bluuebunny/crossref_metadata_2025 huggingface dataset:
Trench Advance in Collisional settings: insights from large scale 2D and 3D models
Authors: Laik Arijit , Schellart Wouter P. , Strak Vincent
Published: March 2021

Continental collision, which leads to mountain building (e.g. Himalayas, Alps), has been under the geodynamic modelling lenses for the last few decades. Such processes subjected to physical and numerical investigations, in conjunction with observational studies, enrich knowledge on mountain belts and have worked out the general architectural large-scale structure and crustal shortening in such regions. The intent to understand the driving forces of long term (~50 Ma) and consistent convergence at the India-Eurasia collisional zone is the goal of the dynamic self-consistent buoyancy-driven whole-mantle scale 2D and 3D models presented in this contribution. The maximum post-collisional convergence rate (~0.362 cm/year) in 2D models, is less than 2 cm/year convergence of India considering it advanced ~1000 km in about 50 Ma.  Additionally, the 2D models are inadequate in exploring the spatio-temporal evolution and dynamics of natural systems, thus necessitating modelling large scale subduction and subsequent continental collision resolving the 3D components of mantle flow.  With a whole mantle reservoir and buoyancy-driven 2D models, the observed trench advance rate, with a large and fixed overriding plate, is relatively novel and higher than previous studies and the high resolution in 2D models also shows crustal-scale localisation in conjunction with large scale mantle flow. The computationally intensive simulations have significantly large (11520 km) trench-perpendicular (in 2D and 3D) and parallel (in 3D) lengths, include two sets of modelled depths: whole mantle (2880 km) and, upper mantle + partial lower mantle (960 km) and use the Underworld2 framework. In 3D, the interaction of an adjacent subducting oceanic plate(s) significantly aids the indentation and trench advance in the collisional margin. These would help understand the dynamics of analogues system(s) in nature such as the Sunda subduction zone and the India-Eurasia collision zone.
Comparative fungal community analyses using metatranscriptomics and ITS-amplicon sequencing from Norway spruce
Authors: Schneider Andreas , Sundh John , Sundström Görel , Richau Kerstin , Delhomme Nicolas , Grabherr Manfred , Hurry Vaughan , Street Nathaniel
Published: March 2021

Microbial communities are major players in carbon and nitrogen cycling globally and are of particular importance for plant communities in the nutrient poor soils of boreal forests. Especially relevant are the fungal communities in the soil that interact with the plants in multiple ways, indirectly through their pivotal role in the breakdown of organic matter and, more directly, through mycorrhizal symbiosis with plant roots. Large-scale disturbances of these complex microbial communities can lead to shifts in soil carbon storage with unknown and global-scale long-term consequences. To understand the dynamics of these communities and their relationship to associated plants in response to climate change and anthropogenic influence, we need a better understanding of how modern “omics” methods can help us to understand compositional and functional shifts of these microbiomes. Microbial gene expression and functional activity can be assayed with RNA sequencing (RNA-Seq) data from environmental samples. In contrast, currently phylogenetic marker gene amplicon sequencing data is generally used to assess taxonomic composition and community structure of the microbiome. Few studies have considered how much of this structural and taxonomic information is included in RNA-Seq transcriptomic data from matched samples. Here we describe fungal communities using both RNA-Seq and fungal ITS1 DNA amplicon sequencing to compare the outcomes between the methods. We used a panel of root and needle samples from mature stands of the coniferous tree species Picea abies (Norway spruce) growing in untreated (nutrient deficient) and nutrient enriched plots at the Flakaliden forest research site in boreal northern Sweden. We created an assembly-based, reproducible and hardware agnostic workflow to taxonomically and functionally annotate fungal RNA-Seq data obtained from Norway spruce roots, which we compared to matching ITS amplicon sequencing data. We show that the community structure indicated by the fungal transcriptome is in agreement with that generated by the ITS data, while also identifying limitations imposed by current database coverage. Furthermore, we show examples to demonstrate how metatranscriptomics data additionally provides biologically informative functional insight at the community and individual species level. These findings highlight the potential of metatranscriptomics to advance our understanding of interaction, response and effect both between host plants and their associated microbial communities, and among the members of microbial communities in environmental samples in general.
Statistical Downscaling of Temperature Using Global Climate Model Outputs - Effect of Bias correction
Authors: Wagh Poonam , Srivastav Roshan
Published: March 2021

General Circulation Models (GCMs) are the primary source of knowledge for constructing climate scenarios and provide the basis for quantifying the climate change impacts at multi-scales and from local to global. However, the climate model simulations have a lower resolution than the desired watershed or hydrologic scale. Different downscaling methodologies are adopted to transform the global scale (coarser resolution) climate information to the local scale (finer resolution). One of the drawbacks of the GCM simulations is the systematic bias relative to historical observations. Bias correction is thus required to adjust the simulated values to reflect the observed distribution and statistics. In this study, the effect of bias correction is evaluated on the statistical downscaling models' performance to predict the temperature. Three statistical downscaling models are used: (i) Multi-linear Regression (MLR); (ii) Generalized Regression Neural Network (GRNN); and (iii) Cascade Neural Network (CasNN). The average daily temperature simulations generated by 25 GCMs of Coupled Model Intercomparison Project Phase-5 (CMIP5) are used in the study. The analysis is carried out at 22 stations of the Upper Thames River Basin (UTRB) in Canada during the baseline period of 1950 to 2005. The downscaling models' performance is evaluated using the Pearson Correlation Coefficient (CC) and Nash Sutcliffe Efficiency (NSE). The results indicated that bias correction had improved all the downscaling models' performance at all stations of UTRB. The respective increase in CC and NSE values for (i) MLR is 8% and 10%; (ii) GRNN is 4% and 7%; and (iii) CasNN is 4% and 8%. Among the three downscaling models, multi-linear regression and cascade neural network models have shown similar performance.
Methods for soil enhancement in geoheritage research: a case study from Veglia-Devero Natural Park (Lepontine Alps)
Authors: Masseroli Anna , Bollati Irene M. , Trombino Luca , Pelfini Manuela
Published: March 2021

In mountain environments, the high variability of soil forming factors (i.e., parent material, climate, relief, organism, time) is responsible for the presence of different soil types, which not only contribute to the pedodiversity but are also a component of the local cultural heritage.

Up to now, scarce attention has been paid to the soil in the geoheritage/geoconservation scientific analyses.

To promote soil as element concurring to mountain geoheritage definition, we propose a strategy to include pedological topics within a multidisciplinary trail planned in the Veglia-Devero Natural Park (Lepontine Alps). The geomorphological dynamicity and environmental change affecting during times the small mountain catchment of Buscagna hydrographic basin are illustrated with a specific address to soil characteristics. The physical and chemical properties, and pedological features of soils reflect the interaction among the other ecosystem components (i.e. geology, geomorphology and vegetation), underlining the role of soil as natural archive for reconstructing landscape evolution and for achieving a more complete assessment of Late Quaternary geomorphic events, especially surface processes.

Geopedological researches carried out in the study area, allowed to detect 7 soil profiles as potential sites of pedological interest, located in safe and accessible places, along already existing hiking paths. The selected soil profiles not only mirror the main soil types that characterize the area but also represent evidence of past environmental conditions and geomorphic dynamics.

The opportunities for hikers and mountaineers, to observe the exposed soils along the Buscagna valley, thanks to the presence of erosional scarps and subsidence areas, allow also to get more awareness of the need of geoheritage conservation strategies addressed to soil, especially in the mountain landscape where soil characteristics reflect the striking influence of its forming factors.
Comparative analysis of the bacterial community of the Patagonian lichen Peltigera frigida and its soil substrate
Authors: Leiva Diego , Fernández-Mendoza Fernando , Acevedo José , Carú Margarita , Grube Martin , Orlando Julieta
Published: March 2021

The lichen microbiome includes a diverse community of organisms, spanning widely across the bacterial tree of life. Lichens have been proposed to form partially open symbiotic systems, in which some microorganisms may be transmitted along within lichen propagules, while others are acquired from the surrounding environmental community.

In this survey, we discuss the extent to which the lichen microbiome is connected to that of its immediate substrate. For this we sampled ten specimens of the Patagonian foliose cyanolichen Peltigera frigida and their underlying soil substrates in two forest sites of the Coyhaique National Reserve (Aysén Region, Chile). Using 16S metabarcoding with primers that exclude cyanobacteria, we identified a significant taxonomic divergence between the bacterial communities of lichens and substrates.

At the Phylum level, Proteobacteria (37% of relative abundance) are most abundant within lichens, while soil substrates are dominated by Acidobacteriota (39%). At the Genus level, some bacteria are significantly more abundant in lichens, such as Sphingomonas (8% in lichens vs 0.2% in substrates) or an unassigned genus of Chitinophagaceae (10% vs 2%). Conversely, genera like the unassigned acidobacterial genus SCN-69-37 (0.9% vs 12%) are more abundant in substrates.

Overall, our results are consistent with the idea that lichens shape their microbiome obtaining components from various sources, including reproductive propagules and the substrate on which they grow. Further experimental and ecological approaches are needed to assess the contribution of these microorganisms to the fitness of the symbiotic system.

Funding: FONDECYT 1181510.
Organic carbon stabilization controlled by geochemistry in tropical rainforest soils
Authors: Reichenbach Mario , Fiener Peter , Garland Gina , Griepentrog Marco , Six Johan , Doetterl Sebastian
Published: March 2021

Stabilization of organic carbon in soils (SOC) depends on several soil properties, including the soil weathering stage and the mineralogy of parent material. As such, tropical SOC stabilization mechanisms likely differ from those in temperate soils due to contrasting soil development. To better understand these mechanisms, we investigated SOC dynamics at three soil depths under pristine tropical african mountain forest along a geochemical gradient from mafic to felsic and a topographic gradient covering plateau, slope and valley positions. We conducted a series of soil C fractionation experiments in combination with an analysis of the geochemical composition of soil and a sequential extraction of pedogenic oxides. Overall, we found that reactive secondary mineral phases drive SOC properties together with aggregation. These key mineral stabilization mechanisms for SOC were strongly related to soil geochemistry and independent of topography in the absence of detectable erosion processes. We also detected fossil organic carbon (FOC) at several sites, constituting up to 52.0 ± 13.2 % of total SOC stock in the C depleted subsoil. FOC decreased strongly towards more shallow soil depths, indicating decomposability of FOC by microbial communities under topsoil conditions. Regression analysis showed that variables affiliated with soil weathering, parent material geochemistry and soil fertility, together with soil depth, explained up to 75 % of the variability of SOC stocks and Δ14C. Furthermore, the same variables explained 44 % of the variability in the relative abundance of C associated with microaggregates versus free silt and clay associated C fractions. We conclude that despite long-lasting weathering, geochemical properties of soil parent material leave a footprint in tropical soils that affects SOC stocks and links two of the most important mineral related C stabilization mechanisms. While the identified stabilization mechanisms and controls are similar to less weathered soils in other climate zones, their relative importance is markedly different in the investigated tropical soils.
Marine heatwaves and cold-spells, and their impact on fisheries in the southern North Sea
Authors: Wakelin Sarah , Townhill Bryony , Engelhard Georg , Holt Jason , Renshaw Richard
Published: March 2021

The marine environment experiences temperature variability both in the short and long term due to a combination of variable surface heating, ocean transport and mixing effects. The impact of temperature anomalies on the marine ecosystem depends on their duration and amplitude compared with timescales of the ecological response and the susceptibility of various components of the ecosystem to the change. Even relatively short events can affect reproduction and growth, and potentially cause mortality when organism tolerance limits are exceeded.
We focus on sustained (lasting longer than 5 days) temperature events that are extreme relative to the phase of the seasonal cycle and consider both heatwaves and cold-spells. We used daily-mean near-bed temperatures from the CMEMS (https://marine.copernicus.eu/) northwest European Shelf reanalysis and analysis/forecast simulations to identify heatwaves and cold-spells for the period 1993 to 2019. Monthly fisheries landings data for 1993 to 2016 from the Cefas Fisheries Activity Database for England and Wales (https://www.gov.uk/guidance/fishing-activity-and-landings-data-collection-and-processing) were analysed to identify potential impacts of the extreme temperature events on fish and shellfish.
Widespread heatwaves and cold-spells occurred in the southern North Sea throughout the period 1993 to 2019 but with no significant trends in the extent or magnitude of events. Winter cold-spells occurred in 1994, 1996, 1997, 2010, 2011, 2013 and 2018 and there were widespread heatwaves in 1998, 2002, 2003, 2006, 2007 and 2014 to 2019. Statistical analysis of the fisheries landings data identified a link between extreme temperature events and key fish and shellfish stocks in the North Sea. Catches of sole and sea bass increased in years with cold-spells, while catches of red mullet and edible crabs decreased. For heatwaves, the impact on fisheries catch data lagged the temperature events by five years: sole, European lobster and sea bass catches increased whilst red mullet catches reduced. 
Cloud from a chip: Quantifying the activity of ice-nucleating particles in microfluidic droplets
Authors: Shardt Nadia , Isenrich Florin , Rösch Michael , Stavrakis Stavros , Marcolli Claudia , Kanji Zamin A. , deMello Andrew J. , Lohmann Ulrike
Published: March 2021

To improve the precision of climate models, it is paramount to accurately quantify the probability of ice formation under conditions (e.g., temperatures and cooling rates) that closely resemble those in the atmosphere. In recent years, microfluidic approaches have emerged as a new tool in atmospheric research. Polydimethylsiloxane (PDMS) microfluidic chips have been used to study the ice nucleation behavior of aqueous drops containing ice nucleating particles. However, PDMS readily takes up water, which compromises the stability of droplets for prolonged times. Additionally, careful temperature calibration has been required due to significant temperature gradients that arise between the bottom area of the chip that is cooled and the location of the droplets. In contrast to past work, our generated droplets are stored in fluoropolymer tubing that is impermeable to water and is immersed in an ethanol bath. Such a design has two main advantages: (i) small aqueous droplets are stable in the structure for extended periods of time beyond those possible in PDMS chips; and (ii) immersion in a liquid bath reduces the temperature gradient between droplets and chip-bottom since cooling instead occurs over all exposed surfaces. These benefits impart an ability to study individual droplets with diameters that approach the sizes of cloud droplets over several freeze-thaw cycles. Herein, we present our instrument design (with an automated droplet-freezing image detection algorithm) and report data on the nucleation of ice in pure water droplets and in aqueous suspensions of ice-nucleating particles. This work will be used as the basis for future investigations in atmospheric ice nucleation that aim to better constrain the influence of ice-nucleating particles on cloud optical properties and precipitation formation.
New directional wave observations from CFOSAT : impact on ocean/wave coupling in the Southern Ocean
Authors: Aouf Lotfi , Hauser Daniele , Law-Chune Stephane , chapron Bertrand , Dalphinet Alice , Tourain Cedric
Published: March 2021

The Southern ocean is a complex ocean region with uncertainties related to surface wind forcing and fluxes exchanges at the air/sea interface. The improvement of wind wave generation in this ocean region is crucial for climate studies. With CFOSAT satellite mission, the SWIM instrument provides directional wave spectra for wavelengths from 70 to 500 m, which shed light on the role of correcting the wave direction and peak wave number of dominant wave trains in the wind-waves growth phase. This consequently induced a better energy transfer between waves and a significant bias reduction of wave height in the Southern Ocean (Aouf et al. 2020). The objective of this work is to extend the analysis of the impact of the assimilation of wave number components from SWIM wave partitions on the ocean/wave coupling. To this end, coupled simulations of the wave model MFWAM and the ocean model NEMO are performed during the southern winter period of 2019 (May-July). We have examined the MFWAM/NEMO coupling with and without the assimilation of the SWIM mean wave number components. Several coupling processes related to Stokes drift, momentum flux stress and wave breaking inducing turbulence in the ocean mixing layer have been analyzed. We also compared the coupled runs with a control run without wave forcing in order to evaluate the impact of the assimilation. The results of coupled simulations have been validated with satellite Sea Surface Temperature and available surface currents data over the southern ocean. We also investigated the impact of the assimilation during severe storms with unlimited fetch conditions.

Further discussions and conclusions will be commented in the final paper.

Aouf L., New directional wave satellite observations : Towards improved wave forecasting and climate description in Southern Ocean, Geophysical Research Letters, DOI: 10.1029/2020GL091187 (in production).

 

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State, global and local parameter estimation using local ensemble Kalman filters: applications to online machine learning of chaotic dynamics
Authors: Malartic Quentin , Bocquet Marc , Farchi Alban
Published: March 2021

In a recent methodological paper, we have shown how a (local) ensemble Kalman filter can be used to learn both the state and the dynamics of a system in an online framework. The surrogate model is fully parametrised (for example, this could be a neural network) and the update is a two-step process: (i) a state update, possibly localised, and (ii) a parameter update consistent with the state update. In this framework, the parameters of the surrogate model are assumed to be global.

In this presentation, we show how to extend the method to the case where the surrogate model, still fully parametrised, admits both global and local parameters (typically forcing parameters). In this case, localisation can be applied not only to the state update, but also to the local parameters update. This results in a collection of new algorithms, depending on the localisation method (covariance localisation or domain localisation) and on whether localisation is applied to the state update, or to both the state and local parameter update. The algorithms are implemented and tested with success on the 40-variable Lorenz model. Finally, we show a two-dimensional illustration of the method using a multi-layer Lorenz model with radiance-like non-local observations.
Simulating Future Distributions of Northern Permafrost Peatlands
Authors: Fewster Richard , Morris Paul , Ivanovic Ruza , Swindles Graeme , Peregon Anna , Smith Chris
Published: March 2021

Northern permafrost peatlands represent one of Earth’s largest terrestrial carbon stores and are highly sensitive to climate change. Whilst frozen, peatland carbon fluxes are restricted by cold temperatures, but once permafrost thaws and saturated surficial conditions develop, emissions of carbon dioxide (CO2) and methane (CH4) substantially increase. This positive feedback mechanism threatens to accelerate future climate change globally. Whilst future permafrost distributions in mineral soils have been modelled extensively, the insulating properties of organic soils mean that peatland permafrost responses are highly uncertain. Peatland permafrost is commonly evidenced by frost mounds, termed palsas/peat plateaus, or by polygonal patterning in more northerly regions. Although the distribution of palsas in northern Fennoscandia is well-studied, the extent of palsas/peat plateaus and polygon mires elsewhere remains poorly constrained, which currently restricts predictions of their future persistence under climate change.  

Here, we present the first pan-Arctic analyses of the modern climate envelopes and future distributions of permafrost peatland landforms in North America, Fennoscandia, and Western Siberia. We relate a novel hemispheric-scale catalogue of palsas/peat plateaus and polygon mires (>2,100 individual sites) to modern climate data using one-vs-all (OVA) binary logistic regression. We predict future distributions of permafrost peatland landforms across the northern hemisphere under four Shared Socioeconomic Pathway (SSP) scenarios, using future climate projections from an ensemble of 12 general circulation models included in the Coupled Model Intercomparison Project 6 (CMIP6). We then combine our simulations with recent soil organic carbon maps to estimate how northern peatland carbon stocks may be affected by future permafrost redistribution. These novel analyses will improve our understanding of future peatland trajectories across the northern hemisphere and assist predictions of climate feedbacks resulting from peatland permafrost thaw. 
An insight on the polyphase thermal history of the Ghomarides and Upper Sebtides in the Internal Rif (North Morocco) by means of Raman spectroscopy on organic matter
Authors: Schito Andrea , Atouabat Achraf , Calcagni Rocco , Corrado Sveva , Muirhead David , Romano Claudia , Pozzi Alessandro , Galimberti Roberto , Spina Amalia
Published: March 2021

The correct assessment of maximum temperatures experienced by rocks is an essential tool to unravel the evolution of the thermal structure of the crust during the main phases of an orogenesis. Given to broad P-T stability field of classical metamorphic mineralogical indicators, maximum temperatures derived from the analyses of carbonaceous material dispersed in rocks by means of Raman spectroscopy has shown to be a suitable alternative to classical geothermometer. Initially developed for high metamorphic rocks the use of this tools has recently been extended also at lower metamorphic degree and diagenesis. This allowed us to extend the analyses of paleotemperatures experienced by rocks from Ghomarides and Sebtides from the Internal Rif in North Morocco with respect to previous works. Ghomaride and Sebtides in this portion of the Rif-Betic-Tell chain, represent respectively the upper and lower plates of a metamorphic core complex  and are composed, the first, by Paleozoic rocks with a partially preserved Mesozoic-Cenozoic cover and the second by lower Paleozoic to Triassic deep-crustal mica-schists, migmatites and granulites associated with peridotites (Beni Bousera complex).

Our data suggest that the uppermost Tiszgarine Unit of the Upper Sebtides experienced warmer condition than previously observed. Moreover, we calculate the maximum temperatures experienced by the Ghomarides  during both the Eo and Late Variscan cycles showing that differences in temperature exist among the vary units that compose the complex. Finally, in the southern area our data suggest a less severe alpine heating related to the emplacement of the Beni Bousera peridotite, than previously calculated.
A new airborne aerosol sampling system: development, validation, and application in vertical measurement of black carbon mixing state
Authors: Zhu Shaowen , Ma Nan , Xie Linhong , Lu Nan , Li Minglu , Chen Shuqing , Mao Jingying , Yu Pengfei , Deng Zhaoze , Ran Liang , Su Hang , Cheng Yafang
Published: March 2021

Vertical measurements of aerosol physical-chemical properties have important significance for better addressing the environment and climate effects of atmospheric aerosol. Traditional in-situ vertical observations of those properties are mainly based on aircraft platforms which are costly and restrictive, and not applicable for near-ground (<500 m) measurements. Within the boundary layer, tethered balloon and unmanned aerial vehicle (UAV) are ideal observation platforms but cannot carry heavy online aerosol instruments due to payload limitations. In this study, a new lightweight airborne aerosol sampling system is developed for tethered balloon and UAV platform. The system can collect airborne aerosol samples at up to 12 heights with conductive bags, and the samples can be analyzed later by online instruments such as aerosol mass spectrometer and single particle soot photometer (SP2). During an intensive field campaign conducted in Lhasa in summer of 2020, the new developed system was applied together with a SP2 to determine the vertical profile of refractory black carbon (rBC) mixing state. Preliminary results show that most rBC containing particles are external mixture and the proportion of internally mixed rBC increases with height. The vertical profiles of rBC mixing state are affected by surface emissions, the development of atmospheric boundary layer and meteorological conditions.
Tracing migration of larger benthic foraminifera across atolls in the South China Sea
Authors: Goeting Sulia , Briguglio Antonino , Kocsis Laszlo , Roslim Amajida
Published: March 2021

The distribution of modern benthic foraminifera is studied from offshore reefs of Brunei Darussalam located in northwest Borneo with enhanced siliclastic influence, and from Louisa Reef, an atoll in the Southern Spratly Islands under fully carbonatic environment. The main families of larger benthic foraminifera found from offshore reefs of Brunei are the Calcarinidae, Amphisteginidae and the Operculinidae, while at the Louisa Reef are the Calcarinidae, Amphisteginidae and the Soritidae. Larger benthic foraminifera are mainly concentrated in the tropical regions and in shallow waters, and their distribution depends on important environmental factors such as water depth, sunlight and type of sediment. Migration of LBF has been recorded since the Paleogene from the Americas to Africa and the Mediterranean Sea, and later to the Indo-Pacific where the modern biodiversity hotspot occurs. Hence looking into any possible migration throughout certain groups of LBF could help in understanding their biogeographic distribution through time within the Indo-Pacific region. Along the atolls in South China Sea the marine environments meet their living preferences, hence tracing their presence, distributions, and abundances could shed further light on their regional migration pattern.
Traceability of extra virgin olive oil: geochemical and environmental fingerprints revealed by ICP-MS-QQQ analysis
Authors: Telloli Chiara , Tagliavini Silvia , Passarini Fabrizio , Rizzo Antonietta , Salvi Stefano
Published: March 2021

Studies on food traceability are of great importance nowadays, involving high demanding processes to cover all food chain steps. Extra virgin olive oil is a typical product that has a strong linkage with the Mediterranean area, and its origin protection is continuously improved both by European Regulations about its quality policy and by the development of analytical techniques increasingly appropriate. Simultaneous multi-element approach like Inductive Coupled Plasma Mass Spectrometry (ICP-MS) makes possible the representation of EVO oil’s mineral composition. Involving a ICP-MS Triple Quadrupoles (ICP-MS-QQQ) it becomes even more a powerful tool for interference-free quantitative analysis of trace and ultra-trace elements. This study aims at elaborating a method to better determine mineral composition of this matrix and at validating the method used to determine its reliability. EVO oil’s fingerprint shows its predominant elements and it points out its possible contamination with toxic elements.
Wave climate extremes from the Sea State CCI satellite data
Authors: Ramirez Marta , Menendez Melisa , Dodet Guillaume
Published: March 2021

The knowledge of ocean extreme wave climate is of significant importance for a number of coastal and marine activities (e.g. coastal protection, marine spatial planning, offshore engineering). This study uses the recently released Sea State CCI v1 altimeter product to analyze extreme wave climate conditions at global scale. The dataset comprises 28-years inter-calibrated and denoised significant wave height data from 10 altimeter missions.

First, a regional analysis of the available satellite information of extreme waves associated with both, tropical and extratropical cyclones, is carried out. As tropical cyclones, we analyze two intense events which affected the Florida Peninsula and Caribbean Islands: Wilma (in October 2005) and Irma (in August 2017) hurricanes. As extratropical cyclones, we focused on the extreme waves during the 2013-2014 winter season along the Atlantic European coasts. The extreme waves associated with these events are identified in the satellite dataset and are compared with in situ and high-resolution simulated data. The analysis of the satellite data during the storm tracks and its comparison against other data sources indicate that satellite data can provide added value for the analysis of extreme wave conditions that caused important coastal damages.

After assessing the quality of extreme wave data measured by altimeters from this regional analysis, we explore a method to characterize wave height return values (e.g. 50yr return period significant wave height) from the multi-mission satellite data. The method is validated through comparisons with return values estimated from long-term wave buoy records. The extreme analysis is based on monthly maxima of satellite significant wave height computed over marine areas of varying extensions and centered on a target location (e.g. the wave buoy location for comparison and validation of the method).  The extension of the areas is defined from a seasonal study of the spatial correlation and the error metrics of the satellite data against the selected coastal location. We found a threshold of 0.85 correlation as the isoline to select the satellite data subsample (i.er. larger areas to select satellite maxima are found during winter seasons). Finally, a non-stationary extreme model based on GEV distribution is applied to obtain quantiles of low probability. Outcomes from satellite data are validated against extreme estimates from buoy records.
Electrodynamics surrounding polar cap auroral arcs
Authors: Hovland Amalie Ø. , Oksavik Kjellmar , Reistad Jone P. , Hairston Marc R.
Published: March 2021

This multi-instrument case study investigates the electrodynamics surrounding polar cap auroral arcs. A long-lasting auroral arc is observed in the high latitude dusk-sector at ~80° Apex latitude in the northern hemisphere. Ion drift measurements from the SSIES system on the DMSP spacecraft have been combined with multiple ground-based observations. Line of sight velocity data from three polar latitude high-frequency Super Dual Auroral Radar Network (SuperDARN) radars show mesoscale structure in the ionospheric convection in the region surrounding the arc. The convection electric field in this region is modelled using a Spherical Elementary Convection Systems (SECS) technique, using curl-free basis functions only. The result is a regional model of the ionospheric convection based on the fairly dense and distributed flow observations and the curl-free constraint. The model is compared to optical data of the auroral arc from two high latitude Redline Emission Geospace Observatory (REGO) all-sky imagers as well as UV images and particle measurements from the DMSP spacecraft to describe the local electrodynamics in the vicinity of the high latitude arc throughout the event.
Methodologies for risk mapping of radon gas at various scales in Tondela and Oliveira do Hospital region (center of Portugal)
Authors: Santiago Gustavo , Pereira Alcides
Published: March 2021

Inhalation of radon gas exposes the lungs to ionizing radiation which significantly contributes to the equivalent dose received by a human body. European Union advises Member States to identify radon prone areas (RPA), characterized by a significant percentage of dwellings above the national reference level (RL).

The presented work aims to evaluate the use of Receiver Operating Characteristic (ROC) curve analysis to map RPAs at a small-scale (from 1:25 000 to 1:1 000, henceforward called “regional” and “local” scale respectably), using interpolated surfaces of total gamma radiation (TGR) as proxy and point data of radon concentration in dwellings as the observed variable.

The case-study areas are in the center of Portugal (Tondela and Oliveira do Hospital) where outcrops different coarse-grained biotite granites (Beira’s Granite) and metasediments of Beiras’ Group, frequently as small enclaves hosted in the granites. An intense network of faults is also characteristic of these regions.

At Tondela area the geospatial analysis and ordinary kriging interpolation of TGR, on a regional scale, evidenced: a) a geological control on this variable; b) a structural control on anomalies by N35ºW orientated faults and by the intersection of these structures with others, namely N75ºE and N55ºE; c) and an anisotropic covariance of equally spaced points with N35oE oriented major axis. At Oliveira do Hospital, where at a regional scale just data of anomalies was available, the log-normal distribution of background values was simulated based on high-definition data obtained at a local scale. The results are consistent with the structural control pattern identified at Tondela. The best classifiers identified by the ROC analysis were 175 cps and 450 cps, respectably for Tondela and Oliveira do Hospital regions.

Establishing a 10% probability of dwellings with concentrations of radon above RL ( ) to define an RPA, all the areas were classified as RPAs. At Tondela region, the lowest risk area represents 25% probability of exceeding the RL and the highest risk area 52%. At Oliveira do Hospital almost the entire region represents 56% exceedance probability. The highest risk area is spatially related to intense anomalies and represent 78% exceedance probability.

For the geological context studied, the use of TGR proved to be suitable for radon gas risk mapping. The ROC curve analysis enabled to significantly classify higher and lower risk areas within high-risk regions, considering the small-scale variability. The ROC analysis did not produce a classifier properly calibrated to the RL but one that improves the cost-benefit of the classification relatively to the natural prevalence of the studied areas.
Sensitivity Operator Inverse Modeling Framework for Advection-Diffusion-Reaction Models with Heterogeneous Measurement Data
Authors: Penenko Alexey , Penenko Vladimir , Tsvetova Elena , Gochakov Alexander , Pyanova Elza , Konopleva Viktoriia
Published: March 2021

Air quality monitoring systems vary in temporal and spatial coverage, the composition of the observed chemicals, and the data's accuracy. The developed inverse modeling approach [1] is based on sensitivity operators and ensembles of adjoint equations solutions. An inverse problem is transformed to a quasi-linear operator equation with the sensitivity operator. The sensitivity operator is composed of the sensitivity functions, which are evaluated on the adjoint ensemble members. The members correspond to the measurement data elements. 

This ensemble construction allows working in a unified way with heterogeneous measurement data in a single operator equation. The quasi-linear structure of the resulting operator equation allows both solving and analyzing the inverse problem. More specifically, by analyzing the sensitivity operator's singular structure, we can estimate the informational content in the measurement data with respect to the considered process model. This type of analysis can estimate the inverse problem solution before its actual solution and evaluate the monitoring system efficiency with respect to the considered inverse modeling task [1,2]. 

Numerical experiments with the emission source identification problem for air pollution transport and transformation model were carried out to illustrate the developed framework. In the numerical experiments, we considered in-situ, image-type, and integral-type measurement data.

The work was supported by the grant №075-15-2020-787 in the form of a subsidy for a Major scientific project from Ministry of Science and Higher Education of Russia (project "Fundamentals, methods and technologies for digital monitoring and forecasting of the environmental situation on the Baikal natural territory").

References

[1] Penenko, A. Convergence analysis of the adjoint ensemble method in inverse source problems for advection-diffusion-reaction models with image-type measurements // Inverse Problems & Imaging, American Institute of Mathematical Sciences (AIMS), 2020, 14, 757-782 doi: 10.3934/ipi.2020035

[2] Penenko, A.; Gochakov, A. & Penenko, V. Algorithms based on sensitivity operators for analyzing and solving inverse modeling problems of transport and transformation of atmospheric pollutants // IOP Conference Series: Earth and Environmental Science, IOP Publishing, 2020, 611, 012032 doi: 10.1088/1755-1315/611/1/012032
Enhanced atmospheric solubilization of iron due to anthropogenic activities
Authors: Bergas-Massó Elisa , Gonçalves Ageitos María , Myriokefalitakis Stelios , van Noije Twan , Miller Ron , Pérez García-Pando Carlos
Published: March 2021

Atmospheric deposition of soluble iron (Fe) to the ocean has an impact on oceanic primary productivity, thus on carbon dioxide uptake. Understanding how anthropogenic activity influences the atmospheric Fe cycle is key to project ocean biogeochemical cycles and has been barely explored.

In this study, we assess past, present, and future soluble Fe deposition to the ocean, accounting for natural and anthropogenic sources, using an advanced atmospheric Fe cycle module implemented into the EC-Earth3 Earth System Model. This version of the model considers primary emissions of insoluble and soluble Fe forms associated with dust minerals, and anthropogenic and biomass burning combustion aerosols. Fe solubilization processes in the atmosphere include 1)  proton-promoted, 2)  oxalate-promoted (with oxalate calculated on-line), and 3) photo-reductive Fe dissolution. We run time-slice simulations using the atmosphere-chemistry model configuration constrained by past, present, and future ocean states. The necessary sea surface temperature and sea ice concentration climatologies are obtained from EC-Earth3 CMIP6 coupled model experiments. Future projections rely on three CMIP6 scenarios representing different socio-economic pathways and end-of-the-century forcing levels: SSP1-2.6, SSP2-4.5, and SSP3-7.0. 

Our setup allows us to estimate the soluble Fe deposition into the ocean while quantifying the contribution from dust, biomass burning, and anthropogenic combustion sources separately under a range of scenarios. Our preliminary results suggest nearly a 50% increase in soluble Fe deposition for the present time since the industrial revolution, attributed to increased atmospheric acidity and oxalate concentrations that result in a more efficient atmospheric processing. Future projections of soluble Fe show a high correlation between anthropogenic activity and solubility of deposited Fe, scenarios with higher anthropogenic emissions consistently yield a higher fraction of soluble over total deposited Fe. Our results also suggest diverging trends for the different ocean basins. Disentangling the factors that drive those differences in regions where Fe is known to be the limiting nutrient, such as the North Pacific or the Southern Ocean, is fundamental to improve our understanding of the atmospheric Fe cycle and its consequences for  the ocean biogeochemistry.  
Bioavailability and remineralization of sediment-derived dissolved organic carbon from the Baltic Sea depositional area
Authors: Lengier Monika
Published: March 2021

Sediment pore waters in the depositional areas of the Baltic Sea are enriched with the dissolved organic carbon (DOC), which results in a diffusive flux of DOC to the water column. It was found that up to 30% of OM deposited in the sediments returns to the water column and may alter processes occurring there e.g. increase the oxygen demand in the bottom waters. Still little is known about the bioavailability of sediment-derived DOC and its remineralization dynamics. Thus, the aim of this study was to assess the bioavailability, degradation rate constant and half-life time of sediment-derived DOC.

Bottom water and pore water, collected during r/v Oceania cruise in March 2018 in the Gdańsk Deep, have been mixed in a volume ratio of 4:1. To ensure oxic conditions in the experiment, the mixture was bubbled with the ambient air to reach 100% O2 saturation. Incubation of such prepared samples was conducted in 23±0.1°C for 126 days. At the beginning (t=0) and after 1, 2, 6, 18, 35, 73 and 126 days of the incubation the individual samples were analyzed for total dissolved organic carbon DOC. In parallel, untreated bottom water was incubated as a control, while the obtained results have been used to decouple the remineralization dynamics in the mixture.

The DOC decay had an exponential character. The highest dynamics of DOC remineralization was at the beginning of the experiment and it gradually decreased over time. During the incubation period pore water DOC concentration decreased from 1408 to 850 µmol l-1, which corresponds to almost 40% loss. In the control samples (bottom water) DOC concentration decreased from 304 to 260 µmol l-1 i.e. by ~14%.

In the experiment three different DOC fractions have been identified: labile DOC (DOCL), semi-labile DOC (DOCSL) and refractory DOC (DOCR). To quantify the DOC remineralization rate constants (k) and half-life times (t1/2) the first order kinetics was used. The total bioavailable fraction of pore water DOC (DOCL+DOCSL) amounted to 54%, while k and t1/2 were 0.0958 d-1 and 7.24 d for DOCL and 0.0082 d-1 and 84.53 d for DOCSL, respectively.

This study shows that about half of sediment-derived DOC is bioavailable, which gives a new insight on the Baltic Sea carbon cycle and O­2 consumption in deeper water layers.
Changing intensity and seasonality of wet extremes over Europe 
Authors: John Amal , Douville Hervé , Yiou Pascal
Published: March 2021

Daily precipitation extremes are projected to intensify with global warming. Here the focus is on how extreme precipitation scales with the changing global mean surface air temperature (GSAT) and how much their inherent seasonality will change, using historical and SSP5-8.5 scenario simulations from 18 CMIP6 models for different sub-domains over Europe. With strong future global warming, the annual maximum precipitation (RX1DAY) is found to occur later in the year, although this shift is model-dependent and hardly significant in the multi-model distribution. Using generalized extreme value theory also provides evidence for the intensification of wet extremes in the future. In addition, we use monthly model outputs to decompose changes in RX1DAY occurring at the peak of the extreme season into several contributions, which gives insights into the underlying physical mechanisms that control the response of precipitation extremes and their inter-model spread.
Seismic quality factor measured for compressional and shear waves in the firn column of Korff Ice Rise, West Antarctica
Authors: Agnew Ronan , Clark Roger , Booth Adam , Brisbourne Alex
Published: March 2021

Comprehensive descriptions of the seismic properties of glaciers and ice masses require that both compressional (P-) and shear (S-) wave components are considered. Among these properties is the seismic attenuation, expressed by the Quality Factor (Q). Q is valuable for two reasons: first, to correct measurements of seismic amplitude for wavelet propagation effects, as in reflection amplitude-versus-angle (AVA) studies. Second, Q is an indicator of ice properties such as temperature and impurity content, and laboratory/field studies of soils and geological materials suggests that the ratio of the compressional- and shear-wave quality factors, Qp/Qs, may indicate fluid saturation (particularly when considered jointly with the velocity ratio Vp/Vs). Thus, a measurement of Qp/Qs could usefully inform the hydrological structure of the firn and indicate variations in the density of the firn column.

Despite its importance, few studies appear to have measured Qp in firn columns and none appear to have measured Qs in firn. Doing so for either compressional- or shear-wave arrivals is challenging, due to the ray paths followed by the diving wave first arrivals and their accurate representation in attenuation measurement methods. In preparation for an AVA study of bed properties at Korff Ice Rise, West Antarctica, we have used spectra of diving wave first arrivals and a modified spectral-ratio method to measure Qp and Qs as a function of depth in the firn column. Shot gathers with vertically oriented geophones at offsets of 2.5 - 1000m were used to measure Qp. For detecting the shear component, the geophones were oriented horizontally; in this configuration, diving and reflected shear phases were recorded with high signal-to-noise ratios. The variation of Q with depth is represented as discrete constant-Q layers with thicknesses between 6 and 27 m. Qp shows progressive increases in depth from 21 ± 3 in the uppermost 20 m (where Vp < 3000 m/s), to 246 ± 30 between 74 and 80 m depth (3750 m/s < Vp < 3770 m/s). Qs increases from 14 ± 4 in the uppermost 20m, to 80 ± 6 between 80 and 90m depth. The ratio Qp/Qs varies throughout the depths measured, from Qp/Qs ~ 1.5 at the surface, to Qp/Qs ~ 3 at 80 m. This is broadly consistent with previously quoted values, but the variation may imply that Qp/Qs is influenced by firn structure.

Similar measurements at a variety of sites could help to inform a relationship between Qp, Qs and firn properties. In the immediate future, the measurement of Q in the firn will aid measurements of bed reflectivity, and help to determine the material properties of the ice-bed interface.