bluuebunny/crossref_metadata_2025 huggingface dataset:
Modular collaborative resilient robots for mining operations
Authors: Gomez Virgilio , Hernando Miguel
Published: March 2022

In the framework of the ROBOMINERS project, we are developing a set of modular collaborative robots that can perform mining operations. The purpose of this work is to face the challenge of taking modular robots out of the academic context and to provide robotic miners with the needed resilience which will be based on four pillars: redundancy, physical reconfiguration, adaptive behavior, and system reconfiguration. To do so, we are working on a scaled prototype based on a highly configurable modular robot that allows the connection between several autonomous robots (modules) and functional submodules (e.g., sensors, mining tools, locomotion devices) where resilience, energy sharing, self-reconfigurability, modularity, and self-awareness capabilities will be tested both in simulation and real-world scenarios. For each robot module, a lightweight and compact main structure is composed of three compartments and three docking ports for each of the robot legs. In each of these compartments most of the electronic components that allow the proper functioning of the robot are located, while in the legs a 4 degrees of freedom closed chain parallel mechanism powered by multi-turn servomotors is responsible of moving the interchangeable end effectors (screws, continuous tracks, legs) designed with a common coupling interface. In addition, an innovative soft telescopic robot arm (Patent pending) is placed at the front of the robot module and allows the coupling of another robot, sensing or actuation module. In parallel to the robot prototype development, a digital twin is being developed in order to test and improve different configurations, localization, mine mapping, and control algorithms techniques before deploying them in the robot.
The effects of wave scale, non-linearity, spectral bandwidth and direct wind shear stress on air entrainment and bubble size distributions in laboratory breaking waves
Authors: Cao Rui , Callaghan Adrian
Published: March 2022

Bubble plumes within the two-phase flow generated by sufficiently energetic surface breaking waves (whitecaps) enhance the exchange of gas, mass and heat between the atmosphere and ocean. The bubbles formed inside whitecaps range in size from order tens of microns to centimetres, and accurate measurements of the space- and time-evolving bubble size distribution is central to achieving a better understanding of air-sea gas exchange and aerosol production flux.

In the present study, we describe the measurements of time- and space-evolving bubble size distribution in 2-D laboratory breaking waves. The bubbles were measured with high resolution digital images using a range of novel image processing and object detection techniques. A wide range of breaking waves were considered by altering the underlying scale, nonlinearity and spectral bandwidth of the dispersively-focused wave groups. The experiments were initially conducted in the absence of wind, and again under influence of direct wind shear stress. A variety of wind speeds were examined to replicate the effects of varying wave age on the breaking process, air entrainment and resulting bubble size distribution.

Our experimental results demonstrate that underlying wave scale, non-linearity, spectral bandwidth and wind speed (wave age) all have a measurable influence on the evolution of the two-phase flow and bubble size distributions within the breaking waves studied here, highlighting the complexity of the air entrainment over the breaking process. The relative magnitude and importance of these influences will be discussed in detail in this work. For instance, compared to breaking waves without wind stress, wave in the presence of wind tend to break at lower wave steepness, resulting in a reduction of total air entrainment and significantly different spatial distribution of bubbles.
Examining the climate impacts of future volcanic eruptions 
Authors: Chim Man Mei , Aubry Thomas J. , Abraham Luke N. , Schmidt Anja
Published: March 2022

Large explosive volcanic eruptions can induce global climate impacts on decadal to multi-decadal timescales. In current climate models, future volcanic eruptions are represented in terms of a time-averaged volcanic forcing that ignores the sporadic nature of volcanic eruptions. This conventional representation does not account for how climate change might affect the dynamics of volcanic plumes and the stratospheric sulfate aerosol lifecycle and, ultimately, volcanic radiative forcing. To account for these climate-volcano feedbacks in climate projections, we perform model simulations from 2015 to 2100 with two key innovations: (1) a stochastic resampling approach to generate realistic future eruption scenarios based on historical volcanic eruptions recorded by ice cores and satellites in the past 11,500 years; and (2) a new modelling framework, UKESM-VPLUME, which couples a 1-D eruptive plume model (Plumeria) with an Earth System Model (UKESM) to consider the impacts of changing atmospheric conditions on eruptive plume heights. Our results show that considering sporadic small-magnitude volcanic eruptions in a future warming scenario can lead to a noticeable difference in global surface temperatures as well as on the time at which temperatures exceed 1.5°C above pre-industrial levels. Our study highlights the importance of considering sporadic eruptions and the changes in eruptive plume heights in a future warmer climate.  The UKESM-VPLUME model framework enables us to quantify the impacts of climate change on volcanic radiative forcing in an Earth System model, which in future research allows us to better evaluate the climate impacts of volcanic eruptions under global warming.
High-speed Magnetosheath Jet Generation due to Shock Reformation
Authors: Raptis Savvas , Karlsson Tomas , Vaivads Andris , Pollock Craig , Plaschke Ferdinand , Johlander Andreas , Trollvik Henriette , Lindqvist Per-Arne
Published: March 2022

Magnetosheath jets are transient localized structures of enhanced dynamic pressure observed downstream of the Earth’s bow shock. They may exhibit an increase of velocity reaching solar wind levels, while their density is typically much higher than typical magnetosheath and solar wind values. Jets have been associated to several magnetospheric effects such as, magnetopause reconnection, excitations of surface eigenmodes and even direct plasma penetration in the magnetosphere. While their exact origin is unknown, many mechanisms have been proposed. One of the most prominent explanations involves the interaction of solar wind with local inclinations of the bow shock (ripples) while others include solar wind discontinuities, and foreshock structures.

In this work, by using Magnetosphere Multiscale (MMS) we show in-situ observations of a super-magnetosonic magnetosheath jet being generated as a direct result of the bow shock reformation cycle. The observed jet origin appears to be the result of the dynamical evolution of the shock and the emergence of a spatially de-attached compressive magnetic structure that acts as a local shock front. Due to this, the solar wind particles are effectively transferred downstream without experiencing a strong interaction with the shock, which allows compressed high velocity plasma to be observed downstream of the bow shock.

The proposed mechanism does not require external phenomena (e.g., solar wind discontinuities) or specific configuration of the bow shock (e.g., ripples) to take place. On the contrary, it allows the magnetosheath jet phenomenon to directly originate from the dynamical evolution of the quasi-parallel collisionless shock.
Altitudinal dependence of historical and future extreme events in the Great Alpine Region modelled with WRF
Authors: Napoli Anna , von Hardenberg Jost , Pasquero Claudia , Parodi Antonio
Published: March 2022

Climate change has a strong impact on the environment in mountain areas, especially since mountain ecosystems depend on climatic conditions that vary with altitude. In recent years, it has become clear that warming strongly depends on elevation. In this study, we examine projected climate change in the Greater Alpine Region using the Weather Research Forecasting (WRF) model. Historical 30-year simulations (1979-2008) and climate change projections (2039-2068) were performed at high spatial resolution (4 km grid spacing) and with initial and boundary conditions provided by the global EC-Earth model. A focus on the altitudinal dependence of historical and future ETCCDI Climate Change indices is presented here: the results indicate that both temperature and precipitation are affected by climate change with an altitude dependence changing seasonally. Physical mechanism at the base of those differences are discussed.
3D Hybrid Simulations of the Interaction between Self-Consistently Generated Extreme Solar Events and the Terrestrial Geo-Environment
Authors: Cazzola Emanuele , Fontaine Dominique , Savoini Philippe
Published: March 2022

In this work we present some results from 3D hybrid simulations of the interaction between extreme solar events, such as Coronal Mass Ejections (CMEs) or Co-rotating Interaction Regions (CIRs), and a 3D Earth-like geo-environment. The events are generated and let evolve self-consistently in order to represent their typical realistic Earth-hitting characteristics as described by the averaged profiles obtained from decades of observations at 1 AU. Both shock-less and shock-driven configurations are considered to highlight the differences between the two scenarios in terms of their kinetic dynamics, as well as in terms of the effects on the Bow-Shock / Magnetosheath / Magnetosphere system.
Performance of satellite rainfall products for landslide prediction in India
Authors: Brunetti Maria Teresa , Melillo Massimo , Gariano Stefano Luigi , Ciabatta Luca , Brocca Luca , Amarnath Giriraj , Peruccacci Silvia
Published: March 2022

Landslides are among the most dangerous natural hazards, especially in developing countries. In these areas, where rain gauge networks are scarce, satellite rainfall products can be a viable alternative for landslide prediction. To date, only a few studies have investigated the capability and effectiveness of these products in regional-scale landslide prediction. We performed a comparative study on the reliability of ground-based rainfall products and satellite rainfall products for landslide prediction in India. We used a catalog of 197 rainfall-induced landslides over the 13-year period between April 2007 and October 2019. We calculated frequentist rainfall thresholds using GPM, SM2RAIN-ASCAT satellite products, and their merging, at daily and hourly temporal resolution, and ground-based data from the rainfall network of the Indian Meteorological Department (IMD) at daily resolution. The results indicate that satellite rainfall products outperform ground-based observations in the prediction of landslides due to their improved spatial (0.1° vs. 0.25°/pixel) and temporal (hourly vs. daily) resolutions. The best performance is achieved through the merging of GPM and SM2RAIN-ASCAT. These results open up the possibility for using satellite rainfall products in landslide early warning systems, particularly in poorly gauged areas.
Biotic, lithologic and geomorphic control on sediment production from detrital apatite geochemistry and thermochronology
Authors: Madella Andrea , Glotzbach Christoph , Ehlers Todd
Published: March 2022

Where, and how much sediment is produced and transported in hillslope and fluvial systems depends upon the topographic slope, soil production rate, lithology, precipitation, and biota. In this study we investigate the patterns of sediment production in two catchments of the Coastal Cordillera (Chile) situated in semi-arid and mediterranean bioclimates. We do this by measuring 29 bedrock and 6 detrital apatite trace elements and apatite cooling ages with the U/Pb, fission track, U-Th(-Sm)/He thermochronometric systems. Detrital samples were collected from fluvial sediment and provide a catchment-scale view of the upstream areas. The compositional and geochronologic data measured in bedrock are analized with a Principal Component Analysis and a clustering algorithm to find the parameters that are best suited to trace sediment provenance at the sub-catchment scale. Next, we analyse the distribution of the same parameters within the detritus to infer the relative contribution of different areas within the catchments. Results indicate that spatial variations of bedrock cooling age and geochemical composition are significant even within small-scale (10-100 km2) granitoid catchments. Therefore, the combination of detrital apatite geochronology and geochemistry allows discrimination among source areas with acceptable confidence. Preliminary results show that the impact of vegetation distribution, hillslope angles and bedrock weatherability on sediment production differs in the two bioclimatic settings. In particular, hillslope angles and lithology exert a greater impact in the semi-arid catchment.
Towards interpretation of the radio-stratigraphy of Antarctic ice shelves from modeling and observations: A case study for the Roi Baudouin Ice Shelf, East Antarctica  
Authors: Visnjevic Vjeran , Drews Reinhard , Schannwell Clemens , Koch Inka , Franke Steven , Jansen Daniela
Published: March 2022

Ice shelves surrounding the Antarctic perimeter buttress ice flow from the continent towards the ocean, and their disintegration leads to an increase in ice discharge and sea level rise. The evolution and integrity of ice shelves is governed by surface accumulation, basal melting, and ice dynamics. We find history of these processes imprinted in the ice-shelf stratigraphy, which is mapped using isochrones imaged with radar. As an observational archive, the radar obtained stratigraphy combined with ice flow modeling has high potential to assist model calibration and reduce uncertainties in projections for the ice-sheet evolution. In this study we use a simplistic and observationally driven ice-dynamic forward model to predict the ice-shelf stratigraphy. We validate this approach with the full Stokes ice-flow model Elmer/Ice, and present a test-case for the Roi Baudouin Ice Shelf (East Antarctica) - where our model predictions agree well with radar obtained observations. The presented method enables us to investigate whether ice shelves are in steady-state, as well as to map spatial variations of how much of the ice-shelf volume is determined by its local surface mass balance. In the case of Roi Baudouin, we find the ice-shelf volume in the western part to be dominated by ice inflowing from the ice sheet, while the eastern part of the ice shelf is dominated by ice locally accumulated on the shelf. Such analysis serves as a metric for the susceptibility of ice shelves to climate change. We further apply our approach to other ice shelves in Antarctica.
Spatial prediction of soil type maps with Neural Networks including quantification of model uncertainty
Authors: Rau Kerstin , Gläßle Thomas , Hennig Philipp , Scholten Thomas
Published: March 2022

Artificial neural networks (ANN), which are mainly used in pattern and image recognition, have now found a wide range of applications. In recent years, different variants of ANN have also been increasingly used in the geosciences. They have proven to be a useful tool for complex questions that also involve a large amount of data. In their basic form, however, deep-learning algorithms do not provide interpretable predictive uncertainty. In the geosciences in particular, they have been used more as black-box models that require interpretation by an expert or do not allow for specific interpretation. Therefore, we implement in our explorative study on soil classification a Bayesian deep learning approach (i.e. a method to add uncertainty to deep networks) known as last layer Laplace approximation. This is a technique that can be applied as a post-hoc "add-on" without destroying the otherwise good performance of deep classifiers.
Our target soil type variable provides us with a large amount of information about soil processes and properties, which is a great advantage since it would take a lot of time and money to collect all this information individually. At the same time, soil maps are in high demand by authorities, construction companies or farmers. In our study area around Tübingen in southern Germany, there are 39 different soil types, determined according to the German soil systematics, which we consider individually for the prediction, but also combine into superordinate categories with similar properties, which is possible at low computational cost under the Laplace approximation. In addition to the underlying soil map, remotely sensed variables such as satellite imagery, a digital elevation model and its derivatives, and climate data are used as input to the model, which is designed to learn the relationship between these and the soil type.  As a test case, we then explicitly include the Swabian Jura as a prediction region for the environment. This region is characterised by very different soil types due to its extremely different development and the resulting geology, climate and terrain.
Our goal is then to enrich soil type maps with a structured uncertainty, which is estimated to be high in the area of the Swabian Jura. This will help to better understand the causality of machine learning models in soil science and their transferability to regions other than the training and validation area.
The role of salt in mountain building, from minibasin formation to orogen dynamic
Authors: Callot Jean-Paul , Célini Naim , Jourdon Anthony , Legeay Etienne , Mouthereau Frederic , Le Pourhiet Laetitia , Ringenbach Jean-Claude
Published: March 2022

Evaporites levels have long been considered to have a major impact on the evolution of tectonically-driven as well as gravity-driven fold-and-thrust belts. If initially thin and planar, the role of pre-tectonic salt can be limited to an efficient décollement level during the convergence. Nevertheless, as a décollement level, pre-kinematic salt rock already deeply modifies the shape of the orogenic wedge, favouring large and low taper prisms. In addition, a thick pre-kinematic evaporite level, triggering salt tectonics from the time of the deposition on, modifies the architecture of the sedimentary packages and subordinate basins later incorporated within the orogenic wedge, creating structurally deceiving inherited geometries. Syn-orogenic salt levels also controls the fold-and-thrust belt development, favouring large scale decoupling and strain partitioning. At a much larger scale, it appears that salt levels influences also the development of the orogenic prism itself, modifying the topographical evolution of the taper. Examples from the Western Alps, the Pyrenees and the Sivas basin illustrate the various roles of salt, generating strong inheritance at almost all scales of observation. In addition, two dimensional numerical experiments of collision built by the inversion of rifted margins reveal that mechanically, a weak décollement layer formed by salt rocks delays the formation of the collisional orogen. The thicker the salt layer, the wider is the orogen and the lower the altitude of the mountain belt, leading to a quasi-absence of topography and widespread salt tectonics, which obliterates classical thrusts propagation.
Assessing basal melt parameterisations for Antarctic ice shelves using a cavity-resolving ocean model
Authors: Burgard Clara , Jourdain Nicolas C. , Reese Ronja , Jenkins Adrian , Mathiot Pierre
Published: March 2022

Ice shelves at the outskirts of the Antarctic ice sheet are thinning due to warm ocean water intruding into their cavities. Thinning reduces the ice shelves' buttressing potential, which means that the restraining force that they exert on the ice flowing across the grounding line is lower and more ice is discharged into the ocean. Taking into account ocean-induced melt, or basal melt, is therefore crucial for accurate sea-level projections. Still, its current representation in ice-sheet models is the main source of uncertainty associated with the Antarctic contribution to global sea-level rise in climate projections.

An increasing amount of high-resolution ocean models are now able to resolve the circulation in the cavities below the ice shelves. However, running such models on multi-centennial scales or in a large ensemble is computationally expensive, especially when coupled with ice-sheet models. Instead, several parameterisations of varying complexity have been developed in past decades to describe the link between hydrographic properties in front of the ice shelf and basal melt rates. Previous studies have shown that the performance of these parameterisations depends on the ice shelf and that individual adjustments and corrections are needed for each ice shelf when applying them on the circum-Antarctic scale.

In this study, we assess the potential of a range of existing basal melt parameterisations to emulate basal melt rates simulated by a cavity-resolving ocean model on the circum-Antarctic scale, without regional adjustments. To do so, we re-tune the parameters of the different parameterisations using an ensemble of simulations from the ocean model NEMO as our reference. We find that the quadratic dependence of melt to thermal forcing and the plume parameterisation yield the best compromise, in terms of integrated shelf melt rates and spatial melt rate patterns. Parameterisations based on the box model, however, yield basal melt rates further from the reference. Additionally to the newly tuned parameters, we also provide uncertainty estimates for the tuned parameters, for applications in large ensembles.
AMOC thresholds in CMIP6 models: NAHosMIP
Authors: Jackson Laura , Alastrue-De-Asenjo Eduardo , Bellomo Katinka , Danabasoglu Gokhan , Hu Aixue , Jungclaus Johann , Meccia Virna , Saenko Oleg , Shao Andrew , Swingedouw Didier
Published: March 2022

The Atlantic meridional overturning circulation (AMOC) is an important part of our climate system, which keeps the North Atlantic relatively warm. It is predicted to weaken under climate change. The AMOC may have a tipping point beyond which recovery is difficult, hence showing quasi-irreversibility (hysteresis). Although hysteresis has been seen in simple models, it has been difficult to demonstrate in comprehensive global climate models.

We present initial results from the North Atlantic hosing model intercomparison project, where we applied an idealised forcing of a freshwater flux over the North Atlantic in 9 CMIP6 models. The AMOC weakens in all models from the freshening, but once the freshening ceases, the AMOC recovers in some models, and in others it stays in a weakened state. We discuss how differences in feedbacks affect the AMOC response.  
The impacts of near-bed flow characteristics on sediment transport under varying ice-cover conditions of a seasonally frozen river
Authors: Lotsari Eliisa , Lintunen Karoliina , Kasvi Elina , Alho Petteri , Blåfield Linnea
Published: March 2022

The global climatic change has been projected to affect hydrology, ice-covered flow period and river morphology, including changed sediment transport conditions, in northern high-latitude regions. For understanding the impacts of expected shortening of frozen period on sediment transport, it is needed to understand the present sediment transport conditions in high-latitude northern rivers with annually occurring ice cover. Thus, the aims of this paper are 1) to define the impacts of ice-cover on near-bed flow characteristics during hydrologically varying years, and 2) to analyze the impacts of these mid-winter flow-characteristics on sediment transport potential. The analyzes are based on Acoustic Doppler Current Profiler (ADCP: 2016–21) and Acoustic Doppler Velocimeter (ADV: 2020-21) measurements performed in mid-winter ice-covered conditions of sandy and small (circa 20 m wide) Pulmanki River, Northern Finnish Lapland.

 

Despite the ice-covered river conditions, there is sediment transport throughout the year. The critical shear velocities of mid-winter conditions were exceeded each winter (2016-21), bedload transport occurred according to bedload measurements, and calculated bed capture rates (Gaeuman and Jacobson [2006] method) indicate transport. Three different situations occurred regarding the sediment transport and near-bed velocity conditions: 1) high measured mid-winter discharges indicate high velocities throughout the meander bend; 2) low measured mid-winter discharges inidate low near-bed velocities throughout the meander bend; 3) winters having intermediate discharges indicate near-bed velocities and sediment transport potential being higher at the upstream inlet and apex sections of the meander bend, but clearly lower downstream of the apex. The confinement by the river ice cover, i.e. bottom-fast ice, explains the velocity variation. The near-bed velocities were the highest at the upstream inlet section of a symmetrical meander bend, where the measurement cross-sections were narrower and shallower. The velocities were the lowest downstream of the apex, where the channel changed from relatively narrow to wider and deeper.
Conjugate no more: redefining the pre-rift relationship between the Flemish Cap and the Goban Spur prior to the North Atlantic opening
Authors: Yang Pei , Welford J. Kim
Published: March 2022

With increased geophysical scrutiny of the NE Newfoundland-Irish margin pair (North Atlantic), the previously assumed conjugate relationship and rift-perpendicular extension between the Flemish Cap and Goban Spur are increasingly questioned. We present multichannel reflection profiles along the Flemish Cap, the Porcupine Bank, and the Goban Spur, along which structural domains (proximal, necking, hyperextended, and/or exhumed mantle domains included) are defined. Features of each structural domain along these profiles on the Flemish Cap and the Goban Spur are strikingly different, whereas similar structural features are observed in the necking domains along seismic profiles on the Porcupine Bank and the Flemish Cap. The variability in basement features suggests oblique rifting between the Flemish Cap and the Goban Spur-Porcupine Bank region, as well as a connection between the Porcupine Bank and the Flemish Cap during Early Jurassic rifting. This understanding is consistent with crustal thickness evolution calculated from a deformable plate reconstruction model that is locally updated based on seismic interpretation constraints and previously published plate reconstructions. The updated deformable plate model shows varying extension obliquity between the Porcupine Bank, Goban Spur, and Flemish Cap, which are strongly influenced by inherited Caledonian and Variscan structures, resulting in the conclusion that the Flemish Cap and the Goban Spur were not conjugate margins prior to the opening of the modern North Atlantic Ocean.
Relationship between the hydrodynamic response and the geometrical and topological properties of the karst conduit network
Authors: Aliouache Mohammed , Jiang Chuanyin , Jourde Hervé
Published: March 2022

In karst catchments, groundwater is generally drained from recharge zones towards main outlets (springs). Karst systems develop mainly in limestone and have three different porosities which are the result of sedimentation, diagenesis, tectonics but also dissolution that generate the conduits.  Continuous monitoring at high temporal resolutions is largely used to characterize the hydrodynamic behavior and variability of karst systems hydrological functioning Hydrologic models are used in order to better asses the functioning of karst systems but can also help identifying the impact of global change on water resources. Though these models require an adequate representation of main heterogeneities and processes, the heterogeneity of karst systems is often poorly characterized by available data. For these reasons, most of hydrological models considered for the understanding of karst systems hydrodynamic are lumped parameters models. In this study, we simulate precipitation-discharge relationship as a function of different karst geometries and topologies using two dimensional distributed models. We then investigate the relationship between the hydrodynamic response (e.g. flow rate at discharge point) and topology of the karst conduit network. Lumped approaches are later on compared to distributed models in term of predicting hydrodynamic response to precipitation.
Representing seasonal water in ECMWF ECLand system
Authors: Choulga Margarita , Boussetta Souhail , Balsamo Gianpaolo , McNorton Joe
Published: March 2022

In 2015 lake parametrization was introduced at European Centre for Medium-Range Weather Forecasts (ECMWF) to take into account the impact of lake on the boundary layer and near surface atmosphere. All inland water bodies (lakes, reservoirs, rivers, coastal waters) have constant size distribution and are simulated by the Fresh-water Lake model FLake.

To introduce water seasonality and reduce errors caused by the constant water distribution, time-varying water maps based on Global Surface Water Explorer (GSWE) data are being introduced in the ECMWF ECLand system. Techniques used to adapt GSWE to create monthly water fraction maps for the use of global NWP modelling and first evaluation results will be presented.
Postglacial fire regime changes and vegetation dynamics at Lake Victoria, Africa
Authors: Temoltzin-Loranca Yunuén , Gobet Erika , Vannière Boris , van Leeuwen Jacqueline F.N. , Courtney-Mustaphi Colin , Wienhues Giulia , Szidat Sönke , Grosjean Martin , Tinner Willy
Published: March 2022

Lake Victoria is the largest tropical lake on the planet. Located in East Africa at an altitude of 1135 m asl, it lies across the limits between two major climatic zones with a temperature and moisture gradient and associated tropical biomes, the rain forest, and the savanna. At higher altitudes > 1200–2500 m a.s.l. temperatures are significantly lower and vegetation forms an Afromontane belt. Primarily triggered by climate shifts, these three biomes and fire regimes have been dynamically interspersing over the last 17,000 years.

Here, we present a robust 14C chronology mainly based on macroscopic charcoal using the MICADAS system of LARA at the University of Bern, new palynological data used as biostratigraphic control, and the first continuous charcoal record in Lake Victoria to establish the fire history.

Our pollen and macro–charcoal records, support the assumption that throughout time regional fire dynamics are controlled by biome’s changes, and that climate was the main driver of these vegetation shifts at least until the Iron Age. Our results indicate that during the Last Glacial Maxima and Heinrich Stadial 1, under dry and colder climates the savanna was dominating, with low fire regimes before 15,000 cal yr BP and increased fire occurrence between 15,000 and 14,000 cal yr BP. After this period, the Afromontane forest started to expand, and warmer and humid climates promoted the growth of rain forests and reduced fire events, which is particularly observed in the African Humid Period (between ca. 11,500 and 5000 cal yr BP). Subsequently, our records indicate a global maximum of fire occurrence at 5000 cal yr BP, followed by unexpectedly low fire regimes during the Iron Age and the subsequent periods.

This work is part of a SINERGIA project funded by the Swiss National Foundation which seeks to unravel the long-term causes and consequences of Lake Victoria’s ecosystem dynamics with a special focus on the evolution of fish species and other biotas from the late Pleistocene to the present.
Quantifying and modeling methane from the North Sea region with ICON-ART
Authors: Scharun Christian , Ruhnke Roland , Braesicke Peter
Published: March 2022

The release of greenhouse gases (GHG) like CH4 into the atmosphere plays a key role in driving the climate change. With the optimization of atmospheric chemistry climate models, the accuracy in assessing future scenarios is improved, which is an important factor in our efforts to mitigate climate change.

Within this work we introduce the WALLACE workflow, a method for the quantification and adjustment of wrong or missing emissions in well-established GHG-inventories, which are used as input data in atmospheric chemistry transport or climate models. The overall goal of WALLACE is to highlight emission hotspots and it therefore includes spatiotemporal proxy data and a selection algorithm. For the North Sea as a show case region we apply WALLACE to quantify methane emission fluxes of oil and gas platforms. The adjusted emissions are implemented as pointsources into our model and idealized simulations are performed to derive their impact on the spatial distribution of methane and its global and regional budget. Additionally, we take a look at the anti-correlation between methane and its main sink in the atmosphere, the hydroxyl radical (OH), which is implemented as a simple OH-chemistry mechanism into the model. This work makes a new and innovative contribution to achieve an accurate quantification of environmentally harmful gases – in particular CH4 - that drive man-made climate change.

In conjunction with WALLACE we use the global model ICON-ART (ICOsahedral Nonhydrostatic model - Aerosols and Reactive Trace gases). ART is an online-coupled model extension for ICON that includes chemical gases and aerosols. One aim of the model is the simulation of interactions between the trace substances and the state of the atmosphere by coupling the spatiotemporal evolution of tracers with atmospheric processes, thus testing the impact of WALLACE-adjusted emissions on the CH4 distribution in the atmosphere.
The Holocene climate changes, fire history and palsa peatland dynamics: case study from Yenisei Siberia
Authors: Novenko Elena , Mazei Natalia , Kupryanov Dmitry , Prokushkin Anatoly , Shatunov Anton , Andreev Rodion , Makarova Ekaterina , Serikov Sergey
Published: March 2022

Recent climate change in Siberia is increasing the probability of dangerous forest fires. Our paleoecological study is focused on one of the palsa mires located at the eastern edge of the West Siberian Lowlands (Yenisei Siberia) in the forest-tundra ecotone. Perennial frost mounds, often called as palsas and peat plateaus, are the dominant landscape type in this region. The reconstruction of the Holocene fire history is based on high resolution macroscopic charcoal records and detailed AMS radiocarbon dating from a 8 m long peat sequence, obtained from the palsa mire situated near the town of Igarka (N 67°31’53.77’ E 86°38’05.65’). The comparison of the obtained results with multy-proxy paleoecological evidence included pollen, plant macrofossils, stable isotope and loss on ignition data from this peatland provides important new data on fire, climate and peatland interrelations during the last 6500 cal yr BP.

The obtained data show that peat inception in the studied mire occurred at about 6200 cal yr BP during the Holocene Thermal Maximum. The time interval between 6500 and 5360 cal yr BP was characterized by warm and dry climate conditions and the highest charcoal accumulation rate throughout the Mid and Late Holocene. The fire return period was 70-120 years that is shorter then at present. The main stages of palsa uplift occurred at about 5360 cal yr BP and 2250 cal yr BP and coincided with the periods of climatic cooling and moistening and permafrost aggradation in the Russian Arctic region. Since 5360 cal yr BP charcoal accumulation in the palsa decreased significantly and in some time intervals ceased. The fire return period extended to 1500-1800 years. The increase of the charcoal accumulation rate in the peatland under study occurred at the end of 14th – beginning 15th centuries and during the 20th century charcoal input declined. We supposed that human induced fires led to the biomass burning. According to historical data the Russian colonization of this part of Siberia began in the 17th century, but the first Russian settlers already found a local hunter population in the area of Igarka. The settlement lies on the banks of the Yenisei River, historically one of the main trading routes in Siberia. During the 20th century wood-using industry and a river harbor were developed in Igarka, was obviously accompanied by active deforestation that led to some reducing the forest fire occurrence.

The studies were supported by the Russian Science Foundation (grant 20-17-00043).
The role of poroelasticity and dilatancy in governing the transition from aseismic to seismic slip during fluid injection
Authors: Heimisson Elías Rafn , Liu Shengduo , Lapusta Nadia , Rudnicki John
Published: March 2022

Most faults at seismogenic depths can be described as fractures or discontinuities in a fluid-saturated porous medium and thus, the theory of poroelasticity offers a practical mechanical description of the natural fault environment. However, poroelasticity is rarely considered in simulations of fault slip. Poroelasticity incorporates the two-way coupling of solid and fluid phases where pore-pressure change,  e.g., due to slip, strains the rock matrix and volumetric strain causes changes in pore pressure. During earthquake nucleation, inelastic dilatancy may also induce pore pressure changes. A complex interplay of pore pressure in the bulk and shear zone emerges when we consider the multiple processes coupled to slip on a fault governed by rate-and-state friction. Here, we present an efficient spectral boundary integral code that allows for 2D quasi-dynamic rate-and-state simulations of slow and fast slip with fully coupled and simultaneous state-dependent dilatancy, fluid injection, and two-way coupled diffusive poroelastic bulk response. The method allows for anisotropic shear-zone permeability, while the bulk is considered to be isotropic and homogenous. We can thus simulate three diffusion time scales at once: along the shear zone, across the shear zone, and due to wavelength-dependent bulk diffusion. We apply the code to understand nucleation and repeated fault ruptures with a realistic pore-pressure injection history from a field experiment. We compare different cases with and without dilatancy, larger or smaller differences in drained and undrained poroelastic properties, and varying bulk diffusivity. By systematically increasing the dilatancy coefficient, we observe a transition from highly unstable seismic slip to a migrating slow slip front to quasi-static slip localized to highly pressurized areas. More surprisingly, we find that differences in drained and undrained poroelastic properties and bulk diffusivity strongly influence fault slip stability. A larger difference between drained and undrained Poisson’s ratio or higher bulk diffusivity results in more stable slip during injection, fewer ruptures, and delayed nucleation. These effects appear to be of comparable importance to dilatancy. We conclude that the poroelastic properties of the bulk, which are typically ignored, play a critical role in the stability and determining if slip is seismic or aseismic.
Coastal wetlands and seagrass dynamics with environmental change
Authors: Leonardi Nicoletta
Published: March 2022

Hard engineering solutions are becoming economically unviable due to the high costs of construction, maintenance and adaptation to changes in sea level and storms. ‘Engineering with Nature’ (including the creation of salt marshes, seagrass beds) offers a more economically viable alternative for coastal protection.

However, despite the growing recognition of the necessity to move towards this greener alternative for coastal protection, there are still large uncertainties about factors determining the resilience of these systems to environmental change. As a consequence of sea-level rise, and of the increased occurrence of extreme weather conditions, coastal habitats are at risk of degradation and possible recession.  Human interactions add a layer of complexity to natural processes. Among the others, the sediment delivery to coastal areas has significantly changed over the years, for instance due to changes in catchment management, with consequences for the resilience of coastal systems.

This work uses numerical models to investigate the morphological and hydrodynamic features of coastal systems with environmental change. These numerical tools consist of hydrodynamic models coupled with morphological and sediment transport modules. Results investigate feedbacks between the shape of existing shorelines, wetlands resilience and external forcing such as tidal currents and wind waves. Results provide information useful for the study and management of ‘Engineering with Nature’ interventions and highlights the importance of a whole-system approach for the correct management of coastal areas.
Aggregate stability and potential erodibility of dry steppe soils
Authors: Koza Moritz , Pöhlitz Julia , Prays Aleksey , Mikutta Robert , Kaiser Klaus , Conrad Christopher , Vogel Cordula , Akshalov Kanat , Bondarovich Andrey , Schmidt Gerd
Published: March 2022

Erosion caused by extreme climate conditions and intense agricultural use is a severe threat to the soil quality of dry steppe ecosystems. The susceptibility of soil to erosion depends mainly on the stability of its structure against mechanical stress, which is directly related to the stability of aggregates. However, there is no generally accepted method to determine soil aggregate stability and most tests cannot be adequately linked to disruptive forces soils experience under field conditions. Thus, our main objective was to explore the aggregate stability of steppe soils against disruptive stresses by wind and water to assess their potential erodibility. We examined 132 topsoil samples from northern Kazakhstan under two land-use types (grassland and cropland), covering a large range of physico-chemical soil properties (texture, organic carbon, inorganic carbon, pH, and electrical conductivity). We combined several methods that capture the soil`s susceptibility against mechanical stresses common in the dry continental climate: An adjusted drop-shatter technique (energy input of 60 Joule) was used to estimate the stability of dry soil against weak mechanical forces, such as wind stroking over bare soil after tillage and before crop emergence. In addition, three wet-aggregate stability tests (fast wetting, slow wetting, and wet mechanical breakdown) were used to estimate the stability of soil aggregates under various stresses caused by precipitation. Results indicate that aggregate stability was generally higher for grassland than cropland soils. Aggregate stability under both land-use types decreased along with increasing sand and decreasing organic carbon contents. The drop-shatter method suggested that only 5% of cropland soils were at high risk of wind erosion (i.e., erodible fraction <60%). In contrast, the fast wetting test revealed that  98% of the samples are unstable after a heavy rain event or snowmelt. Even after a light rain event or the raindrop impact, 54-58% of the samples were unstable and prone to erosion.

We conclude that cropland in the dry steppe of Kazakhstan is much more vulnerable to the disruptive forces caused by water than by wind. Especially the severe breakdown of aggregates during heavy rain events or snowmelts goes well in line with the increasing erosion risk under current and future climate scenarios.
Assessment of streamflow trends in snow and glacier melt dominated catchments of SW Spitsbergen
Authors: Osuch Marzena , Wawrzyniak Tomasz , Łepkowska Elżbieta
Published: March 2022

The study focuses on the changes in the regime of the four High Arctic catchments in the last 40 years taking into account different percentages of glacial coverage. The selected catchments include Breelva, Ariebekken, Bratteggbekken and Fuglebekken with glacial coverage of 61%, 11.8%, 5.9% and 0% respectively.

The flow time series in the selected catchments were simulated using a glacio-hydrological model calibrated and validated based on the available archival hydro-meteorological data.

In the second step, the reconstructed flows from the period 1979-2020 were filtered and smoothed. This allowed for delineation of the seasonal pattern by filtering out small scale variability. The changes in flow regime were assessed with trend analysis for each calendar day.

Similar trends of change were detected in all studied catchments due to similar locations in the SW Spitsbergen and climatic conditions. These changes include the earlier onset of snowmelt driven floods, large increases in autumn flows, prolongation of the hydrologically active season (starts earlier and lasts longer), decrease in flows in the latter half of June and the early part of August (except for the Breelva catchment). These changes resulted in the changes of flood regime from snowmelt-dominated to the bi-modal with peaks in both July/August and September.

A comparison of the changes between the four catchments indicated differences in the magnitude of hydrological response depending on the percentage of glacial coverage in the catchments. The larger the glacierized area is, the larger the changes in the flow regime. The estimated changes are larger than observed in lower latitudes due to larger changes in climatic conditions.
Aeolian fluxes from arid landscape dynamics in the Lut Desert (Iran)
Authors: Barrier Laurie , Chanteloube Colin , Derakhshani Reza , Gadal Cyril , Braucher Régis , Payet Vincent , Léanni Läetitia , Narteau Clément
Published: March 2022

Wind-blown sand and dust emissions shape singular landscapes in arid environments and globally impact climate, life and human activities. However, the accurate quantification of aeolian sediment fluxes are still subject to considerable uncertainties. Since extensive measurements are difficult to implement in the field, this quantification rely essentially on remote sensing data and transport laws that integrate a large number of parameters for the airflow and granular bed. However, confronted with all the sources of natural variability (wind regime, air recirculation, grain-size distribution, soil composition, etc.), a complete mass balance of aeolian transport remains challenging. Here we consider long time scales to smooth out such variability and integrate arid landscape dynamics into the source-to-sink assessment of aeolian mass transfers in the Lut Desert (Iran). Taking advantage of new remote sensing imagery and dating techniques, together with more accurate wind data and a deeper understanding of dune dynamics, we analyze major landforms of this desert to provide a comprehensive picture of aeolian transport on time scales from decades to millions of years. We map the modern sandflows, along which we evaluate the volume and chronology associated with the excavation of mega-yardangs upwind and the formation of giant dunes downwind. Sediment discharges deduced from long-term erosion and deposition are of the same order of magnitude (105 to 106 m3yr-1)  as short and medium-term sand discharges derived from wind data and dune morphodynamics. At the scale of the internal aeolian sediment-routing system of the Lut, we establish an overall sediment budget constrained by the joint development of the erosional and depositional landforms. Our findings thus quantify the geomorphic controls of aeolian processes on arid landscapes at multiple length and time scales, while providing information on mass exchanges between continents and atmosphere.