bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigating the value of regional water isotope data on transit time and SAS modelling
Authors: Borriero Arianna , Lutz Stefanie , Kumar Rohini , Nguyen Tam , Attinger Sabine , Fleckenstein Jan
Published: March 2021

High nutrient concentrations despite mitigation measures and reduced inputs are a common problem in anthropogenically impacted catchments. To investigate how water and solutes of different ages are mixed and released from catchment storage to the stream, catchment-scale models based on water transit time from StorAge Selection functions (SAS) are a promising tool. Tracking fluxes of environmental tracers, such as stable water isotopes, allows to calibrate and validate these models. However, this requires collection of water samples with an adequate temporal and spatial resolution, while sampling in catchments at the management scale is often limited by the high costs of the instruments, maintenance and chemical analysis. Therefore, temporal and spatial interpolation techniques are needed. This study demonstrates how to deal with sparse tracer data in space and time, and evaluates if these data are valuable to constrain the subsurface mixing dynamics and transit time with SAS modelling. We simulated water isotope data in diverse sub-basins of the Bode catchment (Germany) and calibrated the SAS function parameters against the measured streamflow isotope data. We tested four different combinations of spatial and temporal interpolation of the measured precipitation isotope data. In terms of temporal interpolation, monthly oxygen isotopes in precipitation (δ18OP) collected between 2012 and 2015 were converted to a daily time step with a step function and sinusoidal interpolation. In terms of spatial interpolation, the model was tested with raw values of δ18OP collected at a specific sampling point and with δ18OP interpolated using kriging to gain the spatial pattern of precipitation. The effect of the spatial and temporal interpolation techniques on the modeled SAS functions was analyzed using different parameterizations of the SAS function (i.e., power law time-invariant, power law time-variant and beta law). The results show how tracer input data with different distribution in time and space affect the SAS parameterization and water transit time. Moreover, they reveal preference of the sub-basins to mobilize either younger or older water, which has implications on how water flows through a catchment and on the fate of solutes.
Emergence time of regional signals in tropical rainfall and sea surface temperature in CMIP5/6 simulations
Authors: Gopika Suresh , Suresh Iyyappan , Lengaigne Matthieu , Vialard Jerome , Izumo Takeshi
Published: March 2021

The concept of emergence time allows to define when anthropogenically-forced signals become larger than the ambient natural climate noise and thus become detectable. While anthropogenic signals in globally-averaged Sea Surface Temperature (SST) usually emerge quite early in the 20th century, regional SST changes are more difficult to detect due to large aliasing by internal climate variability. Yet, changes in relative SST (RSST, SST minus its tropical mean) influence the stability of the atmosphere, and hence rainfall or extreme events like cyclones. Here, we focus on regional SST trends by computing the RSST emergence time in CMIP5/6 simulations and investigate their relationship with rainfall emergence time.

We first propose a new method for estimating the emergence time, based on an actual significance estimate rather than a simple signal to noise ratio, and compare the results with the estimates from traditional methods. By 2100, CMIP projections indicate enhanced warming relative to the tropical mean (positive RSST signal) in the equatorial Pacific, equatorial Atlantic, and the Arabian Sea, and reduced warming in the three subtropical gyres of the southern hemisphere. In broad agreement with observations, the Arabian Sea relative warming and South-Eastern Pacific relative cooling are already detectable in most models (median emergence time < 2020), making those regions suitable for testing a model's ability to predict a regional SST trend. In contrast, the RSST signals in other regions only become detectable after 2050. Patterns of rainfall changes are broadly consistent with the above RSST signals (more/less rain in positive/negative RSST area) but generally emerge one or two decades later. The only region where a rainfall signal emerges before an RSST signal is the central and eastern tropical Pacific, where increasing rainfall signals emerge around 2050 (CMIP median). The absence of currently-detectable regional rainfall trends in CMIP makes it difficult to validate climate models' ability to predict tropical regional rainfall trends.

 
Deep CO2 from the Central Atlantic Magmatic Province during the end-Triassic mass extinction
Authors: Capriolo Manfredo , Marzoli Andrea , Aradi László E , Callegaro Sara , Dal Corso Jacopo , Newton Robert J. , Mills Benjamin J. W. , Wignall Paul B. , Bartoli Omar , Baker Don R. , Youbi Nasrrddine , Remusat Laurent , Spiess Richard , Szabo Csaba
Published: March 2021

Throughout Earth’s history, the coincidence in time between Large Igneous Province eruptions and mass extinctions points out a potential causality, where volcanic degassing may drive the global-scale climatic and environmental changes leading to biotic crises. The volcanic activity of the Central Atlantic Magmatic Province (CAMP, ca. 201 Ma), one of Earth’s most voluminous Large Igneous Provinces, is synchronous with the end-Triassic mass extinction event, among the most severe extinctions during the Phanerozoic. Combining different in situ analytical techniques (optical microscopy, confocal Raman microspectroscopy, EMP, SEM-EDS, and NanoSIMS analyses), bubble-bearing melt inclusions within basaltic rocks revealed the abundance of CO2 (up to 1.0 wt.%) in CAMP magmas [1]. Gaseous CO2 and solid elemental C, alternatively preserved by gas exsolution bubbles within melt inclusions mainly hosted in clinopyroxene crystal clots, represent direct evidence for large amounts of volcanic CO2 (up to 105 Gt) emitted into Earth’s surface during the entire CAMP activity [1]. The entrapment conditions of these melt inclusions within clinopyroxene aggregates constrain the degassed CO2 to a mantle and/or lower-middle crustal origin, indicating a deep source of carbon which may favour rapid and intense CAMP eruption pulses. Each magmatic pulse may have injected CO2 into the end-Triassic atmosphere in amounts similar to those projected for the anthropogenic emissions during the 21st century [1]. Therefore, volcanic CO2 degassed during CAMP eruptions likely contributed to end-Triassic global warming and ocean acidification with catastrophic consequences for the biosphere.

 

[1] Capriolo et al. (2020), Nat. Commun. 11, 1670.
ULF Wave Power During Geomagnetic Storms and Implications for Radial Diffusion Processes
Authors: Sandhu Jasmine , Rae Jonathan , Wygant John , Breneman Aaron , Tian Sheng , Staples Frances , Walach Maria-Theresia , Hartley David , Watt Clare , Murphy Kyle , Elsden Tom , Horne Richard , Ozeke Louis , Georgiou Marina
Published: March 2021

Ultra Low Frequency (ULF) waves drive radial diffusion of radiation belt electrons, where this process contributes to and, at times, dominates energisation, loss, and large scale transport of the outer radiation belt. In this study we quantify the changes and variability in ULF wave power during geomagnetic storms, through a statistical analysis of Van Allen Probes data for the time period spanning 2012 – 2019. The results show that global wave power enhancements occur during the main phase, and continue into the recovery phase of storms. Local time asymmetries show sources of ULF wave power are both external solar wind driving as well as internal sources from coupling with ring current ions and substorms.

The statistical analysis demonstrates that storm time ULF waves are able to access lower L values compared to pre-storm conditions, with enhancements observed within L = 4. We assess how magnetospheric compressions and cold plasma distributions shape how ULF wave power propagates through the magnetosphere. Results show that the Earthward displacement of the magnetopause is a key factor in the low L enhancements. Furthermore, the presence of plasmaspheric plumes during geomagnetic storms plays a crucial role in trapping ULF wave power, and contributes significantly to large storm time enhancements in ULF wave power.

The results have clear implications for enhanced radial diffusion of the outer radiation belt during geomagnetic storms. Estimates of storm time radial diffusion coefficients are derived from the ULF wave power observations, and compared to existing empirical models of radial diffusion coefficients. We show that current Kp-parameterised models, such as the Ozeke et al. [2014] model, do not fully capture the large variability in storm time radial diffusion coefficients or the extent of enhancements in the magnetic field diffusion coefficients.
Stable carbon isotopes as powerful tools for studying land-atmosphere flux exchanges and improving land surface models
Authors: Lavergne Aliénor , Andreu-Hayles Laia , Belmecheri Soumaya , Guerrieri Rossella , Graven Heather
Published: March 2021

The stable isotopic compositions of carbon and oxygen in terrestrial plants can provide valuable insights into plant eco-physiological responses to environmental changes at seasonal to annual resolution. Yet, the potential of these datasets to study land-atmosphere interactions remains under-exploited. Here, we present some examples of how stable carbon isotopes (δ13C) measured in plant materials (leaves and tree-rings) can be used to explore changes in the magnitude and variability of carbon and water flux exchanges between the vegetation and the atmosphere and to improve land surface models.

First, we show that the discrimination against 13C (Δ13C), calculated as the difference in δ13C between the source atmospheric CO2 and the plant material studied, varies strongly between regions and biomes and is useful for better understanding the CO2 fertilisation effect of plant growth. For example, tree-ring Δ13C records from boreal evergreen forests in North America increased linearly with rising CO2 during the 20th century, suggesting that those forests have actively contributed to the land carbon sink by removing CO2 from the atmosphere at a relatively constant rate. However, such an increase in Δ13C with rising CO2 is not observed everywhere. We found that over the same time period, while some forests had a fairly constant Δ13C, others exhibited a slight decrease in Δ13C over time, which might indicate a reduction of the capacity of trees to absorb CO2. Using a response function approach, we show that the differences between sites and regions are most likely the result of different evaporative demands and soil water availability conditions experienced by forests.

We then discuss how predictions of the coupled carbon and water cycles by vegetation models can be improved by incorporating stable carbon isotopes to constrain the model representation of carbon-water fluxes regulation by leaf stomata. Specifically, we examine and evaluate simulations from the JULES vegetation model at different eddy-covariance forest sites where stable carbon isotopic data and canopy flux measurements are available. Overall, our analyses have strong implications for the understanding of historical changes in the strength of the CO2 fertilisation effect and in the water use efficiency of terrestrial ecosystems across regions.

 
Data-informed trait-based modeling of microbial carbon cycling in soil
Authors: Pagel Holger , Uksa Marie , Poll Christian , Kandeler Ellen , Streck Thilo
Published: March 2021

Soil microbial functional traits control carbon (C) decomposition and stabilization in soil. Integrating metabolic trade-offs and life-history strategies of microbial communities into models enhances the representation of feedbacks between microbial diversity and soil biogeochemical functions. This has great potential to improve our understanding of microbial C allocation and how microbial processes affect C storage and use efficiency in soil. The current challenge is, however, to quantify and identify ecologically meaningful microbial traits. This study utilizes data from a 13C pulse-labelling litter decomposition experiment to inform a new soil C turnover model that captures microbial life-history traits and dormancy in combination with soil organic matter accessibility. Quantitative data from 13C DNA stable isotope probing and high-throughput sequencing is used to parameterize the C utilization of copiotrophic and oligotrophic microorganisms. The new model is then applied to quantify C utilization of functional microbial groups and C turnover in soil.  In scenario analyses we investigate the sensitivity of functional microbial groups and its feedback on C cycling to C input.
Incorporating Backward-forward Stochastic Particle Tracking Model into the EFDC model for Probable Sedimentation Source identification in Typhoon events
Authors: Liu Wen-Jia , Tsai Christina W.
Published: March 2021

The reservoir siltation has been of critical environmental concerns in recent years. The vulnerability and the overdevelopment in the reservoir watershed are the causes of the reservoir sedimentation. While typhoon events happen, in addition to the great amount of sediment volume transported from the upstream to the reservoir region, the density currents may evolve, which will steeply increase turbidity levels for the periods of time. In particular, the Shihmen Reservoir, one of essential hydraulic engineering projects in northern Taiwan, has been exposed to crisis that the sedimentation may fill up in the next few decades. Therefore, in order to maintain the reservoir capacity to an operational extent, modeling the sediment transport patterns in Shihmen Reservoir will utilize the three-dimensional Environmental Fluid Dynamics Code (EFDC) for quantifying sediment concentrations during the typhoon event. Calibration and validation of EFDC are performed by comparing two independent sets of event-based hydrodynamic and sediment concentration data with assistance of the parameter optimization algorithm. Next, the Backward-forward Stochastic Particle Tracking Model (BF-SPTM) is further incorporated into the EFDC hydrodynamic module to check the likelihood of the potential source of sediment particles. Results of simulations are expected to provide a more precise release timing for flow regulation to ensure the effective slag removal for density currents. Additionally, with probable sedimentation sources available for a reservoir, effective land use change and restrictions on overdevelopment of the risk prone areas can be enforced to decrease the sediment yields into the reservoir. It is expected that this incorporation of BF-SPTM into EFDC can be applied to simulate sediment transport in typhoon events, and to provide appropriate reservoir management alternatives.

Keywords: Environmental Fluid Dynamics Code (EFDC), suspended sediment concentration, Backward-forward Stochastic Particle Tracking Model, Probable sedimentation source
Intercomparison between Surrogate, Explicit and Full Treatments of VSL Bromine Chemistry within the CAM-Chem Chemistry-Climate Model
Authors: Fernandez Rafael P. , Barrera Javier Alejandro , López-Noreña Ana I. , Kinnison Douglas E. , Nicely Julie , Salawitch Ross J. , Wales Pamela A. , Toselli Beatriz M. , Tilmes Simone , Lamarque Jean-Francois , Cuevas Carlos A. , Saiz-Lopez Alfonso
Published: March 2021

Many Chemistry Climate Models (CCMs) include a simplified treatment of brominated very short-lived (VSLBr) species by assuming long-lived methyl bromide (CH3Br) as a surrogate for VSLBr. However, given that VSLBr (i.e., bromoform CHBr3 and dibromomethane CH2Br2) decompose more rapidly than CH3Br, their impact on upper tropospheric chemistry and lowermost stratospheric ozone cannot be neglected. Thus, a mistreatment of VSLBr in CCMs may yield an unrealistic representation of their associated impacts. Here, we present a comprehensive intercomparison between various VSLBr chemical approaches with increasing degrees of complexity (i.e., surrogate, explicit, and full), and quantify the global impacts of these natural bromocarbons on tropospheric and stratospheric ozone, as well as on other oxidizing agents.  Differences between chemical schemes maximize in the lowermost stratosphere and mid-latitude free troposphere, resulting in a latitudinally dependent reduction of ~1−7 DU in total ozone column and a ~5−15 % decrease of the OH/HO2 ratio, for full compared to surrogate. These bromine-driven changes in HOx abundances are expected to slow-down the oxidative processing of greenhouse gases (i.e., to increase the CH4 lifetime) in a region where these long-lived species have a final chance to undergo tropospheric degradation before injection to the stratosphere. Given the negligible additional computational cost and chemical complexity, we encourage all CCMs oriented to projecting the coupled evolution of stratospheric ozone within a changing climate to include a complete tropospheric representation of VSLBr sources and chemistry in the troposphere and stratosphere.
Hotspots of extreme compound drought and heatwaves: Role of feedback and climate oscillations
Authors: Ul Hassan Waqar , Ahmad Nayak Munir
Published: March 2021

Compound weather events arise from combination of multiple climatic drivers or hazards and often result in disastrous socio-economic impacts. Compound drought and heatwave (CDHE) events have received considerable attention in recent years, but limited attention is given towards the understanding of feedback relationships between droughts and heatwaves at global hotspots of the compound events. Here, we identify the potential hotspots of extreme compound drought and heatwaves (ECDH) over the globe using standardized precipitation index (SPI) and Excess heat factor (EHF) as metrics for droughts and heatwaves, respectively. Besides the well know positive feedback between droughts and heatwaves, i.e., heatwaves amplify droughts and vice-versa, we hypothesize and test the possibility of negative feedback at distinct hotspots where heatwaves tend to abate droughts. Multiple hotspots were identified with positive and negative feedbacks among drought and heatwave intensities, supporting our hypothesis. We also analyzed the role of different local and large-scale global drivers (such as El-Niño Southern Oscillation) on the feedbacks at the hotspots. Our analysis has implications in predicting extreme compound droughts and heatwaves and provides new insights that will foster further research in this direction.
Hygroscopicity of HULIS in urban aerosol and its relationship with sources
Authors: Zhou Ruichen , Deng Yange , Kunwar Bhagawati , Chen Qingcai , Chen Jing , Ren Lujie , Vodicka Petr , Deshmukh Dhananjay , Fu Pingqing , Kawamura Kimitaka , Mochida Michihiro
Published: March 2021

Atmospheric aerosol affects the Earth’s radiation budget by directly scattering and absorbing solar radiation and indirectly acting as cloud condensation nuclei. Both of the effects are responsible for the uncertainties in the prediction of global climate change. A better understanding of the hygroscopicity of the organic aerosol is important because it is poorly characterized to date. In this study, the hygroscopicity of humic-like substances (HULIS), a ubiquitous mixture of water-soluble organic matter, isolated from aerosol samples collected in Beijing in different seasons, was measured using a hygroscopicity tandem differential mobility analyzer (HTDMA). The hygroscopicity parameter of the isolated HULIS fraction (κHULIS) was in the range of 0.03–0.13 (mean: 0.06). Considering the possible influence from small amounts of inorganic salts, the hygroscopicity parameter of pure organic HULIS (κ*HULIS) was found to be slightly lower (0–0.11, mean: 0.04). The κHULIS showed a seasonal variation; the values were highest in summer (0.08), followed by spring (0.06), autumn (0.06), and winter (0.04). The κ*HULIS showed a similar seasonal variation, with the highest and lowest values in summer (0.07) and autumn (0.01), respectively. Both κHULIS and κ*HULIS were correlated positively with the O/C ratio of the HULIS. Comparison of the hygroscopicity parameter values with factors from positive matrix factorization (PMF) analysis of the mass spectra of the HULIS fractions showed that κHULIS correlated positively with more-oxidized oxygenated organic aerosol (MO-OOA) and less-oxidized OOA (LO-OOA), and correlated negatively with cooking-like OA (COA) and biomass burning OA (BBOA). The relationship between the hygroscopicity parameter and sources was further explored based on a multi-liner regression analysis. The variation in the hygroscopicity of HULIS and its connection to sources provide an insight into the contribution of organics to aerosol hygroscopicity, toward a better understanding of its link to climate.
The isotopic composition of phloem water and its relations to xylem water at daily and sub-daily resolutions
Authors: Nehemy Magali F. , Paolo Benettin , Rinaldo Andrea , McDonnell Jeffrey J.
Published: March 2021

Isotopic tracing is de rigueur in ecohydrology and for quantifying tracing water sources that contribute to xylem water. But, tree transpiration is not a one dimensional process from roots to leaves. Three dimensional storages actively participate in water transport within the stem complicating in unknown ways, the otherwise straightforward tracing from source to xylem. Phloem is the largest elastic storage and works as a hydraulic capacitor, and as such is of great importance to tree water transport and functioning. Water stored in phloem moves into xylem vessels buffering changes in xylem water potential and sustaining tree hydraulic integrity. Although phloem water is of great importance to transpiration, we lack understanding about the relationship between xylem and phloem water isotopic composition. Assessing the isotopic composition of phloem is a needed next step to fully comprehend patterns of tree water use and improve understanding about isotopic offset between xylem and source water. Here we show daily and sub-daily dual-isotope measurements of phloem water in relation to xylem and leaf water in Salix viminalis along with high-resolution measurements of plant water status and transpiration rates in a large lysimeter. We found that phloem was more depleted in heavier isotopes than xylem and leaves. On average δ2H phloem water was 2.05 ‰ and δ18O phloem water was 0.66 ‰ more negative than xylem water. The largest difference observed between phloem and xylem isotopic composition occurred at night during a period of tree water deficit. Although, there was variability in the observed difference between xylem and phloem throughout the experiment, xylem and phloem isotopic composition were highly correlated (δ2H r = 0.89; δ18O r = 0.75). Our sub daily measurements showed that xylem and phloem differences decreased during predawn and morning compared to previous evening and midday measurements. We observed that the δ2H difference between phloem and xylem increased with the increase in daily use of phloem water storages, while δ18O difference between phloem and xylem increased with transpiration rate. Our results show that xylem and phloem isotope composition are in sync and that observed differences can be related to changes in plant water status and possible fractionation associated with transport within phloem-xylem. Further studies are necessary to understand how phloem affects source water interpretations across different tree species and larger trees, where phloem contribution to daily transpiration may be larger.
Astronomical forcing and climate : insights from ice core records
Authors: Masson-Delmotte Valérie
Published: March 2021

Ice cores provide a wealth of insights into past changes in climate and atmospheric composition.

Obtaining information on past polar temperature changes is important to document climate variations beyond instrumental records, and to test our understanding of past climate variations, including the Earth system response to astronomical forcing.

Since the 1960s, major breakthrough in ice core science have delivered a matrix of quantitative Greenland and Antarctic ice core records.

Temperature reconstructions from polar ice cores document past polar amplification, and provide quantitative constraints to test climate models.

Climate information from the air and ice preserved in deep ice cores has been crucial to unveil the tight coupling between the carbon cycle and climate and the role of past changes in atmospheric greenhouse gas composition in the Earth system response to astronomical forcing.

Ice core constraints on past changes in ice sheet topography are also key to characterize the contribution of the Greenland and Antarctic ice sheets to past sea level changes.

The construction of a common chronological framework for Greenland and Antarctic ice core records has unveiled the bipolar sequence of events during the glacial-interglacial cycle, and the interplay between abrupt change and the response of the climate system to astronomical forcing.

International efforts have started to obtain the oldest ice cores (hopefully back to 1,5 million years) from Antarctica, in order to understand the reasons for the major shifts in the response of the climate system to astronomical forcing at that time, leading to more intense and longer glacial periods. 
M3G: an expanding catalogue of permanently tracking GNSS stations in Europe
Authors: Fabian Andras , Bruyninx Carine , Miglio Anna , Legrand Juliette
Published: March 2021

The Metadata Management and Distribution System for Multiple GNSS Networks (M3G, https://gnss-metadata.eu), hosted by the Royal Observatory of Belgium, is one of the services of the European Plate Observing System (EPOS, https://www.epos-eu.org) and EUREF (http://euref.eu).

M3G provides the scientific as well as the non-scientific community with a state-of-the-art archive of information on permanently tracking GNSS stations in Europe, including the station description, the GNSS networks the stations contribute to, whether station observation data are publicly available, and how to access them. 

Since its first public release (2018), M3G has been under continuous development, to respond to the evolving needs of the GNSS community, to progress towards FAIR data principles and comply with GDPR. 

M3G offers APIs and an interactive user interface where any GNSS station manager, after registration, can insert all information relative to its GNSS stations and make this information publicly available. Consequently, the commitment of station managers to insert GNSS station metadata in M3G and their willingness to keep the information up to date is crucial for the success of M3G.

At the moment, M3G is used by 127 GNSS agencies and includes data from more than 2500 GNSS stations all over Europe, and more still in the process of being collected.

We will illustrate the rationale underlying M3G, the data that it provides and how these data can be accessed.
2D thermo-mechanical-chemical coupled numerical models of interactions between a cooling magma chamber and a visco-elastic host rock
Authors: Kiss Dániel , Moulas Evangelos , Rummel Lisa , Kaus Boris
Published: March 2021

A recent focus of studies in geodynamic modeling and magmatic petrology is to understand the coupled behavior between deformation and magmatic processes. Here, we present a 2D numerical model of an upper crustal magma (or mush) chamber in a visco-elastic host rock, with coupled thermal, mechanical and chemical processes, accounting for thermodynamically consistent material parameters. The magma chamber is isolated from deeper sources of magma (at least periodically) and it is cooling, and thus shrinking. We quantify the changes of pressure and stress around a cooling magma chamber and a warming host rock, using a compressible visco-elastic formulation, considering both simplified idealized and more complex and realistic geometries of the magma chamber.

We present solutions based on a self-consistent system of the conservation equations for coupled thermo-mechanical-chemical processes, under the assumptions of slow (negligible inertial forces), visco-elastic deformation and constant chemical bulk composition. The thermodynamic melting/crystallization model is based on a pelitic melting model calculated with Perple_X, assuming a granitic composition and is incorporated as a look-up table. We will discuss the numerical implementation, show the results of systematic numerical simulations, and illustrate the effect of volume changes due to temperature changes (including the possibility melting and crystallization) on stress and pressure evolution in magmatic systems.
 Microplastic in marine, nearshore waters of South Georgia: a study of background environmental levels of microplastic contamination
Authors: Buckingham Jack , Waller Cath , Waluda Claire , Manno Clara
Published: March 2021

Microplastics are ubiquitous in the global ocean and have even been found in remote polar environments, including in Arctic snowfall and Antarctic subtidal sediments. Levels in some areas of the Southern Ocean have been shown to be 100,000 times higher than predictions.

This is the first comprehensive survey of microplastic in the nearshore waters of South Georgia, a sub-Antarctic South Atlantic island noted for its biodiversity. Microplastic has been previously documented in resident populations of higher predators. This is likely to originate from their food, but the degree to which their prey is exposed to microplastics from background environments has yet to be examined.

Surface water samples were collected from 12 sites at 1km intervals around the accessible shoreline of the Thatcher Peninsula, South Georgia, including adjacent to the outflow pipes of the research station, King Edward Point (KEP). Additionally, samples were taken directly from: (i) outflow pipes at KEP and Grytviken (a nearby whaling station, occupied in summer), in order to determine the level of local input from anthropogenic wastewater systems; (ii) Gull Lake, a freshwater system isolated from oceanographic influence; and (iii) directly from falling snow to evaluate the potential risk of atmospheric transfer of microplastics via precipitation. Preliminary results using FT-IR spectroscopy have confirmed over 24,000 suspected anthropogenic particles/fibres as being microplastic. Microplastics were present in every sample, from every site and range in size from 0.05-3mm.

Here we present the following results:

1) the amount of microplastic in the background environment to which local biodiversity is exposed and;

2) the similarity between the microplastic profiles of an anthropogenic point source and the local environment.

 
The diurnal evolution of anthropogenic aerosol impacts on clouds
Authors: Rahu Jorma , Post Piia , Toll Velle
Published: March 2021

Reducing uncertainty in aerosol-cloud interactions is necessary for more reliable climate projections. Understanding the effects of anthropogenic aerosols on clouds remains a challenge due to complex processes governing the cloud adjustments to increased cloud droplet numbers. Using SEVIRI data, we study the daily evolution of polluted cloud tracks induced by strong pollution sources in the European part of Russia. We use semi-automated cloud droplet effective radius based statistical classification algorithm to differentiate between polluted and nearby unpolluted pixels in the satellite images. We use the 15-minute resolution Cloud Physical Properties product by KNMI to study changes in polluted cloud properties during the daytime. In some cases, cloud water increases during the day and in some cases decreases in polluted clouds compared to the nearby unpolluted clouds. On average, the diurnal evolution of cloud water is very similar between polluted and unpolluted clouds. Interestingly, there is less cloud water in polluted clouds already in the morning, suggesting that cloud water decreases more in polluted clouds during the night. The relatively weak average decrease in cloud water agrees with MODIS-based estimate (Toll et al 2019, Nature, https://doi.org/10.1038/s41586-019-1423-9).
Winter wheat and maize under varying soil moisture: from leaf to canopy
Authors: Nguyen Thuy Huu , Langensiepen Matthias , Gaiser Thomas , Webber Heidi , Ahrends Hella , Hueging Hubert , Ewert Frank
Published: March 2021

Drought is one of the most detrimental factors limiting crop growth and production of important staple crops such as winter wheat and maize. For both crops, stomatal regulation and change of canopy structure responses to water stress can be observed. A substantial range of stomatal behavior in regulating water loss was recently reported while the crop growth and morphological responses to drought stress depend on the intensity and duration of the imposed stress. Insights into the responses from leaf to the canopy are important for crop modeling and soil-vegetation-atmosphere models (SVAT). Stomatal responses and effects of soil water deficit on the dynamic change of canopy photosynthesis and transpiration, and seasonal crop growth of winter wheat and maize are investigated based on data collected from field-grown conditions with varying soil moisture treatments (sheltered, rainfed, irrigated) in 2016, 2017, and 2018. A reduction of leaf net photosynthesis (An), stomatal conductance (Gs), transpiration (E), and leaf water potential (LWP) was observed in the sheltered plot as compared to the rainfed and irrigated plots in winter wheat in 2016, indicating anisohydric stomatal responses. Maize showed seasonal isohydric behaviour with the minimum LWP from -1.5 to -2 MPa in 2017 and -2 to -2.7 MPa in the extremely hot and dry year in 2018. Crop growth (biomass, leaf area index, and yield) was substantially reduced under drought conditions, particularly for maize in 2018. Leaf water use efficiency (An/E) and crop WUE (total dry biomass/canopy transpiration) were not significantly different among treatments in both crops. The reduction of tiller number (in winter wheat) and leaf-rolling and plant size (in maize) resulted in a reduction of canopy transpiration, assimilation rate, and thus biomass. The seasonal isohydry in maize and the seasonal variability of LWP in winter wheat suggest a possibility to use the same critical LWP thresholds for maize and wheat to simulate the stomatal control in process-based crop and SVAT models. The canopy response such as dynamically reducing leaf area under water stress adds complexity in simulating gas exchange and crop growth rate that needs adequate consideration in the current modeling approaches.
A New Method for Gas-Flux Calculation in Atmospheric Boundary Layer Based on the Active Detection of LiDAR System
Authors: Ma Rong , Yao Wei , Lu Meng , Yu Zhitong
Published: March 2021

The Flux information based on momentum, energy and matter is an important link between different components of the earth system. Flux observation is of great significance for understanding the energy and matter exchange in each circle of the earth system, revealing the carbon cycle process at the same time. Fluxes between the atmosphere and the Earth's surface must pass through the atmospheric boundary layer and have considerable influence on the state of the atmospheric boundary layer. Therefore, the observation and analysis of vertical turbulent flux in the atmospheric boundary layer has become a hot topic of atmospheric research. Based on the development of turbulence theory, the method of calculating gas-flux in the atmospheric boundary layer is constantly improved. In recent years, with the development of lidar detection system, doppler lidar system and differential absorption lidar system have also been effectively used to measure the mean wind speed and small-scale dynamic turbulence parameters, which can be applied to directly detect gas flux of the atmospheric boundary layer. For major scientific issues in the global carbon cycle and carbon emission reduction monitoring needs, this paper has developed a new method of gas-flux calculation of atmospheric boundary layer, while obtaining the wind profile information and gas concentration profile information at the same time and at the same place by the detection of lidar system. This method calculates flux takes into account the atmospheric stability judgment, surface friction velocity and the Monin-Obukhov stability parameter based on the turbulent transport theory of atmospheric boundary layer. It can quickly and effectively realize the active remote sensing detection of the gas flux information of atmospheric boundary layer under different atmospheric stability conditions，which has been proved to be effective and accurate by comparing with other gas-flux data.
High Latitude Dust: contemporary emissions and geomorphic interactions
Authors: Bullard Joanna
Published: March 2021

The world’s largest contemporary dust sources are in low-lying, hot, arid regions, however the processes of dust production and emission also operate in cold climate regions at high latitudes and altitudes.  This lecture focuses on contemporary dust emissions originating from the high latitudes (≥50°N and ≥40°S) and explores three themes before setting out an integrated agenda for future research.  The first theme considers how much dust originates from the high latitudes and methods for determining this.  Estimates from field studies, remote sensing and modelling all suggest around 5% of contemporary global dust emissions originate in the high latitudes, a similar proportion to that from the USA (excluding Alaska) or Australia.  This estimate is a proportion of a highly uncertain figure as quantification of dust emissions from Eurasian high latitudes is limited, and the contribution of local and regional emissions (from any latitude) to the global total is thought to be considerably under-estimated.  Emissions are particularly likely to be under-estimated where dust sources are topographically constrained, and where cold climates reduce vertical mixing of dust plumes restricting the altitudes to which the dust can rise, because both these characteristics present particular challenges for modelling and remote sensing approaches. The second theme considers the drivers of contemporary high latitude dust emissions that reflect complex interactions among sediment supply, sediment availability and transport capacity across different geomorphic sub-systems.  These interactions determine the magnitude, frequency and timing of dust emissions at a range of time scales (diurnal, seasonal, decadal) but both the drivers and response can be nonlinear and hard to predict.  The third and final theme explores the importance of high latitude dust cycling for facilitating cross-boundary material fluxes and its impact in the atmosphere, cryosphere, and terrestrial and marine ecosystems.  This is influenced not only by the quantity and timing of dust emissions but also by dust properties such as particle-size and geochemistry.  Landscape sensitivity, spatial environmental transitions and temporal environmental change are highlighted for their importance in determining how the interactions among drivers and cycles are likely to change in response to future environmental change.
The advective Brewer-Dobson circulation in the ERA5 reanalysis: climatology, variability, and trends
Authors: Diallo Mohamadou , Ern Manfred , Ploeger Felix
Published: March 2021

The stratospheric Brewer-Dobson circulation (BDC) is an important element of climate as it determines the transport and distributions of key radiatively active atmospheric trace gases, which affect the Earth’s radiation budget and surface climate.
Here, we evaluate the inter-annual variability and trends of the BDC in the ERA5 reanalysis and inter-compare with the ERA-Interim reanalysis for the 1979–2018 period. We also assess the modulation of the circulation by the Quasi-Biennial Oscillation (QBO) and the El Niño-Southern Oscillation (ENSO), and the forcings of the circulation by the planetary and gravity wave drag. A comparison of ERA5 and ERA-Interim reanalyses shows a very good agreement in the morphology of the BDC and in its structural modulations by the natural variability related to QBO and ENSO. Despite the good agreement in the spatial structure, there are substantial differences in the strength of the BDC and of the natural variability impacts on the BDC between the two reanalyses, particularly in the upper troposphere and lower stratosphere (UTLS), and in the upper stratosphere. Throughout most regions of the stratosphere, the variability and trends of the advective BDC are stronger in the ERA5 reanalysis due to stronger planetary and gravity wave forcings, except in the UTLS below 20 km where the tropical upwelling is about 40 % weaker due to a weaker gravity wave forcings at the equatorial flank of the subtropical jet. In the extra-tropics, the large-scale downwelling is stronger in ERA5 than in ERA-Interim linked to significant differences in planetary and gravity wave forcings. Analysis of the BDC trend shows a global acceleration of the annual mean residual circulation with an acceleration rate of about 1.5 % per decade at 70 hPa due to the long-term intensification in gravity and planetary wave breaking, consistent with observed and future climate model predicted BDC changes.
Colorisation of archival aerial imagery using deep learning
Authors: Ishii Ryusei , Carbonneau Patrice , Miyamoto Hitoshi
Published: March 2021

Archival imagery dating back to the mid-twentieth century holds information that pre-dates urban expansion and the worst impacts of climate change.  In this research, we examine deep learning colorisation methods applied to historical aerial images in Japan.  Specifically, we attempt to colorize monochrome images of river basins by applying the method of Neural Style Transfer (NST).    First, we created RGB orthomosaics (1m) for reaches of 3 Japanese rivers, the Kurobe, Ishikari, and Kinu rivers.  From the orthomosaics, we extract 60 thousand image tiles of `100 x100` pixels in order to train the CNN used in NST.  The Image tiles were classified into 6 classes: urban, river, forest, tree, grass, and paddy field.  Second, we use the VGG16 model pre-trained on ImageNet data in a transfer learning approach where we freeze a variable number of layers.  We fine-tuned the training epochs, learning rate, and frozen layers in VGG16 in order to derive the optimal CNN used in NST.  The fine tuning resulted in the F-measure accuracy of 0.961, 0.947, and 0.917 for the freeze layer in 7,11,15, respectively.  Third, we colorize monochrome aerial images by the NST with the retrained model weights.  Here used RGB images for 7 Japanese rivers and the corresponding grayscale versions to evaluate the present NST colorization performance.  The RMSE between the RGB and resultant colorized images showed the best performance with the model parameters of lower content layer (6), shallower freeze layer (7), and larger style/content weighting ratio (1.0 x10⁵).  The NST hyperparameter analysis indicated that the colorized images became rougher when the content layer selected deeper in the VGG model.  This is because the deeper the layer, the more features were extracted from the original image.  It was also confirmed that the Kurobe and Ishikari rivers indicated higher accuracy in colorisation.  It might come from the fact that the training dataset of the fine tuning was extracted from these river images.  Finally, we colorized historical monochrome images of Kurobe river with the best NST parameters, resulting in quality high enough compared with the RGB images.  The result indicated that the fine tuning of the NST model could achieve high performance to proceed further land cover classification in future research work.
Application of Google Earth Engine (GEE) to obtain calibration data for a large-scale hydrosedimentological model: a test case in South America
Authors: Rossoni Renata , Fan Fernando , Laipelt Leonardo
Published: March 2021

In hydrosedimentological modelling, the lack of high temporal resolution field data is a limiting factor for the assessment of the performance of models. This way, the remote sensing images have been studied to correlate imagery information with suspended sediment concentration (SSC) in the last decades, aiming to complement field data, by improving the SSC information temporal and spatial resolution. Thus, the present work used the Google Earth Engine (GEE), a cloud-based platform, to systematically obtain red band reflectance information from Landsat 5 imagery to support large-scale hydrosedimentological modelling. The test case was to the Rio Grande do Sul state hydrological region in Brazil, a South American region with scarce SSC data. The methodology applied consisted in nine steps using GEE code: (1) river width analysis using remote sensing imagery to localize the virtual gauge stations (VGS) from the intersection between the discretization of hydrosedimentological model and the chosen rivers, (2) TM sensor definition, onboard of Landsat 5 satellite, (3) collection of red reflectance information between 1990 and 2010, based on previous works that presented better correlation between red reflectance and SSC, (4) in each VGS, we created a circle of radius equal to 1000 m, (5) to each image, we removed clouded-pixels, using the Landsat 5 quality bands, (6) we generated a dynamic water mask to each image to ensure that only pixels with water would be used to collected reflectance information, (7) finally, we calculated the mean of red band reflectance inside the intersection of water mask and circle buffer, removing the clouded-pixels, (8) we calculated a filter to remove remnants clouded-pixels and random errors from imagery, (9) we used the MGB-SED model to simulate long-term SSC in the region and we calibrated the model with the GEE data based on a correlation approach. The results found were: (i) 1267 virtual gauge stations, approximately 20 times the number of in situ SSC gauging stations available in the region, (ii) a larger area of data and greater temporal resolution, (iii) improvement in the correlation between model results and red reflectance, when we assess the model with SSC observed data. In conclusion, the work shows the potential of GEE to simply obtain large-scale reflectance data that could be used to improve the calibration processes of large-scale hydrosedimentological modelling.
Introducing digital information products of the four GeoERA groundwater projects for assessment and sustainable use of water resources and the subsurface in a changing climate
Authors: Hinsby Klaus , Gourcy Laurence , Broers Hans Peter , Højberg Anker Lajer , Bianchi Marco , van der Keur Peter
Published: March 2021

Sustainable evolution of groundwater quantity and quality is essential for sustainable development and protection of society and nature, globally, as acknowledged in the UN sustainable development goals and the European Green Deal. Too much? – too little? – and/or too polluted? are important questions to pose and answer in a changing climate with increasing pressures on water resources, severe loss of biodiversity, and a projected increase in extreme events resulting in an increasing risk of floods, droughts, landslides and land subsidence.   

Easy access to digital and FAIR (Findable, Accessible, Interoperable and reusable) data on groundwater quantity and quality is imperative for informed decision making and efficient climate change mitigation and adaptation to which sustainable groundwater management will contribute. Here we briefly present selected highlights and digital data products from the four GeoERA groundwater projects developed for and made available on the digital subsurface information platform of the European geological survey organizations. The ambition is to develop the digital information platform, EGDI (the European Geological Data Infrastructure) as the leading information platform for sustainable and integrated management of subsurface resources in Europe and one of the leading platforms, globally.