modeling of deep water renewal through cold convective plumes abstract in only a few regions in the world ocean surface water is transformed into deep water by open ocean convection in this paper small areas of vertical flow or plumes are studied using a steady state model integrated in streamline coordinates we use an entrainment hypothesis based on knowledge about in mixing of water across the shear zone from an area of low turbulence into an area of high turbulence this results in a model using conservation equations for momentum heat and salt and a nonlinear equation of state effects of earth rotation are included the depth reached by surface water when moving through stationary plumes is predicted and found strongly dependent on the properties in the surface layer this layer has to be colder but only slightly denser than the water just below it to be a source for steady state plumes the thermobaric effect the dependency of compressibility on the temperature plays a major role for the plume penetration depth in weakly stratified cold water like in the greenland sea deep convection is found to be possible and efficient through steady state plumes initial excess density of less than 5 10 3 kg m 3 caused by low temperature can give convection deeper than 1500 m through plumes with horizontal scales of a few hundred meters and vertical velocities of order a few tens of centimeters per second

large scale spreading of deep waters in the western mediterranean sea by submesoscale coherent eddies abstract two large scale free drifting isobaric floats experiments sofargos marine science and technology programme phase 2 mast2 and mass transfer and ecosystem response mater mast3 undertaken in 1994 95 in the northwestern mediterranean sea and in 1997 98 in the algerian basin respectively have revealed for the first time that western mediterranean deep water newly formed by deep convection in the gulf of lion the so called medoc site can be advected several hundreds of kilometers away from the formation area by anticyclonic submesoscale coherent vortices scvs this behavior implies that scvs participate actively in the large scale thermohaline circulation and deep ventilation of the western mediterranean sea these scvs are characterized by small radius 5 km very low potential vorticity high aspect ratio 0 1 and extended lifetime 0 5 yr

near surface dynamical structure of the kuroshio extension 1 lagrangian data from 657 svp drifters cnes aviso archiving validation and interpretation of satellite oceanographic data time variable satellite altimeter sea level anomaly and levitus 98 hydrographic data are used to develop 0 25 spatial resolution maps of the mean and eddy circulations in the northwestern pacific during the 1990s drifter velocities at 15 m depth and 200 m temperature data clearly indicate in the kuroshio extension ke jet two prominent meanders that culminate in a 300 km northward deflection east of the shatsky rise at 160 e the interannual trends of aviso mesoscale variance are absent along the path of the meandering ke jet three anticyclonic recirculations can be identified south or southeast of the kuroshio the southernmost around daito island being a new discovery about 3 of the drifters with drogues attached crossed the kuroshio front the aviso currents are correlated at 0 8 with drifter geostrophic velocity the aviso geostrophic currents are adjusted in amplitude to the contemporaneous drifter observations and are further used to compute an unbiased mean geostrophic circulation and the quasi geostrophic reynolds stresses in the ke region the principal axes of the eddy reynolds stresses are oriented along the unbiased mean velocity vectors within the meandering ke jet the time mean horizontal momentum balance that includes both the mean and eddy momentum convergences is used to compute absolute sea level map and its uncertainty at 145 e the 2000 m depth absolute dynamic height referenced to the sea level reveals a heretofore unknown 70 dynamic cm drop from 25 to 42 n

partitioning of kinetic energy in the arctic ocean s beaufort gyre kinetic energy ke in the arctic ocean s beaufort gyre is dominated by the mesoscale eddy field that plays a central role in the transport of freshwater heat and biogeochemical tracers understanding beaufort gyre ke variability sheds light on how this freshwater reservoir responds to wind forcing and sea ice and ocean changes the evolution and fate of mesoscale eddies relate to energy pathways in the ocean e g the exchange of energy between barotropic and baroclinic modes mooring measurements of horizontal velocities in the beaufort gyre are analyzed to partition ke into barotropic and baroclinic modes and explore their evolution we find that a significant fraction of water column ke is in the barotropic and the first two baroclinic modes we explain this energy partitioning by quantifying the energy transfer coefficients between the vertical modes using the quasi geostrophic potential vorticity conservation equations with a specific background stratification observed in the beaufort gyre we find that the quasi geostrophic vertical mode interactions uphold the persistence of ke in the first two baroclinic modes consistent with observations our results explain the specific role of halocline structure on ke evolution in the gyre and suggest depressed transfer to the barotropic mode this limits the capacity for frictional dissipation at the sea floor and suggests that energy dissipation via sea ice ocean drag may be prominent

patterns of recent sea level rise in the east japan sea from satellite altimetry and in situ data 1 patterns of recent sea level rise in the east japan sea ejs are investigated through the analyses of topex poseidon t p sea level anomalies thermosteric sea level tsl and long term tide gauge data the 9 year long t p analyses reveal average trends of 5 4 0 3 mm yr 1 for all of ejs and 6 6 0 4 mm yr 1 for the southern ejs these are much larger than the global rates of 3 1 0 4 mm yr 1 reported by cabanes et al 2001 and 2 8 0 4 mm yr 1 by cazenave and nerem 2004 this t p rate compares relatively well with those from tsl data and tidal sea level gauges indicating that sea level rise in the ejs is mainly due to thermal expansion the southern ejs shows a nonuniform sea level trend pattern with the western part of the ulleung and yamato basins having values of 10 mm yr 1 and larger this nonuniform pattern is discussed in terms of variable thermal expansions arising from a recent decadal trend in the temperature anomaly in the upper layer of the two basins the 40 year long tsl time series also reveals a decadal oscillation in the ulleung and yamato basins that can be explained by interannual to decadal variations in temperature in the upper ocean layers with weaker anomalies at most of the other ejs locations it is hypothesized that the long term oscillation in the southern ejs may be related to the decadal variability of heat content anomaly in the upper 300 m of the pacific ocean as reported by levitus et al 2000 and to the north south migration of the warm tsushima current and eddies in the southern ejs

a heton model of the spreading phase of open ocean deep convection abstract a point vortex heton model of the lateral dispersion of cold water formed in open ocean deep convection is developed and studied as an idealized representation of the sinking and spreading phase of open ocean deep convection the overturning and geostrophic adjustment of dense fluid on and below the radius of deformation scale formed by cooling on the large scale are parameterized in the model by introducing paired discrete point vortices hetons of cyclonic sense in the surface layer anticyclonic below driving a cold baroclinic vortex the convection site is imagined to be made up of many such baroclinic vortices each with a vertically homogeneous core carrying cold convectively tainted waters the point vortices are introduced at a rate that depends on the large scale cooling and the intensity assumed for each vortex the interaction of many cold baroclinic vortices making up a cloud is studied using point vortex green s function techniques the current solenoids of the individual ele

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

a numerical study of local convection in the benthic ocean induced by episodic hydrothermal discharges a nonhydrostatic primitive equation model is used to investigate motions and water column property distributions accompanying the rise of hot hydrothermal fluids into a rotating water column stratified in temperature and salinity after preliminary model experiments used to fix the level of turbulent mixing the model is applied to a megaplume event the release of a large amount of hydrothermal heat into the benthic ocean over a period of several days events of this kind have produced water masses with anomalous temperature and salinity distributions 20 km in diameter 800 m thick centered vertically 700 1000 m off the seafloor the model allows the study of the initial time development and maturation of the plume from such an event preliminary experiments demonstrate the sensitivity of plume rise to the level of turbulent mixing and to the ratio of turbulence viscosity to turbulence diffusivity i e prandtl number rise to maximum plume height occurs in 4 6 n 1 where n is buoyancy frequency consequences of a megaplume sized release of heat are examined over an initial 30 day period vertical circulation accompanying a hydrothermal event leads to a slight negative salinity anomaly below the plume s temperature anomaly core the plume s heat potential temperature anomaly is shown to be a composite of hydrothermal heat and ambient heat that has been redistributed by the same vertical circulation cell horizontal circulation is dominated by an anticyclonic flow vortex centered just above the temperature anomaly maximum at 800 m above bottom and a cyclonic flow vortex at the seafloor azimuthal flow accounts for the largest fraction of kinetic energy within 4 5 hours 1 7 1 after the start of heat release azimuthal velocities reach maximum values of 70 cm s 1 90 of which is attained within the initial 10 hours even as much as 4 weeks past cessation of heat release maximum azimuthal velocities are of the order of 10 cm s 1 the balance of vertical forces is hydrostatic by 12 hours save for near bottom frictional effects during plume formation the radial force balance is primarily cyclostrophic near axis and geostrophic at a distance

a heton perspective of baroclinic eddy transfer in localized open ocean convection a simple point vortex heton model is used to study localized ocean convection in particular the statistically steady state that is established when lateral buoyancy transfer effected by baroclinic instability offsets the localized surface buoyancy loss is investigated properties of the steady state such as the statistically steady density anomaly of the convection region are predicted using the hypothesis of a balance between baroclinic eddy transfer and the localized surface buoyancy loss these predictions compare favorably with the values obtained through numerical integration of the heton model the steady state of the heron model can be related to that in other convection scenarios considered in several recent studies by means of a generalized description of the localized convection this leads to predictions of the equilibrium density anomalies in these scenarios which concur with those obtained by other authors advantages of the heton model include its inviscid nature emphasizing the independence of the fluxes affected by the baroclinic eddies from molecular processes and its extreme economy allowing a very large parameter space to be covered this economy allows us to examine more complicated forcing scenarios for example forcing regions of varying shape by increasing the ellipticity of the forcing region the instability is modified by the shape and as a result no increase in lateral fluxes occurs despite the increased perimeter length the parameterization of convective mixing by a redistribution of potential vorticity implicit in the heton model is corroborated the heton model equilibrium state has analogous quantitative scaling behavior to that in models or laboratory experiments that resolve the vertical motions the simplified dynamics of the heton model therefore allows the adiabatic advection resulting from baroclinic instability to be examined in isolation from vertical mixing and diffusive processes these results demonstrate the importance of baroclinic instability in controlling the properties of a water mass generated by localized ocean convection a complete parameterization of this process must therefore account for the fluxes induced by horizontal variations in surface buoyancy loss and affected by baroclinic instability

tsushima warm current paths in the southwestern part of the japan sea abstract we compiled a long term record of monthly mean sea surface currents in the japan sea from satellite altimetry and satellite tracked drifter data the record covers the entire japan sea for the period from may 1995 through january 2009 using these data we examined the path of the tsushima warm current in the southwestern part of the japan sea the mean sea surface current field revealed a triple branch pattern the first branch through the eastern channel of the tsushima strait flows along the coast of japan with a mean current velocity of 20 cm s 1 the second branch flows along the continental shelf edge at around the 200 m isobath with a mean current velocity of 12 cm s 1 the third branch flows along the east coast of the korean peninsula with a mean current velocity of 25 cm s 1 we investigated seasonal variation in the path of each branch the first branch flowing along the japanese coast throughout the year is highly stable the second branch is stable throughout the year except in november the third branch flowing along the east coast of korea is highly stable until 38 n downstream of the third branch around 38 n the current bifurcates into northeastward and southeastward currents the northeastward current exhibits stable flow from june to february except in january this current joins an eastward current originating around 39 n 128 5 e the southeastward current flows stably in june september and december there were two current paths east of 131 e over the continental shelf off the san in coast of japan the nearshore current flows along the japanese coast with a mean current velocity of 23 cm s 1 and the offshore current flows around the continental shelf area with a mean current velocity of 19 cm s 1 these two currents are highly stable throughout the year a current flows to the west of oki island to around 38 5 n and is highly stable in all months except march to july these results provide a schematic view of the paths of the tsushima warm current in the southwestern part of the japan sea

submesoscale sea ice ocean interactions in marginal ice zones signatures of ocean eddies fronts and filaments are commonly observed within marginal ice zones mizs from satellite images of sea ice concentration and in situ observations via ice tethered profilers or underice gliders however localized and intermittent sea ice heating and advection by ocean eddies are currently not accounted for in climate models and may contribute to their biases and errors in sea ice forecasts here we explore mechanical sea ice interactions with underlying submesoscale ocean turbulence we demonstrate that the release of potential energy stored in meltwater fronts can lead to energetic submesoscale motions along mizs with spatial scales o 10 km and rossby numbers o 1 in low wind conditions cyclonic eddies and filaments efficiently trap the sea ice and advect it over warmer surface ocean waters where it can effectively melt the horizontal eddy diffusivity of sea ice mass and heat across the miz can reach o 200 m 2 s 1 submesoscale ocean variability also induces large vertical velocities order 10 m d 1 that can bring relatively warm subsurface waters into the mixed layer the ocean sea ice heat fluxes are localized over cyclonic eddies and filaments reaching about 100 w m 2 we speculate that these submesoscale driven intermittent fluxes of heat and sea ice can contribute to the seasonal evolution of mizs with the continuing global warming and sea ice thickness reduction in the arctic ocean submesoscale sea ice ocean processes are expected to become increasingly prominent

the effect of hammer mass and velocity on flake mass abstract this paper presents the results of controlled fracture experiments designed to investigate the effects on flake mass of varying the mass and velocity of the hammer it was found that the contribution of these two independent variables are almost negligible for a given combination of exterior platform angle and platform thickness though they must be sufficient to initiate production of a flake of a given potential mass

thermocline circulation and ventilation of the east japan sea part i water mass characteristics and transports abstract the east japan sea ejs has unique water mass characteristics in the western pacific marginal seas due to limited exchange with the open north pacific the major inflow of source water mass is north pacific subtropical water npsw carried by the kuroshio branching and tsushima current the locally formed cold fresh waters from the tatar strait and russia coast by winter convection mix with npsw contributing to water mass transformation especially during winter when upper isopycnal surfaces outcrop and thermocline is ventilated the geographic limit of the korea tsushima strait kts with a sill depth of about 120 140 dbar confines the inflow of lower npsw and so the ejs thermocline layer is somewhat truncated with a rather thin layer for about 100 dbar this study uses high resolution conductivity temperature depth ctd and argo data with a third decimal or higher accuracy for temperature and salinity obtained mainly by research institute of oceanography seoul national university through domestic and international collaboration with several korean ocean research institutes and russia and usa partners since early 1990s the basin covered data were divided into summer and winter half year representing seasonal difference since most ctd surveys were conducted purposely in summer and winter analysis is made for the upper layer about 50 70 dbar from the surface to the upper main thermocline and the thermocline layer down to about 150 180 dbar south of the subpolar front spf the lower thermocline is defined slightly below the sill depth of the kts considering the deepening of npsw after passing through the kts the thermocline layer is encompassed by three selected neutral density surfaces n 25 8 26 4 and 27 0 with a distance of about 40 dbar between two neighboring surfaces the core of thermocline is followed by the n 25 8 surface characterized by a salinity maximum and a minimum of potential vorticity winter convection is discussed and compared with three other major convection sites of the world s oceans the gulf of lions labrador sea and greenland sea showing some common and distinctive features especially the extremely low salinity of the ejs water mass properties on neutral density surfaces are analyzed with the water mass turner angle wtu and circulation and transport are deducted from geostrophic calculations from the 15 year mean hydrography a basin wide net annual mean transport of about 2 10 0 29 sv 1 sv 106 m3 s 1 is estimated with summer and winter transports of 2 56 0 36 and 1 63 0 23 sv respectively this transport is slightly less than the annual mean transport of the tsushima current at the kts 2 4 sv from cable and 2 3 sv from other direct current meter and geostrophic methods but matches the 14 error bar of 0 29 sv adjusted by 150 dbar from the reference level of 800 dbar this error bar is close to the error of 0 34 sv determined from water mass conservation residual in a separated study three mechanisms are discovered to explain the seasonal difference in the tsushima current transports the stronger winter ekman pumping outcropping and southward crossing flow during winter the tsushima current branches are imposed under strong wind stress curl in the ulleung basin and yamato basin showing a doubling ekman downwelling transport partly weakening the tsushima current flow in the eastern boundary meanwhile the thermocline isopycnal surfaces outcrop in winter reducing volume transport due to reduced space and thickness the southward currents in the southern ulleung basin and yamato basin are perpendicular to the tsushima current branches west of japan which weakens the eastern boundary current in winter

comparisons between observations and numerical simulations of japan east sea flow and mass fields in 1999 through 2001 abstract the princeton ocean model pom as implemented for the japan east sea jes with mesoscale admitting resolution is driven by seasonal throughflow and synoptic atmospheric forcing for 1999 through 2001 temperature and salinity profiles from shipborne and palace float ctds and horizontal velocities at 800 m from palace float trajectories plus horizontal velocities at 15 m from woce surface drifters for 1988 through 2001 are used to assess the performance of the numerical simulations for a base case general agreement exists in the circulation at 15 and 800 m and the horizontal and vertical structure of the upper ocean temperature and salinity fields the mean observed flow at 15 m defines the two branches of the tsushima warm current and hints at the existence of a large cyclonic gyre over the japan basin which the simulations also produce the mean observed flow at 800 m defines a large cyclonic recirculation gyre over the japan basin that validates the simulated flow pattern variances of the observed and simulated flows at 15 and 800 m have similar patterns the main discrepancies are associated with the strength of the seasonal thermocline and halocline and the location of the subpolar front when smoother topography and smaller lateral friction are used in other cases the thermocline and halocline strengthen agreeing better with the observed values and when 80 of total outflow transport is forced to exit through soya strait the subpolar front extends along the coast to the north of tsugaru strait which is an observed feature absent in the base case

connections between surface fluxes and the deep circulation in the sea of japan 1 the extent to which seasonably variable surface fluxes and bottom friction can exert a control on the abyssal circulation above localized bottom topography is analyzed in the japan sea region through the use of a three dimensional eddy resolving ocean model our simulations show that the bottom friction exerts a first order control on the magnitude of the eddy driven deep circulation over f h geostrophic contours which is inversely dependent on the bottom drag in accordance with theory seasonal surface flux variability acts as a modifier to this theory depending on the timescale of active forcing relative to bottom friction spin down time possible physical mechanisms for a varying bottom drag coefficient are proposed winter ventilation of isopycnals during deep convection is followed by enhanced drain energy to small scale turbulence and strong energy dissipation in intermediate layers leading to a weakening of deep circulation that contradicts the classic ventilation theory

statistical parameterization of heterogeneous oceanic convection abstract a statistical convective adjustment scheme is proposed that attempts to account for the effects of mesoscale and submesoscale variability of temperature and salinity typically observed in the oceanic convective regions temperature and salinity in each model grid box are defined in terms of their mean variance and mutual correlations subgrid scale instabilities lead to partial mixing between different layers in the water column this allows for a smooth transition between the only two states convection on and convection off allowed in standard convective adjustment schemes the advantage of the statistical parameterization is that possible instabilities associated with the sharp transition between the two states which are known to occasionally affect the large scale model solution are eliminated the procedure also predicts the generation of correlations between temperature and salinity and the presence of convectively induced upgradient fluxes that have been obtained in numerical simulati

the three dimensional circulation near the eastern north pacific subtropical front abstract the purpose of our study is to describe and compute the large scale three dimensional circulation near the subtropical front in the eastern north pacific along 31 n this was accomplished through the use of four extensive hydrographic surveys historical wind stress data and also the movement of surface drifters our results indicate that in wintertime surface water sinks on the north side of the front and rises on its south side during the summer however the subtropical salty surface water overflows the frontal area to the north potential vorticity and heat are best conserved in a vertical flow pattern where the annual mean ekman convergence sinks to a depth of 300 m and water upwells throughout the main thermocline the computed horizontal flow below 700 m amounts to less than 0 6 cm s 1 both strength and direction depend greatly on the treatment of noise within the data set and also on the conservation statement that is specified in addition to geostrophic and hydrostatic dynamics a q

the energetic surface circulation patterns of the japan east sea abstract in the period of 1988 2001 226 argos fixed drifters were deployed in the japan east sea jes from these and the historical file of temperature at a depth of 100 m 15 m depth circulation and its variances in relationship to the seasonal mean warm and cold water regions were constructed on 0 5 resolutions the strongest seasonal currents were the east korean warm current ekwc the tsushima current tc the north korean cold current nkcc and local eastwards intensifications along the sub polar frontal patterns the tc and nkcc were observed during summer and drifters passed through the soya strait only in summer the sub polar front occurred along 40 n in the northeastern jes a separate front occurred in winter that was associated with the flow of warm water restricted to the southern jes small eddy energy was found in the cold water regime and large eddy energy in the warm water regime satellite altimeter and drifter tracks were used to mark the wonsan eddy found in the east korean bay a yearly late summer occurrence mechanical energy flux from the mean circulation to mesoscale eddies occurred in ekwc tc and the sub polar front in the eastern jes with eddy kinetic energy doubling time of 15 60 days the yearly mean circulation east of the korean coast is organized into a broad eddy filled east sea current that contains weak anticyclonic gyres in the ulleung and yamato basins it accelerates toward the yamato rise and against the eastern coast of the jes the published numerical model solutions show several historical circulation features but fail to capture many of the new structures described by the drifter data

a three dimensional numerical model of deep ventilation in temperate lakes because of the variation in the temperature of maximum density with depth it is known that the upper above 250 m and lower water columns circulate separately in deep temperate lakes while near surface water overturns twice per year the deep waters often mix only partially during a complete annual cycle it is believed that deep convection is triggered by storm surge forcing of some of the relatively cold upper water column downward through its compensation depth so that it becomes unstable and sinks the scale and intensity of the resulting deep water forming plumes are studied numerically a high resolution model based on the nonhydrostatic boussinesq equations is used deep water formation is initiated by applying a statically unstable initial temperature profile over various regions of the domain at depths below 300 m the grid spacing is small enough to resolve individual plumes which carry surface water to the lake bottom the domain of study is also large enough that the geostrophic eady 1949 wave breakup of newly formed deep water can be observed it is found that when the initial instability is applied in midbasin remote from the solid sidewalls relatively little fresh deep water is formed and the fluid quickly reaches a geostrophic and hydrostatic balance vigorous vertical mixing ceases after 4 days and the resulting baroclinic fluid has a well defined and predictable scale in contrast when the initial instability is applied immediately adjacent to a solid boundary vigorous plume motion continues for the duration of the numerical simulations 12 days producing a much greater volume of fresh deep water a parametric study investigates the scale and intensity of this boundary mixing it is found that reduced surface water temperature coriolis acceleration or higher horizontal diffusion coefficients increase the rate of deep water renewal

in situ measurement of mesopelagic particle sinking rates and the control of carbon transfer to the ocean interior during the vertical flux in the global ocean vertigo voyages in the north pacific abstract among the parameters affecting carbon transfer to the ocean interior particle sinking rates vary three orders of magnitude and thus more than primary production f ratios or particle carbon contents e g boyd p w trull t w 2006 understanding the export of marine biogenic particles is there consensus progress in oceanography 4 276 312 doi 10 1016 j pocean 2006 10 007 very few data have been obtained from the mesopelagic zone where the majority of carbon remineralization occurs and the attenuation of the sinking flux is determined here we report sinking rates from 300 m depth for the subtropical station aloha june 2004 and subarctic station k2 july 2005 north pacific ocean obtained from short 6 5 day deployments of an indented rotating sphere irs sediment trap operating as an in situ settling column peterson m l wakeham s g lee c askea m a miquel j c 2005 novel techniques for collection of sinking particles in the ocean and determining their settling rates limnology and oceanography methods 3 520 532 to separate the flux into 11 sinking rate fractions ranging from 820 to 2 m d 1 that are collected by a carousel for further analysis functioning of the irs trap was tested using a novel programming sequence to check that all particles have cleared the settling column prior to the next delivery of particles by the 6 hourly rotation cycle of the irs there was some evidence from the flux distribution among the cups and photomicroscopy of the collected particles that very slow sinking particles may have been under collected because they were unable to penetrate the brine filled collection cups but good evidence for appropriate collection of fast settling fractions approximately 50 of the particulate organic carbon poc flux was sinking at greater than 100 m d 1 at both stations at aloha more than 15 of the poc flux sank at 820 m d 1 but low fluxes make this uncertain and precluded resolution of particles sinking slower than 137 m d 1 at k2 less than 1 of the poc flux sank at 820 m d 1 but a large fraction 15 45 of the flux was contributed by other fast sinking classes 410 and 205 m d 1 pic and bsi minerals were not present in higher proportions in the faster sinking fractions but the observations were too limited to rule out a ballasting contribution to the control of sinking rates photographic evidence for a wide range of particle types within individual sinking rate fractions suggests that biological processes that set the porosity and shape of particles are also important and may mask the role of minerals comparing the spectrum of sinking rates observed at k2 with the power law profile of flux attenuation with depth obtained from other vertigo sediment traps deployed at multiple depths buesseler k o lamborg c h boyd p w lam p j trull t w bidigare r r bishop j k b casciotti k l dehairs f elskens m honda m karl d m siegel d silver m steinberg d valdes j van mooy b wilson s e 2007b revisiting carbon flux through the ocean s twilight zone science 316 5824 567 570 doi 10 1126 science 1137959 emphasizes the importance of particle transformations within the mesopelagic zone in the control of carbon transport to the ocean interior

paleoenvironmental changes in the east japan sea during the last 48 ka indications from high resolution x ray fluorescence core scanning paleoceanographic changes in the east japan sea during the late quaternary based on high resolution elemental variations particularly correlations between dark light laminations and millennial scale climatic changes have remained poorly understood because of the lack of the high resolution proxies the recent application of micro x ray fluorescence xrf core scanning provides the potential for high resolution study on the laminations deposited in the east japan sea in this study we present a geochemical study by using micro xrf core scanning on a 730 cm core recovered from the east japan sea elemental variations and factor analysis indicate that the sedimentary environment changed from anoxic to suboxic conditions from marine isotope stage mis 2 3 to mis 1 which is induced by increased contribution of high salinity sea water from the open ocean due to the rising sea level the dark and light laminations during mis 2 3 were correlated with dansgaard oeschger cycles and summer monsoon proxy with dark colored sediments related to higher terrigenous concentration corresponding to warm moist and enhanced summer monsoon period during the interstadial period more terrigenous sediments were transported to the east japan sea via the strengthened fluvial discharge from the surrounding continents caused by enhanced monsoon rainfall thus the development of the east asian summer monsoon and consequent variations in fluvial discharge would have significantly affected the paleoceanographic conditions in the east japan sea during the mis 2 3 sea level lowstand copyright 2012 john wiley sons ltd

toward disentangling stages in mixed assemblages of flake debris from biface reduction an experimental approach abstract their abundance in the archaeological record makes assemblages of lithic debris popular subjects of analysis archaeologists study them to identify both kinds and stages of reduction using approaches that range in scale from attribute analysis to typology and size distributions experiments demonstrate meaningful pattern in flake assemblages by both kind and stage yet empirical assemblages often are mixtures of flake debris from various reduction kinds and stages mixing confounds the patterns often found in controlled experimental data to address this problem we use stahle and dunn s 1982 data and a similar constrained regression method quadprog in r to allocate hypothetical mixed assemblages of biface reduction stages to their constituent stages in combining their stages 2 and 3 a measure that stahle and dunn themselves advocated quadprog improves their allocation results methods like these deserve further testing on a wider range of flake assemblages to address the challenge that mixing poses

a statistical theory for the patchiness of open ocean deep convection the effect of preconditioning within basins that exhibit open ocean convection convectively mixed fluid is often observed in regions of upward doming isopycnal surfaces preconditioned by either cyclonic circulation and or bottom topography here an equilibrium statistical theory for open ocean convection developed in the context of two layer heton models is adapted to study the outcome of basinwide cooling events over preexisting large scale ambient flow a range of prototype ambient flows is studied including cyclonic and anticyclonic gyres purely barotropic circulations and topographically induced flow about a localized seamount and within a broad bowl like depression the critical element of these elementary ambient flows is the position of the fluid interface separating the upper and lower layers it is displaced upward within the cyclonic gyre and the upwelling seamount downward within the anticyclonic gyre and the bowl like depression and is flat for purely barotropic flow the authors then consider the effect of applying cooling by introducing cold hetons over the preconditioned flow the most probable postconvection state is found by maximizing the entropy contained in the coarse grained vorticity field subject to key large scale constraints consistent with observations the most probable distribution of the coldtemperature anomalies introduced by the convective overturning that follows a basin scale surface cold air outbreak is indeed concentrated about the peaks of upwelling isopycnals in contrast ambient flows with isopycnal surfaces that slope downward fail to confine the cold temperature anomalies as hetons tend to cluster along the edges and corners of the basin with much weaker displacements

wind driven freshwater buildup and release in the beaufort gyre constrained by mesoscale eddies recently the beaufort gyre has accumulated over 20 km3 of freshwater in response to strong anticyclonic atmospheric winds that have prevailed over the gyre for almost two decades here we explore key physical processes affecting the accumulation and release of freshwater within an idealized eddy resolving model of the beaufort gyre we demonstrate that a realistic halocline can be achieved when its deepening tendency due to ekman pumping is counteracted by the cumulative action of mesoscale eddies based on this balance we derive analytical scalings for the depth of the halocline and its spin up time scale and emphasize their explicit dependence on eddy dynamics our study further suggests that the beaufort gyre is currently in a state of high sensitivity to atmospheric winds however an intensification of surface stress would inevitably lead to a saturation of the freshwater content a constraint inherently set by the intricacies of the mesoscale eddy dynamics

multiple dipole eddies in the alaska coastal current detected with landsat thematic mapper data seventeen dipole eddies including five large well formed ones three second generation eddies and two double eddies were observed in the alaska coastal current near kayak island in one single scene of the landsat thematic mapper tm on april 22 1985 the digital landsat tm satellite data were computer analyzed to extract details in the near coastal circulation in the northern gulf of alaska enhancement techniques were applied to the visible and thermal ir bands the features are evident only in the visible bands because of the ability of these bands to detect the distribution of sediments in the near surface these eddies did not have a significant thermal signature the sources of these sediments are the glacial streams found throughout the gulf of alaska coast eddies of this configuration and frequency have never been observed here previously however the oceanographic and meteorological conditions are typical for this time of year these eddies should be important to the cross shelf mixing processes in the alaska coastal current and are an indicator that the flow here can be unstable at certain times of the year

microflint in archaeological sediments from boker tachtit israel a new method for quantifying concentrations of small flint fragments abstract flint is one of the most common rock types used for producing stone tools during flint knapping huge amounts of microscopic sized flint particles are produced thus the presence of high concentrations of microflint in a sedimentary layer could be a good indication that flint was knapped at that location we have developed and tested a method for quantification of microflint concentrations in sediments the method involves concentrating the microflints in specific density fractions and then counting a representative proportion of the flint fragments using a polarized light microscope we show that the method successfully identifies a knapping layer in an initial upper palaeolithic level at the site of boker tachtit israel this level also contains macroscopic flint debitage including refitted artifacts microflint quantification can aid in identifying knapping areas and be useful for better understanding site formation processes

generation and separation of mesoscale eddies from surface ocean fronts abstractthis study is motivated by arctic ocean observations of sub mixed layer eddies found at large distances from their assumed formation region of a surface ocean front eddy formation is explored through high resolution numerical simulations of surface fronts separating two mixed layers with a range of configurations similar to those observed in the arctic ocean this study finds that frontal instabilities lead to the development of self propagating dipoles which have the potential to propagate far from the front if interactions with other eddies are avoided however most dipoles are unbalanced consisting of a dominating surface cyclone and a weaker anticyclone below and thus propagate on curved trajectories with eventual recirculation back to the front their maximum separation distance from the front depends on the ratio of self advecting velocities balanced dipoles that have 1 and the ability to propagate far from the front for dipoles generated numerically this study estimates u

parameterization of mixed layer eddies part i theory and diagnosis ageostrophic baroclinic instabilities develop within the surface mixed layer of the ocean at horizontal fronts and efficiently restratify the upper ocean in this paper a parameterization for the restratification driven by finite amplitude baroclinic instabilities of the mixed layer is proposed in terms of an overturning streamfunction that tilts isopycnals from the vertical to the horizontal the streamfunction is proportional to the product of the horizontal density gradient the mixed layer depth squared and the inertial period hence restratification proceeds faster at strong fronts in deep mixed layers with a weak latitude dependence in this paper the parameterization is theoretically motivated confirmed to perform well for a wide range of mixed layer depths rotation rates and vertical and horizontal stratifications it is shown to be superior to alternative extant parameterizations of baroclinic instability for the problem of mixed layer restratification two companion papers discuss the numerical implementation and the climate impacts of this parameterization

low frequency current observations in the korea tsushima strait abstract high resolution continuous current measurements made in the korea tsushima strait between may 1999 and march 2000 are used to examine current variations having time periods longer than 2 days twelve bottom mounted acoustic doppler current profilers provide velocity profiles along two sections one section at the strait entrance southwest of tsushima island and the second section at the strait exit northeast of tsushima island additional measurements are provided by single moorings located between korea and tsushima island and just north of cheju island in cheju strait the two sections contain markedly different mean flow regimes a high velocity current core exists at the southwestern section along the western slope of the strait for the entire recording period the flow directly downstream of tsushima island contains large variability and the flow is disrupted to such an extent by the island that a countercurrent commonly exists in the lee of the island the northeastern section is marked b

characterizing the eddy field in the arctic ocean halocline ice tethered profilers itp deployed in the arctic ocean between 2004 and 2013 have provided detailed temperature and salinity measurements of an assortment of halocline eddies a total of 127 mesoscale eddies have been detected 95 of which were anticyclones the majority of which had anomalously cold cores these cold core anticyclonic eddies were observed in the beaufort gyre region canadian water eddies and the vicinity of the transpolar drift stream eurasian water eddies an arctic wide calculation of the first baroclinic rossby deformation radius rd has been made using itp data coupled with climatology rd 13 km in the canadian water and 8 km in the eurasian water the observed eddies are found to have scales comparable to rd halocline eddies are in cyclogeostrophic balance and can be described by a rankine vortex with maximum azimuthal speeds between 0 05 and 0 4 m s the relationship between radius and thickness for the eddies is consistent with adjustment to the ambient stratification eddies may be divided into four groups each characterized by distinct core depths and core temperature and salinity properties suggesting multiple source regions and enabling speculation of varying formation mechanisms

the scales and equilibration of midocean eddies freely evolving flow quasigeostrophic turbulence theory and numerical simulation are used to study the mechanisms determining the scale structure and equilibration of mesoscale ocean eddies the present work concentrates on using freely decaying geostrophic turbulence to understand and explain the vertical and horizontal flow of energy through a stratified horizontally homogeneous geostrophic fluid it is found that the stratification profile in particular the presence of a pycnocline has significant qualitative effects on the efficiency and spectral pathways of energy flow specifically with uniform stratification energy in high baroclinic modes transfers directly quickly within a few eddy turnaround times and almost completely to the barotropic mode by contrast in the presence of oceanlike stratification kinetic energy in high baroclinic modes transfers intermediately to the first baroclinic mode whence it transfers inefficiently and incompletely to the barotropic mode the efficiency of transfer to the barotropic mode is reduced as the pycnocline is made increasingly thin the b effect on the other hand improves the efficiency of barotropization but for oceanically realistic parameters this effect is relatively unimportant compared to the effects of nonuniform stratification finally the nature of turbulent cascade dynamics is such as to lead to a concentration of first baroclinic mode kinetic energy near the first radius of deformation which in the case of a nonuniform and oceanically realistic stratification has a significant projection at the surface this may in part explain recent observations of surface eddy scales by topex poseidon satellite altimetry which indicate a correlation of surface height variance with the scale of the first deformation radius

lateral mixing across ice meltwater fronts of the chukchi sea shelf summer and fall hydrographic sections in the northeastern chukchi sea frequently capture 5 20 m thick intrapycnocline lenses or horizontal plumes of warm moderately salty summer bering sea water flowing northward from bering strait these features occur within the shallow 20 m depth pycnocline separating cold dilute surface meltwater from near freezing salty winter formed waters beneath the pycnocline an idealized numerical model suggests that the features arise from eddies and meanders generated by instability of the surface front separating meltwater from bering sea water warm bering sea water is transported across the front and into the pycnocline by the cross frontal velocities associated with the instabilities the accompanying lateral eddy heat fluxes may be important both in summer for promoting ice melt and in fall by delaying the onset of ice formation over portions of this shelf lateral heat flux magnitudes depend upon the stratification of the bering sea water

possible sources driving the potential vorticity structure and long wave instability of coastal upwelling and downwelling currents it is well known that upwelling and downwelling currents are unstable to perturbations less is however known about the physical mechanism responsible for the observed and modeled instabilities it is shown that the origin of the long wave barotropic baroclinic instability observed on upwelling currents has to be sought among diabatic or thermobaric mechanisms in particular the role of mixing associated with kelvin helmholtz instability and of wind forcing is investigated low richardson numbers occur when the pycnocline outcrops at the sea surface the criterion for instability ri 1 4 can be reached in a narrow region close to the upwelling front permitting kelvin helmholtz instability and mixing this can precondition the current for long wave instability by transforming the current s potential vorticity a constant wind can likewise modify the potential vorticity the resulting potential vorticity anomaly is always negative for both upwelling and downwelling currents and this anomaly interacts with the outcropped front destabilizing it examples are provided via numerical calculations using an idealized front a wind stress is an effective means of inducing the negative pv necessary for instability with wind kelvin helmholz instability when present merely modifies the instability characteristics in addition upwelling fronts are always less stable than comparable downwelling fronts

upper circulation patterns in the ulleung basin abstract continuous acoustic travel time measurements from a two dimensional array of pressure gauge equipped inverted echo sounders spanning the entire ulleung basin of the southwestern japan east sea between june 1999 and july 2001 are used to examine the upper temperature and current patterns a new method referred to as the residual gem technique interprets the travel time data into a three dimensional x y p time series of daily synoptically mapped current and temperature fields during the two year measurement period at least five non repeating persistent flow patterns are found the patterns during the first year coincide with changes in the total volume transport through the korea tsushima strait while the patterns of the second year do not the mean temperature of the basin displays strong interannual variability and is correlated with the total korea tsushima strait transport with a higher mean temperature in the first year when total volume transport was higher in addition a new framework for describing the flow patterns is presented a newly described cold core eddy referred to as the dok cold eddy is about 60 km in diameter and typically forms southwest of dok island when the subpolar front loops southward between ulleung and dok takeshima islands and sheds an eddy the dok cold eddy is highly variable in space and time and it tends to propagate westward towards the coast of korea where it merges with cold waters from the north three such propagation events preceed the disappearance of the east korean warm current which then remains absent between june and november 2000 the offshore branch forms by branching in the korea tsushima strait and is present during much of our two year observation period

eddies in the canada basin arctic ocean observed from ice tethered profilers five ice tethered profilers itps deployed between 2004 and 2006 have provided detailed potential temperature and salinity s profiles from 21 anticyclonic eddy encounters in the central canada basin of the arctic ocean the 12 35 m thick eddies have center depths between 42 and 69 m in the arctic halocline and are shallower and less dense than the majority of eddies observed previously in the central canada basin they are characterized by anomalously cold and low stratification and have horizontal scales on the order of or less than the rossby radius of deformation about 10 km maximum azimuthal speeds estimated from dynamic heights assuming cyclogeostrophic balance are between 9 and 26 cm s 1 an order of magnitude larger than typical ambient flow speeds in the central basin eddy s and potential vorticity properties as well as horizontal and vertical scales are consistent with their formation by instability of a surface front at about 80 n that appears in historical ctd and expendable ctd xctd measurements this would suggest eddy lifetimes longer than 6 months while the baroclinic instability of boundary currents cannot be ruled out as a generation mechanism it is less likely since deeper eddies that would originate from the deeper reaching boundary flows are not observed in the survey region

note on the rate of restratification in the baroclinic spindown of fronts abstractthis paper revisits how the restratifying buoyancy flux generated by baroclinic mixed layer instabilities depends on environmental conditions the frontal spindown is shown to produce buoya

energetics of the surface circulation of the japan east sea during the period of august 1987 to june 1998 96 argos tracked drifters traversed through the japan east sea the displacement data from these drifters were used to compute 1 3 day average current vectors which described the circulation at 15 m depth the drifters that passed through the korea strait via the western channel were caught by the east korean warm current and the drifters that passed through the eastern channel were caught by the tsushima current individual observations of the 3 day average current over 40 cm s 1 were made in the warm waters south of the subpolar front and along the coasts there was a distinct decrease of eddy energy northward across the subpolar front conversion rates of eddy kinetic energy due to eddy mean flow interaction showed significant regions of both dissipation and production

a model of buoyant throughflow with application to branching of the tsushima current abstract a reduced gravity model is used here to investigate the dynamics of a buoyant flow through a strait driven by pressure difference of the adjoining basins assuming the flow to be hydraulically controlled so that the transport is maximized flow structures in the upstream basin during its transit through the strait and along the downstream coast are determined it is found in particular that the combined effect of friction exerted by the sill and stretching of the buoyant layer as it exits the strait may cause the downstream flow to exhibit two velocity maxima along the layer outcrop and the coastal boundary when applied to the tsushima current of the japan east sea the required conditions for branching are amply satisfied the model thus provides a plausible explanation of this observed feature in addition a favorable comparison between predicted and observed transports supports the hydraulic control of the flow

observed near surface flows under all tropical cyclone intensity levels using drifters in the northwestern pacific 1 data from drifters of the surface velocity program and tropical cyclones tcs of the joint typhoon warning center during 1985 2009 were analyzed to demonstrate strong currents under various storm intensities such as category 4 to 5 category 2 to 3 and tropical storm to category 1 tcs in the northwestern pacific current speeds over 2 0 m s 1 are observed under major tcs with the strongest mean currents to the right of the storm track this study provides the characterization of the near surface velocity response to all recorded tcs and agrees roughly with geisler s theory 1970 our observations also verify earlier modeling results of price 1983

idealized study on the effect of bottom topography on the seasonality of the stability of the iceland faeroe front abstractwe investigate the effects of bottom topography on the instability eddy driven heat flux and overturning of a front that sits atop a ridge by varying the initial location of an idealized

the mixture problem in flake analysis allocating flake samples to segments of reduction using clsr methods abstract flake assemblages often are mixtures from knapping episodes that vary by reduction mode or stage stahle and dunn 1982 developed a constrained least squares regression clsr method to allocate hypothetically mixed chert assemblages to successive biface reduction stages a partial solution to the mixing problem conreg is a recently developed alternative validated against stahle and dunn s and our own experimental controls from replication of obsidian biface preforms using both controls we apply conreg to the unmixing of flake assemblages from north american great basin obsidian quarries controls produce different solutions their separate comparison to independent analytical results of stage composition favor conreg used with our controls what appeared to be relatively similar early stage assemblages are resolved to finer proportional allocation across wider ranges of the reduction continuum in the process showing considerable variation between samples that otherwise might escape detection the mixture problem is a challenge to all approaches to flake analysis not just mass analysis but one that conreg can help us surmount

modeling the deep convection in the northwestern mediterranean sea using an eddy permitting and an eddy resolving model case study of winter 1986 1987 1 in the northwestern mediterranean sea winter 1986 1987 was particularly cold inducing a strong open ocean convection event in order to investigate the impact of numerical models spatial resolution on the convection representation and the effects of deep convection on the northwestern mediterranean circulation we perform two numerical three dimensional simulations eddy permitting versus eddy resolving models are forced at the surface by the era40 atmospheric fluxes with a simple heat flux correction to better mimic the observed value we examine the characteristics of the deep convection mixed layer water masses characteristics convection zone and mesoscale structures and perform temporal analysis of this event in terms of kinetic energy buoyancy equilibrium and deep water dw evolution the convection characteristics are similarly represented on a global scale by both models and are in good agreement with observations except for the size of the convection region however the eddy resolving model better reproduces the mesoscale structures whose role in the dw formation mixing and transport is shown to be essential the boundary circulation and the overturning are enhanced during the convection event sixty six percent of the dw spreading is due to the bleeding effect into the catalan sea during the convection event whereas 33 is due to the mesoscale structures southwestward advection after the event sixty percent of the restratification with respect of the water column initial structure occurs before july 1987 and is due to light water advection afterward restratification is due to the mixing and is not complete before next year convection

mixed layer instabilities and restratification abstract the restratification of the oceanic surface mixed layer that results from lateral gradients in the surface density field is studied the lateral gradients are shown to be unstable to ageostrophic baroclinic instabilities and slump from the horizontal to the vertical these instabilities which are referred to as mixed layer instabilities mlis differ from instabilities in the ocean interior because of the weak surface stratification spatial scales are o 1 10 km and growth time scales are on the order of a day linear stability analysis and fully nonlinear simulations are used to study mlis and their impact on mixed layer restratification the main result is that mlis are a leading order process in the ml heat budget acting to constantly restratify the surface ocean climate and regional ocean models do not resolve the scales associated with mlis and are likely to underestimate the rate of ml restratification and consequently suffer from a bias in sea surface temperatures and ml depths in a

western arctic shelfbreak eddies formation and transport abstract the mean structure and time dependent behavior of the shelfbreak jet along the southern beaufort sea and its ability to transport properties into the basin interior via eddies are explored using high resolution mooring data and an idealized numerical model the analysis focuses on springtime when weakly stratified winter transformed pacific water is being advected out of the chukchi sea when winds are weak the observed jet is bottom trapped with a low potential vorticity core and has maximum mean velocities of o 25 cm s 1 and an eastward transport of 0 42 sv 1 sv 106 m3 s 1 despite the absence of winds the current is highly time dependent with relative vorticity and twisting vorticity often important components of the ertel potential vorticity an idealized primitive equation model forced by dense weakly stratified waters flowing off a shelf produces a mean middepth boundary current similar in structure to that observed at the mooring site the model boundary current is also highly v

rapid water transport by long lasting modon eddy pairs in the southern midlatitude oceans water in the ocean is generally carried with the mean flow mixed by eddies or transported westward by coherent eddies at speeds close to the long baroclinic rossby wave speed modons dipole eddy pairs are a theoretically predicted exception to this behaviour which can carry water to the east or west at speeds much larger than the rossby wave speed leading to unusual transports of heat nutrients and carbon we provide the first observational evidence of such rapidly moving modons propagating over large distances these modons are found in the midlatitude oceans around australia with one also seen in the south atlantic west of the agulhas region they can travel at more than ten times the rossby wave speed of 1 2 cm s 1 and typically persist for about six months carrying their unusual water mass properties with them before splitting into individual vortices which can persist for many months longer

vertical scales and dynamics of eddies in the arctic ocean s canada basin a decade of moored measurements from the arctic ocean s northwestern beaufort gyre collected as a component of the beaufort gyre exploration project are analyzed to examine the range of mesoscale eddies over the water column and the dynamical processes that set eddy vertical scales a total of 58 eddies were identified in the moored record all anticyclones with azimuthal velocities ranging from 10 to 43 cm s these are divided into three classes based on core depths shallow eddies core depths around 120 m are shown to be vertically confined by the strong stratification of the halocline typical thicknesses are around 100 m deep eddies core depths around 1200 m are much taller thicknesses around 1300 m owing to the weaker stratification at depth consistent with a previous study eddies centered around mid depths all have two cores vertically aligned and separated in depth characterized by velocity maxima and anomalous temperature and salinity properties one core is located at the base of the halocline around 200 m depth and the other at the depth of the atlantic water layer around 400 m depth these double core eddies have vertical scales between those of the shallow and deep eddies the strongly decreasing stratification in their depth range motivates a derivation for the quasi geostrophic adjustment of a nonuniformly stratified water column to a potential vorticity anomaly the result aids in interpreting the dynamics and origins of the double core eddies providing insight into transport across a major water mass front separating canadian and eurasian water

quantifying lithic curation an experimental test of dibble and pelcin s original flake tool mass predictor this paper describes an experimental test of a method proposed by dibble pelcin 1995 for reconstructing the original flake mass from striking platform dimensions the results of this test indicate that while there is a correlation between flake mass and flake attributes for hard hammer lithic production systems using the specific variables identified by dibble pelcin exterior platform angle and platform thickness consistently underestimates original flake mass the reasons for this discrepancy and possible future research directions to resolve it are explored

subduction of a surface vortex under an outcropping front the possibility for a preexisting surface intensified anticyclone to subduct beneath a surface front is investigated using an isopycnal numerical model subduction occurs for strong coherent vortices and is usually accompanied by strong dissipation two main mechanisms cause the erosion of the vortex core the first one is induced by the velocity shear associated with the front it results in the peeling of the vortex potential vorticity pv core sometimes leading to its complete disappearance the second mechanism occurs after the vortex has subducted entrainment of high positive pv fluid parcels from the front above the vortex low negative pv core modifies the stability properties of the latter meanders are observed to grow at the rim of the structure which favors the formation of pv filaments the erosion rates caused by each mechanism are discussed in relation to the jet and vortex characteristics and to the background stratification the trapping of high pv fluid parcels above the vortex is also shown to be partly responsible for the decrease and eventual loss of the eddy altimetric signal after it has subducted

generation of subsurface anticyclones at arctic surface fronts due to a surface stress isolated anticyclones are frequently observed below the mixed layer in the arctic ocean some of these subsurface anticyclones are thought to originate at surface fronts however previous idealize

observations of submesoscale variability and frontal subduction within the mesoscale eddy field of the tasman sea abstractsubmesoscale lenses of water with anomalous hydrographic properties have previously been observed in the east australian current eac system embedded within the thermocline of mesoscale a

vorticity and vertical circulation at an ocean front abstract density and velocity data with 4 km horizontal resolution from a survey of a front during fasinex frontal air sea interaction experiment are combined to describe the structure of the top 300 m of the ocean the geostrophic velocity field is derived and is used to examine the relative importance of stratification relative vorticity and twisting terms in ertel s potential vorticity q tenfold isopycnic changes in q are found across a horizontal scale of only 10 km these changes are confined to isopycnals that outcrop from the seasonal thermocline into the mixed layer the ageostrophic velocity field is quantified by solution of the omega equation and vertical velocities of up to 40 m day 1 are found small 40 km surface trapped top 200 m eddies are found to play a crucial role in the transport and effective diffusion of properties across the thermocline out of the mixed layer

orbital and millennial scale changes of radiolarian assemblages during the last 220 kyrs in the japan sea abstract significant abundance changes of seven radiolarian species during the last 220 kyrs in the japan sea are reported herein based on three sediment cores during the interglacial periods warm water species the tetrapyle octacantha group and warmer high nutrient water species lithomelissa setosa occurred commonly which may indicate inflows of the tsushima warm current on the other hand cold water species such as ceratospyris borealis and stylochlamydium venustum dominated the assemblage during the glacial periods when the japan sea was mostly isolated from the adjacent seas due to lower eustatic sea level however at glacial maxima the habitat of s venustum was strongly limited due to low salinity surface waters the abundance of the deep water species cycladophora davisiana seems to have changed significantly possibly related to the intrusion of oxygen and organic materials into deeper waters higher abundances of this species in mis marine isotope stage 1 mis 3 and mis 5c resulted from well ventilated deep water and high organic flux while its low abundance during the glacial maxima and mis 5e was probably caused by oxygen poor deep water millennial scale variations of c davisiana abundance show high abundance at the transition intervals from interstadial to stadial periods of the dansgaard oeschger cycles the disappearance events of lychnocanoma nipponica sakaii and amphimelissa setosa were recognized at 54 ka and 85 ka respectively both of these events in the japan sea can be correlated with those in the north pacific bering sea and sea of okhotsk

close interactions between two pairs of heton like vortices under sea ice close interactions between two pairs of vertically stacked counterrotating eddies under sea ice were investigated in numerical experiments the numerical model contains a stratified ocean capped by an ice layer under the ice layer a shallow brine source produces a top cyclone and a submerged anticyclone while a shallow freshening source generates a top anticyclone and a submerged cyclone ice exerted friction dissipates the top eddies in time leaving submerged ones in lone existence in this work winning vortices are sought from a brine brine pair a freshening brine pair and a freshening freshening pair brine and freshening sources are made equal in strength to level the playing field when closely paired fission an increase in the number of subsurface vortices occurs from a brine brine pair and a freshening brine pair but not from a freshening freshening pair consequences of fission invariably increase the number of submerged anticyclones a heuristic argument is given to explain this polarity the strong interaction among closely packed eddies operates in timescales of tens of days helping to explain the predominance of submerged anticyclones under the arctic sea ice

the application and misapplication of mass analysis in lithic debitage studies the technique of debitage mass analysis based upon size grades of debitage populations is shown to be prone to errors when making interpretations about the kind of tool produced or the kind of lithic reduction technology used significant sources of error may originate from differences in individual flintknapping styles and techniques raw material size and shape variants and mixing of debitage from more than one reduction episode these sources of error render debitage mass analysis ineffective for determining the kind of stone tool reduction activities practiced at excavated sites mass analysis may be effective for determining artifact reduction sequences if it is used on debitage from a single reduction episode or part of a reduction episode however it is shown that mass analysis when used for assessing reduction sequence information must also control for the effects of raw material variability assemblage mixing and flintknapping styles

eddies in the western arctic ocean from spaceborne sar observations over open ocean and marginal ice zones the western arctic ocean is a host to major ocean circulation systems many of which generate eddies that can transport water masses and corresponding tracers over long distances from their formation sites however comprehensive observations of critical eddy characteristics are currently not available and are limited to spatially and temporally sparse in situ observations here we use high resolution spaceborne synthetic aperture radar measurements to detect eddies from their surface imprints in ice free sea surface roughness and in sea ice patterns throughout marginal ice zones we provide the first estimate of eddy characteristics extending over the seasonally ice free and marginal ice zone regions of the western arctic ocean including their locations diameters and monthly distribution using available synthetic aperture radar data we identified over 4 000 open ocean eddies as well as over 3 500 eddies in marginal ice zones from june to october in 2007 2011 and 2016 eddies range in size between 0 5 and 100 km and are frequently found over the shelf and near continental slopes but also present in the deep canada basin and over the chukchi plateau we find that cyclonic eddies are twice more frequent compared to anticyclonic eddies at the surface distinct from the dominating anticyclonic eddies observed at depth by in situ moorings and ice tethered profilers our study supports the notion that eddies are ubiquitous in the western arctic ocean even in the presence of sea ice and emphasizes the need for improved ocean observations and modeling at eddy scales

oceanic restratification forced by surface frontogenesis potential vorticity pv conservation implies a strong constraint on the time evolution of the mean density at a given depth the authors show that on an f plane and in the absence of sources and sinks of pv it only depends on two terms namely the time evolution of the product between density anomaly and relative vorticity and the vertical pv flux this primitive equation result which applies at any depth suggests that the ageostrophic dynamics induced by baroclinic eddies strongly affect the mean oceanic stratification profile this result is illustrated for two simple initial value simulations of a baroclinic balanced jet for initial situations propitious to surface frontogenesis the simulations show a restratification over the whole water column characterized by the amplification in time of the brunt vaisala frequency in the upper oceanic layers in the absence of surface frontogenesis such as when the jet is initialized at the middepth of the water column the restratification is much weaker and slower because both simulations have similar kinetic energy and growth rate of baroclinic instability the results clearly reveal that the restratification is driven by surface frontogenesis in the first case and by vertical pv flux in the interior in the second case the authors also point out that the dynamics of the interior pv is tightly related to the surface dynamics because of total mass conservation

structure of velocity and temperature in the northeast pacific as measured with lagrangian drifters in fall 1987 abstract in october 1987 49 lagrangian surface drifters tristar ii were released in a 200 km 200 km square area southeast of ocean station papa as part of the ocean storms experiment the drifters measured temperature at the drogue level and reported their position through argos approximately 11 times per day thirty one of the drifters retained drogues for longer than three months and data from those instruments are used to describe the evolving fall 1987 pattern of current and temperature structures at 15 m in the area between 46 and 49 n 142 w and 132 w time variable currents were dominated by mesoscale eddies of anticyclonic rotation with horizontal radii of 53 86 km and rotational speeds of 10 20 cm s 1 these eddies persisted for at least 90 days as evidenced by successive drifter trajectories through the eddies currents with periods longer than 1 day had a mean to the east of 4 4 cm s 1 and a mean to the north of 0 7 cm s 1 background eddy kinetic energy levels were 40 cm s 2 thus eddy

microdebitage analysis initial considerations abstract microdebitage is defined as all stone flaking residue less than 1 mm in maximum dimension experimental replication indicates that it is produced in great quantities by stone tool manufacture and can permeate site matrices as a permanent signature of past cultural activity initial sampling studies suggest that microdebitage analysis may have considerable utility as a means of lithic site surveying

temporal variability of the large scale geostrophic surface velocity in the northeast pacific abstract data from argos tracked mixed layer drifters in fall and winter 1987 49 drifters and 1989 16 drifters are used to investigate the differences in the large scale surface velocity and eddy activity in the northeast pacific the velocities were corrected for wind induced slippage and corrected for wind driven ekman flow by matching an ekman model to the observed currents the model which explains 15 30 of the variance indicates that the currents are at 60 to the right of the wind the magnitude of the currents is 30 of the magnitude of the wind stress in 1987 88 the geostrophic motion in the region from 46 5 to 48 5 n 142 to 133 w was characterized by an eastward flow of 0 9 0 4 cm s 1 and a northward flow of 0 7 0 4 cm s 1 in 1989 90 for the same region the geostrophic eastward component was 3 8 0 5 cm s 1 more than four times as large as in 1987 88 and the northward component was 0 3 0 5 cm s 1 in this region ageostrophic contributions to the velocities are small

examining stage and continuum models of flake debris analysis an experimental approach abstract flake debris produced from a number of flintknapping experiments is used to explore stage and continuum models of lithic reduction using metric attributes flakes produced during core reduction are separated from those produced during tool production theoretically this should allow the utilization of continuum approaches in the analysis of archaeological assemblages that represent a mix of reduction strategies i e core reduction and tool production further continuum based analyses are refined by providing a standardized scale although this work demonstrates the potential utility of a continuum based model for analysing archaeological lithic assemblages stage analyses retain utility and can be fruitfully used in conjunction with the refined continuum model developed here

multiscale observations of deep convection in the northwestern mediterranean sea during winter 2012 2013 using multiple platforms during winter 2012 2013 open ocean deep convection which is a major driver for the thermohaline circulation and ventilation of the ocean occurred in the gulf of lions northwestern mediterranean sea and has been thoroughly documented thanks in particular to the deployment of several gliders argo profiling floats several dedicated ship cruises and a mooring array during a period of about a year thanks to these intense observational efforts we show that deep convection reached the bottom in winter early in february 2013 in a area of maximum 28 3 109 m2 we present new quantitative results with estimates of heat and salt content at the subbasin scale at different time scales on the seasonal scale to a 10 days basis through optimal interpolation techniques and robust estimates of the deep water formation rate of 2 0 0 2 sv we provide an overview of the spatiotemporal coverage that has been reached throughout the seasons this year and we highlight some results based on data analysis and numerical modeling that are presented in this special issue they concern key circulation features for the deep convection and the subsequent bloom such as submesoscale coherent vortices scvs the plumes and symmetric instability at the edge of the deep convection area

beaufort gyre freshwater reservoir state and variability from observations 1 we investigate basin scale mechanisms regulating anomalies in freshwater content fwc in the beaufort gyre bg of the arctic ocean using historical observations and data collected in 2003 2007 specifically the mean annual cycle and interannual and decadal fwc variability are explored the major cause of the large fwc in the bg is the process of ekman pumping ep due to the arctic high anticyclonic circulation centered in the bg the mean seasonal cycle of liquid fwc is a result of interplay between the mechanical ep and thermal ice transformations factors and has two peaks one peak occurs around june july when the sea ice thickness reaches its minimum maximum ice melt the second maximum is observed in november january when wind curl is strongest maximum ep and the salt input from the growing ice has not yet reached its maximum interannual changes in fwc during 2003 2007 are characterized by a strong positive trend in the region varying by location with a maximum of approximately 170 cm a 1 in the center of ep influenced region decadal fwc variability in the period 1950 2000 is dominated by a significant change in the 1990s forced by an atmospheric circulation regime change the center of maximum fwc shifted to the southeast and appeared to contract in area relative to the pre 1990s climatology in spite of the areal reduction the spatially integrated fwc increased by over 1000 km 3 relative to climatology