bluuebunny/crossref_metadata_2025 huggingface dataset:
Development real-time flood modelling technique reflecting regional characteristics of Jeju Island
Authors: Yoon Jungsoo , Hwang Seokhwan , Kang Narae , Seong Hoje , Park Changyeol
Published: March 2024

Jeju Island is located in the path of typhoons, making it an extremely vulnerable environment to natural disasters. The mountainous effect caused by Mt. Halla. increases the risk of flash flood in rivers and the impact of climate change is worsening the risk on Jeju Island. Nevertheless, its disaster prevention technology in Jeju Island have been relatively lacking, comparing inland areas in Korea. This study developed flood modeling technology that reflects the characteristics of Jeju Island to improve disaster prevention technology in the Jeju Island. First, we developed rainfall scenarios considering the spatial and temporal distribution characteristics of heavy storm in the Jeju Island. AWS data and radar data were used to consider rainfall spatio-temporal characteristics (rainfall amount, duration, movement, spatial distribution, etc.). Second, we used the real-time flood model using inundation and flood risk index developed by KICT(Korea Institute of Civil Engineering and Building Technology). The flood model uses distributed model on a 1km grid basis and environmental variables such as geology or slope related to runoff are set independently for each 1km grid.Acknowledgement : This work was supported by the Technology Development Program (20025869, Development of Safety Support Technology based on Real-Time Flood Risk Detection in Jeju Island) funded by the Ministry of the Interior and Safety(MOIS, korea) 
The impact of drought on the water-food nexus at the global scale
Authors: Rinaldo Tobia , Ridolfi Elena , Moccia Benedetta , Marconi Flavia , D'Odorico Paolo , Russo Fabio , Napolitano Francesco
Published: March 2024

The demand for farmland products is increasing worldwide, causing unprecedented stress on the global agricultural system and, consequently, on water resources. Here we analyse the impact of drought events on rainfed agriculture, a topical issue given the prolonged and severe drought events currently occurring around the world and thus including highly productive areas. We investigate the agricultural yields of key crops that represent 61% of the world’s production of proteins for human consumption (i.e. corn, wheat, rice, and soybeans). Our analysis spans from the early 1900s to 2022, allowing us to assess the total agricultural area under drought stress per year and the most vulnerable types of crops. We identify significant trends in the extent of agricultural land under stress, considering both historical and recent periods. This comprehensive analysis enables us to estimate the frequency of occurrences of crop-specific cultivated areas under stress over time, unravelling the pattern of drought impact on global agriculture.
Discrepant stress distributions around instability regions: A new view for earthquake nucleation zones prediction
Authors: Zhang Lin , Chen Jianye , Yu Bowen , Zhang Miao
Published: March 2024

It is believed that seismic failure conditions are sensitive to strain-softening behavior of nominal rock or fault gouge, and that precursors prior to a big earthquake (i.e., tectonic trains, water level changes, and Vp/Vs anomalies, etc) are provided by the acceleration of local slip. Previous studies of earthquake nucleation on laboratory faults show that the initiation of unstable fault slip is spatiotemporal dependent and consists of an interval of fault preslip (or creep) that localizes and accelerates to a dynamically propagating rupture. We pose that perturbation-type experiments can provide a natural condition to help analyze the potential mechanisms between instability events and the stress loading. In this study, we conducted three sets of double-direct shear experiments on a 300 mm long fault filled with gypsum-rich gouges, under normal stress of 10 MPa superimposed with perturbations of various amplitudes (i.e., 0-0.5 MPa) and a fixed frequency (0.1 Hz). The result showed that during each cycle of the stick slip behavior, the applied normal stress perturbations were redistributed along the fault zone as revealed by the along-fault strain measurement in the normal direction. As such, the fault can be divided into different zones characterized by varied coupling with respect to the applied perturbations. We found, coincidently, nucleation of the final instability, as revealed by the strain measurement in the shear direction, tended to occur at the boundary between the so-called strong and weak coupling zones (‘Transition Zone). Moreover, local normal stress near the nucleation zone also showed some weakening prior to the instability, which was similar to that seen in the local shear stress, and hereafter referred to as ‘normal failure’. Based on these observations, we proposed an empirical equation to fit the normal strain or stress data, giving the distribution of the coupling coefficient (c-value) and the anomaly (a-value) along the simulated fault. Finally, we applied the proposed equation to fit the water level data from 6 monitoring stations along the fault that hosted a nature earthquake (~ML 4). The fitting results predicted a Transition Zone, which was close to the hypocenter. In the end, we propose that this approach can be tested widely to natural observations of various precursory signals, especially those considered to be sensitive to fault-normal deformation (“dilatation” or “compaction”), such as water level, soil gas, and Vp/Vs anomalies. Hopefully, the results can shed some lights on the location of the earthquake nucleation zone. 
Oceanic turbulence observations from autonomous profiling floats
Authors: ten Doeschate Anneke , Juteau Jean-Phillipe , Wolk Fabian , Lueck Rolf
Published: March 2024

Turbulent mixing is the dominant driver in the exchange of oceanic properties across vertical layers and lateral fronts. However, oceanic turbulence is episodic and patchy which merits the expansion of observations over a wider range of spatial and temporal scales than is typically achievable with turbulence profilers deployed from ships. Autonomous platforms provide an opportunity to sample for longer periods of time, across a range of conditions and environments.
Experiments have been performed with turbulence sensors on autonomous profiling floats for more than a decade. More recent technological advancements, amongst which are enhanced sensor durability, downsized electronics, and reduction in power consumption, have facilitated the development of more specialized microstructure turbulence packages. Through the development of on-board data processing capabilities and data reduction schemes typically large volumes of data measured with microstructure sensors can be reduced to be suitable for satellite transmission.  
The turbulence sensor packages typically consist of fast probes to capture velocity and scalar fluctuations.  The microstructure velocity measurements result in direct estimates of the turbulent kinetic energy dissipation rate, using methods that are increasingly standardised. The analysis of microstructure scalar measurements remains subject to more variability. However, profiling floats used in the Argo program typically travel through the water at speeds favorable for the use of the scalar measurements to obtain indirect estimates of dissipation rates. Data from these platforms is therefore well suited for the further development of microstructure scalar analysis methods.
Here we will present an overview of results from test-and field data from profiling floats equipped with turbulence packages. Co-located microstructure temperature and velocity shear measurements are used to evaluate the suitability of the platforms, develop analysis methods for scalar microstructure measurements, and to validate the data reduction scheme.
Quantification and evaluation of TROPESS ozone trends
Authors: Pennington Elyse , Neu Jessica , Bowman Kevin , Miyazaki Kazuyuki , Osterman Gregory
Published: March 2024

We present an analysis of ozone data products retrieved from multiple satellite observations. Specifically, we highlight data from the TRopospheric Ozone and its Precursors from Earth System Sounding (TROPESS) project which is a NASA effort that provides retrievals of atmospheric ozone utilizing radiances from a variety of different satellite instruments. The multispectral retrievals of ozone utilize the Multi-Spectra, Multi-Species, Multi-Sensors Retrievals of Trace Gases (MUSES) retrieval framework to produce consistent estimations of ozone from different satellite radiances. TROPESS ozone data products are retrieved from the Atmospheric Infrared Sounder (AIRS), the Ozone Monitoring Instrument (OMI), the Cross-track Infrared Sounder (CrIS) instruments, and combinations of these satellites.Trends in ozone are presented and evaluated using records dating from 2002 to the present. Trends are investigated globally and regionally, and validated against ozonesonde measurements. We find that the magnitude of ozone vertical profiles and columns agree between satellites to a high degree, but we are still investigating the trends seen in the different data sets. We investigate the causes of these differences between satellites, including instrument type and vertical sensitivity of the retrievals. We show ongoing work investigating comparisons between the TROPESS ozone data products, chemical reanalysis products using the MOMO-Chem framework, other satellite products, and ground-based observations, as well as trends in ozone precursors.
Investigating Quaternary climate sensitivity to orbital variations using an energy and moisture balance climate model.
Authors: Gunning Daniel
Published: March 2024

A comprehensive understanding of what caused the repeated growth and decay of northern hemisphere ice sheets (otherwise known as glacial-interglacial cycles) during the Quaternary Period has remained allusive. The importance of changes in the Earth’s orbital parameters for ‘pacing’ these cycles is widely acknowledged. However, the transition from 41 kyr to quasi-100 kyr glacial-interglacial cycles at the Mid-Pleistocene Transition (MPT) occurs without any significant variations in the Earth’s changing orbit. Even the dominance of 41 kyr cycles in the Early Pleistocene is unusual, given the notable absence of strong 19 and 23 kyr precession cycles. Put simply, climatic precession is the orbital parameter that alters the time of the year when the Earth is closest to the Sun, which considerably influences the intensity of summer insolation. As summer insolation is considered critical for the growth and decay of northern hemisphere ice sheets according to Milankovitch Theory, it would be expected that precession cycles would strongly feature throughout the Quaternary. Explanations that account for this absence of strong precession cycles during the Early Pleistocene include an anti-correlation between summer insolation intensity and summer duration or the cancellation of out-of-phase precession cycles between the northern hemisphere ice sheets and Antarctica. Here, we introduce a zonally averaged energy and moisture balance climate model to investigate the response of the Quaternary climate system to changes in the Earth’s orbital parameters. The purpose of the model is to investigate these problems related to glacial-interglacial cycles of the Early Pleistocene. We present equilibrium simulations of the model for the pre-industrial period and the Last Glacial Maximum, to demonstrate the suitability of the model to study climate change on these large spatial and temporal scales of interest. In addition, we show the equilibrium and transient sensitivity of the model to changes in the Earth’s orbital parameters. Factors that influence the relative contributions of obliquity and precession on global temperatures and/or ice volume will be investigated in the context of the 41 kyr cycles of the Early Pleistocene.
Experimental Confirmation of Emergence of Fast- and Slow- Attaching Subpopulations from Identical Individuals Produces Non-Exponential Decreases in Colloid Concentrations with Distance from Source under Unfavorable Conditions
Authors: Ullauri Luis , Johnson William , Bolster Diogo , Al-Zghoul Bashar
Published: March 2024

The cause of non-exponential decreases in colloid concentrations with distance from source was posited to derive from the emergence of fast- and slow- attaching populations from identical individuals (Johnson, 2018).  Fast-attachers were posited to attach according to a rate coefficient corresponding to favorable conditions, whereas the remainder of the population were posited to attach according to a slower rate coefficient.  This talk demonstrates the emergence of fast- and slow- attaching populations in pore network transport experiments under unfavorable conditions.  We explain the segregation into two subpopulations as being driven by colloid-surface repulsion, topological impacts of the flow field (incomplete pore scale mixing), and consequent impacts on the number of interceptions incurred prior to attachment. 
Observations of Io with the Juno Microwave Radiometer:  First Results and Implications for Global Heat Flow
Authors: Brown Shannon , Bolton Scott , Levin Steve , Zhang Zhimeng , Siegler Matthew , Feng Jianqing
Published: March 2024

The NASA Juno mission performed two close fly-bys of Jupiter’s moon Io on December 30, 2023 and February 3, 2024. Juno carries a 6-channel microwave radiometer (MWR) operating between 0.6-22 GHz. The first fly-by observed Io’s north pole and the 2nd pass mapped latitudes within +/- 45o on the Jovian facing hemisphere. The broad frequency range of the MWR probes successively deeper into the Io sub-surface with the 0.6GHz channel probing the deepest.  The sub-surface temperature, dielectric and surface roughness properties are encoded in the spectra obtained by the MWR. Here we report on the first spatially resolved observations of Io at frequencies below 22 GHz.  We find the brightness temperatures decrease with increasing latitude and are coldest at the north pole, consistent with prior infrared observations of the surface skin temperature. We observe a strong spectral gradient in the lowest frequency channels (increasing with depth) reflecting the sub-surface temperature profile from which we can infer endogenic heat flow. We will give an overview of the MWR observations and initial inferences about the sub-surface thermal and compositional properties.    
Large-scale climate variability behind the wave energy extremes in the Yellow Sea during an unusual season
Authors: Lee Dong Eun , Kim Hye-Ji , Yoo Jeseon , Baek Haedo
Published: March 2024

The Yellow Sea (YS) is exposed to various weather systems, such as typhoons, monsoon activities, and extratropical cyclones, which can pose  a major threat to the adjacent coastal regions through the development of powerful oceanic surface waves. Unusually severe surface wave events in the YS occur with considerable frequency during the boreal spring (March-April-May), but have received less attention compared to winter and summer. This study focuses on the characteristics of spring extreme wave events in the YS, based on observational and long-term reanalysis datasets. Our analysis shows that the extreme waves, defined as waves with a daily maximum height in the upper 5% of all springs, start to build up about 12 hours before the peak waves and continue for a longer period after the peak have been reached. During the extreme events, the Siberian High is found to extend anomalously eastward compared to spring climatology. Such an anomalous extension contributes to the increase of the sea level pressure gradient and the intensification of the surface wind speed in the YS. Meanwhile, in the range of 6~24 hours following the peaks of the extreme wave events in the YS, swells propagating from the far western North Pacific arrive in the YS. These swells from the western North Pacific, possibly generated by the same mesoscale system that has caused the extreme wave heights in the YS a few days in advance and has traveled northeastward, contribute to maintaining higher wave energy levels in the YS for longer after the atmospheric source has been removed. The large-scale environmental conditions can provide the predictability of extreme waves in the basin developed by these findings. Our analysis further reveals that more intense events tend to occur with eastward shift of the Siberian High, while the events occur more frequently with El Niños.  This study presents implications for assessing the risks associated with extreme waves in coastal regions and improving coastal management strategies in the YS.
Statistical correlations between geomagnetic activity and high-latitude TIDs investigated with the Tromso Dynasode
Authors: Negrea Catalin , Zabotin Nikolay , Echim Marius , Rietveld Mike
Published: March 2024

Travelling Ionospheric Disturbances (TID) and the underlying Atmospheric Gravity Waves (AGW) have long been associated with cases of extreme geomagnetic activity. This is especially true for geomagnetic storms that have been linked to large scale TIDs (LSTID). However, in the case of mid-scale TIDs (MSTID), a clear correlation has yet to be shown with geomagnetic activity, except for isolated cases. Such a correlation has been long suspected and assumed, since the mechanism by which these waves are generated must be linked to particle precipitation and localized heating, which occurs to some extent at all levels of geomagnetic activity due to the solar wind - magnetosphere - ionosphere coupling.Our study used 7 years of measurements from the Tromso dynasonde, specifically the electron density and ionospheric tilts height profiles. These are generally available at a 2-minute cadence and thus can be used to resolve the bulk of the gravity wave spectrum. The excellent height resolution of the data, as well as the directionality of the two ionospheric tilts allow us to quantify the TID activity using an estimator based on the power spectral density integral. This proxy for overall TID activity accounts for all waves from all sources: auroral, orographic, from tropospheric weather, etc. We then demonstrate the relative importance of auroral waves by showing that TIDs with a north-south propagating direction correlate very well with geomagnetic indices indicative of geomagnetic disturbances at high-latitude (the AE, Kp and Polar Cap Indices), while less so for the SYM-H index, which is more indicative of lower latitudes. Long-term correlations are discussed, with an emphasis on changes to the statistical distribution describing the correlation. Finally, a high-precision analysis was performed to pin-point the time-delay between geomagnetic and TID activity at Tromso. The results show a dominant population of TIDs characterized by a delay of 2-6 hours, with a secondary population with delays larger than 10 hours.
A multi-model analysis of the PMIP LGM AMOC
Authors: Sherriff-Tadano Sam , Klockmann Marlene , Kobayashi Hidetaka , Kapsch Marie , Liu Bo , Ivanovic Ruza , Abe-Ouchi Ayako
Published: March 2024

Simulating and reproducing the past Atlantic meridional overturning circulation (AMOC) with comprehensive climate models are essential to test the ability of models to simulate different climates. At the Last Glacial Maximum (LGM), reconstructions show a shoaling of the AMOC compared to modern climate. However, almost all state-of-the-art climate models simulate a deeper LGM AMOC. Here, we conduct a multi-model analysis using outputs from all PMIP phases (PMIP2 to PMIP4) to consistently explore the causes of this paleodata-model mismatch. The analysis focuses on the role of sea-surface temperature biases in the piControl simulation as well as changes in ocean temperature, salinity and density in each oceanic basin. We further compare the deepwater formation regions in each model and explore potential implications on the interpretation of paleodata-model comparison.
Stomatal conductance modeling: a novel leaf-scale mechanistic approach tailored for large-scale applications 
Authors: Chaput Amélie , Fatichi Simone , Pappas Christoforos
Published: March 2024

Understanding and predicting plant responses in current and future climates is vital due to tight land-atmosphere interactions from the local to global scales. More specifically, understanding how stomata respond to environmental stressors (e.g., lack of water, increasing CO2, extreme temperatures) is necessary, as they regulate water and carbon exchanges across the soil-plant-atmosphere continuum. Although a wealth of stomatal models exists, they still have limitations emerging, for example, by the underlying empirical assumptions or optimization-based hypotheses. These models are strongly hinged on observations, thus, hampering their scope in different environmental conditions. Indeed, the difficulty of balancing between the complexity of ecophysiological processes and the parsimony required in land surface and earth system models presents a challenge. Here, to address this, a novel mechanistic model is proposed that resolves basic ecophysiological functions while still being parsimonious and agile so it can be seamlessly integrated into larger-scale modelling frameworks. The model resolves guard and epidermal cells turgor, leaf hydraulic paths and gas diffusion through stomata, mesophyll conductance, and carbon assimilation (Farquhar model of photosynthesis) and includes explicitly the roles of both ABA and CO2 in regulating stomatal aperture. Published data on plant responses to different environmental variables, e.g., VPD, water stress, light, CO2, and temperature, were combined to parametrize and test the model capabilities in a range of different conditions. In addition, a global leaf gas exchange database was utilized as a further confirmation of the model skill to represent a wide range of stomatal responses under different environmental conditions.
Title: How Expansion and Contraction of Colloid-Surface Interactions Drives Rise and Fall of Repulsive Barriers and Stochastic Colloid Attachment
Authors: Johnson William
Published: March 2024

The magnitude of repulsive barriers is of primary importance in colloid transport and surface interaction.  Experimentally observed colloid retention typically decreases and increases with rises and falls of repulsive barriers in response to decreases and increases in solution ionic strength, respectively. However, despite the observation that colloid attachment increases as barriers decrease, the mean field barriers remain hundreds to thousands of times too large to explain attachment.  Incorporation of nanoscale charge heterogeneity amplifies the rise and fall of repulsive barriers via expansion and contraction of the zone of colloid-surface interaction around heterodomains in response to decreased and increased ionic strength, respectively. This amplified impact of nanoscale heterogeneity explains experimentally observed attachment and introduces a stochastic nature to attachment that underlies explanation of non-exponential decreases of colloid concentrations with distance from source.  This success in prediction highlights the need for further efforts to directly characterize nanoscale heterogeneity.
Ground magnetic survey on Mars from theZhurong rover
Authors: Du Aimin , Ge Yasong , Wang Huapei , Zhang Ying , Luo Hao
Published: March 2024

Mars’ magnetic field has been measured at large scale by orbiting spacecraft and at very small scale via Martian meteorites. Here we report on a ground magnetic survey on metre to kilometre scales. The Zhurong rover made vector measurements at 16 sites along a 1,089 m track in the Utopia Basin on Mars. It recorded an extremely weak magnetic field, with an order of the average intensity less than that inferred from orbit, in contrast to the large magnetic field in Elysium Planitia measured by InSight. A spacecraft measurement samples an area with radius comparable to its altitude, while a ground measurement samples an area with radius comparable to the depth of the magnetized body. The weak magnetic field measured by Zhurong indicates no magnetization anomalies for a depth of many kilometres around and below the rover’s traverse. We suggest two possible explanations for the weak magnetic field: the entire Utopia Basin may have remained unmagnetized since its formation about 4 billion years ago or that the 5-km-radius ghost crater where Zhurong landed may have been been demagnetized by impact.
Relationship and determinants of water and carbon dioxide (CO2) exchange in desert ecosystem, China 
Authors: Yu Tengfei , Han Tuo , Xi Haiyang , Li Baofeng
Published: March 2024

Knowledge on relationship and determinants of water and carbon dioxide (CO2) exchange is crucial to land managers and policy makers especially for the desertified land restoration. However, it remains highly uncertain in terms of water use and carbon sequestration for artificial plantation in desert. Here, the continuous water and carbon fluxes were measured using eddy covariance (EC) in conjunction with hydrometeorological measurements over an artificial C4 shrub, Haloxylon ammodendron (C. A. Mey.) Bunge, from July 2020 to 2021 in Tengger Desert, China. In the entirely 2021, evapotranspiration (ET) was 189.5 mm, of which 85% (150 mm) occurred during growing season, that was comparable with precipitation (132.2 mm) plus dew (33.5 mm) and potential other sources (e.g. deep subsoil water). This ecosystem was a strong carbon sink with net ecosystem production (NEP) up to 446.4 g C m-2 yr-1, which was much higher than surrounding sites. Gross primary production (GPP, 598.7 g C m-2 yr-1) was comparable with other shrubs but ecosystem respiration (Re, 152.3 g C m-2 yr-1) was lower. Random Forest showed that environmental factors can explain 71.56% and 80.07% variation of GPP and ET, respectively. However, environmental factors have divergent effect on water and carbon exchange, of which soil hydrothermic factors (e. g. soil moisture content and soil temperature) determine the magnitude and seasonal pattern of ET and Re, while aerodynamics factors (e.g., net radiation, atmospheric temperature and wind speed) determine GPP and NEP. As such, divergent response of abiotic factors resulted in the decoupling of water and carbon exchange. Our results suggest that H. ammodendron was a suitable species for large-scale afforestation in desert or desertification-prone region given its low water use but high carbon sequestration. Therefore, we concluded that artificial planting H. ammodendron in dryland could provide an opportunity for climate change mitigation, however, the long-term time series data would be needed to confirm it.
SWEET (Snow Water Equivalent Estimation Tool): A new tool to generate updated SWE estimates for poorly monitored regions
Authors: Schauwecker Simone , Ayala Álvaro , Cortés Gonzalo , Yáñez Eduardo , MacDonell Shelley , Goubanova Katerina , Orrego Cristian
Published: March 2024

In the dry Chilean North, the impact of the mountain snowpack on freshwater availability in the adjacent lowlands areas is crucial. The correlation between the snow water equivalent record and regionally averaged river discharges suggests that ~85% of the streamflow variance could be explained by the snowpack record alone. As seasonal snow cover depends on few winter events, there is a large year-to-year variability in the snow water equivalent (SWE). Typically, there are some dry years with very low annual precipitation which are compensated by wet years. However, since around 2010, the almost continuous extraordinarily dry conditions (so-called Central Chile “mega drought”) and increased water consumption in the region have led to significant stress on the water system. Hence, for an efficient water allocation and water management, it is crucial to know the actual SWE stored in the mountain snowpack. Until now, decisions have been based on scarce point measurements of the SWE or snow area estimates from MODIS. A drawback of these estimates is the large uncertainty that hampers efficient water allocation with important implications for water security of different sectors such as hydropower, agriculture and domestic use. To address this problem, we have developed a new operational SWE Estimation Tool for water resources decision making in the Coquimbo region (SWEET-Coquimbo), able to estimate current SWE in near real-time with a latency of ~10 days. SWE is estimated using a data assimilation framework that combines bias-corrected meteorological forcing ensembles from reanalysis data (ERA5, 5-day latency), hydrological modeling (Snowmodel) and satellite observations (Landsat) of the snow-covered area. SWEET-Coquimbo is placed in an open-access web platform, visualizing the current state of the SWE of five main catchments. The data can be downloaded and used for research and diagnostic purposes. The newly generated data show SWE for the period 2000-2023. We can now better understand the response of the regional snow cover to the Central Chile megadrought on snow cover and general trends in SWE over the last two decades. SWEET-Coquimbo has allowed, for the first time, a catchment-based estimation of the water available from the snowpack, which can now be used to improve seasonal runoff forecasts. Furthermore, our method has a great potential to be validated and applied to other mountainous regions with sparse in-situ data, as it does not rely directly on in-situ data.
Validation of seismic bedload saltation model: From laboratory flume to field-scale experiments
Authors: Chao Wei-An , Hung Chi-Yao , Chen Yu-Shiu
Published: March 2024

Reliable bedload flux estimations are necessary for a variety of applications such as sedimentation engineering, flood risk mitigation and river restoration. Several seismic physical models with considering different bedload transport mechanisms have been proposed, which provided an opportunity to have quantitative observation in practical. However, a lack of direct measurements of bedload fluxes in field application cause a challenge for the validation of seismic models. In the practical application, the bedload impact kinematics (elasticity and velocity) and particle dynamics assumed in models are crucial for achieving high accuracy in bedload inversion. In-situ seismic parameters such as shear-wave velocity and seismic quality factor are also required to reduce the uncertainty in model prediction. Thus, this study first conducts bedload transport experiments in a flume laboratory to understand the kinematics and mechanics of particle transport by using the smart rock embedded with accelerometer and gyroscope, geophone and hydrophone. For the field-scale experiments, we further studied distributed acoustic sensing (DAS) measurement during the experiments, which can record the dynamic strain in fiber optic cable under riverbed. Both case of laboratory flume and field-scale experiments, we will evaluate the performance of the different physical models by comparing in-situ measurements of bedload mass and impact forces recorded by the smart rock. In the case of field experiment, we adopted the active and passive seismic surface wave exploration to investigate the properties of wave propagation and attenuation. The effect of the process of rolling and/or sliding particles, as opposed to saltating particles, contributing in seismic signal generation, was also explored.   
A Bayesian transdimensional approach to estimate temporal changes in the b-value distribution without truncating catalogs
Authors: Laporte Marine , Durand Stéphanie , Gardonio Blandine , Bodin Thomas , Marsan David
Published: March 2024

The frequency/magnitude distribution of earthquakes can be approximated by an exponential law whose exponent is the so-called b-value. The b-value is routinely used for probabilistic seismic hazard assessment. In this context we propose to estimate the temporal variations of the b-value together with its uncertainties. The b-value is commonly estimated using the frequentist approach of Aki (1965), but biases may arise from the choice of completeness magnitude (Mc), the magnitude below which the exponential law is no longer valid. Here we propose to describe the full frequency-magnitude distribution of earthquakes by the product of an exponential law with a detection law. The latter is characterized by two parameters, μ and σ, that we jointly estimate with b-value within a Bayesian framework. In this way, we use all the available data to recover the joint probability distribution for b-value, μ and σ. Then, we extend this approach for recovering temporal variations of the three parameters. To that aim, we randomly explore with a Markov chain Monte Carlo (McMC) method in a transdimensional framework a large number of time variation configurations of the 3 parameters. This provides posterior probability distributions of the temporal variations in b-value, μ and σ.  For an application to a seismic catalog of far-western Nepal, we show that the probability distribution of the b-value remains stable with larger uncertainties during the monsoon period when the detectability decreases significantly . This confirms that we can see variations in the b-value that are independent of variations in detectability. Our results can be compared with the results and interpretations obtained using the b-positive approach. We hope that further applications to real and experimental data can provide statistical constraints on the b-value variations and help to better understand the physical meaning behind these variations.
A critical review of coastal retreat in the USA 
Authors: Young Robert , Coburn Andrew , Peek Katie , Tormey Blair , Thompson Holli
Published: March 2024

There are very few examples of managed retreat in the coastal zone of the USA. Those that exist are primarily the last, desperate acts for communities with limited financial resources (e.g., Isle de Jean Charles, Louisiana and the Blue Acres Program in New Jersey). The vast majority of retreat in the coastal United States is either completely unmanaged with some government assistance at the household level, or autonomous relocation driven by economic factors like the inability to rebuild following a storm or lack of insurance. Surprisingly, those properties at greatest exposure to storms (those in resort communities along the oceanfront) have almost no history of retreat. Retreat/relocation in the American coastal zone occurs almost entirely inland in working class and underrepresented communities. The explanation for this dichotomy is simple, coastal protection in the USA is funded largely by the public sector and based almost entirely on a cost/benefit analysis that considers only property values. If your property values are high, you are typically offered protection through coastal engineering like beach nourishment. If your property values are modest, you will be left to find your own solution to the hazards you face. If you are lucky, there may be some assistance available to raise or buyout your home, but this happens in a way with very little planning or foresight. In the United States, even the suggestion of managed retreat from the oceanfront is typically dismissed as too expensive to implement or too harmful to the economic prosperity of the community. In an effort to argue for the consideration of retreat as a reasonable option for the expenditure of public funds on the oceanfront, we have conducted a fiscal analysis of the cost of buying out highly-exposed, oceanfront investment homes rather than spending those same funds on long-term coastal protection. This analysis has recently been completed for portions of North Topsail Beach and Rodanthe, North Carolina where large-scale, coastal protection is planned. In both cases, the costs of large-scale buyouts are cheaper than the costs of long-term protection and a full consideration of lost tax revenues from the removed/relocated structures. Furthermore, the fiscal analysis does not include many unquantifiable benefits from the proposed targeted acquisition. These are things like transfer of amenity value to other properties, reduced emergency management costs for the municipality, reduced need for consulting engineering fees, improved beach access for all residents and renters, and significant environmental benefits for the beach/dune system. Ultimately, it is our hope that funds used in a more efficient manner for investment properties on the oceanfront could result in greater availability of funds to assist those in residential communities that have a far greater need for a well-managed response to rising sea levels and future storms.
Insights into Post-Fire Dynamics: Evaluating Short-Term Vegetation Recovery During Mega Drought in Central Chilean Mediterranean Forests
Authors: Hernandez-Duarte Ana , Saavedra Pimentel Freddy
Published: March 2024

Native forest landscapes globally face unprecedented challenges due to land use changes and climate changes, impacting terrestrial biodiversity conservation. Despite efforts to control forest loss, fragmentation, and degradation, uncertainty persists regarding the effects of climate change on forest dynamics, including shifts in productivity, species composition, and disturbance patterns. This study focuses on the Mediterranean ecosystems in Central Chile, known for their resilience to stressors like drought and wildfires. However, changing disturbance regimes in recent decades have tested their adaptive mechanisms. Understanding the effects of new disturbance regimes and their interactions on forest recovery is crucial, particularly in poorly studied ecosystems like the Mediterranean region in South America. Using remote sensing-based vegetation indices, we analyzed short-term (5-year) vegetation recovery after wildfires in Central Chile during the Mega Drought period (2010-2022) and compared it with two preceding decades (1992-2009). Normalized Difference Vegetation Indices (NDVI) were employed, and environmental variables, including climate, topography, and burn severity, were considered to model post-fire recovery from Random Forest models. Drought duration emerged as the most influential factor negatively affecting post-fire vegetation recovery, particularly in hillside areas. Fire severity showed a complex relationship with recovery, positively correlated in humid years but negatively in dried years. Our findings emphasize the critical role of drought in shaping post-fire vegetation recovery in Mediterranean forests. With the ongoing Mega Drought in Central Chile, understanding these dynamics becomes paramount for adaptive management. The study underscores the importance of comprehensive remote sensing monitoring to assess ecological processes, model ecosystem vulnerability, and study climate and disturbance regime interactions. These insights are essential for developing effective strategies to protect and manage forest ecosystems in the face of changing environmental conditions.
Exploring the Development of Shear Wave Radial Anisotropy in the Lower Mantle due to Slab-induced Plume Generation from LLSVPs
Authors: Roy Poulami , Steinberger Bernhard , Faccenda Manuele , Dannberg Juliane
Published: March 2024

Seismic anisotropy, which involves directionally dependent wave propagation, is likely to occur in the lowermost few hundreds km of the mantle, especially at the edges of Large Low Shear Velocity Provinces (LLSVPs). This anisotropy may be indicative of significant deformation, potentially due to mantle flow interacting with the sides of these provinces or the generation of mantle plumes. In this study, we investigate subducted slab induced plume generation from an LLSVP boundary and the flow behaviour of the lower mantle using compressible 2-D and 3-D mantle convection models in the geodynamic modeling software ASPECT combined with mantle fabric simulation in ECOMAN. In our geodynamic simulation, we assume that the LLSVPs are chemically distinct piles with intrinsically high viscosity. We use the Clapeyron slope of the phase transition from Bridgmanite to post-Perovskite from the previous mineralogical study by Oganov & Ono (2004) in the mantle fabric calculation. Modeling lattice preferred orientation of Bridgmanite and post-Perovskite in the lower mantle reveals that the lower mantle is overall isotropic except the regions of plume conduits and the surroundings of the subducted slab where vertically polarized shear wave (Vsv ) is faster. The generation of anisotropy are caused by the accumulation of high finite strain in these regions. The bottom 300 km of the lower mantle is characterized by fast horizontally polarized shear wave (Vsh ) beneath the subducted slab which deflects to fast Vsv at the margins of the LLSVPs due to the rheological contrast between the highly viscous LLSVP and less viscous ambient mantle. Our result shows that six possible slip systems [100](010), [100](001), [010](100), [001](100), [110](-110) and [-110](110) of Bridgmanite and the slip system [100](001) of post-Perovskite can produce a fast Vsv in the plume generation zones where post-Perovskite transforms to Bridgmanite and fast Vsh at the base of the subducted slab where post-Perovskite is preserved in the D”. However, our models do not show anisotropy inside of the LLSVPs and the subducted slab, possibly because of their high viscosity. Our findings are comparable with the previous seismic observations beneath the Iceland plume where Vsv > Vsh and the slab-driven flow at the base of the mantle beneath the northeastern Pacific Ocean where Vsh > Vsv .
In-situ Weathering of Alluvial Sediments in the Southern Central Andes Recorded by Ground- and Space-Based Hyperspectral Reflectance
Authors: Crawford Henry , D'Arcy Mitch , Ruby Andreas , Schildgen Taylor , Martínez López Ana Laura
Published: March 2024

Alluvial fans comprise abandoned sedimentary surfaces undergoing physical and chemical weathering. While weathering pathways and kinetics have been described over seconds to decades, few field-based studies have quantified these processes in alluvial deposits over geologic timespans. We examine 14 alluvial-fan surfaces flanking the Sierra del Aconquija, southern Central Andes, which have ages between 3 and 320 ka as determined by cosmogenic nuclide exposure dating. These fans present an opportunity to study the evolution of alluvial sediments across late-Quaternary timescales; including silicate weathering pathways, products, rates, and sensitivity to known past climate changes. We use space- and ground-based hyperspectral reflectance measurements to characterize surface mineralogy, and we test whether in-situ weathering records signals of landform age and regional climatic history. We collect fan-surface reflectance using both a handheld spectroradiometer and the PRISMA hyperspectral satellite sensor. In both datasets, bridging several orders of magnitude in spatial scale, we detect spectral features indicative of changing quantities of primary minerals, clays, and iron oxides. These patterns suggest a gradual increase in absolute weathering with surface age, but at progressively slower rates over time. Superimposed on the long-term weathering kinetics, secondary minerals are generated in amounts and at rates that correlate systematically with ~23 kyr precessional cycles and millennial-scale climate perturbations.  We interpret that these alluvial fans are sensitive archives of past weathering, which was more pronounced during episodes of wetter and warmer climate. Furthermore, the surface signals are corroborated by the downward accumulation of iron oxide, as shown in soil profiles from four alluvial fan units which were spectrally scanned from the surface to below the weathering front. Our findings highlight the geomorphological applications of hyperspectral data for (i) quantifying weathering processes over 1-100 kyr timescales; (ii) developing novel chronometers for alluvial sediments; and (iii) recovering new palaeoclimate signals from terrestrial sedimentary archives.
Automatic determination of focal depth with the optimal period of Rayleigh wave amplitude spectra and uncertainty assessment in 3D velocity model
Authors: He Xiaohui , Zhang Peizhen , Ni Sidao , Wu Wenbo , Chu Risheng , Wang Yi , Zheng Kaiyue
Published: March 2024

Focal depth of earthquakes is essential for studies of seismogenic processes and seismic hazards. Surface waves are usually the strongest seismic phases at local and regional distances, and its excitation is sensitive to source depth. We observe that the optimal period (the period corresponding to the maximum amplitude) of Rayleigh waves at local distances shows an almost linear correlation with focal depth, based on which we propose a method for resolving the focal depth of local earthquakes. We propose an automated data processing workflow, and applications to earthquakes in diverse tectonic settings demonstrate that reliable focal depth with uncertainty of 1~2 km can be determined even with one or a few seismic stations. Then, we use the Longmenshan region as a case study to systematically assess the impact of the 3D velocity model on the results through forward simulation. A total of 191 events at depths ranging from 5 to 20 km are simulated. The standard deviation between the focal depths determined by this method and the input values is approximately 1.5 km, with 95% events having errors within 2 times the standard deviation. This indicates that the method exhibits good applicability even in regions with complex velocity structures, and highlights the applicability of the method in scenarios characterized by sparse network coverage or historical events.
Present-day global patterns of the ocean carbonate pump and the key drivers of CaCO3 dissolution
Authors: Kwon Eun Young , Dunne John , Lee Kitack
Published: March 2024

Calcifying organisms produce calcium carbonate (CaCO3) shells and skeletons. When they die, biogenic CaCO3 is vertically exported from the euphotic zone and dissolves throughout the water column and in sediments. The alkalinity generated from this process can influence the ocean’s buffer capacity for absorbing atmospheric CO2. However, the magnitude and driver of surface CaCO3 export and subsequent dissolution in the ocean’s interior – a process called the carbonate pump – are highly uncertain. We present key drivers of pelagic CaCO3 dissolution constrained by an inverse ocean biogeochemistry model combined with multiple observation databases. Within the upper twilight zone (shallower than 300 m), we found a tight association between particulate organic carbon remineralization rates and the CaCO3 dissolution efficiency (the fraction by which the surface exported CaCO3 dissolves), which is further supported by the observed particle flux and concentration data. In the deep ocean (deeper than 300 m), dissolution of CaCO3 is primarily driven by conventional thermodynamics of CaCO3 solubility with reduced fluxes of CaCO3 burial to marine sediments beneath more corrosive North Pacific deep waters. Shallow CaCO3 dissolution, shown to be sensitive to ocean export production, can increase the neutralizing capacity for respired CO2 by up to 6% in low-latitude thermocline waters. Without shallow dissolution, the ocean might lose 20% more CO2 to the atmosphere through the low-latitude upwelling regions – the world’s largest area of CO2 outgassing in the contemporary climate. Our work identifies a previously overlooked sensitivity of oceanic CO2 uptake to the biological pump. We suggest that Earth system models need to include the respiration driven CaCO3 dissolution processes for a better projection of future oceanic carbon sink.