bluuebunny/crossref_metadata_2025 huggingface dataset:
Comprehensive comparison of mesospheric wind from Fabry-Perot interferometer and meteor radar at King Sejong Station, Antarctica
Authors: Lee Changsup , Jee Geonhwa , Wu Qian , Kim Jeong-Han , Kam Hosik , Kim Yong Ha
Published: March 2020

Neutral winds in the mesosphere and lower thermosphere (MLT) have been simultaneously observed by Fabry-Perot interferometer (FPI) and meteor radar (MR) at King Sejong Station (KSS), Antarctica from 2017. Because  the airglow emission height sensitively varies with a solar local time and a season, it is not possible to precisely determine what altitude airglow emission occurs from the traditional assumption of fixed airglow layers. Even though a few previous studies suggested representative heights of airglow emission such as OH band and 557.7 nm line, the true height information of these emission are still unknown. In this study, we try to figure out the temporal dependence of the airglow emissions using the KSS FPI and satellite (SABER/MLS) measurements. We also perform a direct comparison between the FPI and the meteor radar wind measurements considering time-varying airglow emission properties based on a correlation analysis. This study presents how the background wind structure can affect wind estimates from the airglow emissions.
A look beneath the ice shelves of western Dronning Maud Land, East Antarctica: subglacial topography linked to ice shelf stability
Authors: Eisermann Hannes , Eagles Graeme , Ruppel Antonia , Smith Emma C. , Jokat Wilfried
Published: March 2020

Antarctica’s ice shelves play a key role in stabilizing their related ice sheets. The ice shelves of western Dronning Maud Land – including the Ekström, Atka, Jelbart, Fimbul and Vigrid ice shelves – currently buttress a catchment that comprises an ice volume equivalent to 0.95 meters of sea level. Any future increase in ice shelf mass loss, with basal melting likely being the main cause, will inevitably accelerate ice sheet drainage and contribute to global sea level rise. Since basal melting largely depends on ice-ocean interactions, it is crucial to attain reliable and consistent bathymetry models to estimate water and heat exchange beneath these ice shelves. We have constructed bathymetry models for an area of about 63,000 km2 beneath the ice shelves of western Dronning Maud Land by inverting airborne gravity data, tied to radar, seismic, and offshore depth reference points. New high-resolution airborne magnetic data across the ice shelves point to Jurassic intrusions and seaward-dipping reflectors originating from Gondwana breakup; enabling us to consider geological density variations as part of the bathymetry modelling process. Our bathymetric models reveal deep glacial troughs beneath the ice shelves, and sills close to the continental shelf breaks which currently limit the possible entry of Warm Deep Water from the Southern Ocean. The present-day average thermocline depth is comparable to the average depths of saddles along the sills, which present gateways into the sub-ice cavities. This leads us to suggest a high sensitivity for these ice shelves to changes in ocean temperature and especially thermocline depth in the future. Once a significant amount of warm water overtops the sills, the deep troughs will allow for fast access to the grounding line, after which it seems there may be little to stop basal melting from rapidly eroding the ice shelves of western Dronning Maud Land.
Assessing the Impacts of Climate Change and Land Use/Cover Change on Runoff Based on Multiple Water-Energy Balance Models
Authors: Xiong Manling
Published: March 2020

The runoff in river systems has been significantly changed by climate change and land use/cover change (LUCC), while the magnitude and patterns vary because of the factors. Investigating the major factor impacting runoff variation is necessary for water resource management. In this work, five different water-energy balance models are used to analyze the cause of runoff variations; of these models, three are based on the Budyko framework and two are based on the ecohydrological conceptual framework. The approach is demonstrated using the upper-midstream of the Heihe Rivers. The results suggest LUCC is the dominant cause of runoff change in the range of 59.92% ~ 65.14%. The estimated impacts of climate change and LUCC are consistent among the five models. Cropping is the major human activity resulting in LUCC at the upper-midstream of the Heihe River. Meanwhile, the change in runoff is more sensitive to precipitation than to potential evapotranspiration. Our work summarizes five widely used water-energy balance models used to explain the impacts of climate change and LUCC on runoff, which may be of importance in explaining the mechanism of runoff change.
Influence of the North Pacific Victoria mode on the Madden–Julian Oscillation
Authors: Wen Tao , Chen Quanliang , Li Jianping , Ding Ruiqiang , Tseng Yu-heng , Hou Zhaolu
Published: March 2020

The influence of the North Pacific Victoria mode (VM) on the Madden–Julian Oscillation (MJO) are examined in this analysis. The results show that the February–April (FMA) VM had a significant influence on the development and propagation of the MJO over the equatorial central–western Pacific (ECWP) during spring (March–May) between 1979 and 2017. Specifically, MJO development was favored more by positive VM events than negative VM events. One probably description for these complicated connections is that the SST gradient anomalies associated with positive VM events enhance the convergence of low-level over the ECWP, which, combined with the warm SST anomalies (SSTAs) in the equatorial central Pacific that lead to a boost in the Kelvin wave anomalies, results in the enhanced MJO activity over the ECWP. These conclusions indicate that the VM is an important factor in MJO diversity.
Water isotope and chemical records in a recent snow pit from Hercules Neve, northern Victoria Land, Antarctica
Authors: Kim Songyi , Han Yeongcheol , Hur Soon Do , Hwang HeeJin , Han Changhee , Hong Sang-Bum , Jun Seong Joon , Chang Chaewon , Lee Seungmi , Jung Hyejin , Lee Jeonghoon
Published: March 2020

A snow pit samples contain information of atmospheric composition and weather condition for recent years. In this study, water isotope ratio and concentrations of major ions and rare earth elements (REE) were determined from a 2 m snow pit sampled at 5 cm intervals at Hercules Neve in northern Victoria Land, Antarctica (73° 03'S, 165° 25'E, 2900m). The water stable isotope ratios range from -45.10 to -29.51 ‰ for δ18O and from 355.8 to -229.2 ‰ for δD. From their clear seasonality, the snow pit is expected to cover the period of 2012–2015. The REE patterns reveal that there exist at least two distinct sources of terrestrial aerosols; One that makes superior contribution when sea salt input is high is likely located closer than another. 
888 – 444 Ma global plate tectonic reconstruction with emphasis on the formation of Gondwana
Authors: Vérard Christian
Published: March 2020

The formation of Gondwana results from a complex history, which can be linked to many orogenic sutures. Those sutures have often been gathered in the literature under broad orogenies — in particular the Eastern and Western Pan-African Orogenies — although their ages may vary a lot within those wide belts.

The Panalesis model is a plate tectonic model, which aims at reconstructing 100% of the Earth’s surface, and proposes a geologically, geometrically, kinematically, and geodynamically coherent solution for the evolution of the Earth from 888 Ma to 444 Ma. Although the model confirms that the assembly of Gondwana can be considered complete after the Damara and Kuunga orogenies, it shows above all that the detachment and amalgamation of “terranes” is a roughly continuous process, which even persisted after the Early Cambrian.

By using the wealth of Plate Tectonics, the Panalesis model makes it possible to derive numerous additional data and maps, such as the age of the sea-floor everywhere on the planet at every time slices, for instance. The evolution of accretion rates at mid-oceanic ridges and subduction rates at trenches are shown here, and yields results consistent with previous estimates. Understanding the variation of the global tectonic activity of our planet through time is key to link plate tectonic modelling with other disciplines of Earth sciences.
Vortical flow in the plasma sheet: Non-linear growth of flow burst surface wave?
Authors: Chong Ghai Siung , De Spiegeleer Alexandre , Hamrin Maria , Pitkanen Timo , Aizawa Sae , Juusola Liisa , Andersson Laila
Published: March 2020

In contrast to the simple conventional plasma flow convection governed by the Dungey Cycle, past studies have revealed that the plasma flows in the magnetotail region are more complicated, hosting high-speed bursty and meandering vortical flows. We have utilized magnetic field and plasma data from the Cluster mission to investigate a high speed earthward propagating flow burst with a peak velocity of ~530 km/s in the magnetotail plasma sheet (XGSM ~ -17RE) on 20 September 2002. In the vicinity of this flow burst, a vortical flow, whose plasma vectors are first directed tailward then earthward, is also observed. The plasma data shows that the plasma population in the vortical flow is likely to originate from the associated flow burst. In addition, the boundaries of both structures are also found to be tangential discontinuities, clearly surrounded by the ambient slow moving plasma sheet. Inside the vortical flow, there exists a region where plasma originating from the flow burst and ambient plasma sheet are mixed. The local segment of inbound boundary crossing of the vortical flow is shown to have a thickness that is non-uniform. Coupled with the flow evolution in the vortical flow, these characteristics are consistent to a boundary crossing of a vortical flow. The magnetic field on the flow burst is quasi-perpendicular to the large velocity shear (~460 km/s) across the flow burst boundary. These results suggest that the formation of vortical flow can arise from the development and subsequent growth of flow burst boundary wave as a result of Kelvin-Helmholtz instability. In summary, this article presents a detailed observational study of a vortical flow and the formation of which would serve as the first direct observational consequence of an excited and growing flow burst boundary wave. Continuous scattering of the detached vortices may play an important role in the braking mechanism of earthward propagating flow bursts. 
Historical land degradation strongly influences soil geography – a case in Ethiopia’s mountains
Authors: Nyssen Jan , Tielens Sander , Teka Kassa , Haile Mitiku , Zenebe Amanuel , Munro R. Neil , Poesen Jean , Dondeyne Stefaan , Frankl Amaury , Deckers Seppe , Tsegay Alemtsehay
Published: March 2020

Understanding the geographical distribution of soils is indispensable for policy and decision makers to achieve the goal of increasing agricultural production and reduce poverty, particularly in the Global South. The soilscapes of the Giba catchment (900-3300 m a.s.l.; 5133 km²) in northern Ethiopia were studied, in support of sustainable soil use and land management. Based on their morphologic, physical and chemical properties, 141 soil profile pits and 1381 additional augered profiles were classified according to the World Reference Base for soil resources. The dominant soil units are Leptosols (19% coverage), Vertic Cambisols (14%), Regosols and Cambisols (10%), Skeletic and Leptic Cambisols and Regosols (9%), Rendzic Leptosols (7%), Calcaric and Calcic Vertisols (6%), Chromic Luvisols (6%) and Chromic and Pellic Vertisols (5%). The soilscapes are best explained by the topography and parent material that are the major factors determining the geomorphic processes in the area. Besides these two factors, land cover that is strongly impacted by human activities, may not be overlooked. Except for the Vertisols and patchy Phaeozems that are stable since the Mid-Holocene, all other soil units in the study area are the result of profile truncation on the one hand, and colluviation more downslope on the other hand. In addition, due to three millennia of soil tillage, lynchets have been formed at many places along the slope, and rock fragments concentrated on the surface, leading to armouring that locally prevents deeper erosion. Our soil suitability study shows that currently, after thousands of years of agricultural land use and concomitant land degradation, a new dynamic equilibrium has come into existence in the soilscape, in which ca. 65% of the catchment remains suitable  for agricultural production.
The dominant environmental driver of leaf water stable isotope enrichment differs for H-2 compared to O-18
Authors: Cuntz Matthias , Cernusak Lucas A ,   Isotopists
Published: March 2020

Several important isotopic biomarkers derive at least part of their signal from the stable isotope composition of leaf water (e.g., leaf wax δ2H, cellulose δ2H and δ18O, lignin δ18O). In order to interpret these isotopic proxies, it is therefore helpful to know which environmental variable most strongly controls a given leaf water stable isotope signal. We collated observations of the stable isotope compositions of leaf water, xylem water, and atmospheric vapour, along with air temperature and relative humidity, to test whether the dominant driver of leaf water 2H concentration could differ from that of 18O concentration. Our dataset comprises 690 observations from 35 sites with broad geographical coverage. We limited our analysis to daytime observations, when the photosynthetic processes that incorporate the leaf water isotopic signal primarily take place. The Craig-Gordon equation was generally a good predictor for daytime bulk leaf water stable isotope composition for both δ2H (R2=0.86, p<0.001) and δ18O (R2=0.63, p<0.001). It showed about 10% admixture of source water was caused by unenriched water pools such as leaf veins or the Péclet effect. Solving the Craig-Gordon equation requires knowledge of relative humidity, air temperature, and the stable isotope compositions of source water and atmospheric vapour. However, it is not possible to invert the Craig-Gordon equation to solve for one of these parameters unless the others are known. Here we show that the two isotopic signals of δ2H and δ18O are predominantly driven by different environmental variables: leaf water δ2H correlated most strongly with the δ2H of source water (R2=0.68, p<0.001) and atmospheric vapour (R2=0.63, p<0.001), whereas leaf water δ18O correlated most strongly with air relative humidity (R2=0.46, p<0.001). We conclude that these two isotopic signals of leaf water are not simply mirror images of the same environmental information, but carry distinct signals of different climate factors, with crucial implications for the interpretation of downstream isotopic biomarkers.
The effects of climate change on the Atacama Desert as a pertinent Mars analog model
Authors: Azua-Bustos Armando , G. Fairén Alberto
Published: March 2020

Since 2003 the Atacama Desert in northern Chile is well-known as Mars analog model due to its extreme aridity, high UV radiation and highly saline soils containing highly oxidizing chemical species. Is in this frame that our team and others for the past decades have described a number of sites in the Atacama and their pertinence as Mars analog. However, since 2015 a number of climatic events never reported before have affected the Atacama, thought to be caused by climate change, with effects yet to be fully understood. Given that new instruments, techniques and rovers are, and will be tested in the Atacama before to be sent to Mars, is critical to be aware of these changes in order to properly plan new explorations and testing missions in this desert. Here we present some of the evidences of the changes brought by these environmental alterations, suggesting also the regions of the Atacama that still may be less or unaffected by them.
Early exhumation of the Frontal Cordillera (southern Central Andes at ~33.5°S) and implications for Andean mountain-building
Authors: Lacassin Robin , Riesner Magali , Simoes Martine , Habel Tania , Margirier Audrey , Carrizo Daniel
Published: March 2020

The Andes are the modern active example of a Cordilleran-type orogen, with mountain-building  and crustal thickening within the upper plate of a subduction zone. Despite numerous studies of  this emblematic mountain range, several primary traits of this orogeny remain unresolved or poorly documented. The timing of uplift and deformation of the Frontal Cordillera basement culmination of  the Southern Central Andes is such an example, even though this structural unit appears as a first-order topographic and geological feature. Constraining this timing and in particular the onset of uplift is a key point in the ongoing debate about the initial vergence of the crustal-scale thrusts at the start of the Cenozoic Andean orogeny. To solve for this, new apatite and zircon (U-Th)/He ages from granitoids of the Frontal Cordillera at ~33.5°S are provided here. These data, interpreted as an age-elevation thermochronological profile, imply continuous exhumation initiating well before ~12–14 Ma, and at most by ~22 Ma when considering the youngest zircon grain from the lowermost sample (Riesner et al. 2019). The inverse modeling of the thermochronological data using QTQt software confirms these conclusions and point to a continuous cooling rate since onset of cooling. The minimum age of exhumation onset is then refined to ~20 Ma by combining these results with data on sedimentary provenance from the nearby basins. Such continuous exhumation since ~20 Ma needs to have been sustained by tectonic uplift on an underlying crustal-scale thrust ramp. Such early exhumation and associated uplift of the Frontal Cordillera question the classically proposed east-vergent models of the Andes at this latitude. Additionally, this study provides further support to recent views on Andean mountain-building proposing that the Andes-Altiplano orogenic system grew firstly over west-vergent basement structures before shifting to dominantly east-vergent thrusts. 
Riesner M. et al. 2019, Scientific Reports, DOI: 10.1038/s41598-019-44320-1
Interactions between ocean heat transport and Arctic sea ice
Authors: Docquier David , Fuentes-Franco Ramon , Wyser Klaus , Koenigk Torben
Published: March 2020

Arctic sea ice has been retreating at fast pace in the last decades, with potential impacts on the weather and climate at mid and high latitudes, as well as the biosphere and society. Sea-ice loss is driven by anthropogenic global warming, atmospheric circulation changes, climate feedbacks, and ocean heat transport. To date, no clear consensus regarding the detailed impact of ocean heat transport on Arctic sea ice exists. Previous observational and modeling studies show that the poleward Atlantic Ocean heat transport and Arctic sea-ice area and volume are generally anti-correlated, suggesting a decrease in sea-ice area and volume with larger ocean heat transport. In turn, the changing sea ice may also affect ocean heat transport, but this effect has been much less studied. Our study explores the two-way interactions between ocean heat transport and Arctic sea ice. We use the EC-Earth global climate model, coupling the atmosphere and ocean, and perform different sensitivity experiments to gain insights into these interactions. The mechanisms by which ocean heat transport and Arctic sea ice interact are analyzed, and compared to observations. This study provides a way to better constrain model projections of Arctic sea ice, based on the relationships between ocean heat transport and Arctic sea ice.
Downstream intensification of hydrological drought along a large Central Asian River over the past decades: the individual roles of climate variability and land use change
Authors: Roodari Artemis , Hrachowitz Markus , hassanpour farzad
Published: March 2020

The Helmand Transboundary River is the main drainage system in the southern part of Afghanistan and has a significant impact on the socioeconomic balance of the Sistan region in Iran. The persistent and intensifying hydrological drought causing the scarcity of water and depleted supplies for irrigation has been effective in reducing agricultural production and increasing migration in the Sistan region. For drought management, knowledge of factors affecting the development of hydrological droughts is essential. Due to the significant rise of drought in the Sistan region in recent decades, we quantified the drought characteristics throughout the basin to reveal the temporal and spatial pattern of drought in the Sistan Plain. The meteorological and hydrological droughts were reanalyzed based on the precipitation and streamflow records using the multi-month timescales during 1970–2006, a period of 37 years. To reproduce the river discharge to evaluate the hydrological drought, the distributed process-based hydrological model was first developed. The results indicate that the hydrological model performed quite well in both calibration and validation periods in the entire basin. The drought analysis represented that the trend of hydrological droughts in the Sistan Plain considerably changed in the last decade of the study period due to the increasing abstractions from the Helmand River associated with the rising evaporation, which have led to extending the severe drought of long duration in the Sistan area.
Urban greenhouse gas emissions from the Berlin area: A case study using airborne CO2 and CH4 in situ observations in summer 2018
Authors: Klausner Theresa , Mertens Mariano , Huntrieser Heidi , Galkowski Michal , Kuhlmann Gerrit , Baumann Robert , Fiehn Alina , Jöckel Patrick , Pühl Magdalena , Roiger Anke
Published: March 2020

Urban areas are recognised as a significant source of greenhouse gas emissions (GHG), such as carbon dioxide (CO2) and methane (CH4). The total amount of urban GHG emissions, especially for CH4, however, is not well quantified. Here we report on airborne in situ measurements using a Picarro G1301-m analyser aboard the DLR Cessna Grand Caravan to study GHG emissions downwind of the German capital city Berlin. In total, five aircraft-based mass balance experiments were conducted in July 2018 within the Urban Climate Under Change [UC]2 project. The detection and isolation of the Berlin plume was often challenging because of comparatively small GHG signals above variable atmospheric background concentrations. However, on July 20th enhancements of up to 4 ppm CO2 and 21 ppb CH4 were observed over a horizontal extent of roughly 45 to 65 km downwind of Berlin. These enhanced mixing ratios are clearly distinguishable from the background and can partly be assigned to city emissions. The estimated CO2 emission flux of 1.39 ± 0.75 t s-1 is in agreement with current inventories, while the CH4 emission flux of 5.20 ± 1.61 kg s-1 is almost two times larger than the highest reported value in the inventories. We localized the source area with HYSPLIT trajectory calculations and the high resolution numerical model MECO(n) (down to ~1 km), and investigated the contribution from sewage-treatment plants and waste deposition to CH4, which are treated differently by the emission inventories. Our work highlights the importance of a) strong CH4 sources in the surroundings of Berlin and b) a detailed knowledge of GHG inflow mixing ratios to suitably estimate emission rates.
The influence of soil structure on heterotrophic respiration response to soil water content
Authors: Herbst Michael , Tappe Wolfgang , Kummer Sirgit , Vereecken Harry
Published: March 2020

Soil respiration causes one of the largest terrestrial carbon fluxes and its accurate prediction is still a matter of on-going research. Understanding the functional link between soil heterotrophic respiration and soil water content is relevant for the estimation of climate change impacts on soil CO2 emissions. 
In order to quantify the effect of air-drying and sieving with 2 mm meshes on the soil heterotrophic respiration response to water content we incubated intact cores and sieved samples of two loamy and two sandy agricultural topsoils for six levels of effective soil water saturation. We further measured soil textural properties and the soil water retention characteristics of the soils with the aim to identify potential correlations between soil physical parameters and moisture sensitivity functions of heterotrophic respiration. 
The incubation of sieved and intact soils showed distinct differences in the response of soil heterotrophic respiration to soil water saturation. The sieved soils exposed threshold-type behaviour, whereas the undisturbed soils exposed a quadratic increase of heterotrophic respiration with increasing effective soil water content. Additionally, we found significant correlations between the moisture response functions of the undisturbed soils and soil textural properties.
From the comparison of intact and sieved soil incubations we conclude that the destruction of soil structure by sieving hampers the transferability of measured soil moisture response of heterotrophic respiration to real-world conditions. For modelling purposes we suggest the use of a quadratic function between relative respiration and effective saturation for soils with a clay fraction < 20 %.
A novel approach for oceanic spreading terrain classification at the Mid-Atlantic Ridge using Eigenvalues of high-resolution bathymetry
Authors: Alodia Gabriella , Green Chris , McCaig Andrew , Paton Douglas
Published: March 2020

Terrain classification at slow-spreading ridges has been a topic of interest since the significant discovery of mantle rocks exhumed by detachment faults in various segments of the Mid-Atlantic spreading axis. These rocks commonly form domed massifs, so-called core complexes, in contrast to the linear fault-bounded abyssal hills of magmatic spreading terrains. However, there is still limited quantitative description of these two distinct structures. We present analysis of high-resolution bathymetry data 21-24 N over the Mid-Atlantic Ridge and its derivatives to highlight the shapes and directionality of the two oceanic crust features. We assign an optimized 8 arc-minute (~14.8 km) window, mimicking the average size of core complexes, in which we compute the Eigenvalues from each cell within the window based on its directionality and slope. We use the two most dominant Eigenvalues – representing the window’s overall horizontal directionality – to compute eccentricity values and weight them with the sine of the slope. From the computation, we found that areas with weighted eccentricity of 0-0.6 represent the omnidirectional terrains that result from tectonic activities; 0.6-0.9 represents the extended terrain or the buffer zone between the tectonic and magmatic terrains; values >0.9 highlight bidirectional magmatic terrains. Based on this classification, we found significantly more evidence of detachment faulting west of the spreading axis compared to the eastern side. This analysis also highlights neo-volcanic activity that started at around 2 Ma that propagates to the south, cutting a fracture zone before it became inactive. The result contributes to a new approach in mining information from high-resolution bathymetry data to assess oceanic spreading type and its symmetry at a slow-spreading ridge through time.
Smart City Technologies for Cultural Heritage Protection
Authors: Moßgraber Jürgen , Hellmund Tobias , Hertweck Philipp , van der Schaaf Hylke
Published: March 2020

Climate change (CC) will morph the environmental landscape, thus leading to climate stress imposed on Cultural Heritage (CH). Especially, tangible CH, like castles, palaces, monuments and churches as well as gardens are exposed to CH effects. Such effects are heat waves, flooding, higher sea level, just to name a few.

The management and preservation of such CH buildings and whole sites, particularly in the context of CC, is a complex task in which authorities and decision makers need to aggregate and oversee information from diverse sources and domains. Yet, only by considering all relevant and available information, stakeholders can make well-grounded decisions. This imposes a complex task upon the authorities, not only due to the diversity and heterogeneity, but also to the quantity of available data.
Only if the current and future situation of the CH in focus is understood, strategies for protecting them can be developed.

The first challenge is to apply different kind of sensors to the buildings and gardens to collect data about the weather (temperature, precipitation, etc.), the situation of walls incl. cracks and the state of plants. After that, this data needs to be managed and made accessible in homogeneous way for further processing and analysis.
The domain of smart city research faces the exact same problems. Sensors are applied all over the city for example about traffic, infrastructure, air and water quality and weather data. In contrast to CH the community is much larger and the industry is involved as well.

Therefore, it is beneficial to look into technologies developed for smart cities and analyze how they can be applied to the monitoring of CH sites. For retrieving, managing and processing sensor data there are open standards evolving, for example the SensorThings API standard by the Open Geospatial Consortium (OGC). Currently, many tools evolve around such standards from which some are available as open source.
First results of successfully applying these technologies from different CH and smart city projects will be presented.
Detailed study of 137Cs distribution in soil-litter-moss cover within the undisturbed woodland test site in the Chernobyl abandoned zone, Russia
Authors: Dolgushin Denis , Korobova Elena , Baranchukov Vladimir , Dogadkin Nikolay
Published: March 2020

Cs-137 distribution was studied in the regular grid and in landscape cross-sections characterizing the ELGS system (top-slope-closing depression) in the “Vyshkov-2” test site located in the Chernobyl abandoned zone, the Bryansk region, Russia. The test site (70×100 m) located on the Iput’ river terrace in a pine forest formed on sod-podzolic soils is characterized by a pronounced elevation gradient (ca 4.5 m). In 1986 the level of 137Cs contamination of the area varied from 1480 kBq/m2 to 1850 kBq/m2. The distribution of 137Cs was studied in the topsoil, soil, moss and litter cover in a grid manner with a step of 10 m and along cross-sections with 1 m step. To assess the influence of water regime on radiocaesium migration moisture content was also determined in the studied objects. The data showed that the major part of 137Cs is now fixed in the soil layer 2-10 cm thick while the highest activity of radiocaesium is found at a depth of 2-8 cm that can be explained mainly by the burial of the initially contaminated layer under the annual leaf fall. In the ELGS system the content of 137Cs in the top soil layer (0-2 cm) determined in laboratory conditions by Canberra gamma-spectrometer with HPGe detector correlated with the surface Cs-137 activity measured by field gamma-spectrometer Violinist III (r=0.643, n=15). Cs-137 activity in the green part of moss samples correlated with the radionuclide activity in soil layer samples 4-6 cm deep (r=0.627, n=15). In the moss samples the highest correlation was observed between the green and rhizoid moss parts (r0.01=0.718, n=60, along cross-sections), (r0.05=0.858, n=20, in regular grid). Correlation between radiocesium activity of the green part of mosses and the underlain litter samples was lower, but also significant (r0.01=0.617, n=60, along cross-sections), (r0.05=0.481, n=20, in regular grid). Cs-137 activity in the rhizoid part of moss and in litter were also positively linked, but to a lower degree (r0.01=0.402, n=60). Studies performed in 2015-2019 confirmed our earlier finding that radiocaesium had not moved in unidirectional manner down the slope to the closing depression, but formed a more complex polycentric structure in ELGS.

The study was financially supported by the Russian Foundation for Basic Research (grant # 19-05-00816).
Passive Seismic Marchenko Imaging
Authors: Jin Zhongyuan
Published: March 2020

In recent years, seismic interferometry (SI) has been widely used in passive seismic data, it allows to retrieve new seismic responses among physical receivers by cross-correlation or multidimensional deconvolution (MDD). Retrieval of reflected body waves from passive seismic data has been proved to be feasible. Marchenko method, as a new technique, retrieves Green’s functions directly inside the medium without any physical receiver there. Marchenko method retrieves precise Green’s functions and the up-going and down-going Green’s functions can be used in target-oriented Marchenko imaging, and internal multiples related artifacts in Marchenko image can be suppressed. 

Conventional Marchenko imaging uses active seismic data, in this abstract, we propose the method of passive seismic Marchenko imaging (PSMI) which retrieves Green’s functions from ambient noise signal. PSMI employs MDD method to obtain the reflection response without free-surface interaction as an input for Marchenko algorithm, such that free-surface multiples in the retrieved shot gathers can be eliminated, besides, internal multiples don’t contribute to final Marchenko image, which means both free-surface multiples and internal multiples have been taken into account. Although the retrieved shot gathers are contaminated by noises, the up-going and down-going Green’s functions can be still retrieved. Results of numerical tests validate PSMI’s feasibility and robustness. PSMI provides a new way to image the subsurface structure, it combines the low-cost property of passive seismic acquisition and target-oriented imaging property of Marchenko imaging, as well as the advantage that there are no artifacts caused by internal multiples and free-surface multiples.

Overall, the significant difference between PSMI and conventional Marchenko imaging is that passive seismic data is used into Marchenko scheme, which extends the Marchenko imaging to passive seismic field. Passive seismic Marchenko imaging avoids the effects of free-surface multiples and internal multiples in the retrieved shot gathers. PSMI combines the low-cost property of passive seismic acquisition and target-oriented imaging property of Marchenko imaging which is promising in future field seismic survey.

This work is supported by the Fundamental Research Funds for the Central Universities (JKY201901-03). 
Submarine glacial landforms in Southeast Greenland fjords reveal contrasting outlet-glacier behaviour since the Last Glacial Maximum
Authors: Batchelor Christine , Dowdeswell Julian , Rignot Eric , Millan Romain
Published: March 2020

The Southeast (SE) Greenland margin, which includes the SE sector of the Greenland Ice Sheet (GIS) and the eastern Julianehåb Ice Cap (JIC), is drained by a number of fast‐flowing, marine‐terminating outlet glaciers. Although the SE Greenland margin is suggested to have been highly sensitive to past climatic changes, mountainous terrain and a lack of ice‐free areas have largely prevented analysis of the deglacial and Holocene behaviour of these outlet glaciers. Here we use bathymetric data, from multibeam echo-sounding acquired by NASA’s Earth Venture Sub‐orbital Oceans Melting Greenland (OMG) mission and from gravity inversion derived from Operation Icebridge (OIB) gravity data, from 36 fjords along the SE Greenland margin to map the distribution of more than 50 major submarine moraines. The moraines are up to 3 km long in the former ice‐flow direction, reach up to 150 m above the surrounding seafloor, and span the width of the fjord.

Inner‐fjord moraines are widespread along the SE Greenland margin, occurring in 65% of the surveyed fjords of the SE GIS and the JIC. Their locations beyond the oldest ice‐margin position where it is known from aerial photographs and correlation with prominent terrestrial moraines suggest that the inner‐fjord moraines were produced sometime during the Neoglacial (since approximately 4 ka).

Major moraine ridges are present in a midfjord setting in all of the nine fjords of the eastern JIC yet are generally absent from the deeper and wider fjords of the SE GIS. Given the distribution of published deglacial ages, we hypothesize that the midfjord moraines of the eastern JIC were formed during an ice‐margin still‐stand or advance that occurred during the early Holocene. It is possible that this still‐stand or advance had a climatic control, for example, the 8.2‐ka event that has been recorded from Greenland ice cores. The absence of midfjord moraines from the deeper and wider fjords of the SE GIS to the north suggests relatively rapid and continuous ice retreat occurred during the last deglaciation. The contrasting behaviour of the SE GIS and the eastern JIC during the last deglaciation probably reflects differences in fjord geometry and exposure to ocean heat.
Chemical weathering and physical erosion rates along a vegetation and climate gradient, Chilean Coastal Cordillera (26° – 38°S)
Authors: Schaller Mirjam , Ehlers Todd A.
Published: March 2020

Chemical weathering and physical erosion are important processes shaping topography, producing soils, and providing nutrients for life.  The rates of these processes are influenced not only by tectonics, but also by climate and biota.  The Chilean Coastal Cordillera from 26° to 38°S is a natural laboratory to investigate chemical weathering and physical erosion rates over different climatic settings.  From North to South, climate changes from arid (Pan de Azúcar), semi-arid (Santa Gracia), Mediterranean (La Campana) to temperate humid (Nahuelbuta).  Here we present chemical weathering and physical erosion rates based on published and new in situ-produced cosmogenic nuclides and immobile elements published from soil pedon depth profiles in the four study areas.

Calculated chemical weathering rates range from zero in Pan de Azúcar to an high value of 211 t/(km2 yr) in La Campana.  Chemical weathering rates are comparable in Santa Gracia and Nahuelbuta (~20 t/(km2 yr).  Physical erosion rates are low in Pan de Azúcar (~11 t/(km2 yr)) and increase towards the South (~ 40 t/(km2 yr)).  Combined chemical weathering and physical erosion rates indicate that denudation rates are lowest in Pan de Azúcar and highest in La Campana.  The contribution of chemical weathering to total denudation rates is increasing and then decreasing with increasing mean annual precipitation from North to South.  The observation that the calculated chemical weathering rates in the southernmost location with the highest mean annual precipitation and the highest chemical index of alteration are not the highest of all four study areas is evaluated and discussed.   We investigate possible influence of precipitation and vegetation on chemical weathering and physical erosion rates.
Sensitivity analysis of SKEB method in Regional ensemble forecast system GRAPES-REPS
Authors: Li Hongqi , Chen Jing
Published: March 2020

In order to solve the problem of excessive energy dissipation near the sub-grid scale in numerical weather model, the Stochastic Kinetic Energy Backscatter (SKEB) method is introduced into the GRAPES-REPS regional ensemble prediction system, and the first-order autoregressive stochastic process is used in the horizontal direction. Calculate the random pattern obtained by spherical harmonic expansion in the direction, calculate the local dynamic energy dissipation rate caused by the numerical diffusion scheme, construct the random flow function forcing, and convert it into horizontal wind speed disturbance, compensate the dissipated kinetic energy, and carry out A 10-day ensemble prediction test and a randomized time and space scale sensitivity test in September and October 2018 (choose 1st, 7th, 13th, 19th, and 25th), and evaluate the test results. The main conclusions of the research work are as follows: By comparing the ensemble prediction results of the test using the SKEB method and the test without the SKEB method, the use of the SKEB scheme increases the large aerodynamic energy of the GRAPES regional model in the small and medium-scale region, and improves the GRAPES model to the actual atmosphere to some extent. The simulation ability of kinetic energy spectrum; the introduction of SKEB scheme in regional ensemble prediction can significantly improve the dispersion of U and V in horizontal wind field of regional model, and the problem of insufficient dispersion of large-scale dynamic energy dissipation rate in Qinghai-Tibet Plateau region is improved. The SKEB program has improved the forecasting skills to a certain extent, such as reducing the CRPS scores of the horizontal wind fields U and V, reducing the outliers scores of the horizontal wind field, temperature, and 10 m wind speed; the introduction of the SKEB method can improve the light rain. The precipitation probability prediction skill score, but the improvement of the score did not pass the significance test, so it is considered that the SKEB method is difficult to effectively improve the probability prediction technique of precipitation.

Sensitivity tests based on the SKEB method for five time scales of random pattern (1h, 3h, 6h, 9h and 12h of the time series τ) show that the ensemble prediction is sensitive to the five time scales of the stochastic model of the SKEB method. And the 12h experiment show the best performance than the others.
Carbon emission related to thermokarst processes in wetlands of NE European Tundra
Authors: Zabelina Svetlana , Shirokova Liudmila , Klimov Sergey , Chupakov Artem , Lim Artem , Polishchuk Yuri , Polishchuk Vladimir , Bogdanov Alexander , Muratov Ildar , Guerin Frederic , Karlsson Jan , Pokrovsky Oleg
Published: March 2020

Emission of greenhouse gases (GHG) from inland waters is recognized as highly important and understudied part of terrestrial carbon (C) biogeochemical cycle. These emissions are still poorly quantified in permafrost regions containing a vast amount of surface C in frozen peatlands. This is especially true for NE European peatlands, located within sporadic to discontinuous permafrost zone which is highly vulnerable to thaw. For a first quantification of the C emission from lentic waters of the Bolshezemelskaya Tundra (BZT, 200,000 km²), we measured CO2 and CH4 concentrations and fluxes to the atmosphere in 98 depressions, thaw ponds and thermokarst lakes ranging from 0.5 to 5x106 m² in size. The CO2 fluxes decreased by an order of magnitude when lake size increased by > 3 orders of magnitude, while CH4 fluxes showed large variability that were not related to lake size By using a combination of Landsat-8 and GeoEye-1 images we found that lakes cover 4% of BZT, and calculated the overall C emission (CO2+CH4) from the lakes of the territory to 3.8 Tg C y-1 (99% C-CO2, 1% C-CH4). Large lakes (> 10,000 m²) dominated GHG emissions whereas small thaw ponds (< 1000 m²) had a minor contribution to overall lake surface area (< 2%) and GHG emission (< 5 % of CO2; < 20% of CH4). The results suggest that, if permafrost thaw in NE Europe leads to the disappearance of large thermokarst lakes and formation of new small thaw ponds and depressions, this will decrease GHG emission from lentic waters of this region. However, due to temporal and spatial variations of C fluxes, the uncertainties on areal GHG emission are at least one order of magnitude in small thaw ponds and a factor of 3 to 5 in thermokarst lakes.

This work was supported by the State Task AAAA-A18-118012390200-5, RFBR grant No. 18-05-70087 “Arctic Resources”, 19-07-00282, 18-45-860002, 18-45-703001 and 18-47-700001, and the Swedish Research Council (grant no. 2016-05275).
Seamless Detection of Cutoff Low and Preexisting Trough
Authors: Honda Meiji , Kasuga Satoru , Ukita Jinro , Yamane Shozo , Kawase Hiroaki , Yamazaki Akira
Published: March 2020

Cutoff lows are cyclones existing in the upper troposphere developing from precursory preexisting troughs. We introduce a new method to seamlessly detect cutoff lows and even preexisting troughs aiming to improve lead time of meso scale disturbances like tornadoes. The method is based on a geometric character; in this method, a slope defined as the tangential line from a minimum point of each height depression is measured on an isobaric surface. This slope evaluates an intensity and horizontal extension (radius) of each depression. Adopting a mathematical assumption, we successfully achieved to make an algorithm to separate the depression and the local background flow. To remove the background flow enables us to detect both cutoff lows and preexisting troughs seamlessly in reanalysis height fields. So, our method would allow the life cycle to be illustrated continuously from the birth of the cutoff low, that is, from the precursory preexisting trough, and is expected to contribute to the improvement of the lead time for predicting severe weathers. Some further application examples, including tornado accompanying cases, and even for blocking highs, would be shown.
Kinematic orbit positioning applying the raw observation approach
Authors: Suesser- Rechberger Barbara , Mayer-Guerr Torsten , Krauss Sandro
Published: March 2020

The kinematic strategy for precise orbit determination (POD) of low earth orbit (LEO) satellites uses only geometric observations to estimate the satellite orbit and does not take any forces into account. This strategy requires a large amount of observation data for one epoch to determine the three-dimensional satellite position. One possibility to get these data is the usage of the spaceborne global navigation satellite system (GNSS) technology, which provides a high number of accurate observations. Following Zehentner (2016) the kinematic orbit positioning applying the raw observation approach by using a least-squares adjustment has shown promising results with a high accuracy.

By applying this approach the kinematic orbits for several LEO satellite missions are estimated and subsequently validated by a comparison with state of the art gravity field solutions. Furthermore due to the fact that solar events causes an orbit decay, these precise determined orbit data are used to analyze solar event impacts on LEO satellites.