bluuebunny/crossref_metadata_2025 huggingface dataset:
Fluid-induced Seismicity Depends on Injection Rate
Authors: Dresen Georg , Wang Lei , Kwiatek Grzegorz , Rybacki Erik , Bonnelye Audrey , Bohnhoff Marco
Published: March 2021

Fluid injection causes fault slip that is partitioned in aseismic and seismic moment release. EGS stimulation campaigns have shown that in addition to total fluid volume injected also the rates of injection and fluid pressure increase affect seismic moment release. We investigate the effect of injection rate on slip characteristics, strain partitioning and energy budget in laboratory fluid injection experiments on reservoir sandstone samples in a triaxial deformation apparatus equipped with a 16-channel acoustic emission (AE) recording system. We injected fluid in sawcut samples containing a critically stressed fault at different pressurization rates. In general, fluid-induced fault deformation is dominantly aseismic. We find slow stick-slip events are induced at high fluid pressurization rate while steady fault creep occurs in response to low fluid pressurization rate. The released total seismic moment is found to be related to total injected volume, independent of fault slip behavior. Seismic moment release rate of AE is related to measured fault slip velocity. Total potential energy change and fracture energy release rate are defined by fault stiffness and largely independent of injection rate. Breakdown power density scales with slip rate and is significantly higher for fast injection and pressurization rates. The relation between moment release and injected volume is affected by fault slip behavior, characterized by a linear relation for slip at constant rate and fault creep while a cubic relation is evident for unstable and dynamic slip. Our experimental results allow separating a stable pressure-controlled injection phase with low rate of energy dissipation from a run-away phase, where breakdown power is high and cumulative moment release with injected volume is non-linear.
Mapping faults in an urban environment from borehole data (Oviedo, NW Spain)
Authors: Pando Luis , López-Fernández Carlos , Flor-Blanco Germán , Llana-Fúnez Sergio
Published: March 2021

The detailed geological mapping in built-up areas presents challenges that arise mainly from the covering of outcrops, and the erase of natural geomorphological features during earthmoving works related to urban development. However, it also benefits from the existence of closely spaced site investigation data, including boreholes, not commonly available outside the cities.

This contribution explains the procedure carried out to improve the interpretation of faults below the city centre of an urban core located in NW Spain. Oviedo is placed on a basin formed by an alternation of sub-horizontal carbonate and siliciclastic formations of Cretaceous age, over which lies an unconformable cover of Paleogene fluvial-lacustrine deposits mostly composed by clays and marls. The paleorelief over which the Paleogene was deposited results in great lateral changes in the thickness of these sediments. Moreover, the basin was deformed during the Alpine convergence in northern Iberia developing an open syncline oriented East-West. During the shortening, a number of minor faults cutting across the gently dipping Cretaceous and Paleogene deposits affect moderately the cartographic pattern of lithostratigraphic units.

Therefore, this research was focused on the preferential use of information on the ground provided by hundreds of rotary boreholes managed through a GIS-type geotechnical database. The procedure of semiautomatic identification consisted essentially of investigating the spatial variations of the boundary between two Cretaceous formations, in order to find anomalies attributable to fault displacements. In using this boundary as a strain marker for post-depositional deformation, two scales were approached, one aimed at the identification of large faults, and another with greater detail based on trend-surface analysis for fractures of smaller size and local incidence (vertical offset less than 10 m).

The research has allowed to discuss faults deduced in previous geological maps, helping to interpret thickenings related to the paleorelief, and also to recognize the existence of structures not described in the regional literature. This study provides also better constrains to the analysis of the structural relationships between the faults affecting the Mesozoic-Palaeogene basin, and the Alpine reactivation of the underlying Palaeozoic basement.
Intense dB/dt variations driven by near-Earth Bursty Bulk Flows (BBFs): A case study
Authors: Wei Dong , Dunlop Malcolm , Yang Junying , Dong Xiangcheng , Yu Yiqun , Wang Tieyan
Published: March 2021

During geomagnetically disturbed times the surface geomagnetic field often changes abruptly, producing geomagnetically induced currents (GICs) in a number of ground based systems. There are, however, few studies reporting GIC effects which are driven directly by bursty bulk flows (BBFs) in the inner magnetosphere. In this study, we investigate the characteristics and responses of the magnetosphere-ionosphere-ground system during the 7 January 2015 storm by using a multi-point approach which combines space-borne measurements and ground magnetic observations. During the event, multiple BBFs are detected in the inner magnetosphere while the magnetic footprints of both magnetospheric and ionospheric satellites map to the same conjugate region surrounded by a group of magnetometer ground stations. It is suggested that the observed, localized substorm currents are caused by the observed magnetospheric BBFs, giving rise to intense geomagnetic perturbations. Our results provide direct evidence that the wide-range of intense dB/dt (and dH/dt) variations are associated with a large-scale, substorm current system, driven by multiple BBFs.
Revisiting non-tidal ocean loading corrections for high precision terrestrial gravimetry
Authors: Antokoletz Ezequiel D. , Wziontek Hartmut , Dobslaw Henryk , Tocho Claudia N.
Published: March 2021

In modelling of atmospheric loading effects in terrestrial gravimetry by numerical weather models, often the Inverse Barometer (IB) hypothesis is applied over oceans. This simple assumption implies an isostatic compensation of the oceans to atmospheric pressure changes, causing no net deformation of the seafloor. However, the IB hypothesis is in general not valid for periods shorter than a few weeks and, consequently, the ocean dynamics cannot be neglected. In particular, for the correction of high precision gravity time series as e.g. obtained from superconducting gravimeters, it is essential to model even small contributions in order to separate different effects. When including non-tidal ocean loading effects from ocean circulation models into atmospheric models, special care has to be taken of the interface between the atmosphere and the oceans in order not to account contributions twice.

The established approach for modelling non-tidal ocean loading effects is revised in this study. When combining it with the modelling of atmospheric effects for terrestrial gravimetry, it is shown that Newtonian attraction contributions from the atmosphere may be accounted twice. To solve this problem, an alternative is proposed and tested which further reduces the variability of the gravity residuals, as shown for a set of four superconducting gravity meters globally distributed.

The improvement is achieved by a different treatment of the Newtonian attraction component related to the IB effect. Discrepancies up to the μGal level are demonstrated, depending on the location of the station. With several simplifications, the approach can be made operational and included in existing services, further improving the compatibility of terrestrial gravity time series with satellite gravity observations.
An updated national-scale mangrove forest map in China Using Sentinel-1 and Sentinel-2 Time-Series Data with Google Earth Engine
Authors: Hu Luojia , Yao Wei , Yu Zhitong , Huang Yan
Published: March 2021

A high resolution mangrove map (e.g., 10-m), which can identify mangrove patches with small size (< 1 ha), is a central component to quantify ecosystem functions and help government take effective steps to protect mangroves, because the increasing small mangrove patches, due to artificial destruction and plantation of new mangrove trees, are vulnerable to climate change and sea level rise, and important for estimating mangrove habitat connectivity with adjacent coastal ecosystems as well as reducing the uncertainty of carbon storage estimation. However, latest national scale mangrove forest maps mainly derived from Landsat imagery with 30-m resolution are relatively coarse to accurately characterize the distribution of mangrove forests, especially those of small size (area < 1 ha). Sentinel imagery with 10-m resolution provide the opportunity for identifying these small mangrove patches and generating high-resolution mangrove forest maps. Here, we used spectral/backscatter-temporal variability metrics (quantiles) derived from Sentinel-1 SAR (Synthetic Aperture Radar) and sentinel-2 MSI (Multispectral Instrument) time-series imagery as input features for random forest to classify mangroves in China. We found that Sentinel-2 imagery is more effective than Sentinel-1 in mangrove extraction, and a combination of SAR and MSI imagery can get a better accuracy (F1-score of 0.94) than using them separately (F1-score of 0.88 using Sentinel-1 only and 0.895 using Sentinel-2 only). The 10-m mangrove map derived by combining SAR and MSI data identified 20,003 ha mangroves in China and the areas of small mangrove patches (< 1 ha) was 1741 ha, occupying 8.7% of the whole mangrove area. The largest area (819 ha) of small mangrove patches is located in Guangdong Province, and in Fujian the percentage of small mangrove patches in total mangrove area is the highest (11.4%). A comparison with existing 30-m mangrove products showed noticeable disagreement, indicating the necessity for generating mangrove extent product with 10-m resolution. This study demonstrates the significant potential of using Sentinel-1 and Sentinel-2 images to produce an accurate and high-resolution mangrove forest map with Google Earth Engine (GEE). The mangrove forest maps are expected to provide critical information to conservation managers, scientists, and other stakeholders in monitoring the dynamics of mangrove forest.
Scalar compensation of shipboard three-component magnetic measurements and applications for marine geophysical mapping
Authors: reiller hugo , munschy marc , oelher jean-françois , lucas sylvain , rouxel didier
Published: March 2021

Since the 70’s, ship-mounted three-component magnetometers are used for marine geophysical mapping, with the benefits of being able to be operated permanently with a minimum of technical maintenance. However, to obtain accuracies similar to those of ship-towed absolute scalar magnetometers, the intense interfering magnetic fields generated by the hull and steel parts of the ship have to be removed. The most common correction method, called “vector compensation”, uses high precision inertial navigation systems in order to correct the measured data for the ship’s magnetic field and calculate the vector of the compensated magnetic field in the Earth coordinated system.

This work alternatively uses the “scalar compensation” method applied in airborne magnetism since the 60’s. The aim is to compute the intensity of the compensated magnetic field without measurements of the attitude of the vector and using linear least-square regression analysis. This correction method is applied to shipboard three-component magnetometer data acquired on different vessels during different surveys. Results are compared to those obtained with ship-towed absolute scalar magnetic measurements.

Keywords: shipboard three-component magnetic measurements; magnetic compensation; marine magnetics.
Is large-scale terrestrial hydrological cycling well represented in Earth System Models?
Authors: Ghajarnia Navid , Kalantari Zahra , Destouni Georgia
Published: March 2021

This paper addresses how large-scale terrestrial water cycling is represented in the land surface schemes of Earth System Models (ESMs). Good representation is essential, for example in regional planning for climate change adaptation and in preparation for hydro-climatic extremes that have recently set records world-wide in devastating consequences for societies and deaths of thousands of people. ESMs provide simulations and projections for the climate system and its interactions with the terrestrial hydrological cycle, and are widely used to study and prepare for associated impacts of climate change. However, the reliability of ESMs is unclear with regard to their representation of large-scale terrestrial hydrology and its changes and interactions between its key variables‎. Despite being crucial for model realism, analysis of co-variations among terrestrial hydrology variables is still largely missing in ESM performance evaluations. To bridge this research gap, we have studied and identified large-scale co-variation patterns between soil moisture (SM) and the main freshwater fluxes of runoff (R), precipitation (P), and evapotranspiration (ET) from observational data and across 6405 hydrological catchments in different parts and climates of the world. Furthermore, we have compared the identified observation-based relationships with those emerging from ESMs and reanalysis products. Our results show that the most strongly correlated freshwater variables based on observational data are also the most misrepresented hydrological patterns in ESMs and reanalysis simulations. In particular, we find SM and R to have the generally strongest large-scale correlations according to the observation-based data, across the numerous studied catchments with widely different hydroclimatic characteristics. Compared to the SM-R correlation signals, the observation-based correlations are overall weaker for the commonly expected closer dependencies of: R on P; ET on P; SM on P; and ET on SM. Nevertheless, this strongest SM-R correlation and the P-R correlation are the most misrepresented hydrological patterns in reanalysis products and ESMs. Our results also show that ESM outputs can perform relatively well in simulating individual hydrological variables, while exhibiting essential inconsistencies in simulated co-variations between variables. Such investigations of large-scale terrestrial hydrology representation by ESMs can enhance our understanding of fundamental ESM biases and uncertainties while providing important insights for systematic ESM improvement with regard to the large-scale hydrological cycling over the world’s continents and regional land areas.
Interaction of Atlantic Meridional Overturning Circulation and Sub-Polar Gyre on decadal timescale
Authors: Ogungbenro Stephen , Borchert Leonard , Brune Sebastian , Koul Vimal , Caesar Levke , Düsterhus André
Published: March 2021

North Atlantic climate variability is dominated by two important subsystems, the Atlantic Meridional Overturning Circulation (AMOC) and the Sub-Polar Gyre (SPG). While the AMOC is responsible for the transport of mass and heat into higher latitudes, SPG has been linked with large-scale changes in the subpolar marine environment. The changes in strength, intensity and positions of the constituent currents of the SPG impose variabilities in the distribution of heat and salt in the North Atlantic Ocean. Consequently, the predictability on decadal scales of the two subsystems is of huge importance for the understanding of variability in the North Atlantic.

Our contribution investigates the decadal and multi-decadal predictability of these subsystems within the Max Planck Institute for Meteorology Earth System Model (MPI-ESM). We analyse the model’s capability to predict these subsystems as well as the dependence of the two subsystems on each other. These investigations open new opportunities for a better understanding of the impact of the North Atlantic onto important marine ecosystems and its changes in the upcoming decade.
Emergent constraints on the Southern Ocean anthropogenic carbon and heat uptake
Authors: Frölicher Thomas , Terhaar Jens , Joos Fortunat
Published: March 2021

The Southern Ocean south of 30°S, occupying about a third of global surface ocean area, accounts for approximately 40% of the past anthropogenic carbon uptake and about 75% of excess heat uptake by the ocean. However, Earth system models have large difficulties in reproducing the Southern Ocean circulation, and therefore its historical and future anthropogenic carbon and excess heat uptake. In the first part of the talk, we show that there exists a tight relation across two Earth system model ensembles (CMIP5 and CMIP6) between present-day sea surface salinity in the subtropical-polar frontal zone, the formation region of mode and intermediate waters, and the past and future anthropogenic carbon uptake in the Southern Ocean. By using observations and Earth system model results, we constrain the projected cumulative Southern Ocean anthropogenic carbon uptake over 1850-2100 by the CMIP6 model ensemble to 158 ± 6 Pg C under the low-emissions scenario SSP1-2.6 and to 279 ± 14 Pg C under the high emissions scenario SSP5-8.5. Our results suggest that the Southern Ocean anthropogenic carbon sink is 14-18% larger and 46-54% less uncertain than estimated by the unconstrained CMIP6 Earth system model results. The identified constraint demonstrated the importance of the freshwater cycle for the Southern Ocean circulation and carbon cycle. In the second part of the talk, potential emergent constraints for the Southern Ocean excess heat uptake will be discussed.
Two decades of Antarctic coastal-change revealed by satellite imagery and deep learning
Authors: Baumhoer Celia A. , Dietz Andreas , Dirscherl Mariel , Kuenzer Claudia
Published: March 2021

Antarctica’s coastline is constantly changing by moving glacier and ice shelf fronts. The extent of glaciers and ice shelves influences the ice discharge and sea level contribution of the Antarctic Ice Sheet. Therefore, it is crucial to assess where ice shelf areas with strong buttressing forces are lost. So far, those changes have not been assessed for entire Antarctica within comparable time frames.

We present a framework for circum-Antarctic coastline extraction based on a U-Net architecture. Antarctic coastal-change is calculated by using a deep learning derived coastline for the year 2018 in combination with earlier manual derived coastlines of 1997 and 2009. For the first time, this allows to compare circum-Antarctic changes in glacier and ice shelf front position for the last two decades. We found that the Antarctic Ice Sheet area decreased by -29,618±1,193 km2 in extent between 1997-2008 and gained an area of 7,108±1,029km2 between 2009 and 2018. Retreat dominated for the Antarctic Peninsula and West Antarctica and advance for the East Antarctic Ice Sheet over the entire investigation period. The only exception in East Antarctica was Wilkes Land experiencing simultaneous calving front retreat of several glaciers between 2009-2018. Biggest tabular iceberg calving events occurred at Ronne and Ross Ice Shelf within their natural calving cycle between 1997-2008. Future work includes the continuous mapping of Antarctica’s coastal-change on a more frequent temporal scale.  
The influence of the solid Earth on the contribution of marine sections of the Antarctic ice sheet to future sea level change
Authors: Yousefi Maryam , Wang Jeannette , Pan Linda , Gomez Natalya , Latychev Konstantin , Mitrovica Jerry , Pollard David
Published: March 2021

The future retreat of marine-based sectors of the Antarctic Ice Sheet (AIS) and its consequent global mean sea level (GMSL) rise is driven by various climatic and non-climatic feedbacks between ice, ocean, atmosphere, and solid Earth. The primary mode of ice loss in marine sectors of the AIS is dynamic flow of ice across the grounding line into the ocean. The flux of ice across the grounding line is strongly sensitive to the thickness of ice there, which is in turn proportional to the water depth (sea level) such that sea level rise enhances ice loss and grounding line retreat while sea level fall acts to slow or stop migration of the grounding line. In response to the unloading from removal of ice mass, the underlying bedrock deforms isostatically leading to lower local sea surface which promotes stabilization of the grounding line. In addition to its effect on AIS evolution, solid Earth deformation also alters the shape and size of the ocean basin areas that are exposed as marine areas of ice retreat and influences the amount of meltwater that leaves Antarctica and contributes to global sea-level rise. The solid Earth deformational response to surface loading changes, in terms of both magnitude and timescales, depends on Earth rheology. Seismic tomography models indicate that the interior structure of the Earth is highly variable over the Antarctica with anomalously low shallow mantle viscosities across the western section of the AIS. An improved projection of the contribution from AIS to sea level change requires a consideration of this complexity in Earth structure. Here we adopt a state-of-the-art seismic velocity model to build a high-resolution 3D viscoelastic structure model beneath Antarctica. We incorporate this structure into a high spatiotemporal resolution sea-level model to simulate the influence of solid Earth deformation on contributions of the AIS evolution to future sea-level change. Our sea-level model is coupled with the dynamics of PSU ice sheet model and our calculations are based on a range of future climate forcings. We show that the influence of applying a spatially variable Earth structure is significant, particularly in the regions of West Antarctica where upper mantle viscosities are lower and the elastic lithosphere is thinned.
A physical model demonstrating critical zone structure and flow processes in headwaters
Authors: Shen Xuhui , Liu Jintao , Wang Wanjie , Han Xiaole , Zhang Jie , Li Guofang
Published: March 2021

Equipped with complex terrain structure, physical models provide an alternative way in understanding and modeling how critical zone shapes hydrologic processes in headwaters for research and education in hydrology. However, this type of physical models is limited by frustrating rain-erosion or gully-erosion. Herein, in order to replace the real-world backfilling soil, we drew on the experience of normal concrete workmanship and adjusted the raw material’s proportion for three times. And it is found that saturated hydraulic conductivity (SHC) and field moisture capacity (FMC) are both well correlated with bulk density (BD) for the developed materials in three cases. Thereby, based on the strongest correlation (R2=0.75) between SHC and BD, two-layer alternative soil has been designed through altering BD in the physical model with complex terrain. The SHC values of alternative soil are close to that of the natural soil while the FMC values are far lower. Additionally, the non-uniform scaling of bedrock terrain was applied for the convenience of teaching and construction by zooming out a steep 0.31-ha zero-order basin 130 times horizontally and 30 times vertically. And multiple observation items, including free water level, temperature and humidity of soil, as well as outflow could provide potential opportunity to explore the role of single or combined critical zone’s element in modulating streamflow. We’d like to share this effective tool to facilitate the development of critical zone science and enrich experimental teaching methods.
The discontinuous Galerkin method for sequences of earthquakes and aseismic slip
Authors: Uphoff Carsten , May Dave , Gabriel Alice-Agnes
Published: March 2021

Earthquakes and aseismic slip are typically modelled as a displacement discontinuity on a prescribed infinitesimally thin fault surface embedded in linear elastic or viscoelastic media. The fault slip behaviour can be described by laboratory-derived rate and state friction laws, which are suitable to model frictional sliding throughout the complete seismic cycle, i.e. interseismic, coseismic, and post-seismic phase. The governing time scales vary from years in the interseismic phase to seconds in the coseismic phase and the respective spatial scales vary from hundreds of kilometres of tectonic structures  to metres (or less) on-fault. Therefore, simulating the entire seismic cycle is computational challenging and as such mandates utilization of high performance computing (HPC).

We present the open-source code tandem which is designed to model quasi-dynamic sequences of earthquakes and aseismic slip (SEAS). In tandem we explore the usefulness of the symmetric interior penalty Galerkin (SIPG) method using unstructured simplicial meshes for the computation of the elastostatic response to a displacement discontinuity. The potential of the SIPG method for SEAS models lies in (i) its geometric flexibility, (ii) its high-order approximation spaces, (iii) and its natural ability to deal with discontinuities.

Using a number of 2D and 3D SCEC community benchmarks (Erickson et al., 2020) we verify the tandem SIPG implementation. Based on the same reference models, we demonstrate benefits of using highly refined unstructured meshes and a high-order geometric representation of the fault. We also explore whether using a high-order discretisation in space is advantageous. Lastly, we outline how tandem may leverage modern supercomputing resources.
Multiple crises before the big crisis: Early Messinian Eastern Mediterranean paleoclimate reconstruction inferred from biomarkers and stable isotopes (Crete, Greece)
Authors: Butiseaca Geanina-Adriana , van der Meer Marcel T. J. , Kontakiotis Giorgos , Agiadi Konstantina , Antonarakou Assimina , Mulch Andreas , Vasiliev Iuliana
Published: March 2021

Messinian Mediterranean (7.24‒5.33 Ma) was a highly dynamic environment governed by global climatic and regional tectonic activity. The impact of these two environmental factors is highly distinguishable especially during the latest Messinian (5.97–5.33 Ma), when the famous Messinian salinity crisis (MSC) affected the Mediterranean realm. However, the interplay between climate and tectonics is less studied for the earliest Messinian. Here we use biomarker analysis, coupled with compound-specific hydrogen (δ2H) and carbon isotopes (δ13C), to track changes in the hydrological budget, mean annual air temperature (MAAT), vegetation and reconstruct the sea-land climate conditions in Eastern Mediterranean between 7.2‒6.5 Ma. Our data from Agios Myron section on Crete (Greece) confirms a series of drastic environmental changes in the Eastern Mediterranean during the mentioned time interval. δ2H values of alkenones indicate highly evaporitic events accompanied by shifts in vegetation, from dominant >C3 plants to marked increasing dominance of C4, with recurrence of C3 vegetation at ~6.99 and 6.78 Ma respectively. The MAAT data indicate average values of 14⁰C and the overall trend suggests an orbitally paced continental climate, with maximum temperatures registered during eccentricity maxima. The reconstructed paleo-soil pH record follows a stepwise increasing trend towards slightly-alkaline soils, supporting an enhanced open vegetation contribution resulting from the ongoing continentalisation. These results provide new insights into the Messinian environmental conditions of the Mediterranean Sea, suggesting an ongoing restriction after 7 Ma, with multiple restrictive phases marked by increasing intensity until the final MSC event.
Climate and land-use effects on hydrological and vegetation signals during the last three millennia in southwestern Morocco
Authors: Baqloul Asmae , Schefuß Enno , Kölling Martin , Dupont Lydie , Groeneveld Jeroen , Zhao Xueqin , Reddad Hanane , Bouchaou Lhoussaine , Bouimetarhan Ilham
Published: March 2021

The southwest of Morocco is considered to be an area of refuge within the Mediterranean region, hosting the endemic tropical Argan tree. This region is presently subject to severe droughts, desertification, and land degradation, and likely facing increased climate variability and socio-economic stress in the future. Here, we use the stable hydrogen and carbon isotope composition (δD and δ13C) of plant-waxes in a high-resolution marine sediment core (GeoB8601-3) collected off Cape Ghir in southwestern Morocco, in combination with published data on pollen and XRF element ratios from the same archive. We aim to reconstruct the hydroclimate and vegetation history during the last 3000 years. Stable carbon isotope compositions of leaf waxes (δ13Cwax) show that natural vegetation in southwestern Morocco consists of C3 plants. Minor variations in δ13Cwax were positively correlated to changes in stable hydrogen isotope compositions of leaf waxes (δDwax) before 700 CE. Changes in rainfall amounts and water use efficiency indicate a clear vegetation response to precipitation changes and thus to climate forcing. After 700 CE, δDwax and δ13Cwax became de-coupled suggesting that the plant wax discharge and their isotope signals were no longer solely controlled by climate; the waxes likely mainly originate from the lowlands and carry an enriched (dry) δD signal but a depleted 13C signature. The depletion of δ13Cwax correlates with the increase of Argan pollen concentration in the record. The period between ~700 and 900 CE coincides with the Arabization of Morocco which had an impact on the demographic composition of the country leading to new agricultural habits and, as a result, on the land-use triggering a higher erosion of lowland material by the Souss River.
Assessment of global ionospheric maps performance in the Brazilian region using ionosonde data
Authors: Jerez Gabriel , Hernández-Pajares Manuel , Prol Fabricio , Alves Daniele , Monico João
Published: March 2021

In this work, we present a new method for assessing global ionospheric maps (GIM) by means of ionosonde data. The method proposed is based on the critical frequency at the F2 layer directly measured by pairs of ionosondes to assess VTEC (vertical total electron content) values from GIMs. Four strategies were investigated and, the best one was the linear interpolation of squared foF2 based on the VTEC ratio. The analysis was based on the root mean square (RMS) of the differences between the measured and estimated foF2 values at the first ionosonde from each pair. The foF2 were estimated using the values measured at the second ionosonde and interpolated to the position of the first ionosonde with the VTEC values from the GIMs. Besides the RMS values, additional ionospheric indicators (slab thickness and shape function peak) were used to complement the daily analysis. This method was tested over one of the most challenging scenarios, the Brazilian region and near the last solar cycle peak. The assessment considered four ionosondes (combined in six pairs) and thirteen GIM products available at CDDIS (Crustal Dynamics Data Information System), CORG, CODG, EHRG, ESRG, ESAG, IGRG, IGSG, JPLG, UPRG, UPCG, UQRG, WHRG and WHUG. Analysis was conducted using daily, weekly, one year, and four years of data. The analysis with daily data showed that slab thickness and shape function peak could be helpful to identify periods and regions where this method could be applied. The weekly analysis was performed to select the best strategy to interpolate the foF2 values. The analysis of one-year data (2015) was performed considering all GIMs previously mentioned. CODG, IGSG, JPLG, UQRG, WHRG, and WHUG provided the best results, with mean rates of improvement up to 42% in comparison to not using any GIM. The four-year time series (2014-2017) were analyzed considering the two products with better performance for the one-year analysis (CODG and UQRG). With data from 2014-2017, CODG and UQRG provided improvement rates of up to 49%. In general, regional and temporal ionospheric influences could be noticed in the results, with expected larger errors closer to the solar cycle peak in 2014 and at locations with pairs of ionosondes with the larger distance apart. Therefore, we have confirmed the viability of the developed approach as an assessment method to analyze GIMs quality based on ionosonde data.
Manifestation of the Pacific Decadal Oscillation in the stationary planetary waves activity
Authors: Sobaeva Daria , Zyulyaeva Yulia , Gulev Sergey
Published: March 2021

Strong quasi-decadal oscillations of the stratospheric polar vortex (SPV) intensity are in phase with the Pacific decadal oscillation (PDO). A stronger SPV is observed during the positive phase of the PDO, and during the negative phase, the intensity of the SPV is below the mean climate values. The SPV intensity anomalies, formed by the planetary waves and zonal mean flow interaction, lead to the weakening/intensification of the vortex.

This research aimed to obtain the differences in the characteristics and the spatial propagation pattern of the planetary waves in the middle troposphere and lower stratosphere during different PDO phases. We analyzed composite periods of years when the PDO index has extremely high and low values. Two periods were constructed for both positive and negative phases, the first consisting of years with El-Nino/La-Nina events and the second without prominent sea surface temperature anomalies in the tropics. 

During the wintertime in the Northern Hemisphere (December-February), wave 2 with two ridges (Siberian and North American Highs) and two troughs (Icelandic and Aleutian Lows) dominates in the middle troposphere, along with wave 1 dominating in the lower stratosphere. In the middle troposphere, at the positive phase ​​of the PDO, the amplitude of wave 2 is higher than in years with negative values of the PDO index. The differences in the Aleutian Low and the North American High intensity between the two phases are significant at the 97.5% level. In the lower stratosphere, the wave amplitude is lower at the negative phase ​​of the PDO, but we can also talk about a slight shift of the wave phase to the east. The regions of the heavy rains in the tropics during El-Nino events are the planetary waves source. They propagate from low to high latitudes, which results in modifying the characteristics and locations of the intensification of the stationary planetary waves in mid-latitudes.
ESM-Tools Version 5.0: A modular infrastructure for stand-alone and coupled Earth System Modelling (ESM)
Authors: Barbi Dirk , Andrés-Martínez Miguel , Ural Deniz , Cristini Luisa , Gierz Paul , Wieters Nadine
Published: March 2021

During the last two decades, modern societies have gradually understood the urge to tackle the climate change challenge, and consequently, a growing number of national and international initiatives have been launched with the aim of better understanding the Earth System. In this context, Earth System Modelling (ESM) has rapidly expanded, leading to a large number of research groups targeting the many components of the system at different scales and with different levels of interactions between components. This has led to the development of increasing number of models, couplings, versions tuned to address different scales or scenarios, and model-specific compilation and operating procedures. This operational complexity makes the implementation of multiple models excessively time consuming especially for less experienced modellers.

ESM-Tools is an open-source modular software written in Python, aimed to overcome many of the difficulties associated to the operation of ESMs. ESM-Tools allows for downloading, compiling and running a wide range of ESM models and coupled setups in the most important HPC facilities available in Germany. It currently supports multiple models for ocean, atmosphere, biochemistry, ice sheet, isostatic adjustment, hydrology, and land-surface, and six ocean-atmosphere and two ice-sheet-ocean-atmosphere coupled setups, through two couplers (included modularly through ESM-Interface). The tools are coded in Python while all the component and coupling information is contained in easy-to-read YAML files. The front-end user is required to provide only a short script written in YAML format, containing the experiment specific definitions. This user-friendly interface makes ESM-Tools a convenient software for training and educational purposes. Simultaneously, its modularity and the separation between the component-specific information and tool scripts facilitates the implementation and maintenance of new components, couplings and versions. ESM-Tools team of scientific programmers provides also user support, workshops and detailed documentation. The ESM-Tools were developed within the framework of the project Advance Earth System Model Capacity, supported by Helmholtz Association and has become one of the main pillars of the German infrastructure for Climate Modelling.
The Septentrional–Oriente strike-slip Fault Zone: polyphase deformation and fault strand switching in the Northern Caribbean plate boundary (Windward Passage)
Authors: Oliveira de Sa Alana , d’Acremont Elia , Leroy Sylvie , Lafuerza Sara
Published: March 2021

The northern border of the Caribbean plate is characterized by the oblique collision between the Caribbean and North American tectonic plates. Increasing obliquity of the collision between these two plates lead to complex strike-slip fault zones, which successively jump southward to accommodate the eastward escape of the Caribbean plate and the collisional indentation against the Bahama carbonate platform. The present-day Septentrional–Oriente Fault zone (SOFZ) defines the northern limit of the Caribbean plate, accommodating much of the obliquity of the convergence. Since its inception, at the end of the Oligocene, the current active style of the strike-slip boundary evolves over time. We focus our study on the Windward Passage area between the south-east of Cuba and the north-west of Haiti coast. Currently crossed by the SOFZ, the tectono-sedimentary framework of this large strait displays critical evidences to constrain the Neogene evolution of the northern boundary of the Caribbean plate. Based on seismic reflection and swath-bathymetric dataset we shed light on the structure and tectonic pattern of the Windward Passage. Our study provides structural and stratigraphic insights into relative timing of deformation along the Windward Passage and new elements to constrain the southeastward shift of the north Caribbean plate boundary until its present-day position. Contrasts in patterns of deformation on the Windward Passage area reveal a polyphase tectonic history of dominant strike-slip faulting impacted by the rate and obliquity variations of the convergence. Deformation phases recorded by the offshore sedimentary cover in the Windward Passage correlate well with the major paleogeographic reorganization episodes described onland (Late Eocene, Late Oligocene, Middle Miocene and Late Pliocene). A left-lateral shift of at least ~80 km is demonstrated by the restoration of the offset of the seismic units, estimating a Pliocene age for the onset of the SOFZ segments activity in this area.
Erosion and sediment transport models with reference to the needs of small scale
Authors: Raza Ahsan , Gaiser Thomas , Habib-Ur-Rahman Muhammad , Ahrends Hella
Published: March 2021

Information on field scale soil erosion and related sedimentation process is very important for natural resource management and sustainable farming. Plenty of models are available for study of these processes but only a few are suitable for dynamic small scale soil erosion assessments. The available models vary greatly in terms of their input requirements, analysis capabilities, process [t1] complexities, spatial and temporal scale of their intended use, practicality, the manner they represent the processes, and the type of output information they provide. The study aims in examining, theoretically, 51 models classified as physical, conceptual, and empirical based on their representation of the processes of soil erosion. The literature review shows that there is no specific model available for soil erosion prediction under agroforestry systems.   It is further suggested that models like EPIC, PERFECT, GUEST, EPM, TCRP, SLEMSA, APSIM, RillGrow, and CREAMS can be potentially used for soil erosion assessment at plot/field scale at daily time steps. Most of these models are capable to simulate the soil erosion process at small scale; further model development is needed regarding their limitations with respect to components interaction i.e., rainfall intensity, overland flow, crop cover, and their difficulties in upscaling. The research suggested that SIMPLACE network can provide modules with LintulBiomass, HillFlow, Runoff to develop new dynamic components to simulate overland flow and soil erosion incorporating improved upscaling capabilities
The Venus Climate Database
Authors: Lebonnois Sebastien , Millour Ehouarn , Martinez Antoine , Pierron Thomas , Spiga Aymeric , Chaufray Jean-Yves , Montmessin Franck , Cipriani Fabrice
Published: March 2021

We have over the years developed a state of the art Venus Global Climate Model (GCM, Lebonnois et al. 2016; Gilli et al. 2017; Garate-Lopez & Lebonnois 2018). With funding from ESA in the context of the preparation of the possible upcoming EnVision mission, we have, in the footsteps of what has been done for Mars with the Mars Climate Database (), built a Venus Climate Database (VCD) based on GCM outputs.

The VCD dataset and software overall enable users to:

- extract atmospheric quantities (temperature, pressure, winds, density, …) from the surface to the exobase (~250km) over a climatological Venusian day.

- to better bracket reality, several scenarios are provided, in order to reflect the possible range of solar activity (Extreme UV input from the Sun) which strongly affects the thermosphere (above ~150km), as well as a realistic range of UV albedo cloud top.

- in addition to a baseline climatology, the VCD software provides statistics (internal short term and day-to-day variability) along with means to add perturbations to represent Venusian weather.

At EGU we will present the VCD and its features, emphasizing how it can be useful for scientific users wanting to compare with their models or analyze observations, and for engineers planning future missions.
Remote sensing study of Ozone, NO2, and CO: Contrary effect of Indian lockdown in the free troposphere
Authors: Rawat Prajjwal , Naja Manish
Published: March 2021

We utilized IASI, OMI, TROPOMI, and GOME-2 data to quantify the effect of lockdown on the changes in ozone, CO, and NO2 concentration over India, with a primary focus on the tropospheric profiles of ozone and CO as compared to the years 2018 and 2019. Twelve populated cities and India's largest thermal power plants (TPPs) were further selected to quantify lockdown effects. Changes in ozone and CO have not been uniform over the different regions in India, including their vertical distribution. An increase (up to ~20%) in vertical ozone distribution during lockdown was observed over central and western India compared to both 2019 and 2018. However, it decreased over the southern coastal regions. Further, a significant reduction (> 20%) is observed over northern and northeast regions when compared with 2018 while a dramatic increase (> 20%) compared to 2019 is observed over northern regions. The increased ozone over north India, particularly in contrast to 2019 further shows a successive increase at higher altitudes and exhibits the role of dynamics, while, for other places like western and central India, the enhanced ozone decreases with higher altitude, which shows the effect of photochemistry and surface emissions. For CO, the lockdown effect seems to have emerged more effectively in the boundary layer, where a reduction in the range of 2 - 18% is seen except in western regions. In-contrast, a consistent yearly increase (as high as 29%) was observed from 2018 to 2020 in the free troposphere. Similar to the profiles, the total CO shows an increase (~20%) over central and western India while a moderate decrease (5%) over northern India. Like CO, an increase of NO2 (~ 15%) over the western region is also observed, particularly compared to 2019. The persistent increase of CO and NO2 over western India suggests to have contributed more from the nearby coal-based thermal power plants, which have increased their production in 2020. Contrary to other surface-based studies during the lockdown, which has shown an apparent decrease in pollutant levels, the present study shows an increase in CO, NO2, and ozone at several locations and at different altitude regions. An analysis between OMI and TROPOMI tropospheric NO2 columns show a considerable difference (> 30%) in NO2 VCD retrieval around the remote locations, e.g., the Himalaya, the remote Tibetan plateau, and oceanic regions. Further, an investigation of the ozone production regime showed NO2 limited regime over India's major part, while VOC limited regime over thermal power plants regions during the lockdown.
Will the temperature sensitivity of Arctic soil bacterial communities alter under warmed soil conditions?
Authors: Rijkers Ruud , Rousk Johannes , Aerts Rien , Weedon James Taylor
Published: March 2021

Soil temperatures are rising in the Arctic and will likely increase soil microbial activity. The magnitude of subsequent carbon effluxes is difficult to predict but is critical for evaluating the strength of the soil carbon-climate feedback as climate change intensifies. Soil respiration in the Arctic has a relatively high sensitivity to temperature increases. This is hypothesized to be a consequence of physiological adaptation of soil microbial communities to low temperatures. A variety of experimental and gradient studies have suggested that the growth-temperature relationship of bacterial communities will adapt to soil warming.  It remains an open question whether this is driven by changes in community structure. In order to test this hypothesis, we collected 8 soils from the sub- to High Arctic and exposed them to a 0-30 ⁰C temperature gradient. We determined the temperature relationships and community composition of the resulting bacterial communities. To account for substrate depletion we sampled both after 100 days, as well as after a standardized amount of respiration. Temperature relationships were computed by fitting a square root model to leucine incorporation rates measured from 0-40 ⁰C. We will show the relationship between legacy effects of the soil thermal regime and the degree of temperature adaption and discuss whether the soil bacterial community structure is likely to influence soil respiration in Arctic soils under future climate conditions.
Impact of above and below canopy air temperatures in simulation of sub-canopy longwave radiation in snow-covered boreal forests
Authors: Rutter Nick , Essery Richard
Published: March 2021

Above canopy air temperatures, as simulated prognostic variables in earth system models or as driving data in snow-physics models, are used as a basis to calculate energy transfers through forest canopies and down to the snow surface. Consequently, simulations of absorption of solar radiation, emission of longwave radiation and coupling between canopy and air temperatures become critical. Parts of the forest canopy, especially the shaded downward-facing elements, are often in equilibrium with sub-canopy air temperatures.

Measurements of sub-canopy incoming longwave radiation, air temperatures, and forest canopy structure were made in a snow-covered boreal forest, March through April 2012 in Sodankylä, Finland. Accurate simulations of longwave radiation to the snow surface were enabled by using measured sub-canopy air temperatures as a proxy for downward-facing forest canopy temperatures. However, there was a notable decoupling of measured above and below forest canopy air temperatures in stable conditions (air temperatures warmer above the canopy than below), which was enhanced during night-time. Hence, here we present results of an experiment using a multi-physics snow model including a forest canopy (FSM2.1.1) to investigate the impact of above and below canopy air temperature decoupling on simulations of sub-canopy longwave radiation. Simulations compare the use of 1- and 2-layer canopy models, and application of Monin–Obukhov similarity theory across a wide range of forest densities.