anatomy of north pacific decadal variability abstract a systematic analysis of north pacific decadal variability in a full physics coupled ocean atmosphere model is executed the model is an updated and improved version of the coupled model studied by latif and barnett evidence is sought for determining the details of the mechanism responsible for the enhanced variance of some variables at 20 30 yr timescales the possible mechanisms include a midlatitude gyre ocean atmosphere feedback loop stochastic forcing remote forcing or sampling error decadal variability in the model is expressed most prominently in anomalies of upper ocean streamfunction sea surface temperature sst and latent surface heat flux in the kuroshio oyashio extension koe region off japan the decadal signal off japan is initiated by changes in strength and position of the aleutian low the atmospheric perturbations excite sst anomalies in the central and eastern north pacific with opposing signs and canonical structure the atmospheric perturbations also change the ekm

initial testing of a numerical ocean circulation model using a hybrid quasi isopycnic vertical coordinate abstract an ocean circulation model developed for the study of mesoscale to gyre scale circulation and heat transport is described and tested the model employs density as vertical coordinate except in the immediate vicinity of possible coordinate surface intersections with the ocean surface test simulations are carried out for a double gyre ocean basin of the type used by holland 1978 but with better resolution in the upper 1000 m of the model ocean the final state of a 5 year coarse mesh 50 km resolution on a 2400 km 1200 km domain spin up is used as the initial state for mesoscale experimentation on a 25 km mesh basin energetics as well as mean mass transport streamfunction and mean potential vorticity fields are given for three mesoscale experiments in which the magnitude and formulation of lateral dissipation are varied each of these experiments run for approximately five years exhibits vigorous mesoscale activity associated with western boundary current separation and the free jet

atlantic forcing of pacific decadal variability this paper investigates the atlantic ocean influence on equatorial pacific decadal variability using an ensemble of simulations where the ictpagcm speedy is coupled to the nemo opa ocean model in the indo pacific region and forced by observed sea surface temperatures in the atlantic region it is shown that the atlantic multidecadal oscillation amo has had a substantial influence on the equatorial pacific decadal variability according to amo phases we have identified three periods with strong atlantic forcing of equatorial pacific changes namely 1 1931 1950 minus 1910 1929 2 1970 1989 minus 1931 1950 and 3 1994 2013 minus 1970 1989 both observations and the model show easterly surface wind anomalies in the central pacific cooling in the central eastern pacific and warming in the western pacific indian ocean region in events 1 and 3 and the opposite signals in event 2 the physical mechanism for these responses is related to a modification of the walker circulation because a positive negative amo leads to an overall warmer cooler tropical atlantic the warmer cooler tropical atlantic modifies the walker circulation leading to rising sinking and upper level divergence convergence motion in the atlantic region and sinking rising motion and upper level convergence divergence in the central pacific region

rectification of enso variability by interdecadal changes in the equatorial background mean state in a cgcm simulation the link between the changes in equatorial background stratification and el nino southern oscillation enso modulation is investigated using a simulation from a 260 yr long coupled general circulation model cgcm the work focuses on the role of nonlinearities associated with equatorial wave dynamics as a first step the low frequency change in mean stratification is diagnosed and documented from the shallow water parameters derived from a vertical mode decomposition of the cgcm the parameters vary differently according to the baroclinic mode order which may explain why a flattening thermocline does not necessarily lead to reduced enso activity estimations of baroclinic mode contributions to zonal current anomalies indicate that the decadal variability projects differently for the baroclinic modes as compared to the interannual variability in particular the high order modes associated with decadal variability have a more pronounced signature in the western pacific whereas that associated with interannual variability i e enso shows more energy in the eastern pacific in the light of the results of the cgcm vertical mode decomposition an intermediate coupled model icm is used to test whether the nonlinearities associated with the changes in the baroclinic mode energy distribution can lead to coherent enso modulation the results indicate that rectification of the interannual variability enso time scales by the interdecadal variability associated with changes in the oceanic mean states takes place in the icm the rectified effect results mostly in an increased variability and skewness of the zonal advection which tends to produce a zonal seesaw of the sea surface temperature anomaly a tropical mechanism for producing enso modulation is then proposed that reconciles both the rectified effect resulting from nonlinearities associated with equatorial wave dynamics and the tropical decadal mode of thermocline depth arising from ekman pumping anomalies located in the central south pacific

interannual and decadal variability of the subsurface thermal structure in the pacific ocean 1961 90 heat content anomalies are analyzed to understand subsurface variability on both aparticular focus on the evolving basinwide patterns and oceanic connections between the extratropics and tropics various analyses indicate two distinct modes one interannual and the other decadal that involve the tropics and the north pacific subtropical gyre respectively interannual variability is associated with el nino in the tropics with a prominent see saw pattern alternately on and off the equator and in the east and west respectively the interannual cycle features a coherent propagation of subsurface signals around the tropical pacific eastward along the equator but westward off the equator at 10 15 n decadal signals are dominant in the subtropics and midlatitudes but also have a tropical component that appears to be independent of interannual variations an oceanic connection can be seen between subsurface anomalies in the midlatitudes in the subtropics and tropics on decadal time scales subsurface thermal anomalies associated with midlatitude decadal variability can propagate through the subtropics into the tropics which may modulate the intensity of interannual variability in the tropics for example in the middle and late 1970s a significant warm temperature anomaly appeared to penetrate into the western and central tropics at depth warming the tropical upper ocean and depressing the thermocline during the development of el nino therefore an extratropically preconditioned subsurface state e g an enhanced positive heat content anomaly in the western and central tropical pacific would favor a warmer sea surface temperature anomaly in the eastern equatorial pacific potentially increasing the intensity of ocean atmosphere coupling these changes in the thermocline structure and possibly in the coupling strength can further alter the very character of tropical air sea interactions this may help to explain decadal variability of el nino evolution in the tropical pacific as observed in the 1980s our subsurface variability analysis presents observational evidence for the detailed space time structure of decadal oceanic links between the extratropics and the tropics

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

characteristic variations of sea surface temperature with multiple time scales in the north pacific abstract temporal evolution and spectral structure of sea surface temperature sst anomalies in the north pacific over the last 37 years are investigated on the three characteristic time scales shorter than 24 months hf 24 60 months es and longer than 60 months dc the leading empirical orthogonal function eof for the dc time scale is characterized by a zonally elongated monopole centered at around 40 n 180 the leading eof for the hf time scale is somewhat similar to that for the dc time scale although there are two centers of action with the same polarity at the mid and western pacific the leading eof for the es time scale however exhibits a different pattern whose center of action at the mid pacific is located farther southeastward in the time evolution of the sst anomalies associated with the leading eof of the dc time scale several anomaly periods can be identified that last five years or longer the transition from a persistent period to another with the opposite polarity is gene

north pacific thermocline variations on enso timescales abstract the north pacific thermocline 250 to 400 m is studied using xbt observations acquired during the 1970s and 1980s interannual variations 3 5 yr timescales in thermocline temperature with o 0 1 c amplitude at 400 m are found to exhibit westward propagation throughout the extratropical north pacific up to 45 n southward of 30 n the features propagate intact across the basin from the eastern boundary to the western boundary northward of 30 n the features can be observed to propagate only as far as the date line the observed midlatitude thermocline anomalies are often related to tropical enso events in that they occur most strongly after the development of tropical el nino or la nina conditions and propagate westward from near the eastern boundary in the midlatitudes but it is found that the observed midlatitude thermocline anomalies have larger phase speeds than theoretically predicted free baroclinic rossby waves also the observed anomalies have larger wavelength and faster propagati

long range correlations in the extratropical atmospheric circulation origins and implications abstract the atmospheric general circulation often enters into regimes that cause weather anomalies departures from an average state to persist over areas of the globe by considering 500 hpa measurements the authors demonstrate the existence of scale invariance in the variability of extratropical atmospheric circulation anomalies over the whole range of timescales resolved by the available data from a week to a decade this scale invariance indicates an absence of characteristic timescales and the presence of positive long range correlations meaning that if an anomaly of a particular sign exists in the past it will most likely continue to exist in the future moreover this scale invariance indicates that the dynamics of small scales are connected to the dynamics of large scales via a simple power law a consequence of this finding is that the memory of the system is not confined only to large scales but extends to small scales as well by investigating the hemispheric structure of 500 hpa fields ove

stress in the contorted nazca plate beneath southern peru from local earthquakes we study earthquake focal mechanisms in a region of highly contorted subducting lithosphere to identify dominant sources of stress in the subduction process we observe a stress pattern in the contorted nazca plate beneath southern peru from an analysis of hypocentral trend and focal mechanisms of intermediate depth earthquakes expanding on previous studies we examine the hypocentral trend using 1673 of 2178 well located local events from the nine station arequipa network the dip of the plate beneath southern peru averages 25 30 from 25 to 100 km depth below this depth there is an 80 to 100 km wide contortion between a zone of increasing dip convex to the southeast and a flat lying concave zone to the northwest using more than 6000 p wave first motions of events deeper than 50 km we derive stress orientations from a moving average of composite focal mechanisms across a 200 by 350 km region including the contortion the in plate distribution of tension t and compression p axes reveals a coherent stress pattern the trend is most clear beneath south central peru nw section and below 100 km depth in southernmost peru se section both t and p axes tend to be dominantly in plate especially below 100 km depth t axes orient toward the contortion in a fan shaped trend which suggests that the deepest part of the seismic zone within the convex se section is sinking and pulling the more buoyant nw section we conclude that from 50 to 200 km depth slab pull forces are dominant in the observed stress our results suggest that a significant amount of plate extension occurs in this region of intermediate depth subduction

on the nature and causes of large scale thermal variability in the central north pacific ocean abstract long range naval aircraft using axbt s obtained meridional temperature sections from the central pacific ocean along 158 and 170 w between 30 and 50 n at approximately monthly intervals between november 1974 and april 1977 29 months analyses of these sections show that the seasonal cycle in the central ocean is confined largely to the upper 100 m the phase of the seasonal cycle increases with depth so that at 100 m it lags the surface by three months exceptions to the above statements occur in two narrow bands centered on latitudes 42 and 36 n where the seasonal cycle apparently penetrates in phase to the limit of observations 300 m except in the interval 100 150 m which lags the surface by 1 2 months approximately 90 95 of the variance in the seasonal change of heat storage in the study region can be accounted for by air sea heat exchange and some type of vertical mixing horizontal and vertical advection were of limited and little use respectively in reproducing the seasonal cycle va

simulation of the atlantic circulation with a coupled sea ice mixed layer isopycnal general circulation model part i model description abstract a diabatic ocean general circulation model based on primitive equations is described it uses isopycnals as lagrangian coordinates in the vertical and predicts a free surface prognostic fields of temperature and salinity enter the dynamics as active tracers through a realistic equation of state the surface boundary layer is parameterized by a detailed mixed layer model a sea ice model with a viscous plastic rheology is coupled to the mixed layer thermal forcing wind stress and surface input of turbulent kinetic energy are determined from monthly mean values of atmospheric quantities while the freshwater flux still is parameterized by a newtonian relaxation towards the observed surface salinity the model equations are written in layer formulation each interface represents an isopycnal as the equations are written in flux form the mass flux and the content of mass heat and salt are conserved in the model domain a potential vorticity conserving scheme is included except for the mixed

decadal interactions between the western tropical pacific and the north atlantic oscillation the relationship between interdecadal variations of tropical sea surface temperature sst in the last 120 years and circulation anomalies related to the north atlantic oscillation nao is investigated in this study using an atmospheric general circulation model agcm we confirm observational evidence that variations in the sst gradient in the western tropical pacific are related to the nao anomalies on decadal timescale and may be contributing to the shift towards the positive nao phase observed in the late 20th century the role played by the indian ocean nao teleconnection advocated in recent studies focused on the last 50 years is also assessed in the context of the 120 year long record it is suggested that a positive feedback between the pacific sst and the hemispheric circulation pattern embedding the decadal nao signal may act to enhance the internal variability of the coupled ocean atmosphere system and justify the stronger teleconnection found in observational data than in sst forced agcm experiments

model assessment of decadal variability and trends in the tropical pacific ocean abstract in this report global coupled ocean atmosphere models are used to explore possible mechanisms for observed decadal variability and trends in pacific ocean ssts over the past century the leading mode of internally generated decadal 7 yr variability in the model resembles the observed decadal variability in terms of pattern and amplitude in the model the pattern and time evolution of tropical winds and oceanic heat content are similar for the decadal and enso timescales suggesting that the decadal variability has a similar delayed oscillator mechanism to that on the enso timescale the westward phase propagation of the heat content anomalies however is slower and centered slightly farther from the equator 12 vs 9 n for the decadal variability cool sst anomalies in the midlatitude north pacific during the warm tropical phase of the decadal variability are induced in the model largely by oceanic advection anomalies an index of observed sst over a broad triangular region of the tropi

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

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

decadal changes in the north pacific oceanic frontal zones as revealed in ship and satellite observations 1 influence of decadal climate changes upon the north pacific subarctic and subtropical oceanic frontal zones np safz and np stfz respectively is documented both satellite and ship measured sea surface temperature sst data reveal the strong confinement of wintertime decadal sst anomalies to those frontal zones the satellite data indicate that the wintertime np safz tended to be narrow and shift northward under the weakened surface westerlies during a warm event in the early 1990s the opposite was the case under the enhanced westerlies during a cool event in the mid 1980s decadal scale modulations in the frontal intensity are also evident in the satellite data a diagnosis based on a simple linearized mixed layer model suggests that the observed anomalous frontal intensity was contributed by the sign reversal of anomalous wind stress curl through the ekman processes and by an anomaly dipole of the net heat flux around the safz these decadal scale modulations in the np safz and their relationships with decadal fluctuations in the local surface westerlies are confirmed in the ship measured data over the 4 recent decades it is found that the safz happens to be a region where the decadal variability in the surface westerlies are unlikely to be masked by the higher frequency fluctuations as it almost coincides with the ridge trough line of the remote atmospheric response to the el nino southern oscillation

simulation of the response of the north pacific ocean to the anomalous atmospheric circulation associated with el nino during el nino events when positive sea surface temperature sst anomalies form in the equatorial pacific sst anomalies also tend to develop in the north pacific this study attempts to model and explain the large scale features of the observed sst anomaly field in the north pacific during the fall and winter of the el nino year the experiment design consists of a mixed layer ocean model of the north pacific which is forced by atmospheric surface fields from two sets of community climate model ccm integrations the el nino set with prescribed positive sst anomalies in the tropical pacific and the control set which is obtained from an extended ccm integration with prescribed climatological ssts the response of the midlatitude ocean to atmospheric surface fields associated with el nino is obtained by compositing each set of model integrations el nino and control and then taking the difference between the composites the ocean model is able to reproduce the general features of the observed midlatitude sst anomaly pattern warm water in the northeast pacific and an elliptically shaped cold pool in the central pacific in these regions a large fraction of the temperature anomalies are significant at the 95 level as indicated by a two tailed t test the ocean temperature anomalies simulated by the model are primarily caused by changes in the sensible and latent heat flux and to a lesser extent the longwave radiation flux entrainment of cold water from below the mixed layer also influences ocean temperatures however the entrainment anomaly pattern has a complex spatial structure which does not always coincide with the simulated mixed layer temperature anomalies

modes of interannual and interdecadal variability of pacific sst abstract the multichannel singular spectrum analysis has been used to characterize the spatio temporal structures of interdecadal and interannual variability of sst over the pacific ocean from 20 s to 58 n using the comprehensive ocean atmosphere data set from 1950 to 1993 three modes with distinctive spatio temporal structures were found they are an interdecadal mode a quasi quadrennial qq oscillation with a period of 51 months and a quasi biennial qb oscillation with a period of 26 months the interdecadal mode is a standing mode with opposite signs of sst anomalies in the north pacific and in the tropical pacific the amplitude of this mode is larger in the central north pacific than in the tropical pacific this mode contributes 11 4 to the total variance it is associated with cooling in the central north pacific and warming in the equatorial pacific since around 1976 77 the qq oscillation exhibits propagation of sst anomalies northeastward from the philippine sea and then eastward along 4

wind driven shifts in the latitude of the kuroshio oyashio extension and generation of sst anomalies on decadal timescales abstract the causes of decadal variations of north pacific sea surface temperatures ssts are examined using a hindcast performed with an ocean general circulation model thermodynamically coupled to an atmospheric mixed layer model ogcm aml model and forced by the time history of observed surface winds the shift in north pacific ocean climate that occurred around 1976 77 is focused on since this is the best observed example available after the 1976 77 shift the aleutian low deepened and moved to the southeast of its previous position this placed anomalous cyclonic flow over the north pacific the sst response as simulated by the ocean model consisted of two components a fast and local part and a delayed and remote part in the central pacific stronger westerlies cool the ocean by increased equatorward ekman drift here the dynamical cooling is sufficiently large that the surface fluxes damp the sst anomaly this ekman response is fast and local and cools the ssts beginning in 1977 and persistin

synoptic eddy feedback and air sea interaction in the north atlantic region this paper explores the role of synoptic eddy feedback in the air sea interaction in the north atlantic region particularly the interaction between the north atlantic oscillation nao and the north atlantic sea surface temperature anomalies ssta tripole a linearized five layer primitive equation atmospheric model with synoptic eddy and low frequency flow self interaction is coupled with a linearized oceanic mixed layer model to investigate this issue in this model the climatological storm track activity or synoptic eddy activity is characterized in terms of spatial structures variances decay time scales and propagation speeds through the complex empirical orthogonal function ceof analysis on the observed data which provides a unique tool to investigate the role of synoptic eddy feedback in the north atlantic air sea coupling model experiments show that the nao like atmospheric circulation anomalies can produce tripole like ssta in the north atlantic ocean and the tripole like ssta can excite a nao like dipole with an equivalent barotropic structure in the atmospheric circulation which suggests a positive feedback between the nao and the ssta tripole this positive feedback makes the nao ssta tripole like mode be the leading mode of the coupled dynamical system the synoptic eddy feedback plays an essential role in the origin of the nao ssta tripole like leading mode and the equivalent barotropic structure in the atmosphere without synoptic eddy feedback the atmosphere has a baroclinic structure in the response field to the tripole like ssta forcing and the leading mode of the dynamic system does not resemble nao ssta tripole pattern

simple coupled midlatitude climate models a set of simple analytical models is presented and evaluated for interannual to decadal coupled ocean atmosphere modes at midlatitudes the atmosphere and ocean are each in sverdrup balance at these long timescales the atmosphere s temperature response to heating determines the spatial phase relation between sst and sea level pressure slp anomalies vertical advection balancing heating produces high low slp lying east of warm cold sst anomalies as observed in the antarctic circumpolar wave acw the decadal north pacific mode and the interannual north atlantic mode zonal advection in an atmosphere with a rigid lid produces low slp east of warm sst however if an ad hoc equivalent barotropic atmospheric response is assumed high slp lies east of warm sst relaxation to heating produces behavior like the observed north atlantic decadal pattern with low slp over warm sst meridional advection in the atmosphere cannot produce the observed sst slp patterns the dominant balance in the ocean s temperature equation determines the phase speed of the modes the coupled mode is nondispersive in all models examined here indicating the need for additional processes for modes with an sst slp offset as observed in the acw and north pacific ekman convergence acting as a heat source causes eastward propagation relative to the mean ocean flow sverdrup response to ekman convergence acting on the mean meridional temperature gradient causes westward propagation relative to the mean ocean flow when the ocean temperature adjusts through surface heat flux alone the mode is advected by the mean ocean flow and is damped relaxation to heating in the atmosphere when operating with sverdrup response in the ocean produces the only complete solution presented here that exhibits growth with an e folding timescale of order 100 days this solution appears appropriate for the north atlantic decadal mode in northern hemisphere basins with meridional boundaries the same sets of dynamics create the observed sst slp phase relation an additional factor is the creation of sst anomalies through variations in the western boundary current strengths which are related to the zonally integrated wind stress curl over the whole basin if barotropic and hence fast adjustment is assumed the resulting positive feedback can maintain or strengthen the coupled anomalies in the north pacific and interannual north atlantic modes

atmosphere ocean coupled variability in the south atlantic abstract the climate variability of the south atlantic region is determined from 40 yr 1953 92 of comprehensive ocean atmosphere data set monthly sea surface temperature sst and sea level pressure slp data using the empirical orthogonal function eof and the singular value decomposition svd analysis methods the eof method is applied to each field separately whereas the svd method is applied to both fields simultaneously the significance of the atmosphere ocean interaction is revealed by a strong resemblance between individual eof and coupled svd modes of sst and slp the three leading modes of coupled variability on interannual and interdecadal timescales are discussed in some detail the first coupled mode which accounts for 63 of the total square covariance represents a 14 16 yr period oscillation in the strength of the subtropical anticyclone accompanied by fluctuations of a north south dipole structure in the sst the atmosphere ocean coupling is strongest during the southern summe

interannual to decadal predictability of tropical and north pacific sea surface temperatures abstract a multivariate empirical model is used to show that predictability of the dominant patterns of tropical and north pacific oceanic variability el nino southern oscillation enso and the pacific decadal oscillation pdo is mostly limited to little more than a year despite the presence of spectral peaks on decadal time scales the model used is a linear inverse model lim derived from the observed simultaneous and 1 yr lag correlation statistics of july june averaged sst from the hadley centre global sea ice and sea surface temperature hadisst dataset for the years 1900 2002 the model accurately reproduces the power spectra of the data including interannual and interdecadal spectral peaks that are significant relative to univariate red noise eigenanalysis of the linear dynamical operator yields propagating eigenmodes that correspond to these peaks but have very short decay times and thus limited predictability longer term predictability does exist however due to two stationary eigen

decadal variability of the kuroshio extension observations and an eddy resolving model hindcast abstract low frequency variability of the kuroshio extension ke is studied using observations and a multidecadal 1950 2003 hindcast by a high resolution 0 1 eddy resolving global ocean general circulation model for the earth simulator ofes in both the ofes hindcast and satellite altimeter observations low frequency sea surface height ssh variability in the north pacific is high near the ke front an empirical orthogonal function eof analysis indicates that much of the ssh variability in the western north pacific east of japan is explained by two modes with meridional structures tightly trapped along the ke front the first mode represents a southward shift and to a lesser degree an acceleration of the ke jet associated with the 1976 77 shift in basin scale winds the second mode reflects quasi decadal variations in the intensity of the ke jet both the spatial structure and time series of these modes derived from the hindcast are in close agreement with observations a linear rossby wave

the 2014 2015 warming anomaly in the southern california current system observed by underwater gliders large scale patterns of positive temperature anomalies persisted throughout the surface waters of the north pacific ocean during 2014 2015 in the southern california current system measurements by our sustained network of underwater gliders reveal the coastal effects of the recent warming regional upper ocean temperature anomalies were greatest since the initiation of the glider network in 2006 additional observed physical anomalies included a depressed thermocline high stratification and freshening induced biological consequences included changes in the vertical distribution of chlorophyll fluorescence contemporaneous surface heat flux and wind strength perturbations suggest that local anomalous atmospheric forcing caused the unusual oceanic conditions

an examination of historical mixed layer depths along line p in the gulf of alaska 1 mixed layer depth mld is computed based upon historical measurements along line p in the gulf of alaska forty six years of data are used for the monthly climatological calculations to examine variability the data are divided into two periods pre and post 1976 mixed layers deepen in winter post 1976 in a number of coastal stations offshore including at station p shoaling after 1976 is observed in february but there is also a phase shift with the deepest winter mixed layers occurring in april during the same period and reaching depths comparable to those seen in february prior to 1976 a pentadal analysis of mlds at station p is also carried out and no obvious regime shift in mld is seen significant variability is seen in all seasons but the variability does not correlate strongly with any of the identified north pacific patterns of climate variability

interdecadal dynamics of the north pacific ocean abstract an isopycnal ocean model forced by ncep ncar reanalysis wind stresses and heat fluxes is used to study the interdecadal variability of the pacific ocean in the 1958 97 period a reasonable agreement is found between the model s modes of variability and those obtained by other researchers from both 100 years of observations and theoretical predictions in agreement with previous observational work decadal and interdecadal timescales have different descriptions and from this study it is suggested that they indeed have different dynamics this study focuses on the dynamics of the ocean s interdecadal variability that is of timescales of about 20 yr the decadal timescale that is 10 yr is briefly outlined and compared with previous studies it is found that atmospheric heat fluxes play a key role in establishing the interdecadal sst pattern in the midlatitudinal north pacific these fluxes would excite a high baroclinic mode igniting a series of events that move around the basin in midlatitu

decadal variability of temperature at a depth of 400 meters in the north pacific ocean the gyre scale structure and evolution of decadal ocean thermocline variability in the north pacific is described by analyzing historical temperature data at a depth of 400 meters decadal thermocline anomalies are characterized by a distinct see saw pattern in the midlatitudes and subtropics that appears to circulate coherently in the north pacific basin with a period on the order of 20 years there are coherent spatial and temporal relationships between temperature anomalies around the subtropical gyre with phase differences at depth and at the sea surface suggesting that thermocline variability evolves independently of local sst anomalies in the subtropics subsurface anomalies can be seen to propagate all the way across the basin and thereby lead sst anomalies providing a possible phase transition mechanism for sst the basinwide anomaly pathways suggest a clockwise advection of subsurface temperature anomalies around the subtropical gyre an active role played by the mean geostrophic flow in decadal variability

the impact of air mass circulation dynamics on late holocene paleoclimate in northwestern north america paleoclimate records from northern british columbia southwestern yukon and adjacent alaska suggest that late holocene climate may have been influenced by specific air mass circulation dynamics the aleutian lowpressure index alpi is a measure of sea level pressure fluctuations in the pacific northwest associated with the aleutian low al pressure system in this study we show that the al has a strong influence on historical climate change in the study area and explore the relationships between alpi polarity and changes in late holocene paleoclimate records analyses of weather station data in the study area indicate positive correlations r 0 63 between mean wintertime december march temperature and alpi values total wintertime snowfall accumulation and total precipitation show moderate and weak negative correlations respectively a late holocene increase in exotic western hemlock tsuga heterophylla pollen has been observed in regional paleoclimate studies a sustained positive alpi phase during the late holocene is considered as a causative mechanism under such conditions warm maritime air masses would more frequently penetrate inland potentially resulting in eastward pollen transfer enhanced growing conditions at coastal sites and an increase eastwards in the range limit of these species this study indicates that apparent conflicts in the timing and magnitude of late holocene climate change may be the result of a strong regional climate forcing mechanism that exhibits both temporal and geographical variation r 2002 elsevier science ltd and inqua all rights reserved

last century patterns of sea surface temperatures and diatom 38 μm variability in the southern california current abstract a time series reconstruction for the last 100 years of the variability of diatoms 38 m from laminated sediments off the southern baja california margin shows the susceptibility of this phytoplankton group to oceanographic variability in the california current on different timescales here we show that cool warm years are associated with higher lower diatom accumulation values with two important exceptions one during the early 1940s associated to a strong and persistent el nino event of 1939 1942 and the second one in mid 1980s lasting into the 1990s associated with the two warmest decades in the record the anomalously high diatom accumulation values observed during these two decades are interpreted in terms of the advantage that larger diatoms have with respect to nutrient uptake over the rest of the phytoplankton under turbulent conditions there is a clear direction in the changes of the opaline flora community structure throughout the past century that parallels the observed trend towards higher ssts in the southern part of the california current the diatom succession is reflected in three types of assemblages that show a clear progression from cool spring to early summer bloom species in the earlier part of the century towards alternating cool california current and warm subtropical waters during the mid century to subtropical and tropical assemblages reflecting more stratified oligotrophic conditions during the latter part of the last century this association between opaline floral succession and the sst anomalies trend implies a long term change that cannot be explained by the same mechanisms that are commonly associated with the typical interannual or interdecadal oceanographic variability a small group of diatom species appears to follow the periodic swings of the large scale pacific decadal oscilation index the coscinodiscus argus radiatus and coscinodiscus decrescens marginatus complexes commonly found in california current waters closely follow the interdecadal variability patterns over the pacific although with a decreasing amplitude after the mid 1970s shift another variability pattern is revealed by paralia sulcata and a group of neritic tycopelagic diatom species we interpret their close resemblance with the sea level record as a tidally controlled production of this benthic assemblage into the basin with a potentially greater use as a lunar clock to fine tune ultra high resolution marine records

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

what determines the spatial pattern in summer upwelling trends on the u s west coast 1 analysis of sea surface temperature sst from coastal buoys suggests that the summertime over shelf water temperature off the u s west coast has been declining during the past 30 years at an average rate of 0 19 c decade 1 this cooling trend manifests itself more strongly off south central california than off oregon and northern california the variability and trend in the upwelling north of off san francisco are positively correlated with those of the equatorward wind indicating a role of offshore ekman transport in the north in contrast ekman pumping associated with wind stress curls better explains the stronger and statistically more significant cooling trend in the south while the coast wide variability and trend in sst are strongly correlated with those of large scale modes of climate variability they in general fail to explain the southward intensification of the trend in sst and wind stress curl this result suggests that the local wind stress curl often topographically forced may have played a role in the upwelling trend pattern

evidence for a wind driven intensification of the kuroshio current extension from the 1970s to the 1980s the spatial and temporal characteristics of oceanic thermal variations in the mixed layer and main thermocline of the midlatitude north pacific are distinctive suggesting different physical origins within the main thermocline 400 m depth the variability is dominated by a westward intensified pattern of decadal scale indicative of enhanced eastward geostrophic flow along the southern flank of the kuroshio current extension during the 1980s relative to the 1970s the authors argue that the decadal scale change in the strength of the kuroshio extension was a result of the dynamical adjustment of the oceanic circulation to a decadal variation in wind stress curl according to sverdrup theory four times daily wind stress fields from the national center for atmospheric research national centers for environmental prediction reanalysis project are used to compute the decadal change in sverdrup transport associated with the 1976 77 climate transition it is shown that the decadal changes in sverdrup transport inferred from the wind stress curl field and in observed geostrophic flow inferred from the upper ocean thermal field are consistent both in terms of spatial pattern and magnitude the decadal change in depth averaged geostrophic transport along the kuroshio extension referenced to 1 km is 11 6 sv similar to the sverdrup transport change 11 5 13 9 sv the decadal scale thermocline variation along the western boundary between 308 and 408n exhibits a lag of approximately 4 5 yr relative to the decadal variation in the basin wide wind stress curl pattern this delay may be indicative of the transient adjustment of the gyre scale circulation to a change in wind stress curl via long baroclinic rossby waves

interdecadal variability of the pacific ocean model response to observed heat flux and wind stress anomalies variability of the pacific ocean is examined in numerical simulations with an ocean general circulation model forced by observed anomalies of surface heat flux wind stress and turbulent kinetic energy tke over the period 1970 88 the model captures the 1976 77 winter time climate shift in sea surface temperature as well as its monthly seasonal and longer term variability as evidenced in regional time series and empirical orthogonal function analyses examination of the surface mixed layer heat budget reveals that the 1976 77 shift was caused by a unique concurrance of sustained heat flux input anomalies and very strong horizontal advection anomalies during a multi month period preceding the shift in both the central pacific region where cooling occurred and the california coastal region where warming occurred in the central pacific the warm conditions preceding and the cold conditions following the shift tend to be maintained by anomalous vertical mixing due to increases in the atmospheric momentum flux tke input into the mixed layer which deepens in the model after the shift from the early 1970s to the late 1970s and 1980s since the ocean model does not contain feedback to the atmosphere and it succeeds in capturing the major features of the 1976 77 shift it appears that the midlatitude part of the shift was driven by the atmosphere although effects of midlatitude ocean atmosphere feedback are still possible the surface mixed layer heat budget also reveals that in the central pacific the effects of heat flux input and vertical mixing anomalies are comparable in amplitude while horizontal advection anomalies are roughly half that size in the california coastal region in contrast where wind variability is much weaker than in the central pacific horizontal advection and vertical mixing effects on the mixed layer heat budget are only one quarter the size of typical heat flux input anomalies

radiolarian assemblages from santa barbara basin sediments recent interdecadal variability santa barbara basin contains a sedimentary record ideal for high resolution paleoclimate studies because of the annual varves and regional to global scale climate signals preserved in the sediments lange et al 1990 kennett and ingram 1995 even though it does not lie directly in the path of the california current a nearly 100 year annual time series 1909 1991 of polycystine radiolarian assemblages from santa barbara basin sbb sediments was analyzed to the species level counts on a replicate sbb core dated 1870 1987 indicate that results are reproducible and the flux of a few representative species can be extrapolated to estimate fluxes of environmentally sensitive groups the frequency of species occurrences resembles a lognormal curve and year by year comparisons of species fluxes revealed only modest changes in the assemblages from 1909 1991 indicating that the assemblages represent a single oceanic province for paleoceanographic analysis of the radiolarian record species were combined into groups according to the water mass in which they occur to test this method temperature sensitive species were identified using t tests this generated warm and cool classes exhibiting trends in relative flux similar to those of the water mass groups both total flux and relative fluxes of water mass groups relate to low frequency decadal scale temperature fluctuations but not strongly to el nino southern oscillation events generally fluxes of species from different water masses covary suggesting changing carrying capacities and productivity through time while the consistent inverse relationship in relative fluxes indicate variability in climate the subtle decadal scale changes in assemblages diversity and increase in percent warm water fauna are consistent with a spin down of the california current system suggested by other records

state of disequilibrium between 238u 234u 226ra and 222rn in groundwater from bedrock abstract approximately one thousand drilled wells were investigated for their natural radioactivity the determinations of 238u 234u 226ra and 222rn from 310 samples showed a high state of radioactive disequilibrium between the members of the uranium series present in water the 238 u 226 ra activity ratio usually fell in the range 1 20 and the 238 u 222 rn activity ratio in the range 1 20 10 4 the highest activity ratios being from samples with an elevated uranium content the 234 u 238 u activity ratio varied between 0 76 and 4 67 the most frequent values showing a 60 excess of 234u in the samples most of the 234 u 238 u activity ratios near unity were found in samples with a high uranium content several drilled wells with anomalously high uranium contents were found in southern finland the average 226ra and 222rn contents of these wells were not exceptionally high which suggests high mobility of uranium in groundwater from the areas involved

statistics of synoptic circulation weather in the north sea as derived from a multiannual ogcm simulation a 15 yr simulation of an ocean general circulation model exposed to atmospheric forcing as provided by the ecmwf reanalysis 1979 93 is analyzed with respect to the statistics of the surface circulation of the north sea on timescales of days to several weeks in winter the first two eofs of surface circulation are found to represent the bulk of the variability 72 they are broadly consistent with the limited observational record the first eof represents regimes with one gyre flushing the entire north sea either with clockwise orientation 15 of time or with counterclockwise orientation 30 of time these regimes are excited by northeasterly and respectively southwesterly wind the second eof is representative for two opposite regimes with two bipolar patterns in the northern and southern part of the north sea 45 of time for a certain range of both eofs coefficients the north sea circulation ceases 10 of time the circulation of the north sea in winter is highly variable the regimes change frequently only 40 of the one gyre regimes persist for longer than 5 days and the bipolar pattern regimes rarely extend for more than 5 days

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

the little ice age in the canadian rockies abstract this paper reviews the evidence and history of glacier fluctuations during the little ice age lia in the canadian rockies episodes of synchronous glacier advance occurred in the 12th 13th early 18th and throughout the 19th centuries regional ice cover was probably greatest in the mid 19th century although in places the early 18th century advance was more extensive glaciers have lost over 25 of their area in the 20th century selective preservation of the glacier record furnishes an incomplete chronology of events through the 14th 17th centuries in contrast varve sequences provide continuous annually resolved records of sediments for at least the last millennium in some highly glacierized catchments such records have been used to infer glacier fluctuations evaluation of recent proxy climate reconstructions derived from tree rings provides independent evidence of climate fluctuations over the last millennium most regional glacier advances follow periods of reduced summer temperatures reconstructed from tree rings particularly ca 1190 1250 1280 1340 1690s and the 1800s reconstructed periods of higher precipitation at banff alberta since 1500 are 1515 1550 1585 1610 1660 1680 and the 1880s glacier advances in the early 1700s the late 1800s and in places the 1950 1970s reflect both increased precipitation and reduced summer temperatures negative glacier mass balances from 1976 to 1995 were caused by decreased winter balances the glacier fluctuation record does not contain a simple climate signal it is a complex response to several interacting factors that operate at different timescales evaluation of climate proxies over the last millennium indicates continuous variability at several superimposed timescales dominated by decade century patterns only the 19th century shows a long interval of sustained cold summers this suggests that simplistic concepts of climate over this period should be abandoned and replaced with more realistic records based on continuous proxy data series the use of the term lia should be restricted to describing a period of extended glacier cover rather than being used to define a period with specific climate conditions

interannual variability of the kuroshio extension system and its impact on the wintertime sst field altimetry data from the first 7 yr topex poseidon t p mission october 1992 september 1999 are analyzed to investigate the interannual variability in regions of the kuroshio extension and its southern recirculation gyre large scale interannual changes of the kuroshio extension system are characterized by the oscillation between an elongated state and a contracted state in the elongated state the kuroshio extension has a larger eastward surface transport a greater zonal penetration and a more northerly zonal mean path all these characteristics are closely connected to the presence of an intense zonally elongated southern recirculation gyre in its contracted state the kuroshio extension has a smaller eastward surface transport a more southerly mean path and is accompanied by a weaker southern recirculation gyre during the t p period the kuroshio extension changed from the elongated state in 1992 93 to the contracted state in 1996 97 and back to the elongated state since late 1997 in addition to these large scale changes the mesoscale eddy field also exhibited prominent interannual changes in the kuroshio extension region in the upstream region between the izu ridge and the shatsky rise the eddy kinetic energy level was generally low while the kuroshio extension was in its elongated state and high while in the contracted state downstream of the shatsky rise on the other hand the eke level was high low when the kuroshio extension was in the elongated contracted state the large scale interannual changes in the kuroshio extension system have a significant impact on the regional wintertime sst anomaly field the warm cold wintertime sst anomalies tend to persist in years when the kuroshio extension is in its elongated contracted state a diagnostic analysis of the surface ocean heat balance indicates that the nonseasonal geostrophic advection by the ocean circulation works to reduce increase the wintertime sst anomalies when the kuroshio extension changes from an elongated contracted state to a contracted elongated state the sst anomalies associated with the large scale changes of the kuroshio extension have an area averaged peak topeak amplitude of 18c and appear independent of the interannual sst changes in the tropical pacific ocean

sea surface temperature anomalies planetary waves and air sea feedback in the middle latitudes the mechanisms that contribute to the generation and damping of large scale mid latitude sea surface temperature sst anomalies are discussed the sst anomalies reflect primarily the response of the upper ocean to the changes in air sea fluxes that are associated with daily weather fluctuations heat flux forcing is dominant in the lower middle latitudes while wind driven entrainment may be most effective in the high latitudes advection by anomalous ekman current is generally less important and ekman pumping is negligible the sst anomalies decay in part because of entrainment effects associated with mixed layer deepening and oceanic mixing and in part because of heat exchanges with the atmosphere the three approaches commonly used to model the evolution of sst anomalies are reviewed case studies based on monthly or seasonal anomaly maps of the large scale sst and atmospheric anomalies numerical simulations with one dimensional mixed layer models and stochastic forcing models we stress the similarities in the different approaches and discuss their main advantages and limitations the response of the atmosphere to mid latitude sst anomalies is considered first we discuss the poorly known relationship between sst anomalies and diabatic heating using a crude assumption for the air sea coupling we consider a two layer quasi geostrophic channel model and discuss the stationary wave response to sst anomaly forcing and the resulting air sea feedback it is found that the back interaction of the sst anomalies onto the atmosphere causes a weak sst anomaly damping at large scales and a strong one at small scales the air sea coupling should also act as an eastward propagator for the sst anomalies the response of more realistic linear wave models to prescribed diabatic heating is then reviewed and it is suggested that realistic mid latitude sst anomalies have a weak influence on the atmospheric circulation corresponding to changes in the geopotential height of 10 30 m at most this order of magnitude is consistent with the results of general circulation model experiments and with the limited climate predictability associated with mid latitude sst anomalies

the continuum of north pacific sea level pressure patterns intraseasonal interannual and interdecadal variability this study combines k means cluster analysis with linear unidimensional scaling to illustrate the spatial and temporal variability of the wintertime north pacific sea level pressure slp field daily wintertime slp data derived from the ncep ncar reanalysis are used to produce 16 slp anomaly patterns that represent a discretized approximation of the continuum of north pacific slp patterns this study adopts the continuum perspective for teleconnection patterns which provides a much simpler framework for understanding north pacific variability than the more commonly used discrete modal approach the primary focus of this research is to show that variability in the north pacific on intraseasonal interannual and interdecadal time scales can be understood in terms of changes in the frequency distribution of the cluster patterns that compose the continuum each of which has a time scale of about 10 days this analysis reveals 5 6 pacific north american like pna like patterns for each phase as well as dipoles and wave trains a self organizing map som analysis of coupled slp and outgoing longwave radiation data shows that many of these patterns are associated with convection in the tropical indo pacific region on intraseasonal time scales the frequency distribution of these patterns in particular the pna like patterns is

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

a modelling and observational study of the relationship between sea surface temperature in the north west atlantic and the atmospheric general circulation results from four pairs of 50 day wintertime integrations of the meteorological office s 5 level general circulation model with warm and cold sea surface temperature s s t anomalies of about 3 k in the northwest atlantic are described difference fields between the warm and cold integrations are statistically significant at the 1 level with positive geopotential height over the central north atlantic and weaker negative height over europe the storm track over the atlantic is displaced from its normal position results from four further pairs of integrations with halved s s t anomalies are also described the response is approximately linear with systematic differences in 500 mb geopotential height over the atlantic parts of which are just significant at the 10 level with half the full s s t anomaly overall however the model s response is weaker than could be obtained with tropical s s t anomalies of the same magnitude results from the model integrations are compared with results from an observational study of the relationship between wintertime s s t in the north west atlantic and mean sea level pressure and 500mb height two independent 30 year periods were chosen for study thus minimizing the influence of long term trends in s s t over the atlantic and europe the model results compared well with the observations with s s t data lagging the atmosphere by one month the observational study appears to show that the s s t anomalies are initially forced by perturbations in the atmospheric circulation with s s t data leading the atmosphere by one month results show that atmospheric and s s t anomalies are most persistent in the period october to december throughout the winter these lagged relationships are much weaker and not statistically significant diagnostics of e vector divergence from the gcm experiments are used to suggest that anomalous baroclinic wave activity over the atlantic is important as a momentum forcing for the anomalous time mean flow pattern on the other hand the role of thermal forcing provided by anomalous diabatic heating and transient eddy heat flux convergence may be important to substantiate this statement a simple linear steadystate two layer model of the response to extratropical thermal forcing is described with a suitable basic state flow and a mid tropospheric heat source given mainly by the transient eddy heat flux convergence the response is shown to be equivalent barotropic with a downstream ridge and ascent over the thermal source conversely results from an ocean mixed layer model are discussed which suggest that warm s s t anomalies could be maintained by a positive surface pressure perturbation positioned downstream of the anomaly through anomalous northward advection of warm ocean water by ekman drift currents this northward advection would balance the sensible and latent heat loss into the atmosphere over the s s t anomaly hence it is possible that some positive ocean atmosphere feedback may account for the persistence of such atmospheric and oceanic anomalies

origin of decadal scale eastward propagating heat content anomalies in the north pacific abstractupper ocean heat content ohc is at the heart of natural climate variability on interannual to decadal time scales providing climate memory and the source of decadal prediction skill in the midlatitude north pacific ocean ohc signals are often found to propagate eastward as opposed to the frequently observed westward propagation of sea surface height another variable that represents the ocean subsurface state this dichotomy is investigated using a 150 yr coupled gcm integration simulated ohc signals are distinguished in terms of two processes that can support eastward propagation higher baroclinic rossby wave rw modes that are associated with density perturbation and spiciness anomalies due to density compensated temperature and salinity anomalies the analysis herein suggests a unique role of the kuroshio oyashio extension koe region as an origin of the spiciness and higher mode rw signals wind forced westward propagating equivalent barotropic rws cause meridional shifts of the sub