bluuebunny/crossref_metadata_2025 huggingface dataset:
Glacial-driven sea-level changes in the Late Triassic
Authors: Wang Meng , Li Mingsong , Kemp David B. , Boulila Slah
Published: March 2021

Projecting future anthropogenic sea-level rise requires a comprehensive understanding of the mechanistic links between climate and short-term sea-level changes under a warming climate. Two different hypotheses, glacioeustasy and groundwater aquifer eustasy, have been proposed to explain short-term, high amplitude sea-level oscillations during past greenhouse intervals. However, the aquifer eustasy hypothesis – supported by subjective evidence of sequence stratigraphy in the Late Triassic greenhouse, has never been rigorously tested. Here we test these competing hypotheses using a recently proposed, objective approach of sedimentary noise modeling for both sea- and lake-level reconstructions for the first time. Sedimentation rate estimates and astronomical calibration of multiple paleoclimate proxies from the lacustrine Newark Basin and the marine Austrian Alps enable the construction of a highly resolved astronomical time scale for the Late Triassic. Using this timescale, sedimentary noise modeling for both lacustrine and marine successions is carried out through the Late Triassic. Lake level fluctuations reconstructed by sedimentary noise modeling and principal component analysis revealed that million-year scale lake-level variations were linked to astronomical forcing with periods of ~3.3 Myr, ~1.8 Myr, and ~1.2 Myr. Our objective water-depth reconstructions demonstrate that lake-level variations in the Newark Basin correlate with sea-level changes in the Austrian Alps, rejecting the aquifer eustasy hypothesis and supporting glacioeustasy as the sea-level driver for the Late Triassic. This study thus emphasizes the importance of high-resolution, objective reconstruction of sea- and lake-levels and supports the hypothesis that fluctuations in continental ice mass drove sea-level changes during the Late Triassic greenhouse.
A life cycle perspective on the land use and ecosystem services of energy transitions
Authors: Jordaan Sarah
Published: March 2021

Life cycle assessment (LCA) is a cradle-to-grave method that quantifies the environmental impacts of products and processes from materials extraction to waste disposal.  While LCA is frequently applied to better understand greenhouse gas emissions, land use is much less explored.  The relationship between energy infrastructure and land use will be explored using a life cycle perspective, elucidating impacts related to an energy transition to high growth in renewable energy.  Renewable power is often correlated with higher land use than its fossil fuel counterparts, but it is increasingly recognized that more consistent, robust methods are required to confirm such results.  By developing a systematic method to estimate the life cycle land use of electricity generated from natural gas in the Barnett shale region of Texas, recent results suggest that the land use of gas-fired power can be comparable to renewable options.  Going beyond land use alone, ecosystem services provide a useful approach to characterizing impacts associated with land use. Using the Economics of Ecosystems and Biodiversity (TEEB) framework, both land requirements and ecosystem services can be quantified using a life cycle perspective.  An analysis of three types of power plants in the United States portion of the Chihuahuan Desert – natural gas, solar, and wind – provides insight into the ecosystem impacts of energy transitions.  Our results suggest that wind development in the region ranks lowest in terms of both land requirements (in meters squared per Megawatt-hour (m2/MWh)) and ecosystem services value (in dollars per MWh), followed by natural gas-fired electricity then solar.  Ecosystem services costs for developments in this region are low relative to levelized costs of electricity (<5%) but are subject to relatively low values compared to other regions - results will vary with regionalized ecosystem services values and different products.  Methods and results will illuminate areas of future research for better understanding land use and ecosystem impacts of energy transitions.

References

Jordaan, S.M., Heath, G.A., Macknick, J., Bush, B.W., Mohammadi, E., Ben-Horin, D., Urrea, V. and Marceau, D., 2017. Understanding the life cycle surface land requirements of natural gas-fired electricity. Nature Energy, 2(10), p.804.

Jordaan, S. M., J. Lee., M. McClung, and M. Moran (in press). Quantifying the ecosystem services of electricity generation in the U.S. Chihuahuan Desert using a life cycle perspective.  Journal of Industrial Ecology.
Tectonic controls on the sedimentation patterns in the Danakil Depression, Afar, Ethiopia
Authors: Rime Valentin , Foubert Anneleen , Perrochet Léa , Jaramillo-Vogel David , Negga Haileyesus , Atnafu Balemwal , Kidane Tesfaye
Published: March 2021

The Danakil depression in the northern part of the Afar is the only modern example of a rift undergoing the active transition from continental to marine settings, a crucial stage in rift and passive margin development. Thick evaporite deposits in its central part, and fringing Pleistocene coralgal reef terraces along its margins evidence at least four Red Sea incursions in to the basin and subsequent desiccation. The two youngest coralgal reef terraces were dated as respectively MIS 5e and MIS 7. Recent field expeditions measuring the paleo-shorelines' elevation provide a precious record of neotectonic activity in the basin. The margins show varied uplift while outcrops situated closer to the rift axis subsided below sea level. MIS 7 sediments at the northern, western margin, were uplifted up to 170 masl. Neotectonic movements are smaller on the eastern margin of the Danakil depression but moderate uplift was sufficient to avoid flooding of the depression during the Holocene. Syn-rift sedimentary patterns in the Danakil basin illustrate that the transition from continental to marine conditions is not gradual but marked by alternating marine and continental episodes. This alternation is controlled by the interaction between eustatic, tectonic and volcanic processes. Significant increase in accommodation space and sediment deposition can happen at very short time intervals.
Understanding performance of GPROF precipitation retrievals over the Netherlands in relation to precipitation characteristics as derived from ground-based dual-polarization radars
Authors: Bogerd Linda , Leijnse Hidde , Overeem Aart , Uijlenhoet Remko
Published: March 2021

The Global Precipitation Measurement mission (GPM) is one of the recent efforts to provide satellite-based global precipitation estimates. The GPM Profiling Algorithm (GPROF) converts microwave radiation measured by passive microwave (PMW) sensors onboard constellation satellites into precipitation. Over land, precipitation estimates are obtained from high frequency PMW-channels that measure the radiance scattered by ice particles in rain clouds. However, due to the limited scattering related to shallow and light precipitation, it is challenging to distinguish these signals from background radiation that is naturally emitted from the Earth’s surface.

Increased understanding of the physical processes during precipitation events can be used to improve PMW-based precipitation retrievals. This study couples overpasses of GPM radiometers over the Netherlands to two dual-polarization radars from the Royal Netherlands Meteorological Institute (KNMI). The Netherlands is an ideal setting for this study due to the availability of high-quality ground-based measurements, the frequent occurrence of shallow events, the absence of ground-clutter related to mountains, and the varying background emission related to its coastal location.

The coupling of overpasses with ground-based precipitation radars provides the opportunity to relate GPROFs performance to physical characteristics of precipitation events, such as the vertical reflectivity profile and dual-polarization information on the melting layer. Furthermore, simultaneous radiometer estimates and space-based reflectivity profiles from the dual-frequency precipitation radar (DPR) onboard the GPM core satellite are coupled to the ground-based reflectivity profiles for selected case studies. Because the a-priori database implemented in the GPROF algorithm is based on observations from the DPR, the comparison of the reflectivity profiles further unravels discrepancies between GPROF and ground-based estimates.
A hotter-drought fingerprint on Earth’s forest mortality sites–warming accelerates risks
Authors: Hammond William M. , Williams A. Park , Abatzoglou John T. , Adams Henry D. , Klein Tamir , Rodríguez Rosana López , Sáenz-Romero Cuauhtémoc , Hartmann Henrik , Breshears David D. , Allen Craig D.
Published: March 2021

Earth’s forests face grave challenges in the Anthropocene, including hotter droughts increasingly associated with widespread forest die-off. But despite the vital importance of forests—especially historical forests—to global ecosystem services, their fates in a warming world remain highly uncertain. Critically missing is quantitative determination of hotter-drought climatic drivers at globally-distributed, ground-based, tree-mortality sites. We established a precisely geo-referenced global database documenting climate-induced mortality events spanning all tree-supporting biomes from 154 studies since 1970. Here we quantify a lethal global hotter-drought fingerprint from these tree-mortality sites across 675 locations encompassing 1,303 database plots. Frequency of these lethal climate conditions accelerates under projected warming, up 140% by +4℃. Our database, soon available at tree-mortality.net, provides initial footing for further community development of quantitative, ground-based monitoring of global tree mortality (e.g., still including peer-reviewed observations, but importantly also those from forestry professionals, land managers, and citizen scientists). Furthermore, our database immediately enables critical predictive model validation and improved remote sensing of mortality. While our initial database enabled empirical quantification of a global climate signal for hotter-drought triggered tree mortality, ongoing and online contributions to the database (with efforts to be more spatially representative) will enable myriad future analyses and progress toward understanding the role of hotter-drought in the mechanistically complex process of tree mortality. Our global fingerprint of lethal hotter-drought confirms many of Earth’s forests are increasingly imperiled by further warming.
Missing lawsonite found ! Resolving paradoxes of the metamorphic structure of the Western Alps
Authors: Manzotti Paola , Ballèvre Michel , Pitra Pavel , Schiavi Federica
Published: March 2021

Lawsonite is a strongly hydrated (12 weight % H2O) Ca- and Al-rich silicate, exclusively stable along low P/T gradients, typical of subduction zones. The distribution and preservation of lawsonite at the scale of a subduction/collision belt reflect the occurrence of rocks with favourable chemical composition (mainly hydrothermally altered metabasalts and marly limestones (i.e. calcschists), two lithologies especially common in the oceanic units) and their pressure-temperature-fluid history (with preservation favoured by decreasing T during decompression).

The distribution of lawsonite in the Western Alps has been investigated since several decades. In the blueschist-facies units from the South-Western Alps (Queyras, Ubaye), lawsonite is well preserved in the external domain, at the contact with the Briançonnais domain, but is largely pseudomorphed in the more internal domain, at the contact with the Viso Unit. Further North, neither lawsonite nor lawsonite pseudomorphs have been reported in the supposedly blueschist-facies Combin Zone, taken by most studies as an equivalent of the Queyras-Ubaye units. This constitutes a paradox with respect to the overall metamorphic structure of the Alpine belt.

This study documents for the first time several occurrences of lawsonite and garnet in the calcschists from the Combin Zone. Field and metamorphic data (thermodynamic modelling and Raman spectroscopy on carbonaceous material) point to the occurrence of two tectonometamorphic units within the Combin Zone, characterised by distinct geometry, lithological content and Alpine P-T conditions.

In the higher grade unit, lawsonite and garnet were stable at peak P-T conditions (~14-16 kbar and ~460-490 °C) at very low X(CO2) values. Although lawsonite is systematically pseudomorphed, we have been able to recognize hourglass zoning in lawsonite or preservation of an internal fabric associated with the prograde ductile deformation.

The lower grade unit (~8 ± 1 kbar ~370-400 °C) is discontinuously exposed along the western base of the Dent Blanche nappe and records Alpine P-T conditions similar to those reached by the Dent Blanche nappe (Manzotti et al. 2020).

Our data show that lawsonite is not missing in the Combin Zone, and resolve a paradox about the large-scale metamorphic structure of the Alps.

 

Manzotti, P., Ballèvre, M., Pitra, P., Müntener, O., Putlitz, B., Robyr, M. (2020). Journal of Petrology, egaa044, https://doi.org/10.1093/petrology/egaa044.
Present-day sediment dynamics and provenance of the Gornergletscher
Authors: De Doncker Fien , Herman Frédéric , Prasicek Günther , Adatte Thierry , Mettra François , Belotti Bruno
Published: March 2021

Glacial erosion processes shape the Earth’s surface. Nevertheless, the processes that drive glacial erosion and the subsequent export of sediments are poorly understood and quantified. These processes include ice sliding, which controls erosion by abrasion and quarrying, and meltwater availability, which is essential to flush out sediment stocks that form a protective layer of sediments impeding bedrock erosion. Mapping glacial erosion rates can help understand the role of these different processes through the spatial relationships between the subprocesses and erosion rates. Here we report timeseries of glacial erosion rate maps inferred from the inversion of suspended sediment loads and their provenance. Geographically, we focus on the Gornergletscher complex (VS, Switzerland) where we collected data for the summer of 2017. The erosion rate timeseries are then compared to records of temperature, precipitation and estimates of discharge and turbidity of the meltwater river. Erosional activity seems to increase with rising temperatures and meltwater discharge, leading to an increased proportion of suspended sediments coming from the north-eastern (and occasionally western) side of the glacier. Interestingly, the peak in sediments from the north-eastern side is always preceded by a peak in sediments from the western side of the glacier. Sediments of these two zones are predominant in the suspended load signal when the maximal temperature at the Equilibrium Line Altitude (ELA) is above 10°C and on the rising limb of the hydrograph. Furthermore, the obtained erosion rate maps suggest that sliding velocities are not the only explanatory factor of the erosion rate patterns. We therefore postulate from these preliminary results that the present-day sediment output of the Gornergletscher complex is largely influenced by short term variations in temperature and meltwater availability.
Isotopic hydrograph separation in a small agricultural catchment
Authors: Széles Borbála , Parajka Juraj , Holko Ladislav , Wyhlidal Stefan , Schott Katharina , Stumpp Christine , Hogan Patrick , Pavlin Lovrenc , Strauss Peter , Blöschl Günter
Published: March 2021

Exploring the isotopic composition of precipitation and streamflow in small catchments and the event and pre-event components of precipitation events using two-component isotopic hydrograph separation may better explain the overall catchment behaviour, more specifically the sources of water origin. This study’s main objective is to investigate the origin of water for different streamflow gauges in a small agricultural catchment, which represent different runoff generation mechanisms. The analysis will be performed in the Hydrological Open Air Laboratory (HOAL) in Austria, a 66 ha experimental catchment dominated by agricultural land use (Blöschl et al., 2016). One of the main specialities of this research catchment is that several tributaries of the catchment representing different runoff generation mechanisms are gauged, such as tile drainage flow or saturation excess runoff from erosion gullies. Two-component isotopic hydrograph separation (for both 18O and 2H) will be conducted for five streamflow gauges (catchment inlet and outlet, two erosion gullies and a tile drainage system) for multiple events in the period 2013-2018. The results will be linked and interpreted using additional observations such as time-lapse images of overland flow, electric conductivity measurements, groundwater level changes, evapotranspiration measurements, etc. The aim is to explain and discuss the processes of rainfall-runoff generation in small agricultural catchments.

 

Reference:

Blöschl, G., et al. (2016). The Hydrological Open Air Laboratory (HOAL) in Petzenkirchen: A hypothesis‐driven observatory. Hydrol. Earth Syst. Sci., 20(1), 227–255. doi: 10.5194/hess‐20‐227‐2016.
Realism of simulated internal variability in Arctic sea ice
Authors: Wyburn-Powell Christopher , Jahn Alexandra , England Mark
Published: March 2021

Arctic summer sea ice has decreased dramatically over the last few decades, particularly in the summer months. The observed decline is faster than most CMIP5 models, but if internal variability is considered, models and observations are not inconsistent. With only one realization of reality in observations, it is difficult to disentangle the role of internal variability from the forced response. We directly compare one metric of internal variability by resampling both observations and models. So far we have compared five CMIP5 models from the CLIVAR multi-model large ensemble archive (CanESM2, CESM1, CSIRO MK36, GFDL ESM2M, and MPI ESM1). For the pan-Arctic, these models were found to have higher internal variability than observed by approximately 10-50% across models and seasons. Spatially, we find the variability in ice edge region is consistently modelled well in March. In September, although the member mean of the models shows both smaller absolute declines and smaller variation of such declines with resampling, the models have at least one member consistent with observations. This allows us to conclude that the models’ representation of this specific metric of internal variability is consistent with observations.
 The carbon story: A textile-geoscience collaboration to represent changing atmospheric CO2 concentrations through time
Authors: Gill Fiona , Bailey-Cooper Naomi
Published: March 2021

Dr Naomi Bailey-Cooper, a fashion textiles designer, and Dr Fiona Gill, a geochemist and palaeontologist, are exploring ways of communicating changes in atmospheric CO2 concentration through geological time and in the future, and its relationship to life on Earth, visually and haptically through beadwork installations.

 

This collaboration, initially enabled through the Leeds Creative Labs programme at the University of Leeds, draws on the scientist’s research into chemical signatures preserved in fossils to contextualise the scale and effect of carbon cycling in the Earth system. The artist’s expertise in embellishment, combined with her focus on the environmental impact of fashion and textile production, has driven the physical structure of the proposed works, as well as the focus on future scenarios of increased atmospheric carbon dioxide.

 

Working with geological materials and yarn representative of CO2, variations of knitting and weaving techniques are explored in combination with embellishment. The aim is that the first artefact for installation will depict changing CO2 levels through the Phanerozoic eon, as well as reflecting key species at different time periods and their interactions with changing atmospheric conditions. The second artefact will explore in more depth the Quaternary period, including human history and the Anthropocene, as well as incorporating predictions for future atmospheric CO2 concentrations and linking those to comparable geological times. Together, these artefacts will invite the audience to consider humans’ impact on Earth, including their use and exploitation of natural resources, within a geological context.

 
Comparative Analysis of the Various Generalized Ohm's Law Terms in Magnetosheath Turbulence as Observed by Magnetospheric Multiscale
Authors: Stawarz Julia , Matteini Lorenzo , Parashar Tulasi , Franci Luca , Eastwood Jonathan , Gonzalez Carlos , Gingell Imogen , Burch James , Ergun Robert , Ahmadi Narges , Giles Barbara , Gershman Daniel , Le Contel Olivier , Lindqvist Per-Arne , Russell Christopher , Strangeway Robert , Torbert Roy
Published: March 2021

Electric fields (E) play a fundamental role in facilitating the exchange of energy between the electromagnetic fields and the changed particles within a plasma. Decomposing E into the contributions from the different terms in generalized Ohm's law, therefore, provides key insight into both the nonlinear and dissipative dynamics across the full range of scales within a plasma. Using the unique, high‐resolution, multi‐spacecraft measurements of three intervals in Earth's magnetosheath from the Magnetospheric Multiscale mission, the influence of the magnetohydrodynamic, Hall, electron pressure, and electron inertia terms from Ohm's law, as well as the impact of a finite electron mass, on the turbulent electric field spectrum are examined observationally for the first time. The magnetohydrodynamic, Hall, and electron pressure terms are the dominant contributions to E over the accessible length scales, which extend to scales smaller than the electron gyroradius at the greatest extent, with the Hall and electron pressure terms dominating at sub‐ion scales. The strength of the non‐ideal electron pressure contribution is stronger than expected from linear kinetic Alfvén waves and a partial anti‐alignment with the Hall electric field is present, linked to the relative importance of electron diamagnetic currents within the turbulence. The relative contributions of linear and nonlinear electric fields scale with the turbulent fluctuation amplitude, with nonlinear contributions playing the dominant role in shaping E for the intervals examined in this study. Overall, the sum of the Ohm's law terms and measured E agree to within ∼ 20% across the observable scales. The results both confirm a number of general expectations about the behavior of E within turbulent plasmas, as well as highlight additional features that may help to disentangle the complex dynamics of turbulent plasmas and should be explored further theoretically.
Characteristics and Variability of Antarctic Intermediate Water in the UKESM1-0-LL CMIP6 model
Authors: Meuriot Ophélie , Plancherel Yves , Lique Camille
Published: March 2021

Antarctic Intermediate Water (AAIW) is the dominant intermediate water mass in the Southern Hemisphere. AAIW plays a key role in the hydrological cycle and also contributes to the replenishment of nutrients at low latitudes. It is characterised by a mid-depth salinity minimum. Although its salinity minimum signature can be clearly identified, the formation mechanisms and how its properties evolve with climate change are unclear.

The aim of this study is to assess the ability of the UKESM1-0-LL CMIP6 model to represent the key characteristics and variability of AAIW and to evaluate its evolution under radiative forcing (with the SSP5-8.5 and SSP2-4.5 scenarios).

A diagnostic is developed to identify the core of AAIW in the different basins and scenarios. AAIW can be identified in the UKESM1-0-LL model but it is lighter than in observations. The Pacific, Atlantic and Indian type of AAIW have core density values of 26.5 kg/m3, 26.6 kg/m3 and 26.9 kg/m3 respectively. AAIW presents different properties across each basin with different depth, temperature and salinity properties. The Pacific type of AAIW is lighter and fresher than the Atlantic and Indian types of AAIW. Under radiative forcing, it is found that AAIW shoals and becomes warmer. The largest changes in temperature, salinity and density are found in the Pacific. The outcrop location of the salinity minimum remains constant in the different scenarios in spite of the surface conditions changing with climate change.

A change in depth could have major implications on the overturning circulation. Ongoing and future work focuses on identifying which mechanisms need to be improved in CMIP6 models to reduce the bias observed in AAIW.
What is the most threatening for citizens of a mid-latitude city: cold stress or heat stress?
Authors: Top Sara , Milošević Dragan , Caluwaerts Steven , Savić Stevan
Published: March 2021

Both heat and cold waves cause extreme human thermal discomfort and a clear excess in mortality. This shows the importance of knowing the prevailing thermal comfort conditions and how thermal comfort conditions vary in various environments so measures can be taken. Microclimatic and outdoor human thermal comfort conditions are investigated in various built-up and green areas in the city of Ghent (Belgium) using meteorological measurements of six weather stations of the MOCCA (Monitoring the Cities Climate and Atmosphere) network in combination with calculations done by RayMan.

Normal to extreme summer heat wave periods show that dangerous strong heat stress prevails during the daytime periods at all locations. Comparison of thermal comfort during normal and extreme summer heat wave periods showed that heat stress is more extreme when a heat wave is more intense. Overall the urban park in Ghent was the most comfortable location during heat waves since it effectively mitigates heat stress in the city. These results should be taken into account in urban planning and design to keep mid-latitude cities livable.

Further, a one year data series revealed that outdoor cold stress was more apparent during 2017 in the mid-latitude city of Ghent that experiences a mild maritime climate. During spring and summer, both heat stress and cold stress occurred due to the larger diurnal temperature range compared to the other seasons. Even though high Physiological Equivalent Temperatures (PET) were obtained during a heat wave in summer, heat stress did not occur as intensely and as frequently compared to cold stress on annual level. It could thus be stated that outdoors, cold stress is a bigger threat than heat stress. However, one should keep in mind that the study was executed for outdoor thermal heat comfort and that people will take shelter or take measures when feeling uncomfortable. The question is thus rather, how are citizens protected against heat and cold stress? Currently, the Belgian society is better adapted to cold stress since most buildings contain central heating, while air conditioning is not standard. Future projections predict an increase in temperature, causing more occurrence of extreme heat stress, while extreme cold stress will be reduced. Additionally, the urban heat island effect currently has mainly a positive effect on the average annual outdoor thermal comfort conditions, while it will become a negative effect in the warmer future. Measures should thus be taken to reduce the threat of future heat stress.
Modelling of soil carbon sequestration by use of rice-straw mulching in two citrus orchards in Valencia (Spain)
Authors: Pesce Simone , Balugani Enrico , De Paz Josè Miguel , Visconti Fernado , Carlini Carlotta , Marazza Diego
Published: March 2021

In the context of sustainable development, agriculture holds a promising potential for CO2 sequestration and, accordingly, for the mitigation of climate change. This potential capacity can be developed through the adoption of less conventional farming techniques, such as the mulching of the topsoil with agricultural by-products where they are available, e.g., rice straw in the semiarid Valencia province (Eastern Spain). In general, the use of straw as mulching material has been found beneficial for soil quality as it reduces temperature excursions both daily and yearly, increases soil water content overall, and increases the activity of microbes. Moreover, it encourages the binding of organic matter and mineral particles into macro and micro aggregates, leading to: enhancement of the aggregate stability, restoration of stable C, and increase in the soil organic carbon (SOC) content and, thus, soil carbon sequestration. SOC dynamic models, like the widely used RothC, are useful to assess the soil carbon sequestration potential of different agricultural practices and to project their effects on the long term. However, there is a lack of studies focusing on the modelling of straw mulch effects on SOC dynamics.

Our work aimed at modelling the rice straw mulch degradation and its effects on the SOC dynamics in two citrus orchards, as observed during a short-term field experiment (2 years). In the orchards, the straw mulch was applied to the inter-rows once a year, and its effects on soil water content, temperature, respiration rate, and SOC contents (amidst other chemical and biological parameters) were compared with bare soil and natural grass formation

The RothC carbon dynamics model was modified by including the straw mulch effects on SOC dynamics as observed on the field and, additionally, by modelling the soil water dynamics with the HYDRUS1D model. The SOC pools for the RothC simulations were assessed following the fractionation of Zimmerman et al. (2007). The model parameters were calibrated with the soil respiration data.

The straw mulch model can be used for the estimation of the effects of the rice straw on the SOC in the short term. By changing the soil, climatic and agricultural practices inputs, the model can be applied to different fields in semiarid conditions, allowing the assessment of the soil carbon sequestration potential of different agricultural practices. However, the model still needs to be verified on long term field studies to deliver reliable long term sequestration projections.
Effect of different rates and modes of artificial upwelling on particle flux and potential POC deep export
Authors: Baumann Moritz , Taucher Jan , Paul Allanah Joy , Heinemann Malte , Vanharanta Mari , Bach Lennart Thomas , Spilling Kristian , Ortiz-Cortes Joaquin , Arístegui Javier , Riebesell Ulf
Published: March 2021

To counteract climate change, measures to actively remove carbon dioxide from the atmosphere are required, since the reduction of global CO2 emissions alone will not suffice to meet the 1.5 °C goal of the Paris agreement. Artificial upwelling in the ocean has been discussed as one such carbon dioxide removal technique, by fueling primary production in the surface ocean with nutrient-rich deep water and thereby potentially enhancing downward fluxes of organic matter and carbon sequestration. In this study we tested the effect of different rates and modes of artificial upwelling on carbon export and its potential attenuation with depth in a five-week mesocosm experiment in the subtropical Northeast Atlantic. We fertilized oligotrophic surface waters with different amounts of deep water in a pulsed (deep water fertilization once at the beginning) and a continuous manner (deep water fertilization every four days) and measured the resulting export flux as well as sinking velocities and respiration rates of sinking particles. Based on this, we applied a simple one-dimensional model to calculate flux attenuation. We found that the export flux more than doubled when fertilizing with deep water, while the C:N ratios of produced organic matter increased from values around Redfield (6.6) to ~8-13. The pulsed form of upwelling resulted in a single export event, while the continuous mode led to a persistently elevated export flux. Particle sinking velocity and remineralization rates were highly variable over time and showed differences between upwelling modes. We stress the importance of experiments with a prolonged application of artificial upwelling and studies including real world open water application to validate the CO2 sequestration potential of artificial upwelling.
Effects of Dubai coastline extreme urbanization in land and sea on local near-surface climate variables patterns
Authors: Elhacham Emily , Alpert Pinhas
Published: March 2021

Over a billion people currently live in coastal areas, and coastal urbanization is rapidly growing worldwide. Here, we explore the impact of an extreme and rapid coastal urbanization on near-surface climatic variables, based on MODIS data, Landsat and some in-situ observations. We study Dubai, one of the fastest growing cities in the world over the last two decades. Dubai's urbanization centers along its coastline – in land, massive skyscrapers and infrastructure have been built, while in sea, just nearby, unique artificial islands have been constructed.

Studying the coastline during the years of intense urbanization (2001-2014), we show that the coastline exhibits surface urban heat island characteristics, where the urban center experiences higher temperatures, by as much as 2.0°C and more, compared to the adjacent less urbanized zones. During development, the coastal surface urban heat island has nearly doubled its size, expanding towards the newly developed areas. This newly developed zone also exhibited the largest temperature trend along the coast, exceeding 0.1°C/year on average.

Overall, we found that over land, temperature increases go along with albedo decreases, while in sea, surface temperature decreases and albedo increases were observed particularly over the artificial islands. These trends in land and sea temperatures affect the land-sea temperature gradient which influences the breeze intensity. The above findings, along with the increasing relative humidity shown, directly affect the local population and ecosystem and add additional burden to this area, which is already considered as one of the warmest in the world and a climate change 'hot spot'.

 

References:

E. Elhacham and P. Alpert, "Impact of coastline-intensive anthropogenic activities on the atmosphere from moderate resolution imaging spectroradiometer (MODIS) data in Dubai (2001–2014)", Earth’s Future, 4, 2016. https://doi.org/10.1002/2015EF000325

E. Elhacham and P. Alpert, "Temperature patterns along an arid coastline experiencing extreme and rapid urbanization, case study: Dubai", submitted.
Unraveling anthropogenic causes of subsidence in the coastal plain of Friesland (NL) 
Authors: Koster Kay , Candela Thibault , Esteves Martins Joana , Fokker Peter , Lourens Aris , Dabekaussen Willem , Molhoek Madelon , De Bakker Merijn , Verberne Manon , Bocin-Dumitriu Andrei
Published: March 2021

The coastal plains of the Netherlands are subject to anthropogenic and natural subsidence with rates which are an order of magnitude higher than sea-level rise. Because one-third of the Netherlands lies below mean sea level, subsidence may threaten the country’s subsistence with major socio-economic consequences. Subsidence is a normal natural process but is overprinted and accelerated by anthropogenic activities which drives deep or shallow processes. Deep processes are caused by the extraction of hydrocarbons and salt, whereas shallow processes are primarily caused by lowering of phreatic groundwater levels. At present, the relative contribution of each process to total subsidence (i.e. natural plus anthropogenic) is unclear. Such information is important for stakeholders to support decision making on subsidence mitigation and it should be substantiated with independent scientific studies.

We present the outline of a hybrid Artificial Intelligence (AI) big data and model workflow to disentangle different subsidence forcing and we report on preliminary results for an area covering a gas field in the peat-rich Friesland coastal plain. The proposed workflow is a hybrid approach between a knowledge-based physical model and machine-learning techniques. The big input data comprises a suite of static (structural model) and time-dependent subsurface data (phreatic groundwater level, reservoir pressure), and geodetic measurements. Geomechanical models provide the connection between the drivers (groundwater levels and reservoir pressures) and the surface movement.
Spatio-temporal dynamics of erosion and deposition in a partially restored valley-bottom gully
Authors: Alfonso-Torreño Alberto , Gómez-Gutiérrez Álvaro , Schnabel Susanne
Published: March 2021

Soil erosion by water is a frequent soil degradation process in rangelands of SW Spain. The two main erosive processes in these areas are sheetwash erosion in hillslopes and gully erosion due to concentrated flow in valley bottoms. Land use changes and overgrazing play a key role in the genesis and development of gullies and gully erosion is a frequent process with negative consequences at the valley bottoms of these landscapes.

The development of new techniques allows monitoring of gully dynamics with an increase at spatial and temporal resolutions. Here we present a detailed study of a valley-bottom gully in a Mediterranean rangeland with a savannah-like vegetation cover that was partially restored in February 2017. Restoration activities included check dams (gabion weirs and fascines) and livestock exclosure by fencing. The objectives of this study were: (1) to analyze the effectiveness of the restoration measures, (2) to study erosion and deposition dynamics before and after the restoration activities, (3) to examine the role of micro-morphology on the observed topographic changes and (4) to compare the current and recent channel dynamics with previous studies conducted in the same study area through different methods and spatio-temporal scales, quantifying medium-term changes. Topographic changes were estimated using multi-temporal high-resolution DEMs produced using Structure-from-Motion (SfM) photogrammetry and aerial images acquired by a fixed-wing Unmanned Aerial Vehicle (UAV). DEMs and orthophotographs with a Ground Sampling Distance of 0.02 m were produced by means of SfM photogrammetric techniques. The average Root Mean Square Error (RMSE) estimated during the SfM processing was 0.03 m.

The performance of the restoration activities was satisfactory to control gully erosion. Check dams were effective favoring sediment deposition and reducing lateral bank erosion. Nevertheless, erosion was observed immediately downstream in 9% of the check dams. Livestock exclosure in the most degraded area promoted the stabilization of bank headcuts and revegetation. The sediments retained behind check dams reduced the longitudinal slope gradient of the channel bed and established a positive feedback mechanism for channel revegetation.

Keywords: gully erosion, restoration, topographic change, UAV+SfM, rangeland.
A new reference loess-paleosol archive spanning the last 850 kyrs near Pleven (Bulgaria) – first results
Authors: Laag Christian , Jordanova Diana , Lagroix France , Jordanova Neli , Guyodo Yohan
Published: March 2021

Loess-paleosol sequences (LPSs) are proven valuable archives for continental paleoclimatic reconstructions. However, studied LPSs worldwide, spanning multiple glacial-interglacial cycles, are seldomly sampled and analyzed at a continuous high resolution. Exceptionally, in a quarry setting near the city of Pleven (Bulgaria), a new LPS, with a thickness of 27 m, was continuously sampled at a 2 cm resolution resulting in 1340 bulk-samples. We present herein first rock magnetic results suggesting that the site archives aeolian deposition and soil formation over the last 850 kyrs.  Room temperature bulk mineral magnetic parameters including magnetic susceptibility, hysteresis loop derived parameters, IRM, and ARM (underway) were acquired on all samples. Variations in mineral magnetic data clearly show the alternation of strongly developed paleosols overlying loess units indicative of interglacial and glacial climate cycles. We created a correlative age model by comparing Xferri/Ms to inverted LR04 benthic oxygen isotope ratios and adjustments undertaken by the Imbrie & Imbrie ice model. This initial correlative age model leads to an assumed continuous dust accumulation for the last 850 kyrs, from MIS 19 to present. In addition to the regionally widely observed L2-tephra, which is observed outcropping along the Pleven LPS, several other sharp spikes in concentration dependent magnetic characteristics suggest that the sedimentary record had preserved also other tephra layers, clearly identified in the magnetic record due to the accomplished high-resolution sampling design. Additional geochemical and mineralogical data are however necessary for an unequivocal source (age) identification of these events. A tentative scheme of a possible correspondence with well dated tephra layers from sedimentary core at Fucino Basin is established. It implies the occurrence of westerly wind directions during the last 850 kyrs in SE Europe. In summary, the Pleven LPS provides new insights into late-Pleistocene climatic regimes, prevailing wind directions and preservation of tephra layers, essential for further correlative terrestrial-aeolian-coupled age models, regional stratigraphic correlations and paleoclimate reconstructions.
Monitoring Rock Slope Instabilities Using Frequency Domain Decomposition Modal Analysis
Authors: Häusler Mauro , Michel Clotaire , Burjánek Jan , Fäh Donat
Published: March 2021

Measuring ambient seismic vibration provides a promising tool to monitor unstable rock slopes due to its independence from actual surface deformations. It is generally observed that the seismic wavefield, arising from ambient vibrations, polarizes perpendicular to open fractures and that unstable slopes exhibit strong wavefield amplifications compared to stable reference sites. Rock slope instabilities dominated by deep persistent fracture sets exhibit normal mode behaviour due to standing wave phenomena within individual compartments of the unstable volume. Techniques to assess such behavior are well established in mechanical and civil engineering to assess the dynamic response and possibly the structural integrity of the structure studied.

 

We performed enhanced frequency domain decomposition modal analysis on ambient vibration data acquired in real-time on an unstable rock site with a volume larger than 150,000 m3 near Preonzo, Switzerland. We tracked the resonance frequency and normal mode polarization of the first two modes over a period of four years. In addition, we show the development of the modal damping ratio of the fundental mode over time, which is a measure of energy dissipation within and out of the system. We found that the dynamic properties of the rock structure experienced annual variations and that they are primarily controlled by temperature and only secondarily by the exension and closure of large-scale fractures. Even though no large slope failure was observed during the monitoring period, the dataset provides a reference model for ongoing slope monitoring, as the resonance frequency and damping ratio is expected to change significantly prior to failure.
The influence of meteoric smoke particles on the artificial heating effect in the D-region
Authors: Myrvang Margaretha , Baumann Carsten , Mann Ingrid
Published: March 2021

Artificial heating increases the electron temperature by transferring the energy of powerful high frequency radio waves into thermal energy of electrons. Current models most likely overestimate the effect of artificial heating in the D-region compared to observations [1, 2]. We investigate if the presence of meteoric smoke particles can explain the discrepancy between observations and model. The ionospheric D-region varies in altitude range from about 50 km to 100 km. In the D-region, the electron density is low, the neutral density is relatively high and it is here that meteors ablate. The ablated meteoric material is believed to recondense to form meteoric smoke particles (MSP). The presence of MSP in the D-region can influence plasma densities through charging of dust by electrons and ions, depending on different ionospheric conditions. Charging of dust influence the electron density mainly through electron attachment to the dust, which results in height regions with less electron density. The heating effect varies with electron density height profile [3], since the reduction in radio wave energy is due to absorption by electrons. We study artificial heating of the D-region and consider MSP by using a one-dimensional ionospheric model [4], which also includes photochemistry. In the ionospheric model, we assume that artificial heating only influences the chemical reactions that depend on electron temperature. We model the electron temperature increase during artificial heating with an electron density calculated from the ionospheric model, where we will do the modelling with and without the MSP and compare day and night condition. Our results show a difference in electron temperature increase with the MSP compared to without the MSP and between day and night condition.

References:

[1] Senior, A., M. T. Rietveld, M. J. Kosch and W. Singer (2010): «Diagnosing radio plasma heating in the polar summer mesosphere using cross modulation: Theory and observations». Journal of geophysical research, Vol. 115, A09318.

[2] Kero, A., C.-F Enell, Th. Ulich, E. Turunen, M. T. Rietveld and F. H. Honary (2007): «Statistical signature of active D-region HF heating in IRIS riometer data from 1994-2004». Ann. Geophys., 25, 407-415.

[3] Kassa, M., O. Havnes and E. Belova (2005): «The effect of electron bite-outs on artificial electron heating and the PMSE overshoot». Annales Geophysicae, 23, 3633-3643.

[4] Baumann, C., M. Rapp, A. Kero and C.-F. Enell (2013): «Meteor smoke influence on the D-region charge balance –review of recent in situ measurements and one-dimensional model results». Ann. Geophys., 31, 2049-2062.
How do polar clouds and precipitation affect global warming?
Authors: Kay Jennifer
Published: March 2021

Understanding the influence of clouds and precipitation on global warming remains an important unsolved research problem. This talk presents an overview of this topic, with a focus on recent observations, theory, and modeling results for polar clouds. After a general introduction, experiments that disable cloud radiative feedbacks or “lock the clouds” within a state‐of‐the‐art,  well‐documented, and observationally vetted climate model will be presented. Through comparison of idealized greenhouse warming experiments with and without cloud locking, the sign and magnitude cloud feedbacks can be quantified. Global cloud feedbacks increase both global and Arctic warming by around 25%. In contrast, disabling Arctic cloud feedbacks has a negligible influence on both Arctic and global surface warming. Do observations and theory support a positive global cloud feedback and a weak Arctic cloud feedback?  How does precipitation affect polar cloud feedbacks? What are the implications especially for climate change in polar regions?  