bluuebunny/crossref_metadata_2025 huggingface dataset:
Anthropogenic Carbon in the Arctic Ocean: Perspectives from different TTD Approaches and Tracer Pairs
Authors: Raimondi Lorenza , Wefing Anne-Marie , Casacuberta Arola Núria
Published: February 2023

At present, it is well-known that the fast increase in atmospheric carbon dioxide (CO2) concentrations resulting from human activities (Cant), drives the dramatic changes observed in our environment such as global warming and ocean acidification. The Arctic Ocean has been identified as one of the fastest-changing regions of the world ocean and can therefore be considered as a sentinel for future global scenarios.Here, Cant-rich waters coming from the Atlantic Ocean become isolated from the atmospheric input of CO2 as they flow at an intermediate depth below the mixed layer, making the Arctic Ocean a key region for intermediate-to-long-term storage of Cant. Despite having such an important role, the magnitude of the Cant inventory and its change over time in the region is yet not fully understood, particularly if we are to consider future changes in ice coverage and therefore ocean circulation.A way of estimating oceanic Cant inventories is by applying the so-called Transit Time Distribution (TTD) method, which implies the use of transient tracers such as the anthropogenically produced CFC-12 and SF6.In this work we present a new estimate of Cant inventory for the Arctic Ocean in 2015 assessed with the TTD method using both well-established tracers (CFC-12 and SF6, both having a global source) as well as novel ones (anthropogenic radionuclides 129I and 236U, both having primarily a point-like source represented by European nuclear reprocessing plants, as well as a global one represented by the global fallout from nuclear bomb testing).The TTD was here applied following a relatively novel approach to infer the statistical parameters that describe the age distribution within a water sample, the mean (G) and the width (D). Unlike the “classical TTD” approach, the one used in this study allows the statistical parameters of the TTD to be constrained for each individual sample rather than finding values that are most representative of the region and time studied. We first show a comparison of the two TTD approaches by comparing mean and mode ages as well D/G ratios of this study (new TTD method) to those presented in Rajasakaren et al. 2019 (classical TTD method), using CFC-12 and SF6 as our tracers’ pair. We then compare TTD results obtained from the two tracers’ pairs, CFC-12/SF6 and 129I-/236U, using the new TTD method.Finally, we estimate and compare Cant concentrations and inventories obtained with the two pairs of transient tracers to one-another as well as to previous estimates of Cant in the region by Rajasakaren et al (2019) obtained with the “classical TTD”. This study demonstrates for the first time the feasibility of using anthropogenically produced radionuclides with input functions and chemical properties different than CO2 as proxies for Cant estimates.  
Improving SO2 emissions over the Middle East.
Authors: Ukhov Alexander , Stenchikov Georgiy
Published: February 2023

The Middle East is one of the most polluted regions on Earth. Besides strong natural air pollution caused by frequent dust storms, anthropogenic emissions of SO2 from power and desalination plants significantly deteriorate air quality and, as a consequence, reduce life expectancy. Additionally, sulfate aerosol formed through the chemical oxidation of SO2 has an effect on climate and cloud formation. Therefore, accurate modeling of SO2 emissions is crucial, especially in such harsh conditions as the Middle East.In this work, we attempt to improve existing SO2 emissions using inversion modeling, a high-resolution regional WRF-Chem model, and satellite observations of SO2 columns available from OMI and TOMS instruments. Obtained SO2 emission dataset is planned to be open to the community.
A comparison of methods for gap-filling sensible and latent heat fluxes in different climatic conditions
Authors: Rinne Erkka , Vekuri Henriikka , Tuovinen Juha-Pekka , Aurela Mika
Published: February 2023

Eddy covariance flux measurements need to be gap-filled when utilising the data for the calculation of annual balances. The measurement technique itself is prone to errors and technical failures may also lead to gaps of various lengths. Gap-filling of the flux time series is typically based on estimating statistically representative values based on various environmental variables through linear regression, lookup tables or machine learning methods.A large number of methods for the imputation of energy fluxes have been applied and compared in recent literature (Zhu et al. 2022; Mahabbati 2022; Khan, Jeon, and Jeong 2021; Foltýnová, Fischer, and McGloin 2019). Both latent and sensible heat fluxes are strongly driven by the incoming solar radiation, and it is usually used as an independent variable in gap-filling models. Vekuri et al. showed that a widely used method for gap-filling carbon dioxide fluxes creates a systematic bias in northern ecosystems, where the distribution of incoming radiation is highly skewed.Here, we assess if a similar bias error emerges for sensible and latent heat fluxes after gap-filling with the standard methods or suggested alternatives. We use global data from openly available flux measurement databases and compare the bias and other metrics between different latitudes. We assume that the errors in total energy balances are not as significant as in carbon budgets, but the results could still indicate which methods should be preferred when complete time series of energy flux data are needed. ReferencesFoltýnová, L., M. Fischer, and R.P. McGloin, ‘Recommendations for Gap-Filling Eddy Covariance Latent Heat Flux Measurements Using Marginal Distribution Sampling’, Theoretical and Applied Climatology, Vol. 139, No. 1–2, September 11, 2019, pp. 677–688.Khan, M.S., S.B. Jeon, and M.-H. Jeong, ‘Gap-Filling Eddy Covariance Latent Heat Flux: Inter-Comparison of Four Machine Learning Model Predictions and Uncertainties in Forest Ecosystem’, Remote Sensing, Vol. 13, No. 24, January 2021, p. 4976.Mahabbati, A., ‘Investigating the Application of Machine Learning Models to Improve the Eddy Covariance Data Gap- Filling’, The University of Western Australia, 2022.Vekuri, H., J.-P. Tuovinen, L. Kulmala, D. Papale, P. Kolari, M. Aurela, T. Laurila, J. Liski, and A. Lohila, ‘A Widely-Used Eddy Covariance Gap-Filling Method Creates Systematic Bias in Carbon Balance Estimates’, Scientific Reports, forthcomig.Zhu, S., R. Clement, J. McCalmont, C.A. Davies, and T. Hill, ‘Stable Gap-Filling for Longer Eddy Covariance Data Gaps: A Globally Validated Machine-Learning Approach for Carbon Dioxide, Water, and Energy Fluxes’, Agricultural and Forest Meteorology, Vol. 314, March 1, 2022, p. 108777.
Projection of Snow droughts under climate change scenarios in the Urmia Lake basin
Authors: Habibi Maral , Babaeian Iman , Schöner Wolfgang
Published: February 2023

Abstract Mountains are a crucial water source, especially for the mountainous catchments in arid and semiarid regions. Climate Change is a severe hazard to mountain regions as global temperatures rise and snowpack melt. Snowmelt more effectively infiltrates the subsurface than rainfall. So, more rain, less snow, and early snow melting could significantly impact the groundwater levels in mountainous systems. In arid and semiarid mountainous regions, surface water resources are generally limited, and groundwater is critical for water supply due to local accessibility and high reliability during drought.Urmia lake as a mountainous catchment has recently faced extreme droughts, and since snow is a significant part of the precipitation in this region, understanding the impact of climate change on snow changes and spatiotemporal projection of the snow-covered surface and the impact of these changes is vital.For this purpose, in our study, snow drought index of SMRI (Snow-Melt Runoff Index) over ULB were projected using the statistically downscaled runoff output of CMIP6 global climate models under the SSPs scenarios of SSP1-2.6, SSP2-4.5, SSP5-8.5. To remove model bias over the catchment, historical runoff retrieved from CMIP6 models have been compared with ERA5 runoff Output. Based on our results, more frequent, longer lasting, and stronger drought events are projected in the catchment. The findings of this study could be further used for future water management in the catchment.Keywords: Urmia Lake, Mountainous catchments, CMIP6, SSP scenarios, Snow drought projection
Common mechanisms of centennial-scale AMOC variability in CMIP6 models
Authors: Mehling Oliver , Bellomo Katinka , von Hardenberg Jost
Published: February 2023

It has been hypothesized that climate variability on centennial timescales – in the North Atlantic region and beyond – is linked to unforced variability of the Atlantic Meridional Overturning Circulation (AMOC). Because of the presence of external forcings, uncertainties in proxy reconstructions of the AMOC and the short observational record, coupled climate models represent a key tool in assessing low-frequency AMOC variability. However, sufficiently long pre-industrial control (piControl) simulations with state-of-the-art climate models have only become widely available during the past decade. While significant centennial-scale AMOC variability has been identified in several single-model studies, proposed physical mechanisms differ considerably.Here, we assess mechanisms of AMOC variability on centennial timescales in the CMIP6 multi-model piControl ensemble. We find that a relatively large number of models – 11 out of the 15 analyzed – exhibit a statistically significant mode of centennial-scale MOC variability in the Atlantic. We review previously proposed mechanisms for centennial-scale AMOC variability and test whether their key elements are present in the CMIP6 ensemble.We find that salinity exchanges between the Arctic and North Atlantic basins, which have previously been proposed as drivers of multi-centennial AMOC variability in two CMIP6 models (IPSL-CM6A-LR and EC-Earth3), can also be identified in other CMIP6 models using the same ocean component (NEMO). However, we find only a weak or no signature of this mechanism in models that do not include NEMO. Even among NEMO models, the amplitude and timescale of centennial-scale AMOC variability is model-dependent, and we assess the relative role of deep-water formation sites in shaping these differences. Because AMOC fluctuations are linked to surface temperature anomalies and related impacts over land, our results motivate the need for more paleoclimate evidence at sub-centennial resolution, which would help constrain the CMIP6 inter-model spread in centennial-scale AMOC variability.
Validation of Boreas: an instrument for simultaneous measurement of amount fraction and stable isotope ratios in methane
Authors: Yeo Cameron , Rennick Chris , Safi Emmal , Arnold Tim
Published: February 2023

Methane (CH4) is the second most important anthropogenic greenhouse gas in terms of its impact on climate to date and its current rates of emissions. It has a wide variety of emission sources including agriculture, landfills and fossil fuel combustion alongside a short atmospheric lifetime, making it a justifiable short-term target of emissions mitigation strategies. To aid the global drive on reducing emissions, it is integral to quantify emissions estimates for the validation of CH4 inventories. Each source of CH4 is identified by distinct isotopic ratios which proves a useful appliance in the sectoral division of amount fraction measurements.We have developed Boreas, an automated preconcentrator sample preparation system coupled to an infrared laser spectrometer, capable of making hourly measurements of δ13C(CH4) and δ2H(CH4) of ambient air samples. Deployed at National Physical Laboratory’s atmospheric monitoring site in May 2021, Boreas makes continuous, high-frequency hourly measurements capable of capturing pollution events.As concentration calibration and linearity has been verified using synthetic mixtures, we present a method of validation of Boreas measurements, comparing them to simultaneous one-minute-average measurements made by cavity-ring down spectroscopy. We use Keeling and Miller-Tans analysis to examine the source signature δ13C(CH4) and δ2H(CH4) of local pollution events, distinguishing agricultural sources from northern hemisphere background. We will show that the calibrated concentration reported by Boreas agrees with that of a Picarro G2401 making simultaneous measurements over a wide range of ambient background and polluted air. Moreover, we will show that the preconcentration step has no concentration dependence e.g., breakthrough or carry over.
Estimation of transmissivity across the conterminous US using large water table and surface water datasets
Authors: Luijendijk Elco , Bresciani Etienne
Published: February 2023

The transmissivity of the subsurface controls groundwater flow but is highly variable and often uncertain. Here we use large datasets of groundwater level measurements and surface drainage to calculate transmissivity for 5000 points in the conterminous US. We designed a new algorithm that uses water table data, elevation and surface water location data to reconstruct the groundwater flow path, the groundwater discharge location and the groundwater divide for each data point. We subsequently calculate the ratio of recharge over transmissivity for each point using an analytical solution of the groundwater flow equation. Finally, we use independent estimates of groundwater recharge to estimate transmissivity. The results demonstrate the viability of combining large sets of water level data to quantify the spatial distribution of transmissivity. The algorithm will be published as an open-source code that can be used to automatically find groundwater flow paths and estimate transmissivity for large water level datasets.
Can the atmospheric aerosol impact on the functioning of a peatland?
Authors: Harenda Kamila , Markowicz Krzysztof , Poczta Patryk , Stachlewska Iwona , Bojanowski Jędrzej , Czernecki Bartosz , Mac Arthur Alasdair , Schüttemeyer Dirk , Chojnicki Bogdan
Published: February 2023

The productivity of terrestrial ecosystems is determined, among other things, by solar radiation and its degree of scattering can increase or reduce it. The intensity of scattering is determined by the optical properties of the atmosphere due to the presence of particles suspended in the atmosphere, i.e. clouds and aerosols. Additionally, the amount of these substances and also the physical properties affect the radiation transfer and thus the plants ability of CO2 absorption. In the presented research, an attempt to quantify the impact of the different types of aerosols presence in the atmosphere on the amount of gross ecosystem production (GEP) in a transitional peatland in northwestern Poland was made. Three classes of cloudiness were assumed in the simulations: cloudless, medium and full cloud conditions, and an atmosphere-ecosystem model was used to assess the peatland productivity under these conditions. It was found that changes in the physical parameters of aerosols in the atmosphere can both increase and decrease the amount of CO2 uptake by peatlands by up to 8.2% and 6%, respectively. Thus, the research is extremely relevant to the global carbon balance, as peatlands are one of the largest reservoirs of organic carbon in the biosphere.
An asymmetric change in circulation and nitrate transports around the Bay of Bengal
Authors: Jardine Jenny , Wakelin Sarah , Holt Jason , Katavouta Anna , Partridge Dale
Published: February 2023

The Bay of Bengal is a dynamic region that experiences intense freshwater runoff, extreme meteorological events, and seasonal reversing surface currents. The region is particularly susceptible to anthropogenic climate change, driven in part by large air-sea fluxes, persistent freshwater stratification, and low overturning rates. Predicting how this ecosystem is likely to change in the future is paramount for planning effective mitigation strategies. Using a relocatable, coupled physics-ecosystem model (NEMO-ERSEM), we investigate the future changes in surface circulation and coastal nitrate pathways in the Bay of Bengal from 1980 to 2060, using a “business-as-usual" (RCP 8.5) climate change scenario. We find that future surface currents during the Summer and Fall Inter-monsoon seasons are reduced in the north/north-eastern Bay and strengthened in the south-western Bay. Coastal nitrate transports around the Bay mirror this asymmetric change, with coastal nitrate transports at 17.5oN decreasing by 185.7 mol N s-1, despite increased riverine runoff from the Ganges and Irrawaddy River systems. This results in a positive feedback loop whereby the northern Bay becomes progressively fresher and more nutrient-rich, strengthening the barrier layer and increasing the risk of toxic algal blooms and eutrophication events. Conversely, in the south-western Bay (12oN), coastal nitrate transports increase by 1317.8 mol N s-1, driven primarily by an intensified Sri Lanka Dome, that promotes localised diatom blooms despite negligible changes in regional river runoff. This work highlights the need for more rigorous ecosystem modelling and future scenario testing. 
The occurrence and distribution of microplastics in epipelagic zone of the western Indian Ocean
Authors: Baek Eun-Ran , Kim Minju , Kang Dong-Jin , Kang Jung-Hoon
Published: February 2023

This study investigated the occurrence and distribution of microplastics utilizing zooplankton samples collected in the Western Indian Ocean because there is no information concerning epipelagic zone in the open ocean. We collected microplastics from three water layers [surface mixed layer(SML), middle layer(ML), lower layer(LL)] within 200 m using a Multiple Opening/Closing Net and Environmental Sensing (opening: 1 ㎡) at 22 stations of 1 degree interval between 5°N and 16°S along the 67°E of Western Indian Ocean in 2017. The microplastics were consistently found in almost all samples and the microplastic abundance ranged between 0.00-2.01 particles/㎥ from the 3 layers. And the average microplastic abundance was highest in the lower layer (0.30±0.09 particles/㎥) and lowest in middle layer (0.26±0.08 particles/㎥). The percentage of fiber was highest in the SML (55.7%) and the LL (45.9%), and the percentage of film was highest in ML (46.8%). The microplastic abundance in the size of 1.0-5.0 ㎜ was highest in SML (42.0%), while the abundance in the size of 0.2-0.5 ㎜ was highest in ML(56.8%) and LL(54.5%). The stations can be divided into four sections including upwelling characterized by Seychelles-Chagos Thermal Ridge (SCTR) based on the 20℃-isotherm depth (D20). The average microplastic abundance was the highest in SML (0.23±0.06 particles/㎥) in 1°S~5°S, and in LL (0.50±0.25 particles/㎥) at latitudes of 10°S~16°S and in LL (0.32±0.16 particles/㎥) at latitudes between 5°N~EQ. However, the average microplastic abundance at latitudes of 6°S ~9°S corresponding to the upwelling zone was highest in the ML (0.65±0.38 particles/㎥) with the high percentage of film (68.7%). Cluster analysis by microplastics occurred in each water layers showed that the stations were divided into 3 groups in each layer. Groups in SML and LL were mainly clustered by fiber, whereas groups in ML was mainly clustered by film, which was associated with the upwelled region of Seychelles-Chagos Thermal Ridge (SCTR). Fourier transform infrared spectroscopy analysis showed that the main types of microplastics were dominated by fiber (40.6%) and film (73.2%) characterized by polycarbonate. Present results showed that meridional and vertical distribution of microplastics in the epipelagic zone varied with the physical characteristics of upwelling zone characterized by Seychelles-Chagos Thermal Ridge (SCTR) in the Western Indian Ocean.
Self-consistent Reconstructions of the Earth's Mantle in Space and Time using Nonlinear Rheologies
Authors: Ghelichkhan Sia , Davies Rhodri
Published: February 2023

Reconstructing the spatial and temporal evolution of Earth’s mantle through the recent geological past stands as one of the grand challenges in Geodynamics. One method to invert for the mantle’s evolution is to reformulate mantle flow as an optimisation problem using the adjoint method, where uncertain properties, such as the mantle’s previous thermo-chemical states, are found by minimising a misfit functional that represents the difference between model predictions and geodynamic inferences from various disciplines, including seismology, geodesy, and geochemistry. While the rapid growth in high-performance computing capacities has underpinned an ever-growing number of such reconstruction models, they often make several simplifying physical assumptions, or are limited in the number of assimilated datasets, thus limiting their applicability.Here we present our latest attempts at reconstructing the evolution of Earth’s mantle using complex non-linear rheologies. Our approach builds upon a novel algorithmic differentiation method as implemented in dolfin-adjoint, together with state-of-the-art optimisation methods, developed using the Rapid Optimisation Library. Using analytical and synthetic examples, we show that the self-consistent derivation of the adjoint equations in our approach provides a pathway for accurate inversions for past-mantle flow.
Rapid streamflow monitoring with drones
Authors: Westerberg Ida , Mansanarez Valentin , Lyon Steve , Lam Norris
Published: February 2023

Accurate and reliable streamflow monitoring data are urgently needed for many new locations to tackle the on-going climate emergency, where we now see increasingly severe impacts on society from extreme flows. Yet, traditional river monitoring methods depend on empirical rating-curve methods for which it typically takes many years or decades to obtain reliable data, in particular for extreme flows. This gap between increasing needs and current monitoring capabilities calls for new methods to be developed.Drones provide an unprecedented ability to measure both the physical and hydraulic characteristics of a river in an efficient manner. Topography, water surface slope, surface water velocity and even bathymetry can be derived from drone images and drone lidar data. We exploited this potential by incorporating drone data into the framework for Rating curve Uncertainty estimation using Hydraulic Modelling (RUHM). The RUHM framework combines a one-dimensional hydraulic model with Bayesian inference and together with drone data it allows us to efficiently estimate a reliable rating curve and its associated uncertainty based on as few as three gaugings.We present our results from applying RUHM to Swedish gauging stations where we model rating curves and streamflow based on drone data. We primarily used low-cost camera drones to collect both the input (DEM, vegetation, bathymetry) and calibration data (water surface slope, surface velocity) for the hydraulic model, but also tested the capabilities of drone lidar data. Our aim was to estimate reliable rating curves with RUHM based only on data from the drone flights. We assessed the uncertainty in the drone-derived model input and calibration data compared to traditional fieldwork techniques, as well as their impact on the RUHM-modelled rating curves and streamflow results.We find that careful planning of when to fly the drone is important for obtaining good-quality model input and calibration data. Using a combination of drone camera and drone lidar data we were able to obtain all the data needed for RUHM from the drone flights. Extreme low and high flows were reliably modelled with RUHM with constrained uncertainty based on as few as three low and middle flow gaugings, without the need for gauging extreme flows. We conclude that using RUHM with drone data is an efficient and promising alternative to traditional streamflow monitoring methods, being much less time-consuming and costly, as well as involving fewer risks to field staff.
Present and projected humid heat exposure and precipitation extremes in Turkey
Authors: Donmez Berkay , Donmez Kutay , Yuruk Sonuc Cemre , Unal Yurdanur
Published: February 2023

Regional intensification of precipitation extremes and the emergence of humid heat stress conducive to periling vulnerable populations suggest the need for further nation-specific risk assessments. Here, we conduct the first analysis of present and projected population exposure to extreme wet-bulb temperature (Tw) values in Turkey and concurrently use the generalized extreme value (GEV) theory to model extreme precipitation based on multiple intensity, duration, and frequency metrics. Using simulations dynamically downscaled to 0.11-degree resolution via the COSMO-CLM model, we provide a nationwide picture of the trends in these metrics and derive the number of people exposed to Tw extremes based on the population estimates in the Shared Socioeconomic Pathways (SSPs) under the high-emission RCP 8.5 scenario. As part of the GEV analysis, our main goal is to show how precipitation extremes in Turkey evolve and transform due to the changing climate not only in stationary but also in non-stationary climate settings. Our results convey a detailed understanding of the potentially dangerous conditions across climatologically different regions of Turkey and are relevant for decision-makers.
Seasonal and interannual variations in evapotranspiration and energy budget over a rainfed maize field in the Chinese Loess Plateau
Authors: Zheng Han , Sun Yuchen
Published: February 2023

Evapotranspiration (ET) is an important part of surface hydrological cycle and energy exchange process. Under the background of frequent drought and water resource shortage, it is of great significance to study the seasonal and interannual variations in ET and energy budget of farmland ecosystem in arid regions. This will help to reveal the process of crop ET and water consumption in farmland ecosystems and its response to drought conditions and environmental factors. Based on continuous eddy-covariance observation data, this study analyzed the seasonal and interannual variations in ET and energy budget of one maize farmland ecosystem in the semi-arid region of Chinese Loess Plateau and its response to environmental changes during 2019-2020. Results showed that ET and meteorological factors presented obvious seasonal and interannual changes during the study period. The annual total ET was 339.3 mm/yr and 386.5 mm/yr during the drought year 2019 and the normal year 2020, respectively. It was 16.4% and 30.4% lower than the annual total precipitation (P) in the same period. The ET/P ratio for two years was 0.84 and 0.70, respectively. While the latent heat flux and sensible heat flux showed obvious seasonal and interannual variation trends, it also reflected that the latent heat flux dominated the net radiation energy budget in the growing season and the sensible heat flux is the main consumption component of the net radiation energy budget in the non-growing season. During 2020, due to better moisture conditions, the Bowen ratio was smaller and sensible heat exchange was more moderate, making the air more stable. The volatility of albedo in 2020 was significantly greater than that in 2019, which was closely related to the frequent precipitation in the normal year. The results of the path analysis model showed that soil water content (SWC) had stronger impacts on the ET variation during the drought year (2019) at the scales of entire year, growing season and non-growing season. Meanwhile, leaf area index (LAI) had more significant impacts on the ET variation during the hydrologically normal year (2020) when the water supply was much more sufficient. We also found that there was a strong coupling relationship between the atmosphere and vegetation during the study period (decoupling factor Ω varied between 0 and 0.5), indicating that the ecosystem ET is mainly controlled by canopy conductance(gs) and vapor pressure deficit (VPD). Moreover, gs decreased with the increase of VPD, and VPD played a stronger role in controlling gs during 2020 which was with better water supply condition.
Atmospheric radon measurements to assess the relative representativeness of radon flux models
Authors: Kikaj Dafina , Chung Edward , Saba Mareya , Karstens Ute , Manning Alistair , Rennick Chris , Ganesan Anita , Foster Grant , O’Doherty Simon , Wenger Angelina , Arnold Tim
Published: February 2023

The unique physical and chemical characteristics of radon make it an excellent tracer of atmospheric mixing and transport processes. As such, it has long been a species of interest to the climate change research communities. However, reliable, high resolution radon flux maps are essential for the use of atmospheric radon in climate studies.Validation of the existing radon flux maps and inventories is currently limited by the availability of systematic measurements of radon fluxes and other process-relevant parameters (e.g., physical characteristics and moisture content of soil). Localised measurements of radon flux, soil moisture and soil physical properties can provide some information to validate and improve flux maps.  On the other hand, high sensitivity atmospheric radon measurements in conjunction with atmospheric transport models would determine the relative representativeness of radon flux models over larger scales.To tackle the validation of radon flux maps, atmospheric radon measurements were compared to the results of modelled radon concentrations calculated using the Lagrangian particle model, the Met Office Numerical Atmospheric Modelling Environment (NAME) and two available versions of European radon flux maps1. For this purpose, radon data from three UK greenhouse gases atmospheric monitoring stations located in Heathfield (an inland, 100 m tall tower), Tacolneston (an inland, 185 m tall tower), and Weybourne (a coastal site, 10 m tower) were used. The differences between measured and modelled radon concentrations on diurnal and monthly scales will be presented and discussed. The ratio of measured-modelled radon concentrations shows the potential to objectively assess the reliability of radon flux maps under different wind directions and atmospheric mixing conditions.  1 2015: doi:10.1594/PANGAEA.854715 and 2022: ICOS data search (icos-cp.eu).
The signature of heavy halogens across the evolution of a Sn-W-Cu mineralized system: a fluid inclusion study
Authors: Bongiovanni Mauro , Fusswinkel Tobias , Marks Michael
Published: February 2023

The recent need of a green-energy transition has sparked even more interest on critical elements such as tungsten and tin, whose genesis in ore deposits is linked to fluids exsolving from granitic plutons, but some mechanisms of formation remain unclear. Most authors in the past have proposed the mixing with meteoric, metamorphic or basinal fluids to be critical, while others believe that these deposits can form by simple cooling of magmatic fluids.Given the modern advances in analytical techniques, it is nowadays possible to characterize fluid inclusions in-situ also for trace elements such as bromine and especially iodine with the LA-ICP-MS. This study aims to apply a novel technique of measuring Br/Cl and I/Cl in individual fluid inclusions and bring some new insights on the Sn-W ore deposits genesis from a different perspective. In fact, halogens are well known to be highly incompatible in most minerals, retaining the fluid source reservoir signature, and to behave conservatively in fluid-rock interaction, therefore they can be regarded as suitable tracers for fluid evolution. These characteristics make heavy halogen studies particularly suitable for tackling the open question on the formation of Sn-W mineralized systems.The study area is the well-studied Cornubian batholith, in south-west England, which has been extensively mined in the past mostly for tin, copper and tungsten. It consists of 5 types of granites, divided into two main fractionation series, and cross-cut by mineralized veins rich in cassiterite, Cu-sulphides and W-oxides (among others), outcropping mainly in proximity of the contacts with the country rock.Despite significant mineralogical variation across the samples, representing different stages of the transition from magmatic to hydrothermal environments, halogen ratios are relatively homogeneous, especially under the hydrothermal regime, with magmatic fractionation as the only candidate process for a shift to higher Br/Cl and I/Cl values. On the other hand, alkalis and metals in fluid inclusions display variations of several orders of magnitude, with Li and B peaking in pegmatites and base metals being particularly abundant in the magmatic stage.These results suggest that even moderate changes in P-T conditions (from granitic stage to low-T mineralisation) do not affect significantly the halogen signature of the evolving fluids in the Cornubian batholith. Additionally, given the linear relation between fluid salinity and alkali/metal content, it can be postulated that meteoric water is the main diluting agent throughout the evolution of the system, as mixing with metamorphic fluids or basinal brines would also significantly change the halogen signatures. 
Influence of gross primary productivity and soil carbon content on soil CO2 efflux in dry grasslands
Authors: Balogh János , Fóti Szilvia , de Luca Giulia , Mészáros Ádám , Pintér Krisztina , Nagy Zoltán
Published: February 2023

Soil respiration of grasslands is highly variable both in time and space reflecting the topographic characteristics, the changing environmental constrains and biological activity of the vegetation. The aim of this study was to describe the effect of gross primary productivity (GPP) and soil organic carbon content (SOC) on soil respiration under varying environmental conditions in a dry grassland site in Hungary. We made spatially explicit measurements of variables including soil respiration, aboveground biomass, green vegetation index, soil water content, and soil temperature during an 8-year study in the vegetation periods. Sampling was conducted 23 times in 80 x 60 m grids of 10 m resolution with 78 sampling points. Altitude, slope, and soil organic carbon were used as background factors at each sampling position. Site-level GPP data were derived from eddy-covariance measurements and used for the estimation of GPP at every sampling position as a weighted metric on the basis of the biomass and green vegetation index of the positions. Data were analyzed using generalized additive models (GAM). Spatially, soil respiration had negative correlation with soil temperature, altitude and slope, while it was positively correlated with soil water content, aboveground biomass, green vegetation index and SOC. Soil respiration was significantly different between SOC groups (low-medium-high carbon content), mean soil respiration increased with soil carbon content. According to the GAM analysis, the shape of the GPP response was almost linear in each SOC groups and GPP had a strong influence on soil respiration in all of the groups besides temperature and soil water content. The results suggest that GPP and the resulting belowground carbon allocation affecting mainly the autotrophic components of soil respiration have similar influence on soil respiration as the main environmental variables.
A process-oriented model evaluation using EURECA water isotope field observations in the North Atlantic trades reveals the imprint of the atmospheric circulation at different scales
Authors: Aemisegger Franziska , Villiger Leonie
Published: February 2023

Shallow clouds, ubiquitous in the trade-wind region, substantially contribute to the cooling of the Earth's climate through their shortwave radiative effect. Their response to climate change is unclear, contributing to a large part of the uncertainty of climate projections. The cloud fraction at cloud base, in particular, has been identified as a key parameter for the spread of modelled feedback of these clouds to climate change. Therefore, understanding the processes controlling the variability of cloudiness at cloud base is of utmost importance. Stable water vapour isotopes reflect the integral of moist atmospheric processes encountered by the vapour since evaporation from the ocean surface. This study focuses on stable water isotopes variability from aircraft observations with the French ATR research aircraft and high-resolution isotope-enabled simulations in the winter trades near Barbados at cloud base. Nested convection resolving COSMOiso simulations at 10, 5 and 1 km grid spacing during the EUREC4A field experiment period are used, which have been thoroughly evaluated using observations from different platforms. The three main findings are: (i) contrasting isotope and humidity characteristics in clear-sky versus cloudy cloud base environments emerge due to vertical transport on time scales of 12 hours, which (ii) are associated with local, convective circulations, and show a clear diel cycle; (iii) the cloud base isotope signals are, in addition, sensitive to variations in the large-scale circulation on time scales of several days, which shows on average a Hadley-type subsidence but occasionally much stronger descent related to extratropical dry intrusions. This investigation, based on stable water isotopes in high-resolution simulations in combination with trajectory analyses reveals, in a physically plausible way, how dynamical processes at different scales act in concert to produce the observed humidity variations at the cloud base of trade wind cumuli.
Flank collapse, sediment failure and flow-transition: the multi-stage deposition of a volcanic sector collapse offshore Montserrat, Lesser Antilles
Authors: Kühn Michel , Berndt Christian , Krastel Sebastian , Karstens Jens , Watt Sebastian , Kutterolf Steffen , Huhn Katrin , Freudenthal Tim
Published: February 2023

Volcanic sector collapses generated some of the most voluminous mass transport deposits on Earth and triggered devastating tsunamis with numerous casualties. The associated sector collapse deposits occur around many volcanic islands all over the world. The shelf around the volcanic island of Montserrat (Lesser Antilles) and the adjacent Montserrat-Bouillante-Graben host more than ten surficial or buried landslide deposits with most of them classified as volcanic debris avalanche deposits by previous studies. The most intensively studied deposit (Deposit 2) is associated with a landslide that occurred at ~ 130 ka and comprises a volume of 10 km³, including remnants of the volcanic flank and secondarily mobilized seafloor sediments. Here, we present new 2D and 3D seismic data as well as MeBo drill core data from Deposit 2 that reveal multi-phase deposition including an initial blocky volcanic debris avalanche followed by secondary seafloor failure and a late- erosive event. Late-stage erosion is evidenced by a channel-like incision on the hummocky surface of Deposit 2 about 15 km from the source region. Erosional incisions into the top of sector collapse deposit have also been reported from Ritter Island, Papua New Guinea – the only other volcanic landslide deposit that was studied at similarly high resolution. This may imply that late stage erosive turbidites are a common process during volcanic sector collapse. This requires geological and oceanographic processes that can create high flow velocities close to the source of the collapse area leading to a late down-slope acceleration of sediments that were suspended in the water column.
Assessment of changes in wood anatomical traits to forecast drought-induced dieback in Mediterranean oak forests
Authors: Colangelo Michele , Rita Angelo , Borghetti Marco , Camarero J. Julio , Sánchez-Salguero Raúl , Matias Luis , Pericolo Osvaldo , Ripullone Francesco
Published: February 2023

Some tree species have shown to be very vulnerable to drought and heat waves in the Mediterranean Basin, causing a loss of important socio-economic and ecosystem forest services.  In this regard, oaks are important but vulnerable species which are showing losses in terms of productivity and growth and rising mortality rates. Dendroecological studies using retrospective analysis of wood anatomical traits and tree rings have demonstrated their potential to assess long-term patterns of growth and vigor in several Mediterranean oak species. Moreover, the long-term reconstruction of wood anatomical traits such as transversal lumen area, allows investigating hydraulic adjustments of trees through time.In this study, we reconstructed changes in wood anatomy for a 38-year long period (1980-2017) to investigate how drought impacted the hydraulic functionality and triggered dieback in five ring-porous oak species from Italy and Spain (Quercus robur, Quercus frainetto, Quercus cerris, Quercus canariensis, Quercus pubescens). We compared non-decaying (ND) and decaying (D) coexisting trees of each species showing low and high defoliation levels, respectively. We analyzed earlywood anatomical traits (vessel area, hydraulic diameter, vessel density, theoretical hydraulic conductivity, etc.) in these species and analysed them considering a ranking of increasing drought tolerance: Q. robur, Q. frainetto, Q. cerris, Q. canariensis, and Q. pubescens.We observed differing growth patterns and xylem conduit area responses in D trees compared with ND trees. The D trees formed narrower EW vessels than ND and the Dh were lower in D trees compared with ND trees. We discuss the relationships between radial growth, changes in wood anatomy and hydraulic functioning of trees focusing on those proved more sensitive to growth decline and mortality in order to highlight the climatic triggers of dieback in ring-porous oak species as related to hydraulic failure.
Stockwater - Advances in reservoir stock monitoring from space
Authors: Peña Luque Santiago , Nicolas Gael , Yesou Herve , Ledauphin Thomas , Amzil Sabrine , Maxant Jerome , Ferrant Sylvain , Grippa Manuela , Ribeiro Afredo , Bailly Jean Stéphane , Molenat Jerome , Puech Fabien , Reis Rafael
Published: February 2023

Dams are strategic tools for countries and their management of water resources. Within the Space for Climate Observatory (SCO) initiative and SWOT Downstream program, the StockWater project aims to put in place a system for monitoring water volume in dams. It is based on satellite data, and a specific processing system, thereby facilitating the work of the public authorities in this area.Water resources monitoring, including surface and groundwater, is a vital issue for governments and public institutions. Water resources are essential for society and economic activity (drinking water, irrigation, hydroelectricity, industry, flood control) and for natural and water ecosystems.Generally, reservoir stock information is collected and held by the local reservoir managers (public or private). Regional and national authorities might access this information with a certain latency, which depends on national water policies. Central authorities are then confronted with two issues: long latencies to retrieve water stock information and sparse or inexistent information about small reservoirs.The project proposes a global solution to monitor reservoir stock volumes based on frequent satellite measurements. This solution is based on reservoir water extent monitoring by imaging satellites (Sentinel 1&2) based in the Surfwater processing chain, which integrates a multitemporal approach to improve water masks. Furthermore, StockWater innovation relies on reservoir estimation of Area/Elevation/Volume relationships just from a DEM, even when acquired after the reservoir construction. Recent total volume estimations from DEM estimations have been qualified on hundreds reservoirs in France, ranging from 10 to 10000 hectares, providing errors lower than 20% on 77% of the reservoirs. About the general system assesment, Filling rates estimates yield an error lower than 8% on 75% of the measurements.New versions are evaluated on Spain, France, India and Brazil and deployed on  Burkina-Faso and Tunisia over more than 100 reservoirs. Results are available here: https://www.sco-stockwater.org/  This system will also easily allow volume estimations from Elevation measurements (altimeters Jason, Sentinel3 with limited coverage or SWOT globally).StockWater project, led by CNES and developed with CS-Group and SERTIT,  holds a partnership initiative with CESBIO, GET, LISAH and FUNCEME/Université Pernambuco laboratories and their local partners in Tunisia, Laos, Burkina-Faso, Brazil and India. StockWater is open to new countries willing to participate in future project expansions.
Tree resilience to extreme heatwave events in a semi-arid forest
Authors: Mau Yair , Feuer Erez , Preisler Yakir
Published: February 2023

Extreme heatwave events can impose great stress on plant functioning, including desiccation, over-heating, and the risk of irreversible damage to tissues. We study here the resilience of pine trees in a semi-arid forest in Israel to heatwaves. The backdrop of the heatwaves is a long dry season, along which average water and carbon fluxes decrease, as plants adjust to atmospheric and soil drought. The harsh and short heatwaves, characterized by vapor-pressure deficit exceeding the 85th percentile for the season, punctuate the long dry-down period, and their effect on the trees is monitored through plant water status indicators such as sap flow and stem diameter. First, we developed an index, the cumulative heatwave unit, to quantify heatwaves and compare between them (e.g., heatwave A is 50% harsher than the one that came before it). We then defined two resilience metrics for our non-stationary indicators, that quantify the immediate decrease in water status, and the typical recovery time. Our main result is the identification of compounding effects of heatwaves on tree resilience, showing that long-lasting damage accumulates non-linearly, i.e., the total damage over the drydown is greater than the sum of damage from all individual heatwaves. Plotting the temporal changes in resilience of the trees on the 2-dimensional impact-recovery space, we see a typical loop over the hydrological year, indicating the months when the trees are especially vulnerable to long-lasting damage. We hope that the conceptual tools developed to quantify heatwave disturbances and to quantify resilience are useful to the community in other contexts, especially with expected increases in climatic variability and extreme weather events.
Treasure from trash: Using nuclear waste to trace ocean circulation around Iceland
Authors: Dale Duncan , Christl Marcus , Macrander Andreas , Ólafsdóttir Sólveig , Middag Rob , Casacuberta Núria
Published: February 2023

Iceland stands at an important gateway where Arctic and Atlantic waters interact. Atlantic waters pass northward and circulate in the Arctic before returning southward in the East Greenland Current (EGC). Zones of deep water formation in the Nordic Seas contribute to overflows of the Iceland-Scotland Ridge such as Denmark Strait Overflow Water (DSOW). These are key processes in Arctic warming and deep ocean ventilation.This system has been tagged with anthropogenic radionuclides 129I and 236U by bomb tests in the 1950-60s and point-source nuclear reprocessing plants (NRPs) at Sellafield (UK) and La Hague (FR) since the 1960s providing an opportunity to trace the origins of water masses in the region and their transit timescales. Here we present the results of measurements on samples taken during two cruises around Iceland in 2021 by the Marine and Freshwater Research Institute (MFRI) of Iceland (winter) and the NIOZ MetalGate Cruise of the GEOTRACES program (summer). Models for the origin of waters transiting Denmark Strait and of the evolution of Iceland Scotland Overflow Water (ISOW) are presented that provide a tracer-based perspective for comparison with models based on physical oceanographic tools. This forms a baseline for tracking changes to circulation in the Subpolar North Atlantic using the transient nature of the tracer signals.