bluuebunny/crossref_metadata_2025 huggingface dataset:
The first prayer to the Sun
Authors: Krukowski Janusz
Published: March 2020

The first prayer to the Sun (abstract)

 

At the end of Pleistocene, from the 15th to the 12th millennia BP people of the Magdalenian culture one of the last cultures of Paleolith were living in Pyrenean at the basin of Ariège River. Magdalenian people had left great works of art on the walls of the caves in the region. Also many tools and sculptures had been found inside these caves. According to the French archeologists who were investigating the caves  (i.a. Pailhaugue 1998, Clottes 1999), Magdalenians were hunting in the tundra for the bison, reindeer, horse, deer and antelope during the Summer. During the cold Winter they were moving to the Pyrenees, and that time they had been visiting the Pyrenean caves. On the basis of the paintings and sculptures found in Ariège, French archeologists draw conclusions concerning the structure of the social groups and shamanism.

After electrification of the Grotte de la Vache (one of the caves in Ariège), a very modest image became visible. French archeologists agreed that it represents the image of sun. However, nobody has been analyzing it in a more detailed way.

According to the proposed paper, this modest image of the sun on the wall of the Grotte de la Vache is the most important among all other images and paintings. This is because it shows the transition from shamanism to the first religion, the Sun worship. Basing on the chronology of the known volcanic eruptions and the data gathered in the framework of the Greenland Ice Core Project (2009) we are able to place this transition in time as 12 945 (+/- 15) years BP.

Keywords: shamanism, first religion, Sun worship, Magdalenian culture, Ariége, Niaux, Vache
UAS Imaging Applications to Monitor Restored Peatlands
Authors: Ikkala Lauri , Marttila Hannu , Ronkanen Anna-Kaisa , Ilmonen Jari , Similä Maarit , Haapalehto Tuomas , Rehell Sakari , Kumpula Timo , Klöve Björn
Published: March 2020

Peatlands are globally threatened by the increasing exploitation. Majority of peatlands in Finland are severely degraded by land use and drainage activities. Peatland restoration is an effective way to increase biodiversity, return natural function of peatlands in catchment hydrology and reduce negative impacts of drainage.

Restoration activities recover the wet and open habitats crucial for many valuable species and peatlands ability to store water and nutrients. Restoration activates peat forming processes, and thus reduces greenhouse gas (GHG) emissions and returns peatlands to act as carbon sinks.

Restored sites are monitored to determine whether the restoration has succeeded and to gather the experiences to further develop restoration methods. The traditional restoration monitoring demands intensive field work with high labor costs and special ecological expertise. Evaluation is mainly based on visual assessment at present. In addition, monitoring typically cannot cover the entire restored site.

There is strong need to develop unbiased indicators and new cost-effective methods producing spatially representative high-quality information on restoration success. We will study new technical possibilities for evaluation of peatland restoration success with unmanned aerial systems (UAS).

The latest image processing techniques and their use in mapping and analyzing peatland areas are to be studied. UAS provides prospects not only to ease the demanding restoration field work but also to transform the discrete nature of conventional single data points into a spatial continuum over the whole restored peatland.
A simple but robust model for the buttressing of calving glaciers through ice mélange
Authors: Schlemm Tanja , Levermann Anders
Published: March 2020

Under future warming scenarios, both ice sheets on Greenland and Antarctica are likely to discharge ice into the ocean at an accelerating rate. In many regions along the coast of the ice sheets, the icebergs are discharged into a bay. If the addition of icebergs through calving is faster than their transport out of the embayment, the icebergs will be frozen into a mélange with surrounding sea ice. In this case, the buttressing effect of the ice mélange can be considerably stronger than any buttressing by mere sea ice would be. This in turn stabilizes the glacier terminus and leads to a reduction in calving rates. Here we propose a simple but robust buttressing model of ice mélange. 
Assessments of in situ and remotely sensed CO2 observations in a Carbon Cycle Fossil Fuel Data Assimilation System to estimate fossil fuel emissions
Authors: Scholze Marko , Kaminski Thomas , Rayner Peter , Vossbeck Michael , Buchwitz Michael , Reuter Maximilian , Knorr Wolfgang , Chen Hans , Agusti-Panareda Anna , Löscher Armin , Mejer Yasjka
Published: March 2020

The Paris Agreement establishes a transparency framework that builds upon inventory-based national greenhouse gas emission reports, complemented by independent emission estimates derived from atmospheric measurements through inverse modelling. The capability of such a Monitoring and Verification Support (MVS) capacity to constrain fossil fuel emissions to a sufficient extent has not yet been assessed. The CO2 Monitoring Mission, planned as a constellation of satellites measuring column-integrated atmospheric CO2 concentration (XCO2), is expected to become a key component of an MVS capacity. 

Here we provide an assessment of the potential of a Carbon Cycle Fossil Fuel Data Assimilation System using synthetic XCO2 and other observations to constrain fossil fuel CO2 emissions for an exemplary 1-week period in 2008. We find that the system can provide useful weekly estimates of country-scale fossil fuel emissions independent of national inventories.  When extrapolated from the weekly to the annual scale, uncertainties in emissions are comparable to uncertainties in inventories, so that estimates from inventories and from the MVS capacity can be used for mutual verification. 

We further demonstrate an alternative, synergistic mode of operation, which delivers a best emission estimate through assimilation of the inventory information as an additional data stream.  We show the sensitivity of the results to the setup of the CCFFDAS and to various aspects of the data streams that are assimilated, including assessments of surface networks.
Land use effect on microbial growth and respiration under future climate
Authors: Guliyev Vusal , Pfeiffer Melissa , Udovenko Maria , Fasching Christina , Reitz Thomas , Blagodatskaya Evgenia
Published: March 2020

Fresh input of organic material in soil is continuously transformed and processed by growing microorganisms using this organic input as a substrate. Therefore, the quality and quantity of soil organic C stock is strongly dependent on the intensity of mineralization processes through microbial respiration and growth. We aimed to prove the sensitivity of microbial respiration and growth parameters to indicate an interactive effect of land use and climate warming. For this we used Global Change Experimental Facility in Bad Lauchstädt, UFZ, Halle, Germany. This long-term experiment is designed in 5 land use strategies (Organic Farming, Conventional Farming, Intensive Meadow, Extensive Meadow, and Extensive Pasture) and 2 climate scenarios (ambient and future). We determined basal respiration by CO2 emission, microbial growth parameters by substrate-induced growth respiration (SIGR), and the quality of soil organic matter by Fourier-transformed infrared spectroscopy (FTIR). The effect of biotic (vegetation type) and abiotic (temperature and moisture) factors on microbial attributes and on chemical composition of soil organic matter will be compared.
Measuring slope-scale crack propagation in weak snowpack layers
Authors: Bergfeld Bastian , van Herwijnen Alec , Bobillier Gregoire , Schweizer Jürg
Published: March 2020

For a snow avalanche to release, a weak layer has to be buried below a cohesive snow slab. The slab-weak layer configuration must not only allow failure initiation but also crack propagation across a slope. While in the past failure initiation was extensively studied, research focusing on the onset and dynamics of crack propagation only started with the introduction of the Propagation Saw Test (PST), a meter scale fracture mechanical field test. Since then, various studies used particle tracking analysis of high-speed video recordings of PST experiments to gain insight into crack propagation processes and to measure crack propagation speeds. At the slope scale, a few crack speed estimates have been obtained from seismic sensors, videos or visual observation. However, due to experimental limitations, these latter studies can only provide rather crude crack speed estimates and direct comparisons to PST measurements are still missing. Sure, performing experiments in avalanche terrain is challenging and limited for security reasons, but crack propagation occurs also in slopes not sufficiently steep to release an avalanche. This phenomena is called a whumpf. Since crack propagation in whumpfs is presumably similar to that in avalanches, we developed instrumentation to measure crack speeds on artificially triggered whumpfs. We designed small wireless time synchronized accelerometers with a sampling rate of 400 Hz that can be placed on the snowpack. These measure the downward acceleration of the slab when a crack in the weak layer below passes by. Though triggering whumpfs is difficult and unpredictable, we performed a successful experiment with seven sensors placed over a distance of 25 m. Our experiment revealed a crack speed around 50 ms-1. In addition, we obtained very similar crack speed measurements from a 5.3 m long PST carried out close-by (42 ms-1) and a video-based speed estimate of an avalanche triggered two days later (42 – 55 ms-1). Our unique whumpf measurement is the first slope scale speed value that can be directly compared to results obtained with other speed measurement techniques. The similarity between the measured speeds suggests that the one-dimensional crack propagation in PSTs is also similar to the 2-dimensional crack propagation in Whumpfs and real avalanches. PSTs are therefore well suited to investigate crack propagation processes of dry snow slab avalanches.
Influence of Mantle Structures on Measurements of Anisotropy in the Inner Core
Authors: Beiers Sandra , Thomas Christine
Published: March 2020

The seismological exploration of the Earth’s inner core has revealed some structural complexities such as seismic anisotropy and hemispherical separation. Investigating the travel times of PKP waves from at least two different ray paths, a polar and an equatorial one, is one of the commonly used methods to probe the inner core’s anisotropy. Since the waves are traversing anomalous structures in the lowermost mantle before entering the core, these heterogeneities have to be taken into account when investigating anisotropy in the inner core.

In this study we use data from an equatorial path with events from Indonesia recorded in Morocco and a nearly polar one with earthquakes in New Zealand recorded in England. The two waves used in our study, PKPdf and PKPab, both propagate through mantle and outer core and PKPab additionally traverses the inner core. Within this work, we do not only analyse the travel times of the waves but rather investigate their deviations from the originally assumed path along with their incidence angle. This is done with the methods of array seismology, mainly its two parameters slowness and backazimuth.

The results of this study reveal opposite deviations of slowness and backazimuth of the polar in contrast to the equatorial path. While the polar waves travel shallower and closer to North, the equatorial waves propagate deeper and farther from North than predicted by ak135. Additionally we observe hemispherical differences between waves that sample the eastern and the ones that sample the western hemisphere for both ray paths, PKPdf and PKPab, which leads us to the assumption that the deviations are not caused by the inner core but are rather due to mantle structures.
Modelling coronal mass ejection flux ropes signatures using Approximate Bayesian Computation: applications to Parker Solar Probe
Authors: Weiss Andreas , Möstl Christian , Nieves-Chinchilla Teresa , Amerstorfer Tanja , Palmerio Erika , Reiss Martin , Bailey Rachel , Hinterreiter Jürgen , Amerstorfer Ute , Bauer Maike
Published: March 2020

We present an updated three-dimensional coronal rope ejection (3DCORE) model and an associated pipeline that is capable of producing extremely large ensembles of synthetic in-situ magnetic field measurements from simulated coronal mass ejection flux ropes. The model assumes an empirically motivated torus-like flux rope structure that expands self-similarly and contains an embedded analytical magnetic field. Using an Approximate Bayesian computation (ABC) algorithm we validate the model by showing that it is capable of qualitatively reproducing measured flux rope signatures. The ABC algorithm also gives us uncertainty estimates in the form of probability distributions for all model parameters. We show the first results for applying our model and algorithms to coronal mass ejections observed in situ by Parker Solar Probe, specifically the event on 2018 November 12 at 0.26AU, where we attempt to reproduce the measured magnetic field signatures and furthermore reconstruct the global flux rope geometry.
Melt at grounding line controls observed and future retreat of Smith, Pope, and Kohler Glaciers
Authors: Lilien David , Joughin Ian , Smith Benjamin , Gourmelen Noel
Published: March 2020

Smith, Pope, and Kohler glaciers and the corresponding Crosson and Dotson ice shelves have undergone speedup, thinning, and rapid grounding-line retreat in recent years, leaving them in a state likely conducive to future retreat. We conducted a suite of numerical model simulations of these glaciers and compared the results to observations to determine the processes controlling their recent evolution. Simulations were forced using estimates of the distribution and intensity of melt from 1996-2014. The model simulations indicate that the state of these glaciers in the 1990s was not inherently unstable, i.e., that small perturbations to the grounding line would not necessarily have caused the large retreat that has been observed. Instead, sustained melt, at rates higher than the 1990s and concentrated at the grounding line, was needed to cause the observed retreat. Weakening of the margins of Crosson Ice Shelf may have hastened the onset of grounding-line retreat but is unlikely to have initiated these rapid changes without an accompanying increase in melt. In the simulations that most closely match the observed thinning, speedup, and retreat, modeled grounding-line retreat and ice loss continue unabated throughout the 21st century, and subsequent retreat along Smith Glacier's trough appears likely. Given the modeled retreat, thinning associated with the retreat of Smith Glacier may reach the ice divide and undermine a portion of the Thwaites catchment as quickly as changes initiated at the Thwaites terminus. Thus, while the Smith, Pope, Kohler catchment is small compared to Thwaites, these smaller glaciers may be important when considering the centennial-scale evolution of the Amundsen Sea region.
A satellite-based Lagrangian perspective on Atlantic Water fractionation in the Nordic Seas
Authors: Chafik Léon , Broomé Sara
Published: March 2020

The Arctic Ocean has been receiving more of the warm and saline Atlantic Water in the past decades. This water mass enters the Arctic Ocean via two Arctic gateways: the Barents Sea Opening and the Fram Strait. Here, we focus on the fractionation of Atlantic Water at these two gateways using a Lagrangian approach based on satellite-derived geostrophic velocities. Simulated particles are released at 70N at the inner and outer branch of the North Atlantic current system in the Nordic Seas. The trajectories toward the Fram Strait and Barents Sea Opening are found to be largely steered by the bottom topography and there is an indication of an anti-phase relationship in the number of particles reaching the gateways. There is, however, a significant cross-over of particles from the outer branch to the inner branch and into the Barents Sea, which is found to be related to high eddy kinetic energy between the branches. This cross-over may be important for Arctic climate variability.
Exploring pedestrian thermal comfort in hot climates
Authors: Dzyuban Yuliya , Redman Charles , Hondula David , Coseo Paul , Middel Ariane , Vanos Jennifer
Published: March 2020

Designing cities for thermal comfort should be a priority in the warming and urbanizing world. As cities continue to break extreme heat records, it is necessary to develop new sensing approaches capable of tracking thermal sensations of actual users of urban spaces. The Influence of built infrastructure on the microclimate at a human scale and residents’ thermal sensations is not well explored, but combining sensing techniques with simultaneous collection of user experiences is a promising research direction to shorten the gap.

We explored the relationships between the built environment, heat perception, and behavioral coping mechanisms in one of the most heat vulnerable Phoenix neighborhoods. Using Phoenix as an example, where extreme summer temperatures are a norm, can help to address heat challenges of other cities that have started facing temperature extremes in the recent years.

This study is an experimental citizen science project in which participants helped to create a “heat map” of the neighborhood. Participants were engaged in a 1-hour walk around the neighborhood and recorded their experience in a field guide. A smaller group participated in walking interviews and wore GPS devices and UV meters to gain deeper insights on subjective heat perception and physical body heat accumulation during the walk. Results revealed the differences in heat perception across a variety of urban landscapes. Participants identified preferred and most challenging locations, and gave ideas on what could improve their experience. Combined heart rate, UV exposure and microclimate data mapped in GIS visualized dependencies between the streetscape and physiological conditions of the study participants.

This project is one of the first to examine the impact of urban environment on dynamic psychological and physiological responses to heat. Using sensing techniques and qualitative research instruments, this research will inform the design changes in the neighborhood that will undergo redevelopment. It can serve as an example for other cities striving to adapt urban microclimates to new extremes.
Centennial variability driven by salinity exchanges between the Atlantic and Arctic in a coupled climate model
Authors: Jiang Weimin , Gastineau Guillaume , Codron Francis
Published: March 2020

The centennial to multi-centennial variability of the Atlantic Meridional Overturning Circulation (AMOC) is studied in a 1200-yr pre-industrial control simulation of the IPSL-CM6-LR atmosphere-ocean coupled model. In this run, a spectrum analysis finds a periodicity of the low-frequency variability of AMOC, with a period of about 200-year. This variability alters the Northern Hemisphere climate over the land and modulates the Arctic sea ice extent and volume. The associated density variations show large positive (negative) salinity-driven density anomalies in the Nordic Seas and subpolar gyre associated with a strong (week) AMOC state. The positive salinity anomalies in the Greenland Sea are found to be generated by anomalous southward salinity transport in the Fram Straits. The gradual AMOC increase and the associated oceanic northward heat transport melt the sea ice in the Arctic and build shallow negative salinity anomalies in the central Arctic. In parallel, the AMOC is also associated with a northward salt transport into the Eastern Arctic, by an inflow of Atlantic water from the Barents Sea to the East Siberian Ocean. The accumulated surface freshwater in the central Arctic is ultimately exported into the Atlantic mainly through the Fram Strait via intensified East Greenland Current, lowering the upper ocean density and enhancing the stratification at the regions where the cold deep limb of AMOC is formed. The positive salinity anomalies at subsurface then slowly reach the surface though diffusion, increasing the surface salinity. The oscillation then turns into the opposite phase.
Large-Scale Circulation Anomalies Associated with Extreme Heat in South Korea and Southern–Central Japan
Authors: Xu Ke
Published: March 2020

    The large-scale circulation anomalies associated with extreme heat (EH) in South Korea and southern–central Japan are examined using data during the time period 1979–2016. Statistical analysis indicates that EH days in these two regions are concentrated in July and August and tend to occur simultaneously. These EH days are therefore combined to explore the physical mechanisms leading to their occurrence. The composite results indicate that the anomalous atmospheric warming during EH days is dominantly caused by a significant subsidence anomaly, which is associated with a deep anomalous anticyclone over East Asia. Further investigation of the evolution of circulation anomalies suggests that the anomalous anticyclone over East Asia related to EH is primarily initiated by wave trains originating from upstream regions, which propagate eastward along the Asian westerly jet in the upper troposphere. These wave trains can be categorized into two types that are characterized by the precursor anticyclonic and cyclonic anomalies, respectively, over central Asia. The distinction between these two types of wave train can be explained by the wavenumbers of the Rossby waves, which are modulated by both the intensity and the shape of the Asian westerly jet as the background basic flow.
Sensitivity analysis of drought indices under substantially different agricultural systems in North and South Koreas
Authors: Park Seonyoung , Yeom Jongmin , Lee Jeongho , Lee Jaese , Im Jungho , Lee Hongtak , Kim Heeseob , Chae Tae-Byeong
Published: March 2020

Rice is a staple food in the North and South Koreas. Rice yield is closely related to water supply including irrigation, precipitation, and soil water. Drought typically occurs due to the lack of precipitation, and prolonged drought leads to the decrease of soil water, which results in plant water stress. Drought monitoring is crucial for agricultural mitigation because it enables us to estimate rice production in a timely manner. The purpose of this study is to suggest an optimal drought index for monitoring agricultural drought over North and South Koreas. Although North and South Koreas have similar climate conditions, they have different levels of infrastructure for agriculture such as irrigation facilities. In this study, nine satellite-based drought indices were used and evaluated based on in situ measurements at weather stations including Standardized Precipitation Index (SPI) and rice yield. Drought indices were calculated using the Global Land Data Assimilation System (GLDAS) soil moisture, Tropical Rainfall Measuring Mission (TRMM) precipitation, Moderate Resolution Imaging Spectroradiometer (MODIS) Land Surface Temperature (LST) and Normalized Difference Vegetation Index (NDVI). Since various drought indices have been developed with their own purpose, considering the characteristics of the study area under investigation, their applications for other regions are relatively limited. Thus, comparison of various drought indices is needed to identify an optimal drought index for a certain area. The measurable objectives of this research were to 1) compare the characteristics of drought depending on the properties of drought indices such as temperature, vegetation, precipitation, and soil moisture and 2) evaluate various drought indices using SPIs and rice yield data. The performance of the drought indices was evaluated using correlation coefficient values (R) for reference data (i.e., SPI and rice yield). As expected, drought indices including NDVI showed positive relationships with rice yield in both regions (averaged R=0.37). Meanwhile, temperature based drought indices showed negative relationships with rice yield in both regions because high temperature means high solar radiation, which is essential to rice production. While the correlation coefficient between precipitation based indices and rice yield was positive in North Korea (averaged R=0.34), it was negative in South Korea (averaged R=-0.26). The opposite pattern by area is because South Korea (117,457 irrigation Canals) has more artificial controls over agricultural land such as irrigation facilities and reservoirs than North Korea (51,400 irrigation Canals).
Ammonia-biosphere interaction from IASI and ERA5
Authors: Abeed Rimal , Safieddine Sarah , Clarisse Lieven , Van Damme Martin , Coheur Pierre-François , Clerbaux Cathy
Published: March 2020

The global concentration of reactive nitrogen (e.g. NH3, NOx and N2O) has intensely increased since the pre-industrial era. Ammonia (NH3) is one of the main sources of reactive nitrogen in the atmosphere and plays a crucial role in the formation of inorganic particulate matter, which harms health and deteriorates air quality. In addition to that, the wet/dry deposition of ammonia derivatives affects ecosystems through acidification and eutrophication of soil and water bodies; leading to a loss in biodiversity and intensification of the response to climate change. NH3 is mainly emitted by biomass burning and agricultural activities. Agriculture contributes to air pollution and is affected by atmospheric composition, meteorology and climate change.

Several studies proved the efficiency of the IASI instrument aboard Metop satellites in measuring ammonia from space. For the last ten years, hotspots of ammonia point sources have been identified and categorized around the world.

In this poster, we explore the interaction of atmospheric ammonia with land, meteorological, and leaf conditions. We look at the temporal variability of ammonia in different regions of the world. The relationship land-ammonia volatilization is assessed by comparing the variability of surface soil moisture and the skin temperature products from the ECMWF latest reanalysis (ERA5) with IASI NH3 total columns. The meteorology-ammonia relation is examined, by looking at air temperature, humidity, precipitation, planetary boundary layer height, and wind speed/direction. Agricultural seasons in studied regions are detected from space in matter of leaf area per ground area. The crop-ammonia relation is assessed by looking at the Leaf Area Index (LAI) products. The regions examined have been identified as point sources and/or hotspots of ammonia of agricultural and industrial sources (mainly fertilizer industry).

The result of this work will improve our understanding of biosphere-atmosphere interactions, in particular, the relationship between ammonia on the one hand and land, meteorology and crops on the other hand, in different regions in the world.
Modelling the effect of agricultural policy scenarios on soil ecosystem services at the continental level
Authors: Garrote Luis , Santillan David , Iglesias Ana
Published: March 2020

The study presents a geographically explicit model that uses multiple layers of environmental and social information to assess the environmental footprint of soil management practices at a 10 x 10 km resolution at the continental scale. Changes in soil environmental footprint are quantified in terms of the effect of management practices on soil productivity, nutrients and biodiversity. Changes in soil environmental footprint are quantified in terms of their effects on soil organic carbon, productivity and biodiversity. The central actor in the analytical process is the farmer, who is managing a plot of land where a certain crop is grown under a typical farming system. This plot of land is subject to policy scenarios, determined by the combination of agro-environmental determinants at the regional level, defined within the targets of the Common Agricultural Policy, environmental policy, market conditions and socio-economic development. Functional relations to define the effect of agricultural management practices on ecosystem services are formulated in qualitative terms. Results of different soil quality indicators are then combined to produce descriptions of improvement of soil environmental footprint. Soil Environmental footprint scenarios are then analysed in terms of improvements with respect to the current situation. Our results show that the Expected scenario is not enough to make significant contributions towards improving the soil environmental footprint and the Towards 2050 scenario delivers important benefits. The Regional Targets scenario delivers important benefits in key challenging areas, where the effects improve greatly the soil environmental footprint. The content of the study is based on the results of the iSQAPER (http://www.isqaper-project.eu/) H2020 project.
C:N:P stoichiometry regulates soil organic carbon mineralization and concomitant shift of microbial community in paddy soil
Authors: Zhu Zhenke , Wei Xiaomeng , Ge Tida , wu Jinshui , Richter Andreas
Published: March 2020

Soil carbon (C), nitrogen (N), and phosphorus (P) contents and their stoichiometric ratios play modifying the microbial metabolism of C. Microbial populations vary in their strategies for C and nutrient acquisition to maintain the microbial biomass C:N:P balance. However, the regulation of soil C mineralization and microbial activities by stoichiometric ratios in input substrates becomes unpredictable in flooded soils because of the frequent redox fluctuations and general oxygen limitation. Stoichiometric control on input substrate (glucose) and soil organic carbon (SOC) mineralization were assessed by a manipulation experiment based on N or P fertilization in paddy soil. Glucose mineralization increased by nutrient addition up to 11.6% with combined N and P applications compared with addition without nutrients. During 100-days incubation, about 4.5% of SOC was mineralized in all five treatments, being increased by glucose and reduced by P fertilization. Glucose and SOC mineralization increased exponentially with the dissolved organic carbon (DOC):NH4+-N, DOC:Olsen P, and microbial biomass (MB)C:MBN ratios. The glucose mineralization was negatively associated with the MBC:MBP ratio, suggesting that P addition relieved P limitation for microorganisms and increased microbial activities of labile C mineralization. The shift of bacterial community structure was significantly affected by the soil available and microbial biomass C:N:P stoichiometric ratios. The decrease of negative associations between bacterial taxa in the P-added soil indicated that microbial competition for nutrients was alleviated. 16S rRNA amplicon sequencing showed that combined C and nutrients application stimulated the Clostridia and β-Proteobacteria (r strategists) and increased the enzyme activities of β-glucosidase and β-acetyl-glucosaminidase. In contrast, after 100-day incubation, when the available substrate was exhausted, Syntrophus (K strategist) was found as the keystone species. Hence, soil microbial communities shifted their keystone species to acquire necessary elements to maintain the microbial biomass C:N:P stoichiometric balance in response to the change of resource C:N:P stoichiometry.
The effect of pre-existing faults on the development of extensional basins: insights from wet clay experiments
Authors: Bonini Lorenzo , Basili Roberto , Bertone Nicolò , Fracassi Umberto , Maesano Francesco Emanuele , Valensise Gianluca
Published: March 2020

Most of the present-day extensional systems formed in areas that already experienced an older phase of tectonic activity. Therefore, understanding how a pre-existing structural setting may affect the development of an extensional basin is a crucial interplay to decipher. Depending on the kinematics of these phases, the resulting inherited faults can be extensional, contractional, or transcurrent. Consequently, a new extensional basin forms atop or across pre-existing faults that can dip at a low- (e.g., inherited thrust faults) or high-angle (e.g., inherited extensional faults). Furthermore, the inherited structures can have a non-optimal attitude with respect to the new extensional stress field, thereby determining different instances for reactivation. In this study, we analyzed the impact of dip and strike of inherited faults on the development of an extensional basin using wet clay (kaolin) analogue modeling. We reproduced sixteen different setups by varying the dip (30°, 45°, 60°) and the strike (15°, 30°, 45°, 60°, 75°) of the pre-existing faults that we introduced in the experiments before applying extension. The results show that the orientation of pre-existing faults has a direct effect onto the shape of the new extensional basins. When the pre-existing faults are reused to accommodate the new extensional phase, the formed basins are asymmetric and the rate of growth of the new faults is lower.
Earth’s magnetotail as the reservoir of accelerated single- and multicharged oxygen ions replenishing radiation belts
Authors: Parkhomenko Elena , Kalegaev Vladimir , Malova Helmi , Panasyuk Mikhail , Popov Victor , Vlasova Natalia , Zelenyi Lev
Published: March 2020

In this work we are studying multicharged oxygen ion acceleration during substorms in the Earth's magnetotail as the source of ring current replenishment by energetic ion population. We used measurements obtained by the CRRES spacecraft for the comparison of experimental spectra of oxygen charge state in the outer region of the ring current and proton radiation belt with model results. We present a numerical model that allows to evaluate acceleration of oxygen ions O+-O+8 in the course of two possible perturbation processes: A) passage of multiple dipolarization fronts in the magnetotail; B) passage of fronts followed by electromagnetic turbulence. It is shown that acceleration processes depend on particle charges and time scale of electric field variations. Oxygen ions O+8 with average initial energies 12 keV are accelerated efficiently during multiple dipolarization processes of type (A) and their energies increased up to 7.4 MeV, whereas ions O+1 with the same energies were energized up to 1.9 МeV. It is shown that oxygen ions O+-O+2 are able to penetrate into the ring/radiation belts region with L between L=4.5 and L=7.5 in the process of plasma transfer on dipolarization fronts. For oxygen O+-O+8 the additional acceleration mechanism is required, such as large-scale electromagnetic turbulence, when the ions can get energies comparable with experimentally observed ones in the indicated range of L shell values. It is shown that the taking into account electromagnetic fluctuations, accompanying magnetic dipolarization, may explain the appearance of oxygen ion flows with energies greater than 3MeV in the near- Earth’s space.
Salt intrusion in an estuarine network, a study with an exploratory model
Authors: de Swart Huib E. , van Tongeren Inge
Published: March 2020

Many estuarine systems experience increased salt intrusion, which is harmful for ecology and agriculture and may cause problems for fresh water supply to cities. Some causes of salt intrusion are extraction of fresh water in the upper reaches of the estuary and climate change. Besides, anthropogenic measures, like deepening of channels, are known to have a strong impact on the salt balance.

This contribution focuses on salt intrusion in estuarine networks, which consist of multiple connected channels. The motivation of the study arose from observations in the Yangtze estuary that reveal frequent overspill of salt between its different channels. To understand the underlying physics of such behaviour, an exploratory, width- and tidally averaged model has been developed and analysed. This model describes the competition between export of salt by river flow and import of salt by density-driven flow and horizontal diffusion. Its key new aspect is that it generalises an earlier model MacCready (2004) from a single channel to estuarine networks. The new model calculates the distribution of salt in, and salt exchange between the channels, as well as the distribution of river water over the different channels.  

Here, results will be presented for a simplified estuarine network consisting of the South Channel, South Passage and North Passage of the Yangtze Estuary. It will be shown that, for the present-day situation, dry season and spring tide, salt intrusion is larger in the South Passage than in the North Passage. As will be explained, this is mainly due to the different geometry of the two channels. Furthermore, it will be shown that there is slightly more river water transport through the South Passage than through the North Passage, except during high river discharge and neap tide. These results agree with field data and results from numerical studies.

Other results that will be presented are the sensitivity of salinity intrusion length and distribution of river water over the different channels to changes in, respectively, upstream river discharge, tidal currents and human interventions. Specifically, the effects of the creation of a Deepwater Navigation Channel in the North Passage on salt dynamics will be shown and discussed.

Reference:
MacCready, P. 2004. Toward a unified theory of tidally-averaged estuarine salinity structure. Estuaries 27, 561-570.
Energy conversion by electron beam-driven waves in a compressed reconnection separatrix
Authors: Holmes Justin , Nakamura Rumi , Roberts Owen , Schmid Daniel , Nakamura Takuma , Vörös Zoltan
Published: March 2020

We investigate magnetic compression near the reconnection separatrix observed by Magnetospheric MultiScale (MMS) on July 11th 2017. A clear transition between inflow and outflow in both ions and electrons is observed across an ion gyro-scale region of enhanced magnetic field. Multispacecraft techniques for magnetic curvature and local gradients along with timing of highly-correlated wave packets are used to determine the spatial configuration of the compressed region. Structure of the system is found to be inherently three dimensional; electron beam-driven modes propagating parallel to the magnetic field are observed concurrent with perpendicular-propagating lower hybrid waves. Larger scale surface waves are also present behind the compression front. Transforming to a deHoffmann-Teller frame across the boundary results in a distinctly non-rotational discontinuity with structure similar to a quasi-2D, Petschek-like slow shock. However, MHD jump conditions are not satisfied, indicating kinetic dissipation may occur within the thin layer. The largest amplitude measurements of $\mathbf{J}\cdot\mathbf{E}$ energy conversion are associated with an inflowing electron beam and parallel electric fields near the magnetic peak. Spikes in $\mathbf{J}\cdot\mathbf{E}$ are predominantly negative, suggesting electron-scale mixing between the reconnection inflow and outflow is partially responsible for the observed magnetic compression.
Bipartite response in the Black Sea sediment record to Greenland-Interstadial 10
Authors: Czymzik Markus , Nowaczyk Norbert , Dellwig Olaf , Wegwerth Antje , Muscheler Raimund , Christl Marcus , Arz Helge
Published: March 2020

High-latitude climate variations during Greenland Interstadials (GI) are expected to transfer globally in a complex way through interactions of fast atmospheric as well as slower cryospheric and oceanic processes. Prerequisite for an investigation of the evolution of GI is a climate independent synchronization of the considered paleoenvironmental archives. Measuring and aligning globally common production rate variations of the cosmogenic radionuclide 10Be in different archives provides a tool for such synchronizations and the investigation of environmental gradients in space and time, with minimized uncertainties in the relative timing.

A 10Be time-series at < 40-year resolution was measured along with new proxy records down to sub-mm step size from Black Sea sediment core M72/5-22-GC8 around GI-10 (~41 ka BP). We synchronized our 10Be time-series to that from Central Greenland ice cores based on the globally common production rate variations using the globally optimal fit.

Comparing the synchronized environmental proxy records points to a bipartite response of the Black Sea sediment record at the onset of GI-10. First, synchronous with the abrupt temperature increase in Greenland, costal sea ice decreases on the Black Sea, reflected by reduced sedimentary ice rafted debris contents. Second and with a lag of ~190 years, abrupt increases in the K/Ti proxy point to enhanced regional precipitation causing higher riverine sediment supply into the basin.

This bipartite structure might be connected to both differential thresholds of proxy responses in Black Sea sediments to locally abrupt environmental forcing and/or a bipartite climate transition in the region in response to GI-10. The latter could possibly be explained by an initial fast atmospheric-transmitted warming in the Black Sea region synchronous to the onset of GI-10, followed by a shift from predominantly continental to Mediterranean weather systems ~190 years later, after regional oceanic adjustments. However, further investigations during more GIs are necessary to test the robustness of these results.
Quaternary molluscan assemblages of cold-water coral mounds: a new perspective on deep-sea ecosystem dynamics in the western Mediterranean
Authors: Korpanty Chelsea , Hoffman Leon , Titschack Jürgen , Wienberg Claudia , Hebbeln Dierk
Published: March 2020

Cold-water corals (CWC) act as ecosystem engineers and thus contribute to biodiversity on continental margins worldwide. CWC mounds – built over geologic time by the interplay of biological, sedimentological, and oceanographic processes – create ecological niches for a variety of macrobenthic marine taxa (e.g. molluscs, sponges, bryozoans). The growth of CWC mounds is discontinuous over time due to changes in environmental and ecological conditions, such as food supply, water temperature, and dissolved oxygen concentration. While surficial distribution patterns of living and recently-dead mound macrobenthic communities have been described, their temporal ecological relationship with coral growth and mound formation is yet largely unexplored. Therefore, this project aims to determine what effects stagnations in CWC growth (i.e. repeated periods of ecosystem “turn off”) have on the local biodiversity and community structure of other CWC mound taxa, and thus what influences CWC mound development may have on regional biodiversity and biogeography in the deep sea over geologic time. Focusing on a single taxonomic group with high preservation potential, this study 1) quantitatively assesses temporal ecological trends of coral mound molluscan assemblages (bivalves and gastropods), and 2) statistically correlates those data with coral growth and palaeoceanographic records. Preliminary results from two CWC mound gravity cores through Brittlestar Ridge I in the Alboran Sea, western Mediterranean (~13.2 – 2.9 ka) indicate that throughout both cores the molluscan assemblages are typically quantitatively dominated by sessile benthic filter-feeding bivalves, particularly Heteranomia squamula and Hiatella arctica. Although bivalves are more abundant and diverse than gastropods in both cores, these taxonomic groups yield generally similar downcore dynamics in abundance and diversity. Comparisons of total molluscan assemblages (bivalves and gastropods combined) suggest that the older assemblages – those associated with the Bølling-Allerød interstadial (13.5-12.8 ka) and Early Holocene (11.3-9.8 ka) – are more similar to one another than to younger assemblages in the cores. Rotational vector fitting analyses indicate that these older assemblages are significantly related to higher productivity and different hydrodynamics (and sediment input), which are factors that have also been linked to CWC growth in the region. Altogether, our paleoecological reconstructions so far reaffirms the connectivity of benthic communities with local oceanographic conditions and adjacent taxa. Additional ecological assessments will further refine our understanding of the relationships between CWC growth and benthic communities, and in turn the temporal drivers and dynamics of CWC mound biodiversity.
On the inter-connectivity of volume transports through Arctic Straits
Authors: De Boer Agatha , Gavilan Pascual-Ahuir Estanislao , Stevens David , Chafik Léon , Hutchinson David , Zhang Qiong , Sime Louise , Willmott Andrew
Published: March 2020

Arctic heat and freshwater budgets are highly sensitive to volume transports through Arctic-Subarctic straits. Here we investigate how the volume transports through these straits adjust to each other to maintain a mass balance in the Arctic on annual timescales. To this end, we use three models; two coupled global climate models, one with a third-degree horizontal ocean resolution (HiGEM1.1) and one with a twelfth-degree horizontal ocean resolution (HadGEM3), and one ocean-only model with an idealized polar basin (tenth-degree horizontal resolution). The two global climate models indicate that there is a strong anti-correlation between the Bering Strait throughflow and the transport through the Nordic Seas, a second strong anti-correlation between the transport through the Canadian Artic Archipelago (CAA) and the Nordic Seas transport, and a third strong anti-correlation between the Fram Strait and the Barents Sea throughflows. We find that part of the strait correlations is due to the strait transports being coincidentally driven by large-scale atmospheric forcing patterns such as the Arctic Oscillation. However, there is also a role for fast wave adjustments of some straits flows to perturbations in other straits since atmospheric forcing of individual strait flows alone cannot lead to near mass balance fortuitously every year. Idealized experiments with an ocean model (NEMO3.6) that investigate such causal strait relations suggest that perturbations in the Bering Strait are compensated preferentially in the Fram Strait due to the narrowness of the western Arctic shelf and the deeper depth of the Fram Strait.