bluuebunny/crossref_metadata_2025 huggingface dataset:
Response of four peatland emergent macrophytes to salinity and short salinity pulses
Authors: Batistel Cheryl , Porsche Christian , Jurasinski Gerald , Schubert Hendrik
Published: March 2022

Sea-level rise intensifies saltwater influx into coastal wetlands causing osmotic stress and probably changing vegetation composition. To determine especially the impact of salinity pulses as occurring during flooding events, dominant peatland macrophytes, Typha latifolia, Carex acutiformis, Schoenoplectus tabernaemontani and Phragmites australis, were exposed to different salinity regimes, consisting of control (permanently freshwater and permanently brackish water) and brackish-water treated groups with different durations of alternating exposure before returning to freshwater conditions (2 days brackish then 2 days fresh; 4 days brackish then 4 days fresh; 2 days brackish then 4 days fresh).  We measured plant height, leaf area and chlorophyll fluorescence weekly and determined the root:shoot ratio and photosynthetic pigment concentrations upon termination of study.

Salinity suppressed the growth of T. latifolia and C. acutiformis resulting in shorter plants, smaller mean leaf area and higher root:shoot ratios whereas photosynthetic pigment ratios and chlorophyll fluorescence were not affected. Moreover, shorter, but frequent salinity pulses (alternate 2 days brackish water then 2 days freshwater, and 2 days brackish water then 4 days freshwater) decreased the height of T. latifolia while C. acutiformis did not react negatively. Height and root:shoot ratio of both P. australis and S. tabernaemontani were neither affected by salinity nor by the frequency of salinity pulses. Also photosynthetic pigment ratios and chlorophyll fluorescence yield did not differ between treatments in S. tabernaemontani. In contrast, P. australis showed signs of successful acclimation through decreased chlorophyll a:carotenoid ratio and high chlorophyll fluorescence yield under both low and high irradiances. These results imply that with increasing seawater influx into coastal peatlands, T. latifolia and C. acutiformis will probably experience growth retardation or may even be replaced eventually by S. tabernaemontani or P. australis since they are more resilient against salinity and frequent salinity pulses.
Improving interpretation of sea-level projections through a machine-learning-based local explanation approach
Authors: Rohmer Jeremy , Thieblemont Remi , Le Cozannet Goneri , Goelzer Heiko , Durand Gael
Published: March 2022

Sea-level projections are usually calculated from numerical simulations using complex long-term numerical models (or a chain of models) as part of multi-model ensemble studies. Because of their importance in supporting the decision-making process for coastal risk assessment and adaptation, improving the interpretability of these projections is of great interest. Specifically, it is assumed that clear and transparent explanations of projected sea-level changes can increase the trust of the end-users, and ultimately favor their engagement in coastal adaptation. To this end, we adopt the local attribution approach developed in the machine learning community, and we combine the game-theoretic approach known as ‘SHAP’ (SHapley Additive exPlanation, Lundberg & Lee, 2017) with tree-based regression models. We applied our methodology to sea-level projections for the Greenland ice sheet computed by the ISMIP6 initiative (Goelzer et al., 2020) with a particular attention paid to the validation of the procedure. This allows us to quantify the influence of particular modelling decisions and to express the influence directly in terms of sea level change contribution. For Greenland, we show that the largest predicted sea level change, 19cm in 2100, is primarily attributable to >4.5cm (i.e. nearly 25%) to the choice of the model parameter that controls the retreat of marine-terminating outlet glaciers, i.e. to the modelling of the retreat rate of tidewater glaciers; other modelling decisions (choice of global climate model, formulation of the ice sheet model ISM, model grid size, etc.) have only a low-to-moderate influence for this case (with contribution of 1-2cm). This type of diagnosis can be performed on any member of the ensemble, and we show how the aggregation of all local attribution analyses can help guide future model development as well as scientific interpretation, particularly with regard to model spatial resolution or the selection of a specific model formulation.

This study was supported by the PROTECT project, which received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No 869304.

References

Goelzer, H., et al. (2020). The future sea-level contribution of the Greenland ice sheet: a multi-model ensemble study of ISMIP6. The Cryosphere 14, 3071-3096.

Lundberg, S.M., & Lee, S.I. (2017). A unified approach to interpreting model predictions. In Proceedings of the 31st international conference on neural information processing systems (pp. 4768-4777).
Analysis of the land cover impact on boundary layer height from WRF and BLLAST data
Authors: Román-Cascón Carlos , Lothon Marie , Lohou Fabienne , Hartogensis Oscar , Vila-Guerau de Arellano Jordi , Pino David , Yagüe Carlos , Pardyjak Eric
Published: March 2022

The effects of the land-cover (LC) type on the surface fluxes have been investigated using observational data and numerical weather prediction models in numerous studies. Most of these works stress the need for a realistic and accurate representation of the LC within the models, including appropriate soil and vegetation parameters. This is needed to obtain more realistic near-surface atmospheric processes, leading to better forecasts of atmospheric variables of common interest (2-m temperature, 10-m wind speed, relative humidity, etc.). In a previous work, we have studied these effects focusing on a fair-weather day in a heterogeneous area of southern France. To this aim, we used the Weather Research and Forecasting (WRF) model at 1 km with an improved (30-m and more realistic) representation of the LC, configured with four land surface models (LSM): Noah, Noah-MP, CLM4 and RUC.

The results showed that the influence of LC on surface fluxes were important but differed depending on the LSM, displaying some extreme flux values for specific LC categories (e.g., urban and conifer). This opened the question of how these effects impacted the development of the atmospheric boundary layer (ABL), which motivated the present work. To this aim, we analysed the ABL height (zi) simulated by WRF in each LC category using the different LSM. These values were compared to those observed with multiple instrumentation (radiosoundings, unmanned aerial vehicles, wind profilers, etc.) available during the Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST) field campaign, which took place in the area of study in summer 2011.

The zi simulated values were similar in magnitude and in temporal evolution than those observed, indicating a good performance of the model for the 4 LSMs. However, some LSM displayed a higher variability in the simulated zi depending on the sensible/latent heat partitioning and on the type of LC. These results indicate that the important effects of the LC type on the surface fluxes are transferred to the top of the PBL, affecting zi even from an analysis of this variable at a model resolution of 1x1 km.

In order to disentangle whether the spatial variability of the modelled zi is close to the reality, for future works we highlight the importance of intensive and frequent zi measurements at the field over different nearby sites with contrasting LC. This will help to continue understanding how the surface forcing affects the PBL development and to what extent the processes reproduced in the model differ from those observed in the reality.
Global hybrid modeling of ultra-low frequency solar wind foreshock waves at Mercury, Venus and Mars
Authors: Jarvinen Riku , Kallio Esa , Pulkkinen Tuija
Published: March 2022

We study the solar wind interactions of Mercury, Venus and Mars in a global hybrid model, where ions are treated as particles and electrons form a charge-neutralizing fluid. We concentrate on the formation of large-scale, ultra-low frequency (ULF) waves in planetary ion foreshocks and their dependence on solar wind and interplanetary magnetic field conditions in the inner solar system. The ion foreshock forms in the upstream region ahead of the quasi-parallel bow shock, where the angle between the shock normal and the magnetic field is small enough. The magnetic connection to the bow shock allows the backstreaming of solar wind ions leading to the formation of the ion foreshock. This kind of beam-plasma configuration is a source of free energy for the excitation of plasma waves. The foreshock ULF waves convect downstream with the solar wind flow and encounter bow shock and transmit in the downstream region. The analyzed simulation runs use more than two hundred simulation particles per cell on average to allow fine enough velocity space resolution for resolving the foreshocks and waves self-consistently. We find significant differences in wave and foreshock properties between these three planets and discuss their causes.
Spatio-temporal variation of water soluble organic carbon in an intermittent catchment (Hesse, Germany) 
Authors: Santowski Alexander , Chifflard Peter
Published: March 2022

The terrestrial carbon cycle is a well researched topic, but for this we basically assume a perennial water flow, which transports the organic carbon along terrestrial flow pathways from the soils to the fluvial network. Climate change will accelerate hydrological processes within water basins and lead to more intermittent catchments, where internal water fluxes will be interrupted and subsurface water flow pathways disturbed due to dry periods. From this perspective, the question arises, what is the impact of an intermittent catchment in the low mountain range on water-soluble carbon transport in the headwaters? To meet this question soil samples were taken seasonally including snowmelt events both in an intermittent and a perennial catchment of a headwater stream over a period of one year. A total number about 700 soil samples were collected in five field campaigns. A transect-based system was used to sample the slopes along the upper slope, middle slope and lower slope. The sample points were chosen to cover all catchment slopes and also the exposures. In the laboratory, the following indicators were determined with the help of a TOC analyser (Shimadzu), C/N analyser (Elementar), photometer (Thermo Fischer) and fluorescence spectrometer (Shimadzu): DOC (WSOC), TOC, SUVA254, spectral slopes, BIX, FI and freshness index. The analysis of the comprehensive dataset aimed to build a bridge between the clear changes in the individual events and the annual course and to show how changes, such as the dry fall in the intermittent catchment, 'first flush' effects during heavy rainfall events and new carbon input in autumn through leaf fall impact the spatial and temporal variability of WSOC, which indicates changing of subsurface transport pathways. Preliminary results indicate that indices and total dissolved carbon in the intermittent catchment show differences (factor 0.9) compared to the perennial catchment.
The long-term  biogeochemical fate of C in Subarctic thawing peat plateaus
Authors: Kjær Sigrid Trier , Nedkvitne Nora , Westermann Sebastian , Dörsch Peter
Published: March 2022

Global warming causes permafrost to thaw at an unprecedented rate. In Northern Scandinavia, permafrost peat plateaus have been found to decline rapidly during the last decades, releasing old organic carbon to decomposition and runoff. Thawing peat plateaus can partly turn into thermokarst ponds, with consequences for the biogeochemical fate of the released carbon. We investigated carbon degradation of thawing permafrost peat by incubating permafrost peat and thermokarst sediments from three peat plateaus in Northern Norway. The samples were incubated field moist at 10oC for almost one year. Initial decomposition was dominated by CO2 production which strongly responded to oxygen availability, while methane (CH4) production was small. Methane production increased drastically after more than ten months, indicating that thawed permafrost peat has a considerable potential to produce CH4 after a time lag. The cumulative CH4 production of thawed permafrost peat after one year of incubation exceeded that of overlaying active layer peat by up to 641 times, illustrating the potential of thawing subarctic permafrost to act as an additional CH4 source. Comparing laboratory thawed permafrost peat to thermokarst peat revealed remarkable differences in CH4 production, with much higher CH4 production potentials in thermokarst sediments during the first months of incubation and in some samples exceeding CH4 production measured in permafrost peat after one year. This suggests that the potential to produce CH4 increases dramatically with thermokarst formation. Interestingly, thawed permafrost peat produced more DOC over the period of one year than gaseous C (CO2 and CH4), which suggests that hydrological conditions are key to the understanding of the fate of C released from thawing peat plateaus.
Impacts of mineral dust on soils and vegetation at Lù’àn Mân (Kluane Lake), Yukon Territory).
Authors: Pouillé Sophie , Talbot Julie , King James
Published: March 2022

Dust is a major aerosol in the atmosphere. Atmospheric dust originates from human activities or natural processes and the deposition of dust affects several ecological and biogeochemical processes. Lù’àn Mân (61°13’03’’ N, 138°37’34’’ W) is located between the Ruby Ranges on the east and the Kluane Ranges in the St. Elias mountains on the west, and on the traditional lands of Kluane, Champagne-Ashihik, and White River First Nations. Kaskawulsh Glacier, located 25 km from the A’ą̈y Chù (formerly the Slims River) delta, began to retreat in the nineteenth century and this retreat accelerated in the late twentieth and early twenty-first centuries. In 2016, Slims Lake had partially drained, leading the water to be re-routed from A’ ą̈y Chù into Kaskawulsh River. Therefore, the level of Lù’àn Mân fell, and the drying of the riverbed became an important source of aeolian sediments and important dust storms were observed. We studied dust and trace elements deposition in the area in lichens and soils. The objective of this study was to determine the impacts of dust deposition on trace elements concentrations in vegetation and soils along a deposition gradient. To do this, we sampled lichens (Peltigera canina) and soils at sixty sites in the zone affected by the dust storms. We analyzed six trace elements (Ni, Cu, Zn, As, Cd, Pb) by ICP-MS. The results showed that the sites close to the delta had higher trace element concentrations than the sites 10 and 20 km away.
Multiple equilibria of the vegetation-atmosphere system in radiative-convective equilibrium storm-resolving simulations with interactive leaf phenology
Authors: Lee Junhong , Hohenegger Cathy , Chlond Andreas , Schnur Reiner
Published: March 2022

Storm-resolving simulations where deep convection can be explicitly resolved are performed in the idealized radiative-convective equilibrium framework to explore multiple equilibria in the vegetation-atmosphere system and the role of interactive leaf phenology. Firstly, by initializing the system with different initial soil moisture and leaf area index (LAI) conditions, we find three equilibrium states: a hot desert state without vegetation, an intermediate sparsely vegetated state, and a wet vegetated state. The existence of the three equilibrium states is subdued only to initial soil moisture conditions, not to initial LAI. The wet vegetated state is the most probable state among the multiple equilibria starting at different initial soil moisture and LAI. This indicates that a quite harsh environment, with soil moisture values very close to the permanent wilting point, is needed to kill leaves. It also implies that the vegetation-atmosphere system is more stable with interactive leaf phenology and can be interpreted as Amazon may be more resilient to the disturbances than we have thought. Secondly, interactive leaves allow an earlier transition between the intermediate to the wet vegetated state. These results imply that the vegetation-atmosphere system is more stable with interactive leaf phenology and can be interpreted as Amazon may be more resilient to the disturbances than we have thought. In our set-up, interactive leaves are only important for soil moisture larger than 54%, and their effect could be well approximated by prescribing the LAI to its maximum value. Finally, our sensitivity experiments reveal that leaves influence the climate equally through their controls on canopy conductance and vegetation cover, whereas albedo plays a negligible role.
A data-driven approach to understanding the equilibria behaviour of salt mixtures in built cultural heritage
Authors: Orr Scott Allan , Godts Sebastiaan , De Kock Tim
Published: March 2022

Salt weathering is a complex and active area of research, with implications for tangible cultural heritage worldwide. A preventive conservation approach is often taken to limit salt crystallisation cycles, which requires an understanding of the relative risks of scenarios and their respective heritage characteristics, salts present, and the climate, including climate change. Equilibrium relative humidity is an important property that indicates this risk: typically, it is represented by specific RH% and temperature derived from a single salt. The behaviour of single salts does not accurately represent the behaviour of salt mixtures, which are far more common in cultural heritage contexts. To address this, 11412 salt mixtures present in the built environment have been analysed using the ECOS/Runsalt model to predict their mixture-based mutual relative humidity of crystallisation and deliquescence points, the salt mixture composition, as well as the relative humidity of crystallisation and deliquescence for individual salts in the mixtures. This dataset, although sampled primarily from Belgian cultural heritage sites, is representative of the general classes of salt mixtures found in the built environment globally. This analysis represents an important step in developing a generalised statistical method for parameterising environmental time series data for salt weathering risk within climate change scenarios, as well as progressing fundamental knowledge on the behaviour of salt mixtures in built cultural heritage.
FindAScienceBerth: connecting underrepresented groups in marine science with available berths on scientific research vessels
Authors: Fisher Ben J. , McGregor Anna , Hendry Katharine R. , Van Ladeghem Katrien J.J. , Marzocchi Alice , Fielding Sophie , Darlington Eleanor , Anderson Madeline , Joshi Siddhi , Sieradzan Katie
Published: March 2022

Scientific research vessels are highly specialist resources in constant demand, often scheduled many years in advance of a research cruise and typically awarded to a narrow selection of permanently employed eligible investigators. The ability to access vessels is essential for a wide range of geoscientific research from paleoenvironmental sedimentary studies through to understanding modern day marine biodiversity. The high demand and low supply problem of accessing cruises means that participation can often be limited to small networks within the awarded discipline. This can present a barrier to marine scientists who wish to gain offshore experience, despite the fact that research vessels may have greater capacity than is required by any one scientific party. This is particularly true for early career scientists who usually work on timelines shorter than those required for cruise planning, and those from non-traditional academic backgrounds who may be less well connected to funded networks.

FindAScienceBerth is a project aiming to match those who wish to partake in a scientific cruise with spare capacity through identifying available berths on scheduled cruises. The long term goal of FindAScienceBerth is to provide opportunities to those who would otherwise be excluded from conducting offshore research to gain experience essential for career development, and in turn better utilise available ship capacity. Here, we will present our background research, quantifying unused berths on UK research vessels, demonstrating the potential of our initiative. Additionally, we will introduce the interface of FindAScienceBerth, showing how we have adapted the existing pan-European Marine Facilities Planning tool for cruise scheduling in order to identify and advertise spare capacity. We will demonstrate how principal scientific officers can advertise spare berths and how prospective participants can identify and apply for these roles. Finally, we will give an overview of the process we have developed to ensure an EDI compliant recruitment practice for filling ship berth vacancies and our EDI monitoring work throughout the application process. Such a process could be applicable to similar schemes across the geosciences which seek to increase equality, diversity and inclusivity by creating opportunities for the development of practical skills.

For further information please see our project site: findascienceberth.wordpress.com
Transition Probabilities of Wind-driven Ocean Flows
Authors: van Westen René , Dijkstra Henk
Published: March 2022

The quasi-geostrophic wind-driven double-gyre ocean circulation in a midlatitude rectangular basin is a multi-stable system. Under time-independent forcing, the number of steady states is controlled by the Reynolds number. For a specific range of Reynolds numbers, at least two stable steady states exist. In the quasi-geostrophic model, sub-grid scale processes are usually heavily parameterised, either by deterministic or stochastic representation. In the stochastic case, noise-induced transitions between the steady states may occur.

A standard method to determine transition rates between different steady states is a Monte Carlo approach. One obtains sufficient independent realisations of the model and simply counts the number of transitions. However, this Monte Carlo approach is not well-suited for high-dimensional systems such as the quasi-geostrophic wind-driven ocean circulation. Moreover, when transition probabilities are rare, one needs long integration times or a large number of realisations.

Here we propose a new method to determine transition rates between steady states, by using Dynamically Orthogonal (DO) field theory. The stochastic dynamical system is decomposed using a Karhunen-Loéve expansion and separate problems arise for the ensemble mean state and the so-called time-dependent DO modes. Each DO mode has a specific probability density function, which represents the probability in that direction of phase space. In the case of two steady states, at least one of the DO modes has a bimodal distribution. We analyse transition probabilities using this specific DO mode, which is more efficient compared to the ordinary Monte Carlo approach. We will present the general method and show results for transition probabilities in the quasi-geostrophic wind-driven double-gyre ocean circulation.
Combining CMIP data with a convection-permitting model and observations to project extreme rainfall under climate change
Authors: Klein Cornelia , Parker Douglas J. , Jackson Lawrence S. , Marsham John H. , Taylor Christopher M. , Rowell David P. , Guichard Françoise , Vischel Théo , Famien Adjoua Moise , Diedhiou Arona
Published: March 2022

Due to associated hydrological risks, there is an urgent need to provide plausible quantified changes in future extreme rainfall rates. Convection-permitting (CP) climate simulations represent a major advance in capturing extreme rainfall and its sensitivities to atmospheric changes under global warming. However, they are computationally costly, limiting uncertainty evaluation in ensembles and covered time periods. This is in contrast to the Climate Model Intercomparison Project (CMIP) 5 and 6 ensembles, which cannot capture relevant convective processes, but provide a range of plausible projections for atmospheric drivers of rainfall change. Here, we quantify the sensitivity of extreme rainfall within West African storms to changes in atmospheric rainfall drivers, using both observations and a CP projection representing a decade under the Representative Concentration Pathway 8.5 around 2100. We illustrate how these physical relationships can then be used to reconstruct better-informed extreme rainfall changes from CMIP, including for time periods not covered by the CP model. We find reconstructed hourly extreme rainfall over the Sahel increases across all CMIP models, with a plausible range of 37-75% for 2070-2100 (mean 55%, and 18-30% for 2030-2060). This is considerably higher than the +0-60% (mean +30%) we obtain from a traditional extreme rainfall metric based on raw daily CMIP rainfall, suggesting such analyses can underestimate extreme rainfall intensification. We conclude that process-based rainfall scaling is a useful approach for creating time-evolving rainfall projections in line with CP model behaviour, reconstructing important information for medium-term decision making. This approach also better enables the communication of uncertainties in extreme rainfall projections that reflect our current state of knowledge on its response to global warming, away from the limitations of coarse-scale climate models alone.
Evolution of the reservoir of volatiles in the protosolar nebula 
Authors: Schneeberger Antoine , Mousis Olivier , Aguichine Artem , Lunine Jonathan
Published: March 2022

How volatiles were incorporated in the building blocks of planets and small bodies in the protosolar nebula remains an outstanding question. Some scenarios invoke the formation of planetesimals from a mixture of refractory material and amorphous ice in the outer nebula while others argue that volatiles have been incorporated in clathrate or pure condensate forms in these solids. Here we study the fate of volatiles (H2O, CO, CO2, CH4, H2S, N2, NH3, Ar, Kr, Xe, and PH3) initially delivered in the forms of amorphous ice or pure condensates to the protosolar nebula. We investigate the radial distribution of these volatiles via a transport module coupled with an accretion disk model. In this model, multiple icelines are considered, including the condensation fronts of pure condensates, as well as those of clathrates when enough crystalline water is available at given time and location. Our simulations show that a significant fraction of volatiles can be trapped in clathrates only if they have been initially delivered in pure condensate forms to the disk. Under specific circumstances, volatiles can be essentially trapped in clathrates but, in many cases, the clathrate of a given species coexists with its pure condensate form. Those findings have implications for the compositions of giant planets and comets.
Using machine learning for defining distributed monitoring variables correlated to the occurrence of rainfall-induced shallow landslides and debris flows: a case study in Campania region, Italy
Authors: Calvello Michele , Pecoraro Gaetano , Esposito Massimo , Pota Marco , Rianna Guido , Reder Alfredo
Published: March 2022

Rainfall-induced shallow landslides and debris flows often cause casualties and significant damage to property. Territorial landslide early warning systems are recognized as an important countermeasure to avoid or reduce fatalities during rainfall events. A reliable warning model is a key component of these systems. Warning models operating over large areas usually relate the occurrence of landslides to rainfall monitoring data adopting appropriate thresholds (e.g., intensity-duration, cumulated rainfall-duration, hourly/daily rainfall indicators). The increasing availability of large sets of atmospheric and land monitoring data represents an opportunity to upgrade and improve existing landslide warning models. At the same time, appropriately treating such data may pose a significant challenge to analysts that are used to deal with much smaller amounts of data.

The objective of this preliminary study is to demonstrate that machine learning techniques can be effectively used to process monitoring data over large areas at regional scale, with the aim of defining and selecting the variables that best correlate with the initiation of shallow landslides and debris flows. The machine learning models have been tested in one of the warning zones defined by the regional civil protection agency for hydrogeological risk management in Campania (Italy). Two categories of data are used for the analyses: distributed monitoring data, and a landslide inventory. The monitoring variables are derived from the fifth generation of ECMWF atmospheric reanalysis (ERA5), available with a spatial resolution of about 31 km and a temporal resolution of 1 h (http://dx.doi.org/10.24381/cds.adbb2d47). Data on landslide events come from “FraneItalia”, a geo-referenced openly available catalogue of Italian landslides created consulting online news from 2010 onwards (http://dx.doi.org/10.17632/zygb8jygrw.2). Different machine learning models have been defined, trained, and tested to relate the occurrence of landslides in the case study area to multiple variables arising from different combinations of the adopted monitoring data, mainly rainfall and soil water content. The performance of these models is evaluated by means of standard contingencies and skill scores. The best performing variables are used to define an optimal multivariate threshold to be adopted in the landslide warning model. The results of the optimal model are also compared with the outcomes of an application of a more classical exceedance probability statistical methodology based on cumulated rainfall-duration thresholds.
Meso and submesoscale oxygen and particle variability in the northern Benguela Upwelling System from glider and model data
Authors: Lovecchio Elisa , Henson Stephanie , Carvalho Filipa , Briggs Nathan
Published: March 2022

The northern Benguela Upwelling System is characterized by significant oxygen and particle anomalies due to the lateral influx of both oxygenated water from the south and low-oxygen water that flows south across the northern Angola-Benguela front (ABF). Mesoscale features developing at the front and in the shelf region of the upwelling system further modulate these anomalies. Here we present the results of a study based on high-resolution glider data collected from the surface to 1000 m depth in February – June 2018 at 100 km off the coast of the northern Benguela (18°S). These in-situ data are further interpreted and generalized using high-resolution model output from the physical Regional Ocean Modeling System (ROMS) coupled to the Biogeochemical Ecosystem Cycling (BEC) model. Using the glider data, we discuss the prevalence of low oxygen events characterized by O2 < 120 µmol (sub-lethal level), O2 < 60 µmol (hypoxia) and O2 < 30 µmol (severe hypoxia) as a function of depth and time. We present two different impacts of eddies on oxygen concentrations: extreme hypoxia associated to a subsurface anticyclone generated at the Benguela shelf, and mixing between high and low oxygen water at the rim of a large surface anticyclone generated at the ABF. Through a spike analysis of the glider data, we study the distribution of large and small particles as a function of depth and time, and relate them to the identified mesoscale structures. We find that the subsurface eddy corresponds to a local low in small particle concentrations, while the frontal anticyclone is associated to a deep export event of both small and large particles. Further, we find that the region is characterized by a deep particle layer between 300 m and 500 m. Using the model output, we identify the drivers of this deep particle layer and deep export events and discuss the relative role of physics and biology in the determination of the vertical distribution of particles in the region of study.
Multi-instrumental investigation of the solar flares impact on the ionosphere occurring in December 2006
Authors: Barta Veronika , Natras Randa , Srećković Vladimir , Koronczay David , Schmidt Michael , Šulic Desanka
Published: March 2022

The sudden increase of X-radiation and EUV emission following solar flares causes additional ionization and increased absorption of electromagnetic (EM) waves in the sunlit hemisphere of the Earth’s ionosphere. The solar flare impact on the ionosphere above Europe on 05 and 06 December 2006 was investigated using ground-based (ionosonde and VLF) and satellite-based data (Vertical Total Electron Content (VTEC) derived from Global Navigation Satellite Systems (GNSS) observations and VLF measurements from the DEMETER satellite). Based on the geomagnetic indices Kp and Dst, 05 December was a quiet day, while there was a geomagnetic storm on 06 December 2006.

The total fade-out of the EM waves emitted by the ionosondes was experienced at all investigated stations during an X9 class flare on 05 December. The variation of the fmin parameter ( representing the minimum frequency of the echo trace observed in the ionogram, and is a rough measure of the “nondeviative” absorption) and its difference between the quiet period and during the flares have been analyzed. A latitude dependent enhancement of fmin (2-9 MHz) and Delta_fmin (relative change of about 150-300 %) was observed at every station at the time of the X9 (on 05 December) and M6 (on 06 December) flares.

Furthermore, we analyzed VTEC changes during and after the flare events with respect to the mean VTEC values of reference quiet days. During the X9 solar flare, VTEC increased depending on the latitude (2-3 TECU and 5-20 %). On 06 December, the geomagnetic storm increased ionization (5-10 TECU) representing a „positive” ionospheric storm. However, an additional peak in VTEC related to the M6 flare could not be detected.

We have also observed a quantifiable change in transionospheric VLF absorption of signals from ground transmitters detected in low Earth orbit associated with the X9 and M6 flare events on 05 and 06 December in the DEMETER data. Moreover, amplitude and phase of ground-based, subionospherically propagating VLF signals were measured simultaneously during the investigated flares to analyze ionosphere reaction and to evaluate the electron density profile versus altitude. For the X9 and M6 flare events we have also calculated the ionospheric parameters (sharpness, reflection height, etc.) important for the description and modeling of this medium under forced additional ionization.
Evaluation of the new 4D-variational inverse modeling system, CIF-CHIMERE: Inversion of NOx emissions over China using OMI NO2 observations
Authors: Savas Dilek , Dufour Gaëlle , Coman Adriana , Siour Guillaume , Fortems-Cheiney Audrey , Pison Isabelle , Berchet Antoine , Bessagnet Bertrand
Published: March 2022

Nitrogen oxides (NOx = NO2 + NO) are primary pollutants that are mainly produced by anthropogenic activities. They play a key role in oxidation processes in the troposphere. They control the photochemical production of Ozone (O3) and affect the concentration of the hydroxyl radical (OH), thus causing air quality degradation. Industrialized countries with high air quality degradation such as China, are implementing mitigation strategies with the aim of improving air quality. The evaluation of these strategies requires having precise and rapidly updated emission inventories. Inverse modeling approaches based on satellite observations are useful tools as they can provide independent inventories to complement the traditional bottom-up inventories. In this study, we propose to evaluate the potential of the new 4D-Var inverse modeling system, CIF (Community Inversion Framework), coupled with the CHIMERE chemistry-transport model to inverse NOx emissions. We focus on the case study of NOx emissions over China for the year 2015 and use OMI satellite NO2 observations as constraints. The HTAP NOx emissions from 2010 are used to prescribe prior emissions and the inversion is performed at 0.5° resolution. The posterior NOx emissions are validated against surface NO2 concentration measurements and compared to the recent MEIC bottom-up inventory from the year 2015.
Sulfur transfer along a metasomatized serpentinite-metagabbro contact in the Voltri Massif, Italy
Authors: Schwarzenbach Esther , Streicher Linus , Dragovic Besim , Scicchitano Maria Rosa , Wiechert Uwe , Codillo Emmanuel , Klein Frieder , Marschall Horst , Scambelluri Marco
Published: March 2022

Subduction zones provide a key link between the surficial biogenic, atmospheric and hydrospheric geochemical cycles with the Earth’s internal reservoirs. Sediment compaction and dehydration of variably altered oceanic lithosphere during subduction release volatile species (containing e.g., S, H, C, N) to the overlying mantle wedge. In particular, sulfur plays a key role in the formation of porphyry ore deposits and has a major control on redox processes in subduction zones, given it occurs in variable oxidation states from oxidized sulfate (S6+) to reduced sulfide (S2-). Here we studied samples from a contact between serpentinite and partly metasomatized eclogitic metagabbros in the Voltri Massif (Italy). We determined the bulk rock and in situ sulfur isotope composition of pyrite grains and combined this with detailed mineralogic and petrologic investigations. Along the serpentinite-metagabbro contact, the metagabbros are metasomatized to actinolite-chlorite schists and metagabbros rich in epidote and Na- and Na-Ca amphiboles. The serpentinites as well as the actinolite-chlorite schists along the serpentinite-metagabbro contact have very low sulfide contents and provide evidence for the oxidation of sulfides, including formation of Fe-oxides. Sulfur input from the serpentinite-metagabbro contact towards the less metasomatized eclogitic metagabbros is observed. This sulfur input is reflected by bulk rock δ34S values that increase from initially around +1.5‰ in samples distant from the contact to +7.3 to +12.5‰ in samples near the contact. This trend correlates with a general increase in the in situ δ34S values from core to rim of individual pyrite grains. Distinct Co and Ni growth zones in pyrite and variations in the in situ δ34S values indicate multiple phases of pyrite growth during subduction and exhumation of these rocks, with the last stage of pyrite growth clearly related to Mg-metasomatism along the serpentinite-metagabbro contact. Thus, this study provides new insight into processes of sulfur migration during metasomatism of gabbroic rocks within the subducting slab and at the slab–mantle interface.
Effect of radial geometry on autocatalytic reaction-diffusion-advection fronts 
Authors: Comolli Alessandro , Brau Fabian , De Wit Anne
Published: March 2022

The understanding of the dynamics of reaction diffusion (RD) fronts is crucial for a wide variety of applications in chemistry, biology, physics and ecology, and it is especially important for hydrogeological problems involving chemical reactions. Reactive transport in geological media is generally controlled by the interplay of physical and chemical processes, which can give rise to complex dynamics of the reaction front. An important subset of RD fronts is represented by autocatalytic fronts, for which it is well known that the coupling of diffusion and chemical processes gives rise to self-organization phenomena and pattern forming instabilities [1]. When the initial interface between the reactant and the catalyst is a straight line, the autocatalytic front behaves as a solitary wave, which means that the shape of the front remains unchanged as it travels towards the nonreacted species [2]. The coupling with uniform advection does not change the picture, provided that the system is described in the proper comoving reference frame.

However, in this work we show that the geometrical properties of the injection source have a significant impact on the reaction front dynamics. Indeed, if the injection of one reactant into the other is performed radially at a constant flow rate, the pre-asymptotic dynamics of the front is strongly affected by the nonuniform velocity field. Moreover, although at long times the front still behaves as a solitary wave, the efficiency of the reaction is strongly increased in virtue of the increasing volume occupied by the radial front. We show how injecting a finite amount of reactant into the catalyst gives rise to collapsing fronts and we characterize their dynamics in terms of their position, width and the production rate. In contrast, when the reactant is injected into the catalyst at a constant flow rate, a stationary regime is reached where, unlike the case of solitary waves, the autocatalytic front does not move.      

 

References:

[1] I. R. Epstein and J. A. Pojman, An Introduction to Nonlinear Dynamics: Oscillations, Waves, Patterns, and Chaos (Oxford University Press, Oxford, 1998)

[2] P. Gray, K. Showalter, and S. K. Scott, J. Chim. Phys. 84, 1329 (1987)
Future weakening of southeastern Tropical Atlantic Ocean interannual SST variability in a nested coupled model
Authors: Prigent Arthur , Imbol Koungue Rodrigue Anicet , Lübbecke Joke F. , Brandt Peter , Bayr Tobias , Harlaß Jan , Latif Mojib
Published: March 2022

Tropical Atlantic interannual sea surface temperature (SST) variability has significantly weakened since 2000. Here, we use a coupled ocean-atmosphere model with an embedded high-resolution nest in the tropical Atlantic Ocean to investigate future changes in the southeastern tropical Atlantic SST variability in response to anthropogenic global warming. In the model, the Angola-Benguela Area (ABA) is among the regions in the tropical Atlantic that exhibit the largest surface warming. Relative to 1970-1999, the SST variability in the ABA during the peak season, May-June-July (MJJ), decreases by about 24% during 2070-2099 under the worst-case scenario of the Shared Socioeconomic Pathway 5-8.5 (SSP5-8.5). The MJJ interannual temperature variability weakens along the Angolan and Namibian coasts in the top 40 m of the ocean. This reduction appears to be due to a smaller temperature response to thermocline-depth variations, i.e. a weaker thermocline feedback. The weaker thermocline feedback is found where the thermocline deepens the most. Our model results suggest that the trend towards a weakening of the interannual SST variability in the ABA observed during the recent decades could persist in the future under a worst-case global warming scenario.
Cross-checking of the nationwide Ground Motion Service (GMS) of Sweden with the previous InSAR-based results: Case studies of Uppsala and Gävle Cities
Authors: Nilfouroushan Faramarz , Gido Nureldin Ahmed Adam , Darvishi Mehdi
Published: March 2022

The interest for using Interferometric Synthetic Aperture Radar (InSAR) for ground motion detection and monitoring is rapidly increasing, thanks to the Copernicus Senetinel-1 satellites which cover relatively large areas with a 6-days revisit time. Ground motion of many locations, especially urban areas around the world have been studied using Sentienl-1 data and the rate and distribution of the ground movements have been reported. For Sweden, for example, Fryksten and Nilfouroushan (2019) and Gido et al. (2020) studied the active ground subsidence in Uppsala and Gävle cities using the Senetinel-1 data collected between 2015-2020. The Persistent Scatterer Interferometry (PSI) technique was used to estimate the subsidence rate and the results were validated with the help of precise levelling data and correlated with the geological observations. Today, fortunately, we have the nationwide GMS of Sweden (https://insar.rymdstyrelsen.se) covering almost the entire country, which provides an opportunity to compare and cross-check the results of this new service with previous studies, for example the ones reported for Uppsala and Gävle cities. The temporal coverage of satellite data used for the GMS of Sweden has an overlap with the data used in previous studies for Uppsala and Gävle cities, and the same PSI technique has been used to generate the displacement map and time series.

In this study, we used the previous PSI results of Uppsala and Gävle cities to validate the newly launched nationwide GMS of Sweden. The Line Of Sight (LOS) displacement time-series at some deforming locations  were compared for both PSI-results. Although the number and imaging date of Senetinel-1 data, and the parameters used for PSI processing are not completely the same, the compared results show a good agreement between corresponding studies on the localization and rate of the subsidence in those two cities in last  ~5 years. The validation phase of the new GMS of Sweden is in progress and our study shows the promising results, at least for urban areas in those two cities.  

References

Fryksten J., Nilfouroushan F., Analysis of Clay-Induced Land Subsidence in Uppsala City Using Sentinel-1 SAR Data and Precise Leveling. Remote Sens. 2019, 11, 2764. https://doi.org/10.3390/rs11232764

Gido N.A.A., Bagherbandi M., Nilfouroushan F., Localized Subsidence Zones in Gävle City Detected by Sentinel-1 PSI and Leveling Data. Remote Sens. 2020, 12, 2629. https://doi.org/10.3390/rs12162629
Spatiotemporal assessment of multi-sourced groundwater salinization in a coastal aquifer (Rhodope, Northern Greece)
Authors: Tziritis Evangelos , Sachsamanoglou Katerina , Aschonitis Vassilios , Dalampakis Paschalis , Doulgeris Charalampos , Panagopoulos Andreas , Pisinaras Vassilios , Kinigopoulou Vicky , Vrouhakis Ioannis
Published: March 2022

The coastal aquifer of the Rhodope region (NE Greece) is a complex groundwater system impacted by various processes that increase groundwater salinization (seawater intrusion, trapped saline lenses, geothermal fluid impact, irrigation return). In the context of the MEDSAL Project (www.medsal.net), a thorough study of its hydrogeochemical characteristics was performed to assess the spatiotemporal variations of groundwater salinization and identify the dynamics of the phenomenon.

To this aim, we used a combination of tools, including multivariate statistics analysis (MVSA) and hydrogeochemical modelling, to decipher the mechanism(s) of groundwater salinization and their evolution in time and space.

Results from Hierarchical Cluster Analysis (HCA) classified water samples into four (4) diverse groups and seven (7) subgroups that denote different hydrogeochemical and salinization phases. The different processes that control hydrogeochemistry were further assessed using R-mode factor analysis. The outcomes outlined three (3) factors that supplemented the HCA. The dominant factor is related to the cascading processes of salinization, and the secondary factors are related to anthropogenic contamination (N surplus due to agricultural activities) and the impact from the substrate (water-rock interaction).

Hydrogeochemical modelling further supported assessments and provided an overview of the spatiotemporal variability of factors and processes affecting groundwater chemistry. A set of saturation indices of key minerals related to the dominant processes identified by the MVSA were calculated and interpolated to capture the spatiotemporal dynamics. Results facilitated the development of a more representative conceptual model about salinization and the key hydrogeochemical processes affecting water quality in the area.