dipole structure of interannual variations in summertime tropical cyclone activity over east asia the present study examines variations in summertime july september tropical cyclone tc activity over east asia during the period 1951 2003 to represent tc activity a total of 853 tc best tracks for the period were converted to tc passage frequencies tpfs within 5 5 latitude longitude grids tpfs are defined as the percentage values obtained by dividing the number of tc appearances in each grid box by the total number of tcs each year empirical orthogonal function analysis of the tpf showed three leading modes two tropical modes that represent the long term trend and the relationship with enso and one midlatitude mode that oscillates between south of korea and southeast of japan with an interannual time scale the latter proved to be the most remarkable climatic fluctuation of summertime tc activity in the midlatitudes and is referred to as the east asian dipole pattern eadp in this paper anomalous atmospheric flows directly connected to the eadp are an enhanced anticyclonic cyclonic circulation centering around japan when the tpf is high south of korea southeast of japan thereby showing an equivalent barotropic structure in the entire troposphere this regional circulation anomaly varies in conjunction with the zonally oriented quasi stationary rossby wave train in the upper troposphere this wave train is meridionally trapped in the vicinity of the summer mean jet stream therefore the mean jet stream alters its internal meandering structure according to the phase of the wave train

recent changes in the pacific subtropical cells inferred from an eddy resolving ocean circulation model abstract in this study the subtropical cells stc in the pacific ocean are analyzed using an eddy resolving ocean general circulation model driven by atmospheric forcing for the years 1992 2003 in particular the authors seek to identify decadal changes in the stcs in the model and to compare them with observations in order to understand the consequences of such changes for the equatorial ocean heat and mass budgets the simulation shows a trend toward increasing pycnocline volume transport at 9 n and 9 s across the basin from 1992 to 2003 this increase 4 9 1 0 sv sv 106 m3 s 1 is in qualitative agreement with observations and is attributed primarily to changes in the interior ocean transport which are partially compensated by opposing western boundary transports the subtropical meridional volume transport convergence anomalies in the model pycnocline are found to be consistent with anomalous volume transports in both the observed and modeled equatorial undercurrent as well as with the magni

a tropical ocean recharge mechanism for climate variability part ii a unified theory for decadal and enso modes abstract decadal to interdecadal timescale variability in the pacific region commonly referred to as the pacific decadal oscillation pdo is studied in this research using analytical and numerical models a coupled analytical model is formulated to analyze the physical mechanism of both the pdo and enso it has the equatorial plane dynamics of a reduced gravity model coupled with the wind stress of fixed spatial patterns the amplitude of the latter is proportional to the sea surface temperature sst anomaly in the eastern equatorial pacific the sst anomaly is governed by a simple thermal dynamic equation used for enso modeling it is found that when a warm sst is coupled with cyclonic wind stress patterns in the eastern subtropical pacific an oscillation with a timescale of around 10 15 yr could be generated in contrast when a warm sst is coupled with only a westerly wind stress in the central equatorial pacific an enso like oscillation could be generated with a timescale of around 3 5 yr thu

asymmetric impact of the north and south pacific on the equator in a coupled climate model 1 relative contributions of the north and south pacific to the equatorial ocean are estimated in a coupled climate model idealized experiments show that the south pacific contributes 30 50 more than the north pacific to the equatorial ocean temperature change because the warming in the north pacific can induce an additional cold rossby wave at around 20 n that tends to block the warm effect from the central north pacific while the south pacific influence can be easily convoyed to the equator through the interior pathway

tropical oceanic response to extratropical thermal forcing in a coupled climate model a comparison between the atlantic and pacific oceans abstractthe tropical oceanic response to the extratropical thermal forcing is quantitatively estimated in a coupled climate model this work focuses on comparison of the responses between the tropical atlantic and pacific under the same extratropical forcing the tropical sea surface temperature responses are comparable however the responses in the tropical subsurface in the two oceans are distinct the tropical subsurface response in the atlantic can be twice of that in the pacific the maximum subsurface temperature change in the tropical pacific occurs in the eastern lower thermocline while that in the tropical atlantic occurs in the west and well below the lower thermocline the different responses in the tropical atlantic and pacific are closely related to the different changes in the meridional overturning circulations the pacific shallow overturning circulation or the subtropical cell tends to slow down speed up in response to the extratropical warming cooling forcing the changes in the

pacific thermocline bridge revisited abstract the coupling on decadal time scales of the mid latitude and tropical pacific via an oceanic bridge in the thermocline is investigated using ocean general circulation model hindcasts and a coupled ocean atmosphere model results indicate that in the tropics decadal anomalies of isopycnal depth are forced by ekman pumping and are largely independent of the arrival of subducted anomalies in the thermocline that originate in the mid latitudes of either hemisphere in the coupled model temperature anomalies on isopycnals show little coupling from the tropics to the northern hemisphere but are lag correlated between southern hemisphere mid and low latitudes however anomaly magnitudes on the equator are small these results suggest that the oceanic bridge to the northern hemisphere explains only a small part of the observed decadal variance in the equatorial pacific coupling to the southern mid latitudes via temperature anomalies on isopycnals remains an intriguing possibility

interdecadal changes in summertime typhoon tracks abstract the present work examines interdecadal variations of typhoon tracks in the western north pacific wnp during the boreal summer june september for the period 1951 2001 typhoon tracks are expressed as percentage values of the total number of typhoon passages into a 5 5 latitude longitude grid box with respect to the total number of typhoons formed in the wnp the analysis period is divided into two interdecadal periods id1 1951 79 and id2 1980 2001 from id1 to id2 typhoon passage frequency decreased significantly in the east china sea and philippine sea but increased slightly in the south china sea the time series of typhoon passage frequency over the east china sea and south china sea further reveal a regime shift in the late 1970s while those over the philippine sea indicate a continuous downward trend of 9 decade 1 the interdecadal changes in typhoon tracks are associated with the westward expansion of the subtropical northwestern pacific high snph in the late 1970s the e

interdecadal change of the structure of the enso mode and its impact on the enso frequency in the late 1970s the enso cycle exhibited frequency change the oscillation period increased from 2 4 yr high frequency during 1962 75 to 4 6 yr low frequency during 1980 93 observations suggest that this frequency change was accompanied by a significant change in the structure of the coupled enso mode in comparison with the high frequency regime the structure of the coupled mode in the low frequency regime shows three distinctive features during the warm phase of enso the eastward shift of the westerly anomalies the meridional expansion of the westerly anomalies and the weaker intensity of the easterly anomalies in the eastern pacific to test the robustness of the relationship between the oscillation period and the structure of the coupled mode the authors designed empirical atmospheric models based on observations and coupled them with the ocean model of zebiak and cane numerical experiments demonstrate that the enso period is sensitive to changes in the wind anomaly pattern in a way much like the observed enso frequency structure relation the increase of the enso period after 1980 is mainly due to the eastward shift of the zonal wind stress with respect to the sst anomalies physical explanations of the dependence of enso frequency on the structure of the coupled mode are provided by diagnosing the relative contributions of the thermocline feedback and zonal advection feedback on enso evolution

interdecadal sea surface temperature variability in the equatorial pacific ocean part ii the role of equatorial off equatorial wind stresses in a hybrid coupled model abstract many modeling studies have been carried out to investigate the role of oceanic rossby waves linking the off equatorial and equatorial pacific ocean although the equatorial ocean response to off equatorial wind stress forcing alone tends to be relatively small it is clear that off equatorial oceanic rossby waves affect equatorial pacific ocean variability on interannual through to interdecadal time scales in the present study a hybrid coupled model hcm of the equatorial pacific between 12 5 s and 12 5 n was developed and is used to estimate the magnitude of equatorial region variability arising from off equatorial poleward of 12 5 latitude wind stress forcing the hcm utilizes a reduced gravity ocean shallow water model and a statistical atmosphere derived from monthly output from a 100 yr australian bureau of meteorology research centre now the centre for australian weather and climate research coupled general circulation model integration the equatorial region wind stress forcing i

decadal variability of the pacific subtropical cells and its relevance to the sea surface height in the western tropical pacific during recent decades decadal variability of the pacific subtropical cells stcs and associated sea surface height ssh in the western tropical pacific during recent decades are examined by using an historical ogcm simulation the model represents decadal variations of the stcs concurrent with tropical pacific thermal anomalies the eastern tropical pacific is warmer when the stcs are weaker and cooler when they are stronger the spatial patterns of the ssh in the western tropical pacific show different features depending on events associated with decadal variability during the warm phase 1977 1987 the ssh anomalies exhibit deviations from a meridionally symmetric distribution with weakly positive strongly negative anomalies in the western tropical north south pacific analysis of the heat budget in the upper tropical pacific indicates that the termination of the warm phase around 1985 results from a poleward heat transport anomaly that is induced by a horizontal gyre associated with the ssh anomalies during the cold phase 1996 2006 in contrast the ssh anomalies are nearly meridionally symmetric with positive anomalies in both hemispheres enhanced easterly wind anomalies contribute to the development of the cold phase after the late 1990s

birth of a volcanic passive margin in cambrian time rift paleogeography of the ossa morena zone sw spain abstract mapping at 1 10000 scale of both north n and south s flanks of the variscan monesterio antiform in the ossa morena zone southern spain in association with detailed petrographic and major element analyses of magmatic rocks has revealed the building of a passive but volcanically active oceanic margin in cambrian time this margin was located in northern gondwana and represents the beginning of an extensional tectonic regime that concluded with the opening of the rheic ocean at time of eruption middle cambrian the n flank was located on the northern coastline of a marine basin in the process of passive rifting the vents mainly located in its western part were subaerial continental and or shallow marine on the s flank eruptions and deposits were shallow marine occurring as lava flows and pillows interstratified within shallow marine sediments on both flanks intrusives were emplaced after the extrusives lateral thickness variations of the sedimentary deposits testify to the building during four distinct periods of a rifted passive margin with a shifting locus of volcanic activity over time the composition of magmas was bimodal the mafic magmas are silica saturated alkaline to sub alkaline and somewhat ti rich perhaps originating from partial melting of a subcontinental mantle that was less metasomatized with time the youngest magmatism with an affinity close to that of morb likely had an asthenospheric source the alkaline felsic products are diverse and may have originated from a very heterogeneous continental crust in each set partial melting relationships prevail suggesting that the melts rose along open fractures as soon as they formed in the context of lithospheric thinning it is possible that mantle and crustal melting was triggered by decoupling between rheologically different materials

the role of mean state on changes in el nino s flavor recently many studies have argued for the existence of two types of el nino phenomena based on different spatial distributions the conventional el nino or eastern pacific ep el nino and the central pacific cp el nino here we investigate the decadal modulation of cp el nino occurrences using a long term coupled general circulation model simulation focusing in particular on the role of climate state in the regime change between more and fewer cp el nino events the higher occurrence regime of the cp el nino coincides with the lower occurrence regime of ep el nino and vice versa the climate states associated with these two opposite regimes resemble the leading principal component analysis pca modes of tropical pacific decadal variability indicating that decadal change in climate state may lead to regime change in terms of two different types of el nino in particular the higher occurrence regime of cp el nino is associated with a strong zonal gradient of mean surface temperature in the equatorial pacific along with a strong equatorial trade wind over the area east of the dateline in addition the oceanic variables the mixed layer depth and the thermocline depth show values indicating increased depth over the western to central pacific the aforementioned climate states obviously intensify zonal advective feedback which promotes increased generation of the cp el nino frequent cp el nino occurrences are not fully described by oceanic subsurface dynamics and dynamical or thermodynamical processes in the ocean mixed layer and air sea interaction are important contributors to the generation of the cp el nino furthermore the atmospheric response with respect to the ssta tends to move toward the west which leads to a weak air sea coupling over the eastern pacific these features could be regarded as evidence that the climate state can provide a selection mechanism of the el nino type

observed interannual variability of zonal currents in the equatorial indian ocean thermocline and their relation to indian ocean dipole interannual variability of zonal currents in the eastern equatorial indian ocean thermocline is significantly correlated with sea surface temperature sst in the eastern pole of the indian ocean dipole iod this relationship is more significant than for zonal currents and the dipole mode index the latter of which measures zonal sst anomaly gradient the variability of zonal currents in the thermocline is consistent with the variations of eastward pressure gradient force in the thermocline and the equatorward geostrophic thermocline flows associated with the shallow meridional overturning circulations in the eastern tropical indian ocean our analysis suggests a positive feedback between zonal currents in the thermocline and sst in the eastern pole of iod the combination of equatorial wind and off equatorial wind stress curls associated with sst anomalies in the eastern pole of the iod drives interannual variability in equatorial zonal thermocline flows and its covariability with the shallow meridional overturning cells

origin of upper ocean warming and el nino change on decadal scales in the tropical pacific ocean the cause of decadal scale variability in the tropical pacific ocean such as that marked by the 1976 77 shift in the el nino southern oscillation1 2 3 4 5 6 7 is poorly understood unravelling the mechanism of the recent decade long warming in the tropical upper ocean is a particularly important challenge given the link to el nino variability but establishing the hypothesized interannual decadal oceanic connections between middle latitudes and tropics has proved elusive8 here we present observational evidence that pacific upper ocean warming and decadal changes in the el nino southern oscillation after 1976 may originate from decadal mid latitude variability in the middle 1970s the north pacific ocean is observed to have undergone a clear phase transition a see saw subsurface temperature anomaly pattern that rotates clockwise around the subtropical gyre at middle latitudes a subsurface warm anomaly formed in the early 1970s from subducted surface waters and penetrated through the subtropics and into the tropics thus perturbing the tropical thermocline and driving the formation of a warm surface water anomaly that may have influenced el nino in the 1980s the identification of this teleconnection of extratropical thermal anomalies to the tropics through a subsurface ocean bridge may enable improved prediction of decadal scale climate variability

interdecadal thermocline variability in the north pacific for 1958 97 a gcm simulation an ocean general circulation model is forced with the ncep reanalysis wind stress for 1958 97 to understand mechanisms of ocean subsurface variability with relatively high horizontal 1 83 18 and vertical 41 levels resolutions the model produces mode waters on a range of density surfaces in the western central and eastern north pacific in qualitative agreement with observations these mode waters appear as a thermostad or a region of weak stratification in the upper thermocline as they flow southward from their formation regions in the kuroshio and its extension in the model subsurface temperature variability in the central subtropical gyre reaches a maximum within the thermostad in contrast to what might be expected from the linear baroclinic rossby wave theory this variance maximum is associated with the longitudinal shift in the path of mode waters in particular deepened mixed layer and accelerated eastward currents in the kuroshio extension by wind changes in the mid 1970s act cooperatively to move the central mode waters toward the east causing large subsurface temperature anomalies besides the local maximum in the central north pacific subtropical gyre two additional maxima of the subsurface anomaly are identified in the northwestern and southern parts of the gyre respectively among these subsurface anomaly centers the one in the northwestern north pacific has a strong effect on the model sea surface temperature suggesting that the kuroshio and its extension are a key region to decadal interdecadal ocean atmosphere interaction finally possible effects of atmospheric thermal forcing are discussed

seasonal variability of the south equatorial current bifurcation in the atlantic ocean a numerical study abstract in this study a reduced gravity primitive equation ogcm is used to investigate the seasonal variability of the bifurcation of the south equatorial current sec into the brazil current bc to the south and the north brazil undercurrent current nbuc nbc system to the north annual mean meridional velocity averaged within a 2 longitude band off the south american coast shows that the sec bifurcation occurs at about 10 14 s near the surface shifting poleward with increasing depth reaching 27 s at 1000 m in both observations and model the bifurcation latitude reaches its southernmost position in july 17 s in the top 200 m and its northernmost position in november 13 s in the top 200 m the model results show that most of the seasonal variability of the bifurcation latitude in the upper thermocline is associated with changes in the local wind stress curl due to the annual north south excursion of the marine itcz complex as the sec bifurcation latitude moves south north the nbuc tra

a new paleomagnetic pole for the neoproterozoic uinta mountain supergroup central rocky mountain states usa abstract hematite cemented strata of the neoproterozoic age 800 750 ma uinta mountain group umg provide a new well defined mid neoproterozoic paleomagnetic pole for laurentia thermal demagnetization results and rock magnetic experiments reveal the presence of two discrete magnetizations in umg rocks both magnetizations are carried by hematite the dominant characteristic remanent magnetization chrm is an east directed or antipode shallow positive to negative inclination magnetization that is typically unblocked over a narrow range of high laboratory temperatures between 660 and 680 c the second magnetization exclusively of normal polarity is north to northeast directed and has a moderate to steep positive inclination and probably represents a recent or modern day viscous remanent magnetization the response of umg samples to thermal and chemical demagnetization comparison with previously obtained data from umg rocks in the area results from rock magnetic experiments and the inferred low latitude of laurentia during umg deposition in the neoproterozoic are all consistent with the interpretation that the west or east directed shallow magnetization is a near primary remanence the presence of dual polarities of the chrm with the west directed remanence inferred to be of normal polarity and the east directed of reverse polarity suggests that magnetization acquisition in the umg rocks took place over a sufficient amount of time to average secular variation of the geomagnetic field the mean paleomagnetic pole derived from the inferred primary magnetizations from umg strata 0 8 n 161 3 e 95 4 6 n 9 sampling localities consisting of 79 sites is fully consistent with recently reported results from rocks of mid neoproterozoic age for southwest laurentia which define a tight counterclockwise loop located in the south pacific in the apparent polar wander path for laurentia during the neoproterozoic

influence of extratropical thermal and wind forcings on equatorial thermocline in an ocean gcm the equatorial thermocline variability in the pacific in response to the extratropical thermal and wind forcings is investigated with an ocean general circulation model modular ocean model version 3 mom3 sensitivity experiments show that the extratropical wind forcing and thermal forcing contribute equally to the equatorial variability the wind induced response is attributed to the off equatorial wind within 30 8 of the equator the thermal induced response can be traced to higher latitudes the thermal forcing affects the equator mainly through the equatorward transport of the perturbation temperature by mean subduction flow the wind forcing affects the equator by changing the strength of meridional overturning circulations it is also found that the southern hemisphere contributes more to the equatorial variability than the northern hemisphere under both external forcings

generation mechanism of quasidecadal variability of upper ocean heat content in the equatorial pacific ocean 1 we investigate the relationship between oceanic and atmospheric anomaly fields in the tropical pacific on the quasidecadal qd 10 to 18 years scale is explored it is suggested that the anomalous wind stress curl in the tropical south pacific can generate the equatorial upper ocean heat content ohc anomalies on the qd scale via the sverdrup transport resembling that of the recharge discharge oscillator model for the dynamics of el nino southern oscillation enso the results also show that the wind stress curl anomalies in the tropical south pacific are accompanied by enso like qd scale anomaly patterns of the sea level pressure and sea surface temperature furthermore the results indicate that the equatorial qd scale ohc anomalies can also be generated by the enso like propagations of the ohc anomalies in the tropical north and south pacific this study presents a systematic linkage between the enso like qd scale ohc propagation in the tropical north and south pacific the sverdrup transport variation in the tropical south pacific and the enso like qd scale sst and slp anomalies in the tropical pacific

neoproterozoic and cambrian arc magmatism along the eastern margin of the victoria lake supergroup a remnant of ganderian basement in central newfoundland abstract the eastern margin of the composite and structurally complex victoria lake supergroup has previously been mapped where the silurian rogerson lake conglomeratic rocks unconformably overlie cambrian tally pond volcanic rocks however the recognition that the form of this contact changes between an unconformity and a brittle ductile fault in conjunction with the neoproterozoic age of the crippleback intrusive suite dictate that the above interpretation of the nature of this margin requires revision these discrepancies are resolved by the recognition of a neoproterozoic largely bimodal volcanic sequence sandy brook group which is unconformably overlain by rogerson lake rocks to the east with these combined units in fault contact with the tally pond group to the west the sandy brook group and crippleback intrusive suite form a terrane of ca 563 ma rocks with continental arc like geochemical signatures the distinctly negative nd 563 values for the felsic rocks mean 3 of this terrane imply derivation from a crystalline basement older than the largely pan african crust that underlies contemporaneous volcanic rocks in west avalonia but similar to that inferred for the gander zone thus this terrane is likely to be the leading edge of the peri gondwanan microcontinent ganderia the ca 511 ma tally pond group arc magmatism represent some of the oldest products of iapetean subduction in newfoundland although the tally pond group are only observed to be in fault contact with the ca 50 million year older sandy brook group the high proportion of felsic volcanic rocks sandy brook crippleback age inherited zircons and pb isotopic data all support the inference that the tally pond group was formed on sandy brook crippleback continental crust

paleomagnetism of the 550 ma skinner cove volcanics of western newfoundland and the opening of the iapetus ocean the skinner cove formation of western newfoundland is an alkali volcanic suite transported in the ordovician onto laurentia s iapetus ocean margin it has previously yielded a u pb zircon age of 550 5 3 2 ma has no penetrative deformation and has only been affected by zeolite facies metamorphism at 10 sites flows and dykes of the skinner cove formation exhibit a stable characteristic a remanence carried by magnetite this a remanence is shown to be primary by an intraformational conglomerate test using 20 trachybasalt clasts whereas 11 alkali basalt clasts were overprinted probably because they originally contained titanomagnetite from which rutile exsolved soon after burial by overlying flows after tilt correction the mean a remanence direction is southeast and down d 144 i 32 95 11 k 21 n 10 sites the paleolatitude calculated from the ten a site virtual geomagnetic poles is 19 s 9 which likely represents the paleolatitude of laurentia s iapetan margin at 550 ma evidence that the skinner cove formation originated at this margin includes its structural position within the humber arm allochthon its within plate trace element geochemistry and its similarity in age to other alkali magmatism that more certainly represents laurentia s iapetan margin comparison with other laurentian paleomagnetic data implies that laurentia drifted very rapidly northward from the south polar region to the equator between 570 and 550 ma we suggest that the start of this rapid northward drift at 570 ma marked the onset of iapetus sea floor spreading between laurentia and west gondwana further well constrained paleomagnetic data of 570 to 550 ma age are needed from laurentia to test its high rate of northward drift and from west gondwanan cratons to test that they remained relatively stationary

propagation of north pacific interdecadal subsurface temperature anomalies in an ocean gcm propagation of subsurface north pacic inter decadal variations is investigated with an ocean general cir culation model forced by observed sea surface temperature anomalies subsurface temperature anomalies subducted in the central subtropical north pacic take a more westward pathway than a passive temperature tracer and reach the western boundary to the north of the bifurcation latitude this prevents them from extending into the equator on the boundary between the subtropical and the subarctic gyres on the other hand the upper 500 m heat content anomaly is found to propagate eastward as high vertical modes of rossby waves advectedbythemean eastward cur rent this notion is supported by a sign reversal in temper ature anomaly underneath

paleozoic terranes of eastern australia and the drift history of gondwana abstract critical assessment of paleozoic paleomagnetic results from australia shows that paleopoles from locations on the main craton and in the various terranes of the tasman fold belt of eastern australia follow the same path since 400 ma for the lachlan and thomson superterranes but not until 250 ma or younger for the new england superterrane most of the paleopoles from the tasman fold belt are derived from the lolworth ravenswood terrane of the thomson superterrane and the molong monaro terrane of the lachlan superterrane consideration of the paleomagnetic data and geological constraints suggests that these terranes were amalgamated with cratonic australia by the late early devonian the lolworth ravenswood terrane is interpreted to have undergone a 90 clockwise rotation between 425 and 380 ma although the tamworth terrane of the western new england superterrane is thought to have amalgamated with the lachlan superterrane by the late carboniferous geological syntheses suggest that movements between these regions may have persisted until the middle triassic this view is supported by the available paleomagnetic data with these constraints an apparent polar wander path for gondwana during the paleozoic has been constructed after review of the gondwana paleomagnetic data the drift history of gondwana with respect to laurentia and baltica during the paleozoic is shown in a series of paleogeographic maps

decadal variations in the subtropical cells and equatorial pacific sst 1 a mechanism for generating decadal sea surface temperature sst variability in the equatorial pacific is investigated using an ocean general circulation model forced by observed wind stress equatorial sst variability is governed by different ocean dynamics on interannual and decadal time scales at interannual time scales equatorial sst anomalies are mainly driven by equatorial winds at decadal time scales on the other hand they are forced both by equatorial winds and by off equatorial winds in the tropics while the contribution from midlatitude winds poleward of 25 is negligible trade wind variations in the off equatorial tropics force equatorial sst variability by spinning up and down the subtropical cells that transport cold water into the equatorial upwelling zone equatorial sst anomalies induced by this mechanism lag behind the response to local equatorial winds by about two years

the cadomian unconformity in the saxo thuringian zone germany palaeogeographic affinities of ediacaran terminal neoproterozoic and cambrian strata abstract the most complete ediacaran terminal neoproterozoic to early cambrian record in the saxo thuringian zone is provided by the cadomian deformed ediacaran rothstein formation and the unconformably overlying early cambrian zwethau formation in the torgau doberlug syncline tds conglomerates and greywackes of the marine rothstein formation are of continental magmatic arc provenance and record detrital zircon shrimp ages that indicate a late cryogenian to early ediacaran 700 580 ma age for the arc source and its emplacement into palaeoproterozoic 2000 ma crust tuffaceous intercalations record extrabasinal eruptions of evolved calc alkaline lavas that point to ongoing cadomian continental arc magmatism shrimp zircon ages from a tuffaceous layer date this volcanic activity and the formation s deposition as late ediacaran 566 10 ma close correlation in provenance and age to other ediacaran units of the saxo thuringian zone points to a common palaeogeographic setting in the avalonian cadomian belt detrital and inherited zircon ages and nd isotopic ratios from these ediacaran siliciclastic rocks suggest a position on the active margin of gondwana near the west african craton the early cambrian zwethau formation records the erosion of the underlying ediacaran rocks followed by the successive evolution of i a carbonate dominated subtidal ramp with calcimicrobial archaeocyathan buildups ii a shallow subtidal to intertidal mixed ramp with peritidal sediments and oolite shoal complexes and iii a more siliciclastic depositional environment calcimicrobial archaeocyathan buildups oolite shoals and sulfate nodules in intertidal sediments indicate warm arid to semi arid climatic conditions and a palaeogeographic setting in equatorial to sub equatorial latitudes archaeocyaths the trilobite taxon dolerolichia and the sedimentary facies assemblages compare closely to those of the mediterranean early cambrian constraining the palaeogeographic setting to the european sub equatorial western gondwana shelf realm archaeocyaths record a mid early cambrian middle issendalenian ovetian age making these the oldest cambrian sediments in both the saxo thuringian zone and the bohemian massif the middle cambrian lithological and palaeontological records of the tds closely resemble those of the frankenwald area of the saxo thuringian zone as well as those of other fragments of the western gondwana shelf in spain morocco and bohemia archaeocyaths early cambrian trilobites and correlations with morocco suggest cambrian deposition commenced at ca 520 ma such that the cadomian unconformity represents a time gap of about 35 55 ma latest ediacaran to early lower cambrian this gap which is related to the cadomian orogeny and so common to all areas of the cadomian belt obscures some of palaeobiological palaeogeographic and climatic change that marks the precambrian cambrian transition

a simple model of the mass exchange between the subtropical and tropical ocean abstract a simple ventilated thermocline model is used to study the subtropical tropical mass exchange it is found that the water subducted in the western subtropical gyre recirculating window tends to recirculate within the subtropical gyre while the water subducted in the eastern part exchange window tends to penetrate equatorward the exchange window expands with an increased easterly wind or basin width on the southern boundary of the subtropical gyre but shrinks with an increased wind curl within the subtropical gyre furthermore the total exchange transport increases with the easterly wind or the width of the basin on the southern boundary of the subtropical gyre but it is independent of subtropical wind the ventilation mechanism is important in supporting the exchange transport for wind with realistic strength at the southern boundary the reduction of the exchange transport is about 15 30 of the ekman transport finally relative to the exchange transport in the interior of the ocean

a north pacific decadal variability in subduction rate 1 analysis of results from a global eddy resolving general circulation model has revealed the existence of a north pacific decadal variability in subduction rate this decadal variability corresponds well with the pacific decadal oscillation pdo the zero lag correlation between the two time series reaches 0 61 for the period of integration 1950 2003 and increases to as high as 0 80 after the climate shift in the mid 1970s much of the north pacific decadal variability in subduction rate is due to changes in winter mixed layer depth which in turn are closely related to changes in surface wind and heat flux

interdecadal sea surface temperature sea level pressure coupled variability in the south pacific ocean 1 the main coupled sea surface temperature sst sea level pressure slp variability at interdecadal timescale in the south pacific is studied by means of correlation and combined complex empirical orthogonal function cceof analyses the sst slp coupled variability presents a bidecadal cycle from mid 1950s to 1970s and a decadal cycle from 1980s to early 1990s reproducing the enso like interdecadal oscillation particularly the first sst slp cceof mode describes the bidecadal cycle characterized by westward progression of sst and slp anomalies along the tropical pacific while the second sst slp cceof mode shows the decadal cycle with eastward development during both bidecadal and decadal cycles the sst fluctuations in the eastern equatorial pacific and along the western coast of south america are primarily forced by equatorial zonal wind variability specially during the bidecadal cycle the alongshore sst variability south of 30 s is maintained and reinforced by meridional coastal wind fluctuations associated with a stationary slp pattern off southern chile this stationary slp pattern appears connected to sst fluctuations in the central tropical pacific

upper ocean thermal variations in the north pacific during 1970 1991 abstract a newly available extensive compilation of upper ocean temperature profiles was used to study the vertical structure of thermal anomalies between the surface and 400 m depth in the north pacific during 1970 1991 a prominent decade long perturbation in climate occurred during this time period surface waters cooled by 1 c in the central and western north pacific and warmed by about the same amount along the west coast of north america from late 1976 to 1988 comparison with data from coads suggests that the relatively sparse sampling of the subsurface data is adequate for describing the climate anomaly the vertical structure of seasonal thermal anomalies in the central north pacific shows a series of cold pulses beginning in the fall of 1976 and continuing until late 1988 that appear to originate at the surface and descend with time into the main thermocline to at least 400 m depth individual cold events descend rapidly 100 m yr 1 superimposed upon a slower cooling 15 m yr 1 the inter

multi year predictability in a coupled general circulation model multi year to decadal variability in a 100 year integration of a bmrc coupled atmosphere ocean general circulation model cgcm is examined the fractional contribution made by the decadal component generally increases with depth and latitude away from surface waters in the equatorial indo pacific ocean the relative importance of decadal variability is enhanced in off equatorial wings in the subtropical eastern pacific the model and observations exhibit enso like decadal patterns analytic results are derived which show that the patterns can in theory occur in the absence of any predictability beyond enso time scales in practice however modification to this stochastic view is needed to account for robust differences between enso like decadal patterns and their interannual counterparts an analysis of variability in the cgcm a wind forced shallow water model and a simple mixed layer model together with existing and new theoretical results are used to improve upon this stochastic paradigm and to provide a new theory for the origin of decadal enso like patterns like the interdecadal pacific oscillation and pacific decadal oscillation in this theory enso driven wind stress variability forces internal equatorially trapped kelvin waves that propagate towards the eastern boundary kelvin waves can excite reflected internal westward propagating equatorially trapped rossby waves rws and coastally trapped waves ctws ctws have no impact on the off equatorial sub surface ocean outside the coastal wave guide whereas the rws do if the frequency of the incident wave is too high then only ctws are excited at lower frequencies both ctws and rws can be excited the lower the frequency the greater the fraction of energy transmitted to rws this lowers the characteristic frequency reddens the spectrum of variability off the equator relative to its equatorial counterpart at low frequencies dissipation acts as an additional low pass filter that becomes more effective as latitude increases at the same time enso driven off equatorial surface heating anomalies drive mixed layer temperature responses in both hemispheres both the eastern boundary interactions and the accumulation of surface heat fluxes by the surface mixed layer act to low pass filter the enso forcing the resulting off equatorial variability is therefore more coherent with low pass filtered decadal enso indices e g nino3 sea surface temperature sst than with unfiltered enso indices consequently large correlations between variability and nino3 extend further poleward on decadal time scales than they do on interannual time scales this explains why decadal enso like patterns have a broader meridional structure than their interannual counterparts this difference in appearance can occur even if enso indices do not have any predictability beyond interannual time scales the wings around 15 20 s and sub surface variability at many other locations are predictable on interannual and multi year time scales this includes westward propagating internal rws within about 25 of the equator the slowest of these take up to 4 years to reach the western boundary this sub surface predictability has significant oceanographic interest however it is linked to only low levels of sst variability consequently extrapolation of delayed action oscillator theory to decadal time scales might not be justified

decadal variability of shallow cells and equatorial sea surface temperature in a numerical model of the atlantic 1 the relative role of extraequatorial mechanisms modulating decadal sea surface temperature anomalies ssta in the equatorial atlantic is investigated using a suite of sensitivity experiments based on an ocean general circulation model the model is forced by observed wind stress and or computed heat flux from an associated advective atmospheric mixed layer model in addition the surface forcing is optionally applied on the equator or in off equatorial regions the long term response of equatorial sst is dominated by local forcing however a weak but significant part of the response that is not in phase with the locally induced sst variability is caused by remote forcing subtropical cells stcs provide the oceanic bridging of the climate signals the dynamical forcing leads to a spin up and spin down of the shallow cells which in the case of local forcing included coincides with cold and warm ssta the local heat flux forcing reveals an overall damping tendency on the dynamical sst response when excluding the local forcing the isolation of the effect of the northern remote forcing from the one in the south appears to be essential in understanding the respective mechanisms at work in the northern hemisphere the spin up and spin down of the stc is highly correlated with the lagging ssta and the effect of off equatorial heat flux forcing on ssta is negligible in the southern hemisphere both momentum and heat fluxes in the subtropics lead to a significant sst response on the equator

oxygen carbon and strontium isotope records of ediacaran carbonates in central iberia spain carbon oxygen and strontium isotope ratios were determined in the uppermost neoproterozoic carbonate rocks at pastores sw salamanca central iberia the low 18o v smow values 15 19 indicate an alteration of the whole stratigraphic series however the alteration process does not seem to have affected most of the 13c and 87sr 86sr data these data reveal that only one particular level of the carbonate section shows simultaneous relative increases in mn sr and 87sr 86sr ratios decreases in the 18o and 13c values and covariations between 87sr 86sr and the other parameters despite this most of the carbonate section lacks these covariations and its 13c 4 6 to 0 5 and 87sr 86sr 0 70845 0 70853 ratios probably reflect the seawater isotopic features at the time of sedimentation the data for c and sr isotopes at the pastores carbonate section and the presence of cloudina in platform carbonates together with an overlying major sub cambrian unconformity following a relative sea level fall are features comparable to those frequently shown by proterozoic cambrian boundary series across the world thus our results consistently support the notion that the carbonates at pastores are equivalent to other carbonates deposited close to the ediacaran cambrian boundary

connections between the pacific ocean tropics and midlatitudes on decadal timescales abstract connections between the tropical and midlatitude pacific on decadal timescales are examined using a 137 yr run of a fully coupled ocean atmosphere general circulation model it is shown that the model does a credible job of simulating both enso scale and decadal scale variability and that there are statistically significant correlations between the midlatitudes and tropics on decadal timescales three physical mechanisms linking the regions are examined 1 oceanic advection along isopycnal surfaces from the midlatitude subduction regions to the tropics 2 coastally trapped or kelvin wave propagation between the tropics and midlatitudes and 3 near simultaneous communication between the regions affected by changes in the atmosphere it is found that communication via the atmosphere explains the strongest correlations found in the model further evidence is presented that is consistent with the idea that midlatitude sea surface temperature anomalies drive changes in the trade wind system that a

enso like interdecadal variability 1900 93 a number of recent studies have reported an enso like eof mode in the global sea surface temperature sst field whose time variability is marked by an abrupt change toward a warmer tropical eastern pacific and a colder extratropical central north pacific in 1976 77 the present study compares this pattern with the structure of the interannual variability associated with the enso cycle and documents its time history back to 1900 the analysis is primarily based on the leading eofs of the sst anomaly and anomaly deviation fields in various domains and the associated expansion coefficient or principal component time series which are used to construct global regression maps of sst sea level pressure slp and a number of related variables the use of anomaly deviations i e departures of local sst anomalies from the concurrent global mean sst anomaly reduces the influence of global mean sst trends upon the structure of the eofs and their expansion coefficient time series an important auxiliary time series used in this study is a southern oscillation index based on marine surface observations by means of several different analysis techniques the time variability of the leading eof of the global sst field is separated into two components one identified with the enso cycle related variability on the interannual timescale and the other a linearly independent residual comprising all the interdecadal variability in the record the two components exhibit rather similar spatial signatures in the global sst slp and wind stress fields the sst signature in the residual variability is less equatorially confined in the eastern pacific and it is relatively more prominent over the extratropical north pacific the corresponding slp signature is also stronger over the extratropical north pacific and its counterpart in the cold season 500 mb height field more closely resembles the pna pattern the amplitude time series of the enso like pattern in the residual variability reflects the above mentioned shift in 1976 77 as well as a number of other prominent features including a shift of opposite polarity during the 1940s

decadal scale variability of upper ocean heat content in the tropical pacific 1 decadal scale variability of upper ocean heat content ohc in the tropical pacific is investigated and is compared with that of enso scale the decadal scale ohc anomaly with a period of about 13 years shows anticlockwise propagations in the tropical north pacific like as that of enso scale it is also shown that the entire equatorial ohc anomaly leads nino 3 index anomaly by about a quarter about 3 years of the period of the decadal variability in the tropical pacific this time lag of a quarter of the period is consistent with the idea of the recharge oscillator model for enso dynamics further it is shown that the magnitude of leading ohc anomalies in the entire equatorial pacific is linearly related to the subsequent magnitudes of nino 3 and nino 3 4 indices this relationship is also similar with that of enso scale but there are several different points between them particularly in contrast with the enso scale the amplitude is larger in central equatorial pacific nino 3 4 region than in the eastern region nino 3 region

seasonality of decadal sea surface temperature anomalies in the northwestern pacific abstract the seasonality of the decadal sea surface temperature sst anomalies and the related physical processes in the northwestern pacific were investigated using a three dimensional bulk mixed layer model in the kuroshio oyashio extension koe region the strongest decadal sst anomaly was observed during december february while that of the central north pacific occurred during february april from an examination of the seasonal heat budget of the ocean mixed layer it was revealed that the seasonal scale enhancement of the decadal sst anomaly in the koe region was controlled by horizontal ekman temperature transport in early winter and by vertical entrainment in autumn the temperature transport by the geostrophic current made only a slight contribution to the seasonal variation of the decadal sst anomaly despite controlling the upper ocean thermal conditions on decadal time scales through the slow rossby wave adjustment to the wind stress curl when averaging over the entire koe region the cont

tearing up rodinia the neoproterozoic palaeogeography of south american cratonic fragments rodinia was initially defined as a long lived supercontinent that assembled all the continental fragments around laurentia and remained stable from 1000 up to 750 ma nonetheless recent work has cast doubt on the rodinia palaeogeography and even on the timing of its assembly and break up the geochronological and palaeomagnetic databases accumulated for south america and africa in the last decade show that most of these continental fragments were not part of rodinia a wide brasiliano ocean separated most of the south american and african cratons from the laurentia amazonia rio apa west africa margin this ocean was closed between 940 and 630 ma along the pampean paraguay araguaia pharusian mobile belts moreover accretion along the south american and african platforms was a diachronous and long lived process that involved several intra oceanic and continental magmatic arcs and microcontinents this evolution started at around 1000 ma and ended at around 520 ma with the final assembly of gondwana

mechanisms of decadal variability in the shallow subtropical tropical circulation of the atlantic ocean a model study a suite of basin scale models of the thermohaline and wind driven circulation in the atlantic ocean is used to study the mechanisms of decadal variability in the shallow subtropical tropical cells stcs the emphasis is on the spatial patterns of the transport anomalies in the tropical thermocline particularly their manifestation in the equatorial current system and on the relative role of changes in the deep meridional overturning cell moc associated with variations in the formation of labrador sea water lsw in the subpolar north atlantic using wind stress and heat flux variations based on ncep ncar reanalysis products the variability of the zonally integrated stc transports is similar to that obtained in a recent regional model study corroborating the role of both the southern and northern stc in supporting wind driven transport anomalies of o 2 sv near the equator sensitivity experiments indicate that changes in subarctic moc transports associated with the strong variability in lsw formation during the last decades contributed a signal of o 0 3 sv to the upper layer equatorial transports whereas the local wind driven variability clearly dominates on interannual decadal timescales and is confined to depths down to 150 m the weak moc related signal is primarily reflected in an interdecadal modulation of the stc transports while a strong part in the stc s transport anomalies is associated with the western boundary current nbc there is an important contribution also by weaker interior ocean flow anomalies which tend to counteract the variability of the nbc

fault controlled emplacement of arc related magmas along the neoproterozoic northern gondwanan margin an example from the antigonish highlands nova scotia abstract in the antigonish highlands nova scotia neoproterozoic ca 620 605 ma magmatism is a local representative of regional arc related tectonothermal activity that typifies avalonia and related terranes located along the northern gondwanan margin three distinct types of coeval magma are represented by volcanic rocks of the georgeville group and by syn to post tectonic plutons e g greendale complex i calc alkalic subduction related basaltic andesites and andesites ii crustally derived rhyodacites and rhyolites and iii fe ti rich continental tholeiites derived from the melting of subcontinental lithosphere these magmas were probably generated in an extensional arc regime with deep seated faults providing conduits for rising magmas the georgeville group was polydeformed by thrusts isoclinal folds and upright folds associated with movement along ne trending faults very soon after it was deposited a 85 km long 1 2 km wide magnetic anomaly transects georgeville group strata and connects outcrops of fe ti rich continental tholeiites and ultramafic cumulate rocks of the greendale complex the n s orientation of this anomaly is compatible with coeval sinistral shear along ne trending faults and its magnetic signature suggests that it is a shallow regional studies indicate that the kinematic reversal and the cessation of magmatism is a local expression of the neoproterozoic early paleozoic termination of subduction and generation of a transform fault along the northern gondwanan margin possibly by ridge trench collision analogous to the cenozoic evolution of the san andreas fault system in the western united states

el nino modoki and its possible teleconnection 1 using observed data sets mainly for the period 1979 2005 we find that anomalous warming events different from conventional el nino events occur in the central equatorial pacific this unique warming in the central equatorial pacific associated with a horseshoe pattern is flanked by a colder sea surface temperature anomaly ssta on both sides along the equator empirical orthogonal function eof analysis of monthly tropical pacific ssta shows that these events are represented by the second mode that explains 12 of the variance since a majority of such events are not part of el nino evolution the phenomenon is named as el nino modoki pseudo el nino modoki is a classical japanese word which means a similar but different thing the el nino modoki involves ocean atmosphere coupled processes which include a unique tripolar sea level pressure pattern during the evolution analogous to the southern oscillation in the case of el nino hence the total entity is named as el nino southern oscillation enso modoki the enso modoki events significantly influence the temperature and precipitation over many parts of the globe depending on the season the impacts over regions such as the far east including japan new zealand western coast of united states etc are opposite to those of the conventional enso the difference maps between the two periods of 1979 2004 and 1958 1978 for various oceanic atmospheric variables suggest that the recent weakening of equatorial easterlies related to weakened zonal sea surface temperature gradient led to more flattening of the thermocline this appears to be a cause of more frequent and persistent occurrence of the enso modoki event during recent decades

the response of a stochastically forced enso model to observed off equatorial wind stress forcing abstract this study investigates the response of a stochastically forced coupled atmosphere ocean model of the equatorial pacific to off equatorial wind stress anomaly forcing the intermediate complexity coupled enso model comprises a linear first baroclinic mode ocean shallow water model with a steady state two pressure level 250 and 750 mb atmospheric component that has been linearized about a state of rest on the plane estimates of observed equatorial region stochastic forcing are calculated from ncep ncar reanalysis surface winds for the period 1950 2006 using singular value decomposition the stochastic forcing is applied to the model both with and without off equatorial region wind stress anomalies i e poleward of 12 5 latitude it is found that the multiyear changes in the equatorial pacific thermocline depth background state induced by off equatorial forcing can affect the amplitude of modeled sea surface temperature anomalies by up to 1 c moreover off equatorial wind stress anom

indices of el nino evolution abstract to characterize the nature of el nino southern oscillation enso sea surface temperature sst anomalies in different regions of the pacific have been used an optimal characterization of both the distinct character and the evolution of each el nino or la nina event is suggested that requires at least two indices i sst anomalies in the nino 3 4 region referred to as n3 4 and ii a new index termed here the trans nino index tni which is given by the difference in normalized anomalies of sst between nino 1 2 and nino 4 regions the first index can be thought of as the mean sst throughout the equatorial pacific east of the date line and the second index is the gradient in sst across the same region consequently they are approximately orthogonal tni leads n3 4 by 3 to 12 months prior to the climate shift in 1976 77 and also follows n3 4 but with opposite sign 3 to 12 months later however after 1976 77 the sign of the tni leads and lags are reversed

tropical pacific decadal variability and the subtropical tropical cells abstract the decadal scale variability in the tropical pacific has been analyzed herein by means of observations and numerical model simulations the two leading modes of the sea surface temperature sst variability in the central western pacific are a decadal mode with a period of about 10 yr and the enso mode with a dominant period of about 4 yr the sst anomaly pattern of the decadal mode is enso like the decadal mode however explains most variance in the western equatorial pacific and off the equator a simulation with an ocean general circulation model ogcm forced by reanalysis data is used to explore the origin of the decadal mode it is found that the variability of the shallow subtropical tropical overturning cells is an important factor in driving the decadal mode this is supported by results from a multicentury integration with a coupled ocean atmosphere general circulation model cgcm that realistically simulates tropical pacific decadal variability finally the sensitivity of the shal

pacific shallow meridional overturning circulation in a warming climate abstractby analyzing a set of the coupled model intercomparison project phase 3 cmip3 climate model projections of the twenty first century it is found that the shallow meridional overturning of the pacific subtropical cells stcs show contrasting trends between two hemispheres in a warming climate the strength of stcs and equivalently the stc surface layer transport tend to be weakening strengthening in the northern southern hemisphere as a response to large scale surface wind changes over the tropical pacific the stc pycnocline transport convergence into the equatorial pacific ocean from higher latitudes shows a robust weakening in the twenty first century this weakening is mainly through interior pathways consistent with the relaxation of the zonal pycnocline tilt whereas the transport change through western boundary pathways is small and not consistent across models it is found that the change of the western boundary pycnocline transport is strongly affected by the shoaling of the pycnocl

el nino variability in simple ocean data assimilation soda 1871 2008 1 a new ocean reanalysis that covers the period from 1871 to 2008 is used to explore the time evolving characteristics of el nino the new reanalysis assimilates all available hydrographic and sea surface temperature data into a model of the global ocean forced with surface boundary conditions from an atmospheric reanalysis that also covers the period from 1871 through 2008 using traditional measures of el nino our reanalysis shows that the timing of el nino events is in agreement with sea surface temperature reconstructions but el nino in the reanalysis is stronger particularly from 1871 to 1920 a new index based on the first moment of the temperature anomaly is introduced the new index is used to characterize the strength and location of el nino events and has the advantage that it is independent of the location of el nino using the new index el nino in the reanalysis shows prominent decadal variability of strength but relatively little long term trend el nino events were strong in the last part of the 19th century and first part of the 20th century and again in the latter part of the 20th century with weak el nino events in the middle of the 20th century the location of el nino also varies considerably ranging from the western to the eastern pacific near the coast of south america however the null hypothesis that the location of el nino can be represented as a random distribution about a central longitude of about 140 w cannot be rejected

anti correlated variability in subduction rate of the western and eastern north pacific oceans identified by an eddy resolving ocean gcm analysis of results from an eddy resolving ocean general circulation model has revealed the existence of an anti correlated variability in subduction rate of the western and eastern north pacific oceans consistent with the leading mode of pacific decadal oscillation pdo a composite analysis shows that during the positive phase of pdo the winter mixed layer depth mld generally gets deeper in the west and shallower in the east being closely related to the variability in surface heat flux stemming from an enhanced aleutian low and the situation during the negative phase of pdo is reversed changes in mld are primarily responsible for the anti correlated variability in subduction rate though changes in subtropical gyre circulation also play a role the result also provides useful evidence for the interior and western boundary pathways through which variability in eastern subtropical mode water can be conveyed into the equatorial region citation chen j t qu y n sasaki and n schneider 2010 anti correlated variability in subduction rate of the western and eastern north pacific oceans identified by an eddy resolving ocean gcm geophys res lett 37 l23608 doi 10 1029 2010gl045239

interdecadal sea surface temperature variability in the equatorial pacific ocean part i the role of off equatorial wind stresses and oceanic rossby waves the australian bureau of meteorology research centre cgcm and a linear first baroclinic mode ocean shallow water model swm are used to investigate ocean dynamic forcing mechanisms of the equatorial pacific ocean interdecadal sea surface temperature sst variability an eof analysis of the 13 yr low pass butterworth filtered sst anomalies from a century time scale cgcm simulation reveals an sst anomaly spatial pattern and time variability consistent with the interdecadal pacific oscillation results from an swm simulation forced with wind stresses from the cgcm simulation are shown to compare well with the cgcm and as such the swm is then used to investigate the roles of uncoupled equatorial wind stress forcing off equatorial wind stress forcing offeqwf and rossby wave reflection at the western pacific ocean boundary on the decadal equatorial thermocline depth anomalies equatorial pacific wind stresses are shown to explain a large proportion of the overall variance in the equatorial thermocline depth anomalies however offeqwf beyond 12 5 latitude produces an interdecadal signature in the nino 4 nino 3 region that explains approximately 10 1 5 of the filtered control simulation variance rossby wave reflection at the western pacific boundary is shown to underpin the offeqwf contribution to these equatorial anomalies the implications of this result for the predictability of the decadal variations of thermocline depth are investigated with results showing that offeqwf generates an equatorial response in the nino 3 region up to 3 yr after the wind stress forcing is switched off further a statistically significant correlation is found between thermocline depth anomalies in the offequatorial zone and the nino 3 region with the nino 3 region lagging by approximately 2 yr the authors conclude that there is potential predictability of the offeqwf equatorial thermocline depth anomalies with lead times of up to 3 yr when taking into account the amplitudes and locations of off equatorial region rossby waves

wind driven interdecadal variability in the eastern tropical and south pacific 1 simulated interface elevation anomalies with a reduced gravity model forced by observed wind stress are used to investigate the origin of thermocline depth fluctuations in the eastern tropical and south pacific at interdecadal timescales it is found that interdecadal thermocline depth fluctuations in the eastern equatorial pacific and along the western coast of the americas are fundamentally driven by zonal wind fluctuations in the western equatorial pacific thus positive negative interface elevation anomalies which correspond to shallower deeper thermocline depths in the eastern tropical pacific and along the west coast of central and south america are related to easterly westerly anomalies in the western sector of the equatorial pacific however off equatorial wind fluctuations maintain and reinforce the interdecadal variability observed along the eastern equatorial pacific and along the west coast of south america in the latter region equatorial off equatorial wind forcing is relatively more important equatorward poleward of 30 s in the eastern equatorial pacific interface elevation anomalies are negatively correlated with sea surface temperature sst at interdecadal timescales according to our results the sst interdecadal anomalies are in part 50 60 driven by wind fluctuations likely through the modulation of vertical advection of cold waters which depends primarily on the thermocline depth forced remotely or locally by winds this relationship was especially strong during the 1970s and 1980s a period characterized by the larger zonal wind stress interdecadal fluctuations observed in the western equatorial pacific

dipolar redistribution of summertime tropical cyclone genesis between the philippine sea and the northern south china sea and its possible mechanisms 1 recent observational records show that the dipole oscillation between the philippine sea ps and the northern south china sea nscs is a leading empirical orthogonal function eof of summertime tropical cyclone tc genesis in the western north pacific wnp this ps nscs oscillation is characterized by a distinguished decadal variability in addition to an interannual variability meanwhile the typical el nino southern oscillation enso related mode is found in the second eof mode which is predominantly interannual with regard to the ps nscs oscillation its interannual component appears to be linked with the previous wintertime enso event but the linkage is not so robust in the sense that about half of its significant events are classified as the enso related case whereas its decadal component is coupled to a sea surface temperature anomaly ssta in the central pacific with its equatorial core near the nino 4 region which is flanked by an opposite ssta on both sides along the latitudinal belt interestingly this ssta pattern resembles that related to the enso modoki and equivalently the transitional phase of enso the enso modoki is regionally manifested by the anomalous zonal sst gradient between the equatorial western and central pacific thus the decadal modulation of this anomalous zonal sst gradient can be regarded as an actual forcing that forms and modulates the decadal ps nscs oscillation in addition the decadal ps nscs oscillation is compared with the decadal basin wide tc genesis variation in terms of the pacific ssta pattern and the associated anomalous large scale environments

interdecadal variability of western north pacific tropical cyclone tracks abstract this study examines the interdecadal variability of the tropical cyclone tc tracks over the western north pacific wnp during the 1960 2005 period an empirical orthogonal function analysis of the 10 yr gaussian filtered annual frequency of tc occurrence shows three leading modes of tc occurrence patterns the first mode is related to the variation of tc activity in the areas near japan and its east the second mode is characterized by a northeast southwest dipole of tc occurrence anomalies along the southeast coast of china and an east west dipole near japan and its east the third mode is similar to the second mode except for the absence of the east west dipole these patterns are shown to be related to the decadal changes in the prevailing tc tracks two characteristic flow patterns related to the first and third modes of tc occurrence pattern are identified the first pattern is characterized by a north south dipole of 500 hpa geopotential anomalies over the wnp such a pattern may affect

new late proterozoic paleomagnetic pole for the rio de la plata craton implications for gondwana abstract major uncertainties remain on the precise kinematic and temporal aspects of gondwana assembly in order to provide new constraints on them a paleomagnetic study was carried out on the ediacaran succession of red claystones exposed in sierra de los barrientos 37 8 s 59 0 w buenos aires province argentina this succesion belongs to the late proterozoic early paleozoic sedimentary cover of the rio de la plata craton sixty two oriented samples from 13 sites were submitted to standard stepwise demagnetization procedures yielding a characteristic remanence carried by hematite a primary origin for the remanence is suggested by the apparent recording of secular variation along the stratigraphic column including a reversal of the earth magnetic field and an improvement in clustering of mean site directions after application of bedding corrections although the latter is not statistically significant since the study samples show a significant anisotropy of magnetic susceptibility ams degree p up to 1 2 and an ellipsoid shape compatible with significant compaction during diagenesis remanence inclination shallowing was investigated through oriented isothermal remanent magnetization irm acquisition and demagnetization experiments these permitted to confirm significant inclination shallowing and to compute a correction factor that was applied to the mean site directions producing a significantly further improvement in the statistical parameters a paleomagnetic pole was computed for the los barrientos claystones at 15 1 s 252 6 e dp 10 9 dm 14 2 when rotated into a gondwana framework this new pole agrees with previous poles of ca 550 ma from several gondwanan cratons allowing the construction of a single apwp for the whole of gondwana since that time and suggesting that by ca 550 ma gondwana was already assembled or in the final stages of that process

meridional extent and interannual variability of the pacific ocean tropical subtropical warm water exchange altimetric observations of sea surface height anomaly ssha from the topex poseidon and ers satellites hydrography and the ecmwf and florida state university wind products are used to track warm water 20 c as it is exchanged between the equatorial pacific ocean and the higher latitudes during 1993 2003 the large el nino event of 1997 98 resulted in a significant discharge of warm water toward the higher latitudes within the interior of the pacific ocean the exchange of anomalous warm water volume with the northern hemisphere appears to be blocked under the intertropical convergence zone consistent with most current ideas on the time mean tropical subtropical exchange little of the warm water discharged northward across 5 and 8 n during the 1997 98 el nino event could be traced as far as 10 n to the south however these anomalous volumes of warm water were visible at least as far as 20 s primarily in the longitudes around 130 160 w in both hemispheres most of the warm water appeared to flow westward before returning to the tropics during the recharge phase of the el nino la nina cycle the buildup of warm water in the tropics before the 1997 98 el nino is shown to be fed primarily by warm water drawn from the region in the western pacific within 5 s 15 n the exchange cycle between the equatorial band and the higher latitudes north of the equator leads the cycle in the south by 6 8 months these results are found in all three datasets used herein hydrography altimetric observations of ssha and sverdrup transports calculated from multiple wind products which demonstrates the robustness of the results

megadroughts in the indian monsoon region and southwest north america and a mechanism for associated multidecadal pacific sea surface temperature anomalies abstract a 1360 yr control run from a global coupled climate model the parallel climate model is analyzed it simulates megadroughts in the southwestern united states and indian monsoon regions the megadroughts represent extreme events of naturally occurring multidecadal precipitation variations linked to the dominant pattern of multidecadal sst variability in the indian and pacific oceans gaining insight into the occurrence of megadroughts thus requires an understanding of the mechanism that is producing this multidecadal sst variability analysis of the model variability shows that the mechanism involves atmosphere ocean and tropical midlatitude interactions with a crucial element being wind forced ocean rossby waves near 20 n and 25 s in the pacific whose transit times set the decadal time scale at the western boundary the rossby waves reflect into the equatorial pacific to affect thermocline depth the resulting feedbacks involving surface temperature winds and the strength of the subtropi

paleomagnetic confirmation of the laurentian origin of the argentine precordillera abstract several recent tectonic models have portrayed the argentine precordillera has been recently portrayed as an early paleozoic laurentian derived exotic terrane now found in southwestern south america these models have primarily been based on strong biogeographic and stratigraphic evidence however no paleomagnetic data have previously been available to independently test them a paleomagnetic study was therefore carried out on the early cambrian cerro totora formation exposed in the northern reaches of the argentine precordillera after stepwise thermal demagnetization a pre folding remanence was identified in ten sites of this formation yielding a paleomagnetic pole ct at 37 0 n 314 1 e a95 5 8 this pole is not consistent with the latest proterozoic early paleozoic apparent polar wander path for gondwana but it agrees with the early cambrian section of the laurentian path if the argentine precordillera is positioned as the conjugate margin of the ouachita embayment in southeast laurentia this result confirms that the precordillera is an allochthonous terrane derived from laurentia in cambrian times that was later accreted to gondwana probably in middle ordovician times

formation mechanism for isopycnal temperature salinity anomalies propagating from the eastern south pacific to the equatorial region abstract equatorward propagation of temperature salinity or spiciness anomalies on an isopycnal surface emanating from the eastern subtropical south pacific and their formation mechanism are investigated based on a hindcast simulation with an eddy resolving quasi global ocean general circulation model because of density compensating meridional distributions of temperature and salinity the meridional density gradient is weak at the sea surface in the eastern subtropical south pacific with these mean fields cool sea surface temperature anomalies sstas can make the outcrop line of an isopycnal surface migrate equatorward more than 5 and induce warm and salty anomalies on the isopycnal surface subducted warm salty anomalies propagate to the equatorial region over approximately 5 yr and may influence equatorial isopycnal temperature salinity anomalies although the associated effects are unclear if these anomalies could further induce warm eastern equatorial sstas that are positively correlated wit

circa 546 ma plume related dykes in the 1 ga novillo gneiss east central mexico evidence for the initial separation of avalonia abstract the 1 ga novillo gneiss exposed in an inlier in the front ranges of the laramide belt in east central mexico is cut by an unmetamorphosed ne trending mafic dyke swarm the gneiss represents the northernmost inlier of the oaxaquia terrane that underlies the backbone of mexico titanite and biotite from metasedimentary rocks yielded ages of 928 2 ma concordant u pb age and duplicate 40 ar 39 ar plateau ages of 697 7 and 697 10 ma which are inferred to represent cooling through 660 and 300 350 c respectively on the other hand hornblende from cross cutting ne trending mafic dykes yielded a 40 ar 39 ar plateau age of 546 5 ma which is inferred to closely post date the time of intrusion combined with published ages u pb zircon sm nd garnet k ar hornblende the data suggest that following granulite facies metamorphism at 982 6 ma 8 9 9 7 kbar and 730 775 c the novillo gneiss cooled at a rate of 1 45 c my if this latter rate is extrapolated it would place the rocks at the surface 30 c by 497 ma about 50 my after dyke emplacement geochemistry of the dykes indicates that they are fe rich tholeiites with i low mgo but high tio 2 and other hfse ii smooth mantle normalized incompatible trace element patterns peaking at nb and la and iii intraplate tectonic affinities these features are typical of enriched tholeiites associated with plumes current precambrian paleogeographic reconstructions place avalonia against oaxaquia and subsequently separate avalonia by way of ridge trench collision at 550 ma giving rise to the unique avalonian cambrian fauna and a rapid phase of early cambrian subsidence these events are contemporaneous with emplacement of the novillo mafic dykes suggesting that the plume related magmatism and separation of avalonia from oaxaquia are linked