bluuebunny/crossref_metadata_2025 huggingface dataset:
Determining permafrost active layer thermal properties of the Qinghai–Tibet Plateau using field observations and numerical modelling
Authors: de Bruin Jelte , Bense Victor , van der Ploeg Martine
Published: March 2021

Permafrost has become thermally instable as a result of surface warming, which has an uncertain impact on future hydrogeological conditions and the associated mobilisation of carbon and release into the atmosphere. Numerical modelling can provide insights into future permafrost spatial and temporal dynamics. However, crucial observational data of permafrost active-layer thermal properties; thermal conductivity and heat capacity are sparse, resulting in a large uncertainty in forecasts of the future development of the active layer. Therefore, our study aims to develop a methodology to numerically determine the permafrost thermal and soil properties from observations of temperature time-series in the subsurface, in order to reduce the current model uncertainty.

We used an ensemble of 786 numerical 1D permafrost models fitted against observed active layer temperature data from the Qinghai-Tibetan Plateau (QTP)1 to find the optimal values for the soil thermal conductivity, heat capacity and porosity. Optimal parameter values are determined by finding the minimum RMSE, KGE and using the Russell error measure. We find optimized values for bulk volumetric heat capacity 1.3-1.85 106J/m3°C , bulk thermal conductivity 0.9-1.1 W/m°C and porosity between 0.25-0.35 (-), which are in agreement with typical ranges reported in literature for similar settings on the QTP. In a further sensitivity study, the 3 optimal parameter combinations were used to model the active layer thickness over a 100-year period with a gradual hypothetical air temperature increase of 5°C. The results indicate a substantial difference in rate of thawing and increase in depth of the active layer for these models, with a maximum time-lag of roughly 15 years in before the models reach the same active layer thawing depth. The study shows how numerical models can be applied to determine active layer thermal properties without the need for field samples, opening up new possibility for in-situ permafrost temperature observation.

1. Luo, D. L., Jin, H. J., He, R. X., Wang, X. F., Muskett, R. R., Marchenko, S. S., & Romanovsky, V. E. (2018). Characteristics of water-heat exchanges and inconsistent surface temperature changes at an elevational permafrost site on the Qinghai-Tibet Plateau. Journal of Geophysical Research: Atmospheres, 123, 10,057–10,075. https://doi.org/10.1029/2018JD028298
Photosensitization is in the air and impacts SOA generation and properties
Authors: George Christian
Published: March 2021

Despite the importance of aerosols in atmospheric chemistry, climate and air pollution, our ability to assess the impact of aerosols on atmospheric physics and chemistry is still limited due to insufficient understanding of many processes associated with sources of particles, their chemical composition and morphology, and evolution of their composition and properties during their atmospheric lifetime. Indeed, atmospheric aerosols can be viewed as a complex conglomerate of thousands of chemical compounds forming a system that evolves in the atmosphere by chemical and dynamical processing including chemical interaction with oxidants.

Multiphase processes have also been shown to produce light absorbing compounds in the particle phase. The formation of such light absorbing species could induce new photochemical processes within the aerosol particles and/or at the gas/particle interface. A significant body of literature on photo-induced charge or energy transfer in organic molecules from other fields of science (biochemistry and water waste treatment) exists. Such organic molecules are aromatics, substituted carbonyls and/or nitrogen containing compounds – all ubiquitous in tropospheric aerosols. Therefore, while aquatic photochemistry has recognized several of these processes that accelerate degradation of dissolved organic matter, only little is known about such processes in/on atmospheric particles.

This presentation will discuss photosensitization in the troposphere as having a significant role in SOA formation and ageing as studied by means of laser transient absorption spectroscopy, flow tube and simulation chamber experiments, all coupled to advanced analytical techniques. We will provide kinetic and mechanistic information on how photosensitization may introduce new chemical pathways, so far unconsidered, which can impact both the chemical composition of the atmosphere and might thus contribute to close the current SOA underestimation.
Sounding Heavy Precipitating Vertical Cloud Structures with Polarimetric Radio Occultations aboard PAZ
Authors: Padullés Ramon , Cardellach Estel , Turk F. Joseph , Ao Chi O. , Wang Kuo Nung , De la Torre Juárez Manuel , Oyola Mayra
Published: March 2021

The Radio Occultation and Heavy Precipitation (ROHP) experiment aboard the Spanish PAZ satellite was activated in May 2018 with the objective to demonstrate the Polarimetric Radio Occultation (PRO) concept for rain detection. This technique enhances standard RO by measuring GNSS signals at two orthogonal linear polarizations (H and V). Owing to hydrometeor asymmetry, electromagnetic signals propagating through regions of heavy precipitation would experience a differential phase delay expected to be measurable by the ROHP experiment.

After 2+ years of operations, the initial hypothesis has been verified and the main scientific goals have been achieved. Soon after the activation of the experiment it became clear that PRO observables were sensitive to heavy precipitation, showing positive signatures correlated with the presence and intensity of precipitation. After a thorough on-orbit calibration, it has been demonstrated that the PAZ polarimetric observable can be used as a proxy for heavy precipitation. Furthermore, PRO measurements were shown to be sensitive to the horizontally oriented frozen hydrometeors present throughout the vertical cloud extent, providing valuable information on the vertical structure of precipitating clouds.

In addition, PRO can retrieve standard thermodynamic RO products such as temperature, pressure, and water vapor. These products, provided with high vertical resolution, globally distributed and seamlessly over ocean and over land, make PRO observations a unique dataset, with potential applications ranging from the study of deep convection processes to the evaluation and diagnosis of NWP forecast models.

In this presentation we will report on the status of the experiment and current data availability. We will also show the results of the sensitivity studies to heavy precipitation and frozen particles, performed using collocated observations between PAZ and GPM-DPR, GPM-GMI, and other radiometers from the GPM constellation, as well as a-priory information from the Cloudsat radar. Finally, we will address potential level-2 products we can expect from PAZ observations.
A large-scale instability competing with Kelvin-Helmholtz at Mercury’s boundary layer
Authors: Dargent Jérémy , Lavorenti Federico , Henri Pierre , Califano Francesco
Published: March 2021

Magnetic reconnexion and Kelvin-Helmholtz (KH) instability are usually recognized as the two main mixing processes along magnetopauses. However, a recent work [Dargent et al., 2019] showed that in Mercury’s conditions, another instability can grow faster than the KH instability along the magnetopause. This instability seems to rely on gradients of density and/or magnetic field and develops large-scales finger-like structures that prevents the growth of the KH vortices. In this work, I will characterize this instability and try to identify it. In particular, I will look at the dependance of the growth rate of this instability to the different parameters of the plasma and compare it to the growth rate of the Kelvin-Helmholtz instability.
Past century increases of terrestrial nutrient inputs impact both the coastal and open ocean carbon cycle
Authors: Lacroix Fabrice , Ilyina Tatiana , Mathis Moritz , Laruelle Goulven Gildas , Regnier Pierre
Published: March 2021

Past century increases in terrigenous N and P inputs to the ocean due to industrialization, agricultural practices and wastewater have been reported to have dramatic consequences for ecosystems in various coastal regions. Yet, the impacts of increased nutrient inputs through river transports and atmospheric deposition on the coastal and open ocean carbon cycle have yet to be quantitatively investigated at the global scale. To address this gap of knowledge, we enhanced the ocean biogeochemical model HAMOCC at a horizontal resolution of around 0.4° in order to improve the representation of temporal changes of riverine fluxes and of coastal ocean dynamics in the model. Through a series of simulations with differing model forcings, we isolated individual effects arising from (1) increasing atmospheric CO2 levels, (2) a changing physical climate and (3) alterations in oceanic inputs of terrigenous P and N inputs, all over the 1905 to 2010 period. Our results indicate a strong response of the coastal ocean ecosystem to increased terrestrial nutrient inputs, which induce the global coastal Net Primary Production (NPP) to increase by 14% over the simulation time span. This eutrophication signal is, furthermore, partly exported to the open ocean, which undergoes an increase in NPP of 1.75 Pg C yr-1, or 4 % in relative terms, in the simulations, owing to the cross-shelf export of 33-46% of the anthropogenic P and N inputs to the coastal ocean. As a whole, increased P and N inputs lead to an overall global ocean NPP rise of around 2.15 Pg C yr-1, or 5% (combined coastal and open ocean). This net increase attributed to land-ocean couplings exceeds the simulated global oceanic NPP decrease of 4 % associated with stronger upper ocean thermal stratification over the time span, a feedback that been under stronger scrutiny in published literature. Our results suggest that increased riverine nutrient concentrations due to anthropogenic activities may also have substantial impacts for ecosystems in the open ocean, in contrary to what was assumed until now, although this is dependent on the rate of transfer of the nutrients from the coastal to the open ocean.
The Effect of Droughts on Ecosystem Water-Use-Efficiency in Europe
Authors: Poppe Teran Christian , Naz Bibi , Baatz Roland , Hendricks-Franssen Harrie-Jan , Nikolaidis Nikolaos , Vereecken Harry
Published: March 2021

Hydrological extremes in Europe, such as droughts, are expected to increase in frequency and severity with advancement of climate change. The consequences for ecosystem functioning and processes, including biomass production and evapotranspiration, have not yet been thoroughly mapped. 

Ecosystem water use efficiency (WUE) describes the amount of carbon assimilated as biomass per unit of water. WUE was examined for various case studies and global assessments, yet disagreements in the methodologic approach and uncertainties hinder generic understanding of WUE variability. As a link between the carbon cycle, water cycle and vegetation states, disclosure of WUE courses across European ecosystems enables important estimates of past, present and future ecosystem dynamics. 

Here we generated a long-term and high resolution observational and reanalysis data-set of WUE over Europe by interpolation of high level observation products (GLASS, CRU TS v4) and reanalysis data sets (ERA5-Land, COSMO-REA6, ESSMRA) to a 3 x 3km grid. This European Drought and Water Use Efficiency data-set (EDWUE) contains variables for calculating WUE using three different approaches, as well as indicators of meteorological and agricultural droughts.  

Drought effects on WUE will be analyzed to investigate the sensitivity of ecosystem processes to extreme weather conditions at regional and local scale by comparison of WUE and drought indices time-series. Spatiotemporal analyses of the EDWUE data-set across European ecosystems will discover differences in patterns and potential trends of WUE between regions and decode the dependencies on ecosystem composition, geographical characteristics, and climate and occurring weather extremes. Intercomparisons between the different WUE calculations will allow to draw conclusions on the roots of particular WUE dynamics.
Preliminary safety assessments in the high-level radioactive waste site selection procedure in Germany
Authors: Hoyer Eva-Maria , Behrens Christoph , Bjorge Merle , Dannemann Julia , Gawletta Dennis , Kreye Phillip , Lohser Thomas , Luijendijk Elco , Müller Paulina , Panitz Florian , Schlüter Florian , Wengorsch Tobias , Rühaak Wolfram
Published: March 2021

The Federal Company for Radioactive Waste Disposal mbH (BGE mbH) is as Germans waste management organization responsible to implement the search for a site with the best possible safety for the disposal of high-level radioactive waste for at least one million years, following the amendments of the Repository Site Selection Act in 2017. The selection procedure is meant to be a participatory, transparent, learning and self-questioning process based on scientific expertise.

This contribution will provide an overview of the methodology of the forthcoming preliminary safety assessments as a major part of the next steps in the site selection procedure. This procedure overall consists of three phases with increasing level of detail for identification of the best site. The first phase consists of two steps. The objective of the first step was to determine sub-areas in the three considered host rocks, salt (halite), clay and crystalline rock, by applying legally defined exclusion criteria, minimum requirements and geoscientific weighing criteria. 90 sub-areas that cover approximately 54 % of the area of Germany were identified due to their general suitable geological conditions. The result was published in September 2020.

The second step of phase one is currently in progress and consists of representative preliminary safety assessments that aim to assess the safety of the repository system as well as its robustness. The requirements for the preliminary safety assessments in the site selection procedure are defined by a governmental directive released in October 2020. Representative preliminary safety assessments have to be performed for each sub-area and consist of the compilation of all geoscientific information relevant to the safety of a repository, the development of preliminary safety and repository concepts and the analysis of the repository system. In addition, a systematically identification and characterization of uncertainties has to be undertaken and the need for exploration, research and development must be determined. The application of the representative preliminary safety assessments as well as the following renewed application of geoscientific weighing criteria will lead to the identification of siting regions within the larger sub-areas of step one. These regions will be considered, first for surface-based geoscientific and geophysical exploration, including i.e. seismic exploration and drilling of boreholes. Subsequently the last phase of the site selection will proceed with subsurface exploration. Finally, all suitable sites will be proposed and the German government will decide the actual site. This process is expected to be finalized in 2031.
The role of mesoscale cloud organization in the daily cycle of trade-wind cumuli
Authors: Vial Jessica , Vogel Raphaela , Schulz Hauke
Published: March 2021

The role of spatial organization of clouds at mesoscale in the daily cycle of shallow cumulus clouds and precipitation is here explored, for the first time, using three years of high-frequency satellite- and ground-based observations. We focus on the four prominent patterns of cloud organization – Sugar, Gravel, Flowers and Fish – which were found recently to characterize well the variability of the North Atlantic winter trades. Our analysis is based on a simple framework to disentangle the parts of the daily cycle of trade cloudiness that are due to changes in (i) the occurrence frequency of patterns and (ii) cloud cover for a given pattern. Our investigation reveals that the contribution of mesoscale organization to the daily cycle in cloudiness is largely mediated by the frequency of pattern occurrence. All forms of mesoscale organization exhibit a pronounced daily cycle in their frequency of occurrence, with distinct 24-hour phasing. The patterns Fish and Sugar can be viewed as daytime patterns, with a frequency peak around noon for Fish and towards sunset for Sugar. The patterns Gravel and Flowers appear rather as nighttime patterns, with a peak occurrence around midnight for Gravel and before sunrise for Flowers. The cloud cover for a given pattern, however, always maximizes at nighttime (between 00LT and 03LT), regardless of the specific pattern. The daily variability in the occurrence of Sugar, Gravel and Flowers together seem to reflect the evolution of the daytime shallow cloud population (peaking around sunset) and of the nighttime population of deeper cumuli (peaking near dawn), which were identified in previous work. Finally, some insight on the role of large-scale environmental conditions shows that the near-surface wind speed can explain a large part of the diurnal variability in pattern frequency and cloudiness.
On the modelling of self-gravitation for full 3D global seismic wave propagation
Authors: van Driel Martin , Kemper Johannes , Boehm Christian , Khan Amir
Published: March 2021

The last decade has witnessed an unprecedented increase in high quality long period seismic data. This is because of the occurrence of several very large Earthquakes that were recorded on an exponentially growing number of broadband seismic stations that are installed in very dense networks such as the USarray. While for surface and body waves, tomography based on full waveform observables and 3D numerical simulations has become a standard tool in seismology, this is not the case for the normal modes. The main reason for this discrepancy is the fact that there is no established method to model the full physics of long period seismology in 3D and compute gradients with respect to material properties at reasonable computational cost.

Here, we present a new approach to the inclusion of the full gravitational response to spectral element wave propagation solvers. We leverage the Salvus meshing software to include the external domain using adaptive mesh refinement and high order shape mapping. Together with Neumann boundary conditions based on a multipole expansion of the right hand side this minimizes the number of additional elements needed. Initial conditions for the iterative solution of the Poisson equation based on temporal extrapolation from previous time steps together with a polynomial multigrid method reduce the number of iterations needed for convergence. In summary this approach reduces the extra cost for simulating full gravity to a similar order as the elastic forces.

We demonstrate the efficacy of the proposed method using the displacement from an elastic global wave propagation simulation at 200s period as the right hand side in the Poisson equation.
Global Ionospheric Scintillation Model: current status and further development strategies
Authors: Vasylyev Dmytro , Beniguel Yannick , Wilken Volker , Kriegel Martin , Berdermann Jens
Published: March 2021

When a electromagnetic wave propagates through a random inhomogeneous medium, scattering by the refractive index inhomogeneities can lead to a wide variety of phenomena that have been the subject of extensive study and modelling. The Global Ionospheric Scintillation Model (GISM) is primarily intended to model the phenomena relevant for the GNSS applications and provides the amplitude and phase scintillation indices. Due to the three dimensional nature of the GISM model it is capable to describe a variety of communication geometries such as satellite-ground station or satellite-satellite communication link. Moreover, it can calculate the scintillation maps at specific altitude allowing to obtain the 3D picture of scintillation.

Recently the GISM model has been handed over to the newly established DLR Institute of Solar-Terrestrial Physics. Since then the model underwent several modernization steps. For example, the programming paradigm has been changed to the object-oriented one in order to bring more flexibility into the code.  In the present contribution we present the first results of our works and discuss strategies for further development, extension, and validation of the GISM.
The Impact of Aeolus wind observations on the West African Monsoon
Authors: Borne Maurus , Knippertz Peter , Weissmann Martin , Rennie Michael , Cress Alexander
Published: March 2021

Tropical Africa is characterized by the world-wide largest degree of mesoscale convective organisation. During boreal summer, the wet phase of the West African Monsoon (WAM), the midlevel African easterly jet (AEJ) over the Sahel allows for the formation of synoptic-scale African easterly waves (AEWs) with a maximum intensity close to the West African coast. AEWs interact with convection and its mesoscale organization through modifications in humidity, temperature and vertical wind shear, and often serve as initial disturbances for tropical cyclogenesis. In addition, rainfall can be modulated by other types of tropical waves such as Kelvin or mixed Rossby gravity waves. Upper-tropospheric conditions are dominated by the Tropical Easterly Jet (TEJ), whose variability appears to be connected to convective activity. Overall, our quantitative understanding of the WAM system is still limited. The observational network over the region is sparse and rainfall forecasts with current Numerical Weather Prediction models are hardly better than climatology.

The Aeolus satellite launched in 2018 offers a great opportunity to further investigate the WAM with an unprecedented density of free-tropospheric wind data. Assimilating Aeolus wind observations in denial experiments using the current operational system of the European Centre for Medium-Range Weather Forecasts (ECMWF) shows that the main circulation features of the WAM are greatly impacted: the AEJ and the TEJ are systematically weaker and stronger respectively by~1m/s in the analysis fields including Aeolus data. As a consequence AEWs also show a weakening in the propagation amplitude. We are currently investigating the contributions of the HLOS (horizontal line-of-sight) Rayleigh and Mie wind observations to these observed differences. Mie observations (i.e., those related to backscatter from hydrometeors and aerosol particles) seems to contribute strongly to the difference in the AEJ, which lies within a convectively active region with a high aerosol load. On the other hand, the difference seen in the TEJ appears to originate mostly in the Rayleigh (i.e., clear air) observations. Surprisingly, the ascending and descending HLOS observations contribute differently to the data impact, possibly revealing a remaining bias or model problems with the diurnal cycle. Future work will include systematic comparisons between the operational systems of DWD and ECMWF to understand the influence of different data assimilation approaches as well as the impact on forecasts.
The Importance of Mineral Dust and Proteinaceous Ice Nucleating Particles in the Canadian High Artic During the Fall of 2018 
Authors: Yun Jingwei , Evoy Erin , Worthy Soleil , Fraser Melody , Veber Daniel , Platt Andrew , Anderson Kevin , Sharma Sangeeta , Leaitch Richard , Bertram Allan
Published: March 2021

Ice nucleating particles (INPs) can initiate ice formation in clouds, which has a large impact on the hydrological cycle and radiative budget of the Earth. Constraints on the concentration and composition of INPs are needed to predict ice formation in clouds and hence the climate. Despite previous INP measurements in the Arctic, our understanding of the concentrations, composition, and sources of Arctic INPs is insufficient. Here we report daily concentrations of INPs at Alert, a ground site in the Canadian High Arctic, during October and November of 2018. The contributions of mineral dust and proteinaceous particles to the total INP population were evaluated by testing the responses of the samples to heat and ammonium treatments. Possible source locations of the most effective INPs were investigated using back-trajectory simulations with a Lagrangian particle dispersion model. The results show that the INP concentrations in October were higher than that in November. Combining our results with previous INP measurements at Alert, a seasonal trend was observed for the INP concentrations at -18 °C and -22 °C, with a higher concentration in the late spring, summer and early fall, and a lower concentration in the early spring, late fall, and winter. For the October samples, proteinaceous INPs were detected at T > -21 °C with a fraction of 60% to 100% and mineral dust INPs were detected at T < -21 °C. For the November samples, proteinaceous INPs were only detected at T > -16 °C with a fraction of 88% to 100% and mineral dust INPs were detected at T < -20 °C. The most effective INPs were possibly from South China and California based on 20-day backward simulations using the FLEXible PARTicle dispersion model and the correlations between INP concentrations and Al, , Na+, and Cl- measured at the site.  
Global 3D modelling of Martian CO2 clouds
Authors: Mathé Christophe , Määttänen Anni , Audouard Joachim , Listowski Constantino , Millour Ehouarn , Forget François , Spiga Aymeric , Bardet Déborah , Teinturier Lucas , Falletti Lola , Vals Margaux , González-Galindo Franscico , Montmessin Franck
Published: March 2021

In the Martian atmosphere, carbon dioxide (CO2) clouds have been revealed by numerous instruments around Mars from the beginning of the XXI century. These observed clouds can be distinguished by two kinds involving different formation processes: those formed during the winter in polar regions located in the troposphere, and those formed during the Martian year at low- and mid-northern latitudes located in the mesosphere (Määattänen et al, 2013). Microphysical processes of the formation of these clouds are still not fully understood. However, modeling studies revealed processes necessary for their formation: the requirement of waves that perturb the atmosphere leading to a temperature below the condensation of CO2 (transient planetary waves for tropospheric clouds (Kuroda et al., 20123), thermal tides (Gonzalez-Galindo et al., 2011) and gravity waves for mesospheric clouds (Spiga et al., 2012)). In the last decade, a state-of-the-art microphysical column (1D) model for CO2 clouds in a Martian atmosphere was developed at Laboratoire Atmosphères, Observations Spatiales (LATMOS) (Listowski et al., 2013, 2014). We use our full microphysical model of CO2 cloud formation to investigate the occurrence of these CO2 clouds by coupling it with the Global Climate Model (GCM) of the Laboratoire de Météorologie Dynamique (LMD) (Forget et al., 1999). We recently activated the radiative impact of CO2 clouds in the atmosphere. Last modeling results on Martian CO2 clouds properties and their impacts on the atmosphere will be presented and be compared to observational data.
Tomato plants reuptake root exudates and alter carbon isotope fractionation under phosphorus deficiency
Authors: Tiziani Raphael , Trevisan Fabio , Pii Youry , Celletti Silvia , Cesco Stefano , Mimmo Tanja
Published: March 2021

Plant roots are able to exude vast amounts of metabolites into the rhizosphere especially when subjected to phosphorus (P) deficiency to increase P solubility and thus its´ uptake. This causes noteworthy costs in terms of energy and carbon (C) for the plants. For this reason, we suggested that exudates reacquisition by roots could represent an energy saving strategy of plants. This study aimed at investigating the effect of P deficiency on the ability of hydroponically grown tomato plants to re-uptake specific metabolites generally present in root exudates by using 13C-labelled molecules. Hence, tomato plants have been grown for 21 days in full and P deficient nutrient solution. Exudates reuptake has been assessed by immersion of roots in a solution containing 13C labeled glycine, glucose, fructose, citrate, and malate. δ13C analysis was performed using a Continuous Flow Isotope Ratio Mass Spectrometer (CFIRMS). Results revealed that P deficient tomato plants were able to take up significantly more citrate (+37%) and malate (+37%), when compared to controls. While also glycine (+42%) and fructose (+49%) uptake was enhanced in P shortage, glucose acquisition was not affected by plants nutritional status. Unexpectedly, results also highlighted that P deficiency leads to a 13C enrichment in both tomato roots and shoots over time (shoots +2.66 ‰, roots +2.64 ‰, compared to control plants). This could be explained by stomata closure triggered by P deficiency resulting in an increased use of 13CO2 in respect to 12CO2, normally preferred by RuBisCO. Our findings highlight that tomato plants are able to take up a wide range of metabolites belonging to root exudates, thus optimizing C trade off. This trait is particularly evident when plants grew in P deficiency.
Alpine stream characterization through the lens of hydrochemistry: a comparison study from two high-elevation catchments (Eastern Italian Alps) 
Authors: Engel Michael , Brighenti Stefano , Tirler Werner , Nadalet Rudi , Mair Volkmar , Tagliavini Massimo , Comiti Francesco
Published: March 2021

High-elevation catchments are rapidly changing as glaciers retreat and permafrost thawing intensifies. Consequently, alpine stream hydrochemistry is shifting but the interaction with complex hydrological and geological settings often confounds the effect of the climatic signal. To evaluate the effect of different glacier coverage and rock glacier presence, our study involves a multi-parameter approach of different tracers in two high-elevation catchments. Both catchments (Schnals and Martell; Eastern Italian Alps) share a comparable metamorphic geology but contrast in their glacier cover (4% and 22%, respectively) and abundance of active rock glaciers (numerous in the Schnals catchment).

Based on these different settings, we hypothesized that i) the glacier melt contribution at the daily and monthly scale in Martell is larger than in Schnals, ii) metamorphic catchments share similar hydrochemical patterns along the river network, and iii) rock glacier meltwaters affect more strongly the hydrochemistry of the main stream in Schnals than in Martell, given the higher abundance of active rock glaciers in the former catchment.

From June 2019 to October 2020, we carried out a monthly sampling of stream water along the main river, major tributaries, springs and a rock glacier. Snowmelt and ice melt (only at Martell) were occasionally sampled as well. Rain was collected on a monthly basis. Electrical conductivity of water samples was measured on-site while stable water isotopes and concentrations of major, minor, and trace elements were measured in the laboratory.

Our results indicate that the isotopic composition of streams and tributaries in Martell mainly originated from snowmelt and ice melt, with a minor contribution from groundwater. In contrast, the contribution of precipitation, shallow groundwater, and rock glaciers was larger in the Schnals catchment. The two catchments showed distinct hydrochemical patterns, based on their different elemental concentrations. Mostly during the glacier ablation period and autumn, alkali elements dominated Schnals hydrochemistry, whereas arsenic and strontium characterized the stream hydrochemistry of Martell. Concentrations of metals and metalloids had a sharp increase during autumn, when thawing permafrost and the subglacial drainage was highest, thus affecting the hydrochemistry of the entire river network. As thawing permafrost increasingly influences the quality of freshwaters in deglaciating catchments, efforts must be dedicated to the long-term monitoring of alpine river networks, given the potential implications for human health and ecosystem quality.
The use of seismic ground particle motion for snow avalanche release area identification
Authors: Roig Lafon Pere , Suriñach Emma , Tapia Mar
Published: March 2021

Knowledge of the snow avalanche release area is key information in snow avalanche studies. However, it is not easy to obtain from a remote location. The study of the seismic vibrations produced in the initial stages of the snow avalanche, makes possible to identify their origin and to link them to the starting area of the snow avalanche. We developed a methodology for this purpose, applied to seismic data acquired from a 3D seismic station (2Hz eigenfrequency) placed at Cavern A in Vallée de la Sionne experimental site (VDLS, WSL-SLF), deployed in 2013 by UB-RISKNAT. This is the closest position to the snow avalanche release areas, at 700 m to the farthest point. We focus on spontaneous triggered snow avalanches to achieve better signal-to-noise ratio and to be more realistic on its application.

For the isolation of the Signal Onset (SON) section of seismic data, which corresponds to those vibrations produced by the initial stage of the snow avalanche, we use the STA/LTA ratios and seismic signal amplitude, common methodologies in seismology. The STA/LTA is used for the identification of the first vibrations produced by the movement of the snow mass and the seismic signal amplitude thresholds for the identification of the end of the SON section -when the snow avalanche front reaches the seismic sensor position-. The 3D seismic data [ZNE components] of the SON section were processed in time windows. The study of polarization of the particle motion to obtain the direction of the back-azimuth of the signal (Vidale, 1986; Jurckevicks, 1988) was carried out for each time window of the seismic signal. The accumulation of back-azimuth directions for the entire SON section is related to the origin of the vibrations and, by extension, to the snow avalanche release area.

The entire algorithm has been automated. In its application on all the trigger activations at VDLS since 2015 until 2020, it was achieved a success rate of 78% on snow avalanche release area identification. In addition, we defined an algorithm based on STA/LTA ratio to select the snow avalanches from other seismic events, used with a success rate of 95%.

We present the application of our method in a case study, a large spontaneous snow avalanche released on 16th February 2018 at VDLS. The snow avalanche had two main release areas, clearly identified in photos of the site. The two developed fronts can be recognized in the seismic data. The directions to the release areas from Cavern A position can be identified using the presented method. Also, more interpretations can be done on the downhill snow avalanche path.
The Open-Air Laboratory Italy
Authors: Ruggieri Paolo ,   OAL-Italy
Published: March 2021

The Open-Air Laboratory is a novel concept developed by the EU-funded Operandum project (OPEn-air laboRAtories for Nature baseD solutions to Manage Environmental risk) to co-design, implement and assess the effectiveness of Nature-Based Solutions (NBSs). 

In this work we present the Open-Air Laboratory Italy (OAL-Italy) and discuss the application of the OAL as a framework for the development of innovative NBSs to mitigate the impact of hydro-meteorological hazards in present and future climate.  By combining consolidated practices in an original multidisciplinary frame, the OAL-Italy deploys novel modelling strategies, laboratory measurements and targeted monitoring open-field campaigns. In three operational sites, the NBSs are implemented via a co-design, co-development  and co-deployment approach based on a thorough interaction with key stakeholders. By describing the structure and the approach of the OAL we illustrate salient features of the methodology developed in Operandum that are instrumental for the replicability and the upscaling of the NBSs. 

Presented results address the use of the NBSs to mitigate a range of hydrometeorological hazards such as coastal erosion, flooding, storm surge and salt wedge intrusion. Innovative NBSs tested and developed by the OAL include: deep-rooted plants installed on a river embankment to prevent levee failures, special plants that can live in high salt concentration and remove salt from the river mouth water, an artificial dune and marine seagrass to mitigate the impact of storm surges and coastal erosion. We argue that the OAL constitutes an unprecedented holistic effort towards sustainable land management, adaptation to climate change and the acceptance of Nature-Based Solutions. 
A geoachaeological view on the Roman economy of Baetica – The case study Munigua (Seville, SW-Spain).
Authors: Kirchner André , Herrmann Nico , Matras Paul , Müller Iris , Meister Julia
Published: March 2021

The economy of Roman cities in Baetica, was largely diversified and depending on the city for example specialized in olive oil, halieutic or metallurgical production. The economy of the Hispano-Roman city Munigua (municipium Flavium Muniguense) was particularly based on mining and in the 1st and 2nd centuries CE Munigua was the largest producer of copper and iron in the Sierra Morena. This contribution focuses on the evaluation of soil potential for practicing agriculture and evidences for prehistoric and historic land use in the vicinity of Munigua. It aims to provide new information to the food supply strategy of Munigua and furthermore a geoarchaeological few on the diversification debate of the urban economy in the conventus Hispalensis. Applying a pedo-geomorphic approach the present study i) shows that the landscape around Munigua has the potential for an agricultural use in larger areas and would have certainly allowed a production of agricultural goods in Roman times. Additionally, the study ii) provides clear evidence for prehistoric and historic land use in region documented by multi-layered colluvial deposits and a preserved Roman hortic soil. Hence, the results pointing to a local cultivation of agricultural products as an active contribution to the food supply of Munigua. Moreover, the study provides geoarchaeological evidences supporting the concept of an economic diversification of Roman cities in Baetica province and Hispania.
No continuous suture between Kudi and Oytag: new evidence from geochronology and geochemistry data
Authors: Rembe Johannes , Sobel Edward R. , Kley Jonas , Zhou Renjie , Thiede Rasmus , Chen Jie
Published: March 2021

A lateral continuity between belts of mafic and ultramafic Paleozoic rocks found in the West Kunlun of Northern Tibet and comparable rocks, known from an outcrop in the Chinese North Pamir, has long been proposed. This led to the concept of an originally generally straight, E–W trending Oytag–Kudi suture zone. In turn, this paleogeographic model formed a key constraint for the hypothesis, that the Pamir has indented 300 km northward with respect to Tibet during the Cenozoic. We show, that the arc volcanic rocks found in the North Pamir are distinguishable from the units known from the West Kunlun.
The North Pamir is dominated by Paleozoic arc volcanic rocks. We present new geochemical and geochronological data to give a holistic view of an early to mid-Carboniferous arc complex. This belt was previously identified as an intraoceanic arc in the northeastern North Pamir. Our data yields evidence for a gradual lateral change towards the west into a Cordilleran-style arc in the Tajik North Pamir. Large leucocratic granitoid intrusions are hosted in part by Devonian to Carboniferous oceanic crust and the metamorphic Kurguvad basement block of Ediacaran age (maximum deposition age) in Tajikistan. LA-ICP-MS U-Pb dating of zircons, together with whole rock geochemistry derived from tonalitic to granodioritic intrusions, reveal a major Visean to Bashkirian intrusive phase between 340 and 320 Ma ago.
The West Kunlun experienced two major intrusive phases, connected with arc-volcanic activity — a first phase during Proto-Tethys closure in Ordovician and Silurian times and a second phase connected to the Triassic Paleo-Tethys closure. The Carboniferous arc-volcanic phase in the North Pamir clearly postdates Paleozoic arc-magmatic activity in the West Kunlun by ~100 Ma. This observation, along with geochemical evidence for a more pronounced mantle component in the Carboniferous arc-magmatic rocks of the North Pamir, disagrees with the common model of a continuous Kunlun belt from the West Kunlun into the North Pamir. Moreover, Paleozoic oceanic units younger than and west of Tarim cratonic crust challenge the idea of a continuous cratonic Tarim-Tajik continent beneath the Pamir.
Legacy effects of drought on gross primary productivity from eddy-covariance measurements
Authors: Yu Xin , Orth René , Reichstein Markus , Bastos Ana
Published: March 2021

The frequency and severity of droughts are expected to increase in the wake of climate change. Drought events not only cause direct impacts on the ecosystem carbon balance but also result in legacy effects during the following years. These legacies result from, for example, drought damage to the xylem or the crown which causes impaired growth, or from higher vulnerability to pests and diseases. To understand how droughts might affect the carbon cycle in the future, it is important to consider both direct and legacy effects. Such effects likely affect interannual variability in C fluxes but are challenging to detect in observations, and poorly represented in models. Therefore, the patterns and mechanisms inducing the legacy effects of drought on ecosystem carbon balance are necessarily needed to improve.

In this study, we analyze gross primary productivity (GPP) from eddy-covariance measurements in Germany to detect legacy effects from recent droughts. We follow a data-driven modeling approach using a random forest model trained in different sets of drought and non-drought periods. This approach allows quantifying legacy effects as deviations of observed GPP from modeled GPP in legacy years, which indicates a change in the vegetation response to hydro-climatic conditions as compared with the training period.
Ribbed bedforms, markers of palaeo-ice stream margins, basal meltwater drainage and ice flow dynamic
Authors: Vérité Jean , Ravier Édouard , Bourgeois Olivier , Pochat Stéphane , Lelandais Thomas , Clark Christopher D. , Bessin Paul , Mourgues Régis , Peigné David , Atkinson Nigel
Published: March 2021

Over the three last decades, great efforts have been undertaken by the glaciological community to characterize the behaviour of ice streams and better constrain the dynamics of ice sheets. Studies of modern ice stream beds reveal crucial information on ice-meltwater-till-bedrock interactions, but are restricted to punctual observations limiting the understanding of ice stream dynamics as a whole. Consequently, theoretical ice stream landsystems derived from geomorphological and sedimentological observations were developed to provide wider constraints on those interactions on palaeo-ice stream beds. Within these landsystems, the spatial distribution and formation processes of subglacial periodic bedforms transverse to the ice flow direction – ribbed bedforms – remain unclear. The purpose of this study is (i) to explore the conditions under which these ribbed bedforms develop and (ii) to constrain their spatial organisation along ice stream beds.  

We performed physical experiments with silicon putty (to simulate the ice), water (to simulate the meltwater) and sand (to simulate a soft sedimentary bed) to model the dynamics of ice streams and produce analog subglacial landsystems. We compare the results of these experiments with the distribution of ribbed bedforms on selected examples of palaeo-ice stream beds of the Laurentide Ice Sheet. Based on this comparison, we can draw several conclusions regarding the significance of ribbed bedforms in ice stream contexts:

Ribbed bedforms tend to form where the ice flow undergoes high velocity gradients and the ice-bed interface is unlubricated. Where the ribs initiate, we hypothesize that high driving stresses generate high basal shear stresses, accommodated through bed deformation of the active uppermost part of the bed.

Ribbed bedforms can develop subglacially from a flat sediment surface beneath shear margins (i.e., lateral ribbed bedforms) and stagnant lobes (i.e., submarginal ribbed bedforms) of ice streams, while they do not develop beneath surging lobes.

The orientation of ribbed bedforms reflects the local stress state along the ice-bed interface, with transverse bedforms formed by compression beneath ice lobes and oblique bedforms formed by transgression below lateral shear margins.

The development of ribbed bedforms where the ice-bed interface is unlubricated reveals distinctive types of discontinuous basal drainage systems below shear and lobe margins: linked-cavities and efficient meltwater channels respectively.

Ribbed bedforms could thus constitute convenient geomorphic markers for the reconstruction of palaeo-ice stream margins, palaeo-ice flow dynamics and palaeo-meltwater drainage characteristics.
GlacierMap: a citizen science mapping tool for evaluating glacier change and contributing to climate literacy
Authors: Clason Caroline , Rangecroft Sally , Kallis Gina , Lewin Shaun , Mullier Tom , Blake Will , Stewart Iain
Published: March 2021

Glacier retreat provides clear, visual evidence of environmental change in response to warming temperatures around the world. In the tropical Andes of Peru, glaciers act as critical buffers to water supply essential to water, food, and energy security downstream, especially during the dry season. The direct and indirect impacts of glacier change are an important part of the global sustainability challenge within the context of both climate change and increased pressures on resources. Public understanding around glacier-fed water supplies, and subsequent threats to this for millions of people due to climate change, is an important component of climate literacy.

In this context, we have developed a web-based interdisciplinary citizen science glacier mapping tool (GlacierMap) to help to raise awareness of these issues, particularly amongst UK high school pupils, and to contribute to increased public support for mitigating and adapting to the impacts of climate change. Users of GlacierMap undertake an interactive learning experience by mapping a glacier from two different periods (1984 and 2018) from freely available Landsat data, resulting in a visual demonstration of glacier retreat within Peru’s Cordillera Blanca, while learning more about the impacts of this retreat from information provided by the project. 

During the first four months of data collection we integrated pre- and post-mapping questionnaires into the GlacierMap app to evaluate the extent to which participation in mapping impacted understanding of glacier change and concern regarding the associated impacts. We also assessed the value of ‘crowd-sourcing’ glacier mapping for the purposes of glacier monitoring and data generation through comparison of mapping conducted by the general public and that of a control group with previous education and/or work experience in glaciology. In doing so, we have identified a number of challenges and opportunities with regards to the use of a citizen science-based educational activity for climate learning. Challenges relate to recruitment of participants, evaluation, and ethics (particularly when working with children and young people), while opportunities were identified in terms of increasing public awareness, the provision of alternative forms of learning, and global reach.  