bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of IDS contribution to ITRF2020
Authors: Bogusz Janusz , Klos Anna , Moreaux Guilhem
Published: March 2022

We examine DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) position time series processed by the IDS (International DORIS Service) within “ids21wd02” reprocessing, serving as an official input into the newest International Terrestrial Reference Frame, namely ITRF2020. The ids21wd02 set includes the North, East and Up coordinate time series of the 201 stations located at the 87 DORIS sites since 1993.0. These coordinate time series were delivered by the IDS as a byproduct of the IDS contribution to the 2020 realization of ITRF (International Terrestrial Reference Frame). From a number of 201 stations distributed globally, we choose a number of 115 sites, whose time series are longer than 5 years.  Position time series are carefully pre-processed by means of removing outliers and offsets. To reliably describe the DORIS position time series, we use a time series model of long-term non-linear signal, linear trend, seasonal oscillations and a stochastic part. Both deterministic and stochastic components are determined using maximum likelihood estimation. Our analysis is performed in three different ways. Firstly, we search for a preferred noise model and demonstrate, that there is an ongoing improvement of noise parameters over years. This is related to the persisting improvement in background models, antenna types, etc. Then, both deterministic and stochastic parameters are compared to the ITRF2014 IDS solution, to find the usefulness of a newly applied models or strategies, especially to prove an impact of the new C STAREC antenna type. Finally, we compare DORIS position time series to the GPS (Global Positioning System) position time series for a number of 267 co-located stations (official input of International GNSS Service into ITRF2020); both deterministic and stochastic components are compared, with a special attention paid to the differences of velocities and their errors, as they are employed for kinematic reference frames realization or in geodynamical interpretations.
Multivariate bias corrections of global compound dry and hot events in CMIP6 model simulations 
Authors: Meng Yu , Hao Zengchao
Published: March 2022

Climate extremes induced by global warming have remarkable impacts on water resources, agricultural production, and terrestrial ecosystems. Climatic model simulations provide useful information to analyze changes in extremes (e.g., droughts, heatwaves) under global warming for climate policies and mitigation measures. However, systematic biases exist in climate model simulations, which hinders accurate assessments of extremes changes. Bias correction methods have been employed to correct biases in climate variables (e.g., precipitation, temperature) in model simulations. Previous studies mostly focus on individual variables while the correction of inter-variable correlation (e.g., precipitation-temperature dependence) is still limited. Moreover, the concurrence of climate extremes (e.g., droughts and hot extremes), which is closely related to the dependence among contributing variables, may amplify the impacts. However, bias correction of the contributing variables of compound events is still limited but growing. In this study, we employ the multivariate bias correction (MBC) approach to correct the precipitation, temperature, and their dependence from CMIP6 simulations. We found that the MBC can improve the simulation of precipitation-temperature dependence and associated compound dry and hot events. This study can provide useful insights for improving model simulations of compound weather and climate extremes for impact studies and mitigation measures.
Changes in net CO2 uptake, photosynthesis, and ecosystem respiration and their relationships with climate and snow characteristics in central Siberia
Authors: Park Sung-Bin , Park Sang Seo
Published: March 2022

Anomalous or extreme climate conditions in high northern latitudes are likely to become more frequent and intense for the last several years. Based on the eddy covariance flux data from 2013-2017 collected at a boreal forest and peatland in central Siberia, net CO2 uptake in spring 2015 was the highest compared with the 2013-2017 average because of the anomalous surface warming over the region > 60N. This enhanced spring net CO2 uptake may be associated with more snowfall amount in winter. However, an increased spring net CO2 uptake may be compensated with summertime net CO2 uptake due to the relatively cool summer surface temperature in 2015. Spring 2020 in central Siberia has experienced even more substantial surface warming than in spring 2015, probably associated with excessive spring snowmelt. This suggests that further investigations in the effects of anomalous seasonal climate and snow conditions on net CO2 uptake, photosynthesis and ecosystem respiration are necessary to better understand annual CO2 balance. To characterize carbon fluxes and underlying mechanisms related to climate condition and snow characteristics from 2012-2020, we analyzed upscaling carbon flux dataset based on a random forest model by Jing et al. (2021), satellite-based net ecosystem exchange of CO2 (i.e., Soil Moisture Active Passive (SMAP) L4 data), snow characteristics (e.g. freeze-thaw cycle, snow depth), and reanalysis dataset. We will focus on seasonal CO2 uptake, photosynthesis and ecosystem respiration under the anomalous temperature and snowfall/snowmelt conditions, then discuss factors regulating annual net CO2 uptake capacity in boreal forests and peatlands in central Siberia.
Geographical inhomogeneity and temporal variability in mixing property and driving mechanism in the Arctic Ocean
Authors: You Jia , Xu ZhenHua , Robertson Robin , Li Qun , Yin BaoShu
Published: March 2022

   Upper ocean mixing plays a key role in the atmosphere-ocean heat transfer and sea ice extent and thickness via modulating the upper ocean temperatures in the Arctic Ocean. Observations of diffusivities in the Arctic that directly indicate the ocean mixing properties are sparse. Therefore, the spatiotemporal pattern and magnitude of diapycnal diffusivities and kinetic energy dissipation rates in the upper Arctic Ocean are important for atmosphere-ocean heat transfers and sea ice changes. These were first estimated from the Ice-Tethered Profilers dataset (2005–2019) using a strain-based fine-scale parameterization. The resultant mixing properties showed significant geographical inhomogeneity and temporal variability. Diapycnal diffusivities and dissipation rates in the Atlantic sector of the Arctic Ocean were stronger than those on the Pacific side. Mixing in the Atlantic sector increased significantly during the observation period; whereas in the Pacific sector, it weakened before 2011 and then strengthened. Potential impact factors include wind, sea ice, near inertial waves, and stratification, while their relative contributions vary between the two sectors of the Arctic Ocean. In the Atlantic sector, turbulent mixing dominated, while in the Pacific sector, turbulent mixing was inhibited by strong stratification prior to 2011, and is able to overcome the stratification gradually after 2014. The vertical turbulent heat flux constantly increased in the Atlantic sector year by year, while it decreased in the Pacific sector post 2010. The estimated heat flux variability induced by enhanced turbulent mixing is expected to continue to diminish sea ice in the near future. 
Lake-level fluctuations from Lake Iznik seismic stratigraphy (NW Turkey): Implications for past climate.
Authors: Gastineau Renaldo , Anselmetti Flavio S. , Fabbri Stefano C. , Roeser Patricia , Sabatier Pierre , Şahin Mustafa , Gündüz Serkan , Gebhardt A. Catalina , Franz Sven O. , Niessen Frank , De Sigoyer Julia
Published: March 2022

Understanding past water-level changes are essential to human development. Changes in lake levels can result in the displacement of populations due to rising water levels, or be a limiting factor in the case of irrigation for agriculture or in terms of water resources. Lake-level fluctuations can be the consequence of outlet modification, human activity, or on a longer time scale, of climatic change or tectonic activity.

In Turkey, several studies showed that the water level of numerous lakes significantly changed since the Last Glacial Maximum (LGM). Here, we present the history of Lake Iznik (83 m above sea level) which is the fifth-largest lake in Turkey. Based on high-resolution seismic profiles, sediment cores and bathymetry, we document new insights into its lake-level variations since the late Pleistocene. An important transgressional phase with a highstand (> 50 m above the modern lake level) of uncertain age is documented during the late Pleistocene, preceding the LGM (> 40 ka BP). Before this highstand, the lake level was substantially lower by at least ~ 60 m. The stepwise transgression that led to this highstand is associated with the formation of a series of up to 13 buried paleoshorelines. This phase of high lake level is followed by a sedimentation pattern marked by strong lateral differences in sediment accumulation in the northern part of the lake. These pronounced lateral differences are partly caused by lacustrine contourite drifts due to strong currents, or by prograding delta clinoforms. The younger phases (< 18 ka BP) are characterized by different regressional/transgressional cycles with a major lowstand at ~ 50 m below the present-day lake level during the early Holocene, probably related to a dryer climate. Today, the lake level continues to fluctuate as shown by one of the most important archaeological discoveries of this decade. During a 2014 aerial photo survey, the fourth to fifth century CE St. Neophytos Basilica was discovered underwater in Lake Iznik, 20 m from the shore at an average depth of 2 m (e.g. Şahin & R. Fairchild, 2018). However, it is more difficult to distinguish anthropogenic from climatic influences in recent times.

Reference: Şahin, M., & Fairchild, M. R. (2018). Nicea's underwater basilica. Biblical Archaeology Review, 44(6), 30–37.
Arbuscular mycorrhiza symbiosis improves plant water status and soil-root hydraulic conductance under drought 
Authors: Abdalla Mohanned , Ahmed Mutez
Published: March 2022

Recent studies have identified soil drying as a dominant driver of transpiration reduction at the global scale. Although Arbuscular Mycorrhiza Fungi (AMF) are assumed to play a pivotal role in plant response to soil drying, studies investigating the impact of AMF on plant water status and soil-plant hydraulic conductance are lacking. Thus, the main objective of this study was to investigate the influence of AMF on soil-plant conductance and plant water status of tomato under drought. We hypothesized that AMF limit the drop in matric potential across the rhizosphere, especially in drying soil. The underlying mechanism is that AMF extend the effective root radius and hence reduce the water fluxes at the root-soil interface. The follow-up hypothesis is that AMF enhance soil-plant hydraulic conductance and plant water status during soil drying. To test these hypotheses, we measured the relation between transpiration, soil and leaf water potential of tomato with reduced mycorrhiza colonization (RMC) and the corresponding wild-type (WT). We inoculated the soil of the WT with Rhizophagus irregularis spores to potentially upsurge symbiosis initiation. During soil drying, leaf water potential of the WT did not drop below -0.8 MPa during the first six days after withholding irrigation, while leaf water potential of RMC dropped below -1 MPa already after four days. Furthermore, AMF enhanced the soil-plant hydraulic conductance of the WT during soil drying. In contrast, soil-plant hydraulic conductance of the RMC declined more abruptly as soil dried. We conclude that AMF maintained the hydraulic continuity between root and soil in drying soils, hereby reducing the drop in matric potential at the root-soil interface and enhancing soil-plant hydraulic conductance of tomato under edaphic stress. Future studies will investigate the role of AMF on soil-plant hydraulic conductance and plant water status among diverse plant species growing in contrasting soil textures.
Unravelling the complex interplay between drought and conflict
Authors: Wanders Niko , Hoch Jannis , de Bruin Sophie , van Beek Rens , Buhaug Halvard , von Uexkull Nina
Published: March 2022

In the past decade, several efforts have been made to project armed conflict risk into the future. However all of these approaches neglected the impact of hydrological extremes, specifically drought, on potential conflicts. This study broadens current approaches by presenting a first-of-its-kind application of machine learning (ML) methods to project sub-national armed conflict risk over the African continent along three Shared Socioeconomic Pathway (SSP) scenarios and three Representative Concentration Pathways towards 2050 including hydrological feedbacks.

We specifically assessed the role of hydro-climatic indicators as drivers of armed conflict. Overall, their importance is limited compared to main conflict predictors but results suggest that changing climatic conditions may both increase and decrease conflict risk, depending on the location: in Northern Africa and large parts of Eastern Africa climate change increases projected conflict risk whereas for areas in the West and northern part of the Sahel shifting climatic conditions may reduce conflict risk.

With our study being at the forefront of ML applications for conflict risk projections, we identify various challenges for this arising scientific field. A major concern is the limited selection of relevant quantified indicators for the SSPs at present. Specifically, the links between drought and conflicts are mostly region specific and not necessarily well reflected in the available data. Nevertheless, ML models such as the one presented here are a viable and scalable way forward in the field of armed conflict risk projections, and can help to inform the policy-making process with respect to climate security under changing hydroclimatic conditions.
Quantifying drainage-divide migration from orographic rainfall over geologic timescales: Sierra de Aconquija, southern Central Andes
Authors: Schildgen Taylor , van der Beek Peter , D'Arcy Mitch , Roda Boluda Duna , Elizabeth Orr , Hella Wittmann
Published: March 2022

Drainage-divide migration, controlled by rock-uplift and rainfall patterns, may play a major role in the geomorphic evolution of mountain ranges. However, divide-migration rates over geologic timescales have only been estimated by theoretical studies and remain empirically poorly constrained. Geomorphological evidence suggests that the Sierra de Aconquija, on the eastern side of the southern Central Andes, northwest Argentina, is undergoing active westward drainage-divide migration. The mountain range has been subjected to steep rock trajectories and pronounced orographic rainfall for the last several million years, presenting an ideal setting for using low-temperature thermochronometric data and exhumation rates derived from in situ produced 10Be to explore its topographic evolution.

We perform three-dimensional thermal-kinematic modeling of previously published thermochronometric data spanning the windward and leeward sides of the range to explore the most likely structural and topographic evolution of the range. We find that the thermochronometric data can be explained by scenarios involving drainage-divide migration alone, or by scenarios that also involve changes in the structures that have accommodated deformation through time. By combining new 10Be-derived catchment-average denudation rates with geomorphic and stratigraphic constraints on fault activity, we conclude that the evolution of the range was likely dominated by west-vergent faulting on a high-angle reverse fault underlying the range, together with westward drainage-divide migration at a rate of several km per million years. Our findings place new constraints on the magnitudes and rates of drainage-divide migration in real landscapes, quantify the effects of orographic rainfall and erosion on the topographic evolution of a mountain range, and highlight the importance of considering drainage-divide migration when interpreting thermochronometer age patterns.
Drivers and reversibility of abrupt ocean cold-to-warm and warm-to-cold transitions in the Amundsen Sea, Antarctica
Authors: Caillet Justine , Jourdain Nicolas , Mathiot Pierre
Published: March 2022

Ocean warming around Antarctica has the potential to trigger marine ice-sheet instabilities. It has been suggested that abrupt and irreversible cold-to-warm ocean tipping points may exist, with possible domino effect from ocean to ice-sheet tipping points (Hellmer et al. 2017). Here we investigate the existence of drivers of ocean tipping points in the Amundsen Sea. This sector is currently relatively warm, but a cold-to-warm tipping point may have occurred in the past. The conditions for an hypothetic abrupt return to a cold state are also investigated. A 1/4° ocean model configuration of the Amundsen Sea, representing interactions with sea-ice and ice-shelves, is used to characterize warm-to-cold and cold-to-warm oceanic transitions induced by perturbations of the atmospheric forcing and their influence on ice-shelf basal melt. We apply idealized perturbations of heat, momentum and freshwater fluxes to identify the key physical processes at play. We find that the Amundsen Sea switches permanently to a cold state for an air cooling of 2.5°C and intermittently for either an air cooling of 0.5°C, precipitations decreased by 30% or a 2° northward shift of the winds. All simulated transitions are reversible, i.e. restoring the forcing to its state before the tipping point is sufficient to restore the ocean to its original state although the recovery time is correlated to the amplitude of the perturbations. Perturbations of the heat and freshwater fluxes modify the properties of the ocean by impacting the buoyancy flux, either through their impact on the sea-ice or, directly, to a lesser extent. Perturbations of the momentum flux involve more complex mechanisms as it combines both an Ekman effect and an indirect effect on the buoyancy flux related to changes in sea-ice advection.
The AI-CORE Project - Artificial Intelligence for Cold Regions
Authors: Dietz Andreas , Baumhoer Celia ,   AI-CORE Team
Published: March 2022

Artificial Intelligence for Cold Regions (AI-CORE) is a collaborative approach for applying Artificial Intelligence (AI) methods in the field of remote sensing of the cryosphere. Several research institutes (German Aerospace Center, Alfred-Wegener-Institute, Technical University Dresden) bundled their expertise to jointly develop AI-based solutions for pressing geoscientific questions in cryosphere research. The project addresses four geoscientific use cases such as the change pattern identification of outlet glaciers in Greenland, the object identification in permafrost areas, the detection of calving fronts in Antarctica and the firn-line detection on glaciers. Within this presentation, the four AI-based final approaches for each addressed use case will be presented and exemplary results will be shown. Further on, the implementation of all developed AI-methods in three different computer centers was realized and the lessons learned from implementing several ready-to-use AI-tools in different processing infrastructures will be discussed. Finally, a best-practice example for sharing AI-implementations between different institutes is provided along with opportunities and challenges faced during the present project duration.
Implementation of soil moisture data into landslide rainfall thresholds: two case studies in Italy and Norway
Authors: Distefano Pierpaolo , Piciullo Luca , Peres David J. , Scandura Pietro , Cancelliere Antonino
Published: March 2022

Prediction of rainfall-induced landslides is a complex task, due to the multitude of processes involved, heterogeneity of soil properties, spatial variability of rainfall and uncertainty in landslide inventories. Rainfall thresholds can provide a useful insight on the prediction of rainfall-induced landslides; however, they just describe a part of the problem, completely neglecting the hydrological conditions. Empirical thresholds, generally focus on the characteristics of precipitation, expressed in terms of intensity and duration (I-D threshold). Although an increasing number of studies is aiming at defining the link between precipitation characteristics and soil moisture data, few are describing the usefulness of soil moisture together with empirical thresholds for rainfall-induced landslide prediction. Soil moisture data are generally used in physically based models being a function of the characteristics of the soils therefore highly site-specific and obtainable with instrumental observations and/or in situ or laboratory analyzes.

In this study, a preliminary analysis on the use of soil moisture data for the definition of empirical rainfall thresholds is carried out. The newly released fifth-generation reanalysis product of the European Center for Medium Range Weather Forecasts (ECMWF), i.e., ERA5, provides soil moisture data even for those areas in which no measuring instruments are available. ERA5 data are available in the Climate Data Store on regular latitude-longitude grids at 0.1° x 0.1° resolution covering a period from 1950 to the present with hourly resolution. The goodness of the product has been verified comparing in situ available data with those obtained with ERA by statistical analysis including the Taylor diagram that links correlation coefficient, standard deviation and root mean squared difference between two analyzed series. Soil moisture data have been collected for several stations located in Norway and Italy.

Soil moisture data for Norway has been collected from stations in two different places near Oslo, while soil moisture data for Italy comes from the International Soil Moisture Network (ISMN), specifically, Calabria region stations have been used. Rainfall-soil moisture thresholds have been defined for two case studies and the performance of thresholds considering and neglecting the soil moisture has been evaluated.

 
Non-linear internal waves in two-layer stratified flows
Authors: Makarenko Nikolay , Maltseva Janna , Cherevko Alexander
Published: March 2022

We consider an analytical model of internal waves propagating in a weakly stratified two-layer fluid. A new model equation extents the long-wave approximation suggested in [1,2] for the non-linear Dubreil-Jacotin - Long equation. This model takes into account a slight density gradient in stratified layers, which can be comparable with the density jump at the interface between layers. Parametric range of solitary waves is determined in the framework of considered mathematical model. We demonstrate that solitary wave modes can be subject to the Kelvin-Helmholtz instability arising due to wave-induced velocity shear in layered flow. Such a marginal stability of internal waves could explain the formation mechanism of billow trains leading to the mixing in abyssal near-bottom flows.

This work was supported by the grant of the Russian Science Foundation (Project No 21-71-20039).

References

[1] Makarenko N.I., Maltseva J.L., Morozov E.G., Tarakanov R.Yu., Ivanova K.A. Internal waves in marginally stable abyssal stratified flow, Nonlin. Proc. Geophys. 2018, 25, 659-669

[2] Makarenko N.I., Maltseva J.L., Morozov E.G., Tarakanov R.Yu., Ivanova K.A.  Steady internal waves in deep stratified flow, J. Appl. Mech. Tech. Phys. 2019, 60(2), 248-256
Intraseasonal Variability in Barrier Layer Thickness in the Bay of Bengal and its Causes
Authors: Li YiXuan , Wang Xidong
Published: March 2022

Based on SODA reanalysis data set from 1980 to 2016, this paper combined with a variety of mathematical statistical methods to study the intraseasonal variability characteristics of barrier layer thickness and its physical correlation with climate modes in the Bay of Bengal, and quantitatively explored the dynamic mechanism of intraseasonal variability of barrier layer in different sea areas in the Bay of Bengal by means of Marine dynamic diagnosis method. The relative contributions of different physical processes, such as oceanic advection, Kelvin waves, Rossby waves and freshwater fluxes (rainfall and river runoff), to the barrier layer were evaluated. The physical relationship between the seasonal variation of barrier layer thickness and the Indian Ocean dipole (IOD) is also discussed. The results show that the thickness of the barrier layer varies most obviously in the northern coast of the bay of Bengal and the western coast of Sumatra, and the maximum value of the barrier layer occurs in November ~ December every year, while the variation of the barrier layer in the northern coast is more regular than that in the southern coast. Horizontal advance and entrainment affect the thickness of barrier layer by affecting the salinity of the mixed layer. However, the thickness of barrier layer is mainly caused by the change of isothermal layer due to the obvious stratification of sea surface salinity in the Bay of Bengal. In the southern part of the Bay of Bengal near the equator, during the positive IOD events, the isothermal layer shallowness was caused by the negative anomaly of equatorial zonal wind stress from October to December. In negative IOD events, the equatorial zonal wind stress appears positive abnormality after June, which leads to the increase of isothermal layer in this period. As a result, the thickness of barrier layer In positive IOD years is smaller than that in normal years from October to December, and that in negative IOD years is greater than that in normal years from June to September. However, in the northern Bay of Bengal, the seasonal variability of barrier layer caused by different IOD events was not obvious. At the same time, the net heat flux upward at the air-sea interface will lead to instability and deepen the local mixed layer.
Radiocarbon and stable C isotope variability of two Holocene stalagmites from the high-alpine Spannagel Cave
Authors: Welte Caroline , Fohlmeister Jens , Wertnik Melina , Eglinton Timothy Ian , Spötl Christoph
Published: March 2022

Stable carbon (C) isotope records from stalagmites are readily available as they are often measured alongside stable oxygen isotopes (δ18O). Their interpretation, however, remains challenging due to several processes contributing to changes in the C-isotope ratio (e.g., fractionation, mixing). Spatially resolved radiocarbon (14C) data can help to interpret 13C signatures [1] but are rarely available due to expensive and time-consuming analysis. Rapid and continuous analysis of 14C concentration in carbonate samples at spatial resolution down to 100 μm has been recently made possible with the new LAAMS (laser ablation accelerator mass spectrometry) technique [2].

This novel technique has previously been applied to a Holocene stalagmite (SPA 127) from the high-alpine Spannagel Cave, Austria. Combined δ13C and 14C profiles (expressed as dead carbon fraction, dcf) allowed to hypothesize on the interplay of regional climate and contribution of an old organic C reservoir to stalagmite growth [3]. Here, we present LA-AMS results from a second Holocene stalagmite from Spannagel Cave (SPA 128). This stalagmite grew at a location close to that of SPA 127 with overlapping growth periods and consistent δ18O signals [4]. Both stalagmites show large and fast variations in the dcf and δ13C. SPA 128 has a generally higher dcf (with values above 60%) and a more negative δ13C signal that point towards contribution of an old organic C reservoir to the stalagmite C.

 

 

[1]D. Rudzka et al., (2011), GCA 75, 4321-4339.

[2] C. Welte, et al., (2016), Anal. Chem. 88, 8570– 8576.

[3] C. Welte et al., (2021), Clim. Past 17, 2165–2177.

[4] J. Fohlmeister et al., (2013), The Holocene 23, 749-754.

 

 
Characterization of a fractured rock mass using Geological Strength Index (GSI): A Discrete Fracture Network (DFN) and Machine learning (ML) approach
Authors: Singh Jaspreet , Pradhan Sarada Prasad , Singh Mahendra
Published: March 2022

The rock mass is strongly influenced by the presence of discontinuities and their role is also strongly regarded in rock mass characterization. Different traditional methods were developed for accessing the rock mass condition for safely designing engineering projects such as slopes, tunnels, foundations, etc. The progress in computational techniques has led to a significant understanding of rock mass related problems. Among them, the discrete fracture network (DFN) technique based on statistical distribution gains significant importance in examining the rock mass. The applicability of remote sensing techniques such as photogrammetry has made it easy to collect the essential data, which otherwise was difficult to acquire using scanline survey or window mapping. The study aims application of DFN in estimating block volume distribution and Rock Quality Designation (RQD) for finding the Geological strength index (GSI) of the rock mass. The results also compare the aggregate and disaggregate DFN with GSI estimated using traditional methods in the field. Along with the estimation of GSI using the existing chart method, the work also proposed the applicability of machine learning (ML) in predicting the GSI value. It is easy and handy to use a chart but becomes time-consuming when dealing with a larger dataset. We have developed a ML inbuilt python-based GUI tool to estimate the GSI value from block volume and joint condition parameters quickly.
Insights from 3D Firn Microstructure into Near-Surface Snow Melt Conditions
Authors: Moser Dorothea Elisabeth , Freitag Johannes , Thomas Elizabeth R.
Published: March 2022

Coastal low-elevation ice caps of the (Ant-)Arctic and mountain glaciers are at the forefront of climate change. Retrieving ice core records from these regions is crucial to assess current, and predict future, environmental changes.  However, climate reconstruction from melt-affected ice cores is challenging. It requires a comprehensive understanding of the site-specific, near-surface melt conditions, which are fundamental to consequent melt-induced alteration of climate proxies.

Here, we use core-scale microfocus X-ray computer tomography to investigate melt layer microstructure in firn core sections from three (sub-)Antarctic sites (Young Island, Smyley Island, and Sherman Island) at 120-µm resolution. We present density, pore and grain cluster size of 3D melt features and discuss how the secondary imprint of the melt-refreeze process is visible in firn microstructure. We further show that the appearance of melt features varies both within profiles and from site to site. Given that local climate drives the near-surface snow properties and melt conditions, we suggest that melt layer microstructure could be further developed as a useful climate proxy itself.
Rhine flood stories: Spatio-temporal analysis of historic and projected flood formation in the Rhine River basin
Authors: Rottler Erwin , Bronstert Axel , Bürger Gerd , Rakovec Oldrich
Published: March 2022

The genesis of riverine floods in large river basins often is complex. Streamflow originating from precipitation and snowmelt and different tributaries can superimpose and cause high water levels threatening cities and communities along the river banks. In this study, we develop an analytical framework that captures and shares the story behind major historic and projected streamflow peaks in the large and complex basin of the Rhine River. Our analysis is based on hydrological simulations with the mesoscale Hydrolgical Model (mHM) forced with an ensemble of climate projections. The spatio-temporal analysis of the flood formation includes the assessment and mapping of antecedent liquid precipitation, snow cover changes, generated and routed runoff, flood extent and the excess runoff from major sub-basins up to ten days before a streamflow peak. An interactive web-based viewer provides easy access to result figures of major historic and projected streamflow peaks at four locations along the Rhine River. Our results indicate that each streamflow peak is driven by a specific sequence of precipitation and snowmelt from different areas in the Rhine River basin. Furthermore, we map how rising temperatures increase liquid precipitation in the Alps, in turn, increasing streamflow peaks along the Rhine River. The highest streamflow peak simulated at Cologne using climate projections exceeds the historic record by almost 50 % and was driven by excessive rainfall over several days over large parts of the Rhine River basin. Such an event taking place today would have catastrophic consequences. Further research is required to assess the impacts of changes in the persistence of circulation patterns on flood extent and hazard.
Arctic Coastal Bluff Erosion on Disko Island, Greenland
Authors: Luetzenburg Gregor , Townsend Dominique , Svennevig Kristian , Bendixen Mette , Bjørk Anders A. , Eidam Emily F. , Kroon Aart
Published: March 2022

The coasts of Greenland mostly consist of hard rock with relatively small rates of erosion. However, isostatic uplift following the retreat of Holocene ice sheets is creating soft sediment bluffs consisting of deltas or beach ridges. Hitherto, very little has been known about the rates and processes of soft sediment bluff erosion along the coast of Greenland. Here, we investigate a bluff section at the south coast of Disko Island in western Greenland. The height of the bluff ranges from one to 30 m along a three km long section of the coast. The bluff consists of a heterogeneous matrix of hard rock outcrops with pockets of coarse clastic sediments in between, overlain by parallel beach ridges with discontinuous permafrost. Sea ice along the coast limits wave activity between December and May.

A series of oblique aerial images from July 2019 and July 2021 was obtained to create Structure from Motion Multi-View Stereo (SfM MVS) point clouds. Changes were detected by multi-scale model-to-model cloud comparison (M3C2). Climate data from the nearby town of Qeqertarsuaq were used to identify precipitation events to estimate erosion events at the bluff. This data were utilized in conjunction with satellite derived bathymetry and wave data to estimate wave run-up and erosion at the coastline for a series of hydrodynamic conditions.

We find the absence of soil on top of the uplifted beach ridges strongly influences runoff patterns. Without the water retention capability of the soil, water directly infiltrates into the soft sediments, or runs off the surface of the hard rock areas. This leads to an accumulation of water in the soft sediment pockets and gullies, making them especially vulnerable to erosion. The sedimentary bluff is eroding by two coupled processes: (i) Precipitation-driven surface runoff downslope the bluff face and (ii) wave-driven erosion at the bluff base of sediment that is delivered by the surface runoff. Typical erosion rates are up to half a meter per year. Longer ice-free periods with extended wave action should further increase coastal bluff erosion rates in Greenland in the future.
Development of a new forest snow mapping algorithm using MODIS data, machine learning and time-lapse photography
Authors: Dong Chunyu , Luo Jianfeng
Published: March 2022

Remotely sensed MODIS (Moderate Resolution Imaging Spectroradiometer) data and the NDSI (Normalized Difference Snow Index) based approach have been applied globally for snow cover mapping. However, this method displays severe omission errors in forested areas, due to the forest canopy shading of snow. In this study, we developed a new forest snow mapping algorithm based on MODIS reflectance data, time-lapse observations of forest snow, and a random forest model. We built a time-lapse camera network in the eastern Qilian Mountains in northwestern China to monitor the forest snow processes and obtain the ground truth data. The random forest (RF) model seems to be powerful in capturing the relationships between the MODIS surface reflectance bands and the forest snow presence. The presented approach significantly improved the accuracy of binary snow cover (BSC) mapping in forests. We evaluated the performance of the proposed algorithm with the traditional NDSI-based method. The results show that the new algorithm has a superior performance in forest BSC mapping, compared to the NDSI-based BSC. The proposed RF-BSC can retrieve ~70% of all real forest snow pixels, while the NDSI-BSC can only detect 8-14%. We further investigated the geographical influence (e.g. topography, forest coverage, and solar illumination) of the algorithm performance. This study suggests that the fusion of optical remote sensing data and ground-based observations using machine learning techniques has a great potential in improving the accuracy of land cover mapping.
How to creep and when? Deformation mechanisms at the eclogite type locality (Saualpe-Koralpe Complex, Eastern Alps, Austria).
Authors: Rogowitz Anna , Huet Benjamin , Schorn Simon
Published: March 2022

The presence of large volumes of eclogite in collision and subduction zones makes their formation and deformation highly relevant for the dynamics of convergent zones. There is however no consensus on the deformation behavior of eclogite. On the one hand, mylonitic eclogite shear zones showing evidence of dominant deformation by dislocation creep have frequently been reported. On the other hand, fluid supported formation and deformation has been recently suggested as a potential mechanism in eclogite whereby the main accommodating mechanism is dissolution-precipitation creep. This raises the question of the factors controlling the deformation behavior of eclogite.

In this contribution, we present microstructural, petrographical and chemical data from a series of eclogite samples derived from low Mg – high Ti gabbro collected at the eclogite type locality (Saualpe-Koralpe Complex, Eastern Alps, Austria). The rocks are characterized by a pronounced foliation defined by the shape preferred orientation of the major minerals (omphacite, amphibole, epidote and garnet). Minor quartz is observed at dilation sites. Overall, grains show rather straight grain boundaries and a uniform extinction. These features are interpreted as evidence of diffusion and dissolution-precipitation dominated formation and strain accommodation. Thermodynamic forward modelling indicates that eclogitization occurred at around 2 GPa and 640–680°C and was supported by fluid. Locally, the eclogite fabric is crosscut by veins showing a similar paragenesis as the host eclogite. However, they are enriched in quartz and epidote, depleted in garnet and show overall a coarser grain size. Depending on their initial orientation, the veins were either reactivated as flanking structures or foliation sub-parallel shear zones. The reactivated veins are characterized by undulatory extinction, twinning and subgrain formation, all being indicative of dislocation creep. The identical paragenesis and similar mineral chemistry indicates that reactivation occurred at conditions close to those of eclogitization. The investigated samples therefore testify that eclogite can deform by two different mechanisms at similar pressure-temperature conditions. Our investigations document that dissolution-reprecipitation is bound to the process of eclogitization and low strain rate whereas post-eclogitization strain localization is accommodated by dislocation creep.
Public perception assessment on climate change and natural disaster influence using social media big-data: A case study of USA
Authors: Heo SungKu , Ifaei Pouya , Moosazadeh Mohammad , Yoo ChangKyoo
Published: March 2022

Climate change is a global crisis to the world which influences the human race and society's development. Threatens of climate change have become increasingly recognized to the public and government in both environments, society, and economy across the globe; because the consequence of climate change is not only shown up as the increasing of global temperature, also expressed in an intensive natural hazard, such as floods, droughts, wildfires, and hurricanes. For the sustainability development in the globe, it is crucial to provide a response to mitigating climate change through the government’s policy and decision-making; however, the public's engagement in the actions towards the critical environmental crisis still needs to be largely promoted. Analyzing the relationship between the public awareness of climate change and natural disasters is an essential aspect in climate change mitigation and policymaking. In this study, based on the abundance of the text message in social media, especially Twitter, the public understanding and discussions upon climate change from the surrounding environment was recognized and analyzed through the human as the sensor which receiving information of climate change. Twitter content analysis and filed data impact analysis were conducted; text mining algorithms are implemented in the Twitter big-data information to find the similarity based on a cosine similarity score (CSS) between the climate change corpus and the natural events corpora. Then, the factors of nature disaster influence were predicted utilizing a multiple linear regression model and climate change tweets dataset. This research shows that the public is more pretend to link the natural events with climate change when they tweeting when serious natural disasters happened. The developed regression model indicated that natural events caused by the consequence of climate change influenced the people’s social media activity through messages on Twitter with having the awareness of climate change. From this study, the results indicated that the public experience of natural events including intensive disasters can lead them to link the climate change with the natural events easily; when compared with the people who rarely experience natural events.

Acknowledgment

This research was supported by the project (NRF-2021R1A2C2007838) through the National Research Foundation of Korea (NRF) and the Korea Ministry of Environment (MOE) as Graduate school specialized in Climate Change.
Rapid fluid infiltration recorded in the brucite-rich reaction zone along the antigorite veins from the Oman ophiolite
Authors: Yoshida Kazuki , Okamoto Atsushi , Oyanagi Ryosuke , Kimura Masao
Published: March 2022

Fluid flow in subduction zones is related to geological processes such as seismic and volcanic activities. However, the timescale of fluid flow and its flux in the supra-subduction setting is unclear. In this study, we report the novel texture of the antigorite veins with a brucite-rich reaction zone in dunite in the crust-mantle transition zone of the Oman ophiolite, and investigated the timescale and time-integrated fluid flux during the vein formation.

The antigorite veins occur in the drilling cores of serpentinized dunite in the crust-mantle transition zone taken from the Oman Drilling Project CM1 site (Wadi Zeeb, Northern Sharqiyah). The dunite samples are completely serpentinized and consist mainly of lizardite, brucite, magnetite, and Cr-rich spinel and are cut by the antigorite vein networks and later chrysotile. These features indicate that the antigorite veins formed at the stage of obduction of the Oman ophiolite. The antigorite veins, which are distinct by ‘bright’ networks by X-ray CT due to magnetite, occur preferentially in dunite (at 160 – 313 m along the CM1A). The veins are filled with a mixture of randomly orientated antigorite crystals and fine chrysotile. Some antigorite vein contains fragments of the host rock. The brucite-rich reaction zone was developed at both sides of the antigorite veins with a thickness of 0.5 – 4 mm. The reaction zone is composed of brucite (39.4 area%), chrysotile (59.3 area%), and magnetite (1.3 area%). The microtexture of the reaction zone indicates the brucite silicification after the brucite reaction zone formation. Mass balance and thermodynamic calculation suggest that silica was leached from the host rock lizardite during antigorite vein crystallization, resulting in the formation of the brucite reaction zone. Given solution chemistry and the amount of leached SiO2 during vein formation, the time-integrated fluid flux was estimated to be 105 - 106 m3(fluid) m-2(rock). A diffusion-controlled model suggests that the reaction zone was formed in a short time, ~10-1 - 100 years. These results suggest that a large amount of high-temperature fluid passed through the fracture network over several hundred meters in a short time at the earlier stage of the obduction of the Oman ophiolite.
Proper grazing is nature-based solutions to restore soil nematodes and ecosystem multifunctionality in degraded grasslands
Authors: Yang Jingjing , Wu Donghui , Wang Deli
Published: March 2022

    Grassland ecosystems worldwide are facing habitat degraded due to human activities. Although it is commonly proposed that livestock can have negative repercussions for multiple ecosystem functions in degraded grasslands, this question has yet to receive explicit scientific attention. We used a 3-year field-manipulated grazing experiment, including livestock grazing by sheep across three grasslands with different levels of degradation to evaluate the role of large herbivore in regulating soil nematodes and ecosystem multifunctionality. Our findings reveal the context dependency of this role in grassland degradation. We show that livestock show higher levels of soil nematode biomass and ecosystem multifunctionality than lightly degraded grassland with enclosure, and facilitate soil nematode diversity and maintain ecosystem multifunctionality in moderately and severely degraded grasslands. We propose that moderate herbivore grazing should be considered as nature-based solutions to improve and maintain both soil nematodes and ecosystem multifunctionality in degraded grasslands. The information is fundamental for improving nature’s benefits to people and considering conservation efforts of grassland restoration.
Variations of estuarine metabolic alkalinity loads: Consequences for the biogeochemistry of a shelf sea (North Sea)
Authors: Paetsch Johannes , Thomas Helmuth , Norbisrath Nora
Published: March 2022

Recent studies have shown that anaerobic remineralisation in estuaries of the North Sea, a semi-enclosed shelf sea of the Northeast Atlantic, generates a large amount of alkalinity which is subsequently flushed into the North Sea basin. The anaerobic processes within the estuaries fed by high anthropogenic nitrate loads peaked in the 1980s. Under pristine conditions, these nutrient loads are lowered by about 90 %.

On the other hand, the goals of the 2015 Paris agreement can only be achieved with zero or even negative CO2 emissions. Such scenarios often include the use of terrestrial bioenergy requiring an increasing usage of fertilizers. Simply by leakage, such applications induce additional nutrient (and thus alkalinity) loads into the adjacent seas.

Using a 3-D biogeochemical model for the Northwest European shelf, we investigated the North Sea – wide consequences of the different scenarios described above. Assuming only aerobic regeneration within the estuaries of the North Sea, the annual uptake of atmospheric CO2 is reduced by about one third within a coastal band of 100 km width. More drastic changes of alkalinity discharge into the North Sea, described above, also impact areas of the central North Sea and are able to alter the annual CO2 uptake in the order of the magnitude of the air-to-sea flux itself.