bluuebunny/crossref_metadata_2025 huggingface dataset:
Forms of life on Early Earth as model for Exoplanets?
Authors: Moelling Karin
Published: March 2020

The recent discovery of exoplanets with putative habitable zones which may be as frequent as 1025 stimulate the interest in the origin of life on the exoplanets but also on the Earl Earth (EE). Meteorites and missions to Mars or Moon teach us about their composition, and make us think about the origin of life in general. Prebiotic molecules such as amino acids, nucleosides, and fullerenes arrived from extraterrestric space and cyanobacteria and archaea are inhabitants of the EE. They exhibit properties such as protein synthesis, which requires advanced machineries adapted to our Earth. What could be early precursors of such mechanisms. What kind of life can we envision in its simplest form? Molecules which can replicate, mutate, and evolve are signatures of life.

The simplest such biomolecules on Earth may be non-protein-coding (nc)RNA catalytic RNA, the ribozymes and viroids, which can fulfill many protein functions, including replication, evolution, and are a prerequisite for peptide synthesis. Ribozymes/viroids can evolve to higher complexity. Archaea and bacteria resemble giant viruses suggesting a continuous transition from dead to living matter. Archaea are extremophiles which revolutionalized our view on what life can be like in respect to environmental conditions and specialized metabolic pathways. Some exotic spots on Earth can teach us about other habitable zones. Meteorites help to understand chemical compositions on other planets and the consequences for life. During evolution loss and gain of of genetic information are important evolutionary driving forces. Viroids  are discussed as models for potentially other forms of life. Simulators of Mars environment are under study to determine possible effects on biological sepcimens.

Ref: Broecker and Moelling Geosciences (2019), Annals NY Acad Sci. (2019), Frontiers Microbiol (2019). Book: Moelling:Viruses more friends than foes World Scientific Press ( 2017)

 

 
Hydrogen storage in porous rocks: the storage capacity of the UK continental shelf
Authors: Scafidi Jonathan , Wilkinson Mark , Gilfillan Stuart , Heinemann Niklas
Published: March 2020

Increasing the amount of renewable energy in the UK reduces greenhouse gas emissions but will also lead to intermittency of supply, especially on a seasonal timescale. Over-producing energy when demand is low and under producing when demand is high requires large-scale storage to redress the balance.  Hydrogen stored over seasonal timescales in subsurface porous rocks can act as a giant battery for the UK and is a flexible energy vector that can be used for heat, transport and electricity generation.

No large scale assessment of the hydrogen storage capacity of an industrialised region has yet been undertaken. Here, we present a novel method for calculating the hydrogen storage capacity of gas fields and saline aquifers on the UK continental shelf using data previously used to assess carbon-dioxide storage potential.
Adaptive Structure Design of Raingarden in Shanghai Coastal Saline Alkali Area for Improving Urban Resilience
Authors: Yu Bingqin , Che Shengquan , Wang Lu
Published: March 2020

Shanghai is one of the demonstration sites of Sponge City which is a typical coastal saline-alkali area. To improve the urban resilience and mitigate storm water, green infrastructure as raingarden, bioswale and green roof, etc. are used to regulate runoff. However, the design of raingarden have the disadvantage of solutions for high groundwater levels and soil salinization in Shanghai. In order to improve the regional adaptability and optimize the design of the raingarden, the indoor rainfall simulation experiments and orthogonal experiments were used to analyze the effect of salt isolation and rain infiltration impacted by different structures (salt-insulated layer material, salt-insulated layer position, filler layer thickness). The results show that the order of influence on salt isolation is: salt-insulated material>filler layer thickness>salt-insulated layer position. The order of impact on rain infiltration is: salt-insulated material>salt-insulated layer location>filler layer thickness. Three types of rain garden structures are proposed. The first is strong salt-insulated rain garden suitable for severe saline-alkali areas. The second is suitable for the comprehensive rain garden in the moderate saline-alkali area. The third is suitable for the permeable rain garden in the light saline-alkali area.
Dealing with Semantic Heterogeneity of Geographic Concepts: A Geometric Algebra-Based Encoding Method
Authors: Wu Fan , Gao Hong , Yu Zhaoyuan
Published: March 2020

A conceptual consensus, as well as a unified representation, on a certain geographic concept across multiple contexts, can be of great significance to the communication, retrieval, combination, and reuse of geographic information and knowledge. However, geographic concept is a rich synthesis of semantics, semiotics, quality (e.g., vagueness or approximation). The generation, representation calculation and application of a certain geographic concept, consequently, can be of great heterogeneity, especially considering different interests, domains, language, etc. In light of these semantic heterogeneity problems, to code core concepts uniquely can be a lighter alternative to tradition ontology-based method, the reason for which is numeric codes can be a symbolism of consensus on concept across domains and even languages. Consequently, this paper proposed a unified semantic model as well as an encoding framework for representation, reasoning, and computation of geographic concept based on geometric algebra (GA). In this method, a geographic concept can be represented as a collection of semantic elements, which can be further encoded based on its hierarchy structure, and all the semantic information of the concept can be preserved across the encoding process. On the basis of the encoding result, semantic information can be reasoned backward by some well-defined operators, semantic similarity can also be computed for information inference as well as semantic association retrieval. In the case study, the implementation of the proposed framework shows that this GA-based semantic encoding model of can be a promising method to the unified expression, reasoning, and calculation of geographic concepts, which, reasonably, can be further regarded as a prospect lighter alternative of the solution to semantic heterogeneity.
Nonstationary frequency analysis for annual runoff and sediment load of the Wujiang River
Authors: Li Rongrong
Published: March 2020

The hydrological series can no longer meet the stationarity hypothesis due to the influence of climate variability and human activities. The process of runoff and sediment load changed significantly under a changing environment. Analyzing the variations of runoff and sediment load and exploring the main influencing causes leading to their changes will be of great help to understand the dynamic process of water and sediment in river basin. Many studies have considered the effects of rainfall and reservoir on the downstream runoff or sediment: the impact of rainfall on runoff or sediment load is normally performed by comparing the statistical characteristics before and after an extreme weather event (e.g. heavy rain of the Yangtze river in 1998); the effect of reservoirs is usually determined by comparing the pre-dam and post-dam frequencies of runoff or sediment load. In this study, the major influencing factors of annual runoff and sediment load in Wujiang River basin were identified firstly based on the results of trend analysis and change-point diagnosis for runoff and sediment load. Then, Generalized Addictive Models in Location, Scale, and Shape (GAMLSS) is used to describe the rainfall and reservoir impacts on nonstationarity of runoff and sediment load, in which, distribution parameters (including the location, scale and shape parameter) are expressed as a function of the explanatory variables. The results show that: (1) runoff and sediment load of Wujiang River decrease with the intensification of climate change and human activities; (2) runoff is mainly affected by rainfall, the operation of cascade reservoirs has critical effect on the sediment load; (3) the correlation between runoff and sediment closely related to the nonstationarity of sediment load, namely, the sediment load change can directly lead to the alteration of dependence between runoff and sediment.
Why do Benguela Niños lead Atlantic Niños?
Authors: Illig Serena , Bachèlery Marie-Lou , Lübbecke Joke
Published: March 2020

We investigate the lag between warm interannual Sea Surface Temperature (SST) events in the eastern equatorial Atlantic, the Atlantic Niños, and the occurrence of Benguela Niños along the southwestern Angolan coast. It is commonly agreed that both events are associated with equatorial and subsequent coastal-trapped wave propagations driven remotely by a relaxation of the trade-winds. Yet, we observe that coastal SST anomalies off Angola tend to precede the ones in the equatorial cold tongue region by ~1 month.

We explain this counter-intuitive behavior using experimentation with a tropical Atlantic Ocean model. Using idealized wind-stress perturbations from a composite analysis, we simulate warm equatorial and coastal events over a stationary and then, seasonally-varying ocean mean-state. Results show that when wind-stress perturbations are confined to the western central equatorial Atlantic, the model yields equatorial events leading the coastal variability, consistent with the propagation path of the waves. This implies that neither the differences in the ocean stratification between the two regions (thermocline depths or modal wave contributions) nor its seasonal variability controls the timing between events. Only if wind-stress anomalies are prescribed in the coastal fringe, the coastal warming precedes the eastern equatorial SST anomaly peak, emphasizing the role of the local forcing in the phenology of Benguela Niños.

Both warmings originate from a reduction in the strength of the South-Atlantic Anticyclone. Nevertheless, local processes initiate the coastal warming before the remotely-forced equatorial waves impact the eastern equatorial SST. Then, equatorward coastal wind anomalies, driven by a convergent anomalous circulation located on the warm Atlantic Niño, stop the remotely-forced coastal warming prematurely.

In conclusion, this study shows evidence that Atlantic and Benguela Niños are connected via an ocean teleconnection associated with equatorial and coastal wave propagations, but they are also tied by a large-scale atmospheric circulation and ocean-atmosphere interactions.
230Th normalization: New insights on an essential tool for quantifying sedimentary fluxes in the modern and Quaternary ocean
Authors: Costa Kassandra ,   GEOTRACES Working Group 3: Particle Fluxes
Published: March 2020

230Th-normalization is a valuable paleoceanographic tool for reconstructing high-resolution sediment fluxes during the late Pleistocene (last ~500,000 years). As its application has expanded to ever more complex marine environments, the nuances of 230Th systematics, with regards to particle type, particle size, lateral advective/diffusive redistribution, and other processes, have emerged. We synthesized over 1000 sedimentary records of 230Th from across the global ocean at two time slices, the Late Holocene (0-5000 years ago, or 0-5 ka) and the Last Glacial Maximum (18.5-23.5 ka), and investigated the spatial structure of 230Th-normalized mass fluxes. On a global scale, sedimentary mass fluxes were significantly higher during the Last Glacial Maximum (1.79-2.17 g/cm2kyr, 95% confidence) relative to the Holocene (1.48-1.68 g/cm2kyr, 95% confidence). We then examined the potential confounding influences of boundary scavenging, nepheloid layers, hydrothermal scavenging, size dependent sediment fractionation, and carbonate dissolution on the efficacy of 230Th as a constant flux proxy. Anomalous 230Th behavior is sometimes observed proximal to hydrothermal ridges and in continental margins where high particle fluxes and steep continental slopes can lead to the combined effects of boundary scavenging and nepheloid interference. Notwithstanding these limitations, we found that 230Th-normalization is a robust tool for determining sediment mass accumulation rates in the majority of pelagic (> 1000 m) marine settings.
Temporal measurements of the interstellar helium focusing cone by the Magnetospheric Multiscale Mission(MMS)
Authors: Gomez Roman , Fuselier Stephen , Burch James , Mukherjee Joey , Gonzalez Carrie , Trattner Karlheinz , Starkey Michael , Strangeway Robert
Published: March 2020

The Sun and its associated heliosphere travels through the local interstellar medium (LISM) at 26 km/s.  This results in a flow of neutral particles constantly entering the heliosphere at the same velocity.  Neutral atoms with trajectories close to the Sun, which survive its ionizing radiation environment, become gravitationally attracted to it resulting in a focusing cone, a region of enhanced neutral density, downwind of the Sun.  The increased neutral density in these regions leads to a higher density of pickup ions created by charge-exchange of the neutrals.  In near-Earth orbit, the Magnetospheric Multiscale spacecraft (4 in all) have orbital apogees on the dayside during Earth’s annual encounter with the helium focusing cone (from mid-November to mid-December).  Since launching in March of 2015, regular acquisitions with the Hot Plasma Composition Analyzers (HPCAs) have been conducted, with acquisitions from 2017 through 2019 occurring with a 29 RE apogee, ensuring long intervals in the pristine Solar Wind.   We provide measurements of the focusing cone during the declining phase of the previous solar cycle. These measurements are used to investigate the effect of solar radiation on the focusing cone.
Design and implementation of the seismotectonic Atlas of Greece v1.0
Authors: Kassaras Ioannis , Kapetanidis Vasilis , Ganas Athanassios , Tzanis Andreas , Papadimitriou Panayotis , Kouskouna Vicki , Karakonstantis Andreas , Valkaniotis Sotirios , Chailas Stylianos , Sakkas Vasileios , Kosma Chrysanthi , Bozionelos George , Tsironi Varvara , Giannaraki Georgia
Published: March 2020

Knowledge of the present-day relationships between earthquakes, active tectonics, and crustal deformation is a key for understanding the geodynamics, ongoing surface processes (i.e. erosion, sedimentation, etc.) and is also essential for the risk assessment and management of geo-reservoirs for energy and waste.

Greece is characterized by the most tectonically active regime in the eastern Mediterranean, involving (a) intense crustal deformation and thickening, with an uplift rate of a few mm/yr along the Hellenic Arc due to accretion of sediments of the African plate beneath the overriding Aegean plate, (b) wide-spread extension in the back-arc region (for example in the Gulf of Corinth) due to retreat of the African slab and (c) significant strike-slip motions due to offset between oceanic-continental subduction in the west and the westward propagation of Anatolia in the east. Study of the complexity of the contemporary Greek tectonics has been the subject of intense efforts of our working group during the last decade, employing multidisciplinary state-of-the-art methodologies regarding geological mapping, seismological and geodetic surveying and numerical analyses at various scales. The products of these studies are the pieces of a puzzle that we aim to merge with existing data (topography, bathymetry, land-use, etc) in order to compose the digital version of the modern Seismotectonic Atlas of Greece.

It has been over 30 years since the first edition of the seismotectonic map was published by Greece's Geological Institute in 1989, which emerges the need for an update, as soon as dozens of strong earthquakes have occurred both on mainland and offshore, whose locations and fault kinematics have been studied and this information has to be taken into account in city and infrastructure planning. Moreover, the patterns of active tectonics and stress, the tectonic strain distribution, the annual ratio between seismic and geodetic moment release, the precise location of onshore active faults and the slip-rates of major faults are much better known today than they were 30 years ago.

Open-source mapping software and GIS tools are being used to showcase important up-to-date seismotectonic features together with critical geospatial information (motorways, railways, gas pipelines, electricity plants, etc) at a nationwide scale of 1:500,000. This updated product aims to reveal a comprehensive image of the regional crustal deformation in a useful manner for scientists, students, and stakeholders to obtain a first-order perception of seismic risk in the Greek territory, but, also, to be used as a basis for other applications in Geosciences.
Viscoelastic crustal deformation in the Aira caldera before and after the 1914 eruption of the Sakurajima volcano
Authors: Yamasaki Tadashi , Sigmundsson Freysteinn , Iguchi Masato
Published: March 2020

 Long-term volcano deformation cannot be well understood without considering crustal viscoelasticity because the presence of magma is expected to significantly lower the crustal viscosity beneath volcanoes. In this study, we examine viscoelastic crustal response to continuous magma supply into the upper crust and its sudden discharge. We use a three-dimensional (3-D) finite element model composed of an elastic layer underlain by a linear Maxwell viscoelastic layer with spatially uniform viscosity, in which a sill emplaced at the bottom of the elastic layer inflates with constant rate, during which the deflation due to an eruption suddenly occurs. Our numerical experiment finds that viscoelastic response to the sill deflation causes post-eruption surface uplift, depending on how much viscoelastic relaxation progresses in response to sill inflation due to pre-eruption magma supply and how much the sill deflates during the eruption. However, the recovery of the post-eruption surface is always later than that of the sill volume, because the viscoelastic response to the sill inflation reduces the surface uplift. Magma recharge is required to bring the surface to the elevation that was at immediately before the eruption. We adopt our viscoelastic model to geodetic data in and around the Aira caldera, southern Kyushu, Japan. It is found that the observed exponential-like surface recovery after the 1914 eruption can be explained if: (1) The effective crustal viscosity is ∼5×1018 Pa s, (2) the sill emplacement, whose equatorial radius is ∼2 km, occurs at a depth of ∼11 km, (3) a constant inflation rate of the sill is ∼0.009 km3/yr, which has continued since ∼50 yr before the 1914 eruption, and (4) the sill deflates by ∼0.4 km3 during the 1914 eruption, ∼4 times less than the eruptive volume. The sill inflation during the first ∼50 yr after the eruption is lower than that predicted by an elastic model, but larger thereafter. Fit to geodetic data after ∼1975 can be improved by introducing temporal variation of the inflation rate, which is a topic of investigation for a future study.
Flux Transfer Events are Made in Pairs
Authors: Russell Christopher , Strangeway Robert
Published: March 2020

Flux transfer events are transient magnetized plasma structures that are self-balancing, rope-like phenomena that appear when the interplanetary magnetic field is southward. Using measurements of particles and magnetic fields on the MMS spacecraft, we find that these structures contain magnetospheric energetic electrons in exactly half of their observations, independent of external conditions or locations. This implies that two flux ropes are created for each event, one connected to the magnetosphere and one not connected. We show that this dual nature occurs independent of solar wind properties and location of observation. These observations are consistent with a recent model of flux transfer event generation.
Sensitivity analysis of gully sidewall expansion to topography and rainfall factors
Authors: Yulei Ma , Xiangzhou Xu
Published: March 2020

Gully sidewall expansion is an essential process of gully development, and its trigger condition and dynamic process are subject to multifactor effects. This study consisted of 10 sets of experiments, and three factors were considered: three rainfalls (60 mm, 48mm and 24mm), two initial slope gradients (70° and 80°) and two slope heights (1 m and 1.5 m). Then the increase-rate-analysis method was used to evaluate the variations in the changes of slope gradients of sidewall and retreat rates of gully shoulder-line with respect to changes in other causal parameters of rainfall and topography. The results are shown as follows: (1) The area of land loss of the upper gentle slope was positively correlated with the volume of gravity erosion. The correlation coefficient between the volume of gravity erosion and the area of land loss of the upper gentle slope, r1, is 0.91. The correlation coefficient between the volume of water erosion and the area of land loss of the upper gentle slope, r2, is 0.59. This shows that mass failure was the main cause to induce the land loss of the upper gentle slope in the process of sidewall expansion. (2) The rainfall duration and initial slope gradient had significant influences on the change of slope gradient of landform in the experiments. The sensitivity coefficients of rainfall intensity, rainfall duration, initial slope gradient and slope height for the change of slope gradient of the sidewall were 0.3, 2.2, 1.3 and -0.2, respectively. The increased initial slope gradient and rainfall duration may have caused the increases of the volume and number of gravity erosion, ultimately resulting in a remarkable change of slope gradient of the sidewall. (3) The most significant factor affecting the retreat rate of gully shoulder-line were rainfall intensity and initial slope gradient. The sensitivity coefficients of the rainfall intensity, rainfall duration, initial slope gradient and slope height for the retreat rate of gully shoulder-line were 3.0, 1.5, 3.0 and -0.1. As a result, the retaining wall construction was preferable to control the gully sidewall erosion. The results of this study may be referred for analyzing the mechanism of sidewall expansion and controlling the loess sidewall expansion.
The Generic Mapping Tools and Community-Maintained Open Source Software
Authors: Wessel Paul
Published: March 2020

The Generic Mapping Tools (GMT; www.generic-mapping-tools.org) is a well-known set of software for the geosciences, in particular in the marine and solid earth disciplines. GMT is used by many other well-known software infrastructures, including USGS’s ShakeMap for near-real-time maps of ground motion and shaking intensity following significant earthquakes, MBARI/LDEO’s MB-System for multibeam processing and mapping of the seafloor, and Scripps Institution of Oceanography’s GMTSAR for radar interferometric analysis and imaging of crustal deformation. Today, GMT has tens of thousands of users all over the world and remains essential for many terrestrial and planetary data processing and map-making workflows. GMT began its life over 30 years ago when I was a graduate student, and it has enjoyed continuous US National Science Foundation funding since 1993. Leveraging this funding, GMT has succeeded in establishing itself as a collaborative Open Source community resource from the start. Many scientists globally, particularly European scientists, have been instrumental in designing, maintaining, and improving GMT since the early 2000s. As I and several of our core developers approach the end of our academic careers, the GMT team has been pondering how to preserve these collective investments and position GMT to remain an essential geoinformatics infrastructure well into the future. In response, we have made fundamental changes to how GMT works, enabling access to GMT modules from external interfaces such as MATLAB, Python, and Julia, simplifying user access to large global DEM datasets, and extending our support for the Google Earth platform. However, the biggest impact delivered by the Fall 2019 release of GMT 6 will likely be “modern mode”. Modern mode coexists with classic mode (the only previous mode) so that thousands of GMT 4 and 5 scripts will still run as expected. Furthermore, new users will start with modern mode and experience a much-simplified GMT scripting syntax. A new aspect of GMT made possible by modern mode is a greatly simplified animation production. It is clear to all scientists that animations make it easier to elucidate temporal changes, yet very few scientists create animations as they are traditionally difficult to design. The GMT team aspires to make animations a task every scientist can do with ease. In this lecture, I will discuss the latest news on GMT, outline modern mode and the external environment access to our modules, highlight a few simple GMT animations, and present other aspects of our succession planning for strengthening the GMT community.
Analyzing the Shifts of Land Use for Agricultural Land Planning under Climate Change– A Case Study of Northern Yilan County, Taiwan
Authors: Lin Wen - Yen , Hung Chi-Tung
Published: March 2020

Taiwan belongs to the edges of sub-tropical and tropical climate zones, and has been indicated as a high risk edge area by international climate change researches. According to the Intergovernmental Panel on Climate Change (IPCC), Taiwan is threatened by global warming, changes of rainfall pattern, sea level rising and high frequency and influence of extreme weather, which will result in great impacts to agriculture industry and the future of food security. Unfortunately, along with the rapid economic development and urbanization in Taiwan since the 1960’s, agricultural land use has become less competitive to industrial, commercial, and residential types of land uses under land use competition. Therefore, to effectively enhance the resilience and conserve the agricultural lands which under the threats of climate change and the competitions of other types of land use, Taiwan’s Spatial Planning Act (promulgated on 2016/1/6) enlists Agricultural Development Zones, one of four major functional zones in National Spatial Plan, into demarcated functional zone and applying land use control. The zoning plan is expected to be completed by every city and county before the year of 2022, and one of the major issues is to consider the land use function changes of different locations. By comparing the 2007 and 2016 land utilization maps investigated by National Land Surveying and Mapping Center (Taiwan), this study is able to identify the 10-year changes of agricultural lands of northern Yilan county. To further investigate the spatial distribution of agricultural land changes, spatial analysis techniques such as multi-distance spatial cluster analysis (Ripley’s K Function) and point pattern analysis (Kernel density) are employed to analyze the spatial clustering of changes. The spatial analysis results overlays with climate change related and hazard risk maps, such as flooding, landslide, soil liquefaction, to support the decision making of future agricultural land planning and agriculture development zoning plan.

Keywords: agricultural land, land use changes, climate change, spatial analysis
Paleoceanographic reconstruction of Maastrichtian from the hemipelagic sediments of Pakistan, Eastern Tethys
Authors: Wadood Bilal , Khan Suleman , Li Hong , Liu Yiqun
Published: March 2020

The evolution of planktonic foraminifera in Cretaceous is forced by the paleo-oceanographic changes associated with Oceanic Anoxic Events (OAEs). The paleo-oceanographic conditions including global sea level rise, loss of ocean stratifications and subsequent loss of niche partitioning, ocean acidification and warming were common during early-middle Cretaceous. The evolution of planktonic foraminifera is associated globally with such changes in oceans. The global warming of early to middle Cretaceous was replaced by a period of cooling during early Maastrichtian. The stratification in global oceans resumed and the diversity of planktonic foraminifera increased. This study deals with signals of paleo-oceanographic conditions of Maastrichtian time preserved in Mughal Kot Section, Eastern Tethys.

A thick succession of hemipelagic sediments of Maastrichtian age is exposed in Mughal Kot Formation, Indus Basin, Pakistan. The studied section revealed abundant taxa of Globotruncana, Globotruncanita and Heterohelix. Based on these taxa a local assemblage biozone of Maastrichtian (~76-~69 Ma) age is erected. The overall species richness in the studied section is very low. This significantly low richness is thought to be associated with high sedimentation rate as 1100 meter thick strata is deposited during Maastrichtian. Presence of turbidite beds supports such high sedimentation rates. However, a consistent decrease in species richness from base (early Maastrichtian) to the top (late Maastrichtian) is recorded in the section. This decrease is associated with the dominance of opportunistic taxa of Heterohelix. The proliferation of opportunistic taxa at the expense of specialized taxa during late Maastrichtian gives a strong clue that the global cooling of early Maastrichtian was replaced by warming during late Maastrichtian. Such warming may have resulted in the melting of polar ice, uniformity in the physical properties of water masses in global oceans and hence destruction of habitat for the dwelling of specialized foraminifera. 
Memory effects of Eurasian land processes cause enhanced cooling in response to sea ice loss
Authors: Nakamura Tetsu , Yamazaki Koji , Sato Tomonori , Ukita Jinro
Published: March 2020

Amplified Arctic warming and its relevance to mid-latitude cooling in winter have been intensively studied. Observational evidence has shown strong connections between decreasing sea ice and cooling over the Siberian/East Asian regions. However, the robustness of such connections remains a matter of discussion because modeling studies have shown divergent and controversial results. Here, we report a set of general circulation model experiments specifically designed to extract memory effects of land processes that can amplify sea ice–climate impacts. The results show that sea ice–induced cooling anomalies over the Eurasian continent are memorized in the snow amount and soil temperature fields, and they reemerge in the following winters to enhance negative Arctic Oscillation-like anomalies. The contribution from this memory effect is similar in magnitude to the direct effect of sea ice loss. The results emphasize the essential role of land processes in understanding and evaluating the Arctic–mid-latitude climate linkage.
Fragmentation of steaming Surtseyan bombs
Authors: McGuinness Mark , Greenbank Emma
Published: March 2020

A Surtseyan volcanic eruption involves a bulk interaction between water and hot magma, mediated by the return of ejected ash. Surtsey Island, off the coast of Iceland, was born during such an eruption process in the 1940s. Mount Ruapehu in New Zealand also undergoes Surtseyan eruptions, due to its crater lake. 

One feature of such eruptions is ejected lava bombs, trailing steam, with evidence that watery slurry was trapped inside them during the ejection process. Simple calculations indicate that the pressures developed due to boiling inside such a bomb should shatter it. Yet intact bombs are routinely discovered in debris piles. In an attempt to crack this problem, and provide a criterion for fragmentation of Surtseyan bombs, a transient mathematical model of the flashing of water to steam inside one of these hot erupted lava balls is developed, with a particular focus on the maximum pressure attained, and how it depends on magma and fluid properties. Numerical and asymptotic solutions provide some answers for volcanologists.
Land degradation and soil conservation in the Barlad Plateau, Romania: a case study from Racova catchment
Authors: Niacsu Lilian , Ionita Ion , Samoila Claudia , Grigoras Georgel , Belebea-Apostu Ana-Maria
Published: March 2020

Land degradation by soil erosion, gullying, landslides and reservoir sedimentation is a major environmental threat in the Barlad Plateau of Romania. This paper reviews both land degradation and the development of soil conservation measures in a representative 32,908 ha catchment. Previous studies focused on larger regional areas and provided insufficient detailed information about land degradation and land improvements. Results estimated the mean value of soil loses at 22.7 t ha-1 y-1 based mostly on the USLE. Gully erosion is very limited in extent (covering 3% of the catchment area), but has considerable impacts in terms of sediment production and triggering or reactivating landslides. The 1:5,000 scale landslide distribution map shows that 56% of Racova Catchment is covered by landslides, in any shape or age. Most of them are shallow seated and inactive landslides. Traditional agriculture in the Barlad Plateau focused on ‘up-and-down slope’ farming on small plots. Soil conservation measures were actively undertaken over a 20-year period (1970-1989). However, more recent legislation (No. 18/1991 Agricultural Real Estate Act) includes two provisions that discourage maintaining and extending soil conservation practises. Hence, the former contour farming system has been abandoned in favour of the traditional, degradational farming methods. The mean annual sedimentation rate in reservoirs is moderate at 2.7 cm y-1 in the upper Racova Catchment and almost double that rate in Puscasi Reservoir at the catchment outlet. Consequently, land degradation remains a serious problem in the study area and effective soil conservation is urgently needed.
Along-stream variations in valley flank erosion rates measured using 10Be concentrations in colluvial deposits from Atacama canyons: implications for valley widening
Authors: Zavala Valeria , Carretier Sebastien , Regard Vincent , Bonnet Stephane , Riquelme Rodrigo , Choy Sandrine
Published: March 2020

The downstream increase in valley width is an important feature of fluvial landscapes that may be evident to anyone: even if local exceptions exist, wide fluvial valleys in plains are distinctive of narrow upstream mountainous ones. Yet, the processes and rates governing along-stream valley widening over timescales characteristic of landscape development (>1-10 ka) are largely unknown. No suitable law exists in landscape evolution models, thus models imperfectly reproduce the landscape evolution at geological timescales, their rates of erosion and probably their response to tectonics and climate. Here, we study two 1 km-deep canyons in northern Chile with diachronous incision initiation, thus representing two time-stage evolutions of a similar geomorphic system characterized by valley widening following the upward migration of a major knickzone. We use 10Be cosmogenic isotope concentrations measured in colluvial deposits at the foot of hillslopes to quantify along-stream valley flank erosion rates. We observe that valley flank erosion rate increases quasi-linearly with valley-bed slope and decreases non-linearly with valley width. This relation suggests that lateral erosion increases with sediment flux due to higher channel mobility. In turn, valley width exerts a negative feedback on lateral valley flank erosion since channels in wide valleys have a lower probability of eroding the valley sides. This implies a major control of river divagation on valley flank erosion rate and valley widening. Our study provides the first data for understanding the long-term processes and rates governing valley widening in landscapes.
Terrestrial CO2 Fluxes, Concentrations, Sources and Budget in Northeast China: Observational and Modeling Studies
Authors: Li Xiaolan , Hu Xiao-Ming , Cai Changjie , Jia Qingyu , Zhang Yao , Liu Jingmiao
Published: March 2020

CO2 fluxes and concentrations are not well understood in Northeast China, where dominant land surface types are mixed forest and cropland.  Here, we analyzed the CO2 fluxes and concentrations using Eddy Covariance (EC) measurements, satellite observations, and the Weather Research and Forecasting model coupled with the Vegetation Photosynthesis and Respiration Model (WRF-VPRM).  We also used WRF-VPRM outputs to examine CO2 transport/dispersion, and to quantify the biogenic and anthropogenic contributions to atmospheric CO2 concentrations.  Finally, we investigated the uncertainties of simulating CO2 fluxes related to four VPRM parameters (including maximum light use efficiency, photosynthetically active radiation half-saturation value, and two respiration parameters) using offline ensemble simulations with randomly selected parameter values.  The results indicated that mixed forests acted as a larger CO2 source and sink than rice paddies on average in 2016 due to a longer growth period and stronger ecosystem respiration, although the minimum EC-measured daily mean net ecosystem exchange (NEE) was smaller at rice paddy (-10 μmol m-2 s-1) than at mixed forest (-6.5 μmol m-2 s-1) during the growing season (May through September).  The monthly fluctuation of column-averaged CO2 concentrations (XCO2) exceeded 10 ppm in Northeast China during 2016.  Biogenic contribution (large negative in summer and insignificant in other months) offset about 70% of anthropogenic contribution of XCO2 in this region.  WRF-VPRM modeling successfully captured seasonal and episodic variations of NEE and CO2 concentrations, however, the NEE in mixed forest was overestimated during daytime, mainly due to the uncertainties of VPRM parameters, especially maximum light use efficiency.
Modification of Zero Valent Iron Nanoparticles by Sodium Alginate and Bentonite: Enhanced Transport, Effective Hexavalent Chromium Removal and Reduced Bacterial Toxicity
Authors: Zhang Mengya , Yi Kexin , Zhang Xiangwei , Han Peng , Liu Wen , Tong Meiping
Published: March 2020

The rapid aggregation/sedimentation and decreased transport of nanoscale zero-valent iron (nZVI) particles limit their application in groundwater remediation. To decrease the aggregation/sedimentation and increase the transport of nZVI, sodium alginate (a neutral polysaccharide) and bentonite (one type of ubiquitous clay) were employed to modify nZVI. Different techniques were utilized to characterize the modified nZVI. We found that modification with either sodium alginate or bentonite could disperse the nZVI and shifted their zeta potentials from positive to negative. Comparing with the bare nZVI, the sedimentation rates of modified nZVI either by sodium alginate or bentonite are greatly decreased and their transport are significantly increased. The transport of modified nZVI can be greatly increased by increasing flow rate. Furthermore, Cr(VI) can be efficiently removed by the modified nZVI (both sodium alginate and bentonite modified nZVI). Comparing with bare nZVI, the two types of modified nZVI contain lower toxicities to Escherichia coli. The results of this study indicate that both sodium alginate and bentonite can be employed as potential stabilizers to disperse nZVI and improve their application feasibility for in situ groundwater remediation.
Test of gravitational redshift based on tri-frequency combination of frequency links between Atomic Clock Ensemble in Space and a ground station
Authors: Sun Xiao , Shen Wen-Bin , Shen Ziyu , Cai Chenghui , Xu Wei , Zhang Pengfei , Ashry Mostafa
Published: March 2020

Atomic Clock Ensemble in Space (ACES) is an ESA mission designed mainly to test gravitational redshift with high-performance atomic clocks in space and on the ground. Here we develop tri-frequency combination (TFC) method based on the measurements of frequency shifts of three independent microwave links between ACES and a ground station. The potential scientific object requires an accuracy of at least 3×10-16, thus we need to consider various effects including Doppler effect, second-order Doppler effect, atmospheric frequency shift, tidal effects, refraction caused by atmosphere, Shapiro effect, with accuracy level of tens of centimeters. The ACES payload will be launched in middle of 2021, and the formulation proposed in this study will enable us to test gravitational redshift at an accuracy level at least 2×10-6 level, one order more higher than the present accuracy level. This study is supported by NSFCs (grant Nos. 41721003, 41631072, 41874023, 41804012, 41429401, 41574007) and Natural Science Foundation of Hubei Province of China (grant No. 2019CFB611).
Data mining and machine learning to enhance new-particle formation identification and analysis
Authors: Zaidan Martha A. , Fung Pak L. , Wraith Darren , Nieminen Tuomo , Hussein Tareq , Kerminen Veli-Matti , Petäjä Tuukka , Kulmala Markku
Published: March 2020

Data Mining (DM) and Machine Learning (ML) have become very popular modern statistical learning tools in solving many complex scientific problems. In this work, we present two case studies that used DM and ML techniques to enhance new-particle formation (NPF) identification and analysis. Extensive measurements and large data sets related to NPF and other ambient variables have been collected in arctic and boreal regions. The focus area of our studies is the SMEAR II station located in Hyytiälä forest, Finland that is in the area of interest of the Pan-Eurasian Experiment (PEEX).

Atmospheric NPF is an important source of climatically relevant atmospheric aerosol particles. NPF is typically observed by monitoring the time-evolution of ambient aerosol particle size distributions. Due to the noisiness of the real-world ambient data, currently the most reliable way to classify measurement days into NPF event/non-event days is through a manual visualisation method. However, manual labour, with long multi-year time series, is extremely time-consuming and human subjectivity poses challenges for comparing the results of different data sets. In this case, ML classifier is used to classify event/non-event days of NPF using a manually generated database. The results demonstrate that ML-based approaches point towards the potential of these methods and suggest further exploration in this direction.

Furthermore, NPF is a very non-linear process that includes atmospheric chemistry of precursors and clustering physics as well as subsequent growth before NPF can be observed. Thanks to ongoing efforts, now there exists a tremendous amount of atmospheric data, obtained through continuous measurements directly from the atmosphere. This fact makes the analysis by human brains difficult, on the other hand, enables the usage of modern data science techniques. Here, we demonstrate the use of DM method, named mutual information (MI) to understand NPF events and a wide variety of simultaneously monitored ambient variables. The same results are obtained by the proposed MI method which operates without supervision and without the need of understanding the physics deeply.
Dictionary learning algorithms for the downward continuation of the gravitational potential
Authors: Schneider Naomi , Michel Volker
Published: March 2020

A fundamental problem in the geosciences is the downward continuation of the gravitational potential. It enables us to learn more about the system Earth and, in particular, the climate change.

Mathematically, we can model a (downward continued) signal in a 'best basis' consisting of local and global trial functions from a dictionary. In practice, our dictionaries include spherical harmonics, Slepian functions and radial basis functions. The expansion in dictionary elements is obtained by one of the Inverse Problem Matching Pursuit (IPMP) algorithms.

However, it remains to discuss the choice of the dictionary. For this, we further developed the IPMP algorithms by introducing a learning technique. With this approach, they automatically select a finite number of optimized dictionary elements from infinitely many possible ones. We present the details of our method and give numerical examples.

See also: V. Michel and N. Schneider, A first approach to learning a best basis for gravitational field modelling, arxiv: 1901.04222v2
Investigating Spatiotemporal Variation of Heatwave and its Association with Blocking in the Northeastern Asia
Authors: Fang Beijing , Lu Mengqian
Published: March 2020

Severe heatwaves in recent decades caused tremendous financial loss and even deaths. And both the occurrence and characteristics of heatwave are changing under global warming. The spatiotemporal variation and characteristics of heatwave in Northeastern Asia are investigated on both grid and event bases in this study. We find that persistent, extensive and intense heatwave has become more frequent during the last four decades. Such trend is found significantly correlated with the increase of temperature.

As most dreadful heatwaves are reported to be accompanied by blocking, we also thoroughly analyze the association between heatwave and blocking using two leading blocking indices, examining 500hpa geopotential height (TM index) and vertically averaged potential vorticity anomaly (PV index), respectively. A discrepancy between blocking climatology of TM index and PV index is exhibited, with the former displaying two high-frequency zonal bands at the south and north regions, while the latter only showing one high frequency band in the north. However, grid-based concurrence analysis using the two blocking indices agreeably suggests that blocking favors the occurrence of heatwave, especially in the north region where blocking often occurs. We further explicitly investigate their extended temporal association with time lags, which has not been done before in the literatures. It reveals that heatwave mostly occurs after or on the onset day of blocking and ends after or at the end of blocking. It indicates that blocking is more of a favorable environmental condition to trigger heatwave than maintain it. Lastly, the impact of blocking on the characteristics of heatwave events is explored on an event basis, using the 3D object model newly proposed by this study. Blocking related heatwave events are more likely to be more persistent, extensive and intense than unrelated events.