bluuebunny/crossref_metadata_2025 huggingface dataset:
How Continents Break-up and New Ocean Ridges are Established 
Authors: Pérez-Gussinyé Marta , García-Pintado Javier , Liu Zhonglan , Mezri Leila
Published: March 2022

The processes that lead to the transition from continental extension and break-up to steady-state mid-ocean ridge formation are not well understood. Particular unknowns are the paleo-water depths at which the continental lithosphere breaks up, the nature of the crust at the so-called continent-ocean transition and when and how a steady-state mid-ocean ridge is established. To understand these questions we use numerical models that couple tectonic deformation, sedimentation, hydrothermal cooling, serpentinisation and melting, as a virtual laboratory. We present results of models run with different velocities that simulate natural examples observed in nature such as the South China sea and the West Iberia-Newfoundland margins. We focus on the evolution of subsidence, heat-flow and nature of the basement as the rift transforms into a steady-state mid-ocean ridge and show how the interplay between tectonics and hydrothermal cooling lead to the different configurations observed in nature.

 
Modeling the kinetics of cell enlargement of Larix gmelinii Rupr (Rupr) in Central Siberia
Authors: Popkova Margarita , Shishov Vladimir , Fonti Marina , Kirdyanov Alexander
Published: March 2022

Trees are a kind of natural archives of information about the environment. The internal factors of cell growth and maturation in combination with external conditions code the tree-ring structure of conifers. The process-based models of tree-ring growth contribute to better understanding of the link between environment, wood formation and structure and allow projecting further growth. In this study we apply the VS-model to model and analyse the intra-annual cell anatomy of Larix gmelinii Rupr (Rupr) growing in continuous permafrost zone of Central Siberia. Anatomical measurements obtained between 1950 and 2011 have demonstrated the low number of cells determining low tree-ring growth is due to the challenging climatic conditions of the permafrost zone. The parameterization of the VS-model provided highly significant positive correlations between simulated growth curves and initial tree-ring chronology (R = 0.65). The results of timing procedure show that VS-model makes it possible to link climate and the tree-ring structure. The procedure revealed strong relationships between modelled growth rates and measured tracheid radial sizes for the full period 1950 - 2011. Seasonal observations of the number of cells during the season allow some important comparisons to be made. The results of timing procedure the growth rates modeled for the 2011 growing season fit well the timing (R = 0.91) and the observed number of cambial and enlarging cells (R = 0.78 and 0.87, respectively). Moreover the comparision the number of days from the start of the growth season to when the first cell moved into the enlargement zone with the average growth rates during this period showed that years with low growth rates at the beginning of the growing season correspond to continuous lags in the cells escape from the cambial zone. Using a novel approach of timing of cell enlargement the number of enlarging cells modeled for the 2011 growing season was well matched with the number of enlarging cells observed on micro-cores collected in the field. However, the model was unsuccessful in accurately determining the end of the growing season, overestimating the season by a several weeks. This study has shown that the VS model successfully simulates xylogenesis for larch growing in the permafrost zone both in case of “average tree” and for individual plants. Even at the individual tree level, this approach to modelling intra-annual dynamics has great potential for studying how climate affects tree-ring growth and formation.

This work was supported by the Russian Ministry of Science and Higher Education (project  #FSRZ-2020-0010) and the Russian Science Foundation (Grant 18-14-00072 P).
Combining low-N2 background and 15N soil gas flux - lessons from the field
Authors: Matson Amanda , Lempio Dirk , Höppner Frank , Well Reinhard
Published: March 2022

Accurate models of soil N cycling are an important tool for optimizing N use efficiency within agricultural systems and predicting N emissions to the environment. However, due to the methodological limitations for the measurement of N2 emissions, in particular high atmospheric N2, only a very limited number of soil N2 flux datasets are available to validate model estimates of denitrification. As part of the DFG-research unit “Denitrification in Agricultural Soils: Integrated Control and Modelling at Various Scales (DASIM)”, we are building on existing methods to take in situ measurements of denitrification under a variety of field conditions, with an emphasis on the detection of non-peak events. Using static chambers, we establish a low-N2 background through headspace and soil flushing, and then use stable isotope techniques (natural abundance and 15N labeling of the soil mineral N pool) to assess the response of soil denitrification to combinations of climate, soil and plant factors found in the field. Here we present results of N2 and N2O fluxes from the field, which highlight both the potential and the challenges of using this combined method.  
Evaluating flood sensitivity to changes in high and low frequency precipitation using a discrete wavelet transform 
Authors: Meresa Hadush , Murphy Conor
Published: March 2022

Climate change has a significant role in increasing extreme precipitation, including the intensity, frequency, and magnitude of events due to increases in atmospheric moisture and climate variability. This means that future increases in floods due to climate change must be considered in the construction of flood defenses, as well as the planning of new infrastructure and hydraulic structures. Previous approaches for stress testing the design of flood defenses have relied on the scenario neutral approach and the use of harmonic functions to represent changes in the seasonality and mean of precipitation. Such approaches may inadequately account for changes in extreme precipitation, especially in runoff dominated catchments. Here, we adapt the scenario neutral approach by integrating a discrete wavelet transform (DWT) to develop the flood response surface. Such an approach allows evaluation of flood sensitivity to high and low frequency components of precipitation. Using 39 catchments in Ireland, we examine the sensitivity of flooding (QT20) to changes in low and high frequency precipitation and air temperature. A sensitivity domain of 525 extreme precipitation scenarios is applied by combining 21 low frequency and 25 high frequency sets of precipitation and air temperature changes, with short duration frequency incorporated in each harmonic wavelet function. Clustering and discriminant analysis are used to create a typology of catchment sensitivity based on generated response surfaces, the mean of annual maximum precipitation, and the mean of annual maximum flows. Results allow characterization of catchment sensitivity in gauged and ungauged locations and the integration of a wider spectrum of precipitation changes when assessing sensitivity allowances for climate change.  

 
Infrasound Propagation with Realistic Terrain and Atmospheres Using a Three-Dimensional Finite-Difference Time-Domain Method
Authors: Bishop Jordan W. , Blom Philip S. , Fee David
Published: March 2022

Infrasound observations and complimentary numerical simulations have shown that infrasound propagation is strongly influenced by topography within approximately 10 km from the source. Recent computational efforts using ray theory have shown that topographic influence extends over hundreds of km and is especially strong when considering propagation through the troposphere. Wind and temperature gradients also have a strong influence on propagation at these distances, which suggests that both topography and 3-D atmospheric structure need to be accounted for in long range waveform modeling. Here we show preliminary results from numerical simulations of linear acoustic propagation through a moving, inhomogeneous atmosphere using an in-development 3-D finite difference time-domain (FDTD) propagation code. We compare our synthetic waveforms in two and three dimensions with existing community infrasound propagation codes and discuss future developments, including open source licensing. Lastly, we present preliminary results from applying this code to the Humming Roadrunner experiments and similar data sets.
The long-term floodplain forest modifications of a regulated tropical river
Authors: Salerno Luca , Moreno-Martínez Alvaro , Izquierdo-Verdiguier Emma , Clinton Nicholas , Siviglia Annunziato , Camporeale Carlo
Published: March 2022

The regular flood pulse of large tropical rivers is the main driver of ecological and biogeochemical process in large Amazonian floodplains. Endemic vegetation species developed adaptation to survive in seasonal flood environments and tune their vital process with periodic flood events, water levels, and sedimentary processes. The construction of hydroelectric dam causes alterations of natural hydrological regime and sediment supply, threatening downstream floodplain forest.

An assessment of impact of river regulation on floodplain vegetation is crucial to develop a modern approach to the regulated rivers management in the Neotropics and to mitigate the impact of damming on floodplain environment. Nevertheless, floodplain forest monitoring requires high resolution mapping as vegetation dynamics are in the narrow area at the interface terrestrial and aquatic systems. Most of the existing satellite images that afford land observations have severe limitations due to their coarse resolution or missing  data caused by the extreme cloudiness conditions in of tropical regions.

In the present work, we propose an innovative approach based on high-resolution mapping for the monitoring long-term evolution of vegetation in a highly impacted environment (Uatama river) due to Balbina dam regulation.  We combine Landsat (30m spatial resolution and 16 days revisit cycle) and the MODIS missions (500m spatial resolution and daily revisit cycle), using HISTARFM algorithm, to reduce noise and produce monthly gap-free high-resolution (30 m) observations over land. Areas characterized by vegetation changes are identified through the analysis of of vegetation index products derived from the high-resolution reflectance data.  Furthermore, hydrological modification within these areas are assessed by using a global water surface dataset.

We found a deep redistribution of floodplain forest concentrated in areas that experienced a hydrologic regime transition after dam construction. The vegetation changes comprise not only vegetation degradation of areas with greater hydrological stress but also with large floodplain areas not flooded afterwards, which were invaded by upland forest. Although the dam was built more than 30 years ago, its effects on the vegetation continue and the situation seems far from reaching a new environmental equilibrium.

The framework proposed offers a practical and novel tool to accurately monitor riparian vegetation dynamics over time even for very remote and poorly accessible areas such as tropical floodplains. Furthermore, the assessment of the impact that the human footprint has on tropical floodplain allows a more careful management of the watersheds.
Dynamics of freezing and thawing of water in saturated sand and soil: Magnetic resonance imaging study
Authors: Snehota Michal , Koestel John , Pohlmeier Andreas , Princ Tomas , Sobotkova Martina , Cislerova Milena , Sklenar Jan
Published: March 2022

Magnetic resonance imaging (MRI) of the freezing and thawing process was performed on a series of repacked samples of sand, soil, and sand-soil mixture. The freezing/thawing is performed in the sample container placed inside the vertical bore MRI scanner within the 66 mm inner diameter of the radiofrequency coil. The sample container was vacuum insulated from the sides and bottom to allow for the minimum thickness of the insulation layer. The vacuum was constantly maintained by a vacuum pump. The sample assembly was built from PMMA and other nonmetallic - MRI compatible materials. A porous material in the sample container was cooled at the top by the flow of cold gaseous nitrogen released from the liquid nitrogen stored in the Dewar flask. The cooling took place across the glass plate positioned at the top of the sample in the headspace above the sample. The temperature of the gas that was delivered to the headspace and leaving the headspace was monitored. Additionally, the temperature was monitored in the headspace above the glass disk and directly in the glass disk by fiber optics temperature probes. A 4.7 T magnet at the FZJ was used for MRI. Multiple-Slice Spin-Echo and Zero Echo Time pulse sequences were utilized. The contrast between the frozen and unfrozen water is given by the difference in T1 and T2 relaxation times. The time-lapse 3D imaging was done during the entire course of the experiment. Once the freezing front reached the bottom of the sample, the thawing process was induced. The small changes in sand structure as a consequence of volumetric ice-water changes were studied. The spatiotemporal analysis of the freezing front advancement and frozen water volume has been performed. The data are available for the development of two-phase ice-water simulation models.
VS-Cambium-Developer (VS-CD) model within the scope of new opportunities to evaluate a cambium activity of conifer species 
Authors: Belousova Daria , Shishov Vladimir
Published: March 2022

One of the fundamental problems of modern ecology is assessment of the response of woody plants to environmental effects under changing climate. Various simulation models of tree ring growth can serve as an effective tool for solving this problem.

We developed a new cambium model which reproduces a seasonal cambial activity of conifer species and can be applied to different habitats, depending on the action of the principal climatic factors. It is based on the hypothesis of the presence of a cytoplasmic inhibitor of cell differentiation. The inhibitor functioning is connected with temperature, soil moisture, and light. The new algorithm was developed based on the existing cambial block of the Vaganov–Shashkin simulation model of tree ring growth (VS-model).

The model is calibrated and verified by the direct and proxy observations of xylogenesis for conifer trees in cold semi-arid environment of Southern Siberia (the Republic of Khakassia) over 1964-2012. Accuracy of seasonal cell production simulation for the average tree of studied site was ± 1 cell .

A software implementation of the new cambial model based on the R Shiny technology can be easily adapted to the on-line platform of the VS-model (VS-GENN http://www.vs-genn.ru/). The developed widgets (process visualization tools) make it possible to track the growth dynamics of the cambial zone in high resolution time scale (up to one hour).

The work was supported by the Russian Ministry of Science and Higher Education (# FSRZ 2020-0010) and Russian Science Foundation (RSF#18-14-00072)
Climate and sediment mobility modulate topography-tectonic link in the Andes
Authors: Harries Rebekah , Aron Felipe
Published: March 2022

The strong gradients in climate and tectonics along the Chilean-Argentine Andes offer the perfect opportunity to study wider landscape controls on mountain topography.

Between 33 and 37oS we observe the largest variability in mountain elevation and erosion rates. For this region, we isolate the tectonic contribution to topography by modelling the mechanical dislocation of the crustal scale faults in response to plate convergence. We then use this spatially variable uplift field to determine to what extent the existing topography records this tectonic signal. While local relief and channel steepness do record responses to faulting on the Chilean side of the cordillera, the broader areas of highest uplift in Argentina have the lowest local relief and channel steepness. We therefore explore how this relationship between tectonics and topography may have been modified by the spatial variability in bedrock lithology, sediment cover and mean annual precipitation. We find that channel steepness does not vary significantly with bedrock lithology but does map onto trends in precipitation and sediment cover. The lowest local relief and channel steepness regions have low precipitation rates and widespread sediment cover, suggesting sediment mobility, modulated by climate, maybe an important control on bedrock incision rates in this high uplift zone. We therefore highlight the importance of climate in the recovery of post-glacial landscapes and the modulatory effect sediment cover can have in the evolution of large scale topography.
Modelling the thermal and mechanical interaction of an ice-sheet with a partly frozen bedrock
Authors: Zwinger Thomas , Cohen Denis , Gladstone Rupert , Råback Peter
Published: March 2022

In recent years, subglacial hydrological models as well as till deformation models have been coupled to ice-flow models in order to determine mechanical basal conditions underneath ice sheets and glaciers. These models, nevertheless, often ignore the thermo-dynamical aspects, in particular, not including the influence of permafrost in proximity to or underneath glaciers. Here we present a thermo-mechanically coupled ice-sheet bedrock model. The latter includes components of saturated aquifer water transport, soil deformation, salinity transport and – most important – energy balance including phase change of the solvent. Using synthetic flow-line setups we present studies of ice-sheet fronts, advancing either over existing permafrost or largely unfrozen soils. We investigate the heat- and meltwater-transfer between the ice-body and its substrate and discuss their impact on ice-dynamics. As the results suggest that in certain situations the water balance further demands the existence of a hydrological system between ice and bedrock, we currently work to include this third model component in form of a subglacial hydrological model. All model components are implemented in the Finite Element software Elmer, which renders their mutual coupling relatively easy, yet, numerically demanding.
Regional differences in gully network connectivity based on graph theory: a case study on the Loess Plateau, China
Authors: Cheng Jianhua , Luo Lanhua , Li Fayuan , Liu Lulu
Published: March 2022

Gullies are some of the areas with the most frequent material exchanges in loess landforms. By studying the influence of the spatial structure of gully networks on material transport and describing the difficulty of material transport from sources to sinks, it is of great significance to understand the development and evolution of loess landforms. This study is based on graph theory and digital terrain analysis and describes the relationship between gully networks and terrain feature elements via a gully network graph model. The adjacency matrix of the gully network graph model is constructed to quantify the connectivity. Taking six typical small watershed sample areas of the Loess Plateau as the research objects, the changes in the gully network connectivity characteristics in different loess geomorphic areas are analyzed from the aspects of overall network connectivity and node connectivity. The results show that (1) From Shenmu to Chunhua (the sample areas from north to south), the average values of the gully network edge weights first decrease and then increase. The maximum value is 0.253 in the Shenmu sample area, and the minimum value is 0.093 in the Yanchuan sample area. These values show that as the gully development increases, the greater the capacity of the gully network to transport materials is, and the less resistance the material receives during the transfer process. (2) The average node strength reaches the minimum in the Yanchuan sample area, and from Yanchuan to the north and south sides, it gradually increases. It can be concluded that the overall connectivity of the gully network shows a gradually weakening trend from the Yanchuan sample area to the north and south sides. (3) The potential flow (Fi) and network structural connectivity index (NSC) show similar characteristic changes; from north to south, the connectivity of nodes from the Shenmu to Yanchuan sample areas gradually increases, and from the Yanchuan to Chunhua sample areas, it gradually weakens. The accessibility from source to sink (Shi) shows the opposite trend. At the same time, the connectivity index values of the gully network nodes in the six typical areas all show clustered spatial distribution characteristics. (4) By comparing the results of the connectivity indicators calculated by the Euclidian distance used in the previous study and the sediment transport capacity index used in this study and by comparing the variation in the gully network quantitative indicators and the gully network connectivity indicators, this comparison result indicates the rationality of connectivity indicators in this paper. The connectivity of the gully network contains abundant and important information on the development and evolution of loess gullies. Research on the connectivity of the gully network will help deepen the understanding of the evolution process and mechanism of loess gullies.
MHD avalanches in truly curved coronal arcades: proliferation and heating
Authors: Reid Jack , Threlfall James , Hood Alan W.
Published: March 2022

MHD avalanches involve small, narrowly localized instabilities spreading across neighbouring areas in a magnetic field. Cumulatively, many small events release vast amounts of stored energy. Straight cylindrical flux tubes are easily modelled, between two parallel planes, and can support such an avalanche: one unstable flux tube causes instability to proliferate, via magnetic reconnection, and then an ongoing chain of like events. True coronal loops, however, are visibly curved, between footpoints on the same solar surface. With 3D MHD simulations, we verify the viability of MHD avalanches in a more physical, curved geometry, in a coronal arcade. MHD avalanches thus amplify instability across strong astrophysical magnetic fields and disturb wide regions of plasma. Contrasting with the behaviour of straight cylindrical models, a modified ideal MHD kink mode occurs, more readily and preferentially upwards. Instability spreads over a region far wider than the original flux tubes and their footpoints. Consequently, sustained heating is produced in a series of 'nanoflares', collectively contributing substantially to coronal heating. Overwhelmingly, viscous heating dominates, generated in shocks and jets produced by individual small events. Reconnection is not the greatest contributor to heating, but rather facilitates those processes that are. Localized and impulsive, heating shows no strong spatial preference, except a modest bias away from footpoints, towards the loop's apex.
Geophysical imaging for local landslide early warning systems
Authors: Whiteley Jim , Watlet Arnaud , Kendall John-Michael , Chambers Jonathan
Published: March 2022

A complete assessment of slope stability is achieved by identifying and monitoring the subsurface properties and processes leading to slope failure conditions. Monitoring technologies need to be applied at appropriate scales and resolution, and with sufficient coverage, to be able to assess these conditions in local landslide early warning systems. A holistic understanding of the subsurface at the slope-scale is not always captured by some landslide monitoring approaches, such as remote sensing observations with limited depth penetration or sparse resolution, or point sensor measurements with highly localised information. Geophysical techniques have demonstrable capacity to link between the different scales, resolutions and coverage of these established landslide monitoring techniques. Here, we present a novel framework identifying the benefits and limitations of including geophysical imaging and monitoring techniques at different stages of local landslide early warning system strategies. These include the use of geophysical inputs to aid the design of local landslide early warning systems, monitor slopes at risk of failure, inform forecasting, and support decision making for stakeholders.
Interactive analysis prospective on implementation of the NET-VISA in the IDC bulletin production
Authors: Qorbani Ehsan , Ali Sherif M. , Le Bras Ronan , Rambolamanana Gérard
Published: March 2022

Data from the stations of the International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) organization are being processed by automatic processing, Global Association (GA), and interactively analyzed and reviewed by analysts, resulting in the International Data Centre (IDC) bulletins. The Network Processing Vertically Integrated Seismic Analysis (NET-VISA) is a Bayesian seismic monitoring system designed to process data from the IMS to reduce the number of missed and false events in the automatic processing stage. NET-VISA has been implemented in the automatic process as an additional event scanner in operation at the IDC since January 15, 2018. In this study we assess the influence of NET-VISA automatic scanner on the number of events in the IDC bulletins, LEB (Late Event Bulletin) and REB (Reviewed Event Bulletin). In particular, the impact of NET-VISA scanner on the number of scanned events during the interactive analysis is assessed. We use three distinct time periods, each including 1200 days, two before and one after the NET-VISA implementation to evaluate the NET-VISA influence as well as the effect of the other possible factors such as global seismicity and network performance. The results show a 4.6% increase in the number of LEB events after including the NET-VISA scanner in operation, with an average of 7 events per day, and a notable increase of 17.90% in the number of scanned events. We also discuss the effect of other possible factors on such increase and conclude it can be attributed to the implementation of the NET-VISA scanner.
High resolution coupled climate-hydrology-dynamical Malaria transmission modeling for regional Malaria transmission in sub-Saharan Africa
Authors: Bousso Dieng Mame Diarra , Arnault Joël , Tompkins Adrian , Sié Alie , Munga Stephan , Franke Jonas , Kunstmann Harald
Published: March 2022

Malaria remains a major health problem predominantly in tropical countries and is still being one of the biggest causes of mortality worldwide. It is an ancient vector borne infectious disease caused by parasitic protozoans of the genus Plasmodium and is transmitted by female mosquitos of the Anopheles species. The spatiotemporal distribution of this vector is sensitive to climate conditions and the distribution of hydrometeorological variables, particularly temperature, precipitation, and humidity. We present first results of a joint high resolution hydrometeorological- and subsequent dynamical vector transmission modelling. Our approach uses the couple atmospheric- and terrestrial model system WRF-Hydro, with a 1km grid spacing for the atmospheric part and a 100m grid spacing for the hydrological part. Besides traditional hydrometeorological variables, WRF-Hydro further resolves the surface water, which is potentially a crucial step forward for the grid cell distributed dynamical vector transmission model VECTRI. Our study addresses two Health and Demographic Surveillance Systems (HDSS) site regions at Nouna in Burkina Faso and Kisumu in Kenya. We present an analysis of the performance of the hydrometeorological model system and first results of the VECTRI modeling.

Preliminary results of the WRF-Hydro -VECTRI model system capture the Malaria seasonal variations correctly and show reasonable reproduction of the year-to-year variability of HDSS observed total Malaria cases.
Support Vector Machine Quantile Regression based ensemble postprocessing
Authors: Jobst David , Möller Annette , Groß Jürgen
Published: March 2022

Current practice in predicting future weather is the use of numerical weather prediction (NWP) models to produce ensemble forecasts. Despite of enormous improvements over the last few decades, they still tend to exhibit bias and dispersion errors and consequently lack calibration. Therefore, these forecasts need to be statistically postprocessed.

Support vector machines are often used for classification and regression tasks in a wide range of applications, as e.g. energy, ecology, hydrology and economics. In this study, ensemble forecasts of 2m surface temperature are post-processed using a quantile regression approach based on support vector machines (SVMQR). This approach will be compared to the benchmark postprocessing methods ensemble model output statistics (EMOS), boosted EMOS and quantile regression forests (QRF). Instead of only regarding temperature variables as predictors, other weather variables including time dependence are taken into account as independent variables. The considered dataset consists of observations and forecasts for five years which cover Germany including three different forecast horizons. Despite of a shorter training period for SVMQR in contrast to e.g. boosted EMOS or QRF, SVMQR yields more calibrated quantile ensemble forecasts than the other approaches. Additionally, a comparable performance in terms of CRPS to the benchmark methods and a great improvement in comparison to the raw ensemble forecasts could be detected.
Channel-flow induced ‘normal faulting’ in the Himalaya: a case study from the Jhala Normal Fault, Garhwal Higher Himalaya, NW India
Authors: Bose Narayan , Imayama Takeshi , Kawabata Ryoichi , Gupta Saibal , Yi Keewook
Published: March 2022

The ‘channel flow’ concept is generally associated with the collisional mountain belts (such as the Himalaya) to explain the exhumation of deeper crustal materials. According to the concept, the top part of the subducting plate gets ‘molten’ and tries to return to the surface following the ‘pipe flow’ mechanism via a combination of Poiseuille- and Couette Flows. In this study, we employed these concepts to address a long-standing debate related to the existence and cryptic nature (normal/ reverse) of an orogen parallel discontinuity, named the Jhala Normal Fault (JNF) present in the Bhagirathi River section of the Garhwal Higher Himalaya. More importantly, while a group of researchers consider the JNF to be the northern boundary of the Higher Himalayan channel (i.e., the South Tibetan Detachment System), another group put the JNF well inside the channel. In this scenario, understanding the mechanism of deformation at the JNF will not only solve this local issue but will also provide us with new insights into the geodynamic evolution of an orogeny. Based on fresh field observations and SHRIMP geochronological data (zircon and monazite), a model is being proposed in the current study to explain the origin and evolution of the JNF. The presence of amphibolite-grade rocks across the JNF, along with the lack of well-developed extensional markers, confirm that the fault is located within the Higher Himalayan channel, and not at the channel boundary. The U-Pb zircon rim ages of 33.8 ± 0.8 Ma and 30.7 ± 0.5 Ma obtained from the JNF hanging wall (northern block) and footwall (southern block), respectively, are considered as the ages of peak metamorphism. The hanging wall, which was present at the slow-moving marginal part of the channel during Eocene, eventually lagged behind the relatively faster and warmer central part. As a result, the footwall (southern) block experienced a faster exhumation, resulting in normal-sense movement along the JNF, as documented by sparse extension markers. At 21.4 ± 2.3 Ma (monazite U-Pb age), tourmaline-bearing leucogranite intruded in the JNF hanging wall, rupturing the host. This indicates the passive uplift of the JNF hanging wall (in a brittle domain) as a part of the Higher Himalaya. Hence the JNF originated as an intra-channel discontinuity, and our proposed model predicts the origin of a ‘normal fault’ during crustal channel flow.
Physical constraints on actual decadal prediction skill of internal sea surface temperature variability
Authors: Koul Vimal , Borchert Leonard , Brune Sebastian , Menary Matthew , Schrum Corinna , Baehr Johanna
Published: March 2022

Decadal prediction of internal (unforced) sea surface temperature (SST) variability relies on proper initialisation of the ocean as well as on the ability of the models to capture the observed internal modes of SST variability. Yet the specific origins of internal decadal SST prediction skill remain unidentified. In this work, we combine physical constraints to allow an a-priori identification of regions that show high actual decadal prediction skill of unforced SST signals. 

Specifically, we examine the hypothesis that skillful actual decadal SST prediction requires a combination of: reproduction of large scale persistence of SST in observations by the prediction model; initialization of the ocean state close to observations; and a strong imprint of ocean over atmosphere dynamics on the SST signal. In a MPI-ESM-LR-based decadal prediction system we find that all three criteria are met in the subpolar North Atlantic Ocean, the western Indian Ocean, and the northeast Pacific Ocean. The examined prediction system shows significant skill against HadISST observations in those three regions as well, indicating how the hypothesized physical constraints may identify regions where a decadal prediction system shows actual prediction skill.

Our work shows that internal decadal variations of ocean variables can be predicted beyond the North Atlantic region, highlighting the western Indian Ocean and the northeast Pacific Ocean as potential new hot spots of decadal prediction.
Observational implications on the presence of selected bioaerosols in exoplanetary atmospheres
Authors: Garrido Zornoza Miguel , Mitarai Namiko , Haerter Jan Olaf
Published: March 2022

On Earth, atmospheric instabilities drive the aerosolization of distinct microorganisms directly from the biosphere. Particle diameters of these (bio)aerosols typically range from ∼1nm to ∼100μm, and their residence times in the atmosphere have been suggested to range from a few days to weeks or even months. Found even beyond the troposphere, they have been shown to, in some cases, be metabolically active as well as involved in cloud processing mechanisms, depending on their surface properties, by acting as cloud condensation nuclei (CCN) or ice nuclei (IN), and thus effectively changing cloud life time and optical properties via a change in the droplet size distribution within the cloud.

Even though the immediate sample we can observe from the Solar System already suggests a wide variety of planetary climates and that any particular planetary atmosphere exhibits a high degree of complexity, it is reasonable to assume that a finite set of physical and chemical processes are the major agents governing the climate. One of these processes is the phase change of volatiles in the atmosphere and its inhomogeneous impact on the radiation budget of the planet, altering the radiatively-induced temperature gradients and thus the general circulation of the atmosphere.

With the help of a Global Climate Model (GCM), we will study the radiative forcing caused by selected bioaerosols, under different hypothesized behaviours, in a simplified model atmosphere representing a plausible exoplanetary environment. In the end, a synthetic spectrum will be generated and compared to a “bioaerosol-free’’ sample in search for discrepancies that might, or not, be regarded as biosignatures. Furthermore, with the launch of the James Webb space telescope towards L2 we shall have access to new empirical data of exoplanetary atmospheres that constitute the ideal playground for this way of hypothesis testing. 
A new process-based and scale-respecting dust emission scheme for global climate models
Authors: Leung Danny , Kok Jasper , Li Longlei , Mahowald Natalie , Prigent Catherine , Okin Gregory , Klose Martina , Pérez García-Pando Carlos , Menut Laurent , Lawrence David
Published: March 2022

Desert dust is an important aerosol component that produces large uncertainties in assessments of Earth’s radiative budget and global climate change. However, current global climate model (GCM) simulations show that modeled dust poorly captures the observed dust in both spatial and temporal variability, which inhibits accurate assessments of aerosol radiative effects. Furthermore, dust emission is a local-scale process that varies on scales less than 1–10 km and thus current GCMs with typical grid-scale of > 100 km inherently have difficulties capturing dust spatial distribution and its sensitivity to local-scale meteorological variability. To tackle these problems, we develop a new dust emission scheme for GCMs that includes several more physical aeolian processes, and use the Community Earth System Model version 2.1 (CESM2.1) as a case study. First, we account for the dissipation of surface wind momentum by surface roughness elements included plants and rocks, which reduce the wind momentum exerted on the bare soil surface over deserts. The roughness of plants is a function of time-varying leaf area index (LAI), improving the sensitivity of the modeled emissions to climate and land use/land cover (LULC) changes. Second, we account for the effects of soil particle size distribution (PSD) on dust emission threshold by implementing a realistic soil median diameter inferred from a compilation of soil PSD observations. Third, we account for intermittent dust emissions induced by boundary-layer turbulence using a recently proposed saltation parameterization, which further couples dust with boundary-layer dynamics. With more aeolian processes, CESM2 dust emission matches better in spatial variability, seasonality, and dust activation frequency when compared against dust satellite retrievals. Modeled dust aerosol optical depth (DAOD) also shows better agreement in both spatial and temporal correlations with satellite-derived and ground-based AOD. Fourth, in addition to improving the description of aeolian processes, we conduct dust emission simulations across multiple grid resolutions and show that the high-resolution simulations generally produce a better dust spatial distribution. We then generate a map of correction factors to dust emissions for the coarse-gridded simulations to reduce the scale-dependency of dust emission parameterizations, and results indicate further improved agreement with dust observations for coarse-gridded CESM2. Our results suggest that including more physical processes into climate models can lessen bias, improve simulation results, and eliminate the use of empirical source functions. Therefore, our dust emission scheme could improve assessments of dust impacts on the Earth system and future climate changes.
Effect of vegetation roots on soil hydraulic and mechanical characteristics under rainfall
Authors: Gao Xu-Guang , Wang Ji-Peng , Tan Yi-Ran , Zhang Jiong , François Bertrand
Published: March 2022

Rainfall infiltration is the main inducing factor for the instability of unsaturated soil slopes, and root water uptake and reinforcement play an important role in preventing shallow landslide. In order to explore the influence of vegetation root on the soil hydraulic and mechanical properties under rainfall, a self-designed soil permeability coefficient measuring device considering the effects of vegetation was used to study the soil water characteristic curve (SWCC) and permeability coefficient of Festuca Arundinacea, Ophiopogon Japonicus, Ligustrum Vicaryi and bare soil under two different rainfall conditions (3.0mm/h and 5.0mm/h) were studied. Then, the direct shear tests of root-soil composite with different water contents and root contents were carried out. Finally, the slope stability under different rainfall and vegetation was simulated by GeoStudio. Results show that: root water uptake can effectively reduce soil water content and increase soil suction, and its influence range is about 2-3 times the length of the root system. Root water uptake can also significantly improve the soil water retention capacity. The air entry value of vegetation soil is larger than that of bare soil, and the permeability coefficient of vegetation soil is about one order of magnitude lower than that of bare soil. Among the three different types of vegetation, the effect of Festuca Arundinacea and Ophiopogon Japonicus on soil water content and suction is more significant than Ligustrum Vicaryi. Root reinforcement mainly increases the soil shear strength by improving the cohesion of the root-soil composite, but has little effect on the internal friction angle. The cohesion of the root-soil composite is affected by soil water content, root content and root distribution, which increases with the increase of root content, and decreases with the increase of water content. When the roots are vertically distributed, the cohesion of the root-soil composite is greater than when the roots are placed horizontally and inclined. Vegetation can effectively improve the stability of the shallow slope under various rainfall conditions, but has little effect on the stability of a deep slope. The safety factor of all three types of vegetated slopes is higher than that of bare soil slopes.
Absolute dating of deep ice cores with argon and krypton isotopes.
Authors: Landais Amaelle , Orsi Anaïs Orsi , Fourré Elise Fourré , Jacob Roxanne , Crotti Ilaria , Ritterbusch Florian , Lu Zheng-Tian , Yang Guo-Min , Jiang Wei
Published: March 2022

In the search for very old ice, finding the age of the ice is a key parameter necessary for its interpretation. Most ice core dating methods are based on chronological markers that require the ice to be in stratigraphic order. However, the oldest ice is likely to be found at the bottom of ice sheets, where the stratigraphy is disturbed, or in ablation areas, where the classical methods cannot be used. Absolute dating techniques have recently been developed to provide new constraints on the age of old ice. In particular, 81Kr measurements provide strong dating constraints for the old ice cores. Still, these measurements are limited in deep ice cores because of the large sample size required (5-6 kg). In addition to 81Kr dating, we discuss here the analytical performances of a new technique for 40Ar dating, which allows us to provide a reliable age with 80g of ice rather than 800g, as previously published. Finally, we present two applications for the 81Kr and 40Ar dating on the bottom of the TALDICE and Dome C ice cores.
Quantifying the effect on shallow landslide activity of actual and potential poplar and pine stands in New Zealand hill country.
Authors: van Zadelhoff Feiko , Schwarz Massimiliano , Cohen Denis , Philips Chris
Published: March 2022

In New Zealand shallow landslides are a prominent contributor to soil erosion in unvegetated slopes (hill country) and to water quality degradation. Selective well-planned re-vegetation of steep slopes can reduce shallow landslide hazard with comparatively low economic consequences.

The main non-native planted tree species that contribute to slope stability are Poplar species (Populus sp.) and Pine (Pinus radiata). We will present field data quantifying the root distribution and root strength of poplar and pine trees from New Zealand. 4 poplar trees with a medium Diameter at Breast Height (DBH) of 0.48 m are included. Circular trenches have been dug at fixed distances from stem and the roots counted and their diameter measured systematically. 64 root pull-out tests over varying soil depth and root diameter provide calibration for lateral root reinforcement (Gehring et al., 2019; equation 3). The combination of root counts and root reinforcement calibration enables the parametrization of root reinforcement on a single tree scale. The Pinus radiata calibration is the adopted from Giandrossich et al., 2020 which applied a similar methodology.

Using the slope stability model SlideforMap, we assess and compare (re)vegetation scenarios and their effect on slope stability. In addition to a detailed inclusion of vegetation, SlideforMap takes local soil and hydrology into account in the parametrization. Scenarios without poplar/radiata stands, dispersed trees and plantations are run and compared under varying precipitation conditions.

We believe this approach enables regional decision makers to optimize tree planting to significantly reduce slope instability at minimal economic costs.

Literature:

Gehring, E., Conedera, M., Maringer, J., Giadrossich, F., Guastini, E., & Schwarz, M. (2019). Shallow landslide disposition in burnt European beech (Fagus sylvatica L.) forests. Scientific Reports, 9(1), 1–11. https://doi.org/10.1038/s41598-019-45073-7

Giadrossich, F., Schwarz, M., Marden, M., Marrosu, R., & Phillips, C. (2020). Minimum representative root distribution sampling for calculating slope stability in pinus radiata d.Don plantations in New Zealand. New Zealand Journal of Forestry Science, 50, 1–12. https://doi.org/10.33494/nzjfs502020x68x
Vegetation variability and temperature forecasts
Authors: Rousta Iman , Olafsson Haraldur
Published: March 2022

Recent research, based on remote sensing of Normalized Difference Vegetation Index (NDVI) has revealed substantial interannual variability in the maximum vegetation in Iceland.  This variability is primarily related to temperature, but also to some extent to precipitation.  Most, if not all, operational numerical weather prediction models for that region do however use climatological values for vegetation with no interannual variability.

A preliminary investigation of temperature forecasts in the highlands of Iceland indicates that high NDVI correlates with positive bias of temperature forecasts.  This is presumably associated with the impact of increased vegetation on the Bowen ratio in sparsely vegetated regions, but local circulation may also play a role.  
EARThD: an effort to make East African tephra geochemical data available and accessible
Authors: DiMaggio Erin , Mana Sara , VanHazinga Cora
Published: March 2022

Tephra deposits are excellent chronostratigraphic markers that are prolific and widespread in portions of the East African Rift (EAR). Arguably one of the most powerful applications of tephrochronology is the establishment of regional chronological frameworks, enabling the integrated study of the timescales and interaction of the geosphere, hydrosphere, and biosphere. In order for these disparate disciplines to integrate and fully utilize the growing number of available tephra datasets, infrastructural efforts that centralize and standardize information are required. Of particular importance to these efforts is digitizing and standardizing previously published datasets to make them discoverable in alignment with current FAIR data reporting practices.  

EARThD is a NSF funded data compilation project that has integrated and standardized geochemical and geochronological data from over 400 published scientific papers investigating tephra datasets from the East African Rift. Our team has trained 15 undergraduate students in spreadsheet data entry and management, data mining, scientific paper comprehension, and in East African tephrochronology. We utilize an existing NSF-supported community-based data facility, Interdisciplinary Earth Data Alliance (IEDA), to store, curate, and provide access to the datasets. We are currently working with IEDA to ensure that data generated from EARThD is ingested into the IEDA Petrological Database (PetDB) and ultimately EarthChem, making it broadly available. Here we demonstrate our data entry process and how a user can locate, retrieve, and utilize EARThD tephra datasets. With this effort we aim to preserve available geochemical data for posterity, fulfilling a crucial data integration role for researchers working in East Africa --especially those working at paleontological and archeological sites where tephra dating and geochemical correlations are critical. The EARThD compilation also enables data synthesis efforts required to address new science questions.