inertial currents estimated from surface trajectories of argo floats 1 we have developed an analysis method to determine the amplitude of inertial motion from surface trajectory data of argo profiling floats this method gives an estimate of inertial current speed and phase from satellite fixes transmitted while a float drifts at the surface over a time which is typically about one local inertial period the error of this method is about 3 4 cm sec for data records with at least 6 positions with accuracy of 500 m spanning longer than 68 of the inertial period whereas inertial amplitudes are as large as 40 cm sec with a median of about 12 0 cm sec in the japan east sea globally distributed argo floats could provide useful information on the co variability of wind forced inertial currents and mixed layer depths in the ocean

horizontal circulation and volume transports in the weddell gyre derived from argo float data argo floats provide both hydrographic and trajectory data affording the opportunity to investigate surface to mid depth ocean dynamics here argo float data are used to determine the absolute geostrophic velocity field of the upper 50 2000 m of the weddell gyre from which the overall circulation pattern is investigated the weddell gyre plays a pivotal role in the modification of climate by advecting heat towards the antarctic ice shelves and by modifying the water masses that feed into the lowest limb of the global ocean overturning circulation warm deep water the source water mass that delivers heat to the weddell gyre is conveniently located within the upper 2000 m domain covered by the floats we investigate its volume transport as it circulates the gyre full depth volume transports are estimated by applying a quadratic function to extrapolate the relative dynamic height field component to the full ocean depth using ctd profiles from ship based surveys to determine an extrapolation error major new insights are provided by this study there is an established double gyre structure to the circulation with a strong eastern cell and a weaker western cell regional variation of the baroclinic component of the flow field is revealed indicating a northeast to southwest reduction in the baroclinic flow along with a strong meridional gradient of baroclinic flow along the northern limb of the gyre especially east of 25 w the zonal mean gyre strength away from the shelf edge is 32 5 sv 1 sv 1 106 m3 s 1 of which 13 3 sv are associated with the advection of warm deep water there is a considerable amount of recirculation within the gyre interior where water does not traverse the full zonal extent of the gyre the recirculation is stronger in the eastern cell of the observed double gyre structure the interior circulation cells partly explain the large variations in previous gyre strength estimates we provide an extensive review of previous estimates in context of the new results obtained

microstructure observations of turbulent heat fluxes in a warm core canada basin eddy abstractan intrahalocline eddy was observed on the chukchi slope in september of 2015 using both towed ctd and microstructure temperature and shear sections the core of the eddy was 6 c significa

the impact of stored solar heat on arctic sea ice growth high resolution measurements of ocean temperature and salinity in the arctic ocean s canada basin reveal the importance of the release of solar derived stored ocean heat on sea ice growth locally absorbed summer solar heat is stored in a near surface temperature maximum nstm layer underlying the mixed layer the heat content of the nstm layer was anomalously large following summer 2007 which saw considerable sea ice losses and intense solar absorption into the exposed surface ocean measurements provide evidence for the entrainment of nstm layer heat in fall winter 2007 2008 by shear driven mixing and convective mixing by the release of dense salty plumes during sea ice growth while at least a portion of the nstm layer was eroded deeper warm ocean layers remained unaffected it is shown that the release of solar heat stored following summer 2007 was sufficient to have reduced sea ice thickness at the end of the 2008 growth season by about 25

observational and laboratory insights into salt finger convection improving observational capabilities in the ocean are revealing a substantial body of evidence that the double diffusive instability known as salt fingers is widely present and plays a significant role in oceanic mixing this evidence includes unique fine and microstructure features in particular regions and distinct patterns in the temperature and salinity variations over large areas laboratory experiments have also advanced our understanding of salt fingers the insights gleaned from both laboratory and ocean are reviewed and related to large scale ocean structure and climate modeling

a review of oceanic salt fingering theory salt fingering is a potentially important mechanism for mixing different water masses in those parts of the ocean where warm salty waters overlie cooler fresher this review surveys advances in salt fingering theory as they pertain to ocean mixing basic equations are presented along with steady maximum buoyancy flux and fastest growing finger solutions attempts to quantify theoretically finger induced fluxes of heat salt and buoyancy and to understand staircase formation and maintenance are described also considered are the confounding influences of internal wave shear and strain and intermittent internal wave shear driven turbulence which are present in the ocean but in few theories finally outstanding theoretical questions about the role of salt fingers in the ocean are raised

origin of thermohaline staircases hypotheses concerning the origin of thermohaline staircases in salt fingering regions are reviewed and assessed one such hypothesis that staircases arise from thermohaline intrusions is developed into a quantitative theory it is shown that growing intrusions evolve toward staircases when the background density ratio lies below a threshold value and nonlinear computations confirm that staircases are viable intrusion equilibria staircase properties such as step heights lateral density ratios and layer slopes lie closest to observed values when salt fingers are assumed not to contribute to shear stress and when turbulent mixing rates are smaller than usual thermocline values

on the total input of antarctic waters to the deep ocean a preliminary estimate from chlorofluorocarbon measurements 1 deep ocean inventories of dissolved chlorofluorocarbon 11 cfc 11 along representative sections off antarctica provide the first estimate of the overall strength of all dense water sources in the southern ocean their formation rates are reported for three density layers that span the main water masses involved in the lower limb of the thermohaline circulation thc the bottom layer is supplied via sinking of antarctic bottom water aabw produced at a few continental shelves the middle layer receives the offshore injection of ventilated modified circumpolar deep water mcdw produced along much of the lengthy antarctic slope front the top layer is ventilated by northward export of antarctic surface water into the upper circumpolar deep water of the antarctic circumpolar current average southern ocean inputs to the upper two layers of the deep ocean for the 1970 1990 period are derived on the basis of the cfc 11 distributions along meridional sections the mean cfc 11 saturations of all water mass ingredients and the inferred mixing leading to production of dense source waters about 5 4 1 7 sv 1 sv 10 6 m 3 s 1 of near freezing shelf water ventilate the bottom layer and 4 7 1 7 sv and 3 6 1 3 sv of cold antarctic surface water ventilate the middle and top layers therefore the total contribution of ventilated southern ocean waters to the lower limb of the global thc is about 14 sv this is close to the about 17 sv estimated for north atlantic near surface sources from cfc 11 inventories their entrainment of 7 4 2 4 sv of cfc poor subsurface lower circumpolar deep water during the formation and sinking of aabw and mcdw raises the total southern ocean input to the deep ocean to about 21 sv

revisiting internal waves and mixing in the arctic ocean 1 to determine whether deep background mixing has increased with the diminishment of the arctic sea ice we compare recent internal wave energy and mixing observations with historical measurements since 2007 the north pole environmental observatory has launched expendable current probes xcps as a part of annual airborne hydrographic surveys in the central arctic ocean mixing in the upper 500 m is estimated from xcp shear variance and conductivity temperature depth ctd derived brunt vaisala frequency internal wave energy levels vary by an order of magnitude between surveys although all surveys are less energetic and show more vertical modes than typical midlatitude garrett munk gm model spectra survey averaged mixing estimates also vary by an order of magnitude among recent surveys comparisons between modern and historical data reanalyzed in identical fashion reveal no trend evident over the 30 year period in spite of drastic diminution of the sea ice turbulent heat fluxes are consistent with recent double diffusive estimates both mixing and internal wave energy in the beaufort sea are lower when compared to both the central and eastern arctic ocean and expanding the analysis to mooring data from the beaufort sea reveals little change in that area compared to historical results from arctic internal wave experiment we hypothesize that internal wave energy remains lowest in the beaufort sea in spite of dramatic declines in sea ice there because increased stratification amplifies the negative effect of boundary layer dissipation on internal wave energy

the relationship between double diffusive intrusions and staircases in the arctic ocean abstractthe origin of double diffusive staircases in the arctic ocean is investigated for the particular background setting in which both temperature and salinity increase with depth motivated by observations that show the coexistence of thermohaline intrusions and double diffusive staircases a linear stability analysis is performed on the governing equations to determine the conditions under which staircases form it is shown that a double diffusive staircase can result from interleaving motions if the observed bulk vertical density ratio is below a critical vertical density ratio estimated for particular lateral and vertical background temperature and salinity gradients vertical background temperature and salinity gradients dominate over horizontal gradients in determining whether staircases form with the linear theory indicating that perturbations to stronger vertical temperature gradients are more likely to give rise to a staircase examination of arctic ocean temperature and salinity measurements

vertical heat transfer in the arctic ocean the role of double diffusive mixing 1 microstructure profiles collected in the central amundsen basin are analyzed in order to quantify the role of double diffusive mixing for vertical heat transfer from the atlantic layer in the profiles a persistent but laterally incoherent thermohaline staircase structure is identified in the 200 260 m depth range the staircase contains homogeneous layers with average height of 1 3 m and thin high gradient interfaces with average temperature and salinity jumps of about 0 065 c and 0 015 respectively when inferred from a commonly used diffusive convection parameterization the average vertical heat flux within the staircase is 0 6 w m 2 this is one order of magnitude larger than the molecular diffusion alone and of the same order as the overall heat loss from the atlantic layer in the deep basins of the arctic ocean the parameterization is evaluated using observed turbulent heat fluxes and is found to overestimate diffusive convective fluxes with up to an order of magnitude especially for weak thermal forcing small temperature jumps in staircase staircases coexist with thermohaline intrusions in the vertical temperature and salinity profiles lomonosov ridge is identified as a potential region for formation of intrusions it is found that salt fingering is the dominant process during intrusion growth whereas diffusive convection is the dominant process in maintaining the intrusions at steady state in the deep basins

remotely induced warming of antarctic bottom water in the eastern weddell gyre 1 four repeat hydrographic sections across the eastern weddell gyre at 30 e reveal a warming by 0 1 c and lightening by 0 02 0 03 kg m 3 of the antarctic bottom water aabw entering the gyre from the indian sector of the southern ocean between the mid 1990s and late 2000s historical hydrographic and altimetric measurements in the region suggest that the most likely explanation for the change is increased entrainment of warmer mid depth circumpolar deep water by cascading shelf water plumes close to cape darnley where the indian sourced aabw entering the weddell gyre from the east is ventilated this change in entrainment is associated with a concurrent southward shift of the antarctic circumpolar current s acc southern boundary in the region this mechanism of aabw warming may affect wherever the acc flows close to antarctica

spatial variability of the arctic ocean s double diffusive staircase the arctic ocean thermohaline stratification frequently exhibits a staircase structure overlying the atlantic water layer that can be attributed to the diffusive form of double diffusive convection the staircase consists of multiple layers of o 1 m in thickness separated by sharp interfaces across which temperature and salinity change abruptly through a detailed analysis of ice tethered profiler measurements from 2004 2013 the double diffusive staircase structure is characterized across the entire arctic ocean we demonstrate how the large scale arctic ocean circulation influences the small scale staircase properties these staircase properties layer thicknesses and temperature and salinity jumps across interfaces are examined in relation to a bulk vertical density ratio spanning the staircase stratification we show that the lomonosov ridge serves as an approximate boundary between regions of low density ratio approximately 3 to 4 on the eurasian side and higher density ratio approximately 6 to 7 on the canadian side we find that the eurasian basin staircase is characterized by fewer thinner layers than that in the canadian basin although the margins of all basins are characterized by relatively thin layers and the absence of a well defined staircase a double diffusive 4 3 flux law parametrization is used to estimate vertical heat fluxes in the canadian basin to be o 0 1 wm 2 it is shown that the 4 3 flux law may not be an appropriate representation of heat fluxes through the eurasian basin staircase here molecular heat fluxes are estimated to be between o 0 01 wm 2 and o 0 1 wm 2 however many uncertainties remain about the exact nature of these fluxes this article is protected by copyright all rights reserved

ice tethered profiler observations of the double diffusive staircase in the canada basin thermocline vertical heat fluxes through the staircase are in the range 0 05 0 3 w m 2 only about one tenth of the estimated mean surface mixed layer heat flux to the sea ice it is thus concluded that the vertical transport of heat from the atlantic water in the central basin is unlikely to have a significant impact to the canada basin ocean surface heat budget icebreaker conductivity temperature depth data from the beaufort gyre freshwater experiment show that the staircase is absent at the basin periphery turbulent mixing that presumably disrupts the staircase might drive greater flux from the atlantic water at the basin boundaries and possibly dominate the regionally averaged heat flux

double diffusive interleaving on horizontal gradients results are presented from laboratory experiments on lateral intrusive flows driven by horizontal gradients of properties in double diffusive systems these are variations on the classical experiments in which salt stratified fluid was separated from a sugar stratified fluid by a removable barrier with the removal of this barrier lateral intrusions of sugar solution into the salt solution alternated in the vertical with salt intrusions into the sugar solution in our present study the fluid has continuous horizontal gradients of sugar density compensated by opposing horizontal gradients of salt rather than the discontinuity of properties in the classical experiments observations of these new experiments include shadowgraphs ptv particle tracking velocimetry showing the structure of the flow and piv particle image velocimetry from which velocity vector fields on a vertical plane were obtained from these mean flows reynolds stresses and associated momentum fluxes were computed these experiments have been conducted for three regimes of vertical stratification i salt finger favourable hot and salty above ii diffusive convection favourable hot and salty below iii doubly stable cold and salty below one of our main conclusions concerns the driving mechanism for the horizontal intrusive flow away from the front or nose of the intrusions the lateral flows are no longer tilted but are horizontal here finger layers alternate in the vertical with convecting layers in these convecting layers vertical transport of horizontal momentum by the reynolds stress plays a major role in maintaining the lateral motion against viscous dissipation

mooring based observations of double diffusive staircases over the laptev sea slope abstracta yearlong time series from mooring based high resolution profiles of water temperature and salinity from the laptev sea slope 2003 04 2686 m depth 78 26 n 125 37 e shows six remarkably persistent staircase layers in the depth range of 140 350 m encompassing the upper atlantic water aw and lower halocline despite frequent displacement of isopycnal surfaces by internal waves and eddies and two strong aw warming pulses that passed through the mooring location in february and late august 2004 the layers preserved their properties using laboratory derived flux laws for diffusive convection the authors estimate the time averaged diapycnal heat fluxes across the four shallower layers overlying the aw core to be 8 w m 2 temporal variability of these fluxes is strong with standard deviations of 3 7 w m 2 these fluxes provide a means for effective transfer of aw heat upward over more than a 100 m depth range toward the upper halocline these findings suggest that double diffusion is an imp

double diffusive recipes part ii layer merging events this study explores the dynamics of thermohaline staircases well defined stepped structures in temperature andsalinityprofiles commonlyobservedin regionsofactive doublediffusion theevolutionofstaircases in time is frequently characterized by spontaneous layer merging events these phenomena the authors argue are essentialin regulating theequilibriumlayerthicknessin fullydevelopedstaircases thepatternand mechanics of merging events are explained using a combination of analytical considerations direct numerical simulations and data analysis the theoretical merger model is based on the stability analysis for a series of identical steps and pertains to both forms of double diffusion diffusive convection and salt fingering the conceptual significance of the proposed model lies in its ability to describe merging events without assuming fromtheoutsetspecificpowerlawsfortheverticaltransportofheatandsalt theapproachadoptedbyearlier merging models the analysis of direct numerical simulations indicates that merging models based on the four thirds flux laws offer adequate qualitative description of the evolutionary patterns but are less accurate than models that do not rely on such laws specific examples considered in this paper include the evolution of layers in the diffusive staircase in the beaufort gyre of the arctic ocean

intrusions in double diffusively stable arctic waters evidence for differential mixing abstract intrusions like those observed in double diffusively stable regions of the arctic ocean can grow from uniform ambient temperature and salinity gradients if diapycnal mixing of these two components differs assuming this to be the driving mechanism the observed 40 60 m intrusion heights constrain the turbulent diffusivity for heat to be less than about 0 01 cm2 s 1 and the salt to heat turbulent diffusivity ratio to be greater than about 0 6 if the diffusivities are constant observations indicate that the intrusions slope across isopycnals in a sense that is consistent with such a scenario although the along intrusion density ratio is greater than that predicted by linear theory for the fastest growing intrusions numerical solutions for growing intrusions resemble observed temperature and salinity profiles

the diffusive regime of double diffusive convection the diffusive regime of double diffusive convection is discussed with a particular focus on unresolved issues that are holding up the development of large scale parameterizations some of these issues such as interfacial transports and layer interface interactions may be studied in isolation laboratory work should help with these however we must also face more difficult matters that relate to oceanic phenomena that are not represented easily in the laboratory these lie beneath some fundamental questions about how double diffusive structures are formed in the ocean and how they evolve in the competitive ocean environment

heat flux at the ice ocean interface the role of the oceanic heat flux fw in the sea ice energy and mass balance is discussed and a method is described for determining fw from measurements of the temperature and thickness of sea ice results obtained using this method and data collected in the fall of 1988 during a drift in the eastern arctic northeast of fram strait are presented estimates of fw ranged from 0 to 37 w m 2 and varied in both time and space the gradual variation over the course of the drift reflects transformation of the west spitsbergen current into arctic water masses a significant intersite variability on horizontal scales of 10 to 100 m is ascribed to the interaction between under ice topographic features and turbulent energy and mass transfer in the boundary layer in addition there is a variability in the ice growth rate on horizontal scales of 0 1 to 1 m which is ascribed to the instability of the ice ocean phase boundary in the presence of turbulent flow these observations have implications for modeling and future experiments

observational validation of the diffusive convection flux laws in the amundsen basin arctic ocean the low levels of mechanically driven mixing in many regions of the arctic ocean make double diffusive convection virtually the only mechanism for moving heat up from the core of atlantic water towards the surface in an attempt to quantify double diffusive heat fluxes in the arctic ocean a temperature microstructure experiment was performed as a part of the north pole environmental observatory npeo 2013 field season from the drifting ice station barneo located in the amundsen basin near the lomonosov ridge 89 5 n 75 w a diffusive convective thermohaline staircase was present between 150 and 250 m in nearly all of the profiles typical vertical heat fluxes across the high gradient interfaces were consistently small o 10 1 w m 2 our experiment was designed to resolve the staircase and differed from earlier arctic studies that utilized inadequate instrumentation or sampling our measured fluxes from temperature microstructure agree well with the laboratory derived flux laws compared to previous studies which could find agreement only to within a factor of two to four correlations between measured and parameterized heat fluxes are slightly higher when using the more recent flanagan et al 2013 laboratory derivation than the more commonly used derivation presented in kelley 1990 nusselt versus rayleigh number scaling reveals the convective exponent to be closer to 0 29 as predicted by recent numerical simulations of single component convection rather than the canonical 1 3 assumed for double diffusion however the exponent appears to be sensitive to how convective layer height is defined

on the horizontal extent of the canada basin thermohaline steps abstract microstructure profiles of temperatures through the diffusive thermohaline staircase above the atlantic layer core in the canada basin of the arctic ocean are used to investigate the horizontal scales of layers daily profiles during two periods 23 march 3 april and 17 26 april 1985 show that diffusive steps are present throughout the 200 km drift track a 20 hour series on 22 april sampled at about 5 profiles per hour indicates that particular diffusive layers can be traced for at least 600 m the temperature of some layers varies by up to 0 01 c h 1 30 m lateral motion therefore we cannot reliably trace steps in this location if the sampling distance is larger than about 15 m analysis of a longer time series with variable spacing from 0 4 to 5 km indicates that layers can rarely be traced between profiles more than 1 km apart

nonlinear equilibration of thermohaline intrusions abstract the nonlinear behavior of thermohaline intrusions on a wide front is investigated using a one dimensional numerical model the model is used to follow the evolution of a field of intrusions from infinitesimal amplitude to a large amplitude state characterized by inversions in temperature and salinity it is thus possible to extend the analytical studies of toole and georgi and others to large amplitude allowing for the effects of amplitude dependent diffusivities and for the appearance of stably stratified diffusively stratified and statically unstable regions in the water column as the intrusions grow the model runs are initialized with infinitesimal disturbances that grow exponentially in time until inversions in temperature and salinity occur after inversions appear the intrusions evolve toward an equilibrium state in which friction balances buoyancy forces for both finger and diffusive sense basic state stratifications these equilibrium states are characterized by statically unstabl

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

an examination of double diffusive processes in a mesoscale eddy in the arctic ocean temperature and salinity measurements of an atlantic water mesoscale eddy in the arctic ocean s canada basin are analyzed to understand the effects of velocity shear on a range of double diffusive processes double diffusive structures in and around the eddy are examined through the transition from low shear outside the eddy and within its solid body core to high geostrophic shear zones at the eddy flanks the geostrophic richardson number takes large values where a double diffusive staircase is observed and lowest values at the eddy flanks where geostrophic velocity is largest and a well formed staircase is not present a thorpe scale analysis is used to estimate turbulent diffusivities in the flank regions double diffusive and turbulent heat salt and buoyancy fluxes from the eddy are computed and used to infer that the eddy decays on time scales of around 4 9 years fluxes highlight that atlantic water heat within the eddy can be fluxed downward into deeper water layers by means of both double diffusive and turbulent mixing estimated lateral variations in vertical fluxes across the eddy allow for speculation that double diffusion speeds up the eddy decay having important implications for the transfer of atlantic water heat in the arctic ocean

grain size information from the statistical properties of digital images of sediment abstract the autocorrelation technique for estimating grain size from digital images ofsand beds has been extended and validated for use on coarse sand 0ae7 mm and gravel up to 20 mm a number of aspects of the technique have beenexplored and some potential improvements suggested autocorrelation is justone suitable statistical method sensitive to the grain size of sediment in digitalimages four additional techniques are presented and their relative meritsdiscussed a collective suite of techniques applicable to the general problem ofgrain size estimation from digital images of sediment might broaden theapplicability to more sedimentary environments as well as improve itsaccuracy these techniques are compared using a large data set from a gravelbarrier beach in southern england based on over 180 samples mean grain sizeof sieved and imaged sediments correspond to within between 8 and 16 some theoretical aspects of the spatial arrangement of image intensity indigital images of natural sediments are addressed including the fractal natureof sediments in images which has potential implications for derivation ofgrain size distributions from images of sand sized material throughsegmentation and thresholding the methods outlined in this contributionmay also nd application in further uncovering the geometric structure ofsediment beds as well as in the simulation of sedimentation processes keywordsgrain size analysis digital images statistical models gravel beach introductiongrain size information from natural environ ments traditionally is obtained using methodssuch as sieving laser diffraction and settling which do not help measure equivalent propertiesof the sample in addition the slow and labour intensive nature of these methodologies has lim ited the spatial and temporal resolution at whichgrain size data are obtained where grain size isan important parameter such as in determiningsediment transport studies can be limited funda mentally by the dif culty in sampling for sedi ment at the required frequency a furtherdisadvantage is that sediment must be removedfrom the natural environment potentially alteringsubsequent system development in contrast photographic methods can be used to measuresediment size at a resolution comparable withmeasurements of hydraulic hydrodynamic andmorphological topographical conditions withoutdisrupting the sediment body by direct sampling the problem of deriving sediment size infor mation from digital images of sediment has beenapproached using two different families of tech niques the rst is based on edge detection andimage segmentation principles e g butler et al 2001 sime ferguson 2003 graham et al 2005 such techniques rely on marked image intensity contrasts between grains and gapsbetween grains interstices such that thresholdscan be speci ed to discriminate individual grainsfrom the background intensity levels e g sime ferguson 2003 thus far these methods aresedimentology 2009 56 421 438

atlantic water circulation over the mendeleev ridge and chukchi borderland from thermohaline intrusions and water mass properties 1 hydrographic and tracer data from 2002 illustrate atlantic water pathways and variability in the mendeleev ridge and chukchi borderland cblmr region of the arctic ocean thermohaline double diffusive intrusions zigzags dominate both the fram strait fsbw and barents sea branch waters bsbw in the region we show that details of the zigzags temperature salinity structure partially describe the water masses forming the intrusions furthermore as confirmed by chemical tracers the zigzags peaks contain the least altered water allowing assessment of the temporal history of the atlantic waters whilst the fsbw shows the 1990s warming and then a slight cooling the bsbw has continuously cooled and freshened over a similar time period the newest boundary current waters are found west of the mendeleev ridge in 2002 additionally we show the zigzag structures can fingerprint various water masses including the boundary current using this tracer data and the advection of the 1990s warming we conclude the strongly topographically steered boundary current order 50 km wide and found between the 1500 m and 2500 m isobaths crosses the mendeleev ridge north of 80 n loops south around the chukchi abyssal plain and north around the chukchi rise with the 1990s warming having reached the northern but not the southern northwind ridge by 2002 pacific waters influence the atlantic layers near the shelf and over the chukchi rise the northwind abyssal plain is comparatively stagnant being ventilated only slowly from the north there is no evidence of significant boundary current flow through the chukchi gap

oceanic thermohaline intrusions observations intrusions are commonly observed in the upper deep and coastal oceans and are closely linked to lateral fluxes of heat salt and momentum this is a review of observations of intrusions and the results of comparisons of properties such as scale slopes microstructure activity and fluxes with theoretical models a summary of estimates of lateral heat fluxes indicates a wide range of lateral diffusivities we conclude by noting that our present knowledge is insufficient to predict the structure length scales and lateral fluxes of thermohaline intrusions with confidence and list a number of unresolved questions suggestions are made for compilation of existing data into a database for exploratory analysis and testing of theoretical hypotheses an outline is given of a potential collaborative field experiment using ctd fluorescent dye and microstructure observations

evolution of a mediterranean salt lens scalar properties abstract the evolution of a mediterranean salt lens meddy over a two year period is examined several nondimensional numbers can be used to describe the overall decay in the structure of the moddy two rossby numbers one using the central relative vorticity and another using the radius and velocity of the azimuthal velocity maximum did not change over the two year period however the burger number n2h2 f2l2 increased as the meddy decayed another burger number the ratio of total kinetic energy to total available potential energy decreased from 1 1 to 0 6 over a one year period the rates at which the meddy lost salt and heat are consistent with estimates of horizontal fluxes by intrusions a horizontal diffusivity of o 5 m2 s 1 is needed if this flux by intrusions is parameterized by an eddy coefficient simple models of the evolution of an isolated eddy by horizontal and vertical mixing of mass and momentum are examined these simple attempts to explain the evolution of the meddy suggest more c

eastern arctic ocean diapycnal heat fluxes through large double diffusive steps abstractthe diffusive layering dl form of double diffusive convection cools the atlantic water aw as it circulates around the arctic ocean large dl steps with heights of homogeneous layers of