bluuebunny/crossref_metadata_2025 huggingface dataset:
Warm water flow and mixing beneath Thwaites Glacier ice shelf, West Antarctica
Authors: Wåhlin Anna , Queste Bastien , Graham Alastair , Hogan Kelly , Boehme Lars , Heywood Karen , Larter Robert , Pettit Erin , Wellner Julia
Published: March 2020

The fate of the West Antarctic Ice Sheet is the largest remaining uncertainty in predicting sea-level rise through the next century, and its most vulnerable and rapidly changing outlet is Thwaites Glacier . Because the seabed slope under the glacier is retrograde (downhill inland), ice discharge from Thwaites Glacier is potentially unstable to melting of the underside of its floating ice shelf and grounding line retreat, both of which are enhanced by warm ocean water circulating underneath the ice shelf. Recent observations show surprising spatial variations in melt rates, indicating significant knowledge gaps in our understanding of the processes at the base of the ice shelf. Here we present the first direct observations of ocean temperature, salinity, and oxygen underneath Thwaites ice shelf collected by an autonomous underwater vehicle, a Kongsberg Hugin AUV. These observations show that while the western part of Thwaites has outflow of meltwater-enriched circumpolar deep water found in the main trough leading to Thwaites, the deep water (> 1000 m) underneath the central part of the ice shelf is in connection with Pine Island Bay - a previously unknown westward branch of warm deep water flow. Mid-depth water (700 - 1000 m) enters the cavity from both sides of a buttressing point and large spatial gradients of salinity and temperature indicate that this is a region of active mixing processes. The observations challenge conceptual models of ice-ocean interactions at glacier grounding zones and identify a main buttressing point as a vulnerable region of change currently under attack by warm water inflow from all sides: a scenario that may lead to ungrounding and retreat more quickly than previously expected.
Origami and space research: classroom activities
Authors: Budinski Natalija
Published: March 2020

When origami is mentioned, the first associations are paper cranes.  But origami is much more, and it is actually a mathematical discipline, so powerful that even NASA uses origami in its space research. Flat origami, where figures are as such as the above mentioned crane, is full of mathematical problems. There are seven origami axioms, widely known as Huzita-Hatori axioms, that describe creases. They represent the mathematically formal description of origami constructions. But when talking about involving origami and space science, we need to mention Miura folding  This form of origami folding is proposed by Japanese astrophysicist Koryo Miura. Miura-ori is a way of folding paper or another flat surface into smaller area.  In the presentation we describe how we have made Miura-ori folding, how we 3D printed and made a model of a space craft in our classroom. Connecting different disciplines and inquiry students learned about the most recent scientific research and applied their knowledge during the project. 
Environmental sustainability of increasing silk demand in India
Authors: Ricciardi Livia , Karatas Seda , Chiarelli Davide Danilo , Rulli Maria Cristina
Published: March 2020

Natural resources competition between food and cash crops is a current challenge in many developing countries that are experiencing both lack of food availability and a fast growing economy, such as India. Silk industry has always been significant for the Indian economy since it provides high profits and employment. Almost 90% of the world commercial silk production is mulberry silk. Recently, to the aim of increasing silk production in the Country, the Central Silk Board of the Indian Ministry of Textile and the Indian Space Research Organization have identified potential suitable areas for mulberry cultivation through horizontal expansion in wastelands. Here, taking India as a case study, we analyse if the current cultivation of mulberry silk and the horizontal expansion of moriculture is environmentally sustainable. To this end, using the present land cover, we use a dynamic spatially distributed crop water balance model evaluating mulberry water requirement, the green and blue water provision and analysing both water scarcity at pixel scale and the impact of present and future moriculture on its increase.

Results show in the baseline scenario some States (e.g. West Bengal, Bihar, Tamil Nadu, Madhya Pradesh, Uttar Pradesh, Karnataka, Telangana) suitable for mulberry horizontal expansion already experiencing water scarcity conditions and high prevalence of malnutrition that will be exacerbated, both on yearly and monthly scale, by increasing moriculture. Other States (i.e. Orissa, Chhattisgarh, Mizoram, Assam, Manipur, Tripura, Meghalaya and Nagaland) show Mulberry expansion as the triggering factor of water scarcity condition. Particularly affected by water scarcity will be the North-Eastern Indian districts where potential mulberry areas are clustered.

The analysis of the population exposure to water scarcity due to mulberry horizontal expansion shows 11 million people potentially affected in India, where more than 65% living in the North-Eastern States. Compared to the total North-Eastern Region inhabitants, affected population accounts for more than the 15%.
Subsurface scattering effects in the ASCAT soil moisture product
Authors: Hahn Sebastian , Wagner Wolfgang , Quast Raphael , Salentinig Andreas
Published: March 2020

Microwave remote sensing has been recognized as an effective method for monitoring soil moisture, since the dielectric properties of a soil medium are strongly connected with the water content held within the soil. As a result, a positive relationship between backscatter measurements from active microwave instruments and soil moisture can be observed. However, it has been noticed that this behavior may change unexpectedly in case of very dry soils and the presence of strong subsurface scatterer. Such anomaly has been found in backscatter measurements from the Advanced Scatterometer (ASCAT) on-board the series of Metop satellites in arid and semi-arid regions. This unusual behavior was detected initially due to strong negative correlations in validation studies of the ASCAT soil moisture product, which is derived using the TU Wien change detection method. The current formulation of the TU Wien soil moisture retrieval algorithm is not able to model the impact of strong subsurface scattering effects, which leads to a wrong (wet) interpretation of dry soils.

In this study we analyze and evaluate a new method to account for subsurface scattering effects in the TU Wien soil moisture retrieval algorithm. The new approach assumes a negative relationship between backscatter and soil moisture in areas with temporal persistent subsurface scattering effects. More challenging are regions where subsurface scattering only occurs during dry periods, which requires to identify the transition between the alternating backscatter and soil moisture relationship first. In fact, this leads to a V-shaped function between backscatter and soil moisture and requires a reference soil moisture data set to determine the exact time period dominated by subsurface scattering.

The new ASCAT soil moisture product with a better interpretation of subsurface scattering from dry soils is globally validated against other remotely sensed soil moisture products (ESA CCI Passive) and soil moisture information from land surface models (Noah GLDAS). The results indicate that in areas with persistent subsurface scattering the assumed inverse relationship between backscatter and soil moisture compares well to other soil moisture products. Better results are also achieved in areas with a temporal dependency of subsurface scattering, but future work is needed to better characterize the exact time period when scattering mechanism start to mix and shift.
Decadal Sea level Variability in the subtropical South Pacific
Authors: Albrecht Frauke , Pizarro Oscar , Zorita Eduardo
Published: March 2020

Observational altimetry data and data of 18 phase 5 of the Coupled Model Intercomparison Project (CMIP5) are investigated to analyze decadal sea level variability for the subtropical South Pacific. The altimetry data covers the period 1993 to 2017. In order to analyze decadal variability yearly means of detrended data are considered. An Empirical Orthogonal Function (EOF) analysis of the Region 20°S to 60°S is performed in to analyze sea level variablility in the subtropics. The tropical region has been omitted in order to avoid the strong El Niño Southern Oscillation (ENSO) signal masking other subtropical variability in the analysis. The first EOF of the altimetry data shows a clear pattern with a North-South dipole explaining 30% of the variance and the corresponding time series shows a decadal periodicity. The decadal variability of this pattern is reproduced by the CMIP5 models. Analyzing model ocean circulation data show consistent decadal variability in the North-South velocity. As a possible forcing zonal (westerly) surface winds are analyzed. Their pattern confirm Ekman transport to the North (South) in the lower (higher) latitudes, leading to a convergence zone and therefore explaining the sea level rise as seen in the EOF pattern, consistently with the Ekman transport a deep compensatory poleward flow is observed.
Discerning Between Real and Artificial Velocity Change in Time-Dependent Seismic Tomography
Authors: Hobé Alex , Tryggvason Ari , Gudmundsson Olafur ,   SIL Seismological Group
Published: March 2020

Volcanoes and volcanic systems are very dynamic. The influx of new magma, changes in the hydrothermal system, and eruptions produce large changes in the velocity structure. Such changes can be inferred using Time-Dependent Seismic Tomography (TDST), as has been done by multiple authors (e.g. Koulakov et al. 2013, Hobé et al. 2020). Due to the nature of the inversion process inherent to tomographic methods, it is difficult to discern between real and artificial differences between epochs. In TDST, such artificial differences can arise from differences in raypath-geometry (due to differences in station and earthquake distributions), the employed regularization in the inversion process, and errors due to multiple sources (e.g. travel-time picks, and assumptions in the forward model). This study provides two novel ways of inferring the influence of these artificial sources of velocity change in tomographic models: a baseline reconstruction (Hobé et al. 2020) and time-varying reconstructions. These reconstructions are produced for the Krysuvik volcanic system. The velocity differences produced by the "true" data are then compared to those produced in the synthetic reconstructions. We show that the differences in the obtained models cannot solely have been produced artificially and therefore that there must have been significant velocity changes in the area.

References:

Hobé et al. (2020): Imaging the 2010-2011 inflationary source at Krysuvik, SW Iceland, using time-dependent Vp/Vs tomography, WGC 2020, forthcoming

Koulakov et al. (2013): Rapid changes in magma storage beneath the Klyuchevskoy group of volcanoes inferred from time-dependent seismic tomography, J. Volcanol. Geotherm. Res.
Text Mining of Loss Data
Authors: Margutti Jacopo , van den Homberg Marc
Published: March 2020

Structured datasets of loss data, i.e. data on the impact of past natural disasters, are of paramount importance for informing disaster preparedness programs and forecasting the impact of future disasters. Most of existing initiatives aim at manually building such datasets from information of goverments, humanitarian agencies and researchers. Unfortunately, the quality and completeness of such information is often insufficient, especially for small disasters and/or in areas where these organisations are not active. More often, it's local and national newspapers that report on small disasters. In this contribution, we present a series of algorithms to automatically extract structured loss data from online newspapers, even small ones that are not captured by common news aggregator (e.g. Google News). The algorithms are validated both in terms of accuracy of extraction and consistency with existing datasets; we argue that they provide a valuable tool to collect loss data in data-poor regions.
Parker Solar Probe Observations of a Dust Trail in the Orbit of 3200 Phaethon
Authors: Battams Karl , Stenborg Guillermo , Howard Russell , Gallagher Brendan , Knight Matthew , Kelley Michael
Published: March 2020

We present details on the first white-light detection of a dust trail following the orbit of asteroid 3200 Phaethon, seen in images recorded by the Wide-field Imager for Parker Solar Probe (WISPR) instrument on the NASA Parker Solar Probe (PSP) mission. In this talk we will present a brief introduction to the PSP mission and the WISPR instrument. We will then show observations returned by WISPR in multiple perihelion 'encounters' that clearly show a diffuse dust trail perfectly aligned with the perihelion portion of the orbit of 3200 Phaethon, recorded while the asteroid itself was near aphelion. We will discuss the physical parameters that we have derived for the dust trail, including its visual magnitude, surface brightness and mass. We also speculate on the relationship of this trail to the Geminid meteor shower, of which Phaethon is assumed to be the parent, and demonstrate why the trail has not been detected visually until now, despite a number of dedicated observing campaigns. We also hope to present initial analyses of the most recent set of WISPR observations (January 2020), where we anticipate the trail should again be visible in the WISPR observations.
Active deformation evidence in the offshore of western Calabria (southern Tyrrhenian Sea) from ultra-resolution multichannel seismic reflection data: results from the Gulf of Sant'Eufemia
Authors: Pepe Fabrizio , Kanari Mor , Burrato Pierfrancesco , Corradino Marta , Duarte Henrique , Ferranti Luigi , Monaco Carmelo , Sacchi Marco , Tibor Gideon
Published: March 2020

An ultra-resolution, multichannel seismic reflection data set was collected during an oceanographic cruise organised in the frame of the “Earthquake Potential of Active Faults using offshore Geological and Morphological Indicators” (EPAF) project, which was founded by the Scientific and Technological Cooperation (Scientific Track 2017) between the Italian Ministry of Foreign Affairs and International Cooperation and the Ministry of Science, Technology and Space of the State of Israel. The data acquisition approach was based on innovative technologies for the offshore imaging of stratigraphy and structures along continental margins with a horizontal and vertical resolution at decimetric scale. In this work, we present the methodology used for the 2D HR-seismic reflection data acquisition and the preliminary interpretation of the data set. The 2D seismic data were acquired onboard the R/V Atlante by using an innovative data acquisition equipment composed by a dual-sources Sparker system and one HR 48-channel, slant streamers, with group spacing variable from 1 to 2 meters, at 10 kHz sampling rate. An innovative navigation system was used to perform all necessary computations to determining real-time positions of sources and receivers. The resolution of the seismic profiles obtained from this experiment is remarkable high respect to previously acquired seismic data for both scientific and industrial purposes. In addition to the seismic imaging, gravity core data were also collected for sedimentological analysis and to give a chronological constraint using radiocarbon datings to the shallower reflectors. The investigated area is located in the western offshore sector of the Calabrian Arc (southern Tyrrhenian Sea) where previous research works, based on multichannel seismic profiles coupled with Chirp profiles, have documented the presence of an active fault system. One of the identified faults was tentatively considered as the source of the Mw 7, 8 September 1905 seismic event that hit with highest macroseismic intensities the western part of central Calabria, and was followed by a tsunami that inundated the coastline between Capo Vaticano and the Angitola plain. On this basis, the earthquake was considered to have a source at sea, but so far, the location, geometry and kinematics of the causative fault are still poorly understood. In this study we provide preliminary results of the most technologically advanced ultra-high-resolution geophysical method used to reveal the 3D faulting pattern, the late Quaternary slip rate and the earthquake potential of the marine fault system located close to the densely populated west coast of Calabria.
Involvement of stakeholders in the selection and implementation of Nature-Based Solutions for hydro-meteorological risk reduction
Authors: Ruangpan Laddaporn , Plavšić Jasna , Voijnovic Zoran , Bahlmann Tobias , Alves Alida , Randelović Anja , Todorović Andrijana , J. Franca Mário
Published: March 2020

The evidence to date shows that hydro-meteorological risks are likely to become more extreme in the foreseeable future. The continuously changing climate has also led to increasing pressure on the environment and human society. For these reasons, effective and sustainable methods for hydro-meteorological risk management are becoming more important. As an umbrella concept, Nature-Based Solutions (NBS) have been promoted due to their potential in reducing hydro-meteorological risk, adapting to climate change, and providing a wide range of co-benefits to nature and human well-being. The procedure of efficient planning and selection of NBS is a complex process that requires the involvement of multiple stakeholders. Measures need to be evaluated taking into account their primary function for hydro-meteorological risk reduction, potential co-benefits and specific local requirements. This paper presents a methodology to select NBS measures for reducing hydro-meteorological risk and increase co-benefits at the river basin scale. This is achieved by using stakeholder opinion to identify the importance of benefits and NBS in the area under consideration. A broad range of benefits has been included, such as risk reduction, water quality, habitat structure, biodiversity, socio-economic, and human well-being. This methodology has been applied to the case study of Tamnava River Basin in Serbia from RECONECT project. The results from this case study highlight the importance of involving local stakeholders in early stages of selection and implementation of NBS as part of the wider stakeholder co-creation process. The results also indicate the potential of the new methodology to assist decision-makers in the selection and implementation of NBS.
Seismicity in the Northern German basin - from simple model to complex regime
Authors: Mokelke Gregor , Joswig Manfred
Published: March 2020

The Nothern German basin was considered aseismic in most of the seismic hazard maps of last century. Then seismic events occurred in the last decades, and were located in the vicinity of gas production. Until now more than 70 earthquakes are documented with magnitudes ranging from ML 1.0 to 4.5. Especially the 2004 Rotenburg ML 4.5 event caused much concern, and first locations of different authors disagreed in depth. Dahm et al (2007) argued for 5 km depth close to the horizons of gas production, and suggested a depletion-induced event. Macroseismic studies and other authors, however, determined focal depths of 8-12 km, clearly below gas production.
Within the last 15 years new stations from BGR (Bundesanstalt für Geologie und Rohstoffe) and the BVEG (Bundesverband Erdöl, Erdgas und Geoenergie e.V.) were established in the region between Cloppenburg and Soltau. Our own work is based on a small-scaled, but dense network with arrays and single stations that were installed from 2014 to 2018 in the eastern central part of the gas fields near Rotenburg. Results resolve that seismic activity can occur in a great range of depths down to 30 km, and it is not exclusively focussed on the reservoir horizons. We found strong dependence of depth determinations from parameter settings – notably vP/vS – and station selection. Besides obvious mis-locations of weak, low SNR events based on few phase readings we also traced this dependency back to the 2004 Rotenburg event which at that time was recorded only by a sparse network of remote stations.
In summary, the Northern German basin offers a complex regime of weak seismicity, ranging from single low-crust earthquakes to frequent, induced events of gas production. The 2004 Rotenburg event does not fit either category, and geomechanical modelling will be needed to decide on its relation to gas production.
Volatile Organic Compounds in the atmosphere of the Great Athens area: The case of a port site close to Piraeus, Greece
Authors: Liakakou Eleni , Panopoulou Anastasia , Grivas Georgios , Sauvage Stéphane , Kritikou Theodora , Gerasopoulos Evangelos , Mihalopoulos Nikolaos
Published: March 2020

VOCs are key atmospheric constituents for both health and climate issues and further knowledge is still needed about their sources and fate. The presence of volatile organic compounds in ambient air is strongly dependent on the site characteristics and a harbor area undergoes many source typologies such as road transport, ship emissions and contaminants of commercial activities, the shipbuilding zone and other operating facilities. The current work was implemented at the recently established Atmospheric Pollution Monitoring Station of the Municipality of Keratsini-Drapetsona located in the close vicinity of the Piraeus port. Since December 2018 an automatic gas chromatograph with flame ionization detector (FID) continuously monitors at a 30 minutes time resolution non methane hydrocarbons (NMHCs) focusing on hazardous compounds (aromatics) and strong precursors (aromatics, monoterpenes) of secondary pollutants like ozone and secondary organic aerosols. High levels of benzene were observed, especially during the morning to noon period, and the mean concentration of both benzene and toluene were two-folded in summer (July and August 2019) compared to winter (January and February 2019). Ethylbenzene follows the same pattern, whereas xylenes presented comparable levels during the cold and warm periods. Preliminary results based on source apportionment techniques are presented. In general terms the NMHC levels present their maximum under the impact of low wind speed, addressing thus the role of local emission sources, which are further investigated by the ratios used as tracking tools of processes of different origin (e.g. the traffic related ratio of toluene/benzene).
What does really happen in a dust impact?
Authors: Kempf Sascha , Goode William , Srama Ralf , Postberg Frank
Published: March 2020

Our current understanding of the solar system’s micrometeoroid environment relies to a substantial extent on in-situ data acquired by impact ionization dust detectors such as Ulysses’ and Galileo’s DDS or Cassini’s CDA. Such detectors derive the mass and speed of striking dust particles from the properties and evolution of the plasma created upon impact. In particular, empirical evidence suggests that the impact speed is a function of the duration of impact charge delivery onto the target - the so-called plasma rise time. Often, this dependence has been attributed to secondary impacts of target and projectile ejecta. 

During recent years the capabilities of laboratory impact detectors have been significantly improved. In particular we now have ample evidence that secondary ejecta impacts are not responsible for the rise-time dependence. In fact the plasma rise-time is rather related to the ionization of target contaminants in the vicinity of the impact site. 

In this talk we present new experimental data obtained with state-of-the-art impact ionization mass spectrometers, which shed new light on what is really going on during a hypervelocity dust impact. We further discuss the implications for the interpretation of dust data obtained with previous generations of impact ionization detectors.
Listening to glaciers in Greenland
Authors: Evers Läslo G. , Smets Pieter S.M. , Shani-Kadmiel Shahar , Assink Jelle D.
Published: March 2020

Inaudible sound, i.e., infrasound, from glaciers is generated by glacier run-off and during calving events. Such sounds can be continuously monitored with microbarometer arrays. Changes in the rate of events can be retrieved with a resolution of a few seconds. Applying array processing techniques enables the identification of individual glaciers over ranges of tens of kilometers. We concentrated on the remote region around Qaanaaq in northwestern Greenland and found coherent infrasound of at least five glaciers over a period of 16 years. Knowledge on the dynamical behavior of these remote glaciers, and other glaciers, is important for assessing hazards due to glacier melt and calving, mass balance of ice sheets and consequently sea level rise. Here we use a novel technique involving passive infrasound measurements to show that remote land and sea terminating glaciers behave differently in terms of their temporal behavior during the seasons and years. Strong fluctuations in infrasonic activity are found over time, with the highest activity rates in 2019. Increased activity over the years of the land- ans sea-terminated glaciers is retrieved. We anticipate that monitoring glacier infrasound can contribute to complementary knowledge of the behavior of remote glaciers, as the glacial dynamics can be passively observed on a fine temporal scale.
White-light observations of features in the Zodiacal dust cloud from within the solar corona
Authors: Howard Russell , Stenborg Guillermo , Hess Phil , Gallagher Brendan , Battams Karl
Published: March 2020

The Parker Solar Probe (PSP) mission has completed four solar encounters, observing the solar corona from distances significantly closer to the Sun than from previous missions (to 36 solar radii during the first three perihelia and to 28 solar radii during the fourth). During these encounters, the Wide-field Imager for Solar Probe (WISPR) onboard PSP has been observing the F-corona/Zodiacal light - probing the dust environment in the solar corona as PSP moves through the corona. This allowed WISPR to find 1) a gradual decrease of the expected brightness of the F-corona for distances shorter than about 0.1 AU, 2) dust trails of short-period asteroid/cometary objects (e.g., 3200 Pheathon and 2P/Encke) and 3) a changing rate of dust impacts on the S/C throughout the encounter period. In this presentation, we will present these findings, discuss their nature, and elaborate on the novelty of these results. The authors acknowledge support from the NASA Parker Solar Probe program.
XPS-like evaluation of valence-to-core X-ray emission spectra of germanates
Authors: Spiekermann Georg
Published: March 2020

With this work, we aim at exploring the extent to which valence-to-core X-ray emission spectroscopy (vtc-XES) can provide this first- and second-coordination-shell information from amorphous germanium oxides.

We measured the vtc-XES spectra of germanium oxides at ambient and high pressure. The Kbeta’’ emission line, part of the vtc-XES spectra, is sensitive to coordination and oxygen-germanium bond distance as first coordination shell effects. Furthermore, it reflects the different binding energies of bridging and non-bridging oxygen atoms. The Kb’’ emission line may thus allow for tracking the coordination and the state of polymerization of a germanium oxide glass under pressure in diamond anvil cells or in other confining environments.

 

Spiekermann et al. (2019) Persistent octahedral coordination in amorphous GeO2 up to 100 GPa revealed by Kbeta'' X-ray emission spectroscopy, Physical Review X, 9, 011025.
Improving flood damage assessments in data-scarce areas by retrieving building characteristics through automated UAV image processing
Authors: de Moel Hans , Wouters Lucas , de Ruiter Marleen , Couasnon Anais , van den Homberg Marc , Teklesadik Aklilu , Margutti Jacopo
Published: March 2020

Reliable information on building stock and its vulnerability is important for understanding societal exposure to flooding and other natural hazards. Unfortunately, this often lacks in developing countries, resulting in flood damage assessments that use aggregated information collected on a national- or district level. In many instances, this information does not provide a representation of the built environment, nor its characteristics. This study aims to improve current assessments of flood damage by extracting structural characteristics on an individual building level and estimating flood damage based on its related susceptibility. An Object-Based Image Analysis (OBIA) of high-resolution drone imagery is carried out, after which a machine learning algorithm is used to classify building types and outline building shapes. This is applied to local stage-dependent damage curves. To estimate damage, the flood impact is based on the flood extent of the 2019 mid-January floods in Malawi, derived from satellite remote sensing. Corresponding water depth is extracted from this inundation map and taken as the damaging hydrological parameter in the model. The approach is applied to three villages in a flood-prone area in the Southern Shire basin in Malawi. By comparing the estimated damage from the individual object approach with an aggregated land-use approach, we highlight the potential for very detailed and local damage assessments using drone imagery in low accessible and dynamic environments. The results show that the different approaches on exposed elements make a significant difference in damage estimation and we make recommendations for future assessments in similar areas and scales.
Reduced tree growth in the semiarid United States due to asymmetric responses to intensifying precipitation extremes
Authors: Dannenberg Matthew , Wise Erika , Smith William
Published: March 2020

Earth’s hydroclimatic variability is increasing, with changes in the frequency of extreme events that may negatively affect forest ecosystems. We examined possible consequences of changing precipitation variability using tree rings in the conterminous U.S. While many growth records showed either little evidence of precipitation limitation or linear relationships to precipitation, growth of some species (particularly those in semiarid regions) responded asymmetrically to precipitation, such that tree growth reductions during dry years were greater than, and not compensated by, increases during wet years. The U.S. Southwest in particular showed both a large increase in precipitation variability coupled with asymmetric responses of growth to precipitation. Simulations suggested roughly a two-fold increase in the probability of large negative growth anomalies across the Southwest resulting solely from 20th century increases in the variability of cool-season precipitation. Models project continued increases in precipitation variability, portending future growth reductions across semiarid forests of the western U.S.
Inferring deglacial ventilation ages in Western Mediterranean waters using cold-water corals
Authors: de la Fuente Maria , Skinner Luke , Ercilla Gemma , d'Acremont Elia , Somoza Luis , González Sanz Francisco Javier , Lo Iacono Claudio , Corbera Guillem , Pena Leopoldo D. , Sadekov Aleksey , Scott Pete , Zhang Pu , Cheng Hai , Cacho Isabel
Published: March 2020

Mediterranean Outflow Water (MOW) acts as a net source of salt and heat into North Atlantic intermediate depths that ultimately contributes to the Atlantic Meridional Overturning Circulation. On this basis, it has been hypothesised that MOW variability might influence global climate. Although several studies have documented major glacial-interglacial changes in deep- and intermediate Mediterranean circulation patterns, little is known about associated impacts on MOW properties, in particular its residence time and geochemical signature. Using a set of cold-water coral samples from along the ‘pre-MOW’ and MOW path, i.e. from the Alboran Sea to the northern Galician Bank including the Strait of Gibraltar and the Gulf of Cadiz, we aim to identify changes in both the ventilation state of the water masses flowing out of the Mediterranean and the distribution of coral growth.With this purpose, paired Uranium-series and AMS radiocarbon ages have been obtained in the same coral samples allowing any potential change in the reservoir age to be inferred accurately, as well as allowing a spatio-temporal ‘coral map’ to be created. Furthermore, these results have been complemented by trace element measurements in benthic foraminifera from the Alboran coral mound sediment core.

Our results show a particular spatio-temporal coral distribution with glacial presence only at the deepest sites of the Gulf of Cadiz (~1000m), followed by ~300m Western Mediterranean (WMed) coral appearance across the deglaciation/mid Holocene (14-4 kyr), to end with a proliferation at the Strait of Gibraltar and Galicia Bank from ~6 kyr towards the present. We hypothesise 1) that ~300m WMed area might have been bathed in Atlantic waters inflow during the glacial due to sea-level drop, returning to LIW (Levantine Intermediate Water) influence over the deglaciation, and 2) that MOW reached deeper areas outside of the Mediterranean Sea in the Gulf of Cadiz during the glacial period. Regarding the reservoir age, little change at the WMed is observed at 150-450m across the deglaciation as compared to the large ventilation excursion detected in the Iberian Margin at ~1000m. However, a ventilation age gradient of ~300 yr related to water depth is observed within WMed corals when appearing at the Bølling-Allerød, in synchrony with significant changes in hydrographical parameters inferred from foraminiferal trace element from the same area. Overall, our results suggest a water mass reorganization at the surface-intermediate layer of the WMed during the deglaciation and early Holocene, but the ultimate nature of these changes needs yet to be explored by further analysis of Nd isotopes as well as of trace elements beyond the deglaciation.
New prototype of 6-component seismograph Rotaphone CY: laboratory testing and pilot measurements
Authors: Vackar Jiri , Malek Jiri , Brokesova Johana
Published: March 2020

Rotaphones are seismic sensor systems consisting of parallel pairs of geophones attached to a rigid frame anchored to ground. Such an arrangement allows to measure both translational and rotational ground motions. Translations are measured by individual geophones while rotations are determined using differential records from the paired geophones. The individual geophones are calibrated simultaneously with each measurement utilizing overdetermined rotational components. A new prototype, Rotaphone CY has been recently developed. The design has been improved taking into account experience with field measurements performed using older prototypes. The device is optimized for recording weak ground motions from local microearthquakes, both natural or induced, in a high-frequency range. The instruments were carefully tested in laboratory conditions. Tests were followed by pilot field deployments in various places in the Czech Republic. A local network of six Rotaphones CY has been deployed in the scope of Litomerice geothermal project to investigate induced seismicity related to the production of geothermal energy. The instrument has also been recently deployed at the nuclear power plant Dukovany to monitor local seismicity with the aim to improve seismic hazard estimate. A small-aperture array of four these instruments was installed at the Geophysical Observatory Fürstenfeldbruck, Germany, in the frame of a comparative rotation sensors experiment. Examples of 6-component records from these pilot measurements are shown.
Physical preconditioning of oxygen depletion in shelf seas
Authors: Williams Charlotte , Mahaffey Claire , Palmer Matthew , Greenwood Naomi
Published: March 2020

The global ocean dissolved oxygen (DO) inventory is decreasing and the areal extent of DO deficiency is increasing. In the shelf sea BML, net DO removal can occur as a result of restricted ventilation due to seasonal thermal stratification, oxygen consumption via pelagic and benthic respiration of organic matter, and nitrification. DO decline is becoming evident in several shelf seas, with recent model studies estimating that large regions of the Northwest European continental shelf seas (325,000 to 400,000 km2) have the potential to become seasonally deficient in DO in late summer. It is therefore of vital importance that DO is monitored accurately and effectively in shelf seas.

Here we present results from AlterECO project, which aimed to provide an alternative, novel framework for the monitoring of shelf sea ecosystem health indicators, including DO, via the deployment of 20 gliders in the North Sea (NW European shelf). Between November 2017 and May 2019 the gliders provided 18 month continuous measurements of T, S, chlorophyll fluorescence, and DO in the seasonally stratified study area, capturing the onset and breakdown of two spring blooms. In both years the gliders captured a weakly stratified, deep (>60m) thermocline in late autumn which was responsible for oxygen deplete (75%)  ‘pools’ in the North Sea. Our results show that preconditioning of pre-bloom transitional periods as well as episodic mixing events drive inter-annual differences in BML DO concentrations. Large inter-annual variability between pre-bloom physical conditions was observed, with the occurrence of anticyclone Hartmut in February 2018 resulting in a much colder water column (and therefore higher solubility of DO) in spring 2018 than 2019. Additionally we will demonstrate that the erosion of mini-blooms during the onset of stratification results in mixing of supersaturated DO surface water into the BML, helping to prevent DO deficiency in the BML in late summer. Comparisons of our high resolution glider data with the latest state of the art biogeochemical models (AMM15-ERSEM) will also be presented. We postulate that understanding the drivers of inter-annual variability in pre-bloom physical conditions is crucial in terms of understanding and predicting DO depletion in shelf seas.

 
Future hydrology of Alpine rivers of Italy: the Interreg project GE.RI.KO Mera
Authors: Bocchiola Daniele , Casale Francesca , Stucchi Leonardo , Bombelli Giovanni
Published: March 2020

We present preliminary results in fulfilment of the IT-CH Interreg project “GE.RI.KO Mera”. The main aim of the project is to create a common strategy for the management of common water resources, in the transboundary Mera catchment, laid for ¼ in Switzerland, and for ¾ in Italy. Mera river sources in the Maloja mountains of Switzerland, crosses the Bregaglia valley, and reaches Valchiavenna of Italy, then receiving Liro river’s water, and then flows into the Novate-Mezzola lake, and in Como lake soon after.

This area is particularly important, for hydropower production, and large exploitation of water resources for fishing, and leisure in general.

Bregaglia valley carries large sediment load in the river, which affect aquatic species during floods, and lead to progressive filling of hydropower basins, and sediment accumulation along the river, with potential for increased flood risk, and often need for removal. GE.RI.KO project aims to jointly manage the transboundary waters of the Mera river to i) limit alteration of riverbed morphology and erosion, ii) avoid biodiversity loss, and iii) reduce flood risk along the river.

Here we report modelling of hydrology of this high altitude basin with Poli-Hydro model, and an analysis of future climatic conditions in the area of Valchiavenna for different Representative Concentration Pathways (RCP). We use several RCPs from IPCC’s AR5/6, and several GCMs, for a grand total of 21 climate scenarios (plus local downscaling) to force the Poli-Hydro model to depict future hydrological scenarios in the area.

We report main potential hydrological variations, and depict main challenges for water management in the Mera catchment under future scenarios, to be explored by the GE.RI.KO project.
A supermodel to enhance climate prediction
Authors: Counillon Francois , Keenlyside Noel , Shen Mao-Lin , Koseki Shunya , Devilliers Marion , Gupta Alok , Duane Gregory
Published: March 2020

We present the first results from a supermodel constructed using three state-of-the-art earth system models: NorESM, CESM, MPIESM. A supermodel is an interactive ensemble in which models are optimally combined so that the systematic errors of the individual models compensate to achieve a model with superior performance. In the supermodel, the individual models are synchronized every month using data assimilation to handle the discrepancies of grid, resolution and variable representativity between the models. In particular, we assimilate a pseudo sea surface temperature (SST) that is computed as a weighted combination of the SST of the individual models. The synchronization of the models distinguishes this approach from the standard multi-model ensemble approach in which model outputs are combined a-posteriori. The data assimilation method used is the Ensemble Optimal Interpolation (EnOI) scheme, for which the covariance matrices are constructed from preindustrial control simulations of the individual models. The performances of a first version of the supermodel based on equal weights is compared to the individual models performances for the period 1980 to 2010. Synchronisation of the surface ocean is achieved in most places and dynamical regimes such as ENSO are occurring in phase. The biases of each model are reduced and the pathway of the Gulf Stream improved. The variability of the supermodel is not larger than in the super ensemble mean, but it is shown with an idealized model that the deflation is cause by a misconstruction of the pseudo observation and can be counteracted by perturbing them.  The Perspectives for performing predictions and climate change experiments with the supermodel method are presented and discussed.
Large VOC enhancements in recent massive wildfires observed from space
Authors: Franco Bruno , Clarisse Lieven , Hadji-Lazaro Juliette , Hurtmans Daniel , Lecomte Gilles , Turquety Solène , Clerbaux Cathy , Coheur Pierre-François
Published: March 2020

Massive wildfires erupted in Amazonia and through the subarctic region in summer 2019, and in Australia in winter 2019-2020. During such biomass burning events, sizeable amounts of volatile organic compounds (VOCs) can be emitted directly by the fires as well as rapidly produced in plumes via the degradation of short-lived gas precursors. The VOCs have a significant impact on tropospheric chemistry by, e.g., affecting the oxidative capacity of the atmosphere. Nadir-viewing infrared sensors onboard meteorological satellites provide global and spatially dense observations that are very useful to track biomass burning events throughout the globe and to provide trace gas quantification in fire plumes.

We apply a general retrieval framework, based on an artificial neural network, to derive the integrated abundance (total column) of several major VOCs from the infrared radiance spectra recorded by IASI (Infrared Atmospheric Sounding Interferometer) embarked on the Metop platforms. Quasi-global distributions of methanol (CH3OH), formic (HCOOH) and acetic (CH3COOH) acids, PAN, acetone (CH3COCH3), acetylene (C2H2) and hydrogen cyanide (HCN) column abundance are produced twice-daily from the a.m. and p.m. overpasses of the satellite instrument. In particular, we use the IASI data to produce daily regional snapshots over biomass burning areas of interest and to quantify the VOC enhancements in the plumes from the recent Amazonian, Australian and subarctic wildfires. Finally, the abundance ratios of these VOCs to IASI carbon monoxide (CO) are presented and discussed.
Microbial diversity drives carbon use efficiency in a model soil
Authors: Domeignoz-Horta Luiz A. , Pold Grace , Liu Xiao-jun A. , Frey Serita D. , Melillo Jerry M. , DeAngelis Kristen M.
Published: March 2020

Empirical evidence for the response of soil carbon cycling to the combined effects of warming, drought and diversity loss is scarce. Microbial carbon use efficiency (CUE) plays a central role in regulating the flow of carbon through soil, yet how biotic and abiotic factors interact to drive it remains unclear. Here, we combined distinct community inocula (biotic factor) with different temperature and moisture conditions (abiotic factors) to manipulate microbial diversity and community structure within a model soil system. Abiotic factors indirectly influenced CUE through their impacts on diversity and community structure, which were the strongest predictors of CUE. We also found that abiotic factors modulated the relationship between diversity and CUE, with CUE being positively correlated with bacterial diversity under high moisture. Altogether these results indicate that drier soils diminished the synergistic effect between diversity and CUE, with potential consequences for the fate of C in soils.
New insights on sediment provenance in the Dead Sea since the last glacial maximum using grain-size distribution
Authors: Blanchet Cecile , Jurikova Hana , Fusco Julia , Tjallingii Rik , Schwab Markus , Andermann Christoff , Brauer Achim
Published: March 2020

Sedimentary records from the Dead Sea constitute unique paleoclimatic archives that enable investigating the response of environments to climatic changes. Large lake-level fluctuations (>100 m) occurred during the past glacial-interglacial cycles due to reorganizations of the hydroclimatic regime and drastically modified the morphology of the drainage area. We aim here to reconstruct past sedimentary dynamics at times of varying lake level to gain insights into paleoclimate and landscape evolution.

For this study, we have compared present-day surface sediments (fluvial and soil sediments) retrieved on both the eastern Jordanian and western shores of the present Dead Sea with downcore sediment archives including the ICDP Dead Sea Deep Drilling Program Site 5017-1. Streams originating from various parts of the watershed can be distinguished by their grain-size distribution, with northern and south-western streams having generally finer grain-size modes when compared with streams from the eastern side. We find that all modes identified in the fluvial sediments were present in the ICDP downcore samples from the last deglaciation, when lake levels were up to 250m higher than today. This suggests that the whole watershed contributed to the sediment input at that time. In contrast, Holocene sediments from the deep core and shore deposits are enriched in fluvial particles showing similar grain-size modes as the northern and south-western streams. This suggests that these regions were prime sediment sources during lower lake-level stands. An additional mode, tentatively related to aeolian particles, was also identified in the Holocene samples, pointing to the remobilization of deposited dust in the watershed or to a more arid regional climate.

Our results provide a first synoptic view on sedimentary dynamics in the Dead Sea watershed and help to relate sediment provenance to the drainage morphology and paleo-hydrological regimes. They constitute a solid basis for further assessment of sedimentary provenance using geochemical indicators.