modification of the intermediate waters in the northeastern subpolar pacific the modification of the intermediate layers in and around the alaskan gyre are investigated in relation to general circulation features of the region using tracer data from the world ocean circulation experiment p17n line the alaskan gyre ag core lies between the north pacific current and the alaskan stream as in the 52 54 5 n range and to the west of 144 w the north pacific current feeds the transition zone tz and the western subpolar waters wsw which consequently constitute the inflow to the region from the northwestern pacific the alaska current ac is observed to the west of 144 w between the north american coast and the ag the ac halocline 26 7 has distinct property distributions low chlorofluorocarbon and oxygen saturations and high nutrient concentrations which are correlated with eddies that are characterized by higher salt content and warmer temperatures most significantly at 26 0 the ag is found to act as a reservoir where water mass modification takes place and the as transports a mixture of waters from the ag and the ac west ward out of the region the residence time estimate for the intermediate and upper layer water in the ag 27 2 is about 2 years which corresponds to a volume exchange between the gyre and the surrounding circulation of 4 7 sv in the 0 1000 m range the layers above 26 9 0 200 m are modified by vertical mixing mostly of wsw in the ag the flux of modified waters out of the ag is approximately 0 9 sv comparison of the present data with the 1984 1989 period suggests that mixing of water from different regimes has not changed dramatically

sea surface temperature and salinity changes near the soya strait during the last 19 ka past sea surface temperature sst and salinity sss changes in the northeastern east sea japan sea since 19 cal ka bp have been reconstructed by using an alkenone unsaturation index and the oxygen isotope ratio of planktonic foraminifera neogloboquadrina pachyderma s in core mr0604 pc03b coretop alkenone temperature and calcification temperature correspond to the temperature of seawater in summer and spring at the depth of 10 30 m respectively based on the records from this core and previous studies spatio temporal changes in alkenone temperature of the east sea japan sea have been reconstructed to investigate changes of surface circulations and the subpolar front spf position during the transitional period from the glacial to the holocene the sst was lower about 2 3 c than that of today and the sss dramatically increased at that time in the entire east sea japan sea but it was still lower than that of today however the northern sss was higher than that of the southern part the source of the cold and saline seawater could have been the oyashio current oy inflow from the north not the tsushima warm current twc inflow from the south probably sea level rose rapidly at that time there might be no strong development of the spf during the transitional period due to the restricted inflow of the twc during the early holocene the sst and sss of the east sea japan sea increased compared to the transitional period due to increased seawater exchange through straits the spf was tilted orienting from southwest to northeast because the inflow of the twc was not fully developed due to lower sea level subsequently the surface condition of the east sea japan sea was similar to that of today at 6 cal ka bp the forerunner of soya warm water fsww that flowed out through the soya strait in early spring did not affect the formation of the okhotsk sea intermediate water and the north pacific intermediate water during the glacial and interglacial periods

currents associated with the quasi stationary jet separated from the kuroshio extension abstractthe hydrographic structure of a quasi stationary jet separated from the kuroshio extension a phenomenon that possibly leads to deepening of the winter mixed layer is revealed via intensive observations using a conductivity temperature depth profiler and a ship mounted acoustic doppler current profiler adcp carried out in september 2009 data collected from profiling floats set to drift isopycnal layers and time series of sea surface buoys and satellite altimeters were also analyzed to understand the continuity water characteristics and time variation of the jet although the flow field was complex due to disturbances such as energetic eddies the jet transported subtropical water to the downstream northeastern observation region in a layer shallower than 400 dbar and its highest velocity was concentrated in the mid and deep layers 0 30 m s 1 at the sea surface and 0 05 m s 1 at 800 m depth the velocity axes of the jet detected from the satellite data corresponded to those detected th

fine scale variability of isopycnal salinity in the california current system this paper examines the finescale structure and seasonal fluctuations of the isopycnal salinity of the california current system from 2007 to 2013 using temperature and salinity profiles obtained from a series of underwater glider surveys the seasonal mean distributions of the spectral power of the isopycnal salinity gradient averaged over submesoscale 12 30 km and mesoscale 30 60 km ranges along three survey lines off monterey bay point conception and dana point were obtained from 298 transects the mesoscale and submesoscale variance increased as coastal upwelling caused the isopycnal salinity gradient to steepen areas of elevated variance were clearly observed around the salinity front during the summer then spread offshore through the fall and winter the high finescale variances were observed typically above 25 8 kg m 3 and decreased with depth to a minimum at around 26 3 kg m 3 the mean spectral slope of the isopycnal salinity gradient with respect to wavenumber was 0 19 0 27 over the horizontal scale of 12 60 km and 31 to 35 of the spectra had significantly positive slopes in contrast the spectral slope over 12 30 km was mostly flat with mean values of 0 025 0 32 an increase in submesoscale variability accompanying the steepening of the spectral slope was often observed in inshore areas e g off monterey bay in winter where a sharp front developed between the california current and the california under current and the lower layers of the southern california bight where vigorous interaction between a synoptic current and bottom topography is to be expected

improved estimates of the dynamical state of the north pacific ocean from a 4 dimensional variational data assimilation 1 a 4 dimensional variational data assimilation system has been used to better define the mean seasonal state of the north pacific the synthesis of available observational records and a sophisticated general circulation model produces a dynamically consistent time varying dataset which exhibits realistic features of the global ocean circulation and requires no artificial sources or sinks for the temperature and salinity fields the dataset enables us to clarify the water mass formation and movement processes a sensitivity experiment using our system reveals that the origin of the north pacific intermediate water can be traced back to the okhotsk and bering seas in the subarctic region and to the subtropical kuroshio region further south consistent with recent observational findings this result illustrates that the ocean state derived from our data assimilation has greater information and forecast potential than that obtained from earlier methods

the bering sea and paleoceanography abstract this paper serves as an introduction to the bering sea preceding the 14 contributed papers contained in this volume several parts of the paper are allocated for current reviews of the bering sea included in the review topics are geomorphology surface water circulation and the importance of the formation of intermediate waters representative results of previous paleoceanographic studies are also presented in particular focusing on spatial and temporal distributions of biosiliceous microfossils as well as isotopic analyses of carbon and nitrogen concerning changes in productivity and nutrients motivations behind the scientific expeditions conducted which resulted in the many papers included here are briefly discussed in order to illustrate the recent trend in paleoceanography in the bering sea and the adjacent regions brief summaries or highlights of each of the contributed papers are given in order to provide an overview of the volume

assessment of the effects of tidal mixing in the kuril straits on the formation of the north pacific intermediate water abstract to assess accurately the effect of tidal mixing in the kuril straits on the formation of the north pacific intermediate water npiw the spatial distribution of diapycnal diffusivity recently obtained by the present authors is incorporated into an eddy permitting ogcm it is shown that the npiw is successfully reproduced although the diapycnal diffusivity averaged over the entire kuril straits is an order of magnitude less than has previously been assumed as a tuning parameter to reproduce the npiw in low resolution ogcms this strongly suggests that the effect of tidal mixing in the kuril straits on the formation of the npiw is relatively minor and that the physical processes omitted by the low resolution ogcms such as isopycnal mixing along the kuroshio extension region are much more important this suggestion gives warning of the danger that some misleading conclusions might be derived from ogcms that employ diapycnal diffusivity just as a tuning parameter to reproduce the observed features

three dimensional structure of frontal waves and associated salinity minimum formation along the kuroshio extension abstract high resolution hydrographic observations were conducted in september 2002 to describe the detailed structure of frontal waves along the kuroshio extension frontal waves were observed both in the upper and intermediate layers which corresponded to the depths of north pacific subtropical mode water and north pacific intermediate water respectively the frontal wave in the upper layer preceded the intermediate depth frontal wave by about 1 4 wavelength the vertical phase lag created situations in which the low salinity oyashio water in the intermediate layer was superimposed below the upper layer high salinity kuroshio water thus forming a vertical salinity minimum the frontal waves with a wavelength of about 200 km and a phase speed of 0 2 0 3 m s 1 propagating in the downstream direction were consistent with those from satellite images vertical velocity fields were estimated with the quasigeostrophic omega equation downwelling around the trough from the crest to trough of the intermedia

polynya dynamics a review of observations and modeling 1 polynyas are nonlinear shaped openings within the ice cover ranging in size from 10 to 105 km2 polynyas play an important climatic role first winter polynyas tend to warm the atmosphere thus affecting atmospheric mesoscale motions second ocean surface cooling and brine rejection during sea ice growth in polynyas lead to vertical mixing and convection contributing to the transformation of intermediate and deep waters in the global ocean and the maintenance of the oceanic overturning circulation since 1990 there has been an upsurge in polynya observations and theoretical models for polynya formation and their impact on the biogeochemistry of the polar seas this article reviews polynya research carried out in the last 2 decades focusing on presenting a state of the art picture of the physical interactions between polynyas and the atmosphere sea ice ocean system observational and modeling studies the surface heat budget and water mass transformation within these features are addressed

direct current measurements at kruzenshterna strait in summer flow measurements at kruzenshterna strait one of the two major gaps connecting the sea of okhotsk and the north pacific were performed with a lowered acoustic doppler current profiler in summer of 1999 nearly one day time series at 2 stations were obtained by eleven consecutive casts each being started every 2 and a half hours the tidal components are estimated by least square fittings the flow consists of a two layer exchange flow and the tide of the comparable magnitude a volume transport of the upper layer is estimated to be 1 6 sv 1 sv 106 m s from the okhotsk sea to the north pacific while that of the lower layer is 1 3 sv in the opposite direction hydrographic and oxygen data support the existence of the residual exchange flow

the production of ice and dense shelf water in the okhotsk sea polynyas this paper examines the ice and dense water production in the okhotsk sea coastal polynyas for the 1990 1995 winters the dominant polynyas occur on the northwest and northern shelves and in shelikhov bay we use an algorithm developed for the special sensor microwave imager ssm i to derive for each polynya the area and composition of thin ice and open water and a heat flux algorithm to derive the ice and brine production historic oceanographic observations show that the northwest shelf is the only north pacific region where the 26 8 potential density surface outcrops to the surface and is also that part of the okhotsk shelf where the densest water is observed to occur in support of these observations we find that the northwest shelf polynya is the dominant ice and brine producer contributing on average about 55 of the total production shelikhov bay is the second largest producer with about 25 of the total this region has been previously neglected by both oceanographic and remote sensing studies using a combination of two dense water production models we find that the 6 year average dense water production lies between 0 2 0 4 sv the ice and brine production for the dominant northwest shelf vary interannually by a factor of 3 while the production from all the northern polynyas varies by factor of 2 the source of the variability for the northwest shelf comes from the fact that the southwest to northeast trend of the coastline and the mean winter geostrophic wind velocities are roughly parallel which means that small variations in the wind direction yield large changes in the ice production

homogenization of potential vorticity in planetary gyres the mean circulation of planetary fluids tends to develop uniform potential vorticity q in regions where closed time mean streamlines or closed isolines of mean potential vorticity exist this state is established in statistically steady flows by geostrophic turbulence or by wave induced potential vorticity flux at the outer edge of the closed contours the expelled gradients of q are concentrated beyond this transition lies motionless fluid or a different flow regime in which the planetary gradient of q may be dominant the homogenized regions occur where direct forcing by external stress or heating within the closed isoline is negligible upon the potential density surface under consideration in the stably stratified ocean such regions are found at depths greater than those of direct wind induced stress or penetrative cooling in channel models of the atmosphere we again find constant q when mesoscale eddies cause the dominant potential vorticity flux in the real atmosphere the results here can apply only where internal heating is negligible the derivations given here build upon the prandtl batchelor theorem which applies to non rotating steady two dimensional flow supporting evidence is found in numerical circulation models and oceanic observations

flow and water property structures between the bering sea and fiji in the summer of 1993 an overview is given of the top to bottom flow thermohaline oxygen and nutrient structures between the bering sea and the fiji islands based on high resolution field measurements along 179 e the zonal flow is dominated by a banded mesoscale structure reflecting the highly sheared structure and instabilities of the major ocean currents crossing the date line the major midlatitude currents are 100 200 km wide have maximum speeds of 40 cm s 1 and extend to 2000 m when measured by the 5 cm s 1 isotach el nino conditions in 1993 caused a merger of the north equatorial countercurrent with the equatorial undercurrent leading to a 600 km wide band of equatorial eastward flow 40 60 cm s 1 in the upper 300 m beneath a 400 km wide and 1 2 km deep westward jet 10 30 cm s 1 is found between 1500 and 3500 m the equatorial flow is predominately to the southeast and between 3500 and 5000 m it is toward the northwest consonant with banded shear flow and flow topography interactions the physical and chemical property distributions along 179 e are complicated reflecting the effects of differential property advection mixing and water mass transformation well defined property fronts occur in shear zones between currents of different origin the thermohaline oxygen and nutrient tongues associated with north and south pacific intermediate and deep waters have considerable internal structure indicative of mesoscale processes and contorted flow paths the abyssal flow near the date line indicates northward movement of lower circumpolar water to the hess rise whence it turns westward and north west of the emperor seamounts properties east of this seamount chain are very uniform the deep and abyssal waters of the isolated aleutian basin differ substantially from those in the adjacent pacific by being warmer 0 1 c less saline 0 01 poorer in oxygen 50 mol kg 1 and much richer in silicate 80 mol kg 1 an isolated basin within the wake necker ridge also shows some unusual bottom water characteristics below sill depth

quasi two dimensional simulation of scour and deposition in alluvial channels most existing sediment routing models are one dimensional models and hence they cannot be used to simulate lateral channel bed deformations conversely a two dimensional model is computationally time consuming and is not suitable for long term simulation using the stream tube concept a one dimensional model is extended to a quasi two dimensional model in this study it is capable of simulating lateral variations of channel cross section through the adjustments of stream tube boundaries the model has an option to treat the suspended load and bed load separately and hence is able to simulate the deposition behavior of the suspended sediment under a nonequilibrium process the model also provides options to solve either de saint venant equation or energy equation and hence can be applied in both steady and unsteady flow conditions an assess ment of this model s performance has been conducted through a comparison to an analytical solution and a set of experimental data the application of this model to the keelung river and the shiemen reservoir in taiwan also gave convincing results

foraging destinations and marine habitat use of short tailed albatrosses a multi scale approach using first passage time analysis abstract we used satellite telemetry remotely sensed data bathymetry chlorophyll a chl a sea surface temperature sst wind speed and first passage time fpt analysis to determine the distribution movement patterns and habitat associations of short tailed albatrosses phoebastria albatrus during the non breeding season 2002 and 2003 satellite transmitters were deployed on birds immediately prior to their departure from a breeding colony at torishima japan n 11 or at sea in the aleutian islands n 3 tracking durations ranged from 51 to 138 days for a total of 6709 locations after filtering 131 808 per bird fpt time required to transit a circle of given radius revealed the location and spatial scale of area restricted search ars patterns along flight paths on average ars occurred within 70 km radii consequently the fit of the habitat use models increased at spatial scales beyond a 40 km fpt radius r 2 0 31 and stabilized for scales of 70 km and larger r2 0 40 0 51 at all scales wind speed depth or depth gradient and chl a or chl a gradient had a significant effect on fpt i e residence time fpt increased within regions of higher gradients of depth and chl a in contrast fpt decreased within regions of greater depth and wind speed with a significant interaction of wind speed and depth at some scales sea surface temperature or its interactions were only significant at large spatial scales 160 km fpt radius albatrosses engaged in ars activities primarily over the shelf break and slope including kuroshio and oyashio regions off the western subarctic gyre occasionally birds transited the northern boundary of the kuroshio extension while in route to the aleutian islands and bering sea but overall spent little time in the western gyre in the aleutian islands ars occurred within straits particularly along the central and western part of the archipelago in the bering sea ars occurred along the northern continental shelf break the kamchatka current region and east of the commander islands non breeding short tailed albatross concentrate foraging in oceanic areas characterized by gradients in topography and water column productivity this study provides an understanding of the foraging ecology for a highly migratory imperiled seabird and confirms the importance of shelf break and slope regions as hot spots for a variety of top marine predators in the north pacific

influence of okhotsk sea intermediate water on the oyashio and north pacific intermediate water 1 the volume transport between the okhotsk sea and western subarctic north pacific is estimated on the basis of direct current measurements made by a lowered acoustic doppler current profiler ladcp and hydrographic data taken in august and september 1999 near the kuril islands the estimated southwestward oyashio transport was 11 12 sv 106 m3 s in the density range of 26 7 27 4 the net transport of the okhotsk sea water osw was 3 4 sv of which 1 3 sv was coming out through the kruzenshterna strait and 2 1 sv was coming out through the bussol strait a bidirectional flow was observed in the bussol strait inflow in the northern part of the strait and outflow in the southern part 0 6 sv of osw recirculated along the western subarctic gyre the remaining 2 8 sv of osw could contribute to the formation of north pacific intermediate water as a cross subarctic front transport along the coast 1 4 sv and across the offshore saf 1 4 sv the production rate of the dense shelf water dsw through sea ice formation was estimated to be at least 1 1 sv when the intermediate osw is formed through the mixing between cold and fresh dsw and warm and salty waters from the pacific and japan sea 16 8 tw 1012 w of heat 0 007 sv of freshwater and 2 3 105 kg s of salt are exchanged the net flux of oxygen and anthropogenic co2 ex co2 from the okhotsk sea into the pacific in 26 7 27 4 is estimated to be 10 5 and 2 1 tmol yr 0 025 gtc yr respectively the ex co2 transported by osw accounts for about 10 of the accumulation of ex co2 in the subarctic and subtropical pacific

numerical experiments on the seasonal variations of the oyashio near the east coast of japan abstract seasonal variations of the oyashio near the east coast of japan are examined using a simple layered model with a localized diapycnal transport due to the strong tidal mixing around the kuril islands the modeled southernmost latitude is located at around 40 n in spring and 42 n in autumn the southwestward oyashio transport in the upper layers and depth integrated transport become large small during winter spring summer autumn these results are in agreement with observations the seasonal variation of the southernmost latitude is mainly caused by the baroclinic velocity anomalies off tohoku and hokkaido japan which have been excited by the wind stress changes along the west coast of north america the kamchatka peninsula and the model northern boundary this is different from the previous studies that emphasized the importance of direct barotropic response of the ocean to the basin scale wind stress changes for comparison an additional experiment in which the diapycnal transport around

water mass structure of warm and cold anticyclonic eddies in the western boundary region of the subarctic north pacific vertical profile data of temperature and salinity from various sources were analyzed together with satellite altimeter data to investigate the water mass characteristics of warm and cold anticyclonic eddies in the western boundaryregionof the subarctic north pacific a densedistributionof anticyclonic eddieswith warm and saline core water occurred near the kuroshio extension and the distribution extends northward northeastward into the western subarctic gyre along the japan and kuril kamchatka trenches eddies with cold and fresh core water are found mainly around the oyashio southward intrusions and farther north near the kuril islands based on the heat content anomaly integrated over 50 200 dbar 85 of the anticyclonic eddies within the study area 358 508n 1408 1558e have a warm and saline core and 15 have a cold and fresh core warm and saline eddies around the japan and kuril kamchatka trenches have a double core structure with a cold and freshwater mass located below the warm core the northward propagation of these eddies along the trench line results in a large northward heat salinity transport in the upper 400 dbar 250 dbar and a negative salinity transport below 350 dbar the lower core water is colder and fresher on isopycnal surfaces at around 26 70sucompared with the climatology given that the 26 70su isopycnal surface does not outcrop in the open north pacific an alignment process is suggested to occur between the warm and saline and the cold and fresh anticyclonic eddies in the upper and intermediate layers respectively

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

transport and modification processes of dense shelf water revealed by long term moorings off sakhalin in the sea of okhotsk 1 the region off the east coast of sakhalin is thought of as an important pathway of dense shelf water dsw from its production region in the northwestern okhotsk sea to the southern okhotsk sea from july 1998 to june 2000 the first long term mooring experiment was carried out in this region to observe the southward flowing east sakhalin current esc and dsw moored and associated hydrographic data show considerable modification of cold dense water via mixing with warm offshore water in the slope region off northern sakhalin significant onshore eddy heat flux was observed at the northernmost mooring 54 9 n which suggests the occurrence of baroclinic instability the eddy heat flux was not significant farther south at moorings along 53 n cold anticyclonic eddies were identified that were consistent with isolated eddies seen in the hydrographic data the three years of hydrographic data also showed large differences in extent and properties of dsw furthermore the mooring data show that seasonal variability of dsw was quite different in the two years the average dsw transport for 26 7 evaluated using the moored data at 53 n for 1 year 1998 1999 was 0 21 sv 106 m3 s 1 this value is at the lower end of the previous indirect estimates along with the dsw modification this transport estimate indicates that dsw was not only carried southward by the esc but was spread offshore by eddies off northern sakhalin

an atlantic pacific ventilation seesaw across the last deglaciation it has been proposed that the rapid rise of atmospheric co2 across the last deglaciation was driven by the release of carbon from an extremely radiocarbon depleted abyssal ocean reservoir that was vented to the atmosphere primarily via the deep and intermediate overturning loops in the southern ocean while some radiocarbon observations from the intermediate ocean appear to confirm this hypothesis others appear to refute it here we use radiocarbon measurements in paired benthic and planktonic foraminifera to reconstruct the benthic planktonic 14c age offset i e ventilation age of intermediate waters in the western equatorial atlantic our results show clear increases in local radiocarbon based ventilation ages during heinrich stadial 1 hs1 and the younger dryas yd these are found to coincide with opposite changes of similar magnitude observed in the pacific demonstrating a seesaw in the ventilation of the intermediate atlantic and pacific oceans that numerical model simulations of north atlantic overturning collapse indicate was primarily driven by north pacific overturning we propose that this atlantic pacific ventilation seesaw would have combined with a previously identified north atlantic southern ocean ventilation seesaw to enhance ocean atmosphere co2 exchange during a collapse of the north atlantic deep overturning limb whereas previous work has emphasized a more passive role for intermediate waters in deglacial climate change merely conveying changes originating in the southern ocean we suggest instead that the intermediate water seesaw played a more active role via relatively subtle but globally coordinated changes in ocean dynamics that may have further influenced ocean atmosphere carbon exchange

adcp referenced kuroshio and oyashio water transports for north pacific intermediate water formation abstract the adcp referenced geostrophic circulation of the oyashio and kuroshio waters in the density range 26 6 27 2 in the kuroshio oyashio interfrontal zone is examined by synoptic observations with a ctd and shipboard adcp in may 1992 and may 1994 in order to investigate the absolute transports of the source waters for north pacific intermediate water npiw formation the kuroshio and oyashio components are calculated by the adcp referenced transport combined with the mixing ratio assuming isopycnal mixing between pure kuroshio and oyashio waters as a result the kuroshio transport involved in the npiw formation is estimated to be 7 8 sv sv 106 m3 s 1 which is the net component along the kuroshio extension ke from the separation point near the cape nojima to the east side of the first crest of the ke the oyashio transport is estimated to be 5 6 sv which consists of coastal 1 2 sv and offshore 3 4 sv separated by warm core rings and which subsequently merges with the ke at the east side

distribution and circulation of labrador sea water abstract labrador sea water is the final product of the cyclonic circulation of subpolar mode water in the open northern north atlantic mccartney and talley 1982 the temperature and salinity of the convectively formed subpolar mode water decrease from 14 7 c 36 08 to 3 4 c 34 88 on account of the cumulative effects of excess precipitation and cooling the coldest mode water is labrador sea water which spreads at mid depths and is found throughout the north atlantic ocean north of 40 n and along its western boundary to 18 n a vertical minimum in potential vorticity is used as the primary tracer for labrador sea water labrador sea water is advected in three main directions out of the labrador sea 1 northeastward into the irminger sea 2 southeastward across the atlantic beneath the north atlantic current and 3 southward past newfoundland with the labrador current and thence westward into the slope water region crossing under the gulf stream off cape hatteras the labrador sea water core is

ventilation of north pacific intermediate waters the role of the alaskan gyre hydrographic data tritium data and potential vorticity calculations suggest that although north pacific intermediate water is formed in the northwest the alaskan gyre might be an additional ventilation site the proposed ventilation is quantified by a vertical column tritium inventory which indicates an excess of 0 08 kg of tritium in the alaskan gyre an evaluation of the energy stored in the water column and of wind and buoyancy forcing shows that during winter conditions enough energy can be pumped into the system to force 26 80 to outcrop in the alaskan gyre model results suggest that relatively limited outcrops in time and space tens of days and several hundred kilometers in diameter can account for the excess tritium

sediment transport modeling review current and future developments the use of computational models for solving sediment transport and fate problems is relatively recent compared with the use of physical models several considerations govern the choice between physical and computational models namely the nature of the problem that needs to be solved the available resources and the overall cost associated with the problem solution in some specific problems a combination of physical and computational models can be used to obtain a better understanding of the processes under investigation de vries 1973 using computational hydrodynamic sediment transport models in general involves the numerical solution of one or more of the governing differential equations of continuity momentum and energy of fluid along with the differential equation for sediment continuity an advantage of computational models is that they can be adapted to different physical domains more easily than physical models which are typically constructed to represent site specific conditions another advantage of computational models is that they are not subject to distortion effects of physical models when a solution can be obtained for the same flow conditions identical reynolds and froude numbers same length scale in the three directions etc as those present in the field with the rapid developments in numerical methods for fluid mechanics computational modeling has become an attractive tool for studying flow sediment transport and associated pollutant fate processes in such different environments as rivers lakes and coastal areas representative processes in these environments include bed aggradation and degradation bank failure local scour around structures formation of river bends fining coarsening and armoring of streambeds transport of point source and nonpoint

why is the spreading of the north pacific intermediate water confined on density surfaces around σθ 26 8 abstract the north pacific intermediate water characterized by a salinity minimum confined to density surfaces of 26 7 26 9 exists throughout the subtropical gyre and has been observed to originate in the subarctic north pacific the physical processes that determine the density range on which the npiw resides are not yet well understood this study attempts to clarify these processes by combining observational data and a simple advection diffusion isopycnal model due to the regional excessive precipitation over evaporation the salinity in the upper layer subarctic north pacific generally decreases with decreasing water depth both alongisopycnal advection and diffusion work to carry this salinity depth characteristic into the subtropical circulation for the isopycnal surfaces overlying the npiw however this transport mechanism is hindered by the seasonal outcropping the outcropping not only blocks the fresh subarctic water from advecting and diffusing along these isopycnals into the subtropi

development and tropical transition of an alpine lee cyclone part ii orographic influence on the development pathway abstract the development and subsequent tropical transition of a subsynoptic scale cyclone over the gulf of genoa gog on 15 november 2007 led to the rapid onset of tropical storm force winds near the islands of corsica and sardinia this study evaluates the influence of two key ingredients on the cyclogenesis event a near surface warm potential temperature perturbation in the lee of the alps and a mountain scale potential vorticity pv banner a high resolution modeling system is used to perform a set of attribution tests in which modifications to the alpine orography control the presence of the cyclogenetic ingredients when either feature exists in the initial state a gog cyclone develops even when the alpine barrier is removed however when neither the warm perturbation nor the pv banner is present there is insufficient lower level pv to couple with the upper level trough to promote cyclogenesis a conceptual model involving the complimentary interaction of the two pv features is presented that

last glacial holocene change in intermediate water ventilation in the northwestern pacific abstract the modern north pacific is the terminus for deep water circulation while no deep water mass is formed today the region is the source of north pacific intermediate water 300 800 m formed primarily in the sea of okhotsk however the source and strength of intermediate water in the glacial north pacific was likely different from the present intermediate water here we present microfossil evidence of late quaternary ventilation changes associated with changes in intermediate water intermediate water ventilation decreased drastically at the glacial termination when it switched to the modern circulation system the ventilation change appears to have been widespread and synchronous in the north pacific glacial microfossil assemblages indicate that there was relatively strong ventilation of intermediate water which seems to have been cold and well oxygenated as if produced by brine rejection during the formation of sea ice on the basis of the glacial distribution of microfossils in the north pacific we suggest that intermediate water was derived from the bering sea during the glacials rather than the sea of okhotsk

chlorofluorocarbons in the sea of okhotsk ventilation of the intermediate water 1 ventilation of the intermediate layer in the sea of okhotsk is studied with regard to the ventilation of north pacific intermediate water npiw measurements of chlorofluorocarbons cfcs from 1998 to 2000 reveal that the okhotsk intermediate water is ventilated in two ways the first consists of dense water formation in the polynyas that form on the northern shelves during winter measurements show that on the northwestern shelf because of atmospheric cooling and brine rejection the cold water that forms is dense enough to enter the intermediate layer the cfc concentration in this dense shelf water dsw is high and almost saturated with respect to atmospheric cfcs indicating that the dsw experiences active air water gas exchange during its formation away from the shelves the cfc distribution shows that the dsw directly ventilates the upper level of the okhotsk sea intermediate water osiw the second ventilation process is driven by the strong tidal mixing around the bussol strait the observed distribution of cfcs at the 27 4 level suggest that diapycnal mixing around the strait transports cfcs from the surface to this deeper layer ventilating the osiw combination of both processes means that the osiw is more ventilated than pacific water at the same density levels

impact of earthquake induced dammed lakes on channel evolution and bed mobility case study of the tsaoling landslide dammed lake summary on may 12 2008 a mega earthquake measuring 8 0 on the richter scale hit wenchuan sichuan province of china causing severe casualties and damages the tremor was felt by nearly all of asia the quake induced landslides and sliding slopes also formed 34 dammed lakes of various sizes each of which may bring serious potential disasters understandably the earthquake triggered dammed lakes and their ensuing disasters cause grave concerns worldwide similar devastation took place in taiwan on september 21 1999 when an earthquake of 7 3 on the richter scale occurred with the epic center at jiji in central taiwan the earthquake affected changes in the channel course and induced landslides to form several dammed lakes among which a large dammed lake was created in the upstream chingshui river with reservoir capacity of 42 000 000 m 3 its size and potential problems therefore caused serious apprehension a series of subsequent typhoon induced torrential flooding events affected the channel forming processes to diverge drastically between the dammed lake and the landslide area which presented a rare phenomenon for data observation and research in the last century five dammed lakes had been formed in the area due to landslides suggesting high possibility of future recurrence particularly from earthquake activities an investigation of the channel evolution in this area prior and post a quake therefore can assist in current disaster handling protocols and provide policy guidelines for future crisis management when landslides occur topographic changes in the study watershed historical channel surveys and past studies were gathered to aid the geomorphologic analysis channel evolution in the tsaoling dammed lake and the landslide area was also investigated using a netstars channel scour deposition model by simulating the trends of erosion and deposition patterns under the influence of different recurrence interval flood peaks and streamflow time series this simulation analysis demonstrated that the modeling not only successfully predicted the variations of hydraulics and sedimentation along the steep reaches under the influence of various streamflow conditions but also properly reflected the trend of scouring and deposition in the entire study reach and the upstream migration of head cut

intermediate water ventilation change in the subarctic northwest pacific during the last deglaciation 1 the laminated sediments suggest significant depletion in dissolved oxygen of intermediate water in the north pacific during the last deglaciation however the cause of depleted oxygen during deglaciation is still a matter of debate here we present foraminiferal mg ca based intermediate and surface temperatures and 18o of seawater 18ow a proxy of salinity in the oyashio region in order to investigate intermediate water circulation through the last deglaciation results indicate that the intermediate water temperature and 18ow increased in association with ventilation age at the bolling allerod period suggesting that the poor ventilation at that time the surface record shows that the decrease of salinity preceded the slowdown of intermediate ventilation the coupled variation of intermediate and surface water suggests that the supply of cold fresh intermediate water diminished because of poor ventilation at the high latitude due to surface freshening

rapid thermohaline transition in the pacific western subarctic and oyashio fresh core eddies seven years of conductivity temperature depth data enable direct computations of volume transport and a description of the temporal changes of water properties in the western subarctic pacific the cooling of the western subarctic surface layer is shown through the observation of the thermohaline transition which occured in the western subarctic during 1990 1997 its main consequences were changes of the oyashio path and restratification of the western subarctic water the example presented here uses data obtained during the canada russia international north pacific ocean climate study as well as the russian project subarctic to show that a warming and ventilation of the midlayers of the western subarctic 200 1000 dbar occurred because of the influx of warm subtropical waters to the oyashio and sea of okhotsk and to the weak coastal oyashio before the transition this influx appears to have reversed in the early 1990s now subarctic intermediate waters displace the remnants of subtropical waters that penetrated to the sea of okhotsk through the soya strait and create strong stratification in the oyashio area this transition appears to have begun during the reinforcement in the coastal oyashio

climatology of polar lows over the sea of japan using the jra 55 reanalysis abstractpolar lows are intense meso scale cyclones that develop over the oceans poleward of the main baroclinic zone a number of previous studies have reported polar low formation over the sea of japan within the east asian winter monsoon to understand the climatology of polar lows over the sea of japan a tracking algorithm for polar lows is applied to the recent jra 55 reanalysis the polar low tracking is applied to 36 cold seasons october march from october 1979 to march 2015 the polar lows over the sea of japan reach their maximum intensity on the southeastern side of the midline between the japanese islands and the asian continent consistent with previous case studies composite analysis demonstrates that the polar low development is associated with the enhanced northerly flow on the western side of a synoptic scale extratropical cyclone with the cold trough in the midtroposphere and with increased heat fluxes from the sea surface furthermore the present climatological study has revealed

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

distribution and modification of north pacific intermediate water in the kuroshio oyashio interfrontal zone abstract a multiship ctd survey was conducted in the kuroshio oyash interfrontal zone in the area of 30 41 n 140 e 180 from may to june 1992 to examine the distribution modification process and formation site of north pacific intermediate water npiw low salinity oyashio water and high salinity kuroshio water merge along the kuroshio extension just off the east coast of japan and together flow eastward eastward geostrophic transport and salinity across the kuroshio strong current indicate that the mixture of the kuroshio and oyashia waters along the kuroshio extension can produce new npiw transport estimate suggests that the new npiw bifurcates into the interfrontal zone and into the recirculation of the subtropical gyre a salinity minimum structure can he also created due to the isopycnal mixing along the kuroshio extension between the oyashio and kuroshio waters which have different salinity and vertical velocity structures the low salinity oyashio water seen along the oyashio branches and t

transport of north pacific intermediate water in the kuroshio oyashio interfrontal zone abstract we have estimated the volume transports of the subarctic and subtropical waters in the intermediate layer in the potential density range of 26 6 27 5 in the kuroshio oyashio interfrontal zone using hydrographic data and directly measured velocity data with a ladcp from the r v soyo maru cruise performed in may june 1998 the subarctic water flowing into this area along the oyashio near hokkaido 5 2 sv and from the subarctic front 2 0 sv merged with the subtropical water 13 5 sv along the kuroshio near japan and formed 20 7 sv of north pacific intermediate water npiw npiw mainly flowed eastward along the kuroshio extension and the transport across 158 e was about 18 8 sv 7 2 sv of subarctic water and 11 6 sv of subtropical water another 2 3 sv of the subtropical water were transported farther northward across 39 n these results support the hypothesis that npiw is mainly formed along the kuroshio extension

intermediate water formation in the bering sea during glacial periods evidence from neodymium isotope ratios changes in the flux and location of overturning circulation may have large effects on marine ecosystems and co 2 exchange between the ocean and atmosphere however unlike the atlantic little is known about ocean circulation and ventilation under glacial boundary conditions in the north pacific especially in regard to intermediate water circulation here we present new records of neodymium nd isotopes e nd in fe mn oxyhydroxides of bering sea sediments 884 m water depth we found a systematic variation between radiogenic values up to 0 8 e nd during cold periods and relatively less radiogenic values nd during warm periods there are no water masses with such radiogenic nd isotope signatures in the intermediate or deep north pacific potential sources of radiogenic values in the subarctic north pacific are limited to surface waters adjacent to the aleutian arc and kamchatka peninsula therefore the radiogenic e nd values of fe mn oxyhydroxides observed at the intermediate depth during glacial periods are best explained by subduction of the surface water to the intermediate depth at least 800 m due to brine rejection our data strongly indicate that the northwestern bering sea off northeastern kamchatka was a possible source region of glacial intermediate water in the bering sea and the subarctic north pacific

unit stream power equation for gravel the basic assumptions used in the derivation of bedload or gravel transport equations are reviewed and examined to determine their validities laboratory data indicate that unit stream power is mor

effects of temporal variation in tide induced vertical mixing in the kuril straits on the thermohaline circulation originating in the okhotsk sea abstract tidally induced vertical mixing is important for thermohaline circulation previous estimations of tidal mixing have aimed to obtain time averaged values and ocean general circulation models ogcms typically parameterize such mixing using a temporally constant strength however tidal mixing is known to vary temporally during tidal or spring neap cycles here we investigate the effects of temporal change in tidally induced vertical diffusivity t in the kuril straits using an ogcm the results demonstrate that variations of vertical mixing on diurnal 2 week and 1 2 year timescales induce significant differences in the net effect of mixing and therefore in the thermohaline circulation originating in the okhotsk sea for diurnal and 2 week variations the strength of the tidal mixing effect depends on 1 the period and length of the duration over which t is larger than the temporal average and 2 the amplitude of the temporal variation of t even if the time averaged values are the same this is explained by the relative importance of two states in a quasi equilibrium state a larger t results in weaker stratification and vice versa and thus the net tidal mixing effect is weaker when t is variable than when it remains constant conversely in an adjustment stage just after an increase in t a larger t acts on stronger stratification and vice versa resulting in a stronger mixing effect for a 1 2 year variation the strength of the tidal mixing effect also depends on the phase relationship with seasonal variation in stratification these results imply the necessity of considering temporal change when estimating tidal mixing from observations specifying it in ogcms and understanding its effects

observations of watermass modification by mesoscale eddies in the subtropical frontal region of the indian ocean sector of southern ocean abstract two eddies one cyclonic and the other anticyclonic in the subtropical frontal region stf of the indian ocean sector of southern ocean so and their role on the watermass modification are described here using the hydrographic data collected during the austral summer february of 2012 and 2013 and also by using argo profiles sampled during the austral summer from 2004 to 2012 the cyclonic eddy transports cold fresh and deeper antarctic intermediate water aaiw to much shallower depths but the anticyclonic eddy pushes the warm more saline subtropical surface water stsw to deeper depths significant changes in the properties of watermasses in terms of temperature and salinity viz stsw colder by 1 c and less saline by 1 psu and subtropical mode water stmw temperature decreased by 0 5 c and salinity by 0 7 psu were noticeable in the centre of cyclonic eddy on the other hand no such changes were found in the stmw properties in the anticyclonic eddy region the observed changes in the properties of watermasses were confirmed with the argo profiles sampled from the cyclonic and anticyclonic eddy regions of the stf a striking feature observed both in the cyclonic eddy and the anticyclonic eddy was the freshening of aaiw and this is consistently evident both in the cruise based observations as well as in the argo profiles it is hypothesized that the freshening in the aaiw at a given depth in the cyclonic eddy is due to shoaling of the pycnocline causing further intrusion of fresh saline water from deeper depths whereas the corresponding freshening in the anticyclonic eddy is due to the conservation of potential vorticity

the generation of large amplitude unsteady lee waves by subinertial k1 tidal flow a possible vertical mixing mechanism in the kuril straits numerical experiments with a two dimensional nonhydrostatic model are performed to investigate tidally generated internal waves in the kuril straits and their effect on vertical mixing the results show that sill scale internal waves at the k1 tidal frequency are confined to the sill slopes because the k1 tide is subinertial in the kuril straits in contrast to previous theories the authors show that intense short internal waves generated at the sill breaks by the subinertial k1 tidal current can propagate upstream as the tidal current slackens theoretical considerations identify these short waves as unsteady lee waves which tend to be trapped at the generation region and grow into large amplitude waves eventually inducing vigorous mixing along their ray paths in particular superposition of a propagating unsteady lee wave and a newly generated lee wave over a sill causes significant wave breaking leading to a maximum vertical diffusivity of 103 cm2 s21 this quite intense mixing reaches down to the density layer of the north pacific intermediate water npiw in contrast the m2 tidal current does not cause such strong vertical mixing because most of generated internal waves propagate away as first mode internal tides and because the barotropic flow amplitude is small the authors therefore suggest the possibility that generation of lee waves through interactions between the k1 current and the bottom topography of the kuril straits contributes to the observed modification of the okhotsk sea water required in the formation of the npiw

paleoceanographic history of the northwest pacific ocean over the past 740kyr discerned from radiolarian fauna abstract the northwest pacific ocean is characterized by a strong mixing of water masses due to the interplay of three distinct currents i e the kuroshio the tsugaru and the oyashio the c9001c drill core site located east of the shimokita peninsula and directly influenced by the tsugaru warm current and the oyashio subarctic current was used here to reconstruct the paleoceanographical history of this region especially focusing on the mid brunhes event mbe and its consequences this core provides a continuous record from marine isotope stage mis 18 740 ka to the present polycystine radiolarian assemblages were analyzed to highlight paleoceanographic and sea surface temperature changes at this site based on the radiolarian fauna seven time periods are defined which coincide with changes in the dynamics of the tsugaru and oyashio currents respectively the oldest time interval covered by our analysis i e vii 740 621 ka was marked by generally sluggish ocean circulation the tsugaru current influence increased during the following interval vi 621 478 ka which encompasses interglacials mis 15 and 13 while the oyashio current strengthened during the interval v 478 337 i e from glacials mis 12 to 10 these latter intervals vi to v constitute a long climatic transitional period where tsugaru current and oyashio current influences are strengthened in the time period from interval iv to interval i 0 337 ka the warming intensity of interglacials mis 9 mis 5 appears to be close to the modern one however several unusually warm glacials associated with a relatively strong tsugaru current flow were identified during this interval e g mis 8 and mis 6 radiolarian productivity data suggest that during intervals vii to v deep water masses are rich in nutrient content however a high vertical mixing event is recorded after interval iv when high nutrient concentrations appear to shift to the surface layer

north pacific intermediate water transports in the mixed water region abstract initial mixing between the subtropical and subpolar waters of kuroshio and oyashio origin occurs in the mixed water region interfrontal zone between the kuroshio and oyashio the relatively fresh water that enters the kuroshio extension from the mixed water region is this already mixed subtropical transition water subtropical transition water in the density range 26 64 27 4 can be considered to be the newest north pacific intermediate water npiw in the subtropical gyre this density range is approximately that which is ventilated in the subpolar gyre with significant influence from the okhotsk sea freshening of the kuroshio extension core occurs between 140 and 165 e in the upper part of the npiw 26 64 27 0 with the greatest freshening associated with the eastern side of the first and second kuroshio meanders kuroshio extension freshening in the lower part of the npiw 27 0 27 4 occurs more gradually and farther to the east there is nearly no distinction in water properties

unstable frontal waves along the kuroshio extension with low potential vorticity intermediate oyashio water abstract a linear stability analysis was conducted for a three layer primitive equation model including viscosity with a basic state which modeled the stratification and velocity fields with the vertical and horizontal variations across the kuroshio extension an unstable wave with a wavelength of 220 km and a phase speed of 0 24 m s 1 propagating in the downstream direction was found to grow the fastest characteristics of this unstable baroclinic wave were similar to those of waves observed along the kuroshio extension the growth rate of the fastest growing waves became greater with an increase of the cross stream difference of the potential vorticity pv in the intermediate layer for a cross frontal stratification structure without the pv gradient in the intermediate layer which is similar to that in the gulf stream the wavelength of the fastest growing unstable wave changed to 390 km and the unstable wave had a much different structure thus the unstable frontal waves observed along the kuroshi

carbon isotopes and habitat of polar planktic foraminifera in the okhotsk sea the carbonate ion effect under natural conditions the upper 500 or 1000 m of the water column in the okhotsk sea was sampled for living planktic foraminifera the polar species neogloboquadrina pachyderma sinistral strongly dominates the foraminiferal assemblage the subpolar to temperate species globigerina bulloides accounts for 10 25 other species account for up to 3 only the shell 18o and 13c values of the species n pachyderma sin are compared to water 18o values and 13c values of dissolved inorganic carbon dic the strong gradient in 18o composition and temperature in the upper water column is reflected in the 18o of n pachyderma sin relative to the values expected for inorganic calcite precipitated under equilibrium conditions n pachyderma sin displays a vital effect of about 1 in 18o the 13c composition of n pachyderma sin is about constant with water depth and the reflection of 13cdic in the foraminiferal shell seems to be masked by other effects most foraminifera are found above or slightly below the thermocline and can be assumed to calcify in the upper 200 m of the water column the gradient of 13cdic extends well below this depth therefore the lack of correlation can partly be attributed to this fact the remaining discrepancy between 13c of n pachyderma sin and 13cdic correlates with the carbonate ion concentration in the water column this leads to the conclusion that the carbonate ion effect cie which has been derived from culturing experiments for other species spero et al 1997 nature 390 497 500 is found here under natural conditions when the magnitude of the cie derived for g bulloides is applied to n pachyderma sin cie corrected 13c of n pachyderma sin is a direct reflection of 13cdic in the water column with a constant offset of 1 2

structure and seasonal variability of the east sakhalin current abstract in order to clarify the structure and seasonal variability of the flow field near the western boundary of the sea of okhotsk long term mooring measurements were carried out from 1998 to 2000 in this region in most of the mooring period a persistent southward flow the east sakhalin current was observed which extends from the surface to a depth around 1000 m the speed of this southward flow clearly changed seasonally the peak monthly mean speed along 53 n at a depth of 200 m attained a maximum of 37 9 cm s 1 in january and a minimum of 10 8 cm s 1 in july three different cores of intense flow were identified in the southward flow the first core was centered over the continental slope and had rather large vertical extent reaching the bottom on the slope the second core was trapped over the shelf near the surface and was observed from october to november this core was associated with less saline surface water affected by the amur river discharge the third core was intensified toward

a sensitivity study of the dense shelf water formation in the okhotsk sea 1 sensitivity of dense shelf water dsw formation to tidal mixing around the kuril straits wind stress and river runoff in the okhotsk sea is examined by an ice ocean coupled model horizontal resolution of the model is set to 3 8 km in the northern okhotsk sea for well resolving the coastal polynyas which is believed to be the principal region of dsw formation the model shows a good performance in terms of sea ice production and the consequent dsw formation dsw is also found to be formed in the offshore region apart from the coastal polynya dsw is defined independently for each experiment such that it identifies the water influenced by brine by introducing such definition the sensitivity of the dsw formation is assessed separately for change of density and that of formation rate the density of dsw exhibits high sensitivity to all the elements considered herein while its formation rate is sensitive only to winds winds affect the dsw formation rate mainly by influencing that occurs in the offshore region

direct breaking of large amplitude internal waves in the urup strait abstract observations and model data have been analyzed for the urup strait one of the kuril straits focusing on processes driving the extremely strong vertical mixing observations over 1 day on the pacific side of the sill of the urup strait show the generation of a large amplitude internal wave laiw characterized by the depression of potential density surfaces caused by a strong off sill flow when the laiw developed the potential density surface of 26 7 was depressed downward by more than 300 m and vertical mixing was markedly elevated within the 400 m thick layer 26 6 26 7 with a layer mean maximum energy dissipation rate and vertical diffusivity of 1 2 10 6 7 9 10 6 w kg 1 and 4 0 10 1 2 8 m2 s 1 respectively a three dimensional model simulation of the kuril straits driven by the diurnal barotropic tide reproduces well the observed features relevant to the generation of laiws in and around the urup strait the structure and generation pattern of laiws in the urup strait are consistent with those of the arrested lee waves observed in the hawaiian ridge and luzon strait although the depth at the top of the sill is far shallower in the urup strait it is suggested that barotropic tidal energy with diurnal frequency is converted into laiws through the excitation of topographically trapped waves with hydraulically supercritical velocity near the sill top and it is these waves that are responsible for the extremely strong mixing on the sill flanks of the shallow kuril straits

observation of frontal waves and associated salinity minimum formation along the kuroshio extension 1 high resolution observations with a towed conductivity temperature depth system were conducted along the kuroshio extension where the kuroshio and the oyashio merge and new north pacific intermediate water npiw is formed large amplitude frontal waves at an intermediate depth corresponding to a density range of npiw 26 6 26 9 were discovered here along the main stream of the kuroshio extension a remarkable salinity minimum due to the intense intrusions of oyashio water was observed near the trough of the frontal wave with an apparent wavelength of 100 km around the troughs crests of the frontal waves the horizontal velocity in the intermediate layer was directed to the southern kuroshio water side northern oyashio water side relative to the upper layer horizontal velocity fields converged diverged around the wave trough crest indicating downwelling upwelling the amplitude of the frontal waves was observed to grow in the downstream direction where isolated eddies were observed this suggests that the development of frontal waves and wave breaking enhance isopycnal mixing and cross frontal exchange across the main stream of the kuroshio extension

satellite passive microwave studies of the sea of okhotsk ice cover and its relation to oceanic processes 1978 1982 this paper describes the use of the nimbus 7 scanning multichannel microwave radiometer smmr satellite data to study the ice cover in the sea of okhotsk during the four winters of 1978 1982 the ice concentration estimates obtained from smmr are used to study two different polynyas one over the kashevarova bank and the other over the northwest continental shelf for the kashevarova polynya this study shows that the polynya which may be related to the upwelling observed in historic summer cruises occurs directly over the bank for the continental shelf which because of strong offshore winds and cold temperatures is a region of high ice production the polynya areas are combined with heat flux estimates from weather station data to yield the production rates of ice salt and dense shelf water as a previous study by kitani 1973 shows the mixing of this dense shelf water with pacific water yields a water mass unique to the okhotsk which is the layer of cold low salinity intermediate water between depths of 150 and 800 m from our calculations we estimate that the dense shelf water is produced at an annual rate of about 0 5 sv and that the intermediate water is produced at a rate of 1 2 sv which yields a renewal time for this layer of 10 40 years

environmental fluctuations in the northwestern pacific ocean during the last interglacial period evidence from radiolarian assemblages abstract the last interglacial period from 130 to 117 ka was as warm as or warmer than the present and thus it is relevant for our understanding of the possible effects of recent global warming in this study we used radiolarian assemblages in a sediment core to reconstruct environmental fluctuations in the northwestern pacific ocean during the last interglacial period the sediment core md012421 was collected where the warm kuroshio current meets the cold oyashio current we used the ratio of warm water to the total of warm and cool water radiolarian species tr as an indicator of the dominant surface water masses relative importance of the warm kuroshio and cool oyashio currents and we used the relative abundance of cycladophora davisiana as an indicator of cold oxygen rich intermediate waters related to seasonal sea ice formation at high latitudes tr results indicated that a transitional surface water mass off kashima was replaced by a subtropical water mass between 131 ka late marine isotope stage mis 6 and 125 ka last interglacial period mis 5e furthermore the relative abundance of c davisiana changed from 19 6 at 133 ka late mis 6 to 0 at 126 ka mis 5e this change suggests a reduction of cold oxygen rich waters at intermediate depths off kashima in association with weakened ventilation at high latitudes in the north pacific as this reduction took place 1 kyr earlier than the shift of surface water masses at the core site we inferred that changes of insolation the main driver of glacial interglacial cycles controlling the variation of sea ice formation at high latitudes occurred earlier than the lower latitude change in the atmospheric pressure pattern controlling the surface water shifts high resolution time series analysis indicated that fluctuations in the surface water mass occurred cyclically with a periodicity of approximately 500 years during the second half of the last interglacial period this periodicity may be attributable to fluctuations in solar radiation

expansion of the southern california oxygen minimum zone during the early to mid holocene due to reduced ventilation of the northeast pacific abstract oceanic deoxygenation observed since the 1950s has drawn increasing concern as dissolved oxygen do regulates marine biodiversity and biogeochemical cycles yet the do time series from direct instrumental measurements is insufficiently long several decades to constrain the centennial to millennial variability here we present redox sensitive metal re u and mo records from santa barbara basin sbb california to reconstruct subsurface do through the holocene significantly higher authigenic metal fluxes and coherent benthic foraminifera faunal responses along a published depth transect reveal vertical expansion and intensification of the southern california oxygen minimum zone omz prior to 6 ka comparison with post industrial trace metal records suggests low oxygen conditions were more extreme during early to mid holocene mh highlighting the magnitude of omz variability in the absence of anthropogenic influences inconsistencies between authigenic metal fluxes and local oxygen control indicate a remote weakening of the north pacific intermediate water npiw formation prior to the mh reduced ventilation of the mid depth north pacific is supported by state of the art earth system model simulations with realistic mh 6 ka forcing highlighting the importance of brine rejection during sea ice formation in changing the buoyancy of npiw and its basin wide influences on north pacific omz evidence from holocene marine lake records and model simulations further suggests a southward intertropical convergence zone itcz migration and a consequent deepening of the aleutian low al towards late holocene which favors more sea ice brine rejection thus mid depth ventilation in the north pacific was closely associated with atmospheric circulation during the holocene

the origin of the north pacific intermediate water possible source regions of the north pacific intermediate water npiw were investigated with synoptic conductivity temperature depth surveys in the okhotsk sea kuril basin a pycnostad referred to as the okhotsk sea mode water osmw was found in the density range of 26 6 27 the pycnostad is not seen in the western subarctic gyre wsag thus it is an indicative water peculiar to the okhotsk sea the maximum thickness is at 26 7 26 9 centered at 26 8 which coincides with the npiw density range in the north pacific subtropical gyre in the oyashio area east of the southern kuril islands and hokkaido waters that have intermediate temperature salinity and potential vorticity between the osmw and the wsag water were distributed suggesting a following transport route of the npiw source water the thick thus low q q is potential vorticity and low salinity water mass outflowing from the okhotsk sea mixes with the relatively warm saline and high q wsag water to form the oyashio water a coastal part of the oyashio water flows southwestward along the east coast of the southern kuril islands and hokkaido retaining the pycnostad q minimum a large part of the low q oyashio water flows further southward and merges with the kuroshio extension and then flows eastward forming new npiw in this process a salinity minimum develops and the q minimum disappears because of the mixing with a saline kuroshio water old npiw without a pycnostad in the npiw density range these results suggest that the origin of npiw is the water mass in the okhotsk sea osmw and the density of the water mass primarily determines the npiw density centered at around 26 8

effects of along shore wind on dsw formation beneath coastal polynyas application to the sea of okhotsk 1 it is known that salinity anomaly under a polynya reaches and remains an equilibrium value s after termination of its initial increase associated with brine rejection at the surface in this paper we investigate effect of along shore downwelling favorable wind on the equilibrium salinity anomaly by idealized numerical calculations and scale based estimates numerical calculations showed that high saline water beneath polynya is advected downstream by wind driven circulations over the shelf besides baroclinically developed eddies which consequently induces a decrease in s beneath polynya the downwelling favorable wind generates an offshore overturning flow through lower layers referred to as ekman compensation flow ecf which causes a great offshore salinity flux as well as an along shore current we also constructed an equation for estimation of s from the viewpoint of salinity budget over the polynya region in which lateral salinity fluxes caused by ecf along shore wind driven current and baroclinic eddies are scaled the solution s was also verified by a series of numerical calculations furthermore we investigated the effects of along shore wind on dense water generation beneath the okhotsk coastal polynyas we conducted simplified numerical experiments assuming the okhotsk situation in which fs and offshore width b of polynya are predicted by a thermodynamic polynya model with ecmwf meteorological variables the simulated salinity shows a good agreement with the direct measurements the theoretical estimates for s was also applied to two okhotsk polynyas northwestern polynya nwp and northern polynya np in conclusion we found that the along shore wind causes greater salinity decrease in np than in nwp whose variations substantially depend on the aleutian low activity

reduced upwelling of nutrient and carbon rich water in the subarctic pacific during the mid pleistocene transition abstract reduction in atmospheric pco2 has been hypothesised as a causal mechanism for the mid pleistocene transition mpt which saw global cooling and increased duration of glacials between 0 6 and 1 2 ma sea ice modulated high latitude upwelling and ocean atmospheric co2 flux is considered a potential mechanism for pco2 decline although there are no long term nutrient upwelling records from high latitude regions to test this hypothesis using nitrogen isotopes and opal mass accumulation rates from 0 to 1 2 ma we calculate a continuous high resolution nutrient upwelling index for the bering sea and assess possible changes to regional co2 fluxes and to the relative control of sea ice sea level and glacial north pacific intermediate water gnpiw on deep mixing and nutrient upwelling in the region we find nutrient upwelling in the bering sea correlates with global ice volume and air temperature throughout the study interval from 1 ma and particularly during the 900 ka event suppressed nutrient upwelling would have lowered oceanic fluxes of co2 to the atmosphere supporting a reduction in global pco2 during the mpt this timing is consistent with a pronounced increase in sea ice during the early pleistocene and restriction of flow through the bering strait during glacials after 900 ka both of which would have acted to suppress upwelling we suggest that sea level modulated gnpiw expansion during glacials after 900 ka was the dominant control on subarctic pacific upwelling strength during the mid late pleistocene while sea ice variability played a secondary role

cold core anticyclonic eddies south of the bussol strait in the northwestern subarctic pacific abstract summer hydrographic surveys from 1993 to 1997 in the area south of the kuril islands in the northwestern subarctic pacific showed the existence of anticyclonic eddies south of the bussol strait at almost the same location but with variable sizes and intensities depending on the year every eddy had a cold low salinity and low potential vorticity core suggesting a strong influence from the okhotsk sea water two formation processes and annual variations were found with satellite data analyses one is the case where eddies are locally formed south of the bussol strait and intensified from summer to fall with the supply of okhotsk sea water as observed in 1993 in the other case kuroshio warm core rings that had translated northeastward are arrested near the bussol strait and amplified with the supply of okhotsk sea water as seen from summer to autumn in 1995 in winter eddies tend to move northeastward with decay the 1992 eddy moved northeastward then northward in winter and was eventually

a comparison of arctic and antarctic mesoscale vortices the mesoscale less than 100km vortices occurring in the two polar regions are considered in terms of their geographical and seasonal distribution satellite cloud signatures and forcing mechanisms environmental conditions important in the development of the vortices are considered including sensible heat flux stability throughout the troposphere and synoptic factors such as baroclinicity and upper air cold pools a scheme to classify the observed vortices in the two polar regions in terms of the physical mechanisms behind their formation and development is proposed the processes considered important are baroclinic instability convection and vorticity generation through cyclonic vorticity advection and topographic forcing the major difference between the systems observed in the two polar regions is the lack of deep convection in the southern hemisphere which precludes the development of many of the vigorous types of system found in the north and the major role that topography plays in the antarctic coastal region the most common type of vortex found in the antarctic occurs over the ice free ocean to the west of synoptic scale disturbances and is similar to the type of northern system know as a comma cloud

anomalous southward intrusions of the oyashio east of japan 2 two layer numerical model anomalous southward intrusions of the oyashio along the japanese coast in the northwestern pacific occur from winter to late spring with cold sea surface temperatures exerting various influences on the temperature in japan and on aquaculture a two layer numerical model is employed to examine the interannual response of the ocean to the observed wind stress change over 1961 1987 with special reference to the occurrence of the anomalous southward oyashio intrusion since 1971 anomalous southward oyashio intrusions were observed in winter of 1974 1981 1984 and 1986 and the significant southward shift of the oyashio is well simulated in these years because the observed southward latitude of no wind stress curl in the north pacific and the sverdrup transport show clear simultaneous correlation with the calculated southernmost latitude of the subarctic circulation the anomalous southward intrusion of the oyashio is found to be essentially due to the barotropic response of the ocean to the change in the wind stress characterized by the southward development of the enhanced aleutian low the model also shows that a baroclinic response from the eastern boundary is mainly confined to a region east of 140 w and an uplift of the interface in a central area of the subarctic circulation is also formed by the divergence of the surface ekman layer in winter of the anomalous southward oyashio intrusion the calculated upper layer thickness south of the subarctic circulation has a clear positive simultaneous correlation with the observed southernmost latitude of the oyashio defined by the 5 c isotherm at a depth of 100 m which has been used as an index however the observed southernmost latitude of the oyashio follows the observed latitude of no wind stress curl and the sverdrup transport by 2 4 months while the calculated southernmost latitude of the subarctic circulation shows simultaneous correlation with no wind stress curl and the sverdrup transport from this it is pointed out that the observed southernmost latitude of the oyashio defined by the 5 c isotherm at a depth of 100 m lags by 2 4 months the barotropic response of the ocean which appears in the surface pressure fields and upper layer velocity

tidally induced diapycnal mixing in the kuril straits and its role in water transformation and transport a three dimensional nonhydrostatic model experiment 1 baroclinic processes generated by the k1 tidal flow around the kuril straits and their role in the linkage between the okhotsk sea and the north pacific are investigated using a three dimensional nonhydrostatic model large amplitude unsteady lee waves are generated around sill tops all along the kuril island chain and induce significant density inversions from the sea surface down to the 27 6 density layer along with this wave breaking a large flow of energy takes place from the swift tidal flow regions to greater depths as a result of the clockwise propagation of both the topographically trapped waves around the islands and the remaining unsteady lee waves such wave generation and energy exchange eventually cause intense diapycnal mixing over the shallow topographic features and near the bottom leading to a maximum diapycnal diffusivity of over 103 cm2 s 1 even in the deep bussol strait which is thought to be the main exit of the okhotsk sea water considerable mixing corresponding to diapycnal diffusivity values of between 10 50 cm2 s 1 occurs vigorous mixing in the shallow regions produces low potential vorticity pv water in the upper layer and high pv water below accordingly pv fronts are formed along the island chain and sustain instabilities that in turn release baroclinic eddies with low core pv values these features are indicated in recent satellite imagery and in situ observations suggesting that the tide is the controlling factor in the formation of fronts observed in the kuril straits tidally induced mean transport across the straits is estimated to reach 26 sv 1 sv 106 m3 s 1 which is much larger than in the barotropic case however most of the exchanged water tends to circulate around the islands due to the effect of bottom topography whereas eddies pinched off from the tidal fronts carry the exchanged water offshore the amount of eddy driven offshore transport away from the islands reaches 14 sv with roughly half being directed to the north pacific this significant offshore transport spreads the effect of the diapycnal mixing taking place in the straits over wider areas of the north pacific and the okhotsk sea for example the pv values generated in the eddies differ by 30 40 from the ambient water on average whereas sea surface salinity within the eddies is 0 1 psu higher than the surroundings corresponding to the density increase of 0 08 thus the eddy transport provides significant pv and salinity fluxes to both the north pacific and the okhotsk sea hence we infer that a combination of tidally driven processes taking place at the passages leads to the formation of eddies that play a central role in water transport and transformation and are an essential aspect of the physical interplay between the okhotsk sea and the north pacific

an arctic hurricane over the bering sea abstract a mesoscale arctic hurricane developed over the western bering sea on 7 march 1977 and traveled eastward parallel to the ice edge along a zone of large sea surface temperature gradient satellite imagery reveals spiral cloud bands of unusual symmetry and mesoscale dimension associated with the mature stage of the low the track of the low pressure center passed over the rawinsonde station at st paul island where time series of surface data show a pronounced maximum in equivalent potential temperature at the core of the low the storm made landfall with surface winds 30 m s 1 at cape newenham alaska on 9 march and rapidly dissipated thereafter synoptic analyses show that the arctic hurricane formed at the leading edge of an outflow of arctic air that originated over the ice and passed over the open water of the western bering 5u in the mid and upper troposphere a large cold core low dominated the bering sea region quasi geostrophic analysis at 0000 utc 7 march 1977 reveals conditions co

recent variability in the pacific western subarctic boundary currents and sea of okhotsk abstract the objective of this research is to describe physical processes which are the cause of the recent variability of the pacific western subarctic waters rapid thermohaline changes have occurred within the oyashio and kamchatka current during the last decade this variability has included a warming of the kamchatka current warm intermediate layer but a cooling and freshening of the upper layer in the oyashio and sea of okhotsk the example presented here uses data obtained during the canada russia inpoc and woce projects as well as the new russian studies with high resolution station grid the possible physical mechanism that generated the upper layer freshening during the thermohaline transition is examined major components of the fresh water budget of the okhotsk sea are considered in order to describe the dramatic changes in salinity which have recently occurred in the pacific subarctic significant changes in precipitation and other fresh water inputs are demonstrated it is suggested that upper layer of the oyashio and kamchatka current became cooler and fresher because of the export of cold fresher waters from the bering and okhotsk seas these waters from the marginal seas have cooled the bottom of the halocline reducing evaporation and acting as a feedback that has kept the upper layer of the western subarctic boundary currents fresh it is also shown that the outflow of the cold sea of okhotsk water has changed its path during this recent thermohaline transition

seasonal succession vertical distribution and dissolution of planktonic foraminifera along the subarctic front implications for paleoceanographic reconstruction in the northwestern pacific abstract the regional spatial and depth distribution of planktonic foraminifera were studied through sediment trap observations at two stations stations wct 5 about 41 n 150 e and wct 6 about 42 n 155 e along the subarctic front in the northwestern pacific ocean the sediment traps were moored at 1000 and 4500 m depths at station wct 5 and 1091 2051 and 4871 m depths at station wct 6 the samples were collected from 17 august 1998 to 10 august 1999 at station wct 5 and from 15 august 1999 to 6 august 2000 at wct 6 at station wct 5 two distinct annual periods of increased total foraminiferal and species production were evident the period of highest production was in autumn with a secondary period in early summer at station wct 6 high total foraminiferal shell fluxes occurred in april may and september october the april may spring bloom of planktonic foraminifera apparently began each year as the sea surface temperature sst increased after winter and the decrease of thickness of the mixed water layer during june july in every year following the cessation of bloom the most common foraminiferal species in the study region were globigerina quinqueloba neogloboquadrina pachyderma neogloboquadrina dutertrei neogloboquadrina incompta globigerinita glutinata globigerina bulloides globigerina falconensis globorotalia theyeri globorotalia scitula and globigerinella calida foraminiferal fluxes displayed a distinct seasonality at all trap depths at both stations at station wct 5 in 1998 1999 foraminiferal species were scarce in the surface water during spring and summer and the dominant foraminiferal species were most productive during winter and autumn at station wct 6 the dominant foraminiferal species were most productive during late winter to spring and all species showed a peak in middle spring may a comparison of seasonal patterns of dominant foraminiferal species between the northwestern and northeastern pacific demonstrated that foraminiferal productivity was a good proxy for sea surface temperature and mixing of water column significant dissolution of foraminiferal tests was evident in the deepwater column and was used to estimate the foraminiferal lysocline depth 4500 m in the northeastern pacific basin

distribution and circulation of the coastal oyashio intrusion abstract the distribution and circulation of the coastal oyashio intrusion were examined with a ctd and shipboard adcp survey conducted in the vicinity of the east coast of japan in may 1994 the estimate of mixing ratios in the density range of 26 4 27 2 assuming isopycnal mixing between the pure oyashio and kuroshio waters and the adcp velocity data showed the following new results 1 the distribution of the oyashio water is horizontally and vertically patchy and some of the oyashio water patches formed mesoscale eddies with both cyclonic and anticyclonic circulations 2 the anticyclonic oyashio eddy had cold and low salinity cores with low potential vorticity pv suggesting that the origin was the okhotsk sea the cyclonic oyashio eddy with high pv was considered to originate from the western subarctic gyre wsag in the north pacific a new image of the intermediate oyashio water circulation near the oyashio kuroshio confluence is proposed in which the eddies from the okhotsk sea and the wsa

meridional transport of the north pacific intermediate water in the kuroshio oyashio interfrontal zone meridional transport and origin of the north pacific intermediate water npiw in the kuroshio oyashio interfrontal zone k o zone were examined using hydrographic and velocity data with ladcp lowered acoustic doppler current profiler along 37 n in the northwestern pacific dominant northward transports were observed west of the shatsky rise coast 157 e in both upper 26 6 27 0 and lower npiw 27 0 27 5 in the upper npiw northward transports of 4 3 sv which consist of the dominant kuroshio 3 2 sv and small oyashio component 1 1 sv were observed suggesting that the upper npiw in the k o zone was formed by the mixing between the southward oyashio water across the oyashio front and the kuroshio water bifurcated from the kuroshio extension in the lower npiw 9 4 sv of northward transports kuroshio 5 5 sv and oyashio 3 9 sv were observed suggesting that the lower npiw in the k o zone was maintained by the northward transport of the npiw formed near the kuroshio extension

intraseasonal to seasonal variability of the intermediate waters along the kuroshio path east of taiwan the variability of the intermediate water iw east of luzon and taiwan is investigated using data acquired from moored instrumented lines and shipboard hydrographic and current velocity surveys the iw is defined as the water mass with a local salinity minimum along the kuroshio path an empirical formula is developed to estimate the iw salinity minimum east of taiwan using temperature measurements around 580 m depth properties of the iw east of taiwan vary greatly as a result of variable contributions from three water masses including the high salinity south china sea intermediate water scsiw the low salinity north pacific intermediate water npiw and the intermediate salinity kuroshio intermediate water kiw our analysis concludes that npiw is predominantly found east of taiwan and the northward transport of kiw from northeast of luzon to east of taiwan is not a steady process concurrent mooring measurements at these two locations enable us to correlate the variations of the layer thickness of the kuroshio near its origin klto northeast of luzon to the nature of the iw east of taiwan when the kuroshio is deep i e large klto kiw is transported northward across the luzon strait where its salinity increases presumably due to turbulence mixing with scsiw this modified kiw is then transported to the east of taiwan when the kuroshio is shallow i e small klto the kiw transport east of luzon is nil or southward east of taiwan npiw feeds in below the kuroshio and is transported northward beyond the i lan ridge

roles of the okhotsk sea and gulf of alaska in forming the north pacific intermediate water recently obtained world ocean circulation experiment woce sections and pre woce hydrography are used to study the water mass structure and formation and transformation of north pacific intermediate water npiw five neutral density surfaces are selected and mapped encompassing npiw from 400 to 900 m in the subtropical latitudes with a distance of 100 m between a pair of surfaces npiw is defined as a subtropical gyre salinity minimum which is well followed by a neutral density surface n 26 9 formation and transformation of npiw is examined by the mapped turner angle on neutral density surfaces apparent diffusive double diffusion is found in the alaskan gyre on n 26 5 neutral surface in the northwest subpolar gyre and the okhotsk sea on n 26 9 neutral surface and mainly in the okhotsk sea on the two deep neutral surfaces n 27 2 and n 27 4 these diffusive regions indicate transformation sources for npiw along with additional information of potential vorticity and stream function it is found that there are two different npiw formation sources one in the gulf of alaska characterized by high potential vorticity and the other in the okhotsk sea characterized by low potential vorticity the former lies shallower at n 26 2 26 5 but its effect deepens to npiw core density level at n 26 8 on the basis of potential vorticity distribution the latter includes the influence of the northwest subpolar gyre and extends much deeper to n 27 4 we call them gulf of alaska intermediate water gaiw and okhotsk intermediate water oiw respectively gaiw contributes to npiw in the eastern part of the subtropical gyre east of date line whilst oiw dominates in the west and entire lower part of npiw seasonal flow stream function mapped on neutral surfaces shows that the contribution of gaiw to npiw occurs mainly in the wintertime because in winter a significant northward shift of zero wind stress curl makes the gulf of alaska an additional source for npiw

quasi decadal variation in intensity of the western part of the winter subarctic sst front in the western north pacific the influence of kuroshio extension path state abstractvariations of the subarctic front saf which is extracted as a strong sea surface temperature sst gradient in the longitudinal band of 146 152 e were investigated over 30 winters january march from 1982 to 2011 using high spatial resolution satellite derived sst dataset and hydrographic observations the saf had little meridional movement in this longitudinal band lying between 40 and 41 n throughout the analysis period the saf intensity had a dominant quasi decadal time scale about 8 yr its intensity in the strong phase was up to about 50 higher than in the weak phase the saf intensity strongly reflected upper ocean conditions in the kuroshio oyashio confluence koc region just south of the saf in the strong saf phase large positive anomalies in both temperature and salinity were found in the koc region not only at the sea surface but also below 300 m and the water properties in the koc region were those of the kuroshio water the warm salty water in the koc region was supp

mesoscale cyclogenesis dynamics over the southwestern ross sea antarctica previous work has shown that frequent mesoscale cyclogenesis adjacent to franklin island is linked to the strong and persistent katabatic winds from east antarctica which funnel into terra nova bay and then blow out over the southwestern ross sea four mesoscale cyclones that formed near terra nova bay between february 16 and 20 1988 are examined to more clearly define the governing mechanisms these events are investigated using all available observations including automatic weather station data high resolution satellite images satellite soundings and hemispheric synoptic analyses the first two cyclones formed on low level baroclinic zones established by the synoptic scale advection of warm moist air toward the cold continental air blowing gently from east antarctica in the second case baroclinic instability of this small scale cold front was apparently triggered by the enhanced upward vertical motion associated with the approach of a midtropospheric trough the third mesocyclone formed shortly after on a baroclinic zone over the polar plateau the second vortex completely disrupted the usual katabatic drainage over the plateau and forced warm moist air over the coastal slopes all three cyclones moved to the north in the prevailing cyclonic flow but the plateau vortex lasted for only 6 hours the fourth mesoscale low formed in conjunction with an abrupt and intense surge of katabatic air from terra nova bay which resharpened the coastal baroclinic zone at the same time a transiting midtropospheric trough probably associated with lower tropospheric upward vertical motion apparently accelerated the katabatic winds and triggered the vortex formation a similar katabatic wind forced mesocyclone formed near byrd glacier the two vortices moved to the east southeast and northeast respectively apparently being steered by the generating katabatic airstreams and merged just to the north of the ross ice shelf the combined vortex reintensified as another trough passed overhead and moved eastward to west antarctica where it dissipated two days later

distributions of dissolved organic carbon and nitrogen in the western okhotsk sea and their effluxes to the north pacific abstract the okhotsk sea is considered the only ventilation source area for north pacific intermediate water npiw which is widely distributed in the low and middle latitudes of the north pacific previous studies have confirmed high levels of dissolved organic carbon doc in npiw yet the amounts and the processes driving doc export from the okhotsk sea are poorly understood in this study concentrations of doc and dissolved organic nitrogen don were measured in the western okhotsk sea during the summer of 2006 and additional doc measurements were made during the late spring of 2010 results indicate that doc transport to the intermediate waters 26 7 27 0 occurs through two processes the first process involves the spread of water discharged from the continental shelf dense shelf water which contributes to a doc and turbidity maxima in the 250 300 m layer of okhotsk sea mode water osmw located off the eastern sakhalin coast the second process involves diapycnal mixing in the kuril basin and the bussol strait where doc is transported to a depth greater than 800 m the ratio of doc don in osmw was significantly higher in the kuril basin and bussol strait than off of the sakhalin coast which suggests that the transport of terrigenous organic matter from the bottom occurs in the former regions doc and don efflux from the okhotsk sea to the intermediate layer in the north pacific water 26 7 27 0 were estimated to be 68 72 tg c yr 1 and 5 4 tg n yr 1 respectively for which the doc transported by diapycnal mixing accounts for 37 we conclude that diapycnal mixing in the kuril basin and bussol strait regions could play a significant role in regulating the quality and quantity of doc exported to the intermediate water in the north pacific

bomb radiocarbon invasion into the northwestern north pacific invasion of the bomb radiocarbon was investigated in the northwestern north pacific including the subarctic oyashio region the subtropical kuroshio region and the subarctic subtropical mixing transition areas after the geosecs pacific expedition in 1973 the bomb radiocarbon decreased in the oyashio region and increased in the kuroshio region the former was caused by rapid ventilation of the oyashio water the latter was owing to accumulation of the bomb radiocarbon in the intermediate water of the kuroshio region the reverse trends in the temporal variation of radiocarbon between the oyashio and the kuroshio regions lead to virtually small temporal change of the bomb radiocarbon in the transition area where the two waters mix the temporal changes of the bomb radiocarbon suggest that the north pacific intermediate water is formed in the northwestern north pacific

distribution and formation of okhotsk sea intermediate water an analysis of isopycnal climatological data 1 in order to clarify the distribution and formation of okhotsk sea intermediate water osiw an isopycnal climatological data set based on all of the available historical observations is developed and examined the isopycnal maps clearly show that there are two direct ventilation sources for osiw dense shelf water dsw with cold and fresh properties influenced by sea ice formation in the northwest shelf region and forerunner of soya warm current water fscw which has warm and saline properties originating in the japan sea the cold and fresh water extends southward from the northwest shelf to the shelf slope off sakhalin island it suggests that dsw is transported southward by the east sakhalin current the dsw enters the kuril basin and mixes with fscw and western subarctic water wsaw originating from the north pacific to form osiw the annual mean production rate of dsw estimated from the total volume of dsw over the shelf in spring and summer is 0 67 sv 1 sv 106 m3 s the annual mean volume transport of fscw is estimated to be 0 08 sv on the basis of its cross section area and the current speed assumption of isopycnal mixing yields a mixing ratio of 1 1 0 1 among dsw wsaw and fscw to form osiw we estimate the annual production rate of osiw to be 1 4 sv the corresponding osiw s renewal time is 7 years continued assumption of isopycnal mixing yields a mixing ratio of 0 6 0 4 between wsaw and osiw to form oyashio intermediate water oyiw

decrease of dissolved oxygen after the mid 1980s in the western north pacific subtropical gyre along the 137 e repeat section 1 the japan meteorological agency has acquired dissolved oxygen do concentration data each year since 1967 along the 137 e repeat section in the western north pacific in this data set we found significant regional temporal trends of decreasing or increasing do concentrations on various isopycnal surfaces do decreases were particularly significant after the mid 1980s in the subtropical gyre mean rates of do change at 20 25 n for 1985 2010 were 0 28 0 08 mol kg 1 yr 1 on 25 5 in north pacific subtropical mode water npstmw 0 36 0 08 mol kg 1 yr 1 on 26 8 in north pacific intermediate water npiw and 0 23 0 04 mol kg 1 yr 1 on 27 3 in the o2 minimum layer oml the cause of do decrease differed among isopycnal surfaces on density surfaces shallower than 26 0 less than about 400 m the deepening of isopycnal surfaces and decline of oxygen solubility due to ocean warming have had the greatest influence in particular between 25 2 and 25 8 near the npstmw their combined contributions accounted for 50 of the do decrease in the npiw core at roughly 26 8 700 m the decline in do was attributable to the do decrease in the formation region in the oml between 27 0 and 27 3 1000 m the do decrease likely resulted from an increase in westward transport of low o2 water due to strengthening of the subtropical gyre the result of this study shows the importance of the long term and high frequency along the 137 e repeat section