bluuebunny/crossref_metadata_2025 huggingface dataset:
Moisture fluxes in the tropics dominated by deep convection up to near tropical tropopause levels
Authors: Bolot Maximilien , Fueglistaler Stephan
Published: March 2021

The role played by tropical storms in the tropical tropopause layer (TTL), the transitional layer regulating the flux into the stratosphere of trace gases affecting radiation and the ozone layer, has been a long-standing open question. Progress has been slow because of computational limitations and challenging conditions for measurements and most numerical studies have used simulations over limited domains whose results must be upscaled to the tropical surface to infer global impacts. We compute the first global observational estimate of the convective ice flux at near tropical tropopause levels by using spaceborne lidar measurements from CALIOP. The calculation uses a method to convert from lidar extinction to sedimenting ice flux and uses error propagation to provide margins of uncertainty. We show that, at any given level in the TTL, the sedimenting ice flux exceeds the inflow of vapor computed from ERA5 reanalysis, revealing additional ice transport and allowing to deduce the advective ice flux as a function of altitude. The contribution to this flux of large-scale motions (resolved by ERA5) is computed and the residual is hypothesized to represent the flux of ice on the convective scale. Results show without ambiguity that the upward ice flux in deep convection dominates moisture transport up to close to the level of the cold point tropopause.
Examining the relative effects of obliquity and precession on variables important for glacial inception in Scandinavia and Baffin Island using linear reconstructions
Authors: ONeill Grainne , Broccoli Anthony
Published: March 2021

Glacial cycles are driven by cyclical changes in Earth’s three orbital parameters: obliquity, precession, and eccentricity.  A common interpretation of Milankovitch’s orbital theory suggests that June insolation at 65°N is the dominant forcing in driving glacial cycles. This places emphasis on precession which has the greatest effect on June insolation at 65°N. However, there is abundant evidence for the importance of obliquity in driving glacial cycles. We compare the relative strengths of obliquity and precession on climate to further explore the possibility that obliquity could be more important than common interpretations of Milankovitch’s orbital theory would suggest. We use a set of coupled atmosphere-ocean general circulation model simulations to produce time series of key climate variables. Such variables include snowfall and positive degree-days (the sum of mean daily temperature for all days above 0°C), which are proxies for accumulation and ablation, respectively. We focus our analysis on glacial inception in Scandinavia and Baffin Island, the locations where the Scandinavian and Laurentide ice sheets were initiated. We show that obliquity causes changes in positive degree-days of larger magnitude than those of precession in both Scandinavia and Baffin Island. Snowfall is dominated by obliquity in Scandinavia and by precession in Baffin Island. The location dependence of the importance of obliquity and precession may have implications for deglaciation which occurred at lower latitudes than the inception locations. Additionally, our positive degree-day time series were most closely represented by Milankovitch’s caloric summer insolation metric than June insolation at 65°N.
Predictability of extreme events in UFS at subseasonal time scale
Authors: Stan Christiana
Published: March 2021

The predictability of extreme events over the continental United States (CONUS) in the Unified Forecast System (UFS) Couple Model is studied at subseasonal time scale. The benchmark runs of UFS (GFSv15), a coupled model consisting of atmospheric component (FV3GFS) with 28 km resolution and ocean (MOM6) and sea ice (CICE5) components with global 0.25° resolution, for the period April 2011–December 2017 have been assessed. The model’s month-long forecasts initiated on the first and fifteenth of each month are used to examine the predictability of extreme events in precipitation and 2m temperature. The atmospheric and ice initial conditions are from CFSR data, and the ocean initial conditions are from 3Dvar CPC. The errors in the week 1–4 predictions and the corresponding spatial correlation between model and observation over CONUS are presented. The differences in the predictability of the extreme events between the boreal summer and winter are discussed. Two categories of extreme events are evaluated: 95th and 99th percentile, respectively. The forecast skill of extreme events in the 95th percentile is higher than the forecast skill of events in the second category. The forecast skill of warm and cold events in the 95th percentile shows seasonal dependence and is higher during the boreal winter.
Exploring rift magmatism and evolution through gravity analysis of North America's failed rifts
Authors: Elling Reece , Stein Seth , Stein Carol , Keller G. Randy
Published: March 2021

Comparative study of North America’s failed continental rifts allows investigation of the effects of extension, magmatism, magmatic underplating and rift inversion in the evolution of rifting. We explore this issue by examining the gravity signatures of the Midcontinent Rift (MCR), Reelfoot Rift (RR), and Southern Oklahoman Aulacogen (SOA). The ~1.1 Ga MCR records aspects of the complex assembly of Rodina, while the structures related to the ~560 Ma RR and SOA formed during the later breakup of Rodinia and subsequent assembly of Pangea. Combining average gravity anomalies along each rift with seismic data, we examine whether these data support the existence of high-density residual melt underplates (“rift pillows”), reflect the possible amounts of inversion, and whether these rifts should be considered analogs of one another at different stages in rift evolution. The MCR and SOA have strong gravity highs along much of their length. Furthermore, the west and east arms of the MCR have different gravity signatures. The west arm of the MCR has a positive gravity anomaly of 80-100 mgals, while the east arm and SOA have positive anomalies of only 40-50 mgals. The RR does not exhibit a high positive anomaly along much of its length. The positive anomalies of both arms of the MCR and SOA reflect 10-20 km thick underplates at the base of the crust. These gravity anomalies also reflect greater amounts of inversion, during which the rift-bounding normal faults are reactivated by later compression, bringing the high-density igneous rocks closer to the surface. By averaging gravity data along the length of each failed rift, we can more easily distinguish between the history of individual rifts and general features of rifting that apply to other failed or active rifts around the world.
Dynamics of the Deep Chlorophyll Maximum in the Black Sea as depicted by BGC-Argo floats
Authors: Capet Arthur , ricour florian , D'Ortenzio Fabrizio , Delille Bruno , Grégoire Marilaure
Published: March 2021

The deep chlorophyll maximum (DCM) is a well known feature of the global ocean. However, its description and the study of its formation are a  challenge, especially in the peculiar environment that is the Black Sea. The retrieval of chlorophyll a (Chla) from fluorescence (Fluo) profiles recorded by biogeochemical-Argo (BGC-Argo) floats is not trivial in the Black Sea, due to the very high content of colored dissolved organic matter (CDOM) which contributes to the fluorescence signal and produces an apparent increase of the Chla concentration with depth.

Here, we revised Fluo correction protocols for the Black Sea context using co-located in-situ high-performance liquid chromatography (HPLC) and BGC-Argo measurements. The processed set of Chla data (2014–2019) is then used to provide a systematic description of the seasonal DCM dynamics in the Black Sea and to explore different hypotheses concerning the mechanisms underlying its development.

Our results show that the corrections applied to the Chla profiles are consistent with HPLC data. In the Black Sea, the DCM begins to form in March, throughout the basin, at a density level set by the previous winter mixed layer. During a first phase (April-May), the DCM remains attached to this particular layer. The spatial homogeneity of this feature suggests a hysteresis mechanism, i.e., that the DCM structure locally influences environmental conditions rather than adapting instantaneously to external factors.

In a second phase (July-September), the DCM migrates upward, where there is higher irradiance, which suggests the interplay of biotic factors. Overall, the DCM concentrates around 45 to 65% of the total chlorophyll content within a 10 m layer centered around a depth of 30 to 40 m, which stresses the importance of considering DCM dynamics when evaluating phytoplankton productivity at basin scale.
SWIRRL API for provenance-aware and reproducible workspaces. The EPOS and IS-ENES approach.
Authors: Spinuso Alessandro , Striewski Friedrich , van der Neut Ian , Veldhuizen Mats , Langeland Tor , Page Christian , Bailo Daniele
Published: March 2021

Modern interactive tools for data analysis and visualisation are designed to expose their functionalities as a service through the web. We present an open source web API (SWIRRL) that allows Science Gateways to easily integrate such tools in their websites and re-purpose them to their users. The API, developed in the context of the ENVRIFair and IS-ENES3 EU projects, deals on behalf of the clients with the underlying complexity of allocating and managing resources within a target container orchestration platform on the cloud. By combining storage and third parties' tools, such as JupyterLab and the Enlighten visualisation software, the API creates dedicated working sessions on-demand. Thanks to the API’s staging workflows, SWIRRL sessions can be populated with data of interest collected from external data providers. The system is designed to offer customisation and reproducibility thanks to the recording of provenance, which is performed for each method of the API’s affecting the session. This is implemented by combining a PROV-Templates catalogue and a graph database, which are deployed as independent microservices. Notebooks can be customised with new or updated libraries, and the provenance of such changes is then exposed to users via the SWIRRL interactive JupyterLab extension. Here, users can control different types of reproducibility actions. For instance, they can restore the libraries and data used within the notebook in the past, as well as creating snapshots of the running environment. This allows users to share and rebuild full Jupyter workspaces, including raw data and user generated methods. Snapshots are stored to Git as Binder repositories, thereby compatible with  mybinder.org. Finally, we will discuss how SWIRRL is and will be adopted by existing portals for Climate analysis (Climate4Impact) and for Solid Earth Science (EPOS), where advanced data discovery capabilities are combined with customisable, recoverable and reproducible workspaces.
Modeling debris flow triggered by snow melting in the Barsemdara river valley, Tajikistan
Authors: Kurovskaia Viktoriia , Chernomorets Sergey , Vinogradova Tatyana , Krylenko Inna
Published: March 2021

Debris flow is one of the most hazardous events that occur in all mountain regions.  Direct debris flow damage includes loss of human life, destruction of houses and facilities, damage to roads, rail lines and pipelines, vehicle accidents, and many other losses that are difficult to quantify. In July 2015, in the valley of the Barsemdara River (Gorno-Badakhshan Autonomous Region, Tajikistan), plenty of debris flows were observed. As a result, residential areas, social facilities, and infrastructure in Barsem village and neighboring settlements were destroyed and flooded. Besides, debris flow deposits blocked the Gunt River with the subsequent formation of a dammed lake with a maximum volume of 4.0 million m3. 
The aim of this study was to obtain hydrographs of debris flow waves in the source and detailed zoning of the Barsemdara river valley. For the debris flow source, we applied transport-shift model. Equations of this model were developed by Yu.B. Vinogradov basing on Chemolgan experiments of artificial debris flows descending. Previously, the model characteristics were compared with the observational data of the Chemolgan experiments, and the results were found to be satisfactory [Vinogradova, Vinogradov, 2017]. Based on the equations, a computer program was created in the programming language Python. Besides, we improved the model by adding flow velocity calculations, and eventually it became possible to obtain hydrographs. To investigate quantitative characteristics of the debris flow in the river valley we implied a two-dimensional (2D) model called FLO-2D PRO. It is based on the numerical methods for solving the system of Saint-Venant equations. Besides, in this model, it is assumed that debris flows move like a Bingham fluid (viscoplastic fluid) [O'Brien et al., 1993]. The input information for modeling was digital elevation model (DEM) and previously obtained hydrographs. The output information included flow depth, velocity distribution and hazard level of the territory. The results of the study will be reported.

1.    Vinogradova T.A., Vinogradov A.Y. The Experimental Debris Flows in the Chemolgan River Basin // Natural Hazards. – 2017. – V. 88. – P. 189-198.
2.    O'Brien J. S., Julien P.Y., Fullerton W.T. Two-dimensional water flood and mudflow simulation //Journal of hydraulic engineering. – 1993. – V. 119, No 2. – P. 244-261.
COVID-19 lockdown effects on gender inequality: the case of the Italian Astronomy & Astrphysics Community
Authors: Inno Laura , Rotundi Alessandra , Piccialli Arianna
Published: March 2021

Among European countries, Italy was the first to be heavily hit by the outbreak of COVID-19 and quickly decreed on 9 March 2020 that the entire national territory be locked down to prevent its further spread, establishing an unprecedented situation for its citizens, including researchers. Italy hosts a large (~2000) and lively community of researchers in the fields of Astronomy and Astrophysics, which contains the largest fraction of female researchers (~30%) among the world’s leading countries in astronomy (defined as the ones with IAU members >150). Therefore, the Italian community poses as an ideal testbed to investigate the consequences of the lockdown on research productivity, also by gender. 

In order to do so, we used the INAF and MIUR websites to compile a complete database of the Italian researchers, considered by gender, and matched it with the first authors of preprints posted on the largest preprint archive of natural science publications, arXiv, for each year from 2017 to 2020.

The submission rate over the previous three years is about 38.6 ± 8.2 (one standard deviation, σ) papers per month,  with the fraction of papers published by women consistently close to 30%, which well reflects the percentage of women in the community. As expected, the overall production in the first semester of 2020  (i.e. during the first lockdown) was lower than the average value estimated above. But if we break down this difference by the assigned first-author gender, we find that the decrease only concerns the submissions by female researchers, while submissions by male researchers actually increased during the lockdown by up to 10% (or a difference of 3.5σ).  We discuss this difference in productivity between male and female researchers during the lockdown as a possible reflection of the unbalanced distribution of the unpaid workload at home between partners.
Geomorphologically-controlled seismic signals at Mount St. Helens volcano
Authors: De Siena Luca , Gabrielli Simona , Spagnolo Matteo
Published: March 2021

In volcanoes, topography and shallow morphology can substantially modify seismic signals, tracing anisotropic signatures in the crust's most surficial layers. To better understand the influence of key morphologies, forward modelling of the seismic waveforms is fundamental.  Here, we introduce a forward model of the seismic wave equation developed with finite-differences schemes in anisotropic viscoelastic media. The observation of geomorphological features and the surficial geology map of Mount St. Helens are used to reproduce the scattering and anisotropic effects caused by shallow heterogeneity on seismic signals. The main aim is to understand if and to which lengths lateral anisotropic variations in geomorphological features control the generation and propagation of low-frequency seismic signals, focusing especially on the timing of surface-wave enhancement.

The model shows how the geomorphology-derived anisotropy controls the travel times of the horizontally polarized S waves (SH), in particular along with two directions: WNW-ESE, following the trend of a buried fault, and NS, consistent with the main morphological difference between southern (mostly untouched by the 1980 eruption) and northern (collapsed in 1980’s blast) flanks of the volcano. An analysis of the waveforms of a shallow event of 2005 (during the last eruption of Mt. St. Helens), located in the crater, shows how an isotropic model can reproduce the arrival of the SH wave at high frequencies (10 Hz). The introduction of an effective anisotropic medium is necessary to explain the arrivals for stations deployed across the north-northwestern flank of the volcano at lower frequencies (1 Hz and 6 Hz). The heterogeneity in the crater (e.g., the glacier inside the crater covered by a rock-debris layer) can create interfaces made mostly of unconsolidated materials. As also demonstrated by radiative transfer simulation, the crater acts as a primary source of surface waves dominating the seismic signals.
SALT: from rifted margins to fold-and-thrust belts. Insights from analogue modelling and case studies
Authors: Granado Pablo , Santolaria Pablo , Wilson Elizabeth , Ferrer Oriol , Muñoz Josep Anton
Published: March 2021

Salt and related structures have a strong influence on the formation of extensional basins during lithospheric stretching and thermal subsidence at rifted margins. Salt significantly influences as well the structural styles and kinematics of fold-and-thrust belts. We aim to characterize the structure of inverted minibasins and salt-influenced fold-and-thrust belts, but the challenge is to understand, and to match, the present day contractional structures with reasonable pre-orogenic configurations. Yet, we still lack proper understanding on the development of these salt-sediment systems and particularly, how salt tectonics is initially triggered and evolves through space and time. Two fundamental triggering mechanisms on rift to passive margin salt tectonics are known: (1) extension by gravitational collapse, and (2) differential loading. Key questions are: do these mechanisms occur at the same time or does one commonly follow the other? Which one is first and which one dominates? Does it depend on the location and timing of deformation on the passive margin? Which are the stratigraphic evidences and structural geometries that may help us to answer these questions? Recognizing the initial structural geometries of these minibasins once they have been incorporated into a fold and thrust belt is challenging but of paramount importance.

In this contribution we address some of these questions by showing a brief historical review of concepts and show end-member analogue models of fold-and-thrust belts developed from the inversion and incorporation of rift to passive margin salt basins. Our work is inspired by field observations from the Pyrenees and the Northern Calcareous Alps, as well as from present day continental margins.
Snow on Arctic sea ice in a warming climate as simulated in CESM
Authors: Webster Melinda , DuVivier Alice , Holland Marika , Bailey David
Published: March 2021

Snow on Arctic sea ice is important for several reasons: it creates a habitat for microorganisms and mammals, it changes sea-ice growth and melt, and it affects the speed at which ships and people can travel through sea ice. Therefore, investigating how snow on Arctic sea ice may change in a warming climate is useful for anticipating its potential effects on ecosystems, sea ice, and socioeconomic activities. Here, we use experiments from two versions of the Community Earth System Model (CESM) to study how snow conditions change over time. Comparison with observations indicates that CESM2 produces an overly-thin, overly-uniform snow distribution, while CESM1-LE produces a variable, excessively-thick snow cover. The 1950-2050 snow depth trend in CESM2 is 75% smaller than in CESM1-LE due to CESM2 having less snow. In CESM1-LE, long-lasting, thick sea ice, cool summers, and excessive summer snowfall facilitate a thicker, longer-lasting snow cover. In a warming climate, CESM2 shows that snow on Arctic sea ice will: (1) have greater, earlier spring melt, (2) accumulate less in summer-autumn, (3) sublimate more, and (4) cause marginally more snow-ice formation. CESM2 reveals that snow-free summers can occur ~30-60 years before an ice-free central Arctic, which may promote faster sea-ice melt.
An integrated geophysical-petrological view of the lithosphere of the northern Apennines, Dinarides and Pannonian Basin.
Authors: Torne Montserrat , Zhang Wentao , Jimenez-Munt Ivone , Negredo Ana , Bravo Estefania , Vergés Jaume , García-Castellanos Daniel
Published: March 2021

The present-day structure of the lithosphere and uppermost mantle of Northern Apennines and Dinarides region results from a complex tectonic scenario mainly driven by subduction of Tethyan oceanic domains. The study area and surrounding regions have been the goal of a large number of geophysical studies that have provided information on the velocity, density and temperature distribution in the lithosphere and uppermost mantle. However, the majority of them do not consider the contribution of the chemical composition and phase transitions on the physical properties in the lithospheric mantle. By applying and integrated petrological-geophysical approach -LitMod2D_2.0- we aim at constraining and characterizing the present-day lithosphere and mantle structure along a NE-SW trending 730 km long geo-transect crossing the Northern Tyrrhenian Sea, the Northern Apennines, the Adriatic Sea, the Dinarides fold belt and the Pannonian back-arc basin. Along the modelled geotransect, we infer the spatial distribution of density, thermal conductivity and seismic velocities based on the variations of gravity, geoid, elevation and heat flow consistently with the thermochemical conditions and with isostatic equilibrium. Our results show significant lateral variations in the lithospheric structure, affecting crustal and lithospheric mantle thickness, temperature, density distribution, and mantle composition that reveals the imprint of the complex geodynamic evolution of the area. This is a GeoCAM contribution (PGC2018-095154-B-I00)

Keywords: Alpine Mediterranean orogeny, geoid and gravity anomalies, elevation, integrated petrological-geophysical modelling, mantle seismic P and S-wave velocity.
Mapping and assessment of future land use change impacts on habitat quality in Lithuania
Authors: Pereira Paulo , Gomes Eduardo , Inacio Miguel , Bogdzevič Katarzyna , Karnauskaite Donalda , Kalinauskas Marius
Published: March 2021

Abstract

Human activity is directly responsible for land use and land cover changes, affecting different ecosystem services. Thus, from the perspective of land use management is critical to project potential future land-use changes. This study aimed: (i) to detect possible changes in land-use structure in response to different four scenarios, namely: business as usual, urbanization, afforestation and land abandonment, and agricultural intensification scenario; and (ii) to measure the landscape habitat quality (an ecosystem services proxy) according to those projected futures. We selected as case study Lithuania due to the potential future increased human pressures on the landscape, and due to the high landscape value of this territory. The projected year was 2050, and we used the Cellular Automata method (applying the Dinamica EGO software) to project future land-use changes, and the InVEST model to assess the habitat quality. The land-use scenarios outcomes were validated using a fuzzy comparison function, and 80% of accuracy was achieved (comparing a simulated land use map of 2018, and the observed map for the same year). The results showed that the agricultural intensification scenario represents the greatest predicted landscape deterioration (from 0.71 in 2018 to 0.64). In the urbanization scenario, the highest landscape degradation prediction is identified around the most important cities (Vilnius, Kaunas, and Klaipėda). In the opposite direction, the afforestation and land abandonment scenario show the highest improvement on the habitat quality, from 0.71 in 2018 to 0.74. 

Acknowledgements

“Lithuanian National Ecosystem Services Assessment and Mapping (LINESAM)” No. 09.3.3-LMT-K-712-01-0104 is funded by the European Social Fund according to the activity “Improvement of researchers’ qualification by implementing world-class R&D projects” of Measure No. 09.3.3-LMT-K-712.
         Towards Analysing multivariate weather/climate extremes
Authors: Hannachi Abdel , Trendafilov Nickolay
Published: March 2021

Extreme analysis, via e.g., GEV, was developed to deal with univariate time series, and is very difficult to extend beyond that dimension. Here we explore a different method, the archetypal analysis, which focuses on multivariate extremes. The method seeks to approximate the convex hull in high-dimensional state space, by identifying corners representing "pure" types, i.e. archetypes. The method, encompasses, in particular, the virtues of EOFs and clustering. The method is presented with a new manifold-based optimization algorithm, and applied to a number of atmospheric fields, including SST and SLP gridded data. The application to SST, in particular, reveals important features related to SST extremes. The strengths and weaknesses of the method and possible future perspectives will be discussed.
Attribution of the relative contributions of anthropogenic aerosols and decadal variability to the mid-20th century global “cooling”: a focus on tropospheric temperature latitudinal gradient
Authors: Diao Chenrui , Xu Yangyang
Published: March 2021

The global mean surface temperature went through a cooling period during the mid-20th century despite the continuous increase in greenhouse gas concentration. This generates a renewed interest to look at the multi-decadal climate variabilities across the 20th century, which are often believed to be related to the internal variabilities caused by ocean-atmosphere interaction.

At the same time, an obvious interhemispheric tropospheric temperature trend asymmetry is found in both reanalysis datasets and model simulations during this time. Considering the rapid increase of industrial activities in North America and Europe, it generates another possibility that anthropogenic emissions play a role during this period. And if anthropogenic emissions do have significant effects, then the relative contributions of anthropogenic emissions and internal variabilities to the mid-20th-century cooling is worth understanding because of the increasing importance of human activities to the natural environment.

To test this hypothesis, we did a detailed analysis on the global temperature trend and the interhemispheric temperature trend asymmetry from the surface to the mid-troposphere based on Coupled Model Intercomparison Project phase 5 (CMIP5) multi-model ensemble and multiple reanalysis datasets. Our results show that the anthropogenic aerosol emissions contribute to global cooling and particularly asymmetry during the mid-20th century, and the fingerprint of anthropogenic emissions is more obvious in the mid-troposphere compared with the surface.

By different attribution methods (such as multi-linear regression and pattern correlation), we quantified the relative contributions of Anthropogenic Emissions and Internal variabilities based on single forcing simulations of seven CMIP5 models. We conclude that a superposition of Internal Variabilities originating from the Atlantic Ocean and anthropogenic aerosol emissions overwhelms the warming influence of GHGs and lead to the mid-20th century cooling period.
Using Micro-CT and petrographic analysis to select optimal U-Th samples from challenging stalagmites.
Authors: Oster Jessica , de Wet Cameron , Neal Kate , Sharp Warren
Published: March 2021

Speleothem deposits can provide a wealth of critical, detailed paleoclimate information from low and mid-latitude terrestrial environments. A key strength of these archives is that they may be dated precisely using U-Th techniques. Yet, depending on the cave environment, overlying geology, seepage water flow characteristics, and speleothem growth habit, accurate, precise dating of speleothems can be challenging. For example, contamination by Th-bearing detritus degrades precision and accuracy when model-based corrections for initial 230Th are applied, and partial dissolution or secondary infilling of porosity can also lead to inaccurate ages, thereby confounding interpretations of paleoclimatic change. Here we present a new chronology from a Holocene stalagmite, WMC2, from White Moon Cave in the Santa Cruz Mountains of California, USA, that exhibits multiple challenges. Stalagmite WMC2 was not active at the time of collection, but it was in situ, with a top age of 3267 ± 28 yrs BP 1950.  WMC2 calcite has relatively high U (3-7 ppm), however, the stalagmite contains sporadically distributed sub-millimeter pockets of silicate detritus, leading to 100-fold differences in common Th (232Th) concentrations in dating samples (i.e., >80 to <1ppb). Additionally, ages that appear to be anomalously young are associated with zones containing high densities of fluid inclusions, suggesting possible secondary calcite growth. We overcome these challenges using a combination of micro-CT imaging, transmitted-light microscopy and assessing replicate samples.  Micro-CT provides a non-destructive method for imaging the internal structure of the stalagmite, allowing for the sampling of dense, pure calcite. Using this approach, we are able to avoid sub-millimeter pockets of silicate detritus that are not visible from the cut surface of the sample, thereby reducing 232Th concentrations and associated initial 230Th corrections, and obtaining more precise and accurate ages. Dating replicate samples from individual growth bands can confirm or refute whether diagenesis suspected from petrographic study has measurably affected U-Th ages since corrupt ages should scatter more than expected from analytical errors alone. We use our carefully screened ages for WMC2 to evaluate various age modeling approaches typically used for stalagmite proxy records, including those that apply Monte Carlo methods and Bayesian approaches. By employing multiple techniques to optimize stalagmite dating samples, reliable, precise U-Th ages (median 2s ~30 yr) may be obtained from stalagmites previously deemed too flawed for accurate dating, thereby broadening our ability to develop accurately dated speleothem paleoclimate records.
The Mw7.1 September 19th Puebla-Morelos (Mexico) earthquake triggered by brucite and antigorite dewatering
Authors: Gutiérrez-Aguilar Fabián , Hernández-Uribe David , M. Holder Robert , B. Condit Cailey
Published: March 2021

Subduction controls key geological processes at convergent margins including seismicity and resultant seismic hazard. The September 19th 2017 Mw7.1 Mexican earthquake nucleated ~250 km from the trench within the Cocos plate near its Moho, ~57 km below Earth’s surface. The prevailing hypothesis suggests that this earthquake resulted from bending stresses occurring at the flat-to-steep subduction transition. Here, we present an alternative, but not mutually exclusive, hypothesis: the dehydration reaction brucite + antigorite = olivine + H2O in the slab mantle controls intermediate-depth seismicity along the flat portion of the subducted Cocos plate. This reaction releases a substantial amount of H2O, resulting in a large positive volume change, and thus in an increase in pore fluid pressure at the appropriate depth–temperature conditions to cause the Puebla-Morelos and other intraslab earthquakes in Mexico. The amount of H2O released by this reaction depends on the degree of serpentinization of the oceanic mantle prior to subduction. Only oceanic mantle with > 60% serpentinization—as expected along abundant deep extensional faults at the mid-ocean-ridge or where the plate bends at the outer rise—will stabilize brucite, and thus, will experience this reaction at the same depths where the September 19th 2017 earthquake nucleated.
Study of the relationship between the observations of electron distributions in the solar wind and interplanetary magnetic field fluctuations 
Authors: Silva Javier , Moya Pablo , Viñas Adolfo
Published: March 2021

The space between the Sun and our planet is not empty. It is filled with the expanding plasma of the solar corona called the Solar Wind, which is a tenuous weakly collisional plasma composed mainly by protons and electrons. Due to the lack of sufficient collisions, the electron velocity distribution function in the Solar Wind usually exhibits a variety of non-thermal characteristics that deviate from the thermodynamic equilibrium. These deviations from equilibrium provide a local source for electromagnetic fluctuations, intimately related to the shape of the distribution function, and associated with the commonly observed kinetic instabilities such as the whistler-cyclotron for T⊥/ T∥>1, and firehose for T⊥/ T∥<1 and large enough plasma beta. In this work we carry out systematic statistical study of correlations of various plasma moments and interplanetary magnetic fluctuations as a function of time, in order to describe the role and evolution of these parameters in the solar plasma through the solar cycle. We consider a large time interval during solar cycle 23, ranging from solar minimum (1995-1996) to solar maximum (2000-2001). Using NASA's Wind space mission and its SWE and High-Resolution MFI instruments with resolutions of 6-15 sec and 11 vectors/sec, respectively, we show that collisionless kinetic instabilities can regulate the electron distribution as the whistler-cyclotron and firehose instability thresholds bound the temperature and plasma beta electron distributions, and such regulation is more effective during solar minimum. Subsequently, the magnetic fluctuations level increases as the electron VDF acquires a configuration close to the thresholds. In addition, we note that there is a high difference between the fast and slow wind regimes given a greater tendency towards larger collisionallity and isotropization for low speeds streams, and magnetic fluctuations amplitude decreases as collisional age increases. In summary, our results indicate that collisionless plasma processes and Coulomb collisions effects coexist and both seem to play relevant roles in shaping the observed electron distributions.
The impact of atmospheric circulation on wind energy resource using self-organizing maps
Authors: Philippopoulos Kostas , Tzanis Chris G.
Published: March 2021

The sensitivity of wind to the Earth’s energy budget and the changes it causes in the climate system has a significant impact on the wind energy sector. The scope of this work is to examine the association of atmospheric circulation with the wind speed distribution characteristics on different timescales over Greece. Emphasis is given to the effect of specific regimes on the wind speed distributions at different locations. The work is based on using synoptic climatology as a tool for providing information regarding wind variability. This approach allows a more detailed description of the effect of changes in large-scale atmospheric circulation on wind energy potential. The atmospheric classification methodology, upon the selection of relevant atmospheric variables and domains, includes a Principal Components Analysis for dimension reduction purposes and subsequently, the classification is performed using an artificial neural network and in particular self-organizing maps. In the resulting feature map, the neighboring nodes are inter-connected and each one is associated with the composites of the selected large-scale variables. Upon the assignment and the characterization of each day in one of the resulting patterns, a daily catalog is constructed and frequency analysis is performed. In the context of estimating wind energy potential variability for each atmospheric pattern, the fit of multiple probability functions to the surface wind speed frequency distributions is performed. The most suitable function is selected based on a set of difference and correlation statistical measures, along with the use of goodness-of-fit statistical tests. The study employs the ERA5 reanalysis dataset with a 0.25° spatial resolution from 1979/01/01 up to 2019/12/31 and the wind field data are extracted at the 10m and the 100m levels. The approach could be valuable to the wind energy industry and can provide the required scientific understanding for the optimal siting of Wind Energy Conversion Systems considering the atmospheric circulation and the electricity interconnection infrastructure in the region. Considering the emerging issue of energy safety, accurate wind energy production estimates can contribute towards the establishment of wind as the primary energy source and in meeting the increasing energy demand.
Machine Learning Emulation of 3D Cloud Radiative Effects
Authors: Meyer David , Hogan Robin J. , Dueben Peter D. , Mason Shannon L.
Published: March 2021

The treatment of cloud structure in radiation schemes used in operational numerical weather prediction and climate models is often greatly simplified to make them computationally affordable. Here, we propose to correct the current operational scheme ecRad – as used for operational predictions at the European Centre for Medium-Range Weather Forecasts – for 3D cloud radiative effects using computationally cheap neural networks. The 3D cloud radiative effects are learned as the difference between ecRad’s fast Tripleclouds solver that neglects 3D cloud radiative effects, and its SPeedy Algorithm for Radiative TrAnsfer through CloUd Sides (SPARTACUS) solver that includes them but increases the cost of the entire radiation scheme. We find that the emulator increases the overall accuracy for both longwave and shortwave with a negligible impact on the model’s runtime performance.
Earthquakes induced by ice-mass loss: A case example for southern Greenland
Authors: Steffen Rebekka , Steffen Holger , Weiss Robert , Lecavalier Benoit , Milne Glenn , Woodroffe Sarah , Bennike Ole
Published: March 2021

Due to their large mass, ice sheets induce significant stresses in the Earth’s crust. Stress release during deglaciation can trigger large-magnitude earthquakes, as indicated by surface faults in northern Europe. Thus, the current ice-mass loss in Greenland can be accompanied by earthquakes. Here, we will present an example of a possible large magnitude earthquake that occurred during the large melting period of the Greenland Ice Sheet in the early Holocene. The glacially induced stresses showed an instability occurring at 10,600 years ago. An offset in past sea level indicators falls within the same time frame, which gave us indications that the stresses have been released by an earthquake. The potential fault could have slipped up to 47 m, resulting in a large magnitude earthquake, if only one event occurred. The earthquake may have shifted relative sea level observations by several meters. In addition, as the potential fault is located offshore, the earthquake could have produced a tsunami in the North Atlantic Ocean with runup heights of up to 7.2 m in the British Isles and up to 7.8 m along Canadian coasts. Thus, ice-mass loss is strongly linked to the occurrence of earthquakes and even earthquakes-related tsunami. These scenarios due to a changing cryosphere can have effects for all countries bordering the North Atlantic Ocean and are in addition to the well-known sea-level rise.
Recent JunoCam Revelations About Discrete Features in Jupiter’s Atmosphere
Authors: Orton Glenn , Hansen Candice , Momary Thomas , Caplinger Michael , Ravine Michael , Rogers John , Eichstaedt Gerald , Breushaber Shawn , Wong Michael H. , Guillot Tristan , Ingersoll Andrew
Published: March 2021

JunoCam, the visible imager on the Juno mission’s payload that was designed primarily for public-outreach purposes, continues to produce images of Jupiter that provide unexpected scientific benefits.  Juno’s polar orbits enable observing regions of the planet that have not previously been detected at such high resolution by any previous spacecraft. JunoCam has a single CCD detector with an integral color-strip filter that enables the instrument to image in four color bands—blue, green, red and an 889-nm methane band.  JunoCam maps a field of view of 58° across the width of the detector, perpendicular to the spacecraft scan direction. We will describe characteristics and likely origins of bright white compact (~50 km) clouds, informally dubbed “pop-up” clouds by the JunoCam team.  We used the length of shadows of these and other features to determine the relative heights of clouds and assigned a provisional chemical classification based on relative altitudes from equilibrium-chemistry predictions. We tracked the continued interactions of small anticyclonic ovals with Jupiter’s Great Red Spot (GRS) that drew off high-altitude reddish haze into strips (commonly called “flakes”) on its western edge.  A lightning flash was detected in one of the compact circumpolar cyclones in late December. Observations of the south-polar circumpolar cyclones showed that the original unequally sided pentagon becoming a hexagon – with a cyclone filling in an open area, then a pentagon again over the course of 110 days.  In a collaboration with amateur astronomer Clyde Foster (S. Africa), we observed the morphology of an unexpected upwelling in late May of 2020, now known as “Clyde’s Spot”, and tracked its evolution in concert with several ground-based observations.  We also measured ~40-50 m/s winds around the sinuous jet bounding the South Polar Hood, an upper-level haze generated by auroral-related chemistry.  Lightly processed and raw JunoCam data continue to be posted on the JunoCam webpage at https://missionjuno.swri.edu/junocam/processing.   Citizen scientists download these images and upload their processed contributions.
Compound-specific radiocarbon ages of soil and sedimentary leaf wax biomarkers in an arid high-altitude environment
Authors: Aichner Bernhard , Rethemeyer Janet , Gierga Merle , Stolz Alexander , Mętrak Monika , Wilk Mateusz , Suska-Malawska Małgorzata , Sachse Dirk , Rajabov Ilhomjon , Rajabov Nasimjon , Mischke Steffen
Published: March 2021

Compound-specific radiocarbon analysis (CSRA) of leaf waxes has revealed significant lag times before compounds are deposited in marine and lacustrine sediments. No such data so far exist for a cold and arid high altitude lake system, where carbon turnover and biomarker fluxes to sediments are expected to be relatively low. To elucidate transport dynamics of terrestrial leaf waxes in such an environment (MAT: -4°C, MAP <100mm), we determined CSRA-ages of selected long-chain n-alkanes in surface soil samples (0-10 cm), collected from alpine meadows in the catchment of Lake Karakul (Pamirs, Tajikistan), and in two sections  of a well dated sediment core from the same lake. We aimed to answer the question if there is a potential bias in the interpretation of biomarker records, in case the leaf wax compounds are significantly older than the sediment age-model suggests.

nC29- and nC31-alkanes in the soil samples exhibited variable ages, ranging from 105±79 to 2260±155 cal. yrs BP. In the two sediment core samples, three of the four obtained ages for nC29 and nC31 felt on the very lower ends of the 1ϭ-uncertainty ranges of modelled ages (based on AMS 14CTOC and OSL dating results).

The large span of CSRA-ages of soils gives evidence for heterogeneous decomposition and transport conditions in the lake catchment. We hypothesize that compounds with longest pre-aging contributed in lower proportions to the accumulated lake sediments and further suggest that sedimentary leaf waxes represent compounds with intermediate turnover time in soils, for example originating from alluvial plains close to the shores. Overall, the obtained results give evidence that sedimentary leaf wax compounds in this cold and arid high altitude setting are potentially older than the conventional age-model indicates. On the other hand, these findings need to be interpreted in context of the generally large uncertainty ranges of such age-models, which are further influenced by unknown factors for example changes of reservoir effects. 
How is the increase in the variability of ENSO events over the last 6000 years linked to the mean state change of the tropical Pacific Ocean ?
Authors: Abdelkader Di Carlo Isma , Braconnot Pascale , Marti Olivier , Elliot Mary
Published: March 2021

El Niño events are the dominant mode of tropical interannual climate variability. This phenomenon, coupled with changes in atmospheric pressure related to the Southern Oscillation, modifies the distribution of surface water temperatures and weather conditions via atmospheric teleconnections. To better understand the linkages between changes in ENSO characteristics and changes in the Pacific ocean mean state, we use two transient simulations of the last 6000 years performed with the IPSL model that differ in resolution and presence (or not) of dynamical vegetation. The objective is to test several hypothesis raised in the literature on the role of the thermocline and the different factors constraining its changes with time.

This study will put an emphasis on the role of ocean dynamics. Several modelling studies indicate that an insolation-forced reduced equatorial upwelling feedback during the Mid-Holocene may be responsible for the less frequent ENSO events compared to modern. A few hypotheses have been made to explain this reduction in ENSO variability and equatorial upwelling feedback in the Mid-Holocene compared with today : subduction of warmer-than-normal South Pacific mode waters into the equatorial subsurface and tilt of the thermocline in the Warm Pool. Using specific diagnoses, we discuss the relative strength of different processes and highlight the differences between the processes explaining the long-term trend in variability and those characterising multidecadal to centennial variability.
Causal inference for extremes on river networks
Authors: Tran Ngoc , Buck Johannes , Kluppelberg Claudia
Published: March 2021

Causal inference for extreme aims to discover cause and effect relation between large observed values of random variables. This is a fundamental problem to in many applications, from finance, engineering risks, nutrition to hydrology, to name a few. Unique challenges to
extreme values are lack of data and lack of model smoothness due to the max operator. Existing methods in extreme value statistics for dimensions d ≥ 3 are limited due to an intractable likelihood, while techniques for learning Bayesian networks require a large amount of data to fit nonlinear models. This talk showcases the max-linear model and new algorithms for fitting them. Our method performs well on real data, recovering a directed graph for both the Danube and the Lower Colorado with high accuracy purely through extreme measurements. We also compare our method to state-of-the-art algorithms for causal inference for nonlinear models, and outline open problems in hydrology, extreme value statistics and machine learning.