bluuebunny/crossref_metadata_2025 huggingface dataset:
N:P imbalance effects on the seasonal C cycle in a Mediterranean Tree-Grass Ecosystem
Authors: Nair Richard , El-Madany Tarek , Carrara Arnaud , Luo Yunpeng , Kolle Olaf , Moreno Gerardo , Reichstein Markus , Schrumpf Marion , Wutzler Thomas , Migliavacca Mirco
Published: March 2021

N limited ecosystems worldwide are shifting towards other limitations due to anthropogenic N deposition exceeding the rate of change in other drivers. Mediterranean ecosystems are among those thought to be shifting to P limitation and ‘N:P imbalances’ but this occurs alongside strong environmental limits on C uptake in both winter and summer in a distinct bimodal phenological cycle. At the ecosystem scale, carbon cycle components such as gross and net primary productivity, respiration or ecosystem carbon use efficiency, are a result of accumulation of physiological and community effects in both plants and soils. The functioning of such systems is commonly measured at plot or individual level, but scalable, inter-site comparisons are complicated because multiple interacting gradients of driving factors, weather and seasonal timing do not correlate through geographic space. 

Here, we explore the interaction of seasonal conditions and nutrient treatment on eddy-covariance derived C cycle properties in a ecosystem-scale ‘stoichiometry manipulation experiment in a Mediterranean tree-grass system (5 years after a large, one off fertilization, 'MANIP experiment') where the close location means sites can be compared with similar local weather and seasonality. 

During the 5 year study period, N:P ratios in soil pools regress towards pretreatment conditions in both N and NP treated footprints, and generally plant level effects decline through time. Nonetheless, holistic C uptake differences between nutrient treatments (e.g. in GPP) remain for the entire 5 year study period. Effects are particularly strong in spring (late in the phenological year) where the accumulation of biomass magnifies treatment differences and water is not limiting.  The effects of increased nutrient availability and altered N:P stoichiometry are also visible on resource use in winter, a relatively fallow period rarely studied in non-continuous measurements. Treatment effects in these winter periods differ from effects in spring, but both contribute to overall ecosystem-level responses to the nutrient treatments. The effect of nutrient balance on carbon cycling and carbon use efficiency is seasonally driven as fertilized treatments have both higher ecosystem-scale carbon use efficiency and light use efficiency, including in winter. However the fertilized treatments are also relatively less affected by years with warmer winter temperatures than the unfertilized treatments. N:P imbalanced treatments are also more water sensitive than those with balanced stoichiometry. Physiological and community change response studies in such systems must consider both year round and multi-year representation for scalable and transferable understanding. 
Rock magnetism as a tool for investigating the use of archaeological artefacts from baked clay
Authors: Tema Evdokia , Ferrara Enzo , Zamboni Lorenzo , Venturino Marica , Reboldi Margherita , Egea Guevara Albert , Casas Lluís
Published: March 2021

Even though multidisciplinary approaches applied to the investigation of archaeological findings are widely used, the use of rock magnetic properties is still poorly exploited in the determination of the use of ancient artefacts. In this study, we present the results of a combined archaeological, morphological and magnetic analyses applied on the ring-shape clay artefacts found at the archaeological site of Villa del Foro, in Northern Italy. The materials studied are dated between the sixth and the first half of fifth century BC and are found in large quantities in different trenches of the archaeological excavation. To investigate their thermal history and to exploit their possible use as kiln supports, cooking stands, or loom weights, we have investigated their natural remanent magnetization (NRM) and the magnetic mineralogy changes occurred during laboratory heating. Magnetic analysis used for the determination of the firing temperatures show thermal stability up to 500-600 o C, while further laboratory heating at 700 o C introduces magnetic alteration. Thermal demagnetization of the samples generally shows a strong and stable thermal remanent magnetization. In few cases, a clear secondary component is present, suggesting partial re-heating or displacement at temperatures ranging from 200 oC to 450 °C. Such secondary magnetic component can be indicative of a secondary heating or of a displacement of the rings from their initial firing position while still hot. Even though the studied rings belong to casually different morphological typologies, no connection among type and magnetic behavior was observed, suggesting that the ring’s morphology does not define neither their production conditions nor the final use of the artefacts. The estimated firing temperatures of around 600-700 oC are compatible with the heating of the rings during their manufacture rather than related to cooking activities. In combination with the archaeological evidence and the morphological analysis it is thus suggested that the rings were used as weight looms and baked only during their production procedures. Such a pilot study can be used as reference for the identification of similar objects found in Italy and Europe during the Iron Age and confirms the great potential of rock magnetic analysis in the investigation of the technology and use of ancient baked clays.
Validation of Aeolus winds using radiosonde observations and NWP model equivalents
Authors: Martin Anne , Weissmann Martin , Geiß Alexander , Reitebuch Oliver , Cress Alexander
Published: March 2021

Aeolus is a European Space Agency (ESA) Earth Explorer mission, launched on 22 August 2018 as part of the Living Planet Programme. Providing atmospheric wind profiles on a global basis, the Earth Explorer mission is expected to demonstrate improvements in the quality of numerical weather prediction (NWP). A crucial prerequisite for the use of meteorological observations in NWP data assimilation systems is a detailed characterization of the quality to minimize systematic observation errors. As part of the German initiative EVAA (Experimental Validation and Assimilation of Aeolus Observations) validation and monitoring activities for Aeolus are performed using collocated radiosonde measurements and NWP forecast equivalents from two different global models, the ICOsahedral Nonhydrostatic model (ICON) of DeutscherWetterdienst (DWD) and the European Centre for Medium-Range Weather Forecast (ECMWF) Integrated Forecast System(IFS) model, as reference data. Systematic differences and bias dependencies are investigated and estimates for the Aeolus instrumental error are determined. Furthermore, impact experiments using the global ICON model are analyzed.    
Space-Time Dependent features of the Unified Scaling Law for Earthquakes in Northeastern Italy
Authors: Peresan Antonella , Nekrasova Anastasia
Published: March 2021

The space concept of the Unified Scaling Law for Earthquakes (USLE), which generalizes the Gutenberg-Richter relationship making use of the fractal distribution of earthquake sources in a seismic region, has been applied to seismicity in Northeastern Italy. In particular, the temporal variations of USLE coefficients have been investigated, with the aim to get new insights in the evolving dynamics of seismicity within different tectonic domains of Friuli-Venezia Giulia region (FVG) and its surroundings.

For this purpose, we resorted to the catalog compiled at the National Institute of Oceanography and Applied Geophysics (OGS), considering earthquakes occurred in the period 1995 – 2019, with epicenters within three sub-regions of the territory under investigation, delimited based on main geological and tectonic features (Bressan et al. 2018,  J. Seismol. 22, 1563–1578). To quantify the observed variability of seismic dynamics, a multi-parametric analysis has been carried out for each sub-region by means of several moving averages, including: the inter-event time, τ; the cumulative Benioff strain release, Σ; the USLE control parameter, η and the USLE coefficients, estimated for moving six-years time intervals. The analysis evidenced that the USLE coefficients in FVG region are time-dependent and show up correlated (Nekrasova and Peresan 2021, Frontiers in Earth Science, 8, 624). Moreover, the dynamical features of the considered parameters in the three sub-regions highlighted a number of different seismic regimes; in particular, major changes in the parameters are associated to occurrence of the 12 April 1998 (M5.6) and the 12 July 2004 (M5.1) Kobarid (Slovenia) earthquakes within the corresponding sub-region.

The results obtained for seismicity in Northeastern Italy and surrounding areas confirm similar analysis performed on a global scale, in advance and after the largest earthquakes worldwide. In addition, the analysis evidenced the spatially heterogeneous and non-stationary features of seismicity, in agreement with results from independent analysis of background seismicity within the investigated territory (Benali et al. 2020, Stoch. Environ. Res. Risk. Assess. 34, 775–791), thus suggesting the opportunity of resorting to time-dependent models of earthquakes occurrence for improving local seismic hazard assessment.
Constraints on the mantle transition zone structure using triplicated body waves
Authors: Bissig Felix , Khan Amir , Giardini Domenico
Published: March 2021

The mantle transition zone (MTZ) is bounded by seismic discontinuities at average depths of 410 km and 660 km, which are generally associated with major mantle mineral transformations. A body wave impinging from above on these discontinuities develops a refracted and reflected branch, leading to multiple arrivals of the same wavetype within a short time window. These so-called triplicated body waves are observed at regional epicentral distances (15-30°) and carry information on MTZ structure due to their strong interaction with the 410 km and 660 km discontinuities. Careful data selection and processing as well as the assessment of source parameters are necessary steps in obtaining a high quality triplication data set. In this study, we consider recordings of events in Central America at permanent and transportable USArray stations, which are inverted for mantle structure. Our methodology is based on a joint consideration of mineral physics and seismic data in a probabilistic inversion framework and allows for determination of mantle thermo-chemical and seismic velocity structure. We present constraints on the mantle structure underneath the Gulf of Mexico.
The Atmospheric Controls of Extreme Convective Events over the Southern Arabian Peninsula during the Transition Seasons
Authors: Nelli Narendra Reddy , Francis Diana , Fonseca Ricardo , Abida Rachid , Weston Michael , Wehbe Youssef , Al Hosary Taha
Published: March 2021

In this paper, the processes behind severe convective events over the Arabian Peninsula during spring and autumn seasons and their local-scale impacts are investigated using reanalysis data, satellite-derived and observational products. The focus on the transition seasons is justified as Mesoscale Convective Systems (MCSs) are more common at that time of the year, in particular in the months of March and April. The analysis of 48 events from 2000 to 2019 revealed that they are triggered by low-level wind convergence and moisture advection from the Arabian Sea, Arabian Gulf and/or Red Sea. An equatorward displacement and strengthening of the subtropical jet also precondition the environment, as does the presence of a mid-level trough. The latter is generally part of a large-scale pattern of anomalies that are equivalent barotropic in nature, and therefore likely a response to tropical or subtropical forcing. At more local-scales, a drying of the mid-troposphere between 850 and 250 hPa typically by 50%, a reduction of the upper-level winds by about 5 m s-1, and an increase in the upper-tropospheric and lower-stratospheric temperature on averaged by 2-3 K, are typically observed during a MCS event. Over the 20-year period, a statistically significant increase in the MCSs’ spatial extent, intensity and duration over the UAE and surrounding region has been found, suggesting that such extreme events may be even more impactful in a hypothetical warming world. The rainfall they generate, on the other hand, shows an increase that is not statistically significant.
Unpacking the role of agency in the emergence of differentiated environmental institutions: the case of the territorial classification of native forests in the Argentinian Chaco
Authors: Ceddia Michele Graziano , Christopoulos Dimitris , Frey Sara , Inguaggiato Carla , Mioni Walter , Montani Rodrigo , Tschopp Maurice , Zepharovich Elena
Published: March 2021

The Gran Chaco represents an important habitat that is undergoing significant changes, as a result of the expansion of the agricultural frontier, with a range of negative social and environmental consequences. Such a change is the result of a “bad transition” from an extensive/subsistence agricultural system towards a capital-intensive one, to which corresponds a completely different level of anthropization. The largest part of the Gran Chaco is located in Argentina. Partially as a response to the rapid loss of natural habitat in the region, Argentina passed a federal forest law in 2007. The law requires the different provinces to introduce a set of implementing regulations and adopt a territorial classification of native forests (TCNF), denoting different conservation values (high, medium and low). Although referring to the same federal law, the TCNFs developed by the various provinces in the Argentinian Chaco ecoregion differ significantly. We first develop a theoretical framework, which combines historical materialism with the theory of socio-ecological systems, to explain the emergence of institutional configurations. Through this framework, we hypothesise that the heterogeneity in the TCNFs results from the combination of contextual factors (i.e., differences in the physical environment among the provinces), material/economic conditions (i.e., production processes, social relationships and reproduction processes) and different forms of agency. We test the hypothesis by developing thick case-studies on the various Argentinian provinces in the Gran Chaco region via qualitative comparative analysis. The results allow determining which configurations co-occur with certain outcomes in terms of TCNFs. The results shed light on the process of emergence of differentiated environmental institutions in the region from the interactions of different conditions, contexts and forms of agency. This knowledge, in turn, could be extremely useful in navigating the Anthropocene while promoting a “good transition” towards sustainability.
Investigation scaling behavior of earthquake-related signals in magnetotelluric measurements, Northern Algeria
Authors: Kasdi Ahmed Seddik , Bouzid Abderrezak , Hamoudi Mohamed , Abtout Abdslem
Published: March 2021

The north-central region of Algeria has been characterized by a swarm-type seismicity, after the strong Mw6.8 Boumerdès earthquake of May 21, 2003, culminating with the earthquake that occurred on July 17, 2013 of magnitude Mw=5. A magnetotelluric station was installed on December 2014 in the Medea region, 60 km south of the capital Algiers. We measured the five components of the telluric and magnetic field with a sampling frequency of 15 Hz. The seismic activity in the region provided the opportunity to observe and study the earthquake’s related electromagnetic signal. The scaling properties of the recorded electric and magnetic time series were investigated. On the basis of multifractal detrended fluctuation analysis, which is a powerful method for detecting scaling in non-stationary time series, deviations from the uniform scale of the power law were identified and quantified. We investigated the time dynamics of the earthquake related electromagnetic time series measured at the magnetotelluric station. The multifractal detrended fluctuation analysis showed the different multifractality properties of electromagnetic signals before, during and after the seismic event. The results of this work show an unstable scaling behavior in electromagnetic data during the occurrence of the seismic event. These first results could be useful in the framework of seismo-electromagnetic signals studies.
Constraining the Origin Altitude of the first Satellite-Detected Reverse-Beam Terrestrial Gamma-ray Flash Produced by a Cloud-to-Ground Lightning Leader. 
Authors: Chaffin Jeffrey , Smith David , Cummer Steven , Pu Yunjiao , Splitt Michael
Published: March 2021

We provide an updated analysis of the gamma-ray signature of a terrestrial gamma ray flash (TGF) detected by the Fermi Gamma-ray Burst Monitor first reported by Pu et al. 2020. Gamma-ray photons were produced 3ms prior to a negative cloud-to-ground return stroke and were close to simultaneous with an isolated low frequency radio pulse during the leaders propagation, with a polarity indicating downward moving negative charge. This ‘slow’ low frequency signal occurring prior to the main discharge has previously been strongly correlated with upward directed TGF events (Pu et al. 2019, Cummer et al. 2011) leading the authors to conclude that the Fermi detected counts just prior to the return stroke are the result of a reverse positron beam generating upward directed gamma rays.  We investigate the feasibility of this scenario and constrain the limits on the origin altitude from the perspective of the gamma-ray signature timing uncertainties, TGF Monte Carlo simulations, estimates of intrinsic brightness as a function of altitude, and meteorological analysis of the storm and its possible charge structure and altitude.
Carbon storage in phosphorus limited grasslands may decline in response to elevated nitrogen deposition: a long term field manipulation and modelling study 
Authors: Taylor Christopher , Janes-Bassett Victoria , Phoenix Gareth , Keane Ben , Hartley Iain , Davies Jessica
Published: March 2021

In ecosystems where nitrogen (N) limits plant productivity, N deposition can stimulate plant growth, and consequently, promote carbon (C) sequestration by increasing input of detrital C and other forms of plant C to the soil. However, other forms of nutrient limitation such as phosphorus (P) limitation and N-P co-limitation are widespread and may increase in prevalence with N deposition. Our understanding of how terrestrial ecosystem C, N and P cycling may be affected by N deposition when N is not the sole limiting resource is fairly limited. In this work, we investigate the consequences of enhanced N addition on C, N and P cycling in grasslands that exhibit contrasting forms of nutrient limitation.

We do so by collecting data from a long-term nutrient manipulation experiment on two N-P co-limited grasslands; an acidic grassland of stronger N-limitation and a calcareous grassland of stronger P limitation, and integrating this into a mechanistic C, N and P cycling model (N14CP). To simulate the experimental grasslands and explore the role of P access mechanisms in determining ecosystem state, we allowed P access to vary, and compared the outputs to plant-soil C, N and P data. Combinations of organic P access and inorganic P availability most closely representing data were used to simulate the grasslands and quantify their temporal response to nutrient manipulation.

The modelled grasslands showed contrasting responses to simulated N deposition. In the acidic grassland, N addition greatly increased C stocks by stimulating biomass productivity, but the same N treatments reduced the organic C pool in the calcareous grassland. Nitrogen deposition exacerbated P limitation in the calcareous grassland by reducing the size of the bioavailable P pool to plants, reducing biomass input to the soil C pool. Plant acquisition of organic P played an important role in determining the nutrient conditions of the grasslands, as both simulated grasslands increased organic P uptake to meet enhanced P demand driven by N deposition. Greater access to organic P in the acidic grassland prevented a shift to P limitation under elevated levels of N deposition, but organic P access was too low in the calcareous grassland to prevent worsening P limitation.

We conclude that grasslands of differing limiting nutrients may respond to N deposition in contrasting ways, and stress that as N deposition shifts ecosystems toward P limitation, a globally important carbon sink risks degradation.
Potential Morphologic Responses of Tropical River Deltas in Colombia to Future Sediment Supply Scenarios
Authors: Paniagua-Arroyave Juan F. , Nienhuis Jaap H. , Dunn Frances E.
Published: March 2021

Riverine sediment yield changes by human-induced catchment alterations can have important implications for river delta morphology. Here, we assess the potential response of 99 tropical deltas along the Caribbean and Pacific coasts of Colombia to projected human land use intensifications by deforestation and river damming. We assess delta morphology through the balance of wave, tidal, and (modern and future) river sediment transport processes at their mouths. We find that most Colombian deltas along the Caribbean coast are wave-dominated, except for large catchments with high riverine sediment load, which are river-dominated. Most deltas are wave-river dominated along the Pacific coast, with few examples of river-tide and wave-tide dominance. We predict Colombian deltas to become more wave and tide-dominated under river damming scenarios. In contrast, deforestation scenarios suggested virtually no future morphological changes.
Bridging the Gap between Seismicity and Exhumed Faults: Insights from a Seismically Active Strike-Slip Fault Zone in the Rawil Depression (Northern Valais, Switzerland)
Authors: Truttmann Sandro , Diehl Tobias , Herwegh Marco
Published: March 2021

The Rawil depression north of the Rhone Simplon fault zone (southwestern Swiss Alps) was host of the Mw = 5.8 Sion earthquake in 1946 (Fäh et al., 2011). It is nowadays one of the seismically most active regions in Switzerland and seismicity forms a cluster, which is elongated approximately in WSW-ENE direction over 40-50 km. In November 2019, a remarkable earthquake sequence occurred within the center of this cluster north of the village of Anzère, with more than 300 earthquakes up to ML = 3.3 recorded by the Swiss Seismological Service within 20 days.

Detecting associated full-scale 3D fault patterns solely based on earthquake hypocenters is challenging because of commonly too limited spatial resolution and insufficient number of seismic events. Within the framework of SeismoTeCH, we aim to improve these limitations by a combination of high-precision hypocenter relocation techniques, reconstruction of subsurface fault patterns and correlative links between surface and subsurface data. Assuming that a fault is seismically active multiple times and that the seismic stress-release is initiated at different locations along the fault, we can calculate 3D fault plane orientations from the hypocenter locations. Together with the 17 focal mechanisms derived for the Anzère sequence, we are able to gain geometrical and kinematic information of the seismic faults in 3D. Our analysis reveals a seismically active transpressional step-over structure within a dextral strike-slip fault zone. With remote sensing and field observations, we detect exhumed faults with similar orientations and kinematics that presumably represent step-over structures, interconnecting previously known strike-slip fault zones.

Although seismic activity occurs at depths between 3-5 km, we conclude that the observed surface fault systems in the Rawil depression can be correlated in terms of fault patterns with those assumed at depth. The linkage of the recent seismicity with structural observations of exhumed, potentially paleo-seismic faults in combination with recent hypocenter relocation techniques therefore have great potential to provide further insights into fault linkage and earthquake rupturing processes.

 

References

Fäh, D., Giardini, D., Kästli, P., Deichmann, N., Gisler, M., Schwarz-Zanetti, G., Alvarez-Rubio, S., Sellami, S., Edwards, B., Allmann, B., Bethmann, F., Wössner, J., Gassner-Stamm, G., Fritsche, S., Eberhard, D., 2011. ECOS-09 Earthquake Catalogue of Switzerland Release 2011. Report and Database. Public catalogue, 17.4.2011. Swiss Seismological Service ETH Zürich, Report SED/RISK/R/001/20110417.
Potential and limitations of processing smartphone GNSS raw observation data in PPP
Authors: Glaner Marcus Franz , Gutlederer Klaus , Weber Robert
Published: March 2021

Since the release of Android 7.0 in 2016, raw GNSS measurements tracked by smartphones operating with Android can be accessed. Before this date, solely the position solution of the smartphone's internal "black box" algorithm could be further processed in various applications. Now the smartphone's GNSS observations can be used directly to estimate the user position with specialized self-developed algorithms and correction data. Since smartphones are equipped with simple, cost-effective GNSS chips and antennas, they provide challenging, low-quality GNSS measurements. Furthermore, most smartphones on the market offer GNSS measurements on just one frequency. 

Precise Point Positioning (PPP) is one of the most promising processing techniques for Global Navigation Satellite System (GNSS) data. PPP is characterized by the use of precise satellite products (orbits, clocks, and biases) and the application of sophisticated algorithms to estimate the user's position. In contrast to relative positioning methods, PPP does not rely on nearby reference stations or a regional reference network. Furthermore, the concept of PPP is very flexible, which is another advantage considering the challenging nature of (single frequency) GNSS measurements from smartphones.

In this contribution, we present PPP results applying the uncombined model on raw GNSS observations from various smartphone devices. In contrast to the typical use of the ionosphere-free linear combination for PPP, this flexible PPP model applies the raw GNSS observation equations, is suitable for any number of frequencies, and allows the utilization of ionosphere models as an ionospheric constraint. We explore the potential and limitations of using raw GNSS observations from smartphones for PPP to reach a position accuracy at the decimeter level. Therefore, we test different correction data types and algorithms and examine diverse ways to handle the tropospheric and ionospheric delay. The PPP calculations are performed with our self-developed in-house software raPPPid.
Listen to a spectre – the potential role of environmental seismology in desert process research
Authors: Dietze Michael
Published: March 2021

Desert research has a bold track record in deciphering the evolution of landforms. While iconic objects such as inselbergs, yardangs, wadis or dune fields have attracted the attention of scientists for decades and inspired them to develop numerous formation concepts, it is the actual processes, which are suggested to govern their formation, that are usually quite hard to survey as they happen in nature. This amiguitity is due to the often unpredictable, event based, rapid yet episodic nature of their occurrence. While dedicated devices for measuring these processes inevitably exist, they are either confronted with a small spatial footprint (point measurement) or temporal discontinuousity (time lapse data), or even both of these drawbacks. As a consequence, important processes like flash floods, bedload agitation, mass movement on hillslopes, thermal weathering, dune migration rate and mechanism, or averaged information about ground moisture change, substrate rheology, and temperature diffusion can be studied as they happen under natural conditions only in exceptional cases.

Here I summarise recent developments from the field of environmental seismology, an emerging discipline that studies the seismic signals emitted by Earth surface processes, with a focus on existing and potential applications to desert environments. I present seismic approaches to detecting, tracking and quantifying flash floods and the sediment they convey, provide an overview of the capabilites of seismology to survey hillslope activity at the catchment scale, and discuss the potential to monitor surface and subsurface activity at the plot scale. The overarching aim of the contribution is to foster a discussion about potential research questions that could be tackled in future joint (i.e., established and seismic sensor) instrumentation projects.
Nonlinear Interaction between the Drivers of the Monsoon and Summertime Stationary Waves
Authors: Garfinkel Chaim , White Ian , Adam Ori , Gerber Ed , Jucker Martin
Published: March 2021

An intermediate complexity moist General Circulation Model is used to investigate the forcing of the Asian monsoon and the associated upper level anticyclone by land-sea contrast, net horizontal heat transport by the ocean, and topography. The monsoonal pattern is not simply the linear additive sum of the response to each forcing; only when all three forcings are included simultaneously does the monsoonal circulation extend westward to India. This nonadditivity impacts the location of the upper level anticyclone, which is shifted eastward and weaker if the forcings are imposed individually. Sahelian precipitation, and also austral summer precipitation over Australia, southern Africa, and South America, are likewise stronger if all forcings are imposed simultaneously. The source of the nonlinearity can be diagnosed using gross moist stability, but cannot be accounted for using the land-sea breeze paradigm. This non-additivity implies that the question of which forcing is most important is ill-posed.
Late Oligocene Warming Event (LOWE) possibly preserved on top of a reef drowning sequence in NW Italy: insights from an integrated stratigraphic approach.
Authors: Briguglio Antonino , Vannucci Maria Grazia , Bruzzone Clarissa , Crobu Simone , Lutaj Eleni , Piazza Michele
Published: March 2021

The Oligo-Miocene Transition (OMT) is one of the most important climatic transitions of younger earth history. This short period of climate warming coincides with a few biotic turnovers. OMT follows the Late Oligocene Warming Event which marks the last warming pulse of a generally cool interval and represents a time frame that could potentially fit well with modern climate change predictions.

The Case Cné section located within the Tertiary Piedmont Basin (TPB) represents a gradual transgressive event, which shows the drowning of a locally developed reef complex and a development of a deeper marine sedimentary setting influenced by gravity flow mechanics. Larger foraminifera association indicate a late Oligocene (SBZ23) time and this seems confirmed by Sr isotopes data.

By usage of sedimentological, semi-quantitative microfacies and geochemical analysis the sedimentary history of the section could be reconstructed and divided into four major phases. 1) The growth and establishment of the reef directly on the metamorphic substrate, 2) its development over the basement and the construction of a modest reefal body, 3) the slow drowning of the reef complex due to enhanced prograding fluvial activity and finally 4) the onset of gravity flows passing to turbiditic influence which cap the transgression and that continue regionally throughout into the Miocene. 

The benthic fauna seems to register the warming period by change in biodiversity and abundance. Below the warming event, larger foraminfera are rather sparse over the section and the benthic community seems dominated by suspension feeders. Toward the top of the section, where the LOWE seems to occur, the gravity flows transport a very large amount of operculinid foraminifera that are well adapted to warm and eutrophic conditions as the ones that possibly characterized the LOWE time span in this tectonically active region.
The impact of Secondary Ice Processes on a stratocumulus-to-cumulus transition during a Cold-Air Outbreak
Authors: Karalis Michail , Sotiropoulou Georgia , Abel Steven J. , Bossioli Elissavet , Georgakaki Paraskevi , Methymaki Georgia , Nenes Athanasios , Tombrou Maria
Published: March 2021

The representation of boundary layer clouds during marine Cold-Air Outbreaks (CAO) remains a great challenge for weather prediction models. Recent studies have shown that the representation of the transition from stratocumulus clouds to convective cumulus open cells largely depends on microphysical and precipitation processes, while Abel et al. (2017) further suggested that Secondary Ice Processes (SIP) may play a crucial role in the evolution of the cloud fields. In this study we use the Weather Research Forecasting model to investigate the impact of the most well-known SIP mechanisms (rime-splintering or Hallet-Mossop, mechanical break-up upon collisions between ice particles and drop-shattering) on a CAO case observed north of UK in 2013. While Hallet-Mossop is the only SIP process extensively implemented in atmospheric models, our results indicate that collisional break-up is also important in these conditions.

 

Abel, S. J., Boutle, I. A., Waite, K., Fox, S., Brown, P. R. A., Cotton, R., Lloyd, G., Choularton, T. W., & Bower, K. N. (2017). The Role of Precipitation in Controlling the Transition from Stratocumulus to Cumulus Clouds in a Northern Hemisphere Cold-Air Outbreak, Journal of the Atmospheric Sciences, 74(7), 2293-2314. Retrieved Jan 9, 2021, from https://journals.ametsoc.org/view/journals/atsc/74/7/jas-d-16-0362.1.xml
Late Pleistocene to Holocene shallow marine – coastal changing environments and human interaction in the South Bay of Dor, Israel
Authors: Shtienberg Gilad , Gadol Omri , Levy Thomas , Norris Richard , Rittenour Tammy , Yasur-Landau Assaf , Tamberino Anthony , Lazar Michael
Published: March 2021

The Tel-Dor embayment located along the Carmel coast provides a valuable opportunity to study environmental and human interaction due to its protecting geomorphic properties that are unique for the generally linear Israeli coast. Interpretations of seismic profiles collected from transects across the bay show five seismic units that have been correlated to dated and well-analyzed sediment units in coastal cores, enabling a detailed deep time reconstruction of the coastal system over the last ~77 ka. The earliest borehole deposits are low-stand aeolian followed by terrestrial sediments including wetland remains that were subsequently flooded by the mid-Holocene transgression. Evidence of the earliest human settlement submerged Pottery-Neolithic (8.25-7 ka) remains, found immediately above the wetland deposits landward of a submerged aeolianite ridge at the mouth of the bay. The wetland deposits and Pottery-Neolithic settlement remains are at present buried by coastal sand recording middle Holocene sea-level rise and thus, suggesting that these coastal communities were displaced by sea-level transgression ca. 7.6–6.5 ka. The sedimentological and archaeological evidence identified in the stratigraphical sequence of the sheltered bay is a good example of better understanding the essential environmental changes on the shallow shelf and the coastline migration especially in bays and the human settlement adaptations to these changes. This high-resolution reconstruction based on seismic methods in the shallow water and core analysis on land combined with detailed archaeological data from the studied area provides an important addition to the puzzle of the Mediterranean story, the cradle of Western Civilizations.
Dayside Magnetopause Reconnection and Flux Transfer Events: BepiColombo Earth-Flyby
Authors: Sun Wei-Jie , Slavin James , Nakamura Rumi , Heyner Daniel , Mieth Johannes
Published: March 2021

BepiColombo is a joint mission of the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) to the planet Mercury. The BepiColombo mission consists of two spacecraft, which are the Mercury Planetary Orbiter (MPO) and Mercury Magnetospheric Orbiter (Mio). The mission made its first planetary flyby, which is the only Earth flyby, on 10 April 2020, during which several instruments collected measurements. In this study, we analyze MPO magnetometer (MAG) observations of Flux Transfer Events (FTEs) in the magnetosheath and the structure of the subsolar magnetopause near the  flow stagnation point. The magnetosheath plasma beta was high with a value of ~ 8 and the interplanetary magnetic field (IMF) was southward with a clock angle that decreased from ~ 100 degrees to ~ 150 degrees.  As the draped IMF became increasingly southward several of the flux transfer event (FTE)-type flux ropes were observed. These FTEs traveled southward indicating that the magnetopause X-line was located northward of the spacecraft, which is consistent with a dawnward tilt of the IMF. Most of the FTE-type flux ropes were in ion-scale, <10 s duration, suggesting that they were newly formed. Only one large-scale FTE-type flux rope, ~ 20 s, was observed. It was made up of two successive bipolar signatures in the normal magnetic field component, which is evidence of coalescence at a secondary reconnection site. Further analysis demonstrated that the dimensionless reconnection rate of the re-reconnection associated with the coalescence site was ~ 0.14. While this investigation was limited to the MPO MAG observations, it strongly supports a key feature of dayside reconnection discovered in the Magnetospheric Multiscale mission, the growth of FTE-type flux ropes through coalescence at secondary reconnection sites.
Perceptions of Flash Drought in the U.S.: How do End-Users and Researchers Compare?
Authors: Haigh Tonya , Lisonbee Joel , Skumanich Marina , Woloszyn Molly
Published: March 2021

Defining flash drought is important not only for the development of the science but also for ensuring clear and useful early warning information to end users. In preparation for a December 2020 U.S-based workshop on flash drought, the National Integrated Drought Information System (NIDIS) and National Drought Mitigation Center (NDMC) undertook a survey of NIDIS contacts to explore how flash drought is understood within and outside of the research community. End users represented in the survey include researchers (outside of flash drought specialty), policy-makers, decision-makers, communicators, and educators and public engagement specialists, largely working within universities or federal agencies across the U.S. Flash drought researchers were asked to describe how they intend for the term “flash drought” to be interpreted when they use it. End users (whether they had heard/used the term before or not) were asked to describe what they think of when they hear the term “flash drought”. Their answers emerged into themes, including: onset/intensification, duration, drivers, impacts, seasonality, predictability, intensity, spatial scale, and uncertainty about its meaning. In this presentation, we will elaborate upon these themes, and discuss similarities and differences in how flash drought researchers and end users conceptualize flash drought.
Implementation and Validating of the Regional Ocean Model System (ROMS) for the Sunda Strait connecting the Java Sea to the Indian Ocean
Authors: Mujiasih Subekti , Beckers Jean-Marie , Barth Alexander
Published: March 2021

Regional Ocean Model System (ROMS) has been simulated for the Sunda Strait, the Java Sea, and the Indian Ocean. The simulation was undertaken for thirteen months of data period (August 2013 – August 2014). However, we only used four months period for validation, namely September – December 2013. The input data involved the HYbrid Coordinate Ocean Model (HYCOM) ocean model output by considering atmospheric forcing from the European Centre for Medium-Range Weather Forecasts (ECMWF), without and with tides forcing from TPXO and rivers. The output included vertical profile temperature and salinity, sea surface temperature (SST), seas surface height (SSH), zonal (u), and meridional (v) velocity. We compared the model SST to satellite SST in time series, SSH to tides gauges data in time series, the model u and v component velocity to High Frequency (HF) radial velocity. The vertical profile temperature and salinity were compared to Argo float data and XBT. Besides, we validated the amplitude and phase of the ROMS seas surface height to amplitude and phase of the tides-gauges, including four constituents (M2, S2, K1, O1).
Improved sea-ice prediction in the Weddell Sea using sea-ice thickness initialization
Authors: Morioka Yushi , Iovino Doroteaciro , Cipollone Andrea , Masina Simona , Behera Swadhin
Published: March 2021

Skillful sea-ice prediction in the Antarctic Ocean remains a big challenge due to paucity of sea-ice observations and insufficient representation of sea-ice processes in climate models. This study demonstrates that the Antarctic sea-ice concentration (SIC) prediction is significantly improved using a coupled general circulation model (SINTEX-F2) in which the model’s SIC and sea-ice thickness (SIT) are initialized with the ocean/sea-ice reanalysis product (C-GLORSv7). It is found that the wintertime SIT initialization adds positive values to the prediction skills of the summertime SIC, most effectively in the Weddell Sea where the SIT climatology and variability are the largest among the Antarctic Seas. Examination of the SIT balance during low sea-ice years of the Weddell Sea shows that negative SIT anomalies initialized in June retain the memory throughout austral winter (July-September) owing to horizontal advection of the SIT anomalies by sea-ice velocities. The negative SIT anomalies continue to develop in austral spring (October-December) owing to more incoming solar radiation via ice-albedo feedback and the associated warming of mixed layer. This results in further sea-ice decrease during austral summer (January-March). Concomitantly, the model reasonably reproduces atmospheric circulation anomalies in the Amundsen-Bellingshausen Seas as well as the Weddell Sea during the development of the negative sea-ice anomalies. These results provide solid evidence that the wintertime SIT initialization benefits skillful summertime sea-ice prediction in the Antarctic Seas.
Greenhouse-gas feedbacks estimated from Dansgaard-Oeschger events
Authors: Liu Mengmeng , Menviel Laurie , Prentice Iain Colin , Harrison Sandy P.
Published: March 2021

There are large uncertainties in the estimation of greenhouse-gas feedbacks: model-based estimates vary considerably; recent observations are too short provide strong constraints. Rapid climate changes during the last glacial period (Dansgaard-Oeschger, D-O, events) are potentially valuable because they are comparable in rate and magnitude to projected future climate warming, and are registered near-globally. Here we use D-O events to quantify the centennial-scale feedback strength of feedbacks involving CO2, CH4 and N2O. We use climate model simulations of the D-O events to estimate the relationship between global mean and Greenland temperature. We then relate global mean temperature changes to changes in greenhouse-gas concentrations derived from ice-core records, and then estimate the associated radiative forcing. We found the magnitude of the feedbacks (expressed in gain, with 95 % confidence interval) to be 0.07 ± 0.02 for CO2, 0.04 ± 0.01 for CH4, 0.04 ± 0.01 for N2O. These estimates are more constrained than previous model-based estimates but comparable to estimates based on recent observations.
The impact of diurnal precipitation over Sumatra Island, Indonesia, on synoptic disturbances and its relation to the Madden-Julian Oscillation
Authors: Seiki Ayako , Yokoi Satoru , Katsumata Masaki
Published: March 2021

The impact of diurnal precipitation over Sumatra Island, the Indonesian Maritime Continent (MC), on synoptic disturbances over the eastern Indian Ocean is examined using high-resolution rainfall data from the Global Satellite Mapping of Precipitation project and the Japanese 55-year Reanalysis data during the rainy season from September to April for the period 2000–2014. When the diurnal cycle is strong, the high precipitation area observed over Sumatra in the afternoon migrates offshore during nighttime and reaches 500 km off the coast on average. The strong diurnal events are followed by the development of synoptic disturbances over the eastern Indian Ocean for several days, and apparent twin synoptic disturbances straddling the equator develop only when the convective center of the Madden–Julian Oscillation (MJO) lies over the Indian Ocean (MJO-IO). Without the MJO, the synoptic disturbances develop mainly south of the equator. The differences in the locations and behaviors of active synoptic disturbances are related to the strength of mean horizontal winds in the lower troposphere. During the MJO-IO, the intensification of mean northeasterly winds in the northern hemisphere blowing into the organized MJO convection in addition to mean southeasterly winds in the southern hemisphere facilitate the formation of the twin disturbances. These results suggest that seed disturbances arising from the diurnal offshore migration of precipitation from Sumatra develop differently depending on the mean states over the eastern Indian Ocean. Furthermore, it is shown that the MJO events with the strong diurnal cycle tend to have longer duration and continuing eastward propagation of active convection across the MC, whereas the convective activities of the other MJO events weaken considerably over the MC and develop again over the western Pacific. These results suggest that the strong diurnal cycle over Sumatra facilitates the smooth eastward propagation of the intraseasonal convection across the MC.