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This article discusses the field of paleolimnology, which studies lake and wetland sedimentary profiles to understand past environmental changes. These sedimentary archives provide valuable information about natural and human-induced changes in the environment, allowing researchers to investigate the interactions between past climate dynamics and human activities. The article highlights the importance of accurate dating methods and the integration of modern environmental data into paleoenvironmental studies. It also presents several case studies from different regions, showcasing the diverse applications of paleolimnology in studying climate change, biogeochemical cycles, environmental pollution, and species invasions. The article concludes by emphasizing the growing importance of paleolimnology and its contribution to our understanding of long-term environmental changes. [Extracted from the article]

The element mercury (Hg) is a key pollutant, and much insight has been gained by studying the present-day Hg cycle. However, many important processes within this cycle operate on timescales responsive to centennial- to millennial-scale environmental variability, highlighting the importance of also investigating the longer-term Hg records in sedimentary archives. To this end, we here explore the timing, magnitude, and expression of Hg signals retained in sediments over the past ∼ 90 kyr from two lakes, linked by a subterranean karst system: Lake Prespa (Greece, North Macedonia, and Albania) and Lake Ohrid (North Macedonia and Albania). Results suggest that Hg fluctuations are largely independent of variability in common host phases in each lake, and the recorded sedimentary Hg signals show distinct differences first during the Late Pleistocene (Marine Isotope Stages 2–5). The Hg signals in Lake Prespa sediments highlight an abrupt, short-lived peak in Hg accumulation coinciding with local deglaciation. In contrast, Lake Ohrid shows a broader interval with enhanced Hg accumulation and, superimposed, a series of low-amplitude oscillations in Hg concentration peaking during the Last Glacial Maximum, which may result from elevated clastic inputs. Divergent Hg signals are also recorded during the Early and Middle Holocene (Marine Isotope Stage 1). Here, Lake Prespa sediments show a series of large Hg peaks, while Lake Ohrid sediments show a progression to lower Hg values. Since ∼ 3 ka , anthropogenic influences overwhelm local fluxes in both lakes. The lack of coherence in Hg accumulation between the two lakes suggests that, in the absence of an exceptional perturbation, local differences in sediment composition, lake structure, Hg sources, and water balance all influence the local Hg cycle and determine the extent to which Hg signals reflect local- or global-scale environmental changes. [ABSTRACT FROM AUTHOR]

Moraine complexes formed by multiple glaciations are well-preserved in the Mount Geladandong area, the largest center of current glaciation in the Tanggula Mountains in western China. Studies of these glacial landforms provide insights into past glacier changes and contribute to understanding palaeoclimate and palaeoenvironment in the central Tibetan Plateau (TP). Here we report on 10Be surface exposure dating of thirteen rock samples collected from a sequence of glacial landforms associated with the Gangjiaquba Glacier. Based on the dating results, historical records (topographical maps) and morphological relationships, clear Little Ice Age (LIA) landforms are identified, and other landforms are tentatively assigned Neoglacial and global Last Glacial Maximum (LGM G) ages. Dating results for samples from modern glacial landforms demonstrate that the boulders were not affected by nuclide inheritance, and that 10Be surface exposure dating may be used to constrain glacier fluctuations during the past century in high-altitude areas that have high 10Be production rates. A comparison of the ages of a glacially polished surface and adjacent glacial deposits indicates that subglacial erosion by abrasion of the rock surface was insufficient to remove cosmogenic nuclide inventories. Thus the apparent exposure age on the polished surface includes inheritance and over-estimates the actual age for the exposure of this surface. Samples from hummocky moraine have wide age spreads, indicating long-lasting surface instability after deposition of this landform. Successive reduction in glacial extent in the Mount Geladandong area since the LGM G reflects temperature and precipitation changes over this timeframe in the central TP, with climate forcing for glacial advances correlated with cooling signals in the North Atlantic that may have been transmitted to this area by the westerlies. [ABSTRACT FROM AUTHOR]

Shelf-incised valleys, carved by ancient rivers and estuaries during periods of continental shelf exposure, were primarily shaped by base-level fluctuations in the Quaternary. These geological features are prevalent in the western South Atlantic shelf but often go unnoticed as key indicators of the region's evolution. This research unveils the outcomes of a comprehensive investigation that combined sub-bottom profiling (SBP) surveys, historical bathymetric data, and the application of Geographic Information System (GIS) tools to extract drainage patterns within the Santos Basin, a significant sedimentary basin in Brazil.The study provides an unprecedented overview of the interconnected network of the ancient drainage system across the continental shelf, totalizing 91 thalwegs associated with 80 incised valleys in the study area, ranging in length from 250 m to 148 km. This connection between the mapped incised valleys and the upper slope evolved through three distinct phases during the Late Pleistocene. The first phase (Phase A) was characterized by the formation and subsequent destruction of incised valleys, driven by high-frequency sea-level oscillations during MIS5. The second phase (Phase B, with subphases B1 and B2) witnessed the construction of incised valleys during a period of forced regression at MIS4 and MIS3. The final phase (Phase C) marked the establishment of fully developed valleys, connecting them to upper slope canyons during the Last Glacial Maximum (LGM). The correlation of these sea-level changes with the presence of underfilled incised valleys in the Santos Basin shelf represents a significant breakthrough in understanding the geological history of the western South Atlantic shelf. These valleys typically eroded until reaching depths near the transient base level, offering a valuable glimpse into the geological chronicles of sea-level fluctuations over time. [ABSTRACT FROM AUTHOR]

The insular region of Wallacea has become a focal point for studying Pleistocene human ecological and cultural adaptations in island environments, however, little is understood about early burial traditions during the Pleistocene. Here we investigate maritime interactions and burial practices at Ratu Mali 2, an elevated coastal cave site on the small island of Kisar in the Lesser Sunda Islands of eastern Indonesia dated to 15,500–3700 cal. BP. This multidisciplinary study demonstrates extreme marine dietary adaptations, engagement with an extensive exchange network across open seas, and early mortuary practices. A flexed male and a female, interred in a single grave with abundant shellfish and obsidian at Ratu Mali 2 by 14.7 ka are the oldest known human burials in Wallacea with established funerary rites. These findings highlight the impressive flexibility of our species in marginal environments and provide insight into the earliest known ritualised treatment of the dead in Wallacea. [ABSTRACT FROM AUTHOR]

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The dominant paradigm is that large tracts of Southeast Asia's lowland rainforests were replaced with a "savanna corridor" during the cooler, more seasonal climates of the Last Glacial Maximum (LGM) (23,000 to 19,000 y ago). This interpretation has implications for understanding the resilience of Asia's tropical forests to projected climate change, implying a vulnerability to "savannization". A savanna corridor is also an important foundation for archaeological interpretations of how humans moved through and settled insular Southeast Asia and Australia. Yet an up-to-date, multiproxy, and empirical examination of the palaeoecological evidence for this corridor is lacking. We conducted qualitative and statistical analyses of 59 palaeoecological records across Southeast Asia to test the evidence for LGM savannization and clarify the relationships between methods, biogeography, and ecological change in the region from the start of Late Glacial Period (119,000 y ago) to the present. The pollen records typically show montane forest persistence during the LGM, while δ13C biomarker proxies indicate the expansion of C4-rich grasslands. We reconcile this discrepancy by hypothesizing the expansion of montane forest in the uplands and replacement of rainforest with seasonally dry tropical forest in the lowlands. We also find that smooth forest transitions between 34,000 and 2,000 y ago point to the capacity of Southeast Asia's ecosystems both to resist and recover from climate stressors, suggesting resilience to savannization. Finally, the timing of ecological change observed in our combined datasets indicates an 'early' onset of the LGM in Southeast Asia from ~30,000 y ago. [ABSTRACT FROM AUTHOR]

In this study, we evaluated the historical demography of a cactophilic Drosophila species (Drosophila gouveai) based on previously published mitochondrial DNA (mtDNA) data ecological niche modelling. We particularly aimed to test the effect of climate change on the historical demography of D. gouveai during the late Quaternary and the future of the species. For this, we also modelled its host cacti species in its distribution range to reach a more robust biogeographic conclusion. Our results indicate that D. gouveai was as sensitive to climate change as its hosts were. This species experienced an almost complete range shift, range contraction after the Last Interglacial (130,000 years ago) but before the Last Glacial Maximum (22,000 years ago). Afterwards, its range contracted in the Present, and this species will experience complete range shift once again in the Future (based on 2050 and 2070 projections) as its hosts will do. In conclusion, the Last Interglacial played a significant role in shaping the demographic history of D. gouveai and its hosts, and this species will have a different distribution or will be extinct in the near future. [ABSTRACT FROM AUTHOR]

Aim: Contemporary environmental, historical and evolutionary factors are increasingly used to decipher the drivers of spatial patterns of species richness. Evidence of such correlations for Chinese reptiles is scarce and poorly understood. We therefore explored the validity of the environmental capacity, historical climatic stability and diversification rates hypotheses on Chinese lizard richness. Location: Mainland China. Taxon: Squamata: Sauria. Methods: We mapped the distribution ranges of all 237 lizards in mainland China using a combination of different datasets. We used current environmental conditions (ambient energy, environmental productivity, and habitat heterogeneity), historical climate stability indices (long term: since ~3.3 Ma and short term: since the last glacial maximum) and mean tip diversification rates, to test whether current environmental conditions, historical climate change and diversification rates drive contemporary richness patterns of lizards in China. We applied piecewise structural equation models (pSEM) to jointly evaluate our hypotheses, considering direct and indirect effects. Results: Chinese lizards showed strong latitudinal diversity gradients. We found consistent support for contemporary climatic and environmental factors relationships with richness. Richness was also positively correlated with short‐term climatic stability, but less so with long‐term stability. Diversification rates were seldom found to be positively correlated with lizard richness. Main Conclusions: Our results support the environmental capacity and historical climate hypotheses, which link high richness to highly productive warm and stable regions (and low richness to cold and unstable regions). We conclude that post‐speciation dispersal and short‐term climatic oscillations quickly swamp the long‐term signal of diversification rates and climatic fluctuations, creating strong current climate–richness associations. [ABSTRACT FROM AUTHOR]

Characterizing the mechanisms influencing the distribution of genetic variation in aquatic species can be difficult due to the dynamic nature of hydrological landscapes. In North America's Central Highlands, a complex history of glacial dynamics, long-term isolation, and secondary contact have shaped genetic variation in aquatic species. Although the effects of glacial history have been demonstrated in many taxa, responses are often lineage- or species-specific and driven by organismal ecology. In this study, we reconstruct the evolutionary history of a freshwater mussel species complex using a suite of mitochondrial and nuclear loci to resolve taxonomic and demographic uncertainties. Our findings do not support Pleurobema rubrum as a valid species, which is proposed for listing as threatened under the U.S. Endangered Species Act. We synonymize P. rubrum under Pleurobema sintoxia —a common and widespread species found throughout the Mississippi River Basin. Further investigation of patterns of genetic variation in P. sintoxia identified a complex demographic history, including ancestral vicariance and secondary contact, within the Eastern Highlands. We hypothesize these patterns were shaped by ancestral vicariance driven by the formation of Lake Green and subsequent secondary contact after the last glacial maximum. Our inference aligns with demographic histories observed in other aquatic taxa in the region and mirrors patterns of genetic variation of a freshwater fish species (Erimystax dissimilis) confirmed to serve as a parasitic larval host for P. sintoxia. Our findings directly link species ecology to observed patterns of genetic variation and may have significant implications for future conservation and recovery actions of freshwater mussels. [ABSTRACT FROM AUTHOR]

Schreiber's bent-winged bat Miniopterus schreibersii (Chiroptera) is a widespread, cave-dwelling, regionally migrating species whose genetic diversity was studied throughout its distribution area using mitochondrial and nuclear markers. Previous studies revealed little to no structuring of populations and established Anatolia to be a single refugium during the last glacial maximum. The Balkans were well covered in these studies but usually lacked samples from Serbia. We sequenced the mitochondrial hypervariable region 1 (HV1) gene in M. schreibersii collected at seven sites in Serbia to assess their genetic relatedness to other European and Asia Minor populations and check whether the Balkans exhibit a higher genetic diversity than Western Europe due to its closeness to Anatolia. We recorded nine haplotypes from Serbia, six of which had not been previously reported, with a haplotype diversity of 0.585. The remaining three were shared with individuals from Portugal, Greece, and Turkey. A single most common haplotype was present throughout the species distribution range, pointing to a well-connected population and as indicated by the shape of the haplotype network, a common origin, and a sudden population expansion. Results complement existing data on M. schreibersii having a non-structured population, adding valuable new data from the Balkans supporting the previous hypothesis about its Anatolian origin. [ABSTRACT FROM AUTHOR]

The Last Glacial Maximum (LGM; ca. 24–18 ka), the most recent widespread cold event of the later Pleistocene epoch, is thought to have had profound impacts on human evolution and behavior in many ways, including the reduction of population density of prehistoric hunter-gatherers. Although data are limited, decreasing numbers of sites on the West Loess Plateau (WLP) in northern China are considered evidence of depopulation of that area. More occupations dating to the LGM have been reported recently, and new discoveries provide additional information for understanding the demographic history of the West Loess Plateau and northern China. Here, we report new dating results, examine lithic technology, and provide a paleoenvironmental reconstruction based on pollen recovered at Shixiakou Locality 1. Two archaeological layers at the site dating to 20–16.5 ka add new late LGM occupations to a previously reported post-LGM occurrence at Shixiakou. Reconstruction of the paleoenvironment reveals a cold and dry temperate steppe or steppe-desert environment during the LGM, generally in accord with the regional environmental framework. Lithic technology and raw material use were similar during the LGM and post-LGM periods, but great energetic investments, such as the use of beads, were discovered in post-LGM occupation contexts. This might indicate relatively sophisticated social behavior, such as building group identity, although more data are required. A review of known LGM occupations in northern China demonstrates that hunter-gatherers were then distributed widely from the West Loess Plateau to the Nihewan Basin and to Northeast China. Occupation density during the post-LGM period varied greatly in different parts of northern China. This scenario implies that demographic dynamics during the LGM and post-LGM periods in northern China were complex. The Shixiakou case study demonstrates that understanding the adaptations of ancient hunter-gatherers has been enhanced by exploring material culture changes against a background of local and regional paleoenvironmental records. [ABSTRACT FROM AUTHOR]

Sedimentary sequences up to 4.71 m thick and up to ~24 ka were made by drilling the bottom sediments in three lakes of the Boguty depression. This is the highest mountain (2390–2470 m a.s.l.) and longest sedimentary record for the neighboring areas of Altai, Tuva, and Mongolia, which reflects the course of natural processes in the highest and most arid part of Russian Altai from the Last Glacial Maximum until the present day. As early as in the first stage of this study, the reservoir effect for moraine-dammed Upper Boguty Lake is estimated at 290 years for the present and 1.2 and 1.3 ka for the boundaries at ~5.7 and ~9.6 ka, respectively. Using a complex of analytical methods, the sedimentological transition zone between the Late Pleistocene glacial–lacustrine clays and the Holocene biogenic–terrigenous silts is identified at 16–13 ka ago; the size of glaciers in MIS-2 and in the Younger Dryas, as well as the time of formation of thermokarst lakes (no later than 8.7 ka), within the upper terminal moraine complex is established. Widespread tree vegetation in the now treeless Boguty depression in the first third of the Holocene is confirmed. [ABSTRACT FROM AUTHOR]

Archaeological evidence indicates that initial coastal settlement of western South America took place near the end of the Last Glacial Maximum (LGM) when sea level was between 40 and 100 m lower than today. Beginning around 15,000 cal BP, and for roughly the next 8,000 years, sea levels rose, eventually covering these formerly exposed and potentially human-occupied landscapes. We use bathymetric data and the reconstructed global mean sea level curve from the Last Glacial Maximum to the Holocene to describe the paleolandscapes associated with the Late Pleistocene and Early Holocene coastal occupations at five sites located in far southern Peru. We constructed cross-sections perpendicular to the modern shoreline at the various locales to determine the approximate extent of the exposed land surface and the proximity of the communities at the sites of Quebrada de los Burros, Quebrada Tacahuay, the Ring Site, Kilometer 4 (K4), and Quebrada Miraflores to the ocean and various littoral habitats. Our analysis identifies previously undocumented littoral habitats consisting of large, shallow-water bays, significant rocky headlands, and beach habitats. We propose several methods of future research to identify potentially submerged sites and the marine paleolandscape of the study region. Knowing the paleolandscapes contributes to refining Pacific coast migration and settlement models for South America. [ABSTRACT FROM AUTHOR]

SUMMARY: 'Living fossils', that is, ancient lineages of low taxonomic diversity, represent an exceptional evolutionary heritage, yet we know little about how demographic history and deleterious mutation load have affected their long‐term survival and extinction risk. We performed whole‐genome sequencing and population genomic analyses on Dipteronia sinensis and D. dyeriana, two East Asian Tertiary relict trees. We found large‐scale genome reorganizations and identified species‐specific genes under positive selection that are likely involved in adaptation. Our demographic analyses suggest that the wider‐ranged D. sinensis repeatedly recovered from population bottlenecks over late Tertiary/Quaternary periods of adverse climate conditions, while the population size of the narrow‐ranged D. dyeriana steadily decreased since the late Miocene, especially after the Last Glacial Maximum (LGM). We conclude that the efficient purging of deleterious mutations in D. sinensis facilitated its survival and repeated demographic recovery. By contrast, in D. dyeriana, increased genetic drift and reduced selection efficacy, due to recent severe population bottlenecks and a likely preponderance of vegetative propagation, resulted in fixation of strongly deleterious mutations, reduced fitness, and continuous population decline, with likely detrimental consequences for the species' future viability and adaptive potential. Overall, our findings highlight the significant impact of demographic history on levels of accumulation and purging of putatively deleterious mutations that likely determine the long‐term survival and extinction risk of Tertiary relict trees. Significance Statement: The evolution of mutation load is a key genetic factor affecting species survival. Here we showed contrast patterns of mutation load of two 'living fossil' tree species. Our results highlight the significant impact of demographic history on levels of accumulation and purging of putatively deleterious mutations that likely determine the long‐term survival and extinction risk of Tertiary relict trees. [ABSTRACT FROM AUTHOR]

Past studies have demonstrated that Ruppia cirrhosa (Ruppia), which typically grows in brackish water, is far too unreliable to serve as the chronological basis for radiocarbon dating because of the hard water effect (HWE). Despite this unreliability, Ruppia seeds have been used to date footprints along the margins of paleo-Lake Otero in southern New Mexico to around 23,000–21,000 cal yr BP. In this study, we employ a modern analog approach using δ13C values and radiocarbon dates from modern Ruppia plants growing in Salt Creek to calculate a maximum limiting age range for the footprints. Those plant samples with higher δ13C values produced greater age discrepancies. This simple relationship can be used to correct for the HWE and demonstrates that the human footprints purported to have been made during the local last glacial maximum could be at least ~7500 yr younger. [ABSTRACT FROM AUTHOR]

Constraining the timing and extent of Quaternary glaciations in the Tibetan Plateau (TP) is significant for the reconstruction of paleoclimatic environment and understanding the interrelationships among climate, tectonics, and glacial systems. We investigated the late Quaternary glacial history of the Qinggulong and Juequ valleys in the Taniantaweng Mountains, southeastern TP, using cosmogenic 10Be surface exposure dating. Four major glacial events were identified based on 26 10Be ages. The exposure ages of the oldest late Quaternary glaciation correspond to Marine Oxygen Isotope Stage (MIS) 6. The maximum glacial extent was dated to 48.5–41.1 ka (MIS 3), during the last glaciation, and was more advanced than that of the last glacial maximum (LGM). Geochronology and geomorphological evidence indicate that multiple glacial fluctuations occurred in the study area during the Early–Middle Holocene. These glacial fluctuations likely were driven by the North Atlantic climate oscillations, summer solar insolation variability, Asian summer monsoon intensity, and CO2 concentration. [ABSTRACT FROM AUTHOR]

Changes in Pacific tracer reservoirs and transports are thought to be central to the regulation of atmospheric CO2 on glacial–interglacial timescales. However, there are currently two contrasting views of the circulation of the modern Pacific; the classical view sees southern sourced abyssal waters upwelling to about 1.5 km depth before flowing southward, whereas the bathymetrically constrained view sees the mid-depths (1–2.5 km) largely isolated from the global overturning circulation and predominantly ventilated by diffusion. Furthermore, changes in the circulation of the Pacific under differing climate states remain poorly understood. Through both a modern and a Last Glacial Maximum (LGM) analysis focusing on oxygen isotopes in seawater and benthic foraminifera as conservative tracers, we show that isopycnal diffusion strongly influences the mid-depths of the Pacific. Diapycnal diffusion is most prominent in the subarctic Pacific, where an important return path of abyssal tracers to the surface is identified in the modern state. At the LGM we infer an expansion of North Pacific Intermediate Water, as well as increased layering of the deeper North Pacific which would weaken the return path of abyssal tracers. These proposed changes imply a likely increase in ocean carbon storage within the deep Pacific during the LGM relative to the Holocene. [ABSTRACT FROM AUTHOR]

Sedimentary records of environmental conditions retrieved from archeological sites provide valuable insight into the milieux of ancient humans and context to understand societal and cultural changes. At Jordan River Dureijat, an open-air site in Israel's Hula Valley documenting the entire Epipaleolithic period as well as the Early Neolithic, sediments exposed on the walls of the excavation pit reveal a sequence of lacustrine deposits accumulated continuously between c. 21.1 and 11.3 cal ka BP near the southeast margin of Paleolake Hula. Through sediment-grain-size, geochemical, and paleontological analyses, we describe the nature of the Paleolake Hula from the Last Glacial Maximum (LGM) to the start of the Holocene. Until c. 17.2 cal ka BP, Paleolake Hula existed as a relatively large and well-buffered waterbody. A rapid and substantial drawdown of the lake occurred at 17.2 cal ka BP, followed by more frequent changes in the position of the shoreline in a smaller and shallower lake, resulting in the deposition of alternating near-shore and deeper lacustrine facies. Since the LGM, seven beds of structureless, silty sediments preserve archeological artifacts belonging to three Epipaleolithic cultures as well as the Early Neolithic pre-pottery Neolithic A culture. These sediments were deposited during phases of low lake level during which times humans waded into the shallow part of the lake, leaving behind stone and bone tools such as bladelets, lunates and burins, fishing hooks, line weights and net sinkers. Using radiocarbon-dated charcoal and a Bayesian statistical model, we produced a chronostratigraphic model for the archeological site, which enables the comparison of proxy paleoclimate records produced from this site's sediments with regional archives as well as with global trends and changes in the Northern Hemisphere climate. Periods of low lake stands are correlated with the end of the LGM, Heinrich Event 1, and the beginning of the Younger Dryas Stadial. High water stands occurred contemporaneously with the peak of the LGM and during the Bølling–Allerød interstadial. This new water-level record from Lake Hula confirms that lake-level changes here broadly paralleled those of the Dead Sea and Sea of Galilee during the late Pleistocene, highlighting the importance of northern water sources to the overall water balance of the lakes along the Dead Sea Transform. [ABSTRACT FROM AUTHOR]

Estimating past aerosol radiative effects and their uncertainties is an important topic in climate science. Aerosol radiative effects propagate into large uncertainties in estimates of how present and future climate evolves with changing greenhouse gas emissions. A deeper understanding of how aerosols affected the atmospheric energy budget under past climates is hindered in part by a lack of relevant paleo-observations and in part because less attention has been paid to the problem. Because of the lack of information we do not seek here to determine the change in the radiative forcing due to aerosol changes but rather to estimate the uncertainties in those changes. Here we argue that current uncertainties from emission uncertainties (90 % confidence interval range spanning 2.8 W m -2) are just as large as model spread uncertainties (2.8 W m -2) in calculating preindustrial to present-day aerosol radiative effects. There are no estimates of radiative forcing for important aerosols such as wildfire and dust aerosols in most paleoclimate time periods. However, qualitative analysis of paleoclimate proxies suggests that changes in aerosols between different past climates are similar in magnitude to changes in aerosols between the preindustrial and present day; plus, there is the added uncertainty from the variability in aerosols and fires in the preindustrial. From the limited literature we crudely estimate a paleoclimate aerosol uncertainty for the Last Glacial Maximum relative to preindustrial of 4.8 W m -2 , and we estimate the uncertainty in the aerosol feedback in the natural Earth system over the paleoclimate (Last Glacial Maximum to preindustrial) to be about 3.2 W m -2 K -1. In order to more accurately assess the uncertainty in historical aerosol radiative effects, we propose a new model intercomparison project, which would include multiple plausible emission scenarios tested across a range of state-of-the-art climate models over the historical period. These emission scenarios would then be compared to the available independent aerosol observations to constrain which are most probable. In addition, future efforts should work to characterize and constrain paleo-aerosol forcings and uncertainties. Careful propagation of aerosol uncertainties in the literature is required to ensure an accurate quantification of uncertainties in projections of future climate changes. [ABSTRACT FROM AUTHOR]

Multi-proxy analysis (spore-pollen, dinoflagellate cysts, other non-pollen palynomorphs (NPPs), radiocarbon dating and lithology) was performed on marine sediments from three new cores retrieved during the two cruise expeditions on board the Research Vessel "Akademik" in 2009 and 2011. The Varna transect comprises three cores extending from the outer shelf, continental slope and deep-water zone. The record spans the last 26000 years (all ages obtained in this study are given in calendar years BP (cal. yrs BP)). The pollen record reveals the spreading of steppe vegetation dominated by Artemisia and Chenopodiaceae, suggesting cold and dry environments during the Late Pleniglacial – Oldest Dryas (25903–15612 cal. yrs BP). Stands of Pinus and Quercus reflect warming/humidity increase during the melting pulses (19.2–14.5 cal. ka BP) and the Late Glacial interstadials Bølling and Allerød. The Younger Dryas (13257–11788 cal. yrs BP) coldest and driest environments are clearly demonstrated by the maximum relative abundance of Artemisia and Chenopodiaceae. During the Early Holocene (Preboreal and Boreal chronozones, 11788–8004 cal. yrs BP), Quercus appeared as a pioneer species and, along with other temperate deciduous arboreal taxa, formed open deciduous forests as a response to the increased temperature. The rapid expansion of these taxa indicates that they survived in Glacial refugia in the coastal mountains. During the Atlantic chronozone (8004–5483 cal. yrs BP), optimal climate conditions (high humidity and increased mean annual temperatures) stimulated the establishment of species-rich mixed temperate deciduous forests. During the Subboreal chronozone (5483–2837 cal. yrs BP), Carpinus betulus and Fagus expanded simultaneously and became more important components of mixed oak forests and probably also formed separate communities. During the Subatlantic chronozone (2837 cal. yrs BP to pre-industrial time), climate-driven changes (an increase of humidity and a cooling of the climate) appear to be the main drivers of the specific vegetation succession expressed by increased abundance of Alnus, Fraxinus excelsior and Salix along with lianas, suggesting formation of flooded riparian forests (so called 'Longoz') lining the river valleys along the Black Sea coast. The first indicators of farming and other human activities have been recorded since 7074 cal. yrs BP. The dinoflagellate cyst (dinocyst) assemblages have been analysed to assess the changes in the Black Sea environment over the last 26000 years in terms of fluctuation in paleoproduction and surface water conditions related to changes in climate, freshwater input and Mediterranean water intrusion. Two major dinocyst assemblages were distinguished: one dominated by stenohaline freshwater/brackish-water species and a successive one dominated by euryhaline marine species. The changes in the composition of the assemblages occurred at 7668 cal. yrs BP. The abrupt decrease of stenohaline freshwater/brackish-water species Pyxidinopsis psilata and Spiniferites cruciformis was followed upwards by a gradual increase in euryhaline marine species, such as Lingulodinium machaerophorum, Spiniferites belerius, S. bentorii and acritarch Cymatiosphaera globulosa. The first occurrence of euryhaline marine species took place synchronously with the onset of sapropel deposition. Modern marine conditions were established after 6417 cal yrs BP when an abundance of Mediterranean-related species, such as Operculodinium centrocarpum and Spiniferites mirabilis, along with other heterotrophic species, occurred. After the stable cold and dry environment during the Last Glacial Maximum, the phytoplankton record of core AKAD 11-17 shows that Pediastrum boryanum var. boryanum has a cyclical abundance associated with the deposition of four red-brown clay layers between 19.2 and 14.5 cal. ka BP. This event is associated with the major melting phase of European Ice drained by the Danube and Dnieper Rivers in response to climate warming observed after the end of the Last Glacial Maximum. During the Early Holocene, P. psilata, characterised by a preference to warmer temperatures, demonstrates its ecological optimum for growth concerning SST reaching maximum relative abundance of 94% between 11072 and 8638 cal. yrs BP. This maximum was interrupted by an abrupt significant short-term decrease in the relative abundance of P. psilata centred between 8500 and 8300 cal. yrs BP reflecting cold conditions similar to those of Younger Dryas. This finding, also confirmed by the rapid significant decrease of arboreal pollen, particularly of Quercus in the same studied core, is considered a regional expression of the well-known '8.2 ka cold event' which is commonly linked to a meltwater-related perturbation of the Atlantic Meridional Overturning Circulation (AMOC) and associated collapse of oceanic northward heat transport. Our fossil pollen and dinocyst data confirm that the high amplitude temperature anomaly associated with 'the 8.2 ka cold event' may have also occurred in south-eastern Europe, at lower latitudes of the western Black Sea coastal area, most probably due to atmospheric transition and/or river discharge. [ABSTRACT FROM AUTHOR]

This study presents a 25 ka reconstruction of the Pleistocene paleoclimate in the South German Molasse Basin. Deep groundwater was sampled at 19 wells in the Upper Jurassic aquifer (UJA). Calculating gas temperatures (NGT) using the UA model with the noble gases Ar, Kr, and Xe led to groundwater recharge temperatures between 0.4 and 4.7°C. Combined with innovative 14CDOC groundwater dating, calculated NGTs revealed up to 8°C cooler soil temperatures during the Pleistocene compared with modern soil temperature. This interpretation agrees well with the observed depleted stable water isotope signature ranging from −83.3 to −86.1 for δ2H and from −10.66 to −11.77 for δ18O, which is characteristic of groundwater of Pleistocene origin in Southern Germany. The temperature differences (∆T) agree remarkably well with calculated NGTs within other European basins (∆T 6–9.5°C) and suggest widespread pronounced terrestrial cooling during the Last Glacial Maximum through the interior of the European continent. Plain Language Summary: To characterize the climate in Southern Germany during the last ice age, we first determined 14CDOC for dating the deep groundwater of the Upper Jurassic aquifer. Subsequently, we looked closer at noble gases and stable water isotopes. The contents in groundwater are mainly controlled by temperature when the groundwater is in contact with the atmosphere during the formation on the earth's surface. Our results show that the calculated noble gas temperatures during this time were up to 8°C colder than modern temperatures. Our findings help to gain a better understanding of Earth's climatic history. Key Points: The noble gas temperatures from deep groundwater in Southern Germany show substantial cooling up to 8°C during the PleistoceneNoble gas temperatures in combination with groundwater dating using the 14CDOC method are helpful for reconstructing the paleoclimateThe deep groundwater in the Upper Jurassic aquifer may be a mixture of meteoric water and Pleistocene glacial meltwater [ABSTRACT FROM AUTHOR]

Vertical profiles of benthic foraminiferal oxygen and carbon isotopes (δ18O and δ13C) imply the volume of southern source water (SSW) in the Atlantic basin expanded during the Last Glacial Maximum. Shoaling of the boundary between SSW and northern source water (NSW) may reduce mixing between the two watermasses, thereby isolating SSW and enhancing its ability to store carbon during glacial intervals. Here we test this hypothesis using profiles of δ18O and δ13C from the Brazil Margin spanning the last glacial cycle (0–150 ka). Shoaling of the SSW‐NSW boundary occurred during Marine Isotope Stage (MIS) 2, 4, and 6, consistent with expansion of SSW and greater carbon sequestration in the abyss. But the watermass boundary also shoaled during MIS 5e, when atmospheric CO2 levels were comparable to MIS 1. Additionally, we find there was little change in watermass structure across the MIS 5e‐d transition, the first major decline in CO2 of the last glacial cycle. Thus, the overall pattern in glacial‐interglacial geometry is inconsistent with watermass mixing acting as a primary control on atmospheric pCO2. We also find that δ13C values for MIS 5e are systematically lower than MIS 1, with the largest difference (∼1‰) occurring in the upper water column. Low δ13C during MIS 5e was most likely due to a long‐term imbalance in weathering and deposition of calcium carbonate or input of 13C‐depleted carbon from a reservoir external to the ocean‐atmosphere system. Key Points: Southern source water expansion during MIS 2, 4, and 6 is consistent with the hypothesis that reduced watermass mixing contributes to lower atmospheric pCO2But Southern source water expansion also occurred during MIS 5e and there is little change in watermass geometry across MIS 5e/d transitionThe MIS 5e carbon isotope profile is systematically lighter than MIS 1 throughout water column, with the largest anomalies above 2,000 m water depth [ABSTRACT FROM AUTHOR]

All else equal, if the ocean's "biological [carbon] pump" strengthens, the dissolved oxygen (O2) content of the ocean interior declines. Confidence is now high that the ocean interior as a whole contained less oxygen during the ice ages. This is strong evidence that the ocean's biological pump stored more carbon in the ocean interior during the ice ages, providing the core of an explanation for the lower atmospheric carbon dioxide (CO2) concentrations of the ice ages. Vollmer et al. (2022, https://doi.org/10.1029/2021PA004339) combine proxies for the oxygen and nutrient content of bottom waters to show that the ocean nutrient reservoir was more completely harnessed by the biological pump during the Last Glacial Maximum, with an increase in the proportion of dissolved nutrients in the ocean interior that were "regenerated" (transported as sinking organic matter from the ocean surface to the interior) rather than "preformed" (transported to the interior as dissolved nutrients by ocean circulation). This points to changes in the Southern Ocean, the dominant source of preformed nutrients in the modern ocean, with an apparent additional contribution from a decline in the preformed nutrient content of North Atlantic‐formed interior water. Vollmer et al. also find a lack of LGM‐to‐Holocene difference in the preformed 13C/12C ratio of dissolved inorganic carbon. This finding may allow future studies to resolve which of the proposed Southern Ocean mechanisms was most responsible for enhanced ocean CO2 storage during the ice ages: (a) coupled changes in ocean circulation and biological productivity, or (b) physical limitations on air‐sea gas exchange. Plain Language Summary: Recent studies have sealed the case that the concentration of oxygen was reduced in the deep ocean during the ice ages. Vollmer et al. (2022, https://doi.org/10.1029/2021PA004339) combine the oxygen results with data on deep ocean nutrient concentrations. They find that, relative to modern, more of the ice age deep ocean's nutrient reservoir arrived as sinking organic matter from surface waters, leading to more storage of carbon dioxide in the deep ocean. Moreover, they calculate that the entire observed drawdown in atmospheric carbon dioxide levels during ice ages can be explained by this strengthening of the ocean's "biological carbon pump." The findings bring the scientific community an important step closer to explaining why and how ice ages occur and end. The Southern Ocean, the ocean region around Antarctica, must have played a major role. However, it remains unclear whether the carbon dioxide was trapped in the Southern Ocean by changes in its circulation and biology or by limitations on air‐sea gas exchange across the Southern Ocean surface, such as might have occurred due to sea ice cover. Vollmer et al.'s reconstruction of the carbon isotopes in Southern Ocean surface waters may help to answer this question. Key Points: Proxies indicate less dissolved O2 in the ocean interior during ice ages than during interglacialsThis suggests an increase in CO2 storage by the ocean's biological pump adequate to explain the lower atmospheric CO2 of the ice agesReconstructed nutrient use implicates the Southern Ocean but does not yet resolve the roles of circulation, biology, and gas exchange [ABSTRACT FROM AUTHOR]

Parabolic dunes form and migrate in almost every climate and geographic zones of the world, ranging from the tropical coastlines to the arid continental deserts. Despite their extensive distribution and their importance within the aeolian sediment landscape, the understanding of their morphological development, activity and link with climates remains somewhat limited to local or regional scales. A good understanding of the present climate conditions under which parabolic dunes are formed and/or reactivated would be significantly helpful to constrain past climate models. Similarly, an improved knowledge of parabolic dunes behaviour during past climatic episodes would provide some valuable long‐term data to better predict their future activity. This review first aims at providing a non‐exhaustive global database on parabolic dune morphology and the present wind regimes with which they are associated. To do so, the morphology of 750 dunes distributed worldwide was first analysed using a high‐resolution global digital elevation model, suggesting an intrinsic relationship between the different measured morphoparameters. The analysis of the associated local wind regimes shows that parabolic dunes develop under strong unidirectional winds, which are more conspicuous in coastal than continental environments. Dunes of different ages are globally aligned with present prevailing winds, which suggests a prevalent control of long‐term global atmospheric circulation on dune orientations. Finally, this study explores the link between parabolic dune activity and climates over the past 20 000 years by reviewing ages from the literature and combining them with the ones compiled in the INQUA Dunes Atlas Chronologic Database. Overall, it appears that changes towards drier conditions have triggered dunes migration during both warm and cold periods of the Last Glacial Maximum, Holocene Climate Optimum, Roman Climate Optimum, Medieval Climate Optimum and Little Ice Age. The present day aeolian activity is predominantly linked with deteriorating environmental conditions caused by human disturbances. [ABSTRACT FROM AUTHOR]

We review geochronological data relating to the timing and rate of Laurentide Ice Sheet recession in the northeastern United States and model ice margin movements in a Bayesian framework using compilations of previously published organic 14C (n = 133) and in situ cosmogenic 10Be (n = 95) ages. We compare the resulting method-specific chronologies with glacial varve records that serve as independent constraints on the pace of ice recession to: (1) construct a synthesis of deglacial chronology throughout the region; and (2) assess the accuracy of each chronometer for constraining the timing of deglaciation. Near the Last Glacial Maximum terminal moraine zone, 10Be and organic 14C ages disagree by thousands of years and limit determination of the initial recession to a date range of 24-20 ka. We infer that 10Be inherited from pre-glacial exposure adds 2-6 kyr to many exposure ages near the terminal moraines, whereas macrofossil 14C ages are typically 4-8 kyr too young due to a substantial lag between ice recession and sufficient organic material accumulation for dating in some basins. Age discrepancies between these chronometers decrease with distance from the terminal moraine, due to less 10Be inherited from prior exposure and a reduced lag between ice recession and organic material deposition. 14C and 10Be ages generally agree at locations more than 200 km distal from the terminal moraines and suggest a mostly continuous history of ice recession throughout the region from 18 to 13 ka with a variable pace best documented by varves. [ABSTRACT FROM AUTHOR]

The Severnaya Dvina River valley crosses the former south-eastern margin of the last Scandinavian Ice Sheet. Despite a long research history, there remains considerable controversy about the maximum ice-sheet extent and the expansion of proglacial lakes within the Severnaya Dvina fluvial system. The goal of this study was to address these issues using new material from the valleys of the Severnaya Dvina and the lower Vychegda, thereby contributing to an understanding of the history of the south-eastern sector of the last Scandinavian Ice Sheet and its periglacial areas. We studied a number of geological sections using radiocarbon and optically stimulated luminescence (OSL) dating, pollen and carpological analyses, and found that the Last Glacial Maximum (LGM) proglacial lake occupied the Severnaya Dvina valley between 20-19 ka and about 15.5 ka. The lake was localized within the proglacial isostatic depression and occupied only the Severnaya Dvina valley extending no further than the confluence of the Vychegda River, no more than 110 km from the edge of the ice sheet. The lake formation did not cause any drainage reorganization within and outside the Vychegda fluvial system. Given the small size of the lake and presence of the oldest OSL ages along the entire length of the former lake, we suggest that the onset of the proglacial lake marks the maximum extent of the ice sheet in the area. Consequently, the onset of the local LGM may be dated to 20-19 ka, somewhat earlier than assumed by most previous researchers. The LGM ice sheet boundary was located in the Severnaya Dvina valley downstream from the Vychegda confluence and did not extend into the Vychegda valley, despite previous suggestions. During deglaciation, the lake disappearance together with crustal rebound caused an incision episode in the Vychegda - Severnaya Dvina system and the formation of the Lateglacial alluvial terrace with relative height rising downstream due to the uneven rates of the postglacial uplift. [ABSTRACT FROM AUTHOR]

In recent decades, most glaciers have been melting, thinning and retreating globally in response to continuously increasing temperatures. We simulated ice thicknesses and volumes on the east and west slopes of Mt Noijin Kang-Sang, Southern Tibetan Plateau (TP), since the Last Glacial Maximum (LGM), using a glacial flowline model. The simulated average ice thicknesses during the LGM and Lateglacial (LG), Early Holocene, Neoglacial and the Little Ice Age (LIA) periods were 1.4, 1.3, 1.1 and 1.2 times greater than those of modern glaciers in the Gangbu (eastern slope) and western valleys, respectively. In the Gangbu Valley, areas from the LGM-LG to LIA periods were 1.7, 1.5, 1.4 and 1.2 times greater than the modern glacier area, and the volume expansion indexes were 2.2, 1.9, 1.5 and 1.4. In the western valleys, the area expansion indexes were 2.2, 1.9, 1.5 and 1.4 times greater than the modern glacier, and volumes were 5.4, 4.4, 3.4 and 2.9 times greater, respectively. Glaciers in the western valleys retreated more extensively than those on the eastern slopes of Gangbu Valley after the LGM-LG, probably due to the smaller glaciers on the leeward western slopes with lower elevations. Equilibrium-line altitudes dropped ~425 m in Gangbu Valley and ~385 m in the western valleys during the LGM-LG, corresponding to a 3.8-4.1 ℃ temperature decrease in this region, which was consistent with cooling on the central Tibetan Plateau, but lower than cooling at the southeastern edge of the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

A sediment core from the salt marsh fringing Loch Duart, NW Scotland, UK, containing Lateglacial to Holocene sediments, was analysed using a multi-element geochemical approach to elucidate the relative sea level (RSL) and palaeoenvironmental changes associated with the deglaciation of the British and Irish Ice Sheet. Elemental and isotopic measurements of rhenium, osmium, carbon and nitrogen, X-ray fluorescence scanning, radiocarbon dating, and foraminiferal analysis produced a suite of data that complements the existing biostratigraphic framework. This suite of bio-, litho- and chemostratigraphic analyses permits discussion of RSL changes that reflect the interplay between post-glacial eustatic rise and glacio-isostatic adjustment. The osmium-isotope (187Os/188Os) data, coupled with a new age-depth model, depict an RSL fall between 16.8 and 14.1 ka cal BP at an average rate of 2 mm a-1. Falling RSL culminates in basin isolation and is followed by subsequent marine inundation from 11.6 ka cal BP. This RSL record preserves the local interaction between glacial isostatic adjustment and glacio-eustatic sea-level change, a relationship that is reflected in the sediment's 187Os/188Os signature. This is the first known application of the osmium isotope system in an isolation basin that is shown to be a viable proxy for RSL change, a technique that could be applied to glacially influenced isolation basins globally. [ABSTRACT FROM AUTHOR]

The lack of continental ice sheets in Alaska during the Last Glacial Maximum (LGM; 26–19 ka) has long been attributed to extensive aridity in the western Arctic. More recently, climate model outputs, a few isolated paleoclimate studies, and global paleoclimate synthesis products show mild summer temperature depressions in Alaska compared to much of the high northern latitudes. This suggests the importance of limited summer temperature depressions in controlling the relatively limited glacier growth during the LGM. To explore this further, we present a new statewide map of LGM alpine glacier equilibrium line altitudes (ELAs), LGM Δ ELAs (LGM ELA anomalies relative to the Little Ice Age, LIA), and Δ ELA-based estimates of temperature depressions across Alaska to assess paleoclimate conditions. We reconstructed paleoglacier surfaces in ArcGIS to calculate ELAs using an accumulation area ratio (AAR) of 0.58 and an area–altitude balance ratio (AABR) of 1.56. We calculated LGM ELAs (n= 480) in glaciated massifs in the state, excluding areas in southern Alaska that were covered by the Cordilleran Ice Sheet. The data show a trend of increasing ELAs from the southwest to the northeast during both the LGM and the LIA, indicating a consistent southern Bering Sea and northernmost Pacific Ocean precipitation source. Our LGM–LIA Δ ELAs from the Alaska Range, supported with limited LGM–LIA Δ ELAs from the Brooks Range and the Kigluaik Mountains, average to - 355 ± 176 m. This value is much greater than the global LGM average of ca. - 1000 m. Using a range of atmospheric lapse rates, LGM–LIA Δ ELAs in Alaska translate to summer cooling of < 2–5 ∘ C. Our results are consistent with a growing number of local climate proxy reconstructions and global data assimilation syntheses that indicate mild summer temperature across Beringia during the LGM. Limited LGM summer temperature depressions could be explained by the influence of Northern Hemisphere ice sheets on atmospheric circulation. [ABSTRACT FROM AUTHOR]

The Last Glacial Maximum (LGM, from ∼26 to 20 ka BP) was the most recent period with large ice sheets in Eurasia and North America. At that time, global temperatures were 5–7 ∘ C lower than today, and sea level ∼125 m lower. LGM simulations are useful to understand earth system dynamics, including climate–ice sheet interactions, and to evaluate and improve the models representing those dynamics. Here, we present two simulations of the Northern Hemisphere ice sheet climate and surface mass balance (SMB) with the Community Earth System Model v2.1 (CESM2.1) using the Community Atmosphere Model v5 (CAM5) with prescribed ice sheets for two time periods that bracket the LGM period: 26 and 21 ka BP. CESM2.1 includes an explicit simulation of snow/firn compaction, albedo, refreezing, and direct coupling of the ice sheet surface energy fluxes with the atmosphere. The simulated mean snow accumulation is lowest for the Greenland and Barents–Kara Sea ice sheets (GrIS, BKIS) and highest for British and Irish (BIIS) and Icelandic (IcIS) ice sheets. Melt rates are negligible for the dry BKIS and GrIS, and relatively large for the BIIS, North American ice sheet complex (NAISC; i.e. Laurentide, Cordilleran, and Innuitian), Scandinavian ice sheet (SIS), and IcIS, and are reduced by almost a third in the colder (lower temperature) 26 ka BP climate compared with 21 ka BP. The SMB is positive for the GrIS, BKIS, SIS, and IcIS during the LGM (26 and 21 ka BP) and negative for the NAISC and BIIS. Relatively wide ablation areas are simulated along the southern (terrestrial), Pacific and Atlantic margins of the NAISC, across the majority of the BIIS, and along the terrestrial southern margin of the SIS. The integrated SMB substantially increases for the NAISC and BIIS in the 26 ka BP climate, but it does not reverse the negative sign. Summer incoming surface solar radiation is largest over the high interior of the NAISC and GrIS, and minimum over the BIIS and southern margin of NAISC. Summer net radiation is maximum over the ablation areas and minimum where the albedo is highest, namely in the interior of the GrIS, northern NAISC, and all of the BKIS. Summer sensible and latent heat fluxes are highest over the ablation areas, positively contributing to melt energy. Refreezing is largest along the equilibrium line altitude for all ice sheets and prevents 40 %–50 % of meltwater entering the ocean. The large simulated melt for the NAISC suggests potential biases in the climate simulation, ice sheet reconstruction, and/or highly non-equilibrated climate and ice sheet at the LGM time. [ABSTRACT FROM AUTHOR]

The last deglaciation (21 to 8 ka) of the Eurasian ice sheet (EIS) is thought to have been responsible for a sea level rise of about 20 m. While many studies have examined the timing and rate of the EIS retreat during this period, many questions remain about the key processes that triggered the EIS deglaciation 21 kyr ago. Due to its large marine-based parts in the Barents–Kara (BKIS) and British Isles sectors, the BKIS is often considered to be a potential analogue of the current West Antarctic ice sheet (WAIS). Identifying the mechanisms that drove the EIS evolution might provide a better understanding of the processes at play in the West Antarctic destabilization. To investigate the relative impact of key drivers on the EIS destabilization, we used the three-dimensional ice sheet model GRISLI (GRenoble Ice Shelf and Land Ice) (version 2.0) forced by climatic fields from five Paleoclimate Modelling Intercomparison Project phases 3 and 4 (PMIP3, PMIP4) Last Glacial Maximum (LGM) simulations. In this study, we performed sensitivity experiments to test the response of the simulated Eurasian ice sheets to surface climate, oceanic temperatures (and thus basal melting under floating ice tongues), and sea level perturbations. Our results highlight that the EIS retreat simulated with the GRISLI model is primarily triggered by atmospheric warming. Increased atmospheric temperatures further amplify the sensitivity of the ice sheets to sub-shelf melting. These results contradict those of previous modelling studies mentioning the central role of basal melting on the deglaciation of the marine-based Barents–Kara ice sheet. However, we argue that the differences with previous works are mainly related to differences in the methodology followed to generate the initial LGM ice sheet. Due to the strong sensitivity of EIS to the atmospheric forcing highlighted with the GRISLI model and the limited extent of the confined ice shelves during the LGM, we conclude by questioning the analogy between EIS and the current WAIS. However, because of the expected rise in atmospheric temperatures, the risk of hydrofracturing is increasing and could ultimately put the WAIS in a configuration similar to the past Eurasian ice sheet. [ABSTRACT FROM AUTHOR]

Globally, caves provide important refugia for bats. The Grand Canyon, more than 400 km (250 mi) long, consists of steep-sided, rocky formations with hundreds to thousands of natural caves. Two of these, Double Bopper and Leandras Caves, are remarkable because of the presence of desiccated bat carcasses, ranging in condition from skeletal to well-preserved animals identifiable to species. Both caves are complex but differ in length and structure. Double Bopper Cave, >60 km (37 mi) long, is variable with narrow passages. Leandras Cave, 24 km (15 mi) long, has wide, open passages. We surveyed both caves, collecting information for 482 specimens. We initially hypothesized that a single catastrophic event caused the deaths of many individuals or that bats died of various causes over a long period. We expected bat communities to differ between caves, since different cave structures would favor different species based on flight maneuverability. Radiocarbon dating of 67 samples found ages ranged from modern to >45,800 cal BP, spanning the Last Glacial Maximum. The dominant bat species in each cave differed, with Townsend's big-eared bat (Corynorhinus townsendii), a cave obligate, dominant in Double Bopper Cave and silver-haired bat (Lasionycteris noctivagans) dominant in Leandras Cave. Bats continue to use these caves today, as evidenced by the presence of fresh guano. The remarkable evidence of long-term continuous use of these caves by bats illustrates the importance of protection and conservation to provide habitat for them. The caves also provide an unprecedented time machine to study bat communities from the past, understand long-term patterns of habitat use, and prepare for climate change. [ABSTRACT FROM AUTHOR]

The dynamics of the ice sheets on glacial-interglacial time scales are highly controlled by interactions with the solid Earth, i.e., glacial isostatic adjustment (GIA). Particularly at marine ice sheets, competing feedback mechanisms govern the migration of the ice sheet's grounding line and hence the ice sheet stability. In this study, we run coupled ice sheet–solid Earth simulations over the last two glacial cycles. For the ice sheet dynamics we apply the Parallel Ice Sheet Model PISM and for the load response of the solid Earth we use the three-dimensional viscoelastic Earth model VILMA, which, in addition, considers the gravitationally consistent redistribution of water (the sea level equation). We decided on an offline coupling between the two model components. By convergence of trajectories of the Antarctic Ice Sheet deglaciation we determine optimal coupling time step and spatial resolution and compare patterns of inferred relative sea level change since the Last Glacial Maximum with the results from previous studies. With our coupling setup we evaluate the relevance of feedback mechanisms for the glaciation and deglaciation phases in Antarctica considering different 3D Earth structures resulting in a range of load-response time scales. For rather long time scales, in a glacial climate associated with far-field sea level low stand, we find grounding line advance up to the edge of the continental shelf mainly in West Antarctica, dominated by a self-amplifying GIA feedback, which we call the 'forebulge feedback'. For the much shorter time scale of deglaciation, dominated by the Marine Ice Sheet Instability, our simulations suggest that the stabilizing GIA feedback can significantly slow-down grounding line retreat in the Ross sector, which is dominated by a very weak Earth structure (i.e. low mantle viscosity and thin lithosphere). This delaying effect prevents a Holocene grounding line retreat beyond its present-day location, which is discussed in the scientific community, supported by observational evidence at the Siple Coast and by previous model simulations. The described coupled framework, PISM-VILMA, allows for defining restart states to run multiple sensitivity simulations from. It can be easily implemented in Earth System Models (ESMs) and provides the tools to gain a better understanding of ice sheet stability on glacial time scales as well as in a warmer future climate. [ABSTRACT FROM AUTHOR]

Introduction: Post-glacial climate variation is known to have influenced the distribution of marine species in the North Atlantic. In particular, the Atlantic side of the Arctic has experienced strong fluctuations in both atmospheric and sea surface temperature, as well as seasonal ice coverage since the last glacial maximum (LGM). Here, we aim to unveil the phylogeography and historical demography of three rocky intertidal marine invertebrates showing a trans-Atlantic distribution and presently inhabiting the Arctic: Gammarus oceanicus, Littorina saxatilis and Semibalanus balanoides. Methods: We used a large amount of mitochondrial DNA barcode data, both newly-obtained and stored in public databases. We performed phylogeographic and demographic analyses on 1119 G. oceanicus, 205 L. saxatilis, and 884 S. balanoides sequences. Results: Our results show that all three of these boreal species have expanded their effective population sizes in the high Arctic Svalbard Archipelago since the LGM. Analyses investigating the origin of all these populations point to the eastern Atlantic. Discussion: Based on our results we conclude that the expansion of these boreal species to the Arctic possibly happened during an earlier warm cycle of the Holocene era, and is probably not the result of the recent 'Atlantification' of the Arctic. We also discuss the effects of dispersal potential on population structure as an important aspect of comparative biogeographical studies. [ABSTRACT FROM AUTHOR]

Introduction: The ability of species to colonize newly suitable habitats under rapid climate change can be constrained by migration processes, resulting in a shift of the leading edge lagging behind the ameliorating climate, i.e. migration lag. The importance and extent of such migration lags during the forest expansion after the Last Glacial Maximum (LGM) are still debated. Similarly, the relative importance of the main drivers of post-glacial vegetation dynamics (temperature, dispersal limitation, and competition) is still discussed in the literature. Methods: We used the dynamic global vegetation model LPJ-GM 2.0 to reconstruct the range shifts of 16 competing major European tree species after the LGM (18.5 ka BP) until recent times (0 ka BP). We simulated two dispersal modes by allowing free establishment whenever the climatic conditions suited the species (free dispersal), or by accounting for migration processes in the simulated vegetation dynamics (dispersal limitation). We then calculated thermal and range shift velocities, competition at establishment, thermal and dispersal lags for each species and dispersal mode. Finally, we compared our simulated range shift velocities with pollen-derived migration rates. Results: The simulation assuming limited dispersal resulted in more accurate migration rates as compared to pollen-derived migration rates and spreading patterns. We found no marked migration lags in the post-glacial establishment of pioneer species (Pinus sylvestris and Betula pubescens). Under the free dispersal mode, the remaining temperate species expanded rapidly and almost synchronously across central Europe upon climate warming (Bolling-Allerod interstadial). Differently, the northward spread of temperate species simulated under dispersal limitation happened mainly during the Holocene and in successive waves, with late spreaders (e.g. Fraxinus excelsior) experiencing multi-millennial dispersal lags and higher competition. Discussion: Our simulation under dispersal constraints suggests that the postglacial tree expansion in Europe was mainly driven by species-specific thermal requirements and dispersal capacity, which in turn affected the order of taxa establishment and thus the degree of competition. Namely, taxa with less cold-tolerance and relatively low dispersal ability experienced the highest migration lags, whereas the establishment of pioneer species was mostly in equilibrium with the climate. [ABSTRACT FROM AUTHOR]

In this study, we differentiate wet processes from dry processes in shaping the extratropical thermal stratification during the Last Glacial Maximum. Our findings indicate that even during the dry glacial period the influence of wet processes on thermal stratification cannot be overlooked. The applicability of dry and wet baroclinic adjustment theory strongly depends on the seasonality rather than the glaciation as the warm season is characterized by a weaker meridional temperature gradient and increased precipitation than the cold season. Despite that the baroclinic adjustment theory based on effective static stability can be proficiently applied to all seasons, the classical dry baroclinic adjustment theory may be better suited for use during relatively cold seasons. These findings have important implications for understanding processes governing the extratropical thermal stratification, particularly in the context of cold climate. Plain Language Summary: In this study, we examined how different processes affect the formation of the extratropical thermal stratification during the Last Glacial Maximum. We found that both dry and wet processes play a crucial role, with the wet processes being particularly important during warm seasons. Our results suggest that the importance of wet process is largely dependent on the seasonality instead of glaciation. These findings help to improve our understanding of the extratropical thermal stratification and its governing processes, particularly in the context of cold climates. Key Points: The study differentiates wet process from dry process in shaping extratropical thermal stratification during the Last Glacial MaximumEven during the dry glacial period, wet processes still poses a significant influence on thermal stratificationSeasonality governs dry and wet baroclinic adjustment theory applicability, with the dry theory being more suited for cold seasons [ABSTRACT FROM AUTHOR]

The interpretation of stalagmite δ18O in terms of reflecting Asian summer monsoon (ASM) precipitation is still elusive. Here, we present high‐resolution stalagmite trace element ratios (X/Ca, X = Mg, Sr, Ba) records from southwest China covering 116.09 to 4.07 ka BP. δ18O, δ13C, and X/Ca values exhibit clear precessional cycles, with δ18O values reflecting ASM circulation/intensity, while X/Ca ratios capture local precipitation or evapotranspiration variations. Our results show that Northern Hemisphere summer insolation (NHSI) is the main driver of ASM intensity and precipitation phase variation, but global ice volume modulates the response magnitude of summer precipitation to insolation. During the Last Glacial Maximum, high ice volumes caused significant monsoon precipitation to decrease. In contrast to modern observations of the tripolar distribution of precipitation in China, our record is consistent with paleo‐precipitation records in southern and northern China. Plain Language Summary: While it is well known that global changes have led to variations in the intensity and spatial distribution of Asian monsoon precipitation, the mechanisms behind this are not well understood. Paleoclimate records are essential for revealing the drivers behind monsoon variation. However, speleothem records from the Asian monsoon region rarely provide direct information on the amount of rainfall. Here we report on multiple indicator data sets from a stalagmite in southwestern China. It could help explore the variation of monsoon precipitation over the last ∼100,000 years. We find that the increase/decrease of Northern Hemisphere summer insolation controls the increase/decrease of Asian summer monsoon rainfall. In addition, global ice volume moderates the magnitude of rainfall response to insolation, and precipitation decreases significantly during high ice volume periods. Based on the present paleo‐precipitation records evidence, the existence of the spatial pattern of increasing/decreasing rainfall in central China corresponding to decreasing/increasing rainfall in northern and southern China remains ambiguous on the orbital scales, although the feature has been captured by some of the model simulations. Key Points: Stalagmite trace elements are indicators of regional hydrological environmental variations in Southwestern ChinaNorthern Hemisphere summer insolation and global ice volume modulate the phase and amplitude variations of regional hydrological environmentThe meridional tripolar spatial pattern of precipitation in monsoon region in China on the orbital scale remains ambiguous [ABSTRACT FROM AUTHOR]

Marine primary producers are largely dependent on and shape the Earth's climate, although their relationship with climate varies over space and time. The growth of phytoplankton and associated marine primary productivity in most of the modern global ocean is limited by the supply of nutrients, including the micronutrient iron. The addition of iron via episodic and frequent events drives the biological carbon pump and promotes the sequestration of atmospheric carbon dioxide (CO2) into the ocean. However, the dependence between iron and marine primary producers adaptively changes over different geological periods due to the variation in global climate and environment. In this review, we examined the role and importance of iron in modulating marine primary production during some specific geological periods, that is, the Great Oxidation Event (GOE) during the Huronian glaciation, the Snowball Earth Event during the Cryogenian, the glacial–interglacial cycles during the Pleistocene, and the period from the last glacial maximum to the late Holocene. Only the change trend of iron bioavailability and climate in the glacial–interglacial cycles is consistent with the Iron Hypothesis. During the GOE and the Snowball Earth periods, although the bioavailability of iron in the ocean and the climate changed dramatically, the changing trend of many factors contradicted the Iron Hypothesis. By detangling the relationship among marine primary productivity, iron availability and oceanic environments in different geological periods, this review can offer some new insights for evaluating the impact of ocean iron fertilization on removing CO2 from the atmosphere and regulating the climate. [ABSTRACT FROM AUTHOR]

Glycine soja is the wild relative species of cultivated soybean. In this study, we investigated the population divergence and genetic basis of the local adaptation of wild soybean in China using genome-wide single-nucleotide polymorphisms (SNPs) of a population of 72 G. soja accessions. Using phylogenetic analysis, we observed that G. soja accessions clustered into three distinct groups, each corresponding to a specific geographic region, the northeastern region (NER), central region (CR), and southern region (SR), consistent with previous studies. Notably, we found a significant positive correlation between genetic and geographic distances. Further population structure analysis revealed each group was associated with an ancestral population and a specific geographic area. By utilizing the genome sequencing data of accessions from 16 different locations, we inferred the population history of these wild soybean groups. Our results indicate that the three groups diverged ~25,000 years ago, coinciding with the time of the last glacial maximum. The effective population size of the SR group expanded first, and subsequently, the NER and CR groups expanded approximately 5000 and 2500 years ago, respectively. Moreover, 83, 104, and 101 significant associated loci (SALs) were identified using genome-wide association analysis for annual mean temperature, annual precipitation, and latitude, respectively. Functional analysis of genes located in SALs highlighted candidate genes related to local adaptation. This study highlights the significant role of geographic isolation and environmental factors in shaping the genetic structure and adaptability of wild soybean populations. Furthermore, it emphasizes the value of wild soybean as a crucial genetic resource for enhancing the adaptability of cultivated soybeans, which have experienced a loss of genetic diversity due to domestication and intensive breeding practices. The insights gained from our research provide valuable information for the protection, conservation, and utilization of this important genetic resource. [ABSTRACT FROM AUTHOR]

The Atlantic Meridional Overturning Circulation (AMOC) and the associated water masses have changed dramatically during the glacial–interglacial cycle. Here, I review some recent progress in the modelling of the AMOC and water masses since the Last Glacial Maximum and discuss the relevance of these past AMOC studies to the present and future AMOC study. Recent studies suggested that Atlantic water masses were constrained by carbon isotopes (δ13C) and neodymium isotopes (εNd), while the strength of the AMOC better was constrained by protactinium/thorium ratio (231Pa/230Th) and the spatial gradient of calcite oxygen isotopes (δ18Oc). In spite of the shallower AMOC at the glacial period, its intensity did not differ substantially from the present because of the cancellation of opposite responses to the rising CO2 and the retreating ice sheet. This article is part of a discussion meeting issue 'Atlantic overturning: new observations and challenges'. [ABSTRACT FROM AUTHOR]

Understanding how anthropogenic disturbances affect the genetics of tree species is crucial; however, how tree populations in the wild can tolerate these activities remains unexplored. Given the ongoing and intensifying anthropogenic disturbances, we conducted a study using Ailanthus altissima to gain new insights into the effects of these pressures on genetic variability in undisturbed and disturbed forests. We analyzed the genetic diversity and population structure of A. altissima using nuclear (EST-SSR) and chloroplast (cpSSR) microsatellite markers. The genetic diversity across the 34 studied populations based on ESTSSRs was found to be moderate to high (nHE = 0.547–0.772) with a mean nHE of 0.680. Bayesian clustering, principal coordinate analysis (PCoA), and discriminant analysis of principal component (DAPC) consistently divided the populations into three distinct groups based on EST-SSRs. Allelic combinations of 92 different chloroplast size variants from 10 cpSSR loci resulted in a total of 292 chloroplast haplotypes. The mean haplotype diversity was relatively high (cpHE = 0.941), and the mean haplotype richness was 2.690, averaged across the 34 populations of A. altissima. Values of FST in A. altissima from chloroplast and nuclear markers were 0.509 and 0.126, respectively. Modeling results showed evidence for population range contraction during the Last Glacial Maximum with subsequent population expansion in the Holocene and the future. Although genetic variation did not differ substantially across disturbed and undisturbed sites, there were small trends indicating higher genetic diversity and population bottlenecks in disturbed forests. As a result, disrupted ecosystems might display surprising genetic patterns that are difficult to predict and should not be overlooked. [ABSTRACT FROM AUTHOR]

The study of diatoms from the sediments of core Gz-1 (Gryazevoe Lake, Magadan oblast) has made it possible to identify the response of diatom communities to environmental changes in the Late Pleistocene and Holocene and to establish the main stages of the transformation of the lake ecosystem. Three diatom zones and four subzones, reflecting the evolution trend of the lake diatom flora during the transition period from the last glacial maximum to the Holocene, are distinguished based on the changes in the concentration of diatom valves in sediments, the ratio of representatives of ecological groups and dominants. This trend is similar to the changes in the lacustrine diatom communities of the Arctic regions noted in the last millennium in terms of the change in taxonomic composition and dominants. The data of diatom studies, lithological and petrophysical characteristics of sediments indicate that the most significant changes in the natural environment occurred at the Pleistocene–Holocene boundary from 12.6 to 11.1 ka. [ABSTRACT FROM AUTHOR]

Coastal marine ecosystems are highly productive and important for global fisheries. To mitigate over exploitation and to establish efficient conservation management plans for species of economic interest, it is necessary to identify the oceanographic barriers that condition divergence and gene flow between populations with those species, and that determine their relative amounts of genetic variability. Here, we present the first population genomic study of an Octopus species, Octopus insularis, which was described in 2008 and is distributed in coastal and oceanic island habitats in the tropical Atlantic Ocean. Using genomic data, we identify the South Equatorial current as the main barrier to gene flow between southern and northern parts of the range, followed by discontinuities in the habitat associated with depth. We find that genetic diversity of insular populations significantly decreases after colonization from the continental shelf, also reflecting low habitat availability. Using demographic modelling, we find signatures of a stronger population expansion for coastal relative to insular populations, consistent with estimated increases in habitat availability since the Last Glacial Maximum. The direction of gene flow is coincident with unidirectional currents and bidirectional eddies between otherwise isolated populations. Together, our results show that oceanic currents and habitat breaks are determinant in the diversification of coastal marine species where adults have a sedentary behavior but paralarvae are dispersed passively, shaping standing genetic variability within populations. Lower genetic diversity within insular populations implies that these are particularly vulnerable to current human exploitation and selective pressures, calling for the revision of their protection status. [ABSTRACT FROM AUTHOR]

Aim: Current distributions of widespread North American (NA) species have been shaped by Pleistocene glacial cycles, latitudinal temperature gradients, sharp longitudinal habitat transitions and the vicariant effects of major mountain and river systems that subdivide the continent. Within these transcontinental species, genetic diversity patterns might not conform to established biogeographic breaks compared to more spatially restricted taxa due to intrinsic differences or spatiotemporal differences. In this study, we highlight the effects of these extrinsic variables on genetic structuring by investigating the phylogeographic history of a widespread generalist squamate found throughout NA. Location: North America. Taxon: Common gartersnake, Thamnophis sirtalis. Methods: We evaluate the effects of major river basins and the forest‐grassland transition into the Interior Plains on genetic structure patterns using phylogenetic, spatially informed population structure and demographic analyses of single nucleotide polymorphism data and address range expansion history with ecological niche modelling using locality and historic climate data. Results: We identify four phylogeographic lineages with varying degrees of connectivity between them. We find discordant population structure patterns between sex‐linked and autosomal loci with respect to the relationship between the central NA lineage relative to coastal lineages. We find support for southeast Pleistocene refugia where recent secondary contact occurred during the Last Glacial Maximum and evidence for both northern and southern refugia in western NA. Main Conclusion: Our results provide strong evidence for a Pliocene origin for T. sirtalis in central‐southeastern NA preceding its rapid expansion across the continent prior to middle Pleistocene climate‐mediated lineage formation. We implicate major riverine networks within the Mississippi watershed in likely repeated westward expansion events across the Interior Plains. Finally, we corroborate prior conclusions that phenotypic differences between subspecies do not reflect shared evolutionary history and note that the degree of separation between inferred lineages warrants further investigation before any taxonomic revisions are proposed. [ABSTRACT FROM AUTHOR]

Onchidoris muricata (Gastropoda: Nudibranchia: Onchidorididae) is a well-known nudibranch species, which has a wide amphiboreal range confirmed by molecular data. However, O. muricata shows a high degree of variation in external morphology among distant populations, which may indicate the presence of cryptic diversity within this species. There are also two closely related species with an unconfirmed taxonomic status, which were recently described from the northwestern Pacific based on morphological data. In this paper we study the taxonomic status and population structure of O. muricata based on an integrative approach combining morphological and molecular data and using O. muricata as a model we explore issues of boreal marine fauna connectivity and glaciation-driven isolation. The external morphology, spicule composition, and features of the buccal armature and the reproductive system were studied using light microscopy, scanning electron microscopy and mCT scan technology. The molecular study included various population genetic analyses as well as divergence time estimation and ancestral area reconstruction analyses. Onchidoris muricata represents a true amphiboreal species, which shows a high degree of heterogeneity in morphological characters, especially in the radular morphology and in features of the reproductive system. Our new data question the validity of the North-West Pacific species O. macropompa and O. pavli as the morphology of both these species fall within the phenotypic diversity of O. muricata. Although our sampling does not include the type localities of these two species, the observed morphological variability in O. muricata and the lack of molecular data for the North Pacific species O. macropompa and O. pavli suggest the latter two species are in fact part of O. muricata morphological diversity. Phylogeographic analyses indicate a genetic separation of the North Pacific and North Atlantic-Arctic populations of O. muricata, suggesting restricted gene flow between these areas. We show that this divergence may be a result of glacial cycles during the late Pleistocene, which were a key factor in the reduction of gene flow across the Arctic Ocean. Our molecular results also suggest that the White Sea population experienced a bottleneck event during the last Glacial Maximum. [ABSTRACT FROM AUTHOR]

Simple Summary: Northwest China is characterized by unique geological and historical dynamics and endemic biota, but the joint influence of geography and past climate changes on the evolutionary history of endemic animals is poorly understood. We used two mtDNA genes (ND4 and Cytb) and ecological niche modeling (ENM) to explore how the Quaternary climatic fluctuations and complex geography in Northwest China have shaped genetic diversity, genetic structure, and demographic history of the Alashan pit viper (Gloydius cognatus). Our results clearly show that the lineage diversification of G. cognatus is related to the expansions of deserts and/or the early Pleistocene integration of the Yellow River. The strong spatial genetic structure fits an isolation-by-distance model. The signature of demographic and range contractions during the last glacial maximum (LGM) is rejected by both mitochondrial evidence and ENM. In addition, the suitable habitat of G. cognatus is predicted to be decreased in the future, suggesting that conservation and management of evolutionary significant units (ESUs) should be a priority. Our findings provide the first insights on the evolutionary history of G. cognatus in arid Northwest China and adjacent areas throughout the Quaternary. The joint impacts of historical geological events and Quaternary climatic oscillations in Northwest China on species evolution have been examined extensively in plant under a phylogeographic perspective. However, animal phylogeographic analyses in this region are still limited. The Alashan pit viper, Gloydius cognatus, occurs primarily in arid Northwest China and adjacent areas. Based on variation at two mtDNA genes (ND4 and Cytb) in 27 individuals representing 24 populations, the spatial genetic structure and demographic history of G. cognatus were examined across its geographic range. Phylogenetic analyses revealed two well-supported allopatric clades (each with two distinct subclades/lineages), distributed across the southern (Qaidam Basin, Lanzhou Basin, and Zoige Basin [S1]; Loess Plateau [S2]) and northern (Ily Basin [N1]; Junggar Basin and Mongolian Plateau [N2]) regions. AMOVA analysis demonstrated that over 76% of the observed genetic variation was related to these lineage splits, indicating substantial genetic differentiation among the four lineages. A strong pattern of isolation-by-distance across the sampling populations suggested that geographic distance principally shaped the genetic structure. The four lineages diverged by 0.9–2.2% for the concatenated data, which were estimated to have coalesced ~1.17 million years ago (Mya), suggesting that the expansions of the Badain Jaran, Tengger, and Mu Us deserts during the Xixiabangma glaciation likely interrupted gene flow and triggered the observed divergence in the southern and northern regions. Subsequently, the early Pleistocene integration of the Yellow River and associated deserts expansion promoted the differentiation of S1 and S2 lineages (~0.9 Mya). Both mitochondrial evidence and ecological niche modeling (ENM) reject the signature of demographic and range contractions during the LGM for G. cognatus. In addition, ENM predicts that the suitable habitat of G. cognatus will contract in the future. As such, the conservation and management of ESUs should be a priority. Our findings provide the first insights on the lineage diversification and population dynamics of the Alashan pit viper in relation to geological history and Pleistocene climatic oscillations in arid Northwest China. [ABSTRACT FROM AUTHOR]