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Understanding the causes of the ~90 ppmv atmospheric CO2 swings between glacial and interglacial climates is an important open challenge in paleoclimate research. Although the regularity of the glacial-interglacial cycles hints at a single driving mechanism, Earth System models require many independent physical and biological processes to explain the full observed CO2 signal. Here we show that biologically sequestered carbon in the ocean can explain an atmospheric CO2 change of 75 ± 40 ppmv, based on a mass balance calculation using published carbon isotopic measurements. An analysis of the carbon isotopic signatures of different water masses indicates similar regenerated carbon inventories at the Last Glacial Maximum and during the Holocene, requiring that the change in carbon storage was dominated by disequilibrium. We attribute the inferred change in carbon disequilibrium to expansion of sea-ice or change in the overturning circulation. Atmospheric CO2 was ~ 90 ppmv lower at the Last Glacial Maximum (LGM) than during the Holocene. Based on a carbon isotope budget, this study infers that at the LGM biological production pumped carbon into the deep ocean and sea ice kept it there. [ABSTRACT FROM AUTHOR]

Climate change is an emerging challenge that is triggering natural variabilities and disasters globally. In Gilgit–Baltistan (GB) region of Pakistan, Glacial Lake Outburst Floods (GLOFs) have been occurring frequently due to glacier surges, increasing the vulnerability of mountain communities, particularly small farmers. This research aims to investigate the climate change-induced GLOFs of the Shishper glacier in Hunza valley of GB with the intent of studying the farming activities; local awareness and perceptions toward climate change; impacts of climate change and GLOFs on agriculture; and adaptation mechanisms based on indigenous knowledge. Mixed-methods research approach was employed for a field survey in two villages inhabited by farmers of the Burusho community. Quantitative data were gathered from a sample of 180 respondents by using a structured questionnaire, whereas field observation coupled with photography and spot interviews were undertaken to accumulate qualitative data. Results revealed that many farmers lost their fertile land, and their crops and fruit orchards were severely damaged as a result of the devastating effects of climate change and recent GLOFs in 2019 and 2020, resulting in low crop yield and agricultural income. Local communities typically respond to GLOFs through self-help strategies and indigenous methods to sustain their livelihoods. However, our findings suggest that current adaptation practices are insufficient in light of rising climate risks. Thus, there is an urgent need to assist mountain communities by providing maximum support and interventions to enhance their resilience to future GLOFs and to increase people's adaptive capacity by strengthening their socioeconomic conditions. [ABSTRACT FROM AUTHOR]

Helianthemum songaricum and H. ordosicum are two shrubs disjunctively distributed in Central Asia and northwestern China. For conservation purposes, we used genotyping by sequencing (GBS) to investigate the genetic diversity and genetic structure of their populations. Based on the GBS data, H. songaricum populations showed considerable genetic differences from H. ordosicum populations. Helianthemum songaricum populations also showed a stronger population genetic structure within the isolated valleys in the Tianshan Mountains than was seen in previous studies. We speculated that the two species may represent two cotemporal migration events between the Middle East and Central Asia/Ordos Plateau since the early Pliocene. Due to the intense uplift of the Tianshan Mountains in the late Pliocene, populations of H. songaricum were isolated in different valleys. Subsequently, the cold glacial climate during the Pleistocene intensified the in situ intraspecific differentiation of the species. Based on our single nucleotide polymorphism data, we propose habitat damage by anthropological activities, where the two species inhabit should be urgently prohibited by executive management. In addition, a nursery for germplasm resources should be urgently set up to culture adequate progenies for the purpose of expanding the populations. [ABSTRACT FROM AUTHOR]

High-resolution ice core records from coastal Antarctica are particularly useful to inform our understanding of environmental changes and their drivers. Here, we present a decadally resolved record of sea-salt sodium (a proxy for open-ocean area) and non-sea salt calcium (a proxy for continental dust) from the well-dated Roosevelt Island Climate Evolution (RICE) core, focusing on the time period between 40–26 ka BP. The RICE dust record exhibits an abrupt shift towards a higher mean dust concentration at 32 ka BP. Investigating existing ice-core records, we find this shift is a prominent feature across Antarctica. We propose that this shift is linked to an equatorward displacement of Southern Hemisphere westerly winds. Subsequent to the wind shift, data suggest a weakening of Southern Ocean upwelling and a decline of atmospheric CO2 to lower glacial values, hence making this shift an important glacial climate event with potentially important insights for future projections. Antarctic ice core records provide insights into past environmental conditions. Here, an abrupt, synchronous increase in dust from ice cores in Antarctica is identified that suggests a sudden equatorward shift of westerly winds and coincides with a reduction in atmospheric CO2. [ABSTRACT FROM AUTHOR]

The community stability is the main ability to resist and be resilient to climate changes. In a world of climate warming and melting glaciers, alpine gravel encroachment was occurring universally and threatening hillside grassland ecosystem. Gravel encroachment caused by climate warming and glacial melting may alter community structure and community stability in alpine meadow. Yet, the effects of climate warming-induced gravel encroachment on grassland communities are unknown. Here, a 1-year short-term field experiment was conducted to explore the early stage drive process of gravel encroachment on community structure and stability at four different gravel encroachment levels 0%, 30%, 60%, and 90% gravel coverage at an alpine meadow on the Qinghai Tibetan Plateau, by analyzing the changes of dominant species stability and species asynchrony to the simulated gravel encroachment processes. Gravel encroachment rapidly changed the species composition and species ranking of alpine meadow plant community in a short period of time. Specifically, community stability of alpine meadow decreased by 61.78–79.48%, which may be due to the reduced dominant species stability and species asynchrony. Species asynchrony and dominant species stability were reduced by 2.65–17.39% and 46.51–67.97%, respectively. The results of this study demonstrate that gravel encroachment presents a severe negative impact on community structure and stability of alpine meadow in the short term, the longer term and comprehensive study should be conducted to accurate prediction of global warming-induced indirect effects on alpine grassland ecosystems. [ABSTRACT FROM AUTHOR]

Understanding genetic patterns at the regional level and the environmental influence on them is important for the conservation and sustainable use of economically important plant species. In this study, we focused on Thespesia populnea, a coastal species valued for its ecological and economic benefits across its pantropical distribution range. We aimed to understand the phylogeographic pattern, the current spatial distribution of genetic diversity, and range dynamics of the species with changing environmental conditions to better inform conservation and development actions. We genotyped 482 individuals, collected from 33 natural populations, at five chloroplast DNA loci and identified the influence of historical processes on the contemporary population structure of the species in the Indo-West Pacific (IWP) region. Environmental niche modeling (ENM) was used to identify the species' glacial and future climate refugia. High genetic diversity at the species level was observed. Nearly one-third of the populations showed no polymorphism, possibly due to extinction-recolonization events induced by glacial sea-level changes, as evident from the analysis of demographic history. The evolutionary relationship between the haplotypes suggested a strong phylogeographic structure. The clustering algorithms identified two genetic lineages that diverged around the Pleistocene epoch. The difference between the climatic niches of the two lineages was not significant. The ensembled ENM indicated range expansion of the species in the future. Based on the findings, we proposed sustainable use of genetically diverse populations, outlined measures to preserve the evolutionary potential of the lineages, and identified areas that should be prioritized for conservation actions of this important plant species. [ABSTRACT FROM AUTHOR]

Damage to speleothems is a common phenomenon in mid-latitude caves, and multiple causes have been proposed. Here we report on one of such type of damage, namely stalagmites that are broken and partially sheared near their base but are still in upright position. Such stalagmites occur in the Obir Caves (Austria) associated with cryogenic cave carbonates, demonstrating the former presence of cave ice. 230Th dating suggests damage to the speleothems during the Last Glacial Maximum. Numerical modelling combined with laboratory measurements demonstrates that internal deformation within a cave ice body cannot fracture stalagmites, even on a steep slope. Instead, temperature changes lead to thermoelastic stresses within an ice body that reach values equaling to and exceeding the tensile strength of even large stalagmites. Differences in thermal expansion coefficients cause a sharp vertical jump in stress between the stalagmite and the surrounding ice body, and the ice lifts the stalagmite as it expands with increasing temperature. This study refutes the previously accepted model that flow of ice breaks stalagmites, and suggests a link between glacial climate variability and corresponding cooling and warming cycles in the subsurface that weaken and eventually fracture stalagmites due to the opposing thermoelastic properties of calcite and ice. [ABSTRACT FROM AUTHOR]

The Qilian Mountains, located in the northeastern Qinghai-Tibet Plateau, is a sensitive zone of both East Asian summer monsoon (EASM) and westerly winds (WW). The evolution history and driving mechanism of the ecosystem and hydrologic cycle in this region on long-term timescales have not yet been clarified. In this study, we comprehensively study the hydrologic and ecological evolution history in the sensitive zone since the Last Glacial Maximum (LGM) by integrating surface sediments, paleoclimate records, TraCE-21ka transient simulations, and PMIP3-CMIP5 multi-model simulation. Results show that hydrologic and ecological proxies from surface sediments are significantly different from west to east and mainly divided into three sections: the monsoon-affected region in the eastern Qilian Mountains, the intersection region in the central Qilian Mountains, and the westerly-affected region in the western Qilian Mountains. Meanwhile, paleo-ecological and paleohydrologic reconstructions from the surroundings uncover a synchronous climate evolution that the EASM mainly controls the eastern Qilian Mountains and penetrates the central Qilian Mountains in monsoon intensity maximum, while the WW dominates the central and western Qilian Mountains on both glacial-interglacial and millennial timescales. The simulation results further bear out the glacial humid climate in the central and western Qilian Mountains caused by the enhanced WW, and the humidity maximum in the eastern Qilian Mountains controlled by the strong mid-Holocene monsoon. In general, east-west differences in climate pattern and response for the EASM and the WW are integrally stable on both short-term and long-term timescales. [ABSTRACT FROM AUTHOR]

Changes in convective activity and hydroclimate over Northeastern Kalimantan are key features to understand glacial to interglacial climate evolution in the center of the West Pacific Warm Pool during the Late Pleistocene to Holocene. We use high-resolution X-ray fluorescence (XRF) scanner-derived elemental ratios in sediment Core SO217-18522 (1º 24.106' N, 119º 4.701'E, 975 m water depth) recovered from the northern Makassar Strait to reconstruct changes in precipitation-related weathering and erosion over Northeastern Kalimantan over the last 50 kyr. Enhanced seasonality of rainfall and an extended dry season during Heinrich Stadials (HS4 to HS1) and the Younger Dryas (YD) suggest weakening of the tropical convection associated with a southward shift of the tropical rain belt and the annual mean position of the Intertropical Tropical Convection Zone. Increasing sediment discharge and intensification of convective activity occurred during the early to mid-Holocene during an interval of high Northern Hemisphere insolation, elevated atmospheric pCO2 levels and global warming. Our reconstructions in comparison with regional terrestrial and marine records highlight the high spatial variability of Kalimantan hydroclimate on millennial to glacial-interglacial timescales. [ABSTRACT FROM AUTHOR]

Climate change is causing glaciers to retreat across much of the Himalaya, leading to a rapid shift of the vegetation cover to higher altitudes. However, the rate of vegetation shift with respect to glacier retreat, climate change, and topographic parameters is not empirically quantified. Using remote sensing measurements, we estimate (a) the rate of glacier-ice mass loss, (b) the upward vegetation line shift rate, (c) regional greening trends, and (d) a relationship between the factors influencing the greenness of the landscape and vegetation change in the Himalaya. We find that the glacier mass loss rate is 10.9 ± 1.2 Gt/yr and the mean vegetation line shifts upward in altitude by 7–28 ± 1.5 m/yr. Considering the land use/land cover change pattern, the grassland area is found to be expanding the most, particularly in the de-glaciated regions. The vegetation change is found to be controlled by soil moisture and slope of the area. [ABSTRACT FROM AUTHOR]

Fjords in Svalbard are sensitive to the enhanced climate warming-induced glacial meltwater discharge (fresher, nutrient-rich, turbid) that influences its hydrography and biological processes. This study attempts to explain the impacts of underwater light environment and nutrient limitation on the phytoplankton biomass, composition, and light absorption in the sunlit zone of the Kongsfjorden (KG)–Krossfjorden (KR) twin fjord ecosystem during summer when the meltwater discharge is at maximum. Observations conducted in two phases in each fjord revealed pronounced spatial hydrographic variations between the phases and among the fjords. Intrusion of warm Atlantic water into both fjords and occurrence of subsurface chlorophyll maxima were observed. Meltwater-induced higher concentrations of optically active constituents in KG resulted in a comparatively shallow euphotic zone than KR. Nitrate and silicate limitation (N/P < 5, N/Si > 1, Si/P < 3) was evident in both fjords. Higher phytoplankton light absorption coefficient (aph, m−1) and chlorophyll-a in KR implied its higher productivity potential. However, the light absorption efficiency of microplankton (at surface) was affected by pigment package effect. Phytoplankton pigments analyses revealed an inter-fjord difference in surface phytoplankton composition predominated by microphytoplankton (49–100%) followed by pico- (0-38%) and nanoplankton (0–18%). The average diversity index for phytoplankton group (H') was higher in KR (0.71) than KG (0.55), which was possibly controlled by microzooplankton grazing. This study reveals that environmental settings in both fjords were quite different, which drives their productivity potential and species diversity. Thus, increased warming climate can have different levels of impacts on fjord ecosystems despite their close geographical proximity. [ABSTRACT FROM AUTHOR]

Seed and soil microbiomes strongly affect plant performance, and these effects can scale-up to influence plant community structure. However, seed and soil microbial community composition are variable across landscapes, and different microbial communities can differentially influence multiple plant metrics (biomass, germination rate), and community stabilizing mechanisms. We determined how microbiomes inside seeds and in soils varied among alpine plant species and communities that differed in plant species richness and density. Across 10 common alpine plant species, we found a total of 318 bacterial and 128 fungal operational taxonomic units (OTUs) associated with seeds, with fungal richness affected by plant species identity more than sampling location. However, seed microbes had only marginally significant effects on plant germination success and timing. In contrast, soil microbes associated with two different plant species had significant effects on plant biomass, and their effect depended both on the plant species and the location the soils were sampled from. This led to significant changes in plant-soil feedback at different locations that varied in plant density and richness, such that plant-soil feedback favored plant species coexistence in some locations and opposed coexistence at other locations. Importantly, we found that coexistence-facilitating feedback was associated with low plant species richness, suggesting that soil microbes may promote the diversity of colonizing plants during the course of climate change and glacial recession. [ABSTRACT FROM AUTHOR]

Although the global environmental impact of Laurentide Ice-Sheet destabilizations on glacial climate during Heinrich Events is well-documented, the mechanism driving these ice-sheet instabilities remains elusive. Here we report foraminifera-based subsurface (~150 m water depth) ocean temperature and salinity reconstructions from a sediment core collected in the western subpolar North Atlantic, showing a consistent pattern of rapid subsurface ocean warming preceding the transition into each Heinrich Event identified in the same core of the last 27,000 years. These results provide the first solid evidence for the massive accumulation of ocean heat near the critical depth to trigger melting of marine-terminating portions of the Laurentide Ice Sheet around Labrador Sea followed by Heinrich Events. The repeated build-up of a subsurface heat reservoir in the subpolar Atlantic closely corresponds to times of weakened Atlantic Meridional Overturning Circulation, indicating a precursor role of ocean circulation changes for initiating abrupt ice-sheet instabilities during Heinrich Events. We infer that a weaker ocean circulation in future may result in accelerated interior-ocean warming of the subpolar Atlantic, which could be critical for the stability of modern, marine-terminating Arctic glaciers and the freshwater budget of the North Atlantic. The mechanism driving past Laurentide Ice-Sheet instabilities remains elusive Here, the authors present a sediment record from the subpolar western North Atlantic and show that massive warming of the upper interior ocean was the likely trigger for repeated collapses of the Laurentide Ice-Sheet and iceberg discharge into the North Atlantic, known as Heinrich Events. [ABSTRACT FROM AUTHOR]

The Last Glacial Termination (T1) featured major changes in global circulation systems that led to a shift from glacial to interglacial climate. While polar ice cores attest to an antiphased thermal pattern at millennial timescales, recent well-dated moraine records from both hemispheres suggest in-phase fluctuations in glaciers through T1, which is inconsistent with the bipolar see-saw paradigm. Here, we present a glacier chronology based on 30 new 10Be surface exposure ages from well-preserved moraines in the Lago Palena/General Vintter basin in northern Patagonia (~ 44°S). We find that the main glacier lobe underwent profound retreat after 19.7 ± 0.7 ka. This recessional trend led to the individualization of the Cerro Riñón glacier by ~ 16.3 ka, which underwent minor readvances at 15.9 ± 0.5 ka during Heinrich Stadial 1, during the Antarctic Cold Reversal with successive maxima at 13.5 ± 0.4, 13.1 ± 0.4, and 13.1 ± 0.5 ka, and a minor culmination at 12.5 ± 0.4 ka during Younger Dryas time. We conclude that fluctuations of Patagonian glaciers during T1 were controlled primarily by climate anomalies brought by shifts in the Southern Westerly Winds (SWW) locus. We posit that the global covariation of mountain glaciers during T1 was linked to variations in atmospheric CO2 (atmCO2) promoted by the interplay of the SWW-Southern Ocean system at millennial timescales. [ABSTRACT FROM AUTHOR]

Quaternary palynology in the Tibetan Plateau (TP) was initiated in the 1960s to meet the needs of economic development in western China. Pollen analysis was conducted for the first time on a 200-m long core of Quaternary lacustrine sediments taken from the main body of the TP in order to study pollen assemblages as well as vegetation and climate changes of glacial (cold)/interglacial (warm) periods. Pollen analysis of alpine snow and ice began at the first scientific expedition to the TP in the 1970s. After the 1980s, a series of international collaborative programs were carried out under Sino-French, Sino-German, Sino-Australian, and Sino-American cooperation, marking the integration of Chinese Quaternary palynology society with the international community. New methods for Quaternary palynology were gradually promoted and applied, changing the vegetational and climatic interpretation of Quaternary palynology from qualitative to quantitative. Since the 1990s, many palynologists have carried out extensive Quaternary palynological studies on fossil pollen sites of more than 60 lakes/sections and alpine glaciers in the TP to discuss the spatiotemporal vegetation changes and climatic and environmental evolution of the TP since the Pleistocene. Over the past half-century, Quaternary palynology in the TP has contributed to the establishment of the Chinese Quaternary pollen database and the study of vegetation and climate evolution since the Last Glacial Maximum (LGM) in the TP. Currently available pollen records revealed the spatial and temporal distribution of vegetation in the TP since the LGM, exhibiting expansions and shrinkages of forest, meadow, grassland and desert in different periods such as the LGM, the last deglaciation, and Holocene optimum period. The paleomonsoon reflected by paleovegetation since the LGM has undergone the changes of weak-strengthening-strong-weakening but still active-shrinking, which is mainly affected by solar insolation. [ABSTRACT FROM AUTHOR]

In a period of ongoing climate changes, identifying drivers of overall and endemic species diversity is a key element in constructing new ecological patterns and determining the main goals of conservation. Such studies are especially crucial if they concern biodiversity hotspot areas. In this study, we explore patterns and drivers of plant endemism (the proportion of endemic plant species to overall plant species richness; PE) in Tajikistan. We used three groups of climatic measures featuring the contemporary and glacial climates as well as climatic changes since the Last Glacial Maximum in the Pleistocene (LGM). To explore relationships between PE and climatic groups, and the most important climatic variables, we applied the Generalised Additive Model and regression trees method respectively. Glacial climate predicted PE variation the most (74.3%), followed by climate stability (55.4%) and current climate (62.4%). The most important variables represented change in precipitation of driest quarter, glacial mean annual temperature and current annual precipitation. LGM climate and its change to date have the greatest influence on contemporary PE patterns in Tajikistan, revealing the evolutionary dependencies between limited-range plants and past climate. Accordingly, annual temperature and precipitation regimes have been the most crucial drivers of PE since the LGM until today. The study revealed the dependence of the PE on a stabilized water-energy supply. The changing temperature and precipitations regimes during the ongoing climate warming may, therefore, increases the threat to geographically isolated cryophilous plants of Tajikistan, while their escape potential to suitable cold habitats is highly topographically limited. [ABSTRACT FROM AUTHOR]

Stephanodiscus niagarae Ehrenberg is currently restricted to specific regions of central Mexico, however, during the late Pleistocene, it had a wider distribution in the country. This change in distribution is similar to those observed for several organisms that migrated southwards during cold, glacial climates, supporting the hypothesis that central Mexico acted as glacial refugia for these species. This study aims to support this hypothesis for S. niagarae as well as to analyze its ecological distribution in modern environments in central Mexico. For this purpose we studied 18 samples from 16 lakes located around Mexico City, selected among 46 lakes along the Trans-Mexican Volcanic Belt. Diatom assemblages in superficial sediments, and climatic, hydrochemistry, and nutrient parameters of each lake were analyzed by means of canonical correspondence analyses. Additionally, we created an ecological niche model (ENM) with modern occurrence data (n = 47) and environmental variables (WorldClim) to produce potential distribution maps of S. niagarae during the present time and under the LGM conditions in the Nearctic realm. S. niagarae was recorded only in 4 sites in central Mexico (abundances < 10%) associated with temperate, subhumid conditions in freshwater lakes with [Mg2+] − [Ca2+] − [HCO3−] ionic dominance and high turbidity, mesotrophic to hypertrophic systems (based on chlorophyll a values), but with a tendency to P-limitation. In our study sites S. niagarae showed low abundances in diatom assemblages dominated by Aulacoseira spp. Temperature (annual mean, coldest and warmest quarters means) was identified by ENM as the main environmental variable controlling its distribution, with its highest modern support in the USA, southern Canada, and a restricted distribution in the highlands of western and central Mexico. Whereas, the LGM scenario (− 5.5 °C) identified the western and central highlands in Mexico and southern USA as the highest probability distribution areas supporting the approach that the Sierra Madre Occidental could have acted as a migration corridor offering suitable habitats for a southward migration into central Mexico during colder (glacial) periods. In conclusion, S. niagarae distribution in the central and western mountains of Mexico is controlled by temperature changes and its presence may be associated with colder (glacial) periods. [ABSTRACT FROM AUTHOR]

We report high resolution measurements of the stable isotope ratios of ancient ice (δ18O, δD) from the North Greenland Eemian deep ice core (NEEM, 77.45° N, 51.06° E). The record covers the period 8–130 ky b2k (y before 2000) with a temporal resolution of ≈0.5 and 7 y at the top and the bottom of the core respectively and contains important climate events such as the 8.2 ky event, the last glacial termination and a series of glacial stadials and interstadials. At its bottom part the record contains ice from the Eemian interglacial. Isotope ratios are calibrated on the SMOW/SLAP scale and reported on the GICC05 (Greenland Ice Core Chronology 2005) and AICC2012 (Antarctic Ice Core Chronology 2012) time scales interpolated accordingly. We also provide estimates for measurement precision and accuracy for both δ18O and δD. Measurement(s) isotope analysis • water ice core Technology Type(s) cavity ring-down spectroscopy Factor Type(s) δ18O • δD Sample Characteristic - Location Greenland Ice Sheet Machine-accessible metadata file describing the reported data: https://doi.org/10.6084/m9.figshare.14216441 [ABSTRACT FROM AUTHOR]

Data availability and temporal resolution make it challenging to unravel the anatomy (duration and temporal phasing) of the Last Glacial abrupt climate changes. Here, we address these limitations by investigating the anatomy of abrupt changes using sub-decadal-scale records from Greenland ice cores. We highlight the absence of a systematic pattern in the anatomy of abrupt changes as recorded in different ice parameters. This diversity in the sequence of changes seen in ice-core data is also observed in climate parameters derived from numerical simulations which exhibit self-sustained abrupt variability arising from internal atmosphere-ice-ocean interactions. Our analysis of two ice cores shows that the diversity of abrupt warming transitions represents variability inherent to the climate system and not archive-specific noise. Our results hint that during these abrupt events, it may not be possible to infer statistically-robust leads and lags between the different components of the climate system because of their tight coupling. Palaeodata resolution and dating limit the study of the sequence of changes across Earth during past abrupt warmings. Here, the authors show tight decadal-scale coupling between Greenland climate, North Atlantic sea ice and atmospheric circulation during these past events using two highly resolved ice-core records. [ABSTRACT FROM AUTHOR]

Rwenzori Mountains National Park, which straddles the border between the Democratic Republic of Congo and Uganda, has experienced rapid glacier loss since the beginning of the twentieth century, yet there has been little investigation of aquatic biodiversity change in the park. This study presents a paleolimnological analysis from Lake Mahoma (2990 m asl), which is situated in the bamboo-forest transition zone. Diatom and organic geochemistry data from a 39-cm-long sediment core with a basal age of c. 1715 CE were compared with new analyses of previously published data from Lakes Bujuku (3891 m asl) and Lower Kitandara (3989 m asl), in the alpine zone. Comparisons were made to determine if aquatic ecosystem changes exhibited similar inter-lake patterns over the past ~ 150 years of climate warming and glacial recession, or if only local change was apparent. The diatom flora of Lake Mahoma is acidophilous, dominated by Aulacoseira ikapoënsis since at least the mid eighteenth century. In recent decades, the obligate nitrogen-heterotroph Nitzschia palea increased in importance, concurrent with declining δ15Norg values. We suggest that these late twentieth century changes were linked to regional warming and increased thermal stratification of Lake Mahoma. Regional comparisons of the Rwenzori lakes were done using existing organic geochemistry records (total organic carbon, C/N and δ13Corg) and through diatom compositional turnover analyses, and categorisation of species into one of four diatom growth morphology traits, or guilds: tychoplanktonic, high-profile, low-profile and motile. Over the past 150 years, all three lakes showed unidirectional, compositional diatom turnover, indicating that deterministic processes had affected diatom communities. Declining turnover at each site is broadly mirrored by an increase in tychoplanktonic taxa, along with concomitant declines in high-profile diatoms at Lake Mahoma, and low-profile diatoms at Lake Bujuku, and at least for the past 60 years, at Lower Kitandara. The interplay between diatom guilds at all sites is mainly a consequence of competition for available resources. Sediment organic carbon at all sites comes from both autochthonous and allochthonous sources, the relative abundances of which are influenced by the time elapsed since lakes had glaciers in their catchment. [ABSTRACT FROM AUTHOR]

Eco-environmental changes during interglacials with an astronomical background similar to that of the Holocene are potentially helpful for understanding the future climatic evolution. Marine oxygen isotope stage (MIS) 19 is similar to the Holocene in astronomical background, both being characterized by a low eccentricity of the Earth's orbit. However, MIS 19 has attracted research attention only recently and therefore less is known about eco-environmental changes during this interval, especially based on terrestrial records. In the Chinese Loess Plateau (CLP), the S7 paleosol can provide valuable terrestrial paleoclimatic and paleoenvironmental record for MIS 19. Here, high-resolution terrestrial snail records from the L8-L7 strata of the Huining, Xifeng and Luochuan sequences in the CLP were analyzed in order to characterize spatio-temporal changes in climate and eco-environment during MIS 20–18. The results show that in all three sections the late part of MIS 20 was dominated by abundant cold-aridiphilous mollusc species, indicating that cold and dry climatic conditions prevailed across the entire CLP, under the strong influence of the winter monsoon. The mollusc fauna of MIS 19 were dominated by warmth-loving and thermohumidiphilous species that enable the definition of two climatic stages. The early part of MIS 19 (∼790–778 ka) was marked by warm and humid conditions, as evidenced by high abundances of warmth-loving and thermo-humidiphilous species. This interval was slightly warmer than today and it lasted for ∼12 kyr. The climate of the later part of MIS 19 (∼778–761 ka) was more moderate, and increased proportions of cold-aridiphilous and warmth-loving species were recorded. The warmth of this period was similar to that of today, but the climatic fluctuations were stronger. During the early part of MIS 18 (∼761–745 ka), the Xifeng and Luochuan sections in the eastern CLP still maintained high abundances of warmth-loving and thermo-humidiphilous species, indicating that the moderate climatic conditions during late MIS 19 continued during early MIS 18, lasting for another ∼15 kyr, and that the influence of the summer monsoon remained strong in the eastern CLP during early MIS 18. However, in the western CLP, cold-aridiphilous species in the Huining section became dominant during early MIS 18, reflecting the prevalence of a cold and dry glacial climate, with the strong influence of the winter monsoon. These findings indicate that a steeper climatic gradient and a pronounced regional environmental difference existed between the eastern and western CLP during the early part of MIS 18. Comparison of our mollusc results with the variation of Earth orbital parameters suggested that climate changes in the CLP during MIS 20-18 were likely controlled mainly by insolation changes forced by the configuration of Earth orbital parameters. The unique orbital configuration during the low eccentricity interglacial-to-glacial transition could have strengthened the East Asian summer monsoon which favored the amelioration of the eco-environment in the CLP, especially in the eastern CLP where the summer monsoon exerted a strong influence. Thus we speculate that, under natural climatic conditions, the climate of the CLP may remain in a warm, humid state for another 30 kyr, although climatic instability and the seasonal differences between winter and summer could strengthen. [ABSTRACT FROM AUTHOR]

The uncertain response of marine terminating outlet glaciers to climate change at time scales beyond short-term observation limits models of future sea level rise. At temperate tidewater margins, abundant subglacial meltwater forms morainal banks (marine shoals) or ice-contact deltas that reduce water depth, stabilizing grounding lines and slowing or reversing glacial retreat. Here we present a radiocarbon-dated record from Integrated Ocean Drilling Program (IODP) Site U1421 that tracks the terminus of the largest Alaskan Cordilleran Ice Sheet outlet glacier during Last Glacial Maximum climate transitions. Sedimentation rates, ice-rafted debris, and microfossil and biogeochemical proxies, show repeated abrupt collapses and slow advances typical of the tidewater glacier cycle observed in modern systems. When global sea level rise exceeded the local rate of bank building, the cycle of readvances stopped leading to irreversible retreat. These results support theory that suggests sediment dynamics can control tidewater terminus position on an open shelf under temperate conditions delaying climate-driven retreat. Tidewater glaciers in fjords can advance/retreat independent of climate due to stabilization by sediments at their termini. We show that an Alaskan paleo-ice stream behaved similarly on an open shelf, suggesting that increased sediment flux may delay catastrophic retreat of outlet glaciers in a warming world. [ABSTRACT FROM AUTHOR]

Weddell Sea-derived Antarctic Bottom Water (AABW) is one of the most important deep water masses in the Southern Hemisphere occupying large portions of the deep Southern Ocean (SO) today. While substantial changes in SO-overturning circulation were previously suggested, the state of Weddell Sea AABW export during glacial climates remains poorly understood. Here we report seawater-derived Nd and Pb isotope records that provide evidence for the absence of Weddell Sea-derived AABW in the Atlantic sector of the SO during the last two glacial maxima. Increasing delivery of Antarctic Pb to regions outside the Weddell Sea traced SO frontal displacements during both glacial terminations. The export of Weddell Sea-derived AABW resumed late during glacial terminations, coinciding with the last major atmospheric CO2 rise in the transition to the Holocene and the Eemian. Our new records lend strong support for a previously inferred AABW overturning stagnation event during the peak Eemian interglacial. The Southern Ocean plays a key role in glacial-interglacial transitions and today, Weddell Sea derived Antarctic Bottom Water is one of the most important deep water masses. New records show that in contrast to today, no Weddell Sea water was exported during the last two glacial maxima, providing new insights towards the condition of Antarctic Bottom Water formation in extreme climate states. [ABSTRACT FROM AUTHOR]

Glacier recession is a globally occurring trend. Although a rich body of work has documented glacial response to climate warming, few studies have assessed vegetation cover change in recently deglaciated areas, especially using geospatial technologies. Here, vegetation change at two glacier forefronts in Glacier National Park, Montana, U.S.A. was quantified through remote sensing analysis, fieldwork validation, and statistical modeling. Specifically, we assessed the spatial and temporal patterns of landcover change at the two glacier forefronts in Glacier National Park and determined the role of selected biophysical terrain factors (elevation, slope, aspect, solar radiation, flow accumulation, topographic wetness index, and surficial geology) on vegetation change (from non-vegetated to vegetated cover) at the deglaciated areas. Landsat imagery of the study locations in 1991, 2003, and 2015 were classified and validated using visual interpretation. Model results revealed geographic differences in biophysical correlates of vegetation change between the study areas, suggesting that terrain variation is a key factor affecting spatial-temporal patterns of vegetation change. At Jackson Glacier forefront, increases in vegetation over some portion or all of the study period were negatively associated with elevation, slope angle, and consolidated bedrock. At Grinnell Glacier forefront, increases in vegetation associated negatively with elevation and positively with solar radiation. Integrated geospatial and field approaches to the study of vegetation change in recently deglaciated terrain are recommended to understand and monitor processes and patterns of ongoing habitat change in rapidly changing mountain environments. [ABSTRACT FROM AUTHOR]

(B) El Capitan Cave speleothem EC-16-5-F carbon and oxygen isotope record. Finally, in Figure 3b the blue and red lines representing the El Capitan Cave speleothem EC-16-5-F carbon and oxygen isotope record are incorrect. [Extracted from the article]

This study evaluates paleoclimate sensitivity over the past 800,000 years from proxy-based reconstructions of changes in global temperature, ice sheets and sea level, vegetation, dust, and greenhouse gases. This analysis uses statistical methods that are not biased by the variable (heteroscedastic) uncertainty in the reconstructions, and applies a Monte Carlo-style probabilistic framework to quantify several sources of measurement and structural uncertainty. Not addressing the heteroscedastic uncertainty would result in regression results that underestimate paleoclimate sensitivity by over 30%, and not using a probabilistic framework could underestimate the credible interval by fivefold. A comparison of changes in global temperature (ΔT) and changes in radiative forcing from greenhouse gases, ice sheets, dust, and vegetation (ΔR[GHG,LI,AE,VG]) over the past 800 kyr finds that the two are closely coupled across glacial cycles with a correlation of 0.81 (0.6 to 0.9, 95% credible interval). The variation of ΔT with ΔR over the past 800 kyr is non-linear, with lower correlation and lower responsiveness at colder temperatures. The paleoclimate sensitivity parameter estimates (S[GHG,LI,AE,VG]) are 0.84 °C/W/m2 (0.20 to 1.9 °C/W/m2, 95% interval) for interglacial periods and intermediate glacial climates and 0.53 °C/W/m2 (0.08 to 1.5 °C/W/m2, 95% interval) for full glacial climates, 37% lower at the median. The estimates of S[GHG,LI,AE,VG] and the pattern of state dependence are similar across glacial cycles over the past 800 kyr. This analysis explicitly includes several sources of uncertainty and is still able to provide a strong upper bound for the paleoclimate sensitivity parameter for interglacial periods and intermediate glacial climates: over 1.5 °C/W/m2 is < 10% probability, 1.7 °C/W/m2 is < 5% probability, and over 1.9 °C/W/m2 is < 2.5% probability. [ABSTRACT FROM AUTHOR]

To better understand what determines the Last Glacial Maximum (LGM) cold and dry climate, a suite of numerical experiments with the Nanjing University of Information Science and Technology Earth System Model version 1 are conducted to assess the relative contributions of individual external forcings, including greenhouse gases (GHGs), ice sheets (IS), land-sea configuration (LSC) and the Earth's orbital parameters, and the contribution of their combination in the LGM mean climate change. Results of the single-forcing sensitivity experiments not only reveal spatial patterns of temperature and precipitation changes that are different from today's climate, but also shed light on understanding the underlying processes through which each forcing contributes to the formation of the LGM climate. The full forcing experiment simulates a 5.3 K global cooling and an 11.8% reduction of the global mean precipitation, thus yielding a hydrological sensitivity of 2.2% K−1, which is larger than that caused by the present-day GHG forcing. The excessive hydrological sensitivity is primarily attributed to the land-sea configuration change, since its dynamic factor (circulation change) amplifies the precipitation reduction at the tropical convergence zones over both hemispheres. The GHG forcing is the largest contributor to the tropical cooling, whereas ice sheets are responsible for the large hemispheric temperature asymmetry and meridional gradients of the zonal mean temperature change during the LGM period. The LGM precipitation is characterized by decreased precipitation over the Indo-Pacific Ocean and a salient wave train pattern over the Northern Hemisphere (NH). The GHG and LSC forcings are the major contributors to the former since they can change the Indo-Pacific sea surface temperature and the associated Walker circulation, while ice sheets lead to the wave train pattern over the NH by changing the North Atlantic jet stream/storminess and shifting the Intertropical Convergence Zone southward. The climate responses to the LGM forcings are nonlinear. The nonlinearity mainly comes from the overlapping effects induced by the IS and LSC forcings. [ABSTRACT FROM AUTHOR]

The relationship between soil formation and sedimentation on the floodplain of the Utyaganka River (the Ural River basin) in the Arkaim Reserve (Chelyabinsk oblast, Southern Ural, Russia) was studied. Pedological, palynological, and mineralogical research methods were applied, and 15 radiocarbon dates of soil humus and sediments were obtained. The thickness of the Holocene sediments on the low floodplain is 4–5 m. Their top 1.5-m-thick layer formed in the recent 2000 yr contains three buried (partially superposed) soils formed at the mean rate of 13.3 cm/100 yr. Alluvial soddy soils with solonetzic and salinity features reflect intensive anthropogenic erosion in the river basin and characterize the Little Ice Age and the dry and warm Viking Age. At the depth of 1.5–5 m, there are up to five buried soils separated from one another by alluvium layers; they were formed in the period of 12 000–2000 BP at the rate of 1.9–3.1 cm/100 yr. Among them, the soils that developed 4200–2000 BP are characterized by varying humus content and solonetzicity; they are enriched with carbonates and reflect sharp fluctuations in atmospheric moistening against the background of dominating arid and continental climate. The soils formed 5500–4200 BP are gleyed, moderately humified, and calcareous; they testify to a more humid and warm climate than now. This period was characterized by the maximal area of forests (the pollen of tree species reaches 67%). The period of 8000–5500 BP was specified by warm and dry climate, which is indicated by soil properties and palynological data (15% of tree pollen). Soils formed 9500–8000 BP on stony proluvium-alluvium are eroded mucky gley soils; they reflect sharp fluctuations of the climate at the end of the glacial epoch. Floods were probably accompanied not only by alluvium accumulation but also by regular erosion of the surface and a decrease in the thickness of the humus horizon. This resulted in the renewal of soils and slowed down the increase in the thickness of humus horizon and in the intensity of alluvium accumulation. The average portion of humified soil layers reaches 26% of the total thickness of alluvial sediments. [ABSTRACT FROM AUTHOR]

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

Modeling of the bioclimatic niches of the complex of tall herb communities in the current and predicted climatic conditions by 2070, as well as in the conditions of the climate of the Last Glacial Maximum (about 21 thousand years ago), has been performed. The most important bioclimatic parameters controlling the geographical distribution of tall herbs are the amount of snow precipitation (snow depth), Kira's warmth and coldness indices, and the continentality index. Under the conditions of the Last Glacial Maximum, bioclimatic refugia of tall herbs could be preserved on the Kuril Islands, but were absent on Sakhalin Island and Kamchatka Peninsula. Current trends of climate change will lead to an increase of the area suitable for tall herb communities in the Russian Far East, but will reduce their distribution in Japan. [ABSTRACT FROM AUTHOR]

Increasing glacial discharge may influence future recruitment patterns and growth rates of marine benthos in glacial fjords as changes in surface-water temperature and salinity as well as an increase in ice-scouring events. We deployed settling plates at three spatial and temporal scales in a sub-Arctic glacial fjord system to quantify spatial and temporal variation in the recruitment rates and early growth of subtidal marine benthos, and to determine potential drivers of recruitment. We found significant spatial variation in recruitment of benthos (flora and fauna) at both the small (20 m) and large (> 30 km) scale, indicating that both abiotic and biotic factors may be important. We observed that substrate modification by bushy macroalgae facilitated Mytilus spp. settlement, yet limited Semibalanus balanoides recruitment, underlining that timing in settlement of different species is important in structuring benthic communities. Spatial variation in physical parameters, such as temperature and salinity, likely affected growth and recruitment patterns of benthos (S. balanoides). Finally, we found large spatial and temporal variation in kelp recruitment varying from none to 5866 ind. m−2, with an annual production of more than 6000 g dw m−2 year−1. This large growth potential of kelp suggests recruitment as a bottleneck in kelp population dynamics. Conclusively, variation in sub-Arctic benthic recruitment and growth patterns may respond to changes in temperature and salinity, yet further effort is needed to elucidate potential drivers of benthic recruitment in a fast changing Arctic environment. [ABSTRACT FROM AUTHOR]

Common basal moraines display diverse glaciodynamic structures inherited from the parental moraine-containing ice. Since these glacial diamictons are marked by instable structure and composition, they can resemble sediments of another origin and their identification is a difficult task. We cannot make substantiated genetic conclusions based on certain lithological properties typical of glacial diamictons. Only a set of specific features can provide sufficiently reliable determination of their glacial nature. Other methodical approaches applied in different regions, the Barents Sea included, for the identification of glacial diamictons based on the highly superficial analysis of some (usually secondary) features lead to a biased genetic interpretation of moraines. [ABSTRACT FROM AUTHOR]

The cumulative effect of repeated extensive glaciations represents a poorly constrained component in the understanding of landscape evolution in mid-latitude mountain ranges such as the Alps. Timing, extent, and paleo-climatic conditions of these glaciations are generally poorly understood due to the often-fragmentary character of terrestrial Quaternary records. In this context, the sedimentary infills of subglacial basins may serve as important archives to complement the Quaternary stratigraphy over several glacial-interglacial cycles. In this study, sedimentary facies, valley-fill architecture, and luminescence dating are used to describe nine erosional and depositional cycles (Formations A-I) in the Lower Glatt valley, northern Switzerland. These cycles can be related to the ‘Birrfeld’ Glaciation (~ MIS2), the ‘Beringen’ Glaciation (~ MIS6), and up to three earlier Middle Pleistocene glaciations that can be tentatively correlated to the regional glaciation history. Evidence suggests that deep bedrock trough incision and/or partial re-excavation last occurred mainly during the ‘Beringen’ and ‘Habsburg’ Glaciations. Second-order, ‘inlaid’ glacial basins document separate glacier re-advances during the Beringen Glaciation. The arrangement of subglacial basins in the Glatt valley with different sub-parallel or bifurcating bedrock troughs, re-excavated segments, and inlaid basins document changes in the magnitude and the spatial focus of subglacial erosion over time. The Glatt valley may thus serve as a key example for the glacial landscape evolution in many other repeatedly glaciated forelands. [ABSTRACT FROM AUTHOR]

Earth's modern climate is defined by the presence of ice at both poles, but that ice is now disappearing. Therefore understanding the origin and causes of polar ice stability is more critical than ever. Here we provide novel geochemical data that constrain past dynamics of glacial ice on Greenland and Arctic sea ice. Based on accurate source determinations of individual ice-rafted Fe-oxide grains, we find evidence for episodic glaciation of distinct source regions on Greenland as far-ranging as ~68°N and ~80°N synchronous with ice-rafting from circum-Arctic sources, beginning in the middle Eocene. Glacial intervals broadly coincide with reducedCO2, with a potential threshold for glacial ice stability near ~500 p.p.m.v. The middle Eocene represents the Cenozoic onset of a dynamic cryosphere, with ice in both hemispheres during transient glacials and substantial regional climate heterogeneity. A more stable cryosphere developed at the Eocene-Oligocene transition, and is now threatened by anthropogenic emissions. [ABSTRACT FROM AUTHOR]

The remains of a small volcanic centre are preserved on a thin bedrock ridge at Harrow Peaks, northern Victoria Land, Antarctica. The outcrop is interpreted as a monogenetic tuff cone relict formed by a hydrovolcanic (phreatomagmatic) eruption of mafic magma at 642 ± 20 ka (by Ar-Ar), corresponding to the peak of the Marine Isotope Stage 16 (MIS16) glacial. Although extensively dissected and strewn with glacial erratics, the outcrop shows no evidence for erosion by ice. From interpretation of the lithofacies and eruptive mechanisms, the weight of the evidence suggests that eruptions took place under a cold-based (frozen-bed) ice sheet. This is the first time that a tuff cone erupted under cold ice has been described. The most distinctive feature of the lithofacies is the dominance of massive lapilli tuff rich in fine ash matrix and abraded lapilli. The lack of stratification is probably due to repeated eruption through a conduit blasted through the ice covering the vent. The ice thickness is uncertain but it might have been as little as 100 m and the preserved tephra accumulated mainly as a crater (or ice conduit) infill. The remainder of the tuff cone edifice was probably deposited supraglacially and underwent destruction by ice advection and, particularly, collapse during a younger interglacial. Dating using Be cosmogenic exposure of granitoid basement erratics indicates that the erratics are unrelated to the eruptive period. The Be ages suggest that the volcanic outcrop was most recently exposed by ice decay at c. 20.8 ± 0.8 ka (MIS2) and the associated ice was thicker than at 642 ka and probably polythermal rather than cold-based, which is normally assumed for the period. [ABSTRACT FROM AUTHOR]

Palynological records were selected from the profiles of three research sites in the mountainous interior of southern China (Dajiuhu at Shennongjia in the western part of Hubei Province, Dahu in the Nanling Mountains, and Gantang in the northern part of Fujian Province). It can be inferred that the forest vegetation growing in the south of the Qinling Mountains-Huaihe River was luxuriant during the late glaciation. The species succession with ecological significance in palaeoflora ( Abies sp., Fagus sp. and Alnus sp.) revealed that there was a certain amount of precipitation and effective humidity in the mountain lands between Qinling Mountains-Huaihe River and Nanling Mountains. This ecological environment favored the zonal distribution of mountainous forest vegetation. The late glacial maximum featured a cold, wet climate that completely differed from the cold-dry climate on the Loess Plateau, and on the steppe and desert steppe of the Qinghai-Tibet Plateau. Besides being influenced by the predominant factors driving the Northern Hemisphere climate, the cold-wet climate feature of the mountainous interior of southern China was closely associated with some geographical factors such as the latitudinal position, proximity to the ocean, and the topography and landforms. [ABSTRACT FROM AUTHOR]

It was previously revealed that the total CO concentration in seawater decreased during the Late Archean. In this paper, to assess the secular change of total CO concentration in seawater, we focused on the Paleoproterozoic era when the Earth experienced its first recorded global glaciation. The 2.4 Ga Ongeluk Formation outcrops in the Kaapvaal Craton, South Africa. The formation consists mainly of submarine volcanic rocks that have erupted during the global glaciation. The undeformed lavas are mostly carbonate-free but contain rare disseminated calcites. The carbon isotope ratio of the disseminated calcite (δC vs. VPDB) ranges from − 31.9 to − 13.2 ‰. The relatively low δC values clearly indicate that the carbonation was partially contributed by C-depleted CO derived from decomposition of organic matter beneath the seafloor. The absence of δC higher than − 13.2‰ is consistent with the exceptionally C-depleted CO in the Ongeluk seawater during glaciation. The results suggest that carbonation occurred during subseafloor hydrothermal circulation just after the eruption of the lavas. Previously, it was reported that the carbonate content in the uppermost subseafloor crust decreased from 3.2 to 2.6 Ga, indicating a decrease in total CO concentration in seawater during that time. However, the average CO (as carbonate) content in the Ongeluk lavas (< 0.001 wt%) is much lower than those of 2.6 Ga representatives and even of modern equivalents. This finding suggests that the total CO concentration in seawater further decreased during the period between 2.6 and 2.4 Ga. Thus, the very low content of carbonate in the Ongeluk lavas is probable evidence for the extremely low CO concentration in seawater during the global glaciation. Considering that the carbonate content of the subseafloor crusts also shows a good correlation with independently estimated atmospheric pCO levels through the Earth history, it seem highly likely that the low carbonate content in the Ongeluk lavas reflects the low atmospheric pCO at that time. We conclude that the continuous decrease in CO concentration of seawater/atm. from 3.2 Ga was one of the contributing factors to the Paleoproterozoic global glaciation. [ABSTRACT FROM AUTHOR]

The paper provides a comprehensive review of all aspects of Adriatic Sea level research covered by the literature. It discusses changes occurring over millennial timescales and documented by a variety of natural and man-made proxies and post-glacial rebound models; mean sea level changes occurring over centennial to annual timescales and measured by modern instruments; and daily and higher-frequency changes (with periods ranging from minutes to a day) that are contributing to sea level extremes and are relevant for present-day flooding of coastal areas. Special tribute is paid to the historic sea level studies that shaped modern sea level research in the Adriatic, followed by a discussion of existing in situ and remote sensing observing systems operating in the Adriatic area, operational forecasting systems for Adriatic storm surges, as well as warning systems for tsunamis and meteotsunamis. Projections and predictions of sea level and related hazards are also included in the review. Based on this review, open issues and research gaps in the Adriatic Sea level studies are identified, as well as the additional research efforts needed to fill the gaps. The Adriatic Sea, thus, remains a laboratory for coastal sea level studies for semi-enclosed, coastal and marginal seas in the world ocean. [ABSTRACT FROM AUTHOR]

Freshwater lakes in Antarctica fluctuate from ice-free state (during austral summer) to ice-cover state (during austral winter). Hence the lakes respond instantly to the seasonal climate of the region. The Antarctic seasons respond sharply to the glacial and interglacial climates and these signatures are archived in the lake sediments. A sediment core from Sandy Lake, a periglacial lake located in Schirmacher Oasis of East Antarctica records distinct changes in grain-size, C, N, C/N ratios (atomic), δC and δN contents during the last 36 ky. The contents of the sedimentary organic matter (OM) proxies (C ~ 0.3 ± 0.2%, C/N ratios ~9 ± 5 and δC ~−18 ± 6‰) indicate that the OM in this lake sediment is a product of mixing of terrestrial and lacustrine biomass. Distinctly lower contents of C (~0.2%) and sand (~50%), low C/N ratios (~8) and depleted δC (~−20‰) during the Last Glacial Maximum (LGM: 32-17 ky BP based on Vostok Temperatures) suggest greater internal (autochthonous) provenance of organic matter and limited terrestrial (allochthonous) inputs probably due to long and intense winters in the Antarctic. Such intense winters might have resulted the lake surface to be ice-covered for most part of the year when the temperatures remained consistently colder than the Holocene temperatures. The denitrification within the lake evident by enriched δN (>10‰) during Antarctic LGM might have resulted from oxygen-limitation within the lake environment caused by insulated lake surface. The gradual increases in δC, C/N and sand content starting at ~11 ky BP and attaining high values (~−11‰, ~10 and ~80% respectively) at ~6 ky BP together suggest a subtle change in the balance of sources of organic matter between algal and macrophyte/bryophyte nearly 8-9 ky later to the beginning of the deglaciation. Thus the seasonal opening-up of the Sandy Lake similar to the modern pattern started with the establishment of the optimum temperature conditions (i.e., 0 °C anomaly) in the Antarctic, prior to which the lake environment might have remained mostly insulated or closed. [ABSTRACT FROM AUTHOR]

The finless porpoise (genus Neophocaena ) is a poorly known cetacean of great conservation concern. Within its range, from western Pacific to northwestern Indian Ocean, there are currently two species recognized ( N. asiaeorientalis and N. phocaenoides ), thought to be reproductively isolated since last glacial maximum, with the only sympatric overlap zone in Taiwan Strait. However, the genetic variation across the genus’ distribution has not yet been extensively studied, especially in the Indian Ocean. We performed an exhaustive review of molecular data of the finless porpoise across its range. Neighbor-net networks analyses based on two mitochondrial loci (control region/CR and cytochrome b/ cyt b ) suggest that finless porpoises from the Indian and Pacific Ocean constitute two distinct clades, well-defined by fixed mutations at both loci. A molecular clock analyses indicate early split (CR: 13.1 Ma, cyt b : 12.9 Ma) between these two oceanic lineages, while spatial genetic analyses further suggest that in the Pacific the divergence was primarily due to the taxon from Japanese waters rather than inter-species divergence across the Taiwan Strait. As extinction risks can be substantially underestimated if threatened species are pooled together with non-threatened, especially in the absence of long-distance migration, we suggest that the present 2-species taxonomy of the genus Neophocaena should be given further examination, with concerted sampling effort in the Western Indian Ocean. More research effort and genomic information is needed before taxonomic revisions can be considered; such further studies are strongly recommended as they may affect the current status classification of the species constituting the genus Neophocaena . Most notably, the narrow-ridged finless porpoise off Japan merits urgent conservation attention. [ABSTRACT FROM AUTHOR]

This study is concerned with numerical simulation of the strain due to glaciation and glacial melting, when a magma zone (a layer containing inclusions of magma and magma cumulates) is present at the crust-mantle boundary. According to analytical solutions of this problem that involves viscous relaxation of an uncompensated depression at the place of the molten glacier, the depth to the zone of increased shear stresses beneath the depression is proportional to its width, while the relaxation duration is proportional to viscosity of the lithosphere and is a few thousand years. These fundamental estimates are corroborated by our numerical simulation. According to it, the magma zone at the Moho boundary shields the zone of increased shear stresses, limiting it from below. The maximum values (12-25 MPa) with glacial thickness 500-1000 m are reached at the top of this layer of low viscosity. The directions of maximum compression (s) as calculated for the time after the melting indicate that the magma that rises along dikes is displaced from the center of the magma lens toward its periphery. It is found that glacial unloading makes the dipping faults in the crust above the low-viscosity layer attractors for the rising magma. Glacial unloading accelerates, by factors of a few times, the magma generation in the mantle that occurs following the mechanism of adiabatic decompression, as well as facilitating the accumulation of mantle fluids in the zone of increased shear stresses at the boundary of the low viscosity layer. The magma traverses this deep fluid collector and increases the intensity and explosivity of eruptions at the beginning of an interglacial period. Our numerical simulation results are in general agreement with published data on Early Holocene volcanic eruptions that occurred after the second phase of the Late Pleistocene glaciation in Kamchatka. [ABSTRACT FROM AUTHOR]

Multiproxy investigation of sediment core AF-0731 from the Mendeleev Rise revealed several epochs of high bioproductivity corresponding to climate amelioration and surface water mass warming in the Arctic. During these periods, sediments became enriched in carbonate microfossils as well as in coarsegrained ice- and iceberg-rafted debris (IRD) that precipitated from melting sea ice and icebergs. Variability in the δО composition of planktic foraminifers also reflects glacial-interglacial periodicity. Low δО values correspond to glacial epochs and, especially, glacial terminations with strong meltwater inputs. Increased δО values characterize interglacial epochs of sea-level rise and growing salinity due to enhanced water exchange with neighboring oceans. The Sr/Sr ratio was measured in foraminifers from basal core layers, and their SIS-age was estimated at 670 + 50 ka. Sedimentation rates at AF-0731 core site on the Mendeleev Rise varied between 0.4 and 0.6 cm/kyr. [ABSTRACT FROM AUTHOR]

The glacial morphology of southern South American presents invaluable evidence to reconstruct former glacier behaviour and its relation to climate and environmental changes. However, there are still spatial and temporal gaps in the reconstruction of the Holocene Patagonian glacial landscape. Here we present the first geomorphological record for the Sierra Baguales Mountain Range (SBMR), forming the eastern foothills of the Southern Patagonian Andes 200 km from the Pacific coast. This area is topographically isolated from the Southern Patagonian Ice Field (SPIF), and is affected by the Westerly Winds. The study area shows evidence of ice sheet and alpine glaciations related to Andean uplift, which caused a marked climatic contrast between its western and eastern flanks since the Last Glacial Maximum (LGM). The regional rock mass strength and precipitation gradient acted as a controlling factor in the glacial cirque distribution and sizes, as well as in the development of glaciation types. We report new radiocarbon dates associated with warm/dry to cold/wet climatic changes during the middle Holocene, when former small alpine glaciers were located in the uppermost section of the SBMR basins, and eventually converged to form a small ice field or a composite valley glacier at lower elevations. This can be explained by an estimated regional temperature drop of 3.8°C±0.8°C, based on a 585±26 m Equilibrium Line Altitude (ELA) descent, inferred by geomorphological evidence and the Accumulation Area Ratio (AAR), in addition to a free-air adiabatic lapse rate. Subsequently, the glaciers receded due to climatic factors including a rise in temperature, as well as non-climatic factors, mainly the glacier bedrock topography. [ABSTRACT FROM AUTHOR]

Glacial isostatic adjustment (GIA) encompasses a suite of geophysical phenomena accompanying the waxing and waning of continental-scale ice sheets. These involve the solid Earth, the oceans and the cryosphere both on short (decade to century) and on long (millennia) timescales. In the framework of contemporary sea-level change, the role of GIA is particular. In fact, among the processes significantly contributing to contemporary sea-level change, GIA is the only one for which deformational, gravitational and rotational effects are simultaneously operating, and for which the rheology of the solid Earth is essential. Here, I review the basic elements of the GIA theory, emphasizing the connections with current sea-level changes observed by tide gauges and altimetry. This purpose is met discussing the nature of the 'sea-level equation' (SLE), which represents the basis for modeling the sea-level variations of glacial isostatic origin, also giving access to a full set of geodetic variations associated with GIA. Here, the SLE is employed to characterize the remarkable geographical variability of the GIA-induced sea-level variations, which are often expressed in terms of 'fingerprints'. Using harmonic analysis, the spatial variability of the GIA fingerprints is compared to that of other components of contemporary sea-level change. In closing, some attention is devoted to the importance of the 'GIA corrections' in the context of modern sea-level observations, based on tide gauges or satellite altimeters. [ABSTRACT FROM AUTHOR]

Well-preserved Late Glacial moraines in the Barenduo and Yuqiongqu valleys on the eastern slope of the Samdainkangsang Peak present an opportunity to reconstruct glacier extents and examine the character of the climate during the Late Glacial stage in the Nyaiqentanggulha Mountains. This study employs a coupled mass-balance and ice-flow model to reconstruct the glacier extents in the two valleys and assess the magnitudes of temperature and precipitation change during the Late Glacial period. Model results indicate that during the Late Glacial, the Barenduo valley contained an ice volume of 1.67×108 m3, with the equilibrium-line altitude (ELA) being ~5500 m asl; and the Yuqiongqu valley had an ice volume of 5.56×108 m3, with the ELA being ~5470 m asl. A climate scenario, temperature depression of 2.6-2.8°C and 60-70%, percent of modern (1981-2010) precipitation, can sustain both of the Late Glacial glacier extents in the two valleys. A 50% increase or decrease from modern precipitation would have been coupled with the respective Late Glacial temperature depressions of 1.6 and 3.0°C in the Barenduo valley, and 2.1 and 2.8°C in the Yuqiongqu valley. [ABSTRACT FROM AUTHOR]

The study of lavas and pyroclastics from Anyui Volcano made it possible to reconstruct succession of its eruption events. The age of the eruption is estimated by isotopic methods to be 0.248 ± 0.030 Ma. It is established that the last episode of volcanic activity in northeastern Russia occurred 0.2-0.5 Ma ago (in its continental part, 0.2-0.3 Ma ago). This episode is chronologically close to the last peak in activation of volcanism in the Arctic and Subarctic regions. The absence of features indicating glacial influence on lavas from Anyui Volcano provides grounds for an assumption that no significant glaciations took place in the continental areas of western Chukotka during the last 250 ka. [ABSTRACT FROM AUTHOR]

Two enhanced temperature-index (T-index) models are proposed by incorporating meteorological parameters viz. relative humidity, wind speed and net radiation. The models are an attempt to explore different climatic variables other than temperature affecting glacier surface melting. Weather data were recorded at Chorabari Glacier using an automatic weather station during the summers of 2010 (July 10 to September 10) and 2012 (June 10 to October 25). The modelled surface melt is validated against the measured point surface melting at the snout. Performance of the developed models is evaluated by comparing with basic temperature-index model and is quantified through different efficiency criteria. The results suggest that proposed models yield considerable improvement in surface melt simulation . Consequently, the study reveals that glacier surface melt depends not only on temperature but also on weather parameters viz. relative humidity, wind speed and net radiation play a significant role in glacier surface melting. This approach provides a major improvement on basic temperature-index method and offers an alternative to energy balance model. [ABSTRACT FROM AUTHOR]

During the last deglaciation (from approximately 21 to 11 thousand years ago), the high latitudes of the Atlantic Ocean underwent major changes. Besides the continuous warming, the polar and subpolar ocean surface received a large amount of meltwater from the retracting ice sheets. These changes in temperature and salinity affected deep waters, such as the Antarctic Bottom Water (AABW) and the North Atlantic Deep Water (NADW), which are formed in the Southern Ocean and in the northern North Atlantic, respectively. In this study, we present the evolution of the physical properties and distribution of the AABW and the NADW since the last glacial maximum using the results of a transient simulation with NCAR-CCSM3. In this particular model scenario with a schematic freshwater forcing, we find that modern NADW, with its characteristic salinity maximum at depth, was absent in the beginning of the deglaciation, while its intermediate version-Glacial North Atlantic Intermediate Water (GNAIW)-was being formed. GNAIW was a cold and relatively fresh water mass that dominated intermediate depths between 60 and 20°N. At this time, most of the deep and abyssal Atlantic basin was dominated by AABW. Within the onset of the Bølling-Allerød period, at nearly 15 thousand years ago (ka), GNAIW expanded southwards when the simulated Meridional Overturning Circulation overshoots. The transition between GNAIW and NADW ocurred after that, when AABW was fresh enough to allow NADW to sink deeper in the water column. When the NADW appears (~11 ka), AABW retracts and is constrained to lie near the bottom. [ABSTRACT FROM AUTHOR]

Significant uncertainties remain regarding the temporal evolution of natural vegetation during the Quaternary, and drivers of past vegetation change, on the Chinese Loess Plateau (CLP). This study presents analyses of total organic carbon isotopic composition (TOC) and n-alkane ratios (C31/C27) from the Lingtai loess-palaeosol sequence on the central CLP over the last 450 kyr. The results demonstrate that the vegetation in this region comprised a mix of C and C plants of herb and woody growth-form. C plants dominated for most of the last 450 kyr, but this did not lead to extensive forest. C woody plants were more abundant in MIS9 (S3 period) and MIS5 (S1 period) during warm and humid climate conditions. Herbs increased in the region since 130 kyr, possibly as a result of increased aridity. On the orbital timescales, there was a reduction of C herbal plants in MIS11 (S4) than in MIS12 (L5), and in Holocene than in the last glacial period. Our isotope and n-alkane proxy records are in agreement with Artemisia pollen changes in the region, which is/was the dominant species in this area and varying due to different heat and water conditions between glacial and interglacial periods. Though the climate in MIS1 (S0) was similar to that in MIS11 (S4), a significant increase in woody plants during the Holocene suggests the impact of human activities and ecological effects of changes in fire activity. [ABSTRACT FROM AUTHOR]

The Earth's cryosphere comprises those regions that are cold enough for water to turn into ice. Recent findings show that the icy realms of polar oceans, glaciers and ice sheets are inhabited by microorganisms of all three domains of life, and that temperatures below 0 °C are an integral force in the diversification of microbial life. Cold-adapted microorganisms maintain key ecological functions in icy habitats: where sunlight penetrates the ice, photoautotrophy is the basis for complex food webs, whereas in dark subglacial habitats, chemoautotrophy reigns. This Review summarizes current knowledge of the microbial ecology of frozen waters, including the diversity of niches, the composition of microbial communities at these sites and their biogeochemical activities. [ABSTRACT FROM AUTHOR]