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A high‐resolution palynological record from northwest Belgium is presented. The record encompasses the second part of the Younger Dryas and the Early Holocene. The basal part of the pollen record reflects a relatively open landscape, characteristic for the Younger Dryas. The transition to the Holocene is marked by an expansion of birch woodland, followed by an expansion of pine in the Late Preboreal (~11.2–10.7 cal. ka BP). Subsequently, the record shows an expansion of mixed deciduous forest with hazel, elm and oak, characteristic for the Boreal (~10.7–8.6 cal. ka BP). Early Holocene forest expansion was interrupted by a number of short‐lived fluctuations, presumably driven by climatic changes. The most distinct event is the Rammelbeek phase (~11.4–11.2 cal. ka BP), during which forest development was temporarily interrupted in favour of grasses, while wildfires increased. Following this climatic event, hunter‐gatherers returned to the area after a period of almost 1.5 millennia of low population density. They most likely were attracted by the increased temperatures and abundance of edible plants present in the birch‐pine forests and on the banks of the river Kale/Durme. A temporary expansion of pine during the Boreal (~10.7–8.6 cal. ka BP) may correspond with the 9.3‐ka event. At this time, superimposed on a trend of gradual infilling of the channel, a temporary change to drier conditions is observed. The significant drop in the number of prehistoric sites in the Moervaart region clearly cannot be attributed to this short‐term climatic event alone but was most likely caused by a combination of environmental changes, such as the decreasing availability of hazelnuts as well as freshwater and edible (semi‐)aquatic plants as the Kale/Durme river gradually turned dry. The study provides insight into, partly climate‐driven, Early Holocene environmental changes and the effect this may have had on human occupation. [ABSTRACT FROM AUTHOR]

Antarctica has been proposed as a significant source of the meltwater that entered the oceans during meltwater pulse 1B (MWP1B) approximately 11 500 yr ago. Support for this scenario has been provided by evidence that the deep fjords of coastal Antarctica, which were heavily glaciated at the maximum of glaciation, were deglaciated at this time. Further support for this scenario was provided by the observation that the inter-hemispheric sea-level teleconnection associated with significant Southern Hemisphere deglaciation at this time provided an explanation of the highly non-monotonic relative sea-level histories recorded at sites on the coast of Scotland, a region which had also been heavily glaciated at the last glacial maximum. Furthermore, it has been argued that a significant contribution to MWP1B must have also been delivered to the oceans by the abrupt Northern Hemisphere warming that occurred at the end of the Younger Dryas (YD) cold reversal, which also occurred approximately 11 500 yr ago. Our focus in this paper is to distinguish between these two possible primary sources of MWP1B. The investigation of how local alterations to ice thicknesses are able to explain evidence which has previously been used to argue for an Antarctic dominant MWP1B will lead us to the conclusion that the Laurentide may be primary source of MWP1B. [ABSTRACT FROM AUTHOR]

The paleoenvironmental evolution of the Abrolhos Depression (AD) on the southern Abrolhos Shelf during the global post-Last Glacial Maximum (LGM) transgression is investigated through benthic foraminifera analysis. Downcore sediment samples (core DA03A-5B) collected at a depth of 63 m provide insights into the formation and paleoenvironmental variations of AD over the past 18 kyr BP. The core is divided into four biofacies based on foraminifera assemblages. At the base, the presence of carbonate concretions indicates a karstic surface, marking the initiation of the paleolagoon formation at approximately 13 kyr BP with low density of foraminifera, where species such as Elphidium sp. and Hanzawaia boueana (EH Biofacies) were more abundant. During the Younger Dryas (YD) (12.8–12.5 kyr BP), the AD exhibits two distinct phases: an initially confined lagoon environment with reduced circulation characterized by the dominance of the species Ammonia tepida (At Biofacies), followed by increased circulation characterized by higher density, richness, and diversity of benthic foraminifera. The end of the YD is identified by a significant biofacies change, indicative of a shallow marine environment, where the dominant species were A. tepida and Elphidium excavatum (AE Biofacies), supported by sedimentological and geochemical proxies. This paleoenvironmental shift is associated with Meltwater Pulse (MWP) -1B, suggesting a connection to a shallow marine environment. As sea levels continue to rise, the AD transitions into an open marine setting. However, around 8 kyr BP, a change occurs with the absence of A. tepida and the occurrence of planktonic and other benthic foraminifera typical of the outer shelf, indicating depths greater than 50 m (HQ Biofacies). The findings highlight the complex interplay between climate fluctuations, sea-level changes, and the formation of coastal environments during the LGM transgression. This study contributes to our understanding of paleoenvironmental dynamics, adding valuable insights to the evolutionary history of AD. The results emphasize the importance of integrating benthic foraminifera analysis, radiocarbon dating, and geochemical proxies to reconstruct paleoenvironments accurately. Overall, this research enhances our knowledge of global continental shelf evolution during the post-LGM transgression and provides valuable information for future paleoenvironmental studies. [ABSTRACT FROM AUTHOR]

Eurasian permafrost soils contain large amounts of organic carbon (OC) and mercury (Hg), sequestered by vegetation during past and present interglacial periods. Lake sediment archives may help understand past OC and Hg dynamics and how they interact with climate‐related variables. We investigated Hg accumulation, OC dynamics, and Hg and OC stable isotopes in a 14,000‐year sediment record from Lake Malaya Chabyda (Central Yakutia, Russia). Sediment Hg was correlated to OC (p value < 0.01), with lower OC and Hg accumulation rates (OCAR, HgAR) during the cold Younger Dryas (YD, 12,900–11,700 cal BP), when the lake level was low. Elevated sediment Δ200Hg (0.05‰ ± 0.11‰), representing dominant HgII deposition, and low δ13C, indicates low lake primary productivity during the YD. During the early Holocene, Δ200Hg and Δ199Hg decreased, while δ13C, δ202Hg, OCAR, and HgAR increased, suggesting enhanced algal primary productivity in deeper, more turbid waters. From 4,100 cal BP to present, Hg/OC ratios and HgAR increased at constant OCAR, indicating an additional Hg source to the lake. Analysis of Hg isotopes suggests direct Hg0 uptake into lake waters, potentially driven by primary production and efficient Hg burial. Our observations suggest that the gradual climate warming since the Last Glacial Termination and into the early Holocene led to enhanced OC and Hg burial in northern lakes and watersheds. Late Holocene enhanced Hg burial, but not OC, is possibly related to a renewed increase in lake primary productivity. Continued global warming may lead to further Hg sequestration in northern aquatic ecosystems. Plain Language Summary: The frozen soils in Eurasia contain a lot of organic carbon (OC) and mercury. As the climate gets warmer and the soil thaws, carbon and mercury might be released into the air and water. To understand these dynamics, a study was conducted on sediment archives from a lake in Russia that go back 14,000 years. The study found that the amount of mercury in the sediment was connected to OC. During a very cold period called the Younger Dryas, when the lake level was low, both mercury and carbon in the sediment were low. The lake had poor conditions for life during this time. As the climate warmed, carbon and mercury inputs increased in the sediment, especially during the early Holocene period. This suggests that more aquatic algae and plant growth traps carbon and mercury. From 4,100 years ago until now, the ratio of mercury to OC kept increasing, indicating more mercury being deposited into the lake. The type of mercury in the sediment changed, showing that more of it was directly taken up by the water. This happened because of more plant growth and better trapping of mercury in the sediment. Key Points: Permafrost soils in Eurasia hold significant amounts of organic carbon (OC) and mercury from past and present periodsClimate warming and permafrost thawing may release OC and mercury to rivers, lakes and the atmosphereLake sediment records reveal that gradual climate warming has led to increased OC and mercury burial in northern lakes, with recent pre‐industrial enhanced Hg burial possibly linked to increased lake productivity [ABSTRACT FROM AUTHOR]

High-resolution sedimentological and geochronological investigations of paleochannel systems in the Ried Central d'Alsace (northeastern France) allow for the reconstruction of the late glacial and Holocene fluvial evolution of this section of the Upper Rhine alluvial plain. During the Oldest Dryas, the landscape featured a dominant braided Rhine system and, to a lesser extent, a braided Fecht system. The shift to the Bølling-Allerød saw a narrowing of the Rhine's active channel belt, the development of a complex channel pattern, and the genesis of the Ill River. The river channel patterns remained unchanged during the Younger Dryas. In the Early Holocene, the Rhine's active belt narrowed further, and the Rhine and Ill Rivers developed braided-anastomosing and anastomosing channel patterns, respectively. Throughout the Holocene, both rivers maintained their channel patterns while migrating east and west across the alluvial plain, respectively. In the late glacial, fluvial dynamics in this section of the Upper Rhine plain were primarily influenced by climate-related environmental and hydrogeomorphological changes. Conversely, during the Holocene, the evolution of the fluvial hydrosystems was driven by a complex interaction of climatic and non-climatic factors, including human activity at the catchment scale, alluvial plain architecture, and local neotectonics. [ABSTRACT FROM AUTHOR]

In this article, we propose an approach to reconstruct the timing of human activity at Points Cave, an Upper Paleolithic rock art site located in the middle of the Ardèche River Gorge (Rhône valley, France), based on the dating and characterisation of a stalagmite containing soot. Points Cave ('Grotte aux Points' in French), also called the 'little sister of Chauvet Cave', is famous for its parietal art including a series of dots made of palm prints. A large number of stalagmites formed in the cave during the last 500 ka. However, quarrying of the cave floors during historic times led to the partial destruction of the sedimentary deposits, and many of the stalagmites were found lying on the floor. In particular, one of them (STM‐18‐04) showed the presence of at least four dark layers in cross‐section, which appeared as possible remnants of fire‐related activities in the cave. Despite being present at the same site, no other specific link between STM‐18‐04 and the rock art has been documented. This stalagmite, however, allows us to identify phases of human presence, located at the cave entrance. To do so, we performed a series of analyses to determine its period of growth and the nature of the dark layers that it contains. Scanning electron microscopy and Raman microspectroscopy confirmed that the dark layers include soot, and uranium‐series dating indicated that the fire events occurred, respectively, around 14,200–14,100 and 12,500 years ago, in agreement with the radiocarbon ages of charcoal specimens recovered from the excavation areas nearby. We thus highlighted phases of human activity at the site during the Upper Magdalenian and/or beginning of the Epipaleolithic. By comparing our results with the regional paleoclimatic record, the soot layers trapped in the stalagmite appear to be synchronous with two cold periods, likely the Older Dryas and the Younger Dryas. [ABSTRACT FROM AUTHOR]

Abstract Currently in NW Europe little is known about the human response to the extensive cold reversal at the end of the Pleistocene, the Younger Dryas (ca. 12,850 till ca. 11,650 cal BP), mainly due to the poor chronological resolution of the archaeological sites belonging to the Ahrensburgian Culture. Here we present a series of 33 radiocarbon dates performed on the seminal cave site of Remouchamps, situated in the Belgian Meuse basin. Combined with a revision of the available radiocarbon evidence along the southern North Sea basin (Belgium, southern Netherlands, western Germany), it is suggested that the first half of the Younger Dryas, characterized as extremely cold and wet, faced a significant population reduction. Repopulation started around the middle of the Younger Dryas, from ca. 12,200 cal BP onward, probably in response to a slight climatic improvement leading to somewhat warmer summers. This might be considered a prelude to the subsequent population boost of the Early Holocene (Mesolithic).

Global warming during the Last Glacial Termination was interrupted by millennial-scale cool intervals such as the Younger Dryas and the Antarctic Cold Reversal (ACR). Although these events are well characterized at high latitudes, their impacts at low latitudes are less well known. We present high-resolution temperature and hydroclimate records from the tropical Andes spanning the past ~16,800 y using organic geochemical proxies applied to a sediment core from Laguna Llaviucu, Ecuador. Our hydroclimate record aligns with records from the western Amazon and eastern and central Andes and indicates a dominant long-term influence of changing austral summer insolation on the intensity of the South American Summer Monsoon. Our temperature record indicates a ~4 °C warming during the glacial termination, stable temperatures in the early to mid-Holocene, and slight, gradual warming since ~6,000 y ago. Importantly, we observe a ~1.5 °C cold reversal coincident with the ACR. These data document a temperature change pattern during the deglaciation in the tropical Andes that resembles temperatures at high southern latitudes, which are thought to be controlled by radiative forcing from atmospheric greenhouse gases and changes in ocean heat transport by the Atlantic meridional overturning circulation. [ABSTRACT FROM AUTHOR]

Currently in NW Europe little is known about the human response to the extensive cold reversal at the end of the Pleistocene, the Younger Dryas (ca. 12,850 till ca. 11,650 cal BP), mainly due to the poor chronological resolution of the archaeological sites belonging to the Ahrensburgian Culture. Here we present a series of 33 radiocarbon dates performed on the seminal cave site of Remouchamps, situated in the Belgian Meuse basin. Combined with a revision of the available radiocarbon evidence along the southern North Sea basin (Belgium, southern Netherlands, western Germany), it is suggested that the first half of the Younger Dryas, characterized as extremely cold and wet, faced a significant population reduction. Repopulation started around the middle of the Younger Dryas, from ca. 12,200 cal BP onward, probably in response to a slight climatic improvement leading to somewhat warmer summers. This might be considered a prelude to the subsequent population boost of the Early Holocene (Mesolithic). [ABSTRACT FROM AUTHOR]

A comprehensive paleoecological study of permafrost peat deposits from three locations in the middle reaches of the Yuribei River in the subzone of modern subarctic shrub tundra of the Yamal Peninsula has been performed. Based on the results of palynological and carpological methods and of radiocarbon dating, the changes in regional and local vegetation and climatic conditions of Central Yamal in the Late Glacial and the Postglacial periods are reconstructed. It is found that shrubby tundra with Betula nana was widespread in this area under climatic conditions close to modern ones in the Younger Dryas about 12.6–11.7 cal ka BP. The penetration of tree species (Betula sect. Betula, Picea obovata, and Larix sibirica) and accompanying boreal herbaceous plants began due to more favorable climatic conditions during the Early Holocene warming about 10.2–9.7 cal ka BP. The most favorable conditions for the growth of birch tree, larch, and spruce existed in Central Yamal in the Early and the Middle Holocene in the range of 10.2–4.4 cal ka BP. At that time, open woodlands or even closed forests were common, and the climate was much warmer than the modern one. Forest vegetation degraded and open landscapes with tundra communities were formed at the end of the Middle Holocene (4.5–4.4 cal ka BP). The climatic conditions became similar to modern ones. [ABSTRACT FROM AUTHOR]

The highest cycle of post‐Lake Bonneville Great Salt Lake in the Bonneville basin, Utah, USA, was thought for many years to have formed the 'Gilbert shoreline' (quotation marks indicate lack of scientific support). Mapping of the 'shoreline' is not reproducible and the concept has multiple problems, including that the 'shoreline' cannot be correlated with the well‐documented major rise of Great Salt Lake during the terminal Pleistocene. To avoid confusion, we propose abandoning the name Gilbert, which previously had been applied informally to both the hypothetical shoreline and lake cycle, and instead we use the name Currey cycle for the lake rise. During the Younger Dryas Currey cycle, Great Salt Lake became fresh to brackish about 12 700 cal a bp, and rose roughly 15 m higher than the modern lake. The end of the Currey cycle marked the beginning of extensive human occupation of the Old River Bed inland delta. [ABSTRACT FROM AUTHOR]

This article provides information about Obersee, a lake in Kißlegg, Germany. It describes the size and depth of the lake, as well as the surrounding landscape. The article also discusses the sediment core of the lake, which contains ancient sediments dating back to 6500 BC. The document includes a pollen record based on samples from the Obersee region, showing changes in vegetation and human impact over time. The authors acknowledge the assistance of individuals who helped with the research. No conflicts of interest were reported. [Extracted from the article]

We analysed the BSi (Biogenic Silica) contents of the marine core SK-313/1 from the southeastern Arabian Sea which is dated up to ~14.5 kyr BP. Results show that the maximum and minimum BSi contents are 2.5 and 0.5%, respectively. This is because of the low supply of silica skeleton and the high dissolution and dilution of terrigenous materials. The BSi mass accumulation rates indicate a trend of reduced paleoproductivity during the late Glacial period and increase during the Holocene, with global climatic shifts. Insolation changes at low latitudes, which regulate temperatures, may affect nutrient availability and, consequently productivity variations on a glacial–interglacial timescale. Notably, millennial events like the Younger Dryas (YD) periods, exhibited lower paleoproductivity, in contrast to the Bølling/Allerød (B-A) period and the middle Holocene, which displayed elevated levels of paleoproductivity. These millennial-scale fluctuations in siliceous productivity may be due to the changes in nutrient supply caused by the Indian summer monsoon (ISM). The period of increased paleoproductivity could be influenced by intensified chemical weathering and a boosted nutrient supply, which are consequences of the strengthened ISM during periods of relatively higher temperature. [ABSTRACT FROM AUTHOR]

The dynamics of the last Fennoscandian Ice Sheet (FIS) are relatively well constrained in the Nordic countries. Ice‐sheet dynamics in NW Russia, however, are comparatively less well understood owing to the scale and resolution of existing studies. New large‐scale glacial geomorphological datasets from NW Russia based on high‐resolution remotely sensed imagery allow for an independent reassessment of the extent and dynamics of the FIS during the Younger Dryas and Early Holocene (c. 12.9–10 ka) in NW Russia. The reconstruction provides a more detailed link between geomorphological expressions of palaeoglaciation than previous proposals. Rather than a continuous Younger Dryas ice marginal zone (IMZ) stretching from Finland to northern Norway, the geomorphological signature of NW Russia reveals 14 IMZs that document discrete stationary ice‐margin positions (possibly standstill and/or readvance events) during the overall retreat. The relative age sequence of the IMZs, supported by an updated numerical age database, suggests that they formed time‐transgressively during the Younger Dryas and Early Holocene rather than contemporaneously. Moreover, specific landform assemblages reveal contrasting glacial landsystems in NW Russia: (i) a northern subpolar glacial landsystem; and (ii) a southern temperate glacial landsystem. The model presented herein provides robust empirical constraints for testing and validating numerical ice‐sheet models and understanding ice‐sheet responses to rapid climate change. [ABSTRACT FROM AUTHOR]

Vegetation dynamics data since the Last Glacial Maximum (LGM) are essential for our understanding of ecosystem shifts and vegetation responses to climate change. Here, we present a pollen record covering the last 25,000 years from Lake Fuxian in central Yunnan, southwest China. Our study shows seven stages of vegetation dynamics since the LGM: The early LGM (stage 7 of 25,000–21,200 cal. a BP) witnessed less dense regional vegetation dominated by pine forests, evergreen broadleaved forests (EBFs), deciduous broadleaved forests (DBFs), montane hemlock forests, and fir/spruce forests. The late LGM (stage 6 of 21,200–17,500 cal. a BP) saw an expansion of grasslands, wetlands, and montane fir/spruce forests as well as a shrinkage of EBFs and DBFs. During the last deglaciation (stage 5 of 17,500–13,300 cal. a BP), dense regional vegetation was dominated by EBFs as well as deciduous oak and alder forests. The densest regional vegetation occurred in stage 4 of 13,300–11,200 cal. a BP, roughly equal to the Younger Dryas Chron, when pine forests, DBFs, EBFs, grasslands, and wetlands grew in the Lake Fuxian catchment. During the early to mid-Holocene (stage 3 of 11,200–5000 cal. a BP), dense regional vegetation was dominated by sweetgum forests, in addition to some pine forests and EBFs. After 5000 cal. a BP, the regional vegetation density became lower and lower, and forests became thinner and thinner. Pine forests expanded to their maximum of the entire sequence in stage 2 of 5000–2500 cal. a BP. A big deforestation event occurred in stage 1 (the last 2500 years), when grasslands, wetlands, and cultivated vegetation dominated regional vegetation in the catchment of Lake Fuxian. The regional vegetation since the LGM in the catchment of Lake Fuxian also experienced six major transitions, five centennial shift events, and one big large-scale and long-term deforestation event. These resulted from the responses of regional vegetation to climate changes during the LGM, last deglaciation, and early–mid-Holocene, as well as human influence in the late Holocene. The vegetation density since the LGM has changed with the 25° N summer insolation. [ABSTRACT FROM AUTHOR]

The Younger Dryas stadial was characterised by a rapid shift towards cold-climate conditions in the North Atlantic realm during the last deglaciation. While some climate parameters including atmospheric temperature and glacier extent are widely studied, empirical constraints on permafrost temperature and snow thickness are limited. To address this, we present a regional dataset of cryogenic cave carbonates (CCCs) from three caves in Great Britain that formed at temperatures between - 2 and 0 °C. Our CCC record indicates that these permafrost temperatures persisted for most of the Younger Dryas. By combining ground temperatures with surface temperatures from high-resolution ground-truthed model simulations, we demonstrate that ground temperatures were approximately 6.6 ± 2.3 °C warmer than the mean annual air temperature. Our results suggest that the observed temperature offset between permafrost and the atmosphere can be explained by an average snow thickness between 0.2 and 0.9 m , which persisted for 233 ± 54 d per year. By identifying modern analogues from climate reanalysis data, we demonstrate that the inferred temperature and snow cover characteristics for the British Isles during the Younger Dryas are best explained by extreme temperature seasonality, comparable to continental parts of today's Arctic Archipelago. Such a climate for the British Isles necessitates a winter sea ice margin at approximately 45° N in the North Atlantic Ocean. [ABSTRACT FROM AUTHOR]

The dynamics shaping the El Niño‐Southern Oscillation's (ENSO) response to present and future climate change remain unclear, partly due to limited paleo‐ENSO records spanning past abrupt climate events. Here, we measure Mg/Ca ratios on individual foraminifera to reconstruct east Pacific subsurface temperature variability, a proxy for ENSO variability, across the last 25,000 years, including the millennial‐scale events of the last deglaciation. Combining these data with proxy system model output reveals divergent ENSO responses to Northern Hemisphere stadials: enhanced variability during Heinrich Stadial 1 (H1) and reduced variability during the Younger Dryas (YD), relative to the Holocene. H1 ENSO likely intensified through meltwater‐induced changes to ocean/atmospheric circulation, a response observed in models, but the lack of a similar response during the YD challenges model simulations. We suggest the tropical Pacific mean state during H1 primed ENSO for larger fluctuations under meltwater forcing, whereas the YD mean state likely buffered against it. Plain Language Summary: The El Niño‐Southern Oscillation (ENSO) is one of the planet's largest and most influential recurring climate patterns. The fluctuation between warm (El Niño) and cold events (La Niña) every several years has a substantial impact on global weather patterns that carry important socioeconomic consequences. How the frequency and severity of ENSO events may change in response to present and future climate change is largely uncertain, although lessons from past abrupt climate events can help inform our projections of future ENSO. To that end, we analyzed the chemical composition of small, individual zooplankton shells buried in marine sediments to reconstruct "snapshots" of subsurface temperature variability in the eastern Pacific, a feature closely linked to ENSO, over the last 25,000 years. During this time, two abrupt climate events induced by melting glacial ice ("Heinrich Stadial 1" and the "Younger Dryas") were characterized by different ENSO responses (stronger and weaker, respectively). We suggest that the average climate conditions in the tropical Pacific (temperature, wind strength, etc.) played an important role by either priming the ENSO system for disruption by meltwater (Heinrich Stadial 1) or buffering against it (Younger Dryas). Key Points: Single‐shell foraminiferal trace element ratios reveal a deglacial history of El Niño‐Southern Oscillation's (ENSO) variability from the eastern equatorial PacificMeltwater‐induced changes to ocean and atmospheric circulation likely amplified ENSO during Heinrich Stadial 1A similar amplification during the Younger Dryas is not observed, suggesting mean state may mediate millennial‐scale ENSO variability [ABSTRACT FROM AUTHOR]

The integration of high-resolution seismic profiles, core data and radiocarbon plus U-Th datings, allows to document the late Quaternary succession of the Trieste Gulf, which represents the easternmost part of the northern Adriatic Sea. This succession consists of an alternation of shallow-marine and continental deposits organized to compose four transgressive-regressive sequences down to ca. 90 m below present sea level. The sequences terminate landwards against a stepped surface bounding the Eocene Trieste Flysch and produced by alternating episodes of wave erosion during transgressions and subaerial exposure during stages of relative sea-level fall and lowstand. Two shallow-marine wedges, in addition to the Holocene one, have been recognized; they are associated with the Marine Isotopic Stage (MIS) 5.5 (Tyrrhenian) and probably at least one of the peaks of MIS 7. The recognized shallow-marine wedges typically prograde just seaward of a buried wave-cut platform lying in front of a receding paleo-coastal cliff. A previously unrecognized stratigraphic hiatus of ca. 25 ka duration, containing the whole Last Glacial Maximum (LGM) phase, was found at the top of palustrine deposits that accumulated on the MIS 5.5 marine sediments until ca. 40 cal ka B.P. and a post-LGM peat bed accumulated during the Younger Dryas stadial. The beginning of the Holocene was characterized by marked fluvial aggradation preceding the marine transgression at ca. 11-10 cal ka B.P. This new evidence is invaluable for better understanding late Quaternary sedimentary and erosional episodes that characterized the easternmost part of the norther Adriatic Sea, in the frame of the well-known glacio-eustatic sea-level changes. [ABSTRACT FROM AUTHOR]

A detailed record of sea level changes and climate oscillations in the Gulf of Saros during the late Pleistocene to the Holocene is provided by high-resolution seismic reflection profiles and analysis of a sediment core. The seismic stratigraphy reveals the formation of four main depositional units bounded by prominent reflection surfaces, reflecting high sea level variations. The Last Glacial Maximum period in the gulf is associated with the lowstand sea level, forming the deepest marine terrace at −148 m. The increasing sea level due to post-glacial warming was accompanied by the deposition of transgressive units characterized by coastal onlaps together with local channel-fills. This transgressive phase was modulated by three brief still-stands sea levels at 17 cal ka BP, 14.6 cal ka BP and 13.6 cal ka BP, producing the younger marine terraces in the gulf at −135 m, −112 m and −90 m, respectively. A comparison of their depths with the global sea level curve reveals elevation differences with decreasing subsidence rates from the older to younger ages, implying tectonic subsidence along the gulf floor. The close correlation of multi-proxy data from core SAG-22 in the gulf with the northern Aegean and Anatolia data strongly indicates that the timings of the past climate events generally agree with the global and regional climate patterns. The warm climate around the gulf during the late phase of Bølling/Allerød (13.3–12.6 cal ka BP) is represented by high marine biological productivity and improved ventilation in the deeper water due to subsequent transgression. Permafrost formation in the catchment area during the following cold and dry Younger Dryas period (12.6–11.7 cal ka BP) resulted in reduced soil erosion and sediment input to the gulf. Noticeable warming during the Early Holocene between 11.2 cal ka BP and 9.4 cal ka BP is recorded by the multi-proxy data of the core when the enhanced marine biological productivity occurred above the poorly oxygenated deep water column. The climatic deterioration to a cooler and drier phase during the Early to Middle Holocene transition (9.4–7.8 cal ka BP) resulted in intense physical weathering and erosion, causing the highest sedimentation in the gulf. The later period of the Holocene is associated with the formation of two discrete sapropels at 7.8 cal ka BP and 5.4 cal ka BP that were accompanied by warm and wet climates around the gulf. [ABSTRACT FROM AUTHOR]

This research explored the origin and paleoenvironmental significance of sediments from the Cosmonaut Sea, Antarctica, focusing on the period since the Last Glacial Maximum (LGM, 26,000 cal a BP). Sediment samples from core ANT37-C5/6-07 were subjected to AMS14C dating, clay-mineral assemblage analysis, grain size evaluation, and geochemical testing. Results indicated illite as the dominant clay mineral (average 46%), followed by kaolinite (22%) and smectite (21%), with chlorite (11%) being the least abundant. Comparison with previous studies suggested that these sediments are largely derived from weathered material from Prydz Bay and Enderby Land coastal regions. The study of mineral ratios, geochemical elements, and sediment grain size, alongside δ18O values from the East Antarctica EDML ice core, revealed that the ice sheet in the study area retreated around 18600 cal a BP, melted more markedly during 16800-15000 cal a BP, tended to expand during 14800-13500 cal a BP, and then the ice sheet remained in a state of retreat until it expanded again around 5000 cal a BP. It is largely synchronous with the phased changes in the Antarctic climate since the LGM (26ka) of the Cosmonaut Sea. Notably, the sediment record aligns with major paleoclimatic events, including Heinrich Stadial 1 and the Younger Dryas in the northern hemisphere and the Antarctic cold reversal, reflecting a climatic ‘seesaw’ effect. These findings suggest that the sedimentary record in the Cosmonaut Sea is a sensitive indicator of climatic conditions, highlighting a history of glacial movements and revealing East Antarctica’s climatic fluctuations. Additionally, the research indicates that the regional ice sheet is more sensitive to climatic changes than previously believed, underscoring its instability. [ABSTRACT FROM AUTHOR]

Proxy-based paleoclimate reconstructions in the central Zagros region suggest the occurrence of several climatic events during the Last Glacial Maximum (LGM) to Holocene. The central Zagros region is situated in a unique transition zone between mid-latitude temperate climate in the north and sub-tropical arid climate in the south and was affected in different climatic periods by the strengthening and weakening of the Indian monsoons, the inter tropical convergence belt, the westerlies and the low-pressure systems of the Mediterranean and the Atlantic Ocean. Our results suggest that a transition occurred from dry and dusty conditions during the LGM to a relatively wetter period with higher carbon accumulation rates in the Early Holocene (11600 cal yr BP). Between 30000 and 19000 cal yr BP, cold and dry climatic conditions with the dominance of Amaranthaceae and semi-desert steppe prevailed in the region. High values of magnetic susceptibility, decrease in organic matter, and increase in allogenic elements indicate the presence of cold and dry climate in the region during the LGM. The Holocene was characterized by relatively less dry and dusty conditions, which is consistent with orbital changes in insolation that affected much of the northern hemisphere. Numerous episodes of high aeolian input spanning a few decades to millennia are prevalent during the Holocene. Dry events identified in the area occurred at 10200, 9200, 8200, 5200, 4200, 3200, 2200, and 1600 cal yr BP. Also Younger Dryas, occurred in the region 12300-11600 years ago, and it was cold and dry period with a decrease amount of pollen and increase in dust. [ABSTRACT FROM AUTHOR]

Only a few palaeo-records extend beyond the Holocene in Yakutia, eastern Siberia, since most of the lakes in the region are of Holocene thermokarst origin. Thus, we have a poor understanding of the long-term interactions between terrestrial and aquatic ecosystems and their response to climate change. The Lake Khamra region in southwestern Yakutia is of particular interest because it is in the transition zones from discontinuous to sporadic permafrost and from summergreen to evergreen boreal forests. Our multiproxy study of Lake Khamra sediments reaching back to the Last Glacial Maximum 21 cal ka BP, includes analyses of organic carbon, nitrogen, XRF-derived elements, sedimentary ancient DNA amplicon sequencing of aquatic and terrestrial plants and diatoms, as well as classical counting of pollen and non-pollen palynomorphs (NPP). The palaeogenetic approach revealed 45 diatom, 191 terrestrial plant, and 65 aquatic macrophyte taxa. Pollen analyses identified 34 pollen taxa and 28 NPP taxa. The inferred terrestrial ecosystem of the Last Glacial comprises tundra vegetation dominated by forbs and grasses, likely inhabited by megaherbivores. By 18.4 cal ka BP a lake had developed with a high abundance of macrophytes and dominant fragilarioid diatoms, while shrubs expanded around the lake. In the Bolling-Allerod at 14.7 cal ka BP both the terrestrial and aquatic systems reflect climate amelioration, alongside lake water-level rise and woodland establishment, which was curbed by the Younger Dryas cooling. In the Early Holocene warmer and wetter climate led to taiga development and lake waterlevel rise, reflected by diatom composition turnover from only epiphytic to planktonic diatoms. In the Mid-Holocene the lake water level decreased at ca. 8.2 cal ka BP and increased again at ca. 6.5 cal ka BP. At the same time mixed evergreen-summergreen forest expanded. In the Late Holocene, at ca. 4 cal ka BP, vegetation cover similar to modern conditions established. This study reveals the long-term shifts in aquatic and terrestrial ecosystems and a comprehensive understanding of lake development and catchment history of the Lake Khamra region. [ABSTRACT FROM AUTHOR]

The high rate of biological productivity in the North Atlantic is stimulated by the advective supply of nutrients into the region via the Gulf Stream (nutrient stream). It has been proposed that the projected future decline in the Atlantic Meridional Overturning Circulation (AMOC) will cause a reduction in nutrient supply and resulting productivity. In this work, we examine how the nutrient stream changed over the Younger Dryas climate reversal that marked the transition out of the last ice age. Gulf Stream nutrient content decreased, and oxygen content increased at the Florida Straits during this time of weakened AMOC. The decreased nutrient stream was accompanied by a reduction in biological productivity at higher latitudes in the North Atlantic, which supports the link postulated in theoretical and modeling studies. [ABSTRACT FROM AUTHOR]

Mass movements and delta collapses are significant sources of tsunamis in lacustrine environments, impacting human societies enormously. Paleotsunamis studies play an essential role in understanding historical events and their consequences, along with their return periods. This study investigates a paleotsunami induced by a subaqueous mass movement during the Younger Dryas to Early Holocene transition, ca. 11,700 years ago in Lake Aiguebelette (NW Alps, France). Utilizing high‐resolution seismic and bathymetric surveys associated with sedimentological, geochemical, and magnetic analyses, we uncovered a paleotsunami triggered by a seismically induced mass transport deposit. Numerical simulations of mass movement have been conducted using a visco‐plastic Herschel‐Bulkley rheological model and corresponding tsunami wave modeled with dispersive and nondispersive models. Our findings reveal for the first time that dispersive effects may be negligible for subaqueous landslides in a relatively small lake. This research reconstructs a previously unreported paleotsunami event and enhances our understanding of tsunami dynamics in lacustrine environments. Plain Language Summary: This study explores an ancient landslide and its ability to potentially generate a tsunami. This event took place in Lake Aiguebelette, located in the NW Alps, France. By applying advanced underwater mapping techniques and computer modeling, we were able to reconstruct the origins and impact of this underwater prehistoric landslide. Our work revealed that this underwater landslide may have triggered a significant tsunami wave. These findings are crucial as they provide new insights into the dynamics of such geological events in lake environments, enhancing our understanding of their potential impacts and aiding in the preparation for future similar hazards. Key Points: Uncovered a 11,700‐year‐old subaqueous landslide‐induced paleotsunami in Lake Aiguebelette (NW Alps, France)Numerical model is constrained to reproduce the available geological dataFound dispersion effects to be of minimal importance in the modeling of this historical tsunami event [ABSTRACT FROM AUTHOR]

The high-resolution pollen record retrieved from dated sediments of the Khanka Depression has made it possible for the first time to reconstruct evolution of vegetation in the south of the Russian Far East that occurred during one of the coldest phase of MIS 2 – the Younger Dryas. The results of the spore-pollen analysis have shown that worsening of climate conditions between 18 200 and 15 500 cal yr BP that occurred after the first, slight warming during MIS 2, caused boreal flora plants, dominating in the south of Russian Far East, to spread again in the drier and colder climate comparable to the Gydan Stage of the Sartan Glaciation. Their distribution areas in the cold climate that differed significantly from the modern ones again started to shift to the south due to increasing cooling. The spruce and small-leaved forests, sparse larch and dwarf birch, alder and dwarf pine forests, and also sphagnum bogs dominated in the ecosystems of the region. [ABSTRACT FROM AUTHOR]

The main objective of this study is to investigate the spatial–temporal variability and climate forcing influence during the last 21,000 years of the South American Monsoon System (SAMS) and its components. TraCE-21k simulations, including Full and Single Forcings experiments, were employed. The identification of spatial variability patterns associated with the core of the monsoon region (SAMS) and the South Atlantic Convergence Zone (SACZ), the main components of SAMS during the austral summer, is based on multivariate EOF analysis (precipitation, humidity, zonal and meridional wind). This analysis produces two main modes: the first one is the South American Large Scale Monsoon Index (LISAM), representing the primary oscillation mode for SAMS, and the second one is the SACZ mode, representing the SACZ oceanic portion variability. The TraCE-21k EOF modes demonstrated the ability to represent the SAMS and SACZ patterns when compared to the 20th Century reanalysis. LISAM time series proved to be an important tool for identifying monsoon precipitation variability, consistent with the regime changes recorded in climatic proxies. The freshwater pulses forcing in TraCE-21k are a determining factor for the observed changes in the precipitation regime, mainly during the periods between Heinrich Stadial 1 and the Younger Dryas. The results indicate that the observed and modeled SACZ southward shift in the Late Holocene is primarily modulated by insolation changes, with a stronger correlation observed since the Mid-Holocene period. Through wavelet analysis, it was noted that energy was transferred from low frequencies to high frequencies during the Bølling–Allerød period for the full forcing and freshwater pulse experiments in the Northern Hemisphere. The SAMS multidecadal variability increased from the early Holocene with direct influences of orbital forcing and ice cover. [ABSTRACT FROM AUTHOR]

The response of aquatic ecosystems in the Sierra Nevada (California, USA) to late Quaternary hydroclimate changes remains mostly unknown. Mono Lake, a large endorheic lake just east of the Sierra Nevada, contains an expanded archive of laminated sediments that can be used to examine the response of benthos to environmental changes. Fossil ostracodes from a radiocarbon‐dated core were used to examine paleoecologic changes from ~16.6 to 4.3k cal a bp. Seven species were identified, with the co‐occurrence of Limnocythere ceriotuberosa and Limnocythere staplini indicating a large SO42−‐rich lake in the Pleistocene. The Younger Dryas was complex, with Fabaeformiscandona caudata reflecting a cold and deep lake ~13.0–12.2k cal a bp, followed by an interval of extensive littoral habitat from ~12.2–11.6k cal a bp. Ostracode diversity, valves g–1 and the ratio of adult:juvenile valves declined after ~10.7k cal a bp due to regression, altered hydrochemistry and seasonal anoxia. Strong seasonality during the Early Holocene is suggested by the presence of reworked ostracodes and macrocharcoal, delivered to Mono Lake by erosion of ancient lake beds in the basin. A depauperate ostracode fauna in the Middle Holocene suggests a strong sensitivity to drought in this ecosystem, which has implications for biodiversity in the future. [ABSTRACT FROM AUTHOR]

Many have tagged the Younger Dryas Impact Hypothesis (YDIH), a supposition, lacking convincing evidence in support. The core of criticism lies squarely on uniformitarianism, that is, uniform processes moving uniformly with no room for catastrophic events, specifically cosmic catastrophic forces. Beyond philosophically based aversion to the YDIH, specific criticism comes from megafauna and archaeologic corners, related to the near coeval disappearance of specific Late Pleistocene species on the one hand, and relation to disruption and temporary disappearance of the Clovis people et al. on the other. The Younger Dryas geologic paradigm, originally in place with meltwater release into the Atlantic in tow, attention slowly drifted to explanation of an innocuous looking, thin (~1–3 cm), black sediment bed found in lacustrine and fluvial deposits of the American southwest, and other intercontinental places. Thus, with thin dark beds of Gubbio in mind, the quest to explain black mat (BM) beds took on a cosmic aspect, one with growing, supporting evidence on several continents. The impossible hypothesis, now the probable explanation of the Younger Dryas climatic reversal, is at center stage, set at 12.8 ka, with a burgeoning corpus of evidence its cornerstone. [ABSTRACT FROM AUTHOR]

Surface exposure–age dating was applied to rock surfaces associated with ice‐marginal moraines at elevations of ~1520–1780 m a.s.l. on the slopes of Galdhøpiggen and Glittertinden, the two highest mountains in Scandinavia located in the Jotunheimen mountains of central southern Norway. This is important for understanding the pattern and timing of wastage of the Scandinavian Ice Sheet at the Younger Dryas–Holocene transition. Cosmogenic exposure dating (here 10Be dating) of boulders from the moraine ridges yielded overall mean ages (corrected for glacio‐isostatic uplift, surface erosion and snow shielding) of ~11.6 ka from Galdhøpiggen and ~11.2 ka from Glittertinden. Similar 10Be ages were also obtained from additionally collected proximal and distal erratic boulders and bedrock samples. These enabled age calibration of Schmidt‐hammer R‐values and independent Schmidt‐hammer exposure‐age dating (SHD) of the moraine ridges, which yielded comparable mean SHD ages of ~10.8 and ~10.6 ka from the Galdhøpiggen and Glittertinden sites, respectively. Taking account of the age resolution and other limitations of both dating techniques, the results suggest that the two sets of moraines have approximately the same age but that neither technique can distinguish unambiguously between moraine formation in the late Younger Dryas or Early Holocene. Together with features of moraine‐ridge morphology and estimates of equilibrium‐line altitude depression of ~360–575 m (corrected for land uplift), the results imply moraine formation during short‐lived re‐advances of active glaciers, at least the lower reaches of which were warm‐based. It is concluded that the local glaciers remained active and advanced during deglaciation either very late in the Younger Dryas or very early in the Holocene, possibly in response to the Preboreal Oscillation at ~11.4 ka. The study supports the concept of a thin Younger Dryas ice sheet and places time constraints on the timing of final deglaciation in southern Norway. [ABSTRACT FROM AUTHOR]

The shift in climate that occurred between the Last Glacial Maximum (LGM) and the Early Holocene (ca. 18–12 kyr BP) displayed rates of temperature increase similar to present-day warming trends. The most rapid recorded changes in temperature occurred during the abrupt climate oscillations known as the Bølling–Allerød interstadial (14.7–12.9 kyr BP) and the Younger Dryas stadial (12.9–11.7 kyr BP). Reconstructing ice sheet dynamics during these climate oscillations provides the opportunity to assess long-term ice sheet evolution in reaction to a rapidly changing climate. Here, we use glacial geomorphological inversion methods (flowsets) to reconstruct the ice flow dynamics and the marginal retreat pattern of the southwestern sector of the Laurentide Ice Sheet (SWLIS). We combine our reconstruction with a recently compiled regional deglaciation chronology to depict ice flow dynamics that encompass the time period from pre-LGM to the Early Holocene. Our reconstruction portrays three macroscale reorganizations in the orientation and dynamics of ice streaming followed by regional deglaciation associated with rapid warming during the Bølling–Allerød interstadial. Initial westward flow is documented, likely associated with an early set of ice streams that formed during the advance to the LGM. During the LGM ice streaming displays a dominant north to south orientation. Ice sheet thinning at ∼15 ka is associated with a macroscale reorganization in ice stream flow, with a complex of ice streams recording south-eastward flow. A second macroscale reorganization in ice flow is then observed at ∼14 ka, in which southwestern ice flow is restricted to the Hay, Peace, Athabasca, and Churchill river lowlands. Rates of ice sheet retreat then slowed considerably during the Younger Dryas stadial; at this time, the ice margin was situated north of the Canadian Shield boundary and ice flow continued to be sourced from the northeast. Resulting from these changes in ice sheet dynamics, we recognize a three-part pattern of deglacial landform zonation within the SWLIS characterized by active ice margin recession, stagnation and downwasting punctuated by local surging (terrestrial ice sheet collapse): the outer deglacial zone contains large recessional moraines aligned with the direction of active ice margin retreat; the intermediate deglacial zone contains large regions of hummocky and stagnation terrain, in some areas crosscut by the signature of local surges, reflecting punctuated stagnation and downwasting; and the inner deglacial zone contains inset recessional moraines demarcating progressive regional ice margin retreat. We attribute these macroscale changes in ice flow geometry and associated deglacial behaviour to external climatic controls during the Bølling–Allerød and Younger Dryas but also recognize the role of internal (glaciological, lithological and topographic) controls in SWLIS dynamics. [ABSTRACT FROM AUTHOR]

As prominent abrupt climatic events during the last deglaciation and the early Holocene, the Younger Dryas (YD) and the 8.2 ka events have been intensely discussed to reveal the relationship between their phases and intensities, and their underlying mechanisms based on massive marine and terrestrial archives. However, the related paleoclimate records with sufficient resolution and/or precise age constraints from the Southern Hemisphere, especially East Africa, are relatively sparse, hindering our comprehensive understanding about the phases of these two events. Here, we provide a precisely dated record of an aragonite-calcite stalagmite covering 11.3–13.5 ka BP from northwest Madagascar to unravel the arid conditions during the YD, in contrast to the pluvial conditions in the 8.2 ka event that has been evidenced before. Changes in austral summer precipitation related to the Intertropical Convergence Zone (ITCZ) have always been interpreted to be the primary means of controlling regional rainfall amounts and thus the δ18O variations in stalagmite. However, ITCZ's meridional migration alone is not enough to interpret the opposite hydroclimatic conditions during the YD and the 8.2 ka events in northwest Madagascar. The variation in convection intensity within the ITCZ combined with the rainfall dipole mode in East Africa, and the redistribution of the duration of the ITCZ's presence at different latitudes might be responsible for this phenomenon. In addition, sea surface temperature could play a nonnegligible role. [ABSTRACT FROM AUTHOR]

We compare depth and temporal distributions of sub‐fossil assemblages of two cold‐water scleractinian corals on seamounts in the Southwest Pacific to help define the temporal variations of water mass properties in the Southern Ocean (SO) during deglaciation. Peaks in the deep‐water abundance of the two species complement one another, with Desmophyllum dianthus peaking around the Antarctic Cold Reversal (ACR), and Solenosmilia variabilis briefly during the late Heinrich Stadial 1 (HS1) and during the Younger Dryas (YD). Environmental tolerances of the two species and the geochemistry of S. variabilis carbonate skeletons suggest that their secular distributions reflect complementary effects of temperature (higher at Antarctic Intermediate Water/Upper Circumpolar Deep Water depths during the YD and late HS1) and surface productivity (lower during the YD and HS1). Higher temperatures at depth we interpret as evidence of increased Zonal West Wind (ZWW)‐driven Ekman pumping during the late HS1 and YD, whereas coeval low surface production reflects poleward expansion of sub‐tropical water masses as a result of correlated poleward shifts of the ZWW belt and the Intertropical Convergence Zone. More broadly, a continuous deep coral population in the southwest Pacific that spans two species and three deglacial periods (HS1, ACR and the YD) and an early Holocene shift in coral distribution from deeper to shallower habitats appear to reflect large‐scale changes during deglaciation in SO temperature profiles and productivity. Plain Language Summary: The dynamics of the Southern Ocean are critical for understanding the development of global climate after the last glaciation, but information on the transition is fragmentary and often sparse. We help fill this gap by examining the environmental tolerances and distribution on sea mounts in the Southwest Pacific of two species of cold‐water corals to help better define oceanic conditions during deglaciation. The two species largely alternate in abundance, which suggests alternating periods of warm, but relatively unproductive conditions during the late Heinrich Stadial 1 and the Younger Dryas and a colder, but more productive intervening Antarctic Cold Reversal. These combinations appear to derive from increased wind‐driven upwelling of deep water in the Southern Ocean during the late HS1 and YD, but a coeval poleward shift in low productivity sub‐tropical surface water, driven by correlated shifts in the latitudes of the Southern Ocean zonal wind belt and the tropical Intertropical Convergence Zone. Key Points: Deep populations of two cold‐water corals alternate across the late Heinrich Stadial 1, the Antarctic Cold Reversal and the Younger DryasThe alternation reflects interleaving periods of high temperature/low productivity (HS1 and YD) and low temperature/high productivity (ACR)Drivers appear to be enhanced wind‐driven upwelling of warm Circumpolar Deep Water and coeval poleward shifts in low nutrient surface waters [ABSTRACT FROM AUTHOR]

The reconstruction of environmental changes at the termination of the Last Glaciation range in NE Europe during the Late Glacial is hampered by the multiplicity of processes underway at that time and during the Holocene that dynamically modified the Young Glacial landscape. In lake sediments, these changes are recorded in a manner that is almost always incomplete or disturbed. For this reason, the succession that was successfully reconstructed in two profiles from the Osinki site in NE Poland is extremely valuable. Palynological, Cladocera and geochemical analyses, as well as fragmentary malacofauna and diatom analyses, made it possible to trace the changes in the environment that took place in two differently functioning parts of a single lake, in not interrupted periods from the Oldest Dryas to the Younger Dryas. Detailed research results show that despite the proximity of natural environment components, their developments in both cases were conducted in different ways, what they prove to the changes in pollen record, Cladocera, and geochemical composition of sediments. Climate changes affected the changes in the vegetation, the composition of malacofauna, Cladocera and diatoms. They also influenced the erosion processes within the catchment and the oxidation-reduction conditions. On the basis of the research results, changes in water trophy, from oligotrophic to eutrophic, were also observed. In this case, we also observe significant differences between the two analysed profiles. These changes first occurred in Allerød in the shallow part of the lake, and then in its deeper zone in Young Dryas. In addition, Late Weichselian profiles from the Poland–Belarus–Lithuania borderland area were analysed in detail, and the age of the bottom of sediments is usually estimated to the Allerød, and the Bølling. The results of analyses from Osinki and Osinki2 profiles (beginning of sedimentation in the Oldest Dryas) indicate that the reason for this discrepancy is to be found in, among other things, the methodological limitations of the palynological analysis for most of the sites. The above-standard amount of mineral sediment allows the age of the sediment to be established as being much older than if determined using only pollen analysis of organic sediments. [ABSTRACT FROM AUTHOR]

This study investigates the responses of the depositional environments of Soda Lake sediments to climatic shifts from the Last Glacial Maximum to the Holocene epoch based on the results of major and trace elements of the North Soda Lake (NSL) NSL1A core. The NSL1A core records the sedimentary evolution of the Soda Lake watershed since at least 25 cal ka BP. Element analyses provide evidence that Soda Lake sediments are mostly derived from marine sequences in the Southern Coast Ranges of California. Variation in proxies for paleoweathering, paleoclimate, paleosalinity, paleoproductivity, paleoredox, and water depth is utilized to reconstruct the evolution of the sedimentary environment. The Chemical Index of Alteration (CIA) values indicate low to moderate chemical weathering in the sediment source regions. Paleoredox proxies indicate that the NSL1A core formed in a mainly subreduction environment. The NSL1A core is divided into four zones based on the results of the proxies. Zone 4 (5.0–5.8 m) of the sediment core indicates stable hydroclimatic conditions with low and constant sand and silt content, suggesting a warm and relatively humid environment. Zone 3 (3.35–5.0 m) represents the early half of the Last Glacial Maximum interval and a high lake stand. The elevated sand content suggests postflood events due to the northerly migration of westerly storm tracks. Zone 2 (1.075–3.35 m) reveals nuanced changes, including decreasing salinity, slight increases in wetness, detrital trace metals, and paleoproductivity. These subtle shifts suggest a multifaceted environmental evolution: a trend toward wetter conditions alongside a prolonged shift from cooler to warmer periods. Zone 1 (0.15–1.075 m) spans the Lateglacial to Holocene transition as well as Early and Middle Holocene, marked by significant hydrologic and ecologic variability including rapid warming during the Bølling–Allerød and rapid cooling linked to the Younger Dryas. [ABSTRACT FROM AUTHOR]

Alpine glacier-based temperature reconstructions spanning the last deglaciation provide critical constraints on local to regional climate change and have been reported from several formerly glaciated regions around the world yet remain sparse from high-northern-latitude regions. Using newly and previously 10 Be-dated moraines, we report paleo-glacier equilibrium line altitudes (ELAs) for 15 time slices spanning the Last Glacial Maximum (LGM) to the Little Ice Age (LIA) for a valley in the western Alaska Range. We translate our ELA reconstructions into a proxy for summer temperature by applying a dry adiabatic lapse rate at each reconstructed ELA relative to the outermost LIA moraine. We observe ∼4 °C warming through the last deglaciation at our site that took place in two steps following initial gradual warming: ∼1.5 °C abrupt warming at 16 ka, ∼2 kyr after the onset of global CO 2 rise, and ∼2 °C warming at ∼15 ka, near the start of the Bølling. Moraine deposition and modest summer cooling during Heinrich Stadial 1 and the early Younger Dryas (YD) suggest that despite these events being expressed more strongly in wintertime, the classic blueprint of North Atlantic climate variability extends to the western Arctic region. [ABSTRACT FROM AUTHOR]

The Baltic Sea basins, some of which only submerged in the mid-Holocene, preserve Stone Age structures that did not survive on land. Yet, the discovery of these features is challenging and requires cross-disciplinary approaches between archeology and marine geosciences. Here, we combine shipborne and autonomousunderwater vehicle hydroacoustic data with up to a centimeter range resolution, sedimentological samples, and optical images to explore a Stone Age megastructure located in 21 m water depth in the Bay of Mecklenburg, Germany. The structure is made of 1,673 individual stones which are usually less than 1 m in height, placed side by side over a distance of 971 m in a way that argues against a natural origin by glacial transport or ice push ridges. Running adjacent to the sunken shoreline of a paleolake (or bog), whose youngest phase was dated to 9,143 ±36 ka B.P., the stonewall was likely used for hunting the Eurasian reindeer (Rangifer tarandus) during the Younger Dryas or early Pre-Boreal. It was built by hunter-gatherer groups that roamed the region after the retreat of the Weichselian Ice Sheet. Comparable Stone Age megastructures have become known worldwide in recent times but are almost unknown in Europe. The site represents one of the oldest documented man-made hunting structures on Earth, and ranges among the largest known Stone Age structure in Europe. It will become important for understanding subsistence strategies, mobility patterns, and inspire discussions concerning the territorial development in the Western Baltic Sea region. [ABSTRACT FROM AUTHOR]

The Younger Dryas-Holocene transition represents a period of significant thermal change, comparable in magnitude to modern warming, yet in a colder context and without the effect of anthropogenic disturbance. This is useful as a reference to tackle how biodiversity is affected by temperature in natural conditions. Here, we addressed the thermal change during this period in a southern Baltic coastal lake (Konarzewo Lake, Poland), as inferred by chironomid remains. We evaluated changes in chironomid communities and used Hill numbers to explore how commonness and rarity underlie biodiversity changes attributable to warming. We found evidence of warming at Konarzewo Lake during the Younger Dryas-Holocene transition, with inferred temperatures in the Younger Dryas period supporting the NW–SE gradient in Younger Dryas summer temperatures across Europe. Chironomid communities drastically changed during the thermal transition. However, Hill numbers showed no response to temperature when rare morphotypes were emphasized (order q = 0) or a weak response when they were balanced with common morphotypes (order q = 1). Hill number of order q = 2, emphasizing the most common morphotypes, consistently increased with temperature across different sample sizes or coverages. This illustrates how common morphotypes, rather than the rare ones, may boost biodiversity facing warming. [ABSTRACT FROM AUTHOR]

Stabilized and active dunes and sand sheet deposits abound in a small lake‐dotted semi‐arid region of the Western Pampean Dunefield, Argentina. Here, a multi‐scale and multi‐proxy study of three sites, across a hydrologic gradient from lakes to a dryland with groundwater levels at more than 25 m depth, analyzes calcareous and ferruginous rhizoliths, calcareous crusts, hypocoatings, pedogenic carbonate and amorphous Mn‐oxide precipitates within blowout dunes. These palustrine‐related features indicate significantly wetter conditions that allowed the development of shallow lakes and expanding wetlands during the Pleistocene–Holocene transition, limited by associated optically stimulated luminescence ages between ca. 14.7 and 11.6 ka. These wetter conditions, also identified in other nearby proxy records, may be associated with a strengthened South American Monsoon System, potentially during the Younger Dryas Chronozone, though other geological, ecological and climatic forcings cannot be ruled out with available data. Such a scenario lacks a modern analogue, since current hydrologic excess, evidenced in the formation of lakes and new rivers, is not observed in the localities which record paleolakes. This study underlines the variable conditions for pronounced hydrologic excess in semi‐arid eolian environments in western Argentina with complex ecological, anthropogenic and climatic linkages. [ABSTRACT FROM AUTHOR]

On glacial‐interglacial time scales, changes in the Earth's orbital configuration control climate seasonality and mean conditions. Tropical coral skeletons can be sampled at a sufficient resolution to reconstruct past seasonality. Here, last deglacial Porites skeletons from Integrated Ocean Drilling Program Expedition 310 to Tahiti are investigated and, supported by a modern calibration, monthly resolved time series in geochemical proxies (Sr/Ca, δ18O, δ13C) are constructed. For most of the deglaciation, Sr/Ca seasonality was similar to modern (0.139 ± 0.010 mmol mol−1; 2.8 ± 0.2°C) reflecting the small change in insolation seasonality. However, during the Younger Dryas, high values in Sr/Ca seasonality (0.171 ± 0.017 mmol mol−1; 3.4 ± 0.3°C) suggest a reduced mixed layer depth and enhanced influence of the South Pacific Subtropical Gyre due to South Pacific Convergence Zone (SPCZ) inactivity. Furthermore, high amplitudes in Younger Dryas skeletal δ18O (0.40 ± 0.22 ‰) and δ13C (0.86 ± 0.22 ‰) seasonality compared to modern (δ18O = 0.29 ± 0.08 ‰; δ13C = 0.27 ± 0.08 ‰) point to elevated winter‐summer discrepancies in rainfall and runoff. Mean coral Sr/Ca variability suggests an influence of Northern Hemisphere climate events, such as the Younger Dryas cooling (+0.134 ± 0.012 mmol mol−1;−2.6 ± 0.2°C), or the Bølling–Allerød warming (+0.032 ± 0.040 mmol mol−1; −0.6 ± 0.4°C). Deglacial mean coral Δδ18O (δ18Oseawater contribution to skeletal δ18O), corrected for the ice volume effect, was elevated pointing to more saline, thus dryer conditions, likely due to a northward migration of the SPCZ. Seasonal cycles in coral δ13C were likely caused by variations in linear extension rates that were reduced during the last deglaciation (1.00 ± 0.6 cm year−1) compared to today (1.6 ± 0.3 cm year−1). Plain Language Summary: Changes in the Earth's movement around the sun are the primary cause of changes in the annual cycle and annual mean of environmental conditions during the last glacial‐interglacial periods. Distinct from most climate archives, the annual bands of coral skeletons can be sampled at a monthly resolution that allows for reconstructions of past seasonal cycles. In this study, the chemical composition of coral skeletons from the genus Porites that grew during the last deglaciation at Tahiti (∼15,000–9,000 years ago) was analyzed to infer seasonal variations and mean conditions in past sea surface temperature and salinity. Prior to application, the methods were successfully calibrated using modern coral skeletons from Tahiti. Results showed that sea surface temperature seasonality was similar to today during most of the deglaciation. However, for the Younger Dryas, a particular cold interval, a marked increase in sea surface temperature seasonality suggests that Tahiti was at that time located outside the South Pacific Convergence Zone, a rain band extending across the tropical Southwest Pacific. Furthermore, coral reconstructions revealed that, although distant, North Atlantic last deglacial climate events influenced mean climate conditions at Tahiti. In addition, we show that last‐deglacial coral growth rates were reduced compared to today. Key Points: Last deglacial changes in Tahiti coral Sr/Ca suggest an influence of Northern‐Hemisphere climate events on the tropical South PacificVariations in last deglacial Tahitian climate were modulated by meridional migrations of the South Pacific Convergence ZoneLast deglacial Porites corals revealed reduced linear extension rates (1.0 ± 0.6 cm year−1) compared to today (1.6 ± 0.3 cm year−1) [ABSTRACT FROM AUTHOR]

Understanding Holocene temperature changes is vital for resolving discrepancies between proxy reconstructions and climate models. The intricate temperature variations across the Tibetan Plateau (TP) add complexity to studying continental climate change during this period. Discrepancies between model-based and proxy-based reconstructions might stem from seasonal biases and environmental uncertainties in the proxies. Employing multiple proxies from a single sediment core for quantitative temperature reconstructions offers an effective method for cross-validation in terrestrial environments. Here, we present an ice-free-season temperature record for the past 15 kyr from a shallow, freshwater lake on the eastern TP, based on brGDGTs (branched glycerol dialkyl glycerol tetraethers). This record shows that the Holocene Thermal Maximum lags the pollen-based July temperature recorded in the same sediment core. We conclude that the mismatch between the brGDGT-based and pollen-based temperatures is primarily the result of seasonal variations in solar irradiance. The overall pattern of temperature changes is supported by other summer temperature records, and the Younger Dryas cold event and the Bølling–Allerød warm period are also detected. A generally warm period occurred during 8–3.5 ka, followed by a cooling trend in the late Holocene. Our findings have implications for understanding the seasonal signal of brGDGTs in shallow lakes and provide critical data for confirming the occurrence of seasonal biases in different proxies from high-elevation lakes. To further investigate the significance of the brGDGTs and temperature patterns on the TP, we examined existing brGDGT-based Holocene temperature records, which interpret these compounds as indicators of mean annual or growing season temperatures. The existing and available temperature records show complicated patterns of variation, some with general warming trends throughout the Holocene, some with cooling trends, and some with a warm middle Holocene. We analyzed the possible reasons for the diverse brGDGTs records on the TP and emphasize the importance of considering lake conditions and modern investigations of brGDGTs in lacustrine systems when using brGDGTs to reconstruct paleoenvironmental conditions. [ABSTRACT FROM AUTHOR]

The high-resolution analysis of radiolarians and silicoflagellates in sediments from Holes U1545A and U1549A drilled during IODP Expedition 385 in the Guaymas Basin, in the Gulf of California provides detailed insights into the evolution of ocean circulation and water masses, and its relation to Eastern Tropical Pacific Ocean climate conditions, over the past 31,000 cal years BP (based on AMS radiocarbon dates). In the pre-Last Glacial Maximum, the Guaymas Basin experienced alternating circulation patterns of California Current Water (CCW) and Gulf of California Water (GCW), with an extended presence of the Pacific Intermediate Water (PIW) owing to: amplified jet streams; southern movement of the California Current System (CCS) and the incursion of CCW into the gulf; and increased North Pacific Intermediate Water (NPIW) formation. The Last Glacial Maximum witnessed the incursion of CCW due to the stronger CCS. The dominance of the PIW indicates the expansion and formation of NPIW. The Heinrich-I event as manifested in the core record, displays two distinct patterns, one suggesting GCW-like dominance and the other, the occurrence of CCW. The Bølling-Ållerød interstadial featured the entry of Tropical Surface Water (TSW), GCW, and CCW, linked with the northward migration of the Intertropical Convergence Zone. In the Younger Dryas, CCW dominated, transitioning to GCW as colder climatic conditions and more intense CCS. The Holocene displayed alternating periods of TSW and GCW, with a modern monsoon regime from 7,600 to 1,000 cal years BP. From 1,000 cal years BP to the present the ITCZ shifted to the south. [ABSTRACT FROM AUTHOR]

The South China Sea (SCS) is the largest marginal sea in the western Pacific, fed by large Asian rivers, characterized by substantial volumes of sediment derived from surrounding Asian continents and islands. This study utilizes the rare earth elements (REEs), Sr isotopes (87Sr/86Sr), and Nd isotopes (ƐNd) in detritus fractions of MD05-2901 sediments in northwestern SCS, to evaluate the relative contribution among the Mekong River, the Red River, the Pearl River, and rivers in SW Taiwan over the last 32 ka. This deep-sea core is located off the coast of central Vietnam, an upwelling region with only minor continental inputs, and this study is important for a better understanding of the main sources of terrigenous material and their temporal variations in the region. In addition, potential particle exchange is examined using the same proxies in the Fe-Mn oxyhydroxide fractions. The obtained records are systematically compared with the available climatic archives in the region. The REEs in the Fe-Mn oxyhydroxides support the argument of water mass signature separation in bulk sediments by chemical leaching procedures. These 87Sr/86Sr in the Fe-Mn oxyhydroxides phase fall in a range between 0.709262 and 0.709313, deviating significantly from the modern seawater. ƐNd values vary >3Ɛ, being more radiogenic in the Fe-Mn oxyhydroxides, where the lowest value occurred in the Bølling/Allerød (B/A) and higher values occurred during the Younger Dryas (YD). The latter implies increased contribution of loess dusts or Taiwanese rivers under dry/cold climatic conditions, compared with the situation in modern times. The Red River and the Mekong River together may have contributed >60% during the Last Glacial Maximum (LGM) and YD. In contrast, the Pearl River components have increased sharply to ~60% during the warm B/A. These results demonstrate that the MD05-2901 sediments sensitively record changes in weathering intensity on land and transport pathways in the coastal regions in the Holocene. [ABSTRACT FROM AUTHOR]

In recent years, various early warning signals of critical transition have been presented, such as autocorrelation at lag 1 [AR(1)], variance, the propagator based on detrended fluctuation analysis (DFA-propagator), and so on. Many studies have shown that the climate system has the characteristics of long-term memory (LTM). Will the LTM characteristics of the climate system change as it approaches possible critical transition points? In view of this, the present paper first studies whether the LTM of several folding (folded bifurcation) models changes consistently as they approach their critical points slowly by the rescaled range (R/S) analysis. The results of numerical experiments show that when the control parameters of the folding model are close to its critical threshold, the Hurst exponent H exhibits an almost monotonic increase (significance level α = 0.05). We compare the performance of R/S with the existing indicators, including AR(1), variance, and DFA-propagator, and find that R/S is a perfectly valid alternative. When there is no extra false noise, AR(1) and variance have good early warning effects. After the addition of extra Gaussian white noise of different intensities, the values of AR(1) and variance change significantly. As a result, the DFA-propagator based on AR(1) calibration also changed significantly. Compared with the other three indicators, the early warning effect of H has stronger ability to resist the interference of external false signals. To further verify the validity of increasing H, paleoclimate reconstruction of Cariaco Basin sediment core grayscale record with long trends filtered out is studied by R/S analysis. The other three early warning signals are calculated in the same way. The data contain a well-known abrupt climate change: the transition between the Younger Dryas (YD) and the Holocene. We find that approximately 300 years before this abrupt climate change occurred, before 11.7 kyr BP, the LTM exponents for Cariaco Basin deglacial grayscale data present an obvious increasing trend at a significant level of α = 0.05. Meanwhile, the variation trend of H and DFA-propagator is basically similar. This shows that increasing H by R/S analysis is an effective early warning signal, which indicates that a dynamic system is approaching its possible critical transition points; H is a completely valid alternative signal for AR(1) and DFA-propagator. The main conclusion of this paper is based on numerical experiments. The precise relationship between H and the stability of the underlying state approaching the transition needs to be further studied. [ABSTRACT FROM AUTHOR]

In the highest tributaries of the Upper Garonne Basin, Central Pyrenees, cirques up to 2600 m a.s.l. were already deglaciated by 15–14 ka. The long‐term deglaciation during Termination‐1 (T‐1) was interrupted by glacial advances within the cirques during the Bølling–Allerød (B‐A) interstadial and the Younger Dryas stadial. The cirques preserve a variety of glacial and periglacial landforms whose chronologies are poorly known. This study is focused on the Lòcampo cirque (42°38′06″N and 0°59′10″E), Upper Garonne Basin, where a detailed geomorphological map and 10Be terrestrial cosmic ray exposure (CRE) dating allowed us to constrain the chrono‐sequence between the glacial and periglacial domains. In the small Lòcampo cirque, a glacier formed a cirque moraine between 2200 and 2300 m a.s.l., which surrounds a relict rock glacier encompassing several transversal ridges. Additionally, longitudinal ridges typically observed in debris‐covered glaciers are preserved between the moraine and the rock glacier. The eight‐sample data set of CRE ages indicates the formation of the cirque moraine during the second half of the B‐A, by 13.2±1.1 ka. Exposure ages from the rock glacier boulders show a range between 13.6±0.9 and 11.9±0.7 ka, which did not allow its formation to be chronologically constrained. Therefore, the environmental evolution following the moraine stabilization could follow the formation of a debris‐covered glacier at the bottom of the Lòcampo cirque, with the subsequent formation of the rock glacier. After the rock glacier formation, its front rapidly ceased at 13.6±0.9 ka, while the upper ridges gradually stabilized until it became definitively relict at 11.9±0.7 ka or afterwards. These results show evidence of the complex glacial to periglacial transition that needs more robust chronological data sets to better understand the role of climate forcing and local topography during the deglaciation in mid‐latitude mountain environments. [ABSTRACT FROM AUTHOR]

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

The isotope values of fossil snail shells can be important archives of climate. Here, we present the first carbon (δ13C) and oxygen (δ18O) isotope values of snail shells in interior Alaska to explore changes in vegetation and humidity through the late-glacial period. Snail shell δ13C values were relatively consistent through the late glacial. However, late-glacial shell δ13C values are 2.8‰ higher than those of modern shells. This offset is best explained by the Suess effect and changes in the δ13C values of snail diet. Snail shell δ18O values varied through the late glacial, which can be partially explained by changes in relative humidity (RH). RH during the snail growing period was modeled based on a published flux balance model. Results suggest a dry period toward the beginning of the Bølling–Allerød (~14 ka) followed by two distinct stages of the Younger Dryas, a wetter stage in the early Younger Dryas from 12.9 to 12.3 ka, and subsequent drier stage in the late Younger Dryas between 12.3 and 11.7 ka. The results show that land snail isotopes in high-latitude regions may be used as a supplementary paleoclimate proxy to help clarify complex climate histories, such as those of interior Alaska during the Younger Dryas. [ABSTRACT FROM AUTHOR]

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

Jenny's soil formation equation places soil morphogenesis as a response to climate (cl), biota (o), relief (r), parent material (p), and time (t), written thus: s= f (cl, o, r, p, t...), where each variable is considered independent. Because some soils and paleosols contain cosmic impact/airburst evidence, recent soil morphogenesis research requires a rewritten equation: s= f (cl, o, r, p, t, c...), where c = cosmic. This addition serves to alert researchers to the presence of cosmic input to soils under investigation as part of geological and geomorphological projects. In particular, research targeting the cause of the Younger Dryas Climatic Divide (YDCD) might focus only on pollen in European glaciolacustrine sediments, reversal of the marine thermohaline circulation in the N. Atlantic Ocean, and possible reversal of postglacial warming at the Allerød termination (12.8 ka), when a search for cosmic grains may change the research outcome. Hence, the importance of the 'c' addition to Jenny's factor analysis of soil morphogenesis. [ABSTRACT FROM AUTHOR]