Field-and petrographic investigations,together with microanalytical major-and traceelement studies,were carried out on clinopyroxene and amphibole from high-Mg diorite in the subduction-related Chelyabinsk granitic ma...Field-and petrographic investigations,together with microanalytical major-and traceelement studies,were carried out on clinopyroxene and amphibole from high-Mg diorite in the subduction-related Chelyabinsk granitic massif to understand its petrogenesis and source.The clinopyroxene composition(high Mg#,Cr-content,sum of REE and Ti/Eu ratio;depletion in HREE;negative Eu-anomaly)indicates that it formed from a reduced melt derived from a mantle source metasomatized by fluids/melts having crustal affinity.Melt compositions in equilibrium with clinopyroxene and amphibole were calculated using solid/liquid partition coefficients.The high Nb/Y and Zr/Y ratio values of a liquid simulated from clinopyroxene,which appears to have very similar characteristics to sanukitoid melts,indicate a low degree of melting of the mantle source.Melt simulated from amphibole is more evolved and more felsic(dacitic).It displays a geochemical“amphibole fractionation”signature,indicating the peritectic transformation of clinopyroxene to amphibole in the lower crust.Rock textures and major element mineral compositions suggest that further amphibole was precipitated directly from the melt in the middle crust.The results show that the Chelyabinsk highMg diorite was probably formed as a cumulate from sanukitoid-like melt during its ascent and cooling below dacitic liquidus inside the amphibole stability field.展开更多
Observational analyses demonstrate that the Ural persistent positive height anomaly event(PAE) experienced a decadal increase around the year 2000, exhibiting a southward displacement afterward. These decadal variatio...Observational analyses demonstrate that the Ural persistent positive height anomaly event(PAE) experienced a decadal increase around the year 2000, exhibiting a southward displacement afterward. These decadal variations are related to a large-scale circulation shift over the Eurasian Continent. The effects of underlying sea ice and sea surface temperature(SST) anomalies on the Ural PAE and the related atmospheric circulation were explored by Atmospheric Model Intercomparison Project(AMIP) experiments from the Coupled Model Intercomparison Project Phase 6 and by sensitivity experiments using the Atmospheric General Circulation Model(AGCM). The AMIP experiment results suggest that the underlying sea ice and SST anomalies play important roles. The individual contributions of sea ice loss in the Barents-Kara Seas and the SST anomalies linked to the phase transition of the Pacific Decadal Oscillation(PDO) and Atlantic Multidecadal Oscillation(AMO) are further investigated by AGCM sensitivity experiments isolating the respective forcings.The sea ice decline in Barents-Kara Seas triggers an atmospheric wave train over the Eurasian mid-to-high latitudes with positive anomalies over the Urals, favoring the occurrence of Ural PAEs. The shift in the PDO to its negative phase triggers a wave train propagating downstream from the North Pacific. One positive anomaly lobe of the wave train is located over the Ural Mountains and increases the PAE there. The negative-to-positive transition of the AMO phase since the late-1990s causes positive 500-h Pa height anomalies south of the Ural Mountains, which promote a southward shift of Ural PAE.展开更多
In recent decades,the rapid climate warming in polar and alpine regions has been accompanied by an expan-sion of shrub vegetation.However,little is known about how changes in shrub distribution will change as the dist...In recent decades,the rapid climate warming in polar and alpine regions has been accompanied by an expan-sion of shrub vegetation.However,little is known about how changes in shrub distribution will change as the distribution of tree species and snow cover changes as temperatures rise.In this work,we analyzed the main environmental factors influencing the distribution and structure of Juniperus sibir-ica,the most common shrub species in the Southern Ural Mountains.Using mapping and digital elevation models,we demonstrated that J.sibirica forms a well-defined vegeta-tion belt mainly between 1100 and 1400 m a.s.l.Within this zone,the abundance and cover of J.sibirica are influenced by factors such as rockiness,slope steepness,water regime and tree(Picea obovata)cover.An analysis of data spanning the past 9 years revealed an upward shift in the distribution of J.sibirica with a decrease in its area.The primary limit-ing factors for the distribution of J.sibirica were the removal of snow cover by strong winter winds and competition with trees.As a consequence of climatic changes,the tree line and forest limit have shifted upward,further restricting the distribution of J.sibirica to higher elevations where com-petition for light with trees is reduced and snow cover is sufficiently deep.展开更多
Climate has changed sufficiently over the last 150 years and forced out upper treeline advance at the most studied sites around the world.The rate of advance has been extremely variable–from tens to hundreds meters i...Climate has changed sufficiently over the last 150 years and forced out upper treeline advance at the most studied sites around the world.The rate of advance has been extremely variable–from tens to hundreds meters in altitude.This is because the degree at which tree frontal populations respond to climate change depends on the complex interaction of biological and physical factors.The resulting stand pattern is the consequence of the interaction between dispersal and survival functions.A few publications have addressed the question of how this pattern is generated.In order to understand how the spatial structure of tree stands was formed at the upper limit of their distribution in the Ural Mountains,we assessed the distance and direction of dispersal of offspring from maternal individuals.We found that in frontal Larix sibirica Ledeb.populations,‘effective’dispersal of offspring ranges from 3 to 758 m(with a median of 20–33 m in open forest and 219 m in single-tree tundra in the Polar Urals and 107 m in open forest in the Northern Urals).We revealed that most of the offspring effectively dispersed not only in the direction of the prevailing winds,but also in the opposite direction up the slope,and the distance can reach 500–760 m.The data obtained can be used to develop an individual-based model which is capable of simulating in detail the dynamics of tree stands at the upper limit of their growth and reliably predicting the future position and pattern of treeline ecotone as growth conditions continue to improve in the face of observed climate change.展开更多
Arctic sea ice has undergone a significant decline in the Barents-Kara Sea(BKS)since the late 1990s.Previous studies have shown that the decrease in sea ice caused by increased poleward moisture transport is modulated...Arctic sea ice has undergone a significant decline in the Barents-Kara Sea(BKS)since the late 1990s.Previous studies have shown that the decrease in sea ice caused by increased poleward moisture transport is modulated by tropical sea temperature changes(mainly referring to La Niña events).The occurrence of multi-year La Niña(MYLA)events has increased significantly in recent decades,and their impact on Arctic sea ice needs to be further explored.In this study,we investigate the relationship between sea-ice variation and different atmospheric diagnostics during MYLA and other La Niña(OTLA)years.The decline in BKS sea ice during MYLA winters is significantly stronger than that during OTLA years.This is because MYLA events tend to be accompanied by a warm Arctic-cold continent pattern with a barotropic high pressure blocked over the Urals region.Consequently,more frequent northward atmospheric rivers intrude into the BKS,intensifying longwave radiation downward to the underlying surface and melting the BKS sea ice.However,in the early winter of OTLA years,a negative North Atlantic Oscillation presents in the high latitudes of the Northern Hemisphere,which obstructs the atmospheric rivers to the south of Iceland.We infer that such a different response of BKS sea-ice decline to different La Niña events is related to stratospheric processes.Considering the rapid climate changes in the past,more frequent MYLA events may account for the substantial Arctic sea-ice loss in recent decades.展开更多
Starting in mid-November,China was hit by several cold events during the early winter of 2020/21.The lowest temperature observed at Beijing station on 7 January reached−19.6°C.In this paper,we show that the outbr...Starting in mid-November,China was hit by several cold events during the early winter of 2020/21.The lowest temperature observed at Beijing station on 7 January reached−19.6°C.In this paper,we show that the outbreak of the record-breaking extreme cold event can be attributed to a huge merging Ural blocking(UB)ridge over the Eurasian region.The sea-ice cover in the Kara and East Siberia Seas(KESS)in autumn was at its lowest value since 1979,which could have served as a precursor signal.Further analysis shows that several successive UB episodes occurred from 1 September 2020 to 10 January 2021.The persistent UB that occurred in late September/early October 2020 may have made an important contribution to the October historical minimum of sea ice in the KESS region.Our results also show that,after each UB episode in winter,significant upward propagation of wave activity occurred around 60°E,which resulted in weakening the stratospheric vortex.Meanwhile,each UB episode also caused a significant reduction in sea-ice extent in KESS and a significant weakening of the westerly jet in mid-high-latitude Eurasia.Results suggest that the Arctic vortex,which is supposed to enhance seasonally,became weaker and more unstable than the climatic mean under the seasonal cumulative effects of UB episodes,KESS warming,and long-lasting negative-phase North Atlantic Oscillation(NAO-).Those seasonal cumulative effects,combined with the impact of La Niña winter,led to the frequent occurrence of extreme cold events.展开更多
An unprecedented cold wave intruded into East Asia in early January 2021 and led to record-breaking or historical extreme low temperatures over vast regions.This study shows that a major stratospheric sudden warming(S...An unprecedented cold wave intruded into East Asia in early January 2021 and led to record-breaking or historical extreme low temperatures over vast regions.This study shows that a major stratospheric sudden warming(SSW)event at the beginning of January 2021 exerted an important influence on this cold wave.The major SSW event occurred on 2 January 2021 and subsequently led to the displacement of the stratospheric polar vortex to the East Asian side.Moreover,the SSW event induced the stratospheric warming signal to propagate downward to the mid-to-lower troposphere,which not only enhanced the blocking in the Urals-Siberia region and the negative phase of the Arctic Oscillation,but also shifted the tropospheric polar vortex off the pole.The displaced tropospheric polar vortex,Ural blocking,and another downstream blocking ridge over western North America formed a distinct inverted omega-shaped circulation pattern(IOCP)in the East Asia-North Pacific sector.This IOCP was the most direct and impactful atmospheric pattern causing the cold wave in East Asia.The IOCP triggered a meridional cell with an upward branch in East Asia and a downward branch in Siberia.The meridional cell intensified the Siberian high and low-level northerly winds,which also favored the invasion of the cold wave into East Asia.Hence,the SSW event and tropospheric circulations such as the IOCP,negative phase of Arctic Oscillation,Ural blocking,enhanced Siberian high,and eastward propagation of Rossby wave eventually induced the outbreak of an unprecedented cold wave in East Asia in early January 2021.展开更多
The 1998 summer-time floods at the Yangtze River basin of China, the severest in last 50 years or so, directly resulted from the abnormal extension of Meiyu (rainy season), which was related to a weak East Asian summe...The 1998 summer-time floods at the Yangtze River basin of China, the severest in last 50 years or so, directly resulted from the abnormal extension of Meiyu (rainy season), which was related to a weak East Asian summer monsoon and persistent anomalies of extratropical circulation. The long persistence of blocking over the Ural Mountains is a conspicuous feature. The physical processes responsible for the prolonged maintenance of this key system are investigated in terms of internal forcing (transient eddy upon basic flow) and external forcing (tropical heating forcing) via diagnosis and numerical experiments in the paper. Using the adjoint method, the location and structure of optimal perturbations favorable for the development and maintenance of Ural blocking are identified, which shows an apparent coincidence with the observed storm track at the eastern Atlantic to Europe sector. The diagnosis of E-vector and the response of baroclinic stationary wave to transient forcing both suggest further that the enhanced transient eddy activity favors the occurrence and maintenance of positive anomalies. The upper-level jet and heat sources (sinks) during that period are calculated, and the results indicate that the anomaly of upper jet and tropical heating is evident. The ensemble forecasting experiments by a GCM, IAP T42L9 show that the anomalous heating over the tropics, especially over the central-western Pacific and Atlantic, favors the formation of positive anomalies of height at the Ural region. Finally, a self-sustain mechanism of positive anomalies through two-way interaction between planetary stationary wave and transient eddy under the stimulation of anomalous tropical heating is proposed.展开更多
Background:Recent warming is affecting species composition and species areal distribution of many regions.However,although most treeline studies have estimated the rates of forest expansion into tundra,still little is...Background:Recent warming is affecting species composition and species areal distribution of many regions.However,although most treeline studies have estimated the rates of forest expansion into tundra,still little is known about the long-term dynamic of stand productivity at the forest-tundra intersection.Here,we make use of tree-ring data from 350 larch(Larix sibirica Ledeb.)and spruce(Picea obovata Ledeb.)sampled along the singular altitudinal treeline ecotone at the Polar Urals to assess the dynamic of stand establishment and productivity,and link the results with meteorological observations to identify the main environmental drivers.Results:The analysis of stand instalment indicated that more than 90%of the living trees appeared after 1900.During this period,the stand became denser and moved 50m upward,while in recent decades the trees of both species grew faster.The maximum afforestation occurred in the last decades of the twentieth century,and the large number of encountered saplings indicates that the forest is still expanding.The upward shift coincided with a slight increase of May-August and nearly doubling of September-April precipitation while the increase in growth matched with an early growth season warming(June+0.27°C per decade since 1901).This increase in radial growth combined with the stand densification led to a 6-90 times increase of biomass since 1950.Conclusion:Tree-ring based twentieth century reconstruction at the treeline ecotone shows an ongoing forest densification and expansion accompanied by an increased growth.These changes are driven by climate change mechanism,whereby the leading factors are the significant increase in May-June temperatures and precipitation during the dormant period.Exploring of phytomass accumulation mechanisms within treeline ecotone is valuable for improving our understanding of carbon dynamics and the overall climate balance in current treeline ecosystems and for predicting how these will be altered by global change.展开更多
Formation of the Urals volcanic-hosted massive sulphide(VHMS) deposits is considered to be related with the intra-oceanic stage of island arc(s) development in the Upper Ordoviciane Middle Devonian based on the biostr...Formation of the Urals volcanic-hosted massive sulphide(VHMS) deposits is considered to be related with the intra-oceanic stage of island arc(s) development in the Upper Ordoviciane Middle Devonian based on the biostratigraphic record of ore-hosting sedimentary rocks. However, the direct Re-Os dating of four known VHMS systems in the Urals gives significantly younger Re-Os isochron ages ranging from355 ± 15 Ma up to 366 ± 2 Ma. To address this discrepancy, we performed SHRIMP U-Pb dating on zircons extracted from rhyodacites(Eifelian biostratigraphic age of 393 -388 Ma) from the footwall of the Alexandrinka VHMS deposit which has a Re-Os isochron age of sulphides of 355 ± 15 Ma.New ^(206) Pb/^(238) U mean age of 374 ± 3 Ma(MSWD ? 1.4 and probability ? 0.11) is considered to be the crystallisation age of the host volcanic rock. This age is ca. 15 Ma younger than the Eifelian(393 -388 Ma)biostratigraphic age and overlaps the Frasniane Famennian boundary(372 ± 2 Ma), characterised by the final stages of Magnitogorsk Arc e East European continent collision. Such an inconsistency with geochronological age may be due to a reburial of conodonts during resedimentation as a result of erosion of older rocks in younger sedimentary sequences.展开更多
In terms of Kuo-Qian pesigma incorporated coordinate five-level primitive equation spheric band (70°N-30°S)model with the Ural high's effect introduced into it as initial and boundary conditions, study i...In terms of Kuo-Qian pesigma incorporated coordinate five-level primitive equation spheric band (70°N-30°S)model with the Ural high's effect introduced into it as initial and boundary conditions, study is made of the high's influence on Asian summer monsoon circulation and dryness / wetness of eastern China based on case contrast andcontrol experiments. Rusults show that as an excitation source, the blocking high produces a SE-NW stationarywavetrain with its upper-air atnicyclonic divergent circulation oust over a lower-level trough zone) precisely over themiddle to lower reaches of the Changjiang River, enhancing East Asian westerly jet, a situation that contributes toPerturbation growth, causing an additional secondary meridional circulation at the jet entrance, which intensifies theupdraft in the monsoon area. As such, the high's presence and its excited steady wavetrain represent the large-scalekey factors and acting mechanisms for the rainstorm over the Changjiang-Huaihe River catchment in the easternpart of the land.展开更多
The Polar Urals region of northern Russia is well known for large chromium （Cr）-bearing massifs with major chromite orebodies, including the Centralnoye I deposit in the Ray-Iz ultramafic massif of the Ural ophiolit...The Polar Urals region of northern Russia is well known for large chromium （Cr）-bearing massifs with major chromite orebodies, including the Centralnoye I deposit in the Ray-Iz ultramafic massif of the Ural ophiolite belt. New data on platinum （Pt）-group elements （PGE）, geochemistry and mineralogy of the host dunite shows that the deposit has anomalous iridium （Ir） values. These values indicate the predominance of ruthenium--osmium--iridium （Ru--Os--Ir）-bearing phases among the platinum-group mineral （PGM） assemblage that is typical of mantle-hosted chromite ores. Low Pt values in chromites and increased Pt values in host dunites might reflect the presence of cumulus PGM grains. The most abundant PGM found in the chromite is erlichmanite （up to 15 μm）. Less common are cuproiridsite （up to 5 μm）, irarsite （up to 4--5 μm）, and laurite （up to 4 μm）. The predominant sulfide is heazlewoodite, in intergrowth with Ni--Fe alloys, sporadically with pentlandite, and rarely with pure nickel. Based on the average PGE values and esti- mated Cr-ore resources, the Centralnoye I deposit can be considered as an important resource of PGE.展开更多
Two successive severe cold waves invaded eastern China from the end of 2020 to early 2021,leading to an extensive,severe,and persistent drop in temperature.The paper investigates the features and formation mechanisms ...Two successive severe cold waves invaded eastern China from the end of 2020 to early 2021,leading to an extensive,severe,and persistent drop in temperature.The paper investigates the features and formation mechanisms of the two cold waves.The main results are as follows:(1)An anticlockwise turning of the transverse trough was observed in both cold waves.However,a broad ridge was maintained over the Ural area from mid-December 2020 till mid-January 2021.No breakdown or discontinuous westward shift of the blocking high was observed,which is different from typical cold waves in eastern Asia.(2)The maintenance and strengthening of northerly winds in front of the Ural high led to an increase in baroclinicity in-situ.In the downstream region,the gradient of the geopotential height contour in the south of the transverse trough rapidly increased and the advection of cold temperature consistently enhanced and advanced southwards.This in turn caused the intensification and southward expansion of the Siberian high.(3)Energy propagation of the quasi-stationary wave was a reason for the development and persistence of the Ural blocking.Prior to the occurrence of the two cold waves,the energy of the low-frequency stationary wave originating from near 0°E(or even to the west)propagated eastwards,which helped the Ural ridge intensify and maintain.Meanwhile,it also contributed to the development of the trough downstream of the ridge and resulted in the anticlockwise turning of the transverse trough,providing a favorable condition for the southward outbreak of cold air.展开更多
To discuss the nature of the compositional heterogeneity of the peridotite massifs of the Polar Urals(Russia), the geochemical study by LA-ICP-MS of pyroxenes and amphiboles from these mantle formations was performed....To discuss the nature of the compositional heterogeneity of the peridotite massifs of the Polar Urals(Russia), the geochemical study by LA-ICP-MS of pyroxenes and amphiboles from these mantle formations was performed. The trace element compositions in clinopyroxenes indicate the existence of the mantle protolith of two types. The first protolith type, represented by lherzolites and diopside harzburgites,was originated from the partial melting(5%–10%) under the spinel facies conditions, while the second one,represented by diopside harzburgites, was formed under the polybaric partial melting(17%–19%) under garnet and spinel facies conditions. Subsequently, the mantle peridotite protolith was subject to fluidinduced partial melting in the suprasubduction setting that was resulted in the formation of harzburgites.Being affected by penetrating melts and fluids peridotites experienced the refertilization(LREE enrichment of clinopyroxenes) and high-temperature hydratation with subsequent development of pargasite and Mg amphibole. The high-T fluid-induced metamorphism at the subduction zone was accompanied by the formation of metaperidotites with clinochlore and REE-depleted tremolite.展开更多
The Beloretsk Metamorphic Complex in the SW Urals formed at a convergent eastern margin of Baltica during the Neoproterozoic–Early Cambrian Timanide orogeny.It comprises three major units with lenses of facies-critic...The Beloretsk Metamorphic Complex in the SW Urals formed at a convergent eastern margin of Baltica during the Neoproterozoic–Early Cambrian Timanide orogeny.It comprises three major units with lenses of facies-critical metabasites within metasedimentary rocks:A lowermost eclogite unit,an intermediate garnet amphibolite unit and an upper amphibolite-greenschist unit.Pressure(P)-temperature(T)-paths of four rocks from the two lowermost units were determined mainly by PT pseudosection techniques showing similar clockwise loops at different peak metamorphic,watersaturated conditions:A phengite-bearing eclogite shows peak PT conditions of 16.5–18.5 kbar/525–550℃(stage I)followed by stage II at 11.5–13.0 kbar/585–615℃.A garnet amphibolite from the intermediate unit yields lower peak conditions of 11.7–14.5 kbar/480–510℃(stage I)followed by stage II at 9.5–11.0 kbar/535–560℃.However,a granite gneiss in the eclogite unit shows similar maximum pressures as the eclogite,but higher temperatures at 15.6–16.2 kbar/660–675℃,whereas a garnet micaschist contains comparable high pressure relicts,but underwent an advanced midcrustal reequilibration at 7.5–9.0 kbar/555–610℃.We dated the eclogite by a 7-point Rb/Sr mineral isochron(phengite,omphacite,apatite)at 532.2±9.1 Ma interpreted as age of crystallisation of the eclogitic peak PT assemblage.This age is the youngest compared to the known Timanide metamorphic and magmatic ages.展开更多
The lithological and geochemical composition and conditions of formation of the coal-bearing deposits of the Kizel Coal Basin in the Perm region of the Urals(central Russia)are described using the two most representat...The lithological and geochemical composition and conditions of formation of the coal-bearing deposits of the Kizel Coal Basin in the Perm region of the Urals(central Russia)are described using the two most representative sections,Gubakha-Stary Most and Krestovaya Mountain,based on a detailed“layer-by-layer”technique.Brief characteristics of the Lower Carboniferous paleosols from fossil paleosol(FPS-)profiles of the studied region are given.Special attention is paid to the parent vegetation of the coal-forming processes,based on an analysis of both plant macrofossils and palynoflora.The peat accumulation in conditions of permanent incoming of clastic material from the Paleo-Urals to the Kizel Basin was probably effective only in more or less stable environments,when the accumulated organic matter produced by plant mortmass was not dissolved by clastic particles.Thus,the conditions of coal-forming are reconstructed as a forest swamp,where the main dominants are represented by lycopodiopsids of the order Lepidodendrales,predominantly Lepidodendron veltheimii.These plants in particular were the source of the initial organic matter for the peat(and later coal)of the Kizel Coal Basin.展开更多
Shrub expansion into arctic and alpine tundra is one of the prominent vegetation changes currently underway.We studied the expansion of shrub vegetation into high elevation tundra in the Kvarkush Range of the Northern...Shrub expansion into arctic and alpine tundra is one of the prominent vegetation changes currently underway.We studied the expansion of shrub vegetation into high elevation tundra in the Kvarkush Range of the Northern Ural mountains,Russia.Age structure analysis of the dominant shrub Juniperus sibirica Burgsd.seems to support ongoing upslope advance of shrubs,a process particularly active in the second half of the 20 th century.We found a close connection between the expansion of shrub vegetation and the general change in climatic conditions of the cold season(months with mean airtemperature below 0°Сfrom November to March).In general,the greatest influence on the distribution of J.sibirica is exerted by the climate conditions of the beginning(November-January)and the end(March)of the cold season.With increasing elevation,the correlation coefficients between the establishment of J.sibirica shrubs and the precipitation of the beginning of the cold season increased,and reached maximum values at the top elevation level of the study area.However,the upwards shift of J.sibirica into typical mountain tundra does not lead to changes in the ecological structure of vegetation at this stage,but simply a decrease in the area of mountain tundra.展开更多
This paper presents a dendroclimatic analysis of Siberian larch trees sampled along a latitudinal 260-km transect located in the Polar Urals,Russia. Three standardised chronologies were built over a length of 230–293...This paper presents a dendroclimatic analysis of Siberian larch trees sampled along a latitudinal 260-km transect located in the Polar Urals,Russia. Three standardised chronologies were built over a length of 230–293 years using 79 individual tree-ring chronologies collected in the southern,middle and northern parts of the Polar Urals.Bootstrapped correlation functions showed that the annual growth of the larches was mainly influenced by the air temperatures in June and July. The relative role of the temperatures increased from south to north. Daily air temperature data analysis revealed that the duration of the growing season in the northern part of the Polar Urals is 24 days less than that in the southern part. At the present time, air temperatures exceeded threshold of 8~℃, 5 days earlier than it did in the beginning of the 20 th century In response to the increase in the duration of the growing season and the changing winter conditions in the Polar Urals over the last 130 years, radial growth–temperature relationships in larches have weakened;this effect was strongly pronounced in the southern part of the Polar Urals.展开更多
文摘Field-and petrographic investigations,together with microanalytical major-and traceelement studies,were carried out on clinopyroxene and amphibole from high-Mg diorite in the subduction-related Chelyabinsk granitic massif to understand its petrogenesis and source.The clinopyroxene composition(high Mg#,Cr-content,sum of REE and Ti/Eu ratio;depletion in HREE;negative Eu-anomaly)indicates that it formed from a reduced melt derived from a mantle source metasomatized by fluids/melts having crustal affinity.Melt compositions in equilibrium with clinopyroxene and amphibole were calculated using solid/liquid partition coefficients.The high Nb/Y and Zr/Y ratio values of a liquid simulated from clinopyroxene,which appears to have very similar characteristics to sanukitoid melts,indicate a low degree of melting of the mantle source.Melt simulated from amphibole is more evolved and more felsic(dacitic).It displays a geochemical“amphibole fractionation”signature,indicating the peritectic transformation of clinopyroxene to amphibole in the lower crust.Rock textures and major element mineral compositions suggest that further amphibole was precipitated directly from the melt in the middle crust.The results show that the Chelyabinsk highMg diorite was probably formed as a cumulate from sanukitoid-like melt during its ascent and cooling below dacitic liquidus inside the amphibole stability field.
基金jointly supported by the National Key Research and Development Program of China (Grant No.2018YFA0606403)the National Natural Science Foundation of China (Grant No.41790473)the Beijing Natural Science Foundation (8234068)。
文摘Observational analyses demonstrate that the Ural persistent positive height anomaly event(PAE) experienced a decadal increase around the year 2000, exhibiting a southward displacement afterward. These decadal variations are related to a large-scale circulation shift over the Eurasian Continent. The effects of underlying sea ice and sea surface temperature(SST) anomalies on the Ural PAE and the related atmospheric circulation were explored by Atmospheric Model Intercomparison Project(AMIP) experiments from the Coupled Model Intercomparison Project Phase 6 and by sensitivity experiments using the Atmospheric General Circulation Model(AGCM). The AMIP experiment results suggest that the underlying sea ice and SST anomalies play important roles. The individual contributions of sea ice loss in the Barents-Kara Seas and the SST anomalies linked to the phase transition of the Pacific Decadal Oscillation(PDO) and Atlantic Multidecadal Oscillation(AMO) are further investigated by AGCM sensitivity experiments isolating the respective forcings.The sea ice decline in Barents-Kara Seas triggers an atmospheric wave train over the Eurasian mid-to-high latitudes with positive anomalies over the Urals, favoring the occurrence of Ural PAEs. The shift in the PDO to its negative phase triggers a wave train propagating downstream from the North Pacific. One positive anomaly lobe of the wave train is located over the Ural Mountains and increases the PAE there. The negative-to-positive transition of the AMO phase since the late-1990s causes positive 500-h Pa height anomalies south of the Ural Mountains, which promote a southward shift of Ural PAE.
文摘In recent decades,the rapid climate warming in polar and alpine regions has been accompanied by an expan-sion of shrub vegetation.However,little is known about how changes in shrub distribution will change as the distribution of tree species and snow cover changes as temperatures rise.In this work,we analyzed the main environmental factors influencing the distribution and structure of Juniperus sibir-ica,the most common shrub species in the Southern Ural Mountains.Using mapping and digital elevation models,we demonstrated that J.sibirica forms a well-defined vegeta-tion belt mainly between 1100 and 1400 m a.s.l.Within this zone,the abundance and cover of J.sibirica are influenced by factors such as rockiness,slope steepness,water regime and tree(Picea obovata)cover.An analysis of data spanning the past 9 years revealed an upward shift in the distribution of J.sibirica with a decrease in its area.The primary limit-ing factors for the distribution of J.sibirica were the removal of snow cover by strong winter winds and competition with trees.As a consequence of climatic changes,the tree line and forest limit have shifted upward,further restricting the distribution of J.sibirica to higher elevations where com-petition for light with trees is reduced and snow cover is sufficiently deep.
基金supported by the Russian Center for Scientific Information under grant RFBR–21–54–12016 for the sampling and treating of collected materialsby the Russian Scientific Foundation under grant RSF-24–14-00206 for data analysis and preparation of the manuscript.
文摘Climate has changed sufficiently over the last 150 years and forced out upper treeline advance at the most studied sites around the world.The rate of advance has been extremely variable–from tens to hundreds meters in altitude.This is because the degree at which tree frontal populations respond to climate change depends on the complex interaction of biological and physical factors.The resulting stand pattern is the consequence of the interaction between dispersal and survival functions.A few publications have addressed the question of how this pattern is generated.In order to understand how the spatial structure of tree stands was formed at the upper limit of their distribution in the Ural Mountains,we assessed the distance and direction of dispersal of offspring from maternal individuals.We found that in frontal Larix sibirica Ledeb.populations,‘effective’dispersal of offspring ranges from 3 to 758 m(with a median of 20–33 m in open forest and 219 m in single-tree tundra in the Polar Urals and 107 m in open forest in the Northern Urals).We revealed that most of the offspring effectively dispersed not only in the direction of the prevailing winds,but also in the opposite direction up the slope,and the distance can reach 500–760 m.The data obtained can be used to develop an individual-based model which is capable of simulating in detail the dynamics of tree stands at the upper limit of their growth and reliably predicting the future position and pattern of treeline ecotone as growth conditions continue to improve in the face of observed climate change.
基金supported by the National Key R&D Program of China(Grant No.2022YFE0106300)the National Natural Science Foundation of China(Grant Nos.42105052 and 42106220)+1 种基金the Guangdong Basic and Applied Basic Research Foundation(Grant No.2020B1515020025)the fundamental research funds for the Norges Forskningsråd(Grant No.328886).
文摘Arctic sea ice has undergone a significant decline in the Barents-Kara Sea(BKS)since the late 1990s.Previous studies have shown that the decrease in sea ice caused by increased poleward moisture transport is modulated by tropical sea temperature changes(mainly referring to La Niña events).The occurrence of multi-year La Niña(MYLA)events has increased significantly in recent decades,and their impact on Arctic sea ice needs to be further explored.In this study,we investigate the relationship between sea-ice variation and different atmospheric diagnostics during MYLA and other La Niña(OTLA)years.The decline in BKS sea ice during MYLA winters is significantly stronger than that during OTLA years.This is because MYLA events tend to be accompanied by a warm Arctic-cold continent pattern with a barotropic high pressure blocked over the Urals region.Consequently,more frequent northward atmospheric rivers intrude into the BKS,intensifying longwave radiation downward to the underlying surface and melting the BKS sea ice.However,in the early winter of OTLA years,a negative North Atlantic Oscillation presents in the high latitudes of the Northern Hemisphere,which obstructs the atmospheric rivers to the south of Iceland.We infer that such a different response of BKS sea-ice decline to different La Niña events is related to stratospheric processes.Considering the rapid climate changes in the past,more frequent MYLA events may account for the substantial Arctic sea-ice loss in recent decades.
基金the financial support from the National Natural Science Foundation of China(Grants Nos. 41975068, 41790473, and 41975099)the Chinese Academy of Sciences Strategic Priority Research Program (Grant No. XDA19070403).
文摘Starting in mid-November,China was hit by several cold events during the early winter of 2020/21.The lowest temperature observed at Beijing station on 7 January reached−19.6°C.In this paper,we show that the outbreak of the record-breaking extreme cold event can be attributed to a huge merging Ural blocking(UB)ridge over the Eurasian region.The sea-ice cover in the Kara and East Siberia Seas(KESS)in autumn was at its lowest value since 1979,which could have served as a precursor signal.Further analysis shows that several successive UB episodes occurred from 1 September 2020 to 10 January 2021.The persistent UB that occurred in late September/early October 2020 may have made an important contribution to the October historical minimum of sea ice in the KESS region.Our results also show that,after each UB episode in winter,significant upward propagation of wave activity occurred around 60°E,which resulted in weakening the stratospheric vortex.Meanwhile,each UB episode also caused a significant reduction in sea-ice extent in KESS and a significant weakening of the westerly jet in mid-high-latitude Eurasia.Results suggest that the Arctic vortex,which is supposed to enhance seasonally,became weaker and more unstable than the climatic mean under the seasonal cumulative effects of UB episodes,KESS warming,and long-lasting negative-phase North Atlantic Oscillation(NAO-).Those seasonal cumulative effects,combined with the impact of La Niña winter,led to the frequent occurrence of extreme cold events.
基金jointly supported by the National Natural Science Foundation of China (Grant Nos.41790471, 41991284, and 41875104)the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No.XDA20100304).
文摘An unprecedented cold wave intruded into East Asia in early January 2021 and led to record-breaking or historical extreme low temperatures over vast regions.This study shows that a major stratospheric sudden warming(SSW)event at the beginning of January 2021 exerted an important influence on this cold wave.The major SSW event occurred on 2 January 2021 and subsequently led to the displacement of the stratospheric polar vortex to the East Asian side.Moreover,the SSW event induced the stratospheric warming signal to propagate downward to the mid-to-lower troposphere,which not only enhanced the blocking in the Urals-Siberia region and the negative phase of the Arctic Oscillation,but also shifted the tropospheric polar vortex off the pole.The displaced tropospheric polar vortex,Ural blocking,and another downstream blocking ridge over western North America formed a distinct inverted omega-shaped circulation pattern(IOCP)in the East Asia-North Pacific sector.This IOCP was the most direct and impactful atmospheric pattern causing the cold wave in East Asia.The IOCP triggered a meridional cell with an upward branch in East Asia and a downward branch in Siberia.The meridional cell intensified the Siberian high and low-level northerly winds,which also favored the invasion of the cold wave into East Asia.Hence,the SSW event and tropospheric circulations such as the IOCP,negative phase of Arctic Oscillation,Ural blocking,enhanced Siberian high,and eastward propagation of Rossby wave eventually induced the outbreak of an unprecedented cold wave in East Asia in early January 2021.
基金the CAS Key project KZCX2-203 the Research Program for the Excellent State Key Laboratory! (Grant No.49823002)the Study on F
文摘The 1998 summer-time floods at the Yangtze River basin of China, the severest in last 50 years or so, directly resulted from the abnormal extension of Meiyu (rainy season), which was related to a weak East Asian summer monsoon and persistent anomalies of extratropical circulation. The long persistence of blocking over the Ural Mountains is a conspicuous feature. The physical processes responsible for the prolonged maintenance of this key system are investigated in terms of internal forcing (transient eddy upon basic flow) and external forcing (tropical heating forcing) via diagnosis and numerical experiments in the paper. Using the adjoint method, the location and structure of optimal perturbations favorable for the development and maintenance of Ural blocking are identified, which shows an apparent coincidence with the observed storm track at the eastern Atlantic to Europe sector. The diagnosis of E-vector and the response of baroclinic stationary wave to transient forcing both suggest further that the enhanced transient eddy activity favors the occurrence and maintenance of positive anomalies. The upper-level jet and heat sources (sinks) during that period are calculated, and the results indicate that the anomaly of upper jet and tropical heating is evident. The ensemble forecasting experiments by a GCM, IAP T42L9 show that the anomalous heating over the tropics, especially over the central-western Pacific and Atlantic, favors the formation of positive anomalies of height at the Ural region. Finally, a self-sustain mechanism of positive anomalies through two-way interaction between planetary stationary wave and transient eddy under the stimulation of anomalous tropical heating is proposed.
基金N.D.,V.K.,A.G.,and A.G.were supported by the Russian Science Foundation(Grant No.17-14-01112)V.M.was supported by the Russian Foundation of Basic Research(Grant No.19-05-00756)Data collection was partly performed within the frameworks of a state contract with the Institute of Plant and Animal Ecology,Ural Branch,Russian Academy of Sciences.
文摘Background:Recent warming is affecting species composition and species areal distribution of many regions.However,although most treeline studies have estimated the rates of forest expansion into tundra,still little is known about the long-term dynamic of stand productivity at the forest-tundra intersection.Here,we make use of tree-ring data from 350 larch(Larix sibirica Ledeb.)and spruce(Picea obovata Ledeb.)sampled along the singular altitudinal treeline ecotone at the Polar Urals to assess the dynamic of stand establishment and productivity,and link the results with meteorological observations to identify the main environmental drivers.Results:The analysis of stand instalment indicated that more than 90%of the living trees appeared after 1900.During this period,the stand became denser and moved 50m upward,while in recent decades the trees of both species grew faster.The maximum afforestation occurred in the last decades of the twentieth century,and the large number of encountered saplings indicates that the forest is still expanding.The upward shift coincided with a slight increase of May-August and nearly doubling of September-April precipitation while the increase in growth matched with an early growth season warming(June+0.27°C per decade since 1901).This increase in radial growth combined with the stand densification led to a 6-90 times increase of biomass since 1950.Conclusion:Tree-ring based twentieth century reconstruction at the treeline ecotone shows an ongoing forest densification and expansion accompanied by an increased growth.These changes are driven by climate change mechanism,whereby the leading factors are the significant increase in May-June temperatures and precipitation during the dormant period.Exploring of phytomass accumulation mechanisms within treeline ecotone is valuable for improving our understanding of carbon dynamics and the overall climate balance in current treeline ecosystems and for predicting how these will be altered by global change.
基金the funding obtained through the state program with reference number AAAA-A18-118052590028
文摘Formation of the Urals volcanic-hosted massive sulphide(VHMS) deposits is considered to be related with the intra-oceanic stage of island arc(s) development in the Upper Ordoviciane Middle Devonian based on the biostratigraphic record of ore-hosting sedimentary rocks. However, the direct Re-Os dating of four known VHMS systems in the Urals gives significantly younger Re-Os isochron ages ranging from355 ± 15 Ma up to 366 ± 2 Ma. To address this discrepancy, we performed SHRIMP U-Pb dating on zircons extracted from rhyodacites(Eifelian biostratigraphic age of 393 -388 Ma) from the footwall of the Alexandrinka VHMS deposit which has a Re-Os isochron age of sulphides of 355 ± 15 Ma.New ^(206) Pb/^(238) U mean age of 374 ± 3 Ma(MSWD ? 1.4 and probability ? 0.11) is considered to be the crystallisation age of the host volcanic rock. This age is ca. 15 Ma younger than the Eifelian(393 -388 Ma)biostratigraphic age and overlaps the Frasniane Famennian boundary(372 ± 2 Ma), characterised by the final stages of Magnitogorsk Arc e East European continent collision. Such an inconsistency with geochronological age may be due to a reburial of conodonts during resedimentation as a result of erosion of older rocks in younger sedimentary sequences.
文摘In terms of Kuo-Qian pesigma incorporated coordinate five-level primitive equation spheric band (70°N-30°S)model with the Ural high's effect introduced into it as initial and boundary conditions, study is made of the high's influence on Asian summer monsoon circulation and dryness / wetness of eastern China based on case contrast andcontrol experiments. Rusults show that as an excitation source, the blocking high produces a SE-NW stationarywavetrain with its upper-air atnicyclonic divergent circulation oust over a lower-level trough zone) precisely over themiddle to lower reaches of the Changjiang River, enhancing East Asian westerly jet, a situation that contributes toPerturbation growth, causing an additional secondary meridional circulation at the jet entrance, which intensifies theupdraft in the monsoon area. As such, the high's presence and its excited steady wavetrain represent the large-scalekey factors and acting mechanisms for the rainstorm over the Changjiang-Huaihe River catchment in the easternpart of the land.
文摘The Polar Urals region of northern Russia is well known for large chromium （Cr）-bearing massifs with major chromite orebodies, including the Centralnoye I deposit in the Ray-Iz ultramafic massif of the Ural ophiolite belt. New data on platinum （Pt）-group elements （PGE）, geochemistry and mineralogy of the host dunite shows that the deposit has anomalous iridium （Ir） values. These values indicate the predominance of ruthenium--osmium--iridium （Ru--Os--Ir）-bearing phases among the platinum-group mineral （PGM） assemblage that is typical of mantle-hosted chromite ores. Low Pt values in chromites and increased Pt values in host dunites might reflect the presence of cumulus PGM grains. The most abundant PGM found in the chromite is erlichmanite （up to 15 μm）. Less common are cuproiridsite （up to 5 μm）, irarsite （up to 4--5 μm）, and laurite （up to 4 μm）. The predominant sulfide is heazlewoodite, in intergrowth with Ni--Fe alloys, sporadically with pentlandite, and rarely with pure nickel. Based on the average PGE values and esti- mated Cr-ore resources, the Centralnoye I deposit can be considered as an important resource of PGE.
基金funded by a National Key Research and De-velopment Program Project[grant number 2018YFC1505601]National Natural Science Foundation of China[grant number 41975072]。
文摘Two successive severe cold waves invaded eastern China from the end of 2020 to early 2021,leading to an extensive,severe,and persistent drop in temperature.The paper investigates the features and formation mechanisms of the two cold waves.The main results are as follows:(1)An anticlockwise turning of the transverse trough was observed in both cold waves.However,a broad ridge was maintained over the Ural area from mid-December 2020 till mid-January 2021.No breakdown or discontinuous westward shift of the blocking high was observed,which is different from typical cold waves in eastern Asia.(2)The maintenance and strengthening of northerly winds in front of the Ural high led to an increase in baroclinicity in-situ.In the downstream region,the gradient of the geopotential height contour in the south of the transverse trough rapidly increased and the advection of cold temperature consistently enhanced and advanced southwards.This in turn caused the intensification and southward expansion of the Siberian high.(3)Energy propagation of the quasi-stationary wave was a reason for the development and persistence of the Ural blocking.Prior to the occurrence of the two cold waves,the energy of the low-frequency stationary wave originating from near 0°E(or even to the west)propagated eastwards,which helped the Ural ridge intensify and maintain.Meanwhile,it also contributed to the development of the trough downstream of the ridge and resulted in the anticlockwise turning of the transverse trough,providing a favorable condition for the southward outbreak of cold air.
基金the Project IGCP-649 and the IGG UB RAS (No. АААА-А18118052590029-6)
文摘To discuss the nature of the compositional heterogeneity of the peridotite massifs of the Polar Urals(Russia), the geochemical study by LA-ICP-MS of pyroxenes and amphiboles from these mantle formations was performed. The trace element compositions in clinopyroxenes indicate the existence of the mantle protolith of two types. The first protolith type, represented by lherzolites and diopside harzburgites,was originated from the partial melting(5%–10%) under the spinel facies conditions, while the second one,represented by diopside harzburgites, was formed under the polybaric partial melting(17%–19%) under garnet and spinel facies conditions. Subsequently, the mantle peridotite protolith was subject to fluidinduced partial melting in the suprasubduction setting that was resulted in the formation of harzburgites.Being affected by penetrating melts and fluids peridotites experienced the refertilization(LREE enrichment of clinopyroxenes) and high-temperature hydratation with subsequent development of pargasite and Mg amphibole. The high-T fluid-induced metamorphism at the subduction zone was accompanied by the formation of metaperidotites with clinochlore and REE-depleted tremolite.
文摘The Beloretsk Metamorphic Complex in the SW Urals formed at a convergent eastern margin of Baltica during the Neoproterozoic–Early Cambrian Timanide orogeny.It comprises three major units with lenses of facies-critical metabasites within metasedimentary rocks:A lowermost eclogite unit,an intermediate garnet amphibolite unit and an upper amphibolite-greenschist unit.Pressure(P)-temperature(T)-paths of four rocks from the two lowermost units were determined mainly by PT pseudosection techniques showing similar clockwise loops at different peak metamorphic,watersaturated conditions:A phengite-bearing eclogite shows peak PT conditions of 16.5–18.5 kbar/525–550℃(stage I)followed by stage II at 11.5–13.0 kbar/585–615℃.A garnet amphibolite from the intermediate unit yields lower peak conditions of 11.7–14.5 kbar/480–510℃(stage I)followed by stage II at 9.5–11.0 kbar/535–560℃.However,a granite gneiss in the eclogite unit shows similar maximum pressures as the eclogite,but higher temperatures at 15.6–16.2 kbar/660–675℃,whereas a garnet micaschist contains comparable high pressure relicts,but underwent an advanced midcrustal reequilibration at 7.5–9.0 kbar/555–610℃.We dated the eclogite by a 7-point Rb/Sr mineral isochron(phengite,omphacite,apatite)at 532.2±9.1 Ma interpreted as age of crystallisation of the eclogitic peak PT assemblage.This age is the youngest compared to the known Timanide metamorphic and magmatic ages.
基金This work was funded by the State Program(Grant No.0135-2019-0044)of the Geological Institute of the Russian Academy of Sciences.
文摘The lithological and geochemical composition and conditions of formation of the coal-bearing deposits of the Kizel Coal Basin in the Perm region of the Urals(central Russia)are described using the two most representative sections,Gubakha-Stary Most and Krestovaya Mountain,based on a detailed“layer-by-layer”technique.Brief characteristics of the Lower Carboniferous paleosols from fossil paleosol(FPS-)profiles of the studied region are given.Special attention is paid to the parent vegetation of the coal-forming processes,based on an analysis of both plant macrofossils and palynoflora.The peat accumulation in conditions of permanent incoming of clastic material from the Paleo-Urals to the Kizel Basin was probably effective only in more or less stable environments,when the accumulated organic matter produced by plant mortmass was not dissolved by clastic particles.Thus,the conditions of coal-forming are reconstructed as a forest swamp,where the main dominants are represented by lycopodiopsids of the order Lepidodendrales,predominantly Lepidodendron veltheimii.These plants in particular were the source of the initial organic matter for the peat(and later coal)of the Kizel Coal Basin.
基金part of the state assignment of the Institute of Plant and Animal Ecology,Ural Branch of the Russian Academy of Sciences(No.AAAA-A19-119111990097-4No.AAAA-A19-119031890084-6No.AAAA-A19-119111390057-4)。
文摘Shrub expansion into arctic and alpine tundra is one of the prominent vegetation changes currently underway.We studied the expansion of shrub vegetation into high elevation tundra in the Kvarkush Range of the Northern Ural mountains,Russia.Age structure analysis of the dominant shrub Juniperus sibirica Burgsd.seems to support ongoing upslope advance of shrubs,a process particularly active in the second half of the 20 th century.We found a close connection between the expansion of shrub vegetation and the general change in climatic conditions of the cold season(months with mean airtemperature below 0°Сfrom November to March).In general,the greatest influence on the distribution of J.sibirica is exerted by the climate conditions of the beginning(November-January)and the end(March)of the cold season.With increasing elevation,the correlation coefficients between the establishment of J.sibirica shrubs and the precipitation of the beginning of the cold season increased,and reached maximum values at the top elevation level of the study area.However,the upwards shift of J.sibirica into typical mountain tundra does not lead to changes in the ecological structure of vegetation at this stage,but simply a decrease in the area of mountain tundra.
基金supported by the Russian Scientific Foundation (RSF) (Grant No. 17-1401112)
文摘This paper presents a dendroclimatic analysis of Siberian larch trees sampled along a latitudinal 260-km transect located in the Polar Urals,Russia. Three standardised chronologies were built over a length of 230–293 years using 79 individual tree-ring chronologies collected in the southern,middle and northern parts of the Polar Urals.Bootstrapped correlation functions showed that the annual growth of the larches was mainly influenced by the air temperatures in June and July. The relative role of the temperatures increased from south to north. Daily air temperature data analysis revealed that the duration of the growing season in the northern part of the Polar Urals is 24 days less than that in the southern part. At the present time, air temperatures exceeded threshold of 8~℃, 5 days earlier than it did in the beginning of the 20 th century In response to the increase in the duration of the growing season and the changing winter conditions in the Polar Urals over the last 130 years, radial growth–temperature relationships in larches have weakened;this effect was strongly pronounced in the southern part of the Polar Urals.
