bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamics of riparian vegetation as impacted by sedimentation in reservoirs
Authors: Segura Jimenez Olga , Gonzalez Sosa Enrique , Breil Pascal
Published: March 2020

Riparian vegetation along the rivers is one of the ways that allows restoration of surface water quality, stabilizing the banks, reducing erosion risks and offering habitat to flora and fauna. The modification of these ecosystems affects sediment transport and deposition in rivers. Sediments retained in a reservoir suggest an impact on the dynamics of the erosion processes and on the equilibrium of riparian ecosystems. If this tendency continues, it will not only affect the generation of electricity, but it will also impact ecosystems, either due to the excess of sediments or to lack of them. This paper analyzes the dynamics of the riparian ecosystems, upstream and downstream of “El Caracol”, a hydroelectric dam located in Guerrero, Mexico, based on Landsat TM and ETM + images corresponding to early spring (March-April) for the period of 1984-2010. The analysis was established by mapping the dynamics of the NDVI as an indicator of the areas affected by the migration of the vegetation and the erosion of the margins. The results show a decrease in NDVI in the study period. While degraded areas have a negative NDVI trend, there are areas within the same reservoir, where the index increases, indicating an increase in sediment deposition being an important factor in explaining vegetation migration.
Fracture growth during exhumation in low-permeability rock formations—the role of fluid PVT properties
Authors: Eichhubl Peter
Published: March 2020

Detailed fluid inclusion analyses of fracture cements in tightly cemented hydrocarbon-bearing sandstones and shales reveal that natural fractures tend to form under conditions approaching maximum burial, coinciding with hydrocarbon generation, and during incipient exhumation. Fluid inclusion analyses also reveal that these fractures form under abnormal (above-hydrostatic) pore fluid pressures. While compaction disequilibrium can account for elevated pore fluid pressures that promote fracture growth during early prograde burial, hydrocarbon maturation is likely the primary driver for fracture growth under peak burial conditions. Tectonic processes and thermal stresses provide secondary drivers. Thermal contraction with exhumation and cooling of the rock mass can promote fracture growth depending on the PVT properties of the fluid phase. The possible contribution of hydrocarbon generation after peak burial as a driver for fracture growth during incipient exhumation is discussed.
Observations of migrating tides in the mid-latitude MLT using an array of SuperDARN HF-radars
Authors: van Caspel Willem E. , Espy Patrick J. , Hibbins Robert E. , McCormack John P.
Published: March 2020

Solar thermal (migrating) atmospheric tides play an important role in shaping the day-to-day and seasonal variability of the Mesosphere-Lower-Thermosphere (MLT) region. Due the planetary scale of the migrating tides, observations have, however, remained sparse. This study uses meteor-echo wind measurements from a longitudinal array of SuperDARN HF-radars to isolate the amplitude and phase of the migrating diurnal, semidiurnal, and terdiurnal tide. The array of SuperDARN radars, covering nearly 180 degrees longitude at 60±5 degrees North, provide hourly horizontal wind measurements at approximately 95km altitude. The migrating components of the tides are isolated by fitting wave surfaces in space and time. The results are compared with global synoptic wind analyses from the high-altitude version of the Navy Global Environmental Model (NAVGEM-HA) to validate the method. The tides are also compared against those measured at a single station by the Trondheim (66N, 10E) meteor radar. We will present the method, a comparison between (migrating) tidal components in SuperDARN, NAVGEM-HA and the Trondheim meteor radar between 2014 and 2015, and migrating tide climatologies based on 21 years of SuperDARN data.
Multi-scale Analysis of Electromagnetic Energy Input using Swarm: Quantifying Key Scales in Magnetosphere-Ionosphere Coupling
Authors: Pakhotin Ivan , Mann Ian , Xie Kai , Knudsen David , Burchill Johnathan
Published: March 2020

Electromagnetic energy transfer in magnetosphere-ionosphere coupling (MIC) is an inherently multiscale process, where the relative contributions of various scale sizes, linked to various auroral phenomena, are largely unknown. While work in previous decades has largely focused on large scales, in recent years with the development of new instrumentation smaller scale electromagnetic disturbances have once again come into focus. Recent work by the authors has demonstrated evidence that small-scale processes appear to be so important as to potentially account for a global interhemispheric asymmetry in ionospheric energy input. This study attempts to statistically quantify the contribution of energy at the small and mesoscales using Poynting flux, calculated using the unprecedented ESA Swarm mission dataset of simultaneous electric and magnetic field measurements at 16 Hz, with statistics now spanning several years. We find important contributions at small scales to the total energy budget, while at the same time noting that there appears to be a limit above which energy content tends to drop off. In the context of previous observations from other spacecraft this may shed light on key small-scale processes happening in and around the auroral acceleration region, in particular discrete arcs and Alfvén wave reflection from the ionosphere, which are important in forming inputs to coupled magnetosphere-ionosphere-thermosphere modelling studies.
Composition and Properties of the Natural Aerosol over the Boreal and Tropical Forests
Authors: Hansson Hans-Christen , Artaxo Paulo , Andreae Meinrat , Kulmala Markku
Published: March 2020

We, together with 50 of our colleagues present a review on the interaction between tropical and boreal forests and the atmosphere, especially addressing their influence in the climate system. With its emissions of VOCs, aerosols and trace gases, with strong atmosphere interactions, forests are a key component of the climate system. These emissions and atmospheric processing regulates atmospheric chemistry and are the major source of cloud condensation nuclei (CCN) affecting cloud formation and development, and thus temperature and precipitation. Emissions from forests are thus closely connected to the hydrological and the carbon cycles, being  an essential integrated part of the climate system.

In terms of meteorology, tropical and boreal forests are very different. Temperature, solar radiation, precipitation, evapotranspiration, albedo, cloud structure and cover, convection etc., are all very different. However, the aerosols in the two systems show similarities as Primary Biological Aerosol Particles are the major component (70%) of coarse mode particles in Amazonia while Secondary Organic Aerosol in the tropics are mainly isoprene driven giving a slightly more hygroscopic SOA than the boreal monoterpene driven SOA. The organics constitutes 70 to 85% of PM1 mass for both boreal and tropical forests. In Amazonia, sulfates, nitrates and BC shows very low concentrations, while the boreal sites shows 2-3 times higher concentrations. The Siberian continental site and Amazonian site show remarkable similarities in the lack of new particle formation (NPF) which will be  discussed.

In the tropics dry season and boreal spring and early summer, increasing biomass burning emissions in both forest types dominates the aerosol composition, with high OC and BC concentrations while anthropogenic pollution influences boreal forest atmospheric composition during wintertime. The changes in diffuse to direct radiation due to scattering aerosols has important effects in tropical forests but minor in boreal, enhancing the net ecosystem exchange by 30% and 10% respectively. Thus the natural forest emissions affects the direct as well as the indirect forcing.

An Amazonia high altitude NPF process chain was recently observed at the top of the troposphere, and is an interesting interaction between forest emissions, cloud transport and processing and particle formation and aging at high altitudes that are brought back to the boundary layer, populating the CCN. For boreal forests, the complex relationship between GPP, BVOC, SOA, CCN, clouds, radiation, temperature and CO2 show multiple pathways and feedbacks, and some of them can be quantified. All showing the complexity of the interaction between forests, atmosphere and climate.
Sediment connectivity in Alpine basins: from isolated storms to turbidity currents in deep peri-Alpine lakes (examples from the Rhône basin and Lake Geneva, Switzerland)
Authors: Mettra François , Blanckaert Koen , Lemmin Ulrich , Barry David Andrew
Published: March 2020

In the main river canyon of a deep peri-Alpine lake (Rhône River canyon in Lake Geneva, Switzerland), occasional turbidity currents have been observed and monitored using acoustic Doppler current profilers (ADCP) during summer. It has been hypothesized that floods at catchment basin scale and slides of sublacustrine deltaic deposits are the main cause of these turbidity currents. Here, using discharge and turbidity measurements in the Rhône River, 6 km upstream of Lake Geneva and observations from small sub-catchments (as small as 4 km2), we show that single isolated storms in such sub-catchments can lead to turbidity currents in the deep Lake Geneva without a significant flood at the catchment basin scale (~5500 km2).

We analyzed several examples of hyper-concentrated and debris flows generated in small sub-catchments, reaching the Rhône channel and leading to turbidity currents in Lake Geneva. The relatively high discharge of the Rhône River and its straight man-made channel induced a rapid and intense transfer of sediment toward Lake Geneva. The continuous measurements in the Rhône River allowed tracking these sediment clouds and estimating sediment volumes. Then, using the ADCP measurements, we were able to mesure the intensity of the subsequent sediment pulses in the form of turbidity currents inside the Rhône River canyon in the deep part of Lake Geneva.

In summary, this study shows that a significant fraction of the annual sediment yield of the whole catchment basin is released from specific high-alpine areas due strong but localized storms. These sub-catchments have the specificity to be highly connected with the main channel of the catchment basin, thus permitting a rapid transfer along the sediment cascade (in one single event).
A technique for reconstructing the spatial characteristics of a long-lived meteor trails on all-sky cameras
Authors: Syrenova Tatiana , Vasilyev Roman , Beletsky Alexander , Mikhalev Alexander , Maxim Eselevich
Published: March 2020

Over the years, reports of meteor trails lasting up to one hour have periodically appeared in the literature. These observations are usually associated with particularly strong meteor showers, such as Leonids. In [Kelley et al. 2000] some interesting observations of such trails related to the 1998 Leonid meteor shower event are presented [2]. In publications devoted to the study of this phenomenon in the optical range, the main attention is paid to processes that cause a prolonged luminescence of meteor showers [Kelley et al., 2000]. Meanwhile, this phenomenon is of great interest for diagnosing the Earth upper atmosphere state and the ionosphere. The bulk of the work in this direction is based on radar observations of ionization traces, the duration of which in some cases reaches several minutes [Kashcheev et al., 1967].

This paper reports on long-lived meteor trails (LMT), which was recorded simultaneously using two optical instruments recording night sky emissions. The first all-sky camera is located at the Geophysical Observatory of the ISTP SB RAS, near the Tory (51.80 N, 103.10 E) and is designed to record the spatial picture of the 630 nm emission intensity [http: // atmos. iszf.irk.ru/ru/data/keo]. The second all-sky camera is located in the Sayan Solar Observatory of the ISTP SB RAS, near the Mondy (51.60 N, 100.90 E). A meteor trail lasting 35-40 minutes was recorded on November 18, 2017 after a meteoroid explosion on 22.23.19 UT with two cameras from different directions. Further, an algorithm was developed with the Python programming language the geographical coordinates of this event were calculated, as well as the height of the highlight

. The meteoroid explosion height and the ellipsoidal trail was being 65-70 km. Then the meteor track bow spread horizontally in a southward for 30-40 minutes at an average velocity of 58 m/s. This technique can be used to determine the main characteristics of various phenomena in the atmosphere, such as waves, SAR-arcs, meteor tracks and others.

This work was supported by a grant from the Russian Foundation for Basic Research N19-35-90093.
Hydrogeochemical modelling of mineral precipitation potentials in carbon capture and storage (CCS)
Authors: Maier Ulrich , Tatomir Alexandru , Sauter Martin
Published: March 2020

Reduction of atmospheric greenhouse gas emissions have become a main focus of research and policy debates and are most likely among the primary environmental concerns of the upcoming decades. One of several options is carbon capture and storage (CCS) after electricity production. Storage of carbon dioxide in geological reservoirs is attributed to three different processes, i) filling of pore space within the reservoir by gaseous or supercritical CO2 (pore trapping), ii) dissolution of the CO2 into the formation water (solubility trapping) and iii) precipitation of carbonate as mineral phase (mineral trapping). The potential of the latter is considerably uncertain, but has probably the most long-term potential of carbon sequestration in the subsurface. Underlying concepts of geochemical equilibria computation are discribed for the conditions of pressure and temperature in deep reservoirs up to 300°C and 1000 atmospheres. The geochemical codes Phreeqc and MIN3P have recently been upgraded for that purpose and were applied in the study. Models using field data from the Heletz oil field (Israel) sandstone formation are presented, focusing on the shift of saturation index (SI) of carbonates due to injection of CO2. Alterations of the mineral phase over time become visible and potentials to precipitate were observed for the minerals Ankerite > Dolomite > Siderite ~ Calcite > Magnesite, and for the mineral Dawsonite during early stages when only Na+ is present in high ionic concentrations. Observed variability of water chemistry and the database records provide an amount of uncertainty, which was used as input to delineate the range of the mineralization potential. Simple approaches of principal component analysis leading to sensitivity coefficients are shown.
Using empirical orthogonal functions to interpret the spatiotemporal variability of crop yields in presence of shallow restrictive soil layer
Authors: Kim Seongyun , Daughtry Craig , Russ Andrew , Pachepsky Yakov
Published: March 2020

Shallow restrictive soil layer may enhance plant growth and development in dry years due to the creation of subsurface-minipond-like water storages in dry years and may hamper plant development in wet years due to overwetting. These effects may manifest itself differently under different nutrient management. The objective of this work was to see there exist spatial patterns that are temporally stable (do not change over several years), can explain substantial proportions of spatiotemporal variation of maize yield, and can be related to subsurface restrictive layer topography and fertilizer application. Empirical orthogonal functions (EOFs) were good candidates to express such patterns. Data were collected with yield monitors across maize fields with manure applications, uniform chemical fertilization, and precision farming-based chemical fertilizer application over the six-year period. The subsurface restrictive layer was found at depths from one to three meters using the ground penetration radar. Three EOFs explained around 60, 30 and 10 % of interannual yield variation, respectively. As evidenced by semivariograms, the spatial structure was well pronounced in EOFs at the manured field and to a lesser extent at the chemical fertilizer fields. Little difference was observed in cumulative probability distributions of the first EOF across fields with different fertilizer applications. The topography of the restrictive layer was analyzed to determine the subsurface preferential flow lateral flow pathways that could provide water accumulation in dry years and enhanced drainage in wet years. The first EOF on average increased as the distance to the subsurface flow pathways decreased both at the manure and uniform chemical fertilized field, but not at the precision fertilization field where unfavorable water availability conditions could be compensated by the improved fertilizer availability. Differences in the soil surface topography could be reflected by the second EOF. Overall, the temporal stability in crop yields reveals the topography of the shallow vadose zone boundary as the powerful control of yield variation in space and time.  
Anthropogenic Transformation of Russian Arctic: dividing the area into zones based on cluster analysis
Authors: Eremenko Ekaterina , Bredikhin Andrei , Kharchenko Sergei , Belyaev Yury , Matlakhova Ekaterina , Romanenko Fedor , Bolysov Sergei , Fuzeina Yulia
Published: March 2020

In this study we analyzed the information about the presence of different types of anthropogenic objects (settlements, transport infrastructure, mining areas, etc.) in the Arctic zone of Russia. This information was taken from open Internet-sources: maps, cartographic projects, databases, schemes of regional development of the Russian Federation. Data analysis shows than only about 20% of Russian Arctic’s area is affected by economic development, meanwhile on the other 80% of the area there are practically no anthropogenic objects.

The economic development of the Arctic region decreases from West to East of Russia. The Republic of Karelia is characterized by the highest economic development level (only 13,1% of the area are not affected by any economic activities), the lowest levels have Krasnoyarskiy krai (95,2%) and the Republic of Sakha (Yakutia) (87,2%). Data on the presence, position, and types of anthropogenic objects were subjected to the k-means method of cluster analysis in order to identify characteristic combinations of objects corresponding to different types of development. Within the Arctic zone of Russia six main types of economical use of the territory were identified. Each of these types was characterized by the dominance of a certain type of anthropogenic objects (settlements, roads, mining industry objects, oil and gas transport infrastructure, wood industry objects).

Each type of the economical use of the territory is characterized by specific anthropogenic transformation of the topography of the area. The greatest transformation of the topography and geomorphological processes was found within the open mining areas. The least influence on the topography is connected with some of the linear transport structures (unpaved roads and underground gas pipelines). In general, economic activity in Russian Arctic is relatively low. Anthropogenic transformation of topography and geomorphic processes ​​is typical for the area about 667 thousand square km, that is about 18% of the total area of ​​the Russian Arctic.

This study is supported by Russian Foundation for Basic Research (RFBR) Project № 18-05-60200 "Anthropogenic transformation of Arctic Landscapes for the last 100 years".
Impacts of Tropical Deforestation on Local Climate
Authors: Smith Callum , Spracklen Dominick , Baker Jessica
Published: March 2020

Tropical forests play a critical role in maintaining the balance of biophysical surface fluxes and strongly influence the local and regional climate. Tropical deforestation is therefore increasingly recognised as an issue of global importance as the environmental and climatic consequences of prolific land-cover changes are beginning to be better understood. Using remotely sensed atmospheric and land-surface datasets from 2000 to 2016, climate impacts of deforestation were analysed over three tropical forest domains; the Amazon basin, the Congo basin and South-East Asia (SEA). Trends in local climate responses were observed with increasing deforestation across all tropical regions. Climate analysis was conducted on co-located pixels to ensure geographical differences were accounted for. Land that was deforested over the analysis period showed a decrease in evapotranspiration (ET) and leaf area index (LAI) and a significant increase in daytime land surface temperature (T). Whilst the Amazon saw the greatest relative decrease in LAI (0.2 m2/ m2), SEA showed the largest decrease in ET (1.5 mm/month) over the period. The climate response in Africa to deforestation is muted, with T increases of only 0.1◦C compared with 0.18◦C and 0.4◦C for SEA and the Amazon respectively. In all regions the response of precipitation was not significant. Increasing temperatures will heighten ecosystem stress for the remaining vegetation and forest adjacent to regions of deforestation will be more susceptible further degradation. The results of this study highlight the differences in climate responses between the tropical regions and the need to consider each separately when conducting future analysis.
Progress towards coupling ice sheet and ocean models
Authors: Galton-Fenzi Ben , Gladstone Rupert , Zhao Chen , Gwyther David , Moore John , Zwinger Thomas
Published: March 2020

With recent developments in the modelling of Antarctica and its interactions with the ocean several coupled model frameworks now exist.  This talk will focus on presenting the Framework for Ice Sheet - Ocean Coupling (FISOC), developed to provide a flexible platform for performing coupled ice sheet - ocean modelling experiments. We present progress and preliminary results using FISOC to couple the Regional Ocean Modelling System (ROMS) with Elmer/Ice, a full-Stokes ice sheet model. Idealised experiments have been used that also contribute to the WCRP Marine Ice Sheet-Ocean Model Intercomparison Project (MISOMIP).  A recent focus is on testing emergent behaviour of the coupled system and the model numerics. The talk will outline future technological applications and developments conducted as part of a broader international consortium effort. These efforts include coupling to sub-glacial hydrology, sea ice and atmospheres to form a complete system-downscaling technology from which to examine the influence of future climate on ice sheet evolution and hence sea level and global climate impacts. Developments to apply the technology to the Greenland Ice Sheet are presently underway.
Ohmic dissipation induced by Earth's nutation
Authors: Triana Santiago , Trinh Antony , Rekier Jeremy , Dehant Veronique
Published: March 2020

Radio signals from distant quasars allow us to determine Earth's rotation variations with exquisite accuracy. These observations can be used to estimate the amplitudes, frequencies and damping constants associated with Earth's rotational modes, particularly the Free Core Nutation (FCN) and the Free Inner Core Nutation (FICN). These estimates suggest, however, fluid core viscosities many orders of magnitude higher than expected, or rms magnetic fields at the core-mantle boundary (CMB) incompatible with downward continuation of the observed surface field. Aiming at resolve this difficulty, we have developed a proof-of-concept model where we incorporate an approximate fluid-dynamical treatment of the core flow associated with the FCN and the FICN. We show that, at least for the FCN, no abnormally high viscosities or magnetic fields are required. The model might provide in fact a robust, independent estimate of the rms magnetic field strength in the fluid core. Additionally, the model illustrates the importance of considering inter-mode resonances involving inertial modes (i.e. Coriolis-restored) and the rotational normal modes.
Inheritance processes of active extensional deformation in ocean-continent subduction zones: the example of the northern Andes compressional margin in Ecuador
Authors: Bulois Cédric , Michaud François , Saillard Marianne , Espurt Nicolas , Regnier Marc , Hernandez Salazar María-José , Font Yvonne , Reyes Benítez Pedro , Collot Jean-Yves , Proust Jean-Noël , D'Acremont Elia , Schenini Laure , Barba Diego
Published: March 2020

Over the last 23 Myr, the roughly east-directed subduction of the Nazca Plate beneath South America led to the formation of several mountain ranges associated with the overall northern Andes evolution. Along the active southwestern Ecuadorian margin, the compressional setting involves the Cretaceous-Miocene Chongón-Colonche / Santa Elena terranes, overlain by recent sedimentary basins. This geological setting, generally interpreted as an onshore-offshore forearc system, evolves in close relation with the active tectonic escape of the North Andean Sliver and the opening of the Gulf of Guayaquil. This region is characterised by a widespread extensional deformation in the upper plate that overprints moderate subduction and crustal earthquakes.

To better document such extensional processes, we specifically explore the offshore shelf and the littoral area of the Santa Elena Peninsula using academic and industrial 2D seismic profiles calibrated with local wells and field observations. We document a trench-parallel fault network, composed of >20km-long normal faults that take place on top of the former Chongón-Colonche accretionary wedge. These faults are linearly-steep along the trench, and are listric toward the continent where they clearly control fault-block rotation. They separate flexural basins developing on the platform ahead the Chongón-Colonche Cordillera, and are associated with immerged terraces most likely formed during the Last Glacial Maximum. They also may link to further onshore marine terraces developing since the Pleistocene across the coastline.

These observations suggest a peculiar dismantlement of the margin, mainly affected by tectonic erosion involving reactivation of former compressional features. Normal faults are specifically interpreted as a regional syn-orogenic collapse of the Chongón-Colonche Cordillera, which may result from transecting subducting ridges, fracture zones and seamounts controlling, at least partially, the geometry and the nature of the deformation along the southwestern Ecuadorian margin. This deformation pattern is likely linked to a weak interseismic coupling along the subduction interface to which the active opening of the Gulf of Guayaquil overlaps. This project is funded by the project ANR MARACAS ANR-18-CE31-0022 (MARine terraces along the northern Andean Coast as a proxy for seismic hazard ASsessment).
iMUSH Autocorrelation Reflectivity and Active Seismic Imaging of the Magma Plumbing System under Mount St Helens, Washington, USA
Authors: Levander Alan , Kiser Eric
Published: March 2020

We have developed a 3D model of the Mount St Helens (MSH) magmatic plumbing system extending from the upper magma storage zone (> 3.5 km bsl) to Moho depths (40-45 km) by combining results from 2D and 3D active source seismic tomography and reflection imaging, and autocorrelation reflectivity imaging. The data are from the ~6000 high frequency seismographs used in the 2014 iMUSH active seismic experiment.

We developed a 3D Vp tomography model of melt distribution in the upper-middle crust (Kiser et al, 2018). The model suggests the plumbing system is a complex sill structure consisting of several interconnected bodies that lie beneath MSH at 3.5-14 km depth and that extend ~25 km laterally. Bright reflections in 3D autocorrelation reflectivity depth migrations are strongly correlated with the melt model, illuminating its interior as well as a system of more geographically extensive thin sills that are invisible to the tomography. High amplitude reflectivity occurs near the top of the sill complex, suggesting the system grows by successive emplacement at the top of the complex. Inversion of the autocorrelation reflection volume for melt content suggests melt concentrations exceed 30% locally in the sill complex.  The highly reflective center of the sill complex is likely the magma storage zone that feeds dacitic composition MSH eruptions. We speculate that some of the more geographically widespread dikes feed the Indian Heaven basalt fields.

Deeper reflectivity trends to the northeast of MSH and intersects the Lower Crustal Conductor in Bedrosian et al’s (2018) MT interpretation. They interpret high conductivity values as indicative of 3-10% interconnected melt in the crust at depths > 20 km, which is consistent with our reflectivity images. We also observe asymmetric crustal thickening toward and thinning away from MSH along the strike of the Cascades. Moho reflectivity is weak directly beneath MSH, agreeing with previous studies (Kiser et al, 2016; Hansen et al, 2016). Zones of strong autocorrelation and wide-angle reflectivity cross the refraction Moho and extend some distance into the upper mantle. 
The use of multiple dendrochronological techniques to develop a 200-year drought record for subtropical Southeast Queensland, Australia
Authors: Haines Heather A , Palmer Jonathan G , English Nathan B , Hua Quan , Gadd Patricia S , Kemp Justine , Olley Jon M
Published: March 2020

In Australia the majority of tropical and subtropical regions lack any long-term (multi-decadal to centennial scale) instrumental climate records highlighting a need for alternatives such as proxy climate reconstructions. Despite this need, only a limited number of terrestrial proxy sources are available. Tree-rings provide one of the few options for climate reconstructions yet very little dendrochronological investigation has been undertaken as early assessments of tropical Australian species in the 1970s and 1980s indicated most species had short life-spans, poorly preserved timbers, or were compromised by having many ring anomalies. There has also been limited effort into understanding the growth-climate relationships of these trees with only a few studies undertaken targeting specific species that have unfortunately been heavily cleared from the region (eg. Toona ciliata). One exception noted in the early species assessment suggested that trees in the Araucariaceae family, a common tree family along the tropical Australian east coast, is longer lived than many other species in the region, contains growth rings which are annual in nature, and grows in response to climatic conditions.

Here we describe the results from a stand of Araucaria cunninghamii trees located in Lamington National Park, a World Heritage listed rainforest in subtropical Southeast Queensland, Australia (a region known for experiencing extreme hydroclimatic events). Our assessment discovered the presence of false, faint, locally absent, and pinching rings. By combining traditional dendrochronological analysis (eg. crossdating) with more recent techniques such as age validation by bomb-pulse radiocarbon dating and tree-ring density analysis, a robust ring-width chronology from 1805-2014 was developed. Dendrometers installed on four trees at the Lamington site confirmed that tree growth was annual and that moisture sensitivity was driving growth. Further growth-climate analysis indicated that the strongest correlation to the tree-ring chronology was specifically related to drought conditions in the region. The strength of this response was compared to both local and regional spatial areas and to drought indices such as the self-calibrating Palmer Drought Severity Index (scPDSI), the Standardized Precipitation Evaporation Index (SPEI), and the long-term drought conditions shown by the Australian and New Zealand Drought Atlas (ANZDA). The combined analysis led to the development of a 200-year drought reconstruction for the region and demonstrates influences from both the El Niño Southern Oscillation (ENSO) and the Interdecadal Pacific Oscillation (IPO).
A new Bayesian hierarchical geostatistical model based on two spatial fields with case studies with short records of annual runoff in Norway
Authors: Steinsland Ingelin , Roksvåg Thea , Engeland Kolbjørn
Published: March 2020

We present a new Bayesian geostatistical hierarchical model that is particularly suitable for interpolation of hydrological data when the available dataset has short records, for including overlapping catchments consistently and for combining areal (runoff) and point (precipitation) observations. A key feature of the proposed framework is that several years of runoff are modeled simultaneously with two Gaussian random fields (GRFs): One that is common for all years under study and represents the runoff generation due to long-term climatic conditions, and one that is year specific. The framework is demonstrated by filling in missing values of annual runoff and by predicting mean annual runoff for about 200 catchments in Norway. The predictive performance is compared to Top-Kriging (interpolation method) and simple linear regression (method for exploiting short records). The results show that if the runoff is driven by weather patterns that are repeated over time, the value of including short records is large, and that we for partially gauged catchments perform better than comparable methods for both annual spatial interpolation and mean annual runoff. We also find that short records, even of length one year, can safely be included in the model.

In a smaller case study of ten years of annual runoff in Voss in Norway it is demonstrated that by combining runoff and precipitation data in the model framework that includes consistently modelling of overlapping catchments on average preforms better compared to using only one of the data sources. Further, the interaction between nested areal data and point data gives a geostatistical model that takes us beyond smoothing: The model can give predictions that are higher (or lower) than any of the observations.

A finding is that in Norway the climatic effects dominates over annual effects for annual runoff. Through a simulation study we demonstrate that in this case systematic under- and overestimation of runoff over time can be expected. On the other hand, a strong climate implies that short records of runoff from an otherwise ungauged catchment can lead to large improvements in the predictability of runoff.
Rate and pattern of drainage network growth and induced drainage divide migration in natural (Aude river catchment, France) and laboratory-scale landscapes
Authors: de Lavaissière Léopold , Bonnet Stéphane , Regard Vincent , Voinchet Pierre , Carretier Sébastien , Guyez Anne , Bahain Jean-Jacques
Published: March 2020

The topography of continents is a dynamic interface that evolves in response to several external (tectonics, mantle dynamics, climate) or internal factors to the geomorphic system. If these systems tend naturally toward a steady-state, they often show transient regimes as evidenced by retreating knickpoints, fluvial captures or migrating divides. These two last phenomena are indicative of drainage reorganization and imply the growth of a network at the expense of another. Yet, the rate of drainage network growth is very poorly known. To our knowledge for example, only one study (Craddock et al., 2010) has attempted to constrain the rate of growth of a natural drainage network, in the specific case of a growth by sequential captures of endorheic systems.

Our aim here is to constrain the mechanism, timing and rates of network growth and drainage reorganization in a natural setting located in southwest France (Aude river catchment), in a current anorogenic setting in the northern foreland of the Pyrenees.

Geomorphic evidence indicate that this catchment is enlarging with about 40 km of displacement of its main divide in the last few hundreds of thousand years (precise timing under investigation). The Aude river and main tributaries show flight of strath terraces that converge downward over ~150 km long distance. This specific fan-shape of paleo-longitudinal profiles implies an upward increase of fluvial incision that we interpret as the consequence of a long-term growth of the Aude drainage network. The dating of these terrace system using cosmogenic isotopes (in-situ 10Be depth-profiles and 10Be-26Al burial isochrones) and Electron Spin Resonance (ESR) is under progress and will allow us to quantify the longitudinal trend of differential incision through time, which we will use to estimate the rate of drainage network growth and divide migration. To support these results, an analysis of the catchment-wide erosion rates on both sides of the migrating divide is also performed. First preliminary results indicate catchment-wide erosion rates of 0.06-0.08 mm.yr-1 in the Aude river catchment.

In complement to this natural case study, the main question of network growth dynamic is also addressed through laboratory-scale experiments performed at the Géosciences Environnement Toulouse (GET) laboratory. The first results show that the divide migration rate related to drainage network growth depends positively on the uplift/base level fall rate. In the detail, the divide migration rate is however non-linear, it evolves step by step with periods of acceleration when cyclic retreating knickpoints hit the divide.
Evaluation and scientific exploitation of CryoSat ocean products for oceanographic studies
Authors: Mir Calafat Francisco , Banks Chris , Snaith Helen , Gommenginger Christine , Shaw Andrew , Cipollini Paolo , Dayoub Nadim , Bouffard Jérôme , Meloni Marco
Published: March 2020

CryoSat’s ability to operate in different operating modes over water surfaces led to the first in-orbit evidence of the value of SAR-mode altimetry for oceanography, with the mission continuing to provide high-quality data and information not just over ice but also over the open ocean, polar waters and coastal regions. Approaching ten years in orbit, CryoSat routinely delivers a number of oceanographic products for global ocean applications. A dedicated operational CryoSat ocean processor (COP) has existed since April 2014 generating data products available in near real time (FDM/NOP), within ~3 days (IOP) and a geophysical ocean product (GOP) available within a month. An improved processing baseline was introduced in late 2017 and the same processing chain has now been applied to provide consistent ocean data products from the start of the mission. 
Within the ESA funded CryOcean-QCV project, the National Oceanography Centre (NOC) in the UK is responsible for routine quality control and validation of CryoSat Ocean Products. Activities include the production of daily and monthly reports containing global assessments and quality control of sea surface height anomaly (SSHA), significant wave height (SWH), backscatter coefficient (Sigma0) and wind speed, as well as a suite of validation protocols involving in situ data, model output and data from other satellite altimetry missions. This presentation will review some of the metrics and results obtained for CryoSat Ocean Products for SSHA, SWH and wind speed when assessed against data from tide gauges, wind and wave buoys, WaveWatch III wave model output, HF radar surface current data and comparisons with Jason-2 and Jason-3. Example metrics include SSHA along-track power spectra and the characterisation of offsets and variability regionally and in different sea states. 
In this presentation, we demonstrate the quality and scientific value of the CryoSat data in the open ocean where the altimeter operates mainly in conventional low-resolution-mode (LRM) but also over selected ocean regions where CryoSat operates in SAR-mode. 
Finally, scientific exploitation of the CryoSat data for oceanographic studies will be illustrated, focusing on CryoSat sea surface height anomalies. We will present examples of the benefits of CryoSat ocean products for oceanographic studies based on a dedicated Level 3 gridded product, featuring investigations of propagating ocean features (e.g. Rossby-type wave propagation) and their signatures in CryoSat in comparisons with data from other sources including SMOS, Sentinel 3A and 3B. 
DeepDust - A Proposed Drilling Project to Probe Continental Climate of the Late Paleozoic Icehouse-Greenhouse Transition
Authors: Soreghan Gerilyn , Beccaletto Laurent , Benison Kathleen , Bourquin Sylvie , Hamamura Natsuko , Hamilton Michael , Heavens Nicholas , Hinnov Linda , Looy Cindy , Pfeifer Lily , Pochat Stephane
Published: March 2020

The climatic, biotic, and tectonic events of the Permian are amongst the most profound in Earth history. Global orogeny leading to Pangaean assembly culminated by middle Permian time, and included multiple orogenic belts in the equatorial Central Pangaean Mountains, from the Variscan-Hercynian system (east) to the Ancestral Rocky Mountains (west). Earth’s penultimate global icehouse peaked in early Permian time, transitioning to full greenhouse conditions by late Permian time, thus archiving the only example of icehouse collapse on a fully vegetated Earth. The Late Paleozoic Icehouse was the longest and most intense glaciation of the Phanerozoic, with hypothesized low-elevation glaciation posited for both eastern and western tropical Pangaea during early Permian time. Reconstructions of atmospheric composition record the lowest CO2 and highest O2 levels of the Phanerozoic, with average CO2 levels comparable to the Quaternary, rapidly warming climate. Fundamental shifts occurred in atmospheric circulation: a global megamonsoon developed and the tropics became anomalously arid with time. Extreme environments are well documented in the form of voluminous dust deposits, acid-saline lakes and groundwaters, extreme continental temperatures and aridity, and major extinctions/extirpations, ultimately culminating at the Permo-Triassic boundary with the largest extinction of Earth history.

We seek to elucidate paleoclimatic conditions and forcings through the Permian at temporal scales ranging from the millennial to the Milankovitch  and beyond by acquiring continuous core in continental lowlands known to harbor stratigraphically complete records dominated by loess and lacustrine strata. We have identified sites in the western U.S. and Europe as the key sites globally to achieve our objectives, as these represent the western and eastern limits, respectively of the Pangaean tropics. Identified sites harbor arguably the most complete continental Permian sections in the paleoequatorial region, with adjacent paleo-uplands hypothesized to have hosted glaciation. We will also address the nature and character of the modern and fossil microbial biosphere, Mars-analog conditions, and exhumation histories of source regions.
Muon Tomography applied in the Lousal Mine (Portugal)
Authors: Teixeira Pedro , Cazon Lorenzo , Caldeira Bento , Blanco Alberto , Borges José , Adringa Sofia , Assis Pedro , Tomé Bernardo , Luz Ricardo , Nogueira José , Lopes Luís , Bezzeghoud Mourad , Ferreira Miguel , Nogueira Pedro , Espírito Santo Catarina , Galaviz Daniel , Barão Fernando , Pimenta Mário
Published: March 2020

Muon Tomography is an imaging technique that uses muons, a natural background radiation, as a means of observing the the earth’s subsurface. Muons are elementary particles like electrons but with a much greater mass that gives them a high penetrative power across matter. With suitable detectors it is possible to create muographs (muon radiographs) to obtain the column density distribution of the surveyed region. This project is a collaboration between University of Évora and the Laboratory of Instrumentation and Experimental Particle Physics (LIP). Both are Portuguese institutions that intend to apply the muon tomography in the geophysics field. The chosen location was the Lousal Mine, an abandoned and well mapped mine in Portugal with all the support infrastructures necessary that make it an ideal location to test the muon telescope developed by us. The detection will take place inside a mine gallery about 18 m below the surface. The telescope will do a geological reconnaissance of the ground above the gallery with the intention of mapping structures and ore masses already known and of improving the existing information with new data. This will serve to test the performance and sensitivity of the muon telescope, made of particle detectors called RPCs. A working prototype was put in place to gather preliminary information and establish the requirements of the equipment. After that, a muon telescope equipped with four RPC detectors, with an area of 1 m2 each, was assembled and has been collecting muons inside the Lousal Mine for the last few months. The tomographic aspect of the work is born from placing the telescope in different locations inside the mine and by orienting it to observe in different directions. Simulations of the muons detection have been made using GEANT4 software. The simulations allow to study the expected result of muographs produced by the muon flux passing through a simulated ground with different characteristics. The aim of this work is to combine the muography information with gravimetry data, from a gravimetric survey that will be carried on site, through a joint inversion of both data sets in order to obtain 3D density profiles of the observed region. Other geophysical methods are being applied above the mine to survey the surface, using photogrammetry, and the ground, using GPR and seismic refraction. These methods give knowledge about the arrangement of the ground, can be compared with previous acquired information and will help to perfect the 3D density profiles.
The correction for polar motion in gravimetry and in 3-D positioning
Authors: Mäkinen Jaakko
Published: March 2020

In the correction for polar motion, terrestrial gravimetry and 3-D positioning follow different conventions. The 3-D positions are corrected to refer to the "mean pole" (IERS Conventions 2010) or to the "secular pole" (IERS update working version since 2018). In any case, the pole reference evolves in time and describes the track of secular or low-frequency polar wander. However, in terrestrial gravimetry the gravity values are corrected to refer to the IERS Reference Pole, a fixed quantity. This may lead to discrepancies when for instance gravity change rates from absolute gravity measurements are compared with vertical velocities from GNSS. I discuss the size and geographical distribution of the possible discrepancies.