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Over the last 12,000 y, human populations have expanded and transformed critical earth systems. Yet, a key unresolved question in the environmental and social sciences remains: Why did human populations grow and, sometimes, decline in the first place? Our research builds on 20 y of archaeological research studying the deep time dynamics of human populations to propose an explanation for the long-term growth and stability of human populations. Innovations in the productive capacity of populations fuels exponential-like growth over thousands of years; however, innovations saturate over time and, often, may leave populations vulnerable to large recessions in their well-being and population density. Empirically, we find a trade-off between changes in land use that increase the production and consumption of carbohydrates, driving repeated waves of population growth over thousands of years, and the susceptibility of populations to large recessions due to a lag in the impact of humans on resources. These results shed light on the long-term drivers of human population growth and decline. [ABSTRACT FROM AUTHOR]

To reconstruct the history of organic carbon (OC) aerosol over south‐eastern Europe, dissolved organic carbon (DOC) and its 14C signature (DO14C) were investigated along an ice core drilled at the Mount Elbrus (ELB) in Caucasus. In summer, compared to pre‐1945 levels, the DOC concentrations increased by 45% after 1960, the mean DO14C depletion in recent ELB ice relative to atmospheric 14CO2 of 32% being attributed to fossil‐fuel sources. DO14C content of ice deposited during the bomb‐peak era (1955–1980) closely followed atmospheric 14CO2 changes caused by atmospheric nuclear tests, suggesting the living biosphere as the main biogenic source of DOC in summer in this region. ELB data contrast with those previously obtained in summer Alpine (western Europe) ice in which a post‐1950 doubling of DOC was observed and attributed to enhanced emissions of organic compounds from vegetation in France. This regional difference is discussed with respect to changes of biogenic organic compound emissions in response to past change of use‐land and global warming. ELB data document, for the first time, changes of DOC and DO14C in winter mountain ice showing an increase by 44% of DOC levels associated with a 14C signature being 47% lower than that of atmospheric 14CO2 in ELB ice deposited after 1960. The 14C winter ELB ice record followed atmospheric 14CO2 changes with a delay of ∼3 years, suggesting that remaining emissions from the living biosphere, together with a small contribution from wood burning, are the main biogenic sources of DOC in winter in this region. Plain Language Summary: A good knowledge of past aerosol load and composition is important for climate change. In addition to sulfate, organic carbon aerosol (OC) is a major constituent of present‐day aerosol but its budget remains far less understood. Ice‐core chemical studies help to quantify natural versus anthropogenic sources over the past. Previous investigations of OC and its radiocarbon signature in Alpine ice had shown a doubling of summer OC due to enhanced emissions from vegetation contrasting with a weak impact of fossil‐fuel emissions in western Europe. The regional character of biogenic emissions motivated, however, further studies conducted in other regions. Investigations of OC and its radiocarbon signature in an ice core extracted in the Caucasus permitted to reconstruct past OC changes in the south‐eastern Europe. It is shown that, even in 1970, vegetation emissions still dominate fossil‐fuel emissions as source of OC in summer. A quite large temporal variability of OC is observed and attributed to variations of vegetation emissions in response to past fluctuations of summer temperature in this region. After 1960, fossil‐fuel emissions in winter became almost as large as biogenic emissions that were related to the living biosphere with a small contribution from wood burning at that season. Key Points: Biogenic sources dominate fossil‐fuel sources of present‐day summer organic carbon aerosol (70% vs. 30%) in south‐eastern EuropeLarge pre‐industrial variability of organic carbon aerosol in summer driven by vegetation emissions modulated by past temperaturesLiving biosphere with a small contribution from wood burning slightly exceeds present‐day fossil‐fuel sources of organic carbon in winter [ABSTRACT FROM AUTHOR]

Most canopy species in lowland tropical rain forests in Southeast Asia, represented by Dipterocarpaceae, undergo mast reproduction synchronously at community level during a general flowering event. Such events occur at irregular intervals of 2–10 years. Some species do not necessarily participate in every synchronous mast reproduction, however. This may be due to a lack of carbohydrate resources in the trees for masting. We tested the hypothesis that interspecific differences in the time required to store assimilates in trees for seed production are due to the frequency of masting and/or seed size in each species. We examined the relationship between reproductive frequency and the carbon accumulation period necessary for seed production, and between the seed size and the period, using radiocarbon analysis in 18 dipterocarp canopy species. The mean carbon accumulation period was 0.84 years before seed maturation in all species studied. The carbon accumulation period did not have any significant correlation with reproductive frequency or seed size, both of which varied widely across the species studied. Our results show that for seed production, dipterocarp masting species do not use carbon assimilates stored for a period between the masting years, but instead use recent photosynthates produced primarily in a masting year, regardless of the masting interval or seed size of each species. These findings suggest that storage of carbohydrate resources is not a limiting factor in the masting of dipterocarps, and that accumulation and allocation of other resources is important as a precondition for participation in general flowering. [ABSTRACT FROM AUTHOR]

Here, we present the results of a comprehensive study of air quality in two tunnels located in the city of Krakow, southern Poland. The study comprised three PM fractions of suspended particulate matter (PM1, PM2.5 and PM10) sampled during campaigns lasting from March 14 to April 24, 2016 and from June 28 to July 18, 2016, in the road tunnel and the tram tunnel, respectively. The collected samples had undergone comprehensive chemical, elemental and carbon isotope analyses. The results of these analyses gave the basis for better characterization of urban transport as a source of air pollution in the city. The concentrations of particulate matter varied, depending on the analysed PM fraction and the place of sampling. For the tram tunnel, the average concentrations were 53.2 µg·m−3 (PM1), 73.8 µg·m−3 (PM2.5), 96.5 µg·m−3 (PM10), to be compared with 44.2 µg·m−3, 137.7 µg·m−3, 221.5 µg·m−3, respectively, recorded in the road tunnel. The isotope-mass balance calculations carried out separately for the road and tram tunnel and for each PM fraction, revealed that 60 to 79% of carbon present in the samples collected in the road tunnel was associated with road transport, to be compared with 15–33% obtained in the tram tunnel. The second in importance were biogenic emissions (17–21% and 41–49% in the road and tram tunnel, respectively. Sixteen different polycyclic aromatic hydrocarbons (PAHs) have been identified in the analysed samples. As expected, much higher concentrations of PAHs were detected in the road tunnel when compared to the tram tunnel. Based on the analysed PAHs concentrations, health risk assessment was determined using 3 different types of indicators: carcinogenic equivalent (CEQ), mutagenic equivalent (MEQ) and toxic equivalent (TEQ). [ABSTRACT FROM AUTHOR]

Sampling and 14C detection of biomass are now essential steps to ensure the accuracy of the 14C method, but they require additional time and economic investment. When there are multiple types of biomass fuels, it is not possible to guarantee the uniformity of sampling. The 14C activity of biomass fuels exhibits variability, and this value significantly impacts the precision of the 14C method. Therefore, this study aims to investigate the influencing factors of 14C activity in biomass fuels. It also provides predicted values of 14C activity for different types of biomass fuels for each year from 2020 to 2030. Additionally, this study discusses the potential blending ratio measurement errors that may arise due to the uncertainties of the predicted values. The reduction in the 14C activity of biomass fuels can occur due to the utilization of fossil fuels, human activities, and the photosynthesis mode of C3 plants. This study presents a prediction method for determining the reduction factor. The other component of the prediction methodology involves determining the original 14C activity of biomass fuels. The 14C activity of the annual biomass is equal to the 14CO2 activity (the 14C activity of CO2) of the surrounding environment, and it experiences a decline of 0.355 pMC/year. The 14C activity has ranges of five types of perennial biomass fuels, including wood chips and branches, bark, leaves, wasted furniture, and abandoned building wood, for the time period between 2020 and 2030, are 97.34~102.84, 96.35~106.27, 96.35~102.64, 111.00~118.60, and 111.32~129.47 pMC, respectively. Based on these, this study introduces a new formula for calculating blending ratios, which enhances the current methodology. The calculation errors of blending ratios caused by the uncertainties of the predicted values are generally negligible, with the exception of wasted furniture and construction wood. The annual decrease in the blending ratio calculation error, caused by the uncertainty associated with the predicted value, can be observed. This study aims to reduce the implementation time and economic cost of the 14C method while ensuring the accuracy of biomass blending ratio detection. [ABSTRACT FROM AUTHOR]

The spread of trapeze industries (the creation of trapeze-shaped flint tips) during Late Mesolithic is one of the most disruptive phenomena of technological change documented in the European Prehistory. Understanding the chronological patterns of this process requires (i) a critical evaluation of stratigraphic relationship between trapeze assemblages and radiocarbon samples, and (ii) considering different levels of chronological uncertainty according to the inbuilt age of the samples and the calibration process. In this paper, we critically evaluate and analyze the radiocarbon record of the first trapeze industries in the Iberian Peninsula. A dataset of 181 radiocarbon dates from 67 sites dated to 8800–8200 cal BP was collected and evaluated following a strict data quality control protocol, from which 135 dates of 53 sites were retained and classified according to a reliability index. Then, three different phase Bayesian chronological models were created to estimate the duration of the first spread of trapezes across Iberia, considering different levels of chrono-stratigraphic resolution. We find that trapeze industries appeared in the eastern half of Iberia, over an area of 330,000 km2 between 8505–8390 and 8425–8338 cal BP, spanning 0–85 yr (95.4% CI). When the oldest evidence of trapezes from Portugal are considered, the probability distribution expands (8943–8457 and 8686–7688 cal BP), due to the chronological uncertainty of human samples with marine diet and regional ΔR values applied. For the eastern half of Iberia, the current evidence indicates a very rapid spread of trapeze industries initiated in the Central-Western Pyrenees, suggesting cultural diffusion within Mesolithic social networks as the main driving mechanism. [ABSTRACT FROM AUTHOR]

Three hundred forty‐one radiocarbon dates from the Groningen radiocarbon database are compiled in this study. They show for the first time that organic sediment samples from the eastern Netherlands and mammal bones from Doggerland reflect shifts in the presence and the density of vegetation (food for herbivores) and mammal biomass during the last ice age (Weichselian Stage, ~119–14.7 ka cal bp). Comparison with oxygen isotope curves of Greenland ice cores and geomorphological data shows that cold climate, in particular during the younger part of the Weichselian Middle Pleniglacial and during the Late Pleniglacial, and related scarcity or even absence of vegetation, were limiting factors for the carrying capacity of the landscape and thus for the population density of large herbivores during the period covered by 14C dating (last ca. 55 000 years). A 'fossil gap' during the Late Pleniglacial lasted ca. 13 000 years from ca. 28 to 15 ka cal bp. Previous research from the nearby Eifel region in Germany shows that environmental conditions were less extreme ('refugium conditions') than in the Netherlands, taking into account the continuous presence of spores of coprophilous fungi in the Eifel, indicating uninterrupted food supply for herbivores. [ABSTRACT FROM AUTHOR]

Abstract Trace elements and stable isotope ratios in otoliths have been used as proxies for the migration history of teleosts; however, their application in oceanic fishes remains limited. This study reports the first use of radiocarbons in otoliths to evaluate the horizontal migration histories of an oceanic fish species, the walleye pollock Gadus chalcogrammus. We conducted radiocarbon analyses of three stocks sourced from Hokkaido, Japan. The radiocarbon concentrations from the outermost portion of the otoliths from the Japanese Pacific, Northern Japan Sea (JS), and Southern Okhotsk Sea (OS) stocks were in general agreement with the seawater radiocarbon concentration of the sampling region, suggesting that pollock of all three stocks generally inhabited the within the sea region where each pollocks were sampled throughout their life cycle. However, the radiocarbon signals also provided some indications that some JS and OS stocks may be migrating between different sea regions. The proposed novel approach of reconstructing the individual migration history of marine fish using radiocarbon in otoliths may help examine fish migration with a higher temporal and spatial resolution that could not be achieved by trace elements and stable isotope ratios.

Abstract The Amazon River mobilizes organic carbon across one of the world's largest terrestrial carbon reservoirs. Quantifying the sources of particulate organic carbon (POC) to this flux is typically challenging in large systems such as the Amazon River due to hydrodynamic sorting of sediments. Here, we analyze the composition of POC collected from multiple total suspended sediment (TSS) profiles in the mainstem at Óbidos, and surface samples from the Madeira, Solimões and Tapajós Rivers. As hypothesized, TSS and POC concentrations in the mainstem increased with depth and fit well to Rouse models for sediment sorting by grain size. Coupling these profiles with Acoustic Doppler Current Profiler discharge data, we estimate a large decrease in POC flux (from 540 to 370 kg per second) between the rising and falling stages of the Amazon River mainstem. The C/N ratio and stable and radiocarbon signatures of bulk POC are less variable within the cross‐section at Óbidos and suggest that riverine POC in the Amazon River is predominantly soil‐derived. However, smaller shifts in these compositional metrics with depth, including leaf wax n‐alkanes and fatty acids, are consistent with the perspective that deeper and larger particles carry fresher, less degraded organic matter sources (i.e., vegetation debris) through the mainstem. Overall, our cross‐sectional surveys at Óbidos highlight the importance of depth‐specific sampling for estimating riverine export fluxes. At the same time, they imply that this approach to sampling is perhaps less essential with respect to characterizing the composition of POC sources exported by the river.

Abstract Dissolved organic carbon (DOC) in the global oceans is an important long‐term carbon sink. Connections between molecular size, reactivity, and isotopic characteristics show that DOC exists on a continuum from biologically reactive to recalcitrant. The driving mechanisms behind the creation and persistence of recalcitrant DOC remain unknown. We show mean recalcitrant DOC (isolated via solid‐phase extraction; SPE‐DOC) δ13C values are 1.3 ± 0.6‰ lower than mean total DOC δ13C between depth ranges 0–200 m and 2–4 km on three GO‐SHIP Repeat Hydrography cruises. Lowest observed δ13C values correlate with low ∆14C and proximity to deep ocean hydrothermal systems. These data support the hypothesis that reworking of DOC through the microbial carbon pump is a key driver of the ocean's long‐term carbon sink. Mass‐balance modeling shows deep‐ocean DOC not captured by SPE is enriched in 13C, highlighting the need for continued research on non‐retained DOC to predict mechanisms that drive ocean carbon storage.

A 1 MV Accelerator Mass Spectrometer (AMS) was established at TÜBİTAK, MRC Türkiye in December 2015. The 1MV TÜBİTAK AMS system is based on a Pelletron tandem accelerator, operating up to 1.1MV. Built by National Electrostatics Corporation (NEC), its design was unique at time of production. The TÜBİTAK 1MV AMS is based on the design of an XCAMS 0.5MV AMS also produced by NEC, but with a higher energy tandem accelerator. The higher energy accelerator features better precision (1% or less) for 10Be measurements. This new AMS also has larger magnets than the XCAMS. Larger magnets make it possible to measure 41Ca and 129I at the two-anode gasionization detector. In this article, the technical features; the parameters of ion source, terminal and other operations, and measurement quality are explained for accomplished performance of the five isotopic ratios, 14C/12C, 10Be/9Be, 26Al/27Al, 41Ca/40Ca, 129I/127I. This article also presents five years of data for 14C/12C ratio measurement quality control are represented as well.

The paper presents six samples originating from archaeologically investigated contexts in the Early Iron Age site of Saharna–Țiglău. Three samples were collected, after anthropological analysis, from funerary features excavated in 2022, and the remaining samples were taken from pits within the settlement. Calibration of the six AMS radiocarbon data places the chronological sequence with a 95.4% probability in the range calBC 1284-797. From the association of the data, it is almost obvious to conclude that one of the earliest known dates for an Early Iron Age context with stamped pottery in the Carpathian-Balkan area has been recorded at Saharna–Țiglău.

The Gubbio Revisited project, initiated to reinterpret the archaeological evidence collected during the 1980s Gubbio Project, primarily by a conversion from a paper to a digital record, has revealed significant insights into the evolving settlement patterns and religious expression in the Gubbio valley in Central Italy. This reanalysis of the survey evidence underscores the rhythms of settlement and ritual practice from the Neolithic through the Bronze and Iron Ages, into Roman times. Key excavations in the 1980s at Monte Ingino, Monte Ansciano, San Marco Romano, and San Marco Neolitico added details not only of settlement activity but also of embedded ritual, evidenced by material culture including pottery, faunal remains, and votive offerings. The foundation myth of indigenous religious practices, even amidst Roman influence, is documented through the Iguvine Tables alongside the introduction of new cults, showcasing a blend of local and imperial religiosity, a common feature in the Roman world. This research enriches the understanding of Gubbio’s historical and cultural landscape, emphasizing the demographic rhythms of the valley alongside the integral role of ritual in its societal evolution.

Spectroscopic detection of radiocarbon dioxide (14CO2) offers several advantages, including real‐time detection, on‐site measurement capability, and ease of operation. Here, we propose a novel 14CO2 detection technique that utilizes optical feedback linear cavity enhanced absorption spectroscopy. The feedback phase is actively compensated by adjusting the light path length. The combination of cavity‐based technique and optical feedback enables the recording of stable and enhanced 14CO2 spectra. Through Allan deviation analysis, a minimal detectable 14CO2 concentration of 3.5 parts‐per‐trillion is achieved. This technique has the potential to contribute to the monitoring of the radiocarbon emissions in the air of nuclear power plants. [ABSTRACT FROM AUTHOR]

The construction materials of the Santalla de Bóveda Monument, one of the most studied buildings in Galicia (Spain), are analysed to date the mortars and bricks of walls and vaults by combining three dating techniques: optically stimulated luminescence, radiocarbon and thermoluminescence. Petrological characterisation of the mortars themselves is carried out. Until now, the paintings on the vault have been interpreted as Roman, early Christian or Pre-Romanesque, depending on the interpretative framework used by the researcher who studied them. There is also no consensus on their functionality. A total of 21 samples were collected, and 39 datings were made. The results are conclusive: the original building dates from the second half of the fourth century AD, the paintings date from the beginning of the seventh century or the upper floor from the tenth to twelfth centuries. These results make it necessary to review the history of Galician architecture between Late Antiquity and the Early Medieval Ages. [ABSTRACT FROM AUTHOR]

Connecting changes in erosion and vegetation is necessary for predicting topographic and ecologic change in thawing permafrost landscapes. Formerly periglacial landscapes serve as potential analogs for understanding modern permafrost landscape change, yet compared to paleoenvironmental records at these sites, less is known about concurrent geomorphic processes, particularly their rates and relationships to climate change. Here, we target sediments preserved in a central Appalachian peat bog to reconstruct sedimentation across the last deglacial warming. We use ground-penetrating radar and geochemistry of cored bog sediments to quantify sedimentation timing, style, and provenance. Using 14C dating of sedimentary and geochemical shifts, we connect depositional changes to global climate and local vegetation change. We show that deglacial warming promoted deep soil disturbances via solifluction at ca. 14 ka. In contrast, relatively wetter conditions from ca. 10–9 ka promoted shallow disturbance of hillslopes via slopewash, which corresponds to a time of vegetation change. Our results highlight climate-modulated erosion depth and processes in periglacial and post-periglacial landscapes. The existence of similar erosion and vegetation records preserved regionally implies these dynamics were pervasive across unglaciated Appalachian highlands, aiding in reconstructing erosion responses to warming at a resolution with implications for predicting high-latitude landscape responses to disturbance. [ABSTRACT FROM AUTHOR]

Soils store large quantities of carbon in the subsoil (below 0.2 m depth) that is generally old and believed to be stabilized over centuries to millennia, which suggests that subsoil carbon sequestration (CS) can be used as a strategy for climate change mitigation. In this article, we review the main biophysical processes that contribute to carbon storage in subsoil and the main mathematical models used to represent these processes. Our guiding objective is to review whether a process understanding of soil carbon movement in the vertical profile can help us to assess carbon storage and persistence at timescales relevant for climate change mitigation. Bioturbation, liquid phase transport, belowground carbon inputs, mineral association, and microbial activity are the main processes contributing to the formation of soil carbon profiles, and these processes are represented in models using the diffusion–advection–reaction paradigm. Based on simulation examples and measurements from carbon and radiocarbon profiles across biomes, we found that advective and diffusive transport may only play a secondary role in the formation of soil carbon profiles. The difference between vertical root inputs and decomposition seems to play a primary role in determining the shape of carbon change with depth. Using the transit time of carbon to assess the timescales of carbon storage of new inputs, we show that only small quantities of new carbon inputs travel through the profile and can be stabilized for time horizons longer than 50 years, implying that activities that promote CS in the subsoil must take into consideration the very small quantities that can be stabilized in the long term. [ABSTRACT FROM AUTHOR]

Given the importance of soil for the global carbon cycle, it is essential to understand not only how much carbon soil stores but also how long this carbon persists. Previous studies have shown that the amount and age of soil carbon are strongly affected by the interaction of climate, vegetation, and mineralogy. However, these findings are primarily based on studies from temperate regions and from fine‐scale studies, leaving large knowledge gaps for soils from understudied regions such as sub‐Saharan Africa. In addition, there is a lack of data to validate modeled soil C dynamics at broad scales. Here, we present insights into organic carbon cycling, based on a new broad‐scale radiocarbon and mineral dataset for sub‐Saharan Africa. We found that in moderately weathered soils in seasonal climate zones with poorly crystalline and reactive clay minerals, organic carbon persists longer on average (topsoil: 201 ± 130 years; subsoil: 645 ± 385 years) than in highly weathered soils in humid regions (topsoil: 140 ± 46 years; subsoil: 454 ± 247 years) with less reactive minerals. Soils in arid climate zones (topsoil: 396 ± 339 years; subsoil: 963 ± 669 years) store organic carbon for periods more similar to those in seasonal climate zones, likely reflecting climatic constraints on weathering, carbon inputs and microbial decomposition. These insights into the timescales of organic carbon persistence in soils of sub‐Saharan Africa suggest that a process‐oriented grouping of soils based on pedo‐climatic conditions may be useful to improve predictions of soil responses to climate change at broader scales. [ABSTRACT FROM AUTHOR]

Tidal salt marshes produce and emit CH4. Therefore, it is critical to understand the biogeochemical controls that regulate CH4 spatial and temporal dynamics in wetlands. The prevailing paradigm assumes that acetoclastic methanogenesis is the dominant pathway for CH4 production, and higher salinity concentrations inhibit CH4 production in salt marshes. Recent evidence shows that CH4 is produced within salt marshes via methylotrophic methanogenesis, a process not inhibited by sulfate reduction. To further explore this conundrum, we performed measurements of soil–atmosphere CH4 and CO2 fluxes coupled with depth profiles of soil CH4 and CO2 pore water gas concentrations, stable and radioisotopes, pore water chemistry, and microbial community composition to assess CH4 production and fate within a temperate tidal salt marsh. We found unexpectedly high CH4 concentrations up to 145,000 μmol mol−1 positively correlated with S2− (salinity range: 6.6–14.5 ppt). Despite large CH4 production within the soil, soil–atmosphere CH4 fluxes were low but with higher emissions and extreme variability during plant senescence (84.3 ± 684.4 nmol m−2 s−1). CH4 and CO2 within the soil pore water were produced from young carbon, with most Δ14C‐CH4 and Δ14C‐CO2 values at or above modern. We found evidence that CH4 within soils was produced by methylotrophic and hydrogenotrophic methanogenesis. Several pathways exist after CH4 is produced, including diffusion into the atmosphere, CH4 oxidation, and lateral export to adjacent tidal creeks; the latter being the most likely dominant flux. Our findings demonstrate that CH4 production and fluxes are biogeochemically heterogeneous, with multiple processes and pathways that can co‐occur and vary in importance over the year. This study highlights the potential for high CH4 production, the need to understand the underlying biogeochemical controls, and the challenges of evaluating CH4 budgets and blue carbon in salt marshes. [ABSTRACT FROM AUTHOR]

Cave guano deposits are increasingly being recognized as valuable repositories of paleoclimatic and paleo-environmental information. However, that value is constrained by rates of guano decomposition, and these rates have not been previously well-studied. Here we show that field and laboratory studies of deep insectivorous bat guano sequences in the caves of Borneo demonstrate the extreme dependence of decomposition rate on guano water content. Under tropical conditions, moist guanos exhibit decomposition coefficients (k) values of ~0.01, implying the loss of most of the organic content on decadal timescales. Under similar temperatures but drier conditions, k values drop to ~3 x 10-6, permitting significant organic (chitin) content to persist for tens of thousands of years. One of the implications of these findings for paleo-environmental records older than the limit of carbon dating is that a value for k can be calculated based on a single carbon date, which then allows an estimate of likely age at base of deposit. [ABSTRACT FROM AUTHOR]

Correctly estimating the maximum lifespan of plant species is a necessary component of demographic and life-history studies, which, in turn, are needed for understanding climatic impacts. Arboreal monocotyledons, which can grow to >30 m in height and >5 m in trunk perimeter, are difficult to age because they do not undergo seasonal dormancy; hence, their longevity has been estimated using various size-related methods. In this study, we tested radiocarbon (14C) dating with Accelerator Mass Spectrometry (AMS) as an additional tool for determining the age of two iconic monocotyledons: the Canary Island palm and the dragon tree. A total of 25 samples were collected from the basal stem of four palms and five dragon trees on Gran Canaria and Tenerife and then processed using the most advanced 14C-AMS analysis available. Calibration curves provided by the "IntCal group" were used to determine the oldest possible age of each sample, and 16 of them were found to be "modern", i.e., formed after the 1950s. Nine samples that were either collected from exterior, but lignified, palm tissues or from interior, and lignified, dragon tree tissues suggested ages > 300 years. Given the constant improvement of 14C-AMS tools, they can contribute to the further refinement of existing scientific knowledge on Macaronesian charismatic megaflora. [ABSTRACT FROM AUTHOR]

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Cabo Pulmo National Park (CPNP), within the East Cape of Baja California Sur, Mexico, is the location of a highly productive rocky reef ecosystem that was likely attractive to people throughout the Holocene. AMS radiocarbon dates from sites along the coast and faunal data from two excavated sites, D20 and D27, indicate people were present in the region by at least 7120–6755 cal b.p. (D34), but evidence of persistent occupation and possibly higher population densities postdates 2110–1945 cal b.p. (D27, Unit 1). The most prominent sites with intact stratified archaeological deposits appear to be focused adjacent to prominent rocky points, where assemblages include a variety of marine mollusks, fish, birds, terrestrial and marine mammals, and sea turtle remains. At both D20 and D27, there is evidence people targeted small fishes including sardines, likely with nets. This study highlights the strong archaeological potential in CPNP to address questions about human coastal adaptations and population history during the Holocene, emphasizing the importance of protecting cultural resources in an area at risk from growing tourism and residential development. [ABSTRACT FROM AUTHOR]

In this paper, we discuss the issues of handling reactor graphite. The content of 14C in RBMK graphite is compared with the natural content and emissions from other technogenic impacts. The scale of natural fluctuations in the natural content of 14C and their relationship with technogenic impacts are discussed. Possible doses due to the release of 14C from a hypothetical near-surface storage of reactor graphite during normal operation and accidents are estimated. [ABSTRACT FROM AUTHOR]

We present the results of the 2022 excavations at the Bluff Field site (9CH160), wherein we consider the juxtaposition of Bayesian radiocarbon modeling against the current ceramic chronologies derived for the Georgia coast. New evidence from AMS radiocarbon dating and statistical modeling pushes both the timing and span of Wilmington series ceramics beyond the ranges afforded by current models. Short-lived carbonized hickory nuts from within excavation units and shovel tests returned dates that are hundreds of years later in time than the currently accepted timing for Wilmington ceramics. These ceramics contribute the largest proportion of the ceramic assemblage recovered from the site and within the levels from which we dated for chronological modeling. Our modeling of these dates that are in stratigraphic sequence calls into question not only the use history of the Wilmington ceramic series, but also the demographic history of the island that is currently predicated upon the timing of this and other ceramic styles. We recommend reinterrogating existing chronologies in order to bring the settlement chronologies for the Georgia coastal region up to present-day methodological and statistical standards. [ABSTRACT FROM AUTHOR]

As an important carbon emitter, China faces the stress of carbon peaking and carbon neutrality goals and international carbon reduction duty. The accurate data of carbon emissions are important to evaluate the carbon peaking and carbon neutrality goals and fulfill the international duty of carbon reduction. The Intergovernmental Panel on Climate Change (IPCC) report recommends the combination of top-down atmospheric CO2 observation with atmospheric inversion to verify the bottom-up inventory of carbon emissions, and the atmospheric 14CO2 observation can make the verification more accurate. Radiocarbon (14C) is the most precise tracer of fossil fuel CO2 and is widely recommended by the international community to evaluate the carbon emissions. Based on the international developing trends and the situation in China for atmospheric 14CO2 observation, this study suggests to establish the atmospheric 14CO2 observation network as soon as possible, with more supporting; to conduct training to unify the standard, and to participate in international exchanges; and to combine the 14CO2 observation with atmospheric inversion to obtain the carbon emissions. The purpose of the 14CO2 observation is to make the research level of Chinese carbon emissions in line with the international standards, to improve the reliability of carbon emission data in China, and then to serve the carbon peaking and carbon neutrality goals and climate diplomacy negotiations. [ABSTRACT FROM AUTHOR]

In the 21st century, glaciers are perceived as a distinct biome that has taken on special significance in today's world of retreating ice. In this paper, we review the results of recent studies of organomineral formations on glaciers, their diversity, genesis, functioning, and the role in the biosphere. The question is raised about the possibility of involving supraglacial organomineral formations in the range of objects of soil science. We review the supraglacial zone as an area of soils and soil-like bodies, the biogeochemical processes in which affect the glacial biome and the surrounding landscapes. Interpretation of supraglacial organomineral formations from a pedological point of view allows us to identify several typical soil processes: accumulation and stabilization of organic matter (OM), its heterotrophic transformation, formation of dark-colored humified OM, accumulation of residual solid-phase products of functioning in situ, fine earth aggregation, and biochemical weathering. Among supraglacial formations, we distinguish pre-soils and soil-like bodies in ice and snow, metastable soil-like bodies on cryoconite, and soils with microprofiles under moss communities on ice, as well as relatively stable soils with macroprofiles on silicate gravelly to fine-earth deposits underlain by moving glacier and dead glacier ice. Labile dissolved OM accumulated and transformed in supraglacial soils and soil-like bodies has a significant impact on the periglacial zone, leading to the reservoir and priming effects. The studies of supraglacial organomineral systems are of fundamental importance for understanding the evolution of ecosystems on Earth, as well as for modeling supraglacial formations of extraterrestrial bodies with a vast cryosphere. Supraglacial soil formation is also a model object for studying common soils under conditions of a continuous external input of organic and mineral components, the contribution of which beyond the glaciers is no less significant, but is masked by the polymineral substrate of soils and parent rocks themselves. [ABSTRACT FROM AUTHOR]

The response of terrestrial ecosystems to increased atmospheric CO2 concentrations is controversial and not yet fully understood, with previous large‐scale forest manipulation experiments exhibiting contrasting responses. Although there is consensus that increased CO2 has a relevant effect on instantaneous processes such as photosynthesis and transpiration, there are large uncertainties regarding the fate of extra assimilated carbon in ecosystems. Filling this research gap is challenging because tracing the movement of new carbon across ecosystem compartments involves the study of multiple processes occurring over a wide range of timescales, from hours to millennia. We posit that a comprehensive quantification of the effect of increased CO2 must answer two interconnected questions: How much and for how long is newly assimilated carbon stored in ecosystems? Therefore, we propose that the transit time distribution of carbon is the key concept needed to effectively address these questions. Here, we show how the transit time distribution of carbon can be used to assess the fate of newly assimilated carbon and the timescales at which it is cycled in ecosystems. We use as an example a transit time distribution obtained from a tropical forest and show that most of the 60% of fixed carbon is respired in less than 1 year; therefore, we infer that under increased CO2, most of the new carbon would follow a similar fate unless increased CO2 would cause changes in the rates at which carbon is cycled and transferred among ecosystem compartments. We call for a more frequent adoption of the transit time concept in studies seeking to quantify the ecosystem response to increased CO2. [ABSTRACT FROM AUTHOR]

The East Sea (also known as the Japan Sea) is connected to the Northwest Pacific via shallow straits and has independent deep water circulation, as a model miniature ocean. The radiocarbon age of dissolved organic carbon (DOC) in the East Sea ranged from 2,000 to 3,700 years, exceeding the water turnover time (∼100 years). The oldest DOC was found in the subsurface layer characterized by the Tsushima Warm Water. Comparison of the radiocarbon content and concentration of DOC in the East Sea to those in the ocean suggests that aged DOC was transported conservatively from the Northwest Pacific to the East Sea via the shallow Tsushima Warm Current. The fractions of DOC released by serial‐oxidation of the oldest DOC sample had identical radiocarbon ages, implying that refractory DOC was produced in situ and added to the DOC pool in the East Sea. Plain Language Summary: The East Sea (also known as the Japan Sea) is connected to the Northwest Pacific exchanging surface water only through shallow passages. The radiocarbon age of DOC in the East Sea is old, ranging from 2,000 to 3,700 years. This cannot be explained by DOC production and aging in the East Sea. Instead, it appears that old DOC is transported into the East Sea from the Northwest Pacific. The oldest DOC was found in the subsurface layer instead of the deepest layer. We show that this oldest DOC is a mixture of the old DOC from the North Pacific and modern DOC produced in the East Sea however their characteristics in terms of resistance to oxidation were modified. These findings provide clues for understanding the global DOC cycling especially in the surface ocean. Key Points: Radiocarbon ages of dissolved organic carbon (DOC) in the East Sea (Japan Sea) ranged from 2,000 to 3,700 years, exceeding the water turnover timeThe oldest DOC at subsurface depths in the East Sea was transported from the North Pacific via the Tsushima Warm CurrentThe aged DOC from the North Pacific is mixed with younger DOC produced in situ and spreads to the deep waters in the East Sea [ABSTRACT FROM AUTHOR]

Compound- and compound class-specific radiocarbon analysis of source-diagnostic 'biomarker' molecules has emerged as a powerful tool to gain insights into terrestrial carbon cycling. While most studies thus far have focused on higher plant biomarkers (i.e. plant leaf-wax n-alkanoic acids and n-alkanes, lignin-derived phenols), tracing paedogenic carbon is crucial given the pivotal role of soils in modulating ecosystem carbon turnover and organic carbon (OC) export. Here, we determine the radiocarbon (14C) ages of glycerol dialkyl glycerol tetraethers (GDGTs) in riverine sediments and compare them to those of higher plant biomarkers as well as markers of pyrogenic (fire-derived) carbon (benzene polycarboxylic acids, BPCAs) to assess their potential as tracers of soil turnover and export. GDGT Δ14C follows similar relationships with basin properties as vegetation-derived lignin phenols and leaf-wax n-alkanoic acids, suggesting that the radiocarbon ages of these compounds are significantly impacted by intermittent soil storage. Systematic radiocarbon age offsets are observable between the studied biomarkers, which are likely caused by different mobilization pathways and/or stabilization by mineral association. This article is part of the Theo Murphy meeting issue 'Radiocarbon in the Anthropocene'. [ABSTRACT FROM AUTHOR]

As part of the CarbonWatch-NZ research programme, air samples were collected at 28 sites around Auckland, New Zealand, to determine the atmospheric ratio (RCO) of excess (local enhancement over background) carbon monoxide to fossil CO2 (CO2ff). Sites were categorized into seven types (background, forest, industrial, suburban, urban, downwind and motorway) to observe RCO around Auckland. Motorway flasks observed RCO of 14 ± 1 ppb ppm−1 and were used to evaluate traffic RCO. The similarity between suburban (14 ± 1 ppb ppm−1) and traffic RCO suggests that traffic dominates suburban CO2ff emissions during daytime hours, the period of flask collection. The lower urban RCO (11 ± 1 ppb ppm−1) suggests that urban CO2ff emissions are comprised of more than just traffic, with contributions from residential, commercial and industrial sources, all with a lower RCO than traffic. Finally, the downwind sites were believed to best represent RCO for Auckland City overall (11 ± 1 ppb ppm−1). We demonstrate that the initial discrepancy between the downwind RCO and Auckland's estimated daytime inventory RCO (15 ppb ppm−1) can be attributed to an overestimation in inventory traffic CO emissions. After revision based on our observed motorway RCO, the revised inventory RCO (12 ppb ppm−1) is consistent with our observations. This article is part of the Theo Murphy meeting issue 'Radiocarbon in the Anthropocene'. [ABSTRACT FROM AUTHOR]

We present new 14C results measured on subfossil Scots Pines recovered in the eroded banks of the Drouzet watercourse in the Southern French Alps. About 400 new 14C ages have been analysed on 15 trees sampled at annual resolution. The resulting Δ14C record exhibits an abrupt spike occurring in a single year at 14 300–14 299 cal yr BP and a century-long event between 14 and 13.9 cal kyr BP. In order to identify the causes of these events, we compare the Drouzet Δ14C record with simulations of Δ14C based on the 10Be record in Greenland ice used as an input of a carbon cycle model. The correspondence with 10Be anomalies allows us to propose the 14.3 cal kyr BP event as a solar energetic particle event. By contrast, the 14 cal kyr BP event lasted about a century and is most probably a common Maunder-type solar minimum linked to the modulation of galactic cosmic particles by the heliomagnetic field. We also discuss and speculate about the synchroneity and the possible causes of the 14 cal kyr BP event with the brief cold phase called Older Dryas, which separates the Bølling and Allerød millennium-long warm phases of the Late Glacial period. This article is part of the Theo Murphy meeting issue 'Radiocarbon in the Anthropocene'. [ABSTRACT FROM AUTHOR]

The direct way to estimate the regional fossil fuel CO2 surplus (ΔffCO2) at a station is by measuring the Δ14CO2 depletion compared with a respective background. However, this approach has several challenges, which are (i) the choice of an appropriate Δ14CO2 background, (ii) potential contaminations through nuclear 14CO2 emissions and (iii) masking of ΔffCO2 by 14C-enriched biosphere respiration. Here we evaluate these challenges and estimate potential biases and typical uncertainties of 14C-based ΔffCO2 estimates in Europe. We show that Mace Head (MHD), Ireland, is a representative background station for the Integrated Carbon Observation System (ICOS) atmosphere station network. The mean ΔffCO2 representativeness bias when using the MHD Δ14CO2 background for the whole observation network is of order 0.1 ± 0.3 ppm. At ICOS sites, the median nuclear contamination leads to 25% low-biased ΔffCO2 estimates if not corrected for. The ΔffCO2 masking due to 14C-enriched heterotrophic CO2 respiration can lead to similar ΔffCO2 biases as the nuclear contaminations, especially in summer. Our evaluation of all components contributing to the uncertainty of ΔffCO2 estimates reveals that, due to the small ffCO2 signals at ICOS stations, almost half of the 14C-based ΔffCO2 estimates from integrated samples have an uncertainty that is larger than 50%. This article is part of the Theo Murphy meeting issue 'Radiocarbon in the Anthropocene'. [ABSTRACT FROM AUTHOR]

Lateral carbon transport through the land-to-ocean-aquatic-continuum (LOAC) represents a key component of the global carbon cycle. This LOAC involves complex processes, many of which are prone to anthropogenic perturbation, yet the influence of natural and human-induced drivers remains poorly constrained. This study examines the radiocarbon (14C) signatures of particulate and dissolved organic carbon (POC, DOC) and dissolved inorganic carbon (DIC) transported by Swiss rivers to assess controls on sources and cycling of carbon within their watersheds. Twenty-one rivers were selected and sampled during high-flow conditions in summer 2021, a year of exceptionally high rainfall. Δ14C values of POC range from −446‰ to −158‰, while corresponding ranges of Δ14C values for DOC and DIC are −377‰ to −43‰ and −301‰ to −40‰, respectively, indicating the prevalence of pre-aged carbon. Region-specific agricultural practices seem to have an influential effect on all three carbon phases in rivers draining the Swiss Plateau. Based on Multivariate Regression Analysis, mean basin elevation correlated negatively with Δ14C values of all three carbon phases. These contrasts between alpine terrain and the lowlands reflect the importance of overriding ecoregional controls on riverine carbon dynamics within Switzerland, despite high spatial variability in catchment properties. This article is part of the Theo Murphy meeting issue 'Radiocarbon in the Anthropocene'. [ABSTRACT FROM AUTHOR]

We provide here a model-based estimate of the transit time of carbon through the terrestrial biosphere, since the time of carbon uptake through photosynthesis until its release through respiration. We explored the consequences of increasing productivity versus increasing respiration rates on the transit time distribution and found that while higher respiration rates induced by higher temperature increase the transit time because older carbon is respired, increases in productivity cause a decline in transit times because more young carbon is available to supply increased metabolism. The combined effect of increases in temperature and productivity results in a decrease in transit times, with the productivity effect dominating over the respiration effect. By using an ensemble of simulation trajectories from the Carbon Data Model Framework (CARDAMOM), we obtained time-dependent transit time distributions incorporating the twentieth century global change. In these simulations, transit time declined over the twentieth century, suggesting an increased productivity effect that augmented the amount of respired young carbon, but also increasing the release of old carbon from high latitudes. The transit time distribution of carbon becomes more asymmetric over time, with more carbon transiting faster through tropical and temperate regions, and older carbon being respired from high latitude regions. This article is part of the Theo Murphy meeting issue 'Radiocarbon in the Anthropocene'. [ABSTRACT FROM AUTHOR]

Fire can play an important role in peatlands by modifying plant communities and carbon (C) stocks. However, baseline disturbance data on peatland fire history are lacking in the hemi-boreal region. We sampled 29 peatlands in northern Michigan, Wisconsin, and Minnesota and used peat core records, radiocarbon dating, and infrared spectrometry to identify and date past fire events in 4 major hemi-boreal peatland ecotypes including open poor fens, treed poor fens, forested poor fens, and forested rich fens. In this region all types of poor fens had widely variable fire frequencies between sites. The poor fens experienced 2.1 fires per thousand years, or once every 476 years, on average, while the rich fens experienced almost no fire. Overall C stocks ranged from 10.1 to 263.3 kg C m−2 with a mean of 94.6 and median of 90.5 kg C m−2. The long-term apparent rate of carbon accumulation (LARCA) varied between 10–45 g m−2 y−1 with an average of 28 g m−2 y−1. We found a significant negative relationship between fire frequency and LARCA. Our research indicates that fire frequency is not consistent across peatland types and increases in fire frequency will likely diminish peat C stocks. These findings provide a historical context for management decisions concerning wildland fires and their consequences for ecosystem C storage in hemi-boreal peatlands. [ABSTRACT FROM AUTHOR]

Boreal forests harbor as much carbon (C) as the atmosphere and significant amounts of organic nitrogen (N), the nutrient most likely to limit plant productivity in high‐latitude ecosystems. In the boreal biome, the primary disturbance is wildfire, which consumes plant biomass and soil material, emits greenhouse gasses, and influences long‐term C and N cycling. Climate warming and drying is increasing wildfire severity and frequency and is combusting more soil organic matter (SOM). Combustion of surface SOM exposes deeper older layers of accumulated soil material that previously escaped combustion during past fires, here termed legacy SOM. Postfire SOM decomposition and nutrient availability are determined by these layers, but the drivers of legacy SOM decomposition are unknown. We collected soils from plots after the largest fire year on record in the Northwest Territories, Canada, in 2014. We used radiocarbon dating to measure Δ14C (soil age index), soil extractions to quantify N pools and microbial biomass, and a 90‐day laboratory incubation to measure the potential rate of element mineralization and understand patterns and drivers of legacy SOM C decomposition and N availability. We discovered that bulk soil C age predicted C decomposition, where cumulatively, older soil (approximately −450.0‰) produced 230% less C during the incubation than younger soil (~0.0‰). Soil age also predicted C turnover times, with old soil turnover 10 times slower than young soil. We found respired C was younger than bulk soil C, indicating most C enters and leaves relatively quickly, while the older portion remains a stable C sink. Soil age and other indices were unrelated to N availability, but microbial biomass influenced N availability, with more microbial biomass immobilizing soil N pools. Our results stress the importance of legacy SOM as a stable C sink and highlight that soil age drives the pace and magnitude of soil C contributions to the atmosphere between wildfires. [ABSTRACT FROM AUTHOR]

Geochemical tracers have the potential to provide valuable insights for constructing conceptual models of groundwater flow, especially in complex geological contexts. Nevertheless, the reliability of tracer interpretation hinges on its integration into a robust geological framework. In our research, we concentrated on delineating the groundwater flow dynamics in the Innisfil Creek watershed, located in Ontario, Canada. We amalgamated extensive hydrogeological data derived from a comprehensive 3D geological model with the analysis of 61 groundwater samples, encompassing major ions, stable water isotopes, tritium, and radiocarbon. By seamlessly incorporating regional physiographic characteristics, flow pathways, and confinement attributes, we bolstered the efficiency of these tracers, resulting in several notable findings. Firstly, we identified prominent recharge and discharge zones within the watershed. Secondly, we observed the coexistence of relatively shallow and fast-flowing paths with deeper, slower-flowing channels, responsible for transporting groundwater from ancient glacial events. Thirdly, we determined that cation exchange stands as the predominant mechanism governing the geochemical evolution of contemporary water as it migrates toward confined aquifers situated at the base of the Quaternary sequence. Fourthly, we provided evidence of the mixing of modern, low-mineralized water originating from unconfined aquifer units with deep, highly mineralized water within soil–bedrock interface aquifers. These findings not only contribute significantly to the development a conceptual flow model for the sustainable management of groundwater in the Innisfil watershed, but also offer practical insights that hold relevance for analogous geological complexities encountered in other regions. [ABSTRACT FROM AUTHOR]

Biospheric particulate organic carbon (POCbio) burial and rock petrogenic particulate organic carbon (POCpetro) oxidation are opposing long‐term controls on the global carbon cycle, sequestering and releasing carbon, respectively. Here, we examine how watershed glacierization impacts the POC source by assessing the concentration and isotopic composition (δ13C and Δ14C) of POC exported from four watersheds with 0%–49% glacier coverage across a melt season in Southeast Alaska. We used two mixing models (age‐weight percent and dual carbon isotope) to calculate concentrations of POCbio and POCpetro within the bulk POC pool. The fraction POCpetro contribution was highest in the heavily glacierized watershed (age‐weight percent: 0.39 ± 0.05; dual isotope: 0.42 (0.37–0.47)), demonstrating a glacial source of POCpetro to fjords. POCpetro was mobilized via glacier melt and subglacial flow, while POCbio was largely flushed from the non‐glacierized landscape by rain. Flow normalized POCbio concentrations exceeded POCpetro concentrations for all streams, but surprisingly were highest in the heavily glacierized watershed (mean: 0.70 mgL−1; range 0.16–1.41 mgL−1), suggesting that glacier rivers can contribute substantial POCbio to coastal waters. Further, the most heavily glacierized watershed had the highest sediment concentration (207 mgL−1; 7–708 mgL−1), and thus may facilitate long‐term POCbio protection via sediment burial in glacier‐dominated fjords. Our results suggest that continuing glacial retreat will decrease POC concentrations and increase POCbio:POCpetro exported from currently glacierized watersheds. Glacier retreat may thus decrease carbon storage in marine sediments and provide a positive feedback mechanism to climate change that is sensitive to future changes in POCpetro oxidation. Plain Language Summary: Particulate organic carbon (POC) in rivers can come from bedrock and the biosphere. When POC produced by vegetation and soils gets buried in fjords, it can be stored for hundreds of thousands of years. In contrast, when bedrock erodes and rock organic carbon reacts with oxygen, carbon previously stored long term can enter the atmosphere as carbon dioxide. Thus, understanding the balance between these two sources of POC and their fates can help predict future carbon cycling. Here, we study POC in glacial rivers, where bedrock erosion produces rock derived POC and where soil and forests produce biospheric POC. We show how much POC comes from each source across the glacial melt season in four rivers in Southeast Alaska whose watershed range in percent glacier coverage from 0% to 49%. The watershed with the largest glacier coverage produces the most rock‐derived POC, providing evidence of the glacial source of rock‐derived carbon that can occur in Southeast Alaskan fjords. However, the most glacial watershed also carries the highest concentration of POC from the biosphere and the most sediment, suggesting that glacier rivers play an outsized role in carrying both rock‐ and plant‐derived carbon to fjords where its burial can help mitigate climate change. Key Points: Carbon isotope data show a petrogenic source contributed to glacier river particulate organic carbon (POC) entering Southeast Alaska fjordsGlacier erosion and melt increased the river petrogenic POC:biospheric POC ratio, while non‐glacial runoff lowered the ratioHeavily glacierized rivers can have high biospheric POC and sediment concentrations, implying high carbon burial potential in fjord sediments [ABSTRACT FROM AUTHOR]

Several studies have analyzed the ice margin behavior of the Quelccaya Ice Cap (QIC), Earth's largest tropical ice cap, through the Holocene. However, continuous integration of new information to produce a more cohesive history of the QIC is necessary. Here, the radiocarbon dates of 33 rooted plant specimens collected in situ along the western ice margin between 2002 and 2018 reveal the timing of its past extent as it advanced during the mid‐Holocene. The most recent evaluation of collected specimens indicates that the QIC margin advanced ∼350 m down the Challpacocha Valley between 7.1 and 4.5 ka BP. Past studies of documented ice extent on the western side of the QIC based on a variety of techniques are compiled to create a more comprehensive history of the QIC's behavior throughout the Holocene. Records of documented ice extent, as well as other proxy records, indicate a climate transition ∼5–7 ka BP that created the proper environmental conditions for the expansion of the QIC. Evidence from nearby valleys indicates that the QIC behaved similarly to the documented ice extent in the Challpacocha Valley in response to Holocene climatic fluctuations. The ability to collect the plant specimens and recent analysis of satellite imagery reveals rapid retreat rates of the western outlet glaciers from 1985 to 2020, leaving the western margin of the QIC at its smallest extent since the mid‐Holocene. Plain Language Summary: The area around the Quelccaya Ice Cap (QIC) is unique as wetland plant samples have been found preserved in their growth positions, buried by past advancing ice, whereas the ice typically removes vegetation and soil in its advance down a valley. Using the 14C dates of these plants, we map a 350‐m advance of the ice margin between 7.1 and 4.5 ka BP. Combined with a variety of previous studies involving different methods and records from ice and lacustrine sediment cores, a larger picture of the QIC's behavior comes into view. A largely accepted global climate shift between ∼7 and 5 ka BP occurred in tandem with the QIC's advance. Although the QIC has fluctuated before, at no time has the western margin receded to the current extent since the mid‐Holocene. This is indicated by the exposure of the plants and current margin retreat rates calculated from satellite imagery (1985–2020). Key Points: Mid‐Holocene advance of the Quelccaya Ice Cap (QIC) is documented using 14C dating of in situ vegetation exposed during the recent retreatPlant ages of ∼4.5 to ∼7.1 ka BP provide evidence of a mid‐Holocene climate transition and the QIC ice‐margin expansionAnalysis of satellite imagery from 1985 to 2020 documents a recent rapid retreat (∼20 m/yr) of the QIC margin [ABSTRACT FROM AUTHOR]

Abstract The Southern Ocean regulates atmospheric CO2 and Earth's climate as a critical region for air‐sea gas exchange, delicately poised between being a CO2 source and sink. Here, we estimate how long a water mass has remained isolated from the atmosphere and utilize 14C/12C ratios (Δ14C) to trace the pathway and escape route of carbon sequestered in the deep ocean through the mixed layer to the atmosphere. The position of our core at the northern margin of the Southern Indian Ocean, tracks latitudinal shifts of the Southern Ocean frontal zones across the deglaciation. Our results suggest an expanded glacial Antarctic region trapped CO2, whereas deglacial expansion of the subantarctic permitted ventilation of the trapped CO2, contributing to a rapid atmospheric CO2 rise. We identify frontal positions as a key factor balancing CO2 outgassing versus sequestration in a region currently responsible for nearly half of global ocean CO2 uptake.

Non-growing season CO2 emissions from Arctic tundra remain a major uncertainty in forecasting climate change consequences of permafrost thaw. We present the first time series of soil and microbial CO2 emissions from a graminoid tundra based on year-round in situ measurements of the radiocarbon content of soil CO2 (Δ14CO2) and of bulk soil C (Δ14C), microbial activity, and temperature. Combining these data with land-atmosphere CO2 exchange allows estimates of the proportion and mean age of microbial CO2 emissions year-round. We observe a seasonal shift in emission sources from fresh carbon during the growing season (August Δ14CO2 = 74 ± 4.7‰, 37% ± 3.4% microbial, mean ± se) to increasingly older soil carbon in fall and winter (March Δ14CO2 = 22 ± 1.3‰, 47% ± 8% microbial). Thus, rising soil temperatures and emissions during fall and winter are depleting aged soil carbon pools in the active layer and thawing permafrost and further accelerating climate change.

Foraminifera are widely used in paleoclimatic and paleoceanographic studies, providing information about past ocean conditions. However, in order to use these tracers, it is essential to obtain an accurate chronology. Radiocarbon has proven to be a powerful tool in developing robust chronologies. Sample sizes of a few milligrams of carbonate material are needed for precise radiocarbon determination using accelerator mass spectrometry (AMS). In the specific case of paleoceanographic and paleoenvironmental studies, Foraminifera microfossils are the most important indicator of oceanic conditions. However, for establishing the chronology of deposition, sample availability is often limited. In AMS facilities using solid ion sources, such as the Radiocarbon Laboratory of the Universidade Federal Fluminense (LAC-UFF), in Brazil, CO2 samples need to be converted to graphite after physical and chemical pre-treatment to remove contamination. Reducing the sample sizes increases the relative contribution of contamination and can favor increased background levels. In this work, we tested different amounts of 14C-free carbonate samples as a means to evaluate the pattern of contamination. For the sealed tube Zn/TiH2 graphitization method, we tested prebaking the graphitization tubes and compared storage procedures. As a result, the background for regular-sized samples was decreased, and accurate measurement of carbonate samples containing ca. 0.5 mg C could be performed. Prebaked graphitization tubes can safely be stored in desiccator cabinets for up to 4 weeks. Foraminifera samples with mass as low as 1 mg (ca. 0.1 mg C) can now be measured at the LAC-UFF AMS facility, provided that C contamination can be estimated and corrected. The developments presented in this work allowed for the study of species-specific Foraminifera and other small-sized carbonate samples.

Managed grasslands have the potential to store carbon (C) and partially mitigate climate change. However, it remains difficult to predict potential C storage under a given soil or management practice. To study C storage dynamics due to long-term (1952-2009) phosphorus (P) fertilizer and irrigation treatments in New Zealand grasslands, we measured radiocarbon (14C) in archived soil along with observed changes in C stocks to constrain a compartmental soil model. Productivity increases from P application and irrigation in these trials resulted in very similar C accumulation rates between 1959 and 2009. The ∆14C changes over the same time period were similar in plots that were both irrigated and fertilized, and only differed in a non-irrigated fertilized plot. Model results indicated that decomposition rates of fast cycling C (0.1 to 0.2 year-1) increased to nearly offset increases in inputs. With increasing P fertilization, decomposition rates also increased in the slow pool (0.005 to 0.008 year-1). Our findings show sustained, significant (i.e. greater than 4 per mille) increases in C stocks regardless of treatment or inputs. As the majority of fresh inputs remain in the soil for less than 10 years, these long term increases reflect dynamics of the slow pool. Additionally, frequent irrigation was associated with reduced stocks and increased decomposition of fresh plant material. Rates of C gain and decay highlight trade-offs between productivity, nutrient availability, and soil C sequestration as a climate change mitigation strategy.Supplementary informationThe online version contains supplementary material available at 10.1007/s10533-021-00838-z.

A forest bed of tree stumps currently in the intertidal zone at Girdwood, south-central Alaska, records coseismic submergence during the penultimate great earthquake. Tree-ring samples from ten spruce stumps were crossdated to develop a 149-year-long ring-width chronology. Radiocarbon wiggle-matching found that single-ring ages from the chronology were offset 28 ± 7 years older than the IntCal20 calibration curve and that the last ring of the chronology dated as 1169 to 1189 CE (781–761 cal. yr. BP) at the 95% confidence level. Bark was observed on some stumps, six samples had the same year for the last growth ring, and so this wiggle-match date is also the best estimate of the date of the penultimate great earthquake. This date is in good agreement with a date for this event in a seismo-turbidite record from Skilak Lake but not with previous dates from Bayesian models of maximum- and minimum-limiting ages from coastal salt marshes. Reanalysis of the coastal salt marsh ages with the data grouped by area, context and material found that outer wood samples from stumps at coseismic submergence sites and a Bayesian limiting age model based on just herbaceous plant ages from Turnagain Arm and the Copper River area are both consistent with our wiggle-match date. Furthermore, coseismic emergence ages from Cape Suckling and Yakataga are older than the penultimate earthquake and so likely relate to an earlier uplift event in this eastern area. The rupture extent during the penultimate great earthquake appears to have been less than in the 1964 great earthquake and the interseismic interval between these two events was 785 ± 10 years.

In 2015-2017, East Jutland Museum excavated a series of well-preserved prehistoric and early historic trackways at Kastbjerg Å in the Kastbjerg Å river valley (eastern Jutland, Denmark). In this article, we will present the earliest of the in situ preserved structures, the Middle Neolithic trackway A20, and the high-precision dating of this structure. Dendrochronological dating of wood sequences provides very precise ages for archaeological timbers from buildings or structures, such as bridges or ships. This is not possible, however, when the dendrochronological samples lack sapwood, if the wood sequence has too few rings to provide definite placement on the dendrochronological master curve, if the wood sequence falls outside the range of the master curves or if the species of wood is not suitable for dendrochronological analysis. Here, we date a wood sequence of an alder tree from trackway A20 using the radiocarbon wiggle-match method to 2911 ±5 BC. The function of the trackway and the significance of the Neolithic river crossing at the Kastbjerg Å site are discussed in the light of European parallels and the regional cultural context.

Abstract The East Sea (also known as the Japan Sea) is connected to the Northwest Pacific via shallow straits and has independent deep water circulation, as a model miniature ocean. The radiocarbon age of dissolved organic carbon (DOC) in the East Sea ranged from 2,000 to 3,700 years, exceeding the water turnover time (∼100 years). The oldest DOC was found in the subsurface layer characterized by the Tsushima Warm Water. Comparison of the radiocarbon content and concentration of DOC in the East Sea to those in the ocean suggests that aged DOC was transported conservatively from the Northwest Pacific to the East Sea via the shallow Tsushima Warm Current. The fractions of DOC released by serial‐oxidation of the oldest DOC sample had identical radiocarbon ages, implying that refractory DOC was produced in situ and added to the DOC pool in the East Sea.