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The UN's Paris Agreement goal of keeping global warming between 1.5 and 2°C is dangerously obsolete and needs to be replaced by a commitment to restore Earth's climate. We now know that continued use of fossil fuels associated with 1.5–2°C scenarios would result in hundreds of millions of pollution deaths and likely trigger multiple tipping elements in the Earth system. Unexpected advances in renewable power production and storage have radically expanded our climate response capacity. The cost of renewable technologies has plummeted at least 30‐year faster than projected, and renewables now dominate energy investment and growth. This renewable revolution creates an opportunity and responsibility to raise our climate ambitions. Rather than aiming for climate mitigation—making things less bad—we should commit to climate restoration—a rapid return to Holocene‐like climate conditions where we know humanity and life on Earth can thrive. Based on observed and projected energy system trends, we estimate that the global economy could reach zero emissions by 2040 and potentially return atmospheric CO2 to pre‐industrial levels by 2100–2150. However, this would require an intense and sustained rollout of renewable energy and negative emissions technologies on very large scales. We describe these clean electrification scenarios and outline technical and socioeconomic strategies that would increase the likelihood of restoring a Holocene‐like climate in the next 100 years. We invite researchers, policymakers, regulators, educators, and citizens in all countries to share and promote this positive message of climate restoration for human wellbeing and planetary stability. Plain Language Summary: New research in global ecology and public health shows that the consequences of burning fossil fuels are much more severe than previously understood. Current global warming targets are not enough to protect us from sea level rise, ecosystem collapse, and hundreds of millions of human deaths from fossil fuel pollution. Thankfully, the cost of renewable energy technologies has dropped below the cost of fossil fuels decades faster than predicted. This has triggered a renewable revolution that is transforming the global energy system. Our paper considers the feasibility of accelerating this transition through policy, investment, and strategic research. We conclude that there is a viable pathway to restoring Earth's climate through clean electrification and carbon capture. We call for a global commitment to restore pre‐industrial climate conditions within a century and describe what approaches would increase our chances of success. Accelerating the renewable revolution would move us toward a sustainable civilization by eliminating air pollution, stabilizing climate, reducing energy costs, and enhancing living standards worldwide. Because there is no safe level of climate disruption or pollution death, we believe it is our responsibility to restore a Holocene‐like climate, which we know can support human civilization and other life on Earth. Key Points: Goals of 1.5–2°C are not safe given current understanding of ecosystem climate sensitivity and high social costs of fossil fuel pollutionClimate restoration‐rapidly reestablishing Holocene‐like conditions‐has not been fully considered because of socioeconomic obstaclesStrategic financing and prioritization of clean electrification could create pathways back to the Holocene within a century [ABSTRACT FROM AUTHOR]

This paper develops a composite absolute paleointensity record for Holocene paleomagnetic secular variation (PSV) from central North America. Twelve full‐vector (inclination, declination, paleointensity) PSV records were assessed in order to build the composite record. Nine of the paleointensity records come from sediment paleomagnetic studies and are considered relative in intensity. Three of the paleointensity records come from absolute paleointensity measurements of archeological materials and lava flows. This paper develops a new method to normalize the sediment relative paleointensity records to the absolute intensity records. The final composite paleointensity record describes intensity variability over a region of Central North America delineated by 35°–48.6°N and 240.4–291.4°E (∼14° × 50°). This composite record shows a distinctive long‐duration (∼104 year) oscillation and a series of millennial‐scale intensity oscillations that are consistent over our study region. Plain Language Summary: This study develops a composite record of geomagnetic field intensity for the central North America for the last 8,000 years. This record is important for considering the total geomagnetic field variability I this region and its dynamo source(s). Key Points: We develop a new composite absolute paleointensity record for Holocene Central North AmericaWe develop a new renormalization technique to combine absolute paleointensity records and sediment relative paleointensity recordsThe final composite absolute paleointensity record has a distinctive long‐term trend and millennial‐scale variability [ABSTRACT FROM AUTHOR]

Recent climate and environment over the Tibetan Plateau (TP) have undergone significant changes, dominated by variations in the Westerlies and the Indian summer monsoon. However, long‐term shifts in atmospheric circulation during the transitional seasons are still lacking. Here we investigate the modern distribution of Tsuga pollen over the central‐western TP and confirm it as an indicator of variable atmospheric circulation in spring. By combining our Tsuga record from Taro Co with existing records in the Tsuga pollen source area, we suggest that a potential particle transport pathway from the southern slope of the Himalayas to the interior of the plateau appeared in the spring of the late Holocene. Our results show that the springtime atmospheric circulation over the southwestern TP during the early and late Holocene is closely related to the substantial remnants of ice sheets at northern high latitudes and the frequency of El Niño events, respectively. Plain Language Summary: The spring climate over the Tibetan Plateau (TP) is undergoing significant changes that yield profound impacts on environmental changes such as variations in vegetation phenology and alpine treeline. Knowledge of long‐term variations in atmospheric circulation during spring can improve the understanding of current climatic and environmental change and the projection of future variability. In this paper, we use an exotic pollen grain, which can be transported long distances in the air, as an indicator to trace the variability of spring atmospheric circulation over the TP. The results indicate that the spring meridional atmospheric circulation from the southern slope of the TP to its interior has been enhanced in the last four thousand years, which is mainly influenced by the frequency of El Niño events. Key Points: Spring atmospheric circulation change over the southwestern Tibetan Plateau (TP) during Holocene is reconstructedMeridional atmospheric circulation in spring over the southwestern TP is strengthened in the late HoloceneHigh‐(low‐) latitude forcing mainly influence the variations in spring atmospheric circulation during the early (late) Holocene [ABSTRACT FROM AUTHOR]

The North American Monsoon (NAM) is a critical component of the hydrologic cycle in southwestern North America. However, our understanding of the long‐term evolution of this monsoon system is incomplete due to a paucity of long‐term paleoclimatic records from the core and periphery of the NAM domain. C. Routson et al. (2022, https://doi.org/10.1029/2022gl099772) leverage a new compilation of Holocene proxy records to generate a new composite index of NAM evolution over the Holocene. They identify a relationship between NAM strength and the latitudinal temperature gradient over the Holocene. The authors suggest that shifts in the strength of the westerlies altered NAM convection via ventilation, a process whereby the large‐scale circulation imports low moist entropy air into the monsoon domain. These results highlight the importance of paleoclimatic records, especially from past "warm" intervals, for generating new insights about the evolution of regional monsoons. Plain Language Summary: The North American Monsoon is a circulation that brings summer rain to regions of the US southwest and western Mexico. Despite the fact that this circulation provides a majority of the precipitation in many parts of the arid southwest, we do not fully understand the factors that govern long‐term changes in this monsoon. A new paper by C. Routson et al. (2022, https://doi.org/10.1029/2022gl099772) uses proxy indicators of past summer rainfall, stretching from Central America to Arizona, to reconstruct changes in the monsoon over the geologic epoch known as the Holocene, or the last 11,000 years of Earth history. The results of this study suggest that Holocene changes in the temperature difference between the equator to pole, known as the "latitudinal temperature gradient," exerted an important influence over monsoon strength in the southwest. This has implications for the future of the summer monsoon, especially as the high latitudes of the northern hemisphere are expected to warm in the future. Key Point: The strength North American Monsoon tracks changes in the position of the midlatitude westerlies over the Holocene [ABSTRACT FROM AUTHOR]

The englacial stratigraphic architecture of internal reflection horizons (IRHs) as imaged by ice‐penetrating radar (IPR) across ice sheets reflects the cumulative effects of surface mass balance, basal melt, and ice flow. IRHs, considered isochrones, have typically been traced in interior, slow‐flowing regions. Here, we identify three distinctive IRHs spanning the Institute and Möller catchments that cover 50% of West Antarctica's Weddell Sea Sector and are characterized by a complex system of ice stream tributaries. We place age constraints on IRHs through their intersections with previous geophysical surveys tied to Byrd Ice Core and by age‐depth modeling. We further show where the oldest ice likely exists within the region and that Holocene ice‐dynamic changes were limited to the catchment's lower reaches. The traced IRHs from this study have clear potential to nucleate a wider continental‐scale IRH database for validating ice sheet models. Plain Language Summary: Ice‐penetrating radar is widely used to measure the thickness of ice sheets, critical to assessments of global sea level rise potential. This technique also captures reflections from chemical contrasts within the ice sheet, caused by the atmospheric deposition of conductive impurities, known as "internal reflection horizons" (IRHs) that can be traced over large distances. As these deposits are laid down in distinct events, most IRHs are isochronous age tracers and contain valuable information on past ice sheet processes. In this paper we trace and place age constraints on stratigraphic horizons across a large portion of the West Antarctic Ice Sheet, including regions where fast ice flow has disrupted the ice sheet stratigraphy. The resulting data set allows us to identify where the oldest ice is buried in the study region and provides evidence that flow of the ice sheet interior has been stable during the Holocene. Our results can be used to test the performance of ice sheet models, which seek to simulate the response of ice sheets to long‐term environmental change. Key Points: We measure and date individual isochronal radar internal reflection horizons across the Weddell Sea sector of the West Antarctic Ice SheetHorizons dated to 1.9–3.2, 3.5–6.0, and 4.6–8.1 ka are widespread and linked to previous radar surveys of the Ross and Amundsen Sea sectorsThese form the basis for a wider database of ice sheet architecture for validating and calibrating ice sheet models of West Antarctica [ABSTRACT FROM AUTHOR]

Cyclic facies variations in shallow‐water carbonate platforms often show repetitive facies patterns that are frequently interpreted to reflect the sedimentary response to variations in sea‐level related to changes in climate linked to orbital variations, the Milankovitch frequencies. Whether these shallow‐marine carbonates represent a complete infill of accommodation space, or are subtidal cycles, has been discussed in numerous papers. The extent to which the thickness of a single depositional cycle is a direct measure of the amplitude of relative sea‐level change is not fully understood. New shallow seismic data from Great Bahama Bank reveal that accommodation space created during the Holocene sea‐level rise is not filled in a predictable way. Three seismic horizons were identified: the seabed, the Pleistocene top, and a horizon within the Pleistocene. Depth surface and thickness maps of the Holocene and Pleistocene layers were combined with 326 in situ water‐depth measurements to assess the upper limit of the present accommodation space. The analysis showed that accommodation space and Holocene sediment thickness, and water depth are not correlated. In addition, the actual water depth and inner platform facies distribution showed no straightforward link. The energy distribution across the shallow‐water platform appears to control the facies type rather than water depth. Mud‐dominated sediments prevail in shallow low‐energy areas protected by a topographic barrier, whereas mud‐free coarse‐grained sediments mainly occur in deeper areas with hydrodynamic energy induced by strong tidal currents, ocean water influx, and winds. Hence, the uneven energy distribution not only results in unpredictable differences in the carbonate‐cycle thickness on the platform but also to a water depth independent facies distribution pattern within the inner platform. Therefore, care should be taken when deducing sea‐level signals from inner platform facies distribution and sediment thickness patterns on ancient platforms. [ABSTRACT FROM AUTHOR]

Aim Projections of human impact on the environment and biodiversity patterns are crucial if we are to prevent their destruction. Such projections usually involve the assumption that the same human activities always affect biodiversity in the same way, either in geographically distant areas within the same time-scale or in the same areas in different periods. In this paper, plant and snail fossils from central Europe that cover the last 12,000 years provide evidence against this assumption. Location Central Europe. Methods We examined fossil data on central European plants and snails and extracted time-series of (1) local species richness (alpha diversity) at a scale of approximately 300 m × 300 m and decays of (2) the Jaccard index and (3) Simpson's beta with increasing distance (up to approximately 400 km) through time. Results We show that two vital biodiversity patterns follow neither oxygen-isotope nor borehole temperature proxies, but instead vary between archaeologically known periods, with the most noticeable and irreversible breaks (1) when arable agriculture was introduced into central Europe, (2) when the Roman Empire collapsed, and (3) during the event known as the 12th-century colonization in central Europe. The patterns computed from data across time sometimes contradicted the patterns computed across space. Main conclusions We therefore infer that people can, and sometimes have, contributed to temporal changes in ecological rules that are seemingly general across space. Our findings indicate that the changes in ecological rules are so substantial that efforts to project future biodiversity based on space-for-time substitution might fail, unless we gain knowledge about how these general rules are altered. [ABSTRACT FROM AUTHOR]

Nitrous oxide (N2O) is an important greenhouse gas which destroys the ozone in the stratosphere. Primary sources of atmospheric N2O are nitrification and denitrification in terrestrial soils and the ocean, and the main sink is photolysis in the stratosphere. Studies have mostly focused on the climate‐related response of N2O during glacial‐interglacial periods. However, its mechanism of variation during the Holocene remains unclear. We present a high‐resolution N2O record from the South Pole Ice (SPICE) core covering the Holocene epoch. The millennial‐scale N2O trend agrees with existing records. We constructed a Holocene composite consisting of the new N2O measurements in SPICE and existing records from other ice core sites. The N2O composite reveals four distinct periods of N2O variation during 11.5–10.0 ka, 10.0–6.2 ka, 6.2–2.2 ka, and 2.2–1.4 ka, including two maxima in 11.0–10.0 ka and 3.0–2.2 ka and minima in 8.8–6.2 ka and approximately 1.4 ka. Apart from these, our new high‐resolution record from SPICE shows a short‐term N2O decrease around 2.8 ka which is not observed in other records possibly due to lower sample resolution and/or higher age smoothing. Comparison of our new Holocene N2O composite with the paleo‐proxy records suggests the plausible linkage of major monsoon (Asian, North African, South and North American, and Australian‐Indonesian monsoon) and upwelling (Arabian Sea and Eastern Tropical South Pacific) regions in regulating the atmospheric N2O during the Holocene. Plain Language Summary: Nitrous oxide (N2O) is an important greenhouse and ozone‐depleting gas. The growing level of N2O in the atmosphere is of global concern, and records of past N2O variations can provide an essential context for understanding the links between N2O and climate change. In this study, we report a new, high‐quality N2O record covering the Holocene epoch using an ice core obtained from the South Pole. Our record shows four important periods of N2O variation during 11.5–10.0 ka, 10.0–6.2 ka, 6.2–2.2 ka, and 2.2–1.4 ka. These include two local N2O maxima in 11.0–10.0 ka and 3.0–2.2 ka and minima in 8.8–6.2 ka and approximately 1.4 ka. Comparison with climate records suggests that the variation in monsoon precipitation and ocean productivity contributed to centennial‐ to millennial‐scale N2O variations during the Holocene. Key Points: High‐resolution N2O record from the South Pole Ice core covering the Holocene epoch is investigated for N2O variationInsight into the key drivers of atmospheric N2O on millennial time scales during the Holocene is providedN2O exhibits two local maxima during 11.0–10.0 ka and 3.0–2.2 ka, and two local minima during 8.8–6.2 ka and at around 1.4 ka [ABSTRACT FROM AUTHOR]

This paper addresses the surface and Holocene aeolian deposits in the southeastern Mu Us Desert, N. China, systematically analysing the evolution of the geochemical characteristics of aeolian sand-palaeosol sequences and their environmental significance. Our results indicate that the geochemical components of the Holocene aeolian deposits and surface deposits had the similar material sources, sediment transport and deposition processes in the study region, which were dominated by SiO2, Al2O3, and Na2O. In the weathering process of the Jinjie (JJ) profile, the Na, K, and Si presented the slight leaching and migration in general, while the other elements were relatively accumulated. The Holocene aeolian deposits and surface deposits incurred weaker geochemical weathering under cold and dry conditions and were only weakly leached, which implies a relatively arid environment in the Holocene epoch and the modern era. The weathering degree was controlled by the regional temperature and precipitation, and was probably more sensitive to the precipitation changes. In the sedimentary profile, the geochemical parameters and migration of elements demonstrated that there have been several alternating warm-wet and cold-dry intervals in the Mu Us Desert in the Holocene epoch; there were relatively warm and wet conditions prior to 4.6 ka, and it has been cold and dry since then. Six millennial-scale dry events were recorded during the Holocene, which were not only accordant with the history of palaeoclimatic changes in the different latitudes and archives of the Northern Hemisphere, but also correspond to the millennial-scale variation of cosmic radiation and solar activity during that period. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Holocene evolutionary history of the Banni Plain in the Great Rann of the Kachchh Basin is reconstructed from a subsurface sediment core of ca 50 m. Detailed data on textural and lithofacies variations, grain‐size analysis, environmental magnetism and accelerator mass spectrometry 14C dates on seven samples were generated on the sediment core retrieved from the Banni Plain near Berada. A high‐resolution record extending back to 10 ka has been reconstructed from the top ca 40 m of the core section comprising shallow marine sediments. The core is divisible into five depositional units. The basal part is a fluvial depositional unit followed upward by estuarine, sub‐tidal, intertidal and supra‐tidal environments. The sediment accumulation rate is highest in the sub‐tidal to intertidal facies (1.9 cm year−1) and decreases towards the supra‐tidal facies to 0.09 cm year−1. Environmental magnetic analysis, χlf coupled with the S‐ratio, indicates high magnetic mineral concentrations during the Early Holocene, suggesting a wet period accompanied by high monsoon precipitation. This is followed by the onset of semi‐arid conditions in the Great Rann of the Kachchh Basin as indicated by the low values of the χlf and S‐ratios. A westward and northward shift in the shoreline towards the deeper part of the basin is suggested during the Late Holocene, which is coupled with aridity and reduced monsoonal conditions. The change in depositional pattern from the retrogradational deposit of fluvial (Unit 1) to estuarine sediment (Unit 2), progressing to sub‐tidal (Unit 3), is attributed to sea‐level transgression followed by regressive intertidal (Unit 4) to supra‐tidal deposition (Unit 5), culminating in complete withdrawal of the sea, aided by tectonic uplift, during the Late Holocene. The results reveal that the sediment accumulation rates and depositional environments changed over time in response to changes in sea level from minima to maxima and then eventually to the present level. [ABSTRACT FROM AUTHOR]

The interaction between climate change and disturbances affects forest composition and dynamics, but most of our empirical knowledge comes from short‐term studies of the past century. Pollen and charcoal analyses of lake sediment cores retrieved from three sites in Nova Scotia were used to produce a landscape‐level analysis of long‐term forest cover dynamics and fire disturbances of the past ~2500 years. The present‐day forests had been established by that time, although a long‐term increase in Picea at the expense of northern hardwoods was seen at all sites, consistent with other pollen records found across New England and Eastern Canada. The driving influences of forest change prior to European settlement were a combination of climate and disturbance, acting on site characteristics of each region. Fires were relatively infrequent in this region and did not have a major impact on the evolution of the forests of central Nova Scotia. Changes in the relative abundances of the tree taxa occurred in response to long‐term cooling during the past 3000 years and century‐scale climate variability such as the Little Ice Age (ce 1450–1850) and Medieval Warm Period (ce 800–1300). The impact of climate variability on the fire regime depends on the landscape and vegetation type. "Borealization" of the Acadian Forest, noted during the period of European colonization, has been occurring for millennia. [ABSTRACT FROM AUTHOR]

The desiccation (extreme drying) of rivers has important implications for the broader Earth System. However, the desiccation history and its linkage to climate are rarely known for numerous major river systems, primarily due to difficulties in recognizing desiccation events from available stratigraphic records. Here, using a combination of geochemical techniques (major and rare‐earth element geochemistry, detrital zircon geochronology, and optically stimulated luminescence dating), we demonstrate that the Yellow River, which maintains the highest sediment load on Earth, became desiccated during the Last Glacial Maximum at approximately 20 thousand years ago. This finding implies that transportation of sediments and dissolved constituents to the oceans via the Yellow River may have decreased substantially or ceased during glacials, which would have ramifications for ocean chemistry and biology. Furthermore, our work highlights the importance of desiccated riverbed sediments as potential dust sources during glacial periods, a finding that is different from what is observed today. Plain Language Summary: Understanding the characteristics of major rivers is important for better constraining changes in the Earth System. Based on new geochemical data, we find that during the period dominated by overall drier and colder climate conditions ∼20,000 years ago, water flow in the upper reaches of the Yellow River was reduced to the point that flow effectively ceased downstream of the Hetao Basin. In other words, the Yellow River was no longer a perennial river between the upper and middle‐low reaches until re‐integrating ∼10,000–5,000 years ago. Moreover, we demonstrate that surface processes related to the Yellow River system are substantially different between colder‐drier and warmer‐wetter intervals, at least for the last ∼40 thousand years, and we suggest caution when using modern observations to infer regional environments and geomorphology related to rivers during colder‐drier periods. Key Points: Provenance changes at the outlet of the Hetao Basin indicate the desiccation and re‐integration of the upper Yellow River over the last ∼40 kaPaleo‐lake shorelines and geochemical proxies confirm that the west Hetao Basin contained the terminal lake for the desiccated Yellow RiverClimate‐river feedbacks across glacial‐interglacial cycles have implications for constraining terrestrial‐marine source‐to‐sink processes [ABSTRACT FROM AUTHOR]

Studying the evolution history of the southwest summer monsoon (SSM) throughout geological time, particularly during its strongest period in the Holocene, can improve our understanding of its variation and driving mechanisms, and even help predict future climate changes, due to its significant social and economic implications. Here, we reconstructed the history of chemical weathering intensity since the Last Glacial Maximum (LGM) based on clay mineral proxies [(illite/smectite)/(illite + chlorite) and illite crystallinity] obtained from Qionghai Lake sediments and examined its response to paleoclimate and SSM. Our findings indicate that the intensity of chemical weathering generally aligned with changes in paleoclimate, exhibiting strong chemical weathering intensity during warm and humid climate conditions. In addition, the intensity of chemical weathering basically tracks the evolution of the SSM since the LGM. Our results support the view that the highest SSM intensity occurred during the early‐middle Holocene, followed by gradual weakening during the late Holocene, with Northern Hemisphere summer insolation being the primary driver of the SSM evolution. The variations of the SSM and the corresponding intensity of chemical weathering were also influenced by the cumulative effects of glacier boundary conditions, North Atlantic climate fluctuations, and Intertropical Convergence Zone migrations. Key Points: Clay minerals can effectively reflect regional chemical weathering intensityChemical weathering intensity was following the monsoon variabilityThe strongest southwest summer monsoon occurred in the early‐middle Holocene [ABSTRACT FROM AUTHOR]

Estuaries comprise channels vital for economic activity and bars as valuable habitats. They are increasingly under human‐induced pressures (e.g. sea‐level rise and dredging), resulting in morphological changes that affect navigability, flood safety and ecology. Antecedent geology may strongly steer how estuary channels will adapt to these pressures, but is surprisingly absent in most models. Here geological data and a unique bathymetry dataset covering 200 years from the Ems‐Dollard estuary (Netherlands/Germany) were used to demonstrate how local resistant layers force the position and dimensions of confluences and bars on the scale of an entire estuary. These layers limit channel depth and consequently cause widening, resulting in mid‐channel bar formation and increased channel curvature. This could lead to unexpected estuary widening and may cause land loss in densely populated areas. With increasing channel volume (as may happen again under future sea‐level rise), resistant layers in the estuary's substrate become more exposed, which enhances their effects. Many systems around the world contain shallow resistant layers that potentially constrain estuary channel dimensions and steer bank erosion. This highlights that resistant layer effects are important to consider as part of mixed depositional processes in coastal environments. It is therefore necessary to globally account for the effects of inherited resistant layers in the possible response of estuaries to sea‐level rise and increased tidal penetration. [ABSTRACT FROM AUTHOR]

Dating of the Tibetan ice cores is often challenging with great uncertainties. The significant age difference between the Guliya ice core (∼760 ka [thousand years]) and other Tibetan ice cores (Holocene origin) necessitates new approaches to resolve the inconsistency. Here, we present the atmospheric O2δ18O (δ18Oatm) profile of the 216.6 m Chongce ice core. Our data suggest that post depositional alterations significantly changed δ18Oatm. We reject samples with melt layers, and reconstruct the δ18Oatm values with two extreme correction approaches: a minimum isotopic correction based on gas loss fractionation, and a maximum isotopic correction based on respiration fractionation. We consequently estimate the age range of the Chongce ice core to be 2.763–7.192 ka at the depth of 215.14 m, and ∼3–9.799 ka at the depth of 215.61 m. Our work provides an independent line of evidence for the Holocene origin of the Chongce ice core. Plain Language Summary: Dating of the Tibetan ice cores is often challenging with great uncertainties, mainly due to rapid thinning at the ice core bottom sections. There is a significant difference between the published ages of the Tibetan Guliya ice core (∼760,000 yr) and those of other Tibetan ice cores, all of which were confined to the Holocene (∼10,000 yr). The direct distance between the Guliya and Chongce ice core drilling sites is only ∼30 km. Here, we present the gas chronology based on the 18O/16O isotopes of trapped air O2 for the Chongce ice core. We apply corrections to eliminate the isotopic fractionations caused by post depositional alterations. The dating results based on the trapped air 18O/16O constrain the maximum age for the Chongce bottom ice to be within 9.799 ka at 215.61 m, indicating that the Chongce ice core is of Holocene origin. Key Points: We present the profile of δ18O of paleoatmospheric O2 and its implied gas chronology of a Tibetan ice coreThe trapped air δ18O synchronization with the Antarctic Siple Dome ice core yields an upper age limit of 9.799 kaThe age deduced from the trapped air δ18O confirms the Holocene origin of the Chongce ice core [ABSTRACT FROM AUTHOR]

Alpine ecosystems are hotspots of biodiversity despite their cold climates. Here we investigate spatial patterns in the phylogenetic diversity (i.e. the degree of species relatedness) of European alpine floras and quantify the influence of climatic conditions since the late Pleistocene and historical climatic instability in shaping these patterns. We collected species‐pool data for 22 alpine regions in central and southern Europe and calculated phylogenetic diversity within and between regions using two metrics sensitive to terminal branching in the phylogeny. We regressed phylogenetic diversity against macroclimatic variables representing seasonal extremes between the Last Glacial Maximum (LGM; 21 000 years BP) and the present at 1000‐year intervals. We found the lowest phylogenetic diversity in the Carpathians and the central Alps, and the highest in the north‐eastern and southern Iberian Peninsula. Phylogenetic diversity decreased with temperature seasonality and low winter temperature. While the effect of temperature seasonality was relatively constant over time, the influence of winter temperature decreased after the LGM. We also found that phylogenetic diversity decreased with historical climatic instability. Between regions, phylogenetic diversity was mainly explained by current climatic distance rather than geographic distance, suggesting that alpine floras were primarily driven by species sorting along climatic gradients. Our results confirm the role of environmental filtering in shaping the current phylogenetic diversity of alpine floras, resulting in more closely related lineages in regions with relatively cold and unstable climates. We also highlight the importance of explicitly incorporating climatic variation through time to better understand the processes structuring the current biodiversity of alpine floras. [ABSTRACT FROM AUTHOR]

The source and seasonality of rainfall in southern Arabia during the early‐ to mid‐Holocene and preceding humid periods are controversial because fossil lacustrine sediments provide solely indirect information on the amount of rainfall. Hydrogen and oxygen isotope measurements on fluid inclusion water trapped in Holocene and Pleistocene stalagmites from Hoti Cave in Northern Oman are direct indicators of the isotopic composition of paleoprecipitation. Isotope values of fluid inclusions formed during peak interglacial periods plot along monsoonal water lines and are indicative of a southern monsoonal moisture source. The last monsoon‐dominated period lasting from ∼10,100 to 6,300 years before present was terminated within a few decades in southeastern Arabia. The subsequent reduction in rainfall amount and change from predominantly summer to predominantly winter rainfall had a profound impact on human communities living in this area and triggered migration from inland to coastal areas where resources were more abundant. Plain Language Summary: During the Quaternary period, the Arabian Peninsula experienced short intervals of enhanced rainfall, turning the Arabian Desert into a savannah‐type landscape with abundant lakes and wetlands. These intervals are well‐documented in lake sediments and cave deposits throughout Arabia, whereas the source of rainfall is uncertain. Ancient rainwater trapped in fluid inclusions in stalagmites from Hoti Cave, Northern Oman, allows us to determine moisture source changes over the last 350,000 years before present. Using new analytical methods to extract the water from fluid inclusions and measure its hydrogen and oxygen isotopic composition, we are able to show that greatly enhanced rainfall was caused by an intensification and greater northward extension of the African and Indian monsoons into Arabia. For the last humid period between ∼10,500 and 6,300 years before present, stalagmites from Hoti Cave reveal an abrupt termination of the monsoon‐dominated period, a sharp decline in precipitation and change from a summer‐ to winter‐dominated rainfall regime in southeastern Arabia. As a result, human communities were severely affected by this major climatic change and forced to migrate from inland to coastal areas, where water and resources were more abundant. Key Points: Hydrogen and oxygen isotopes in fluid inclusions in stalagmites from Hoti Cave, Northern Oman, reveal changes in the source of rainfallRainfall during the early and middle Holocene originated from the Indian Ocean and was associated with the Indian summer monsoonA change in the seasonality and reduction in rainfall at ∼6,300 years before present had a profound impact on communities in Northern Oman [ABSTRACT FROM AUTHOR]

We investigated the population dynamics of a highly clonal marine angiosperm, Cymodocea nodosa, in the eastern Mediterranean Sea, to identify the historical dynamics, demography, and connectivity of the species in the area. Eighteen microsatellite loci were used in conjunction with coalescent methods to investigate the genetic structure and demographic history of C. nodosa meadows. Approximate Bayesian computation (ABC) modeling was used to examine the pattern of divergence over time in the context of environmental change over the course of the Quaternary period. ABC analysis revealed an initial split of the C. nodosa populations between the north‐western, northern, and north‐eastern Aegean Sea during the Pleistocene epoch, followed by a more recent divergence of the north‐western population and the central‐western part of the Aegean Sea. According to the results, the most parsimonious historical scenario is that of a pervasive genetic signature of the effects of the drop in sea level during the Pleistocene epoch. This scenario supports the isolation of the north‐western, north, and north‐eastern area, and the subsequent recolonization after post‐glaciation sea level rise that may explain the north‐western differentiation as well present‐day detected dispersion of C. nodosa. [ABSTRACT FROM AUTHOR]

Insolation changes play an important role in driving monsoon changes at orbital time scales. One key issue that has remained outstanding is whether the Asian monsoon is driven by local insolation from the Northern Hemisphere (NH) or remote insolation from the Southern Hemisphere (SH) at orbital band. Here, we perform a set of sensitivity experiments to quantify the impacts of local and remote insolation changes on the Afro‐Asian summer monsoon at 11 ka BP relative to the present. We show that the Afro‐Asian summer monsoon is overwhelmingly driven by the precession induced local insolation change in the tropical‐subtropical NH. The insolation from NH high latitudes also affects the Afro‐Asian summer monsoon. In contrast, the insolation from SH plays a negligible role. Our model experiments support the idea that the Afro‐Asian summer monsoon are driven predominantly by the direct forcing of NH low latitudes summer insolation for the Holocene. Plain Language Summary: The Afro‐Asian summer monsoon response to solar insolation has been studied extensively both in observation evidences and model simulations. However, whether the Afro‐Asian summer monsoon is driven by local insolation from the Northern Hemisphere (NH) and remote insolation from the Southern Hemisphere (SH) still remains an open question. This work, for the first time, systematically isolates local and remote insolation impacts on Afro‐Asian summer monsoon using insolation from 11 ka BP. Our study suggests that the Afro‐Asian summer monsoon is driven by local precession insolation change. The increased local summer insolation at 11 ka increases the land‐sea thermal contrast, migrating the subcloud moist static energy maximum and westerly jet northward. These processes lead to a belt of increased monsoon precipitation stretching from North Africa eastward into South and East Asia, resulting in enhanced monsoon circulation and precipitation. The remote insolation from NH high latitude can also drives the incremental Afro‐Asian summer monsoon precipitation but the magnitude is much smaller compared with local effect. The insolation from SH has negligible role. Our model experiments support the idea that NH summer monsoons are driven predominantly by the direct forcing of NH low latitudes summer insolation for the Holocene. Key Points: The first study to completely isolate the local and remote insolation effect on Afro‐Asian summer monsoon at geological timeThe Afro‐Asian summer monsoon during Holocene is driven by local precession forcing in the tropical‐subtropical Northern HemisphereThe "latent heat" hypothesis is not supported by this study [ABSTRACT FROM AUTHOR]

The forcing of multicentennial climate variability in the Western Pacific Warm Pool (WPWP) region is not fully understood. Here, we generated 6‐kyr‐long continuous charcoal records from five peatlands in Borneo. Every several hundred years, peaks of charcoal influx were identified in the composite record, indicating that the peatlands repeatedly experienced dry conditions and wildfires. Major fire events were identified at ∼5.4, 4.7, 4.4, 3.7, 3.2, 2.7, 2.4, 2.2, 1.7, 1.1, 0.6, and 0.3 ka. Most of these coincided with the maxima of Borneo speleothem δ18O and occurred in the high solar activity periods following the solar minima. This suggests that the higher solar activity decreased rainfall, increasing dryness and wildfire frequency. This result challenges the hypothesis that high solar activity intensifies atmospheric convection in the WPWP area. Plain Language Summary: The charcoal influx in peat sequences shed light on the wildfire history in northern Borneo during the last 6,000 years. The sequences indicate peaks of charcoal influx every several hundred years, suggesting that the peatlands repeatedly experienced dry conditions and wildfires. The major fire events occurred in the high solar activity period after the solar activity was at a minimum. This suggests that the climate was drier when the solar activity was stronger. This result challenges the idea that high solar activity induces more rainfall in the tropical Western Pacific area. Key Points: Charcoal influx in peats was evaluated to understand wildfire history and climate change in northern BorneoThe charcoal record showed that fire events occurred every several hundred years in response to changes in solar activityMajor fire events occurred in the high solar activity periods following the preceding solar minima [ABSTRACT FROM AUTHOR]

Wildfire activity is an important activity in evolution of vegetation and carbon cycling. Whether wet weather will suppress wildfire or promote them by increasing fuel reserves during the Holocene is not clear. We obtained a record of black carbon from a sediment core spanning the last 14.8 kyr from Gonghai Lake, in North China. There is a close relationship between the timing of wildfire activity and vegetation development driven by the East Asian summer monsoon intensity. On a millennial timescales, wet climatic conditions provide a sufficient biofuels reserve, in the same period wildfire increase; thus, the regional potential biofuels reserve is shown to be an important controlling of regional wildfire activity in the monsoon region of China, under natural conditions. We infer that with the strengthening of Asian summer monsoon caused by global warming, the wildfire carbon emission in Asian monsoon region may increase in the future. Plain Language Summary: Much attention has been paid to the response of wildfire activity to climate change. Understanding the past history of wildfires and their triggering factors may help us to mitigate the effects of future wildfires. Our study of the black carbon record of the sediments from an alpine lake (Gonghai Lake) in North China indicates that the level of biofuels (mainly woody vegetation) was the main control on the intensity of wildfire on a millennial timescales over the past ∼14,800 yr. When the climate was wetter, more biofuels were available as a result of increased biomass storage, wildfires were more intense with a relatively stable ignition probability. So, climate trends that favor vegetation development will lead to a higher intensity of wildfire and carbon emission in the Asian monsoon region in the future, with the strengthening of Asian summer monsoon caused by global warming. Key Points: The variation of wildfire and summer monsoon is consistent on the millennial scale, wet climate drives wildfire enhancingBiofuels reserve has controlled wildfire for the Holocene in Asian summer monsoon regionStronger monsoons caused by global warming would increase wildfire carbon emission [ABSTRACT FROM AUTHOR]

The Ross Sea has the world's largest marine protected area. Modified Circumpolar Deep Water (MCDW) has significant effects on physical and biological processes in the Ross Sea. Totally 13 penguin ornithogenic sediment profiles were collected from Inexpressible Island, Ross Sea, and the Cd/P ratios were used as a proxy of MCDW intrusion, enabling to reconstruct the variability of MCDW intrusion into the Ross Sea during the past 6,000 years. During the intervals of ∼0.7–1.6 and ∼2.8–6.0 kyr BP, enhanced MCDW intrusion increased the heat supply which warmed the surface water and reduced the coastal sea ice concentration. By contrast, reduced MCDW intrusion during ∼1.6–2.8 kyr BP caused a decrease in the penguin population via restricting food supply and/or increasing sea ice concentration. Thus, changes in MCDW were responsible for driving millennial changes in sea ice and penguin population in the Ross Sea. Plain Language Summary: Modified Circumpolar Deep Water (MCDW) has important impacts on physical and biological processes in the Ross Sea. Although high‐resolution spatiotemporal records of MCDW intrusion into the modern Ross Sea have been obtained using various methods, the intrusion of this water mass into the Ross Sea during the Holocene has not previously been reconstructed. Here, we use measurements of the Cd/P ratio in ornithogenic sediments to reconstruct the variability of the intrusion of the MCDW into the Ross Sea during the past 6,000 years. MCDW intrusion was enhanced during the intervals of ∼0.7–1.6 and ∼2.8–6.0 kyr BP, when the resulting increased heat supply warmed the surface water and reduced the concentration of coastal sea ice. By contrast, when MCDW intrusion was reduced during ∼1.6–2.8 kyr BP, the resulting restriction of the food supply and/or increased coastal sea ice concentration caused a decrease in the penguin population. Our results demonstrate that the Cd/P ratio can be used as a proxy of MCDW intrusion and that changes in the intrusion of the MCDW were responsible for driving millennial‐scale changes in sea ice and the penguin population in the Ross Sea. Key Points: Cd/P profiles from ornithogenic sediments can be used as a proxy of Modified Circumpolar Deep Water (MCDW) intrusionReconstruction of MCDW intrusion in the Ross Sea during the past 6,000 yearsMCDW intrusion drives millennial changes in sea ice concentration and penguin population in the Ross Sea [ABSTRACT FROM AUTHOR]

The integrated effects of ocean‐atmosphere dynamics on the temperature evolution in the western North Pacific marginal seas have remained elusive. In order to study mechanisms controlling southern Yellow Sea (YS) temperature changes, bottom water temperature (BWT) changes were reconstructed for the last 8.8 kyr by using the TEXL86 index, which archives temperature signal of the winter season Yellow Sea Warm Current. Our results reveal a series of abrupt multi‐centennial to millennial scale BWT changes (∼1°C), superimposed on a gradual long‐term cooling (>3°C) trend starting from ∼5 ka to the present. The YS BWT changes are positively correlated with subsurface water temperature changes in the Western Pacific Warm Pool (WPWP). The Western Pacific Warm Pool subsurface water cooling signal was most likely transmitted by the Kuroshio Current into the southern YS, highlighting the role of WPWP in influencing thermodynamics of the extratropical regions during the Holocene. Plain Language Summary: The Yellow Sea (YS) is a semi‐closed marginal sea located in the northwestern Pacific Ocean. During the winter season, the Yellow Sea Warm Current (YSWC) is driven by northwesterly winds, flowing into the southern YS along the west flank of the central trough. The YSWC, a continuation of the Kuroshio Current, brings warm equatorial Pacific water into the YS, leading to milder winters in the surrounding coastal cities compared with other cities on the same latitude in China. The YSWC is sensitive to changes in ocean‐atmosphere dynamics. However, its evolution during the Holocene is not well understood. We reconstruct the winter season temperature changes of the YSWC during the last 8.8 kyr. We found warm temperatures during the mid‐Holocene (8.8‐5 ka) and a gradual cooling trend over the last 5 kyr, which coincides with subsurface water temperature changes in the Western Pacific Warm Pool (WPWP). We suggest that the tropical subsurface water temperature changes of the WPWP are most likely transmitted via the Kuroshio Current into the YS. Our results shed new light on our understanding of the role played by the WPWP water masses in regulating subtropical ocean dynamics and climate during the mid‐to‐late Holocene. Key Points: The temperature evolution of the winter season Yellow Sea Warm Current was reconstructed over the past 8.8 kyrAbrupt multi‐centennial to millennial scale changes are superimposed on a gradual cooling trend starting from ∼5 ka to the presentWestern Pacific Warm Pool subsurface water cooling signal was transmitted by the Kuroshio Current into the southern Yellow Sea [ABSTRACT FROM AUTHOR]

Aim: Knowledge of the drivers of ecosystem changes in the past is key to understanding present ecosystem responses to changes in climate, fire regimes and anthropogenic impacts. Northern Hemisphere‐focussed studies suggest that climate and human activities drove turnover during the Holocene in temperate ecosystems. Various drivers have been invoked to explain changes in Southern Hemisphere temperate vegetation, but the region lacks a quantitative assessment of these drivers. To better understand the regional drivers of past diversity, we present a quantitative meta‐analysis study of turnover and richness during the lateglacial and Holocene in Australian temperate ecosystems. Location: South‐east Australia (Tasmania, Bass Strait, SE mainland). Methods: We conducted a meta‐analysis study of 24 fossil pollen records across south‐east Australian temperate ecosystems, applying an empirical turnover threshold to fossil records to identify periods of major turnover for the first time in Australia. We tested pollen richness as a proxy for vegetation richness to estimate past richness and applied this to fossil pollen data. The resulting reconstructions were compared to independent records of climate, sea‐level change and fire through generalized linear modelling. Results and conclusion: Our results show changes in available moisture and sea level drove turnover and richness in most parts of SE Australia in the past, explaining up to c. 97% deviance. However, fire mainly drove turnover in Bass Strait. Our richness reconstructions also support the intermediate disturbance hypothesis, suggesting that high biodiversity was partially maintained by anthropogenic‐managed fire regimes. While temperature change is considered key to Northern Hemisphere palaeodiversity, past turnover and richness in Southern Hemisphere temperate ecosystems responded mainly to moisture availability and sea‐level change (considering its role in modulating regional oceanic climate). [ABSTRACT FROM AUTHOR]

Here we present, to date, the highest‐resolved (~5 years) and most precisely dated Holocene monsoon climate reconstruction for the western Chinese Loess Plateau based on five replicated stalagmite δ18O records from Wuya Cave, eastern Gansu, China. Our record suggests the wettest period occurred between 10,500 and 6,600 a BP in this region. After this period, the amplitude of Asian summer monsoon decadal‐scale variability progressively increased likely in response to increasing ENSO frequency since the middle Holocene. Our study reveals similar asymmetric centennial‐scale double‐plunging structures of the 8.2, 5.5, and 2.8 ka events in the western Chinese Loess Plateau, suggesting a possible role of solar activity whose impact was amplified around 8.2 ka BP by the meltwater flood. In contrast, the 4.2 ka event exhibit gradually declining monsoon rainfall with centennial‐ to decadal‐scale fluctuations. Key Points: A 5 year‐resolved Holocene Asian summer monsoon record was reconstructed for the western Loess Plateau based on speleothemsThe wettest period occurred between 10,500 and 6,600 a BP, after that, the amplitude of decadal‐scale monsoon variability increasedSimilar structures were observed during the 8.2, 5.5, and 2.8 ka weak monsoon events, which are different from the 4.2 ka event [ABSTRACT FROM AUTHOR]

The East Asian summer monsoon and winter monsoon (EASM and EAWM) are two important components of the East Asian monsoon system. However, the relationship between the two components during the Holocene remains debated in the observation. Here, we use a set of simulations in CCSM3 to investigate the EASM‐EAWM relation across different timescales during the Holocene. It is shown that the intensities of EASM and EAWM are positively correlated at orbital timescale but negatively correlated from millennial down to multidecadal timescales. The positive correlation at orbital timescales is forced by the seasonal insolation forcing, while the negative correlation at millennial and shorter timescales is caused mainly by the internal variability of the Atlantic Meridional Overturning Circulation (AMOC) and the subsequent teleconnection to East Asia via land‐sea thermal contrast. Plain Language Summary: The East Asian summer monsoon (EASM) and East Asian winter monsoon (EAWM) are important factors that affect regional climate. However, it has remained controversial whether EASM and EAWM vary in‐phase or out of phase in the Holocene. Our simulations show that EASM correlates with EAWM positively at orbital timescale due to the seasonal precessional forcing but negatively correlated from multidecadal to millennial timescales because of the impact of the Atlantic Meridional Overturning Circulation (AMOC). Key Points: Anticorrelations are found in EASM and EAWM variations from multidecadal to millennial timescales during the HoloceneThe negative EASM‐EAWM relation is likely caused by the AMOC [ABSTRACT FROM AUTHOR]

Meandering rivers are abundant on Earth, from the largest rivers to the smallest tributaries. The classical view of meandering rivers is a sinuous planform with rounded bends, which grow and migrate until they are cut‐off. However, many low‐energy meandering rivers have planforms that are much more complex than this classical view due to the heterogeneity of their alluvium, and show relatively limited channel migration. Based on a detailed palaeogeographic study of the Dommel River in The Netherlands, it is inferred that low‐energy meandering rivers may develop tortuous planforms with sharp bends, owing to self‐formed deposits that increasingly constrain the channel mobility. This mechanism is corroborated by data from 47 meandering river reaches of varied scale from around the world, which show that erosion‐resistant floodplain deposits are preserved in the river banks when the river energy is below a critical threshold. The term 'self‐constraining' is proposed for low‐energy rivers where an increase in bank stability over time results in progressive tortuous planforms and reduced mobility. A conceptual model, based on the dataset, shows that the increase in bank stability over time also increases the energy required to break out of the tendency to self‐constrain. Self‐constraining thereby enhances the resilience of the system to bank erosion, while an unexpected increase in bank erosion may occur if river energy exceeds the critical threshold. This study provides a novel explanation for the evolution of low‐energy river planforms and dynamics, and provides new insights on their responses to climate changes. [ABSTRACT FROM AUTHOR]

Arctic summer temperatures mostly cooled over the last ~7 kyr, owing to decreasing summer insolation. However, knowledge of the winter season is limited in the Arctic paleoclimate literature. Here we develop a composite record of δ18O from ice wedges—a winter precipitation archive—to reconstruct changes in winter climate in the northwestern Canadian Arctic since ~7.4 kyr b2k. Our record shows a long‐term δ18O enrichment (+(0.14 ± 0.10)‰ kyr−1), suggesting winter temperatures increased since the mid‐Holocene, a finding that is corroborated by reconstructions from the Siberian Arctic. Winter warming over the last ~7 kyr is consistent with increasing winter insolation and greenhouse gas forcing. This study provides some of the first insights on the sensitivity of winter temperatures in the Canadian Arctic to past, and potentially future, climate forcings, and contributes to a more seasonally holistic understanding of the Arctic system. Plain Language Summary: The history of climate change during the last 11,700 years, a period known as the Holocene Epoch, has been traditionally studied using natural climate proxies such as tree rings or pollen in the sedimentary record. Such records allow us to better understand past climate variability in response to changing greenhouse gas concentrations, solar radiation, and other boundary conditions. However, most traditional climate proxies are biological and sensitive mainly to growing‐season conditions, whereas changes in cold‐season conditions are not well described in the literature. This is especially true in the Arctic where recent climate warming has been most pronounced in the winter season, but few cold‐season‐specific proxy records are available. In this study, we develop a ~7,400‐year record of the δ18O isotope composition of relict ice wedges in the northwestern Canadian Arctic, a proxy type that is specifically sensitive to cold‐season conditions. We observe a long‐term increase in ice‐wedge δ18O over the past ~7,400 years, indicating warming winter temperatures since the mid‐Holocene. This warming corresponds to increasing winter solar radiation and greenhouse gas concentrations and is in agreement with recent reports from ice wedges in the Siberian Arctic. Key Points: Ice‐wedge δ18O reveals an enrichment trend over the last ~7.4 kyrThe enrichment reflects a long‐term winter warming trend, coinciding with increasing winter insolation and greenhouse gas forcingThis record provides key insights on winter Holocene climate not previously described by other records in this region [ABSTRACT FROM AUTHOR]

Aim: Domestic animals first appeared in the archaeological record in northern Africa c. 9000 years before present and subsequently spread southwards throughout the continent. This geographic expansion is well studied and can broadly be explained in terms of the movement of pastoralist populations due to climate change. However, no studies have explicitly evaluated changes in the climatic niche of these domesticates. A priori, one cannot assume a relationship between the geographic spread of animal production and changes in climatic niche breadth because their relationship is highly variable. Therefore, we investigated Holocene changes in the climatic niche of domestic animals (animal production) and compared these to changes in the climatic niche of hunted terrestrial ungulates. Location: The African continent. Time period: 9000–500 BP. Major taxa studied: Domestic animals, hunted (wild) terrestrial ungulates. Methods: For the first time, we applied methods from environmental niche dynamics to archaeological data to reconstruct and quantify changes in the climatic niche breadth of animal production during the African Holocene. We used faunal remains from archaeological assemblages and associated radiocarbon dates to estimate the proportion of the African climate space used for animal production and hunting at 500‐year intervals. Results: We found that the climatic niche of domestic species broadened significantly with the geographic spread, most notably during the termination of the African Humid Period, whilst no such broadening occurred for the climatic niche of hunted species. Main conclusions: Our results provide a quantitative measure of the extent to which humans have constructed and adapted the climatic niche of animal production to manage their domestic animals across increasingly diverse ecological conditions. By incorporating ecological analysis into estimations of past land use, our methods have the potential to improve reconstructions of land use change, and to provide a foundation on which further niche construction hypotheses may be tested. [ABSTRACT FROM AUTHOR]

Over the past decades, coralline algae have increasingly been used as archives of palaeoclimate information due to their seasonal growth bands and their vast distribution from high latitudes to the tropics. Traditionally, these reconstructions have been performed mainly on high latitude species, limiting the geographical area of their potential use. Here we assess the use of temperate crustose fossil coralline algae from shallow water habitats for palaeoenvironmental reconstruction to generate records of past climate change. We determine the potential of three different species of coralline algae, Lithothamnion minervae, Lithophyllum stictaeforme and Mesophyllum philippii, with different growth patterns, as archives for pH (δ11B) and temperature (Mg/Ca) reconstruction in the Mediterranean Sea. Mg concentration is driven by temperature but modulated by growth rate, which is controlled by species‐specific and intraspecific growth patterns. L. minervae is a good temperature recorder, showing a moderate warming trend in specimens from 11.37 cal ka BP (from 14.2 ± 0.4°C to 14.9 ± 0.15°C) to today. In contrast to Mg, all genera showed consistent values of boron isotopes (δ11B) suggesting a common control on boron incorporation. The recorded δ11B in modern and fossil coralline specimens is in agreement with literature data about early Holocene pH, opening new perspectives of coralline‐based, high‐resolution pH reconstructions in deep time. [ABSTRACT FROM AUTHOR]

Arctic climate is uniquely sensitive to ongoing warming. The feedbacks that drive this amplified response remain insufficiently quantified and misrepresented in model scenarios of future warming. Comparison with paleotemperature reconstructions from past warm intervals can help close this gap. The Early Holocene (11.7–8.2 ka BP) is an important target because Arctic temperatures were warmer than today. This study presents centennially resolved summer temperature reconstructions from three Svalbard lakes. We show that Early Holocene temperatures fluctuated between the coldest and warmest extremes of the past 12 ka, exceeding the range of instrumental observations and future projections. Peak warmth occurred ~10 ka BP, with temperatures 7 °C warmer than today due to high radiative forcing and intensified inflow of warm Atlantic waters. Between 9.5 and 8 ka BP, temperatures dropped in response to freshwater fluxes from melting ice. Facing similar mechanisms, our findings may provide insight into the near‐future response of Arctic climate. Plain Language Summary: The Arctic warms much faster than the global average. This amplified response can trigger feedbacks that affect the trajectory of future change. In areas formerly covered by ice, darker open water or rocks reflect less solar heat, enhancing warming. However, freshwater from melting ice may slow ocean circulation, leading to cooling. The climate impact of these mechanisms remain insufficiently understood, restricting efforts to predict future change. To reduce uncertainty, our research uses geological information from the most recent past period when the Arctic was warmer than the present, the Early Holocene, which lasted from 11,700 to 8,200 years ago. We analyzed fats from algae preserved in Svalbard lakes that yield information about past summer temperatures. Our findings show that the Early Holocene was characterized by the coldest and warmest extremes experienced since the last Ice Age. During peak warmth, summer temperatures were 7 °C warmer than today as more solar radiation and warm water reached the Arctic. However, Early Holocene warming was much slower than today. But warming was interrupted when freshwater pulses from melting Ice Sheets lowered temperatures. As we face a warmer Arctic with a melting Greenland Ice Sheet, our findings provide a rare window into the region's future. Key Points: Temperatures exceeded instrumental and projected values ~10 ka BP as reinvigorating ocean circulation compounded radiative forcingTemperatures drop ~9.5–8 ka BP as the impact of freshwater from the melting Laurentide Ice Sheet overwhelms warmingFirst terrestrial evidence from the Nordic Seas of surface cooling in response to the meltwater‐driven 9.3 and 8.2 ka climate events [ABSTRACT FROM AUTHOR]

Independent inference of the Asian winter monsoon (AWM), albeit achieved at several sparse sites, has reached no consensus for its variability through the Holocene. A sediment core from the northern coast of the South China Sea (SCS) was utilized to analyze organic biomarkers at (bi‐)decadal resolution, unveiling how SCS oceanic conditions fingerprint the AWM signal. Generally, alkenone sea surface temperature (SST) record, resembling the temporal structures of integrated tropical SST over the past 7,500 years, shows abnormal cool temperatures (up to ~4 °C) during the Little Ice Age and between ~1,200 and 2,500 years BP, when windborne terrigenous hopane compounds experienced considerable increases superimposed on a general increasing trend. Our results, together with augmented SST gradient between the SCS coast and open ocean, consistently suggest AWM strengthening toward the late Holocene. An intensified AWM during cold intervals like the Little Ice Age would have provided strong positive feedback to enhance coastal cooling. Plain Language Summary: Reconstructions of the Holocene Asian winter monsoon (AWM) history from terrestrial proxies are not only limited but also opposite, with both strengthening and weakening trends as reported. This study sheds additional insight into this controversy by analyzing the organic geochemistry of a sediment core at the northern coast of the South China Sea, where oceanic conditions such as sea surface temperature intensively interact with the AWM. We observed substantial surface cooling and a remarkable increase in terrestrial‐sourced hopane content concurrently toward the late Holocene, with the maximum taking place during the Little Ice Age and between 1,200 and 2,500 years ago. Together with enhanced temperature contrast between the coast and open ocean, our results clearly demonstrate an overall intensification of the Holocene AWM toward the present, antiphased with Asian summer monsoon changes. Key Points: Bi‐decadal alkenone SST changes at the northern SCS coast over the past ~7,500 yearsSharp increase in flux of terrestrial‐sourced hopane compounds during cool intervalsStrengthened winter monsoon toward the late Holocene, particularly at the LIA [ABSTRACT FROM AUTHOR]

Accretion rates of Holocene tropical coral reefs in three areas in the Atlantic, Pacific and Indian Oceans have been quantified in 79 dated core sections in 34 reef cores from Belize, the Maldives and French Polynesia. Holocene vertical reef accretion rate averages 5.05 m/kyr and has decreased during the past 10 kyr. Accretion rates in branched and massive coral facies are statistically similar. Reef accretion rate is positively correlated with the rate of sea‐level rise, that is the degree of creation of accommodation space, and with climate as expressed in a Holocene sea surface temperature anomaly. Accommodation space is also created by subsidence, but at a rate one to two orders of magnitude lower than that created by glacio‐eustasy (0.04 to 0.16 m/kyr). Lagoonal background sedimentation in adjacent reef lagoons averages 0.89 m/kyr as measured in 72 dated core sections in 28 cores. Lagoonal carbonate sedimentation on top of underlying mangrove peat usually starts after a considerable hiatus of ca 3 kyr on average. The lagoonal background sedimentation rate increased during the Holocene, probably due to deepening. The differences between vertical reef accretion and lagoonal background sedimentation rates are a major factor in the production of the widely known saucer shapes typical of tropical reefs and carbonate platforms, that is the creation of unfilled accommodation space. Reef core recovery, used as a proxy for reef consolidation, and core depth exhibit a statistically negative correlation based on data from 326 core barrels. Recovery and marine cement abundance (average volume 8.6%) also decrease from windward to leeward core positions. These observations are presumably a result of both a decrease in the rate of sea‐level rise that is the increase in time available for submarine cementation during the Holocene and the amount of flushing of reef interstices by marine waters. [ABSTRACT FROM AUTHOR]

The Miami Limestone is an oolite depositional body that is used as an analog model for geological interpretation of the rock record. Barrier‐bar complex, oolite banks, extensive bryozoan flats and tidal creeks, referred to as transverse glades, have been described. High‐resolution LiDAR data are used to produce unprecedented, detailed topographic maps of the transverse glades in the southern Atlantic Coastal Ridge. These maps were originally used to calculate historic discharge from the Everglades but revealed features inconsistent with the prevailing theory that the topography is of a depositional origin. Field observations verified an epikarst terrain truncated by collapsed subsurface conduits creating valleys, previously described as palaeotidal creeks. Observations of the 12 southern tidal creeks or transverse glades provided a sequence of six stages in the development of these karst valleys. After Late Pleistocene deposition of the Miami Limestone, sea‐level dropped producing conditions of: (a) epikarst which reduced the surface elevation preferentially, forming the southern Everglades Basin and modifying Biscayne Bay and Florida Bay precursor basins and (b) downward water movement producing vertical solution features. As Holocene sea‐level approached the South Florida carbonate platform margin a freshwater lens formed and groundwater movement became horizontal. Two sets of cavernous zones developed during the Middle and Late Holocene. Solution pipes and dolines provide a connection between the surface and groundwater along alignments which delineate subsurface conduits. Stages of valley formation are associated with the collapse of these conduits first forming a series of pocket valleys followed by narrow blind valleys and half blind or through valleys linking the Everglades to the coastal plain. Valleys then expanded in width until: (a) completion of cavernous zone collapse, (b) most boulder fields and valley margins reduced by weathering and (c) the valleys filled with wetland soils. [ABSTRACT FROM AUTHOR]

We report a new high‐resolution Holocene 10Be record from Huguangyan Maar Lake in subtropical‐tropical South China, aimed to detect the atmospheric 10Be production signal in low‐latitude regions. After minimizing climatic effects by regression analyses between 10Be concentration and climatic proxies from the same archive, we successfully distinguished variations in geomagnetic field intensity and solar activity using 2,000‐year low‐ and high‐pass filtering, respectively, of the residual 10Be record (a proxy of the atmospheric 10Be production rate). The resulting 10Be‐derived record of geomagnetic field intensity is generally comparable with geomagnetic models, and the solar‐modulated 10Be signal shows significant correlations with solar activity proxies. The preservation of 10Be production signal in the sediments of this low‐latitude maar lake highlights the largely unexplored potential as well as limitations of 10Be as a tool to reconstruct variations in solar activity and geomagnetic field intensity. Plain Language Summary: The atmospheric production rate of cosmogenic 10Be depends on the cosmic ray flux penetrating the atmosphere, a process that is mainly controlled by the geomagnetic field strength and solar activity. The geomagnetic imprint on 10Be has been well established in previous studies of ice cores and marine sediments. The relationship between solar activity and 10Be has also been studied in ice cores and high‐latitude lakes. Here we for the first time present a high‐resolution 10Be record from Huguangyan Maar Lake in subtropical‐tropical South China over the Holocene. We successfully separated the atmospheric 10Be production signal from climatic effects that contribute to up to ~52% of the variance in 10Be concentration. After eliminating the climatic effects, variations in both geomagnetic field intensity and solar activity signals were reconstructed from the residual 10Be record, using 2,000‐year low pass, and high‐pass filtering, respectively. The geomagnetic‐ and solar‐modulated 10Be production signals are evaluated by comparisons with independent records. This result unambiguously indicates that the 10Be‐derived solar activity signal at a low‐latitude subtropical site can be obtained, even when the 10Be signal is dominated by regional climate, in our case, accounting for up to ~65% of the variance in the record during the early‐middle Holocene. Key Points: We for the first time report on a multidecadal to centennial‐scale 10Be record throughout the Holocene in subtropical‐tropical South ChinaWe separated atmospheric 10Be production signal from regional environmental effects that account for ~52% of variance in 10Be concentrationGeomagnetic‐ and solar‐derived 10Be signals were reconstructed by 2,000‐year low‐ and high‐pass filtering, respectively, of the residual record [ABSTRACT FROM AUTHOR]

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Disturbances such as fires and grazing have major impacts on biodiversity. While it has been suggested that species richness is highest with intermediate levels of disturbance, currently there is no consensus due to an absence of data covering large temporal and spatial scales.We developed a new method to examine disturbance‐diversity relationships (DDR) using sedimentary pollen data linked with species' disturbance ecology. We reconstructed disturbance and diversity dynamics in the region of the European temperate zone over the last 12,000 years and calculated DDR for 900‐year sequential temporal windows.Disturbance frequency was highest in the early and late Holocene, while remaining low in the mid‐Holocene. Diversity increased continuously from the start of the Holocene. Our results demonstrate that over the past 12,000 years DDR changed from hump‐shaped into monotonic increasing pattern. While both highly disturbed and undisturbed sites were strongly impoverished in the early Holocene, as species migrated, biodiversity levels have subsequently affected disturbance regimes with highly disturbed sites now being the highest in species richness.Synthesis. Land‐use changes in the last 4,000 years created an increasingly patchy landscape, allowing invasive species adapted to high‐frequency disturbance to migrate across the landscape. The link between high diversity and disturbed areas is relatively recent and may anticipate even greater disturbance frequencies in future. Our findings also support a hypothesis that species migration, and the structure of the species pool critically determines the response of biota to external factors such as disturbance. [ABSTRACT FROM AUTHOR]

Conifer forests of the western US are historically well adapted to wildfires, but current warming is creating novel disturbance regimes that may fundamentally change future forest dynamics. Stand‐replacing fires can catalyze forest reorganization by providing periodic opportunities for establishment of new tree cohorts that set the stage for stand development for centuries to come. Extensive research on modern and past fires in the Northern Rockies reveals how variations in climate and fire have led to large changes in forest distribution and composition. Unclear, however, is the importance of individual fire episodes in catalyzing change. We used high‐resolution paleoecologic and paleoclimatic data from Crevice Lake (Yellowstone National Park, Wyoming, USA), to explore the role of fire in driving low‐elevation forest dynamics over the last 2820 yr. We addressed two questions: 1) did low‐elevation forests at Crevice Lake experience abrupt community‐level vegetation changes in response to past fire events? 2) Did the interaction of short‐term disturbance events (fire) and long‐term climate change catalyze past shifts in forest composition? Over the last 2820 yr, we found no evidence for abrupt community‐level vegetation transitions at Crevice Lake, and no evidence that an interaction of climate and fire produced changes in the relative abundance of dominant plant taxa. In part, this result reflects limitations of the datasets to detect past event‐specific responses and their causes. Nonetheless, the relative stability of the vegetation to fires over the last 2820 yr provides a local baseline for assessing current and future ecological change. Observations of climate–fire–vegetation dynamics in recent decades suggest that this multi‐millennial‐scale baseline may soon be exceeded. [ABSTRACT FROM AUTHOR]

The hazards posed by infrequent major floods to communities along the Susquehanna River and the ecological health of Chesapeake Bay remain largely unconstrained due to the short length of streamgage records. Here we develop a history of high‐flow events on the Susquehanna River during the late Holocene from flood deposits contained in MD99‐2209, a sediment core recovered in 26 m of water from Chesapeake Bay near Annapolis, Maryland, United States. We identify coarse‐grained deposits left by Hurricane Agnes (1972) and the Great Flood of 1936, as well as during three intervals that predate instrumental flood records (~1800–1500, 1300–1100, and 400–0 CE). Comparison to sedimentary proxy data (pollen and ostracode Mg/Ca ratios) from the same core site indicates that prehistoric flooding on the Susquehanna often accompanied cooler‐than‐usual winter/spring temperatures near Chesapeake Bay—typical of negative phases of the North Atlantic Oscillation and conditions thought to foster hurricane landfalls along the East Coast. Plain Language Summary: Despite the vulnerability of many mid‐Atlantic cities to flooding, including Washington D.C., few long‐term records exist to assess the risks posed by extreme, infrequent, storm events. Here we document recent and prehistoric floods on the Susquehanna River, which has the largest watershed on the U.S. Eastern Seaboard, using sediment cores collected from Chesapeake Bay. Our analysis finds that much of the Susquehanna's observed centennial‐millennial scale flood variability may be driven by the frequency of hurricane landfalls along the U.S. East Coast. Key Points: Recent and prehistoric flood deposits are recorded in Chesapeake Bay sedimentsFlood frequency is higher during negative phases of the North Atlantic OscillationNegative NAO conditions may increase hurricane landfalls along the U.S. East Coast [ABSTRACT FROM AUTHOR]

The long‐term morphodynamic evolution of estuaries depends on a combination of antecedent topography and boundary conditions, including fluvial input, sea‐level change and regional‐landscape interactions. Identifying effects of such boundary conditions on estuary evolution is important to anticipate future changes in specific boundary conditions and for hindcasting with numerical and physical models. A comprehensive synthesis of the evolution of the former Old Rhine estuary is presented here, together with its boundary conditions over its full lifespan from 6,500 to 1,000 cal. yr bp. This system formed during a period of sea‐level high stand, during which the estuary served as the main River Rhine outlet. The estuary went through three stages of evolution: a maturation phase in a wide infilling back‐barrier basin, a stable mature phase and an abandoning phase, both in a laterally confined setting. The Old Rhine River formed by a river avulsion around 6,500 cal. yr bp that connected to a tidal channel within a large back‐barrier basin. Decelerating sea‐level rise caused the back‐barrier basin to silt up around 5,700 cal. yr bp, resulting in shoreline progradation by beach‐barrier formation until ∼2,000 cal. yr bp. Beach‐barrier formation along the coast and natural levee formation along the river triggered peat formation in the coastal plain, laterally constraining the estuary and limiting overbank deposition, which caused most sediment to accumulate offshore. The abandoning phase started around 2,200 cal. yr bp when a series of upstream avulsions led to a substantial reduction in fluvial input. This induced a period of enhanced estuarine overbank clay deposition that continued into near‐complete silting up and estuary closure around 1200 ad. These findings exemplify how tidal systems, formed in wide coastal plains during sea‐level high stand, depend on antecedent conditions, and how they respond to connection and disconnection of a large river over long, millennial timescales. We present a comprehensive synthesis of the evolution of the former Old Rhine estuary and its boundary conditions over its full lifespan from 6,500 to 1,000 yr bp. The estuary went through three stages of evolution: a maturation phase in a wide infilling back‐barrier basin, a stable mature phase and an abandoning phase, both in a laterally confined setting. The evolution of the Old Rhine estuary exemplifies how tidal systems, formed in wide coastal plains during sea‐level high stand, depend on antecedent conditions, and how they respond to connection and disconnection of a large river over long, millennial, timescales. [ABSTRACT FROM AUTHOR]

The detailed Holocene inundation history of the Bermuda North Lagoon may be used as model for transgressive and highstand sequences in carbonate platforms. Sedimentation and facies development were controlled largely by sea‐level rise and antecedent topography. Four late Pleistocene to Holocene sequences may be identified in North Lagoon based on a combined analysis of 200 km shallow reflection seismics and 39 cores including 29 radiometric and U/Th‐ages. The sequences were deposited during sea‐level highstands and are separated by subaerial exposure horizons that formed during sea‐level lowstands. Sequence 1 (inferred MIS 7) consists of well‐cemented carbonate sands. Sequence 2 (MIS 5) is up to 20 m thick and consists of well‐sorted, inter‐reefal sands and reef sediments with mound‐like structures. Sequence 3 (inferred MIS 3) is up to ca 6 m thick and accumulated in topographic lows of the underlying sequences some 20 m below modern sea‐level. Sequence 4 (MIS 1, Holocene) includes lagoonal sediments up to 10 m thick, and reefs that accumulated on topographic highs of the MIS 5 sequences. Holocene sediments in topographic lows include peat, peaty sediment, freshwater mud, restricted marine carbonates, and open lagoonal carbonate sediments deposited in seagrass beds, shallow water, and deeper lagoon areas. Upward fining is an expression of deepening and the development of a reef‐protected lagoon environment. Holocene sedimentation on topographic highs usually lacks freshwater and transitional facies and starts with shallow marine mollusc shell accumulations overlain by carbonate sediments that show fining upward. Packstone (68%), wackestone (22%), grainstone (9%) and mudstone (1%) textures occur in cores, with Halimeda, molluscs, coralline algae and foraminifera being the most common constituent particles; coral fragments are rare. During the Holocene, an estimated volume of 1 km3 of carbonate sediments was deposited in North Lagoon. Average sedimentation rates are estimated to be 0.32 m/kyr. Four late Quaternary sequences may be identified on the Bermuda carbonate platform based on a combined analysis of 200 km shallow reflection seismics and 39 cores including 29 radiometric and U/Th‐ages. The sequences were deposited during late Pleistocene and Holocene sea‐level highstands and are separated by subaerial exposure horizons that formed during sea‐level lowstands. The detailed Holocene inundation history of this modern carbonate platform may be used as model for transgressive sequences in such environments in the fossil record. [ABSTRACT FROM AUTHOR]

On St. Paul Island, a remnant of the Bering Land Bridge, woolly mammoths persisted until 5,600 yr BP with no known predators or competitors, providing a natural system for studying hypothesized environmental drivers of extinction. These include overheating due to rising temperatures, starvation, and drought. Here, we test these hypotheses using Niche Mapper and LPJ‐GUESS to mechanistically estimate mammoth metabolic rates and dietary and freshwater requirements and, from these, estimate variations in island carrying capacity on St. Paul for the last 17,000 yr. Population carrying capacity may have been several hundred individuals at the time of initial isolation from the mainland. Adult mammoths could have fasted for two to three months, indicating a necessary ability to access snow‐buried forage. During the Holocene, vegetation net primary productivity increased, but shrinking island area overrode increased net primary productivity (NPP), lowering carrying capacity to ~100 individuals. NPP and freshwater availability alternated as critical limiting factors for this island population during the environmental changes of the late Pleistocene and Holocene. Only two or three individuals could have been sustained by the freshwater surplus in crater lakes (up to 18 individuals under the most optimistic parameter sensitivity experiments), suggesting that the St. Paul mammoth population was highly dependent on coastal freshwater sources. The simulations are consistent with the available proxy data, while highlighting the need to retrieve new paleohydrological proxy records from the coastal lagoons to test model predictions. More broadly, these findings reinforce the vulnerability of island megaherbivore populations to resource limitation and extinction. [ABSTRACT FROM AUTHOR]

A high-resolution diatom sequence was developed from continuously laminated lake sediments in southwestern Québec, which spanned the Holocene (~11,000 yr). General and species-specific changes in the diatom record were synchronous with patterns of vegetation succession inferred from regional palynological studies, demonstrating significant influences of terrestrial ecosystems on lake water chemistry and aquatic biota. Principal components analysis was used to identify three major diatom biostratigraphic zones corresponding broadly to early, mid-, and late Holocene climate intervals. Benthic alkaliphilus diatom taxa were abundant when the landscape was a Picea-dominated woodland in the early Holocene (11.1-8.0 ka), and when climate conditions were inferred as relatively cool and dry. In the mid-Holocene (8.0-3.6 ka), warmer temperatures resulted in a stabilization of soils and forests in the catchment area. Shade-tolerant tree species (Tsuga, Fagus, and Betula) increased during this time, and planktonic diatom taxa (Discostella stelligera and Fragilaria tenera) were abundant in the lake. The well-known decline in Tsuga across eastern North America between 6.0 and 5.0 ka corresponded to a shift toward more nutrient-rich lake conditions for several centuries, indicated by an increase in benthic diatom taxa and a lower ratio of chrysophytes relative to diatoms. Neoglacial cooling in the late Holocene (3.6 ka to present) triggered an initial decline in D. stelligera, which later recovered as a result of nutrient inputs that were associated with increased abundances of hardwood, deciduous species (Betula and Alnus) in the catchment. In addition to providing a high-resolution record of lake ontogeny for the region, the full Holocene record from this lake adds a new perspective on the spatial extent of regional aridity during the MedievalWarm Period (1.2-0.8 ka). [ABSTRACT FROM AUTHOR]

Abstract: Grasslands are globally extensive; they exist in many different climates, at high and low elevations, on nutrient‐rich and nutrient‐poor soils. Grassland distributions today are closely linked to human activities, herbivores, and fire, but many have been converted to urban areas, forests, or agriculture fields. Roughly 80% of fires globally occur in grasslands each year, making fire a critical process in grassland dynamics. Yet, little is known about the long‐term history of fire in grasslands. Here, we analyze sedimentary archives to reconstruct grassland fire histories during the Holocene. Given that grassland locations change over time, we compare several charcoal‐based fire reconstructions based on alternative classification schemes: (a) sites from modern grassland locations; (b) sites that were likely grasslands during the mid‐Holocene; and (c) sites based on author‐derived classifications. We also compare fire histories from grassland sites, forested sites, and all sites globally over the past 12,000 years. Forested versus grassland sites show different trends: grassland burning increased from the early to mid‐Holocene, reaching a maximum about 8000–6000 years ago, and subsequently declined, reaching a minimum around 4000 years ago. In contrast, biomass burning in forests increased during the Holocene until about 2000 years ago. Continental grassland fire history reconstructions show opposing Holocene trends in North versus South America, whereas grassland burning in Australia was highly variable in the early Holocene and much more stable after the mid‐Holocene. The sharp differences in continental as well as forest versus grassland Holocene fire history trajectories have important implications for our understanding of global biomass burning and its emissions, the global carbon cycle, biodiversity, conservation, and land management. [ABSTRACT FROM AUTHOR]

Geochemistry, sediment provenance, and the Holocene paleoenvironmental evolution of the Southern Po River coastal plain (Italy) were examined based on the geochemical analysis of 279 sediment samples from 35 cores. The Holocene succession is subdivided into four major facies associations: back‐barrier, transgressive barrier, shallow‐marine, and beach‐ridge deposits. Bulk chemical composition shows remarkable differences between facies associations, and the poly‐modal behavior in the related frequency curves suggests distinct sources of sediment. Using MgO and Ni as geochemical tracers, changes in sediment provenance were assessed with the aim to reconstruct the Holocene paleoenvironmental evolution of the area. The Po River and the Apenninic rivers represented the main sources of sediment during the early stages of transgression and highstand sea‐level conditions, whereas transgressive barrier and early shallow‐marine facies associations exhibit a clear North Adriatic river (eastern Alpine) provenance. The Holocene paleoenvironmental evolution of the study area, between about 10 ky and the present, indicates the presence of a bypass zone in front of the Po River mouth between 9 and 6 ky BP. At that time, sediment supplied by the North Adriatic rivers was transported southward by the longshore drift, bypassed the weak Po River influx and accumulated close to the Apennines. Comparison between Holocene facies associations and current back‐barrier and shallow‐marine sediments confirms that the present‐day basin circulation is similar to the one that acted during the last episode of sea‐level rise. [ABSTRACT FROM AUTHOR]

Results of analyses of a shallow marine sediment vibrocore from the Atlantic seafloor just west of the Aran Islands, western Ireland, are presented. The sediments range from ~16,000 to younger than 9,000 cal BP in age, based on 14C dating of foraminifers and molluscs. One sample within the core is dated at 12804 ± 125 cal BP and lies a very short distance stratigraphically below a conspicuous horizon containing isolated pebbles and sand‐size clasts, in what is an otherwise fine‐grained sequence of sediment. These outsized clasts are interpreted to be ice‐rafted debris. Approximately coeval with this horizon, the diversity and abundance of foraminifers decrease significantly and the foraminifer Nonionellina labradorica makes its first appearance in the core sediment. Stable isotope analysis shows a significant increase in values of δ18O approaching the horizon containing ice‐rafted debris. These results show the effects of a relatively sudden cooling of this part of the Atlantic Ocean at middle latitudes coincident with, or just after, the onset of the Younger Dryas event and demonstrate the extent of floating icebergs and probable later pack ice as a result of this temperature decrease. [ABSTRACT FROM AUTHOR]

In northern Idaho ( USA), more than 100 vascular plant species are disjunct >160 km from their main distribution along the Pacific Northwest coast. It remains unclear whether most species within this interior forest disjunction, including Tsuga mertensiana, survived the last glacial period in a north-Idaho refugium or whether these species colonized the region via long-distance dispersal during the Holocene., Sediment cores were extracted from three mid- to high-elevation lakes within T. mertensiana-dominated forests in the Northern Rocky Mountains of Idaho. Pollen and macrofossils were used to reconstruct forest composition, determine the timing of T. mertensiana establishment, examine the hypothesis that the region was a glacial refugium, and contrast how climate, competition and/or dispersal limitation have influenced its modern distribution., The modern distribution of T. mertensiana was analysed by constructing a range map and modelling the potential species distribution. The presence of outlier populations surrounding the Idaho disjunction along with broad areas of unoccupied suitable habitat indicates that the range of T. mertensiana is currently expanding. To assess the accuracy of T. mertensiana pollen at detecting its range limit, a network of pollen surface samples was used to analyse the probability of detecting T. mertensiana pollen as a function of distance from its geographical range limit. Consistent T. mertensiana pollen occurrence at ≥1% abundance is likely only within 42 km of its range limit., Tsuga mertensiana first appears in the pollen and macrofossil record at the highest-elevation site at c. 4,100 cal year bp, then at the next highest-elevation site at c. 1,600 cal year bp, and last at the mid-elevation site at 800 cal year bp. Tsuga mertensiana pollen occurs continuously at ≥1% at all three sites by c. 300 cal year bp suggesting regional presence. The timing of arrival suggests that T. mertensiana is a recent component of the forests of Idaho, having arrived during the Holocene via long-distance dispersal from coastal populations over 160 km away., Synthesis. Comparison with palaeoclimate reconstructions from the broader region suggests that climate was a greater limiting factor than dispersal in the Holocene establishment in the interior, indicating little difficulty overcoming a large dispersal barrier. However, T. mertensiana remained at low abundances for millennia until Little Ice Age climates promoted its recent increase in abundance. Unoccupied areas of suitable habitat suggest that competition, rather than climate or dispersal, is a limiting range infilling in the interior mesic forests today. [ABSTRACT FROM AUTHOR]

During the warmest time of the last 10 000 years (Holocene Thermal Maximum), approximately 6000–4000 cal yr bp in the western Pacific, sea level is known to have reached as much as 2.1 m above its present mean level before declining subsequently. Records throughout the region show that sea level fell an average 0.7 m in the period 3500–2000 cal yr bp during which the earliest (culturally distinct) period of human occupation occurred in five western Pacific island groups [Bismarck Archipelago (Papua New Guinea), Fiji, Mariana Islands, New Caledonia, Vanuatu]. In the interest of testing whether there is evidence for climate forcing of cultural change in this region, dates are presented for the archaeologically conspicuous termination of early‐period settlement in these island groups which show that it ended in each around 2570 cal yr bp. From the contemporaneity of this, it is argued that sea‐level fall was the principal driver of this cultural transformation, forcing coastal peoples who had previously depended (largely) on foraging from nearshore‐marine ecosystems to reconfigure their subsistence economy, something that invariably involved moving their settlements to places where horticulture and agriculture could be practiced more successfully. This research provides an example of where insights into causation of cultural change can be gleaned from comparing precise chronologies of human occupation to equally precise palaeoclimate chronologies. [ABSTRACT FROM AUTHOR]

Aim Broad-scale diversity gradients are strongly correlated with climate. This correlation may reflect direct control of richness by contemporaneous climate. Alternatively, factors that were collinear with contemporaneous climate may have affected richness (e.g. temperature during the Last Glacial Maximum, LGM). We tested the hypothesis that contemporaneous climate directly controls broad-scale patterns of richness. If climate directly (i.e. causally) controls richness, then when climate changes, richness should vary with climate through time in the same way that richness varies with climate through space. We also tested hypotheses that suggest that patterns of richness are primarily determined by processes associated with climate at the LGM. Location North America, north of Mexico. Methods We used temperature changes over the last 14,000 years in North America as a 'natural experiment'. We compared a proxy of woody plant family richness (based on fossilized pollen) with two reconstructions of the spatio-temporal variation of temperature across North America at 1000-year intervals. Results We found that the spatial and temporal regional variations in richness of woody plant families, observed at 1000-year intervals and expressed as a function of temperature, remained quite congruent during the changing climate since the end of the Pleistocene (the last c. 11,000 years). Between 14,000 and 11,000 yr bp, lags occurred during cooling periods, when richness remained anomalously high; however, richness was not anomalously low during the rapid warming in the late Pleistocene. Richness was significantly less strongly related to climate change since the LGM. Main conclusions Our results provide a strong test of the hypothesis that, in ecological time, contemporaneous climate controls most of the broad-scale variation in patterns of richness. Richness, independently of the responses of individual species, is likely to track current climate change, except possibly when temperature changes are very rapid. [ABSTRACT FROM AUTHOR]

Cordimus, a new genus of cricetid rodent, is described from Neogene deposits on the islands of Curaçao and Bonaire, Dutch Antilles. The genus is characterized by strongly cuspidate molars, the presence of mesolophs in most upper molars and the absence of mesolophids in lower molars. Similarities with the early cricetid Copemys from the Miocene of North America coupled with apparent derived characters shared with the subfamily Sigmodontinae suggest that Cordimus may be close to the root of the sigmodontine lineage, a possibility that remains to be tested through explicit phylogenetic analysis. Three species are recognized on the basis of size and details of molar morphology. Cordimus hooijeri sp. nov. is described from Bonaire on the basis of Holocene owl pellet material that consists of dentaries and postcranial material only. This species is presumed to be extinct, but focused surveys are needed to confirm this hypothesis. Cordimus debuisonjei sp. nov. and Cordimus raton sp. nov. are described from deposits on Tafelberg Santa Barbara in Curaçao. Although the age of these deposits is not known, they are most likely of late Pliocene or early Pleistocene age. Both are represented by numerous isolated molars and some osteological material. [ABSTRACT FROM AUTHOR]