bluuebunny/crossref_metadata_2025 huggingface dataset:
Testing different machine learning techniques for runoff routing in a highly glacierized Djankuat river basin (the North Caucasus, Russia).
Authors: Rets Ekaterina , Fomichev Sergey , Belozerov Egor
Published: March 2021

Distributed, physically based modelling of runoff routing in highly glacierized river basins is an extremely complicated task as glacier drainage systems functioning is very sophisticated, close to karst river systems but also dynamically developing within very short time periods. Accordingly, runoff routing of glacier melt water is most often based on the concept of linear storage. The number of reservoirs generally vary from 1 to 3. For example, one  ‘fast’ reservoir for melt  and  rain  in  glacierized  grid  cells in GERM model, three parallel different linear reservoirs representing snow, firn and ice in GSM-SOCONT model.

Here we test applicability of different machine learning techniques (gradient boosting, random forest, LSTM) for runoff routing in a highly glacierized river basin. We use the data from Djankuat alpine research catchment located in the North Caucasus (Russia) for the period of 2007­­-2019. The dataset contains different parameters measured with an hourly or sub-daily time step: water runoff, conductivity, turbidity, temperature, 18O, D content at the main gauging station; measurements of precipitation amount, standard meteorological parameters and radiation fluxes. Results of snow and ice melting modelling in the Djankuat river basin over a regular net with an hourly time step using energy-balance distributed A-Melt model are also used as input data.

Total runoff from the Djankuat river basin (1) and meltwater runoff according to isotopic hydrograph separation (2) were chosen as target functions. Different sets of features to predict the target functions were generated from the original time series using different combinations of the input parameters as well as variable lag times. To score different machine learning techniques and sets of features to predict target function we use correlation coefficient, Nash-Sutcliff efficiency index (NSE), root mean square error (RMSE).

The study was supported by the Russian Foundation for Basic Research, grant No. 20-35-70024
AI for Fast Atmospheric Chemistry
Authors: Albrecht Frauke , Stiehler Felix , Sinnhuber Björn-Martin , Versick Stefan , Weigel Tobias
Published: March 2021

In coupled global circulation models, chemical interaction between atmospheric trace gases is modelled through dedicated atmospheric chemistry submodels. As these components tend to be computationally expensive, one is often faced with the situation to either run the models with chemistry in relatively coarse resolution, or to ignore atmospheric chemistry altogether. Here an alternative approach is presented in order to overcome the high computational costs while attaining comparable quality of results. A fully connected neural network is used to make predictions of chemical tendencies. As input data of the neural network serve chemical mixing ratios, temperature, pressure, the ozone column and the solar zenith angle, all resulting from the global numerical atmosphere-chemistry model EMAC. The time period considered is 3 month, divided in time steps of consecutive 11 hours. In total, 181 time steps are analysed, from which the first 128 are used as training data, the following 26 as validation data and the last 27 are kept for final testing. The EMAC model produces results of 110 chemicals at a horizontal grid of 160x320 and 90 vertical levels. In our preliminary approach, only 6 of these chemicals - which correspond to the chemicals describing the Chapman mechanism and the nitrogen oxides - are predicted and the analysis area is restricted to the stratosphere. Further, chemicals that are zero at 95% or more of the data points have been deleted from the input data. The results of the neural network represent the spatial patterns of the climate model data very well and are in the same order of magnitude. Spatial correlations depend on the chemical and the vertical level, but are in general >0.95 at levels where the considered variable is present. However, errors are increasing during the validation period, which is probably due to trends in the analysed data. This work presents a proof of concept that neural networks are able to predict atmospheric chemistry tendencies. Left for future work is a detailed hyperparameter tuning in order to optimize the model and the extension to longer time periods to overcome modelling problems due to seasonal trends in the data. 
Borderless Heat Stress
Authors: Brimicombe Chloe , Di Napoli Claudia , Cornforth Rosalind , Pappenberger Florian , Petty Celia , Cloke Hannah
Published: March 2021

Heatwaves are increasing in intensity, duration and frequency. One of the impacts of heatwaves is heat stress, which can lead to death and raised morbidity. This project, uses a mixed method approach. Using the ERA5.HEAT reanalysis data of the UTCI – a bio-meteorological heat stress index- and temperature, to study the climatology and trends of heat at a global level and at a regional and country level for African nations. In addition, we review a range of literature from academic papers, international reports and EM-DAT the international disaster database. All of this reveals the extent to which heat risk is communicated. As well as, revealing the growing size of heatwaves. These together provide evidence of whether more preparedness measures are needed.
Authigenic nanoscale magnetite within methanic marine sediments
Authors: Lin Zhiyong , Sun Xiaoming , Roberts Andrew , Strauss Harald , Brunner Benjamin , Peckmann Jörn
Published: March 2021

Magnetic studies of methanic sediments focus mainly on magnetic iron sulfide (greigite, 3C pyrrhotite) formation and magnetic iron oxide (magnetite, titanomagnetite) dissolution, which mainly result from the release of hydrogen sulfide during sulfate-driven anaerobic oxidation of methane. In some instances, authigenic fine-grained magnetite within methanic environments is recognized from magnetic parameters, but the mechanisms for explaining its occurrence remain unclear. We report a novel authigenic nanoscale magnetite source in methanic marine sediments. The magnetite occurs in large concentrations in multiple horizons in a 230-m long sediment core with gas hydrate-bearing intervals. In contrast to typical biogenic magnetite produced by magnetotactic bacteria and dissimilatory iron-reducing bacteria, most particles have sizes of 200-800 nm and many are aligned in distinctive structures that resemble microbial precipitates. This new type of magnetite is interpreted to be a by-product of microbial iron reduction within methanic sediments. It will record younger paleomagnetic signals than surrounding sediments, which is important for paleomagnetic interpretations in methanic sediments.
Trends in noctilucent clouds
Authors: Lübken Franz-Josef , Baumgarten Gerd
Published: March 2021

Noctilucent clouds are often cited as potential indicators of climate change in the middle
atmosphere. They owe their existence to the very cold summer mesopause region (~130K) at mid
and high latitudes. We analyze trends derived from the Leibniz-Institute Middle Atmosphere
Model (LIMA) and the MIMAS ice particle model (Mesospheric Ice Microphysics And tranSport model)
for the years 1871-2008 and for middle, high and arctic latitudes, respectively.
Model runs with and without an increase of carbon dioxide and water vapor (from methane oxidation)
concentration are performed. Trends are most prominent after ~1960 when the increase of both
carbon dioxide and water vapor accelerates. Negative trends of (geometric) NLC altitudes are primarily
due to cooling below NLC altitudes caused by carbon dioxide increase. Increases of ice particle
radii and NLC brightness with time are mainly caused by an enhancement of water vapor.
Several ice layer and background parameter trends are similar at high and arctic latitudes but are
substantially different at middle latitudes. This concerns, for example, occurrence rates, ice water
content (IWC), and number of ice particles in a column. Considering the time period after 1960,
geometric altitudes of NLC decrease by approximately 260m per decade, and brightness increases by
roughly 50% (1960-2008), independent of latitude. NLC altitudes decrease by approximately 15-20m
per increase of carbon dioxide by 1ppmv. The number of ice particles in a column and also at the
altitude of maximum backscatter is nearly constant with time. At all latitudes, yearly mean NLC
appear at altitudes where temperatures are close to 145+/-1K. Ice particles are present nearly
all the time at high and arctic latitudes, but are much less common at middle latitudes. Ice water
content and maximum backscatter are highly correlated, where the slope depends on latitude. This
allows to combine data sets from satellites and lidars. Furthermore, IWC and the concentration of
water vapor at the altitude of maximum backscatter are also strongly correlated. Results from
LIMA/MIMAS agree nicely with observations.
Numerical modeling on landfast ice in Arctic region
Authors: Liu Yuqing , Losch Martin
Published: March 2021

Sea ice is regarded as a significant indicator of climate change in the Arctic Ocean. Landfastice is sea ice that is immobile or almost immobile in coastal regions, decreasing the transfer of heat, moisture, and momentum. As an extension of the land for travel and hunting, landfast ice also influences the construction of ice roads and arctic shipping routes in the summertime. Despite the important role of landfast ice in the climate system, the formation and maintenance of landfast ice are not well simulated by current sea ice models. Lemieux (2015) came up with the grounding scheme, by adding a basal stress term according to the water depth, improving landfast ice representation in shallow regions while underestimating in deep regions especially in the Kara Sea. The two different resolution model configurations with the MIT General Circulation Model (MITgcm) sea ice package is compared in landfast ice simulation in the arctic region. Preliminary results show that a higher resolution model better represents landfast ice in deep regions. The proper illustration of coastlines, which serve as pinning points for sea ice arches, in the high-resolution model can improve the representation of landfast ice. We also apply a new parameterization lateral drag term, a function with sea ice thickness, drift velocity, and coastline intricacy, in the model to better simulate landfast ice. The results suggest a combination of lateral drag and basal stress terms successfully simulates fast ice in most regions
A multi-decade assessment of the impact of large fire events on sediment redistribution using LAPSUS - the Águeda catchment, north-central Portugal
Authors: Föllmi Dante , Baartman Jantiene , Nunes João Pedro , Benali Akli
Published: March 2021

Abstract

Wildfires have become an increasing threat for Mediterranean ecosystems, due to increasing climate change induced wildfire activity and changing land management practices. Apart from the initial risk, fire can alter the soil in various ways depending on different fire severities and thus post-fire erosion processes are an important component in assessing wildfires’ negative effects. Recent post-fire erosion (modelling) studies often focus on a short time window and lack the attention for sediment dynamics at larger spatial scales. Yet, these large spatial and temporal scales are fundamental for a better understanding of catchment sediment dynamics and long-term destructive effects of multiple fires on post-fire erosion processes. In this study the landscape evolution model LAPSUS was used to simulate erosion and deposition in the 404 km2 Águeda catchment in northern-central Portugal over a 41 year (1979-2020) timespan. To include variation in fire severity and its impact on the soil four burnt severity classes, represented by the difference Normalized Burn Ratio (dNBR), were parameterized. Although model calibration was difficult due to lack of spatial and temporal measured data, the results show that average post-fire net erosion rates were significantly higher in the wildfire scenarios (5.95 ton ha-1 yr-1) compared to those of a non-wildfire scenario (0.58 ton ha-1 yr-1). Furthermore, erosion values increased with a higher level of burnt severity and multiple fires increased the overall sediment build-up in the catchment, fostering an increase in background sediment yield. Simulated erosion patterns showed great spatial variability with large deposition and erosion rates inside streams. Due to this variability, it was difficult to identify land uses that were most sensitive for post-fire erosion, because some land-uses were located in more erosion-sensitive areas (e.g. streams, gullies) or were more affected by high burnt severity levels than others. Despite these limitations, LAPSUS performed well on addressing spatial sediment processes and has the ability to contribute to pre-fire management strategies. For instance, the percentage soil loss map (i.e. comparison of erosion and soil depth maps) could identify locations at risk.
Effects of tributary inflow and sediment input on reservoir turbidity current formation and evolution
Authors: Sun Yining , Li Ji , Cao Zhixian , Borthwick Alistair G.L.
Published: March 2021

For reservoirs built on a hyper-concentrated river, tributary inflow and sediment input may affect the formation and evolution of reservoir turbidity current, and accordingly bed morphology. However, the understanding of tributary effects on reservoir turbidity currents has remained poor. Here a series of laboratory-scale reservoir turbidity currents are investigated using a coupled 2D double layer-averaged shallow water hydro-sediment-morphodynamic model. It is shown that the tributary location may lead to distinctive effects on reservoir turbidity current. Clear-water flow from the tributary may cause the stable plunge point to migrate upstream, and reduce its front speed. Sediment-laden inflow from the tributary may increase the discharge, sediment concentration, and front speed of the turbidity current, and also cause the plunge point to migrate downstream when the tributary is located upstream of the plunge point. In contrast, if the tributary is located downstream of the plunge point, sediment-laden flow from the tributary causes the stable plunge point to migrate upstream, and while the tributary effects on discharge, sediment concentration, and front speed of the turbidity current are minor. A case study is presented as of the Guxian Reservoir (under planning) on the middle Yellow River, China. The present finding highlights the significance of tributary inflow and sediment input in the formation and propagation of reservoir turbidity current and also riverbed deformation. Appropriate account of tributary effects is warranted for long-term maintenance of reservoir capacity and maximum utilization of the reservoir.
Water-balance response to climate variability, a small-to-large scale Italian dataset
Authors: Bruno Giulia , Avanzi Francesco , Gabellani Simone , Ferraris Luca , Cremonese Edoardo , Galvagno Marta , Massari Christian
Published: March 2021

Understanding how deficit of precipitation impacts the hydrological cycle is of growing interest and is essential for water resource management. It has been recently observed that the relationship between precipitation and runoff during droughts is subjected to a shift in the sense that the predicted runoff is much less than the one expected due to the deficit in precipitation. Unraveling why this occurs requires an accurate knowledge of all the components of the water balance equation. However, large-scale and consistent samples of precipitation, runoff, evapotranspiration, ET and change in storage have always been challenging to collect. Here, we hypothesized that blending ground-based and remote-sensing data products could fill this gap. We present a countrywide dataset of catchment-scale water balance, covering the last 10 water years in Italy. Italy shows a broad variety of climatic and topographic features and faced several droughts over recent years. We use ground-based daily runoff data, interpolated precipitation maps, and a remote-sensed daily evapotranspiration dataset from the LSASAF ET product. The ET dataset is additionally compared with flux towers data across the country, obtaining root mean square errors on the order of 30 mm/month. Lastly, changes in storage are estimated to close the water balance. More than 100 catchments - including the major Italian basins - are selected, according to data availability and reliability. These catchments cover a wide range of size, morphologic and climatic characteristics. 

This dataset is a strategic source of information to analyze catchment-scale runoff, ET and storage response to climatic variability across climates and landscapes.
Reducing full-field training data to time series
Authors: Edeling Wouter , Crommelin Daan
Published: March 2021

It is well known that the wide range of spatial and temporal scales present in geophysical flow problems represents a (currently) insurmountable computational bottleneck, which must be circumvented by a coarse-graining procedure. The effect of the unresolved fluid motions enters the coarse-grained equations as an unclosed forcing term, denoted as the ’eddy forcing’. Traditionally, the system is closed by approximate deterministic closure models, i.e. so-called parameterizations. Instead of creating a deterministic parameterization, some recent efforts have focused on creating a stochastic, data-driven surrogate model for the eddy forcing from a (limited) set of reference data, with the goal of accurately capturing the long-term flow statistics. Since the eddy forcing is a dynamically evolving field, a surrogate should be able to mimic the complex spatial patterns displayed by the eddy forcing. Rather than creating such a (fully data-driven) surrogate, we propose to precede the surrogate construction step by a procedure that replaces the eddy forcing with a new source term which: i) is tailor-made to capture spatially-integrated quantities of interest, ii) strikes a balance between physical insight and data-driven modelling , and iii) significantly reduces the amount of training data that is needed. Instead of creating a surrogate model for an evolving field, we now only require a surrogate model for one scalar time series per quantity-of-interest. We derive the new source terms for a simplified an ocean model of two-dimensional turbulence in a doubly periodic square domain, and show that the time-series training data produces the same statistics for our quantities of interest as the full-field eddy-forcing.
Constraining Neoproterozoic subtropical low-level clouds to assess the plausibility of near-Snowball Earth states
Authors: Braun Christoph , Voigt Aiko , Hörner Johannes , Pinto Joaquim G.
Published: March 2021

Stable waterbelt climate states with close to global ice cover challenge the classical Snowball Earth hypothesis because they provide a robust explanation for the survival of advanced marine species during the Neoproterozoic glaciations (1000 – 541 Million years ago). Whether Earth’s climate stabilizes in a waterbelt state or rushes towards a Snowball state is determined by the magnitude of the ice-albedo feedback in the subtropics, where dark, bare sea ice instead of snow-covered sea ice prevails. For a given bare sea-ice albedo, the subtropical ice-albedo feedback and thus the stable range of the waterbelt climate regime is sensitive to the albedo over ice-free ocean, which is largely determined by shortwave cloud-radiative effects (CRE). In the present-day climate, CRE are known to dominate the spread of climate sensitivity across global climate models. We here study the impact of uncertainty associated with CRE on the existence of geologically relevant waterbelt climate regimes using two global climate models and an idealized energy balance model. We find that the stable range of the waterbelt climate regime is very sensitive to the abundance of subtropical low-level mixed-phase clouds. If subtropical cloud cover is low, climate sensitivity becomes so high as to inhibit stable waterbelt states.

The treatment of mixed-phase clouds is highly uncertain in global climate models. Therefore we aim to constrain the uncertainty associated with their CRE by means of a hierarchy of global and regional simulations that span horizontal grid resolutions from 160 km to 300m, and in particular include large eddy simulations of subtropical mixed-phase clouds located over a low-latitude ice edge. In the cold waterbelt climate subtropical CRE arise from convective events caused by strong meridional temperature gradients and stratocumulus decks located in areas of large-scale descending motion. We identify the latter to dominate subtropical CRE and therefore focus our large eddy simulations on subtropical stratocumulus clouds. By conducting simulations with two extreme scenarios for the abundance of atmospheric mineral dust, which serves as ice-nucleating particles and therefore can control mixed-phase cloud physics, we aim to estimate the possible spread of CRE associated with subtropical mixed-phase clouds. From this estimate we may assess whether Neoproterozoic low-level cloud abundance may have been high enough to sustain a stable waterbelt climate regime.
The physical sustainability of the coastal zone of the Ganges-Brahmaputra-Meghna delta under climatic and anthropogenic stresses
Authors: Darby Stephen , Rahman Md. Munsur , Haque Anisul , Nicholls Robert , Dunn Frances
Published: March 2021

The Ganges-Brahmaputra-Meghna (GBM) delta is one of the world’s largest deltas, and consists of large areas of low flat lands formed by the deposition of sediment from the GBM rivers. However, recent estimates have projected between 200~1000 mm of climate-driven sea-level rise by the end of the 21st century, at an average rate of ~6 mm/yr. Eustatic sea-level rise is further compounded by  subsidence of the delta, which in the coastal fringes varies from 0.2 to 7.5 mm/yr, at an average value of ~2.0 mm/yr. Therefore, the combined effect of sea-level rise and subsidence (termed relative sea-level rise, RSLR) is around 8.0 mm/yr. Such high values of RSLR raise the question of whether sediment deposition on the surface of the delta is sufficient to maintain the delta surface above sea level. Moreover, as the total fluvial sediment influx to the GBM delta system is known to be decreasing, the retained portion of fluvial sediment on the delta surface is also likely decreasing, reducing the potential to offset RSLR. Within this context, the potential of various interventions geared at promoting greater retention of sediment on the delta surface is explored using numerical experiments under different flow-sediment regime and anthropogenic interventions.  We find that for the existing, highly managed, conditions, the retained portion of fluvial sediment on the delta surface varies between 22% and 50% during average (when about 20% of the total floodplain in the country is inundated) and extreme (> 60% of the total floodplain in the country is inundated) flood years, respectively. However, the degree to which sediment has the potential to be deposited on the delta surface increases by up to 10% when existing anthropogenic interventions such as polders that act as barriers to delta-plain sedimentation are removed. While dismantling existing interventions is not a politically realistic proposition, more quasi-natural conditions can be reestablished through local- sediment management using tidal river management, cross dams, dredging, bandal-like structures and/or combinations of the above measures.
Combining static and portable Cosmic Ray Neutron Sensor (CRNS) data to assess catchment scale heterogeneity in soil water content and implications for runoff generation
Authors: Dimitrova Petrova Katya , Rosolem Rafael , Soulsby Chris , Wilkinson Mark , Lilly Allan , Geris Josie
Published: March 2021

Soil water content (SWC) dynamics can strongly influence catchment runoff generation processes. Knowledge about the amount and spatiotemporal distribution of SWC at the catchment scale can be useful for constraining and evaluating rainfall-runoff models.  While it is still challenging to obtain catchment scale-representative measurements of SWC, recent advances in cosmic ray neutron sensor (CRNS) technology have provided opportunities to obtain hectare scale data on SWC. Here we present a new method for obtaining spatially variable near-surface SWC by combining a high temporal resolution static CRNS sensor with ‘snapshot’ surveys using a portable CRNS. We also explored the role of these soil water storage data for catchment in rainfall-runoff generation models. We used ~4-years of near-surface SWC data from a static CRNS located in a humid mixed-agricultural catchment (~10km2) in Scotland. These data were complemented with at least three ‘snapshot’ portable CRNS surveys in each of the four main soil-land use (SLU) units in the catchment to produce SWC timeseries for each of these units. Two SLU units involved rotational crops under poorly or imperfectly draining mineral soils; one SLU unit typically supports livestock farming on freely draining mineral soils and the fourth, moorland on organic-rich soils.  While the moorland SLU unit on organic soils had the greatest difference in SWC dynamics under the static CRNS and other SLUs, we also found subtle SWC differences between mineral soil SLU units under different agricultural management. We then evaluated the additional information generated by the combined CRNS method in a rainfall-runoff model (HBV-light) calibration of dynamic catchment storage. For the purpose, we used areal weighted SLU SWC timeseries and compared the model calibration to that using the static CRNS alone. In this case, differences were marginal and model efficiencies similar, suggesting that static CRNS data from a landscape-representative location may be sufficient to inform rainfall-runoff model calibration at the catchment scale.  However, this may depend on model structure and the degree to which SWC dynamics vary within the landscape. This study demonstrated the potential of expanding the information value of permanently installed CRNS sensors using portable CRNS surveys in the context of humid mixed-agricultural environment, although testing in different environments would be required to evaluate wider applicability.
Different Surface Charged Plastic Particles Have Different Cotransport Behaviors with Kaolinite Particles in Porous Media
Authors: Li Meng , He Lei , Zhang Xiangwei , Rong Haifeng , Tong Meiping
Published: March 2021

The wide utilization of plastic related products leads to the ubiquitous presence of plastic particles in natural environments. Plastic particles could interact with kaolinite (one type of typical clay particles abundant in environment) and form plastic-kaolinite heteroaggregates. The fate and transport of both plastic particles and kaolinite particles thus might be altered. The cotransport and deposition behaviors of micron-sized plastic particles (MPs) with different surface charge (both negative and positive surface charge) with kaolinite in porous media in both 5 and 25 mM NaCl solutions were investigated in present study. Both types of MPs (negatively charged carboxylate-modified MPs (CMPs) and positively charged amine-modified MPs (AMPs)) formed heteroaggregates with kaolinite particles under both solution conditions examined, however, CMPs and AMPs exhibited different cotransport behaviors with kaolinite. Specifically, the transport of both CMPs and kaolinite was increased under both ionic strength conditions when kaolinite and CMPs were copresent in suspensions. While, when kaolinite and positively charged AMPs were copresent in suspensions, negligible transport of both kaolinite and AMPs were observed under examined salt solution conditions. The competition deposition sites by kaolinite (the portion suspending in solution) with CMPs-kaolinite heteroaggregates led to the increased transport both CMPs and kaolinite when both types of colloids were copresent. In contrast, the formation of larger sized AMPs-kaolinite heteroaggregates with surface charge heterogeneity led to the negligible transport of both kaolinite and AMPs when they were copresent in suspensions. The results of this study show that when plastic particles and kaolinite particles are copresent in natural environments, their interaction with each other will affect their transport behaviors in porous media. The alteration in the transport of MPs or kaolinite (either increased or decreased transport) is highly correlated with the surface charge of MPs.
Variability of warm water intrusions onto the Bellingshausen Sea continental shelf
Authors: Oelerich Ria , Heywood Karen J. , Damerell Gillian M. , Thompson Andrew F.
Published: March 2021

The continental shelf of the Bellingshausen Sea, located between the West Antarctic Peninsula and the Amundsen Sea, Antarctica, is poorly investigated, compared with its neighbours. Here, the southernmost frontal jet of the Antarctic Circumpolar Current is adjacent to the continental slope which impacts the transport of warm Circumpolar Deep Water onto the shelf. This in turn can influence the transport of heat southward across the shelf and therefore the melting of vulnerable ice shelves.

We present model-based investigations using the GLORYS12V1 1/12° reanalysis monthly output (GLOBAL_REANALYSIS_PHY_001_030) over 19 years from 2000 to 2018. By connecting the location of the frontal jet to SSH contours we identify seasonal and interannual variability in this current system and demonstrate that the closer the frontal jet is to the continental slope, the greater the flow of warm deep water onto the shelf. This onshore flow is limited to specific areas closest to the frontal jet, predominantly in the eastern Bellingshausen Sea. In contrast, other areas, specifically those troughs where water flows towards the West Antarctic Peninsula and close to the coastline of Antarctica show opposite behaviour with respect to onshelf heat content. Further analyses of flow patterns also indicate the involvement of a coastal jet close to the shore that is weaker when more warm water is on the shelf. Understanding the variability in the current structures throughout the continental shelf of the Bellingshausen Sea in response to a changing frontal jet is essential to gain knowledge about the distribution of heat and therefore the melting of ice shelves.
On the transmission of compressional fluctuations from the solar wind to the magnetosphere: an analysis of critical aspects  
Authors: Villante Umberto , Di Matteo Simone , Recchiuti Dario
Published: March 2021

An important aspect of the interaction between the solar wind (SW) and the magnetosphere concerns the relationship between the SW structures/fluctuations and the onset/transmission of the magnetospheric wave modes. Several critical aspects may influence the results of similar analysis: for example, the frequency of fluctuations that are expected to impinge the magnetosphere may be not the same when they are observed by spacecraft at different places in front of the magnetosphere and the choice of the analytical methods adopted for the spectral analysis might influence the frequency estimate (as well as the wave identification) both in the SW and in the magnetosphere (Di Matteo and Villante, 2017, 2018). Focusing attention on these aspects, we present an analysis of SW compressional fluctuations (f ≈ 1-5 mHz), following two interplanetary shocks, as observed by two spacecraft at different places and compared them with the magnetospheric fluctuations following the corresponding sudden impulses, observed by two satellites at geostationary orbit and at several ground-based stations. Our results confirm that the comparison of different methods of spectral analysis is crucial to obtain a definite estimate of the characteristics of fluctuations in each region. For a case study, in which SW fluctuations at the same frequencies were observed by both interplanetary spacecraft, we found that all fluctuations observed in the magnetosphere were related to SW compressional fluctuations approximately at the same frequencies, with no evidence for wave activity of internal origin, or directly driven by the shock impact.

 
Temperature Sensitivity of Intracellular and Extracellular Soil Enzyme Activities
Authors: Adekanmbi Adetunji Alex , Dale Laurence , Shaw Liz , Sizmur Tom
Published: March 2021

Predicting the pattern of soil organic matter (SOM) decomposition as a feedback to climate change, via release of CO2, is extremely complex and has received much attention. However, investigations often do not differentiate between the extracellular and intracellular processes involved and work is needed to identify their relative temperature sensitivities. Samples were collected from a grassland soil at Sonning, UK with average daily maximum and minimum soil temperature of 15 °C and 5 °C. We measured potential activities of β-glucosidase (BG) and chitinase (NAG) (extracellular enzymes) and glucose-induced CO2 respiration (intracellular enzymes) at a range of assay temperatures (5 °C, 15 °C, 26 °C, 37  °C, and 45 °C). The temperature coefficient Q10 (the increase in enzyme activity that occurs after a 10 °C increase in soil temperature) was calculated to assess the temperature sensitivity of intracellular and extracellular enzymes activities. Between 5 °C and 15 °C intracellular and extracellular enzyme activities had equal temperature sensitivity, but between 15 °C and 26°C intracellular enzyme activity was more temperature sensitive than extracellular enzyme activity and between 26 °C and 37 °C extracellular enzyme activity was more temperature sensitive than intracellular enzyme activity. This result implies that extracellular depolymerisation of higher molecular weight organic compounds is more sensitive to temperature changes at higher temperatures (e.g. changes to daily maximum summer temperature) but the intracellular respiration of the generated monomers is more sensitive to temperature changes at moderate temperatures (e.g. changes to daily mean summer temperature). We therefore conclude that the extracellular and intracellular steps of SOM mineralisation are not equally sensitive to changes in soil temperature. The finding is important because we have observed greater increases in average daily minimum temperatures than average daily mean or maximum temperatures due to increased cloud cover and sulphate aerosol emission. Accounting for this asymmetrical global warming may reduce the importance of extracellular depolymerisation and increase the importance of intracellular catalytic activities as the rate limiting step of SOM decomposition.
Opportunistic magnetotelluric transects from 3D CSEM surveys in the SW Barents Sea
Authors: Corseri Romain , Planke Sverre , Faleide Jan Inge , Senger Kim , Gelius Leiv Jacob , Johansen Ståle Emil
Published: March 2021

Magnetotelluric (MT) data allow for electrical resistivity probing of the earth’s subsurface. Integration of resistivity models in passive margin studies could help disambiguate non-unique interpretations of crustal lithologies from seismic and potential field data. In this contribution, we present the first marine MT data in the Barents Sea, derived from industrial controlled-source electromagnetic (CSEM) surveys and characterize its quality, dimensionality and depth penetration to elaborate a modelling strategy. This MT database consists of 337 receivers located along 7 regional transects, emanating from ~70,000 km2 of 3D CSEM surveys acquired for hydrocarbon exploration from 2007 to 2019. High-quality MT data are extracted for periods ranging from 0.5 s to 5000 s with no apparent contamination by the active source, nor effects related to large time-gaps in data collection and variable solar activity. Along receiver profiles, abrupt lateral variations of apparent resistivity and phase trends coincide with major structural boundaries and underline the geological information contained in the data. Dimensionality analysis reveals a dichotomy between the “western” domain of the SW Barents Sea, dominated by a single N-S electromagnetic strike, and the “eastern” domain, with a two-fold, period-dependent strike. 35 receivers show 3D distortion caused by nearby bathymetric slopes, evidenced by elevated skew angle values. We delimit geographical areas where the 2D assumption is tenable and lay the foundation for future 2D and 3D MT modelling strategies in the SW Barents Sea. We performed 2D MT inversion along one of the regional transects, a ~220 km-long, E-W profile encompassing a major structural high and distal basin approaching the continent-ocean boundary. The resistivity model shows low crustal resistivity values (1-10 Ω.m) beneath the sedimentary cover in western distal basins, in stark contrast with high resistivity values (1000 - 5000 Ω.m) of the thick crystalline crust in the proximal domain on the structural high. We interpret this abrupt lateral resistivity variation as a crustal necking zone with a rapid transition to a hyperextended continental crust. In the proximal domain, a 50-100 Ω.m and 20 km-wide, intra-crust vertical contact hints at a plausible paleo-plate suture. Integration of resistivity with velocity, density and magnetic susceptibility models will further refine these tectonic models and related processes in the SW Barents Sea margin. Our methodology is applicable globally where 3D CSEM surveys are acquired and has a large potential for harvesting new knowledge on the electrical resistivity properties of the lithosphere.
Point simulation of snow cover in Peñalara Massif (Sierra de Guadarrama, Central Spain)
Authors: González-Cervera Álvaro , Durán Luis
Published: March 2021

The Factorial Snowpack Model (FSM, Essery, 2015) has been applied for the winters ranging from 2008 to 2021 to predict snow height in a location at 1800 m of altitude in Peñalara Massif (Sierra de Guadarrama, Central Spain). Data from an automatic meteorological station is used as input after a thorough validation and completion using different methods. Several configurations of the model have been tested and sensitivity runs regarding long-wave and short-wave radiative flux, air temperature, liquid and solid precipitation rate, surface pressure, relative humidity and wind velocity, have been performed. Comparison of predictions versus automatic and manual in-situ measurements show a coherent evolution of the snow height. A satisfactory degree of precision regarding the beginning and end of the snow cover has been found but also a high sensitivity to radiative flux, mainly long-wave, air temperature and total solid precipitation rates that need further research. Future work will be carried out testing other snowpack models, developing new parametrizations and performing predictions for the  whole basin considering side effects and other factors.
Properties of A Supercritical Quasi-Perpendicular Interplanetary Shock Propagating in Super-Alfvénic Solar Wind: from MHD to Kinetic Scales
Authors: Liu Mingzhe , Yang Zhongwei , Liu Ying D. , Lembege Bertrand , Issautier Karine , Wilson III Lynn. Bruce , Zhao Siqi , Jagarlamudi Vamsee Krishna , Zhao Xiaowei
Published: March 2021

We investigate the properties of an interplanetary shock (MA=3.0, θBn=80°) propagating in Super-Alfvénic solar wind observed on September 12th, 1999 with in situ Wind/MFI and Wind/3DP observations. Key results are obtained concerning the possible energy dissipation mechanisms across the shock and how the shock modifies the ambient solar wind at MHD and kinetic scales:  (1) Waves observed in the far upstream of the shock are incompressional and mostly shear Alfvén waves.  (2) In the downstream, the shocked solar wind shows both Alfvénic and mirror-mode features due to the coupling between the Alfvén waves and ion mirror-mode waves.  (3) Specularly reflected gyrating ions, whistler waves, and ion cyclotron waves are observed around the shock ramp, indicating that the shock may rely on both particle reflection and wave-particle interactions for energy dissipation.  (4) Both ion cyclotron and mirror mode instabilities may be excited in the downstream of the shock since the proton temperature anisotropy touches their thresholds due to the enhanced proton temperature anisotropy.  (5) Whistler heat flux instabilities excited around the shock give free energy for the whistler precursors, which help explain the isotropic electron number and energy flux together with the normal betatron acceleration of electrons across the shock.  (6) The shock may be somehow connected to the electron foreshock region of the Earth’s bow shock, since Bx > 0, By < 0, and the electron flux varies only when the electron pitch angles are less than PA = 90°, which should be further investigated. Furthermore, the interaction between Alfvén waves and the shock and how the shock modifies the properties of the Alfvén waves are also discussed.
Post-fire mobilization of metals in a recently burnt area in North-Central Portugal: a contamination risk for waterbodies?
Authors: Serpa Dalila , Machado Ana , Santos Martha , Campos Isabel , Jesus Fátima , Oliveira Bruna , Gholamahmadi Behrouz , Martins Martinho , González-Pelayo Oscar , Jacob Keizer Jan , Abrantes Nelson , Consortium Life-Reforest
Published: March 2021

Wildfires constitute a diffuse source of contamination to aquatic ecosystems. In burnt hillslopes, ash and sediments transported by overland flow are a source of potentially hazardous substances, like metals, posing a risk for downstream water bodies. In the present study, post-fire metal mobilization by overland flow was evaluated in 16 m2 bounded plots at a eucalypt stand in Albergaria-a-Velha (Aveiro district, North-Central Portugal) that burnt with moderate severity in September 2019. Overland flow samples were collected on a weekly to bi-weekly basis, depending on the occurrence of rain, during the first 6 months after fire. Aside from overland flow samples collected at slope scale, water and sediment samples were also collected in a fire-affected stream within the Albergaria burned catchment, to assess the contamination risk posed by the fire. Samples were collected at three sites along the stream: one upstream, one within and another downstream from the burnt area, after major rainfall events. The metals analysed in this study included, vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), cadmium (Cd) and lead (Pb). Results showed that most metals exhibited a peak in exports immediately after the first significant post-fire rainfall event likely due to the wash-off of the ash layer and high sediment losses, but for some elements like Zn and Cu, exports were more or less constant over time. The fire seems to have had a low impact on the water quality of the affected stream, since metal concentrations were similar between the three study sites. The quality of stream sediments, on the other hand, was clearly affected by the fire, especially after the rainy season. As fire severity and frequency is forecasted to increase in the near future due to climate changes, the results of this work reinforce the importance of water managers to define adaptative strategies to effectively protect freshwater bodies.
Global-scale assessment of agrochemicals contamination — the case study of glyphosate 
Authors: Maggi Federico , Tang Fiona , la Cecilia Daniele
Published: March 2021

The need for comprehensive assessments of agrochemicals use and its potential risk of environmental contamination are imperative, but studies currently exist only at regional and watershed scales. By coupling the recently developed PEST-CHEMGRIDS data product to the BRTSim (BioReactive Transport Simulator) computational framework, we conducted the first mechanistic assessment of the environmental hazard of glyphosate (GLP) use at global scales. PEST-CHEMGRIDS provides the annual application rate of 95 active ingredients, including GLP, on various dominant and aggregated crops (Maggi et al., 2019), and is used to feed the biogeochemical reaction network of GLP biogeochemistry embedded in BRTSim (la Cecilia et al., 2018). Deployment of BRTSim over a georeferenced global-scale grid allowed us to assess four key quantities that determine the level of environmental hazard, namely: (i) soil residue, (ii) biodegradation recalcitrance, (iii) leaching rate below the root zone, and (iv) persistence in the root zone. Our assessment (Maggi et al., 2020) shows that the total average residue in the root zone and leaching below root zone is important only in minor areas globally, but also show that biodegradation recalcitrance and persistence can lead to an environmental hazard in vast agricultural areas worldwide. The latter were largely related to the GLP transformation product, aminomethylphosphonic acid (AMPA), because of slow reaction kinetics, further inhibited by the presence of aqueous inorganic phosphate. With the four key quantities, we have mapped the aggregated hazard geographically to identify hotspots where GLP contamination may have to be assessed with greater level of detail. High hazard hotspots cover less than 1% of the agriculture area (inclusive of pastures) and are identified in north Europe, USA, Brazil, and China.

Maggi F., Tang F.H.M., la Cecilia D., McBratney A., (2019), Scientific Data 6(1), 1-20.

la Cecilia D., Tang F.H.M., Coleman N., Conoley C., Veervort R.W., and Maggi F., (2018), Water Research, 146, 37-54.

Maggi F., la Cecilia D., Tang F.H., & McBratney A., (2020). Science of the Total Environment, 717, 137167.
Triggering of the 2012 Ahar-Varzaghan earthquake doublet (Mw6.5&6.3) by the Sahand Volcano and North Tabriz fault (NW-Iran); Implications on the seismic hazard of Tabriz city
Authors: Momeni Seyyedmaalek
Published: March 2021

Seismic history of the North Tabriz fault (NTF), the main active fault of Northwestern Iran near Tabriz city, and its relation to the Sahand active Volcano (SND), the second high mountain of the NW Iran, and to the 11 August 2012 Ahar-Varzaghan earthquake doublet (Mw6.5&6.3) (AVD), is investigated. I infer that before AVD seismicity of the central segment of NTF close to SND was very low compared to its neighbor segments. Magmatic activities and thermal springs near central NTF close to Bostan-Abad city and low-velocity anomalies reported beneath SND toward NTF in tomography studies suggest that the existing heat due to SND magma chamber has increased the pore-fluid pressure that overcomes the effective normal stress on the central NTF, resulting in its creep behaviour. Two peaks of cumulative scalar seismic moments of earthquakes observed on both lobes of the creeping segment, confirming the strong difference in the deformation rate between these segments. On 2012, AVD struck in the 50 km North of NTF, in the same longitude range to SND and with the same right-lateral strike-slip mechanism to NTF, as a result of partial transfer of the right-lateral deformation of NW Iran toward the North of NTF on the Ahar-Varzaghan fault system. A cumulative aseismic slip equal to an Mw6.8 event is estimated for the creeping segment of NTF, posing half of the 7mmy-1 geodetic deformation has happened in the creep mode. This event has transferred a positive Coulomb stress field of >1 bar on the AVD and triggered them. Also, the western and eastern NTF segments received >4 bar of positive Coulomb stresses from the creeping segment and are probable nucleation locations for future earthquakes on NTF. The observed creep may be the reason for the NTF segmentation during the 1721AD M7.6 and 1780 AD M7.4 historical earthquakes.