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

observed energy exchange between low frequency flows and internal waves in the gulf of mexico abstracta long term mooring array deployed in the northern gulf of mexico is used to analyze energy exchange between internal waves and low frequency flows in the subthermocline 245 450 m there

annual cycle and depth penetration of wind generated near inertial internal waves at ocean station papa in the northeast pacific abstractthe downward propagation of near inertial internal waves following winter storms is examined in the context of a 2 yr record of velocity in the upper 800 m at ocean station papa the long time series allow accurate estimation of wave frequency whereas the continuous data in depth allow separation into upward and downward propagating components near inertial kinetic energy kein dominates the record at all measured depths energy in downgoing motions exceeds that of upward propagating motions by factors of 3 7 whereas kein is elevated by a factor of 3 5 in winter relative to summer the two successive winters are qualitatively similar but show important differences in timing and depth penetration energy is seen radiating downward in a finite number of wave groups which are tagged and catalogued to determine the vertical group velocity cgz which has a mean of about 1 5 10 4 m s 1 13 m day 1 case studies of three of these are presented in detail downward energy flux is estimated as cgz

redistribution of energy available for ocean mixing by long range propagation of internal waves ocean mixing which affects pollutant dispersal marine productivity and global climate1 largely results from the breaking of internal gravity waves disturbances propagating along the ocean s internal stratification a global map of internal wave dissipation would be useful in improving climate models but would require knowledge of the sources of internal gravity waves and their propagation towards this goal i present here computations of horizontal internal wave propagation from 60 historical moorings and relate them to the source terms of internal waves as computed previously2 3 analysis of the two most energetic frequency ranges near inertial frequencies and semidiurnal tidal frequencies reveals that the fluxes in both frequency bands are of the order of 1 kw m 1 that is 15 50 of the energy input and are directed away from their respective source regions however the energy flux due to near inertial waves is stronger in winter whereas the tidal fluxes are uniform throughout the year both varieties of internal waves can thus significantly affect the space time distribution of energy available for global mixing

near inertial internal waves and multiple inertial oscillations trapped by negative vorticity anomaly in the central sea of japan abstract this study aims to reveal the interaction between wind induced internal waves and mesoscale features in a frontal region of the central sea of japan a mooring system with an upward looking acoustic doppler current profiler was deployed over a meandering pathway of the tsushima warm current the annual record of horizontal current showed an extraordinary event of near inertial internal waves niws that were trapped in a mesoscale warm core eddy characterized by negative vorticity anomaly near the critical depth inside the eddy where background vorticity vanishes the amplitude of downward traveling niw reached 50 70 cm s 1 in root mean square current magnitude the amplified niws were concurrent with the emergence of superinertial oscillations peaking at multiple inertial mi frequencies i e double triple and quadruple inertial the mi oscillations are regarded as arising through nonlinear resonance of niw examining local surface winds suggest that a fast moving cyclone passing over the site initially generated the niw event the trapping and amplification processes of wind generated niw are examined by a series of ray tracing simulations where background vorticity is reconstructed from in situ hydrographic observations based on the results above a specific picture model of kinetic energy circulation around the sea of japan can be presented the atmospheric event provides momentum energy into the ocean surface resulting in the generation of niws and trapping within anticyclonic vortices a part of the near inertial kinetic energy is then transferred into the mi oscillations if niw is vigorously amplified near the critical depth then it likely dissipates into turbulence

internal swell generation the spatial distribution of energy flux from the wind to mixed layer near inertial motions the energy flux from the wind to inertial mixed layer motions is computed for all oceans from 50 8 st o 508n for the years 1996 99 the wind stress t is computed from 6 h 2 58 resolution ncep ncar global reanalysis surface winds the inertial mixed layer response ui and the energy flux p5 t ui are computed using a slab model the validity of the reanalysis winds and the slab model is demonstrated by direct comparison with wind and adcp velocity records from ndbc buoys at latitudes 508 the inertial response is too fast to be resolved by the reanalysis wind 6 h output interval midlatitude storms produce the greatest fluxes resulting in broad maxima near 40 8 latitude during each hemisphere s winter concentrated in the western portion of each basin northern hemisphere fluxes exceed those in the southern hemisphere by about 50 the global mean energy flux from 1996 to 1999 and 508 st o 508n is 0 98 6 0 08 3 1023 wm 22 for a total power of 0 29 tw 1 tw 5 1012 w this total is the same order of magnitude as recent estimates of the global power input to baroclinic m2 tidal motions suggesting that windgenerated near inertial waves may play an important role in the global energy balance

estimating the mean diapycnal mixing using a finescale strain parameterization abstractfinescale methods are currently being applied to estimate the mean turbulent dissipation rate and diffusivity on regional and global scales this study evaluates finescale estimates derived from isopycnal strain by comparing them with average microstructure profiles from six diverse environments including the equator above ridges near seamounts and in strong currents the finescale strain estimates are derived from at least 10 nearby argo profiles generally 60 km distant with no temporal restrictions including measurements separated by seasons or decades the absence of temporal limits is reasonable in these cases since the authors find the dissipation rate is steady over seasonal time scales at the latitudes being considered 0 30 and 40 50 in contrast a seasonal cycle of a factor of 2 5 in the upper 1000 m is found under storm tracks 30 40 in both hemispheres agreement between the mean dissipation rate calculated using argo profiles and mean from microstructure profiles is wi

storms modify baroclinic energy fluxes in a seasonally stratified shelf sea inertial tidal interaction observations made near the celtic sea shelf edge are used to investigate the interaction between wind generated near inertial oscillations and the semidiurnal internal tide linear baroclinic energy fluxes within the near inertial f and semidiurnal m2 wave bands are calculated from measurements of velocity and density structure at two moorings located 40 km from the internal tidal generation zone over the 2 week deployment period the semidiurnal tide drove 28 48 w m 1 of energy directly on shelf little spring neap variability could be detected horizontal near inertial energy fluxes were an order of magnitude weaker but nonlinear interaction between the vertical shear of inertial oscillations and the vertical velocity associated with the semidiurnal internal tide led to a 25 43 increase in positive on shelf energy flux the phase relationship between f and m2 determines whether this nonlinear interaction enhances or dampens the linear tidal component of the flux and introduces a 2 day counter clockwise beating to the energy transport two very clear contrasting regimes of a tidally and b inertially driven shear and energy flux are captured in the observations

seismic exploration scale velocities and structure from ambient seismic noise 1 hz the successful surface waves retrieval in solid earth seismology using long time correlations and subsequent tomographic images of the crust have sparked interest in extraction of subsurface information from noise in the exploration seismology subsurface information in exploration seismology is usually derived from body wave reflections 1 hz which is challenging for utilization of ambient noise we use 11 h of noise recorded in the sirte basin libya first we study the characteristics of the noise we show that the bulk of the noise is composed of surface waves at frequencies below 6 hz some noise panels contain nearly vertically traveling events we further characterize these events using a beamforming algorithm from the beamforming we conclude that these events represent body wave arrivals with a fairly rich azimuthal distribution having body wave arrivals in the noise is a prerequisite for body wave reflections retrieval we crosscorrelate and sum the recorded ambient noise panels to retrieve common source gathers following two approaches using all the noise and using only noise panels containing body wave arrivals likely to contribute to the reflections retrieval comparing the retrieved gathers with active seismic data we show that the two way traveltimes at short offsets of several retrieved events coincide with those of reflections in the active data and thus correspond to apexes of reflections we then compare retrieved stacked sections of the subsurface from both approaches with the active data stacked section and show that the reflectors are consistent along a line the results from the second approach exhibit the reflectors better

strong inertial currents and marginal internal wave stability in the central north sea solar insolation stabilizes the water column and suppresses vertical exchange observations from the central north sea clearly show that increased heating in summer is accompanied by enhanced de stabilizing vertical current differences shear surprisingly to such extent that the equilibrium state is marginally stable under calm weather conditions the shear is predominantly generated by near inertial motions while the internal wave spectrum primarily results from nonlinear interaction between the dominating tidal and near inertial motions in terms of the associated enhanced vertical mixing across the largest vertical temperature gradients shelf seas are not different from the abyssal ocean despite the proximity to energy sources near boundaries in the former by the lack of sufficiently strong wind and tidal mixing this internal mixing is considered to be responsible for the diapycnal transport of nutrients leading to the observed increase in near surface values and triggering the late summer phytoplankton bloom

quantifying high frequency wind energy flux into near inertial motions in the southeast pacific abstractwind forced internal waves close to the inertial frequency are ubiquitous throughout the world s oceans but observational constraints on their global energetics and impact on subsurface mixing remain scarce this study reports on velocity measurements from three electromagnetic autonomous profiling explorers em apex deployed in february 2009 these floats observed downward propagating near inertial internal waves near the subantarctic and polar fronts of the antarctic circumpolar current these waves were episodic and enhanced at middepth between 500 and 1000 m depth integrated kinetic energy varied between 1 and 7 kj m 2 and averaged 1 6 kj m 2 with typical group velocities of 40 m day 1 implying an average energy flux of 3 mw m 2 at the mixed layer base decreasing to approximately 25 of that value at 1500 m modeled currents forced by reanalysis winds along each float track agree with observed surface currents from em apex provided that mixed layer depth is restricted to the layer of weak

the energy flux from the wind to near inertial motions in the surface mixed layer abstract time series of wind stress computed from long term meteorological buoy data off north america are used to examine the forcing of surface inertial currents by the wind a simple damped slab model of the mixed layer is used to compute h the average flux of energy from the wind to mixed layer inertial currents in a mixed layer of fixed depth h the forcing of mixed layer inertial motions is highly intermittent most of the forcing occurs during the winter months with a few dozen events accounting for typically over half the total energy flux major forcing events are usually associated with translating cold fronts or small lows with scales of about 100 km the larger synoptic scale features have little energy at the inertial frequency and thus result in only weak forcing of inertial currents a strong seasonal signal exists in the inertial forcing at ows p 50 n 145 w 50 m is largest from october to february and is a factor of 12 above the june and july values if seasonally varying

improved global maps and 54 year history of wind work on ocean inertial motions 1 the global distribution and 54 year time dependence of the energy flux from the wind to near inertial motions is computed by driving a slab mixed layer model with ncep ncar reanalysis winds improving upon previous estimates alford 2001 watanabe and hibiya 2002 the slab model is solved spectrally with frequency dependent damping the resulting solutions are more physically sensible than the previous and more skillful at high latitudes where the inertial frequency approaches the 4 daily sampling of the reanalysis winds this enables alford s calculation whose domain was limited to 50 to be extended to the poles the high latitude reliability is demonstrated by direct comparison with a high resolution regional model remo in the ne atlantic the total power input 0 47 tw has increased by 25 since 1948 paralleling observed increases in extratropical cyclone frequency and intensity if believable the trend may have important consequences for modulation of the meridional overturning circulation

the relation of near inertial motions observed in the mixed layer during the jasin 1978 experiment to the local wind stress and to the quasi geostrophic flow field abstract oscillations with near inertial frequencies were an energetic component of the upper ocean velocity field observed at each of two moorings separated by 44 km during the joint air sea interaction jasin experiment during the late summer of 1978 at each mooring the amplitude of the inertial motion was highest in the mixed layer where it was nearly depth independent previous work pollard and millard 1970 pollard 1980 had found that the amplitude and phase of inertial motion in the mixed layer was related to the local wind stress in this case the loacal winds measured at each mooring were coherent but the time series of mixed layer near inertial motion at one mooring bore little resemblance to that at the other mooring during jasin 1978 the differences in the inertial response at the two moorings coincided with differences in the quasi geostrophic flow field in the vicinity of the two moorings inclusion of the horizontal gradients of the quasi geostrophic flow in model equations prov

how important are diapycnal mixing and geothermal heating for the deep circulation of the western mediterranean the dissipation rate of turbulent kinetic energy e and the associated diapycnal turbulent mixing is inferred from a set of microstructure observations collected over several cruises from year 2012 to 2014 the geographical distribution of e highlights several regions of enhanced levels of turbulence ranging from 10 9 to 10 6 w kg 1 the sicily channel the corsica channel and the ligurian sea elsewhere e was small often below 10 10 w kg 1 below 1300 m geothermal heating provides three fold more buoyancy than small scale turbulence geothermal heating and turbulent diffusion provide enough buoyancy to balance 15 to 50 of a mean yearly deep water formation rate of 0 9 to 0 3 sverdrup 106 m3 s respectively the remaining part has to eventually overflow through the strait of gibraltar

global patterns of low mode internal wave propagation part i energy and energy flux abstract extending an earlier attempt to understand long range propagation of the global internal wave field the energy e and horizontal energy flux f are computed for the two gravest baroclinic modes at 80 historical moorings around the globe with bandpass filtering the calculation is performed for the semidiurnal band emphasizing m2 internal tides generated by flow over sloping topography and for the near inertial band emphasizing wind generated waves near the coriolis frequency the time dependence of semidiurnal e and f is first examined at six locations north of the hawaiian ridge e and f typically rise and fall together and can vary by over an order of magnitude at each site this variability typically has a strong spring neap component in addition to longer time scales the observed spring tides at sites northwest of the hawaiian ridge are coherent with barotropic forcing at the ridge but lagged by times consistent with travel at the theoretical mode 1 group speed from the ridge phase c

impact of tidal mixing on water mass transformation and circulation in the south china sea abstractusing a high resolution regional ocean model the impact of tidal mixing on water mass transformation and circulation in the south china sea scs is investigated through a set of numerical experiments with different configurations of tide induced diapycnal diffusivity the results show that including tidal mixing in both the luzon strait ls and scs has significant impact on the ls transport and the intermediate deep layer circulation in the scs basin analysis of the density field indicates that tidal mixing in both the ls and scs are essential for sustaining a consistent density gradient and thus a persistent outward directed baroclinic pressure gradient both between the western pacific and ls and between the ls and scs basin so as to maintain the strong deep water transport through the ls further analysis of water mass properties suggests that tidal mixing in the deep scs would strengthen the horizontal density gradient intensify the basin scale cyclonic circulation induce more vigorous o

reduced mixing from the breaking of internal waves in equatorial waters in the oceans heat salt and nutrients are redistributed much more easily within water masses of uniform density than across surfaces separating waters of different densities but the magnitude and distribution of mixing across density surfaces are also important for the earth s climate as well as the concentrations of organisms most of this mixing occurs where internal waves break overturning the density stratification of the ocean and creating patches of turbulence predictions of the rate at which internal waves dissipate were confirmed earlier at mid latitudes here we present observations of temperature and velocity fluctuations in the pacific and atlantic oceans between 42 degrees n and 2 degrees s to extend that result to equatorial regions we find a strong latitude dependence of dissipation in accordance with the predictions in our observations dissipation rates and accompanying mixing across density surfaces near the equator are less than 10 of those at mid latitudes for a similar background of internal waves reduced mixing close to the equator will have to be taken into account in numerical simulations of ocean dynamics for example in climate change experiments

space time scales of shear in the north pacific abstractthe spatial temporal and directional characteristics of shear are examined in the upper 1400 m of the north pacific during late spring with an array of five profiling moorings deployed from 25 to 37 n 1330 km and simultaneous shipboard transects past them the array extended from a regime of moderate wind generation at the north to south of the critical latitude 28 8 n where parametric subharmonic instability psi can transfer energy from semidiurnal tides to near inertial motions analyses are done in an isopycnal following frame to minimize contamination by doppler shifting approximately 60 of rms shear at vertical scales 20m and 80 for vertical scales 80 m is contained in near inertial motions an inertial back rotation technique is used to index shipboard observations to a common time and to compute integral time scales of the shear layers persistence times are o 7 days at most moorings but o 25 days at the critical latitude simultaneous shipboard transects show that these sh

role of near inertial internal waves in subthermocline diapycnal mixing in the northern gulf of mexico abstractmoored adcp data collected in the northern gulf of mexico are analyzed to examine near inertial internal waves and their contribution to subthermocline diapycnal mixing based on a finescale parameterization of deep ocean mixing the focus of the study is on the impact of near inertial internal waves generated by an extreme weather event that is hurricane katrina and by month to month variation in weather patterns on the diapycnal mixing the inferred subthermocline diapycnal mixing exhibits pronounced elevation in the wake of katrina both the increased near inertial 0 8 1 8f where f is the coriolis frequency and superinertial 1 8f shear variances contribute to the elevated diapycnal mixing but the former plays a more dominant role the intense wind work on near inertial motions by the hurricane is largely responsible for the energetic near inertial shear variance energy transfer from near inertial to superinertial internal waves however appears to play an important role in elevating th

seaglider surveys at ocean station papa circulation and water mass properties in a meander of the north pacific current a seaglider autonomous underwater vehicle augmented the ocean station papa osp 50 n 145 w surface mooring measuring spatial structure on scales relevant to the monthly evolution of the moored time series during each of three missions from june 2008 january 2010 a seaglider made biweekly 50 km 50 km surveys in a bowtie shaped survey track horizontal temperature and salinity gradients measured by these surveys were an order of magnitude stronger than climatological values and sometimes of opposite sign geostrophically inferred circulation was corroborated by moored acoustic doppler current profiler measurements and aviso satellite altimetry estimates of surface currents confirming that glider surveys accurately resolved monthly scale mesoscale spatial structure in contrast to climatological north pacific current circulation upper ocean flow was modestly northward during the first half of the 18 month survey period and weakly westward during its latter half with rossby number 0 01 this change in circulation coincided with a shift from cool and fresh to warm saline oxygen rich water in the upper ocean halocline and an increase in vertical finestructure there and in the lower pycnocline the anomalous flow and abrupt water mass transition were due to the slow growth of an anticyclonic meander within the north pacific current with radius comparable to the scale of the survey pattern originating to the southeast of osp this article is protected by copyright all rights reserved

near inertial kinetic energy budget of the mixed layer and shear evolution in the transition layer in the arabian sea during the monsoons we present the horizontal kinetic energy ke balance of near inertial currents in the mixed layer and explain shear evolution in the transition layer using observations from a mooring at 15 26 n in the arabian sea during the southwest monsoon the highly sheared and stratified transition layer at the mixed layer base varies between 5 m and 35 m and correlates negatively with the wind stress results from the mixed layer near inertial ke nike balance suggest that wind energy at times can energize the transition layer and at other times is fully utilized within the mixed layer a simple two layer model is utilized to study the shear evolution in the transition layer and shown to match well with observations the shear production in this model arises from alignment of wind stress and shear although the winds are unidirectional during the monsoon the shear in the transition layer is predominantly near inertial the near inertial shear bursts in the observations show the same phasing and magnitude at near inertial frequencies as the wind shear alignment term

upper ocean inertial currents forced by a strong storm part i data and comparisons with linear theory abstract a strong isolated october storm generated 0 35 0 7 m s 1 inertia frequency currents in the 40 m deep mixed layer of a 300 km 300 km region of the northeast pacific ocean the authors describe the evolution of these currents and the background flow in which they evolve for nearly a month following the storm instruments included ctd profilers 36 surface drifters an array of 7 moorings and air deployed velocity profilers the authors then test whether the theory of linear internal waves propagating in a homogeneous ocean can explain the observed evolution of the inertial frequency currents the subinertial frequency flow is weak with typical currents of 5 cm s 1 and steady over the period of interest the storm generates inertial frequency currents in and somewhat below the mixed layer with a horizontal scale much larger than the rossby radius of deformation reflecting the large scale and rapid translation speed of the storm this scale is too large for significant linear propagation of the

volcanic rock hosted gold and base metal mineralization associated with neoproterozoic early paleozoic back arc extension in the carolina terrane southern appalachian piedmont volcanogenic mineral deposits in the carolina terrane southern appalachian piedmont include kuroko type polymetallic massive sulfide deposits and disseminated gold pyrite deposits associated with propylitic silicic argillic and advanced argillic alteration host rocks are metavolcaniclastic and metaepiclastic rocks of a neoproterozoic early cambrian magmatic arc the favorable gold horizon is the transition from a lower succession of andesitic and rhyolitic pyroclastic rocks with basal mafic lavas to an upper sequence of epiclastic sedimentary units and minor lava and ash flows kuroko type deposits are associated with mafic to bimodal volcanic rocks in the upper sequence whole rock oxygen isotope analyses indicate that gold mineralization is associated with a transition from hydrothermal systems dominated by isotopically relatively light 18o 6 to 10 waters typical of high latitude subaerial systems to seawater 18o 0 plots of 18o vs sio2 of the host rocks show a compositional gap associated with mineralization at the subaerial to submarine transition values of 18o for the hydrothermal waters lithostratigraphic analyses and tectonic models of the carolina terrane demonstrate that mineralization coincided with extension in a rifted arc

observations of near inertial internal gravity waves radiating from a frontal jet abstractshipboard adcp and towed ctd measurements are presented of a near inertial internal gravity wave radiating away from a zonal jet associated with the subtropical front in the north pacific three dimensional spatial surveys indicate persistent alternating shear layers sloping downward and equatorward from the front as a result depth integrated ageostrophic shear increases sharply equatorward of the front the layers have a vertical wavelength of about 250 m and a slope consistent with a wave of frequency 1 01f they extend at least 100 km south of the front time series confirm that the shear is associated with a downward propagating near inertial wave with frequency within 20 of f a slab mixed layer model forced with shipboard and ncep reanalysis winds suggests that wind forcing was too weak to generate the wave likewise trapping of the near inertial motions at the low vorticity edge of the front can be ruled out because of the extension of the features well south of it instead the authors

estimates of m2 tidal energy dissipation from topex poseidon altimeter data most of the tidal energy dissipation in the ocean occurs in shallow seas as has long been recognized however recent work has suggested that a significant fraction of the dissipation perhaps 1 tw or more occurs in the deep ocean this paper builds further evidence for that conclusion more than 6 years of data from the topex poseidon satellite altimeter are used to map the tidal dissipation rate throughout the world ocean the dissipation rate is estimated as a balance between the rate of working by tidal forces and the energy flux divergence computed using currents derived by least squares fitting of the altimeter data and the shallow water equations such calculations require dynamical assumptions in particular about the nature of dissipation to assess sensitivity of dissipation estimates to input assumptions a large suite of tidal inversions based on a wide range of drag parameterizations and employing both real and synthetic altimeter data are compared these experiments and monte carlo error fields from a generalized inverse model are used to establish error uncertainties for the dissipation estimates owing to the tight constraints on tidal elevation fields provided by the altimeter area integrals of the energy balance are remarkably insensitive to required dynamical assumptions tidal energy dissipation is estimated for all major shallow seas excluding individual polar seas and compared with previous model and data based estimates dissipation in the open ocean is significantly enhanced around major bathymetric features in a manner consistent with simple theories for the generation of baroclinic tides

the impact of oceanic near inertial waves on climate abstractthe community climate system model version 4 ccsm4 is used to assess the climate impact of wind generated near inertial waves niws even with high frequency coupling ccsm4 underestimates the strength of niws so that a parameterization for niws is developed and included into ccsm4 numerous assumptions enter this parameterization the core of which is that the niw velocity signal is detected during the model integration and amplified in the shear computation of the ocean surface boundary layer module it is found that niws deepen the ocean mixed layer by up to 30 but they contribute little to the ventilation and mixing of the ocean below the thermocline however the deepening of the tropical mixed layer by niws leads to a change in tropical sea surface temperature and precipitation atmospheric teleconnections then change the global sea level pressure fields so that the midlatitude westerlies become weaker unfortunately the magnitude of the real air sea flux of niw energy is poorly con

on the behavior of internal waves in the wakes of storms abstract the rossby adjustment process in the wake of a storm is studied with a view to finding within the context of linear theory how wave dispersion in both the vertical and meridional directions spreads energy which is initially confined entirely to the mixed layer comparisons are made between three cases 1 a periodic storm on the f plane where dispersion is purely vertical 2 a bounded storm on the f plane and 3 a bounded storm centered 2700 km from the equator on an equatorial beta plane particular attention is paid to the initial rate of loss of energy from the mixed layer and some simple formulas which work very well in the cases studied are derived these show that the rate of loss goes up when the mixed layer depth is increased and also that the rate scales as the square of the wavenumber values of the rates are sufficient to provide a major source of energy for internal waves below the mixed layer the often observed tendency for phase lines to propagate upward is found in all case

parametric subharmonic instability of the internal tide at 29 n observational evidence is presented for transfer of energy from the internal tide to near inertial motions near 298n in the pacific ocean the transfer is accomplished via parametric subharmonic instability psi which involvesinteractionbetweena primarywave the internaltide in this case andtwo smaller scale waves of nearly half the frequency the internal tide at this location is a complex superposition of a low mode waves propagating north from hawaii and higher mode waves generated at local seamounts making application of psi theory challenging nevertheless a statistically significant phase locking is documented between the internal tide and upward and downward propagating near inertial waves the phase between those three waves is consistent with that expected from psi theory calculated energy transfer rates from the tide to nearinertial motions are modest consistent with local dissipation rate estimates the conclusion is that while psi does befall the tide near a critical latitude of 298n it does not do so catastrophically

a near inertial internal wave spectrum for the sargasso sea in late summer abstract independent estimates of the frequency wavenumber spectrum of near inertial waves for the sargasso sea in late summer were made using 8 time series of horizontal velocity from a single moored vertical array and 58 vertical profiles of horizontal velocity from a horizontal array of expendable velocity profilers the profiler data were analyzed to produce an internal wave frequency wavenumber spectrum with sufficient resolution to resolve the details of the inertial peak and compute the vertical energy flux comparison with the lower resolution spectrum from the moored array shows qualitative agreement the differences are most likely due to biases in both techniques and to intermittency of the internal wave field these data reveal a marked asymmetry of the near inertial internal wave field with a net downward enemy flux of 0 12 0 12 ergs cm 2 s 1 the downward propagating waves have more energy a larger horizontal scale and a lower frequency than the upward propagating waves the magnitude of t

longitudinal and topographic variations in north atlantic tidal and inertial energy around latitudes 30 10 n 1 open ocean kinetic energy is investigated at dominant inertial and semidiurnal tidal frequencies using historic current observations from the north atlantic ocean around midlatitudes focus is on possible energy variations due to major topography changes between the eastern canary and western hatteras sohm basins thereby crossing the mid atlantic ridge mar while in open basins on both sides of mar semidiurnal kinetic energy drops in magnitude by some 50 between latitudes 20 n 28 n in agreement with tpxo elevation data an even larger longitudinal dependence is observed west of mar semidiurnal energy is up to 30 times less than east of it inertial kinetic energy is either decreasing by a factor of 2 4 westward or more or less independent of longitude this contrasts strongly with westward intensified near surface inertial energy fluxes previously found the latter fluxes also did not show an increase by a factor of 5 10 for 25 n 30 n as observed here for inertial energy in both basins west of mar the internal wave background level for frequencies up to sixth diurnal is much less by a factor of 3 10 at tidal inertial interaction frequencies than east of mar no significant atmospheric or large scale vorticity influence or seasonal variations therein is found on inertial energy content across the basin as no individual peaks are observed at frequencies k1 o1 and m1 s1 direct diurnal tidal forcing and subharmonic resonance must be accompanied by nonlinear interactions in possibly enhancing inertial energy at the critical diurnal latitude

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

internal waves and mixing near the kerguelen plateau abstractin the stratified ocean turbulent mixing is primarily attributed to the breaking of internal waves as such internal waves provide a link between large scale forcing and small scale mixing the internal wave field north of the kerguelen plateau is characterized using 914 high resolution hydrographic profiles from novel electromagnetic autonomous profiling explorer em apex floats altogether 46 coherent features are identified in the em apex velocity profiles and interpreted in terms of internal wave kinematics the large number of internal waves analyzed provides a quantitative framework for characterizing spatial variations in the internal wave field and for resolving generation versus propagation dynamics internal waves observed near the kerguelen plateau have a mean vertical wavelength of 200 m a mean horizontal wavelength of 15 km a mean period of 16 h and a mean horizontal group velocity of 3 cm s 1 the internal wave characteristics are dependent on regional dynamics suggesting tha

significant dissipation of tidal energy in the deep ocean inferred from satellite altimeter data how and where the ocean tides dissipate their energy are long standing questions1 that have consequences ranging from the history of the moon2 to the mixing of the oceans3 historically the principal sink of tidal energy has been thought to be bottom friction in shallow seas4 5 there has long been suggestive evidence6 7 however that tidal dissipation also occurs in the open ocean through the scattering by ocean bottom topography of surface tides into internal waves but estimates of the magnitude of this possible sink have varied widely3 8 9 10 11 here we use satellite altimeter data from topex poseidon to map empirically the tidal energy dissipation we show that approximately 1012 watts that is 1 tw representing 25 30 of the total dissipation occurs in the deep ocean generally near areas of rough topography of the estimated 2 tw of mixing energy required to maintain the large scale thermohaline circulation of the ocean12 one half could therefore be provided by the tides with the other half coming from action13 on the surface of the ocean

on the nature of internal wave spectra near a continental slope 1 amongst the most energetic motions in the deep ocean are internal waves supported by stable vertical stratification in density previously these waves were considered freely propagating as described by a smooth continuum internal wave band iwb frequency spectrum we studied details of the iwb using yearlong current observations from the bay of biscay instead of observing continuum iwb spectra near a continental slope we show that at least the first half decade of the iwb is dominated by motions at localized frequencies determined by strong non linear interactions between waves at the fundamental semidiurnal tidal and atmospherically induced inertial frequencies

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

spatial and temporal variability of global ocean mixing inferred from argo profiles 1 the influence of turbulent ocean mixing transcends its inherently small scales to affect large scale ocean processes including water mass transformation stratification maintenance and the overturning circulation however the distribution of ocean mixing is not well described by sparse ship based observations since this mixing is both spatially patchy and temporally intermittent we use strain information from argo float profiles in the upper 2 000 m of the ocean to generate over 400 000 estimates of the energy dissipation rate indicative of ocean mixing these estimates rely on numerous assumptions and do not take the place of direct measurement methods temporally averaged estimates reveal clear spatial patterns in the parameterized dissipation rate and diffusivity distribution across all the oceans they corroborate previous observations linking elevated dissipation rates to regions of rough topography we also observe heightened estimated dissipation rates in areas of high eddy kinetic energy as well as heightened diffusivity in high latitudes where stratification is weak the seasonal dependence of mixing is observed in the northwest pacific suggesting a wind forced response in the upper ocean

sustained full water column observations of internal waves and mixing near mendocino escarpment abstract the relative strength and spatiotemporal structure of near inertial waves niw and internal tides it are examined in the context of recent moored observations made 19 km south of mendocino escarpment an abrupt ridge step feature in the eastern pacific in addition to strong internal tide generation steps and ridges give rise to the possibility of shadowing wherein near inertial energy is prevented from reaching depths beneath a characteristic intersecting the ridge top a combination of two moored profilers and a long range acoustic doppler current profiler adcp yielded velocity and shear measurements from 100 to 3640 m 60 m above bottom and isopycnal depth strain and overturn inferred turbulence dissipation rate from 1000 to 3640 m sampling intervals 20 min in the upper 1000 m and 1 5 h below that were fast enough to minimize aliasing of higher frequency internal wave motions the 67 day long record is easily sufficient to isolate niw and it via bandpass filtering and to capture

doppler sonar observations of internal waves the wavenumber frequency spectrum abstract in may 1980 an 18 day sequence of velocity profiles of the top 600 m of the sea was collected off the coast of southern california the measurements were obtained using a pair of doppler sonars mounted on the research platform flip from these data estimates of the wavenumber frequency spectrum of the oceanic internal wavefield are obtained the spectra are characterized by a series of ridges which occur at near internal and tidal frequencies as well as higher harmonics and sums of these fundamentals the ridges run parallel to the wavenumber axis there is a pronounced near inertial spectral peak the near inertial motions are dominated by a few identifiable wave groups there is a net downward energy propagation in the near inertial frequency band the vertical wavenumber dependence of a the spectrum is decidedly asymmetric in this region the asymmetry extends to five times the inertial frequency making much of the so called continuum asymmetric a high wavenumber cutoff at approximately 60

decay of a near inertial wave abstract the decay of a downward propagating near inertial wave was observed over four days during this short period the energy of the near inertial wave decreased by 70 the shear layers produced by the wave were regions of enhanced turbulent dissipation rates the authors estimate that 44 of the observed change in the near inertial energy was lost to turbulence estimates of the wave energy lost at the survey site due to the wave propagating out of the region were smaller energy lost by horizontal advection of the wave out of the survey region was more difficult to estimate the horizontal extent of the near inertial energy was unknown advection could account for more than half of the observed energy lost however the authors did not detect the near inertial wave during a 40 km 40 km adcp survey after completing the six day station

observations of the transition layer abstract the transition layer is the poorly understood interface between the stratified weakly turbulent interior and the strongly turbulent surface mixed layer the transition layer displays elevated thermohaline variance compared to the interior and maxima in current shear vertical stratification and potential vorticity a database of 91 916 km or 25 426 vertical profiles of temperature and salinity from seasoar a towed vehicle is used to define the transition layer thickness acoustic doppler current measurements are also used when available statistics of the transition layer thickness are compared for 232 straight seasoar sections which range in length from 65 to 1129 km with typical horizontal resolution of 4 km and vertical resolution of 8 m transition layer thicknesses are calculated in three groups from 1 vertical displacements of the mixed layer base and of interior isopycnals into the mixed layer 2 the depths below the mixed layer depth of peaks in shear stratification and potenti

internal tide radiation from mendocino escarpment abstract strong semidiurnal internal tides are observed near mendocino escarpment in full depth profile time series of velocity temperature and salinity velocity and density profiles are combined to estimate the internal tide energy flux divergence of this flux demonstrates that its source is the barotropic tide interacting with the escarpment a baroclinic energy flux of 7 kw m 1 radiates from the escarpment corresponding to 3 of the 220 kw m 1 fluxing poleward in the surface tide energy and energy flux are concentrated in packets that emanate from the flanks of the ridge surmounting the escarpment and one site 90 km north of the escarpment coherent beamlike structure along semidiurnal ray paths remains identifiable until the first surface reflection beyond the first surface reflection north of the escarpment the energy flux drops by 2 kw m 1 and beams are no longer discernible turbulence as inferred from finescale parameterizations is elevated by over two orders of magnitude relative to th