bluuebunny/crossref_metadata_2025 huggingface dataset:
Near-complete loss of fire-resistant primary tropical forest cover in Sumatra and Kalimantan
Authors: Nikonovas Tadas , Spessa Allan , Doerr Stefan , Clay Gareth , Mezbuhaddin Symon
Published: March 2021

Deforestation in Indonesia in recent decades has made increasingly large parts of the region vulnerable to fires. Burning is particularly widespread in deforested peatlands, and it leads to globally significant carbon emissions. Here we use satellite-based observations to assess loss and fragmentation of primary forests and associated changes in fire regimes in Sumatra and Kalimantan between 2001 and 2019. We find that fires did not penetrate undisturbed primary forest areas deeper than two kilometres from the forest edge irrespective of drought conditions. However, fire-resistant forest now covers only 3% of peatlands and 4.5% of non-peatlands; the majority of the remaining primary forests are severely fragmented or degraded due to proximity to the forest edge. We conclude that protection and regeneration of the remaining blocks of contiguous primary forest, as well as peatland restoration, are urgently needed to mitigate the impacts of potentially more frequent fire events under future global warming.
Mitigation of greenhouse gas emissions from global croplands under a changing climate and increasing food demand
Authors: Smerald Andrew , Kraus David , Fuchs Kathrin , Haas Edwin , Butterbach-Bahl Klaus , Scheer Clemens
Published: March 2021

Agricultural nitrogen (N) inputs have grown massively over the last century, driving increases in crop yields, but also resulting in increased greenhouse-gas emissions and nutrient overloading of ecosystems. Of particular note is the increase in emissions of N2O, a greenhouse gas with 300 times the warming potential of CO2.  While the total global yearly N2O emissions can be easily deduced from atmospheric measurements, much less is known about the contribution of different cropping systems, and how increasing food demand will affect these emissions in the future. This knowledge is important for developing well-targeted mitigation strategies that reduce N2O emissions while increasing crop production. In order to help resolve this issue, we have simulated global croplands, one of the main beneficiaries of increased N inputs, using a process-based model that captures both crop growth and nitrogen and carbon cycling through the soil. This allows us to quantify total N2O emissions by crop type, identify hotspots and explore how a changing climate and increasing food demand are likely to impact future emissions. The idea is that this will aid in the search for agricultural management strategies that ensure food security while reducing the climate impact.

 
Stress Drops from Trench to Depth in the Northern Chilean Subduction Zone
Authors: Folesky Jonas , Hofman Rens , Kummerow Jörn
Published: March 2021

At the northern Chilean subduction zone the IPOC network monitors seismicity since 2007. During the observation time period two very large earthquakes occurred, the 2007 MW 7.7 Tocopilla earthquake and the 2014 MW 8.1 Iquique earthquake and until today the subduction zone shows a vast amount of seismic activity. A large catalog was compiled and published including over 100000 events by Sippl et al. 2018. Therein, seismicity ranges from close to the trench till deep into the mantle to about 300km depth. Consequently, events occur under a broad variability of physical conditions.

We extend the aforementioned catalog by applying a template matching technique to identify additional events, that are colocated with catalog events. Based on these events we apply an empirical Green’s function method called spectral ratio approach to estimate stress drops. The results cover different nucleation provinces i.e. the data set includes stress drops obtained at the interface, within the subducting plate, from crustal events, intermediate depth events, and from deep to very deep seismicity. The study therefore bears a great potential to better understand the stress drop distribution within an entire subduction zone.

First results show no depth dependency in the shallowest 100 km but spatial variability with high stress drops focused to particular regions on the interface. We also find increased stress drop values in the crust when compared to events close or at the interface.
Fractal tools to analyse the spatial variability of Blue Green Solutions in an urban area
Authors: Otranto-da-Silva Gustavo
Published: March 2021

A city's response to a rainfall event depends not only on the rainfall spatial-temporal variability, but also on the spatial distribution and the initial state of its Blue Green Solutions (BGS), such as green roofs. They hold back runoff and may prove being critically important elements of blue-green build environment.

The aim of this study was first to adapt the existing hydrological model to the urban area of Melun (France), to validate it and then to assess numerically an optimal configuration of green roofs to mitigate pluvial floods for particularly vulnerable areas. The main focus was put on the investigation of interactions between rainfall space-time scales and resulting hydrological response over fine scales, all being controlled by the performance assessment of BGS.

This presentation will particularly illustrate how fractal tools were used to:

- highlight the scale dependency of the input variables and its effects on gridded model performance;

- explore, analyse and represent the influence of BGS location and configuration on the mitigation of runoff associated with short-duration, high-intensity rainfall at neighborhood scale;

 - identify the urban design options that maximize the potential for runoff reduction.

In overall, these results may serve as a referential for upscaling the optimized implementation of BGS in urban areas, by considering other urban infrastructures and their interactions.
Can you make your science more reproducible?
Authors: Rosenberg David
Published: March 2021

Science and engineering rest on the concept of reproducibility. Yet across numerous fields like psychology, computer systems, and water resources there are great problems to reproduce research results. In this presentation, I identify reasons for low reproducibility in science. I share tools to make results more reproducible. I introduce financial incentives and awards to encourage you and our colleagues to make our research more reproducible. Finally, I advance a vision for what our future reproducible science should look like and I ask each attendee to identify and commit to take at least one step to make their research results more reproducible.

 
Studying the transport and retention of naturally occurring microplastics (MPs) in sandy soils using column experiments
Authors: Ameen Ahmad , Stevenson Margaret , Blaschke Alfred Paul
Published: March 2021

In the 1950’s, plastics were introduced as a miracle material and since then it has revolutionised human society in almost every domain of our daily life. The benefits of plastics are countless but their inherent resistance to degradation has ultimately led to their accumulation in the environment in the form of micro and nano plastics. In recent years, the presence of microplastics (MP) in fresh water sources has raised questions related to the protection of drinking water. In Austria, the exact status of groundwater contamination by MP is unknown. To understand the behaviour of MP that are present in the environment, a study was conducted to investigate the transport and distribution of MP in groundwater using column experiments.

Polyethylene MP were produced from 3D fluorescent printing material using a milling technique and in a well-defined size range of 1-200 μm. A borosilicate glass column (1.5 cm diameter and 10 cm long) was used as our experimental setup. The columns were packed with quartz and coarse sand. A layer of homogenized MP-sand mixture (approximately 3 to 5% w/w) was applied at the top of a soil column. The transport behaviour of MP were analysed in terms of various physical and chemical factors like MP-concentration, soil particle size, inflow rate, ionic strength and straining effect. The outflow from the column was collected at different pore volume intervals and analysed for the presence of MP. The breakthrough curves (BTCs) were obtained by measuring the MP concentrations of the effluent.
Quantifying geodiversity with alpha, beta and gamma components
Authors: Tukiainen Helena , Alahuhta Janne , Hjort Jan , Lindholm Marja , Maliniemi Tuija , Salminen Henriikka , Snåre Henna , Toivanen Maija , Vilmi Annika , Heino Jani
Published: March 2021

A variety of ways can be used to measure geodiversity, but no consensus on quantifying it exists to date. Most quantifications have thus far focused on the abiotic diversity of individual sites, which offers only limited views on variation of abiotic nature. It is, therefore, important to examine the between-site geodiversity, i.e., the dissimilarities of geofeatures (elements of geodiversity) between different sites. For instance, it would be interesting to recognize not only the most geodiverse sites of an area, but also the sites that have the most unique compositions of geofeatures. This extended geodiversity information could be further applied in nature conservation or land-use planning. We propose that geodiversity research would benefit from adopting the alpha, beta and gamma concepts of species diversity research to provide a more holistic framework for geodiversity assessments. In particular, the inclusion of distance metrics for measuring beta biodiversity could open new perspectives in evaluating beta geodiversity. The integration of these diversity concepts into geodiversity research would also allow a better joint understanding of biotic and abiotic diversity.
Uncertainties in SST datasets and implications for El Niño event classification
Authors: Zhu Mengke , Wright Jonathon , Ilyas Maryam , Brierley Chris
Published: March 2021

Identification of El Niño warm events and their types has traditionally been deterministic, based mainly on whether a pre-defined index exceeded a critical value. However, uncertainties in both sea surface temperature (SST) measurements and their interpolation into a gridded analysis can impact identification of and confidence in El Niño variability, particularly earlier in the record. Although several different classification methods for El Niño exist, researchers lack an effective reference and evaluation system to identify advantages and disadvantages of a given index for a given application. Therefore, this study quantifies the impacts of both data- and method-related uncertainties on different El Niño classification methods, considering different types of uncertainty, different types of analysis, different teleconnection mechanisms and expressions of El Niño impact and different types of climate data. To aid in these objectives, El Niño classification methods are evaluated from five aspects: reliability, accuracy, precision, flexibility, and simplicity. The core analysis is based on probabilistic, uncertainty-aware classifications applied to a large ensemble of historical SST realizations. The results are then used to conduct a more general evaluation of how different types of uncertainty propagate through the different classification methods, and provide guidance on the strengths and weaknesses of these indices for different applications.
Modelling the Southeast African regional Climate
Authors: Benestad Rasmus , Nhantumbo Bernardino , Prosper Ayabagabo , Ndakize Sebaziga Joseph , Tuyisenge Aminadab , Vanya Charles , Chaimite Berny , Bopape Mary-Jane
Published: March 2021

The aim of the Flagship Pilot Study (FPS) “Modelling the Southeast African regional Climate” is to study processes and phenomena relevant to regional climate change in south-eastern Africa. The region is vulnerable to climate change due to socio-economic factors as well as its exposure to weather and climate extremes such as floods, droughts and heat waves. The FPS will foster regional collaboration on modelling and the analysis of precipitation and temperature that will be beneficial for the society in general. The FPS South-eastern Africa includes various scientists from the National Meteorological and Hydrological Services (NMHSs) and academia of South Africa, Mozambique, Zimbabwe, Malawi, Tanzania, Kenya, Rwanda, Burundi and Norway. The research will involve analysis of local observations, reanalysis, simulations from regional climate models (RCMs) and empirical-statistical downscaling (ESD) to study dependencies between large-scale conditions and local variability in the rain and temperature statistics. The expected impacts of the FPS are skills development in data analysis and modelling, and a better understanding of regional climate that is fundamental to climate services and provides guidance to decision-makers and planners. The involvement of NMHS in the project provides access to their observational networks, whose use will assist with verification of model simulations, and also increase the value of NMHSs’ work with observations and data management. Actionable information will be extracted for decision-makers, based on a synthesis of multiple sources of information which take into account the local climate, past and future trends, models’ skill, known weather/climatological phenomena, and other geographical information. Biases between the model climate and observations will be adjusted through appropriate adjustment methods such as the Quantile Mapping approach. The work will also involve capacity building on R programming language as well as other tools (e.g. CDO, python) and use R-based shiny web applications in distillation efforts and to provide a gateway to the information embedded in complex data structures.
Simulation study on gravity field determination with small satellites in NGGM 
Authors: Pfaffenzeller Nikolas , Pail Roland
Published: March 2021

In the context of an increased public interest in climate-relevant processes, a number of studies on Next Generation Gravity Missions (NGGMs) have been commissioned to better map mass transport processes on Earth. On the basis of the successfully completed gravity field missions CHAMP, GOCE and GRACE as well as the current satellite mission GRACE-FO, different concepts were examined for their feasibility and economic efficiency. The focus is on increasing the spatiotemporal resolution while simultaneously reducing the known error effects such as the aliasing of temporal gravity fields due to under-sampling of signals and uncertainties in ocean tide models. An additional inclined pair to a GRACE-like satellite pair (Bender constellation) is the most promising solution. Since the costs for a realization of the Bender constellation are very high, this contribution focuses on alternative concepts in the form of different constellations and formations of small satellites. The latter includes both satellite pairs and chains consisting of trailing satellites. The aim is to provide a cost-effective alternative to the previous gravity field satellites while simultaneously increasing the spatiotemporal resolution and minimizing the above mentioned error effects. In numerical closed-loop simulations, various scenarios will be conducted which differ in orbit parameters like shape and number of orbits, the number of satellites per orbit and instrument performances. Additionally, the impacts from the co-parametrization of non-tidal temporal gravity field signal and ocean tides on the gravity field solutions, obtained by the different concepts, will be investigated. In particular the possibilities and limits with multiple satellites pairs for achieving the highest possible spatial and temporal resolution in (sub-)daily temporal gravity fields shall be analysed in detail.
Disentangling Effects of Soil Abiotic and Biotic Factors on Tree Seedling Regeneration Following Boreal Forest Wildfire
Authors: Ibáñez Theresa S. , Wardle David A. , Gundale Michael J. , Nilsson Marie-Charlotte
Published: March 2021

Changes in fire regime of boreal forests are predicted to alter plant and soil community structure and cause elevated tree mortality, increased loss of soil organic matter and reduced survival and functioning of soil microbial communities. While the impact of wildfire disturbance on plant mortality and post-fire successions in boreal forests has been studied extensively, little is known about how changes in soil properties after fire, including biotic and abiotic properties, individually and interactively impact tree seedling regeneration. The aim of this study was therefore to disentangle how tree seedling performance is independently and interactively controlled by soil biotic versus abiotic properties following wildfire.

We performed two greenhouse experiments in which seedlings of Betula pendula, Pinus sylvestris and Picea abies were grown in soils collected from forest stands in east-central Sweden that had been subjected to three burn severities (high, low and unburnt) following a large-scale wildfire. The first experiment consisted of live soil originating from every stand in each burn severity class crossed with each tree species. The second experiment was similar, except that all soil was first sterilized, and then was crossed with live soil inoculum originating from each of the burn severity classes and grown with each tree species. The results showed that tree seedlings subjected to live soil grew best in soil from unburnt stands (experiment 1), and that P. abies and P. sylvestris seedlings increased growth when planted in soil inoculated with biota from low burn severity stands compared to high burn severity or unburnt stands (experiment 2). In contrast, B. pendula was not responsive to soil inoculum treatments, but instead was driven by post-fire abiotic properties of soils. These results indicate that fire disturbances may lead to reduced regeneration of conifers, unless soil biota is maintained or has recovered, and further suggests that soil from high burn severity stands may constrain seedling regeneration, whereas soil biota from low burn severity stands promotes growth and regeneration of conifers. Our study also shows that different seedling species respond differently to abiotic and biotic soil properties altered by different burn severities, which is relevant because burn probability and fire intensity are projected to increase and become more common in many parts of the boreal region as the climate warms.
Quantifying spatial correlations and trends in rainfall data under a Mediterranean climate using non-parametric statistical and machine learning approaches
Authors: Alilou Hossein , Hipsey Matt , Oldham Carolyn
Published: March 2021

Numerous studies have highlighted the rapid pace of climate change in South Western Australia and quantifying hydrological shifts may provide insights into climate impacts in other Mediterranean regions. Identifying connections in data from spatially distributed rainfall stations using different interpolation approaches, can fill gaps in historical datasets and allow effective installation of new rain gauges based on optimal density and location. Different insights were revealed by using multiple approaches across the time series: the Seasonal Mann-Kendall Test, the Mann-Kendall Test under the Scaling Hypothesis (MKLTP), the Lanzante’s test (LAT) as single change point detection tests, the E-Agglomerative (ECP) and E-Divisive (EDP) change detection algorithms as multiple change point detection tests. Twenty seven loading factors (e.g. seasonal and annual Sen’s slope, the year and number of change points) were calculated from daily rainfall data collected over 100 years (1920-2019) from 107 meteorological stations in South Western Australia. The results illustrated that the rate of rainfall fluctuation in terms of Sen’s slope varied from -2.6 mm yr-1 in coastal areas to 0.9 mm yr-1 in inland areas. The scaling trend analysis identified that 53% of the stations were effected by long-term persistence in the wet season, in contrast to only 20% in the dry season. The single change point methods identified a change in the 1940s-1950s and the multiple change point methods identified two changes, in the 1940s and 2000s. The spatial correlation of stations were also mapped using an unsupervised machine learning approach (K-Means), the Multiscale Bootstrap Resampling (MBR), and loading factors, into three optimal clusters, indicating that rainfall in the coastal areas continue to decline, whereas rainfall in the inland areas has increased over the previous 100 years. These statistical and machine learning approaches are effective in identifying spatial and temporal variability in climate change trends.
CME arrival time predictions with a deformable front
Authors: Hinterreiter Jürgen , Amerstorfer Tanja , Reiss Martin A. , Weiss Andreas J. , Möstl Christian , Temmer Manuela , Bauer Maike , Bailey Rachel L. , Amerstorfer Ute V.
Published: March 2021

We present the first results of our newly developed CME arrival prediction model, which allows the CME front to deform and adapt to the changing solar wind conditions. Our model is based on ELEvoHI and makes use of the WSA/HUX (Wang-Sheeley-Arge/Heliospheric Upwind eXtrapolation) model combination, which computes large-scale ambient solar wind conditions in the interplanetary space. With an estimate of the solar wind speed and density, we are able to account for the drag exerted on different parts of the CME front. Initially, our model relies on heliospheric imager observations to confine an elliptical CME front and to obtain an initial speed and drag parameter for the CME. After a certain distance, each point of the CME front is propagating based on the conditions in the heliosphere. In this case study, we compare our results to previous arrival time predictions using ELEvoHI with a rigid CME front. We find that the actual arrival time at Earth and the arrival time predicted by the new model are in very good agreement.
Magma transport beneath mid-ocean ridges
Authors: Sim Shi , Spiegelman Marc , Stegman Dave , Wilson Cian
Published: March 2021

Melt transport beneath the lithosphere is elusive. With a distinct viscosity and density from the surrounding mantle, magmatic melt moves on a different time scale as the surrounding mantle. To resolve the temporal scale necessary to accurately capture melt transport in the mantle, the model simulations become numerically expensive quickly. Recent computational advances make possible two-phase numerical explorations to understand magma transport in the mantle. We review results from a suite of two-phase models applied to the mid-ocean ridges, where we varied half-spreading rate and intrinsic mantle permeability using new openly available models, with the goal of understanding melt focusing beneath mid-ocean ridges and its relevance to the lithosphere-asthenosphere boundary (LAB). Here, we highlight the importance of viscosities for the melt focusing mechanisms. In addition, magmatic porosity waves that are a natural consequence of these two-phase flow formulations. We show that these waves could explain long-period temporal variations in the seafloor bathymetry at the Southeast Indian Ridge.
Swiss Emissions of Halogenated Greenhouse Gases derived from Atmospheric Measurements at Beromünster
Authors: Rust Dominique , Vollmer Martin K. , Katharopoulos Ioannis , Henne Stephan , Hill Matthias , Emmenegger Lukas , Zenobi Renato , Reimann Stefan
Published: March 2021

Synthetic halocarbons reach the atmosphere due to a wide range of anthropogenic activities. They are, for example, used as propellants in foam blowing or as cooling agents in refrigeration and air conditioning. Long-lived halocarbons act as strong greenhouse gases. They are responsible for about 11% of the radiative forcing by long-lived greenhouse gases (LLGHGs). In addition, chlorinated or brominated halocarbons contribute to stratospheric ozone depletion. There are only two in situ long-term measurement programs, operated by the Advanced Global Atmospheric Gases Experiment (AGAGE) and the National Oceanic and Atmospheric Administration (NOAA) that monitor the worldwide abundance of halocarbons in the atmosphere. Based on these observations, halocarbon emissions are estimated by top-down box- or inverse modelling approaches on a global to transnational scale. However, to capture regional pollution sources and to validate country-specific bottom-up emission estimates by top-down methods, additional regional-scale measurements are required.

We present the first continuous halocarbon measurements at the Beromünster tall tower, representing the most industrialized and densely populated area of Switzerland, the Swiss Plateau. During one year, high precision, high accuracy atmospheric measurements were performed with the analytical setup of the global AGAGE network. This involves sample pre-concentration at low temperatures (down to -180 oC), and analyte separation and detection by gas chromatography and quadrupole mass spectrometry. All halocarbon compound classes of the Montreal and Kyoto Protocols are covered by our measurements. This includes the banned chlorofluorocarbons (CFCs) and halons, the regulated hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs), as well as the recently introduced unregulated hydrochfluoroolefins (HFOs). The results improve our understanding of important source areas in Switzerland, and, for the first time offer the possibility to robustly quantify Swiss national halocarbon emissions with observation-based top-down methods, i.e. the tracer ratio method and Bayesian inverse modeling.
Predicting extreme precipitation effects on the geomorphology of small mountain catchments, northern Apennines (Italy)
Authors: segadelli stefano , grazzini federico
Published: March 2021

Meteorological events characterized by extreme rainfall intensity have recently struck the hilly and mountainous territory of the northern Apennines (Italy) as well as many other geographic areas of the world. These extreme rainfall events trigger fast flows of debris along the slopes, stream channels, landslides, and floods, which damage many man-made structures such as roads, houses, water-pipes, etc. There is thus a strong practical interest in predicting the frequency and intensity of these effects for emergency management and to reduce the vulnerability of the territory.

In 2015 an intense rainfall event hit the Valleys of the Trebbia, Nure, and Aveto watercourses in the emilian-ligurian Apennines. In about 6 h a mesoscale convective system deployed a stunning amount of precipitation of 340 mm, with an extreme hourly rainfall intensity of >100 mm/h. During this event, several types of widespread effects on the ground developed i.e., fast flows of debris along the slopes and stream channels (a total number of 305 occurrences), shallow landslides (342) and overbank flooding occurred. Instrumental as well as geological and historical data clearly suggest that extreme rainfall events are increasing in the northern Apennines, in good agreement with the international literature. Through the optimal combination of rainfall data and radar volumes, in this work we present a detailed rainfall analysis, which will serve as a basis to create a quantitative correlation with debris flows over elementary hydrological units. The meteorological analysis of the storm led us to consider the 3 h accumulation rain field as the most relevant for flood triggering. This time interval is short enough to describe the intensity peak of macro precipitating structures, and at the same time it is long enough to allow the development of the debris and stream-flow processes described. The very good match between the 3 h peak intensity and the distribution of high-discharge and hillslope-debris flow support the hypothesis. The 3 h interval further emphasizes the meteorological event with respect to its overall duration of 6 h.

We aim at providing an objective basis for future predictions, starting from the recognition of the forcing meteorological events, allowed us to clearly identify high-intensity-precipitation thresholds triggering flood in small mountain catchments.

Keywords: floods; catchment; threshold; extreme rainfall events; northern Apennines
Wormhole dynamics, competition for the flow and changes in transport behavior: an intermediate-scale experiment
Authors: Trabucchi Michela , Fernàndez-Garcia Daniel , Carrera Jesús
Published: March 2021

Salt flats (Salares) are complex evaporitic systems of economic interest and environmental value. On the one hand, these aquifers are usually exploited for variety of minerals, including dissolved species (e.g. Lithium and Potassium) extracted from the brines. On the other hand, the genesys of salares favors that they are surrounded by uncommon ecosystems, which must be protected. In this context, it is fear that brine pumping might favor the development of dissolution channels (Wormholes) that could connect the Salar nucleus with the environmental sensitive surroundings. Thus, a full understanding of the conditions and processes involved in wormhole formation and evolution has to be achieved. The hydraulic and geochemical conditions for conduits growth have been widely discussed in carbonate environments, while little has been done in halitic and gypsum environments. But we unknowledge experimental works aimed at understanding wormhole dynamics and the mechanism of competition for the flow that influence dissolution pattern evolution.

In this study, we want to improve the understanding of multiple wormholes growth in the context of wormhole competition and consequent changes in transport behaviors. For that purpose, we designed and performed a laboratory intermediate-scale tank experiment under controlled conditions. Halite in the form of granular medium is used to reproduce the aquifer. Hydrodynamics and geochemical conditions are set as to reproduce a dominant wormhole dissolution regime. Several coloured tracer tests are carried out to characterize the medium before, during and after the dissolution experiment.  Tracer concentration, hydrogeochemical and flow parameters, as well as tank images are continuously recorded. In particular, the use of fluorescent tracer jointly with image processing analysis highlights wormholes growth, shape and propagation through the medium at different times. Experimental results allow visualizing and analyzing several features related to wormhole competition, e.g. wormhole growth rate and density evolution, as well the redistribution of the flow towards areas where dominant wormholes are developing. Results are compared to available numerical and analytical solutions. Lastly, the interpretation of BTCs allows to understand changes in flow and trasport behavior and related processes, given the developing dissolution pattern.
Glacial isostatic adjustment near the center of the former Patagonian Ice Sheet (48°S) during the last 16.5 kyr
Authors: Troch Matthias , Bertrand Sebastien , Lange Carina B. , Cardenas Paola , Arz Helge , De Pol-Holz Ricardo , Kilian Rolf
Published: March 2021

Our understanding of glacial isostatic rebound across Patagonia is highly limited, despite its importance to constrain past ice volume estimates and better comprehend relative sea-level variations. With this in mind, our research objective is to reconstruct the magnitude and rate of Late Glacial to Holocene glacial isostatic adjustment near the center of the former Patagonian Ice Sheet. We focus on Larenas Bay (48°S; 1.26 km2), which is connected to Baker Channel through a shallow (ca. 7.4 m) and narrow (ca. 150 m across) inlet, and hence has the potential to record periods of basin isolation and marine ingression. The paleoenvironmental evolution of the bay was investigated through a sedimentological analysis of a 9.2 m long, radiocarbon-dated, sediment core covering the last 16.8 cal. kyr BP. Salinity indicators, including diatom paleoecology, alkenone concentrations and CaCO3 content, were used to reconstruct the bay’s connectivity to the fjord. Results indicate that Larenas Bay was a marine environment before 16.5 cal. kyr BP and after 9.1 cal. kyr BP, but that it was disconnected from Baker Channel in-between. We infer that glacial isostatic adjustment outpaced global sea-level rise between 16.5 – 9.1 cal. kyr BP. During the Late Glacial - Holocene transition, the center of the former Patagonian Ice Sheet rose ca. 96 m, at an average rate of 1.30 cm/year. During the remainder of the Holocene, glacial isostatic adjustment continued (ca. 19.5 m), but at a slower average pace of 0.21 cm/year. Comparisons between multi-centennial variations in the salinity indicators and existing records of global sea-level rise suggest that the glacial isostatic adjustment rate fluctuated during these time intervals, in agreement with local glacier dynamics. More specifically, most of the glacial isostatic adjustment registered between 16.5 – 9.1 cal. kyr BP seems to have occurred before meltwater pulse 1A (14.5 – 14.0 kyr BP). Likewise, it appears that the highest Holocene glacial isostatic rebound rates occurred during the last 1.4 kyr, most likely in response to glacier recession from Neoglacial maxima. This implies a relatively rapid response of the local solid earth to ice unloading, which agrees with independent modelling studies investigating contemporary uplift. We conclude that the center of the former Patagonian Ice Sheet experienced a glacial isostatic adjustment of ca. 115 m over the last 16.5 kyr, and that >80% occurred during the Late Glacial and early Holocene.
Exploring the effects of the land surface on tropical precipitation
Authors: Pietschnig Marianne , Swann Abigail L. S. , Geen Ruth , Lambert F. Hugo , Vallis Geoffrey K.
Published: March 2021

Projected precipitation changes over tropical land tend to be enhanced by vegetation responses to CO2 forcing in Earth System Models. Projected decreases in rainfall over the Amazon basin and increases over the Maritime Continent are both stronger when plant physiological changes are modelled than if these changes are neglected, but the reasons for this amplification remain unclear. The responses of vegetation to increasing CO2 levels are complex and uncertain, but changes in stomatal conductance likely dominate the evapotranspiration response in Earth System Models.

We investigate why vegetation changes cause precipitation to increase more strongly over the Maritime Continent while decreasing more strongly over the Amazon basin. We employ an idealized Atmospheric General Circulation Model with a simplified vegetation scheme that captures CO2-driven stomatal closure.

We find that – counter-intuitively – rainfall is enhanced over a narrow rectangular island when terrestrial evaporation falls to zero with high CO2. Strong heating and ascent over the island trigger moisture advection from the surrounding ocean. In contrast, over larger continents rainfall depends on continental moisture recycling.

Simulations with two large rectangular continents representing South America and Africa reveal that the stronger decrease in rainfall over the Amazon basin is due to a combination of local and remote effects:

Finally, we investigate the impact of land-surface hydrology on continental rainfall on seasonal timescales. Using our idealized model and realistic continents, we study the strength of the South East Asian monsoon for different continental evaporation schemes. Surprisingly, when terrestrial evapotranspiration is unlimited (i.e. does not depend on soil moisture availability), monsoon precipitation is much weaker than when terrestrial evapotranspiration is limited by soil moisture. In order to explain this behavior, we compare the atmospheric energy budgets and circulation between the simulations.

Our results show that the land-surface hydrology plays an important role in modifying tropical precipitation and atmospheric dynamics on seasonal timescales and in the long-term under climate change, and that further investigation into the topic is called for.
Monitoring soil retention properties in a riverbank susceptible to fluvial erosion
Authors: Gragnano Carmine Gerardo , Gottardi Guido , Toth Elena
Published: March 2021

One of the principal source of vulnerability for riverbanks is given by slopes instabilities, which is triggered on the riverside by fluvial erosion. In order to mitigate such erosion, the establishment of a dense herbaceous cover aims at promoting the slope protection and reducing the likelihood of embankment failure. In fact, the aerial parts of vegetation reduce the mechanical impact of river level fluctuations and rainfall on the embankment and retain sediment transported, while the belowground parts reinforce mechanically the materials forming the top of the embankment, facilitating drainage in the topmost layers and promoting plant water uptake, thus contributing to the regulation of the drying/wetting cycle.

Plating deep-rooting perennial, herbaceous species on earth embankments therefore represent a sustainable, green intervention for the protection of a riverbank susceptible to fluvial erosion, contributing to the preservation of the fluvial ecosystem environment and avoiding a wide use of grey solutions. The European research project OPERANDUM is testing also this typology of NBS, with an experimental site selected on the river Panaro, one of the main tributary of the main Po River, Italy. To investigate the effect of vegetation on the riverbank soil, a monitoring system has been installed at shallow depths. The system estimates soil water content, matric suction and pore water pressure, in order to quantify the effects of the growth of different vegetation species, which have been recently seeded on site, for analyzing the plant-soil-atmosphere interaction. The work will present the site preparation and the system implementation. The analysis of the first collected data and the outcomes of the preliminary investigations, including site and laboratory experiments, will then be discussed. Monitoring data collected along the entire vegetation growth cycle, that is expected to take around two years, will allow to quantify the influence of vegetation in the soil-atmosphere interaction processes and, on the long-term, verify its effective contribution in riverbank protection.
The power distribution between the symmetric and anti-symmetric components of the tropical wavenumber-frequency spectrum
Authors: Shamir Ofer , Schwartz Chen , Garfinkel Chaim , Paldor Nathan
Published: March 2021

A yet unexplained feature of the tropical wavenumber-frequency spectrum is its parity distributions, i.e., the distribution of power between the meridionally symmetric and anti-symmetric components of the spectrum. Due to the linearity of the decomposition to symmetric and anti-symmetric components and the Fourier analysis, the total spectral power equals the sum of the power contained in each of these two components. However, the spectral power need not be evenly distributed between the two components. Satellite observations and reanalysis data provide ample evidence that the parity distribution of the tropical wavenumber-frequency spectrum is biased towards its symmetric component. Using an intermediate-complexity model of an idealized moist atmosphere, we find that the parity distribution of the tropical spectrum is nearly insensitive to large-scale forcing, including topography, ocean heat fluxes, and land-sea contrast. On the other hand, by adding a small-scale (stochastic) forcing, we find that the parity distribution of the tropical spectrum is sensitive to asymmetries on small spatial scales compared to the observed large-scale spectrum. Physically, such forcing can be thought of as small-scale convection, which is believed to trigger some of the Tropics' large-scale features via an upscale (inverse) turbulent energy cascade. These results are qualitatively explained by considering the effects of triad interactions on the parity distribution. According to the proposed mechanism, any small-scale asymmetry (symmetric or anti-symmetric) in the forcing leads to symmetric bias in the spectrum, regardless of the source of variability providing the forcing.
Jupiter's Zonal Vorticity Profile Observed by JunoCam
Authors: Eichstädt Gerald , Rogers John , Orton Glenn , Hansen Candice
Published: March 2021

We derive Jupiter's zonal vorticity profile from JunoCam images, with Juno's polar orbit allowing the observation of latitudes that are difficult to observe from Earth or from equatorial flybys.  We identify cyclonic local vorticity maxima near 77.9°, 65.6°, 59.3°, 50.9°, 42.4°, and 34.3°S planetocentric at a resolution of ~1°, based on analyzing selected JunoCam image pairs taken during the 16 Juno perijove flybys 15-30. We identify zonal anticyclonic local vorticity maxima near 80.7°, 73.8°, 62.1°, 56.4°, 46.9°, 38.0°, and 30.7°S.  These results agree with the known zonal wind profile below 64°S, and reveal novel structure further south, including a prominent cyclonic band centered near 66°S. The anticyclonic vorticity maximum near 73.8°S represents a broad and skewed fluctuating anticyclonic band between ~69.0° and ~76.5°S, and is hence poorly defined. This band may even split temporarily into two or three bands.  The cyclonic vorticity maximum near 77.9°S appears to be fairly stable during these flybys, probably representing irregular cyclonic structures in the region. The area between ~82° and 90°S is relatively small and close to the terminator, resulting in poor statistics, but generally shows a strongly cyclonic mean vorticity, representing the well-known circumpolar cyclone cluster.

The latitude range between ~30°S and ~85°S was particularly well observed, allowing observation periods lasting several hours. For each considered perijove we selected a pair of images separated by about 30 - 60 minutes. We derived high-passed and contrast-normalized south polar equidistant azimuthal maps of Jupiter's cloud tops. They were used to derive maps of local rotation at a resolution of ~1° latitude by stereo-corresponding Monte-Carlo-distributed and Gauss-weighted round tiles for each image pair considered. Only the rotation portion of the stereo correspondence between tiles was used to sample the vorticity maps. For each image pair, we rendered ~40 vorticity maps with different Monte-Carlo runs. The standard deviation of the resulting statistics provided a criterion to define a valid area of the mean vorticity map. Averaging vorticities along circles centered on the south pole returned a zonal vorticity profile for each of the perijoves considered. Averaging the resulting zonal vorticity profiles built the basis for a discussion of the mean profile.

JunoCam also images the northern hemisphere, at higher resolution but with coverage restricted to a briefer time span and smaller area due to the nature of Juno's elliptical orbit, which will restrict our ability to obtain zonal vorticity profiles.
Modelling of interactions between dykes, inclined sheets and faults at Santorini volcano
Authors: Drymoni Kyriaki , Browning John , Gudmundsson Agust
Published: March 2021

Dykes and inclined sheets are known occasionally to exploit faults as parts of their paths, but the conditions that allow this to happen are still not fully understood. Here we report field observations from a well-exposed dyke swarm of the Santorini volcano, Greece, that show dykes and inclined sheets deflected into faults and the results of analytical and numerical models to explain the conditions for deflection. The deflected dykes and sheets belong to a local swarm of 91 dyke/sheet segments that was emplaced in a highly heterogeneous and anisotropic host rock and partially cut by some regional faults and a series of historic caldera collapses, the caldera walls providing, excellent exposures of the structures. The numerical models focus on a normal-fault dipping 65° with a damage zone composed of parallel layers or zones of progressively more compliant rocks with increasing distance from the fault rupture plane. We model sheet-intrusions dipping from 0˚ to 90˚ and with overpressures of alternatively 1 MPa and 5 MPa, approaching the fault. We further tested the effects of changing (1) the sheet thickness, (2) the fault-zone thickness, (3) the fault-zone dip-dimension (height), and (4) the loading by, alternatively, regional extension and compression. We find that the stiffness of the fault core, where a compliant core characterises recently active fault zones, has pronounced effects on the orientation and magnitudes of the local stresses and, thereby, on the likelihood of dyke/sheet deflection into the fault zone. Similarly, the analytical models, focusing on the fault-zone tensile strength and energy conditions for dyke/sheet deflection, indicate that dykes/sheets are most likely to be deflected into and use steeply dipping recently active (zero tensile-strength) normal faults as parts of their paths.
Revealing mechanisms of change in the Atlantic Meridional Overturning Circulation under global heating
Authors: Sonnewald Maike , Lguensat Redouane , Balaji Venkatramani
Published: March 2021

The North Atlantic ocean is key to climate through its role in heat transport and storage, but the response of the circulation’s drivers to a changing climate is poorly constrained. The transparent machine learning method Tracking global Heating with Ocean Regimes (THOR) identifies drivers of circulation with minimal input: depth, dynamic sea level and wind stress. Beyond a black box approach, THOR's predictive skill is transparent. A dataset is created with features engineered and labeled by an explicitly interpretable equation transform and k-means application. A multilayer perceptron is then trained, explaining its skill using relevance maps and theory. THOR reveals a weakened circulation with abrupt CO2 quadrupling, due to a shift in deep water formation areas and locations of the Gulf Stream and Trans Atlantic Current transporting heat northward. If CO2 is increased 1% yearly, similar but transient patterns emerge. THOR could accelerate model analysis and facilitate process oriented intercomparisons.