bluuebunny/crossref_metadata_2025 huggingface dataset:
Soil water flow behavior of abandoned farmland restored with different vegetation communities in the Loess Plateau of China
Authors: Wang Rui , Zhou Zhengchao , Wang Ning , Xue Zhijing , Cao Liguo
Published: March 2020

Natural vegetation succession in abandoned farmlands simulate the changes in near surface soil characcteristics over the Loess Plateau of China, and hence likely induce temporal variation in the distribution and the movement of soil water in soil layers. In order to assess the effect of the natural vegetation succession on soil water flow behavior, four vegetation communities at different stages of sucession (Artemisia scoparia, Artemisia sacrorum, Bothriochloa ischaemum, Periploca sepium Bunge) in Fangta watershed of Yan River were selected and dye tracer experiments were performed. Both the soil physicochemical properties (e.g., soil bulk density, the particle size, water stable aggregate (>0.25 mm) content, and soil organic matter) and the root systems (e.g., root mean diameter, root mass density, root surface area, and root volume density) tended to increase along with vegetation sucessional development. Results of the dye tracer experiment and the image analysis indicated that the preferential flow was the dominant type in the four field sites. Compared to the site in early stage of sucession, the preferential flow proportion (FFP), preferential infiltration volume (PIV), and the contribution of the preferential infiltration to the total infiltration (Con) in the late stage enhanced by 6.65-7.34 times, 2.73-4.08 times, and 2.52-3.75 times, respectively. Correlation analysis suggested that the plant roots and their morphometric features played more important role on the preferential flow in comparison with the soil physicochemical properties. The abundant lateral root and the steeper slope may have caused the presence of lateral flow. Along with increasing degree of preferential flow, the spatial variability of the soil water through the vertical soil profiles increase during the process of restoration and succession of vegetation communities. Our study demonstrated the improvement of the preferential flow in the abandoned farmland during natural vegetation restoration helped soil water storage in the deep soil layer.

 
Global Adjoint Reconstructions of Earth’s Mantle
Authors: Ghelichkhan Sia , Oeser Jens
Published: March 2020

Mantle convection is the driving mechanism for plate tectonics and associated geological activities, including earthquakes, surface dynamic uplift and subsidence, and volcanoes. Mantle convection can be regarded as the central framework for linking the sub-disciplines of solid Earth science, e.g., geochemistry, seismology, mineral physics, geodesy and geology.

In theory, it is possible to model mantle convection by integrating the principial conservation equations in time, given a past mantle-state as the starting point. Nonetheless, there remains a fundamental lack of knowledge on any past mantle-states. Without such knowledge any direct comparison of convection models and solid Earth observations is challenging and often impractical. One can, however, pose the problem differently, and obtain a past flow history by minimising ‘a misfit’ functional between observations and models of Earth’s mantle. The recent applications of adjoint method in geodynamics, together with the ever-increasing computational power, has facilitated solutions to such minimisation problems, where a unique flow history in Earth’s mantle can be generated, subject to assumed geodynamic modelling parameters.

Here, we build on previously published adjoint models and present a suite of eight high resolution (11 kms) reconstruction models going back to 50 Ma ago. These models incorporate many improvements. First, we take advantage of the recent advances in surface and body waveform tomography to obtain high resolution images of present-day structures in Earth’s mantle. Our thermodynamic modelling of mantle structures rely on the most recent datasets of mantle mineralogy and account for effects of anelasticity. Furthermore, we assume a wide range of viscosity profiles, including published models consistent with observations of geoid, mantle mineralogy, and post-glacial rebound studies. Finally, we verify these models by comparisons against a range of different geologic observations.
Numerical modelling of igneous processes
Authors: Keller Tobias
Published: March 2020

Magma matters. From magmatism facilitating the differentiation of terrestrial planets into core, mantle and crust, to the magmatic activity that modulates plate tectonics and deep volatile cycles to maintain a habitable Earth, to volcanism that causes terrible hazards but also provides rich energy and mineral resources – igneous processes are integral to Earth and other planets. Our understanding of volcanoes and their deep magmatic roots derives from a range of disciplines including field geology, petrology and geochemistry, and geophysical imaging. Observational and experimental studies, however, are hampered by incomplete access to processes that play out across scales ranging from sub-micron size to thousands of kilometres, and from seconds to billions of years. Computational modelling provides tools for investigating igneous processes across these scales.

Over the past decade, my research has been focused on advancing the theoretical description and numerical application of multi-phase reaction–transport processes at the volcano to planetary scale. Mixture theory provides a framework to represent the spatially averaged behaviour of a large sample of microscopic phase constituents such as mineral grains, melt films, and vapour bubbles. This approach has been used successfully to model both porous flow of melt percolating through compacting partially molten rock, as well as suspension flow of crystals settling in convecting magma bodies. My recent work has introduced a new modelling framework to bridge the porous and suspension flow limits, and to extend beyound solid-liquid systems to multi-phase systems including several solid, liquid, and vapour phases. These advances provide new insights into the dynamics of crustal mush bodies, the outgassing and eruption of shallow magma reservoirs, and the generation of mineral resources by exsolution of exotic magmatic liquids.
GEOPHYSICAL MEASUREMENTS IN AN ABANDONED OLD RAILWAY TUNNEL (MARSICO NUOVO, Italy)
Authors: De Martino Gregory , Capozzoli Luigi , Giampaolo Valeria , Rizzo Enzo
Published: March 2020

In Europe, there are many abandoned railway tunnels. These structures are generally placed in mountainous or hardly accessible territories, where their use was no longer necessary for the improvement of the road communications and the favourite use of the private car. However, in some cases, they could be an important point of observation to monitor the mountains, where important hydrogeological resource are located. This is the case of an old tunnel sited in Marsico Nuovo village, where the rail way “Atena-Marsico Nuovo” was realized in the early 20th century and worked until the in ’60. The studied tunnel has a total length of 1229 m and, from geological point of view, it is located in the carbonate complex of the Maddalena Mountains and is characterized by the presence of stratified and fractured carbonate rocks. In proximity of this structure, there is also an important karstic cave (Castel di Lepre) already subject to geophysical measurements realized in the past [1]. The presence of a tunnel offers an advantageous perspective to monitor the aquifer improving the knowledge of the fluid circulation in a carbonate rock formation [2].

However, no engineering and geotechnical information about the realization of the construction and the geological setting of the area are available. In order to characterize, from an engineering point of view, the correlation between the hydrogeological formation and the engineering structure, several geophysical surveys, based on electric and electromagnetic acquisitions, were carried out along the gallery. The results obtained show the potentialities of the geophysical methods for monitoring and characterizing engineering structures also providing useful and detailed information for the identification of shallower geological structures in the first meters surrounding the tunnel. 

 

 

 

References 

[1] E. Rizzo, M. Guerriero, E. Gueguen, L. Capozzoli, G. De Martino and F. Perciante, Cave-surface Electrical Resistivity Tomography in “Castello di Lepre” Karst System (Marsico Nuovo, Southern Italy),  Monitoring and Characterization of the Shallow Subsurface I, EAGE 2017, DOI: 10.3997/2214-4609.201702078; 

[2] M. Guerriero, L. Capozzoli, G. De Martino, V. Giampaolo, E. Rizzo, F. Canora and F. Sdao, Geophysical techniques for monitoring carbonate karstic rocks (2019), Italian Journal of Engineering Geology and Environment, DOI: 10.4408/IJEGE.2019-01.S-10; Project: Landslide Risk Assessment along roads (LaRIS), Special Issue 1 (2019) Sapienza Università Editrice. 
Potential Tipping Points of Antarctic Ice Sheet Basins
Authors: Sun Sainan , Pattyn Frank , Durand Gael , Zipf Lars , Bulthuis Kevin , Goelzer Heiko , Haubner Konstanze
Published: March 2020

Antarctica is loosing mass in an accelerating way and these losses are considered as the major source of sea-level rise in the coming centuries. Ice-sheet mass loss is mainly triggered by the decreased buttressing from ice shelves mainly due to ice-ocean interaction. This loss could be self-sustained in potentially unstable regions where the grounded ice lies on a bedrock below sea level sloping down towards the interior of the ice sheet, leading to the so-called marine ice sheet instability (MISI).
Recent observations on accelerated grounding-line retreat and insights in modelling the West Antarctica ice sheet give evidence that MISI is already on its way. Moreover, similar topographic configurations are also observed in East Antarctica, particularly in Wilkes Land. We present an ensemble of simulations of the Antarctic ice sheet using the f.ETISh ice-sheet model to evaluate tipping points that trigger MISI by forcing the model with sub-shelf melt pulses of varying amplitude and duration. As uncertainties in ice-sheet models limit the ability to provide precise sea-level rise projections, we implement probabilistic methods to investigate the influence of several sources of uncertainty, such as basal conditions. From the uncertainty analysis, we identify confidence regions for grounded ice interpreted as regions of the Antarctic ice sheet that remain ice-covered for a given level of probability. Finally, we discuss for each Antarctic basin the total melt energy needed to reach tipping points leading to sustained MISI. 
A new similarity model for the stratified under-ice boundary layer in lakes and its application to ice-covered Lake Baikal
Authors: Kirillin Georgiy , Aslamov Ilya , Granin Nikolai , Zdorovennov Roman
Published: March 2020

Seasonal ice cover on lakes and polar seas creates seasonally developing boundary layer at the ice base with specific features: fixed temperature at the solid boundary and stable density stratification beneath. Turbulent transport in the boundary layer determines the ice growth and melting conditions at the ice-water interface, especially in large lakes and marginal seas, where large-scale water circulation can produce highly variable mixing conditions. Since the boundary mixing under ice is difficult to measure, existing models of ice cover dynamics usually neglect or parameterize it in a very simplistic form. We propose a model of the turbulent energy budget in the stably stratified boundary layer under ice, based on the length scale incorporating the dissipation rate and the buoyancy frequency (Dougherty-Ozmidov scaling). The model was verified on fine-scale measurements in Lake Baikal and demonstrated a good agreement with data. The measured ice-water heat fluxes in were among the largest reported in lakes (up to 40 W m−2) and scaled well against the proposed relationship. The model yields a scaling relationship for the ice-water heat flux as a function of the shear velocity squared that suggests the traditional bulk parameterizations may significantly underestimate the ice-water heat flux, especially at strong under-ice current velocities. The ultimate result consists in a strong dependence of the water-ice heat flux on the shear velocity under ice. 
Borehole-based study of CO2-rich air transport in the vadose zone of a Mediterranean karst system (Malaga, southern Spain)
Authors: Ojeda Lucía , Benavente José , Vadillo Iñaki , Liñán Cristina , P. Sanchez-Cañete Enrique
Published: March 2020

The characterization of CO2 transport, and other C compounds (CH4, DIC, organic matter, etc.), in the vadose zone of a karst aquifer is key in order to quantify sources and sinks of carbon. In karst environments, most of the studies are focused on the dynamics of CO2 in caves, but only a few studies are related to field measurements of the CO2 content in boreholes, which provides direct insights about the vadose zone. Located at the east of the Nerja Cave (Malaga, Andalusia), one of the most important tourist caves in Spain, the vadose zone was accessed by 9 boreholes drilled into the vadose zone of a Triassic carbonate aquifer, with depths ranging between 15 and 30 m. The karst network in the study area is characterized by a great vertical heterogeneity, with significant cavities and voids at specific intervals. Groundwater levels at different altitudes are a consequence of this heterogeneity. Similarly, CO2 distribution and transport are clearly determined by the complex karst network.

Our study aims to identify significant horizontal gradients of CO2 in the karst vadose air, both spatial and temporally. We present monthly measurements of CO2 concentration, relative humidity, air temperature and 222Rn inside boreholes. In addition, we present CO2 results from an 18 hours-atmospheric air injection test. Linking them to the geophysical knowledge of voids in the study area, the results allow us to identify lateral fluxes of CO2-rich air in the vadose zone and how these fluxes are favoured by the incidence of the main karst discontinuity orientations. We observe different ventilation patterns:  in spring the vadose air seems to be stored in specific orientations, while in summer there is a lower convective ventilation. The results contribute to explain the temporal variations of the chemical composition of recharge water in karst systems, as well as to support studies on the global carbon budget.
Temporal variability of inferred surface energy fluxes derived from the ERA5 energy budget
Authors: Mayer Johannes , Mayer Michael , Haimberger Leopold
Published: March 2020

We use the new Copernicus ERA5 reanalysis dataset to evaluate the global atmospheric energy budget using a consistent diagnostic framework and  improved numerical methods. A main outcome of this work are mass consistent divergences of moist static plus kinetic energy fluxes. These divergences are combined with top-of-the-atmosphere fluxes based on satellite observations and reconstructions back to 1985 to obtain net surface energy fluxes (FS) with unprecedented accuracy. The global mean of these FS fields is unbiased by construction. Hence, this product is well-suited for climate studies and model evaluations.  Here, the temporal variability and stability of inferred FS, the land-ocean energy transport and the corresponding water cycle are presented and compared with previous evaluations, which used ERA-Interim. 

The inferred FS fields exhibit a much smaller noise level, and sampling errors are drastically reduced due to the high temporal resolution (hourly) of the ERA5 dataset. Energy budget residuals over land are on the order of 17.0 Wm-2, which represents a 63 % reduction compared to ERA-Interim. We also present time series of FS averaged over the global ocean. Its global mean is 2.0 Wm-2, which is in much better agreement with ocean heat uptake than widely used satellite-derived surface flux products. Moreover, it exhibits reasonable temporal stability at least from 2000 onwards. We compare the annual cycles of FS over the ocean and ocean heat content variations derived from ocean reanalysis products and find good agreement. Overall, our results demonstrate clear improvements over earlier evaluations, but more work is needed to optimally use the available data and further reduce uncertainties.
COnstraining ORographic Drag Effects (COORDE): A model intercomparison of resolved and parametrized orographic drag
Authors: VanNiekerk Annelize , Sandu Irina
Published: March 2020

Mountains are know to impact the atmospheric circulation on a variety of spatial scales and through a number of different processes. They exert a drag force on the atmosphere both locally through deflection of the flow and remotely through the generation of atmospheric gravity waves. The degree to which orographic drag parametrizations are able to capture the complex impacts on the circulation from realistic orography in high resolution simulations is examined here. We present results from COnstraing ORographic Drag Effects (COORDE), a project joint with the Working Group on Numerical Experimentation (WGNE) and Global Atmospheric System Studies (GASS). The aim of COORDE is to validate parametrized orographic drag in several operational models in order to determine both systematic and model dependent errors over complex terrain. To do this, we compare the effects of parametrized orographic drag on the circulation with those of the resolved orographic drag, deduced from km-scale resolution simulations which are able to resolve orographic low-level blocking and gravity-wave effects. We show that there is a large spread in the impact from parametrized orographic drag between the models but that the impact from resolved orography is much more robust. This is encouraging as it means that the km-scale simulations can be used to evaluate the caveats of the existing orographic drag parametrizations. Analysis of the parametrized drag tendencies and stresses shows that much of the spread in the parametrized orographic drag comes from differences in the partitioning of the drag into turbulent and flow blocking drag near the surface. What is more, much of the model error over complex terrain can be attributed to deficiencies in the parametrized orographic drag, particularly coming from the orographic gravity wave drag.
Plio-Pleistocene submarine glaciogenic morphology of the Chukchi Shelf, Arctic Ocean
Authors: Lehmann Carsten , Jokat Wilfried , Altenbernd Tabea
Published: March 2020

Ongoing research aims to constrain the extent of grounded ice shelves around the Arctic Ocean during the last glacial periods. Here, the Chukchi region is of special interest because of its broad, shallow shelf. In general, little is known about possible sources and the areal extent of ice sheets if any existed on the Chukchi shelf.

Bathymetric and sub bottom profiler data from the Chukchi Sea margins as well as from the Arlis Plateau to the west show complex patterns of glaciogenic erosion like Mega Scale Glacial Lineations (MSGL) at water depths of more than 500 m. The different directions of those MSGL indicate the presence of ice shelves and streams and point to an East Siberian Ice Sheet of unknown size. On the Chukchi Shelf, no evidences for the existence of an ice shelf for water depths shallower than 350 m have been described yet.

We re-processed 2D multi-channel seismic data acquired in 2011 from R/V Marcus G. Langseth to investigate glaciogenic features on the shallow shelf. These data reveal new insights into the formation of the northern Chukchi Shelf. The first up to 500 ms TWT of the seismic data show strongly eroded reflectors and reworked sediments. Additionally, small-scale channels with a few tens of meters width and a depth of 20 ms TWT disrupt the horizons below the reworked layers. Furthermore, the seismic data show channels with widths up to few km and depths up to 150 ms TWT as well as truncated well stratified reflectors. All above described features can be observed on parts of the Chukchi shelf with water depths shallower than 900 m.

 
An approach to assess drought vulnerability with multi criteria analysis
Authors: Lee Gyumin , Jun Kyung Soo , Kwon Minsung
Published: March 2020

This study is aimed to establish an approach for estimating drought vulnerability using multi criterion decision making methods. Drought has spatially wide-ranging effects, its duration is difficult to predict, and long-lasting damages. For this reason, the conversion of drought damage into an amount of money or physical quantity is difficult. Accordingly, policy makers and researchers have difficulty in securing grounds for determining countermeasures against drought disasters. Thus, to determine drought vulnerability, factors with long-term impact on social and economics need to be taken into account. The evaluation approach consisted of three stages: evaluation factor and weight identification, database construction, evaluation data and weight combination. In this study, the factors to assessing drought vulnerability was identified using Delphi method, and the drought vulnerability was determined by the TOPSIS method which is a widely used MCDM method.
Modelling perennial firn aquifers in the Antarctic Peninsula
Authors: van Wessem Jan Melchior , van den Broeke Michiel , Steger Christian , Wever Nander , Ligtenberg Stefan
Published: March 2020

We predict the location of perennial firn aquifers (PFAs) in the Antarctic Peninsula using the updated regional atmospheric climate model RACMO2.3p2, that is specifically adapted for use over the polar regions. With RACMO2 output we force two sophisticated firn models, IMAU-FDM and SNOWPACK, with surface mass fluxes and surface energy fluxes, respectively. These firn models explicitly calculate processes in the snowpack, such as densification, meltwater penetration, refreezing, retention and runoff.

In this presentation, we focus on the Antarctic Peninsula (AP), where conditions are favorable for the formation of PFAs: there is both sufficient meltwater production and snowfall to store the meltwater in the firn during winter without refreezing, as the fresh snow insulates the meltwater from the winter cold wave. These conditions are similar to those locations where PFAs were discovered in Greenland and Svalbard.

While slightly different in behavior, both firn models calculate PFAs on Wilkins ice shelf and the northwestern AP mountain range, but also near the grounding lines of unstable or disintegrated ice shelves such as Prince Gustav, Larsen B and Wordie. The PFAs exist in different forms, e.g. long-lasting, shallow, deep or multi-layer, and are sensitive to the magnitude and timing of atmospheric forcing conditions. We carefully explore processes controlling their formation and/or longevity, discuss their implications for ice shelf stability, and their potential to exist elsewhere in Antarctica.
Dynamical Systems Theory Sheds New Light on Compound Climate Extremes in Europe and Eastern North America
Authors: Pons Flavio , De Luca Paolo , Messori Gabriele , Faranda Davide
Published: March 2020

We propose a novel approach to the study of compound extremes, grounded in dynamical systems theory. Specifically, we present the co-recurrence ratio (α), which elucidates the dependence structure between maps by quantifying their joint recurrences. This approach is applied to daily climate extremes, derived from the ERA-Interim reanalysis over the 1979-2018 period. The analysis focuses on concurrent (i.e. same-day) wet (total precipitation) and windy (10m wind gusts) extremes in Europe and concurrent cold (2m temperature) extremes in Eastern North America and wet extremes in Europe. Results for wet and windy extremes in Europe, which we use as a test-bed for our methodology, show that α peaks during boreal winter. High αvalues correspond to wet and windy extremes in north-western Europe, and to large-scale conditions resembling the positive phase of the North Atlantic Oscillation (NAO). This confirms earlier findings which link the positive NAO to a heightened frequency of extra-tropical cyclones impacting north-western Europe, resulting in frequent wet and windy extremes. For the Eastern North America-Europe case, α extremes once again reflect concurrent climate extremes -- in this case cold extremes over North America and wet extremes over Europe. Our analysis provides detailed spatial information on regional hotspots for these compound extreme occurrences, and encapsulates information on their spatial footprint which is typically not included in a conventional co-occurrence analysis. We conclude that α successfully characterises compound extremes by reflecting the evolution of the associated meteorological maps. This approach is entirely general, and may be applied to different types of compound extremes and geographical regions.
Development of iFTEM fixed-wing time-domain airborne electromagnetic instrument
Authors: Ben Fang , Li Junfeng , Huang Wei , Liu Junjie , Wu Shan , Liu Lei , Cao Zhanhong , Wang Hao
Published: March 2020

    The fixed-wing time-domain airborne electromagnetic system transmits low-frequency electromagnetic pulse waves with large magnetic moments, receives weak secondary response electromagnetic field signals generated by the underground medium. It can realize deep depth airborne electromagnetic exploration. After 10 years of research and development, the Institute of Geophysical and Geochemical Exploration of the Chinese Academy of Geological Sciences successfully developed the first-generation fixed-wing time-domain airborne electromagnetic system of China in 2016——iFTEM. The peak transmit current is 600A, and the peak magnetic moment is 5.0 × 105Am2. The exploration depth is 350m. Test flights measurement were taken in 2016. Based on the first-generation iFTEM system, we upgraded the system. The new transmitter has a peak transmit current of more than 1000A and a peak magnetic moment of more than 1,000,000Am2. It has multi-wave transmit capability. The static noise of the three-component induction coil receiving sensor is better than 0.1nT/√Hz@1kHz. We are developing a time-domain airborne electromagnetic data processing software platform, which includes the data organization, denoising and correction software modules. This paper mainly introduces the development of China's first fixed-wing time-domain airborne electromagnetic instrument. This paper is financially supported by National Key R&D Program of China (2017YFC0601900) and CGS Research Fund (JYYWF20180103).
Status of Air Pollutant Emissions and Health Impact of LNG Cogeneration Plant in Administrative City, Republic of Korea
Authors: Kim Yumi
Published: March 2020

Along with the development of new cities, the construction of LNG cogeneration plant in urban areas is being promoted, and the facility has been pointed out as one of the major air pollution sources along with many vehicles in urban areas. For example, the construction of a new administrative city in Korea has led to the relocation of major government buildings and the influx of more than 300,000 people. The city has a 530 MW power plant + 391 Gcal/h district heating facility. The facility released 294,835 kg and 325,381 kg of NOx annually in 2017 and 2018, respectively. When examining the impact, we analyzed the impact of air pollutants (PM2.5, O3, NO2, etc.) through CMAQ modeling. In addition, the impact prediction using AERMOD related to the release of carcinogenic air pollutants is estimated to be no more than 10-5 (risk level), but measurement and verification are required. In addition to concentration-based risk assessments, health impact assessments are needed that consider the number of populations exposed. In this study, QGIS was used to calculate population. In conclusion, even if the same LNG power plant is constructed, the LNG cogeneration plant located adjacent to a large residential facility requires air pollutant management measures according to the exposure population by radius of influence

 
Mitigating Spatial Leakage in Monthly GRACE/GRACE-FO Gravity Fields for the Separation of Barystatic Sea-Level Variations and Residual Ocean Circulation Effects
Authors: Klemann Volker , Dobslaw Henryk , Bagge Meike , Dill Robert , Thomas Maik , Dahle Christoph , Flechtner Frank
Published: March 2020

Temporal variations in the total ocean mass representing the barystatic part of present-day global mean sea-level rise can be unambiguously inferred from time-series of global gravity fields as provided by the GRACE and GRACE-FO missions. A spatial integration over all ocean regions, however, largely underestimates present-day rates as long as the effects of spatial leakage along the coasts of in particular Antarctica, Greenland, and the various islands of the Canadian Archipelago are not properly considered.

Based on the recent release 06 of monthly gravity fields processed at GFZ, we quantify (and subsequently correct) the contribution of spatial leakage to the post-processed mass anomalies of continental water storage and ocean bottom pressure. Utilising the sea level equation allows to predict spatially variable ocean mass trends out of the (leakage-corrected) terrestrial mass distributions from GRACE and GRACE-FO. Consistent results for the global mean barystatic sea-level rise are obtained also from spatial integrations over ocean masks with different coastal buffer zones ranging from 400 to 1000 km, thereby confirming the robustness of our method. Residual month-to-month variations in ocean bottom pressure are indicative for errors in the monthly-mean estimates of the applied de-aliasing model AOD1B RL06 and will be thus contrasted against very recent MPIOM experiments considered for AOD1B RL07. The in this way improved leakage correction will be implemented in future GravIS versions (http://gravis.gfz-potsdam.de).
Characterizing two distinct biomass burning regimes over Southeast Asia and their impacts on regional air quality
Authors: Marvin Margaret , Palmer Paul , Yao Fei , Latter Barry , Siddans Richard , Kerridge Brian
Published: March 2020

Mainland and maritime Southeast Asia is home to more than 655 million people, representing nearly 10% of the global population. The dry season in this region is typically associated with intense biomass burning activity, which leads to a significant increase in surface air pollutants that are harmful to human health, including ozone (O3) and fine (radii smaller than 2.5 microns) particulate matter (PM2.5). Latitude-based differences in dry season timing and land use distinguish two regional biomass burning regimes: (1) agricultural waste burning on the peninsular mainland from February through April and (2) coastal peat burning across the equatorial islands in September and October. The type and amount of material burned determines the chemical composition of emissions and subsequently their impact on regional air quality. Understanding the individual and collective roles of these biomass burning regimes is a crucial step towards developing effective air quality mitigation strategies for Southeast Asia. Here, we use the nested GEOS-Chem atmospheric chemistry transport model (horizontal resolution of 0.25° x 0.3125°) to simulate fire-atmosphere interactions over Southeast Asia during March and September of 2014, when emissions peak from the two regional burning seasons. Based on our analysis of model output, we report how these two distinct biomass burning regimes impact the photochemical environment over Southeast Asia and what the resulting consequences are for surface air quality. We will also present a critical evaluation of our model using ground-based and satellite observations of atmospheric composition across the region.
Can we avoid coastal squeeze through nature-based coastal adaptation?
Authors: Schuerch Mark , Spencer Tom , Temmerman Stijn , Kirwan Matthew
Published: March 2020

Intertidal coastal wetlands, including tidal marshes and mangrove forests, are at risk of disappearing under the influence of global sea level rise (SLR). Loss of their ecosystem services could significantly impact global carbon budgets, increase coastal erosion and flooding and lead to loss of fisheries, particularly along densely populated coastal zones such as large estuaries and deltas. Regional to global-scale projections suggest a reduction in present-day coastal wetland area by 20% to 90% in response to projected rates of future SLR. Recent studies have highlighted the importance of coastal squeeze, i.e. the inhibition of inland migration of tidal coastal wetlands due to the existence of anthropogenic infrastructure, in combination with wetland loss due to sea level rise, which is aggravated by a global decline in coastal sediment supply.

Nature-based adaptation, consisting of the reservation or creation of space for inland wetland expansion, is widely regarded as a promising strategy to counteract coastal squeeze and create/restore natural habitats through inland migration. Based on global and regional modelling outputs, this paper discusses how different scenarios of global population growth, expected declines in global sediment supply, delta subsidence and various coastal management strategies impact on global areas of intertidal coastal wetlands, and coastal squeeze in particular. For example, we estimate that until the year 2100 up to 280,000 km2 of coastal wetlands may be lost due to coastal squeeze. If strategically implemented on a regional to global scale nature-based solutions to coastal management could increase the global total area of intertidal coastal wetlands by up to 60%.

However our current understanding of this process is very limited, partly due to the limited field evidence in sedimentary archives (e.g. during the early Holocene where SLR were high). We argue that this is related to the combined effects of wetland inland migration and wetland drowning during periods of high SLR rates, raising the question as to whether or not future coastal wetland will be able to provide ecosystem services comparable to those of natural systems.
Modelling the Interaction between Tibet and Climate and Biosphere during the Cenozoic.
Authors: Valdes Paul , Farnsworth Alex , Su Tao , Spicer Robert , Ding Lin , Li Shufeng , Zhou Zhekun , Li Shihu
Published: March 2020

The Cenozoic uplift history of Tibet and its impact on the Asian monsoon and vegetation is complex. The building of the Tibetan Plateau is not a simple story of the rise of a single geological entity driven by the relentless northward passage of India as depicted in numerous modelling exercises, but was a complex process involving a succession of collisions of several Gondwanan terranes with Asia. The talk will review our current understanding of the uplift history of Tibet and show new climate model simulations of how Tibet has influenced climate, vegetation and biodiversity in the region. We make use of isotope-enabled Earth System models, as well as high resolution models to show that the complex history of Tibet has important consequences for understanding the evolution of both the summer and winter Asian monsoon. We show that post-Oligocene growth of north and north-eastern Tibet is crucial for the evolution of vegetation and biodiversity in the region by altering the strength of the winter monsoon system over Asia.
Geomagnetic field variations and low success rate of archaeointensity determination experiments for Iron Age sites in Bulgaria
Authors: Kostadinova-Avramova Maria , Kosterov Andrei , Jordanova Neli , Dimitrov Petar , Kovacheva Mary
Published: March 2020

Bulgarian archaeomagnetic database is the longest local geomagnetic field record covering almost completely the last 8000 years. However, very poorly constrained periods in need of elucidation still exist. Among the most problematic are the last 1200 years BC corresponding to the Iron Age in Bulgarian lands. In contrast to the relatively well studied Neolithic, Eneolithic and Bronze Age settlements, the Iron Age sites (especially in the Early Iron Age phase) are not sufficiently investigated from the archaeological point of view. The lack of precise stratigraphic frames significantly hampers the specification of sites chronology, and as a result, baked clay features that could serve as reliable reference points are rather scarce.

The most recent compilation of the Bulgarian archaeomagnetic database contains 18 intensity and 16 directional reference points belonging to the Iron Age, which have very uneven temporal distribution. To extend the coverage, 26 baked clay structures from nine different archaeological sites were sampled and archaeomagnetically studied producing ten new directional, but only five intensity data. It seems quite often materials from Iron Age combustion structures to possess magnetic properties unfavorable for archaeomagnetism, generally reflected in non-linear and concave Arai plots. Hereby, the lowest success rate of archaeointensity determination experiments is registered for this period within the whole database. Usually it is much easier to determine the past geomagnetic field direction compared to the intensity and the failure of the Thellier experiment is not surprising. Nevertheless, more than 90% of the investigated features belonging to all the other epochs except Iron Age normally display success rates over 50%, as only for 1-2% the archaeointensity determination experiments fail completely. In contrast, in the Iron Age the successful features comprise only 56% of the total number studied with 28% failure. A possible explanation for this observation was sought in some specific inappropriate conditions during firing/burial time that affect magnetic properties of baked clay materials during and/or after their thermoremanence acquisition.

This study is supported by the grant KP-06-Russia-10 from the Bulgarian National Science Fund and Russian Foundation of the Basic Research grant 19-55-18006.
Improving our understanding of Bangladesh tropical cyclone risk: decision making insights using kilometre scale numerical modelling and Bayesian data analysis
Authors: Steptoe Hamish , Economou Theo , Becker Bernd
Published: March 2020

We present results from state-of-the-art kilometre scale numerical models of tropical cyclones over Bangladesh.  We demonstrate how the latest generation of numerical models are filling the data gap in regions of the world with sparse observational networks, and compare our results to the latest generation global reanalyses.  We show how an ensemble of simulations expands our understanding of plausible events beyond our limited observations record.  Utilising this ensemble information in a Bayesian data analysis framework, we can robustly estimate prediction intervals for various parameters, such as peak wind speed or extreme rainfall, which when combined with Decision Theory and a loss function offer a coherent data-to-decision framework supporting disaster risk assessment and management strategies. We show how this decision making could be integrated into current global weather and climate forecast ensembles to provide forecasting of hazards and impacts up to 5 days ahead of an event, and in a future climate context.  We end with some thoughts on the ways this could influence the future of risk management and insurance underwriting and the challenges of working with big numerical model datasets.
Spatial delineation of a new fog-driven ecosystem in the tropical lowlands
Authors: Pohl Marius
Published: March 2020

A recent review about diversities of epiphytes in tropical forests of the Neotropics revealed an unexpected high diversity at lower elevations in an area in French Guiana where the formation of nocturnal radiation fog, intensified by katabatic drainage flows from the surrounding terrain fosters epiphytic growth. Consequently, the new diversity hotspot has been termed ’Tropical Lowland Cloud Forest‘ (TLCF) in analogy to the well-known Tropical Montane Cloud Forests. In this new project funded by the German Research Foundation, we test the hypothesis that the new forest type is widespread in the Tropics if the local terrain allows the formation of nocturnal radiation fog. The presented study is based on satellite data because no operational fog measurements from natural rain forests are available. Since fog in TLCFs is a nocturnal / early morning phenomenon, we use all overflights by the MODIS Aqua platform with 1 km resolution. Fog / low stratus clouds are derived by using a machine learning approach which is trained by MODIS and CALIPSO data. Potential lowland forest areas will be derived from ASTER Global Digital Elevation Model  and Landsat Vegetation Continous Fields

 

 
Integrated seismic and geomechanical/flow modelling study of focused fluid flow
Authors: Yarushina Viktoriya , Lakhlifi Assia , Wang Hongliang , Connolly David , Wangen Magnus , Kocsis Gabor , Fæstø Ingrid
Published: March 2020

The improved resolution of recent seismic surveys has made seismic chimney structures a common observation in sedimentary basins worldwide and on the Norwegian Continental Shelf. Focused fluid flow in vertical chimneys is an important and poorly understood feature in a petroleum system. Oil and gas migrate through preferential pathways from source rocks to structural traps where they form reservoirs. Further migration or leakage from reservoirs leads to formation of shallow hydrocarbon accumulations and gas pockets. In some cases, leakage through preferential pathways can be traced up to the surface or to the sea floor, where it leads to formation of mud volcanoes, mounds and pockmarks. Here, we present results of an integrated case study, which is performed on a 3D seismic data set that covers an area of approximately 3000km2. The seismic sequence stratigraphic interpretation is complemented with a study of seismic fluid migration paths. Detection of seismic chimneys is a challenging task. State-of-the-art chimney cube technology based on self-educating neural networks was used to automatically identify possible structures. The results of seismic inversion in combination with available well data provided a set of surfaces distinguishing various stratigraphic layers and their properties. Obtained geological model was used as a basis for coupled geo-mechanical / fluid flow modelling that reconstructed the fluid flow processes in the geological past that lead to formation of chimney structures. Our numerical model of chimney formation is based on the two-phase theory of fluid flow through (de)compacting porous rocks. Viscous bulk rheology and strong nonlinear coupling of deforming porous rocks to fluid flow are key ingredients of the model. Chimney formation is linked to pressure build-up in the underlying reservoir. We reconstruct the fluid flow processes in the geological past that lead to formation of chimney structures and provide expectations for their present-day morphology, porosity and fluid pressure. Conditions of chimney formation, their sizes, spatial distribution and times of formation are investigated. The fate of the chimney after it has been created and its role as a fluid pathway in the present-day state is studied.
Long-term feedbacks result in the recovery of the CO2 sink in a remnant peatland following water table lowering
Authors: Ratcliffe Joshua , Campbell David , Schipper Louis , Wall Aaron , Clarkson Beverley
Published: March 2020

Peatland biological, physical and chemical properties change over time in response to the long-term water table position. Such changes complicate predicting the response of peatland carbon stocks to sustained drying. Here we use Eddy Covariance measurements of CO2 exchange to study the effect of sustained water table lowering on peatland carbon dynamics. We compare measurements from a near-pristine peatland with those of a drying remnant, both raised bogs dominated by Empodisma robustum (Restionaceae), across two different time periods separated by a 16-year interval. We found that the remnant bog was initially a source of CO2 following water table lowering. However, the CO2 sink recovered and strengthened after the 16-year interval between measurements. The increase in CO2 sink strength in the remnant bog was primarily due to increased photosynthetic uptake of CO2, which exceeded that of the near-pristine site in both time periods. Additionally we found the loss of CO2 via ecosystem respiration to have declined with time, however, ecosystem respiration remained elevated compared to the near-pristine site. These trends of increasing photosynthesis and declining ecosystem respiration resulted in the CO2 sink in the dry bog reaching half the sink strength of the near-pristine bog. We consider two factors to have been key for the recovery of the CO2 sink in the remnant bog. These were 1) resilience of the peat-forming plant community to water-table change and 2) the expansion of ericoid shrubs. Our results demonstrate that the peatland carbon sink can recover from drying over a multi-decadal timescale, but questions remain as to the long-term trajectory of dry bogs and the stability of carbon fixed after water table lowering.
Mineralogical Characteristics of Carbonate Rock-Hosted Naturally Occurring Asbestos from Republic of Korea
Authors: Roh Yul , Park Byungno Park , Kim Yongun , Park Jaebong , Kim Hyesu , Jeong Hyeonyi , Yoon Sungjun
Published: March 2020

Naturally occurring asbestos (NOA) occurs in rocks and soils as a result of natural weathering and human activities. It is proved that inhalation of asbestos fibers can lead to increase risk of developing several diseases such as lung cancer and malignant mesothelioma. The parent rocks of asbestos have been mainly associated with (ultra)mafic and carbonate rock. The previous studies on NOA were mainly limited to (ultra)mafic rock-hosted asbestos in S. Korea, but studies on carbonate rock-hosted asbestos are relatively rare in S. Korea. Therefore, this study was aimed to examine mineralogical characteristics of carbonate rock-hosted NOA. Types of rocks at the several sites mainly consisted of Precambrian metasedimentary rocks, carbonate rock, and Cretaceous and Jurassic granites. Asbestos-containing carbonate rock samples were obtained for mineralogical characterization. XRD, PLM, EPMA, SEM and EDS analyses were used to characterize mineralogical characteristics of the carbonate rock-hosted NOA. From the carbonate rock, fibrous minerals were occurred acicular and columnar forms in the several sites. Fibrous minerals were composed of mainly tremolite, actinolite, and associated minerals included possibly asbestos containing materials (ACM) such as talc, vermiculite, and sepiolite. The length and aspect ratios of tremolite and actinolite were similar to the standard asbestiform (length >5 ㎛, length:width = 3:1). These results indicate that both non-asbestiform and asbestiform tremolite and actinolite with acicular forms occurred in carbonate rocks at several sites. Geological and geochemical characteristics and mineral assemblages indicate tremolite and associated minerals might be formed by hydrothermal alternation and/or hydrothermal veins of carbonate rocks due to intrusion of acidic igneous rocks.