bluuebunny/crossref_metadata_2025 huggingface dataset:
Whether enzyme activity is the same in different soil pores
Authors: Kravchenko Alexandra , Guber Andrey
Published: March 2021

Soil microorganisms preferably occupy intermediate-sized pores, which are the arena for most biochemical reactions due to high nutrient contents and beneficial air and water regimes in these pores. Extracellular enzymes produced by microorganisms for organic matter transformations are assumed to reside in the same pores. However, there is a lack of direct experimental evidence of enzymatic activity being associated with pores of particular sizes. In this study we measured activity of ß-glucosidase in soil pores Ø<14 μm, 14<Ø<164 μm and Ø<164 μm. Undisturbed soil cores (5 cm Ø, 5 cm height) were taken at continuous sorghum (G2), switchgrass (G5) and restored prairie (G10) treatments of KBS Great Lakes Bioenergy Research Center's Biofuel Cropping System Experiment. Soil cores were drained at 500 kPa, and undisturbed subsamples (0.8 cm Ø, 1 cm height) were taken from them and placed at ceramic plates connected to a vacuum system. The same quantities of 4-Methylumbelliferyl β-D-glucoside were applied to soil subsamples at vacuum corresponded to saturation of the three studied groups of pores and kept in soil for 30 min. Produced 4-methylumbelliferone (MUF) was then extracted from the soil. The results demonstrated that the enzyme activity increased in all groups of pores in the order G2<G5<G10, but was significantly different only between G2 and G10 treatments for Ø<14 μm pores (p<0.05). The enzyme activity was lower in Ø<14 μm pores than in the 14<Ø<164 and Ø<164 μm pores (p<0.05), with only numerically higher activity in Ø<164 μm compared to the 14<Ø<164 μm pores. Interconnectivity of pores drained at different matrix pressures likely results in an overestimation of the enzyme activity associated with Ø<14 μm pores and an underestimation of that associated with 14<Ø<164 μm pores, hence the observed differences among the pore sizes are likely smaller than the actual pore effects. Thus, the results support our earlier observations and confirm that the activity of extracellular enzymes is higher within intermediate-sized pores than within fine pores. Support for this research was provided by the USDA NIFA Program (Award # 2019-67019-29361), by the NSF LTER Program (DEB 1027253) at the Kellogg Biological Station, by USDA NC1187 project, by the Great Lakes Bioenergy Research Center, U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research under Award Number DE-SC0018409.
Impacts of human intervention through irrigation on hydrological responses of Lake Tana sub-basin, upper Blue Nile, Ethiopia.
Authors: Taye Meron Teferi , Haile Alemseged Tamiru
Published: March 2021

Lake water balance studies in Ethiopia are commonly conducted for natural conditions without considering the impact of water abstraction. However, hydrological changes are a function of changes caused by human interventions as much as through natural processes. The Lake Tana sub-basin is one of the important basins in Ethiopia as the source of the Blue Nile river and supporter of various livelihoods including considerable number of small-scale farmers. With Ethiopia’s ambitious plan to expand irrigation at different scales to feed the growing population, the Lake Tana sub-basin is one of the selected areas by the federal government for medium scale irrigation. Moreover, the basin is experiencing booming small-scale irrigation users due to initiations by local governments, NGOs and individual farmers. Small-scale community managed irrigation schemes and farmer-led irrigations schemes are common in the basin. While communities are expected to benefit from the expanding irrigation use, there is limited information on how this irrigation expansion impacts the water balance of the sub-basin.

In this study the area under small-scale irrigation is estimated through inventory survey of woredas (districts) that are within the Lake Tana sub-basin and cover the four main tributaries (Gilgel Abay, Ribb, Gumara, and Megech).  The inventory from 16 woredas showed more than 30,000 ha is under small-scale irrigation in the Lake Tana sub-basin in 2020. The dominant water source for irrigation is found to be surface water through diversion from rivers and streams. This accounts for 80% of irrigation water source. The other 20% comes from shallow groundwater sources, which are mainly located in the eastern part of the sub-basin in the floodplain in the Fogera area.

This study investigates the current situation of irrigation water abstraction through water abstraction surveys in selected locations in the dry-season and evaluates the impact of water abstraction on the long-term water balance of the sub-basin. Previous studies indicate that Gilgel Abay sub-basin, for instance, shows a decreasing dry season flow in the past decades, which might be associated with dry season water abstraction. The current survey provides the gross diversion of water from rivers to canals in the selected schemes. Preliminary results show large amount of water is being diverted by medium irrigation schemes but also collectively by small-scale irrigation schemes. Continuation of such water abstraction levels will be a concern to the water balance of the sub-basin as it increases losses without productive use and calls for better water management practices. 
Modelling future evolution of glaciation in the Central Caucasus
Authors: Dymova Taisiya , Rybak Oleg , Zekollary Harry , Huss Matthias , Korneva Irina , Gubanov Afanasy , Nosenko Gennady
Published: March 2021

The retreat of glaciers of the Greater Caucasus in the second half of the 20th and early 21st centuries was recorded by a variety of methods, including both direct instrumental observations and remote sensing. It is natural to expect that in the conditions of a gradually warming climate, the general trend of glacier retreat will continue in the future.

In the foothills of the North Caucasus, an important agricultural region, the problem of expected changes in mountain glaciation is particularly acute, since fluctuations in the flow regime of local rivers depend on the evolution of glaciers: the contribution of glacial runoff to total discharge is very significant. Retreating glaciers can also cause lakes to appear in local depressions in the underlying relief. Their possible breakthrough could cause significant damage to the economy and threaten human lives. The forecast of runoff and lake formation are associated with the projections on the future state of mountain glaciation.

Here, we present the work in progress to assess the rate of future glacier change in the Central Caucasus throughout the 21st century. The aim is to determine how the characteristics of mountain glaciation (its area, volume, position of the glacier fronts) of the Central Caucasus will change, depending on the climate scenario. In order to accomplish this goal, we use the GloGEMflow model (Zekollari et al., 2019) with an updated radiation block (Rybak et al., 2021, in press) and a set of CMIP5/CMIP6 climate scenarios. The GloGEMflow model features an ice flow block which is calibrated to match the Huss & Farinotti (2012, updated to RGI6.0) glacier geometry data. Validation of the model is based on the assessment of discrepancies arising when comparing data about glaciers boundaries changes for the period from ~2000 (RGI6.0) to 2018 (Department of Glaciology RAS).

The reported study was funded by RFBR and RS, project number 21-55-100003.
Seismic imaging with focusing surface waves obtained from USArray noise correlation functions
Authors: Tsarsitalidou Christina , Boué Pierre , Hillers Gregor , Giammarinaro Bruno , Campillo Michel , Seydoux Leonard , Stehly Laurent
Published: March 2021

Dense seismic arrays are equivalent to medical ultrasound transducers in the sense that both “devices” allow the reconstruction of refocusing wave fields at near-field distances. In this work we explore the imaging potential of refocusing surface waves constructed from USArray noise correlation functions using sensors located between the US west coast and -90 degrees West. So-called focal spots---a term adopted from elastography---are constructed from the noise correlation amplitude field at zero lag time around the origin, i.e., each sensor in the array. Similar to the related SPAC method, properties of the Bessel-function-shaped focal spot are controlled by the local medium properties, which underpins the local imaging approach. Unlike USArray SPAC applications in the 5 – 40 s period range, however, we proceed in the spirit of elastographic local measurements and demonstrate the possibility to estimate properties of Rayleigh wave propagation between 80 – 300 s period using the vertical-vertical and vertical-radial focal spot components of the Green’s tensor. Clearly, the up to five-fold extension of the period range compared to noise- based USArray surface wave tomography studies are an intriguing asset of the approach that suggests a significantly increased depth resolution. In addition to demonstrating the general applicability of the focal spot method using dense array data, we address the biasing effects of less-than-ideal ambient wave field properties on our measurements. Impinging body wave energy and non- isotropic surface wave energy flux contribute to focal spot shapes and properties that are not compatible with the theoretical assumptions and used model functions and parametrizations. We show the space and period dependent distributions of these biasing components based on the focal spot representation in the wave number domain. Numerical and theoretical work discussed in an accompanying abstract is used to assess the impact on the dispersion measurements, and to test the effectiveness of filtering strategies for making improved estimates.
Mapping and dynamic analysis of faults in the Hengill volcanic area, SW-Iceland 
Authors: Blanck Hanna , Vogfjörd Kristín , Geirsson Halldór , Hjörleifsdóttir Vala
Published: March 2021

From 1993 to 1998, the Hengill volcanic area in SW-Iceland was subjected to a volcano-tectonic event which caused a local uplift of the crust of 8 cm and triggered over 90.000 earthquakes. Relocating a sub-set of 12.000 earthquakes in the direct vicinity of the uplift centre improved resolution and enabled the mapping of 25, mostly NNE-SSW and ENE-WSW oriented sub-vertical groups of earthquake which are interpreted as faults. Focal mechanisms were calculated, using the best fitting plane through a group of earthquakes as additional constraint. Slip on the interpreted faults could be estimated averaging slip of all earthquakes within that group. Most faults show strike-slip movement with a small normal component. Right-lateral slip prevails. We modelled Coulomb stress changes that the uplift would have caused and compared them to out results. The Coulomb stress changes can only explain the observed movement on some of the faults but on others fault movements is impeded, that is, the Coulomb stress change is negative. Varying the location of the uplift within its error margin increases the number of faults on which the observed movement is promoted but the slip on a number of faults remains unexplained.  
Thermal controls on the development of fractures in dolostones of the Niagara Escarpment, Hamilton, Ontario, Canada
Authors: Gage Henry , Eyles Carolyn , Lee Rebecca
Published: March 2021

Little research has been conducted to clarify the mechanism, extent, or factors involved in the fracturing of rocks exposed along the Niagara Escarpment in Ontario. Of particular interest are the effects of fluctuating temperatures during region’s cold winters which may be a contributor to the formation and expansion of fractures within these rocks. The results of a preliminary field-based study of temperature changes in fractured sedimentary rocks exposed at several sites along the Escarpment in Hamilton, Ontario are reported here. The objectives of the study were to examine the characteristics of operant thermal processes and to determine the effectiveness of mechanisms such as freeze-thaw and thermal stress in contributing to fracture formation and development. Fractured dolostone units were identified at three field sites along the escarpment that varied in their aspect, vegetation, and proximity to water. At each site, temperature probes were affixed to the exposed rock surface and inserted into a nearby fracture. Temperature measurements were taken at one-minute intervals throughout the winter of 2020-21.  In-situ field measurements of thermal changes within fractured dolostones on the escarpment were supplemented with recordings of rock surface and interior temperatures taken from unfractured dolostone blocks placed in a ‘controlled’ outdoor environment throughout the winter.  Initial results from the escarpment probes in the early winter show frequent, rapid shifts from warm to sub-zero temperatures and indicate that changes in temperature recorded at the rock surface closely follow diurnal atmospheric oscillations in both magnitude and timing.  However, temperature changes recorded within fractures are less extreme and show a temporal lag. Temperature fluctuations recorded at the field site with the highest degree of exposure, a southeasterly aspect, and little vegetation cover, are significantly higher and show larger thermal responses within fractures. Temperature fluctuations recorded from unfractured blocks in the ‘controlled’ outdoor environment show similar diurnal trends to those recorded on the escarpment but with reduced differential between temperatures at the block surface and interior. Together, these data indicate that temperature fluctuations sufficient to generate freeze-thaw cycles are abundant during the early winter months, temperature variability within fractures does occur, and slope aspect and exposure plays an important role in the determining the magnitude of diurnal temperature fluctuations experienced by surface rocks on the escarpment. The role of thermal stress in fracture development, created by rapid and substantial thermal changes, has yet to be determined.  
Towards a coastal marine litter observatory with combination of drone imagery, artificial intelligence, and citizen science
Authors: Topouzelis Konstantinos , Papakonstantinou Apostolos , Batsaris Marios , Moutzouris Ioannis , Spondylidis Spyros , Moustakas Argyris
Published: March 2021

The presence of plastic litters in the coastal zone has been recognized as a significant problem. It can dramatically affect flora and fauna and lead to severe economic impacts on coastal communities, tourism and fishing industries. Traditional beach litter reports include individual transects on the beach, reporting on the litter's presence through a dedicated measuring protocol. In the new era of drone imagery, a new integrated coastal marine litter observatory is proposed. This observatory is based on aerial images acquired through citizen science using low cost self-owned drones and the automatic identification of litter accumulation zones through computer vision. The methodology consists of four steps: i) a dedicated protocol for acquiring drone imagery from non-experienced citizens using commercial drones, ii) image pre-processing (image tiling and geo-enrichment) and crowdsourced annotation, iii) data classification to litter and no litter though an artificial intelligence classification approach and iv) marine litter density maps creation and reporting. The resulted density maps currently are produced calculating the tiles containing litter at areas of hundred square meters on the beach and the entire process requires some minutes to run once the aerial data is uploaded online. The density maps automatically are reported to a spatial data infrastructure, ideal for time series analysis. Classification accuracy calculated against manual identification of 77.6%. The coastal marine litter observatory presents several benefits against traditional reporting methods, i.e. improved measurement of the policies against plastic pollution, validating marine litter transportation models, monitoring the SDG Indicator 14.1.1, and most important, guiding the cleaning efforts towards areas with a significant amount of litter.
Dynamics of the Martian bow shock location
Authors: Garnier Philippe , Jacquey Christian , Génot Vincent , Sanchez-Cano Beatriz , Gendre Xavier , Mazelle Christian , Fang Xiaohua , Gruesbeck Jacob R , Hall Benjamin , Halekas Jasper S , Jakosky Bruce M
Published: March 2021

The Martian interaction with the solar wind is unique due to the influence of multiple internal and external drivers, including remanent crustal magnetic fields that make the interaction unique. In this work we focus on the analysis of the dynamics of the plasma boundaries that shape the interaction of the planet with its environment, and in particular of the shock whose location varies in a complex way. We use multi spacecraft datasets from three missions (Mars Global Surveyor, Mars Express, Mars Atm-osphere and Volatile Evolution) to provide a coherent picture of the shock drivers. We show how the use of different statistical parameters or cross correlations may modify conclusions. We thus propose the use of refined methods, such as partial correlation analysis or Akaike Information Criterion approach to analyse the multiple drivers of the shock location and rank their relative importance: solar wind dynamic pressure, extreme ultraviolet fluxes, magnetosonic mach number, crustal magnetic fields, but also solar wind orientation parameters. Seasonal effects of crustal fields on the shock, through ionospheric coupling, are also investigated.
Prospects of real time tsunami inundation estimates with TsunAWI - Studies in the LEXIS project 
Authors: Rakowsky Natalja , Goubier Thierry , Harig Sven
Published: March 2021

Based on the shallow water equations,the tsunami wave propagation in the deep ocean and an assessment of the wave height at the coast can easily
be simulated online during an event. To simulate the estimated inundation, however, poses higher demands on model physics and mesh
resolution. Whereas in the deep ocean, a simple balance between pressure gradient force and acceleration is sufficient for first estimates of the
wave propagation, additional nonlinear factors like bottom friction and momentum advection gain importance close to the coast.

For a seamless simulation of the transition from wave propagation to inundation, the finite element model TsunAWI has been developed as part
of the efforts within the GITEWS project (German Indonesian Tsunami Early Warning System) and in the meantime, the code has evolved
considerably with applications in several projects. The triangular mesh approach allows for large freedom in the resolution of coastline and
bathymetric features, however is also numerically demanding. In the ongoing EU-project LEXIS (Large-scale Execution for Industry & Society),
the simulation of earthquake and tsunami events is one of the pilot study cases and on the tsunami side puts focus on the optimization of
TsunAWI on modern HPC architectures.

Targeting FPGAs, an accelerator for TsunAWI is being designed. It relies on a software-distributed shared memory (S-DSM) allowing sharing
of the memory between distributed nodes and the accelerator(s), and is showing that TsunAWI optimisations, namely single precision and
unstructured mesh traversal, are key elements to reach high performance and efficiency.

For HPC systems, an MPI parallelization was implemented, based on domain
decomposition. The MPI parallel code shows good scaling, making high
resolution simulations feasible during an event.

The developments are evaluated in simulations of tsunami inundation in
hypothetical and real events in Indonesia and Chile. It turns out that
the optimized approach allows for improved fast estimates of the tsunami
impact in the application cases.
Importance of mosses and vascular plants in peat soil carbon sequestration
Authors: Kasimir Åsa , Jansson Per-Erik
Published: March 2021

Nutrient rich peat soils have earlier been shown to loose carbon despite higher photosynthesis and litter production compared to nutrient poor soils, where instead carbon accumulated. To understand this phenomena data from two drained Finnish sites, nutrient poor Kalevansuo and nutrient rich Lettosuo, was combined with a process-oriented model (CoupModel). Uncertainty based calibrations were made using eddy-covariance data (hourly values of net ecosystem exchange) and tree growth data. The model design was three vegetation layers: trees, smaller vascular plants and a bottom layer with mosses, all with different LAI and degree of coverage. Adding a moss layer was a new approach, having a modified physiology compared to vascular plants. Soil organic carbon was described by two separate litter pools for vascular plants and mosses together with a common inert pool of decomposed organic matter. Over a period of 10 years the model showed similar photosynthesis rate for the two sites but higher biomass accumulation for the fertile stand. Moss biomass did not increase, instead mosses delivered high litter inputs with low turnover rates compared with litter from vascular plants. Both the soil organic carbon received from vascular plant litter and the old decomposed matter declined by time, while litter originating from mosses was accumulating by time. Large differences between the sites were obtained during dry spells where soil heterotrophic decomposition was enhanced in the vascular plants dominated site, due to a larger water depletion by roots. Important for carbon accumulation in the poor soil was the mosses, adding larger litter quantities with a resistant quality together with less water depletion in dry spells.

This project was funded by the Swedish Research Council FORMAS, the Research Council of Norway (MYR-project), and the Swedish strategic research area BECC.
Investigations on spatial and vertical variations of airborne pollen in Sydney, Australia
Authors: Jetschni Johanna , Al Kouba Jane , Beggs Paul J. , Jochner-Oette Susanne
Published: March 2021

The prevalence of pollen allergy is increasing worldwide, as is the proportion of people living in cities. Thus, there is an increasing importance to investigate pollen distribution across city districts. We conducted two sampling campaigns to investigate the spatial and temporal variation of airborne pollen in the Sydney metropolitan area and the vertical variation within a forest in north-western Sydney.

Spatial assessment of pollen deposition was made for eight weeks in the exceptionally dry summer in 2019/2020 using gravimetric samplers. These samplers were set up at ten locations characterised by different degrees of urbanisation and distance to the sea. We focussed on the most abundant pollen types and investigated statistical relationships with land use and meteorology. In addition, we compared our results with pollen data of previous years sampled at a pollen monitoring station located in north-western Sydney in a semi-rural environment. We measured vertical pollen concentrations in a native forest, which mostly consists of Eucalypt trees (family Myrtaceae) in north-western Sydney. A scaffolding was equipped with five portable volumetric pollen samplers installed at different heights (1, 4, 10, 16, 20.5 m above ground level (agl)). We measured pollen concentration every second hour between 9 am and 4 pm on a total of four days in January 2020. We compared concentrations between days, heights, and times of the day.

The most abundant pollen type registered within our sampling campaigns belonged to the family Myrtaceae. Grass pollen (Poaceae) was also detected, but in much smaller quantities which can be attributed to the drought and temporal setting of the campaign, which started in the post-peak period of a comparably weak pollen season associated with a smaller number of days with medical relevance (> 50 pollen grains/m3). Our data showed spatial variations between the ten locations, but no relationship with land use (grass and tree cover) and meteorology could be found. This suggests the influence of other factors such as long-range pollen transport or resuspension of pollen. In the forest, Myrtaceae concentrations varied between days, sampling height and time of the day: the highest concentration was recorded on the second day of measurement between 9 and 10 am at 10 m agl. Peak values were generally reached between 1 and 2 pm. Considering sampling height, concentrations were on average highest at 4 m agl. The location of pollen sources as well as meteorological conditions such as turbulence and variation in wind speed may be key determinants of small-scale differences of pollen concentrations.

The drought preceding this study did not only influence the length but also the strength of the pollen season. Data on vertical variations could support investigations related to turbulence, which is also responsible for resuspension processes.
Extreme events at historical time-scales: are they visible in the paleoenvironmental records?
Authors: Izdebski Adam
Published: March 2021

To a large extent, the temporal definition of an extreme event depends on the context and the level of analysis that we are able to deploy. It should be massive and concentrated compared to the challenges a system is facing on everyday basis, it should provide a shock, and it should require major efforts to absorb its impacts. On historical timescales, extreme events happen over hours, days, months, at the longest, years. Compared to the process through which environmental archives develop, these are very short timescales, possibly with no chance of being recorded in the sediments. However, if we consider that an extreme event should have massive impacts, and these should be last for longer than the event itself, there is a good chance we could actually observe the environmental change associated with the extreme event in the sediments.

In my talk, I will look at two plague pandemics – the first, 6th-8th c. AD, and the second, 14th-18th c. AD – and their initial outbreaks (known as the Justinianic Plague and the Black Death) in order to see their reflection in the sediments throughout Europe and the Mediterranean, primarily in the pollen data. As I will demonstrate, in some cases the impact was minimal, barely visible, while in others it was indeed massive. This will bring me back to the definition of the extreme event: is it possible to have an extreme event that did not have any impact? Can the same event – the spread of a new pathogen, in our case – become extreme in one social-geographical context and not in another?
Delineation of soil drainage class by electromagnetically measurements of soil magnetic susceptibility
Authors: Shirzaditabar Farzad , Heck Richard , Catalano Mike
Published: March 2021

Soil has the most important role in agriculture. For instance, it prevents run off and also through its capacity for storing water, it acts as a water reservoir and provide water resources for plant roots. Water retention characteristics, nutrient holding capacities and solute transport of soil can affect its productivity. So, the plant growth is directly associated with the type of soil drainage. The prediction of soil drainage classes is one of the major steps in developing crop modelling. Among different physical and chemical soil health indicators, soil magnetic susceptibility (MS) is a promising factor for soil surveying because it is strongly affected by soil drainage class. The extremely reducing conditions, present in hydric soils, significantly enhance dissolution of soil ferrimagnetic minerals such as magnetite and maghemite. Since the MS of soils is mainly controlled by magnetite and maghemite concentrations, therefore MS values are typically very low in hydric, i.e. poorly drained or gleyed, soils.

The common method for measuring soil MS is utilizing handheld or laboratory MS meters (e.g. Bartington MS2 sensors). Such MS meters are required soil specimen to be available to directly measure MS of that specimen. So, their application is limited to surface soils, soil exposures and sampled soils. Other types of instruments for quickly measuring soil properties are electromagnetic induction (EMI) instruments. Although the EMI instruments were primarily invented to measure electrical conductivity (EC) of the topsoil for assessment of soil salinity, they can also be utilized to measure absolute value of the volume MS of the topsoil. These volume MS values can be further processed and inverted to reveal MS variations of soil layers.

In this study, 1-D inversion of volume MS data, measured by Geonics EM38 instrument in both vertical and horizontal magnetic dipole configurations, was done to calculate MS of selected soil profiles in order to delineate soil drainage classes. Besides, laboratory measurements of volume and mass-specific MS of soil core samples, collected in the same soil profiles, were done using Bartington MS2B and MS2C sensors. Results show a strong and positive relationship between MS values measured in the laboratory and volume MS recovered from inversion technique. Furthermore, the results reveal that MS in a well drained profile is higher than that of a poorly drained profile. Since EMI measurements of soil MS are done quickly in the field, then using surface MS measurements facilitates hydric soil delineation in a faster and more precise way.
The contribution of melt ponds to enhanced Arctic sea-ice melt during the Last Interglacial
Authors: Diamond Rachel , Sime Louise , Schroeder David , Guarino Maria-Vittoria
Published: March 2021

HadGEM3 is the first coupled climate model to simulate an ice-free Arctic during the Last Interglacial (LIG), 127 000 years ago. This simulation appears to yield accurate Arctic surface temperatures during the summer season. Here, we investigate the causes and impacts of this extreme simulated ice loss. We find that the summer ice melt is predominantly driven by thermodynamic processes: atmospheric and ocean circulation changes do not significantly contribute to the ice loss. We demonstrate these thermodynamic processes are significantly impacted by melt ponds, which form on average 8 days earlier during the LIG than during the pre-industrial control (PI) simulation. This relatively small difference significantly changes the LIG surface energy balance, and strengthens the albedo feedback. Compared to the PI simulation: in mid-June, of the absorbed flux at the surface over ice-covered cells (ice concentration>0.15), ponds account for 45-50%, open water 45%, and bare ice and snow 5-10%. We show that the simulated ice loss leads to large Arctic sea surface salinity and temperature changes. The sea surface temperature and salinity signals we identify here provide a means to verify, in marine observations, if and when an ice-free Arctic occurred during the LIG. Strong LIG correlations between spring melt pond and summer ice area indicate that, as Arctic ice continues to thin in future, the spring melt pond area will likely become an increasingly reliable predictor of the September sea-ice area. Finally, we note that models with explicitly modelled melt ponds seem to simulate particularly low LIG sea-ice extent. These results show that models with explicit (as opposed to parameterised) melt ponds can simulate very different sea-ice behaviour under forcings other than the present-day. This is of concern for future projections of sea-ice loss.
Abel transform of exponential functions for planetary and cometary atmospheres with application to observation of 46P/Wirtanen and to the OI 557.7 nm emission at Mars.
Authors: Hubert Benoit , Munhoven Guy , Moulane Youssef , Hutsemekers Damien , Manfroid Jean , Opitom Cyrielle , Jehin Emmanuel , Aoki Shohei , Soret Lauriane , Gkouvelis Leonardos , Gérard Jean-Claude
Published: March 2021

Line-of-sight integration of emissions from planetary and cometary atmospheres is the Abel transform of the emission rate, under the spherical symmetry assumption. Indefinite integrals constructed from the Abel transform integral are useful for implementing remote sensing data analysis methods, such as the numerical inverse Abel transform giving the volume emission rate compatible with the observation. We obtain analytical expressions based on a suitable, non-alternating, series development to compute those indefinite integrals. We establish expressions allowing absolute accuracy control of the convergence of these series depending on the number of terms involved. We compare the analytical method with numerical computation techniques, which are found to be sufficiently accurate as well. Inverse Abel transform fitting is then tested in order to establish that the expected emission rate profiles can be retrieved from the observation of both planetary and cometary atmospheres. We show that the method is robust, especially when Tikhonov regularization is included, although it must be carefully tuned when the observation varies across many orders of magnitude. A first application is conducted over observation of comet 46P/Wirtanen, showing some variability possibly attributable to an evolution of the contamination by dust and icy grains. A second application is considered to deduce the 557.7 nm volume emission rate profile of the metastable oxygen atom in the upper atmosphere of planet Mars.
Electrojet estimates from mesospheric magnetic field measurements
Authors: Laundal Karl , Yee Jeng-Hwa , Gjerloev Jesper , Vanhamäki Heikki , Reistad Jone , Madelaire Michael , Sorathia Kareem
Published: March 2021

The auroral electrojet is traditionally measured remotely with magnetometers on ground or in low Earth orbit (LEO). The sparse spatial coverage of measurements, combined with a vertical distance (~100 km to ground and typically >300 km to LEO satellites) means that smaller scale sizes cannot be detected.  Because of this, our understanding of the spatiotemporal characteristics of the electrojet is incomplete. Recent advances in measurement technology allow us to overcome these limitations by multi-point remote detections of the magnetic field in the mesosphere, very close to the electrojet. We present a theoretical prediction of the magnitude of these disturbances, inferred from the spatiotemporal characteristics of magnetic field-aligned currents. We further discuss how the Electrojet Zeeman Imaging Explorer (EZIE) satellites that will carry Zeeman magnetic field sensors will be used to essentially image the equivalent current at unprecedented spatial resolution.  The electrojet imaging is demonstrated by combining carefully simulated measurements with a spherical elementary current representation using a novel inversion scheme.  This new capability will allow us to finally resolve long-standing controversies such as – what is the substorm current wedge configuration?
Combined use of Raman Lidar and DIAL measurements and MESO-NH model simulations for the characterization of complex water vapour field structures, their genesis and their role in the activation of Mesoscale Convective Systems
Authors: Di Girolamo Paolo , Bouin Marie-Noelle , Flamant Cyrille , Summa Donato , De Rosa Benedetto , Franco Noemi
Published: March 2021

As part of the Cevennes-Vivarais site, the University of Basilicata Raman lidar system BASIL (Di Girolamo et al., 2009, 2012, 2916) was deployed in Candillargues (Cévennes-Vivarais Southern France Lat: 43°37′ N; Long: 04°04′ E; Elev: 1 m) and operated throughout the duration of HyMeX-SOP 1 (September-November 2012), providing high-resolution and accurate measurements, both in daytime and night-time, of atmospheric temperature, water vapour mixing ratio and particle backscattering and extinction coefficient at three wavelengths.

Measurements carried out by BASIL on 28 September 2012 reveal a water vapour field characterized by a quite complex vertical structure. Reported measurements were run in the time interval between two consecutive heavy precipitation events, from 15:30 UTC on 28 September to 03:30 UTC on 29 September 2012. Throughout most of this observation period, lidar measurements reveal the presence of four distinct humidity layers.

The present research effort aims at assessing the origin and transport path of the different humidity filaments observed by BASIL on this day. The analysis approach relies on the comparison between Raman lidar measurements and MESO-NH and NOAA-HYSPLIT model simulations. Back-trajectory analyses from MESO-NH reveal that air masses ending in Candillargues at different altitudes levels are coming and are originated from different geographical regions.

The four distinct humidity layers observed by BASIL are also identified in the water vapour mixing ratio profiles collected by the air-borne DIAL LEANDRE 2 on-board of the French research aircraft ATR42. The exact correspondence, in terms of back-trajectories computation and water budget, between the humidity layers observed by BASIL and those identified in LEANDRE2 measurements has been verified based on a dedicated simulation effort.

In this research work we also try to identify the presence of dry layers and cold pools and assess their role in the genesis of the mesoscale convective systems and the heavy precipitation events observed on 29 September 2012 based on the combined use of water vapour mixing ratio and temperature profile measurements from BASIL and water vapour mixing ratio profile measurements from LEANDRE 2, again supported by MESO-NH simulations.
Uncertainties in the variation of compound dry and hot events due to differences in drought indices
Authors: Feng Sifang , Hao Zengchao
Published: March 2021

Compound dry and hot events (CDHEs) are commonly defined as the concurrent or consecutive occurrences of the two events, which could lead to larger negative impacts than do individual extremes. The variation of CDHEs has gained increased attention in the past decades. Previous studies have detected changes in the frequency, duration, and spatial extent at regional and global scales based on observations and model simulations. However, these studies mainly focus on a single drought indicator. In the past decades, different drought indicators have been applied to characterize drought conditions, such as Standardized Precipitation Index (SPI), and Standardized Precipitation-Evapotranspiration Index (SPEI), and Palmer Drought Severity Index (PDSI). Due to the difference in these drought indicators in characterizing droughts, evaluation of CDHEs based on different drought indices may lead to a different magnitude of changes (or even opposite direction of changes). However, quantitative analysis of the uncertainties in the variation of CDHEs is still lacking. In this study, we quantitatively evaluate the uncertainties of CDHEs variations ove global areas due to differences in drought indices. Results from this study could further our understanding of changes in CDHEs under global warming.
Extending the paleo-tsunami record along the west coast of Sumatra, Indonesia
Authors: Majewski Jędrzej , Daly Patrick , Switzer Adam , Ismail Nazli , Afrizal Tomi , Horton Benjamin
Published: March 2021

The 2004 Indian Ocean Tsunami tragically underscored the practical implication of understanding the Sumatran subduction zone and its tsunami potential. Further paleo-tsunami research is needed to fully inform the assessment of future tsunami hazards for coastal regions of the Indian Ocean. However, the Covid-19 pandemic has severely limited the ability of many international teams to conduct field investigations of paleo-tsunami sites in Southeast Asia. In collaboration between Syiah Kuala University in Indonesia and Nanyang Technological University in Singapore our team has been investigating the paleo-tsunami history of Sumatra for more than 10 years. This year, in order to facilitate training of junior staff at Syiah Kuala University we recorded a number of coring, sampling and sediment description videos combined with virtual workshops. Written material, as well as regular meetings via zoom, have made co-ordination of fieldwork possible. We also uploaded all data to cloud services immediately following fieldwork to allow everyone in the project to have access to it quickly. This data now consists of more than 500 photographs, field description files, and field reports.

Previously our efforts have concentrated along the northern half of the Aceh province, which was devastated by the 2004 Indian Ocean Tsunami. Over the past 12 months, we have extended our field research ~250 km southwards along the western coastline of Sumatra. Despite the pandemic, we have been able to investigate 4 new coastal wetland sites and identify between 1 and 5 potential paleo-tsunami layers at each site at depths of 1.7 to 4.5 m. More than 50 samples of the sediments have been sampled and are currently being analyzed to confirm their marine origin and the chronology of the events they represent.
From poorly-ordered precursors to crystals: Factors contributing to spherulitic growth of dolomite
Authors: Rodriguez Blanco Juan Diego , Szucs Adrienn Maria
Published: March 2021

Dolomite is one of the most abundant carbonate minerals in the geological record, yet it barely forms in the present. The contrast in the abundance of dolomite between geological and modern records combined with the impossibility of synthesizing stoichiometric dolomite in the laboratory at ambient conditions are known as the 'dolomite problem'. This enigma has been in the scope of research for decades, trying to understand dolomite formation, mechanisms and the contributing factors. Dolomite is known to form via two abiotic mechanisms; through (1) dolomitization or (2) dolomite cementation. Also, the contribution of microorganisms can result in biotic dolomite crystallization. The mechanisms of dolomite formation at the molecular and nanoscale in biotic and abiotic environments are relatively well-described, but we still struggle to develop a unified model of dolomite formation in modern and ancient settings. In this contribution, we summarize the development of research related to the dolomite formation processes and in particular the direct dolomite precipitation via spherulitic growth of proto-dolomite.
On the role of parent material for predictive mapping of soil properties in mountain forests 
Authors: Simon Alois , Wilhelmy Marcus , Klosterhuber Ralf , Geitner Clemens , Katzensteiner Klaus
Published: March 2021

Parent material is widely recognised as an important factor for soil formation. Thus, quantitative information on the lithogenetic, geochemical, and physical characteristics of the subsolum geological substrates (SSGS) are essential input parameters for digital soil mapping (DSM). Forming the interface between bedrock – the domain of geologists, and soil – the domain of soil scientists, spatial information on SSGS is however scarce. Recognising these shortcomings, a novel geochemical-physical classification system for subsolum geological substrates has been developed, in order to support DSM at a regional scale. The units of the classification system reflect the properties of the SSGS also considering multilayering structure of quaternary deposits. The basis for the classification are mineral component groups, namely dolomite, calcite, and felsic, mafic, and clay minerals. In order to test the relevance of SSGS for the prediction of spatially continuous physical and chemical soil properties, Generalized Additive Models (GAMs) were applied to the forested area of Tyrol, Austria. The plant-available water storage capacity, as a physical soil property, was predicted with r² = 0.56. The Ellenberg´s mean soil reaction indicator value for vegetation turned out to be a suitable proxy for soil pH value and was predicted with r² = 0.75. Topography and associated morphometric terrain features are formative characteristics of mountain areas and, due to its various effects on redistribution processes as well as on water and energy budget of forest sites, are considered as the most essential soil forming factors. Thus, variables derived from digital terrain models, which are available in high spatial resolution, are assumed to be one of the most important predictors for digital soil mapping. In our study we could show however, that SSGS information is the most relevant predictor for both investigated soil properties. In the plant-available water storage capacity model, the predictor variables related to SSGS account for around 76% of the variance explained. Accordingly, a special focus should be placed on the predictive relevance of parent material and the frequently unlocked potential of quantitative geological substrate information. Thus, the newly developed subsolum geological substrate information could stimulate further developments in digital soil mapping, especially in mountain environments.
Stable isotopes in precipitation and water vapor simulated by isotope-incorporated NICAM
Authors: Tanoue Masahiro , Takano Yuki , Yoshimura Kei , Yashiro Hisashi
Published: March 2021

The stable water isotopes (SWIs) (δ18O and δD) are used as an indicator of the intensity of the atmospheric hydrological cycle due to their large variability in time and space. Although data about vapor isotope ratio with high frequency and high resolution are now available by satellite observations and spectroscopic analyses, there is some room for discussion on the variability of isotope ratios in vapor and precipitation related to cloud microphysical processes.

Here, we incorporated SWI tracer into the latest version of a global cloud system resolving model (the Nonhydrostatic Icosahedral Atmospheric Model (NICAM)), iso-NICAM, and investigated the contribution of cloud microphysical processes to the variability of isotope ratios in precipitation and vapor. One of the merits used NICAM is that its physical process can cover from low spatial resolution to high spatial resolution. We conducted two mode simulations (GCM and CRM). The GCM mode simulation is based on the Arakawa-Schubert scheme as convective parameterization and a large-scale condensation scheme as the cloud physical process. In contrast, the CRM mode simulation is based on the a single-moment bulk cloud microphysics scheme with 6 water categories as cloud microphysical scheme, convective parameterization scheme was not used. These simulations are set to about 223 km of horizontal mesh resolution and 78 vertical layers. We conducted an AMIP-type climate experiment for one year from 1979.

The simulated precipitation δ18O showed the latitude effect pattern (high δ18O in low latitude region, low δ18O in high latitude region), but those values in the CRM mode was slightly lower than that in the GCM mode . The simulated precipitation δ18O in the CRM mode was lower in high altitude or inland regions compared with those in the GCM mode . Besides, the precipitation d-excess in the CRM mode shows large spatial variability compared with the GCM mode. Although the low spatial resolution was set in this study, these simulations indicated cloud microphysical processes are important for understanding the variability of isotope physics. We will conduct these simulations with finer spatial resolution and a more extended simulation period.