decadal variability in the kuroshio oyashio extension simulated in an eddy resolving ogcm abstract through analysis of a hindcast integration of an eddy resolving quasi global ocean general circulation model decadal variability in the kuroshio oyashio extension region is investigated with particular emphasis on that of the subarctic oyashio and the kuroshio extension ke fronts the ke front is deep and is accompanied by a sharp sea surface height ssh gradient with modest sea surface temperature sst gradient in contrast the subarctic front is shallow and is recognized as a zone of tight gradient in sst but not ssh as a decadal scale change from a warm period around 1970 to a cool period in the mid 1980s those fronts in the model migrate southward as observed and the associated pronounced cooling is confined mainly to those frontal zones reflecting the distinctive vertical structure of the fronts the mixed layer cooling is the strongest along the subarctic front whereas the subsurface cooling and the associated salinity changes are most pronounced along the ke front concomitan

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

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

interannual and decadal modulations recently observed in the pacific storm track activity and east asian winter monsoon abstract interannual variability of the north pacific storm track observed over 17 recent winters is documented the local storm track activity is measured by a meridional flux of sensible heat associated with the lower tropospheric subweekly fluctuations the interannual variability in the heat flux over the northwestern nw pacific is found to be strongest in midwinter the first empirical orthogonal function of the interannual variability in midwinter captures the decadal tendency toward the enhanced storm track activity in midwinter over the nw pacific in association with the decadal weakening of the east asian winter monsoon siberian high and the aleutian low that occurred in the late 1980s the most marked signature of this enhancement is that the midwinter minimum in the storm track activity which had been apparent in the early to mid 1980s almost disappeared afterward as opposed to linear theory of baroclinic instability the enhanced activity occurred despite the weakening of the pacific j

decadal response of the kuroshio extension jet to rossby waves observation and thin jet theory abstractthis study examines interannual to decadal variability of the kuroshio extension ke jet using satellite altimeter observations from 1993 to 2010 the leading empirical orthogonal function eof mode of sea level variability in the ke region represents the meridional shift of the ke jet followed by its strength changes with a few month lag this shift of the ke jet lags atmospheric fluctuations over the eastern north pacific by about three years broad sea level anomalies slas emerge in the eastern north pacific 3 4 years before the upstream ke jet shift and propagate westward along the ke jet axis in the course of the propagation the meridional scale of the slas gradually narrows and their amplitude increases this westward propagation of slas with a speed of about 5 cm s 1 is attributed to the westward propagation of the meridional shift of the jet consistent with the thin jet theory whose importance has been suggested by previous numerical studies in addition the westward propagatin

a comparison between the generalized digital environmental model and levitus climatologies two ocean climatologies of temperature and salinity the generalized digital environmental model gdem and the climatological atlas of the world ocean are compared dynamic height fields are computed by season from each climatology for the north atlantic north pacific and indian oceans and are compared on a 1 latitude longitude grid large scale oceanographic features are generally found to be similarly represented in both climatologies gdem appears to render better representations of seasonal variability and regions of high current shear such as the gulf stream because of a different smoothing method and a finer grid spacing maps of dynamic heights from both climatologies are presented and their similarities and differences are discussed the methodology for the construction of gdem is also described in detail

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

kuroshio extension variability and forcing of the pacific decadal oscillations responses and potential feedback abstract a forcing mechanism is sought for the large scale circulation changes in the kuroshio extension region of the western north pacific ocean as inferred by topex poseidon sea surface height ssh data the low frequency signal of the kuroshio extension over the last decade was characterized by a modulation in its zonal mean flow intensity the mean kuroshio extension jet weakened progressively from 1993 to 1996 and this trend reversed after 1997 the ability to simulate the major trends in the observed ssh signals with linear vorticity dynamics leads the authors to conclude that the modulation in the zonal mean jet was remotely forced by wind stress curl anomalies in the eastern north pacific ocean related to the pacific decadal oscillations pdos to be specific the weakening strengthening trend in 1993 96 1997 2001 was caused by westward expansions of negative positive ssh anomalies south of the kuroshio extension and positive negative ssh anomalies north of the kuroshio extension emerg

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

northern hemisphere winter atmospheric transient eddy heat fluxes and the gulf stream and kuroshio oyashio extension variability abstractspatial and temporal covariability between the atmospheric transient eddy heat fluxes i e t and q in the northern hemisphere winter january march and the paths of the gulf stream gs kuroshio extension ke and oyashio extension oe are examined based on an atmospheric reanalyses and ocean observations for 1979 2009 for the climatological winter mean the northward heat fluxes by the synoptic 2 8 days transient eddies exhibit canonical storm tracks with their maxima collocated with the gs and ke oe the intraseasonal 8 days 3 months counterpart while having overall similar amplitude shows a spatial pattern with more localized maxima near the major orography and blocking regions lateral heat flux divergence by transient eddies as the sum of the two frequency bands exhibits very close coupling with the exact locations of the ocean fronts linear regression is used to examine the lead lag relationship between interannual changes in the northward heat fluxes by the transient

western boundary currents and frontal air sea interaction gulf stream and kuroshio extension abstract in the northern hemisphere midlatitude western boundary current wbc systems there is a complex interaction between dynamics and thermodynamics and between atmosphere and ocean their potential contribution to the climate system motivated major parallel field programs in both the north pacific kuroshio extension system study kess and the north atlantic climate variability and predictability clivar mode water dynamics experiment climode and preliminary observations and analyses from these programs highlight that complexity the gulf stream gs in the north atlantic and the kuroshio extension ke in the north pacific have broad similarities as subtropical gyre wbcs but they also have significant differences which affect the regional air sea exchange processes and their larger scale interactions the 15 yr satellite altimeter data record which provides a rich source of information is combined here with the longer historical record from in situ data to describe and compare the curr

effect of decadal kuroshio extension jet and eddy variability on the modification of north pacific intermediate water abstract salinity modifications in the north pacific intermediate water npiw core layer of 26 7 26 8 in the western north pacific ocean are investigated using temperature salinity data from available profiling float and hydrographic measurements in 2002 09 during 2002 05 when the kuroshio extension ke jet was intense and zonally elongated coherent positive salinity anomalies appeared along the inflow ke jet southeast of japan and in the downstream mixed water region east of 152 e broad scale negative salinity anomalies were detected south of the ke jet and in the upstream mixed water region west of 152 e the signs of these observed salinity anomalies were reversed in 2006 09 when the ke jet transitioned to a weakened and zonally contracted dynamic state by adopting an isopycnal advection diffusion model and conducting model runs with the time dependent advective field inferred from the eddy resolving satellite altimeter sea surface height data it is found that the observed salinity anomalie

evaluation of hycom in the kuroshio extension region using new metrics 1 a high resolution 0 08 at equator hybrid coordinate ocean model hycom simulation is evaluated using observations for the period 1993 2003 for a western pacific region containing the kuroshio extension ke 25 45 n and 135 180 e comparisons are made for the ke path and strength and for the upper ocean heat budget the mean strength and path agree well with observations except near the ke separation point where the jet is as much as 2 of latitude too far south however the model path variations are considerably more energetic than observed and this likely obscures the observed tendency for weaker meandering when the ke is strong the model accurately reproduces seasonal variations of upper ocean heat content but the long period about 10 yr variations of heat content and ke strength clearly differ in the region upstream of 150 e the long period variations in model ssh do not show the same relationship to wind forcing that is seen in the observations and in a low resolution ocean model simulation the hycom upper ocean heat budget is similar to a diagnostic heat budget inferred from observations in that the dominant contribution is from lateral fluxes advection however advection fluctuations again primarily in the upstream region are much larger in the model this evaluation of hycom shows realistic mean quantities and realistic variations away from the separation region however an overly energetic jet upstream of 150 e can obscure the longer period variability and its contribution to the upper ocean heat budget

ocean frontal effects on the vertical development of clouds over the western north pacific in situ and satellite observations abstract a suite of shipboard and satellite observations are analyzed and synthesized to investigate the three dimensional structure of clouds and influences from sea surface temperature fronts over the western north pacific sharp transitions are observed across the kuroshio extension ke front in the marine atmospheric boundary layer mabl and its clouds the ocean s influence appears to extend beyond the mabl with higher cloud tops in altitude along the ke front than the surroundings in winter intense turbulent heat release from the ocean takes place on the southern flank of the ke front where the cloud top penetrates above the mabl and reaches the midtroposphere in this band of high cloud tops frequent lightning activity is observed the results of this study suggest a sea level pressure mechanism for which the temperature gradient in the mabl induces strong surface wind convergence on the southern flank of the ke front deepening the clouds there in early summer sea fog frequently occurs on

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

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

variability of the kuroshio extension jet recirculation gyre and mesoscale eddies on decadal time scales abstract twelve years of sea surface height ssh data from multiple satellite altimeters are used to investigate the low frequency changes and the interconnections of the kuroshio extension ke jet its southern recirculation gyre and their mesoscale eddy field the dominant signal is characterized by the steady weakening of the ke jet recirculation gyre from 1993 to 1996 followed by a gradual strengthening after 1997 during the weakening period of 1993 96 the ke path migrated southward in general and this path migration reversed in direction during the strengthening period of the ke jet and recirculation gyre after 1997 by hindcasting the ssh signals using linear vorticity dynamics it was found that weakening strengthening in the ke jet and recirculation gyre is consistent with westward propagation of negative positive ssh anomalies generating in the eastern north pacific and strengthening during their westward propagation when the ke jet and recirculation gyre were in a weak mode during 19

observed influence of north pacific sst anomalies on the atmospheric circulation abstract a lagged maximum covariance analysis mca of monthly anomaly data from the ncep ncar reanalysis shows significant relations between the large scale atmospheric circulation in two seasons and prior north pacific sea surface temperature sst anomalies independent from the teleconnections associated with the enso phenomenon regression analysis based on the sst anomaly centers of action confirms these findings in late summer a hemispheric atmospheric signal that is primarily equivalent barotropic except over the western subtropical pacific is significantly correlated with an sst anomaly mode up to at least 5 months earlier although the relation is most significant in the upper troposphere significant temperature anomalies are found in the lower troposphere over north america the north atlantic europe and asia the sst anomaly is largest in the kuroshio extension region and along the subtropical frontal zone resembling the main mode of north pacific sst anomaly variability in late winter

eddy mean flow interaction in the decadally modulating kuroshio extension system abstract satellite altimeter sea surface height ssh data of the past 16 years are used to investigate the decadal changes of the kuroshio extension ke system that oscillated between a stable and an unstable dynamic state during the stable state of 10 1992 06 1995 and 01 2002 12 2004 the ke jet was intense and had a northerly zonal mean path and a well defined southern recirculation gyre during the unstable state of 07 1995 12 2001 and 01 2005 present the ke jet had a reduced eastward transport and a more southerly flow path transitions between the two dynamic states are caused by the basin scale wind stress curl forcing in the eastern north pacific related to the pacific decadal oscillations pdos or the north pacific gyre oscillations npgos during the positive pdo or negative npgo phase the intensified aleutian low generates negative ssh anomalies in the eastern north pacific through ekman divergence as these wind induced negative ssh anomalies propagate to the west as baroclinic rossby waves they weaken the zonal ke jet and shift its path southward as its path is pushed southward 32 n the deep reaching ke jet has to ride over the shallow shatsky rise generating localized disturbances that lead to their subsequent development along the ke jet west of the shatsky rise the sequence opposite to that listed above occurs when the pdo npgo changes to its negative positive phase after the ke system transitions from a stable to unstable state the enhanced eddy interaction is found to strengthen both the southern recirculation gyre and quasi stationary meanders along the ke s upstream path this nonlinear eddy interaction is important in determining the amplitude of the observed decadal ke variability

large scale variability in the midlatitude subtropical and subpolar north pacific ocean observations and causes abstract altimetric data from the 8 yr topex poseidon t p mission oct 1992 jul 2000 are used to investigate large scale circulation changes in the three current systems of the midlatitude north pacific ocean the north pacific current npc the alaska gyre and the western subarctic gyre wsg to facilitate the understanding of the observed changes a two layer ocean model was adopted that includes first mode baroclinic rossby wave dynamics and barotropic sverdrup dynamics the npc intensified steadily over the t p period from 1992 to 1998 much of this intensification is due to the persistent sea surface height ssh drop on the northern side of the npc a similar ssh trend is also found in the interior of the alaska gyre both of these ssh changes are shown to be the result of surface wind stress curl forcing accumulated along the baroclinic rossby wave characteristics initiated from the eastern boundary in addition to the interior ssh signals the intensity of the alaska gyre is shown to depend

predicting western north pacific ocean climate abstract it is shown that wintertime sea surface temperature anomalies in the confluence region of the kuroshio oyashio currents in the western north pacific can be skillfully predicted at lead times of up to 3 yr the predictions are based on the history of the wind stress over the north pacific and oceanic rossby wave dynamics the predictions may be exploitable in fisheries research and other ecological applications

hawaiian lava flows in the third dimension identification and interpretation of pahoehoe and a a distribution in the kp 1 and soh 4 cores 1 hawaiian lava flows are classified as pahoehoe or a a by their surface morphology as surface morphology reflects flow emplacement conditions the surface distribution of morphologic flow types has been used to study the evolution and eruptive history of basaltic volcanoes we extend this analysis to the third dimension by determining the distribution of flow types in two deep drill cores the scientific observation hole 4 soh 4 core drilled near kilauea s east rift zone erz and the pilot hole kahi puka 1 kp 1 for the hawaiian scientific drilling project hsdp drilled through distal flows from mauna loa and mauna kea flows are classified using both internal structures and groundmass textures with the latter useful when identification based on mesoscopic flow features e g surface morphology and vesicle content and distribution is ambiguous we then examine the temporal distribution of pahoehoe and a a flows in proximal soh 4 and distal kp 1 settings sequence analysis shows that the two flow types are not randomly distributed in either core but instead are strongly clustered the proximal soh 4 core is dominated by thin pahoehoe flows 60 by volume consistent with the common occurrence of surface fed pahoehoe flows in near vent settings the distal kp 1 core has a high proportion of a a 58 by volume although the proportion of pahoehoe and a a varies dramatically throughout the mauna kea sequence thick inflated pahoehoe flows dominate when the drill site was near sea level consistent with the numerous inflated pahoehoe fields on the current coastal plains of kilauea and mauna loa a a flows are abundant when the site was far above sea level as slope increases from the coastal plains to mauna kea s flank this correlation may reflect the combined effect of long transport distances and increased slopes on flow emplacement these results demonstrate that flow type and thickness variations in cores provide valuable information about both vent location and local site environment observed variations in flow type within the kp 1 core raise interesting questions about feedback between volcano evolution and flow morphology and suggest that flow type is an important variable in models of volcano growth and related models for lava flow hazard assessment

annual and interannual variability in the kuroshio current system abstract individual seasonal 300 m temperature maps were constructed over the kuroshio current system from 130 e to 170 w for a 4 year period from summer 1976 through spring 1980 using transpac xbt data and jodc temperature depth data quasi stationary meanders in the kuroshic current system occurred at 137 c i e kuroshio meander at 144 e and 150 e i e lee wave meanders and near 160 e i e meander over the shatsky rise a composite of the paths of the kuroshio i e the 12 c isotherm from the individual seasonal maps and the total variance map finds nodes i e minima and anti nodes i e maxima of variability to have existed along the mean kuroshio path the anti nodes coincided with the location of the quasi stationary meanders the nodes in between zonal propagation of temperature anomalies accounted for 20 30 of the total interannual variance these temperature anomalies propagated eastward at 0 5 1 5 cm s 1 in the region 140 155 e and westward at 1 to 2 cm s 1 in the re

north pacific decadal variability in the community climate system model version 2 abstract north pacific decadal oceanic and atmospheric variability is examined from a 650 yr control integration of the community climate system model version 2 the dominant pattern of winter sea surface temperature sst variability is similar to the observed pacific decadal oscillation with maximum amplitude along the kuroshio extension sst anomalies in this region exhibit significant spectral peaks at approximately 16 and 40 yr lateral geostrophic heat flux divergence caused by a meridional shift of the kuroshio extension forced by basin scale wind stress curl anomalies 3 5 yr earlier is responsible for the decadal sst variability local surface heat flux and ekman heat flux divergence act as a damping and positive feedback respectively a simple linear rossby wave model is invoked to explicitly demonstrate the link between the wind stress curl forcing and decadal variability in the kuroshio extension the rossby wave model not only successfully reproduces the two decadal spectral peaks but a

on the existence of storm tracks abstract given that middle latitude weather systems transport heat in a manner such as to weaken the baroclinicity that is thought to be crucial to their growth it is perhaps surprising that concentrated regions of such eddy activity i e storm tracks are found in the northern hemisphere winter the existence and possible self maintenance of storm tracks is investigated using a linear stationary wave model with storm track region forcings taken from data averaged over a number of winters it is found that the direct thermal effect of the eddies does indeed act against the existence of the storm track their vorticity fluxes lead to some reduction of this effect it is argued that the mean diabatic heating in the storm track region is an indirect eddy effect this heating is found to maintain the mean maximum in baroclinicity in the region further the mean low level flow induced by the eddy effects is such as to enhance the warm western oceanic boundary currents that are crucial to the existence of t

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

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

wave formed sand ripples at duck north carolina a recently developed acoustic multiple transducer array was utilized to measure small scale bed forms in the nearshore and inner shelf regions at duck north carolina two populations of wave formed ripples were observed short wave ripples swr with heights ranging from 3 mm to 2 cm and lengths ranging from 4 to 25 cm and long wave ripples lwr with heights ranging from 3 mm to 6 cm and lengths ranging from 35 to 200 cm the swr were only present sometimes and their presence or absence was determined by a critical value of the near bed mobility number the swr were highly dynamic sometimes flattening during wave groups and reforming over several incident wave periods the lwr in contrast were almost always present they were longer and lower relief than predicted by models or generally observed previously both swr and lwr were often observed to migrate shoreward but were rarely observed to migrate seaward the dimensions of the swr when they were present were predictable by the nielsen 1981 model or the wiberg and harris 1994 model to within approximately a factor of 2

north pacific gyre oscillation synchronizes climate fluctuations in the eastern and western boundary systems abstract recent studies have identified the north pacific gyre oscillation npgo as a mode of climate variability that is linked to previously unexplained fluctuations of salinity nutrient and chlorophyll in the northeast pacific the npgo reflects changes in strength of the central and eastern branches of the subtropical gyre and is driven by the atmosphere through the north pacific oscillation npo the second dominant mode of sea level pressure variability in the north pacific it is shown that rossby wave dynamics excited by the npo propagate the npgo signature in the sea surface height ssh field from the central north pacific into the kuroshio oyashio extension koe and trigger changes in the strength of the koe with a lag of 2 3 yr this suggests that the npgo index can be used to track changes in the entire northern branch of the north pacific subtropical gyre these results also provide a physical mechanism to explain coherent decadal climate variations and ecosystem changes between the no