bluuebunny/crossref_metadata_2025 huggingface dataset:
Seasonal carbon dynamics in the Southern Ocean based on a neural network mapping of ship measurements
Authors: Keppler Lydia , Landschützer Peter , Gruber Nicolas , Lauvset Siv , Stemmler Irene
Published: March 2020

 We present a monthly climatology of dissolved inorganic carbon (DIC) in the upper 2000 m of the Southern Ocean north of 65°S, based on a 2-step neural network method that establishes and applies statistical relationships between global fields of physical and biogeochemical properties and direct DIC measurements from the GLODAPv2.2019 database from 2004 trough 2017. We test our method using synthetic data from a global hindcast simulation of the HAMOCC ocean biogeochemistry model, and independent observational datasets. At the month and location of biogeochemical floats from the SOCCOM array, our estimate is on average ~10 μmol kg-1 lower than the calculated DIC based on the float measurements. This difference can be partially explained by the difference in time period (SOCCOM floats used: 2014 through 2017; our estimate: 2004 through 2017). We find that the surface seasonal cycle of DIC has a mean amplitude of ~20 μmol kg-1 in the Southern Ocean, and the months of the highest surface DIC concentrations tend to be in austral spring when vertical mixing dominates the seasonal maximum. We also find that the nodal depth of DIC, the depth where the phase of the seasonal cycle of DIC shifts due to photosynthesis near the surface and remineralisation below, partially extends to several hundred meters. Using the nodal depth allows us for the first time to estimate the basin-wide seasonal net community production (NCP) based on direct DIC measurements. We find a mean NCP of ~2 mol C m-2, which is considerably lower than in the temperate northern hemisphere.
Investigating the spatial characteristics of GIS visibility analyses and their correlation to visual impact perception with stochastic tools
Authors: Ioannidis Romanos , Dimitriadis Panagiotis , Meletopoulos Ilias Taygetos , Sargentis Georgios Foivos , Koutsoyiannis Demetris
Published: March 2020

In the effort to manage and mitigate landscape impact from works of infrastructure, various methods have been developed to quantify and evaluate visual impact, ranging from photo-montage and digital representation to Geographic Information Systems (GIS) viewshed analyses. These methods can be divided into two broad categories; quantitative methods that mainly focus on calculating the extents of the area affected, in each case, and qualitative methods that focus on the perception of the landscape transformation by individuals.

In this study we develop an evaluation methodology for quantitative methods of visibility analysis that generate Zone of Theoretical Visibility (ZTV) maps. In particular, we utilize stochastic tools to correlate spatial patterns of visibility analysis maps to increased qualitative concerns that are connected with opposition to projects of infrastructure. A stochastic computational tool (2D-C) is used of the analysis of images. 2D-C is a tool capable of characterizing the degree of variability in images using stochastic analysis, and thus, the change in variability vs. scale, among images. The methodology investigated incorporates 2D-C in a GIS environment for landscape impact management and proposes a procedure to assess impacts which can aid relevant policy.  
Using a precipitation nowcasting algorithm and 3DVAR assimilation in a cloud resolving Numerical Weather Prediction system to enhance a hydrometeorological nowcasting chain
Authors: Poletti Maria Laura , Lagasio Martina , Silvestro Francesco , Parodi Antonio , Pignone Flavio , Rebora Nicola
Published: March 2020

The use of the best input for an hydrometeorological chain is one of the key elements to improve the discharge prediction in the framework of early warning system. This fact gains in importance in a region such as Liguria Region , where the presence of many catchments with very small drained area and response time in the order of few hours make the prediction of severe events a critical point.

The work main scope is to exploit both observations and modelling sources to improve the discharge prediction in small catchments with lead time of 2-8 hours. To pursue this aim in this study the output from the nowcasting technique PhaSt, a spectral-based nowcasting procedure, is used together with the rainfall prediction of WRF NWP model with an hourly cycling 3DVAR data assimilation procedure to produce rainfall scenarios; the continuous distributed hydrological model Continuum, transforms these latter in streamflow scenarios. The connection between the forecasting models outputs is performed through the so called blending  technique, that tries to combine the rainfall fields according to their reliability function of the lead time. The blending has been modified with respect to the standard application using the information retrieved from the NWPS about the total volume on the domain considered and in terms of location of the rainfall structures. The whole chain is applied on some case events of 2014 all over Liguria Region, northern Italy.
Experimental study on tsunamis generated by landslides
Authors: Meng Zhenzhu , Ancey Christophe , Maeder Ivan
Published: March 2020

Tsunami generated by landslides is one of the major threats to populations in coastal areas. A recent example is the 2017 Nuugaatsiaq tsunami. The village in Greenland was partially swept by a tsunami created by a landslide that fell into the Karrat Fjord.

We carried out laboratory experiments to understand how the wave characteristics are related to the landslide features. Emphasis was put on slide-water interactions and efficiency of momentum transfers between the two media. We manufactured granular slides made of differently sized particles using plasticine clay, whose density is close to that of real-world materials. The granular mixture could be shaped, which made it possible to study how the leading edge’s shape affected momentum transfer. The mixture was initially placed in a reservoir upstream of a chute, which entered into a water basin. The angle of chute and water depth were kept constant in all our experiments, whereas the material properties and volume were varied systematically. Wave amplitudes and heights were determined from the free-surface variations, which were recorded using a high-speed camera. The velocity field within the water basin was measured using Particle image velocimetry (PIV).  

To compare the waves generated by slides exhibiting different properties, empirical equations for prediction of wave characteristics were used. We discuss the differences between experimental results and predictions based on empirical equations. Among other things, we found that the lower the material’s permeability, the larger the wave amplitude.
An MSE budget view on seasonal and CO2-induced ITCZ shifts in the TRAC-MIP model ensemble
Authors: Bala Elzina , Voigt Aiko , Knippertz Peter
Published: March 2020

One of the grand challenges of climate is predicting and modeling tropical rainfall. Here, we address a specific problem of this grand challenge, namely how does the vertical structure of the atmosphere affect the tropical circulation and the position of the ITCZ during the seasonal cycle and in response to increased CO2. The tropical circulation can be described by the column-integrated budget of moist static energy (MSE). We use this framework in the TRAC-MIP model ensemble to investigate the role of the vertical structure of the tropical atmosphere in setting the anti-correlation between the ITCZ location and the atmospheric energy transport.

TRACMIP "The Tropical Rain belts with an Annual cycle and Continent - Model Intercomparison Project" is a set of idealized simulations that are designed to study the tropical rain belt response to past and future forcings. TRACMIP includes 13 comprehensive CMIP5-class atmosphere models and one simplified atmospheric model. Importantly, TRACMIP includes a slab ocean with prescribed ocean heat transport. This leads to a closed surface energy balance and forces the annual-mean ITCZ to be north of the equator, consistent with today’s climate.

We use the MSE budget framework to diagnose the seasonal evolution of vertical velocity from the energetic terms in the MSE budget equation. We obtain a diagnostic expression for the vertical velocity. By means of the MSE budget framework we estimate the efficiency of exporting energy from the atmospheric column, which is defined as the gross moist stability (GMS). The GMS characterizes the stability of the tropical troposphere related to moist convective processes in the tropospheric column. We use the MSE and GMS analysis to disentangle the impact of deep and shallow circulations on energy transport, vertical velocity and hence precipitation in an objective manner.

Through this work we aim to elucidate to what extent model uncertainty in simulations of future ITCZ changes are caused by model differences in the vertical structure of the atmosphere. We also hope to use the results to advance our understanding of the tropical climate and to assess the plausibility of simulated changes in tropical rainfall.
Soil organic matter dynamics in changing forests: linking ecosystem manipulation experiments with soil inventories across Switzerland
Authors: Hagedorn Frank , Gosheva Sia , Zimmermann Stephan , Gavazov Konstantin
Published: March 2020

Forest soils are storing large quantities of carbon, but their quantitative role in sequestering C is less certain. In principal, soils developed over millennia are assumed to be ‘in equilibrium’ with minimal C stock changes. This concept is challenged by forest soil inventories (in Germany and France) indicate a substantial increase in soil C storage. However, soil organic matter (SOM) storage is susceptible to recent changes in forests - climate warming and droughts, increasing forest disturbances, and a more intensive forest management are all potentially increasing SOM turnover which may turn forest soils into C sources. Here, I will critically discuss the role in Swiss forest soils as C sinks by presenting data from 1000 soil profiles across environmental gradients and from flux measurements in large scale ecosystem manipulation experiments.

Swiss forests soils are among the C-richest soils in Europe storing on average 140 t C/ha. Analysis of 1000 forest soils show that these SOM stocks are caused by their high contents in potential SOM sorbents (pH, Al+Fe-oxides, Ca, clay), but also by the cool temperatures and high amounts of precipitation. Climate manipulation experiments suggest Swiss forest soils are vulnerable to loose C with expected climatic changes. A six year long soil warming experiment at treeline revealed soil C losses, while a 15 year long irrigation experiment in a dry forest induced C gains in the mineral soil, implying that a warmer and more frequent droughts will lead to C losses.

Switzerland - as other European mountainous areas – is currently experiencing a major change in land-use due to land abandonment, with the forests expanding by 3 to 4% per decade. Forest expansion affects a multitude of factors driving SOM cycling and storage, including the quantity and quality of organic matter inputs above and below the ground, a cooler and drier microclimate, and change in microbial diversity and activity. In contrast to the intuitive assumption that forests expansion leads to C gains in soils, measurements along an afforestation chronosequence of alpine grassland show that forest expansion leads to minimal changes in SOM stocks but a strong change in SOM quality. Soils gains in particulate organic matter with increasing forest age but lose C in mineral-associated organic matter. In support, reconstructing forest cover ages of 850 soil profiles showed that forest age and hence time since conversion into forest (predominantly from grasslands) did not significantly affect total SOM stocks, while other factors, especially physico-chemical soil characteristics and climate were more important. Overall, these results show that the inherently C rich forest soils in Switzerland are unlikely to gain additional C but rather loose it in response to the ongoing changes in climate and land-use.
Does accounting for the direct-radiative effect of prognostic aerosols improve 5-day temperature forecast of the ECMWF weather forecast model ?
Authors: Flemming Johannes , Bozzo Alessio , Barre Jerome , Engelen Richard , Garrigues Sebastien , Hogan Robin , Huijnen Vincent , Inness Antje , Kipling Zak , Parrington Mark , Remy Samuel , Tsonevsky Ivan , Peuch Vincent-Herni
Published: March 2020

The Copernicus Atmosphere Monitoring Service (CAMS) produces operationally global 5-day forecast of atmospheric composition and the weather using ECMWF’s Integrated Forecasting System (IFS) since 2015.Beginning with a system upgrade in June 2018 (45r1), the ozone and aerosol fields have been used in the radiation scheme to account for their radiative impact in the global CAMS forecasts. This approach replaced an aerosol and ozone climatology, which had been used before and which is still used in ECMWF's operational high-resolution medium-range NWP forecasts. The CAMS forecast system, which runs at a resolution of about 40 km, is applied here as a test-bed to explore the importance of aerosol direct feedback in an operational configuration, which can guide developments on composition-weather feedbacks for ECMWF's medium-range, monthly and seasonal forecasts.

We will discuss the changes and improvements of temperature forecast errors (i) using typical NWP scores and (ii) by applying an event based approach that focuses on episodes of high aerosol burdens such as the transport of Sahara dust to Europe during the heatwave in June 2019. In more detail we will show to what extent the realism of the prognostic aerosol fields influences the temperature response by considering aerosol forecast which were, or were not, improved by data assimilation of aerosol optical depth at the start of the forecast. We will further demonstrate that the consistent updates of both the climatological and prognostic aerosol fields are an important prerequisite for a making progress.
Post-extraction of flood hydrographs under limited and heterogeneous information: Case study of Western Attica event, November 2017
Authors: Ntigkakis Charalampos , Nezi Maria , Efstratiadis Andreas
Published: March 2020

In November 2017, a storm event of substantial but unknown local intensity caused a flash flood in Western Attica, Greece, which was responsible for 24 human fatalities and large-scale economical losses. Our focus is to the neighbouring catchment of Sarantapotamos, which has been equipped with an automatic stage recorder that was destroyed during the rising of the flood. Our overall objective is the estimation of the rainfall over the broader area of interest, through a reverse rainfall-runoff modelling approach at this specific catchment. Several sources of information are accounted for in order to reproduce the “observed” flood hydrograph, including photos and videos. We then employ Monte Carlo simulations to evaluate the uncertainty induced from limited and even missing data. Utilising the outcome of these analyses, we provide probabilistic estimations of the modelled rainfall, as well as risk evaluations, by estimating the maximum intensities and associated return periods of the storm event across multiple time scales.
InSAR on-demand services and data processing pipelines for deformation modelling
Authors: Caumont Herve , Brito Fabrice , Sagona Manuela , Pishehvar Panteha , Reitano Danilo , Guglielmino Francesco
Published: March 2020

EUROVOLC is developing case studies over European Volcanoes in Iceland, Italy, Spanish Canary islands and Portuguese Azores island. For the case of Etna, data access and processing automation levels for simultaneous and integrated strain tensor estimation from GNSS and satellite-based InSAR are applied to the modelling of deformation and seismicity data.

A Cloud platform environment is configured to this end for the EUROVOLC community. A community gathers its members around common thematic areas, in this case volcanoes.  The EUROVOLC community includes several “Thematic Apps” per European country volcanoes. For instance, the Italian Volcanoes Thematic App is focussed on the Etna, Vesuvius, Campi Flegrei and Stromboli volcanoes.

Each “Thematic App” includes a Geobrowser which is the access point to several services related to the Earth Observation (EO) data exploitation. The services include data discovery, access, processing and exploitation/visualization. 

The data discovery service provides the EUROVOLC community with custom and tailored catalogue access for several EO missions. At this stage, the platform provides access to Sentinel-1, Sentinel-2, Sentinel-3, Envisat ASAR, Landsat-8 and ASTER. The EO data discovered can be downloaded if needed.

The access to on-demand data processing services exploiting such EO missions is available from the Thematic Apps. This includes several services according to the nature of the EO data used. For Sentinel-1, there are InSAR processing services for interferometry (e.g. DIAPASON and SNAP) and for coherence and backscatter generation. For Sentinel-2, Sentinel-3, Landsat-8 and ASTER, there are the INGV Hot Spot detection services. 

In the scope of the simultaneous and integrated strain tensor estimation from GNSS and InSAR data activities, the access to Envisat ASAR IMS data is feeding an InSAR data processing pipeline, to generate and deliver interferogram stacks used as inputs to INGV’s  strain tensor estimation tool.
High sensitivity of Bering Sea winter sea ice to winter insolation and carbon dioxide over the last 5,500 years
Authors: Jones Miriam C. Jones , Berkelhammer Max , Keller Katherine , Yoshimura Kei , Wooller Matthew J.
Published: March 2020

Anomalously low winter sea-ice extent and early retreat in CE 2018 and 2019 challenges previous notions of relatively stable winter sea ice in the Bering Sea over the instrumental record, but long-term sea-ice records from sediment proxies remain limited.  Here we use a record of peat-cellulose oxygen isotopes from St. Matthew Island, along with isotope-enabled general circulation model (IsoGSM) simulations to generate a 5,500-year record of Bering Sea winter sea-ice extent.  Results show that over the instrumental period (CE 1979-2018), oxygen isotope variability is largest over the late winter to spring (February, March, April, May [FMAM]) and highly correlated (-0.77, p<0.00001) with maximum winter sea-ice extent, months in which Bering sea ice reaches its winter maximum and then rapidly diminishes. We find that over the last 5,500 years, sea ice in the Bering Sea decreased in response to increasing winter insolation and atmospheric CO2, and on shorter, centennial timescales, small (<10 ppmv)  perturbations in atmospheric CO2, suggesting that the North Pacific is highly sensitive to small (<3 W m-2) changes in radiative forcing. However, we find that reconstructed sea-ice loss lags CO2 concentrations by ~120 years, indicating that the extremely anomalous recent conditions are a legacy of the early 20th century and that even with a complete cessation of greenhouse gas emissions today. As a consequence, the Bering Sea could lose all winter sea ice by mid-century, which it may not recover for millennia.
Asian paleoenvironments, paleogeography and paleobiodiversity interactions during the Greenhouse-Icehouse transition
Authors: Dupont-Nivet Guillaume , Meijer Niels , Kaya Mustafa , Westerweel Jan , Tardif Delphine , Barbolini Natasha , Rohrmann Alexander , Aminov Jovid , Ruiz Diego , Woutersen Amber , Huang Huansheng , Poblete Fernando , Licht Alexis , Roperch Pierrick , Hoorn Carina , Proust Jean-Noël , Fluteau Frederic , Donnadieu Yannick , Guillot Stéphane
Published: March 2020

The ongoing surge of international research on Asian Climate and Tectonics enables to better assess interactions between forcing mechanisms (global climate, India-Asia collision, Tibetan Plateau growth) and paleoenvironmental changes (monsoons, aridification), land-sea distribution, surface processes, paleobiogeographic evolution and the global carbon cycle. We review here the progress of the ERC MAGIC project (Monsoons in Asia caused Greenhouse to Icehouse Change?) integrating regional geodynamic constraints, well-dated environmental / biodiversity records and climate modeling. MAGIC focuses on the Paleogene period that includes the global Greenhouse to Icehouse cooling, the early collision and plateau growth and associated regional development of monsoons and westerlies over the Proto-Paratethys sea. Our work focuses on three areas constraining Asian paleoenvironments. (1) In Myanmar, paleomagnetic results, new dating of magmatic rocks and sediments along with additional detrital geochronology and basin analysis of the Burmese subduction margin and implications for the history of India-Asia convergence. (2) Along the Northeastern Tibetan Plateau margin, the combination of multiple proxies (leaf wax stable isotope, pollen, grain size, etc…)  applied to an extended lacustrine Paleogene record enables to identify precisely Asian climate changes and their consequences on ecosystems. (3) In westernmost China and Tajikistan, the proto-Paratethys sea fluctuations and the sedimentary records of Pamir tectonic evolution are now precisely dated enabling to constrain driving mechanisms and paleoenvironmental consequences. Together these results are used to constrain climate modeling experiments which permit validation of hypotheses on interactions between paleogeography, paleoenvironments and paleobiodiversity at Asian and global scales in response to long-term and short-term events.
Low-Temperature-Low-Pressure Mineral Paragenesis of the Lower-Middle Jurassic Volcanics in the Eastern Pontides, NE Turkey
Authors: Bak Tülay , Şen Cüneyt , Aydin Faruk , Uysal İbrahim
Published: March 2020

The Lower-Middle Jurassic volcanic rocks in the eastern Pontides were formed in a subduction zone under the extensional tectonic regime. These volcanic rocks were experienced seawater alteration during forming. They also were exposed to the burial metamorphism under the Cretaceous and Eocene aged formations. In addition, the Cretaceous and Eocene granitoids cut these volcanic rocks in some places and metamorphosed them. In this study, the mineralogical changes of the volcanic rocks they have experienced since their formation were examined.

Plagioclase (An>42) + augite/diopside (En38-52Wo25-46 Fs7-25) + Fe-Ti oxides (Fe+3/(Fe+3+Fe+2) > 0.80) ± magnesiohornblende (Mg/(Mg+Fe+2) > 0.92) are the main rock-forming minerals in these volcanic rocks. Mineralogical traces of seawater alteration are mostly masked by subsequent geological events. However, Na-enrichment of the plagioclases, increased 87/86Sr(i) isotope ratios (0.70462 to 0.70611) and some clay minerals, laumontit,  analsime minerals, which are observed in the XRD peaks of some samples, refer to the alteration of the seawater. The pumpelyite (Fe+2/Fe+2+Mg = 0.60-0.90), chlorite (Fetotal/Fe+2 + Mg = 0.15-0.95), sphene, calcite, dolomite and secondary quartz minerals were formed during burial metamorphism. The Fe-Ti oxides reached the chemical re-equilibrium under the new P-T conditions (magnetite Fe+3/(Fe+3+Fe+2) = 0.40-0.62; ilmenite Fe+3/(Fe+3+Fe+2) = 0.01-0.20). Epidote (Fe+2/(Fe+2+Mg) = 0.75-0.95) accompany the mineral paragenesis in some areas affected by Upper Cretaceous and Eocene granitoids.

Temperature estimations using the chlorite geothermometer and the phase relationships on the P-T diagrams show that the volcanics were heated up above 200°C in the buried areas where the granitoids were not effective. The temperatures were above 250°C in the areas where the magmatic rocks were effective. Taking into consideration the thickness of the formations that overlie the Jurassic volcanics, it can be suggested that the pressure affecting the Jurassic volcanics reached up to 1.5 kilobars.

Acknowledgement

This work was financially supported by Scientific and Research Projects Unit of Karadeniz Technical University with grant # 8920.
Effects of meteorology on forest fires in India: A modeling study
Authors: Barik Anasuya , Baidya Roy Somnath
Published: March 2020

Meteorology has a strong impact on forest fires. Meteorological parameters such as temperature, relative humidity, wind speed and precipitation alter the fuel loading in forests, control the changes in spatial distribution, intensity and frequency of forest fires and changes in forest fire season. Hence, it is important to understand the relationship between forest fires and meteorological factors and build models that can simulate these relationships.

The Canadian Forest Fire Danger Rating System (CFFDRS) has been used globally to assess and predict the fire behavior in various forest ecosystems. The Fire Weather Index (FWI) of CFFDRS models the relationship between meteorology and forest fires. In this study we calibrate the FWI over Indian forests using percentile analysis and logistic regression technique and test the performance using satellite-derived (MODIS daily fire data from 2003-2018) fire count and Fire Radiative Power (FRP). As the Indian forest landscape is highly heterogeneous, we calibrate the FWI over 4 FWI zones namely Himalayan, Deciduous, Western Ghats and Thorn forests based on IGBP forest classification and Koppen climatic zones.  Five fire danger classes having thresholds of 99th, 95th, 90th, 80th and 70thof FWI percentiles have been defined with decreasing severity. Results show that the calibrated FWI is capable of simulating the forest fire behavior over India. Sensitivity studies show that temperature and relative humidity are the key controlling factors of forest fires over India.

This study is one of the first attempts to use fire models to simulate fire behavior over India. It can serve as a launchpad for further work on fire hazard prediction and effects of climate change on fire hazard in India.

 
Calibrating and validating an inundation model with and without crowdsourced water depths and velocities
Authors: Popescu Ioana , Assumpção Thaine H. , Jonoski Andreja , Solomatine Dimitri P.
Published: March 2020

Remote sensing and crowdsourcing data are new sensing methods that have the potential to improve significantly inundation modelling. That is especially true in data-scarce situations, for example when resources for acquiring sufficient traditional data are limited or when field conditions are not favourable. Crowdsourced water depths and velocities have been demonstrated to be useful for improving inundation models, ranging from the calibration of 1D models to data assimilation in 2D models. In this study, we aim to further evaluate how much the amount and type of crowdsourced data influence model calibration and validation, in comparison with data from traditional measurements. Further, we aim to assess the effects of combining both sources. For that, we developed a 2D inundation model of the Sontea-Fortuna area, a part of the Danube Delta in Romania. This is a wetland area, where data was collected during two 4-day field campaigns, using boat navigation together with the involved citizens. Citizens obtained thousands of images and videos that were converted into water depth and velocity data, while technicians collected ADCP data. We calibrated and validated the model using different combinations of data (e.g. all water depth data, half water depth and half water velocity). Results indicated that velocity data by themselves did not yield good calibration results, being better used in conjunction with water depths or by combining them into discharge. We also observed that calibration by crowdsourced water depths is comparable to the use of water depths from traditional measurements.
The climate impact of municipal land policy
Authors: Koebsch Franziska , Huth Ulrike , Kahle Petra
Published: March 2020

Ecosystems can store significant amounts of carbon dioxide and are therefore often considered as nature-based solutions to combat climate change. However, anthropogenic perturbations can turn these natural sinks to substantial sources for greenhouse gases. The climate impact of land use and land use change is well recognized on national and international level. Yet, municipalities which implement concrete measures on the ground, lack a tool to quantify the climate effect of their land use decisions.

Using the German city of Rostock (200.000 inhabitants) as an example, we present an approach to evaluate the climate effect of different land use trajectories in urban areas. The approach makes uses of municipal land use maps and complies with the IPCC inventory guidelines. Based on this emission assessment we can provide generic recommendations to exploit nature-based solutions for climate protection in municipal land policy.
Response of Elbe estuary ecosystem to changed riverine nitrogen loads
Authors: Pein Johannes , Daewel Ute , Stanev Emil , Schrum Corinna
Published: March 2020

The present day Elbe estuary ecosystem dynamics are largely determined by high loads of river borne inorganic and organic nitrogen. Similar to most European tidal rivers, the Elbe estuary is highly eutrophied. The eutrophication leads to high primary production in the shallow limnic reach, followed by heterotrophic decay, sedimentation and summertime oxygen depletion in the deepened channel and harbor area. For several decades, the estuary has been subject to adverse trends regarding the forcing of the heterotrophic turnover: While the ambient temperature increases, the nitrogen loads are decreasing (Radach and Pätsch, 2008). The projected long-term and climatic changes imply these trends to continue (Radach and Pätsch, 2008; Huang et al., 2010). In this study we use an unstructured 3D coupled bio-physical model of the Elbe estuary to study the effect of long-term changes of riverine nitrogen loads onto the estuarine ecosystem. As a first step we change the riverine nitrogen forcing i) reducing equally the dissolved inorganic and organic nitrogen loads by 50 % each, ii) reducing the inorganic load and organic loads by 80 % and 40 %, respectively, iii) reducing both inorganic and organic loads towards pre-industrial levels (Serna et al., 2010). Our results indicate a decrease of primary production and heterotrophic turnover under all scenarios. The decrease of primary production is mainly due to reduced diatom growth. Consequently summertime nitrification and oxygen depletion also decrease. This effect is more pronounced in case of equal reduction of inorganic and organic loads than of strong reduction of inorganic nitrogen loads only. Other than diatoms, cyano-bacteria are less affected by applied changes and associated biomass even increases in comparison with the reference case under scenario ii). In the second part of the study we will increase the temperature forcing to determine to which degree the projected increase of ambient temperatures will affect the projected reduced nitrogen turnover.
An independent solution for the precise orbit determination of Mercury planetary orbiter (MPO)
Authors: HosseiniArani Alireza , Bertone Stefano , Arnold Daniel , Jäggi Adrian , Thomas Nicolas
Published: March 2020

Navigation of deep space probes is most commonly operated using the spacecraft Doppler
tracking technique. Orbital parameters are determined from a series of repeated measurements of the frequency shift of a microwave carrier over a given integration time. This study addresses the work that is done on Doppler orbit determination of MPO - one of the two spacecraft of the European Space Agency’s BepiColombo mission- using Bernese software.

For modelling the orbit of MPO around Mercury, we use a full force model, including Mercury gravity field GGMES-100V07 (up to degree and order 50), solid tides and third body perturbations. We also have an extensive modelling of non-gravitational forces that act on the orbit of spacecraft. This modelling includes the solar radiation pressure and planetary IR and albedo radiation together with a 33-plates macromodel of MPO. We propagate the orbit using this force model. Our simulations of Doppler tracking measurements include 2-way X-band and K-band Doppler measurements, station and planetary eclipses and the relativistic corrections. 

The imperfect knowledge of the non-gravitational forces due to the proximity of Mercury to the Sun, together with the effect of desaturation maneuvers uncertainties, makes the use of the accelerometer necessary. Therefore, in our modelling of the orbit recovery, the models for the non-conservative forces were replaced by the noisy simulated accelerometer measurements. We find out that the modelling of the accelerometer noise has a huge impact on the results of the POD.

We perform several orbit reconstruction tests using daily arcs with noise modulated Doppler data with different settings on the arc lengths, arcs initial conditions, dynamical model, observation mode and orbit determination process and we solve for the initial state vector of each arc. We also run sensitivity analysis with respect to the different accelerometer model. The final goal of this study is to provide an independent solution for the precise orbit determination of Mercury planetary orbiter (MPO) using the planetary extension of the Bernese GNSS software. We present out latest results and then compare our results with the existing ones from the MORE team.
Temperature and CO2 density distribution in Mars upper atmosphere from the ACS-MIR / TGO solar occultations at 2.7 μm absorption band
Authors: Belyaev Denis , Fedorova Anna , Trokhimovskiy Alexander , Korablev Oleg , Montmessin Franck , Alday Juan , Olsen Kevin S. , Lopez-Valverde Miguel
Published: March 2020

The mid-infrared channel of the Atmospheric Chemistry Suite (ACS-MIR) is a cross-dispersion echelle spectrometer dedicated to solar occultation measurements in the 2.3–4.3 μm wavelength range [1]. The instrumental resolving power λ/Δλ reaches ~30 000, while the altitude resolution is ~1 km. ACS-MIR began regular science operations in April 2018 on board the ExoMars Trace Gas Orbiter (TGO). Each occultation session covers a spectral interval with one or a few CO2 absorption bands appropriate for the atmospheric density and temperature retrievals.

In this paper, we present results from data analysis in the 2.65-2.7 μm spectral range hosting strong CO2 absorption bands detectable up to 180 km. It provides us with unprecedented capability to profile CO2 from 20 to 180 km, covering the troposphere, the mesosphere and the thermosphere of Mars. The homopause is found around ~130 km and CO2 mixing ratio decreases from 96% to 20-40% at 180 km due to photolysis and molecular diffusion. A multiple iteration scheme was applied to retrieve CO2 density and temperature from the rotational absorption lines, while pressure was estimated assuming hydrostatic equilibrium. The vertical profiles coincide well with the simultaneous occultations performed below 100 km by the near-infrared channel ACS-NIR [2]. At the moment, our MIR channel dataset is made of >100 profiles encompassing the second half of MY34 and the beginning of MY35 in both martian hemispheres. The retrievals of density/temperature profiles in IKI are funded by the RSF grant #20-42-09035.

REFERENCES

[1] Korablev O. et al., 2018. The Atmospheric Chemistry Suite (ACS) of three spectrometers for the ExoMars 2016 Trace Gas Orbiter. Space Sci. Rev., 214:7. DOI 10.1007/s11214-017-0437-6.

[2] Fedorova A. et al., 2020. Stormy water on Mars: The distribution and saturation of atmospheric water during the dusty season. Science, eaay9522. DOI: 10.1126/science.aay9522.
Towards ready-to-use open source automated geodynamic diagnostics and fair representation of numerical models
Authors: Crameri Fabio
Published: March 2020

Advances in numerical modelling of geological processes are based upon, and driven by, diagnosing models. Such model diagnostics are often performed by hand, by eye, or else, by individually written routines that are neither tested or testable, nor reproducible.

Collecting geodynamic diagnostics, automating them in a robust manner to be applied to the multitude of different geodynamic models and codes, and providing them back to the community can foster additional progress within the modelling community.

In this presentation, I introduce the latest version of StagLab (Crameri 2018; www.fabiocrameri.ch/StagLab; currently version 5.0), which is a growing resource of geodynamic diagnostics, openly available, and easy to use. StagLab works seamlessly with StagYY (Tackley 2008) and can be made compatible with any other mantle convection code, if the respective developers start to provide machine-readable and documented output. Moreover, StagLab represents model data fairly to its users and to the readers of their papers. StagLab allows its users, whether professional or beginner, to produce state-of-the-art post-processing of geodynamic models, and publication-ready figures and movies, in a blink of an eye; all fully tested, testable and reproducible.

 

Crameri (2018), Geodynamic diagnostics, scientific visualisation and StagLab 3.0, Geosci. Model Dev., http://dx.doi.org/10.5194/gmd-11-2541-2018

Tackley (2008), Modelling compressible mantle convection with large viscosity contrasts in a three-dimensional spherical shell using the Yin-Yang grid, PEPI, http://dx.doi.org/10.1016/j.pepi.2008.08.005.
Using a novel electrical measurement approach to measure the effects of liming on rooting parameters in German beech forests
Authors: van Straaten Oliver , Čermák Jan , Kulp Larissa , Talkner Ulrike
Published: March 2020

Hundreds of thousands of hectares have been limed in German forests in the last three decades to mitigate the effects of soil acidification. To understand the long-term impacts of liming on tree rooting behaviour and the implications for soil organic matter, we used a novel electrical approach to quantify rooting parameters of mature beech forests and compared it to the standard monolith excavation approach. At each of the three experiment sites located in northern Germany, we looked at rooting behaviour in limed plots (overall eight tons of lime per hectare applied in the 1980s and 1990s) in comparison to adjacent control plots. First, we used the standard monolith excavation approach to determine fine root biomass at the stand level. With an electrical approach called the “earth impedance method” (EIM) we subsequently estimated tree absorbing root surface area (ARSA; this is the contact area where roots take up nutrients and water). This experimental, non-destructive approach uses a low frequency alternating electric current that flows from the roots to the soil and vice versa, and the electrical impedance (resistivity) is recalculated to estimate ARSA for the sample tree. We measured the ARSA of six mature trees per plot (12 trees per site).

To summarize the results of the sampling approaches, (1) both root estimation approach measurements were positively correlated, validating the EIM; (2) the ARSA was positively correlated with tree size at each site, further substantiating the rapid and cost effective EIM; (3) however this method is vulnerable to variables that effect electrical conductivity, such as soil moisture and the thickness and makeup of the organic horizons.

Overall, no significant differences between limed and control plots were detected with either measurement approach, suggesting that despite improved soil pH conditions the tree root systems in limed plots remain relatively constant in size and capacity to take up nutrients and water.
Plasmasphere observations with Cluster data supplemented with data from the Dynamics Explorer-1 and Van Allen Probes missions
Authors: Darrouzet Fabien , De Keyser Johan , Décréau Pierrette , Gallagher Dennis , Verbanac Giuli , Bandic Mario
Published: March 2020

Since 2000 the four Cluster spacecraft have crossed the Earth's plasmasphere along a polar orbit every 2.5 days, with various perigee altitudes (from 1.5 to 4 RE), different configurations (string of pearls, tetrahedron) and changing separations (from 10 to 100 000 km). The resulting dataset allows different types of inner magnetosphere studies and provides insight in plasmasphere dynamics, including changes in plasmapause position. Plasmaspheric plumes can also be studied on a case-by-case basis, in a statistical manner and in relation with wave activity (EMIC, electromagnetic rising tone, whistler waves).

Moreover, data from an old mission, Dynamics Explorer-1, have recently become available. In particular, densities and temperatures for many ions (H+, He+, He++, O+, and O++) have been derived from the RIMS (Retarding Ion Mass Spectrometer) instrument and are available from October 1981 to January 1985. Such composition data, not available from the Cluster satellites, allow in particular to analyze the distributions of those ions in the plasmasphere boundary layer, as a function of magnetic local time and geomagnetic activity.

Finally, since 2012, the two Van Allen Probes satellites are orbiting the inner magnetosphere in the magnetic equatorial plane and with a low perigee, allowing a crossing of the plasmasphere every 9 hours. The EMFISIS (Electric and Magnetic Field Instrument Suite and Integrated Science) instrument onboard both spacecraft can determine the electron density in a very large density range (up to 3000 cm-3) using several methods. This gives a different opportunity to analyze the plasmapause and plasmaspheric plumes from a different perspective.
Metamorphic evolution and geochronology of gneisses from the Wanni Complex, Sri Lanka
Authors: Masten Marcel , Hauzenberger Christoph A. , Lechner Nikolaus , Gallhofer Daniela , Fernando G.W.A. Rohan
Published: March 2020

The Wanni Complex is found in the northwestern part of Sri Lanka. The boundary to the Highland complex occurring to the south is partly ill defined. Differences in isotopic model ages were used to seperate both units (Kitano et al. 2018; Milisenda et al. 1994). While the Highland Complex has gained a lot of attention due to the UHT metamorphic overprint (up to 1150°C and 8-12kbar)(Sajeev and Osanai 2004) detailed petrological and geochronological work in the Wanni Complex is missing. Only a few studies focus on the border area between the Wanni Complex and the Highland Complex (Kitano et al. 2018; Wanniarachchi and Akasaka 2016).

Large areas of the Wanni Complex are covered by biotite gneisses, mostly migmatic, partly with occurrences of arrested charnockites or displaying potassium metasomatism (Cooray 1994; Kröner et al. 2003). However, charnockitic gneisses, garnet bearing gneisses and in the southwestern part cordierite bearing gneisses and metapelites occur which can be used for obtaining the PTt history of this complex. PT conditions of the Wanni Complex obtained from garnet bearing rocks place the metamorphic overprint clearly into the granulite facies and partly into the UHT field. Compared to the Highland Complex, temperatures are somewhat lower at 800-1000°C at 7-9kbar.

LA-ICP-MS U/Pb dating was performed on zircons from different locations of the Wanni Complex and shows igneous protolith ages of 855-963Ma. The ages were obtained from felsic hornblende-biotite gneisses and charnockitic gneisses. The wide range of ages could be a result of resetting shortly after magmatic crystallisation. CL images of some zircons show dark zones separated from oscillatory zoned cores by thin bright fronts. Taken together with core/rim dating of these zircons, this could be a sign of transgressive recrystallization (Hoskin and Black 2000).

 

 

Cooray, P.G. 1994. Precambrian Research 66(1–4):3–18.

Hoskin, P.W. and Black L.P. 2000. Journal of Metamorphic Geology 18:423–39.

Kitano, I., Osanai, Y., Nakano, N., Adachi, T. and Fitzsimons, I.C.W. 2018. Journal of Asian Earth Sciences 156:122–44.

Kröner, A., Kehelpannala, K.V.W. and Hegner, E. 2003. Journal of Asian Earth Sciences 22(3):279–300.

Milisenda, C.C., Liew, T.C., Hofmann, A.W. and Köhler, H. 1994. Precambrian Research 66:95–110.

Sajeev, K. and Osanai, Y. 2004. Journal of Petrology 45(9):1821–44.

Wanniarachchi, D.N.S. and Akasaka, M. 2016. Journal of Mineralogical and Petrological Sciences 111(5):351–62.
Isotopic constraints on water balance of tundra lakes and watersheds affected by permafrost degradation, Mackenzie Delta region, Northwest Territories, Canada
Authors: Wan Chengwei , Zhou Zhou
Published: March 2020

Widespread permafrost thaw in Canada's western Arctic has led to formation of shoreline retrogressive thaw slumps (SRTS), a process influential in modifying water and biogeochemical balances of tundra lakes. To investigate hydrological effects of SRTS, water sampling campaigns were conducted in 2004, 2005 and 2008 for paired lakes (pristine vs catchments disturbed by SRTS) in the upland region adjacent to the Mackenzie Delta, Northwest Territories, Canada. An isotope balance model to estimate evaporation/inflow, precipitation/inflow, water yield and runoff ratio was developed incorporating seasonal evaporative drawdown effects and a vapour mixing model to simulate gradients in Beaufort Sea marine air versus continental moisture sources. Site- specific water balance results reveal systematically higher evaporation/inflow and precipitation/inflow for lakes with active SRTS compared to undisturbed lakes, and typically higher ratios for lakes with stabilized versus active SRTS. For lake catchments, water yield is found to be higher for active SRTS sites compared to undisturbed and stabilized SRTS sites, suggesting that slumping is an initial but not a sustained source of water delivery to lakes. Catchments with history of wildfire are found to have lower water yields, attributed to reduced permafrost influence. Conceptually, we define a thaw trajectory whereby undisturbed sites, active SRTS, stabilized SRTS, and ancient- SRTS define progressive stages of permafrost thaw. We postulate that release of additional runoff is mainly due to permafrost thaw in active SRTS which also promotes lake expansion, talik formation, and subsurface connectivity. Eventual stabilization of slumps and reduced runoff is expected once permafrost thaw sources are exhausted, at which time lakes may become more reliant on replenishment by direct precipitation. The effect of snow catch in slumps appears to be subordinate to thawing based on eventual decline in runoff once thaw slumps stabilize. Improved, site-specific hydrologic understanding will assist ongoing research into carbon cycling and biogeochemical feedbacks.
Is there a Seasonality of the Martian Seismic Event Rate?
Authors: Knapmeyer Martin , Stähler Simon C. , van Driel Martin , Clinton John F. , Banerdt W. Bruce , Böse Maren , Ceylan Savas , Charalambous Constantinos , Garcia Raphael F. , Horleston Anna , Kawamura Taichi , Khan Amir , Lognonne Philippe , Panning Mark , Giardini Domenico , Pike William T. , Scholz John-Robert , Weber Renee C.
Published: March 2020

We analyze the sequence of seismic events of different types as recorded by the SEIS instrument of the InSight mission. After several weeks without any detection, event counts started to increase at the end of May 2019. The majority of recorded events belongs to the class of 2.4 Hz events, which prominently excite a continuously observed natural resonance frequency.

After a sudden onset of seismic detections by the end of May 2019 (about sol 180, LS≈32°), especially the combined event rate of the High Frequency, Very High Frequency, and 2.4 Hz family of events increased from 3.6 events/sol in June 2019 to more than 9 events/sol until late August 2019, i.e. increased by a factor of about 3.

Estimating event rates as if events are the result of a constant-rate Poisson process leads to contradictions with the statistical properties of those, either in the cumulative event count or in the lag time distribution. These contradictions can be overcome by assuming a step-wise increase of the event rate.

Any deviation from a purely random occurrence of quakes, in both time and space, requires a mechanism to suppress or support the source process. The seismic activity of the Moon is mainly controlled by tidal deformation, at least in terms of source time. What controls the event rate of Martian high frequency events is currently elusive.