bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Continuous Terrestrial Archive of Environmental Change during the Last Interglacial/Glacial Cycle – The Loess-Palaeosol-Sequences of the Schwalbenberg (Middle Rhine Valley, Germany)
Authors: Fischer Peter , Jöris Olaf , Vött Andreas , Fitzsimmons Kathryn , Vinnepand Mathias , Hambach Ulrich , Prud'homme Charlotte , Schulte Philipp , Lehmkuhl Frank , Zeeden Christian , Schirmer Wolfgang
Published: March 2020

Over the last interglacial/glacial cycle climate variability and forcing in the northern hemisphere is best documented in high resolution from marine and ice core records. The response of land surface processes to climate over this period, however, remains poorly defined. Understanding landscape response to climate change is nevertheless of critical importance not only because as humans we live on and interact with the land, but also in order to identify potential feedbacks and forcings between land and atmosphere which cannot be ascertained from marine and ice core records. In this context, Loess-Palaeosol-Sequences (LPS) are outstanding terrestrial archives allowing detailed reconstruction of palaeoclimate and palaeo­environ­mental changes. However, regarding their complexity, LPS represent polygenetic and multiphase archives over different spatial and temporal scales. Consequently, a solid understanding of geomorphological and pedogenic processes involved in LPS formation, and the interplay with changes in ecological conditions, must be considered before LPS can be correlated with other archives.

Against this background, extensive fieldwork has been carried out at the Schwalbenberg site near Remagen (Middle Rhine valley, Germany) combining geophysical exploration with Direct Push borehole geophysical measurements and sediment coring. We will present a first comprehensive data set for the Schwalbenberg key area based on a transect from up- to downslope. The integration of grain size, organic carbon and weathering indices from long sediment cores (up to 30 m) and profile sections contribute to a better understanding of processes involved in the Schwalbenberg LPS formation. These data combined with age constraints based on radiocarbon and luminescence dating lead to a first robust chronostratigraphic model of the Last Interglacial/Glacial Cycle suggesting the Schwalbenberg LPS to be a terrestrial archive of palaeoclimate variations in phase with northern hemispheric ice and marine records.
Towers, Chambers & UAVs: Exploring the drivers of carbon sink strength at a temperate peatland
Authors: Simpson Gillian , Helfter Carole , Nichol Caroline , Wade Tom
Published: March 2020

Peatlands are terrestrial carbon sinks of global significance, storing an estimated one-third of global soil carbon. Net Ecosystem Exchange (NEE) of carbon dioxide (CO2) can however vary substantially on seasonal and inter-annual timescales, with some peatlands switching from a sink to a source of CO2. Complex and sometimes competing processes, such as meteorology and phenology, regulate a peatland’s net carbon sink strength. Understanding seasonal and inter-annual variability in NEE requires studying these environmental controls at multiple spatial and temporal scales. The role of vegetation in regulating NEE can be particularly difficult to ascertain at the finer timescales (e.g. seasonal) and at sites with abundant plant diversity, non-uniform distribution and complex micro-topography, such as peatlands. Vegetation surveys are traditionally conducted every few years and, because of this, they might not capture the shorter-term variations that can result from meteorological anomalies such as drought. New technologies, such as Unmanned Aerial Vehicles (UAVs), offer novel opportunities to improve the temporal resolution and spatial coverage of traditional vegetation survey approaches. UAVs are a more flexible, often cheaper alternative to satellite products, which can be used to collect data at the sub-centimetre scale. Such high resolution is particularly valuable in peatland environments, which typically display strong heterogeneity at the micro-site level (< 0.5 m). We employ UAV surveys with a Parrot Sequoia multispectral camera to map vegetation and track its phenology using vegetation indices such as the Normalised Difference Vegetation Index (NDVI) over the course of two growing seasons at a temperate Scottish peatland. By combining this multispectral data with in-situ NEE measurements (closed chambers and eddy-covariance) and meteorological data, this project aims to quantify the impact of weather and phenology on carbon balance at the site. An improved understanding of these two drivers of peatland carbon cycling will allow for better prediction of the impact of climate change at the site.
Resolving submesoscale processes and cross-scale interactions in the Gulf of Oman
Authors: Queste Bastien
Published: March 2020

The physical dynamics of the Sea of Oman are well resolved on meso- and basin-scales. The most prominent features are the slope current of the Persian Gulf Water (PGW), an energetic field of persistent eddies and circulation driven by seasonal monsoon wind regimes. Past work has shown that both oxygenation of the deep oxygen minimum zone and stimulation of local surface primary production are driven by submesoscale processes. In contrast to the pronounced summer-monsoon upwelling in the Arabian Sea, upwelling at the northern Omani shelf appears in the form of short irregular events. The main drivers for local upwelling and the exchange of water and its properties across the shelf break are not fully resolved. In particular, the relative importance of the two dominant causes of upwelling (ekman dynamics and eddy/topography interactions) and their interactions with the PGW slope-current are not known. Cross-shelf coupling is strongly determined by processes on the sub-mesoscale with weak surface signatures preventing analysis through remote sensing. The high system complexity and the lack of adequate observations explain past difficulties in resolving cross-shelf transport and local upwelling responsible for increased primary productivity and OMZ oxygenation.

Here we present new results identifying the submesoscale processes which control productivity and oxygenation in the region at a scale not previously described. These observations build on past work and illustrate how autonomous underwater vehicles can bring forward a full system understanding from basin-wide circulation and description of large ocean currents to submesoscale processes responsible for controlling biogeochemical cycling from a single campaign using standard ocean sensors and utilising the vehicles' inherent ability to measure upwelling and currents. We hope to illustrate the multidisciplinarity and flexibility of autonomous platforms in situations where vessels may not easily survey.
Counter-Earths – Planetary models beyond operational images
Authors: Heinicker Paul , Likavčan Lukáš
Published: March 2020

This contributions deals with an extensive apparatus of sensing and modelling the Earth, producing numerous fragmented Counter-Earths - the digital models and data visualizations of the planetary ecosystem. We center our analysis around this increasingly non-human visual culture, in order to seek possible theoretical framings of global climate sensing and modelling. After a historical and theoretical introduction to emergence and composition of this infrastructure - drawing from the works of Jennifer Gabrys and Paul N. Edwards -, we elaborate a framework in which we can see machine production of images of the planet as continuous algorithmic process of transformation of planetary circumstances. Contesting interpretation of the imagery that facilitates this process as representations of the planet, we categorize climate models and satellite visual outputs as operational images, following insights by Vilem Flusser and Harun Farocki. While fully acknowledging its historical and theoretical importance, this terminology is in this contribution further assessed as still too human-centric, and for this reason, we proceed with Dietmar Offenhuber’s concept of autographic visualization that endows non-human assemblages with capacity of self-presentation and self-diagrammatization. Consequently, we conclude with several examples of autographic visualization of climate change on a planetary scale, discovering Earth’s tendency to be externalized, geological memory of modernity, that can be read through machine sensing systems uncovering these hidden traces of the past.
20 years of forest change in Natura 2000 protected areas network
Authors: Chețan Marinela-Adriana , Dornik Andrei
Published: March 2020

Natura 2000 network, the world's largest network of protected areas, is considered a success for habitat and biodiversity protection, in the last decades. Our objective is to develop an algorithm for satellite data temporal analysis of protected areas, and to apply subsequently this algorithm for analysis of all Natura 2000 sites in Europe. We have developed an algorithm for satellite data temporal analysis of protected areas using JavaScript in Google Earth Engine, which is a web interface for the massive analysis of geospatial data, providing access to huge amount of data and facilitating development of complex workflows. This work focused on analysis of Global Forest Change dataset representing forest change, at 30 meters resolution, globally, between 2000 and 2018. Our results show that at least regarding forest protection, the network is not very successful, the 25350 sites losing 35246.8 km2 of forest cover between 2000 and 2018, gaining only 9862.1 km2. All 28 countries recorded a negative forest net change, with a mean value of -906.6 km2, the largest forest area change recording Spain (-5106.4 km2 in 1631 sites), Poland (-4529 km2 in 962 sites), Portugal (-2781.9 km2 in 120 sites), Romania (-1601.4 km2 in 569 sites), Germany (-1365.7 km2 in 5049 sites) and France (-1270.9 km2 in 1520 sites). Among countries with the lowest values in net forest change is Ireland (-17.4 km2 in 447 sites), Estonia (-104.1 km2 in 518 sites), Netherlands (-132.3 km2 in 152 sites), Finland (-268.6 km2 in 1722 sites) and Sweden (-341.6 km2 in 3786 sites).
Shrub clearing as Active Management strategy to control land abandonment in the Central Spanish Pyrenees: The effects and the limits
Authors: Khorchani Makki , Nadal-Romero Estela , Lasanta Teodoro
Published: March 2020

The Mediterranean mountains have been subject to significant land abandonment processes during the second half of the 20th century.  The subsequent natural revegetation following abandonment in rural areas has been widely documented to have significant implications on the hydrological cycle and the vegetation dynamics. The Spanish Pyrenees, are one of the most affected areas by these land transformations which could threaten their importance for water supply and agricultural activities in the downstream lowland areas.

Management strategies of these abandoned areas have been debatable during the last decades between scientists, policy-makers and stakeholders. Active Management strategy through shrub clearing is one of the proposed practices that have shown advantages to deal with land abandonment in some regions of Spain. Nevertheless, little is known on the effects of this practice on the hydrological cycle and water resources in abandoned areas. In this study we used the Regional Eco-Hydrological Simulation System RHESSys to estimate shrub clearing effects on water resources in the Aisa valley in the Central Spanish Pyrenees, subject to land abandonment and natural revegetation processes during the past decades. Our results show an increase of annual streamflow and a decrease of annual evapotranspiration following shrub clearing. Nevertheless, the magnitude of these changes may decrease with the age of abandonment and climate change.
Spatial Analysis of Soil Water Content in Newly Implemented Agricultural Bench Terraces in the Ethiopian Plateau
Authors: Castelli Giulio , Mesfin Shimbahri , Almeida Olivera Lucas Allan , Bresci Elena , Yazew Eyasu
Published: March 2020

In arid areas prone to desertification and soil erosion, the effectiveness of agricultural bench terraces in increasing soil moisture is dependent on their correct implementation. However, despite its relevance for securing food production in many areas of the world, the relationship between proper terracing implementation and the landscape capacity of holding soil moisture is still not understood. Moreover, spatial patterns of Soil Water Content (SWC) within the same terraced hillslope are weakly studied. The present work analyses SWC variations in four newly implemented terraced sites in Tigray Region, Ethiopia: Teshi, Ruba Feleg, Michael Emba and Enda Chena. Field SWC data were collected for the dry season of 2017 (February, March and April) from the upper, middle and lower part of each terraced site, including a non-terraced benchmark area. In all sites, terraced areas show SWC significantly higher than non-terraced ones (p < 0.05), with the lower part of the terraced hillslope more humid than the others for the whole period analyzed. A Multiple Linear Regression (MLR) analysis of SWC was conducted in order to highlight possible dependencies of SWC values. MLR highlighted significant dependency of SWC from the date of analysis, the position of the sample in the terraced slope, as well as a significant positive correlation of SWC with the percent of Water Stable Aggregates (WSA) analyzed at the study sites. Since high soil disturbance induces low soil aggregates stability, this result shows how measures to reduce soil disturbance during implementation can significantly increase SWC of radical terraces. Overall, the results of the present paper testify the good performances of bench terraces in Northern Ethiopia in terms of water conservation, and this first benchmark study can inform future terracing implementation in some arid and semi-arid agricultural areas of the world.

The abstract is based on Mesfin, S.; Almeida Oliveira, L.A.; Yazew, E.; Bresci, E.; Castelli, G. Spatial Variability of Soil Moisture in Newly Implemented Agricultural Bench Terraces in the Ethiopian Plateau. Water 2019, 11, 2134.
An improved regional flood frequency analysis approach at the global scale
Authors: Zhao Gang , Bates Paul , Neal Jeff , Pang Bo
Published: March 2020

Design flood estimation in data-poor regions is a fundamental task in hydrology. In this paper, we propose a regional flood frequency analysis approach to estimate design floods anywhere on the global river network. This approach involves two stages: (i) clustering global gauging stations into subareas by a K-means model based on twelve globally available catchment descriptors and (ii) developing a regression model in each subarea for design flood estimation using the same descriptors. Nearly 12,000 discharge stations globally were selected for model development and a benchmark global index-flood method was adopted for comparison. The results showed that: (1) the proposed approach achieved the highest accuracy for design flood estimation when using all catchment descriptors for clustering; and the regression model accuracy improved by considering more descriptors in model development; (2) a support vector machine regression showed the highest accuracy among all regression models tested, with relative root mean squared error of 0.67 for mean flood and 0.83 for 100-year return period flood estimations; (3) 100-year return period flood magnitude in tropical, arid, temperate, continental and polar climate zones could be reliably estimated with relative mean biases of -0.18, -0.23, -0.18, 0.17 and -0.11 respectively by adopting a 5-fold cross-validation procedure; (4) the proposed approach outperformed the benchmark index-flood method for 10, 50 and 100 year return period estimates; We conclude that the proposed RFFA is a valid approach to generate design floods globally, improving our understanding of the flood hazard, especially in ungauged areas.
Estimating the style and duration of former glaciation in the mountains of Britain and Ireland
Authors: Barr Iestyn , Ely Jeremy , Spagnolo Matteo , Evans Ian , Tomkins Matt
Published: March 2020

With a view to better understanding landscape evolution, we model the style and duration of former mountain glaciation in Britain and Ireland during the Quaternary (i.e., the past 2.6 Ma). We use a simple mass balance model, driven by published temperature depression data from the Greenland Ice Core Project (for the past 120 ka), and from a benthic δ18O stack (for the Quaternary as a whole). Though there are limitations to this approach, results provide first-order estimates and indicate that during the Quaternary as a whole, the mountains of Britain and Ireland were glacier-free for 1.1 ± 0.5 Ma; occupied by small (cirque) glaciers for 0.3 ± 0.2 Ma; and occupied by large glaciers for 1.1 ± 0.4 Ma. During the most recent glacial cycle specifically (i.e., the last 120 ka), these areas were glacier-free for an average of 52.0 ± 21.2 ka; occupied by small (cirque) glaciers for 16.2 ± 9.9 ka; and occupied by large glaciers, including ice sheets, for 51.8 ± 18.6 ka. Here, we investigate some of the regional variability in these estimates, and consider implications for long-term landscape evolution.
Geochemistry and uranium-lead isotopic ages of volcanic rocks associated with Ladakh batholith, western Himalaya: Implications for petrogenesis and tectonic evolution
Authors: Lakhan Singh Nongmaithem , Krishnakanta Singh Athokpam
Published: March 2020

We present zircon U-Pb ages and whole-rock geochemistry along with mineral chemistry of the Khardung volcanic rocks outcropped in the northern margin of the Ladakh batholith in order to constrain their origin and tectono-magmatic history. These volcanic rocks are sandwiched between the Ladakh batholith in the south and the Shyok suture zone in the north and span a continuous compositional range from basalt to rhyolite, although mafic rocks are minor and intermediate to felsic rocks are volumetrically predominant. New zircon U-Pb dating for andesite coupled with two rhyolitic rocks yield 69.71 Ma, 62.49 Ma, and 66.55 Ma, defining the probable span of their magmatism from Late Cretaceous to Palaeogene. Based on their mineralogical and geochemical compositional diversity, the Khardung volcanic rocks are categorized as intermediate volcanic rocks (basaltic andesite-andesite) and felsic volcanic rocks (dacite-rhyolite). The intermediate volcanic rocks are marked by low SiO2 (52.80-61.31 wt.%), enriched LREEs, and negative HFSEs (Nb, Ti, Zr) anomalies whereas,  felsic volcanic rocks are characterized by high SiO2 (64.52-79.19 wt.%), pronounced negative Eu anomalies, enriched LREE and concave-downward HREE’s and negative HFSE’s (Nb, Ti) anomalies. Both the intermediate and felsic volcanic rocks exhibit quartz, sanidine, albite, bytownite, and diopside as their dominant mineral phases. Geochemical signatures indicate that the fractional crystallization and crustal contamination played a significant role in the evolution of the Khardung volcanic rocks and their geochemical diversity probably resulted from the partial melting of the common primary source, which had been metasomatized by variable contributions of fluids released from down going Neo-Tethyan oceanic crust. Thus, the Khardung volcanic rocks could be considered as a product of mature stage of arc magmatism during the subduction of the Neo-Tethyan oceanic crust, which occurred during Early Cretaceous to Palaeogene, prior to the main collision between the Indian and Asian plates.
A reproducible solar irradiance estimation process using Recurrent Neural Network
Authors: Muralikrishna Amita , Santos Rafael , Vieira Luis Eduardo
Published: March 2020

The Sun have a constant action on Earth, interfering in different ways on life in our planet. The physical, chemical and biological processes that occur on Earth are directly influenced by the variation of solar irradiance, which is a function of the activity in the Sun’s different atmospheric layers and their rapid variation. Studying this relationship may require the availability of a large amount of collected data, without significant gaps that could be caused from many kinds of issues. In this work, we present a Recurrent Neural Network as an option for estimating the Total Solar Irradiance (TSI) and the Spectral Solar Irradiance (SSI) variability. Solar images collected on different wave components were preprocessed and used as the input parameters, and TSI and SSI data collected by instruments onboard of SORCE were used as reference of the results we expected to achieve. Complementary to this approach, we opted for developing a reproducible procedure, for which we chose a free programming language, in attempt to offer the same kind of results, with same accuracy, for future studies which would like to reproduce our procedure. To achieve this, reproducible notebooks will be generated with the intention of providing transparency in the data analysis process and allowing the process and the results to be validated, modified and optimized by those who would like to do it. This approach aims to obtain a good accuracy in estimating the TSI and SSI, allowing its reconstruction in gap scales and also the forecast of their values six hours ahead.
Geothermal prospecting at Cumbre Vieja volcano (La Palma, Canary Islands) by ground radon and thoron measurements
Authors: Pitti-Pimienta Lía , Weidner Anson , Shah Rishi , McClintock Rae L. , Martín-Lorenzo Alba , Rodríguez-Pérez Claudia , Padrón Eleazar , Asensio-Ramos María , Hernández Pedro A. , Rodríguez Fátima , Pérez Nemesio M.
Published: March 2020

During geothermal exploration, the geochemical methods play a major role in both exploration and exploitation phases. Discovery of new geothermal systems requires exploration of areas where the resources are either hidden or lie at great depths. A good example of young volcanic territory with high geothermal potential where geothermal resources are either hidden or lie at great depths is La Palma island (Canary Islands). La Palma is one of the youngest and westernmost island of the Canarian archipelago, located at the West African continental margin. Cumbre Vieja volcano (220 km2) is the last stage in the geological evolution of the island and has suffered 8 volcanic eruptions in the last 500 years, the last one in 1971. Among geochemical methods for geothermal exploration, soil gas surveys are useful for delineating main upflow regions and areas of increased subsurface permeability related to high temperature hydrothermal activity at depth. Soil gas Rn surveys are particularly useful since it is a naturally occurring radioactive gas present in geofluids that may serve as a subsurface tracer of geothermal reservoirs. An intensive soil gas was carried out from June to September 2019 in order to study the potential geothermal resource in Cumbre Vieja and the presence of vertical permeability structures related to high temperature hydrothermal reservoirs. A total of 1200 samples were taken with an average distance between sites of ≈250 m. Soil gas Rn-222 activity were measured by means of a portable SARAD RTM 2010-2 radon monitor; the instrument pumped gas through a stainless steel probe inserted at 40 cm depth and measured the Rn activity by electrostatic detection of the positively charged daughter isotopes. The soil gas Rn values ranged from atmospheric levels to 8.7 kBq m-3, with an average of 1.5 kBq m-3. The spatial distribution of soil Rn displays enrichments along the three main volcanic-rift zones: N-S, N-W and N-E, and confirms a strong structural control in the degassing processes of the volcano. The three volcanic-rift areas are zones of enhanced permeability for deep gas migration and preferential routes for degassing. It is worth noting the presence of an important soil gar Rn anomaly located at the eastern part of Cumbre Vieja, out of the three volcanic-rift areas. The data presented here are important to  identify  main  upflow  regions  and  areas  of  increased  and  deep  permeability at Cumbre Vieja.
Saturn’s ring current observed during Cassini’s Grand Finale
Authors: Provan Gabrielle , Bradley Tom , Bunce Emma , Cowley Stan , Dougherty Michele , Hunt Greg , Roussos Elias , Staniland Ned , Tao Chihiro
Published: March 2020

The presence of a substantial azimuthal current sheet in Saturn’s magnetosphere was identified in Voyager and Pioneer magnetometer data.  Data from these spacecraft showed depressions in the strength of the field below that expected for the internal field of the planet alone.  This ring current was  modelled  as a simple axisymmetric current system by Connerney et al. [1980, 1983].  In this study we utilise the Connerney ring current model to look at the size, shape, current density and total current of Saturn’s ring current as observed during the Cassini proximal orbits.  We compare the variations in these parameters with the phases of the planetary period oscillations and with the occurrence of magnetospheric storms as determined from propagated solar wind data and LEMMS electron and proton data. Overall, we find that Saturn’s ring current is a dynamical environment which varies in size and magnitude due to  both  planetary period oscillations and solar-driven storms.  
Stochastic Advection for eddy parameterisation in Primitive Equation Models
Authors: Patching Stuart
Published: March 2020

A major challenge of modern ocean modelling is how to represent in ocean models small-scale features with length scales smaller than the grid spacing. It is known that small scale eddies are important for maintaining Western boundary currents such as the Gulf Stream and Kuroshio; it is therefore of great importance that these are well represented in any global ocean model. The small scales are often parameterised by viscosity closures or GM parameterisations. The Stochastic Advection by Lie Transport (SALT) method is a propsed alternative which is defined so as to preserve important physical properties of the flow solution. Stochasticity is introduced into the fluid dynamical variational principle so that the resulting Euler-Poincaré equations give a stochastic version of the fluid equations which maintain a Kelvin circulation theorem and conservation of potential vorticity. The stochastic terms are then tuned using empirical orthogonal functions obtained from fine-grid model runs in order to capture the small-scale effects. This method has been shown to be effective for quasigeostrophic models and the 2D Euler equations. Here we present an application to the Finite volumE Sea-ice Ocean Model (FESOM2.0), a primitive equation model; we show preliminary results from this implementation.
Mobility and storage of hydrophobic urban pollutants in an agricultural river in southwestern Germany (Ammer River)
Authors: Schwientek Marc , Renner Dominik , Glaser Clarissa , Rügner Hermann , Grathwohl Peter
Published: March 2020

Hydrophobic pollutants in rivers are transported to varying degrees either in the dissolved or particle-bound phase. For either very turbid rivers or very strongly sorbing compounds, transport dynamics are closely coupled to the cascading sediment movement throught the stream network. Hence, an understanding of sediment storage and mobilisation/movement, including the interaction of suspended and bed sediment phases is the basis for properly discribing contaminant transport.

Suspened sediments from the Ammer River in southwestern Germany show a gradual decrease of polycyclic aromatic hydrocarbons (PAH) loadings in a downstream direction, reflecting urban sources in the headwaters. The decrease of PAH loading is, however, only weak which we attribute to only moderate inputs of more or less clean sediments along the river profile, capable of diluting the contaminant signal. The bed sediments of the river comprise a large fraction of grain sizes < 250 µm and constitute an important storage compartment for hydrophobic contaminants. Transformation or leaching into the water phase may reduce the stored amounts. Furthermore, the particle-bound mobility of the stored contaminants clearly depends on the distribution among grain size fractions. We have, therefore, also sampled the bed sediments < 250 µm along the river profile and separated into four grain size fractions (< 19 µm, 19-54 µm, 54-100 µm, 100-250 µm) using vacuum filtration and fine stainless steel meshes. The fractions have been analyzed for urban pollutants of different origins (PAH, heavy metals and the musk fragrance galaxolide) and particulate organic carbon (POC) content. First results show that POC is enriched in the 19-54 µm fraction and that metal contents are neither correlated with POC nor with grain size. This contradicts the common assumption that compounds typically sorbing to surfaces acumulate in the finest fractions due to the large specific surface area. Final results for PAH and galaxolide concentrations as a function of POC contents and particle sizes will also be presented (analysis still pending). At least for PAH a strong affinity to organic carbon is anticipated, while not much is known to date about the sorption and storage behaviour of galoxolide.

The results will give further insights into the environmental behaviour of the investigated compound groups. Comparison with data from suspended sediment sampling will enhance our understanding of mobile and immobile phase interactions and, hence, the transport dynamics of these sediment-associated pollutants.
Ammonia measurements from space with the Cross-track Infrared Sounder (CrIS): characteristics and applications
Authors: Shephard Mark , McLinden Chris , Dammers Enrico , Kharol Shailesh , Cady-Pereira Karen , Zhang Junhua , Bittman Shabtai , Chow Evan , White Evan
Published: March 2020

Satellite data are helping to fill monitoring gaps in order to better inform decision makers and assess the impact of ammonia-related policies.  Presented is an overview demonstrating the current capabilities of the ammonia (NH3) data product derived from the CrIS satellite instrument for monitoring, air quality forecast model evaluation, dry deposition estimates, and emissions estimates.  This includes examples of daily, seasonal, and annual observations of CrIS ammonia that demonstrate the spatiotemporal variability of ammonia globally. These results further demonstrate the ability of CrIS to observe regional changes in ammonia concentrations, such as spring maximum values over agricultural regions from the fertilizing of crops.  Also shown is the importance contribution of wildfires, especially in regions where there is little or no agriculture sources, such as the northern latitudes in North America during summer.  Initial comparisons of CrIS NH3 satellite observations with air quality model simulations show that while there is general agreement on the spatial distribution of the anthropogenic hotspots, some areas are markedly different.  Some key findings are that dry deposition estimates of NH3 and NO2 from CrIS and the Ozone Monitoring Instrament (OMI), respectively, indicate that the NH3 dominates over most regions across North America. Their 2013 annual ratio shows NH3 accounting for ~82% and ~55 % of the combined reactive nitrogen dry deposition from these two species over Canada and the U.S.  Furthermore, we show the use of CrIS satellite observations to estimate annual and seasonal emissions over Concentrated Animal Feeding Operations (CAFOs).  These results are used to evaluate the seasonal and temporal emissions profiles used in bottom-up inventories over an agriculture hotspot, which are often underreported
Land-atmosphere interactions and agricultural climate impacts
Authors: Mueller Nathan
Published: March 2020

Agricultural climate impact projections routinely rely upon temperature-based statistical models to characterize historical variability and project future crop yields, and exposure to extremely hot temperatures is associated with severe crop losses. However, high temperatures over land can be strongly influenced by land surface conditions, including shifts in evapotranspiration arising from variations in vegetation productivity and soil moisture. This talk will highlight the ways in which such land-atmosphere interactions should be considered in agricultural climate impact assessments. I will show how crop intensification of both rainfed and irrigated production modified extreme temperature trends in the US and around the world. I will then show how the coupling between soil moisture and temperatures can bias climate impact projections based solely on temperature. Shifts in soil moisture-temperature coupling will be examined using earth system models.
First Amburana cearensis (Fabaceae) tree-ring chronology in Brazil in a dry forest shows great potential for climate reconstruction
Authors: Godoy-Veiga Milena , Locosselli Giuliano , Regev Lior , Boaretto Elisabetta , Ceccantini Gregório
Published: March 2020

Tree-ring chronologies are an excellent climate archive for their spatial and temporal resolution. While networks of chronologies have been built outside the tropics helping to understand past regional climate trends, tropical regions still lag behind in terms of spatial coverage. Dendrochronological studies, however, may succeed in seasonally dry tropical forests where the growing season is well defined. Amburana cearensis, found in both dry and wet forests in South America, is poorly explored for dendrochronological purposes, with no previous study in Brazil. Therefore, we sampled trees growing in a seasonally dry forest in a karstic area in Central-Eastern Brazil, under the South American Monsoon domain, in order to explore this species potential for dendroclimatological studies in the region. We build a tree-ring width chronology using 26 trees. We found a strong common growth signal among trees, with an r-bar of 0.51 and an average mean sensitivity of 0.50. The standard tree-ring width chronology showed a significant negative correlation with Vapor-Pressure Deficit during the entire wet season (0.54), negative correlation with temperature at the end of the wet season (0.45), and a positive correlation with the sum of precipitation during the wet season (0.46). Further stable isotopic analysis will provide additional records of climate variability in the region. Since Amburana cearensis occurs across most of the seasonally dry forests and savannas from South America, it has a great potential to be used to develop climate reconstructions and verify the effects of climate change currently affecting the region.
Modeling lowland catchment hydrology: A comparison of model versions
Authors: Wagner Paul D. , Bieger Katrin , Arnold Jeffrey G. , Fohrer Nicola
Published: March 2020

The hydrology of rural lowland catchments in Northern Germany is characterized by near-surface groundwater tables and extensive tile drainage. Previous research has shown that representing these characteristics with the hydrologic model SWAT (Soil and Water Assessment Tool) required an improvement of groundwater processes, which has been achieved by dividing the shallow aquifer into a fast and a slow shallow aquifer. The latest version of the Soil and Water Assessment Tool (SWAT+) features several improvements compared to previous versions of the model, e.g. the definition of landscape units that allow for a better representation of spatio-temporal dynamics. To evaluate the new model capabilities for lowland catchments, we assess the performance of SWAT+ in comparison to previous SWAT applications in the Kielstau Catchment in Northern Germany. The Kielstau Catchment is about 50 km² large, is dominated by agricultural land use, and has been thoroughly monitored since 2005. In particular, we explore the capabilities of SWAT+ in terms of watershed configuration and simulation of landscape processes by comparing two model setups. The first setup is comparable to previous SWAT models for the catchment, i.e. yields from hydrologic response units are summed up at subbasin level and added directly to the stream. In the second SWAT+ model, subbasins are divided into upland areas and floodplains and runoff is routed across the landscape before it reaches the streams. Model performance is assessed with regard to measured stream flow at the outlet of the catchment. Results from the new SWAT+ model confirm that two groundwater layers are necessary to represent stream flow in the catchment. The representation of routing processes from uplands to floodplains in the model further improved the simulation of stream flow. The outcomes of this study are expected to contribute to a better understanding and model representation of lowland hydrology.
Random movement of mesoscale eddies in the global ocean
Authors: Zhai Xiaoming , Ni Qinbiao , Wang Guihua , Marshall David
Published: March 2020

In this study we track and analyze eddy movement in the global ocean using 20 years of altimeter data and show that, in addition to the well-known westward propagation and slight polarity-based meridional deflections, mesoscale eddies also move randomly in all directions at all latitudes as a result of eddy-eddy interaction. The speed of this random eddy movement decreases with latitude and equals the baroclinic Rossby wave speed at about 25° of latitude. The tracked eddies are on average isotropic at mid and high latitudes, but become noticeably more elongated in the zonal direction at low latitudes. Our analyses suggest a critical latitude of approximately 25° that separates the global ocean into a low-latitude anisotropic wavelike regime and a high-latitude isotropic turbulence regime. One important consequence of random eddy movement is that it results in lateral diffusion of eddy energy. The associated eddy energy diffusivity, estimated using two different methods, is found to be a function of latitude. The zonal-mean eddy energy diffusivity varies from over 1500 m2 s-1 at low latitudes to around 500 m2 s-1 at high latitudes, but significantly larger values are found in the eddy energy hotspots at all latitudes, in excess of 5000 m2 s-1. Results from this study have important implications for recently-developed energetically-consistent mesoscale eddy parameterization schemes which require solving the eddy energy budget.  
Mutual Iinformation exchange in solar wind density fluctuations
Authors: Sorriso-Valvo Luca , Carbone Francesco , Telloni Daniele
Published: March 2020

The fluctuations of proton density in the slow solar wind are analyzed by means of joint Empirical Mode Decomposition (EMD) and Mutual Information (MI) analysis. The analysis reveal that, within the turbulent inertial range, the EMD modes associated with nearby scales have their phases correlated, as shown by the large information exchange. This is a qunatitative measure of the information flow occurring in the turbulent cascade. On the other hand, at scales smaller than the ion gyroscale, the information flow is lost, and the mutual information is low, suggesting that in the kinetic range the nonlinear interacions are no longer sustaining a turbulent energy cascade.
Characterization of Active Faults Through the Gulf of Guayaquil, Ecuador: implication for the southern boundary of the North Andean Sliver
Authors: Regnier Marc , Ponce Gabriela , Saillard Marianne , Audin Laurence , Vaca Sandro , Alvarado Alexandra , Ruiz Mario
Published: March 2020

Along the Ecuadorian margin, the North Andean Sliver is moving in the northeastward direction due to the oblique subduction of the Nazca plate. The opening of the gulf of Guayaquil is a consequence of this motion. Two principal models compete to explain the opening. One proposes an opening achieved essentially with strike-slip motion along a single major fault through the gulf, the other with a combination of strike-slip and normal faulting on both sides of the gulf. The consequences in term of seismic hazard are very different. A single strike-slip fault model could imply a long fault segment capable of generating large magnitude events. In contrast, a multi-segments composite fault system will give conditions for producing small to medium size earthquakes. The southern Ecuador subduction zone is characterized by the absence of large historical earthquake. Data from the historical and instrumental seismicity for magnitude above 4 show the forearc has a high level of moderate seismic activity within and around the gulf that connects to the crustal seismic activity of the volcanic arc. In contrast, the forearc elsewhere shows very little or no seismic activity between the marine forearc zone and the volcanic arc. Regional and global CMTS data show a large number of mechanisms within the gulf that do not line up on a simple straight fault system. We present new earthquake data from the recently upgraded national seismic network of Ecuador. They provide the first image of SW-NE trending crustal faults stretching in the central part of the gulf and running eastward south of the Puna island. The main seismic belt appears to be discontinuous, made of short length segments with variable trends. The variety of focal solutions also indicates complex faulting. As the shape of this seismic belt is in good agreement with the orientation of the GPS velocity vectors, this new fault zone is readily interpreted as the southernmost segment of the actual NAS boundary. Others seismic clusters are observed parallel to the northern coast of the gulf, indicating active structures eventually accommodating the North-South opening of the gulf through normal faulting. b-value analysis of the main seismic belt seismicity shows high b value (>1) indicating either highly fractured or heterogeneous medium, or/and low stress level within the gulf of Guayaquil. This is again in agreement with a multi-segmented faulting system and also with the lack of large magnitude event in the historical seismic data. A cross-section for the entire seismic belt shows a depth extend of the crustal seismic activity down to 30 km which confirms the seismic belt to be a sliver boundary.
Does ocean resolution aﬀect the rate of AMOC weakening?
Authors: Hewitt Helene , Jackson Laura , Roberts Malcolm , Iovino Dorotea , Koenigk Torben , Meccia Virna , Roberts Christopher , Ruprich-Robert Yohan , Wood Richard
Published: March 2020

We examine the weakening of the Atlantic Meridional Overturning Circulation (AMOC) in response to increasing CO2 at different horizontal resolutions in HadGEM3-GC3.1 and in a small ensemble of models with differing resolutions. There is a strong influence of the ocean mean state on the AMOC weakening: models with a more saline western subpolar gyre have a greater formation of deep water there. This makes the AMOC more susceptible to weakening from an increase in CO2 since weakening ocean heat transports weaken the contrast between ocean and atmospheric temperatures and hence weaken the buoyancy loss. In models with a greater proportion of deep water formation further north (in the Greenland-Iceland-Norwegian basin), deep-water formation can be maintained by shifting further north to where there is a greater ocean-atmosphere temperature contrast.

We show that ocean horizontal resolution can have an impact on the mean state, and hence AMOC weakening. In the models examined, those with higher resolutions tend to have a more westerly path of the North Atlantic Current and hence greater impact of the warm, saline subtropical Atlantic waters on the western subpolar gyre. This results in greater dense water formation in the western subpolar gyre. Although there is some improvement of the higher resolution models over the lower resolution models in terms of the mean state, both still have biases and it is not clear which biases are the most important for influencing the AMOC strength and response to increasing CO2.

 
Reconnection site and ion scale turbulence generation
Authors: Vaivads Andris , Liu Chengming , Khotyaintsev Yuri V. , Graham Daniel B. , Lindqvist Per-Arne , Torbert Roy B. , Burch Jim L. , Russell Christopher T. , Contel Olivier Le , Giles Barbara L. , Gershman Daniel J.
Published: March 2020

We analyze in detail a reconnection site observed by the Magnetospheric Multiscale (MMS) mission in the magnetotail. The interval around the X-line is identified based on the ion jet reversal, Hall electric fields and other reconnection signatures. At the reconnection site strong electric fields with amplitudes above 100mV/m are observed. In addition, the region shows strong turbulent variations on ion scales, including magnetic island-like structures. We discuss the cause of strong electric fields, their relation to ion scale structures and associated particle acceleration in this region. Of particular interest is the relation of the reconnection site to the generation of kinetic Alfven waves.
Soil CO2 fluxes and surface microtopography in a mixed hemiboreal forest: space, time and models.
Authors: Krasnov Dmitrii , Krasnova Alisa , Noe Steffen
Published: March 2020

The understanding of biophysical mechanisms influencing the spatial and temporal distribution of CO2 flux is important for predicting the response of forest ecosystem on any environmental changes. It has been shown, that the most important controlling factors responsible for CO2 flux fluctuation from the forest soils are soil moisture, temperature and the type of the forest stand. In our work, we present three years of soil CO2 flux measurements in the hemiboreal forest that is characterized by high spatial heterogeneity of vegetation and soil. Three sample plots that represent the main common tree species (Pinus sylvestris, Picea abies and Betula sp) were chosen to assess the influence of tree species composition on the soil CO2 flux. The chosen sample plots have clear microtopographical structure with depressions, elevations and flat zones. The data were collected from three sample plots according to forest floor microtopography using manual closed dynamic chamber equipped with IRGA sensor (The Vaisala GMP343 probe), humidity and temperature sensors (Vaisala HMP155). Obvious temporal resolution limitation of manual chamber method is compensated by higher spatial coverage.

Previous research has indicated that one of the major sources of uncertainties in the flux estimation is the choice of the model for flux calculation. We compared the commonly used models (linear, exponential and HMR) using two available R packages: “gasflux” and “flux” packages. Additionally, we developed the algorithm that allows for automatically choosing the best model based on widely used criteria (MAE, RAE, AIC, RMSE).

The results showed that in most of the cases linear and exponential models performed better. The comparison of sample plot showed that the biggest influence of microtopography was in the birch forest but the moisture had a bigger effect in the pine forest stand.