bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rapid Mass Loss in West Antarctica Revealed by Swarm Gravimetry in the Absence of GRACE
Authors: Zhang Chaoyang , Shum C. K. , Bezděk Aleš , Bevis Michael , de Teixeira da Encarnação João , Tapley Byron D. , Zhang Yu , Su Xiaoli , Shen Qiang 
Published: November 2021

AbstractGRACE observations revealed that rapid mass loss in the West Antarctic Ice Sheet (WAIS) abruptly paused in 2015, followed by a much lower rate of mass loss ( Gt yr−1) until the decommissioning of GRACE in 2017. The critical 1‐year GRACE intermission data gap raises the question of whether the reduced mass loss rate persists. The Swarm gravimetry data, which have a lower resolution, show good agreement with GRACE/GRACE‐FO observations during the overlapping period, i.e., high correlation (0.78) and consistent trend estimates. Swarm data efficiently bridge the GRACE/GRACE‐FO data gap and reveal that WAIS has returned to the rapid mass loss state ( Gt yr−1) that prevailed prior to 2015 during the GRACE intermission data gap. The changes in precipitation patterns, driven by the climate cycles, further explain and confirm the dramatic shifts in the WAIS mass loss regime implied by the Swarm observations.
Predicting Patagonian Landslides: Roles of Forest Cover and Wind Speed
Authors: Parra Eric , Mohr Christian H. , Korup Oliver 
Published: November 2021

AbstractDense tree stands and high wind speeds characterize the temperate rainforests of southern Chilean Patagonia, where landslides frequently strip hillslopes of soils, rock, and biomass. Assuming that wind loads on trees promote slope instability, we explore the role of forest cover and wind speed in predicting landslides with a hierarchical Bayesian logistic regression. We find that higher crown openness and wind speeds credibly predict higher probabilities of detecting landslides regardless of topographic location, though much better in low‐order channels and on midslope locations than on open slopes. Wind speed has less predictive power in areas that were impacted by tephra fall from recent volcanic eruptions, while the influence of forest cover in terms of crown openness remains.
Development of Heterogeneous Ice Nucleation Rate Coefficient Parameterizations From Ambient Measurements
Authors: Cornwell Gavin C. , McCluskey Christina S. , DeMott Paul J. , Prather Kimberly A. , Burrows Susannah M. 
Published: November 2021

AbstractIce nucleating particles (INPs) are a rare subset of particles that can have an outsized impact relative to their prevalence. To simulate INP variability, models require parameterizations for the most important sources of INPs. Most parameterizations in the literature were developed from laboratory experiments that used proxies for ambient particles. Whether these laboratory models effectively represent ambient aerosol is still not well understood and parameterizations developed from field measurements may be more atmospherically relevant. Expanding on previous work in which we used an ice chamber and a single‐particle mass spectrometer (SPMS) to characterize INP composition, we calculate heterogeneous ice nucleation rate coefficients for ambient particles. We find good agreement between our dust and previous measurements of airborne dust. We also use a Monte Carlo approach to assess the relative contribution of each measurement to the uncertainty and find that the biggest source is the sampling efficiency of the SPMS.
Do There Exist Energy Closures to the Observed Mirror Waves?
Authors: Hau L.‐N. , Chang C.‐K. , Wang B.‐J. 
Published: November 2021

AbstractLow‐frequency mirror waves are frequently observed in the planetary magnetosheaths for the plasma conditions of and . This study first shows that the thermodynamic conditions of the observed mirror events may well be described by a set of double‐polytropic (DP) laws first proposed by Hau and Sonnerup (1993, https://doi.org/10.1029/93gl01706), and , with the polytropic values being in the ranges of and . The physical basis of the empirical thermodynamic relations is then examined based on the mixed Vlasov‐MHD formulation for low‐frequency linear mirror instability (Ferrière & Andre, 2002, https://doi.org/10.1029/2002JA009273) which shows that the theoretical energy equations possess the DP forms with and being functions of ; in particular, for mirror unstable cases and . The theoretical predictions are found to be in high agreements with the empirical polytropic values with the average errors of ∼6.5%.
The Spontaneous Nature of Lightning Initiation Revealed
Authors: Sterpka C. , Dwyer J. , Liu N. , Hare B. M. , Scholten O. , Buitink S. , Veen S. ter , Nelles A. 
Published: November 2021

AbstractHere, we present new radio interferometer beamforming observations of lightning initiation using data from the Low‐Frequency Array (LOFAR). We show that the first lightning source in the flash increases exponentially in intensity by two orders of magnitude in 15 μs, while propagating 88 m away from the initiation location at a constant speed of 4.8 ± 0.1 × 106 m/s. A second source replaces the first source at the initiation location, and subsequent propagation of the lightning leader follows. We interpret the first source to be a rapidly propagating and intensifying positive streamer discharge that subsequently produces a hot leader channel near the initiation point. How lightning initiates is one of the greatest unsolved problems in the atmospheric sciences, and these results shed light on this longstanding mystery.
Pacific Warming Pattern Diversity Modulated by Indo‐Pacific Sea Surface Temperature Gradient
Authors: Zhang Leying , Zhao Jiuwei , Kug Jong‐Seong , Geng Xin , Xu Haiming , Luo Jingjia , Park Jae‐Heung , Zhan Ruifen 
Published: November 2021

AbstractThe multi‐model ensemble mean sea surface temperature (SST) of CMIP5 models shows an El Niño‐like Pacific warming (PW) trend, contradictory with the observational result which manifests a La Niña‐like PW pattern. Here, we demonstrate that these two SST PWs coexist in the CMIP5 models and they are largely determined by the model's tropical Indo‐Pacific SST gradient. When the Pacific warms faster than the Indian Ocean (IO), the model tends to project an El Niño‐like PW pattern. In contrast, a La Niña‐like warming trend prevails if a more rapid IO warming is simulated. We suggest that the PW pattern in an individual model is nonstationary and may transform from a La Niña‐like to an El Niño‐like when its interbasin SST gradient changes with more robust warming in the Pacific, and vice versa. Our conclusions shed great light on the future SST PW pattern change projected by the coupled models.
High Remanent Magnetization Measured in Hydrothermally Altered Lavas
Authors: Kanakiya Shreya , Turner Gillian M. , Rowe Michael C. , Adam Ludmila , Lindsay Jan M. 
Published: November 2021

AbstractMagnetic surveys are used to identify and monitor hydrothermally altered regions on volcanoes. Commonly such magnetic data are interpreted on the premise that hydrothermal alteration consumes Fe‐Ti oxides in the host rocks, reducing their total magnetization. Here, we report a contrasting observation from Whakaari (White Island) volcano in New Zealand. We study the magnetic properties of 42 conduit‐filling and surficial lithologies that have undergone varying degrees of acid‐sulfate alteration. We find that while the induced magnetization of lavas decreases with hydrothermal alteration, some altered lavas have an order of magnitude higher remanent magnetization than fresh lavas. We discuss plausible mechanisms by which altered lavas can retain high remanent magnetization including the importance of magnetic mineralogy and grain size. Our results urge caution in correlating reduced magnetization with hydrothermally altered regions. Furthermore, they highlight the importance of measuring both the induced and remanent magnetization of samples used to interpret field‐scale data.
The Fractal Nature of Clouds in Global Storm‐Resolving Models
Authors: Christensen Hannah M. , Driver Oliver G. A. 
Published: November 2021

AbstractClouds in observations are fractals: they show self‐similarity across scales ranging from 1 to 1,000 km. This includes individual storms and large‐scale cloud structures typical of organized convection. It is not known whether global storm‐resolving models reproduce the observed fractal scaling laws for clouds and organized convection. We compute the fractal dimension of clouds using Himawari satellite data and compare this to global storm‐resolving model simulations completed as part of the DYAMOND intercomparison project. We find cloud fields in these simulations are indeed fractal, and reproduce the observed fractal dimension to within 10%. We find the fractal dimension is sensitive to the choice of boundary layer parametrization scheme used in each model simulation, and not to the convection parametrization as might have been expected.
Conjugate Observation of Magnetospheric Chorus Propagating to the Ionosphere by Ducting
Authors: Shen Yangyang , Chen Lunjin , Zhang Xiao‐Jia , Artemyev Anton , Angelopoulos Vassilis , Cully Christopher M. , James H. Gordon , Yau Andrew W. , Howarth Andrew D. , Bortnik Jacob , Wu Jiashu , Tian Sheng , Hartinger Michael D. , Connors Martin , Horne Richard B. 
Published: November 2021

AbstractWhistler‐mode chorus waves are critical for driving resonant scattering and loss of radiation belt relativistic electrons into the atmosphere. The resonant energies of electrons scattered by chorus waves increase at increasingly higher magnetic latitudes. Propagation of chorus waves to middle and high latitudes is hampered by wave divergence and Landau damping but is promoted otherwise if ducted by density irregularities. Although ducting theories have been proposed since the 1960s, no conjugate observation of ducted chorus propagation from the equatorial magnetosphere to the ionosphere has been observed so far. Here we provide such an observation, for the first time, using conjugate spacecraft measurements. Ducted chorus waves maintain significant wave power upon reaching the ionosphere, which is confirmed by ray‐tracing simulations. Our results suggest that ducted chorus waves may be an important driver for relativistic electron precipitation.
The Role of a Weakened Atlantic Meridional Overturning Circulation in Modulating Marine Heatwaves in a Warming Climate
Authors: Ren Xianglin , Liu Wei 
Published: November 2021

AbstractWe explore the effect of Atlantic meridional overturning circulation (AMOC) slowdown on global marine heatwaves (MHWs) under anthropogenic warming by maintaining AMOC strength in climate model simulations throughout the 21st century. The AMOC slowdown has an insignificant effect on global MHWs during the past four decades, except those over the North Atlantic warming hole (NAWH) where the weakened AMOC reduces the occurrence and duration of MHWs by about half by creating a cooler mean‐state sea surface temperature. As the AMOC continues weakening in current century, its effect becomes significant on MHWs in the North Atlantic and Pacific Oceans. The weakened AMOC induces a bipolar‐seesaw‐like change in MHW frequencies, with more frequent MHWs in the Southern Hemisphere but less frequent MHWs in the North Hemisphere except over the NAWH. The reason for the exception is that the NAWH region would enter a near‐permanent MHW state without an AMOC slowdown.
Terrestrial Resonant Oscillations During the 11 April 2012 Sumatra Doublet Earthquake
Authors: Nayak Srinivas , Bagiya Mala S. , Maurya Satish , Hazarika Nava Kumar , Kumar A. S. Sunil , Prasad D. S. V. V. D. , Ramesh D. S. 
Published: November 2021

AbstractThe Earth's background free oscillations at ∼3.7 and ∼4.4 mHz resonantly couple with the atmospheric acoustic modes and thus energy cross‐talk between the earth‐atmosphere system is maximum at these frequencies. The present study proposes resonant coupling between the Earth's surface and atmosphere during the 11 April 2012 Sumatra doublet earthquake and offer a possible explanation to this occurrence. Following both these earthquakes, prolonged ionospheric oscillations centered at frequency of ∼4 mHz were observed in GPS (Global Positioning System) derived total electron content (TEC) towards north‐northeast of the epicenters. We scrutinize these oscillations in terms of the manifestations of plausible non‐tectonic and tectonic forcing mechanisms surrounding the epicentral region. Non‐tectonic forcing such as the geomagnetic field coupling factor and observation geometry played a critical role in determining the amplitude anisotropy of resonant ionospheric signatures. Further, the Rayleigh waves of the first earthquake (Mw 8.6) were already characterized by an excess of energy at ∼4 mHz. We propose this could make the Mw 8.6 earthquake particularly efficient to excite the 4 mHz resonance in the atmosphere. The resonant ionospheric signatures after the second earthquake (Mw 8.2) were observed to be closely associated with the Earth's free oscillations caused by R2 Rayleigh wave train of the Mw 8.6 earthquake event. Together, all the above point to a scenario where the resonant ionospheric signatures during the Sumatra doublet event were indeed related to the seismic source. Therefore, resonant co‐seismic ionospheric signatures could provide additional information on the low‐frequency features of seismic ruptures.
On Optimum Solar Wind‐Magnetosphere Coupling Functions for Transpolar Voltage and Planetary Geomagnetic Activity
Authors: Lockwood Mike , McWilliams Kathryn A. 
Published: November 2021

AbstractUsing 65,133 hourly averages of transpolar voltage (ΦPC) from observations made over 25 yr by the SuperDARN radars, with simultaneous SML and interpolated am geomagnetic indices, we study their optimum interplanetary coupling functions. We find mean lags of 18, 31, and 45 min for ΦPC, am, and SML, respectively, and fit using a general coupling function with three free fit exponents. To converge to a fit, we need to average interplanetary parameters and then apply the exponent which is a widely used approximation: we show how and why this is valid for all interplanetary parameters, except the factor quantifying the effect of the clock angle of the interplanetary magnetic field, sind(θ/2), which must be computed at high time resolution and then averaged. We demonstrate the effect of the exponent d on the distribution, and hence weighting, of samples and show d is best determined from the requirement that the coupling function is a linear predictor, yielding d of 2.50 ± 0.10, 3.00 ± 0.22, and 5.20 ± 0.41 for ΦPC, am, and SML, respectively. To check for overfitting, fits are made to half the available data and tested against the other half. Ensembles of 1,000 fits are used to study the effect of the number of samples on the distribution of errors in individual fits and on systematic biases in the ensemble means. We find only a weak dependence of solar wind density for ΦPC and SML but a significant one for am. The optimum coupling functions are shown to be significantly different for ΦPC, am, and SML.
Parametric Dependence of Polarization Reversal Effects on the Particle Pitch Angle Scattering by EMIC Waves
Authors: Lou Yuequn , Cao Xing , Ni Binbin , Wu Mingyu , Zhang Tielong 
Published: November 2021

AbstractElectromagnetic ion cyclotron (EMIC) waves play an important role in the loss of radiation belt electrons and ring current protons. After EMIC waves are excited near the magnetic equator, they will propagate to high latitudes and suffer a polarization reversal from left‐handed to right‐handed polarized at the crossover frequency. To improve the current understanding of the EMIC wave‐induced loss of radiation belt electrons and ring current protons, we perform a detailed analysis of the sensitivity of polarization reversal effects to L‐shell, electron number density, and wave frequency spectrum. Our results show that polarization reversal contributes significantly to the pitch angle diffusion coefficients at low pitch angles extending to the loss cone angle for various parameter sets. Compared with the diffusion coefficients only using L‐mode dispersion relation, inclusion of polarization reversal mainly enhances the electron scattering loss at several MeV and weaken the proton scattering loss over a broad energy range from a few keV to 1 MeV. While the increase of electron diffusion coefficients can be up to a factor of 5, the decrease of proton diffusion coefficients can be larger than an order of magnitude. As L‐shell or electron density increases, the affected resonant region by polarization reversal for both electrons and protons tends to expand to lower energies, while an increase of peak wave frequency will shift the resonant region to higher energies. Our results confirm the vital importance of including polarization reversal in understanding the EMIC wave‐induced scattering loss of radiation belt electrons and ring current protons.
An Early‐Time Solution of Pulse‐Decay Method for Permeability Measurement of Tight Rocks
Authors: Wang Yue , Nolte Steffen , Gaus Garri , Tian Zhiguo , Amann‐Hildenbrand Alexandra , Krooss Bernhard , Wang Moran 
Published: November 2021

AbstractThis contribution presents an early‐time solution for permeability evaluation in pulse‐decay tests. A nonlinear governing equation for gas transport in the sample is derived considering the pressure dependence of gas compressibility and Klinkenberg slippage effect, and the early‐time solution is obtained through the integral balance analysis. The permeability coefficient can be determined by the proposed solution through the pressure transients during the early‐time stage of the tests, that is, before the upstream pressure pulse penetrates through the core sample and reaches the downstream side. To test the proposed solution, measurements were performed on a core sample of the Cretaceous Eagle Ford shale, Texas, USA, under different pore and confining pressures. Helium was used as the testing fluid to minimize the Joule‐Thomson effect and adsorption. The experimental results show that the permeability coefficients obtained from this new solution agree well with those from the late‐time solution, and prove our solution accurate and efficient for permeability evaluation. The present approach provides a good supplement to the pulse‐decay method and is suitable for measurements of low‐permeable rocks.
Influence of Deformation and Fluids on Ti Exchange in Natural Quartz
Authors: Bestmann Michel , Pennacchioni Giorgio , Grasemann Bernhard , Huet Benjamin , Jones Michael W. M. , Kewish Cameron M. 
Published: November 2021

AbstractUsing a combination of microstructural, spectroscopic, and geochemical analyses, we investigate how subgrain rotation recrystallization and fluid migration affect Ti concentration [Ti] in naturally deformed quartz veins from the Prijakt Nappe (Austroalpine Unit, Eastern Alps). These coarse‐grained quartz veins, that formed at amphibolite facies conditions, were overprinted by lower greenschist facies deformation to different degrees. During the overprint, subgrain rotation recrystallization was dominant during progressive deformation to ultramylonitic stages. The initial [Ti] (3.0–4.7 ppm) and cathodoluminescence (CL) signature of the vein crystals decrease during deformation mainly depending on the availability of fluids across the microstructure. The amount of strain played a subordinate role in resetting to lower [Ti] and corresponding darker CL shades. Using a microstructurally controlled analysis we find that the most complete re‐equilibration in recrystallized aggregates ([Ti] of 0.2–0.6 p.m.) occurred (a) in strain shadows around quartz porphyroclasts, acting as fluid sinks, and (b) in localized microshear zones that channelized fluid percolation. [Ti] resetting is mainly observed along wetted high angle boundaries (misorientation angle >10–15°), with partial [Ti] resetting observed along dry low angle boundaries (<10–15°). This study shows for the first time that pure subgrain rotation recrystallization in combination with dissolution‐precipitation under retrograde condition provide microstructural domains suitable for the application of titanium‐in‐quartz geothermobarometry at deformation temperatures down to 300–350°C.
Magma Chamber Formation by Dike Accretion and Crustal Melting: 2D Thermo‐Compositional Model With Emphasis on Eruptions and Implication for Zircon Records
Authors: Melnik O. E. , Utkin I. S. , Bindeman I. N. 
Published: November 2021

AbstractWe present a 2D thermo‐elastic model of a magma body formation in a granitic crust by injection of rhyolitic or basaltic dikes and sills. Elastic analytical solutions enable the computation of rock displacement in response to magma intrusion and evacuation during volcanic eruptions. Phase diagrams for magma and rocks govern melting/crystallization behavior and temperature evolution in 16 million computational cells. Calculated temperature histories are used to predict zircon crystallization/dissolution, their ages, and isotopic ratios within individual batches of magma and rocks. Incremental dike injection naturally generates magma batches of melt that form kilometer‐wide clusters appearing in different parts of the domain with diverse shapes, horizontal and vertical interconnectivity. The volume of eruptive melt strongly depends on magma influx rates Q, the width of the injection region W, and eruptions. For example, rhyolitic dike injection with Q = 0.125 m3/s with W = 5 km during 100 ka generates ∼50 km3 of eruptive melt while no significant melt forms if W = 10 km. Injection of basaltic dikes into the granitic crust generates comparable amounts of rhyolitic melt from dike‐residual and country rocks. High injection intensities produce magma reservoirs capable of large eruptions, while repetitive eruptions lead to shrinkage of magma bodies. High heat input causes host rock zircons to lose a significant portion of their old cores. Magmatic zircons in the periphery form quickly due to rapid cooling of intruded dikes while in the central part crystals can grow during several hundreds of ka. The model predicts highly heterogeneous O and Hf isotopic ratios recorded in zircons.