near inertial internal wave field in the canada basin from ice tethered profilers abstractsalinity and temperature profiles from drifting ice tethered profilers in the beaufort gyre region of the canada basin are used to characterize and quantify the regional near inertial internal wave field over one year vertical displacements of potential density surfaces from the surface to 750 m depth are tracked from fall 2006 to fall 2007 because of the time resolution and irregular sampling of the ice tethered profilers near inertial frequency signals are marginally resolved complex demodulation is used to determine variations with a time scale of several days in the amplitude and phase of waves at a specified near inertial frequency characteristics and variability of the wave field over the course of the year are investigated quantitatively and related to changes in surface wind forcing and sea ice cover

turbulent mixing near the yermak plateau during the coordinated eastern arctic experiment during the ice camp component of the coordinated eastern arctic experiment cearex in march april 1989 1500 profiles of temperature conductivity and velocity shear microstructure were obtained near the yermak plateau the dominant signal in isopycnal displacements was the diurnal variability near the plateau consistent with the enhanced diurnal currents found in this region previously from the fram iii and fram iv ice camps the dissipation rate of turbulent kinetic energy e reached maximum values of about 10 6 w kg 1 in two distinct regions the surface mixing layer and the pycnocline between 120 and 220 m there was a significant component of diurnal variability in e in each region in the surface layer e was proportional to the cube of the ice relative current speed at 30 m below the ice and it decayed approximately exponentially with increasing depth major mixing events in the pycnocline were correlated with large amplitude short duration isopycnal displacements the lowest dissipation rates were recorded over the deep nansen basin north of the plateau and in the subsurface core of a submesoscale baroclinic eddy in northern fram strait the time averaged vertical eddy diffusivity near the slope of the plateau was about 2 5 10 4 m2 s 1 in the pycnocline above the atlantic layer implying an upward heat flux of 25 w m 2 although only a small fraction of this heat reached the base of the mixed layer the results confirm that current interactions with steep topography are critical to the modification of atlantic water in the eastern arctic ocean

observations and models of inertial waves in the deep ocean the structure of the inertial peak in deep ocean kinetic energy spectra is studied here records were obtained from polymode arrays deployed in the western north atlantic ocean 40 w to 70 w 15 n to 42 n the results are interpreted both in terms of local sources and of turning point effects on internal waves generated at lower latitudes in most of the data there is a prominent inertial peak slightly above f however the peak height above the background continuum varies with depth and geographical environment three classes of environment and their corresponding spectra emerge from peak height variations class 1 is the 1500 m level near the mid atlantic ridge with the greatest peak height of 18 db class 2 includes a the upper ocean depth less than 2000 m b the deep ocean depth greater than 2000 m over rough topography and c the deep ocean underneath the gulf stream with intermediate peak height of 11 5 db class 3 is the deep ocean over smooth topography with the lowest peak height of 7 5 db near f the horizontal coherence scale is 0 60 km at depths from 200 m to 600 m and the vertical coherence scale is 0 200 m in the lower part of the main thermocline and 0 1000 m in the deep water the phase difference suggests a downward energy propagation in the lower thermocline and standing waves in the deep water a one turning point model is developed to describe inertial waves at mid latitudes based on the assumption that inertial waves are randomly generated at lower latitudes global generation where their frequency wave number spectrum is given by the model of garrett and munk 1972 1975 using the globally valid wave functions obtained by munk and phillips 1968 various frequency spectra near f are calculated numerically the model yields a prominent inertial peak of 7 db in the horizontal velocity spectrum but no peaks in the temperature spectrum the model is latitudinally dependent the frequency shift and bandwidth of the inertial peak decrease with latitude energy level near f is minimum at about 30 and higher at low and high latitudes the observations of class 3 can be well described by the model a low zonal wave number cutoff is required to produce the observed frequency shift of the inertial peak the differences between the global generation model and the observations of class 1 and class 2 are interpreted as the effects of local sources a locally forced model is developed based on the latitudinal modal decomposition of a localized source function asymptotic eigensolutions of laplace s tidal equation are therefore derived and used as a set of expansion functions the forcing is through a vertical velocity field specified at the top or bottom boundaries of the ocean for white noise forcing the horizontal velocity spectrum of the response has an inertial peak which diminishes in the far field with the forcing located at either the surface or the bottom several properties of the class 2 observations can be described qualitatively by a combination of the global and local models the reflection of inertial waves from a turbulent benthic boundary layer is studied by a slab model of given depth frictional effects are confined to the boundary layer and modeled by a quadratic drag law for given incident waves reflection coefficients are found to be greater than 0 9 for the long waves which contain most of the energy this result suggests that energy containing inertial waves can propagate over great distance as is required by the validity of the model of global generation

upper ocean temperature structure inertial currents and richardson numbers observed during strong meteorological forcing abstract upper ocean currents and temperature in the northeastern pacific were measured during a 14 day period in november 1980 as part of strex velocities in the upper ocean are dominated by near inertial frequency oscillations thew oscillations are modified by wind stress variations associated with the passage of a strong cold front the change in the inertial currents both in the mixed layer and below is qualitatively consistent with linear internal wave dynamics if turbulent stresses during the storm are assumed to extend 10 20 m below the mixed layer the ratio of mean squared buoyancy frequency n2 and mean squared shear s2 computed over a 10 m interval defines an average richardson number r0 n2 s2 r0 is approximately 2 5 except in regions of high inertial shear in particular values as low as 0 7 are obtained in a 20 m thick region immediately below the base of the mixed layer the data are consistent with a model of the oecanic shear field consisting of a background shear corresponding to a va

experimental studies of gas escape and water escape structures mechanisms and morphologies abstract water escape and gas escape structures were generated in the laboratory to assess variations in deformational structures generated during these events particulate fluidization was observed to be the method by which grains were redistributed during water escape resulting structures of particulate fluidization comprised disrupted and downward deflected primary laminations and a massive appearing column of sand above the point source gas experiments with a low flow rate 6 167 10 6 m3 s allowed gas to disperse through fractures and only subtle deformation was achieved aggregative fluidization i e fluid movement through sediment as bubbles was the mechanism for grain displacement during gas escape with increased flow rate 7 67 10 5 m3 s aggregative fluidization occurred and particles were carried upward in the wake of the passing gas bubble aggregative fluidization resulted in broken upwards warping laminations and convoluted bedding experiments illustrate a significant morphological difference between water escape and gas escape water escape structures were bounded by downwards warping laminations consistent with water escape structures encountered in the rock record gas escape structures displayed upwards warping laminations and could represent a formation mechanism for convolute bedding

internal waves in the arctic ocean comparison with lower latitude observations abstract a thermistor chain was moored below the pack ice from 50 150 m in the arctic ocean for five days in 1981 oscillations in temperature are attributed to the vertical dispalcement of internal waves the spectral shape of isotherm dispalcement is consistent with the garrett munk model and other internal wave observations but the spectral level is significantly lower other observations from the arctic ocean also exhibit lower internal wave energy when compared with historical data from lower latitudes the lower energy may be related to the unique generation and dissipation mechanisms present in the ice covered arctic ocean significant peaks in vertical coherence occur at 0 81 and 2 6 cph the peak at 2 6 cph coincides approximately with the high frequency spectral cutoff near the local buoyancy frequency this feature has been observed in many other internal wave experiments the coherent oscillations at 0 81 cph exhibit a node in vertical dispalcement at 75 100 m this is consistent with either

hydrography and microstructure of an arctic cyclonic eddy hydrographic and velocity profiles were made through a small baroclinic cyclonic eddy during the arctic internal wave experiment in the canada basin in april 1985 the maximum measured azimuthal velocity was 0 38 m s 1 at a depth of 115 m with velocities decaying to near zero at 30 and 270 m maximum isopycnal displacements at the closest approach to the eddy s axis were about 40 m the deduced radius of maximum velocity is r0 7 2 km and the total radius is about 13 km kinetic energy dissipation rate e was enhanced within 70 m of the surface throughout the transect and for radius r r0 near 60 m and 180 m the subsurface maxima in e do not correspond to regions of low richardson number but are colocated with locally reduced shear consistent with the observed dissipation rates being merely the remnants of recent more energetic mixing events the time scale for the decay of the eddy based on its total energy and the measured dissipation rates is o 10 years given this large dissipation time scale critical layer absorption of vertically propagating internal wave momentum may be dynamically significant to the eddy s evolution the arctic internal wave experiment aiwex was conducted from an ice camp drifting in the canada basin of the arctic ocean during march may 1985 velocity temperature and conductivity were sampled at fixed depths and profiles of these variables from the surface to below 300 m were made toward the end of the experiment the camp drifted across a small eddy with a total inferred radius see section 3 1 of about 13 km from both the hydrographic data and current meter records the rotation sense parity of the eddy was cyclonic with an azimuthal velocity maximum near 115 m decreasing to approximately zero near 30 m and 270 m small eddies are a common feature of the canada basin being present in about 25 of the hydrographic and current meter profiles during the extensive arctic ice dynamics joint experiment aidjex program in 1975 1976 manley and hunkins 1985 they contain much of the kinetic energy in the depth range 0 250 m and transport significant amounts of anomalous heat salt and nutrients within the canada basin understanding these eddies is therefore essential to modeling the upper ocean in the canada basin manley and hunkins 1985 found that approximately 95 of eddies identified during aidjex were anticyclonic hunkins 1974 documented one cyclonic eddy extending from near the surface to below 200 m from the aidjex pilot program in 1972 manley and hunkins 1985 found three cyclonic eddies during the main aidjex program in 19751976 but two of these were below the atlantic layer core i e below 500 m while the third was very weak d asaro

mesoscale eddies of the arctic ocean subsurface baroclinic eddies in the arctic ocean have a diameter of 10 20 km and are confined in depth between 50 and 300m during the arctic ice dynamics joint experiment aidjex in the central beaufort sea between march 1975 and may 1976 extensive information on eddy characteristics statistics and behavior was collected from four manned drifting ice camps during this 14 month period 146 eddies were encountered of which 19 were found to be repeated crossings making a total of 127 separate eddies observed during this period on the basis of the 1975 1976 aidjex data set it is concluded that eddies are 1 prevalent in the amerasia basin of the arctic ocean and in particular the beaufort sea where they may occupy up to a quarter of the available surface area 2 located in the depth range of 50 300 m although a few deeper eddies are also present 3 the second largest producers 32 of kinetic energy found within the upper 200 m of the beaufort sea and 4 predominantly anticyclonic in rotational tendency these eddies apparently originate north of point barrow alaska as a result of instability in the eastward flowing alaskan coastal current and transfer seasonally varying water properties from the chukchi sea and alaskan shelf into the arctic ocean they appear to translate in response to barotropic forcing over short time scales and over longer time periods move with the mean geostrophic field the season of formation for an eddy may be identified by the anomalous thermal properties still residing in its core

near inertial internal waves and sea ice in the beaufort sea the evolution of the near inertial internal wavefield from ice free summertime conditions to ice covered wintertime conditions is examined using data from a yearlong deployment of six moorings on the beaufort continental slope from august 2008 to august 2009 when ice is absent from july to october energy is efficiently transferred from the atmosphere to the ocean generating near inertial internal waves when ice is present from november to june storms also cause near inertial oscillations in the ice and mixed layer but kinetic energy is weaker and oscillations are quickly damped damping is dependent on ice pack strength and morphology decay scales are longer in early winter november january when the new ice pack is weaker and more mobile decreasing in late winter february june when the ice pack is stronger and more rigid efficiency is also reduced as comparisons of atmospheric energy available for internal wave generation to mixed layer kinetic energies indicate that a smaller percentage of atmospheric energy is transferred to nearinertial motions when ice concentrations are 90 however large kinetic energies and shears are observed during an event on 16 december and spectral energy is elevated above garrett munk levels coinciding with the largest energy flux predicted during the deployment a significant amount of near inertial energy is episodically transferred to the internal wave band from the atmosphere even when the ocean is ice covered however damping by ice and less efficient energy transfer still leads to low arctic internal wave energy in the near inertial band increased kinetic energy below 300m when ice is forming suggests some events may generate internal waves that radiate into the arctic ocean interior

observations of small eddies in the beaufort sea the horizontal and vertical variations of velocity temperature density and turbulent kinetic energy dissipation in the central beaufort sea were measured with helicopter borne expendable current profilers and conductivity temperature depth units almost all velocity differences larger than 0 05 m s 1 could be consistently interpreted as being due to nearly circular eddies with a diameter of 10 20km a thickness of 50 500 m peak velocities of 0 07 0 3 m s 1 and little expression at the top of the ocean four such eddies were found two anticyclones were found and accurately sampled two cyclones were found but were only poorly sampled both were beneath and close to one of the anticyclones relative vorticity could be computed for two anticyclones and one cyclone within experimental error the two anticyclones and all historical beaufort sea anticyclones had a relative vorticity of and thus zero potential vorticity at the center the cyclone had a central relative vorticity of about 0 5 and thus a different value of potential vorticity than the surrounding fluid one anticyclonic eddy b was sampled seven times over a period of 23 days its measured velocity and density fields were in approximate gradient wind balance its central core contained values of temperature nitrate and silicate that were different from those outside the core at the same density it moved eastward at about 0 02 m s 1 through the surrounding fluid measurements of turbulent kinetic energy dissipation were almost always less than the noise level of the instrument about 10 9 w kg 1 corresponding to a mean dissipation much less than this and a minimum decay time due to turbulence much longer than 0 3 year the nondimensional strength rossby number and shape burger number of anticylcone b are very similar to those of other beaufort sea anticyclones and similar to those of small mid latitude eddies each of the eddies observed here was centered on a temperature maximum associated with one of the warm water masses that advect into the arctic ocean the two anticyclones were centered on temperature maxima originating in the pacific ocean whereas the two cyclones were centered on temperature maxima from the atlantic ocean this is consistent with the hypothesis that the eddies are formed as these water masses enter the arctic ocean

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

characterizing horizontal variability and energy spectra in the arctic ocean halocline energy transfer from the atmosphere into the upper arctic ocean is expected to become more efficient as summer sea ice coverage decreases and multiyear ice thins due to recent atmospheric warming however relatively little is known about how energy is transferred within the ocean by turbulent processes from large to small scales in the presence of ice and how these pathways might change in future this study characterises horizontal variability in several regions of the eurasian arctic ocean under differing sea ice conditions historic along track ctd data collected by a royal navy submarine during summer 1996 allows a unique examination of horizontal variability and associated wavenumber spectra within the arctic ocean halocline spectral analysis indicates that potential energy variance under perennial sea ice in the amundsen basin is o 100 less than within the marginal ice zone miz of fram strait spectra from all regions show a transition in scaling at wavelengths of approximately 5 to 7 km at scales greater than the transition wavelength to 50 km energy spectra are consistent with a k 3 scaling where k is wavenumber and interior quasi geostrophic dynamics the scaling of spectra at these scales is extremely similar between regions suggesting similar dynamics and energy exchange pathways the k 3 scaling is steeper than typically found in regions of mid latitude open ocean at scales below the transition wavelength to 300 m spectra are close to a k 5 3 scaling or flatter indicating a change in dynamics which is potentially due to internal waves dominating variability at small scales this article is protected by copyright all rights reserved

vertical diffusivity of the western arctic ocean halocline a nearly year long series of upper ocean temperature conductivity and temperature microstructure profiles were collected from an ice camp drifting in the beaufort gyre as part of the 1997 1998 surface heat budget of the arctic experiment sheba geographically the record includes portions over the deep canada basin and the steep bathymetry of the chukchi borderlands region hydrographically the record includes cool pacific origin haloclines which contain a variety of subsurface temperature maxima and cold haloclines typical of the eurasian basins we present estimates of the vertical turbulent diffusivity derived from the dissipation rate of thermal variance and calculations of the associated vertical heat fluxes we find that vertical diffusion proceeds at molecular rates in the deep basins and away from topographic features while still relatively small diffusivity is enhanced by 1 order of magnitude near and above the chukchi borderlands the enhanced diffusivity is correlated to an increase in water column strain variance above the borderlands providing a linkage between bathymetry internal wave activity and turbulence the chukchi borderlands play a significant role in heat transport in the western arctic they are a pathway for horizontal heat transport and a hot spot for vertical heat transport vertical fluxes make a substantial contribution to the energy balance of the sea ice cover in this region heat fluxes between the halocline and underlying atlantic water are shown to be small and lacking vertical connection near surface waters

observations of internal gravity waves under the arctic pack ice internal gravity waves measured under the arctic pack ice were strikingly different from measurements at lower latitudes the total wave energy integrated over the internal wave frequency band was lower by a factor of 0 03 0 07 and the spectral slope at high frequency was nearly 1 in contrast to the 2 observed at lower latitudes this result has implications for theoretical investigations of the generation evolution and destruction of internal waves and is also important for other processes such as the propagation of sound and the wave induced turbulent diffusion of heat plankton and chemical tracers

thermohaline circulation in the arctic mediterranean seas the renewal of the deep north atlantic by the various overflows of the greenland scotland ridges is only one manifestation of the convective and mixing processes which occur in the various basins and shelf areas to the north the arctic ocean and the greenland iceland and norwegian seas collectively called the arctic mediterranean the traditional site of deep ventilation for these basins is the greenland sea but a growing body of evidence also points to the arctic ocean as a major source of deep water this deep water is relatively warm and saline and it appears to be a mixture of dense brine enriched shelf water with intermediate strata in the arctic ocean the deep water exits the arctic ocean along the greenland slope to mix with the greenland sea deep water conversely very cold low salinity deep water from the greenland sea enters the arctic ocean west of spitsbergen within the arctic ocean the lomonosov ridge excludes the greenland sea deep water from the canadian basin leaving the latter warm saline and rich in silica in general the entire deep water sphere of the arctic mediterranean is constrained by the greenland scotland ridges to circulate internally therefore it is certain of the intermediate waters formed in the greenland and iceland seas which ventilate the north atlantic these waters have a very short residence time in their formation areas and are therefore able to rapidly transmit surface induced signals into the deep north atlantic

shear flow dispersion internal waves and horizontal mixing in the ocean abstract two models of advection diffusion in the oscillatory sheared velocity field of an internal wave are discussed our goal is to develop intuition about the role of such currents in horizontal ocean mixing through the mechanism of shear dispersion the analysis suggests simple parameterizations of this process i e those in eqs 7 36 and 42 the enhanced horizontal diffusion due to the interaction of the vertical diffusion and vertical shear of the wave field can be described by an effective horizontal diffusivity which is equal to the actual horizontal diffusivity plus a term equal to the mean square vertical shear of horizontal displacement times the vertical diffusivity provided the vertical length scale of the horizontal velocity field is not too small in the limit of small vertical length scale the expression reduces to taylor s 1953 result in which the effective horizontal diffusivity is inversely proportional to the actual vertical diffusivity the solutions also incidentally

controls on turbulent mixing on the west antarctic peninsula shelf the ocean to atmosphere heat budget of the west antarctic peninsula is controlled in part by the upward flux of heat from the warm circumpolar deep water cdw layer that resides below 200 m to the antarctic surface water aasw a water mass which varies strongly on a seasonal basis upwelling and mixing of cdw influence the formation of sea ice in the region and affect biological productivity and functioning of the ecosystem through their delivery of nutrients in this study 2 5 year time series of both acoustic doppler current profiler adcp and conductivity temperature depth ctd data are used to quantify both the diapycnal diffusivity and the vertical heat flux q at the interface between cdw and aasw over the period of the study a mean upward heat flux of 1 w m 2 is estimated with the largest heat fluxes occurring shortly after the loss of winter fast ice when the water column is first exposed to wind stress without being strongly stratified by salinity differences in mixing mechanisms between winter and summer seasons are investigated whilst tidally driven mixing at the study site occurs year round but is likely to be relatively weak a strong increase in counterclockwise polarized near inertial energy and shear is observed during the fast ice free season suggesting that the direct impact of storms on the ocean surface is responsible for much of the observed mixing at the site given the rapid reduction in sea ice duration in this region in the last 30 years a shift towards an increasingly wind dominated mixing regime may be taking place

near inertial mixing in the central arctic ocean observations were made in april 2007 of horizontal currents hydrography and shear microstructure in the upper 500m from a drifting ice camp in the central arctic ocean an approximately 4 day long time series collected about 10 days after a storm event shows enhanced near inertial oscillations in the first half of the measurement period with comparable upward and downward propagating energy rough estimates of wind work and near inertial flux imply that the waves were likely generated by the previous storm the nearinertial frequency band is associated with dominant clockwise rotation in time of the horizontal currents and enhanced dissipation rates of turbulent kinetic energy the vertical profile of dissipation rate shows elevated values in the pycnocline between the relatively turbulent underice boundary layer and the deeper quiescent water column dissipation averaged in the pycnocline is near inertially modulated and its magnitude decays approximately at a rate implied by the reduction of energy over time observations suggest that near inertial energy and internal wave induced mixing play a significant role in vertical mixing in the arctic ocean

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

enhanced diapycnal mixing due to near inertial internal waves propagating through an anticyclonic eddy in the ice free chukchi plateau abstractthe arctic ocean is known to be quiescent in terms of turbulent kinetic energy tke associated with internal waves to investigate the current state of tke in the seasonally ice free chukchi plateau arctic ocean this study performed a 3 week fixed point observation fpo using repeated microstructure hydrographic and current measurements in september 2014 during the fpo program the microstructure observation detected noticeable peaks of tke dissipation rate e during the transect of an anticyclonic eddy moving across the fpo station particularly e had a significant elevation in the lower halocline layer near the critical level reaching the order of 10 8 w kg 1 the adcp measured current displayed energetic near inertial internal waves niws propagating via the stratification at the top and bottom of the anticyclone according to spectral analyses of horizontal velocity the waves had almost downward energy propagation and its current amplitude reached 10 cm s 1 the wkb scaling inco

upper ocean internal waves in the marginal ice zone of the northeastern greenland sea oceanographic measurements obtained in the northeastern greenland sea fram strait region were studied in order to characterize internal wave activity in the marginal ice zone miz of the arctic ocean experiments were performed with an array of four horizontally separated current meters and a ctd instrument in 1984 as part of the marginal ice zone experiment spectra of horizontal and vertical motion show that within the frequency range from the inertial frequency to 3 cph the miz internal wave field is similar in spectral shape and energy content to the wave field found beneath arctic pack ice above 3 cph the miz spectra contain more energy than expected based upon both beneath ice measurements and the garrett munk model spectra elevated energy levels at high frequencies are shown to be caused by intermittent increases in internal wave activity occurring on time scales from 2 to 12 hours phase differences between pairs of time series computed during the passage of several packets of internal waves are used to estimate horizontal wave number vectors a comparison of the calculated wave number vectors to a dispersion relation derived from a simple normal mode model of internal waves suggests that the wave packets may be adequately described as being comprised of lowest mode horizontally propagating internal waves the interaction of ice bottom topography with a sharp elevated pycnocline is explored as a possible source of the intermittent increases in wave activity spectra of vertical displacement and velocity computed from time series of both temperature and density are presented in order to show the influence of intrusive activity in the miz differences in both spectral shape and energy content found at frequencies below 2 5 cph emphasize the need for careful interpretation of temperature based measurements of vertical motion obtained over long periods of time in the miz

thermohaline staircases in the amundsen basin possible disruption by shear and mixing as part of the 2013 and 2014 north pole environmental observatories npeo in the amundsen basin of the arctic ocean two similar temperature microstructure experiments were performed with different results in 2013 vertical fluxes were through a thermohaline staircase and in 2014 the thermohaline staircase was largely absent here we investigate the reasons for this difference the 2013 data set was characterized by an extensive thermohaline staircase indicative of the diffusive convective type of double diffusion dc from 120 250 m depths the staircase was absent above 200 m in 2014 even though analysis of density ratio r still shows high susceptibility to ddc in the depth range of interest survey averaged r 3 8 in 2013 and r 3 6 in 2014 indicating that the temperature salinity structure in the pycnocline was not the cause of the lack of a staircase in 2014 we propose that exceptionally weak turbulent mixing even for the typically quiescent arctic ocean allowed formation of the staircase in 2013 average thermal diffusivity kt between 50 120 m is elevated in 2014 2 x 10 5 m2s 1 compared to 2013 1 x 10 6 m2s 1 however vertical atlantic water aw dc heat fluxes in 2013 are remarkably consistent with turbulent heat fluxes in 2014 similar data sets collected in 2007 and 2008 both resemble 2014 showing consistently higher mixing values compared to 2013 the suppression of turbulence during npeo 2013 resulted from increased near surface stratification possibly caused by a different large scale circulation pattern that year

internal waves and tides in the western weddell sea observations from ice station weddell the upper ocean current and temperature fields in the western weddell sea were measured from the drifting pack ice at ice station weddell 1 isw and nearby sites using a vertical profiler and an array of moored sensors in january june 1992 these data document the structure and variability of the internal gravity wave field and tidal currents in this remote region the variance of the internal wave continuum frequency n at isw was 0 2 0 6 of the garrett munk gm universal level for the first 60 days increasing to near gm levels during the final 10 days of the deployment in contrast the energy density at site c 50 km west of isw and farther up the continental slope was always near gm levels variations may be due to a combination of spatial and temporal gradients of the internal wave field at isw coherence between vertically separated sensors was used to estimate vertical wave number bandwidth energy and bandwidth estimates are compared with previous studies in both ice covered and temperate oceans using our measurements of the internal wave field and existing parameterizations of mixing we estimate the vertical heat flux from the warm deep water toward the surface at isw the upward heat flux due to mixing associated with the internal waves was about 1 w m 2 much less than the 20 w m 2 average flux required to balance the heat budget for the weddell gyre tidal currents contributed significantly to the total measured horizontal velocity variance the tides were primarily barotropic and increased toward the west in both the semidiurnal and diurnal frequency bands it is suggested that the stronger tidal currents to the west over the shallower water of the upper continental slope are indirectly responsible for the higher internal wave energy at site c relative to isw

ice flexure forced by internal wave packets in the arctic ocean tiltmeters on the arctic ocean were used to measure flexure of the ice forced by an energetic packet of internal waves riding the crest of diurnal internal bores emanating from the yermak plateau north of the svalbard archipelago the waves forced an oscillatory excursion of 36 microradians in tilt of the ice corresponding to an excursion of 16 micrometers per second in vertical velocity at the surface and of 3 5 millimeters in surface displacement strainmeters embedded in the ice measured an excursion of 3 x 10 7 in strain consistent with ice flexure rather than compression the measured tilt is consistent with direct measurements of excursions in horizontal current near the surface 12 centimeters per second and in vertical displacement 36 meters of the pycnocline 100 meters below the surface

influence of eddy momentum fluxes on the mean flow of the kuroshio extension in a 1 10 ocean general circulation model abstractthis study explores the role of the momentum flux divergence due to mesoscale eddies for the maintenance of the kuroshio extension ke jet for that purpose the zonal momentum budget in a high resolution ocean general circulation model is examined on the basis of the temporal residual mean framework the momentum budget analysis is performed for two control volumes the upstream region of the ke jet flanked by the robust recirculations 33 38 n and 142 2 149 4 e and the downstream region to the east 33 38 n and 149 4 160 0 e both fully covering the meridional width of the ke jet in both regions the ke jet decelerates to the east which can be well accounted for by sum of zonal reynolds stress and coriolis force on mean ageostrophic flow the former tends to decelerate the ke jet and the latter to accelerate it in the upstream region respectively but these effects are switched in the downstream region the mean ageostrophic coriolis force is partially balanced by the horizontal gradien

generation of internal waves by sea ice observations in the greenland sea marginal ice zone suggest that when strong stratification occurs near the surface momentum flux into the internal wave field of the upper ocean can be a major component of the force balance that governs ice drift since energy is radiated away by the internal waves turbulent mixing and heat flux are also affected we investigate the downward flux of momentum and energy by internal waves in an ice covered ocean with an idealized model comprising a mixed layer overlying a deep uniformly stratified layer a buoyancy jump separates the mixed layer from the pycnocline drag from a single wave number component of the under ice roughness spectrum is derived as the product of a drag coefficient based on ice speed under ice roughness wave number and amplitude and uniform stratification to the ice ocean interface times an attenuation factor that depends additionally on mixed layer depth and the buoyancy jump at the base of the mixed layer the model is extended to a plausible spectrum of under ice roughness by integration over wave number space internal wave effects are parameterized in terms of the drag coefficient from the integrated spectrum and incorporated into an upper ocean turbulence model model calculations show that plausible values for the peak wave number of the idealized spectrum and roughness variance can account for 1 decreased ice velocity relative to the wind 2 decreased heat exchange coefficient between the ice and ocean and 3 lack of mixed layer deepening all of which were observed during the last week of the 1984 marginal ice zone experiment

internal wave observations from the arctic environmental drifting buoy a free drifting buoy serving as an ice anchor and flotation sphere for a 125 m instrumented mooring line was deployed in the arctic pack ice by the r v polarstern in august 1987 at the northernmost point achieved by the arktis iv expedition current measurements were made from this arctic environmental drifting buoy aedb using a 150 khz acoustic doppler current profiler adcp attached to the mooring line at a depth of 16 m below the flotation sphere with the transducers facing downward velocity profiles spanning depths between 35 and 327 m with 15 m resolution were collected at half hour intervals over a period of 216 days while the buoy drifted from its starting point near 86 n 22 e to about 70 n 16 w the full experimental record was separated into three sections corresponding to periods of the drift spent in the nansen basin over the yermak plateau and in the greenland sea velocity time series and spectra were computed and results for the three analysis sections were compared spectra in the nansen basin were found to have energy levels significantly less than those typical for mid latitudes roughly one third of the canonical garrett munk gm level and a spectral slope between and 2 5 that was significantly flatter than that expected from the gm model between 83 n and 81 n as the buoy passed over the yermak plateau internal wave energy increased to levels comparable to gm isolated energetic near inertial wave packets with upward group velocity were observed in this portion of the record presumably generated by interaction of the barotropic tide with the bottom topography of the plateau estimates of the upward energy flux from these near inertial packets were comparable to the downward fluxes from typical surface sources interpretation of the greenland sea section was complicated by adcp sampling problems and a lack of argos fixes but the available data showed internal wave spectral levels that were intermediate between those of the nansen basin and yermak plateau and no evidence of upward propagating near inertial energy

generation of submesoscale vortices a new mechanism small scale intense vortices composed of water with anomalous values of quasi conservative tracers have been observed in many oceans they are particularly numerous in the beaufort gyre of the arctic ocean possible mechanisms responsible for the generation of these features are examined conservation of temperature salinity and nutrients requires that beaufort sea vortices be created from water that flows into the arctic ocean from the pacific ocean across the broad shallow chukchi sea much of this water passes through barrow canyon near point barrow alaska observations in the canyon show the generation of vortices of approximately the same size as those observed in the beaufort sea barrow canyon is therefore a likely site for the generation of beaufort sea vortices most observed beaufort sea vortices have a central potential vorticity near zero because of a relative vorticity close to their chukchi sea source water is typically stratified with little relative vorticity so that its potential vorticity is nonzero a key step in the generation of the vortices is therefore the reduction of the potential vorticity of chukchi sea water to nearly zero it is proposed that this occurs through the action of frictional torques occurring as the chukchi sea water flows through barrow canyon rather than througji the action of vertical mixing because this flow is driven by a downstream pressure gradient it is concentrated on the right hand wall of the canyon by the coriolis force the frictional torques thus preferentially reduce the potential vorticity of the fluid anticyclonic vortices are therefore preferentially generated it is suggested that a similar scenario may play a role in the generation of submesoscale vortices containing water from the mediterranean and labrador seas