reconstruct the larch forest are problematic due to low pollen representation caused by severely poor pollen productivity and dispersal. New proxy of microfossils is needed to solve this problem. Using coniferous stomata as a proxy to reconstruct the evolution of conifers has some advantages, such as well preserved, locally deposited, continuously remained in lake sediments and can be accurately identified to the genus level. Therefore, a high-resolution stomata record covering 20.3–10.8 cal ka BP from Lake Moon was presented, in order to reconstruct larch forest history from the Last Glacial Maximum to early Holocene in the Great Khingan Mountain Region, Northeast China. Reference conifer stomata from fresh leaves of the local coniferous species and lake surface samples were prepared for the identification of the fossil stomata. Larix , Sabina and Picea stomata were identified from the sedimentary sequence of Lake Moon, and the results of stomata influx from this study and pollen influx from the previous study indicate that the vegetation evolution has gone through distinct stages. Before 15.0 cal ka BP, no Larix existed in the vicinity of study site. The first arrival of larch is inferred by the continuous presence of stomata at 15.0 cal ka BP, which manifests that the vegetation turned into forest steppe. The coverage of forest increases slightly from 15.0 to 12.8 cal ka BP with an interruption between 14.3 and 14.0 cal ka BP. During 12.8–11.8 cal ka BP, the vegetation were characterized by the expansion of conifers mainly Larix and the shrinkage of broadleaves and herbs. From 11.8 to 10.8 cal ka BP, the vegetation type remained as forest steppe with the shrinkage of conifers dominated by Larix , in conjunction with the expansion of broadleaves and herbs with high vegetation coverage. The establishment of larch forest inferred by the continuous presence of stomata marks the onset of the late glacial in the Great Khingan Mountain Region at 15.0 cal ka BP. The application of stomata analysis provides detailed scenes of coniferous evolution surrounding the Lake Moon. It is suggested that the analysis of fossil stomata is a valuable tool to demonstrate unambiguous evidence for the local presence of the conifers in study region, even better than pollen records when the component of larch is low in vegetation. The evolution of the forest communities in the late glacial period in the Great Khingan Mountain Region is comparable with the vegetation evolution of other regions at different latitudes in East Asian monsoon region, which indicates that the climate change at millennial/centennial scale in late glacial is roughly synchronous in East Asian monsoon region. The series of climatic periods in this study revealed by the stomata and pollen records is also similar to that of Europe, like Meiendorf interstadial, Oldest Dryas cold event, Bolling-Allerod warm phases, Younger Dryas cold event, warm and humid early Holocene. The temperature change is probably the main factor to impact the vegetation change. The study shows that the vegetation succession in the study area is responsive to the temperature change of the Northern Hemisphere controlled by the global ice volume, and reveals the synchronization of the late glacial climate change in the mid latitude region of East Asia and the North Atlantic region.