bluuebunny/crossref_metadata_2025 huggingface dataset:
On sources and sinks of bioavailable nitrogen on the Scotian Shelf: Insights from nutrient distributions and nitrate isotope ratios
Authors: Lehmann Nadine , Kienast Markus , Normandeau Claire , Thamer Peter , Buchwald Carolyn
Published: March 2022

The northwestern North Atlantic, and the extensive Northwest Atlantic Shelf in particular, are among the areas of the world’s ocean most dramatically affected by ongoing climate change. Profound alterations of nitrogen (N) cycling both in the water column and in the sediment are expected in response to rapidly changing ocean and biogeochemical conditions. Despite the importance of bioavailable nitrogen in shaping this marine environment and ultimately sustaining large commercial fisheries, significant uncertainties remain regarding the main sources and sinks of this key macronutrient.

In this study, we use hydrographic data (T, S, O2) and nutrient concentrations collected during the Atlantic Zone Monitoring Program (AZMP) in an extended Optimum Multiparameter Analysis (eOMPA) to quantify the fractional contribution of nearshore versus slope waters on the Scotian Shelf. In combination with nitrate N and O isotope ratios (δ15NNO3 and δ18ONO3) these results will help to constrain the relationship between physical forcing (on-shelf nutrient transport) and biologically mediated sources and sinks of bioavailable N on the Scotian Shelf. Tracer distributions indicate different hydrographic sources between coastal and offshore slope stations. Nearshore subsurface (> 50 m) waters are characterized by low temperatures and a pronounced deficit in nitrate relative to phosphate (-4 µmol/L; assuming Redfield stoichiometry), highlighting the dominance of cold, fresh water from the Gulf of St. Lawrence along the inner shelf. Off-shelf, higher temperatures along with higher salinity and lower O2 concentrations indicate the presence of nutrient-rich slope waters, with contributions from both the Labrador Sea and the Gulf Stream. N and O isotope ratios show lower δ18ONO3 (0.0 – 0.4‰) and higher δ15NNO3 (~5.0‰) near the coast relative to stations further offshore (> 2.0‰ and ~4.0‰, respectively). Increased temperatures along with higher values of δ18ONO3 (~2.0‰) and a surplus in nitrate over phosphate (4 µmol/L) reflect the intrusion of warm slope waters into deep basins on the shelf. Tracer distributions further show an imprint of remineralization on bottom water properties along the shelf. These new data and results from the eOMPA will be discussed in the context of the regional circulation and N biogeochemistry.
Physicochemical and morphological features of unique example of agrosoil in Russian Arctic
Authors: Nizamutdinov Timur , Abakumov Evgeny , Morgun Evgeniya , Suleymanov Azamat
Published: March 2022

Agricultural practices beyond the Arctic Circle are currently being actively discussed both within the Circumpolar Agricultural Association. Arctic farming has a long history, for example, research on forage and vegetable growing, which were conducted at the Yamal zonal vegetable experimental station (which located in vicinities of Salekhad city, 66.5° North latitude). This station up to the collapse of the Soviet Union gave not only scientific results for agricultural science and give indirect results in the form of constructed unique soils with more than a century of history. At present, the field is a 2-year abandoned ground covered with meadow cereal-grass vegetation.

Long-term agricultural usage of this area resulted in the formation of a unique soil profile, fundamentally different from the common soils of the region. Over almost a century of agricultural activities, there was formed a powerful (up to 30 cm) humus-accumulative (Ap) horizon. The humus-accumulative horizon is underlain by a thick (45 cm) Iron-illuvial, with placic layers horizon (Bs), which changes into sandy horizons BCg and Cg with reductimorphic spots (Soil name: Plaggic Podzol (Turbic)).

Soils of tundra of Western Siberia are normally acidic, which caused measures to be taken to regulate the acidity/alkalinity regime of the soil when it was used in agriculture, but even at present the soil of Yamal experimental station is acidic (pH H2O 4.8-5 in the topsoil). Acidity decreases down the profile to close to neutral (pH H2O 6.6) in the Cg horizon. The soil organic carbon content in the humus-accumulative horizon is up to 2%, and its stock is 6912 g/m2. In the middle and deep horizons, the carbon content highly decreases to 0.02 % in the Cg horizon.

That soil is enriched with basic nutrients; the content of mobile phosphorus in Ap horizon is up to 450 mg/kg, mobile potassium - 60 mg/kg, with peak values occurring at the lower border (20-30 cm) of the humus-accumulative horizon, indicating the presence of eluviation processes. The content of mineral forms of nitrogen is low: ammonium nitrogen - 6 mg/kg in topsoil, 2.6 mg/kg in deep horizons; nitrate nitrogen - 21.5 mg/kg in topsoil, 0.22 mg/kg in deep horizons.

Literally, a century history of science-based farming makes the soil of the Yamal experimental agricultural station unique, it deserves not only a detailed study, but perhaps even assignment of the status of a protected natural object. There are almost no such objects still left in the Arctic zone of the Russian Federation and it is critical to prevent its loss due to the growing urbanization in the Arctic region.

This paper is supported by the Ministry of Science and University Education of the Russian Federation under agreement № 075-15-2020-922
Laser Ranging Interferometers in GRACE-FO and for NGGM - Status
Authors: Müller Vitali , Müller Laura , Misfeldt Malte , Wegener Henry , Hauk Markus , Heinzel Gerhard , Voss Kai , Nicklaus Kolja
Published: March 2022

The Laser Ranging Interferometer (LRI) onboard the GRACE Follow-On mission is operational for almost four years. It provides high-quality ranging data with a noise below 1 nm/√Hz at Fourier frequencies around 1 Hz, as well as attitude information with respect to the line-of-sight between the two spacecraft. Future missions are being developed by ESA under the name Next Generation Gravity Mission (NGGM) and on US-side as so-called Mass Change Mission (MCM), and in a joint frame as Mass Change and Geosciences International Constellation (MAGIC).

In this presentation, we discuss the basic working principle of the LRI and show some advantages of the design. The low ranging noise below 35 mHz Fourier frequency allows to retrieve finer structures of Earth’s gravity field than possible with conventional microwave ranging. In contrast, the low fluctuations at higher frequencies are useful to characterize the satellite platforms, e.g., thrusters and impulse-like non-gravitational accelerations, potentially from impacts of micrometeorites. We address the learned lessons from the instrument so far and sketch the challenges and development efforts ongoing for the upcoming missions.
Numerical analysis of Seismic and Hydrobiological data around lake Mavrovo in the period Jul.2020-Nov.2021
Authors: Sinadinovski Cvetan , Smiljkov Stoe
Published: March 2022

Two moderate earthquakes with magnitude ML5.0 happened on 11th of November 2020 near the Mavrovo lake in northwestern Macedonia. The lake is an artificial lake with a dam built between 1947 and filled by 1953. Its maximum length is 10km, width is 5km and the depth is 50m. Given its water volume, it is possible that geological factors causing earthquakes could also affect the hydrobiological characteristics of the flow system surrounding the lake.

A list of 180 earthquakes registered by the local stations with magnitudes equal or greater than ML1.7 was analysed in terms of temporal and spatial distribution around the lake. No specific clustering of events was noticed in the foreshock period from July 2020. In the aftershock period, the most numerous events lasted about a month after the main events. However, there was another period of increased seismicity during March 2021, followed by gradual decrease onwards. The distribution of epicentres was mainly along the terrain of Radika river and a few smaller tributaries to the lake system.

A comparative analysis was done with the dataset collected by the program run at the department of Biology at the Faculty of Natural Sciences, University UKIM in Skopje. Environmental investigations in Europe have shown stress reactions of hydrobionts in respect to water temperature and heavy metal pollution, for example the influence of radioactive radiation. Earthquake-induced seismic changes most often affect the chemical-physical properties of water quality and temperature stratification, i.e., mixing of water masses. In our research, we analyse for the first time the relationship between the seismological activities in the Jul 2020-Nov 2021 period in details and a possible impact to environment thru the population of macrozoobenthos from Mavrovo Lake.
Sub-cloud Rain Evaporation in the North Atlantic Ocean during ATOMIC Campaign
Authors: Sarkar Mampi , Bailey Adriana
Published: March 2022

Sub-cloud rain evaporation in trade-wind regions significantly contributes to the boundary layer mass and energy budgets. However, parameterizing marine rain evaporation is difficult due to the sparse availability of well-resolved rain observations and the challenges of sampling short-lived marine cumulus clouds. In this study, 1-Hz raindrop size distribution (RSD) observations, sampled during the Atlantic Tradewind Ocean-Atmosphere Mesoscale Interaction Campaign (ATOMIC) held in January-February 2020, are used to initialize a one-dimensional evaporation model to evaluate rain evaporation flux (Fe) in the sub-cloud layer for 22 case studies. Fe varies from 1 to 70 Wm−2 for 7 out of 22 cases where rain is sampled within ±100 m of ceilometer-based cloud base (700 m). These Fe values are comparable to radiative and surface fluxes in previous modeling and observational shallow cloud studies. The remaining cases where rain is sampled 800-1300 m above the cloud base have less reliable Fe due to unaccounted collision-coalescence growth as raindrops fall from sampling height to cloud base. The role of collision-coalescence growth is evident from the lower total raindrop concentration (N0) and slightly higher geometrical mean diameter (Dg) near cloud base compared to those sampled at higher altitudes. These microphysical parameters are found to not only influence the magnitude of vertically integrated Fe but also impact its vertical distribution. Comparatively, thermodynamic factors only influence the vertical distribution of Fe and not its vertically integrated magnitude. The rain evaporation is also detected by the modeled enrichment of stable isotope ratios of deuterium and oxygen in precipitation (dDp and d18Op, respectively). The enriched dDp and d18Op modeled at surface closely match observations from three independent surface sources, validating our isotope model. The enrichment modeled in both dDp and d18Op is proportional to Fe for the 7 cases close to cloud base. Compared to precipitation isotope ratios, water vapor isotope ratios cannot resolve the evaporation signals due to small ratio of evaporated to background water vapor. This increases our confidence in using rainwater isotope sampling to study sub-cloud rain evaporation in future campaigns. The substantial Fe in these shallow precipitating cumulus clouds also confirms the importance of rain evaporation in boundary layer energy budgets.
Punctuated river incision: implications for deriving climate signals, river incision and rock uplift rates from Quaternary strath terraces
Authors: Zondervan Jesse , Stokes Martin , Mather Anne , Telfer Matt , Boulton Sarah , Buylaert Jan-Pieter , Jain Mayank , Murray Andrew , Belfoul Mhamed
Published: March 2022

We demonstrate how assumptions about strath terrace formation affect the interpretation of climatic control on landscapes, calculation of incision and rock uplift rates, and recommend strategies for geochronological sampling and interpretation. An innovative approach to OSL dating terrace gravels allows us to produce a detailed ~200 kyr history of punctuated river incision and strath terrace formation spanning two stratigraphic landform levels in the High Atlas Mountains (NW Africa). Extensive preservation and exposure of strath-top gravels, within a post-orogenic setting unaffected by eustatic influences, enables the derivation of rates of base-level fall, integrated over periods of strath-top deposition, metastable equilibrium, and incision, that are consistent with independently constrained regional rock uplift rates. Combining a punctuated river incision model with our well-constrained terrace formation history allows us to demonstrate how assumptions concerning Quaternary river incision and deposition can lead to the problematic Sadler Effect, an apparent dependence of incision rates on measured time interval. Subsequently, we demonstrate that an approach to reinterpreting previously published data using the punctuated incision model, even when combined with limited terrace age data, results in more consistent and parsimonious conclusions about rates of river incision, rock uplift and base-level lowering across the mountain belt. Our recommendations for sampling strategies to constrain rock uplift rates require samples to be taken just above the strath surface, and in addition towards the top of the deposit for river incision rates. In a setting with punctuated river incision and strath terrace formation, both rock uplift and incision rates require burial dates, as exclusive use of abandonment ages will not yield constraints on accurate rates of rock uplift or incision. Furthermore, we find that only with multiple along-stream locations and multiple burial dates in each terrace deposit, could a reliable climatic signal be extracted; this signal would not have shown up in terrace abandonment ages such as those derived from cosmogenic exposure dates. The demonstrated effects of assumptions about strath terrace formation, and the recommended approaches for sampling and interpretation, have implications for those attempting to constrain palaeoclimatic, tectonic, and geomorphic histories from strath terrace records in regions exhibiting punctuated river incision.
Inversion of geoelectrical data constrained by CWT analysis
Authors: Barbolla Dora Francesca , Fedi Maurizio , Negri Sergio
Published: March 2022

We introduce a new method for the inversion of DC resistivity data. The method is based on constructing constraints based on the analysis of the Continuous Wavelet Transform (CWT) of the measured potential differences. We analyze the dipole-dipole geoelectric data through the wavelets belonging to the Poisson kernel semigroup and show that the CWT analysis of the measured electric potential differences is able to identify the main parameters of the buried sources such as depth, position and extent. Such source parameters are estimated with no need to know the resistivity contrast between the sources and the background. In general, the depth and the lateral thickness of the sources are estimated with a good accuracy, thanks to a diagram relating the singular points estimations vs. the different values of the dipole separation factor n. We proved the method by application to synthetic data and real data acquired under controlled conditions. Coupling CWT and inversion revealed to be really advantageous: after constraining the inverse problem with the a priori information from our CWT analysis, we obtained an inverse resistivity model well consistent with the known source.
Filtration and Scattering of Interstellar Neutral Helium beyond the Heliopause
Authors: Swaczyna Paweł , Bzowski Maciej , Fuselier Stephen , Galli André , Heerikhuisen Jacob , Kubiak Marzena , McComas David , Möbius Eberhard , Rahmanifard Fatemeh , Schwadron Nathan , Zirnstein Eric
Published: March 2022

The pristine very local interstellar medium (VLISM) is not available for in situ observations even with the Voyager spacecraft because the influence of the heliosphere on the VLISM plasma extends up to several hundred au from the Sun. Therefore, observations of interstellar neutral (ISN) helium, the species least modified at the heliospheric boundaries, are used to determine the pristine VLISM flow speed, direction, and temperature. For more than one solar cycle, the Interstellar Boundary Explorer (IBEX) has sampled ISN helium atoms at 1 au, significantly reducing the statistical uncertainties of the ISN helium flow parameters. Launching in 2025, the Interstellar Mapping and Acceleration Probe (IMAP) will further lower these uncertainties thanks to the utilization of a pivot platform, which provides a range of viewing orientations and reduces the parameter degeneracy seen from IBEX data. Even though interstellar helium is the least modified ISN species, recent studies show that the ISN helium flux is affected by charge exchange and elastic collisions beyond the heliopause. Charge exchange collisions outside the heliopause filter the primary ISN helium and produce a secondary population from perturbed He+ ions in the interstellar plasma. The secondary helium population, originally called the Warm Breeze, was discovered from IBEX observations. Moreover, the distribution function of the primary ISN helium population is modified by elastic collisions with slowed down and heated plasma ahead of the heliopause. Consequently, the combined primary and secondary ISN helium populations at 1 au are complex and cannot be separated. Furthermore, the modifications of the population properties are larger than the statistical uncertainty of IBEX observations. We use global heliosphere models to estimate the magnitude of the filtration and scattering caused by charge exchange and elastic collisions. Together with other sources of information about the VLISM, these estimates allow us to assess the pristine VLISM conditions outside of heliosphere influences. 
Magma Mixing in Igneous Systems 
Authors: Morgavi Daniele , Laumonier Mickael , Petrelli Maurizio , Dingwell Donald B.
Published: March 2022

Since the first hypothesis, evidences of magma mixing processes have been accumulated in the literature allowing this natural phaenomenon to be defined as fundamental petrological processes playing a role in activating volcanic eruptions and generating compositional variability in igneous systems. Here, we review the key concepts to provide the best understanding of the physical and chemical processes occurring during magma mixing. In particular: 1) an historical perspective, recounting the discovery and evolution of our understanding of magma mixing through time; 2) definitions of mixing and mingling and their major geological evidence from the field; 3) scaling rules and numerical modelling, with a deep overview on the kinematics of magma mixing; 4) a synopsis of experimental investigations of the complexity of magma mixing processes; 5) the implications of magma mixing in volcanic systems together with highlights, outstanding issues and possible future developments.
Trade-offs in strategies for climate-smart forestry in Europe
Authors: Gregor Konstantin , Knoke Thomas , Krause Andreas , Reyer Christopher , Lindeskog Mats , Papastefanou Phillip , Lansø Anne-Sofie , Smith Benjamin , Rammig Anja
Published: March 2022

Forests are a major component of climate change mitigation strategies. However, forests are affected by climate change and measures need to be taken to adapt them to changing conditions. In this context it is also important to consider forests not only as carbon stocks because they provide numerous other important ecosystem services.

“Climate-smart forestry” aims at combining the three aspects of mitigation, adaptation, and continued provision of ecosystem services. Finding concrete strategies for climate-smart forestry is complicated since future climate projections have large uncertainties. Here, we combine dynamic vegetation modeling with robust multi-criteria optimization to assess potentials and issues when trying to make European forest management “climate-smart”.

We applied the dynamic vegetation model LPJ-GUESS and simulated multiple simplified forest management options for a range of climate change scenarios defined by four representative concentration pathways (RCPs). We then defined indicators to measure the performance of various ecosystem services such as global climate change mitigation, local climate regulation through biogeophysical effects, timber provision, and biodiversity. Finally, we used robust multi-criteria optimization to compute forest management portfolios that ensure continued provision of these ecosystem services for all RCPs.

Our optimized portfolios contain large fractions (between 20 and 30%) of unmanaged forest because of its benefits for biodiversity and local climate regulation. Concerning mitigation, unmanaged forests play a divided role, depending on the assumptions about future use of wood products and the carbon-intensity of non-wood products that could be substituted, e.g. concrete. In addition, a higher share of broadleaved species is proposed throughout Europe, whereas coppice was only found to be beneficial in certain regions, typically regions where it is not a major forest type currently.

Overall, we found that climate-smart forestry cannot eliminate all trade-offs: An implementation of the portfolios would lead to strong decreases in harvests which lowers the important mitigation potential of wood products. Furthermore we argue that the decrease in harvests could lead to increases in wood imports of possibly unsustainable sources. We thus conclude that while our method offers important insights for forest management strategies, careful considerations need to be made to constrain its application. Namely, concrete prioritization of some ecosystem services will likely be necessary.
Pre-Holocene glaciovolcanism in the Katla area, south Iceland
Authors: Cole Rosie , Gudmundsson Magnús , Óskarsson Birgir , Gallagher Catherine , Larsen Guðrun , White James
Published: March 2022

The Katla volcanic system is one of the most productive in Iceland. Frequent basaltic and occasional silicic phreatomagmatic eruptions through the ice cap Mýrdalsjökull have provided a rich Holocene tephra record. Understanding of pre-Holocene eruptions and the thickness and extent of ice cover during glacial periods is much more limited.

We present eruption and emplacement models for three formations exposed on the flanks of the Katla volcano. Two are rhyolitic nunataks and one is an alkali basaltic sequence. These formations rise above the surrounding ice and topography, respectively, and show evidence for ice-confined emplacement, indicating their formation at a time when ice cover was thicker and more extensive.

Our models of each formation are based on field study, a photogrammetry survey, and major element geochemical analyses. The basaltic formation of Morinsheiði is an intercalated sequence of volcaniclastic rocks, pillow lavas and pillow breccias, entablature-jointed and lobate lavas, and more massive pahoehoe lava sheets, intruded by several dykes. The top of the sequence is a glacially eroded surface and it is bounded on all sides by deep valleys. The Enta nunatak is a kinked ridge or possibly two en-echelon ridges. A silicic volcaniclastic unit is intercalated with and intruded by fluidal and heavily jointed rhyolite lobes, spines and sheets. This formation is capped by a segment of crater wall composed of scoria. The Kötlujökull nunatak is tabular in shape, has a clastic base and is capped by jointed lava with lobate margins and breakout lobes descending the steep slopes.

Each formation exhibits evidence of multiple eruption styles in varying hydrological conditions, and at least for Morinsheiði a fluctuating water level. These are the preliminary results from the project “SURGE: Uncapping subglacial eruption dynamics and glacier response”, which aims to better understand the relative influences of magma chemistry, eruption style and glacial conditions on meltwater production and retention, glacial response, and the feedback effects for continued eruptions. These models, combined with new 40Ar-39Ar dating of the lavas, will also provide greater insight into the form of Katla and the glacial conditions that prevailed during the late Pleistocene.
How landslide debris grainsize controls sediment transport and dynamics
Authors: Xie Jun , Coulthard Tom
Published: March 2022

The grain size of sediment delivered to a river by hillslope processes is crucial for fluvial erosion, sediment transport and associated geomorphic changes. Grain size distribution (GSD) is increasingly recognized an important factor for the impact of landslides on sediment pulses and long-term erosion rates. Therefore a better understanding of grain size control on landslide generated sediment transport and dynamics is crucial and imperative for post-seismic fluvial process and landscape evolution. In this study, we modelled the recovery of the Hongxi river catchment affected by landslides triggered from the Wenchuan Earthquake under different GSD scenarios. Using the CAESAR-Lisflood (CL) model we simulated three different GSD scenarios (Original, Coarser, Finer) by altering original sediment GSD data set observed from a post-earthquake basin. In particular we analysed the fate of landslide-generated sediment using a new sediment tracing function embedded in CAESAR-Lisflood. This enabled us to evaluate the role of landslide GSD variation on the spatial-temporal heterogeneity of sediment transport and landform changes. Our results show that the GSD variations of landslide material exerts an evident impact on both sediment yield and spatial distribution of sediment transport with Finer scenarios showing an overall higher sediment yield. The content of fine sediment display a predominant control when the daily sediment yield is less than 5*10 m³ at the basin outlet. The impact of GSD on sediment transport process varies from landslide to landslide based on their characteristics. These findings highlight the importance of grain size distribution of landslide material and thus shed some light to determine the complete role of landslides on basin sediment dynamics.
Geomagnetic Excursion Record Preserved In The Speleothem From Western Caucasus: First Data
Authors: Gavrushkin Dmitriy , Pasenko Alexander , Veselovskiy Roman , Rudko Dmitriy
Published: March 2022

The study of the geomagnetic field evolution on minor timescales, in particular of such significant events as geomagnetic reversals and excursions, has acquired particular relevance nowadays due to the increased attention of mankind to the environment. The question of how exactly abrupt changes in the characteristics of the geomagnetic field affect the climate and biosphere remains largely debatable; the idea of ​​the speed and dynamics of these changes is also very vague. "Classical" geological objects and existing methods provide limited opportunities for highly detailed reconstructions of geomagnetic field variations; therefore, paleomagnetologists are looking for new objects and approaches to solve this problem. The research that we have begun involves the use of speleothems to study secular variations of the geomagnetic field.

This study presents paleomagnetic records of two drill-cores from the flowstone from Vorontsovskaya cave, located on the western flank of the Caucasus Mountains in the valley of the river Kudepsta. Preliminary results indicate the presence of a geomagnetic excursion record in both drill-cores. Further study of the samples from Vorontsovskaya cave will make it possible to compare the discovered event with known excursions, as well as to clarify its age, duration, and dynamics.
The origin of parent brine of the Badenian (Middle Miocene) primary gypsum deposits in the western part of the Carpathian Foredeep Basin: insights from strontium isotopes
Authors: Dopieralska Jolanta , Zieliński Mateusz , Belka Zdzislaw , Walczak Aleksandra , Górka Marcin , Wysocka Anna , Poberezhskyy Andriy
Published: March 2022

Middle Miocene crystals of sabre gypsum and subcrystal of giant gypsum intergrowth cropping out in southern Poland near Busko have been analysed for their Sr isotope composition. The new isotopic data revealed fluctuations in 87Sr/86Sr values within the primary gypsum crystals providing new insight into paleohydrological conditions during the Badenian salinity crisis in the Polish part of the Carpathian Foredeep Basin. The isotopic composition of a glassy gypsum subcrystal decreased progressively with the subcrystal growth, ranging from 0.70892 to 0.70884 near the crystal apex. The 87Sr/86Sr ratios of the sabre gypsum crystals are in the range of 0.70887–0.70934 and there are significant fluctuations within each gypsum layer tested. Similar intra-layer fluctuation patterns observed in various sections provide a strong argument for the synchronous origin of the investigated portions of the sulphate successions.  

The studied primary gypsum has a more radiogenic composition than the Badenian seawater. Its isotope signatures reflect spatial and temporal changes in the supply of continental derived radiogenic Sr to the Carpathian Foredeep Basin. Contrary to previous studies, the Palaeozoic clastic rocks of the Holy Cross Mountains are suggested as potential sources of radiogenic strontium. The new Sr isotope data support a salina model for the evaporitic basin of the Carpathian Foredeep.

This study was supported by the Polish National Science Centre, grant No. 2017/27/B/ST10/00493.
Integrative multivariate study of past African climate variability
Authors: Marwan Norbert , Donges Jonathan F. , Donner Reik V. , Eroglu Deniz
Published: March 2022

Based on a set of various marine palaeoclimate proxy records, we investigate African climate variations during the past 5 million years. We use a collection of modern approaches from non-linear time series analysis to identify and characterise dynamical regime shifts as changes in signal predictability, regularity, complexity, and higher-order stochastic properties such as multi-stability. We observe notable nonlinear transitions and important climate events in the African palaeoclimate, which can be attributed to phases of intensified Walker circulation, marine isotope stage M2, the onset of northern hemisphere glaciation, and the mid-Pleistocene transition, and relate them to variations of the Earth's orbital parameters.
Evaluating the effectiveness of soil conservation at the basin scale using floodplain sedimentary archives
Authors: Wang Xiaolei , Blake William , Taylor Alex , Kitch Kitch , Millward Geoffrey
Published: March 2022

Evaluation of the spatial and temporal composition of floodplain sediments and soils is critical in the creation of advanced soil management strategies for riverine catchments. The fertile catchment of the River Avon (Southwest, England) has natural and anthropogenic impacts that require enhanced definition aiding the development of a catchment management plan. The catchment was compartmentalized into its main functional units namely, cultivated land, pasture, woodland, wet moorland, and channel bank. Sediment samples were collected in each unit as surface soils and four cores were obtained along the floodplain. The samples were analyzed for particle size, fallout radionuclides and elemental concentrations. Sediment particle sizes and sediment accumulation rates (SARs) were affected by the construction of a reservoir, whereby the distributions of silt and clay in the floodplain were most affected over the past 60 years. Fertilizer components, Cr and P, were correlated in the mid-catchment, which unraveled downstream due to elevated concentrations of Cr from a geological source. Copper, As, Pb and Sn had variable down-core distributions, with pulses in concentrations due to mining inputs. The contributions of the end-member sources of particulate elements were evaluated, quantitatively, using a Bayesian Mixing Model. The statistics showed that cultivated land made a significant contribution to the sediment mixtures, independent of space and time. The results contribute to improvements in soil quality and soil conservation measures for the Avon which maybe applicable to other small catchments in the UK and elsewhere.
The gravity wave parameterization calibration problem: A 1D QBO model testbed
Authors: Shamir Ofer , Yang L. Minah , Connelly David S. , Gerber Edwin P.
Published: March 2022

An essential step in implementing any new parameterization is calibration, where the parameterization is adjusted to work with an existing model and yield some desired improvement. In the context of gravity wave (GW) momentum transport, calibration is necessitated by the facts that: (i) Some GWs are always at least partially resolved by the model, and hence a parameterization should only account for the missing waves. Worse, the parameterization may need to correct for the misrepresentation of under-resolved GWs, i.e., coarse vertical resolution can bias GW breaking level, leading to erroneous momentum forcing. (ii) The parameterized waves depend on the resolved solution for both their sources and dissipation, making them susceptible to model biases. Even a "perfect" parameterization could then yield an undesirable result, e.g., an unrealistic Quasi-Biennial Oscillation (QBO).  While model-specific calibration is required, one would like a general "recipe" suitable for most models. From a practical point of view, the adoption of a new parameterization will be hindered by a too-demanding calibration process. This issue is of particular concern in the context of data-driven methods, where the number of tunable degrees of freedom is large (possibly in the millions). Thus, more judicious ways for addressing the calibration step are required. 

To address the above issues, we develop a 1D QBO model, where the "true" gravity wave momentum deposition is determined from a source distribution and critical level breaking, akin to a traditional physics-based GW parameterization. The control parameters associated with the source consist of the total wave flux (related to the total precipitation for convectively generated waves) and the spectrum width (related to the depth of convection). These parameters can be varied to mimic the variability in GW sources between different models, i.e., biases in precipitation variability. In addition, the model’s explicit diffusivity and vertical advection can be varied to mimic biases in model numerics and circulation, respectively. The model thus allows us to assess the ability of a data-driven parameterization to (i) extrapolate, capturing the response of GW momentum transport to a change in the model parameters and (ii) be calibrated, adjusted to maintain the desired simulation of the QBO in response to a change in the model parameters. The first property is essential for a parameterization to be used for climate prediction, the second, for a parameterization to be used at all. We focus in particular on emulators of the GW momentum transport based on neural network and regression trees, contrasting their ability to satisfy both of these goals.  

 
Interactive effects of land use and soil erosion on soil organic carbon in the dry-hot valley region of southern China 
Authors: Li Yawen , Duan Xingwu , Li Ya , Li Yuxiang , Zhang Lanlan
Published: March 2022

Changes in land use can result in soil erosion and the loss of soil organic carbon (SOC). However, the individual contribution of different land use types on SOC variability as well as the combined impacts of land use and soil erosion are still unclear. The aims of the present study were to: (1) evaluate soil erosion and SOC contents under different land use types, (2) identify the influences of soil depth and land use on SOC content, and (3) determine the contribution of land use and soil erosion on SOC variability. We assessed the SOC and total soil nitrogen (TSN) contents under three types of land use in the dry-hot valley in southern China. Caesium-137 ( 137Cs) and excess lead-210 ( 210Pbex) contents were also measured to determine soil-erosion rates. Land use was found to significantly affect soil erosion, and erosion rates were higher in orchard land (OL) relative to farmland (FL), which is in contrast with previous study results. SOC and TSN contents varied significantly between the three land use types, with highest values in forest land (FRL) and lowest values in OL. SOC was found to decrease with decreasing soil depth; the highest rate of reduction occurred in the reference site (RS), followed by FRL and FL. The interaction between soil erosion and land use significantly impacted SOC in the soil surface layer (0–12 cm); the direct impact of soil erosion accounted for 1.5% of the SOC variability, and the direct or indirect effects of land use accounted for the remainder of the variability. SOC content in deep soil was mainly affected by factors related to land uses (89.0%). This quantitative study furthers our understanding on the interactive mechanisms of land use and soil erosion on changes in soil organic carbon.
Studying spatial agreement of catchment response to climate and landuse change under uncertainty for prioritizing investment into hydropower catchments 
Authors: Ding Zhaowei , Angarita Hector , Montesino Cárceres Christian , Lavado-Casimiro Waldo , David Barreto Escobedo Cesar , Guerrero Leo , Zheng Hua , Schmitt Rafael
Published: March 2022

Joint climate and land cover change can significantly alter catchment hydrologic response, e.g., in terms of runoff and sediment delivery, and thus key determinants for downstream hydropower outcomes. While many studies highlight climate risk for hydropower operation, it is less clear how climate and landuse change together will impact hydropower outcomes, if managing landuse can reduce those impacts, and how to prioritize effective investments in the face of uncertainty about the future climatic drivers.

In this study, we use Chaglla Dam, Peru’s third largest electricity generator, to develop an ensemble approach to identify parts of Chaglla’s contributing area with consistent changes in runoff and sediment under climate change. Those areas could then be targeted for maintaining or restoring natural land cover to increase baseflow and decrease sediment. We use SWAT to model catchment response for a large ensemble of climate trajectories based on latest CMIP 6 data, downscaled using multiple state-of-the-art algorithms and high-resolution regional weather observations (Figure 1 A and B). Based on the results, we identify parts of the catchment with greatest changes in water yield.  We find that 35 % of the watershed area shows consistent trends in water yield and sediment across all climate scenarios.

Climate risks will increase in the near and midterm future with increases the length of low-flow periods (up to 40 %) and increases in sediment (up to 17 %). Compared to that, additional changes in water and sediment because of projected land use change are relatively minor (+ 0.3 % in low-flow length and + 0.7 % in sediment).

Yet, our study introduces a spatially-explicit framework for analyzing large ensembles of climate and landuse projections to identify where future change will translate in most change in hydrologic parameters related to hydropower. Results enable to study if investing in catchment conservation in those areas will significantly improve hydropower outcomes and will thus help to develop management plans for hydropower catchment that are robust under future change.
Spatially Highly Resolved Solar-wind-induced Magnetic Field on Venus
Authors: He Maosheng , Vogt Joachim , Dubinin Eduard , Zhang Tielong , Rong Zhaojin
Published: March 2022

The current work investigates the Venusian solar-wind-induced magnetosphere at a high spatial resolution using all Venus Express (VEX) magnetic observations through an unbiased statistical method. We first evaluate the predictability of the interplanetary magnetic field (IMF) during VEX's Venusian magnetospheric transits and then map the induced field in a cylindrical coordinate system under different IMF conditions. Our mapping resolves structures on various scales, ranging from the ionopause to the classical IMF draping. We also resolve two recently reported structures, a low-ionosphere magnetization over the terminator, and a global "looping" structure in the near magnetotail. In contrast to the reported IMF-independent cylindrical magnetic field of both structures, our results illustrate their IMF dependence. In both structures, the cylindrical magnetic component is more intense in the hemisphere with an upward solar wind electric field (E^SW) than in the opposite hemisphere. Under downward E^SW, the looping structure even breaks, which is attributable to an additional draped magnetic field structure wrapping toward −E^SW. In addition, our results suggest that these two structures are spatially separate. The low-ionosphere magnetization occurs in a very narrow region, at about 88°–95° solar zenith angle and 185–210 km altitude. A least-squares fit reveals that this structure is attributable to an antisunward line current with 191.1 A intensity at 179 ± 10 km altitude, developed potentially in a Cowling channel.
Vertical distribution of 137Cs in bottom sediments as representing the time changes of water contamination: Chernobyl and Fukushima
Authors: Konoplev Aleksei , Wakiyama Yoshifumi , Wada Toshihiro , Igarashi Yasunori , Laptev Gennady , Golosov Valentin , Ivanov Maxim , Komissarov Mikhail , Nanba Kenji
Published: March 2022

Bottom sediments of lakes and dam reservoirs can provide an insight into understanding the dynamics of 137Cs strongly bound to sediment particles. On this premise, a number of cores of bottom sediments were collected in deep parts of lakes Glubokoe, Azbuchin, and Cooling Pond in close vicinity of the Chernobyl NPP in Ukraine, in Schekino reservoir (Upa River) in the Tula region of Russia (2018) and in Ogaki reservoir (Ukedo River) in Fukushima contaminated area (2019). Each layer of bottom sediments can be attributed to a certain time of suspended particles sedimentation. With 137Cs activity concentration in a given layer of bottom sediments corresponding to 137Cs concentration on suspended matter at that point in time, we were able to reconstruct the post-accidental dynamics of particulate 137Cs activity concentrations. Using experimental values of the distribution coefficient Kd, changes in the dissolved 137Cs activity concentrations were estimated. The annual mean particulate and dissolved 137Cs wash-off ratios were also calculated for the period after the accidents. Interestingly, the particulate 137Cs wash-off ratios for the Ukedo River at Ogaki dam were found to be similar to those for the Pripyat River at Chernobyl in the same time period after the accident, while the dissolved 137Cs wash-off ratios in the Ukedo River were an order of magnitude lower than the corresponding values in the Pripyat River. The estimates of particulate and dissolved 137Cs concentrations in Chernobyl cases were in reasonable agreement with monitoring data and predictions using the semi-empirical diffusional model. However, both the particulate and dissolved 137Cs activity concentrations and wash-off ratios in the Ukedo River declined faster during the first eight years after the FDNPP accident than predicted by the diffusional model, most likely, due to greater natural attenuation and, to some extent, remediation measures implemented on the catchments in Fukushima.

This research was supported by Science and Technology Research Partnership for Sustainable Development (SATREPS), Japan Science and Technology Agency (JST)/Japan International Cooperation Agency (JICA) (JPMJSA1603), by bilateral project No. 18-55-50002 of Russian Foundation for Basic Research (RFBR) and Japan Society for the Promotion of Science (JSPS), and JSPS Project KAKENHI (B) 18H03389.
Observations of Higher-band ECH waves and its impact on radiation belt energetic electrons
Authors: Qiwu Yang , Fuliang Xiao , Qinghua Zhou , Si Liu , Zhonglei Gao , Yihua He , Sai Zhang , Zhoukun Deng , Jiawen Tang
Published: March 2022

Electron cyclotron harmonic (ECH) waves which mainly observed in the first harmonic band are believed to play a part in scattering diffuse aurora electrons in the Earth's magnetosphere. Here we report two enhanced ECH emission events with nominal wave magnitudes exceeding 1mV/m in higher bands ( up to the 4th harmonic bands) observed from Van Allen Probes mission during geomagnetic disturbance periods in the low density area. Based on actual measurements sampled by Van Allen Probes, we model the electron distribution using a superposition of bi-Maxwellian functions and then numerically evaluate the local growth rates and diffuse coefficients. These differences in frequency distribution for two events can be explained by differences in the loss cone feature of hot electron components. The scattering properties in the first four bands for two events are debated, these results suggest ECH waves in higher band can still cause efficient pitch angle scattering which are similar to ECH waves in the first band. This work broadens our understanding in the formation of diffuse aurora contributed by ECH waves.
An efficient ray-tracing based algorithm to compute terrain horizon and sky view factor to consider topographic effects on surface radiation in spatially distributed land surface models
Authors: Steger Christian R. , Steger Benjamin , Schär Christoph
Published: March 2022

In mountainous regions, incoming surface radiation is strongly influenced by surrounding and local terrain. The direct beam part of incoming shortwave radiation depends both on local slope angle and azimuth as well as on neighbouring terrain, which can induce topographic shading. Shortwave radiation can be reflected (multiple times) by terrain, which leads to enhanced incoming diffuse shortwave radiation for locations with a reduced sky view factor (SVF) – particularly under snow-covered conditions when surface reflectivity is high. Finally, incoming longwave radiation can also be modulated by neighbouring terrain due to radiation exchange between facing slopes.

Considering these effects in spatially distributed land surface models – either stand-alone or embedded in weather and climate models – typically requires the following topographic quantities: slope angle, slope aspect, terrain horizon and SVF. The first two quantities can be computed rapidly because they only depend on local terrain. The computation of the latter two quantities is however expensive, particularly for high-resolution (~30 m) digital elevation models (DEMs), because a large quantity of non-local DEM information has to be processed. We developed a new efficient algorithm for terrain horizon computation, which is based on a high-performance ray-tracing library. A benchmark against conventional algorithms confirmed its high performance – particularly for DEMs with very high resolution and for large terrain horizon search distances. Furthermore, due to the smooth representation of terrain by a triangle mesh, the new algorithm does not reveal artefacts in the computed horizon line in cases where the horizon is formed by proximal terrain. Finally, we demonstrate that the new algorithm is also eligible to compute sub-grid SVF for large spatial domains in a very efficient way. Sub-grid SVF is a useful quantity to parameterise above-mentioned topographic effects on surface radiation in weather and climate models applied on regional or even global scales.