bluuebunny/crossref_metadata_2025 huggingface dataset:
Long-term trends and transport of surface pollutants to UTLS  during the Asian summer monsoon
Authors: Lau William K.M. , Kim Kyu-Myong
Published: March 2021

Using MERRA2 reanalyses, we have examined the long-term (2000-2019) trends and transport of surface pollutants, CO, BC and OC from surface to the upper troposphere and lower stratosphere (UTLS) during the Asian summer monsoon.    We find a strong linear trend indicating an expansion and strengthening of the Asian Monsoon Anticyclone (AMA), in conjunction with increased concentration of CO, BC and OC in the UTLS, including the Aerosol Tropopause Aerosol Layer (ATAL). 

The UTLS trend in CO can be tracked to increased upward transport primarily from surface sources near 25-35oN, in association with the expansion/strengthening of the AMA, and a northward displacement of ascending branch of the monsoon meridional circulation.  In contrast, near 25-35oN, BC and OC trends show significant reduction from surface to mid-troposphere, coupled a weak increase at UTLS (above 250 -100 hPa).  The reduction in surface and tropospheric BC and OC likely reflects reduced emission due to the clean air acts in East Asia.  Additionally, heavier rainfall associated with the enhanced ascent and wet scavenging may also contribute to the strong reduction in tropospheric BC and OC.  The increase in UTLS OC/BC appears to stem from increased and extended biomass burning near surface sources located in extratropical latitudes (70-130o E, 55-70o N).  The OC/BC aerosols are transported upward by vertical mixing over the source regions, and enter the tropical UTLS through horizonal diffusive processes.   Additionally, enhanced penetrative convection in the anomalous ascent regions during the peak monsoon season may also play a role in further enhancing the monsoon ascent, lifting ambient hydrophobic OC/BC and water vapor in the mid-to-upper troposphere to higher elevations, resulting in enhanced ice-cloud fraction, increased latent and radiative heating in the UTLS/ATAL region.

 
A multi-sensor satellite method to spatial and temporal detection of landslides and flash floods in cloud-covered tropical environments: the western branch of the East African Rift
Authors: Deijns Axel , Kervyn François , Dewitte Olivier , Thiery Wim , Malet Jean-Philippe , d'Oreye Nicolas
Published: March 2021

Geomorphic hazards such as landslides and flash floods (hereafter called GH) often result from a combination of complex interacting physical and anthropogenic processes across multiple spatial and temporal scales. In many instances, landslides and flash floods occur very quickly, sometimes in a matter of a few hours occasionally leading to catastrophic impact on human lives. Given that they are mostly related to common meteorological events, landslides and flash floods frequently co-occur and interact, leading to more severe impacts. The tropics are environments where GH are under-researched while, in the meantime, GH disproportionately impact these regions. In addition, GH frequency and/or risks in the tropics are expected to increase in the future in response to increasing demographic pressure, climate change and land use/cover changes. To understand the role of climate and landscape (topographic and land use/cover) in controlling the spatio-temporal distribution of GH in the context of environmental changes, establishing a regional-scale inventory of GH events that are localised accurately in space and time is essential. Since the tropics are frequently cloud covered, an accurate characterization of the timing of GH at a regional scale can only be achieved through the combined use of optical and Synthetic Aperture Radar (SAR) remote sensing. Here, the objective is to present the first phase of the ongoing development of a remote sensing methodology that aims to identify accurately in space and time the GH events in the western branch of the East African Rift using a multi-temporal change analysis approach combining optical and SAR amplitude and phase coherence data. Copernicus Sentinel 1 (SAR imagery) and Sentinel 2 (optical imagery) are the key satellite products used. Next to being open access, they offer a very good trade-off between frequency of acquisition and spatial resolution. The detection methodology is calibrated and validated using information from three citizen observer networks and higher spatial resolution imagery. Preliminary results show clear changes in SAR amplitude and phase coherence time-series at the time of GH event occurence. Various change detection approaches (difference, log-ratio, normalized difference, correlation) are explored and provide ideas for detection of GH timing within the time-series. We present the ongoing method development with a specific focus on recent extreme GH events in the region.
Will the Pyrenees suffer less rainfall-triggered landslides in the future? Results of regional-scale stability modelling in the Val d’Aran focussing on land cover and rainfall predictions. 
Authors: Hürlimann Marcel , Guo Zizheng , Puig-Polo Càrol , Medina Vicente
Published: March 2021

The occurrence of rainfall-induced landslides in high-mountain areas will be affected by future environmental changes. We analysed the influence of climate changes as well as land use and land cover (LULC) changes on shallow slope failures in the Val d’Aran region (Central Pyrenees) applying the simplified physically-based susceptibility model FSLAM. In this study, the event rainfall as well as the root strength were defined as the two input parameters that will be affected by the future changes.

On one side, the climate changes were analysed by the rainfall projections that are defined in the 26 regional climate models available at the moment in the EURO-CORDEX database using RCP 8.5 scenarios. Future precipitation return periods up to 2100 were calculated by a simplified peaks-over-threshold method based on storm events frequency analysis. Finally, daily rainfall scenarios for the entire study were estimated by weighting current rainfall extremes using a multiplier factor. On the other side, the LULC changes were calculated by the IDRISI TerrSet software suite. All the predictions were performed for three time periods (near, mid and far future).

The results of the climate change prediction showed that the daily rainfall will increase between 15 and 27 % assuming a return period of 100 years. In addition, the LULC predictions foresee a strong increase of the forest area, while in particular grassland, but also shrubs, decrease in area. Using the different rainfall and LULC predictions, multiples scenarios were defined and the corresponding susceptibility maps calculated. The stability calculations by the FSLAM model indicate that the overall stability conditions in the study area reduces when only the future rainfall prediction is considered. In contrast, the overall stability largely improves when only considering the LULC predictions (due to the increase of forest area and the corresponding higher root strength). However, the effect of LULC-changes is more important than the influence of rainfall-changes. Therefore, the overall stability conditions will improve in the future.

Many simplifications were incorporated in this susceptibility assessment and there are many uncertainties. Nonetheless, these results may help future studies to improve our knowledge on the impacts of future environmental changes on landslide occurrence in high-mountain areas.
Magnetospheric response to solar wind driving
Authors: Výbošťoková Tatiana , Němeček Zdeněk , Šafránková Jana
Published: March 2021

Interaction of solar events propagating throughout the interplanetary space with the magnetic field of the Earth may result in disruption of the magnetosphere. Disruption of the magnetic field is followed by the formation of the time-varying electric field and thus electric current is induced in Earth-bound structures such as transmission networks, pipelines or railways. In that case, it is necessary to be able to predict a future state of the magnetosphere and magnetic field of the Earth. The most straightforward way would use geomagnetic indices. Several studies are investigating the relationship of the response of the magnetosphere to changes in the solar wind with motivation to give a more accurate prediction of geomagnetic indices during geomagnetic storms. To forecast these indices, different approaches have been attempted--from simple correlation studies to neural networks.

We study the effects of interplanetary shocks observed at L1 on the Earth's magnetosphere with a database of tens of shocks between 2009 and 2019. Driving the magnetosphere is described as integral of reconnection electric field for each shock. The response of the geomagnetic field is described with the SYM-H index. We created an algorithm in Python for prediction of the magnetosphere state based on the correlation of solar wind driving and magnetospheric response and found that typical time-lags range between tens of minutes to maximum 2 hours. The results are documented by a large statistical study.
Estimating peak water in glaciated basins: the importance of scale, process, and terminology
Authors: Rangecroft Sally , Van Tiel Marit , Blake Will , Morera Sergio , Clason Caroline
Published: March 2021

Peak water is a concept that is increasingly used to describe a tipping point in time for glaciated drainage basins, where annual discharge reaches a maximum and thereafter is in continual decline. Millions of people across the globe depend on glacial meltwater, especially in regions such as the Himalayas and the Andes, and therefore current and future changes in meltwater generated flow and downstream water availability are important for society and ecosystem services. Due to the long-term negative consequence of glacier retreat on freshwater resources, peak water in glaciated basins has received more attention in recent years. Using an example case study from the Peruvian Andes, we highlight crucial considerations around scale, process, and terminology when measuring, modelling, and communicating peak water in glaciated basins. Through the application of commonly used peak water calculation methods, we explore the influence of these considerations on the estimation of peak water timing. One such consideration is the processes affecting discharge aside from direct glacial melt, such as catchment storage (aquifers, wetlands, lakes), precipitation, and human activities. In our example case study of the Rio Santa basin in Peru, we find that these factors may all play a much larger role than originally assumed. Subsequently, some peak water estimates may not isolate glacial melt peak water, but instead represent “basin peak water”. Depending on the basin of interest, these aspects can play a significant role in water availability, and thus in peak water estimates. We believe that these nuisances are important for ensuring that the peak water concept is appropriately communicated to end-users, and to inform suitable water management. As a scientific community, we now have an opportunity to assess and find ways to move forward with a unified approach to the terminology and communication of peak water.
Space-based detection of CO2 emission reductions due to COVID-19 at Europe's largest fossil fuel power plant and implications for CO2 emission monitoring
Authors: Nassar Ray , Mastrogiacomo Jon-Paul , Bateman-Hemphill William , McCracken Callum , MacDonald Cameron , Hill Tim , O'Dell Chris , Nelson Robert , Kiel Mattheaus , Pavlick Ryan , Eldering Annmarie , Crisp David
Published: March 2021

In 2020, many countries implemented lockdowns to control the spread of the novel coronavirus disease (COVID-19), leading to reported decreases in anthropogenic CO2 emissions based on bottom-up estimates. Some studies reported that the resulting atmospheric CO2 changes were below the detection limit of current observing systems on the ground or in space. We quantify CO2 emissions from Europe’s largest fossil fuel burning power plant before and during lockdown using space-based CO2 observations from NASA’s Orbiting Carbon Observatory (OCO) 2 and 3 missions. The results show clear emission reductions of >20% in April 2020, demonstrating the ability of space-based CO2 observations to quantify emission reductions at the facility level. This research reinforces the value of space-based CO2 data for verifying future CO2 emission reductions expected from climate change mitigation policies and the importance of monitoring emissions at sub-national scales.
A new multi-year database of current sheets at 1AU
Authors: Sagitov Timofey
Published: March 2021

We announce the first open access multi-year database of current sheets systematically identified with the one second cadence at 1 AU. The current sheet list comes from an automated method of current sheet identification that suggests a formalization of the long-time experience of observers in the visual finding of CSs based on the analysis of the IMF and plasma parameters that vary sharply at CSs of different origins in the solar wind (Behannon et al. 1981; Blanco et al. 2006; Zhang et al. 2008; Suess et al. 2009; Simunac et al. 2012; Zharkova and Khabarova, 2012, 2015; Khabarova et al. 2015, 2016; Khabarova and Zank 2017; Malova at al. 2017; Adhikari et al. 2019). The main features seen with a resolution not worse than one minute that may characterize a CS crossing are as follows: (i) a decrease in the IMF magnitude B, (ii) a decrease in V_A/V (V_A is the Alfvén speed and V is the solar wind speed), and (iii) an increase in the plasma beta (the ratio of the plasma pressure to the magnetic pressure). Since the automatization of the CS recognition process requires setting the same rules for CSs occurring in different plasmas under different conditions, normalization should be performed. After obtaining B, VA/V, and β with a one second cadence, we calculate their one-second derivatives. Spikes of the derivatives occurring out of the noise level indicate the CS location. Only the spikes that appear simultaneously in dB/dt and any of two other parameters are considered as pointing out the CS location. The database is available at csdb dot izmiran dot ru
Architecture and Neogene kinematic of the Seagap fault, offshore Tanzania, West Somali Basin
Authors: Iacopini David , Tavani Stefano , Pentagallo Sara , Ebinger Cynthia , Dottore Stagna Marina , Reynolds Dave , Maselli Vittorio
Published: March 2021

In the West Somali Basin, the classic plate tectonic reconstructions describe an early Cretaceous intraplate deformation of oceanic crust (Hauterivian to Aptian) followed by the activation of a major transform fault (Davie Fracture Zone) displacing Madagascar southward for more than 1000 km. In this contribution, using vintage and new high-resolution 2D, 3D seismic reflection data and exploration wells, we show the first clear images of a poorly known tectonic structure: the Seagap fault. The Seagap fault is represented by a complex fault zone of several hundred kilometres of extent, oriented parallel to the Davie Fracture Zone and defined by segment faults, relay zones and step overs structures. It appears to have continuously acted as left-lateral strike slip fault during the Paleogene and most of the Neogene. From structural and stratigraphic observations of both existing and newly interpreted 3D seismic data, the Seagap appears nucleating as a strike-slip fault by reactivating failed Jurassic oceanic spreading zones. At regional scale the main fault appears to cut the main Neogene pervasive extensional oblique rift structures and at place to re-work some of the major Cenozoic inherited structure, creating apparent restraining bend structure. The sinistral kinematic nature of the transcurrent history, suggests that the Seagap fault acted as an independent feature respect to the Davie Fracture Zone. During the Quaternary the Seagap, which also parallels the seismically active Kerimbas rift, shows reduced offsets and appears to slip with normal displacement. We discuss the tectonic significance of the Seagap fault with respect to both to the major extensional oblique rift structural trend offshore Tanzania and the Davie Fracture Zone.
Tracing seismic landslide-derived sediment dynamics in response to climate change
Authors: Xie Jun , Coulthard Thomas
Published: March 2021

Mass movement such as landslides and rock fall is a prominent source of sediment in active mountain belt. Earthquake triggered landslides can generate substantial loose sediment and have significant geomorphic effects on long term landscape evolution. More importantly, these landslide impacts to land surface vary a lot due to the divergence of landslide characteristics and surrounding environment settings. Downslope and downstream transport of sediment into the channel network is fairly sensitive to climatic perturbations especially for extreme rainfall events. A wide variety of studies attempt to quantify or determine the contribution of landslide generated material to gross sediment budget and the corresponding retention time scale of landslide generated deposit in the mountain basin, whereas no established techniques can explicitly fingerprint/track landslide derived sediment. In this study, we first generated the hourly future extreme rainfall under two emission scenario (RCP4.5, RCP8.5) using ‘NASA Earth Exchange Global Daily Downscaled Projections (NEX-GDDP)’ dataset. A new tracing function is incorporated into CAESAR-lisflood to track the landslide derived sediment footprint and dynamics in response to climate change. The landscape evolution at the Hongxi catchment, which is suffered tremendous damage from Wenchuan earthquake (Ms 8.0), are then simulated using CAESAR-lisflood under two climate scenarios. The results show that more than 80 percent of material generated by seismic landslides are still retained at the hillslope even after a sufficient time (e.g. 100 year). This study is to compare the spatial-temporal evolution pattern of landslides-derived sediment under two climatic scenarios (RCP4.5, RCP8.5), thus probing into the landslide generated sediment transport and budget respond to the climate change especially the impact of extreme rainfall events. Numerical modelling can provide a quick and effective tool for broad scale predictions of sediment produced by landslide events under different climatic predictions, which is of great importance for seismic induced disaster protection and reduction under climate change.
Can climate models capture the high amplitudes circumglobal waves and their surface imprints?  
Authors: Luo Fei , Kornhuber Kai , Selten Frank , Coumou Dim
Published: March 2021

Pronounced circumglobal waves can trigger and maintain persistent summer weather conditions by remaining in their preferred phase-locked positions for several weeks in a row. This phenomenon, especially important for wave numbers 5 and 7, has been observed in recent years, but it is unclear whether climate models can reproduce circulation types and their surface imprints.

Here we assess three climate models (EC-Earth3, CESM1.2, and MIROC5)  for their representation of amplified circumglobal waves and associated surface imprints in summer (June, July and August) over 1979-2016. ERA5 reanalysis data is used as reference to assess the models’ performance. We run a series of modeling experiments to understand the source of biases in the climate models: free interactive atmosphere and soil moisture runs (AISI), atmospheric nudged runs (AFSI), soil moisture prescribed runs (AISF), and both atmosphere and soil moisture nudged experiments (AFSF).

We show that all models reasonably well reproduce the climatological wave spectra. Further, both wave 5 and wave 7 are found to exhibit phase-locking behaviors across all models, resulting in similar wave patterns across the hemisphere as compared to reanalysis. The surface imprints are observed in the models as well, but depending on the model, the results vary in strength. We also found the biases in surface temperature and precipitation anomalies mainly come from the atmospheric circulation in the models as these biases reduced considerably from AISI runs to AFSI and AFSF runs where upper atmosphere levels were nudged. Nudging soil moisture also minimizes some biases in the models but not as obvious as nudging the atmosphere. 

 
Subseasonal Forecasts of Opportunity Identified by an Explainable Neural Network
Authors: Mayer Kirsten , Barnes Elizabeth
Published: March 2021

Midlatitude prediction on subseasonal timescales is difficult due to the chaotic nature of the atmosphere and often requires the identification of favorable atmospheric conditions that may lead to enhanced skill ("forecasts of opportunity"). Here, we demonstrate that an artificial neural network can identify such opportunities for tropical-extratropical teleconnections to the North Atlantic circulation at a lead of 22 days using the network's confidence in a given prediction. Furthermore, layer-wise relevance propagation, an ANN interpretability technique, pinpoints the relevant tropical features the ANN uses to make accurate predictions. We find that layer-wise relevance propagation identifies tropical hot spots that correspond to known favorable regions for midlatitude teleconnections and reveals a potential new pattern for prediction over the North Atlantic on subseasonal timescales.
On the rock magnetic properties and petrofabric (AMS) analyses of trachytic, phonolitic, basaltic dikes and conesheets emplaced on the Miocene Tejeda caldera complex, on Gran Canary Island, Spain.
Authors: Herrero-Bervera Emilio , Calvo Rathert Manuel
Published: March 2021

The Miocene Tejeda Complex on Gran Canaria (Canary Islands) is characterized by more than 500 trachytic and phonolitic conesheets, dikes, hypabyssal syenite stocks and subordinate radial dikes from a 20-km diameter intrusive complex in the volcaniclastic fill of the Miocene Tejeda caldera (20 x 35 km) on Gran Canaria, Canary Islands. The dikes intruded concentrically around a central axis or radial symmetry and dip uniformly an average of~41 degrees toward the center.We have conducted a pilot study of magnetic properties as well as Anisotropy of Magnetic Susceptibility (AMS) on a variety of dikes (trachytic and phonolitic and basaltic in composition) to investigate the possibility of obtaining petrofabrics results that would allow us to test the origin of the formation of the Tejeda conesheets that most likely resulted from deformation processes due to resurgent doming initiated by recurrent replenishment of a flat  laccolith-like magma chamber. The current ideas indicate that the formation of the cone-shaped fractures were originated by a magma supply exceeding the volume that could be compensated for by up-doming of the overlying caldera fill. Thus far, our AMS results indicate that all the ten intrusives studied despite their different lithologies are susceptible of carrying a measurable magnetic signal. Low-field magnetic susceptibility vs temperature (k-T 28-700oC) experiments have identified mainly one primary magnetic mineral phase namely stoichiometric magnetite, Curie temperature of 585oC,  SIRM, hysteresis loops and back-field were performed and yielded a series of secondary magnetic mineral present as well and corroborated by FORC’s results. The petrofabric in the intrusive bodies results show coherent flow azimuths regardless of their time of emplacement. Three main types of magnetic fabrics, (i.e. A to C) were found. Fabric type A (plane Kmax-Kint parallel to the dike plane) represents magma flow direction within the intrusives and is the dominant fabric (~60% of all the intrusives) studied thus far. The Kmax axis inclinations show that about 70% of the intrusives were fed by inclined vertical magma fluxes (inclinations greater than 30o), and the rest of them (~30%) by horizontal to sub-horizontal magma fluxes. Vertical magma flow means inclined magma injection inside fractures, and become more probable as the source is therefore located very close to the origin of the caldera
Calcium carbonate crystal fans: Geologic occurrences and controls on growth
Authors: Woods Adam
Published: March 2021

Fans and hemispheres comprised of crystals of calcium carbonate that directly grew on the seafloor are an intriguing feature of ancient carbonate environments. Calcium carbonate fans from across Earth history are typically made up of crystals of neomorphosed calcium carbonate that maintain an acicular morphology that is pseudohexagonal in cross – section with blunt terminations, pointing to an aragonite precursor. Crystal fans may occur as isolated bodies, or may form larger aggregates that are sometimes associated with microbialites, and form larger, reef – like structures. Some of the first occurrences of these features are within Neoarchean carbonates, when the crystals fans grew to impressive sizes, with lengths of over 1 m, formed layers of marine cement that reached thicknesses of up to several meters, are laterally continuous over 10s of km or more, and formed across carbonate platform settings from high energy subtidal settings to lower intertidal environments. Crystalline carbonate fans become less common and smaller (cm – scale) in the Paleoproterozoic, and nearly disappear prior to the Neoproterozoic, when they are associated with cap carbonates, and are primarily found in deeper water or outer shelf settings with low sedimentation rates. Seafloor cements are rare during the Phanerozoic, and are typically limited to small geographic areas with unusual sedimentary conditions, or are found in void spaces, where seawater chemistry was able to undergo modifications that would allow precipitation of cement fans. The exception is during the interval of time that followed the Permian – Triassic mass extinction, when small, cm – scale fans and hemispheres are found in Lower Triassic and lowermost Middle Triassic rocks. These cement fans occur in a variety of settings, although they are typically found in deeper water environments. Calcium carbonate fans that formed following the Permian – Triassic extinction may have microbial remains preserved within the cements, and are frequently found in close lateral or stratigraphic association with microbialites. However, some examples of post – extinction carbonate fans appear to have formed abiotically, without any microbial influence. Overall, crystalline calcium carbonate fans signal high levels of calcium carbonate supersaturation in ancient oceans. The initial decline in seafloor cement growth from the Neoarchean into the Proterozoic may have been the result of accelerated micrite production, while Neoproterozoic calcium carbonate fan growth is associated with glacial decay and retreat. Lower Triassic seafloor cements are likely the result of stratification and stagnation of the deep oceans that led to enhanced alkalinity. Calcium carbonate crystal fans are an intriguing feature of ancient carbonates that signal depositional systems and ocean chemistry that is much different from modern ocean, and provide a fascinating glimpse into non – uniformitarian sedimentary environments.
Seeing and hearing quasi-static shear band localization in a sandstone
Authors: Cartwright-Taylor Alexis , Main Ian G. , Butler Ian B. , Fusseis Florian , Mangriotis Maria-Daphne , Curtis Andrew , Bell Andrew , Ling Martin , Andò Edward , Rizzo Roberto , Marti Sina , Leung Derek , Magdysyuk Oxana
Published: March 2021

The localisation of structural damage, in the form of faults and fractures, along a distinct and emergent fault plane is the key driving mechanism for catastrophic failure in the brittle Earth. However, due to the speed at which stable crack growth transitions to dynamic rupture, the precise mechanisms involved in localisation as a pathway to fault formation remain unknown. Understanding these mechanisms is critical to understanding and forecasting earthquakes, including induced seismicity, landslides and volcanic eruptions, as well as failure of man-made materials and structures. We used time-resolved synchrotron x-ray microtomography to image in-situ damage localisation at the micron scale and at bulk axial strain rates down to 10-7 s-1. By controlling the rate of micro-fracturing events during a triaxial deformation experiment, we deliberately slowed the strain localisation process from seconds to minutes as failure approached. This approach, originally established to indirectly image fault nucleation and propagation with acoustic emissions, is completely novel in synchrotron x-ray microtomography and has enabled us to image directly processes that are normally too transient even for fast synchrotron imaging methods. Here, we first present the experimental apparatus and control system used to acquire the data, followed by damage localisation and shear zone development in a sample of Clashach sandstone viewed in unprecedented detail. Time-resolved microtomography images demonstrate a strong intrinsic correlation between shear and dilatant strain in the localised zone, with bulk shear strain accomodated by the nucleation and rotation of en-echelon tensile microcracks within a grain-scale shear band. Rotation is accompanied by antithetic to synthetic shear sliding of neighbouring crack surfaces as they rotate. The evolving 4D strain field, measured with incremental digital volume correlation between pairs of recorded x-ray tomographic volumes, independently confirm the correlation between shear and dilatant strain and show how strain localises spontaneously, first through exploration of several competing shear bands at peak stress before transitioning to failure along the optimally-oriented final fault plane. In order to ‘ground-truth’ inferences made from bulk measurements and seismic waves (the primary method of detecting deformation at the field-scale where direct imaging of the subsurface is impossible), we (a) compare rupture energy estimates from local slip measurements with those from bulk slip data, and (b) use AE source location estimates to identify individual cracks and other local changes in the microstucture that may explain the AE source.
Biochar Effects on Soil Compaction in Two Contrasting Soils
Authors: Ul Haq Sami , Verheijen Frank G.A , Möerz Tobias , Gonzalves Pelayo Oscar
Published: March 2021

Although research on biochar use in soils has increased, its influence on soil compaction has been reported relatively little. The primary objective of this study was to measure the effects of biochar amendment on soil compaction, including infiltration capacity and aggregation, of two contrasting soils: a low soil organic carbon and hydrophilic degraded vineyard soil and a wildfire-degraded high soil organic carbon and hydrophobic forest soil.

We conducted a controlled laboratory soil column study (6 replicates), with PVC tubes filled with control soils and soil-biochar mixtures at a range of moisture contents. The mixtures were compacted under a falling load height that mimicked the standard proctor test. After the compaction procedure, infiltration capacity was determined with a mini disk infiltrometer, and bulk density and mean weight diameter were determined for the upper and lower halves of the soil column.
Substorm evolution of the auroral zone boundaries on the dawn and dusk flanks: DMSP and POES/MetOp observations
Authors: Decotte Margot , Laundal Karl M. , Hatch Spencer , Reistad Jone
Published: March 2021

We present a method for tracking the evolution of the auroral boundaries on the dawn and dusk flanks during magnetospheric substorms by using a combined database of auroral zone boundaries derived from DMSP and POES/MetOp satellite particle measurements. Auroral boundaries can be identified by the Kilcommons et al. (2017) algorithm which use electron energy fluxes from the DMSP spectrometer (SSJ instrument). We show how auroral boundaries may also be obtained from precipitating electron observations from the POES/MetOp Total Energy Detector (TED) instrument by subjecting the TED electron measurements to an algorithm similar to that presented by Kilcommons et al. (2017). Boundaries derived from the two satellite missions are similar, suggesting that the technique for auroral oval boundary identification is physically meaningful.
Topographic response to Neogene variations in slab geometry, climate and drainage reorganization in the Northern Andes of Colombia
Authors: Perez-Consuegra Nicolas , Ott Richard , Hoke Gregory D. , Galve Jorge Pedro , Pérez–Peña Jose Vicente
Published: March 2021

The tropical Northern Andes of Colombia are one the world's most biodiverse places, offering an ideal location for unraveling the linkages between the geodynamic forces that build topography and the evolution of the biota that inhabit it. In this study, we utilize a geomorphic analysis to characterize the topography of the Western and Central Cordilleras of the Northern Andes. We supplement our topographic analysis with erosion rate estimates based on gauged suspended sediment loads and river incision rates from volcanic sequences. In the northern segment of the Central Cordillera, an elevated low-relief surface (2,500m in elevation, ~40x110 km in size) with uniform lithology and surrounded by knickpoints, indicates a recent increase in rock and surface uplift rate. Whereas, the southern segment of the Central Cordillera shows substantially higher local relief and mostly well graded river profiles consistent with longer term uplift stability. These changes in the topography fit with the proposed location of a slab tear and flat slab subduction under the northern Central Cordillera, as well as with a major transition in the channel slope of the Cauca River. We identify several areas of major drainage reorganization, including captures and divide migrations that are supported by our erosion and incision rate estimates. We identify slab flattening as the most likely cause of strong and recent uplift in the Northern Andes leading to ~2 km of surface uplift since 8–4 Ma. Large scale drainage reorganization of major rivers is probably mainly driven by changes in upper plate deformation in relation to development of the flat slab subduction geometry; however, other factors such as climate and emplacement of volcanic rocks likely play secondary roles in this process. Several isolated biologic observations above the area of slab flattening suggest that surface uplift isolated former lowland species on the high elevation plateaus, and drainage reorganization may have driven diversification of aquatic species.
Fractionation of clumped isotopes of CO2 during photosynthesis
Authors: Adnew Getachew A. , Hofmann Magdalena E.G. , Pons Thijs L. , Koren Gerbrand , Ziegler Martin , Lourens Lucas J. , Peters Wouter , Röckmann Thomas
Published: March 2021

Stable isotope (δ13C and δ18O) and mole fraction measurements of CO2 are used to constrain the carbon cycle. However, the gross fluxes of the carbon cycle, especially photosynthesis and respiration, remain uncertain due to the challenging task of distinguishing individual flux terms from each other. The clumped isotope composition (Δ47) of CO2 has been suggested as an additional tracer for gross CO2 fluxes since it depends mainly on temperature but not on the bulk isotopic composition of leaf, soil and surface water, unlike δ18O of CO2.

In this study, we quantify the effect of photosynthetic gas exchange on Δ47 of CO2 using leaf cuvette experiments with two C3 and one C4 plants and discuss challenges and possible applications of clumped isotope measurements. The experimental results are supported by calculations with a leaf cuvette model. Our results demonstrate how the effect of gas exchange on Δ47 is controlled by CO2-H2O isotope exchange (using plants with different carbonic anhydrase activity), and kinetic fractionation as CO2 diffuses into and out of the leaf (using plants with different stomatal and mesophyll conductance). We experimentally confirm the previously suggested dependence of Δ47­­ on the stomatal conductance and back-diffusion flux.
Impact of urban development on waterbodies during medieval and early modern ages in Bad Waldsee (Germany)
Authors: Haas Kristin , Krahn Kim J. , Saeidi Ghavi Andam Sara , Tjallingii Rik , Hinderer Matthias , Marinova Elena , Rösch Manfred , Schwalb Antje
Published: March 2021

Seasonally laminated lacustrine sediments of Lake Stadtsee, located in the city of Bad Waldsee (Southern Germany), offer a continuous archive that allows a unique and yearly correlation of sedimentary signals and historic documents since medieval times. Comparison of the economic and environmental history of an urban centre will provide detailed insight into how the history of a city and its periphery region affected lake development and water quality, and how fast water quality and aquatic ecosystem recovered from human impact and activities. An interdisciplinary research team consisting of geologists, biologists, and historians from various universities and institutions has been established and started its work recently. The common goal of the different working groups and disciplines is to investigate temporally highly resolved sediment records of diatom and pollen spectra, geochemical proxies, and sediment facies of profundal sediment cores from Lake Stadtsee and to compare and calibrate these results with historic documents, stock books, archive records, dendrochronology records, and maps. So far, continuous geochemical sediment records of Lake Stadtsee were acquired non-destructively using X-ray fluorescence (XRF) core scanning. These element intensity records of the major elements (e.g. Al, Si, K, Ca, Ti, Fe) were measured every 2 mm. Sampling and subsequent analyses (e.g. pollen, PAH, isotopes) are ongoing.

Overall, the environmental impact of socio-economic development for the preindustrial development phase of a city from AD 1200 to 1800 will be assessed for the first time. The research will focus on the effects of population growth or decrease, farming intensity, economic production, trade activity in relation to environmental, and climate change, including catastrophic events such as fires and floods. The results will provide important insights about the response of urban surface waters to changing emissions of the city and the long-term behaviour of persistent pollutants on lakes. The project will thereby contribute to the knowledge of historic human impact on the environment in Germany, pre-medieval reference conditions, and the limits of resilience of aquatic systems. Thus, it will target the past environmental footprint of anthropogenic induced events on urbanized lake ecosystems and help to understand the mechanism behind such processes in the future.
Future Projections of Heat Mortality Risk for Major European Cities due to Heat Waves
Authors: Karwat Alexia , Franzke Christian L. E.
Published: March 2021

Over the last few decades heat waves have intensified, become more common, pose severe health risks, especially in densely populated cities, and have led to excess mortality. While the probability of being adversely affected by heat stress has significantly increased over the last few decades, the risk of heat mortality is rarely quantified. This quantification of heat mortality risk is necessary for systematic adaptation measures. Furthermore, heat mortality records are sparse and short, which presents a challenge for assessing heat mortality risk for future climate projections. It is therefore crucial to derive indicators for a systematic heat mortality risk assessment. Here, risk indicators based on temperature and mortality data are developed and applied to major cities in Germany, France and Spain, using regional climate model simulations. These simulations have biases of up to 3°C with respect to observations and, thus, need to be bias-corrected. Bias-corrected daily maximum, minimum and wet-bulb temperatures show increasing trends in future climate projections for most considered cities. Additionally, we derive a relationship of daily maximum temperatures and mortality for producing future projections of heat mortality risk due to extreme temperatures based on low (Representative Concentration Pathway; RCP2.6) and high (RCP8.5) emission scenario future climate projections. Our results illustrate that heat mortality increases by about 0.9%/decade in Germany, 1.7%/decade in France and 7.9%/decade in Spain for RCP8.5 by 2050. The future climate projections also show that wet-bulb temperatures above 30°C will be reached regularly with maxima above 40°C likely by 2050. Our results suggest a significant increase of heat mortality in the future, especially in Spain. On average, our results indicate that the mortality risk trend is almost twice as high in all three countries for the RCP8.5 scenario compared to RCP2.6.
Thin current sheets as key structures in space plasma
Authors: Malova Helmi , Zelenyi Lev , Popov Victor , Grigorenko Elena
Published: March 2021

Plasma structures with extremely small transverse size (named thin current sheets or TCSs) have been discovered and investigated by spacecraft observations in the Earth's magnetotail, then in other planetary magnetospheres and the solar wind. Their formation is related with complicated dynamic processes in collisionless space plasma near the magnetic reconnection regions. The proposed models describing TCSs in space plasma, based on the assumption of a quasi-adiabatic proton dynamics and magnetized electrons were successful. Various modifications of the initial equilibrium allowed describing such current sheets as the system of current sheets where the central sheet is supported by magnetized electron drifts, and the external sheets are supported by quasi-adiabatic protons and sometimes oxygen ions. Such current configurations are shown to have properties that are completely different from the well-known Harris model, particularly the multiscale structure, embedding and metastability. The structure and evolution of TCSs under the tearing mode as well as the related paradox of complete tearing mode stabilization in configurations with a nonzero normal magnetic field component is highlighted.

This work is supported by the Russian Science Foundation grant № 20-42-04418.
Beneficial role of diurnal smoothing for grid integration of wind power
Authors: Gangopadhyay Anasuya , Seshadri Ashwin K , Toumi Ralf
Published: March 2021

Smoothing of wind generation variability is important for grid integration of large-scale wind power plants. One approach to achieving smoothing is aggregating wind generation from plants that have uncorrelated or negatively correlated wind speed. It is well known that the wind speed correlation on average decays with increasing distance between plants, but the correlations may not be explained by distance alone. In India, the wind speed diurnal cycle plays a significant role in explaining the hourly correlation of wind speed between location pairs. This creates an opportunity of “diurnal smoothing”. At a given separation distance the hourly wind speeds correlation is reduced for those pairs that have a difference of +/- 12 hours in local time of wind maximum. This effect is more prominent for location pairs separated by 200 km or more and where the amplitude of the diurnal cycle is more than about  0.5 m/s. “Diurnal smoothing” also has a positive impact on the aggregate wind predictability and forecast error. “Diurnal smoothing” could also be important for other regions with diurnal wind speed cycles.
Antarctic ice dynamics amplified by Northern Hemisphere sea level forcing
Authors: Gomez Natalya , Weber Michael , Clark Peter , Mitrovica Jerry , Han Holly
Published: March 2021

A longstanding hypothesis for near-synchronous evolution of global ice sheets over ice-age cycles invokes an interhemispheric sea-level forcing whereby sea-level rise due to ice loss in the Northern Hemisphere in response to insolation and greenhouse gas forcing causes grounding-line retreat of marine-based sectors of the Antarctic Ice Sheet (AIS). Recent studies have shown that the AIS experienced substantial millennial-scale variability during and after the last deglaciation, with several times of recorded increased iceberg flux and grounding line retreat coinciding, within uncertainty, with well documented global sea-level rise events, providing further evidence of this sea-level forcing. However, the sea level changes associated with ice sheet mass loss are strongly nonuniform due to gravitational, deformational and Earth rotational effects, suggesting that the response of the AIS to Northern Hemisphere sea-level forcing is more complicated than previously modelled.

We adopt an ice-sheet model coupled to a global sea-level model to show that a large or rapid Northern Hemisphere sea-level forcing enhances grounding-line advance and associated mass gain of the AIS during glaciation, and grounding-line retreat and AIS mass loss during deglaciation. Relative to models without these interactions, including the Northern Hemisphere sea-level forcing leads to a larger AIS volume during the Last Glacial Maximum (about 26,000 to 20,000 years ago), subsequent earlier grounding-line retreat and millennial-scale AIS variability throughout the last deglaciation. These findings are consistent with geologic reconstructions of the extent of the AIS during the Last Glacial Maximum and subsequent ice-sheet retreat, and with relative sea-level change in Antarctica. 
Do Beaver Dam Analogues Really Mimic Beaver Dams?
Authors: Westbrook Cherie , Cooper David
Published: March 2021

Beavers profoundly alter streams by building dams. Beaver dams change how water, sediment, nutrients and energy flow through stream corridors enhancing both habitat diversity and landscape connectivity. Humans are captivated by learning from nature and trying to mimic it, especially in human-degraded environments. There is considerable eagerness for using beaver dam analogues (BDAs), also called simulated beaver structures, as low-tech, low cost solutions for restoring the functioning of degraded streams where beavers are not present and cannot survive. The use of BDAs in stream enhancement projects, especially in the western United States, is outpacing the research, leading to questions about whether BDAs do, in fact, yield similar ecosystem-scale effects as natural beaver dams. We review the different names used for BDAs, discuss the many ways these structures can be built and how different types function, and how they compare to real beaver dams. We conclude the talk by exploring what we can expect from various types of BDAs in the short and long term and whether these structures can lead to stream and riparian zone restoration that can facilitate the return of beavers. 