bluuebunny/crossref_metadata_2025 huggingface dataset:
Atmospheric Blocking: The Impact of Topography in an Idealized General Circulation Model
Authors: Narinesingh Veeshan , Booth James , Clark Spencer , Ming Yi
Published: March 2020

Atmospheric blocking can have important impacts on weather hazards, but the fundamental dynamics of blocking are not yet fully understood. As such, this work investigates the influence of topography on atmospheric blocking in terms of dynamics, spatial frequency, duration and displacement. Using an idealized GCM, an aquaplanet integration, and integrations with topography are analyzed. Block-centered composites show midlatitude aquaplanet blocks exhibit similar wave activity flux behavior to those observed in reality, whereas high-latitude blocks do not. The addition of topography significantly increases blocking and determines distinct regions where blocks are most likely to occur. These regions are found near high-pressure anomalies in the stationary waves and near storm track exit regions. Focusing on block duration, blocks originating near topography are found to last longer than those that are formed without or far from topography but have qualitatively similar evolutions in terms of nearby geopotential height anomalies and wave activity fluxes in composites.  Integrations with two mountains have greater amounts of blocking compared to the single mountain case, however, the longitudinal spacing between the mountains is important for how much blocking occurs. Comparison between integrations with longitudinally long and short ocean basins show that more blocking occurs when storm track exits spatially overlap with high-pressure maxima in stationary waves. These results have real-world implications, as they help explain the differences in blocking between the Northern and Southern Hemisphere, and the differences between the Pacific and Atlantic regions in the Northern Hemisphere.
Cold pool collisions as a triggering mechanism of convection
Authors: Halvorsen Gustav , Meyer Bettina , Härter Jan
Published: March 2020

Cold pools are produced by rain evaporation from
convective thunderstorms and play an important role 
in many atmospheric phenomena (e.g. transition to deep convection and convective self-aggregation). From observational
and numerical studies, it has been found that intersecting cold pools
increase the likelihood of triggering convection.
We test this hypothesis by combining observational
radar data from Darwin (Australia) with a simple conceptual model.

We identify precipitation objects in the radar data. It is assumed that each rain event produces a cold pool
that is initialized at the center of the precipitation cell. Cold pools are simulated with a stochastic surface growth model.
The spatial coordinate of each collision event is recorded. 
Collectively these points take the shape of a Voronoi diagram. 
According to our hypothesis, the probability of new rain events should decay with spatial distance to the Voronoi.

Our preliminary results suggest that rain events cluster in the
vicinity of the Voronoi with a higher frequency that one would expect if cold pool collisions did not stimulate convection. 
To conclude, our findings suggest that dynamic collisions between cold pools increase the likelihood of convection in the surrounding area.
This work allows us to study the effect of cold pools from radar data, despite cold pools being invisible to the radar images,
using a simple object-based model of convective cold pools. 
Where are the proto-South China Sea slabs? SE Asia plate tectonic and mantle flow insights from TERRA global mantle convection models
Authors: Lin Yi-An , Colli Lorenzo , Wu Jonny
Published: March 2020

In this study we explored the contrasted plate tectonic reconstructions proposed for the proto-South China Sea and SE Asia. We implemented four different end-member plate models into global geodynamic models to test their predicted mantle structure against tomography. All models reproduced the Sunda slabs beneath Peninsular Malaysia, Sumatra and Java and the proto-South China Sea (PSCS) slabs beneath present Palawan, northern Borneo, and offshore Palawan; some models also predicted slabs under the southern South China Sea. PSCS slabs generated from double-sided PSCS subduction and earlier Borneo rotation generated a slightly better fit to tomography but pure southward PSCS subduction was also viable. A smaller Philippine Sea plate (PSP) with a short ~1000 km restored northern slab (i.e. Ryukyu slab) was clearly superior to a very long >3000 km slab. Mantle flows generated from our geodynamic models suggest strong upwellings under Indochina during the late Eocene to Oligocene. Our models generated strong downwellings under the South China Sea in the late Cenozoic that did not support a deep-origin ‘Hainan plume’. 

The following plate models variants were assimilated in the geodynamic models: (1) southward vs. double-sided PSCS subduction; (2) early Borneo counterclockwise rotations during the Oligocene to Early Miocene vs. later rotations (mid- to Late Eocene and Early Miocene); (3) a smaller Philippine Sea plate restored with a shorter ~1000 km northern slab vs. a longer >3000 km slab. This study assimilates four different plate models into the numerical model TERRA (Bunge et al., 1998). We digitally re-built in GPlates (Boyden et al., 2011) the implemented the plate models as a set of continuously closing plates in order to generate a global self-consistent velocity field to be assimilated into the convection models. The temperature fields were converted to seismic velocities assuming a Pyrolite composition and equilibrium mineralogy. We quantify the correlation between our geodynamic models and seismic tomography within SE Asia. For the tomography models S40RTS and LLNL-G3Dv-JPS we explicitly accounted for their finite resolution (Ritsema et al., 2011; Simmons et al. 2019).
Simulating collisions of charged cloud drops in an ABC flow
Authors: Auerswald Torsten , Ambaum Maarten
Published: March 2020

Calculating the electric force between cloud drops is not straightforward. Since water drops are conducting, the electric force is not just simply the force between point charges, but instead the charge in each drop induces an infinite number of image charges in the other drop. The effect of these image charges can cause the electric force between two like charged cloud drops to become attractive on very short distances, when only applying Coulomb's law would result in a repulsive force. The attractive effect of image charges could potentially increase the collision rate of cloud drops. Within the United Arab Emirates Rain Enhancement Program (UAE REP) we are investigating the potential for rain enhancement by charging clouds.

Simulating the behaviour of cloud drops is numerically very expensive. A large number of drops needs to be simulated to obtain stable collision statistics. Additionally, the drops move in a complex turbulent environment with eddies spanning several orders of magnitude in size. Simulating the turbulent flow alone is an expensive task. Because of the typical sizes of cloud drops, their motion is predominantly influenced by the smallest turbulent scales in the flow. Therefore, Direct Numerical Simulation (DNS) is necessary and used to simulate the influence of turbulent flow on drop motion. In this work, instead of using DNS, we use an ABC flow to simulate the turbulent effect on cloud drops. This simple approximation for the turbulent flow allows to simulate the drop motion using much less computational resources then needed by DNS and therefore, allows to include the very expensive effect of electrical drop charge in our simulation of colliding drops in a turbulent environment.

To investigate the effect of electrical charge on drop collisions, a Lagrangian particle code for the interaction of cloud drops is used. It calculates the motion of individual drops based on the aerodynamical force due to the ABC flow and the gravitational force and registers drop collisions from which collision statistics can be calculated. In the cloud model all drops carry positive charges. The effect of the electric force is calculated by an approximation which uses Coulomb's law for the effect of the point charges and an additional term to approximate the effect of image charges which produce an attractive force on short distance.

Results for the collision kernel with and without charge will be presented. The effect of the additional term to Coulomb's law will be shown for different drop sizes and drop charges. It will be discussed if the attractive force for like charged drops on short distances can lead to an enhancement in drop collisions and under which conditions the effect is the largest.
Development of Agricultural Damage Estimation Technique Considering Regional Characteristics
Authors: Heesup Lee , moojong Park
Published: March 2020

Due to the effects of extreme weather conditions, extreme disasters such as floods and droughts are becoming more frequent worldwide.

In particular, drought is one of the long-term disasters unlike floods, with the greatest damage occurring in the agricultural sector in the event of a drought disaster.

This study investigated and analyzed the history of drought damage in Korea in the past, how the government responded to drought, and how to calculate the amount of drought damage in agriculture.

Based on the survey and analysis data, the methods for calculating agricultural drought damage in the past were supplemented, and realistic and practical methods for calculating agricultural drought damage were developed in consideration of regional characteristics in future drought disasters.

This research was supported by a grant(2019-MOIS31-010) from Fundamental Technology Development Program for Extreme Disaster Response funded by Korean Ministry of Interior and Safety(MOIS).
Participatory-Exploratory Modeling of Coupled Socio-Economic and Environmental Systems for Adaptive Management of Water Resources
Authors: Alizadeh Mohammadreza , Adamowski Jan , Malard Julien , Inam Azhar
Published: March 2020

Water and environmental resources exist in complex and deeply uncertain systems of social-economic and environmental components.  As such, natural resource systems are impacted simultaneously by the diverse effects of many interacting human-environmental components. While conventional environmental planning commonly stresses estimation and prediction, preferring top-down initiatives and technocratic solutions, this approach often overlooks socio-economic impacts and interactions, leading to unexpected long-term outcomes. In response, it is now widely acknowledged that frameworks capturing the complex dynamics of society and the environment are needed to develop more sustainable environmental and water resources management strategies. Moreover, for robust policy-making, the performances of potential policies must be considered under multiple plausible conditions to enhance the chances of desired outcomes and limit the risk of undesirable results. This research addresses these challenges by considering deep uncertainty in coupled socio-economic and environmental systems.  In this study, a computational model-based approach to support adaptive decision-making under deep uncertainty is developed and applied to adaptive policy-making of sustainable water resources management for human-water systems in developing countries. The Rechna Doab region of Pakistan is considered as a case study. Qualitative-quantitative participatory exploratory modeling is performed by incorporating a physical-socioeconomic system dynamics model, a systematic scenario selection method and a scenario discovery approach.  The Driver-Pressure-State-Impact-Response (DPSIR) model is used through storytelling approaches to identify vulnerabilities in policy options in the coupled socio-economic and environmental system by considering its response to drivers, pressures, states, and impacts. Storytelling methods are used to develop qualitative storylines in order to support a detailed and stakeholder-led description of future adaptive management policies. The proposed methodology is used for systematic scenario discovery to uncover vulnerabilities across a range of possible futures and test the performance of stakeholder proposed policies. Also, the tradeoffs between water resources management alternatives, in terms of stakeholder objectives, and their robustness to deep uncertainty are assessed. The proposed approach simulates qualitative and quantitative cause-effect relationships between the environmental system and socio-economic interactions to assess candidate policies, their vulnerabilities and associated adaptive strategies.
The potential predictability of Singapore and Maritime Continent weather regimes in relation to the MJO and ENSO
Authors: Hassim Muhammad Eeqmal , Lee Joshua
Published: March 2020

The Madden-Julian Oscillation (MJO) is a well-known source of predictability on sub-seasonal-to-seasonal (S2S) time scales and a major driver of intraseasonal weather variability around the globe. For example, the MJO’s interaction with and influence on daily regional weather in the Maritime Continent-Southeast Asia (MC-SEA) region is thought to be most pronounced during boreal winter (November through February), given that the amplitude of MJO activity is often much stronger during that period compared to other times of the year.

In this study, we examine the relationship of the MJO to eight weather regimes (WR) that have been previously defined for Singapore and the MC-SEA region using k-means clustering of daily sounding data from reanalysis. These weather regimes cover the whole annual cycle of rainfall with well-defined peak frequency times and mean spatial structures that correspond to the seasonal movement of the Inter-tropical Convergence Zone (ITCZ) across the Equator. Following previous work, we use a statistical method to compute the lagged relationship between each MJO phase and daily WR occurrence between December 1980 - November 2014 to quantify the change in the likelihood that a certain regime will occur relative to climatology, given an MJO phase in advance. Bimonthly analysis indicates that strong lag relationships exist between MJO phases and certain regimes in different two-month periods, thus giving potential predictability of the type of mean weekly weather in the MC-SEA up to 3-4 weeks ahead. In addition, we consider the modulation of the MJO-WR relationships stratified by the ENSO phase to determine whether the expected WR frequency response to MJO activity varies substantially in different background states.
Exposure analysis of Chinese railways under the Change of Extreme-Precipitation in the future
Authors: Zhao Jing , liu Kai , Wang Ming
Published: March 2020

Abstract: Rainfall-induced disaster is the most frequent disaster affected Chinese Railway System. Climate change will lead to more extreme rainfall in the future. A better understanding of extreme precipitation in the future and the exposure of railway infrastructures to extreme precipitation will facilitate railway planning and disaster risk management. This paper employs climate model simulations to calculate the changes of the extreme precipitation under different global warming scenarios. The return periods of the present 50-yr/100-yr return-period precipitation amount in the future are obtained. Based on this, the changes of the exposure of Chinese railways to extreme precipitation are analyzed. The results reveal that 58.61% (55.46) of China’s region will experience an increase in the 50-yr(100-yr) return-period precipitation under 1.5°C warming in comparison with the present period (2001–2020), the value will be 64.44% and 59.53% due to the additional 0.5°C warming. By calculating the exposure of Chinese railways, we found that 28.49% (32.15) of China's railways are in the region where 50-yr return-period rainfall at this stage will occur less than 20 years under 1.5°C (2.0°C) warming, and 36.85% (41.39)of China's railways are in the region where 100-yr return-period rainfall at this stage will occur less than 50 years under 1.5°C (2.0°C) warming in the future. This study quantified the exposure of China’s railway to extreme precipitation under the 1.5°C/2.0°C global warming. The results provided in this study have profound significance for the fortification planning of China's railway system for rainfall-induced disasters and provide useful experience for other countries.
Characterization of Tectonic - Magmatic Seismic Source at Chiles - Cerro Negro Volcanic Complex (CCNVC)
Authors: Córdova Andrea , Espin Pedro , Pacheco Daniel
Published: March 2020

The Chiles - Cerro Negro Volcanic Complex (CVCCN) is located in the Western cordillera at the Ecuador – Colombia border. This volcanic complex has showed an anomalous seismic activity since late 2013, with high activity peaks in 2014, specially in October and November with up to 6000 earthquakes per day mostly volcanic-tectonics events. The most important earthquake in this sequence occurred on October 20, 2014 with a 5.7 Mw. In order to obtain a better characterization of the seismic source in the CVCCN area, a new 1D velocity model was computed using 300 earthquakes with magnitudes larger than 3.0 MLv, and high quality of P and S pickings.  This model has 8 layers over a semi-space and starts with a Vp = 2.96 Km/s and  Vs = 1.69 Km/s highlighting strong variations at 7km with Vp = 5.87 Km/s and  Vs = 3.52 Km/s and at 24 km Vp = 6.58 Km/s and  Vs = 3.79 Km/s . A value of 1.73 of Vp/Vs was determined, which is a normal for the continental crust. Computed hypocenters with the new velocity model highlighted two sources: one is defined by a concentration of shallow earthquakes on the southern flank of Chiles Volcano, and the second one contains events deeper than 7 km and follows a N-S tectonic structure that crosses the CVCCN and matches the Cauca-Patía fault. This structure obtained with this new model is confirmed by interferograms from Sentinel images after the earthquake MLv 4.2 of September 27, 2019 where a mostly dextral movement is defined. Focal mechanisms were computed for earthquakes larger than MLV 4.0 using waveform inversion (SeisComp3). Most events show ~N-S planes and dextral with inverse component. Focal mechanisms exhibit a Non-Double Couple component (CLVD), which in most of these events is more than 40 percent including the CLVD = 71% calculated for the earthquake of Mw 5.7 on October 20, 2014. This value suggests the presence of a volumetric component that could be induced by magma or fluid movements. This is corroborated by the presence of LP and VLP events inside of the CVCCN system.
Size-segregated ions and carbonaceous fractions of ambient aerosol in Bogota
Authors: Mateus Lady , Burbano Kelly , Jimenez Rodrigo , Rojas Nestor
Published: March 2020

Elemental and Organic Carbon (EC/OC) make up a significant fraction of particulate matter emitted by combustion process and water-soluble ions provide an important information about the origin of ambient aerosols. The sized-segregated chemical characterization of ambient aerosol is useful to understand its sources and formation mechanisms and complements well the information obtained from the bulk aerosol composition. Previous studies in Bogota determined the chemical composition and source contribution of PM10 in Bogota, as well as the temporal and spatial variability of polycyclic aromatic hydrocarbons (PAH) in the same city. However, the size-segregated chemical composition of ambient particles has not been studied in Colombian cities. This work aims to better understand the variability of size-segregated PM chemical composition in Bogota, one of the main Latin American megacities. Eight sets of samples were collected using an Andersen 8-stage cascade impactor in the southwest area of the city, where the highest concentrations of PM2.5 usually occur, over two periods in 2018. The concentration of OC/EC and ions (ammonium, sodium, potassium, magnesium, calcium, chloride, nitrate, sulfate and oxalate) were quantified. The average PM1 concentration was 30.3 mg/m3 (75% of PM2.5). The mass size distribution was bimodal, with a coarse mode between 5.8 and 4.7 mm aerodynamic diameter and an accumulation mode between 0.43 and 0.65mm. Most of the mass (75%) of PM1 consists of carbonaceous species, being EC the main constituent. The main inorganic ions in PM1 were sulfate, nitrate and ammonium. These and other results from this work will contribute to the validation of models within the PAPILA (Prediction of Air Pollution In Latin America and the Caribbean) project, funded by the EU MSCA action for research and innovation staff exchange (GA 777544).
Slope thermokarst transforms permafrost preserved glacial landscapes and effects propagate through Arctic drainage networks.
Authors: Kokelj Steve , Kokoszka Justin , van der Sluijs Jurjen , Rudy Ashley , Tunnicliffe Jon , Shakil Sarah , Tank Suzanne , Zolkos Scott
Published: March 2020

Recent intensification of slope thermokarst is transforming permafrost preserved glaciated landscapes and causing significant downstream effects. In this paper we: A) Describe the thaw-related mechanisms driving the evolution of slope to stream connectivity; B) define the watershed patterns of thermokarst intensification; and C) project the cascade of effects through the Arctic drainage networks of northwestern Canada. The power-law relationships between disturbance area and volume, and thickness of permafrost thawed, in conjunction with a time-series of disturbance mapping show that the non-linear intensification of slope thermokarst is mobilizing vast stores of previously frozen glacial sediments linking slopes to downstream systems. Mapping across a range of catchment scales indicates that slope thermokarst predominantly affects first and second order streams. Slope sediment delivery now frequently exceeds fluvial transport capacity of these streams by several orders of magnitude indicating long-term perturbation. Mapping shows slope thermokarst is directly affecting over 6760 km of stream segments, over 890 km of coastline and over 1370 lakes across the 1,000,000 km2 Arctic drainage basin from continuous permafrost of northwestern Canada. The downstream projection of thermokarst disturbance increases affected lakes by a factor of 4 and stream length by a factor of 7, and suggests that fluvial transfer has the potential to yield numerous thermokarst impact zones across coastal areas of western Arctic Canada. The Prince of Wales Strait between Banks and Victoria Islands is identified as a hotspot of downstream thermokarst effects, and the Peel and Mackenzie rivers stand out as principle conveyors of slope thermokarst effects to North America’s largest Delta and to the Beaufort Sea. The distribution of slope thermokarst and the fluvial pattern of sediment mobilization signal the climate-driven rejuvenation of post-glacial landscape change and the triggering of a time-transient cascade of downstream effects. Geological legacy and the patterns of continental drainage dictate that terrestrial, freshwater and marine environments of western Arctic Canada will be a hotspot of climate-driven change through the coming centuries. 
The dissipation of the internal tide inferred from a global ocean model, altimetry, and in-situ observations
Authors: Buijsman Maarten , Kaur Harpreet , Zhao Zhongxiang , Waterhouse Amy , Whalen Caitlin
Published: March 2020

In this presentation we combine several model and observational data sets to better understand the dissipation of the diurnal and semidiurnal internal tide in the global ocean, which is relevant for maintaining the global overturning circulation. We compute depth-integrated internal tide dissipation rates from a realistically-forced global HYbrid Coordinate Ocean Model (HYCOM) simulation with a horizontal resolution of 4 km (1/25 degrees) and 41 layers. We also compute dissipation rates from altimetry in two ways: 1) from the low-mode flux divergence away from topography and 2) by fitting exponential decay curves along low-mode internal tide beams. The internal-tide sea-surface height amplitude is computed with a least-squares harmonic analysis over a 20+ year altimetry data set. Hence, the altimetry-inferred dissipation rates both reflect the tidal dissipation and the energy scattered from the stationary to the nonstationary internal tide. To account for the dissipation of the nonstationary tide, we apply a spatially-varying correction factor to the stationary dissipation inferred from altimetry.  This correction factor is computed from a global 8-km HYCOM simulation with a duration of 6 years, from which the stationary and nonstationary internal tides can be easily isolated. We compare the simulated and the corrected altimetry-inferred dissipation rates with dissipation rates from finescale and microstructure observations. Preliminary results show that the simulated dissipation is up to a factor of two larger than the depth-integrated dissipation rates inferred from finescale methods, but smaller than the dissipation rates from microstructure.
Three-dimensional slope stability study using a Coupled Eulerian-Lagrangian method
Authors: Liu Fang-Cing , Liu Chih-Hsuan , Hung Ching
Published: March 2020

  In slope stability analysis, two-dimensional (2D) analysis techniques are usually applied due to its simplicity and extensive applicability. Given that slope failures are three-dimensional (3D) in nature, especially in the slope with complex geometry, a 3D slope stability analysis could lead to more reasonable results [1]. In slope stability analyses, limit equilibrium method (LEM) and finite element method (FEM) are widely used. Note that LEM only satisfies equations of statics and does not consider strain and displacement compatibility; FEM may encounter significant mesh distortion during large deformations where convergence difficulty and the analysis may be terminated before the slope reaches failure [2]. In the study, a Coupled Eulerian-Lagrangian (CEL) method, which allows materials to flow through fixed meshes regardless of distortions, was utilized to investigate 3D slope stability [3]. Validation of the numerical modeling was first presented using a typically assumed 3D slope. After the validation, various types of slopes (i.e. turning corners, convex- and concave-shaped surfaces) with various boundary conditions (unrestrained, semi-restrained, and fully restrained) are carefully conducted to examine the 3D slope stability. It is anticipated the 3D analyses can shed some light on the slope stability analysis with extreme or complex geometry cases and provide more reasonable results.

 

REFERENCE

T.-K. Nian, R.-Q. Huang, S.-S. Wan, and G.-Q. Chen (2012): Three-dimensional strength-reduction finite element analysis of slopes: geometric effects. Canadian Geotechnical Journal, 49: 574–588.

C. Hung, C.-H. Liu, G.-W. Lin and Ben Leshchinsky (2019): The Aso-Bridge coseismic landslide: a numerical investigation of failure and runout behavior using finite and discrete element methods. Bulletin of Engineering Geology and the Environment. doi: 10.1007/s10064-018-1309-3.

C. Han. Lin, C. Hung and T.-Y. Hsu (2020): Investigations of granular material behaviors using coupled Eulerian-Lagrangian technique: From granular collapse to fluid-structure interaction. Computers and Geotechnics (under review).

 

 
A case study of the 2018 Camp Fire event using HYSPLIT-based emission inverse modeling system with GOES Advanced Baseline Imager (ABI) observations and other measurements for wildfire smoke forecasts
Authors: Chai Tianfeng , Kim HyunCheol , Stein Ariel , Tong Daniel , Li Yunyao , Kondragunta Shobha
Published: March 2020

An emission inverse modeling system to estimate wildfire smoke source strength, vertical distribution, and temporal variations by assimilating satellite observations with the HYSPLIT dispersion model for smoke forecasting has been built. In this so-called HEIMS-fire system, a cost function is defined to quantify the differences between the satellite smoke products and their model counterparts, weighted by the model and observation uncertainties. Smoke sources that minimize this cost function provide the optimal smoke emission estimates. It has been successfully applied to hindcast smoke distribution during a Southeast US wildfire event in 2016 using GOES GASP products. A new Advanced Baseline Imager (ABI) sensor onboard GOES-16 has become fully operational since December 2017. The ABI smoke products have better spatial and temporal resolutions than those from its predecessors. In this study, the ABI observations during the 2018 Camp Fire event in California USA are tested in the HEIMS-fire system. Hindcasts using the emission estimates by the HEIMS-fire system will be performed. Comparison between this new emission estimation system and other emission estimates will be conducted. In addition, the impact of additional observations including the tailored ones will be investigated.
Gradual build up and episodic character of glacier velocity preceding and during the surge of a Karakorum glacier enabled by open-access image-processing
Authors: Delaney Ian , Aati Saif , Beaud Flavian , Gremion Shan , Adhikari Surendra , Avouac Jean-Phillipe
Published: March 2020

Glacier surging provides a unique opportunity to examine rapid changes in glacier sliding that occur when some glaciers alternate between slower-than-normal (quiescence) and faster-than-normal (surge) velocities. On surging glaciers, mechanical instabilities within the glacier set off a regime of fast glacier flow, which causes these glaciers to accelerate and advance. The precise processes that cause a surging remain uncertain and likely vary between glaciers. However, the uptake of studies on glacier surging over the past decade continues to yield invaluable insights in glacier dynamics. In this study, we combine optical remote sensing and numerical modeling to examine the recent surge of Shishper glacier, in the Pakistani Karakorum. This glacier started surging in 2018, showed a dramatic terminus advance that reached rates of several meters per day. In the process, it dammed the adjacent valley, forming a lake which drained in June 2019 flooding the downstream valley, damaging the Karakorum Highway and threatening nearby communities. We leverage a high spatio-temporal resolution dataset of glacier velocities, using roughly 100 open-access images, across the Landsat-8 and Sentinel-2 record, thus encompassing the quiescence (2013-2018) and surge (2018-2019) phases. We created the dataset in an updated and nearly automated workflow by using the COSI-Corr software package to calculate displacements between images combined with a unique algorithm to filter data and remove artifacts. The result consists in high-resolution velocity maps with resolution with time intervals as short as five days. Such dataset provide a complete time-series of the spatio-temporal evolution of ice-surface velocities during a surge. One of the most notable finding is that the surge onset occurs progressively. In the two years leading up to the surge, spring speed-ups became increasingly larger in than the long-term median. We further identify three periods with  surge velocities far higher than the long-term median that likely coincide with hydrological events. Two periods occur in the spring (2018 and 2019) and the third corresponds with the lake formation in the winter of 2018-2019. Finally, we establish that the surge termination coincided with the lake drainage at the end of June 2019. The current availability of open-access imagery and  glacier topography allow us to  make an increased quantity of observations and thus better quantify glacier dynamics.
Dynamics of organic matter decomposition during iron redox fluctuations in soils
Authors: Thompson Aaron
Published: March 2020

It is well-understood that iron redox dynamics can lead to both organic matter persistence—through the stabilization of organic matter in iron mineral associations or in Fe-cemented aggregate structures—as well as organic matter decomposition—through microbial respiration on ferric iron and through the production of hydroxyl radicals during the oxidation of ferrous iron (i.e., Fenton chemistry). However, we do not understand how the relative impact of each of these processes manifests during redox fluctuations. For instance, we do not understand how the net decomposition of organic matter via Fenton chemistry during the oxidation of ferrous iron compares with the net protection of organic matter via newly formed short-range-ordered (SRO) ferric minerals; nor do we understand how much of that recently-protected organic matter will be lost during a transient anoxic event. Certainly, some of the key parameters determining the balance of iron-mediated OM protection vs. decomposition include the timescales of the redox fluctuations (the duration of the oxic or anoxic periods), the rates of iron oxidation, and critically, the dynamics of the resident microbial community. Here, we explore these parameters using upland soils from the Calhoun and Luquillo Critical Zone Observatories in laboratory experiments. (1) We quantified Fe-stimulated OM protection vs. decomposition by amending 13C-labeled dissolved OM (DOM) and 57Fe-labeled FeIIaq to soil slurries incubated under either static oxic or fluctuating redox conditions. (2) We tracked the rates of Fe reduction, CO2 production, and CH4 production from soils during multiple redox fluctuations with three different lengths of O2 exposure and equal lengths of anoxia. From these experiments we find that (1) the addition of iron only conferred net protection to newly added organic matter and only under strict oxic conditions, whereas in treatments without added DOC or that were exposed to transient anoxia, the addition of iron stimulated net organic matter decomposition. (2) That the length of O2 exposure altered the balance of Fe reduction and methanogenesis during the anoxic periods with longer O2 exposure suppressing Fe reduction and enhancing methanogenesis. These findings suggest iron redox dynamics will likely tend to enhance organic matter decomposition in soils. But, importantly, these studies have specifically focused on localized iron dynamics and biogeochemical coupling with organic matter by using well-mixed systems. Spatial heterogeneity and soil structural features have yet to be evaluated in this context.

 
Transpressional deformation in the mantle below the North Anatolian fault system, Turkey
Authors: Tikoff Basil , Chatzaras Vasili , Chapman Timothy , Barshi Naomi , Aldanmaz Ercan , Kiesow Maggie
Published: March 2020

The North Anatolian Fault Zone (NAFZ) is a 1200-km-long, dextral intracontinental transform fault zone, and initiated ca. 13–11 Ma ago.  The NAFZ formed in response to the N-S convergence of the Eurasian and Arabian plates, accommodated by the westward motion of the Anatolia plate relative to Eurasia plate.  Mantle xenoliths were sampled in late Miocene (11.68±0.25 to 6.47±0.47 Ma) alkali basalts and basanites, immediately N of the trace of the North Anatolian fault, and were previously interpreted to sample the mantle portion of the North Anatolian fault/shear zone at depth.  The studied xenoliths are mainly spinel lherzolites and harzburgites.  Equilibration temperatures estimated from two-pyroxene geothermometers range from 775 to 975 °C, while pressures estimated from the Cr in clinopyroxene geobarometer and pseudosection modelling range from 12 to 22 kbar, which correspond to depths of 40–80 km.  We used high‐resolution X-ray computed tomography to quantify the xenolith fabric defined by the 3D shape preferred orientation of spinel grains.  Spinel displays dominantly oblate fabric ellispoids, consistent with flattening strain.  Olivine has two main crystallographic preferred orientation patterns, the axial-[010] and the A-type, determined with electron backscatter diffraction.  The axial-[010] pattern is consistent with the spinel fabric and other microstructures that show flattening strains.  To further constrain the strain path, we analyze the crystallographic vorticity axes in olivine, which show a complex pattern.  Our results are consistent with an interpretation of transpressional deformation in the upper mantle below the NAFZ, during the early stages of the development of the transform system.  Transpressional deformation is consistent with collision-induced, strike-slip extrusion of Anatolia.
Pasture species behaviour on sulfide mine tailings rehabilitated with a designed Technosol
Authors: Arán Diego , Santos Erika , Abreu Maria Manuela , Antelo Juan , Macías Felipe
Published: March 2020

The uranium mineralization from Fé mining area (Spain) contains sulfides, resulting mine wastes generators of acid mine drainage rich in potentially hazardous elements (PHE). The improvement of the physicochemical characteristics and biogeochemical processes of sulfide mine tailings as well as their socioeconomic valorisation can be achieved by the application of a green technology based on circular economy: Technosol. The efficiency of the application of a superficial layer of a designed Technosol with specific properties to the rehabilitation of the sulfide tailings from Fé mining area was tested. Also, the risk assessment of the land recovery by this technology to pasture was evaluated through a microcosm experiment.

After 20 months of the Technosol application in the field, composite samples of Technosol, recovered tailing (bottom of the Technosol) and tailings without recuperation (control tailing) were collected. These samples were used for microcosm assay and characterized for pH, electric conductivity, fertility, PHEs concentration in total fraction and available fraction extracted with rhizosphere-based method. The substrate effect on development of Lollium perenne and Trifolium pratense (visual signs of phytotoxity, percentage of plant cover and dry shoots biomass) and multielemental composition in their of shoots was evaluated in microcosm assay under greenhouse conditions.

Mine wastes from control tailing had pH ≈4 and high total concentrations of several PHEs (g/kg; Al: 46.2; As, Co and Pb: 0.02-0.03; Cu: 0.04; Fe: 63.2 Mn: 1.3; Ni and Zn: 0.1-0.2). Potentially toxic concentrations of Co, Mn and Ni were identified in the available fraction pointing out the serious environmental risk posed by the control tailing. These chemical characteristics together lack of structure iin mine wastes from control tailing contributed to total inhibition of Trifolium germination and a significant diminution of Lollium growth. Both species growing in Technosol and recovered tailing produced significant plant cover and quite similar amounts of shoot biomass.

The improvement of the overall physicochemical properties in the recovered tailing materials (e.g. the decrease of the hazardous element concentrations in available fraction, and the improvement of the fertility and structure) allowed a quick and secure plant cover with pasture species. The results evidenced the efficiency of the designed Technosol in the sulfide mine tailing rehabilitation and potential land recovery to pastures.

The authors thank ENUSA for technical cooperation and providing the study area and soil samples.
Comparison of 137Cs activity between an ocean general circulation model and the global database
Authors: Tsumune Daisuke , Bryan Frank , Lindsay Keith , Misumi Kazuhiro , Tsubono Takaki , Inomata Yayoi , Aoyama Michio
Published: March 2020

We investigate the oceanic dispersion of 137Cs (half-life of 30.1 years) and its impact on the environment. 137Cs has been released into the ocean due to the atmospheric weapons tests, discharge from nuclear reprocessing plants, the Chernobyl accident, and most recently due to Fukushima Daiichi Nuclear Power Plant (1F NPP) accident. 137Cs activities measured for scientific purposes as well as environmental health and safety monitoring have been summarized in a historical database by IAEA. The spatio-temporal density of the observations varies widely, therefore simulation by an ocean general circulation model (OGCM) can be helpful in the interpretation of these observations. Although simulations of 137Cs activity by OGCMs have been carried out previously, the input condition of 137Cs still has large uncertainties due to a lack of observations of global fallout. The horizontal resolution of the previously available estimated global fallout of 137Cs was 10 degree longitude x latitude. We have produced a new estimate of the global fallout of 137Cs with 2.5-degree resolution using the Global Precipitation Climatology Project (GPCP) data, and investigated the impact of the revised input condition on the simulation of distribution of 137Cs in the ocean. In addition, discharges of 137Cs from the reprocessing plants (Sellafield and La Hague) were also considered. We used the Parallel Ocean Program version 2 (POP2) of the Community Earth System Model version 2 (CESM2). The horizontal resolution is 1.125 degree of longitude, and from 0.28 degree to 0.54 degree of latitude. There are 60 vertical levels with a minimum spacing of 10 m near the ocean surface, and increased spacing with depth to a maximum of 250 m. The simulated period was from 1945 to 2010 with the circulation forced by repeating (“Normal Year”) atmospheric conditions. We estimated the global distribution of 137Cs deposition from 1945 to 2010 by using these geographical distribution data, the observed time-series data of annual 137Cs deposition at the MRI from 1958 to 2010, and time-series data of 137Cs deposition from 1945 to 1958 estimated from ice-core data. Simulated 137Cs activities derived from the 2.5-degree deposition data were in good agreement with observations, particularly in the Pacific Ocean. Simulated 137Cs activities were strongly influenced by the discharge of 137Cs from the reprocessing plants. Transport processes were also investigated in the simulated results.
Marie Tharp: Seafloor mapping and ocean plate tectonics
Authors: Cannat Mathilde , Smith Deborah , Fornari Daniel , Ferrini Vicki , Escartin Javier
Published: March 2020

The pioneering seafloor mapping by Marie Tharp played a key role in the acceptance of the plate tectonic theory. Her physiographic maps,  published with Bruce Heezen,  covered the Earth’s oceans and revealed with astonishing accuracy the submarine landscape. She exposed the full extent of the global mid-ocean ridge system, documented features such as seamounts and volcanic chains, trenches, and transform faults. Marie Tharp co-authored the first papers describing the major fracture zones in the Central Atlantic (Chain, Romanche, Vema). In 1952, she also discovered that the Atlantic ridge has a central valley (the axial valley), and convinced her colleague Bruce Heezen that it, which corresponds to sustained seismicity (highlighted by other researchers at the same time thanks to the worldwide networking of seismological stations), is a rift that separates the eastern and western provinces of the Atlantic Ocean. Tharp and Heezen were not yet talking about plate tectonics at this time. But when, at the beginning of the 1960s, the first magnetic anomaly maps showed that the oceans were "young", and that the age of the seabed increased with the distance from the ridges, their physiographic map became an essential element in understanding the role that these ridges play, as well as the distribution of the main current terrestrial plates. In this poster, we present original maps and sketches that document this key contribution to the understanding of the Earth's tectonics.
Dry season water availability changes attributed to human-induced climate change
Authors: Padrón Ryan S. , Gudmundsson Lukas , Ducharne Agnès , Lawrence David M. , Mao Jiafu , Peano Daniele , Decharme Bertrand , Krinner Gerhard , Kim Hyungjun , Seneviratne Sonia I.
Published: March 2020

Human-induced climate change poses potential impacts on the availability of water resources. Previous assessments of warming-induced changes in dryness, however, are influenced by short observational records and show conflicting results due to uncertainties in the response of evapotranspiration. In this study we use novel observation-based water availability reconstructions from data-driven and land surface models from 1902 to 2014; a period during which the Earth has warmed approximately 1°C relative to pre-industrial conditions. These reconstructions reveal consistent changes in average water availability of the driest month of the year during the last 30 years compared to the first half of the 20th century. We conduct a simple attribution approach based on a spatial correlation analysis between the reconstructions and different climate model simulations. Results indicate that the spatial pattern of changes is extremely likely influenced by human-induced greenhouse gas emissions as it is consistent with climate model estimates that include historical radiative forcing, whereas the pattern is not expected from natural climate variability given by climate simulations with greenhouse gas levels set to pre-industrial conditions. Changes in water availability are characterized by drier dry seasons predominantly in extratropical latitudes and including Europe, Western North America, Northern Asia, Southern South America, Australia, and Eastern Africa. Finally, we find that the intensification of the dry season is generally a consequence of increasing evapotranspiration rather than decreasing precipitation.
Convective-Permitting Modeling for Retrospective Subseasonal-to-Seasonal (S2S) Forecasting Using the Framework of the Coordinated Regional Ensemble Downscaling Experiment (CORDEX)
Authors: Castro Christopher L. , Chang Hsin-I , Prein Andreas F. , Bukovsky Melissa
Published: March 2020

Convective-permitting modeling (CPM) yields step improvements in the representation of precipitation, as has been demonstrated in applications of numerical weather prediction and climate modeling. While CPM has been used in the context of historical climate simulations and climate change projections, its application to the sub-seasonal to seasonal (S2S) forecast timescale (weeks to months) is comparatively underexplored. New, long-term S2S reforecast products have recently been generated from operational global forecast models, for example as part of the S2S Project and North American Multimodel Ensemble (NMME). These are analogous to CMIP models used for climate change projection. It is now technically possible to dynamically downscale these reforecast data to CPM scale, to asess potential improvement in S2S forecast skill and create new S2S forecast metrics for extreme events. The Coordinated Regional Ensemble Downscaling Experiment (CORDEX) provides an existing robust community framework that can be leveraged to dynamically downscale S2S reforecast data, in a globally unified way. This overview presentation will highlight outcomes from a community discussion on this topic that took place at the 2019 Latsis Symposium "High-Resolution Climate Modeling: Perspectives and Challenges" at ETH Zurich, including a summary of the current state of the science, collective identification of research priorities, and proposed action items proceeding forward.