bluuebunny/crossref_metadata_2025_split huggingface dataset:
Warmer, Wetter Climates Accelerate Mechanical Weathering in Field Data, Independent of Stress‐Loading
Authors: Eppes M. C. , Magi B. , Scheff J. , Warren K. , Ching S. , Feng T. 
Published: December 2020

AbstractWeathering is a foundational process in most Earth systems, but there has been a lack of data directly quantifying what influences mechanical weathering. Here we use multiple years of in situ field data, “listening” to acoustic emissions of naturally cracking rocks, to test a hypothesized link between climate and subcritical crack‐tip processes (i.e., the bond‐breaking mechanism thought to embody most mechanical weathering). Our results challenge the assumption of a singular dependence of mechanical weathering on stresses. We find that mechanical weathering rates exponentially increase as functions of atmospheric vapor pressure (VP), temperature, and relative humidity, even when controlling for stress‐loading. VP exerts the most pronounced influence on the observed mechanical weathering rates. Put in the context of global climate change, our results underscore the potential for climate‐dependent subcritical crack‐tip processes to influence all weathering‐allied problems including the long‐term stabilization of the climate by weathering‐carbon‐cycle feedbacks.
The Implications of Temporal Variability in Wave‐Particle Interactions in Earth's Radiation Belts
Authors: Watt C. E. J. , Allison H. J. , Thompson R. L. , Bentley S. N. , Meredith N. P. , Glauert S. A. , Horne R. B. , Rae I. J. 
Published: December 2020

AbstractChanges in electron flux in Earth's outer radiation belt can be modeled using a diffusion‐based framework. Diffusion coefficients D for such models are often constructed from statistical averages of observed inputs. Here, we use stochastic parameterization to investigate the consequences of temporal variability in D. Variability time scales are constrained using Van Allen Probe observations. Results from stochastic parameterization experiments are compared with experiments using D constructed from averaged inputs and an average of observation‐specific D. We find that the evolution and final state of the numerical experiment depends upon the variability time scale of D; experiments with longer variability time scales differ from those with shorter time scales, even when the time‐integrated diffusion is the same. Short variability time scale experiments converge with solutions obtained using an averaged observation‐specific D, and both exhibit greater diffusion than experiments using the averaged‐input D. These experiments reveal the importance of temporal variability in radiation belt diffusion.
Subpolar Activation of Halogen Heterogeneous Chemistry in Austral Spring
Authors: Zambri Brian , Kinnison Douglas E. , Solomon Susan 
Published: December 2020

AbstractHeterogeneous halogen chemistry plays a dominant role in driving changes in polar chemical composition and ozone depletion. Activation of halogens outside the polar regions may result in depletion of local ozone, along with changes in the chemical budgets of various species in the lower stratosphere (LS). In this study, the means and distributions of NO2 measurements from the Stratospheric Aerosol and Gas Experiment III (SAGE3m) are compared to simulations from a coupled climate‐chemistry model, in order to better characterize and quantify subpolar heterogeneous halogen chemistry. NO2 abundances from a simulation with heterogeneous chemistry are drawn from the same distribution as the SAGE3m observations, while the NO2 distribution is different in a simulation without heterogeneous chemistry. Results indicate that heterogeneous chemistry plays a significant role in determining the chemical composition of the subpolar LS in austral spring and show how analysis of distribution functions can provide useful insights into chemical processes.
Lake Morphometry and River Network Controls on Evasion of Terrestrially Sourced Headwater CO2
Authors: Brinkerhoff C. B. , Raymond P. A. , Maavara T. , Ishitsuka Y. , Aho K.S. , Gleason C. J. 
Published: December 2020

AbstractLakes are central components of the inland water system distinct from, yet inextricably connected to, river networks. Currently, existing network‐scale biogeochemistry research, although robust, typically treats each of these components separately or reductively. Here, we incorporate lake morphometry into a fully connected stream/lake network for the Connecticut River watershed and model potential evasion of terrestrially sourced headwater CO2 as transported through the network, ignoring in‐stream production. We found that approximately 25%–30% of total potential soil CO2 evasion occurs in lakes, and percent evasion is inversely related to streamflow. A lake's ability to evade CO2 is controlled by residence time and size: most lakes with residence time over 7 days or surface area greater than 0.004 km2 evade functionally all terrestrial CO2 entering from upstream, precluding further downstream transport. We conclude that lakes are important for soil CO2 degassing and that this coupled river/lake approach is promising for CO2 studies henceforth.
Deformation Precursors to Catastrophic Failure in Rocks
Authors: McBeck J. A. , Aiken J. M. , Mathiesen J. , Ben‐Zion Y. , Renard F. 
Published: December 2020

AbstractForecasting the timing of catastrophic failure, such as crustal earthquakes, has been a central concern for centuries. Such forecasting requires identifying signals that evolve or accelerate in the precursory phase leading to failure, and the subset of signals that may be detected in the crust. We develop machine learning models to predict the proximity of catastrophic failure in synchrotron X‐ray tomography triaxial compression experiments on rocks using characteristics of evolving fracture networks. We then examine the characteristics that most strongly influence the model results, and thus may be considered the best predictors of the proximity of macroscopic failure. The resulting suite of predictive parameters underscores the importance of dilation in the precursory phase leading to catastrophic failure. The results indicate that the evolution of the strain energy density field may provide more robust predictions of the proximity of failure than other existing metrics of rock deformation.
Enhanced PM2.5 Decreases and O3 Increases in China During COVID‐19 Lockdown by Aerosol‐Radiation Feedback
Authors: Zhu Jia , Chen Lei , Liao Hong , Yang Hao , Yang Yang , Yue Xu 
Published: December 2020

AbstractWe apply an online‐coupled meteorology‐chemistry model (WRF‐Chem) embedded with an improved process analysis to examine aerosol‐radiation feedback (ARF) impacts on effectiveness of emission control due to Coronavirus Disease 2019 (COVID‐19) lockdown over North China Plain. Emission reduction alone induces PM2.5 decrease by 16.3 μg m−3 and O3 increase by 10.2 ppbv during COVID‐19 lockdown. The ARF enhances PM2.5 decrease by 2.7 μg m−3 (16.6%) and O3 increase by 0.8 ppbv (7.8%). The ARF‐induced enhancement of PM2.5 decline is mostly attributed to aerosol chemistry process, while enhancement of O3 rise is ascribed to physical advection and vertical mixing processes. A set of sensitivity experiments with emission reductions in different degrees indicate that the ARF‐induced enhancements of PM2.5 declines (O3 rises) follow a robust linear relationship with the emission‐reduction‐induced PM2.5 decreases. The fitted relationship has an important implication for assessing the effectiveness of emission abatement at any extent.
On the Fluctuations in Volcanic Plumes
Authors: Woitischek Julia , Edmonds Marie , Woods Andrew W. 
Published: December 2020

AbstractSome basaltic open vent volcanoes show that spectroscopic SO2 measurements of a volcanic gas plume are characterized by a fluctuating signal. Understanding the origin of these fluctuations is of great interest for interpreting volcanic gas emission regimes. Although some fluctuations may be associated with intermittency in the source flux, some may be associated with the turbulence in the flow. A simple laboratory experiment, in which we release dye pulses into a turbulent wake in a small water‐filled channel, suggests that when the intermittency of the source has comparable or smaller timescale as the turbulence, the fluctuations are similar, whereas when the intermittency of the source has longer timescale than the turbulence, the fluctuations can be distinguished. We also present some small‐scale laboratory experiments of turbulent buoyant plumes produced from a steady source; these demonstrate a time‐fluctuating concentration of source fluid downstream and the fluctuation period tends to increase with distance.
Sea Ice Thickness in the Western Ross Sea
Authors: Rack Wolfgang , Price Daniel , Haas Christian , Langhorne Patricia J. , Leonard Greg H. 
Published: December 2020

AbstractUsing airborne measurements, we provide a first direct glimpse of the sea ice thickness distribution in the western Ross Sea, Antarctica, where the distinguishing sea ice process is the regular occurrence of the Ross Sea, McMurdo Sound, and Terra Nova Bay polynyas. Two flights in November 2017 over a length of 800 km reveal a heavily deformed ice regime with a mean thickness of 2.0 ± 1.6 m. Supported by satellite image analysis, we identify regional variability in ice thickness based on formation history. Sea ice thickness gradients are highest within 100 and 200 km of the Terra Nova Bay and McMurdo Sound polynyas, respectively, where the mean thickness of the thickest 10% of ice is 7.6 m. Overall, about 80% of the ice is heavily deformed, concentrated in ridges with thicknesses of 3.0–11.8 m. This is evidence that sea ice is much thicker than in the central Ross Sea.
Rectification of the Intraseasonal SST Variability by the Diurnal Cycle of SST Revealed by the Global Tropical Moored Buoy Array
Authors: Yan Yunwei , Zhang Lei , Yu Yi , Chen Changlin , Xi Jingyuan , Chai Fei 
Published: December 2020

AbstractIt has been suggested that the intraseasonal sea surface temperature (SST) variability in the tropical oceans can be amplified by the diurnal cycle of SST (dSST). Here, by analyzing the global tropical moored buoy array for the first time, we find that the intraseasonal SST variability is indeed amplified by the dSST in most of the tropical oceans, especially in the Indo‐Pacific warm pool, but weakened in the equatorial cold tongues of the Pacific and Atlantic Oceans. Such a divergent response is associated with the difference in atmosphere‐ocean interaction processes over these two regions. In the warm pool region, SST responds to the intraseasonal atmospheric variability, resulting in in‐phase intraseasonal fluctuations between SST and dSST that amplify the intraseasonal SST variability. However, in the cold tongue region, SST drives the atmospheric changes, which leads to out‐of‐phase intraseasonal fluctuations between SST and dSST and thus the inhibition of the intraseasonal SST variability.
Evolution of a Tornado and Debris Ball Associated With Super Typhoon Hagibis 2019 Observed by X‐Band Phased Array Weather Radar in Japan
Authors: Morotomi Kazuomi , Shimamura Shigeharu , Kobayashi Fumiaki , Takamura Tamio , Takano Toshiaki , Higuchi Atsushi , Iwashita Hisato 
Published: December 2020

AbstractA tornado associated with category 5 Super Typhoon Hagibis occurred on October 12, 2019 in Ichihara City, Chiba Prefecture, Japan. An X‐band phased array weather radar revealed the occurrence of the tornado at the south edge of its parent cloud, which had several characteristics of a classic supercell (mesocyclone, hook‐shaped echo, bounded weak echo region, and vault shape). Phased array radar observation also revealed a three‐dimensional multiscale structure of the tornado with a mesocyclone and misocyclone at different altitudes. The misocyclone, the vorticity of which intensified for several minutes under the mesocyclone, resulted in the formation of a tornado and debris ball. The echo top height of the debris ball abruptly increased at the time when the vorticity of the misocyclone maximized at low levels, suggesting a rapid evolution of tornadic vortex and the associated damage on the ground.
Retrogressive Thaw Slumps on Ice‐Rich Permafrost Under Degradation: Results From a Large‐Scale Laboratory Simulation
Authors: Costard F. , Dupeyrat L. , Séjourné A. , Bouchard F. , Fedorov A. , Saint‐Bézar B. 
Published: December 2020

AbstractIn the ice‐rich permafrost of the Arctic regions, thermokarst erosion on slopes induces the formation of large‐scale retrogressive thaw slumps (RTS). They have significant geomorphological, hydrological, and biogeochemical impacts on the landscape. Further research is thus needed to better understand the respective effect of ice content and permafrost heterogeneities on the dynamics of these erosional features. Here, we present results of a full‐scale physical modeling of RTS development in a cold room. The experimental setup was designed to simulate and compare two ground‐ice settings (ice wedges, icy layers) with the thawing of ice‐poor permafrost (i.e., reference model). Our results show that the melting of the icy layers induces a loss of decohesion of the overlapping frozen soil. The heterogeneous frozen soil with ice wedges needs a longer time until degradation, but undergoes a stronger and faster decohesion of its structure during the thawing phase.
Forecasting the Permanent Loss of Lake Ice in the Northern Hemisphere Within the 21st Century
Authors: Sharma Sapna , Blagrave Kevin , Filazzola Alessandro , Imrit M. Arshad , Hendricks Franssen Harrie‐Jan 
Published: December 2020

AbstractLake ice cover is essential to conserving the global freshwater supply for the 50 million lakes that freeze each winter. Here, we ask when lakes across the Northern Hemisphere may permanently lose ice cover. A K‐means cluster analysis from 31 lakes identified four clusters of lakes vulnerable to losing ice cover, including shallow and deep lakes in regions where winter air temperatures hover ∼0 °C and larger and deeper lakes in colder regions. By the end of this century, we estimate that up to 5,679 lakes of 1.35 million HydroLAKES may permanently lose ice cover if greenhouse gas emissions (GHG) continue to be emitted at current levels. In the Northern Hemisphere, lakes in southern and coastal regions, some of which are among the largest lakes in the world and in close proximity to large human populations, are the most vulnerable to permanently losing ice.
Centennial‐Scale Shifts in Storm Frequency Captured in Paleohurricane Records From The Bahamas Arise Predominantly From Random Variability
Authors: Wallace Elizabeth J. , Coats Sloan , Emanuel Kerry , Donnelly Jeffrey P. 
Published: December 2020

AbstractEvent‐based paleohurricane reconstructions of the last millennium indicate dramatic changes in the frequency of landfalling hurricanes on centennial timescales. It is difficult to assess whether the variability captured in these paleorecords is related to changing climate or randomness. We assess whether centennial‐scale active and quiet intervals of intense hurricane activity occur in a set of synthetic storms run with boundary conditions from an earth system model simulation of the last millennium. We generate 1,000 pseudo sedimentary records for a site on South Andros Island using a Poisson random draw from this synthetic storm data set. We find that any single pseudo sedimentary record contains active and quiet intervals of hurricane activity. The 1,000‐record ensemble average, which reflects the common signal of climate variability, does not. This suggests that the record of paleohurricane activity from The Bahamas reflects variability in hurricane frequency dominated by randomness and not variability in the climatic conditions.
Air‐Sea Interactions in the Cold Wakes of Tropical Cyclones
Authors: Pasquero Claudia , Desbiolles Fabien , Meroni Agostino N. 
Published: December 2020

AbstractTropical cyclones generate a large and wide cold wake along their trajectories, which conditions the subsequent evolution of the tropical cyclone themselves. The cold wakes persist for weeks, impacting both the upper ocean, the air‐sea fluxes, and the atmosphere. The study by Z. Ma et al. (2020, https://doi.org/10.1029/2020GL088873) for the first time analyzes a composite of remotely sensed data sets to show that cold wakes modify surface winds and reduce cloud coverage and rainfall. These results contribute to shedding light on the mechanisms at the origin of the air‐sea feedbacks, which can differ at different latitudes depending on the stability of the marine atmospheric boundary layer. The work stimulates further research to assess whether the cloud cover anomalies induced by tropical cyclones significantly modify the radiative budget of the Earth.
Improved Decadal Predictions of North Atlantic Subpolar Gyre SST in CMIP6
Authors: Borchert Leonard F. , Menary Matthew B. , Swingedouw Didier , Sgubin Giovanni , Hermanson Leon , Mignot Juliette 
Published: December 2020

AbstractDue to its wide‐ranging impacts, predicting decadal variations of sea surface temperature (SST) in the subpolar North Atlantic remains a key goal of climate science. Here, we compare the representation of observed subpolar SST variations since 1960 in initialized and uninitialized historical simulations from the 5th and 6th phases of the Coupled Model Intercomparison Project (CMIP5/6). Initialized decadal hindcasts from CMIP6 explain 88% of observed SST variance post‐1980 in the subpolar gyre at lead years 5–7 (77% in uninitialized simulations) compared to 42% (8%) in CMIP5, indicating a more prominent role for forcing in driving observed subpolar SST changes than previously thought. Analysis of single‐forcing experiments suggests much of this correlation is due to natural forcing, explaining ∼55% of the observed variance. The amplitude of observed subpolar SST variations is underestimated in historical simulations and improved by initialization in CMIP6, indicating continued value of initialization for predicting North Atlantic SST.
Ring Current Decay During Geomagnetic Storm Recovery Phase: Comparison Between RBSP Observations and Theoretical Modeling
Authors: Chen Ao , Yue Chao , Chen Hongfei , Zong Qiugang , Fu Suiyan , Wang Yongfu , Ren Jie 
Published: December 2020

AbstractRing current decay during storm recovery phase may be affected by different loss processes. In this study, we have investigated the lifetimes of ring current ions (H+ and O+) of energies from 1 keV to several hundred keV at L shell from 3 to 6 during the storm recovery phase through a statistical survey. The observational data of 48 geomagnetic storms from March 2013 to May 2019 are collected based on Van Allen Probe observations. We find that (1) the observed lifetimes of H+ and O+ in general increase with L shell and (2) the lifetimes of H+ is short than that of O+ when E < ∼50 keV while the situation is reversed when E > ∼50 keV. In addition, we have made use of the charge exchange theory, combined with previous experimental results on the charge exchange cross section and two distribution models of neutral hydrogen atoms in the exosphere, so as to directly estimate the ring current ions decay caused by charge exchange mechanism only. Through the comparison between the model predictions of charge exchange lifetime and the observed lifetimes, we find that (3) the observed lifetimes are in general consistent with model results, which confirms that charge exchange is a dominant loss mechanism of ring current ions during storm recovery phase.
Surface‐Wave Attenuation From Seismic Ambient Noise: Numerical Validation and Application
Authors: Magrini Fabrizio , Boschi Lapo 
Published: December 2020

AbstractWe evaluate, by numerical tests, whether surface‐wave attenuation can be determined from ambient‐noise data. We generate synthetic recordings of numerically simulated ambient seismic noise in several experimental setups, characterized by different source distributions and different values of attenuation coefficient. We use them to verify that the source spectrum can be reconstructed from ambient recordings (provided that the density of sources and the attenuation coefficient are known) and that true attenuation can be retrieved from normalized cross correlations of synthetic signals. We then apply the so validated method to real continuous recordings from 33 broadband receivers distributed within the Colorado Plateau and Great Basin. A preliminary analysis of the signal‐to‐noise ratio as a function of azimuth reveals a SW‐NE preferential directionality of the noise sources within the secondary microseism band (6–8 s), consistent with previous studies. By nonlinear inversion of noise data we find the attenuation coefficient in the area of interest to range from ∼ 1 × 10−5 m−1 at 0.3 Hz to ∼ 4.5 × 10−7 m−1 at 0.065 Hz, and confirm the statistical robustness of this estimate by means of a bootstrap analysis. The result is compatible with previous observations based on both earthquake‐generated and ambient Rayleigh waves. In this regard, the method proves to be promising in accurately quantifying surface‐wave attenuation at relatively high frequencies.
Structure of the Offshore Obducted Oman Margin: Emplacement of Semail Ophiolite and Role of Tectonic Inheritance
Authors: Ninkabou D. , Agard P. , Nielsen C. , Smit J. , Gorini C. , Rodriguez M. , Haq B. , Chamot‐Rooke N. , Weidle C. , Ducassou C. 
Published: December 2020

AbstractThe northern Oman margin is a key area for understanding the emplacement of the Semail Ophiolite and obduction processes in general. This study uses a grid of 2D‐multichannel seismic lines tied to well data to characterize the offshore domain of the Semail Ophiolite and reappraises the obduction and post‐obduction history of the Oman margin. West of Muscat, in the Sohar basin, the late Cretaceous to Paleogene tectonic mega‐sequence records syn‐ to late‐obduction stages and the deposition of erosional products of the autochthonous Arabian sediments, including a major mass transport complex. Syn‐obduction thrusting is documented in this sector only, as a major fault emplacing a distal basement high (likely volcanic) onto Campanian sediments over >10 km. To the east, the Hatat and Tiwi basins are characterized by a less‐copious Maastrichtian‐Paleogene sequence. These basins developed above a domain characterized by the northern equivalent of the Saih Hatat dome and later extensional faults. This sector distinctively records the extensional phase associated with the exhumation and erosion of the subducted continental margin. The dichotomy between the two sectors is linked due to a structural high located offshore, in the continuation of the Semail Gap transfer fault. We propose that this transfer fault, coincident with a major Pan‐African structure, affected the architecture of the passive margin during both rifting of the Neotethys and later ophiolite emplacement, that is, during (continental) subduction and obduction.
Calsequestrin: a well-known but curious protein in skeletal muscle
Authors: Woo Jin Seok , Jeong Seung Yeon , Park Ji Hee , Choi Jun Hee , Lee Eun Hui 
Published: December 2020

AbstractCalsequestrin (CASQ) was discovered in rabbit skeletal muscle tissues in 1971 and has been considered simply a passive Ca2+-buffering protein in the sarcoplasmic reticulum (SR) that provides Ca2+ions for various Ca2+signals. For the past three decades, physiologists, biochemists, and structural biologists have examined the roles of the skeletal muscle type of CASQ (CASQ1) in skeletal muscle and revealed that CASQ1 has various important functions as (1) a major Ca2+-buffering protein to maintain the SR with a suitable amount of Ca2+at each moment, (2) a dynamic Ca2+sensor in the SR that regulates Ca2+release from the SR to the cytosol, (3) a structural regulator for the proper formation of terminal cisternae, (4) a reverse-directional regulator of extracellular Ca2+entries, and (5) a cause of human skeletal muscle diseases. This review is focused on understanding these functions of CASQ1 in the physiological or pathophysiological status of skeletal muscle.