bluuebunny/crossref_metadata_2025 huggingface dataset:
Resin harvesting’s effect on maritime pine growth varies with tree age
Authors: Moura Mikael , Campelo Filipe , Nabais Cristina , García-Forner Núria
Published: March 2022

Resin is a natural defensive substance produced by trees in response to injury and infection and is a sustainable and valuable non-timber forest product. Resin tapping is a traditional activity that besides increasing the economic profit of forest plantations, it provides ecosystem services and promotes the development of rural areas. However, the effect of resin tapping on tree growth remains elusive. Furthermore, there is evidence connecting resin production with climatic conditions, but tree-growth responses to climatic conditions and stand characteristics in resin-tapped and non-tapped trees remains unclear. Our aim is to understand if resin tapping affects tree growth, and how tree age, edaphoclimatic conditions and stand characteristics interplay. A dendrochronological study was conducted in six Pinus pinaster stands across a latitudinal gradient from North to the Centre of Portugal. The stands that had been resin-tapped for 5 to 7 years, presented different climate conditions and characteristics, i.e. different cambial ages. When tree-growth (tree ring-width; TRW) on tapped and untapped trunk sides was compared during the resin-extraction period, there was a slight enhancement of growth in the resin-tapped side of the youngest populations (<30 years) and no changes in older populations (>40 years). Annual resin-tapping impact (RTI), calculated as the ratio between TRW during resin harvesting years and the 5-year average TRW before tapping, was below (above) 1 in the younger (older) stands. Among other stand characteristics, RTI was negatively correlated with tree competition. Climatic conditions did not have a major influence on tree growth in response to resin tapping. In conclusion, the effect of resin extraction on growth is age dependent, with younger trees being more negatively affected. Our results seem to indicate that the co-production of resin and timber should be performed in pine populations older than 40 years.

 
UAV applications to assess short-term dynamics of slow-moving landslides under dense forest cover
Authors: Ilinca Viorel , Șandric Ionuț , Chițu Zenaida , Irimia Radu , Gheuca Ion
Published: March 2022

The paper focuses on presenting a methodology that can be used to rapidly assess and map kinematics of landslides when these occur in areas with dense vegetation cover. The method is based on using aerial imagery collected with UAV (Unmanned Aerial Vehicle) and their derived products obtained by applying the Structure from Motion (SfM) technique. The landslide occurred on May 3, 2021, and is located in the Livadea village, Curvature Subcarpathians (Romania). It affected several houses from the vicinity, and the people were relocated because of the high probability of landslide reactivation. To mitigate the consequences of this landslide, a preliminary investigation, based on three UAV surveys and field geological-geomorphological surveys, was carried out to delineate active parts of the landslide and to define evacuation measures. Three UAV flights (May 6, May 25 and July 10) were performed using DJI Phantom 4 and Phantom 4 RTK drones. Because it is a heavily forested area, a semi-automated processing of the landslide kinematics and change detection analysis were not possible. The landslide displacement rates and the changes in terrain morphology between flights were assessed by manual interpolating of collected landmarks on all three UAV flights. Tilted trees were used to estimate the landslide direction and evolution. The results show an average displacement of 9.55 m (minimum 1.2 m, maximum 20.6 m) between the first and the second flight and an average of 19.27 m (minimum 1.98 m and maximum 46.3 m) between the second and the third flight, respectively. This approach proved quick and efficient for rapid landslide investigations when fast response and measures are necessary to reduce landslide consequences.

Acknowledgement

This work was supported by a grant of the Romanian Ministry of Education and Research, CCCDI - UEFISCDI, project number PN-III-P2-2.1-PED-2019-5152, within PNCDI III (project coordinator Ionuț Șandric, https://slidemap.gmrsg.ro) and by the project PN19450103 / Core Program (project coordinator Viorel Ilinca).
Learn from the mummies: water wise resilience and adaptation in Egypt along the Nile River.
Authors: Casale Francesca , Fuso Flavia , Cecchetti Alessia , Bocchiola Daniele
Published: March 2022

We preliminary investigate potential effects of climate change on Egypt water wise, and adaptation thereby based upon wisdom from the ancient Egyptians. Recent investigation linked socio-economic crises, and collapse events of ancient Egypt since 2200 BC to climate, e.g., droughts, and floods of the Nile, and heavy rainfalls in Northern Egypt. Dry, arid spells were associated to decrease of summer precipitation in the Ethiopian Highlands, while intensive rainfalls could be triggered by the North Atlantic Oscillation.

Here we couple climate, and hydrological modelling, with archaeological and historical investigation, to understand long-term adaptation to the ever-changing climate. We assess past climate of Egypt and consequent changing hydrology of the Nile, including situations of flood risk and food insecurity. We highlight a nexus between changing in climate and hydrology, conflicts, and social disorders.

We tune the Poli-Hydro model for Nile River basin for the XX century, and then use it to simulate future scenarios under climate change projections from six GCMs, of the AR6 of IPCC. We compare future scenarios of climate, and hydrology against past climates patterns. We analyse typical adaptation patterns as from the history of ancient Egypt (e.g. changes of diet, irrigation and cropping strategies, etc.), and we discuss their application for adaption to future climate. Our work may provide a tool to build upon past resilience/adaptation strategies, to conceive viable countermeasures to future climate change here, and in similarly arid areas, to counteract potential food insecurity, flood risk, and conflicts.
Abundance and community composition of free-living nematodes as a function of soil structure under different vineyard managements
Authors: Schlüter Steffen , Gil Eshel , Doniger Tirza , Applebaum Itaii , Steinberger Yosef
Published: March 2022

Organic farming aims at improving soil fertility in vineyard soils through a combination of farming practices. We studied the effect of organic management on community traits of free-living nematodes as well as bulk and microstructure properties of soil by comparing them to conventional management, both within vine rows and in interrows. The objectives of this study were to: 1) identify differences between management systems in terms of nematode abundance and molecularly measured community composition, and 2) to scrutinize, whether these changes can be explained by microstructural properties measured with X-ray computed tomography (X-ray CT) of individual soil aggregates. Nematode abundance was mainly  governed by habitat constraints, which was reflected in significant correlations with soil moisture and with porosity in the habitable size range of 20–220 μm obtained with X-ray CT. The lack of bioturbation by fine roots and the absence of irrigation reduced the abundance of water-filled, habitable pores, which resulted in the lowest nematode abundance in conventionally managed interrows without a grass cover. Community composition in terms of diversity and maturity, in turn, was not affected by habitat constraints but mainly governed by resource availability for the soil food web estimated by particulate and dissolved organic matter contents. The permanent grass cover and lack of tillage in interrows of the organic vineyard improved resource availability and promoted the build-up of omnivores and predators that are especially sensitive to disturbance. The organically managed interrows therefore had lower diversity and higher maturity than conventionally managed interrows. Differences between conventional and
organic management were in general greater in interrows than within vine rows.
These findings highlight the added value of pore structure investigations via X-ray CT in understanding trophic interactions of nematodes. At the same time, they stress the importance of exact sampling locations on nematode traits especially for perennial, woody crops.
Influence of PDO and ENSO on Indian summer monsoon rainfall and its changing relationship before and after climate shift
Authors: K Xavier Anupama , Varikoden Hamza , Chethalan Anthony Babu
Published: March 2022

Indian summer monsoon provides rainfall over a large area during 01 June to 30 September and it plays vital role for the water needs of the population of India. It is intense because strong differential heating prevails over the region due to geographical features of India. Further, it can be viewed as a synoptic scale ocean - atmosphere interactive system. In this study, we investigated the possible relation between the Indian summer monsoon and the combination of the different phases of Pacific Decadal Oscillation (PDO) and El Niño Southern Oscillation (ENSO) before and after the climate shift in 1976. This study is carried out using IMD’s precipitation dataset, HadISST v1.1 dataset and twentieth century reanalysis dataset by comparing anomalies of the respective parameters from 1901 to 2020. It is found that when positive (negative) phases of PDO and El Niño (La Niña) co-occur, deficit (surplus) rainfall are likely to occur over entire India. SST signatures of both phenomena are evident in this context. However, when negative (positive) PDO and El Niño (La Niña) co-occur, the signal is mixed and it is unlikely that either surplus or deficit rainfall conditions will occur over entire India. SST signatures are disrupted and minimized. In other words, when ENSO and PDO are in (out of) phase they enhance (counteract) the conventional monsoon-ENSO relation. Further, the study periods were divided into pre and post climate shift periods based on Niño 3.4 index and PDO index and analysed their impact on the Indian summer monsoon rainfall. In the pre-shift period, in-phase conditions exhibit similar qualities to those described above. Rainfall patterns are more indicative of ENSO than PDO. In the post-shift situation, the positive anomaly of SST in the PDO and Niño region is significantly stronger than that of the pre-shift phase. When compared to the pre-shift, positive rainfall anomalies are amplified during positive PDO and El Niño,  while negative PDO and La Niña show a weakening of positive rainfall anomalies. The out of phase condition has a balancing effect due to the counteracting impact, but with an increased positive anomaly of SST. In that combination, rainfall patterns with PDO characteristics rather than ENSO characteristics emerge. Significant warming of the Indian Ocean basin was also evident in the above combinations after the climate shift in 1976. Low level wind anomalies and other circulation features are consistent with the above result.
Multi-ensemble MHD coronal modeling to improve background wind for CME propagation for EUHFORIA 2.0
Authors: Perri Barbara , Leitner Peter , Brchnelova Michaela , Baratashvili Tinatin , Kuzma Blazej , Zhang Fan , Lani Andrea , Poedts Stefaan , Kochanov Andrey , Samara Evangelia , Brun Allan Sacha , Strugarek Antoine
Published: March 2022

Space weather has the difficult task to try to anticipate the propagation of eruptive events such as coronal mass ejections (CMEs) in order to assess their possible impact on the Earth’s space environment. This requires an accurate description of the background in which CMEs propagate, mainly the continuum ejecta of particles that is the solar wind and the dynamo-generated heliospheric magnetic field. This proves challenging as the solar wind and dynamo magnetic field are interacting with each other depending on the activity cycle of our star, both at large and small scales. To be able to model accurately such a wide variety of scales and parameter regimes, the approach used by the EUHFORIA 2.0 project is to use a chain of models, taking advantage of existing codes to combine their strengths through numerical coupling across the heliosphere. The first step of this chain is the data-driven modeling of the inner corona, from photosphere measurements up until 0.1 AU, and it proves especially critical as it serves as boundary condition for the rest of the models.

 

In that regard, we will present here two coronal MHD models implemented as an alternative to the semi-empirical WSA and SCS models used so far in EUHFORIA. By using the COOLFluiD framework, we developed a new coronal model with implicit solving methods and unstructured meshes, which proves faster than traditional explicit methods on regular grids. We used the coronal code Wind-Predict to benchmark this new model for the simple polytropic approximation in the first place, and we present the similarities and differences obtained for data-driven configurations and compare them with observations (white-light images, coronal hole boundaries, in-situ data at 1 AU after coupling with EUHFORIA). We then present the improvements foreseen for each codes, especially for the heating terms: Wind-Predict will incorporate self-consistent Alfvén waves while COOLFluiD will use ad-hoc heating terms and a multi-species treatment. We will finally discuss the implications for the coupling with EUHFORIA and the CME propagation between 0.1 and 1 AU.
Enhanced jet stream waviness induced by suppressed tropical Pacific convection during boreal summer
Authors: Ding Qinghua , Sun Xiaoting , Wang Shih-Yu Simon , Topál Dániel , Li Qingquan , Castro Christopher , Teng Haiyan , Luo Rui , Ding Yihui
Published: March 2022

Consensus on the cause of recent midlatitude circulation changes toward a wavier manner in the Northern Hemisphere has not been reached, albeit a number of studies collectively suggest that this phenomenon is driven by global warming and associated Arctic amplification. Here, through a fingerprint analysis of various global simulations and a tropical heating-imposed experiment, we suggest that the suppression of tropical convection along the Inter Tropical Convergence Zone induced by sea surface temperature (SST) cooling trends over the tropical Eastern Pacific contributed to the increased summertime midlatitude waviness in the past 40 years through the generation of a Rossby-wave-train propagating within the jet waveguide and the reduced north-south temperature gradient. This perspective indicates less of an influence from the Arctic amplification on the observed mid-latitude wave amplification than what was previously estimated. This study also emphasizes the need to better predict the tropical Pacific SST variability in order to project the summer jet waviness and consequent weather extremities.
Investigating root water uptake dynamics of a grassland species under varying hydro-climatic conditions with non-destructive isotopic monitoring
Authors: Deseano Diaz Paulina Alejandra , van Dusschoten Dagmar , Kübert Angelika , Brüggemann Nicolas , Javaux Mathieu , Merz Steffen , Vanderborght Jan , Vereecken Harry , Dubbert Maren , Rothfuss Youri
Published: March 2022

Traditional destructive plant and soil water isotopic monitoring has provided important insights into root water uptake changes in drought and evapotranspiration partitioning across scales. Recently, non-destructive isotopic monitoring coupled with laser-based spectroscopy allow a better understanding of these and other questions with a higher spatial and temporal resolution. We investigated the changes in root water uptake profiles and eco-physiological characteristics (e.g. stomatal conductance, leaf water potential) of the grassland species Centaurea jacea under varying environmental conditions (i.e. atmospheric demand, soil water availability) with a labeling experiment in fully-controlled laboratory conditions. We measured non-destructively the isotopic composition of soil water and of plant transpiration. With these measurements, daily root water uptake profiles were obtained using a multi-source mixing model embedded in a Bayesian statistical framework. We analyzed the daily changes of these profiles together with changes in environmental conditions and plant physiology-related variables to discover potential adaptation strategies of C. jacea to water scarcity. Even in a dry soil (~ 10% soil water content), the studied grassland species was able to sustain high transpiration rates. This was accompanied by a very negative leaf water potential (~-3 MPa). Root water uptake profiles in both dry and wet conditions were very similar: root water uptake was highest in the soil layer 0-15 cm (up to 87%) and second highest (up to 40%) in the soil layer 45-60 cm. Before soil water content dropped below 12%, transpiration rate was mainly controlled by vapor pressure deficit. After this, a reduction of canopy conductance restricted gas leaf exchange. Instantaneous water use efficiency dropped when the soil was very dry, but intrinsic water use efficiency was maintained. Our comprehensive data set of plant-related and environmental variables allowed us to investigate at a 1-cm and daily scales the plant’s response to varying hydro-climatic conditions.
Stochastic modeling of the multimodal behavior of spatially heterogeneous calcite dissolution rate at the nanoscale
Authors: Recalcati Chiara , Siena Martina , Riva Monica , Guadagnini Alberto
Published: March 2022

Mineral dissolution/precipitation reactions are critical in several contexts (e.g., geologic sequestration of CO2 or reservoir hydraulic fracturing). High-resolution imaging techniques such as Atomic Force Microscopy (AFM) allow direct observation of the (nanometer-scale) evolution of the crystal topography during the reaction, thus enhancing our knowledge on the various dissolution mechanisms occurring at the liquid-solid interface. These mechanisms are imprinted onto the highly heterogeneous patterns observed and are originated from the presence of inhomogeneities and defects in the mineral lattice, resulting in a broad range of local reaction rate values. We rely on a multimodal Gaussian model to capture the spatial heterogeneity of dissolution rates from AFM (in-situ and in real time) topography measurements collected on calcite samples subject to dissolution at far from equilibrium conditions. We resort to an imaging segmentation technique to cluster reaction rate data into regions associated with diverse dissolution mechanisms and relate each region to a component of the Gaussian mixture. We analyze the temporal trend of model parameters to provide quantitative insights on the dynamic evolution of the spatial heterogeneity of dissolution rate.
Observation-based estimates of Eulerian-mean boundary downwelling in the western subpolar North Atlantic
Authors: liu Yingjie , Desbruyeres Damien , Mercier Herle , Spall Michael
Published: March 2022

A significant fraction of the Eulerian downwelling feeding the lower limb of the Atlantic Meridional Overturning Circulation (AMOC) has been proposed to occur around the subpolar North Atlantic's continental slopes. While this downwelling ultimately takes place in a thin boundary layer where relative vorticity can be dissipated via friction, it is maintained by a large-scale geostrophic balance and an along-shore densification of the boundary current. We here use modern hydrography data (Argo and shipboard hydrography mainly) to map the long-term mean density field along the continental slope via an optimal interpolation method specifically adapted to the length scales of the boundary current. The overall downstream densification of the boundary region implies a Eulerian-mean downwelling of 2.12 ± 0.43 Sv at 1100 m depth between Denmark Strait and Flemish Cap. While seasonal variations appear to be relatively limited, a clear regional pattern emerges with Eulerian-mean downwelling in the Irminger Sea and western Labrador Sea and upwelling along Greenland western continental slope. Comparisons with independent cross-basin estimates confirm that overturning transport across the marginal seas of the subpolar North Atlantic is mainly explained by vertical volume fluxes along the continental slopes, and suggest the usefulness of hydrographic data alone to estimate the regional pattern of the sinking branch of the AMOC. 
Biotoxicological risks and hazards of a warming Arctic
Authors: Miner Kimberley
Published: March 2022

 

Climate change accelerates permafrost degradation throughout the Arctic, introducing previously sequestered known and unknown biotoxicological hazards.1 While infrastructure failures due to permafrost thaw are well documented, biological and chemical hazards are less understood. Minimally characterized bacteria, viruses, and pathogens are bringing unknown paleo-ecosystem dynamics into the modern age.2 These species join various anthropogenic materials, including banned organic pesticides, mercury, oil, and nuclear remnants. Though research is ongoing, Arctic permafrost variability presents additional uncertainty in the location, timing, and rate of emergence for these hazards.

 

In order to understand the dynamics of this emergent risk from the new Arctic, there is an urgent need to quantify the risks before they emerge. To do this, a combination of remote sensing, in-situ field work, and modeling are needed to better integrate micro-scale dynamics (including permafrost thaw) into Earth systems models. Paralleling the growing impacts of Arctic carbon release, biotoxicological hazards are poised to become a new source of contaminants across the Arctic environment.

 

 

Miner, K. R. et al. Emergent biogeochemical risks from Arctic permafrost degradation. Nat. Clim. Chang. (2021) doi:https://doi.org/10.1038/s41558-021-01162-y.

Edwards, A. et al. Microbial genomics amidst the arctic crisis. Microb. Genomics 6, 1–20 (2020).

Miner, K. R. et al. A screening-level approach to quantifying risk from glacial release of organochlorine pollutants in the Alaskan Arctic. J. Expo. Sci. Environ. Epidemiol. 29, (2018).
Planetary wave-driven enhanced NO descent into the top of the Arctic polar vortex during major and minor sudden stratospheric warmings
Authors: Harvey V. Lynn , Pedatella Nicholas , Datta-Barua Seebany , Randall Cora , Siskind David , Greer Katelynn , Goncharenko Larisa
Published: March 2022

The polar vortices play a central role in vertically coupling the Sun-Earth system by facilitating the descent of reactive odd nitrogen (NOx = NO + NO2) produced in the atmosphere by energetic particle precipitation (EPP-NOx). Downward transport of EPP-NOx from the mesosphere-lower thermosphere (MLT) to the stratosphere inside the winter polar vortex is particularly impactful in the wake of prolonged sudden stratospheric warming (SSW) events. This work is motivated by the fact that state-of-the-art global climate models severely underestimate EPP-NOx abundances in the polar MLT. It is not clear whether this deficiency is due to a missing NOx source or to inadequate transport processes. As a step toward understanding the transport pathways by which MLT air enters the top of the polar vortex, we explore the extent to which planetary waves impact the geographic distribution of NO near the polar winter mesopause in the Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension combined with data assimilation using the Data Assimilation Research Testbed (WACCMX+DART). We present planetary wave-driven NO patterns near the polar winter mesopause during 16 case studies from the Arctic winters of 2005/2006 through 2018/2019. During all cases the model is in reasonable agreement with Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) derived zonal winds and Solar Occultation For Ice Experiment (SOFIE) and Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS) NO measurements. Superposed Epoch Analysis is employed to diagnose typical mesopause planetary wave behavior and vertical transport characteristics during 10 minor and 6 major SSW events. Results show that descent of NO into the top of the polar vortex is enhanced by about a factor of 4 in traveling planetary wave troughs vs. in ridges and that this planetary wave-driven enhanced NO descent occurs during both minor and major SSW events. These results present a new conceptual model of zonally varying, vs. zonally uniform, polar descent in the MLT.
Ground Penetrating Radar survey at the archaeological site of Qubbet El-Hawa, Aswan, Egypt
Authors: Peláez José A. , Soler Juan L. , Sawires Rashad , Jiménez Alejandro , Alba José M.
Published: March 2022

The necropolis of Qubbet el-Hawa is located in West-Aswan, Upper Egypt. It looks like a huge dune covering the massive Nubian Sandstone Group, hosting one of the most densely occupied cemeteries of Ancient Egypt, dating back to c. 2500 B.C. to the Roman Period. Here we present the used methodology and the conducted ground-penetrating radar (GPR) survey accomplished in the Qubbet El-Hawa site.

Three different geological formations have been differentiated in the studied area. From bottom to top, the Abu Agag, the Timsah and the Um Barmil formations, which mainly belong to the Nubian Sandstone Group. The conducted GPR survey was accomplished in the Timsah Formation, the most heterogeneous formation of all of them, in which along its outcrops can be observed several stratigraphic discontinuities, being usually the alternation of lutite (mainly claystone), sandstone, and iron oxides, arranged in alternating layers varied in thickness from 5 to 10 cm, and from 30 to 50 cm thick blocks.

The studied area, 20 m width × 45 m length, showing a near-constant slope of about 35°, was surveyed using 250 and 500 MHz shielded antennas in a dense array pattern. Although dry eolian sand and sandstone rocks do not display a clear difference in their electromagnetic characteristics, the conducted survey was able to discriminate/define the interface among the underlying sandstone and the sand cover. This good behavior could be attributed to the different overlapping layers including ferruginous sediments and claystone. This was possible even when the studied area exhibits a steep slope, as well as many loose rocks in some parts, coming from the outcrops, that made the measurement difficult to carry out in some cases.

The interface among the underlying sandstone formation and the sand cover is acceptably resolved, providing some very useful data to archaeologists about the near-surface shape of the bedrock and their possible willingness to host some graves.
Why does the heated needle probe method underestimate snow thermal conductivity?
Authors: Fourteau Kevin , Hagenmuller Pascal , Domine Florent
Published: March 2022

Thanks to its ease of use, the heated needle probe method is broadly employed to measure snow thermal conductivity, both in the field and in laboratory. However, recent studies have highlighted that when compared to other measurement techniques, the needle probe shows a systematic underestimation bias. Here, we examine the theory at the base of the needle probe method and show that for a light and insulating material such as snow, the standard measurement protocol using heating times around 100 s leads to underestimations, as observed. Moreover, the damage done to the snow microstructure when manually inserting the probe leads to a further underestimation, that can exceed 50%. Nonetheless, needle probes remain the only easily deployed technique to measure snow thermal conductivity in remote areas. We thus propose a new measurement protocol to correct this underestimation and to obtain reasonably reliable values of snow thermal conductivity.
Impact of Different Phase Center Correction Values on Geodetic Parameters: A Standardized Simulation Approach
Authors: Kröger Johannes , Kersten Tobias , Breva Yannick , Brekenkamp Mareike , Schön Steffen
Published: March 2022

For highly precise and accurate positioning and navigation solutions with GNSS, it is mandatory to take all error sources – including phase center corrections (PCC) – adequately into account. These corrections are provided by different calibration facilities and are published in the official IGS antenna exchange format (ANTEX) file for several geodetic antennas.

Currently, the IGS antenna working group (AWG) is discussing which metrics should be used as a basis for accepting new calibration facilities as an official IGS calibration facility. To this end, requirements have to be set for comparing different sets of PCC for the same type of antenna.

Mostly, characteristic values of difference patterns (dPCC) are analysed, e.g. maximum deviations, RMS of dPCC, or percentage of dPCC values that are smaller than 1 mm. For users and station providers, however, it is most interesting to investigate the impact of dPCC on geodetic parameters, e.g. topocentric coordinate deviations and troposphere estimates. Since the impact is not only depending on the antenna in use and the station’s location but also on the applied processing strategies, a standardized comparison strategy is needed.

In this contribution, we present the impact of different PCC values on geodetic parameters using a standardized simulation approach. We show results for several globally distributed stations using different processing strategies and their respective impact on the geodetic parameters. This includes the application of different elevation cut-off angles, observation weightings w.r.t satellite coverages and elevation angles as well as use of different frequencies and linear combinations. The obtained results are analysed in detail, repeated behaviours are grouped and compared to widely used characteristic values of dPCC. Thus, an overall conclusion of the similarity of different PCC models can not only be drawn on the pattern level, but also their impact on geodetic parameters can be assessed.
Practical notes on lossy compression of scientific data
Authors: Kouznetsov Rostislav
Published: March 2022

Lossy compression methods are extremely efficient in terms of space and performance and allow for reduction of network bandwidth and disk space needed to store data arrays without sacrificing the number of stored values.  Lossy compression involves an irreversible transformation of data that reduces the information content of the data.  The transformation introduces a distortion that is normally measured in terms of absolute or relative error. The error is higher for higher compression ratios.  A good choice of lossy compression parameters maximizes the compression ratio while keeping the introduced error within acceptable margins.  Negligence or failure to chose a right compression method or its parameters leads to poor compression ratio, or loss of the data.

A good strategy for lossy compression would involve sepcification of the acceptible error margin and choice of compression parameters and storage format. We will discuss specific techniques of lossy compression, and illustrate pitfalls in choice of the error margins and tools for lossy/lossless compression. The following specific topics will be covered:

1. Packing of floating-point data to integers in NetCDF is sub-optimal in most cases,   and for some quantities leads to severe errors.
2. Keeping relative vs absolute precision: false alternative.
3. Acceptible error margin depends on both the origin and the intended application of data.
4. Smart algorithms to decide on compression parameters have limited area of applicability,   which has to be considered in each individual case.
5. Choice of a format for compressed data (NetCDF, GRIB2, Zarr): tradeoff between size, speed and precision.
6. What "number_of_significant_digits" and "least_significant_digit" mean in terms of relative/absolute error.
7. Bit-Shuffle is not always beneficial.
Repeat hydrography and Deep-Argo reveal a warming-to-cooling reversal of overflow-derived water masses in the Irminger Sea during 2002-2021.
Authors: Desbruyères Damien , Prieto Bravo Eva , Thierry Virginie , Mercier Herlé , Lherminier Pascale
Published: March 2022

Sustained shipboard hydrography surveys along the A25-Ovide section (2002 – 2018) are combined with data from a regional pilot array of Deep Argo floats (2016 – 2021) to estimate the decadal variability and linear trends in the temperature of overflow-derived waters in the Irminger Sea. Removing local or remote dynamical influences (heave) enables to identify a new statistically-significant trend reversal in Iceland Scotland Overflow Water (ISOW) and Denmark Strait Overflow Water (DSOW) core temperatures (spice). The latter took place in 2014 and interrupted a long-term warming of those water masses that was prevailing since the late 1990’s. Deep-Argo floats further reveal an overall acceleration of this cooling since 2014, with a mean rate of change estimated at -18 m°C yr-1 during 2016 – 2021, as well as a boundary-intensified pattern of change. This, along with the absence of apparent reversal in the Nordic Seas and with DSOW warming and cooling twice as fast as ISOW, points out the entrainment of subpolar intermediate signals within the overflow plumes near the Greenland-Iceland-Scotland sills as a most likely driver.
Investigation of debris-flow impact forces on bridge superstructures – laboratory experiments on the influence of bridge profiles
Authors: Friedl Caroline , Scheidl Christian , Wernhart Susanna , Proske Dirk
Published: March 2022

Mountainous areas tend to have a high density of bridges due to their topography and mobility requirements. Furthermore, such areas are often characterized by frequent debris-flow activity, which in turn can endanger the structural integrity of bridges. The influence of debris flows on bridge piers has already been analyzed in the past, but mechanisms and consequences of debris-flow impact on bridge superstructures remain unclear.

We hypothesize that in addition to horizontal forces, frictional shear-forces and uplift forces may play a considerable role in bridge failure caused by debris-flow impacts. We also conjecture that the type of the bridge superstructure, specifically the bridge profile has an influence on the occurring forces.

In order to obtain a deeper understanding of impact forces on bridge superstructures, we aim to measure and quantify the forces exerted on different bridge profiles during debris-flow impact based on small scale experiments. We will investigate debris-flow impact on five different bridge profiles in the course of the project “Debris-flow impact forces on bridge superstructures (DEFSUP)”, funded by the Austrian Science Fund (FWF).

The laboratory setup consists of a 4 m long semi-circular channel with a diameter of 0.3 m and an inclination of 20°. The cement miniature bridge in the scale of 1:30 is mounted on a metal frame and is installed at the end of the flume. The debris-flow material corresponds to a granular debris flow, the mass is fixed at 50 kg for each experiment. The flume itself has been optimized in preliminary studies and ensures high reproducibility of stationary debris flows with predictably sufficient flow-heights for the impact on the miniature bridge. Each profile is subjected to at least three impacts. The impact forces on the bridge profile are measured with 3-axis-force sensors at both abutments of the bridge. Thereby it is possible to determine horizontal impact forces as well as uplift and shear forces. Additionally, flow heights, pore water pressure and normal stresses are gauged.

The results of the study are intended to contribute to recommendations for the structural design of bridges in vulnerable areas. This aims not only to protect human lives and to increase the safety of structures, but also to provide financial relief in the future, since there is evidence that the areas prone to debris-flow events are likely to increase as a consequence of climate change.
Energy transfer, discontinuities and heating in the inner solar wind measured with a weak and local formulation of the Politano-Pouquet law
Authors: David Vincent , Galtier Sébastien , Sahraoui Fouad , Hadid Lina
Published: March 2022

The solar wind is a highly turbulent plasma for which the mean rate of energy transfer ε has been measured for a long time using the Politano-Pouquet (PP98) exact law. However, this law assumes statistical homogeneity that can be violated by the presence of discontinuities. Here, we introduce a new method based on the inertial dissipation DI whose analytical form is derived from incompressible magnetohydrodynamics (MHD); it can be considered as a weak and local (in space) formulation of the PP98 law whose expression is recovered after integration is space. We used DI to estimate the local energy transfer rate from the THEMIS-B and Parker Solar Probe (PSP) data taken in the solar wind at different heliospheric distances. Our study reveals that discontinuities near the Sun lead to a strong energy transfer that affects a wide range of scales σ. We also observe that switchbacks seem to be characterized by a singular behavior with an energy transfer varying as σ−3/4, which slightly differs from classical discontinuities characterized by a σ−1 scaling. A comparison between the measurements of ε and DI shows that in general the latter is significantly larger than the former.

https://arxiv.org/pdf/2201.02377.pdf
Evaluation of hydrological cycle intensification in response to temperature variability
Authors: Pratap Shailendra , Markonis Yannis
Published: March 2022

As the climate warms, the hydrological cycle is expected to intensify. Also, in response to climate warming, hydrologic sensitivity is a major concern for the coming decades. Here, we aim to understand the relationship between hydroclimate and temperature variability during the past. The periods selected for investigation are the Mid-Miocene Climate Optimum (MMCO), the Eemian Interglacial (EI) Stage, the Last Glacial Maximum, the Heinrich and Dansgaard–Oeschger Events, the Bølling-Allerød, the Younger Dryas, the 8.2 ka event, the Medieval Climate Anomaly, and the Little Ice Age. In general, the proxy records suggest that the hydrological cycle is intensified under warmer climate conditions and weakened over colder periods. However, the spatial signals are not uniform worldwide. For instance, during the MMCO and EI, the global temperature was higher than the pre-industrial time; some regions were wetter, (northern Eurasia and Sahara Arabian desert), while others were more arid (Argentina, Bolivia, and Africa). Therefore, the hypothesis “a warmer climate is a wetter climate” could be considered as a simplified pattern of regional changes as a result of global warming. The reason is that the water cycle response is spatiotemporally not similar. Due to its wide distribution, hydroclimate variability is difficult to quantify on a regional, continental, and global scale. In this context, investigation of paleo-hydroclimatic changes, specifically during the warm periods, could provide relevant insights into the present and future climate.
The vertical structure and entrainment of subglacial melt water plumes
Authors: Burchard Hans , Bolding Karsten , Jenkins Adrian , Losch Martin , Reinert Markus , Umlauf Lars
Published: March 2022

Basal melting of marine-terminating glaciers, through its impact on the forces that control the flow of the glaciers, is one of the major factors determining sea level rise in a world of global warming. Detailed quantitative understanding of dynamic and thermodynamic processes in melt-water plumes underneath the ice-ocean interface is essential for calculating the subglacial melt rate. The aim of this study is therefore to develop a numerical model of high spatial and process resolution to consistently reproduce the transports of heat and salt from the ambient water across the plume into the glacial ice. Based on boundary layer relations for momentum and tracers, stationary analytical solutions for the vertical structure of subglacial non-rotational plumes are derived, including entrainment at the plume base. These solutions are used to develop and test convergent numerical formulations for the momentum and tracer fluxes across the ice-ocean interface. After implementation of these formulations into a water-column model coupled to a second-moment turbulence closure model, simulations of a transient rotational subglacial plume are performed. The simulated entrainment rate of ambient water entering the plume at its base is compared to existing entrainment parameterizations based on bulk properties of the plume. A sensitivity study with variations of interfacial slope, interfacial roughness and ambient water temperature reveals substantial performance differences between these bulk formulations. An existing entrainment parameterization based on the Froude number and the Ekman number proves to have the highest predictive skill. Recalibration to subglacial plumes using a variable drag coefficient further improves its performance.
Global attribution of anthropogenic and lightning fires
Authors: Veraverbeke Sander , Finney Declan , van  der Werf Guido , van Wees Dave , Xu Wenxuan , Jones Matthew
Published: March 2022

Fires can have anthropogenic or lightning origins. The spatiotemporal niches of anthropogenic and lightning fires are different. Lightning fires usually occur during a discrete apex in seasonal lightning occurrence. Conversely, anthropogenic fires have an expanded temporal niche and occur throughout the year. In addition, lightning and anthropogenic fires occupy different parts of the landscape. While human accessibility is a key determinant of anthropogenic ignitions, lightning ignitions prevail in remote landscapes.

We used these differing temporal and spatial niches between anthropogenic and lightning fires to construct random forest models that attribute causes, lightning vs. anthropogenic, to global fire activity. We built two separate models. The first model predicts the fraction of lightning fires, whereas the second model predicts the fraction of burned area from lightning. Our model ingests two geospatial predictor variables that quantify the differences between the temporal and spatial niches of lightning and anthropogenic fires. The first predictor is the seasonal correlation between lightning and burned area. The second predictor is the fraction of low impact land. These fire cause predictors capture 47 % of the spatial variability in ignition cause, and 40 % of the spatial variability in burned area cause, compared to reference data from six different parts of the world.

Our global fire cause attribution contrasts savannas and agricultural lands with human-dominated fire regimes from temperate and boreal forests with lightning-dominated fire regimes. Our global fire cause attribution can be implemented in fire and Earth system models to further optimize projections of future fire activity under changing socio-economic and climatological conditions.
Internal tsunamigenesis and mixing driven by glacier calving in Antarctica
Authors: Meredith Michael , Inall Mark , Brearley Alexander , Munday David , Ehmen Tobias , Sheen Katy , Retallick Katherine , Annett Amber , Jones Rhiannon , Carvalho Filipa , Van Landeghem Katrien , Naveira Garabato Alberto , Gerrish Laura , Scourse James , Cook Alison , Bull Christopher
Published: March 2022

Ocean mixing around Antarctica is a key process that influences the vertical distributions of heat and nutrients, affecting glacier and ice shelf retreats, sea ice formation and marine productivity, with implications for regional ecosystems, global sea level and climate. Here we show that collapsing glacier fronts associated with calving events trigger internal tsunamis, the propagation and breaking of which can lead to significant mixing. Observations of one such event at the West Antarctic Peninsula, during which 3-20 megatonnes of ice were discharged to the ocean, reveal rapidly-elevated internal wave kinetic energy and upper-ocean shear, with strong homogenisation of the water column. Scaling arguments indicate that, at the West Antarctic Peninsula, just a few such events per summer would make this process comparable in magnitude to winds, and much more significant than tides, in driving shelf mixing. We postulate that this process is likely relevant to all regions with calving marine-terminating glaciers, including also Greenland and the Arctic. Glacier calving is expected to increase in a warming climate, likely strengthening internal tsunamigenesis and mixing in these regions in the coming decades.
On singularity point for acoustic orthorhombic model
Authors: Stovas Alexey
Published: March 2022

The singularity points are very important for elastic waves propagation in low-symmetry anisotropic media (Stovas et al., 2021a). Being converted into the group velocity domain, they result in internal refraction cone with anomalous amplitudes and very complicated polarization fields. I analyze the conditional singularity point in acoustic orthorhombic (ORT) model which is very popular in processing and analysis of 3D seismic data. The elliptic ORT model has one singularity point in one of the symmetry planes (Stovas et al., 2021b). The elastic ORT model has 1 to 6 singularity points. It is shown that for acoustic ORT model the only one S1-S2 wave singularity point (per quadrant) can conditionally be defined in-between the symmetry planes. The required conditions and position of singularity point are computed. The projection of the slowness vector    for singularity point are given by

where  are the elements of the stiffness coefficients matrix. I show that the singularity point for this model has the stable conical type of degeneracy (Shuvalov, 1998), which means that the internal refraction cone is always represented by ellipse in 3D space. The slowness surface for acoustic orthorhombic model that consists of three sheets corresponding to P (the inner one) and S1-S2 waves. The image of singularity point in the group domain and its three projections on the symmetry planes can be computed analytically.

 

References

Shuvalov, A.L., 1998, Topological features of the polarization fields of plane acoustic waves in anisotropic media, Proc. R. Soc. Lond., A., 454, 2911–2947.

Stovas, A., Roganov, Yu., and V. Roganov, 2021a, Geometrical characteristics of P and S wave phase and group velocity surfaces in anisotropic media, Geophysical Prospecting, 68(1), 53-69.

Stovas, A., Roganov, Yu., and V. Roganov, 2021b, Wave characteristics in elliptical orthorhombic medium, Geophysics, 86(3), C89-C99.