bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulating coastal storm hazards at the Algarve coast (Portugal)
Authors: Garzon Juan L. , Ferreira Oscar
Published: March 2020

Many important European cities are under the threat of coastal storm-related hazards. Recent examples in Portugal, England, France, etc. have demonstrated the vulnerability of their coasts, and this risk is expected to increase under a scenario of global warming. Numerical models are very valuable tools to predict and simulate these hazards, and ultimately, help coastal managers and authorities to reduce damages in goods and people's lives. In this research, the numerical model XBeach was applied to investigate the vulnerability of two risk hotspots located in the south Portuguese coast of the Algarve: Quarteira and Praia de Faro. XBeach is a widely used state of the art model and it is capable of simulating interactions between hydrodynamics and beach morphology. The beaches at these study sites can be classified as dominantly reflective turning to intermediate during high energetic events.  The study site of Quarteira consists of a set of three sandy beaches laterally limited by rock groins and backed by a long promenade with several touristic facilities. In contrast, Praia de Faro is a natural open sandy beach located in the narrow Ancão Peninsula, promoting a natural barrier between the ocean and an interior lagoon. The urbanized area is either directly exposed or naturally protected by the dune that helps to reduce damages in buildings and other services. Two different 2D-XBeach models have been developed and calibrated to simulate coastal hazards including overwash, overtopping, inundation and erosion impacting these sites. The models have been calibrated and validated using topographical measurements of cross-shore profiles, along with visual inspections of the inundated areas after the impact of severe storms. Specifically, data from the coastal storm Emma (2018), that hit the region with dramatic consequences were used in this study. The observed vertical erosion reached more than 3 m at Praia de Faro, while the runup promoted important overwash at both study areas. Additionally, storm Elsa (2019) hit the sites driving significant erosion. To obtain realistic results, the models display a high resolution that captures all natural and manmade features. The results provided by XBeach at both sites demonstrated that within the same study site, the calibration of only one profile was sufficient to properly reproduce the erosion along the site. However, the results of the calibration cannot be transferred from Praia de Faro to Quarteira and vice-versa, even if the study sites are separated by less than 10 km. Moreover, the model successfully simulated the flooding extension that was observed in the field after the storm Emma (2018). These validation efforts are the base for the development of an Early Warning System that will provide advice to coastal managers, civil protection and population in general about the risk associated with severe storms. Furthermore, the findings of this research can provide guidance for modellers working in similar environments.
The Intriguing Relation Between Earth's Rotation, Geomagnetic Field, and Climate at Multidecadal Time Scales: Insights from NCEP 20th Century Reanalysis
Authors: Lambert Sébastien
Published: March 2020

High correlations between length-of-day (LOD) and climate variables (sea-surface temperature, surface air temperature) have been pointed out in numerous studies (e.g., Lambeck and Cazenave 1976, Dickey et al. 2011, Marcus 2016) in the recent years at both decadal and multidecadal time scales. Moreover, the multidecal LOD variations (that reach several milliseconds) have been shown to have their origin in variations in the core angular momentum and are associated with variations of the Earth magnetic field now modeled back to the middle of the 19th century. Though the climate variations unlikely arise from the core, some authors suggested that they could result from modulation of incoming cosmic ray flux by Earth's magnetic field through cloud formation. In this study, we propose to check correlations between LOD, Earth dipolar magnetic field, and climate variables as taken from a century reanalysis (gridded air temperature and cloud coverage from NCEP 20th Century Reanalysis V2 and V3) in order to (i) confirm results of previous studies about a possible causality between geomagnetism, LOD, and climate, and (ii) locate the hot spots where the link between geomagnetism and cloud formation could be significant.
CME evolution and the corresponding Forbush decrease: modelling vs multi-spacecraft observation
Authors: Dumbovic Mateja , Vrsnak Bojan , Guo Jingnan , Heber Bernd , Dissauer Karin , Carcaboso-Morales Fernando , Temmer Manuela , Veronig Astrid , Podladchikova Tatiana , Möstl Christian , Amerstorfer Tanja , Kirin Anamarija
Published: March 2020

One of the very common in-situ signatures of ICMEs, as well as other interplanetary transients are Forbush decreases (FDs), i.e. short-term reductions in the galactic cosmic ray (GCR) flux. A two-step FD is often regarded as a textbook example, which presumably owns its specific morphology to the fact that the measuring instrument passed through the ICME head-on, encountering first the shock front (if developed), then the sheath and finally the magnetic structure. The interaction of GCRs and the shock/sheath region as well as CME magnetic structure occurs all the way from Sun to Earth, therefore, FDs are expected to reflect the evolutionary properties of CMEs and their sheaths. We apply modelling to different ICME regions in order to obtain a generic two-step FD profile, which qualitatively agrees with our current observation-based understanding of FDs. We next adapt the models for energy dependence to enable comparison with different GCR measurement instruments (as they measure in different particle energy ranges). We test these modelling efforts against a set of multi-spacecraft observations of the same event.
Draining and Filling of an Interconnected Sub-glacial Lake Network in East Antarctica
Authors: Hogg Anna , Gourmelen Noel , Rigby Richard , Slater Thomas
Published: March 2020

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.
The link between precipitation and recent outbreak of anthrax in North-West Siberia
Authors: Ezhova Ekaterina , Orlov Dmitry , Suhonen Elli , Kaverin Dmitry , Mahura Alexander , Gennadinik Victor , Kukkonen Ilmo , Drozdov Dmitry , Lappalainen Hanna , Melnikov Vladimir , Petäjä Tuukka , Kerminen Veli-Matti , Zilitinkevich Sergey , Malkhazova Svetlana , Christensen Torben , Kulmala Markku
Published: March 2020

Anthrax is a bacterial disease affecting mainly livestock but also posing a risk for humans. During the outbreak of anthrax on Yamal peninsula in 2016, 36 humans were infected and more than 2.5 thousand reindeer died or were killed to prevent further contamination [1]. Anthrax is a natural focal disease, which means that its agents depend on climatic conditions. The revival of bacteria in previously epidemiologically stable region was attributed to thawing permafrost, intensified during the heat wave of 2016. We studied recent dynamics of air temperature as well as summer and winter precipitation in the region. In addition, we analysed the effect of winter precipitation and air temperature on the dynamics of active layer thickness using data from Circumpolar Active Layer Monitoring sites [2]. Our analysis suggests that permafrost was thawing intensively during several years before the outbreak, when snowy cold winters followed warmer winters. Thick snow prevented soil from freezing and enhanced permafrost thawing. In addition, we showed that summer precipitation drastically decreased in the region of outbreak during recent years, likely contributing to the spread of disease.  

[1] Popova, A.Yu. et al. Outbreak of Anthrax in the Yamalo-Nenets Autonomous District in 2016, Epidemiological Peculiarities. Problemy Osobo Opasnykh Infektsii [Problems of Particularly Dangerous Infections]. 4, 42–46 (2016).

[2] Circumpolar Active Layer Monitoring site: https://www2.gwu.edu/~calm/ [2/08/2019].
Ensemble generation strategies for the short-range forecast of flash floods: the 12-13 September 2019 event in Eastern Spain
Authors: Hermoso Alejandro , Homar Victor , Amengual Arnau
Published: March 2020

The Mediterranean region is frequently affected by heavy precipitation and flash flooding during the extended warm season. A precise meteorological forecast of socially relevant aspects of these phenomena such as location, timing and intensity is crucial to prevent personal and material losses. However, forecasting these aspects becomes extremely challenging due to small-scale processes involved in the triggering, development and subsequent evolution of convective systems.

 

On 12 and 13 September 2019 widespread flash flooding caused devastating effects across Murcia and Valencia, eastern Spain. Seven fatalities were reported, hundreds of homes were flooded and economic losses were estimated at 200 M€. The performance of various ensemble generation strategies for short-range convection-permitting ensemble prediction systems (EPS) are evaluated for this episode. Different sources of error are coped by the implemented ensemble generation approaches.  Uncertainty in the initial and lateral boundary conditions uncertainty is sampled in two ways: (i) the dynamical downscaling of the ECMWF global EPS and, (ii) a new tailored breeding technique that accounts for perturbations across the multiple scales of interest for short-range forecasting. Additionally, errors in mesoscale model formulation are encompassed by combining different parameterization schemes and stochastic physics.

 

This study contributes to the identification of the most relevant sources of uncertainty hampering an accurate spatial and temporal forecasting of heavy precipitation resulting in flash flooding over the Spanish Mediterranean region. These cutting-edge EPS can contribute to implement more reliable and effective hydrometeorological prediction chains with lead times up to 24 h, providing a valuable support to civil protection and emergency management authorities.
Atmospheric methane monitoring and analysis using tropOMI retrievals at ECMWF.
Authors: Barre Jerome , Aben Ilse , Ades Melanie , Agusti-Panareda Anna , Balsamo Gianpaolo , Bousserez Nicolas , Choulga Margarita , Engelen Richard , Flemming Johannes , Inness Antje , Kipling Zak , Landgraf Jochen , Lorente-Delgado Alba , Massart Sebastien , McNorton Joe , Parrington Mark , Peuch Vincent-Henri
Published: March 2020

The European Union’s Copernicus Atmosphere Monitoring Service (CAMS) operationally provides daily forecasts of global atmospheric composition. It uses the ECMWF Integrated Forecasting System (IFS), which includes meteorological and atmospheric composition variables, such as reactive gases, greenhouse gases and aerosols, for its global forecasts and reanalyses. The current green-house gases operational suite monitors CH4 and CO2 and assimilates TANSO and IASI retrievals for both species. The TROPOspheric Monitoring Instrument (TROPOMI) on board the Sentinel-5 Precursor (S5P) satellite launched in October 2017 yields a wealth of atmospheric composition data, including CH4 retrievals at unprecedented high horizontal resolution (7km) and up to daily revisit time. We used the IFS to perform monitoring experiments at different horizontal resolutions (25 km and 9 km). We also performed first data assimilation experiments at 25 km horizontal resolution.

This first set of monitoring experiments shows the potential of the TROPOMI CH4 retrievals to correct known biases that exist in the current CAMS analyses and forecasts. Assimilation experiments of TROPOMI CH4 shows that adding the instrument in the operational chain would significantly improve the analysis and forecasts. Detection of CH4 sources seen by TROPOMI compared to CAMS also shows the potential of the instrument to inform on and infer anthropogenic and natural sources. For example, discrepancies between TROPOMI retrievals and CAMS fields in the CH4 levels associated with oil and gas extraction activities show very promising perspectives for monitoring and analysis of CH4 concentration and emissions. We will finally discuss the challenges and progress made towards performing inversions using the IFS operational system.  
How well do we know our models?
Authors: Degen Denise , Veroy Karen , Cacace Mauro , Scheck-Wenderoth Magdalena , Wellmann Florian
Published: March 2020

In Geosciences, we face the challenge of characterizing uncertainties to provide reliable predictions of the earth surface to allow, for instance, a sustainable and renewable energy management. In order, to address the uncertainties we need a good understanding of our geological models and their associated subsurface processes.

Therefore, the essential pre-step for uncertainty analyses are sensitivity studies. Sensitivity studies aim at determining the most influencing model parameters. Hence, we require them to significantly reduce the parameter space to avoid unfeasibly large compute times.

We distinguish two types of sensitivity analyses: local and global studies. In contrast, to the local sensitivity study, the global one accounts for parameter correlations. That is the reason, why we employ in this work a global sensitivity study. Unfortunately, global sensitivity studies have the disadvantage that they are computationally extremely demanding. Hence, they are prohibitive even for state-of-the-art finite element simulations.

For this reason, we construct a surrogate model by employing the reduced basis method. The reduced basis method is a model order reduction technique that aims at significantly reducing the spatial and temporal degrees of freedom of, for instance, finite element solves. In contrast to other surrogate models, we obtain a surrogate model that preserves the physics and is not restricted to the observation space. As we will show, the reduced basis method leads to a speed-up of five to six orders of magnitude with respect to our original problem while retaining an accuracy higher than the measurement accuracy.

In this work, we elaborate on the advantages of global sensitivity studies in comparison to local ones. We use several case studies, from large-scale European sedimentary basins to demonstrate how the global sensitivity studies are used to learn about the influence of transient, such as paleoclimate effects, and stationary effects. We also demonstrate how the results can be used in further analyses, such as deterministic and stochastic model calibrations. Furthermore, we show how we can use the analyses to learn about the subsurface processes and to identify model short comes.
Origin and Geodynamic significance of opx granitoids from Bunger Hills Area, East Antarctic
Authors: Borovkov Nikita , Kusiak Monika A. , Nawrot Adam , Koreshkova Marina , Leichenkov German
Published: March 2020

The information on magmatic orthopyroxene (opx) granitoids (charnockites) is essential for geodynamic models of continent collision, amalgamation, and postorogenic events. There is also the petrological issue - the role of the crust and mantle material in the formation of opx granitoids in orogenic and post-orogenic settings. Our research objects are three multiphase coeval plutons of the opx granitoids in the Banger Oasis, East Antarctica. Only two phases can be distinguished: the first phase comprising of silica and potassium rich middle-coarse grained qz opx monzodiorites, monzonites and granites with porphyric perthite alkali feldspar, whereas the second phase is more basic and comprises of alkali feldspar less fine-middle grained qz gabbroes and qz-opx diorites and gabbro-diorites with gabbroic and ophitic microstructure.  These plutons intrude granulite facies metamorphic bedrock. The age of those plutons is around 1170 ± 10 Ma. The first phase has the age around 1170-1190 Ma, whilst the second phase has the age of 1150 1170 Ma. The interval of peak metamorphism is constrained by 1250-1170 Ma. We combine together thermodynamic modelling and geochemistry (isotope geochemistry in Sm-Nd, Rb-Sr and Pb-Pb systems, Hf and O stable isotopes data on zircons) to create a petrological model for opx granitoids formation. As a result of such modelling we are able to prove that pluthons were crystallized at grnulitic facies and dry conditions. Within the first phase of the crystal fractionation the process is traced. These phases have also different isotope characteristics. For example, the ε(Nd)0 is around -7 to -12 for the second more basic phase and – 16 to -22 for the first opx granitoids phase. It is assumed that the structures of the Banger oasis are the result of the reworking of the Yilgarn craton in the Early Proterozoic. Afterwards there was a collision and amalgamation of the supercontinent Rodinia, and at the final stage, the intrusion of opx granitoids occurred. We consider a presence of mantle material in the formation of charnockite melts. It is possible that the differentiation of tholeiitic magma and the mixing with the crustal component took place.  That might also go along with delamination of the thickened continental crust after the completion of collisional orogeny. Mixing with mantle material could occur at lowest levels of the crust and afterwards the mixed melt moves consequently to the higher levels and differentiates in chambers. Last phases are more enriched in mantle component according to modelling and geochemistry.
Overview of the 2019 Sentinel-5p TROpomi vaLIdation eXperiment (TROLIX)
Authors: Apituley Arnoud , Kreher Karin , Piters Ankie , Sullivan John , vanRoozendael Michel , Vlemmix Tim , den Hoed Mirjam , Frumau Arnoud , Henzing Bas , Speet Bart , Vonk Jan , Veefkind Pepijn , Alves Diego , Cacheffo Alexandre ,   TROLIX-Team
Published: March 2020

For the validation of Sentinel-5p/TROPOMI the TROpomi vaLIdation eXperiment (TROLIX) was held in the Netherlands based at the Cabauw Experimental Site for Atmospheric Research during September 2019. TROLIX consisted of active and passive remote sensing platforms in conjunction with several balloon-borne and surface measurements.

The intensive observations will serve to establish the quality of TROPOMI L2 main data products (UVAI, Aerosol Layer Height, NO2, O3, HCHO, Clouds) under realistic conditions with varying cloud cover and a wide range of atmospheric conditions.

Since TROPOMI is a hyperspectral imager with a very high spatial resolution of 3.6 x 5.6 km2, understanding local effects such as inhomogeneous sources of pollution, sub-pixel clouds and variations in ground albedo is important to interpret TROPOMI results. Therefore, the campaign included sub-pixel resolution local networks of sensors, involving MAXDOAS and Pandora instruments, around Cabauw (rural) and within the city of Rotterdam (urban). Utilising its comprehensive in-situ and remote sensing observation program in and around the 213 m meteorological tower, Cabauw was the main site of the campaign with focus on vertical profiling using lidar instruments for aerosols, clouds, water vapor, tropospheric and stratospheric ozone, as well as balloon-borne sensors for NO2 and ozone.

The data set collected can be directly compared to the TROPOMI L2 data products, while measurements of parameters related to a-priori data and auxiliary parameters that infuence the quality of the L2 products such as aerosol and cloud profiles and in-situ aerosol and atmospheric chemistry were also collected.

This paper gives an overview of the campaign, and an overview of the participating main and ancillary instrumentation and preliminary results.

Future activities include the deployment in 2020 of an airborne hyperspectral imager.
Nonlinear boosting during extreme El Niño through local air-sea interaction
Authors: An Soon-Il , Xie Shang-Ping
Published: March 2020

The delayed negative feedback is a key process for the turnabout between El Niño and La Niña. Since the intensity of this dynamical negative feedback is determined by itself, the stronger event is supposed be strongly damped during the decaying phase. However, the extreme El Niño actually lived longer than the normal El Niño. Here, we propose that the far-eastward extension of the warm pool promotes the positive SST tendency during the decaying phase of El Niño so disrupting a strong decay. The warm pool expansion accompanies by the expansion of the convective threshold region toward the eastern Pacific. During and after the mature phase of the extreme El Niño, therefore the rainfall band and the enhanced westerly anomalies over the eastern Pacific move to the east, which enhances the upwelling. This eastward migration of surface winds also plays a role of out-of-phase relationship between SST anomaly and subsurface temperature anomaly. All these processes results in the positive SST tendency through the positive nonlinear dynamical heating. This positive SST tendency maintains the warm eastern Pacific until the following summer.
Evaluation of Satellite-Based Optical and Thermal Trapezoid Methods for Groundwater Table Depth Monitoring in Estonian Bogs
Authors: Burdun Iuliia , Sagris Valentina , Bechtold Michel , Komisarenko Viacheslav , Mander Ülo , De Lannoy Gabrielle
Published: March 2020

Groundwater table depth and peat moisture content are of crucial importance for many peatland processes, like for example their greenhouse gas budget. Thus, there is a strong need for remote sensing techniques that allow to spatially monitor these critical moisture conditions to quantify the hydrological responses to climate change and other anthropogenic disturbances. Previous studies have demonstrated the usefulness but also limitations of microwave observations for peatland moisture monitoring at the large scale. Here, we explore the potential of techniques based on optical and thermal imagery for smaller scale applications.

Satellite-derived land surface temperature (LST) as well as shortwave infrared transformed reflectance (STR) are sensitive to soil moisture conditions in mineral soils. Both data form, together with remotely sensed vegetation indices (VIs), trapezoids in the LST-VI and STR-VI space with the highest range of possible LST and STR for bare soil conditions. The lowest and highest LST and STR along the vegetation cover gradient define the wet and dry edge, respectively. In this study, we used Landsat 7 and Landsat 8 satellite data for the vegetation periods from 2008 through 2019 to calculate various VIs, LST and STR for hemiboreal raised bogs in Estonia. Two common approaches for the determination of wet and dry edges for the LST-based method were applied and compared. The first approach estimates the edges directly from the observed values of VIs and LST for each scene; while the second one relies on modelled theoretical edges for each scene. In contrast, the STR-VI trapezoid is derived from observed values from all scenes as proposed in literature. The trapezoids are used to calculate the dryness index of each Landsat pixel by linearly scaling between the wet and dry edge. These indices are evaluated with measured groundwater table depth time series. Preliminary results indicate that, for our study area, suitable LST-based trapezoids cannot be derived from satellite observations alone, indicated by the low dependency of the resulting dryness index on groundwater table depth. Evaluation of the theoretically-derived trapezoids and the STR-VI is ongoing and will be discussed.
InSAR Imaging of White Island from 2014 to 2020: Insights into the 2019 Phreatic Eruption
Authors: Cao Yunmeng , Trippanera Daniele , Li Xing , Nobile Adriano , Yunjun Zhang , Passarelli Luigi , Xu Wenbin , Jónsson Sigurjón
Published: March 2020

At 14:11 NZDT (01:11 UTC) on 9 December 2019, an explosive eruption (VEI=2) occurred on White/Whakaari Island in New Zealand’s northeast Bay of Plenty. The sudden eruption claimed 20 lives among the 47 tourists who were on the island at the time of the eruption. Several volcano-tectonic features overlap in the island such as a major caldera rim collapsing scarp to the west, a landslide, a crater lake and a large shallow hydrothermal system at the center, making complex the understanding of the eruption triggering factors. Here we use Sentinel-1 Interferometric Synthetic Aperture Radar (InSAR) data from 3 different tracks (1 ascending and 2 descending) spanning the period of 2014-2020 to investigate the spatio-temporal surface deformation evolution of White Island in the years before the eruption. By analyzing the InSAR time-series displacements between the two eruptions of April 2016 and December 2019, at least 4 separate stages can be identified that possibly relate to different parts of the volcanic eruptive cycle:  1) During April 2016 - February 2018, the crater lake edge and the western sub-crater wall rapidly moved downslope at a rate of ~6 cm/yr, while the central sub-crater area uplifted at a rate of ~3 cm/yr; 2) From February 2018 to January 2019, both the western and the central sub-craters uplifted at a rate of ~5 cm/yr; 3) During  the following six months, from January 2019 to June 2019, the western sub-crater started moving downslope again at a rate of ~3 cm/yr, while the central sub-cater kept moving up at a rate of ~4 cm/yr; 4) And finally, during June 2019 - December 2019 (until the eruption), uplift occurred around the western sub-crater again at a similar rate as in the central sub-crater area (~ 4 cm/yr). Seismic records before the eruption show that approximately 500 volcanic earthquakes located at a depth of ~ 5 km occurred at the southwestern part of White Island on June 2019, that may point to a shallow level intrusion of new magma. This upcoming magma might then have pressurized the shallow hydrothermal system during the fourth-stage uplift. Modeling of the uplift during June 2019 to December 2019 indicates a shallow source located at only ~200 m below the surface in the vicinity of the crater lake, likely coinciding with the shallow hydrothermal system responsible for the final 2019 phreatic eruption.
Laser Ranging Interferometer on GRACE Follow-On: Current Status
Authors: Müller Vitali ,   GRACE Follow-On LRI Team
Published: March 2020

The GRACE Follow-On satellites were launched on 22nd May 2018 to continue the measurement of Earth’s gravity field from the GRACE satellites (2002-2017). A few weeks later, an inter-satellite laser link was established with the novel Laser Ranging Interferometer (LRI), which offers an additional measurement of the inter-satellite range next to the one provided by the conventional microwave ranging instrument. The LRI is the first optical interferometer in space between orbiters, which has demonstrated to measure distance variations with a noise below 1 nm/rtHz at Fourier frequencies around 1 Hz, well below the requirement of 80 nm/rtHz.

In this talk, we provide an overview on the LRI and present the current status and results regarding the characterization of the instrument. We will address the scale factor, which is needed to convert the phase measurements to a displacement, and the removal of phase jumps that are correlated to attitude thruster activations. Moreover, the results comprise the coupling of attitude variations into the measured range, which is determined by means of the center-of-mass calibration maneuvers. This coupling is expected to be one of the major error sources at low frequencies, however, it is not directly apparent due to the large gravity signal.

We conclude with some learned lessons and potential modifications of the interferometry for future geodetic missions.
Seismic and geodetic response to crustal deformation in Krísuvík volcanic system, southwest Iceland
Authors: M. Parameswaran Revathy , Th. Bjarnason Ingi , Sigmundsson Freysteinn
Published: March 2020

The Reykjanes Peninsula (RP) is a transtensional plate boundary in southwest Iceland that marks the transition of the Mid-Atlantic Ridge (MAR) from the offshore divergent Reykjanes Ridge (RR) in the west to the South Iceland Seismic Zone (SISZ) in the east. The seismicity here trends ~N80°E in central RP and bends to ~N45°E at its western tip as it joins RR. Seismic surveys, geodetic studies, and recent GPS-based kinematic models indicate that the seismic zone is a collection of strike-slip and normal faults (e.g., Keiding et al., 2008). Meanwhile, the tectonic processes in the region also manifest as NE-SW trending volcanic fissures and normal faults, and N-S oriented dextral faults (e.g., Clifton and Kattenhorn, 2006). The largest of these fissure and normal-fault systems in RP is the Krísuvík-Trölladyngja volcanic system, which is a high-energy geothermal zone. The seismicity here predominantly manifests RP’s transtentional tectonics; however, also hosts triggered events such as those following the 17 June 2000 Mw6.5 earthquake in the SISZ (Árnadottir et al., 2004) ~80 km east of Krísuvík. Stress inversions of microearthquakes from 1997-2006 in the RP indicate that the current stress state is mostly strike-slip with increased normal component to the west, indicating that the seismicity is driven by plate diverging motion (Keiding et al., 2009). However, the geothermal system in Krísuvík is a potential secondary source for triggered seismicity and deformation. This study uses seismic and geodetic data to evaluate the activity in the Krísuvík-Trölladyngja volcanic system. The seismic data is used to identify specific areas of focused activity and evaluate variations in the stress field associated with plate motion and/or geothermal activity over space and time. The data used, within the time period 2007-2016, was collected by the the South Icelandic Lowland (SIL) seismic network operated and managed by the Iceland Meterological Office (IMO). Furthermore, variations in seismicity are compared to crustal deformation observed with TerraSAR-X images from 2009-2019. Crustal changes in the Krísuvík area are quantified to develop a model for corresponding deformation sources. These changes are then correlated with the stress-field variations determined with seismic analysis.
A new elevation change time series of the Antarctic Ice Sheet from Envisat and CryoSat-2 radar altimetry
Authors: Zhang Baojun , Yang Quanming , Wang Zemin , Geng Hong , An Jiachun , Zhang Shengjun
Published: March 2020

Satellite altimetry is an important data source for ice sheet change observation. The long-term time series of ice sheet changes can be obtained by combining satellite altimetry missions with similar sensor characteristics. Then, how to correct the inter-mission offsets becomes an important scientific issue. Review of previous studies, we found that the observations of satellite ascending and descending orbits also have an important influence on the estimation of inter-mission offsets. On this basis, have created a new least-square fitting mathematical model to estimate and correct the errors of ascending and descending orbits and inter-mission offsets by introducing the inter-mission offsets terms related to the observations of ascending and descending orbits. Utilizing this model, we developed a time series of monthly Antarctic ice sheet elevation changes of 5 km grid from May 2002 to April 2019. A validation with surface elevation from airborne observations and a comparison with surface elevation changes from ICESat proved that the proposed model can successfully estimate and correct the errors and be used to construct multi-mission surface elevation time series. Without a doubt, the temporal and spatial changes of Antarctic ice sheet elevation can be obtained from our monthly grid time series. From the time series, we find that over the period May 2002 to April 2019 the loss of ice and snow in the Antarctic ice sheet mainly occurred in the glaciers along the Amundsen coast in the West Antarctic and the Totten glacier in the East Antarctic, while the accumulation took place in Queen Maud of the East Antarctic. In May 2002, the Antarctic ice sheet experienced a volume loss of -71.4 ± 11.7 km3/yr, with an acceleration of –5.8 ± 1.2 km3/yr2 over the period May 2002 to April 2019, including 45.0 ± 9.6 km3/yr and 0.1 ±1.0 km3/yr2 for the East Antarctic ice sheet, -97.0 ± 4.4 km3/yr and -7.6 ±0.5 km3/yr2 for the West Antarctic ice sheet and -19.5 ± 5.3 km3/yr and 1.7 ±0.5 km3/yr2 for the Antarctic Peninsula ice sheet.
A dynamic Stern layer model to explain high salinity zeta potential measurements on sandstones
Authors: Leroy Philippe , Li Shuai
Published: March 2020

Exploring the electrical properties of the mineral-water interface for interpreting geophysical electrical measurements is a very challenging work because of the low specific surface area of minerals such as quartz or calcite. Only few methods exist to probe the properties of the electrical double layer (EDL) compensating the surface charge of minerals. Among them, there is the streaming potential (SP) method where the applied water pressure difference generates a pore water flow displacing the mobile counter-ions in excess in the EDL, hence creating a measurable electrical potential difference, the streaming potential. During SP measurements, the exact position of the shear plane from the mineral surface is not known and it is widely accepted that the shear plane is located between the compact Stern layer and the diffuse layer. In our study, we show that the assumption that there is no water flow in the Stern layer has no physical basis for sandstones in contact with a NaCl electrolyte because water molecules around counter-ions in the Stern layer may have bulk-like properties. Using a basic Stern model to simulate surface complexation reactions and considering water flow in the Stern layer, we reproduced the zeta potential measurements on sandstones over a large salinity range from about 10-2 to 5.5 M NaCl. The “anomalous” high salinity zeta potential data can not be reproduced by a surface complexation model considering water flow only in the diffuse layer. Our ability to explain these measurements suggests that the shear plane may be located between the mineral surface and the Stern layer, i.e. closer to the surface than previously thought, which may have strong implications for the modelling of the surface electrical properties of the minerals.
Geophysical and Geological investigations of a major Miocene fault system within the city of Vienna: evidence for active tectonics
Authors: Salcher Bernhard , Otto Jan-Christoph , Neuhuber Stephanie , Lüthgens Christopher , Grupe Sabine , Payer Thomas , Fiebig Markus
Published: March 2020

We present investigations of a major Miocene fault system crossing the city of Vienna by using sedimentological, geophysical, remote sensing and numerical age dating methods. The fault zone is located at the western edge of the Vienna Basin, a c. 55 km wide and c. 200 km long rhomb-shaped pull-apart basin, separating the mountain ranges of the Alps and Carpathians. At its western edge a major sidewall fault, the Leopoldsdorf Fault System  vertically offsets alpine units by up to 5 km. In this study, we focus on Pleistocene fluvial sediments of the Danube deposited along this fault zone. Distribution and facies provide suitable conditions to speculate on Quaternary fault activity. Fluvial gravels rest on top of fine-grained, marine sediments of the Miocene. Quaternary uplift preserved these sediments in the form of terraces that were extensively covered by Pleistocene aeolian deposits (i.e. loess). Later, solifluction affected those fine-grained sediments and obliterated the terrace steps resulting in a relative homogenously inclined top as well as a flat accumulation zone at the toe of the slope. Age brackets of Quaternary deposits are provided from redeposited quartz gravels using cosmogenically produced 26Al and 10Be as well as luminescence ages of the loess-like cover sediments.

The high resistivity contrast of the coarse-grained sediments to the underlying fine-grained marine sediments and the overlying loess deposits provided excellent conditions to infer the geometry of the fluvial deposits. Accordingly, we used electrical resistivity tomography and data derived from driller’s lithologic logs to constrain possible vertical offset of terraces. Possible surface ruptures were discussed by utilizing data from LiDAR-based high-resolution digital elevation models.
Volcanic fluxes over the last millennium as recorded in the GV7 ice core (Northern Victoria Land, Antarctica)
Authors: Traversi Rita , Becagli Silvia , Severi Mirko , Nardin Raffaello , Caiazzo Laura , Amore Alessandra , Frezzotti Massimo , Stenni Barbara
Published: March 2020

Explosive volcanic eruptions are able to affect significantly the atmosphere for 2‐3 years. During this time, volcanic products (mainly H2SO4) with high residence  time are stored in the stratosphere/troposphere, and eventually deposited onto polar ice caps; snow layers may thus record signals providing a history of past  volcanic events. A high resolution sulphate concentration profile along a 197 m long ice core drilled at GV7 (Northern Victoria Land) was obtained by Ion Chromatography. The relatively high accumulation rate (241±13 mm we yr-1) and the 5‐cm resolution allowed a preliminary counted age scale. The obtained stratigraphy covers roughly the last millennium and 24 major volcanic eruptions were identified, dated and  ascribed to a source volcano. The deposition flux of volcanic sulfate was calculated and the results were compared with data from other Antarctic ice cores at regional and continental scale. Our results show that the regional variability is of the same order of magnitude  of the continental scale.
Climate projections in fine resolution downscaling over South America: trends and classification of cyclonic systems
Authors: Porfírio da Rocha Rosmeri , Reboita Michelle Simões , Crespo Natália Machado , de Jesus Eduardo Marcos , Cardoso Andressa Andrade , Dutra Lívia Márcia Mosso , Nunes Ana Maria Bueno
Published: March 2020

Cyclones developing in eastern coast of South America impact weather and control the climate in most parts of the continent as well as over the South Atlantic Ocean. Current knowledge of these cyclones shows that they can have different thermal and dynamic structures along their lifecycles being classified as tropical, subtropical or extratropical. Cyclones occurring over the sea generate intense near-surface winds with major impacts on human activities and ecosystems. Given this context, we are producing fine resolution (~25 km) dynamic downscaling with RegCM4 to investigate the climatic trends of the different phases of cyclones over the southwest South Atlantic Ocean. Special emphasis will be given on the contribution of subtropical cyclones causing extreme events (rainfall and wind) in eastern Brazil. The simulations cover South America and wider area of South Atlantic Ocean. For evaluation simulation RegCM4 is forced by ERA-Interim reanalysis, while for the projections by CMIP5 models under RCP4.5 and RCP8.5 scenarios. Cyclones are tracked using an algorithm based on cyclonic relative vorticity. In this study we present the climatology of all cyclones provided by the ERA-Interim evaluation simulation in the period 1979-2015. Basically, we discuss the ability of fine resolution simulation in reproducing the main cyclogenetic areas over the continent, seasonality and interannual variability of cyclones. Comparisons with previous simulations allow discussing the impact of fine resolution downscaling on the climatological features of all cyclones and their classification in South America domain.    
Reconstruction of Early Holocene jokulhlaups along the Hvita River and Gullfoss waterfall, Iceland
Authors: Wells Greta , Sæmundsson Þorsteinn , Luzzadder-Beach Sheryl , Beach Timothy , Dugmore Andrew
Published: March 2020

Glacial lake outburst floods (GLOFs) have occurred across the planet throughout the Quaternary and are a significant geohazard in Arctic and alpine regions today. Iceland experiences more frequent GLOFs—known in Icelandic as jökulhlaups—than nearly anywhere on Earth, yet most research focuses on floods triggered by subglacial volcanic and geothermal activity. However, floods from proglacial lakes may be a better analogue to most global GLOFs.

As the Icelandic Ice Sheet retreated across Iceland in the Late Pleistocene-Early Holocene, meltwater pooled at ice margins and periodically drained in jökulhlaups. Some of the most catastrophic floods drained from ice-dammed Glacial Lake Kjölur, surging across southwestern Iceland from the interior highlands to the Atlantic Ocean. These floods left extensive geomorphologic evidence along the modern-day course of the Hvítá River, including canyons, scoured bedrock, boulder deposits, and Gullfoss—Iceland’s most famous waterfall. The largest events reached an estimated maximum peak discharge of 300,000 m3 s-1, ranking them among the largest known floods in Iceland and on Earth.

Yet, all our evidence for the Kjölur jökulhlaups comes from only one publication to date (Tómasson, 1993). My research employs new methods to better constrain flood timing, routing, magnitude, and recurrence interval at this underexplored site. This talk presents new and synthesized jökulhlaup geomorphologic evidence; HEC-RAS hydraulic modeling results of flow magnitude and routing; and ongoing geochronological analyses using cosmogenic nuclide exposure dating and tephrochronology. It also situates these events within Icelandic Ice Sheet deglaciation chronology and environmental change at the Pleistocene-Holocene transition. Finally, it examines the Kjölur floods as an analogue to contemporary ice sheet response, proglacial lake formation, and jökulhlaup processes and landscape evolution in Arctic and alpine regions worldwide, where GLOFs pose an increasing risk to downstream communities due to climate-driven meltwater lake expansion.  

Citation: Tómasson, H., 1993. Jökulstífluð vötn á Kili og hamfarahlaup í Hvítá í Árnessýslu. Náttúrufræðingurinn 62, 77-98.
Impact of large-scale atmospheric circulation changes over the North Atlantic on the wind climate of the Baltic Sea area for the period 1948/49-2018/19
Authors: Post Piia , Lehmann Andreas
Published: March 2020

A detailed assessment of climate variability of the Baltic Sea area for the period 1958-2008 (Lehmann et al. 2011) revealed that changes in the warming trend since the mid-1980s, were associated with changes in the large-scale atmospheric circulation over the North Atlantic. The analysis of winter sea level pressure (SLP) data highlighted considerable changes in intensification and location of storm tracks, in parallel with the eastward shift of the North Atlantic Oscillation (NAO) centres of action. Additionally, a seasonal shift of strong wind events from autumn to winter and early spring exists for the Baltic area. Lehmann et al. (2002) showed that different atmospheric circulation regimes force different circulation patterns in the Baltic Sea. Furthermore, as atmospheric circulation, to a large extent, controls patterns of water circulation and biophysical aspects relevant for biological production, such as the vertical distribution of temperature and salinity, alterations in weather regimes may severely impact the trophic structure and functioning of marine food webs (Hinrichsen et al. 2007). To understand the processes linking changes in the marine environment and climate variability, it is essential to investigate all components of the climate system which of course include also the large-scale atmospheric circulation. Now, since extended time series data (1948-2018) for additional 20 years are available, it is interesting to investigate recent changes/shifts of the large-scale atmospheric conditions and their impact on the wind climate over the Baltic Sea area.