asian origin of interannual variations of summer climate over the extratropical north atlantic ocean abstractthe authors have identified an interannual relationship between asian tropospheric temperature and the north atlantic ocean sea surface temperature sst during summer may september and discussed the associated features of atmospheric circulation over the atlantic eurasian region when tropospheric temperature is high low over asia positive negative sst anomalies appear in the extratropical north atlantic this relationship is well supported by the changes in background atmospheric circulation and ocean atmosphere land thermodynamic processes when heat transfer from the land surface to the atmosphere over asia strengthens local tropospheric temperature increases and positive temperature anomalies propagate westward from asia to the north atlantic leading to an increase in summer tropospheric temperature over the atlantic eurasian region accordingly a deep anomalous ridge occurs over the extratropical north atlantic ocean with low level southerly anomalies over the western portion of t

an interannual link between arctic sea ice cover and the north atlantic oscillation this work investigates links between arctic surface variability and the phases of the winter djf north atlantic oscillation nao on interannual time scales the analysis is based on era reanalysis and model data from the ec earth global climate model our study emphasizes a mode of sea ice cover variability that leads the nao index by 1 year the mechanism of this leading is based on persistent surface forcing by quasi stationary meridional thermal gradients associated thermal winds lead a slow adjustment of the pressure in the following winter which in turn feeds back on the propagation of sea ice anomalies the pattern of the sea ice mode leading nao has positive anomalies over key areas of south davis strait labrador sea the barents sea and the laptev ohkostsk seas associated to a high pressure anomaly over the canadian archipelago baffin bay and the laptev east siberian seas these anomalies create a quasi annular quasi steady positive gradient of sea ice anomalies about coastal line when leading the positive nao phase and force a cyclonic vorticity anomaly over the arctic in the following winter during recent decades in spite of slight shifts in the modes spectral properties the same leading mechanism remains valid encouraging actual models appear to reproduce the same mechanism leading model s nao relative to model areas of persistent surface forcing this indicates that the link between sea ice and nao could be exploited as a potential skill source for multi year prediction by addressing the key problem of initializing the phase of the nao ao arctic oscillation

arctic sea ice variability in the context of recent atmospheric circulation trends abstract forty years 1958 97 of reanalysis products and corresponding sea ice concentration data are used to document arctic sea ice variability and its association with surface air temperature sat and sea level pressure slp throughout the northern hemisphere extratropics the dominant mode of winter january march sea ice variability exhibits out of phase fluctuations between the western and eastern north atlantic together with a weaker dipole in the north pacific the time series of this mode has a high winter to winter autocorrelation 0 69 and is dominated by decadal scale variations and a longer term trend of diminishing ice cover east of greenland and increasing ice cover west of greenland associated with the dominant pattern of winter sea ice variability are large scale changes in sat and slp that closely resemble the north atlantic oscillation the associated sat and surface sensible and latent heat flux anomalies are largest over the portions of the marginal sea ice zone in which the tr

a coupled decadal prediction of the dynamic state of the kuroshio extension system abstractbeing the extension of a wind driven western boundary current the kuroshio extension ke has long been recognized as a turbulent current system rich in large amplitude meanders and energetic pinched off eddies an important feature emerging from recent satellite altimeter measurements and eddy resolving ocean model simulations is that the ke system exhibits well defined decadal modulations between a stable and an unstable dynamic state here the authors show that the decadally modulating ke dynamic state can be effectively defined by the sea surface height ssh anomalies in the 31 36 n 140 165 e region by utilizing the ssh based ke index from 1977 to 2012 they demonstrate that the time varying ke dynamic state can be predicted at lead times of up to 6 yr this long term predictability rests on two dynamic processes 1 the oceanic adjustment is via baroclinic rossby waves that carry interior wind forced anomalies westward into the ke region and 2 the low frequency ke variability influenc

the transient atmospheric circulation response to north atlantic sst and sea ice anomalies abstract the objective of this study is to investigate the transient evolution of the wintertime atmospheric circulation response to imposed patterns of sst and sea ice extent anomalies in the north atlantic sector using a large ensemble of experiments with the ncar community climate model version 3 ccm3 the initial adjustment of the atmospheric circulation is characterized by an out of phase relationship between geopotential height anomalies in the lower and upper troposphere localized to the vicinity of the forcing this initial baroclinic response reaches a maximum amplitude in 5 10 days and persists for 2 3 weeks diagnostic results with a linear primitive equation model indicate that this initial response is forced by diabatic heating anomalies in the lower troposphere associated with surface heat flux anomalies generated by the imposed thermal forcing following the initial baroclinic stage of adjustment the response becomes progressively more barotropic and increases in both spatial extent an

transient response of an atmospheric gcm to north atlantic sst anomalies abstract a high resolution atmospheric general circulation model gcm is used to evaluate the atmospheric response to north atlantic sea surface temperature sst anomalies the transient evolution of the response is studied in detail the linear and nonlinear effects can thus be contrasted and separated by their different time scales baroclinic patterns related directly to the surface anomalies quickly reach their maximum manifestation however barotropic patterns related to the mid and upper troposphere eddy vorticity fluxes have longer time scales with much more important amplitude able to gradually replace the initial baroclinic response this study thus provides an evolutional picture of the two types of response in a gcm

a preliminary discussion on genesis of xinqiao s fe orefield the xinqiao s fe cu au ore field is located in the tongling ore cluster in middle lower yangtze valley there have been various opinions concerning the genetic type of this orefield put forward by different geologists in recent years such as sedimentary reformation type stratabound skarn type and sedimentary submarine rock hosted exhalative type based on nearly ten years of systematic geological field observation and analysis of pb and s isotopic composition of the xinqiao orefield the authors hold that it was formed in two ore forming periods the first period took place during the syngenetic sedimentary process whereas massive sulphide ore bodies were mainly formed during the second period i e the yanshanian granitic magnatism the sulfide metallic mineral associations show zoning around a granite intrusion in order of magnetite pyrite pyrite chalcopyrite and native gold pyrite sphalerite and galena the gold ore bodies occur outside the contact zone of the granite intrusion

the basic ingredients of the north atlantic storm track part ii sea surface temperatures abstractthe impact of north atlantic sst patterns on the storm track is investigated using a hierarchy of gcm simulations using idealized aquaplanet and semirealistic boundary conditions in the atmospheric component hadam3 of the third climate configuration of the met office unified model hadcm3 this framework enables the mechanisms determining the tropospheric response to north atlantic sst patterns to be examined both in isolation and in combination with continental scale landmasses and orography in isolation a gulf stream sst pattern acts to strengthen the downstream storm track while a north atlantic drift sst pattern weakens it these changes are consistent with changes in the extratropical sst gradient and near surface baroclinicity and each storm track response is associated with a consistent change in the tropospheric jet structure locally enhanced near surface horizontal wind convergence is found over the warm side of strengthened sst gradients associated with ascending air and i

investigating the local atmospheric response to a realistic shift in the oyashio sea surface temperature front abstractthe local atmospheric response to a realistic shift of the oyashio extension sst front in the western north pacific is analyzed using a high resolution hr 0 25 version of the global community atmosphere model version 5 cam5 a northward shift in the sst front causes an atmospheric response consisting of a weak surface wind anomaly but a strong vertical circulation extending throughout the troposphere in the lower troposphere most of the sst anomaly induced diabatic heating is balanced by poleward transient eddy heat and moisture fluxes collectively this response differs from the circulation suggested by linear dynamics where extratropical sst forcing produces shallow anomalous heating balanced by strong equatorward cold air advection driven by an anomalous stationary surface low to the east this latter response however is obtained by repeating the same experiment except using a relatively low resolution lr 1 version of cam5 comparison to observations suggests that the hr respo

enhanced framboidal pyrite formation related to anaerobic oxidation of methane in the sulfate methane transition zone of the northern south china sea abstract many studies have confirmed that size distributions of framboidal pyrite can be an effective indicator of bottom water redox conditions in modern as well as ancient sedimentary environments however one environment in which production of framboidal pyrite has not been sufficiently studied to date is the sulfate methane transition zone smtz in which anaerobic oxidation of methane aom is coupled with microbial sulfate reduction msr to enhance iron sulfide mineral precipitation e g fes2 fes and fe3s4 here we document for the first time size distributions for pyrite framboids from the smtz based on data from two sites in the methane hydrate bearing region of the northern south china sea on the basis of framboid size pyrite concentration and sulfur isotope data we propose new insights into the formation process of authigenic pyrite framboids within the smtz we conclude that 1 enhanced anaerobic oxidation of methane aom not only plays a dominant role in the accumulation of 34s enriched pyrite but also is responsible for formation of highly variable and sometimes exceptionally large pyrite framboids in the smtz 2 most framboids occur in framboid clusters which commonly exhibit rod like shapes secondary overgrowths heavier 34s values and unusual size distributions e g mean size 20 m and standard deviation 3 0 m in the smtz 3 pyrite framboids formed in the smtz which have characteristics different from those formed in the sulfate reduction zone srz do not comment on redox conditions of the overlying water column and 4 framboid occurrences with similar characteristics in ancient marine deposits may be considered indicators of enhanced aom and mark the former position of the smtz in the paleo marine system in addition significant quantities of elemental sulfur were observed in the smtz possibly related to anaerobic oxidation of hydrogen sulfide and fluctuations of the smtz

local wintertime tropospheric response to oceanic heat anomalies in the nordic seas area abstracta regression analysis between observed summertime atlantic water temperature anomalies at the entrance to the barents sea and atmospheric fields in the following winter from the ncep ncar reanalysis in the period 1982 2006 is carried out it shows that the ocean plays a key role in shaping wintertime tropospheric variability in the nordic seas greenland iceland norwegian and barents seas region the oceanically driven atmospheric circulation anomaly around the nordic seas marginal ice zone is intensified at the surface as a result of a thermally direct baroclinic adjustment frictional convergence in the cyclonic disturbance corresponding to warm ocean temperature anomalies forces ascending motion at the top of the planetary boundary layer and a compensating divergence aloft which over the barents sea is extreme at the tropopause a quasi meridional overturning circulation anomaly is closed by descending motion south of the cyclonic disturbance in addition an equivalent barotropic flow anomal

the effects of north atlantic sst and sea ice anomalies on the winter circulation in ccm3 part i main features and storm track characteristics of the response observed multidecadal trends in extratropical atmospheric flow such as the positive trend in the north atlantic oscillation nao index may be attributable to a number of causes this study addresses the question of whether the atmospheric trends may be caused by observed trends in oceanic boundary forcing experiments were carried out using the ncar atmospheric general circulation model with specified sea surface temperature sst and sea ice anomalies confined to the north atlantic sector the spatial pattern of the anomalous forcing was chosen to be realistic in that it corresponds to the recent 40 yr trend in sst and sea ice but the anomaly amplitude was exaggerated in order to make the response statistically more robust the wintertime response to both types of forcing resembles the nao to first order even for an exaggerated amplitude the atmospheric response to the sst anomaly is quite weak compared to the observed positive trend in the nao but has the same sign indicative of a weak positive feedback the anomalies in sea ice extent are more efficient than sst anomalies at exciting an atmospheric response comparable in amplitude to the observed nao trend however this atmospheric response has the opposite sign to the observed trend indicative of a significant negative feedback associated with the sea ice forcing additional experiments using sst anomalies with opposite sign to the observed trend indicate that there are significant nonlinearities associated with the atmospheric response the transient eddy response to the observed sst trend is consistent with the positive nao response with the north atlantic storm track amplifying downstream and developing a more pronounced meridional tilt in contrast the storm track response to the observed sea ice trend corresponds to a weaker southward shifted more zonal storm track which is consistent with the negative nao response

relationships between atmospheric internal variability and the responses to an extratropical sst anomaly abstract the january and february responses of a gcm to an imposed extratropical pacific sst anomaly are compared with the patterns of the model s internal variability relevant patterns of internal variability are diagnosed from ensembles of model control runs by regressing monthly mean geopotentials and temperatures against low level temperatures in the vicinity of the sst anomaly and by eof analysis these patterns are found to play a significant role in determining the local and the remote responses to the sst anomaly different responses to the sst anomaly in the gcm s january and february climates are largely explained by the differences in the regression patterns and in the leading eof the gcm response may be considered as comprising a direct linear response to low level heating that is local to the forcing and baroclinic and an eddy forced component that closely resembles patterns of the model s internal variability it is equivalent barotropic and extends over the entire hemisphere the results

mechanisms determining the winter atmospheric response to the atlantic overturning circulation abstractin climate models an intensification of the atlantic meridional overturning circulation amoc precedes a warming in the north atlantic subpolar basin by a few years in the ipsl cm5a lr model this warming may explain the atmospheric response to the amoc observed in winter which resembles a negative phase of the north atlantic oscillation nao to firmly establish the causality links between the ocean and the atmosphere and illustrate the underlying mechanisms in this model ensembles of atmosphere only simulations are conducted prescribing the sst and sea ice anomalies that follow an amoc intensification in late winter the north atlantic sst and sea ice anomalies drive atmospheric circulation anomalies similar to those found in the coupled model simulations only driven by the sst anomalies related to the amoc show that the largest oceanic influence is due to the warm subpolar sst anomaly which enhances the oceanic heat release and decreases the lower tropospheric baroclinicity in the reg

the general circulation model response to a north pacific sst anomaly dependence on time scale and pattern polarity abstract a general circulation model was integrated with perpetual january conditions and prescribed sea surface temperature sst anomalies in the north pacific a characteristic pattern with a warm region centered northeast of hawaii and a cold region along the western seaboard of north america was alternately added to and subtracted from the climatological sst field long 1350 day runs as well as short 180 day runs each starting from different initial conditions were performed the results were compared to a control integration with climatological ssts the model s quasi stationary response does not exhibit a simple linear relationship with the polarity of the prescribed sst anomaly in the short runs with a negative sst anomaly over the central ocean a large negative height anomaly with an equivalent barotropic vertical structure occurs over the gulf of alaska for the same sst forcing the long run yields a different response pattern in which an anomalous high prevails over northern canada and

the effects of north atlantic sst and sea ice anomalies on the winter circulation in ccm3 part ii direct and indirect components of the response the wintertime atmospheric circulation responses to observed patterns of north atlantic sea surface temperature and sea ice cover trends in recent decades are studied by means of experiments with an atmospheric general circulation model here the relationship between the forced responses and the dominant pattern of internally generated atmospheric variability is focused on the total response is partioned into a portion that projects onto the leading mode of internal variability the indirect response and a portion that is the residual from that projection the direct response this empirical decomposition yields physically meaningful patterns whose distinctive horizontal and vertical structures imply different governing mechanisms the indirect response which dominates the total geopotential height response is hemispheric in scale with resemblance to the north atlantic oscillation or northern hemisphere annular mode and equivalent barotropic in the vertical from the surface to the tropopause in contrast the direct response is localized to the vicinity of the surface thermal anomaly sst or sea ice and exhibits a baroclinic structure in the vertical with a surface trough and upper level ridge in the case of a positive heating anomaly consistent with theoretical models of the linear baroclinic response to extratropical thermal forcing both components of the response scale linearly with respect to the amplitude of the forcing but nonlinearly with respect to the polarity of the forcing the deeper vertical penetration of anomalous heating compared to cooling is suggested to play a role in the nonlinearity of the response to sst forcing

observed atmospheric response to cold season sea ice variability in the arctic abstractthe relation between weekly arctic sea ice concentrations sics from december to april and sea level pressure slp during 1979 2007 is investigated using maximum covariance analysis mca in the north atlantic sector the interaction between the north atlantic oscillation nao and a sic seesaw between the labrador sea and the greenland barents sea dominates the nao drives the seesaw and in return the seesaw precedes a midwinter spring nao like signal of the opposite polarity but with a strengthened northern lobe thus acting as a negative feedback with maximum squared covariance at a lag of 6 weeks statistical significance decreases when slp is considered in the whole northern hemisphere but it increases when north pacific sic is included in the analysis the maximum squared covariance then occurs after 8 weeks resembling a combination of the nao response to the atlantic sic seesaw and the aleutian icelandic low seesaw like response to in phase sic changes in the bering and okhotsk seas w

mechanisms determining the atmospheric response to midlatitude sst anomalies abstract previous gcm experiments demonstrated that a model atmosphere produces two different responses to a midlatitude warm sst anomaly over the pacific under perpetual january and february conditions to elucidate the mechanisms responsible for the different gcm responses and their dependence on the background flow experiments with two idealized models are conducted experiments with a linear baroclinic model reveal that the gcm responses at equilibrium are primarily maintained by the anomalous eddy forcing the anomalous flow induced directly by an idealized initial heat source exhibits little sensitivity to the background flow eddy feedbacks on the heating induced anomalous flow are examined using a linear storm track model the anomalous eddy forcing produced by the storm track model is sensitive to the basic state the eddy forcing in january acts to shift the heating induced upper level ridge toward the northeast of the gulf of alaska while in february it acts to reinforce the ridge this sugge

influence of the meridional shifts of the kuroshio and the oyashio extensions on the atmospheric circulation abstract the meridional shifts of the oyashio extension oe and of the kuroshio extension ke as derived from high resolution monthly sea surface temperature sst anomalies in 1982 2008 and historical temperature profiles in 1979 2007 respectively are shown based on lagged regression analysis to significantly influence the large scale atmospheric circulation the signals are independent from the enso teleconnections which were removed by seasonally varying asymmetric regression onto the first three principal components of the tropical pacific sst anomalies the response to the meridional shifts of the oe front is equivalent barotropic and broadly resembles the north pacific oscillation western pacific pattern in a positive phase for a northward frontal displacement the response may reach 35 m at 250 hpa for a typical oe shift a strong sensitivity since the associated sst anomaly is 0 5 k however the amplitude but not the pattern or statistical significance strongly depends on the lag and an

cmip5 model simulations of warm arctic cold eurasia pattern in winter surface air temperature anomalies the second empirical orthogonal function mode eof2 of winter surface air temperature sat over 0 180 e 40 90 n during 1979 2005 is defined as warm arctic cold eurasia wace pattern the present study evaluates the performance of 25 coupled model inter comparison project phase 5 cmip5 models in simulating the wace pattern based on historical runs there exist large inter model spreads in the simulation of the wace pattern analyses show that the ability of a cmip5 model in capturing the wace pattern is connected with the model s performance in representing the observed atmospheric circulation anomalies related to the winter sea ice concentration sic variation over barents kara seas sea ice loss over barents kara seas can induce significant positive geopotential height anomalies over arctic region and negative geopotential height anomalies around the baikal lake resulting in warm anomalies over barents kara seas and cold anomalies over eurasia further analysis shows that cmip5 model s performance in representing the sat anomalies related to the wace pattern is partly due to simulation of the amplitude of winter sic variability over barents kara seas larger standard deviations of winter sic over barents kara seas can instigate stationary wave train more easily which further induces the sat anomalies

winter weather patterns over northern eurasia and arctic sea ice loss abstractusing ncep ncar reanalysis and japanese 25 yr reanalysis jra 25 winter daily 1 december 28 february data for the period 1979 2012 this paper reveals the leading pattern of winter daily 850 hpa wind variability over northern eurasia from a dynamic perspective the results show that the leading pattern accounts for 18 of the total anomalous kinetic energy and consists of two subpatterns the dipole and the tripole wind patterns the dipole wind pattern does not exhibit any apparent trend the tripole wind pattern however has displayed significant trends since the late 1980s the negative phase of the tripole wind pattern corresponds to an anomalous anticyclone over northern eurasia during winter as well as two anomalous cyclones occurring over southern europe and in the mid to high latitudes of east asia these anomalous cyclones in turn lead to enhanced winter precipitation in these two regions as well as negative surface temperature anomalies over the mid to high latitudes of asia the

a response climatology of idealized midlatitude thermal forcing experiments with and without a storm track several gcm studies indicate that eddy activity may have a considerable influence on the atmospheric response to midlatitude sea surface temperature anomalies the effect of eddy activity on the atmospheric equilibrium response to idealized midlatitude thermal forcing is analyzed for an atmosphere with or without an idealized storm track experiments using a simplified global circulation model forced by thermal anomalies of different sign and location are discussed consistent with the linear theory the geopotential height field displays a baroclinic response with a shallow low high somewhat downstream of the warm cold anomaly farther downstream an equivalent barotropic response occurs with positive negative amplitude increasing with height eddy feedbacks have weak impact on the baroclinic part but the equivalent barotropic response is strongly enhanced if the bandpass filtered streamfunction tendency is in phase with the linear geopotential height response this is the case in an experiment with a warm anomaly near 408n located southwesterly of the idealized storm track in the corresponding experiment with a cold anomaly the two patterns are out of phase and the equivalent barotropic response is slightly reduced it is weakened strengthened if a warm cold anomaly is shifted about 108 poleward or equatorward relative to the idealized storm track midlatitude heat sources generate wave trains that extend equatorward and poleward developing large scale correlations between the flow at remote locations teleconnections the space time variability can be changed considerably by eddy feedbacks developing stronger variance for large scale retrogressive traveling and standing waves partially blocking like events develop

the transient atmospheric response to midlatitude sst anomalies abstract to study the transient atmospheric response to midlatitude sst anomalies a three layer quasigeostrophic qg model coupled to a slab oceanic mixed layer in the north atlantic is used as diagnosed from a coupled run in perpetual winter conditions the first two modes of sst variability are linked to the model north atlantic oscillation nao and eastern atlantic pattern eap respectively the dominant atmospheric modes in the atlantic sector the two sst anomaly patterns are then prescribed as fixed anomalous boundary conditions for the model atmosphere and its transient responses are established from a large ensemble of simulations in both cases the tendency of the air sea heat fluxes to damp the sst anomalies results in an anomalous diabatic heating of the atmosphere that in turn forces a baroclinic response as predicted by linear theory this initial response rapidly modifies the transient eddy activity and thus the convergence of eddy momentum and heat fluxes the latter transforms t

stochastic atmospheric forcing as a cause of greenland climate transitions abstractan unforced simulation of the community climate system model version 4 ccsm4 is found to have greenland warming and cooling events that resemble dansgaard oeschger cycles in pattern and magnitude with the caveat that only three transitions were available to be analyzed it is found that the transitions are triggered by stochastic atmospheric forcing the atmospheric anomalies change the strength of the subpolar gyre leading to a change in labrador sea sea ice concentration and meridional heat transport the changed climate state is maintained over centuries through the feedback between sea ice and sea level pressure in the north atlantic indications that the initial atmospheric pressure anomalies are preceded by precipitation anomalies in the western pacific warm pool are discussed the full evolution of the anomalous climate state depends crucially on the climatic background state

transient atmospheric response to interactive sst anomalies abstract the transient atmospheric response to interactive sst anomalies in the midlatitudes is investigated using a three layer qg model coupled in perpetual winter conditions to a slab oceanic mixed layer in the north atlantic the sst anomalies are diagnosed from a coupled run and prescribed as initial conditions but are free to evolve the initial evolution of the atmospheric response is similar to that obtained with a prescribed sst anomaly starting as a quasi linear baroclinic and then quickly evolving into a growing equivalent barotropic one because of the heat flux damping the sst anomaly amplitude slowly decreases albeit with little change in pattern correspondingly the atmospheric response only increases until it reaches a maximum amplitude after about 1 3 5 months depending on the sst anomaly considered the response is similar to that at equilibrium in the fixed sst case but it is 1 5 2 times smaller and then slowly decays away

tracing water rock interaction in carbonate replacement deposits a sims pyrite s pb isotope perspective from the chinese xinqiao system abstract deciphering the sources of metals is a prerequisite to establishing genetic models of ore formation and is of importance for developing exploration models for most magmatic hydrothermal deposits non magmatic sourced components e g fluids sulfur and metals are suggested to have minor or negligible contributions on the other hand there is substantial evidence to indicate that external ore forming components could be crucial for the mineralization of some magmatic hydrothermal deposits here we conduct a detailed pyrite sulfur and lead isotope study on the xinqiao stratabound deposit south china with the aim of constraining the contributions of ore forming components from sedimentary rocks and existing mineralization through water rock interaction traditionally the source of mineralization at xinqiao is debated for example a cretaceous magmatic hydrothermal origin was proposed as the sole source of metals in sharp contrast a carboniferous sedimentary sulfide layer as proto ore which was enriched later by the cretaceous magmatic hydrothermal fluids is required in a remobilization model crystallized pyrite grains from the stratabound orebody py1 have a 34s value of 4 09 1 42 2 sd which is similar to that of pyrite grains from the garnet bearing skarn ore py3 colloform pyrite ore which is composed of fine grained 500 nm cubic pyrite grains py2a has a 34s value of 0 20 1 14 the sulfur isotope composition of pyrite grains from the sandstone hosted quartz pyrite veins is bimodal with 34s values of 3 28 6 46 py4a and 11 87 5 43 py4b the pb isotope compositions 206 204pb 18 5 207 204pb 15 5 of py1 py4a and py4b are broadly the same as that of k feldspar from the cretaceous jitou diorite while py2a are more radiogenic 206 204pb 21 5 207 204pb 18 our pyrite s and pb isotope data show no support for the presence of a carboniferous sedimentary sulfide layer as proto ore but instead suggest that leaching sulfur and metals from permian shales and an unexposed mineralization through water rock interaction is a vital mechanism for the mineralization at xinqiao in line with previous studies contributions from the late permian shales are complementary for the stratabound orebody and recycling existing mo au rich mineralization is key for the formation of sandstone hosted gold rich pyrite quartz veins the existing mineralization is not exposed yet and should be considered in future mineral exploration limited sulfur isotope fractionation between py1 py2 and py3 0 4 further indicates a relatively reducing condition during their formation while significant lower sulfur isotope composition 34s 12 of py4 could imply an oxidizing condition during its formation our study highlights that detailed in situ sulfur and lead isotope analyses under robust geological and petrographic frameworks can tightly constrain the source of ore forming components yield insights into oxygen fugacity during ore formation and offer clues for future mineral exploration

transient eddy forcing of the time mean flow as identified by geopotential tendencies abstract the forcing of the time mean flow by transient eddies is examined within the framework of a quasi geostrophic equation relating the geopotential tendency to the convergence of transient eddy transports of heat and vorticity the forcing functions of this equation are computed using observed circulation statistics for the wintertime northern hemisphere and solutions are sought for the three dimensional structure of geopotential and temperature tendencies associated with eddies of different time scales in general the geopotential tendencies associated with vorticity fluxes are of the same sign within a given atmospheric column whereas the polarity of the geopotential tendencies associated with heat fluxes in the lower troposphere is opposite to that in the upper troposphere the geostrophic wind tendencies associated with synoptic scale eddies with periods between 2 5 and 6 days are strongest in the vicinity of the oceanic storm tracks the enhanced poleward heat transports by active disturbanc

a diagnostic and modeling study of the monthly mean wintertime anomalies appearing in a 100 year gcm experiment abstract the nature of simulated atmospheric variability on monthly time scales has been investigated by analyzing the output from a 100 year integration of a spectral gcm with rhomboidal wavenumber 15 truncation in this experiment the seasonally varying climatological sea surface temperature was prescribed throughout the world oceans the principal modes of variability in the model experiment were identified by applying a rotated empirical orthogonal function eof analysis to the northern hemisphere monthly averaged 515 mb geopotential height for the winter season november through march the individual leading spatial modes are similar to the observed north south dipoles over the north atlantic and north pacific as well as wavelike patterns in the pacific north american and northern asian sectors quasigeostrophic geopotential tendencies forced by synoptic scale 2 5 6 day eddy vorticity and heat fluxes were computed for those months when the individual eof modes are particularly active the comp

observed evidence of an impact of the antarctic sea ice dipole on the antarctic oscillation abstracta lagged maximum covariance analysis mca is applied to investigate the linear covariability between monthly sea ice concentration sic and 500 mb geopotential height z500 in the southern hemisphere sh the dominant signal is the atmospheric forcing of sic anomalies throughout the year but statistically significant covariances are also found between austral springtime z500 and prior sic anomalies up to four months earlier the mca pattern is characterized by an antarctic dipole adp like pattern in sic and a positively polarized antarctic oscillation aao in z500 such long lead time covariance suggests the forcing of the aao by persistent adp like sic anomalies the leading time of sic anomalies provides an implication for skillful predictability of springtime atmospheric variability

iron isotope fractionation during skarn type metallogeny a case study of xinqiao cu s fe au deposit in the middle lower yangtze valley abstract fe isotope compositions of mineral separates and bulk samples from xinqiao cu s fe au skarn type deposit were investigated an overall variation in 57 fe values from 1 22 to 0 73 has been observed which shows some regularity the 57 fe values of endoskarn and the earliest formed fe mineral phase magnetite are ca 1 2 and ca 0 3 lower respectively relative to the quartz monzodiorite stock indicating that fluid exsolved from the stock is enriched in light fe isotopes moreover spatial and temporal variations in 57 fe values are observed which suggest iron isotope fractionation during fluid evolution precipitation of fe bearing minerals results in the fe isotope composition of residual fluids evolving with time precipitation of fe iii minerals incorporating heavy iron isotopes preferentially leaves the remaining fluid enriched in light isotopes while precipitation of fe ii minerals preferentially taking up light iron isotopes and makes the fe isotopic composition of the fluid progressively heavier the regularity of fe isotope variations occurred during fluid exsolution and evolution indicates that the dominant fe source of xinqiao deposit is magmatic overall this study demonstrates that fe isotope composition has great potential in unraveling ore forming processes as well as constraining the metal sources of ore deposits

recent climate variation in the bering and chukchi seas and its linkages to large scale circulation in the pacific the thermal state of the bering sea exhibits interdecadal variations with distinct changes occurred in 1997 1998 after the unusual thermal condition of the bering sea in 1997 1998 we found that the recent climate variability 1999 2010 in the bering sea is closely related to pacific basin scale atmospheric and oceanic circulation patterns specifically warming in the bering and chukchi seas in this period involves sea ice reduction and stronger oceanic heat flux to the atmosphere in winter the atmospheric response to the recent warming in the bering and chukchi seas resembles the north pacific oscillation npo pattern further analysis reveals that the recent climate variability in the bering and chukchi seas has strong covariability with large scale climate modes in the pacific that is the north pacific gyre oscillation and the central pacific el nino in this study physical connections among the recent climate variations in the bering and chukchi seas the npo pattern and the pacific large scale climate patterns are investigated via cyclostationary empirical orthogonal function analysis an additional model experiment using the national center for atmospheric research community atmospheric model version 3 is conducted to support the robustness of the results

on the feedback of the winter nao driven sea ice anomalies satellite derived sea ice concentration sic and re analysed atmospheric data are used to analyse the potential feedback of the north atlantic oscillation nao driven sea ice anomalies in winter onto the atmosphere during 1979 2013 a maximum covariance analysis shows that this feedback can be detected with monthly data when sic leads the covariability between atlantic sic and the euro atlantic atmospheric circulation in february is statistically significant but shows intra seasonal differences the december sic influence is dominated by anomalies east of greenland with maximum amplitude in the greenland sea gs while the january sic influence is dominated by anomalies west of greenland in the davis strait labrador sea dl region the lagged atmospheric anomalies are likewise different a reduction of sic over gs in december is followed in february by a negative nao like pattern near the surface and a hemispheric signature in the upper troposphere thus acting as a negative feedback on the other hand a reduction of sic over dl in january is followed by an atmospheric anomaly over the north atlantic that projects on the positive phase of the east atlantic pattern the dynamics associated with these atmospheric anomalies is described indicating that transient eddy activity is likely at work in settling the large scale patterns the role of concomitant north atlantic sea surface temperature anomalies is discussed

the arctic oscillation signature in the wintertime geopotential height and temperature fields the leading empirical orthogonal function of the wintertime sea level pressure field is more strongly coupled to surface air temperature fluctuations over the eurasian continent than the north atlantic oscillation nao it resembles the nao in many respects but its primary center of action covers more of the arctic giving it a more zonally symmetric appearance coupled to strong fluctuations at the 50 hpa level on the intraseasonal interannual and interdecadal time scales this arctic oscillation ao can be interpreted as the surface signature of modulations in the strength of the polar vortex aloft it is proposed that the zonally asymmetric surface air temperature and mid tropospheric circulation anomalies observed in association with the ao may be secondary baroclinic features induced by the land sea contrasts the same modal structure is mirrored in the pronounced trends in winter and springtime surface air temperature sea level pressure and 50 hpa height over the past 30 years parts of eurasia have warmed by as much as several k sea level pressure over parts of the arctic has fallen by 4 hpa and the core of the lower stratospheric polar vortex has cooled by several k these trends can be interpreted as the development of a systematic bias in one of the atmosphere s dominant naturally occurring modes of variability

genesis of the xinqiao cu s fe au deposit in the middle lower yangtze river valley metallogenic belt eastern china constraints from u pb hf rb sr s and pb isotopes abstract the xinqiao cu s fe au deposit in the tongling ore district one of important part of middle lower yangtze river valley metallogenic belt in eastern china is located along the northern margin of the yangtze craton it consists of two major types of mineralization a more economically significant stratiform orebody with pyrite bearing quartz veins in its footwall and the less economically important skarn type orebodies an integrated study of zircon u pb hf and trace elements analysis for the quartz diorite in xinqiao jitou stock rb sr isotope analysis for quartz fluid inclusions from the footwall stockwork mineralization as well as a systematic s pb isotope analysis of sulfides was carried out all based on detailed field investigations u pb zircon dating of jitou stock yielded an age of 139 6 1 5 ma mswd 0 80 close to the rb sr isotope isochron age 138 0 2 3 ma mswd 5 40 an initial 87 sr 86 sr value of 0 71138 0 00014 of quartz fluid inclusions from the footwall stockwork mineralization the e hf t values of zircon grains vary from 15 3 to 8 5 with t dm2 ranging from 2151 to 1729 ma suggesting that the magma for jitou stock was probably dominant in crustal derived magmas with minor mantle material inputs based on the previous studies on sr isotope compositions nb ta ratios and mg the fmq values 4 44 to 7 77 average 4 36 suggest that the jitou stock was derived from the highly oxidized magma and favorable for the cu mineralization the systematic s pb isotope data and the initial 87 sr 86 sr values demonstrate that the stratiform orebody and the footwall stockwork mineralization were likely to be genetically linked to magmatic hydrothermal events of yanshanian jurassic cretaceous age as confirmed by closeness of ages of mineralization and magmatism therefore it is interpreted that the xinqiao stratiform mineralization may have resulted from yanshanian magmatic hydrothermal fluids associated with the jitou stock as may be the case also for the skarn type mineralization hosted in the contact between the yanshanian jitou stock and the lower permian qixia formation limestone based on the basis of ore deposit geology generally the xinqiao cu s fe au mineralization may have been generated by the yanshanian tectono thermal event in eastern china

intraseasonal and interdecadal jet shifts in the northern hemisphere the role of warm pool tropical convection and sea ice abstractthis study uses cluster analysis to investigate the interdecadal poleward shift of the subtropical and eddy driven jets and its relationship to intraseasonal teleconnections for this purpose self organizing map som analysis is applied to the ecmwf interim re analysis era interim zonal mean zonal wind the resulting som patterns have time scales of 4 8 5 7 days and undergo notable interdecadal trends in their frequency of occurrence the sum of these trends closely resembles the observed interdecadal trend of the subtropical and eddy driven jets indicating that much of the interdecadal climate forcing is manifested through changes in the frequency of intraseasonal teleconnection patterns two classes of jet cluster patterns are identified the first class of som pattern is preceded by anomalies in convection over the warm pool followed by changes in the poleward wave activity flux the second class of patterns is preceded by sea ice and stratospheric polar vortex anomalies when the arctic se

seasonal evolutions of atmospheric response to decadal sst anomalies in the north pacific subarctic frontal zone observations and a coupled model simulation abstractpotential impacts of pronounced decadal scale variations in the north pacific sea surface temperature sst that tend to be confined to the subarctic frontal zone safz upon seasonally varying atmospheric states are investigated by using 48 yr observational data and a 120 yr simulation with an ocean atmosphere coupled general circulation model cgcm sst fields based on in situ observations and the ocean component of the cgcm have horizontal resolutions of 2 0 and 0 5 respectively which can reasonably resolve frontal sst gradient across the safz both the observations and cgcm simulation provide a consistent picture between sst anomalies in the safz yielded by its decadal scale meridional displacement and their association with atmospheric anomalies correlated with sst anomalies persistent in the safz from fall to winter a coherent decadal scale signal in the wintertime atmospheric circulation over the north pacific starts emerging in november and develops into an equivalent barotropic an

patterns of asian winter climate variability and links to arctic sea ice abstractthis paper describes two dominant patterns of asian winter climate variability the siberian high sh pattern and the asia arctic aa pattern the former depicts atmospheric variability closely associated with the intensity of the siberian high and the latter characterizes the teleconnection pattern of atmospheric variability between asia and the arctic which is distinct from the arctic oscillation ao the aa pattern plays more important roles in regulating winter precipitation and the 850 hpa meridional wind component over east asia than the sh pattern which controls surface air temperature variability over east asia in the arctic ocean and its marginal seas sea ice loss in both autumn and winter could bring the positive phase of the sh pattern or cause the negative phase of the aa pattern the latter corresponds to a weakened east asian winter monsoon eawm and enhanced winter precipitation in the midlatitudes of the asian continent and east asia for the sh pattern sea ice loss in the