bluuebunny/crossref_metadata_2025 huggingface dataset:
Exploring dynamic (dis)connectivity of surface runoff on multiple catchments through a shallow water model
Authors: Özgen-Xian Ilhan , Morales-Hernández Mario , Caviedes-Voullième Daniel
Published: March 2022

Runoff generation and the consequent overland flow result from the interactions between gravity-driven flow over complex topography, Earth’s roughness, and infiltration. These processes mostly occur at small spatio-temporal scales, but aggregate throughout the landscape to produce a hydrodynamic response at catchment and stream scales during a rainfall event. While this response is highly transient and spatially heterogeneous, it is mostly studied through aggregated signatures, such as hydrographs. It is therefore of importance to understand how the hydrodynamic response builds up across scales in the landscape into such signatures. Arguably, hydrological (dis)connectivity, which describes how different parts of a hydro-system (dis)connect through fluxes, is a useful concept to describe this multiscale behaviour. In this contribution, we explore the dynamic connectivity behaviour of surface runoff in first order catchments (ranging between 0.06 and 15 km2) in response to singular rainfall events. We further analyse the connectivity response, mainly in terms of the number of disconnected clusters and the flooded areas, together with hydrological signatures. To do this, we use the GPU-enabled shallow water solver SERGHEI-SWE, which allows us to solve the shallow water equations at below-metre resolution (with tens of millions of grid cells per catchment). The extremely high spatial resolution of the model accurately captures spatial heterogeneity of topography and surface properties and thus, correctly represents the structural connectivity of the system. In the same manner, the hydrodynamics obtained on these high-resolution grids accurately capture the dynamic connectivity. Based on the simulated water depths, we assess dynamic connectivity at different spatial scales, and at different stages of runoff development, and study how the connectivity properties vary in different catchments. Furthermore, we perform a first analysis of how connectivity changes with scale and its relation to hydrological signatures and catchment features. Additionally, we explore the effects of coarser resolution simulations on dynamic connectivity on the same catchments.
Horticultural Additives influence soil biogeochemistry and increase CO2 emissions from peat
Authors: Sharma Bidhya , Roulet Nigel , Moore Tim , Knorr Klaus-Holger , Teickner Henning , Strachan Isabel , Douglas Peter
Published: March 2022

Peat is used as the chief ingredient of growing media in horticulture. The high cation exchange capacity, water retention capacity, low bulk density, and appropriate physical properties make peat-based growing media desirable for horticulture. Peat in its natural form is acidic and low in nutrient composition. Therefore, for suitability as a growing media, peat is mixed with liming agents, nutrients, surfactants, perlite among several other possible additives.

Using lab incubations, we assessed the change in soil biogeochemistry and CO2 fluxes because of horticultural additives. We obtained samples of raw peat and additive mixed growing media (n=52) from four different peat extraction companies in Canada. Our analysis shows that the key soil biogeochemical parameters C: N ratio, pH, dissolved organic carbon, bulk density, C content differs significantly (p<0.01) between raw peat and growing media. There is a more than a two-fold increase in CO2 from growing media as compared to raw peat. Further experiment showed the longer-term contribution of carbonates borne CO2 to the total flux. 

IPCC (2007) calculates that all C from harvested peat is lost in the atmosphere in the first year. However, our initial results estimate less than 10% of peat C loss in the first year from growing media. Although the influence of horticultural additives in C loss from peat is significant, the current accounting from IPCC is an overestimation.
A carbon data integrating system supporting Carbon neutrality
Authors: Zhao Jing , Li Guoqing , Li Zefeng
Published: March 2022

Since initiated by the Chinese Academy of Sciences (CAS) and the National Earth Observation Data Center (NODA) of China, Cooperation on Reanalysis of Carbon Satellite Data (CASA) had already advanced to the second stage. China aims to hit peak emissions before 2030 and for carbon neutrality by 2060.Carbon neutrality research involves Terrestrial-Marine-Atmospheric multiple fields, which inevitably require the support of scientific big data and Scientific Data e-Infrastructure (SDI). Open space-borne carbon data interconnectivity and interoperability across the massive carbon data (GOSAT, GOSAT-2, OCO-2/3, TanSat, Sentinel-5P, FY-3D, GF-5 and the second generation carbon satellites) and related auxiliary data resources integrated into the CASA platform is a key enabler to become more data-driven, to broader data value, and to meet the major demand of global and regional monitoring of anthropogenic carbon emissions. This study explores the technological barriers for carbon satellite data interconnectivity, discusses the concepts of carbon data interoperability and integration, management and governance in more detail, highlight some useful tools, and demonstrate examples in urban air pollution and CO2 emissions that can help researchers in their application studies upon estimation of anthropogenic carbon emissions based on “top-down” methods. We linked carbon data connection and interoperability both to carbon data collection and use within programmatic cycles and reflected interoperability both in organizational practices and data management plans that cover the full breadth of the data value chain. This will extend carbon data information service and provide better ways to utilizing carbon data across domains where innovation and integration are now necessarily needed.
Collection of valuable polar data and increase in nature awareness among travellers by using Expedition Cruise Ships as platforms of opportunity
Authors: Meraldi Verena , Morgan Tudor , Lynnes Amanda
Published: March 2022

Hurtigruten Expeditions, a member of the International Association of Antarctica Tour Operators (IAATO) and the Association of Arctic Expedition Cruise Operators (AECO) has been visiting the fragile polar environments for two decades, witnessing the effects of climate change. Tourism and the number of ships in the polar regions has grown significantly. As a stakeholder aware of the need for long-term protection of these regions, we promote safe and environmentally responsible operations, invest in the understanding and conservation of the areas we visit, and focus on the enrichment of our guests.

For the last couple of years, we have supported the scientific community by transporting researchers and their equipment to and from their study areas in polar regions and we have established collaborations with numerous scientific institutions. In parallel we developed our science program with the goal of educating our guests about the natural environments they are in, as well as to further support the scientific community by providing our ships as platforms of opportunity for spatial and temporal data collection. Participation in Citizen Science programs that complement our lecture program provides an additional education opportunity for guests to better understand the challenges the visited environment faces while contributing to filling scientific knowledge gaps in remote areas and providing data for evidence-based decision making.

We aim to continue working alongside the scientific community and developing partnerships. We believe that scientific research and monitoring in the Arctic and Antarctic can hugely benefit from the reoccurring presence of our vessels in these areas, as shown by the many projects we have supported so far. In addition, our partnership with the Polar Citizen Science Collective, a charity that facilitates interaction between scientists running Citizen Science projects and expedition tour operators, will allow the development of programs on an industry level, rather than just an operator level, increasing the availability and choice of platforms of opportunity for the scientific community.
Mapping 35 years of change in Leaf Mass per Area across the globe from multispectral satellite data
Authors: Hinojo Hinojo Cesar , Bohner Teresa , Chacon-Labella Julia , Falco Nicola , Frazier Amy , Hemingway Benjamin , Nikolopoulos Efthymios I. , Wainwright Haruko , Enquist Brian
Published: March 2022

With thousands of plant functional trait observations across the world, there is still a lack of spatially and temporally explicit estimates of traits that help inform how biodiversity, ecological and biogeochemical processes are changing across the globe. The Leaf Mass per Area (LMA) is a key trait that influences plant ecological strategies, and it is strongly correlated with leaf photosynthesis, plant growth, vegetation primary production and decomposition rates. Based on biophysical principles of the radiative transfer in canopies, we designed a new multispectral remote sensing index that is highly sensitive to the community weighted mean of LMA. We called this index iLMA, as an acronym for “index for LMA''. We tested and calibrated this index with ground data of a wide range of forest types and herbaceous communities  collected at 510 plots from 77 sites located in the American continent (R2 = 0.64). Using Landsat imagery, iLMA and the resulting calibrating equation, we made a 30m resolution global map of LMA. The LMA spatial pattern is consistent with our current understanding of LMA variation across major terrestrial biomes but at an unprecedented high-resolution. Then, we used Landsat imagery from 1985 to 2019 to produce yearly global estimates of LMA and map its rate of change. This map of change in LMA indicates that there has been a widespread decrease in LMA across the globe over the last 35 years, with the fastest and strongest declines happening in evergreen conifer forests in boreal and mountainous regions of the world, and tropical evergreen broadleaf forests in Africa and Asia. We discuss potential causes of such widespread decrease in LMA, including climate change and widespread changes in vegetation composition and structure, and its potential consequences for biogeochemical processes.
Slope incline as a factor influencing the ejection of two-phase soil splashed material
Authors: Beczek Michał , Ryżak Magdalena , Mazur Rafał , Sochan Agata , Polakowski Cezary , Bieganowski Andrzej
Published: March 2022

Soil, i.e. the natural outer layer of the lithosphere and an important component of many ecosystems, may be subjected to various degradation processes dependent on different factors. One of the forms of physical degradation is water erosion, where the first stage is the splash phenomenon caused by water drops hitting the soil surface during rainfall. This process results in detachment and ejection of splashed material and transport thereof over different distances. One of the factors that influences the magnitude of soil splash is the incline of the surface (slope). The aim of this study was to check the effect of the slope on the course of the splash phenomenon caused by single-drop impact, with respect to the mass and proportions of the ejected material, taking into account its division into solid and liquid phases i.e. soil and water.

The measurements were conducted on three types of soil differentiated in terms of texture, in moistened conditions (pressure head corresponding to -1.0 kPa). Three slope inclines were investigated: 5°, 15°, and 30°. After a single-drop impact (with a diameter of 4.2 mm), the ejected material was collected using a splash cup. Based on this the following quantities of splashed material were measured: the total ejected mass, the mass of the ejected solid phase and the mass of the ejected liquid phase. Also, the distribution and proportions (soil/water) of the splashed material were analysed in both the upslope and downslope directions. The results showed that: a) the change of slope had a variable influence on the measured quantities for different soils; b) the measured values were mainly influenced by the texture; c) with the increase of slope, the splashed material was mostly ejected in the downslope direction; d) the ejected material consisted mostly of water, this occurred for material ejected both upslope and downslope.

 

This work was partly financed from the National Science Centre, Poland; project no. 2018/31/N/ST10/01757.

 

References:

Beczek M., Ryżak M., Mazur R., Sochan A., Polakowski C., Bieganowski A.: Influence of slope incline on the ejection of two-phase soil splashed material. PLOS ONE 17(1): e0262203, 2022
High-quality probabilistic predictions for existing hydrological models with common objective functions    
Authors: Thyer Mark , Hunter Jason , McInerney David , Kavetski Dmitri
Published: March 2022

Probabilistic predictions describe the uncertainty in modelled streamflow, which is a critical input for many environmental modelling applications.  A residual error model typically produces the probabilistic predictions in tandem with a hydrological model that predicts the deterministic streamflow. However, many objective functions that are commonly used to calibrate the parameters of the hydrological model make (implicit) assumptions about the errors that do not match the properties (e.g. of heteroscedasticity and skewness) of those errors. The consequence of these assumptions is often low-quality probabilistic predictions of errors, which reduces the practical utility of probabilistic modelling. Our study has two aims:

1. Evaluate the impact of objective function inconsistency on the quality of probabilistic predictions;

2. To demonstrate how a simple enhancement to a residual error model can rectify the issues identified with inconsistent objective functions in Aim 1, and thereby improve probabilistic predictions in a wide range of scenarios.

Our findings show that the enhanced error model enables high-quality probabilistic predictions to be obtained for a range of catchments and objective functions, without requiring any changes to the hydrological modelling or calibration process. This advance has practical benefits that are aimed at increasing the uptake of probabilistic predictions in real-world applications, in that the methods are applicable to existing hydrological models that are already calibrated, simple to implement, easy to use and fast. Finally, these methods are available as an open-source R-shiny application and an R-package function.
Development and evaluation of the xGEOID20 Digital Elevation Model at NGS
Authors: Krcmaric Jordan
Published: March 2022

The U.S. National Geodetic Survey (NGS), an office of the National Oceanic and Atmospheric Administration (NOAA), is preparing for the release of a new vertical datum, the North American-Pacific Geopotential Datum of 2022 (NAPGD2022). This new datum will be based on a high degree spherical harmonic model of the Earth’s gravitational potential, and will yield a geoid undulation model (GEOID2022) to calculate orthometric heights from GNSS-derived ellipsoid heights.

As part of the preparation for the new vertical datum, NGS has computed annual experimental geoid models (xGEOID) since 2014. The xGEOID model released in 2020 (xGEOID20) uses an updated digital elevation model (DEM) composed of TanDEM-X, MERIT, and USGS 3DEP data. The DEMs are merged together to create a seamless elevation model across the extent of the xGEOID20 model. The accuracy of the merged DEM is tested using independent datasets such as GPS observations on leveled bench marks and ground elevations from ICESat-2. The effect of the updated DEM on the geoid model is also determined by comparing geoid models computed with previous DEMs to the new xGEOID20 model, and with comparisons to the NGS Geoid Slope Validation Survey lines.
Morphological characteristics and evolution model of loess gully cross section
Authors: Liu Lulu , Li Fayuan , Yang Xue , Cheng Jianhua
Published: March 2022

Gully morphology is an important part of loess geomorphology research. Along with gully development, the variation of its cross section is the most important aspect, and it can intuitively reflect the characteristics of the lateral widening of the gully slope. Therefore, in-depth research of the variation of the cross-sectional morphology of the gully is important to understanding the development process of the loess gully. Based on the data of nine periods of an indoor simulated loess small watershed, this paper deeply studies the evolution model of a complete branch ditch in the watershed from many aspects by using the theory and method of digital terrain analysis. Firstly, we analyse the morphological characteristics of the gully cross section in the simulated small watershed. The test shows that with the development of the gully, the average slope of the slope decreases continuously, and the slope morphology is mostly a concave slope along the slope direction. The degree of downward concave first increases and then gradually tends to be gentle. The gully erosion mode is gradually transformed from downward cutting erosion to lateral erosion. The more mature the gully development, the lower the depth of gully bottom cutting is compared with the width of gully widening. Furthermore, the surface cutting depth tends to be stable and the slope is stable. Then, the transformation law of the slope morphology of the gully cross section with the development of the gully is studied, and the prediction model of the transformation of the slope morphology of the gully cross section is established by using the Markov chain. The Markov model can better reflect the dynamic change of the slope morphology of the gully cross section, which is of considerable importance to revealing the external performance and internal mechanism of the gully morphology.
Multi-model forecast quality assessment of CMIP6 decadal predictions
Authors: Delgado-Torres Carlos , Donat Markus G. , Gonzalez-Reviriego Nube , Caron Louis-Philippe , Athanasiadis Panos J. , Bretonnière Pierre-Antoine , Dunstone Nick J. , Ho An-Chi , Pankatz Klaus , Paxian Andreas , Pérez-Zanón Núria , Samsó Cabré Margarida , Solaraju-Murali Balakrishnan , Soret Albert , Doblas-Reyes Francisco J.
Published: March 2022

Decadal climate predictions are a new source of climate information for inter-annual to decadal time scales, which is of increasing interest for users. Forecast quality assessment is essential to identify windows of opportunity (e.g., variables, regions, and lead times) with skill that can be used to develop a climate service and inform users in several sectors. Also, it can help to monitor improvements in current forecast systems. The Decadal Climate Prediction Project Component A (DCPP-A) of the Coupled Model Intercom-parison Project Phase 6 (CMIP6) now provides the most comprehensive set of retrospective decadal predictions from multiple forecast systems. The increasing availability of these simulations leads to the question of how to best post-process the raw output from the forecast systems so that the most useful and reliable information is provided to users.

This work evaluates the quality of deterministic and probabilistic forecasts for spatial fields of near-surface air temperature and precipitation, and time series of the Atlantic multi-decadal variability index (AMV) and global near-surface air temperature anomalies (GSAT) generated from all the available decadal predictions contributing to CMIP6/DCPP-A (169 members from 13 forecast systems). The predictions generally show high skill in predicting temperature and the AMV and GSAT time series, while the skill is more limited for precipitation. Also, different approaches for building a multi-model forecast are compared (pooling all ensemble members versus combining the averages from individual forecast systems), finding small differences. Besides, the multi-model ensemble is compared to the individual forecast systems. The best system usually provides the highest skill. However, the multi-model ensemble is a reasonable choice for not having to select the best system for each particular variable, forecast period and region. Furthermore, the decadal predictions are compared to the uninitialized historical climate simulations (195 members from the same forecast systems as the decadal prediction members) to estimate the impact of initialization. An added value is found for temperature over several ocean and land regions, and for the AMV and GSAT time series, while it is more reduced for precipitation. Moreover, the full DCPP-A ensemble is compared to a sub-ensemble of predictions that could be provided in near real-time for a potential operational product generation. The comparison shows a benefit of using a large ensemble over several regions, especially for temperature. Finally, the implications of these results in a climate services context are discussed.

 
Terrestrial carbon dynamics through time - insights from downcore radiocarbon dating
Authors: Smittenberg Rienk , Galy Valier , Bernasconi Stefano , Gierga Merle , Birkholz Axel , Hajdas Irena , Wacker Lukas , Haghipour Negar , Ponton Camilo , Eglinton Timothy
Published: March 2022

A relatively small change in the balance of in- and outgoing fluxes between terrestrial Carbon (Cterr) and the atmosphere, sustained over centuries to millennia can change Cterr from a carbon source to a sink. The net carbon balance of any ecosystem is mainly determined by climate (temperature, humidity, seasonality) via its influence on primary productivity, respiration and preservation, and by geomorphology (erosion). More recently, human perturbance has increasingly also become a major factor. In particular, the slow cycling component of Cterr, with turnover times of centuries to millennia, is relevant for the long-term carbon balance on land. Build-up of this carbon pool is inherently slow, but loss can be rapid and thereby form a significant carbon source to the atmosphere. One way to gain insight in the dynamics of this slow cycling carbon pool is to interrogate sedimentary records that, through time, have stored snapshots of terrestrial carbon, the latter being a mixture of pre-aged, long-stored Cterr and fresh material. By downcore measurements of the radiocarbon age of specific plant-derived organic compounds, interferences by aquatically produced organic carbon or petrogenic organic carbon can be circumvented, and insights can be gained into the carbon cycle processes in the corresponding catchment area. This study presents compound-specific 14C data compiled from studies over the last 20 years of sedimentary records derived from small lake catchments to deltaic and submarine fan deposits near large river mouths. The main conclusions that can be drawn are: 1) Modern but also (pre)historic human perturbance through land-use change has released long-stored ecosystem carbon that otherwise would have escaped mobilization. 2) Both positive and negative correlations between millennial-scale hydroclimate change and Cterr dynamics are evident, and are attributed to the opposing effects on primary productivity, respiration and erosion rates.  3). Catchment size and geomorphology also influence the extent of net ecosystem carbon storage. 4). The Younger Dryas cold period promoted release of Cterr built up during the preceding warm Bølling-Allerød period, illustrating the role rapid climate change can play in carbon dynamics.
Large scale carbon mapping of forest-steppe ecotones using multispectral satellite data
Authors: Donnerhack Oliver , Guggenberger Georg
Published: March 2022

Environmental changes, such as altered precipitation patterns and temperatures, but also the type of
land management, have strong impact on the vegetation structure and the associated soil carbon
storage. Vulnerable ecosystems that have always grown at the limits of system stability have small
resilience and therefore respond to the smallest changes. This is also true for the forest-steppe
ecotones at the southern border of the Mongolian taiga, with their two subtypes of light and dark
taiga. Due to drought stress, this forest only grows on the northern slopes, where the rate
evapotranspiration is smaller. Climatic change, which is very pronounced in these highly continental
areas, leads to water scarcity and thus to higher drought stress as well as an increased risk of forest
fires. In the forest-steppe ecotone in northern Mongolia, light taiga dominated by Betula is increasingly
spreading into areas previously covered by dark taiga representing coniferous forests dominated by
Pinus and Larix. Since soil organic carbon stocks are known to be related to vegetation, in this study
we aimed at assessing the spatial carbon stocks distribution of different forest-steppe ecotones
characterized by different tree compositions by using a multispectral satellite image approach. Based
on Sentinel-2 data, a supervised random forest classification was carried out using the MSAVI index
and carbon stocks from 50 soil profiles of these sites as training data. For the first time, a mean of
multi-year MSAVI was used to compensate the temporal gap between the actual image of vegetation
vitality and the comparatively inert soil organic carbon. The results were validated by ground truthing
on further 36 soil profile measurements. The validation confirmed the accuracy of the classification
and thus led to a valid area calculation. The map based on the measurement results, which was created
by the use of machine learning, illustrates that the significant differences in the spatial distribution of
the taiga subtypes and their soil organic carbon stocks balance each other out in the areas under
consideration. Since the resulting map could be validated by both soil investigations and field survey
experiences, we assume that the applied remote sensing method can be used as a basis for a realistic
area monitoring of the ecosystem under consideration to calculate the spatial change of the carbon
pool. 
Joint inversion of tectonic stress and magma pressures using dyke trajectories
Authors: Maerten Frantz , Maerten Laurent , Plateaux Romain , Cornard Pauline
Published: March 2022

In volcano-tectonic regions, dyke propagation from shallow magmatic chambers are often controlled by ambient perturbed stress field. The variations of the stress field result from combining factors including, but not exclusively, the regional tectonic stress and the pressurized 3D magma chambers. In this contribution, we describe and apply a new multiparametric inversion technique based on geomechanics that can invert for both the far field stress attributes and the pressure of magma intrusions, such as stocks and magma chambers, constrained by observed dyke orientations. This technique is based on a 3D boundary element method (BEM) for homogeneous elastic half-space where magma chambers are modelled as pressurized cavities. To verify this approach, the BEM solution has been validated against the known 3D analytical solution of a pressurized cylindrical cavity. Then, the effectiveness of this technique and its practical use, in terms of mechanical simulation, is demonstrated through natural examples of dyke network development affected by magma intrusions of two different volcanic systems, the Spanish Peaks (USA) and the Galapagos Islands (Ecuador). Results demonstrate that regional stress characteristics as well as pressure of magma chambers can be recovered from observed radial and circumferential dyke patterns.
 
New i3elvis: Robust visco-elasto-plastic geodynamic modelling code based on staggered finite differences and marker in cell
Authors: Gerya Taras
Published: March 2022

In the recent decade, numerical modelling approaches based on combination of staggered finite differences with marker in cell techniques became increasingly popular in geodynamics due to their simplicity, flexibility and computational efficiency. Here, I present new version of popular 3D thermomechanical code i3ilvis, which has been fundamentally revised to include the following methodological advances (Gerya, 2019 and references therein):

Full thermomechanical coupling (through global Picard iteration) including compressible time-dependent mass conservation equation and adiabatic and shear heating effects in the energy conservation equation.

Regularized visco-elasto-viscoplastic rheological model with/without dilation. (Duretz et al., 2019) based on global thermomechanical Picard iteration.

Accurate continuity-based velocity interpolation for marker advection applicable for both compressible and incompressible flows.

Free surface stabilization against “drunken sailor” instability.

Accurate 3D rotation of elastic stresses on markers.

Dislocation-diffusion creep rheology with grainsize evolution(Bercovici and Ricard, 2012) including newton iteration for dislocation creep to compute effective viscosity for markers.

The new code is OpenMP parallel and has already been successfully tested for cases of realistic 3D geodynamic modeling including tectono-magmatic model of continental breakup to oceanic spreading transition and spontaneous subduction initiation scenario associated with slab bending and normal faulting.

 

Bercovici, D., Ricard, Y. (2012) Mechanisms for the generation of plate tectonics by two- phase grain-damage and pinning. Phys. Earth. Planet. Inter. 202-203, 27–55.

Duretz, T., de Borst, R., Le Pourhiet, L. (2019) Finite thickness of shear bands in frictional viscoplasticity and implications for lithosphere dynamics. Geochemistry, Geophysics, Geosystems, 20, 5598–5616.

Gerya T.V. (2019) Introduction to Numerical Geodynamic Modelling. Second Edition. Cambridge University Press, 472 pp.

 
Statistical Analysis of Extreme Wave Run-up on Steep Slopes
Authors: Kalisch Henrik , Lagona Francesco , Roeber Volker , Bjørnestad Maria
Published: March 2022

Some rock coasts around the world feature very steep coastal profiles which often continue past the waterline, and may quicly drop to one or two-hundred meters depth. We consider the interaction of ocean waves with such steep coastal topography. It has been shown that shoaling ocean waves may experience significant amplification in the last 50 to 100 meters before they run up on the shore, leading to potentially hazardous run-up events even under relatively calm conditions. We study the distribution of simulated run-up heights on steep and gentle slopes for a range of sea states, and compare the results to the distribution of offshore wave elevation.
Intense mid-Holocene warming on highland Sumatra: insights from biomarker proxies
Authors: Hällberg Petter , Martínez Cortizas Antonio , Hapsari Anggi , Rifai Hamidi , Eisele Steffen , Bouvet de Maisonneuve Caroline , Kylander Malin , Schenk Frederik , Smittenberg Rienk
Published: March 2022

Despite immense progress in the last decades, the Holocene climate evolution is still poorly resolved, in particular in the tropics, and especially from a terrestrial perspective. Here we reconstruct 11 000 years of paleo-climate and environment in the western Indo-Pacific Warm Pool – “the heat and steam engine of the world” – by analysing biomarker and geochemical proxies in peat sediments from Sumatra.

We discuss the composition of archaeal and bacterial membrane lipids (branched and isoprenoid glycerol dialkyl glycerol tetraethers; GDGTs) and their relationship with temperature and other environmental conditions. By analysing the hydrogen isotopes of leaf waxes (dDwax) we reconstruct past rainfall amounts.

X-Ray Fluorescence (XRF) derived geochemical composition reveals changes in erosional regimes. Additionally, we use long-chain n-alkane distributions, carbon and nitrogen analysis, and attenuated reflectance Fourier-Transform Infrared analysis (FTIR-ATR) to investigate changes in vegetation on the peatland.

Three main climate-environmental phases emerge in our record: 1) Relatively cold, dry and unstable conditions during the Early Holocene which is marked by high detrital input into the peatland. 2) Warm, wet and stable conditions coincided with the mid-Holocene period, 8.2 – 3.2 ka BP. Using a global peat-specific temperature calibration based on branched GDGTs (Naafs et al., 2017), we derive mean annual air temperatures peaking at 4.8 ka BP that are ~3 °C warmer compared to core-top and modern local weather station data. The warmest period is also the wettest according to dDwax, which is further supported by GDGT and alkane distributions, and d13C values indicating aquatic biomass production. 3) At 3.2 ka BP, the climate abruptly deteriorated into colder and drier conditions and re-intensified erosion.

Surprisingly, slope wash events resulting in input of coarse detrital material into the core were most frequent during the dry periods. We suggest that this is related to a more variable hydroclimate with droughts and episodic heavy rains, likely associated with ENSO variability, causing increased erosion during the Early and Late Holocene.

 
The ‘rtry’ R package for preprocessing plant trait data
Authors: Lam Olee Hoi Ying , Tautenhahn Susanne , Walther Gabriel , Boenisch Gerhard , Baddam Pramod , Kattge Jens
Published: March 2022

From evolutionary biology, functional ecology, earth system modelling to landscape management, plant trait data are used to determine how the plants respond to the environmental factors and can act as indicators of ecosystem functions. In 2007, the TRY initiative was founded as an integrated database of trait data and all additional attributes relevant to understanding and interpreting a given trait value. Since then, the TRY database has integrated more than 400 datasets, including both original datasets and collective databases.

Due to the unique long table structure, the relevant information (e.g. trait names, species names, ancillary data representing context information, units of trait data, and identifiers for duplicates and outliers) for trait data filtering is stored at different places of the released TRY data. This makes the process to find all relevant information to select or remove trait data not straightforward without knowledge of the inherent data structure.

The ‘rtry’ package is an R package that provides a set of easily applicable functions for the basic steps of data preprocessing and is designed in particular to support the data exploration and removal of the plant trait data, taking advantage of the features of trait data released from the TRY database. This package is supposed to be applicable without advanced knowledge of the data structure released from TRY or the R software. Most importantly, despite the ‘rtry’ package being developed to support the application of plant trait data received via the TRY database, it is also applicable to other trait data.

 
An experimental investigation of seismic and acoustic harmonic tremor gliding and implication for churn-like flow
Authors: Spina Laura , Cannata Andrea , Morgavi Daniele , Privitera Eugenio , Perugini Diego
Published: March 2022

The gradual shift over time of the spectral lines of harmonic seismic and/or acoustic tremor, that is commonly known as spectral gliding, has been largely observed at different volcanoes. Despite the clear advantage of the experimental approach in providing direct observation of degassing processes and of the related elastic radiation, experimental studies on gliding tremor are lacking. To fill this gap, we investigated different episodes of gliding of acoustic and seismic tremor observed during analogue degassing experiments performed under different experimental conditions, by systematically changing: 1) analogue magma viscosity (10-1,000 Pa s), 2) gas flux (5-180x10-3 l/s) and 3) conduit surface roughness (fractal dimension of 2-2.99). The occurrence of gliding experimental seismic and acoustic tremor was linked to high gas flux rates and viscosities and generally associated with an increasing trend and often preceding a major burst. In a few cases we observed decreasing secondary sets of harmonic spectral lines. Results suggest that gliding episodes are mainly related to the progressive volume variation of shallow interconnected gas pockets. Spectral analyses performed on acoustic signals provided the theoretical length of the resonator. The latter was compared against the temporal evolution of the gas pockets, quantified from video analyses. The similarities between the observed degassing regime and churn-annular flow in high viscous fluids encourages further studies on churn dynamics in volcanic environments.
Adding Quantization to the NetCDF C and Fortran Libraries to Enable Lossy Compression
Authors: Hartnett Edward , Zender Charles
Published: March 2022

The increasing volume of Earth science data sets continue to present challenges for large data producers. In order to support lossy compression in the netCDF C and Fortran libraries, we have added a quantize feature for netCDF floating point variables. When the quantize feature is enabled, the data creator specifies the number of significant digits. As data are written, the netCDF libraries apply a quantization algorithm which guarantees that the number of significant digits (for BitGroom and Granular BitRound algorithms) or bits (for BitRound algorithm) will be preserved, while setting unneeded bits to a constant value. This allows zlib lossless compression (or any other lossless compression) to achieve better and faster compression.
Using ROV video photogrammetry to reconstruct seafloor landforms of Arctic cold seep environments
Authors: Fallati Luca , Savini Alessandra , Argentino Claudio , Bünz Stefan , Panieri Giuliana
Published: March 2022

Cold seeps are locations on the seafloor where reduced compounds from subsurface hydrocarbon reserves enrich sediment fluids or emanate freely as gas from the seabed. Associated with these spots, numerous underwater landscapes and various chemosynthetic communities were uncovered during the last decades of seafloor exploration. 

Arctic cold seeps offshore Svalbard were explored using Ægir6000, a work-class ROV (Remotely Operated Vehicle) equipped with three HD video cameras that filmed the ocean floor at different angles. The ROV, moving at a constant speed of 1 knot, followed predefined routes to guarantee optimal lateral overlap between adjacent transects. From the videos of the nadiral camera, a photogram every two seconds was automatically extracted. Then, the images were processed in Agisoft Metashape® following a well-established photogrammetry workflow. As final outputs, we obtained 3D mesh, orthomosaics and DTMs at ultra-high-resolution (mm) allowing us to obtain detailed morphometric maps.

These data allowed us to reconstruct accurate georeferenced 3D models representing a variety of small-scale (sub-cm) seabed features and provide essential information for a better understanding of the spatial pattern associated with submarine biogeochemical and physical processes at the seafloor. Moreover, the realized models present the locations where push corers were collected. This correspondence will allow us to integrate fine-scale habitat mapping and pore fluid datasets to quantify the areal methane fluxes.

This work was supported by the Research Council of Norway, for AKMA - Advancing Knowledge on Methane in the Arctic, project number 287869.

Keywords: Submarine geomorphology, ROV, Underwater 3D Photogrammetry, optical 3D models, Cold Seeps, Arctic Ocean
What controls the warming of the Antarctic Bottom Water supply to the Atlantic Ocean?
Authors: Auckland Christopher , Abrahamsen Povl , Meredith Michael , Naveira-Garabato Alberto , Frajka-Williams Eleanor
Published: March 2022

Antarctic Bottom Water has experienced a marked contraction and warming, particularly in the Atlantic sector, in the past three decades. Much of the global abyssal waters are composed of this bottom water and these changes have seen concomitant ocean heating and global sea level rise via thermal expansion. This warming has been linked to a contraction in export of the densest classes of bottom water from the Weddell Gyre due to processes that are not well determined but potentially including changes in wind forcing or source water formation. With regard to wind forcing, several mechanisms have been suggested, however their relative scale and whether they occur concurrently remains unclear. Using two mooring sites within the Weddell Sea, we estimate lag times between temperature anomalies at 3000m depth finding changes in the strength of the boundary current connecting the two sites. These changes in flow speed are synchronous with changes in wind forcing and bottom water transport. In particular, bottom water temperatures increased in response to anomalously strong wind forcing in 2015 and to a lesser extent in 2018 over a period of six months, indicating a contraction in export of the most dense water classes from the Antarctic. These findings reaffirm the importance of wind forcing in driving changes in the export of dense water to the lower limb of the Atlantic overturning circulation, with potential consequences for long-period climate evolution.
Aeolian-Fluvial response to late-Pleistocene dunefield encroachments along the northwestern Negev dunefield margins (Israel)
Authors: Robins Lotem , Roskin Joel , Yu Lupeng , Greenbaum Noam
Published: March 2022

Aeolian-Fluvial (A-F) processes formed vast and flat landscapes during the late-Pleistocene along dunefield margins. A-F research examines the impacts of extrinsic processes of the aeolian and fluvial systems on one another, which formed these unique landscapes. However, the mechanisms and depositions of A-F processes are not fully understood. In this study, a 120 m wide and 7 m high, wadi bank exposure of an A-F sequence reveals the sedimentary units, where the northwestern Negev (Israel) dunefield desert margins interact with the Atadim fluvial system (64 km2). A chrono-stratigraphic analysis by laboratory measurements (Particle size distribution & Total of carbon), relative and absolute luminescence dating (POSL & OSL), radiocarbon and archeological dating, enabled conclusions regarding the depositional mechanisms and environment. Finally, DEM (~12.5 m pixel) and GPS-RTK (0.3 m resolution) were used to assess A-F depositional boundary.

The results demonstrate a unique perseverance of aeolian sand units covered by low-energy fluvial deposits. The sand and dune units illustrate several sand incursions into the fluvial system since the Last Glacial Maximum until the mid-Holocene. We observed  low-energy fluvial deposits, which resulted from these sand incursions: (a) couplets deposited in an ever-emptying waterbody, impounded by a dune-dam. (b) massive fine-grained formation – deposition of suspended sediments in an impounded waterbody, near the damming-dune where the waterbody is the deepest. (c) Fining upwards with fine laminas deposits – embedded between couplet formations, deposited in a low-energy fluvial environment. The fine laminas indicate small tributaries income to the main low-energetic flow.

We demonstrate that in A-F sequences, not only are the aeolian sand units preserved but also they act as palaeo-fluvial archives. The section reflects that late-Pleistocene dune-damming build-up resulted in a lagged fluvial response enabled by a climatic change during the early-Holocene. The combination of stabilized dune-dams within the fluvial systems and high discharge flows with large available sediment supply resulted in vast aggregation of A-F sediments, forming the alluvial plain.
Long-term trends and variations in sea level of the Black Sea
Authors: Saçu Şehriban , Şen Olgay
Published: March 2022

The Black Sea is an almost enclosed basin interacted with the Mediterranean Sea through the Bosporus. It has a large catchment area receiving freshwater from the second longest river in Europe, the Danube, and other rivers spread over Europe and Asia. The total riverine discharge is 350 km3/year where the Danube contributes about 65% of the total discharge. Although evaporation rates (280 km3/year) exceed precipitation rates (200 km3/year), large riverine discharge makes the Black Sea an estuarine type basin.  The main feature of the Black Sea is a basin-wide cyclonic circulation, namely Rim Current. The cyclonic circulation causes a lower sea level in the inner part of the basin and a higher sea level in the shelf region. The freshwater budget and thermal expansion of the water are other factors affecting sea level of the Black Sea.  The North Atlantic Oscillation (NAO) could also influence sea level through changes in atmospheric pressure and the above-mentioned factors.  

 

In this study, firstly we investigated long term trends in sea level of the Black Sea on the basis of the tide gauge measurements, satellite altimetry, and gravity measurements from the Gravity Recovery and Climate Experiment (GRACE). Then, we assessed role of the wind curl, freshwater budget, and NAO on sea level variations through temporal and spatial data analysis. The tide gauge measurements suggest a positive sea level trend of about 1.05 – 2.37 mm/years, for a time period >50 years. Basin mean sea level derived from altimeter and GRACE (years between 2003-2019), does not exhibit a statistically significant trend (p<0.05) which might result from the shift towards a positive NAO condition in the last 30-years. We found that sea level variations both in the coastal and inner part of the basin are significantly correlated (p<0.05) with Danube discharge but these correlations are smaller in the inner part. The agreement between interannual variations of Danube discharge and the NAO index suggests that sea level variations are also associated with NAO index. An Empirical Orthogonal Function (EOF) analysis with associated time series (Principal Components, PC) is applied to the gridded altimeter data to capture space and time features of sea level variability. The first mode of the EOF explained about %81.9 of the total variability and showed the same sign over the basin indicating an in-phase oscillation of the whole Black Sea. The PC1 shows interannual variations in accordance with freshwater budget (r=0.76, p<0.05). The second mode of the EOF accounts for %5.7 of the total variability, has opposite signs in coastal and inner parts, the oscillation implied by this mode could be related to the Rim Current intensity governed by wind curl.

 
Retrieving riming in arctic mixed phase clouds from collocated remote sensing and in situ aircraft measurements during ACLOUD 
Authors: Maherndl Nina , Maahn Maximilian , Tridon Frederic , Dupuy Regis
Published: March 2022

Ice crystal formation and growth processes in mixed-phase clouds (MPCs) are not sufficiently understood. This leads to uncertainties of atmospheric models in representing MPCs. This presentation is centered around riming, which occurs when liquid water droplets freeze onto ice crystals. While it is challenging to observe riming directly, we retrieve a proxy for riming from airborne radar measurements using data collected during the (AC )3 aircraft campaign ACLOUD performed in 2017. For this campaign, two closely collocated aircraft were flying in formation for obtaining collocated in situ and remote sensing observations. We aim to quantify the normalized riming fraction 𝑀 by matching measured to simulated radar reflectivities 𝑍𝑒 . For the latter we use the Passive and Active Microwave radiative TRAnsfer tool (PAMTRA) to calculate 𝑍𝑒 from the in situ observed particle size distributions. Liquid droplets are assumed to be spheres and Mie scattering is applied, while we use the self-similar Rayleigh Gans approximation (SSRGA) for ice crystals. We present an Optimal Estimation algorithm to obtain ice crystal mass size - as well as SSRGA parameters from measured 𝑍𝑒 and in situ parameters. We exploit the fact that mass size and SSRGA parameters depend on 𝑀. We evaluate including empirical relationships derived via model calculations done by an aggregation and riming model as forward operators in the algorithm. Also we use the model calculations directly to restrict the prior information. We validate the obtained 𝑀 values by looking at in situ ice crystal images for selected time periods. We compare our findings to macrophysical cloud properties and meteorological conditions to understand external drivers and variability of riming. This will lead to a better understanding of riming as a key process occurring in arctic MPCs.