bluuebunny/crossref_metadata_2025 huggingface dataset:
Causal Discovery for Climate Time Series in the Presence of Unobserved Variables
Authors: Gerhardus Andreas , Runge Jakob
Published: March 2020

Scientific inquiry seeks to understand natural phenomena by understanding their underlying processes, i.e., by identifying cause and effect. In addition to mere scientific curiosity, an understanding of cause and effect relationships is necessary to predict the effect of changing dynamical regimes and for the attribution of extreme events to potential causes. It is thus an important question to ask how, in cases where controlled experiments are not feasible, causation can still be inferred from the statistical dependencies in observed time series.

A central obstacle for such an inference is the potential existence of unobserved causally relevant variables. Arguably, this is more likely to be the case than not, for example unmeasured deep oceanic variables in atmospheric processes. Unobserved variables can act as confounders (meaning they are a common cause of two or more observed variables) and thus introduce spurious, i.e., non-causal dependencies. Despite these complications, the last three decades have seen the development of so-called causal discovery algorithms (an example being FCI by Spirtes et al., 1999) that are often able to identify spurious associations and to distinguish them from genuine causation. This opens the possibility for a data-driven approach to infer cause and effect relationships among climate variables, thereby contributing to a better understanding of Earth's complex climate system.

These methods are, however, not yet well adapted to some specific challenges that climate time series often come with, e.g. strong autocorrelation, time lags and nonlinearities. To close this methodological gap, we generalize the ideas of the recent PCMCI causal discovery algorithm (Runge et al., 2019) to time series where unobserved causally relevant variables may exist (in contrast, PCMCI made the assumption of no confounding). Further, we present preliminary applications to modes of climate variability.
Pliocene-Pleistocene stratigraphic paleobiology at Altavilla Milicia (Palermo, Sicily): tectonic, climatic and eustatic forcing
Authors: Dominici Stefano , Benvenuti Marco , Garilli Vittorio , Uchman Alfred , Pollina Francesco , David Arpad
Published: March 2020

The integration of sedimentary facies analysis, ichnology and benthic mollusc quantitative paleoecology allowed to interpret factors controlling deposition of the Altavilla Milicia alluvial to marine succession, near Palermo, Sicily. Two major composite units are recognised, separated by an angular unconformity and internally subdivided into elementary depositional sequences. Calcareous nannoplankton biostratigraphy allowed to recognize the upper Pliocene and lower Pleistocene, a time interval that covers the onset of the Quaternary glaciation. The main asset of the succession is driven by tectonic compression and accommodation by transpressional faults, a regime that led to a change in the direction of fluvial sediment delivery, from axial to transverse with respect to the basin elongation. High-frequency eustatic changes have driven the formation of elementary depositional sequences. The upper Piacenzian is characterised by marine bioclastic strata, deposited during maximum flooding intervals of the two large composite units. Mixed carbonate-siliciclastic lithosomes show a good correlation with shallow marine shell-rich detrital carbonates of Northern and Southern Italy and with Mediterranean deep-water sapropel clusters, suggesting common climatic forcing. Some tropical species previously thought to disappear from the Mediterranean at around 3.0 Ma, are instead present in the upper Piacenzian of Sicily. The study suggests that the Pliocene macrobenthos with tropical affinities disappeared from different sectors of the Mediterranean at different times.
Quantification of the dissolution kinetics of natural gypsum and particle transport processes in the evolution of dissolution cavities
Authors: Zaier Imen , Billiotte Joël , Charmoille Arnaud , Laouafa Farid
Published: March 2020

The north-eastern suburbs of Paris are most prone to sinkhole development due to the natural dissolution of gypsum rocks in contact with groundwater flow. This dissolution induces a loss of solid material creating underground voids with different shapes and sizes that can lead to large underground collapse or subsidence. Until now, there is still a high uncertainty regarding the dissolution mechanisms of natural gypsum and the hydrodynamic, chemical and mechanical conditions involved in this process.

This work has two broad aims: a) to evaluate the variability of gypsum dissolution rate as function of the surface roughness and heterogeneity; b) to identify the respective role of particle transport and dissolution processes in the formation of cavities in gypsum horizons. In fact, for gypsum with interstitial porosity, the release of grains and their transport by the flow (suffusion phenomenon) could very strongly increase the growth of the cavity compared to taking into account only the dissolution.

A variety of experimental protocols have been developed to quantify the parameters controlling the studied phenomena. Rotating disk and batch experiments are employed to determine the kinetic rate model parameters of different varieties of natural gypsum with different porosity and insoluble contents  following the empirical rate expression derived from mixed kinetic theory. To get results more representative of in-situ conditions, they are adjusted according to the specific roughness and texture of each sample. The impact of erosion and particle transport related to gypsum dissolution is determined by controlled leaching tests on external surfaces. It consists of immersing entirely a block of gypsum in a horizontal canal filled with water circulating at a low velocity (≃ 10-4 to 10-3 m/s) so that the grains detached during dissolution are not carried out by the flow but collected in a container placed under the block. These grains are then observed microscopically and analyzed by X-ray diffraction to better determine their mineralogy. For each gypsum block tested, the particlar flux is found low composed mostly of insoluble grains with only few gypsum grains released. The distribution of insoluble at the interface has a large influence on the dissolution. When they are present as a form of thin layers, they create local reliefs, depending on their cohesion, which disturbs the flow and locally enhance the gypsum dissolution. When they are distributed at the boundary of gypsum grains, they serve as a coating which protects them and drastically slows down the dissolution kinetics. 
Local and remote Rossby wave responses to an anomalously dry or wet Australian continent
Authors: Martius Olivia , Wehrli Kathrin , Seneviratne Sonia
Published: March 2020

An ensemble of CESM atmosphere only experiments with varying soil moisture anomalies over Australia (+1 , 0 ,-1 STD) is analysed with respect to the atmospheric response. Locally an intensification of the surface heat low and an upper-level anticyclone is found for the negative anomaly. The local response to the low soil moisture content is driven by increase sensible heat fluxes and associated positive near-surface temperature anomalies.

A remote response of the upper-level flow consists of a downstream Rossby wave train extending along the jet waveguide and an upstream response projecting upon the main mode of variability the southern annular. The downstream response is driven by linear wave dynamics while the upstream response is modulated by non-linear wave dynamics and associated eddy fluxes. The sensitivity of the response to the background flow, i.e., different phases of ENSO is explored.
An Interplanetary Travel
Authors: Hernàndez Romero Carme
Published: March 2020

To promote STEAM vocations among our teenage students aged between 12 and 16, our institute has designed and implemented a project called "AN INTERPLANETARY TRAVEL" thanks to the collaboration of the EUROPEAN OFFICE RESOURCES FOR SPACE EDUCATION OF SPAIN (CESERO Spain) which provides us with a kit of materials for our purpose.

The project is structured in different parts:

-First, we propose our students the possible fictitious alien invasion by recreating a radio program where all countries are informing of the alien threat existing by aliens who want to invade our planet.

Through a previous brainstorm the students consider the possibility of colonizing other planets of the Solar System in order to survive.

-Second, to be able to choose the ideal future home, they must investigate various planets that match the requirements for the human being to live and do experiments in order to detect the existence of life.

-Third, while some students are dedicated to designing and selling one-way tickets for this new place, through the creation of their own travel agency, and all the logistics involved others are dedicated to studying how to plan that trip . Subsequently, the "clients" select the agency that provides the best services.

-Fourth, for the planning of the trip it is necessary that our students become spaceships engineers to design the space vehicle and the pertinent tests for its takeoff.

To be able to build that spacecraft, it is necessary to investigate the different properties of the materials to find the perfect features that the different parts of the space vehicle must have: impact resistance, magnetism, densities, electrical properties and thermal conductivity, etc. and select the suitable ones to carry it out Both the water rocket and the reentry capsule are designed and tested in an open field. The idea is to land in our future home.

-Fifth, calculations are made for the different phases of our trip: launch phase, space phase and reentry phase. (Level adapted for high school students). For the reentry phase the parachute is designed and tested with an egg so that it can land without breaking.

-Sixth, the students study the possible health consequences of future colonizers.

-And finally, all student groups teach their peers the achievements through exhibitions.

Good trip !!!
Variations of polar CO2 caps during the first Martian year of FREND onboard TGO
Authors: Golovin Dmitry , Mitrofanov Igor , Anikin Artem , Djachkova Maya , Lisov Denis , Litvak Maxim , Lukyanov Nikita , Malakhov Alexey , Nikiforov Sergey , Sanin Anton
Published: March 2020

Fine Resolution Epithermal Neutron Detector (FREND) is an instrument onboard ExoMars’ Trace Gas Orbiter (TGO). It uses neutron measurements to detect hydrogen (and thus water) variations in the shallow subsurface of the Martian soil. In case of sub-polar regions, it is quite sensitive to the thickness of seasonal deposition of CO2, which it well-sees in neutrons, as “dry” layer on top of the hydrogen-rich polar permafrost soil.

This presentation is aimed to give a first look at variations of seasonal depositions of Carbone dioxide at winter vs summer seasons on Mars. Similar studies have been performed by neutron instruments earlier, however FREND’s major advantage is its much better spatial resolution: by shielding from the neutron flux coming from off-nadir directions, the instrument’s spatial resolution is improved down to a 60-200 km diameter spot. The orbiter’s inclination is currently 74 deg, so the experiment is capable to observe the rim of the polar permafrost northern and southern regions with seasonal coverages of atmospheric Carbone dioxide over them.

We re-define and improve the shape of polar CO2 caps boundaries and the column density of seasonal deposits thanks to improved spatial resolution and present data of FREND’s first Martian year of observations of high Martian latitudes.
Examining erosion in New Zealand over millennial timescales using in-situ 10Be and 14C
Authors: Roda-Boluda Duna , Schilgen Taylor , Lupker Maarten , Hella Wittmann , Jeff Prancevic , Stefanie Tofelde , Aaron Bufe
Published: March 2020

Landslides are the major erosional process in many orogens, and one of the most sensitive erosional process to tectonic and climatic perturbations. However, it remains extremely difficult to constrain long-term or past rates of landslide activity, and hence their contribution to long-term landscape evolution and catchment sediment fluxes, because the physical records of landsliding are often removed in <102 yrs. Here, we use the in-situ 10Be and in-situ 14C concentrations of recent landslide deposits and catchments from the Fiordland and the Southern Alps of New Zealand to: (a) estimate landslide frequencies over 103-104 yr timescales, which we compare against landslide inventories mapped from air photos (<102 yrs) to estimate changes in landslide activity, (b) quantify catchment-averaged erosion rates, and landslide’s contribution to those erosional fluxes, and (c) test whether paired 14C-10Be measurements can be used to trace erosional depth-provenance and identify transient erosion rate changes. We show that 10Be concentrations on landslide deposits can be used to estimate landslide recurrence intervals and frequency over 103 yr timescales, and that 14C/10Be ratios reflect the depth-provenance of sediment, and possibly transient changes in erosion rates. The comparison of our 10Be-based long-term landslide frequencies with short-term published inventories suggests that landslide frequencies have increased towards the present by up to an order of magnitude. We compare sediment fluxes inferred from these long- and short-term landslide inventories with sediment flux estimates derived from 10Be catchment-averaged erosion rates, which allows us to examine fluctuations in erosion rate estimates from 101 to 103 yrs timescales. 
A remote sensing based integrated approach to quantify the impact of fluvial and pluvial flooding in an urban catchment
Authors: Muthusamy Manoranjan , Rivas Casado Monica , Salmoral Gloria , Irvine Tracy , Leinster Paul
Published: March 2020

Pluvial (surface water) flooding is often the cause of significant flood damage in urban areas. However, pluvial flooding is often overlooked in catchments which are historically known for fluvial floods. In this study, we present a conceptual remote sensing-based integrated approach to enhance current practice in the estimation of flood extent and damage and characterise the spatial distribution of pluvial and fluvial flooding. Cockermouth, a small town in England which is highly prone to flooding, was selected as a study site and the flood event caused by storm Desmond in 2015 (5-6/12/2015) was selected for this study. A high-resolution digital elevation model (DEM) was produced from a composite digital surface model (DSM) and a digital terrain model (DTM) obtained from the Environment Agency. Using this DEM, a 2D flood model was developed in HEC-RAS (v5) 2D for the study site. Simulations were carried out with and without pluvial flooding. Calibrated models were then used to compare the fluvial and combined (pluvial and fluvial) flood damage areas for different land-use types. The number of residential properties affected by fluvial and combined flooding was compared using a combination of modelled results and data collected from Unmanned Areal System (UAS). As far as the authors are aware, this is the first time remote sensing data, hydrological modelling and flood damage data at property level have been combined to differentiate between the flood extents and damage caused by fluvial and pluvial flooding in the same event. Results show that the contribution of pluvial flooding should not be ignored even in a catchment where fluvial flooding is the major cause of the flood damages. Although the additional flood depths caused by the pluvial contribution were lower than the fluvial flood depths, the affected area is still significant. Pluvial flooding increased the overall number of affected properties by 25%. In addition, it increased the flood depths in a number of properties that were identified as being affected by fluvial flooding, in some cases by more than 50%. These findings show the importance of taking pluvial flooding into consideration in flood management practices. Further, most of the data used in this study were obtained via remote sensing methods, including UASs. This demonstrates the merit of developing a remote sensing-based framework to enhance current practice in the estimation of flood extent and damage.
Mode-2 internal solitary waves offshore Central America discovered by seismic oceanography method
Authors: Fan Wenhao , Song Haibin , Gong Yi , Sun Shaoqing , Zhang Kun
Published: March 2020

In the past, most of the internal solitary waves (ISWs) found by seismic oceanography (SO) method were mode-1 ISWs. We discover many mode-2 ISWs in the Pacific coast of Central America by using SO method for the first time. These mode-2 ISWs are convex mode-2 ISWs with the maximum amplitudes of about 10 m, and most of them are ISWs with smaller amplitudes. The pycnocline for the mode-2 ISWs on the shelf (ISW3) is displaced 6.4% of the total seawater depth from the mid-depth of the total seawater. The deviation is large, and it shows a strong asymmetry feature of the peaks and troughs on the seismic profile. This is consistent with the results of previous numerical simulation. Observing the changes in the fine structure of mode-2 ISWs packet through pre-stack migration, it was found that the overall waveform of the three mode-2 ISWs (ISW1, ISW2, and ISW3) on the shelf during the acquisition time period of about 40 seconds is stable. The apparent phase velocity of these mode-2 ISWs calculated by the pre-stack migration section using the Common Offset Gathers is about 0.5 m/s, and their apparent propagation directions are from SW to NE along the seismic line (44 ° N, 0° pointing north). The vertical amplitude distribution and estimated apparent velocities of these mode-2 ISWs are basically consistent with the theoretical values ​​calculated from the KdV equation. By analyzing the apparent velocities of the three mode-2 ISWs (ISW1, ISW3, and ISW5) with relatively small apparent velocity errors, it is found that the apparent velocity of mode-2 ISWs generally increases with the increasing depth of seawater. In addition, the apparent phase velocity of the mode-2 ISWs with a larger maximum amplitude is generally larger. Based on the analysis of hydrological data in the study area, it was found that a strong anticyclone developed on the northwest side of the seismic survey line and a weaker anticyclone developed on the southeast side. These anticyclones will increase the depth of the thermocline in the surrounding seawater. According to previous studies, the deepening of the thermocline (pycnocline) maybe conducive to the generation of mode-2 ISWs.
A Wet Layered Sloping Sponge? The Role of Volcanic Ash Soils in Water Transport and Tracer Mixing at a Tropical Hillslope
Authors: Mosquera Giovanny , Windhorst David , Breuer Lutz , Crespo Patricio
Published: March 2020

Hillslope soils developed on volcanic ash (Andosols) provide key hydrological services such as water storage and streamflow regulation in montane environments. Yet, little is known about how they influence subsurface water flow paths and flow transport and mixing dynamics. To fill this knowledge gap, we analyzed a unique 3-year dataset of hourly precipitation, soil moisture, and groundwater level and weekly precipitation and soil water stable isotope data collected along a steep hillslope transect underlain by Andosols. In combination with a detailed characterization of soil properties, we investigated how these soils influence water transport and tracer mixing in the subsurface. Our results indicate that the high organic matter (33-42%) and clay (29-31%) content of the soils’ organic horizon and an abrupt change in hydraulic conductivity between the highly conductive rooted soil layer and a low conductive underlying layer results in a perched water layer that remains near saturated year-round. Despite the formation of the latter, our isotope-based water age estimations depict that water resides within the organic horizon of the soils for short periods (2-4 weeks). The dynamics of soil moisture suggest a fast transfer of hydraulic potentials (few hours) along the entire soil profile in response to rainfall events. This hydraulic response is explained by the exponential shape of the soils’ water retention curves that facilitate a rapid vertical mobilization of water through the porous soil matrix. These findings indicate that the hydrological behavior of volcanic ash soils resemble that of a “layered sponge” in which vertical flow paths are dominant despite the formation of a perched water layer. 
Impacts of future land cover and climate changes on landslide susceptibility. Results obtained from regional-scale modelling in the Pyrenees.
Authors: Hürlimann Marcel , Medina Vicente , Guo Zizheng , Puig-Polo Carol , Lloret Antonio , Vaunat Jean
Published: March 2020

Future environmental changes will strongly affect the occurrence of rainfall-induced landslides in mountainous regions. In our ongoing study, we focus on the effects of climate changes as well as land use and land cover (LULC) changes on shallow slope failures in the Pyrenees. For this reason, a physically-based susceptibility model was developed, which calculates the landslide susceptibility at regional scale. The model merges two different approaches for the calculation of pore fluid pressure and also includes the option of defining the values of input parameters stochastically.

The model was validated using landslide inventories from two different study areas located in the Central and Eastern Pyrenees. One is the inventory of historic shallow slides and debris flows in Andorra country. The other one is the inventory of the catastrophic landslide episode in Val d’Aran area in June 2013, which includes 393 landslide initiation points. The susceptibility modelling of these two validation cases produced acceptable results and showed that our physically-based model is producing consistent stability conditions.

In the next step, the future LULC and climate changes until the end of the 21th century were simulated for Val d’Aran study area. The LULC changes were determined with the IDRISI TerrSet software suite, while the climate changes were obtained from the ensemble of regional climate models using RCP 4.5 and 8.5 scenarios. The results of the susceptibility modelling showed that the impacts of future LULC changes increase the overall stability because of the larger area of forest and shrubs (and consequently higher cohesion due to root strength). In contrast, the impact of future climate changes, which was principally incorporated by higher rainfall intensity, reduced the overall slope stability. However, when we compared the impacts of both future changes, the results showed that the influence of the vegetation expansion is more important than the effect of higher rainfall intensity. Therefore, the overall stability conditions in the study area seem to slightly improve in the future.

As always in such studies, there are many uncertainties in the input data and additional simulations are necessary to confirm the observed trends. Nonetheless, the outcomes provide helpful information for researchers and practitioners that deal with the impacts of future changes on landslide susceptibility in mountainous regions.
Systematic and Random error correction of ship based marine meteorological parameters observed across Tropical Indian ocean
Authors: Nunna Kameshwari , Tata Venkata Sai Udaya Bhaskar , Eluri Pattabhi Rama Rao , Jampana Venkata
Published: March 2020

In this study, ship based observations obtained from Indian Meteorological Department (IMD) and Naval Operations Data Processing and Analysis Centre (NODPAC) observed across Tropical Indian ocean (TIO) are combined with International Comprehensive Ocean-Atmosphere Dataset (ICOADS R3.0) and several climatology are generated for TIO. The ship observations from the Voluntary Observing Ships (VOS) have been found to contain both random and systematic errors. An attempt is made to apply a systematic correction upon wind speed (WS) and random error correction upon sea level pressure (SLP), dry bulb temperature (DBT), sea surface temperature (SST), dew point temperature (DPT). The systematic error correction upon WS is actually a correction applied to the old World Meteorological Organization (WMO) 1100 scale, i.e. the Beaufort estimated wind speeds are corrected as the old WMO 1100 scale was found to have errors. The new July scale derived exclusively for TIO rightly reduces the over estimation of high WS and increases the under estimation of lower WS as given by the old WMO 1100 scale. The systematic bias between anemometer measured wind speeds and Beaufort estimated wind speeds reduced from 0.52 m/s (obtained after the correction done by previous scale) to 0.08 m/s with the new scale. The random errors are calculated based on a technique called semi-variogram analysis technique. The fluxes derived from the observation error corrected variables are analyzed and the net heat flux across TIO was observed to reduce by 14 W/m2.
Realistic numerical simulations of upwelling and downwelling in the middle Adriatic: the May 2017 episode
Authors: Beg Paklar Gordana , Orlic Mirko , Dzoic Tomislav , Grbec Branka , Mihanovic Hrvoje , Pasaric Zoran , Stanesic Antonio
Published: March 2020

Regional Ocean Modeling System (ROMS) is used to reproduce and analyse upwelling detected in the middle Adriatic Sea during May 2017. The ROMS domain covers the entire Adriatic, with a rectangular grid having horizontal resolution of 2.5 km and 22 unequally spaced s levels along the vertical. Surface momentum, heat and water fluxes in the ROMS simulations are calculated using atmospheric fields from the operational ALADIN model (Tudor et al., 2013; Termonia et al., 2018), having a horizontal resolution of 8 km for scalar fields (air pressure, air temperature, relative humidity, cloudiness, precipitation, and shortwave radiation) and 2 km resolution for wind fields. The ROMS model, in addition to the atmospheric agents, is forced by river inflows, tides and water mass exchange through the Strait of Otranto. Along the Adriatic coast, 41 rivers are discharging into the sea and their climatological flow rates (Raicich, 1994) are used in the simulations. Tidal forcing is applied on the open boundary taking into account seven tidal harmonics (M2, S2, N2, K2, K1, O1 and P1) crucial for the Adriatic dynamics. The open boundary conditions for the free surface, temperature, salinity, and velocity are taken from the wider Adriatic AREG model operationally run under the Adriatic Forecasting System (Oddo et al., 2006). Baseline ROMS simulation is run for the period from 1 August 2016 to 31 December 2018 and its quality is assessed with available CTD and HF radar measurements, satellite sea surface temperatures (SST) and data collected during May 2017 and June 2018 cruises by the yo-yo CTD profiler and shipborne ADCP. Numerical experiments focus on May 2017 when upwelling induced by prevailing NW wind was recorded. Baseline experiment qualitatively reproduces the upwelling but several sensitivity experiments are needed to increase agreement between model and measurements. Various intensities of horizontal viscosity and diffusivity and drag coefficient are tested in sensitivity studies. Moreover, a third order upwind advection scheme is tested as is the behaviour of solar shortwave radiation along the water column. Significant improvement in the model results is obtained using increased drag coefficient. Circulation pattern recorded by shipborne ADCP with inflowing currents in the first 10 km from the eastern middle Adriatic coast and wind-controlled two-layer flow further offshore is also reproduced by the ROMS model. Upwelling was clearly documented in the SST satellite images of 28 and 29 May 2017 by patches of cold water close to the eastern coast. Similar structure is reproduced by ROMS, although the modelled SST underestimates the measured values by approximately 1 °C. The area of upwelling is correctly located as is the cyclonic circulation indicated by ADCP measurements along the transect.
How does land-use influence the composition of DOM in peatland surface waters?
Authors: Moody Catherine
Published: March 2020

Peatlands export large quantities of dissolved organic matter (DOM) into surface waters. The characteristics of the peatland (e.g. vegetation cover, scale, land use) effect the concentration and composition of DOM in the water. In the UK, water companies use surface water from peatlands as a source of drinking water, and the efficiency of the treatment process depends on the concentration and composition of DOM in the incoming water. In order to better understand the link between peatland characteristics and water treatment efficiency, the composition and concentration of DOM in surface waters draining peatlands across the UK was investigated. Water samples were collected from peatland surface waters from over 300 sites across the UK. Sites with different land uses, vegetation cover, management regimes and restoration states were included.

The DOM was extracted from the water and analysed, to determine the elemental composition of the DOM. In future, targeted restoration and revegetation of peatlands could be used to alter the composition of DOM in the surface water, to produce DOM that can be more easily treated for drinking water, or treatment processes can be improved to increase treatment efficiency, based on a better understanding of the composition of DOM.
Statistical approaches and tools for IntCal20
Authors: Bronk Ramsey Christopher , Heaton Timothy , Blaauw Maarten , Blackwell Paul , Reimer Paula , Reimer Ron , Scott Marian
Published: March 2020

The construction of the new IntCal20 calibration curve was undertaken using a number of new statistical approaches (Heaton et al. 2020), when compared to previous versions.  This was partly due to the nature of some of the new datasets; partly to improve the robustness of the curve; and partly to address particular aspects of radiocarbon within the Earth System such as reservoir effects, incorporation of geological carbon in speleothems, and the uncertainties associated with different timescales.  Here the main approaches taken are summarised with a perspective on their strengths and potential weaknesses.

In particular, the high-resolution extensions to the Hulu speleothem radiocarbon record (Cheng et al. 2018) allow it to be used to anchor the chronology for other key records (Suigetsu, Cariaco, and the Pakistan and Iberian Margins), providing a coherence in the timescale not possible before.  Further, for the first time, we incorporate time varying marine reservoir ages, constrained by the Hamburg Large Scale Geostrophic Ocean General Circulation Model (LSG OGCM)(Butzin et al. 2020).  In addition, work on the relationship to the Greenland ice core timescales (Adolphi et al. 2018) enables us to make direct comparison between radiocarbon dated records and the ice core timescale and here we report on tools to assist with this.

Along with the update to the calibration curve itself, the associated tools for calibration, age-depth modelling and Bayesian modelling have also been updated to make best use of the new resolution and characteristics of the curve.  Here we summarise updates to Bacon, Calib and OxCal.

Heaton, TJ. et al (2020) The IntCal20 approach to radiocarbon calibration curve construction: A new methodology using Bayesian splines and errors-in-variables Radiocarbon: in review.

Cheng, H. et al. (2018) Atmospheric 14C/12C changes during the last glacial period from Hulu Cave. Science, 362(6420), pp.1293-1297. doi:10.1126/science.aau0747

Adolphi, F. et al. (2018) Connecting the Greenland ice-core and U/Th timescales via cosmogenic radionuclides: Testing the synchronicity of Dansgaard-Oeschger events. Climate of the Past, 14, pp.1755-1781. doi:10.5194/cp-2018-85

Butzin, M. et al. (2020) A short note on marine reservoir age simulations used in IntCal20. Radiocarbon: in press.
Understanding drought induced responses in leaf and root CO2 and VOC fluxes through position specific isotope labelling
Authors: Daber Lars Erik , Bamberger Ines , Ladd S. Nemiah , Kreuzwieser Jürgen , Fudyma Jane , Loaiza Juliana Gil , De Leeuw Jason , Shi Lingling , Bai Xuejuan , Purser Gemma , Krechmer Jordan E. , Meredith Laura , Werner Christiane
Published: March 2020

Climate change exerts increasing pressure on tropical rainforests enhancing their susceptibility to environmental stress. Plants' abilities to rapidly adjust their metabolism are critical for reducing the stress effects caused by extreme external conditions. Plants produce a wide spectrum of volatile organic compounds (VOCs) to cope with oxidative and thermal stress. The distribution and amount of VOC production thereby vary greatly not only among species but also organs, such as leaves and roots. Within the framework of our large-scale ecosystem manipulation experiment, Biosphere 2 Water, Atmosphere, and Life Dynamics (B2-WALD), we aimed to produce deeper insights into carbon partitioning between primary and secondary metabolism under drought stress, notably into CO2 and VOCs.

In particular, we investigated how drought stress influences organ-specific carbon allocation between processes of primary and secondary metabolisms and to what extent allocation into secondary metabolism protects plants from drought. The tropical rainforest mesocosm in Biosphere 2, University of Arizona, provides a unique system for ecosystem manipulation studies. We implemented a drought stress experiment, excluding rainfall for two months. To investigate changes in carbon allocation, we performed labelling experiments with position-specific 13C-labelled pyruvate on leaves and roots of several tropical tree and shrub species before and during the drought period. We used 13CO2 laser spectroscopy and high-sensitivity proton-transfer-reaction time-of-flight mass spectrometry to enable real-time analysis of metabolic pathways and carbon turnover, using leaf- and root-chambers to quantify fluxes.

Considering our preliminary results, net CO2 assimilation strongly declined under rain exclusion, due to stomatal closure. Consequently, respiration rates declined strongly in leaves as well as in roots. The response of VOC emissions, however, varied among organs. In leaves, we found that the emission of some VOCs declined under drought stress (acetone, monoterpenes), while other fluxes increased or stayed the same (isoprene). We will present detailed data on [1-13C]- and [2-13C]-pyruvate allocation within primary and secondary metabolism, such as decarboxylation processes and VOC-production. To our knowledge, this is the ﬁrst time that real-time measurements of 13C-labelled root VOC-emissions were conducted, enabling this comparative analysis of drought induced stress eﬀects on leaf- and root-emissions.
A Case Study of Weather Radar Data Assimilation into the Harmonie Numerical Weather Prediction System
Authors: Michaelides Silas , Ivanov Serguei , Ruban Igor , Charalambous Demetris , Tymvios Filippos
Published: March 2020

Quantitative Precipitation Forecasting (QPF) is among the most central challenges of atmospheric prediction systems. The primary aim of such a task is the generation of accurate estimates of heavy precipitation events associated with severe weather, atmospheric fronts and heavy convective rainfalls. QPF is still among the most intricate challenges of Numerical Weather Prediction. The efforts in this direction are mainly concentrated on improving model formulations for microphysics and convective process and remote sensing data assimilation.

This paper describes the first results with the regional radar signal processing chain that provides the radar data assimilation (RDA) in the Harmonie convection permitting numerical model. This task is performed for a case study focusing on a wintertime frontal cyclone over the island of Cyprus. Reflectivity measurements from two weather radars, at Larnaka and Paphos, are exploited for simulations of severe weather conditions associated with this synoptic-scale system. Through the variational assimilation procedure, the model takes into account the atmospheric processes occurring in the upstream flow which can be outside the area of radar measurements. The focus is on the precipitable water vapor content and its changes during the cyclone evolution, as well as on the impact of the radar data assimilation on precipitation estimates.

The results show that the numerical experiments exhibit, in general, a suitable simulation of precipitable water at different stages of the cyclone. In particular, the bulk of the rainfall volume exhibits three stages: intensive rain on the cyclone's frontal zone, weaker precipitation immediately behind the front, and the secondary enhancement of rainfall. The largest corrections due to RDA are of up to 5 mm and occur during the approach of the cyclone frontal zone in a form of enhanced rainfall over the whole area, but more prominently in weak precipitation locations.
Squeezed Under the Sheet: White Mica Records High Tectonic Stresses Within a Decollement Thrust
Authors: Häkkinen Miisa , Angiboust Samuel , Dubacq Benoit , Simoes Martine
Published: March 2020

Tectonic stresses at the base of decollement thrusts are generally expected to be low due to the presence of mechanically weak evaporites. Yet, the presence of abundant micro-seismicity in the region expected to correspond to the evaporitic layer remains paradoxical. We study here a fossil thrust zone from the base of the Digne nappe (SE France) where exotic thrust slices formed by brecciated Paleozoic basement micaschists are observed within the Mio-Pliocene decollement. Petrographic investigations reveal the presence of highly-substituted phengitic rims (up to Si=3.43 apfu) around pre-alpine muscovitic cores. Similar micaschists sampled in a basement high further North do not exhibit these phengitic rims around muscovite, thus suggesting that white mica zoning relates to a younger overprint. Such high-Silica phengites are commonly found in high-pressure terranes (i.e. 7-15 kbars depending on the buffering assemblage) but are not expected in foreland regions, such as in the Digne area where the overburden has never been thicker than c.5km (i.e. approximately 1.3 kbar). We propose that the mica zoning observed reflects the former presence of non-lithostatic stresses (possibly on the order of several kilobars) related to the elastic charging of a thrust slice “squeezed” at the base of the moving nappe. This finding sheds light on stress distribution as well as on the origin of micro-seismicity along active decollement thrusts in orogenic belts.
Quantifying how plants with different species-specific water-use strategies cope with the same drought-prone hydro-ecological conditions
Authors: Khare Deepanshu , Bodner Gernot , Javaux Mathieu , Vanderborght Jan , Leitner Daniel , Schnepf Andrea
Published: March 2020

Plant transpiration and root water uptake are dependent on multiple traits that interact with site soil characteristics and environmental factors such as radiation, atmospheric temperature, relative humidity, and soil-moisture content. Models of root architecture and functions are increasingly employed to simulate root-soil interactions. Root water uptake is thereby affected by the root hydraulic architecture, soil moisture conditions, soil hydraulic properties, and the transpiration demand as controlled by atmospheric conditions. Stomatal conductance plays a vital role in regulating transpiration in plants. We performed simulations of plant water uptake for plants having different mechanisms to control transpiration, spanned by isohydric/anisohydric spectrum. Isohydric plants follow the strategy to close their stomata in order to maintain the leaf water potential at a constant level, while anisohydric plants leave their stomata open when leaf water potentials fall due to drought stress. Modelling the stomatal regulation effectively will result in a more reliable model that will regulate the excessive loss of water. We implemented hydraulic and chemical stomatal control
of root water uptake following the current approach where stomatal control is regulated by simulated water potential and/or chemical signal concentration. In order to maintain water uptake from dry soil, low plant water potentials are required, which may lead to reversible or permanent cavitation. We parameterise our model with field data, including climate data and soil hydraulic properties under different tillage conditions. This helps us to understand the behaviour of different crops under drought conditions and predict at which growing stage the stress hits the plant. We conducted the simulations for different scenarios to study the effect of hydraulic and chemical regulation on root system performance under drought stress.
Slip modes and interaction in a simplified strike-slip fault system with increasing geometrical complexity
Authors: Rudolf Michael , Podlesny Joscha , Rosenau Matthias , Kornhuber Ralf , Oncken Onno
Published: March 2020

The release of elastic energy along an active fault is accommodated by a wide range of slip modes. It ranges from long-term slow slip events (SSEs) and creep to short-term tremors and earthquakes. They vary not only in their characteristic duration but also in their magnitude, spatial extend and slip velocities. As all slip modes are related to earthquakes, the understanding of the relationships between the different slip modes and the underlying mechanisms is crucial to assess earthquake hazards in various regions. The exact relation is unclear, as in some regions many slip modes occur simultaneously (e.g. Tohoku-Oki) and in others certain slip modes are completely absent (e.g. Cascadia).

One of the driving factors in the generation of this large variety of slip modes is the interplay of fault heterogeneity and geometrical complexity of the fault system. Using a scaled physical model we test various settings in terms of fault heterogeneity and geometrical complexity. The experimental results are then validated and benchmarked using multi-scale numerical simulations. We describe the system using the rate-and-state frictional framework and introduce the on-fault heterogeneity with variable frictional properties. All properties are the same for analogue and simulation as far as they can be determined or realized experimentally (a-b, vload, Shmax, Shmin, etc...). As analogue material we use segmented, decimetre sized neoprene foam blocks in multiple configurations (e.g. biaxial shear at forces <1 kN) to simulate the elastic upper crust. The contact surfaces are spray-painted with acrylic paint to generate velocity weakening characteristics in between the blocks. The major advantage of using neoprene over other materials, such as gelatine or polyurethane foams, is that it has closed pores and thus exhibits a more favourable Poisson’s ratio in comparison with rocks and shows better elastic strain propagation in the block. Furthermore, all used materials are inert and do not change their properties over time.

We are able to reliably generate frequent stick-slip events of variable size and recurrence intervals. The slip characteristics, such as slip distribution, are in good agreement with analytical solutions of fault slip in elastic media. In this contribution we will highlight the material properties, experimental results and used methodologies to monitor and process the experimental data. Additionally, we are going to give an outlook on the interaction behaviour of multiple faults in dependence of their geometric configuration and the generation of power-law type magnitude scaling relations.
Evaluation of E-Layer Dominated Ionosphere Events Using CHAMP, COSMIC/FORMOSAT-3 and FY3C Data
Authors: Kamal Sumon , Jakowski Norbert , Hoque Mohammed M. , Wickert Jens
Published: March 2020

Under certain space weather conditions the ionization level of the ionospheric E layer can dominate over that of the F2 layer. This phenomenon is known as “E layer dominated ionosphere” (ELDI) and occurs primarily at high latitudes in the polar regions. The corresponding electron density profiles show their peak ionization at the E layer height between 80 km and 150 km above the Earth’s surface. In this work we have evaluated the influence of space weather and geophysical conditions on the occurrence of ELDI events at high latitudes in the northern and southern hemispheres. For this, we used electron density profiles derived from ionospheric radio occultation measurements aboard CHAMP, COSMIC and FY3C satellites. The used CHAMP data covers the years from 2001 to 2008, the COSMIC data the years from 2006 to 2018 and the FY3C data the years from 2014 to 2018. This provides us continuous data coverage for a long period from 2001 to 2018, containing about 4 million electron density profiles. In addition to the geospatial distribution, we have also investigated the temporal occurrence of ELDI events in the form of the diurnal, the seasonal and the solar activity dependent variation. We have further investigated the influence of geomagnetic storms on the spatial and temporal occurrence of ELDI events.
The water footprint of different diets within European sub-national geographical entities
Authors: Vanham Davy
Published: March 2020

The water footprint concept has been recognized as being highly valuable for raising awareness of the large quantity of water resources required to produce the food we consume. We present, for three major European countries (the United Kingdom, France and Germany), a geographically detailed nationwide food-consumption-related water footprint, taking into account socio-economic factors of food consumption, for both existing and recommended diets (healthy diet with meat, healthy pescetarian diet and healthy vegetarian diet). Using socio-economic data, national food surveys and international food consumption and water footprint databases, we were able to refine national water footprint data to the smallest possible administrative boundaries within a country (reference period 2007–2011). We found geographical differences in water footprint values for existing diets as well as for the reduction in water footprints associated with a change to the recommended healthy diets. For all 43,786 analysed geographical entities, the water footprint decreases for a healthy diet containing meat (range 11–35%). Larger reductions are observed for the healthy pescetarian (range 33–55%) and healthy vegetarian (range 35–55%) diets. In other words, shifting to a healthy diet is not only good for human health, but also substantially reduces consumption of water resources, consistently for all geographical entities throughout the three countries. Our full results are available as a supplementary dataset. These data can be used at different governance levels in order to inform policies targeted to specific geographical entities.

This presentation is based on a recent paper published in Nature Sustainability