bluuebunny/crossref_metadata_2025 huggingface dataset:
Predicting climate model response to changing emissions
Authors: Mansfield Laura , Nowack Peer , Voulgarakis Apostolos
Published: March 2021

In order to make predictions on how the climate would respond to changes in global and regional emissions, we typically run simulations on Global Climate Models (GCMs) with perturbed emissions or concentration fields. These simulations are highly expensive and often require the availability of high-performance computers. Machine Learning (ML) can provide an alternative approach to estimating climate response to various emissions quickly and cheaply. 

We will present a Gaussian process emulator capable of predicting the global map of temperature response to different types of emissions (both greenhouse gases and aerosol pollutants), trained on a carefully designed set of simulations from a GCM. This particular work involves making short-term predictions on 5 year timescales but can be linked to an emulator from previous work that predicts on decadal timescales. We can also examine uncertainties associated with predictions to find out where where the method could benefit from increased training data. This is a particularly useful asset when constructing emulators for complex models, such as GCMs, where obtaining training runs is costly. 
Modelling mass changes of Dokriani (Central Himalaya) and Chhota Shigri (Western Himalaya) glaciers, India using energy balance approach
Authors: Srivastava Smriti , Azam Mohd Farooq
Published: March 2021

Processes controlling the glacier wastage in the Himalaya are still poorly understood. In the present study, a surface energy-mass balance model is applied to reconstruct the long-term mass balances over 1979-2020 on two benchmark glaciers, Dokriani and Chhota Shigri, located in different climatic regimes. The model is forced with ERA5 reanalysis data and calibrated using field-observed point mass balances. The model is validated against available glacier-wide mass balances. Dokriani and Chhota Shigri glaciers show moderate wastage with a mean value of –0.28 and –0.34 m w.e. a-1, respectively over 1979-2020. The mean winter and summer glacier-wide mass balances are 0.44 and –0.72 m w.e. a-1 for Dokriani Glacier and 0.53 and –0.85 m w.e. a-1 for Chhota Shigri Glacier, respectively, showing a higher mass turn over on Chhota Shigri Glacier. Net radiation flux is the major component of surface energy balance followed by sensible and latent heat fluxes on both the glaciers. The losses through sublimation is around 10% to the total ablation. Surface albedo is one of the most important drivers controlling the annual mass balance of both Dokriani and Chhota Shigri glacier. Summer mass balance (0.76, p<0.05) mainly controls the annual glacier-wide mass balance on Dokriani Glacier whereas the summer (0.91, p<0.05) and winter (0.78, p<0.05) mass balances together control the annual glacier-wide mass balance on Chhota Shigri Glacier.
Structural characterization and permeability estimation for soil regions at the interface between biopore coating and soil matrix
Authors: Pires Barbosa Luis Alfredo , Gerke Horst H.
Published: March 2021

During preferential flow events, soil macropores such as cracks and biopores (decayed root channels and earthworm burrows) may allow water and solutes to bypass the lower permeable soil matrix. The biopore walls are inherently compacted by the locomotion mechanism employed by earthworms and roots. In addition, there are the excretion of biopolymers and the hydrophobicity of mucilage excreted by the roots of plants or mucus by earthworms. This gives to the biopore a coating with physicochemical properties distinct from the soil matrix, such as wettability, sorption and cation exchange capacity. Consequently, changes in the mechanical properties of the material in that region are also expected, ensuring greater mechanical stability.

However, micro structural features (i.e. crack size distribution) are still poorly explored. The objective is to analyze such features in detail, in order to better understand the effects of the coating material on soil macro mechanical behaviour (i.e. tensile strength) to explain the flow exchange between biopore and the soil matrix.

Therefore, soil samples were collected from Bt horizons of two Haplic Luvisols located in northern Bohemia (Hnevceves, near Hradec Kralove, Czech Republic; 50°18′47′′ N, 15°43′03′′ E). From these air dried samples, three earthworm burrows were identified and carefully separated from soil matrix.

The samples were scanned with X-ray microtomography (X-TEk XCT 225, Nikon Metrology), using 100 keV, 120μA and no filter. The reconstruction of three-dimensional images was done with the CT Pro 3D software package (version 3.1) at a spatial resolution of 10μm and 8-bit gray scale resolution. The permeability in each region was calculated along the biopore and perpendicularly to the biopore from matrix to coating using stokes solver.

The calculated hydraulic permeability for coating and matrix was 55 and 0.4 μm2 along biopore direction and 11 and 3 μm2 perpendicularly to the biopore. The results from image analysis show no differences in crack size distribution between the materials, but the number of cracks and connections were superior for the coating material, suggesting that the differences in the pore structure can strongly affect the macropore-matrix mass exchange.
Unsupervised Classification of Convective Organisation in EUREC4A with Deep Learning
Authors: Denby Leif
Published: March 2021

The representation of shallow tradewind cumulus clouds in climate models accounts for majority of inter-model spread in climate projections, highlighting an urgent need to understand these clouds better. In particular their spatial organisation appears to cause a strong impact of their radiative properties and dynamical evolution. The precise mechanisms driving different forms of convective organisation which arise both in nature and in simulations are however currently unknown.

The EUREC4A field campaign presents an unprecented oppertunity to study the ambient conditions (e.g. windshear, horizontal convergence, subsidence) while simultaneously measuring the cloud properties. Using an unsupervised neural network able to autonomously discover discover different patterns of convective organisation this work quantifies the ambient and cloud-properties present in differently organised regimes and in transitions between these regimes.

The model is trained on GOES-R imagery of the tropical Atlantic. Spatial maps of convective organisation and temporal evolution of these will be presented together with large-scale influences on their development, helping unpick the dynamics of convective clouds in this region.
Mapping arsenic vulnerability at different spatial scales using statistical and machine learning models 
Authors: Bindal Sonal
Published: March 2021

In the recent years, prediction modelling techniques have been widely used for modelling groundwater arsenic contamination. Determining the accuracy, performance and suitability of these different algorithms such as univariate regression (UR), fuzzy model, adaptive fuzzy regression (AFR), logistic regression (LR), adaptive neuro-fuzzy inference system (ANFIS), and hybrid random forest (HRF) models still remains a challenging task. The spatial data which are available at different scales with different cell sizes. In the current study we have tried to optimize the spatial resolution for best performance of the model selecting the best spatial resolution by testing various predictive algorithms. The model’s performance was evaluated based of the values of determination coefficient (R2), mean absolute percentage error (MAPE) and root mean square error (RMSE). The outcomes of the study indicate that using 100m × 100m spatial resolution gives best performance in most of the models. The results also state HRF model performs the best than the commonly used ANFIS and LR models.
Drivers of the water mass transformations that set the overturning circulation in the subpolar North Atlantic
Authors: Evans D. Gwyn , Holliday N. Penny , Oltmanns Marilena
Published: March 2021

The OSNAP (Overturning in the Subpolar North Atlantic Program) array at ~60°N has provided new and unprecedented insight into the strength and variability of the meridional overturning circulation in the subpolar North Atlantic. OSNAP has identified the region of the subpolar North Atlantic east of Greenland as a key region for the water mass transformation and densification that sets the strength and variability of the overturning circulation. Here, we will investigate the drivers of this water mass transformation and their roles in driving the overturning circulation at OSNAP. Using a water mass analysis on both model-based and observational-based datasets, we isolate diathermal (across surfaces of constant temperature) and diahaline (across surfaces of constant salinity) transformations due to air-sea buoyancy fluxes, and mixing. We show that the time-mean overturning strength is set by both the air-sea buoyancy fluxes and the strength of subsurface mixing. This balance is apparent on a seasonal timescale, where we resolve large seasonal fluctuations in the both the air-sea buoyancy fluxes and mixing. The residual of this seasonal cycle then corresponds to the mean overturning strength. On interannual timescales, mixing becomes the dominant driver of variability in the overturning circulation. To determine the location of these water mass transformations and the dynamical processes responsible for the mixing-driven variability, our water mass analysis is projected onto geographical coordinates.
Stable isotope composition of fluid inclusions in quartz minerals : New method for paleoaltimetry
Authors: Melis Raphaël , Gardien Véronique , Mahéo Gweltaz , Lécuyer Christophe , Leloup Philippe-Hervé , Jame Patrick , Bonjour Eric
Published: March 2021

Paleoaltimetry is a powerful tool to study tectonic, climate and surface processes interactions. Indeed, stable isotope composition of meteoric water can be correlated with the elevation of reliefs. The δ18O and δD of orogenic rainfall decrease while the elevation increase. Current paleoaltimetric methods based on stable isotope, including the study of pedogenic carbonates and micas associated with fault or shear zones, represent an indirect way to obtain stable isotope « paleometeoric fluid » composition. These methods do not provide simultaneously the δ18O and δD values implying the use of isotope exchange equation, source of signficant errors (up to +/- 1000m).

We have developed a new method which allow to directly acces at both the δ18O and δD of « paleometeoric » fluids with a good precision and margin of error less than +/- 200m . This method has been developed on the stable isotope composition of fluid inclusion trapped in quartz veins. The developed experimental protocol allows to extract small quantity of fluid (~10mL) and directly analyse both the δ18O and δD with a OA-ICOS Spectroscopy. Tested on 18 Miocene alpine quartz veins from the Mont-Blanc and the Chenaillet massifs the stable isotope composition of the fluids fit very well with meteoric isotopic signature and highlight the robustness of stable isotope ratio through geological time.

More over, our results indicate that Miocene precipitation was way more positive (-4,8 to -9 ‰ for δ18O and -38,2 to 68,8‰ for δD) in the Mont-Blanc massif area than modern precipitation (-12,9 to -18 ‰ for δ18O and -101,1 to -144,25‰ for δD) which indicate that the massif was still at low elevation at this time. In contrast the « paleoprecipitation » of the Chenaillet massif fall in the same range than modern precipitation (-83 to -120,3 ‰ for δD and -11,8 to -16,9 ‰ for δ18O) which indicate this massif has already reached his present altitude (~ 2500m).
Impact of Horizontal Resolution on Indian Summer Monsoon in coupled Atmosphere-Ocean Regional Model over CORDEX-SA
Authors: Kumar Pankaj , Mishra Alok Kumar , Dubey Aditya Kumar , Saharwardi Md. Saquib , Sein Dimitry
Published: March 2021

The correct representation of air-sea coupling is crucial towards improving the Indian summer monsoon. In this study, a coupled atmosphere-ocean regional model ROM is employed to investigate the impact of horizontal resolution (0.440 and 0.220) in simulating the mean Indian summer monsoon characteristics and associated dynamical and thermodynamical processes. Regional model, REMO, and global ocean model, MPIOM is taken as atmospheric and ocean components of the coupled system. Interestingly, ROM at both resolutions performs well in simulating the mean monsoonal characteristics. However, increasing horizontal resolution from 0.440 to 0.220 adds value in simulating the JJAS mean precipitation by reducing the biases both over ocean and land. The detailed results from the analysis will be discussed in the general assembly.

Keywords: Indian summer monsoon, coupled regional model, horizontal-resolution, CORDEX-SA

 

Acknowledgement: This work is jointly supported by the Department of Science and Technology (DST), Govt. of India, grant number DST/INT/RUS/RSF/P-33/G and the Russian Science Foundation (Project No.: 19-47-02015).
Evaluating stratospheric ozone and water vapor changes in CMIP6 models from 1850-2100 
Authors: Keeble James , Hassler Birgit , Banerjee Antara , Checa-Garcia Ramiro , Chiodo Gabriel , Davis Sean , Eyring Veronika , Griffiths Paul , Morgenstern Olaf , Nowack Peer , Zeng Guang , Zhang Jiankai
Published: March 2021

Stratospheric ozone and water vapor are key components of the Earth system, and past and future changes to both have important impacts on global and regional climate. Here we evaluate long-term changes in these species from the pre-industrial (1850) to the end of the 21st century in CMIP6 models under a range of future emissions scenarios. There is good agreement between the CMIP multi-model mean and observations for total column ozone (TCO), although there is substantial variation between the individual CMIP6 models. For the CMIP6 multi-model mean, global mean TCO has increased from ~300 DU in 1850 to ~305 DU in 1960, before rapidly declining in the 1970s and 1980s following the use and emission of halogenated ozone depleting substances (ODSs). TCO is projected to return to 1960’s values by the middle of the 21st century under the SSP2-4.5, SSP3-7.0, SSP4-3.4, SSP4-6.0 and SSP5-8.5 scenarios, and under the SSP3-7.0 and SSP5-8.5 scenarios TCO values are projected to be ~10 DU higher than the 1960’s values by 2100. However, under the SSP1-1.9 and SSP1-1.6 scenarios, TCO is not projected to return to the 1960’s values despite reductions in halogenated ODSs due to decreases in tropospheric ozone mixing ratios. This global pattern is similar to regional patterns, except in the tropics where TCO under most scenarios is not projected to return to 1960’s values, either through reductions in tropospheric ozone under SSP1-1.9 and SSP1-2.6, or through reductions in lower stratospheric ozone resulting from an acceleration of the Brewer-Dobson Circulation under other SSPs. In contrast to TCO, there is poorer agreement between the CMIP6 multi-model mean and observed lower stratospheric water vapour mixing ratios, with the CMIP6 multi-model mean underestimating observed water vapour mixing ratios by ~0.5 ppmv at 70hPa. CMIP6 multi-model mean stratospheric water vapor mixing ratios in the tropical lower stratosphere have increased by ~0.5 ppmv from the pre-industrial to the present day and are projected to increase further by the end of the 21st century. The largest increases (~2 ppmv) are simulated under the future scenarios with the highest assumed forcing pathway (e.g. SSP5-8.5). Tropical lower stratospheric water vapor, and to a lesser extent TCO, show large variations following explosive volcanic eruptions.
Terrestrial ecosystem Si budgets, past and present
Authors: Cooke Julia
Published: March 2021

Estimates of silicon (Si) pools and fluxes in diverse extant ecosystems have been published, including for grasslands, and deciduous and evergreen forests.  These illustrate diversity in dominant pools of biogenic Si in soils versus living biomass, reflecting the vegetation type and variation in Si accumulation of plant groups. This presentation will explore potential to estimate Si pools and fluxes for a selection of past environments, based on the species recorded in fossil records teamed with Si accumulation data from extant relatives. Where possible, changes over time will also be considered incluing impacts of vegetation on weathering and other envrionmental feedbacks.
The (un)balance between tectonic and erosion in analog accretionary wedges
Authors: Reitano Riccardo , Faccenna Claudio , Funiciello Francesca , Corbi Fabio , Sternai Pietro , Willett Sean D. , Lanari Riccardo , Sembroni Andrea
Published: March 2021

In convergent systems, tectonics, erosion, and sedimentation control orogenic evolution. The nature of the interaction between these factors is still to be unraveled, because of their complex feedback that goes through different time and spatial scales. Here, we try to bind tectonics, erosion, and sedimentation by running laboratory-scale coupled analog models of landscape evolution, in which both tectonic forcing and surface processes are modeled, trying to unravel the nature of these multiple-interrelated processes. The analog apparatus consists of a rectangular box filled with a water-saturated granular material. The deformation is imposed by the movement of a rigid piston (backstop), while surface processes are triggered by simulated rainfall and runoff. We systematically vary the convergence velocity and the rainfall rate, testing how different boundary conditions affect the balance between tectonics and surface processes and the onset of steady-state configurations. We measure the competition between input fluxes (tectonics) and output fluxes (erosion) of material. The results show how analog models never achieve a steady-state configuration in which tectonic rates are perfectly balanced by erosion rates. Tectonics add more material to the accretionary wedge than is removed by erosion (about 2-5 times more). Still, erosional fluxes seem to reach an equilibrium with the applied tectonic flux. The foreland is always overfilled with sediments, and we argued how the storage of sediments in front of a wedge can strongly divert the orogenic system from the “classical” steady state configuration. This work analyzes which are the main differences between analog and theoretical models and if/how the results coming from analog models can be exportable when interpreting natural landscape morphologies and force balance.
Seismic radiation patterns of mine blasts
Authors: Bleibinhaus Florian , Trabi Bernd
Published: March 2021

Seismic vibrations induced by mine blasting are often a nuisance to residents and may even threaten the integrity of sensitive structure in the vicinity of mines. In this study we investigate the potential to reduce such vibrations through the interference with a second blast sequence. Assuming perfectly repeatable source wavelets and an acoustic, homogeneous model, we predict the radiation patterns of blast sequences with the Fourier shift theorem as a function of azimuth and incidence, and we benchmark those predictions with observations from a seismic array deployed at the iron ore mine Mt Erzberg, Austria. We then use our model to optimize the delay times of blast sequences with an inverse algorithm geared towards minimizing the predicted vibrations in certain target zones. Due to its symmetry, a single row of blasts has no azimuthal reduction potential. A second, quasi-simultaneous mine blast can, however, reduce blast-induced vibrations by up to 20% according to our model. In this study, we discuss the principles and the potential of this approach to vibration reduction. In a second study, we will present applied results obtained with a fully elastic model.
Nonlinear dynamics of sand waves in sediment scarce environments
Authors: Damveld Johan , Porcile Gaetano , Blondeaux Paolo , Roos Pieter
Published: March 2021

Field observations in the Dover Strait (Le Bot and Trentesaux, 2004) show sandy bed patterns in an environment where sand is scarce. Their morphological features closely resemble tidal sand waves, however, these type of bed forms are characterized by a crest-to-crest spacing which is larger than the wavelength of sand waves in the same surveyed area where sand is abundant. Based on stability theory, Porcile et al (2017) developed a morphodynamic model that was able to explain these features. They found that where the motionless substratum is exposed due to the growth of dunes, the lack of sand affects sediment transport, and consequently the morphology of the bed patterns. Their results also showed that the continuous growth leads to a lengthening of the dunes, and an increasing irregularity of the spacing. The found that their results were supported by the field observations.

Since the model by Porcile et al (2017) is partly based on the perturbation principle, the results are only valid for small amplitude patterns. To further understand the nonlinear behaviour of these sand starved dunes (e.g. shape, height), we here apply the fully numerical sand wave model by Damveld et al (2020). We extend this model by accounting for the presence of a hard substrate just below a thin layer of sand. Moreover, we start with a randomly perturbed bed pattern to give the morphodynamic system the freedom of self-organization.

Preliminary results show that the numerical model is able to reproduce the results found by Porcile et al (2017). In situations where sand is less abundant, wavelengths increase, and so does the spacing irregularity. Moreover, it is found that the average height of the sandy dunes is becoming increasingly smaller with decreasing sand availability. Further analysis should reveal dependencies to different environmental parameters, such as grain size, depth and tidal current strength.

Le Bot, S., & Trentesaux, A. (2004). Types of internal structure and external morphology of submarine dunes under the influence of tide- and wind-driven processes (Dover Strait, northern France). Marine Geology, 211(1), 143-168. doi:10.1016/j.margeo.2004.07.002

Damveld, J. H., Borsje, B. W., Roos, P. C., & Hulscher, S. J. M. H. (2020). Horizontal and Vertical Sediment Sorting in Tidal Sand Waves: Modeling the Finite-Amplitude Stage. Journal of Geophysical Research: Earth Surface, 125(10), e2019JF005430. doi:https://doi.org/10.1029/2019JF005430

Porcile, G., Blondeaux, P., & Vittori, G. (2017). On the formation of periodic sandy mounds. Continental Shelf Research, 145(Supplement C), 68-79. doi:10.1016/j.csr.2017.07.011
Mapping pond aquaculture for the entire coastal zone of Asia using high resolution Sentinel-1 and Sentinel-2 data 
Authors: Ottinger Marco , Bachofer Felix , Huth Juliane
Published: March 2021

Asia is the world’s most important region for aquaculture and generates almost 90 percent of the total production. The farming of fish and shrimp in land-based aquaculture systems expanded mainly along the shorelines of South Asia, Southeast Asia, and East Asia, and is a primary protein source for millions of people. The production of fish and shrimp in freshwater and brackish water ponds in coastal regions of Asia has increased rapidly since the 1990s due to the rising demand for protein-rich foods from a growing (world) population. The aquaculture sector generates income, employment and contributes to food security, has become a billion-dollar industry with high socio-economic value, but has also led to severe environmental degradation. In this regard, geospatial information on aquaculture can support the management of this growing food sector for the sustainable development of coastal ecosystems, resources and human health.

With free and open access to the rapidly growing volume of data from the European Sentinel satellites as well as using machine learning algorithms and cloud computing services, we extracted coastal aquaculture at a continental-scale. We present a multi-sensor approach which utilizes Earth Observation time series data for the mapping of pond aquaculture within the entire Asian coastal zone, defined as a buffer of 200km from the coastline. In this research, we developed an object-based framework to detect and extract aquaculture at single pond level based on temporal features derived from high spatial resolution SAR and optical satellite acquired from the Sentinel-1 and Sentinel-2 satellites. In a second step, we performed spatial and statistical data analyses of the Earth observation derived aquaculture dataset to investigate spatial distribution and to identify production hotspots in various administrative units at regional, national, and sub-national scale.
Spatial distribution of denudation processes in Bhutan
Authors: Mazurek Małgorzata , Zwoliński Zbigniew , Niedzielski Przemysław
Published: March 2021

Bhutan, being a Himalayan mountain country, extends ca. 305 km from west to east and 145 km from south to north, covering an area of 47,000 km2. Bhutanese Himalaya mountains are divided into three latitudinal belts from south to north: the sub-Himalayas or Himalayan foothills (up to 1,500 m in altitude), the inner Himalayas or middle ranges with flat valleys (from 1,500 to 4,500 m), and the Great Himalayas of high mountains (about 4 500 m). The Black Mountain Range, stretching longitudinally, divides this country into the eastern and western parts. The belt system of landforms is closely related to the geological structure. In the north, metamorphic and crystalline rocks (mainly gneisses and granites) dominate, while in the south there are sedimentary rocks associated with the molasse-like sediments in the Siwalik range. The distribution of precipitation from approx. 500 mm in the north to 5000 mm in the south of the country relates to this geological and morphological belt system. The main rivers flow longitudinally and have perpendicular tributaries. The digital elevation model of Bhutan was analysed geomorphometrically and, on this basis, places with high potential mechanical denudation were identified. The most evident manifestation of this denudation are numerous landslides occurring on the valley slopes. These landslides, especially in the monsoons period, deliver enormous amounts of landslide material to the valley bottoms, and most often directly to the river channels. The landslide material in the form of fluvial material is further transported along the rivers and deposited in the foreland of the Himalayas. After the summer monsoon period, water samples were collected in selected rivers. The collected water samples were subjected to hydrochemical analyzes. The studied river waters in the middle part of the country are characterized by low mineralization. The obtained results allow for a preliminary characterization of the spatial diversification of the denudation potential of Bhutan's river waters. Referring to the physiographic division of Bhutan, it can be confirmed that the middle zones, meridional ridges and valleys of this country are characterized by low chemical denudation and high mechanical denudation, while the southern tips of the country Front Hills and Piedmont are dominated by accumulation processes due to a significant reduction in river gradient.
Pre-Columbian palaeodemography in the Atlantic Forest (Brazil): evaluating the role and influence of extreme hydroclimatic oscillations
Authors: Riris Philip , Gregorio de Souza Jonas
Published: March 2021

The Atlantic Forest is a major biogeographic zone of Brazil, encompassing biodiverse evergreen, semi‐deciduous, and Araucaria forests. It is presently home to millions of people, and, consequently, has experienced high levels of defaunation/deforestation through fragmentation and habitat loss in recent years. A growing archaeological and palaeoecological consensus indicates growing anthropic influences on forest distribution during the pre-Columbian period, hand-in-hand with land use intensification and increasing social complexity over time. 

Against this backdrop, this paper expands upon recent palaeodemographic work in South America to evaluate the role of long-term (centennial-scale) hydroclimatic oscillations (and the antiphasing thereof) in the Atlantic Forest domain as a potential "push factor" engendering human-driven forest expansion. It will synthesise archaeological, palaeoclimatological, and palaeoecological records, evaluate data quality, and identify areas for expansive future research. 
Statistical Study of ICW Events and Associated Ion Velocity Distributions in the Inner Heliosphere
Authors: Zhu Xingyu , He Jiansen , Verscharen Daniel , Duan Die , Owen Christopher , Horbury Timothy
Published: March 2021

Ion cyclotron waves (ICWs) frequently occur in the solar wind and are detected by PSP within 0.3 AU (Bowen et al. 2020), by MESSENGER from 0.3 AU to 0.7 AU (Jian et al. 2010, Boardsen et al. 2015) and by STEREO at 1 AU (Jian et al. 2009; He et al. 2011). However, the relation between the wave properties and the kinetic features of different ion components (proton core, proton beam and helium) are not widely discussed in the existing literature. We statistically analyze the polarization and propagation properties of hundreds of ICW events using measurements from the Solar Orbiter spacecraft. We find three types of ICW events in terms of their occurrence and duration: clustering ICW events with long durations; sporadic ICW events immersed in a quiet background magnetic field; and ICW events alongside discontinuities. We perform an investigation of the ion velocity distribution functions (VDFs) and draw comparisons of the kinetic behavior of each ion component during intervals with and without ICWs. The plasma parameters of the different ion components are acquired by our newly developed fitting program.
Dynamic permeability evolution during fluid injection and production in ultra-deep geothermal reservoirs
Authors: Scott Samuel , Yapparova Alina , Weis Philipp , Houde Matthew
Published: March 2021

A geothermal well drilled into a reservoir at temperatures exceeding the critical point of pure water (>374 °C) could generate substantially greater quantities of energy than conventional geothermal wells. Although these temperatures can be found at shallow depths (<2-3 km) in high-grade geothermal resources located in volcanically active areas, similar temperatures are only found at depths >10 km beneath vast areas of continental crust with lower heat fluxes. Permeability decreases markedly with increasing depth below 2-3 km, so exploiting the tremendous heat resources of high temperature rock at such great depths will require permeability stimulation by the injection of high-pressure fluids. In this study, we use the CSMP++ platform to perform 3D simulations of transient permeability evolution around a geothermal doublet drilled to depths between 10-16 km. The simulations incorporate a well model initially devised by Peaceman (1978) to calculate well pressures and rates of fluid production/injection. The dynamic permeability model is based on Weis et al. (2012), initially developed to simulate the evolution of ore-forming magmatic-hydrothermal systems, and links a failure criterion for critically-stressed crust with depth-dependent permeability profiles characteristic for tectonically active crust as well as pressure- and temperature-dependent relationships describing hydraulic fracturing and the transition from brittle to ductile rock behavior. We investigate the permeability changes in response to high-pressure fluid injection in brittle and ductile rock, the timescales over which the zone of permeability stimulation migrates towards production wells, and dynamic permeability evolution in response to changes in injection and production parameters. These simulations aim to mitigate resource risks that could limit the ability to extract heat from geothermal resources in ductile upper crust and to help anticipate the conditions that would be required to make the exploitation of ultra-deep supercritical geothermal resources a reality. 

References

Peaceman, D. W. (1978) Interpretation of Well-Block Pressures in Numerical Reservoir Simulation. SPE 6893, 183–194.

Weis, P., Driesner, T., & Heinrich, C. A. (2012). Porphyry-copper ore shells form at stable pressure-temperature fronts within dynamic fluid plumes. Science, 338(6114), 1613–1616.
Artificial intelligence reconstructs missing climate information
Authors: Kadow Christopher , Hall David , Ulbrich Uwe
Published: March 2021

Historical temperature measurements are the basis of global climate datasets like HadCRUT4. This dataset contains many missing values, particularly for periods before the mid-twentieth century, although recent years are also incomplete. Here we demonstrate that artificial intelligence can skilfully fill these observational gaps when combined with numerical climate model data. We show that recently developed image inpainting techniques perform accurate monthly reconstructions via transfer learning using either 20CR (Twentieth-Century Reanalysis) or the CMIP5 (Coupled Model Intercomparison Project Phase 5) experiments. The resulting global annual mean temperature time series exhibit high Pearson correlation coefficients (≥0.9941) and low root mean squared errors (≤0.0547 °C) as compared with the original data. These techniques also provide advantages relative to state-of-the-art kriging interpolation and principal component analysis-based infilling. When applied to HadCRUT4, our method restores a missing spatial pattern of the documented El Niño from July 1877. With respect to the global mean temperature time series, a HadCRUT4 reconstruction by our method points to a cooler nineteenth century, a less apparent hiatus in the twenty-first century, an even warmer 2016 being the warmest year on record and a stronger global trend between 1850 and 2018 relative to previous estimates. We propose image inpainting as an approach to reconstruct missing climate information and thereby reduce uncertainties and biases in climate records.

From:

Kadow, C., Hall, D.M. & Ulbrich, U. Artificial intelligence reconstructs missing climate information. Nature Geoscience 13, 408–413 (2020). https://doi.org/10.1038/s41561-020-0582-5

The presentation will tell from the journey of changing an image AI to a climate research application.
Current stability to improve AMS precision for cosmogenic 10Be applications
Authors: Carracedo Plumed Ana , Fabel Derek , Shanks Richard
Published: March 2021

With the present AMS 10Be uncertainties (~2% best case scenario) and the increasing need for more precise cosmogenic 10Be data it has become imperative to improve AMS measurements. Precision depends on counting statistics which in turn depend on ion beam current stability and sample longevity. The ion beam currents are dependent on the metal matrix in which BeO is dispersed; the matrix:BeO ratio; homogeneity of the mixture and the packing of the AMS cathode. We aim to understand the effect of cathode homogeneity in generating stable beam currents. We have performed a series of experiments using different metal matrices (Nb, Ag, Fe) in different forms (solid and in solution). The metals have been added to different stages of the sample precipitation process and both BeO and Be(OH)2 have been pressed into AMS cathodes and analysed at SUERC. We will discuss results of these experiments and introduce an innovative use of polyoxometalates (molibdanate and niobate) to create a homogeneous compound that has the potential to generate stable ion beam currents from sputter ion sources.
Upscaling Subsurface Transport from the Column to the Field: A Focus on the Meso-Scale
Authors: Stevenson Margaret , Oudega Thomas , Lindner Gerhard , Scheidl Andreas , Eder Alexander , Strauss Peter , Blaschke Alfred Paul
Published: March 2021

Upscaling groundwater transport from the column scale to the field scale is relevant because field tests with various tracers are often too expensive or not permissible, due to public health or environmental concerns.  Therefore, when testing chemical or pathogenic tracers, work is often done using small scale columns in the laboratory and results are extrapolated to the field. Several studies compare tracer transport in small-scale columns to tests in the field, but there is yet to be a study that compares groundwater transport using a meso-scale as well. Within a framework of upscaling, three scales are considered: small laboratory columns (0.1 m scale), a large intact core (1 m scale), and a real-world gravel aquifer (10 m scale).  The small column is filled with gravel material taken from boreholes at the field site, which is close to Vienna, Austria.  The meso-scale consists of an undisturbed gravel column, which was taken from a gravel pit near Neuhofen an der Ybbs, Austria. It was found that scale effects observed may be due to heterogeneity at the macropore scale versus preferential flowpaths at the meso-scale and field scale. Additionally, differences may be observed due to the small columns being repacked with aquifer material and the large column and field site being “undisturbed”.  The meso-scale column allows us to gain insight into the upscaling processes by incorporating an in-between step when comparing groundwater transport at the column to the field scale.
Validation of recent altimeter missions at non-dedicated tide gauge stations in the Southeastern North Sea
Authors: Esselborn Saskia , Illigner Julia , Schöne Tilo , Weiß Robert , Artz Thomas , Huang Xinge
Published: March 2021

The absolute and relative accuracy of sea surface heights derived from six altimeter missions (Jason-1/2/3, Envisat, Saral, Sentinel-3A) is evaluated at five GNSS-controlled tide gauge stations in the German Bight (SE North Sea). The precision of the total water level envelope (TWLE) is assessed for the period 2000 to 2019 based on RMS errors and explained variances. The comparison is based on TWLE instead of dealiased sea level data since the tidal and barotropic dynamic is not known with sufficient accuracy in this area. The tide gauges are partly located at the open sea, partly at the coast close to mudflats. The tide gauge data is available every minute, the 20 Hz level 2 altimetry data is interpolated to virtual stations at distances between 2 and 15 km to the tide gauges. The altimeter data is based on standard retrackers, the correction models are adjusted to coastal applications and exclude the corrections for ocean tides and dynamic atmosphere to allow a direct comparison to the tide gauge data. To account for slight differences of the tidal dynamics between gauge and altimetry an optimal time shift and scale between each pair of locations is estimated and applied. This tidal correction improves the RMS errors by 15-75%. The explained variances are excellent at all stations (> 96%). The resultant RMS errors are mainly between 2-5 cm depending on location and mission. The RMS errors rise up to 10 cm where coastal dynamics play a dominant role or the altimeter approaches the land very closely (<7 km). The accuracy of the absolute biases is strongly dependent on the knowledge of the mean sea surface heights in the region.
Quantifying thermal variability in subduction zones via data-driven reduced-order modelling
Authors: May Dave , England Philip
Published: March 2021

Subduction zones can give rise to severe natural hazards, e.g. earthquakes, tsunami & volcanism. Improved hazard assessment may be realised through physics based modelling. The thermal structure of a subducting plate has a first order control on many aspects of the subduction zone, including: dehydration reactions; intermediate depth seismicity; melt production; formation of arc volcanoes. Subduction zones exhibit a wide variability with respect to slab age, velocity, dip, rheology and mechanical behaviour of the overriding plate. For many subduction zones the assumption of a thermo-mechanical steady-state is reasonable, hence forward models often assume the form of a kinematically driven slab causing traction-driven mantle wedge flow. Even for this simplified forward model, our understanding of how the parameters and their uncertainties influence the thermal structure is incomplete. 

To address this uncertainty, here we use a data-driven model reduction technique, specifically the interpolated Proper Orthogonal Decomposition (iPOD), to define a fast-to-evaluate and surrogate model of a steady-state subduction zone that is valid over a high-dimensional parameter space. The accuracy of the iPOD surrogate model is controlled using a hyper-rectangle tree-based adaptive sampling strategy combined with a non-intrusive error estimator. To illustrate the applicability of the iPOD, we present examples in which reduced-order models are constructed for combinations of parameters related to the kinematics, rheology and geometry of the subduction zone. The examples will characterize the efficiency and accuracy of the iPOD reduced-order model when using parameter spaces that vary in dimension from 1 to 7.
The response of deep soil carbon to climate change: From experiments to meta-analysis
Authors: Pries Caitlin , Heckman Katherine , Templer Pamela , Frey Serita , Crow Susan
Published: March 2021

Over half of global soil organic carbon (SOC) is stored in subsurface soils (>20 cm depth), but the vulnerability of this deeper SOC to climate change has only recently been tested. Most soil warming experiments have either only warmed surface soils or only examined the response of the surface carbon dioxide flux, so the sensitivity of SOC at different soil depths to climate change is undetermined. As predictive models of terrestrial carbon storage move toward more mechanistic representations, we need to understand how the carbon cycle differs across soil depths. We present depth-explicit measurements of soil CO2 production from six studies, including four in situ deep soil warming experiments. The experiments’ locations ranged from coniferous to hardwood temperate forests in the United States to volcanic soils in Hawaii. We have found that in temperate forests, deep soil carbon is just as vulnerable to warming-induced losses as surface soils. However, where minerals are strongly associated with organic carbon, as in Hawaii, or in degraded soils where much of the organic matter has been lost, deep soil carbon resists warming-induced losses. Thus, the response of deep soil to climate change is dependent on its availability to microbes. This conclusion is supported by a worldwide meta-analysis of radiocarbon data among soil density fractions, which found that the amount of carbon in the particulate free light fraction decreased with mean annual temperature, but the carbon in the heavy, mineral-associated fraction did not.
Modelling reactive two-phase flow: challenges and implications
Authors: Frendak Andrey , Podladchikov Yury , Räss Ludovic
Published: March 2021

The ongoing warming of Earth's climate is about to trigger significant change in global sea-level and temperature distribution. Among first evidence is the thawing of hydrate-rich subsurface sediments leading to the potential release of large amounts of greenhouse gases into the oceans and the atmosphere. We hypothesise sea-level and water temperature variations to trigger abrupt changes in the stability of natural systems leading to the spontaneous localisation of flow and deformation. The sedimentary stacks we consider represent fluid saturated deformable porous environments described by interacting thermal, hydrological, chemical and mechanical processes. Resolving the multi-physics interactions or coupling is vital in order to accurately predict the rapid, non-linear and non-trivial evolution of natural systems in fragile equilibrium.

We here investigate how interactions among chemical, hydrological and mechanical processes lead to the spontaneous localisation of flow. We employ a novel numerical modelling framework based on the iterative implicit pseudo-transient method to understand how the relative role of reactions and pore fluid distribution impacts the local deformation in saturated porous media. Resolving strongly coupled multi-physical systems is challenging because accurate results require high resolution calculation in space and time.

Our study aims at better understanding how external forcing parameters such as e.g. pressure and temperature may lead to abrupt changes in the dynamic of complex systems. Ultimately, such investigations should permit further assessment of the longer term evolution and stability of natural systems.
The role of latent heat in heterogeneous ice nucleation
Authors: Pakarinen Olli , Pulido Lamas Cintia , Roudsari Golnaz , Reischl Bernhard , Vehkamäki Hanna
Published: March 2021

Understanding the way in which ice forms is of great importance to many fields of science. Pure water droplets in the atmosphere can remain in the liquid phase to nearly -40º C. Crystallization of ice in the atmosphere therefore typically occurs in the presence of ice nucleating particles (INPs), such as mineral dust or organic particles, which trigger heterogeneous ice nucleation at clearly higher temperatures. The growth of ice is accompanied by a significant release of latent heat of fusion, which causes supercooled liquid droplets to freeze in two stages [Pruppacher and Klett, 1997].

 

We are studying these topics by utilizing the monatomic water model [Molinero and Moore, 2009] for unbiased molecular dynamics (MD) simulations, where different surfaces immersed in water are cooled below the melting point over tens of nanoseconds of simulation time and crystallization is followed.

 

With a combination of finite difference calculations and novel moving-thermostat molecular dynamics simulations we show that the release of latent heat from ice growth has a noticeable effect on both the ice growth rate and the initial structure of the forming ice. However, latent heat is found not to be as critically important in controlling immersion nucleation as it is in vapor-to-liquid nucleation [Tanaka et al.2017].

 

This work was supported by the ERC Grant 692891-DAMOCLES, the Academy of Finland Flagship funding (grant no. 337549), and the University of Helsinki, Faculty of Science ATMATH project. Supercomputing resources were provided by CSC–IT Center for Science, Ltd., Finland.

 

REFERENCES

 

Pruppacher, H. R. and J. D. Klett (1997). Microphysics of Clouds and Precipitation. Vol. 18. Kluwer Academic.

Molinero, V. and E. B. Moore (2009). J. Phys. Chem. B 113, 4008.

Tanaka, K. K et al. (2017). Phys. Rev. E 96, 022804.