bluuebunny/crossref_metadata_2025 huggingface dataset:
Constructing magma plumbing systems
Authors: Magee Craig , Jackson Christopher
Published: February 2023

The structure of magma plumbing systems controls a variety of processes that are critical to keeping people safe, secure, and prosperous. These processes include the: (i) location, threat, and early warning signals of volcanic eruptions; (ii) accumulation of magma-related ore deposits; and (iii) distribution of subsurface heat. Yet magma plumbing systems are themselves controlled by a multitude of geological factors, such as host rock lithology and structure, and magma dynamics, each of which unique to different geological settings. Deciphering how entire magma plumbing systems are constructed is thus challenging: at active volcanoes we cannot see the subsurface geology at a high resolution, and exposed ancient intrusions only provide a snapshot of the systems evolution. We therefore have to infer how magma plumbing systems are constructed, and use various modelling approaches to test these interpretations. These models underpin many recent advances in volcanology but, by necessity, are simplified compared to natural magmatic systems and their host rock.In this presentation, we will explore how ground deformation is used to understand the structure and growth of subsurface magma plumbing systems. In particular, we will demonstrate how seismic reflection data, which provides ultrasound-like images of Earth’s crust, and structural geological mapping of active and ancient systems can be integrated to test model-based hypotheses concerning how magma emplacement translates into ground deformation. For example, graben-bounding, dyke-induced faults are commonly observed on Earth and many planetary bodies, but can we assume that their surficial graben properties (e.g. width and cumulative extension) reflect the underlying dyke depth and thickness? Similarly, how do surface uplift patterns relate to subsurface magma plumbing system structure? Overall, this presentation will emphasise the need to integrate geological, geophysical, and modelling-based approaches to advance our understanding of plumbing system construction.
Return on carbon investment for plant water transport tissues: functional life span matters
Authors: Krieger Louis , Schymanski Stanislaus
Published: February 2023

Trees invest carbon in stem growth every year, and allocate the carbon to build xylem vessels, varying in length and diameter, which serve as a path for the transport of water and nutrients from the soil to the leaves.

To assess the cost and benefits of carbon investment into xylem and the resulting hydraulic conductivity, we used a combination of two methods. The first was a novel method of measuring hydraulic conductivity under suction using a syringe pump. The second used dye and cryo-microscopy to determine the ratio and dimensions of conducting vessels in individual year rings. Using these methods, we were able to determine that for Fagus sylvatica, larger vessels did not have lower carbon costs per conductivity due to the shorter functional lifespan, whereas the hydraulic conductivity per cross-sectional area was not larger than smaller vessels. In fact, we found a greater wood density for samples with larger median vessel diameter, implying that larger vessels need more carbon for structural support.

Here we present these findings and discuss the potential application of the methods to understand how plants adapt their xylem carbon allocation across species and environmental conditions.

 
A pan-European service for hydrological seasonal forecasts at C3S
Authors: Yang Wei , Berg Peter , Hutjes Ronald , McKnight Ursula , Nauta Lisanne , Paparrizos Spyros
Published: February 2023

As contractor and sub-contractor for C3S, SMHI and WU-DES have set up a multi-model operational service for hydrological seasonal forecasts. The service currently produces forecasts of monthly mean river discharge for a pan-European domain using several hydrological models, namely E-HYPEcatch, on irregular catchment delineations, and E-HYPEgrid and VIC-WUR on regular 5km gridded drainage network of EFAS. Also, the EFAS-Lisflood forecasts from the separate ECMWF production line are included in the final data set. All forecasts use the SEAS5 meteorological forecasts with 51 ensemble members. The data from all models are available from the CDS data portal for a re-forecast (https://doi.org/10.24381/cds.13c18212) and a forecast period (https://doi.org/10.24381/cds.52f45864). Further, the most probable forecast is displayed in an online application (https://cds.climate.copernicus.eu/cdsapp#!/software/app-hydrology-seasonal-forecast-explorer?tab=app).Ongoing work is aimed at introducing a second meteorological forecasting system, and adding more output variables at a higher daily temporal resolution. The quality of the forecasts is at this point mainly addressed by working on the input data and statistical downscaling and bias adjustment. The new system is expected to be operational in mid-2024.
Oblique continental rifting. Insights from 3-D forward coupled geodynamic-surface process modelling and application to the Equatorial passive margins formation.
Authors: Theunissen Thomas , Huismans Ritske S. , Rouby Delphine , Wolf Sebastian , May Dave
Published: February 2023

Continental rifting is often oblique to the rift axis or plate boundary, comprising many active rifts and mature rifted margins on Earth. Previous research has identified the role of vertical strike-slip and transform structures in oblique extension but has also shown that the initiation of long-distance syn-rift vertical strike-slip motion requires preexisting weaknesses. The Southern part of the Equatorial passive rifted conjugate margins is a typical example that exhibits orthogonal rift segments separating with transform faults with different lengths and orientation. We aim in this study to 1) understand the influence of these inherited weaknesses on the pattern of faulting, 2) to evaluate the consequences of oblique margin formation for rift related topography, and 3) to explore the interaction between tectonic and surface processes in the context of oblique rifting. We use most recent advances in 3-D forward geodynamic modeling coupled with surface processes. Preliminary results support the importance of inherited weak zones in shaping segmented oblique continental margins, with highly contrasting tectonic and subsidence histories in the orthogonal and transform segments. These results compare well with observations from the Equatorial passive rifted conjugate margins and provide insight into the factors that may drive the timing and magnitude of vertical motions and associated sediment flux.
Influence of bioturbation on sediment redistribution along climate gradient in Chile estimated by combining semi-empirical modelling, remote sensing and machine learning
Authors: Grigusova Paulina , Larsen Annegret , Brandl Roland , Kraus Diana , Farwig Nina , Bendix Jörg
Published: February 2023

Soil bioturbation activity affects soil texture, bulk density, soil water content and redistribution of nutrients. All of these factors influence surface and subsurface sediment and hydrological processes, and thus are expected to shape the surface on large temporal scales. Previous studies have shown that the impact of bioturbation on these processes is not homogenous.However, the factors, which determine if bioturbation will positively or negatively affect the named processes, remain unknown. For this reason, the inclusion of bioturbation into erosion and landscape models have up until now been limited. The few models which include it in their algorithms assume a linear positive relationship between bioturbation rates, and erosion, soil mixing and vegetation cover.In our study, we tested the possibilities and limitations of including bioturbation into soil erosion modelling. We modelled the impact of bioturbation on sediment redistribution, surface runoff, subsurface runoff and infiltration capacity within several climate zones and identified environmental parameters determining the positive or negative impact of bioturbation on surface processes.Our study area was located along Chilean climate gradient. We measured the needed soil properties and location of burrows created by bioturbating animals in the field. Then we applied machine learning algorithms and used satellite data as predictors to upscale the soil properties and burrow distribution into the catchment. At each of the predicted burrow locations we adjusted the topography, soil properties and vegetation cover accordingly. We implemented the predicted parameters into a semi-empirical model and ran the model for a time period of 3 years under two conditions: With and without integrated bioturbation. We validated the model using sediment fences located at the base of each catchment.Model with integrated bioturbation activity had an R2 of 0.71 while a model without bioturbation activity had an R2 = 0.45. Bioturbation increased sediment redistribution in all but humid climate zone. The surface runoff increased in semi-arid zone while the infiltration capacity and subsurface runoff increased in the mediterranean and humid climate zone. Bioturbation increased sediment erosion at high and middle values of elevation, at high values of inclination and connectivity, and at low values of profile curvature. Bioturbation increased sediment accumulation at high values of surface roughness and topographic wetness index and at low values of vegetation cover.
Do fine root morphological and functional adaptations support regrowth success in a tropical forest restoration experiment?
Authors: Hofhansl Florian , Valverde Barrantes Oscar , Chacón-Madrigal Eduardo , Hietz Peter , Weissenhofer Anton , Prommer Judith , Wanek Wolfgang , Fuchslueger Lucia
Published: February 2023

In early stages of forest succession plants have a high nutrient demand, but it is still a matter of debate if regrowth success of pioneer species is related to plant functional traits favoring fast soil colonization and nutrient acquisition. In general, we would expect trade-offs between plant growth performance and fine root morphological properties in association with different plant life-history strategies. Hence, we hypothesized that fast growing plants should have a more efficient root system that allows them to outcompete slow-growing neighbors in a resource-limited environment.To test our hypothesis we monitored plant successional growth dynamics in a tropical lowland rainforest reforestation experiment conducted in southwest Costa Rica. We collected absorptive roots (<2mm diameter) from plant individuals (comprising 20 tree species and 11 plant families) with different growth dynamics (as indicated by measurements of stem diameter and height). For these samples we assessed a suite of fine root morphological traits, such as legume nodulation status, and furthermore quantified fine root nutrient concentration and phosphatase activities, as well as microbial biomass and phosphatase activity in soils in the close vicinity of fine roots.We found stark differences in fine root characteristics between the tree species investigated in this study, such that fast growing species exhibited relatively larger specific root length and higher turnover, whereas slow growing species tend to rely on mechanical resistance by increasing root tissue density and root life span. Our results suggest that the identified differences in the root trait spectrum between fast and slow growing species reflect plant functional adaptions to resource limitation, edaphic properties and soil microbial symbioses. Our findings further highlight the crucial need to foster our understanding of belowground root morphological and physiological traits during forest succession, especially so when aiming to restore forest ecosystem functioning in formerly intensified land-use systems.
Global analysis of deviations in climate sensitivity of tree-growth after extreme drought events
Authors: Leifsson Christopher , Buras Allan , Rammig Anja , Zang Christian
Published: February 2023

In the course of climate change, forests around the globe will be exposed to more frequent and more severe extreme drought events. Direct and lagging impacts of drought events on forests, so-called drought legacies, are often estimated from tree-ring derived secondary growth measurements which easily translate into biomass and are available globally. However, secondary growth is a result from multiple internal mechanisms and therefore does not reveal potential impacts on the underlying physiology, such as hydraulic dysfunction, repair mechanisms and altered carbon allocation. Instead, the carbon demand of these impacts translates to less carbon being available for secondary growth which therefore results in temporarily altered relationships between climate and growth.Here, we advance the concept of drought legacies by additionally quantifying simultaneous “functional legacies” as climate sensitivity deviations (CSD) of secondary growth. We quantified legacies in both growth and climate sensitivity after extreme drought events using linear mixed-effects models on a global-scale, multi-species tree-ring dataset. We further differentiated the responses by clade, site aridity and hydraulic safety margins in order to determine common factors which convey heightened or lessened vulnerability to extreme drought events.Our results show that while depressed growth was common after droughts across most of the analysed groups, although with varying legacy lengths, post-drought climate sensitivity deviations were more nuanced. The climate sensitivity of growth was decoupled for gymnosperms with small hydraulic safety margin, i.e. those with a more risk-prone hydraulic growth strategy. In comparison, the climate sensitivity of growth tightened for angiosperms growing in arid sites, a response which occurred in conjunction with a post-drought growth overshoot. These responses are consistent with current understanding of impaired hydraulic function and increased carbon allocation towards xylogenesis, respectively. In conclusion, climate sensitivity deviations reveal physiological responses not discernible from growth legacies alone and therefore serves as a promising avenue for a more comprehensive identification of drought impacts on tree growth at large scales.
Volcanic activity of Campi Flegrei Caldera (Italy) during 2013-2020 from surface deformation mapping and modeling
Authors: Astort Ana , Trasatti Elisa , Polcari Marco , Di Vito Mauro Antonio , Acocella Valerio
Published: February 2023

The current unrest phase at Campi Flegrei Caldera, Italy from 2000 to present is evidenced by increasing seismicity rates and magnitude, gas emissions and remarkable ground deformation. We consider multi-technique geodetic data to constrain the recent surface deformations and study the possible hazard implications. Time-series from the COSMO-SkyMed satellite mission and GNSS data in the period 2013-2020 show an increasing rate of uplift at the caldera center, reaching a total of about 1 m in the town of Pozzuoli during 2010-2020. Horizontal deformation confirms the inflationary trend. Also, new GNSS seafloor measurements, located in the Gulf of Pozzuoli and available from 2017 to 2020, show a nearly radial pattern. The use of these data in the analysis, in addition to the inland GNSS and InSAR data, helps constraining the 3D pattern of deformation also in the submerged part of the Campi Flegrei caldera.3D finite element models are developed including the elastic heterogeneous structure of the medium based on the newest seismic tomography of the area of Campi Flegrei. We consider the potential action of a plumbing system composed of a general (without fixing the shape a-priori) “central” source, and a deep tabular layer placed at 7.5 km depth.The results show that the central source is placed below the caldera floor, at 4.5 km depth, and has a shape of a thick spheroid with axes ratio of about 0.8 and 0.5. The use of the sill-like source, as suggested by several previous studies for the 2011-2013 time window, lead to three-four fold higher misfits. We interpret our solution as a thickened sill for which the vertical dimension is not negligible such as for the sill-like source, but has a finite dimension of about half the horizontal extension.No significant contributions from the deep tabular layer are evidenced by the inversions,  but the hypothesis of a deep reservoir cannot be fully ruled out, since its activity may be masked by the central shallower source. Also, the implementation of seafloor measurements leads to results compatible with the inland GNSS data alone. In order to understand the evolution of the current inflation process, the results are compared to previous models from the beginning of the present unrest phase (2011 - 2013) and also previous unrest phases (1980-1984).This work is part of the multidisciplinary project LOVE-CF, financed by the Istituto Nazionale di Geofisica e Vulcanologia, to study the dynamics of Campi Flegrei caldera.
Electron populations observed by Mercury Electron Analyzer onboard Mio/BepiColombo during its second Mercury flyby
Authors: Aizawa Sae , Andre Nicolas , Saito Yoshifumi , Persson Moa , Sauvaud Jean-Andre , Fedorov Andrei , Yokota Shoichiro , Barthe Alain , Penou Emmanuel , Rojo Mathias , Murakami Go
Published: February 2023

BepiColombo was launched in October 2018 and is currently en route to Mercury. Although its orbit insertion is planned for December 2025, BepiColombo will acquire new measurements during planetary flybys. During the cruise phase, the two spacecraft are docked together with Mio being protected behind the MOSIF sun shield. Thus, only partial observations of plasma distribution functions can be obtained by the Mercury Plasma Particle Experiment (MPPE) onboard Mio. However, since electrons have small Larmor radii and more isotropic distributions even in the solar wind, the two Mercury Electron Analyzer (MEA) of MPPE will provide us with new and unique measurements in the range of 5 eV to 3 keV when in solar wind mode and 3 eV to ~ 26 keV when in magnetospheric mode. We will present the interesting observations obtained by MEA onboard Mio/BepiColombo during its second Mercury flyby that happened on the 23rd of June, 2022. In particular we will focus on the properties of the low- and high-energy electron populations observed during its crossing of Mercury’s magnetosphere.
Late Pleistocene-Holocene coccolithophore variations in the Subantarctic South Pacific
Authors: Malinverno Elisa , Saavedra-Pellitero Mariem , Jones Amy , Cerri Sofia , Dunkley Jones Tom ,   IODP-383 Scientific Party
Published: February 2023

International Ocean Discovery program (IODP) Expedition 383 Dynamics of the Pacific Antarctic Circumpolar Current (DYNAPACC) (Lamy et al., 2019; 2021) drilled a series of cores from the Pacific sector of the Southern Ocean in order to explore atmosphere-ocean-cryosphere glacial-interglacial dynamics their implications for regional and global climate changes. IODP Expedition 383 sites constitute the first continuous drill cores at key locations of the Subantarctic Pacific Southern Ocean extending through the Pleistocene and back into the Pliocene.Here we focus on coccolith relative and absolute abundance as well as productivity variations for the last 0.5 Million year, in order to understand the nannofloral response to glacial-interglacial cycles and related changes in carbonate production and export. Our data has been generated at IODP Sites U1539 (56°09.0655′S, 115°08.038′W, ~1600 nmi west of the Strait of Magellan at 4070 m water depth) and U1540 (55°08.467′S, 114°50.515′W, ~1600 nmi west of the Strait of Magellan at 3580 m water depth), drilled at a southern and northern location in the central Pacific within the ACC, respectively. Coccolithophore diversity and coccolith numbers change dramatically in the studied cores, ranging from high values during interglacials (up to ca. 1011 coccoliths per gram of sediment, as in MIS11, Saavedra-Pellitero et al., 2017) to low values during the glacials, where they are outcompeted by siliceous microfossils, mostly diatoms.ReferencesLamy, F., Winckler, G., Alvarez Zarikian, C.A., and the Expedition 383 Scientists, 2019. Expedition 383 Preliminary Report: Dynamics of the Pacific Antarctic Circumpolar Current. International Ocean Discovery Program. https://doi.org/10.14379/iodp.pr.383.2019Lamy, F., Winckler, G., Alvarez Zarikian, C.A., and the Expedition 383 Scientists, 2021. Dynamics of the Pacific Antarctic Circumpolar Current. Proceedings of the International Ocean Discovery Program, 383: College Station, TX (International Ocean Discovery Program). https://doi.org/10.14379/iodp.proc.383.2021Saavedra-Pellitero M., Baumann K.-H., Lamy F., and Köhler P., 2017. Coccolithophore variability across Marine Isotope Stage 11 in the Pacific sector of the Southern Ocean and its potential impact on the carbon cycle. Paleoceanography, 32, 864–880, doi:10.1002/2017PA003156.
Prognostic epidemiological indices and the fate of ongoing infectious disease outbreaks
Authors: Trevisin Cristiano , Rinaldo Andrea
Published: February 2023

Prognostic indices, such as the reproduction number or the epidemicity index, help assess the fate of ongoing infectious disease epidemics. While the first is of established importance, the latter focuses on the instantaneous reactivity of the infective compartment to new flare-ups. When subthreshold values of such indices apply (respectively, below the unity for the first and below zero for the latter), they warrant long-term disease-free and unreactive epidemiological conditions. These prognostic indicators benefit policymakers during the assessment and implementation of containment measures to reduce the disease burden. They may depend on an array of factors, including environmental forcings and the effect of containment measures on disease transmission.We showcase a possible implementation of such prognostic indices with reference to the disastrous 2010-2019 Haiti cholera outbreak. To this end, we use a compartmental model that considers rainfalls as an environmental forcing and societal actions tackling the disease's spread. We thus test several scenarios considering a different deployment of intervention measures and we evaluate the outcome of the evolution of the prognostic indices and the epidemiological trajectory in the Haitian regions. We find that subthreshold values of these indices lead to faster waning-disease conditions.As these indices can recap diverse epidemiological signatures induced by the spatial and temporal deployment of containment measures and potentially by evolving environmental forcings, their implementation could enable policymakers to strategically adopt containment measures in response to both evolving epidemiological and climate forcings.
Drought effect on urban plane tree ecophysiology and its isoprene emissions
Authors: Puga Freitas Ruben , Claude Alice , Maison Alice , Leitao Luis , Repellin Anne , Nadam Paul , Kalalian Carmen , Boissard Christophe , Gros Valérie , Sartelet Karine , Tuzet Andrée , Leymarie Juliette
Published: February 2023

Urban trees emit a wide range of biogenic Volatile Organic Compounds (bVOC). Some of these bVOC, like isoprene can react with atmospheric oxidants to form secondary compounds, such as ozone (O3) and secondary organic aerosols (SOA), which have impacts on air quality and climate. In addition, isoprene emissions are strongly influenced by environmental factors and urban sites are known as stressful environment, characterized for example by water scarcity. However, little is known on the contribution of urban trees to air quality, notably during drought periods. In a semi-controlled experiment, fourteen young plane trees (Platanus x hispanica, known as a strong isoprene emitter) were grown in containers, in an urban site (at Vitry-sur-Seine, near Paris), since 2020. In June 2022, half the trees were subjected to drought by total rainfall exclusion and by withholding watering. A comprehensive characterization of tree response to drought, including plant morphology (leaf density and area), water status (i.e., leaf water potential, δ13C isotopic composition) and physiology (stomatal conductance, net photosynthesis, leaf pigment contents, stress molecular markers, chlorophyll fluorescence) analyses, was undertaken along with the characterization of bVOC emissions by an original leaf scale method (portable GC-MS coupled to a leaf chamber). All together, these parameters provided relevant information on the relation between bVOC emissions and plant morphology, its water use efficiency and photosynthetic energy conversion.
Shortly after the onset of drought, the isoprene emissions of the plane trees remained unchanged even though typical responses to drought stress were observed, such as partial stomatal closure leading to a decrease in carbon assimilation. With the progression of drought stress, progressive leaf shedding occurred. When almost completely defoliated, the trees emitted lower amounts of isoprene emissions likely due to disruption of the photosynthetic energy conversion process. Despite the moderate decrease in absolute isoprene emissions rates (as expressed per dry leaf mass) induced by the drought treatment on plane trees with nearly zero gas exchange, total emissions were strongly affected because defoliation significantly reduced the total leaf area. We emphasize that this phenomenon should be taken into account in atmospheric models especially in species highly subjected to drought induced defoliation. Here, a simple parameterisation of this effect on plane tree-bVOC emissions is proposed.
Lagrangian pathways for heat, carbon and nutrients subdction with sub-Antarctic mode waters
Authors: Fernández-Castro Bieito , Mazloff Matthew , Williams Richard G. , Naveira Garabato Alberto
Published: February 2023

Sub-Antarctic Mode Waters (SAMW), forming in the deep winter mixed layers in the Sub-Antarctic Zone (SAZ) to the north of the Antarctic Circumpolar Current (ACC), connect the ocean thermocline with the atmosphere, contributing to ocean carbon and heat uptake and transporting high-latitude nutrients northward, to fuel primary production at low latitudes. The important climatic role of SAMW is controlled by the rate of fluid subduction from the deep winter mixed layers and the concentration of heat, carbon and nutrients at the end of winter. These concentrations depend on a range of processes, both physical (air-sea exchange, transport of Antarctic waters across the ACC, along ACC advection, eddy fluxes, diapycnal mixing, etc.) and biogeochemical ( biological uptake, export and remineralisation), whose relative contributions are very poorly understood. With a Lagrangian particle-tracking experiment in a data-assimilative coupled physico-biogeochemical model of the Southern Ocean (B-SOSE), we assess the origin of the water masses reaching SAMW formation regions and the physico- and biogeochemical transformations occurring along their transport pathways. Our results underline the importance of the advection of subtropical waters along the ACC for the sequestration of heat and anthropogenic carbon and in modulating the fertilization of the low-latitude thermocline.
Crustal geometries of the Eastern North American Margin and a comparison with the West African conjugate
Authors: Shotton Mike , Mortimer Estelle , Gouiza Mohamed , Green Chris , Collier Richard
Published: February 2023

Rifted margins typically show variations in evolution and geometries along strike and across the conjugate system. These changes can be driven by pre-rift inheritance and/or the  processes operating during continental rifting and breakup, particularly where the latter is asymmetric. The conjugate Eastern North American (ENAM) and the West African margins (WAM) show major variations; salt distribution, syn- and post-rift sequence thicknesses, crustal and structural architectures, and rift-related volcanics.

This contribution focusses on the ENAM, where we constrain the crustal, structural, and stratigraphic architectures by integrating interpreted seismic reflection data and robust gravity modelling.  A particular interest is given to the continent-ocean transition (COT), where there remains a significant gap in the characterisation of the nature(s) of the crust. We show that this is not a typical magma-rich margin archetype, rather that there is considerable along strike variation – a wide continental block with fault-bound syn-rift basins and seaward dipping reflectors characterising the COT in the North of the margin, while moving along strike to the South extrusive volcanics are absent, replaced by a magmatic crust and a considerably thinner continental block as the physiognomy of the margin changes considerably along strike.

Furthermore, we compare and contrast our findings from the ENAM with published work from the conjugate West African Margin to allow for an understanding of the evolution of the conjugate margins as a whole, gaining insights into the complex three-dimensional nature of the development of the margin geometries we observe today.
Optimal transport for the multi-model combination of sub-seasonal ensemble forecasts
Authors: Le Coz Camille , Tantet Alexis , Flamary Rémi , Plougonven Riwal
Published: February 2023

Combining ensemble forecasts from several models has been shown to improve the skill of S2S predictions. One of the most used method for such combination is the “pooled ensemble” method, i.e. the concatenation of the ensemble members from the different models. The members of the new multi-model ensemble can simply have the same weights or be given different weights based on the skills of the models. If one sees the ensemble forecasts as discrete probability distributions, then the “pooled ensemble” is their (weighted-)barycenter with respect to the L2 distance.Here, we investigate whether a different metric when computing the barycenter may help improve the skill of S2S predictions. We consider in this work a second barycenter with respect to the Wasserstein distance. This distance is defined as the cost of the optimal transport between two distributions and has interesting properties in the distribution space, such as the possibility to preserve the temporal consistency of the ensemble members.We compare the L2 and Wasserstein barycenters for the combination of two models from the S2S database, namely ECMWF and NCEP. Their performances are evaluated for the weekly 2m-temperature over seven winters in Europe (land) in terms of different scores. The weights of the models in the barycenters are estimated from the data using grid search with cross-validation. We show that the estimation of these weights is critical as it greatly impacts the score of the barycenters. Although the NCEP ensemble generally has poorer skills than the ECMWF one, the barycenter ensembles are able to improve on both single-model ensembles (although not for all scores). At the end, the best ensemble depends on the score and on the location. These results constitute a promising first step before implementing this methodology with more than two ensembles, and ensembles having less contrasting skills.
Double machine learning for geosciences
Authors: Cohrs Kai-Hendrik , Varando Gherardo , Reichstein Markus , Camps-Valls Gustau
Published: February 2023

Hybrid modeling describes the synergy between parametric models and machine learning [1]. Parts of a parametric equation are substituted by non-parametric machine learning models, which can then represent complex functions. These are inferred together with the parameters of the equation from the data. Hybrid modeling promises to describe complex relationships and to be scientifically interpretable. These promises, however, need to be taken with a grain of salt. With too flexible models, such as deep neural networks, the problem of equifinality arises: There is no identifiable optimal solution. Instead, many outcomes describe the data equally well, and we will obtain one of them by chance. Interpreting the result may lead to erroneous conclusions. Moreover, studies have shown that regularization techniques can introduce a bias on jointly estimated physical parameters [1].We propose double machine learning (DML) to solve these problems [2]. DML is a theoretically well-founded technique for fitting semi-parametric models, i.e., models consisting of a parametric and a non-parametric component. DML is widely used for debiased treatment effect estimation in economics. We showcase its use for geosciences on two problems related to carbon dioxide fluxes: Flux partitioning, which aims at separating the net carbon flux (NEE) into its main contributing gross fluxes, namely, RECO and GPP.
Estimation of the temperature sensitivity parameter of ecosystem respiration Q10.
First, we show that in the case of synthetic data for Q10 estimation, we can consistently retrieve the true value of Q10 where the naive neural network approach fails. We further apply DML to the carbon flux partitioning problem and find that it is 1) able to retrieve the true fluxes of synthetic data, even in the presence of strong (and more realistic) heteroscedastic noise, 2) retrieves main gross carbon fluxes on real data consistent with established methods, and 3) allows us to causally interpret the retrieved GPP as the direct effect of the photosynthetically active radiation on NEE. This way, the DML approach can be seen as a causally interpretable, semi-parametric version of the established daytime methods. We also investigate the functional relationships inferred with DML and the drivers modulating the obtained light-use efficiency function. In conclusion, DML offers a solid framework to develop hybrid and semiparametric modeling and can be of widespread use in geosciences. [1] Reichstein, Markus, et al. “Combining system modeling and machine learning into hybrid ecosystem modeling.” Knowledge-Guided Machine Learning (2022). https://doi.org/10.1201/9781003143376-14[2] Chernozhukov, Victor, et al. “Double/debiased machine learning for treatment and structural parameters.” The Econometrics Journal, Volume 21, Issue 1, 1 (2018): C1–C68. https://doi.org/10.1111/ectj.12097
Carbonaceous fraction contents of soil cultural layers from different ages from the area of Verona (NE Italy)
Authors: Bortolini Mara , Agnoletto Federica C. , Argiriadis Elena , Nicosia Cristiano , McWethy David B. , Devos Yannick , Stortini Angela M. , Baldan Maela , Roman Marco , Vendrame Tiziano , Scaggiante Raffaella , Bruno Brunella , Pojana Giulio , Battistel Dario
Published: February 2023

Cultural layers are deposits resulting from settlement and human activity on natural soil in the past. Materials from past domestic activities that become buried in the soil can be used to reconstruct human impact in a specific area in the past. The use of fire from early human societies since our times produced an enrichment of fire-related products such as charcoal. The presence and fluxes of charcoal particles in soils and sediments have been associated with the human occupation of a site in specific periods. But not only does the presence of charcoal permits us to infer the presence of human populations, but, in addition, assessing the abundance and degradation level of charcoal fragments can clarify anthropic activities in cultural deposits. In European towns, cultural layers with similar characteristics, have been defined as urban “Dark Earth” (DE) but their age, formation, and composition often differ significantly across sites. This study examined three archaeological sites in Verona, Italy, where DE layers with similar characteristics had been identified. The primary aim of this research was to understand the anthropogenic influence on the development of DE layers, by characterizing their geochemistry and the carbonaceous materials. To pursue this goal, we provided a micromorphological description of the soil and the abundance of charred material. The characterization of the amorphous/crystalline degree through µ-Raman spectroscopy was also investigated. Bulk material was described in terms of amounts of total organic carbon (TOC), recalcitrant organic carbon (ROC), total inorganic carbon (TIC), and trace element concentration. Radiocarbon dating of charred and humin fractions was performed to clarify the dynamics underlying DE origin. The different aspects studied were compared to outline the behavior and the development of the soil under the conditions of human exploitation, investigating the correlations and relationships of the variables. The results showed that a diverse pattern of human activities, including metal tools and/or ceramic manufacturing, was related to the formation of DE layers in urban contexts. Moreover, the investigation of carbonaceous fractions highlighted differences in soil organic carbon and charred material fraction, even if both of which were correlated with human influence.
Plant wax n-alkane distributions, concentrations, carbon and hydrogen isotope compositions in modern plants from the central Congo peatlands
Authors: Guardiola Mélanie , Bouka Gaël , Abaye Carolia , Menges Johanna , Rostek Frauke , Leduc Guillaume , Bard Edouard , Schefuß Enno , Garcin Yannick
Published: February 2023

The central Congo Basin in central Africa hosts the world largest tropical peatland complex, which is covered by tropical swamp forest. Understanding the factors that determine the nature and dynamics of the peatland vegetation cover is an important issue in the face of climate change and ongoing/planned human activities in the region.Studying lipid biomarkers preserved in environmental archives and peat, such as plant wax n-alkanes, allows the reconstruction of past vegetation changes and environmental conditions. Long-chain n-alkanes are recalcitrant molecules not affected by low temperature decomposition processes of organic matter and represent robust palaeo-environmental and palaeo-climatic proxies.However, there is little information on how the production of plant waxes by different plant types may influence the abundance and isotopic composition of sedimentary n-alkanes in peat and sediment archives in the Congo Basin. A sound interpretation of the sedimentary data requires knowledge of the distribution, concentration, stable carbon isotope composition (δ13C) and hydrogen isotope composition (δD) of plant wax n-alkanes from the current vegetation in the region. Therefore, calibration studies of these proxies in the central Congo Basin region are needed.To fill this knowledge gap, we sampled the dominant plant types (trees, shrubs, herbs) in the peatlands from the Cuvette Department, Republic of the Congo. In total, 53 samples were collected from 13 families, 27 species and across five different environments. Environmental meteoric waters (e.g., river waters, channels, standing ponds) were also sampled for their isotopic composition to identify the isotopic composition of hydrogen used during lipid biosynthesis. In this study we assess the variation of plant wax n-alkane δ13C and δD values according to photosynthetic pathways (C3 vs. C4), plant types (dicots, monocots) and source water δD values. It provides a framework for detailed paleo-environmental and paleo-climatic reconstructions in the central Congo Basin.
 

 
What drives the variability in isotopic fractionation of O2 during enzymatic reactions?
Authors: F. M. de Carvalho Carolina , Lehmann Moritz F. , Pati Sarah G.
Published: February 2023

Molecular oxygen (O2) is one of the most important electron acceptors for a large variety of biotic and abiotic processes in the environment. A wide range of oxygen isotopic fractionation associated with biological O2 consumption (e.g., respiration) has been reported in field and laboratory studies (18ɛO2 from -29 to -1 ‰). The observed variability in 18ɛO2 values has mainly been attributed to the different types of respiring organisms. But, to better understand what ultimately causes the variation in isotopic fractionation of O2, it is necessary to start investigating at the lowest level of biological complexity. All biological O2 consumption, including respiration, detoxification, and biosynthesis, occurs at the enzyme-level. A few 18ɛO2 values have been reported for isolated enzymatic O2 reduction reactions. However, these laboratory-scale studies also displayed a wide range of O-isotope effects (18ɛO2 from -33 to -10 ‰), without any systematic correlation between 18ɛO2 values and the type of enzyme, substrate, or O2-reduction mechanism. In this study, we aimed at applying O2 stable isotope analysis to a systematic selection of O2 consuming enzymes, to improve our molecular understanding of isotopic fractionation of O2 at the enzyme-level. In a first series of experiments, we have determined kinetic parameters, as well as 18ɛO2 (and 17ɛO2) values of O2 reduction for a series of copper- and flavin-dependent oxidase enzymes. O2 reduction by these oxidase enzymes occurs separately from substrate oxidation, i.e., O2 is reduced to water (four-electron reduction) or to hydrogen peroxide (two-electron reduction), independently from the type of substrate. Thus, the variability in observed O isotopic fractionation should only depend on the active-site structure and/or the O2 reduction mechanism. Our experimental 18ɛO2 values covered the same range as those previously reported for laboratory-scale studies with other enzymes. Most of the studied flavin- and copper-dependent oxidases displayed no deviation from mass-dependent fractionation (17ɛO2/18ɛO2 ≈ 0.52). We demonstrate that 18ɛO2 values systematically correlate with a given enzyme’s affinity for O2 in flavin-dependent oxidases. Furthermore, our data suggest that the range of 18ɛO2 and 17ɛO2 values differs significantly between flavin- and metal-dependent O2 consuming enzymes. These results represent an important first step towards an improved understanding and generalization of the isotopic fractionation of O2 at the enzyme- and, ultimately, at the organism-level.
Does the polymorphic transition in quartz trigger lower crustal earthquakes?
Authors: Gilio Mattia , Morana Marta , Angel Ross , Mihailova Boriana , Alvaro Matteo
Published: February 2023

Earthquakes are generated through the brittle failure of rocks at depth. While earthquakes are generally caused by far–field tectonic stresses, the atomic–scale mechanisms that actually trigger brittle failure in dry ductile crustal rocks are still uncertain. Quartz, a widespread mineral in the lower crust, undergoes an instantaneous polymorphic transformation from the α to β phase at pressure and temperature conditions compatible with the estimates of several lower–crustal paleo–earthquakes recorded as pseudotachylytes. The α–β quartz transition is displacive, reversible and, as α–quartz approaches the transition temperature at constant pressure, its volume increases non–linearly but without sudden jumps. In contrast, near the phase–transition temperature, the bulk modulus of quartz drops from ~30 GPa to almost zero and then abruptly rises to more than 70 GPa within a temperature range of only 10 K (Lakshtanov et al., 2007).Due to the confined space, near the α–β transition, a quartz inclusion in a garnet host is expected to develop strong differential strains and consequently will impose strong differential stresses on the surrounding host crystal. To check this hypothesis, we have applied in situ high–temperature Raman spectroscopy to quartz inclusions in garnet to monitor the development of structural deformation via the atomic dynamics at temperatures across the phase transition temperature Tc = 847 K for a free quartz crystal at atmospheric pressure. The temperature behaviour of the phonon wavenumbers ω of a quartz inclusion, in particular the hardening and disappearance of a minimum in ω(T) for the A modes near 208 and 464 cm-1 (involved in the α-β phase transition) as well as the persistence of Raman activity of the modes at ~128 cm-1 and ~355 cm-1 above Tc, reveals the accumulation of abnormally high strain in the confined quartz grains in the vicinity of the expected phase transition. Consequently, the corresponding stored elastic energy in the inclusion is released through the inclusion-host boundary into the host matrix while crossing the α–β transition, causing the garnet around the quartz inclusion to fracture or even, in some cases, shatter due to the large differential stresses developing in the inclusion at its transition.  Inclusions of apatite and zircon in the same garnets remain unchanged at the same conditions, excluding the fracturing being caused by the host garnet itself.We propose that this process can create sufficient fracturing in lower–crustal garnets, which can in turn accumulate into planar fractures along garnet-rich layers and thus trigger brittle failure and seismicity.ReferencesLakshtanov, D.L., Sinogeikin, S.V., Bass, J.D., 2007. High-temperature phase transitions and elasticity of silica polymorphs. Physics and Chemistry of Minerals 34, 11-22.
Soil C Impacts of Organic Amendments: Practical Models for Farmer Decision Support
Authors: Hughes Helen , Hillier Jonathan
Published: February 2023

Managing soil carbon (C) is an important part of agriculture’s role in both mitigating and adapting to climate change, whilst feeding a growing global population. Adding organic materials to the soil surface can be a valuable practice for C storage. However, regular on-farm measurement to monitor soil C is often impractical due to costs and spatial heterogeneity of soil C stocks. Soil C models can be utilised instead, but their data requirements must be reasonable to provide a useful alternative to farmers.Ideally, decision support tools should provide the most information from the fewest data points. Sub-field scale equilibrium and saturation dynamics of the soil C pool introduce complexity. The result is that environmental, management and time factors must be represented within modelling approaches.This analysis will compare the utility of several model approaches (including IPCC Tier 1) for predicting the impact of organic amendments in realistic farmer data scenarios. The impact of equilibrium concepts will be considered through factors such as time, baseline soil C values, as well as climate, environment and soil type. How should these factors be prioritised to focus farmer data requirements when providing decision support? What is the information cost of reducing the data burden?
Unsupervised clustering to jointly interpret geophysical datasets across the Alhama de Murcia active fault, Spain.
Authors: Hernandez i Pineda Adrià , Feyzullayev Tural , Marzan Ignacio , Alcalde Juan , Martí David , Carbonell Ramon
Published: February 2023

Joint interpretation of multidisciplinary geophysical data is the best way to reduce ambiguity in subsurface exploration. The combination of seismic velocity and electricalresistivity has proven to be an excellent geological characterization strategy, however, the integration of these geophysical parameters is a complex process. In this work, we use unsupervised clustering to jointly interpret three geophysical datasets (P wave velocity, S wave velocity, and electrical resistivity). The target is a cross-section across the Alhama de Murcia Fault (FAM), which is one of the main active faults in the Iberian Peninsula. In our approach, we first join the three datasets into a common multiparametric grid. Then, in order to find data clusters that can be correlated with known lithologies in the area, we investigated the performance of three unsupervised machine learning algorithms: one hierarchical, one centroid-based, and one model-based. The latter proved to be the most efficient for clustering our highly mixed data and providing geological meaning. The three classes obtained correlated well with the lithological units present in the area and, from their relationship, it was possible to deduce structural elements not yet well understood, providing new perspectives in the characterization of the Alhama de Murcia fault zone. Research supported by grants: VECTOR EU project ID 101058483, and SIT4ME -EITRawMaterials.