bluuebunny/crossref_metadata_2025_split huggingface dataset:
Emergent and urgent otologic surgeries during the SARS‐CoV‐2 pandemic: a protocol and review of literature
Authors: Zhao Elise E. , Lee Joshua A. , McRackan Theodore R. , Nguyen Shaun A. , Meyer Ted A. 
Published: May 2020

ObjectiveTo review guidelines for otologic procedures during the SARS‐CoV‐2 pandemic and to present a protocol for emergent or urgent mastoidectomy at our institution.Data sourcesGuidelines regarding emergent and urgent otologic procedures from otolaryngologic societies are reviewed. We described a protocol for emergent or urgent mastoidectomy at our institution.ConclusionPatients requiring urgent or emergent mastoidectomy during the COVID‐19 pandemic require prompt treatment. We make the following recommendations: Emergent or urgent otologic procedures should be performed in a contained environment, such as a tent created by the microscope drape. The surgical team should practice using instruments in the tent setup to prepare for real cases. Otologic procedures should adhere to guidelines set for high‐risk procedures.
Constraining an Ocean Model Under Getz Ice Shelf, Antarctica, Using A Gravity‐Derived Bathymetry
Authors: Millan Romain , St‐Laurent Pierre , Rignot Eric , Morlighem Mathieu , Mouginot Jeremie , Scheuchl Bernd 
Published: May 2020

AbstractGetz Ice Shelf, the largest producer of ice shelf meltwater in Antarctica, buttresses glaciers that hold enough ice to raise sea level by 22 cm. We present a new bathymetry of its sub‐ice shelf cavity using a three‐dimensional inversion of airborne gravity data constrained by multibeam bathymetry at sea and a reconstruction of the bedrock from mass conservation on land. The new bathymetry is deeper than previously estimated with differences exceeding 500 m in a number of regions. When incorporated into an ocean model, it yields a better description of the spatial distribution of ice shelf melt, specifically along glacier grounding lines. While the melt intensity is overestimated because of a positive bias in ocean thermal forcing, the study reveals the main pathways along which warm oceanic water enters the cavity and corroborates the observed rapid retreat of Berry Glacier along a deep channel with a retrograde bed slope.
Spatial Variation of Reactive Nitrogen Emissions From China's Croplands Codetermined by Regional Urbanization and Its Feedback to Global Climate Change
Authors: Xu Peng , Chen Anping , Houlton Benjamin Z. , Zeng Zhenzhong , Wei Song , Zhao Chenxu , Lu Haiyan , Liao Yajun , Zheng Zhonghua , Luan Shengji , Zheng Yi 
Published: May 2020

AbstractReactive gaseous nitrogen (Ngr) emissions significantly affect Earth's climate system. Disagreement exists, however, over Ngr contributions to short‐ versus long‐term climate forcing, from local to global scales and among different gaseous forms, including NH3, NOx, and N2O. Here, we provide a comprehensive inventory of Ngr from China's croplands based on a new bottom‐up, mass flow‐based approach integrated with fine‐resolution agricultural activity data and nitrogen emission factors. We demonstrate that China's croplands emit about 8.87 Tg N to the atmosphere in 2014. Across different prefectures, Ngr emission per capita conforms to a “Kuznets curve,” that is, first increases then decreases, along the gradient of increasing urbanization. Ngr emission per gross domestic productivity (GDP) decreases exponentially with increasing urbanization or per capita GDP. Furthermore, climate change impact analyses suggest that the global‐scale warming effect of China's cropland N2O emissions dominate over local cooling effects ascribed to its NH3 and NOx emissions.
Attenuation of Rock Salt: Ultrasonic Lab Analysis of Gulf of Mexico Coastal Samples
Authors: Zong Jingjing , Stewart Robert R. , Dyaur Nikolay 
Published: May 2020

AbstractIn an effort to achieve higher‐resolution imaging as well as detailed lithology descriptions, it is important to consider attenuation as an aid in compensating for seismic wave amplitude and phase distortions due to the viscoelastic properties of natural rocks. We have evaluated elastic‐wave attenuation on a variety of Gulf of Mexico (GoM) rock salt samples (>95% halite by weight) in the laboratory using the ultrasonic pulse‐transmission technique and the spectral ratio (SR) method. Under conditions of 297 K (75°F) and relative humidity of 46%, the estimated P‐ and S‐wave quality factors QP and QS range from 26 to 74 and 29 to 44 in the unjacketed core samples, respectively. Increasing triaxial pressure elevates Q (decreases attenuation), possibly due to the crack closure and rock frame compaction. For example, a 40 MPa confining pressure increases QP to 275 at 297 K (75°F). Elevating temperature does not show a significant effect on Q values until raised from 339 to 366 K (150°F to 200°F), during which QP drops sharply (attenuation increases). The attenuation mechanisms may include thermal cracking and grain boundary condition changes. We have determined well‐constrained empirical relationships between Q and velocity (V) for both P‐ and S‐waves. These measurements and empirical relationships can further inform us about salt properties and assist with images of and through salt bodies.
Indo‐Pacific Hydroclimate in Response to Changes of the Intertropical Convergence Zone: Discrepancy on Precession and Obliquity Bands Over the Last 410 kyr
Authors: Zhang Peng , Xu Jian , Holbourn Ann , Kuhnt Wolfgang , Beil Sebastian , Li Tiegang , Xiong Zhifang , Dang Haowen , Yan Hong , Pei Renjie , Ran Yazhou , Wu Hanning 
Published: May 2020

AbstractThe Intertropical Convergence Zone (ITCZ), which is the heaviest rain belt on Earth, significantly influences global hydroclimate change and livelihood of nearly 40% of the global population. However, long‐term precipitation records are sparse from the Indo‐Pacific region, especially from the southern margin of the Indo‐Pacific ITCZ, restricting our understanding of the overall natural variability of the ITCZ in the past. In this study, we present a new summer monsoonal precipitation record that spans the last 410 kyr from the southern margin of the Indo‐Pacific ITCZ, based on the logarithmic ratio between terrigenous fraction K and pelagic fraction Ca (ln(K/Ca)). Contents of both elements were derived from X‐ray fluorescence scanning on sediment cores from Site U1483 (13°05.24′S, 121°48.25′E, water depth 1,733 m) that was drilled offshore northwestern Australia during International Ocean Discovery Program Expedition 363. Comparison of the new precipitation record with published precipitation records from the northern margin and meteorological center of the Indo‐Pacific ITCZ shows that precipitation changed nearly in‐phase between the hemispheres on the precession band, possibly linked to expansion and contraction in the latitudinal extent of the Indo‐Pacific ITCZ. In contrast, interhemispheric precipitation was nearly in anti‐phase on the obliquity band, likely due to latitudinal migration of the Indo‐Pacific ITCZ. Our findings imply that tropical hydroclimate cycles were regulated by the orbital forcing but with significantly different response to changes of the ITCZ on precession and obliquity bands.
Assessing Temperate Forest Growth and Climate Sensitivity in Response to a Long‐Term Whole‐Watershed Acidification Experiment
Authors: Malcomb Jacob D. , Scanlon Todd M. , Epstein Howard E. , Druckenbrod Daniel L. , Vadeboncoeur Matthew A. , Lanning Matthew , Adams Mary Beth , Wang Lixin 
Published: May 2020

AbstractAcid deposition is a major biogeochemical driver in forest ecosystems, but the impacts of long‐term changes in deposition on forest productivity remain unclear. Using a combination of tree ring and forest inventory data, we examined tree growth and climate sensitivity in response to 26 years of whole‐watershed ammonium sulfate ((NH4)2SO4) additions at the Fernow Experimental Forest (West Virginia, USA). Linear mixed effects models revealed species‐specific responses to both treatment and hydroclimate variables. When controlling for environmental covariates, growth of northern red oak (Quercus rubra), red maple (Acer rubrum), and tulip poplar (Liriodendron tulipifera) was greater (40%, 52%, and 42%, respectively) in the control watershed compared to the treated watershed, but there was no difference in black cherry (Prunus serotina). Stem growth was generally positively associated with growing season water availability and spring temperature and negatively associated with vapor pressure deficit. Sensitivity of northern red oak, red maple, and tulip poplar growth to water availability was greater in the control watershed, suggesting that acidification treatment has altered tree response to climate. Results indicate that chronic acid deposition may reduce both forest growth and climate sensitivity, with potentially significant implications for forest carbon and water cycling in deposition‐affected regions.
Understanding Anthropogenic Impacts on pH and Aragonite Saturation State in Chesapeake Bay: Insights From a 30‐Year Model Study
Authors: Shen Chunqi , Testa Jeremy M. , Li Ming , Cai Wei‐Jun 
Published: May 2020

AbstractOcean acidification (OA) is often defined as the gradual decline in pH and aragonite saturation state (ΩAr) for open ocean waters as a result of increasing atmospheric pCO2. Potential long‐term trends in pH and ΩAr in estuarine environments are often obscured by a variety of other factors, including changes in watershed land use and associated riverine carbonate chemistry and estuarine ecosystem metabolism. In this work, we investigated the anthropogenic impacts on pH and ΩAr over three decades (1986–2015) in Chesapeake Bay using retrospective coupled hydrodynamic‐biogeochemical model simulations. Simulation results demonstrated a clear estuarine acidification signal in the midbay region, with a long‐term increase in the annual duration of acidified bottom waters (pH < 7.5, ~2 days/yr) as well as a shallowing of the saturation horizon (~0.1 m/yr). In contrast, scenario results revealed basification in the upper bay consistent with increased alkalinization of the Susquehanna River. Significant long‐term pH and ΩAr declines in the lower bay were driven by nearly equal contributions from OA and lowered surface ecosystem production. The midbay pH variability was primarily influenced by OA and biological processes, while river basification along with OA played a key role in regulating the long‐term ΩAr variability. This study quantifies the contributions from multiple anthropogenic drivers to changes in estuarine carbonate chemistry over three decades, highlighting the complex interactions in regulating the dynamics of pH and ΩAr and informing regional natural resource management and ecosystem restoration.
A Flow‐Dependent Targeted Observation Method for Ensemble Kalman Filter Assimilation Systems
Authors: Wu Yanling , Shen Zheqi , Tang Youmin 
Published: May 2020

AbstractIn this study, we developed a flow‐dependent sequential assimilation‐based targeted observation method by minimizing the analysis error variance under the framework of the ensemble Kalman filter (EnKF). This approach considers the flow‐dependent variation in background error statistics when identifying optimal observational sites through the sequential assimilation method. Covariance localization is also introduced in this method, enabling computational efficiency and eliminating impacts from spurious observations. By quantifying the reduction in analysis error variances, the proposed method could estimate the potential improvements by each optimal observation while assimilated. With this method, we design an optimal observational array for sea level anomaly (SLA) prediction in the tropical Indian Ocean (TIO), which is implemented using a fully coupled climate model, the Community Earth System Model (CESM), in conjunction with a coupled assimilation system. The optimal observational array detected from this method was found to theoretically reduce the initial uncertainty by up to approximately 60% of the error variance. An observing system simulation experiment (OSSE) using the CESM and the coupled assimilation system, which was designed for validation purposes, confirms the theoretical reduction in the analysis error variance by the optimal observation array.
CO2 Dissolution Trapping Rates in Heterogeneous Porous Media
Authors: Gilmore K. A. , Neufeld J. A. , Bickle M. J. 
Published: May 2020

AbstractThe rate of carbon dioxide (CO2) dissolution in saline aquifers is the least well‐constrained of the secondary trapping mechanisms enhancing the long‐term security of geological carbon storage. CO2 injected into a heterogeneous saline reservoir will preferentially travel along high permeability layers increasing the CO2‐water interfacial area which increases dissolution rates. We provide a conservative, first‐principles analysis of the quantity of CO2 dissolved and the rate at which free‐phase CO2 propagates in layered reservoirs. At early times, advection dominates the propagation of CO2. This transitions to diffusion dominated propagation as the interfacial area increases and diffusive loss slows propagation. As surrounding water‐filled layers become CO2 saturated, propagation becomes advection dominated. For reservoirs with finely bedded strata, ∼10% of the injected CO2 can dissolve in a year. The maximum fraction of CO2 that dissolves is determined by the volumetric ratio of water in low permeability layers and CO2 in high permeability layers.
Lipid Biomarker Record Documents Hydroclimatic Variability of the Mississippi River Basin During the Common Era
Authors: Muñoz Samuel E. , Porter Trevor J. , Bakkelund Aleesha , Nusbaumer Jesse , Dee Sylvia G. , Hamilton Brynnydd , Giosan Liviu , Tierney Jessica E. 
Published: May 2020

AbstractFloods and droughts in the Mississippi River basin are perennial hazards that cause severe economic disruption. Here we develop and analyze a new lipid biomarker record from Horseshoe Lake (Illinois, USA) to evaluate the climatic conditions associated with hydroclimatic extremes that occurred in this region over the last 1,800 years. We present geochemical proxy evidence of temperature and moisture variability using branched glycerol dialkyl glycerol tetraethers (brGDGTs) and plant leaf wax hydrogen isotopic composition (δ2Hwax) and use isotope‐enabled coupled model simulations to diagnose the controls on these proxies. Our data show pronounced warming during the Medieval era (CE 1000–1,600) that corresponds to midcontinental megadroughts. Severe floods on the upper Mississippi River basin also occurred during the Medieval era and correspond to periods of enhanced warm‐season moisture. Our findings imply that projected increases in temperature and warm‐season precipitation could enhance both drought and flood hazards in this economically vital region.
Cold Pools as Conveyor Belts of Moisture
Authors: Fuglestvedt Herman F. , Haerter Jan O. 
Published: May 2020

AbstractObservations and simulations have found convective cold pools to trigger and organize subsequent updrafts by modifying boundary layer temperature and moisture as well as by lifting air parcels at the outflow boundaries. We study the causality between cold pools and subsequent deep convection in idealized large‐eddy simulations by tracking colliding outflow boundaries preceding hundreds of deep convection events. When outflow boundaries collide, their common front position remains immobile, whereas the internal cold pool dynamics continues for hours. We analyze how this dynamics “funnels” moisture from a relatively large volume into a narrow convergence zone. We quantify moisture convergence and separate the contribution from surface fluxes, which we find to play a secondary role. Our results highlight that dynamical effects are crucial in triggering convection, even in radiative‐convective equilibrium. However, it is the low‐level convergence resulting from this dynamics that removes inhibition, moistens the atmosphere aloft, and ultimately permits deep convection.
Quantifying the Solar Cycle Modulation of Extreme Space Weather
Authors: Chapman S. C. , McIntosh S. W. , Leamon R. J. , Watkins N. W. 
Published: May 2020

AbstractBy obtaining the analytic signal of daily sunspot numbers since 1818 we construct a new solar cycle phase clock that maps each of the last 18 solar cycles onto a single normalized 11 year epoch. This clock orders solar coronal activity and extremes of the aa index, which tracks geomagnetic storms at the Earth's surface over the last 14 solar cycles. We identify geomagnetically quiet intervals that are 40% of the normalized cycle, ±2π/5 in phase or ±2.2 years around solar minimum. Since 1868 only two severe (aa>300 nT) and one extreme (aa>500 nT) geomagnetic storms occurred in quiet intervals; 1–3% of severe (aa>300 nT) geomagnetic storms and 4–6% of C‐, M‐, and X‐class solar flares occurred in quiet intervals. This provides quantitative support to planning resilience against space weather impacts since only a few percent of all severe storms occur in quiet intervals and their start and end times are quantifiable.
Comparison and Verification of Point‐Wise and Patch‐Wise Localized Probability‐Matched Mean Algorithms for Ensemble Consensus Precipitation Forecasts
Authors: Snook Nathan , Kong Fanyou , Clark Adam , Roberts Brett , Brewster Keith A. , Xue Ming 
Published: May 2020

AbstractWhen applied to precipitation on large forecast domains, the probability‐matched ensemble mean (PM mean) can exhibit biases and artifacts due to using distributions from widely varying precipitation regimes. Recent studies have investigated localized PM (LPM) means, which apply the PM mean over local areas surrounding individual points or local patches, the latter requiring far fewer computational resources. In this study, point‐wise and patch‐wise LPM means are evaluated for 18–24‐hr precipitation forecasts of a quasi‐operational ensemble of 10 Finite‐Volume Cubed‐Sphere (FV3) forecast members. Point‐wise and patch‐wise LPM means exhibited similar forecast performance, outperforming PM and simple means in terms of fractions skill score and variance spectra while exhibiting superior bias characteristics when light smoothing was applied. Based on the results, an LPM mean using local patches of 60 × 60 km and calculation domains of 180 × 180 km is well suited for operational warm‐season precipitation forecasting over the contiguous United States.
Adiabatic Acceleration in a Magnetotail Flux Rope
Authors: Dahlin J. T. 
Published: May 2020

AbstractA new study of Magnetospheric Multiscale Mission (MMS) measurements in the Earth's magnetotail, presented by Zhong et al. (2020, https://doi.org/10.1029/2019GL085141) finds that enhanced energetic electrons in a reconnection‐generated ion‐scale flux rope in the magnetotail are due to the adiabatic processes of betatron and Fermi (curvature drift) acceleration. These mechanisms act, respectively, on the perpendicular and parallel components of the distribution function so that the role of these mechanisms may be distinctly identified. This study presents a useful template for studying in situ electron energization and contributes significantly to the ongoing discussion of the role of mesoscale structure in reconnection‐driven particle acceleration throughout the heliosphere.
Lifetimes of Relativistic Electrons as Determined From Plasmaspheric Hiss Scattering Rates Statistics: Effects of ωpe/Ωce and Wave Frequency Dependence on Geomagnetic Activity
Authors: Agapitov O. , Mourenas D. , Artemyev A. , Claudepierre S. G. , Hospodarsky G. , Bonnell J. W. 
Published: May 2020

AbstractWhistler‐mode hiss waves generally determine MeV electron lifetimes inside the plasmasphere. We use Van Allen Probes measurements to provide the first comprehensive statistical survey of plasmaspheric hiss‐driven quasi‐linear pitch‐angle diffusion rates and lifetimes of MeV electrons as a function of L*, local time, and AE index, taking into account hiss power, electron plasma frequency to gyrofrequency ratio ωpe/Ωce, hiss frequency at peak power ωm, and cross correlations of these parameters. We find that during geomagnetically active periods with hiss observations, ωpe/Ωce and ωm decrease, leading to faster electron loss. We demonstrate that spatiotemporal variations of ωm and ωpe/Ωce with AE, together with wave power changes, significantly affect MeV electron loss, potentially leading to short lifetimes of less than 1 day. A parametric model of MeV electron lifetime driven by AE for L > 2.5 up to the plasmapause is developed and validated using Magnetic Electron Ion Spectrometer (MagEIS) electron flux decay database.
Limited Retreat of the Wilkes Basin Ice Sheet During the Last Interglacial
Authors: Sutter J. , Eisen O. , Werner M. , Grosfeld K. , Kleiner T. , Fischer H. 
Published: May 2020

AbstractThe response of the East Antarctic Ice Sheet to global warming represents a major source of uncertainty in sea‐level projections. Thinning of the East Antarctic George V and Sabrina Coast ice cover is currently taking place, and regional ice‐sheet instability episodes might have been triggered in past warm climates. However, the magnitude of ice retreat in the past cannot yet be quantitatively derived from paleo‐proxy records alone. We propose that a runaway retreat of the George V coast grounding line and subsequent instability of the Wilkes Basin ice sheet would either leave a clear imprint on the water isotope composition in the Talos Dome region or prohibit a Talos Dome ice‐core record from the Last Interglacial altogether. Testing this hypothesis, our ice‐sheet model simulations suggest that Wilkes Basin ice‐sheet retreat remained relatively limited during the Last Interglacial and provide a constraint on Last Interglacial East Antarctic grounding line stability.
Differentiating Between Tornadic and Nontornadic Supercells Using Polarimetric Radar Signatures of Hydrometeor Size Sorting
Authors: Loeffler Scott D. , Kumjian Matthew R. , Jurewicz Michael , French Michael M. 
Published: May 2020

AbstractSupercell storms are the most prolific producers of violent tornadoes, though only a fraction of supercells produce tornadoes. Past research into the differences between tornadic and nontornadic supercells have provided some insights but are of little utility to a real‐time warning decision process. Operational weather radars provide consistent observations in real time, but conventional radar techniques have not been able to effectively distinguish between tornadic and nontornadic supercells. After the national radar network upgrade to polarimetric capabilities in 2013, a polarimetric signature frequently observed in supercells is the separation of low‐level enhanced differential reflectivity ZDR and specific differential phase KDP regions. We analyzed this signature in tornadic and nontornadic supercell cases and found that, although the separation distances are similar, the separation orientations are statistically significantly different. Tornadic supercells have orientations more orthogonal to storm motion and nontornadic supercells have more parallel orientations. Possible reasons for these differences are discussed.