role of nonlinear ocean dynamic response to wind on the asymmetrical transition of el nino and la nina to understand why el nino is frequently followed by la nina while the opposite occurs rarely we analyze the inherent asymmetry in a delayed negative feedback loop in the framework of delayed oscillator theory using observational data the asymmetrical response of the ocean wave to wind is much larger than that of the wind intensity to sst and that of the subsurface temperature to thermocline strong oceanic response during el nino compared to la nina is presumably due to the relatively shallow mean thermocline over the western pacific which efficiently traps the atmospheric momentum in the shallow upper ocean and the asymmetrical wind pattern response to sst a modified delayed oscillator model experiment verifies that the asymmetrical ocean wave response to wind is more important in the asymmetrical transition of el nino and la nina than asymmetrical wind intensity response to sst and asymmetrical subsurface temperature response to thermocline

paleomagnetic study of plio pleistocene sediments in the concentrated deformation zone along the eastern margin of the japan sea abstract paleomagnetic results are presented for a concentrated deformation zone cdz in a convergent plate boundary region along the eastern eurasian margin we sampled late pliocene early pleistocene tuffs and clastic sediments of the sasaoka formation 750 m thick in northeastern honshu japan to test whether the late pliocene quaternary crustal deformation within the cdz along the eastern margin of the japan sea was accompanied by rotation about a vertical axis rock magnetic experiments suggest that the principal magnetic carrier is magnetite in the fine tuffs and magnetic iron sulfide in the fine sandstones pre folding characteristic remanent magnetization was confirmed using a positive bootstrap fold test we obtained 21 acceptable site mean characteristic directions that include our preliminary published results and which cover an interval from ca 2 7 to 1 7 ma on the basis of magnetostratigraphic correlations an updated age depth model is given and this allowed us to make numerical age estimates for key interbedded tuff beds tephras a positive fold test also suggests that the gojome syncline began to develop after 1 7 ma which means the folding began long after the initiation of late pliocene crustal shortening in northeastern honshu after 100 unfolding the overall mean direction d 359 7 i 54 9 95 6 7 is indistinguishable from the geocentric axial dipole field direction indicating that the gojome syncline the most prominent structural element in the study area developed without vertical axis rotation a comparison of our results with plio pleistocene directions reported from other areas reveals no paleomagnetically detectable rotation in or adjacent to the cdz except for local rotation near strike slip faults in central honshu

western pacific interannual variability associated with the el nino southern oscillation observations of sea surface temperature sst sea level pressure slp surface wind and outgoing longwave radiation olr show that the el nino southern oscillation enso displays western pacific anomaly patterns in addition to eastern pacific anomaly patterns during the warm phase of enso warm sst and low slp anomalies in the equatorial eastern pacific and low olr anomalies in the equatorial central pacific are accompanied by cold sst and high slp anomalies in the off equatorial western pacific and high olr anomalies in the off equatorial far western pacific also while the zonal wind anomalies over the equatorial central pacific are westerly those over the equatorial far western pacific are easterly the nearly out of phase behavior between the eastern and western tropical pacific is also observed during the cold phase of enso but with anomalies of opposite sign these western pacific interannual anomaly patterns are robust features of enso independent of data sets it is argued that equatorial easterly westerly wind anomalies over the far western pacific during the warm cold phase of enso are initiated by off equatorial western pacific cold warm sst anomalies and that these winds are important for the evolution of enso an atmosphere model is employed to demonstrate that small off equatorial western pacific cold warm sst anomalies compared to those in the east are sufficient to produce equatorial easterly westerly wind anomalies as observed over the far western pacific the coupled ocean atmosphere model of zebiak and cane is then modified to investigate the evolution of the western pacific interannual anomaly patterns in a coupled ocean atmosphere system by including a meridional structure to the subsurface temperature parameterization in the western pacific the modified model produces both western and eastern pacific interannual anomaly patterns

planetary scale selection of the madden julian oscillation in an air sea coupled dynamic moisture model the authors present an air sea coupled dynamic moisture asdm model to explore the mechanism of preferred planetary scale of the madden julian oscillation mjo this asdm model extended from the original frictionally coupled dynamic moisture model and a mixed layer model can present a good simulation of planetary scale characteristics of the mjo including a slow eastward propagation of 5 m s 1 coupled rossby kelvin wave like structure and phase leading of convective center by warm sea surface temperature sst it is interesting that the planetary scale selection in terms of instability is only found in the nonlinear asdm model with the assumption of positive only heating such a scale selection however cannot be found in the asdm model with linear heating or in an uncoupled atmosphere model the essential mechanism for the scale selection is nonlinear positive only heating and the air sea interaction primarily provides an instability source to support this scale selection this scale selection is attributed to different phase speeds of coupled moist rossby kelvin waves and dry kelvin waves from short wave initial perturbations the easterly wind anomalies of eastward propagating dry kelvin waves from a stronger wave component will catch up with other weaker moist components and suppress their westerly wind anomalies resulting in weak sst gradient as well as reduced moisture convergence and precipitation for these suppressed components as a result the wavenumber one structure is selected the warm pool like mean state will select the stronger component among the initial short wave perturbations and accelerate this scale selection process these results provide new insight into mjo mechanism in terms of air sea interaction

relationship between optimal precursory disturbances and optimally growing initial errors associated with enso events implications to target observations for enso prediction by superimposing initial sea temperature disturbances in neutral years we determine the precursory disturbances that are most likely to evolve into el nino and la nina events using an earth system model these precursory disturbances for el nino and la nina events are deemed optimal precursory disturbances because they are more likely to trigger strong enso events specifically the optimal precursory disturbance for el nino exhibits negative sea surface temperature anomalies sstas in the central eastern equatorial pacific additionally the subsurface temperature component exhibits negative anomalies in the upper layers of the eastern equatorial pacific and positive anomalies in the lower layers of the western equatorial pacific the optimal precursory disturbance for la nina is almost opposite to that of el nino the optimal precursory disturbances show that both el nino and la nina originate from precursory signals in the subsurface layers of the western equatorial pacific and in the surface layers of the eastern equatorial pacific we find that the optimal precursory disturbances for el nino and la nina are particularly similar to the optimally growing initial errors associated with el nino prediction that have been presented in previous studies the optimally growing initial errors show that the optimal precursor source areas represent the sensitive areas for target observations associated with enso prediction combining the optimal precursory disturbances and the optimally growing initial errors for enso we infer that additional observations in these sensitive areas can reduce initial errors and be used to detect precursory signals thereby improving enso predictions

relative roles of elevated heating and surface temperature gradients in driving anomalous surface winds over tropical oceans abstract elevated heating by cumulus convection and sea surface temperature gradients are both thought to contribute to surface winds over tropical oceans the relative strength and role of each mechanism is examined by imposing forcing derived from data on a linear primitive equation model with idealized parameterizations for the two forcings and comparing the response with observed surface winds two test cases are studied one related to the el nino southern oscillation and the other related to the dipole mode in the tropical atlantic it is found that in both cases elevated heating dominates the surface zonal wind response and contributes significantly to the meridional wind response especially in the subtropics and the south pacific and south atlantic convergence zone regions surface temperature gradients dominate the meridional wind forcing in regions near the equator with strong meridional temperature gradients

the south pacific meridional mode as a thermally driven source of enso amplitude modulation and uncertainty abstractthis study seeks to identify thermally driven sources of enso amplitude and uncertainty as they are relatively unexplored compared to wind driven sources pacific meridional modes are argued to be wind triggers for enso events this study offers an alternative role for the south pacific meridional mode spmm in enso dynamics not as an enso trigger but as a coincident source of latent heat flux lhf forcing of enso ssta that if correctly incorrectly predicted could reduce increase enso prediction errors we utilize a coupled model simulation in which enso variability is perfectly periodic and each el nino experiences identical wind stress forcing differences in el nino amplitude are primarily thermally driven via the spmm when el nino occurs coincidentally with positive phase spmm the positive spmm lhf anomaly counteracts a fraction of the lhf damping of el nino allowing for a more intense el nino if the spmm phase is instead negative the spmm lhf amplifies the lhf damping of el nin

dynamics and thermodynamics of a warming event in a coupled tropical atmosphere ocean model abstract a simple coupled ocean atmosphere model similar to that of zebiak and cane is used to examine the dynamic and thermodynamic processes associated with el nino southern oscillation enso the model is run for 300 years the interannual variability which results is regular with a period of either 3 or 4 years quantized by the annual cycle the amplitude 1 5 m s 1 wind and 2 c sst anomalies period and structure of the interannual variability compare well with observations the model warm event is initiated in the spring prior to the event peak and is well described as an instability of the coupled system during instability growth the sea surface temperature sst anomaly is primarily generated by vertical upwelling processes the sst anomaly can be approximately described by the expression t t kth t where t is the sst anomaly t time h the upper layer thickness pycnocline perturbation and an effective damping time which includes heat loss to the atmosphere kt parameterizes

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

atmospheric convergence feedback in a simple model for el nino abstract a parameterization is developed for the feedback between dynamics and heating associated with moisture convergence in the tropical atmospheric boundary layer the feedback improves the ability of a simple model to simulate observed anomalies of the tropical atmosphere during el nino events in particular two features of the observations are reproduced by including the feedback process the smaller scale of atmospheric anomalies as compared to sst anomalies and the focusing of the anomalies in the vicinity of the mean convergence zones the principal remaining shortcomings of the model are discussed

on the relationship between sst gradients boundary layer winds and convergence over the tropical oceans a linear mixed layer model that skillfully reproduces observed surface winds and convergence over the tropicaloceans is used to examine the relative influenceof boundarylayer and free tropospheric processes on the distribution of climatological surface winds and convergence the semiempirical model assumes a subcloud layer momentum force balance between pressure gradients coriolis acceleration linearized friction and downward momentum mixing and it utilizes boundary conditions from the 40 yr ecmwf re analysis era 40 observed pressure gradients are linearly decomposed into boundary layer defined as the region below 850 hpa and free tropospheric components and the surface winds and convergence associated with these components are computed results show that surface zonal winds are predominantly associated with a combination of free tropospheric pressure gradients and downward momentum mixing whereas the distribution of convergence is primarily due to boundary layer temperature gradients which are closely related to sst gradients the authors conclude that the climatological distribution of boundary layer convergence is primarily a function of the pattern of sst gradients and is better regarded as a cause rather than a consequence of deep convection

contributions of the north pacific meridional mode to ensemble spread of enso prediction abstractseasonal prediction of el nino southern oscillation enso employs the ensemble method which samples the uncertainty in initial conditions while much attention has been given to the ensemble mean the ensemble spread limits the reliability of the forecast spatiotemporal coevolution of intermember anomalies of sea surface temperature sst and low level winds over the pacific is examined in ensemble hindcasts two types of evolution of intermember sst anomalies in the equatorial pacific are identified the first features an apparent southwestward propagation of the sst spread from the subtropical northeastern pacific southeast of hawaii to the central equatorial pacific in boreal winter spring indicative of the precursor effect of the north pacific meridional mode npmm on enso variability extratropical atmospheric variability generates ensemble spread in enso through wind evaporation sst wes in the subtropical northeastern pacific and then bjerknes feedback on the equator in the second ty

influences of enso teleconnection on the persistence of sea surface temperature in the tropical indian ocean abstractthis study confirms a weak spring persistence barrier spb of sea surface temperature anomalies sstas in the western tropical indian ocean wio a strong fall persistence barrier fpb in the south china sea scs and the strongest winter persistence barrier wpb in the southeastern tropical indian ocean seio during el nino events a less abrupt sign reversal of sstas occurs in the wio during spring an abrupt reversal occurs in the scs during fall and the most abrupt reversal occurs in the seio during winter the sign reversal of ssta implies a rapid decrease in ssta persistence which is favorable for the occurrence of a persistence barrier the present results indicate that a more abrupt reversal of ssta sign generally corresponds to a more prominent persistence barrier el nino induced changes in atmospheric circulation result in reduced evaporation and suppressed convection this in turn leads to the warming over much of the tio basin which is an important mechanism for the abrupt

a new paradigm for the predominance of standing central pacific warming after the late 1990s canonical el nino has a warming center in the eastern pacific ep but in recent decades el nino warming center tends to occur more frequently in the central pacific cp the definitions and names of this new type of el nino however have been notoriously diverse which makes it difficult to understand why the warming center shifts here we show that the new type of el nino events is characterized by 1 the maximum warming standing and persisting in the cp and 2 the warming extending to the ep only briefly during its peak phase for this reason we refer to it as standing cp warming cpw global warming has been blamed for the westward shift of maximum warming as well as more frequent occurrence of cpw however we find that since the late 1990s the standing cpw becomes a dominant mode in the pacific meanwhile the epochal mean trade winds have strengthened and the equatorial thermocline slope has increased contrary to the global warming induced weakening trades and flattening thermocline we propose that the recent predominance of standing cpw arises from a dramatic decadal change characterized by a grand la nina like background pattern and strong divergence in the cp atmospheric boundary layer after the late 1990s the anomalous mean cp wind divergence tends to weaken the anomalous convection and shift it westward from the underlying sst warming due to the suppressed low level convergence feedback this leads to a westward shift of anomalous westerly response and thus a zonally in phase sst tendency preventing eastward propagation of the sst anomaly we anticipate more cpw events will occur in the coming decade provided the grand la nina like background state persists

towards optimal observational array for dealing with challenges of el nino southern oscillation predictions due to diversities of el nino this paper investigates the optimal observational array for improving the initialization of el nino southern oscillation predictions by exploring the sensitive areas for target observations of two types of el nino predictions the sensitive areas are identified by calculating the optimally growing errors oges of the zebiak cane model as corrected by the optimal forcing vector that is determined by assimilating the observed sea surface temperature anomalies sstas it is found that although the oges have similar structures for different start months of predictions the regions covered by much large errors for the ssta component tend to locate at different zonal positions and depends on the start months furthermore these regions are also in difference between two types of el nino events the regions covered by large errors of oges represent the sensitive areas for target observations considering the dependence of the sensitive areas on related el nino types and the start months of predictions the present study propose a quantitative frequency method to determine the sensitive areas for target observations associated with two types of el nino predictions which is expected to be applicable for both types of el nino predictions with different start months as a result the sensitive areas that describe the array of target observations are presented with a reversal triangle like shape locating in the eastern pacific specifically the area of 120 w 85 w 0 s 11 s and an extension to the west along the equator and then gathering at the 180 longitude and the western boundary hindcast experiments demonstrated that such observational array is very useful in distinguishing two types of el nino and superior to the tao triton array it is therefore suggested that the observational array provided in the present study is towards the optimal one and the original tao triton array should be further optimized when applied to predictions of the diversities of el nino events

the relationship between thermocline depth and sst anomalies in the eastern equatorial pacific seasonality and decadal variations even though the vital role of thermocline fluctuation in el nino southern oscillation enso cycle has been established previously the direct relationship between the thermocline depth and sea surface temperature sst anomalies in the equatorial pacific is yet to be fully understood especially its seasonality thermocline depth anomalies have been found to lead sst anomalies in time with a longitude dependent delay but our study also suggests that the relationship shows considerable seasonal dependency and is strongest weakest during the boreal spring summer over the eastern equatorial pacific where there is least delay compared to that in the western and central pacific the connection between thermocline and sst is the weakest during the boreal spring this feature may be one of causes for enso spring persistence barrier furthermore the thermocline sst connections exhibit significant decadal variations which are remarkably consistent with the decadal changes in the persistence barrier of sst anomalies over the eastern pacific it is also found that the decadal shift in the timing of the thermocline sst connection barrier is caused by the changes in the seasonal cycle of tropical trade winds and thermocline depths

interhemispheric influence of the atlantic warm pool on the southeastern pacific abstract the atlantic warm pool awp is a large body of warm water comprising the gulf of mexico caribbean sea and western tropical north atlantic the awp can vary on seasonal interannual and multidecadal time scales the maximum awp size is in the boreal late summer and early fall with the largest extent in the year being about 3 times the smallest one the awp alternates with the amazon basin in south america as the seasonal heating source for circulations of the hadley and walker type in the western hemisphere during the boreal summer fall a strong hadley type circulation is established with ascending motion over the awp and subsidence over the southeastern tropical pacific this is accompanied by equatorward flow in the lower troposphere over the southeastern tropical pacific as dynamically required by the sverdrup vorticity balance it is shown by analyses of observational data and ncar community atmospheric model simulations that an anomalously large small awp during the boreal summer f

diagnostic studies of pacific surface winds abstract analyses are performed using surface winds derived from the monthly mean fsu pacific pseudo stress fields vorticity budget calculations reveal the relative contributions of various terms and allow simplification of the full momentum equations based on the simplified equations a procedure is developed for estimating surface pressure and then adjusting the winds the wind field adjustments fall well within the uncertainty of the data while allowing generally large imbalances in the vorticity budget to be removed completely further validation of the procedure is provided by comparisons between estimated and observed pressure anomalies the adjusted winds and pressure are then used to infer boundary layer and upper level forcing within the context of particular model formulations these forcing fields an compared with sea surface temperature outgoing longwave radiation and highly reflective cloud data in order to infer the dominant mechanisms contributing to observed surface circulation anom

double saloon door tectonics in the japan sea fossa magna and the japanese island arc abstract a number of criteria considered diagnostic of double saloon door rifting and seafloor spreading are matched by data from the japanese arc these include i a pair of terranes sw and ne honshu which rotated in opposite directions from 22 21 ma to 14 11 ma ii rotated terranes which comprise a retro arc fold thrust belt attached to an accretionary wedge intruded by a magmatic arc iii contemporaneous backarc extension from 24 to 21 ma which is brought to a halt by progressive collision of the izu bonin and japan arcs from 15 to 5 ma iv isolation of blocks of thicker continental crust by areas of thin continental or oceanic crust during backarc rifting v such isolation may be due to simultaneous rifting or to progressively seaward rifts associated with ridge jumps towards the subduction zone vi opposite rotations are accommodated by subduction rollback demonstrated by seaward migration of the volcanic front from 30 26 ma to 16 15 ma vii concurrent development of a major arc orthogonal rift the fossa magna from 23 18 ma to 14 ma which was thereafter inverted from 15 ma to the recent viii a northeast propagating rift in the northern japan basin demonstrated by the relationship of linear magnetic anomalies to the mapped continent ocean boundary driving mechanisms for double saloon door tectonics are discussed in relation to various reconstructions of the northwest pacific opposite rotational torques leading to opposite terrane rotations may be caused by rollback of a curved trench hingeline or by the divergent slab sinking forces of the pacific and philippine sea plates

exploring the initial errors that cause a significant spring predictability barrier for el nino events 1 within the zebiak cane model we identify two types of initial errors that have significant season dependent evolutions related to the spring predictability barrier spb for el nino events one type includes the sea surface temperature anomaly ssta errors that have a zonal dipolar pattern with positive anomalies in the central equatorial pacific and negative ones in the eastern equatorial pacific the other type consists of the ssta errors with a spatial structure opposite to that of the former type the zonal dipolar pattern shows negative anomalies in the central equatorial pacific and positive anomalies in the eastern equatorial pacific the patterns of these two types of errors are nearly opposite of each other the former causes the el nino event to be underpredicted and the latter causes the el nino event to be overpredicted for strong el nino events the former tends to have a larger effect on the predictions than the latter but for weak el nino events it is very difficult to determine which type of initial errors results in worse predictions it is thought that strong weak el nino events could be affected by strong weak nonlinearities there are also other initial errors however they do not yield considerable season dependent evolutions nor can a common characteristic be extracted from their patterns the two types of initial errors suggest two dynamical behaviors of error growth related to the spb in one case the initial errors grow in a manner similar to the el nino events in the other case the initial errors develop with a tendency opposite to the el nino events the two types of initial errors may capture the errors that exhibit significant season dependent evolutions related to the spb in addition they may provide information regarding the sensitive area of enso predictions because of their localized regions therefore if these types of initial errors exist in the realistic el nino southern oscillation enso predictions and if a data assimilation or a target method can filter them the enso forecast skill may be improved for ensemble forecast studies different signs of prediction errors caused by the two types of initial errors could illustrate why the ensemble mean offers a better forecast than a single prediction

an air sea coupled skeleton model for the madden julian oscillation this work is an extension and improvement of the minimal madden julian oscillation mjo skeleton model developed by majda and stechmann which can capture some important features of the mjo slow eastward propagation quadrupole vortex structure and independence of frequency on wavelength but is unable to produce unstable growth and selection of eastward propagating planetary waves with the addition of planetary boundary layer frictional moisture convergence these deficiencies can be remedied the frictional boundary layer selects the planetary scale eastward propagation as the most unstable mode but the dynamics remains confined to atmospheric processes only here the authors study the role of air sea interaction by implementing an oceanic mixed layer ml model of wang and xie into the mjo skeleton model in this new air sea coupled skeleton model the features of the original skeleton model remain additionally the air sea interaction under mean westerly winds is shown to produce a strong instability that selectively destabilizes the eastward propagating planetary scale waves although the cloud shortwave radiation seasurfacetemperature crs feedbackdestabilizesbotheastwardand westward modes theair sea feedback associated with the evaporation and oceanic entrainment favors planetary scale eastward modes over the western hemisphere where easterly background winds prevail the evaporation and entrainment feedbacks yield damped modes indicating that longitudinal variation of the mean surface winds plays an important role in regulation of the mjo intensity in addition to the longitudinal variation of the mean sea surface temperature or mean moist static stability this theoretical analysis suggests that accurate simulation of the climatological mean state is critical for capturing the realistic air sea interaction and thus the mjo

coastal wetlands as recorders of earthquake subsidence in the aegean a case study of the 1894 gulf of atalantiearthquakes central greece abstract earthquakes may have a major impact on the morphology and evolution of coasts in tectonically active areas in the area of the gulf of atalanti central greece a damaging earthquake sequence in 1894 is reported to have caused nearshore slumping tsunami induced flooding and decimetre to metre scale coastal subsidence the earthquakes caused major changes to coastal configuration in particular the separation of the gaiduronisi peninsula from the mainland detailed stratigraphical microfossil and radiometric 210pb and 137cs analyses of coastal wetlands around the gulf of atalanti show that these environments preserve evidence of sudden lasting subsidence contemporaneous with the 1894 events with foraminiferal assemblages at a site on the mainland opposite the island indicating an abrupt change from supratidal soil to intertidal marine conditions the elevation change indicated by this terrestrial to marine transition is 30 80 cm the coastal stratigraphy in the atalanti area however lacks laterally extensive sharp soil mud contacts or tsunami deposits of the type used in identifying past earthquake subsidence events at plate boundary settings despite the major earthquake induced changes in coastal configuration the stratigraphical signature of the 1894 earthquakes is relatively subtle and is consequently difficult to distinguish from other rapid coastal changes e g storm events or barrier breaching without high resolution dating control and reference to documentary records for this reason coastal wetland stratigraphies are only likely to be useful in identifying pre historical or poorly documented earthquakes in the aegean at sites where metre scale coseismic elevation changes and or major tsunami inundation have occurred in addition the resolution of the biostratigraphic data reported here is insufficient to distinguish between the contrasting fault rupture models for the 1894 events the coastal elevation changes recorded in these wetlands however are best accounted for by a slip of 1 m on a multi segment fault

predictability of a coupled model of enso using singular vector analysis part i optimal growth in seasonal background and enso cycles the fastest initial error growth optimal growth in the zebiak and cane zc forecast model for the el nino southern oscillation enso is analyzed by singular value decomposition of a forward tangent model along a trajectory in a reduced eof space in this paper part i of ii optimal growth about the seasonally varying background and enso cycles from a long model run are discussed among the many forms of nonlinearity in zc the discontinuity of the slope in subsurface temperature at zero thermocline depth and the nonlinear advection of sst are the most significant that positive perturbations grow much faster than negative perturbations around the seasonally varying background is first attributable to the discontinuity and second attributable to nonlinear advection about the seasonally varying background 6 month optimal growth is largest for early boreal spring starts which is related to the enhanced atmospheric heating due to equatorward movement of the itcz one dominant growing structure is found characterized by north south and east west sst dipoles convergent winds on the equator in the eastern pacific and a deepened thermocline in the whole equatorial belt this structure is insensitive to start month and optimization time optimal growth about enso cycles in a long model run is generally much smaller than that about the seasonally varying background as before one dominant growing structure insensitive to start time and optimization time is found during the warm phase of enso optimal growth is modulated by season as is that about the seasonal varying background during the onset and mature phases of enso the final pattern of the optimal structure in 6 months is confined to the eastern pacific during the decay phase of enso it spreads to the western pacific as well during the cold phase of enso optimal growth has two maxima in a year early spring and fall the optimal perturbation propagates westward associated with surface layer wind interaction the authors also compare the singular vector analysis in eof space and the standard one in physical space the importance of norm definition to optimal growth and optimal structure is discussed

stochastic forcing of the north atlantic wind driven ocean circulation part ii an analysis of the dynamical ocean response using generalized stability theory as discussed in part i of this study the magnitude of the stochastic component of wind stress forcing is comparable to that of the seasonal cycle and thus will likely have a significant influence on the ocean circulation by forcing a quasigeostrophic model of the north atlantic ocean circulation with stochastic wind stress curl data from the ncar ccm3 it was found in part i that much of the stochastically induced variability in the ocean circulation is confined to the western boundary region and some major topographic features even though the stochastic forcing is basinwide this can be attributed to effects of bathymetry and vorticity gradients in the basic state on the system eigenmodes using generalized stability theory gst it was found in part i that transient growth due to the linear interference of nonnormal eigenmodes enhances the stochastically induced variance in the present study the gst analysis of part i is extended and it is found that the patterns of wind stress curl that are most effective for inducing variability in the model have their largest projection on the most nonnormal eigenmodes of the system these eigenmodes are confined primarily to the western boundary region and are composed of long rossby wave packets that are doppler shifted by the gulf stream to have eastward group velocity linear interference of these eigenmodes yields transient growth of stochastically induced perturbations and it is this process that maintains the variance of the stochastically induced circulations analysis of the large scale circulation also reveals that the system possesses a large number of degrees of freedom which has significant implications for ocean prediction sensitivity studies show that the results and conclusions of this study are insensitive and robust to variations in model parameters and model configuration

modeling tropical precipitation in a single column abstract a modified formulation of the traditional single column model for representing a limited area near the equator is proposed this formulation can also be considered a two column model in the limit as the area represented by one of the columns becomes very large compared to the other only a single column is explicitly modeled but its free tropospheric temperature rather than its mean vertical velocity is prescribed this allows the precipitation and vertical velocity to be true prognostic variables as in prior analytical theories of tropical precipitation two models developed by other authors are modified according to the proposed formulation the first is the intermediate atmospheric model of j d neelin and n zeng but with the horizontal connections between columns broken rendering it a set of disconnected column models the second is the column model of n o renno k a emanuel and p h stone in the first model the set of disconnected column models is run with a fixed temperature

magnetobiochronology of lower miocene ramblian continental sediments from the tudela formation western ebro basin spain abstract the calibration of european lower miocene continental stages is poorly constrained due to the lack of robust magnetostratigraphic data from continental sediments of this age in this paper we present the first magnetostratigraphic results from the mammal fossil bearing continental sediments of the lower middle miocene tudela formation western ebro basin spain the study is based on 331 paleomagnetic sites distributed along a 790 m thick composite section the resulting magnetostratigraphy provides an independent correlation to the geomagnetic polarity time scale and allows accurate dating of previously known and new ramblian upper lower miocene fossil localities of the tudela formation the new age constraints derived for the tudela formation fossil localities provide together with a revaluation of other iberian faunas the first magnetochronology for the ramblian continental stage the lower boundary of the ramblian is placed at the lower part of chron c6r ca 20 4 ma and the boundary between the lower and upper ramblian is located at the middle of chron c6n ca 19 6 ma the upper boundary of the ramblian and hence the base of the aragonian is placed at the upper middle part of chron c5cr 16 8 17 ma our results also provide the first magnetostratigraphically dated mn3 faunas in spain which together with a revaluation of other iberian and european faunas provide a revised calibration of european mammal zone mn3 the lower boundary of zone mn3 is placed at the boundary between chrons c6r and c6n ca 20 1 ma and its upper boundary is located at the upper middle part of chron c5cr 16 8 17 ma

aperiodic variability in the zebiak cane coupled ocean atmosphere model air sea interactions in the western equatorial pacific abstract the behavior of two coupled ocean atmosphere models of intermediate complexity the zebiak cane zc hereafter and battisti version b88 hereafter of the zc coupled ocean atmosphere model are reviewed and compared to the observed climate record from the tropical pacific region a major difference between each system lies in the modes of variability that each supports in the observations variability at timescales shorter than that associated with el nino and the southern oscillation enso is ubiquitous and difficult to characterize in terms of clearly coupled ocean atmosphere interactions the b88 model supports only a single unstable mode the enso mode in the zc model two distinct modes are present the interannual enso mode and the mobile mode a near annual westward propagating instability it is demonstrated that differences in the basic state climatology and thermodynamic parameters are keys to understanding the differences between the zc and b88 coupled model behaviors it is found

contribution of the location and spatial pattern of initial error to uncertainties in el nino predictions with the zebiak cane model the contribution of the location and spatial pattern of initial error in sea surface temperature anomalies ssta to uncertainty in el nino predictions is investigated using an approach based on conditional nonlinear optimal perturbation cnop which seeks to find the initial error i e the cnop error that satisfies a given constraint and that causes the largest prediction error at the prediction time the computed cnop error of ssta has a dipole pattern in the equatorial central and eastern pacific the initial error from the equatorial central and eastern pacific tends to grow more significantly than those from other locations because of the contribution of annual mean states the location of the initial error plays an important role in the error evolution e g the shallow annual mean thermocline in the eastern pacific favors feedback between the thermocline and sea surface temperature meanwhile the specific dipole structure of the initial error is also crucial for optimal error growth even with the same magnitude as the cnop error random initial error in the equatorial central and eastern pacific does not evolve significantly over time initial errors of ssta with a similar spatial pattern to the cnop error i e the dipole pattern of ssta error give rise to larger prediction errors than those without similar spatial pattern do consequently the magnitude of the prediction error at the prediction time depends on the combined effects of the location and spatial pattern of the initial error if additional observation instruments are deployed to observe sea surface temperature with limited coverage they should preferentially be deployed in the equatorial central and eastern pacific

eocene to miocene magnetostratigraphy biostratigraphy and chemostratigraphy at odp site 1090 sub antarctic south atlantic at ocean drilling program odp site 1090 lat 42854 89s long 8854 09e located in a water depth of 3702 m on the agulhas ridge in the sub antarctic south atlantic 300 m of middle eocene to middle miocene sediments were recovered with the advanced piston corer apc and the extended core barrel xcb u channel samples from the 70 230 meters composite depth mcd interval provide a magnetic polarity stratigraphy that is extended to 380 mcd by shipboard whole core and discrete sample data the magnetostratigraphy can be interpreted by the fit of the polarity zone pattern to the geomagnetic polarity time scale gpts augmented by isotope data and bioevents with documented correlation to the gpts three normal polarity subchrons c5dr 1n c7ar 1n and c13r 1n not included in the standard gpts are recorded at site 1090 the base of the sampled section is correlated to c19n middle eocene although the interpretation is unclear beyond c17r the top of the sampled section is correlated to c5cn late early miocene although in the uppermost 10 m

stress shear deformation and micromorphological clay orientation a synthesis of various concepts summary microscopic oriented clay bodies known as plasma separations to soil micromorphologists show various degrees of symmetry and regularity in their patterns they could be regarded as sensitive and reliable indicators of stress strain regime of a soil empirical and experimental evidence signifies the importance of stress specifically that generated by in situ swelling in the genesis of plasmic fabrics hitherto most work in this field is confined to geometric characterization with limited attempts to dynamic interpretations of their origin this paper enlists appropriate concepts in soil mechanics structural geology and agricultural engineering to interpret the possible stress strain components that rearrange fabric units into plasma separations some pertinent concepts including physico chemical behaviour of the clay water system shrink swell phenomenon stress strain deformation and failure of soil are employed to explain the origin of plasmic fabrics by mechanical principles a conceptual model is suggested to synthesize the conditions changes and consequences related to the formation of plasmic fabrics strongly developed plasma separations in natural soils are attributed to the establishment of an anisotropic state of stress generated by in situ swelling in conjunction with the passive pressure of lateral confinement and vertical overburden the difference between the maximum and minimum principal stresses produces a deviatoric stress that can at certain stages of a shrink swell cycle exceed the shear strength of the soil the extra stress is relieved plastically by shear deformation which is manifested as the alignment of platy particles in domain configuration by rotation and translation along the shear planes soil mainly fails in compressive plastic mode along a large number of small shear planes which form the plasma separations the formation of different types of sepic plasmic fabrics is discussed in relation to the stress strain regimes of soils

magnetostratigraphy of an early middle miocene loess soil sequence in the western loess plateau of china 1 stratigraphy and magnetic susceptibility of the quaternary eolian deposits at different sites in china can be closely correlated confirming their spatial coherence and temporal continuity the extent to which these conclusions are true for the miocene loess soil sequences remains to be addressed here a 231 9 m eolian section qa iii is geomagnetically dated yielding an age span of 21 4 11 4 ma with the portion older than 19 6 ma being partially water reworked the magnetozones litholigic structure and magnetic susceptibility of the sequence are highly correlative with the qa i and qa ii sections 30 km west of qa iii these sequences demonstrate that the miocene loess deposits are also spatially correlative in stratigraphy present a near continuous sequence of paleoenvironment changes and that magnetic susceptibility is a useful tool for stratigraphic correlation the basal age of qa iii confirms again the onset of asian inland deserts and monsoon dominate climates by the early miocene

archaeological soil and pollen analysis of experimental floor deposits with special reference to butser ancient farm hampshire uk archaeological stratigraphies that may contain floors are often encountered for more than a decade soil micromorphologists working on archaeological sequences have benefited from having access to reference thin sections of ethnoarchaeological and experimental floors including those from the floors of iron age houses reconstructed by the late dr peter reynolds at butser ancient farm hampshire uk this paper reports upon experimental studies mainly carried out at butser during 1990 95 and their suggested application to microstratigraphic and microfacies analysis of occupation sites sampling at butser in 1990 was very much a rescue operation nevertheless fundamental differences in soil micromorphology were found between domestic house beaten floor deposits and those formed in a stable these differences were also reflected in the parallel study of pollen from these deposits with microchemical analyses helping to explain anomalous pollen preservation in the unsuitable soil at butser the limited bulk chemical study produced less clear results but when compared with findings from some roman and early medieval sites in london showed that the chemical trends hinted at butser are probably replicated in some ancient floors a preliminary interdisciplinary study of samples from the london guildhall clearly suggested the potential of such microstratigraphical and microfacies analyses and intimates at the potential of attaining rigorous consensus interpretations stable floor deposits are both organic and phosphate rich with homogeneous soil micromorphological and pollen characteristics beaten floors are much more mineralogenic and heterogeneous in terms of their microfabric and pollen that also indicate trampling in of a wide variety of allocthonous materials the last commonly responsible for raised magnetic susceptibility at archaeological sites these findings prove the worth of the ethnoarchaeological simulations carried out at the moel y gar stable and domestic pimperne house this microfacies approach is viewed as complementary to site reconstruction through macrofossil analysis of beetles and plant remains especially where sites are being investigated at the microstratigraphic level the phosphate content of stabling deposits may allow preservation of pollen in what may otherwise be deemed unsuitable material as demonstrated at butser

symmetric and antisymmetric mass exchanges between the equatorial and off equatorial pacific associated with enso 1 mass exchanges in the upper ocean between the equatorial and off equatorial pacific ocean associated with the el nino southern oscillation enso are investigated using the national centers for environmental prediction ncep ocean assimilation data the data show that enso related meridional mass transport in the northern hemisphere nh is larger than that in the southern hemisphere sh we found that the antisymmetric characteristics are mainly due to a southward shift of themaximum zonal wind stress anomaly during the enso mature phase the ekman and geostrophic transports associated with enso are separated into symmetric and antisymmetric components for the symmetric part the mass divergence over the equatorial pacific by the geostrophic transport is generally larger than the convergence by the ekman transport during the el nino mature phase therefore mass is transported from the equator to off the equator at this time as for the antisymmetric part the ekman transport due to antisymmetric wind stress dominates the geostrophic transport so that the mass is transported from the sh to the nh during the el nino mature phase the net mass transport in the nh is larger than that in the sh a theoretical interpretation and intermediate model experiments support these arguments index terms 4522 oceanography physical el nino 4572 oceanography physical upper ocean processes 4512 oceanography physical currents 4504 oceanography physical air sea interactions 0312 4215 oceanography general climate and interannual variability 3309 keywords enso mass exchange wind stress antisymmetry

uranium series accessory crystal dating of magmatic processes complex and protracted crystallization histories over geologic timescales are recorded in accessory minerals e g zircon allanite although magmatic crystallization was traditionally assumed to occur essentially instantaneously for the purposes of interpreting mineral geochronometers with low absolute time resolution for ancient samples it emerged relatively recently that magmatic crystallization can occur over extended durations this discovery arose from applying high spatial resolution accessory mineral dating techniques for uranium series isotopes to young volcanic and cognate plutonic rocks the emerging pattern from these studies is that individual crystals and crystal populations record crystallization episodes lasting from 1 000 to many hundreds of thousands of years accessory mineral dating of volcanic rocks and cognate plutonic xenoliths opens new research avenues for crystal age fingerprinting that correlates pyroclastic deposits lavas and plutonic rocks by using characteristic age dis

pacific east asian teleconnection how does enso affect east asian climate observational evidence is presented to show a teleconnection between the central pacific and east asia during the extreme phases of enso cycles this pacific east asian teleconnection is confined to the lower troposphere the key system that bridges the warm cold events in the eastern pacific and the weak strong east asian winter monsoons is an anomalous lower tropospheric anticyclone cyclone located in the western north pacific the western north pacific wind anomalies develop rapidly in late fall of the year when a strong warm or cold event matures the anomalies persist until the following spring or early summer causing anomalously wet dry conditions along the east asian polar front stretching from southern china northeastward to the east of japan kuroshio extension using atmospheric general circulation and intermediate models the authors show that the anomalous philippine sea anticyclone results from a rossby wave response to suppressed convective heating which is induced by both the in situ ocean surface cooling and the subsidence forced remotely by the central pacific warming the development of the anticyclone is nearly concurrent with the enhancement of the local sea surface cooling both the anticyclone and the cooling region propagate slowly eastward the development and persistence of the teleconnection is primarily attributed to a positive thermodynamic feedback between the anticyclone and the sea surface cooling in the presence of mean northeasterly trades the rapid establishment of the philippine sea wind and sst anomalies implies the occurrence of extratropical tropical interactions through cold surge induced exchanges of surface buoyancy flux the central pacific warming plays an essential role in the development of the western pacific cooling and the wind anomalies by setting up a favorable environment for the anticyclone sst interaction and midlatitude tropical interaction in the western north pacific

review and revision of cenozoic tropical planktonic foraminiferal biostratigraphy and calibration to the geomagnetic polarity and astronomical time scale planktonic foraminifera are widely utilized for the biostratigraphy of cretaceous and cenozoic marine sediments and are a fundamental component of cenozoic chronostratigraphy the recent enhancements in deep sea drilling recovery multiple coring and high resolution sampling both offshore and onshore has improved the planktonic foraminiferal calibrations to magnetostratigraphy and or modified species ranges this accumulated new information has allowed many of the planktonic foraminiferal bioevents of the cenozoic to be revised and the planktonic foraminiferal calibrations to be reassessed we incorporate these developments and amendments into the existing biostratigraphic zonal scheme in this paper we present an amended low latitude tropical and subtropical cenozoic planktonic foraminiferal zonation we compile 187 revised calibrations of planktonic foraminiferal bioevents from multiple sources for the cenozoic and have incorporated these recalibrations into a revised cenozoic planktonic foraminiferal biochronology we review and synthesize these calibrations to both the geomagnetic polarity time scale gpts of the cenozoic and astronomical time scale ats of the neogene and late paleogene on the whole these recalibrations are consistent with the previous work however in some cases they have led to major adjustments to the duration of biochrons recalibrations of the early middle eocene first appearance datums of globigerinatheka kugleri hantkenina singanoae guembelitrioides nuttalli and turborotalia frontosa have resulted in large changes in the durations of biochrons e7 e8 and e9 we have introduced upper oligocene zone o7 utilizing the biostratigraphic utility of paragloborotalia pseudokugleri for the neogene period major revisions are applied to the fohsellid lineage of the middle miocene and we have modified the criteria for recognition of zones m7 m8 and m9 with additional adjustments regarding the globigerinatella lineage to zones m2 and m3 the revised and recalibrated datums provide a major advance in biochronologic resolution and a template for future progress of the cenozoic time scale

the role of the mean state in meridional mode structure and growth abstractthis study uses a simple linear coupled model to investigate the role of the wes feedback and itcz mean states in meridional mode variability optimal structures that maximize transient growth are calculated for mean states characteristic of boreal spring and boreal fall in the tropical atlantic during boreal spring the leading optimal structure is a zonal mode that propagates westward and does not resemble the observed meridional mode in contrast the leading optimal structure during fall is a sea surface temperature sst monopole over the northern hemisphere nh that propagates equatorward and westward and that closely matches meridional mode variability during this season it is found that the boreal fall optimal growth greatly exceeds growth of the corresponding optimal during boreal spring despite the observed boreal spring peak in atlantic meridional mode variance sensitivity studies are used to explore the role of northern or southern hemisphere initial conditions itcz width and itcz

a simple atmospheric model of the local and teleconnection responses to tropical heating anomalies abstract a minimal complexity model of both the local and remote stationary responses of the atmosphere to tropical heating anomalies is described and demonstrated two levels are recast as baroclinic and barotropic components with thermal advection in the tropics neglected the model is linearized about some idealized and realistic background wind fields and forced with a localized heating for illustration in the tropics the baroclinic responses are familiar from the matsuno gill model these excite barotropic responses by advective interactions with vertical background wind shear the barotropic signals are in turn transmitted to high latitudes only in the presence of barotropic background westerly winds for an el nino like equatorial heating the barotropic response has anticyclones to the north and south of the heating reinforcing opposing the anticyclonic cyclonic baroclinic gyres in the upper lower troposphere with realistic background flows the model reproduces the hemispheric asymmetry

relationship between optimal precursors for indian ocean dipole events and optimally growing initial errors in its prediction using the geophysical fluid dynamics laboratory climate model version 2p1 we explored the precursory disturbances that are most likely to develop into a positive indian ocean dipole iod the dominant spatial patterns of these precursors are defined as the optimal precursors oprs of positive iod as they are more inclined to cause a positive iod than other superimposed initial perturbations in the experiments specifically there are two types of oprs with opposite patterns the surface component of opr 1 opr 2 is an indistinctive west east dipole pattern with a small area of negative positive perturbations to the coast of sumatra and java correspondingly there is a significant west east dipole pattern in the subsurface component of the oprs with the largest values located in the eastern equatorial indian ocean the dominant mode of the time dependent evolutions of the precursors features rapid development of positive iod furthermore the oprs are similar to the optimally growing initial errors oges associated with iod predictions that have been presented in previous studies the shortwave radiation latent heat flux and westward rossby waves play an important role in the time dependent evolution of oges moreover the large values of the oprs are located in the same areas as the sensitive areas of targeted observations identified by the oges this infers that intensive observations over these areas would not only reduce initial errors improve the accuracy of initial fields and decrease the prediction errors but would also detect the precursory signals in advance which substantially improves the forecast skill of iod this article is protected by copyright all rights reserved

phase locking of equatorial atlantic variability through the seasonal migration of the itcz the equatorial atlantic is marked by significant interannual variability in sea surface temperature sst that is phase locked to late boreal spring and early summer the role of the atmosphere in this phase locking is examined using observations reanalysis data and model output the results show that equatorial zonal surface wind anomalies which are a main driver of warm and cold events typically start decreasing in june despite sst and sea level pressure gradient anomalies being at their peak during this month this behavior is explained by the seasonal northward migration of the intertropical convergence zone itcz in early summer the north equatorial position of the atlantic itcz contributes to the decay of wind anomalies in three ways 1 horizontal advection associated with the cross equatorial winds transports air masses of comparatively low zonal momentum anomalies from the southeast toward the equator 2 the absence of deep convection leads to changes in vertical momentum transport that reduce the equatorial wind anomalies at the surface while anomalies aloft remain relatively strong 3 the cross equatorial flow is associated with increased total wind speed which increases surface drag and deposit of momentum into the ocean previous studies have shown that convection enhances the surface wind response to sst anomalies the present study indicates that convection also amplifies the surface zonal wind response to sea level pressure gradients in the western equatorial atlantic where sst anomalies are small this introduces a new element into coupled air sea interaction of the tropical atlantic

season dependent predictability and error growth dynamics for la nina predictions the spring predictability barrier spb is a well known characteristic of enso prediction which has been widely studied for el nino events however due to the nonlinearity of the coupled ocean atmosphere system and the asymmetries between el nino and la nina it is worthy to investigate the spb for la nina events and reveal their differences with el nino this study investigates the season dependent predictability of sea surface temperature sst for la nina events by exploring initial error growth in a perfect model scenario within the community earth system model the results show that for the prediction through the spring season the prediction errors caused by initial errors have a season dependent evolution and induce an spb for la nina events two types of initial errors that often yield the spb phenomenon are identified the first are type 1 initial errors showing positive sst errors in the central eastern equatorial pacific accompanied by a large positive error in the upper layers of the eastern equatorial pacific the second are type 2 errors presenting an sst pattern with positive errors in the southeastern equatorial pacific and a west east dipole pattern in the subsurface ocean the type 1 errors exhibit an evolving mode similar to the growth phase of an el nino like event while the type 2 initially experience a la nina like decay and then a transition to the growth phase of an el nino like event both types of initial errors cause positive prediction errors for nino3 sst and under predict the corresponding la nina events the resultant prediction errors of type 1 errors are owing to the growth of the initial errors in the upper layers of the eastern equatorial pacific for the type 2 errors the prediction errors originate from the initial errors in the subsurface layers of the western equatorial pacific these two regions may represent the sensitive areas of targeted observation for la nina prediction in addition the type 2 errors in the equatorial regions are enlarged by the recharge process from 10 n in the central pacific during the eastward propagation therefore the off equatorial regions around 10 n in the central pacific may represent another sensitive area of la nina prediction additional observations may be prioritized in these identified sensitive areas to better predict la nina events

kelvin and rossby wave contributions to the sst oscillation of enso abstract a simple model of interannual sst oscillation is developed using the two wave components of kelvin and lowest symmetric rossby waves the model dynamics is similar to that of a c hirst except the wind stress is simply parameterized in terms of sst the model is used to investigate the standing oscillation character of sst variation and the transition mechanism by wave reflection at the western and eastern boundaries the standing oscillation of sst in the central and eastern pacific and a weak sst variation in the western pacific are examined in terms of the sst tendencies by oceanic kelvin and rossby waves the kelvin and rossby wave contributions to sst are almost completely canceled by each other in the western pacific but in the eastern pacific the sst variation is determined mainly by the kelvin wave and the rossby wave contribution plays a minor role the wave reflections at the eastern and western boundaries play a negative feedback mechanism to an enso like oscillation the variation

effects of ocean initial perturbation on developing phase of enso in a coupled seasonal prediction model coupled prediction systems for seasonal and inter annual variability in the tropical pacific are initialized from ocean analyses in ocean initial states small scale perturbations are inevitably smoothed or distorted by the observational limits and data assimilation procedures which tends to induce potential ocean initial errors for the el nino southern oscillation enso prediction here the evolution and effects of ocean initial errors from the small scale perturbation on the developing phase of enso are investigated by an ensemble of coupled model predictions results show that the ocean initial errors at the thermocline in the western tropical pacific grow rapidly to project on the first mode of equatorial kelvin wave and propagate to the east along the thermocline in boreal spring when the surface buoyancy flux weakens in the eastern tropical pacific the subsurface errors influence sea surface temperature variability and would account for the seasonal dependence of prediction skill in the nino3 region it is concluded that the enso prediction in the eastern tropical pacific after boreal spring can be improved by increasing the observational accuracy of subsurface ocean initial states in the western tropical pacific

tertiary paleomagnetism of north and south china and a reappraisal of late mesozoic paleomagnetic data from eurasia implications for the cenozoic tectonic history of asia abstract to contribute to the understanding of the cenozoic tectonic history of china and eastern eurasia in general we collected paleomagnetic samples from tertiary rocks in both north and south china our miocene paleomagnetic data for northern china are from four widely separated basalt sections in the inner mongolia autonomous region and shandong province both normal and reversed polarities of the characteristic magnetization are present in the stratigraphie sequence and the mean normal and reversed directions are closely antiparallel to each other the fact that the same characteristic direction was carried by both magnetite and hematite suggests that the hematite was probably formed by auto oxidation processes during primary cooling of the basalts the paleomagnetic data from these four areas also pass a regional generalized fold test the corresponding mean miocene paleomagnetic pole for northern china is longitude 261 6 e latitude 88 3 n a 95 6 4 our early tertiary paleomagnetic results for south china are from two sandstone sections around the city of nanning 22 7 n 108 3 e in guangxi zhuang autonomous region high temperature characteristic directions isolated in 31 samples from five sites pass both tilt and reversal tests the paleomagnetic pole position determined from the five sites lies at longitude 228 0 e latitude 83 6 n a 95 8 5 the tertiary paleomagnetic poles for north and south china are statistically indistinguishable from each other and thus confirm that north and south china were fully assembled at least by the tertiary our new tertiary paleomagnetic data are consistent with the hypothesis that the major continental blocks of north and south china were in the same position as today during the tertiary a critical evaluation and selection of paleomagnetic results from the late jurassic onward for siberia europe and north and south china further corroborate this hypothesis most previously existing jurassic and cretaceous paleomagnetic poles from europe siberia are of uncertain reliability and should not be used for tectonic reconstruction using poles derived from transferring reliable data from other continents we show that the previous paleomagnetic inferences of large eastward displacements between these chinese blocks during the cenozoic are no longer warranted the available paleomagnetic data that meet our acceptance criteria are also of interest concerning the boundary conditions of the propagating extrusion model for asian tectonics additional mesozoic and cenozoic paleomagnetic data from siberia and north and south china are still needed to resolve the smaller second order displacements that appear to characterize the cenozoic tectonic history of this part of asia

pacific east asian teleconnection part ii how the philippine sea anomalous anticyclone is established during el nino development the anomalous philippine sea anticyclone psac conveys impacts of el nino to east asian climate during the mature and decay of an el nino from the winter to ensuing summer it is shown that the anomalous psac forms in fall about one season prior to the peak el nino its strength increases with the el nino intensity and its sign reverses during a la nina the psac formation concurs with abnormal deepening of the east asian trough and with increasing number of northward recurvature of tropical storms in the western pacific the psac establishment is abrupt coupling with a swing from a wet to dry phase of an intraseasonal oscillation iso and often concurrent with early retreat of the east asian summer monsoon the iso becomes inactive after psac establishment the development of the psac is attributed to combined effects of the remote el nino forcing tropical extratropical interaction and monsoon ocean interaction the developing el nino induces off equatorial as cending rossby wave responses and land surface cooling in northeast asia both deepen the east asian trough in fall and induces vigorous tropical extratropical exchange of air mass and heat which enhances the cold air outbreak and initiation of the psac through exciting descending rossby waves the el nino induced indonesian subsidence generates low level anticyclonic vorticity over south asia which is advected by mean monsoon westerly instigating the anomalous psac the iso interacting with the underlying ocean plays a critical role in the abrupt establishment of psac the wind evaporation entrainment feedback tends to amplify suppress iso before after winter northeasterly monsoon commences suggesting the roles of atmosphere ocean inter action and the seasonal march of background winds in changing the philippine sea iso intensity and maintaining psac

phase space representation and characteristics of el nino la nina the variability of el nino la nina events was analyzed in a low dimensional phase space a concept derived from dynamic system theory the space time extended eofs derived from the observed monthly mean sst field over tropical pacific were used as the basis of the phase space that describes the time evolution of enso signals it was shown that the essential features of the enso variability such as the irregular oscillation the phase locking to the annual cycle and the interdecadal changes in its propagation and onset can be effectively represented by a three dimensional phase space the typical el nino la nina life cycle is four years with its mature phases in boreal winter the intensity of the enso signal within one life cycle is closely linked to the frequency of its occurrence onset the interdecadal variability of the enso signals is characterized by both the intensity and the frequency of occurrence displaying an irregularity with the gross feature comparable to the regime behavior and intermittency of some low dimensional chaotic systems

pb diffusion in zircon abstract chemical diffusion of ti under anhydrous conditions at 1 atm and under fluid present elevated pressure 1 1 1 2 gpa conditions has been measured in natural zircon the source of diffusant for 1 atm experiments was a zro2 tio2 zircon mixture with experiments run in crimped pt capsules diffusion experiments done in the presence of h2o co2 fluid were run in a piston cylinder apparatus using a source of ground tio2 zrsio4 and sio2 with oxalic acid added to produce h2o co2 vapor and partially melt the solid source material yielding an assemblage of rutile zircon melt vapor nuclear reaction analysis nra with the resonant nuclear reaction 48ti p 49v was used to measure diffusion profiles for both sets of experiments the following arrhenius parameters were obtained for ti diffusion normal to cover the temperature range 1350 1550 c at 1 atm d ti 3 33 10 2 exp 754 56 kj mol 1 r t m 2 s 1 ti diffusivities were found to be similar for experiments run under fluid present conditions a fit to all of the data yields the arrhenius relation d 1 34 102 exp 741 46 kj mol 1 rt m2 s 1 these data suggest that zircon should be extremely retentive of ti chemical signatures indicating that the recently developed ti in zircon crystallization geothermometer watson e b harrison t m 2005 zircon thermometer reveals minimum melting conditions on earliest earth science 308 841 844 will be quite robust in preserving temperatures of zircon crystallization titanium diffuses somewhat faster in zircon than larger tetravalent cations u th and hf but considerably more slowly than pb the ree and oxygen hence ti crystallization temperatures may be retained under circumstances when radiometric ages or other types of geochemical information are lost

geoarchaeology in an urban context the uses of space in a phoenician monumental building at tel dor israel abstract interpretation of past urban societies in the near east whose settlements are known mostly as tell sites is largely based on macro stratigraphy and on the association of architecture with macroscopic artifacts analyses of sediments common in prehistoric sites are rare in tell sites here we show the results of a detailed geoarchaeological study of the micro stratigraphy of a sedimentary sequence associated with early iron age phoenician monumental architecture the study involves mineralogical micromorphological and phytolith analyses and provides new insights into the stratigraphic sequence and the use of architectural spaces the sedimentary sequence examined comprises alternating layers of gray fill deposits and white floors we show that floors made from local calcareous sandstone in the lower part of the sedimentary sequence were heated and are thus in effect plaster floors a concentration of micro laminated trampled fish remains above the most elaborate of these plaster floors indicates activities related to fish processing fine white layers in the upper part of the sedimentary sequence that were considered as plaster based on macroscopic examination are in fact composed almost entirely of opaline grass phytoliths the phytoliths appear in an undulating micro laminated structure and are associated with dung spherulites and phosphate nodules thus probably reflecting livestock penning the formation of phytolith floors involves extensive volume reduction due to the degradation of the organic material and this may result in floor subsidence a phenomenon that is often observed in archaeological sites most fill deposits include macroscopic and microscopic remains of wood ash bones phytoliths charcoal ceramics plaster and mollusk shells reflecting the debris produced from household activities this study shows how a combination of macro stratigraphy with microscopic and mineralogical analyses of the sediments within architectural spaces can provide information on the varying ways in which the space was used through time and also contributes to solving macro stratigraphic problems

the influence of atmospheric convection on the interaction between the indian ocean and enso abstractin recent years it has been proposed that a negative positive indian ocean dipole iod in boreal autumn favors an el nino la nina at a lead time of 15 months observational analysis suggests that a negative iod might be accompanied by easterly anomalies over the western pacific such easterlies can enhance the western pacific warm water volume thus favoring el nino development from the following boreal spring onward however a gill model response to a negative iod forcing would lead to nearly zero winds over the western pacific the authors hypothesize that a negative iod or even a cool western indian ocean alone leads to low level air convergence and hence enhanced convectional heating over the maritime continent which in turn amplifies the wind convergence so as to cause easterly winds over the western pacific this hypothesis is tested by coupling an idealized indian ocean model and a convective feedback model over the maritime continent to the zebiak cane model it is found that for a

on the termination of el nino a feature of the end phase of recent el nino periods is thermocline shallowing to normal depths in the central and eastern equatorial pacific before sea surface temperature sst returns to normal also characteristic of el nino periods is a late in the year shift of the el nino equatorial westerly wind anomalies from symmetric about the equator to centered south of the equator we show that the directly forced ocean response to this shift produces thermocline shallowing like that observed the wind shift may result from the normal seasonal evolution of pacific waters warmer than 28 c these shift from being relatively symmetric about the equator in october november to concentrated south of the equator in december january thus the seasonal cycle may be a central part of the mechanism of el nino termination

oligocene miocene magnetic stratigraphy carried by biogenic magnetite at sites u1334 and u1335 equatorial pacific ocean 1 sediments from the equatorial pacific ocean at the integrated ocean drilling program sites u1334 and u1335 record reliable magnetic polarity stratigraphies back to 26 5 ma late oligocene at sedimentation rates usually in the 5 20 m myr range putative polarity subchrons that do not appear in current polarity timescales occur within chrons c5acr c5adn and c5bn 1r at site u1335 and within chrons c6aar 2r c6br c7ar and c8n 1n at site u1334 subchron c5dr 1n 17 5 ma is recorded at both sites supporting its apparent recording in the south atlantic ocean and has an estimated duration of 40 kyr the oligocene miocene calcareous oozes have magnetizations carried by submicron magnetite as indicated by thermal demagnetization of magnetic remanences the anhysteretic remanence to susceptibility ratio and magnetic hysteresis parameters transmission electron microscopy of magnetic separates indicates the presence of low titanium iron oxide magnetite grains with size 50 100 nm and shape similar to modern and fossil bacterial magnetite supporting other evidence that biogenic submicron magnetite is the principal remanence carrier in these sediments in the equatorial pacific ocean low organic carbon burial arrests microbial pore water sulfate reduction thereby aiding preservation of bacterial magnetite

micromorphological analysis of sediments at the bronze age site of mitrou central greece patterns of floor construction and maintenance the study of settlement sites is usually based on the analysis of architectural or cultural phases the sediments that constitute the excavated deposits inside or outside houses are rarely studied this work presents micromorphological analysis of sediments at the prehistoric site of mitrou a small tidal islet in central greece unusually long archaeological sequences have been excavated ranging from the early bronze age to the early iron age ca 2400 900 bce the occupational deposits in the early and middle bronze age are characterized by meticulous maintenance practices with multiple replastered floor sequences these include surfaces made of debris produced inside houses by day to day activities in this way an impressive thick sequence of overlapping worn out floors and occupational deposits is produced with a characteristic finely layered macroscopic appearance there is no clear association of a building phase with a single floor level but rather with a thick sequence of floor build up this practice ends in the late bronze age and from then on floors are not frequently repaired and their construction technique is more standardized usually a relative thin sequence of one or two floors is associated with a new architectural phase the observed change is broadly correlated with the rise of a prepalatial political elite at mitrou the contrasting maintenance techniques also are relevant to discussions about differences between tells and flat settlements until the beginning of the late bronze age mitrou s indoor surfaces are those of a tell site whereas after that its surfaces resemble those of a flat settlement in mitrou it appears that this change is related to a different perception of construction and maintenance of floors that in turn should be traced to the pattern of reconstruction of entire houses these changes have a social significance that may reflect differences in household processes and use of space

contrasting the indian and east asian monsoons implications on geologic timescales the surface winds over the arabian sea and south china sea are meaningful indicators for the strength of the indian monsoon and east asian monsoon respectively paleo monsoon variability has been studied through analysis of sediment records from these two monsoon regions to facilitate interpretation of these records we focus on the impacts of internal and external forcing of the monsoon system by contrasting the annual cycle and interannual variability of two subsystems the monsoon over the indian sector 40 105 e and over the east asian sector 105 160 e differences in the annual cycle within these subsystems arise primarily from the different land ocean configurations that determines atmospheric response to the solar forcing thus factors that drive intensities of the monsoonal annual cycle share common features with the external geographic and orbital forcing that controls paleomonsoon variability we show that the differences in interannual variations between the two monsoon subsystems are primarily due to internal factors of the coupled atmosphere ocean land system such as remote impacts of el nin o la nin a and local monsoon ocean interactions the mechanisms that operate on interannual to interdecadal timescales may differ fundamentally from that on geologic orbital timescales the low level flows over the east asia and australia are essentially established by geographic forcing the amplification of the australia summer monsoon during increased solar precession is likely caused by an enhanced east asian winter monsoon rather than following an enhanced indian summer monsoon as on the interannual timescale it is also found that el nin o influences the low level flow moderately over the arabian sea but to a greater extent over the south china sea as such large changes in the pacific thermal conditions may significantly alter the intensity of the east asian monsoon but not the indian monsoon

el nino and la nina abstract el nino and la nina are the two complementary phase of the southern oscillation during e1 nina the area of high sea surface temperatures increases while the atmospheric convection zones of the tropical pacific expand and merge so that there is a tendency toward spatially homogeneous conditions la nina is associated with low sea surface temperatures near the equator with atmospheric convergence zones that are isolated from each other and with spatial wales smaller than those of el nina it is proposed that both phases of the southern oscillation can be attributed to unstable interactions between the tropical ocean and atmosphere during el nina the increase release of latent heat to the atmosphere drives the instability during la nina when the heating of the atmosphere decreases the compression of the convection into smaller and smaller areas permits an instability that intensifies the trade winds and the oceanic currents the unstable air sea interactions are modulated by the seasonal m

miocene magnetostratigraphy from equatorial pacific sediments odp site 1218 leg 199 pliocene and miocene magnetostratigraphy from odp site 1218 equatorial pacific has been obtained by measurements made on u channel samples augmented by about 50 discrete samples u channel samples were measured at 1 cm intervals and stepwise demagnetized in alternating fields up to a maximum peak field of 80 mt the component magnetization directions were determined by principal component analysis for demagnetization steps in the 20 60 mt peak field range a relatively small number of discrete samples were subject to both thermal and alternating field af demagnetization and gave results compatible with u channel measurements magnetostratigraphy from u channel samples are compared with shipboard data that were based on blanket demagnetization at peak af fields of 20 mt u channel measurements add more detail to the magnetostratigraphic record and allow identification of thin polarity zones especially in the upper part of the section were the sedimentation rates are very low 2 m myr the component magnetization directions determined from u channel measurements also gave more reliable and precise estimates of inclination paleolatitude the magnetostratigraphy from site 1218 can be unambiguously correlated with the reference geomagnetic polarity time scale and gives a means of dating the sedimentary sequence both miocene pliocene and oligocene miocene stage boundaries were easily identified from the magnetostratigraphic record although calculation of paleomagnetic poles is hindered by the low precision of the cores azimuthal orientation the data from both u channel and discrete samples allow determination of the paleolatitude of the site through time with good precision paleomagnetic data indicate that the paleolatitude of site 1218 has increased form nearly equatorial latitude in the oligocene to

micromorphology of earth building materials toward the reconstruction of former technological processes protohistoric and historic periods abstract earth building materials are often identified in the field but very few microscopic studies focus on the identification of the technological processes which produced them especially in temperate contexts the identification of such processes is crucial as it is the basis of the archaeological investigations concerning both the origin and the diffusion of building technologies the aim of this paper is to describe and expand the definitions of the microscopic features typically associated with the steps associated with the chaines operatoires of earth building on the basis of micromorphological analyses and development of a reference collection of earthen materials the results have identified a range of characteristics associated with past earthen construction processes including microscopic features linked to earth moisture when mixing degree of mixing the moisture of the earth when applied to the walls or on the ground as well as those related to compaction and shear stress that are all important factors that explain former processes strong compaction of earth in a dry state is typical of rammed earth medium compaction together with a higher degree of moisture is typical of cob wall and perpendicular organization of the earth on the face of the wall indicates the use of a formwork or shuttering thus the use of microscopic features identified from analysis of vernacular and ancient materials helps to characterize and identify processes such as roman rammed earth at the site of rirha morocco it also highlights cultural specificities such as the diversity of cob wall and earth flooring processes during the iron age as on the site of lattara southern france and the degree of compaction of rammed earth wall for the roman period analyses carried out in a robust archaeological framework reveal that each wall present a specific vertical and horizontal organization linked to the building processes at macroscopic and microscopic scales which should be taken into account when studying and sampling earthen walls in order to correctly identify former techniques

the response of enso flavors to mid holocene climate implications for proxy interpretation the response of el nino southern oscillation enso to mid holocene boundary conditions remains an open question paleoclimate proxies and climate model simulations do not agree in the magnitude of the reduction of enso variability while recent proxy evidence from fossil corals from the central pacific show that the reduction in mid holocene enso variability compared to the end of the twentieth century is not different from the reduction during other holocene time intervals this is inconsistent with the interpretation of lake and ocean sediment records from the eastern pacific which show a significant reduction compared to all other holocene periods in order to reconcile the seemingly conflicting proxy evidence from the eastern and central pacific we hypothesize that enso remained active during the mid holocene however there was a change in the spatial pattern of the sea surface temperature anomalies also known as enso flavors using national center for atmospheric research s community climate system model version 4 forced with mid holocene orbital conditions we find that the frequency of occurrence of the strongest eastern pacific ep events decreases in the mid holocene and their variance is reduced by 30 while the frequency of central pacific cp events slightly increases and their variance does not change we also find a shift in the seasonality of ep events but not in that of cp events lastly mid holocene ep events develop more slowly and decay faster the differential response of enso flavors to mid holocene forcing is remotely forced by the west pacific where a weakening of the trade winds in early boreal spring in the mid holocene initiates an anomalous downwelling annual kelvin wave which reaches the eastern pacific during the enso development season weakens the upper ocean stratification and results in reduced enso upwelling feedback the simulated reduction in the ep flavor versus the cp flavor in the mid holocene is consistent with proxy evidence the teleconnection patterns of the two flavors with temperature precipitation and salinity are distinct and proxies from different regions of the pacific might be recording variability associated with only one of the flavors or some combination of their relative effects

paleomagnetism of the early miocene kani group in southwest japan and its implication for the opening of the japan sea paleomagnetic directions of a volcanic and sedimentary sequence of the kani basin ranging from 22 to 15 ma show a clockwise declination shift of about 50 degree this result implies that detectable rotation of southwest japan did not occur in this period but after 15 ma the initial opening of the japan sea before 15 ma might have caused a southeastward translation of southwest japan which was then followed by clockwise rotation between 16 and 14 ma

a mechanism for decadal changes of enso behavior roles of background wind changes this study explains why a number of el nino properties period amplitude structure and propagation have changed in a coherent manner since the late 1970s and why these changes had almost concurred with the pacific decadal climate shift evidence is presented to show that from the pre shift 1961 1975 to the post shift 1981 1995 epoch significant changes in the tropical pacific are found in the surface winds and temperature whereas changes in the thermocline are uncertain numerical experiments with the cane and zebiak model demonstrate that the decadal changes in the surface winds qualitatively reproduce the observed coherent changes in el nino properties the fundamental factor that altered the model s el nino is the decadal changes of the background equatorial winds and associated upwelling the annual cycle is also necessary for the mean state to modulate el nino from the pre to post shift epoch the changes in the background winds and upwelling modify the structure of the coupled mode eastward displacement of the equatorial westerly anomalies by reallocating anomalous atmospheric heating and sst gradient along the equator this structural change amplifies the enso cycle and prolongs the oscillation period by enhancing the coupled instability and delaying transitions from a warm to a cold state or vice versa the changes in the mean currents and upwelling reduce the effect of the zonal temperature advection while enhance that of the vertical advection thus the prevailing westward propagation is replaced by eastward propagation or standing oscillation our results suggest a critical role of the atmospheric bridge that rapidly conveys the influences of extratropical decadal variations to the tropics and the possibility that the pacific climate shift might have affected el nino properties in the late 1970s by changing the background tropical winds and the associated equatorial upwelling

mechanisms of locking of the el nino and la nina mature phases to boreal winter the peaks of el nino in the cane zebiak cz model tend to appear most frequently around november when the ocean rossby waves which were amplified during the previous unstable season february may turn back to the eastern pacific and when the local instability in the eastern pacific is very weak the peaks of la nina in the cz model occur most frequently in boreal summer in contrast to the observed counterpart that usually occurs in boreal winter sensitivity experiments indicate that the phase locking of the la nina to boreal summer is primarily caused by seasonal variations of the tropical convergence zone which regulate convective heating through atmospheric convergence feedback the observed thermocline and the wind anomalies in the western pacific exhibit considerable seasonal variations these were missed in the original cz model in a modified cz model that includes the seasonal variations of the western pacific wind anomalies and the basic state thermocline depth the peaks of la nina preferably occur in boreal winter suggesting that the seasonal variation of the western pacific surface wind anomalies and the mean thermocline depth are critical factors for the phase locking of the mature la nina to boreal winter the mechanisms by which these factors affect enso phase locking are also discussed

an investigation of the el nino southern oscillation cycle with statistical models 2 model results we have constructed two sets of linear statistical models for predicting equatorial pacific sea surfaces temperatures ssts from the tropical wind field and from the near global sea level pressure slp field the wind models were constructed to encompass the domains relevant to the forcing of trapped equatorial waves associated with the el nino thus they provide a measure against which the performance of some simple physical models may be compared the slp models were constructed to better define the roles of the observed motion of slp features and changes in the southern oscillation as they relate to subsequent equatorial ssts the wind models were designed to provide forecasts at lead times of 1 to 5 months and the slp models were designed to provide forecasts at lead times of 7 to 16 months the models were constructed using a combination of extended empirical orthogonal functions and canonical correlation analysis a technique we found well suited to the handling of large data sets and the analysis of model structures forecast skills were estimated by cross validation the results show that the wind field models do well at predicting eastern and central pacific ssts during much of the year and their structure is in general agreement with the idea that kelvin rossby waves initiated by remote wind forcing are responsible for much of the observed sst signal however the models do not track the onset of warm and cold events well particularly in the eastern pacific this suggests that well organized consistent wind anomalies are not responsible for the initial temperature anomalies the slp models did not do well in least squares sense but performed skillfully when applied with a simple el nino no el nino decision rule at lead times of up to 16 months

trade wind fluctuations associated with el nino southern oscillation events wind fields associated with el nino southern oscillation enso events are investigated using 20 years 1965 1984 of monthly mean wind vectors along a ship track from 30 s to 30 n in the western pacific ocean the analysis shows that off equatorial trade wind fluctuations play a significant role in enso events in particular the meridional component is found to have strong deviations during enso events southerly deviations from the mean meridional field are noted during the enso events of 1965 1972 1976 and 1982 the trade wind deviations are consistent with atmospheric convergence into an equatorial convection region to the east of the ship track it is hypothesized that these wind fields can cause anomalous oceanic mass convergence toward the equator

paleoposition of southwest japan at 16 ma implication from paleomagnetism of the miocene ichishi group abstract new paleomagnetic data from shallow marine sediments of the ichishi group suggest a clockwise tectonic rotation of southwest japan in the middle miocene samples have been collected from mud or tuff layers at 17 sites stability of remanent magnetization has been examined by using alternating field and thermal demagnetization the polarity sequence composed of four normal and seven reversed polarity sites is correlated to polarity epoch 16 15 2 17 6 ma based on micropaleontological assignment of the upper ichishi group to blow s zone n8 the mean paleomagnetic direction of the 11 sites shows an anomalous declination toward the northeast this result suggests that southwest japan was subjected to a clockwise rotation through 45 since 16 ma the clockwise rotation can be explained by the drift of southwest japan associated with the spreading of the japan sea during the middle miocene

enso simulated by intermediate coupled models and evaluated with observations over 1970 98 part i role of the off equatorial variability enso simulations are investigated in 30 yr integrations of various intermediate coupled models and compared with observed sst wind and thermocline depth anomalies over the tropical pacific the cane and zebiak model simulates warm events with a period close to the observations but with westerlies that are located 30 8 east of them and thermocline anomalies in the western pacific that are much shallower between two warm events the model simulates a series of three weak and short cold sst peaks and hardly ever simulates easterlies the sst in the eastern equatorial pacific is not sensitive to thermocline depth anomalies but to the anomalous downwelling of surface currents induced by ekman shear the model simulates a pair of very strong cyclonic wind stress curl anomalies on both sides of the equator in the eastern off equatorial domain between 78 and 158 lat these are necessary to maintain the oscillatory regime so are the ocean meridional rossby modes higher than 5 the thermocline zonal slopes required to balance the off equatorial curl anomalies are about three times steeper than the ones required to balance the zonal stress along the equator thus the off equator exerts an excess of zonal pressure which by continuity affects the equatorial ocean and plays a crucial role in reversing and triggering the growing events six months after the warm peaks the whole ocean between 158s and 158n is significantly upwelled the equatorial oceanic heat content is recharged from the south prior to a warm event contrary to simulations when the model is driven by observed wind anomalies increasing the friction in the baroclinic ocean does not decrease the off equatorial variability but significantly alters the low frequency oscillations that are no longer enso like introducing the parameterization of subsurface temperature derived from hydrographic profiles in the ocean component does not allow the coupled model to recover cold events as in a forced context introducing the parameterization of convection derived from high cloud temperature measurements is the most effective improvement but results still poorly agree with observations and are in contrast with the simulations driven by observed sst biased toward westerlies in the central pacific upwelled thermocline in the west and warm sst in the east thus modifying the ocean component only or the atmosphere only does not have the same impact on simulations as in a forced context the coupling allows new mechanisms to grow and govern the model behavior one of them is the slow meridional oceanic mass adjusment in quasi sverdrup balance with the winds

earliest salt working in the world from excavation to microscopy at the prehistoric sites of ţolici and lunca romania abstract since the early neolithic salt has played an important role in the social and economic development of populations consequently the study and comprehension of salt management strategies have become a significant component of current archaeological research this study is part of an interdisciplinary research program consisting of excavations and detailed analyses on two early neolithic salt working sites situated in the sub carpathian region of romania lunca and olici county neam these remarkably well preserved sites are characterised by stratified deposits several meters thick detailed stratigraphic descriptions were followed by optical microscopy analysis soil micromorphology and scanning electron microscopy sem coupled with geochemical analysis eds the aim of these analyses was to identify specific sedimentary petrographic and chemical characteristics that could be linked to salt working process the results enable us to describe the main site formation process over time and to detect chemical components of edible salt na and cl in early neolithic ashes these new data consolidate previous interpretations of the operating procedures implemented from the early neolithic to the bronze age two techniques appear to have been preferentially adopted pouring natural brine onto combustion structures during the early neolithic and evaporation in specific ceramic containers from the chalcolithic onwards

age of the n7 n8 m4 m5 planktonic foraminifera zone boundary constraints from the zircon geochronology and magnetostratigraphy of early miocene sediments in ichishi japan abstract the age assigned to the miocene n7 n8 m4 m5 planktonic foraminifera zone boundary is markedly different from the astronomically tuned neogene time scales published in 2004 atnts2004 and 2012 atnts2012 this difference is primarily because of the lack of reliable assignment of the zone boundary to magnetostratigraphy which needs to be resolved for the better refinement of the geologic time scale our previous biostratigraphic results from an onland sedimentary sequence of the upper ichishi group in central japan allow location of the stratigraphic position of the lowest occurrence datum lod of praeorbulina sicana a key planktonic foraminifera species for defining the n7 n8 m4 m5 zone boundary in this study we performed laser ablation multiple collector inductively coupled plasma mass spectrometry u pb dating on zircons from two felsic tuff beds in the ichishi sequence the age of the zone boundary is approximated by a u pb age of 17 03 0 11 ma for a tuff bed 2 m above the boundary we also conducted a magnetostratigraphic analysis in which site mean characteristic remanent magnetization directions were determined for 19 sites and showed a reverse normal reverse r n r stratigraphic change in polarity the n7 n8 m4 m5 zone boundary is within the upper reverse polarity zone the r n r sequence can be correlated with a stratigraphic portion corresponding to chrons c5dr c5dn c5cr hence the age of the zone boundary is within chron c5cr our results are thus compatible with the age 16 97 ma assigned to the boundary in atnts2004 rather than atnts2012 and should be considered when the neogene time scale is updated a normal polarity subzone found in the upper reverse polarity zone can also be dated at 17 0 ma and is probably correlated with a short normal polarity episode in chron c5cr in terms of tectonic rotation the site mean magnetization directions determined in this study suggest an 35 clockwise rotation in ichishi with respect to the north china block in the asian continent since 17 2 ma the upper boundary age of chron c5dn clockwise rotation of southwest japan which occurred in association with backarc opening of the japan sea was probably in progress during deposition of the upper ichishi group sediments

formation of the cold tongue and enso in the equatorial pacific basin abstract this paper proposes a mechanism that explains how coupled dynamics alone can spontaneously give rise to a realistic west east asymmetric mean state and an enso like interannual variability without requiring the existence of an external preexisting west east asymmetry in circulation the essence of the newly proposed mechanism is that the basinwide ocean atmosphere coupling acts to reduce the effective restoring force as a result the coupled oceanic waves travel more and more slowly within the equatorial ocean basin as the coupling strength increases when the coupling strength reaches a critical value the zonally leveled thermocline becomes unstable as a result of the weakening of the effective restoring force at which the theoretical limit of the traveling timescale would be infinite without nonlinearity due to nonlinearity in the coupled system this primary air sea interaction instability leads to a west east asymmetric mean state in which the atmosphere has a prevailing easterly and the

a further investigation of the recharge oscillator paradigm for enso using a simple coupled model with the zonal mean and eddy separated the recharge oscillator paradigm for enso is further investigated by using a simple coupled model which externally includes the equatorial wave dynamics represented by the kelvin and gravest symmetric rossby waves to investigate the role of eddies in the pacific basin wide adjustment to the wind forcing particularly at the western and eastern boundaries the zonal mean and eddy parts are treated separately in the current model it is clearly demonstrated that the basin wide adjustment of the tropical ocean is accomplished by the net mass transport induced by the meridional transport over the tropical ocean interior and the zonal fluxes at the boundaries with a reasonable choice of the reflection coefficient particularly at the western boundary the meridional transport plays a bigger role than the zonal boundary flux and determines the sign of zonal mean thermocline depth tendency in a way that the discharge of equatorial mass in the warm phase and recharge in the cold phase serve as a phase transition mechanism of the coupled system the meridional mass transport is induced mainly by a geostrophic current associated with the east west slope of thermocline depth established quickly by the wind forcing also discussed in this paper is the difference between the recharge oscillator and the delayed oscillator in explaining the phase transition mechanism of enso

chaotic oscillations of tropical climate a dynamic system theory for enso abstract based on first principles a theoretical model for el nino southern oscillation enso is derived that consists of prognostic equations for sea surface temperature sst and for thermocline variation considering only the large scale equatorially symmetric standing basin mode yields a minimum dynamic system that highlights the cyclic chaotic and season dependent evolution of enso for a steady annual mean basic state the dynamic system exhibits a unique limit cycle solution for a fairly restricted range of air sea coupling the limit cycle is a stable attractor and represents an intrinsic interannual oscillation of the coupled system the deepening rising of the thermocline in the eastern western pacific leads eastern pacific warming by a small fraction of the cycle which agrees well with observation and plays a critical role in sustaining the oscillation when the nonlinear growth of sst anomalies reaches a critical amplitude the delayed response of thermocline adjustment provides a n

on the atmospheric responses to tropical pacific heating during the mature phase of el nino the atmospheric heating and sea surface temperature sst anomalies during the mature phase of el nino are observed to show both eastern and western pacific anomaly patterns with positive anomalies in the equatorial eastern central pacific and negative anomalies in the off equatorial western pacific the detailed spatial patterns of the heating anomalies differ from the sst anomalies the heating anomalies are more equatorially confined than the sst anomalies and maxima of positive and negative heating anomalies are located farther to the west than the sst anomalies the gill zebiak atmospheric model assumes that the atmospheric initial heating has the same spatial patterns as the sst anomalies this assumption results in some unrealistic model simulations for el nino when the model heating anomaly forcing is modified to resemble the observed heating anomalies during the mature phase of el nino the model simulations have been improved to 1 successfully simulate equatorial easterly wind anomalies in the western pacific 2 correctly simulate the position of maximum westerly wind anomalies and 3 reduce unrealistic easterly wind anomalies in the off equatorial eastern pacific this paper shows that off equatorial western pacific negative atmospheric heating or cold sst anomalies are important in producing equatorial easterly wind anomalies in the western pacific these off equatorial cold sst anomalies in the western pacific also contribute to equatorial westerly wind anomalies observed in the central pacific during the mature phase of el nino although off equatorial cold sst anomalies in the western pacific are smaller than equatorial positive sst anomalies in the eastern pacific they are enough to produce atmospheric responses of comparable magnitude to the equatorial eastern pacific this is because the atmospheric mean state is convergent in the western pacific and divergent in the equatorial eastern pacific by either removing the atmospheric mean convergence or removing off equatorial cold sst anomalies in the western pacific the atmospheric responses show no equatorial easterly wind anomalies in the western pacific in the gill zebiak model the mean wind divergence field is an important background state whereas the mean sst is secondary

a simple model of climatological rainfall and vertical motion patterns over the tropical oceans abstract a simple model is developed that predicts climatological rainfall vertical motion and diabatic heating profiles over the tropical oceans given the sea surface temperature sst using statistical relationships deduced from the 40 yr ecmwf re analysis era 40 the model allows for two modes of variability in the vertical motion profiles a shallow mode responsible for all boundary layer convergence between 850 hpa and the surface and a deep mode with no boundary layer convergence the model is based on the argument expressed in the authors companion paper that boundary layer convergence can be usefully viewed as a forcing on deep convection not just a result thereof the shallow mode is either specified from satellite observations or modeled using a simple mixed layer model that has sst as well as 850 hpa geopotential height winds and temperature as boundary conditions the deep mode amplitude is empirically shown to be proportional to a simple measure of conditional instability in conve

westerly wind bursts enso s tail rather than the dog westerly wind bursts wwbs in the equatorial pacific occur during the development of most el nino events and are believed to be a major factor in enso s dynamics because of their short time scale wwbs are normally considered part of a stochastic forcing of enso completely external to the interannual enso variability recent observational studies however suggest that the occurrence and characteristics of wwbs may depend to some extent on the state of enso components implying that wwbs which force enso are modulated by enso itself satellite and in situ observations are used here to show that wwbs are significantly more likely to occur when the warm pool is extended eastward based on these observations wwbs are added to an intermediate complexity coupled ocean atmosphere enso model the representation of wwbs is idealized such that their occurrence is modulated by the warm pool extent the resulting model run is compared with a run in which the wwbs are stochastically applied the modulation of wwbs by enso results in an enhancement of the slow frequency component of the wwbs this causes the amplitude of enso events forced by modulated wwbs to be twice as large as the amplitude of enso events forced by stochastic wwbs with the same amplitude and average frequency based on this result it is suggested that the modulation of wwbs by the equatorial pacific sst is a critical element of enso s dynamics and that wwbs should not be regarded as purely stochastic forcing in the paradigm proposed here wwbs are still an important aspect of enso s dynamics but they are treated as being partially stochastic and partially affected by the large scale enso dynamics rather than being completely external to enso it is further shown that wwb modulation by the large scale equatorial sst field is roughly equivalent to an increase in the ocean atmosphere coupling strength making the coupled equatorial pacific effectively self sustained

suppression of el nino during the mid holocene by changes in the earth s orbit a number of recent reports have interpreted paleoproxy data to describe the state of the tropical pacific especially changes in the behavior of the el nino southern oscillation enso over the holocene these interpretations are often contradictory especially for the eastern tropical pacific and adjacent areas of south america here we suggest a picture of the mid holocene tropical pacific region which reconciles the data enso variability was present throughout the holocene but underwent a steady increase from the mid holocene to the present in the mid holocene extreme warm el nino events were smaller in amplitude and occurred less frequently about a mean climate state with a cold eastern equatorial pacific and largely arid coastal regions as in the present climate this picture emerges from an experiment in which a simple numerical model of the coupled ocean atmosphere system in the tropical pacific was driven by orbital forcing we suggest that the observed behavior of the tropical pacific climate over the mid to late holocene is largely the response to orbitally driven changes in the seasonal cycle of solar radiation in the tropics which dominates extratropical influences

comparison of the initial errors most likely to cause a spring predictability barrier for two types of el nino events in this paper the spring predictability barrier spb problem for two types of el nino events is investigated this is enabled by tracing the evolution of a conditional nonlinear optimal perturbation cnop that acts as the initial error with the biggest negative effect on the el nino predictions we show that the cnop type errors for central pacific el nino cp el nino events can be classified into two types the first are cp type 1 errors possessing a sea surface temperature anomaly ssta pattern with negative anomalies in the equatorial central western pacific positive anomalies in the equatorial eastern pacific and accompanied by a thermocline depth anomaly pattern with positive anomalies along the equator the second are cp type 2 errors presenting an ssta pattern in the central eastern equatorial pacific with a dipole structure of negative anomalies in the east and positive anomalies in the west and a thermocline depth anomaly pattern with a slight deepening along the equator cp type 1 errors grow in a manner similar to an eastern pacific el nino ep el nino event and grow significantly during boreal spring leading to a significant spb for the cp el nino cp type 2 errors initially present as a process similar to a la nina like decay prior to transitioning into a growth phase of an ep el nino like event but they fail to cause a spb for the ep el nino events the cnop type errors are also classified into two types ep type 1 errors and 2 errors the former is similar to a cp type 1 error while the latter presents with an almost opposite pattern both ep type 1 and 2 errors yield a significant spb for ep el nino events for both cp and ep el nino their cnop type errors that cause a prominent spb are concentrated in the central and eastern tropical pacific this may indicate that the prediction uncertainties of both types of el nino events are sensitive to the initial errors in this region the region may represent a common sensitive area for the targeted observation of the two types of el nino events

estimates of large scale divergence in the lower troposphere over the western equatorial pacific a network of 915 mhz wind profilers measured half hourly lower tropospheric winds over the western equatorial pacific with vertical resolutions as high as 100 m during november 1992 through february 1993 the intensive observing period iop of the tropical ocean global atmosphere coupled ocean atmosphere response experiment toga coare these wind data are used in conjunction with collocated surface wind measurements to examine the near surface divergent flow over the western pacific warm pool during austral summer as well as the synoptic scale variability of divergence in both time and space the synoptic scale wind field estimated from profiler data exhibits stronger near surf ace divergence than sonde based estimates from the same time period temporal variations of the lower tropospheric divergence profiles are described by three vertical structure functions derived from varimax rotated eigenvector analysis one vertical mode appears to be associated with deep convection one with near surface processes and one with shallower convection these structure functions vary zonally across the coare region with the convective modes having convergence maxima at lower elevations to the west of the intensive flux array ifa than over and east of it

the nonnormal nature of el nino and intraseasonal variability abstract the idea that intraseasonal variability in the tropical west pacific can act as an effective means of stochastically forcing enso episodes is explored using the ideas of generalized linear stability theory as they apply to nonnormal dynamical systems the physical attributes of the coupled ocean atmosphere system in the tropics that allow perturbations with structures that are dissimilar to enso to act as precursors for enso episodes are examined using a coupled ocean atmosphere model two particularly important factors are identified that contribute to the nonnormality of the coupled system nonsolar atmospheric heating directly related to sst changes and the dissimilarity between the equatorial ocean wave reflection process at eastern and western boundaries the latter is intrinsic to the dynamics of the ocean while the former is related to the presence of the west pacific warm pool and its relationship with the walker circulation