bluuebunny/crossref_metadata_2025 huggingface dataset:
Trace metals and Nd isotopes in 3.35 Ga old stromatolites of the Strelley Pool Formation (Australia) unravel the genesis of carbonates and chert
Authors: Viehmann Sebastian , Hohl Simon V. , Tepe Nathalie , Van Kranendonk Martin , Reitner Joachim , Hofmann Thilo , Koeberl Christian , Meister Patrick
Published: March 2021

Stromatolites are laminated, presumably microbial, structures, consisting largely of an authigenic precipitate, thus providing potential geochemical archives of early Earth aqueous environments and their habitability. In this study, we report trace element and Sm/Nd isotope data from Palaeoarchean stromatolites and adjacent cherts of the Strelley Pool Formation (NW Australia), obtained by ICP-MS and TIMS, to test their reliability as archives for palaeo-environmental reconstruction and to understand authigenic mineral formation. Stromatolitic carbonates plot together with the stratigraphically underlying Marble Bar cherts on a linear Sm-Nd regression line yielding an age of 3253 ±320 Ma. In contrast, associated crystal-fan carbonates yield 2718 ±220 Ma, suggesting that their Sm-Nd isotope system was altered after deposition. Geochronological information via Sm-Nd dating of black and white cherts is limited, probably due to a reset of the isotope system during an unknown Paleoproterozoic or younger alteration event. Carbonates, as well as white cherts, show shale-normalized rare earth element and yttrium patterns (REYSN; except for redox-sensitive Ce and Eu) parallel to those of modern seawater, indicating a seawater-derived origin. Positive EuSN anomalies (2.1 - 2.4), combined with heterogeneous ɛNd3.35Ga values (-3.2 to +5.8) within alternating stromatolite laminae, support that seawater chemistry was affected by both continental weathering and high-temperature hydrothermal fluids that episodically delivered chemical elements from young mafic and older felsic rock sources into the stromatolite environment. In contrast, black cherts show REYSN patterns characteristic of a non-seawater source and significant amounts of elements leached from the surrounding rocks, overprinting the pristine geochemical composition of ancient seawater. In conclusion, Archaean stromatolites indeed preserve pristine authigenic phases at the mm-scale that contain signatures representative of the water chemistry prevailing in the depositional environment of the time.
TIN-Copula bias correction of climate modeled daily maximum temperature in the MENA region
Authors: Lazoglou Georgia , Zittis George , Hadjinicolaou Panos , Lelieveld Jos
Published: March 2021

Over the last decades, the use of climate models in the projection and assessment of future climate conditions, both on global and regional scales, has become common practice. However, inevitable biases between the simulated model output and observed conditions remain, mainly due to the variable nature of the atmospheric system, and limitations in representing sub-grid-scale processes that need to be parameterized. The present study aims to test a new approach for increasing the accuracy of daily climate model output. We apply the recently introduced TIN-Copula statistical method to the results of a state-of-the-art global Earth System Model (Hadley Centre Global Environmental Model version 3 - HadGEM3). The TIN-Copula approach is a combination of Triangular Irregular Networks and Copulas that focuses on modeling the whole dependence structure of the studied variables. The study area of the current application is the Middle East and North Africa (MENA) region, a prominent global climate change hot-spot. Considering the lack of accurate and consistent observational records in the MENA, we used the ERA5 reanalysis dataset as a reference. The results of the study reveal that the TIN-Copula method significantly improves the simulation of maximum temperature, both on annual and seasonal time scales. Specifically, the HadGEM3 model tends to overestimate the ERA5 temperature data in the major part of the MENA region. This overestimation is mainly evident for the lower values of the studied data sets during all seasons, while in summer the overestimation is found in the whole data set. However, after the use the TIN-Copula method, the differences between the simulated maximum temperature and the ERA5 data were minimized in more than the 85% of the studied grids.
Phytolith biogeochemistry and silicon regulation of terrestrial biogeochemical carbon cycle
Authors: Song Zhaoliang , Wu Yuntao
Published: March 2021

Phytoliths in most terrestrial plant tissues as a result of silica biomineralization may occlude 0.1–6% of organic carbon (C). Phytolith-occluded carbon (PhytOC) comes mainly from photosynthesis and can be stable in soil and sediment environments for several hundred to thousand years. Phytolith turnover may influence terrestrial biogeochemical C cycle either directly through phytolith C sequestration or indirectly through regulating plant biomass C composition and accumulation, and soil organic carbon (SOC) stability. Phytolith C sequestration rates in terrestrial ecosystems of China increase in the following order: grasslands < forests < croplands. Active management practices including cultivation of silicon (Si)-rich plants and amendment of Si-rich materials (e.g., basalt powder and biochar) to increase aboveground net primary productivity (ANPP) and Si supply can significantly increase phytolith C sequestration. The dissolved Si from silicate weathering and phytolith dissolution can decrease plant lignin content and increase the accumulation of plant biomass C through mitigating abiotic and biotic stresses and improving stoichiometry of C, nitrogen (N) and phosphorus (P). The recovery of plant biomass C in response to Si accumulation usually exhibits an S-shaped curve under biotic stress and a bell-shaped curve under abiotic stresses. Generally, Si can recover approximately 30 to 40% of plant biomass C under abiotic and biotic stresses. Phytolith and related dissolved Si in soils can increase SOC stability through phytolith adsorption, Si and aluminum interaction, and Si and iron interaction.
Advanced monitoring of soil salinization risk in the Neretva Delta agroecosystem
Authors: Gilja Gordon , Kuspilić Neven , Romić Davor , Zovko Monika , Harasti Antonija
Published: March 2021

This paper presents the concept of the project “Advanced monitoring of soil salinization risk in the Neretva Delta agroecosystem” (Delta Sal). Aim of the project is to develop and implement an advanced system for monitoring, forecasting and reporting the water and soil conditions in the Neretva Delta agroecosystem that is primarily used for agriculture. Selected pilot location is specific due to its biodiversity – water network within the delta consists of surface irrigation and drainage canal network, carst aquifer dominated by the tidal regime while also replenished by the freshwater from the upstream river flow, all of which are used for citrus fruits production while at the same time influencing the water regime of adjacent protected salt marshes ecosystem. Neretva Delta is dominated by the traditional farming methods practiced in the polder systems. Salt water intrusion is present in the entire delta, which is reflecting on the irrigation water quality and subsequently on the agricultural production of citruses that are salt-sensitive horticultural crops. Extensive spatial and temporal monitoring of water quality data through multisensory monitoring stations will be used for development of guidelines for salt stress alleviation in citrus fruits. This paper presents the outline of the project, methodology of analysis and selection of representative agricultural parcels for the research, rationale of farmer’s current decision-making that affects the agricultural landscape pattern and proposed monitoring network. Monitoring is focused on continuous real-time measurements of surface water levels and index water velocity using radars, shallow and deep piezometers for monitoring of ground water levels, rain gauges, multiparameter water quality measurements (dissolved oxygen, water depth, electrical conductivity, total dissolved solids, salinity, pH, oxidation reduction potential, temperature, nitrate and chloride). Data is transmitted in real-time to the cloud-based interface for remote access. Integrated data management will be used in the upcoming project stages for analysis of salt water intrusion on Neretva Delta agricultural production. Final outcome of the project are guidelines for Neretva Delta management with the future outlook in the climate change context, compliant with UNFCCC convention under which this area falls into one of the most vulnerable areas in Croatia.

 

Acknowledgment:

„This work has been supported in part by the European Regional Development Fund under the project Advanced monitoring of soil salinization risk in the Neretva Delta agroecosystem (KK.05.1.1.02.0011)“
Extreme event theory applied to the solar wind
Authors: Larrodera Carlos , Nikitina Lidia , Cid Consuelo
Published: March 2021

Society’s dependence on technology has increased during the past years. Therefore, understanding the hazardous events including space weather events that lead to technological problems is now critical. As solar wind is the driver of space weather, identifying extreme solar wind is important. In this work extreme value theory is used to characterize the solar wind parameters most relevant to space weather: interplanetary magnetic field strength and proton speed. This is done using an extreme value distribution for all data above a certain threshold for each parameter. Analysis demonstrates that these thresholds are around 900 km/s for the proton speed and around 95 nT for the interplanetary magnetic field. Based on 20 years of solar wind data, we made an estimation for the interplanetary magnetic field and solar wind proton speed with return periods corresponding to 4 and 6 solar cycles with a 99% confidence interval.
Where and how the East Madagascar Current retroflection originates?
Authors: Ramanantsoa Juliano , Penven Pierrick , Raj Roshin , Renault Lionel , Ostrowski Marek , Dilmahamod Fehmi , Rouault Mathieu
Published: March 2021

In-situ and remote sensing data are used to identify three states of the East Madagascar Current (EMC) southern extension: Early-Retroflection, Canonical-Retroflection and No Retroflection. Retroflections occur 47% of the time. EMC strength regulates the retroflection state, although impinged mesoscale eddies also contribute to the retroflection formation. The Early-Retroflection is linked with the EMC volume transport. Anticyclonic eddies drifting from the central Indian Ocean to the coast favour Early-Retroflection formation, anticyclonic eddies near the southern tip of Madagascar promote the generation of Canonical Retroflection, and No-Retroflection appears to be associated with a lower Eddy Kinetic Energy (EKE). Knowledge of the EMC retroflection state could help predicting: (1) coastal upwelling South of Madagascar, (2) the South-East Madagascar phytoplankton bloom, (3) the formation of South Indian Ocean Counter Current (SICC).
Boreal soil carbon fluxes one year after a forest wildfire: impacts of burn severity and forest management
Authors: Kelly Julia , Ibáñez Theresa , Santín Cristina , Doerr Stefan , Nilsson Marie-Charlotte , Holst Thomas , Lindroth Anders , Kljun Natascha
Published: March 2021

In 2018, an extreme drought affected large parts of Europe and led to the worst fire season in over a century in Sweden. We investigated the impacts of the Ljusdal fire, the largest fire complex that year, on soil CO2 and CH4 fluxes, nutrient concentrations and microclimate in a Scots pine forest. The measurements were conducted during the first growing season after the fire. In three separate analyses, we compared stands that differed in terms of burn severity (unburnt, low and high burn severity), salvage-logging (logged or unlogged) and stand age (young: 12 years old or mature: ~100 years old at the time of the fire).

 

A mature stand affected by a high severity burn (100% tree mortality) had significantly lower soil respiration compared to a stand affected by a low severity burn (nearly 100% tree survival), but there was no difference in soil respiration between the low burn severity and unburn stands. These results indicate that autotrophic respiration plays a key role in determining post-fire soil respiration. After a high severity burn, salvage logging had no significant effects on forest soils compared to a stand where the dead trees had been left standing, although differences between these two stands are likely to become significant in the future. Stand age had a clear impact on most of the soil properties tested. Despite mean soil temperature being 5 °C warmer at a young site compared to a mature site after a high severity burn, soil respiration was lower at the young site. The young site had been clear-cut and undergone soil scarification and replanting 12 years before the fire, which is likely to have contributed to the lower nutrient availability and thinner soil organic layer there compared to the mature site. Short return intervals between disturbances such as harvesting and wildfire that remove part of the soil organic layer can thus have significant and long-term impacts on nutrient cycling and carbon exchange in the boreal forest. The boreal forest is thus vulnerable to becoming a carbon source, especially in regions where climate change is increasing the frequency of high severity wildfire and commercial timber production is expanding.
Submarine Melt Water from the 79 North Glacier (79NG, Nioghalvfjerdsbræ), northeast Greenland
Authors: Huhn Oliver , Rhein Monika , Bulsiewicz Klaus , Kanzow Torsten , Schaffer Janin , Sültenfuß Jürgen
Published: March 2021

The Greenland Ice Sheet faces accelerated melting under warming climate conditions. The involved processes are surface melting, iceberg calving, and submarine melting through the contact of warm water with marine terminating glaciers. The Nioghalvfjerdsfjorden Glacier (79 North Glacier, 79NG) is the largest marine terminating outlet glacier of the Northeast Greenland Ice Stream and has still a floating ice tongue. In the cavity, the heat of inflowing warm and saline Atlantic Water melts the floating ice shelf at its base, and the colder and fresher outflow is exported towards the shelf break and presumably south with the East Greenland Current. However, freshwater from submarine melting is hardly distinguishable from other freshwater sources off the sources by salinity alone. To identify and to quantify the fraction and distribution of submarine melt water on the northeast Greenland shelf, we use helium (He) and neon (Ne) observations, obtained directly at the calving front of the 79NG, in its close and far vicinity on the northeast Greenland shelf, and beyond the shelf break in Fram Strait during a Polarstern expedition in 2016. These lighter and low soluble noble gasses provide a unique tool to identify submarine melt water and to quantify its fractions. We calculate a submarine melt water formation rate of 14.5 ± 2.3 Gt per year, equivalent to a basal melt rate of 8.6 ± 1.4 m per year of the 79NG. Submarine melt water fractions are present on the shelf, but dilute from 1.8% at the 79NG calving front to nonsignificant in Fram Strait. A surplus of Ne on most of the shelf region indicates that up to 10% of the original water mass had been transformed to sea ice.
Effects of using the BBM rheology in the neXtSIM-F forecast platform
Authors: Williams Timothy , Korosov Anton , Rampal Pierre , Einar Olason , Bertino Laurent
Published: March 2021

The neXtSIM-F forecast platform entered into service as part of CMEMS (as product ARCTIC_ANALYSISFORECAST_PHY_ICE_002_011) in July 2020, using the neXtSIM sea ice model . It is a stand-alone sea ice model, forced with atmospheric fields from ECMWF and with ocean fields from TOPAZ4. At that time (July 2021) the model was using the Maxwell Elasto Brittle (MEB) sea ice rheology in its dynamical core. In December 2020, the forecast was upgraded to use the Brittle Bingham Maxwell (BBM) rheology, result in significant improvements to the physical results and in numerical performance and stability. We will present results obtained using this new rheology.
Diffraction imaging of sedimentary basins: An example from the Porcupine Basin 
Authors: Lowney Brydon , Whiting Lewis , Lokmer Ivan , O'Brien Gareth , Bean Christopher
Published: March 2021

Diffraction imaging is the technique of separating diffraction energy from the source wavefield and processing it independently. As diffractions are formed from objects and discontinuities, or diffractors, which are small in comparison to the wavelength, if the diffraction energy is imaged, so too are the diffractors. These diffractors take many forms such as faults, fractures, and pinch-out points, and are therefore geologically significant. Diffraction imaging has been applied here to the Porcupine Basin; a hyperextended basin located 200km to the southwest of Ireland with a rich geological history. The basin has seen interest both academically and industrially as a study on hyperextension and a potential source of hydrocarbons. The data is characterised by two distinct, basin-wide, fractured carbonates nestled between faulted sandstones and mudstones. Additionally, there are both mass-transport deposits and fans present throughout the data, which pose a further challenge for diffraction imaging. Here, we propose the usage of diffraction imaging to better image structures both within the carbonate, such as fractures, and below.

To perform diffraction imaging, we have utilised a trained Generative Adversarial Network (GAN) which automatically locates and separates the diffraction energy on pre-migrated seismic data. The data has then been migrated to create a diffraction image. This image is used in conjunction with the conventional image as an attribute, akin to coherency or semblance, to identify diffractors which may be geologically significant. Using this technique, we highlight the fracture network of a large Cretaceous chalk body present in the Porcupine, the internal structure of mass-transport deposits, potential fan edges, and additional faults within the data which may affect fluid flow pathways.
On the dynamics of physical heights and their use for the determination of accurate orthometric/normal heights
Authors: Godah Walyeldeen , Szelachowska Malgorzata , Krynski Jan
Published: March 2021

Physical heights, e.g. orthometric and normal heights, are, so far, practically considered as static heights in the majority of land areas over the world. They were traditionally determined without considering the dynamic processes of the Earth induced from temporal mass variations within the Earth’s system. The Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO) satellite missions provided unique data that allow the estimation of temporal variations of geoid heights and vertical deformations of the Earth’s surface, and thereby the dynamics of physical heights. They revealed that for the large river basin of a strong hydrological signal (e.g. the Amazon river basin), peak to peak variations of orthometric/normal height changes reach 8 cm. The objective of this research is to discuss the need of considering the dynamics of physical heights for the determination of accurate orthometric/normal heights. An approach to determine the dynamics of physical heights using the release 6 (RL06) GRACE-based Global Geopotential Models (GGMs) as well as load Love numbers from the Preliminary Reference Earth Model (PREM) was proposed. Then, the dynamics of orthometric/normal heights was modelled and predicted using the seasonal decomposition (SD) method. The proposed approach was tested over the area of Poland. The main findings reveal that the dynamics of orthometric/normal heights over the area investigated reach the level of a couple of centimetres and can be modelled and predicted with a millimetre accuracy using the SD method. Accurate orthometric/normal heights can be obtained by combining modelled dynamics of orthometric/normal heights with static orthometric/normal heights referred to a specific reference epoch.

Keywords: dynamics of physical heights, GRACE, accurate orthometric/normal heights, temporal variations of geoid/quasigeoid heights, vertical deformations of the Earth’s surface
Heterogeneous formation and partitioning of nitrous acid on water surfaces: dependency on the acidity
Authors: Zheng Jun , Ma Yan
Published: March 2021

Hydrolysis of nitrogen dioxide (NO2) has long been recognized as a major formation path of atmospheric nitrous acid (HONO), which is regarded as a dominant hydroxyl radical (OH) source, particularly in a polluted environment. Since HONO is moderately water soluble and its solubility can be highly dependent on the acidity of the water solution, the HONO formation rate and its ensuring fate may also be affected by the acidity of the water surfaces. In this work, we investigated the hydrolysis of NO2 on dilute sulfuric acid water solutions with a pH value ranging from ~3 to ~6. Both the gaseous HONO and dissolved nitrous acid solution were quantified by a wet-chemistry based HONO analyzer and ion chromatography analyses, respectively. The results showed that significant amount of HONO can participate into the aqueous phase at low acidity and as the acidity increased gas-phase HONO also increased. These results indicated that liquid water on various surfaces may both provide a reaction site for HONO formation and serve as a reservoir of HONO that can be released when the liquid water was evaporated.
Higher-level geophysical modelling
Authors: Nuterman Roman , Häfner Dion , Jochum Markus
Published: March 2021

Until recently, our pure Python, primitive equation ocean model Veros 
has been about 1.5x slower than a corresponding Fortran implementation. 
But thanks to a thriving scientific and machine learning library 
ecosystem, tremendous speed-ups on GPU, and to a lesser degree CPU, are 
within reach. Leveraging Google's JAX library, we find that our Python 
model code can reach a 2-5 times higher energy efficiency on GPU 
compared to a traditional Fortran model.

Therefore, we propose a new generation of geophysical models: One that 
combines high-level abstractions and user friendliness on one hand, and 
that leverages modern developments in high-performance computing and 
machine learning research on the other hand.

We discuss what there is to gain from building models in high-level 
programming languages, what we have achieved in Veros, and where we see 
the modelling community heading in the future.
Case studies of the relation between upper-tropospheric wave propagation and the Red Sea trough
Authors: Alizadeh Zakieh , Mohebalhojeh Alireza , Ahmadi-Givi Farhang , Mirzaei Mohammad , Khansalari Sakineh
Published: March 2021

In recent history, the eastern Mediterranean and Saudi Arabia have experienced extreme precipitation events involving significant financial and human losses. An important subset of these events is associated with the activation of the Red Sea trough (RST). In this study, the effect and role of Rossby wave propagation during three cases (Dec 1993, Jan 2011 and May 1982) of the active RST is investigated. Meanwhile, the synoptic and dynamic factors related to the tropical-extratropical interaction and the lower and upper levels of troposphere are discussed for each event. The data used were extracted from the Era-Interim subsection of the ECMWF database with a time step of 6 hours and a spatial step of 80 km in both latitude and longitude directions.

Despite differences in humidity sources and the amount of hot and humid air ascent in each event, a general pattern can be deduced in all three events. The results show that in all events from a few days before the maximum rainfall, fluxes of heat and humidity are directed to Saudi Arabia and the eastern Mediterranean and the RST is strengthened and extended to the east of the Mediterranean Sea. At the same time, a trough with varying intensity at the level of 500 hPa in the eastern Mediterranean exerts a southward influence, which is caused by the anticyclonic Rossby wave breaking. At the upper levels, associated with the wave activity flux divergence and convergence areas of the Mediterranean storm track, higher amounts of Rossby wave activity enter the northeast region of Africa. Also the meridional convergence of the wave activity flux strengthens the meridional circulation in the north of the Red Sea. Increased horizontal wave activity flux to the northeast Africa and the Red Sea is led to increased head and humidity flux to the region. On the other hand, the weakening of the extension of the Azores high pressure over Africa facilitates the tropical and extratropical interactions over the region. Also in the north or northeast of the Red Sea, a surface low pressure is formed. Having a different source in each case, the mid-level troughs exhibit a northwest-southeast title with respect to the surface lows which lead to baroclinic development and intensification of precipitation events in the eastern Mediterranean and Saudi Arabia.

Keywords: Extreme precipitation, Rossby wave activity flux, Mediterranean storm track, upper level trough, meridional circulation, baroclinic development
Trading space for time: Assessment of tree habitat shifts under climate change using bioclimatic envelopes
Authors: Enigl Katharina , Schlögl Matthias , Matulla Christoph
Published: March 2021

Climate change constitutes a main driver of altering population dynamics of spruce bark beetles (Ips typographus) all over Europe. Their swarming activity as well as development rate are strongly dependent on temperature and the availability of brood trees. Especially over the last years, the latter has substantially increased due to major drought events which led to a widespread weakening of spruce stands. Since both higher temperatures and longer drought periods are to be expected in Central Europe in the decades ahead, foresters face the challenges of maintaining sustainable forest management and safeguarding future yields. One approach used to foster decision support in silviculture relies on the identification of possible alternative tree species suitable for adapting to expected future climate conditions in threatened regions. 

In this study, we focus on the forest district of Horn, a region in Austria‘s north east that is beneficially influenced by the mesoclimate of the Pannonian basin. This fertile yet dry area has been severely affected by mass propagations of Ips typographus due to extensive droughts since 2017, and consequently has suffered from substantial forest damage in recent years. The urgent need for action was realized and has expedited the search for more robust alternative species to ensure sustainable silviculture in the area.

The determination of suitable tree species is based on the identification of regions whose climatic conditions in the recent past are similar to those that are to be expected in the forest district of Horn in the future. To characterize these conditions, we consider 19 bioclimatic variables that are derived from monthly temperature and rainfall values. Using downscaled CMIP6 projections with a spatial resolution of 2.5 minutes, we determine future conditions in Horn throughout the 21st century. By employing 20-year periods from 2021 to 2100 for the scenarios SSP1-26, SSP2-45, SSP3-70 and SSP5-85,  and comparing them to worldwide past climate conditions, we obtain corresponding bioclimatic regions for four future time slices until the end of the century. The Euclidian distance is applied as measure of similarity, effectively yielding similarity maps on a continuous scale. In order to account for the spatial variability within the forest district, this procedure is performed for the colder northwest and the warmer southeast of the area, individually seeking similar bioclimatic regions for each of these two subregions. Results point to Eastern Europe as well as the Po Valley in northern Italy as areas exhibiting the highest similarity to the future climate in this North-Eastern part of Austria.
Conceptual model of basement deformation beneath the Southern Atlassic front of Tunisia from gravity modeling, seismic reflection profiles and seismotectonic data
Authors: Frifita Nesrine , Gharbi Mohamed , Mickus Kevin
Published: March 2021

The nature of the basement beneath the Southern Atlassic front of Tunisia is relatively unknown. To study the basement, a geophysical study was undertaken using gravity, seismic reflection and seismicity data. Additionally, these data were used to determine the relationship and the tectonic environment between the known seismicity and basement structures under the Chotts fold belt and the surrounding basins. Based on 2.5D gravity modeling, 2D seismic reflection profiles and known geological mapping, the geometry of the basement was modeled as consisting of horsts,grabens and half-grabens. Specifically, the Sidi Mansour and El-Fejej basins are located on basement uplifts. The variations in the depths of the known earthquakes reveal that the deepest events occurred on basement faults beneath the Metlaoui and Sidi Mansour basins. While the surrounding anticlines within the northern Chotts range are probably inverted into graben and half-graben structures by both thin- and thick-skinned tectonic events. The geophysical findings indicate that the geometry of the basement to consist of a series of uplifted and downdropped regions, where the depth to basement increases from south to north and from east to west. This basement structure can explain the concentration of earthquakes in the northwestern portion of the study area by linking a reactivation of pre-existing east trending fault systems that formed during Alpine Orogeny. The results provide a coherent model showed a mixed thick and thin-skinned tectonic style was active within the study area. 
Fast (non-)diffusive Quasi-Geostrophic Magneto-Coriolis Modes in the Earth's core
Authors: Gerick Felix , Jault Dominique , Noir Jerome
Published: March 2021

 Fast changes of Earth's magnetic field could be explained by inviscid and diffusion-less quasi-geostrophic (QG) Magneto-Coriolis modes. We present a hybrid QG model with columnar flows and three-dimensional magnetic fields and find modes with periods of a few years at parameters relevant to Earth's core. These fast Magneto-Coriolis modes show strong focusing of their kinetic and magnetic energy in the equatorial region, while maintaining a relatively large spatial structure along the azimuthal direction. Their properties agree with some of the observations and inferred core flows. We find additionally, in contrast to what has been assumed previously, that these modes are not affected significantly by magnetic diffusion. The model opens a new way of inverting geomagnetic observations to the flow and magnetic field deep within the Earth's outer core.
Evaluation of low-cost eddy covariance for CO2 fluxes over agroforestry and grassland
Authors: van Ramshorst Justus , Markwitz Christian , Hill Timothy , Clement Robert , Knohl Alexander , Siebicke Lukas
Published: March 2021

Agroforestry is an integration of trees in cropland or grassland and is discussed, within Germany and the EU, as a potential “Green Solution” for agriculture. Agroforestry alters the microclimate, productivity, biodiversity, and nutrient and water usage – as compared to standard agricultural practise. A potentially key benefit is the higher carbon sequestration of agroforestry, relative to monoculture systems, which could provide an interesting option for mitigating climate change, while still providing valuable arable land. Net ecosystem exchange studies of CO2 (NEE) of agroforestry systems are rare, in comparison to the extensive studies of NEE of agricultural systems (croplands and grasslands). Therefore, the current study, as part of the SIGNAL (sustainable intensification of agriculture through agroforestry) project, investigates the NEE of agroforestry compared to that of monoculture agriculture.

At five locations across Germany, paired flux measurements above agroforestry and monoculture agronomy are performed using innovative low-cost CO2 eddy covariance sensors (slow response Vaisala GMP343 IRGA, with custom made housing). During the summer of 2020 simultaneous measurements of the low-cost setup and a LI-COR 7200 are performed, above grassland at 3.5 m and adjacent agroforestry grassland at 10 m measurements height.

The low-cost eddy covariance system is able to capture the turbulent (diurnal) CO2 flux dynamics and the response to management activities. After spectral corrections and applying quality control, the low-cost system at the agroforestry site (slope = 0.92, R2 = 0.88) performs better than the low-cost system at the grassland site (slope = 0.67, R2 = 0.80), when compared to the LI-COR measurements. This is probably due to the difference in turbulence caused by different surface roughness and measurement height. The preliminary cumulative carbon flux during the four-month measurement campaign shows a significant difference between the grassland (source of (+) 16-38 gC/m2) and agroforestry grassland (sink of (-) 148-164 gC/m2), in favour of agroforestry. By applying post processing software, we aim to further optimize the frequency corrections for the low-cost system. In the future the obtained post processing scheme will be applied to the other low-cost eddy covariance systems within the project.
Exploring mechanisms and rates of tunnel valley formation beneath deglaciating mid-latitude ice sheets using high-resolution 3D seismic data and numerical modelling
Authors: Kirkham James , Hogan Kelly , Larter Robert , Self Ed , Games Ken , Huuse Mads , Stewart Margaret , Ottesen Dag , Arnold Neil , Ely Jeremy , Dowdeswell Julian
Published: March 2021

The geological record of landforms produced beneath deglaciating ice sheets offers insights into otherwise inaccessible subglacial processes. Large subglacial channels formed by meltwater erosion of sediments (tunnel valleys) are widespread in formerly glaciated regions such as the North Sea. These features have the potential to inform basal melt rate parameterisations, realistic water routing and the interplay between basal hydrology and ice dynamics in numerical ice‑sheet models; however, the mechanisms and timescales over which tunnel valleys form remain poorly understood. Here, we present a series of modelling experiments, informed by geophysical observations from novel high-resolution 3D seismic data (6.25 m bin size, ~3.5 m vertical resolution), which test different hypotheses of tunnel valley formation and calculate the rates at which these features likely form beneath deglaciating ice sheets. Reconstructions of the former British-Irish and Fennoscandian ice sheets from a 3D thermomechanical ice‑sheet model (BRITICE CHRONO version 2) are used to calculate subglacial water routing and steady-state water discharges as these ice sheets retreated across the North Sea Basin during the last glaciation. Using these simulations, we calculate potential meltwater channel erosion rates and estimate how quickly tunnel  valleys are formed beneath deglaciating ice sheets in warmer than present-day climates. We find little evidence for widespread water ponding which may have led to channel formation through outburst floods. Instead, our results demonstrate that seasonal surface melt delivered to the bed could incise large channels of comparable dimensions to tunnel valleys over timescales of several hundred years as these ice sheets deglaciated.  
A new approach to simulate peat accumulation, degradation and stability in a global land surface scheme
Authors: Chadburn Sarah , Burke Eleanor , Gallego-Sala Angela , Smith Noah
Published: March 2021

Representing peatlands in global Earth System Models (ESMs) is a major challenge, but a crucial one since peatlands represent a significant component of the global carbon cycle.

Here we present the first ESM implementation of peat accumulation and degradation that integrates both organic and mineral soils in a single formulation, implemented in JULES - the land-surface component of the UK Earth System Model (UKESM). In this scheme, the soil column is able to expand with the addition of new organic material and to subside as this material decomposes, with variable organic layer thickness, which means that peat can appear and disappear within the landscape without a need for a prescribed peatland fraction.

Thermal and hydraulic characteristics of the soil are dynamically updated depending on the organic matter content and its level of decomposition, using relationships derived from observations. This scheme captures important feedbacks within the soil, such as the way that peatlands - once formed - can be self-sustaining even under conditions where they would not form today. It also captures the loss of carbon and soil structure when peatlands are drained. We demonstrate this behaviour in the model.

This provides a new approach for improving the simulation of organic and peatland soils, and associated carbon-cycle feedbacks in ESMs.

The key remaining challenges for simulating global peatlands are to realistically distribute water around the landscape, in order to represent topographically-controlled peatlands, and to develop appropriate peatland vegetation types.
Evaluation of S2S forecasts over India for renewable energy applications
Authors: Das Aheli , Baidya Roy Somnath
Published: March 2021

This study evaluates S2S forecasts of meteorological variables relevant for the renewable energy sector from six global coupled forecast models: ECMWF-SEAS5, DWD- GCFS 2.0, Météo-France’s System 6, NCEP-CFSv2, UKMO- GloSea5-GC2-LI, and CMCC-SPS3. The variables include 10m wind speed, incoming shortwave radiation, 2 m temperature, and relative humidity because these variables are critical for estimating the supply and demand of renewable energy. The study is conducted over seven homogenous climate regions of India for 1994-2016 April and May when energy demand peaks throughout the country. The evaluation is done by comparing the forecasts at 1, 2, 3, 4, and 5-months lead-times with ERA5 reanalysis data. In order to assess the forecast quality, deterministic metrics such as bias and correlation and probabilistic metrics such as Ranked Probability Score (RPS) and Continuous Ranked Probability Score (CRPS) are calculated by spatially averaging the forecasts and reanalyses over each region. The tercile limits for each variable are determined separately for each homogenous region from the ERA5 reanalysis using leave-one-out cross-validation. The forecasts show the highest skill at 1-month lead-time and the skill reduces with the increase in lead-time. However, deviations from this pattern are observed in some cases. For example, the 2 m temperature forecasts tend to perform better at longer lead-times over the western Himalayas perhaps because the slowly-varying snow dynamics aids in long-term predictability. The 2 m temperature and relative humidity forecasts generally show high correlations with observations over the western coast of the Indian peninsula in May at all lead-times, indicating the ability of the models to simulate presence of moisture prior to monsoon onset. Results show that the model performance depends on time-period of initialisation, better representation of surface fluxes, interaction between radiation and microphysics schemes, land-surface processes and factors governing radiative forcing such as greenhouse gases and aerosols. Overall, the SEAS5 model performs better than other models, although the Météo-France’s System 6 and UKMO- GloSea5-GC2-LI models also perform well in some regions.
The construction of reference conditions under the EU Water Framework Directive
Authors: Krueger Tobias , Linton James
Published: March 2021

With this contribution we connect to the 3rd theme of the session, ‘hydrology as practiced within society’. Based on our recent article Linton & Krueger (2020), we demonstrate how the reference conditions and subsequent water quality targets under the EU Water Framework Directive (WFD) do not exist ‘out there’, waiting to be discovered, but are outcomes of complex negotiations between hydrological, ecological, technical and socio-political realities.

Treating reference conditions and targets as naturally given, as WFD implementation does at least implicitly, upholds a false sense of authority that obscures the manifold choices in the creation of the reference conditions while denying the people charged with implementing the targets or having to live with the resulting water quality an influence over those choices.

We argue that the concept of reference conditions must be abandoned in a world were water everywhere bears the traces of human presence. Instead, water quality targets should be set openly, location-specific and involving those for whom water quality is a matter of concern. We will give examples from other jurisdictions where such an approach is established practice.

References

Linton, J. and Krueger, T. (2020), The Ontological Fallacy of the Water Framework Directive: Implications and Alternatives. Water Alternatives, 13(3): 513-533.
The West Crati Fault, Calabria (southern Italy): refined crustal extension rates constrained by geologic and GPS data.
Authors: Meschis Marco , Zerbini Susanna , Lattanzi Giovanni , Di Donato Miriana , Castellaro Silvia
Published: March 2021

Geologic studies of preserved stairs-like uplifted marine terraces and continuous GPS data collected in subduction zones provide a unique opportunity to investigate, on different time scales, crustal deformation resulting from upper‐plate extension. The West Crati Fault in Calabria, southern Italy, is a normal fault located within the seismically extending upper plate above the Ionian subduction zone. It is of interest because a thorough comparison of the extension rates inferred from geologic and GPS data has not yet been performed. This E-dipping fault lies in an area where a few historical damaging earthquakes occurred, examples are those in 1184 (M 6.7) and 1638 (M 6.7). Fault slip-rates and earthquake recurrence intervals for the West Crati fault are still subject of debate. We investigated raised marine terraces along the strike of the fault, on its footwall over its tips, located above the Ionian subduction zone, to derive refined uplift rates and study the role that known extensional faults contribute to observed coastal uplift. We also estimated short-term vertical and horizontal movements on the hangingwall of this fault by analyzing the data of 7 permanent GPS stations located along the N-S oriented strike of this fault.

Our preliminary results demonstrate that (i) GIS-based elevations of Middle to Late Pleistocene marine terraces, as well as temporally constant uplift rates, vary along the strike of this fault, mapped on its footwall; (ii) rates of short-term vertical movements vary along the strike of this fault on its hangingwall. This confirms active deformation, on different time scales, along the E-dipping West Crati Fault, suggesting that the fault slip-rate governing seismic hazard has also been constant through time. Our preliminary results show the importance of mapping crustal deformation within the upper plate above subduction zones to avoid unreliable interpretations concerning the mechanism responsible for regional uplift.
Decarbonising future heating systems: trade-offs between water use and CO2 emissions
Authors: Kaandorp Chelsea , van de Giesen Nick , Abraham Edo
Published: March 2021

Sustainable energy systems can only be achieved when reducing both carbon emissions and water use for energy generation. Water-energy nexus studies are therefore crucial for supporting environmental policy oriented towards the mobilisation of resources in an optimally integrated way. Decarbonizing heating infrastructures is an important part of achieving low-carbon energy systems because they globally account for 50% of the final energy consumption and 40% of the carbon dioxide (CO2) emissions. In our study, we quantitatively assess the changing water usage of the energy sector due to the integration of low carbon heating infrastructures. Multiple future energy mix scenarios were assessed  by building a multi-scale energy and water use model that quantifies the direct and virtual water footprint of space heating and hot water use in households, services and industry. In this presentation we show an analysis on the water use of heating pathways towards the year 2050 for the Netherlands and its capital, the city of Amsterdam. Additionally, we present preliminary results from our research about the trade-offs between carbon emission reductions, insulation measures and energy reliability in neighbourhoods in Amsterdam.
Urbanisation-induced climate warming in Great Britain
Authors: Bassett Richard , Young Paul , Blair Gordon , Cai Xiaoming , Chapman Lee
Published: March 2021

In Great Britain (GB) 5.8% of the total land area is considered urban, yet the wider impact of Urban Heat Islands (UHIs) beyond city scales has not been fully explored. Through scaling data from a high-resolution urban monitoring network we estimate the current (2014) spatial daily-mean urban warming across GB to be 0.04°C [0.02 °C – 0.06°C]. Despite this GB-wide contribution appearing small (94% of the land cover is still rural), half of GB's population currently live in areas with average daily-mean UHIs of 0.4°C. GB is also experiencing rapid urbanisation, with urban land cover expanding from 4.3 to 5.8% between 1975 and 2014. Purely due to urbanisation in this period, we estimate GB as a whole is warming at a rate that is both equivalent and in addition to ~3% of the background surface-level climate change (i.e. natural and greenhouse gas induced). In areas with the greatest urban expansion, we find UHI-induced warming rates are up to three times this average. Although our study only applies to GB, the simplicity of our method means that it can be equally applied to other countries. Urbanisation is undeniably a global phenomenon with urban expansion in many countries far exceeding that found in GB.
The role of anoxygenic phototrophs in the Baltic Sea
Authors: Xu Peihang , Christiansen Christian Furbo , Löscher Carolin
Published: March 2021

Both oxygenic and anoxygenic phototrophic bacteria (OPB and APB, respectively) are widely distributed in the ocean and play significant roles in carbon cycle and marine productivity. These organisms capture light as energy source via chlorophyll or bacteriochlorophylls-based photosystems. While OPB are relatively well studied, information on APB is rather scarce although they have been shown abundant in some ocean ecosystems and may play an important role in oxygen depleted environments. Here, we investigate the spatial profile of OPB and APB, gene abundance and expression of the key functional marker gene pufM (APB specific photosynthetic reaction center subunit M), in one fjord and three basins of the Baltic Sea using 16S rRNA amplicon sequencing and qPCR. Among the microbial community, abundances of OPB and APB were found to be similar thus emphasizing a potential importance of APB, with APB representing 1.6-17.5% and OPB representing 0.5-20%. Among APB, we identified eleven different orders, with Rhodobacterales being quantitatively dominant. The identified seven orders of OPB were dominated by Synechococcales. OPB were more abundant than APB in surface waters (<8m), while APB were comparably more abundant in deeper waters. Besides a depth-dependent distribution, we observed an impact of salinity on the distribution of APB and OPB, both of which being suggestive of distinct niches for those primary producer clades. pufM gene abundance ranged from 104 to 109 copies/L, with highest counts detectable in the mixed layer (<40m), however, even in deeper waters where gene abundances decreased APB pufM gene expression was high with up to 104 copies/L. These results indicate APB may play a more important role in marine primary productivity which has been underestimated before. 