bluuebunny/crossref_metadata_2025 huggingface dataset:
The Runoff Model-Intercomparison Project over Lake Erie and the Great Lakes
Authors: Tolson Bryan A. , Mai Juliane ,   GRIP-E/GL Project Team
Published: March 2020

The Great Lakes Runoff Inter-comparison Project (GRIP) includes a wide range of lumped and distributed models that are used operationally and/or for research purposes across Canada and the United States. Participating models are GEM-Hydro, WRF-Hydro, MESH, VIC, WATFLOOD, SWAT, mHM, Noah-MP, HYPE, LBRM, GR4J, HMETS, and purely statistical models. The latter are added to assess the information content of the forcing and geophysical datasets. As part of the Integrated Modelling Program for Canada (IMPC) under the Global Water Futures (GWF) program, the project is aiming to run all these models over several regions in Canada. We started with the Lake Erie watershed and then extended the study to the whole Great Lakes domain.

One of the main contributions of the project is that we identified a standard dataset for model building that all participants in the inter-comparison project can access and then process to generate their model-specific required inputs. The common dataset allows identifying differences in model outputs that are solely due to the models and not the data used to setup the models. This presentation will give an update on the design of the inter-comparison and will report on comparative results for two sets of streamflow gauging stations: A) gauge stations with low-human impact upstream watersheds and B) most down-stream gauge stations directly draining into the lake(s).

The main results are: 1) The best performing semi-distributed model calibrated across all stations at once is HYPE. The mHM is the best distributed model calibrated at each station individually (median NSE = 0.78) while LBRM is the lumped model that is on average the best (median NSE = 0.66). 2) The purely statistical model is highly competitive with and even slightly outperforming all hydrologic models except mHM in the calibration period. 3) The performance of most models decreases in urbanized areas. Only models that are calibrated independently at each station are capable of modelling urbanized areas. 4) No significant change in performance can be observed between low-human impact watersheds and watersheds that are mostly downstream, draining directly into a Great Lake.
Copernicus Marine Service: achievements, future challenges and long-term evolution
Authors: Le Traon Pierre-Yves
Published: March 2020

The Copernicus Marine Environment Monitoring Service (CMEMS) provides regular and systematic reference information on the physical state, variability and dynamics of the ocean, ice and marine ecosystems for the global ocean and the European regional seas.  The Copernicus Marine Service has run a successful initial phase over the past five years.  Operational capabilities have been demonstrated, user uptake and user base have been steadily increasing and service evolution activities have allowed regular improvements of the products and services provided to users.  CMEMS now serves a wide range of users (more than 21,000 subscribers are registered to the service) and applications (maritime safety, marine resources, coastal and marine environment, weather, seasonal forecast and climate).  An overview of CMEMS achievements will be given and the presentation will highlight the essential role of R&D activities.  CMEMS priorities and scientific challenges for Copernicus 2 (2021-2027) will then be discussed.   
Modelling of long-term permafrost evolution in the discontinuous permafrost zone of North-West Siberia
Authors: Ezhova Ekaterina , Kukkonen Ilmo , Suhonen Elli , Ponomareva Olga , Gravis Andrey , Gennadinik Viktor , Miles Victoria , Drozdov Dmitry , Lappalainen Hanna , Melnikov Vladimir , Kulmala Markku
Published: March 2020

The rate of climate warming in North-West Siberia is among the highest in the world and this trend is especially pronounced in summer [1]. Analysis of permafrost thermal conditions in this area provides plausible scenarios of permafrost degradation also elsewhere. An increase in the summer mean temperature together with the prolongation of the warm season results in the increase of the thawing degree-days enhancing thawing of permafrost. Here we present the results of decadal temperature observations from three boreholes near Nadym, North-West Siberia. We further use the results and the observed cryolithological structure of soils in two boreholes to model the long-term evolution of the deep permafrost under two climate scenarios, RCP2.6 (climate action, fast reduction of CO2 emissions) and RCP8.5 (‘business as usual’). Both borehole sites have a topmost high-porosity, high-ice content layer of peat which helps prolonging the degradation. The main difference between the boreholes is snow cover resulting from the difference of borehole positions (one is located on the top of the hill). Our results suggest that under RCP8.5 scenario permafrost will degrade in both boreholes. On the contrary, under RCP2.6 scenario permafrost will degrade in one borehole with the deeper snow cover, where it already shows the signs of degradation. For the other borehole, the model predicts that permafrost will not degrade within the next 300 years, although the permafrost temperatures are eventually above -1°C.

[1] Frey K.E. & Smith L.C. Recent temperature and precipitation increases in West Siberia and their association with the Arctic Oscillation. Polar Research 22(2), 287–300 (2003).
Water, land and climate nexus of electricity from biomass
Authors: Souza Nariê , Hernandes Thayse , Bruno Karina M. B. , Henzler Daniele S. , Cavalett Otávio
Published: March 2020

Driven by the expected population growth, the world faces now the challenge of meeting energy demands of about 9 billion people on the next decades and avoid dangerous climate change effects. In this context, Renewable Energy Systems (RES) are a key strategy to decarbonize the power sector and contribute to the climate change mitigation targets. In the Special Report on Climate Change and Land, IPCC calls attention to possible trade-offs, adverse side-effects and implications to sustainable development that the large-scale deployment of bioenergy may cause. A comprehensive understanding of the sustainability profile along the entire life-cycle of electricity production is fundamental if we want to realize the transition to cleaner technologies in the energy sector. In this study we analyze the water, land and climate impacts of electricity production systems in the context of the Sustainable Development Goals (SDGs). We focus our analysis in the electricity production from sugarcane straw in Brazil, since there is a great opportunity for better using this lignocellulosic material for bioenergy applications. We relate appropriate Life Cycle Assessment (LCA) indicators to multiple SDGs, considering attainable and potential sugarcane yields, derived from agroclimatic modeling. When discussing the sustainability of bioenergy production, a broader sustainability analysis, as provided by the SDGs, can help to identify water, land and climate nexus and suggest possible technological solutions for minimizing possible trade-offs among the different impacts. Our analysis demonstrates the nexus implications of electricity production from sugarcane biomass to the context of the SDGs, as well as the spatially explicit environmental implications of electricity production form sugarcane biomass.

Keywords: renewable energy systems, life cycle assessment, climate change mitigation, sustainable development
NetCDF in the Cloud: modernizing storage options for the netCDF Data Model with Zarr
Authors: Fisher Ward , Heimbigner Dennis
Published: March 2020

NetCDF has historically offered two different storage formats for the netCDF data model: files based on the original netCDF binary format, and files based on the HDF5 format. While this has proven effective in the past for traditional disk storage, it is less efficient for modern cloud-focused technologies such as those provided by Amazon S3, Microsoft Azure, IBM Cloud Object Storage, and other cloud service providers. As with the decision to base the netCDF Extended Data Model and File Format on the HDF5 technology, we do not want to reinvent the wheel when it comes to cloud storage. There are a number of existing technologies that the netCDF team can use to implement native object storage capabilities. Zarr enjoys broad popularity within the Unidata community, particularly among our Python users. By integrating support for the latest Zarr specification (while not locking ourselves in to a specific version), we will be able to provide the broadest support for data written by other software packages which use the latest Zarr specification.
Potential of Sentinel-1 and Sentinel-2 Data for Mapping Irrigated Areas at Plot Scale
Authors: Bazzi Hassan , Baghdadi Nicolas , Ienco Dino , Zribi Mehrez , Belhouchette Hatem
Published: March 2020

Potential of Sentinel-1 and Sentinel-2 data for Mapping Irrigated areas at plot scale

Hassan Bazzi 1, Nicolas Baghdadi 1, Dino Ienco 1, Mehrez Zribi 2, Hatem Belhouchette 3

Irrigation plays a significant role in agricultural production in order to meet the global food requirement under changing climatic conditions. To fulfill the high demand for food with an ever-increasing global population, better planning of irrigation is required. Therefore, more focus is being set on the assessment of irrigation performance for improving water management in order to achieve higher water productivity and increase agricultural water sustainability.

In the context of mapping irrigated areas, we propose an innovative approach to map irrigated areas using Sentinel-1 (S1) SAR (Synthetic Aperture Radar) and Sentinel-2 (S2) optical time series. Our proposed approach is based on the use of S1 and/or S2 time series combined with statistical and mathematical functions such as principal component analysis (PCA) and wavelet transformation (WT). The proposed approach was tested over the Catalonia region, Spain with a dataset containing 126 000 irrigated and 67 000 non-irrigated plots. The novelty of our study resides in eliminating the ambiguity between irrigation and rainfall by comparing between the SAR backscattering signal of each plot and that of the corresponding grid (10 km × 10 km). The potential of S2 images to classify irrigated areas by means of NDVI time series was also investigated in this study. Random forest (RF) and convolutional neural network (CNN) approaches were used to build up classification models using the PCA or WT parameters in three different scenarios: The first using only S1 data, the second using only S2 data, and the third using both S1 and S2 data.

The RF classifiers built using the PCA or WT on the S1 time series perform well in mapping irrigated areas with an accuracy of 90.7% and 89.1% respectively. However, the CNN classification on the S1 temporal series produces a significant overall accuracy of 94.1%. The overall accuracy obtained using the NDVI time series in RF classifier reached 89.5% while that in the CNN reached 91.6%. Finally, the combined use of the SAR and optical data enhanced the accuracy of the RF classification but did not significantly change the overall accuracy of the CNN model.
Geocenter Motion from a Combination of GRACE Mascon and SLR Data
Authors: Abbondanza Claudio , Chin Toshio M , Gross Richard S , Heflin Michael B , Parker Jay W , Soja Benedikt S , Wiese David N , Wu Xiaoping
Published: March 2020

GRACE and GRACE Follow-On (FO) Level 2 data provide quasi-monthly, band-limited estimates of Stokes (geopotential, spherical harmonic) coefficients mostly reflecting surface mass variability due to non-tidal atmosphere, ocean, and continental hydrology.    
Although space gravimetry does not directly provide CM-related degree-1 Stokes coefficients, GRACE data have been successfully used over the years to complement time series of station positions from global space-geodetic (SG) network when inverting for Center-of-Mass to Center-of-Network (CM-CN) displacements (Wu et al, 2006).

Surficial mass variability observed through GRACE/GRACE-FO can be conveniently converted into load-induced (ENU) deformations at SG observing sites by adopting a spectral (i.e. load Love-number based) formalism and assuming Earth’s response is fully elastic and isotropic. GRACE-derived elastic displacements at observing sites would represent, if accurate, band-limited (degree 2 to 96, or higher if Mascon solutions are adopted) load-induced deformations that can be removed from SG-derived station displacements  in order to more accurately recover degree-1 surface deformation signature (and therefore geocenter motion). 

In this study, we adopt GRACE JPL Mascon RL06 data in conjunction with Preliminary Reference Earth Model-derived load Love numbers to infer elastic displacement at SG sites and remove them from SLR inherently geocentric time series of station positions.
In so doing, the residual SLR station displacements, consistently expressed in a geocentric frame, would in principle reflect a degree-1 deformation signature that can be recovered via either surface deformation (Chanard et al, 2018) or translational approach.

We will compare the SLR/GRACE (CM-CN) determined in this study to standard estimates of geocenter motion such as ILRS’s and JTRF2014’s estimated via translational approach and spectrally inverted solutions (CM-CF).

References
Chanard K et al, (2018). JGR-Sol Ea doi:10.1002/2017JB015245 
Wu X et al, (2006). JGR-Sol Ea doi:10.1029/2005JB004100. 
The ERA5 Global Reanalysis: achieving a detailed record of the climate and weather for the past 70 years.
Authors: Hersbach Hans , Bell Bill , Berrisford Paul , Dahlgren Per , Horányi András , Muñoz-Sabater Joaquı́n , Nicolas Julien , Radu Raluca , Schepers Dinand , Simmons Adrian , Soci Cornel
Published: March 2020

Reanalysis is a key contribution to the Copernicus Climate Change Service (C3S) that is implemented at the European Centre for Medium-Range Weather Forecasts (ECMWF) on behalf of the European Commission. The most recent ECMWF reanalysis, ERA5, provides hourly estimates of the global atmosphere, land surface and ocean waves at a horizontal resolution of 31km. Daily updates are provided with a latency of 5 days, while an extension back to 1950 is to be made available in the 2nd quarter of 2020.
ERA5 uses a 2016 version of the ECMWF numerical weather prediction model and data assimilation system (Integrated Forecasting System Cy41r2) to assimilate both in situ and satellite observations (95 billion for the period 1979 - 2019), many of which stem from reprocessed data records. The assimilation method includes a variational method for estimating observation biases that respects the heterogeneity within the observing system. Information on random uncertainties in the state estimates is provided by a 10-member ensemble of data assimilations at half the horizontal resolution (63km).
This presentation provides a concise overview of the ERA5 data assimilation system. A basic evaluation of characteristics and performance is presented, which includes an inter-comparison with other reanalysis products, such as its predecessor ERA-Interim and several major reanalyses produced elsewhere. Attention is given to the importance of the specification of the background error covariance matrix that determines the weight given to the model's first guess in the assimilation. In addition, a special focus will be on the back extension from 1950 to 1978, where the absence of satellite data prior to the 1970s puts a more demanding constraint on the data assimilation system.
Assessing z-level modelling of the ice shelf - ocean boundary layer
Authors: Patmore Ryan , Holland Paul , Vreugdenhil Catherine
Published: March 2020

Ice shelf dynamics play a key role in the climate. Melt-rates along the ice shelf-ocean interface are an important aspect in determining the character of global sea level rise. A representation of ice shelf melt is currently implemented in various z-level General Circulation Models (GCMs) by employing parameterisations of the small scale boundary layer dynamics. However, these parameterisations are strongly dependent on the near boundary flow and at the spatial scales for which GCMs are intended the boundary layer is not well resolved. We investigate the ability of a GCM in representing these small scale boundary effects. This is done using MITgcm in an idealised setting with a sloping ice-ocean interface.
Rainfall estimate using Commercial Microwave Links (CML): first outcomes of the MOPRAM project
Authors: Nebuloni Roberto , D'Amico Michele , Cazzaniga Greta , De Michele Carlo , Deidda Cristina
Published: March 2020

The measurement of space-time rainfall fields is of great importance for several purposes including weather forecast, water resource management, evaluation of hydrological risk and monitoring of hydrologic extremes. Conventional methods for rainfall measurement include rain gauges and weather radars, both types of sensor having their own advantages and limitations. A different and not fully tested methodology exploits the power loss (namely, the attenuation) experienced by microwave radio signals when travelling across rain along either terrestrial or ground-to-satellite links. Indeed, it is well known that microwave attenuation due to rain can be calculated from the rain rate along the propagation path. The inverse problem can be solved once the disturbances affecting the radio signal and not induced by rain have been identified and removed.

In this contribution, we present the first results of the experimental campaign carried out in the framework of MOPRAM (MOnitoring Precipitation through a Network of RAdio links at Microwaves). MOPRAM is a scientific project funded by Fondazione Cariplo, which aims at assessing the potential of Commercial Microwave Links (CML) for rainfall estimates and rainfall field retrieval in areas of hydrological interest located in Northern Italy. A network of CMLs, owned by a major mobile operator in Italy, has been exploited to estimate the average rain rate along each link. The available data are the minimum and maximum values of the transmitted and received signal power across each link (two-ways), measured during 15-min time slots.

We start by describing the procedure adopted for the estimation of the baseline, i.e. the received power level immediately before and after a precipitation event. Rain attenuation is subsequently calculated by subtracting the received power during the event from the baseline level. To this aim, every 15-min slot of each link is classified in advance as either wet or dry by taking advantage of the spatial correlation of rain. Path-averaged rainfall intensity can be retrieved from rain attenuation by formulas based on well-known electromagnetic models. Finally, CML-based rainfall is compared with the one obtained from co-located rain gauges and disdrometers.

Despite the CML setup is not optimized for rainfall measurements, preliminary results highlight a good correlation between the occurrence of wet periods detected by CMLs on one side and by rain gauges and disdrometers on the other, as well as a fair agreement between the corresponding time series of accumulated precipitation.
Seasonal storage of hydrogen in porous formations
Authors: Edlmann Katriona , Heinemann Niklas , Mabon Leslie , Mouli-Castillo Julien , Hassanpouryouzband Ali , Butler Ian , Thaysen Eike , Wilkinson Mark , Haszeldine Stuart
Published: March 2020

To meet global commitments to reach net-zero carbon emissions by 2050, the energy mix must reduce emissions from fossil fuels and transition to low carbon energy sources.  Hydrogen can support this transition by replacing natural gas for heat and power generation, decarbonising transport, and facilitating increased renewable energy by acting as an energy store to balance supply and demand. For the deployment at scale of green hydrogen (produced from renewables) and blue hydrogen (produced from steam reformation of methane) storage at different scales will be required, depending on the supply and demand scenarios. Production of blue hydrogen generates CO2 as a by-product and requires carbon capture and storage (CCS) for carbon emission mitigation.  Near-future blue hydrogen production projects, such as the Acorn project located in Scotland, could require hydrogen storage alongside large-scale CO2 storage. Green hydrogen storage projects, such as renewable energy storage in rural areas e.g. Orkney in Scotland, will require smaller and more flexible low investment hydrogen storage sites. Our research shows that the required capacity can exist as engineered geological storage reservoirs onshore and offshore UK. We will give an overview of the hydrogen capacity required for the energy transition and assess the associated scales of storage required, where geological storage in porous media will compete with salt cavern storage as well as surface storage such as line packing or tanks.

We will discuss the key aspects and results of subsurface hydrogen storage in porous rocks including the potential reactivity of the brine / hydrogen / rock system along with the efficiency of multiple cycles of hydrogen injection and withdrawal through cushion gasses in porous rocks. We will also discuss societal views on hydrogen storage, exploring how geological hydrogen storage is positioned within the wider context of how hydrogen is produced, and what the place of hydrogen is in a low-carbon society. Based on what some of the key opinion-shapers are saying already, the key considerations for public and stakeholder opinion are less likely to be around risk perception and safety of hydrogen, but focussed on questions like ‘who benefits?’ ‘why do we need hydrogen in a low-carbon society?’ and ‘how can we do this in the public interest and not for the profits of private companies?’

We conclude that underground hydrogen storage in porous rocks can be an essential contributor to the low carbon energy transition.
Representing Arctic coastal erosion in the Max Planck Institute Earth System Model (MPI-ESM)
Authors: Nielsen David Marcolino , Baehr Johanna , Brovkin Victor , Dobrynin Mikhail
Published: March 2020

The Arctic has warmed twice as fast as the globe and sea-ice extent has decreased, causing permafrost to thaw and the duration of the open-water period to extend. This combined effect increases the vulnerability of the Arctic coast to erosion, which in turn releases substantial amounts of carbon to both the ocean and the atmosphere, potentially contributing to further warming due to a positive climate-carbon cycle feedback. Therefore, Arctic coastal erosion is an important process of the global carbon cycle.

Comprehensive modelling studies exploring Arctic coastal erosion within the Earth system are still in their infancy. Here, we describe the development of a semi-empirical Arctic coastal erosion model and its coupling with the Max Planck Institute Earth System Model (MPI-ESM). We also present preliminary results for historical and future climate projections of coastal erosion rates in the Arctic. The coupling consists on the exchange of a combination of driving forcings from the atmosphere and the ocean, such as surface air temperature, winds and sea-ice concentration, which result in annual coastal erosion rates. In a further setp, organic matter from the eroded permafrost is provided to the ocean biogeochemistry model and, consequently, to the global carbon cycle including atmospheric CO2.
Reconstruction of the trophic levels of a fossil fish community from the Late Jurassic Solnhofen Archipelago
Authors: Dimitrijevic Danijela , Ebert Martin , Kölbl-Ebert Martina , Munnecke Axel
Published: March 2020

Trophic interactions of extinct fishes are central to our understanding of evolution, paleoecology and their role in the paleo-communities, but can be challenging, as these are limited by the incompleteness of the fossil record and by a lack of behavioural data. The extensive fossil record of Actinopterygii comes mostly from Conservation-Lagerstätten. They provide exceptionally rich information on fossil ecosystems and open outstanding windows into the evolution of life. The best-preserved Late Jurassic actinopterygians are known from the Solnhofen Archipelago, Germany. Despite that the diversity ichthyofauna of the Solnhofen Archipelago has been extensively explored in the last several decades, the dietary preferences of most fish remain unknown or have to be deduced by analogy from dentition and jaw morphology.

The aim of this study was to reconstruct the trophic levels of Late Jurassic fish assemblages using Sr/Ca and Ba/Ca measured from phosphatic fish remains, mostly ganoin and cycloid scales recovered from the Ettling locality, which is characterized by exceptionally well-preserved fossil fishes and moderate diagenetic alteration. We classified fish species into four trophic levels (durophagous, lower, middle, and higher trophic level) based on morphology available from the literature. Mean values of Sr, Ca, Ba and their ratios measured by Thermo Scientific iCAP Q inductively coupled plasma mass spectrometer in this study are in accordance with the mean values of previous studies. Differences in values between cleaned and uncleaned samples showed that the cleaning process successfully isolated primary dietary Sr content while dissolving away the diagenetic strontium present in carbonate in the pore spaces. All trophic levels showed low variation of Sr/Ca (0.003 - 0.008 μg/g) and high variation of Ba/Ca values (0.0003 - 0.0014 μg/g). The results showed significant differences between the middle and higher trophic levels (p = 0.03), while durophagous and lower trophic levels fell into the same range of values as the higher trophic level. 

We demonstrate that enamel of fossil vertebrates from the Solnhofen Archipelago still contains near-in vivo Sr, Ba, and Ca. The clear distinction between middle and higher trophic levels offers a new functional perspective on the ecological and evolutionary relationships among fishes. However, future studies should not neglect the importance of diagenetic alteration of the samples; proper sample cleaning before measuring isotopic signatures, and careful selection of the analyzed tissue (i.e. tooth enamel instead of scales or bones due to its resistance to diagenesis).
A scale-independent model for land-locked seas with application to the Messinian salinity crisis
Authors: Meijer Paul
Published: March 2020

While the Mediterranean Sea is, since the Middle Miocene, a nearly completely land-locked basin indeed, it is itself comprised of several smaller semi-enclosed seas. What the Mediterranean Sea as a whole is to the Atlantic Ocean, are the Adriatic Sea or Aegean Sea to the Ionian-Levantine basin, for example. In the discussions regarding the Messinian salinity crisis the marginal basins of the Mediterranean play a prominent role because it is from these parts that the sedimentary record has been uplifted and become exposed.

In view of this and with an aim to contribute insight from the field of modelling, we focus on the basic element: a single marginal basin, subject to atmospheric forcing and exchanging water through a seaway with an adjacent larger basin. The equations are derived in dimensionless form and a universal, scale-independent, solution for basin salinity obtained. The analysis yields two dimensionless ratios which control basin behaviour in terms of salinity and response time. 

Application of the theoretical model to the Messinian salinity crisis sheds new light on the formation of gypsum in marginal basins that were separated from the main Mediterranean by a sill, gives insight about the role of atmospheric heat exchange, and underlines the previous finding that, at elevated salinity, marginal basins respond to periodic climate variation (e.g. due to precession) with a significant lag.
Cold and Fresh Biases of the Arctic Atlantic Water Layer in CMIP6 Models; Potential Origin and Implications
Authors: Khosravi Narges , Koldunov Nikolay , Wang Qiang , Danilov Sergery , Hinrichs Claudia , Semmler Tido , Jung Thomas
Published: March 2020

We examined the Arctic Atlantic Water (AW) layer in the CMIP6 models. Climatological means of temperature and salinity at 400 m depth from multi-model averages are compared with observations, showing significant biases in both variables. Based on the currently available data, we showed that the CMIP6 models have cold and fresh biases in the Arctic AW layer, and warm and saline biases in the East Greenland Current. The temperature biases are comparable to the climate signal magnitude for temperature, predicted by the CMIP6 models for the end of the 21st century. For salinity, the biases are shown to be even more pronounced than the predicted signals. CMIP6 models also show positive sea-level pressure (SLP) and sea-surface height (SSH) biases in the Nordic Seas. We argue that the identified SLP bias leads to an anomalously weak cyclonic gyre circulation in the Nordic seas, as shown through positive SSH bias. This could cause weaker AW inflow through the Fram Strait, which explains the detected hydrography biases in the AW layer. While we do not rule out other possible factors contributing to the weak AW flow to the Arctic Ocean, we suggest that the identified ocean biases within the CMIP6 models are at least partially driven by atmospheric origins.
Loading history dependence of stress field around salt diapirs due to path dependence of visco-elasto-plastic rheology
Authors: Iskander Ibragimov , Podladchikov Yury , Myasnikov Artem
Published: March 2020

One of the most unstable and unpredictable process in sedimentary basin is salt diapir movement. It changes the structure of strata and can break its integrity and make trap structures for hydrocarbons. The movement of salt diapir through geologic timescale can be described in viscous terms, elastic terms were used to predict the geomechanical response of sediment surroundings.

This work describes the workflow of visco-elastic flow modeling of salt diapirism process. Salt has different geomechanical property such as much lower viscosity comparing to typical sediments. Mixed rheology make different geomechanical response such as stress, which cannot be solved in the same timescale.  To solve the problem of different timescales of viscous and elastic flow there was used a pseudo-transient method of solving the system of equations. Used equations calculate full stress tensors and pressure over time which can help in understanding of stress evolution around salt diapir. Maximizing time step during each calculation was accomplished with density scaling, which assumes that inertial forces are negligible.

The used approach allows taking into account the loading history and easily can be supplemented with sedimentation mechanisms.
Stability of control of impounded river reaches
Authors: van Nooijen Ronald , Kolechkina Alla
Published: March 2020

Climate change and economic growth place increasing demands on the management of regional and national waterways. These serve both as part of the drainage network of the catchment and as transport route for raw materials and finished goods. These waterways are often impounded rivers where the management of the weirs must serve both shipping and flood protection. For efficient and effective operation purely local control is no longer sufficient. The flow in these rivers is governed by a pair of nonlinear partial differential equations known as the Saint Venant equations. While there are many possible approaches to the design of a computer control system for such a network, all approaches need to include a test of the stability of the system. Here we apply a test is based on a simplified system model to a series of river reaches separated by weirs. This is used to explore different controller settings. These settings are then used to control a full nonlinear computer model of the river. In this way the sensitivity to deviations from the assumed state around which the linearization is carried out is explored.
Magnetotelluric Constraints on Upper Mantle Viscosity Structure and Basal Melt Beneath the Greenland Ice Sheet
Authors: Conrad Clinton , Selway Kate , Weerdesteijn Maaike , Smith-Johnsen Silje , Nisancioglu Kerim , Karlsson Nanna
Published: March 2020

Mass loss from the Greenland Ice Sheet has accelerated during the past decade due to climate warming. This deglaciation is now considered a major contributor to global sea level rise, and a serious threat to future coastlines. It is therefore vital to measure patterns and volumes of ice sheet mass loss. However, measurements of the ice sheet’s mass and elevation, both of which decrease as the ice melts, are also sensitive to ground deformation associated with glacial isostatic adjustment (GIA), which is the solid Earth’s response to ice loss since the last ice age. For Greenland, GIA is poorly constrained in part because Greenland’s complex geologic history, with a passage over the Iceland Plume, probably created large lateral viscosity variations beneath Greenland that complicate the GIA response.

The Norwegian MAGPIE project (Magnetotelluric Analysis for Greenland and Postglacial Isostatic Evolution) seeks to develop new constraints on mantle viscosity beneath Greenland by collecting magnetotelluric (MT) data on the ice sheet. MT images the Earth’s electrical conductivity, which is sensitive to three of the major controls on mantle viscosity: temperature, partial melt content and water content of solid-state mantle minerals. We therefore plan to use MT data, together with existing seismic data, to map viscosity variations beneath Greenland. During the summer of 2019 we deployed 13 MT stations in a 200 km grid centered on EastGRIP camp on the North-East Greenland Ice Stream. Good quality data were recorded at periods up to 10,000 s, providing good resolution of upper mantle conductivity structure. We also collected a broadband MT traverse across the NE Greenland Ice Stream, which allows us to directly compare MT and radar data to investigate the role of basal melt on ice flow dynamics. During the 2020 summer season we will be collecting additional data over the south-western and central parts of the ice sheet. Here we show preliminary constraints on the conductivity of the asthenosphere, lithosphere, and crust beneath Greenland, which will be used to investigate the upper mantle viscosity structure, including the present-day signature of the Iceland Plume.
Determining parameters and chronology of a sustainable water harvest system in desert oases; case study Qurayyah, northwest Arabian Peninsula
Authors: Prochazka Sabrina , Luciani Marta , Lüthgens Christopher
Published: March 2020

The arid regions of the world occupy 46% of the total surface area, providing a habitat for 3 billion people. More than 630 million people are directly affected by desertification. Extreme events like droughts and flash floods increase the pressure on plants, animals and above all, humans and their settlements. In the context of a climate change with such far-reaching consequences, historical oases settlements stand out as best practice examples, because their water supply systems must have been adapted to the changing climate during the Holocene to guarantee the viability of the oases and their inhabitants. I will focus on the ancient oasis Qurayyah, located in the northwest of the Arabian Peninsula, a unique example in this context. Recent research has proven that, lacking a groundwater spring, the formation of a permanent settlement in Qurayyah was made possible mainly by surface-water harvesting, with local fracture springs potentially only providing drinking water. First numerical dating results for the water harvesting system from optically stimulated luminescence (OSL) dating of quartz confirm that the system was erected in a period characterized by changing climatic conditions from the Holocene climate optimum to the recent arid phase. This study aims to determine parameters and chronology of this sustainable irrigation system and intends to learn and understand how ancient settlers accomplished the construction of such a highly developed water supply system. To reach this research aim the irrigation system was reconstructed using field mapping and remote sensing techniques. It was shown that the reconstructed irrigation system worked as a flood irrigation system. Dams and channels were built to maximize the flooded area and at the same time to prevent catastrophic flooding under high discharge conditions. Contemporaneous historical irrigation systems in comparable size and complexity are known from Mesopotamia or Egypt. In addition to the system’s reconstruction, a new reverse engineering approach based on palaeobotany was developed for Qurayyah to reconstruct the climate conditions during the time of its operation. Compared to today’s precipitation of 32 mm per year in the research area, our results imply that the irrigation system was constructed in a time of significant climate change, because significantly higher amounts of precipitation would have been necessary to enable the cultivation of olive trees (reference plant for the reverse engineering approach), with a sufficient amount of water.
Tsunami Generation, Consequences on Coastlines, and Potential Global Climate Effects due to Asteroids Impacting Earth’s Oceans
Authors: Ezzedine Souheil , Oman Luke , Dearborn David , Miller Paul , Syal Megan
Published: March 2020

Despite that the annual probability of an asteroid impact on earth is low, but over time, such catastrophic events are inevitable and can have negative global consequences. Several institutions around the world have come together to address global consequences of asteroids impacting earth. For example, interest in assessing the tsunami generation and impact consequences has led us to develop a physics-based framework to seamlessly simulate the event from source (asteroid entry) to ocean impact (splash) to long wave generation, propagation, and their catastrophic risk to people and infrastructure in coastal regions such inundation of the shoreline. The non-linear effects of the asteroid impact on the ocean surface are simulated using the hydrocode GEODYN to create the impact source for the shallow water wave propagation code, SWWP. The GEODYN-SWWP coupling is based on the structured adaptive mesh refinement infrastructure; SAMRAI developed at LLNL. Another consequence of ocean impact is the potentially global effects of an event that would otherwise be of only regional or local importance, should it occur on land. Only a fraction of the total impact energy is converted into water waves that have the ability to globally propagate in the oceans. The remaining energy is consumed by the “evaporation” of the asteroid, the ocean water being transformed into vapor and mist and the fractionization of ocean water and vapor into chlorine and bromine which alter the atmospheric chemistry, therefore impacting globally the Ozone layer and earth temperature. In this paper, we present our scheme of creating the source -- including nonlinear transient cratering and nearfield waves, generating the vapor cloud and the chemical speciation source load of chlorine and bromine to assess the global circulation of those plumes and their effects on the climate. We also present our coupling scheme of the hydrodynamic source using GEODYN with the global atmospheric circulation code GEOSCCM and illustrate the scheme on the PDC 2017 and PDC 2019 asteroid impact scenarios. We illustrate the coupling scheme for asteroids impact along the US, Europe and Asia shorelines. We illustrate, by examples, how the predictions of these numerical tools can help international, state and local government agencies reduce the risks and prepare and implement a  response and recovery plan.  This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Backward peaking radiation pattern from a relativistic particle accelerated by lightning leader tip electric field
Authors: Yucemoz Mert
Published: March 2020

Charged particles being accelerated by the lightning leader tip electric field emit electromagnetic radiation due to the Bremsstrahlung process (Celestin et al., JGR, 2012). Bremsstrahlung has a continuous spectrum of radiation which includes radio waves and ionising radiation such as gamma rays which can be recorded by detectors on board the ASIM payload on the International Space Station, the forthcoming TARANIS satellite, or on the ground (Abbasi et al., JGR, 2018).  

The radiation pattern of this Bremsstrahlung is not well known. Displays of radiation patterns of accelerated particles are normally limited either to a low frequency approximation for radio waves, or to linear acceleration in a high frequency approximation for gamma rays. Here we report the radiation patterns from accelerated relativistic particles at low and high frequencies of the Bremsstrahlung process. It is found that the radiation patterns have four relative maxima with two backward peaking and two forward peaking.  

The shape of the radiation pattern is only determined by the velocity of the particle whilst the intensity of the radiation pattern is determined by the velocity and the acceleration of the particle. For example, relativistic particles with a large velocity exhibit a radiation pattern which is more forward peaking when compared to a non-relativistic particle with a smaller velocity. Similarly, relativistic particles with a large acceleration exhibit a radiation pattern with a larger intensity when compared to relativistic particles with a smaller acceleration. All these radiation patterns exhibit backward peaking radiation. The asymmetry of the radiation pattern, I.e., the different intensities of forward and backward peaking lobes, is controlled by the asymmetric frequencies of the Bremsstrahlung radiation caused by the Doppler effect.  

These results are important because they enable a determination of particle properties which can be inferred from observations with networks of radio receivers and arrays of gamma ray detectors. 
Is there active tectonics at the Nile cataracts in Sudan? An archaeoseismological study
Authors: Kazmer Miklos , El Tahir Nada Bushra , Gaidzik Krzysztof , Székely Balázs
Published: March 2020

The Nile is the longest river on earth, accordingly with huge drainage and major floods, regulated by the African monsoon. Significant amount of sediment is carried by the river; its deposition forms alluvial plains along most of its course. However, in Upper Egypt and northern Sudan there are six major and several minor cataracts totalling 327 km in length. There the river flows directly on bedrock, and a multitude of islands and rocks in the riverbed makes navigation hard or impossible throughout much of the year. Obviously, the Nile is unable to remove these obstacles from its flow (despite its ability to carve a deep canyon in the African continent during Messinian lowstand of the Mediterranean Sea). It has been suggested that the Cataract Nile is in a youthful stage, flows along structurally controlled turns and that earthquakes in southern Egypt prove that portions of the Nubian Swell are still tectonically active (Thurmond et al., 2004). However, the Sudan part of the river does not show any seismic activity. An archaeoseismological study is in progress to locate evidence of past earthquakes preserved in monumental architecture erected during the past 3500 years. Pyramids in Meroe display masonry shifted in plane of the wall: this was caused by one or more earthquakes of intensity I0 = 9 on the Archaeological Intensity Scale. We suggest that an ongoing systematic study of monumental stone and adobe buildings along the Nile in the region of the Nubian Swell will find further evidence of major earthquakes in the region, contributing to a better understanding of seismic hazard in Sudan.

Reference

Thurmond, A.K., Stern, R.J., Abselsalam, M.G., Nielsen, K.C., Abdeen, M.M., Hinz, E. (2004): The Nubian Swell. - Journal of African Earth Sciences 39, 401-407.
Modelling a controlled water system as a sampled data system with events
Authors: Kolechkina Alla , van Nooijen Ronald
Published: March 2020

Automatic control of water systems such as canals for shipping, irrigation systems, drainage systems, or sewer systems, is a complex problem. While the system state is continuously changing, in almost all cases the weir, gates, or pumps are adjusted only at set times. This mixes continuous and discrete time. Moreover, it may be necessary to take action in response to the occurrence of an event in the system. So, part of the system evolves continuously, another part changes stepwise at given times, while yet another part responds to events in the system or its surroundings that may occur at arbitrary times.

Basic limitations on controlling these systems when ignoring their hybrid nature are demonstrated for the case of a Dutch sewer system. The control schemes under discussion are: local event driven control for a group of pump stations, sampled data control for a group of pump stations, hierarchical control with sampled data control for the group, and event driven control for the individual stations.
Sensitivity of isotopes in the hydrological cycle to simulated vs. reconstructed Last Glacial Maximum surface conditions
Authors: Paul André , Werner Martin , Cauquoin Alexandre , García-Pintado Javier , Merkel Ute , Tharammal Thejna
Published: March 2020

The evaluation of a specific component of a comprehensive climate model is often hindered by biases in the coupled system, in simulations of the present as well as of past climate conditions. To assess different implementations of water isotopes as part of the hydrological cycle, we carried out atmosphere-only runs using different atmospheric general circulation models (AGCMs, here: CAM and ECHAM) but the same pre-industrial and Last Glacial Maximum (LGM, ~19,000 to ~23,000 a before present) boundary conditions, especially with respect to the monthly sea-surface temperature (SST) and sea-ice fraction fields. For the LGM, we used a new global climatology of the ocean surface during the Last Glacial Maximum mapped on a regular grid (GLOMAP), which is an extension of the Glacial Atlantic Ocean Mapping (GLAMAP) reconstruction of the Atlantic SST based on the results of the Multiproxy Approach for the Reconstruction of the Glacial Ocean Surface (MARGO) project and several recent estimates of the LGM sea-ice extent. This way, we can, on the one hand, avoid the propagation of the SST bias in coupled climate models. On the other hand, by comparing to fully-coupled simulations, we can isolate the impact of the ocean feedback on the simulated distributions of water isotopes over land, ice and ocean. To analyze the results, we calculated the anomalies between the LGM and pre-industrial climate states and compared them between the different models and to data. It turned out that the model response was affected by the amount of global cooling as well as the structure of the SST anomalies. The patterns in the simulated isotopic composition of precipitation for the LGM tended to follow the patterns in the SST boundary condition; a more zonal structure in the SST led to a more zonal response. Our results show the advantage of using water isotopes as a diagnostic tool for an AGCM through direct model-data comparison.