observations of the kuroshio s barotropic and baroclinic responses to basin wide wind forcing 1 observations show that the kuroshio in the east china sea ecs kuroshio responds to the large scale wind stress curl field at two time scales it is argued that these two responses are related to barotropic and baroclinic modes that reach the ecs via different waveguides variability in the ecs kuroshio is assessed by comparing satellite altimetry historical hydrography and the pacific decadal oscillation pdo index with the latter used as a proxy for the large scale wind stress curl forcing sea level difference across the ecs kuroshio is positively correlated with pdo at zero lag and negatively correlated at 7 year lag in contrast pycnocline steepness and pdo are uncorrelated at zero lag and negatively correlated at 7 year lag these signals in the ecs kuroshio considered together with wind stress curl anomalies in the open ocean are consistent with a barotropic response to the wind at zero lag the barotropic response is likely forced in the central north pacific by wind stress curl anomalies of opposite sign one of which is centered at ecs latitudes 27 n while the other sits further north this suggests that in general the absolute transport at a given latitude is not simply that predicted by the sverdrup balance along the latitude this is a consequence of waveguides that can steer the barotropic mode across latitude lines in contrast the signals that lag pdo by 7 years are consistent with a baroclinic mode which represents the ocean s time integrated response to the wind stress curl along a single latitude band between 24 n and 27 n

formation and spreading of subtropical mode water in the north pacific a time averaged description of the formation and spreading of north pacific subtropical mode water npstmw is presented the formation of npstmw is studied using transpac expendable bathythermograph data the data are transformed into a stream coordinate system and averaged the coordinate system uses the position of the kuroshio front as its origin maps are presented of the temperature structure and mixed layer distribution in winter relative to the kuroshio front the formation of npstmw occurs in two separate stages cooling and thickening as water flows at the surface in the kuroshio in winter the water is cooled by the intense ocean atmosphere heat flux taking place in the area when water leaves the kuroshio to the south the thermocline underneath becomes deeper convection is able to penetrate deep into the water column and the heat flux acts more to thicken the surface mixed layer rather than reduce the temperature the area south of the kuroshio where relatively homogeneous waters are found is the source region for npstmw at the end of the winter the thick mixed layers are assumed to be covered over by a seasonal thermocline and become npstmw the levitus 1982 data are used to study the way in which npstmw is spread away from its source region by the subtropical circulation the distribution of potential vorticity pv on four npstmw isopycnals is studied with low pv used as a tracer for npstmw the pv reveals a pattern of differential spreading whereby npstmw formed in the western part of the source region is advected to the west after its formation npstmw formed farther east is advected more to the south or east after formation differential spreading allows npstmw to be found in a large part of the northwestern subtropical gyre well away from its source region the distribution of npstmw described by masuzawa 1969 with npstmw getting colder from west to east is explained as a combination of the distribution of npstmw at its source and the way it is spread after it is formed

estimating eddy stresses by fitting dynamics to observations using a residual mean ocean circulation model and its adjoint a global ocean circulation model is formulated in terms of the residual mean and used to study eddy mean flow interaction adjoint techniques are used to compute the three dimensional eddy stress field that minimizes the departure of the coarse resolution model from climatological observations of temperature the resulting 3d maps of eddy stress and residual mean circulation yield a wealth of information about the role of eddies in large scale ocean circulation in eddy rich regions such as the southern ocean the kuroshio and the gulf stream eddy stresses have an amplitude comparable to the wind stress of order 0 2 n m 2 and carry momentum from the surface down to the bottom where they are balanced

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 north pacific climatology of winter mixed layer and mode waters abstract a climatology of the winter mixed layer in the north pacific ocean was constructed using hydrographic data from historical archives and recent observational programs including the world ocean circulation experiment the main aim was to provide better knowledge about source areas of upper water masses the authors have endeavored to preserve water properties near the frontal regions by keeping the smoothing scale as small as possible the resulting climatology shows considerable differences in the mixed layer depth and its water properties from those derived from the world ocean atlas woa maps of the potential vorticity field of the north pacific pycnocline are presented using the isopycnally averaged climatology hydrobase three distinct lateral minima of potential vorticity are identified as subtropical mode water stmw central mode water cmw and eastern subtropical mode water estmw in the western central and eastern parts of the subtropical gyre respectively the hydrobase isopy

three levels of compartmentation within the overpressured interval of the anadarko basin deep basin pressure compartments can be classified on the basis of their size stratigraphy and pressure regimes detailed investigations of the geologic setting and pressure gradients of numerous reservoirs in the anadarko basin reveal the presence of three distinct levels of compartmentation level 1 is a basinwide feature known as the megacompartment complex mcc this complex is an overpressured volume of rocks that is completely enclosed by seals it is approximately 241 km 150 mi long 113 km 70 mi wide and has a maximum thickness in excess of 4877 m 16 000 ft gas reserves of the overpressured reservoirs within the mcc are speculated to be approximately 20 tcf the other two compartmentation levels are further subdivisions of the internal volume of the mcc level 2 compartmentation consists of multiple district or field sized configurations within a particular stratigraphic interval these compartments are 32 to 49 km 20 to 30 mi long 19 to 32 km 12 to 20 mi wide and 122 to 183 m 400 to 600 ft thick their reserve estimates can exceed 2 tcf examples of this type are the upper morrowan chert conglomerate reservoirs in the cheyenne reydon field area level 3 consists of a single small field or a particular reservoir nested within level 2 these compartments are generally 3 to 6 km 2 to 4 mi long the hierarchical classification of compartments has important implications for petroleum exploration and development recognizing the upper and lower boundaries of the mcc is essential to safe drilling practices the similar pressures within level 2 compartments allow the prediction of approximate reservoir pressures across trend size areas of the basin tens to

multidecadal variations in the early holocene outflow of red sea water into the arabian sea we present holocene stable oxygen isotope data from the deep arabian sea off somalia at a decadal time resolution as a proxy for the history of intermediate upper deep water these data show an overall 18o reduction by 0 5 between 10 and 6 5 kyr b p superimposed upon short term 18o variations at a decadal centennial timescale the amplitude of the decadal variations is 0 3 prior and up to 0 6 subsequent to 8 1 kyr b p we conclude from modeling experiments that the short term 18o variations between 10 and 6 5 kyr b p most likely document changes in the evaporation precipitation balance in the central red sea changes in water temperature and salinity cause the outflowing red sea water to settle roughly 800 m deeper than today

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

heat budget in the kuroshio extension region 1993 99 abstract processes responsible for the seasonal and interannual variations of the sea surface temperature as well as of the heat content of the upper ocean 0 400 m in the kuroshio extension region are examined from a 3d advection diffusion model in finite elements with an embedded bulk mixed layer the geostrophic velocity is specified externally from topex poseidon altimeter data and ekman velocity is specified from ncep wind stress the thermal field from the model shows good agreement with observations while both atmospheric and oceanic processes are required to explain observed nonseasonal sst changes the interannual heat storage rate is dominated by horizontal advection in particular the transition between an elongated and a contracted state of the kuroshio caused by geostrophic advection has a clear signature in the sst there is an indication that this process is accompanied by consistent changes in nonseasonal entrainment when the kuroshio is in an elongated state and warmer waters are pr

subtropical mode water variation in the northwestern part of the north pacific subtropical gyre temporal variations of the north pacific subtropical mode water npstmw are studied with the proper temporal resolution for describing seasonal variation using monthly hydrographic data taken near the ogasawara islands npstmw is formed south of the kuroshio and the kuroshio extension in late winter and advected to the ogasawara site by the southwestward westward return flow of the kuroshio recirculation while npstmw is seen at the ogasawara site in almost all seasons npstmw with a higher core temperature is advected to this site in april and one with a colder core follows in and after june until january or february furthermore the npstmw core temperature shows considerable interannual variation this variation is very similar to that found in other regions away from the ogasawara site suggesting that it reflects the larger scale variation of npstmw and that this site would be suitable for monitoring the npstmw core temperature a significant correlation between the npstmw core temperature and the monsoon index which is defined as the difference in the sea level pressure between nemuro japan and irkutsk russia as an indicator of wintertime cooling indicates that npstmw contains a memory of wintertime cooling in the preceding winter

potential vorticity distribution in the north pacific abstract vertical sections and maps of potential vorticity 1f z for the north pacific are presented on shallow isopycnals high potential vorticity is found in the tropics subpolar gyre and along the eastern boundary of the subtropical gyre all associated with ekman upwelling low potential vorticity is found in the western subtropical gyre subtropical mode water in a separate patch near the sea surface in the eastern subtropical gyre and extending around the gyre and near sea surface outcrops in the subpolar gyre the last is analogous to the subpolar mode water of the north atlantic and southern ocean meridional gradients of potential vorticity are high between the subtropical and subpolar gyres at densities which outcrop only in the subpolar gyre lateral gradients of potential vorticity are low in large regions of the subtropical gyre on these isopycnals on slightly denser isopycnals which do not outcrop in the north pacific there are large regions of low potential vorticity gradients

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

a role of eddies in formation and transport of north pacific subtropical mode water 1 hydrographic data acquired during 2001 by argo profiling floats deployed in the kuroshio recirculation region are used to verify the inference that mesoscale eddies prevailing in the recirculation region play an important role in the formation and transport of north pacific subtropical mode water npstmw that is the deeper winter mixed layer is formed preferentially where the thermocline is deeper in association with anticyclonic eddies in the succeeding seasons mesoscale eddies retain npstmw during their southwestward movement from the npstmw formation region so that anticylonic eddies contribute substantially to the npstmw transportation the spatial distributions of the mixed layer depth in winter and the npstmw thickness in the succeeding seasons based on the float data suggest that they are affected by mesoscale eddies the float data also provide the statistical relations of these quantities against the thermocline depth which are consistent with our inference

observations of the subtropical mode water evolution from the kuroshio extension system study abstract properties and seasonal evolution of north pacific ocean subtropical mode water stmw within and south of the kuroshio extension recirculation gyre are analyzed from profiling float data and additional hydrographic and shipboard adcp measurements taken during 2004 the presence of an enhanced recirculation gyre and relatively low mesoscale eddy variability rendered this year favorable for the formation of stmw within the recirculation gyre stmw formed from late winter convection that reached depths greater than 450 m near the center of the gyre the lower boundary of stmw corresponding to 25 5 kg m 3 was set by the maximum depth of the late winter mixed layer properties within the deep portions of the stmw layer remained largely unchanged as the season progressed in contrast the upper boundary of the stmw layer eroded steadily as the seasonal thermocline deepened from late april to august vertical eddy diffusivity responsible for this erosion was estimated from a budget analysis of

interannual variations in upper ocean heat content and heat transport convergence in the western north atlantic subsurface temperature data in the western north atlantic ocean are analyzed to study the variations in the heat content above a fixed isotherm and contributions from surface heat fluxes and oceanic processes the study region is chosen based on the data density its northern boundary shifts with the gulf stream position and its southern boundary shifts to contain constant volume the temperature profiles are objectively mapped to a uniform grid 0 5 latitude and longitude 10 m in depth and 3 months in time the interannual variations in upper ocean heat content show good agreement with the changes in the sea surface height from the ocean topography experiment topex poseidon altimeter both indicate positive anomalies in 1994 and 1998 99 and negative anomalies in 1996 97 the interannual variations in surface heat fluxes cannot explain the changes in upper ocean heat storage rate on the contrary a positive anomaly in heat released to the atmosphere corresponds to a positive upper ocean heat content anomaly the oceanic heat transport mainly owing to the geostrophic advection controls the interannual variations in heat storage rate which suggests that geostrophic advection plays an important role in the air sea heat exchange the 18 c isotherm depth and layer thickness also show good correspondence to the upper ocean heat content a deep and thin 18 c layer corresponds to a positive heat content anomaly the oceanic transport in each isotherm layer shows an annual cycle converging heat in winter and diverging in summer in a warm layer it also shows interannual variations with the largest heat convergence occurring in even warmer layers during the period of large ocean to atmosphere flux

evolution of the north pacific subtropical mode water in anticyclonic eddies anticyclonic eddies aes trap and transport the north pacific subtropical mode water stmw but the evolution of the stmw trapped in aes has not been fully studied due to the lack of eddy tracking subsurface observations here we analyze profiles from special designed argo floats that follow two stmw trapping aes for more than a year the enhanced daily sampling by these argo floats swirling around the eddies enables an unprecedented investigation into the structure and evolution of the trapped stmw in the aes the upper lower thermocline domes up concaves downward and this lens shaped double thermocline encompasses the thick stmw within the eddy core the lighter stmw 25 0 25 2 trapped in aes dissipates quickly after the formation in winter because of the deepening seasonal thermocline but the denser stmw 25 2 25 4 remains largely unchanged except when the ae passes across the izu ridge the enhanced diapycnal mixing over the ridge weakens the denser stmw appreciably while many aes decay upon hitting the ridge some pass through a bathymetric gap between the hachijojima and bonin islands forming a cross ridge pathway for stmw transport by contrast the north pacific intermediate water npiw underneath is deeper than the eddy trapping depth 600 m and hence left behind east of the izu ridge in argo climatology the shallow stmw 400 m intrudes through the gap westward because of the eddy transport while the npiw 800 m is blocked by the izu ridge

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

modulation of decadal oscillation on surface chlorophyll in the kuroshio extension 1 in the study the responses of chlorophyll to decadal oscillations of kuroshio extension ke between two dynamical states are investigated using satellite data associated with the ke stable and unstable states the surface chlorophyll south of 35 n also undergoes two different contrast patterns low high chlorophyll 12 relative to multiyear mean corresponding to strengthened weakened ke jet i e stable unstable ke two distinct seesaw patterns exist on the north and south side of 35 n for both chlorophyll and sea level anomaly and on the east and west side of 153 e for both chlorophyll and eddy kinetic energy similarly the magnitude of spring bloom was also modulated by decadal variations of ke the spring bloom was suppressed enhanced relative to the magnitude of climatological spring bloom south of 35 n during the ke stable unstable period this change is significant and can reach 35 in extreme years of 2006 and 2009 the decadal variation of chlorophyll in the ke is likely modulated by vertical nutrient supply induced by divergences convergences associated with the westward propagation of wind induced rossby waves in the central and eastern north pacific ocean which are dynamically modulated by the north pacific gyre oscillations npgo or pdo pacific decadal oscillations

effects of mesoscale eddies on subduction and distribution of subtropical mode water in an eddy resolving ogcm of the western north pacific abstract the effects of mesoscale eddies on the subduction and distribution of the north pacific subtropical mode water stmw are investigated using an eddy resolving ocean general circulation model ogcm first the subduction rate is calculated and the contribution of eddies to the subduction of stmw is estimated it is found that eddy subduction significantly contributes to the total subduction of stmw second eddy thickness transport and diapycnal flux are directly diagnosed to investigate the large scale eddy induced transport process of stmw the large southward eddy thickness transport in the stmw core density is consistent with eddy subduction the eddy transport on the isopycnal surface of stmw is directed down the thickness gradient and traverses the mean flow the meridional eddy transport streamfunction indicates two eddy circulation cells south of 30 n associated with the circulation of stmw these cells flatten density surfaces similar to the effect of the gent and mcwilliams gm schem

effect of mesoscale eddies on subtropical mode water variability from the kuroshio extension system study kess abstract forty eight profiling floats have been deployed in the kuroshio extension ke region since may 2004 as part of the kuroshio extension system study kess project by combining the float temperature salinity measurements with satellite altimetry data this study investigates the role played by mesoscale eddies in controlling the property changes in north pacific subtropical mode water stmw following a 3 yr period of low eddy activity in 2002 04 the ke showed a transition to a high eddy kinetic energy state in 2005 this transition is the result of delayed oceanic response to the 2002 shift in the basin scale surface wind forcing in connection with the pacific decadal oscillation the high eddy kinetic energy state of the ke is characterized by successive shedding of strong cold core rings into the recirculation gyre resulting from the interaction of the ke jet with the shatsky rise or the preexisting cutoff rings by transporting northern origin high potential vorticity pv ke water into t

formation region of north pacific subtropical mode water in the late winter of 2003 1 the mixed layer structure and properties in the formation region of the north pacific subtropical mode water stmw east of japan in the late winter of 2003 were examined using temperature and salinity data primarily from argo profiling floats the formation region extends south of the kuroshio extension between 30n and 35n and as far east as 175e it is characterized by a mixed layer with depths greater than 200db and meridionally uniform temperature between 16 5c and 18 2c associated with a mixed layer front at its southern edge the mixed layer in the formation region becomes colder fresher and denser toward the east leading to the formation of warmer saltier and lighter stmw in the western part of the region the spatial variation of the mixed layer depth in the formation region corresponds well with the underlying permanent thermocline depth index terms 4223 oceanography general descriptive and regional oceanography 4283 oceanography general water masses 4572 oceanography physical upper ocean processes citation oka e and t suga formation region of north pacific subtropical mode water in the late winter of 2003 geophys res lett 30 23 2205 doi 10 1029 2003gl018581 2003

the subtropical mode water circulation in the north pacific abstract historical hydrographic data are analyzed to investigate the seasonal variation of the subsurace pycnostad in the northwestern part of the north pacific and to relate it to the circulation of subtropical mode water stmw a gyre scale scheme of stmw circulation is deduced based on its observed climatological formation area and climatological geostrophic flow fields the deduced circulation is supported by climatological features of the subsurface hydrography presented separately for the non large meander period and the large meander period of the kuroshio zonal and meridional sections and isopycnal maps of potential vorticity and apparent oxygen utilization the kuroshio countercurrent composing the kuroshio recirculation system advects stmw formed in the wintertime thick mixed layer immediately off the kuroshio and the kuroshio extension during the non large meander period the recirculation system has a single anticyclonic gyre centered near 30 n 137 e and advects stmw formed off the kurosh