bluuebunny/crossref_metadata_2025_split huggingface dataset:
Magnetic Field and Energetic Particle Flux Oscillations and High‐Frequency Waves Deep in the Inner Magnetosphere During Substorm Dipolarization: ERG Observations
Authors: Miyashita Yukinaga , Chang Tzu‐Fang , Miyoshi Yoshizumi , Hori Tomoaki , Kadokura Akira , Kasahara Satoshi , Wang Shiang‐Yu , Keika Kunihiro , Matsuoka Ayako , Tanaka Yoshimasa , Kasahara Yoshiya , Teramoto Mariko , Jun Chae‐Woo , Asamura Kazushi , Kazama Yoichi , Tam Sunny W. Y. , Wang Bo‐Jhou , Yokota Shoichiro , Kumamoto Atsushi , Tsuchiya Fuminori , Shoji Masafumi , Kurita Satoshi , Imajo Shun , Shinohara Iku 
Published: August 2021

AbstractUsing Exploration of energization and Radiation in Geospace (ERG or Arase) spacecraft data, we studied low‐frequency magnetic field and energetic particle flux oscillations and high‐frequency waves deep in the inner magnetosphere at a radial distance of ~4–5 during substorm dipolarization. The magnetic field oscillated alternately between dipole‐like and taillike configuration at a period of 1 min during dipolarization. When the magnetic field was dipole‐like, the parallel magnetic component of the Pi2 waves was at trough. Both energetic ion and electron fluxes with a few to tens of kiloelectronvolts enhanced out of phase, indicating that magnetosonic waves were in slow mode. Field‐aligned currents also oscillated. These observations are consistent with signatures of ballooning instability. In addition, we found that broadband waves from the Pi1 range to above the electron cyclotron frequency tended to appear intermittently in the central plasma sheet near dipole‐like configuration.
The Winter Heat Budget of Sea Ice in Kotzebue Sound: Residual Ocean Heat and the Seasonal Roles of River Outflow
Authors: Witte Carson R. , Zappa Christopher J. , Mahoney Andrew R. , Goodwin John , Harris Cyrus , Schaeffer Robert J. , Schaeffer Roswell , Betcher Sarah , Hauser Donna D. W. , Laxague Nathan J. M. , Lindsay Jessica M. , Subramaniam Ajit , Turner Kate E. , Whiting Alex 
Published: August 2021

AbstractThe winters of 2017/18 and 2018/19 saw unprecedented sea ice minima in the Bering and Chukchi Seas. Kotzebue Sound, located in the southeastern corner of the Chukchi Sea, remained largely ice‐free throughout the winter in a stark departure from both recorded history and Indigenous oral history. The only sea ice that persisted throughout the winter was landfast ice and most of this occupied a small corner of the Sound near the outflow of the Noatak and Kobuk Rivers. We present oceanographic and atmospheric time series from a heavily instrumented “ice‐tethered observatory” located on this landfast ice above the river outflow channel. This observing station was deployed as part of the Ikaaġvik Sikukun (Iñupiaq for “Ice Bridges”) project, in which hypotheses and subsequent observational programs were co‐produced in partnership with an Indigenous Elder Advisory Council in Kotzebue. The measurements allow us to quantify the heat budget of the ice above the outflow channel, and identify the ocean as the primary source of heat contributing to thinning of the ice, which began in early February and accelerated rapidly before the recovery of the station in April of 2019. In concert with the ice‐tethered observations, we use 2 years of oceanographic measurements from the mouth of Kotzebue Sound to characterize the influence of river outflow on the heat budget of the landfast ice, revealing a seasonal pattern in which the rivers promote ice formation and growth in the fall/winter, but help to drive melting of the ice in spring and early summer.
The Role of Differential Ablation and Dynamic Detachment in Driving Accelerating Mass Loss From a Debris‐Covered Himalayan Glacier
Authors: Rowan Ann V. , Egholm David L. , Quincey Duncan J. , Hubbard Bryn , King Owen , Miles Evan S. , Miles Katie E. , Hornsey Josephine 
Published: August 2021

AbstractSustained mass loss from Himalayan glaciers is causing supraglacial debris to expand and thicken, with the expectation that thicker debris will suppress ablation and extend glacier longevity. However, debris‐covered glaciers are losing mass at similar rates to clean‐ice glaciers in High Mountain Asia. This rapid mass loss is attributed to the combined effects of; (a) low or reversed mass balance gradients across debris‐covered glacier tongues, (b) differential ablation processes that locally enhance ablation within the debris‐covered section of the glacier, for example, at ice cliffs and supraglacial ponds, and (c) a decrease in ice flux from the accumulation area in response to climatic warming. Adding meter‐scale spatial variations in supraglacial debris thickness to an ice‐flow model of Khumbu Glacier, Nepal, increased mass loss by 47% relative to simulations assuming a continuous debris layer over a 31‐year period (1984–2015 CE) but overestimated the reduction in ice flux. Therefore, we investigated if simulating the effects of dynamic detachment of the upper active glacier from the debris‐covered tongue would give a better representation of glacier behavior, as suggested by observations of change in glacier dynamics and structure indicating that this process occurred during the last 100 years. Observed glacier change was reproduced more reliably in simulations of the active, rather than entire, glacier extent, indicating that Khumbu Glacier has passed a dynamic tipping point by dynamically detaching from the heavily debris‐covered tongue that contains 20% of the former ice volume.
Geochemical, Biological, and Clumped Isotopologue Evidence for Substantial Microbial Methane Production Under Carbon Limitation in Serpentinites of the Samail Ophiolite, Oman
Authors: Nothaft Daniel B. , Templeton Alexis S. , Rhim Jeemin H. , Wang David T. , Labidi Jabrane , Miller Hannah M. , Boyd Eric S. , Matter Juerg M. , Ono Shuhei , Young Edward D. , Kopf Sebastian H. , Kelemen Peter B. , Conrad Mark E. ,   The Oman Drilling Project Science Team
Published: August 2021

AbstractIn hyperalkaline () fluids that have participated in low‐temperature (<150) serpentinization reactions, the dominant form of C is often methane (), but the origin of this is uncertain. To assess origin in serpentinite aquifers within the Samail Ophiolite, Oman, we determined fluid chemical compositions, analyzed taxonomic profiles of fluid‐hosted microbial communities, and measured isotopic compositions of hydrocarbon gases. We found that 16S rRNA gene sequences affiliated with methanogens were widespread in the aquifer. We measured clumped isotopologue (D and ) relative abundances less than equilibrium, consistent with substantial microbial production. Furthermore, we observed an inverse relationship between dissolved inorganic C concentrations and across fluids bearing microbiological evidence of methanogenic activity, suggesting that the apparent C isotope effect of microbial methanogenesis is modulated by C availability. An additional source of is evidenced by the presence of ‐bearing fluid inclusions in the Samail Ophiolite and our measurement of high values of ethane and propane, which are similar to those reported in studies of ‐rich inclusions in rocks from the oceanic lithosphere. In addition, we observed 16S rRNA gene sequences affiliated with aerobic methanotrophs and, in lower abundance, anaerobic methanotrophs, indicating that microbial consumption of in the ophiolite may further enrich in 13C. We conclude that substantial microbial is produced under varying degrees of C limitation and mixes with abiotic released from fluid inclusions. This study lends insight into the functioning of microbial ecosystems supported by water/rock reactions.
Reconstructing the Dynamics of the Outer Electron Radiation Belt by Means of the Standard and Ensemble Kalman Filter With the VERB‐3D Code
Authors: Castillo Tibocha Angelica M. , de Wiljes Jana , Shprits Yuri Y. , Aseev Nikita A. 
Published: August 2021

AbstractReconstruction and prediction of the state of the near‐Earth space environment is important for anomaly analysis, development of empirical models, and understanding of physical processes. Accurate reanalysis or predictions that account for uncertainties in the associated model and the observations, can be obtained by means of data assimilation. The ensemble Kalman filter (EnKF) is one of the most promising filtering tools for nonlinear and high dimensional systems in the context of terrestrial weather prediction. In this study, we adapt traditional ensemble‐based filtering methods to perform data assimilation in the radiation belts. By performing a fraternal twin experiment, we assess the convergence of the EnKF to the standard Kalman filter (KF). Furthermore, with the split‐operator technique, we develop two new three‐dimensional EnKF approaches for electron phase space density that account for radial and local processes, and allow for reconstruction of the full 3D radiation belt space. The capabilities and properties of the proposed filter approximations are verified using Van Allen Probe and GOES data. Additionally, we validate the two 3D split‐operator Ensemble Kalman filters against the 3D split‐operator KF. We show how the use of the split‐operator technique allows us to include more physical processes in our simulations and is a computationally efficient data assimilation tool that delivers an accurate approximation of the optimal KF solution, and is suitable for real‐time forecasting. Future applications of the EnKF to direct assimilation of fluxes and nonlinear estimation of electron lifetimes are discussed.
Global Hotspots for Future Absolute Temperature Extremes From CMIP6 Models
Authors: Ajjur Salah Basem , Al‐Ghamdi Sami G. 
Published: August 2021

AbstractTwo questions motivated this study: (a) Are global land regions exposed to future changes in absolute temperature extremes? (b) And to which degree? To answer these questions, we projected the trend in four indices, recommended by the Expert Team on Climate Change Detection and Indices (ETCCDI), through the 21st century. Observational (HadEX3) and reanalyses (ERA5, JRA‐55, NCEP‐R‐1, and NCEP‐R‐2) datasets were used to validate and correct the bias in the Coupled Model Intercomparison Project phase 6 (CMIP6) models. CMIP6 models were then used to evaluate the changes globally and in 44 reference regions under two shared socioeconomic pathways (SSPs): SSP2‐4.5 and SSP5‐8.5. Globally, the analysis showed that, under SSP5‐8.5, TXx and TNx would increase by 0.07°C/year, and TXn (TNn) would increase by 0.09 (0.08)°C/year, during the middle of the 21st century (2021–2050), compared with the reference period (1981–2010). These trends are larger during the end of the 21st century (2071–2100). The analysis also showed that all land reference regions are projected to indices growth up to 3.5°C in TXx; 2.8°C in TNx; 4.5°C in TXn; and 4°C in TNn, during the mid‐21st century under SSP5‐8.5. The latter growth in indices increased by 211% for TXx, 237% for TNx, 242% for TXn, and 300% for TNn during the end‐21st century. The global hotspots affected by absolute temperature extremes are in the Northern Hemisphere, including North America, Iceland, Central Asia, Tibetan Plateau, Russian Arctic, Siberia, Mediterranean, Sahara, and Arabian Peninsula. The study's findings help understand the evolution of climate extremes, which is essential for climate change mitigation and adaptation plans.
PBL Height From AIRS, GPS RO, and MERRA‐2 Products in NASA GES DISC and Their 10‐Year Seasonal Mean Intercomparison
Authors: Ding Feng , Iredell Lena , Theobald Michael , Wei Jennifer , Meyer David 
Published: August 2021

AbstractWithin the planetary boundary layer (PBL), surface forcing response, drag, turbulence, and vertical mixing are important processes and play a more critical role here than in the overlying “free atmosphere.” The PBL height (PBLH) is an important parameter in climate models, weather forecasts, and air quality prediction. The NASA Goddard Earth Sciences Data and Information Services Center (GES DISC) provides data processing, archiving, and distribution services for numerous Earth science products. PBLH is a parameter in three products served by GES DISC, which are from the atmospheric infrared sounder (AIRS), the global positioning system (GPS) radio occultation (RO) experiment, and the NASA reanalysis product Modern‐Era Retrospective analysis for Research and Applications‐2 (MERRA‐2). These products have different spatial and temporal resolutions and coverages, and their PBLH definitions are also different. To better serve the PBL research community, we have summarized the specifications of these products. A 10‐year seasonal mean intercomparison is also conducted to provide further guidance to users. The intercomparison results show that MERRA‐2 has a much shallower PBL than AIRS and GPS RO. An experimental study indicates that the different PBLH definition in MERRA‐2 caused smaller values of PBLH. The improvement of the water vapor retrieval in AIRS version 7 over version 6 results in the version 7 PBLH agreeing better with GPS RO and MERRA‐2 than version 6, especially near the equator and low latitudes.
Shear‐Wave Velocity Structure of Sediments on Cascadia's Continental Margin From Probabilistic Inversion of Seafloor Compliance Data
Authors: Mosher Stephen G. , Audet Pascal , Gosselin Jeremy M. 
Published: August 2021

AbstractSeveral seismic techniques, both passive and active, exist for estimating the shear‐wave velocitystructure of shallow sedimentary structures. In particular, passive compliance signals recorded by broadband ocean‐bottom seismometers (OBSs) can be used to invert forstructure. While compliance‐based imaging studies have been carried out at several locations across the Cascadia Subduction Zone, such an approach has not been extensively applied to OBSs deployed on the continental shelf and slope. In this study, we measure compliance and coherence signals at 13 broadband OBSs deployed along Cascadia's continental shelf and upper slope. We then use a recently developed technique to probabilistically invert compliance signals for shallowstructure that makes use of mixture density neural networks. Finally, we compare and contrast our invertedprofiles and derived properties obtained using this method with previous studies focused on the properties of basin sediments.
Multidisciplinary Constraints on Magma Compressibility, the Pre‐Eruptive Exsolved Volatile Fraction, and the H2O/CO2 Molar Ratio for the 2006 Augustine Eruption, Alaska
Authors: Wasser Valerie K. , Lopez Taryn M. , Anderson Kyle R. , Izbekov Pavel E. , Freymueller Jeffrey T. 
Published: August 2021

AbstractGeodetically modeled reservoir volume changes during volcanic eruptions are commonly much smaller than the observed eruptive volumes. This discrepancy is thought to be partially due to the compressibility of magma, which is largely controlled by the presence of exsolved volatiles. The 2006 eruption of Augustine Volcano, Alaska, produced an eruptive volume that was ∼3 times larger than the geodetically estimated syn‐eruptive subsurface volume change. In this study, we use a multistep methodology that combines constraints from geodetic, volcanic gas, geologic, and petrologic data together with equations relating physical processes to observable parameters. We apply a Monte Carlo approach to quantify uncertainties. Ultimately, we solve for the exsolved volatile volume fraction and the magma compressibility. We estimate Augustine's 2006 pre‐eruptive exsolved volatile phase to be ∼5.5 vol% of the magma at storage depths, yielding a bulk magma compressibility of ∼3.8 × 10−10 Pa−1. We develop a novel approach to estimate the H2O/CO2 ratio of the syn‐eruptive gas emissions in the absence of direct H2O emission measurements which are hard to obtain due to the high background levels in ambient air. We find a best‐fit H2O/CO2 molar ratio of 29. We also investigate the effects of applying different equations of state to our model. We find that the Ideal Gas Law might be used as a first approximation due to its simplicity; however, it overestimates volatile density and compressibility significantly at storage depths. This project capitalizes on the insights that can be gained by integrating multidisciplinary data with models of physical processes.
Multiscale Geoelectrical Properties of the Rochechouart Impact Structure, France
Authors: Quesnel Yoann , Sailhac Pascal , Lofi Johanna , Lambert Philippe , Rochette Pierre , Uehara Minoru , Camerlynck Christian 
Published: August 2021

AbstractThe 205 Ma Rochechouart impact structure (France) is characterized by various impactite formations overlying the Hercynian crystalline basement. New constraints from downhole logging and surface electrical resistivity measurements along >100 m long profiles reveal that the top melt‐bearing breccia layer is more conductive and porous than the underlying melt‐poor breccia layer. The stratigraphy within the impactite and the transition with the basement are irregular at small (∼1–10 m) and medium (>100 m) scales, with vertical amplitude up to 40–50 m. At larger scale (>1 km), audio‐magnetotelluric observations are able to map the lateral and vertical extent of fracturing/brecciation in the basement, reaching 200 m below the surface nearby Chassenon, in the northern part of the structure. Our results also unveil that the impactite deposits and the brecciated basement of the Rochechouart impact structure may have been shifted laterally and vertically during the modification stage of the impact event through displacements of megablocks, which may be associated with the collapse of a central uplift.
Estimated Mortality and Morbidity Attributable to Smoke Plumes in the United States: Not Just a Western US Problem
Authors: O’Dell Katelyn , Bilsback Kelsey , Ford Bonne , Martenies Sheena E. , Magzamen Sheryl , Fischer Emily V. , Pierce Jeffrey R. 
Published: August 2021

AbstractAs anthropogenic emissions continue to decline and emissions from landscape (wild, prescribed, and agricultural) fires increase across the coming century, the relative importance of landscape‐fire smoke on air quality and health in the United States (US) will increase. Landscape fires are a large source of fine particulate matter (PM2.5), which has known negative impacts on human health. The seasonal and spatial distribution, particle composition, and co‐emitted species in landscape‐fire emissions are different from anthropogenic sources of PM2.5. The implications of landscape‐fire emissions on the sub‐national temporal and spatial distribution of health events and the relative health importance of specific pollutants within smoke are not well understood. We use a health impact assessment with observation‐based smoke PM2.5 to determine the sub‐national distribution of mortality and the sub‐national and sub‐annual distribution of asthma morbidity attributable to US smoke PM2.5 from 2006 to 2018. We estimate disability‐adjusted life years (DALYs) for PM2.5 and 18 gas‐phase hazardous air pollutants (HAPs) in smoke. Although the majority of large landscape fires occur in the western US, we find the majority of mortality (74%) and asthma morbidity (on average 75% across 2006–2018) attributable to smoke PM2.5 occurs outside the West, due to higher population density in the East. Across the US, smoke‐attributable asthma morbidity predominantly occurs in spring and summer. The number of DALYs associated with smoke PM2.5 is approximately three orders of magnitude higher than DALYs associated with gas‐phase smoke HAPs. Our results indicate awareness and mitigation of landscape‐fire smoke exposure is important across the US.
Electron Partial Density and Temperature Over Jupiter's Main Auroral Emission Using Juno Observations
Authors: Allegrini F. , Kurth W. S. , Elliott S. S. , Saur J. , Livadiotis G. , Nicolaou G. , Bagenal F. , Bolton S. , Clark G. , Connerney J. E. P. , Ebert R. W. , Gladstone G. R. , Louarn P. , Mauk B. H. , McComas D. J. , Sulaiman A. H. , Szalay J. R. , Valek P. W. , Wilson R. J. 
Published: August 2021

AbstractWe present a survey of electron partial densities (i.e., the portion of the total density measured between ∼0.05 and 100 keV) and temperatures in Jupiter's main auroral emission region using plasma measurements from the Jovian Auroral Distributions Experiment (JADE) on Juno. The electron partial density increases from ∼0.01 or 0.1 cm−3 near the main oval to a few cm−3 at the edge of the measurable part of the UV emission equatorward of the main oval. The electron temperature is highest near the main oval at ∼10–20 keV and decreases equatorward down to ∼0.3–2 keV. The JADE electron partial density agrees within a factor of ∼2 with the total electron densities derived from Juno‐Waves when the comparison is possible. The electron density and temperature trends are consistent for all sampled longitudes, for the north and the south, and there is no significant trend with radial distance in the range examined in this study (1.25–1.96 RJ). The electron density is anti‐correlated with the temperature and the characteristic energy. The ratio of the magnetic field strength to the electron density is maximum near the main oval.
The Importance of Counting: A New Index to Correctly Quantify Equatorial Plasma Bubble Occurrence in COSMIC Radio Occultation Data
Authors: Currie J. L. , Carter B. A. , Dao T. , Terkildsen M. 
Published: August 2021

AbstractThe Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) Radio Occultation data has been previously used as a way of investigating the climatology of Equatorial Plasma Bubbles (EPB). These low‐density regions can cause random phase and amplitude scintillation of satellite signals and forecasting these is an important priority in the space physics community. The ability to build useful forecasting models depends on the underlying data sets used in testing and validating these models. Correctly identifying days of EPB activity is important, but statistical studies using large data sets require the use of automated detection methods. Many of these detection methods heavily reduce data sets by removing unfavorable data, such as COSMIC profiles where the maximum scintillation occurs in the E region. This study presents a new F region s4max9sec index that can be used to study the presence of F region scintillation without excluding profiles that exhibit E region scintillation. The new index is shown to decrease EPB occurrence through the increase in available data, and is also shown to detect EPB events previously excluded from climatological studies. Calculation of the climatology using the new index is shown to resolve some differences that exist in the EPB climatology literature, particularly the location of the maximum scintillation occurrence during the equinox seasons. The use of this index is highlighted as a potential for studying F region scintillation in the presence of E region scintillation; an area of research that needs to be expanded for a complete understanding of EPBs.