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Holocene environmental and climate change on the Tibetan Plateau is intensively studied and discussed with the aim to better understand the factors controlling the hydrology of individual river catchments and especially the availability of water which is of utmost significance for the communities downstream in times of rapid climate change. Thus, a late glacial and Holocene sediment record from Lake Heihai in the Kunlun-Pass region was investigated using ostracod and geochemical analyses. Cold and dry conditions were inferred between ca. 12.9 and 12.3 cal ka BP and higher temperatures before and afterwards. The cold spell probably corresponds to the Younger Dryas (YD) event in the North Atlantic region. Warmer and wetter conditions with highest lake levels and decreased lake-water salinity were recorded from ca. 10.8 to 7.0 cal ka BP when the summer monsoon was strengthened. The cold 8.2 cal ka BP event is not significantly recorded in the region probably due to the predominance of the summer monsoon over the westerlies. A declined lake level and increased lake-water salinity as the result of cold and dry conditions are inferred from ca. 7.0 to 4.5 cal ka BP when the strengthening of the mid-latitude westerly circulation probably triggered glacier advances in the catchment. An even lower lake level existed during cold conditions with glacier advances from ca. 4.5 to 1.2 cal ka BP. The level of Lake Heihai rose again after ca. 1.2 cal ka BP due to warmer conditions, causing the retreat of glaciers and higher runoff. Our record from the Kunlun Pass region provides further evidence for the catchment-specific response of hydrographical systems which are partly controlled by glaciers as major water sources. [ABSTRACT FROM AUTHOR]

The timing and rate of ecosystem response to abrupt climate change is a product of numerous complex interactions between biotic and abiotic drivers. Palaeoecological studies from long sedimentary records, particularly those that span periods of dynamic climate such as the last glacial cycle, can help to contextualise ecosystem responses to climate variability through time. Detailed studies that compare proxy data from multiple sites, with high chronological precision, have the potential to ascribe mutual climate drivers, and, therefore, track spatiotemporal variability in ecosystem responses. Here, we interrogate the vegetation impact of past climate change in the eastern Mediterranean, using three sub-centennially resolved pollen archives from Greece. The widespread Campanian Ignimbrite (CI/Y-5; ca. 39.85 ka BP) tephra marker is used as an isochron to directly correlate pollen records from Ioannina (NW Greece), Tenaghi Philippon (NE Greece), and Megali Limni (NE Aegean). Our results reveal spatiotemporal variability in the timing of vegetation response in the Mediterranean to climate forcing across Heinrich Stadial 4 (40.2–38.3 ka BP), a period of known abrupt climatic change. We identify a decline in tree pollen in all three sites, likely related to the onset of enhanced regional aridity, with vegetation at Tenaghi Philippon responding prior to the CI/Y-5, in contrast to at Megali Limni and Ioannina, where much of the vegetation change occurs following tephra deposition. • The Campanian Ignimbrite (CI/Y-5) tephra marker is used to interrogate the timing of vegetation response to HS4. • The timing of tree pollen minima across HS4 varies between three centennial-scale pollen records. • Temporal offsets may reflect site-specific characteristics and/or the fast and slow components of millennial-scale change. [ABSTRACT FROM AUTHOR]

Speleothems from cold high-elevation (and high-latitude) caves are sensitive paleoenvironmental archives, because they form close to the freezing point of water, and Alpine or Arctic soils – the source of carbon dioxide for carbonic-acid dissolution – are thin and experience a short vegetation period. Climatic cooling is therefore likely to disrupt the growth of these speleothems. However, growth hiatuses may paradoxically be overcome when atmospheric cooling leads to lowering of the equilibrium-line altitude and expansion of temperate glaciers over the karst system, which prevents the latter from freezing. Caves in mountain regions of the mid to high latitudes had a much higher chance of being covered by glaciers during cold climatic periods than caves at lower elevations, which were often in the permafrost zone. These periods without frost in caves covered by temperate glacier ice can be recorded by so-called subglacial speleothems if the host rock contains disseminated pyrite. Widely present in impure limestones, dolostones, and marbles, oxidation of this sulfide mineral gives rise to sulfuric-acid dissolution of the host rock, replacing the carbonic-acid dissolution that operates during warm climate periods. This review summarizes the research history of subglacial speleothems, beginning with seminal studies of Castleguard Cave, which extends beneath the Columbia Icefield in Western Canada. Subsequent work on a number of caves in the Eastern and Western Alps in Europe has shown that speleothems from such subglacial environments are widespread and provide unprecedented opportunities to obtain records of environmental change covering the long glacial periods. However, the proxy system behavior of these settings has yet to be fully developed. We therefore propose a suite of diagnostic criteria, some untested, by which to identify and interpret subglacial speleothems, with recommendations for future research. The combination of high δ13C (at or above host rock values) and low δ18O provide a robust first-order proxy for subglacial environments, while trace-element and sulfate stable-isotope (δ34S and δ18O) data can elucidate the dissolution pathway and redox conditions resulting from ice cover. When studies of subglacial speleothems are combined with conventional warm-climate speleothems controlled by soil dynamics, as well as locally present cryogenic cave carbonates (an indicator of the presence of paleo-cave ice accumulations), the possibility of exploiting the full paleoclimate potential of Alpine and Arctic caves on glacial-interglacial timescales opens up. [ABSTRACT FROM AUTHOR]

Limited understanding of how Indigenous people have created and managed the Australian landscape continues to have repercussions on how landscapes are culturally interpreted and managed today. Addressing this is critically important as climate change is increasing the frequency and intensity of wildfires, whilst challenging the objectives, methods and efficacy of contemporary landscape management practices. Here we compare the palaeoecology of vegetation changes across glacial to interglacial states before (Termination II) and after (Termination I) human occupation of the cool temperate rainforests of western Lutruwita (Tasmania). Sediment from Darwin Crater (Termination II) and Lake Selina (Termination I) were analysed using radiometric dating, fossil pollen, charcoal, geochemical, environmental magnetic and sedimentary methods to produce a comprehensive reconstruction of vegetation and landscape dynamics. Results show marked differences in the rainforest response to the transition from glacial to interglacial climates before and after human arrival at c. 43,000 years ago (ka). In the absence of human disturbance, Phyllocladus aspleniifolius-Nothofagus cunninghamii lowland rainforest taxa dominated the last interglacial period (∼77% of the pollen sum) but was reduced in the current interglacial (∼41%) and largely replaced by Gymnoschoenus sphaerocephalus buttongrass moorland (10–23%). This demonstrates the legacy of Indigenous Palawa managed landscapes, primarily using fire to promote landscape openness and prevent the dominance of an ecologically climax rainforest community, until their forced removal via invasion and colonisation ca. 1806. • We conducted multi-proxy analysis on pre-Palawa lake sediments from western Tasmania. • Cold-resistant glacial vegetation dominated in the Darwin Crater vegetation record, preceding Termination II (ca. MIS-6). • Interglacial rainforest vegetation dominated the Darwin Crater vegetation record, succeeding Termination II (ca. MIS-5e). • Lake infilling occurred abruptly at ca. 474 cm, following Termination II. • Palawa burning maintained landscape openness into the Holocene, suppressing the 'natural' expansion of climax rainforest. We compare vegetation changes across glacial Terminations I and II in lake sediments from western Tasmania (Lutruwita). The data reveal marked differences in the rainforest response to the transition from glacial to interglacial climates before and after human arrival into Lutruwita at c. 43 ka and the influence of fire management on the landscape. [ABSTRACT FROM AUTHOR]

With a rich sequence of floral and faunal remains spanning the past >65,000 years, Boomplaas Cave is among the more important paleoenvironmental archives from South Africa's southern Cape. However, over the last several decades, its paleoenvironmental records have been the subject of conflicting interpretations, fueling uncertainty over fundamental aspects of Quaternary climate change in the region. Most significantly, researchers have variably interpreted the fossil plant and animal assemblages dating to the Last Glacial Maximum (LGM) as indicating harsh and arid or humid and productive conditions. This review critically examines the paleoenvironmental evidence from Boomplaas Cave, focusing on its LGM deposits and how they relate to the contentious problem of moisture availability through time. We show that interpretations of aridity during the LGM either (i) lack robust ecological links between the evidence and the paleoenvironmental interpretation, or (ii) are based on spurious patterns arising from sampling effects. In contrast, interpretations of relatively humid conditions during the LGM are grounded in present-day ecological observations and are consistent with both local and regional paleoenvironmental datasets. Overall, the evidence strongly supports the characterization of the LGM as a time of relatively humid conditions, with the transition to the Holocene characterized by increasing aridity. Several lines of evidence from Boomplaas Cave further suggest that this phase of increased humidity was associated with a dominance of winter rainfall, in contrast to the aseasonal rainfall regime that characterizes the southern Cape today. • Boomplaas Cave is a critical but debated archive of LGM climate in southern Africa. • This study examines its paleo proxies and the interpretations derived from them. • The proxy records indicate greater moisture availability during the LGM. • The proxy records indicate a greater dominance of winter rainfall during the LGM. [ABSTRACT FROM AUTHOR]

[Display omitted] With ongoing global warming and permafrost thawing, weathering processes will change on the Yukon River, with risks for water quality and ecosystem sustainability. Here, we explore the relationship between weathering processes and permafrost cover using elemental concentration and strontium and lithium isotopic data in the dissolved load of 102 samples collected during the summer across most major tributaries of the Yukon River. The Yukon River basin is dominated by silicate weathering with a high contribution from young volcanic rock units. In glaciated mountainous zones, we observe higher carbonate weathering contribution, low Li/Na ratios and low δ 7Li values (<15‰). In these areas, the high denudation rate and high supply of fresh minerals associated with alpine glaciers favor congruent silicate weathering, and sulfide oxidation accelerates carbonate weathering. In floodplains covered by continuous permafrost, we observe a high carbonate weathering contribution, relatively high Li/Na ratios, and low δ 7Li values (∼18‰). We argue that the minimal water–rock interactions in this setting inhibit silicate weathering and favor congruent weathering of easily weatherable minerals (i.e., carbonates). Conversely, in areas with discontinuous or sporadic permafrost, we observe a dominance of silicate weathering, with higher and more variable Li/Na ratios and high δ 7Li values (11–33‰). In this setting, longer water–rock interactions combined with the high supply of fresh minerals from mountain zones favor more incongruent weathering. The unique history of Pleistocene glaciations on the Yukon River basin also influences weathering processes. Many areas of the basin were never glaciated during the Pleistocene, and rivers draining those regions have higher δ 7Li values suggesting more incongruent weathering associated with deeper flow paths and longer water residence time in the regolith. Our work underlines that water–rock interactions, including active layer weathering and groundwater inputs, are highly dependent on climate conditions and glacial processes across the Yukon River basin, with key implications for future water quality in this warming basin. [ABSTRACT FROM AUTHOR]

Evaporites were deposited in every saline lake in the western Qaidam Basin (QB) during the late Quaternary, but the role of the Quaternary glacial environment in the formation of evaporite deposits remains to be clarified. In this paper, five upper Quaternary evaporite-bearing profiles in the western QB are studied. Uranium-thorium (U–Th) dating was applied to obtain the depositional ages of these profiles, and X-ray powder diffraction (XRD) analysis was applied to identify the evaporite minerals. The U–Th dating results indicate that halite (NaCl)-dominated profile D08 and mirabilite (Na 2 SO 4 ·10H 2 O)-dominated profile MXK were deposited between 146.1 ± 53.4 ka and 171.3 ± 27.2 ka, mainly corresponding to Marine Isotope Stage (MIS) 6; the bloedite (Na 2 Mg(SO 4) 2 ·4H 2 O)-dominated profiles WMX1 and WMX2 were deposited between 182.1 ± 2.5 ka and 206.7 ± 7.0 ka, mainly corresponding to the late period of MIS7; and the mirabilite and halite-dominated salt layers in profile D30 were deposited between 9.0 ± 0.7 ka and 14.3 ± 1.6 ka, with mirabilite deposit ages corresponding to MIS2 and early MIS1. The minerals in the profiles identified by XRD analyses are mirabilite, thenardite (Na 2 SO 4), bloedite, gypsum (CaSO 4 ·2H 2 O), starkeyite (MgSO 4 ·4H 2 O), hexahydrite (MgSO 4 ·6H 2 O) and halite. This study, combined with those of previously reported evaporite deposits in the western QB, indicates that MIS7, MIS6 and MIS2 were important evaporite deposition periods in the late Quaternary. Evaporite depositions in the QB during MIS6 and MIS2 were attributed to a decrease in temperature and shrinkage of the saline lake hydrosphere. The cold glacial climate during MIS6 and MIS2 was conducive to mirabilite deposition in the western QB, while the relatively warm climate of the late period MIS7 was conducive to bloedite deposition. [Display omitted] [ABSTRACT FROM AUTHOR]

The influences on climate in the Northwest Tibetan Plateau (NwTP) have changed on millennial to precessional timescales and have been dependent on the size of the Northern Hemisphere ice sheets, Northern Hemisphere summer insolation, and the migration of the Intertropical Convergence Zone (ITCZ). All these influences control the position and intensity of the westerlies over Central Asia and the Tibetan Plateau and of the Asian Monsoon over South Asia. The top 187.4 m of a 309.7-m ice core (2015GP) drilled on the plateau of the Guliya ice cap contains a 41-kyr climate history of the NwTP, a region where information on past climate and environment is limited. The oxygen isotope ratio (δ18O), and ammonium (NH 4 +) and dust concentration records from 2015GP show that during the glacial (41–17.5 ka BP) temperature and precipitation in the NwTP were primarily influenced on the precessional timescale by summer insolation, while at millennial resolution the climate was linked to the North Atlantic temperature via the westerlies. During the deglaciation (17.5–12 ka BP) summer insolation remained an important temperature forcing, but the influence of the North Atlantic climate on the NwTP climate weakened as the westerlies shifted northward. The Guliya Holocene δ18O record shows that NwTP climate was no longer in phase with decreasing summer insolation or with North Atlantic climate, perhaps as the moisture source and pathways were more determinative factors in isotopic fractionation than temperature, and/or incoming solar radiation (insolation) forcing was replaced by rising greenhouse gas concentrations as the primary driver of warming in NwTP. • An ice core from the western Kunlun Mts shows orbital to millennial climate changes. • Summer insolation and westerlies influenced glacial stage climate in western Kunlun. • Ice core δ18O variations in NW Tibet and Greenland were similar in last glacial. • Ice core δ18O variations in NW Tibet and Greenland were opposite after 17.5 ka BP. • Mechanisms influencing δ18O in NW Tibet may vary with changing climatic conditions. [ABSTRACT FROM AUTHOR]

Northern Asia (here, the Russian Federation east of the Urals) played a key role in the spread of anatomically modern humans (AMH) across the Eurasian continent during the Upper Palaeolithic (UP). This time interval witnessed the climatically harshest and most variable part of the last glacial epoch when AMH spread to all continents, with the exception of ice-covered Antarctica, thus raising questions about how humans and environments interacted. Our review of available proxy records shows that the study region was largely dominated by productive steppe and tundra plant communities, which promoted a diverse small- to mega-scale fauna throughout the UP. While this rich fauna was an ideal food resource for AMH populations, its possible influence on the growth of woody plants through grazing is less well resolved. Another non-climatic factor that may have impacted on the spread of woody taxa are human activities (e.g. setting fires to facilitate hunting). Evidence that small populations of woody taxa were distributed in climatically favourable habitats comes from plant macroremains from sediment sequences and archaeological sites and from aDNA data. Contrary to the long-standing view of a generally colder-than-present last glacial climate, these proxy records reveal evidence that summers were warmer than today by several degrees Celsius, providing additional advantages for human activities. Another benefit for large herbivores, and thus human subsistence, were the generally low winter precipitation levels (similar to those of the modern steppe regions of Mongolia), which sustained year-round grazing grounds. These factors apparently outweighed the harsh colder-than-present winter conditions and promoted habitation of AMH in Northern Asia even during the Last Glacial Maximum (LGM) ca. 30‒18 cal kyr BP. While our understanding of qualitative climate trends, mainly based on fossil pollen records, has substantially improved, quantification of climate parameters is still a challenging task. For the last glacial interval in Northern Asia, plant macroremains, chironomids, diatoms and ostracods may provide suitable alternative proxies. [ABSTRACT FROM AUTHOR]

The Late Pleistocene and Early Holocene were time periods of significant transitions between glacial and warm climate states. In this contribution, a study of changes of diatom assemblage compositions in recurrence plots, rarefaction models, and their rank abundance distributions (Fisher's alpha) in the Southeast Baltic is presented. Three sites were studied for this purpose: Lake Kamyshovoye (Kaliningrad Region, Russia), Lake Kašučiai (W Lithuania), and Lake Petrešiūnai (NE Lithuania). The recurrence plots revealed a compositionally stable interval at the end of the Pleistocene and a subsequent continuous and directional turnover (compositional trend) of local diatom communities throughout the Early Holocene. An analysis of rank abundance distributions and rarefaction analysis revealed a persistent long-term increase in the diversity of diatoms which started after the Younger Dryas cold episode; additional data suggest possible effects of the multi-centennial scale "9.3" Ka BP cold event. The close correlation between diatom diversity changes and geographically widespread climatic trends shows strong potential for this algae group in the regional analyses of climatic perturbations. [ABSTRACT FROM AUTHOR]

Beetles of the family Tenebrionidae, particularly those of the subfamily Pimeliinae, are highly diverse and abundant in desert ecosystems. The sensitivity of the many wingless species to geographical and ecological isolation makes them ideal candidates for studying effects of climatological and/or geophysical changes on organismal diversity. Our study focuses on Brinckia , the only genus of the subtribe Hypomelina adapted to coastal sand dune hummocks (nabkhas) and restricted to that environment along the Namib Desert and the transitional Namib south of the Orange River. Today, Brinckia appear to be common along the coast, albeit with different species, wherever the absence of shifting sand dunes enables the beach hummocks to form, mainly around Salsola and Zygophyllum species. Therefore, past diversification can probably be directly attributed to temporary extinctions of this habitat in certain coastal regions. The presumed center of origin and diversification of Brinckia is on the Gariep Karoo coastline between Port Nolloth and Lüderitz. Our molecular phylogenetic analysis suggests that the first split within Brinckia occurred ∼2.3 Ma, i.e., relatively recently, and may be associated with aridification that occurred at that time due to global climate change. However, subsequent speciation is more likely the result of the emergence of extensive dune fields, which may have been responsible for temporary habitat degradation in the supralittoral zone. More recent, recurrent and ongoing diversification since the mid-Pleistocene transition, as observed for tenebrionids along the coast of the Atacama and Peruvian deserts, is not typical of Brinckia and supports the stability of their coastal habitat despite glacial climate oscillations. [Display omitted] • Brinckia is adapted and restricted to beach hummocks along the Namib coastline. • The supposed center of origin and diversification is in the Gariep Karoo. • The first split 2.3 Ma might be related to aridification due to global climate change. • Further splits could be related to local habitat degradation from shifting sand dunes. [ABSTRACT FROM AUTHOR]

The Indian summer monsoon (ISM) is a significant component of global climate and plays a key role in transporting heat and moisture from tropical oceans to the Indian subcontinent. The ISM has a critical role in ecosystem functioning as well as the development of regional agriculture and societies. However, it is difficult to ascertain the extent to which these two drivers interact and impact regional biogeochemistry from contemporary process studies because of the widespread human footprint, and millennial-scale ISM dynamics remain poorly understood over the last 20,000 years. Here we used high-resolution diatoms from alpine lakes at different elevations in the southwest monsoon region to reconstruct summer temperature and environmental variability since the Last Glacial Maximum (LGM). By comparing with other proxy-based temperature reconstructions of the Tibetan Plateau and the monsoon proxy records from South Asia, we found a 3–6 °C warming trend and ISM strengthening since the LGM. Our results indicate that summer temperature began to increase since 17.5 cal. kyr BP, marking the onset of deglacial warming. During the early to middle Holocene, the climate clearly warmed and then decreased afterward. The maximum warm interval occurred during the mid-Holocene, which followed changes in Northern Hemisphere summer insolation. Additionally, examinations of fossil diatom assemblages revealed that changes in compositions were closely linked with global and Indian monsoon climate changes on glacial and interglacial time scales. The abrupt temperature increases from extreme cold to warm transition during the Late-glacial/Holocene boundary (∼3 °C) are strongly associated with regional replacement of major biotic species compositions. The presence of biotic transition and the increased rate of temperature increase during the Late-glacial/Holocene transition confirm the importance of climate change in restructuring biological communities. This suggests that biotic structures necessary to survive such rapid climate regime were susceptible to impacts of the speed and magnitude of temperature change in monsoon region. • Composite mean July temperature inferred by diatoms from multiple lakes and comparison with palaeoclimatic bio-proxies. • Quantitative estimates show a regionally coherent Holocene maximum warmth over the southeastern Tibetan Plateau. • Temperature increases by ca. 1.5–3.4 °C since the Holocene represent a first threshold in ecosystem responses to climate warming [ABSTRACT FROM AUTHOR]

Southern Africa's Greater Cape Floristic Region (GCFR) – a hotspot of biological diversity and palaeo-anthropological evidence for modern human evolution – is a climatically complex region where broad climatic gradients influence the relative importance of plant photosynthetic types in local vegetation. This mix of photosynthetic pathways imprint an isotopic signature on palaeo-records, thereby allowing for the reconstruction of historical climate and vegetation. Here, we use vegetation plot data, coupled with the photosynthetic-type affinities of plant genera, to relate their relative cover to bioclimatic drivers and use these to create spatial distribution models of C 3 and C 4 grasses and CAM shrubs across the contemporary GCFR. We then use palaeodistribution modelling, drawing on downscaled climate models for the Last Glacial Maximum (LGM), to hindcast the LGM distributions of photosynthetic types for the GCFR and its then-exposed offshore areas. In addition, we construct a model to account for the effect of lower atmospheric CO 2 concentration ([CO 2 ]) during the LGM on the competitive interactions between C 3 and C 4 grasses and use this model to hindcast relative C 4 -grass cover across the glacial-era GCFR. Our palaeodistribution models suggest that, even though there were some reductions in CAM cover and shifts in C 3 -/C 4 -dominated grass layers between the LGM and Holocene, these were mostly localised, with changes at the regional scale being relatively muted. For C 3 /C 4 grasses, distributional shifts were even more subtle once sub-ambient glacial [CO 2 ] was accounted for. Our hindcasts of glacial, [CO 2 ]-adjusted grass cover show agreements and inconsistencies with various sedimentary and herbivore-diet records in the palaeo-archive: both lines of evidence suggest the dominance of C 3 species in the strongly winter-rainfall western GCFR; in the eastern GCFR, with muted rainfall seasonality, hindcasts of relative C 3 :C 4 cover and δ13C signals from palaeo-records vary, with greater disparities between them. The lack of significant upheavals in the distribution of photosynthetic types suggests that the GCFR presented a relatively stable and dependable resourcescape for hunter-gatherer populations through the glacial–interglacial cycle of the LGM–Holocene transition. Our maps of relative C 3 -/C 4 -grass and CAM-shrub cover provide a reasonable surrogate for relative biomass of different photosynthetic types in local vegetation at a landscape scale and depict an independent estimate of carbon isoscapes across the GCFR – under both an interglacial (Holocene) and glacial (terminal Pleistocene) climate – against which palaeo-records can be assessed. • Spatial models of relative cover of CAM shrubs and C 3 /C 4 grasses under current and LGM climates • Spatial model of relative C 4 -grass cover under LGM climate and atmospheric CO 2 concentration ([CO 2 ]) • Muted changes in distribution of photosynthetic types through LGM–Holocene transition • Distributional shifts for C 4 grasses more subtle when sub-ambient glacial [CO 2 ] is accounted for • Maps of CAM-shrub and C 3 -/C 4 -grass cover can be used to assess palaeo-records of carbon isoscapes [ABSTRACT FROM AUTHOR]

In addressing the controversial issues of the Late Pleistocene paleogeography of the Caspian basin, an important role is given to the results of the spore-pollen analysis and based on them reconstructions of climate and vegetation changes in the Northern Caspian region during the development of the Early Khvalynian transgression. In this paper we present the main results of the palynological study of deposits (chocolate clays and the overlying and underlying layers from the Srednyaya Akhtuba section) of maximum stage of the Early Khvalynian transgression; the materials are illustrated by pollen diagram with the data of spore-pollen analysis and the detailed list of palynoflora recovered from the studied Lower Khvalynian sequences, and complemented with photographs of pollen belonging to the principal autochtonous taxa and, for comparison, to some redeposited palynomorphs. Palynological materials indicate subaqual (brackish marine and freshwater) sedimentation of the sediments studied in periglacial landscapes and, for the most part, under very harsh climatic conditions. The performed climate-stratigraphic reconstructions do not contradict the data of absolute dating on the accumulation of the studied deposits during the Late Valdai (Ostashkov) late Glacial period. During this interval in the territory of the study area, plant communities of the glacial climate — tundra-steppe, periglacial forest-steppe, periglacial steppe, periglacial parklands and periglacial forests — were developed. The widespread occurrence in the composition of the periglacial vegetation cover of the studied region of the yernik formations from Betula nana and shrub communities from Betula fruticosa , B. nana , Alnaster fruticosus , Juniperus , etc. testifies to the severe climatic conditions and, possibly, the existence of sporadic permafrost in the cold stages (stadials) of the Ostashkov Late Glacial period. [ABSTRACT FROM AUTHOR]

Pollen analysis of pond and spring deposits at the Aubrey Clovis site in North Texas provides a 1300-year record of late glacial grassland vegetation from 17,200 to 15,900 cal years BP. Forty-six pollen taxa are identified in the well-preserved assemblages. The late glacial pollen record at the Aubrey site represents three environments: upland, riparian, and lacustrine-wetland. The pond-related sediments are dominated by 80% Poaceae pollen, an unusually high amount in pollen records; the spring tufa sediments are dominated by Cyperaceae. Cattail (Typha latifolia) and other wetland plants, including green algae Botryococcus, Pediastrum , and Chara were present. The riparian habitat of the wide late glacial alluvial valley had alder (Alnus), willow (Salix), cottonwood (Populus), and water elm (Planera aquatica). The upland vegetation was a treeless grassland with comparatively high amounts of Asteraceae-type pollen; it is therefore called the aster prairie. Quercus, Juniperus , Carya , Ulmus , Ambrosia , and Chenopodiaceae pollen are much less abundant than found in modern grassland pollen records. Small amounts of Artemisia , Pinus , and Picea pollen are present, a consequence of long-distance transport. Regional late glacial cool-wet climate produced moist prairie soils. The Cross Timbers oak forest that occurs near the site today had not yet formed. Dissimilarity analysis of the pollen data shows that the late glacial aster prairie has no analog with modern shortgrass, mixed-grass, or tallgrass prairies. In contrast, a favorable analog exists with fossil pollen data from a lower zone at Patschke Bog, central Texas, and Muscotah Marsh, northeastern Kansas, indicating that a grassland characterized by high amounts of Asteraceae pollen formed a unique late glacial vegetation type in the region, earlier in Texas and later in Kansas. Because of its chronology and location in the eastern Great Plains, the late glacial aster prairie may be ancestral to the modern tallgrass prairie. • The late glacial aster prairie has no analog with modern tallgrass, mixed-grass, or short grass prairies. • The treeless condition of the aster prairie is supported by the absence of bark beetles and other tree-dwelling insects. • The late glacial climate was cooler than today, based on associated insects and mollusks. [ABSTRACT FROM AUTHOR]

High latitude deep water upwelling has the potential to control global climate over glacial timescales through the biological pump and ocean-atmosphere CO 2 exchange. However, there is currently a lack of continuous long nutrient upwelling records with which to assess this mechanism. Here we present geochemical proxy records for nutrient upwelling and glacial North Pacific Intermediate Water (GNPIW) formation in the Bering Sea over the past 850 kyr, which demonstrates that glacial periods were characterised by reduced nutrient upwelling, when global atmospheric CO 2 and temperature were also lowered. We suggest that glacial expansion of sea ice in the Bering Sea, and the simultaneous expansion of low nutrient GNPIW, inhibited vertical mixing and nutrient supply across the subarctic Pacific Ocean. Our findings lend support to the suggestion that high latitude sea ice and the resultant intermediate water formation, modulated deep water upwelling and ocean-atmosphere CO 2 exchange on glacial-interglacial timescales. • Increased Bering Sea sea ice caused expansion of intermediate water in glacials. • Intermediate water expansion inhibited deep water nutrient supply to surface waters. • Region contributed to global ocean-air CO 2 exchange on glacial timescales. • Tight correlation between subarctic nutrient upwelling and global CO 2. [ABSTRACT FROM AUTHOR]

Differentiating thermokarst basin sediments with respect to the involved processes and environmental conditions is an important tool to understand permafrost landscape dynamics and scenarios and future trajectories in a warming Arctic and Subarctic. Thermokarst basin deposits have complex sedimentary structures due to the variability of Yedoma source sediments, reworking during the Late Glacial to Holocene climate changes, and different stages of thermokarst history. Here we reconstruct the dynamic growth of thermokarst lakes and basins and related changes of depositional conditions preserved in sediment sequences using a combination of biogeochemical data and robust grain-size endmember analysis (rEMMA). This multi-proxy approach is used on 10 sediment cores (each 300–400 cm deep) from two key thermokarst sites to distinguish four time slices that describe the Holocene thermokarst (lake) basin evolution in Central Yakutia (CY). Biogeochemical proxies and rEMMA reveal fine-grained sedimentation with rather high lake levels and/or reducing conditions, and coarse-grained sedimentation with rather shallow lake levels and/or oxidizing (i.e. terrestrial) conditions in relation to distal and proximal depositional and post-sedimentary conditions. Statistical analysis suggests that the biogeochemical parameters are almost independent of thermokarst deposit sedimentology. Thus, the biogeochemical parameters are considered as signals of secondary (post-sedimentary) reworking. The rEMMA results are clearly reflecting grain-size variations and depositional conditions. This indicates small-scale varying depositional environments, frequently changing lake levels, and predominantly lateral expansion at the edges of rapidly growing small thermokarst lakes and basins. These small bodies finally coalesced, forming the large thermokarst basins we see today in CY. Considering previous paleoenvironmental reconstructions in Siberia, we show the initiation of thaw and subsidence during the Late Glacial to Holocene transition between about 11 and 9 cal kyrs BP, intensive and extensive thermokarst activity for the Holocene Thermal Maximum (HTM) at about 7 to 5 cal kyrs BP, severely fluctuating water levels and further lateral basin growth between 3.5 cal kyrs BP and 1.5 cal kyrs BP, and the cessation of thermokarst activity and extensive frost-induced processes (i.e. permafrost aggradation) after about 1.5 cal kyrs BP. However, gradual permafrost warming over recent decades, in addition to human impacts, has led to renewed high rates of subsidence and abrupt, rapid CY thermokarst processes. • Small thermokarst lakes and basins grew rapidly during the Holocene Thermal Maximum. • Short-term phases of forcing climate lead to very active thermokarst processes. • Endmember analysis reveals different depositional environments in growing lakes. • Distal and proximal depositional and post-sedimentary conditions are differentiated. • Sedimentological and biogeochemical characteristics are weakly correlated. [ABSTRACT FROM AUTHOR]

The age model of the western Bering Sea core 85 KL was modified through correlation of new and earlier-measured productivity proxies with the Chinese interstadials described by δ18O records of Hulu and Sanbao caves and the relative paleointensity events in the studied core with those in the dated records. Resulted sequence of millennial scale Bering Sea Interstadials recorded by abrupt productivity risings was established during the penultimate glacial consistently with the Chinese interstadials and Antarctica isotope maxima. The pattern of the frequency and amplitude of the millennial productivity/climate variability in the Bering Sea during the penultimate glacial resembles that initially depicted in the δ18O of Chinese cave stalagmites and is quite similar to one of the Dansgaard–Oeschger cycles during last glacial, except for their terminations. Contrary to well-pronounced interstadial A.1 during termination TI, an interstadial B.1 over the TII has lower duration and therefore is weakly observed in Antarctic temperature changes. Our results provide robust evidence that the bipolar seesaw mechanisms of millennial climate changes in the Northern and Southern Hemispheres were similar during the last and penultimate glacials. [ABSTRACT FROM AUTHOR]

The present-day ocean ventilation in the Arctic Mediterranean (Nordic Seas and Arctic Ocean), via transformation of northward inflowing warm Atlantic surface water into cold deep water, affects regional climate, atmospheric circulation and carbon storage in the deep ocean. Here we study the glacial evolution of the Arctic Mediterranean circulation and its influence on glacial climate using radiocarbon reservoir-age reconstructions on deep-sea cores from the Fram Strait that cover the late glacial period (33,000–20,000 yr ago; 33–20 ka). Our results show high Benthic-Planktic 14C age differences of ∼1500 14C years 33–26.5 ka suggesting significant water column stratification between ∼100–2600 m water depth, and reduction and/or shoaling of deep-water formation. This phase was followed by break-up of the stratification during the Last Glacial Maximum (LGM; 26–20 ka), with Benthic-Planktic 14C age differences of ∼250 14C years, likely due to enhanced upwelling. These ocean circulation changes potentially contributed to the final intensification phase of glaciation via positive cryosphere-atmosphere-ocean circulation-carbon cycle feedbacks. Our data also do not support 'extreme aging' of >6000 14C years in the deep Arctic Mediterranean, and appear to rule out the proposed outflow of very old Arctic Ocean water to the Nordic Seas during the LGM and to the subpolar North Atlantic Ocean during the deglacial period. • Strong ocean stratification in the Fram Strait during the late glacial (33–26 ka). • Breakup of ocean stratification during the LGM (26–20 ka) due to enhanced upwelling. • No extreme aging of >6000 yr in the Arctic Mediterranean as previously suggested. [ABSTRACT FROM AUTHOR]

• The glacier area retreat rate in the Chinese Altay Mountains is 0.55% a-1 during 1990–2021. • Glaciers in the Chinese Altay Mountains experienced a more intense retreat in 2000-2009. • Solar radiation and summer temperature have important effects on glacier retreat. Melting glaciers have changed the spatial–temporal distribution of water resources in inland river basins and are one of the important inducements of extreme hydrological events. Most previous studies on glacier changes in the Chinese Altay Mountains have focused on the period 1960–2011; however, there is a lack of glacier data reflecting recent changes (1990–2021) over the past decades, and the response of glaciers to regional climate change is still unclear. In this study, Landsat images and the Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) were used to map glacier outlines from 1990 to 2021 for the whole region and its surrounding areas, and the impacts of temperature, precipitation, and solar radiation variation on glacier retreat were investigated. The results indicate that (1) the glacier area retreat rate of 0.55 %∙a-1 in the Chinese Altay Mountains during 1990–2021 is obviously lower than the glacier area shrinkage rate of 0.75 %∙a-1 from 1960 to 2009, and the retreat rate of glacier volume is 0.60 %∙a-1. (2) More than 80 % of the total glacier area located at elevation ranged from 2600 to 3400 m, and the greatest glacier area loss occurred within the elevation range of 2800–3000 m. Although the glacier area was retreating in all orientations, the south-facing glacier has the largest retreat rate. (3) The rate of change of glacier area was −1.26 %∙a-1, −0.71 %∙a-1 and −0.51 %∙a-1 in the Haba sub-basin, Sawir Mountains region, and Burqin sub-basin, respectively. (4) Owing to the slowdown in the warming rate since 1990, the glacier shrinkage rate was moderate during 1990–2021 compared to the 1960 s–1980 s, and contribution of the increase of solar radiation (35.72 %) and summer temperature (25.3 %) to glacier retreat from 1990 to 2021 were more prominent than other climate factors. [ABSTRACT FROM AUTHOR]

• A multi-biomarker record from Lake Elsinore, CA sediment core spans 32–9 ka. • Deglacial warming and storm-track shifts are consistent with prior studies nearby. • Plant wax hydrogen isotopes indicate storm-track changes during the last glacial. • Lipids show temperatures varied during the last glacial, including extreme warmth. Reconstructions of past hydroclimate provide a means to understand precipitation responses to global ocean-atmosphere climate dynamics beyond the scope of that in the instrumental record. Late glacial climate was characterized by abrupt variability in ice and ocean dynamics, however the implications for hydroclimate are not as well known. Here we present organic geochemical proxy evidence for precipitation isotopes based on plant leaf wax hydrogen isotopic compositions (δ D wax) and temperature proxy evidence based upon the branched glycerol dialkyl glycerol tetraethers (brGDGTs), that derive from the membrane lipids of bacteria, each extracted from a sedimentary archive in Lake Elsinore, California spanning 32–9 ka. We add proxy evidence for vegetation and salinity from additional biomarker analyses and compare to prior pollen and sedimentological evidence from the same core. Our record indicates a strong deglacial warming of 10 °C in Lake Elsinore (beginning at 14.5 ka) that accompanied a D-enrichment of precipitation of +90‰ and more C 4 vegetation (12–10 ka), after a cold, wet and C 3 -dominated phase (20–14.5 ka), indicating winter-dominated precipitation during the Last Glacial Maximum and Heinrich Stadial 1. During the late glacial (32–20 ka) we find abrupt variability, with precipitation isotopic shifts (∼70‰) that are independent of temperature swings implicating changes in storm track, rather than local temperature as drivers of the precipitation isotope signal. Temperature is however not irrelevant for hydroclimate: we find extreme warmth at 29.4 ka and 26.8 ka, the latter coincident with existing reports of an extended dry period (27.5–25.5 ka), suggesting a long hot and dry interlude during the generally cooler glacial period. We compare δ D wax with speleothem δ 18 O from Nevada, also within the winter-dominated precipitation region. Our results corroborate the Last Glacial Maximum and deglacial signals, and fill gaps revealing storm-track instability from 32–20 ka, however the pacing and magnitude of the biomarker signals merit cautious interpretation. [ABSTRACT FROM AUTHOR]

Here we summarize the motivation and issues surrounding the responses of ice sheets and sea level to past climate warming as part of the PALeo constraints on SEA level rise (PALSEA) working group. Papers in this special issue of Quaternary Science Reviews focus on the timescale of glaciations during the late Pliocene, the magnitude of ice-sheet fluctuations and volume leading up to and during the last glacial maximum, the timing and persistence of ice-sheet impacts on deglacial and future relative sea-level change, and relative sea-level change during peak interglacial climate. A more dynamic cryosphere is noted under both late Pliocene and last glacial cycle climate conditions, while relative sea-level changes during the last deglaciation appear to correspond closely with individual ice-sheet deglaciation. Lastly, relative sea-level change during peak interglacial conditions may have fluctuated by as much as a meter, although the sources of such variability (Greenland, Antarctica or elsewhere) remain elusive. [ABSTRACT FROM AUTHOR]

Abstract Knowledge of changes in the distribution of C 3 and C 4 plants in relation to climate change is the key to predicting the biosphere's response to future climatic warming. There are significant differences in the spatiotemporal evolution of C 4 plant abundance at different latitudes since the Last Glacial Maximum (LGM), and the factors responsible remain debated. In this study, we reconstructed the spatiotemporal pattern of C 4 plants in China since the LGM, based on a synthesis of δ13C records of soil organic matter from paleosol sequences and δ13C records of individual n-alkanes from lake and marine sediments. The results indicate that, spatially, maximum C 4 abundance during the LGM was in South China; while maximum C 4 abundance occurred in the Chinese Loess Plateau in North China during the early and mid-Holocene. Temporally, in North China, C 4 plant abundance initially increased since the LGM, reached a maximum during the early and mid-Holocene and then decreased; however, the opposite trend occurred in South China. Combined with a physiological-process model used to study the sensitivity of C 3 and C 4 plants to changes in climate and atmospheric p CO 2 in different regions, our results reveal that temperature was the dominant factor driving C 4 plant expansion in North China, whereas atmospheric p CO 2 and precipitation were the main factors controlling C 4 plant abundance in South China. Highlights • Spatiotemporal pattern of C 4 plant abundance across China since the LGM was reconstructed. • Increase in C 4 abundance in mid-latitude China was triggered by increased temperature. • Decrease in C 4 abundance in low-latitude China was a response to increasing atmospheric p CO 2 and precipitation. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The low sea level and the strong EAWM lead to the higher n -alkanes input. • Moisture was a key factor for controlling the composition of C 3 /C 4 plants. • The drier condition was recorded by n -alkanes in the northern SCS during H1 event. Abstract Variations in n -alkanes proxies (L/H, C 31 /C 27 and ACL), molecular abundances of n -alkanes and stable carbon isotopic compositions of n -alkanes (δ13C alk) from the core STD235 (20°21.15′N, 118°22.56′E) have been used to trace characterize the climatic changes that occurred in the northern South China Sea (SCS) during the last glacial period. The ratio of low to high molecular-weight n -alkanes (L/H) and the concentration of n -alkanes indicated that organic matters in the sediments were derived from the mixture of both marine and terrestrial sources, but dominated by marine autochthonous input over the past 20 ka. Total n -alkanes were higher during the last glacial stage relative to the interglacial stage, implying the low sea level and the strengthened East Asian winter monsoon (EAWM) during the glacial time. The δ13C alk data indicated that the terrestrial plants on the adjacent continent of the present study area were dominated by C 3 plants during the Holocene and experienced the expansion of C 4 plants during the last glacial period. This similar result can be proved by the chain length parameter of n -alkanes (C 31 /C 27 , ACL) and the content of the herb pollen. In addition, n -alkanes distributions and C 4 vegetation proportion calculated by δ13C of long-chain n -alkanes in the core STD235 recorded a short arid duration paralleled by the Heinrich event 1. Thereby we deduced that the occurrence of the dry event and the variation of regional vegetation community at the adjacent lands of the northern SCS were likely under the influence of the climate change emanated from the boreal high-latitudes. [ABSTRACT FROM AUTHOR]

Abstract The Pamir Mountains include peaks exceeding 7000 m, such as Lenin Peak (7134 m) in the northern Zaalai Range. Here, we examine the distribution of soils and geomorphological processes and landforms in its northern slope, from the highest glaciated environments until Alai valley floor. We present the first geomorphological map of the study area as well as an accurate description the main geomorphological units in order to reconstruct landscape dynamics in the area from Quaternary cold stages until present-day. Five main units are distributed: (1) valley floor (2900–3040 m), an area that must have been ice-free during Quaternary glaciations and is currently being reshaped by glaciofluvial processes, with a large alluvial fan reworked by aeolian activity; (2) hummocky terrain (3040–3500 m) including two moraine systems left by a piedmont glacier during the Last Glaciation as well as hilly deposits originated by a catastrophic rockfall event; (3) U-shaped glacial valley (3500–3800 m), including some moraine ridges as well as a sedimentary cover composed of glacial till that is being eroded by fluvial and mass-wasting processes; (4) high mountain valleys (up to 4600–4800 m) adjacent to the main valley floor with small cirque and alpine glaciers and widespread periglacial processes in ice-free environments; (5) glaciers flowing from the Lenin Peak summit until the foot of the mountain, where they form a debris-covered (surge-type) glacier. The existence of abundant glacial, periglacial and rockfall deposits (moraines, till, erratic boulders) allows inferring five different environmental stages since the Last Glaciation. The latest glacial advances took place during the 20th century and the Little Ice Age and deposited two moraine systems near the glacial front. The occurrence of active rock glaciers and protalus lobes indicates that the limit of permafrost conditions is now located at 3400–3500 m, with seasonal frozen ground in lower areas. Graphical abstract Unlabelled Image Highlights • We examine landscape dynamics in the northern Lenin Peak area, Kyrgyzstan. • There is a wide range of glacial and periglacial processes and landforms. • Permafrost is widespread at 3400–3500 m, with seasonal frozen ground in lower areas. • Geomorphic evidence suggests several glacial stages since the Last Glaciation. [ABSTRACT FROM AUTHOR]

Abstract In the last 10 Ma, the northwest Barents Sea passive margin and Svalbard archipelago experienced tectonic reactivation including regional uplift, volcanism and fault movements. Previous studies have variously attributed this reactivation to the establishment of continuous seafloor spreading between the North Atlantic and Arctic oceans within the Fram Strait, mantle convection, or a lithospheric response to climate-driven processes such as fluvial and glacial erosion in a late Pliocene-Pleistocene time (∼1-3 Ma). The relative magnitudes, and the physical relationship between surface processes, plate boundaries and mantle flow, has remained unclear. In this work, I jointy interpret seismological models of the upper mantle, gravity anomalies, rates of glacial isostatic adjustment (GIA) and the spatiotemporal characteristics of earthquakes with the aim to i) constrain the thermal state and rheological structure of the upper mantle beneath Svalbard, ii) infer the magnitude of vertical motion in the late Cenozoic time related to various processes, iii) better understand the likely causes of the tectonic and volcanic activity. Most part of the northwest Barents Sea passive margin including Svalbard is underlain by a thin continental lithosphere (∼50–80 km) and a normal thickness of crust (30–35 km). The geophysical data indicate an average excess mantle temperature of ∼40–100°C beneath western Svalbard compared to the central Barents Sea. The peak of the mantle temperature anomaly coincides with the location of Quaternary basalt eruptions. The predicted long-wavelength (>420 km) non-isostatic uplift of ∼600-800 m correlates with the distribution of pre-glacial uplift previously inferred from geological data in the northwest Barents Sea. The gravity anomalies within an intermediate range of wavelengths (30–420 km) allows me to estimate topography changes due to erosion by ice streams to be ∼200–500 m. I conclude that a transient temperature anomaly in the asthenosphere northeast of Jan Mayen, combined with the northwest absolute plate motion of Eurasia, is the likely primary cause of the late Cenozoic tectonic reactivation in Svalbard. [ABSTRACT FROM AUTHOR]

Abstract This study investigated the late Quaternary sedimentary evolution of the outer shelf of the East China Sea (ECS) using borehole core data (DH02). Three unconformity-bounded sedimentary facies, namely, prodelta facies of marine isotopic stage (MIS) 3, intertidal to subtidal flat facies of the deglacial period, and offshore tidal sand ridge facies of the Holocene, were identified from the base upward according to combined evidence of lithology, microfossil assemblages, and geochronology. Through comparative analysis with other neighboring borehole cores, these three facies, along with the MIS 3 nearshore facies and the last glacial maximum (LGM) river facies, were found to constitute the late Quaternary sediment strata. Sedimentary processes of these five facies were interpreted based on a synthetic consideration of sea-level change, climate variation, paleotopographic setting, and paleoriver-sea interactions. In particular, the development of the delta was attributable to integration of the slow sea-level decline during the later stage of the MIS 3 and abundant sediment supply resulting from the warm-wet climate. The gentle shelf topography suggests the presence of shallow and wide rivers in the delta, and the lateral shift of river channels might have induced the local formation of nearshore facies at the abandoned river mouth. The LGM river facies, which was rarely observed (presumably due to marine erosion with deglacial transgression), was inferred to have been deposited during the latter half of the LGM in response to the rise in river base level. Occurrences of tidal flat facies imply the formation of a tide-dominated estuary with the deglacial transgression. Furthermore, tidal flat sediments were reworked by enhanced tidal currents in the estuary front environment, forming mud ridges during subsequent deglacial transgression. Formation of tidal sand ridges in offshore environments of the Holocene was attributable to the uneven base caused by the underlying estuarine erosion mud ridges, and this promoted the occurrence of tidal depositional processes. The sedimentary evolution in association with sea-level change was constructed using the above-mentioned results. Overall, this study systematically elucidates the late Quaternary sedimentary processes and evolution of the outer ECS shelf, and provides an insight into the sedimentary development of analogous shelves around the world. [ABSTRACT FROM AUTHOR]

Abstract Twelve piston cores were used to characterize late Quaternary lithofacies, depositional processes and deglacial history along the Baffin Bay slope between Lancaster Sound and Home Bay. Core investigations show four distinct laterally correlatable lithofacies along the slope – basal and upper diamicton, laminated red brown mud, tan carbonate gravelly, sandy mud and bioturbated brown mud. Basal diamicton largely represents glacigenic debris flow deposits during a glacial advance from Baffin Island at ~25 cal ka. The distribution and character of laminated red brown mud suggests a lateral supply to Baffin Bay slope from ice-proximal meltwater plumes and turbidity currents sourced in glacial ice from both Baffin Bay shelf and Home Bay between 41.5 cal ka to ~14.2 cal ka. An upper diamicton records a lesser, localized glacial advance that ended at about 14.2 cal ka. Tan carbonate mud events represent ice-rafted, enhanced detrital carbonate delivery to the slope between ~25 cal ka and ~11 cal ka. A gradual thinning of these events, from northern to southern Baffin Bay, corroborates a northern Baffin Bay, Lancaster Sound or Nares Strait iceberg source. Proglacial facies seaward of Home Bay contain beds with slightly elevated detrital carbonate that may represent the distal edge of carbonate ice-rafted from Lancaster Sound. Baffin Bay is a type example of a polar glacial basin in which direct glacial supply predominates over the effects of glacial meltwater. As a result, axial supply from the large ice streams north of Baffin Bay (particularly Lancaster Sound) is dominant in the Baffin Bay basin and lateral supply from smaller ice streams on Baffin Island predominates on the NE Baffin Slope. Highlights • Four correlatable lithofacies characterize the late Quaternary NE Baffin slope. • Basal diamicton represents a Baffin Island glacial advance at ~25 cal ka. • Laminated red brown mud is point-sourced from ice streams on Baffin Island. • Tan carbonate mud is sourced from Lancaster Sound or Nares Strait. • Baffin slope lithofacies differ from Baffin basin except for tan carbonate mud. [ABSTRACT FROM AUTHOR]

Abstract We compare Ethiopian glaciogenic sandstone of the Late Ordovician and Carboniferous–Permian Gondwana glaciations petrographically and geochemically to provide insight into provenance, transport, and weathering characteristics. Although several studies deal with the glacial deposits in northern Africa and Arabia, the distribution of ice sheets and continent-wide glacier dynamics during the two glaciations remain unclear. Provenance data on Ethiopian Palaeozoic sedimentary rocks are scarce. The sandstones of the Late Ordovician glaciation are highly mature with an average quartz content of 95% and an average chemical index of alteration of 85, pointing to intense weathering and reworking prior to deposition. No evidence for sediment recycling was found. In contrast, the Carboniferous–Permian glaciogenic sandstones are less mature with an average quartz content of 75%, higher amounts of feldspar and rock fragments and a chemical index of alteration of 62. Trace and rare earth element concentrations indicate a higher input of juvenile material, most probably from proximal sources. Comparison with stratigraphically corresponding formations in Saudi Arabia shows similar geochemical patterns for the Upper Ordovician, but major differences in the Carboniferous–Permian. This supports previous assumptions of a large, uniform sediment dispersal system during the Late Ordovician glaciation, in which a combination of long transport paths and exceptionally strong weathering prior to the glaciation produced mature sandstone. During the Carboniferous–Permian, the glacial systems seem to have been more localised and glacial abrasion exposed fresh basement material. [ABSTRACT FROM AUTHOR]

Abstract We present the first quality-controlled relative sea-level (RSL) database for the Russian Arctic coast from the Barents Sea in the west to Laptev Sea in the east (29–152oE and 63 to 81oN). The database consists of 385 sea-level index points and 249 limiting dates and spans 24 ka to present. Sea-level indicators are derived from multiple proxies, including isolation basins, raised beaches, glacial erratics, marine terraces, laidas (salt marshes), and deltaic salt marshes. Here, we calculate the indicative meanings for all indicators and evaluated possible elevation errors. We have estimated the ages and uncertainties of index points and limiting dates using the most recent calibration datasets. In the western Russian Arctic (Barents and White Seas), RSL was driven by glacial isostatic adjustment (GIA) due to deglaciation of the Eurasian ice sheet complex. For example, within the Baltic crystalline shield, RSL fell rapidly from 80 to 100 m at 11–12 ka to 15–25 m at ∼4–5 ka. In the Arctic Islands of Franz-Joseph Land and Novaya Zemlya, RSL gradually fell from 25 to 35 m at 9 ka to 5–10 m at 3 ka. The Timan coast and the Kara Sea shelf are characterized by constant RSL rise due to proglacial forebulge collapse; Yamal and the Gydan Peninsula and Novaya Zemlya are all marked by a high LGM position of RSL, followed by a lowstand and consequent rise to a late Holocene highstand of several meters. Data from the Laptev Sea coasts and shelf and the New Siberian Islands demonstrate post-LGM RSL rise with a Holocene highstand of up to 5–10 m, with scatter caused by differential tectonic movements along a diffuse lithospheric plate boundary. The collected database allowed to estimate and discuss the reasons of both spatial and temporal variability of RSL histories in different parts of the Russian Arctic. Highlights • A database of post-glacial relative sea-level in the Russian Arctic was collected. • For the first time, both spatial and temporal uncertainties of RSL histories were estimated. • The main drivers of RSL variability were GIA, deglaciation patterns and vertical tectonic land motion. [ABSTRACT FROM AUTHOR]

Abstract Many studies of Holocene relative sea-level (RSL) changes across Antarctica assume that their reconstructions record uplift from glacial isostatic adjustment caused by the demise of the Last Glacial Maximum (LGM) ice sheets. However, recent analysis of GPS observations suggests that mantle viscosity beneath the Antarctic Peninsula is weaker than previously thought, which would imply that solid Earth motion is not controlled by post-LGM ice-sheet retreat but instead by late Holocene ice-mass changes. If this hypothesis is correct, one might expect to find Holocene RSL records that do not reflect a monotonic decrease in the rate of RSL fall but show variations in the rate of RSL change through the Holocene. We present a new record of late Holocene RSL change from Torgersen Island near Palmer Station in the western Antarctic Peninsula that shows an increase in the rate of relative sea-level fall from 3.0 ± 1.2 mm/yr to 5.1 ± 1.8 mm/yr during the late Holocene. Independent studies of the glacial history of the region provide evidence of ice-sheet changes over similar time scales that may be driving this change. When our RSL records are corrected for sea-surface height changes associated with glacial isostatic adjustment (GIA), the rate of post-0.79 ka land uplift at Torgersen Island, 5.3 ± 1.8 mm/yr, is much higher than the rate of uplift recorded at a nearby GPS site at Palmer Station prior to the Larsen B breakup in 2002 AD (1998-2002 AD; <0.1 mm/yr), but similar to the rates observed after 2002 AD (2002-2013 AD; 6–9 mm/yr). This substantial variation in uplift rates further supports the hypothesis that Holocene RSL rates of change are recording responses to late Holocene and recent changes in local ice loading rather than a post-LGM signal across portions of the Antarctic Peninsula. Thus middle-to-late Holocene RSL data may not be an effective tool for constraining the size of the LGM ice sheet across portions of the Antarctic Peninsula underlain by weaker mantle. In addition, current global-scale GIA models are unable to predict our observed changes in late Holocene RSL. Complexities in Earth structure and neoglacial history need to be taken into consideration in GIA models used for correcting modern satellite-based observations of ice-mass loss. [ABSTRACT FROM AUTHOR]

Abstract Millennial scale events marked by the contribution of detrital sand are recorded in North Atlantic sediments during the Last Glacial Maximum (LGM), between Heinrich events (HE) 1 and 2, and left their imprint on Laurentian Fan (LF – 43°N) sediments off eastern Canada. The LF counterpart of the well-known detrital events consist of glacial red-brick sediments resulting from subglacial flows separated by olive-grey sediments appears at ∼21.4–19.9 and ∼19.5–18.65 cal kyr BP. High-resolution analyses of diatom assemblages and lithic grains coupled with planktonic oxygen isotopic records reveal that while the red sediment is almost barren of diatoms, foraminifera and lithics (>150 μm), they are abundant in the olive-grey sediment. Diatom assemblages reveal three phases during these events: (1) initial relatively warm/temperate conditions followed by (2) very cold surface water and drifting ice, and (3) a final phase characterized by relatively warmer waters and the appearance of detrital carbonate. Although these events possibly reflect the variability specific to the slope water region, they are likely the response to Atlantic Meridional Overturning Circulation perturbations and ice-sheet instability. Through a chain of mechanisms, meltwater inputs into the North Atlantic led ultimately to an increased volume of tropical waters and part of the heat stored in the subsurface was flushed by a brief convective episode that was not sustained, accounting for the return of cold conditions after the events. The sequence of mechanisms deduced from the paleo data here and elsewhere is consistent with previous modeling results. These data suggest that the detrital events between Heinrich event 1 and 2 may be synchronous across the North Atlantic, and that the LGM was probably not a time of prolonged steady state in the climate system. Highlights • Detailed description oceanographic changes of some LGM detrital events. • Diatom records evidence the presence of relatively warmer waters at the beginning and by the end of the events. • Possible links between detrital events, ice-sheets instability and AMOC perturbations. [ABSTRACT FROM AUTHOR]

Abstract Glacial deposits on the high-altitude, arid southern Central Andean Plateau (CAP), the Puna in northwestern Argentina, document past changes in climate, but the associated geomorphic features have rarely been directly dated. This study provides direct age control of glacial moraine deposits from the central Puna (24°S) at elevations of 3900–5000 m through surface exposure dating with cosmogenic nuclides. Our results show that the most extensive glaciations occurred before 95 ka and an additional major advance occurred between 46 and 39 ka. The latter period is synchronous with the highest lake levels in the nearby Pozuelos basin and the Minchin (Inca Huasi) wet phase on the Altiplano in the northern CAP. None of the dated moraines produced boulder ages corresponding to the Tauca wet phase (24–15 ka). Additionally, the volcanic lithologies of the deposits allow us to establish production ratios at low latitude and high elevation for five different nuclide and mineral systems: 10Be, 21Ne, and 26Al from quartz (11 or 12 samples) and 3He and 21Ne from pyroxene (10 samples). We present production ratios for all combinations of the measured nuclides and cross-calibrated production rates for 21Ne in pyroxene and quartz for the high, (sub-)tropical Andes. The production rates are based on our 10Be-normalized production ratios and a weighted mean of reference 10Be production rates calibrated in the high, tropical Andes (4.02 ± 0.12 at g−1 yr−1). These are, 21Ne qtz : 18.1 ± 1.2 at g−1 yr−1 and 21Ne px : 36.6 ± 1.8 at g−1 yr−1 (En 88 – 94) scaled to sea level and high latitude using the Lal/Stone scheme, with 1 σ uncertainties. As 3He and 26Al have been directly calibrated in the tropical Andes, we recommend using those rates. Finally, we compare exposure ages calculated using all measured cosmogenic nuclides from each sample, including 11 feldspar samples measured for 36Cl, and a suite of previously published production rates. Highlights • The most extensive glaciations in the southern Central Andean Plateau predate 95 ka. • Another glacial advance occurred between 46 and 39 ka during the Minchin wet phase. • None of the dated moraines produced boulder ages corresponding to the Tauca wet phase (24–15 ka). • Production rates were cross-calibrated for five different nuclide/mineral pairs. • Exposure ages from six nuclide/mineral pairs from the same samples were compared. [ABSTRACT FROM AUTHOR]

Abstract Geomorphological mapping is a well-established method for examining earth surface processes and landscape evolution in a range of environmental contexts. In glacial research, it provides crucial data for a wide range of process-oriented studies and palaeoglaciological reconstructions; in the latter case providing an essential geomorphological framework for establishing glacial chronologies. In recent decades, there have been significant developments in remote sensing and Geographical Information Systems (GIS), with a plethora of high-quality remotely-sensed datasets now (often freely) available. Most recently, the emergence of unmanned aerial vehicle (UAV) technology has allowed sub-decimetre scale aerial images and Digital Elevation Models (DEMs) to be obtained. Traditional field mapping methods still have an important role in glacial geomorphology, particularly in cirque glacier, valley glacier and icefield/ice-cap outlet settings. Field mapping is also used in ice sheet settings, but often takes the form of necessarily highly-selective ground-truthing of remote mapping. Given the increasing abundance of datasets and methods available for mapping, effective approaches are necessary to enable assimilation of data and ensure robustness. This paper provides a review and assessment of the various glacial geomorphological methods and datasets currently available, with a focus on their applicability in particular glacial settings. We distinguish two overarching 'work streams' that recognise the different approaches typically used in mapping landforms produced by ice masses of different sizes: (i) mapping of ice sheet geomorphological imprints using a combined remote sensing approach, with some field checking (where feasible); and (ii) mapping of alpine and plateau-style ice mass (cirque glacier, valley glacier, icefield and ice-cap) geomorphological imprints using remote sensing and considerable field mapping. Key challenges to accurate and robust geomorphological mapping are highlighted, often necessitating compromises and pragmatic solutions. The importance of combining multiple datasets and/or mapping approaches is emphasised, akin to multi-proxy approaches used in many Earth Science disciplines. Based on our review, we provide idealised frameworks and general recommendations to ensure best practice in future studies and aid in accuracy assessment, comparison, and integration of geomorphological data. These will be of particular value where geomorphological data are incorporated in large compilations and subsequently used for palaeoglaciological reconstructions. Finally, we stress that robust interpretations of glacial landforms and landscapes invariably requires additional chronological and/or sedimentological evidence, and that such data should ideally be collected as part of a holistic assessment of the overall glacier system. [ABSTRACT FROM AUTHOR]

In order to better explore quantitative reconstructions of net primary productivity (NPP) conditions using a dinoflagellate cyst (dinocyst)-based transfer function method, we revised the tropical Atlantic modern dinocyst database n  = 208 (Marret et al., 2008). Modern assemblages from the worldwide dinocyst atlas (Zonneveld et al., 2013) were added to provide a better geographical coverage of the South Atlantic Ocean. The environmental dataset was updated using the World Ocean Atlas 2013 for sea-surface temperature (SST) and sea-surface salinity (SSS) data, as well as for 1997–2017 mean NPP values recorded during SeaWifs and MODIS spatial programs. New environmental datasets were tested using anomalies regarding mean latitudinal SST as a potential index to track past upwelling activity. Finally, preindustrial NPP values, simulated with the IPSL-CM5A-LR model developed at the Institut Pierre Simon Laplace (IPSL) have been added to the dinocyst environmental database to provide NPP values consistent with the mean age of “modern” dinocyst assemblages. The transfer function method using the updated modern database was then applied to fossil dinocyst assemblages of core KZAI-01, retrieved off the Congo River mouth and covering the last 43.2 kyr. Our results indicate a dominant orbital forcing, with higher primary productivity values reconstructed during precession minima (MIS 3 and the last deglaciation) and enhanced by a maximum of obliquity during the last deglaciation and the Holocene. The synchronicity between high upwelling intensity and high terrigenous inputs during high NPP period (e.g. during the last Deglaciation) highlighted the prevalent role of river-induced upwelling activity, which is specific to the Congo River. These results have improved our understanding of the environmental forcing leading to major trophic changes in the intertropical area. [ABSTRACT FROM AUTHOR]

The complex geomorphic and sedimentary evolution of the central Po Plain (northern Italy) during the last 30 ky was reconstructed through the integration of stratigraphic, geomorphological, geochemical and radiocarbon data. A key element of the Late Pleistocene stratigraphy is a 20 km-wide channel-belt sand body, with its top at a depth of ~13 m, fed by the Po River. Whereas the southern boundary of the Po fluvial channel belt coincides with a sharp lithological contact with floodplain muds, its northern boundary is an erosional (sand-on-sand) surface that was traced tentatively in the subsurface with the aid of sediment provenance (Po versus Alpine) proxies and radiocarbon data. Stratigraphic and geomorphological features testify to a decoupled sedimentary and geomorphic response of the Alpine and Po River systems to climate change in the last 30 ky. Contemporaneous Po River incision and Alpine rivers aggradation occurred at the onset of the Last Glacial Maximum (LGM). In contrast, Po River aggradation and Alpine rivers entrenchment took place during early deglaciation. The Holocene stratigraphy records the overall aggradation and northward migration of the Po River, with the consequent erosion of distal Alpine LGM deposits and formation of a fluvial scarp parallel to the Po River course. Late Pleistocene and Holocene climate change influenced river dynamics controlling (i) the balance between sediment supply and water discharge, through glacier and vegetation dynamics, and (ii) the rate of sea-level fall/rise. Apennine, Alpine and Po river systems responded in distinct ways to climate forcing due to the influence of local factors. Lithology, drainage area and mean elevation of river catchments, as well as river and valley gradients, determined the type of sedimentary response (e.g., aggradation versus degradation). This study shows that a combined geomorphic and stratigraphic approach focusing on the geometric relations between exposed and buried features can provide valuable information about the evolution of a fluvial system and its controlling factors. [ABSTRACT FROM AUTHOR]

The last deglacial was marked by tremendous changes in ocean temperature and circulation as well as atmospheric CO 2 and 14 C. We employed the “ 14 C plateau-tuning technique” to a centennial-scale planktic 14 C record of core MD08-3180 retrieved S.W. of the Azores Islands at ∼3060 m water depth to establish both a new standard of absolute age control and a record of past 14 C reservoir ages of ocean surface waters. Both δ 18 O minima of G. bulloides and high planktic reservoir ages of ∼1600 to 2170 yr suggest two major melt water incursions that reached from the Labrador Sea up to the subtropics over Heinrich Stadial 1 (HS-1). In parallel, we established a record of (apparent) benthic ventilation ages that add the planktic 14 C reservoir ages together with the benthic-planktic 14 C age difference at the site and time of deposition, a sum finally adjusted to past changes in atmospheric 14 C that occurred since the time of deep-water formation. Near the Azores apparent deep-water ages of the Last Glacial Maximum were as low as 340–740 yr, which suggests a lateral advection of young North Atlantic Deep Waters (NADW) from subpolar regions south of Iceland, in harmony with recent model simulation and in contrast to a widely assumed major shoaling of glacial deep-water formation. During HS-1, local benthic ventilation ages increased up to 2200–2550 yr, thus suggest an incursion of old southern-source deep waters, an unstable regime that was interrupted by brief pulses of NADW incursion near 16, 15.6 cal. ka, and most salient, near 14.9/14.7 ka. [ABSTRACT FROM AUTHOR]

Abstract The modern southern Mariana Trench is characterized by oligotrophic surface waters, resulting in low primary productivity and well-oxygenated bottom waters. This study investigates changes in the redox conditions of bottom waters in the southern Mariana Trench during the Last Glacial Maximum (LGM) and their potential causes. We measured major, trace, and rare earth elements (REE) in three gravity cores (GC03, GC04, and GC05) and one box core (BC11) retrieved from the southern Challenger Deep at water depths from 5289 to 7118 m. The upper sediment layers of both GC05 and BC11 are dominated by valve fragments of the giant diatom Ethmodiscus rex , forming laminated diatom mats (LDMs). 14C-AMS dates of bulk organic matter show that the LDMs accumulated between 18.4 and 21.8 kyr B.P., corresponding to the LGM. Modest enrichments of U and Mo along with weak or absent Ce anomalies in the LDM point to suboxic conditions during the LGM. In contrast, non-LDM samples exhibit little to no enrichment of redox-sensitive elements as well as negative Ce anomalies, indicating deposition under oxic bottom-water conditions. The Ce anomalies are considered valid proxies for bottom-water redox conditions because REE signatures were acquired in the early diagenetic environment, as indicated by strong P-REE correlations and middle-REE enrichment associated with early diagenetic cycling of Fe-Mn oxyhydroxides in the sediment column followed by capture of the REE signal by biogenic and/or authigenic apatite. We postulate that the more reducing bottom-water conditions during the LGM were linked to increased primary productivity induced by enhanced Asian dust input. As shown in earlier studies, the increased primary productivity associated with Ethmodiscus rex blooms in the eastern Philippine Sea played a significant role in capturing atmospheric CO 2 during the LGM. Consequently, the magnitude of atmospheric CO 2 sequestration by giant diatom blooms during the LGM may have been greater than previously envisaged. Highlights • Elemental and radiocarbon analysis of southern Mariana Trench (SMT) sediments since 30 ka. • Shift to more reducing (suboxic) deep waters during the Last Glacial Maximum (LGM). • Blooms of giant diatom Ethmodiscus rex formed laminated diatom mats (LDMs) during LGM. • Redox changes were due to increased primary productivity induced by enhanced Asian dust inputs. • Biogenic and authigenic apatite are the main carriers of rare earth elements (REEs) in SMT sediments. [ABSTRACT FROM AUTHOR]

Highlights • A novel method is used to monitor in-situ unsaturated soil hydraulic conductivity. • The method is based on heat pulse and water potential measurements. • The method gives reasonable unsaturated soil hydraulic conductivity estimates. Abstract Unsaturated hydraulic conductivity (K) of surface soil changes substantially with space and time, and it is of great importance for many ecological, agricultural, and hydrological applications. In general, K is measured in the laboratory, or more commonly, predicted using soil water retention curve and saturated hydraulic conductivity. In the field, K can be determined through infiltration experiments. However, none of these approaches are capable of continuously monitoring K in-situ at fine depth scales. In this study, we propose and investigate an approach to continuously estimate fine depth-scale K dynamics under field conditions. Evaporation rate and change in water storage in a near-surface soil layer are measured with the heat pulse method. Then, water flux density at the lower boundary of the soil layer is estimated from evaporation rate, change in water storage, and rainfall or irrigation rate using a simple water balance approach. Finally, K values at different soil depths are derived using the Buckingham-Darcy equation from water flux densities and measured water potential gradients. A field experiment is performed to evaluate the performance of the proposed approach. K values at 2-, 4-, 7.5-, and 12.5-cm depths are estimated with the new approach. The results show that in-situ K estimates vary with time following changes in soil water content, and the K -water content relationship changes with depth due to the difference in bulk density. In-situ estimated K -matric potential curves agree well with those measured in the laboratory. In-situ K estimates also show good agreement with the Mualem-van Genuchten model predictions, with an average root mean square error in log 10 (K , mm h−1) of 0.54 and an average bias of 0.17. The new approach provides reasonable in-situ K estimates and has potential to reveal the influences of natural soil conditions on hydraulic properties as they change with depth and time. [ABSTRACT FROM AUTHOR]

Highlights • Water temperature in the Tatras displays temporal and spatial heterogeneity. • Wavelet analysis revealed the presence of 7 configurations of periodical patterns. • Vaucluse springs display a simple configuration with annual periodicity. • Streams and lakes exhibit a complex configuration with several periodicities. • The use of wavelet and PCA analysis helps to explain the observed variability. Abstract In this study, we aim to characterise natural variability of water temperature in surface waters of the Tatra Mts. and determine the dominant factors controlling its spatial diversity and seasonal patterns. For this purpose, a total of 33 time series of water temperature representing lakes, vaucluse springs and streams were analysed using the continuous wavelet transform (CWT). The periodicity analysis were conducted with the Morlet wavelet on hourly sampled data covering a period of 5 years. The principal components analysis (PCA) has been applied to describe the relationships among variables and extract potential sources of water temperature variability. The results showed an extremely high heterogeneity in temporal patterns of water temperature fluctuations among streams when compared to lakes and vaucluse springs. Wavelet analysis of water temperature time series revealed the presence of seven different configurations of periodical patterns. The lowest variability was observed among vaucluse springs that are supplied by groundwaters. Temporal fluctuations of water temperature in lakes contained four different types of oscillations. Streams were among the most diversified in terms of water temperature patterns exhibiting low, medium and high frequency behaviour. The PCA analysis confirmed the dependence of water temperature on weather conditions, catchment characteristics and flow rate explaining 88.97% of the total variability in the data. The results obtained from this study emphasize the importance of continuous data collection for capturing the long-term dynamics and consistent temporal patterns in time series. The study also demonstrates that wavelet analysis is helpful to identify cyclical patterns in time series of water temperature, and therefore may be useful in the classification of thermal regimes in surface waters. [ABSTRACT FROM AUTHOR]

Highlights • Permanently isolated ponds characterized by good all hydrochemical conditions. • Electrical conductivity in ponds is low (<30 µS·cm−1). • Large concentration of nitrogen observed due formation of hydrographic network. • Higher concentrations of Ntot recorded in periodic rivers during high water stages. • Increase in Ptot concentrations observed after the occurrence of extreme phenomena. Abstract The study aims to examine the effect of ponds on changes in water quality in a young glacial river catchment. The goal was to identify situations where a periodic hydrographic network is formed in outflow-free areas, which is connected with a higher order receiving area, as well as to study the circulation of matter in this type of system. This study answers the following key question: Do ponds affected by areal pollution substantially affect water quality in streams in periods where they become joined with the hydrographic network? The purpose of the research was to identify patterns associated with the functioning of ponds in young glacial areas in northern Poland on the example of the Borucinka catchment. Ponds were selected in order to generate a study sample characterized by different types of land use, local hydrology, and pond surface area. The study focused on the effects of catchment land use on pond water quality and the effects of periodic changes in local hydrology (linkage of surface flows with bodies of water) on pond water quality. Research has shown that land use in a pond catchment yields a substantial effect on pond water quality. The basic reason for the higher concentration of selected ions is close proximity to farms that generate wastewater, which reaches bodies of water in the study area. Seasonal changes in the concentration of biogenic substances were not observed in ponds. Only notable changes in the concentration of total nitrogen were observed due the episodic formation of a hydrographic network consisting of a collection of linked depressions. One of the more surprising findings was that permanently isolated ponds, which theoretically collect catchment pollutants all the time, are characterized by good hydrochemical conditions. [ABSTRACT FROM AUTHOR]

Sea-surface conditions in northeastern Fram Strait since the last glacial maximum (LGM) were reconstructed from cores MSM5/5-712-2 and PS2863/1–2 based on palynological assemblages, ecological preferences of dinocysts and application of the modern analog technique. Dinocyst in LGM sediments are sparse, but their assemblages reflect mild summer conditions. Given the regional context and evidence from other tracers, the dinocyst assemblages of the LGM could relate to regional fluxes of dinocysts during exceptional mild summers. From 19 to 14.7 ka, dinocyst data suggest very cold conditions with extensive sea-ice cover, while abundant reworked palynomorphs indicate intense glacial erosion. An abrupt transition at 14.7–14.5 ka was marked by a peak in summer temperatures coinciding with a rapidly deposited sediment layer related to a regional meltwater plume event in western Svalbard. From 14.7 to 12.6 ka, large seasonal temperature contrasts with mild summers and cold winters together with low salinity indicate continuous melting of the Svalbard Barents Sea ice sheet fostered by warm climate. At 12.6 ka, the regional onset of the Younger Dryas was marked by cooling and increased salinity. On a regional scale, the 12.6–12 ka interval corresponds to an important transition involving enhanced circulation of Arctic waters around Svalbard and establishment of coastal fronts along its northern and western margins. Modern-like oceanic conditions with relatively high salinity and low seasonal temperature contrast developed at about 7.6 ka. Since then, a slight cooling is observed, especially in winter. This study offers a comprehensive picture of the deglacial phases in eastern Fram Strait with unique data on the sea-surface salinity, which controls surface water stratification and plays an important role in ocean circulation. [ABSTRACT FROM AUTHOR]

Numerous cases of timing differences between glacier advances recorded in mountain environments have been documented over the last decade, usually suggesting potential age conflicts between the different dating techniques. The frequent use of a single technique to date numerically a given glacial sequence makes it difficult to address to what extent age differences can be an artifact related to biased numerical age results or a paleoclimate signature. Here we present a new set of 43 numerical ages based on three dating techniques — 10 Be surface exposure dating; radiocarbon; and optically stimulated luminescence— that complement the chronology of Pleistocene glacial advances in the Porma valley, in the central Cantabrian Mountains of Spain. Results compliment previous chronologies in the area, supporting an important glacial advance during Marine Isotope Stage 3 (Stage IIa: ∼56 ka) that culminated with the Last Glacial Maximum advance (Stage IIb: ∼33–24 ka) of MIS 2 in response to increased rainfall and solar insolation minima. Glacier fronts reached elevations as low as 1130 m a.s.l. possibly without overriding evidence related to the previous Pleistocene glacial maximum extent. Glacier recession in the Cantabrian Mountains started at 21–20 ka ago, after the global LGM. We suggest that the recession was initiated by increased insolation followed by hyper-cool and dry conditions during Heinrich Stadial 1 in response to meltwater discharges in the North Atlantic. [ABSTRACT FROM AUTHOR]

Many of the Earth's sedimentary basins are affected by glaciations. Repeated glaciations over the last millions of years had great influence on the physical conditions in sedimentary basins and on basin structuring. This paper presents some of the major effects that glaciations have on sedimentary basins including examples of quantifications of their significance. Ice sheets are capable of eroding, transporting and depositing huge amount of sediments. The shape of ice sheets changes over time, and in general the erosion will have concentric pattern forms due to the low ice velocity under the center of the continental glaciers, and the more rapid basal ice velocity near the margins. Glaciations add a degree of difficulty to petroleum exploration. Erosion leads to cooling, which implies that the source rocks will be at a higher degree of maturation than expected from their present depth. The temperature effects of the glacial cycles will add to the erosion effect. A sedimentary basin covered by glacier ice during the last ice age is not in thermal equilibrium, maybe as far as 10–15 °C from equilibrium at 2 km depth. Among the most important effects are also movements of the solid Earth caused by glacier loading and lateral movements of sediments. The driving factor of these movements is isostasy. Sedimentary basins near the former ice margin can be tilted as much as 4 m/km which might significantly alter pathways of hydrocarbon migration. The modeled examples are from Northern Europe, but the conclusions are valid for sedimentary basins beyond this area. [ABSTRACT FROM AUTHOR]

We conducted a multidisciplinary study to provide the stratigraphic and palaeoclimatic context of monsoonal rainfall dynamics and their responses to orbital forcing for the Bay of Bengal. Using sediment lightness we established an age model at orbital resolution for International Ocean Discovery Programme (IODP) Core U1452C-1H that covers the last 200 ka in the lower Bengal Fan. The low-resolution δ 18 O of G. sacculifer is consistent with global δ 18 O records, at least for major glacial-to-interglacial transitions. The variability of total organic carbon, total nitrogen, and the δ 13 C composition of organic matter indicate the marine origin of organic matter. Marine primary productivity likely increased during insolation minima, indicative for an enhanced NE monsoon during glacials and stadials. Pristine insolation forcing is also documented for wet-bulk density, red-green color variability, and grain-size variations, indicating that darker and coarser-grained material deposited at higher sedimentation rates during insolation minima. Stronger NE monsoon likely amplified ocean-atmosphere interactions over the Indian Ocean, leading to stronger upwelling through shoaling the thermocline, and higher delivery of sediment to the Bay of Bengal due to higher soil erosion on land. In addition, lower glacial and stadial sea levels as well as stronger westward surface circulation favored delivery of coarser-grained fluvial material to the lower Bengal Fan. At the same time the stronger NE monsoon might have increased the aeolian supply. Total inorganic carbon, the Ca/Ti ratio, and biogenic silica vary dominantly on obliquity frequencies, suggesting mobilization and transport of lithogenic material primarily during lowered sea levels and/or higher influence of the Northern Hemisphere westerlies on the dust transport from the Tibetan Plateau. The close resemblance of sediment lightness and the climate record of Antarctic ice cores over multiple glacial cycles indicate close relationship between high southern latitude and tropical Asian climate through shifts in position of the Intertropical Convergence Zone. The Bengal Fan monsoonal record shows very clear and strict responses to insolation forcing in the lower part from ~200 ka to the Younger Toba Tuff during Marine Isotope Stage (MIS) 7 – 5, and less distinct response patterns after deposition of the ash during MIS 4 – 2, consistent with low-amplitude changes in insolation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Late Pleistocene glacial landforms and paleoclimate in the Eastern Carpathians. • Presented inventory of 214 glacial cirques and 147 palaeo-glaciers in 14 massifs. • LGM ELA mimics the pattern and magnitude of the modern climatic ELA. • ELA and cirque elevation trends show dominant westerlies in Central Europe during LGM. • Crucial role of orographic induced precipitation in dry continental glacial climate. The Eastern Carpathians are the northeasternmost sector of the European Alpine Mountain system and comprise 14 formerly glaciated massifs that stretch over 300 km into the territories of Ukraine and Romania. In this study we provide a regional overview on Late Pleistocene glaciation in the Eastern Carpathians integrating recently published and new geomorphological data which include mapped glacial landforms and glacier reconstruction of the maximal ice extent (MIE) which is assigned to the global Last Glacial Maximum (LGM). Thus we obtain a complete inventory of glaciation in the Eastern Carpathians, including the documentation of 214 glacial cirques and 147 small mountain glaciers with a total area of 153.2 km2. The estimated LGM equilibrium line altitude (ELA) shows a strong rise of 2.4 m/km from the northwest (1270 m asl) to the southeast (1870 m asl), as well as a consistent eastward rise on several W-E transects (2–3.4 m/km). Similar patterns are shown by the palaeoglaciation level and the cirque floor altitude trend, which mimic the pattern of modern temperature-precipitation ELA (tpELA) in the region. Reconstructed palaeoglacial trends reflect dominant W-NW precipitation-wind regime and an enhanced zonal North Atlantic circulation pattern in the far interior of Europe in full glacial climate. This is consistent with both regonal palaeoclimatic simulations and wind regime proxies which indicate that the pattern of LGM circulation was similar to the present circulation, although the magnitude may have increased during glacial conditions. Additionally, based on the wide array of glacial landscapes inventoried in this study, ranging from traces of small niche/cirques to about 7 km long valley glaciers, we propose a quantitative approach to define the distinct stages of glacial landscape development based on the relationship between the Pleistocene ELA and mountain hypsometry. [ABSTRACT FROM AUTHOR]

Numerical glacier models applied to moraine chronologies provide an opportunity to quantify past climate change. Here we apply a two-dimensional coupled mass balance – ice flow model to well-dated moraine sequences deposited by former alpine glaciers at two central Patagonian sites: Cerro Riñón (43.97°S, 71.64°W) and Río Tranquilo (47.50°S, 72.38°W), to reconstruct the local temperatures during both the Antarctic Cold Reversal (14.7–13 ka) and the Younger Dryas (12.9–11 ka). Modelled temperature anomalies during the Antarctic Cold Reversal are −2.6 ± 0.4 °C at 44°S, and −2.9 ± 0.6 °C at 47°S. At both locations this cold event is followed by temperature increases of +0.6–0.7 °C or precipitation reductions of c. 20% to drive glacier retreat to moraines deposited during Younger Dryas time. The consistent climatic anomalies between these two latitudes suggest this region of Patagonia was responding to a common climatic event. Further, the late-glacial temperature anomalies found here compare well to those determined by similar glacier modelling techniques in New Zealand, at 43–44° S. These results support a trans-Pacific response throughout the southern mid to high latitudes (43–47° S) during the ACR that is best explained by a northward expansion of the south westerly winds. • Glacier modelling reconstructs Patagonian temperatures during late-glacial. • Cooling of −2.7 to −2.9 ° C below modern during the Antarctic Cold Reversal. • Warming of +0.6 ° C from the Antarctic Cold Reversal into the Younger Dryas period. • Climate trends parallel New Zealand glaciers implicating southern westerly winds. [ABSTRACT FROM AUTHOR]

The mechanisms driving the Dansgaard-Oeschger (DO) cycles remain uncertain, but promising hypotheses could explain it, and a comprehensive assessment of its impact is needed. We have identified DO-like millennial-scale climate variability in a glacial simulation based on the salt oscillator hypothesis with the HadCM3B-M2.1 coupled atmosphere-ocean-vegetation model. The simulated DO-like warming shows temperature changes of 7.1 ± 2.5 °C in Greenland, comparable to DO9 and DO6, the smallest temperature changes of the observed DO events. This study focuses on the impacts of DO-like events on climate and vegetation beyond the North Atlantic. We find that the simulated warming in the Northern Hemisphere extratropics during Greenland interstadials agree with available proxy estimates. The simulated tropical hydroclimatic responses during the interstadials, such as northward propagation of the Intertropical Convergence Zone, strengthening of some Northern Hemisphere summer monsoons, and weakening of some Southern Hemisphere monsoons, are also consistent with proxy estimates. Moreover, simulated vegetation cover in the Northern Hemisphere increases during interstadials relative to stadials, while no large-scale dominant vegetation changes are consistent with observed biome changes associated with DO6. Our simulation based on the salt oscillator hypothesis can account for many observed features of DO events. However, it cannot simulate several observed climate responses in the equatorial Indian and western Pacific Oceans, including the East Asian and South African monsoon. The causes of those mismatches need to be further explored, whether they are hypothesis-dependent or model-dependent. • A glacial climate simulation based on the oscillator hypothesis. • Global climate and vegetation changes associated with DO-like oscillations. • This simulation is consistent with many proxy data. [ABSTRACT FROM AUTHOR]

South Westland, New Zealand, and southern Chile, are two narrow continental corridors effectively confined between the Pacific Ocean in the west and high mountain ranges in the east which impart significant influence over regional climate, vegetation and soils. In both these southern mid-latitude regions, evidence for extensive and repeated glaciations during cold phases of the Quaternary is manifested by arrays of successively older glacial drift deposits with corresponding outwash plain remnants. In South Westland, these variably aged glacial landforms are mantled by layered (multisequal) soils characterised by slow loess accretion and pedogenesis in an extreme leaching and weathering environment. These cover-bed successions have undergone repeated coupled phases of topdown and upbuilding soil formation that have been related to fluctuating cycles of interglacial/warm and glacial/cold climate during the Quaternary. In this study, we recognise multisequal soils overlying glacial landforms in southern continental Chile but, unlike the spodic (podzolic) soil sequences of South Westland, these are of dominantly volcanigenic (andic) provenance and are very similar to multisequal soils of andic provenance that predominate in, and adjacent to, areas of rhyolitic to andesitic volcanism in North Island, New Zealand. Here we develop a soil-stratigraphic model to explain the observed occurrence of multisequal soils mantling dominantly glacial landforms of southern continental Chile. Based on proxy data from southern Chile, we propose that persistent vegetation cover and high precipitation on the western side of the Andes, during colder-than-present episodes tended to suppress the widespread production of glacially-derived loessial materials despite the pervasive occurrence of glacial and glacio-fluvial deposits that have frequently inundated large tracts of this landscape during the Quaternary. Given the lack of loess cover-beds that have traditionally assisted in the relative dating of glacial episodes prior to the Late Quaternary, surface exposure dating techniques could provide another chronological alternative to address this issue. However, there have been two main obstacles to successfully apply this dating technique in Patagonia. First, minimum exposure ages may be obtained on moraines older than the last glacial cycle due to erosion, although dating outwash plains is more robust. Second, on the wet western side adjacent to the Andes, persistent vegetation cover during both glacial and post-glacial times, as well as widespread inundation by volcanic mass-flows, appear preventive. We make a case that soil genesis within this region appears to be dominated by a constant flux of intermittently erupted Andean-sourced tephra which has continued to upbuild soils at the ground surface separated by intervals where topdown weathering processes are intensified. As already demonstrated by New Zealand studies, multisequal soil successions have a clear implied connection to coupled glacial and interglacial climate cycles of the Quaternary. On this basis, similar sequences in northwest Patagonia provide a relatively untapped archive to enable Quaternary glacial and environmental changes in this pervasively glaciated volcanic region to be constructed. [ABSTRACT FROM AUTHOR]

Loess is widely distributed over Asia and North America and constitutes one of the most important surficial deposits that serve as terrestrial records of the Quaternary. The oldest Pleistocene loess in China is likely ∼2.6 Ma, thus spanning much or all of the Pleistocene. In North America, most loess is no older than the penultimate glacial period, with the exception of Alaska, where the record may go back to ∼3.0 Ma. On both continents, loess deposits date primarily to glacial periods, and interglacial or interstadial periods are represented by paleosols. Both glacial and non-glacial sources of silts that comprise the bulk of loess deposits are found on both continents. Although loess has been considered to be representative of the average upper continental crust, there are regionally distinctive compositions of loess in both Asia and North America. Loess deposits in Asia from Yakutia, Tajikistan, and China have compositionally distinct major element compositions, due to varying abundances of silicate minerals, carbonate minerals, and clay minerals. In North America, loess in the Mississippi River valley, the Great Plains, and Alaska are also distinguishable with regard to major element composition that reflects highly diverse source sediments. Trace element geochemistry (Sc-Th-Zr and the rare earth elements) also shows regional diversity of loess bodies, in both Asia and North America. On both continents, most loess bodies show significant contributions from later-cycle, altered sedimentary rocks, as opposed to direct derivation from igneous rocks. Further, some loess bodies have detectable contributions from mafic igneous rocks as well as major contributions from average, upper-crustal, felsic rocks. Intercalated paleosols in loess sections show geochemical compositions that differ significantly from the underlying loess parent materials. Ratios of soluble-to-insoluble elements show depletions in paleosols due to chemical weathering losses of calcite, dolomite, plagioclase, mica, apatite, and smectite. In Asia and North America, the last interglacial paleosol is more weathered than equivalent modern soils, which could be due either to a climate that was warmer and more humid, a longer period of pedogenesis, or both. In Asia, early Pleistocene loess and paleosols are both more weathered than those from the middle and late Pleistocene, forming prior to a mid-Pleistocene aridification of Asia from uplift of the Tibetan Plateau. Understanding the geochemistry of loess and paleosols can tell us much about past atmospheric circulation, past temperature and moisture regimes, and even tectonic processes. [ABSTRACT FROM AUTHOR]