bluuebunny/crossref_metadata_2025 huggingface dataset:
Inference of Submarine Meltwater in the Boundary Current System around Greenland in 2015-2019
Authors: Kieke Dagmar , Huhn Oliver , Mertens Christian , Rhein Monika , Steinfeldt Reiner , Wiegand Kevin N.
Published: March 2021

Melting of the Greenland Ice Sheet is one of the major causes that adds to the ice sheet mass loss and subsequently to the global sea level rise. The accelerated melting observed in recent decades is mainly caused by surface melting due to atmospheric warming and submarine melting caused by the increased inflow of warm Atlantic Water into the glacier-inhabited fjords of Greenland. This water reaches the front of marine terminating glaciers or the base of floating ice tongues inducing submarine melting. However, knowledge about submarine melt rates is limited and often inferred from indirect or remote sensing methods. Open questions exist regarding the processes that control the interaction of the oceans with marine terminating glaciers and the subsequent pathway of glacially modified water.
The increasing release of this meltwater into the ocean is expected to have an impact on the deep water formation in the North Atlantic causing it to decrease. Since the deep water formation and spreading contribute to the deep limb of the Atlantic Meridional Overturning Circulation, identifying, tracking, and quantifying the oceanic submarine meltwater content and its variability is of high interest.
The noble gases helium and neon provide a useful tool to identify and to quantify the fraction of glacially modified water in the oceanic water column. In this study we evaluate hydrographic, velocity and noble gas measurements from a number of cruises conducted across the boundary current system around Greenland between 2015 and 2019. With focus on the East and West Greenland Current systems, we aim at obtaining a large-scale view on the submarine meltwater distribution around Greenland and discuss the different regional regimes in two Greenlandic fjord systems and the boundary current around Greenland.
Effects of Fe addition on sediment P dynamics in a eutrophic lake
Authors: Münch Melanie , van Kaam Rianne , As Karel , Peiffer Stefan , ter Heerdt Gerard , Slomp Caroline P. , Behrends Thilo
Published: March 2021

The decline of surface water quality due to excess phosphorus (P) input is a global problem of increasing urgency. Finding sustainable measures to restore the surface water quality of eutrophic lakes with respect to P, other than by decreasing P inputs, remains a challenge. The addition of iron (Fe) salts has been shown to be effective in removing dissolved phosphate from the water column of eutrophic lakes. However, the resulting changes in biogeochemical processes in sediments as well as the long-term effects of Fe additions on P dynamics in both sediments and the water column are not well understood.

In this study, we assess the impact of past Fe additions on the sediment P biogeochemistry of Lake Terra Nova, a well-mixed shallow peat lake in the Netherlands. The Fe-treatment in 2010 efficiently reduced P release from the sediments to the surface waters for 6 years. Since then, the internal sediment P source in the lake has been increasing again with a growing trend over the years.

In 2020, we sampled sediments at three locations in Terra Nova, of which one received two times more Fe during treatment than the other two. Sediment cores from all sites were sectioned under oxygen-free conditions. Both the porewaters and sediments were analysed for their chemical composition, with sequential extractions providing insight into the sediment forms of P and Fe. Additional sediment cores were incubated under oxic and anoxic conditions and the respective fluxes of P and Fe across the sediment water interface were measured.

The results suggest that Fe and P dynamics in the lake sediments are strongly coupled. We also find that the P dynamics are sensitive to the amount of Fe supplied, even though enhanced burial of P in the sediment was not detected. The results of the sequential extraction procedure for P, which distinguishes P associated with humic acids and Fe oxides, as well as reduced flux of Fe(II) across the sediment water interface in the anoxic incubations, suggest a major role of organic matter in the interaction of Fe and P in these sediments.

Further research will include investigations of the role of organic matter and sulphur in determining the success of Fe-treatment in sequestering P in lake sediments. Based on these data in combination with reactive transport modelling we aim to constrain conditions for successful lake restoration through Fe addition.
Intercomparison of Cloud Products based on S5P/TROPOMI Level 1b Data Version 1 and the updated Version 2
Authors: Latsch Miriam , Richter Andreas , Burrows John P. , Wagner Thomas , Sihler Holger , van Roozendael Michel , Loyola Diego , Valks Pieter , Argyrouli Athina , Lutz Ronny , Veefkind Pepijn , Eskes Henk , Sneep Maarten , Wang Ping , Siddans Richard
Published: March 2021

The first European Sentinel satellite for monitoring the composition of the Earth’s atmosphere, the Sentinel 5 Precursor (S5p), carries the TROPOspheric Monitoring Instrument (TROPOMI) to map trace species of the global atmosphere at high spatial resolution. Retrievals of tropospheric trace gas columns from satellite measurements are strongly influenced by clouds. Thus, cloud retrieval algorithms were developed and implemented in the trace gas processing chain to consider this impact.

In this study, different cloud products available for NO2 retrievals based on the TROPOMI level 1b data version 1 and an updated TROPOMI level 1b test data set of version 2 (Diagnostic Data Set 2B, DDS2B) are analyzed. The data sets include a) the TROPOMI level 2 OCRA/ROCINN (Optical Cloud Recognition Algorithm/Retrieval of Cloud Information using Neural Networks) cloud products CRB (cloud as reflecting boundaries) and CAL (clouds as layers), b) the FRESCO (Fast Retrieval Scheme for Clouds from Oxygen absorption bands) cloud product,  c) the cloud fraction from the NO2 fitting window, d) the VIIRS (Visible Infrared Imaging Radiometer Suite) cloud product, and e) the MICRU (Mainz Iterative Cloud Retrieval Utilities) cloud fraction. The cloud products are compared with regard to cloud fraction, cloud height, cloud albedo/optical thickness, flagging and quality indicators in all 4 seasons. In particular, the differences of the cloud products under difficult situations such as snow or ice cover and sun glint are investigated.

We present results of a statistical analysis on a limited data set comparing cloud products from the current and the upcoming lv2 data versions and their approaches. The aim of this study is to better understand TROPOMI cloud products and their quantitative impacts on trace gas retrievals.
Remediation of antibiotic and heavy metal pollution in marine environment
Authors: Zheng Hao , Ma Xiaohan , Zhao Man , Zhang Chenchen , Xing Baoshan
Published: March 2021

Pollution of marine environment by antibiotics and/or heavy metals is a serious global issue. Remediation of polluted marine environments is urgently needed for achieving the United Nations Sustainable Development Goals (SDGs) to end poverty and protect the planet from degradation. Biochar, as an environmentally friendly material, has been widely used as adsorbents to remediate contaminated soil or fresh water. However, application of biochar in remediation of marine environment is poorly understood. Therefore, a batch of biochars produced from pyrolysis of two marine algae residues, Enteromorpha (Enteromorpha prolifera) and blended seaweed wastes, at 300–700 °C was used to investigate their performance in sulfamethoxazole (SMX) sorption in seawater. Additionally, a modified biochar (MBC) was prepared by pyrolyzing AlCl3 pretreated sawdust to improve their performance in remediating a marine sediment contaminated with heavy metals and antibiotics using two mesocosmic experiments. The results showed the algae-derived biochars had relatively low C content, but high contents of O- and S-containing functional groups and crystalline minerals associated with S, Ca, K, and Mg. The maximum adsorption capacity of these algae-derived biochars to SMX was 4880 mg kg-1, equivalent to a commercial coconut shell derived activated carbon. Potential mechanisms responsible for the SMX sorption mainly included pore-filling, cation bridging, negative charge-assisted H-bond [(–)CAHB], and π-π EDA interaction. The surface of MBC was rough with layered homogeneous sheets, and the nano-scale Al minerals formed on the C matrix. Moreover, its settling properties and adsorption capacities to Cu, Cd, SMX, and tetracycline (TC) were highly improved relative to the unmodified sawdust derived biochar (SBC). As a result, addition of MBC at 4% (w/w) performed  better in improving the survival rate and condition index of the clams in the contaminated sediments than SBC. Furthermore, MBC application decreased bioaccumulation of Cu and Cd in the clams. Both SBC and MBC increased the microbial abundance and diversity in the contaminated sediments, and MBC decreased the abundance of Cu resistant bacteria (e.g., Firmicute and Gemmatimonadetes). For the sediment contaminated by antibiotics, lower content of SMX and TC in the overlying water and pore water was observed in the sediment amended with MBC than SBC, leading to the reduction of total antibiotic resistance genes. Therefore, these findings show the potential of functional/modified biochar to remediate marine sediments contaminated with heavy metals and antibiotics.
Semi-automated past landscape visualizations for the Netherlands: solutions to keep national overviews actual and in-sync
Authors: Cohen Kim , Pierik Harm-Jan , Woolderink Hessel , Moree Jelle , Cox Hugo
Published: March 2021

Overwhelming amounts of geological and geomorphological data have accumulated over the last ca. 160 years for the Netherlands. Also, the amounts and diversity of digital map products summarizing all this data also have grown overwhelmingly. Combining, updating and synchronizing the various information sources while keeping matters user-friendly is a challenge. We present the current status of our GIS solutions for managing landform age information and performing palaeo­geographical analysis utilizing past landscape visualizations (i.e. query-generated map time series).

Our mapping uses so-called base maps connected to landform catalogue database to store information, which are published as open data. Base maps and catalogues are to be kept up-to-date with new actual data through iterative manual revision, and are ‘living’ datasets. For palaeogeographical analysis we query the base maps and recombine subselections using scripts. This generates derived map series in which the information is arranged for the analysis, which independently gets open data status. To allow communal maintenance of the information, we designed interfaces to the landform catalogue databases of our base maps to make them editable in wiki-style (i.e.: ‘non-static open data’).

Attitudes like this are needed to get the most out of accumulating data and overcome integration, actuality and divergence challenges felt by users working with different maps claimed to be based on the same shared body of geodata generated in densely populated lowland countries.
On frequency response of Stokes and Hotine-Koch integral transforms in calculation of height anomaly in the local area by means of SRBF
Authors: Sugaipova Leyla , Neyman Yury
Published: March 2021

The problem of determining the height anomaly in a local area of the radius ψ0 using gravity disturbances and gravity anomalies is discussed. The influence of the far zone, as usually, is approximately taken into account using the global gravity field model and the truncation coefficients Qn (ψ0) introduced by M.S. Molodensky [1]. The modification Qn0(ψ0) by O.M. Ostach [2] of these coefficients is described. They provide - in contrast to the original coefficients - the continuity of the used integral transform kernel Ker0 (ψ) in the whole its definition domain. As a consequence, the modified coefficients decrease faster compared to the original ones with an increase of the degree n (frequency). It reduces the error of the far zone influence. Coefficients are interpreted as Fourier coefficients of the outer part of the kernel when it is decomposed into the orthogonal system of nonnormalized Legendre polynomials. The relationship between Qn (ψ0) and Qn0(ψ0) is indicated. In the frequency domain, the expression for the truncated kernel ΔKer0 (ψ) of the integral transform used (Stokes or Hotine-Koch) differs from the corresponding full kernel by a multiplier, which is proposed to be called the frequency characteristic of the kernel truncation operator onto the inner zone of radius ψ0.

In local modeling, when describing the details of the "useful signal", it is advisable to use approximation by means of spherical radial basis functions (SRBF) instead of traditional integration due to their good spatial localization [3, 4]. The procedure of constructing scaling functions and corresponding wavelets is briefly described. New scaling functions, based on the above-mentioned concept of frequency characteristic of the kernel truncation operator onto the inner zone of the radius ψo, are proposed. To prove the effectiveness of these scaling functions, numerical experiments were conducted. Both gravity anomalies Δg and disturbances δg were used as input data. The results of the calculations showed a high accuracy of recovering height anomalies from gravity anomalies. Besides, introduction of frequency characteristic of kernel truncation of corresponding integral transform onto the inner zone allows to cut off implicit influence of far zone. Known scaling functions that do not use this frequency characteristic lead, as experiments have shown, to biased results.

References:
The NEE-PAR relationship for a young spruce plantation
Authors: Lange Holger , Zhao Junbin , Bethke Raika
Published: March 2021

In a young Norway spruce stand (planted in 2012) at Hoxmark, Southeast Norway, Net Ecosystem Exchange (NEE) was measured using Eddy Covariance. The data were carefully processed with time-dependent stand parameters (i.e. canopy height), a detailed footprint analysis and calculated at 30 min temporal resolution. Photosynthetic Active Radiation (PAR) as the primary driver for carbon uptake was also available at the site.

Despite its young age, the plantation already acted as a net carbon sink according to the annual NEE budget, e.g. by ca. 300 g C m-2 in 2019. However, the response of the system depended strongly on hydrometeorological conditions. We demonstrate this by investigating the relationship between NEE and PAR for this system in a temporally local fashion (30 days moving windows), using a Michaelis-Menten approach involving three parameters. Although the regression captured up to ca. 80% of the variance, the parameter estimates differed substantially throughout the season, and were contrasting between the very dry year 2018 and the close to normal year 2019.

Comparison with other EC-equipped sites in a future study will clarify whether this variable sensitivity is due to the young age or is a pattern pertaining also to mature spruce stands.
Efforts toward automatic aftershock sequences processing at the International Data Centre
Authors: Saragiotis Christos
Published: March 2021

The number of aftershocks after a large main shock may increase the daily number of seismic events by an order of magnitude for a few days or even weeks. The large number of incoming arrivals reduces the effectiveness of automatic bulletin generation and significantly increases the work of the analysts. In the verification context such aftershocks may delay the production of the CTBTO Reviewed Event Bulletin, as well as mask clandestine nuclear tests. Consequently, the CTBTO has been investigating ways to improve the performance of the automatic processing during aftershock sequences.  

In line with this investigation, the PTS launched a project with the objective to evaluate three algorithms that could address this issue, namely the Empirical Matched Field developed at NORSAR, the SeisCorr developed at Sandia National Labs and XSEL developed at the IDC. In this abstract we present comparisons on the performance of the three methods on the aftershock sequences of four very strong earthquakes: the Tohoku earthquake in Japan (March 2011), the Gorkha earthquake in Nepal (April 2015), the  Illapel earthquake off the coast of Chile (September 2015) and the devastating earthquake in Papua New Guinea (February 2018).
Rethinking Rehabilitation: Application of the SOTE model to soil rehabilitation following salinity and sodicity induced degradation
Authors: Kramer Isaac , Bayer Yuval , Mau Yair
Published: March 2021

If not carefully managed, use of saline and sodic irrigation waters, a common practice in dryland regions, has the potential to cause significant harm to soils. Application of saline and sodic irrigation waters can lead to reductions in hydraulic conductivity, Ks, the mechanisms of which (e.g., slaking, swelling, clay dispersion) have been the focus of a vast body of scientific literature. The rehabilitation process, by contrast, is far less understood. Despite experimental evidence showing a significant degree of irreversibility, traditionally models have treated the degradation and rehabilitation processes as reversible. We demonstrate how this assumption obfuscates our ability to analyze the risk of long-term degradation and to estimate the resources and time required to rehabilitate. We achieve this by using the SOTE model — a minimalistic model that can be used to study dynamics of soil water content, salinity, and sodicity, as driven by irrigation practices and climatic conditions. Crucially, SOTE also accounts for the feedback between changing salinity and sodicity and soil Ks. This feedback includes irreversible changes in hydraulic conductivity, such that a soil’s history of degradation and rehabilitation informs its future state. We compare SOTE to existing models, which do not include hysteresis in Ks, and demonstrate that SOTE predicts more gradual rehabilitation of degraded soils, in line with the limited experimental evidence that has examined this question. For the test case of a degraded soil in a typical Mediterranean climate, SOTE forecasts that rehabilitation requires 50% more time and water resources, in comparison to models without hysteresis. This difference underscores the need to limit the risk of potential degradation, which SOTE also shows increases by 50% when hysteresis is accounted for. A sensitivity analysis indicates that SOTE is most sensitive to parameters connected to soil texture. The sensitivity analysis further indicates that our results are robust -- under all ranges of parameter values SOTE continues to forecast greater time requirements for rehabilitation and increased risk of soil degradation.
Petrogenesis of the Upper Cretaceous volcanism in the Kefken region, Western Pontides, NW Turkey
Authors: Duzman Turgut , Sağlam Ezgi , Okay Aral I.
Published: March 2021

The Upper Cretaceous volcanic and volcaniclastic rocks crop out along the Black Sea coastline in Turkey. They are part of a magmatic arc that formed as a result of northward subduction of the Tethys ocean beneath the southern margin of Laurasia. The lower part of the Upper Cretaceous volcanism in the Kefken region, 100 km northeast of Istanbul, is represented by basaltic andesites, andesites, agglomerates and tuffs, which have yielded Late Cretaceous (Campanian, ca. 83 Ma) U-Pb zircon ages. The volcanic and volcanoclastic rocks are stratigraphically overlain by shallow to deep marine limestones, which range in age from Late Campanian to Early Eocene.  Geochemically, basaltic andesites and andesites display negative anomalies in Nb, Ta and Ti, enrichment in large ion lithophile elements (LILE) relative to high field strength elements (HFSE). Light rare earth elements (LREE) show slightly enrichment relative to heavy rare earth elements (Lacn/Ybcn =2.51-3.63) and there are slight negative Eu anomalies (Eu/Eu* = 0.71-0.95) in basaltic andesite and andesite samples. The geochemical data indicate that Campanian volcanic rocks were derived from the partial melting of the mantle wedge induced by hydrous fluids released by dehydration of the subducted oceanic slab.

There is also a horizon of volcanic rocks, about 230 m thick, within the Late Campanian-Early Eocene limestone sequence.  This volcanic horizon, which consists of pillow basalts, porphyritic basalts,  andesites and dacites, is of Maastrichtian age based on paleontological data from the intra-pillow sediments and U-Pb zircon ages from the andesites and dacites (72-68 Ma).  The Maastrichtian andesites and dacites are geochemically distinct from the Campanian volcanic rocks. They show distinct adakite-like geochemical signatures with high ratios of Sr/Y (>85.5), high Lacn/Ybcn (16.4-23.7) ratios, low content of Y (7.4-8.6 ppm) and low content of heavy rare-earth elements (HREE). The adakitic rocks most probably formed as a result of partial melting of the subducting oceanic slab under garnet and amphibole stable conditions.

The Upper Cretaceous arc sequence in the Kefken region shows a change from typical subduction-related magmas to adakitic ones, accompanied by decrease in the volcanism.

 

 
MMS Observation of Intermittent Energy Dissipation in Magnetic Reconnection Diffusion Region
Authors: Dong Xiangcheng , Dunlop Malcolm , Wang Tieyan , Zhao Jinsong , Fu Huishan , Chen Zuzheng , Russell Christopher
Published: March 2021

Magnetospheric Multiscale (MMS) data are used to investigate the energy dissipation in a  reconnection diffusion region at the magnetopause. The four MMS spacecraft were separated by about 10 km such that comparative study between each spacecraft within the diffusion region can be implemented. Similar magnetic field and electric current behavior between each spacecraft indicates the formation of a quasi-homogeneous diffusion region structure. However, we find that the energy dissipation results between each spacecraft are different due to the temporal or spatial effect of the out-of-plane merging electric field (EM) during the dissipation region. Our study suggests that the intermittent energy dissipation in the reconnection dissipation region can be a common phenomenon, even under a stable diffusion region structure.
The role of inter- and intra-specific variability in controlling trait measurements in tropical forests
Authors: Rowland Lucy , Bittencourt Paulo , Bartholomew David , Giles Andre , Oliveira Rafael , Mencuccini Maurizio , da Costa Antonio , Banin Lindsay , Burslem David , Meir Patrick
Published: March 2021

Tropical rainforests harbour the greatest diversity of woody plant species in the world. Consequently, within any individual forest plot, replicating functional trait measurements, particularly at species level can be challenging. However, trait variation within and between species can be very large. Limited sampling opportunities in diverse forests poses a huge challenge to understanding the role both inter- and intra-specific variation play when we scale up individual trait measurements to plot or landscape averages. Using data from tropical forests within Latin America and South East Asia, we explore the potential role which inter- and intra-specific variation may play when attempting to compare functional trait values in tropical forests experiencing different environmental conditions. We demonstrate the need for renewed care considering how we construct sampling protocols within these forests for functional trait sampling. This includes considering the size and canopy position of the trees we sample across plots, alongside the number of individual within a species, and the number of species, we sample to generate results concerning how variation in environmental conditions influences plant functional traits. Considering such issues also offers considerable opportunities to advance our knowledge of the processes of acclimation and trait plasticity and how they may influences responses to environmental change. In-turn opening new prospects to better inform vegetation models, particularly individual-based models and therefore to investigate the impact of these properties at larger scales.
Tectono-magmatic evolution of the Karoo and Kerguelen plumes and their impact onto magmatism of the East Antarctica
Authors: Sushchevskaya Nadezda , Leitchenkov German , Belyatsky Boris
Published: March 2021

The Mesozoic Karoo-Maud and Kerguelen plumes had a significant influence on Gondwana and the oceanic lithosphere. Jurassic magmatism, formed under the influence of a huge Karoo plume at 184–178 Ma ago, covered large areas of the Dronning Maud Land in East Antarctica. Later, 130 – 0 m.y. ago, under the influence of the Kerguelen plume, magmatism formed in the area of the Lambert glacier, and the Gaussberg volcano (Quaternary time) appeared, located on the coast opposite the Kerguelen archipelago. We assume that the Karoo mantle plume initiated the formation of a “mega-apophyses” from the main plume manifestation area within the Karoo province in the southeastern African continet (ca. 2000 km in diameter). These mega-apophyses are represented by the Ferrar Igneous Province (ca. 3000 km long area of intrusive activity along the Transantarctic Mountains) and a supposed igneous province (ca. 1500 km long) covering the East Antarctic coast between the Lazarev and Cosmonauts Seas. Based on petrological and geochemical studies, the characteristic features of magmas of the Karoo, Dronning Maud Land, and Ferrar igneous provinces have been determined, which indicate that for all magmas associated with Karoo and Kerguelen plumes, the main source of melt enrichment is a mantle source with characteristics of the EM-II component (most typically for magmas of the Ferrar Province). It reflects the properties of an enriched, fluid-rich, ancient continental mantle, metasomatized at the early stages of the tectonic development of the region and involved in the melting process. A rarer admixture of the ancient lithospheric component (EM-I, with 206Pb/204Pb = 16.5 and 143Nd/144Nd = 0.5122) was revealed in both plumes. The existence of mantle plumes in the Southern Hemisphere and their long-term development had a significant impact on the structure and evolution of the East Antarctica.
El Niño Index forecasting using machine learning techniques 
Authors: Song Wanjiao , Lu Wenfang , Dong Qing
Published: March 2021

El Niño is a large-scale ocean-atmospheric coupling phenomenon in the Pacific. The interaction among marine and atmospheric variables over the tropical Pacific modulate the evolution of El Niño. The latest research shows that machine learning and neural network (NN) have appeared as effective tools to achieve meaningful information from multiple marine and atmospheric parameters. In this paper, we aim to predict the El Niño index more accurately and increase the forecast efficiency of El Niño events. Here, we propose an approach combining a neural network technique with long short-term memory (LSTM) neural network to forecast El Niño phenomenon. The attributes of model are resulted from physical explanation which are tested with the experiments and observations. The neural network represents the connection among multiple variables and machine learning creates models to identify the El Niño events. The preliminary experimental results exhibit that training NN-LSTM model on network metrics time series dataset provides great potential for predicting El Niño phenomenon at lag times of up to more than 6 months.  
Wavelet analysis applied on temporal data sets in order to reveal possible pre-seismic radio anomalies and comparison with the trend of the raw data 
Authors: Nico Giovanni , Biagi Pier Francesco , Ermini Anita , Boudjada Mohammed Yahia , Eichelberger Hans Ulrich , Katzis Konstantinos , Contadakis Michael , Skeberis Christos , Moldovan Iren Adelina , Bezzeghoud Mourad , Nina Aleksandra
Published: March 2021

Since 2009, several radio receivers have been installed throughout Europe in order to realize the INFREP European radio network for studying the VLF (10-50 kHz) and LF (150-300 kHz) radio precursors of earthquakes. Precursors can be related to “anomalies” in the night-time behavior of  VLF signals. A suitable method of analysis is the use of the Wavelet spectra.  Using the “Morlet function”, the Wavelet transform of a time signal is a complex series that can be usefully represented by its square amplitude, i.e. considering the so-called Wavelet power spectrum.

The power spectrum is a 2D diagram that, once properly normalized with respect to the power of the white noise, gives information on the strength and precise time of occurrence of the various Fourier components, which are present in the original time series. The main difference between the Wavelet power spectra and the Fourier power spectra for the time series is that the former identifies the frequency content along the operational time, which cannot be done with the latter. Anomalies are identified as regions of the Wavelet spectrogram characterized by a sudden increase in the power strength.

On January 30, 2020 an earthquake with Mw= 6.0 occurred in Dodecanese Islands. The results of the Wavelet analysis carried out on data collected some INFREP receivers is compared with the trends of the raw data. The time series from January 24, 2020 till January 31, 2000 was analyzed. The Wavelet spectrogram shows a peak corresponding to a period of 1 day on the days before January 30. This anomaly was found for signals transmitted at the frequencies 19,58 kHz, 20, 27 kHz, 23,40 kHz with an energy in the peak increasing from 19,58 kHz to 23,40 kHz. In particular, the signal at the frequency 19,58 kHz, shows a peak on January 29, while the frequencies 20,27 kHz and 23,40 kHz are characterized by a peak starting on January 28 and continuing to January 29. The results presented in this work shows the perspective use of the Wavelet spectrum analysis as an operational tool for the detection of anomalies in VLF and LF signal potentially related to EQ precursors.
A State Space Representation of a Two-Component Energy Balance Model
Authors: Lykke Jingying , Hillebrand Eric , Bennedsen Mikkel
Published: March 2021

Energy Balance models (EBMs) condense the complicated processes underlying temperature change into a single equation that describes the disequilibrium between absorbed radiation and emitted radiation, where the relation between temperature change and radiative forcing is established. The two-component EBM divides the climate into a mixed shallow ocean/atmosphere layer and a deep ocean layer, thereby accommodating the heat exchange between these two layers. However, the predominant nature of non-stationarity in the observations of climate variables poses challenges for standard statistical inference.

This study maps the two-component EBM into a versatile linear state space system (named EBM-SS model) of temperatures in the mixed layer and in the deep ocean layer with radiative forcing. This EBM-SS model allows for the modeling of non-stationarity and time-varying behaviors, the incorporation of multiple alternative variables for one object of interest, and the handling of missing observations. It opens up the possibility to couple with other frameworks to identify the drivers underlying the temperature evolution while maintaining consistency with physical theory. We decompose the latent state of radiative forcing, which is exogenous in this system, into a smooth component and a rough component. The smooth component is modeled as a random walk process with drift to represent the deterministic and stochastic trends of radiative forcing, while the rough component captures the transitory episodes in forcing following major volcanic eruptions.

We conduct an empirical analysis on data series at the global level from the period 1955 -- 2019, where the maximum likelihood estimates of the physical parameters are obtained via outputs from the Kalman Filter. We employ proxy variable for the temperature in the deep ocean layer, which is an integral quantity of the ocean temperature and represents the heat storage in the ocean.
Plate tectonics: what, where, why, and when?
Authors: Palin Richard , Santosh M.
Published: March 2021

The theory of plate tectonics is widely accepted by scientists and provides a robust framework with which to describe and predict the behavior of Earth’s rigid outer shell – the lithosphere – in space and time. Expressions of plate tectonic interactions at the Earth’s surface also provide critical insight into the machinations of our planet’s inaccessible interior, and allow postulation about the geological characteristics of other rocky bodies in our solar system and beyond. Formalization of this paradigm occurred at a landmark Penrose conference in 1969, representing the culmination of centuries of study, and our understanding of the “what”, “where”, “why”, and “when” of plate tectonics on Earth has continued to improve since. Here, we summarize the major discoveries that have been made in these fields and present a modern-day holistic model for the geodynamic evolution of the Earth that best accommodates key lines of evidence for its changes over time. Plate tectonics probably began at a global scale during the Mesoarchean (c. 2.9–3.0 Ga), with firm evidence for subduction in older geological terranes accounted for by isolated plate tectonic ‘microcells’ that initiated at the heads of mantle plumes. Such early subduction likely operated at shallow angles and was short-lived, owing to the buoyancy and low rigidity of hotter oceanic lithosphere. A transitional period during the Neoarchean and Paleoproterozoic/Mesoproterozoic was characterized by continued secular cooling of the Earth’s mantle, which reduced the buoyancy of oceanic lithosphere and increased its strength, allowing the angle of subduction at convergent plate margins to gradually steepen. The appearance of rocks during the Neoproterozoic (c. 0.8–0.9 Ga) diagnostic of subduction do not mark the onset of plate tectonics, but simply record the beginning of modern-style cold, deep, and steep subduction that is an end-member state of an earlier, hotter, mobile lid regime
Effect of forest management on the formation and stability of phytolith and PhytOC in forest ecosystem
Authors: Xu Lin , Shi Yongjun , Lv Wanjie , Niu Zhengwen , Yuan Ning , Zhou Yufeng
Published: March 2021

Forest ecosystem has a high carbon sequestration capacity and plays a crucial role in maintaining global carbon balance and climate change. Phytolith-occluded carbon (PhytOC), a promising long-term biogeochemical carbon sequestration mechanism, has attracted more attentions in the global carbon cycle and the regulation of atmospheric CO2. Therefore, it is of practical significance to investigate the PhytOC accumulation in forest ecosystems. Previous studies have mostly focused on the estimation of the content and storage of PhytOC, while there were still few studies on how the management practices affect the PhytOC content. Here, this study focused on the effects of four management practices (compound fertilization, silicon fertilization, cut and control) on the increase of phytolith and PhytOC in Moso bamboo forests. We found that silicon fertilization had a greater potential to significantly promote the capacity of carbon sequestration in Moso bamboo forests. this finding positively corresponds recent studies that the application of silicon fertilizers (e.g., biochar) increase the Si uptake1 to promote phytolith accumulation and its PhytOC sequestration in the plant-soil system2. Of course, the above-mentioned document2 also had their own shortcomings, i.e., the experimental research time was not long, lacking long-term follow-up trial and the bamboo forest parts were also limited, so that the test results lack certain reliability. We have set up a long-term experiment plot to study the effects of silicon fertilizer on the formation and stability of phytolith and PhytOC in Moso bamboo forests. But anyway, different forest management practices, especially the application of high-efficiency silicon-rich fertilizers1, may be an effective way to increase the phytolith and PhytOC storage in forest ecosystems, and thereby improve the long-term CO2 sequestration capacity of forest ecosystems. Research in this study provides a good "forest plan" to achieve their national voluntary emission reduction commitments and achieves carbon neutrality goals for all over the world.

Refences:

1Li et al., 2019. Plant and soil, 438(1-2), pp.187-203.

2Huang et al., 2020, Science of The Total Environment, 715, p.136846.
Downscaling CESM2 in CLM5 to Hindcast Pre-Industrial Equilibrium Line Altitude for Tropical Mountains
Authors: Heavens Nicholas
Published: March 2021

Highland environments are rarely preserved in the geological record, particularly from as early as the Paleozoic Era. However, several stratigraphic locations are now known which definitely or potentially preserve such environments near the paleoequator during the Late Carboniferous and Early Permian Periods, during which the Earth was in the depths of an icehouse climate like that of the Pliocene and Pleistocene Epochs, the Late Paleozoic Ice Age (LPIA). Several of these locations contain evidence of mountain glaciation at altitudes below 2000 m, leading to questions about the significance of tropical mountain glaciation for global climate during this interval of geologic time. However, climate model simulations for the LPIA have not been able to simulate mountain glaciation like that inferred from the geological record, possibly because of low resolution, incorrect boundary conditions, or climate model bias resulting from incomplete representation of moist convective processes impacting tropical lapse rates. 

The overarching purpose of this study is to develop a climate modeling framework that enables the significance of mountain glaciation for global paleoclimate to be evaluated. Ideally, such a framework would allow low-resolution global model output to be downscaled to the scale of a mountain range to calculate the equilibrium line altitude and similar parameters, enabling evidence of mountain glaciation in the deep past to be used to constrain/tune the low-resolution global models. While this study was designed to inform a specific problem in deep time paleoclimate, its results are likely broadly applicable to assessing how well mountain glaciation is captured by global climate modeling of the past, present, and future.   

Here, I present a framework in which the CMIP6 pre-industrial control simulation for the Community Earth System Model version 2 (CESM2) at 0.9°x1.25° resolution is used to generate a data atmosphere for the Community Land Model version 5 (CLM5) run at 0.01° resolution in 10 tropical and 1 mid-latitude domain to study the surface mass balance over the domain. For computational reasons, glaciation is assumed to cover a small portion of each grid cell, but surface mass balance still can be evaluated. Topographic boundary conditions come from GMTED2010, but most other information is directly interpolated from the CESM2 simulation. CLM5 simulations require a fixed lapse rate to be assumed, which is varied in each CLM5 simulation across six different values. The CLM5 simulation output along with the mean tropical lapse rate in the CESM2 simulation is then used to evaluate the various biases of this framework in comparison with estimated pre-industrial equilibrium line altitudes for the studied domains.

This work is supported by the National Science Foundation (USA) under grant EAR-1849754. 
Impacts of miscanthus growth on soil carbon and water deficit
Authors: Shepherd Anita , Hastings Astley
Published: March 2021

Miscanthus x giganteus thrives on poor soils, requiring little or no farm operations except annual harvest, efficiently recycles nutrients into the rhizome at senescence to be reused the following season and has a high water efficiency compared to other arable crops.  As such it is a popular choice for bioenergy crop growers, it can thrive on waste land, or poor agricultural soils that cannot give sufficient economic returns for food crops in many areas of the world.

We present work to better understand the global potential for M x giganteus yields and impacts as a bioenergy crop grown in the 21st century under IPCC climate RCP 8.5 and using the MiscanFor bioenergy model, showing how bioenergy crops compare across different countries for dry matter yield, water use, and soil carbon. We also show the uncertainty of projections inherent in choosing input data and the sensitivity of the model.
Oral legend and geological evidence for a 16th century giant tsunami in Kiribati, central Pacific
Authors: Terry James , Karoro Robert , Gienko Gennady , Wieczorek Marta , Lau Annie
Published: March 2021

Within Oceania, the vast Central and Western Pacific (CEWEP) is an intriguing anomaly because of the scarcity of historical tsunami observations and the complete absence of dated palaeotsunami events.  This study establishes the first dated high-magnitude palaeotsunami event within the CEWEP region.  Both geological data and oral legend are presented for a palaeotsunami that struck remote Makin atoll in northernmost Kiribati towards the end of the 16th century.  Narration of the euhemeristic myth by the Wiin te Maneaba, traditional storyteller on Makin, offered important details supporting a tsunami hypothesis.  The legend preserves credible information surrounding the giant-wave origin of Rebua and Tokia, two prominent named subaerial reefblocks of megaclast size that were produced and transported shorewards away from the reef edge by the event.  The youngest U-Th age-dates for fossil coral samples in the reefblocks give a maximum age for the palaeotsunami of circa AD 1576.  Several far-field Pacific Rim and regional possibilities exist for tsunamigenesis.  These include subduction-zone seismicity and catastrophic volcanic eruption, both of which have been linked to late 15th century palaeotsunamis recorded elsewhere in the Pacific Islands.  Available evidence, however, suggests that the ~AD 1576 Makin event was more likely locally generated by tsunamigenic submarine slope failure associated with the giant arcuate bight structure that characterises the northern atoll rim.
A Hydrologist’s Guide to Open Science
Authors: Hall Caitlyn , Saia Sheila , Popp Andrea , Schymanski Stan , Drost Niels , Dogulu Nilay , van Emmerik Tim , Hut Rolf , Melsen Lieke
Published: March 2021

To have lasting impact on the scientific community and broader society, hydrologic research must be open, accessible, reusable, and reproducible. With so many different perspectives on and constant evolution of open science approaches and technologies, it can be overwhelming for hydrologists to start down the path towards or grow one’s own push for open research. Open hydrology practices are becoming more widely embraced by members of the community and key organizations, yet, technical (e.g., limited coding experience), resource (e.g., open access fees), and social barriers (e.g., fear of being scooped) still exist. These barriers may seem insurmountable without practical suggestions on how to proceed. Here, we propose the Open Hydrology Principles to guide individual and community progress toward open science. To increase accessibility and make the Open Hydrology Principles more tangible and actionable, we also present the Open Hydrology Practical Guidelines. Our aim is to help hydrologists transition from closed, inaccessible, not reusable, and not reproducible ways of conducting scientific work to open hydrology and empower researchers by providing information and resources to equitably grow the openness of hydrological sciences. We provide the first version of a practical open hydrology resource that may evolve with open science infrastructures, workflows, and research experiences. We discuss some of the benefits of open science and common reservations to open science, and how hydrologists can pursue an appropriate level of openness in the presence of barriers. Further, we highlight how the practice of open hydrology can be expanded. The Open Hydrology Principles, Practical Guide, and additional resources reflect our knowledge of the current state of open hydrology and we recognize that recommendations and suggestions will evolve. Therefore, we encourage hydrologists all over the globe to join the open science conversation by contributing to the living version of this document and sharing open hydrology resources at the community-supported repository at open-hydrology.github.io.
The Generic Mapping Tools and Community-Maintained Open Source Software
Authors: Wessel Paul
Published: March 2021

The Generic Mapping Tools (GMT; www.generic-mapping-tools.org) is a well-known set of software for the geosciences, in particular in the marine and solid earth disciplines. GMT is also a prerequisite for many other well-known software infrastructures, including USGS’s ShakeMap for near-real-time maps of ground motion and shaking intensity following significant earthquakes, MBARI/LDEO’s MB-System for multibeam processing and mapping of the seafloor, and Scripps Institution of Oceanography’s GMTSAR for radar interferometric analysis and imaging of crustal deformation. Today, GMT has tens of thousands of users all over the world and remains essential for many terrestrial and planetary data processing and map-making workflows. GMT began its life over 30 years ago when I was a graduate student, and it has enjoyed continuous US National Science Foundation funding since 1993. Leveraging this funding, GMT has succeeded in establishing itself as a collaborative Open Source community resource from the start. Many scientists globally, particularly European scientists, have been instrumental in designing, maintaining, and improving GMT since the early 2000s. As I and several of our core developers approach the end of our academic careers, the GMT team has been pondering how to preserve these collective investments and position GMT to remain an essential geoinformatics infrastructure well into the future. In response, we have made fundamental changes to how GMT works, enabling access to GMT modules from external interfaces such as MATLAB/Octave, Python, and Julia, simplifying user access to large global datasets, and extending our support for the Google Earth platform. However, the biggest impact delivered by the Fall 2019 release of GMT 6 is likely “modern mode”. Modern mode coexists with classic mode (the only previous mode) so that thousands of GMT 4 and 5 scripts will still run as expected. Furthermore, new users will start with modern mode and experience a much-simplified GMT scripting syntax. A new aspect of GMT made possible by modern mode is a greatly simplified animation production. It is clear to all scientists that animations make it easier to elucidate temporal or spatial changes, yet very few scientists create animations as they are traditionally the domain of experts. The GMT team aspires to make animations a task every scientist can do with ease. In this lecture, I will discuss the latest news on GMT, outline modern mode and the external environment access to our modules, highlight a few GMT animations, and present other aspects of our succession planning for strengthening the GMT community.