bluuebunny/crossref_metadata_2025 huggingface dataset:
Sharp geodetic fault slip models for an improved understanding of volcano flank dynamics
Authors: Gonzalez Pablo
Published: March 2020

The study of the stability of volcano flanks has been an active topic of research for the last few decades. In 2018, two major events renewed attention in this hazardous processes. In May 2018, following the beginning of a flank eruption at Kilauea volcano in Hawai’i, a M6.9 earthquake occurred along the Southern flank of Kilauea marking a dramatic but transient acceleration from its secular deformation rate. Alternatively, in December 2018, an intense period of volcanic activity preceded a catastrophic sector collapse which triggered a devastating tsunami at Anak Krakatou volcano (Indonesia). The two contrasting behavior events reveal our poor understanding of the physical processes controlling volcano stability.

Ultimately, instability of volcano flanks is characterized by the development and evolution of failure surfaces (faults and/or basal shear zones). Once established, for example at a rheological interface, a decollement fault should be a key element in the control of the mechanical interplay between the volcano-tectonic and gravitational forces. In this communication, I review our ability to map surface displacements measured with geodetic techniques into frictionally distinct regions on the fault surface. I explore a range of inverse modeling methods to estimate bounds on the extend of geodetically constrained fault slip areas. I apply the methods to the Southern flank of Kilauea volcano. The range of different solutions for fault slip models allows to critically assess whether there are regions of stable or variable frictional conditions. Mapping accurately the frictional behavior and constraining its location region will allow to generate more realistic dynamic models of volcano flanks and improve our understanding the physical processes controlling volcano stability.
European Commission AI Watch initiative: Artificial Intelligence uptake and the European Geosciences Community
Authors: Nativi Stefano , Craglia Max
Published: March 2020

The European Commission (EC) puts forward a European approach to artificial intelligence and robotics. It deals with technological, ethical, legal and socio-economic aspects to boost EU's research and industrial capacity and to put AI at the service of European citizens and economy.

Artificial intelligence (AI) has become an area of strategic importance and a key driver of economic development. It can bring solutions to many societal challenges from treating diseases to minimising the environmental impact of farming. However, socio-economic, legal and ethical impacts have to be carefully addressed.

It is essential to join forces in the EU to stay at the forefront of this technological revolution, to ensure competitiveness and to shape the conditions for its development and use (ensuring respect of European values). In this framework, the EC and the Member States published a Coordinated Plan on Artificial Intelligence”, COM(2018) 795, on the development of AI in the EU. The Coordinated Plan includes the recognition of common indicators to monitor AI uptake and development in the Union and the success rate of the strategies in place, with the support of the AI Watch instrument developed by the EC. Therefore, AI Watch is monitoring and assessing European AI landscapes from driving forces to technology developments, from research to market, from data ecosystems to applications. 

The presentation will first introduce the main AI Watch methodology and tasks. Then, it will focus on the interest of AI Watch to monitor and understand what has been the AI impact on Geosciences research and innovation –see for example Climate Change studies. Finally, a proposal to connect EGU Community (in particular ESSI division) and AI Watch will be introduced.
Atmospheric electric field measurements in the central United Arab Emirates
Authors: Nicoll Keri , Harrison R. Giles , Marlton Graeme , Airey Martin
Published: March 2020

Measurements of the atmospheric electric field (or Potential Gradient, PG) in arid, desert regions are few in comparison to those in more wet/mid latitude regions, despite the fact that such measurements can provide important insights into dust charging processes. Dust charging is emerging as potentially important in sustaining the long range transport of particles, for which new charge and field data are essential. Here we present new PG data from an electric field mill at Al Ain international airport in the eastern part of the Abu Dhabi Emirate in the United Arab Emirates (UAE).  Measurements were made alongside a visibility sensor and ceilometer to provide information on the background meteorological conditions.  At Al Ain, the conditions are generally fair weather in mid-latitude terms (predominantly no clouds or precipitation), with very occasional fog or thunderstorms, but the PG still demonstrates considerable variability associated with local factors such as dust and aerosol content.  Throughout the data series, the PG is almost entirely positive, with the only negative values occurring during thunderstorms and violent dust storms.  The desert climate of the UAE lead to widespread uplift of dust on a regular basis, as evidenced by the generally low visibility measured at the airport (mean visibility = 9km).  The PG at Al Ain was found to be generally much larger than typical fair weather values at other sites, with a mean of 116 V/m, with 2 kV/m exceeded regularly.  The local influences on the PG at Al Ain are strongly apparent and the daily variation in PG was found to fall into two main categories: 1) convection dominated, 2) sea breeze dominated.   On the convection dominated days the PG followed the daily variation in temperature and wind speed closely, with very large maximum values of PG up to 4 kV/m in the mid afternoon.  The other regular daily feature in Al Ain PG was a sharp positive increase in PG up to several kV/m around 1800-1900 local time.  This feature is associated with the arrival of a sea breeze front, which originates more than 150 km away on the Abu Dhabi coastline.  The extremely large change in PG over a very short time scale (tens of minutes) is thought to be due to the action of dust pickup within the sea breeze front as it travels substantial distances over the flat arid landscape.  Overall, the electrical environment at Al Ain is found to be generally very highly charged and so the local effects (primarily from dust and aerosol) mask Global Electric Circuit influences in the surface data.

 

 

 
The effect of climate change on sediment distribution and delivery within the Rhine-Meuse Delta
Authors: Cox Jana , Dunn Frances , Nienhuis Jaap
Published: March 2020

The morphological and hydrological equilibrium of many deltas worldwide is changing due to anthropogenic activities. A key example of such a delta is the Rhine-Meuse Delta (RMD) in the Netherlands. It is home to an important shipping and economic centre (Rotterdam) and thus has been strongly affected by anthropogenic activities. Changes include embanking, narrowing and deepening of channels, major dredging and sediment relocation, the building of ports and harbours, and dam building upstream. There is currently a net annual loss of sediment from the delta. Considering current and future sea level rise it is crucial that the RMD receives sufficient sediment or it risks drowning, increased flood risk, decreased ecological area and channel bed degradation.

Here, we estimate the future delivery of suspended sediment from upstream using BQART, and the volume and sediment flux from the sea using a 1D morphological model. We ignore bedload fluxes as they make up a small proportion of the annual supply. We use these estimates to investigate sediment redistribution between channels in the RMD based on suspended sediment-discharge relations. Projections for 2050 and 2100 are presented based on region-specific climate scenarios for discharge and sea level and incorporate projected future upstream reservoir construction. The sediment concentration in the branches is compared with discharge-area relations and current bed level trends to demonstrate potential sedimentation-erosion trends for individual branches.

Projections for the 21st century indicate that sediment delivery to the RMD from upstream is likely to decrease slightly, while sea level rise will cause tidally driven suspended sediment delivery to move further inland. It is estimated that the already negative sediment budget of the delta will be exacerbated by dredging, which removes all incoming sediment at the coastal boundary. The severity of sediment starvation depends on the climate change scenario. Our work indicates that certain channels will be at risk of erosion due to this sediment starvation, whilst other branches will experience net sedimentation. Sediment input from the coast could also reach further inland, assuming current dredging practice remain unaltered, which could provide an opportunity for the system to regain equilibrium. We recommend that a sustainable sediment management strategy is undertaken in the region to counteract the negative effects of sediment starvation.  
Responses to dissolved organic nitrogen compounds by recently isolated freshwater microalgae species
Authors: Bayliss Catherine E. , Johnes Penny , Evershed Richard P. , Sanchez-Baracaldo Patricia , Maberly Stephen C.
Published: March 2020

Freshwater microalgae isolates from a UK headwater catchment (collected in 2017) were tested for their growth and media nitrogen speciation changes when presented with low molecular weight dissolved organic nitrogen compounds. The location has input from livestock run off increasing organic matter in stream. Experimental treatments and initial isolation took place in controlled culture cabinets kept at 15°C, with a 16:8 light:dark cycle and light c.a. 50 µmol m-2 s-1. Treatments included separately presented urea and glutamate, alongside negative (no N or P sources) and positive controls (nitrate or ammonium). Nitrogen addition treatments were provided with the same phosphorus source, trace minerals, trace metals and took place for two weeks. Different species isolated from the location showed optimal growth on different organic nitrogen sources. Organic nitrogen compounds caused growth at least comparable to inorganic sources. Cell growth was best on dissolved organic nitrogen compounds for some species. This relatively quick cycling of organic nitrogen compounds in river systems to photosynthetic growth has implications for ecosystem heath and capacity to mitigate organic nitrogen inputs. Anthropogenic activity that increases organic nitrogen may favour certain species compositions, altering downstream ecosystem functions such as algal bloom formation and dominant microalgae species. Further work will use stable isotope investigation of potential uptake mechanisms and wider work is required on understanding how the ecosystem may respond to organic nitrogen changes. 
Patterns in US flood vulnerability revealed from flood insurance "big data"
Authors: Wing Oliver , Pinter Nicholas , Bates Paul , Kousky Carolyn
Published: March 2020

Vulnerability functions are applied in flood risk models to calculate the losses incurred when a flood interacts with the built environment. Typically, these take the form of relative depth–damage relationships: flood depths at the location of a particular asset translate to a damage expressed as a certain percentage of its value. Vulnerability functions are a core component of risk and insurance industry catastrophe (CAT) models, permitting physical models of flood inundation under different scenarios (e.g. certain probabilities) to be translated to more tangible and useful estimates of loss. Much attention is devoted to the physical hazard component of flood risk models, but the final vulnerability component has historically received less attention — despite quantifications of risk being highly sensitive to these uncertain depth–damage functions. For the case of US flood risk models, ‘off-the-shelf’ functions from the US Army Corps of Engineers (USACE) are commonly used. In an analysis of roughly 2 million flood claims under the US National Flood Insurance Programme (NFIP), we find these ubiquitous USACE functions are not reflective of real damages at specified flood depths experienced by policy holders of the NFIP. Particularly for smaller flood depths (<1m), the majority of structural damages are of <10% of the building value compared to the 30–50% stipulated by the USACE functions. A deterministic relationship between depth and damage is shown to be invalid, with the claims data indicating damages at a certain depth form a beta distribution. Most reported damages are either <10% or >90% of building values, with the proportion of >90% damages increasing with water depth. The NFIP data also reveal that newer buildings tend to be more resilient (lower damages for a given depth), surface water flooding to be more damaging than fluvial flooding for a given depth, vulnerability to vary dramatically across space, and even the concept of a relative damage to be untenable in its application to expensive properties (e.g. even for depths >1m, properties worth >$250k rarely experience losses >20% of their value). The findings of this study have significant implications for developers of flood risk models, suggesting current estimates of US flood risk (in $ terms) may be substantial over-estimates.
Point effluent discharges have unclear direct impacts on local biogeochemical P cycling against high background complexity in catchment pollution processes and ecosystem responses
Authors: Stutter Marc , Richards Samia
Published: March 2020

Point discharges of pollution such as effluents, enriched in bioavailable nutrients, organic matter and multiple contaminants, are often considered as having both strong local and cumulative downstream effects on aquatic ecosystem quality. Since potential impacts of effluents involve many multiple stressor interactions it requires an integrated suite of in-situ and ex-situ techniques to evaluate the biotic and abiotic interplay of the ecosystem effects. This study aimed to evaluate impacts using sampling transects around discharges from wastewater treatment works (WWTW) to a range of watercourses. The hypothesis was that major effluent discharges would lead to local downstream enrichment in nutrient and microbial contaminants, altered microbial communities and impairment in P processing rates with downstream recovery distances related to cumulative upstream pollution.

Five river transects were evaluated on two dates comprising points 100m above then 100, 200, 500 m below stream-side WWTW. Stream water samples were collected (effluents where possible) and analysed for C, N, P forms, coliforms, pesticides and pharmaceuticals. Biofilms (grown on tiles between sampling dates) and recovered for analysis alongside bed sediments for stoichiometry, P enzyme activity, substrate induced respiration assays and chlorophyll (biofilms). Catchments were characterised using spatial data on landcover, stream network and cumulative pollution sources.

Patterns of pollution presence in the waters and cycling indicators in the bed and periphyton did not show clear patterns of high local and declining downstream impacts. Instead a surprising complexity of weak transect effects amongst a high background heterogeneity was seen. This likely results from a heterogeneous biophysical environment of the channel as well as the complexity of the catchment ‘diffuse’ pollution inputs. Hence, WWTW impacts on aquatic pollution presence and processing factors were unclear and masked by catchment system heterogeneity and complexity.   
Interpretation and Analysis of Projected Ice Sheet Contributions from a Structured Expert Judgement
Authors: Aspinall Willy , Cooke Roger , Kopp Bob , Bamber Jon , Oppenheimer Michael
Published: March 2020

Despite considerable advances in process understanding, numerical modeling and the quality of the observational record of ice sheet contributions to sea level rise (SLR) since the last IPCC report (AR5), severe limitations remain in the predictive capability of numerical modeling approaches. In this context, the potential contribution of the ice sheets remains the largest uncertainty in projecting future SLR beyond mid-century. Various approaches, including Monte Carlo ensemble emulator simulations, probabilistic or plausibility methods, and Semi Empirical Models have been used in attempts to address these limitations. To explore and quantify the uncertainties in ice sheet projections since the AR5, a Structured Expert Judgement (SEJ) elicitation – involving 23 experts from North America and Europe - was undertaken in 2018; this allowed us to derive a numerically-formalised pooling of cogent uncertainty judgements.

The results of the SEJ indicated that estimates, particularly for probabilities beyond the likely range used in the AR5 (i.e. 17th-83rd percentile), have grown since the AR5. The SEJ results indicated a 5% probability that global mean sea level could exceed 2 m by 2100, for a business-as-usual temperature scenario, with the ice sheets contributing 178 cm. The study elicited contributions for three processes - ice dynamics, accumulation and runoff - for each of the three ice sheets covering Greenland, West and East Antarctica. Here, we investigate how these three main physical processes influence the long upper tails in the probability density functions for the integrated contributions of each ice sheet.  To interpret the findings, we draw on process-based rationales provided by the experts, which relate ice sheet SLR contributions to ocean and atmospheric forcing and to internal instabilities, and discuss our higher total SLR estimates in relation to earlier studies.
Water Quality Autoregression Prediction Model Based on Markov-Switching Theory Using Crow Search Algorithm
Authors: Liu Chunlei , Pan Chengzhong , Chang Yawen , Luo Mingjie
Published: March 2020

Water quality prediction is an important technical means for preventing and controlling water pollution and is crucial in the formulation of reasonable water pollution prevention and control measures. The time series structure of natural water quality is complex and heteroscedastic, so it is difficult for the traditional prediction model to reflect the actual situation well. Hence, Markov-switching (MS) theory is applied to a water quality autoregression (AR) prediction model (MSAR) in this paper. Further, MSAR is improved by introducing the crow search algorithm to obtain model parameters (CSA-MSAR). Then existing water quality time series for CODMn was selected as the data for the CSA-MSAR model after a normality test and the Box–Cox normality transformation. The results show that the CSA-MSAR model for CODMn with (s, p) values of (3, 5) has the best performance. The improvement degree for selection criteria compared with AR model is as follows: Akaike information criterion for MSAR is 32.020% and 31.611% for CSA-MSAR; Bayesian information criterion for MSAR is 10.632% and 13.464% for CSA-MSAR; likelihood value for MSAR is 40.016% and 40.801% for CSA-MSAR; C for MSAR is 63.559% and 64.968% for CSA-MSAR. Moreover, the results show that the average prediction precision of the first- to fifth-order prediction is raised by 89.016% for MSAR and 89.340% for CSA-MSAR compared with AR, indicating that the introduction of MS makes the CSA-MSAR and MSAR models conform to the smoothness of the mean and variance in each state. The results also indicate that the introduction of CSA into the maximum likelihood estimation to obtain the parameters raise the model prediction precision (the average prediction precision of CSA-MSAR is higher than MSAR by 5.231% excluding the fifth-order prediction) and the CSA-MSAR model is scientifically valid and reasonable for water quality prediction.
Empirical dynamic modelling - a promising tool to assess causal links between water quality time series
Authors: Selle Benny , Knorr Klaus-Holger
Published: March 2020

Empirical dynamic modelling (EDM) is a relatively novel method to assess causality from time series in coupled dynamic systems. From the literature, EDM appeared to be useful in a number of applications including analysis of water quality data. It was therefore hypothesized that this technique has a potential to revisit existing long term data of solutes from catchment streams. More specifically, we proposed that causal links between concentration time series could be revealed, which were previously overlooked when only standard linear regression and correlation methods were used. We applied EDM to long term concentrations of dissolved organic carbon (DOC), total Fe and pH from the Lehstenbach stream in Germany, time series that were formerly evaluated using various other techniques in the context of DOC mobilisation from peat catchments. To assess causal links between solute time series, three steps of analysis were conducted. Firstly, the embedding dimension for each time series (that is the number of time lags required for the best possible one-time-step-ahead forecast for a particular time series) was computed. In a second step, using the computed embedding dimension, non-linearity of the system was assessed using a technique called s-mapping to explore if EDM is expected to be a beneficial tool for time series analysis. Finally, convergent cross mapping was applied to test different combinations of variables for causal links. The basic idea of convergent cross mapping is that - if X causes Y - the response variable Y contains information on its driver X but not vice versa (because X is independent of Y) and hence X can be predicted from time series of Y. So X is predicted from Y by mapping nearest neighbours in state space (so called cross mapping). With increasing length of Y, predictions shall improve to a saturation level, that is cross mapping skill converges, which is used as a criterion of causality. We applied EDM to weekly, discharge-corrected, temporal changes of concentration time series. Discharge corrections was conducted to eliminate discharge as a common driver of concentrations. Our data analysis implied a causal interaction between Fe and DOC that was proposed in earlier work. But surprisingly, DOC seems to drive pH but not the other way around, a result that needs to be investigated in more detail, but a likely explanation would be that pH of streamwater is mainly decreasing with acidic inputs of DOC from riparian wetlands. We concluded that using EDM additional insights on the links between catchment time series can be obtained.
Model Assisted Planning of Agricultural Groundwater Development in Bist Doab Interbasin (India)
Authors: Kapoor Aditya , Kashyap Deepak
Published: March 2020

Present study aims at planning of agricultural groundwater development in Bist interbasin (India) that is experiencing excessive water table decline due to intense agricultural groundwater pumping. The interbasin covering an area of 8040 Km2 comprises an alluvial unconfined aquifer that is hydraulically connected to two major perennial rivers viz., Satluj and Beas.  A finite difference based distributed flow model of the study area was calibrated for transmissivity geostatistically on the basis of discrete point data at 15 points, and head fields available at 6 discrete times. The deficit of transmissivity data was overcome by invoking the Pilot point approach wherein transmissivity at additional artificial points are estimated by the least squares approach. The calibrated model was oriented towards the agricultural objective by correlating its sink term with crop areas. The model was used to simulate the long-term stabilized head and the depth fields corresponding to prevailing cropping pattern. The simulation indicates large and unsustainable water table decline. The impact of various moderated cropping patterns on the water table decline was subsequently simulated. It was concluded that replacement of some fraction of area under water intensive rice crop by maize crop area may stabilize the water table depths to acceptable limit.
Impacts of macro-turbulent flow on sediment transport potential during ice-covered and open-channel conditions
Authors: Lotsari Eliisa , Kämäri Maria , Alho Petteri , Kasvi Elina
Published: March 2020

Macro-turbulent flows during ice-covered and open-channel conditions, and their impacts on the total sediment transport, have not been studied widely in northern rivers. Previous studies have detected these processes, for example, only at the inlet area of one meander bend, or only during low discharge conditions. Thus, for understanding their impacts on the total sediment transport, it is needed to detect these macro-turbulent flow structures from a variety of cold region rivers, from multiple years, and also from a variety of different flow magnitude conditions. The pulses of high flow velocities related to these macro-turbulent structures may be important for determining the seasonal total sediment amount transported to the arctic ocean.

 

The aim is 1) to detect the macro-turbulent flow in a meandering river at ice-covered low flow condition, and compare it to both high and low magnitude open-channel flow conditions. 2) Within a meander bend, the macro-turbulent flow will be compared between its inlet, apex and outlet sections. 3) The shear forces will be analyzed to detect the effects of macro-turbulent flow on potential sediment transport and channel development. The analyses are based on 5–10 minutes long moving boat Acoustic Doppler Current Profiler (ADCP) measurements from a meandering sub-arctic river. The measurements have been done in February and May during 2016–2019, and in September during 2016-2018. The preliminary results of this study are presented. The hypothesis is that the sediment transport potential of a sub-arctic river could be higher during all seasons than previously expected due to the pulses of high velocities related to macro-turbulent flow structures.
Etablishing the first continuous Holocene tephrostratigraphy on Kerguelen Archipelago, subantarctic Indian Oean
Authors: Arnaud Fabien , Sabatier Pierre , Leloup Anouk , Servettaz Aymerick , Moine Bertrand , Develle Anne-Lise , Guédron Stéphane , Perrot Vincent , Poulenard Jérôme , Fanget Bernard , Malet Emmanuel , Støren Eivind , Reyss Jean-Louis , Le Viavan Nicolas , Heirman Katrien , De Batist Marc , Michel Elisabeth , de Beaulieu Jacques-Louis , Vanderputten Nathalie , Bakke Jostein
Published: March 2020

Here we present the first Holocene-long continuous chronology of volcanic eruptions on Kerguelen archipelago, where no evidence of Holocene volcanic activity has been published so far. Our chronicle is based upon sedimentological, chronological and geochemical data form two sediment cores, taken in two different depocenters of a large lake, Lake Armor, located ca. 70 km away from the archipelago’s potentially active volcanic area. This allowed us to confidently attribute the origin of pumice-rich or ash-rich layers to contemporaneous volcanic eruptions. Altogther eight main eruptions, as well as three secondary ones, were here documented and dated, among which the youngest occurred during the Middle Age, between 890 and 980 AD. The oldest eruption is also by far the strongest one and deposited more  than 1.2m of up-to 3cm large pumices, 70 km away from the volcanic edifice. It occurred at the very beginnning of the Holocene (11 ka cal. BP), suggesting a climatic control after glacial retreat upon volcanic activity. Additionnal evidences from lake sediment and geological outcrops, both close to Lake Armor and in remote areas over Kerguelen mainland, open the future possibility of a better reconstruction of major eruptions deposit spreading and thus an assessment of their intensity. This established chronostratigraphy will be useful to synchronise paleoenvironment record at least at the scale of the archipelago as well as in surrounding marine areas where Holocene climate reconstructions are particularly sparse.
Pending recovery in the strength of the meridional overturning circulation at 26°N
Authors: Moat Ben , Smeed David , Frajka-Williams Eleanor , Desbruyeres Damien , Beaulieu Claudie , Johns William , Rayner Darren , Sanchez-Franks Alejandra , Baringer Molly , Volkov Denis , Bryden Harry
Published: March 2020

The strength of the Atlantic meridional overturning circulation (AMOC) at 26°N has now been continuously measured by the RAPID array over the period April 2004 - Sept 2018. This record provides unique insight into the variability of the large-scale ocean circulation, previously only measured by sporadic snapshots of basin-wide transports from hydrographic sections. The continuous measurements have unveiled striking variability on timescales of days to a decade, driven largely by wind-forcing, contrasting with previous expectations about a slowly-varying, buoyancy forced large-scale ocean circulation. However, these measurements were primarily observed during a warm state of the Atlantic Multidecadal Variability (AMV) which has been steadily declining since a peak in 2008-2010. In 2013-2015, a period of strong buoyancy- forcing by the atmosphere drove intense watermass transformation in the subpolar North Atlantic and provides a unique opportunity to investigate the response of the large-scale ocean circulation to buoyancy forcing.

Modelling studies suggest that the AMOC in the subtropics responds to such events with an increase in overturning transport, after a lag of 3-9 years. At 45°N, observations suggest that the AMOC my already be increasing. We have therefore examined the record of transports at 26°N to see whether the AMOC in the subtropical North Atlantic is now recovering from a previously reported low period commencing in 2009. Comparing the two latitudes, the AMOC at 26°N is higher than its previous low. Extending the record at 26°N with ocean reanalysis from GloSea5, the transport fluctuations follow those at 45°N by 0-2 years, albeit with lower magnitude. Given the short span of time and anticipated delays in the signal from the subpolar to subtropical gyres, it is not yet possible to determine whether the subtropical AMOC strength is recovering.
Intraplate and petit-spot volcanism originating from hydrous mantle transition zone
Authors: Yang Jianfeng , Faccenda Manuele
Published: March 2020

Most magmatism occurring on Earth is conventionally attributed to passive mantle upwelling at mid-ocean ridges, slab devolatilization at subduction zones, and mantle plumes. However, the widespread Cenozoic intraplate volcanism in northeast China and the peculiar petit-spot volcanoes offshore the Japan trench cannot be readily associated with any of these mechanisms. Furthermore, the seismic tomography images show remarkable low velocity zones (LVZs) sit above and below the mantle transition zone which are coincidently corresponding to the volcanism. Here we show that most if not all the intraplate/petit-spot volcanism and LVZs present around the Japanese subduction zone can be explained by the Cenozoic interaction of the subducting Pacific slab with a hydrous transition zone. Numerical modelling results indicate that 0.2-0.3 wt.% H2O dissolved in mantle minerals which are driven out from the transition zone in response to subduction and retreat of a stagnant plate is sufficient to reproduce the observations. This suggests that critical amounts of volatiles accumulated in the mantle transition zone due to past subduction episodes and/or delamination of volatile-rich lithosphere could generate abundant dynamics triggered by recent subduction event. This model is probably also applicable to the circum-Mediterranean and Turkish-Iranian Plateau regions characterized by intraplate/petit-spot volcanism and LVZs in the underlying mantle.
Identifying Intensively Managed Coffee Forests in Southwest Ethiopia using Satellite Imagery
Authors: Hwang Byongjun , Hundera Kitessa , Mekuria Bizuneh , Wood Adrian , Asfaw Andinet
Published: March 2020

The high forests in southwest Ethiopia, some of the last remaining Afromontane forests in the country, are home to significant forest coffee production. While considered as beneficial in maintaining forests, there have been growing concerns about the degradation caused by intensive coffee production in the forests. However, yet no suitable methods have been developed to map the intensively managed coffee forests. In this study, we explore the feasibility of monitoring the extent of the degradation within the intensively managed coffee forests by using satellite imagery (Landsat-8 and Sentinel-2). For this, we conducted in-situ field canopy photo and tree surveys, and the results were analysed with satellite-derived vegetation indices such as NDVI and NBR. This feasibility study informed us that the detection of the intensively managed forest coffee areas (disturbances caused by this practice) using satellite imagery can be possible, as the dry-season forest structure (canopy, undergrowth) and vegetation indices in the intensively managed coffee forests are significantly distinctive from those in natural forests. This study will contribute to the long-term sustainable management of the coffee forest.
The more hydrologic info the less uncertainties in monthly runoff prediction: The case study of a semi-arid Mediterranean island
Authors: Perra Enrica , Urru Salvatore , Deidda Roberto , Viola Francesco
Published: March 2020

Since the Gravity Recovery and Climate Experiment (GRACE) launch in 2002, a global dataset of Earth’s total water storage (TWS) measures is available, providing additional and useful information for global and regional hydrologic models. In this study we demonstrate how this data can be easily integrated with a simple two-parameter regional water balance model also at the small scale (i.e. area < 50’000 km2). In particular, we show how the inclusion of additional information reduces the predictive uncertainty of the hydrologic model. As test case, the island of Sardinia (Italy) located in the Mediterranean Sea, with an area of about 24000 Km2, is chosen. The water balance model simulates at monthly scale surface and subsurface runoff, actual evapotranspiration fluxes, and terrestrial (surface and ground) water storage of the island during the period 2002–2017. The results show that GRACE data constitutes a reliable dataset for the hydrologic modeling also at the small scale and their integration into the proposed regional water balance model reduces the uncertainties in reconstructing long-term variations of the TWS.
Jet Latitude Regimes and the Predictability of the North Atlantic Oscillation
Authors: Strommen Kristian
Published: March 2020

In recent years, numerical weather prediction models have begun to show notable levels of skill at predicting the
average winter North Atlantic Oscillation (NAO) when initialised one month ahead. At the same time, these model
predictions exhibit unusually low signal-to-noise ratios, in what has been dubbed a `signal-to-noise paradox'.
We analyse both the skill and signal-to-noise ratio of the Integrated Forecast System (IFS), the European Center for
Medium-range Weather Forecasts (ECMWF) model, in an ensemble hindcast experiment. Specifically, we examine the
contribution to both from the regime dynamics of the North Atlantic eddy-driven jet. This is done by constructing a
statistical model which captures the predictability inherent to to the trimodal jet latitude system, and fitting its
parameters to reanalysis and IFS data. Predictability in this regime system is driven by interannual variations in the
persistence of the jet latitude regimes, which determine the preferred state of the jet. We show that the IFS has
skill at predicting such variations in persistence: because the position of the jet strongly influences the NAO, this
automatically generates skill at predicting the NAO. We show that all of the skill the IFS has at predicting the
winter NAO over the period 1980-2010 can be attributed to its skill at predicting regime persistence in this way.
Similarly, the tendency of the IFS to underestimate regime persistence can account for the low signal-to-noise ratio,
giving a possible explanation for the signal-to-noise paradox. Finally, we examine how external forcing drives
variability in jet persistence, as well as highlight the role played by transient baroclinic eddy feedbacks to
modulate regime persistence.
Calibrating large-ensemble European climate projections using observational data
Authors: O'Reilly Christopher , Befort Daniel , Weisheimer Antje
Published: March 2020

In this study methods of calibrating the output of large single model ensembles are examined. The methods broadly involve fitting seasonal ensemble data to observations over a reference period and scaling the ensemble signal and spread so as to optimize the fit over the reference period. These calibration methods are then applied to the future (or out-of-sample) projections. The calibration methods are tested and give indistinguishable results so the simplest of these methods, namely Homogenous Gaussian Regression, is selected. An extension to this method, applying it to dynamically decomposed data (in which the underlying data is separated into dynamical and residual components), is found to improve the reliability of the calibrated projections. The calibration methods were tested and verified using an “imperfect model” approach using the historical/RCP8.5 simulations from the CMIP5 archive. The verification indicates that this relatively straight-forward calibration produces more reliable and accurate projections than the uncalibrated (bias-corrected) ensemble for projections of future climate over Europe. When the two large ensembles are applied to observational data, the 2041-2060 climate projections for Europe for the RCP 8.5 scenario are more consistent between the two ensembles, with a slight reduction in warming but an increase in the uncertainty of the projected changes. 
Quantifying errors and uncertainties in satellite precipitation estimates
Authors: Kidd Chris , Maggioni Viviana
Published: March 2020

The utilization of satellite observations in the estimation of global precipitation is now well established. However, quantifying the errors and uncertainties associated with such estimates is very much in its infancy. While many validation studies have been undertaken, these tend to provide case-specific or longer-term/large area measures of the performance of the precipitation products: statistical performance has largely taken precedence over an assessment of errors and uncertainties within such products. As the requirements for finer spatial and temporal resolutions increase, the assumptions made on the bulk large area/long time-frame products are no longer appropriate: careful assessments of the apportionment of the errors and uncertainties within the precipitation products needs to be made.

The premise of this study is that to truly understand the errors and uncertainties in the final precipitation product it is essential to quantify these within the elements that make up each individual satellite sensor and precipitation retrieval scheme or algorithm. Thus, we start with two fundamental categories: the observation capability of the sensor and the ability of the retrieval scheme. Each sensor provides different observations resulting from the engineering aspects of the sensor itself through to the sampling regime once the sensor is taking measurements: the observation capability is fixed and will be the same for all the subsequent retrieval schemes. The retrieval schemes themselves have a number of assumptions, both in terms of what the sensor actually observes and in the observation-to-rainfall relationships. While many of the errors and uncertainties associated with these assumptions cannot be easily quantified, the relative magnitude of each can be assessed. Initial results are presented here that quantify the effects of the spatial and temporal sampling of sensors, together with the impact of channel selection upon the final products. These results provide an insight into ability of such techniques to retrieve precipitation from the local to global scales, and how such techniques may be improved in the future.
Linking Paleo Vegetation Modelling with a Phytolith Record for the African Humid Period (15 - 5 ka BP) of the Omo-River-Lowlands and the Chew Bahir Basin, southern Ethiopia
Authors: Fischer Markus Lothar , Sittaro Fabian , Manntschke Claudia , Yost Chad , Foerster Verena E , Schäbitz Frank , Schepers Christian , Trauth Martin H , Junginger Annett
Published: March 2020

Modern-day southern Ethiopia exhibits a complex mosaic of vegetation types. These types range from desert scrubland along the shores of Lake Turkana, to woodlands and wooded grasslands in the Omo-River-Lowlands and Chew Bahir catchment, and Afromontane forests of the Ethiopian Highlands. Over the past 20 ka, this region has experienced a variable climate, from the dry Last Glacial Maximum (25-18 ka BP) to the wet African Humid Period (15-5 ka BP), and back to present-day dry conditions. These oscillations likely had an impact on the biosphere and its human inhabitants. The biosphere, especially climate-induced changes in vegetation, in turn have a feedback effect on the local climate – and must therefore be considered in climate models and hydro-balance models. However, there are hardly any data on changes in vegetation during the dry-humid-dry transition of the AHP that could be used to parameterize such models.

As a contribution to an enhanced understanding of the role that paleo-vegetation could have played during those transitions, we present here a new comprehensive vegetation model. This study links a Predictive Vegetation Model (PVM) with the available vegetation-proxy records from southern Ethiopia, including a new phytolith record from Chew Bahir. The PVM uses an 18-year averaged time series of the Global Precipitation Measurement as well as SRTM elevation data to predict an 18-year averaged time series of MODIS landcover and vegetation parameters using boosted regression trees. We linked the PVM and resulting surface parameters (moisture availability, surface drag coefficient, albedo) with an existing hydro-balance model of the southern Ethiopian Rift to calculate precipitation during the AHP and hence also model the paleo-vegetation during this period. Available paleo-vegetation data including a new grass phytolith record from the sediments of an 11 m-meter long sediment core from the margin of paleo-Lake Chew Bahir were then used to compare model and proxy results. Being able to validate our new model data with actual vegetation proxy data for the first time enables us to gain valuable insights into the paleo-dimension of the vegetation mosaic of southern Ethiopia, a possible habitat of early Homo sapiens.
Future extreme precipitation frequency in the eastern Mediterranean: a new approach exploiting climate model projections
Authors: Marra Francesco , Armon Moshe , Zoccatelli Davide , Gazal Osama , Garfinkel Chaim , Adam Ori , Dayan Uri , Rostkier-Edelstein Dorita , Enzel Yehouda , Morin Efrat
Published: March 2020

Understanding extreme precipitation under changing climatic conditions is crucial to manage weather- and flood-related hazards. Global and regional climate models are able to provide coarse scale information on future conditions under different emission scenarios, but large uncertainties affect the projected precipitation amounts, extremes in particular, so that frequency analyses cannot be quantitatively trusted. This study uses, for the first time, the Simplified Metastatistical Extreme Value (SMEV) approach to directly exploit synoptic scale information, better represented by climate models, for obtaining projections of future extreme precipitation frequency.

We use historical rainfall data from >400 stations in Israel and Jordan to (a) provide a climatology of extreme daily precipitation (e.g., the 100-year return period amounts) in the steep climatic gradients of the region and (b) improve understanding of the SMEV description under changing climate. We demonstrate that, using SMEV, it is possible to (c) present the sensitivity of extreme quantiles to occurrence and intensity of Mediterranean lows and other synoptic systems, and (d) project future extreme quantiles starting from synoptic scale information generated by earlier climate-model-based studies. Under our working hypotheses, we project a general decrease of extreme precipitation quantiles for the RCP8.5 scenario; an increase is detected in the coastal region and the Negev arid lands. We discuss the apparent contrast of these results with previous findings.
Variations of oceanic and atmospheric heat fluxes in the North Atlantic and their link to the North Atlantic Oscillation Index
Authors: Iakovleva Diana , Bashmachnikov Igor
Published: March 2020

Interannual variations in the upper ocean heat and freshwater contents in the subpolar North Atlantic has important climatic effect. It affects the intensity of deep convection, which, in turn, forms the link between upper and deep ocean circulation of the global ocean Conveyor Belt.

The upper ocean heat content is primarily affected by two main process: by the ocean-atmosphere heat exchange and by oceanic heat advection. The intensity of both fluxes in the subpolar gyre is linked to the character of atmospheric circulation, largely determined by the phase of the North Atlantic Oscillation (NAO).

To study the interannual variability of the oceanic heat advection (in the upper 500th meters layer) we compare the results from four different data-sets: ARMOR-3D (1993-2018), SODA3.4.2 and SODA3.12.2 (1980-2017), and ORAS5 (1958-2017). The ocean-atmosphere heat exchange is accessed as the sum of the latent and the sensible heat fluxes, obtained from OAFlux data-set (1958-2016).

The oceanic heat advection to the Labrador and to the Irminger seas has high negative correlation (-0.79) with that into the Nordic Seas. During the years with high winter NAO Index (NAOI) the oceanic heat advection into the Subpolar Gyre decreases, while to the Nordic Seas – increases. These variations go in parallel with the intensification of the Norwegian, the West Spitsbergen and the slope East Greenland currents and weakening of the West Greenland and the Irminger Currents. During the years with high NAOI, the ocean heat release (both sensible and latent) over the Labrador and Irminger seas increases, but over the Norwegian Sea it decreases.

In summary, the results show that, during the positive NAO phase, the observed decrease of the heat content in the upper Labrador and Irminger seas is linked to both, a higher oceanic het release and a lower intensity of advection of warm water from the south. In the Norwegian Sea, the opposite sign of variations of the fluxes above leads to a simultaneous warming of the upper ocean.

The investigation is supported by the Russian Scientific Foundation (RSF), number of project 17-17-01151.

 

 