propagation and mechanism of decadal upper ocean variability in the north pacific n n two types of anomaly pathways associated with decadal thermocline variability in the north pacific ocean are identified on constant density surfaces isopycnals one westward and the other southwestward around the subtropical gyre a theory based on two baroclinic planetary wave modes in the thermocline is proposed to account for the observed variability pattern the variability along the westward wave path is ascribed to the non doppler shift ist mode and seems to be forced mainly by wind stress forcing the anomaly along the southwestward subduction path is associated with the advective nature of the 2nd mode and could be excited mainly by surface buoyancy anomalies this study may provide a dynamically unified three dimensional picture of decadal thermocline variability in the north pacific ocean

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

planetary wave response to surface forcing and instability in the presence of mean flow and topography the local response of an ocean with slowly varying mean flow stratification and topography to two sources of disturbance is examined concentrating on whether the resulting surface elevations are observable the first is the ocean response to surface forcing ekman pumping or buoyancy forcing for typical amplitudes of random forcing while much of the ocean response is small surface elevations less than 1 mm there are sufficient near resonances or pseudoresonances involving a critical layer to produce elevations of 1 cm or more in much of the ocean the second source is baroclinic instability the fastest linear growth rate as well as those for specific wavelengths is computed globally almost all of the ocean is baroclinically unstable and the most unstable waves are found to possess a small wavelength often less than 10 km with a disturbance concentrated near the surface e folding times o 20 days are frequently found however the phase speed for the disturbances is almost everywhere slower westward than free planetary waves with mean flow and topography since the free waves propagate at speeds similar to observations instability may be a good source of variability but is probably not responsible directly for observed wave propagation

unravelling carbonatite silicate magma interaction dynamics a case study from the velay province massif central france mechanisms of interaction between a carbonatite magma and a silicate magma are inferred on the basis of the textural and geochemical features of a carbonate bearing tuff from the massif central characterized by the presence of carbonatite globules within a silicate glass matrix a two fluid dynamical model is proposed in order to constrain the formation of the carbonatite globules that underwent no geochemical re equilibration with the trachyte magma due to rapid thermal re equilibration and crystallization of dolomite it is suggested that a viscous fingering instability occurred simultaneously with the injection of a carbonatite magma into a chamber filled with a more viscous trachytic magma instantaneous fragmentation of the fingers induced by the action of gradient stresses resulted in the formation of a magmatic emulsion the replenishment event triggered immediate evacuation of the magma chamber such that interaction between the two magmas occurred over a short time scale and large scale mixing was prevented the exsolution of volatiles perhaps as a consequence of the recharge event shortly before the eruption drove a metasomatic event that produced the subtle chemical variations observed at the interface between carbonatite globules and silicate matrix

large scale propagating disturbances approximation by vertical normal modes abstract propagating features and waves occur everywhere in the ocean this paper derives a concise description of how such small amplitude large scale oceanic internal disturbances propagate dynamically against a slowly varying background mean flow and stratification computed using oceanic data for a flat bottomed ocean assumed here the linear internal modes computed using the local stratification form a useful basis for expanding the oceanic shear modes of propagation remarkably the shear modal structure is largely independent of orientation of the flow the resulting advective velocities which are termed pseudovelocities comprise background flow decomposed onto normal modes and westward planetary wave propagation velocities the diagonal entries of the matrix of pseudovelocities prove to be reasonably accurate descriptors of the speed and direction of propagation of the shear modes which thus respond as if simply advected by this diagonal entry velocity field the complicated three dimensi

on too fast baroclinic planetary waves in the general circulation abstract recent altimetric observations of the ocean surface reveal signatures of long planetary waves near the annual frequency band comparisons of the observed wave speeds and those predicted by standard linear theory suggest that the latter is inadequate as it yields different westward speeds than those measured in the extratropical latitudes the predicted speeds are typically slower than the observations here the problem of long baroclinic wave propagation in a forced stratified ocean is considered theoretically with a view toward explaining these observations of too fast planetary waves from a quasigeostrophic analysis it is argued that baroclinic waves in a sheared environment are accelerated to the west via their interactions with both the mean advective field and the mean potential vorticity field conditions under which the ratio of actual to linear phase speeds matches the observed ratio are computed and found to be typical of the open ocean extensions of these ideas to continuously st

quasi periodicity and global symmetries in interdecadal upper ocean temperature variability recent studies find interannual i e 3 to 7 year decadal i e 9 to 13 year and interdecadal i e 18 to 23 year periodicities and a trend dominating global sea surface temperature sst and sea level pressure slp variability over the past hundred years with the interdecadal signal dominating sub el nino southern oscillation enso frequencies we isolate interdecadal frequencies in sst and slp records by band passing with a window admitting 15 to 30 year periods from 1900 to 1989 the rms of interdecadal filtered sst and slp anomalies is largest in the extratropics and eastern boundaries first mode empirical orthogonal functions eofs explain about half the interdecadal variance in both variables with the tropical warm phase peaking near 1900 1920 1940 1960 and 1980 from 1955 to 1994 eof spatial patterns of interdecadal sst slp and 400m temperature t400 anomalies reveals global reflection symmetries about the equator and global translation symmetries between ocean basins with tropical and eastern ocean ssts warmer cooler than normal covarying with stronger weaker extratropical westerly winds cooler warmer ssts in western central subarctic and subantarctic frontal zones safzs stronger weaker subtropic and subarctic gyre circulations in north pacific and north atlantic oceans and warmer cooler basin and global average ssts of 0 1 c or so evolution of interdecadal variability from the tropical warm phase to the tropical cool phase is propagative also characterized by reflection and translation symmetries during the tropical warm phase cool sst anomalies along western central safzs are advected slowly eastward to the eastern boundaries and subsequently advected poleward and equatorward by the mean gyre circulation the latter conducting extratropical sst anomalies into the tropics a delayed action oscillation model is constructed that yields the quasiperiodicity of interdecadal variability in a manner consistent with these global symmetries in both pattern and evolution

role of the gulf stream and kuroshio oyashio systems in large scale atmosphere ocean interaction a review abstract ocean atmosphere interaction over the northern hemisphere western boundary current wbc regions i e the gulf stream kuroshio oyashio and their extensions is reviewed with an emphasis on their role in basin scale climate variability sst anomalies exhibit considerable variance on interannual to decadal time scales in these regions low frequency sst variability is primarily driven by basin scale wind stress curl variability via the oceanic rossby wave adjustment of the gyre scale circulation that modulates the latitude and strength of the wbc related oceanic fronts rectification of the variability by mesoscale eddies reemergence of the anomalies from the preceding winter and tropical remote forcing also play important roles in driving and maintaining the low frequency variability in these regions in the gulf stream region interaction with the deep western boundary current also likely influences the low frequency variability surface heat fluxes damp the low frequency sst anomalies ove

western boundary sea level a theory rule of thumb and application to climate models abstractto better understand coastal sea level variability and changes a theory that predicts sea levels along a curved western boundary using interior ocean sea level information is proposed the western boundary sea level at a particular latitude is expressed by the sum of contributions from interior sea levels propagating onto the western boundary by long rossby waves between that latitude and a higher latitude and from the western boundary sea level at the higher latitude this theory is examined by using a linear reduced gravity model a comparison between the theory and the model shows good agreement a simple scaling law or rule of thumb derived from the theory provides a measure of the higher latitude sea level and ocean interior sea level contributions the theory is then tested using data from 34 climate models in phase 5 of the coupled model intercomparison project cmip5 for dynamic sea level changes between the end of the twentieth and twenty first centuries the theory captures the nea

linear response of a ventilated thermocline to periodic wind forcing abstractthis article presents a solution for the linear response of a 2 layer ventilated thermocline to large scale periodic wind forcing with a fixed outcrop latitude at the eastern boundary a rossby wave whose vertical structure is similar to the first baroclinic mode is generated and propagates westward in the shadow zone meanwhile the wave is unstable and amplified westward in the southern region in the ventilated zone in addition to the first mode rossby wave generated at the eastern boundary two waves with second mode like vertical structures are generated one wave is generated directly by the wind over the outcrop this wave has a zero zonal wavenumber and southwestward group velocity such that the eastern edge of the wave migrates westward as it propagates southward the other wave is generated by interaction between the westward propagating first mode rossby wave and the outcrop the zonal wavenumber is the same as that of the first mode at the outcrop and the phase of the wave propa

thermocline variability in different dynamic regions abstract the response of thermocline circulation to a variable wind forcing is investigated with quasigeostrophic models the physical mechanism responsible for the different variability features in various dynamic regions has been highlighted special attention is given to the role of density advection that is forced by wind driven currents in affecting baroclinic thermocline variability the strong density advection in the rhines young pool can effectively balance the variability induced by local ekman pumping resulting in weak baroclinic variability in the pool zone in contrast the lack of density advection in the shadow zone enables the local ekman pumping to force significant baroclinic variability there the variability in the barotropic field and the western boundary current system is also discussed

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

structure and cycle of decadal variability of upper ocean temperature in the north pacific abstract yearly upper ocean in situ temperature anomaly data for the period 1961 90 are analyzed to reveal spatial structure and evolution of decadal variability in the north pacific ocean an eof analysis has been performed on individual temperature anomaly fields at upper ocean standard levels as well as simultaneously on the entire upper ocean data to depict the combined three dimensional structure in a coherent manner time evolution of anomaly fields is depicted by using a regression analysis the analyses detect the principal basin scale structure of decadal warm period dwp and decadal cold period dcp there is a well defined subsurface thermal anomaly pattern characterized by a prominent seesaw structure with opposite anomaly polarity between the midlatitude north pacific and the subtropical regions during a dwp a positive temperature anomaly is found in the central midlatitude upper ocean with the maximum at about 100 m depth this is accompanied by a corresponding negative anomaly in the

experimental tests of middle palaeolithic spear points using a calibrated crossbow abstract controlled experiments using a calibrated crossbow to thrust stone tipped spears into animal carcasses reveal a relationship between levallois point morphology and their performance as spear points a comparative study of morphometric variation of levallois points from levantine mousterian contexts supports the hypothesis that the demand for stone spear points was an important factor in levallois point production

quantifying lithic curation an experimental test of dibble and pelcin s original flake tool mass predictor this paper describes an experimental test of a method proposed by dibble pelcin 1995 for reconstructing the original flake mass from striking platform dimensions the results of this test indicate that while there is a correlation between flake mass and flake attributes for hard hammer lithic production systems using the specific variables identified by dibble pelcin exterior platform angle and platform thickness consistently underestimates original flake mass the reasons for this discrepancy and possible future research directions to resolve it are explored

planetary wave modes in the thermocline non doppler shift mode advective mode and green mode a quasi geostrophic theory is proposed for planetary waves in the extratropical thermocline it is shown that planetary wave propagation structure and stability can be affected significantly by the mean thermocline flow one major planetary wave mode is the non doppler shift mode which resembles the first baroclinic mode and has a strong signature in both the sea surface height and the bottom of the thermocline this mode propagates westward regardless of the mean flow however consistent with recent works the westward propagation speed can be modestly enhanced by the mean flow another major planetary wave mode is the advective mode which bears some resemblance to the second baroclinic mode and has a strong signature in the upper thermocline temperature field in the region of strong westward thermocline flow and shear such as the south western part of the north pacific subtropical gyre an unstable green mode is produced by the coupling of the non doppler shift mode and the advective mode this unstable green mode may have e folding times of a few years for a wave hundreds of kilometers in length the structure of the green mode contains the features of the second baroclinic mode with a strong signature in the upper thermocline the green mode always propagates westward finally we discuss the relevance of our theory to recent observations

the local baroclinic instability of geostrophic spirals in the eastern north pacific abstract we analyze the pre 1975 hydrographic data of the northeast pacific and compute the large scale two dimensional geostrophic flow with respect to 3000 m using a linear three level quasi geostrophic model of large scale spiraling flow and vertical density gradient we evaluate the complex dispersion relationships for quasi geostrophic waves we find baroclinically unstable waves with maximum e folding times of 1 3 3 years wave lengths of 120 500 km and periods of 1 4 13 2 years growth rates strongly depend upon the shear magnitude and direction and the wave direction computations with a 34 level model of the spiraling flow reveal that e folding times and periods are 50 200 days and 60 200 km wavelengths the growth rates increase at the south as do the wavelengths in general the most rapidly growing waves have a subsurface maximum of kinetic energy at 200 800 m and a component of the most rapidly growing wave is in a direction encompassed by the spiraling shear at least a six level model is r

long baroclinic rossby waves detected by topex poseidon residual sea surface height anomaly fields are obtained over the north atlantic basin from topex poseidon altimeter data evidence of westward propagating anomalies characterized as first mode baroclinic rossby waves is presented the phase speeds are obtained from the analysis of the autocorrelation matrices of the residual surface height anomaly in three dimensions on a 5 5 grid periods are calculated by least squares fitting a sinusoidal function to the time series at each grid point zonal and meridional wavelengths are obtained from the phase speed and period and are least squares fit to the data as a consistency check zonally averaged westward phase speeds vary between 1 and 27 km d between 50 and 5 n increasing southward phase speeds are directed to the southwest north of approximately 25 n and to the northwest south of this latitude the sea surface height signal is divided into two spectral bands the first with periods between 280 and 450 days and the second with periods between 120 and 280 days for the first band the average of the periods taken over the whole basin is 370 days in the second band a signal of period between 6 and 7 months is evident also throughout the basin the zonally averaged zonal wavelengths associated with the first band are in the range of 400 4600 km between 50 and 5 n and for the second band are in the range 270 2500 km between 45 and 5 n longer wavelengths are found close to the southern boundaries shorter wavelengths are found in the northern portion of the basin comparison with results from numerical models suggests that the baroclinic waves observed at midlatitudes are generated at the eastern boundary by fluctuations of the wind stress curl waves observed south of 20 n support the hypothesis of direct wind forcing

the response of the north pacific ocean to decadal variability in atmospheric forcing wind versus buoyancy forcing abstract both wind and buoyancy forcing result in variability in the north pacific ocean thermocline a vertical modal analysis of the density deviations in a 30 yr run of an ocean general circulation model of the north pacific forced by atmospheric variability is used to identify the spatial and temporal patterns of the different baroclinic modes the different dynamic vertical modes show distinct propagation characteristics with the first baroclinic mode exhibiting consistent westward propagation at all latitudes the higher baroclinic modes show westward phase propagation at low latitudes but propagate eastward at higher latitudes the propagation characteristics of each mode can be understood by the inclusion of the zonal mean flow in the vertical structure equation evaluation of the ekman pumping and diapycnal fluxes in the quasigeostrophic potential vorticity equation for each dynamic vertical mode distinguishes their effects on the thermocline variability wind variability dominantly forces the f

chronological and behavioral contexts of the earliest middle stone age in the gademotta formation main ethiopian rift there is a general consensus that our species emerged first in africa currently the best known skeletal evidence for the earliest anatomically modern homo sapiens amhs derives from sites in the rift valley in ethiopia however archaeological evidence from cave sites in southern and northern africa largely dominates discussions on behaviors that characterize the dawn of modern humans later middle pleistocene open air sites in east africa present unparalleled geochronological control and thus a better chance to study hominin behavior here we present results of a multidisciplinary investigation of the archaeology and geochronology of one of the oldest known middle stone age msa occupations from the gademotta formation fm in the main ethiopian rift renewed excavation lithic analysis fracture mechanics and tephrochronological investigations at gademotta provide a better understanding of the chronological and behavioral contexts during the critical period immediately preceding the origin of our species

the great salinity anomaly in the northern north atlantic 1968 1982 the widespread freshening of the upper 500 800m layer of the northern north atlantic which this paper describes represents one of the most persistent and extreme variations in global ocean climate yet observed in this century though a range of explanations have been advanced to explain this event including in situ changes in the surface moisture flux this paper describes the great salinity anomaly as largely though not entirely an advective event traceable around the atlantic subpolar gyre for over 14 years from its origins north of iceland in the mid to late 1960s until its return to the greenland sea in 1981 1982 the overall propagation speed around this subpolar gyre is estimated at about 3cm s 1 of the total salt deficit associated with the anomaly as it passed south along the labrador coast in 1971 1973 about 72 109 tonnes a deficit equivalent to about two thirds of this figure 47 109 tonnes ultimately passed through the faroe shetland channel to the barents sea arctic ocean and greenland sea during the mid 1970s possible effects on deep water formation and on the representativeness of historical section data are discussed

linkage between the pacific decadal oscillation and the low frequency variability of the pacific subtropical cell the decadal variability of pacific subtropical cell stc and its linkages with the pacific decadal oscillation pdo are investigated in the present study based on a simple ocean data assimilation soda 2 2 4 it is found that on decadal time scales the western boundary and interior pycnocline transports are anticorrelated and the variation of the interior component is more significant which is consistent with previous studies the decadal variability of stc in the northern hemisphere is found to be strongly associated with pdo associated with a positive negative phase of pdo the relaxation acceleration of the northeast trades slows down spins up the stc within a few years through baroclinic adjustment in conjunction with the subduction of the cold warm mixed layer anomalies in the extratropics the cold warm water is then injected into the thermocline and advected further southwestward to the tropics along the isopycnal surfaces leading to the slowdown spin up of stc due to zonal pressure gradient change at low latitude along with the stc weakening strengthening a significant warming cold anomaly appears in the tropics and it is advected to the midlatitude by the kuroshio and north pacific currents thus feeding back to the atmosphere over the north pacific in contrast to the northern hemisphere it is found the stc in the south only passively responds to the pdo the mechanism found here highlights the role of the stc advection of extratropical anomalies to the tropics and horizontal gyre advection of the tropical anomalies to the extratropics in decadal variability of the stc and pdo

the application and misapplication of mass analysis in lithic debitage studies the technique of debitage mass analysis based upon size grades of debitage populations is shown to be prone to errors when making interpretations about the kind of tool produced or the kind of lithic reduction technology used significant sources of error may originate from differences in individual flintknapping styles and techniques raw material size and shape variants and mixing of debitage from more than one reduction episode these sources of error render debitage mass analysis ineffective for determining the kind of stone tool reduction activities practiced at excavated sites mass analysis may be effective for determining artifact reduction sequences if it is used on debitage from a single reduction episode or part of a reduction episode however it is shown that mass analysis when used for assessing reduction sequence information must also control for the effects of raw material variability assemblage mixing and flintknapping styles

the technology of stone age colonization an empirical regional scale examination of clovis unifacial stone tool reduction allometry and edge angle from the north american lower great lakes region abstract there is now broad consensus that the appearance of clovis in northeastern north america great lakes new england represents a colonization pulse into recently deglaciated landscapes due to the increased resource uncertainty that comes with colonizing unfamiliar landscapes it was hypothesized that the majority tool component of clovis assemblages unifacial stone tools should have been knapped on tool blanks possessing the design properties of longevity and functional flexibility to facilitate exploration mobility and guard against the absence of toolstone sources in the new landscape these properties are optimized by large flat flakes possessing large surface area relative to flake thickness since discarded and at times exhausted unifacial stone tools do not preserve the original dimensions of the blank upon which they were created necessary items for a true test of blank morphology selection this study presents a set of predictions for inferring whether clovis unifacial stone tool blanks were selected for the properties of longevity and functional flexibility based on evidence that clovis people actually capitalized on those properties due to the nature of clovis unifacial stone tools tool size was of necessity used as a proxy for tool reduction on the grounds that smaller tools are more likely to have been resharpened than larger tools at least in the case of unifacial flake tools the results showed that less resharpened tools possessed flatter less spherical shapes than the more resharpened tools which possessed more globular spherical shapes suggesting clovis foragers exploited the retouch potential afforded by the larger flatter blanks edge angles showed no relationship with tool reduction suggesting that clovis foragers exploited the functional flexibility afforded by flatter blanks by adjusting the edge angle to be either higher or lower as needed these results are consistent with the notion that human colonizers who did not know the abundance or location of stone outcrops prior to settling an unfamiliar territory not only geared up before leaving a stone source but geared up as efficiently as possible by carefully selecting the blanks they chose to carry broader implications for such careful unifacial stone tool blank selection are discussed

large scale baroclinic instability of the mean oceanic circulation a local approach abstractlarge scale baroclinic instability is investigated as a potential source of rossby waves and large scale variability in the ocean this baroclinic instability is first reviewed in a 2 5 layer model as already noticed by several authors the instability arises in westward surface mean flow when the phase velocities of the two vertical modes are made equal by mean flow influence this large scale instability is stronger at low latitudes and thus is likely to happen in the westward return flow of the subtropical gyres further investigations with a continuous stratification quasigeostrophic model show that the instability is stronger where the mean flow projects negatively on the second baroclinic mode imposing positive vertical modes at the surface the linear stability calculation is then performed on argo derived mean flow along with mean stratification data the results show that the unstable regions are situated at low latitudes in every oceanic basin in western boundary currents and in som

an eddy resolving numerical model of the ventilated thermocline time dependence abstract a primitive equation eddy resolving numerical model is used to study the inherent time scales of variability in the subtropical ocean assuming temporally constant surface forcing three primary scales arise mesoscale variability of roughly 50 day period zonally elongated barotropic bands of 1 1 year period and basin scale undulations of approximately 4 year period the latter are identified as first baroclinic mode rossby waves associated with bursts of ventilation at isopycnal outcrops as a result the equatorward transport required by sverdrup theory in the subtropics occurs not as a broad sluggish drift throughout the interior but as a succession of more intense flows that slowly propagate westward the zonally elongated bands agree in characteristics to those predicted from theory of homogeneous turbulence eddy energy that is generated by baroclinic instability leaks from baroclinic to barotropic mode and thereafter due to rotational constraints seeks low zonal wavenumbers the gr

the effect of bottom pressure decoupling on the speed of extratropical baroclinic rossby waves abstract in layered models of the ocean the assumption of a deep resting layer is often made motivated by the surface intensification of many phenomena the propagation speed of first mode baroclinic rossby waves in such models is always faster than in models with all the layers active the assumption of a deep resting layer is not crucial for the phase speed enhancement since the same result holds if the bottom pressure fluctuations are uncorrelated from the overlying wave dynamics in this paper the authors explore the relevance of this behavior to recent observational estimates of too fast waves by chelton and schlax the available evidence supporting this scenario is reviewed and a method that extends the idea to a continuously stratified fluid is developed it is established that the resulting amplification factor is at leading order captured by the formula where cfast is the enhanced phase speed cstandard the standard phase speed 1 z is the standard first mode for the velocity and pressur

estimating original flake mass from 3d scans of platform area this study confirms the increased capacity to predict flake mass that arises from more accurately measuring surface area in three dimensions using a digital scanner we also reveal the existence of significantly different relationships between platform area and flake mass for flakes with different platform types and ventral and dorsal morphologies these different relationships between platform surface area and mass have not been previously identified and reveal the complexity of platform mass relationships using multivariate regression of 3d platform surface area and external platform angle we improve the accuracy of predictions of original flake mass we propose a method for studying reduction intensity on retouched flakes based on comparing predictions of the initial mass of the flake with measurements of the mass following retouching to estimate the amount of mass removed through retouching we name this approach the initial terminal mass comparison or itmc our experiments demonstrate that the capacity of the 3d platform scans to predict flake mass and by implication the capacity of the itmc to estimate mass loss rivals or exceeds the capacity demonstrated for existing reduction measures

enso like interdecadal variability in the pacific ocean as simulated in a coupled general circulation model spatial and temporal structures of interdecadal variability in the pacific ocean are investigated using results from an atmosphere ocean coupled general circulation model aogcm the model shows a basin wide spatial pattern of the principal sea surface temperature sst variability similar to the observed one both interdecadal and interannual temporal structures of the sst variability agree well between the observation and the aogcm on the other hand a slab ocean model coupled to the same atmospheric model as the aogcm fails to simulate the observed temporal structure therefore the timescale of the coupled variability is associated with dynamical processes in the ocean a distinct interdecadal mode of the coupled atmosphere upper ocean temperature variability is found in the aogcm with a spatiotemporal structure coherent with the sst variability the mode accompanies an el nino southern oscillation enso like spatial pattern of sst and the surface wind and behaves like a delayed oscillator in enso a wedge shaped anomaly pattern of the upper thermocline temperature is formed in the eastern pacific and its northern subtropical signal propagates westward enhanced by a subtropical wind forcing at the central basin arrival of the subtropical signal at the western pacific around 20 n switches the anomaly of subsurface temperature in the equatorial region through anomalous oceanic heat transport along the western boundary the travel time of the trans pacific signal in the subtropics appears to be responsible for the timescale of this mode the aogcm successfully simulated the second mode of sst with a major variation in the midlatitude north pacific as in the observed sst in the upper ocean heat content we found another distinct mode which is characterized by a midlatitude subtropics dipole pattern migrating around the north pacific subtropical gyre however the associated sst variation of this mode shows a poor correspondence in the dominant interdecadal modes for the observed sst