bluuebunny/crossref_metadata_2025 huggingface dataset:
mGEODAR – a new mobile radar for avalanche mass movement monitoring
Authors: Köhler Anselm , Lok Lai Bun , Fischer Jan-Thomas
Published: March 2021

Radar imaging has become increasingly important in either the detection of avalanches or in the scientific characterization of the avalanche flow. Detection radars usually base on the Doppler radar principle that is sensitive to the velocity of moving object but lack sufficient resolution which can be circumvented with frequency-modulated pulsed radars. We present a new radar device as a follow up of the successful GEODAR radar that suit the need for both applications – low resolution detection and high resolution observation. While the original GEODAR is permanently installed in the full-scale avalanche Test site “Vallée de la Sionne" in Valais, Switzerland, our new device is much smaller and can be deployed in fast response to the metrological forecast and avalanche situation. Currently the mGEODAR is installed at Nordkette ski resort above Innsbruck that is known for its frequent artificial avalanche releases. The new radar features a versatile frequency generation scheme using direct digital synthesis and can be quickly reprogrammed into a low-resolution detection mode for continuous data recording that switches to a high-resolution observation mode as soon as an avalanche is detected.

Beside the radar system itself, avalanche data are presented of the winter season 2020/21. A focus is on small to medium sized avalanches that are just on the limit to develop into a powder snow avalanche which is characterized by surging in the intermittent frontal region. Connecting the radar data of the dynamic flow evolution with snow conditions will lead to drivers of this flow regime transition. The snow conditions are taken from nearby weather stations and manual snow profiles but also from the radar itself. A continuous scanning of the resting snow cover in the avalanche path during the season further allows snow cover monitoring. This application allows to identify new snow fall, warming and wetting of surface layers as well as diurnal melt-freeze cycles.

The radar data should be consequently used for model validation, calibration, and development. With the current measurement campaign of small to mid-sized avalanches, we hope to close a gap in data availability for those events as they are increasingly the object of simulation scenarios, but current modelling and simulation tools are usually calibrated for larger and extreme events. In the future, we expect the mGEODAR radar to be deploy on other gravitational mass-movements phenomena like soil slides and rock-fall.
Binding the Ganges-Brahmaputra-Meghna Braids: A review of geomorphic change in the world's largest delta
Authors: Paszkowski Amelia , Goodbred Jr Steven , Borgomeo Edoardo , Khan M. Shah Alam , W. Hall Jim
Published: March 2021

The Ganges-Brahmaputra-Meghna (GBM) rivers deliver the greatest sediment flux to the world’s oceans, generating the Earth’s largest delta system, which is home to over 170 million people. Despite its scale and complexity, the GBM delta system remains a relatively under-researched region, with geomorphic dynamics often overlooked in studies of its vulnerability. A synthesis of these research efforts remains absent, resulting in most geomorphic studies being spatially, temporally, and topically fragmented. In this research, we therefore bind these studies together, providing a holistic, delta-wide account of the GBM’s prevailing dynamics and evolution, as well as identify key areas for future research. We built a sample of 427 peer-reviewed articles published from 1863 to 2020, and applied the Driver-Pressure-State-Impact-Response (DPSIR) framework to the geomorphic dynamics of the delta. We find that the delta has been responding to complex natural and anthropogenic perturbations in the form of subsidence, shifting river flows and sedimentation patterns. These processes subsequently impact on the extent and magnitude of flooding, result in losses to biodiversity, and most critically, severely disrupt local livelihoods. Amongst other key systemic gaps identified in this research, this study finds that (i) the GBM delta is typically assessed and modelled as a physical system with limited recognition of the dynamic interaction with human actions; and (ii) only 5% of studies assessed how the morphology of the delta may change in the future. Ultimately, this systematic review argues that although climate change and sea-level rise remain major concerns for the delta in the coming decades, multi-scale management and policy decisions have a more direct influence on the future geomorphic balance of the GBM delta.
A study of Cloud Vertical Structure and its association with precipitation over Delhi.
Authors: Sharma Saloni , Mishra Amit Kumar
Published: March 2021

Water in the atmosphere (in vapour, liquid or ice form) act as a fuel for various atmospheric processes through addition/removal of latent heat. Formation of clouds involves all these processes and thus it greatly affects atmospheric dynamics and thermodynamics. It is important to know the vertical location of clouds in atmosphere in order to understand it’s effect on other important atmospheric variables. The interaction of cloud vertical distribution with other meteorological variables is very significant in determining the hydrological cycle of any region. Therefore, in this study we have found out the cloud vertical structure over Delhi and associated it with the precipitation. The cloud top height, base height and cloud thickness along with their vertical location in the atmosphere is known as cloud vertical structure (CVS). The association of CVS with precipitation involving the amount of precipitation contributed by different layers of cloud could be very helpful in weather prediction models. We have used the balloon based measurements to calculate the CVS and for precipitation we have used CHIRPS (Climate Hazards Group InfraRed Precipitation with Station data) data. We have done multiple regressions to determine association between Cloud top height, cloud base height and cloud depth with precipitation. We have also related the monthly average of precipitation with monthly frequency of occurrence of single-layer, double-layer and triple-layer clouds. The frequency of occurrence of clouds classified based on their altitude and depth ( i.e., low-level clouds, middle-level clouds, high-level clouds and deep convective clouds) are also correlated with the monthly average precipitation. 
Incorporating vegetation trends to the MEDALUS-ESA approach for assessing environmental sensitivity at the national scale: the case of Kenya
Authors: Symeonakis Elias , Arnau-Rosalén Eva , Wandera Antony , Higginbottom Thomas , Cain Bradley
Published: March 2021

Land degradation is one of the main causes of loss of productivity and ecosystem services worldwide. According to the United Nations Convention to Combat Desertification (UNCCD), sub-Saharan Africa is on a path to experiencing some of the strongest increases in pressures on land and land-based resources than any other continent. Assessing the sensitivity of sub-Saharan African countries to land degradation is, therefore, important for identifying areas of concern, setting a baseline for national land degradation neutrality targets, and for the prioritisation of mitigation measures. The widely used MEDALUS-ESA framework is employed here to assess the sensitivity of Kenya to land degradation using the year 2010 as a baseline. We modify the MEDALUS-ESA approach by adding two important variables that are closely linked with observed land degradation in Kenya: soil erosion and livestock density. Altogether, 16 indicators are estimated from existing global-to-national-scale land cover, vegetation (MCD12Q1, MOD44B), soil (ISRIC African SoilGrids), elevation (SRTM), population and livestock density data, divided into 4 main environmental quality indices (vegetation, soil, climate and management). In order to address the dynamic nature of the land degradation process, we incorporate two additional vegetation indicators: the statistically significant (p≤ 0.05) trend over the last three decades in the Normalised Difference Vegetation Index (NDVI) and the Rain Use Efficiency (RUE; estimated using the GIMMS3g dense NDVI dense time-series and precipitation from CHIRPS). Our results show that ~40% of the country is in critical and ~48% in fragile condition, with respect to environmental sensitivity. Our approach is successful in identifying areas of known long-term degradation, for example the rangelands South and East of Nairobi (e.g. Machacos and Kitengela) and the parts of the northern rangelands (e.g. Yamicha and eastern parts of Isiolo District). It is also successful in mapping the areas of least concern, including some of the major protected areas(e.g. Tsavo National Parks, Meru National Park and the Masai Mara National Reserve) and forested areas (Mt Kenya and the Aberdares). Our modification of the MEDALUS-ESA is an important tool that can be employed at the national scale using free and open-access data to assess environmental sensitivity and assist in the UNCCD efforts to successfully define land degradation neutrality targets.
The use of static chambers in drip irrigation: what should be considered?
Authors: Baram Shahar , Bar-Tal Asher , Gal Alon , Russo David
Published: March 2021

Static chambers are frequently used to evaluate greenhouse gas (GHG) emissions from agro-systems. However, the effects of such chambers on water and nutrient distribution within and under the chamber’s base (i.e., anchor) in drip irrigation and its effects on GHG emissions is not well understood. This study aimed to shed some light on the topic by using field measurements and physically based, three-dimensional (3-D) simulations of flow transport and nitrogen transformations in variably saturated, spatially heterogeneous flow domain. GHG fluxes [methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O)] were measured in the field for two years using a portable FTIR gas analyzer. The main findings of this study suggest that: (i) the chamber’s base modifies the water and nutrient distribution within it. Placement of the dripper inside the base leads to higher water contents, higher nitrate and ammonium concentrations, and higher N2O fluxes relative to an undisturbed area. In contrast, placement of the dripper outside the chamber base reduces all of these parameters, including the N2O fluxes, relative to an undisturbed area. (ii) The dripper’s location relative to the chamber’s base had minor to no effect on CO2 fluxes. The effect on the CH4 fluxes was not conclusive, yet suggested higher emissions when the dripper was located inside the base. (iii) A minimal disturbance is achieved when the dripper is located within a base, and the base’s radius equals the capillary length of the soil.
Soil phosphorus, biology and time: A case for publishing inconclusive data, and the undeniable relevance of tennis balls
Authors: Haygarth Phil , Mezeli Malika , George Timothy , Neilson Roy , Blackwell Martin
Published: March 2021

The association of microorganisms and soil nutrient cycles has been observed for over 200 years, and their importance in the soil phosphorus (P) cycle is well documented. In-soil trophic interactions between bacteria and bacterivorous nematodes have been implicated in increased plant access to soil organic P (Po).However, the existing data remains inconclusive and lacks detail and predictability.  This work aimed to (1) assess the impact of nematodes as an additional trophic-level on Po use by plants in arable systems and (2) further understand the mechanisms of in-soil trophic interactions in improving plant acquisition of Po. To address these aims criteria based meta-analysis, glasshouse plant growth trials, in vitro and soil, and long term experimental (LTE) platforms were used.  Results led to the conclusion that nematodes did not improve plant acquisition of Po per se. Time, soil P concentration and soil biological community composition had significant impacts on plant response. Although these factors were identified in two contrasting studies, their impacts on plant responses were stochastic. Complexity, which describes the average number of trophic links per species, framed an understanding of these data where they evaded predictability, specifically when considering the temporal nature of these relationships. For example, data from the meta-analysis and the plant growth trials demonstrated it was not simply the additive effect of the number of species or the addition of a specific species which resulted in predictable plant P responses.  Nematode community analysis from the LTE’s yielded characteristics indicative of stability in the biotic component of systems previously considered disturbed (arable). This exposed the question of the nature of disturbance (whether natural or anthropogenic). Additionally, it highlighted the importance of which successional time-point was being studied and the impact this has on the data captured.  Data collected from this long-term experiment, plant growth trials and the meta-analysis highlights the importance of the temporal resolution, and the time-point at which we are observing these dynamic systems. It is argued that in-conclusive or negative results could represent true details of these systems, where they represent points of transition between stable and/or predictable states and a usual characteristic of the complex system.  Therefore, inconclusive data should not be omitted from the research library, exclusion of such data could lead to incomplete observations and incorrect assumptions. Better practices should be designed and implemented to ensure publication bias is not a barrier to our understanding of these systems.
The important role of atmospheric composition in advancing Earth System Predictions – a WMO Global Atmospheric Watch Perspective
Authors: Carmichael Gregory R.
Published: March 2021

Significant societal benefits come from services derived from environmental predication. Meeting the growing societal needs requires improved prediction skill at higher resolution and longer lead time.

To  meet societal needs the Seamless predictions of air quality, weather and climate are needed  to address many of the societal problems related to environmental hazards. Improving prediction capabilities via seamless coupling atmospheric composition modelling with weather and climate components via earth systems approaches is a key strategy of GAW to improve prediction capabilities and services. In this paper we describe efforts underway to advance atmospheric composition modelling in earth system models within the context of the recent WMO reforms.
Relating sediment supply to the morphological and hydro-meteorological characteristics of torrent catchments
Authors: Morel Maxime , Piton Guillaume , Le Bouteiller Caroline , Mas Alexandre , Evin Guillaume
Published: March 2021

In mountain areas, the quantification of sediment yield is essential in the diagnosis of a torrential watershed. The objective of this study is to present a prediction method based on multivariate statistical models calibrated from an original data set covering nearly 130 torrential basins in the Northern French Alps. Data on sediment yield and occurrence of torrential events were collected on these catchments thanks to registries from sediment retention basins (average monitoring period of 20 years) and historical archives of the catchment basin managers. On these catchments, several morphological and hydro-meteorological characteristics were calculated (e.g. geological and sediment connectivity indices, the rate of connected eroding areas in the catchment, the Melton index, the slope of the fan, etc.) in order to relate them to sediment production and the frequency of occurrence of torrential events. These models allow the estimation of quantiles of the sediment yield in small torrent catchments. These models could be useful to evaluate sediment yield and the occurrence of torrential events on catchment not equipped with sedimentation structures.
MAFIS-Multiple Actors Forest Information System: EO+AI+ODC for scalable forest monitoring services
Authors: Maranesi Marcello , Picchiani Matteo , Clementini Chiara , Salbitano Fabio , Marchetti Marco , Del Frate Fabio , Chirici Gherardo , Hofierka Jaro , Bertani Remo , Maroè Pietro
Published: March 2021

The Mission of GMATICS is to offer systematic monitoring services based on Earth Observation data, Artificial Intelligence techniques and Open Data Cube architectures.

After the development of two initial services, GMATICS is now focusing on forest monitoring through the ESA funded project MAFIS-Multiple Actors Forest Information System.

What is MAFIS? MAFIS performs a systematic monitoring of forests in natural environments as well as of forests and green areas in urban environments.

What is MAFIS composed of? For the natural environment we use time-series of multi-mission satellite data (Multispectral, SAR, Hyperspectral, and VHR) and in-situ surveys while for forests and green areas in urban environments we also use other geo-spatial data from aerial orthophotos, LIDAR sensing, drone surveys and specialized in situ measurements. All kind of data are organized within an Open Data Cube architecture and are processed and integrated by using various AI techniques. We also use a forest growth model, exploiting extensive meteorological data, and we make MAFIS service accessible through a Web-GIS platform, enabling customer access from desk-top and mobile devices.

What are the MAFIS outputs? A set of information layers suitable for different potential users: main tree species classification, identification of forest clear-cuts and selective cuttings, detection of disturbances due to forest fires, diseases or windstorms, estimation of Above Ground Biomass (AGB) gain and losses, detailed urban and peri-urban green area assessment for planning purpose, estimation and spatial assessment of various ecosystems services (carbon sequestration, pollutant removal, thermal comfort, pollen risks, etc.), monitoring of tree status for maintenance actions identification and prioritization.

Who are MAFIS potential users? Ministries of agriculture and environment, Local Administrations, wood-chain industry, municipalities, architects and urban planners, tree care and nursery companies, multiutility companies, International Organizations, Universities and Research Centres (forests, ecology, architecture).
A stronger predecessor to the M 6.2 Petrinja, Croatia earthquake in Antiquity – archaeoseismology of the 4th century Siscia event
Authors: Kázmér Miklós , Škrgulja Rosana
Published: March 2021

Archaeological excavations of the Roman city of Siscia (Sisak, Croatia) found walls of the city, up to 2 m thick, toppled in the moat. Brick masonry wall segments were found in various orientations: tilted, rotated, twisted, toppled, overturned. Foundations display features of twisting and shearing. There are additional shearing planes within the fallen walls, which allowed the segments to extend during collapse. Much of construction material was robbed in later centuries, so original dimensions are estimates only. Subsoil is alluvial sandy clay. We suggest that a major earthquake damaged the city wall of Siscia. Excitated by site effects of loose soil, high peak ground acceleration caused the wall to be sheared off from its foundation, landing it ultimately in the adjacent moat. Rebuilding of the city wall in the late antique period suggests that the first wall collapsed between the beginning of the 3rd and the middle of the 4th century. This earthquake between ~200 AD and ~350 AD is missing from historical catalogues. Both the Antique and the modern earthquakes were of intensity IX. The St. Quirinus site at Siscia is 12 km from the fault which caused the destruction in Petrinja on 29 December 2020, mere 3 km from the fault. We suggest that the Antique earthquake was stronger than the M 6.2 modern event.
Extreme mass wasting during 2021 Dhauli Ganga event in the Higher Himalaya: insight from the landscape
Authors: Pandey Anand Kumar , Kumar Kotluri Sravan , Tiwari Virendra Mani , Rao Puranchand , Cook Kirsten , Andermann Christoff , Dietze Michael , Pilz Marco , Hovius Niels
Published: March 2021

The slope instability and associated mass wasting are among the most efficient surface gradation processes in the bedrock terrain that produce dramatic landscape change and associated hazards. The wedge failure in periglacial Higher Himalaya terrain on 7th February in Chamoli, Uttarakhand (India) produced >1.5 km high rock avalanche, which amalgamated with the glacial debris on the frozen river bed produced massive debris flow along the high gradient Rishi Ganga catchment. The high-velocity debris flow and a surge of high flood led to extensive loss of life and infrastructures and issuing the extreme event flood warning along the Alakananda-Ganga river, despite there was no immediate extreme climatic event. The affected region is the locus of extreme mass wasting events associated with Glacial Lake Outburst Flood (GLOF) and Landslide Lake Outburst Flood (LLOF) in the recent past. We analyzed the landscape to understand its control on the 7th February 2021 Rishi Ganga event and briefly discuss other significant events in the adjoining region e.g. 1893/1970 Gohna Tal/Lake LLOF and 2013-Uttarakhand events in Chamoli, which have significance in understanding the surface processes in Higher Himalayan terrain.
Hydropower in the Himalayan hazardscape
Authors: Schwanghart Wolfgang , Öztürk Ugur , Sen Sumit , Agarwal Ankit , Korup Oliver
Published: March 2021

The 7 February Chamoli flood once again unveiled the vulnerability of Himalayan hydropower. On its destructive path downstream, the flood inflicted the loss of two nearby hydropower projects and damaged at least two more projects further downstream.

The flood is the third in a series of events with severe impact on the Himalayan hydropower sector. Uttarakhand was among the Indian states affected most by the 2013 Indian floods. Heavy rain, snow melt, and a glacial lake outburst flood damaged and partly destroyed more than 20 hydropower projects. The Gorkha Earthquake in 2015 led to damages to >30 projects, leading to a temporary loss of 34% of the hydropower generated in Nepal.

Analysis of these events reveals that neither flood discharge nor ground shaking were the primary processes responsible for the losses. Instead, the majority of damage was caused by geomorphological processes including landslides and rockfall, debris flows and extreme sediment discharges.

Only 20% of the ~500-GW hydropower potential is currently tapped in the Himalayas. This share is likely to increase given the high energy demands in the rapidly growing economies of the Himalayan countries.

With many opportune sites along large rivers being already occupied, there is a trend towards developing hydropower further upstream at higher elevations and closer to glaciated areas.

We argue that these developments and the past events highlight the need for a reappraisal of the Himalayan hazardscape. Risk analysis should increasingly incorporate processes such as glacial lake outburst floods and extreme sediment discharge events, and particularly aim to better understand hazard cascades which originate in glaciated and steep headwater catchments.
Exploring the flow evolution of the Chamoli event (Uttarakhand, India) of 7 February 2021: From geomorphological mapping to multi-model computer simulations
Authors: Mergili Martin , Sattar Ashim , Carrivick Johnathan , Emmer Adam , Mandli Kyle T. , Jacquemart Mylène , Watson Scott , Westoby Matt , Clague John J. , Haritashya Umesh K. , Shugar Dan H.
Published: March 2021

On 7 February 2021, a 25 million m³ rock/ice avalanche in Uttarakhand, northern India, developed into a far-reaching and devastating debris flow/debris flood, which we refer to as the ‘Chamoli event’. Based on an extensive remote sensing-based geomorphological mapping campaign, the key mechanisms and characteristics of this process chain are largely, but not yet fully understood. Numerical mass flow simulations can help confirm or reject hypotheses regarding spatiotemporal aspects of flow evolution, its magnitude and dynamics, and therefore contribute to a better process understanding. More broadly, geomorphological mapping and numerical modelling of the Chamoli event help us to gain insights of the extent to which we are able to accurately simulate complex high-mountain geohazard process cascades. Such an understanding is invaluable for predictive modelling efforts targeted at informing disaster risk reduction strategies.

In the present work, we back-calculate the flow dynamics of the Chamoli event with three state-of-the-art simulation models operating at different levels of complexity: (i) the one-phase mixture model RAMMS; (ii) the two-phase model GeoClaw, and (iii) the three-phase model r.avaflow. Input parameter sets are optimized against detailed reference data such as mapped trimlines and boulder locations, flow velocities and discharges obtained from video recordings, and erosion/deposition patterns derived by differencing pre- and post-event digital terrain models. The main aims of the study are to: (i) better understand the mechanisms of flow evolution of the Chamoli event; (ii) evaluate the level of model complexity that is necessary for accurating reproducing specific known characteristics of the process chain; and (iii) learn more about the sensitivity of model outputs to differences in initial conditions and model parameters, where these remain uncertain. The findings will facilitate the design of predictive modelling campaigns for hazard mapping purposes.
CFD simulation of atmospheric dispersion over a flat field in low-wind stable conditions using anisotropic turbulence models
Authors: Alam Boulos , Feiz Amir Ali , Ngae Pierre , Kumar Pramod , Kouichi Hamza , Chpoun Amer
Published: March 2021

Low wind conditions (wind speed < 1-2m/s) are the most critical atmospheric states for the dispersion of a pollutant due to highly non-stationary and inhomogeneous diffusion conditions governed by the meandering, weak, sporadic and intermittent turbulence. These atmospheric conditions coupled with thermal stable conditions remain a challenge for the numerical modelling of turbulent flows and dispersion at local scale.

Numerical simulation of a pollutant dispersion in these atmospheric conditions using the RANS (Reynolds Averaged Navier Stokes) equations is known to be highly dependent on selected turbulence models. On one hand, the modelling of turbulence and dynamic of wind field, by means of first order Eulerian closure models based on the turbulent viscosity hypothesis, lacks an adequate and complete representation of the anisotropic effect. On the other hand, the isotropic aspect attributed to the dispersion of the pollutant, through the simple gradient diffusion model, tends to underestimate the horizontal diffusion of the pollutant, thus overestimating the concentration along the plume axis near the source.

Therefore, the purpose of this study is to investigate the behaviour of anisotropic RANS models for dispersion of a pollutant in low wind stable conditions. The models used to simulate the dynamic field are the second order RSM (Reynolds Stress models), whereas the algebraic models used to model the concentration turbulent flux of concentration are either the AFM (Algebraic Flux model) or the GGDH (Generalized Gradient Diffusion Model). The simulations are performed using a 3-dimensional CFD code, Code_Saturne® (EDF), in which these turbulence models are implemented.

The models are validated with a well-known Idaho Falls experiment (USA) for the dispersion of a passive tracer under low-wind stable conditions. Various inflow boundary conditions for wind profiles and turbulence parameters are applied. In order to assess the predictive capacity of these models, a comparative statistical analysis is performed using standard statistical performance measures. The model results are also compared with the results from a Gaussian plume dispersion model.

 
Verification of modeling of convective events based on radar reflectivity
Authors: Svechnikova Ekaterina , Ilin Nikolay , Mareev Evgeny
Published: March 2021

The use of numerical modeling for atmospheric research is complicated by the problem of verification by a limited set of measurement data. Comparison with radar measurements is widely used for assessing the quality of the simulation. The probabilistic nature of the development of convective phenomena determines the complexity of the verification process: the reproduction of the pattern of the convective event is prior to the quantitative agreement of the values at a particular point at a particular moment.

We propose a method for verifying the simulation results based on comparing areas with the same reflectivity. The method is applied for verification of WRF-modeling of convective events in the Aragats highland massif in Armenia. It is shown that numerical simulation demonstrates approximately the same form of distribution of areas of equal reflectivity as for radar-measured reflectivity. In this case, the model tends to overestimate on average reflectivity, while enabling us to obtain the qualitatively correct description of the convective phenomenon.

The proposed technique can be used to verify the simulation results using data on reflectivity obtained by a satellite or a meteoradar. The technique allows one to avoid subjectivity in the interpretation of simulation results and estimate the quality of reproducing the “general pattern” of the convective event.
Cenozoic advance of the East Asian monsoon promoted weathering of the magnesium-rich southern China upper crust and its significance for global geochemical cycles of carbon and magnesium
Authors: Yang Yibo , Galy Albert , Fang Xiaomin , France-Lanord Christian , Wan Shiming , Yang Rongsheng , Zhang Jian , Zhang Ran , Yang Song , Miao Yunfa , Liu Yudong , Ye Chengcheng
Published: March 2021

The Oligocene-Miocene boundary climatic reorganization linked to the northward advance of the East Asian monsoon in subtropical China is a potentially important but poorly constrained atmospheric CO2 consumption process. Here, we performed a first-order estimate of the difference in CO2 consumption induced by silicate chemical weathering and organic carbon burial in subtropical China related to this monsoon advance. Our results show that an increase in CO2 consumption by silicate weathering varies between ~1% and 15% of the current global continental silicate sink with an ~60% contribution of Mg-silicate weathering but a negligible increase in the global organic carbon burial (<3.5%) since the late Oligocene. The results highlight the significant role of weathering of the Mg-rich upper continental crust in East China that would also contribute significantly to the rise in the Mg content of the ocean. Our study thus suggests that the uplift of the Himalaya-Tibetan Plateau can lead to indirect modification of the global carbon and magnesium cycles by changing the regional hydrological cycle in areas of East Asia that are tectonically less active in addition to the well studied direct impact of high erosion-induced atmospheric CO2 consumption along the orogenic belt in South Asia.
Airborne observations of surface cloud radiative forcing over different surface types of the Arctic Ocean during late summer/early autumn
Authors: Becker Sebastian , Stapf Johannes , Ehrlich André , Schäfer Michael , Wendisch Manfred
Published: March 2021

Clouds can cause a significant change to the radiative energy budget of the Earth's surface compared to clear-sky conditions, which is referred to as surface cloud radiative forcing (CRF). The CRF in the Arctic strongly depends on the surface properties (absorbing open ocean vs. strongly reflecting sea ice) and is affected by the low or even absent sun and the special thermodynamic conditions. Therefore, in contrast to the mid and low latitudes, in the Arctic, clouds mostly warm the surface on annual average. However, the CRF will change as the sea ice retreats in a warming climate, which might be accelerated due to the enhanced warming of the Arctic, known as Arctic Amplification. Thus, to quantify the contrast of the CRF over sea ice-covered and sea ice-free ocean surfaces, several airborne campaigns have been conducted in the vicinity of Svalbard in the recent years. The measurements of cloud macrophysical and microphysical properties as well as radiative and turbulent fluxes cover different seasons (spring to early autumn).

Airborne broadband radiation measurements under all-sky conditions were used to calculate the surface CRF during low-level flight sections. In this study, observations from the concurrent campaigns Multidisciplinary drifting Observatory for the Study of Arctic Climate – Airborne observations in the Central Arctic (MOSAiC-ACA) and MOSAiC-Icebird, conducted in August/September 2020, are presented. First results of the CRF over open ocean and the marginal sea ice zone (MIZ) of late summer/early autumn conditions are assessed and compared to the previous airborne spring and early summer campaigns to analyse the seasonal variability of the CRF.
Microbial community composition seasonality and drift over years in small freshwater ecosystems
Authors: Jardillier Ludwig , David Gwendoline , Deschamps Philippe , Bertolino Paola , Moreira David , Alric Benjamin , Restoux Gwendal , Rochelle-Newall Emma , Thébault Elisa , Simon Marianne , López-García Purificación
Published: March 2021

Small freshwater ecosystems are highly diverse, widely distributed, may be identified as major actors in greenhouse gas fluxes and are potential stocks of freshwater for human usages. In principle, they are more sensitive to environmental disturbance than large aquatic ecosystems because their small volumes provide low buffering capacity. However, little is yet known about their microbial biodiversity and function and how it is structured over time. Yet, understanding the structuring of microbial primary producers, predators, parasites and degraders in these ecosystems is essential to appreciate and model their functioning in the next decades. We investigated the spatial distribution and temporal dynamics of microorganisms of the three domains of life (bacteria, archaea, microbial eukaryotes) at the intra- (seasonal) and inter-annual (pluri-annual) scale in five small freshwater ecosystems. We focused on four ponds and a brook located in northwestern France under temperate climate that we studied for eight years (2011-2019) at seasonal frequency. Microbial diversity was assessed through Illumina MiSeq sequencing of 16S and 18S rDNA amplicons. Several abiotic parameters (physical and chemical) were measured in situ and in the laboratory to characterise the environmental conditions. Multivariate statistical analyses were conducted to identify temporal patterns and link them to environment changes. Microbial communities differed among the ecosystems despite their spatial proximity, likely due to differences in local environmental conditions. Microbial eukaryotic and prokaryotic communities exhibited seasonal temporal patterns and a shift in composition over the years. Microbial communities experienced a strong turnover at the seasonal scale leading to a low fraction (< 2%) of recurrent taxa. In each ecosystem, the measured physico-chemical parameters slightly influenced the microbial community variance over time. These results suggest that biotic interactions but also dormancy, immigration and genetic evolution superimpose to environmental selection through time. Understanding their interplay will be essential to explain microbial community composition change in these ecosystems. 
Destruction of microplastics in the natural environment
Authors: Kovalevski Vladimir , Zobkov Mikhail
Published: March 2021

Morphological structure and chemical composition of environmental microplastics (MPs) extracted from water and bottom sediments of Lake Onego were studied. Raman spectroscopy was used to identify MPs polymer types and scanning electron microscopy with energy dispersive microanalysis was used to study the morphology and trace elements composition of inclusions on their surface. The features of the destruction of MPs, as well as the presence of various chemical elements on their surface including heavy metals, were investigated. Four main mechanisms of MPs microdestruction have been identified: (1) Local destruction of monophasic MPs caused by local oxidation and cleavage of thin flakes and fragments with the formation of nanoscale plastics. (2) The destruction of multiphase microplastics predominantly determined by the selective destruction of one of the phases of the composite, for example, the ligament scission between the individual components of the plastic with their separation. (3) Microbiological destruction of MPs under the influence of diatoms by fixing spores of diatoms on defects of MPs with their subsequent growth, deflection, and separation of nanoscale polymer particles. (4) Mineralogical destruction of MPs associated with the sorption of chemical elements and crystallization of nanocrystals, which under appropriate conditions begin to grow and break-up the MPs accelerating the process of its destruction. The last mechanism have not yet been reported. These mechanisms initiate nanoplastics formation, which increases particles mobility in the aquatic environment and their threat to water organisms. At the same time, the fouling with diatoms (with a silica shell) and the sorption of heavy elements increase the bulk specific density of MPs and contribute to its accumulation in bottom sediments.

The study was supported by the Russian Science Foundation grant number 19-17-00035.
Pseudotachylyte veins in accretionary complexes: melt or mechanical wear?
Authors: Moris-Muttoni Benjamin , Raimbourg Hugues , Augier Romain , Champallier Rémi , Le Trong Emmanuel , Chen Yan
Published: March 2021

Whether seismic rupture propagates over large distances to generate mega-earthquakes or on the contrary slows down quickly, is heavily dependent on the slip processes operating within the fault core, such as frictional melting or intense grain-size reduction and amorphization. The record, in fossil fault zones, of seismic slip, consists in many instances in Black Faults Rocks (BFR), that consists in a generally thin dark and aphanitic veins similar to volcanic glasses, which cross-cuts sharply a weakly foliated tectonic mélange, and have been interpreted as resulting from quenching of a melt (i.e. pseudotachylytes). Such interpretation has nevertheless been questioned because identical (micro- and nano-) textures have been observed on intensely comminuted natural fault rocks and on slow creep experiments on crustal rocks.

In this study, we report a new dataset of high spatial-resolution Raman Spectroscopy of Carbonaceous Materials (RSCM) profiles across natural BFR from two accretionary complexes. RSCM is sensitive to both temperature and deformation. We have carried out analyses on Okitsu and Nobeoka BFR from the Shimanto Belt and Kodiak BFR from the Kodiak Accretionary Complex to discriminate the slip weakening process. The Raman Intensity Ratio (i.e. R1 in Beyssac et al., 2002) and the Area ratio (RA1 in Lahfid et al., 2010) show a drastic and discontinuous stepped increase along profiles across the BFR, revealing a higher crystallinity. Moreover, in spite of scattering, highest values have been measured on the rim between the BFR and the host-rock. Fluidization structures, interpreted as injection veins, show similar values to the ones in the host rock. Additionally, using an experimentally calibrated kinetics 1D modelling of Intensity ratio evolution with temperature, we compared the natural Raman spectroscopy profiles to different scenarios of temperature increase during seismic slip. In the three examples of BFR from accretionary complexes interpreted as natural pseudotachylytes, RSCM profiles are not consistent with a molten origin and must reflect mechanical wear during deformation.

Consequently, these results bear major consequences on the dynamics of faulting in accretionary complexes, as the slip-weakening processes that occur during seismic slip rely on extreme grain-size reduction and fluidization rather than melting.
Multi-Array Multi-Phase Back-Projection: Improving the imaging of earthquake rupture complexities
Authors: Vera Felipe , Tilmann Frederik , Saul Joachim
Published: March 2021

We present a teleseismic earthquake back-projection method parameterized with multiple arrays and combined P and pP waveforms, improving the spatiotemporal resolvability of rupture complexity. The contribution of each array to the rupture image is weighted depending on the multi-array configuration. Depth phases also contribute effectively to earthquakes at 40 km depth or deeper.

We examine 31 large earthquakes with moment magnitude greater than 7.5 from 2010-2020, which were back-projected in the 0.5-2.0 Hz band, giving access to the high-frequency rupture propagation. An algorithm estimates rupture length, directivity, and speed based on the back-projection results.

Thrust and normal earthquakes showed similar magnitude-dependent lengths and consistent subshear ruptures, while strike-slip earthquakes presented longer ruptures (relative to their magnitude) and frequently reached supershear speeds. The back-projected lengths provided scaling relations to derive high-frequency rupture lengths from moment magnitudes. The results revealed complex rupture behavior, for example, bilateral ruptures (e.g., the 2017 Mw 7.8 Komandorsky Islands earthquake), evidence of dynamic triggering by a P wave (e.g., the 2016 Mw 7.9 Solomon Islands earthquake), and encircling asperity ruptures (e.g., the 2010 Mw 7.8 Mentawai and 2015 Mw 8.4 Illapel earthquakes). The latter is particularly prevalent in subduction megathrust earthquakes, with down-dip, up-dip, double encircling, and segmented patterns. The automated choice of array weighting and the extraction of basic rupture parameters makes the approach well suited for near-real-time earthquake monitoring.
Long-term MAX-DOAS measurements of formaldehyde in the suburban area of London 
Authors: Donner Sebastian , Dörner Steffen , Buxmann Joelle , Beirle Steffen , Campbell David , Kumar Vinod , Müller Detlef , Remmers Julia , Rolfe Samantha M. , Wagner Thomas
Published: March 2021

Multi-AXis (MAX)-Differential Optical Absorption Spectroscopy (DOAS) instruments record spectra of scattered sun light under different elevation angles. From such measurements tropospheric vertical column densities (VCDs) and vertical profiles of different atmospheric trace gases and aerosols can be determined for the lower troposphere. These measurements allow a simultaneous observation of multiple trace gases, e.g. formaldehyde (HCHO), glyoxal (CHOCHO) and nitrogen dioxide (NO2), with the same measurement setup. Since November 2018, a MAX-DOAS instrument has been operating at Bayfordbury Observatory, which is located approximately 30 km north of London. This measurement site is operated by the University of Hertfordshire and equipped with an AERONET station, a LIDAR and multiple instruments to measure meteorological quantities and solar radiation. Depending on the prevailing wind direction the air masses at the measurement site can be dominated by the pollution of London (SE to SW winds) or rather pristine air (northerly winds).

First results already showed that the highest formaldehyde and glyoxal columns are observed for southerly to southeasterly winds indicating the influence of the anthropogenic emissions of London. However, the detailed patterns of the different trace gases were found to be more complex. Therefore, this measurement site is well suited to study the influence of anthropogenic pollution on the atmospheric composition and chemistry at a rather pristine location in the vicinity of London, a major European capital with about 10 million inhabitants and 4 major international airports.

In this study, trace gas and aerosol profiles are retrieved using the MAinz Profile Algorithm (MAPA) with a focus on tropospheric HCHO which plays an important role in tropospheric chemistry. The HCHO results are combined with the results of other trace species such as NO2, CHOCHO and aerosols in order to identify pollution levels, emission sources and different chemical regimes.
Using the concept of hydrological connectivity to integrate physical and social systems
Authors: Bracken Louise , Croke Jacky
Published: March 2021

The concept of connectivity has found great traction in understanding the movement of fluxes across the surface of the earth through disciplinary perspectives including hydrology, geomorphology and ecology (Bracken and Croke, 2007; Bracken et al 2013;2015). Connectivity-based approaches have also generated new understanding of structural-functional relationships that characterise complex systems, for instance in computational neuroscience, social network science and systems biology (Turnbull et al., 2018). Whilst the concept of hydrological connectivity has been used widely, at all scales and with respect to fluxes of both water and sediment, critique and development of the concept is less frequent in the literature. In this paper we revisit the existing body of work around hydrological connectivity to examine whether the concept has been used to it’s full potential and explore further ways in which the concept of hydrological connectivity could be expanded to continue to drive geomorphological research. One potential avenue for research is to learn from complex systems and use the concept of connectivity to embrace human dynamics (through managing the landscape and guiding policy and regulation) on one hand and climate change (which drives system inputs) on the other.  This opportunity is explored here using the water sector as a case study where planning, and managing for, water security under growing population pressures and future climate change are explored through this broader interpretation of connectivity. We see this wider coupling between humans and system inputs playing a significant role in shaping earth surface processes and sediment dynamics and a widening of definition may enable hydrologists and geomorphologists to better integrate socio-ecological systems into our research.
Kerguelen Plateau – outstanding Southern Indian Ocean archives of Cenozoic climatic and oceanographic changes
Authors: Zirks Eleen , Westerhold Thomas , Schneider Matthias , Uenzelmann-Neben Gabriele
Published: March 2021

Previous scientific ocean drilling expeditions have revealed that sediments deposited in the Kerguelen Plateau region have the potential to provide an out-standing chronicle of regional and global climate changes. In particular, this area is an excellent location to monitor subantarctic and high-latitude climate dynamics and obtain far-field information documenting Antarctic climate history in a world warmer than today.

Here we report first results from site survey RV Sonne cruise SO272 that sailed January 11 to March 4 2020 from Port Louis, Mauritius, to Cape Town, South Africa. During the cruise ~4000 km of high resolution seismic reflection data were recorded along 18 seismic profiles across the central and southern Kerguelen Plateau. At 11 stations sediment cores with recoveries of up to 10m were retrieved [GU1] to complement the seismic studies and provide ages of the outcropping sediment at the sea floor. Three gravity cores targeted the Labuan Basin recovering Plio-Pleistocene diatom ooze with drop stones and rhythmic changes in reflectance. Eight gravity cores targeted the Raggatt Basin with the main objective to penetrate through the upper undifferentiated layer of surface sediment and probe the below much older outcropping sediment. Carbonate rich sediments were successfully retrieved at three locations with microfossil assemblages of late Eocene age. X-ray fluorescence core scanning, benthic stable isotope and bio-stratigraphic data will be presented. Seismic and geological datasets will form the base for an IODP full proposal to drill a complete Miocene to Paleocene high latitude sediment package, build upon the #983-Pre IODP proposal.