bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact of in-cloud OVOC chemistry on tropospheric ozone
Authors: Rosanka Simon , Taraborrelli Domenico
Published: March 2020

In-cloud aqueous-phase chemistry is known to decrease tropospheric ozone (O3) via O3+O2- with the major source of O2- being hydroperoxyl radicals (HO2). Therefore, tropospheric O3 is sensitive to aqueous-phase HOx (HOx=HO2+OH) chemistry. However, most global atmospheric models do not represent this sink reasonably well since they lack explicit representation of in-cloud aqueous-phase chemistry. In this study, a new detailed aqueous-phase mechanism for the oxidation of water soluble oxygenated volatile organic compounds (OVOCs) is developed, suitable for global scale modelling. This improves the representation of aqueous-phase HO2 and thus the removal of tropospheric O3. The mechanism focuses on OVOCs containing up to three-carbon atoms. A detailed box-model analysis under low and high NOx conditions is performed. Afterwards, the developed mechanism is implemented into the global atmospheric model ECHAM/MESSy (EMAC), which is capable to represent the described processes explicitly and integrates the corresponding ODE system with a Rosenbrock solver. EMAC is then used to estimate the global impact of the proposed mechanism with a focus on monsoon systems and biomass burning events. The implemented changes are evaluated using airborne campaign data like OMO for the Asian monsoon. The OVOC oxidation leads to an increase in ozone scavenging and a substantial reduction in tropospheric gas-phase chemical production of ozone. These changes in the free troposphere significantly reduce the modelled tropospheric ozone column, which is known to be overestimated by EMAC and global atmospheric models in general.
Pleistocene carbonates from Dobrogea (E Romania) and their relationship with Black Sea level fluctuations
Authors: Dragusin Virgil , Constantin Silviu , Ersek Vasile , Hoffmann Dirk L. , Hotchkies Alex
Published: March 2020

The eastern part of Romania, bordering on the Black Sea, is generally poor in speleothems and only Piatra Cave has important speleothem occurrences. This cave is positioned close to the present-day shoreline, forcing the local aquifer to completely flood it when it rose synchronously with sea level. The flooding of the cave prevented speleothem formation. Conversely, sub-aerial carbonate deposition took place when the sea level was lower than today and the cave was dry. The study of speleothems from Piatra Cave could bring more insight on past Black Sea level fluctuations, as well as on the isotopic composition of percolating water.

Some 50 km to the south of Piatra Cave, around the town of Mangalia, botryoidal calcite has been deposited inside small voids formed between Sarmatian limestone beds. Such calcite formations are considered to form close to the water table, at the contact with the underground atmosphere. If so, they could be used to track the position of past water tables, as well as the isotopic composition of those waters. Moreover, as these samples are found only close to the present-day shoreline, they might have been deposited from underground water whose level was directly controlled by the sea.

Here we present the results of δ18O and δ13C measurements on 75 samples and sub-samples of botryoidal calcite. We explore the implications of their isotopic variability, by comparison with speleothems from Piatra Cave as well as to other speleothems from Romania. Moreover, we explore their isotopic variability across the sampling area, in order to better assess their possible use as sea level markers.
Modelling fast geomagnetic reversals
Authors: Maffei Stefano , Livermore Philip , Greenwood Sam , Mound Jonathan
Published: March 2020

Field reversals are some of the most prominent and commonly known temporal variations of the geomagnetic field. Polarity changes have been observed in seafloor magnetisation patterns, volcanic records, sediment sequences, speleothem records, and have been reported in geodynamo simulations. However, many open questions remain concerning the phenomenology and underlying causes of this process and whether precursory signals can be detected prior to a reversal. In particular, there is currently no scientific consensus regarding the temporal scales over which geomagnetic reversals occur. Simple order-of-magnitude arguments suggest that the geomagnetic field might reverse over the magnetic diffusion timescale, which for the Earth’s outer core is on the order of tens of thousands of years; numerical simulations aimed at understanding Earth’s million-year evolution have predicted a time scale on the order of thousands of years. On the other hand, analysis of a lacustrine sequence in the central Italian Appennines suggests that the most recent geomagnetic reversal (the Matuyama-Brunhes transition) took place around 786,000 years ago in as short as 13 years [Sagnotti, L. et al. (2015). GJI, 204(2), 798-812.]. This extremely short decadal time scale challenges our current understanding of the geodynamo and present-day numerical models.  

Here we attempt to answer the question: how fast can the axial dipole component of the geomagnetic field to reduce to zero during a magnetic reversal?  To do so, we derive fluid flows at the top of Earth’s outer core that optimise the rate of dipole decay, subject to a minimal number of physical ingredients. Specifically, we neglect the internal dynamics and prescribe a total flow kinetic energy that is consistent with observational bounds. This technique, previously employed for the study of paleomagnetic intensity spikes, is extremely versatile and allows us to explore a wide range of hypotheses concerning the flow geometry, its complexity, and the configuration of the geomagnetic field prior to the onset of the reversal. Although the resulting flows may not be physically realisable, this technique provides justified bounds on the fastest plausible polarity reversal time scale. 
InSAR techniques to determine mining-related deformations using Sentinel-1 data: the case study of Rydułtowy mine in Poland.
Authors: Pawłuszek-Filipiak Kamila , Borkowski Andrzej
Published: March 2020

Since launching Sentinel 1 satellites, the European Space Agency has been providing a huge amount of repeated SAR data. Thanks to 6-days revisiting time, it creates a perfect possibility for the monitoring of ground deformation, caused by underground mining activity, by using Differential SAR interferometry (DInSAR).

Because, DInSAR exploits single interferometric SAR pairs, the accuracy of this technique is limited by spatial and temporal decorrelation and atmospheric artifacts. To minimize the atmospheric influence on DInSAR results, we investigated precipitation and relative humidity data acquired from the Institute of Meteorology and Water Management (IMGW). Theoretically, the summed atmospheric LOS errors due to relative humidity for 106 ascending and 112 descending images are -3.5 cm and 7,5 cm, respectively.  In fact, we observed that there is a moderate correlation between precipitation/relative humidity and “bad” acquisition in relatively small study area. Nevertheless, we were able to remove 33 ascending and 15 descending images from the queue of consecutive DInSAR. Finally, it allowed to estimate up to 1m subsidence in the period of 1 Jan 2017–8 Oct 2018 in the Rydułtowy mine located in the southwest part of the Upper Silesian Coal Basin (USCB), Poland.

To evaluate our DInSAR accuracy due to atmospheric artefacts, we decided to compare the results with “atmospheric-free” results acquired by SBAS technique. SBAS separates diverse interferometric components that correspond to deformation, topographic error, atmospheric error, and orbital errors.

The Root-Mean-Square Error (RMSE) has been calculated between SBAS and DInSAR for selected subsidence profiles. The maximal RMSE was found to be 3.6 cm and 4.1cm for ascending and descending LOS displacements, respectively. This shows that DInSAR cannot be used for monitoring millimeter-level deformation. On the contrary, it can be effectively used to assess quick nonlinear deformations reaching several decimeters /year such as in the presented study case.
Wood diurnal capacitance, water storage and their anatomical drivers across 30 temperate angiosperm tree species.
Authors: Zieminska Kasia , Rosa Emily , Gleason Sean , Holbrook N. Michele
Published: March 2020

Water released from storage into the transpiration stream (termed: capacitance) can play an important role in tree every day hydraulic functioning as well as in tree drought response. However, anatomical underpinnings of capacitance and water storage remain unclear, impeding better understanding of capacitance mechanisms. Across 30 temperate angiosperm tree species, we measured in natura twig wood diurnal capacitance and water content, wood density and anatomical properties: vessel dimensions, tissue fractions and vessel-tissue contact fractions (proportion of vessel circumference in contact with other tissues). We found that wood density and predawn lumen volumetric water content (proportion of wood volume that is occupied by water in lumen) together were the strongest predictors of capacitance (radj2=0.44***). Vessel-tissue contact fractions—vessel-ray, vessel-axial parenchyma and vessel-fibre—each explained an additional ∼10% of variation in capacitance. Parenchyma fraction did not correlate with capacitance challenging the common assumption that parenchyma acts as the main source of capacitance water. Anatomical structure, water content and capacitance relationships differed significantly between diffuse-porous and ring-porous species. Predawn relative water content (water in a fresh sample relative to saturated sample) was on average 0.65±0.13 implying that parts of wood were devoid of water.
Image of the Iberian Tethys paleomargin beneath the eastern Betic mountain range
Authors: Mancilla Flor de Lis , Morales Jose , Molina-Aguilera Antonio , Stich Daniel , Azañon Jose Miguel , Teixido Teresa , Heit Benjamin , Yuan Xiaohui
Published: March 2020

We obtain P-wave receiver functions from recordings at a dense seismic broadband transect, deployed along 170 km across the eastern Betic orogen in south Spain. Migrated images show the crustal structure of the orogen in detail. In particular, they reveal the situation of the subducted Iberian paleomargin, with full preservation of the proximal domain and the ~50 km wide necking domain. Crustal thinning affects the lower continental crust. The Variscan crust of the Tethys margin is bending downward beneath the Betics, reaching ~45 km depth, and terminates abruptly at a major slab tear fault. The distal domain of the paleomargin cannot be reconstructed, but the migrated section suggests that material has been exhumed through the subduction channel and integrated into the Betic Orogene. This supports an origin of the HP-LT Nevado-Filabride units from subducted, hyperextended Variscan crust.
Role of the deep North Pacific in overturning circulation and carbon cycling
Authors: Chao Weng-Si , Jacobi Lara , Lembke-Jene Lester , Tiedemann Ralf , Nürnberg Dirk
Published: March 2020

At present, the North Pacific constitutes one of the main marine natural carbon sinks and thus helps regulate atmospheric CO2 concentrations. Understanding past changes in North Pacific deep water circulation and biological productivity are of particular importance, since the region likely changed these characteristics on both orbital and millennial time scales, and may have even undergone switches between being a carbon source and sink. We present a suite of new sediment records retrieved from the subarctic Northwest Pacific along the Emperor Seamount Chain in order to contribute to the Pleistocene stratigraphy and reconstruct changes in the physical and biological carbon pump on millennial to orbital timescales. We used high-resolution AMS 14C-derived benthic-planktic (B-P) foraminiferal ventilation ages, and stable carbon and oxygen isotopes of epibenthic foraminifera along both meridional and water depth transects in order to establish deep water ventilation patterns and reconstruct nutrient concentrations over the last 200 ka. We used X-ray fluorescence (XRF)-scanning records combined with radiocarbon dating to correlate prominent patterns between sediment cores, and to develop a stratigraphic framework for the study area. We used changes in Ba/Ti, Ca/Ti, Si/Ti ratios to assess variationsin biological productivity. Biogenic Barium (Ba/Ti) and Calcium (Ca/Ti) ratios generally show high values during interglacials and low values during glacials. This pattern resembles subpolar Northwest Pacific ODP Site 882, which shows a good correlation to the global CO2 record. These results provide evidence for the close link between global climate, the ocean carbon cycle and marine biogeochemistry in North Pacific.
Constraining carbon allocation in a terrestrial ecosystem model using long-term forest biomass time series
Authors: Besnard Simon , Koirala Sujan , Santoro Maurizio , Bao Shanning , Cartus Oliver , Gans Fabian , Jung Martin , Trautmann Tina , Carvalhais Nuno
Published: March 2020

Forests cover about 30% of the terrestrial surface of our planet and store a large part of the terrestrial carbon (C), indicating their fundamental role in terrestrial C dynamics. In recent years, significant advances have been made in understanding terrestrial C cycling across scales, albeit uncertainties remain about fundamental processes, such as photosynthesis, allocation, and mortality, which exert dominant controls on vegetation C dynamics. Allocation plays a critical role in forest ecosystem C cycling by partitioning the products of net photosynthesis into leaves, wood, and below-ground components but is still poorly represented mostly given limitations in process understanding as well as in both suitable and commensurate observations.

Here, we explore different approaches in constraining C allocation alongside processes driving assimilation and out fluxes in a terrestrial ecosystem model based on novel forest biomass datasets. More specifically, we use a series of temporally changing above-ground biomass (AGB) data from local (i.e. in-situ forest inventory data) to global (i.e. long-term C-band satellite retrievals from 1992 to 2018) scales, in a multi-constraint approach. We explore the information contained in a novel AGB time series to diagnose the potential of using changes in vegetation C stocks, jointly with C and water fluxes, to constrain and parameterize different C allocation modeling approaches. Both at FLUXNET site level and global scale, we will: i) present these novel AGB datasets, their strengths and limitations, ii) demonstrate the relevance of constraining C allocation with such temporally changing AGB estimates, and iii) provide a comparison of different C allocation approaches (i.e. fixed versus dynamic allocation, and an hybrid modeling approach) and their implications in representing ecosystem dynamics.
Effects of horizontal hydraulic conductivity distributions on groundwater flow
Authors: Liu Hai , Wagener Thorsten , Rahman Mostaquimur
Published: March 2020

Catchment descriptors are used to quantify and summarise catchment properties, representing the characteristics of a catchment.[ASMMR1]  It is meaningful to study how catchment descriptors relate to the integrated catchment dynamic, e.g. groundwater flow. Hydraulic conductivity (K) is a critical catchment descriptor and driving force for groundwater flow. It is well known that hydraulic conductivity is highly variable in space. Some studies have considered the impact of gradual decrease in hydraulic conductivity with depth on groundwater flow, but few considering the spatial variation in horizontal hydraulic conductivity. The purpose of this study was to investigate the effect of horizontal hydraulic conductivity on groundwater flow with an integrated hydrology model using virtual experiments. 

We study the variability of catchment-scale groundwater flow patterns for virtual catchments with identical average and/or dominant hydraulic conductivities, but different horizontal distributions. The results show that the variation in horizontal hydraulic conductivity influences the formation and development of regional flow patterns. We further study the implications of the variation in horizontal hydraulic conductivity for patterns and rates of recharge and discharge, as well as for the groundwater flux.
Soil Functional Mapping: Using Data-Model Integration to Improve Regional-Scale SOC Forecasts
Authors: Lawrence Corey
Published: March 2020

With advances in the understanding of the mechanisms leading to the persistence or vulnerability of soil organic carbon (SOC) at the profile scale, it is essential to develop infrastructure to integrate this knowledge with landscape-scale mapping and models. To address this need, we are developing a soil functional unit framework, intended to better scale mechanistic soil knowledge by merging geospatial datasets with targeted sample collection and analyses. Here we provide a proof of concept of this approach for SOC stocks (the soil function of interest) in the East River study area located near Gothic, Colorado, USA. We first generate a map estimating SOC stocks based only on available geospatial datasets, including factors such as topography, vegetation, geology, and basic soil maps. We then compare the mapped functional units against an independent SOC dataset of 450 soil profiles (~1700 samples) collected from the study region and refine the soil functional map to best capture the spatial variability observed in the dataset.  With the calibrated soil functional unit mapping algorithm, we can then calculate SOC stocks at landscape scales and better constrain the mechanisms that drive the observed heterogeneity.  The resulting data-driven soil functional maps can then be merged with regional scale SOC models to enhance forecasts of SOC change in response to disturbances.
Late- to post-Variscan magmatism in the Lusatian Block occurred during two short episodes: Evidence from zircon dating
Authors: Käßner Alexandra , Tichomirowa Marion , Lapp Manuel , Leonhardt Dietmar
Published: March 2020

In the Late Carboniferous to Early Permian, post-orogenic processes led to the intrusion of compositionally diverse granitoids and to intense silicic volcanism in Central Europe. In the Lusatian Block, which is situated in the eastern part of the Saxothuringian Zone of the Variscan orogen, the late- to post-Variscan granitoids are subordinate in comparison to the Cadomian basement and late- to post-Variscan volcanic rocks are almost absent. The Lusatian Block is bound towards the NE and the SW by major deep reaching fault zones. Both the granitoid and the volcanic rocks are situated near the boundaries of the block and probably associated with the major NW trending faults of the Elbe Fault Zone (e.g. Hammer et al., 1999, Lisowiec et al., 2014, Oberc-Dziezic et al., 2015). The Elbe Fault Zone is a continental scale zone of crustal weakness that was reactivated with different kinematics at different times (Scheck et al., 2002). 

We acquired new precise CA-ID-TIMS U-Pb zircon ages of the Koenigshain and the Stolpen granites and the volcanics of the Weissig Basin. Our new data show that the Variscan magmatism of the Lusatian Block occurred at two distinct periods, depending on the structures on which they are bound. The age difference between the two groups (12 Myr) is clearly evident in both CA-ID-TIMS and evaporation analyses. Consequently, zircon evaporation data of other granitoid and volcanic rocks that were not dated with CA-ID-TIMS can be assigned to one of the two groups in the Lusatian Block. The new age dating allows comparison of the evolution of the investigated rocks to adjacent Variscan magmatic rocks.

 

References:

Hammer et al. (1999), Z. geol. Wiss 27, 401-415.

Lisowiec et al. (2014), Acta Geologica Polonica 64 (4), 457-472.

Oberc-Dziezic et al. (2015), Int. J. Earth. Sci. 104, 1139-1166.

Scheck et al. (2002), Tectonophysics 360, 281-299.
Linking the core heat content to Earth's accretion history
Authors: Deguen Renaud , Clési Vincent
Published: March 2020

The composition of Earth's mantle, when compared to experimentally determined partitioning coefficients, can be used to constrain the conditions of equilibration - pressure P, temperature T, and oxygen fugacity fO2 - of the metal and silicates during core-mantle differentiation.
This places constraints on the thermal state of the planet during its accretion, and it is tempting to try to use these data to estimate the heat content of the core at the end of accretion. To do so, we develop an analytical model of the thermal evolution of the metal phase during its descent through the solid mantle toward the growing core, taking into account compression heating,   viscous dissipation heating, and heat exchange with the surrounding silicates. For each impact, the model takes as initial condition the pressure and temperature at the base of the magma ocean, and gives the temperature of the metal when it reaches the core. The growth of the planet results in additional pressure increase and compression heating of the core. The thermal model is coupled to a Monte-Carlo inversion of the metal/silicates equilibration conditions (P, T, fO2) in the course of accretion from the abundance of Ni, Co, V and Cr in the mantle, and provides an estimate of the core heat content at the end of accretion for each geochemically successful accretion. The core heat content depends on the mean degree of metal-silicates equilibration, on the mode of metal/silicates separation in the mantle (diapirism, percolation, or dyking), but also very significantly on the shape of the equilibration conditions curve (equilibration P and T vs. fraction of Earth accreted). We find that many accretion histories which are successful in reproducing the mantle composition yield a core that is colder than its current state. Imposing that the temperature of the core at the end of accretion is higher than its current values therefore provides strong constraints on the accretion history. In particular, we find that the core heat content depends significantly on the last stages of accretion. 
Post-earthquake hazard assessments might become rapidly ineffective under rapidly-evolving landslide controls
Authors: Yunus Ali P , Fan Xuanmei , Scaringi Gianvito , Catani Filippo
Published: March 2020

Strong earthquakes, especially on mountain slopes, generate unconsolidated deposits of regolith, prone to remobilization by aftershocks and rainstorms. Assessing the hazard they pose and what controls their remobilizations in the years following the mainshock has not yet been attempted, primarily because of the lack of multitemporal landslide inventories. By exploiting a multitemporal inventory (2005–2018) covering the epicentral region of the 2008 Wenchuan earthquake and a set of predictor variables (seismic, topographic, and hydrological), we perform statistical tests to understand the evolution of controlling factors for debris remobilization in time. Our analyses, supported by a random-forest susceptibility assessment model, reveal a prediction capability of seismic-related variables depleting with time, as opposed to hydro-topographic parameters gaining importance and becoming predominant within a decade. Results may have important implications on the way conventional susceptibility/hazard assessment models should be employed in areas where coseismic landslides are the main sediment production mechanism on slopes.
Soil Organic Carbon Prediction at National Scale (Germany)
Authors: Sakhaee Ali , Gebauer Anika , Ließ Mareike , Don Axel
Published: March 2020

Soil Organic Carbon (SOC) plays a crucial role in agricultural ecosystems. However, its abundance is spatially variable at different scales. In recent years, machine learning (ML) algorithms have become an important tool in the spatial prediction of SOC at regional to continental scales. Particularly in agricultural landscapes, the prediction of SOC is a challenging task.

In this study, our aim is to evaluate the capability of two ML algorithms (Random Forest and Boosted Regression Trees) for topsoil (0 to 30 cm) SOC prediction in soils under agricultural use at national scale for Germany. In order to build the models, 50 environmental covariates representing topography, climate factors, land use as well as soil properties were selected. The SOC data we used was from the German Agricultural Soil inventory (2947 sampling points). A nested 5-fold cross-validation was used for model tuning and evaluation. Hyperparameter tuning for both ML algorithms was done by differential evolution optimization. 

This approach allows exploring an extensive set of field data in combination with state of the art pedometric tools. With a strict validation scheme, the geospatial-model performance was assessed. Current results indicate that the spatial SOC variation is to a minor extent predictable with the considered covariate data (<30% explained variance). This may partly be explained by a non-steady state of SOC content in agricultural soils with environmental drivers. We discuss the challenges of geo-spatial modelling and the value of ML algorithms in pedometrics.
Satellite-based monitoring urban environmental change and its implications in the coupled human-nature system
Authors: Zhou Yuyu , Li Xuecao , Asrar Ghassem , Zhu Zhengyuan , Meng Lin
Published: March 2020

Changes in urban environments play important roles in sustainable urban development. Satellite observations in fine spatial and temporal resolutions, together with new computer technologies, provide the possibility to monitor these changes across large geographic areas and over a long time period. In this study, we developed new algorithms to characterize dynamics of urban extent, urban heat island, and phenology (i.e., onsets of green-up and senescence phases) and successfully implemented them on the advanced Google Earth Engine, a start-of-art platform for planetary-scale data analysis, mapping, and modelling. The evaluation indicates that the proposed algorithms are robust and perform well in deriving changes in urban environments. Finally, we explored the implications of urban environment changes in the coupled human-nature system by investigating the responses of building energy use and pollen season to these changes. The resulted products of annual dynamics of urban extents, urban heat island, and phenology indicators from this study offer new datasets for relevant urban studies such as modeling urban sprawl over large areas and investigating ecosystem responses and human activities to urbanization.
Boreal forest carbon exchange and growth recovery after the summer 2018 drought
Authors: Linderson Maj-Lena , Holst Jutta , Heliasz Michal , Klemedtsson Leif , Klosterhalfen Anne , Krasnova Alisa , Läänelaid Alar , Linderson Hans , Martínez García Eduardo , Mölder Meelis , Peichl Matthias , Soosaar Kaido , Tung Chen Tzu , Vestin Patrik , Weslien Per , Lindroth Anders
Published: March 2020

In summer 2018, Northern Europe experienced an extreme summer drought in combination with unusually high temperatures, which had a substantial impact on agricultural yields as well as on forest growth conditions in various ways. An ongoing study, using ICOS and other forest ecosystem stations in the Nordic region, shows that the drought dramatically decreased NEP in the southern Scandinavian and Baltic region, almost nullifying the carbon sinks in some of the forests. However, some of the forests that not were exposed to the most extreme drought actually increased their NEP because of the high evaporative demand. Such severe conditions during a single year could be expected to influence a forest over several following years. Reduced tree storage of carbohydrates leads to a changed carbon allocation pattern in spring that may affect both the woody growth and the resistance to pests. It is thus important to reveal the impact of such climatic events over a longer period.    

This study aims at assessing the carry-over effects of the extreme weather conditions on the carbon fluxes and the forest growth to the year after the event, 2019. The base of the analysis will be eddy covariance data combined with tree ring time series from measurement stations that has been shown to be significantly affected by the drought through reduced carbon fluxes: the spruce forests Hyltemossa and Skogaryd and the mixed forests Norunda, Svartberget, Soontaga and Rumperöd. The eddy covariance and tree ring data will be used to assess the forest ecosystem carbon fluxes and growth recovery in 2019 by comparisons to earlier normal years and extreme events.
Downstream persistence of particulate organic carbon released from thaw slumps on the Peel Plateau, NT, Canada
Authors: Shakil Sarah , Tank Suzanne , Kokelj Steve , Vonk Jorien
Published: March 2020

Underlain by ice-rich permafrost, the Peel Plateau in western Canada is highly susceptible to rapid permafrost degradation in the form of retrogressive thaw slumps and has experienced a non-linear intensification in the area, volume, and thickness of permafrost thawed since 2002. These slumps tend to occur along stream networks, which flow directly into the Peel River, through the Mackenzie Delta, and into the Beaufort Sea. Thus, lateral transport of previously sequestered organic carbon from these features has the potential to propagate far downstream. Upstream-downstream comparisons have shown that thaw slumps mobilize material to stream systems primarily in the form of particulate organic carbon (POC), increasing organic carbon yields by orders of magnitude, and switching stream networks to particle-dominated systems. Furthermore, the bulk POC released from slumps can be upwards of 10,000 14C years old, and base-extracted fluorescence measurements suggest material is more reworked since terrestrial production compared to upstream material.

To determine how far this effect propagates downstream we measured particulate and dissolved organic carbon (DOC) fluxes across stream transects extending 0.4 to 1 km downstream of thaw slumps in 1st to 2nd order streams and found no consistent decrease in TSS or POC fluxes with transit downstream.  In addition, we measured the composition (%POC, C:N, fluorescence, D14C) and flux of DOC and POC within the ~1100 km2 Stony Creek watershed, examining tributary streams representing different vegetative, slump-density, and geological units in addition to the Stony Creek mainstem, to determine contributions to downstream flux. We found organic carbon fluxes were dominated by slump-mobilized POC at all points downstream of disturbance, and that these organic carbon fluxes were greater than any non-disturbed tributary stream. The 14C age of POC along the Stony Creek mainstem increased by thousands of years with the introduction of slump inputs and remained similarly depleted in 14C at the watershed outlet. Using historical suspended sediment, POC, and discharge data for the 75,000 km2 Peel River drainage basin containing the Stony Creek watershed, we will examine whether there have been increases in instantaneous sediment and POC fluxes during the thaw season to track the trends of intensifying slump activity that have been documented on the Peel Plateau. Constraining the downstream effect of these abrupt, localized disturbances may improve detection and prediction of change that will likely cascade through the region over the coming decades.
Estimation of soil moisture from Sentinel data
Authors: Krebs Lange-Willman Stefan , Skriver Henning , Sandholt Inge
Published: March 2020

The present project presents the technical implementation, testing and validation of a soil moisture retrieval algorithm in Python using C-band Sentinel-1 data at high incidence angle (∼42°). The retrieval algorithm is based on the alpha approximation, first developed by [Balenzano et al. 2011]. The alpha approximation utilizes the dense temporal coverage of the Sentinel-1 mission, assuming that changes in backscatter between subsequent acquisitions are only due to variations in soil moisture, such that vegetation and roughness can be neglected. The area used for testing the algorithm was chosen to be the region surrounding the Foulum test center for agricultural studies in Denmark, due to the availability of time series from 2018 of in situ soil moisture measurements to be used for validation. Masking of too densely vegetated areas have been performed using the cross-polarized component of the SAR backscatter, which have been validated using NDVI maps. 

Auxiliary data, including land cover maps and parcel borders enable the computation of backscatter field means, significantly reducing the impact of speckle noise and thus decreasing uncertainty of the estimated soil moisture. Consequently, the results have field scale resolution (i.e. ∼0.1 km). The permittivity to soil moisture inversion is performed using a polynomial model by [Hallikainen et al. 1985], where a soil texture map provide the information necessary to obtain precise results. 

Further work will aim toward applying a change detection algorithm in order to detect sudden temporal changes in vegetation and surface roughness, as the alpha approximation is inherently sensitive to such sudden changes.

The study has received partial funding from Innovation Fund Denmark, contract number: 7049-00004B (MOIST).
New methodology for mapping wildfire risk in the wildland-urban interface
Authors: Taccaliti Flavio , Marzano Raffaella , Rizzolo Rolando , Bell Tina , Fischetti Domenico , Lingua Emanuele
Published: March 2020

Wildfires pose a great threat to the wildland-urban interface (WUI), the zone of contact between wildland vegetation and the human-settled environment. In these areas, high fuel loads often coexist with high value assets, which are more exposed to ignition than equivalent structures in an urban context. At the WUI, wildfires can quickly exhaust the resources normally available to urban firefighters, and the value of assets do not allow the use of large-scale, resource-saving techniques common in wildland fires management.

Mapping the WUI represents a first important step in wildfire risk management due to the primary importance of prevention in a setting that is difficult to defend in the face of emergencies. In addition, as the WUI is not only a possible target for wildfires, it is often a source of them, prevention of fire in these areas is a critical part of risk management.

Several methods are currently available to detect and map the WUI, differing according to the scale and the scope of the analysis. Pioneering methods mainly used aggregated data (e.g. census data, large scale vegetation maps) while recent techniques are increasingly using high precision remote sensing data to identify single structures and local changes in topography and vegetation.

In the context of the UE Interreg project Italia-Slovenija CROSSIT SAFER, a new methodology will be described to analyse and map wildfire risk at the WUI relying on state-of-the-art data and technologies. Specifically, high precision LiDAR data and segmentation processes are used to characterise wildland fuel precisely and efficiently.
Influence of foreshock electrons impact ionization on the amplitude of pickup protons generated waves at Mars
Authors: Mazelle Christian , Meziane Karim , Romanelli Norberto , Mitchell David L. , Ruhunisiri Suranga , Madanian Hadi , Rahmati Ali , Schwartz Steven J. , Espley Jared R. , Halekas Jasper S. , Penou Emmanuel
Published: March 2020

Using MAVEN observations, we report variations of the amplitude of electromagnetic waves observed at the local proton cyclotron frequency upstream from the bow shock on short (plasma) time/length-scales: 1) a sharp sudden increase of the amplitude when crossing the electron foreshock boundary and 2) a decrease of this amplitude clearly correlated with the increasing distance from the shock along the magnetic field inside the foreshock without any simple relation to the planetary radial distance. These waves are excited by unstable ring-beam velocity distributions of newborn protons produced by ionization of exospheric hydrogen atoms. The amplitude of these waves is generally expected to depend only on different drivers including the observed large seasonality of the hydrogen exosphere, the EUV solar flux, the solar wind density and velocity or the IMF cone angle at different levels of importance. No noticeable wave amplitude change is expected when crossing the electron foreshock boundary and inside the pure electron foreshock. Surprisingly, we found that that these waves also display the two same aforementioned properties as the foreshock electrons fluxes at Mars though the wave origin is related to the ions only. We investigate the possibility that the extra free energy necessary to increase the wave amplitude could be due to supplementary ionization of hydrogen atoms by electron impact ionization inside the foreshock. Therefore, the electron foreshock also plays a role in the production of pickup protons which contribute to the planetary escape from high altitude.
Greenland ice sheet contribution to 21st century sea level rise as modelled by the coupled CESM2.1-CISM2.1
Authors: Muntjewerf Laura , Petrini Michele , Vizcaino Miren , Ernani da Silva Carolina , Sellevold Raymond , Scherrenberg Meike , Thayer-Calder Katherine , Bradley Sarah , Lenaerts Jan , Lipscomb William , Lofverstrom Marcus
Published: March 2020

With the Community Earth System Model version 2.1 (CESM2.1) interactively coupled to the evolving Greenland Ice Sheet as simulated by the Community Ice Sheet Model version 2.1 (CISM2.1), we examine the Greenland Ice Sheet (GrIS) mass balance. The model has been run for the period 1850-2100 with historical and SSP5-8.5 scenario forcing, contributing to the coupled experiments within the framework of the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6) (Nowicki et al., 2016).

CESM2.1-CISM2.1 simulates a relatively strong global warming signal and strong weakening of meridional overturning circulation by 2100 compared to CMIP5 models. In our projection, the GrIS contributes 23 mm sea-level equivalent by 2050, and 109 mm by 2100, to global mean sea level rise. The southern GrIS drainage basins contribute 73% of the mass loss by mid-century, but the contribution decreases to 55% by 2100, as surface runoff in the northern basins progressively increases.
Unusual Atmospheric-River-like structures coming from Africa induce extreme precipitation over western Mediterranean Sea
Authors: Lorente-Plazas Raquel , Ramos Alexandre M. , Montávez Juan P. , Jerez Sonia , Trigo Ricardo M. , Jimenez-Guerrero Pedro
Published: March 2020

Long filaments of high integrated water vapor transport (IVT) content, widely known as atmospheric rivers (ARs), play a relevant role in the water cycle being also associated with many extreme flooding events worldwide. In this work, we inspect whether similar structures can be found over the western Mediterranean. The methodology used here to detect these AR-like structures is based on standard ARs detection methods but imposing a strong IVT advection westward component. The ERA5 global reanalysis and Spain02 high resolution gridded observational dataset are used, covering the period 1979-2017, to analyze the composites of mesoscale features and associated impacts on rainfall.

Results show that AR-like structures over the Mediterranean (abbreviated here Med-ARs) have relatively low incidence with an approximately once-per-year frequency. Nevertheless, these rare events are usually associated with extreme precipitation, often amplified by orographic features, contributing to more than 40% to the annual precipitation in some cases (Lorente-Plazas et al., 2020). During a typical Med‐AR, the value of IVT increases significantly due to high horizontal winds and water vapor contents. Med-ARs are always associated to the placement of a cutoff cyclone with the cold core over northwestern Africa and warmer air mass over northern Europe. The vertical structure of Med-ARs suggests an occluded front with a low-level jet in the warmer front where Med‐ARs reside and, moisture penetrating into high atmospheric levels where cold and warm front intersect leading to severe convection. To sum up, long filaments of IVT can be found over the western Mediterranean Sea, traveling in an east-west direction, playing a relevant role in hydrometeorological impacts. Although these structures share some features with ARs over the Pacific/Atlantic Ocean they present so many specific characteristics that can be also considered to constitute a variant of this well-established meteorological phenomenon.

 

Acknowledgments

The author would like to acknowledge the financial support by Fundação para a Ciência e Tecnologia (FCT) through project UIDB/50019/2020 – IDL. A. M. Ramos was supported by the Scientific Employment Stimulus 2017 from FCT (CEECIND/00027/2017).

 

References

Lorente-Plazas, R., Montavez, J. P., Ramos, A. M., Jerez, S., Trigo, R. M., & Jimenez-Guerrero, P. (2019). Unusual Atmospheric-River-like structures coming from Africa induce extreme precipitation over western Mediterranean Sea. Journal of Geophysical Research: Atmospheres, 124. doi: 10.1029/2019JD031280
A new deep-time historical perspective of the terrestrial water cycle that is needed to solve UPH #1:
Authors: Sterling Shannon
Published: March 2020

This work could contribute to solve UPH #1: is the hydrological cycle regionally accelerating/decelerating under climate and environmental change, and are there tipping points (irreversible changes)?

This fundamental question hinges upon the Nature of the hydrologic cycle itself, and for which a geological perspective is needed.  To begin to solve this problem, we thus must have a clear picture of how the water cycle has changed throughout Earth’s History.  However, current narratives of the history of Earth's water cycle lack a coherent description of how life altered water cycling on land. Here I review a body of evidence of plant evolution events in Earth's history and propose how rainfall runoff mechanisms evolved through five key evolutionary phases.  This review reveals that for most of Earth's history, water cycling on land was likely very different from today, with fewer mechanisms available to store water between rainfall events in the critical surface zone, with implications for water availability and surface climate.  A key tipping point occurred during the Silurian-Devonian periods with the greening of the planet. This deep-time perspective illustrates the step-by-step process through which plants optimized the water cycle in which it increased the distribution in space and time, culminating in the development of forests in the late Devonian. Lastly, I review how the past may serve as a key to the future, discussing how the historical perspective illustrates key areas needed to improve our current conceptualization of water availability so that we may better understand and predict changes of water availability during the Anthropocene.
A comparison of legacy and recently acquired multichannel seismic data on 95 Ma Pacific oceanic crust south of the Hawaiian Islands
Authors: Cilli Phil , Watts Tony , Boston Brian , Shillington Donna
Published: March 2020

The oceanic crust in the vicinity of the Hawaiian Islands is of tectonic interest because it formed at a fast spreading mid-oceanic ridge during the Late Cretaceous (Turonian) and has been deformed since the Late Miocene by volcanic loads generated at a deep mantle hotspot. We have used legacy and recently acquired multichannel seismic reflection data to determine the character of oceanic crust and the Moho in a region south of the Hawaiian Islands where the Pacific plate has been flexed upwards partly by volcano loading and partly by the dynamics of the hotspot. The legacy data is based on Common Depth Point (CDP) and Constant Offset Profile (COP) data acquired onboard R/V Robert D. Conrad and R/V Kana Keoki during August/September 1982. Conrad was equipped with a 3.6 km long streamer and a 1864 cu. in. airgun array and Kana Keoki was equipped with a 1864 cu. in. array. During the COP experiment the two ships steamed on a similar heading and a separation distance of 3.6 km, yielding an effective offset for reflection data of 7.2 km. Original field data have been re-processed with ‘state-of-the-art’ seismic processing work flows using Shearwater REVEAL software. The recently acquired data was acquired during October 2018 with R/V Marcus G. Langseth, equipped with a 15 km long streamer and a 6600 cu. in. airgun array. Comparisons between the legacy and recently acquired reflection data have been informative, revealing new methods to process Conrad’s legacy of multichannel data acquired on 31 cruises during 1975 to 1989 and new insights on the structure and nature of the Moho in 95 Ma oceanic crust.
Diapycnal diffusivity induced by the breaking of lee waves
Authors: Eriksen Thomas , Eden Carsten , Olbers Dirk
Published: March 2020

A key component in setting the large scale ocean circulation is the process of diapycnal mixing, since this can drive the meridional overturning circulation. Diapycnal mixing in the interior ocean is predominantly associated with the breaking of internal waves. Traditionally, diapycnal mixing has been represented in ocean models by a diapycnal diffusivity either constant or exponentially decreasing with depth. This approach, however, does not take into account the actual physics behind the breaking of internal waves. The energetically consistent internal wave model IDEMIX (Internal wave Dissipation, Energetics and MIXing), on the other hand, computes diffusivities directly on the basis of internal wave energetics. One such type of internal waves are lee waves. These are generated and subsequently dissipated when geostrophic currents interact with bottom topography and are therefore believed to be a source of energy for deep ocean mixing. In this study IDEMIX is coupled to a 1/12th degree regional model of the Atlantic. The lee wave energy flux is calculated and used as a bottom flux at each time step effectively allowing lee waves to propagate, interact with mean flow and waves, and subsequently dissipate. This setup enables not only an estimate of the lee wave energy flux but also a direct investigation of the influence of lee waves on dissipation, stratification and horizontal and overturning circulation.
Application of Copernicus Global Land Service vegetation parameters and ESA soil moisture data to analyze changes in vegetation with respect to the CORINE database
Authors: Breuer Hajnalka , Szabó Amanda Imola
Published: March 2020

Vegetation and soil moisture monitoring are complicated and expensive with in-situ measurements thus remote sensing is a favorable tool to monitor changes in the land surface. Under the supervision of the European Environment Agency and the Joint Research Centre the Copernicus Global Land Service (GLS) became a prominent service providing satellite data for climatological purposes. In this study the Copernicus GLS provided leaf area index (LAI) and dry matter productivity (DMP) data are used at 1 km resolution over Europe. Based on the LAI, growing season start and length is also determined. Around 18 years of data (2000-2018) is analyzed to look for changes in vegetation. Using the CORINE land cover categories changes in vegetation parameters are also analyzed by differentiating between land cover categories. Furthermore, the ESA (European Space Agency) Climate Change Initiative soil moisture data is coupled with the changes in vegetation parameters. In the case of soil moisture, the data is available at a 0.25° resolution, therefore vegetation parameters are interpolated accordingly.

Initial results show, that the maximum value of LAI increases the most in North Europe, the increase is almost linear. Changes in LAI derived start of growing season shows an earlier start in Central Europe and a later start in North Europe. The connection between vegetation parameters and soil moisture varies based on land cover and location. The strongest correlation is found for summer soil moisture and autumn LAI for arable lands and a negative correlation is found for shrublands.    