Rapid Climate Shifts Research Articles

Riverscape genomics of the endangered freshwater mussel Lampsilis rafinesqueana

Abstract Historical periods of rapid climate change and associated direct and indirect impacts such as glaciation and restructuring of drainage systems are important in shaping biodiversity, lineage divergence, and contemporary genetic variation amongst many aquatic taxa. Through an understanding of the impacts of these ancient changes in land‐ and waterscapes on current diversity, practitioners can account for a species' unique evolutionary history when developing conservation strategies. We investigated intraspecific genetic diversity of the critically endangered freshwater mussel, Lampsilis rafinesqueana, endemic to the interior region of the U.S.A. Our study (1) characterises genetic variation within and amongst populations to infer biogeographic history and (2) applies genetic information to potential conservation strategies. We applied restriction‐site associated DNA sequencing and mitochondrial DNA sequencing to investigate genetic diversity within and amongst populations of L. rafinesqueana from across the species' distribution. We then considered this information in the context of historical riverscape processes and applicability to conservation. Variation within rivers was similar, but we found different genetic populations associated with two major ecoregions, the Central Interior Highlands and Osage Plains. The plains population displayed an Ne value approximately 10‐fold lower than the highlands population. Historical demographic modelling suggests the two populations diverged approximately 1.2 million years ago and then both populations underwent a substantial decrease in population size around 19,700 years ago. These two major events are each correlated with known periods of historic rapid climate change. We identified two distinct populations of a federally endangered mussel, L. rafinesqueana. Contemporary genetic diversity of this species was strongly influenced by direct and indirect impacts of rapid historic shifts in climate. The highlands population has undergone a recent expansion, typical of post‐Pleistocene climate change, while also having a much larger Ne value than the plains population. Our results suggest low levels of gene flow amongst the two distinct populations across generations. We recommend that conservation managers for this species take into account relative difference in diversity between populations when developing management strategies. In many species, assisted gene flow amongst genetically unique populations should only be considered in extreme circumstances; however, in L. rafinesqueana, low levels of assisted migration amongst populations may be a valuable tactic to maintain natural levels of genetic variation. Our study shows that biogeographical frameworks can be useful for developing conservation strategies that serve to retain important genomic variation that represents the evolutionary potential of target freshwater species.

Characteristics and features of Kazakhstan’s water security policy

Amidst the complex geopolitical dynamics of Central Asia, Kazakhstan grapples with urgent water security issues exacerbated by climate change, underscoring the critical need to examine this issue within the context of regional security. Therefore, this study seeks to comprehensively analyze Kazakhstan’s water security policy, examining its various elements and components at national and regional levels. Using system analysis and statistical techniques, data were collected from an array of sources, including strategies, development plans, statistical reports, analytical articles, methodological guidelines, and official government and international organization websites. The analysis revealed key challenges in Kazakhstan’s water security, including deteriorating infrastructure, outdated management practices, vulnerability to floods and low water levels, inadequate training, and regulatory deficiencies. A novel approach is offered by examining current trends in Kazakhstan’s water security domain, which involves scrutinizing the activities of relevant state bodies and analyzing regulatory frameworks amid rapid climate shifts. Additionally, the heightened potential for conflict across the continent was recognized. Despite earnest attempts to mitigate these challenges, the country confronts imminent water shortages exacerbated by heightened consumption and dwindling runoff from neighboring states. In light of these findings, policymakers and stakeholders are urged to devise robust policies and management strategies aimed at fortifying water security and addressing the underlying vulnerabilities in this critical domain.

Plant nutrient stoichiometry appears out of sync from soil: Increasing influences of changing climate on the grassland in inner Mongolia, China

Extremes in weather episodes seem to be the new normal. We need to better understand how changing climatic conditions alter plant growth in grasslands, especially macro nutrient uptake and stoichiometry. However, few studies have examined how warmer/colder or wetter/drier climates influence the nutrient coupling between plants and soils at the ecosystem level. Here, we investigated the changes in carbon (C), nitrogen (N), and phosphorus (P) concentrations and their stoichiometric ratios in plants and soils from 65 grassland sites along a geographic gradient in northern China. Results showed that soil C, N and P were negatively correlated with temperature and aridity. Plant N was positively correlated with temperature and aridity, but plant P was negatively correlated with temperature and aridity. Plant C had no significant relationship with either aridity or temperature. Both temperature and aridity were positively correlated with C:N, but negatively correlated with C:P and N:P in soils. The ratio of plant C:N was negatively correlated with aridity, while plant C:P was positively correlated with temperature. Plant N:P was positively correlated with temperature and aridity. Our findings imply that the often-found positive relationships between plant and soil nutrients at one site might not apply to a broad geographic scale with varying climatic conditions, likely because of the “dilution effect” and disparate plant nutrient utilization strategies. It is conceivable that rapid climate shifts and the resulting changes in element availability, turnover rates, absorption, and use efficiency might cause desynchrony of C, N, and P cycles between plants and soils.

THE FUTURE SETTLEMENT PATTERNS OF EARTH: ANTICIPATING HUMAN HABITATS IN A CHANGING WORLD

The global landscape of human settlement has undergone significant transformations throughout history, driven by technological advancements, societal shifts, and environmental changes. This article aims to explore the potential future settlement patterns of Earth, considering the interplay between various factors such as urbanization, climate change, technological innovation, and social dynamics. By analyzing current trends and projecting them into the future, we attempt to envision the possible scenarios that could shape the distribution and nature of human habitats on Earth. This article underscores the significance of sustainable development, adaptable infrastructure, and proactive policies in crafting resilient and harmonious settlements for forthcoming generations. In an era marked by unprecedented challenges, including rapid urbanization, climatic shifts, and technological leaps, understanding the potential future landscapes of human habitation becomes paramount. This research navigates through the drivers propelling these changes, such as urban growth, climate impacts, transformative technologies, and resource constraints. Addressing the challenges arising from these drivers – sustainable practices, resilient infrastructure, equitable societies, and effective governance – is pivotal. The article outlines conceivable future scenarios, including hyper-connected urban hubs, eco-centric communities, and decentralized rural clusters, each influenced by distinct drivers and dynamics. Navigating these complex trajectories demands interdisciplinary cooperation, informed policy-making, and a collective commitment to ensure that Earth’s future settlements are adaptive, sustainable, and capable of fostering human well-being amidst an ever-evolving backdrop.

Directly Dating Plio‐Pleistocene Climate Change in the Terrestrial Record

AbstractAccurate chronology of climatic shifts is critical to understand the controls on landscape and species evolution. Unfortunately, direct dating of continental climate change is hindered by the scarcity of dateable terrestrial products evidencing climatic shifts. Here we use ferruginous indurations from the arid landscapes of the Nullarbor Plain in southern Australia to constrain the timing of Plio‐Pleistocene aridification in the continental realm. We present (U‐Th)/He goethite data implying active induration processes between c. 2.7 and 2.4 Ma. Chemical‐mineralogical and petrographic examination suggests that formation of ferruginous indurations was linked with a decline of the groundwater table, driven by the rapid climatic shift from humid late Pliocene to arid early Pleistocene conditions. Combined with local to global climatic proxies, we conclude that ferruginous indurations are promising targets to obtain absolute ages on landscape evolution to refine continental climatic chronology and improve understanding of the environmental drivers of species diversification and extinction.

Kill dates from re-exposed black mosses constrain past glacier advances in the northern Antarctic Peninsula

AbstractGlaciers are receding in the northern Antarctic Peninsula and exposing previously entombed soils and plants. We used 39 black (dead) mosses collected from rapidly retreating ice margins at four sites along the Antarctic Peninsula to determine the kill dates using radiocarbon measurements and to constrain the timing of past glacier advances over the last 1500 yr. We established strict new criteria for sample collection to promote robust estimates of plant death. We found distinct phases of ice advance during ca. 1300, 800, and 200 calibrated years before 1950 (cal yr B.P.). We report estimates of the rate of glacier advance at ca. 800 cal yr B.P. at Gamage and Bonaparte Points (southern Anvers Island) of 2.0 and 0.3 m/yr, respectively. Although the range of kill dates is relatively narrow within a region, suggesting multiple glaciers advanced simultaneously, the rates of local advances can vary by almost an order of magnitude and are much less than retreat rates. Our kill dates coincide with evidence for glacier advances from other studies in the northern Antarctic Peninsula at ca. 1300, 800, and 200 cal yr B.P. and for penguin colony abandonment at several sites in the region ranging from 450 to 0 cal yr B.P. The combination of our new terrestrial evidence for glacier advances with other lines of evidence shows the regional synchroneity of glacial dynamics and cryosphere-biosphere connections during rapid climate shifts and the sensitivity of terrestrial ecosystems to climate cooling.

Nest orientation and proximity to snow patches are important for nest site selection of a cavity breeder at high elevation

Timing and location of reproduction are central to reproductive success across taxa. Among birds, many species have evolved specific strategies to cope with environmental variability including shifts in timing of reproduction to track resource availability or selecting suitable nest location. In mountain ecosystems, complex topography and pronounced seasonality result in particularly high spatiotemporal variability of environmental conditions. Moreover, the risk of climate‐induced resource mismatches is particularly acute in mountain regions given that temperature is increasing more rapidly than in the lowlands. We investigated how a high‐elevation passerine, the white‐winged snowfinch Montifringilla nivalis, selects its nest site in relation to nest cavity characteristics, habitat composition and snow condition. We used a combination of field habitat mapping and satellite remote sensing to compare occupied nest sites with randomly selected pseudo‐absence sites. In the first half of the breeding season, snowfinches preferred nest cavities oriented towards the morning sun while they used cavities proportional to their availability later on. This preference might relate to the nest microclimate offering eco‐physiological advantages, namely thermoregulatory benefits for incubating adults and nestlings under the harsh conditions typically encountered in the alpine environment. Nest sites were consistently located in areas with greater‐than‐average snow cover at hatching date, likely mirroring the foraging preferences for tipulid larvae developing in meltwater along snowfields. Due to the particularly rapid climate shifts typical of mountain ecosystems, spatiotemporal mismatches between foraging grounds and nest sites are expected in the future. This may negatively influence demographic trajectories of the white‐winged snowfinch. The installation of well‐designed nest boxes in optimal habitat configurations could to some extent help mitigate this risk.

Active Nordic Seas deep-water formation during the last glacial maximum

The Nordic Seas are the primary location where the warm waters of the North Atlantic Current densify to form North Atlantic Deep Water, which plays a key part in the modern Atlantic Meridional Overturning Circulation. The formation of dense water in the Nordic Seas and Arctic Ocean and resulting ocean circulation changes were probably driven by and contributed to the regional and global climate of the last glacial maximum (LGM). Here we map the source and degree of mixing of deep water in the Nordic Seas and through the Arctic Gateway (Yermak Plateau) over the past 35 thousand years using neodymium isotopes (εNd) measured on authigenic phases in deep-sea sediments with a high spatial and temporal resolution. We find that a large-scale reorganization of deep-water formation in the Nordic Seas took place between the LGM (23–18 thousand years ago) and the rapid climate shift that accompanied the subsequent deglaciation (18–10 thousand years ago). We show that homogeneous εNd signatures across a wide range of sites support LGM deep-water formation in the Nordic Seas. In contrast, during the deglaciation, disparate and spatially variable εNd values are observed leading to the conclusion that deep-water formation may have been reduced during this time.

Coexistence in Times of Climate Crisis: A Participatory Mapping to Understanding Conservation Conflicts in the Central Andes of Chile

PurposeHuman-wildlife conflicts worldwide are arising, representing significant challenges for conservation biologists, decision-makers, and agropastoralist communities. Extreme climatic events, disease outbreaks, and land-use change could be intensifying these conflicts. The multi-species and mountainous landscapes seem prone to conflicts due to a lack of territory planning. These complex, dynamic, and multi-layered conflicts require a multidimensional approach. Currently, in Chile, mountainous landscapes have several threats, such as a lack of territory planning, mega-mining projects, and recently (last 10 years) the effects of the Mega-drought. Many transhumant agropastoralists have been forced to quit their livelihoods while increasing livestock-wildlife conflicts. We aim to build territorial planning within a holistic approach to strengthening the agropastoralists' competence to coexist with local wildlife (puma, condor, and guanaco) in Central Chile's Andes mountains.MethodologyWe conducted participatory mapping workshops with two agropastoralist communities in 2020. They were randomly divided into 4 to 7 people groups and told to draw a map representing their territory, including four elements: (1) natural and human components of the landscape, (2) natural wildlife conflict areas, (3) active grazing areas, and (4) their ideal future scenario, regarding their activity.FindingsResults showed different spatial perceptions of the natural and human components of the territory. All agropastoralists (100%) indicated similar wildlife conflict areas: focusing in the Summerlands. All agreed that Mega-drought was the primary threat to their production, increasing the conflict with wildlife. Summerland areas are identified as suitable areas for working in conflict with wildlife.Research Limitations/ImplicationsThis study highlights the need for a multidimensional approach to conflict and territory planning to address conservation conflicts. The study's implications show that agropastoralists decided to reduce Summerland use and improve Winterland planning to increase livestock productivity and reduce conflict with wildlife. Participatory mapping could help to prioritize areas to mitigate conflicts with wildlife.Originality/ValueThis study is the first in the Aconcagua valley to conduct a transdisciplinary & participatory approach toward coexistence between transhumant agropastoralists and wildlife. It also provides a baseline for similar schemes in semi-arid and mountainous landscapes worldwide facing rapid climate shifts and increasing human-wildlife conflict.

Reorganization of Atlantic Waters at sub-polar latitudes linked to deep-water overflow in both glacial and interglacial climate states

Abstract. While a large cryosphere may be a necessary boundary condition for millennial-scale events to persist, a growing body of evidence from previous interglacial periods suggests that high-magnitude climate events are possible during low-cryosphere climate states. However, the full spectrum of variability, and the antecedent conditions under which such variability can occur, have not been fully described. As a result, the mechanisms generating high-magnitude climate variability during low-cryosphere boundary conditions remain unclear. In this study, high-resolution climate records from Deep Sea Drilling Project (DSDP) site 610 are used to portray the North Atlantic climate's progression through low ice, boundary conditions of Marine Isotope Stage (MIS) 11c into the glacial inception. We show that this period is marked by two climate events displaying rapid shifts in both deep overflow and surface climate. The reorganization between Polar Water and Atlantic Water at subpolar latitudes appears to accompany changes in the flow of deep water emanating from the Nordic Seas, regardless of magnitude or boundary conditions. Further, during both intermediate and low ice boundary conditions, we find that a reduction in deep water precedes surface hydrographic change. The existence of surface and deep-ocean events, with similar magnitudes, abruptness, and surface–deep phasing, advances our mechanistic understanding of, and elucidates antecedent conditions that can lead to, high-magnitude climate instability.

Synchronous or Not? The Timing of the Younger Dryas and Greenland Stadial-1 Reviewed Using Tephrochronology

The exact spatial and temporal behaviour of rapid climate shifts during the Last Glacial–Interglacial Transition are still not entirely understood. In order to investigate these events, it is necessary to have detailed palaeoenvironmental reconstructions at geographically spread study sites combined with reliable correlations between them. Tephrochronology, i.e., using volcanic ash deposits in geological archives as a dating and correlation tool, offers opportunities to examine the timing of events across wider regional scales. This study aims to review the posited asynchrony of the Younger Dryas stadial in comparison with Greenland Stadial-1 by correlating new proxy data from southernmost Sweden to previous palaeoclimate reconstructions in Europe based on the presence of the Hässeldalen Tephra, the Vedde Ash, and the Laacher See Tephra. μ-XRF core-scanning data were projected using a recently published age–depth model based on these tephras and several radiocarbon dates, and compared to previous findings, including by adapting previous chronologies to the recently proposed earlier date of the Laacher See Tephra (13,006 ± 9 cal. a BP). Although the results to some extent support the idea of a more synchronous Younger Dryas event than previously assumed, this issue requires further high-resolution proxy studies to overcome limitations of temporal precision.

Century-scale climatic oscillations during the Last Glacial Maximum revealed by stalagmite isotopic records from Longfugong Cave, China

The isotopic records of two 230Th-dated stalagmites from Longfugong Cave, Mt. Shennongjia, central China, reveal a highly resolved Asian summer monsoon (ASM) history from 29.5 to 14.5 ka BP. The two δ18O records are consistent with other Chinese cave δ18O records, suggesting that our new records are of regional significance. Due to the reservoir mixing of seepage water in the epikarst system, the stalagmite δ18O signals in this cave are more severely muted than those in other caves. Here, we observed that the amplitude of the δ13C variability is approximately twice that of the δ18O signal and can be used as a sensitive proxy of East Asian monsoon climates. First, the two stalagmite δ13C records are consistent with each other on decadal to centennial timescales. Second, there are high correlation coefficients between the δ13C and δ18O signals over shorter timescales. Third, from 25.2 to 19.6 ka BP, six peaks in the δ13C records were identified and are coincident with corresponding warming events in the Greenland ice-core δ18O records, suggesting that strong coupling occurred between the high- and low-latitude northern climates on centennial timescales. Therefore, we propose that atmospheric transmission mechanisms probably played an important role in linking the ASM and Greenland climates on short timescales. A shift in westerly winds associated with variability in the extent of temperature in the North Atlantic likely influenced changes in hydrological and thermal conditions at the cave site, leading to changes in vegetation cover and soil CO2 concentrations above the cave. Therefore, the calcite δ13C records probably had faster and more sensitive responses to rapid climate shifts compared with their related δ18O records.

Alluvial record of an early Eocene hyperthermal within the Castissent Formation, the Pyrenees, Spain

Abstract. The late Palaeocene to the middle Eocene (57.5 to 46.5 Ma) recorded a total of 39 hyperthermals – periods of rapid global warming documented by prominent negative carbon isotope excursions (CIEs) as well as peaks in iron content – have been recognized in marine cores. Documenting how the Earth system responded to rapid climatic shifts during hyperthermals provides fundamental information to constrain climatic models. However, while hyperthermals have been well documented in the marine sedimentary record, only a few have been recognized and described in continental deposits, thereby limiting our ability to understand the effect and record of global warming on terrestrial systems. Hyperthermals in the continental record could be a powerful correlation tool to help connect marine and continental deposits, addressing issues of environmental signal propagation from land to sea. In this study, we generate new stable carbon isotope data (δ13C values) across the well-exposed and time-constrained fluvial sedimentary succession of the early Eocene Castissent Formation in the south central Pyrenees (Spain). The δ13C values of pedogenic carbonate reveal – similarly to the global records – stepped CIEs, culminating in a minimum δ13C value that we correlate with the hyperthermal event “U” at ca. 50 Ma. This general trend towards more negative values is most probably linked to higher primary productivity leading to an overall higher respiration of soil organic matter during these climatic events. The relative enrichment in immobile elements (Zr, Ti, Al) and higher estimates of mean annual precipitation together with the occurrence of small iron oxide and iron hydroxide nodules during the CIEs suggest intensification of chemical weathering and/or longer exposure of soils in a highly seasonal climate. The results show that even relatively small-scale hyperthermals compared with their prominent counterparts, such as PETM, ETM2, and ETM3, can leave a recognizable signature in the terrestrial stratigraphic record, providing insights into the dynamics of the carbon cycle in continental environments during these events.

Phenotypic plasticity and genetic adaptation of functional traits influences intra-specific variation in hydraulic efficiency and safety

Understanding which hydraulic traits are under genetic control and/or are phenotypically plastic is essential in understanding how tree species will respond to rapid shifts in climate. We quantified hydraulic traits in Eucalyptus obliqua L'Her. across a precipitation gradient in the field to describe (i) trait variation in relation to long-term climate and (ii) the short-term (seasonal) ability of traits to adjust (i.e., phenotypic plasticity). Seedlings from each field population were raised under controlled conditions to assess (iii) which traits are under strong genetic control. In the field, drier populations had smaller leaves with anatomically thicker xylem vessel walls, a lower leaf hydraulic vulnerability and a lower water potential at turgor loss point, which likely confers higher hydraulic safety. Traits such as the water potential at turgor loss point and ratio of sapwood to leaf area (Huber value) showed significant adjustment from wet to dry conditions in the field, indicating phenotypic plasticity and importantly, the ability to increase hydraulic safety in the short term. In the nursery, seedlings from drier populations had smaller leaves and a lower leaf hydraulic vulnerability, suggesting that key traits associated with hydraulic safety are under strong genetic control. Overall, our study suggests a strong genetic control over traits associated with hydraulic safety, which may compromise the survival of wet-origin populations in drier future climates. However, phenotypic plasticity in physiological and morphological traits may confer sufficient hydraulic safety to facilitate genetic adaptation.

Community Assembly and Climate Mismatch in Late Quaternary Eastern North American Pollen Assemblages.

Plant community response to climate change ranges from synchronous tracking to strong mismatch. Explaining this variation in climate change response is critical for accurate global change modeling. Here we quantify how closely assemblages track changes in climate (match/mismatch) and how broadly climate niches are spread within assemblages (narrow/broad ecological tolerance, or "filtering") using data for the past 21,000 years for 531 eastern North American fossil pollen assemblages. Although climate matching has been strong over the last 21 millennia, mismatch increased in 30% of assemblages during the rapid climate shifts between 14.5 and 10 ka. Assemblage matching rebounded toward the present day in 10%-20% of assemblages. Climate-assemblage mismatch was greater in tree-dominated and high-latitude assemblages, consistent with persisting populations, slower dispersal rates, and glacial retreat. In contrast, climate matching was greater for assemblages comprising taxa with higher median seed mass. More than half of the assemblages were climatically filtered at any given time, with peak filtering occurring at 8.5 ka for nearly 80% of assemblages. Thus, vegetation assemblages have highly variable rates of climate mismatch and filtering over millennial scales. These climate responses can be partially predicted by species' traits and life histories. These findings help constrain predictions for plant community response to contemporary climate change.

How likely are adaptive responses to mitigate the threats of climate change for amphibians globally?

Whether species are capable of adapting to rapid shifts in climate raises considerable interest. Analyses based on niche models often assume niche conservatism and equilibrium with climate, implying that species will persist only in regions where future climatic conditions match their current conditions and that they will colonize these regions promptly. However, species may adapt to changing climate and persist where future climates differ from their current optimum. Here, we provide a first macroecological generalization to the approach of evolutionary rescue, by comparing the expected shift in mean temperature within the geographic range of 7193 species of amphibians worldwide, under alternative warming scenarios. Expected evolutionary change is expressed in units of standard deviations of mean temperature, per generation (Haldanes) and compared with theoretical models defining the maximum sustainable evolutionary rates (MSER) for each species. For the pessimistic emission scenario RCP8.5, shifts in mean temperature vary between near-zero and 6°C within the geographic ranges for most species, with a median equal to 3.75°C. The probability of evolutionary rescue in temperature peaks is higher than 0.05 for about 55% of the species and higher than 0.95 for only 12% of the species. Therefore, the predicted shift in mean temperature would be too extreme to deal with for almost half of the species. When evolutionary plasticity is incorporated, this scenario becomes more optimistic, with about 44% of the species being likely to shift their thermal peaks tracking future warming. These figures are not random in geographical space: evolutionary rescue would be unlikely in the tropics, especially in South America (Amazonia), parts of Africa, Indonesia, and in the Mediterranean region. Given the uncertainty in demographic and genetic parameters for species’ responses to climate change, we caution that it remains difficult to assess the realism of the macroecological generalization. In any case, it may be precautionary to assume that our results are not liberal, showing low probability of adaptation for most of the species and thus that the persistence of populations by evolutionary rescue may, in general, be unlikely in the long term.

Consistently dated Atlantic sediment cores over the last 40 thousand years

Rapid changes in ocean circulation and climate have been observed in marine-sediment and ice cores over the last glacial period and deglaciation, highlighting the non-linear character of the climate system and underlining the possibility of rapid climate shifts in response to anthropogenic greenhouse gas forcing. To date, these rapid changes in climate and ocean circulation are still not fully explained. One obstacle hindering progress in our understanding of the interactions between past ocean circulation and climate changes is the difficulty of accurately dating marine cores. Here, we present a set of 92 marine sediment cores from the Atlantic Ocean for which we have established age-depth models that are consistent with the Greenland GICC05 ice core chronology, and computed the associated dating uncertainties, using a new deposition modeling technique. This is the first set of consistently dated marine sediment cores enabling paleoclimate scientists to evaluate leads/lags between circulation and climate changes over vast regions of the Atlantic Ocean. Moreover, this data set is of direct use in paleoclimate modeling studies.

Millennial-Scale Climate Variability and Dinoflagellate-Cyst-Based Seasonality Changes Over the Last ~150 kyrs at "Shackleton Site" U1385.

During the last glacial period, climate conditions in the North Atlantic region were determined by the alternation of relatively warm interstadials and relatively cool stadials, with superimposed rapid warming (Dansgaard‐Oeschger) and cooling (Heinrich) events. So far little is known about the impact of these rapid climate shifts on the seasonal variations in sea surface temperature (SST) within the North Atlantic region. Here, we present a high‐resolution seasonal SST record for the past 152 kyrs derived from Integrated Ocean Drilling Program “Shackleton” Site U1385, offshore Portugal. Assemblage counts of dinoflagellates cysts (dinocysts) in combination with a modern analog technique (MAT), and regression analyses were used for the reconstructions. We compare our records with previously published SST records from the same location obtained from the application of MAT on planktonic foraminifera. Our dinocyst‐based reconstructions confirm the impression of the Greenland stadials and interstadials offshore the Portuguese margin and indicate increased seasonal contrast of temperature during the cold periods of the glacial cycle (average 9.0 °C, maximum 12.2 °C) with respect to present day (5.1 °C), due to strong winter cooling by up to 8.3 °C. Our seasonal temperature reconstructions are in line with previously published data, which showed increased seasonality due to strong winter cooling during the Younger Dryas and the Last Glacial Maximum over the European continent and North Atlantic region. In addition, we show that over longer time scales, increased seasonal contrasts of temperature remained characteristic of the colder phases of the glacial cycle.

Emergent freeze and fire disturbance dynamics in temperate rainforests

AbstractThe coastal temperate rainforests of South and North America are part of the most biomass dense forest biome on the planet. They are also subject to rapid climatic shifts and, subsequently, new disturbance processes – snow loss‐driven mortality and the emergence of fire in historically non‐fire‐exposed areas. Here, we compare and contrast Southern and Northern Hemisphere coastal temperate rainforests of the Americas, two of the largest examples of the biome, via synthesis of current literature, future climate expectations and new downscaling of a global fire model. In terms of snow loss, a rapid decline in winter snow is leading to mass mortality of certain conifer species in the Northern Hemisphere rainforests. High‐elevation Southern Hemisphere forests, which are beginning to see similar declines in snow, may be vulnerable in the future, especially bogs and high‐water content soils. Southern Hemisphere forests are seeing the invasion of fire as an ecological force at mid‐to‐high latitudes, a shift not yet observed in the north but which may become more prominent with ongoing climate change. We suggest that research should focus on the flammability of seral vegetation and bogs under future climate scenarios in both regions. By comparing these two drivers of change across similar gradients in the Northern and Southern Hemispheres, this work points to the potential for emerging change in unexpected places in both regions. There is a clear benefit to conceptualising the coastal temperate rainforests of the Americas as two examples of the biome which can inform the other, as change is proceeding in similar directions but at different rates in each region.

Signatures of Obliquity and Eccentricity in Soil Chronosequences

AbstractPeriodic shifts in Earth's orbit alter incoming solar radiation and drive Quaternary climate cycles. However, unambiguous detection of these orbitally driven climatic changes in records of terrestrial sedimentation and pedogenesis remains poorly defined, limiting our understanding of climate change‐landscape feedbacks, impairing our interpretation of terrestrial paleoclimate proxies, and limiting linkages among pedogenesis, sedimentation, and paleoclimatic change. Using a meta‐analysis, we show that Quaternary soil ages preserved in the modern record have periodicities of 41 and 98 kyr, consistent with orbital cycles. Further, soil ages predominantly date to periods of low rates of climatic change following rapid climate shifts associated with glacial‐to‐interglacial transitions. Soil age appears linked to orbital cycles via climate‐modulated sediment deposition, which may largely constrain soil formation to distinct climate periods. These data demonstrate a record of widespread orbital cyclicity in sediment deposition and subsequent pedogenesis, providing a key insight into soil‐landscape evolution and terrestrial paleo‐environment changes.