identification of the kuroshio extension its bifurcation and northern branch from altimetry and hydrographic data during october 1992 august 1999 spatial and temporal variability a methodology is proposed using altimter derived upper layer thickness and baroclinic transport to identify the kuroshio extension the bifurcation point and the northern branch by combining topex poseidon altimeter and climatological data within a two layer reduced gravity model results obtained from the japanese coast to 175 w show that the location of the bifurcation point presents interannual variability that is related with upstream conditions the longitude of the bifurcation point ranged from 147 to 160 e estimates of baroclinic transport at the kuroshio extension and its northern branch decrease steadily to the east trough the region of study from 35 to 11 and from 10 to 3 sv respectively

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

on the subsurface cfc maxima in the subtropical north pacific thermocline and their relation to mode waters and oxygen maxima the spatial structure of the subsurface chlorofluorocarbon cfc concentration maxima in the subtropical north pacific is examined using data from the pacific ocean sector of the world ocean circulation experiment woce hydrographic program collected in the period 1991 1994 comparison with potential vorticity pv sections reveals that the cfc maxima coincide with the pv minimum associated with subtropical mode water stmw in the western pacific as suggested by earlier observations warner et al 1996 in the eastern part of the central pacific the cfc maxima appear to be shallower than the central mode water cmw while they are deeper than the eastern subtropical mode water in the eastern pacific a subsurface oxygen maximum also coincides with stmw and the cfc maxima in the west is located between the cfc maxima and cmw in the central pacific and is absent in the east the collocation in the west is explained by the fact that stmw is the densest water to outcrop in the recirculation to the south of the kuroshio and the kuroshio extension while denser water is not directly ventilated in this region data from two post woce cruises and results from a steady state age model indicate that the cfc maxima are transient and are deepening such that the collocation of the cfc maxima and stmw does not persist in the late 1990s model experiments based on a smooth age profile demonstrate that the deepening of the cfc maxima is closely related to changes in the atmospheric cfc growth rates

ventilation of the subtropical north pacific the shallow salinity minimum abstract the shallow salinity minimum of the subtropical north pacific is shown to be a feature of the ventilated wind driven circulation subduction of low salinity surface water in the northeastern subtropical gyre beneath higher salinity water to the south causes the salinity minimum variation of salinity along surface isopycnals causes variations in density and salinity at the minimum a model of ventilated flow is used to demonstrate how the shallow salinity minimum can arise the model is modified to account for nonzonal realistic winds it is also extended to examine the three dimensional structure of the western shadow zone the boundary between the subtropical and subpolar gyres is given by the zero of the zonal integral of ekman pumping the western shadow zone fills the subtropical gyre at the base of the ventilated layers and decreases in extent with decreasing density for parameters appropriate to the north pacific the eastern shadow zone is of very limited extent observations of salini

frontogenesis subduction and cross front exchange at upper ocean fronts the subduction of water at upper ocean fronts driven by internal instabilities is investigated a simple analytic model which assumes conservation of potential density and potential vorticity is used to characterize the expected structure of subducted parcels as a function of the surface layer depth and the length scale of the parcel parcels subducted from a deep surface layer will be characterized by anomalously low potential vorticity and anticyclonic circulation while shallow surface layers result in subducted parcels with high potential vorticity and cyclonic circulation a nonlinear isopycnal primitive equation model is used to demonstrate how baroclinic instability and the resulting frontogenesis force the subduction of parcels below and across the front frontogenesis generates vertical velocities of 0 30 m d and ageostrophic cross front flows of 3 to 5 cm s the subduction is achieved by the deep ageostrophic flow which carries water from the surface layer below and across the front the subducted parcels quickly develop a circulation through balanced adjustment anticyclonic for deep surface layers and cyclonic for shallow surface layers the characteristics of parcels subducted in winter conditions closely resemble a class of eddies called submesoscale coherent vortices the horizontal and vertical scales of the vortices are determined by the frontogenetic mechanism and the depth of the surface layer the total permanent subduction rate is estimated to be 20 m yr for frontal subduction driven by frontogenesis although local and temporary subduction can be much larger the subducted anticyclonic vortices are often coupled to upper ocean cyclonic vortices thus forming a baroclinic dipole that propagates at approximately 3 5 cm s and is capable of transporting the anomalous water properties far from the region of formation similarities with observations in the north atlantic subtropical convergence zone and near the gulf stream are discussed

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

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

subduction of north pacific central mode water associated with subsurface mesoscale eddy 1 during a shipboard high density hydrographic survey carried out in the western north pacific in fall 2008 we observed an anticyclonic eddy with a thickness of 150 dbar and a diameter of 40 km near 500 dbar depth at 27 5 n 145 e this subsurface mesoscale eddy contains the north pacific central mode water cmw which has anomalously low potential vorticity and high dissolved oxygen compared to the climatological cmw properties in the same region profiling float measurements detect similar cmw patches near and south of the kuroshio extension as well as southward cmw migration within the cmw formation region north of the kuroshio extension these observed facts suggest that cmw is subducted into the permanent pycnocline not only through large scale eastward advection near the northern edge of the subtropical gyre but also through southward cross frontal advection associated with the formation and migration of subsurface mesoscale eddies

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

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

a wind tunnel simulation of the effects of stoss slope on the lee airflow pattern over a two dimensional transverse dune 1 secondary airflow plays an important role in dune formation and development the lee airflow pattern over transverse dunes is important in determining the shape alignment and spacing of dunes and is influenced significantly by the lee slope angle in this paper we present the results of scaled wind tunnel simulations of the effects of stoss slope on the mean lee airflow patterns of transverse dunes the leeward velocity field was measured nonintrusively using particle image velocimetry to assess the airflow pattern we found that the flow separated over the dunes with a leeward angle close to the slip face angle of natural transverse dunes and was insensitive to stoss angle separation cells were characterized by a back eddy reattachment distance height area and aspect ratio were used to characterize the separation cell the first three parameters increased with increasing stoss angle for angles less than 15 but remained constant or decreased slightly with angles greater than 15 on the basis of the leeward velocity profiles six flow regions corresponding to those in previous models were recognized these regions are initially bounded by kinks but gradually transition downwind and merge to recover a uniform velocity profile after a significant distance we suggest that the separation cell is most developed when the angle of stoss slope reaches 15 but the significance of this angle in the evolution of transverse dunes needs further exploration

factors controlling the emanation of radon and thoron in soils of the eastern u s a abstract emanation coefficients proportion of generated rn atoms that escape from a solid material have been measured for 222rn t 1 2 3 8 days and 220rn thoron t 1 2 55 s on 68 disaggregated soil samples from 12 soil profiles representative of the eastern u s a average values for sites are 0 20 for 222rn and 0 16 for 220rn based on distribution of 226ra among the exchangeable organic fe oxide sand silt and clay fractions of the soils a multiple regression indicates that the organic exchangeable fraction occurring mainly as coatings on grains has an emanation coefficient for 222rn of 0 46 and the silt clay fraction has an emanation coefficient of 0 22 the latter value is verified by experiments the organic component makes the largest single contribution to rn in soil gas mineral grains have twice the 222rn emanation as 220rn implying that about half the rn atoms are emanated directly to pore space and the remainder are freed by track etching and diffusion over a period of days emanation for 220rn appears to be dominated by fe oxides the main host for pedogenic 232th surface a and e horizons have low emanation coefficients for su220 rn probably because of a lack of fe oxides in these horizons

climate variability in the north pacific thermocline diagnosed from oxygen measurements an update based on the u s clivar co2 repeat hydrography cruises 1 new observations of oxygen variability in the north pacific ocean are reported on the basis of comparison of the u s climate variability and predictability and carbon clivar co2 repeat hydrography sections conducted along 30 n 2004 and 152 w 2006 with the earlier world ocean circulation experiment woce data and other cruises along these sections the largest changes in apparent oxygen utilization aou continue to occur as found in earlier north pacific repeat section analyses within the thermocline on 26 6 kg m 3 which is the densest isopycnal to outcrop in the open north pacific in climatological data in the northeastern north pacific along 152 w where a total of five cruises 1980 1984 1991 1997 and 2006 spanning a period of 26 years are available the aou changes correspond to an overall increase in aou on 26 6 kg m 3 from the 1980s early 1990s to 2006 however from 1997 to 2006 a decrease in aou is observed within the boundary region between the subtropical and subpolar gyres at 40 45 n along the center axis of the subtropical gyre at 30 n where two cruises are available 1994 and 2004 aou has also substantially increased on 26 6 kg m 3 from 1994 to 2004 in the eastern part of the section the repeat section data along 152 w and 30 n are consistent with a pattern of decadal scale ventilation anomalies that originate in the northwestern pacific possibly through variability including cessation of the 26 6 kg m 3 outcrop travel eastward along the subtropical subpolar gyre boundary and enter the northern portion of the subtropical gyre along the way for the 152 w aou data within the gyre boundary region 40 45 n good agreement exists with the close by time series data from ocean station p 50 n 145 w where a bidecadal cycle in aou has been observed in contrast a sensible correlation with the pacific decadal oscillation could not be found

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

formation and subduction of central mode water based on profiling float data 2003 08 abstract temperature and salinity data from argo profiling floats in the north pacific during 2003 08 have been analyzed to study the structure of winter mixed layer north of the kuroshio extension and the subsurface potential vorticity distribution in the subtropical gyre in relation to the formation and subduction of the central mode water cmw in late winter two zonally elongated bands of deep mixed layer extend at 33 39 and 39 43 n from the east coast of japan to 160 w these correspond to the formation region of the lighter variety of cmw l cmw and that of the denser variety of cmw d cmw and the recently identified transition region mode water trmw respectively in the western part of the l cmw and d cmw trmw formation regions west of 170 e the winter mixed layer becomes deeper and lighter to the east i e to the downstream as a result the formed mode water is reentrained into the mixed layer in the farther east in the following winter and modified to the lighter water and is thus

reemergence areas of winter sea surface temperature anomalies in the world s oceans 1 using datasets of sea surface temperature sst surface heat flux upper ocean thermal data and climatological temperature and salinity profiles we try to detect reemergence areas of winter sst anomalies in the world s oceans and describe characteristics of these areas in terms of mixed layer depth mld annual mean heat flux and properties of waters formed in winter mixed layer eventually seven reemergence areas are found four in the northern hemisphere and three in the southern hemisphere all areas have a large seasonal variation of mld and are the regions where annual mean heat fluxes are relatively small except for two regions in the northern hemisphere in the viewpoint of water properties it is found that these areas correspond to the mode water formation regions subtropical mode waters of the indian ocean south pacific south atlantic north pacific and north atlantic and north pacific central and north atlantic subpolar mode waters

interdecadal variability in dissolved oxygen in the intermediate water layer of the western subarctic gyre and kuril basin okhotsk sea using dissolved oxygen do concentration at isopycnal surfaces we have observed an oscillation in the intermediate water layer of the western subarctic gyre wsg and the kuril basin of the okhotsk sea with a period of about 20 years the interdecadal oscillation in do is strongly correlated with the intensity of the aleutian low pressure cell with a 2 year time lag the interdecadal variations in do in the intermediate water layer of the wsg and the okhotsk sea may be a result of oscillation in the atmospheric forcing leading to variations in the isopycnal fluxes of do at the boundaries of the okhotsk sea western subarctic gyre subtropical region the isopycnal surface replacement in the wsg and in changes in the intermediate water formation rate in the okhotsk sea

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

remote reemergence areas of winter sea surface temperature anomalies in the north pacific 1 taking account of water movement we detect pairs of formation and reemergence areas of winter sea surface temperature sst anomalies in the north pacific by analyzing various kinds of data sets two pairs of formation and reemergence areas are detected one pair is located in the northern subtropical gyre and water properties in both the formation and reemergence areas well correspond to those of north pacific central mode water npcmw another pair is found in the western to central part of the subtropical gyre the formation area corresponds well to that of north pacific subtropical water npstmw but the reemergence area is remote from the formation area examinations on upper ocean current field trace of temperature anomalies in the subsurface and change of water properties from the formation area to the reemergence area clearly indicate that waters with winter sst anomalies move from the formation area to the reemergence area in a year

features of the water mass front in the northwestern north pacific analysis of the hydrographic data taken in the northern north pacific has revealed a water mass front defined as the abrupt change of mixing rates between the two typical water masses typical water masses are situated above the main thermocline in the subtropical and subpolar gyres this front termed water mass front in the present study can be regarded as the boundary between the subtropical gyre and the subpolar gyre the index for detecting the frontal position from the temperature field is given as the 5 c isotherm at the 300 m level comparisons with data from previous studies are also made and this front appears to correspond to the subarctic front in almost every instance

subtropical mode water in the northeast pacific basin a new type of mode water in the upper thermocline of the eastern subtropical north pacific is identified and examined using data from world ocean circulation experiment high resolution repeat expendable bathythermograph xbt section px37 and archives of historical xbt data this water mass labeled eastern subtropical mode water is characterized by a subsurface potential vorticity minimum and is located east of hawaii northeast pacific basin in a density range of 24 25 4 it is a distinct water mass from the classical subtropical mode water stmw of the western pacific eastern stmw is formed as a relatively deep late winter mixed layer associated with the subtropical subpolar water mass boundary near 25 30 n 135 140 w and is capped and subducted into the permanent thermocline along a section between san francisco and honolulu eastern stmw production is seen in every year for which there is adequate data in this section the volume of eastern stmw formed each winter and the temperature of the potential vorticity minimum are similar during the periods 1970 1979 and 1991 1997