upwelling in the alaskan beaufort sea atmospheric forcing and local versus non local response abstract the spin up and relaxation of an autumn upwelling event on the beaufort slope is investigated using a combination of oceanic and atmospheric data and numerical models the event occurred in november 2002 and was driven by an aleutian low storm the wind field was strongly influenced by the pack ice distribution resulting in enhanced winds over the open water of the chukchi sea flow distortion due to the brooks mountain range was also evident mooring observations east of barrow canyon show that the beaufort shelfbreak jet reversed to the west under strong easterly winds followed by upwelling of atlantic water onto the shelf after the winds subsided a deep eastward jet of atlantic water developed centered at 250 m depth an idealized numerical model reproduces these results and suggests that the oceanic response to the local winds is modulated by a propagating signal from the western edge of the storm the disparity in wave speeds between the sea surface height signal traveling at the fast barotropic shelf wave speed versus the interior density signal traveling at the slow baroclinic wave speed leads to the deep eastward jet the broad scale response to the storm over the chukchi sea is investigated using a regional numerical model the strong gradient in windspeed at the ice edge results in convergence of the offshore ekman transport leading to the establishment of an anti cyclonic gyre in the northern chukchi sea accordingly the chukchi shelfbreak jet accelerates to the east into the wind during the storm and no upwelling occurs west of barrow canyon hence the storm response is fundamentally different on the beaufort slope upwelling versus the chukchi slope no upwelling the regional numerical model results are supported by additional mooring data in the chukchi sea

formation of 26 8 26 9 σθ water in the kuril basin of the sea of okhotsk as a possible origin of north pacific intermediate water by using all japanese hydrographic data obtained south of 55 n in latitude in the sea of okhotsk we compile a data set for this study our investigations with these data show that a large quantity of relatively cold fresh oxygen rich homogeneous intermediate water with a density range of 26 8 to 26 9 exists in the kuril basin we name this intermediate water the kuril basin intermediate water kbiw results of isosteric analyses show that a possible origin of kbiw is located in a region off the hokkaido coast in the southwestern sea of okhotsk we suggest that kbiw is produced by the isopycnal mixing of relatively dense soya warm water which appears only in early spring with the colder fresher water which originates from the northwestern okhotsk finally we demonstrate that kbiw may be a source water of the north pacific intermediate water npiw because it has the same density range and water properties

re evaluation of turbulent mixing vertical structure in the bussol strait and its impact on water masses in the okhotsk sea and the north pacific abstract distribution of the turbulent kinetic energy dissipation rate e across the bussol strait was re evaluated by applying an improved method using density inversions to tide resolving density observations the improved estimates without excessive rejection of density inversions provide about three times higher mean values of e 1 45 10 7 w kg vertical diffusivity k 153 10 4 m2 s and depth integrated e 187 mw m2 in comparison with previous estimates one day mean vertical profiles of e in the potential density co ordinate allows us to estimate diapycnal velocity at 3 10 5 m s downwards through the 26 85 isopycnal surface and was almost zero through 26 7 suggesting the thinning of okhotsk sea mode water or of the core of north pacific intermediate water as the water flows through the bussol strait from the sea of okhotsk to the north pacific the re evaluated turbulence and current distributions confirmed following previous knowledge but with quantitative improvements and or expansion of coverage 1 all averaged e and k show distinctive mid depth maxima at 800 1600 m 26 9 27 6 and at a height of 300 400 m above the bottom and enhanced e within 500 m of the bottom corresponding to the enhanced shear and low richardson number at vertical scales of less than 50 m 2 a significant amount of the e variance 14 is explained by the 50 m scale vertical shear composed of mean and diurnal tidal currents 3 the diurnal tidal currents are well approximated by six low mode topographically trapped waves

tidal exchange through the kuril straits abstract the tidal exchange between the okhotsk sea and the north pacific ocean is studied numerically with particular emphasis on the predominant k1 barotropic component the calculated harmonic constants of the k1 tide in and around the okhotsk sea agree well with those obtained from extensive tide gauge observations the features of the simulated tidal fields are similar to those reported in the literature since the k1 tide is subinertial in the okhotsk sea topographically trapped waves are effectively generated contributing to strong tidal currents with a maximum amplitude of over 1 5 m s 1 in the kuril straits the structures of tide induced mean flows in most passages of the straits are characterized by bidirectional currents in which the mean flow exhibits a reversal in direction across the passages this feature is clearly indicated in noaa infrared imagery the mean transport shows significant net exchange of water via several straits in the kuril islands a transport of about 5 0 sv 1 sv

intrusion of warm bering chukchi waters onto the shelf in the western beaufort sea 1 wind driven changes in the path of warm bering chukchi waters carried by the alaska coastal current acc through barrow canyon during late summer are described from high resolution hydrography acoustic doppler current profiler measured currents and satellite measured sea surface temperature imagery acquired from mid august to mid september 2005 2007 near barrow alaska numerical simulations are used to provide a multidecadal context for these observational data four generalized wind regimes and associated circulation states are identified when winds are from the east or east southeast the acc jet tends to be relatively strong and flows adjacent to the shelf break along the southern flank of barrow canyon these easterly winds drive inner shelf currents northwestward along the alaskan beaufort coast where they oppose significant eastward intrusions of warm water from barrow canyon onto the shelf because these easterly winds promote sea level set down over the beaufort shelf and upwelling along the beaufort slope the acc jet necessarily becomes weaker broader and displaced seaward from the beaufort shelf break upon exiting barrow canyon winds from the northeast promote separation of the acc from the southern flank of barrow canyon and establish an up canyon current along the southern flank that is fed in part by waters from the western beaufort shelf when winds are weak or from the southwest warm bering chukchi waters from barrow canyon intrude onto the western beaufort shelf

tides in the sea of okhotsk eight major tidal constituents in the sea of okhotsk have been investigated using a numerical solution of tidal equations on a 59 space grid the tides are dominated by the diurnal constituents diurnal tidal currents are enhanced in shelikhov bay and penzhinskaya guba at kashevarov bank in proximity to the kuril islands and at a few smaller locations the major energy sink for diurnal tides over 60 of the total energy is shelikhov bay and penzhinskaya guba the major portion of semidiurnal tide energy is dissipated in the northwestern region of the sea of okhotsk and in shelikhov bay and penzhinskaya guba nonlinear interactions of diurnal currents are investigated through k1 and o1 constituent behavior over kashevarov bank these interactions generate residual circulation of the order of 10 cm s 21 major oscillations at semidiurnal and fortnightly periods 13 66 days and higher harmonics of basic tidal periods the m2 tidal current caused by the nonlinear interaction of the diurnal constituents over kashevarov bank constitutes approximately a half of the total m2 tide current there the fortnightly current through nonlinear interactions also influences basic diurnal tidal currents by inducing fortnightly variations in the amplitude of these currents

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

strong vertical mixing in the urup strait 1 microstructure measurements were conducted in one of the kuril straits in the summer of 2007 over the course of 1 day of repeated observations across the pacific side of the steep sill of the urup strait extremely strong mixing was observed during periods of pacific ward down sill flows and during the transition from pacific ward to okhotsk ward up sill flows with a turbulent energy dissipation rate of 10 6 to 10 5 w kg 1 and vertical diffusivity of 10 1 to 5 10 1 m2 s 1 during the period of strong mixing we observed homogeneous layers with a thickness of 300 600 m and potential density of 26 6 26 7 occupying the entire water column in one case high values of within this layer indicate the injection of diapycnal flows from the upper and lower layers possibly contributing to southward intrusion of intermediate water into the subtropical gyre

flow of winter transformed pacific water into the western arctic abstract the dynamics of the flow of dense water through barrow canyon is investigated using data from a hydrographic survey in summer 2002 the focus is on the winter transformed bering water the highest volumetric mode of winter water in the chukchi sea which drains northward through the canyon in spring and summer the transport of this water mass during the time of the survey was 0 2 0 3 sv as the layer flowed from the head of the canyon to the mouth it sank decelerated and stretched strong cyclonic relative vorticity was generated on the seaward side of the jet which compensated for the stretching this adjustment was incomplete however in that it did not extend across the entire current possibly because of internal mixing due to shear instabilities the resulting vorticity structure of the flow at the canyon mouth was conducive for baroclinic instability and eddy formation multiple eddies of winter transformed bering water were observed along the chukchi beaufort shelfbreak those to the west of barrow canyon were in the process of being spawned by the eastward flowing shelfbreak current emanating from herald canyon while the single eddy observed to the east originated from the barrow canyon outflow it is argued that such an eddy formation is a major source of the ubiquitous cold core anti cyclones observed historically throughout the canada basin implications for the ventilation of the upper halocline of the western arctic are discussed

seasonal variation of upwelling in the alaskan beaufort sea impact of sea ice cover 1 data from a mooring array deployed from august 2002 to september 2004 are used to characterize differences in upwelling near the shelf break in the alaskan beaufort sea due to varying sea ice conditions the record is divided into three ice seasons open water partial ice and full ice the basic response is the same in each of the seasons roughly 8 h after the onset of easterly winds the shelf break jet reverses followed approximately 10 h later by upwelling of saltier water which is cold near the shelf break pacific winter water and warm at depth atlantic water the secondary circulation at the outer shelf is to first order consistent with a two dimensional ekman balance of offshore flow in the upper layer and onshore flow at depth there are however important seasonal differences in the upwelling overall the response is strongest in the partial ice season and weakest in the full ice season it is believed that these differences are dictated by the degree to which wind stress is transmitted through the pack ice as the strength of the wind forcing was comparable over the three seasons an eof based upwelling index is constructed using information about the primary flow secondary flow and hydrography the ability to predict upwelling using the wind record alone is explored which demonstrates that 90 of easterly wind events exceeding 9 5 m s 1 drive significant upwelling during certain periods the ice cover on the shelf became landfast which altered the upwelling and circulation patterns near the shelf break

pacific water transport in the western arctic ocean simulated by an eddy resolving coupled sea ice ocean model abstract the process of the pacific water transport in the chukchi sea and the southern canada basin is investigated by using an eddy resolving coupled sea ice ocean model the simulation result demonstrates that the pacific water flows into the basin by mesoscale baroclinic eddies which are generated and developed as a result of the instability of a narrow and intense jet through the barrow canyon each eddy has a baroclinic anticyclonic structure and its horizontal and vertical scales grow up by being merged with other ones during august and september they separate into anticyclones whose diameters are about 50 km in october and then they gradually shrink in early winter the pacific water transport across the beaufort shelf break reaches maximum about 0 3 sv where 1 sv 106 m3 s 1 during late summer and early autumn when the eddy activities are enhanced the sensitivity experiments indicate that the shelf to basin transport differs depending on the sea ice condition in the chukchi sea during su

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

dense water production on the northern okhotsk shelves comparison of ship based spring summer observations for 1996 and 1997 with satellite observations for the northern okhotsk sea polynyas five russian ctd surveys taken during 1995 to 1997 are used to examine the evolution of the polynya dense water the surveys show that consistent with other investigations the largest potential densities are 26 99 and the densest water occurs in sakhalin and shelikhov bays the surveys also suggest that the shelikhov water drains directly into the deep okhotsk while on the northern shelves gravity currents transport the dense water west to sakhalin bay for comparison determination of the polynya sizes and ice production from satellite passive microwave and meteorological observations shows that polynyas occur on the northwest shelf nws between ayan and okhotsk city on the northern shelf between okhotsk city and magadan and in shelikhov bay in contrast the observations show that sakhalin bay is a region of land fast ice with no polynyas so that the dense water observed here cannot form locally for all polynyas the satellite observations show that the nws contributes 60 to 70 of the total ice production and due to the warmer 1997 air temperatures the 1996 production is about 1 5 times the 1997 value an estimate of the ice production from the surveys shows a similar regional distribution and enhancement of the 1996 production with the satellite and ship estimates in agreement within their error bars finally analysis of the dense water outflow shows that the upper okhotsk sea mode water has a renewal time of about 4 years the lower part about 14 years

woce line p1w in the sea of okhotsk 2 cfcs and the formation rate of intermediate water from august 30 to september 21 1993 temperature salinity nutrient and cfc data were collected along a section starting in the pacific ocean near bussol strait in the kuril islands crossing the basin and shelf region of the sea of okhotsk and ending near the coastal town of okhotsk at the northwest corner of the sea of okhotsk world ocean circulation experiment woce line p1w water on the continental shelf had potential density as great as 27 0 with high cfc concentrations and low temperature and salinity the sea of okhotsk intermediate water soiw ranging from 26 8 to 27 4 had uniform water properties along isopycnal surfaces that were distinctly different from either the north pacific intermediate water npiw or the shelf water found at the same density since the soiw was colder and fresher than the npiw we postulate that soiw is formed by sinking plumes and diapycnal mixing shelf derived water sdw as dense as 27 0 is formed on the shelf during the winter by cooling and brine rejection during ice formation prevailing winds move the sdw off the shelf where it sinks to an equilibrium depth and subsequently mixes isopycnally with north pacific water npw flowing into the sea of okhotsk through the kuril islands the observations on the shelf suggest that sdw directly modifies soiw to 27 0 using potential temperature salinity s and cfc data we calibrated a simple box model to determine the input of sdw into the soiw model results required a minimum of 0 9 sv 1 sv 10 6 m 3 s 1 of sdw in the formation of soiw and produced a minimum export of 2 7 sv of soiw from the sea of okhotsk our minimum calculated export of soiw into the north pacific ocean makes the sea of okhotsk a significant source of the salinity minimum present in the npiw below 27 2 the box model failed because the cfc concentrations of the sdw were too high this suggests that sdw directly ventilates the soiw to a maximum of 27 2 the unique properties of the soiw below 27 2 must be the result of diapycnal mixing in the sea of okhotsk and isopycnal mixing with inflowing npw

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

winter currents and hydrographic conditions on the northern central bering sea shelf current observations obtained from the northern bering shelf region in winter 1984 1985 indicate that midwinter circulation patterns differed from those during the rest of the year annual mean circulation in this region is dominated by vigorous northward currents from 10 cm s in shpanberg strait to more than 50 cm s in bering strait these northward currents are accompanied by a weak northwestward coastal flow south of st lawrence island in february april 1985 however flow was weakly 0 5 cm s southward through shpanberg strait and southeastward south of st lawrence island while remaining northward through anadyr and bering straits comparison with current data obtained from previous years suggests that midwinter reversal of flow in shpanberg strait is a recurrent winter feature it generally occurs at about the same time that the winter ice cover undergoes its major advance and it is associated with strong northerly winds northward flow through anadyr strait persists conversely through the winter and is the northward extension of a western intensified northward flow over the bering shelf its source is bering sea water farther south rather than water from the northern central shelf the resultant trapping of shelf water on the northern central shelf coupled with intensive regional ice formation during the same period as the flow reversal led in 1985 to significant about 1 5 brine enrichment this salinity increase agrees qualitatively with historical data which suggest that the northern central bering shelf is the site both of sluggish winter circulation and of elevated salinities due to brine enrichment from ice formation

late oxfordian to late kimmeridgian carbonate deposits of nw switzerland swiss jura stratigraphical and palaeogeographical implications in the transition area between the paris basin and the tethys abstract geological sections of the shallow water carbonate dominated sedimentary system of the late jurassic reuchenette formation in northwestern switzerland have been studied between the southern jura mountains and the tabular jura the largest sections show a characteristic cyclic stacking pattern up to now the age of these sediments including the type section linking the boreal and tethyan realms was biostratigraphically poorly constrained in the tabular jura five 3rd order sequences can be assigned to the planula to eudoxus zone late oxfordian to late kimmeridgian using index fossils ammonites and ostracodes jank m 2004 new insights into the development of the late jurassic reuchenette formation of nw switzerland late oxfordian to late kimmeridgian jura mountains dissertationen aus dem geologisch palaontologischen institut der universitat basel 32 121 pp this time control and several new outcrops in combination with mineralostratigraphical and lithological marker beds allow the correlation and dating of the thickest sections of the reuchenette formation and thus serve to improve the previously estimated ages of their sequence boundaries the variability of stacking pattern and facies between sections also reveals distinctive changes in facies evolution related to late palaeozoic basement structures and synsedimentary subsidence these structures acted as important controlling factors for the sediment distribution of the reuchenette formation besides the sea level fluctuations the interplay of sea level changes and synsedimentary subsidence is outlined by lateral thickness variations and shifting depositional environments a close examination of these changes also sheds much light on the nature of platform topography in the transition area between the paris basin in the north and the tethys in the south or more generally between the boreal and tethyan realms during the planula to divisum time intervals the study area was a flat platform with a more or less uniform facies distribution which connected the above mentioned realms during the divisum to acanthicum time intervals this platform changed into a pronounced basin and swell morpoholgy with specific depositional environments and separated the paris basin from the tethys

the arctic circumpolar boundary current we present high resolution simulations and observational data as evidence of a fast current flowing along the shelf break of the siberian and alaskan shelves in the arctic ocean thus far the arctic circumpolar boundary current acbc has been seen as comprising two branches the fram strait and barents sea branches fsb and bsb respectively here we describe a new third branch the arctic shelf break branch asbb we show that the forcing mechanism for the asbb is a combination of buoyancy loss and non local wind creating high pressure upstream in the barents sea the potential vorticity influx through the st anna trough dictates the cyclonic direction of flow of the asbb which is the most energetic large scale circulation structure in the arctic ocean it plays a substantial role in transporting arctic halocline waters and exhibits a robust seasonal cycle with a summer minimum and winter maximum the simulations show the continuity of the fsb all the way around the arctic shelves and the uninterrupted asbb between the st anna trough and the western fram strait the bsb flows continuously along the siberian shelf as far as the chukchi plateau where it partly diverges from the continental slope into the ocean interior the alaskan shelf break current asc is the analog of the asbb in the canadian arctic the asc is forced by the local winds and high upstream pressure in bering strait caused by the drop in sea surface height between the pacific and arctic oceans

fine and microstructure observations in the urup strait kuril islands during august 2006 1 for the first time we performed continuous observations of turbulent mixing upon the sill of the urup strait kuril islands for a period of 1 day during august of 2006 time series of velocity profiles water properties and isopycnal depths show variability with a period of about 1 day however the water mass variability is not explained by simple water exchange between the sea of okhotsk and the north pacific empirical orthogonal function eof analysis of isopycnal coordinates extracted variability presumed to represent tidal flows as major eofs in profiles of the residual flow after subtracting the mean flow and major eofs we detected phase propagations consistent with internal gravity waves with an approximate period of 9 1 11 4 h the turbulent energy dissipation rate and vertical diffusivity k ranged from 1 10 9 to 3 10 8 w kg 1 and from 3 10 5 to 2 10 3 m2s 1 respectively occurrences of high dissipation rates generally corresponded to either strong shear or weak stratification a significant contribution of shear s to the dissipation rate was indicated with a relationship of s1 4 s1 8 probably related to propagating internal waves a strong mixing event was observed within the water column with extremely weak stratification and a richardson number below the critical value of 0 25 when the flow direction changed from up sill to down sill

numerical study on the impact of the 18 6 year period nodal tidal cycle on water masses in the subarctic north pacific 1 a series of numerical experiments is performed to test the hypothesis that temporal variations in localized strong tidal mixing related to the 18 6 year period nodal tidal cycle induce water mass variations it is suggested that enhanced mixing around the bering sea as that around the okhotsk sea have an impact on water masses broadly in the north pacific including the bering sea and the okhotsk sea oscillatory tidal mixing with a 18 6 year period reproduces water mass variations in salinity and isopycnal potential temperature around the subarctic north pacific that are qualitatively consistent with observed variations when the amplitude of oscillatory vertical diffusivity is 15 of the long term mean and even when the amplitude is as small as 3 cm2 s as obtained for a long term mean of 20 cm2 s the amplitude of the salinity variation near regions of strong mixing is smaller than but on the same order of magnitude as that observed the induced salinity anomaly spreads broadly over a distance of several hundreds of kilometers by mean currents with a short lag time of less than 3 years and is suggested to influence the model winter mixed layer over broad regions these results support the hypothesis stated above and suggest that it is necessary to clarify spatial and temporal variations in tidal mixing to reproduce both the mean states of and temporal variations in water masses of the subarctic north pacific

introduction to special section oceanography of the okhotsk sea 1 the okhotsk sea is a 1 5 10 km marginal sea adjacent to the pacific ocean in the northern hemisphere its defining boundaries are hokkaido japan sakhalin island the russian mainland the kamchatka peninsula and the kuril islands in the northern hemisphere the okhotsk is the southernmost sea with a sizable seasonal ice cover which experiences large interannual variations in extent because of the coupling of this ice cover with the okhotsk oceanography the ice can be considered as a sensitive indicator of climate change despite the recent realization of the importance of the okhotsk sea because of severe weather conditions and the presence of sea ice in situ observations have been limited especially in winter 2 part of the importance of the okhotsk is that the north pacific intermediate water npiw is believed to be ventilated in and around it both from hydrographic data talley 1991 and chlorofluorocarbons cfcs observations warner et al 1996 specifically the okhotsk is regarded as the only site where the atmosphere can directly exchange the heat and material including co2 with the npiw ventilation of this water is an important component of the global overturning circulation there are two ventilation sites for the intermediate water in the okhotsk sea the first is the northwest shelf which has large active coastal polynyas that are regarded as the primary area of dense shelf water dsw formation kitani 1973 wong et al 1998 martin et al 1998 gladyshev et al 2000 the second is the area in and around the straits in the kuril islands where strong tidal currents generate diapycnal mixing talley 1991 3 as part of a joint japanese russian u s study of the okhotsk four international joint cruises were carried out in the okhotsk during 1998 2001 on the r v professor khromov these were supported by u s national science foundation and the core research for evolutional science and technology of japan science and technology corporation the participants consisted of representatives from the russian far eastern regional hydrometeorological research institute the u s scripps institution of oceanography and the university of washington and the japanese hokkaido university and japan agency for marineearth science and technology jamstec previously japan marine science and technology center the main focus of the study was the ventilation of the npiw by the okhotsk sea this divides into three parts the northwest okhotsk shelf where brine rejection generates the dsw the east sakhalin current which is the western okhotsk boundary current and dsw pathway to the southern okhotsk mizuta et al 2003 and the bussol strait which is the main exchange between the okhotsk and the pacific and a site of diapycnal mixing 4 as the accompanying papers show the project was an interdisciplinary one consisting of studies of physical oceanography sea ice biogeochemistry paleo oceanography and atmospheric sciences the field methods consisted of hydrographical and chemical observations moorings bottom lander observations lagrangian float measurements lowered acoustic doppler current profiler adcp measurements and sediment corings at the ocean sciences meeting at honolulu in 2002 a meeting of the okhotsk participants showed that there were sufficient potential papers and new results to justify a journal of geophysical special section in this special section eight papers of the thirteen papers are based on the field results others are based on numerical and satellite studies 5 as the papers derived from these field experiments describe direct measurements on the northwest shelf of brine rejection and formation of dsw were carried out for the first time using bottom landers shcherbina et al 2003 2004a these landers directly observed the ventilation of the intermediate water and also suggest that baroclinic instabilities occur on the density front at the journal of geophysical research vol 109 c09s01 doi 10 1029 2004jc002604 2004

circulation and water mass transformation in a model of the chukchi sea 1 the circulation and water mass transformation in a regional ocean ice model of the chukchi sea are discussed the model has horizontal resolution of o 4 km is forced by fluxes derived from daily ncep reanalysis fields and has seasonally varying transport temperature and salinity imposed at bering strait many of the observed characteristics of the mean circulation and seasonal cycle in the chukchi sea are reproduced the discussion focuses on the branching of the inflow transport into pathways following herald canyon central channel and the alaskan coast the pattern of ice melt and the water mass transformation and formation of winter water and hypersaline water the ice melt pattern and timing is strongly influenced by advection through bering strait high frequency forcing results in a larger region of ice melt particularly over the shoals and in the northern chukchi sea compared to monthly mean forcing in the model the seasonal cycle of salinity in the southern and central chukchi sea is dominated by advection through bering strait while local atmospheric forcing and brine rejection are more important north of herald and hanna shoals and in barrow canyon however since the residence time in the chukchi sea is generally less than 1 year interannual variability in the bering strait salinity will be reflected in the salinity across the chukchi sea and at barrow canyon

observed increases in bering strait oceanic fluxes from the pacific to the arctic from 2001 to 2011 and their impacts on the arctic ocean water column 1 mooring data indicate the bering strait throughflow increases 50 from 2001 0 7 sv to 2011 1 1 sv driving heat and freshwater flux increases increase in the pacific arctic pressure head explains two thirds of the change the rest being attributable to weaker local winds the 2011 heat flux 5 1020j approaches the previous record high 2007 due to transport increases and warmer lower layer ll temperatures despite surface temperature sst cooling in the last decade warmer ll waters arrive earlier 1 6 1 1 days yr though winds and sst are typical for recent decades maximum summer salinities likely set in the bering sea remain remarkably constant 33 1 psu over the decade elucidating the stable salinity of the western arctic cold halocline despite this freshwater flux variability strongly driven by transport exceeds variability in other arctic freshwater sources remote data winds sst prove insufficient for quantifying variability indicating interannual change can still only be assessed by in situ year round measurements

circulation on the north central chukchi sea shelf abstract mooring and shipboard data collected between 1992 and 1995 delineate the circulation over the north central chukchi shelf previous studies indicated that pacific waters crossed the chukchi shelf through herald valley in the west and barrow canyon in the east we find a third branch through the central channel onto the outer shelf the central channel transport varies seasonally in phase with bering strait transport and is 0 2 sv on average although some of this might include water entrained from the outflow through herald valley a portion of the central channel outflow moves eastward and converges with the alaskan coastal current at the head of barrow canyon the remainder appears to continue northeastward over the central outer shelf toward the shelfbreak joined by outflow from herald valley the mean flow opposes the prevailing winds and is primarily forced by the sea level slope between the pacific and arctic oceans current variations are mainly wind forced but baroclinic forcing associated with upstream dense water formation in coastal polynyas might occasionally be important winter water mass modification depends crucially on the fall and winter winds which control seasonal ice development an extensive fall ice cover delays cooling limits new ice formation and results in little salinization in such years bering shelf waters cross the chukchi shelf with little modification in contrast extensive open water in fall leads to early and rapid cooling and if accompanied by vigorous ice production within coastal polynyas results in the production of high salinity 33 shelf waters such interannual variability likely affects slope processes and the transport of pacific waters into the arctic ocean interior

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

an exchange flow between the okhotsk sea and the north pacific driven by the east kamchatka current 1 a new mechanism for driving the water mass exchange between the okhotsk sea and the north pacific is presented this exchange flow originates from the east kamchatka current ekc a western boundary current of the subpolar gyre and occurs through the two deepest straits of the kuril island chain the kruzenshtern and bussol straits an inflow toward the okhotsk sea occurs at the northern kruzenshtern strait and an outflow toward the north pacific occurs at the southern bussol strait by using the kelvin s circulation theorem around the island between the two straits we show that the transport of the exchange flow entering the okhotsk sea is determined such that the frictional stresses around the island exerted by the bifurcated ekc integrate to zero this forcing mechanism is different from the dynamical framework of the widely used island rule both an analytical analysis and 1 5 layer model experiments demonstrate that the strait width lateral viscosity and island geometry are controlling parameters for the exchange flow transport because they affect the magnitude and length scales of the frictional stresses inertia of the ekc decreases the exchange flow by enhancing the frictional stress along the northern coast of the kuril island model experiments with realistic topography further reveal that while the steep continental slopes have minor impact on the exchange flow transport the subsurface peninsula located east of the kuril island works to decrease the exchange flow by altering the length scale of the frictional stresses and enabling the ekc to flow past the island

the 18 6 year period moon tidal cycle in pacific decadal oscillation reconstructed from tree rings in western north america 1 time series of pacific decadal oscillation pdo reconstructed from tree rings in western north america is found to have a statistically significant periodicity of 18 6 year period lunar nodal tidal cycle negative positive pdo tends to occur in the period of strong weak diurnal tide in the 3rd and 5th 10th 11th and 13rd year after the maximum diurnal tide mean pdo takes significant negative positive value suggesting that the aleutian low is weak strong western central north pacific in 30 50 n is warm cool and equator eastern rim of the pacific is cool warm this contributes to climate predictability with a time table from the astronomical tidal cycle

water exchange and tidal currents through the bussol strait revealed by direct current measurements 1 an outflow from the sea of okhotsk to the north pacific was measured at the bussol strait the largest strait connecting these basins from 31 august to 11 september 2001 yo yo casts of a lowered acoustic doppler current profiler were performed at 13 stations across the narrowest part of the strait time series covering more than approximately 24 hours were obtained for each station and the semidiurnal and diurnal tides were separated the diurnal tide at the spring tide shows a remarkable peak of the amplitude of 1 1 m s 1 at the depth below 1000 m in the western channel of the strait the upper part of the mean component flows toward the pacific and the lower part flows in the opposite direction the outflow is in excess of the inflow and net transport through the strait is 8 2 to 8 8 sv 1 sv 106 m3 s 1 the outflow is strong in two density ranges the upper layer peak around 26 8 corresponds to the density of north pacific intermediate water and the temperature salinity characteristics of this outflow were actually observed in this density range across downstream the oyashio off the southeastern coast of hokkaido net heat and salt exchanges between the sea of okhotsk and the north pacific are estimated net heat flux of 34 tw and net salt flux of 1 9 106 kg s 1 are exchanged from the sea of okhotsk to the north pacific

quantitative evaluation of iron transport processes in the sea of okhotsk abstract comprehensive observations of the iron fe distribution in the western sea of okhotsk were conducted and revealed the existence of two fe transport processes in the sub polar marginal sea one transport process is fe loading from the amur river and transport by the east sakhalin current esc and the other is fe transport by the intermediate water part of which was reported by nishioka et al 2007 here we report on quantitative evaluations of these two fe transport processes the surface dissolved fe diss fe and low salinity water distribution clearly indicate the influence of fe discharge from the amur river and the fe that is transported by the east sakhalin current the amounts of total dissolvable fe td fe and diss fe that cross the surface of the northeast sakhalin coastal area are estimated at 9 0 108 1 3 109 g yr 1 and 1 0 108 1 5 108 g yr 1 respectively although the esc surface transport system along the sakhalin coast is effective the length scale estimation of td fe transport indicated that only 1 5 of the fe at the mouth of the amur river reached 52 n which may be due to scavenging by biological particulates high fe anomalies were observed at the bottom of the continental shelf and the shelf break along the sakhalin coast the extremely low temperature and low n water indicate that fe resuspension due to the reducing properties of sediment occurred on the shelf and that the fe was introduced to dense shelf water dsw by tidal mixing we estimate that the amounts of td fe and diss fe involved in the dsw on the continental shelf are 8 8 1010 2 5 1011 g yr 1 and 2 3 109 6 6 109 g yr 1 respectively length scale estimates of td fe transport indicate that 20 of the td fe on the continental shelf remained in the kuril basin thus the td fe in the intermediate water was efficiently transported to the kuril basin these results indicate that two orders of magnitude more fe is derived from the continental shelf by the intermediate water than by surface water and that fe is transported a greater distance by intermediate water than by the surface layer additionally the fe that reached the kuril straits was mixed by intensive tidal mixing and influenced the vertical profiles of the water columns on both sides of the kuril straits in the kuril basin and the oyashio region our quantitative evaluation also indicates other fe inputs around the kuril strait

circulation of winter water on the chukchi shelf in early summer abstract using a variety of data sources we investigate the properties and pathways of pacific origin winter water as it spreads across the eastern chukchi shelf in early summer the focus is on the time period june july 2011 during which an extensive shipboard hydrographic velocity survey was undertaken as part of the impacts of climate on ecosystem and chemistry of the arctic pacific environment icescape program a revised circulation scheme is constructed revealing that the transport pathways on the chukchi shelf are more complex than previously thought notably the well known branch progressing northward from the central channel bifurcates as it reaches hanna shoal flowing around both sides of the shoal and dividing into smaller filaments that continue towards barrow canyon mass is conserved in the circulation scheme with approximately 1 sverdrup flowing poleward across the chukchi shelf within these pathways then exiting barrow canyon the salinity of the winter water varied on the shelf in 2011 with saltier water found in the upstream portion of what is defined as the central pathway using sea ice concentration data and atmospheric reanalysis fields we argue that salinization of the winter water in the central pathway occurred via brine rejection as the parcels progressed north and passed through the cape lisburne polynya this demonstrates that winter water pervading the interior shelf can be transformed by convective overturning north of bering strait presumably stirring up nutrients from the sediments and thereby influencing primary productivity in the region of hanna shoal

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

the chukchi slope current abstract using a collection of 46 shipboard hydrographic velocity transects occupied across the shelfbreak and slope of the chukchi sea between 2002 and 2014 we have quantified the existence of a current transporting pacific origin water westward over the upper continental slope it has been named the chukchi slope current which is believed to emanate from barrow canyon the current is surface intensified order 50 km wide and advects both summer and winter waters it is not trapped to a particular isobath but instead is reminiscent of a free jet there is no significant variation in pacific water transport with distance from barrow canyon a potential vorticity analysis suggests that the flow is baroclinically unstable consistent with the notion that it meanders the current is present during all synoptic wind conditions but increases in strength from summer to fall presumably due to the seasonal enhancement of the easterly winds in the region its transport increased over the 12 year period of data coverage also likely in response to wind forcing in the mean the slope current transports 0 50 0 07 sv of pacific water this estimate allows us to construct a balanced mass budget of the chukchi shelf inflows and outflows our study also confirms the existence of an eastward flowing chukchi shelfbreak jet transporting 0 10 0 03 sv of pacific water towards barrow canyon

the western arctic boundary current at 152 w structure variability and transport abstract from august 2002 to september 2004 a high resolution mooring array was maintained across the western arctic boundary current in the beaufort sea north of alaska the array consisted of profiling instrumentation providing a timeseries of vertical sections of the current here we present the first year velocity measurements with emphasis on the pacific water component of the current the mean flow is characterized as a bottom intensified jet of o 15 cm s 1 directed to the east trapped to the shelfbreak near 100 m depth its width scale is only 10 15 km seasonally the flow has distinct configurations during summer it becomes surface intensified as it advects buoyant alaskan coastal water in fall and winter the current often reverses flows westward under upwelling favorable winds between the storms as the eastward flow re establishes the current develops a deep extension to depths exceeding 700 m in spring the bottom trapped flow advects winter transformed pacific water emanating from the chukchi sea the year long mean volume transport of pacific water is 0 13 0 08 sv to the east which is less than 20 of the long term mean bering strait inflow this implies that most of the pacific water entering the arctic goes elsewhere contrary to expected dynamics and previous modeling results possible reasons for this are discussed the mean atlantic water transport to 800 m depth is 0 047 0 026 sv also smaller than anticipated

the role of sea ice and other fresh water in the arctic circulation salinity stratification is critical to the vertical circulation of the high latitude ocean we here examine the control of the vertical circulation in the northern seas and the potential for altering it by considering the budgets and storage of fresh water in the arctic ocean and in the convective regions to the south we find that the present day greenland and iceland seas and probably also the labrador sea are rather delicately poised with respect to their ability to sustain convection small variations in the fresh water supplied to the convective gyres from the arctic ocean via the east greenland current can alter or stop the convection in what may be a modern analog to the halocline catastrophes proposed for the distant past the north atlantic salinity anomaly of the 1960s and 1970s is a recent example it must have had its origin in an increased fresh water discharge from the arctic ocean similarly the freshening and cooling of the deep north atlantic in recent years is a likely manifestation of the increased transfer of fresh water from the arctic ocean into the convective gyres finally we note that because of the temperature dependence of compressibility a slight salinity stratification in the convective gyres is required to efficiently ventilate the deep ocean

phytoplankton blooms beneath the sea ice in the chukchi sea in the arctic ocean phytoplankton blooms on continental shelves are often limited by light availability and are therefore thought to be restricted to waters free of sea ice during july 2011 in the chukchi sea a large phytoplankton bloom was observed beneath fully consolidated pack ice and extended from the ice edge to 4100 km into the pack the bloom was composed primarily of diatoms with biomass reaching 1291 mg chlorophyll a m 2 and rates of carbon fixation as high as 3 7 g c m 2 d 1 although the sea ice where the bloom was observed was near 100 concentration and 0 8 1 2 m thick 30 40 of its surface was covered by melt ponds that transmitted 4 fold more light than adjacent areas of bare ice providing sufficient light for phytoplankton to bloom phytoplankton growth rates associated with the under ice bloom averaged 0 9 d 1

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

numerical study of k1 internal tides in the kuril straits 1 tide induced strong diapycnal mixing in the kuril straits is thought to be one of the essential processes controlling water mass formation in the north pacific in order to make a definite quantification of diapycnal diffusivity in the kuril straits we drive a three dimensional numerical model and examine the generation propagation and dissipation features of internal waves which play an essential role in transferring energy from the predominant k1 barotropic tide to diapycnal mixing processes it is shown that most of the internal wave energy subtracted from the k1 barotropic tide is dissipated within the kuril straits such that the local dissipation efficiency becomes 0 8 1 0 about three times the value previously employed this is because the k1 tidal frequency is subinertial in this area so that significant amount of k1 tidal energy is fed into coastal trapped waves ctws which stay around each island without propagating away from the straits ctws induce strong velocity shear near the ocean bottom causing bottom confined intense mixing with a vertical decay scale 200 m less than half the value previously employed although there remains some uncertainties resulting from the employed parameterizations of viscosity and diffusivity the average diapycnal diffusivity in the kuril straits becomes 25 10 4 m2 s 1 about three times the value previously estimated although it is still an order of magnitude less than assumed for the kuril straits in the existing ocean general circulation models

internal tides and turbulent mixing observed in the bussol strait abstract repeated observations with a period of about 24 h of hydrography current velocity and microstructures were performed at three stations surrounding a seamount in the middle of the bussol strait the deepest and widest one of the kuril straits to reveal spatial and temporal variability of internal tides and associated turbulent mixing it is found that isopycnal displacements are dominated by diurnal tidal components which show phase differences namely time lags between the three stations that can be explained by a first mode topographically trapped wave ttw propagating clockwise around the seamount furthermore at the station located near the center of the strait where energy dissipation rates are largest diurnal variations of isopycnals and velocities are amplified toward the ocean bottom consistent with the vertical structure of the first mode ttw at that station vigorous turbulent mixing with the energy dissipation rate exceeding 10 6 m 2 s 3 and diapycnal diffusivity exceeding 10 1 m 2 s 1 was observed in deep layers when the diurnal tidal current consisting of the first mode ttw flows from the okhotsk sea to the north pacific enhancing the mean current these spatial and temporal variation patterns are confirmed to be reproduced by a previous numerical model successfully for the isopycnals and velocities and partially for the turbulent mixing the total energy dissipation rate is however by up to a factor of 3 10 smaller than predicted by the numerical model although the observations were performed during spring tides suggesting that the actual diapycnal mixing is overall weaker than the previous model estimate and or that extremely strong mixing occurs within highly localized areas

barrow canyon volume heat and freshwater fluxes revealed by long term mooring observations between 2000 and 2008 1 barrow canyon in the northeast chukchi sea is a major conduit for pacific water to enter the interior arctic basins assemblies of annual september 2000 to august 2008 temperature salinity and velocity data acquired from a mooring array in the mouth of barrow canyon and high resolution hydrographic and velocity transects along the mooring array in 2002 2010 and 2011 have enabled a direct computation of volume heat and freshwater fluxes annual mean volume transport through barrow canyon was 0 45 sv which consisted of 0 44 sv of pacific water and 0 01 sv of atlantic water annual mean pacific water transport through barrow canyon represents 55 of the long term mean pacific water inflow through the bering strait during summer more of the pacific inflow was advected to an eastern path as the alaskan coastal current that flows along the alaskan coast to barrow canyon the freshwater flux through barrow canyon was 904 km3 yr which is equivalent to 5 of the freshwater content of the canada basin the annual averaged heat flux displayed substantial interannual variability ranging from 0 93 to 3 02 tw which could melt 88 000 290 000 km2 of 1 m thick ice a relationship exists between the measured barrow canyon transport and local winds such that under southerly winds the northward flow of water through the canyon increases such wind conditions are induced by the weaker sea level pressure contrast between the arctic and north pacific caused by a decrease in the pressure over the arctic and an increase over the north pacific

deep intense vertical mixing in the bussol strait 1 to reveal the intensity of deep mixing in the bussol strait we performed the direct observations of turbulence for the first time vigorous vertical mixing with a turbulent energy dissipation rate e above 10 6 w kg and diapycnal diffusivity k above 103 cm2 s were observed at depths of 600 1300 m potential densities of 27 0 27 5 at the western gap of the bussol strait possibly affecting water mass transformation and thermohaline circulation the strong vertical mixing with a diurnal period occurred when the diurnal tidal current flowed toward the okhotsk sea corresponding to a period of enhanced shear consisting of the mean flow with a two layered structure and the large amplitude diurnal tidal current with a vertical structure explained by a low vertical mode topographically trapped wave the empirical relationship ofe 10 1 46 1 91 s2 16 0 72 is obtained between e and the shear sreconstructed from the 50 m scale mean diurnal and semi diurnal tidal currents

evolution and dynamics of the flow through herald canyon in the western chukchi sea abstract the flow of summer and winter pacific water masses through herald canyon is investigated using data from a high resolution hydrographic velocity survey conducted in summer 2004 the survey was part of the russian american long term census of the arctic rusalca program and consisted of four cross canyon transects occupied over a 2 day period at the time of the survey dense winter water was entering the western side of the canyon from the chukchi sea flowing alongside a poleward jet of summer water on the canyon s eastern flank as the dense water progressed northward it switched sides of the canyon and underwent a sudden increase in layer thickness this coincided with vertical mixing near the interface of the winter and summer water producing a new water mass mode exiting the canyon all of these features are consistent with the notion of hydraulic activity occurring in the canyon a three layer hydraulic theory is applied to the flow which suggests that it is supercritical and that hydraulic control is likely a lock exchange formulation accurately predicts the northward transport of the winter water the origin of the winter water and the manner in which it drains into the canyon is investigated using satellite ice concentration data atmospheric re analysis fields historical in situ data and a simple circulation model finally the fate of the pacific water exiting the canyon and its connection to the chukchi shelfbreak current is discussed

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

wintertime variability of the beaufort gyre in the arctic ocean derived from cryosat 2 siral observations we processed the sea surface height measured by the sar synthetic aperture radar interferometric radar altimeter siral on board cryosat 2 cs 2 and successfully estimated the monthly dynamic ocean topography dot of the arctic ocean the cs 2 monthly dot showed the interannual and monthly variability of the beaufort gyre bg during winter between 2010 2011 and 2014 2015 the northward flow at the western edge of the bg was primarily estimated over the chukchi borderland cbl however the bg extended across the cbl and the northward flow was estimated over the mendeleev ridge in the winter of 2012 2013 our analyses revealed a significantly variable bg in response to changes in the sea surface stress field our analysis indicated that 1 sea ice motion driven by wind fields acts as a driving force for the bg when sea ice motion was intensified during winter and 2 sea ice motion can also act as an inhibiting force for the bg when sea ice motion is weakened during winter in addition the relationship between the dot steric height and ocean bottom pressure implied that the dot during winter responded to varying wind stresses through baroclinic and barotropic adjustments according to a tracer experiment we inferred that in the winter of 2012 2013 the pacific origin water carried into the bg through the barrow canyon was transported to the northern shelf and shelf break of the chukchi sea rather than the cbl which is where the pacific origin water had been transported in the other years of the observation period

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

two configurations of the western arctic shelfbreak current in summer abstractdata from a closely spaced array of moorings situated across the beaufort sea shelfbreak at 152 w are used to study the western arctic shelfbreak current with emphasis on its configuration during the summer season two dynamically distinct states of the current are revealed in the absence of wind with each lasting approximately one month the first is a surface intensified shelfbreak jet transporting warm and buoyant alaskan coastal water in late summer this is the eastward continuation of the alaskan coastal current it is both baroclinically and barotropically unstable and hence capable of forming the surface intensified warm core eddies observed in the southern beaufort sea the second configuration present during early summer is a bottom intensified shelfbreak current advecting weakly stratified chukchi summer water it is baroclinically unstable and likely forms the middepth warm core eddies present in the interior basin the mesoscale instabilities extract energy from the mean flow such

zooplankton inside an arctic ocean cold core eddy probable origin and fate abstract in september 2004 an extensive survey of a cold core eddy in the canada basin western arctic was carried out with high horizontal resolution physical and chemical sampling and lower horizontal resolution biological sampling the eddy was located over the continental slope north of the chukchi shelf and had a radius of 8 km its core was centered at a depth of 160 m water mass characteristics and the presence of copepods from the north pacific ocean neocalanus flemingeri and metridia pacifica demonstrated that the core contained water of pacific origin vertical distributions of zooplankton were associated with the physical structure of the water column for most taxa concentrations in the eddy core were elevated compared with those in similar density water in the surrounding basin based on tracer age estimates and previous observations of eddy formation the eddy is believed to have been formed during the previous spring summer from the chukchi shelfbreak jet surprisingly the eddy also contained elevated abundances of arctic origin copepods metridia longa and calanus glacialis analysis of a shelf basin transect occupied in the region in august 2004 showed that these species were present in high abundances in relatively shallow water 50 m inshore of the shelfbreak due to upwelling of deeper basin water and copepods onto the shelf in response to easterly winds if the formation of the observed eddy occurred during or shortly after a period of such winds upwelled arctic origin copepods on the shelf might have been entrained into the feature our observations suggest that formation and subsequent migration of such eddies may provide a mechanism for transporting zooplankton from the chukchi shelf into the interior canada basin the periodic input of high abundances of zooplankton from productive shelf areas could affect food webs in the less productive basin

near surface circulation and tidal currents of the okhotsk sea observed with satellite tracked drifters 1 near surface circulation of the okhotsk sea was observed with argos drifters from august 1999 to february 2000 the drifters clearly revealed the existence of the southward boundary current the east sakhalin current off the east sakhalin this current is strongly controlled by bottom topography and confined to the region shallower than 1000 m the volume transport of this current is estimated to be in the range of 4 9 sv 1 sv 106m3 s 1 with the increase from summer to winter the current appears to consist of two cores one exists near the coast 50 150 m depths with typical speeds of 0 3 0 4 m s 1 and the other exists over the shelf slope 300 900 m depths with typical speeds of 0 2 0 3 m s 1 a part of this southward current continues as far as the southern tip of sakhalin island while another part turns to the east around terpeniya bay 48 n flowing eastward as far as bussol strait most of the drifters that survived in the okhotsk sea went out to the pacific through bussol strait by less than a half year suggesting that bussol strait is the main pathway for the surface water to flow out from the okhotsk sea mesoscale anticyclonic eddies with diameters of 100 200 km are dominant in the kuril basin diurnal shelf waves were identified over the shelf in the northern part of the east sakhalin shelf large amplification of diurnal tidal currents order of 1 0 m s 1 was observed over kashevarov bank along with the residual anticyclonic circulation both diurnal and semidiurnal tidal currents were found to be enhanced in and around bussol strait

circulation of summer pacific halocline water in the arctic ocean 1 we present an analysis of arctic ocean hydrographic and sea ice observations from the 1990s with a focus on the circulation of water that originates in the north pacific ocean previous studies have shown the presence of two varieties of relatively warm summer halocline water in the vicinity of the chukchi sea i e the relatively fresh alaskan coastal water acw and the relatively saltier summer bering sea water sbsw here we extend these studies by tracing the circulation of these waters downstream into the arctic ocean we find that acw is generally most evident in the southern beaufort gyre while sbsw is strongest in the northern portion of the beaufort gyre and along the transpolar drift stream we find that this separation is most extreme during the early mid 1990s when the arctic oscillation was at historically high index values this leads us to speculate that the outflow to the north atlantic ocean through the canadian archipelago and fram strait may be similarly separated as arctic oscillation index values fell during the later 1990s acw and sbsw began to overlap in their regions of influence these changes are evident in the area north of ellesmere island where the influence of sbsw is highly correlated with a 3 year lag with the arctic oscillation index we also note the presence of winter bering sea water wbsw which underlies the summer varieties all together this brings the number of distinct pacific water types in our arctic ocean inventory to three acw sbsw and wbsw

mechanisms of pacific summer water variability in the arctic s central canada basin pacific water flows northward through bering strait and penetrates the arctic ocean halocline throughout the canadian basin sector of the arctic in summer pacific summer water psw is modified by surface buoyancy fluxes and mixing as it crosses the shallow chukchi sea before entering the deep ocean measurements from ice tethered profilers moorings and hydrographic surveys between 2003 and 2013 reveal spatial and temporal variability in the psw component of the halocline in the central canada basin with increasing trends in integrated heat and freshwater content a consequence of psw layer thickening as well as layer freshening and warming it is shown here how properties in the chukchi sea in summer control the temperature salinity properties of psw in the interior by subduction at isopycnals that outcrop in the chukchi sea results of an ocean model forced by idealized winds provide support to the mechanism of surface ocean ekman transport convergence maintaining psw ventilation of the halocline

distribution formation and seasonal variability of okhotsk sea mode water 1 russian historical data and recently completed conductivity temperature depth surveys are used to examine the formation and spread in the deep ohkotsk sea of dense shelf water dsw produced in the okhotsk sea polynyas isopycnal analysis indicates that all of the main polynyas contribute to the ventilation at 27 1 vigorous tidal mixing leads to outflow of water with a density of only about 26 7 in the western okhotsk sea the east sakhalin current rapidly transports modified dense shelf water along the eastern sakhalin slope to the kuril basin where it is subject to further mixing because of the large anticyclonic eddies and tides most of the dense water flows off the shelves in spring their average flux does not exceed 0 2 sv in summer and fall the shelf water transport and water exchange with the north pacific cause large seasonal variations of temperature at densities of 26 7 27 0 depths of 150 500 m in the kuril basin where the average temperature minimum occurs in april may and the average temperature maximum occurs in september with a range of 0 2 0 7 c the average seasonal variations of salinity are quite small and do not exceed 0 05 psu the soya water mixed by winter convection penetrating to depths greater than 200 m in the southern kuril basin also produces freezing water with density greater than 26 7 using a simple isopycnal box model and seasonal observations the osmw production rate is seen to increase in summer up to 2 2 1 7 sv mainly because of increased north pacific inflow and drops in winter to 0 2 0 1 sv a compensating decrease in temperature in the kuril basin implies a dsw volume transport of 1 4 1 1 sv from february through may the residence time of the osmw in the kuril basin is 2 1 7 years

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

circulation dense water formation and outflow on the northeast chukchi shelf we investigated circulation and water mass modification processes in the chukchi sea using 1 temperature salinity and velocity data collected between september 1991 and september 1992 from moorings in bering strait and the northeast shelf and 2 meteorological data and ice concentrations derived from special sensor microwave imager ssm i imagery in october 1991 and from february to august 1992 the mean monthly circulation was steady and northward from november to january strong northeast winds diverted the low salinity bering inflow onto the western shelf and weakened and reversed flow over the northeast shelf the winds also opened extensive polynyas wherein cold hypersaline salinity 34 waters formed the fall winter circulation enhanced dense water formation by diverting low salinity waters away from and prolonging the residence time of water within the polynyas alongshore convergence of the coastal flow swept some of the cold hypersaline water offshore across isobaths but the coastal current carried most of it into the arctic ocean through barrow canyon the dense outflow mixed little during its descent through the upper canyon where bottom friction and rotation but not entrainment were important in the plume momentum balance if the outflow is not diluted by mixing in the lower canyon where theory suggests this will occur then the densest shelf waters can ventilate layers deeper than the halocline salt rejection estimates using ssm i data and surface heat budget calculations agree within a factor of 2 with independent estimates from the mooring hence remote sensing techniques can monitor winter salt rejection rates in the chukchi sea

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

mechanisms of summertime upper arctic ocean warming and the effect on sea ice melt 1 in this study we use a numerical sea ice ocean model to examine what causes summertime upper ocean warming and sea ice melt during the 21st century in the arctic ocean our first question is what causes the ocean to warm in the pacific sector during the summer we find that about 80 of total heating over this region comes from ocean surface heat flux with the remaining 20 originating in ocean lateral heat flux convergence the latter occurs mostly within a few hundred kilometers of the northwest alaskan coast in the summer of 2007 the ocean gained just over twice the amount of heat it did over the average of the previous 7 years our second question is what causes sea ice to melt in the pacific sector during summer our analysis shows that top melt dominates total melt early in the summer while bottom melt and in particular bottom melt due to ocean heat transport dominates later in the summer as atmospheric heating declines bottom melt rates in summer 2007 were 34 higher relative to the previous 7 year average the modeled partition of top versus bottom melt closely matches observed melt rates obtained by a drifting buoy bottom melting contributes about 2 3 of total volume melt but is geographically confined to the marginal ice zone while top melting contributes a lesser 1 3 of volume melt but occurs over a much broader area of the ice pack

seasonal variation in the in and outflow of the okhotsk sea with the north pacific abstract this paper examines the seasonal variation in the in and outflow of the okhotsk sea with the pacific mainly based on profiling float and satellite altimeter data the motions of the floats at depths of 500 750 m show that the waters of the okhotsk tend to flow out to the pacific through the southern kuril straits mostly bussol strait in winter seasons november march based on data from the floats exiting the sea the mean residence time of the intermediate water in the kuril basin is estimated as about one year isopycnal analysis from the profiling data shows that in the mid eastern area of the okhotsk sea potential temperature of the intermediate water with 26 6 27 2 increases by 0 2 0 5 c in every spring suggesting the inflow from the pacific in the preceding season these suggest that the in and outflow predominantly occurs during winter with the inflow at the northern straits and outflow at the southern straits the surface current field inferred from satellite altimeter data also shows that the inflow to the sea of okhotsk through the northern straits is strengthened in winter linked with strengthening of the east kamchatka current ekc from yearly anomalies of the altimeter data the winter inflow to the okhotsk through the northern straits is significantly correlated with the ekc and sverdrup transport over the north pacific further interannual variations in property of okhotsk sea intermediate water appear to be related with the ekc and wind stress over the north pacific in winter possibly through the change in inflowing pacific water transport these suggest that the seasonal and interannual variations of the in and outflow are to some extent controlled by the large scale wind stress over the north pacific being consistent with island rule qualitatively