bluuebunny/crossref_metadata_2025 huggingface dataset:
Fracture networks in a Late Jurassic Arab-D reservoir outcrop analogue, Upper Jubaila Formation, Saudi Arabia.
Authors: Panara Yuri , Khanna Pankaj , Chandra Viswasanthi , Finkbeiner Thomas , Vahrenkamp Volker
Published: March 2022

Fracture networks are responsible for channeling flow in subsurface reservoirs (hydrocarbon or geothermal) and markedly impact well productivity and ultimate recovery. Yet, methods to provide fracture (network) distribution at sufficiently high resolution are still lacking – mainly because subsurface data do not adequately capture natural fractures at the mesoscale (cm to m in size) beyond the well bore. In this study we utilize an outcrop analogue to bridge this scale gap.  Over the last decades 3D digital photogrammetry drastically improved in terms of measurement amount and quality enabling the collection of large data sets over wide outcrops. Such data provide critical insights on depositional and structural heterogeneities that may then be utilized for reservoir analogue simulations. Subject of this study is an outcrop in Wadi Laban located in SW Riyadh, Saudi Arabia, along the Mecca-Riyadh highway. We constructed a reliable 3D Digital Outcrop Model (DOMs) at high resolution of the Late Jurassic (Kimmeridgian) Upper Jubaila Formation following a ~800m long escarpment without any occlusion or bias. In particular we reconstruct a colorized dense point cloud using the high-quality setting of Agisoft Metashape© software. We investigated DOMs with CloudCompare© software (CloudCompare, 2021) to map the visible fractures 3D exposure and infer general fractures pattern. Four fracture sets are evident in the data: the predominant sets 1 and 2 are roughly E-W oriented, while sets 3 and 4 are roughly NNE-SSW oriented. Most fractures are strata bound and sub-vertical in nature. Fracture intensity (P21) analysis along the entire outcrop enables us to describe and quantify lateral and vertical variability. Laterally natural fractures are concentrated in corridors with a spacing of few tens of meters. Vertically, fracture intensity is heterogeneous. Furthermore, we found a strong correspondence between fracture intensity on the outcrop and a porosity log acquired on core samples from a well drilled only a few meters behind the outcrop. The outcome of this study provides a step forward for the comparison of outcrop and subsurface fractures, and expand the application of outcrop data to generate high resolution and fidelity reservoir analogue models.
A new perspective on permafrost boundaries in France during the Last Glacial Maximum
Authors: Stadelmaier Kim Helen , Ludwig Patrick , Bertran Pascal , Antoine Pierre , Shi Xiaoxu , Lohmann Gerrit , Pinto Joaquim G.
Published: March 2022

During the Last Glacial Maximum (LGM), a very cold and dry period around 26.5–19 kyr BP, permafrost was widespread across Europe. In this work, we explore the possible benefit of using regional climate model data to improve the permafrost representation in France, decipher how the atmospheric circulation affects the permafrost boundaries in the models, and test the role of ground thermal contraction cracking in wedge development during the LGM. With these aims, criteria for possible thermal contraction cracking of the ground are applied to climate model data for the first time. Our results show that the permafrost extent and ground cracking regions deviate from proxy evidence when the simulated large-scale circulation in both global and regional climate models favours prevailing westerly winds. A colder and, with regard to proxy data, more realistic version of the LGM climate is achieved given more frequent easterly winds conditions. Given the appropriate forcing, an added value of the regional climate model simulation can be achieved in representing permafrost and ground thermal contraction cracking. Furthermore, the model data provide evidence that thermal contraction cracking occurred in Europe during the LGM in a wide latitudinal band south of the probable permafrost border, in agreement with field data analysis. This enables the reconsideration of the role of sand-wedge casts to identify past permafrost regions.
Combining residence time and isotopic tracers to better understand  groundwater reservoir and flows in a karst thermal aquifer
Authors: Ranchoux Coralie , Ladouche Bernard , De Montety Véronique , Seidel Jean-Luc , Batiot-Guilhe Christelle
Published: March 2022

Karst hydrosystems are complex systems but often undergo high anthropogenic pressure on their water resources in Mediterranean area since it is shared by many actors. The addition of thermal and/or marine components in these systems makes the interpretation of classical methods more difficult. The thermal karst aquifer of Thau Basin (South of France) illustrates well the complexity of such underpressured karst hydrosystems. In the Balaruc-les-Bains area, groundwater results from the convergence and mixing of (i) young and cold karst water, (ii) old, hot and mineralized thermal water and (ii) marine water (Thau Lagoon and/or seawater). In the framework of the Dem'Eaux Thau CPER/FEDER project (2017-2022), we propose to combine tracers of water-rock interaction processes (Sr, Li) and residence time tracers (4He, 14C, 36Cl) to better understand the origin and mean residence times of flow that takes place in the system, with a focus on the thermal water. In particular, the originality of this work was to constraint geological and hydrogeological informations using natural tracers and to calibrate He dating using 14C ages.

The combination of Si geothermometer and isotopic Sr signature (87Sr/86Sr) indicates that the thermal reservoir is located in the Jurrassic carbonate formation until 2000m depth. In addition Li concentrations show the existence of deep flows from granitic bed-rock. These new geochemical results allowed to better constraint the location of the thermal reservoir on the geological 3D map of the area and points out the major role of a local fault. However, there is significant uncertainty on the porosities of this reservoir impacting He age dating method. We used Carbon-14 dating in a deep karst well to constrain 4He ages and therefore determine the reservoir porosity. In parallel, the identification and quantification of the thermal flux by Li concentrations, allowed us to correct the 4He concentrations, and to propose a residence time of the thermal water of several thousands of years (10 000 to 50 000 years) which were consistent with the 36Cl results. Thermal water subsequently feed a shallow reservoir (100 – 300 m) through local fractures and mix with variable proportions of recent karst flows. 
Wildfire Smoke Highlights Troposphere-to-Stratosphere Pathway
Authors: Magaritz Ronen Leehi , Raveh-Rubin Shira
Published: March 2022

The extensive wildfires during December 2019 – January 2020 in South-East Australia released a mass of smoke into the stratosphere comparable to large volcanic eruptions. The smoke was observed throughout the southern hemisphere stratosphere months after the fires. Pyrocumulunimbus clouds (pyCb) are commonly presented as the main mechanism able to transport wildfire smoke across the tropopause into the stratosphere and were assumed as the driving mechanism also in this case. However, the smoke only appeared in the higher stratospheric levels downstream of the fires in the central south Pacific. Furthermore, there is indication that  pyCb were not active when the smoke was first seen in satellite images.  

In this study, using Lagrangian airmass trajectory analysis together with satellite observations we are able to fill the gap and identify the pathway of the smoke, its entry point into the upper levels and the mechanism that allows the smoke to enter the stratosphere. We find that the transitioning tropical cyclone Sarai merged with an extratropical cyclone to form a troposphere-wide cyclonic system, with a deep potential vorticity cutoff above it. Initially, the smoke traveled in the isentropic layer between 340 and 350 °K, just below the tropopause. Having reached the cyclone, the smoke changed direction, circulated around the low and entered the stratosphere through a dip in the tropopause height within the cutoff.

The cyclonic system described in this case study is not uncommon in these regions, possibly underlining the importance of this mechanism for troposphere-to-stratosphere exchange.
Long term trends in winds in the mesosphere and lower thermosphere over Rothera (67°S, 68°W) from radar observations and WACCM-X
Authors: Noble Phoebe , Wright Corwin , Hindley Neil , Mitchell Nicholas , Cullens Chihoko , England Scott , Pedatella Nicholas , Moffat-Griffin Tracy
Published: March 2022

The Mesosphere and Lower Thermosphere (MLT), at 80-100 km altitude, is critical in the coupling of the middle and upper atmosphere and determining momentum and energy transfer between these two regions. However, despite its importance, General Circulation Models (GCMs) have only recently been extended to the MLT region and remain poorly constrained.

We use a long term meteor radar dataset from Rothera on the Antarctic Peninsula to test the eXtended Whole Atmosphere Community Climate Model (WACCM-X). This radar has been running continuously since 2005, resulting in a uniquely long, consistent measure of the winds in the MLT that we can use to investigate long term variability. We find that although some characteristic features are represented well in WACCM-X, the model exhibits considerable biases. In particular, the observations show a ~10m/s eastward wind in Antarctic winter whereas the model predicts winds of the same magnitude but opposite direction. We propose that this difference is due to the lack of secondary gravity wave modelling in WACCM-X.

We also find interannual variability in both the observations and the model. In order to understand these differences, we further investigate the role of external climate processes in driving the winds in this region. Using a linear regression method, we quantify how the (observed and modelled) winds in the Antarctic MLT respond to Solar activity, the El Nino Southern Oscillation (ENSO), the Quasi-Biennial Oscillation (QBO) and the Southern Annular Mode (SAM). For some indices we find good agreement between the observations and model results while for others we see important differences.
Topographic controls on ice flow and recession for Juneau Icefield (Alaska/British Columbia)
Authors: Davies Bethan , Bendle Jacob , Carrivick Jonathan , McNabb Robert , McNeil Christopher , Pelto Mauri , Campbell Seth , Holt Tom , Ely Jeremy , Markle Bradley
Published: March 2022

Globally, glaciers are losing dramatic volumes of ice, especially in Alaska, which dominates sea-level rise from glaciers. Plateau icefields may be especially sensitive to climate change due to the non-linear controls their topography imparts on their response to climate change. However, Alaskan plateau icefields have been subject to little structural glaciological or regional geomorphological assessment, which makes the controls on their present and former mass balance difficult to ascertain. 

We inventoried 1050 glaciers and 401 lakes of the Juneau Icefield region for the year 2019. We found that 63 glaciers had disappeared since the 2005 inventory, with a reduction of glacier area of 422 km2. We also present the first structural glaciological and geomorphological map for an entire plateau icefield in Alaska. Glaciological mapping of nearly 20,000 features included crevasses, debris cover, foliation, ogives, medial moraines and, importantly, areas of glacier fragmentation, where glaciers either separated from tributaries via lateral recession (n=59), and disconnected within areas of former icefalls (n=281). Geomorphological mapping of >10,000 landforms included glacial moraines, glacial lakes, trimlines, flutes and cirques. These landforms were generated by a temperate icefield during the “Little Ice Age” neoglaciation. These data demonstrate that the present-day outlet glaciers, which have a similar thermal and ice-flow regime, have undergone largely continuous recession since the “Little Ice Age”.

These data document the interactions between topography and glacier change. Importantly, disconnections are occurring within glaciers can separate accumulation and ablation zones, increasing rates of glacier mass loss. We show that glacier disconnections are widespread across the icefield and should be critically taken into consideration when icefield vulnerability to climate change is considered.
The impact of land-sea contrasts in the aggregation of convection
Authors: Dingley Beth , Dagan Guy , Herbert Ross , Stier Philip
Published: March 2022

The self-aggregation of convection in idealised models has been widely studied. Work has been done to identify key physical mechanisms responsible for both driving and maintaining aggregation in a range of idealised radiative-convective equilibrium (RCE) models. These idealised models are typically run without any land, rotation, variation in sea-surface temperatures (SSTs), or a diurnal cycle. Due to these idealisations, a key question in the study of convective aggregation is how these convective processes and mechanisms manifest in the real-world. Several studies have tried to tackle this question by increasing the complexity of processes in the idealised models, such as SST gradients, adding a slab ocean, adding a diurnal cycle, or adding an aerosol diabatic heating perturbation. Particularly, the inclusion of interactive ocean surfaces has been shown to strongly impact the formation of aggregated clusters.

The interactions between land surfaces and aggregation are currently less well understood. Early studies have found that convective aggregation may favour land areas over oceans, and that soil moisture feedbacks can act to oppose the aggregation altogether. Thus, in this study we investigate the relationship between land, oceans, and aggregation, addressing the following questions:

How does the inclusion of an idealised island into a global RCE model impact the aggregation of convection?

Are the physical mechanisms responsible for the aggregation similar to those seen in land-free simulations?

How sensitive are these results to our choice of land parameters, such as initial soil moisture, surface temperature, soil type, and land topography?
Measurement of the mineral dust concentration using an optical-based approach in central Los Angeles
Authors: Sioutas Constantinos , Tohidi Ramin , Jalali farahani Vahid
Published: March 2022

As a primary component of PM10, ambient mineral dust particles have been linked to increased morbidity and health risks in urban environments. Dust particles also alter the Earth's radiation balance because of their absorbance and scattering properties. We employed absorption photometers to investigate the real-time concentration and light absorption of dust particles in central Los Angeles for three different periods. We adopted a novel method by utilizing a coarse particle virtual impactor that increases the concentration of coarse particles by around 20 times to eliminate the effects of light absorption of black carbon, which has a considerably higher light absorption and dominates the PM2.5 light absorption. The concentrated coarse particles were collected on Teflon filters, and their chemical components were measured by the Inductively Coupled Plasma Mass Spectroscopy method. The light absorption of dust particles was determined by subtracting the measured values by aethalometers on two different lines: 1) the virtual impactor line and 2) the PM2.5 line. The light absorption coefficient of the dust particles in central Los Angeles was estimated to be 2.7 1/Mm at 370 nm, while the corresponding value at 880 nm was 0.41 1/Mm. The estimated mineral dust mass concentration showed a similar trend with the reported coarse PM by the California air resource board. Finally, we determine the absorption Angstrom exponent (AAE) of dust particles in the area to be around 2.18 for the entire study period. Our findings affirm that this method can be used to analyze the mineral dust concentration in distinctive urban environments effectively.
Variation in Cenozoic tectonic subsidence in Luconia-Balingian provinces, Sarawak Basin, Malaysia: influence of extensional and compressional tectonics
Authors: Jamaludin Siti Nur Fathiyah , Pubellier Manuel , Madon Mazlan
Published: March 2022

The Luconia-Balingan Provinces are sedimentary basins in Sarawak, Malaysia that presently extends from offshore to onshore, along major NW-SE faults on both sides of the basins. It was formed by several rifting episodes of the Southern China Block, followed by spreading since Eocene. The rifting coeval with the closure of an ancient oceanic crust that induced compression and major uplift in the southern part of the basins. The basins are filled by up to more than 10 km of Cenozoic sediments overlying the Cathaysian derived crystalline basement. Since the Upper Eocene-Oligocene to Upper Miocene, warm-water to tropical carbonate sedimentation has been dominating the stratigraphy mainly in Luconia. To understand the sediment and tectonic subsidence evolution of the Luconia-Balingian Provinces this study analysed data from exploration wells using a Matlab-based open-source tool, the BasinVis 2.0. Updated compaction trend from three different wells to represent the southern-central-north regions of the provinces are adopted. The subsidence history for Luconia-Balingian provinces can be divided into five stages; (i) 37 to 23 Ma: Steadily increase in subsidence is recorded with higher tectonic subsidence rate in the central and west of Luconia-Balingian and moderate tectonic subsidence in the north and south. (ii) 23-18 Ma: Increase in tectonic subsidence for most parts of Luconia-Balingian with slight decrease in total tectonic subsidence recorded in some of the wells. (iii) 18 to 15.5 Ma: Delayed subsidence within the central and northern parts of Luconia-Balingian, coincide with the diachronous timing of Middle Miocene Unconformity. There was minor uplift in the northern section. However, the southern part experienced increased in the total and tectonic subsidence rates. (iv) 15.5 to 11.8 Ma: Overall decrease in tectonic subsidence rate, coinciding with the prolific growth of Middle to Upper Miocene carbonate build-ups. (v) 11.8 to 0 Ma: Increase in tectonic subsidence rate particularly in the wells within the southern part of Luconia-Balingian. Stretching factors ranges between 1.3 to 1.95 are recorded, indicative for foreland basin setting with a very strong influence from the syn- and post-rift phases. It directly related to the effect of extensional tectonics during the South China Sea opening and compressional tectonics during the closure of the proto-South China Sea during the Cretaceous-Eocene, until Middle Miocene. Through this study, accurate subsidence rates are deduced and allows specific characterization of tectonic influences in different parts of Luconia-Balingian at different stages of basin development.
GOCE SGG data downward continuation to the Earth’s Surface
Authors: Vergos Georgios S. , Pitenis Eleftherios A. , Mamagiannou Elisavet G. , Natsiopoulos Dimitrios A. , Tziavos Ilias N.
Published: March 2022

The combination of GOCE Satellite Gravity Gradiometer (SGG) data with local free-air gravity anomalies, towards the estimation of improved geoid and gravity field models, requires their downward continuation to the Earth’s surface (ES). Within the GeoGravGOCE project, which aims to explore the local improvements in geoid and gravity field modeling offered by GOCE, optimal combination of GOCE and surface data was sought in order to acquire insights of their contribution especially over poorly surveyed areas. GOCE SGG data are first pre-processed, to filter out noise and reduce long-wavelength correlated errors, and are consequently reduced to a mean orbit (MO) so that downward continuation to the Earth’s surface can be carried out. The reduction from the orbit level to a MO was performed by estimating GGM gradient grids per 1 km from the MO to the maximum orbital level, and then linearly interpolating for the reduction from the actual satellite height. Having determined the filtered GOCE filtered SGG data to a MO, the next step referred to their downward continuation to the ES. Gravity anomalies from XGM2016 generated on the ES have been used as ground truth and were upward continued to the MO in the spectral domain through the input output system theory method. The evaluation of GOCE SGG data to the MO with GGM-derived gradients is performed using a Monte-Carlo annihilation method finding the global minimum of a cost function that may possess several local minima. The GOCE data that satisfy the aforementioned criteria of this simulated annealing method are frozen and the steps mentioned above are repeated until all generated SGG data meet the criterion. The developed procedure can be successfully applied for downward continuation of GOCE SGG from a MO to the ES for regional gravity field applications. The present work summarizes the results achieved while the evaluation is performed against local free-air gravity anomalies and residuals to XGM2019.
Structure of the Hydrocarbon Sphere of the Earth's Crust
Authors: Galant Yuri
Published: March 2022

 

Earlier (GeoBio 2014, Moscow ) it was reported that an independent domain is observed in the Earth's Сrust - the Hydrocarbon Sphere (HCS). HCS is a sequential alternation of hydrocarbon fields in accordance with geological objects. HCS is a material space-time continuum spread throughout Earth Crust, from Archean to modern precipitation. On the scale of the Earth's crust, HCS is represented by the entire HC spectrum (light CH4, heavy HHC, normal, isoforms, etc.). Globally, chemically, the HCS gas composition of the Earth's Crust of the granite layer is similar to the HCS composition of gas fields and is equal to CH4-HHC, while the basalt layer corresponds to the HCS composition of oil fields and is equal to HHC - CH4. Structure of HCS   of the Earth Crust based on 1 layer  Мodel of the Earth's Crust Galant (MECG), ( AAPG Athens 2007, EGU Vienna 2013) сonsist of separated layers of CH4-HHC (Granite HC Sphere)and separated layers of HHC - CH4 (Basalt HC Sphere ).   Considering that, according to the MECG model, “there is no basalt crust under the granite crust, and there is no granite crust under the basalt crust”, both HCS of the Earth's Crust - Granite HC Sphere and Bazalt HC Sphere lies directly on mantle.

 
Spurious forces can dominate the vorticity budget of ocean gyres on the C-grid
Authors: Styles Andrew , Bell Mike , Marshall David , Storkey David
Published: March 2022

Gyres are prominent surface structures in the global ocean circulation that often interact with the sea floor in a complex manner. Diagnostic methods, such as the depth-integrated vorticity budget, are needed to assess exactly how such model circulations interact with the bathymetry. Terms in the vorticity budget can be integrated over the area enclosed by streamlines to identify forces that spin gyres up and down. We diagnose the depth-integrated vorticity budgets of both idealized gyres and the Weddell Gyre in a realistic global model. It is shown that spurious forces play a significant role in the dynamics of all gyres presented and that they are a direct consequence of the Arakawa C-grid discretization and the z-coordinate representation of the sea floor. The spurious forces include a numerical beta effect and interactions with the sea floor which originate from the discrete Coriolis force when calculated with the following schemes: the energy conserving scheme (ENE); the enstrophy conserving scheme (ENS); and the energy and enstrophy conserving scheme (EEN). Previous studies have shown that bottom pressure torques provide the main interaction between the depth-integrated flow and the sea floor. Bottom pressure torques are significant, but spurious interactions with bottom topography are similar in size. Possible methods for reducing the identified spurious topographic forces are discussed. Spurious topographic forces can be alleviated by using either a B-grid in the horizontal plane or a terrain-following vertical coordinate.
The GBM Rapid Product and the Improvement from Undifferenced Ambiguity Resolution
Authors: Deng Zhiguo , Wang Jungang , Ge Maorong
Published: March 2022

Global Navigation Satellite Systems (GNSS) play a critical role for providing real-time positioning and navigation services, and the precise satellite orbit and clock products are essential for the high-precision GNSS applications. The International GNSS Service (IGS) and its Analysis Centers (ACs) have been working on the study on precise GNSS data processing and provision of the precise products. The German Research Center for Geosciences (GFZ), as one of the ACs, also provides the multi-GNSS rapid products: the GBM product. We introduce the GBM data processing strategy, analyze the precision of GBM multi-GNSS orbits from 2015 to 2021, and present the impact of applying the undifferenced ambiguity resolution on satellite orbits. The GPS orbits of GBM products agree with the IGS final orbits at the level of 11-13 mm in the three directions, and the GPS orbit 6-hour prediction precision is around 6 cm. The 6-hour prediction precision of GLONASS is around 12 cm, slightly worse than that of GALILEO, which hold an average value of 10 cm in the same period but shows a significant improvement to around 5 cm after end of 2016. The prediction precision of BDS MEO satellites are around 10 cm, and that of the BDS GEO satellites and QZSS satellites are at the level of 1 to 3 meter. The Satellite Laser Ranging (SLR) residuals show that the orbit precision of GALILEO, GLONASS, and BD3-MEO is 23 mm, 41 mm, and 47 mm, respectively. Moreover, comparing the double-differenced ambiguity resolution, adopting the undifferenced ambiguity resolution improves the 6-hour orbit prediction precision by 9-15%，15-18%，11-13%，6-17%和14-25% for the GPS, GLONASS, GALILEO, BDS-2 and BDS-3 MEO satellites, respectively.
Intercomparing WRF-LES based turbulence simulations with measurements from a 250-m tall meteorological mast
Authors: Peña Alfredo , Mirocha Jeffrey
Published: March 2022

We present an intercomparison of a one year of atmospheric simulations performed with a numerical atmospheric model system based on the WRF model with tall mast observations. We employ the nestinga capabilities of the WRF model to run up to high resolution large-eddy simulations (WRF-LES). The simulations  aim at describing the wind climatology and the turbulence characteristics at Østeild, Denmark. There, DTU established the National Test Site for Wind Turbines, where some of the largest wind turbines prototypes are under testing. We evaluate the goodness of the simulations using the WRF-LES system by comparison with high-quality mean wind and turbulence observations from a 250-m meteorological mast. The main objective of the work is to demostraste that the WRF model does not only provide long-term time series of wind speed and direction but also turbulence characteristics and parameters, which are needed for the evaluation of the site conditions, and turbine design and peformance.

The WRF-LES based simulations are performed using four nested telescopic domains centered at the Østerild mast position. The outermost and largest domain has a horizontal resolution of 6250 m, whereas the innermost and smallest domain a horizontal resolution of 50 m. By modeling at these scales, we intend to resolve most of the turbulent scales.  We run the two outermost domains in a traditional mesoscale fashion, which means we use a commmonly used planetary boundary layer (PBL) scheme, whereas the two innermost domains are run in large-eddy simulation mode, i.e., without a PBL scheme. A complete year is simulated through parallel ten day long simulations. The output for the innermost domain is produced at the model grid point closest to Østerild every 12 s, whereas that of the other domains is produced every 10-min.

After computing the 10-min statistics for the full year on the model output of the innermost domain output and the 1-Hz data of the cup anemometers at Østerild that cover the range of the mast, we find very good agreement between the observed and simulated wind climatology. Turbulence estimates from both observations and simulations are also in good agreement, even though from the observations the site shows a wide variety of atmospheric stability and turbulence conditions. The turbulence intensity changes with wind speed in a similar way both in the simulations and the measurements. Our work shows that numerical models can be used as a tool to describe turbulent site conditions required, among others, for the efficient siting of wind turbines.
Most carbon is grass-derived in tropical savanna soils, even under woody or forest encroachment
Authors: Zhou Yong , Staver Carla
Published: March 2022

Tropical and subtropical savannas have been increasingly targeted for increased carbon (C) storage via increasing tree cover. These projections typically assume large gains in soil carbon accompanying increasing tree cover, assumptions which may not reflect real changes in soil C under woody encroachment or afforestation. Studies have shown that productive grasses dominate C inputs into soils and that changes in ecosystem structure can sometimes result in losses of grass-derived carbon, but we only poorly understand the contributions of grass-derived C to total soil organic C (SOC) and the determinants of SOC responses to increasing tree cover in savannas. Here we show, using data from a semiarid savanna in Kruger National Park, South Africa, that both SOC concentration and grass-derived C in surface soils (0-20 cm) are predicted by grass biomass and soil texture, but not by tree basal area, stem density, or tree cover. More broadly across tropical savannas, grass-derived C contributes more than half of the SOC within the whole 1-m soil profile even under full tree cover. Although increasing tree cover increases SOC storage marginally, both SOC gain and loss are commonly observed across broad gradients of rainfall and soil sand content. These results highlight the continued high contribution of grasses to savanna SOC and the uncertain effects of increasing tree cover on SOC storage, challenging the widespread assumption that increasing tree cover has ubiquitous benefits to enhance SOC storage.
Subsolidus crystallisation in the A-type Pikes Peak batholith
Authors: Fonseca Teixeira Ludmila Maria , Troch Juliana , Allaz Julian , Bachmann Olivier
Published: March 2022

The granite solidus curve is generally placed around 660-700°C, depending on the pressure conditions and water content of the melt. However, recent studies have documented evidence of subsolidus crystallisation in granitic rocks, with minerals recording temperatures <660 °C, posing a debate on the state of the melt or fluid from which precipitation occurred. We utilise the Ti-in-quartz thermometer in quartz crystals of the Pikes Peak batholith, a 1.1 Ga A-type granitic pluton in Colorado (USA) and one of its many pegmatites, the Wellington Lake Pegmatite, to investigate the range of crystallisation temperatures for this system. In the granite, quartz crystals start to crystallise at typical magmatic temperatures, above 800°C, and progress to very cold conditions, below 500°C, overlapping with temperatures from the monomineralic quartz core of the pegmatite. This very low-temperature crystallisation is observed in cathodoluminescence (CL) images as (1) dark rims in the crystals and (2) fluid inclusion-filled fractures. By linking the quartz growth zones observed in CL images with the Ti content of the crystals, we estimate that a maximum of ~1/3 of the quartz volume, and likely less, corresponds to subsolidus crystallisation in the granite. Further geochemical evidence and comparison with the pegmatite indicates that the chemistry of the dominant precipitating medium undergoes pronounced changes throughout cooling and crystallisation, likely transitioning from a silicate melt at high temperatures to a solute-rich, hydrous supercritical fluid near and below the granite solidus. Further supporting the presence of a hydrous supercritical fluid, the assemblage of the different zones of the pegmatite (a fine-grained graphic granite wall zone, a coarser grained quartz-albite intermediate zone and a pure blocky quartz core) do not record typical eutectic compositions, implying that the pegmatite would not have precipitated from an evolved “granitic” melt. Thus, we suggest that subsolidus precipitation from a solute-rich supercritical fluid is a late, but significant process in the Pikes Peak granite. This event is associated with the progressive enrichment in water and other volatile elements during “second boiling”, ultimately leading to the transition from magmatic to hydrothermal conditions, and sourcing the numerous pegmatite dykes and pods in and around the pluton.
An open-source web application displaying present-day subsurface thermal conditions of the NE Mediterranean region
Authors: Uyanik Ayberk
Published: March 2022

Conversion of dynamic bottom-hole temperatures (BHTs) into static ones and utilizing on the purpose of either calibration for basin modelling or drilling plan is a crucial step for hydrocarbon and geothermal exploration projects. However, records of temperature conversions might be ignored or might get lost from the archives due to various reasons, such as project team change, diversion of focus into other areas or simply deletion of data. Disappearance of previous studies does not only disrupt the geoscientific knowledge but also causes repetition for exploration geoscientists to start the time consuming BHT conversion process all over again.

NE Mediterranean Dashboard v1.0 provides a solution for the issue by benefiting from data science instruments of Python programming language. By implementing Plotly-Dash for the front-end, and PostgreSQL for the back end as the keeper of thermal records in datatables, this open-source project proposes a user-friendly web application displaying temperature, geothermal gradient and heat flow profiles in a dashboard style.

The application is consisted of three tabs. The Overview tab provides statistical information while 2D plots section allows users to interact with cross-plots demonstrating thermal conditions for all wells or a particular well selected by the user. It also compares the results of three different BHT conversion methods known as; Horner-plot method, AAPG correction and Harrison et al. (1983). The last tab, Map View, illustrates the temperature, geothermal gradient, and heat flow maps for every 500 meters from surface to 4.5 km depth. The maps reveal the effects of the regional tectonics and how it controls the subsurface thermal behaviour along the Cilicia and Latakia Basins dominating the NE Mediterranean region.

All maps and cross-plots are interactive, and their styles can be changed according to the user’s preferences. They can also be downloaded as images for possible use in scientific publishment and/or presentations. The same interface and visualisation style, accessed by username and password, can also provide consistency between all project workers.

The source code is available at Github repository with the link; https://github.com/Ayberk-Uyanik/NE-Mediterranean-Thermal-Conditions and can efficiently be implemented for exploration projects in other regions.
Interannual hydrographic variability beneath Thwaites Eastern Ice Shelf, West Antarctica
Authors: Dotto Tiago , Heywood Karen , Hall Rob , Scambos Ted , Zheng Yixi , Nakayama Yoshihiro , Snow Tasha , Wåhlin Anna , Wild Christian , Truffer Martin , Muto Atsuhiro , Pettit Erin
Published: March 2022

Basal melting of the Amundsen Sea ice shelves is caused by relatively warm waters accessing the ice base through turbulent processes at the ice-ocean boundary layer. Here we report hydrographic variability in Thwaites Eastern Ice Shelf (TEIS) from January 2020 to March 2021 using novel subglacial mooring measurements and ocean modelling. The layers ~100 m beneath the ice base warmed considerably (~1˚C) in this period. The meltwater fraction doubled associated with basal melting due to the higher heat, leading to a freshening in the upper layers. The lighter layer contributed to the acceleration of the under-ice circulation, which led to higher basal melting through intensified temperature flux, creating positive feedback beneath the ice. The interannual variability of the water masses in the TEIS cavity is linked to the seasonal strengthening and weakening of the Pine Island Bay gyre. During periods that the sea-ice covers the bay, such as winter 2020 and the 2020-2021 summer season, the momentum transfer from the wind to the ocean surface is less effective and the gyre weakens. The deceleration of the gyre leads to relaxation and shoaling of the isopycnals beneath the TEIS, which brings warmer water upwards closer to the ice base. The results discussed in this work shows that the fate of the Amundsen Sea ice sheet is tightly controlled by adjacent small-scale gyres, which could prolongate warming periods beneath ice shelf cavities and lead to high basal melting rates.
Effects of Microplastics on Soil Hydraulic Properties 
Authors: Yu Yingxue , Flury Markus
Published: March 2022

Agricultural soils have been recognized as a major reservoir of microplastics, and concerns have arisen about the impacts of microplastics on soil properties and functioning. Here, we investigated the effects of microplastics on hydraulic properties of soils and determine the underlining mechanisms contributing to the effects. We measured the responses of a silt loam soil, a typical agricultural soil, to the incorporation of pristine as well as UV-weathered polypropylene granules and polyester fibers, two common types and shapes of microplastics, in terms of bulk density, saturated hydraulic conductivity, field capacity, permanent wilting point, water holding capacity, wet aggregate size distribution, and contact angle. We mixed polypropylene granules and polyester fibers into soil at different volume-based concentrations to elucidate the effect of microplastic shape. We also studied how weathering (UV and soil burial exposure) will affect the impact of microplastics on soil hydraulic properties. Due to the generally hydrophobic nature of plastic particles, the soil was found to lose some of its water holding capacity when contaminated with plastics. Fibrous microplastics rearrange soil structure and thus trigger more pronounced responses of soil hydraulic properties than granular microplastics. The results of this study provide fundamental knowledge about how microplastics interact with soil matrices and affect soil hydraulic properties, and advance current understanding about the impacts of microplastics on soil health.
On reduction of the filtered GOCE SGG data from the orbit level to a mean orbit 
Authors: Tziavos Ilias N. , Mamagiannou Elisavet G. , Pitenis Eleftherios A. , Natsiopoulos Dimitrios A. , Vergos Georgios S.
Published: March 2022

The overall goal of the GeoGravGOCE project, funded by the Hellenic Foundation for Research Innovation, is to employ GOCE data products, mainly the original Satellite Gravity Gradiometry (SGG) data, and model the geoid in the Hellenic area and the surrounding regions. However, to utilize the original GOCE SGG data for geoid modeling, filtering is needed as well as a reduction to a mean orbit (MO) so that downward continuation to the Earth’s surface (ES) can be realized. After investigating various filtering options (Finite Impulse Response - FIR, Infinite Impulse Response - IIR, and wavelet multi-resolution analysis - MRA), both in the frequency and the space domain, it was concluded that an FIR with order 1500 would be the optimal one. This was based on both comparisons with upward continued gradients from the XGM2019 global geopotential model (GGM) and the spectrum cut-off of the various filters tested within the GOCE measuring bandwidth. Then, downward continuation of the filtered data to a mean sphere (MS) was necessary. With a maximum altitude, within the GOCE 3-year mission, close to 295 km and a minimum of about 240km, GOCE data generated at a mean level of 230 km. Regular 5’x5’ grids of the disturbing potential gradients Tij were generated using both XGM2190 and EGM2008 up to their maximum degree and order, while a combined solution using TIM-R6 to degree and order 165 and EGM2008 as fill-in was also used. The GGM information was used to simulate the downward continuation of Tij, so that this can then be applied to the actual GOCE data. The reduction to a MS was performed by estimating GGM gradient grids per 1 km from the MS to the maximum orbital level, and then using a linear interpolation for the reduction from the actual satellite height. It was found that the reduction with height of the gravity gradients varies linearly, while the use of XGM2019 provided the overall best results. After interpolating from the GGM grids, Tij values from XGM were estimated at the initial GOCE points and then used to reduce the GOCE SGGs to the MO. Finally, and in order to estimate residual Tij at the MO, three different options were tested. First, an analytical spherical harmonic synthesis (SHS) of and  at 230km was carried out. Then, the same effects were estimated using a grid of 1’x1’ disturbing potential gradients as well as a 5’x5’ grid. For each of these cases, the rigorous SHS and the two based on interpolation have been determined, showing that even a global 5’x5’ grid of disturbing potential gradients is sufficient and analytical determination of the GGM contribution is not necessary.
Two Spacecraft, Four Flythroughs: Magnetometer Measurements by BepiColombo and Solar Orbiter in the Induced Magnetotail of Venus
Authors: Volwerk Martin ,   The VenusMagTeam
Published: March 2022

In 2020 and 2021 both BepiColombo and Solar Orbiter used Venus for a gravity assist in order to reach Mercury and to finally get into the correct orbit around the Sun, respectively. These flybys were the first since Mariner 10 to sample a long stretch, more than 30 Venus radii of the induced magnetotail of Venus. This brought the opportunity to study the structure and dynamics of the tail during different solar wind conditions. On this poster we will discuss the differences and also the similarities (even though the four flybys took different trajectories through the induced magnetotail) using the magnetometers on both spacecraft. Field line draping, magnetic reconnection, and plasma waves will all pass by on stage.
Differentiating lightning in winter and summer with characteristics of wind field and mass field
Authors: Morgenstern Deborah , Stucke Isabell , Simon Thorsten , Mayr Georg J. , Zeileis Achim
Published: March 2022

Lightning in winter (December, January, February, DJF) is rare compared to lightning in summer (June, July, August, JJA) in central Europe. The conventional explanation attributes the scarcity of winter lightning to seasonally low values of variables that create favorable conditions in summer. Here we systematically examine whether different meteorological processes are at play in winter. We use cluster analysis and principal component analysis and find physically meaningful groups in ERA5 atmospheric reanalysis data and lightning data for northern Germany. Two sets of conditions emerged: Wind-field dominated and mass-field (temperature) dominated lightning conditions. Wind-field type lightning is characterized by increased wind speeds, high cloud shear, large dissipation of kinetic energy in the boundary layer, and moderate temperatures. Clouds are close to the ground and a relatively large fraction of the clouds is warmer than −10 degree Celsius. Mass-field type lightning is characterized by increased convective available potential energy (CAPE), the presence of convective inhibition (CIN), high temperatures, and accompanying large amounts of water vapor. Large amounts of cloud-physics variables related to charge separation such as ice particles and solid hydrometeors further differentiate both mass-field and wind-field lightning. Winter lightning is wind-field driven whereas in summer lightning is mostly mass-field driven with a small fraction of cases being wind-field driven. Consequently, typical weather situations for wind-field lightning in the study area in northern Germany are strong westerlies with embedded cyclones. For mass-field lightning, the area is typically on the anticyclonic side of a southwesterly jet.

Keywords: ERA5, cold-season thunderstorm, k-means clustering, winter lightning.
Thermal convection in a three-layered air-heat-generating porous-air system with internal heat source depending on solid volume fraction
Authors: Kolchanova Ekaterina , Kolchanov Nikolay
Published: March 2022

We explore the convective instability in a vertically three-layered system that consists of a heat-generating porous sublayer sandwiched between two air sublayers in the gravitational field. The heat source strength in the porous sublayer depends on solid volume fraction linearly. This fundamental study is motivated by the analysis of natural convective air ventilation in the storage aria of agricultural raw materials. The materials make up a porous matrix generating heat due to its biological activity. The heat release strength is proportional to the density of their bulk. To maintain an optimal thermal regime in the storage aria, one should remove heat from the overheated parts of materials timely. The passive convective flow can be controlled by the additional air sublayers with the required depth. In our research we focus on the solid volume fraction and depth ratio effects on the convection onset and scale of convective flows.

The three-layered system under consideration is bounded by the impermeable thermally conductive plates with equal constant temperatures. So, flows can arise because of heat release that induces non-uniform thermal profile across the sublayers. We apply a linear stability theory to find the threshold internal Rayleigh-Darcy number for the onset of convection. This similarity criterion is defined through heat source strength in the porous sublayer. The numerical simulation is performed by the shooting method.

It has been shown that marginal stability curves in the three-layered system as well as those in the two-layered system have two minima, i.e. they are bimodal. Either a large-scale convective flow or a local one may generate immediately after the motionless air state has lost its stability. The former penetrates into the porous medium while the latter forms within the upper air sublayer only, where temperature gradient is destabilizing. It has been found that the onset value of both types of flows reduces with increasing a relative depth of the air sublayer. This reduction is accompanied by a transition from the large-scale to local convection. The observed enhancement of convection turns out to be more effective in the three-layered system as compared to that of the system made up of two sublayers. The solid volume fraction demonstrates a similar effect on the convection onset and wavelength of the convective flows induced. Despite the compaction of porous medium due to the growth of solid volume fraction, the onset value decreases and the motionless air state destabilizes. It can be explained by the fact that heat release strengths with increasing solid volume fraction.

The work was supported by the Russian Science Foundation (Grant No. 21-71-10045), https://rscf.ru/en/project/21-71-10045/.