bluuebunny/crossref_metadata_2025 huggingface dataset:
Functional thresholds of plant resistance and recovery to drought
Authors: Ingrisch Johannes , Umlauf Nikolaus , Bahn Michael
Published: March 2021

With ongoing climate change, the predicted increase in climate variability is likely to increase the intensity of extreme drought events. This could significantly amplify the consequences of drought, because ecological responses are often non-linear. The importance of functional thresholds has been widely recognized, where comparably small changes in the stressor can have disproportional large consequences for ecosystem functioning. However, very few studies have actually tested for the functional thresholds of drought responses, which creates large uncertainties in our understanding of drought effects. Here, we aimed to determine the effects of drought intensity on plant productivity and to identify potential thresholds underpinning these responses.

We studied the effects of drought intensity on different measures of plant productivity using a gradient design. In a common garden experiment, we performed an experimental pulse drought of 3.5 weeks on planted monospecific mesocosms composed of the common grass Dactylis glomerata and the common forb Plantago lanceolata, respectively. We imposed a drought intensity gradient, which ranged from well-watered to extremely dry soil conditions. During drought and post-drought recovery we repeatedly measured productivity-related parameters, including gross primary productivity (GPP), Normalized Difference Vegetation Index (NDVI) and vegetative height, and assessed aboveground net primary production (ANPP) at peak drought and after recovery.

Drought intensity had non-linear effects on all studied parameters both during the resistance and the recovery phase. At peak drought we observed threshold responses at two stages of drought intensity. The first threshold occurred at moderate drought intensity and was related to a distinct downregulation of GPP and plant height. The second threshold was reflected in a steep decline of NDVI and leaf water content. During the recovery phase, high drought intensity stimulated productivity and regrowth rates. This resulted in an overshooting of biomass production by up to 100% in mesocosms previously exposed to severe drought, the effect being related to the first drought intensity threshold, which had led to a downregulation of GPP during drought. The overcompensation following exposure to high drought intensities was more pronounced for Plantago than for Dactylis. However, highest drought intensities clearly suppressed the recovery capacity of Plantago but not of Dactylis, which demonstrates species-specific differences in the effects of drought intensity on plant resilience.

We conclude that functional thresholds in drought and recovery responses of productivity are related and that with increasing drought intensity plants compensate decreased resistance with increased recovery to optimize overall resilience of productivity to drought.
The contribution of shipping to air pollution in the Mediterranean region – a model evaluation study 
Authors: Fink Lea , Matthias Volker , Karl Matthias , Petrik Ronny , Majamäki Elisa , Jalkanen Jukka-Pekka , Oppo Sonia , Kranenburg Richard
Published: March 2021

Shipping has major contribution to emissions of air pollutants like NOx and SO2 and the global maritime transport volumes are projected to increase significantly. The Mediterranean Sea is a region with dense ship traffic. Air quality observations in many cities along the Mediterranean coast indicate high levels of NO2 and particulate matter with significant contributions from ship emissions.
To quantify the current impact of shipping on air pollution, models for ship emissions and atmospheric transport can be applied, but model predictions may differ from observational data. To determine how well regional scale chemistry transport models simulate pollutant concentrations, the model outputs from several regional scale models were compared against each other and to measured data.
In the framework of the EU H2020 project SCIPPER, ship emission model STEAM and the regional scale models CMAQ and CHIMERE model were applied on a modelling domain covering the Mediterranean Sea. Modeling results were compared to air quality observations at coastal locations. The impact of shipping in the Mediterranean Sea was extracted from the model excluding shipping emissions.

 
Recent recovery of Antarctic Bottom Water formation in the Ross Sea driven by climate anomalies
Authors: Silvano Alessandro , Foppert Annie , Rintoul Steve , Holland Paul , Tamura Takeshi , Kimura Noriaki , Castagno Pasquale , Falco Pierpaolo , Budillon Giorgio , Haumann Alexander , Naveira Garabato Alberto , Macdonald Alison
Published: March 2021

Antarctic Bottom Water (AABW) supplies the lower limb of the global overturning circulation, ventilates the abyssal ocean and sequesters heat and carbon on multidecadal to millennial timescales. AABW originates on the Antarctic continental shelf, where strong winter cooling and brine released during sea ice formation produce Dense Shelf Water, which sinks to the deep ocean. The salinity, density and volume of AABW have decreased over the last 50 years, with the most marked changes observed in the Ross Sea. These changes have been attributed to increased melting of the Antarctic Ice Sheet. Here we use in situ observations to document a recovery in the salinity, density and thickness (that is, depth range) of AABW formed in the Ross Sea, with properties in 2018–2019 similar to those observed in the 1990s. The recovery was caused by increased sea ice formation on the continental shelf. Increased sea ice formation was triggered by anomalous wind forcing associated with the unusual combination of positive Southern Annular Mode and extreme El Niño conditions between 2015 and 2018. Our study highlights the sensitivity of AABW formation to remote forcing and shows that climate anomalies can drive episodic increases in local sea ice formation that counter the tendency for increased ice-sheet melt to reduce AABW formation.
Investigation of the possibility of GIC development in Greece during the strongest magnetic storms of solar cycle 24 
Authors: Boutsi Adamantia Zoe , Balasis Georgios , Daglis Ioannis A. , Tsinganos Kanaris , Giannakis Omiros
Published: March 2021

Geomagnetically Induced Currents (GIC) constitute an integral part of the space weather research and a subject of ever-growing attention for countries located in the low and middle latitudes. A series of recent studies highlights the importance of considering GIC risks for the Mediterranean region. Here, we exploit data from the HellENIc GeoMagnetic Array (ENIGMA), which is located in Greece, complemented by magnetic observatories in Italy, to calculate corresponding values of the GIC index, i.e., a proxy of the geoelectric field calculated entirely from geomagnetic field variations. We perform our analysis for the most intense magnetic storms (Dst<-150 nT) of solar cycle 24. Our results show a good correlation between the storm sudden commencement (SSC) and an increase of the GIC index value. These investigations indicate that despite the elevated amplitude of the GIC index the associated risk remains at low level for the power networks in Greece and Italy during the considered storm events.
The response of land-atmosphere interactions and the atmospheric circulation across West Africa to intraseasonal variability
Authors: Talib Joshua , Taylor Christopher , Klein Cornelia , L. Harris Bethan , R. Anderson Seonaid , V. Shamsudheen Semeena
Published: March 2021

Across West Africa rain-fed agriculture fulfils approximately 80% of the food needs of the population and employs 60% of the workforce. It is therefore critical to understand the effects of intraseasonal rainfall variability across West Africa. Previous work has shown that land-atmosphere interactions across West Africa can influence daily variability in deep convection characteristics and the impact of 10-25 day precipitation variability. Using earth observations and reanalyses, this study investigates the land surface response to 20-200 day precipitation variability and its impact on land-atmosphere interactions and the West African monsoon.

                Surprisingly, even though the sensitivity of the land surface across the Sahel to strong convection is short-lived (days) and daily precipitation patterns are strongly heterogeneous, a coherent regional-scale land surface response to 20-200 day precipitation variability is observed. This sensitivity of the land surface affects land-atmosphere interactions on a regional scale and perturbs the West African monsoon circulation. For example, during sub-seasonal periods of low rainfall, soil moisture significantly decreases across the Sahel and land surface temperatures increase by up to 2°C. Surface drying and warming across the Sahel is associated with an intensified heat low and a northward shift of low-level monsoon westerlies. During periods of high rainfall, the surface moistens and cools, which is associated with a high pressure tendency across the Sahel. This high pressure tendency dampens the heat low circulation across West Africa and reduces regional moisture fluxes. We show that the land surface response to 20-200 day rainfall variability across West Africa can have a significant impact on the monsoon circulation. This suggests that improving the representation of land-surface processes across West Africa has the potential to improve sub-seasonal forecast predictability and enhance early warning systems.
Tidal Modulation of Antarctic Ice Shelf Melting
Authors: Richter Ole , Gwyther David E. , King Matt A. , Galton-Fenzi Ben K.
Published: March 2021

Tides influence basal melting of individual Antarctic ice shelves, but their net impact on Antarctic-wide ice-ocean interaction has yet to be constrained. Here we quantify the impact of tides on ice shelf melting and the continental shelf seas by means of a 4 km resolution circum-Antarctic ocean model. Activating tides in the model increases the total basal mass loss by 57 Gt/yr (4 %), while decreasing continental shelf temperatures by 0.04 °C, indicating a slightly more efficient conversion of ocean heat into ice shelf melting. Regional variations can be larger, with melt rate modulations exceeding 500 % and temperatures changing by more than 0.5 °C, highlighting the importance of capturing tides for robust modelling of glacier systems and coastal oceans. Tide-induced changes around the Antarctic Peninsula have a dipolar distribution with decreased ocean temperatures and reduced melting towards the Bellingshausen Sea and warming along the continental shelf break on the Weddell Sea side. This warming extends under the Ronne Ice Shelf, which also features one of the highest increases in area-averaged basal melting (128 %) when tides are included. Further, by means of a singular spectrum analysis, we explore the processes that cause variations in melting and its drivers in the boundary layer over periods of up to one month. At most places friction velocity varies at tidal timescales (one day or faster), while thermal driving changes at slower rates (longer than one day). In some key regions under the large cold-water ice shelves, however, thermal driving varies faster than friction velocity and this can not be explained by tidal modulations in boundary layer exchange rates alone. Our results suggest that large scale ocean models aiming to predict accurate ice shelf melt rates will need to explicitly resolve tides.
SaferPLACES platform: a cloud-based climate service addressing urban flooding hazard and risk.
Authors: Bagli Stefano , Mazzoli Paolo , Renzi Francesca , Luzzi Valerio , Persiano Simone , Castellarin Attilio , Mysiak Jaroslav , Essenfelder Arthur , Larosa Francesca , Pasetti Stefania , Folegani Marco , Schröter Kai , Ullrich Sophie , Mediero Luis
Published: March 2021

Floods are a global hazard that may have adverse impacts on a wide-range of social, economic, and environmental processes. Nowadays our cities are flooding with increased occurrence due to more severe weather events but also due to anthropogenic pressures like soil sealing, urban growth and, in some areas,  land subsidence. Frequency and intensity of extreme floods are expected to further increase in the future in many places due to climate change. 

The characterisation of flood events and of their multi-hazard nature is a fundamental step in order to maximise the resilience of cities to potential flood losses and damages. 

SaferPLACES employs innovative climate, hydrological and raster-based flood hazard and economic modelling techniques to assess pluvial, fluvial and coastal flood hazards and risks in urban environments under current and future climate scenarios.

SaferPLACES platform provides a cost-effective and user-friendly cloud-based solution for flood hazard and risk mapping. Moreover SaferPLACES supports multiple stakeholders in designing and assessing multiple mitigation measures such as flood barriers, water tanks, green-blue based solutions and building specific damage mitigation actions.

The intelligence behind the SaferPLACES platform integrates innovative fast DEM-based flood hazard assessment methods and Bayesian damage models, which are able to provide results in short computation times by exploiting the power of cloud computing.

A beta version of the platform is available at platform.saferplaces.co and active for four pilot cities: Rimini and Milan in Italy, Pamplona in Spain and Cologne in Germany.

SaferPLACES (saferplaces.co) is a research project founded by EIT Climate-KIC (www.climate-kic.org).
How fast the earth surface breathe? Gas transport in high permeability soils and earth surface discontinuities
Authors: Weisbrod Noam , Dragila Maria , Levintal Elad
Published: March 2021

Gas movement within the earth’s subsurface and its exchange with the atmosphere are some of the principal processes in soil, ecosystem, and atmospheric environments. For a decade, our group has explored the roles played by atmospheric conditions and matrix properties in gas transport at the earth-atmosphere interface, where surface discontinuities, such as fractures, boreholes and aggregated soils, exist and may affect the process.

The gas transport mechanisms, resulting from the development of a thermal gradient and surface wind, were analyzed both independently and in combination. Two types of experiments were carried out: (1) under field conditions and (2) under highly controlled laboratory conditions. During all studies, temperature and wind conditions across the media and at the media-atmosphere interface were monitored. Results show that the magnitudes of thermal- and wind-induced convection were directly related to the media permeability, given favorable ambient conditions at the media-atmosphere interface. Such ambient conditions included high diurnal temperature amplitude (~± 10 ᵒC) or high surface wind (~2 m/s measured 10 m above ground). In addition, specific results from the field experiment were used to establish an empirical model that predicts gas transport magnitude as a function of wind speed and media permeability.

With respect to other discontinuities, such as boreholes and fractures, the effect of atmospheric conditions was investigated, namely atmospheric pressure and temperature, on air, CO2, and radon transport. Using high-resolution spatiotemporal measurements, it was concluded that diurnal atmospheric pressure oscillations (barometric pumping) and borehole-atmospheric temperature differences (thermal-induced convection) controlled the air transport within the boreholes. For one of the boreholes monitored, the air velocities and CO2 emissions to the atmosphere were quantified (up to ~6 m/min and ~5 g-CO2/min, respectively). This reveals the role of boreholes as a source of greenhouse gas emissions.

The results and conclusions derived from our studies are expected to improve our understanding of the governing mechanisms controlling gas movement in porous media, fractures, and boreholes, and their functions in gas exchange across the earth-atmosphere interface.
Citywide rainfall estimates from hundreds of E-band CMLs
Authors: Rios Gaona Manuel F. , Fencl Martin , Bares Vojtech
Published: March 2021

Commercial Microwave Links (CMLs) have demonstrated to be a valuable complementary measuring technique with regard to rainfall measuring. Their intrinsic characteristics give them an edge over traditional networks such as meteorological radars, satellites, and rain gauges. For instance, given their high density, especially in urban areas, they offer a higher spatial (and even temporal) resolution against rainfall observations from rain gauges. Moreover, they observe rainfall in a close proximity to the ground surface compared to radar and/or meteorological satellites. As their use in monitoring rainfall is in its “early stage”, there are still some challenges to overcome, e.g., a low accuracy when observing light rainfall.

In general, CMLs networks used to operate within the C, X, Ku, K, and Ka bands of the electromagnetic spectrum (i.e., ~4 - 40GHz) over distances varying from hundreds-of-meters to tens-of-kilometres. A big advantage offered by these bands is the linear relationship between rainfall intensity and power attenuation, which actually is the cornerstone of rainfall retrievals from CMLs. Nevertheless, as the continuously increasing demand for a larger throughput in such networks, mobile operators are gradually moving into the 71 - 86 GHz region, i.e., the E band. This fact alone brings more challenges in the retrieval of rainfall as the relationship between rainfall intensity and power attenuation not only starts departing from linearity in this band but also is more sensitive to the drop size distribution of rainfall. On the other hand, over such frequencies/band, it is possible now to reliably monitor rainfall intensities lower than 1 mm/h, which was practically impossible with lower-frequency CMLs.

Our work focuses on the performance of ~250 E-Band CMLs over a continuous period of ~7 months in 2020. These CMLs are part of a larger network located in the city of Prague (Czech Republic) and its surroundings. We evaluate their performance against a local network of ~50 rain gauges. We demonstrate the potential of E-band CMLs in retrieving accurate estimates for both light and heavy rainfall. Recently, there has been only few studies focused on E-band links. Our contribution to the field is in performing analyses over a larger spatio-temporal scale.
Iron fertilization of the Southern Ocean: Synergy between sea ice, icebergs and ice shelves
Authors: Person Renaud , Vancoppenolle Martin , Aumont Olivier , Malsang Manon
Published: March 2021

Glacial iron (Fe) sources associated with continental ice (ice shelves and icebergs) and sea ice have recently been suggested as important to Southern Ocean (SO) biogeochemistry, where Fe limits primary production. Icebergs and ice shelves act as fully external sources of Fe while sea ice, which has a great Fe storage capacity, efficiently conveys Fe from the coasts to offshore locations. Large Fe concentrations in sea ice are typically explained by a sedimentary origin, however recent observations suggest an additional contribution from continental ice to the sea ice Fe inventory. Here, to further explore this hypothesis, we analyze factorial simulations performed with an ocean sea-ice biogeochemical model (NEMO-LIM3-PISCES version 3.6) in which interactive Fe sources from continental and marine glacial sources are activated, separately and in concert. Our simulations indicate that (i) about 15% of the iron content of sea ice comes from icebergs and ice shelves, (ii) sea ice motion conveys this extra Fe to regions where it limits productivity, which results in (iii) a modest increase in primary and export production, reaching ~1% of the SO total, or ~10% of the contribution of the SO cryosphere.
Stratospheric Aerosol and Gas Experiment III on the International Space Station (SAGE III/ISS) Newly Released V5.2 Validation of Ozone and Water Vapor Data
Authors: Kizer Susan , Flittner David , Roell Marilee , Damadeo Robert , Roller Carrie , Hurst Dale , Hall Emrys , Jordan Allen , Cullis Patrick , Johnson Bryan , Querel Richard
Published: March 2021

The Stratospheric Aerosol and Gas Experiment III (SAGE III) instrument installed on the International Space Station (ISS) has completed over three and a half years of data collection and production of science data products. The SAGE III/ISS is a solar and lunar occultation instrument that scans the light from the Sun and Moon through the limb of the Earth’s atmosphere to produce vertical profiles of aerosol, ozone, water vapor, and other trace gases. It continues the legacy of previous SAGE instruments dating back to the 1970s to provide data continuity of stratospheric constituents critical for assessing trends in the ozone layer. This presentation shows the validation results of comparing SAGE III/ISS ozone and water vapor vertical profiles from the newly released v5.2 science product with those of in situ and satellite data .
Arctic amplification as a rapid response to increased CO2
Authors: Janoski Tyler , Previdi Michael , Chiodo Gabriel , Smith Karen , Polvani Lorenzo
Published: March 2021

Arctic amplification (AA), or enhanced surface warming of the Arctic, is ubiquitous in observations, and in model simulations subjected to increased greenhouse gas (GHG) forcing. Despite its importance, the mechanisms driving AA are not entirely understood. Here, we show that in CMIP5 (Coupled Model Intercomparison Project 5) general circulation models (GCMs), AA develops within a few months following an instantaneous quadrupling of atmospheric CO2. We find that this rapid AA response can be attributed to the lapse rate feedback, which acts to disproportionately warm the Arctic, even before any significant changes in Arctic sea ice occur. Only on longer timescales (beyond the first few months) does the decrease in sea ice become an important contributor to AA via the albedo feedback and increased ocean-to-atmosphere heat flux. An important limitation of our CMIP5 analysis is that internal climate variability is large on the short time scales considered. To overcome this limitation – and thus better isolate the GHG-forced response – we produced a large ensemble (100 members) of instantaneous CO2-quadrupling simulations using a single GCM, the NCAR Community Earth System Model (CESM1). In our new CESM1 ensemble we find the same rapid AA response seen in the CMIP5 models, confirming that AA ultimately owes its existence to fast atmospheric processes.
The Role of Mesoscale Cellular Convective Cloud Morphologies in Low Cloud Feedbacks 
Authors: McCoy Isabel L. , McCoy Daniel T. , Wood Robert , Zuidema Paquita , Bender Frida A.-M.
Published: March 2021

Mesoscale cellular convective (MCC) clouds occur in large-scale patterns over the ocean, are prevalent in sub-tropical cloud regions and mid-latitudes, and have important radiative impacts on the climate system. On average, closed MCC clouds have higher albedos than open or disorganized MCC clouds for the same cloud fraction which suggests differences in micro- and macro-physical characteristics between MCC morphologies. Marine cold air outbreaks (MCAOs) influence the development of open MCC clouds and the transition from closed to open MCC clouds in the mid-latitudes. A MCAO index, M, combines atmospheric surface forcing and static stability and can be used to examine global MCC morphology dependencies. MCC cloud morphology occurrence is also expected to shift with sea surface temperature (SST) changes as the climate warms. Analysis of MCC identifications (derived from a neural network classifier applied to MODIS satellite collection 6 liquid water path retrievals) and ECMWF ERA5 reanalysis data shows that closed MCC cloud occurrence shifts to open or disorganized MCC within an M-SST space. Global climate models (GCMs) predict that M will change regionally in strength as SSTs increase. Based on our derived MCC-M-SST relationship in the current climate, closed MCC occurrence frequency is expected to increase with a weakening of M but decrease with an increase in SSTs. This results in a shift to cloud morphologies with lower albedos. Cloud controlling factor analysis is used to estimate the resulting low cloud morphology feedback which is found to be spatially varied and between ±0.15 W m-2 K-1. Because the morphology feedback is estimated to be positive in the extra-tropics and is not currently represented in GCMs, this implies a higher climate sensitivity than GCMs currently estimate.
New Constraints on Fault Nucleation and Propagation Using Dynamic Microtomography Experiments
Authors: Zhu Wen-lu
Published: March 2021

Experimental rock deformation research plays an important role in understanding the mechanical behavior, deformation microstructures, and physical properties of rocks and minerals. In practice, most experiments are designed to isolate a given process, limiting access to the interplay between various processes that takes place in nature. This is in part because changes in microstructure are commonly documented after an experiment has ended. The loss of information during deformation makes quantifying feedback of different mechanisms extremely challenging. However, natural processes often involve concurrent inelastic deformation mechanisms and simultaneous metamorphic or diagenetic reactions. Quantitative accessment of these processes demands better constraints of the feedback between rock deformation and the evolving rock properties and microstructures.

Recent dynamic microtomography experiments have shown great potential in characterizing the evolution of microstructure and strain distribution during fault growth at in-situ pressure and temperature conditions. Using an X-ray transparent deformation apparatus that operates at crustal stress conditions, we have imaged the process of fault nucleation and propagation in natural rocks undergoing brittle faulting.  Applying the digital volume correlation technique to time-resolved 3-dimensional microtomographic datasets, we documented the evolution of strain distribution within a deforming rock. These results elucidate how fractures open, slide, coalesce, and propagate in rock samples responding to increasing shear stress.  

Using dynamic microtomography, it is now possible to address the effect of chemo-mechanical coupling on the emergent properties of rocks by conducting deformation experiments in which several mechanisms operate simultaneously. We studied the effect of chemo-mechanical coupling on fracturing induced by hydration reaction in serpentinite. Quantitative characterization of evolving mechanical behavior and microstructure enables us to understanding the feedback between thermal load, chemical reaction rate, and mechanical failure. Dynamic microtomography provides a promising approach to link evolving mechanical behavior with evolving microstructures. New experimental constraints on microstructural and internal stress-strain evolution can lead to more robust extrapolations of laboratory results to large scale geologic processes.
The NASA-TROPOMI Aerosol Algorithm: Evaluation of first results
Authors: Torres Omar , Jethva Hiren , Ahn Changwoo , Jaross Glen , Loyola Diego
Published: March 2021

The NASA-TROPOMI aerosol algorithm (TropOMAER), is an adaptation of the currently operational OMI near-UV (OMAERUV & OMACA) inversion schemes, that take advantage of TROPOMI’s unprecedented fine spatial resolution at UV wavelengths, and the availability of ancillary aerosol-related information to derive aerosol loading in cloud-free and above-cloud aerosols scenes. In this presentation we will introduce the NASA TROPOMI aerosol algorithm and discuss initial evaluation results of retrieved aerosol optical depth (AOD) and single scattering albedo (SSA) by direct comparison to AERONET AOD direct measurements and SSA inversions. We will also demonstrate TropOMAER retrieval capabilities in the context of recent continental scale aerosol events.
Evidence for efficient non-evaporative leaf cooling mechanism in a pine forest under drought conditions
Authors: Muller Jonathan D. , Rotenberg Eyal , Tatarinov Fyodor , Oz Itay , Yakir Dan
Published: March 2021

The reduced availability of evaporative cooling resulting from a hotter and drier climate can lead to high leaf temperatures resulting in overheating. This can affect a variety of biophysical and biochemical processes that could enhance mortality. Plant resilience to these increasingly stressful conditions could rely on non-evaporative cooling. However, to what extent this plays a role is poorly known at present.

In order to assess heat dissipation under the long summer drought conditions, we measured leaf-to-air temperature differences ΔTleaf-air of pine needles in semi-arid conditions in a drought-exposed and in an experimentally irrigated plot. For this purpose, we developed a novel, high accuracy system based on an infrared camera capable of continuous measurements of leaf temperature under field conditions. Both drought-exposed and irrigated trees, which had a 10x higher transpiration rate, exhibited a similar ΔTleaf-air that remained mostly below 3.5°C. Variations in mean wind speed did not strongly affect ΔTleaf-air, but it depended highly on within-canopy turbulence. This suggests a non-evaporative cooling mechanism that relies on the low leaf resistance to heat transfer, thus generating a large sensible heat flux. The ~30% reduction in resistance between leaves of drought-exposed and irrigated trees in the same species must be a result of changes in leaf characteristics and differences in canopy structure influencing wind penetration into the canopy. This reduction in resistance is required to generate the sufficiently larger sensible heat flux of nearly 100 W m-2 observed between both treatments under high radiation.

Non-evaporative cooling was demonstrated to be an effective leaf- and leaf-branch-scale cooling mechanism in trees with small leaves, which can be a critical factor in forest resistance to drying climates. The generation of a leaf-scale sensible heat flux is considered as a possible mechanism leading to the development of the previously identified canopy-scale ‘convector effect’.
Gas hydrate destabilization and sea-level changes: insights from Miocene seep carbonate deposits of the northern Apennines (Italy)
Authors: Fontana Daniela , Conti Stefano , Fioroni Chiara , Argentino Claudio
Published: March 2021

The effects of global warming on marine gas hydrate stability along continental margins is still unclear and discussed within the scientific community. Long-term datasets can be obtained from the geological record and might help us better understand how gas-hydrate reservoirs responds to climate changes. Present-day gas hydrates are frequently associated or interlayered with authigenic carbonates, called clathrites, which have been sampled from many continental margins worldwide. These carbonates show peculiar structures, such as vacuolar or vuggy-like fabrics, and are marked by light δ13C and heavy δ18O isotopic values. Evidences of paleo-gas hydrate occurrence are recorded in paleo-clathrites hosted in Miocene deposits of the Apennine chain, Italy, and formed in different positions of the paleo foreland system: in wedge-top basins, along the outer slope of the accretionary prism, and at the leading edge of the deformational front. The accurate nannofossil biostratigraphy of sediment hosting paleo-clathrites in the northern Apennines allowed us to ascribe them to different Miocene nannofossil zones, concentrated in three main intervals: in the Langhian (MNN5a), in the upper Serravallian-lower Tortonian (MNN6b-MNN7) and the upper Tortonian-lowermost Messinian (MNN10-MNN11). By comparing paleo-clathrite distributions with 3rd order eustatic curves, they seem to match phases of sea-level lowering associated with cold periods. Therefore, we suggest that the drop in the hydraulic pressure on the plumbing system during sea-level lowering shifted the bottom of the gas hydrate stability zone to shallower depths, inducing paleo gas-hydrate destabilization. The uplift of the different sectors of the wedge-top foredeep system during tectonic migration might have amplified the effect of the concomitant eustatic sea-level drop, reducing the hydrostatic load on the seafloor and triggering gas-hydrate decomposition. We suggest that Miocene climate-induced sea-level changes played a role in controlling gas hydrate stability and methane emissions along the northern Apennine paleo-wedge, with hydrate destabilization roughly matching with sea-level drops and cooling events.

 
Application of a new type of six-component seismometer for underground anomaly detection
Authors: Fang Xinding
Published: March 2021

A new type of portable six-component seismometer is invented and used in the development of a seismic imaging method for shallow subsurface anomaly detection. This new six-component seismometer contains a mini-MEMS-array for acceleration and rotational velocity measurements. The self-noise for acceleration measurement is about 8 µg/√Hz, and the self-noise for rotational velocity measurement is about 5 µrad/s/√Hz. The frequency band is DC-1000 Hz. Different from the traditional seismic imaging methods that require the deployment of an array of either one-component or three-component seismometers, our imaging method is established based on the data recorded at individual six-component seismometer. Because the rotational field (i.e., the curl field) gives information about the spatial gradient of a seismic wavefield, so the translational field together with the rotational field can be used to derive the frequency-dependent velocity (i.e., dispersion) of the formation right beneath a seismic station. This single station velocity inversion approach delivers localized subsurface velocity information, making it suitable for imaging of small-scale underground anomalies. Especially, the Rayleigh wave dispersion is used in our method as Rayleigh wave is generally the dominant signal in surface seismic data. An underground velocity model can be immediately constructed by consolidating the dispersion curves derived from individual receivers. In our study, we first demonstrate the accuracy of our imaging method through numerical modeling of various scenarios of subsurface anomalies and then conduct an experiment to further verify the performance of our self-invented six-component seismometer and the field applicability of our imaging method.
In situ measurements at the Mont Terri rock laboratory to study argillaceous rocks
Authors: Rebscher Dorothee , Beilecke Thies , Costabel Stephan , Furche Markus , Hesser Jürgen , Kneuker Tilo , Schennen Stephan , Schuster Kristof , Ziefle Gesa
Published: March 2021

Safe as well as sensible economic uses of the subsurface demand both the comprehensive knowledge of the present state of a system and the understanding of the relevant dynamical processes. In order to facilitate these requirements, adequate characterisation, sufficient monitoring, and conclusive experiments have to be performed. Following this directive, the German Federal Institute for Geosciences and Natural Resources (BGR) has developed, adapted, and successfully employed methods to prospect Opalinus Clay in the Swiss Mont Terri rock laboratory. These methods encompass geoscientific in situ characterisations as well as investigation techniques as part of long-term monitoring programmes from the complementing fields of e.g. micro-seismics, Electrical Resistivity Tomography, micro-structural petrography, geohydrology, and Nuclear Magnetic Resonance. With this expertise, BGR has contributed numerous experiments, which are embedded and coordinated in the long-standing and fruitful cooperation with the partners of the Mont Terri Consortium.

The knowledge gain, based on now almost 25 years of BGR's engagement in the Mont Terri Project, offers comparison and evaluation of different, complementing methods determining present values and their evolution in time of e.g. moisture, saturation, pressure, deformation, the characterisation of parameter variability, and localisation of heterogeneities. It provides information allowing for programme optimisation of in situ measuring methods concerning penetration, resolution, effort, time, or feasibility. Therefore, the research results can be used for decision-making to refine investigation endevours in regards to specific demands of a certain site or a particular scientific problem not only for Opalinus Clay but also other claystone formations, and in some cases even for non-argillaceous rocks.
Flash drought as a new normal in a warming climate
Authors: Yuan Xing , Wang Yumiao , Zhang Miao
Published: March 2021

Conventional droughts are creeping climate anomalies that take months or years to fully develop, causing devastating impact silently. In contrast, flash droughts have been considered as a type of drought with more rapid onset, develop and terminate at a shorter time scale. There has been a hot debate on the definition of flash drought, and whether it is necessary to investigate the impact of flash drought given the duration is usually shorter than conventional drought. We clarify that flash drought is not a monster, while it has complete onset and recovery processes as conventional drought. Flash drought expands the conventional drought from seasonal-to-decadal scales to sub-seasonal scale, where synoptic land-atmospheric coupling might become critical for its onset. Focusing on a once-in-a-century flash drought in late summer of 2019, we analyze the latest Coupled Model Intercomparison Project Phase 6 (CMIP6) climate model data and show that climate change caused by anthropogenic activities (e.g., emissions of greenhouse gases and aerosols, land use change, etc) has increased the likelihood of such drought onset speed by 42±19%. A further analysis based on CMIP6 multi-model ensemble simulations over the global land areas shows that there was no significant trend in frequency during 1850-1970, but flash drought became more frequency in the recent 40 years. All these results suggest that climate change accelerates the drought development speed, and flash drought might become as a new normal in a warming climate. The eco-hydrological impact of this “new normal” will also be discussed by investigating FLUXNET in-situ observations and MODIS satellite retrievals.
Flow-induced microfracturing of granite in superhot geothermal environments
Authors: Goto Ryota , Watanabe Noriaki , Sakaguchi Kiyotoshi , Chen Youqing , Ishibashi Takuya , Pramudyo Eko , Parisio Francesco , Yoshioka Keita , Nakamura Kengo , Komai Takeshi , Tsuchiya Noriyoshi
Published: March 2021

Superhot geothermal environments with temperatures of approximately 400-500︒C at depth of approximately 2-4 km are expected as a new geothermal energy frontier. In order to efficiently exploit the superhot geothermal resources, fracture systems are necessary as flow path of working fluid. Hydraulic fracturing is a promising technique because it is able to create a new fracture system or enhance the permeability of preexisting fracture system. Laboratory-scale hydraulic fracturing experiments of granite have demonstrated the formation of densely distributed network of permeable fractures throughout the entire rock body at or near the supercritical temperature for water. Though the process has been presumed to involve continuous infiltration of low-viscosity water into preexisting microfractures followed by creation and merger of the subsequent fractures, plausible criterion for the fracturing is yet to be clarified. The possibility that the Griffith failure criterion is available to predict the occurrence of fracturing was shown by hydraulic fracturing experiments with acoustic emission measurements of granite at 400︒C under true triaxial stress. The present study provides a theoretical basis required to establish the procedure for hydraulic fracturing in superhot geothermal environment.
An impact of COVID-19 pandemic on research activities and work-life balance for geoscientists in Japan
Authors: Hori, S. Rie , Abe Natsue , Oguchi, T. Chiaki ,   The Committee for Diversity Management and Talent Pool of JpGU
Published: March 2021

The rapid spread out of the COVID-19 continuous to have a great impact on not only social life but also academic and educational activities. The geoscience fields in Japan are no exception. The committee for Diversity Management and Talent Pool, Japan Geoscience Union (JpGU) launched an urgent survey between 28 June and 9 July, 2020 by. The goal of the survey was quantifying the impact of COVID-19 pandemic on research activities and work-life balance for geoscientists in Japan. The questionnaire was published two languages: Japanese and English. Although the questionnaire system was opened for a short period of time (12 days), over 400 answers were obtained, of which 351 in Japanese and 65 in English. The results revealed that activities of female geoscientists have been damaged by increasing burden of housework and childcare during confinement period by a state of coronavirus emergency, more than male. We present here some highlights of these results of COVID-19 survey by JpGU.

In the free text of the responses, there were specific and earnest appeals regarding the support necessary and expected. The support requests were targeted to various entities, namely JpGU, workplaces, schools, etc. The most common requests made to JpGU were to provide online educational materials and online lecture know-how, and to introduce virtual options to future conferences. Survey responders with childcare responsibilities pointed out the difficulties to attend conferences from home.

In conclusion, we need to reevaluate our consideration for the diverse members, possessing various background and impairments, who are easily left behind in the rapid changes, in academic activities due to COVID-19.
Experimental constraints on volcanic ash generation and clast morphometrics in pyroclastic density currents and granular flows
Authors: Hornby Adrian , Kueppers Ulrich , Maurer Benedikt , Poetsch Carina , Dingwell Donald
Published: March 2021

Pyroclastic density currents (PDCs) present perhaps the greatest proximal primary hazard of volcanic activity and produce abundant fine ash that can present a range of health, environment and infrastructure hazards. However, direct, fully quantitative observation of ash production in PDCs is lacking, and little direct evidence exists to constrain the parameters controlling ash generation in PDCs. Here, we use an experimental approach to investigate the effects of starting mass, material density and ash removal on the efficiency of ash generation and concurrent clast rounding in the dense basal flow of PDCs. We employ a rotary drum to tumble pumice and scoria lapilli clasts over multiple transport “distance” steps (from 0.2 to 6 km). We observe increased ash generation rates with the periodic removal of ash during the experiments and with increasing starting mass. By scaling to the bed height and clast diameter we obtain a general description for ash production in all experiments as a function of flow distance, bed height and average clast diameter. We confirm that changes in lapilli shape factors correlate with the ash fraction generated and that the grain size of ash produced decreases with distance. Finally, we estimate shear rate in our experiments and calculate the inertial number, which describes the ratio between clast-scale and flow-scale rearrangement during flow. We show that, under certain conditions, fractional ash production can be calculated accurately for any starting mass solely as a function of the inertial number and the flow distance. This work sheds light on some of the first systematic and generalizable experimental parameterizations of ash production and associated clast evolution in PDCs and should advance our ability to understand flow mobility and associated hazards.
Modeling Large Deformation Slope Failure Using The Smoothed Particle Hydrodynamics (SPH) Method
Authors: Andreatama Bunyamin , Prakoso Widjojo Adi , Bahsan Erly , Marthanty R.R. Dwinanti Rika , Sjah Jessica
Published: March 2021

The slope stability analyses using limit equilibrium method (LEM) and finite element method (FEM) are mostly concerned about the factor of safety (FS) value of the slope. LEM cannot predict the soil behaviour after failure, while FEM can only be used to measure the material deformation before failure. Currently the Smoothed Particle Hydrodynamics (SPH) method has begun to be used as an alternative to overcome excess distortion of the mesh in FEM analysis due to post-failure large deformations in slope stability analysis. In this study, the behaviour of soil materials will be modelled as particles using the SPH method with reference to the previous research. The Bingham fluid model is used as a viscoplastic model of the soil material, and the Drucker-Prager soil constitutive model is used to describe the elastic-plastic behaviour of the soil. This modelling algorithm uses the equivalent viscosity of the Bingham fluid model as the initial stress between particles, and it uses the Drucker-Prager criterion with the associated flow rule to describe particle displacement due to slope failure. The soil particles are modelled as cohesive soil with a slope angle to the horizontal axis so that they can be compared with previous studies. The failure pattern is expected to be able to show areas of particles that are not deformed and particles that have collapsed. The FS value of the slope is obtained by the strength reduction method which seeks a non-convergent solution of each reduction in soil strength parameters.

Keywords: Smoothed Particle Hydrodynamics (SPH); Slope Stability; Bingham Fluid Model; Drucker-Prager Model; Strength Reduction Method