bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimal detention ponds in urban drainage systems
Authors: Hosseinzadeh Azadeh , Torabi Haghighi Ali , Rossi Pekka M. , Behzadian Kourosh , Karami Mozhgan
Published: March 2022

Urban development and the increase of impervious surfaces have a broad impact on the hydrological cycle leading to increased peak flow and flooding, especially in downstream areas. Surface water detention ponds are among the most common measures to attenuate the peak flow and return it from development to pre-development conditions. The effect of these ponds on reducing a flood depends on the location and the dimensions. This paper presents a new framework for identifying the best strategies for using the detention ponds to flood control in urban drainage systems. The stormwater management model (SWMM) was applied for hydraulic and hydrological simulations of urban drainage systems. In addition, a multi-objective optimisation model was used to find the optimal location and size of detention ponds. The effect of physiographic and social factors on selecting ponds was analysed by simulating and examining the GIS environment. Based on the criteria reviewed in the previous steps, the best management solutions were prioritised by a multi-criteria decision-making method (MCDM) named Compromise Programming (CP). The methodology was then demonstrated on the real-world case study of the Karaj city basin in Iran. The results show that these detention ponds can improve current drainage performance and decrease flooding damage.
Characteristics analysis and correction of GPS precise products in analysis centers based on Lomb-Scargle periodogram
Authors: Hou Yangfei , Chen Junping , Zhang Yize
Published: March 2022

Considering that the precise orbit and clock products provided by international GNSS service (IGS) were of a magnitude different from those required by the global geodetic observing system (GGOS) in accuracy of 1 mm, the Lomb-Scargle periodogram was used to analyze the systematic deviation and the periodical deviation between the precise products of GNSS analysis centers (ACs) and the IGS final precision products. On this basis, a deviation correction model was established based on the least square method for the correction of precision parameters. The deviation correction results show that the standard deviation of the precise clock decreases by 15.4% on average, the standard deviation of the radial orbit decreases by 33.3% on average, and the standard deviation of the ensemble effects of radial orbit and clock decreases by 24.0% on average. The signal-in-space user ranging error (SISURE) also significantly decreases from the level of centimeters to millimeters. The positioning verification results of the 15 stations show that the consistency between the positioning results of the precision products using single AC and the positioning results of IGS final precision products is also improved after deviation correction, and the average improvement ratio of three ACs is 14.3%. It is proved that the deviation correction model can effectively improve the consistency between the precision products of ACs and the final products of IGS.
Modelling the sensitivity of changes in sediment flux and grainsize distributions on flooding in the Kathmandu basin, Nepal
Authors: Thapa Saraswati , Sinclair Hugh D. , Creed Maggie , Mudd Simon M. , Attal Mikael , Muthusamy Manoranjan , Sharma Bholanath
Published: March 2022

Abstract: Climate change and land-use change impact the sediment flux and grainsize delivered to rivers which influences channel morphologies and hence modifies flood risk; this is particularly the case where channels are fed by high mountain catchments. Here, We studied the Nakkhu River which is the largest southern tributary of the Kathmandu basin, Nepal. The mobility of the channel is well documented in response to bank erosion, down-cutting, and accumulation of bar forms; these processes are particularly important during extreme flood events. Comparing satellite images from 2003 to 2020, the river course, which has a medium channel width of 15 m, has migrated laterally up to 130m. Bank erosion and down-cutting reduce the inundation and water storage upstream, whereas aggradation of river bar forms downstream reduces the channel’s conveyance capacity. These vertical and lateral geomorphological alterations result in significant impact on flood risk downstream.

In this research, we investigate how changes in sediment supply, and grain size affect river morphology and flood inundation in the Nakkhu River. We use the landscape evolution model, CAESAR-Lisflood, combined with a newly generated (2019) 10 m digital elevation model, field-derived grainsize data and 20 years (2001 to 2020) of daily discharge data, to simulate erosion and deposition along a 14 km reach of the river. In a set of experiments, we compare river bed cross-sections, flood extent, and water depths for 15 model scenarios where we vary sediment supply and grain size from fine sand to coarse gravel dominated distributions assessing the geomorphic uncertainty of observation of sediment data.

The model results show that channel morphologies are sensitive to changes in sediment grainsize distribution. The study suggests that lack of consideration of sediment impact in flood hazard mapping could lead to increased flood risk. In addition, this study highlights some of the challenges regarding the significance of grain size parameter and uncertainty to the landscape evolution model that need to be addressed in current research.

Keywords: River morphology, sediment flux, grainsize, flood modelling, Nepal
Variation in soil microbial communities following vegetation restoration in a Rare Earth Elements Mine area
Authors: Kong Zhaoyu
Published: March 2022

Rare earth elements (REEs) exploitation has led to severe soil degradation in Southern China. Revegetation is a promising way to minimize the negative environmental impact of abandoned REEs mine tailings. However, little is known about how soil microbial communities respond to the vegetation restoration in degraded REEs mine lands, although much research has emphasized their important roles in ecological restoration. Here, we evaluated soil nutrients, microbial community structure and enzyme activities in both surface and deep soils where vegetation restoration was implemented using arbor-shrub-grass pattern for 9 years. Our results showed that vegetation restoration have significantly altered the diversity, structure and co-occurrence patterns of microbial community, especially in surface soil. The bacterial phyla Proteobacteria, Actinobacteria, and Acidobacteria were more abundant at the restored site than at the unrestored site. Potential plant growth promoting bacteria (PGPB) were identified by comparing 16S sequences against a self-constructed PGPB database via BLAST, and it was found that the abundance of nutrient (e.g. P, N and Fe) accumulating-bacteria was greater, but the abundance of ACC deaminase-producing bacteria was lower at the restored site than at the unrestored site. This provides evidence for the potential role of plant beneficial bacteria in improving the performance of vegetation restoration in degraded mine lands.
Subauroral polarization streams (SAPS): Intrinsic response of geospace during storm time
Authors: Lin Dong , Wang Wenbin , Merkin Viacheslav , Wiltberger Michael , Sorathia Kareem , Pham Kevin , Bao Shanshan , Michael Adam , Shi Xueling , Huang Chaosong , Wu Qian , Zhang Yongliang , Oppenheim Meers , Toffoletto Frank , Lyon John , Garretson Jeffrey , Anderson Brian
Published: March 2022

Subauroral polarization streams (SAPS) typically refer to an enhanced westward plasma flow channel in the duskside subauroral ionosphere. SAPS overlap with the low-latitude part of downward Region-2 field-aligned currents (FACs). The relatively low subauroral conductance in this region requires a strong electric field for current closure, which drives the fast sunward plasma flow. Observations have shown dynamic variability of SAPS under various solar wind and interplanetary magnetic field (IMF) conditions, which are related to the variability of FACs and auroral precipitation, as well as their source regions in the ring current and plasmasheet. In this study, we use satellite observations and numerical simulations with the state-of-the-art Multiscale Atmosphere Geospace Environment (MAGE) model to investigate: 1) The role of diffuse electron precipitation in the formation of SAPS; 2) SAPS variability under IMF BY; and 3) Dawnside (as opposed to the more conventional duskside) SAPS as a unique feature of major geomagnetic storms. With data-model comparison, we will demonstrate that SAPS result from the different behaviors of ring current ions and plasma sheet electrons, and the corresponding self-consistent response of the ionosphere-thermosphere system via electrodynamic and particle coupling with the magnetosphere. We conclude that SAPS distribution and variability represent a fundamental feature of the geospace response to solar disturbances during storm time.
Effect of plant development and N uptake on denitrification in two contrasting crop species
Authors: Rummel Pauline Sophie , Matson Amanda , Eckei Jonas , Well Reinhard , Dittert Klaus
Published: March 2022

Denitrification is the main source of the greenhouse gas N2O emitted from agricultural soils. While N2O emissions and influencing factors have been very well studied in field experiments, there are hardly any reliable data for N2 emissions on the field scale. However, these are essential to understand under which conditions complete denitrification occurs leading to N2 formation and when N2O is the main end product. Whether NO3- is reduced to N2O or N2 depends on several factors: the availability of NO3- and available organic C, as well as pH, oxygen availability, soil moisture, denitrifier community structure, and temperature. All of these parameters are highly dependent on crop development, as growing plants take up NO3- and water while increasing organic C availability via root exudates and dying roots, and alter soil pH as well as microbial communities by rhizosphere dynamics.

The objective of this field trial was to collect reliable measurement data on N2 and N2O emissions in typical German crops. Two crops were chosen that differ greatly in their temporal development: Winter wheat (Triticum aestivum L.) and sugar beet (Beta vulgaris subsp. vulgaris). Both crops were grown site-typically according to the rules of good agricultural practice. To measure N2O and N2 emissions, the improved 15N gas flux method including high enrichment 15N-labeled fertilizer was applied. Prior to gas sampling, chambers were purged with a mixture of helium and oxygen (80:20) to reduce the atmospheric N2 background to < 2%. Soil samples were taken at regular intervals and analyzed for mineral N (NO3- and NH4+) and water-soluble Corg content. In addition, we monitored crop development, plant N uptake, N transformation processes in soil, and N translocation to deeper soil layers.
ENSO Impact on Summer and Fall Temperatures in Western Europe
Authors: Martija-Diez Maialen , Rodríguez-Fonseca Belén , López-Parages Jorge
Published: March 2022

El Niño-Southern Oscillation (ENSO) is the main predictor of global climate variability at interannual time scales. Its impact on European precipitation variability has been deeply studied, but not so much its impact on temperature. Recent studies suggest that the increasing intensity in heatwaves seems to be related to the interannual variability of the mean temperature. Therefore, the predictability of temperature could be very useful for the future adaptation to potentially severe heatwaves. In this study, we investigate the impact of ENSO on maximum and minimum temperature throughout the whole seasonal cycle with the aim of finding some predictability and trends. Due to the observed changing teleconnection between ENSO and remote regions, we consider the possible nonlinear and nonstationary relationship as well. For our study, we choose a region in western Europe that has experienced intense heatwaves, and which is also the main region of air temperature interannual variability in Europe. We found a nonseasonal, nonlinear and nonstationary impact. During decades prior to 1980s, warmer conditions are related to La Niña events in summer. Nevertheless, El Niño events seem to be linked to the increase in fall temperatures during decades after the 1980s. These warmer conditions are found to be correlated as well with ENSO characteristics from previous seasons, which suggest a potential source for improving the seasonal forecast. We analyze the underlying dynamical mechanisms of the detected teleconnection, and we found a circumglobal response for summer and an arching-like pattern in fall. Finally, we investigate the possible reasons explaining this variable impact among seasons and decades.
A review of conceptual model uncertainty in groundwater research
Authors: Batelaan Okke , Enemark Trine , Peeters Luk , Mallants Dirk
Published: March 2022

For more than a century, the strong advice in geology has been to rely on multiple working hypotheses. However, in groundwater research, as supported by modelling, often a stepwise approach with respect to complexity is promoted and preferred by many. Defining a hypothesis, let alone multiple hypotheses, and testing these via groundwater models is rarely applied. The so-called ‘conceptual model’ is generally considered the starting point of our beloved modelling method. A conceptual model summarises our current knowledge about a groundwater system, describing the hydrogeology and the dominating processes. Conceptual model development should involve formulating hypotheses and leading to choices in the modelling that steer the model predictions. As many conceptual models can explain the available data, multiple hypotheses allow assessing the conceptual or structural uncertainty.

This presentation aims to review some of the key ideas of 125 years of research on (not) handling conceptual hydrogeological uncertainty, identify current approaches, unify scattered insights, and develop a systematic methodology of hydrogeological conceptual model development and testing. We advocate for a systematic model development approach based on mutually exclusive, collectively exhaustive range of hypotheses, although this is not fully achievable. We provide examples of this approach and the consequential model testing. It is argued that following this scientific recipe of refuting alternative models; we will increase the learnings of our research, reduce the risk of conceptual surprises and improve the robustness of the groundwater assessments. We conclude that acknowledging and explicitly accounting for conceptual uncertainty goes a long way in producing more reproducible groundwater research. Hypothesis testing is essential to increase system understanding by analyzing and refuting alternative conceptual models. It also provides more confidence in groundwater model predictions leading to improved groundwater management, which is more important than ever.
The synergistic effects of the Air Clean Plan and carbon mitigation on air quality and public health in China from 2014 to 2060
Authors: Wang Zhige , Hu Bifeng , Zhao Ruiying , Wang Yanyu , Shi Zhou
Published: March 2022

Ambient fine particulate matter (PM2.5) induces serious environmental health risks worldwide, particularly in developing countries like Mexico, India and China. Despite the fact that China has achieved tremendous progress by implementing tough air pollution control measures since 2013, there is still a clear gap between the World Health Organization (WHO) guidelines. In order to meet the goals of PM2.5 control and ensure the public health in the context of global climate change, it is critical to well understand the effects of current policy and carbon mitigation on reducing PM2.5 concentrations and attributable health risk. To fill this gap, in this study we integrate remote sensing data, the logarithmic mean Divisia index (LMDI) method, disease-specific concentration-response functions (CRFs) and scenarios setting to comprehensively estimating the PM2.5 and related-death change during Air Clean Plan (ACP, 2014 to 2020), air clean policy effectiveness, carbon-related co-benefits and future related death across mainland China. During ACP (2014-2020), PM2.5 concentrations and attributable death in mainland China reduced by 13.41 μg m-3 and 0.16 million (~11.85%), respectively, indicating the substantial effectiveness and health benefits of ACP. Clean production made the highest contribution among the ACP measures. Since the signing of the Nationally Determined Contribution (NDC) in 2016, the synergistic effects of carbon emission reduction have been emerging as one of the key factors to address the air pollution and its related disease burden in China. Nevertheless, the PM2.5-related disease burden are still severe in 2020, with ~1.19 million premature deaths in mainland China, accounting for ~17.84% of the global air pollution-related death. Under the China carbon neutrality pathway, 0.18 million (~15.13 %) and 0.35 million (~29.41%) premature deaths can be averted by 2030 and 2060, respectively. In addition, holding the air pollution control measures and health care level constant, the maximum low-carbon measures (i.e., 1.5℃ target scenarios) will bring higher health benefits in 2060. However, the population aging accompanies socio-economic development is still the major threat to the public health in long term. Our results could provide important implication for future development pathway setting to achieve the WHO AQG target, the United Nation’s Sustainable Development Goal (SDG) Target and NDC goal in China under the dual pressure from air clean and carbon emission mitigation.
Rapid formation of a bedrock canyon following gravel mining in the Marecchia River, Northern Apennines. 
Authors: Llena Manel , Simonelli Tommaso , Brardinoni Francesco
Published: March 2022

River canyons are characteristic features of transient fluvial systems responding to perturbations in base level and/or sediment supply. Investigating the dynamics of canyon formation and development is challenging due to the typically long time scales and the possible experimental confounding involved. In this context, the lower portion of the Marecchia River, with a history of gravel mining on alluvial deposits resting on highly erodible (i.e., claystones and poorly consolidated sands) bedrock, offers the opportunity to set up a natural experiment and investigate the onset of canyon incision and its subsequent stages of development across five decades (1955-1993). To these ends, we evaluate decadal geomorphic changes of 10-km valley segment of the Marecchia River between Ponte Verucchio and Rimini (Northern Italy) through analysis of Digital Elevation Models derived from the application of Structure from Motion to archival aerial imagery (i.e., 1955, 1969, 1976, 1985, 1993) and from a reference-LiDAR survey (i.e. 2009), in conjunction with analysis of planimetric changes in active channel width and lateral confinement.

During the 1955-2009 period, fluvial incision led to the formation of a 6-km canyon, with average vertical incision of about 15 m (in places exceeding 25 m) and a corresponding annual knickpoint migration rate of about 100 m/yr. In volumetric terms, canyon formation and evolution has involved 6.1 106 m3 (95%) of degradation and 0.29 106 m3 of aggradation (5%), with a corresponding net volume loss of 5.8 106 m3. As a result of canyon development, the active channel has narrowed by about 80%, and channel pattern has drastically changed from braided unconfined to single-thread tightly confined one. These processes were especially important during the 1955-1993 period. Since 1993 to the present, main channel is characterized by a general stability of the active channel width with evidences of a slight recovery through mass wasting processes within it. Local disturbance associated with ongoing canyon development have propagated and are still propagating upstream, posing immediate threat to infrastructures.
Response of the upper ocean circulation to tropical Atlantic interannual modes
Authors: Martín-Rey Marta , Vallès-Casanova Ignasi , Pelegri Josep Lluis
Published: March 2022

The scarcity of in-situ measurements and the variability among individual events has limited our understanding of the drivers and impacts of the tropical Atlantic Ocean circulation. Here we investigate the response of the surface and subsurface ocean circulation to the two main modes of tropical Atlantic Variability (TAV): the Meridional Mode (MM) and Equatorial Mode (EM). For this purpose, we use three oceanic reanalyses and an interannual forced-ocean simulation covering the period 1982-2018. The developing phase of the MM is associated with a spring intensification of the North Equatorial Countercurrent (NECC), the Equatorial Undercurrent (EUC) and the north South Equatorial Current (nSEC) in the eastern equatorial margin. It also triggers Rossby waves that reach the western boundary and are reflected as equatorial Kelvin waves that weaken the ocean surface and subsurface transports and cause anomalous warm equatorial conditions in boreal summer. During the developing spring-summer phase of the EM, the westward surface zonal transport is considerably reduced with no clear impact at subsurface levels. During the fall EM decaying phase, the reflected Kelvin wave reverses the zonal pressure-gradients at the equator and the westward equatorial nSEC is reinforced. This is accompanied by a weakening of the EUC that suggests an additional off-equatorial forcing. Our results reveal that the ocean circulation responds to both MM and EM, endorsing the key role played by the propagating zonal waves in connecting the tropical and equatorial ocean transports.
Climate change impacts on water balancing components for a tropical river basin, Western Ghats India.
Authors: Sinha Rakesh Kumar , Sharma Swatantra Kumar , T.I. Eldho
Published: March 2022

Climate change is considered as the important factor for change in water balancing components (WBCs) at the river basin scale. In this study, the Soil and Water Assessment Tool (SWAT) hydrological model is used for the assessment of WBCs for the Kalada river basin (KRB) in the Western Ghats, India. To assess the climate change impacts of near (2021 – 2040), mid (2041 – 2060), and far (2081 – 2100) future for moderate scenarios under representative concentration pathways (RCP) 4.5 and worse scenarios (RCP 8.5) were considered by using the present (2018) fixed land use. The multi-optimization techniques have been used for model calibration and verification of climatic data of the five General Circulation Models in the study area. The results indicated that the actual evapotranspiration (ET), surface runoff, and water yield are decreased (16 to 27%) in all-time slices for both RCP 4.5 and 8.5 emission scenarios but the decreasing trend is non-uniform. This is because of the decline of rainfall by 50 to 230 mm and the increase of temperature by 2 to 5 ℃ in the study area. Furthermore, results indicated that the wet season showed less decrease in comparison to winter and summer, but impacts are high because more than 80% of rain occurred in the monsoon season.

Keywords: Water Balancing Components; Climate change; Surface runoff; GCMs; SWAT model.
Extreme impacts in the European renewable electricity system as a result of climate variability 
Authors: van der Most Lieke , van der Wiel Karin , Bintanja Richard , Benders René , Leenes Winnie
Published: March 2022

With the need for clean energy that reduces greenhouse gas emissions, the coming decades will see a transition of our energy system towards a higher share of renewable energy sources. With this work we aim at gaining insight in meteorological conditions that lead to extremely low energy generation and extremely high residual load (difference between production and demand) in European countries. We constructed a simplified climate-energy modeling framework in which extreme impact events on the European energy system can be examined. We compute daily electricity demand and the supply from hydropower, wind and photovoltaic solar, based on 2000 years of simulated present and future weather conditions for countries in Europe. From this data the meteorological drivers with high impact on the current energy system were investigated for individual countries and larger regions. Atmospheric blocking in summer can result in heatwaves and droughts that in turn result in long-lasting periods of high energy demands in countries with large cooling capacities (southern Europe) and low energy production in countries that rely on hydropower. In winter, dry and cold periods with lower than normal windspeeds lead to high residual load in northern European countries, especially around the North Sea. These countries have a high share of offshore wind and high installed heating capacities. Dry seasons lead to a higher sensitivity to wind and solar variability due to a decrease in balancing potential of hydropower. Additionally, the co-variability of electricity shortage events between countries is investigated. The goal is to identify balancing potential of transmission between countries. Due to different demand profiles across Europe and the spatial variability of weather the potential of extreme event reduction through cross-border transmission is high.
Rapidly evolving anthropogenic aerosol emissions induce strong and regionally heterogeneous climate impacts on the way to a net-zero world
Authors: Samset Bjorn H. , Persad Geeta , Wilcox Laura
Published: March 2022

Anthropogenic aerosol emissions are expected to change rapidly over the coming decades, driven by a combination of climate mitigation and air quality efforts, as well as continued industrialization. While this fact is well appreciated at the global level, the complex and diverse regional responses to changes in atmospheric aerosol loadings are still largely neglected in the tools and metrics currently used in policy-facing evaluations of near-term climate risks - including the IPCC 6th Assessment Report. 

There is now comprehensive evidence that regional changes in aerosol emissions can drive significant trends in temperature and hydroclimate, at the local to the global scale. Locally, they can dominate over trends induced by global surface warming. Notably, this is true at lower latitudes, meaning that currently under-resourced and highly populated regions are disproportionately exposed to aerosol induced climate hazards and societal impacts. Neglecting or oversimplifying regional aerosol effects, whether near to the emission sources or remotely, in near-term climate risk assessments therefore constitutes a blindspot in society’s ability to adapt to and prepare for future climate change. 

In this talk, we summarize the status of research into the regionally heterogeneous effects of aerosol emissions, in light of ongoing and expected near-term emission changes, and how they modulate climate risks along near-zero GHG trajectories. We also outline a potential pathway towards progress – in particular identifying urgently needed interaction between the aerosol research and impact, risk, and scenario development communities.
Cytotoxicity as a proxy for particle-associated and dissolved organic contaminant loads in rivers during floods
Authors: Glaser Clarissa , Engelhardt Michelle , Escher Beate , Gärtner Andrea , Krauss Martin , König Maria , Schlichting Rita , Zarfl Christiane , Spahr Stephanie
Published: March 2022

Storm events lead to a mobilization of dissolved and particle-associated organic pollutants that pose a risk to river ecosystems. Target screening can hardly capture the broad range of compounds present in stormwater and receiving streams. Thus, an additional monitoring proxy that describes the overall chemical load in stormwater is needed. Each chemical in a mixture contributes, albeit with different potency, to cytotoxicity measured by reduction of cell viability after 24h in four human cell lines. Thus, the aim of this study was to investigate the applicability of cytotoxicity as a proxy for the organic contaminant load of rivers during storm events. Field investigations took place in the Ammer River (annual average discharge 0.87 m³ s-1) close to Tübingen, Germany, during intense precipitation events in June 2021. The sampling site was located at the outlet of the gauged catchment (134 km²), thus, integrating inflowing water from all upstream tributaries and sewer overflows. During storm events, high-resolution temporal monitoring of discharge, suspended particles, particle characteristics, as well as dissolved and particle-associated organic contaminants was conducted using both chemical analyses and cell-based in vitro bioassays. The cytotoxicity in the water phase (expressed as toxic units, TU), was similar among the cell lines. The TU flux followed the course of the hydrograph with highest values at the maximum or slightly after the discharge peak. This finding suggests that the chemical load is controlled by the transported volume of water despite the fact that different contaminant sources are likely to contribute to the water flux and pollutant load in the river at different time points of the hydrograph. For the particle-associated cytotoxicity, the TU flux also followed the course of the events suggesting that the particle-associated cytotoxicity in the river is, similar to the water cytotoxicity, controlled by the particle load in the river. This highlights that the cytotoxicity is a suitable proxy to detect mixtures of organic compounds and, thus, assess the chemical load in rivers during storm events.
The ITRS 2020 realization of DGFI-TUM: DTRF2020
Authors: Seitz Manuela , Angermann Detlef , Glomsda Matthias , Bloßfeld Mathis , Rudenko Sergei , Zeitlhöfler Julian
Published: March 2022

As one of the ITRS Combination Centres of the IERS, DGFI-TUM is in charge of computing an ITRS 2020 realisation. Since the ITRS 2014 realisation, many innovations have occurred. These include the six years longer observation period, but also new observation stations and satellites, and the use of refined background models in the analysis of the space-geodetic techniques. In addition, the combination strategy of the DTRF has also been improved. Namely, non-tidal loading (NTL) corrections over the full observation period and for all three components (atmospheric, hydrological and oceanic) are taken into account, as well as modelled post-seismic deformations (PSD). Both corrections are carried out - according to the combination strategy of DGFI-TUM - on the level of the normal equation (NEQ) by reducing each input NEQ.

Due to all the improvements mentioned above, ranging from observation to analysis and combination, it can be assumed that all ITRS 2020 realisations are not only more up-to-date but also more accurate than their predecessors. In the presentation, we demonstrate the DTRF2020 solution as well as first comparisons and analyses. We will also present the DTRF2020 release which will include SINEX files and an EOP file, plus the time series of SLR translations, NTL and PSD corrections, and station position residuals.
Adaptation to the impacts of climate change and human intervention in the Elbe estuary: model-based identification of possible trade-offs 
Authors: Pein Johannes , Schrum Corinna , Staneva Joanna , Daewel Ute
Published: March 2022

The Elbe estuary ensures the connection between one of the largest ports in Europe, Hamburg, and the North Sea. The need to adapt the navigational channel to the increasing demands of ship transport as well as the necessities of coastal protection and of ensuring the functioning of the ecosystem are leading to contradicting demands. In order to decide on possible trade-offs, a detailed understanding of present and possible future interactions between local and global processes is necessary. In this study, we use realistic modeling and observations to show the functioning of the current hydrodynamic and biogeochemical estuarine system. We demonstrate the increasing importance of the formation of stratification in the low-salinity reaches, which is related to an increase in salt intrusion, sedimentation and the risk of hypoxia. The model results reveal that dry and hot summers are leading to dangerous oxygen minima in the artificially deepened tidal Elbe. To examine the effect of a more natural expansion of the navigational channel, we further use an idealized model of the estuary. In this exercise, we study the influence of sinusoidal meanders on the tides, the thermohaline dynamics and the estuarine ecosystem. It turns out that this deregulation of the shipping channel leads to a reduction of the tidal range and of silting in the port area. Furthermore, the channel curvature enhances oxygen levels in the area of the estuariane oxygen minimum zone in comparison with the straight channel. Sensitivity experiments demonstrate the sustainability of such an adaptation strategy towards the dominant trends of climate change such as sea level rise and global warming. Finally we assess the plausibility of the measure in terms of its potential to conciliate contradicting demands in the intensively used estuarine environment.
Seafloor pockmarks offshore Vancouver Island
Authors: Geersen Jacob , Pesenti Elena , Riedel Michael , Schneider von Deimling Jens , Rollwage Luisa , Schulze Noemi , Scherwath Martin
Published: March 2022

Pockmarks are crater-like depressions of erosive nature in marine or lacustrine sediments. They are often interpreted as the surface manifestation of hydrocarbon venting but may also result from freshwater flow in coastal regions, compaction induced sediment dewatering, or bottom scouring around natural or anthropogenic objects. Hence, they can be of relevance for the global carbon cycle, offshore infrastructure, benthic life, and slope stability. New bathymetric data from offshore Vancouver Island, Canada, indicate the presence of a huge pockmark field that had escaped attention in previous studies. The pockmarks are located between 100 and 200 mt depth around the head of Barkley Canyon. Owing to the presence of a large cabled underwater observatory related to the canyon, a wealth of multi-resolution and multi-disciplinary seafloor data is available from the pockmark field. Available data include multibeam surveys, seafloor video footage, seismic and EK60 echo-sounder profiles, and multibeam water-column information. First results from seafloor mapping indicate that the pockmark field consists of several thousands of pockmarks. By applying workflows that automatically map the pockmarks in digital elevation models, we are able to quantitatively investigate their morphology and spatial distribution. The pockmarks range in size between 100 - 500 m², with some exceptions as large as 900 m². Their mean depth varies between 0.5 - 2 m. Seepage of gas from the seafloor is well known from the area but could not yet been directly associated with the pockmark depressions. Instead, limited video footage from the seafloor indicate that at least some depressions host meter-sized boulders within their craters. We will next investigate possible temporal changes in pockmark morphology and seep activity by individual analysis of datasets that have been repeatedly collected between 2010-2020. By resolving pockmark morphologies and seep activities on an annual time-scale over a decade, the results will hopefully add a level of detail to our understanding of pockmark formation and seep activity within one of North Americas largest pockmark fields.
Mapping Glacier Basal Sliding with Beamforming and Artificial Intelligence
Authors: Umlauft Josefine , Roux Philippe , Lecointre Albanne , Gimbert Florent , Nanni Ugo , Walpersdorf Andrea , Rouet-LeDuc Bertrand , Hulbert Claudia , Trugman Daniel , Johnson Paul
Published: March 2022

The cryosphere is a highly active and dynamic environment that rapidly responds to changing climatic conditions. In particular, the physical processes behind glacial dynamics are poorly understood because they remain challenging to observe. Glacial dynamics are strongly intermittent in time and heterogeneous in space. Thus, monitoring with high spatio-temporal resolution is essential.

In course of the RESOLVE (‘High-resolution imaging in subsurface geophysics : development of a multi-instrument platform for interdisciplinary research’) project, continuous seismic observations were obtained using a dense seismic network (100 nodes, Ø 700 m) installed on Glacier d’Argentière (French Alpes) during May in 2018. This unique data set offers the chance to study targeted processes and dynamics within the cryosphere on a local scale in detail.

 

To identify seismic signatures of ice beds in the presence of melt-induced microseismic noise, we applied the supervised ML technique gradient tree boosting. The approach has been proven suitable to directly observe the physical state of a tectonic fault. Transferred to glacial settings, seismic surface records could therefore reveal frictional properties of the ice bed, offering completely new means to study the subglacial environment and basal sliding, which is difficult to access with conventional approaches.

We built our ML model as follows: Statistical properties of the continuous seismic records (variance, kurtosis and quantile ranges), meteorological data and a seismic source catalogue obtained using beamforming (matched field processing) serve as features which we fit to measures of the GPS displacement rate of Glacier d’Argentière (labels). Our preliminary results suggest that seismic source activity at the bottom of the glacier strongly correlates with surface displacement rates and hence, is directly linked to basal motion. By ranking the importance of our input features, we have learned that other than for reasonably long monitoring time series along tectonic faults, statistical properties of seismic observations only do not suffice in glacial environments to estimate surface displacement. Additional beamforming features however, are a rich archive that enhance the ML model performance considerably and allow to directly observe ice dynamics.
Ambient seismic amplification in extreme topography: instrumental evidence from the Matterhorn
Authors: Weber Samuel , Beutel Jan , Häusler Mauro , Geimer Paul R. , Fäh Donat , Moore Jeffrey R.
Published: March 2022

Amplification of seismic energy in steep topography is widespread and plays an important role affecting the locations of earthquake-induced damage and the distribution of earthquake-triggered landslides. Mountains, and especially the large freestanding massifs of the European Alps, represent extreme topography and may thus exhibit larger topographic amplification than features with less relief. However, suitable broadband seismic data from these locations are rare, in part due to difficult and often dangerous site access. Here we present ambient seismic data collected on two mountains in the Swiss Alps (the Matterhorn and Grosser Mythen), similar in shape but different in scale. At the Matterhorn, comparing data from seismic stations on the summit and ridge to a nearby local reference showed elevated spectral power on the mountain between 0.4 and 1 Hz, and directional site-to-reference spectral amplitude ratios up to 14, which we attribute in part to topographic resonance. We used ambient vibration modal analysis and numerical eigenfrequency modeling to identify the fundamental mode of the Matterhorn at 0.42 Hz, as well as evidence for a second, mutually-perpendicular mode at a similar frequency. Our data further show high modal damping ratios of ∼20% for these modes, which we ascribe to radiative energy loss. A short campaign measurement at Grosser Mythen, showed similar modal properties with a higher fundamental frequency of 1.8 Hz and peak spectral ratios of 6. At the Matterhorn, we analyzed 13 months of continuous data, showing that spectral peaks are stable over time and that the fundamental frequency of the mountain does not measurably vary. Our results aid estimation of topographic amplification for other mountain features.
Super-fast flash flood simulation using steady-state flow solvers
Authors: van den Bout Bastian
Published: March 2022

Flash floods are a rapid burst of flood water that can cause extreme damage to populated areas. The European floods in France, Belgium, Germany and the Netherlands in the summer of 2021 featured a wide range of flash floods with a large number of casualties and vast financial damage. Reflection on the risk reduction strategies have reemphasized the need for early warning systems in the upstream catchments of North-Western Europe. For applications such as this, the speed of flow simulations is critical, as the quality of real-time forecasting often depends on the frequency and amount of simulations that can be carried out as new weather forecasts come in. We present a new type of flood hazard model that, in many typical cases, solves flash flood hazard a 100 times faster with similar accuracy. The developed method employs steady-state solvers for diffusive wave water flow equations to skip the dynamical process and directly estimate relevant parameters such as maximum flow height, maximum flow velocity and relative arrival time of the flood water. These paramters are often the most important for warning systems and descision making in risk reduction. Our adapted algorithm improves upon traditional steady-state flow solvers by employing inversed flow accumulation results and compensation for partial steady-state flow. We show the accuracy of the method is similar to full dynamic water flow simulation in many types of events, such as the extreme 2003 floods in the Fella Basin (Italy), Hurricane-induced flooding on Dominica and the flood impact in Limburg in 2021 (The Netherlands). On average, with highly similar accuracy, calculation time was reduced from approximately 6 hours to 2.5 minutes. We further investigate the limits of the developed methods, in particular to practical applications in different type of flood events. While the sensitivity of the model to initial conditions is similar to that of regular flood models, the sensitivity of the hydraulic aspects is lower. Finally, we discuss potential usage for early-warning, spatial descision support systems and serious gaming approaches. While further investigation is required to fully validate the method, a break-through in flood hazard assessment could be on hand.
Causal Discovery in Ensembles of Climate Time Series
Authors: Gerhardus Andreas , Runge Jakob
Published: March 2022

Understanding the cause and effect relationships that govern natural phenomena is central to the scientific inquiry. While being the gold standard for inferring causal relationships, there are many scenarios in which controlled experiments are not possible. This is for example the case for most aspects of Earth's complex climate system. Causal relationships then have to be learned from statistical dependencies in observational data, a task that is commonly referred to as (observational) causal discovery.

When applied to time series data for learning causal relationships in dynamical systems, methods for causal discovery face additional statistical challenges. This is so because, as licensed by an assumption of stationarity, samples are taken in a sliding window fashion and hence autocorrelated rather than iid. Moreover, strong autocorrelations also often occlude other relevant causal links. The recent PCMCI algorithm (Runge et al., 2019) and its variants PCMCI+ (Runge, 2020) and LPCMCI (Gerhardus and Runge, 2020) address and to some extent alleviate theses issues.

In this contribution we present the Ensemble-PCMCI method, an adaption of PCMCI (and its variants PCMCI+ and LPCMCI) to cases in which the data comprises several time series, i.e., measurements of several instances of the same underlying dynamical system. Samples can then be taken from these different time series instead of a in a sliding window fashion, thus avoiding the issue of autocorrelation and also allowing to relax the stationarity assumption. In particular, this opens the possibility to analyze temporal changes in the underlying causal mechanisms. A potential domain of application are ensemble forecasts.

Related references:
Jakob Runge et al. (2019). Detecting and quantifying causal associations in large nonlinear time series datasets. Science Advances 5 eaau4996.

Jakob Runge (2020). Discovering contemporaneous and lagged causal relations in autocorrelated nonlinear time series datasets. In Proceedings of the 36th Conference on Uncertainty in Artificial Intelligence (UAI). Proceedings of Machine Learning Research 124 1388–1397. PMLR.

Andreas Gerhardus and Jakob Runge (2020). High-recall causal discovery for autocorrelated time series with latent confounders. In Advances in Neural Information Processing Systems 33 12615–12625. Curran Associates, Inc.
GravIS Portal: User-friendly Ice Mass Variations in Greenland and Antarctica from GRACE and GRACE-FO
Authors: Sasgen Ingo , Boergens Eva , Dahle Christoph , Döhne Thorben , Groh Andreas , Dobslaw Henryk , Reißland Sven , Flechtner Frank
Published: March 2022

The German Research Centre for Geosciences (GFZ), together with the Technische Universität Dresden and the Alfred-Wegener-Institute (AWI), maintains the ‘Gravity Information Service’ portal (GravIS, gravis.gfz-potsdam.de). GravIS facilitates the dissemination of user-friendly data of mass variations in the Earth system, based on observations of the GFZ and NASA/JPL satellite gravimetry mission GRACE (Gravity Recovery and Climate Experiment, 2002-2017) and its successor mission GRACE-FO (GRACE-Follow-On, since 2018).

The portal provides mass changes of the Greenland and Antarctic ice sheets on a regular 50 km by 50 km Polar stereographic grid and as basin averages accompanied by empirical uncertainties. Both ice mass balance products rely on the same input data of GRACE/GRACE-FO spherical harmonic coefficients, generated and post-processed by GFZ. Corrections applied to the data include the insertion of estimates of the geocentre motion, replacement of the C20 and C30 coefficients, and the correction for glacial isostatic adjustment with the ICE-6G model.

The gridded data product is processed with sensitivity kernels, tailored explicitly to resolving mass changes of the ice sheets. A regional integration applies these sensitivity kernels to the unfiltered GRACE and GRACE-FO spherical harmonic coefficients. The sensitivity kernels optimise a trade-off between leakage errors and propagated GRACE solution errors.

The basin-average product consists of continent-wide estimates of ice sheet mass changes, and basin averages for seven basins in Greenland and 25 basins in Antarctica. The regional time series are calculated using a forward-modelling  inversion approach, which considers the typical spatial anomalies of the surface-mass balance and dynamic ice discharge.

In addition to the ice mass change data, GravIS provides terrestrial water storage (TWS) variations over the continents and ocean bottom pressure (OBP) variations from which global mean barystatic sea-level rise can be estimated. These data sets are provided either on 1° grids or as regional averages.

The data sets of all Earth system domains can be interactively displayed with the portal and are freely available for download. This contribution aims to show the features and possibilities of the GravIS portal to cryosphere researchers.