bluuebunny/crossref_metadata_2025 huggingface dataset:
Air-Sea Ammonia Fluxes Calculated from High-Resolution Summertime Observations Across the Atlantic Southern Ocean
Authors: Altieri Katye , Spence Kurt , Smith Shantelle
Published: March 2021

Oceanic ammonia emissions are the largest natural source of ammonia globally, but the magnitude of the air-sea flux in remote regions absent human influence remains uncertain. Here, we measured the concentration of surface ocean ammonium and atmospheric ammonia gas every two hours across a latitudinal transect (34.5ºS to 61ºS) of the Atlantic Southern Ocean during summer. Surface ocean ammonium concentrations ranged from undetectable to 0.36 µM and ammonia gas concentrations ranged from 0.6 to 5.1 nmol m-3. Calculated ammonia fluxes ranged from -2.5 to -91 pmol m-2 s-1, and were consistently from the atmosphere into the ocean, even in regions where surface ocean ammonium concentrations were relatively high. As expected, temperature was the dominant control on the air-sea ammonia flux across the latitudinal transect. However, a sensitivity analysis suggests that seasonality in the surface Southern Ocean nitrogen cycle may have a major influence on the direction of the ammonia flux.
Global runoff estimation through a regionalized STREAM model 
Authors: Camici Stefania , Giuliani Gabriele , Brocca Luca , Massari Christian , Tarpanelli Angelica , Restano Marco , Benveniste Jérôme
Published: March 2021

STREAM -SaTellite based Runoff Evaluation And Mapping- is a conceptual hydrological model able to derive daily river discharge and runoff estimates from satellite soil moisture, precipitation and terrestrial water storage anomalies observations. The model is very simple and versatile: It requires a limited number of parameters (only eight) to simulate river discharge.

The model simulates river discharge and gridded runoff at daily time scale with a 25 km spatial resolution. Forced by TRMM 3B42 rainfall data and ESA CCI soil moisture data and GRACE over five pilot large basins (Mississippi, Amazon, Niger, Danube and Murray Darling) the model already provided good runoff estimates especially over Amazon basin, with a Kling-Gupta efficiency (KGE) index greater than 0.92 both at the basin outlet and over several inner stations in the basin. Good results have been also obtained for Mississippi, Niger and Danube with KGE index greater than 0.75 for all the gauging stations.

By considering the good performances of the STREAM model and by the continuous availability (in space and time) of satellite observations, this work presents an attempt to regionalize the STREAM model parameters. The Mississippi river basin has been taken as case study and specific relationships between model parameters and different predictors (climate variables such as precipitation and evaporation, soil vegetation and topography characteristics) have been developed. By using these relationships, STREAM parameter values have been directly obtained from readily available climatic and physiographic basin characteristics and model performances are still satisfactory (median KGE over the basin equal to 0.60). The capability to use these relationships in other hydrologically similar catchments will be investigated for the Danube and Amazon river basins. The final target is to obtain global relationships as to provide to provide daily, 25 km, global runoff maps from the STREAM approach.
Seasonal variability of the net water-mass transport among the four major basins 
Authors: Garcia-Garcia David , Vigo Isabel , Trottini Mario , Vargas Juan
Published: March 2021

Global water cycle involves water-mass transport on land, atmosphere, ocean, and among them. Quantification of such transport, and especially its time evolution, is essential to identify footprints of the climate change and helps to constrain and improve climatic models. In the ocean, net water-mass transport among the ocean basins is a key, but poorly estimated parameter presently. We propose a new methodology that incorporates the time-variable gravity observations from the GRACE satellite (2003-2016) to estimate the change of water content, and that overcomes some fundamental limitations of existing approaches. We show that the Pacific and Arctic Oceans receive an average of 1916 (95% confidence interval [1812, 2021]) Gt/month (~0.72 ± 0.02 Sv) of excess freshwater from the atmosphere and the continents that gets discharged into the Atlantic and Indian Oceans, where net evaporation minus precipitation returns the water to complete the cycle. This salty water-mass transport from the Pacific and Arctic Oceans to the Atlantic and Indian Oceans show a clear seasonal variability, with a maximum transport of 3000 Gt/month during boreal summer, a minimum of 1000 Gt/month or less on February, Mars, and November.

This research has been primarily supported by the Spanish Ministerio de Ciencia, Innovación and Universidades research project DEEP-MAPS (RTI2018-093874-B-I00).
Station Classification and Reference Station Selection
Authors: Legrand Juliette , Bruyninx Carine
Published: March 2021

When using a network approach, expressing reliably GNSS position and velocities in a given reference frame (ITRF2014, IGS14, …) requires the identification of ‘stable’ and ‘rebliable’ reference stations. The choice of these reference stations can have a non-negligible impact on the estimated positions and velocities and of course on the derived geodynamic interpretations.

This study will present the work done to address this issue within EUREF and help the users of the EUREF products (more specifically of the EPN multi-year position and velocity solution) to identify the best reference stations in the EUREF Permanent Network (EPN). To that aim, in addition to a station classification, a web tool (https://epncb.oma.be/_productsservices/ReferenceFrame/) has been developed in order to discover the most suitable EPN reference stations. The primary goal of this tool is to help the user of EUREF reference frame product select suitable EPN reference stations to be added to his network during the preparation of own GNSS processing.

The tool helps the selection of optimal reference stations:

by providing a restricted list of reference stations (based on the station classification and the begin and end date of the user processing)

by giving access to additional information (number of position or velocity discontinuities, post-seismic deformation,…) and plots (detrended position time series, selection criteria values, velocity variability) for the stations.

The web tool as well as the station classification will be presented.
Satellite data processing for optimization of snow albedo parameterization in Noah LSM
Authors: Lee Seung Yeon , Lim Sujung , Lee Ebony , Park Seon Ki
Published: March 2021

To improve the predictability of weather/climate models, a prediction system capable of simulating the land surface-atmosphere interaction is essential. In the land surface model (LSM), the parameter values are applied differently depending on the land cover type. Previous studies reported that the Noah LSM underestimated the snow-related variables such as snow albedo, snow depth, and snow cover, compared to actual observations. In this study, among various processes in Noah LSM, we optimize several parameters related to snow albedo, using the genetic algorithm (GA) and satellite (MODIS) data: the parameters to be optimized include 1) the threshold value of the amount of snow with full coverage, , 2) the distribution shape coefficient related to the maximum albedo of new snowfall, and 3) the maximum albedo coefficient. We propose the MODIS data processing method to extract representative snow albedo values, rather than the point (pixel) values, for different land cover types in a 10 km by 10 km area around a model gridpoint ⸺ the representative values are used to calculate the fitness function in the GA optimization. The snow albedo simulation by Noah LSM has alleviated the underestimation problem with the optimized parameter values: it showed better results with the parameter values optimized using the representative values than those optimized using the point values. We expect to see further improvement in the weather/climate simluations using the coupled land surface-atmosphere model (e.g., WRF-Noah LSM) by implementing the optimized parameter values related to snow albedo.
A new tool to probe lithosphere evolution: OH signatures of pyroxenes
Authors: Ingrin Jannick
Published: March 2021

Four OH stretching bands in the frequency range 3300 – 3700 cm-1 dominate the infrared spectra of lithospheric pyroxenes. Depending on their metasomatic history or geodynamic origin, they have characteristic OH signatures. Pyroxenes from continental lithosphere that undergone “wet” metasomatism have distinct signature of those having undergone “dry” metasomatism. Pyroxenes from oceanic lithosphere have yet a third type of signature. Our most recent analyses of xenoliths and a critical review of the literature show that the phenomenon is widely distributed among continents and oceans. The phenomenon affects simultaneously opx and cpx from the same rock and various lithologies: peridotites, pyroxenites and granulites. In continental lithosphere, pyroxenes affected by “wet” metasomatism are dominated by OH bands at 3600 and 3415 cm-1 for opx and 3635 and 3445 cm-1 for cpx . Whereas pyroxenes affected by “dry” metasomatism are dominated by OH bands at 3570 and 3515 cm-1 for opx and 3595 and 3515 cm-1 for cpx. Opxs from oceanic lithosphere have OH spectra dominated by the band at 3415 cm-1, and with a smaller by bands at 3520 and 3570 cm-1 (Fig. 1).

In all these observations it was not possible to correlate the signatures with a specific major, minor or trace element. Therefore, the exact nature of the observed signatures remains unidentified. Notwithstanding, these OH signatures are representative of specific lithospheric events and offer a potential new benchmark for the study of lithospheric processes.

Fig.1 : Schematic diagram showing the 3 types of signatures for opx. Spectra from opxs in oceanic lithosphere are from Gose, J., Schmadicke, E. and Beran A.: Geology, 37, 543-546, 2009. Drawing of subduction is from WangZ-Z., Liu,J., Xia, Q-K., Hao Y_T. and Wang Q-Y.: Lithos, 360-361, 2020.
Sulfur and Nitrogen Wet Deposition trends at three background monitoring stations of the Russian EANET region.
Authors: Konkova Elizaveta S. , Zhigacheva Ekaterina S. , Gromov Sergey A.
Published: March 2021

The purpose of our research was to evaluate spatial and temporal variations of major acidifying compounds in precipitation. Sulfur (from sulfates), Nitrogen (Dissolved Inorganic Nitrogen), and other major ions. Wet deposition data from three stations of the Russian EANET region was processed and analyzed. The period under investigation is framed from 2007 to 2019. 

Mondy station (51.4 ° N, 101.0 ° E) is located on Mount Chasovye Sopki (plateau between the Eastern Sayan and Khamar-Daban mountain ranges) at an altitude of 2005 meters above sea level. Yailu station (51.5 ° N, 87.4 ° E) is located at the spurs of the Abakan range on the shore of Lake Teletskoye at an altitude of 491 meters above sea level. Primorskaya station (43.4° N; 132.1° E) is located on the western slope of a branch of the Southern Sikhote-Aline Ridge, in the valley of Komarovka river at an altitude of 85 meters above sea level. Yailu station is operated under a Russian integrated background monitoring network, while Mondy and Primorskaya sites are included in EANET.

For evaluation of temporal variations, Mann-Kendall Test and Sen's Slope estimation were applied to check the statistical significance of seasonal and year trends and speed of changes in wet depositions and average weighted concentrations. For calculations, R-statistics and MAKESENS were used. For Mondy station, statistically significant trends at the level over 95% were found for non-sea-salt sulfur and potassium average weighted mean concentrations (with the negative slope approximately 28% and 16 % respectively) and at the level from 90 to 95 % for ammonium nitrogen and conductivity. There was no linear trend found at this station for total wet depositions. At the same time for Komarovka station, statistically significant linear trends were found in average weighted concentrations and wet deposition for magnesium and hydrogen at the level over 95%. For Yailu station, slightly increasing linear trend with the significance of over 90% was found for non-sea-salt sulfate and calcium weighted mean concentrations. And for ammonium nitrogen and calcium wet deposition – with significance over 95%.

This study was carried out in the framework of the Research Project АААА-А20- 120013190049-4 «Development of methods and technologies for monitoring of environmental pollution under the influence of transboundary pollutants transport (UNECE: EMEP, ICP IM) and acid deposition in East Asia (EANET)»
Estimation Of High-Frequency Attenuation Parameter (Kappa) For Hard Rock Stations Of Turkish Strong Motion Network
Authors: Akgün Atınç Özgün , Gülerce Zeynep , Özacar Atilla Arda
Published: March 2021

Site-specific decay in the Fourier Amplitude Spectrum (FAS) at high frequencies, a.k.a. the zero-distance kappa (κ0), is frequently used in seismic analysis of critical infrastructure; especially for the host-to-target adjustment of the design spectrum and the site response analysis. The zero-distance kappa value for hard rock sites is more crucial but harder to constrain because the amount of strong-motion stations on hard-rock sites is limited in the global datasets. The objective of this study is to calculate the zero-distance kappa value for the hard rock strong-motion stations operated by the Disaster and Emergency Presidency of Turkey (AFAD). For this purpose, 6463 recordings from 22 strong-motion stations with measured average shear wave velocities at the first 30 meters (VS30) higher than 740m/s and having at least 100 records have been analyzed. The slope of the decay in the S-wave portion of the FAS (kappa) at high frequencies is determined for a carefully selected and record-specific frequency range. Variation of the kappa with epicentral distance is evaluated to determine the median zero-distance kappa and its uncertainty for each recording station. Estimated median zero-distance kappa values vary between 0.01s to 0.06s and are consistent with the limited amount of previously published data. Only a weak reduction in median zero-distance kappa is observed with increasing VS30 and a rather large scatter in kappa for the same VS30 values is observed. More robust results might be attained by isolating the site amplification effects of weak surficial layers and subcategorization based on available geological and geographical information.
Relative movements of the Bashkirian megazone blocks(the South Urals) according to paleomagnetic data.
Authors: Anosova Maiia , Latyshev Anton , Khotylev Alexey
Published: March 2021

     The research object is magmatic bodies from the southern, central and northern parts of the Bashkirian megazone (the Southern Urals, meridian length of the Bashkirian megazone - 300 km). Most of the study intrusions have the Riphean age. In the Riphean the Bashkirian megazone was part of the East European craton. And in the Late Paleozoic rocks of the Bashkirian megazone were involved in the collision process. The formation of most studies bodies is associated with the Mashak magmatic event (the Riphean), which marks the collapse of the super-continent Nuna.

     The Middle Paleozoic component was isolated in 28 bodies. Probably it is the secondary component, that is widespread on the Southern Urals and has been repeatedly identified by other researchers. Directions comparison from different districts showed that there was a rotation of the southern, northern and central blocks of Bashkirian megazone relative to each other during the Late Paleozoic collision. At the same time, paleomagnetic directions from the northern regions (which are about 40-50 km apart from each other) statistically coincide or differ not so much. Which means that they were stable or relatively stable.

     Besides, the Riphean component was isolated and the paleomagnetic pole for the boundary of the Lower and Middle Riphean of the East European Craton (1349+/-11 Ma) is calculated from 8 thin sheet intrusions. Plat=8.4; Plong=162.4; A95=4.1.
Evaluation of distributions on radioactive materials around the port of Fukushima Daiichi Nuclear Power Plant through both monitoring and numerical simulations on seawater flow
Authors: Yamada Susumu , Machida Masahiko
Published: March 2021

A large amount of radionuclides has been released into the environment by the accident of Fukushima Daiichi Nuclear Power Plant (1F). About 10 years have passed since the accident, and the effects have significantly decreased. However, it should be noted that they still remain in spite of their tiny contributions. On the other hand, there is now an important demand that the radioactive materials should be monitored continuously due to the decommissioning work at 1F being carried. Thus, we evaluate the behavior of the radioactive materials in seawater around the port of 1F using both the monitoring result measured by TEPCO (Tokyo Electric Power Company Holdings) and the simulation results on seawater flow. In this presentation, we introduce the simulation methods and report the insights through the monitoring results. Finally, we reveal the mechanism of spreading the materials in the seawater around 1F port by evaluating with both the monitoring data and the simulation results.

 
An overview of iodine chemistry over the Indian and Southern Ocean waters using ship-based observations and modelling
Authors: Inamdar Swaleha , Tinel Lisolotte , Li Qinyi , Badia Alba , Saiz-Lopez Alfonso , Ram Kirpa , Chance Rosie , Carpenter Lucy , Mahajan Anoop
Published: March 2021

This study presents an overview of observations and modelling of reactive iodine chemistry in the marine boundary layer (MBL) of the Indian and Southern Ocean. Ship observations of iodine oxide (IO) from 2015 to 2017 show its ubiquitous presence with values up to 1 pptv (parts per trillion) in this region. To identify the source of iodine in this region, we computed inorganic fluxes of iodine using tropospheric ozone (O3), sea surface iodide concentration, and wind speed. The estimated fluxes of hypoiodous acid (HOI) and elemental iodine (I2) did not adequately explain the observed IO levels in the Indian and Southern Ocean region. However, a significant correlation of IO with chlorophyll-a indicates a possible biogenic control on iodine chemistry in the Indian Ocean MBL. To understand the role of organic and inorganic precursors in MBL iodine chemistry, we used the Weather Research and Forecast model coupled with Chemistry (WRF-Chem version 3.7.1) incorporating halogen (Br, Cl, and I) chemistry. The modelling study shows that including only organic sources of iodine underestimate the detected IO in the northern Indian Ocean MBL. This highlights the importance of inorganic emissions as a source of iodine over the ocean. However, the inorganic flux emissions in the model had to be reduced by 40% to match the detected IO levels in this region. The reduced emission produces an overall good match between the observed and modelled IO levels. This discrepancy with flux emissions and IO levels in both the modelled IO simulation and observation highlights that there may be uncertainties in estimating the fluxes or that the flux parameterisation does not perform well for the Indian and Southern Ocean region. The model results show that inclusion of iodine chemistry causes significant regional changes to O3 (up to 25%), nitrogen oxides (up to 50%), and hydroxyl radicals (up to 15%) affecting the chemical composition of open ocean MBL and coastal regions of the Indian sub-continent. Accurate estimation of iodine precursors in the MBL calls for an urgent need to improve the existing parameterisation of inorganic fluxes. Direct measurements of the HOI and I2 may prove useful in the accurate quantification of iodine precursors in the marine atmosphere.
Monitoring stability of embankment dams in response to 2019 Iran Flood event
Authors: Haghshenas Haghighi Mahmud , Motagh Mahdi
Published: March 2021

In April 2019, large parts of Khuzestan province in Iran were affected by intense record rainfall in the Zagros mountains. Persian Gulf catchment received approximately 30% of its long-term average rainfall over the course of a few days. Karkheh and Dez, two of the major rivers in this catchment, overflowed their banks. As several dams, including Karkheh, with the country's largest capacity, reached their limits, the water had to be released from the reservoirs, which resulted in flooding downstream of the dams. Several cities and more than 200 villages were flooded, and many people had to be evacuated. Many of the dams affected by the 2019 flood were embankment dams,  previously reported to exhibit post-construction settlements, at places reaching 13 cm/yr. Therefore, during and after the flood,  significant concerns were raised about their health and stability.

In this study, we use Sentinel-1 InSAR to monitor embankment dams' response in Khuzestan to the 2019 flood event. We process the full archive of Sentinel-1 using the Small Baseline Subset approach and estimate the time series of displacement for three different embankment dams in Khuzestan province. The first two studied dams are Karkheh and Gotvand, which have the country's largest capacities and became operational in 2001 and 2012, respectively. The third studied dam is the Masjed-Soleyman dam, previously reported to sustain a high displacement rate since its operation in 2002.

The Sentinel-1 InSAR displacement results indicate that all observed dams exhibit long-term post-construction settlement before the flood, with rates varies from approximately 1 cm/yr for the Karkheh dam to 5 cm/yr for Gotvand dam and 8 cm/yr for Masjed-Soleyman dam. The time series of displacement for Karkheh and Gotvand dams show gentle changes of displacement in response to the increase in water level following the flood. However, for the Masjed-Soleyman dam, the movement accelerates sharply after the flood with more than 2 cm of displacement on the crest in only two months. For the Masjed-Soleyman dam experiencing the most severe effect of the flood, we also analyzed high-resolution data from TerraSAR-X and COSMO-SkyMed. The results provide a detailed picture of the displacement pattern over the crest and the dam's body before and after the flood.
Insights of greenhouse gases (CO2, CH4 and N2O) dynamics in sub-tropical estuaries from a coupled hydrodynamic-biogeochemical estuarine model 
Authors: Huang Peisheng , Wells Naomi S. , Eyre Bradley D. , Paraska Daniel , Hipsey Matthew R.
Published: March 2021

Coastal waters are typically productive aquatic ecosystems and play an important role in the global greenhouse gas (GHG) budget. However, the uncertainty in the estimation of GHG emission from estuaries remains large due to significant variability in GHG concentrations in time and space. This study aimed to provide a more accurate estimation of GHG emissions from sub-tropical estuaries by validating and analyzing results from a 3D hydrodynamic-biogeochemical model used to capture the temporal and spatial dynamics of the major GHG (CO2 CH4, and N2O). The model was applied to the Brisbane, Maroochy, and Noosa Estuary in Queensland, Australia, representing systems under high, median, and low human impacts, and was validated with datasets from long-term monitoring stations and field campaigns along the freshwater-marine continuum. Distinct spatial heterogeneity of GHG distribution was found with the upstream acting as a hotspot for emission to the atmosphere, despite this area occupying a relatively small portion of the rivers. Seasonal variations of pCO2 at the surface were driven mostly by the changes in water temperature and DIC concentrations, while strong diurnal variation was also found, driven by the changes related to tidal forcing. All GHG showed distinct signatures in the three rivers, related to trophic statues and hydrology. The model allowed us to approximate the fraction of incoming carbon and nitrogen that was lost to the atmosphere as GHG emissions, which is a step towards improving regional and national GHG budgets. A link of the biogeochemical model to a parameter optimization software PEST is being used to assist in uncertainty analysis from the model outputs.
Cloud rapid adjustments
Authors: Myhre Gunnar
Published: March 2021

Rapid adjustments play an important role for the climate effect of drivers of climate change. These adjustments to temperature, water vapour and clouds occur before changes to the surface temperature. We show results from CMIP6 models and results of various climate drivers in Precipitation Driver and Model Intercomparison Project (PDRMIP). Rapid adjustments are particularly important for the climate effect of black carbon. The magnitude and sign of the black carbon rapid adjustments depend strongly on the vertical profile of black carbon. Black carbon in the upper troposphere causes a strong reduction of clouds. On the other hand, CO2 increases upper-level clouds resulting in cloud rapid adjustment in some climate models is a substantial fraction of the cloud feedback
A citizen-oriented understanding of nature-based innovations: A case study in Dublin, Ireland
Authors: Sarkar Basu Arunima , Basu Bidroha , Sannigrahi Srikanta , Pilla Francesco
Published: March 2021

Hydro-meteorological hazards such as floods have been a long-standing challenge for urban planners. A substantial increase in urbanization has undeniably pressurized the existing drainage network which has increased the flood proneness. The OPERANDUM project (H2020, grant agreement No 776848) has proposed a unique methodology for handling urban flooding by setting up open-air laboratories (OALs). As a pilot study of open-air laboratory Ireland (OAL-IE), an interdisciplinary methodology is adapted. Flood modeling techniques are identified for better flood risk assessment and flood management. Nature-based innovations are proposed to help identify and improve the existing urban drainage systems. The adaptability of nature-based systems and their efficacy as a supplemental tool to better flood management is a predominant and significant question. The awareness of citizens on their experience, challenges, and narratives are an equally reliable parameter to examine whether the spatio-temporal viability of new flood management techniques through nature-based innovations is a promising path for sustainable urban management. The intermittent relationship of flood hazard and the citizen access to infrastructure such as schools, childcare, old age homes, offices, transportation network holds a place of relevancy. The dynamics of “lived experiences” can help urban planners to pull out the traditional and formal strategies to be implemented for better liveability of citizens. Moreover, the willingness of citizens to maintain and share activities for co-deployment as a successful participatory process for innovative nature-based solutions support the social purpose of the OPERANDUM project. This research focuses on understanding the social background, cognitive thinking, and ideology that holds unique opportunities to OAL-IE for potential retrospective interpretation of nature-based innovations. A detailed survey with the stakeholders is aimed to understand their perspective on flooding, to identify how and where nature-based innovations can assist the city council to develop an efficient sustainable flood management system. This information on how citizens perceived and attributed the delivery of nature-based innovation can provide guidelines for developing better flood management and mitigation policies in Dublin.
Implication of mantle dynamics beneath North-East India through the perspective of SKKS splitting analysis
Authors: Mondal Poulommi , Mohanty Debasis , Biswal Satyapriya , Yadav Rekha
Published: March 2021

SKKS phase being an unique one among other core refracted phases like PKS, SKS etc. is capable of imaging the anisotropic contribution from lower mantle as per its raypath is considered. Its unique property of reflection at the core-mantle boundary enables it to carry forward the lower mantle contribution in case of seismic anisotropy is concerned. The lower mantle as a whole is assumed to be isotropic except the lowermost 200-300km (D’’ layer) which pertain a distinct diversity in the raypath of SKKS phases beyond 130o epicentral distance and thereby manifest the possible influence of lower mantle in the deformation pattern of any region. The present study of SKKS splitting analysis comprising an epicentral range of 140o-180o is primarily intended to complement the existing shear wave splitting dataset associated with north east India as well as to understand the effect of lower mantle on the splitting parameters (fast polarization direction (FPD, ϕ) and delay time (δt)). The motive of the study can be further extended to decipher the implication of such narrow epicentral range on splitting analysis. The analysis suggests that, beneath sub-Himalaya, the Indo-Eurasia collision derived lithospheric force along major thrust faults is the prime source behind the deformation, while Assam foredeep is somewhat influenced by the seismogenic Kopili Fault. There exist a striking difference in anisotropic directions between northern and southern fringe of Shillong plateau where deformations are governed by the absolute plate motion (APM) of Indian plate driven asthenospheric flow and seismically active Dauki and Dapsi faults respectively. Such disparity in splitting attributes can be inferred as the interplay of constricted back-azimuthal distribution and lean range of epicentral distance of seismic events, though the probability of lower mantle involvement cannot be ignored completely.
Autonomous zooplankton profiler reveals high-Arctic zooplankton dynamics during transition to polar night
Authors: Flores Hauke , Wilkinson Jeremy , Valcic Lovro , Hildebrandt Nicole , Hoppmann Mario , Karcher Michael , Kauker Frank , Nicolaus Marcel , Niehoff Barbara , Cornils Astrid , Stroeve Julienne , Veyssiere Gaelle , Castellani Giulia
Published: March 2021

With rapid sea-ice decline, ocean warming and increasing Atlantic inflow, the ecosystem of the Central Arctic Ocean (CAO) is experiencing an unprecedented, potentially disruptive transformation. While this transformation is affecting the biodiversity of marine communities and the ecosystem functions they fulfil, major knowledge gaps about the distribution of pelagic macrofauna (zooplankton and fish) complicate the assessment of the impact of this transformation on biodiversity and marine resources. The largest blind spot remains in the central Arctic Basin, which has been difficult to sample with large sampling gear such as fishing nets due to a year-round ice coverage. However, in the face of increasing human activities and international efforts to implement marine management in the CAO, it becomes important to monitor pelagic fauna in this remote area. One possibility to enable a better sampling of pelagic macrofauna is to use sea-ice thethered autonomous observatories. Within the British/German project EcoLight, we developed a new autonomous sea-ice observatory comprising an ASL Acoustic Zooplankton and Fish Profiler (AZFP). The device has 4 frequencies targeting different size classes of animals. It samples automatically at predefined intervals and transmits the data to a server in Europe via Iridium. It is possible to change the sampling parameters via a remote connection at any time. The AZFP buoy was deployed in the CAO in September 2020, shortly before the end of the MOSAiC expedition. Since then, the buoy has been recording the vertical zooplankton distribution in the water column under the ice. First data show a light-induced change of the vertical distribution of scatterers, transitioning from deep distribution during the polar day, through a short period of diel vertical migration during the twilight period, to a constant presence of scatterers in the surface layer in the polar night. Furthermore, AZFP data suggest an enhancement of zooplankton between the upper pycnocline and ~50 m depth during in an eddie transition. The data collected by the EcoLight AZFP buoy constitute the first hydroacoustic record of zooplankton distribution near the North Pole sampled with a fully autonomous system in the absence of disturbing light sources. They demonstrate the feasibility of year-round automated monitoring of macrofauna in the CAO in relation to environmental properties. Similar autonomous devices may serve as key elements in the future monitoring of biological resources in the CAO and other inaccessible areas.
Supervised Machine Learning Techniques to Assess Tropical Cyclones in Bay of Bengal and Bangladesh
Authors: Hussain Mariam , Park Seon Ki
Published: March 2021

Bangladesh experiences extreme weather events such as heavy rainfall due to monsoon, tropical cyclones, and thunderstorms resulting in floods every year. Regular flood events significantly affect in agricultural industries and human lives for economic losses. One of the reasons for these weather phenomena to sustain is latent heat release from Bay of Bengal (BoB) and Southeast Tropical Indian Ocean (SETIO). As the country has limited observations from stations and oceans, modeling for numerical weather prediction (NWP) are challenging for local operations. For operational NWP, computational resources and time are also concerns for a developing country like Bangladesh. Besides, recent machine learning (ML) techniques are widely applied to study various meteorological events with efficient results. Therefore, this research aims to estimate predictability and accuracy of supervised ML for tropical cyclones by assessing air temperature at 2 meter (AT) and sea surface temperature (SST). For AT and SST, the study utilizes monthly data at 0.25 × 0.25o horizontal resolution provided by the ECMWF reanalysis (ERA5). The gridded data is downscaled to area of interests such as coastal regions, BoB and SEITO with a study period of 40 years from 1979 to 2018. Furthermore, Bangladesh Meteorological Department (BMD) provides AT for 36 years from 1979 to 2015. The experiments segregate into two sections: (1) data normalizations via linear regression (LR) and multi-linear regression (MLR) and (2) supervised ML techniques applications in Matlab 2018b. The pre-processed data for LR show that AT from coastal regions such as Chittagong (CG), Barishal (BR), and Khulna (KL) divisions have stronger correlations (R) to SST in BOB with R = 0.910, 0.850, and 0.846 respectively than SEITO (R = 0.698, 0.675 and 0.678 respectively). Moreover, for these three regions, the correlation of MLR is 0.916 and 0.745 for BoB and SEITO with residual standard error (RSE) 1.312 and 1.218 respectively. For supervised ML applications, coarse decision tree (CDT) predict SST based on AT with train (80%) and test (20%) of the ERA5 data. Finally, the results from CDT model indicate that SST predictions are possible with 98.5% accuracy based on coastal stations. The trained CDT also validated model prediction utilizing observed AT (BMD observations) to forecast monthly SST and found 85% accuracy for monthly time series. In conclusions, CDT can predict SST from station data and assess if there is any possibility for tropical cyclone formation. The future works include further assessment for various categories of tropical cyclone and predict their intensity based on SSTs. This research aims to contribute in disaster mitigation by improving early warning systems. The possibility of cyclone formations will help for preparedness in saving property damages in Bangladesh.
Trace element composition of clinopyroxene in gabbros and dolerites of the Tortuga Ophiolitic Complex, southernmost Patagonia.
Authors: Torres Garcia Fernanda , Calderón Mauricio , Fadel Cury Leonardo , Theye Thomas , Opitz Joachim , Rojo Diego , Hopfenblatt Joaquín , Fuentes Francisco
Published: March 2021

During the Upper Jurassic-Lower Cretaceous times the western margin of Gondwana in southern Patagonia experienced extreme lithospheric extension and generation of rift and marginal back-arc basins. The ophiolitic complexes of the Rocas Verdes basin comprises incomplete ophiolite pseudostratigraphy lacking ultramafic rocks. The Tortuga Ophiolitic Complex, the southernmost seafloor remnant of the Rocas Verdes basin, record the most advanced evolutionary stage of the back-arc basin evolution in a mid-ocean ridge-type setting. The base of the Tortuga Complex consists of massive and layered gabbros, most of which are two pyroxene and olivine gabbros, leucogabbros, and clinopyroxene troctolites intruded by dikes of basalt and diabase with chilled margins. We present new major and trace element composition of clinopyroxene from the gabbros and sheeted dikes complexes to assess the geochemical affinity of parental basaltic magmas. Clinopyroxene in gabbros is mostly augite and have Al contents of 0.06-0.14 a.p.f.u. and Mg# of 80-92. Clinopyroxene in dolerites in the sheeted dike unit (augite and diopside) have Al content of 0.11-0.12 a.p.f.u. and Mg# of 85-92. Some immobile trace elements (e.g. Zr, Ti, Y) are sensitive to the degree of partial melting and mantle source composition, and can be used as a proxy for distinguishing tectonic environments. The Ti+Cr vs. Ca diagram, coupled with moderate-high TiO2 content of clinopyroxene (0.4-1.4 wt.%) suggests their generation in mid-oceanic ridge-type environment (cf. Beccaluva et al., 1989).  The high Ti/Zr ratios (of ~4-11) coupled with low Zr contents (~0.2-1.1) are expected for higher degrees of partial melting or for melting of more depleted mantle sources. Conversely, low Zr/Y ratios (0.05-0.13) plot between the range of arc basalts. Chondrite-normalized REE patterns in clinopyroxene display a strong depletion of LREE compared to HREE and have an almost flat pattern in the MREE to HREE with a positive Eu (Eu*= 0.9-1.1) anomaly, indicating that clinopyroxene crystallized from a strongly depleted mid-ocean-ridge-type basalt, formed by extensive fractional melting of the mantle source and/or fractional crystallization and accumulation of anhydrous phases. The general trend of the incompatible trace elements patterns exhibit depletion in LILEs, minor HFSEs depletion, positive anomaly of Rb and negative anomalies in Ba, Zr, Ti and Nb, consistent with their generation from a refractory mantle source barely influenced by subduction components derived from the oceanic slab. This agrees with basalt generation in a back-arc basin located far away from the convergent margin. This study was supported by the Fondecyt grant 1161818 and the Anillo Project ACT-105.
The role of erosion in the morphometry of composite volcanoes
Authors: van Wees Roos , Tournigand Pierre-Yves , O’Hara Daniel , Grosse Pablo , Kereszturi Gabor , Campforts Benjamin , Lahitte Pierre , Kervyn Matthieu
Published: March 2021

Volcanoes are extremely dynamic landforms. They grow by the accumulation of eruptive products and intrusions and degrade by a range of erosion processes such as superficial runoff, chemical and physical weathering, fluvial and glacial incision, and mass movements. In this study, we aim at documenting and quantifying the morphology of natural composite volcanoes using a range of morphometric indices, to better understand the factors that control erosion rates and patterns.

In addition to standard morphometric indices, including edifice ellipticity and irregularity, computed by the MORVOLC algorithm, a fractal dimension tool is developed to quantitatively report the shape complexity of stratovolcanoes. A convex hull approach is used to derive minimal erosion volumes and estimate erosion rates, considering available geochronological constraints. Morphometric parameters are derived from digital elevation models (DEMs) for a few exemplary stratovolcanoes of contrasted ages from the same volcanic region. To analyse the potential bias induced by the selected DEMs and the identification of the volcanic edifice outline, we also conduct a sensitivity analysis. The morphometric parameters are similarly extracted using the freely and globally available ALOS 30m (AW3D30), SRTM 30m (SRTMGL1), and ASTER 30m (GDEM 003), and compared to values obtained with the TanDEM-X 12m. The subjective user-drawn edifice outlines are compared to outlines generated by available algorithms, i.e. NETVOLC and MBOA, and their impact on the accuracy of morphometric indexes is quantified.  

Our results highlight that erosion increases edifice irregularity and fractal dimension. Preliminary trends between volcano fractal dimension, eroded volume, and age suggest that fractal analysis has the potential to be used as a relative age determination tool. The proposed morphometric characterisation paves the way for a comparison between natural volcanoes and controlled lab experiments reproducing the degradation of pristine volcanic cones by surface runoff to be developed later in our project.  
A Robust Intensification of Wintertime Jet Stream Extremes in Future Climates
Authors: Harvey Ben
Published: March 2021

The east coast of North America experienced a record-breaking jet stream event on 20 Feb 2019, with peak wind speeds exceeding 110 m/s observed by weather balloons over Nova Scotia. At the time this was the strongest wind speed ever recorded over North America. The extreme `jet streak' propagated out over the North Atlantic where it played a key role in the subsequent development of a large and rapidly deepening cyclone on 22 Feb 2019. The cyclone had little societal impact because it did not make landfall. It did however act to amplify a large scale Rossby wave, producing a strong poleward advection of warm air towards western Europe, and leading to record-breaking February warmth in several European countries on 27 Feb 2019. The whole sequence of events took just over a week to complete.

This case provides an illustration of how climate extremes (here the record warmth in western Europe) are often the result of complex and chaotic nonlinear interactions of the atmosphere on weather timescales. The particular sequence of events is not uncommon, but both the strength of the initial jet streak over North America and the resulting temperatures in Europe were. Given the observed trend in surface temperatures, it seems likely that the temperatures were at least partly enhanced in a passive way by the warming climate. A more difficult question to answer is whether climate change is also impacting the frequency or amplitude of the preceding sequence of weather events. As a first step to answering this question, this study asks the question: do we expect extreme jet streak events to intensify in future?

Based on an analysis of CMIP simulations over the North Atlantic, we find a robust intensification of wintertime jet extremes in future climates, with the strongest instantaneous wind speeds increasing in every model. This contrasts with the strength of the time mean jet streams, which do not exhibit a robust change across the ensemble. Possible reasons for the differing behaviour of the mean winds and the extreme winds are discussed and a hypothesis is suggested to explain the robust increase in the latter.
Examining the vulnerability of Australian eucalypts to future drought-induced tree mortality
Authors: De Kauwe Martin , Sabot Manon , Pitman Andrew , Rifai Sami , Meir Patrick , Cernusak Lucas , Medlyn Belinda , Ukkola Anna
Published: March 2021

Australia is the driest inhabited continent. Annual rainfall is low and is accompanied by marked inter-annual variability, leading to multi-year droughts. Climate change is expected to alter the frequency, magnitude, and intensity of future droughts, with potentially major environmental and socio-economic consequences for Australia. However, Australian vegetation is well adapted to extended dry periods, thus, the likelihood of drought-induced mortality in the future depends both on the severity of future drought events and inherent vegetation resilience. Here, we used the Community Atmosphere Biosphere Land Exchange (CABLE) land surface model, coupled with a stomatal optimisation scheme, to examine the projected impact of future drought for 24 Eucalyptus species. We forced CABLE with future climate from four global climate models (MIROC, ECHAM, CCCMA, and CSIRO) dynamically downscaled by three regional climate models. We separated the impact of climate change (e.g. increasing VPD, precipitation variability) from rising CO2 (increasing water use-efficiency) to provide the first assessment of future drought risk to Australian trees.
Understanding how hydrological forecast quality impacts the management of hydroelectric reservoirs
Authors: Ramos Maria-Helena , Cassagnole Manon , Zalachori Ioanna , Thirel Guillaume , Garçon Rémy , Gailhard Joël , Ouillon Thomas
Published: March 2021

The evaluation of inflow forecast quality and value is essential in hydroelectric reservoir management. Forecast value can be quantified by the economic gains obtained when optimizing hydroelectric reservoir operations informed by weather and hydrological forecasts. This study [1] investigates the impact of 7-day streamflow forecasts on the optimal management of hydroelectric reservoirs and the associated economic gains. Flows from ten catchments in France are synthetically generated over a 4-year period to obtain forecasts of different quality in terms of accuracy and reliability. These forecasts define the inflows to ten hydroelectric reservoirs, which are conceptually parametrized. Each reservoir is associated to a downstream power plant with yield 1 which produces electricity valued with a price signal. The system is modelled using linear programming. Relationships between forecast quality and economic value (hydropower revenue) show that forecasts with a recurrent positive bias (overestimation) and low accuracy generate the highest economic losses when compared to the reference management system where forecasts are equal to observed inflows. The smallest losses are observed for forecast systems with under-dispersion reliability bias, while forecast systems with negative bias (underestimation) show intermediate losses. Overall, the losses (which amount to millions of Euros) represent approximately 1% to 3% of the revenue over the study period. Besides revenue, the forecast quality also impacts spillage, stock evolution, production hours and production rates. For instance, forecasting systems that present a positive bias result in a tendency of operations to keep the storage at lower levels so that the reservoir can be able to handle the high volumes expected. This impacts the optimal placement of production at the best hours (i.e. when prices are higher) and the opportunity to produce electricity at higher production rates. Our study showed that when using biased forecasting systems, hydropower production is not only planned during more hours at lower rates but also at hours with lower median prices of electricity. The modelling approaches adopted in our study are certainly far from representing all the complexity of hydropower management under uncertainty. However, they proved to be adapted to obtaining the first orders of magnitude of the value of inflow forecasts in elementary situations.

[1] https://doi.org/10.5194/hess-2020-410