bluuebunny/crossref_metadata_2025 huggingface dataset:
Characteristics of heat exchange between land surface and atmosphere according observations at Research Station “Ice Base Cape Baranova” in 2013 - 2021
Authors: Makshtas Alexander , Makhotina Irina , Laurila Tuomas , Asmi Eija , Bogorodski Petr , Bol’shakova Irina
Published: March 2022

The estimates of seasonal and interannual variability of surface heat balance components on the Bolshevik Island, Severnaya Zemlya archipelago for period from September 2013 to December 2021 are presented. It is shown that seasonal variability of turbulent sensible and latent heat fluxes is fundamentally different. In winter turbulent sensible heat flux H is directed to the surface due to longwave radiative cooling. In summer H, due to strong heating of surface with low albedo by solar radiation, is directed into atmosphere and reaches up to 25% of incoming short-wave radiation. In opposite turbulent latent heat flux LE in winter is directed from the snow-covered surface to the atmosphere, but its values do not exceed 10% of H. In summer variability of soil surface moisture during the snowless period and the relatively high air humidity determined variable, but mainly from the underlying surface to the atmosphere direction of LE.

Data about thermal regime of the soil active layer and the characteristics of surface energy balance allow us to draw a conclusion about the reasons for the abnormally warm state of soil upper layer and extremal permafrost thawing in 2020. It is shown that the timing and intensity of thawing were associated with changes in all components of the surface heat balance, with the main changes occurring in the intensity of incoming long-wave radiation, caused by synoptic processes in troposphere, and absorption of incoming short-wave radiation, determined by earlier onset of snow melting and, accordingly, decrease in surface albedo.
Seismic activity and subglacial sedimentary structure near the grounding zone of the Totten Glacier, East Antarctica 
Authors: Winberry Paul
Published: March 2022

The Totten Glacier is the main conduit for ice leaving the Aurora Subglacial Basin in East Antarctica. During December 2018 and January 2019, we deployed a 12 station broadband seismic array near the grounding zone of the Totten Glacier. Here we report on subglacial sedimentary structure and seismic activity recorded by this network. Previous gravity studies indicated the possibility that erosion had removed most of the subglacial sediments in the region. We use the receiver function analysis to reveal that 100-200 meters of subglacial sediment remain near the grounding zone. We also will summarize a range of glacier generated seismic activity recorded by the array. We find significant occurrence of tidally modulated near surface crevasse related events as well as basal stick-slip seismic activity. We will provide an overview into both the temporal and spatial variability of seismic activity and discuss implications for fast flow in the region.
ENSO induced shifts of the Subarctic Front in the North Pacific over the past 700 ka: Evidence from planktic foraminiferal proxy data
Authors: Jacobi Lara , Chao Weng-si , Nürnberg Dirk , Lembke- Jene Lester , Tiedemann Ralf
Published: March 2022

The subarctic front (SAF) in the pelagic Pacific Ocean is the northernmost front that separates the Oyashio Current, which marks the southern boundary of the subpolar gyre, from the Kuroshio Current, the northern boundary of the subtropical gyre. Its strong sea surface temperature (SST) gradient is not a stable and permanent feature but shifts on timescales from interannual to glacial/interglacial. Yet the complex interplay of different driving mechanisms for this phenomenon is not yet entirely understood. In this study, we present newly retrieved data from the Emperor Seamount chain that reveals a link between long-term ENSO (El Niño /Southern Oscillation) dynamics in the tropics and shifts of the SAF. Here, we use marine sediment core SO264-45-2 (46°33.792’N, 169°36.072’E), recovered from the Emperor Seamount Chain during R/V SONNE Cruise SO264 in 2018 to reconstruct changes in (sub-) surface temperature and salinity via a combined Mg/Ca and δ18O analyses of the shells of the shallow living planktic foraminifera Globigerina bulloides and the near thermocline living Neogloboquadrina pachyderma. This reveals that SST and salinity do not show a clear glacial/interglacial pattern during the last 280 ka and thus we assume that the SAF was south of the core site during this time interval. Prior to 280 ka, SSTs were significantly higher and show greater amplitudes than after 280 ka, while the subsurface temperature stayed relatively constant. Such high SSTs together with the observed higher sea surface salinities prior to 280 ka indicate that water from the Kuroshio-Oyashio transition zone temporarily reached the core site in form of a warm surface water lens. This points to a northward displacement of the SAF of at least 5° so that it was located right above the core site. This way very small north and southward displacements e.g. in relation to glacial/interglacial periods would have caused SST changes as high as we observe them in the time interval 280-700 ka. Notably, this assumed shift of the SAF at 280 ka occurs simultaneously to a change from more La Niña-like to more El Niño-like conditions in the tropical Pacific. Moreover, warm phases in the time interval 280-700 ka seem to occur during times of more La Niña-like conditions in the tropics, while cold phases seem to be related to more El Niño-like conditions. As our study area is linked to the subtropical gyre via the Kuroshio Current, we assume that the observed shifts of the SAF at our study site were caused by the enhancement of the Kuroshio Current in time intervals of more La Niña-like like conditions.
Shear-velocity structure and dynamics beneath the Central Mediterranean inferred from seismic surface waves 
Authors: Agius Matthew , Magrini Fabrizio , Diaferia Giovanni , Kastle Emanuel , Cammarano Fabio , Faccenna Claudio , Funiciello Francesca , van der Meijde Mark
Published: March 2022

The evolution of the Sicily Channel Rift Zone (SCRZ), located south of the Central Mediterranean, is thought to accommodate the regional tectonic stresses of the Calabrian subduction system. It is unclear whether the rifting of the SCRZ is passive from far-field extensional stresses or active from mantle upwelling beneath. To map the structure and dynamics of the region, we measure Rayleigh- and Love-wave phase velocities from ambient seismic noise and invert for an isotropic 3-D shear-velocity and radial anisotropic model. Variations of crustal S-velocities coincide with topographic and tectonic features: slow under high elevation, fast beneath deep sea. The Tyrrhenian Sea has a <10 km thin crust, followed by the SCRZ (∼20 km). The thickest crust is beneath the Apennine-Maghrebian mountains (∼50 km). Areas experiencing extension and intraplate volcanism have positive crustal radial anisotropy (VSH>VSV); areas experiencing compression and subduction-related volcanism have negative anisotropy (VSH<VSV). The crustal anisotropy across the Channel shows the extent of the SW-NE extension. Beneath the Tyrrhenian Sea, we find very low sub-Moho S-velocities. In contrast, the SCRZ has a thin mantle lithosphere underlain by a low-velocity zone. The lithosphere-asthenosphere boundary rises from 40-60 km depth beneath Sicily and Tunisia to ∼33 km beneath the SCRZ. Upper mantle, negative radial anisotropy beneath the SCRZ suggests vertical mantle flow. We hypothesize a more active mantle upwelling beneath the rift than previously thought from an interplay between poloidal and toroidal fluxes related to the Calabrian slab, which in turn produces uplift at the surface and induces volcanism.

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 843696.
Anthropogenic impacts on marine nitrogen and iron biogeochemical feedbacks and their contribution to expanding oxygen minimum zones
Authors: Somes Christopher , Landolfi Angela , Oschlies Andreas
Published: March 2022

Nitrogen and iron are the key limiting nutrients throughout the majority of the global ocean. These nutrient systems have important source and/or sink processes that are highly sensitive to low oxygen thresholds. In this study, we use a global ocean biogeochemical model within an Earth system model of intermediate complexity to investigate anthropogenic controls on marine nitrogen and iron cycling under warming and atmospheric pollutant scenarios. We performed sensitivity simulations to isolate the individual and combined effects of the marine nitrogen and iron internal feedbacks, as well as the impact from increasing atmospheric pollutant deposition. Our model simulations demonstrate strong negative (stabilizing) feedbacks on marine productivity from both the marine nitrogen and iron cycles when feedbacks from only one individual nutrient cycle were considered at a time. However, when the full set of marine nitrogen-iron feedbacks were activated, enhanced iron sources from the atmosphere and sediments under anthropogenic scenarios were sufficient to stimulate additional N2 fixation by 16% globally, with much of it occurring near tropical oxygen minimum zones enhancing regional productivity there. These marine nitrogen-iron biogeochemical feedbacks driven by anthropogenic scenarios including atmospheric pollutant deposition were responsible for a projected 40% expansion in the volume of oxygen minimum zones by year 2100 in the model, whereas a sensitivity simulation with these feedbacks deactivated resulted in a 40% reduction. Our model study suggests that increasing marine nitrogen and iron sources in the Anthropocene can play an important role on future ocean biogeochemistry and productivity that significantly contribute to expanding oxygen minimum zones.
Where do tidal channels begin? Insights from the Venice Lagoon
Authors: Uguagliati Francesca , Tognin Davide , Puppin Alice , Ghinassi Massimiliano , D'Alpaos Andrea
Published: March 2022

Together with salt marshes and tidal flats, tidal channels are one of the fundamental components of tidal environments, because they crucially control the morphodynamic evolution of tidal landscapes. Despite tidal channels play a fundamental role in the hydrodynamics and morphodynamics of tidal environments, the mechanisms that govern their initiation, development, and evolution have received less attention compared to their fluvial counterparts. To address issues of conservation of tidal systems, exposed as they are to the effects of climate changes and increasing human interference, it is therefore of critical importance to improve current understanding of the origins and evolution of tidal channels, of their morphological characteristics, and of the sedimentary structures emerging from their evolution. The present work addresses this important issue, focusing on the study of the erosional and depositional patterns that can be observed in tidal channels cutting through different salt marshes of the Venice Lagoon, from north to south. In particular, we analyzed whether tidal channels are first initiated over tidal-flat surfaces and then inherited by salt marshes, or tidal channels are capable to incise the vegetated salt-marsh surfaces overwhelming the erosion resistance to channel incision provided by vegetation. This study was carried out by combining sedimentological, paleontological, and geomorphic analyses for a total of 30 meanders belonging to small tidal marsh creeks. For the sedimentological analyses, a total of 191 cores were recovered along axial transects of the 30 study bends with normally 6 cores per transect. These analyses allowed us to distinguish four main types of deposits: salt-marsh, point-bar, channel-lag and tidal-flat deposits. Their correlation emphasized the position and the size of the point bars within the different examined transects. Based on the position of the point bar and its brink trajectory within each transect we determined whether the erosive processes that led to channel primary formation occurred over a salt marsh or over a tidal-flat surface. The analyses showed that in most cases the considered channels are originated through the incision of a salt marsh. Lastly, the geomorphic analyses suggested that the analyzed saltmarsh creeks are strongly incised.
On the Instability of Buoyant Coastal Currents
Authors: Marchal Olivier , Condron Alan
Published: March 2022

The fate of buoyant water discharged into the coastal ocean from river or meltwater runoff is a problem of preeminent interest in coastal management, physical oceanography, and climate research. In the northern hemisphere, buoyant water introduced into the ocean is expected to turn to the right of the discharge location and form a buoyant gravity current flowing along the coast. Whilst the fate of coastal discharges has been intensively studied from field observations, laboratory experiments, analytical theories, and numerical simulations, the mechanisms responsible for the observed instability of buoyant currents produced from coastal discharges are not completely understood.

Here the instability of a coastal buoyant current produced from the discharge of glacial meltwater is studied using idealized numerical experiments with a primitive-equation circulation model. It is found that glacial water released from the coast produces a surface plume in front of the release location, turns to the right, and leads to a buoyant current flowing at a speed of O(1 m/s) along the coast. Over the course of the numerical integration, the coastal current becomes unstable and develops dipolar vortices along its offshore boundary. The vortices are the largest near the glacial water inflow and migrate away from the discharge location at a speed of O(1 cm/s). They are asymmetric, with the region of cyclonic flow occupying a larger area than the region of anticyclonic flow, given them the appearance of breaking “backwards” relative to the direction of the current. The vortices occur for both free-slip and no-slip conditions imposed along the coast, suggesting that their development is not associated with vorticity continuously generated by the frictional retardation of the flow at the boundary. Numerical results are compared to laboratory results published in the literature and interpreted in the light of the theory of the baroclinic instability in a two-layer model (a surface buoyant layer flowing relatively to a deeper heavier layer). The implications of our results for the simulation of buoyant coastal discharges with coarse-resolution ocean models, such as used in climate studies, are clarified.
Detectability of polar stratospheric clouds using the colour index retrieved from ground-based spectroscopic measurements
Authors: Lauster Bianca , Dörner Steffen , Frieß Udo , Gu Myojeong , Pukite Janis , Wagner Thomas
Published: March 2022

Polar stratospheric clouds (PSCs) are an important component of the ozone stratospheric chemistry in polar regions. Although satellite observations nowadays provide high spatial coverage, continuous long-term spectroscopic measurements from the ground with high temporal resolution remain a valuable complement. Moreover, the presented method allows the detection of PSCs even in the presence of tropospheric clouds, while this is not possible with ground-based lidar measurements in such cases.

For a comprehensive interpretation of measurement data, the well-established radiative transfer model McArtim is used and spectra of scattered sunlight at different solar zenith angles are simulated for various atmospheric conditions. Investigating the ratio between observed intensities at two wavelengths, i.e. the so-called colour index (CI), enables the detection of PSCs during twilight. Due to the wavelength variability of scattering processes, the choice of the wavelength pair is determining the effect which PSCs exhibit in the spectra. Likewise, the optical properties, altitude and extent of the PSC layer are decisive parameters that are investigated in detail with the help of 3D simulations. In these, the PSC layer is not simulated as horizontally extended, but as a confined area with different sizes.

The findings are then compared to measured spectra from a MAX-DOAS (Multi AXis-Differential Optical Absorption Spectroscopy) instrument, which has been operating at the German research station Neumayer (70° S, 8° W) in Antarctica since 1999. While the simulations already provide insight into the sensitivity of ground-based spectroscopic measurements for the detection of PSCs, the comparison to measurement data confirms the good applicability of this method.
Ambiguity fixing on geometry free like model using modernized GNSS signals
Authors: Tagliaferro Giulio
Published: March 2022

Ambiguity fixing on the geometry free combination presents some desirable characteristics. In particular, it does not require precise ephemeris, modelling of station displacement motion or tropospheric modelling or estimation. For such reasons, it can be particularly interesting in the case where such data and models are not available or if simpler processing is wanted. Such fixing procedure has been studied in the past for dual-frequency and triple frequency cases. Unfortunately, especially in the two frequency case, this procedure is not practical due to the long observation period needed to reliable fix a correct integer set. In this contribution, we review the fixing performances of the “geometry free” model using an undifferenced uncombined approach. Furthermore, we present the case to four and five frequency cases using Galileo and Beidou observations showing that reliable fixing in a reduced time span is possible. All analyses presented are performed using real GNSS data from the IGS permanent network. Finally, some possible applications are presented with a focus on ionospheric studies.
 A quantitative technology for supporting multi-objective decision making in hydropower operation
Authors: Ni Xiaokuan , Dong Zengchuan , Jiang Yong , Yao Hongyi , Jia Wenhao , Yang Guang
Published: March 2022

There is a conflict between the hydropower benefit of hydraulic engineering and other functions such as ecological protection, water supply, flood control, etc. Deciding on an appropriate scheme to balance the interests among multiple objectives is a crucial issue in hydropower operation management. The Pareto set is the carrier and embodiment of a multi-objective mutual feedback relationship. It has a constant increasing or decreasing tendency, and most distribute unevenly, meaning different change rates and sensitivities are embedded. Based on this understanding, a new idea of "profit/loss ratio" is obtained, which constructed the average change rate of each neighbouring non-inferior solution on the Pareto frontier. Processed dimensionless, a new non-dominated subset of Pareto non-inferior solutions is filtered out according to the dominance relationship to limit scheme selection scope. On this basis, a method for calculating the "bias degree" of each Pareto non-inferior solution relative to different objective functions is proposed, which leads to the quantitative evaluation of Pareto solutions and provides quantitative support for decision-makers select operation schemes according to their preferences. Taking the cascade reservoirs in the lower reaches of the Jinsha River Basin in China as a case, the trade-off between the two objectives of hydropower generation and ecological protection is investigated, and the feasibility and effectiveness of the methodology are verified.
Magnetotellurics in the Eger Rift: Regional and local three-dimensional subsurface imaging and modelling of fluid pathways from the crust-mantle boundary to the surface
Authors: Aleid Basel , Weckmann Ute , Platz Anna , Mair Johannes
Published: March 2022

The Bohemian Massif is part of the geodynamically active European Cenozoic Rift System and represents its easternmost termination. The study area is situated at the junction of three different Variscan tectonic units and hosts beside the Eger Rift a series of different fault systems. The entire region is characterized by ongoing magmatic processes in the intra-continental lithospheric mantle expressed by, e.g., the occurrence of repeated earthquake swarms, the presence of Quaternary volcanoes, and massive degassing of mantle-derived CO2 in mineral springs, mofettes as well as. Several geoscientific studies suggest that fluid circulation along the deep-reaching faults seems to play an important role in explaining the underlying geodynamic processes. As part of an ICDP drilling programme, we applied the Magnetotelluric (MT) method with the goal to contribute to the understanding of the physical and chemical processes and interaction that led to the magma and fluid transport by mapping potential fluid pathways from the crust-mantle boundary up to the surface. Here, we present 3D inversion models of two different overlapping regional and one local MT experiments located in the Cheb basin close to the Hartoušov mofette field. The most prominent large-scale conductivity features of the regional models are several channels from the lower crust to the surface, possibly representing pathways for fluids into the earthquake swarm region, mofette fields, and known spas. However, such a conductive channel is absent in the local model beneath the surface expression of the mofettes. We will test two different hypotheses, namely a vertical ascending channel versus lateral fluid migration. Results from synthetic modelling studies and available geoscientific constraints hint that such a channel might exist directly beneath the mofette field, but due to the given data quality, station distribution, and the subsurface conductivity structure within a conductive sediment basin, it might be challenging to resolve.
Potential and limitations of convection-permitting CNRM-AROME climate modelling in the French Alps
Authors: Monteiro Diego , Caillaud Cécile , Samacoĩts Raphaẽlle , Lafaysse Matthieu , Morin Samuel
Published: March 2022

Despite continued progress and a growing literature assessing regional climate change worldwide, modeling and assessing climate characteristics in mountainous regions remain challenging. Yet the stakes are high in these regions. As significant changes affect glaciers and snowpack, having
cascading effects on regional hydrology, quantifying them as accurately as possible is necessary for societal actors to adapt and reduce the growing climate risks.

Convection permitting climate modelling is a promising avenue for climate change research and services, particularly in mountainous regions. Work is required to evaluate the results of high resolution simulations against relevant reference dataset and put them in a broader context against coarser resolution modeling frameworks.

Our research assesses the potentials and limitations of high resolution climate models to represent past and future changes in snow conditions in the European Alps.

Here, we present an insight from the convection permitting climate model (CPRCM) CNRM-AROME ran at 2.5 km horizontal resolution over a large pan-Alpine domain in the European Alps, using either the ERA-Interim or CNRM-CM5 output as boundary conditions.

Annual and seasonal characteristics of four variables (2m temperature, total precipitation, solid fraction of precipitation and snow depths) are compared over the French Alps with the local reanalysis S2M, and raw or adjusted, with the ADAMONT method, simulations of the regional
climate model CNRM-ALADIN driven either by the ERA-Interim reanalysis or the CNRM-CM5 global climate model.

The study generally highlights similar differences in past and future climate between the datasets, as well as obstacles to the use of some CNRM-AROME outputs as they stand. These consist of excessive accumulation of snow on the ground above 1800 m a.s.l., as well as lower temperature
values at same elevations than the S2M reanalysis and the ADAMONT-adjusted outputs.

Nevertheless, clear advantages of CNRM-AROME simulations compared to raw CNRM-ALADIN outputs appear, concerning the temperature fields, the better representation of precipitations, as well as the spatial variability closer to the reference data.
Surface water detection and flood mapping using optical remote sensing and water-related spectral indices
Authors: Albertini Cinzia , Gioia Andrea , Iacobellis Vito , Manfreda Salvatore
Published: March 2022

The use of multispectral satellite imagery for flood mapping and river monitoring is a fast and cost-effective method that can benefit from the growing availability of medium-high-resolution and free remote sensing data. Since the 1970s, several satellites are observing the Earth surface supporting water detection studies and flood management. In addition, many techniques exploiting different spectral indices have been proposed in the literature. Considering the high number of available sensors and their differences in spectral and spatial characteristics, this work aims to examine the applications of satellite remote sensing for water extent delineation and flood monitoring. Focusing on freely available optical imagery, this study presents a discussion of the most used satellites for flood and wetland mapping to highlight trends of current research studies. Furthermore, performances of the most common spectral indices for water segmentation are analysed first qualitatively, based on evidence obtained from a significant literature review, and then quantitatively by comparing different water-related index algorithms applied to a real case study. Performance assessment is carried out to provide an overview of the best sensor-specific spectral index in detecting surface water and expressed in terms of overall accuracy (OA) and Kappa coefficient.
Arctic low-level mixed-phase clouds produce large aggregates predominantly at dendritic-growth temperatures: evidence from long-term remote sensing observations in Ny-Ålesund
Authors: Chellini Giovanni , Gierens Rosa , Kiszler Theresa , Schemann Vera , Kneifel Stefan
Published: March 2022

Low-level mixed-phase clouds (MPCs) occur widely and frequently in the Arctic, and on average introduce a strong positive radiative forcing. While precipitation is expected to affect radiative characteristics of Arctic MPCs, the relevancy of precipitation-formation processes, such as aggregation and riming, has been widely overlooked. An incomplete understanding of precipitation-formation processes in Arctic MPCs is likely to impact our ability to accurately simulate their evolution, macrophysical characteristics, and radiative effects.

We employ a 3-year dataset of remote sensing observations from Ny-Ålesund, Svalbard, including two vertically-pointing Doppler radar systems, measuring at K- and W-band, to statistically assess the relevancy of aggregation and riming in Arctic low-level MPCs. We use the ratio of radar reflectivities measured at the two frequencies as a proxy for particle size, and match it with Doppler velocity information and temperature retrievals, to identify situations when the ice-particle growth is dominated by either aggregation or riming.

We find observational evidence that large ice particles (mass median diameter > 1mm) mostly form when the mixed-phase layer of the low-level MPC is at temperatures compatible with dendritic growth (-15 to -10°C). Fall speeds of these larger particles are incompatible with significant riming. While mixed-phase layer temperatures between -15 and -10°C seem to be essential for the formation of large aggregates, these larger hydrometeors are not uniformly distributed across the cloud field. They are in fact observed in small pockets, suggesting that further dynamical processes might be needed to fully explain these signatures.

Surprisingly, we find no evidence of enhanced aggregation at temperatures above -5°C in Arctic low-level MPCs. This is typically observed in mid-latitude clouds, and in deeper cloud systems in Ny-Ålesund as well. We hypothesize that ice particles sedimenting from higher levels might be an essential component needed to trigger enhanced aggregation above -5°C. We will discuss potential reasons for the absence of this feature, which are likely connected to the specific ice habits growing at these temperatures, as well as enhanced riming.
Evaluating the added value of young water fractions for determining water transit times in diverse catchments
Authors: Borriero Arianna , Kumar Rohini , Nguyen Tam , Fleckenstein Jan , Lutz Stefanie
Published: March 2022

Water transit time distributions (TTDs) are important descriptors of hydrological functioning and solute mobilization in catchments. The use of transport models based on StorAge Selection (SAS) functions is promising for characterizing non-stationary TTDs. Model parameters are typically calibrated using tracer concentration in inflow (e.g., precipitation) and outflow (e.g., streamflow) in order to obtain suitable values of SAS function parameters and, thereby, simulate TTDs at catchment-scale. However, due to uncertainties in tracer data and equifinality problems in SAS modelling, modeled TTDs can be subject to considerable uncertainty. Therefore, we need alternative and independent methods that can help constrain model parameters. An example is the young water fraction (Fyw), which quantifies the proportion of catchment outflow younger than approximately 2–3 months. Our work attempts to explore the robustness of Fyw in constraining SAS model parameter values and, in turn, reducing predictive uncertainty of TTDs in multiple contrasting sub-catchments in the Central European Bode River Basin. We simulated TTDs using sparse (i.e., monthly) stable water isotope data (δ¹⁸O) in streamflow for calibration in an experimental SAS modelling framework. In a subsequent step, we directly compared the model estimates of long-term average (marginal) TTDs with Fyw derived from the seasonal cycles of δ¹⁸O measured in precipitation and streamflow. Our results showcase if and to what extent Fyw is a valuable additional constraint to infer SAS parametrizations as well as improve TTD predictions and the characterization of water age selection dynamics, and identify potentials and gaps in isotope-based TTD models. Our results also show how the effectiveness of Fyw in reducing the predictive uncertainty of TTDs may depend on the water use by plants and land use change across physiographically different sub-catchments. Overall, as the relevance of Fyw in TTD modeling is not yet well established, our aim is to investigate whether additional indicators such as Fyw are useful for TTD modeling and thus allow improving the description of flow and transport in catchment areas, especially in situations where a high-resolution tracer data are lacking.
Mercury anomaly as a proxy for volcanism in an isolated carbonate platform during the end-Triassic mass extinction
Authors: Montanaro Andrea , Falzoni Francesca , Iannace Alessandro , Adatte Thierry , Parente Mariano
Published: March 2022

Massive release of volcanic gases into the ocean-atmosphere system during geologically short periods of time is often invoked as the main trigger of episodes of global paleoenvironmental perturbations, and a link has been proposed between some mass extinction events, OAEs and the activity of Large Igneous Provinces. However, establishing a precise correlation between sections where the volcanic deposits of LIPs are preserved and marine sections, which hold the key records of global biotic and paleoenvironmental changes, is not a trivial effort.  During the past 15 years, mercury concentration in sedimentary rocks has emerged as a useful proxy for bracketing intervals of LIPs activity, because Hg is primarily introduced into the atmosphere, and from there into the sedimentary record, through volcanic inputs. 
The end-Triassic extinction (ETE), one of the big five mass extinction of the Phanerozoic, has been linked to the volcanic activity of the Central Atlantic Magmatic Province (CAMP). Correlation by radiochronologic dating of CAMP basalts has been further supported in recent years by detection of mercury anomalies in marine deposits of key sections recording the ETE, including the Kuhjoch GSSP in the Northern Calcareous Alps (Austria), St Audrie’s Bay (UK) and the New York Canyon (Nevada, USA). However, as the Hg proxy is investigated in more and more sections, a complicated pattern is emerging, which indicates that depositional and diagenetic processes can produce Hg anomalies unrelated to LIP magmatism. For this reason, it is important to test the proxy across a wide range of depositional environments. 
In this study, we present a high-resolution record of Hg concentration in an uppermost Triassic-Lower Jurassic carbonate platform section of the Pelagonian Domain (Greece). In this section the ETE is marked by the abrupt disappearance of megalodontid bivalves and involutinid benthic foraminifers. By integrating bio- and high-resolution carbon isotope stratigraphy, we correlate the studied section with reference sections for which a record of Hg concentration across the ETE has been published. Furthermore, we use facies analysis and geochemistry to unravel the role of local depositional and diagenetic processes in overprinting the global signal of volcanism on Hg concentration.
Elastic vs. plastic: Inversion of analogue magma-induced surface displacements in granular materials in laboratory experiments
Authors: Poppe Sam , Wauthier Christelle , Fontijn Karen
Published: March 2022

When magma ascends through the shallow parts of terrestrial planetary crust, it deforms the surrounding host rocks. The deformation patterns observed at the surface offer indirect means to characterize the position, geometry and volume of subsurface magmatic intrusions. To enable real-time eruption forecasting during volcano unrest, most volcano geodetic models assume that magma intrusion induces linearly elastic deformation of homogeneous shallow planetary crust. Other indirect geophysical volcano monitoring data (e.g., seismology, gravimetry) however offer only limited opportunity for validating geodetic model results. Moreover, recent geological observations at exhumed volcano plumbing systems and geophysical observations of recent intrusion events have shown that plastic behaviour can dominate in heavily fractured and heterogeneous volcanic edifices and tectonically active areas. The question remains how large the effect of unaccounted plastic deformation could be on estimated intrusion characteristics.

Scaled laboratory experiments can be an innovative tool to assess by how much modelled magma intrusion characteristics – volume, geometry, position – deviate from reality in circumstances where plastic deformation processes are important. We used a tensile rectangular dislocation in a homogeneous, linearly elastic half-space to invert the three components of near-surface displacements extracted from X-ray Computed Tomography imagery of laboratory experiments of analogue dyke injection in cohesive mixtures of quartz sand and gypsum powder. The model results favored by the inversions are then compared to the three-dimensional characteristics of the analogue magma intrusions observed in the X-ray CT imagery. To further investigate the effect of more complex model geometry, we also used a tensile distributed-opening dislocation geometry. Preliminary results show that inversion results can be improved by fixing values of parameters that control the position of the modelled dislocation, but significant discrepancies remain between the modelled and observed intrusion geometry, orientation and volume. This test study helps gaining insight on the limitations of commonly used volcano geodetic modelling and inversion methods, and provides a novel basis for interpreting geological, geodetic and geophysical data related to volcanic deformation. The experimental results pave the way for developing complex forward models of magma-induced deformation in the heterogeneous shallow crust of terrestrial planets.
Assessing firn water storage from a multi-data firn-model inversion
Authors: Simonsen Sebastian B. , Hansen Nicolaj , Otosaka Inès , Vandecrux Baptiste , Sandberg Sørensen Louise
Published: March 2022

The ESA 4DGreenland project has the objective of performing an integrated assessment of Greenland’s hydrology through maximizing the use of Earth observation (EO) data. However, as meltwater is activated on the surface of the Greenland ice sheet and percolates into the firn, the firn water storage and delayed runoff are unobservable from EO, and we must resort to modeling to quantify this component. 

The DTU-firn model has previously been used to quantify the change in firn air volume as a leading component of altimetric mass balance estimates and was initially tuned using firn core density observations. Here, we revisit the fundamentals of the model and perform model inversion using as many observational datasets as possible. This observational data ranges from direct measurements of firn compaction derived from “coffee-can” experiments, over traditional observation of densities and temperature from firn cores to regional observation of firn stratigraphy from airborne radar surveys. This large diversity in the data sources ensures the best possible constraints for capturing as many aspects as possible of the firn dynamics.  

One important model feature of the DTU-firn model is its ability to resolve individual precipitation events as model layers. This feature promotes the capability of retaining water and shows promising results in line with the in-situ observation. The updated DTU-firn model is therefore used within the 4DGreenland project to provide updated estimates of meltwater retention and delayed runoff as a function of the available water at the surface of the firn. Combined with results obtained by the HIRHAM- and MAR-firn models, it also enables better quantification of firn model uncertainties. Having built confidence in the model we can treat the retention and delayed runoff as a function of the available water at the surface of the firn. This then gives the possibility of using the observed surface melt, also acquired within 4DGreenland from satellite microwave data, in the assessments of Greenland’s hydrology and thereby increasing the useability of EO data.
Illustrating Climate Science: the Case for Visual Representations of Complex Concepts
Authors: van der Laan Larissa
Published: March 2022

A general challenge of science communication, when addressing complex concepts within e.g. earth science, is to choose an audience and tailor the experience to draw in the specific members of that audience. This can lead to the exclusion of audiences that do not feel spoken to, regardless of their innate interest in the subject. Having been faced with that challenge, I have adopted an alternate approach, by creating visually appealing illustrations to draw the attention of various types of audiences. The members can then choose a path of information from there, ranging from non-interaction with the scientific concept, over elementary-level explanation, up to peer-reviewed scientific publications. This approach can be beneficial in achieving wide engagement and allowing connected groups, e.g. parents and children, to learn together, each at their own level of interest and understanding. 
Constrained Generative Adversarial Networks for Improving Earth System Model Precipitation
Authors: Hess Philipp , Drüke Markus , Petri Stefan , Strnad Felix , Boers Niklas
Published: March 2022

The simulation of precipitation in numerical Earth system models (ESMs) involves various processes on a wide range of scales, requiring high temporal and spatial resolution for realistic simulations. This can lead to biases in computationally efficient ESMs that have a coarse resolution and limited model complexity. Traditionally, these biases are corrected by relating the distributions of historical simulations with observations [1]. While these methods successfully improve the modelled statistics, unrealistic spatial features that require a larger spatial context are not addressed.

Here we apply generative adversarial networks (GANs) [2] to transform precipitation of the CM2Mc-LPJmL ESM [3] into a bias-corrected and more realistic output. Feature attribution shows that the GAN has correctly learned to identify spatial regions with the largest bias during training. Our method presents a general bias correction framework that can be extended to a wider range of ESM variables to create highly realistic but computationally inexpensive simulations of future climates. We also discuss the generalizability of our approach to projections from CMIP6, given that the GAN is only trained on historical data.

[1] A.J. Cannon et al. "Bias correction of GCM precipitation by quantile mapping: How well do methods preserve changes in quantiles and extremes?." Journal of Climate 28.17 (2015): 6938-6959.

[2] I. Goodfellow et al. "Generative adversarial nets." Advances in neural information processing systems 27 (2014).

[3] M. Drüke et al. "CM2Mc-LPJmL v1.0: Biophysical coupling of a process-based dynamic vegetation model with managed land to a general circulation model." Geoscientific Model Development 14.6 (2021): 4117--4141.
Colloid-facilitated Transport of Heavy Metals in Lake Sediments
Authors: Şengör Sema Sevinç , Ünlü Kahraman
Published: March 2022

This work focuses on the development of a mechanistic Fe(hydr)oxide based (HFO) colloid-facilitated reactive transport model which identifies the impact of HFO colloids on the stability and mobility of heavy metals (Zn and Pb) in example subsurface benthic sediments of Lake Coeur d’Alene (LCdA), USA. Ferrihydrite colloids are considered as the major sorbing phases for heavy metals, where the metal adsorption is implemented by surface complexation using double layer modeling and with electrostatic double layer (EDL) implementation using the dual-domain diffusive mass transfer characteristics of the PHREEQC code. The transport of colloidal phases is implemented by using 4 different advective velocities of the solution and colloidal particles (3 x 10-8 cm/s, 3 x 10-7 cm/s, 9 x 10-7 cm/s, and 3 x 10-6 cm/s), which are within the range reported in the literature for similar porous systems with relevant ranges of Peclet numbers. The advective transport simulation results are also compared with pure diffusive transport of solutes (and HFO) in the system, where the effective diffusion coefficient of colloidal particles is determined by the surface characteristics of ferrihydrite mineral discussed in previous studies. The simulations compare the biogeochemical cycling of metals considering colloidal vs. immobile phases of Fe(hydr)oxide minerals in the lake sediments. The impact of colloidal HFO particles on reactive transport and sorption of heavy metals in a natural environment, integrating coupled biotic reaction network with multiple terminal electron acceptors is presented.

The simulation results show that the colloidal HFO runs indicate a significant difference in results when advective transport of solutes (and HFO) is considered, as opposed to pure diffusive transport of ions and colloidal particles in this system. The increase in flow velocity observed to result in an increase in the transport of heavy metals with depth with increases in heavy metal profiles, indicating the importance of colloidal transport in the presence of especially advective transport. Hence, the results of the study reveal that when the potential transport of sorbed contaminants with colloidal particles are ignored, the contaminant concentrations in aqueous environments might be underestimated.
Abrupt climate changes caused by meltwater pulses in the Labrador Sea during the last glacial termination
Authors: You Defang , Stein Ruediger , Fahl Kirsten
Published: March 2022

The last glacial termination is an unstable transition state characterized by abrupt climate changes, while the related physical mechanisms are still not fully understood. Here, we present well-dated high-resolution sedimentary records from the eastern Labrador Sea representing the last 23 ka. Based on our biomarker records, there was seasonal to permanent sea ice cover before 11.7 ka BP. During 11.7 to 8.2 ka BP, ice-free conditions were interrupted by several sea ice expansions, while no sea ice after 8.2 ka BP. Besides Heinrich Event 1, four prominent cold events have been identified during 14 ka to 8.2 ka BP. These abrupt events are marked by increases in sea ice, decreases in sea surface temperature, and weak deep current intensity. We propose that these events were mainly triggered by collapses of the Laurentide Ice Sheet and/or Greenland Ice Sheet, resulting in icebergs/meltwater in pulses into the Labrador Sea. This caused surface freshening, which potentially promoted the stratification of surface water, prevented the northward inflow of Atlantic Water, and limited deep water production in the Nordic Seas, consequently disrupting the climate.
Straw amendment as a double-edge sword controlling N losses and immobilization over winter cooling
Authors: Chen Hao , Blagodatsky Sergey , Rosinger Christoph , Reichel Rüdiger , Li Bo , Kumar Amit , Rothardt Steffen , Luo Jie , Brüggemann Nicolas , Kage Henning , Bonkowski Michael
Published: March 2022

Nitrogen (N) lost from the agricultural field as leachate and nitrous oxide (N2O) gas causes water pollution, accelerates global warming and decreases agricultural N use efficiency. Soil amendments with straw and nitrification inhibitors are used to combat these problems by increasing microbial N immobilization and suppressing nitrification, respectively. The potential N competition between soil microorganisms and subsequent crops under the incorporation of pre-crop straw can be moderated by seasonal temperature variation, but this interfering factor is insufficiently studied. A 99-days mesocosm experiment that simulated the seasonal temperature variation was conducted, to investigate the effects of wheat straw amendment (WSA) and nitrification inhibitor (NI) on the competition for soil N between soil microbes and winter barley under three N fertilization levels (N0 as control, N1 as low N fertilizer, N2 as high N fertilizer), and N lost from soil as N2O and leachate. Strong mineralization was detected after the cooling-warming cycle, which happens in early spring frequently in Germany. Soil NH4+ of all treatments were increased by 34-138 % and soil NO3− of N2 levels were increased by 42-133 % during this process, providing mineral N for barley growth but also imposing the risk of N losses. Straw incorporation stimulated immobilization of N by soil microorganisms, increased soil microbial biomass C and N by 45-123 % till the end of experiment, thus decreased the total N lost by 41 % on average by decreasing N leaching (43-91 %), NI mitigated N2O emission by 40 % in N2 levels, the combination of WSA and NI could mitigate N losses and global warming. However, the immobilized N under WSA was not remineralized timely during barley growth, therefore, barley shoot biomass (by 23-34 %) and N (by 28-46 %) decreased in N0 and N1 fertilizer levels, the shoot nitrogen use efficiency (NUE) decreased in N1 (by 53 %) and N2 (by 30 %) fertilizer levels. Considering the strong (long term) N immobilization induced by straw, we suggest applying straw and N fertilizer separately to avoid N competition between soil microorganisms and crops.