bluuebunny/crossref_metadata_2025_split huggingface dataset:
Finding SEIS North on Mars: Comparisons Between SEIS Sundial, Inertial and Imaging Measurements and Consequences for Seismic Analysis
Authors: Savoie D. , Richard A. , Goutaudier M. , Lognonné P. , Hurst K. J. , Maki J. N. , Golombek M. P. , van Driel M. , Clinton J. , Stutzmann E. , Mimoun D. , Banerdt W. B. , Williams N. R. 
Published: February 2021

AbstractIn this paper, we present the results obtained in the determination of the true north direction on Mars by using a gnomon on the InSight mission and compare the measurements with either the North determination from the Inertial Measurement Unit and imaging analysis. The obtained measurement has been used to populate the SEIS orientation information in the archived SEIS data. Images taken during December 2018 and January 2019 allow to determine the gnomon shadow position and length over a target. By calculating the Sun local coordinates using planetary ephemeris VSOP87, the images are used to estimate the true North direction on the landing site. By using eight different images selected, we obtain the true North direction with an accuracy up to 2.5°, which is confirmed by the IMU and imaging analysis. The true North direction is also confirmed by an image taken near local noon, when the sun crosses the meridian. The North determination precision is then discussed in view of the seismic determination of the back azimuth.
Period‐Multiplying Cycles at the Transition Between Stick‐Slip and Stable Sliding and Implications for the Parkfield Period‐Doubling Tremors
Authors: Mei Cheng , Barbot Sylvain , Wu Wei 
Published: February 2021

AbstractThe recurrence patterns of the Parkfield tremors with period‐multiplying slow and fast ruptures provide new insights on the physics of earthquake cycles. However, the mechanisms behind the peculiar recurrence pattern and the coupling between slow‐slip events and seismic radiations are still unclear. Here, we conduct direct‐shear experiments on polycarbonate and granite fractures under varying stress conditions to investigate the variations of rupture properties near the stability transition. Laboratory slow and fast ruptures sequences produce slip‐predictable period‐multiplying cycles with correlative acoustic energy release, stress drop, event duration, and recurrence intervals. However, gouge accumulation by damage of the granite fracture provokes changes in stiffness and stress drops ratios over multiple cycles, affecting the recurrence intervals and energy release of consecutive slip events. These findings confirm the link between low‐frequency earthquakes and underlying slow‐slip events, with period‐multiplying cycles naturally occurring near the stability transition.
The Summer Heat Balance of the Oregon Inner Shelf Over 2 Decades: Intraseasonal Variability
Authors: Lemagie E. , Kirincich A. , Lentz S. 
Published: February 2021

AbstractThis study examines the heat balance of the inner shelf along the US West Coast using 14 years of summer temperature and velocity observations in 15 m water depth. Previous work at this site found no year‐to‐year variability in the observed mean summer temperature change despite significant warming due to surface heat flux and variable cooling due to across‐shelf heat flux. Here, the processes that affect coastal water temperatures over time scales of days and months are investigated. Synoptic temperature variability (on time scales of several days) was predominantly due to the across‐shelf heat flux, as there was little synoptic variability in the surface heating and no evidence that an along‐shelf heat flux would close the two‐dimensional heat budget when the residual was large. The analyses suggest the across‐shelf heat flux was influenced by multiple mechanisms in addition to Ekman transport by along‐shelf winds. For example, there was a three‐layer vertical across‐shelf velocity structure 40% ± 10% of the time and during downwelling‐favorable winds there was an upwelling circulation 80% of the time. The across‐shelf heat flux was generally highest near the surface and bottom boundaries, where the velocity observations were most limited. The heat budget residual was positive most of the time, likely resulting from uncertainty due to the observational limitations. An improved understanding of the processes that control the across‐shelf heat flux and buffer temperature variability in the coastal ocean has the potential to improve predictions of coastal temperatures under climate change scenarios.
Evaluating the Relationship Between Lightning and the Large‐Scale Environment and its Use for Lightning Prediction in Global Climate Models
Authors: Etten‐Bohm Montana , Yang Junho , Schumacher Courtney , Jun Mikyoung 
Published: February 2021

AbstractThe objective of this study is to determine the relationship between lightning observed by the Tropical Rainfall Measuring Mission (TRMM) Lightning Imaging Sensor (LIS) and seven large‐scale environmental variables obtained from the 3‐hourly Modern‐Era Retrospective analysis for Research and Application version 2 (MERRA‐2) reanalysis in the tropics and subtropics. The large‐scale environmental variables used are: convective available potential energy (CAPE), normalized CAPE (nCAPE), lifting condensation level (LCL), column saturation fraction (r), 700‐hPa omega, low‐level wind shear (LS) from 900 to 700 hPa, and deep wind shear (DS) from 900 to 300 hPa. All environmental variables show a significant shift toward larger values when lightning is present except for shear. DS decreases when lightning is present, while LS shows little mean change. However, strong geographical differences exist in the relationship between the environmental variables and lightning occurrence, particularly between land and ocean and the tropics and subtropics. Using a logistic regression, a lightning parameterization for global climate models (GCMs) is created using the above environmental variables as predictors while also adding geographic indicators (coast, slope, and latitude) and terms representing interactions between the predictors. The logistic regression predicts lightning occurrence accurately up to 86% of the time and is further applied to MERRA‐2. While there are regions of overprediction and underprediction, the lightning parameterization performance shows promising potential for use in GCMs.
Numerical Simulation of Lunar Seismic Wave Propagation: Investigation of Subsurface Scattering Properties Near Apollo 12 Landing Site
Authors: Onodera K. , Kawamura T. , Tanaka S. , Ishihara Y. , Maeda T. 
Published: February 2021

AbstractOne of the most critical issues associated with the analysis of lunar seismic data is the intense scattering, which prevents precise seismic phase identifications, thereby resulting in poor constraints on the internal structure of the Moon. Although some studies estimated subsurface scattering properties from analyses of the Apollo seismic data, the properties have large uncertainties and are still open issues to be resolved to improve the inner structure model of the Moon. While the previous studies tried to constrain the scattering features within the lunar crust mainly from data analysis, this study estimated them from a numerical approach. We constrained the scattering properties near Apollo 12 landing site by conducting seismic wave propagation simulations under various parameter settings and comparing the synthetics with the data. As a result, we succeeded in reproducing seismic signals excited by the Apollo artificial impacts. This led to a constraint on the scattering properties, such as typical scale and thickness of heterogeneity, around the Apollo 12 landing site. The derived structure suggests that the intense scattering structure exists down to 20 km at the northern portion of the region of the Apollo 12 landing site, and to 10 km at the southern region from the landing site. In addition, our model requires a smaller P‐ and S‐wave velocity ratio (1.2–1.4) compared with those conventionally considered (>1.73). This implies a dry and porous environment consistent with laboratory measurements of terrestrial samples and reasonable with the generalized lunar environment.
Time, Hydrologic Landscape, and the Long‐Term Storage of Peatland Carbon in Sedimentary Basins
Authors: Large David J. , Marshall Chris , Jochmann Malte , Jensen Maria , Spiro Baruch F. , Olaussen Snorre 
Published: February 2021

AbstractPeatland carbon may enter long‐term storage in sedimentary basins preserved as either coal or lignite. The time required to account for the carbon in 1–10 m thick coal seams must represent 105–106 years, an order of magnitude more than previously assumed. To understand the process by which this happens requires extrapolation of our understanding of peatland carbon accumulation over timescales that greatly exceed those of Holocene peat. We analyze the consequences of extrapolating peat growth to periods of 106 years. We deduce that that key to sustained peat growth are hydrologic landscapes that can maintain a saturated peat body above the level of clastic deposition. Contrary to current stratigraphic frameworks, we conclude that the generation of accommodation space at low rates of 0.1–0.2 mm/yr can adequately accommodate thick peat accumulation over periods >105 years. However, generation of accommodation space at rates >0.5 mm/yr cannot. The low rates that permit accommodation of thick peat are typical of the rates of subsidence in specific tectonic settings, particularly foreland basins, and this has implications for our understanding of the links between terrestrial carbon burial, tectonics and the carbon cycle. The long‐term stability of extensive peatland required to form coal also requires sediment bypass, modifying basin wide sediment transport and deposition. Limits to peatland growth under very low accommodation rates must exist but the relative importance of the limiting process is not understood. Finally, we discuss the consequences of these factors for predicting the future of the peatland carbon reservoir.
Evolution of Coseismic and Post‐seismic Landsliding After the 2015 Mw 7.8 Gorkha Earthquake, Nepal
Authors: Kincey Mark E. , Rosser Nick J. , Robinson Tom R. , Densmore Alexander L. , Shrestha Ram , Pujara Dammar Singh , Oven Katie J. , Williams Jack G. , Swirad Zuzanna M. 
Published: February 2021

AbstractCoseismic landslides are a major hazard associated with large earthquakes in mountainous regions. Despite growing evidence for their widespread impacts and persistence, current understanding of the evolution of landsliding over time after large earthquakes, the hazard that these landslides pose, and their role in the mountain sediment cascade remains limited. To address this, we present the first systematic multi‐temporal landslide inventory to span the full rupture area of a large continental earthquake across the pre‐, co‐ and post‐seismic periods. We focus on the 3.5 years after the 2015 Mw 7.8 Gorkha earthquake in Nepal and show that throughout this period both the number and area of mapped landslides have remained higher than on the day of the earthquake itself. We document systematic upslope and northward shifts in the density of landsliding through time. Areas where landslides have persisted tend to cluster in space, but those areas that have returned to pre‐earthquake conditions are more dispersed. While both pre‐ and coseismic landslide locations tend to persist within mapped post‐earthquake inventories, a wider population of newly activated but spatially dispersed landslides has developed after the earthquake. This is particularly important for post‐earthquake recovery plans that are typically based on hazard assessments conducted immediately after the earthquake and thus do not consider the evolving landslide hazard. We show that recovery back to pre‐earthquake landsliding rates is fundamentally dependent on how that recovery is defined and measured. Clarity around this definition is particularly important for informing a comprehensive approach to post‐earthquake landslide hazard and risk.
The Impacts of a Subglacial Discharge Plume on Calving, Submarine Melting, and Mélange Mass Loss at Helheim Glacier, South East Greenland
Authors: Everett Alistair , Murray Tavi , Selmes Nick , Holland David , Reeve Dominic E. 
Published: February 2021

AbstractAlmost half of the Greenland ice sheet's mass loss occurs through iceberg calving at marine terminating glaciers. The presence of buoyant subglacial discharge plumes at these marine termini are thought to increase mass loss both through submarine melting and by undercutting that consequently increases calving rates. Plume models are used to predict submarine melting and undercutting. However, there are few observations that allow these relationships to be tested. Here, we use airborne lidar from the terminus of Helheim Glacier, SE Greenland to measure the bulge induced at the surface by the upwelling plume. We use these measurements to estimate plume discharge rates using a high‐resolution, three‐dimensional plume model. Multiyear observations of the plume are compared to a record of calving from camera and icequake data. We find no evidence to suggest that the presence of a plume, determined by its visibility at the surface, increases the frequency of major calving events and also show that mass loss at the terminus driven directly by plume discharge is significantly less than mass loss from major calving events. The results suggest that the contribution of direct plume‐driven mass loss at deep marine‐terminating glaciers may be less than at shallower termini.
Validation of the SMOS Mission for Space Weather Operations: The Potential of Near Real‐Time Solar Observation at 1.4 GHz
Authors: Flores‐Soriano M. , Cid C. , Crapolicchio R. 
Published: February 2021

AbstractSoil Moisture and Ocean Salinity (SMOS) is an ESA mission observing Earth at 1.4 GHz with full polarimetry. SMOS images are affected by a noise of solar origin produced by the Sun appearing in the antenna's field of view. In this paper, we study whether this solar signal is of any use for scientific and space weather observations. We analyze the response of the SMOS Sun brightness temperature (BT) to thermal and nonthermal solar emissions, and compare them with observations from ground radio telescopes, GOES X‐ray flares, and CMEs from SOHO/LASCO. We find that the SMOS Sun BT can detect weak variations in the solar emission such as the progress of the 11‐year activity cycle, the solar rotation, and the thermal emission from flares. Solar radio bursts detected by the SMOS Sun BT are generally observed during flares from the visible hemisphere of the Sun that are associated with a CME. We also find a correlation between the amount of solar flux released at 1.4 GHz and the speed, angular width, and kinetic energy of the CMEs. We conclude that the unique capability of the SMOS mission to perform 24 h near real‐time observation of the Sun with full polarimetry makes it a promising instrument for monitoring solar interferences affecting GNSS, radar, and L‐band wireless communications, as well as for early assessment of flares geoeffectiveness. Nevertheless, the current limitations of the solar data as byproduct of the SMOS data reduction pipeline make it necessary to create a dedicated product for solar observations.
A Physically Based Model for Preferential Water Flow and Solute Transport in Drained Agricultural Fields
Authors: Holbak M. , Abrahamsen P. , Hansen S. , Diamantopoulos E. 
Published: February 2021

AbstractPreferential water flow and associated solute transport in agricultural soils may influence the quality of groundwater and surface waters like streams and lakes. This is due to the rapid transport of agrochemicals, immediately after application, through subsurface drainpipes and surface water. Multiple field experiments attribute this to the occurrence of continuously connected pathways, called here biopores, connecting the soil surface directly with the drainpipes. We developed a physically based model describing preferential flow and transport in biopores directly connecting the upper soil layers with the drainpipes or deeper layers of the soil matrix. Based on field investigations, biopores with specific characteristics can be parameterized as classes with different vertical and horizontal distributions. Water flow and solute transport in biopores are described with a simple mass balance approach assuming instantaneous movement. The model was tested against experimental data from a column experiment with an artificial biopore and showed good results in simulating biopore flow initiation dynamics. However, further field and laboratory experiments are needed to validate the model across the soil profile. We illustrate the performance of the new approach, by conducting five theoretical simulations assuming a two‐dimensional simulation domain with different biopore parametrizations, from none to several different classes. The simulation results agreed with experimental observations reported in the literature, indicating rapid transport from the soil to the drainpipes. Furthermore, the different biopore parametrizations resulted in distinctly different leaching patterns, raising the expectation that biopore properties could be estimated or constrained based on observed leaching data and direct measurements.
Quantifying Shallow Overland Flow Patterns Under Laboratory Simulations Using Thermal and LiDAR Imagery
Authors: Danino Din , Svoray Tal , Thompson Sally , Cohen Ariel , Crompton Octavia , Volk Elazar , Argaman Eli , Levi Asher , Cohen Yafit , Narkis Kfir , Assouline Shmuel 
Published: February 2021

AbstractDesertification processes pose a global environmental threat, impacting 61 × 106 km2 of the terrestrial land area. Changes in overland flow patterns and consequent rainwater redistribution in drylands present a potential pathway to desertification, because vegetation often relies on water inputs from runoff to sustain growth under insufficient rainfall conditions. Of particular importance are the very shallow overland flows that redistribute water, nutrients, and biological matter within arid landscapes. However, characterizing overland flow patterns remains challenging, due to their very shallow depths, their distributed nature, and the poor understanding of how these flows interact with the underlying rough soil surface. This paper describes how coupling thermal images of shallow overland flows with light detection and ranging (LiDAR) scanning of the underlying soil surface in 1 m2 experimental trays allows spatial patterns of shallow overland flow to be quantified. Laboratory experiments were used to explore the behaviors of shallow overland flow as mean slope gradients and soil roughness were varied. The results show that these imaging techniques are able to capture differences in flow patterns arising across soil surfaces with varying slope, roughness, and spatial variation in infiltration properties. Several spatial indices characterizing overland flow patterns were found to correlate with runoff volume. The presence of high permeability soil patches substantially regulated overland flow. A next logical step would be to apply the thermal and LiDAR measurement techniques to the hillslope scale.
Genetic determinants of daytime napping and effects on cardiometabolic health
Authors: Dashti Hassan S. , Daghlas Iyas , Lane Jacqueline M. , Huang Yunru , Udler Miriam S. , Wang Heming , Ollila Hanna M. , Jones Samuel E. , Kim Jaegil , Wood Andrew R. ,   23andMe Research Team, Agee Michelle , Auton Adam , Bell Robert K. , Bryc Katarzyna , Clark Sarah K. , Elson Sarah L. , Fletez-Brant Kipper , Fontanillas Pierre , Furlotte Nicholas A. , Gandhi Pooja M. , Heilbron Karl , Hicks Barry , Hinds David A. , Huber Karen E. , Jewett Ethan M. , Jiang Yunxuan , Kleinman Aaron , Lin Keng-Han , Litterman Nadia K. , Luff Marie K. , McCreight Jennifer C. , McIntyre Matthew H. , McManus Kimberly F. , Mountain Joanna L. , Mozaffari Sahar V. , Nandakumar Priyanka , Noblin Elizabeth S. , Northover Carrie A. M. , O’Connell Jared , Petrakovitz Aaron A. , Pitts Steven J. , Poznik G. David , Sathirapongsasuti J. Fah , Shastri Anjali J. , Shelton Janie F. , Shringarpure Suyash , Tian Chao , Tung Joyce Y. , Tunney Robert J. , Vacic Vladimir , Wang Xin , Zare Amir S. , Weedon Michael N. , Aslibekyan Stella , Garaulet Marta , Saxena Richa 
Published: February 2021

AbstractDaytime napping is a common, heritable behavior, but its genetic basis and causal relationship with cardiometabolic health remain unclear. Here, we perform a genome-wide association study of self-reported daytime napping in the UK Biobank (n = 452,633) and identify 123 loci of which 61 replicate in the 23andMe research cohort (n = 541,333). Findings include missense variants in established drug targets for sleep disorders (HCRTR1,HCRTR2), genes with roles in arousal (TRPC6,PNOC), and genes suggesting an obesity-hypersomnolence pathway (PNOC, PATJ). Association signals are concordant with accelerometer-measured daytime inactivity duration and 33 loci colocalize with loci for other sleep phenotypes. Cluster analysis identifies three distinct clusters of nap-promoting mechanisms with heterogeneous associations with cardiometabolic outcomes. Mendelian randomization shows potential causal links between more frequent daytime napping and higher blood pressure and waist circumference.
Nascent RNA sequencing identifies a widespread sigma70-dependent pausing regulated by Gre factors in bacteria
Authors: Sun Zhe , Yakhnin Alexander V. , FitzGerald Peter C. , Mclntosh Carl E. , Kashlev Mikhail 
Published: February 2021

AbstractPromoter-proximal pausing regulates eukaryotic gene expression and serves as checkpoints to assemble elongation/splicing machinery. Little is known how broadly this type of pausing regulates transcription in bacteria. We apply nascent elongating transcript sequencing combined with RNase I footprinting for genome-wide analysis of σ70-dependent transcription pauses in Escherichia coli. Retention of σ70 induces strong backtracked pauses at a 10−20-bp distance from many promoters. The pauses in the 10−15-bp register of the promoter are dictated by the canonical −10 element, 6−7 nt spacer and “YR+1Y” motif centered at the transcription start site. The promoters for the pauses in the 16−20-bp register contain an additional −10-like sequence recognized by σ70. Our in vitro analysis reveals that DNA scrunching is involved in these pauses relieved by Gre cleavage factors. The genes coding for transcription factors are enriched in these pauses, suggesting that σ70 and Gre proteins regulate transcription in response to changing environmental cues.