bluuebunny/crossref_metadata_2025_split huggingface dataset:
South Asian Summer Monsoon Response to Aerosol‐Forced Sea Surface Temperatures
Authors: Li Xiaoqiong , Ting Mingfang , You Yujia , Lee Dong‐Eun , Westervelt Daniel M. , Ming Yi 
Published: January 2020

AbstractClimate models suggest that anthropogenic aerosol‐induced drying dominates the historical rainfall changes over the heavily populated South Asian monsoon region. The regional response depends on both the aerosol fast radiative effect and the slow process through sea surface temperature (SST) cooling. Two atmospheric general circulation models, NCAR‐CAM5 and GFDL‐AM3, are used to investigate the monsoon response to prescribed aerosol‐forced SSTs. The total SST is separated into uniform cooling and a spatially varying component characterized by interhemispheric asymmetry. The monsoon rainfall is predominantly controlled by the nonuniform SSTs, in the local Indian Ocean, South, and East China Seas (IO‐CSs). The reduced meridional SST gradient in the IO‐CSs leads to weakened monsoon circulation, which drives a north‐south dipole rainfall change. The latitudinal location of the dipole shows model dependence due to differences in local SSTs and their meridional gradient, which determines the latitudinal location of the meridional overturning circulation responses.
Collisionless Magnetic Reconnection in an Asymmetric Oxygen Density Configuration
Authors: Kolstø Håkon Midthun , Hesse Michael , Norgren Cecilia , Tenfjord Paul , Spinnangr Susanne Flø , Kwagala Norah 
Published: January 2020

AbstractCombined with the magnetic field, the distribution of charged particles in the inflow region is expected to control the rate of magnetic reconnection. This paper investigates how the reconnection process is altered by a cold, asymmetrically distributed, oxygen population, which is initially located away from the current layer in the inflow regions. A particle‐in‐cell simulation is used to gain further insight into the dynamics of the system. The time evolution of the reconnection process proceeds rapidly compared to the cyclotron period of O
. Therefore, the oxygen remains, to a good approximation, demagnetized. Thus, Alfvén scaling is not an adequate description of the reconnection rate. A scaling relation for the reconnection rate for an asymmetrically distributed, demagnetized species has been developed. Additionally, we find that an asymmetric density configuration leads to a distinct motion of the reconnection site and generates an asymmetry of the diffusion region and the Hall electric field.
Stability of Marine Organic Matter Respiration Stoichiometry
Authors: Tanioka T. , Matsumoto K. 
Published: January 2020

AbstractThe amount of oxygen consumed during organic matter remineralization critically depends on how much organic carbon is remineralized per unit dissolved oxygen respired (respiratory quotient, RQ) but the global distribution and the mechanisms that control RQ are not well understood. Here we estimate RQ in the surface ocean by using two independent methods, one using satellite‐derived macromolecular composition of phytoplankton and another using objectively gridded nutrient data. Both methods yield mean RQ of ~0.7 with small spatial variability consistent with previous estimates. This pattern is likely to be a result of phytoplankton protein content universally exceeding those of carbohydrates and lipids. At face value, the relative stability of RQ suggests that the remineralization stoichiometry will not affect the ongoing deoxygenation of the world ocean. However, the possibility remains that RQ may increase in the future (e.g., organic matter becoming more carbohydrate‐dominated) and thus ameliorate deoxygenation.
Sensitivity of Blocks and Cyclones in ERA5 to Spatial Resolution and Definition
Authors: Rohrer M. , Martius O. , Raible C. C. , Brönnimann S. 
Published: January 2020

AbstractERA5, the fifth‐generation reanalysis of the European Center for Medium‐Range Weather Forecasts, provides long time series of atmospheric fields at high spatial and temporal resolution. It allows detailed studies of atmospheric flow features such as blocks or cyclones. We investigate characteristics of blocks and cyclones in ERA5 using different algorithms, compare the results to ERA5's predecessor, ERA‐interim, and investigate how these characteristics depend on spatial resolution. Generally, ERA5 and ERA‐interim characterize blocks and cyclones similarly. For Lagrangian detection and tracking methods, blocks are more robust than cyclones to changes in resolution and reanalysis choice. Eulerian methods are robust to changes in resolution. Thus, ERA5 provides a state‐of‐the‐art reanalysis for the synoptic‐scale extratropical circulation. We find that Lagrangian cyclone characteristics are strongly dependent on spatial resolution and therefore recommend that model and reanalysis data should be mapped to a common resolution for verification.
Revisiting the Impact of Sea Salt on Climate Sensitivity
Authors: Paulot Fabien , Paynter David , Winton Michael , Ginoux Paul , Zhao Ming , Horowitz Larry W. 
Published: January 2020

AbstractRecent laboratory and field studies point to an increase of sea salt aerosol (SSA) emissions with temperature, suggesting that SSA may lower climate sensitivity. We assess the impact of a strong (4.2% K
) and weak (0.7% K
) temperature response of SSA emissions on the climate sensitivity of the coupled climate model CM4. We find that the stronger temperature dependence improves the simulation of marine aerosol optical depth sensitivity to temperature and lowers CM4 Transient Climate Response (‐0.12 K) and Equilibrium Climate Sensitivity (‐0.5 K). At
doubling, the higher SSA emission sensitivity causes a negative radiative feedback (‐0.125
), which can only be partly explained by changes in the radiative effect of SSA (‐0.08
). Stronger radiative feedbacks are dominated by more negative low‐level cloud feedbacks in the Northern Hemisphere, which are partly offset by more positive feedbacks in the Southern Hemisphere associated with a weaker Atlantic Meridional Overturning Circulation.
Intraplate Volcanism and Regional Geodynamics in NE Asia Revealed by Anisotropic Rayleigh‐Wave Tomography
Authors: Fan Xingli , Chen Qi‐Fu , Legendre C. P. , Guo Zhen 
Published: January 2020

AbstractSeismic structure related to the magmatic system beneath the potentially hazardous Changbaishan volcano recently becomes hotly debated. In addition, mantle flow dynamics throughout the back‐arc regions in NE Asia remain poorly constrained due to the lack of seismic data in the Korean Peninsula and surrounding ocean regions. In this study we construct a high‐resolution azimuthally anisotropic Rayleigh‐wave phase velocity model in NE Asia, by integrating seismic data from China, North Korea, South Korea, and Japan. The resulting isotropic velocity maps suggest possible existence of a crustal magma chamber beneath the Changbaishan volcano and that the widespread intraplate volcanism in NE Asia likely arises from the upwelling asthenosphere. The obtained anisotropic maps reveal trench‐normal return flow patterns in the back‐arc regions of NE Asia with local variations between East China and northeast China as controlled by the subduction geometry of the Pacific slab.
Direct Evidence of the Pitch Angle Scattering of Relativistic Electrons Induced by EMIC Waves
Authors: Zhu Hui , Chen Lunjin , Claudepierre Seth G. , Zheng Liheng 
Published: January 2020

AbstractIn this study, we analyze an electromagnetic ion cyclotron (EMIC) wave event of rising tone elements recorded by the Van Allen Probes. The pitch angle distributions of relativistic electrons exhibit a direct response to the two elements of EMIC waves: at the intermediate pitch angle, the fluxes are lower; and at the low pitch angle, the fluxes are higher than those when no EMIC was observed. In particular, the observed changes in the pitch angle distributions are most likely to be caused by nonlinear wave‐particle interaction. The calculation of the minimum resonant energy and a test‐particle simulation based on the observed EMIC waves support the role of the nonlinear wave‐particle interaction in the pitch angle scattering. This study provides direct evidence for the nonlinear pitch angle scattering of electrons by EMIC waves.
Does a Damaged‐Fault Zone Mitigate the Near‐Field Impact of Supershear Earthquakes?—Application to the 2018 7.5 Palu, Indonesia, Earthquake
Authors: Oral Elif , Weng Huihui , Ampuero Jean Paul 
Published: January 2020

AbstractThe impact of earthquakes can be severely aggravated by cascading secondary hazards. The 2018
7.5 Palu, Indonesia, earthquake led to devastating tsunamis and landslides, while triggered submarine landslides possibly contributed substantially to generate the tsunami. The rupture was supershear over most of its length, but its speed was unexpectedly slow for a supershear event, between the
wave velocity
and Eshelby's speed
, an unstable speed range in conventional theory. Here, we investigate whether dynamic rupture models including a low‐velocity fault zone can reproduce such a steady supershear rupture with a relatively low speed. We then examine numerically how this peculiar feature of the Palu earthquake could have affected the near‐field ground motion and thus the secondary hazards. Our findings suggest that the presence of a low‐velocity fault zone can explain the unexpected rupture speed and may have mitigated the near‐field ground motion and the induced landslides in Palu.
The Fate of Liquids Trapped During the Earth's Inner Core Growth
Authors: Lasbleis M. , Kervazo M. , Choblet G. 
Published: January 2020

AbstractThe growth history of the inner core is inherently linked to the thermal history of the Earth. The crystallization of the inner core may have been delayed by supercooling and gone through an initial phase of fast growth after the nucleation barrier has been passed, but so far no evidence or constraint has been proposed to time this possible event. With two‐phase flow dynamics, we explore the effect of different growth scenarios for the inner core to determine their effects on its liquid fraction structure. Seismic observations on the melt fraction inside the inner core at present limit the porosity to a maximum of 10% of liquid. Our model provides constraints for the delay in nucleation compared to the time where the first crystal may have started to nucleate, and we find that the supercooling cannot have exceeded 100 K.
The Life Cycle of Annual Waves in the Indian Ocean as Identified by Seamless Diagnosis of the Energy Flux
Authors: Li Zimeng , Aiki Hidenori 
Published: January 2020

AbstractIn previous studies, the role of large‐scale waves in tropical‐extratropical interactions has been little investigated in terms of wave energy transfer owing to the lack of appropriate diagnostic techniques. Using a new seamless scheme, the present study identifies a series of well‐defined horizontal circulation routes of wave energy in the Indian Ocean on an annual basis. One of these features represents a localized cyclonic circulation close to the western boundary in each hemisphere while the other manifests as a basin‐scale cyclonic circulation in the eastern Indian Ocean. For the second baroclinic mode, eastward energy fluxes associated with equatorial Kelvin waves appear when zonal velocity anomaly exhibits eastward and westward peaks (four times per year) in response to the monsoon‐wind cycle. Identification of these key pathways of wave energy circulation enables us to better understand how waves in the tropical and subtropical regions interconnect at the zonal boundaries of the Indian Ocean.
Efficient Image‐Based Simulation of Flow and Transport in Heterogeneous Porous Media: Application of Curvelet Transforms
Authors: Aljasmi Abdullah , Sahimi Muhammad 
Published: January 2020

AbstractFlow, transport, reaction, adsorption, and deformation (FTRAD) are phenomena that occur in a wide variety of heterogeneous porous media and have been studied for decades. Models of heterogeneous porous formations involve approximations, simplifications, and even unjustified assumptions. With advances in instrumentation, obtaining highly resolved images of such media has become feasible, opening the way to direct image‐based simulation of the FTRAD. Such simulations require, however, intensive computations, limiting their utility. We propose a novel methodology whereby (i) the image is taken to the curvelet space, (ii) all the curvelet coefficients that are smaller than a threshold are set to 0, and (iii) the image is reconstructed. By carrying out image‐based simulations of diffusion and fluid flow in two distinct types of heterogeneous porous media, we demonstrate that simulations in the reconstructed images yield as accurate results as those in the original ones while speeding up the computation by 2 orders of magnitude or better. Thus, the methodology represents a significant step toward the ultimate goal of making direct image‐based simulation of the FTRAD in heterogeneous porous media a standard practice.
Submarine Groundwater and Vent Discharge in a Volcanic Area Associated With Coastal Acidification
Authors: Cardenas M. Bayani , Rodolfo Raymond S. , Lapus Mark R. , Cabria Hillel B. , Fullon Jose , Gojunco Gordos R. , Breecker Daniel O. , Cantarero Danica M. , Evaristo Jaivime , Siringan Fernando P. , Zhang Tongwei 
Published: January 2020

AbstractWe investigated submarine groundwater discharge (SGD) in a volcanic coastal area that hosts the world's most biodiverse reefs. Measurements of 222Rn activity in coastal seawater, a tracer for groundwater, indicated prevalent SGD. In areas where seawater 222Rn activity was generally higher, we discovered hydrothermal springs emitting acidic waters (pH ~5.4–6.0) and venting magmatic CO2 that brought local pCO2 levels up to 95,000 ppm. The collection of vents raised CO2 and lowered pH over 1–2 km of coastline. The hydrogen and oxygen isotope compositions of water and chloride concentration revealed that the springs discharge recirculated seawater mixed variably with terrestrial groundwater. Shallower springs and pore water have a higher proportion of terrestrial groundwater than deeper springs, which emit mostly recirculated seawater. This suggests that different SGD mechanisms are present. The SGD could be contributing to the evolution and function of the biodiverse ecosystem, but it also represents myriad pathways for contamination.
Microbial Methane From Methylphosphonate Isotopically Records Source
Authors: Taenzer L. , Carini P. C. , Masterson A. M. , Bourque B. , Gaube J. H. , Leavitt W. D. 
Published: January 2020

AbstractMethane is a potent greenhouse gas commonly supersaturated in the oxic surfaces waters of oceans and lakes, yet canonical microbial methanogens are obligate anaerobes. One proposed methane production pathway involves microbial degradation of methylphosphonate (MPn), which can proceed in the presence of oxygen. Directly tracing dissolved methane to its source in oxic waters, however, remains a challenge. To address this knowledge gap, we quantified the carbon isotopic fractionation between substrate MPn and product methane (1.3‰) in lab experiments, which was 1 to 2 orders of magnitude smaller than canonical pathways of microbial methanogenesis (20 to 100‰). Together, these results indicated that microbial catabolism of MPn is a source of methane in surface oceans and lake waters, but to differentiate sources of MPn in nature a further accounting of all sources is necessary. Methane from this pathway must be considered in constraining the marine carbon cycle and methane budget.
Imaging Stress and Faulting Complexity Through Earthquake Waveform Similarity
Authors: Trugman Daniel T. , Ross Zachary E. , Johnson Paul A. 
Published: January 2020

AbstractWhile the rupture processes of nearby earthquakes are often highly similar, characterizing the differences can provide insight into the complexity of the stress field and fault network in which the earthquakes occur. Here we perform a comprehensive analysis of earthquake waveform similarity to characterize rupture processes in the vicinity of Ridgecrest, California. We quantify how similar each earthquake is to neighboring events through cross correlation of full waveforms. The July 2019 Ridgecrest mainshocks impose a step reduction in earthquake similarity, which suggests variability in the residual stress field and activated fault structures on length scales of hundreds of meters or less. Among these aftershocks, we observe coherent spatial variations of earthquake similarity along the mainshock rupture trace, and document antisimilar aftershock pairs with waveforms that are nearly identical but with reversed polarity. These observations provide new, high‐resolution constraints on stress transfer and faulting complexity throughout the Ridgecrest earthquake sequence.
Burial and Origin of Permafrost‐Derived Carbon in the Nearshore Zone of the Southern Canadian Beaufort Sea
Authors: Grotheer H. , Meyer V. , Riedel T. , Pfalz G. , Mathieu L. , Hefter J. , Gentz T. , Lantuit H. , Mollenhauer G. , Fritz M. 
Published: January 2020

AbstractDetailed organic geochemical and carbon isotopic (δ13C and Δ14C) analyses are performed on permafrost deposits affected by coastal erosion (Herschel Island, Canadian Beaufort Sea) and adjacent marine sediments (Herschel Basin) to understand the fate of organic carbon in Arctic nearshore environments. We use an end‐member model based on the carbon isotopic composition of bulk organic matter to identify sources of organic carbon. Monte Carlo simulations are applied to quantify the contribution of coastal permafrost erosion to the sedimentary carbon budget. The models suggest that ~40% of all carbon released by local coastal permafrost erosion is efficiently trapped and sequestered in the nearshore zone. This highlights the importance of sedimentary traps in environments such as basins, lagoons, troughs, and canyons for the carbon sequestration in previously poorly investigated, nearshore areas.
Variability in Marine Plankton Ecosystems Are Not Observed in Freshly Emitted Sea Spray Aerosol Over the North Atlantic Ocean
Authors: Bates T. S. , Quinn P. K. , Coffman D. J. , Johnson J. E. , Upchurch L. , Saliba G. , Lewis S. , Graff J. , Russell L. M. , Behrenfeld M. J. 
Published: January 2020

AbstractSea spray aerosol (SSA) consists of both sea salt and organic components. These aerosols affect Earth's climate by scattering solar radiation and by altering cloud properties. Here we present observations of SSA particles generated at sea using an over‐the‐side bubbling system (Sea Sweep) and an onboard plunging wave mesocosm (Marine Aerosol Reference Tank—MART) during five cruises in the North Atlantic. The cruises were timed to sample different stages of the North Atlantic plankton bloom and included transects from the oligotrophic Sargasso Sea to the biologically productive western subarctic. The results show that the North Atlantic plankton bloom has little effect on the emission flux, organic fraction, or cloud condensation nuclei (CCN) activity of SSA, and therefore, plankton ecosystems do not need to be included in modeling aerosol indirect effects of primary SSA in global climate models or in chemical transport models.
A Full‐Spectrum Bedrock Thermal Expansion Model and Its Impact on the Global Positioning System Height Time Series
Authors: Lei Jintao , Chen Wu , Li Zhao , Li Fei , Zhang Shengkai 
Published: January 2020

AbstractBedrock thermal expansion includes prominent seasonal (annual and semiannual) terms and intricate nonseasonal variations (high‐frequency change and transient signals). However, the nonseasonal variations are usually ignored in geodetic studies due to defects in analytical solutions. In this study, we calculate the full‐spectrum bedrock thermal expansion displacement using the skin temperature from the ERA5 reanalysis data set. The results show that the nonseasonal variations of bedrock thermal expansion, with a range (maximum minus minimum) reaching 3 mm in some regions, can be observed by geodetic instruments and thus cannot be ignored. Moreover, the mean power of the nonseasonal variations accounts for 20% of the entire thermal expansion. Without considering the influence of the nonseasonal variations, this “noise” would remain in the original observations and contaminate related geophysical inversions.
Surface Heat Flux Induced by Mesoscale Eddies Cools the Kuroshio‐Oyashio Extension Region
Authors: Shan Xuan , Jing Zhao , Gan Bolan , Wu Lixin , Chang Ping , Ma Xiaohui , Wang Shengpeng , Chen Zhaohui , Yang Haiyuan 
Published: January 2020

AbstractSea surface temperature (SST) is a key player in the air‐sea interaction, influencing storm tracks, atmospheric circulation, and climate modes. Although prevailing theories attribute variations of large‐scale SST to atmosphere forcing and ocean internal dynamics, we find that sea surface heat flux anomalies induced by mesoscale eddies exert significant influences on the upper‐ocean heat budget in the Kuroshio‐Oyashio extension region. Despite making nearly no contribution to the net heat exchange at the air‐sea interface, the eddy‐induced heat flux anomalies weaken the thermal stratification in the upper ocean and result in pronounced sea surface cooling. The underlying dynamics is the efficient dissipation of eddy potential energy by eddy‐induced heat flux anomalies. This makes the conversion of eddy potential energy to eddy kinetic energy significantly reduced, corresponding to a weaker eddy‐induced restratification flux. The finding complements the existing theories on large‐scale SST dynamics and has important implications for understanding extratropical climate variability.
10Be/9Be Ratios Reveal Marine Authigenic Clay Formation
Authors: Bernhardt A. , Oelze M. , Bouchez J. , von Blanckenburg F. , Mohtadi M. , Christl M. , Wittmann H. 
Published: January 2020

AbstractAs reverse weathering has been shown to impact long‐term changes in atmospheric CO2 levels, it is crucial to develop quantitative tools to reconstruct marine authigenic clay formation. We explored the potential of the beryllium (Be) isotope ratio (10Be/9Be) recorded in marine clay‐sized sediment to track neoformation of authigenic clays. The power of such proxy relies on the orders‐of‐magnitude difference in 10Be/9Be ratios between continental Be and Be dissolved in seawater. On marine sediments collected along a Chilean margin transect we chemically extracted reactive phases and separated the clay‐sized fraction to compare the riverine and marine 10Be/9Be ratio of this fraction. 10Be/9Be ratios increase fourfold from riverine to marine sediment. We attribute this increase to the incorporation of Be high in 10Be/9Be from dissolved biogenic opal, which also serves as a Si‐source for the precipitation of marine authigenic clays. 10Be/9Be ratios thus sensitively track reverse‐weathering reactions forming marine authigenic clays.
“Garnet” Lherzolites in the Purang Ophiolite, Tibet: Evidence for Exhumation of Deep Oceanic Lithospheric Mantle
Authors: Gong Xiao‐Han , Shi Ren‐Deng , Xu Ji‐Feng , Huang Qi‐Shuai , Huang Xiao‐Xiao , Su Ben‐Xun 
Published: January 2020

AbstractOphiolites commonly sample the uppermost parts (15–20 km) of fossil oceanic lithosphere. However, in recent years, the documentation of diamonds, super‐reducing (e.g., SiC), and other “unusual” minerals from several ophiolitic peridotites and chromitites (e.g., Tibet and the Polar Urals) has caused debate concerning their origin (i.e., deep vs. shallower upper mantle). Here we report on symplectite‐bearing lherzolites from the Purang ophiolite in Tibet, which preserve the first compelling evidence of garnet‐facies protoliths. These lherzolites were previously formed and stabilized at a depth of ~85–100 km, which is much deeper than generally suggested and approaches the depth (~120 km) required for stabilizing the diamonds. Combining with other key observations, we suggest the Purang garnet‐bearing peridotites may represent mixtures of oceanic lithosphere domains with diverse origins; they were rapidly exhumed at a variety of mantle depths within a subduction channel associated with oceanic slab retreat.