bluuebunny/crossref_metadata_2025_split huggingface dataset:
Genesis of Intermediate and Silicic Arc Magmas Constrained by Nb/Ta Fractionation
Authors: Chen Wei , Zhang Guoliang , Ruan Mengfei , Wang Shuai , Xiong Xiaolin 
Published: February 2021

AbstractResolving the geochemical discrepancies in Nb/Ta between the bulk continental crust and its parental mantle melts can provide insights into the processes by which basaltic magmas differentiated into the felsic crust. Deep‐seated garnet pyroxenite cumulates (i.e., arclogite) have high Nb/Ta values due to the presence of high Nb/Ta‐rutile. For this reason, rutile‐bearing arclogites having Nb‐rich composition were proposed to complement the low Nb/Ta nature of the continental crust and evolved arc magmas, that is to say, continental arc magma evolution dominantly occurred in the stability field of garnet. However, this suggestion is challenged by the incomplete understanding of the role of rutile in the Nb/Ta fractionation during arc magma evolution due to insufficient partitioning data at low temperatures (T ≤ 1,000°C). Here, we determined Nb and Ta partitioning ratios in rutile‐felsic melt systems at 2.0 GPa, 850–1,000°C and ∼4–20 wt.% H2O. Our results confirm that equilibrium crystallization of rutile with respect to Nb and Ta will not impart lower Nb/Ta values to any derivative liquids, whereas diffusive fractionation of Nb/Ta in siliceous melts during the growth of rutile can reduce Nb/Ta ratios in melts. However, a positive correlation between Nb/Ta and Dy/Yb for mature continental arc magmas, incipient continental arc magmas, island arc magmas, and global arc magmas indicates that amphibole rather than rutile‐bearing arclogite was responsible for causing low Nb/Ta ratios of many evolved intermediate rocks. Accordingly, the chemical differentiation from primary basaltic to average andesitic compositions of the continental crust mainly occurred in the stability field of amphibole.
Cross Validation of Stress Drop Estimates and Interpretations for the 2011 Prague, OK, Earthquake Sequence Using Multiple Methods
Authors: Pennington Colin N. , Chen Xiaowei , Abercrombie Rachel E. , Wu Qimin 
Published: February 2021

AbstractWe compare source parameter estimates for earthquakes in the 2011 Prague Mw 5.7, Oklahoma, sequence to investigate random uncertainty and systematic bias, and resolve reliable relative variations in stress drop. Source parameters provide insight into the earthquake rupture processes but large variations between studies occur. The Prague earthquake sequence is a prime example of this, with different studies reaching contrasting interpretations of the effects of injection on source parameters. We examine the Prague earthquake sequence using a single coherent catalog for all the events detected by the Oklahoma Geological Survey (OGS) and McMahon et al. (2017). We use three principal approaches to estimate stress drop in order to understand the biases of each: a spectral decomposition method based on stacking, individual event spectral modeling, and a spectral ratio method based on highly correlated events. We also compare our results with previous studies for the Prague sequences aftershocks, as well as past results for the Mw 4.8 foreshock and Mw 4.8 aftershock and Mw 5.7 mainshock. The absolute values of stress drop vary significantly between methods, but the relative patterns remain consistent, except when low quality or low bandwidth data are included. The consistent relative patterns reveal that the stress drops of aftershocks are dependent on the fault orientation and the proximity of the events to the mainshocks slip. These results indicate that fault structure as well as past events play an important role in stress drop patterns.
What Controls Effective Elastic Thickness of the Lithosphere in the Pacific Ocean?
Authors: Lu Zhezhe , Audet Pascal , Li Chun‐Feng , Zhu Shuang , Wu Zhaocai 
Published: February 2021

AbstractThe effective elastic thickness () of the lithosphere is a proxy for mechanical strength and can be used to constrain lithospheric rheology and understand how surface deformation relates to deep Earth processes. Here, we map variations over the Pacific Ocean from the inversion of the admittance between free‐air gravity anomaly and bathymetry data calculated using a continuous wavelet transform, taking both surface and subsurface loads into account. The Pacific lithosphere show ranging between 0 and 80 km with a mean of 13.5 km and a standard deviation of 12.3 km. We find that is generally poorly correlated with plate loading age, crustal age, heat flow and Curie point depth, except for relatively young (<60 Ma) and warm lithospheres. Most oceanic plateaus and seamounts show km, with the lowest values (<5 km) around active spreading centers. The highest estimates (>30 km) are found along subduction zones and around the Hawaiian‐Emperor Seamount Chain (HESC). Taken together, these results support a temperature control on for small loads and warm lithosphere through steady‐state creep processes, but strain hardening operating at large plastic strain and low temperature could explain high associated with large‐amplitude and long‐wavelength loads (subduction zones and the HESC) and should be incorporated in yield strength models of oceanic .
The Route to Spring Phytoplankton Blooms Simulated by a Lagrangian Plankton Model
Authors: Noh Kyung Min , Noh Yign , Brereton Ashley , Kug Jong‐Seong 
Published: February 2021

AbstractA Lagrangian plankton model (LPM) is developed, in which the motion of a large number of Lagrangian particles, representing a parcel of plankton, is calculated under the turbulence field simulated by large‐eddy simulation. A spring phytoplankton bloom is realized using the LPM, and the mechanism for its 1 generation is investigated. The criterion based on these results is proposed as , where δ

E
(= u
∗/f) is the scale for the Ekman boundary layer, δ

S
(= ) is the scale for the depth of a seasonal thermocline, u
∗ is the wind stress, Q
0 is the surface buoyancy flux, f is the Coriolis parameter, and C
1 and C
2 are constants. The critical depth hypothesis can be applied for the onset of a spring bloom, when , using the mixing layer depth instead of the mixed layer depth, as z

c
> C
2
δ

S
, but the critical turbulence hypothesis can be applied, as z

c
> C
1
δ

E
, when . A spring bloom is more likely to occur at higher latitudes, even if the atmospheric forcing is the same. The diurnal variation of Q
0 tends to increase the strength of the spring bloom at small u
∗. Furthermore, various statistics of Lagrangian particles, such as the mixing length of plankton, the residence time of plankton within the euphotic zone, and the growth of plankton clarify the movement and growth of plankton cells.
Drought and Salinization Stress Induced by Stand Development Alters Mineral Element Cycling in a Larch Plantation
Authors: Deng Meifeng , Li Ping , Wang Zhenhua , Guo Lulu , Wu Yuntao , Huang Junsheng , Wang Xuhui , Liu Lingli 
Published: February 2021

AbstractGrassland afforestation promotes carbon sequestration at the expense of consuming water resources. With the development of forest plantations, the increase in aboveground biomass could aggravate the limitations of soil moisture and nutrients, and thus alter understory succession. However, it is unclear how these changes influence the mineral element cycle in plant‐soil systems. We conducted a four‐year experiment in young, middle‐aged, and mature stands in a larch plantation and investigated how stand development affects macronutrient (K, Ca, and Mg) and micronutrient (Na, Fe, and Zn) concentrations in soils and leaves of larch and understory plants. Our results showed that as stand age increased, soil moisture and soil pH decreased. The reduced soil moisture directly led to an increase in soil total sodium (Na) and potassium (K) concentrations. There was no significant difference in mineral element concentrations in the larch leaves among the three stands. However, the understory vegetation in the mature stands had higher foliar K concentration but lower foliar Na concentration than in the young stands. Furthermore, plant calcium (Ca) concentration was positively correlated with plant K:Na ratio. The stoichiometric coupling between leaf [Ca] and K:Na ratio became tighter with increased stand age, which could improve the tolerance of plants to drought and soil salinization. Our findings suggested that water limitation and soil salinization caused by grassland afforestation intensified with increased stand age. To adapt to these stresses, understory vegetation often shifts to species with high K but low Na leaf concentrations.
Understanding the Bioaccumulation of Mercury in Rice Plants at the Wanshan Mercury Mine, China: Using Stable Mercury Isotopes
Authors: Chang Chuanyu , Yin Runsheng , Huang Fang , Sun Guangyi , Mao Kang , Lei Da , Zhang Hua 
Published: February 2021

AbstractRice can accumulate a substantial amount of mercury (Hg). At the Wanshan Mercury Mine (WMM), the bioaccumulation of Hg by rice was complicated by historical large‐scale mining and active artisanal smelting activities. This study investigated the concentration and isotopic composition of Hg in rice roots, leaves and paddy soil collected from abandoned Hg mining sites and active artisanal smelting sites at the WMM. At all sites, correlations between δ202Hg and 1/THg were observed in soil, suggesting a mixing of Hg from waste calcine and unroasted Hg ore. Significantly positive correlations were also observed in THg concentrations between roots and soil (r2 = 0.84, p < 0.01) and between leaves and total gaseous mercury (r2 = 0.87, p < 0.01), reflecting that roots and leaves receive Hg mainly from soil and atmosphere, respectively. Large differences of −0.87 ± 0.57‰ and −1.85 ± 0.57‰ in δ202Hg between the root and soil were observed at abandoned Hg mining sites and active artisanal smelting sites, respectively, suggesting that roots preferentially accumulate lighter Hg isotopes from the soil. Offsets of 0.05‰ and 0.27‰ in Δ199Hg between rice roots and leaves, with higher Δ199Hg values in roots than leaves, were observed at abandoned Hg mining sites and active artisanal smelting sites, respectively. The Hg‐mass‐independent fractionation signal is believed to be caused by Hg(II) photoreduction in paddy water; however, the extent of photoreduction is variable among rice paddies. Overall, this study suggests that Hg isotopes can be a useful tool to understand the sources and bioaccumulation of Hg in rice paddies.
In Situ Estimates of Net Primary Production in the Western North Atlantic With Argo Profiling Floats
Authors: Yang Bo , Fox James , Behrenfeld Michael J. , Boss Emmanuel S. , Haëntjens Nils , Halsey Kimberly H. , Emerson Steven R. , Doney Scott C. 
Published: February 2021

AbstractThe 14C incubation method for net primary production (NPP) has limited spatial/temporal resolution, while satellite approaches cannot provide direct information at depth. With chlorophyll‐a and backscatter measurements from BGC‐Argo floats, we quantified year‐round NPP in the western North Atlantic Ocean using both the Carbon‐based Productivity Model (CbPM) and Photoacclimation Productivity Model (PPM). Comparison with NPP profiles from 14C incubation measurements showed advantages and limitations of both models. CbPM reproduced the magnitude of NPP in most cases. However, in the summer the CbPM‐based NPP had a large peak in the subsurface, which was an artifact from the subsurface chlorophyll maximum caused by photoacclimation. PPM avoided the artifacts from photoacclimation, but the magnitude of PPM‐derived NPP was smaller than the 14C result. Different NPP distribution patterns along a North‐South transect in the Western North Atlantic Ocean were observed, including higher winter NPP/lower summer NPP in the south, timing differences in NPP seasonal phenology, and different NPP depth distribution patterns in the summer months. Using a 6‐months record of concurrent oxygen and bio‐optical measurements from two Argo floats, we also demonstrated the ability of Argo floats to obtain estimates of the net community production to NPP ratio, ranging from 0.3 in July to −1.0 in December 2016. Our results highlight the utility of float bio‐optical profiles and indicate that environmental conditions (e.g., light availability, nutrient supply) are major factors controlling the seasonality and spatial (horizontal and vertical) distributions of NPP in the western North Atlantic Ocean.
Spatiotemporal Change of Marsh Vegetation and Its Response to Climate Change in China From 2000 to 2019
Authors: Shen Xiangjin , Liu Binhui , Jiang Ming , Wang Yanji , Wang Lei , Zhang Jiaqi , Lu Xianguo 
Published: February 2021

AbstractChina has the third largest area of marshes in the world. Understanding the change of marsh, vegetation and its response to climate change in China is important for the protection of wetland ecosystem. Based on the climate and normalized difference vegetation index (NDVI) data, we investigated the spatiotemporal variation in vegetation and its response to climate change for different types of marshes in China. The results indicated that growing season NDVI increased significantly (0.02/decade, P < 0.01) over the whole marshes of China from 2000 to 2019. The increased precipitation and minimum temperature during the growing season could promote the growth of marsh vegetation over China. This study found for the first time that the increase of temperature during the day and at night had asymmetric effects on vegetation growth in marshes of China, and the positive effect of night warming was more significant. Spatially, increasing growing season precipitation was beneficial to the vegetation growth of herbaceous marshes, marsh meadows, inland salt marshes, and seasonal saltwater marshes in eastern Inner Mongolia. Increased growing season minimum temperature could greatly promote the vegetation growth of marsh meadows, herbaceous marshes, inland salt marshes, forest swamp, and bush swamp in cold and high‐altitude regions of Northern Northeast China and the Tibet Plateau. In the context of global climate change, more attention should be paid to the different responses of vegetation to climate change for different marsh types, especially when we use the model to simulate the impact of climate change on vegetation in different marsh regions of China.
Representation of Plant Hydraulics in the Noah‐MP Land Surface Model: Model Development and Multiscale Evaluation
Authors: Li Lingcheng , Yang Zong‐Liang , Matheny Ashley M. , Zheng Hui , Swenson Sean C. , Lawrence David M. , Barlage Michael , Yan Binyan , McDowell Nate G. , Leung L. Ruby 
Published: February 2021

AbstractPlants are expected to face increasing water stress under future climate change. Most land surface models, including Noah‐MP, employ an idealized “big‐leaf” concept to regulate water and carbon fluxes in response to soil moisture stress through empirical soil hydraulics schemes (SHSs). However, such schemes have been shown to cause significant uncertainties in carbon and water simulations. In this paper, we present a novel plant hydraulics scheme (PHS) for Noah‐MP (hereafter, Noah‐MP‐PHS), which employs a big‐tree rather than big‐leaf concept, wherein the whole‐plant hydraulic strategy is considered, including root‐level soil water acquisition, stem‐level hydraulic conductance and capacitance, and leaf‐level anisohydricity and hydraulic capacitance. Evaluated against plot‐level observations from a mature, mixed hardwood forest at the University of Michigan Biological Station and compared with the default Noah‐MP, Noah‐MP‐PHS better represents plant water stress and improves water and carbon simulations, especially during periods of dry soil conditions. Noah‐MP‐PHS also improves the asymmetrical diel simulation of gross primary production under low soil moisture conditions. Noah‐MP‐PHS is able to reproduce different patterns of transpiration, stem water storage and root water uptake during a 2‐week dry‐down period for two species with contrasting plant hydraulic behaviors, i.e., the “cavitation risk‐averse” red maple and the “cavitation risk‐prone” red oak. Sensitivity experiments with plant hydraulic capacitance show that the stem water storage enables nocturnal plant water recharge, affects plant water use efficiency, and provides an important buffer to relieve xylem hydraulic stress during dry soil conditions.
Overlooked Implication of Sediment Transport at Low Flow: Migrating Ripples Modulate Streambed Phototrophic and Heterotrophic Microbial Activity
Authors: Scheidweiler David , Mendoza‐Lera Clara , Mutz Michael , Risse‐Buhl Ute 
Published: February 2021

AbstractSandy streambeds are mobile even at low flow velocities at which sediments can be transported as bedload, more specifically as migrating ripples. Small variations in discharge can result in transitions between sediment transport and no‐transport. Despite being inherent processes of streams and rivers, the effect of sediment transport and transport regime transition on the phototrophic and heterotrophic activity of streambed microbial communities remains unclear. We performed a microcosm experiment mimicking sediment transport as migrating ripples (i.e., migrating) and no sediment transport (i.e., stationary), and their transition to observe the response of the phototrophic and heterotrophic microbial community. Both net community production and community respiration were respectively 77% and 40% suppressed in migrating sediments compared to stationary sediments. In migrating sediments, a combination of mechanical stress, light limitation, and limited habitable area likely hampered microbial metabolism. Stationary conditions facilitated an active community of phototrophs, mainly diatoms, as indicated by high net community production, high rates of dissolved organic carbon release and silicon retention. After transitioning migrating to stationary and vice versa, differences were maintained regardless of the change in mechanical stress and associated stressors, most likely as a result of the interaction between their antecedent transport conditions and developmental stage that shaped the microbial community. Our results indicate that sediment transported as migrating ripples at low flow velocity can strongly modulate streambed metabolism, and discharge oscillations resulting in sediment transport transitions will result in a mosaic of microbial activity and biomass that will emerge at larger scales determining reach‐scale metabolism.
Comparison of Surface Water‐Groundwater Exchange Fluxes Derived From Hydraulic and Geochemical Methods and a Regional Groundwater Model
Authors: Bouchez Camille , Cook Peter G. , Partington Daniel , Simmons Craig T. 
Published: February 2021

AbstractIntercomparison of surface water‐groundwater (SW‐GW) exchange fluxes at the regional scale is rarely undertaken, mainly because estimates are method and scale‐dependent and usually associated with large errors. In the present study, we compare SW‐GW exchange fluxes calculated from a multitracer mass balance in the river, an application of Darcy's law using near‐river piezometers and a surface‐subsurface flow model calibrated at the catchment scale. SW‐GW exchange fluxes are estimated for 7 km long reaches along the 140 km long Campaspe River, a tributary of the Murray River, Australia. Differences are found in the directions and magnitudes of the exchange fluxes estimated by the different methods. The application of Darcy's law in near‐river piezometers seems the most appropriate method to infer SW‐GW flow directions and temporal variability. The tracer mass balance is limited to gaining reaches but gives quantitative estimates of the fluxes. While numerical models should overcome deficiencies associated with some of the intrinsic assumptions of the two field‐methods, the regional‐scale calibration is subject to high uncertainties in the simulated heads near the river, resulting in uncertainty of SW‐GW exchange fluxes. In particular, we show that loosely quantified river abstractions and irrigation patterns directly impact the simulated SW‐GW fluxes. In gaining reaches, additional river chemistry data improved model calibration and SW‐GW flux estimates. While numerical models are crucial for water management, their reliability to estimate SW‐GW fluxes can be limited by their complexity and lacking data availability. Therefore, we recommend comparing numerical model results with easily implemented field‐based methods.
Carrier phase correction for GNSS space‐time array processing based on frequency jerk detection
Authors: Xie Yuchen , Chen Yuwei , Chen Feiqiang , Wang Feixue 
Published: February 2021

AbstractThe signals of Global Navigation Satellite System (GNSS) are so vulnerable that can be easily jammed by intentional or unintentional interferences. One of the effective ways to protect GNSS signals from jamming is to use the Space‐Time Array Processing (STAP) technology. However, undesired carrier phase bias would be induced to the signals because of the STAP, which significantly influences the precision of positioning. Many algorithms have been proposed to deal with this carrier phase bias, but most of them need the directional information of signals or the pre‐test of antennas. In this paper, a carrier phase correction algorithm without the need of prior information is proposed. Alarmed by the jerk of carrier frequency, the algorithm can detect the change of jamming and calculate the induced carrier phase bias. Then it can correct this bias from the signal and alleviate its influence. The simulation results show that the algorithm can limit the bias from more than 60° to less than 10°, which verifies that the proposed algorithm is effective in the low dynamic receiver.
Instantaneous active and reactive load signature applied in non‐intrusive load monitoring systems
Authors: Brito Ricardo , Wong Man‐Chung , Zhang Hong Cai , Da Costa Junior Miguel Gomes , Lam Chi‐Seng , Wong Chi‐Kong 
Published: February 2021

AbstractThe performance of non‐intrusive load monitoring (NILM) systems heavily depends on the uniqueness of the load signature extracted from the electrical appliances. Different load signatures have been proposed. Recently, in particular, v–i trajectory feature extraction is attracting more and more attention due to its unique characteristics. Herein, instantaneous p–q load signature (IpqLS) feature extraction is first proposed and applied in NILM, which shows that conventional methods cannot distinguish load signatures under some situations. Applying IpqLS with several machine learning algorithms is not only extracting unique features compared to the overlapping problems of P–Q and v–i trajectory but also improving load classification accuracy. Simulations and experimental results verified the effectiveness of the proposed method.