bluuebunny/crossref_metadata_2025 huggingface dataset:
Interactions between salt tectonics and crustal tectonics on the Eastern Sardinian Margin (Western Tyrrhenian Sea)
Authors: Gaullier Virginie , Lymer Gaël , Vendeville Bruno , Chanier Frank
Published: March 2021

The METYSS project (Messinian Event in the Tyrrhenian from Seismic Study) is based on high-resolution seismic data acquired along the Eastern Sardinian margin. The main aim is to study the Messinian Salinity Crisis (MSC) in the Western Tyrrhenian Basin, but we also investigated the thinning processes of the continental crust and the timing of crustal vertical movements across this backarc domain. Our first results shown that rifting ended before the MSC, but that crustal activity persisted long after the end of the rifting. This has been particularly observed on the proximal margin, the East-Sardinia Basin, where the Mobile Unit (MU, mobile Messinian salt) is thin or absent. In this study, we examined the distal margin, the Cornaglia Terrace, where the MU accumulated during the MSC and acted as a décollement, thus potentially decoupling the basement from the sedimentary cover. Our observations provide evidence for lateral flow and gravity gliding of the salt and its brittle sedimentary overburden along local basement slopes generated by the post-MSC tilting of some basement blocks formerly generated during the rifting. We also investigated an intriguing wedge-shaped body of MU located in a narrow N-S half graben bounded to the west by a major, east-dipping, crustal normal fault. Classically, one could think that this salt wedge is related to the syn-tectonics deposition of the MU, but we propose an original scenario, in which the post-rift vertical motion of the major fault has been cushioned by lateral flow of an initially tabular salt layer, leaving the supra-salt series apparently unaffected by the crustal motions of the basement. We tested this scenario by comparing natural data and physical (analogue) modelling data. Our results reveal that salt tectonics provides a powerful tool to understand the deep crustal tectonics of the margin and to constrain the timing of vertical motions in the Western Tyrrhenian Basin, results that can be applied to rifted salt-bearing margins worldwide.
Investigation of the lateral continuity of sandstone bedsets containing hummocky cross stratifications
Authors: Douillet Guilhem Amin , Harlet Déborah
Published: March 2021

Hummocky Cross Stratifications (HCS) are low-angle sedimentary structures found in association to sediments from the offshore transition. They are traditionally interpreted as representing storm-induced bedforms, whereby a combined flow is created including an oscillation component from storm waves and a unidirectional component from a density current, with debate on the intensity of each component. 

 

Here, the lateral evolution of bedsets containing HCS is investigated from field exposures. Drone images were collected from outcrops in the Moroccan Anti-Atlas from the Jbel Bani, a several hundred meters thick succession of shoreface to offshore sandstones and shales deposited during the Late Ordovician. Outcrops were targeted specifically for configurations where a vertical series of HCS sandstone bedsets occurred within silty-shale to flazer background interbeds.

 

Over a few hundred meters of lateral distance, HCS beds are found to splay out into channel cuts. Outside these channel features, individual bedsets are seemingly discontinuous, either amalgamating into underlying beds or laterally passing into ripple beds. This preliminary study offers new insights into the depositional dynamics of HCS sandstone beds, feeding a long-lasting discussion over the last 50 years. 
Towards an Improved Parameter-Free Entrainment Model for Snow Avalanches
Authors: Issler Dieter
Published: March 2021

On physical grounds, the rate of bed entrainment in gravity mass flows should be determined by the properties of the bed material and the dynamical variables of the flow. Due to the complexity of the process, most entrainment formulas proposed in the literature contain some ad-hoc parameter not tied to measurable snow properties. Among the very few models without free parameters are the Eglit–Grigorian–Yakimov (EGY) model of frontal entrainment from the 1960s and two formulas for basal entrainment, one from the 1970s due to Grigorian and Ostroumov (GO) and one (IJ) implemented in NGI’s flow code MoT-Voellmy. A common feature of these three approaches is their treating erosion as a shock and exploiting jump conditions for mass and momentum across the erosion front. The erosion or entrainment rate is determined by the difference between the avalanche-generated stress at the erosion front and the strength of the snow cover. The models differ with regard to how the shock is oriented and which momentum components are considered. The present contribution shows that each of the three models has some shortcomings: The EGY model is ambiguous if the avalanche pressure is too small to entrain the entire snow layer, the IJ model neglects normal stresses, and the GO model disregards shear stresses and acceleration of the eroded mass. As they stand, neither the GO nor the IJ model capture situations―observed experimentally by means of profiling radar―in which the snow cover is not eroded progressively but suddenly fails on a buried weak layer as the avalanche flows over it. We suggest a way to resolve the ambiguity in the EGY model and sketch a more comprehensive model combining all three approaches to capture gradual entrainment from the snow-cover surface together with erosion along a buried weak layer.
Draining and Filling of an Interconnected Sub-glacial Lake Network in East Antarctica
Authors: Hogg Anna , Gourmelen Noel , Rigby Richard , Slater Thomas
Published: March 2021

The Antarctic Ice sheet is a key component of the Earth system, impacting on global sea level, ocean circulation and atmospheric processes. Meltwater is generated at the ice sheet base primarily by geothermal heating and friction associated with ice flow, and this feeds a vast network of lakes and rivers creating a unique hydrological environment. Subglacial lakes play a fundamental role in the Antarctic ice sheet hydrological system because outbursts from ‘active’ lakes can trigger, (i) change in ice speed, (ii) a burst of freshwater input into the ocean which generates buoyant meltwater plumes, and (iii) evolution of glacial landforms and sub-glacial habitats. Despite the key role that sub-glacial hydrology plays on the ice sheet environment, there are limited observations of repeat sub-glacial lake activity resulting in poor knowledge of the timing and frequency of these events. Even rarer are examples of interconnected lake activity, where the draining of one lake triggers filling of another. Observations of this nature help us better characterise these events and the impact they may have on Antarctica’s hydrological budget, and will advance our knowledge of the physical mechanism responsible for triggering this activity. In this study we analyse 9-years of CryoSat-2 radar altimetry data, to investigate a newly identified sub-glacial network in the Amery basin, East Antarctica. CryoSat-2 data was processed in ‘swath mode’, increasing the density of elevation measurements across the study area. The plane fit method was employed in 500 m by 500 m grid cells, to measure surface elevation change at relatively high spatial resolution. We identified a network of 10 active subglacial lakes in the Amery basin. 7 of these lakes, located below Lambert Glacier, show interconnected hydrological behaviour, with filling and drainage events throughout the study period. We observed ice surface height change of up to 6 meters on multiple lakes, and these observations were validated by independently acquired TanDEM-X DEM differencing. This case study is an important decade long record of hydrological activity beneath the Antarctic Ice Sheet which demonstrates the importance of high resolution swath mode measurements. In the future the Lambert lake network will be used to better understand the filling and draining life cycle of sub-glacial hydrological activity under the Antarctic Ice Sheet.
Early stress detection in grapevine – can remotely-sensed sun-induced chlorophyll fluorescence do the job?
Authors: Wohlfahrt Georg , Hammerle Albin , Rainer Barbara , Haas Florian
Published: March 2021

Ongoing changes in climate (both in the means and the extremes) are increasingly challenging grapevine production in the province of South Tyrol (Italy). Here we ask the question whether sun-induced chlorophyll fluorescence (SIF) observed remotely from space can detect early warning signs of stress in grapevine and thus help guide mitigation measures.

Chlorophyll fluorescence refers to light absorbed by chlorophyll molecules that is re-emitted in the red to far-red wavelength region. Previous research at leaf and canopy scale indicated that SIF correlates with the plant photosynthetic uptake of carbon dioxide as it competes for the same energy pool.

To address this question, we use time series of two down-scaled SIF products (GOME-2 and OCO-2, 2007/14-2018) as well as the original OCO-2 data (2014-2019). As a benchmark, we use several vegetation indices related to canopy greenness, as well as a novel near-infrared radiation-based vegetation index (2000-2019). Meteorological data fields are used to explore possible weather-related causes for observed deviations in remote sensing data. Regional DOC grapevine census data (2000-2019) are used as a reference for the analyses.
Use of co-created causal loop diagrams and fuzzy-cognitive scenario analysis for water quality management
Authors: Seifollahi-Aghmiuni Samaneh , Kalantari Zahra , Destouni Georgia
Published: March 2021

Current understanding is fragmented of the environmental, economic, and social processes involved in water quality issues. The fragmentation is particularly evident for coastal water quality, impacted both by local land catchment and larger-scale marine pressures and impacts. Research and policy so far has primarily addressed coastal water quality issues from either a land-based or a sea-based perspective, which does not support integrated management of the coupled land-coast-sea systems affecting coastal waters. For example, mitigation measures for improving the severe Baltic Sea eutrophication have mostly focused on land-based drivers, and not yet managed to sufficiently improve coastal or marine water quality. The strong human dimension involved in these water quality issues also highlights a need for participatory approaches to facilitate knowledge integration and drive synergistic strategic planning for sustainable management of coastal water quality. Considering the Swedish water management district of Northern Baltic Proper, including its main Norrström drainage basin and surrounding coastal catchment areas and waters, this study has used a participatory approach to evaluate various land-sea water quality interactions and associated management measures. A causal loop diagram has been co-created with different stakeholder groups, following a problem-oriented system thinking approach. This has been further used in fuzzy-cognitive scenario analysis to assess integrated land-coast-sea system behavior under changing human pressures and hydro-climatic conditions. Results show that synergy of several catchment measures is needed to improve coastal water quality locally, while cross-system/sector cooperation is also needed among all contributing national catchments to mitigate coastal eutrophication at the scale of the whole Baltic Sea. Furthermore, large-scale hydro-climatic changes and long-lived nutrient legacy sources also need to be accounted for in water quality management strategies and measures. System dynamics modelling, based on co-created causal loop diagrams and fuzzy-cognitive scenario analysis like those developed in this study, can support further quantification and analysis of the impacts of various mitigation strategies and measures on regional water quality problems and their possible sustainable solutions.
Variations of the earthquake diffusion rates in the Western Gulf of Corinth (Greece)
Authors: Michas Georgios , Kapetanidis Vasilis , Kaviris George , Vallianatos Filippos
Published: March 2021

Earthquake diffusion is frequently observed in the spatiotemporal evolution of seismic clusters and regional seismicity, a characteristic that is attributed to a triggering mechanism, such as fluid flow, aseismic creep and/or stress transfer effects. In this work, we study the earthquake diffusion properties in the Western Gulf of Corinth (central Greece), an area that presents high extension rates, moderate to large magnitude earthquakes, intense microseismicity and frequent seismic swarms. We focus on the period 2013–2014 that is characterized by intense background microseismic activity along with significant seismic sequences. More specifically, the latter include the 2013 Helike swarm, the 2014 seismic sequence between Nafpaktos and Psathopyrgos, which culminated with an Mw 4.9 event on 21 September 2014, as well as moderate magnitude events that were followed by aftershock sequences. In the herein analysis, we employ a relocated earthquake catalogue of ~9000 events which delineates the activated areas during the study period in high-resolution. We consider the most significant seismic sequences and calculate their respective spatial correlation histograms and the evolution of the mean squared distance of the hypocenters with time, in order to study the earthquake diffusion rates and possible variations that might be related to the triggering mechanisms of seismicity. Our results demonstrate a weak earthquake diffusion process, analogous to subdiffusion within a stochastic framework, for the seismic sequences under consideration, providing further evidence for slow earthquake diffusion in regional and global seismicity. In addition, the earthquake diffusion rates exhibit variations that can be associated with the triggering mechanism. In particular, seismic sequences which are related with pore-fluid pressure diffusion present considerably higher diffusion rates than mainshock/aftershock sequences or the background activity. Such results may provide novel constraints on the triggering mechanisms of clustered seismic activity based on the study of the earthquake diffusion rates. 

Acknowledgements

We would like to thank the personnel of the Hellenic Unified Seismological Network (http://eida.gein.noa.gr/) and the Corinth Rift Laboratory Network (https://doi.org/10.15778/RESIF.CL) for the installation and operation of the stations used in the current article. The present research is co-financed by Greece and the European Union (European Social Fund- ESF) through the Operational Programme «Human Resources Development, Education and Lifelong Learning 2014-2020» in the context of the project “The role of fluids in the seismicity of the Western Gulf of Corinth (Greece)” (MIS 5048127).
Response of hydrological processes to climate and land use changes in Hiso River watershed, Fukushima, Japan
Authors: Peng Shilei , Wang Chunying , Eguchi Sadao , Kuramochi Kanta , Igura Masato , Kohyama Kazunori , Ohkoshi Satoru , Hatano Ryusuke
Published: March 2021

Hydrological processes at basin scale are driven by climate and land-use changes. Hiso River watershed (HRW) is within a radiocesium contaminated area caused by the disaster in Fukushima Daiichi nuclear power plant (FDNPP). It’s urgently needed to make evaluations on how changes of climate and land-use bring impacts on hydrological processes, which control pollutants transport in watershed. This study applied a combination method of Statistical DownScaling Model (SDSM) and Soil and Water Assessment Tool (SWAT) to generate future climatic and hydrologic variables. Future climate data was obtained from three Representative Concentration Pathway (RCP2.6, 4.5 and 8.5) scenarios of a single General Circulation Models (GCMs) in three future periods of 2030s, 2060s and 2090s (2010-2039, 2040-2069, 2070-2099), with a baseline period (1980-2009). Furthermore, according to land-use change in HRW during 2013-2017, three land-use change scenarios under the three future climate scenarios were established. Results suggested that SDSM showed good capabilities in capturing daily maximum/minimum temperature and precipitation. The SWAT model presented good performances in simulating monthly and yearly streamflow. Results also suggested projected higher temperatures and lower rainfall led to decreased annual water yield and evapotranspiration (ET). The annual water yield and ET decreased in most seasons while had a slight increase in spring. RCP8.5 scenario always generated larger magnitudes for climatic variables and water balance components compared with other climate scenarios. Land-use changes had strong impact on surface runoff and groundwater flow. These findings could provide reference for decontamination and revitalization policy-making under complicated land use and climate change conditions.
Half-precession signals in Lake Ohrid and their spatial and temporal connection to proxy records in the European realm
Authors: Ulfers Arne , Zeeden Christian , Voigt Silke , Wonik Thomas
Published: March 2021

Lake Ohrid is located on the Balkan Peninsula between Albania and North Macedonia. It is considered Europe’s oldest lake and thus is a valuable archive for studies that focus on the change of local (hydro-)climate during the last 1.36 million years (e.g., Francke et al. 2016; Wagner et al. 2019). During an International Continental Scientific Drilling Program (ICDP) campaign in 2013, geophysical downhole logging by the Leibniz Institute for Applied Geophysics acquired continuous datasets of physical properties. Additionally, 2100 m of sediment core was obtained from different sites, the deepest with a length of 570 m (Wagner et al. 2014).

Investigations of half-precession (HP) cycles (~9,000 – 12,000 years) have been given only a small role or have been completely neglected in previous cyclostratographic studies. In this study we focus on HP signals in Lake Ohrid and investigate the temporal variability of this signal over the last one million of years. Next to a connection of HP cycles to interglacials, we see a more pronounced correlation of the HP signal to natural gamma radiation logs in the younger part of the record.

We relate the results from Lake Ohrid to a variety of proxy records from the European mainland and marine sediment cores from the Atlantic and the Mediterranean. Certain patterns, such as the increased visibility of the HP signal in interglacials, occur in most records, but differences, like variations in the amplitude modulation of the filtered HP signal, need to be investiagted in more detail. Nevertheless, the HP cycles are contained in all of the investigated sites, although the records are influenced by different climatic systems. This illustrates that HP signals cannot be connected to a certain climatic system, but can occur simultaneously in records with different proxy signal origins.

HP cycles are a relevant part of natural climate variability - also in Europe - and allow a more detailed investiagtion of sedimentary systems.

 

References:

Francke, A., Wagner, B., Just, J., Leicher, N., Gromig, R., Baumgarten, H., … & Giacco, B. (2016). Sedimentological processes and environmental variability at Lake Ohrid (Macedonia, Albania) between 637 ka and the present, Biogeosciences , 13, 1179–1196.

Wagner, B., Wilke, T., Krastel, S., Zanchetta, G., Sulpizio, R., Reicherter, K., …. & Vogel, H. (2014). The SCOPSCO drilling project recovers more than 1.2 million years of history from Lake Ohrid, Sci. Drill. , 17, 19-29.

Wagner, B., Vogel, H., Francke, A., Friedrich, T., Donders, T., Lacey, J. H., … & Zhang, X. . (2019). Mediterranean winter rainfall in phase with African monsoons during the past 1.36 million years, Nature , 573(7773), 256-260.
Seasonal variations in black and organic carbon wet and dry deposition rates at SMEAR III station (60oN), Finland
Authors: Meinander Outi , Heikkinen Enna , Svensson Jonas , Aurela Minna , Virkkula Aki , Vestenius Mika , Hyvärinen Antti
Published: March 2021

Black carbon (BC) and organic carbon (OC, including brown carbon BrC) aerosols in the atmosphere, and their wet and dry deposition, are important for their climatic and cryospheric effects. Seemingly small amounts of BC in snow, of the order of 10–100 parts per billion by mass (ppb), have been shown to decrease its albedo by 1–5 %. Due to the albedo-feedback mechanism, surface darkening accelerates snow and ice melt. In snow, the temporal variability of light absorbing aerosols, such as BC, depends both on atmospheric and cryospheric processes, mostly on sources and atmospheric transport, and dry and wet deposition processes, as well as post-depositional snow processes.

We started a new research activity on BC and OC wet and dry deposition at Helsinki Kumpula SMEAR III station (60°12 N, 24°57 E, Station for Measuring Ecosystem-Atmosphere Relations, https://www.atm.helsinki.fi/SMEAR/index.php/smear-iii). The work included winter, spring, summer and autumn deposition samples during January 2019 - June 2020 (sampling is currently on hold). In winter, wet deposition consisted of snowfall and rainwater samples. Dry deposition samples were separately collected in 2020. For sample collection, a custom-made device, including a heating-system, was applied. The samples were analyzed using the OCEC analyzer of the Finnish Meteorological Institute’s aerosol laboratory, Helsinki, Finland. The special features in our deposition data are: 

seasonal BC, OC, and TC (total carbon, the sum of BC and OC) deposition data for an urban background station at 60 oN

precipitation received as either water or snow  

dry deposition samples included (only in 2020)

data as wet and dry deposition rates [concentration/time/area]

simultaneous atmospheric measurements of the SMEAR III station

Since our deposition samples are collected manually, the data are non-continuous, yet they allow us to provide deposition rates. Such data can be utilized in various modeling approaches including, for example, climate and long-range transport and deposition modeling. According to our knowledge, these data are the first BC (determined as elemental carbon, EC), OC and TC wet and dry deposition data to represent Finland. Our sampling location, north of 60 deg. N, can be useful for other high-latitude studies and Arctic assessments, too.

Acknowledgements. We gratefully acknowledge support from the Academy of Finland NABCEA-project of Novel Assessment of Black Carbon in the Eurasian Arctic (no. 296302) and the Academy of Finland Flagship funding (grant no. 337552).
A Three-dimensional SPH Simulation of Iceberg Calving generated Waves
Authors: Hu Chao , Wang Xiao-liang , Liu Qing-quan
Published: March 2021

The calving of large-scale icebergs into the sea can generate a local tsunami that may threaten coastal communities or passing ships. A three-dimensional smoothed particle hydrodynamics model of rigid-body–fluid system is established to simulate the spatial wave generated by calving iceberg. The model is tested with simulated waves induced by a cube iceberg fall into the water body. Good agreement is obtained between simulation results and experimental data. The generation and evolution processes, and the near flow-field characteristics of the waves are analyzed. The simulation results show that waves generated in iceberg calving can generate not only a huge leading wave but also notable tailing waves. The initial propagation direction of the leading wave is determined by iceberg geometry, but as the leading wave propagates away, the water level displacement gradually develops into a semicircle wavefront which is irrelevant to iceberg geometry.
Determination of site amplifications and moment magnitudes of East-Alpine earthquakes
Authors: Weginger Stefan
Published: March 2021

The Seismological Service of earthquakes Austria located at the Zentralanstalt für Meteorologie und Geodynamik (ZAMG; http://www.zamg.ac.at) is the federal agency for monitoring and seismic hazard assessments in Austria. The ZAMG seismological network currently consists of approximately 60 Stations (28 broadband and ~30 strong motion). The increasing number of earthquake records during the past 20 years - from the local seismic network with addition of surrounded stations from the EIDA archive - are used to determinate the local attenuation of seismic shear wave energies and the site amplifications.

The propagation path of the released seismic energy through the uppermost crust has a considerable influence on the ground movement recorded at the surface. This contribution follows the known method of combining a physical modeling and a statistical approach by separating the source, path and site effects by means of inversion. A geometrical spreading model defines the frequency-independent decay of energy while the frequency dependent decay is parameterized by the parameters Q and Kappa. The moment magnitudes and stress drops of small earthquakes were determined, and a scaling-relationship of local to moment magnitudes could be established.

Taking these site-effects into consideration reduces the uncertainties in the determination of empirical ground motion prediction equations (GMPE) and increases the accuracy of seismic hazard assessments, ShakeMaps and On-Site systems.
Long-term variation of characteristics of local land atmosphere coupling over TP and the possible influence of Southern Asian Monsoon
Authors: Sun Genhou , Hu Zeyong , Ma yaoming , Xie Zhipeng , Wei Wei , Yang Song
Published: March 2021

This study investigates the long-term variations of local land atmosphere coupling (LoCo) over Tibetan Plateau (TP) by applying a mixing diagram to the observational data at six stations over TP and ERA5 and the possible influence of Southern Asian monsoon. The result indicates that the monthly-mean daily variation in T2m, q2m, Hsfc, and LEsfc at Nyingchi, Nagqu, Nam Co, Qomolangma, Ngari, and Muztagata in ERA5 are close to those in observational data. Comparison of mixing diagram analysis using the monthly-mean variables of ERA5 and the observational data indicates ERA5 could provide reliable information of LoCo at six stations. The relationships between Hsfc and daytime PBLH, and the variations of LCL deficit at six stations are different due to the differences in the soil states. The long-term variations in the PBL energy budgets, mean daytime PBLH, and LCL deficits at 31◦N and 90◦E show clear annual variations and have a close relationship between Southern Asian monsoon. The possible influence of the Southern Asian monsoon is also discussed in terms of the relationship between the Webster-Yang index and the PBL energy budgets, mean PBLH and mean LCL over TP.
Error assessment of traffic emission estimates using novel mobility datasets.
Authors: Gensheimer Johannes , Turner Alexander J. , Shekhar Ankit , Wenzel Adrian , Keutsch Frank N. , Chen Jia
Published: March 2021

The COVID-19 pandemic led to widespread reductions in mobility and induced observable changes in the atmosphere. Recent work has employed novel mobility datasets as a proxy for trace gas emissions from traffic, yet there has been little work evaluating these emission numbers.

We systematically compare mobility datasets from TomTom and Apple to traffic data from local governments in seven diverse urban and rural regions to characterize the magnitude of errors in emissions that result from using those mobility datasets as a proxy for traffic. We observe differences in excess of 60% between these mobility datasets and local traffic data, which result in large errors in emission estimates. These differences are in part driven by the usage of different baselines and the neglect of seasonality, but mainly they are caused by the individual representations of the datasets. The relationship varies strongly depending on time and region and therefore no general functional relationship between mobility data and traffic flow over all regions can be determined. Future work should be cautious when using these mobility metrics for emission estimates. Further, we use the local government data to identify actual emission reductions from traffic in the range of 7-22% in 2020 compared to 2019 for our study regions. Our full analysis is summarized in Gensheimer et al. (2020).

Gensheimer, J., Turner, A., Shekhar, A., Wenzel, A., & Chen, J. (2020). What are different measures of mobility changes telling us about emissions during the COVID-19 pandemic? Earth and Space Science Open Archive, 11. Retrieved from doi: 10.1002/essoar.10504783.1
Assessing the role of corrections included in the GRACE/GRACE-FO data in determination of hydrological and cryospheric signal in polar motion excitation
Authors: Śliwińska Justyna , Wińska Małgorzata , Nastula Jolanta
Published: March 2021

Assessing the impact of continental hydrosphere and cryosphere on polar motion (PM) variations is one of the crucial tasks in contemporary geodesy. The pole coordinates, as one of the Earth Orientation Parameters, are needed to define the relationship between the celestial and terrestrial reference frames. Therefore, the variations in PM should be monitored and interpreted in order to assess the role of geophysical processes in this phenomenon.

The role of hydrological and cryospheric signals in PM is usually examined by computing hydrological excitation (hydrological angular momentum, HAM) and cryospheric excitation (cryospheric angular momentum, CAM) of  PM, commonly treated together as HAM/CAM.

The Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO) missions deliver temporal variations of the gravity field resulting from changes in global mass redistribution. The so-called GRACE/GRACE-FO Level-3 (L3) data delivers changes in terrestrial water storage (TWS) that can be used for computation of HAM/CAM.

For best possible representation of TWS, a number of corrections are introduced in the L3 data by computing centres. Such corrections are, among others, glacial isostatic adjustment (GIA) correction, geocenter correction and C20 coefficient correction.

The main goal of this study is to examine the impact of corrections included in GRACE/GRACE-FO data on HAM/CAM determined. More specifically, we test their influence on HAM/CAM trends, seasonal changes and non-seasonal variations. We also examine the change in compliance between HAM/CAM and hydrological plus cryospheric signal in geodetically observed excitation when the corrections are used. To achieve our goals, we use GRACE and GRACE-FO L3 datasets provided by Jet Propulsion Laboratory (JPL), Center for Space Research (CSR), and Goddard Space Flight Center (GSFC).
Sources and pathways of biocides and their transformation products in 2ha urban district
Authors: Linke Felicia , Olsson Oliver , Preusser Frank , Kümmerer Klaus , Schnarr Lena , Lange Jens
Published: March 2021

Biocides used as film protection products to prevent algae and fungi growth on facades wash off during rain events and represent a potential risk to the environment. So far, urban monitoring studies focused mainly on large heterogeneous urban areas. Thus, little information about individual sources and entry pathways were obtained. However, this is important to understand the potential risk of biocide entry to groundwater.

This study investigates biocide emissions from a 2 ha residential area, 13 years after construction has ended. Investigated substances represent commonly used biocides for film protection, i.e. Terbutryn, Diuron and Octylisothiazolinone (OIT) and some of their known transformation products (TPs, Diuron-Desmethyl, Terbumeton, 2-Hydroxy-Terbutylazin and Terbutryn-Desethyl). We used existing urban infrastructure for efficient monitoring and applied a three-step approach to (a) determine the overall relevance of biocides, (b) identify source areas and long-term emission and (c) characterize entry pathways into surface- and groundwater.

Initial sampling in the swale system gave an integrated signal from the entire district and confirmed the relevance of biocide leaching, more than a decade after construction. Concentrations peaked at 174 ng/L for Diuron and 40 ng/L for Terbutryn during a high magnitude event and were above PNEC values. During later events, transformation products were detected, though at lower concentrations. For all substances, source areas were identified in a second step. Artificial elution experiments confirmed expected sources, i.e. façades, but we also found additional sources through sampling of rainfall downpipes from flat roofs. A small part of the roof façade was repainted two years before sampling and thereby showed a magnitude higher leaching rates than the remaining façades. Since all biocide wash-off arrived on a flat roof and was drained by rainfall down pipes, we could estimate net biocide emission and arrived at 155 mg Diuron, 17 mg Terbutryn, 12 mg OIT and 17 mg Diuron-Desmethyl from a 10 m2 painted façade area over a time period of two years. In a third step, we characterized entry pathways comparing samples from a drainage pipe that collected road runoff (surface pathway) with two others that collected infiltrated water on top of an underground garage (soil pathway). All drainage pipes showed Terbutryn, two of them also Diuron but none OIT. The drainage pipe representing the surface pathway showed a smaller number of individual transformation products but similar concentrations of parent compounds. One pipe representing the soil pathway had highest concentrations of Terbutryn and its TPs which suggests a high leaching potential of this biocide also away from concentrated infiltration in urban stormwater management infrastructure.
Fine-scale structures as spots of increased fish concentration in the open ocean
Authors: Baudena Alberto , Ser-Giacomi Enrico , d'Onofrio Donatella , Capet Xavier , Cotté Cedric , Cherel Yves , d'Ovidio Francesco
Published: March 2021

Oceanic Lagrangian Coherent Structures have been shown to deeply influence the distribution of primary producers and, at the other extreme of the trophic web, top predators. However, the relationship between these structures and intermediate trophic levels is much more obscure. In this work we contribute to address this knowledge gap by comparing acoustic measurements of mesopelagic fish concentrations to satellite-derived fine-scale Lagrangian Coherent Structures in the open ocean. The results demonstrate that higher fish concentrations occur more frequently over stronger Lagrangian Coherent Structures. Quantile regression analyses reveal that Lagrangian Coherent Structures represent a limiting condition for high fish concentrations. Therefore, while the presence of a fine-scale feature does not imply a concomitant fish assembly, increased fish densities are more likely to be observed over these structures. Finally, we discuss a model representing fish movement along Lagrangian features, and specifically built for mid trophic levels. Even though it was not possible to validate it with the available data, its results, obtained with realistic parameters, are consistent with the observations. These findings may help to integrate intermediate trophic levels in trophic models, which can ultimately support management and conservation policies.
Multi-GNSS Single-Difference Baseline Processing at NGS with newly developed M-PAGES software
Authors: Stressler Bryan , Bilich Andria , Ogaja Clement , Heck Jacob
Published: March 2021

The U.S. National Geodetic Survey (NGS) has historically processed dual-frequency GPS observations in a double-differenced mode using the legacy software called the Program for the Adjustment of GPS Ephemerides (PAGES). As part of NGS’ modernization efforts, a new software suite named M-PAGES (i.e., Multi-GNSS PAGES) is being developed to replace PAGES. M-PAGES consists of a suite of C++ and Python libraries, programs, and scripts built to process observations from all GNSS constellations. The M-PAGES team has developed a single-difference baseline processing strategy that is suitable for multi-GNSS. This approach avoids the difficulty of forming double-differences across systems or frequencies, which may inhibit integer ambiguity resolution. The M-PAGES suite is expected to deploy to NGS’ Online Positioning User Service (OPUS) later this year. Here, we present the processing strategy being implemented along with a performance evaluation from sample baseline solutions obtained from data collected within the NOAA CORS Network.
Thermospheric densities for the Swarm satellite mission
Authors: van den IJssel Jose , Siemes Christian , Visser Pieter
Published: March 2021

The European Space Agency (ESA) Swarm mission was launched in November 2013 and consists of three identical satellites flying in near-polar orbits. One satellite is flying at about 515 km, while the other two satellites are flying side-by-side at lower altitudes, starting at 480 km altitude and slowly descending due to atmospheric drag to their current 445 km altitude. This coverage of altitudes, together with the satellite payload that includes an accelerometer and GPS receiver, makes the mission particularly suited for atmospheric density retrieval. Unfortunately, the Swarm accelerometers suffer from several anomalies which limits their usefulness for density retrieval. Currently, only accelerometer observations from one of the lower flying satellites (Swarm-C) can be used to generate high-resolution thermospheric densities. However, all satellites deliver high-quality GPS data and an alternative processing strategy has been developed to derive thermospheric densities from these observations as well.

This presentation describes the processing strategy that is used to derive thermospheric densities from the Swarm accelerometer and GPS observations and presents the latest results. The relatively smooth GPS-derived densities have a temporal resolution of about 20 minutes, and show variations due to solar and geomagnetic activity, as well as seasonal, latitudinal and diurnal variation. For analysis of higher-resolution phenomena, only the accelerometer-derived densities can be used. All Swarm thermospheric densities are available for users at the dedicated ESA Swarm website (ftp://swarm-diss.eo.esa.int), as well as at our thermospheric density database (http://thermosphere.tudelft.nl). This database also includes thermospheric densities for the CHAMP, GRACE and GOCE satellites. For future work, it is planned to further improve the Swarm densities, especially for low solar activity conditions, by including a more sophisticated radiation pressure modelling of the Swarm satellites. In addition, it is planned to extend our database with thermospheric densities for the GRACE-FO mission.
Application of Cross-Track Infrared Sounder (CrIS) Instrument for Remote Detection of Agricultural NH3 Emissions over Netherlands
Authors: Bashalkhanova Olga , Shephard Mark , Dammers Enrico , Kovachik Andrew , Wichink Kruit Roy , Cady-Pereira Karen
Published: March 2021

Satellite observations have great potential for monitoring emissions and concentrations of atmospheric species. This is especially true for atmospheric ammonia (NH3), which varies greatly in space and time and is difficult to measure in-situ due to its sticky nature.  NH3 measurements are important as NH3 is a significant contributor to the production of secondary inorganic aerosols (PM2.5) and can add excessive reactive nitrogen to the environment. In this study we demonstrate how satellite remote sensing observations can be used to monitor changes in NH3 concentrations by evaluating timeseries of Cross-Track Infrared Sounder (CrIS) satellite data with in-situ NH3 concentrations and meteorological parameters (i.e. soil temperature and soil moisture). We provide an example demonstrating the capability to monitor the annual springtime increase in atmospheric NH3 concentrations in Netherlands, which is mainly associated with farming practices (e.g. manure spreading on fields in the springtime). We then combine these satellite observations of NH3 with meteorological conditions, with the goal of developing a model to predict the timing of ammonia emissions based on past agricultural practices in the area (e.g. artificial fertilizer and manure spreading).    
Nature-based solutions to mitigate the risk of shallow landslides: a global analysis
Authors: Nehren Udo , Arce Mojica Teresa
Published: March 2021

Landslides claim many lives and cause high financial losses in mountainous regions around the world every year. Especially in high mountain regions, the landslide risk is likely to increase further in the coming years due to the thawing of permafrost soils and the associated activation of slope dynamics. However, a higher landslide risk is also expected regionally in tropical and subtropical mountainous regions, namely where an increase in extreme weather events is projected and at the same time, there is a higher socio-ecological vulnerability and exposure due to population growth, land use pressure and other factors.

To mitigate the risk to people and their assets, various hard and soft infrastructure measures are available. Especially in the European Alps, the concept of protection forests (German: Schutzwälder) in combination with hard infrastructure has been used for years as an ecosystem-based or hybrid measure. Based on a systematic global literature review (275 papers), we investigated which Nature-based Solutions (NbS) to mitigate the risk of shallow landslides are in place worldwide, in which countries and regions they were implemented, and which approaches under the NbS umbrella concept were applied (e.g. Green Infrastructure, Ecological Engineering, Eco-DRR, etc.). 

As a result of this comprehensive analysis, we present a portfolio of measures to mitigate the risk of shallow landslides that are being applied in various (eco)regions and cultural contexts around the world and discuss the success of these measures as well as potential risks, uncertainties, and failures. We also emphasize the need for further research particularly on the effectiveness of ecosystem-based landslide risk reduction in different mountain ecosystems, as well as the cost-effectiveness of NbS compared to hard infrastructure. We conclude that despite a successful implementation in the Alps and few other mountain regions, the protection forest concept has hardly been applied so far, especially in the Global South. In addition, we emphasize the particular challenge of establishing protection forests due to the rapid climatic and ecological changes and related geomorphological process dynamics in mountain regions in the course of global climate change.
Assessing current and future flood risk estimates associated with hurricane rainfall under the 1.5°C and 2°C Paris Agreement goals in Puerto Rico
Authors: Archer Leanne , Neal Jeffrey , Bates Paul , Vosper Emily , Mitchell Dann
Published: March 2021

Record-breaking hydrometeorological disasters such as Hurricane Maria in 2017 have once again highlighted the severe disaster risk exacerbated by a changing climate facing Caribbean small island states. Hurricane rainfall is a key cause of flooding in many Caribbean islands. Yet, despite the projected changes in hurricane rainfall under climate change and the attribution of a climate change signal in particular hurricane rainfall events, estimates of current and future flooding associated with hurricane rainfall are limited in the Caribbean. This research outlines a method for assessing current and future flood risk estimates in the Caribbean, producing an event-based pluvial model using hydrodynamic model LISFLOOD-FP to simulate flood hazard in Puerto Rico for present day, 1.5oC and 2oC Paris Agreement climate projections. An event set of 59,000 hurricane rainfall estimates from a synthetic hurricane rainfall model was applied as the rainfall input to the hydrodynamic model, simulated across time (2-hour timesteps) and space (0.1-degree spatial resolution). The event-based pluvial model was run at the island-scale in Puerto Rico (9104km2) at 20m and 90m resolution to produce event-based flood hazard estimates under present day, 1.5oC and 2oC climate change projections. The flood hazard event set was then combined with population data to get estimates of exposure exceedance under present day, 1.5oC and 2oC climate change projections. The results of this research will provide useful information for both the hydrology and disaster risk reduction communities regarding the potential changes in population exposure to hurricane rainfall-induced flood events in Puerto Rico, as well as how particular characteristics of hurricane rainfall affect flood hazard under 1.5oC and 2oC climate change. This research will also highlight how an event-based pluvial flood model can be utilised to assess a range of possible current and future flood scenarios, as well as how important different aspects of the modelling are for these small island studies. This information is crucial for both current and future disaster risk reduction and climate change adaptation planning in the Caribbean – an ever-increasingly urgent task. 
BioGeoChemical product provided by the Copernicus Marine Service
Authors: Lien Vidar S. , Øie Nilsen Jan Even , Perivoliotis Leonidas , Sotiropoulou Maria , Denaxa Dimitra , Ehrhart Sebastian , Seppälä Jukka , Racapé Virginie
Published: March 2021

We present the in-situ biogeochemical data products distributed by the Copernicus Marine Service since 2018. The products offer available data of chlorophyll, oxygen, and nutrients (nitrate, silicate and phosphate), both in near-real time and as re-processed data, collected across the globe. The re-processing involves careful quality control utilizing tailored automated quality control procedures combined with visual inspection of questionable values by experts. Moreover, oxygen data are provided with uniform units for modelers (µmol/l) and other oceanic applications and monitoring purposes (µmol/kg) The products integrate observations aggregated from the Regional EuroGOOS consortium, as well as from SeaDataNet2, National Data Centers (NODCs) and JCOMM global systems, among others.

We highlight some use cases, including a study showing an overall decline in the nutrient concentration (nitrate and silicate) of the Atlantic Water flowing though the Nordic Seas en-route to the Arctic Ocean, during the period 1990-2019. Moreover, the study shows indications of a delayed-response reduction further downstream in the Arctic Water exiting the Arctic Ocean through Fram Strait. Other use cases include the study of variability in the concentration of dissolved oxygen in the Mediterranean Sea, showing an association with dynamical processes.

The in-situ near-real time biogeochemical product is updated every month whereas the re-processed product is updated two times per year. Products are delivered on NetCDF4 format compliant with the CF1.7 standard and well-documented quality control procedures.