modeling basin scale internal waves in a stratified lake basin scale internal waves provide the driving forces for vertical and horizontal fluxes in a stratified lake below the wind mixed layer thus correct modeling of lake mixing and transport requires accurate modeling of basin scale internal waves examining this capability with a hydrostatic z coordinate three dimensional 3d numerical model at coarse grid resolutions is the focus of this paper it is demonstrated that capturing the correct thermocline forcing with a 3d mixed layer model for surface dynamics results in a good representation of low frequency internal wave dynamics the 3d estuary and lake computer model elcom is applied to modeling lake kinneret israel and is compared with field data under summer stratification conditions to identify and illustrate the spatial structure of the lowest mode basin scale kelvin and poincarewaves that provide the largest two peaks in the internal wave energy spectra the model solves the unsteady reynolds averaged navier stokes equations using a semi implicit method similar to the momentum solution in the trim code with the addition of quadratic euler lagrange dis cretization scalar e g temperature transport using a conservative flux limited approach and elimination of vertical diffusion terms in the governing equations a detailed description is provided of turbulence closure for the vertical reynolds stress terms and vertical turbulent transport using a 3d mixed layer model parameterized on wind and shear energy fluxes instead of the convential eddy viscosity diffusivity assumption this approach gives a good representation of the depth of the mixed layer at coarse vertical grid resolutions that allows the internal waves to be energized correctly at the basin scale wind stresses surface heating and density currents form the driving energy fluxes of a stratified lake the basin scale energy flux from the wind is of particular interest because of its dominant role in setting the thermocline in motion which in the absence of inflows and outflows is the primary energy store for transport and mixing below the wind mixed layer thus modeling the basin scale internal wave behavior is an a priori requirement to modeling and quantifying the flux paths of nutrients in a stratified lake imberger 1994 this paper takes a first step in this direction by analyzing our ability to model basin scale internal waves that are seen in lake kinneret israel energy flux path in a stratified lake energy flux through a stratified lake has a fundamental dependence on forced and free baroclinic motions the wind imparts both momentum and turbulent kinetic energy tke to the water in the sur face layer the tke distributes momentum vertically in the

subinertial flows and transports in cozumel channel 1 the subinertial flow of the cozumel channel is examined with nearly six months of current subsurface pressure and meteorological data in order to a verify the validity of the geostrophic balance in cozumel channel and analyze the influence of other terms of the momentum equation in observed ageostrophic variations and b estimate the transport through the channel using a set of continuous current profile observations at the channel s center and the cross section velocity maps obtained from shipboard adcp observations over periods longer than a month the momentum balance in the channel is mainly geostrophic but on alternative periods of similar duration intense ageostrophic fluctuations are found that have timescales of days to weeks and up to 1 m s amplitudes there is evidence that the advective nonlinear terms are the most probable cause of the lack of geostrophy over these periods other terms such as the local acceleration and the wind stress are found to contribute minimally in the ageostrophic fluctuations a mean transport of approximately 5 sv toward the gulf of mexico is estimated for the 5 months of measurements december 1996 to may 1997 although with great variability a minimum of 1 3 sv around january a maximum of 7 5 sv by the beginning of may and a standard deviation of 1 2 sv neither surface currents nor the geostrophically deduced current is suitable for estimating the observed transport in the channel

potential vorticity structure in the north atlantic western boundary current from underwater glider observations abstractpotential vorticity structure in two segments of the north atlantic s western boundary current is examined using concurrent high resolution measurements of hydrography and velocity from gliders spray gliders occupied 40 transects across the loop current in the gulf of mexico and 11 transects across the gulf stream downstream of cape hatteras cross stream distributions of the ertel potential vorticity and its components are calculated for each transect under the assumptions that all flow is in the direction of measured vertically averaged currents and that the flow is geostrophic mean cross stream distributions of hydrographic properties potential vorticity and alongstream velocity are calculated for both the loop current and the detached gulf stream in both depth and density coordinates differences between these mean transects highlight the downstream changes in western boundary current structure as the current increases its transport downstream upper layer potential vorticity is generall

mindoro strait and sibutu passage transports estimated from satellite data 1 this study investigates the mindoro strait and sibutu passage transports using remotely sensed sea surface height ssh and ocean bottom pressure obp data the analysis reveals the existence of a persistent baroclinic pressure gradient that drives a deepwater overflow from the south china sea into the sulu sea the application of hydraulic theory combined with the geostrophic control formula yields a mean transport estimate of about 2 4 sv 1 sv 106 m3 s 1 through the mindoro strait and about 2 8 sv through the sibutu passage most of this water enters the sulu sea through the bottom layer of the mindoro strait and exits the sulu sea in the upper layer of the sibutu passage the analysis also provides the first satellite based observational evidence on the seasonal and interannual variation of the mindoro strait and sibutu passage transports for the period from january 2004 to december 2007

direct observations of velocity and transport in the passages between the intra americas sea and the atlantic ocean 1984 1996 shipboard acoustic doppler current profiler observations of the velocity in the upper 200 m of the water column collected during 1984 1996 using the national oceanic and atmospheric administration r v malcolm baldrige are used to examine the velocity structure and transport in the passages between the atlantic ocean and the intra americas sea ias data were collected during 23 cruises along the following sections across the straits of florida in the northwest providence channel nwpc across the northern passages into the caribbean sea windward mona and anegada across the eastern caribbean along 63 30 w thereby forming a closed quadrangle and in the grenada passage the florida current the eastern caribbean and the grenada passage share a similar mean velocity structure characterized by high velocity surface intensified flows with strong vertical and horizontal shears the northern caribbean passages nwpc windward mona and anegada share a different common mean velocity structure with subsurface velocity maxima directed into the ias and surface intensified counterflows along one side of each passage on average there is a transport balance in the upper 200 m between waters entering and exiting the ias with the 16 5 2 4 sv 1 sv 106 m3 s transport of the florida current at 27 n comprised of 0 4 0 8 sv from the nwpc 2 2 1 5 sv from the windward passage 2 8 2 1 and 2 4 2 8 sv from the mona and anegada passages respectively and 9 5 4 7 sv across the eastern caribbean for a total of 17 3 sv the four passages north of 17 n from nwpc to anegada passage have a combined transport of 7 8 sv nearly half of the transport of the florida current in the upper 200 m of the 9 5 sv flowing through the eastern caribbean between 11 n and 17 n 4 9 2 6 sv or more than half come from the grenada passage this is significant to the subject of cross equatorial exchange of mass heat and salt as the grenada passage is where the highest transport of waters originating in the southern hemisphere is thought to enter the caribbean

subtidal response of scotian shelf circulation to local and remote forcing part i observations abstract data collected during the canadian atlantic storms program casp suggest that two primary current regimes exist on the scotian shelf during winter moorings inside the 100 m isobath feature currents that are parallel to the general bathymetry and have small eastward mean velocities the time varying part of the flow is nearly rectilinear alongshelf at typical maximum velocities of 0 2 0 3 m s 1 and oscillates on 2 5 day periods in response to meteorological forcing the current at locations beyond the 100 m isobath exhibits a persistent westward flow of about 0 3 m s 1 denoting the dominance of the nova scotian current although smaller magnitude along and cross shelf fluctuations occur at synoptic frequencies flow in both regions is largely uniform with depth at this time of year the velocity response to local and remote sources of forcing was examined using a frequency dependent multiple regression model flow is dominated by nonlocal forcing at 0 2 cpd alongshelf wind stress is t

flow structure and transport in the yucatan channel 1 the direct ocean current observations across the yucatan channel collected during the canek program allow the best description to date of the exchange between the caribbean sea and the gulf of mexico a net transport of 23 8 1 sv 1 sv 106m3s 1 95 confidence interval flowed through the yucatan channel from the caribbean sea into the gulf of mexico during the period between september 1999 and june 2000 this is about 20 percent less than the 30 sv accepted as the nominal transport of the florida current and less also than the 28 sv assumed for yucatan in closing the transport budgets for caribbean passages the discrepancy may be an imbalance due to fluctuations in the transports through other passages of the system especially the old bahama and northwest providence channels which remain poorly known our data corroborate the principal features of the flow through the yucatan channel the northerly surface yucatan current and its southerly under current off mexico and the southerly surface cuban counter current near cuba but previously unobserved mean currents are found to exist at depth especially on the eastern side of the channel fluctuations seen in the deep flows are related to volume anomalies over the gulf of mexico a transport through the yucatan channel smaller than previously thought has significant implications for the dynamics of the gulf of mexico and its modeling since this transport is the principal forcing of its circulation the circulation budgets in the western subtropical atlantic should be revised considering these new results

tides in the strait of gibraltar the strait of gibraltar is where the transition occurs between two distinct tidal regimes the north atlantic where tidal ranges are in excess of 2 m and the western mediterranean where tidal ranges are less than 1 m within the strait the tide is principally semidiurnal observations indicate that on average 96 of the bottom pressure and 74 of the current variability are contained in the semidiurnal band 2 cpd the structure of the local cotidal chart of the m2 tidal constituent is complicated but can be explained in terms of the along and across strait momentum balances along the strait the pressure gradient is mainly balanced by the acceleration of the flow although friction can be of appreciable magnitude corresponding to a decay time scale of 3 16 hours across the strait the momentum balance appears mostly geostrophic but better observations would be required to explain residual terms available observations indicate that the m2 tide has no net energy flux through the strait at the sill the tidal transport in the upper layer exceeds that in the lower layer by nearly a factor of 2 at the eastern end of the strait between algeciras and ceuta the tidal transport is larger in the lower layer this apparent shift in the location of maximum tidal transport is explained in terms of the kinematics of the interface between atlantic and mediterranean waters a mean transport of 0 21 sv due to subinertial and tidal flows carries atlantic water through the strait compensated by an approximately equal return in the lower layer

modeling wind driven circulation and landfast ice edge processes during polynya events in northern baffin bay abstract a high resolution sea ice ocean numerical model of the north water polynya has been developed to study the wind driven circulation during polynya events an idealized three layer stratified ocean is used to initialize the model to characterize the baroclinic response to realistic wind and ice conditions the model general circulation pattern is mainly forced by an along channel sea level gradient between the arctic ocean and baffin bay which determines the magnitude of the southward baffin current and by an across channel sea level gradient in baffin bay which drives the northward west greenland current wgc these two currents are found to be anticorrelated to each other in the smith sound area during strong northerly wind events occurring quite frequently in the winter spring period in the polynya nutrient rich baffin bay waters transported by the wgc are forced toward the greenland shelf coinciding with upwelling events along the greenland coast whenever an ice bridge is present i e

low frequency sea level variability in the vicinity of the east river tidal strait the east river is a narrow tidal strait connecting long island sound with the lower hudson estuary the sound and estuary both communicate with the new york bight subtidal fluctuations in sea level difference between the ends of the strait which are coherent with barotropic flow through the strait are produced mainly by direct setup in the sound and estuary and by sea level fluctuations primarily wind forced in the bight approximately 70 of the variance in subtidal sea level difference can be accounted for by the two components of wind stress the direction of dominant wind forcing wind stress direction producing maximum response varies considerably with frequency response functions relating sea level difference to wind stress components computed for 128 day series for sea level and winds allow us to interpret the direction of dominant forcing in terms of the relative contributions of direct setup and sea level fluctuations in the bight

transport potential vorticity and current temperature structure across northwest providence and santaren channels and the florida current off cay sal bank currents and temperatures were measured using pegasus current profilers across northwest providence and santaren channels and across the florida current off cay sal bank during four cruises from november 1990 to september 1991 on average northwest providence 1 2 sv and santaren 1 8 sv contribute about 3 sv to the total florida current transport farther north e g 27 n partitioning of transport into temperature layers shows that about one half of this transport is of 18 c water 17 c 19 5 c this can account for all of the excess 18 c water observed in previous experiments this excess is thought to be injected into the 18 c layer in its region of formation in the northwestern north atlantic ocean due to its large thickness potential vorticities in this layer in its area of formation are very low in our data lowest potential vorticities in this layer are found on the northern end of northwest providence channel and are comparable to those observed on the eastern side of the florida current at 27 n on average a low potential vorticity 18 c layer was not found in the florida current off cay sal bank

transport and dynamics of the panay sill overflow in the philippine seas abstract observations of stratification and currents between june 2007 and march 2009 reveal a strong overflow between 400 and 570 m depth from the panay strait into the sulu sea the overflow water is derived from approximately 400 m deep in the south china sea temporal mean velocity is greater than 0 75 m s 1 at 50 m above the 570 m panay sill empirical orthogonal function analysis of a mooring time series shows that the flow is dominated by the bottom overflow current with little seasonal variance the overflow does not descend below 1250 m in the sulu sea but rather settles above high salinity deep water derived from the sulawesi sea the mean observed overflow transport at the sill is 0 32 106 m3 s 1 the observed transport was used to calculate a bulk diapycnal diffusivity of 4 4 10 4 m2 s 1 within the sulu sea slab 575 1250 m ventilated from panay strait analysis of froude number variation across the sill shows that the flow is hydraulically controlled a suitable hydraulic control model

comparisons between a continuous 3 year current meter observation at the sill of the yucatan strait satellite measurements of gulf loop current area and regional sea level from october 1977 through november 1980 a current meter mooring was maintained in the yucatan strait the meter was moored halfway between mexico and cuba 145 m above the sill or in 1895 m of water motions of low frequency 14 1 cycles day are oriented approximately parallel to the isobaths 021 030 true net drift for 3 years is to the ssw at an average velocity of 1 8 cm s sustained southward flows at intervals of 8 months which persisted for several months each have average velocities of 5 cm s with randomly spaced bursts as high as 15 cm s energy in subtidal frequency bands has significant peaks near 38 1 and 19 1 cycles day with a broad band of energy between 300 1 and 200 1 cycles day the latter peak is consistent with the approximately 8 month interval between the southward flow events comparison with weekly areal coverage of the gulf loop current from geostationary operational environmental satellite infrared observations shows little covariation except that 8 months is typical of some anticyclonic eddy generation there is little coherence of sill depth velocities with naples sea level at subtidal frequencies but with miami there is coherence at several frequencies notably 38 1 and 19 1 cycles day in the higher frequencies the principal tidal motions are diurnal and are oriented somewhat across the isobaths toward the northwest 346 349 true with counterrotating o1 and k1 constituents no semidiurnal inertial or fortnightly energy is observed above the background continuum

meteorologically forced subinertial flows through the strait of gibraltar the observed transport due to subinertial flows with periods ranging from days to a few months through the strait of gibraltar reaches values up to 106 m3 s 1 and is well correlated with atmospheric pressure fluctuations over the mediterranean sea this transport is barotropic and accounts for 84 of the variance observed at these frequencies a second mode accounts for 12 of the variance and is characterized by a node zero amplitude located at the mean depth of the interface between atlantic and mediterranean waters this baroclinic mode is modulated by the spring neap tidal cycle corresponding to an increased exchange of waters between atlantic and mediterranean at neap tides a simple model of the mediterranean which includes two basins and two straits indicates that the system has two resonant frequencies at periods of 1 2 and 5 6 days the 1 2 day resonance corresponds to the eastern and western basins oscillating through the strait of sicily while that at 5 6 days is the resonance of the mediterranean sea with the north atlantic ocean a good approximation to the observed flows is obtained when this model is forced with the most energetic mode of the atmospheric pressure over the eastern and the western mediterranean and a friction term is included to limit the flow through the strait of gibraltar restricting the flow through the strait of sicily does not improve the agreement between the model and the observations for the flows at gibraltar

circulation along the mexican caribbean coast 1 data from an array of seven subsurface upward looking moored acoustic doppler current profilers adcps and four subsurface pressure sensors deployed from august 2002 to august 2003 along the caribbean coast of mexico showed that the currents in the area have a predominant northeastward direction along the coast are coherent within the upper 130 m of the water column and have a general tendency to increase northward reaching magnitudes of 2 4 m s north of cozumel in addition important weeklong reversal periods southward flows are observed around chinchorro bank a vertical current profile eof analysis at each station indicates high coherence within the study area with the first vertical mode at each station explaining at least 69 of variance and current vectors aligned with the coast a second eof analysis carried out for any uniform depth level using current data from all stations shows high coherence in the horizontal as well the first mode explains at least 59 of the variance and has a dominant 3 month long variability comparison between the current patterns along the mexican caribbean coast and in the yucatan channel suggests that dynamics of the entire area might be strongly influenced by the passage of eddies through the region comparison of a singular spectral analysis ssa of the principal components of currents with the pressure difference across the channels supports the idea of eddies modulating current variability numerical model results indicate that high values of the current intensity indexes are associated with eddies the flow along chinchorro and cozumel channels is in geostrophic balance most of the observation time but with week long ageostrophic periods which are predominant off cozumel these events appear to occur when eddies are traversing the region

deep cyclonic circulation in the gulf of mexico abstract the anticyclonic loop current dominates the upper layer flow in the eastern gulf of mexico with a weaker mean anticyclonic pattern in the western gulf there are reasons however to suspect that the deep mean flow should actually be cyclonic topographic wave rectification and vortex stretching contribute to this cyclonic tendency as will the supply of cold incoming deep water at the edges of the basin the authors find that the deep mean flow is cyclonic both in the eastern and western gulf with speeds on the order of 1 2 cm s 1 at 2000 m historical current meter mooring data as well as profiling autonomous lagrangian circulation explorer palace floats at 900 m suggest that vertical geostrophic shear relative to 1000 m gives a surprisingly accurate result in the interior of the basin the temperature around the edges of the basin at 2000 m is coldest near the yucatan channel where caribbean sea water is colder by 0 1 c the temperature increases steadily with distance in the counter

ageostrophic fluctuations in cozumel channel 1 the cayman current flows to the west and most of it turns north as it approaches the yucatan coast producing a persistent northwesterly flow on both sides of cozumel island the transport between the yucatan peninsula and cozumel island i e through the cozumel channel is close to 5 sverdrups in the mean with velocities at midchannel ranging from 20 to 180 cm s a recent study of the subinertial flow and pressure difference across cozumel channel by chavez et al 2003 showed the existence of periods lasting over 1 month with large 3 day to 1 week ageostrophic fluctuations the flow was measured again for a year now at four locations around cozumel island including two instruments along the axis of the channel 8 6 km apart thus allowing estimations of the along channel velocity gradients the new measurements reveal that as suggested in the previous study the centripetal or curvature acceleration of the current is the most significant contribution in the departure from geostrophy indeed the curvature is at times so large that the pressure difference implies a geostrophic flow in the direction opposite to that of the actual flow that is the curvature is anticyclonic with amplitude in rossby number larger than unity measures of the intensity of suprainertial variations in pressure differences and velocity show that periods of ageostrophic fluctuations are consistently much richer in high frequency fluctuations than periods of nearly geostrophic behavior nonetheless the large scale reynolds stresses play an insignificant role throughout

hydraulically drained flows in rotating basins part i method abstract an asymptotic method for coupling circulations in basins to hydraulically controlled overflows is introduced the method is applicable when the forcing dissipation and coupling with the overflow are weak in which case the lowest order solution for the homogeneous or 1 layer model consists of the natural basin modes including gravity inertia gravity potential vorticity helmholtz and steady geostrophic modes at the next order of approximation the mode amplitudes are found to vary slowly with time as the result of forcing dissipation interior nonlinear mode interactions and most importantly coupling with the overflow even when the latter are absent the overflow dynamics generally introduce nonlinearity although the basin dynamics are assumed linear to lowest order the overflow is intrinsically nonlinear to couple the two systems the overflow model must be adapted to serve as a nonlinear boundary condition on the basin flow to do so a rotating channel model introduced by whiteh

impact of caribbean cyclones on the detachment of loop current anticyclones 1 the western boundary current in the north atlantic is characterized by an intense flow reaching 2 5 ms 1 at the surface that enters the caribbean sea through the lesser antilles passages crosses the entire caribbean and enters the gulf of mexico through the yucatan channel where it is known as the loop current a characteristic feature of the loop current is eddy shedding events i e the detachment of large anticyclonic eddies at irregular intervals moored current measurements between january 2005 and july 2009 in the loop current the yucatan channel and the caribbean coastal waters of mexico i e the western cayman sea along with aviso altimetry are used to evidence the northward propagation of cyclonic anomalies along the caribbean coast of mexico and the marked eastward displacement of the loop current at 23 n latitude just before several anticyclonic eddy shedding events after entering the gulf of mexico these cyclonic anomalies might initiate or enhance existing campeche bank cyclonic eddies which are related to many of the loop current detachment events sixteen of the twenty one detachments that occurred during the study period 76 are related to the cyclonic eddies in the western caribbean sea six of them were not reattached again to the loop current observations thus clearly indicate that cyclonic eddies in the western cayman sea contribute significantly to the loop current eddy shedding process which is complex and in principle not unique

modeling the oceanic circulation in the area of the strait of sicily the remotely forced dynamics in order to describe aspects of the baroclinic dynamics in the region of the strait of sicily a high resolution multilayer numerical model has been implemented in a central mediterranean region including the tyrrhenian and the ionian seas three layers have been considered representing water of atlantic origin maw the levantine intermediate water liw and deep water of the mediterranean quasi stationary circulations representing the local manifestation of the large scale mediterranean conveyor belt are obtained after an adjustment time of o 2 months by imposing steady fluxes along the remote open boundaries in the absence of meteorological forcings these circulations can be interpreted as possible dynamic scenarios of the seasonal variability in the strait of sicily in the numerical simulations an inflow of maw and an outflow of liw through the strait of sardinia an outflow of maw and an inflow of liw through the ionian boundary and an outflow of maw through the corsica channel are imposed resulting in a vanishing total net transport in each layer for realistic values of these transports the model captures the main features of the observed circulation such as i the separation of the algerian current into two branches one directed toward the tyrrhenian sea and the other entering the strait ii a secondary bifurcation of maw within the strait giving rise to a southward moving current that follows the tunisian continental slope and to a current that flows southeastward along the southern sicilian coast and then northward along the southern italian coasts the so called atlantic ionian stream iii a bifurcation of liw at the strait level leading to a main current directed toward the strait of sardinia and to a weaker current that after having crossed the strait bends eastward and enters the tyrrhenian sea sensitivity experiments carried out by imposing different boundary fluxes have shed light on the functioning of the maw and liw bifurcations first of all for a given net transport of maw and liw through the strait imposed indirectly by the boundary fluxes the ratio rmaw between the transport of maw entering the tyrrhenian sea and that entering the strait is found to be virtually independent of the boundary imposed algerian current transport it is on the contrary determined by a local dynamic control which selects the value rmaw 0 43 for a net maw liw strait transport of 61 sv in excellent agreement with observations second for decreasing baroclinic transports the ratio rmaw is found to decrease up to the limiting value rmaw 0 2 corresponding to the linear regime for transports o 0 1 sv finally rmaw is found to be very sensitive to the barotropic transport t through the strait whereas the corresponding ratio for the liw rliw is virtually independent of t for t 5 20 5 sv rmaw 1 1 while for t 51 0 5 sv rmaw decreases by one order of magnitude rmaw 0 1 in other words a weakening of the liw or a strengthening of the maw net transport through the strait reduces the relative intensity of the tyrrhenian branch of maw and vice versa on the other hand for values of t within the same range one always findsrliw 20 3 it thus appears that the local control exerted by the topography through the liw potential vorticity budget forces the transport of the tyrrhenian branch of liw to be always 1 3 of that directed toward the strait of sardinia

subtidal eulerian currents in the upper and lower east river tidal strait spring 1981 subtidal eulerian currents determined from long term current moorings in the east river tidal strait connecting the lower hudson river with long island sound show a well defined two layer circulation pattern within the eastern upper part of the east river mean surface currents flow toward the sound and current at depth flows toward the hudson within the western part of the east river residual currents are vertically sheared but flow is directed toward the sound at all depths with stronger flow near the surface mean current magnitudes are of the order of 5 cm s 1 results from frequency domain regression show that in the western lower portion of the strait current fluctuations at frequencies of 0 25 cycles per day and higher are associated primarily with a barotropic response to fluctuations in hydraulic head at lower frequencies currents exhibit a baroclinic response to fluctuations in the discharge of the hudson river within the upper part of the strait currents respond to along channel winds response to fluctuations in sea level head and hudson river discharge is detectable but not as well defined as within the lower east river these results can provide insight into the relative importance of different forcing functions in maintaining the residual flow through the strait the difference in the response characteristics of the western and eastern segments of the strait could be related to differences in the intensity of tidal mixing along the strait and the degree of water column stratification

topographic control of oceanic flows in deep passages and straits saddle points between neighboring deep ocean basins are the sites of unidirectional flow from one basin to the next depending on the source of bottom water flow in these sites appears to be topographically controlled so the interface between the bottom water and the water above adjusts itself to permit bottom water flow from the basin that contains a source of bottom water into the next examples in the atlantic include flow in the romanche fracture zone the vema channel the ceara abyssal plain the anegada jungfern passage and the discovery gap but there are many more theoretical predictions of volume flux using a method that requires only conductivity temperature depth data archives and detailed knowledge of bathymetry near the saddle point are compared with volume flux estimates using current meters and or geostrophic estimates for seven cases the ratio of prediction to volume flux estimate ranges from 1 0 to 2 7 some ocean straits that separate adjacent seas are also found to critically control bidirectional flows between basins theory of the influence of rotation on such critical flows is reviewed predictions of volume flux in eight cases are compared with ocean estimates of volume flux from traditional methods

eddy properties in the california current system 1 eddy detection and tracking algorithms are applied to both satellite altimetry and a high resolution dx 5 km climatological model solution of the u s west coast to study the properties of surface and undercurrent eddies in the california current system eddy properties show remarkable similarity in space and time and even somewhat in polarity summer and fall are the most active seasons for undercurrent eddy generation while there is less seasonal variation at surface most of the eddies have radii in the range of 25 100 km sea level anomaly amplitudes of 1 4 cm and vorticity normalized by f amplitudes of 0 025 0 2 many of the eddies formed near the coast travel considerable distance westward with speeds about 2 km day consistent with the effect anticyclones and cyclones show equatorward and poleward displacements respectively long lived surface eddies show a cyclonic dominance the subsurface california undercurrent generates more long lived anticyclones than cyclones through instabilities and topographic coastline effects in contrast surface eddies and subsurface cyclones have much more widely distributed birth sites the majority of the identified eddies have lifetimes less than a season eddies extend to 800 1500 m depth and have distinctive vertical structures for cyclones and anticyclones eddies show high nonlinearity rotation speed higher than propagation speed and hence can be efficient in transporting materials offshore

circulation of the caribbean sea a well resolved inverse problem the caribbean sea is selected as a region where the large scale circulation is well determined by historical hydrographic measurements through application of the inverse method a simple example is used to illustrate the technique and to demonstrate how some physically relevant quantities may be well determined in the formally underdetermined inverse problem the geostrophic flow field in the caribbean is found by imposing mass and salt conservation constraints in seven layers separated by surfaces of constant potential density an unsmoothed solution is displayed that has weak dependence on an initial choice of reference level in addition a unique smoothed solution is shown above sigma sub theta 27 4 the total flow leaving the western caribbean is estimated to be 29 x 10 sup 6 m sup 3 s sup 1 in agreement with direct measurements this flow is made up of 22 x 10 sup 6 m sup 3 s sup 1 entering the caribbean from the east and flowing across the southern half of the basin as the caribbean current and 7 x 10 sup 6 m sup 3 s sup 1 in agreement with direct measurements this flow is made up of 22 x 10 sup 6 m sup 3 s sup 1 entering the caribbean from the east and flowingmore across the southern half of the basin as the caribbean current and 7 x 10 sup 7 m sup 3 s sup 1 entering from the north through windward passage both of these currents show small scale variability that diminishes with distance from the respective passages the deep flow has no net transport as required by the shallow exit but a well organized clockwise recirculation is found in the deep eastern caribbean less

a model study of the vertically integrated transport variability through the yucatan channel role of loop current evolution and flow compensation around cuba 1 in the paper a model study of the vertically integrated transport variability through the yucatan channel role of loop current evolution and flow compensation around cuba by lin et al journal of geophysical research 114 c08003 doi 10 1029 2008jc005199 2009 in the last sentence of paragraph 31 the word westward in drives enhanced westward should be eastward

winter transport and sea level fluctuations in hecate strait british columbia observed winter transport and adjusted sea level fluctuations in hecate strait were investigated using empirical orthogonal function and coherence analyses the responses to large scale and local wind forcings were identified by the distinctive spatial patterns of their adjusted sea level responses at the resolved periods of 2 to 48 days the large scale and the local wind forcings were of roughly equal importance in driving transport fluctuations comparison of observations with a conceptual model indicates that the adjusted sea level in the northeast corner of the strait gives a good measure of response to both the local and large scale wind forcings this provides a physical explanation for the observed high correlation between the adjusted sea level at prince rupert and the winter transport fluctuations in hecate strait we also show that the transport fluctuations are associated with a particular spatial pattern of the velocity field which represents roughly 1 4 of the energy in the observed winter velocity fluctuations measured at an array of current meters this has implications for the use of surrogate transport series to hindcast oceanographic conditions in hecate strait

century scale movement of the atlantic intertropical convergence zone linked to solar variability 1 the abundance of the planktic foraminifer globigerinoides sacculifer in gulf of mexico gom sediments is a proxy for the influx of caribbean surface waters the loop current into the gom penetration of the loop current into the gom is related to the position of the intertropical convergence zone itcz northward migration of the itcz results in increased incursion of the loop current into the gom southward migration of the itcz results in decreased penetration of the loop current into the gom abundance variations of g sacculifer in a sediment core from the pigmy basin in the gom show distinct century scale cyclicity over the last 5 000 years the periodicity of these abundance variations is similar to the century scale periodicity observed in proxy records of solar variability which suggests that the average position of the itcz and thus holocene century scale variability in the caribbean gom region is linked to solar variability

the surface circulation of the caribbean sea and the gulf of mexico as inferred from satellite altimetry the surface circulation of the caribbean sea and gulf of mexico is studied using 13 years of satellite altimetry data variability in the caribbean sea is evident over several time scales at the annual scale sea surface height ssh varies mainly by a seasonal steric effect interannually a longer cycle affects the ssh slope across the current and hence the intensity of the caribbean current this cycle is found to be related to changes in the wind intensity the wind stress curl and el nino southern oscillation at shorter time scales eddies and meanders are observed in the caribbean current and their propagation speed is explained by baroclinic instabilities under the combined effect of vertical shear and the b effect then the loop current lc is considered focusing on the anticyclonic eddies shed by it and the intrusion of the lc into the gulf of mexico through time twelve of the 21 anticyclonic eddies observed to detach from the lc are shed from july to september suggesting a seasonality in the timing of these events also a relation is found between the intrusion of the lc into the gulf of mexico and the size of the eddies shed from it larger intrusions trigger smaller eddies a series of extreme lc intrusions into the gulf of mexico when the lc is observed as far as 928w are described the analyses herein suggest that the frequency of such events has increased in recent years with only one event occurring in 1993 versus three from 2002 to 2006 transport through the straits of florida appears to decrease during these extreme intrusions

sea level variability due to meteorological forcing in the northeast gulf of st lawrence in an attempt to understand the causes of low frequency flow through the strait of belle isle we relate sea level data from four stations in the northeast gulf of st lawrence to meteorological forcing our main tool is a multiple regression at each frequency of sea level on local atmospheric pressure and two orthogonal large scale pressure gradients which represent geostrophic winds the results show an inverted barometer response to atmospheric pressure and a frequency dependent response to wind which can be tentatively interpreted in terms of coastal setup due to wind driven longshore currents or barotropic setup of semi enclosed regions such as the northeast gulf or the whole gulf a simple model for barotropic flow through the strait is developed in order to provide an estimate from data at the western end of the strait of sea level changes on the labrador shelf

structure and variability of the kuroshio current in tokara strait four years of mooring array measurements in tokara strait south of kyushu japan from 1992 to 1996 are used to analyze the structure and temporal variability of the kuroshio current the mean kuroshio current in tokara strait shows a nearly permanent subsurface double core structure possibly due to topographic blockage effects the dominant variations of the kuroshio in tokara strait are separated into long term variability typically 100 day period and short term variability 10 days to 1 month according to spectrum and wavelet analysis the long term variability has a large horizontal scale across the strait with a striking twofold banded structure in spatial correlations this is due to the north south kuroshio axis shift that advects the double core structure of the mean current the axis shift can be indexed with the northeastward current velocity at the northernmost station a composite analysis using this index shows well defined northward and southward axis shift structures of the kuroshio current from the composite of the topex poseidon sea level anomaly in terms of this index the kuroshio axis shift and the current structure change are associated with a dipole shape sea level anomaly east of tokara strait on the other hand the short term variability of high kinetic energy only has a small horizontal scale within the northern part of the current which is related to frontal variability there exists a deep southwestward undercurrent below 600 m in the northern part of tokara strait flowing along the isobaths the undercurrent becomes stronger during the northward shift of the kuroshio axis while it almost disappears during the southward shift

the influence of bays on adjusted sea level over adjacent shelves with application to the labrador shelf we examine how low frequency variations in adjusted sea level over a continental shelf are influenced by an inland sea connected to the shelf through a strait an analytical model shows that free continental shelf waves propagating by the mouth of the strait are strongly modified at a period corresponding to a helmholtz like resonance of the inland sea and strait also near this period atmospheric pressure variations over the inland sea result in relatively strong flow through the strait and the resulting cross isobath flow over the exterior shelf efficiently generates continental shelf waves in the region forward of the strait calculations using a fully nonlinear numerical model with more realistic although still idealized topography verify the predictions of the simpler analytical model we apply this theory to the hudson bay labrador shelf system where we find that this mechanism of shelf wave generation strongly influences the shelf response in the energetic meteorological band 2 6 days data from nain labrador are analyzed using multiple linear regression models and lend further support to the theory

three dimensional exchange flows in a semi enclosed bay numerical simulations and high frequency radar observations abstract in this work we present the exchange flows between a semi enclosed bay and the adjacent ocean as measured by a real time coastal observing system in baja california mexico several sources of information as numerical modeling currents profile data high frequency radar observations and drifters tracking all together show an interesting three dimensional structure to the exchange flows the northern entrance relatively shallow 40 m at its deepest portion showed an estuarine like exchange pattern with a net outflow at the shallow parts and inflow at the deepest suggesting that the frictional effect is more important than the earth s rotation as typically observed in relatively small bodies of water like estuaries and coastal lagoons on the other hand the southern entrance with a 400 m deep canyon is more complex with recurrent anticyclonic exchange pattern with inflows at the western limit and outflows at the east we suggest that the vertical structure of this circulation may be sustained by the deep canyon which lowers the thermocline but further investigation is needed

current meter observations in the old bahama channel current meter observations were made at 50 250 and 435 m in 495 m of water at the center of the old bahama channel between november 1990 and november 1991 the mean speed at those depths was 2 6 50 and 26 cm s 1 toward the straits of florida a maximum speed of 193 cm s 1 was found at the 250 m level there was evidence of a speed maximum between 50 and 250 m large internal diurnal tidal currents were observed that produced high shears in the water column under some conditions transport calculated from the single mooring using simple assumptions varied from 2 4 to 6 6 sv with a mean of 1 9 sv toward the straits of florida these values while based on limited data are very significant compared to the mean flow in the straits of florida thus flow through the old bahama channel may be an important component of heat and salt transport in the straits

optimal estimation of hydrographic station data and derived fields abstract optimal estimation is applied to contouring and analysis of hydrographic sections measured fields such as temperature and salinity and derived fields such as geostrophic velocity are decomposed into large scale and small scale components first a heavily sampled basin scale field is estimated and subtracted from the data a small scale field barely resolved by the hydrography is then found from the residuals the power and utility of the technique are illustrated by means of examples using a short section from the straits of florida and a transatlantic section along 24 n

upstream separation in a rotating channel flow the question of upstream separation of a current of dense rotating fluid below a stagnant layer of lower density that is critically controlled by a weir is addressed in laboratory experiments that follow from theoretical calculations for a constant potential vorticity flow in a gradually varying channel it is shown that a range of parameters lead to upstream separation in all cases the flow reattaches before reaching the sill crest so that a closed gyre is produced in laboratory experiments separation and reattachment was observed in numerous cases where the theory predicts closed gyres although the shape and size of the gyre are in accordance with theory the circulation within the gyre differs markedly from theoretical predictions the mechanism that feeds energy into the gyre appears to be an important unsolved problem the results indicate that upstream separation is a fact and that the dynamics of the gyre is significant so the gyre dynamics may modify the volume flux of fluid over the weir

dynamical aspects of the flow through the strait of belle isle abstract we present an analysis of 50 days of current meter and sea revel data collected in a long narrow strait connecting the gulf of st lawrence to the atlantic ocean the dynamical balances implied by a scale analysis of the equation of motion are compared with the data for semidiurnal and diurnal tides and for low frequency flows the main result being that the near surface currents along the strait are as expected in geostrophic balance with the sea level slope across the strait the flow appears to be driven by the sea level difference between opposite ends of the strait produced by large scale meteorological forcing and a regression model involving acceleration and friction suggests a spindown time of 1 1 days the near bottom currents are significantly less than those new the surface at both levels the currants are reasonably uniform across the channel apart from the possibility of nearshore intensification at the lower level the vertical and horizontal structure of the low frequency curre

ground improvement using vacuum loading together with vertical drains abstractthe use of vacuum as a preload together with vertical drains to reduce postconstruction settlement and increase the shear strength of soft ground is increasingly popular however conflicting views concerning preloading by vacuum consolidation continue to be disseminated a review and interpretation of case histories of vacuum loading together with vertical drains indicates that 1 with a novel definition of excess pore water pressure existing theories of consolidation solutions and associated computer programs that have been developed for fill loading can be applied without any modification to vacuum loading 2 vacuum that is available in the drainage blanket remains constant with depth within the vertical drains 3 for vacuum loading as for fill loading vertical drains may display well resistance 4 there is no difference in magnitude and rate of settlement for a vacuum load and an equivalent fill load 5 all empirical concepts of undrained shear strength that have originated from f

kuroshio intrusion into the south china sea a review the kuroshio carrying the northwestern pacific water intrudes into the south china sea scs through the luzon strait significantly affecting the temperature salinity circulation and eddy generation in the scs thus the kuroshio intrusion makes important contributions to the momentum heat and salt budgets in the scs in the past decades much work has been done on the kuroshio intrusion this paper reviews past efforts and summarizes our current understanding of the kuroshio intruding processes from observational evidence laboratory results theoretical analyses and a range of numerical model simulations in addition discrepancies between results simulated by models as well as those between simulations and observations are presented specifically this paper addresses the following topics 1 different types of the kuroshio intrusion into the scs and their identification 2 vertical structure of the kuroshio in the luzon strait 3 an overview of the luzon strait transport resulting from observations and numerical model simulations 4 seasonal and interannual variations of the kuroshio intrusion as well as eddy generation due to the kuroshio path variation and 5 dynamical mechanisms e g wind forcing interbasin pressure gradient beta effect and hysteresis potential vorticity eddy activity controlling the kuroshio intrusion into the scs finally several future research topics for gaining a better understanding of the kuroshio intruding processes are suggested c 2014 the authors published by elsevier ltd

a new approach of vacuum preloading with booster pvds to improve deep marine clay strata this paper presented a new approach for ground improvement of deep marine clay in which the conventional booster tube in the current air booster vacuum preloading technology was replaced by a boost

the kuroshio east of taiwan moored transport observations from the woce pcm 1 array observations from the woce pcm 1 moored current meter array east of taiwan for the period september 1994 to may 1996 are used to derive estimates of the kuroshio transport at the entrance to the east china sea three different methods of calculating the kuroshio transport are employed and compared these methods include 1 a direct method that uses conventional interpolation of the measured currents and extrapolation to the surface and bottom to estimate the current structure 2 a dynamic height method in which moored temperature measurements from moorings on opposite sides of the channel are used to estimate dynamic height differences across the current and spatially averaged baroclinic transport profiles and 3 an adjusted geostrophic method in which all moored temperature measurements within the array are used to estimate a relative geostrophic velocity field that is referenced and adjusted by the available direct current measurements the first two methods are largely independent and are shown to produce very similar transport results the latter two methods are particularly useful in situations where direct current measurements may have marginal resolution for accurate transport estimates these methods should be generally applicable in other settings and illustrate the benefits of including a dynamic height measuring capability as a backup for conventional direct transport calculations the mean transport of the kuroshio over the 20 month duration of the experiment ranges from 20 7 to 22 1 sv 1 sv 106 m3 s 1 for the three methods or within 1 3 sv of each other the overall mean transport for the kuroshio is estimated to be 21 5 sv with an uncertainty of 2 5 sv all methods show a similar range of variability of 10 sv with dominant timescales of several months fluctuations in the transport are shown to have a robust vertical structure with over 90 of the transport variance explained by a single vertical mode the moored transports are used to determine the relationship between kuroshio transport and sea level difference between taiwan and the southern ryukyu islands allowing for long term monitoring of the kuroshio inflow to the east china sea

wintertime circulation off southeast australia strong forcing by the east australian current numerical results and observations are used to examine the sub weather band wintertime circulation off the eastern shelf slope region between tasmania and cape howe the numerical model is forced using wintertime averaged atmospheric fluxes of momentum heat and freshwater and using transports along open boundaries that are obtained from a global ocean model the boundary to the north of cape howe has a prescribed transport of 17 sv which from available observations represents strong forcing by the east australian current eac nonetheless the model results are in qualitative and quantitative agreement with several observational studies in accord with observations water within bass strait is found to be driven to the east and north with speeds of up to 30 cm s 1 off the southeast victorian coast the water is colder and denser than that found farther offshore which is associated with the southward flowing warm eac in agreement with observations the density difference between the two water masses is about 0 6 kg m 3 and leads to a cascade of dense bass strait water to depths of 300 m and as a plume that extends 5 10 km in the cross shelf direction typical vertical velocities of the model cascade are 20 m d 1 along isobath currents become bottom intensified with speeds of 20 cm s 1 or so at depths of 200 m the eac is found to flow along isobaths and to the south and then west past tasmania with speeds of up to 20 cm s 1 mesoscale eddies grow to diameters of 100 km speeds 40 cm s 1 and in accord with observations a semipermanent anticyclonic eddy is found to the east of cape howe

reply to the discussion by mesri and kane on new approach of vacuum preloading with booster prefabricated vertical drains pvds to improve deep marine clay strata 1

tides and sea level variability at the strait of euripus abstract the strong tidal currents in the strait of euripus are one of the first recorded observations of tidal phenomena the analysis of sea level time series from tide gauges located near the narrowest part of the strait show that the amplitude of the semi diurnal tides at the north side of the strait is four times the amplitude at the south side of the strait the two tide gauges are located a few hundred metres apart two dimensional depth averaged tidal modelling of the area shows that the m 2 and s 2 tides are enhanced as they travel through the straits of oreon and trikeri which are the communication of the north evvoikos gulf to the aegean sea the tidal propagation through the strait of euripus itself is severely restricted owing to its small cross section therefore the tides measured at the two tide gauges represent the independent propagation of the tide from the aegean sea through the north and south evvoikos gulfs respectively to the north and south sides of the strait the strong currents are driven by the gradient in sea level across the strait the natural modes of the basins are determined but are not detectable in the records 1997 academic press limited

seasonality of the transitional region of the california current system off baja california hydrographic data collected over the period 1997 2013 are analyzed to investigate the seasonality of hydrographic features and associated geostrophic flows off the baja california peninsula the upper ocean in the region was found to be homogeneous in winter and spring but subdivided into two regions in the summer and autumn in the first case the system typically shows relatively low temperature and salinity waters which give it a subarctic character in the second only the region north of punta eugenia 28 n maintains subarctic characteristics while the southern region receives an inflow of tropical and subtropical waters that results from the weakening of northwesterly winds which allows the poleward advection of surface waters also during this period a positive wind stress curl promotes the zonal advection of north pacific s eastern edge waters into the coast and to the north as a surface coastal flow average seasonal patterns of geostrophic flow at 200 dbar revealed that the differentiation into provinces is also evident at that depth with two clearly defined cyclonic structures in summer and autumn both separated at the latitude of punta eugenia the analyses conducted also showed a clear continuity of the california undercurrent along the shelf break with more diffuse currents in the winter poleward flows were observed throughout the water column especially in summer and autumn although the origin of the surface flow does not necessarily involve a surfacing of the california undercurrent

aspects of the mean wintertime circulation along australia s southern shelves numerical studies abstract a high resolution numerical model is used to study the mean wintertime shelf slope circulation between the gulfs of south australia and the west coast of tasmania the mean downwelling favorable winds for the region result in a continuous eastward coastal current cc extending from cape leeuwin to the eastern coast of tasmania the magnitude of the cc is generally largest over the shelf break has speeds of more than 40 cm s 1 transport 2 4 sv sv 106 m3 s 1 and is generally in good agreement with observations the relative importance of the leeuwin current zonal winds and density gradients to the shelf circulation is established within bass strait the eastward circulation is in good agreement with observations and simple models show that about 30 of the transport arises from local winds and the remainder from the cc the total transport through the strait 0 95 sv is shown to be controlled by sea level on the east coast of tasmania a current of up to 10 cm s 1 is also found to flow

wind forced sea level variability on the southeast brazilian shelf coastal sea level data collected along the southeast coast of brazil from cabo frio to cabo de santa marta for the period august november 1978 were examined together with meteorological data for evidence of wind forced low frequency fluctuations a dominant 9 to 12 day perturbation in sea level atmospheric pressure and wind propagated equatorward from cananeia and appeared to propagate poleward between cananeia and the southernmost station a 6 to 7 day perturbation in sea level and wind propagated equatorward from the southernmost station in agreement with the movement of cold fronts through the area sea level fluctuations in the central and northern portions of the bight for both 9 to 12 and 6 to 7 day bands were better correlated with winds located southward and earlier in time than with the local wind at the time of sea level measurement modeling of sea level response at ubatuba for a period of 90 days using the theory of barotropic continental shelf waves generated by wind forcing presented results that were similar to the observed response

dispersion of a tracer in the deep gulf of mexico a 25 km streak of cf3sf5 was released on an isopycnal surface approximately 1100 m deep and 150 m above the bottom along the continental slope of the northern gulf of mexico to study stirring and mixing of a passive tracer the location and depth of the release were near those of the deep hydrocarbon plume resulting from the 2010 deepwater horizon oil well rupture the tracer was sampled between 5 and 12 days after release and again 4 and 12 months after release the tracer moved along the slope at first but gradually moved into the interior of the gulf diapycnal spreading of the patch during the first 4 months was much faster than it was between 4 and 12 months indicating that mixing was greatly enhanced over the slope the rate of lateral homogenization of the tracer was much greater than observed in similar experiments in the open ocean again possibly enhanced near the slope maximum concentrations found in the surveys had fallen by factors of 104 107 and 108 at 1 week 4 months and 12 months respectively compared with those estimated for the initial tracer streak a regional ocean model was used to simulate the tracer field and help interpret its dispersion and temporal evolution model data comparisons show that the model simulation was able to replicate statistics of the observed tracer distribution that would be important in assessing the impact of oil releases in the middepth gulf