numerical modelling of sea surface temperature and circulation in the great australian bight abstract the blumberg mellor 3d numerical ocean model was employed to investigate the seasonal cycle of sea surface temperature sst and circulation within the great australian bight gab an idealised representation of the gab was modelled results indicated that a warm water mass could be established within the gab with features comparable to observation due to the application of a positive net heat flux at the surface and forcing from the west to east passage of anticyclonic weather systems these systems had a north south migration representative of the shifting subtropical high pressure ridge over southern australia an anticyclonic gyre was established within the gab as a result of the imposed wind stress which contributed towards the formation of a warm tongue spreading across the gab from west to east and a pool of significantly colder water in the eastern gab the sst distribution was found to be sensitive to the bottom topography and north south gradient of heat flux applied to the model domain intrusion of an external current through the western boundary in winter representing the leeuwin current revealed that warm water associated with the intrusion did not penetrate into the gab to any great distance

midshelf to surfzone coupled roms swan model data comparison of waves currents and temperature diagnosis of subtidal forcings and response abstracta coupled wave and circulation model that includes tide wind buoyancy and wave processes is necessary to investigate tracer exchange in the shelf region here a coupled regional ocean model system roms simulating waves nearshore swan model resolving midshelf to the surfzone region of the san pedro bay california is compared to observations from the 2006 huntington beach experiment waves are well modeled and surfzone cross and alongshore velocities are reasonably well modeled modeled and observed rotary velocity spectra compare well in subtidal and tidal bands and temperature spectra compare well in the subtidal band observed and modeled mid and inner shelf subtidal velocity ellipses and temperature variability determined from the first vertical complex eof ceof mode have similar vertical structure although the modeled subtidal velocity vertical shear and stratification are weaker than observed the ratio of stratification to shear is similar suggesting model vertical mixing i

the adjoint method of data assimilation used operationally for shelf circulation a real time shelf circulation model with data assimilation has been successfully used possibly for the first time on the outer nova scotian shelf the adjoint method was used to infer the time histories of flows across the four open boundaries of a 60 km 60 km shallow water equation model of western bank the aim was to hindcast and nowcast currents over the bank so that a patch of water initially 15 km in diameter could be resampled over a 3 week period as part of a study of the early life history of atlantic cod observations available in near real time for assimilation were from 14 drifting buoys 2 telemetering moored current meters the ship s acoustic doppler current profiler and the local wind for the postcruise hindcasts presented here data from two bottom pressure gauges and two more current meters are also available the experiment was successful and the patch was sampled over a 19 day period that included two intense storms in this paper we 1 document the model and how the data are assimilated 2 present and discuss the observations 3 demonstrate that the interpolative skill of the model exceeds that of simpler schemes that use just the current velocity data and 4 provide examples of how particle tracking with the model enables asynoptically acquired data to be displayed as synoptic maps greatly facilitating both underway cruise planning and postcruise data analysis an interesting feature of the circulation on the bank was a nearly stationary eddy atop the bank crest larvae within the eddy were retained on the bank in a favorable environment until the onset of the storms the variable integrity of the eddy may contribute to fluctuations of year class success

perth bermuda sound propagation 1960 adiabatic mode interpretation a 1960 experiment is examined in which sound from three underwater explosions near perth australia was detected near bermuda a recent attempt munk et al j phys ocean 18 1876 1988 to calculate propagation paths for this event included rotational flattening of the earth and horizontal refraction determined from the vertical sound speed minimum that calculation left bermuda in a shadow zone the current work invokes adiabatic mode theory to include refraction due to horizontal variations in the vertical mode structure these results include separate horizontal rays for each of the first few vertical modes using an archival data set of 230 ocean sound profiles to generate the modes numerically where appropriate interaction with bathymetry is included this solution possesses two eigenray groups group a passes just south of the cape of good hope at which point group b is almost 1000 km to the south intermediate rays are blocked by islands group a proceeds unimpeded to bermuda for a total t

australia bermuda sound transmission experiment 1960 revisited abstract detonations at the depth of the sound channel axis off perth australia were recorded on bermuda hydrophones at a 178 2 range 180 is antipodal the analysis by shockley et al of this 1960 transmission experiment allows for the geographic variation in the sound speed profile along the great circle path the agreement between measured and computed travel times is within 10 s we have modified the shockley et al analysis by allowing for earth flattening and lateral refraction the appropriate path on an ellipsoidal earth is the geodesic and this differs significantly from the put circle for nearly antipodal ranges the southernmost point of the geodesic is at 52 1 s as compared to 47 3 s for the great circle and the geodesic travel time lags the great circle travel time by an unacceptable 34 s on account of the cold slow waters at high southern latitudes the effect of lateral refraction is in the opposite sense the appropriate refracted ray path is northward of the great circle in fact

a numerical modeling study of the east australian current encircling and overwashing a warm core eddy 1 warm core eddies wces often form in the meanders of western boundary currents wbcs wces are frequently overwashed with less dense waters sourced from the wbc we use the regional ocean modelling system to investigate the ocean state during the overwashing of one such wce in october 2008 in the east australian current eac comparisons of model outputs with satellite sea surface temperature and vertical profiles show that the model provides a realistic simulation of the eddy during the period when the eac encircled and then overwashed the eddy during the encircling stage an eddy with closed circulation persisted at depth in the surface eac water entered from the north encircled the eddy and exited to the east the overwashing stage was initiated by the expulsion of cyclonic vorticity for the following 8 days after the expulsion waters from the eac washed over the top of the eddy transferring heat and anticyclonic vorticity radially inward after approximately one rotation period of overwashing the eddy separated the overwashing creates a two layer system that forms a subsurface maximum velocity at the interface of the two layers analysis of water mass properties eulerian tracer dynamics and lagrangian particle tracks show that the original eddy sinks 10 50 m during the overwashing period overwashing has been observed in many wbcs and occurs in most wces in the western tasman sea

coupled wind forced controls of the bering chukchi shelf circulation and the bering strait throughflow ekman transport continental shelf waves and variations of the pacific arctic sea surface height gradient abstract we develop a conceptual model of the closely co dependent bering shelf bering strait and chukchi shelf circulation fields by evaluating the effects of wind stress over the north pacific and western arctic using atmospheric reanalyses current meter observations satellite based sea surface height ssh measurements hydrographic profiles and numerical model integrations this conceptual model suggests bering strait transport anomalies are primarily set by the longitudinal location of the aleutian low which drives oppositely signed anomalies at synoptic and annual time scales synoptic time scale variations in shelf currents result from local wind forcing and remotely generated continental shelf waves whereas annual variations are driven by basin scale adjustments to wind stress that alter the magnitude of the along strait meridional pressure gradient in particular we show that storms centered over the bering sea excite continental shelf waves on the eastern bering shelf that carry northward velocity anomalies northward through bering strait and along the chukchi coast the integrated effect of these storms tends to decrease the northward bering strait transport at annual to decadal time scales by imposing cyclonic wind stress curl over the aleutian basin and the western subarctic gyre ekman suction then increases the water column density through isopycnal uplift thereby decreasing the dynamic height sea surface height and along strait pressure gradient storms displaced eastward over the gulf of alaska generate an opposite set of bering shelf and aleutian basin responses while ekman pumping controls canada basin dynamic heights proshutinsky et al 2002 we do not find evidence for a strong relation between beaufort gyre sea surface height variations and the annually averaged bering strait throughflow over the western chukchi and east siberian seas easterly winds promote coastal divergence which also increases the along strait pressure head as well as generates shelf waves that impinge upon bering strait from the northwest

wigwam reverberation revisited operation wigwam was a test of a 30 kt nuclear depth charge conducted in deep water 500 miles southwest of san diego on 14 may 1955 its primary purpose was to determine the effectiveness of that device as an antisubmarine weapon the acoustic pulse from the test initially an intense shockwave radiated throughout the north and south pacific oceans acoustic reflections from topographic features were recorded for several hours after the explosion by sound fixing and ranging sofar hydrophones at point sur california and kaneohe hawaii sheehy and halley 1957 identified peaks of the recorded coda with reflections from specific topographic features at great distances e g the hawaiian islands french polynesia or fiji with modern data for seafloor topography and ocean sound speed these coda were computed with surprising accuracy using simple geodesic rays reflected from islands and seamounts the intensity variations of the coda are mostly determined by simple ray geometry together with modest attenuation coda peaks are often obtained from rays arriving simultaneously from multiple but disparate topographic features online material figures of computed and measured coda and associated geodesic paths

measurements of the aeolian sand transport saturation length the wavelength at which a dune pattern emerges from a flat sand bed is controlled by the sediment transport saturation length which is the length needed for the sand flux to adapt to a change in wind strength the influence of the wind shear velocity on this saturation length and on the subsequent dune initial wavelength has remained controversial in this paper we present direct measurements of the saturation length performed in a wind tunnel experiment complementary to this initial dune wavelengths are measured under different wind conditions in particular after storms using the linear stability analysis of dune formation it is then possible to deduce the saturation length from field data both direct and indirect measurements agree that the saturation length is almost independent of the wind strength this result supports the idea that grain inertia is the dominant dynamical mechanism limiting sediment transport saturation on dunes

numerical model simulations of continental shelf flows off northern california abstract the three dimensional circulation on the continental shelf off northern california in the wind events and shelf transport west experiment region during summer 2001 is studied using the primitive equation regional ocean modeling system roms the simulations are performed with realistic topography and initial stratification in a limited area domain with a high resolution grid forcing consists of measured wind stress and heat flux values obtained from a west surface buoy the general response shows a southward coastal upwelling jet of up to 1 m s 1 and a weakening or reversal of currents inshore of the jet when upwelling winds relax model results are compared to west moored velocity and temperature measurements at five locations to codar surface current observations between pt reyes and bodega bay and to hydrographic measurements along shipboard survey lines the model performs reasonably well with the highest depth averaged velocity correlation 0 81 at the inshore mooring 40 m water depth and lowest correlation 0 68 at the mid depth mooring 90 m depth the model shows generally stronger velocities than those observed especially at the inshore moorings and a lack in complete reversal of southward velocities observed when upwelling winds relax the comparison of surface velocities with codar measurements shows good agreement of the mean and the dominant mode of variability the hydrography compares closely at the southern and northern edges of the survey region correlation coefficients between 0 90 and 0 97 with weaker correlations at the three interior survey lines correlation coefficients between 0 44 and 0 76 mean model fields over the summer upwelling period show slight coastal jet separation off pt arena and significant separation off pt reyes the cape regions also experience relatively strong bottom velocities and nonlinearity in the surface flow across shelf velocity sections examined along the shelf reveal a double jet structure that appears just north of bodega bay and shows the offshore jet strengthening to the south we examine the dynamics during an upwelling and subsequent relaxation event in may 2001 in which the west measurements show evidence of a strong flow response the alongshelf variability in the upwelling and relaxation response introduced by pt reyes is evident analysis of term balances from the depth averaged momentum equations helps to clarify the event dynamics in different regions over the shelf a clear pattern in the nonlinear advection term is due to the spatial acceleration of the southward jet around the capes of pt arena and pt reyes during upwelling results from a three dimensional lagrangian analysis of water parcel displacement show significant southward displacement in the coastal jet region including a strong signal from the double jet alongshelf variability in parcel displacements and upwelling source waters due to the presence of pt arena and pt reyes is also apparent from the lagrangian fields a cyclonic eddy like recirculation feature offshore of pt arena prior to the upwelling event causes large patches of onshore displaced parcels additionally across shelf variability in the response of water parcels along the d line includes decreased vertical displacement and increased alongshelf displacement in the offshore direction

wind driven circulation in a shelf valley part ii dynamics of the along valley velocity and transport abstractthe dynamics controlling the along valley cross shelf flow in idealized shallow shelf valleys with small to moderate burger number are investigated and analytical scales of the along val

a reflected energy prediction model for long range hydroacoustic reflection in the oceans acoustic energy from underwater earthquakes and explosions can propagate over long distances with very little attenuation in the deep ocean when this sound encounters a seamount island or continental margin it can scatter and again propagate over long distances hydrophones in the deep sound channel can detect these reflections tens of minutes or hours after arrivals from the direct source to receiver path this paper presents the reflected energy prediction rep model a model for predicting these reflected arrivals for a given source and receiver the rep model uses a detailed knowledge of the underwater environment and components of the hydroacoustic coverage assessment model hydrocam to predict the impulse response of the ocean when this impulse response is convolved with a source function a waveform envelope prediction is made that can be compared with recorded data in this paper we present the model and a few applications of the model using data recorded from earthquakes and explosions in the atlantic and indian oceans these examples illustrate the use of the model and initial steps toward model calibration

stability of the kuroshio path with respect to glacial sea level lowering 1 we investigate the changes of the kuroshio current in the east china sea during the last glacial maximum based on numerical experiments using an ocean model and geochemical analyses of marine sediments our numerical experimental results indicate that there was little effect of sea level change on the path of the kuroshio during the glacial period geochemical proxy records of marine sediment cores recovered from inside and outside the okinawa trough ot show no significant difference in glacial sea surface temperature and planktonic foraminiferal 18o between the ot and the ryukyu forearc this indicates that the glacial sea surface temperature and salinity were almost the same inside and outside the ot hence during the glacial period kuroshio water most likely intruded into the ot and flowed along the shelf break until it drained out through the tokara strait

a decade of acoustic thermometry in the north pacific ocean 1 over the decade 1996 2006 acoustic sources located off central california 1996 1999 and north of kauai 1997 1999 2002 2006 transmitted to receivers distributed throughout the northeast and north central pacific the acoustic travel times are inherently spatially integrating which suppresses mesoscale variability and provides a precise measure of ray averaged temperature daily average travel times at 4 day intervals provide excellent temporal resolution of the large scale thermal field the interannual seasonal and shorter period variability is large with substantial changes sometimes occurring in only a few weeks linear trends estimated over the decade are small compared to the interannual variability and inconsistent from path to path with some acoustic paths warming slightly and others cooling slightly the measured travel times are compared with travel times derived from four independent estimates of the north pacific 1 climatology as represented by the world ocean atlas 2005 woa05 2 objective analysis of the upper ocean temperature field derived from satellite altimetry and in situ profiles 3 an analysis provided by the estimating the circulation and climate of the ocean project as implemented at the jet propulsion laboratory jpl ecco and 4 simulation results from a high resolution configuration of the parallel ocean program pop model the acoustic data show that woa05 is a better estimate of the time mean hydrography than either the jpl ecco or the pop estimates both of which proved incapable of reproducing the observed acoustic arrival patterns the comparisons of time series provide a stringent test of the large scale temperature variability in the models the differences are sometimes substantial indicating that acoustic thermometry data can provide significant additional constraints for numerical ocean models

wind relaxation and a coastal buoyant plume north of pt conception ca observations simulations and scalings in upwelling regions wind relaxations lead to poleward propagating warm water plumes that are important to coastal ecosystems the coastal ocean response to wind relaxation around pt conception ca is simulated with a regional ocean model roms forced by realistic surface and lateral boundary conditions including tidal processes the model reproduces well the statistics of observed subtidal water column temperature and velocity at both outer and inner shelf mooring locations throughout the study a poleward propagating plume of southern california bight water that increases shelf water temperatures by 5 c is also reproduced modeled plume propagation speed spatial scales and flow structure are consistent with a theoretical scaling for coastal buoyant plumes with both surface trapped and slope controlled dynamics plume momentum balances are distinct between the offshore 30 m depth region where the plume is surface trapped and onshore of the 30 m isobath within 5 km from shore where the plume water mass extends to the bottom and is slope controlled in the onshore region bottom stress is important in the alongshore momentum equation and generates vertical vorticity that is an order of magnitude larger than the vorticity in the plume core numerical experiments without tidal forcing show that modeled surface temperatures are biased 0 5 c high potentially affecting plume propagation distance and persistence

a study of tropical cyclone influence on the generation of internal tides 1 an investigation is made into modifications of the semidiurnal internal tide on the western australian shelf by a passing tropical cyclone current mooring observations are presented taken during the passage of tropical cyclone bobby 1995 over these mooring locations the observations reveal large vertical excursions at near inertial frequency of the isotherm during and following the cyclone s passage this coincides with diminishing semidiurnal baroclinic tides to gain dynamical insight into the observations a fully three dimensional free surface nonlinear hydrostatic model is applied to the western australian shelf the model is initialized with realistic stratification and forced by representative tides and cyclone winds the wind forcing is derived from an idealized analytical cyclone model prescribed from observed cyclone track and central pressure data and the tidal forcing allows for the generation of internal tides the cyclone modifies stratification by turbulent mixing upwelling downwelling and density advection up or down the shelf slope this results in significant changes to internal tide characteristic paths and hence the internal tide generation process on the continental slope mixing is enhanced over the shelf due to shallow topography with respect to the shelf slope region creating a strong density front at the shelf edge observations and modeling show that the water column response to the cyclone passage is most abrupt in shallow water at 125 m then at 300 m depth the model reproduces the main features of the observed inertial oscillations concomitant with the dampening of m2 internal tides after the passage of the cyclone

long term observations of alaska coastal current in the northern gulf of alaska abstract the alaska coastal current is a continuous well defined system extending for 1700 km along the coast of alaska from seward alaska to samalga pass in the aleutian islands the currents in this region are examined using data collected at 20 mooring sites and from 400 satellite tracked drifters while not continuous the mooring data span a 30 year period 1984 2014 using current meter data collected at a dozen mooring sites spread over four lines seward gore point kennedy and stevenson entrances and the exit to shelikof strait total transport was calculated transport was significantly correlated with alongshore winds although the correlation at the seward line was weak the largest mean transport in the alaska coastal current occurred at gore point 1 4 10 6 m 3 s 1 in winter and 0 6 10 6 m 3 s 1 in summer with the transport at the exit to shelikof strait 1 3 10 6 m 3 s 1 in winter and 0 6 10 6 m 3 s 1 in summer only slightly less the transport was modified at the seward line in late summer and fall by frontal undulations associated with strong river discharge that enters onto the shelf at that time of year the interaction of the alaska coastal current and tidal currents with shallow banks in the vicinity of kodiak archipeligo and in kennedy stevenson entrance results in mixing and prolonged primary production throughout the summer

a test of basin scale acoustic thermometry using a large aperture vertical array at 3250 km range in the eastern north pacific ocean broadband acoustic signals were transmitted during november 1994 from a 75 hz source suspended near the depth of the sound channel axis to a 700 m long vertical receiving array approximately 3250 km distant in the eastern north pacific ocean the early part of the arrival pattern consists of raylike wave fronts that are resolvable identifiable and stable the later part of the arrival pattern does not contain identifiable raylike arrivals due to scattering from internal wave induced sound speed fluctuations the observed ray travel times differ from ray predictions based on the sound speed field constructed using nearly concurrent temperature and salinity measurements by more than a priori variability estimates suggesting that the equation used to compute sound speed requires refinement the range averaged ocean sound speed can be determined with an uncertainty of about 0 05 m s from the observed ray travel times together with the time at which the near axial acoustic reception ends used as a surroga

the m2 tide on the amazon shelf as part of a multidisciplinary amazon shelf sediment study amasseds moored and shipboard current measurements made over the amazon shelf during 1990 1991 have been analyzed to determine the dominant semidiurnal tidal constituent the m2 these results have been combined with coastal sea level data from within the amazon and para rivers the adjacent shelf and with satellite derived tidal elevation data from off the shelf to provide a more complete description of the m2 tide in this complex river shelf system near the amazon river mouth the m2 tide propagates across the shelf and through the mouth as a damped progressive wave with its amplitude decreasing and phase increasing upriver over the adjacent shelf north of cabo norte the m2 tide approaches a damped standing wave with large amplitudes greater than 1 5 m near the coast due to near resonance within the coastal embayment formed by the cabo norte shoal to the south and cabo cassipore to the north the observed m2 tidal currents are nearly rectilinear and oriented primarily across the local isobaths comparisons between tidal observations in both the north channel and the cabo norte cabo cassipore embayment and a simple variable width channel tidal model indicate that 1 most of the m2 tidal energy dissipation occurs over the mid and inner shelf in water depths less than 20 m and 2 fluid muds found there cause a significant reduction of order 50 in the effective bottom friction felt by the m2 tide the approximate resonant period of the cabo norte cabo cassipore embayment is 11 9 hours and at resonance the average energy dissipation per forcing period is roughly 2 2 times the average mechanical energy in the embayment this damping rate is large enough that the tidal amplification is rather insensitive to forcing frequency so that the response of the embayment to forcing over the semidiurnal band should be essentially the same the vertical structure of the m2 tidal current is examined at one outer shelf site located in 65 m water depth the observed semimajor axis increases logarithmically with height above bottom within the lowest 1 2 m and reaches a maximum in excess of 0 5 m s at approximately 11 m above bottom the mean ellipticity is small less than 0 1 and positive indicating clockwise rotation of a nearly rectilinear current and the semimajor axis is oriented within 10 of the local cross isobath direction the m2 phase increases with height above bottom with flood at the bottom leading flood at the surface by about 1 hour a simple local homogeneous tidal model with time and space dependent eddy viscosity simulates the observed near bottom velocity reasonably well however the model suggests that stratification above the lowest few meters may significantly affect the tidal boundary layer structure at this site the m2 energy flux onto the amazon shelf and into the amazon and para rivers has been estimated using current and surface elevation data and the best fit variable width channel model results the net m2 energy flux into the mouths of the amazon and para rivers is 0 47 1010w and 0 19 1010w respectively a net m2 energy flux of about 3 3 1010w occurs onto the shelf between the north channel of the amazon river and cabo cassipore this stretch of the amazon shelf accounts for about 1 3 of the global dissipation of the m2 tide

the effects of tides and oscillatory winds on the subtidal inner shelf cross shelf circulation a two dimensional numerical model is used to investigate the effects of tidal forcing and oscillatory winds on the subtidal cross shelf circulation on the inner shelf bottom topography and initial stratification are representative of the south and middle atlantic bights along the u s east coast results from simulations forced by upwelling winds and no tides are consistent with previous studies of inner shelf circulation the inclusion of tidal forcing leads to increased mixing larger eddy viscosity coefficients and reduced stratification over the shallow regions effectively reducing the wind efficiency to drive cross shelf currents on the inner shelf tidally averaged cross shelf currents are weaker compared to when no tides are considered there is an increase in the width of the region of surface wind driven transport divergence which changes the crossshelf location where upwelling occurs lagrangian analyses indicate that tidal forcing substantially reduces the transport of offshore waters toward the coast and increases the residence time over the inner shelf by up to 70 fluctuating winds with zero mean lead to a rectification of the cross shelf flow on the inner shelf resulting in net upwelling the rectification occurs because the cross shelf transport is nonzero during upwelling wind forcing since dense water is brought to the inner shelf maintaining the stratification but is approximately zero during downwelling winds since surface water is forced under near bottom water destroying the stratification the rectification is more clearly observed when stratification is strong when tidal forcing is weak or absent and when the wind fluctuates at low frequency

transport of riverine sediment from different outlets in the pearl river estuary during the wet season abstract riverine sediment is important for the development of river deltas and for carrying both nutrients and contaminants into estuaries and coasts previous studies of sediment transport have focused on single sourced estuaries and paid less attention to multi sourced estuaries estuaries with multiple river discharge sources in this study we used the coupled ocean atmosphere wave sediment transport coawst modeling system to study the sediment transport in the pearl river estuary pre where riverine sediments come from four different outlets during a typical wet season 2007 about 6 8 million tons of riverine sediments were discharged into the pre most of which were trapped in shoals during neap tides while about 11 8 by mass was transported out of the estuary during spring tides the proportions of the multi sourced sediments trapped in the pre or escaping from the estuary depended on the morphology of the estuary and the location of the outlets in relation to the estuarine morphology the distributions of different riverine sediments were mostly independent in neap tides but overlapped more in spring tides the seaward sediment transport was dominated by river freshwater discharge in the upper estuary and by tidal forcing in the lower channels while tides and winds controlled the sediment transport in the lower shoals this study aids our understanding of sediment transport processes in multi sourced estuaries and has implications for coastal environmental management

assessing the horizontal refraction of ocean acoustic tomography signals using high resolution ocean state estimates the analysis of signals for acoustic tomography sent between a source and a receiver most often uses the unrefracted geodesic path an approximation that is justified from theoretical considerations relying on estimates of horizontal gradients of sound speed or on simple theoretical models to quantify the effects of horizontal refraction caused by a realistic ocean environment horizontal refractions of long range signals were computed using global ocean state estimates for 2004 from the estimating the circulation and climate of the ocean ecco2 project basin scale paths in the eastern north pacific ocean and regional scale paths in the philippine sea were used as examples at o 5 mm basin scales refracted geodesic and geodesic paths differed by only about 5 km gyre scale features had the greatest refractive influence but the precise refractive effects depended on the path geometry with respect to oceanographic features refraction decreased travel times by 5 10 ms and changed azimuthal angles by about 0 2 at o 500 km regional scales paths deviated from the geodesic by only 250 m and travel times deviated by less than 0 5 ms such effects are of little consequence in the analysis of tomographic data refraction details depend only slightly on mode number and frequency

on the time mean state of ocean models and the properties of long range acoustic propagation 1 receptions on three vertical hydrophone arrays from basin scale acoustic transmissions in the north pacific during 1996 and 1998 are used to test the time mean sound speed properties of the world ocean atlas 2005 woa05 of an eddying unconstrained simulation of the parallel ocean program pop and of three data constrained solutions provided by the estimating the circulation and climate of the ocean ecco project a solution based on an approximate kalman filter from the jet propulsion laboratory ecco jpl a solution based on the adjoint method from the massachusetts institute of technology ecco mit and an eddying solution based on a green s function approach from ecco phase ii ecco2 predictions for arrival patterns using annual average woa05 fields match observations to within small travel time offsets 0 3 1 0 s predictions for arrival patterns from the models differ substantially from the measured arrival patterns from the woa05 climatology and from each other both in terms of travel time and in the structure of the arrival patterns the acoustic arrival patterns are sensitive to the vertical gradients of sound speed that govern acoustic propagation basin scale acoustic transmissions therefore provide stringent tests of the vertical temperature structure of ocean state estimates this structure ultimately influences the mixing between the surface waters and the ocean interior the relatively good agreement of the acoustic data with the more recent ecco solutions indicates that numerical ocean models have reached a level of accuracy where the acoustic data can provide useful additional constraints for ocean state estimation

numerical treatment of cross shelf open boundaries in a barotropic coastal ocean model abstract using a barotropic coastal ocean model with a straight coastline and uniform cross shelf bottom slope seven different cross shelf open boundary conditions four of which are applied in either implicit or explicit form are compared in three numerical experiments 1 a mound of water is allowed to collapse and radiate waves toward the open boundaries 2 a uniform alongshelf wind stress is applied at zero time over the entire shelf and held constant for the duration of the experiment 3 a uniform cross shelf wind stress is applied at zero time over the entire shelf and held constant for the duration of the experiment the boundary condition which is most transparent to waves consists of a sponge at the outer edge of the model domain with an orlanski radiation condition at the outer edge of the sponge several open boundary conditions perform adequately in the wind stress experiments but the orlanski radiation condition alone without a sponge appears to give the best total performance of thes

long range propagation and associated variability of internal tides in the south china sea the variability of internal tides during their generation and long range propagation in the south china sea scs is investigated by driving a high resolution numerical model the present study clarifies the notably different processes of generation propagation and dissipation between diurnal and semidiurnal internal tides internal tides in the scs originate from multiple source sites among which the luzon strait is dominant and contributes approximately 90 and 74 of the baroclinic energy for m2 and k1 respectively to the west of the luzon strait local generation of k1 internal tides inside the scs is more energetic than the m2 tides diurnal and semidiurnal internal tides from the luzon strait radiate into the scs in a north south asymmetry but with different patterns because of the complex two ridge system the tidal beams can travel across the deep basin and finally arrive at the vietnam coast and nansha island more than 1000 1500 km away during propagation m2 internal tides maintain a southwestward direction whereas k1 exhibit complicated wave fields because of the superposition of waves from local sources and island scattering effects after significant dissipation within the luzon strait the remaining energy travels into the scs and reduces by more than 90 over a distance of 1000 km inside the scs the k1 internal tides with long crests and flat beam angles are more influenced by seafloor topographical features and thus undergo apparent dissipation along the entire path whereas the prominent dissipation of m2 internal tides only occurs after their arrival at zhongsha island this article is protected by copyright all rights reserved

a regional model of shelf circulation near bass strait a new upwelling mechanism abstract a study is made of the low frequency three dimensional circulation and upwelling for the western region of bass strait using oceanographic data and the princeton ocean model a novel radiation condition which simulates the effect of an eastern shelf on kelvin wave scattering is successfully tested against analytic solutions for coastal trapped wave ctw scattering and generation using a realistic bathymetry for the bass strait region the model was forced with 8 day period zonal winds within the strait and a mode 1 ctw at the northwestern boundary results demonstrate the existence of a new mechanism for upwelling whereby at the cessation of westward winds within the strait the residual poleward flow over the steeply sloping tasmanian shelf separates from a gyre that develops over the more gently sloping topography near the mouth of the strait the resultant divergence of the velocity field leads to large vertical velocities 34 m day 1 and a plume of subthermocline water that is upwelle

spatial and temporal variability of the m2 internal tide generation and propagation on the oregon shelf abstracta 1 km horizontal resolution model based on the regional ocean modeling system is implemented along the oregon coast to study average characteristics and intermittency of the m2 internal tide during summer upwelling wind driven and tidally driven flows are simulated in combination using realistic bathymetry atmospheric forcing and boundary conditions the study period is april through august 2002 when mooring velocities are available for comparison modeled subtidal and tidal variability on the shelf are in good quantitative agreement with moored velocity time series observations depth integrated baroclinic tidal energy flux ef its divergence and topographic energy conversion tec from the barotropic to baroclinic tide are computed from high pass filtered harmonically analyzed model results in a series of 16 day time windows model results reveal several hot spots of intensive tec on the slope at these locations tec is well balanced by ef divergence changes in background stratific