bluuebunny/crossref_metadata_2025 huggingface dataset:
The Early-Middle Pleistocene interglacials in the Iberian margin
Authors: Sanchez Goñi Maria Fernanda , Oliveira Dulce , Morales-Molino César , Desprat Stéphanie , Polanco-Martinez Josue M. , Hodell David , Naughton Filipa , Rodrigues Teresa
Published: March 2022

Interglacials older than 450,000 years ago (ka) are still poorly documented at regional and global scale limiting our knowledge of the wide range of their potential variability and the understanding of the causes of such diversity. Here we present δ18O benthic foraminifera measurements along with sea surface temperature reconstructions and pollen data from IODP site U1385, collected during Expedition 339 « Mediterranean Outflow » on the southwestern Iberian margin, for the Early-Middle Pleistocene interglacials MIS 19, 17, 15 and 13 (~800 to 400 ka). The recorded vegetation and climate changes on land have been directly compared with changes in the eastern North Atlantic subtropical gyre and the global ice volume. This comparison reveals a different structure in the evolution of the Mediterranean forest during these interglacials. The highest forest development occurred during MIS 19e and 15e but in the middle part of MIS 13 (MIS 13c). In contrast with MIS 19, 15 and 13 marked by three more or less similar Mediterranean forest expansions, MIS 17 was characterised by one strong expansion in its middle part (MIS 17c), the strongest of the last 800,000 years, occurring just before the end of the Middle Pleistocene Transition, i.e. the establishment of the strong 100-kyr glacial cycles at ~700 ka.  The duration of the first forested phase was also variable depending on the interglacial with a length of ~12,000 years during MIS 19e and 15e, ~9,000 years for MIS 13c and as long as 16,000 years for MIS 17c. Interestingly, two Mediterranean forest expansions are recorded during two phases of ice growth, MIS 19b and 15b, indicating once more the decoupling between the evolution of global ice volume and the southern European environments. The comparison of the U1385 pollen record, located below 40°N, with sequences above 40°N, for example the Lake Orhid pollen record, shows that the structure and magnitude of the interglacials are different below and above this latitude. At Montalbano Jonico, southern Italy at 40°N, the forest expansion is also very strong (80%) during MIS 17 contrasting with the limited development in Lake Orhid. At this site, MIS 19 is further marked by a strong forest development contrasting with the limited expansion of the Mediterranean forest in SW Iberia.
On the influence of rotational processes on the tectonic activation of the Earth
Authors: Литвинова Тамара
Published: March 2022

The rotational hypothesis based on the idea of self-development of the Earth (synergetics) under the action of endogenous forces caused by spontaneously occurring processes is a direction combining the latest achievements in the field of studying the sources of forces and energy of tectonic activation of the Earth, including world transgressions and regressions, magnetic field generation and other phenomena. The basis of the hypothesis is the rotation of the Earth as variations of the rotational regime (Tyapkin K.F. et al. 2009). The manifestation of volcanism is directly connected with it. The rotation speeds of different parts of the Earth's crust are different: from zero at the poles to 1,700 kilometers per hour at the equator, as well as from zero at the center of the Earth to the same values on its surface. Different speeds of the Earth's rotation affect all processes, including ocean currents. Different speeds of movement of surface and deep waters, their different temperatures in combination with the movement of the planet itself, give a complex picture of the dynamic processes occurring inside and on the surface of the Earth. A very important factor is the structure of the earth's crust. A number of regularities are noted: the discharge of planetary stresses in the tectonosphere, accumulating in the process of changing the rotational regime of the Earth, the areas of tectonic-magmatic activation turned out to be unrelated to the features of the Earth's crust and the history of its development: their location on the Earth's surface is determined solely by the distance from the poles of its rotation, and the orientation of these areas by the direction of pole migration. The tectonic activation of the Earth is accompanied by the activation of magmatic activity. According to the New rotational hypothesis of structure formation, as a result of the tectonic activation of the Earth, occurring at least once during the geological era (galactic year), a fault system appeared in two opposite quadrants of the Earth's tectonosphere. Each system is represented by hierarchically subordinated faults of two mutually perpendicular directions, the mutual intersection of which forms the corresponding system of blocks. The presence of the described faults is demonstrated by survey maps of anomalous magnetic and gravitational fields on a scale of 1:2,500,000 of Russia.
Comparison of 3D surfaces from historical aerial images and UAV acquisitions to understand glacier dynamics: The Aneto glacier changes in 40 years
Authors: Vidaller Ixeia , Revuelto Jesús , Izagirre Eñaut , García Jorge , Rojas-Heredia Francisco , López-Moreno Juan Ignacio
Published: March 2022

Pyrenean glaciers have shown a marked area and thickness decrease in the last century, especially in the last decades, and currently are highly threatened by climate change. Out of the 39 glaciers existing in the Pyrenees in 1984, 23 very small glaciers remain in this mountain range, from which only four have more than 10 ha. Probably, the most emblematic glacier of these four is Aneto glacier as it is located in the North-East face of the highest summit in the Pyrenees, the Aneto peak (3404 m a.s.l.). This work presents the Aneto glacier surface reconstruction from aerial images obtained in 1981, and its comparison with the glacier surface obtained in 2021 with Unmanned Aerial Vehicles (UAV) images.

The 1981 and 2021 images have been processed with Structure from Motion (SfM) algorithms to reconstruct the Digital Surface Model (DSM) of the glacier and nearby terrain. Taking advantage of the accurate geolocation of the UAV images in 2021 (GPS with RTK/PPK surveying), the DSM obtained has a precise representation of the glacier surface. Oppositely the aerial images of 1981 lack precise geolocation and thus require a post-processing analysis. The aerial images of the '80s have been firstly geolocated with Ground Control Points (GCPs) of known coordinates within the study area (summits, crests, and rock blocks with unaltered position). After this initial geolocation, the DSM of 1981 was generated with SfM algorithms. Nevertheless, this DSM still lacks a geolocation accuracy. To allow a comparison between the 1981 and the 2021 DSMs, the glacier surface in 1981 was registered to the 2021 surface with an Iterative Close Point (ICP) routine in the surrounding area of the glacier. The technique described in this work may be applicable to other historical aerial images, which may allow studying glacier evolutions all over the world for dates without field observations.

The surface comparison generated with images that have a temporal difference of 40 years has shown the dramatic area and thickness loss of this glacier, with areas decreasing more than 68 m, and an average thickness reduction of 31.5 m. In this period, the glacier has reduced its extent by about a 60%. There is a recent acceleration in the rate of shrinkage if we compare these data with the obtained for the period 2011-2021, in which area loss reaches 15% and thickness reduction almost reaches 10 m. During the 1981-2021 period the shrinkage rate is 0.78 m thickness/year and 1.5% area/year, meanwhile, during the 2011-2021 period the shrinkage rate is 0.99 m thickness/year and 2.7% area/year.
Aftershocks of the announced underground nuclear tests conducted by the DPRK on 12.02.2013 and 06.01.2016 found by waveform cross correlation and confirmed by interactive analysis
Authors: Wang Haijun , Kitov Ivan
Published: March 2022

There was more than a dozen of aftershocks generated by the announced nuclear test conducted by the DPRK on September 3, 2017 (DPRK6) which were found in routine interactive analysis conducted by the International Data Centre. The first DPRK aftershock was found by the method of waveform cross correlation (WCC) on September 11, 2016 after the DPRK5. Dozens of aftershocks were found by cross correlation after the DPRK6 in addition to those found in the routine processing and then confirmed by IDC analysts. The set of robust aftershocks allowed to develop, test, and apply in the routine WCC processing the multi-master method. This method was consistently applied to seismic data at IMS stations KSRS and USRK collected since 2009. Many new aftershocks were found after the third (DPRK3) and the fourth (DPRK4) announced underground nuclear tests conducted by the DPRK on 12.02.2013, and 06.01.2016, respectively. The second DPRK test (25.05.2009) had no reliable aftershock hypotheses at the level of the method sensitivity and resolution. The largest aftershocks of the DPRK3 and DPRK4 could be interpreted as related to the cavity collapse process possibly followed by a chimney collapse, not reaching the free surface. The DPRK3 and DPRK4 aftershocks were confirmed by interactive analysis.
The quantity and quality of organic matter in the sediments of the Firth of Clyde: A new tool to assess the vulnerability of “blue carbon hotspots” in Scotland’s inshore waters.
Authors: Grant Rhiannon , Austin William EN
Published: March 2022

The UK and Scottish Governments have committed to improve and preserve marine habitats including protecting 10% of Scottish waters through the creation of new Highly Protected Marine Areas (HPMAs). Within these commitments, an innovative management perspective was introduced where areas are proposed for protection based on their blue carbon value.  Understanding the physical properties of these environments and establishing evidence for their vulnerability to human impacts is therefore becoming increasingly important. This research identifies “blue carbon hotspots” in the Firth of Clyde. The Firth of Clyde is a sheltered fjord on the west coast of Scotland which has been fundamental to Scottish industry and fishing for hundreds of years. In this study, the vulnerability of these marine carbon stores from direct seabed disturbances is investigated to highlight areas most at risk of carbon loss due to human impacts. Elemental analysis of surface sediment samples were used to identify “blue carbon hotspots” across the basin. Furthermore, the carbon stored in different sediment types was determined using particle size analysis combined with existing broad-scale mapping of this region.  Thermogravimetric analysis indicated the stability of organic carbon within marine sediment providing a useful assessment of the quality of the carbon present. The impacts of benthic fishing (indicated by VMS data) were used to assess the existing pressures on these blue carbon stores together with MPA mapping and environmental properties (such as bathymetry and sedimentology). Mapping results produced in this research can be used in policy and decision making for the prioritisation of protecting blue carbon alongside other designation criteria for the protection of marine habitats in Scotland. Growing recognition of the climate benefits from protecting long-term natural carbon stores mean these findings can be integrated to highlight a blue carbon climate service in addition to implications for local and national management of marine habitats.
Polar Cap Boundary Reaction to Geomagnetic Storms
Authors: Raeder Joachim , Tulegenov Beket , Cramer William D. , Ferdousi Banafsheh , Fuller-Rowell Timothy , Maruyama Naomi , Strangeway Robert J.
Published: March 2022

It is well known that the polar cap, delineated by the Open
Closed field line Bound ary (OCB), responds to changes in the
Interplanetary Magnetic Field (IMF). In general, the boundary
moves equatorward when the IMF turns southward and contracts
poleward when the IMF turns northward. However, observations of
the OCB are spotty and limited in local time, making more
detailed studies of its IMF dependence difficult. Here, we
simulate five solar storm periods with the coupled
OpenGGCM-RCM-CTIM model to estimate the location and dynamics of
the OCB. For these events, polar cap boundary location
observations are also obtained from Defense-Meteorological
Satellite Pro- gram (DMSP) precipitation spectrograms and
compared with the model output. There is a large scatter in the
DMSP observations and in the model output. However, we generally
find good agreement between the model and the observations. On
average, the model overestimates the latitude of the open-closed
field line boundary by 1.61◦. Additional analysis of the
simulated polar cap boundary dynamics across all local times
shows that the MLT of the largest polar cap expansion closely
correlates with the IMF clock angle; that the strongest
correlation occurs when the IMF is southward; that during strong
southward IMF the polar cap shifts sunward; and that the polar
cap rapidly contracts at all local times when the IMF turns
northward.
Constraining the contribution of rock glaciers to the summer hydrology of a high-elevation watershed, Uinta Mountains, Utah, USA
Authors: Munroe Jeffrey , Handwerger Alexander
Published: March 2022

Rock glaciers are common components of mountain landscapes with strong potential to document past and present environmental changes, and a notable vulnerability to future climatic perturbations.  Recent studies have begun to consider the contribution of rock glaciers to high mountain hydrology, with a particular emphasis on the possible role of internal ice as a source of meltwater.  This project utilized automated samplers to collect water discharging from two representative rock glaciers in the Uinta Mountains of Utah, USA.  Additional samplers were deployed at a non-rock glacier spring and along the main stream in this basin.  All samplers ran continuously from the start of July through early October, 2021.  Water from the automated samplers, and from precipitation collectors, was analyzed for stable isotopes with cavity ring-down spectroscopy and hydrochemistry with ICP-MS.  Our findings reveal that water draining from the rock glaciers in mid-summer has a low solute content and notably negative δ18O, consistent with the melting of lingering snowpack.  As summer progresses, values of δ18O rise and total dissolved load increases as the influence of this snow-derived water wanes.  In late summer and early autumn, nearly all of the rock glacier discharge can be distinguished from snowmelt, summer precipitation, and groundwater by intermediate values of δ18O, elevated d-excess, and high abundances of Ca and Mg.  This water is interpreted to come from internal ice that was vulnerable to melting in this warm summer following a snow-poor winter.  The isotopic and hydrochemical fingerprint of this rock glacier discharge can then be used as an end-member, along with groundwater and summer precipitation, for unmixing of the late summer streamwater composition.  This exercise suggests that September discharge in the stream, with a watershed of ~50 km2 above the sampling point, contains a detectable component derived from melting internal ice of unknown age within rock glaciers.  An important implication of this conclusion is that late summer/ autumn baseflow in high-elevation streams could decrease in the future as this reservoir of subsurface ice is depleted, particularly in summers following low-snow winters.
Using AE based Machine Learning Approaches to Forecast Rupture during Rock Deformation Laboratory Experiments
Authors: Vinciguerra Sergio , King Thomas , Benson Philip
Published: March 2022

Parametric analysis of laboratory Acoustic Emission (AE) during rock deformation laboratory experiments has revealed periodic trends and precursory behaviour of the rupture source, as crack damage nucleates, grows and coalesces into a fault zone. Due to the heterogeneity of rocks and the different effective pressures, finding a full prediction of rupture mechanisms is still an open goal. We consider the AE rates and the derived source mechanisms to constrain the stress-strain regime, while scattering and seismic velocity structure define the evolving medium state as the most important attributes for the neural network model to learn. 4x10cm samples of Alzo granite were deformed at confining pressures of 5-40 MPa, whilst AE are recorded. Source mechanisms, as well as AE rates with relation to incremental strain, highlight distinct pre-failure phases. Scattering and seismic velocity measurements indicate the evolving mechanical conditions. A 10MPa simulation test on a model trained with data from 5, 20 and 40 MPa highlights good accuracy when predicting sample failure.

It remains a challenge to generate a ‘generic’ model that can be applied over all experimental conditions. Nonetheless, estimation of parameter importance has highlighted that some physical parameters are better for predicting strain, whilst others are better at stress. This importance can vary in time, suggesting a strong sensitivity of AE properties to the dynamic conditions of the fault zone. Small input changes can strongly affect output, therefore multiple models need to be trained in order to confirm the stability of the forecast. We aim to improve the understanding of the analysis through the search of repeating trends and the identification of consistent variations in key time-varying trends. Seismic scattering shows an early relevance, interpreted as due to the breakup of low frequency surface waves as microcracks begin to coalesce. However the reduction of importance at the later phases of deformation is less obvious. Further investigations are needed to identify at which deformation stage individual parameters are more important and segment time series accordingly.
Using seismology to probe the modern magma reservoir at Taupō volcano, Aotearoa New Zealand
Authors: Mestel Eleanor , Illsley-Kemp Finnigan , Savage Martha , Wilson Colin , Smith Bubs
Published: March 2022

Taupō volcano, in the centre of North Island, Aotearoa New Zealand, is a frequently active rhyolitic caldera volcano that was the site of Earth’s most recent supereruption (Oruanui ~25 ka)1,2. It has erupted 28 times since then, and continues to display signs of unrest (seismicity and surface deformation), with periods of elevated unrest on roughly decadal timescales3. Any resumption of eruptive activity at the volcano poses a major source of hazard, and interactions between the magma reservoir and the regional tectonics that lead to unrest and possible eruption are not well understood. The location of the modern magma reservoir has been previously constrained by study of past eruptive products and some geophysical imaging (gravity, broad-scale tomography)2. Earthquake patterns during a 2019 unrest episode have also been used to infer the location and size (>~250 km3) of the modern-day reservoir4, but its location and extent have not yet been directly imaged. As part of the interdisciplinary ECLIPSE project, seismological methods are being used to investigate the Taupō reservoir, combining data from the national GeoNet seismic network with records from a temporary 13 broadband seismometer network. Development of the ECLIPSE network approximately doubles the number of seismic stations within 10 km of the lake shore.

We present here initial results on the characterisation of the seismicity in the Taupō region. These results include the improvement of earthquake locations with the addition of picks from the ECLIPSE stations and the use of automated machine learning phase picking and association techniques. We also present initial results from the cross correlation of ambient noise between stations in the ECLIPSE network for the use in ambient noise surface wave tomography, with many of the station pairs crossing the region most likely to contain the modern-day magma reservoir.

1 Wilson CJN J. Volcanol Geotherm Res 112, 133 (2001)
2 Barker SJ et al. NZ J Geol Geophys 64, 320 (2021)
3 Potter SH et al. Bull Volcanol 77, 78 (2015)
4 Illsley‐Kemp F et al. G-cubed 22, e2021GC009803 (2021)
Strong Ocean Influence on Seasonal Changes in Shallow Shear-Modulus Structure in Alaska
Authors: Tanimoto Toshiro , Wang Jiong
Published: March 2022

We have developed a method to determine shear-modulus (rigidity) structure for the upper 20-50m of the Earth. The method is based on the analysis of co-located pressure and seismic instruments. We applied this method to about 200 (co-located) stations in Alaska and examined seasonal variation in shallow shear-modulus structure at each site; in this report we quantify this seasonal change by taking the ratio (R) of the highest shear-modulus to the lowest throughout a year and use it as a characteristic feature for each station.

R is smaller than 2 at many stations but there are some stations in and near the Arctic zone that have R larger than 10. Such a large seasonal change implies that there occurs massive melting of shallow permafrost and a significant development of the active layer every summer. As a side product, because of such a huge reduction in near-surface shear-modulus, horizontal amplitudes in seismic noise become 30 times larger in summer than amplitudes in winter.

These seasonal changes may not be surprising because thawing of ice is common every summer in the permafrost region. But regions with large R show a systematic geographic pattern on a large-scale map; large-R stations are typically found near the coast (ocean) and tend to decrease toward the interior of the continent (Alaska and NW Canada). Large R stations are found in the NW Territories in Canada, the North Slope region northern side of the Brooks Range, near the Seaward Peninsula (west), and the Yukon-Kuskokwim Delta (west). These locations suggest a strong influence by the nearby ocean on the climate at each station. Proximity to the ocean (coast) seems to be an important factor in evaluating periglacial hazards.

There are a few exceptions in the northernmost coastal stations as they show small R despite the fact that they are at the coast. But the ICEsat-2 (satellite) data show that sea ice seems to remain thick near the peninsula (near Barrow, Alaska) much longer than other coastal areas in this study; temperature is colder because of thicker sea ice and the amount of melting at these exception sites remains low. This would strengthen the hypothesis that near-coastal ocean has strong influence on the climate of continental interior.
Core drilling in a low altitude permafrost site from temperate regions. Case study: Detunata Goală, Romanian Carpathians
Authors: Popescu Razvan , Vespremeanu-Stroe Alfred , Vasile Mirela , Calisevici Sabina , Andrian Ilie
Published: March 2022

Detunata Goală scree is a talus slope-rock glacier system characterized by persistent snow and ice during springtime and summer in spite of a mean annual air temperature of around +7°C. This is a porous talus made of andesitic basaltic columns affected by chimney circulation that seems to allow for a extrazonal permafrost of low altitude in a temperate climate much lower than the regional limit of alpine permafrost. In the postdoctoral project FrozenCORE electrical resistivity tomography (ERT) and seismic refraction tomography (SRT) were applied in October 2020 in order to check permafrost presence at the end of the warm season and to determine the internal structure of the deposit. The two methods indicated contradictory results, as ERT indicated a high resistive layer in the first 10-15 m while the SRT indicated a high velocity layer at depths greater than 15 m. A borehole was drilled in June 2021 in the coldest sector of the scree and the cores recovered indicated that: 1) the talus is relatively thin, less than 13 m; 2) the deposit has a low amount of ice, several lenses were found between 3 and 10 m each of at most a few centimeters thick; 3) the scree porosity is relatively low, much smaller than at the surface. A thermistor chain was installed in the borehole at depths according to the GTN-P recommendations for future monitoring of the temperatures in the underground. Ice samples were collected from the cores for isotopic analyses in order to check if the ice from the greater depths is older than the upper one assumed to be seasonal. The drilling indicated that ERT is a better method for assessing the stratigraphy of such talus deposits.
The emission of near-fce harmonic waves at small radial distances from the Sun
Authors: F. Tigik Sabrina , Vaivads Andris , M. Malaspina David
Published: March 2022

Near-fce harmonic waves are prevalent in the high-frequency electric field spectrum during Parker Solar Probe's (PSP) close encounters with the Sun. These waves are electrostatic and tend to occur in regions of a relatively stable magnetic field with low broadband magnetic fluctuation levels. We show that the emissions of near-fce harmonic waves are strongly connected to the magnetic field direction. We express the magnetic field direction in terms of spherical angles, where θB is the elevation angle and φB is the azimuthal angle. Then, we show that near-fce harmonics emissions occur when the magnetic field points in a narrow angular range, bounded by 80° ≤ θB ≤ 100° and 10° ≤ φB ≤ 30°, in most of the cases. We also show that the influence of magnetic field direction on near-fce harmonic waves goes down to the shortest time scales the FIELDS instrument can access. These results suggest that cross-scale interaction might play an essential role in the dynamics of the near-fce harmonics measured by PSP at small radial distances from the Sun. It may also provide important clues about the origin of these waves and their role at the early stages of solar wind evolution.
Localized coastal subsidence in Miami Beach and Surfside, Florida
Authors: Wdowinski Shimon , Fiaschi Simone
Published: March 2022

We revisit our study of localized land subsidence in Miami Beach, which relied on SAR data from the 1990s (Fiaschi and Wdowinski, 2020) to detect changes in subsidence patterns and velocities. Our original study used ERS-1/2 data acquired during 1993-1999 and revealed that subsidence occurs in localized patches (< 0.02 km2) with a magnitude of up to 3 mm/yr. Most of the subsidence occurred in the western side of the city in urban areas built on reclaimed wetlands. We also detected one location of localized subsidence in the eastern part of the city, which centered at a 12-story condominium building. This building, Champlain's South Tower (CTS), collapsed on June 24th, 2021 resulting in the tragic death of 98 residents. The study revealed that the CTS slowly settled during the 6-years observation period (1993-1999), which may induce structural damage to the building, 20-30 years before the building’s collapse.

Following the tragic collapse of the CTS, societally important questions were raised by investigating teams, the media, and the public. In the current study we address some of these important questions:

Did the detected subsidence of the CTS in the 1990s have a differential component?

Did the CTS building continue subsiding after 1999?

Did other subsiding areas in Miami Beach continue to subside after 1999?

Did other areas in Miami Beach start subsiding after 1999? 

What is the significance of these findings?

The answer to the first question is based on a new post-processing of the ERS-1/2 solution, which revealed a small (0.5 mm/yr) differential component of the CTS building during 1993-1999. The answers to the next three questions were obtained from the analysis of Sentinel-1 data acquired during 2016-2021, which revealed a somewhat different subsidence field compared to the ERS-1/2 results. Finally, we used soil consolidation theory to explain the significance of the ERS-1/2 and Sentinel-1 results in terms of primary and secondary soil consolidation processes.
Enhanced Climate Data and Analyses for Africa
Authors: Dinku Tufa
Published: March 2022

The use of climate data in Africa for research and applications has been limited mainly due to poor availability of and access to quality climate time series. Weather stations are sparse, and their number has been declining over the last 50 years or so. Access to existing climate data is a challenge mainly because of national data policies, low financial investment, lack of dissemination capacity and tools, and high access costs. The Enhancing National Climate Services (ENACTS) approach led by the International Research Institute for Climate and Society (IRI) at Columbia University has been tackling this problem by working with National Meteorological Services (NMS) in Africa and in other developing countries. This initiative helps NMS to generate long time series of rainfall and temperature. This is accomplished by combining quality-controlled data from national observation networks with satellite estimates for rainfall and climate model reanalysis products for temperature.  This is done using the Climate Data Tool (CDT), which is an open-source software developed by IRI. CDT can be used for data organization, quality control, combining station data with satellite and reanalysis data, evaluating merged and inputs datasets, performing an array of analyses, and visualization.  In addition, ENACTS also enables users to perform climate analyses, including variability and extremes, through a user-friendly online mapping service (maproom). This approach has been implemented in about 20 countries in Africa, and a few countries in Asia and South America.
Filling GRACE Gaps Using GRACE-Derived Time Varying Model  
Authors: Mohasseb Hussein A. , Abd-Elmotaal Hussein A. , Shen WenBin
Published: March 2022

Using time-variable gravity field models has recently become essential for studying the hydrology change, ice melting, Earth’s crust deformation, etc. One of the most successful missions for establishing the time-variable gravity field model is the Gravity Recovery and Climate Experiment (GRACE) mission and its successor GRACE-Follow On (GARCE-FO) mission. However, the eleven-month gap between the end of GRACE's life span and the start of GRACE-FO observations hinders the study continuation. This investigation is devoted to model the GRACE data using time-variable gravity field model employing a smart least-squares regression technique. The GRACE-derived time-variable gravity field model is validated first using available GRACE data used in the modeling technique (to measure the internal precision of the model) as well as using available GRACE data which have not been used in the modeling technique (to measure the external accuracy of the model). The assessment of the derived model has been carried out at two different levels in the frequency domain (through the harmonic coefficients and the degree variances) and in the space domains (through the total water storage change in Africa). The GRACE-derived time-variable gravity field model has then been used to fill in the GRACE/GRACE-FO gap. A comparison among the existing techniques of filling-in the GRACE gaps versus the derived technique within the current investigation is given and widely discussed. This study is supported by the National Natural Science Foundations of China (NSFC) under Grants 41874023, 41721003, 41631072.

Keywords: GRACE, GRACE-FO, Gravity, GRACE gap, TWS, Least square adjustment. 
Linking surface strain signals with frictional heterogeneity of the interface in a laboratory-scale subduction megathrust
Authors: Kosari Ehsan , Rosenau Matthias , Bedford Jonathan , Deng Zhiguo , Metzger Sabrina , Schurr Bernd , Oncken Onno
Published: March 2022

Geodetic, seismological, gravimetric, and geomorphic proxies have widely been used to understand the behavior of the shallow portion of subduction megathrusts and answer questions related to seismic asperities: Where are they located, and how large are they? How close are they to failure, and how strong are they coupled? Our current knowledge of the kinematics and dynamics of megathrust earthquakes is limited due to their offshore location, and that our observations only cover a fraction of one megathrust earthquake cycle. 

The frictional-elastoplastic interaction between the interface and its overriding wedge causes variable surface strain signals such that the wedge strain pattern may reveal the mechanical state of the interface. We here contribute to this discussion using observations and interpretations of controlled analog megathrust experiments highlighting the variability of deformation signals in subduction zones. To examine the interaction, we investigate seismotectonic scale models representing a seismically heterogenous interface and capture the model’s surface displacements by employing a “laboratory-geodetic” method with high spatio-temporal resolution. Our experiments generate physically self‐consistent, analog megathrust earthquake ruptures over multiple seismic cycles at laboratory scale to study the interplay between short-term elastic and long-term permanent deformation. 

Our results demonstrate that frictional-elastoplastic interaction partitions the upper plate into a trench-parallel and -perpendicular strain domain, experiencing opposite strain (contraction vs. extension) during the co- and interseismic phase of the seismic cycle. Moreover, the pattern differs in the off- and onshore segments of the upper plate. This implies that the seismic potential of the shallow (offshore) portion of the megathrust may be underrepresented if only onshore observations are included in the estimate. However, our models suggest that, in the case of strong frictional contrast (velocity weakening vs. strengthening) on the interface, the short-term, onshore strain pattern (dominated by elastic deformation) may suffice to map the frictional heterogeneity of the shallow interface along strike. Finally, the frictional heterogeneity of the shallow interface is well reflected by the permanent surface strain observed offshore and partially in the strain observed at the coastal region. The observed along-trench segmentation predicted by our models is reasonably compatible with short-term, elastic geodetic observations and permanent geomorphic features in nature.
Crustal deformation along the Tell Atlas of Algeria from joint multi-temporal InSAR, GPS results and seismotectonic analysis
Authors: Miloudi Sihem , Meghraoui Mustapha , Bagdi Souhila , Hasni Kamel , Kahlouche Salem
Published: March 2022

Northern Algeria experienced moderate and large earthquakes (with Mw > 6) during the last decades due to the convergence between the African and Eurasian plates. We conduct the joint analysis of multi-temporal SAR-dataset (1995 to 2021), combined with the GPS velocities (2007 to 2018) and seismotectonic studies in the Chlef-El Asnam and Zemmouri Mitidja regions of the Tell Atlas. The multidisciplinary approach adopted in this study has the advantage of integrating the interseismic (paleoseismology, tectonic geomorphology), the coseismic and postseismic (airborne geodesy) crustal deformation. The multi-temporal interferometry is performed using the standard method for persistent scatterers (StaMPS/MTI software) applied to ERS1/2, ENVISAT and Sentinel SAR images, all from C-band dataset on descending and ascending  orbits. The GPS velocities are modeled and re-interpreted  from previous works in order to fit the tectonic block sub-division and related major faulting geometry. The seismicity rate and associated major earthquakes such as the El Asnam in 10/10/1980 (Mw 7.1) and Zemmouri-Boumerdes in 05/21/2003 (Mw 6.8) mark the seismotectonic characteristics of the Tell Atlas. The achieved data analysis and results of the joint InSAR, GPS and seismotectonics reveal that large areas with active deformation undergo uplifting and shortening with a consistent tectonic, geodetic and seismicity rate ranging between 2 and 3 mm/yr.
Predicting Landslide Susceptibility in Cross River State of Nigeria using Machine Learning
Authors: Efiong Joel , Eni Devalsam , Obiefuna Josiah , Etu Sylvia
Published: March 2022

Landslides have continued to wreck its havoc in many parts of the globe; comprehensive studies of landslide susceptibilities of many of these areas are either lacking or inadequate. Hence, this study was aimed at predicting landslide susceptibility in Cross River State of Nigeria, using machine learning. Precisely, the frequency ratio (FR) model was adopted in this study. In adopting this approach, a landslide inventory map was developed using 72 landslide locations identified during fieldwork combined with other relevant data sources. Using appropriate geostatistical analyst tools within a geographical information environment, the landslide locations were randomly divided into two parts in the ratio of 7:3 for the training and validation processes respectively. A total of 12 landslide causing factors, such as; elevation, slope, aspect, profile curvature, plan curvature, topographic position index, topographic wetness index, stream power index, land use/land cover, geology, distance to waterbody and distance to major roads, were selected and used in the spatial relationship analysis of the factors influencing landslide occurrences in the study area. FR model was then developed using the training sample of the landslide to investigate landslide susceptibility in Cross River State which was subsequently validated. It was found out that the distribution of landslides in Cross River State of Nigeria was largely controlled by a combined effect of geo-environmental factors such as elevation of 250 – 500m, slope gradient of >35o, slopes facing the southwest direction, decreasing degree of both positive and negative curvatures, increasing values of topographic position index, fragile sands, sparse vegetation, especially in settlement and bare surfaces areas, distance to waterbody and major road of < 500m. About 46% of the mapped area was found to be at landslide susceptibility risk zones, ranging from moderate – very high levels. The susceptibility model was validated with 90.90% accuracy. This study has shown a comprehensive investigation of landslide susceptibility in Cross River State which will be useful in land use planning and mitigation measures against landslide induced vulnerability in the study area including extrapolation of the findings to proffer solutions to other areas with similar environmental conditions. This is a novel use of a machine learning technique in hazard susceptibility mapping.

 

Keywords: Landslide; Landslide Susceptibility mapping; Cross River State, Nigeria; Frequency ratio, Machine learning
Inertia-gravity wave diffusion by geostrophic turbulence: the impact of flow time dependence
Authors: Cox Michael , Vanneste Jacques , Kafiabad Hossein
Published: March 2022

The scattering of short inertia-gravity waves by large-scale geostrophic turbulence in the atmosphere and ocean can be described as a diffusion of wave action in wavenumber space. When the time dependence of the turbulent flow is neglected, waves conserve their frequency, which restricts the diffusion of energy to the constant-frequency cone. We relax the assumption of time independence and consider scattering by a flow that evolves slowly compared with the wave periods, consistent with a small Rossby number. The weak diffusion across the constant-frequency cone introduced by time dependence leads to a stationary energy spectrum that remains localised around the cone (specifically decaying as 1/σ5 with σ the angular deviation from the cone) corresponding to a small frequency broadening. We contrast our results with unbounded frequency broadening that arises for surface- or shallow-water waves.
Research on integrated modeling of a coupled regional water-food systems based on system dynamics
Authors: Wang Xinkui , Susnik Janez , Dong Zengchuan
Published: March 2022

Water resources supply is closely related to food production and economy development. The importance of such a complex system is increasingly recognized in academia and policy. An integrated System Dynamics Model for the water-stressed Loudi city in Hunan Province, China, assessing water balance, and agricultural yield and revenue to 2050, is presented. Considering the uncertainty of future inflows, the formulation of water supply policies, and changes in cropping regimes, this study simulated multiple scenarios to better understand the impacts on water, food, and economic security and their interactions to highlight Loudi's realization of potential pathways to a more sustainable future. Current water resource over-exploitation can be mitigated while still allowing for agricultural development. While most simulations hinted at continued over-exploitation, some suggested that improvements can be achieved by altering parameters such as per-capita domestic water demand, per-capita industrial water demand and the cropping regime. Relevant policies should be considered in parallel to introduce redundancy into the policy framework. From initial results, it is hypothesized that by producing excess crops, a virtual water trading market can be developed, thereby further improving water balance, yield and revenue. This study used system dynamics as a powerful tool to explore complex, feedback-driven water-food systems, providing a viable framework for water resource management approaches and policies at the regional scale.
Assessing the impact of weak and moderate geomagnetic storms on UK power station transformers
Authors: Wild James , Lewis Zoe , Allcock Matthew
Published: March 2022

It is well documented that space weather can impact electricity infrastructure, and several incidents have been observed in recent decades and directly linked to large geomagnetic storms (e.g. the Hydro Quebec incident in 1989). However, less is understood aboutthe impact of lower-level geomagnetically induced currents (GICs) on the health of transformers in the long term. In this study, the long term impact of geomagnetic activity  on 13 power station transformers in the UK is investigated. Dissolved gas measurements from 2010–2015 were used to look for evidence of a link between degradation of the transformer and heightened levels of the global SYM-H index and dB as measured at Eskdalemuir magnetometer station in southern Scotland. First, case studies of the most significant storms in this time period were examined using dissolved gas analysis (DGA) methods, specifically the Low Energy Degradation Triangle (LEDT). These case studies were then augmented with a statistical survey, including Superposed Epoch Analysis (SEA) of multiple storm events. No evidence of a systematic space weather impact can be found during this time period, likely owing to the relatively quiet nature of the Sun during this epoch and the modernity of the transformers studied.
Observation and prediction of a coastal rogue wave
Authors: Gemmrich Johannes , Cicon Leah , Holmes-Smith Carmen
Published: March 2022

Direct observations of rogue waves in high sea states are rare. However, rogue waves can pose a danger to marine operations, onshore and offshore structures, and beachgoers. Here we report on a 17.6m rogue wave in coastal waters with crest height about twice, and wave height almost three times the significant wave height. These are amongst the largest normalized heights ever recorded.

Simulations of random superposition of Stokes waves in intermediate water depth show good agreement with the observation, whereas non-linear wave modulational instability did not contribute significantly to the rogue wave generation. We present a spectral parameter that can easily be derived from a routine wave forecast as an indicator of rogue wave risk. These results confirm that probabilistic prediction of oceanic rogue waves based on random superposition of steep waves are possible and should replace predictions based on modulational instability. Furthermore, large individual waves offshore do not necessarily result in extreme runup on the beach.
Using Atmosphere and Ocean Angular Momentum for Earth Orientation 
Authors: Stamatakos Nicholas , McCarthy Dennis , Psiaki Mark , Salstein David
Published: March 2022

The accuracy and robustness to input data outages of near real-time estimates and short-term predictions of Earth orientation parameters (EOPs) may be enhanced by using atmosphere and ocean angular momentum data accounting for the global conservation of angular momentum in the Earth system. The US Navy Earth System Prediction Capability (ESPC) data that combines the motion and mass fields of the atmosphere angular momentum information from the NAVY Global Environmental Model (NAVGEM 1.2) with that of the ocean angular momentum information from the HYbrid Coordinate Ocean Model (HYCOM) provides a source that can be used to evaluate the nature of the possible contribution of these physical data to the operational determination of the EOPs.  The rates of change of the EOPs derived from the most recent angular momentum data are evaluated in comparison with observed values of polar motion and UT1-UTC rates from the IERS RS/PC EOP data series, and the stability of statistical models accounting for systematic errors in scaling and bias in the ESPC data was investigated.  Analyses of these data show good agreement and indicate the viability of the practical integration of the rate data alone as well as in combination with data from other techniques in the operational determination of EOPs. Two years of past ESPC data were analyzed to provide estimates of the possible precision of the resulting polar motion and UT1-UTC data.
Model performance in simulating the mid-Holocene Green Sahara
Authors: Tiwari Shivangi , Ramos Riovie , Pausata Francesco S. R. , LeGrande Allegra N. , Griffiths Michael L. , Beltrami Hugo , Chandan Deepak , de Vernal Anne , Litchmore Daniel , Peltier Richard , Tabor Clay R.
Published: March 2022

The Green Sahara Period, spanning about 11,500 to 5,000 years ago, offers an opportunity to test the ability of climate models to simulate large-scale changes in northern African climate through the strengthening of the West African Monsoon. In this study, we evaluate the performance of four models in simulating the mid-Holocene (6,000 BP), namely – EC-Earth, iCESM, CCSM4-Toronto, and the GISS ModelE2.1-G. Two scenarios are considered for each model – a standard PMIP scenario simulated with the mid-Holocene orbital parameters and greenhouse gas concentrations with vegetation prescribed to pre-industrial conditions, as well as a Green-Sahara scenario which additionally considers factors such as enhanced vegetation, reduced dust, presence of lakes, and land and soil feedbacks. All mid-Holocene scenarios capture an increase in monsoonal precipitation in northern Africa. However, a comparison of the two mid-Holocene scenarios reveals significantly higher precipitation in northern Africa for all the Green-Sahara scenarios relative to the PMIP scenarios – an observation consistent across all models. Accompanied by a strengthened Saharan Heat Low, these changes in the West African Monsoon are also linked to polar amplification, a stronger Indian Summer Monsoon and alterations to the Walker circulation. Model results are in agreement with pollen-based SAT records, multi-proxy SST records and African lake level records. This comparison indicates that a realistic simulation of the mid-Holocene Green Sahara requires consideration of multiple factors in addition to orbital and greenhouse gas forcings.