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The history of vegetation and climate change during the Cenozoic has been reconstructed by systematically analyzing the sporopollen assemblage from Borehole ZKA02 in Beihai, Guangxi. Through the analysis of spore-pollen data, four sporopollen assemblages can be recognized. From the Early Miocene to the Middle Miocene, this area was covered mainly by deciduous broad-leaved mixed forest–wet meadow vegetation, with a mild and semi-humid climate. From the end of the Middle Miocene to the early Late Miocene, the study area was dominated by coniferous and broad-leaved mixed forest-wet meadow vegetation, with mild and semi-humid. The middle Late Miocene was a mixed deciduous broad-leaved forest–wet meadow vegetation, with increasing conifers and ferns, and the climate was warm and humid. In the late Late Miocene to Pliocene, it was deciduous broad-leaved mixed forest–wet meadow vegetation. The species of evergreen broad-leaved trees in tropical rain forests and subtropical low mountains increased obviously, and the fern molecules decreased obviously. The climate in the Late Pliocene was warm and semi-arid, drier than the previous three stages. Spore-pollen assemblages reflected the climate change characteristics during the Neogene, which have good comparability with the trend of global climate change.

Spatially variable basal conditions are thought to govern how ice sheets behave at glacial time scales (>1000 years) and responsible for changes in dynamics between the core and peripheral regions of the Laurentide and Fennoscandian ice sheets. Basal motion is accomplished via the deformation of unconsolidated sediments, or via sliding of the ice over an undeformable bed. We present an ice sheet sliding module for the Parallel Ice Sheet Model (PISM) that takes into account changes in sediment cover and incorporates surface meltwater. This model routes meltwater, produced at the surface and base of the ice sheet, toward the margin of the ice sheet. Basal sliding is accomplished through the deformation of water saturated sediments, or sliding at the ice-bed interface. In areas with continuous, water saturated sediments, sliding is almost always accomplished through sediment deformation. In areas with incomplete cover, sliding has a stronger dependence on the supply of water. We find that the addition of surface meltwater to the base is a more important factor for ice sheet evolution than the style of sliding. In a glacial cycle simulation, our model causes a more rapid buildup of the Laurentide Ice Sheet.

Abstract Tree-ring cellulose oxygen isotopic ratios have been widely studied as a hydrological proxy in monsoonal Asia. There has been, however, little attempt to perform proxy assessment of the intra-annual isotopic data to reconstruct hydroclimate with higher temporal resolution. We presented new intra-annual cellulose oxygen isotopic records of Japanese cedar trees spanning A.D. 1918 to 2017, and validated it as a hydrological proxy by comparing with meteorological data. There are significant negative correlations between intra-annual isotopic ratios and summer precipitation/relative humidity, as similar to annual-resolution data of earlier studies. Notably on intra-annual scales, the period showing the highest correlation gradually shifted from May to August, in corresponding to the location within the annual ring. Principal component regression analyses show the regression was more accurate over a wider duration than single regression analysis using the annual data, therefore indicating that the subdivision of the annual ring could contribute to reconstruct higher-resolution hydroclimate.

Profile sampling, which causes missing or overlapping horizons, has been generally used while studying loess stratigraphy and paleoclimate. Conversely, drill sampling of thick loess can provide a relatively complete and actual record of the Quaternary climate and environmental changes. Here, paleomagnetic chronological analysis and particle size and magnetic susceptibility analyses were performed to accurately reveal the loess stratigraphy characteristics of Luochuan loess tableland in Fu County, Shaanxi Province, China. The FX core revealed that the Quaternary loess layer was 167.03 m thick and consisted of 33 layers of developed loess/paleosol sequences and 37 loess/paleosol assemblages. The paleosol horizons indicated relatively warm and humid climatic period, while loess/sand reflected cold and arid climate. Since 2.6 Ma, the climate of the region has undergone 37 warm and cold cycles trending toward an increasingly dry and cold climate. During this time, 10 paleoclimate cycles occurred during 2.6–1.6 Ma, 15 climate cycles occurred during 1.6–0.8 Ma, and 12 loess–paleosol cycles have occurred from 0.8 Ma to the present day. Our study provides a basis for accurately and comprehensively interpreting the paleoclimate and paleoenvironment during loess deposition formation.

Ice streams are sites of ice-sheet drainage and together with other processes, such as calving, have an impact on deglaciation rates and ice-sheet mass balance. Proglacial lake deposits provide records of ice-sheet deglaciation and have the potential to supplement other paleoclimate records. Oneida Lake, northeastern USA, contains a thick proglacial lake sequence that buries evidence of ice streaming and a paleo-calving margin that developed during retreat of the Laurentide Ice Sheet. Previous high-resolution digital elevation models identified the Oneida Ice Stream from glacial landforms northwest of the lake. In this study, we utilize seismic refractions from a multichannel seismic (MCS) reflection dataset to estimate the thickness of glacial deposits using seismic tomography. With this method we constrain the depth to top of Paleozoic strata, especially in areas where the reflection data yielded poor outcomes and validate our reflection data in regions of good coverage. We demonstrate that where long offset seismic data are available, the first-arrival tomography method is useful in studies of formerly glaciated basins. Our study identifies a ~108 m thick sedimentary section and potentially long paleoclimate record in Oneida Lake, and identifies a paleotopographic low that likely encouraged formation of the Oneida Ice Stream.

Abstract This study presents a methodological advancement in the field of clumped‐isotope (∆47) thermometry, specifically tailored for application to freshwater ostracods. The novel ostracod clumped isotope approach enables quantitative temperature and hydrological reconstruction in lacustrine records. The relationship between ∆47 and the temperature at which ostracod shell mineralized is determined by measuring ∆47 on different species grown under controlled temperatures, ranging from 4 ± 0.8 to 23 ± 0.5ºC. The excellent agreement between the presented ∆47 ostracod data and the monitored temperatures confirms that ∆47 can be applied to ostracod shells and that a vital effect is absent outside the uncertainty of measurements. Results are consistent with the carbonate clumped‐isotope unified calibration (Anderson et al., 2021, https://doi.org/10.1029/2020gl092069), therefore, an ostracod‐specific calibration is not needed. The ostracod clumped‐isotope thermometer represents a powerful tool for terrestrial paleoclimate studies all around the world, as lakes and ostracods are found in all climatic belts.

Reconstruction of the depositional environment of the Paleocene-Eocene Sinjar Formation from two outcrop sections in northwestern and northeastern Iraq has been evaluated using the traditional petrographic and facies analysis supported by X-ray diffraction and scanning electron microscopy with a focus on the Paleocene-Eocene (P-E) transition boundary. To this end, major and trace elemental geochemistry was conducted and various paleoenvironmental proxies for the paleoredox, paleoclimate, paleosalinity and paleoproductivity were determined in order to evaluate the changes in widely acknowledged environmental and climatic indicators and the elemental enrichment/depletion across the P–E boundary. The redox-sensitive trace element enrichment and the ir ratios (V/V + Ni, V/Cr, and U/Th) indicate that normal oxygenated circumstances prevailed during the late Paleocene deposition, and that anoxic conditions and a gradual commencement of oxygen depletion occurred during the early Eocene deposition. The coeval increase in the P2O5 content, P/Ti, and P/Al ratios in the Eocene sediments suggests an increase in nutrients and primary productivity due to the effect of upwelling currents during early Eocene. The conditions can be verified by observing a small change in salinity levels from low to high across the P-E boundary, which can be indicated by the Sr/Ba ratios. In addition, certain minerals such as Mg-calcite, dolomite, and palygorskite are commonly present, and paleoclimatic changes can be observed across the P-E transition from arid to semiarid and then to humid conditions, which can be recorded from C-values, Sr-Cu, Rb/Sr ratios, and clay mineralogy. These conditions were noted in the Sinjar Formation, which is made up of many microfacies such as lime mudstone, wackstone, packstone, grainstone and boundstone. These microfacies were deposited in a shallow marine environment that extended from tidal flats to reef slopes, with a developed reef environment that included back reef, reef core, and fore reef environments.

Abstract Nitrous oxide (N2O) is an important greenhouse gas which destroys the ozone in the stratosphere. Primary sources of atmospheric N2O are nitrification and denitrification in terrestrial soils and the ocean, and the main sink is photolysis in the stratosphere. Studies have mostly focused on the climate‐related response of N2O during glacial‐interglacial periods. However, its mechanism of variation during the Holocene remains unclear. We present a high‐resolution N2O record from the South Pole Ice (SPICE) core covering the Holocene epoch. The millennial‐scale N2O trend agrees with existing records. We constructed a Holocene composite consisting of the new N2O measurements in SPICE and existing records from other ice core sites. The N2O composite reveals four distinct periods of N2O variation during 11.5–10.0 ka, 10.0–6.2 ka, 6.2–2.2 ka, and 2.2–1.4 ka, including two maxima in 11.0–10.0 ka and 3.0–2.2 ka and minima in 8.8–6.2 ka and approximately 1.4 ka. Apart from these, our new high‐resolution record from SPICE shows a short‐term N2O decrease around 2.8 ka which is not observed in other records possibly due to lower sample resolution and/or higher age smoothing. Comparison of our new Holocene N2O composite with the paleo‐proxy records suggests the plausible linkage of major monsoon (Asian, North African, South and North American, and Australian‐Indonesian monsoon) and upwelling (Arabian Sea and Eastern Tropical South Pacific) regions in regulating the atmospheric N2O during the Holocene.

IntroductionAstarte borealis holds great potential as an archive of seasonal paleoclimate, especially due to its long lifespan (several decades to more than a century) and ubiquitous distribution across high northern latitudes. Furthermore, recent work demonstrates that the isotope geochemistry of the aragonite shell is a faithful proxy of environmental conditions. However, the exceedingly slow growth rates of A. borealis in some locations (

Abstract An integrated approach considering facies, isotopic, and palynological analyses of lake sediments from the Serra Norte de Carajás, southeastern Amazonia, is presented in this work to refine paleoclimate and paleohydrological changes based on upland lake sediments during the late Quaternary. The sediments have a fining-upward deposition cycle typical of upland swamps/lakes. The origin of organic matter is autochthonous mainly related to C3 terrestrial plants, macrophytes and algae. The pollen records of Hedyosmum during the Early Pleistocene suggest lower temperatures than those observed along Holocene. In the transitional period between the Pleistocene and the Holocene, rainfall decreased, causing the retraction of the flooded area, favoring the development of marshy conditions. The Late and Middle Holocene were marked by higher temperatures and lower humidity. Afterward, the increased pollen concentration from canga and forest vegetation, macrophytes, palms, and algae suggested increased humidity in the Early Holocene. The relative contribution of forest pollen along the records indicated that drier conditions were not strong enough for an extensive expansion of canga over forested areas.

Sedimentation of the Paleogene and Neogene belts in the Indo-Burma Range (IBR) involved a complex tectonic system letting provenance of both the belts poorly constrained. We made an attempt to investigate provenance, tectonic setting, paleoclimate, and depositional environment of the Renji Formation (Paleogene belt) and the Bhuban Formation (Neogene belt) in the Barak basin of western Manipur employing whole-rock geochemistry and petrography. A semi-arid climatic condition has been indicated for the weathering and liberation of sediments in the source terrain. Derivation of first cycle sediments from mafic and felsic rocks with minor contribution from the metamorphic rocks is suggested but the former seems to have dominated the Renji Formation. A shift in the provenance vis-a-vis differential chemical weathering of the mafic-felsic rocks at the source is attributed. Research results also suggest supply from deformed and elevated craton, presumably the Indian craton, during the Himalayan orogeny. Sedimentation of the Renji Formation took place in a sub-oxic deltaic environment in contrast to the Bhuban Formation which developed in an oxic shallow marine mixed tidal flat environment.

Summary: Strong paleoclimatic change and few Late Quaternary megafauna extinctions make mainland Africa unique among continents. Here, we hypothesize that, compared with elsewhere, these conditions created the ecological opportunity for the macroevolution and geographic distribution of large fruits.We assembled global phylogenetic, distribution and fruit size data for palms (Arecaceae), a pantropical, vertebrate‐dispersed family with > 2600 species, and integrated these with data on extinction‐driven body size reduction in mammalian frugivore assemblages since the Late Quaternary. We applied evolutionary trait, linear and null models to identify the selective pressures that have shaped fruit sizes.We show that African palm lineages have evolved towards larger fruit sizes and exhibited faster trait evolutionary rates than lineages elsewhere. Furthermore, the global distribution of the largest palm fruits across species assemblages was explained by occurrence in Africa, especially under low canopies, and extant megafauna, but not by mammalian downsizing. These patterns strongly deviated from expectations under a null model of stochastic (Brownian motion) evolution.Our results suggest that Africa provided a distinct evolutionary arena for palm fruit size evolution. We argue that megafaunal abundance and the expansion of savanna habitat since the Miocene provided selective advantages for the persistence of African plants with large fruits. This article is part of the Special Collection 'Global plant diversity and distribution'. See https://www.newphytologist.org/global-plant-diversity for more details. [ABSTRACT FROM AUTHOR]

We present oxygen isotope and charcoal accumulation records from two lakes in eastern Washington that have sufficient temporal resolution to quantitatively compare with tree‐ring records and meteorological data. Hydroclimate reconstructions from tree‐rings and lake sediments show close correspondence after accounting for seasonal‐ to centennial‐ scale temporal sensitivities. Carbonate δ18O measurements from Castor and Round lakes reveal that the Medieval Climate Anomaly (MCA) experienced wetter November‐March conditions than the Little Ice Age (LIA). Charcoal records from Castor, Round, and nearby lakes show elevated fire activity during the LIA compared to the MCA. Increased multidecadal hydroclimate variability after 1250 CE is evident in proxy records throughout western North America. In the Upper Columbia River Basin, multidecadal wet periods during the LIA may have enhanced fuel loads that burned in subsequent dry periods. A notable decline in biomass burning occurred with Euro‐American settlement in the late nineteenth century. Plain Language Summary: Paleoclimate reconstructions are based on proxy records that are sensitive to particular aspects of the climate system. We compare high‐resolution lake sediment records with nearby tree‐ring chronologies and instrumental data to explore hypotheses about climate variability. Here, we confirm that lake‐sediment oxygen isotope ratios in the Upper Columbia River Basin are primarily sensitive to cool‐season precipitation, whereas many tree‐ring records are primarily sensitive to warm‐season conditions. When lake records are compared with winter‐sensitive tree‐ring width chronologies, the reconstructions are similar. Oxygen isotopes indicate wet and stable winter conditions during the Medieval Climate Anomaly (900–1250 CE) and variable but generally dry conditions during the Little Ice Age (1450–1850 CE). Wet periods of fuel buildup, followed by drought, may have driven greater fire activity during the LIA. An abrupt decline in fire begins occurred Euro‐American settlement, after the 1850s, and is attributed to loss of fuel connectivity and less ignition. Key Points: Sediment δ18O records show heightened hydroclimate variability during the Little Ice AgeDiscrepancies between tree rings and lake sediments from the Pacific Northwest stem from different seasonal and temporal sensitivitiesCharcoal records in the region indicate enhanced fire activity during periods of higher multi‐decadal hydroclimate variability [ABSTRACT FROM AUTHOR]

Arid regions are especially vulnerable to climate change and land use. More than one-third of Earth's population relies on these ecosystems. Modern observations lack the temporal depth to determine vegetation responses to climate and human activity, but paleoecological and archaeological records can be used to investigate these relationships. Decreasing rainfall across the Late Holocene provides a case study for vegetation response to changing hydroclimate. Rock hyrax (Procavia capensis) middens preserve paleoenvironmental indicators in arid environments where traditional archives are unavailable. Pollen from modern middens collected in Dhofar, Oman, demonstrates the reliability of this archive. Pollen, stable isotope (δ13C, δ15N), and microcharcoal data from fossil middens reveal changes in vegetation, relative moisture, and fire from 4000 cal yr BP to the present. Trees limited to moister areas (e.g., Terminalia) today existed farther inland at ~3100 cal yr BP. After ~2900 cal yr BP, taxa with more xeric affiliations (e.g., Senegalia) had increased. Coprophilous fungal spores (Sporormiella) and grazing indicator pollen revealed an amplified signal of domesticate grazing at ~1000 cal yr BP. This indicates that trees associated with semiarid environments were maintained in the interior desert during ~3000-4000 yr of decreasing rainfall and that impacts of human activity intensified after the transition to a drier environment. [ABSTRACT FROM AUTHOR]

Mosses are particularly susceptible to climate change owing to their close biological and ecological associations with climatic conditions. However, there is a limited understanding of the changes in distribution patterns of the moss species in forest ecosystems under climate change, especially in mosses with narrow ranges. Therefore, we reconstructed historical, simulated present, and predicted future potential distribution patterns of Didymodon validus, a narrow-range moss species in the forest ecosystem, using the MaxEnt model. The aim of this study was to explore its unique suitable habitat preference, the key environmental factors affecting its distribution, and the distributional changes of D. validus under climate change at a long spatial-time scale. Our findings indicate that the most suitable locations for D. validus are situated in high-altitude regions of southwestern China. Elevation and mean temperature in the wettest quarter were identified as key factors influencing D. validus distribution patterns. Our predictions showed that despite the dramatic climatic and spatial changes over a long period of time, the range of D. validus was not radically altered. From the Last Interglacial (LIG) to the future, the area of the highly suitable habitat of D. validus accounted for only 15.3%–16.4% of the total area, and there were weak dynamic differences in D. validus at different climate stages. Under the same climate scenarios, the area loss of suitable habitat is mainly concentrated in the northern and eastern parts of the current habitat, while it may increase in the southern and eastern margins. In future climate scenarios, the distribution core zone of suitable habitat will shift to the southwest for a short distance. Even under the conditions of future climate warming, this species may still exist both in the arid and humid regions of the QTP in China. In summary, D. validus showed cold and drought resistance. Our study provides important insights and support for understanding the impact of climate change on the distribution of D. validus, as well as its future distribution and protection strategies. [ABSTRACT FROM AUTHOR]

The seasonal changes in East Asian monsoon precipitation during the Last Glacial Maximum (LGM, 23,000–19,000 years B.P.) and its isotopic expression remain ambiguous. This study investigates changes in the seasonal precipitation δ18O (δ18Op) over East Asia during the LGM relative to the preindustrial (PI) and the underlying mechanisms using an isotope‐enabled atmospheric general circulation model. We show more depleted δ18Op in summer and a meridional tripolar δ18Op pattern in winter during the LGM compared to the PI. The depletion of summer δ18Op resulted from stronger upstream convective rainout due to the intensification of the Intertropical Convergence Zone. In contrast, the mechanisms for winter δ18Op changes were more complicated. With a series of sensitivity tests, we demonstrate that sea surface temperature controlled δ18Op changes across the whole of East Asia in summer and in the southern part of East Asia in winter. The depletion of winter δ18Op in central China arose largely from the suppression of droplet evaporation due to higher snow fraction. Our work provides important insights into the aspect of seasonal isotope changes during the LGM and may help facilitate an improved level of paleoclimatic interpretation of speleothem δ18O records from East Asia. Plain Language Summary: The climate over East Asia during the Last Glacial Maximum (LGM) was colder and drier than it is today according to paleoclimatic records. However, interpretations of paleo‐isotopic records have been inconsistent in previous research, and the seasonal isotope changes are still unclear. Here we use an isotope‐equipped climate model to explore summer and winter precipitation δ18O (δ18Op) behaviors in East Asia during the LGM. Compared to the preindustrial, the LGM was characterized by depleted summer δ18Op, largely due to the intensification of the Intertropical Convergence Zone which resulted in stronger rainout along the moisture transport pathways. The winter δ18Op, however, was more complex and exhibited a tripolar spatial pattern, with δ18Op depletion in central China but enrichment in both south and north. This pattern probably reflected the combined effect of sea surface temperature driven rainout en route and droplet evaporation. Key Points: Isotope‐enabled atmospheric general circulation model reasonably reproduces East Asian climate and precipitation δ18O changes between the Last Glacial Maximum (LGM) and preindustrialDepleted δ18O in LGM summer precipitation was driven by upstream rainout due to an intensification of the Intertropical Convergence ZoneWinter precipitation δ18O changes in southern and central China were controlled by rainout and droplet evaporation, respectively [ABSTRACT FROM AUTHOR]

The year 2020 Common Era (CE) experienced the highest number of named tropical cyclones in the Atlantic Ocean since 1850 CE, but the short instrumental record makes it challenging to assess if this level of activity is statistically meaningful. Here, we present two near‐annually resolved hurricane reconstructions from sediment archived in two blue holes located only 300 m apart on the northern margin of Grand Bahama. These two blue holes provide a replicated signal of hurricanes passing within a 50–100 km radius over the last 1,800 years, and the long‐term reconstructions document multiple 50‐to‐150‐year intervals when hurricane frequency was significantly higher than it has been over the last 100 years. These two records were first merged into a single stack, and then compiled with five other high‐resolution reconstructions from across the Bahamian Archipelago to form a single 1500‐year record of Bahamian hurricane frequency. This new Bahamian Compilation documents more hurricanes passing ∼75°W from 21°N to 26°N during the Little Ice Age (LIA; 1300–1850 CE) relative to the prior millennium and the last 170 years. The US Eastern Seaboard also experienced heightened hurricane activity during the LIA, whereas the Gulf of Mexico and Southern Caribbean were inactive. This suggests that despite a globally cooler climate, regional climate conditions during the LIA remained favorable for cyclogenesis and intensification along certain Atlantic hurricane pathways. Perhaps heightened Sahel rainfall during the LIA indicates an increase in African Easterly waves, which in turn possibly seeded more tropical cyclones in the Atlantic Main Development Region. Key Points: Two new paleo‐hurricane reconstructions from Grand Bahama expand spatiotemporal scope of regional hurricane historyA new regional compilation of Bahamian hurricane activity suggests heightened regional hurricane frequency during the Little Ice AgeRegional hurricane increase may reflect increased cyclogenesis in the Atlantic Main Development Region driven by more African Easterly waves [ABSTRACT FROM AUTHOR]

The low latitude Indian Ocean is warming faster than other tropical basins, and its interannual climate variability is projected to become more extreme under future emissions scenarios with substantial impacts on developing Indian Ocean rim countries. Therefore, it has become increasingly important to understand the drivers of regional precipitation in a changing climate. Here we present a new speleothem record from Anjohibe, a cave in northwest (NW) Madagascar well situated to record past changes in the Intertropical Convergence Zone (ITCZ). U‐Th ages date speleothem growth from 27 to 14 ka. δ18O, δ13C, and trace metal proxies reconstruct drier conditions during Heinrich Stadials 1 and 2, and wetter conditions during the Last Glacial Maximum and Bølling–Allerød. This is surprising considering hypotheses arguing for southward (northward) ITCZ shifts during North Atlantic cooling (warming) events, which would be expected to result in wetter (drier) conditions at Anjohibe in the Southern Hemisphere tropics. The reconstructed Indian Ocean zonal (west‐east) sea surface temperature (SST) gradient is in close agreement with hydroclimate proxies in NW Madagascar, with periods of increased precipitation correlating with relatively warmer conditions in the western Indian Ocean and cooler conditions in the eastern Indian Ocean. Such gradients could drive long‐term shifts in the strength of the Walker circulation with widespread effects on hydroclimate across East Africa. These results suggest that during abrupt millennial‐scale climate changes, it is not meridional ITCZ shifts, but the tropical Indian Ocean SST gradient and Walker circulation driving East African hydroclimate variability. Plain Language Summary: Long term monsoon dynamics in the southern Indian Ocean and Global South are not well constrained due to a lack of observational data. Paleoclimate records generated from archives like speleothems can help us fill gaps in our understanding. Here we use a speleothem record from Madagascar to test whether north‐south shifts in the tropical rain belt or west‐east changes in Indian Ocean temperatures are more important for precipitation in tropical East Africa. We find that ocean temperature gradients are the most important control on precipitation at our study site during previous instances of abrupt climate change linked to variability in the strength of North Atlantic ocean circulation. This work has important implications for how we think about the future of the tropical Indian Ocean sector in a changing climate. Key Points: Speleothem stable isotope and trace metal data agree on a dry Heinrich Stadial 1 and a wet Bølling–Allerød in northwest MadagascarHeinrich Stadial 1 and the Bølling‐Allerød show conditions contrary to responses expected from north‐south Intertropical Convergence Zone shiftsMillennial‐scale tropical East African hydroclimate variability is likely driven by zonal Indian Ocean sea surface temperature gradients [ABSTRACT FROM AUTHOR]

Lake sediments are unique archives of human environment interactions. Lake Prespa is one of the oldest lakes in Europe, lying in the southwestern Balkans and thus on a possible dispersal route of anatomically modern humans from Africa. In this study, we investigated the effects of climate, vegetation and human activity on fire over the last 92,000 years in this region. Sediment samples were taken from Lake Prespa, and nearby Lake Ohrid for comparison of the regional relevance, and analyzed for benzene polycarboxylic acids as markers for burned organic carbon residues (black carbon, BC). Peaking contents of BC (up to 1 g BC kg−1 sediment) coincided with warm and humid phases, when forests expanded at marine isotope stages (MIS) 5 and 1. During the colder and more arid climates of MIS 4 and 2, BC contents were lowered by a factor of 10, with a distinct minimum during the Last Glacial Maximum (0.07 g BC kg−1). The ratio of pentacarboxylic acid to mellitic acid (B5CA/B6CA) declined from 1.2 at MIS 5 to values of 0.3 at MIS 2, confirming a change in fire regime. Overall, BC contents peaked at cycles of solar radiation, vegetation composition and fuel availability, and thus correspond to the BC signal of other environmental archives. However, in the Late Holocene and as a result of human sedentary settlement, BC production increased, independent of decreasing insolation forcing. Key Points: First black carbon record of the Dessarate (Ohrid‐Prespa) Lake regionFire activity over the past 92,000 years has been highest during periods of warm/humid climate and forest vegetation [ABSTRACT FROM AUTHOR]

Wufeng Formation shale is an important source rock of unconventional hydrocarbons in the Lower Paleozoic shales of Sichuan Basin. However, the study on its provenance and paleoclimate is still relatively limited. In this study, mineralogical and geochemical data of the shales from the Upper Ordovician Wufeng Formation in southwestern China has been used to interpret the provenance and conditions of weathering and paleoclimate. The Wufeng shales have intermediate to high SiO2 (57.72–82.38 wt. %, av. = 68.84 wt. %) and Al2O3 (5.26–16.17 wt. %, av. = 10.62 wt. %), are rich in transition metal elements (i.e. V, Ni, Cu, Co and Cr) and Y as well as moderate depletion in Na2O and Sr, relative to the concentrations of the upper continental crust (UCC). In the chondrite-normalized (CN) rare earth elements (REE) distributions, these rocks display light REE (LREE) enrichment (La/YbCN = 6.69–12.63, av. = 9.28), flat heavy REE (HREE) (Gd/YbCN = 1.35–2.41, av. = 1.70), and clearly negative Eu anomalies (Euan = 0.50–0.66, av. = 0.58), showing similar characteristics with the CN post-Archean Australian Average Shales (PAAS). Wufeng Formation shales are immature composition without evident recycling sediments, and they are originated from an intermediate-felsic igneous source composed of tonalite–trondhjemite–granodiorite (TTG), granitic and andesitic igneous rocks. The chemical weathering conditions of studied shales decreased from moderate to low in the provenance region, suggesting a gradual cooling trend of the climate at Late Ordovician Thus, this article will be helpful to discern the provenance and variations of chemical weathering conditions and paleoclimate of Wufeng Formation shales. [ABSTRACT FROM AUTHOR]

The dense minerals (often called heavy minerals, density of more than 2.89 g/cm3) of northwestern Arabian Sea are studied to understand their provenance and implications to paleoclimates during the last 150 kyrs. Two cores: 723A (latitude 18°03.079′N and longitude 57°36.561′E; 808 m water depth) and 722B (latitude16°37.312′N and longitude 59°47.755′E; water depth 2028 m) away from the eastern coastline of Arabian Peninsula are taken. The total carbonate, acid insoluble residue, volume magnetic susceptibility and oxygen isotope data are used to correlate paleoenvironmental changes. A few elemental chemistry of core 722B is also used to understand source rock weathering characteristics. Ilmenite and magnetite are occurring as dominant opaque minerals in both the core sites. The shallower site 723A predominantly consists of hornblende, apatite, fluorite, epidote and chlorite; whereas, the deeper site 722B consists of epidote, fluorite, biotite, apatite and staurolite. The other important heavy minerals found in core sites are tourmaline, rutile, garnet, zircon, chloritoid, kyanite, sillimanite and pyroxenes. Low ZTR indices (< 10%) in both the core sediment samples along with subangular to subrounded grains indicate sediment immaturity, higher rates of weathering, less continental transportation and dominant derivation from the primary source rocks such as granites, pegmatites and basic igneous rocks. The mineral assemblages and roundness data further indicated contributions also occurred from the metamorphic rocks (such as schists, amphibolites, granulites and gneisses) and sedimentary rocks/recycled sediments, respectively. The Arabian Peninsula, Somalia, Iran-Makran regions and the Himalayan Complex have contributed sediments to these sites. Various heavy mineral ratios indicated the mixed provenance. Decrease of dense mineral abundance away from the east coast of Arabian Peninsula indicated early deposition of minerals from the agencies. Glacial stages and millennial cold events are indicated by higher abundance of heavy minerals along with higher terrigenous input, volume magnetic susceptibilities and better roundness indicated that the northwesterly wind originated from the Arabian Peninsula and Iran-Makran regions played a major role in sediment transportation to these sites. [ABSTRACT FROM AUTHOR]

Major shifts in hydroclimate have been documented during the last deglacial period and the Holocene in south‐central Alaska. Rare freshwater calcium carbonate (marl) deposits in lakes on the Kenai Peninsula can be used to reconstruct past changes in hydroclimate, including the influence of groundwater inflow to lakes. Here, the postglacial sediment sequence from groundwater‐fed Kelly Lake (60.514°N, 150.374°W) was analyzed for multiple proxies including isotopes of carbon and oxygen in marl calcite (δ13Cmarl and δ18Omarl), and isotopes of carbon (ẟ13COM) and abundances of C and N in organic matter. Bulk sediment analyses include organic matter and calcium carbonate (CaCO3) contents, visual stratigraphy and sediment flux. These analyses extend those of a previous paleoenvironmental reconstruction from Kelly Lake, which focused on sedimentary diatom oxygen isotopes and mass balance modeling over the past 10 000 years. Here, we show that Kelly Lake was deglaciated prior to 14.6 ka, and that by 14.0 ka marl dominated the sediments, with CaCO3 precipitation probably driven by groundwater input and mediated by shallow‐water charophytes. Marl accumulation decreased as organic and clastic inputs increased between ~12.2 and 11.5 ka. This shift, together with an increase in both δ13Cmarl and δ18Omarl values and a decrease in CaCO3 content, indicates an increase in the influence of meteoric water on the hydrologic budget under wet conditions, possibly driven by a strengthened Aleutian Low atmospheric pressure cell. A shift to lower δ13Cmarl and δ18Omarl values at ~11.5 ka is interpreted as an increase in the proportion of groundwater relative to meteoric water in the lake. Beginning around 9 ka, the proportion of meteoric water input continued to increase, the surrounding coniferous forest was established, and by 8 ka, CaCO3 accumulation ended. Our results elucidate the environmental conditions under which marl was deposited during the Lateglacial and early Holocene in this part of Alaska, and demonstrate how a variety of synoptic‐ and local‐scale climatic variables can converge to influence sedimentation in a groundwater‐fed lake. [ABSTRACT FROM AUTHOR]

The paper presents new data and reviews previously obtained results on the late glacial to Holocene history of peatlands in the southern part of the Baikal region under conditions of regional climate changes. To better understand climate signals, we have combined vegetation and geochemical variation data in 4.6 m thick peat deposits in the Vydrino bog located on the Tankhoi piedmont plain south of Lake Baikal. The territory has been swamped since 13.1 cal ka BP when the peatland started developing as a fen upon a sedimentary substrate. The 13.1–9.5 cal kyr climate record included two events of warming separated by an excursion of dry cold climate. Warming continued till 9.0 cal ka BP and eutrophic peat formation occurred in favorable temperature and moisture conditions. Another warming episode between 9.0 and 8.4 cal ka BP ended up with the Holocene climate optimum while the bog became mesotrophic. About 7.3–6.5 cal ka BP, the temperature and moisture inputs were no longer optimal for fir and spruce forests in the Vydrino area, which led to dramatic changes in landscape and vegetation. The wet and warm climate gradually became drier and colder from 6.5 to 2.3 cal ka BP, with a brief warm excursion about 5.5–5.3 cal ka BP. The peat deposition was interrupted in a cold climate from ∼2.3 cal ka BP to ∼0.7 cal ka BP, and the bog became oligotrophic afterwards. The newly obtained data allowed us to compare the paleoclimatic indicators available for the south Baikal region to determine their compatibility and inconsistency. In addition, we provide a general view to the quality of the climate and environmental reconstructions in the Baikal region by comparison of the data on its peatland study. [ABSTRACT FROM AUTHOR]

The tectonic closure of the Central American Seaway (CAS) during the mid‐Miocene to mid‐Pliocene (∼16–3 Ma BP) is thought of as a key interval for the onset of the present‐day tropical Pacific oxygen minimum zone (OMZ). In this study we investigate the impact of an open CAS on the ocean circulation and the OMZ in the tropical Pacific. We perform a series of sensitivity experiments with the Kiel Climate Model, where we vary the CAS sill depth from shallow to deep. We find that the eastern tropical Pacific OMZ was less developed during the period of an open CAS. This is driven mainly by an enhanced eastward subsurface current that facilitated an increased oxygen supply from the western tropical Pacific. In addition, a small decrease in net marine primary production and subsequent weaker export of particulate organic carbon induced less subsurface oxygen consumption in the Eastern Equatorial Pacific. Plain Language Summary: Oxygen plays a fundamental role for aerobic life and cycling of biogeochemical properties in the ocean. When low rates of oxygen supply combine with high rates of biological oxygen consumption, oxygen minimum zones (OMZs) are generally formed in the ocean. Today the world's largest OMZ is found in the eastern tropical Pacific where the constriction and final closure of the Central American Seaway (CAS) from 16 to 3 Ma BP created specific characteristics of ocean circulation and biogeochemistry. Using simulations with a climate and a marine biogeochemistry model we investigate whether the CAS closure led to the emergence of today's tropical Pacific OMZ. We find that the eastern tropical Pacific OMZ was less developed and oxygen levels were overall higher in the subsurface Eastern Equatorial Pacific (EEP) when the CAS was open. This was driven mainly by an enhanced eastward subsurface current from the northwestern tropical Pacific. In addition, a small decrease in net marine primary production induced less subsurface oxygen consumption from remineralization of particulate organic matter in the EEP. Key Points: An open Central American Seaway promotes higher oxygen concentrations in the subsurface Pacific waters, with strongest changes in the EEPAn increased eastward subsurface flow in the northeastern tropical Pacific transports young, oxygen‐rich waters in from the western PacificThe improved EEP ventilation is a result of the ocean current redirection in the North and South Pacific during open Central American Seaway [ABSTRACT FROM AUTHOR]

Despite decades of effort to constrain equilibrium climate sensitivity (ECS), current best estimates still exhibit a large spread. Past studies have sought to reduce ECS uncertainty through a variety of methods including emergent constraints. One example uses global temperature variability over the past century to constrain ECS. While this method shows promise, it has been criticized for its susceptibility to the influence of anthropogenic forcing and the limited length of the instrumental record used to compute temperature variability. Here, we investigate the emergent relationship between ECS and two metrics of global temperature variability using model simulations and paleoclimate reconstructions over the last millennium (850–1999). We find empirical evidence in support of these emergent relationships. Observational constraints suggest a central ECS estimate of 2.6–2.8 K, consistent with the Intergovernmental Panel on Climate Change's consensus estimate of 3K. Moreover, they suggest ECS "likely" ranges of 1.8–3.3 K and 2.0–3.6 K. Plain Language Summary: Future changes in global‐mean temperatures have substantial implications for climate‐related risks, and global‐mean temperatures will continue to increase in response to carbon emissions (a property known as climate sensitivity). In addition to long‐term, human‐driven warming, the global surface temperature also exhibits short‐term swings due to natural climate variability. Recently, climate model experiments have shown some evidence of a linear relationship between climate sensitivity and climate variability, with potential applications for climate model development and future predictions. We show that this relationship holds when applied to paleoclimate data from the Common Era (850–1999) and use the reconstructed temperature record over this period to estimate climate sensitivity. Our analysis considers a period (∼1,000 years) that is much longer than what has been used in prior studies (∼100 years) and thus paints a fuller picture of past temperature variability. We show that interannual and decadal fluctuations in climate could offer a novel technique for assessing the Earth's sensitivity to external forcing. Our results are consistent with other lines of evidence, increasing confidence in our approach. We hope our findings add value to the existing collection of climate sensitivity estimates and encourage future use of paleoclimate data to verify proposed constraints on climate quantities. Key Points: We use model output and temperature reconstructions from 850 to 1999 to test a proposed emergent constraint on climate sensitivityThe proposed emergent constraint largely holds for this period, which is longer and more stationary than that of prior workOur central estimates of equilibrium climate sensitivity are 2.6–2.8 K, consistent with prior results and the IPCC's consensus estimate [ABSTRACT FROM AUTHOR]

Recent severe droughts, extreme floods, and increasing differences between seasonal high and low flows on the Amazon River may represent a twenty-first-century increase in the amplitude of the hydrologic cycle over the Amazon Basin. These precipitation and streamflow changes may have arisen from natural ocean-atmospheric variability, deforestation within the drainage basin of the Amazon River, or anthropogenic climate change. Tree-ring reconstructions of wetseason precipitation extremes, substantiated with historical accounts of climate and river levels on the Amazon River and in northeast Brazil found in the Brazilian Digital Library, indicate that the recent river-level extremes on the Amazon may have been equaled or possibly exceeded during the preinstrumental nineteenth century. The "Forgotten Drought" of 1865 was the lowest wet-season rainfall total reconstructed with tree-rings in the eastern Amazon from 1790 to 2016 and appears to have been one of the lowest stream levels observed on the Amazon River during the historical era according to firsthand descriptions by Louis Agassiz, his Brazilian colleague Joao Martins da Silva Coutinho, and others. Heavy rains and flooding are described during most of the tree-ring-reconstructed wet extremes, including the complete inundation of "First Street" in Santarem, Brazil, in 1859 and the overtopping of the Bittencourt Bridge in Manaus, Brazil, in 1892. These extremes in the tree-ring estimates and historical observations indicate that recent high and low flow anomalies on the Amazon River may not have exceeded the natural variability of precipitation and streamflow during the nineteenth century. [ABSTRACT FROM AUTHOR]

In this paper, we present a late summer (August-September) temperature reconstruction over the period 1792-2020 based on a tree-ring maximum latewood density (MXD) chronology for the southern Tibetan Plateau (TP). The reconstruction explained 66.2% of the variance in the instrumental temperature records during the calibration period 1960-2020 and captured the warming trend since the 1960s, which would support the current warming on the TP. In addition, a warming hiatus existed during 2001-12 and the last 20 years (2000-20) were the warmest period in the past two centuries. The reconstruction matched other MXD- and mean latewood density (LWD)-based late summer temperature reconstructions from neighboring regions, and fluctuated in synchrony with the Climatic Research Unit (CRU) Northern Hemisphere land surface temperature during 1850-2020. Multitaper method analysis and wavelet analysis revealed significant periodicities of 2-3, 20-30, and 40-60 years in the reconstructed series. Our reconstructed series was very consistent and highly correlated with the Atlantic multidecadal oscillation (AMO). During the warm phase of the AMO, higher pressure and divergent horizontal winds over the TP contribute to warmer summers in the region. In addition, we found that the southern TP experienced the lowest temperature and downward solar radiation in the second year following large volcanic eruptions. The decrease in downward solar radiation may be directly responsible for the occurrence of the lowest temperatures. The results indicate that the AMO and large volcanic eruptions were impacting factors on temperature in our study area. [ABSTRACT FROM AUTHOR]

• First Late Triassic palynological assemblage reported from Nanjing area. • Palynological composition of Fanjiatang Formation indicates a Norian-Rhaetian age. • Paleovegetation was reconstructed combing palynofloral and macrofloral data. • Palynological composition suggests a tropical to subtropical warm and humid climate. The end-Triassic is characterized by a significant biotic crisis in both marine and terrestrial realms. However, terrestrial records in eastern Tethys are relatively limited, especially in eastern China. The Fanjiatang Formation represents the Upper Triassic sequence in southern Jiangsu and Anhui provinces of eastern China, yielding a rich plant and bivalve fossil record. The present study provides the first detailed palynological investigation for the Upper Triassic of Nanjing area, eastern China. Six of twenty processed palynological samples are productive, and more than 70 terrestrial spore and pollen fossil taxa were identified. A palynological assemblage, namely, the Concavisporites – Dictyophyllidites – Kyrtomisporis – Classopollis Assemblage was established, characterized by abundant fern spores, mainly including Concavisporites , Dictyophyllidites and Kyrtomisporis , and much less abundant gymnosperm pollen grains (important taxa include Alisporites , Chasmatosporites , and Classopollis), indicating a Late Triassic Norian–Rhaetian age. In conjunction with previously reported macro-plant data, the palynofloral analysis reveals a vegetation dominated by ferns, with diverse cycadophytes, less abundant lycophytes, bryophytes, equisetales, ginkgophytes and seed ferns, and a few conifers. Paleovegetation and semiquantitative palynological analysis permit a paleoecological interpretation, suggesting a lowland groundcover-dominated vegetation under (sub)tropical warm and humid climate in Nanjing area during this time interval. More detailed palynological and macro-plant data through the whole Upper Triassic in this region are necessary in the future to better reveal the Late Triassic paleoecological settings and variations on land prior to the end-Triassic mass extinction in eastern Tethys. [ABSTRACT FROM AUTHOR]

In this work we present the results of numerical modeling of the age and temperature distribution in ice layers at the Dome B site (79.02° S, 93.69° E, altitude 3807 m a.s.l., ice thickness about 2.5 km), located 300 km west of the Russian Antarctic station Vostok. Dome B is situated on the onset of the ice flow line passing through the deep 5G borehole, and it is considered one of the most promising places to search for and study the earth's oldest ice (with an age reaching 1.5 Ma). According to our calculations, all realistic scenarios show the ice age at 60 m above the ice base to be considerably older than 1 Ma, and the glacier base temperature is well below the pressure melting point (–1.8°С for pressure = 23 MPa). For the most likely scenario (accumulation rate 1.8 g/(cm2 year), effective ice surface temperature –64°С, and geothermal heat flux 60 mW/m2), the ice age is 1.4 Ma and the basal temperature is about –13°С, which is close to the earlier predictions from a 2D model. The maximum estimate of the diffusion length in the old ice (for the scenario in which the basal temperature reaches the melting point and in which 30% of excess diffusion is taken into account) is 5.2 cm. In 1.4-Ma-old ice, a 40-ka climatic cycle is squeezed into a 290-cm-thick ice layer. For this ratio of wavelength and diffusion length, the climatic signal attenuation (ratio between the signal amplitude after and before diffusive smoothing) is 0.6%. Thus, due to the relatively low ice temperature here, we may expect a nearly undisturbed climatic curve in the old ice core that will be drilled one day at Dome B. At the same time, shorter oscillations with wavelengths of <1500 years will be totally erased by diffusion. [ABSTRACT FROM AUTHOR]

Paleoclimate investigations of the peat deposits in the Nilgiri Plateau, an important paleoclimate archive of India, are mainly restricted to the carbon isotope composition ((δ13C) of plant-derived materials and pollen studies. However, it is unclear whether these proxies reflect past variability in temperature or hydrology. Here, we report the hydrogen and carbon isotopic variability of n -alkanoic acid of chain length 28 (δDC28 and δ13CC28, respectively) and demonstrate that the peatland leaf wax hydrogen isotopes provide a sensitive record of past hydrology. The decoupling of δ13CC28 and δD of vegetation-corrected rain during the Holocene indicate that δD of the leaf wax compounds mainly respond to past hydrological variability whereas δ13C variations might reflect the temperature-controlled variability of C3 and C4 vegetation. Conforming with the other paleoclimate records from the region, the δDC28 variations showed a reducing precipitation trend since the early Holocene. However, a large amplitude of reconstructed δD of rain (~44‰) during the Holocene indicated changes in the moisture source and trajectory could be an additional factor contributing to the orbital-scale δD variability of proxies from the Indian region. [ABSTRACT FROM AUTHOR]

Sedimentary organic matter concentrated in source rocks forms the main source for the formation of hydrocarbons. Its deposition and preservation are strongly controlled by the depositional environment and paleoclimate. This study evaluates the paleoenvironment and the paleoclimatic controls of sediments in the Middle Miocene Balikpapan Group, Mahakam Delta of the Lower Kutai Basin, Indonesia. The sedimentary succession of the Mentawir Formation, encountered in three wells (MHK 1, MHK 3, and MHK 4), contains interbedded sandstones, siltstones, shales, and coal. Gamma ray log analysis has revealed four facies associations: (a) funnel-, (b) bell-, (c) cylindrical-, and (d) bow-shaped patterns, which, together with sedimentological and mineralogical analysis, suggest a fluvio-deltaic depositional environment during the Middle Miocene in the study area. Sedimentary successions from wells MHK 1 and MHK 3 comprise interbedded sandstone and siltstones and are interpreted to represent repeatedly occurring delta plain, delta front, and prodelta deposits. The succession encountered in well MHK 4 mostly consists of amalgamated sandstones and indicates a predominantly fluvial to upper delta plain environment with distributary channels and crevasse splays interbedded with only thin delta front deposits. X-ray diffraction–clay fraction analysis shows that the <2 μm clay-sized fraction consists of kaolinite (38%–67%), illite (14%–29%), chlorite (2%–17%), and mixed-layer illite/smectite (I/S) (14%–30%). Kaolinite formation and abundance indicates a hinterland climate classified as type Af (tropical rainforest) and intensive chemical weathering conditions in the source areas related to tropical to sub-tropical climates with high precipitation. Under such climatic conditions, kaolinite and I/S mixed-layer minerals are preferentially formed because the characteristic ions, K+, Na+, Ca2+, and Fe2+, are leached away. Thus, the production, transport, distribution, and preservation of sedimentary organic matter in the onshore Mentawir Formation of the Balikpapan Group are predominantly controlled by the humid tropical climate and fluvio-deltaic processes. [ABSTRACT FROM AUTHOR]

The science of the provenance, sedimentary system, and distribution of sand bodies is unclear, limiting oil and gas exploration. Here, we combined heavy mineral, rare earth element, petrographic, and outcrop data to shed new light on the provenance, depositional environment, and paleoclimatic conditions of the Permian Jiamuhe Formation. The provenance is characterized by "a main provenance system, and four provenance zones," and this result could be interpreted from analyses of its seismic reflection, clastic composition, REES, and heavy minerals. A detailed sedimentological study performed in the excellent outcrops, a comprehensive analysis of logging, and the legalistic cores of this formation allowed for the identification of ten lithofacies and three lithofacies associations. Four distributary/underwater channels were observed. Furthermore, the redox and paleoclimatic conditions based on trace elements (Th/U, V/(V + Ni), V/Cr, Cu/Zn, Sr/Ba, and Sr/Cu) suggested a weak reduction in the environment, as well as semi-humid and semi-dry conditions of the Jiamuhe Formation. These conditions are also supported by the mudstone color and plant fossils. The tectonic setting belongs to the acid island arc area based on the trace element discrimination diagram of La-Th-SC and the values of the La, Ce, ΣREE, L/H, La/Yb, and (La/Yb)N criteria. The research results further confirm that there are differences in the mineral compositions in the same provenance area, and they provide a geological basis for the fine sedimentary facies characterization and a favorable zone prediction in this area. [ABSTRACT FROM AUTHOR]

Old descriptive diaries are important sources of daily weather conditions before modern instrumental measurements were available. A previous study demonstrated the potential of reconstructing historical weather at a high temporal resolution by assimilating cloud cover converted from descriptive diaries. However, cloud cover often exhibits a non-Gaussian distribution, which violates the basic assumptions of most data assimilation schemes. In this study, we applied a Gaussian transformation (GT) approach to cloud cover data assimilation and conducted observing system simulation experiments (OSSEs) using 20 observation points over Japan. We performed experiments to assimilate cloud cover with large observational errors using the Global Spectral Model (GSM) and a local ensemble transform Kalman filter (LETKF). Without GT, meridional wind and temperature exhibited deteriorations in the lower troposphere compared with the experiment with no observations. In contrast, GT reduced the 2-month root-mean-square errors (RMSEs) by 5%–15% throughout the troposphere for wind, temperature, and specific humidity fields. Significant improvements include zonal wind at 500 hPa and temperature at 850 hPa with 6.4% and 7.3% improvements by GT, respectively, compared with the experiment without GT. We further demonstrate that the additional GT application to the precipitation background field improves precipitation estimation by 12.2%, with pronounced improvements over regions with monthly precipitation of less than 150 mm. We also explored the impact of cloud cover GT on a global scale and confirmed improvements extending from around the observation sites. Our results demonstrate the potential of GT in high-resolution historical weather reconstruction using old descriptive diaries. Significance Statement: To reconstruct the historical weather, cloud cover information from old diaries can be used by incorporating high-resolution model simulations. However, cloud cover is not normally distributed and violates an important assumption when combining cloud cover observations with model simulations. Our results demonstrate that transforming the cloud cover distribution into a normal distribution could improve wind speed, temperature, and humidity fields in the model. We demonstrate the critical role of the transformation in a nonnormally distributed variable when combined with models and show the potential of diary-based weather information to reconstruct historical weather. [ABSTRACT FROM AUTHOR]

This paper presents an interpretation of sedimentologic, paleomagnetic, and geochemical data collected in the Upper Kimmeridgian-Valanginian carbonates of the Giewont series (Giewont and Mały Giewont sections, High-Tatric succession, Western Tatra Mountains, Poland). The studied succession provides insight into the sedimentary conditions prevailing in the South Tatric Ridge (Tatricum), a submarine elevation located between the Zliechov Basin (Fatricum) and the Vahic (=South Penninic) Ocean. The sedimentary sequence includes micrites, pseudonodular limestones, cyanoid packstones, lithoclastic packstone, and encrinites. The results are discussed with regards to their significance for detrital input, paleoclimate, and paleoproductivity, which in turn are considered in the context of both local and regional paleoenvironmental trends and events. The greatest depositional depths during the latest Kimmeridgian-earliest Tithonian are documented by the occurrence of pseudonodular limestones. A Tithonian shallowing trend is demonstrated via the increasing size and roundness of cyanoids, while the final (1)emergence and erosion in the South Tatric Ridge is documented by earliest Cretaceous disconformities. This process might have been related to both falling sea-level during the major eustatic regressive cycle and tectonic uplift caused by the mutually related (re)activation in the Neotethyan Collision Belt and rifting in the Ligurian-Penninic-Vahic Oceans. The highest lithogenic influx (although still low; max 0.5% of Al content) during the Late Kimmeridgian is considered as associated with relatively humid climate conditions, whereas a subsequent decreasing trend is thought to result from aridification during the latest Kimmeridgian-earliest Tithonian. Ultimately, deposition in the High-Tatric zone was affected by both large-scale environmental perturbations characteristic of the latest Jurassic (climate changes, variations in seawater pH, monsoonal upwelling, lithogenic input, etc.), as well as local sedimentary controls, predominantly the oxygenation state of bottom waters and tectonic movements. [ABSTRACT FROM AUTHOR]

The sedimentary sequence in Lake Salda has been first documented in detail by analyses of high-resolution seismic profiles and sediment cores together with onshore outcrops along the present shoreline of the lake. Such a multi-proxy approach provides a strong record of changing lake levels and depositional conditions in Lake Salda during the mid to late Holocene. The accurate determination of water-level oscillation and climate conditions relies on the confident deduction from 14C-dated onshore outcrops and sediment cores, which provide calibration for the chronostratigraphic units within high-resolution seismic records. The existence of a dry climate period during the transition from the middle to late Holocene caused the lake level to decrease until 1690 cal years BP. This prominent climate deterioration induced coastal progradation in the lake as inferred from the deltaic sequences in the high-resolution seismic record and favored stromatolite formation, given its oligotrophic water condition. The resultant lowstand of lake level during the late Holocene timely coincided with the Roman Climatic Optimum when a prominent erosional truncation surface and channel incision were formed as observed from the seismic profiles. The late Holocene, during 1690–1050 cal years BP, is represented by a transgressive condition due to lake-level increase, giving rise to a retreat of the deltaic deposit further inland. The ongoing deepening of the lake by contributions of both climate and tectonic activity during the last 650 cal years BP produced Gilbert-type fan deltas along the shoreline and a transgressive sedimentary unit with typical onlapping architecture in the seismic reflection profiles. [ABSTRACT FROM AUTHOR]

The Verkhnyaya Lena Group (Є2–3vl) has been studied in a section on the right bank of the Malaya Chuya River. Concentrations of main oxides and some trace elements (Cr, V, Ni, Cu, Zn, Rb, Sr, Zr, Ba, U, Th, Y, Nb, and Cl) have been determined in samples using an X-ray spectral fluorescence (XRF) analysis. The normative mineral composition has been determined based on the results of the XRF analysis using the MINLITH software. Based on geochemical data, intervals of change in the weathering features (physical/chemical and arid/humid weathering) are clearly differentiated in the denudation area, which are fixed by variations in the values of the Al2O3/K2O and Ln(Al2O3/Na2O) ratios and concentrations of V, Cu, Zn, Rb, and Ni, as well as the normative mineral composition. Apparently, Cr was transported to the basin exclusively by the aeolian process in this case and marks periods of increased wind transport intensity. Under conditions of tectonic activation and progressive isolation of the Upper Lena paleobasin, the described lithological and geochemical features provide some information about the climate changes that accompanied these events. [ABSTRACT FROM AUTHOR]

Ancient greenhouse periods are useful analogs for predicting effects of anthropogenic climate change on regional and global temperature and precipitation patterns. A paucity of terrestrial data from polar regions during warm episodes challenges our understanding of polar climate responses to natural/anthropogenic change and therefore our ability to predict future changes in precipitation. Ellesmere and Axel Heiberg Islands in the Canadian Arctic preserve terrestrial deposits spanning the late Paleocene to middle Eocene (59–45 Ma). Here we expand on existing regional sedimentology and paleontology through the addition of stable (δ13C, δ18O) and clumped (Δ47) isotope analyses on palustrine carbonates. δ13C isotope values range from −4.6 to +12.3‰ (VPDB), and δ18O isotope values range from −23.1 to −15.2‰ (VPDB). Both carbon and oxygen isotope averages decrease with increasing diagenetic alteration. Unusually enriched carbon isotope (δ13C) values suggest that analyzed carbonates experienced repeated dissolution‐precipitation enrichment cycles, potentially caused by seasonal fluctuations in water availability resulting in summer carbonate dissolution followed by winter carbonate re‐precipitation. Stable isotopes suggest some degree of precipitation seasonality or reduction in winter water availability in the Canadian Arctic during the Paleogene. Clumped (Δ47) temperature estimates range from 52 to 121°C and indicate low temperature solid‐state reordering of micritic samples and diagenetic recrystallization in sparry samples. Average temperatures agree with vitrinite reflectance data for Eureka Sound Group and underlying sediments, highlighting structural complexity across the region. Broadly, combined stable and clumped isotope data from carbonates in complex systems are effective for describing both paleoclimatic and post‐burial conditions. Plain Language Summary: Paleogene paleohydrology in Arctic Canada has been a question of much debate in recent years, with competing ideas about conditions characterized as either "polar monsoon" or "ever‐wet" regimes. Proxy records from Ellesmere and Axel Heiberg islands have been central to this debate, but complex stratigraphy and burial histories have hampered a resolution. Here we employ a combined carbonate isotope (δ13C, δ18O, Δ47) approach to disentangle paleoclimate and diagenetic signals. Using palustrine carbonates (which host previously evaluated paleobotanical remains) within a new stratigraphic framework, we demonstrate that δ13C and δ18O values from primary‐fabric samples indicate a distinct, but non‐monsoonal hydrologic seasonality during the late Paleocene/early Eocene. We also demonstrate that Δ47 temperatures reflect both shallow burial reordering and more intense remineralization, which are consistent with vitrinite reflectance studies showing variable deformation and geothermal gradients in the Sverdrup Basin. This combined isotopic approach is novel in the region, and can be applied to other regions of interest in deep time. Key Points: Combined carbonate isotope approach disentangles paleoclimate/diagenesis despite complex environmental histories on Ellesmere/Axel HeibergCarbon and oxygen isotope values highlight hydrologic seasonality in the Arctic during the PaleogeneTemperatures from carbonate clumped isotopes are consistent with vitrinite reflectance burial temperature, suggesting variable deformation [ABSTRACT FROM AUTHOR]

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The impact of recent climate change varies around the world, and understanding the regional variations is important for making accurate deductions and generating future climate predictions and mitigation plans. Borehole temperature reconstruction is one of the common methods to determine the ground surface temperature (GST) history of a region. In this study, high-precision (< 0.01 K) borehole temperature-depth data from five different locations in Western Black Sea Region of Turkey were used for reconstruction of the GST changes for the last century. Four of the measurement sites are located in rural areas in the inland section and free from the urban heat island interference. The reconstructions reveal that GSTs have dropped by an average of 0.1 °C between 1900 and 1970 and have risen by an average of 0.99 °C between 1970 and 2010 in the study area. Results from inland sites show average cooling of 0.24 °C between 1900 and 1975 and average warming of 0.94 °C until 2010. The results in the coastal area show no cooling period. The rapid warming trend in 1990–2010 revealed by GST reconstructions indicates high sensitivity of the region to present-day global warming. [ABSTRACT FROM AUTHOR]

Proxy reconstructions and model simulations of precipitation during Earth's glacial periods suggest that the locations and mechanisms of atmospheric moisture transport have changed considerably during Earth's past. We investigate the hydroclimate of the Last Glacial Maximum (LGM) using simulations with the Community Earth System Model, with a focus on the extratropics and the influence of atmospheric rivers (ARs), a key driver of modern‐day moisture transport globally. Mean and extreme precipitation increase significantly over southwestern Patagonia, Iberia, and southwestern North America—mid‐latitude regions affected by ARs in the modern climate—despite overall decreases elsewhere. In each, the associated moisture transport changes are different, with increased transport and AR activity mainly occurring in the North Atlantic. The overall LGM response is dominated by the response to ice sheets, with other forcings causing additional cooling and drying over the extratropics and a strong decrease of moisture transport over the subpolar North Atlantic. Plain Language Summary: During the last ice age, when glaciers reached their maximum extent, atmospheric CO2 was lower and Earth's orbit was different. All of these influences caused dramatic changes in precipitation patterns around the planet. Using climate model simulations, we find that the majority of the changes to atmospheric moisture transport and precipitation patterns result from the presence of the ice sheets alone, with lower CO2 and insolation differences enhancing the ice sheet‐induced patterns. These changes mainly comprise decreases in moisture transport and lower precipitation, with three notable exceptions in Patagonia, Iberia, and southwestern North America. Of these, precipitation increases over Iberia result from increased transport by plumes of moisture, known as atmospheric rivers , across the North Atlantic. Elsewhere in the world, AR activity decreases. Key Points: Average and extreme precipitation declined globally during the Last Glacial Maximum with three notable mid‐latitude exceptions over landMoisture transport changes mainly caused by ice sheets, with lower CO2 and altered insolation causing enhanced drying regionallyAtmospheric river activity decreased globally except over the North Atlantic, where it enhanced precipitation over Iberia [ABSTRACT FROM AUTHOR]

How the climate responded to orbital forcing during the Neoproterozoic snowball Earth events, the most extreme glaciations on Earth, is still unclear. Here, we investigate this problem using a climate model. To simplify the analysis, continents are removed. The results show that even in this simplified situation, the snowball Earth climate is sensitive to orbital configurations. The globally averaged annual surface temperature can differ by 2.4°C, and the maximum monthly mean temperature can differ by 3.7°C under different orbital configurations. Therefore, a snowball Earth could be deglaciated more easily in some orbital configurations than in others. The climatic effect of a particular orbital parameter is highly dependent on the values of other parameters. For example, the effect of obliquity on tropical surface temperature is generally small (<1°C), but it can become large (3.8°C) when eccentricity is large and the northern autumn occurs at perihelion (precession = 180°). Surprisingly, the global temperature is generally lower at high eccentricity than at near-zero eccentricity, even though the total insolation received by Earth is higher in the former than in the latter. Moreover, we find that the Milankovitch hypothesis is valid not only in the extratropical region, but also in the tropics; the snow thickness in the tropical region is inversely proportional to the maximum monthly insolation received in this region. [ABSTRACT FROM AUTHOR]

Since the Paris Agreement, climate policy has focused on 1.5° and 2°C maximum global warming targets. However, the agreement lacks a formal definition of the nineteenth-century "pre-industrial" temperature baseline for these targets. If global warming is estimated with respect to the 1850–1900 mean, as in the latest IPCC reports, uncertainty in early instrumental temperatures affects the quantification of total warming. Here, we analyze gridded datasets of instrumental observations together with large-scale climate reconstructions from tree rings to evaluate nineteenth-century baseline temperatures. From 1851 to 1900 warm season temperatures of the Northern Hemisphere extratropical landmasses were 0.20°C cooler than the twentieth-century mean, with a range of 0.14°–0.26°C among three instrumental datasets. At the same time, proxy-based temperature reconstructions show on average 0.39°C colder conditions with a range of 0.19°–0.55°C among six records. We show that anomalously low reconstructed temperatures at high latitudes are underrepresented in the instrumental fields, likely due to the lack of station records in these remote regions. The nineteenth-century offset between warmer instrumental and colder reconstructed temperatures is reduced by one-third if spatial coverage is reduced to those grid cells that overlap between the different temperature fields. The instrumental dataset from Berkeley Earth shows the smallest offset to the reconstructions indicating that additional stations included in this product, due to more liberal data selection, lead to cooler baseline temperatures. The limited early instrumental records and comparison with reconstructions suggest an overestimation of nineteenth-century temperatures, which in turn further reduces the probability of achieving the Paris targets. Significance Statement: The warming targets formulated in the Paris Agreement use a "pre-industrial" temperature baseline that is affected by significant uncertainty in the instrumental temperature record. During the second half of the nineteenth century, much of the continental landmasses were not yet covered by the observational station network and existing records were often subject to inhomogeneities and biases, thus resulting in uncertainty regarding the large-scale mean temperature estimate. By analyzing summer temperature reconstructions from tree-rings for the Northern Hemisphere extratropical land areas, we examine an independent climate archive with a typically broader and more continuous spatial extent during the "pre-industrial" period. Despite the additional uncertainty when using climate reconstructions instead of direct observations, there is evidence for an overestimation of land temperature during the summer season in early instrumental data. Colder early instrumental temperatures would reduce the probability of reaching the Paris targets. [ABSTRACT FROM AUTHOR]

The Pliocene Epoch (∼5.3–2.6 million years ago, Ma) was characterized by a warmer than present climate with smaller Northern Hemisphere ice sheets, and offers an example of a climate system in long‐term equilibrium with current or predicted near‐future atmospheric CO2 concentrations (pCO2). A long‐term trend of ice‐sheet expansion led to more pronounced glacial (cold) stages by the end of the Pliocene (∼2.6 Ma), known as the "intensification of Northern Hemisphere Glaciation" (iNHG). We assessed the spatial and temporal variability of ocean temperatures and ice‐volume indicators through the late Pliocene and early Pleistocene (from 3.3 to 2.4 Ma) to determine the character of this climate transition. We identified asynchronous shifts in long‐term means and the pacing and amplitude of shorter‐term climate variability, between regions and between climate proxies. Early changes in Antarctic glaciation and Southern Hemisphere ocean properties occurred even during the mid‐Piacenzian warm period (∼3.264–3.025 Ma) which has been used as an analog for future warming. Increased climate variability subsequently developed alongside signatures of larger Northern Hemisphere ice sheets (iNHG). Yet, some regions of the ocean felt no impact of iNHG, particularly in lower latitudes. Our analysis has demonstrated the complex, non‐uniform and globally asynchronous nature of climate changes associated with the iNHG. Shifting ocean gateways and ocean circulation changes may have pre‐conditioned the later evolution of ice sheets with falling atmospheric pCO2. Further development of high‐resolution, multi‐proxy reconstructions of climate is required so that the full potential of the rich and detailed geological records can be realized. Plain Language Summary: Warm climates of the geological past provide windows into future environmental responses to elevated atmospheric CO2 concentrations, and past climate transitions identify important or sensitive regions and processes. We assessed the patterns of average ocean temperatures and indicators of ice sheet size over hundreds of thousands of years, and compared to shorter‐term variability (tens of thousands of years) during a recent transition from late Pliocene warmth (when CO2 was similar to present) to the onset of the large and repeated advances of northern hemisphere ice sheets referred to as the "ice ages." We show that different regions of the climate system changed at different times, with some changing before the ice sheets expanded. The development of larger ice sheets in the Northern Hemisphere then impacted ocean temperatures and circulation, but there were many regions where no impacts were felt. Our analysis highlights regional differences in the timing and amplitudes of change within a globally‐significant climate transition as well as in response to the current atmospheric CO2 concentrations in our climate system. Key Points: The "stable" warm late Pliocene ∼3.3–3.1 million years ago was a time of climate transition, especially in the southern hemisphereOcean temperatures and ice sheets evolved asynchronously 3.3–2.4 Ma during the onset and intensification of Northern Hemisphere GlaciationClimate variability evolved in complex, non‐uniform ways, most strongly expressed in northern mid‐latitude sea‐surface temperature records [ABSTRACT FROM AUTHOR]

De novo genes are genes that emerge as new genes in some species, such as primate de novo genes that emerge in certain primate species. Over the past decade, a great deal of research has been conducted regarding their emergence, origins, functions, and various attributes in different species, some of which have involved estimating the ages of de novo genes. However, limited by the number of species available for whole-genome sequencing, relatively few studies have focused specifically on the emergence time of primate de novo genes. Among those, even fewer investigate the association between primate gene emergence with environmental factors, such as paleoclimate (ancient climate) conditions. This study investigates the relationship between paleoclimate and human gene emergence at primate species divergence. Based on 32 available primate genome sequences, this study has revealed possible associations between temperature changes and the emergence of de novo primate genes. Overall, findings in this study are that de novo genes tended to emerge in the recent 13 MY when the temperature continues cooling, which is consistent with past findings. Furthermore, in the context of an overall trend of cooling temperature, new primate genes were more likely to emerge during local warming periods, where the warm temperature more closely resembled the environmental condition that preceded the cooling trend. Results also indicate that both primate de novo genes and human cancer-associated genes have later origins in comparison to random human genes. Future studies can be in-depth on understanding human de novo gene emergence from an environmental perspective as well as understanding species divergence from a gene emergence perspective. [ABSTRACT FROM AUTHOR]

Summer cooling is one of the most direct consequences of explosive volcanic eruptions that can affect ecosystems and human societies. Recent studies revealed a multiyear cooling impact on hemispheric and global summer temperatures after tropical eruptions, yet the volcanic responses appear to vary on regional scales. Here, we revisit volcano-induced summer cooling in eastern Canada and northern and central Europe by applying superposed epoch analysis on CMIP6-PMIP4 simulations and millennial temperature reconstructions based on tree-ring density. We then examine potential causes modulating region-specific volcanic impact. While confirming that, on average, tropical eruptions over the last millennium have induced a longer cooling (>4 yr) than eruptions from extratropical Northern Hemisphere in all three North Atlantic regions, we show that the peak magnitude of cooling is stronger in eastern Canada. We also find that the detected volcanic temperature anomalies can be strongly affected by the selection and number of volcanic events and nonvolcanic signals embedded in the climate time series. This study highlights the risks of using highly noisy proxy records to investigate volcanic impacts, especially in regions with strong unforced climate variability. The CMIP6-PMIP4 simulations generally agree with the three reconstructions on the average response to tropical eruptions, but their performance is poorer regarding the production of significant cooling after extratropical eruptions. Our results further suggest that the particular sensitivity to tropical eruptions in eastern Canada is likely related to increased sea ice surrounding Quebec–Labrador associated with the positive Arctic Oscillation and North Atlantic Oscillation formed during the first posteruption winter. [ABSTRACT FROM AUTHOR]

The Buffalo National River in northwest Arkansas preserves an extensive Quaternary record of fluvial bedrock incision and aggradation across lithologies of variable resistance. In this work, we apply optically stimulated luminescence (OSL) dating to strath and fill terraces along the Buffalo River to elucidate the role of lithology and climate on the development of the two youngest terrace units (Qtm and Qty). Our OSL ages suggest a minimum strath planation age of ca. 250 ka for the Qtm terraces followed by a ca. 200 ka record of aggradation. Qtm incision likely occurred near the last glacial maximum (LGM), prior to the onset of Qty fill terrace aggradation ca. 14 ka. Our terrace ages are broadly consistent with other regional terrace records, and comparison with available paleoclimatic archives suggests that terrace aggradation and incision occurred during drier and wetter hydrological conditions, respectively. Vertical bedrock incision rates were also calculated using OSL-derived estimates of Qtm strath planation and displayed statistically significant spatial variability with bedrock lithology, ranging from ~35 mm/ka in the higher resistance reaches and ~16 mm/ka in the lower resistance reaches. In combination with observations of valley width and terrace distribution, these results suggest that vertical processes outpace lateral ones in lithologic reaches with higher resistance. [ABSTRACT FROM AUTHOR]

The White River Badlands (WRB) of South Dakota record eolian activity spanning the late Pleistocene through the latest Holocene (21 ka to modern), reflecting the effects of the last glacial period and Holocene climate fluctuations (Holocene Thermal Maximum, Medieval Climate Anomaly, and Little Ice Age). The WRB dune fields are important paleoclimate indicators in an area of the Great Plains with few climate proxies. The goal of this study is to use 1 m/pixel-resolution digital elevation models from drone imagery to distinguish Early to Middle Holocene parabolic dunes from Late Holocene parabolic dunes. Results indicate that relative ages of dunes are distinguished by slope and roughness (terrain ruggedness index). Morphological differences are attributed to postdepositional wind erosion, soil formation, and mass wasting. Early to Middle Holocene and Late Holocene paleowind directions, 324°± 13.1° (N = 7) and 323° ± 3.0° (N = 19), respectively, are similar to the modern wind regime. Results suggest significant landscape resilience to wind erosion, which resulted in preservation of a mosaic of Early and Late Holocene parabolic dunes. Quantification of dune characteristics will help refine the chronology of eolian activity in the WRB, provide insight into drought-driven landscape evolution, and integrate WRB eolian activity in a regional paleoenvironmental context. [ABSTRACT FROM AUTHOR]

Cosmogenic nuclide measurements in glacial deposits extend our knowledge of glacier chronologies beyond the observational record. The short half-life of in situ cosmogenic 14C makes it particularly useful for studying glacier chronologies, as resulting exposure ages are less sensitive to nuclide inheritance when compared with more commonly measured, long-lived nuclides. An increasing number of laboratories using an automated process to extract carbon from quartz has led to in situ 14C measurements in Antarctic samples at an accelerating rate over the past decade, shedding light on deglaciation in Antarctica. In situ 14C has had the greatest impact in the Weddell Sea Embayment, where inferences on the thickness of ice and timing of deglaciation were limited by inheritance in other cosmogenic nuclide systems. Future subglacial measurements of the nuclide hold much potential as they can provide direct evidence of proposed Holocene thinning and subsequent re-thickening of parts of the Antarctic ice sheets. [ABSTRACT FROM AUTHOR]

A detailed sequential analysis which included thin section petrography, X-ray diffraction, and X- ray fluorescence was applied to investigate the mineral, chemical classifications, provenance, paleo-weathering, paleoclimate, and maturity features of such Zubair oil shale in the Rumaila oilfield in southern Iraq. In core samples and thin sections, the analyzed shales are primarily silty, flaky to subflaky, micaceous, calcareous, well-sorted, poorly cemented, and weakly to moderately compacted silt-grade sandy mudstone. According to XRD analysis, the main mineral is quartz, which is followed by kaolinite, while calcite and dolomite are less common and Illite, Illite/smectite, and pyrite are rarely abundant. Petrographic analysis of the Zubair shales revealed four lithofacies: silty clayey laminated mudstone lithofacies, mica-rich mudstone lithofacies, clay-rich siliceous mudstone lithofacies, and clay-bearing calcareous mudstone lithofacies. Major and trace element concentrations reveal that the oil shales have been formed from felsic rocks such as granodiorite, tonalite, and granite. A passive margin setting was revealed by the tectonic discrimination diagram. Weathering index values like the (CIA) chemical index of alteration, the (PIA) plagioclase index of alteration, and the (CIW) chemical index of weathering imply extensive chemical weathering in the source area. Zubair shales' K2O/Na2O ratio and (ICV) index of compositional variation are uniform with their high maturity. The compositions of mineral and trace elemental ratios, as well as the climatic index "C," indicate a warm to humid subtropical climate with deposition in a shallow oxic and dysoxic environment. [ABSTRACT FROM AUTHOR]