Search

The regional impact of abrupt glacial climate variability remains poorly constrained for arid southwestern Asia, particularly winter dynamics during Marine Isotope Stage 3, due to limited paleoarchives in the Middle East. Here, we present continuous speleothem records of δ18O and δ13C with robust chronologies for southwestern and central Iran, spanning ∼50–30 ka. Stable‐isotope signals in the two stalagmites are generally uncorrelated and do not exhibit a consistent response to Greenland stadials or interstadials; however, both show a positive δ18O excursion that coincides with Heinrich event 4. We explore the potential mechanisms for intermittent coupling of speleothem δ18O across Iran through isotope‐enabled atmospheric modeling outputs, from which we utilize the spatial δ18O gradient as a proxy for wintertime westerly versus southerly jet strength. Our results suggest that during Heinrich event 4 and several Greenland stadials, stronger westerly winds enhanced Mediterranean moisture contributions to both sites and reduced aridity in southern Iran. Plain Language Summary: Stalagmites are useful archives to reconstruct the climate of the past. In order to shed light on the past climate of western Asia and the response of this region to the rapid climate changes, here we present two stalagmites from central and southwestern Iran that span 50,000 to 30,000 yrs ago. Our findings suggest that during extreme cold events, the moisture originates mostly from the west, whereas out of these extraordinarily cold periods moisture comes mostly from the south. Key Points: Continuous high‐resolution speleothem record of climatic change in southwestern and central Iran between 50 and 30 kaDecoupled responses of stable‐isotope gradients in central and southern Iran to glacial climate variability, except during Heinrich event 4Decreased impact of southerly moisture sources and reinforced westerlies during extreme cold events [ABSTRACT FROM AUTHOR]

Quaternary glacial climate oscillation and geographical isolation have significantly influenced the geographic distribution pattern and lineage evolution history of species. However, understanding how these factors specifically impact the genealogical structure of dominant Gramineous species in the Qinghai–Tibet Plateau (QTP) remains a subject of investigation. Elymus sibiricus L. (Gramineae), indigenous to the QTP and widely distributed in Eurasia, exhibits remarkable environmental adaptation and phenotypic diversity, making it an ideal candidate for phylogeographic studies. Based on the analysis of 175 complete chloroplast genome sequences, our results indicated that the ancestors of E. sibiricus originated from the QTP and underwent a complex migration history. After the speciation of E. sibiricus, several geo‐groups exhibited independent differentiation, showing minimal gene flow among them. The current phylogeographic patterns of E. sibiricus are a result of frequent climate alternations and the cold climate during the Quaternary glacial, as well as the presence of several geographical barriers that have restricted the gene flow among different geo‐groups. Our research has revealed for the first time that E. sibiricus has a multilineage origin, and its maternal donors are not limited to a single species. Furthermore, the high quality and mapping depth of the variant file provided reliable data for analyzing the patterns based on raw sequencing data. These findings enhance our understanding of the relationship between plant differentiation and climatic and geographical factors of Eurasia. [ABSTRACT FROM AUTHOR]

With global warming, changes in glaciers and glacial lakes on the Tibetan Plateau call for a serious inspection. The Southeastern Tibetan Plateau (SETP) is a typical monsoonal marine glacier area that is extremely vulnerable to climate change. It is affected by both humid and warm Indian Ocean currents. Outlines of glaciers and glacial lakes in SETP have been extracted from Landsat satellite images with an automatic extraction method based on image compositing with Google Earth Engine and Random Forest algorithm. Alongside the outlines, meteorological data have been collected from 1990 to 2021. The results show that since 1990 the glacier area of SETP has retreated by about 2165.33 km2 (~25.28%), the glacial lake area has increased by about 36.41 km2 (~21.45%), and their number has increased by 477 (~27.32%). The reliability and scientific validity of this study is proven by comparison with existing glacier inventories. By analyzing the meteorological data, the inverse correlation between the glacier area and temperature has been found. Despite decreases in cumulative precipitation, the glacial lake level rise and consequent area expansion have been observed. A fitting equation for the response pattern of glacier changes to temperature and precipitation change is presented and will provide a basis for future studies. [ABSTRACT FROM AUTHOR]

The newly developed paleo‐climate calibrated Community Earth System Model, version 2 (pCESM2) simulates a more realistic global temperature response to external forcing compared to the standard CESM2. Here we show that the code modifications in pCESM2 result in increased atmospheric convection and a northward shift of the Atlantic and eastern Pacific Intertropical Convergence Zones. These changes are exacerbated under Last Glacial Maximum forcing, resulting in tropical precipitation changes that are inconsistent with both proxy data evidence and simulations with other contemporary models. Similar model‐data disagreements are also present in the standard CESM2. Thus, more work is needed to improve the simulated Last Glacial Maximum hydroclimate response in CESM2. We further suggest that well‐constrained paleo climates should be given a larger emphasis in model development more broadly, as these climates can help identify issues with model parameterizations under altered forcing and thus improve the fidelity of simulations of past, present, and future climates. Plain Language Summary: Climate models are a central tool in modern climate science. The realism of any given model is however largely determined by a delicate calibration of the simulated physics in order to capture the observed features of the climate system. A recent study showed that the newly developed paleo‐climate calibrated Community Earth System Model, version 2 greatly improves the global temperature response in simulations of the Last Glacial Maximum compared to the standard model. This was achieved by altering properties of cloud processes in the model code. Here we show that the same changes that improve the overall model sensitivity help exaggerate issues with the distribution of tropical precipitation; similar precipitation issues are also present in the standard model. Understanding the connections between model sensitivity, cloud properties, and precipitation distribution is key for developing a model that can realistically simulate past, present, and future climates. Key Points: The Last Glacial Maximum climate simulated by the paleo‐climate calibrated Community Earth System Model, version 2 (CESM2) (pCESM2) is more realistic than the standard CESM2Both the pCESM2 and the standard CESM2 have large intertropical convergence zone precipitation biases under Last Glacial Maximum forcingSimulations of well‐constrained past climates can help inform model parameterizations and assess model performance [ABSTRACT FROM AUTHOR]

Studies of the Last Glacial Maximum (LGM; 26.5–19 ka) tides showed strong enhancements in open ocean tidal amplitudes and dissipation rates; however, changes prior to the LGM remain largely unexplored. Using two different ice sheet and sea level reconstructions, we explicitly simulate the evolution of the leading semi‐diurnal and diurnal tidal constituents (M2, S2, K1, and O1) over the last glacial cycle with a global tide model. Both sets of simulations show that global changes, dominated by the Atlantic, take place for the semi‐diurnal constituents, while changes for the diurnal constituents are mainly regional. Irrespective of the reconstruction, open ocean dissipation peaks during the sea level lowstands of MIS 2 (∼20 ka) and MIS 4 (∼60 ka), although dissipation values prior to MIS 2 are sensitive to differences in reconstructed ice sheet extent. Using the statistically significant relationship between global mean sea level and dissipation, we apply regression analysis to infer open ocean and shelf dissipation, respectively, over the last four glacial cycles back to 430 ka. Our analysis shows that open ocean tidal energy was probably increased for most of this period, peaking during glacial maxima, and returning to near‐present‐day values during interglacials. Due to tidal resonance during glacial phases, small changes in bathymetry could have caused large changes in tidal amplitudes and dissipation, emphasizing the need for accurate ice margin reconstructions. During glacial phases, once global mean sea level decreased by more than ∼100 m, the amount of open ocean tidal energy available for ocean mixing approximately doubled. Key Points: Tides over the last glacial cycle are explicitly modeled, and tidal dissipation ranging back to 430 ka is inferred with regression analysisEnhanced open ocean dissipation (1.8–2.5 × 5 present day) occurred during glacial maxima, and near‐present‐day values during interglacialsPeak glacial M2 tidal dynamics are very sensitive to changes in ice sheet extent, which may influence ocean mixing and glacial climate [ABSTRACT FROM AUTHOR]

The timing and magnitude of Holocene glacial oscillations in most currently ice‐free areas of Antarctica remain unknown. This work focuses on the recent deglaciation in the northern sector of the Fildes Peninsula, King George Island, northern Antarctic Peninsula. The ice cap covering ca. 90% of the island has receded since the Last Glacial Maximum and exposed ca. 29 km2 of ice‐free land. We reconstruct its glacial history based on a dataset of 12 36Cl exposure ages obtained through cosmic‐ray exposure (CRE) dating of moraine boulders, polished surfaces and erratic boulders surrounding the peninsula's northern plateau. Results reveal that the deglaciation of the northern Fildes Peninsula took place during the Holocene Thermal Maximum at 7–6 ka, when warm conditions promoted a massive glacial retreat. The present arrangement of ice‐free areas was in place by 6 ka. Small cirque moraines suggest the subsequent occurrence of favourable climate conditions for glacial expansion fed by intense snow deflation at 4.6 and 1 ka at the foot of the northern plateau. The deglaciation pattern of the Fildes Peninsula resulted from the combined shrinkage of different ice masses, rather than of the long‐term retreat of the King George Ice Cap. No evidence of glacier expansion during more recent cold periods (i.e. the Little Ice Age) was found. These results fit well with regional deglacial histories inferred from lacustrine sediments and raised beaches and complement the existing chronological framework to help better understand the peninsula's Holocene geoecological dynamics. [ABSTRACT FROM AUTHOR]

Under glacial climates, continental ice sheets such as, e.g., the Greenland Ice Sheet, extended onto the continental shelves and often carved out deep cross‐shelf troughs. The sedimentary infill of such troughs commonly is a product of the complex interactions between the ice sheets, largely driving sediment input into the ocean, and the surrounding water masses. Off West Greenland, research has focused on the Disko and Uummannaq troughs, leaving the northerly adjacent Upernavik trough relatively understudied. Hence, neither the chronology of deglaciation nor the details of its postglacial infill are sufficiently well understood. Here, we combine computed tomography image‐derived information with geochemical and granulometric data from four sediment cores recovered from the Upernavik trough that point to (i) deglaciation of the mid‐shelf probably around 13.4 cal. ka BP that was most likely driven by a northward advection of warmer Atlantic waters during the Bølling–Allerød, (ii) the presence of widespread mass wasting around 8 cal. ka BP on the inner shelf and (iii) the complex interplay between various modes of sediment input, transport and deposition under hemipelagic sedimentation afterwards. While this interplay complicates provenance studies, we identify two major sediment delivery mechanisms that control transport and deposition from four sediment source areas. Through the Early Holocene the relative contributions of sediments from the various sources changed from a predominantly local origin to more southerly sources, mainly driven by decreasing input from the local sources. The integration of relative sediment source contributions with varying sedimentation rates challenges previous studies postulating intensified sediment delivery from the south through a greater influence of the West Greenland Current and highlights the need for the integration of sediment input and transport mechanisms into provenance studies in the area. [ABSTRACT FROM AUTHOR]

The marine dissolved organic carbon (DOC) reservoir rivals the atmospheric carbon inventory in size. Recent work has suggested that the size of the DOC reservoir may respond to variations in sea temperature and global overturning circulation strength. Moreover, mobilization of marine DOC has been implicated in paleoclimate events including Cryogenian glaciation and Eocene hyperthermals. Despite these suggestions, the dynamics of the marine DOC reservoir are poorly understood, and previous carbon cycle modeling has generally assumed this reservoir to be static. In this study, we utilize an Earth system model of intermediate complexity to assess the response of the marine DOC reservoir to various glacial boundary conditions. Our results indicate that the marine DOC reservoir is responsive to glacial perturbations and may shrink or expand on the order of 10–100 Pg C. In contrast to recent studies that emphasize the importance of DOC degradation in driving the mobility of DOC reservoir, our study indicates the importance of DOC production. In the experiment under full glacial boundary conditions, for example, a 19% drop in net primary production leads to an 81 Pg C reduction in the DOC pool, without which the atmospheric CO2 concentration would have been lower by approximately 38 ppm by dissolved inorganic carbon changes alone. Thus, DOC reservoir variability is necessary to fully account for the simulated changes in atmospheric CO2 concentration. Our findings based on glacial experiments are corroborated in a different set of simulations using freshwater flux to induce weakening of the Atlantic meridional overturning circulation. Plain Language Summary: There is a significant reservoir of dissolved organic carbon (DOC) in the ocean originating from the production and decay of microbes, nearly equal to the amount of carbon contained as carbon dioxide (CO2) in the atmosphere. Studies have suggested that the total amount of DOC in the ocean may respond to climate effects on ocean temperatures and circulation, and that releases of DOC from the ocean as CO2 to the atmosphere may have contributed to some climate change events in Earth's history. To date, however, little modeling work has been done to understand this suggestion. In this study, we used a computer model of the earth's ocean and atmosphere to simulate the response of marine DOC to climate conditions representing the height of Earth's last glacial period. We found that the total amount of marine DOC simulated in our model could vary in response to the specific climate conditions applied and the modeled impacts on ocean biological production. Importantly, we found that these changes in the DOC reservoir are sufficiently large that without it, changes in atmospheric CO2 levels cannot be fully understood. Our results suggest that understanding marine DOC is crucial in understanding global climate changes throughout Earth's history. Key Points: The marine dissolved organic carbon (DOC) reservoir is mobile in response to glacial climate forcing and rapid changes in the meridional overturning circulationChanges in the size of the DOC reservoir are primarily driven by changes in DOC production rather than DOC degradationMarine DOC cycling is directly related to atmospheric pCO2 over simulated climate change events [ABSTRACT FROM AUTHOR]

Effective moisture (EM) distribution in the Indian summer monsoon (ISM) region is strongly related to regional topography. An understanding of climate change and the interactions between climate variables can help predict future climate variations. Here, we reconstruct a stack EM record for Southwest China over the past 90 kyr using environmental magnetism in lake sediment. The EM in Southwest China at the orbital scale was closely linked to precession‐induced change in North Hemisphere solar insolation, as well as the ISM variability. However, at the glacial‐interglacial scale, it was decoupled with ISM intensity, being wetter during glacial periods (weakened ISM) and drier during interglacial periods (enhanced ISM). Combined with modern meteorological observations, we suggest that the topographical barrier effect and temperature induced dryness are responsible for the decoupling between ISM intensity and EM. The terrestrial topography and temperature strongly influence EM distribution by altering the dynamics of onshore airflow and evapotranspiration. Plain Language Summary: Effective moisture (EM) directly affects hydrological cycle and wider‐scale socio‐economic development. Reconstruction of prehistoric EM levels is essential for deeper understanding of the global climate system, developing climate models and improving prediction of future climate variations. Here, we reconstruct a high‐resolution EM record over the past ∼90,000 years from lake sediments in Tengchong, Yunnan province, Southwest China. We found that the variation of precession (shifts in the rotational axis of the Earth) and solar insolation are the key contributors to the EM variability at the orbital scale. Unusually, a wetter climate during the glacial period and relatively drier interglacial periods were observed in our records, which is opposite to those found in previous studies (arid glacial and humid interglacial) in monsoon regions, indicating a decoupling pattern between monsoon intensity and EM in study region. Based on a comprehensive analysis of the modern meteorological observations, we conclude that the topography and temperature exert a considerable role in modulating EM distribution and response to the decoupling pattern. Key Points: The long‐term effective moisture (EM) record in Southwest China since ∼90 kyr was reconstructedThe EM variability at the orbital scale in terrestrial Indian summer monsoon region is primarily dominated by precessionThe topographic barrier and temperature induced aridification contribute to the decoupling of monsoon intensity and EM [ABSTRACT FROM AUTHOR]

Climatic warming following the Last Glacial Maximum caused the southern Laurentide Ice Sheet (LIS) to begin ∼2,000‐year cycles of retreat and readvance whose cause remains ambiguous. By developing a marine‐calibrated chronology of southern LIS position, we counterintuitively demonstrate that between 17.6 and 11.3 ka, ice advanced during times of northern‐hemisphere warming and retreated during times of northern‐hemisphere cooling. Here we propose a cyclical feedback: Meltwater from ice retreat cooled the northern hemisphere by weakening the Atlantic Meridional Overturning Circulation (AMOC). This eventually lead to ice‐sheet readvance, which reduced and rerouted meltwater discharge, and thereby allowed the AMOC to strengthen and the northern hemisphere to warm. Our data suggest that this antiphased ice–climate interaction, paced by ice‐sheet response time, was initiated by synchronous warming and ice retreat ∼18.7–17.6 ka (corresponding to the Erie "Interstade") and reached its apex during the Younger Dryas. Plain Language Summary: Twenty thousand years ago, a colder climate allowed glacial ice to flow from northern and eastern Canada into the Great Lakes region. But when climate began to warm, instead of simply melting from south to north, the margin of this ice front repeatedly retreated and re‐advanced in 2,000‐year cycles. First, we track these advances and retreats using records of ancient Gulf of Mexico water, stored in plankton shells retrieved from a sediment cores. Ice advance redirected water bearing "light" oxygen, with fewer neutrons, from Canada and the Great Lakes into the Mississippi River. When ice retreated, these waters found other courses to the sea, shifting Gulf of Mexico chemistry toward heavier oxygen (carrying more neutrons). Next, we ask why these ice‐margin cycles occurred during a time of monotonically increasing solar radiation to the northern hemisphere. We propose that ice‐sheet melt (during retreat) slowed Atlantic Ocean circulation, causing the northern hemisphere to cool and the ice sheet to gradually regrow. However, this same regrowth reduced meltwater flow to the ocean, causing the northern hemisphere to re‐warm and eventually leading the ice margin to retreat once more. This cycle persisted from approximately 17,600 to 11,300 years ago, until North American ice became too small to sustain this feedback. Key Points: δ18O records from the Gulf of Mexico refine the chronology of Laurentide Ice Sheet advance and retreat through the Great LakesCounterintuitively, from 17.6 to 11.3 ka, ice advanced during times of warming and retreated during times of coolingA feedback between meltwater, Atlantic Meridional Overturning Circulation strength, and temperature—paced by ice‐sheet response time—may have set this anticorrelation [ABSTRACT FROM AUTHOR]

Species' ranges are dynamic, particularly at large temporal scales. The reconstruction of range dynamics has an obvious biogeographical interest and might also help to frame current knowledge on the ecology and conservation of a species within a wider biogeographical context. The Bearded Vulture Gypaetus barbatus is a charismatic high‐altitude species occurring along mountain ranges of the Old World. The species has experienced a global range contraction in the last century mainly due to unintentional poisoning and direct persecution. Despite its declining status and high habitat specialization, little is known about how climate change is impacting the distribution of suitable habitat, or about global past range dynamics of the species. We modelled the current distribution of Bearded Vulture throughout its entire range and projected the Last Glacial Maxima (LGM), Mid‐Holocene (MH) and future distribution under 2070s climate change scenarios. Overall, our models predicted that expansion of suitable areas at more northern latitudes for 2070, mostly in Russia and China, does not compensate for range contraction at more southern latitudes, resulting in a global loss of 15% of suitable habitat. Our fine‐scale predictions of habitat contraction due to climate change will assist in identifying current portions of the range that might be particularly vulnerable in coming years. African populations (34% decrease) and more thermic areas in Asia are the most impacted areas, and should be at the forefront of future monitoring and conservation efforts. Our models suggest that the predicted contraction in habitat suitability during the 21st century largely continues the contraction experienced since the LGM (7% decline), albeit over a much shorter period of time. From a biogeographical perspective, our models suggest that there have not been relevant changes in the arrangement of the main suitable areas for the species since the LGM. This result challenges some of the main hypotheses proposed to explain the observed genetic structure of the global population. [ABSTRACT FROM AUTHOR]

In the French north‐western Alps, several lakes of glacial origin, such as Aiguebelette and La Thuile, present some mass‐transport deposits within their sedimentary sequences. These event layers can result from lake sediment destabilization eventually triggered by earthquakes. On Lake Aiguebelette, based on sedimentological, geochemical and magnetic analyses, and high‐resolution seismic and bathymetric surveys a ca 1 m thick event layer was identified in the deepest lake basin and a synchronous ca 2 cm thick deposit in the shallow basin. Age‐depth models based on radiocarbon ages reveal that both mass‐transport deposits in Lake Aiguebelette occurred around the Younger Dryas – Early Holocene climatic transition (i.e. 11 700 cal bp) time range. In Lake La Thuile, located 30 km away, unique mass‐transport deposits (translational slide type) were recorded at the same time range in sedimentary records. Additionally, high‐resolution seismic profiles previously acquired in Lake Annecy and Lake Bourget support the hypothesis of significant mass‐transport deposits occurring at the Younger Dryas – Early Holocene time range. These outcomes on four north‐western peri‐Alpine and Alpine lakes highlight the regional occurrence of mass‐transport deposits in the Younger Dryas – Early Holocene time range. Seismic and rockfall events are discussed as potential sources of these significant and similarly aged mass‐transport deposits. Based on this study and a literature review, the authors suggest that mechanisms induced by rapid climate change and glacial retreat, such as crustal rebound and erosional unloading, could favour the triggering of earthquakes and rockfall events. In the case of mass‐transport deposits archived in north‐western Alpine lakes during this time period, this study favours the hypothesis of increased seismicity as the primary source driving process involved. [ABSTRACT FROM AUTHOR]

The profile of the Lipowo palaeolake (NE Poland) preserves a record of environmental and climate changes from the Last Glacial Termination (16.5k cal ka BP), stretching from the Oldest Dryas to the youngest Allerød warm oscillation. In this interdisciplinary study of the lacustrine succession at Lipowo, we used biological and geochemical indicators and multiproxy analyses to reconstruct environmental changes in the lake ecosystem, such as mollusc, zooplankton and vegetation development, trophic state, water temperature and water level. Four cold and four warm climate oscillations of different durations were identified on this basis: the Older Dryas climate deterioration and two short‐term coolings within the Allerød Interstadial, separated by warm periods in the Bølling and Allerød. The covering of the lake series by diamicton deposits from the melting of dead‐ice blocks is a particularly interesting and rare phenomenon for a postglacial area. The hydrological system of the catchment was generally closed, with a periodically opening and existing flow‐through lake. Over the period of the lake's existence, vegetation changed in general from steppe tundra to forest with birch and pine. For most of this time, the palaeolake was mainly oligotrophic, with increased productivity and a higher trophic level only notable during the middle Bølling. [ABSTRACT FROM AUTHOR]

Indian Ocean sea surface temperatures impact precipitation across the basin through coupled ocean‐atmosphere responses to changes in climate. To understand the hydroclimate response over the western Indian Ocean and equatorial east Africa to different forcing mechanisms, we present four new proxy reconstructions from core VM19‐193 (2.98°N, 51.47°E) that span the last 250 ky. Sub‐surface water temperatures (Sub‐T; TEX86) show strong precessional (23 ky) variability that is primarily influenced by maximum incoming solar radiation (insolation) during the Northern Hemisphere spring season, likely indicating that local insolation dominates the upper water column at this tropical location over time. Leaf waxes, on the other hand, reflect two different precipitation signals: δ13Cwax (in phase with boreal fall insolation) is likely reflecting vegetation changes in response to local rainfall over east Africa, whereas δDprecip (primarily driven by boreal summer insolation) represents changes in regional circulation associated with the summer monsoon. Glacial‐interglacial changes in ocean temperatures support glacial shelf exposure over the Maritime Continent in the eastern Indian Ocean and the subsequent weakening of the Indian Walker Circulation as a mechanism driving 100 ky climate variability across the tropical Indo‐Pacific. Additionally, the 100 ky spectral power in δDprecip supports a basin‐wide weakening of summer monsoon circulation in response to glacial climates. Overall, the proxy records from VM19‐193 indicate that both precession and glacial‐interglacial cycles exert control over hydroclimate at this tropical location. Key Points: New multi‐proxy reconstructions from the tropical western Indian Ocean show both precession and glacial‐interglacial variabilityA new precipitation isotope record likely reflects large‐scale Indian summer monsoon circulation changes over timeGlacial‐scale changes in upper water column structure across the Indian Ocean support shelf exposure as a primary hydroclimate influence [ABSTRACT FROM AUTHOR]

During abrupt climate changes of the last glacial period paleorecords show large amplitude changes in the dust cycle. We use Earth System model simulations to evaluate processes operating across these events. Idealized Heinrich stadial‐like simulations show a southwards migration of tropical rainfall that dries the Sahel and reduces wet deposition causing a widespread enhancement of tropical dust loading. However, several discrepancies with marine core dust deposition reconstructions are evident. Simulations with a more limited freshwater forcing (0.4 Sv instead of 1.0 Sv) and weaker cooling over the North Atlantic (less than 3°C) show a switch in sign of the stadial dust deposition anomaly in several regions, improving agreement with paleorecords. The simulated dust cycle therefore displays in places a non‐linear response to abrupt change. The global‐mean stadial dust radiative forcing in the more realistic simulations is around −0.2 to −0.6 W m−2 and so could represent an amplifying feedback during these events. Plain Language Summary: Mineral dust in the atmosphere is mostly sourced from arid regions like the Sahara desert. The amount and geographical spread of this dust in the atmosphere is sensitive to environmental conditions such as drought. Paleoclimate records show that rapid cooling events centered on the North Atlantic during the last ice‐age also saw large increases in the rate of dust deposited over the ocean. Earth System models are a computational tool that can be used to understand the links between climate and the dust cycle. Using a series of such simulations we found that abrupt cooling events in the North Atlantic can lead to a massive increase in dust over the equatorial (tropical) regions. However, the model's response is in many places non‐linear, meaning that the change in dust is very sensitive to the magnitude of the climate changes occurring. This non‐linearity is mostly due to interactions between changes in the water cycle and the dust. We show that a less severe cooling produces a more realistic dust response when evaluated against paleo‐dust records. Since dust scatters incoming sunlight, increased atmospheric dust during these events may have amplified and even extended the cold phases. Key Points: Freshwater hosing forcing increases tropical dust loading in Earth System model simulations of the last glacial maximumSimulated response is non‐linear with forcing in some regions, particularly North AfricaWeaker events improve agreement with data and emitted dust produces a self‐amplifying feedback [ABSTRACT FROM AUTHOR]

Tertiary relicts often show evolutionary stasis in morphology and ecology and have been hypothesized to retain stable population sizes in refugia. However, recent studies have reported that some relicts evolutionarily shifted their physiology, ecology, and morphology and experienced various patterns of demography. To understand the historical survival of relict plants, a multidimensional study investigating the evolution of ecological and morphological traits as well as population demographic history is needed. The genus Tanakaea (Saxifragaceae) comprises two species in China and Japan. These species share most vegetative characteristics and are sometimes treated as a single species. The distribution pattern is relictual, as the populations are confined to small areas in mesic warm temperate forests less influenced by Quaternary glacial climates. Focusing on the relictual plant group, this study tested the hypotheses of evolutionary stasis and population stability in long‐term refugia. Genetic analyses using plastome sequences and genome‐wide single‐nucleotide polymorphisms revealed divergence of the two species approximately 6.8 million years ago and strong genetic differentiation of the regional populations. Demographic analysis revealed that almost all populations retained stable population sizes during glacial–interglacial climate changes, supporting the traditional view. However, morphological assessments revealed a simultaneous shift in breeding systems (from hermaphrodite to dioecy/non‐clonal to clonal reproduction) in Japanese species and intraspecific differentiation of leaf traits. Therefore, the relict species do not show evolutionary stasis in every aspect. Changes in reproductive characteristics may have contributed to their long‐term in situ survival. [ABSTRACT FROM AUTHOR]

The Asian summer monsoon (ASM), controlled by tropical ocean‐atmosphere systems, and the westerlies, directly linked to high‐latitude climates, interact in mid‐latitude East Asia. Located at a climate junction, the northeastern Qinghai‐Tibetan Plateau (QTP) is a sensitive zone for the interaction of the westerlies and ASM. In the current work, we present a new loess data set from the northeastern QTP since the last deglaciation, including grain size, stable isotope (δ13Corg and δ18Ocarb), total organic carbon, total nitrogen, magnetic susceptibility, and mineral composition. The PMIP3‐CMIP5 multi‐model ensemble and TraCE‐21ka transient simulation are used synthetically to analyze climate mechanisms. All proxies suggest instable glacial climate and stable interglacial climate in the northeastern QTP. The coarser grain size during the last deglaciation compared with the Holocene reflects intensified westerlies controlled by the weakening of Atlantic Meridional Overturning Circulation and existing ice sheets. More positive δ18Ocarb values during abrupt cooling events [Heinrich event 1 (H1) and the Younger Dryas (YD)] indicate the effect of a weakened monsoon triggered by the low‐latitude solar insolation and sea surface temperature. Therefore, the anti‐phase pattern between the ASM and westerlies is the primary reason for differences in climate stability. Moreover, low temperature favors the predomination of C3 plants and the development of permafrost, leading to more negative δ13Corg values and fine grain size during the H1 and YD. Taken together, the anti‐phase relationship between the westerlies and ASM emphasizes the complicated dynamic characteristics of atmospheric systems in the mid‐latitudes and the challenges for future predictions. Plain Language Summary: The relationship between the westerly circulation and Asian summer monsoon (ASM) system at different timescales is still under discussion in both meteorology and paleoclimatology communities in recent years. Due to the huge differences in the dynamic mechanisms of the two circulation systems, relevant previous studies on millennial‐scale climate change distinguished the westerlies and ASM based on various paleoclimate indicators, and rarely defined the meaning and specific process of their interaction. Under global warming, clarifying the interactions of the westerlies and ASM is critical to understanding the pattern and mechanism of climate change in mid‐latitudes. Therefore, the comprehensive analysis of surface sediments, paleoclimate records, and paleoclimate simulation on long‐term timescales are conducted in the northeastern Qinghai‐Tibetan Plateau which is a sensitive zone for the synergistic effect of the westerlies and ASM. The results show that the ASM mainly affects the Holocene climate, while the westerlies dominate during the last deglaciation in the northeastern Qinghai‐Tibetan Plateau. The anti‐phase pattern between the ASM and westerlies leads to instable glacial climate and stable interglacial climate. Key Points: Anti‐phase pattern between the Asian summer monsoon and westerlies triggers the difference in climate stability during glacial and interglacial periodsCoarser grain size during the last deglaciation compared with the Holocene reflects intensified westerlies linked to weakening Atlantic Meridional Overturning CirculationMore positive δ18Ocarb values during abrupt cooling events (H1 and Younger Dryas) indicate the influence of the weakened monsoon [ABSTRACT FROM AUTHOR]

The climate of the southwestern North America has experienced profound changes between wet and dry phases over the past 200 Kyr. To better constrain the timing, magnitude, and paleoenvironmental impacts of these changes in hydroclimate, we conducted a multiproxy biomarker study from samples collected from a new 77 m sediment core (SLAPP‐SRLS17) drilled in Searles Lake, California. Here, we use biomarkers and pollen to reconstruct vegetation, lake conditions, and climate. We find that δD values of long chain n‐alkanes are dominated by glacial to interglacial changes that match nearby Devils Hole calcite δ18O variability, suggesting both archives predominantly reflect precipitation isotopes. However, precipitation isotopes do not simply covary with evidence for wet‐dry changes in vegetation and lake conditions, indicating a partial disconnect between large scale atmospheric circulation tracked by precipitation isotopes and landscape moisture availability. Increased crenarchaeol production and decreased evidence for methane cycling reveal a 10 Kyr interval of a fresh, productive, and well‐mixed lake during Termination II, corroborating evidence for a paleolake highstand from shorelines and spillover deposits in downstream Panamint Basin and Death Valley during the end of the penultimate (Tahoe) glacial (140–130 ka). At the same time brGDGTs yield the lowest temperature estimates (mean months above freezing = 9°C ± 3°C) of the 200 Kyr record. These limnological conditions are not replicated elsewhere in the 200 Kyr record, suggesting that the Heinrich stadial 11 highstand was wetter than the last glacial maximum and Heinrich 1 (18–15 ka). Plain Language Summary: Searles Valley in the Mojave Desert, California, contains a saltpan, the remnants of a former lake. Shoreline features show that the former lake was at times 274 m deep. We studied the ancient lake mud and salt deposits below the valley floor to a depth of 77 m in a sediment core drilled in 2017. The remains of microbes and plants allow us to reconstruct past climate conditions. We find that during cooler glacial periods, conifer forests covered the landscape and plant wax in the core records rainfall that is chemically different from today. These differences are similarly recorded in nearby cave deposits, suggesting changing storm tracks. The wettest climates were found in the cool climate of the penultimate glacial (about 135,000 years ago) when Searles Lake vigorously overflowed into Panamint Basin and Death Valley. Key Points: Biomarker and pollen record from Searles Lake, CA sediment core spanning 200 KyrChanges in plant wax hydrogen isotopes consistent with regional speleothemsArchaeal lipids reveal lake highstands, Termination 2 wetter than Termination 1 [ABSTRACT FROM AUTHOR]

The Eastern Pacific Warm Pool (EPWP) modulates global climate through its connection with tropical Pacific circulation, but sparse paleoceanographic data from this region limits our understanding of its role in past climate variability. We present a 144 kyr alkenone‐sea surface temperature (SST) reconstruction from core NH22P, located in the northern EPWP, that shows local warming occurred during periods of global cooling. Climate model simulations of the Last Glacial Maximum indicate that both ice sheet and greenhouse gas forcing slowed wind speeds over the EPWP, which attenuated glacial cooling of local SST via the wind‐evaporation‐SST feedback. Spectral analysis further suggests precessional pacing of the warming spikes. Vernal equinox insolation could explain this pacing as direct shortwave heating during boreal spring would have contributed to the early seasonal intensification of the EPWP. This work provides crucial constraints on tropical Pacific glacial climate variability and highlights the unique response of the EPWP to global climate forcings. Plain Language Summary: The eastern tropical Pacific (ETP) contains a region of very warm sea surface temperatures (SSTs) (>27.5°C) that is called the Eastern Pacific Warm Pool (EPWP). The interaction between these warm waters and the atmosphere is important for driving rainfall variability in Mexico and Central America. Our understanding of SST variability in the EPWP in the past, however, is limited by a lack of paleoceanographic data. In this study, we present a new record of past changes in EPWP SST based on abundances of algal lipids called alkenones. We use climate models to understand how lower greenhouse gases and increased ice volume affected SST in the EPWP and atmospheric circulation in the ETP. We find that both of these factors result in less evaporation from the EPWP, which limits the amount of cooling the region underwent despite widespread global cooling during the last ice age. Regular intervals of warming occur when radiation from the Sun reaching Earth's surface in Northern Hemisphere spring is greatest as cloud cover over the EPWP is low at this time and warming of the sea surface is enhanced. Key Points: A new reconstruction from the northern Eastern Pacific Warm Pool (EPWP) shows warming during globally cool periods over the last ∼150 kyrsReduced wind‐evaporation‐sea surface temperature feedback key for attenuating glacial cooling in the EPWPPrecessional pacing of EPWP sea surface temperature likely related to direct shortwave heating during spring insolation maxima [ABSTRACT FROM AUTHOR]

Natural forcing from solar and volcanic activity contributes significantly to climate variability. The post‐eruption cooling of strong volcanic eruptions was hypothesized to have led to millennial‐scale variability during Glacials. Cooling induced by volcanic eruption is potentially weaker in the warmer climate. The underlying question is whether the climatic response to natural forcing is state‐dependent. Here, we quantify the response to natural forcing under Last Glacial and Pre‐Industrial conditions in an ensemble of climate model simulations. We evaluate internal and forced variability on annual to multicentennial scales. The global temperature response reveals no state dependency. Small local differences result mainly from state‐dependent sea ice changes. Variability in forced simulations matches paleoclimate reconstructions significantly better than in unforced scenarios. Considering natural forcing is therefore important for model‐data comparison and future projections. Plain Language Summary: Climate variability describes the spatial and temporal variations of Earth's climate. Understanding these variations is important for estimating the occurrence of extreme climate events such as droughts. Yet, it is unclear whether climate variability depends on the mean surface temperature of the Earth or not. Here, we investigate the effects of natural forcing from volcanic eruptions and solar activity changes on climate variability. We compare simulations of a past (cold) and present (warm) climate with and without volcanism and solar changes. We find that overall, the climate system responds similarly to natural forcing in the cold and warm state. Small local differences mainly occur where ice can form. To evaluate the simulated variability, we use data from paleoclimate archives, including trees, ice‐cores, and marine sediments. Climate variability from forced simulations agrees better with the temperature variability obtained from data. Natural forcing is therefore critical for reliable simulation of variability in past and future climates. Key Points: We present Glacial/Interglacial climate simulations and quantify effects of time‐varying volcanic and solar forcing on climate variabilityThe mean global and local response to these forcings is similar in Glacial and Interglacial climate, suggesting low state dependencyIn both climate states, modeled temperature variance agrees better with palaeoclimate data when volcanic and solar forcing is included [ABSTRACT FROM AUTHOR]

While the impact of dust on climate and Atlantic Meridional Overturning Circulation (AMOC) during the interglacial period such as the mid‐Holocene has been studied extensively, its impact during the glacial period is unclear. Here we investigate how the climate and AMOC would change if there had been no dust during the Last Glacial Maximum. Model simulations show that the dust removal leads to a global cooling of over 2.4°C and a weakening of AMOC by ∼30%. Such temperature change is opposite in sign to that for the MH. The cooling is attributed to the increase of snow and ice albedo and weakening of AMOC when dust is removed, and is amplified through a positive feedback between sea ice and AMOC. Our results indicate that the climate and AMOC are more sensitive to dust change during the glacial than the interglacial period. Plain Language Summary: Dust in the atmosphere reflects and absorbs sunlight, reducing the shortwave radiation reaching the surface, while the dust deposited on snow and ice reduces the surface albedo and increases the shortwave radiation received at the surface. Our previous work (Zhang et al., 2021) showed dust reduction during the interglacial period (e.g., mid‐Holocene; MH) would cause a global warming of 0.1°C and a weakening of Atlantic Meridional Overturning Circulation (AMOC) by 6.2%. This warming was due to more sunlight received at the surface when atmospheric dust is removed. Here we show that if dust was removed during the Last Glacial Maximum (LGM), climate will be cooled significantly rather than warmed. The major reason is that snow on land was much more extensive during LGM than MH, such that the increase of snow albedo after dust removal has a dominating effect on climate. Result suggests that the global climate and AMOC in the glacial period are more sensitive to dust change than those in the interglacial period. Key Points: If there were no dust during the Last Glacial Maximum (LGM), global surface temperature would have been lower by 2.4 °CAtlantic Meridional Overturning Circulation would have been 30% weaker if there were no dust during the LGMThe ocean and sea‐ice dynamics amplify the climate impact of dust by a factor of 2 [ABSTRACT FROM AUTHOR]

High‐latitude glacierized coastal catchments of the Gulf of Alaska (GoA) are undergoing rapid hydrologic changes in response to climate change and glacial recession. These catchments deliver important nutrients in the form of both inorganic and organic matter to the nearshore marine environment, yet are relatively understudied with respect to characterization of the sediment and solute generation processes and total yields. Using multiple linear regression informed by Bayesian Information Criterion analysis we empirically demonstrate how watershed characteristics affect suspended sediment and solute generation as represented by concentration‐discharge relationships. We find that watershed mean slope and relief control solute generation and that solute yields are influenced most by glacier coverage. We contribute a new flux and concentration‐discharge based conceptualization for understanding solute cycles across a hydroclimatic gradient of GoA watersheds that can be used to better understand future watershed responses to rapid hydrologic change. Plain Language Summary: The Gulf of Alaska (GoA) region is experiencing rapid changes in climate causing glaciers to recede. Streams and rivers within basins that contain glaciers deliver vital nutrients to the ocean. However, regional studies to quantify the generation and delivery of rock‐derived nutrients from watersheds to the ocean are lacking. This study uses statistical analysis to identify the mechanisms controlling the release of nutrients and to demonstrate the physical watershed characteristics that influence the flux of nutrients at the watershed scale. We find that topographic characteristics (slope and relief) control nutrient‐generating processes and that glacier coverage is an important factor controlling the total amount of nutrients exported by streams. This contribution presents a new conceptualization for understanding nutrient delivery to the GoA that can be used to understand future responses to changing climate regimes. Key Points: Catchment glacial coverage controls annual solute yields consistent with the global trend in basins with similar glacier coverageWatershed geomorphology has strong controls on concentration‐discharge relationshipsSolute yields are most significantly influenced by glacier coverage [ABSTRACT FROM AUTHOR]

The multiple equilibrium behavior of the Atlantic meridional overturning circulation (AMOC) is related to the mode transition of the AMOC, which played an important role in abrupt glacial climate changes. However, the difference between modern and glacial climates is not well understood. Here, we examined the structure of the multiple equilibria of the AMOC under the modern and glacial climates through hysteresis experiments using an earth system model of intermediate complexity. The glacial AMOC exhibited a shallower AMOC mode but not the off mode, and a narrower range of multiple equilibria than the modern AMOC. This glacial hysteresis behavior occurred associated with a shift of deep water formation due to changes in surface air temperature and sea ice, whereas that of the modern AMOC is attributed to the basin‐scale salinity feedback. These features were commonly found in two glacial simulations with different strengths of the AMOC at the Last Glacial Maximum. Plain Language Summary: The Atlantic meridional overturning circulation (AMOC) is the Atlantic part of the density‐driven deep ocean circulation and contributes to the warm climate in the North Atlantic through meridional heat transport. The AMOC is known to have multiple modes and transitions between them are deeply connected to abrupt climate changes during glacial periods. We compared the structures of the AMOC modes during present‐day and glacial climates by imposing a gradually changing freshwater flux on the North Atlantic using an earth system model of intermediate complexity. The glacial AMOC shows a shallow‐AMOC mode that is absent in the modern AMOC. In addition, the range of the bistable regime is narrower in the glacial climate than in the modern climate. These features are explained by different mechanisms that drive mode transitions between the modern and glacial climates. In the present‐day climate, salt transport into the Atlantic by the AMOC itself acts as dominant feedback for mode transitions. In the glacial climate, however, a stable shallow‐AMOC mode appears because of the changes in the deep water formation site caused by atmospheric cooling. Interactions among deep water formation, air temperature, and sea ice are important for the glacial mode shift. Key Points: The glacial Atlantic meridional overturning circulation (AMOC) shows different hysteresis behaviors from the modern AMOC in an earth system model of intermediate complexityThe differences in hysteresis are commonly found in two simulations showing different reproducibility of the glacial AMOCAn atmospheric thermal feedback becomes important rather than basin‐scale salinity feedback for the glacial AMOC mode transitions [ABSTRACT FROM AUTHOR]

We investigate the glacial climate conditions in the southeastern Carpathian Basin (Vojvodina, Serbia) based on the reconstruction of malacological palaeotemperatures and results from a high‐resolution regional climate simulation. Land snail assemblages from eight loess profiles are used to reconstruct July temperatures during the Last Glacial Maximum (LGM). The malacological reconstructed temperatures are in good agreement with the simulated LGM July temperatures by the Weather Research and Forecast model. Both methods indicate increasing temperatures from the northwestern towards the southeastern parts of the study area. LGM aridity indices calculated based on the regional climate model data suggest more arid conditions in the southeastern parts compared with more humid conditions in the northwestern parts. However, for present‐day conditions, the moisture gradient is reversed, exhibiting more humid (arid) conditions in the southeast (northwest). An explanation for the reversed LGM aridity pattern is provided by an analysis of the prevailing wind directions over the South Banat district (Serbia). The prevailing moist northwesterly winds during summer are not able to compensate for the annual lack of moisture induced by the dry winds from the southeast that are more frequent during the LGM for the other seasons. [ABSTRACT FROM AUTHOR]

The loess sequence preserved in the Požarevac brickyard in north‐eastern Serbia comprises eight loess units separated by seven paleosols. Geochronological investigation using amino acid racemization and luminescence dating support stratigraphic correlations of loess units L3, S2LL1 and L1 at the Požarevac section with loess of glacial cycles E [Marine Isotope Stage (MIS) 10], D (MIS 9–8), C (MIS 7–6) and B (MIS 5–2) across central Europe. Correlation with the marine oxygen‐isotope stratigraphy and associated paleoclimatic inferences are further supported by magnetic susceptibility, particle size and carbonate content measured in Požarevac sediments. Malacological investigations at the Požarevac section reveal the continuous presence of the Chondrula tridens and Helicopsis striata faunal assemblages throughout the last 350 ka. The loess malacological fauna, which is characterized by the complete absence of cold‐resistant and cold‐preferring species, suggests a stable, dry and relatively warm glacial and interglacial climate, compared with other central European loess localities. Together these data suggest that the south‐eastern part of the Carpathian (Pannonian, Middle Danube) Basin was a refugium for warm‐preferring and xerophilous land‐snails during the generally unfavorable glacial climates of the late Middle and Late Pleistocene. [ABSTRACT FROM AUTHOR]

Although difficult to resolve, seasonality is an important element in considering paleoenvironmental records and simulated results, and it is therefore critical to address this shortcoming in order to develop more accurate reconstructions of past climate. In this study, climatic proxies with seasonal implications (magnetic susceptibility and mean grain size) are analyzed for several high‐resolution loess sections from mid‐latitude Asia using the Ensemble Empirical Mode Decomposition (EEMD) to detect their response to millennial‐scale oscillations during the last glaciation. In so doing, we are capable to estimate the amplitude and relative contribution of the reconstructed climate components. Combined with an analysis of modern processes, magnetic susceptibility (χ) can be interpreted as representing summer and spring precipitation, while mean grain size (Mz) can be interpreted as representing spring and summer dust activity in the Chinese Loess Plateau (CLP) and southern central Asia (SCA), respectively. Our results show that the spring and summer signals are clearly correlated with Heinrich events, but that the spring signal is more prominent than the summer signal during Dansgaard‐Oeschger (D‐O) oscillations of the last glacial. These results are consistent with modeled simulations. It is proposed that weakening or complete shutdown of AMOC influences the response of seasonal signals to abrupt climate events. The study highlights the need for further high‐resolution climate proxies with robust seasonality indicators in order to develop a deeper understanding of the response of mid‐latitude Asia to rapid climate events. Key Points: The climate over mid‐latitude Asia presented seasonal response to abrupt climate events during the last glacialSpring climate is more sensitive to millennial‐scale abrupt events than summerThe weakening and closing of the Atlantic meridional overturning circulation influence the seasonal response [ABSTRACT FROM AUTHOR]

The Antarctic Intermediate Water (AAIW) is an essential global ocean water mass at intermediate depths. Coupled climate models in isotope‐enabled (δ18O, δD), fully coupled Community Earth System Model and Paleoclimate Model Intercomparison Project Phase 3 consistently show shallower AAIW depth at the Last Glacial Maximum (LGM) due to the northward shift of AAIW. More importantly, modeling results suggest that the northward shift of AAIW can be caused by sea ice expansion and the weakened hydrological cycle under the glacial climate. On the contrary, the AAIW under global warming tends to shift poleward compared to the pre‐industrial period driven by the retreating sea ice and strengthened hydrological cycle. However, the AAIW depth will shallow in response to the ongoing warming, likely due to the overwhelming effects of enhanced stratification and shallowing mixed layer. Plain Language Summary: The Antarctic Intermediate Water (AAIW) is an important component of global ocean circulation, and processes involved in AAIW variability have been extensively studied, particularly for its role in ventilating CO2 from deep oceans to the atmosphere during the last deglaciation. However, there is scarce information about changes in AAIW vertical extent and existing studies even seem to be controversial. In this study, modeling results consistently show a shallowing AAIW depth at the Last Glacial Maximum (LGM), mainly because of the equatorward shift of the entire AAIW. More importantly, we found that the northward shift of AAIW can be caused by the northward expansion of sea ice and the weakened hydrological cycle at the LGM. Under global warming conditions, the AAIW shifts poleward due to the retreating sea ice and strengthened hydrological cycle. However, the AAIW depth also shallows, likely due to overwhelming effects of enhanced stratification and shallower mixed layer. The results in this study are model‐based, and further studies, including more robust paleo observations, are needed to better understand the mechanisms that control the AAIW depth and extent. Key Points: The Antarctic Intermediate Water (AAIW) depth shallows due to the northward shift of AAIW at the Last Glacial Maximum (LGM)The northward shift of AAIW can be forced by sea ice expansion and the weakened hydrological cycle at the LGM [ABSTRACT FROM AUTHOR]

In a conservation and sustainable management perspective, we identify the ecological, climatic, and demographic factors responsible for the genetic diversity patterns of the European silver fir (Abies alba Mill.) at its southwestern range margin (Pyrenees Mountains, France, Europe). We sampled 45 populations throughout the French Pyrenees and eight neighboring reference populations in the Massif Central, Alps, and Corsica. We genotyped 1,620 individuals at three chloroplast and ten nuclear microsatellite loci. We analyzed within‐ and among‐population genetic diversity using phylogeographic reconstructions, tests of isolation‐by‐distance, Bayesian population structure inference, modeling of demographic scenarios, and regression analyses of genetic variables with current and past environmental variables. Genetic diversity decreased from east to west suggesting isolation‐by‐distance from the Alps to the Pyrenees and from the Eastern to the Western Pyrenees. We identified two Pyrenean lineages that diverged from a third Alpine–Corsica–Massif Central lineage 0.8 to 1.1 M years ago and subsequently formed a secondary contact zone in the Central Pyrenees. Population sizes underwent contrasted changes, with a contraction in the west and an expansion in the east. Glacial climate affected the genetic composition of the populations, with the western genetic cluster only observed in locations corresponding to the coldest past climate and highest elevations. The eastern cluster was observed over a larger range of temperatures and elevations. All demographic events shaping the current spatial structure of genetic diversity took place during the Mid‐Pleistocene Transition, long before the onset of the Holocene. The Western Pyrenees lineage may require additional conservation efforts, whereas the eastern lineage is well protected in in situ gene conservation units. Due to past climate oscillations and the likely emergence of independent refugia, east–west oriented mountain ranges may be important reservoir of genetic diversity in a context of past and ongoing climate change in Europe. [ABSTRACT FROM AUTHOR]

We analyze the past 67,000 years of climate using Antarctic ice‐core records to constrain the mechanisms involved in (a) the "bipolar seesaw" relationship between Greenland and Antarctic surface temperature variations, and (b) mechanisms of millennial‐scale atmospheric CO2 concentration variations. Specifically, we determine for each Greenland Stadial the rate of Antarctic temperature and atmospheric CO2 rise. We find that Antarctic warming rates significantly decrease as the climate cools during the glacial period, whereas the rate of atmospheric CO2 rise does not significantly change. Also, we find that the rates of Antarctic warming and atmospheric CO2 rise are both insensitive to whether a given stadial contains a Heinrich event. These results challenge the view that a single Southern‐Ocean‐based mechanism dominates the observed glacial variability in Antarctic temperature and atmospheric CO2. Instead, our results are consistent with an important contribution of low‐ and mid‐latitude processes to millennial‐scale atmospheric CO2 changes. Plain Language Summary: Glacial climate is characterized by millennial‐scale variations in polar temperature and atmospheric CO2 concentration. The observed similarities between the shape of atmospheric CO2 and Antarctic temperature records, derived from Antarctic ice cores, have led to a common view that variations in both are dominated by a common Southern Ocean mechanism. However, a systematic comparison of the rates of change of Antarctic temperature and atmospheric CO2 during these millennia‐scale events has not previously been conducted. Furthermore, it is not clearly demonstrated if the rate of change of the Antarctic temperature and atmospheric CO2 were sensitive to changes in the mean climate state or the occurrence of massive iceberg discharge into the North Atlantic. Here, using ice‐core data, we show that the rate of Antarctic warming reduces as the glacial climate cools. In contrast, the rate of atmospheric CO2 rise is insensitive to glacial cooling. Neither the warming rate nor the rate of atmospheric CO2 rise are affected by iceberg discharge events. Our result is in contrast with a simple common Southern Ocean control on atmospheric CO2 and Antarctic temperature and suggests that the millennial‐scale atmospheric CO2 changes include significant contributions from mid‐to‐low latitudes and processes independent of the background climate. Key Points: The Antarctic warming rate during Antarctic Isotope Maxima significantly decreased as the climate cooled toward the glacial maximumIn contrast, the rate of millennial‐scale CO2 rise is insensitive to the varying background climateThe Antarctic warming rate and the rate of millennial‐scale CO2 rise were insensitive to whether the stadial contained a Heinrich event [ABSTRACT FROM AUTHOR]

Black carbon (BC), primary brown carbon (BrCpri), and secondary brown carbon (BrCsec) are important light-absorbing aerosol. BC and BrC from the surrounding area can reach the Tibetan Plateau (TP) and influence climate change and glacial melting. Here, we presented a study of the light absorption, radiative forcing, and potential source areas of BC and BrC over the northeastern, central, and southwestern TP. The higher light absorption was observed in the northeastern and southwestern sites compared to the central TP site. The major carbonaceous light-absorbing was attributed to BC with the percentages of 65%, 56%, and 82% in Ngari, Qinghai Lake, and Beiluhe, respectively. The heighten contribution of BrCsec to total light absorption indicated the importance of BrCsec in the TP, especially in the northeastern and southwestern areas. The BrCsec radiative forcings relative to BC were much higher than those of BrCpri. The potential BC and BrCpri source distributions were obtained. [ABSTRACT FROM AUTHOR]

Long‐distance dispersal (LDD) outside a species' breeding range contributes to genetic divergence. Previous phylogeographic studies of migratory bird species have not discriminated LDD from vicariant speciation in their diversification process. We conducted an integrative phylogeographic approach to test the LDD hypothesis, which predicts that a Japanese migratory bird subspecies diverged from a population in the coastal region of the East China Sea (CRECS) via LDD over the East China Sea (ECS). Haplotype networks of both mitochondrial and nuclear genes of its three subspecies were reconstructed to examine whether the Japanese subspecies of the Brown Shrike (Lanius cristatus superciliosus) diverged from an ancestral CRECS population. A species distribution model (SDM) for the Japanese subspecies was constructed using bioclimatic variables under the maximum entropy algorithm. It was projected backwards to the climate of the last glacial maximum (LGM) to infer the candidate source area of colonization. A migratory route of L. c. superciliosus, which possibly reflects a candidate past colonization route, was tracked by light‐level geolocators. Molecular phylogenetic networks suggest that the Japanese subspecies diverged from a population in the CRECS and maintained anciently diverged haplotypes. The SDM inferred that the emerged continental shelf of the ECS and the present CRECS were suitable breeding areas for the Japanese subspecies during the LGM. A major migratory route for L. c. superciliosus was inferred between the CRECS and the Japanese archipelago across the ECS. Our integrative approach supported the LDD hypothesis for divergence of the Japanese subspecies of the Brown Shrike. Shrinkage of the ECS may have been responsible for successful population establishment, due to a sufficient number of migrants overshooting to the Japanese archipelago from the CRECS. Our framework provides a new phylogeographic scenario for this region. Discriminating LDD and vicariance models helps improve our understanding of the phylogeographic histories of migratory species. [ABSTRACT FROM AUTHOR]

Aim: The aim of this study is to model the past, current, and future distribution of J. phoenicea s.s., J. turbinata, and J. canariensis, based on bioclimatic variables using a maximum entropy model (Maxent) in the Mediterranean and Macaronesian regions. Location: Mediterranean and Macaronesian. Taxon: Cupressaceae, Juniperus. Methods: Data on the occurrence of the J. phoenicea complex were obtained from the Global Biodiversity Information Facility (GBIF.org), the literature, herbaria, and the authors' field notes. Bioclimatic variables were obtained from the WorldClim database and Paleoclim. The climate data related to species localities were used for predictions of niches by implementation of Maxent, and the model was evaluated with ENMeval. Results: The potential niches of Juniperus phoenicea during the Last Interglacial period (LIG), Last Glacial Maximum climate (LGM), and Mid‐Holocene (MH) covered 30%, 10%, and almost 100%, respectively, of the current potential niche. Climate warming may reduce potential niches by 30% in RCP2.6 and by 90% in RCP8.5. The potential niches of Juniperus turbinata had a broad circum‐Mediterranean and Canarian distribution during the LIG and the MH; its distribution extended during the LGM when it was found in more areas than at present. The predicted warming in scenarios RCP2.6 and RCP8.5 could reduce the current potential niche by 30% and 50%, respectively. The model did not find suitable niches for J. canariensis during the LIG and the LGM, but during the MH its potential niche was 30% larger than at present. The climate warming scenario RCP2.6 indicates a reduction in the potential niche by 30%, while RCP8.5 so indicates a reduction of almost 60%. Main conclusions: This research can provide information for increasing the protection of the juniper forest and for counteracting the phenomenon of local extinctions caused by anthropic pressure and climate changes. [ABSTRACT FROM AUTHOR]

Aim: The Mediterranean Basin is a major hotspot of plant biodiversity, including forest trees. Over the past centuries, Mediterranean forests have been fragmented and over‐exploited, to which the threats of climate change are now added. Our aim is to better understand patterns and processes of tree biodiversity in the Mediterranean and to provide indicators complementing the traditional approaches to biodiversity conservation based on species counts and occurrences, using georeferenced phylogenetic diversity and endemism analyses in a spatial ecological context. Location: Mediterranean Europe. Methods: Using a dated phylogeny of the 64 Euro‐Mediterranean tree genera, we calculated phylogenetic diversity for all 50 × 50 km2 grid cells spanning Mediterranean Europe (n = 643) and compared values with those obtained for genus‐level taxonomic diversity. Then, we tested the relative influence of geography, past and present climate, and soil on tree diversity (phylogenetic or taxonomic) and its geographical turnover. Geographical patterns of phylogenetic endemism were inferred using the Categorical Analyses of Neo‐ and Paleo‐Endemism (CANAPE) methodology. Results: We showed that phylogenetic and taxonomic diversity within and among cells are correlated and influenced by soil parameters as well as current, Holocene and Late Glacial Maximum climate. Southern Spain, Cyprus and some Aegean islands contained areas of disproportionately high phylogenetic diversity and a concentration of phylogenetic paleo‐endemics, while phylogenetic neo‐endemism was high in eastern Sicily. Mixed phylogenetic endemism regions were detected in southern Spain and Portugal, in the Balkans and in Crete. Main conclusions: Our phylogenetic approach provides relevant indicators for better protecting forests of the Mediterranean, encompassing past and present evolutionary processes and factors. We consider areas that show a concentration of evolutionary history manifested by high phylogenetic endemism as high priority targets for the conservation of the European tree flora. [ABSTRACT FROM AUTHOR]

Mineral dust particles from different source regions typically have distinct Pb isotope ratios. Theoretically, Pb isotopic composition of terrigenous minerals isolated from open‐ocean sediments should allow for dust provenance reconstructions. However, Pb isotopes of terrigenous fractions of sediments have frequently been inconsistent with expected source region signatures. This study investigates the reason(s) for offsets between the Pb isotope values of the dust component in sediment cores and those expected from source regions with focus on changes in sediment composition, sediment age, and sediment processing for analysis. Pb isotope ratios from Pacific Ocean core‐top sediments show a general delineation of the Intertropical Convergence Zone (ITCZ). Isotope mixing models support these general trends, though similarity in Pb isotope ratios of disparate source regions makes constraining specific sources challenging. Pb isotope ratios in downcore samples varied on glacial/interglacial time scales, being less radiogenic during the last glacial maximum, suggesting either a weakened ITCZ or the addition of a new, less radiogenic, source to the system. Finally, Pb isotope ratios in some source region samples yielded different Pb isotope signatures in bulk source sample than in the insoluble terrigenous fraction of the source sample, indicating that differential mineral preservation within the terrigenous component in sediments may cause offsets from source signatures. Overall, while Pb isotopes show distinct basin‐scale variations, high‐resolution spatial reconstructions require tight age controls and consistency in analytical treatment if used to define ocean sediment source regions. Plain Language Summary: Dust deposited in the open ocean is sourced from rocks and sediment of various ages and location. The trace amounts of lead in this dust can have distinct isotopic values, theoretically allowing for reconstruction of dust sources. This paper looks at lead isotopes in dust deposited in the Pacific Ocean, specifically the Eastern Equatorial Pacific. Our objective is to understand how well this reconstruction tool works and if it can tell us how dust deposition has changed over glacial cycles. We found that lead isotopes work well to generally distinguish between Northern and Southern Hemisphere dust, though poor characterization and isotopic composition variability within smaller regions makes definitive source determination difficult. However, we did see changes over glacial climate cycles in the Eastern Equatorial Pacific, resulting from either change in wind patterns and/or the addition of a new dust source. Finally, we highlight the importance of consistent sample preparation to limit additional variability. Overall, lead isotopes can distinguish between some source trends, though work best when combined with other dust source tracers. Key Points: Pb isotopic ratios of detrital fractions provide general trends but not definitive determination of dust source regionsMixing models are sensitive to small changes in source isotopic values, highlighting importance of accurate source characterizationGlacial/Interglacial downcore variability in Pb isotopic ratios reflect climate‐driven dust delivery to the Eastern Equatorial Pacific [ABSTRACT FROM AUTHOR]

In unglaciated terrain, the imprint of past glacial periods is difficult to discern. The topographic signature of periglacial processes, such as solifluction lobes, may be erased or hidden by time and vegetation, and thus their import diminished. Belowground, periglacial weathering, particularly frost cracking, may have imparted a profound influence on weathering and erosion rates during past climate regimes. By combining a mechanical frost‐weathering model with the full suite of Last Glacial Maximum climate simulations, we elucidate the meters‐deep magnitude and continent‐spanning expanse of frost weathering across unglaciated North America at ∼21 ka. The surprising extent of modeled frost weathering suggests, by proxy, the broad legacy of diverse periglacial processes. Complementing previous studies that championed the role of precipitation‐driven changes in Critical Zone evolution, our results imply an additional strong temperature control on surficial process efficacy across much of modern North America, both during glacial periods and modern climes. Plain Language Summary: Hillslopes and rivers are shaped by both modern and past climates. Climate and ecosystems drive how fast bedrock weathers, soil is produced, sediment moves downslope and rivers respond. We know that during glacial periods, unglaciated regions beyond the reach of ice sheets were much colder than today. By applying a frost‐weathering model (which predicts changes in porosity, and thus rock damage, due to growth of ice lenses) to Last Glacial Maximum paleoclimatic simulations, we demonstrate the surprising extent and magnitude of periglacial processes 21,000 years ago across much of North America. No matter which paleoclimate simulation one chooses, the results point to just how extensive frost weathering processes were during the last glacial period, and by extension, multiple glacial periods of earth's history. Based on the widespread occurrence of glacial‐period frost weathering over meter‐scale depths, we suggest that past cold climates have had a significant impact on modern landscapes, both through lingering impact on subsurface pathways for water and thus chemical weathering, and the rock damage that contributes to the rate at which rock disaggregates into sediment and potential instability due to nonsteady rates of hillslope and river processes. Key Points: Frost weathering was extensive in unglaciated North America during the Last Glacial Maximum (LGM)LGM frost weathering and by association other periglacial processes occupied an area at least 3x greater than the mapped permafrost extentInherited impacts from frost‐driven weathering during glacial periods has potential to influence modern Critical Zone function and form [ABSTRACT FROM AUTHOR]

Studies on long‐chain n‐alkan‐2‐ones from lake sediments remain sparse. In this study, we present an n‐alkan‐2‐one record from Qionghai Lake, southwest China, to assess the paleoclimate significance of variations in their compositions. A homologous series of n‐alkan‐2‐ones ranging from C21 to C35 were identified, with maximum concentrations of the C29 or C31 chain lengths and a strong odd‐over‐even predominance. This type of n‐alkan‐2‐one is considered to derive mainly from microbial oxidation of the corresponding n‐alkanes, and partial inputs from plants. The n‐alkan‐2‐one‐derived average chain length (ACL) and carbon preference index (CPI) values changed significantly over the past 28k cal a bp, consistent with the sediment grain size and n‐alkane proxies from the same core. Generally, the high CPI27‐33‐ket and low ACL27‐33‐ket values indicated cold and dry climates such as for the Last Glacial Maximum (23.2–19.7k cal a bp), Heinrich 1 event (17.6–15.6k cal a bp) and Younger Dryas (12.8–11.6k cal a bp), but low CPI27‐33‐ket and high ACL27‐33‐ket values denoted a warm and humid Holocene Climatic Optimum (7.0–4.3k cal a bp). Therefore, n‐alkan‐2‐ones have great paleoclimatic potential and can be applied together with other biomarkers to reconstruct a reliable paleoclimate record in lake sediments. [ABSTRACT FROM AUTHOR]

Ecometrics is the study of community‐level functional trait–environment relationships. We use ecometric analyses to estimate paleoenvironment and to investigate community‐level functional changes through time.We evaluate four methods that have been used or have the potential to be used in ecometric analyses for estimating paleoenvironment to determine whether there have been systematic differences in paleoenvironmental estimation due to choice of the estimation method. Specifically, we evaluated linear regression, polynomial regression, nearest neighbor, and maximum‐likelihood methods to explore the predictive ability of the relationship for a well‐known ecometric dataset of mammalian herbivore hypsodonty metrics (molar tooth crown to root height ratio) and annual precipitation. Each method was applied to 43 Pleistocene fossil sites and compared to annual precipitation from global climate models. Sites were categorized as glacial or interglacial, and paleoprecipitation estimates were compared to the appropriate model.Estimation methods produce results that are highly correlated with log precipitation and estimates from the other methods (p < 0.001). Differences between estimated precipitation and observed precipitation are not significantly different across the four methods, but maximum likelihood produces the most accurate estimates of precipitation. When applied to paleontological sites, paleoprecipitation estimates align more closely with glacial global climate models than with interglacial models regardless of the age of the site.Each method has constraints that are important to consider when designing ecometric analyses to avoid misinterpretations when ecometric relationships are applied to the paleontological record. We show interglacial fauna estimates of paleoprecipitation more closely match glacial global climate models. This is likely because of the anthropogenic effects on community reassembly in the Holocene. [ABSTRACT FROM AUTHOR]

The Kingston Peak Formation of the Pahrump Group in the Death Valley region of the Basin and Range Province, USA, is the thick (over 3 km) mixed siliciclastic–carbonate fill of a long‐lived structurally‐complex Neoproterozoic rift basin and is recognized by some as a key 'climatostratigraphic' succession recording panglacial Snowball Earth events. A facies analysis of the Kingston Peak Formation shows it to be largely composed of 'tectonofacies' which are subaqueous mass flow deposits recording cannibalization of older Pahrump carbonate strata exposed by local faulting. Facies include siltstone, sandstone and conglomerate turbidites, carbonate megabreccias (olistoliths) and related breccias, and interbedded debrites. Secondary facies are thin carbonates and pillowed basalts. Four distinct associations of tectonofacies ('base‐of‐scarp'; FA1, 'mid‐slope'; FA2, 'base‐of‐slope'; FA3, and a 'carbonate margin' association; FA4) reflect the initiation and progradation of deep water clastic wedges at the foot of fault scarps. 'Tectonosequences' record episodes of fault reactivation resulting in substantial increases in accommodation space and water depths, the collapse of fault scarps and consequent downslope mass flow events. Carbonates of FA4 record the cessation of tectonic activity and resulting sediment starvation ending the growth of clastic wedges. Tectonosequences are nested within regionally‐extensive tectono‐stratigraphic units of earlier workers that are hundreds to thousands of metres in thickness, recording the long‐term evolution of the rifted Laurentian continental margin during the protracted breakup of Rodinia. Debrite facies of the Kingston Peak Formation are classically described as ice‐contact glacial deposits recording globally‐correlative panglacials but they result from partial to complete subaqueous mixing of fault‐generated coarse‐grained debris and fine‐grained distal sediment on a slope conditioned by tectonic activity. The sedimentology (tectonofacies) and stratigraphy (tectonosequences) of the Kingston Peak Formation reflect a fundamental control on local sedimentation in the basin by faulting and likely earthquake activity, not by any global glacial climate. [ABSTRACT FROM AUTHOR]

Knowledge of the structures and intensities of past glaciations is crucial for understanding Quaternary palaeoclimatic evolution. Terrestrial molluscs are a reliable proxy of past environmental conditions and can provide specific climatic insights into glacials. Here we compare the climatic evolution of the last two glacials, based on mollusc fossils from the L2 and L1 loess units (equivalent to Marine Isotope Stages (MIS) 6 and 4–2, respectively) of the Xifeng and Luochuan sections of the Chinese Loess Plateau (CLP). The results show that both glacials had a tripartite structure but with different intensities, as indicated by variations in the abundance of the dominant cold‐aridiphilous (CA) mollusc species, Vallonia tenera and Pupilla aeoli. The first stage, from ~191 to 184 ka for MIS 6, and from ~71 to 57 ka for MIS 4, was characterized by a cold, arid climate, as indicated by the abundance of V. tenera and P. aeoli, and the limited occurrence of thermo‐humidiphilous (TH) species. The second stage, from ~184 to 155 ka for MIS 6, and from ~57 to 29 ka for MIS 3, was characterized by a relatively mild, humid climate, indicated by a decrease in V. tenera and P. aeoli, and an increase in TH species. The last stage, from ~155 to 130 ka for MIS 6, and from ~29 to 11.7 ka for MIS 2, experienced the coldest and driest conditions, as indicated by the dominance of V. tenera and P. aeoli in late MIS 6 and by the reduced occurrence of the grassland biomass, necessary for the growth of CA species, in MIS 2. The climate during MIS 2 was much colder and drier than that during late MIS 6. We suggest that the structures of the glacials were controlled mainly by insolation driven by changing astronomical configurations, amongst which obliquity likely played the major role. The different glacial intensities across the CLP may also have been related to variations in Northern Hemisphere ice sheets and the temperature of the tropical oceans. [ABSTRACT FROM AUTHOR]

The debate regarding the history of water‐level fluctuations in Lake Baikal extends back to the late 19th century and is rooted in the interpretation of the sequence of palaeo‐shoreline terraces observed around the Baikal trough. Modern studies identify terraces up to 200 m above and down to 40 m below the present‐day Lake Baikal water level, and opinions are split between (i) those who regard the lake‐level fluctuations as a function of shifts in water balance associated with glacial and interglacial periods, and (ii) those who attribute the changes to predominantly tectonic factors, permitting water‐balance fluctuations of not more than a few tens of metres. In either case, a definitive lake‐level scheme must also constrain the relative elevation of the Baikal's outlet, which has not been fixed over time. Here, we focus upon the lake‐level changes over the past 50 000 years with a new set of observations from an outstanding sequence of palaeo‐shoreline terraces on Bolshoi Ushkanii Island located in central Lake Baikal. By determining the 14C age of soils rapidly buried by beach deposits on two terraces, we provide direct evidence of lake‐level highstands at ~120–122 and ~72–83 m during Marine Isotope Stage (MIS) 3 (Karginsk interstadial). By integrating these results with the repeated subsidence of Baikal's outlet threshold since MIS 5e, we show that lake‐level fluctuations closely align with swings in glacial and interglacial climate. [ABSTRACT FROM AUTHOR]

We present a mechanism for self‐sustained ocean circulation changes that cause abrupt temperature changes over Greenland in a multimillennial climate model simulation with glacial CO2 concentrations representative of Marine Isotope Stage 3. The Atlantic meridional overturning circulation (AMOC) and the subpolar gyre (SPG) oscillate on millennial time scales. When the AMOC is strong, the SPG is weak and contracted; when the AMOC is weak, the SPG is strong and extensive. The coupling between the two systems via wind‐driven and density‐driven feedbacks is key to maintaining the oscillations. The SPG controls the transport of heat and salt into the deep‐water formation sites and thus controls the AMOC strength. The strength and location of the deep‐water formation affect the density‐driven part of the SPG and thus control the mean strength and extent of the SPG. This mechanism supports the hypothesis that coupled ocean‐ice‐atmosphere interactions could have triggered abrupt glacial climate change. Plain Language Summary: Between 57.000 and 29.000 years ago, the last glacial period was marked by several abrupt warming and cooling events over Greenland and the North Atlantic. Understanding the mechanism behind these so‐called Dansgaard‐Oeschger events increases our understanding of possible tipping points that cause abrupt change in the Earth system. The role of the ocean in causing these events is still a topic of debate. We find abrupt changes in the North Atlantic circulation that resemble Dansgaard‐Oeschger events in a simulation with a state‐of‐the‐art climate model. These simulated ocean circulation changes are generated without adding external triggers such as meltwater from glaciers. Instead, the events are generated by the interaction of the two large‐scale current systems in the North Atlantic—the Atlantic meridional overturning circulation (AMOC) and the North Atlantic subpolar gyre (SPG). Both current systems are affected by changes in surface winds and the density pattern of the North Atlantic. We find that the location where the densest water is formed controls how the SPG interacts with the AMOC. Under favorable conditions, the effects of wind and density combine in such a way that changes in the SPG cause abrupt changes in the AMOC. Key Points: Millennial‐scale, self‐sustained oscillations of the ocean circulation occur in a climate model simulationThe oscillations are driven by the interaction between the Atlantic meridional overturning circulation (AMOC) and the subpolar gyre (SPG)The AMOC‐SPG coupling is controlled by a wind‐driven and a density‐driven feedback; the coupling sign depends on the dominant feedback [ABSTRACT FROM AUTHOR]

Simulations show that storm tracks were weaker during past cold, icy climates relative to the modern climate despite increased surface baroclinicity. Previous work explained the weak North Atlantic storm track during the Last Glacial Maximum using dry zonally asymmetric mechanisms associated with orographic forcing. Here we show that zonally symmetric mechanisms associated with the hydrological cycle explain the weak Snowball Earth storm track. The weak storm track is consistent with the decreased meridional gradient of evaporation and atmospheric shortwave absorption and can be predicted following global mean cooling and the Clausius‐Clapeyron relation. The weak storm track is also consistent with decreased latent heat release aloft in the tropics, which decreases upper tropospheric baroclinicity and mean available potential energy. Overall, both hydrological cycle mechanisms are reflected in the significant correlation between storm track intensity and the meridional surface moist static energy gradient across a range of simulated climates between modern and Snowball Earth. Plain Language Summary: Storm tracks (low‐ and high‐pressure weather systems) dominate Earth's climate in the middle latitudes. Several modern theories connect storm track intensity to the equator‐to‐pole near‐surface temperature gradient. However, it has been known for some time that this connection fails when applied to simulations of past cold, icy climates such as the Last Glacial Maximum and Snowball Earth. Previous work explained the weak North Atlantic storm track during the Last Glacial Maximum using dry longitudinally dependent dynamical mechanisms associated with orographic forcing. Here we show that the weak Snowball Earth storm track can be explained by hydrological cycle changes that are independent of longitude. In particular, the weak storm track is consistent with the decreased equator‐to‐pole gradient of evaporation, absorption of sunlight, and surface moist static energy, which follow global mean cooling and the Clausius‐Clapeyron relation. The decreased equator‐to‐pole surface moist static energy gradient is correlated with decreased latent heat release aloft in the tropics, which weakens the potential energy that is available to be converted into kinetic energy. Key Points: Snowball Earth storm track is weaker than modern following decreased gradient of latent heat flux, shortwave absorption and latent heat release aloftThe weaker Snowball Earth storm track can be predicted following global‐mean cooling and the Clausius‐Clapeyron relationThe significant correlation between storm track intensity and surface moist static energy gradient reflects the importance of the hydrological cycle [ABSTRACT FROM AUTHOR]

Montane species endemic to the "sky islands" of the North American southwest were significantly impacted by changing climates during the Pleistocene. We combined mitochondrial and genomic data with species distribution modelling to determine whether Aphonopelma marxi, a large tarantula from the nearby Colorado Plateau, was similarly impacted by glacial climates. Genetic analyses revealed that the species comprises three main clades that diverged in the Pleistocene. A clade distributed along the Mogollon Rim appears to have persisted in place during glacial conditions, whereas the other two clades probably colonized central and northeastern portions of the species' range from refugia in canyons. Climate models support this hypothesis for the Mogollon Rim, but late glacial climate data appear too coarse to detect suitable areas in canyons. Locations of canyon refugia could not be inferred from genomic analyses due to missing data, encouraging us to explore the effect of missing loci in phylogeographical inferences using RADseq. Results from analyses with varying amounts of missing data suggest that samples with large amounts of missing data can still improve inferences, and the specific loci that are missing matters more than the number of missing loci. This study highlights the profound impact of Pleistocene climates on tarantulas endemic to the Colorado Plateau, as well as the mixed nature of the region's fauna. Some animals recently colonized from nearby deserts as glacial climates receded, whereas others, like tarantulas, appear to have persisted on the Mogollon Rim and in refugia associated with the region's famous river‐cut canyons. [ABSTRACT FROM AUTHOR]

The isotopic composition of Si in biogenic silica (BSi), such as opal buried in the oceans' sediments, has changed over time. Paleorecords suggest that the isotopic composition, described in terms of δ30Si, was generally much lower during glacial times than today. There is consensus that this variability is attributable to differing environmental conditions at the respective time of BSi production and sedimentation. The detailed links between environmental conditions and the isotopic composition of BSi in the sediments remain, however, poorly constrained. In this study, we explore the effects of a suite of offset boundary conditions during the Last Glacial Maximum (LGM) on the isotopic composition of BSi archived in sediments in an Earth System Model of intermediate complexity (EMIC). Our model results suggest that a change in the isotopic composition of Si supply to the glacial ocean is sufficient to explain the observed overall low(er) glacial δ30Si in BSi. All other processes explored trigger model responses of either wrong sign or magnitude or are inconsistent with a recent estimate of bottom water oxygenation in the Atlantic Sector of the Southern Ocean. Caveats, mainly associated with generic uncertainties in today's pelagic biogeochemical modules, remain. Key Points: We simulate the isotopic composition of biogenic silica archived in the ocean's sedimentOur simulations with an Earth System Model compare modern climate to glacial conditionsOut of several hypotheses tested, altering the isotopic composition of runoff during the LGM is most consistent with proxies [ABSTRACT FROM AUTHOR]

In this study, we reconstruct the style and timing of the late Quaternary glaciation pattern in a monsoon‐influenced precipitation‐deprived region (Dhauliganga basin) of the Central Himalaya, India. We present detailed glacial geomorphological mapping, aided by topographic maps, satellite data, Google Earth images, global positioning system survey, and fieldwork (2012–2016), supported by optically stimulated luminescence dating. Our estimations for the magnitude and timing of glaciations in the Dunagiri Glacier valley suggest five sets of glacial advances. The oldest and most extensive glaciation in the valley is Dunagiri Glacial Stage‐I (DGS‐I), represented by a discontinuous moraine ridge that extends down to ~10 km (~2700 m a.s.l.) from the present‐day snout and formed 13±3 ka ago. The DGS‐II stage is present in the form of a small moraine ridge (~3000 m a.s.l.) that formed 10±2 ka ago. The DGS‐III and DGS‐IV glacial stages are 5–6 and 3.5 ka old, respectively. The youngest stage (DGS‐V) of glaciation belongs to the neoglaciation episode ~1 ka old. DGS‐I was the most extensive glaciation in the valley and corresponds to the global Last Glacial Maximum. The glaciation pattern has been correlated with the estimates of present‐day glacial sensitivity to climate and explained as forcing factors sensitive to temperature and/or precipitation changes in the region. The observations based on prevailing climate correlations aided with available glacial chronologies underline the fact that the glacial valleys situated in precipitation‐deprived regions have preserved a delayed response of glaciations to regional climatic events. Estimates for the timing and pattern of glaciation in the present study suggest a different glacial response for modern climatic changes than previously assumed. We suggest that individual glacier advances differ regionally and, therefore, should not be interpreted as being reflective of a change in the whole geographical belt. [ABSTRACT FROM AUTHOR]

A 150‐ to 220‐year lag between abrupt Greenland warming and maximum Antarctic warming characterizes past glacial Dansgaard‐Oeschger events. In a modeling study, we investigate how the cross‐equatorial oceanic heat transport (COHT) might drive this phasing during an abrupt Northern Hemisphere (NH) warming. We use the MITgcm in an idealized continental configuration with two ocean basins, one wider, one narrower, under glacial‐like conditions with sea ice reaching midlatitudes. An exaggerated eccentricity‐related solar radiation anomaly is imposed over 100 years to trigger an abrupt NH warming and sea‐ice melting. The Hadley circulation shifts northward in response, weakening the NH trade winds, subtropical cells, and COHT in both ocean basins. This induces heat convergence in the Southern Hemisphere (SH) ocean subsurface, from where upward heat release melts sea ice and warms SH high latitudes. Although the small‐basin meridional overturning circulation also weakens, driven by NH ice melting, it contributes at most one‐third to the total COHT anomaly, hence playing a subsidiary role in the SH and NH initial warming. Switching off the forcing cools the NH; yet heat release continues from the SH ocean subsurface via isopycnal advection‐diffusion and vertical mixing, driving further sea ice melting and high latitude warming for ~50–70 more years. A phasing in polar temperatures resembling reconstructions thus emerges, linked to changes in the subtropical cells' COHT, and SH ocean heat storage and surface fluxes. Our results highlight the potential role of the atmosphere circulation and wind‐driven global ocean circulation in the NH–SH phasing seen in DO events. Key Points: Polar temperature phasing linked to changes in cross‐equatorial ocean heat transport and Southern Ocean heat storage in MITgcmCross‐equatorial ocean heat transport mainly driven by subtropical cell weakening due to northward ITCZ shift; smaller role of AMOCMaximum warming in the South delayed with respect to the North due to subsurface heat release and ice melting [ABSTRACT FROM AUTHOR]

There is a growing appreciation of the uncertainties in the estimation of snow‐melt and glacier‐melt as a result of climate change in high elevation catchments. Through a detailed examination of three hydrological models in two catchments, and interpretation of results from previous studies, we observed that many variations in estimated streamflow could be explained by the selection of a best parameter set from the possible good model parameters. The importance of understanding changing glacial dynamics is critically important for our study areas in the Upper Indus Basin where Pakistan's policymakers are planning infrastructure to meet the future energy and water needs of hundreds of millions of people downstream. Yet, the effect of climate on glacial runoff and climate on snowmelt runoff is poorly understood. With the HBV model, for example, we estimated glacial melt as between 56% and 89% for the Hunza catchment. When rainfall was a scaled parameter, the models estimated glacial melt as between 20% and 100% of streamflow. These parameter sets produced wildly different projections of future climate for RCP8.5 scenarios in 2046–2075 compared to 1976–2005. Assuming no glacial shrinkage, for one climate projection, we found that the choice among good parameter sets resulted in projected values of future streamflow across a range from +54% to +125%. Parameter selection was the most significant source of uncertainty in the glaciated catchment and amplified climate model uncertainty, whereas climate model choice was more important in the rainfall dominated catchment. Although the study focuses on Pakistan, the overall conclusions are instructive for other similar regions in the world. We suggest that modellers of glaciated catchments should present results from at least the book‐ends: models with low sensitivity to ice‐melt and models with high sensitivity to ice‐melt. This would reduce confusion among decision makers when they are faced with similar contrasting results. [ABSTRACT FROM AUTHOR]

Many stable isotope paleoaltimetry studies have focused on paleoelevation reconstructions of orogenic plateaus such as the Tibetan or Andean Plateaus. We address the opportunities and challenges of applying stable isotope paleoaltimetry to "smaller" orogens. We do this using a high‐resolution isotope tracking general circulation model (ECHAM5‐wiso) and explore the precipitation δ18O (δ18Op) signal of Cenozoic paleoclimate and topographic change in the European Alps. Results predict a maximum δ18Op change of 4–5‰ (relative to present day) during topographic development of the Alps. This signal of topographic change has the same magnitude as changes in δ18Op values resulting from Pliocene and Last Glacial Maximum global climatic change. Despite the similar magnitude of the isotopic signals resulting from topographic and paleoclimate changes, their spatial patterns across central Europe differ. Our results suggest that an integration of paleoclimate modeling, multiproxy approaches, and low‐elevation reference proxy records distal from an orogen improve topographic reconstructions. Plain Language Summary: Here we use a climate model with water isotopes implemented to explore the maximum precipitation isotopic signal of Cenozoic topographic and paleoclimate change in the European Alps. Our results show that the impact of topography change has the same magnitude as changes in the isotopic composition of local precipitation resulting from Pliocene and Last Glacial Maximum global climatic change. Key Points: High‐resolution isotope tracking general circulation model (ECHAM5‐wiso) is used to explore changes in past oxygen isotope ratios in precipitation in the AlpsModel‐simulated isotopic signals of topographic change and difference between glacials and interglacials show the same magnitudeLow‐elevation proxy records improve reconstructions of paleotopography by reducing long‐term climate change bias [ABSTRACT FROM AUTHOR]

Aim: To investigate cerrado responses to glacial–interglacial climate change and the potential for connective rain forest corridors between the Atlantic Coastal Forest and Amazonian rain forest. Location: The crater lake of Serra Negra (18 °S, 46 °W) in Minas Gerais, Brazil. Taxon: 117 fossil pollen types, 22 non‐pollen palynomorphs were documented. Methods: We recovered 7.82 m of sediment from the lake, and analysed fossil pollen at 62 depth intervals throughout the core. We derived a chronology based on radiocarbon dating with simple rate extrapolation to the base of the core. Results: The c. 90,000‐year fossil record showed a trend towards cooler climates at the Last Glacial Maximum (LGM), but interstadial warming coupled with reduced evaporative stress allowed the expansion of woodlands under cool, moist conditions. Cool‐adapted trees were most abundant between c. 67,000 and 48,000 years ago. A cool cerrado‐like environment marked full glacial conditions between c. 48,000 and 34,000 years ago. The peak of the LGM between c. 34,000 and 17,000 years ago is inferred to have been dry as no sediment accumulated in the system. Main conclusions: Expanded ranges of cold‐tolerant forest taxa led to establishment of a series of assemblages without modern analogue. A system characteristic of modern cerrado was rare in the history of this site. Multiple forest expansions were observed, each differing in composition. The periods of forest abundance at Serra Negra were not temporally aligned with forest expansion in the Atlantic Coastal Forest, and did not provide a continuous corridor of similar forest that connected the cerrado to the Atlantic Coastal Forest. [ABSTRACT FROM AUTHOR]

Aim: Understanding the drivers of speciation within islands is key to explain the high levels of invertebrate diversification and endemism often observed within islands. Here, we propose an insular topoclimate model for Quaternary diversification (ITQD), and test the general prediction that, within a radially eroded conical island, glacial climate conditions facilitate the divergence of populations within species across valleys. Location: Gran Canaria, Canary Islands. Taxon: The Laparocerus tessellatus beetle species complex (Coleoptera, Curculionidae). Methods: We characterize individual‐level genomic relationships using single nucleotide polymorphisms produced by double‐digest restriction site associated DNA sequencing (ddRAD‐seq). A range of parameter values were explored in order to filter our data. We assess individual relatedness, species boundaries, demographic history and spatial patterns of connectivity. Results: The total number of ddRAD‐seq loci per sample ranges from 4,576 to 512, with 11.12% and 4.84% of missing data respectively, depending on the filtering parameter combination. We consistently infer four genetically distinct ancestral populations and two presumed cases of admixture, one of which is largely restricted to high altitudes. Bayes factor delimitation support the hypothesis of four species, which is consistent with the four inferred ancestral gene pools. Landscape resistance analyses identified genomic relatedness among individuals in two out of the four inferred species to be best explained by annual precipitation during the last glacial maximum rather than geographic distance. Main conclusions: Our data reveal a complex speciation history involving population isolation and admixture, with broad support for the ITQD model here proposed. We suggest that further studies are needed to test the generality of our model, and enrich our understanding of the evolutionary process in island invertebrates. Our results demonstrate the power of ddRAD‐seq data to provide a detailed understanding of the temporal and spatial dynamics of insular biodiversity. [ABSTRACT FROM AUTHOR]