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

modeling semidiurnal internal tide variability in the southern california bight abstractthe regional oceanic modeling system roms is applied in a nested configuration with realistic forcing to the southern california bight scb to analyze the variability in semidiurnal internal wave generation and propagation the scb has a complex topography with supercritical slopes that generate linear internal waves at the forcing frequency the model predicts the observed barotropic and baroclinic tides reasonably well although the observed baroclinic tides feature slightly larger amplitudes the strongest semidiurnal barotropic to baroclinic energy conversion occurs on a steep sill slope of the 1900 m deep santa cruz basin this causes a forced near resonant semidiurnal poincare wave that rotates clockwise in the basin and is of the first mode along the radial azimuthal and vertical directions the associated tidal mean depth integrated energy fluxes and isotherm oscillation amplitudes in the basin reach maximum values of about 5 kw m 1 and 100 m and are strongly modulated by the sprin

eddy activity and mixing in upwelling systems a comparative study of northwest africa and california regions a comparative modeling approach is used to study the mesoscale dynamics of coastal transition zones in the upwelling systems of western sahara and central california it is shown that large differences in eddy activity and mixing exist between the two systems since upwelling favorable winds off central california and western sahara have similar amplitudes we suggest that observed and modeled differences in eddy activity are due to differences in configuration parameters it is argued that two of these parameters stratification and topography eventually affect the energy available for the mesoscales through baroclinic instability the large difference in stratification appears to be linked to the salinity structure formed by the large scale circulation and is directly related to available potential energy the shape of the continental shelf affects the position structure and scale of the ekman divergence hence upwelling intensity and frontal formation the potential impact of mesoscale eddy mixing and its variability on upwelling ecosystems is discussed

effects of wind stress and wind stress curl variability on coastal upwelling abstract aircraft measurements during the winter 1989 shelf mixed layer experiment smile and summer 1982 coastal ocean dynamics experiment code were used to characterize the spatial variation of the low level wind and wind stress over the northern california shelf the curl of the wind stress was calculated from directly measured turbulent stress components the accuracy of the computed curl was estimated to be adequate to map the spatial structure wintertime measurements showed a concentration of large positive curl over 1 pa 100 km 1 west of point arena regardless of wind direction due to the effects of the coastal topography on the wind fields results from summertime measurements showed a similar local maximum of positive curl west of point arena larger curl values over 3 5 pa 100 km 1 however were observed across a hydraulic jump propagating from stewarts point for highly supercritical marine boundary layer flow a two layer vertically integrated numerical model of coastal upwellin

circulation and energetics of a model of the california current system abstract data from an eight layer fnoc wind driven eddy resolving limited area quasi geostrophic numerical model have been used to study the dynamics of the california current system ccs with particular emphasis on the energetics the model includes quasi realistic bottom topography and the true coastline and is embedded in a coarser resolution model occupying almost all of the north pacific ocean the model simulates the main components of the ccs such as the california current cc the davidson current the california undercurrent and the southern california eddy the simulated cc is both an active eddy mean flow interaction area and an effective wave source for the north pacific ocean making use of the mean potential vorticity field of the different layers four different regimes are described for the mean circulation inertial intermediate beta and bottom topographic overall the new surface circulation is energetically dominated by the mean flow whereas the deep simulation is ener

altimeter derived variability of surface velocities in the california current system 2 seasonal circulation and eddy statistics abstract satellite surface height and temperature fields are used to examine the seasonal surface circulation in the california current system in spring and summer an equatorward jet develops next to the coast with an initial latitudinal structure that responds to the latitudinal distribution of equatorward alongshore winds this jet moves offshore from spring to fall and develops meanders and closed eddies that contribute eddy kinetic energy and water mass properties to the nearby deep ocean higher eke appears first in spring near the coast and moves offshore with the seasonal jet along altimeter tracks parallel to the coastline 200 and 400 km offshore the greatest eke is found in summer and fall respectively with wavelengths of approximately 300 km these are the wavelengths of the largest meanders and the distance between the largest eddies visible in altimeter snapshots of the jet at 600 800 km offshore the wavelengths are generally smaller 100 150 km similar to eddy sizes reported by others for the quiescent northeast pacific some energy with longer wavelengths arrives at the track 600 km offshore in winter and 800 km offshore in spring which we interpret as the most offshore extension of the eke generated by the jet and eddy system closer to the coast in the previous spring and summer a sequence of snapshots from october 1992 to october 1993 shows details of the evolution of the jet and eddy system over one complete annual cycle

impact of a coastal trapped wave on the near coastal circulation of the peru upwelling system from glider data alongshore velocity data from a glider repetitive section off the coast of peru 14 s are used to study the cross shore structure and temporal variability of the peru current system during a 5 week period in april may 2010 besides providing substantial information on the surface frontal jet associated with the peru coastal current and the surfacing peru chile undercurrent that flows poleward trapped on the continental shelf and slope the glider data reveal the presence of an intense deep equatorward current which transports up to 2 5 sv the dynamics of this current are investigated using an eddy resolving regional model the variability of the vertically sheared alongshore flow is shown to be related to the passage of a poleward propagating coastal trapped wave likely of equatorial origin solutions from a two dimensional linear coastal wave model suggest that the alongshore current observed vertical structure is associated with the second and third baroclinic modes of the coastal trapped wave

on the thermo chemical origin of the stratified region at the top of the earth s core abstract i developed a combined model of the thermal and chemical evolution of the earth s core and investigated its influence on a thermochemically stable region beneath the core mantle boundary cmb the chemical effects of the growing stable region are caused by the equilibrium chemical reaction between silicate and the metallic core the thermal effects can be characterized by the growth of the sub isentropic shell which may have a rapid growth rate compared to that of the chemically stable region when the present day cmb heat flow was varied the origin of the stable region changed from chemical to thermochemical to purely thermal because the rapid growth of the sub isentropic shell can replace the chemically stable region physically reasonable values of the present day cmb heat flow that can maintain the geodynamo action over 4 billion years should be between 8 and 11 tw to constrain the thickness of the thermochemically stable region beneath the cmb the chemical diffusivity is important and should be o 10 8 m 2 s to obtain a thickness of the thermochemically stable region beneath the cmb consistent with that inferred from geomagnetic secular variations 140 km however the strength of the stable region found in this study is too high to be consistent with the constraint on the stability of the stable region inferred from geomagnetic secular variations

statistical analysis of the surface circulation of the california current we use a set of mixed layer drifting buoy trajectories from the california current 20 n 40 n during 1985 1990 to obtain statistically reliable estimates of the mean currents the mean variance field and the geographically varying diffusivity integral timescales and integral space scales typical values for the diffusivity are 1 1 8 7 107 cm2 s 1 while the timescales and space scales are 2 1 7 1 days and 16 59 km respectively the variance field displays a strong westward gradient out to 125 w and diffusivity shows a tendency to decrease toward the southwest part of the domain significant anisotropy is found in the variance field near the coastal boundary and at 30 n 130 w which is the region where the subarctic and northern subtropical fronts approach the california current the antisymmetric component of the diffusivity tensor indicates that cyclonic eddies dominate the mesoscale signature of drifters in this region we seek simple parameterizations to relate the scales of motion of the random velocity field to the diffusivity by testing least squares fits to u02t and u0l where u02 is the velocity variance we found no cases for which these two hypotheses could be distinguished for the meridional component the linear regressions are not successful which suggests that the meridional departure velocities result from a flow regime that is significantly organized by for example waves or coherent structures a subset of the drifters measured temperature along their tracks and we use the resultant data to produce the first direct estimates of the horizontal eddy heat flux divergence based on lagrangian estimates in addition we separately compute the eddy diffusivity parameterization of the eddy heat flux divergence u using our diffusivity estimates and a sea surface temperature climatology the two independent terms agree well which provides a measure of reassurance about the diffusivity estimates the eddy heat flux divergence in the california current is very small 5 w m 2 and does not appear to be significant in the long term heat budget of the upper ocean in this region

low frequency variability in the gulf of alaska from coarse and eddy permitting ocean models 1 an eddy permitting ocean model of the northeast pacific is used to examine the ocean adjustment to changing wind forcing in the gulf of alaska goa at interannual to decadal timescales it is found that the adjustment of the ocean model in the presence of mesoscale eddies is similar to that obtained with coarse resolution models local ekman pumping plays a key role in forcing pycnocline depth variability and to a lesser degree sea surface height ssh variability in the center of the alaska gyre and in some areas of the eastern and northern goa westward rossby wave propagation is evident in the ssh field along some latitudes but is less noticeable in the pycnocline depth field differences between ssh and pycnocline depth are also found when considering their relationship with the local forcing and leading modes of climate variability in the northeast pacific in the central goa pycnocline depth variations are more clearly related to changes in the local ekman pumping than ssh while ssh is marginally correlated with both pacific decadal oscillation pdo and north pacific gyre oscillation npgo indices the pycnocline depth evolution is primarily related to npgo variability the intensity of the mesoscale eddy field increases with increasing circulation strength the eddy field is generally more energetic after the 1976 1977 climate regime shift when the gyre circulation intensified in the western basin where eddies primarily originate from intrinsic instabilities of the flow variations in eddy kinetic energy are statistically significant correlated with the pdo index indicating that eddy statistics may be inferred to some degree from the characteristics of the large scale flow

wind forced modeling studies of currents meanders and eddies in the california current system this process oriented study of the california current system ccs uses a high resolution multilevel primitive equation ocean model on a plane to isolate the response of that eastern boundary oceanic regime to temporal and spatially varying wind forcing to study the generation evolution and maintenance of many of the observed features such as currents meanders and eddies in the ccs the model is forced from rest with seasonal climatological winds in response to the prevailing wind direction surface equatorward currents develop along with upwelling of cooler water along the coast and a poleward undercurrent baroclinic barotropic instabilities in the equatorward surface current and poleward undercurrent result in the generation of meanders near the coast as the meanders intensify cold upwelling filaments develop along the coast and subsequently extend farther offshore in time the meanders form both cyclonic and anticyclonic eddies which subsequently propagate farther offshore longer simulation times 3 4 years in which a quasi equilibrium state for the ccs is reached show a seasonal cycle in response to the wind forcing for the coastal currents upwelling and filaments the meanders and eddies however can be quasi permanent as well as seasonal features the quasi permanent features play a significant role in modifying coastal currents upwelling and filaments which leads to large temporal and spatial variability in the ccs in a sensitivity study the results from several numerical experiments are used to examine the dependence of the generation of the currents meanders and eddies on the type of coriolis parameterization wind forcing and coastline geometry both the meridional variability of plane and the alongshore component of the wind stress are shown to be key ingredients for generating realistic vertical and horizontal structures for the cores of the surface equatorward and the subsurface poleward currents with such structures the currents are baroclinically and barotropically unstable resulting in the generation of meanders filaments and eddies irregularities in the coastline geometry are shown to be important for anchoring upwelling and filaments as well as for enhancing the growth of meanders and eddies cyclonic eddies tend to form in the vicinity of capes while anticyclonic eddies tend to form in the coastal indentations between capes the region off cape blanco is identified as the location where the coastal equatorward flow off oregon leaves the coast to develop a meandering jet off california the results from these experiments support the hypothesis that wind forcing and coastline irregularities on a beta plane are important mechanisms for the generation of many of the observed features of the ccs

a separating coastal upwelling jet at cape blanco oregon and its connection to the california current system the coastal upwelling region near cape blanco oregon 433n o the west coast of the united states was studied using a towed ctd on seasoar a shipboard acoustic doppler current pro ler adcp satellite sea surface temperature maps and surface drifters during august 1995 the equatorward upwelling jet was inshore of the shelfbreak north of cape blanco meandered gently o shore around the cape and then veered sharply o shore just to the south of the cape analysis of vertical sections of density velocity and spicinessa con rmed the separation of an upwelling jet and front the jet was followed from over the shelfbreak north of the cape to 100 km o shore downstream of the cape the separating jet originates from the coastal upwelling jet leaving the shelf but is augmented by an o shore branching of the poleward undercurrent by combining information from adcp streamfunction maps with analysis of hydrographic data including distributions of the tracer like quantity spicinessa a conceptual model of the three dimensional circulation near the cape emerges a mid shelf upwelling jet encounters a coastal promontory then turns o shore stretching and deepening as it crosses the continental margin the jet then turns back shoreward cyclonically where the deepened equatorward ow encounters the top of the poleward undercurrent owing along the continental slope this causes a portion of the undercurrent to turn o shore to join and strengthen the equatorward transport in the separated jet throughout the separation process the coastal upwelling front and jet are continuous robust features separation of a coastal upwelling jet is an important mechanism for cross shelf transport from the coast to the deep ocean cape blanco appears to be the northernmost point where an equatorward jet regularly separates from the coast to become an oceanic jet and thus serves as the northern boundary of the region where an intense meandering current characteristic of the california current system

river runoff effect on the suspended sediment property in the upper chesapeake bay using modis observations and roms simulations ocean color data derived from the moderate resolution imaging spectroradiometer modis on the satellite aqua from 2002 to 2012 and simulations from the regional ocean modeling system roms are used to study the impact of the susquehanna river discharge on the total suspended sediment tss concentration in the upper chesapeake bay since the water in the upper chesapeake bay is highly turbid the shortwave infrared swir based atmospheric correction algorithm is used for deriving the normalized water leaving radiance nlw spectra from modis aqua measurements nlw spectra are further processed into the diffuse attenuation coefficient at the wavelength of 490 nm kd 490 and tss modis aqua derived monthly tss concentration in the upper chesapeake bay and in situ susquehanna river discharge data show similar patterns in seasonal variations the tss monthly temporal variation in the upper chesapeake bay is also found in phase with the monthly averaged river discharge data since the susquehanna river discharge is mainly dominated by a few high discharge events due to winter spring freshets or tropical storms in each year the impact of these high discharge events on the upper chesapeake bay tss is investigated both modis measured daily tss images and sediment data derived from roms simulations show that the susquehanna river discharge is the dominant factor for the variations of tss concentration in the upper chesapeake bay although the high river discharge event usually lasts for only a few days its induced high tss concentration in the upper chesapeake bay can sustain for 10 20 days the elongated tss rebounding stage is attributed to horizontal advection of slowly settling fine sediment from the susquehanna river

the tattered curtain hypothesis revised coastal jets limit cross shelf larval transport exchange and retention of coastal waters modulate dispersal of marine larvae affecting marine ecosystem dynamics a hypothesis was put forward in the 1980s describing the coastal upwelling front as a tattered curtain that retains larvae this front was envisioned to be broken up by squirts and eddies hitting the coast under upwelling relaxation events here we revise this hypothesis by using an idealized ocean model of an eastern boundary upwelling current and an idealized particle larvae model appropriate for shelf spawning benthic species modeled larval settlement patterns were controlled by retention in the core of the upwelling jet bounded by regions of high velocity shear on the flanks of the jet squirts filaments poleward moving eddies and meanders modulated settlement patterns locally while dense packets moved equatorward within the upwelling jet correlation between settlement i e particles 20 40 d old 10 km from shore and wind was low for a lagged wind product r 0 33 and moderate for a 20 d integrated wind product r 0 62 we determined that it is not upwelling relaxation but sustained moderate upwelling that can result in a highly retentive jet that entrains larvae and acts as a barrier to cross shelf transport however the amount of retention is highly variable settlement was low after strong persistent upwelling completely tattered the jet jet cores in general should act as important retentive transport barriers across diverse coastal systems a view supported by dynamical theory modeling studies and larval recruitment observations

linking wind and interannual upwelling variability in a regional model of the southern benguela we quantify the wind contribution to the development of interannual sea surface temperature sst anomalies along the shelf of southern africa we compare numerical simulations that differ only in the amount of variability kept in the ers1 2 derived surface wind forcing surprisingly most of the cold and warm episodes over the agulhas bank are strictly related to local fluctuations of the forcing whereas the shelf of the west coast extending 400 km north of cape columbine is equally sensitive to open sea wind fluctuations we diagnose the respective role of mesoscale eddy activity and of low frequency and intra monthly wind fluctuations in generating interannual sst variability the fair degree of correlation obtained at a few locations between the model and concomitant observations confirms the interest of a regional numerical tool to study anomalous events in the benguela system

intensification of upwelling along oman coast in a warming scenario the oceanic impact of poleward shift in monsoon low level jet mllj is examined using a regional ocean modeling system roms two sets of downscaling experiments were conducted using roms with boundary and initial conditions from six cmip5 models while outputs from the historical run 1981 2000 acts as forcing for the first the second uses rcp8 5 2080 2099 by comparing the outputs it is found that oman coast will experience an increase in upwelling in tune with mllj shift consistent with the changes in upwelling and zonal ekman transport temperature salinity and productivity show significant changes near the oman coast the changes in mllj causes the coastal wind to angle against the oman coast in such a fashion that the net upwelling increases in the next century and so does the marine productivity this study contrasts the general view of weakening of upwelling along the arabian coasts due to the weakening of monsoon winds

poleward propagating subinertial alongshore surface currents off the u s west coast 1 the network comprising 61 high frequency radar systems along the u s west coast uswc provides a unique high resolution and broad scale view of ocean surface circulation subinertial alongshore surface currents show poleward propagating signals with phase speeds of o 10 and o 100 300 km d 1 that are consistent with historical in situ observations off the uswc and that can be possibly interpreted as coastally trapped waves ctws the propagating signals in the slow mode are partly observed in southern california which may result from scattering and reflection of higher mode ctws due to curvature of shoreline and bathymetry near point conception california on the other hand considering the order of the phase speed in the slow mode the poleward propagating signals may be attributed to alongshore advection or pressure driven flows a statistical regression of coastal winds at national data buoy center buoys on the observed surface currents partitions locally and remotely wind forced components isolates footprints of the equatorward propagating storm events in winter off the uswc and shows the poleward propagating signals year round

modeling the east australian current in the western tasman sea the east australian current eac is a western boundary current flowing southward off the east coast of australia its eddy variability has been shown to be vigorous a typical feature being the formation of a large warm core eddy in the western tasman sea the dynamics controlling the development of such an eddy are the subject of this paper the princeton ocean model was tuned for conditions that prevail in the western tasman sea and initialized with features based on the royal australian navy weekly temperature charts a 70 day simulation initialized with summer conditions captures the formation of a large warm core eddy that matches fairly well the observations analyses of the results demonstrate that the formation of these eddies is associated with a wide range of dynamical aspects observed in the region such as oscillation and propagation of the tasman front eac separation from the coast formation of cold core frontal eddies and nutrient enrichment of coastal waters

upwelling filaments and motion of a satellite tracked drifter along the west coast of north america an argos tracked surface buoy deployed off vancouver island in july 1984 reached hawaii in july 1985 we present an analysis of the drifter track with particular emphasis on the equatorward leg seaward of the north american coast for the period july december 1984 a low pass filter is used to separate motions into mean and fluctuating components the mean track was consistently to the right of the direction expected according to the climatological geopotential topography relative to 1000 dbar and the average southward drift speed of 0 20 m s 1 exceeded the mean geopotential flow speed by a factor of 2 3 on the basis of 1 year of drifter positions we estimate that surface waters complete one circuit of the north pacific gyre in 4 5 years the amplitudes of the mesoscale buoy displacements about the mean path were approximately 43 10 km and the root mean square drift speed was 0 32 0 18 m s 1 motions at tidal and near inertial frequencies were negligible from august to october the buoy paralleled a major upwelling regime centered off northern california during this period the track underwent five sinuous zonal perturbations with characteristic amplitudes of approximately 50 km two of the perturbations were associated with abrupt temperature drops of 3 c and maximum seaward currents of 0 70 m s 1 national oceanic and atmospheric administration advanced very high resolution radiometer thermal imagery for these times reveals that the buoy had encountered seaward protruding cold water filaments squirts associated with 100 km length upwelling zones that constitute the large scale upwelling regime southward of the upwelling regime the equatorward drift speed of the buoy was only slightly greater than the equatorward advance of the surface isotherms suggesting that advection rather than winter cooling might be mainly responsible for the shift in the temperature pattern

an observation of the three dimensional structure of a cross shelf penetrating front off the changjiang mouth satellite images and in situ hydrography and nutrient observations are used to study the three dimensional structure of a penetrating front off the changjiang mouth in the east china sea the satellite images of modis terra on october 16 2006 show anomalously high concentrations of chlorophyll and total suspended sediments extending offshore from the mean coastal front off the chiangjiang mouth however the sea surface temperature image of the same satellite shows no signature of this extension at all the in situ hydrography measured during the same time as the satellite images discloses that the surface layer of the front is occupied by low salinity waters from the nearshore area which suggests a cross shelf jet covering a distance of about 50 km a counter intrusion underneath the surface offshore jet is indicated by an increase of the subsurface temperature and salinity during the offshore excursion of the front which leads to a significant temperature inversion at the head of the front the vertical temperature and salinity distribution shows propensity of double diffusive processes which may contribute to the ensuing evolution of the front the nutrient distribution of the front is consistent with the cross shelf jet derived from the hydrographic data with surface and bottom intensified concentrations and minimum mid depth concentrations suggesting that the primary transport of the surface nutrients is in the horizontal cross shelf direction the potential dynamics of the frontal intrusion is discussed in light of wind forcing and frontal instability the intrusion is found to be very important to cross shelf and cross front exchanges in the east china sea c 2010 elsevier ltd all rights reserved

inversion of submesoscale patterns from a high resolution solomon sea model feasibility assessment a high resolution realistic numerical model of the solomon sea which exhibits a high level of variability at mesoscales and submesoscales is used to explore new avenues for data assimilation image data assimilation represents a powerful methodology to integrate information from high resolution observations such as satellite sea surface temperature or chlorophyll or high resolution altimetric sea surface height that will be observed in the forthcoming swot mission the present study investigates the feasibility and accuracy of the inversion of the dynamical submesoscale information contained in high resolution images of sea surface temperature sst or salinity sss to improve the estimation of oceanic surface currents the inversion method is tested in the context of twin experiments with sst and sss data provided by a model of the solomon sea for that purpose synthetic tracer images are built by binarizing the norm of the gradient of sst sss or spiciness the binarized tracer images are compared to the dynamical image which is derived from the finite size lyapunov exponents the adjustment of the dynamical image to the tracer image provides the optimal correction to be applied on the surface velocity field the method is evaluated by comparing the result of the inversion to the reference model solution the feasibility of the inversion of various images sst sss both sst and sss or spiciness is explored on two small areas of the solomon sea we show that errors in the surface velocity field can be substantially reduced through the inversion of tracer images

a mesoscale eddy dipole in the offshore california current there is a transition zone in the california current system between inshore coastal and offshore oceanic flow this transition zone is associated with the main core of the california current and is populated with offshore mesoscale eddies the structure of isolated eddies and dipole eddy pairs found within the transition zone is examined using water mass analysis spiciness and dissolved oxygen the analyses show that these offshore mesoscale eddies have cores which contain california undercurrent water these observations and independent observations of the sitka eddy near sitka alaska support the conclusion that a bathymetrically induced instability of the california undercurrent is a likely generation mechanism for the offshore eddies this conclusion also is consistent with mathematical models of eddy generation in a subsurface poleward baroclinic current the similarity between long term mean conditions caicofi conditions observed during january 1981 and july 1985 and those of the sitka eddy coupled with the bathymetric effects provides a plausible explanation for the recurrence of offshore mesoscale eddies at preferred locations within the transition zone

numerical simulation of flow around a tall isolated seamount part i problem formulation and model accuracy abstract a sigma coordinate ocean circulation model is employed to study flow trapped to a tall seamount in a periodic f plane channel in part i errors arising from the pressure gradient formulation in the steep topography strong stratification limit are examined to illustrate the error properties a linearized adiabatic version of the model is considered both with and without forcing and starting from a resting state with level isopycnals the systematic discretization errors from the horizontal pressure gradient terms are shown analytically to increase with steeper topography relative to a fixed horizontal grid and for stronger stratification as measured by the burger number for an initially quiescent unforced ocean the pressure gradient errors produce a spurious oscillating current that at the end of 10 days is approximately 1 cm s 1 in amplitude the period of the spurious oscillation about 0 5 days is shown to be a consequence of the particular form of the pressure gradient terms in th

numerical simulation of a synoptic event in the southern california bight 1 in the middle of march 2002 a synoptic upwelling event occurred in the southern california bight it was marked by a precipitous cooling of at least 4 c within 10 20 km of the coast by the end of the month the preevent temperatures had slowly recovered the regional oceanic model system roms is used to simulate the event with an atmospheric downscaling reanalysis for surface wind and buoyancy flux forcing lateral boundary conditions of temperature salinity velocity and sea level are taken from a global oceanic product barotropic tidal fields from a global barotropic model are imposed along the open boundaries the simulation reproduces well the upwelling process compared with observed data the sensitivity of the simulation is examined to wind resolution heat flux and tidal forcing the oceanic response to the different wind resolutions converges at the level of the 6 km resolution which is the finest scale present in the terrain elevation data set used in the atmospheric downscaling the combination of an analytical diurnal cycle in the solar radiation and the empirical coupling with the instantaneous roms sea surface temperature produces a similar oceanic response to the downscaled heat flux tidal effects are significant in the upwelling evolution due to the increase in wind energy input through a quasi resonant alignment of the wind and surface current probably by chance

submesoscale instability and generation of mesoscale anticyclones near a separation of the california undercurrent abstractthe california undercurrent cuc flows poleward mostly along the continental slope it develops a narrow strip of large negative vertical vorticity through the turbulent boundary layer and bottom stress in several downstream locations the current separates aided by topographic curvature and flow inertia in particular near point sur ridge south of monterey bay when this happens the high vorticity strip undergoes rapid instability that appears to be mesoscale in eddy resolving simulations but is substantially submesoscale with a finer computational grid the negative relative vorticity in the cuc is larger than the background rotation f and ertel potential vorticity is negative this instigates ageostrophic centrifugal instability the submesoscale turbulence is partly unbalanced has elevated local dissipation and mixing and leads to dilution of the extreme vorticity values farther downstream the submesoscale activity abates and the remaining eddy motions exhibit an upscale organizati

assimilation of surface velocity data into a primitive equation coastal ocean model summer of 1998 are 0 42 and 0 78 respectively demonstrating the effectiveness of the das our estimates of the error covariances are shown to be appropriate through a series of objective statistical tests analysis of the term balances of the model equations show that the dominant modeled dynamical balances are preserved by the das and that uncertainties in the spatial variability of the wind forcing are likely to be one source of model error by varying the relative magnitudes of the estimated forecast and observation error covariances the das is shown to be most effective when approximately 80 of the analysis is made up of the model solution index terms 4263 oceanography general ocean prediction 4219 oceanography general continental shelf processes 4255 oceanography general numerical modeling 3337 meteorology and atmospheric dynamics numerical modeling and data assimilation 4516 oceanography physical eastern boundary currents 4594 oceanography physical instruments and techniques keywords practical data assimilation numerical modeling upwelling highfrequency radar data

cross shore transport variability in the california current ekman upwelling vs eddy dynamics abstract the low frequency dynamics of coastal upwelling and cross shelf transport in the central and southern california current system ccs are investigated using the regional ocean modeling system roms over the period 1965 2008 an ensemble of passive tracers released in the numerical model is used to characterize the effects of linear ekman upwelling and non linear mesoscale eddies circulation dynamics on the statistics of advection of coastal waters the statistics of passive tracers released in the subsurface show that the low frequency variability of coastal upwelling and cross shelf transport of the upwelled water mass are strongly correlated with the alongshore wind stress and are coherent between the central and southern ccs however the offshore transport of tracers released at the surface is not coherent between the two regions and is modulated by intrinsic mesoscale eddy activity in particular cyclonic eddies the transport of cyclonic eddies extends with depth and entrains water masses of southern origin advected by the poleward california undercurrent cuc the cuc water masses are not only entrained by eddies but also constitute a source for the central california upwelling system the interplay between intrinsic eddy activity and deterministic ekman upwelling dynamics in controlling the cross shelf exchanges in the ccs may provide an improved framework to understand and interpret nutrients and ecosystem variability

thermal subsidence and generation of hydrocarbons in michigan basin temperature histories for selected stratigraphic horizons in the michigan basin are computed from three dimensional continually filled subsidence models mechanical evolution of the michigan basin is modeled as flexure of the lithosphere caused by thermal contraction results are compatible with the subsidence record of the sediments and free air gravity anomalies paleotemperature is determined from excess temperature due to the thermal anomaly plus burial temperature predicted from subsidence curves for an equilibrium temperature gradient of 22 c km 1 2 f 100 ft surface temperature of 20 c 68 f and an equilibrium surface heat flow of 1 1 hfu excess temperature paleotemperature and surface heat flow do not exceed 15 c 27 f 110 76 c 230 f and 2 5 hfu respectively these estimates are consistent with upper limits set by paleomagnetic studies the low value for excess temperature is caused by concentration of the thermal anomaly below 15 km 9 mi in agreement with gravity results the great depth of the thermal anomaly can explain the lack of evidence for an initial heating event prior to subsidence once the thermal history of the sediments is specified the oil potential of the basin can be determined from laboratory derived kinetic equations for degradation of kerogen to petroleum for the michigan basin predicted temperature conditions are sufficient for source rock 25 conversion of type i and type ii kerogen only in ordovician and older rocks in the southern peninsula of michigan by this model petroleum found in rocks younger than ordovician would have had to migrate upward from the older rocks geochemical studies of dundee devonian and trenton ordovician crude oils in michigan are compatible with this interpretation niagaran silurian crude oils appear to come from a different source than the dundee and trenton oils if their source is silurian rocks on the flanks of the basin either the scheme used to calculate maturity is not applicable to these oils or the temperature of the source rocks was significantly higher in the past than today more likely the model underestimates the depth of burial of silurian source rocks near the center of the basin especially in local regions of downfaulting

upwelling filaments off cap blanc interaction of the nw african upwelling current and the cape verde frontal zone eddy field 1 the hydrographical and dynamical properties of the upwelling filaments forming off cap blanc mauritania are investigated using remotely sensed and in situ data collected in april may 2009 during the strongest upwelling season the area is situated at the southern edge of the nw african upwelling system where the cape verde frontal zone cvfz separates warmer saltier north atlantic central water nacw and cooler fresher south atlantic central water sacw sea surface temperature images indicated the presence of an upwelling filament extending 280 km offshore rooted over the cap blanc promontory and entrained around a warm core anticyclonic eddy after this filament started to decay a new cold filament developed at the approximate same location high resolution moving vessel profiler mvp and acoustic doppler current profiler adcp surveys of these mesoscale structures revealed that both filaments were carrying south atlantic central water sacw offshore through an intense jet like flow similarity of the relative vorticity structure across the filament with that of the tangent eddy suggested that the latter was responsible for the offshore current tracking of this eddy in altimetric data demonstrated that it originated from the cvfz as implied by its hydrographic structure altimetric data also revealed that another anticyclonic structure centered over the cap blanc promontory was responsible for the northwestward advection of sacw into the base of the filament the results support the idea that some upwelling filaments can be produced by the interaction of an external eddy field including topographic eddies with the upwelled water

northern current variability and its impact on the blanes canyon circulation a numerical study a high resolution 1 2 km 3d numerical model was used to analyze the interaction of the northern current a right bounded flow with the blanes submarine canyon bc nw mediterranean although it refers to a climatological simulation the model properly suites our purpose since it simulates the northern current nc mesoscale variability as well as its seasonal variability model results were validated with satellite sea surface temperature and current meter data the simulated nc tends to be faster and deeper in winter and slower and shallower in summer according to our results nc meanders and eddies are recurrent in the bc area and produce highly fluctuating three dimensional circulation patterns within the canyon we found that nc meanders and anticyclonic eddies propagating along the current pathway tend to be deep and consequently their effects extend down to the deeper part of the bc we also found that the meandering of the nc plays a key role in enhancing vertical motions inside the bc upwelling and downwelling events occurring on timescales of 4 20 days are associated with nc meanders crests and troughs passing over the bc net upwelling downwelling events are accordingly influenced by the nc seasonality they are more predominant in winter while damped in summer our results show the importance of nc meanders in creating local net upwelling downwelling and strengthen the evidence that continuous right bounded downwelling favorable flows can also produce net upwelling inside submarine canyons

inner shelf circulation patterns and nearshore flow reversal under downwelling and stratified conditions off a curved coastline 1 the role of a curved coastline and associated bathymetry in the development of downwelling circulation in a stratified inner shelf is examined through a number of numerical experiments different scenarios include constant versus variable wind forcing and variations in bottom friction the three dimensional response of the shelf within the domain embayment enclosed by capes is associated with the generation of a velocity pycnocline disturbance at the upstream cape and its subsequent downstream advection this disturbance is more pronounced under variable wind conditions its downstream advection through the bay exhibits different patterns depending on the competition between inertia and bottom friction near the cape when inertia dominates the disturbance separates from the cape and travels downwind with an enhanced downstream flow offshore and a countercurrent inshore the separation occurs at a low rossby number ro 0 15 which is attributed to the positive curvature of the coastline forming the cape when friction dominates the advection path is constrained along the coastline resulting in an alongshore temperature gradient and a transient thermal front running almost perpendicular to the coast isobaths simulations with spatially variable bottom friction with higher friction toward the coast result in the generation of eddy like features the numerical results are in agreement with both observations and surface temperature imagery from long bay south carolina an embayment enclosed by two capes and emphasize the role that coastline and associated shelf morphology can play in enhancing cross shelf transport and exchange

coupled effects of ocean current on wind stress in the bay of bengal eddy energetics and upper ocean stratification abstract this study examines the effect of surface current in the bulk formula for the wind stress referred to as the relative wind rw effect on the energetics of the geostrophic circulation and the upper ocean stratification in the bay of bengal bob during the summer monsoon seasons when the rw effect is taken into account in the high resolution scoar wrf roms regional coupled model simulation and compared to the run without such a consideration the kinetic energy both in the mean mke and eddy eke is reduced by more than a factor of two the most significant reduction in the kinetic energy is found along the path of the northward east india coastal current eicc and to the south of its separated latitude the energetics calculations and spectral analysis reveal that this significant damping of eke is primarily due to reduced eddy wind work principally at wavelengths close to the first baroclinic rossby deformation radius indicating the modulation of the wind work by geostrophic mesoscale eddy fields moreover the mixed layer depth mld is significantly shoaled south of the separated eicc latitude the area dominated by anticyclonic eddy activity the shallower mixed layer and enhanced stratification with the rw effect are attributed to doming of the isopycnals by the anomalous upward ekman velocity which itself is generated by the interaction of anticyclonic mesoscale surface current and the prevailing southwesterly monsoonal wind overall the geostrophic circulation and upper ocean stratification along the eicc and south of its separated latitude exhibit the most significant dynamical response this result implies that this southwestern part of the bob is a hot spot for the momentum exchange between the surface circulation and the monsoonal winds thus a potential area for focused field measurements for the ocean circulation energetics and air sea interaction

effect of lower sea level on geostrophic transport through the florida straits during the last glacial maximum 1 we investigate the effect of a 120 m sea level drop on transport through the caribbean sea and the florida straits during the last glacial maximum lgm relative to the present using the regional ocean modeling system roms a geostrophic transport estimate for the florida straits suggests the lgm florida current was weaker than today by one third assuming that the velocity at the bottom of the channel was as small as it is today this is consistent with a decrease in the north atlantic overturning circulation but there are other possible reasons for a flow decrease it is possible that a shallower lgm florida straits sill depth could cause the diversion of some flow from the florida current our model results show that the volume transport through the florida straits is slightly reduced in a lower sea level model simulation when compared to a control sea level simulation 34 8 2 0 sv versus 39 8 2 3 sv the difference in transport is of the order of 5 sv likely representing a maximum limit to the lgm flow reduction due to sea level change therefore the change in sill depth between the lgm and the present is unlikely to have been a cause of the entire observed flow reduction we also use the model output to demonstrate that transport through the florida straits can be accurately calculated from ocean margin density data at the core locations in the work of lund et al 2006 and lynch stieglitz et al 2009 provided that a sufficiently deep reference level is chosen

sensitivity of the northern humboldt current system nearshore modeled circulation to initial and boundary conditions 1 the influence of the eastern pacific equatorial circulation on the dynamics of the northern humboldt current system is studied using an eddy resolving regional circulation model forced by boundary conditions from three distinct ocean general circulation models the seasonal variability of the modeled nearshore circulation and the mesoscale activity are contrasted in order to evaluate the role of the density forcing the seasonal variability of the surface and subsurface alongshore currents strongly depends on the amplitude and timing of the seasonal eastward propagating equatorial waves the equatorward flow and upwelling intensity are also impacted by nonlinear processes such as the seasonal generation of nearshore mesoscale eddies which create alongshore pressure gradients modulating the surface current boundary conditions affect differently the intensity and phase of the eddy kinetic energy as baroclinic instability is triggered by coastal waves during austral summer and fall whereas it is sustained by the wind driven upwelling during austral winter

central south pacific thermocline water circulation from a high resolution ocean model validated against satellite data seasonal variability and el nino 1997 1998 influence 1 the oceanic circulation in french polynesia central south pacific is investigated based on a high resolution model validated with satellite data we focus on the upper 500 m where ocean current variability has been barely documented due to a lack of in situ measurements seasonal and el nino southern oscillation 1997 1999 variability of surface and subsurface currents are characterized in the north the south equatorial current sec follows a seasonal cycle with winter enhancement corresponding to trade wind strengthening during summer the sec slows and the eastward south equatorial countercurrent secc appears across the domain north of an upward ekman pumping region related to the south pacific convergence zone development in the area around the marquesas islands a wind curl dipole is suspected to create westward and eastward marquesas countercurrent mcc jets the eastward subtropical countercurrent stcc is found south of 20 s it is disturbed by eddies and broken into westward and eastward branches during el nino 1997 1998 due to the reversed winds in the equatorial band the sec weakened while eastward countercurrents appeared the secc reinforced and moved northeastward in summer 1998 during la nina 1998 1999 following the trade wind enhancement the sec strengthened the countercurrents weakened or disappeared and the secc moved southwestward in summer 1999 during both el nino and la nina events the stcc eddy activity strengthened while the mcc and associated westward jet were absent these variations and their dynamical origins are discussed and a coherent picture of the french polynesian current system and its variations is proposed

observation and modeling of satellite sensed meanders and eddies off vancouver island abstract a long time series of satellite infrared images spanning the period 21 july 8 october 1980 reveals the evolution of long 160 km and short 80 km wavelength meanders of the california current system off vancouver island midway in the series strong interactions occurred between the two meander scales although the shorter meanders were initially more energetic they were eventually dominated by the longer meanders near the end of the time series detached mesoscale eddies were formed from the longer meanders current meter data from the period before meander growth clearly indicates the presence of a strong vertical shear near 150 m which consists of a southeastward surface current and a northwestward undercurrent it is argued in this paper that the observed shear flow is the energy source for the meanders and eddies seen in the satellite images a four layer quasi geostrophic model is used to represent the california current system off vancouver island the two upper layers represent the

equilibrium structure and dynamics of the california current system this paper addresses the structure and dynamical mechanisms of regional and mesoscale physical variability in the subtropical northeast pacific ocean using the regional oceanic modeling system roms the model is configured with a u s west coast domain that spans the california current system ccs with a mesoscale horizontal resolution up to as fine as 3 5 km its mean seasonal forcing is by momentum heat and water fluxes at the surface and adaptive nudging to gyre scale fields at the open water boundaries its equilibrium solutions show realistic mean and seasonal states and vigorous mesoscale eddies fronts and filaments the level of eddy kinetic energy eke in the model is comparable to drifter and altimeter estimates in the solutions with sufficiently fine resolution because the model lacks nonseasonal transient forcing the authors conclude that the dominant mesoscale variability in the ccs is intrinsic rather than transiently forced the primary eddy generation mechanism is the baroclinic instability of upwelling alongshore currents there is progressive movement of meanseasonal currents and eddy energy offshore and downward into the oceanic interior in an annually recurrent cycle the associated offshore eddy heat fluxes provide the principal balance against nearshore cooling by mean ekman transport and upwelling the currents are highly nonuniform along the coast with important influences by capes and ridges in both maintaining mean standing eddies and launching transient filaments and fronts

what determines the spatial pattern in summer upwelling trends on the u s west coast 1 analysis of sea surface temperature sst from coastal buoys suggests that the summertime over shelf water temperature off the u s west coast has been declining during the past 30 years at an average rate of 0 19 c decade 1 this cooling trend manifests itself more strongly off south central california than off oregon and northern california the variability and trend in the upwelling north of off san francisco are positively correlated with those of the equatorward wind indicating a role of offshore ekman transport in the north in contrast ekman pumping associated with wind stress curls better explains the stronger and statistically more significant cooling trend in the south while the coast wide variability and trend in sst are strongly correlated with those of large scale modes of climate variability they in general fail to explain the southward intensification of the trend in sst and wind stress curl this result suggests that the local wind stress curl often topographically forced may have played a role in the upwelling trend pattern

circulation and multiple scale variability in the southern california bight abstract the oceanic circulation in the southern california bight scb is influenced by the large scale california current offshore tropical remote forcing through the coastal wave guide alongshore and local atmospheric forcing the region is characterized by local complexity in the topography and coastline all these factors engender variability in the circulation on interannual seasonal and intraseasonal time scales this study applies the regional oceanic modeling system roms to the scb circulation and its multiple scale variability the model is configured in three levels of nested grids with the parent grid covering the whole us west coast the first child grid covers a large southern domain and the third grid zooms in on the scb region the three horizontal grid resolutions are 20 km 6 7 km and 1 km respectively the external forcings are momentum heat and freshwater flux at the surface and adaptive nudging to gyre scale soda reanalysis fields at the boundaries the momentum flux is from a three hourly reanalysis mesoscale mm5 wind with a 6 km resolution for the finest grid in the scb the oceanic model starts in an equilibrium state from a multiple year cyclical climatology run and then it is integrated from years 1996 through 2003 in this paper the 8 year simulation at the 1 km resolution is analyzed and assessed against extensive observational data high frequency hf radar data current meters acoustic doppler current profilers adcp data hydrographic measurements tide gauges drifters altimeters and radiometers the simulation shows that the domain scale surface circulation in the scb is characterized by the southern california cyclonic gyre comprised of the offshore equatorward california current system and the onshore poleward southern california countercurrent the simulation also exhibits three subdomain scale persistent i e standing cyclonic eddies related to the local topography and wind forcing the santa barbara channel eddy the central scb eddy and the catalina clemente eddy comparisons with observational data reveal that roms reproduces a realistic mean state of the scb oceanic circulation as well as its interannual mainly as a local manifestation of an enso event seasonal and intraseasonal eddy scale variations we find high correlations of the wind curl with both the alongshore pressure gradient apg and the eddy kinetic energy level in their variations on time scales of seasons and longer the geostrophic currents are much stronger than the wind driven ekman flows at the surface the model exhibits intrinsic eddy variability with strong topographically related heterogeneity westward propagating rossby waves and poleward propagating coastally trapped waves albeit with smaller amplitude than observed due to missing high frequency variations in the southern boundary conditions

dynamics of wind driven upwelling and relaxation between monterey bay and point arena local regional and gyre scale controls 1 in north and central california equatorward winds drive equatorward flows and the upwelling of cold dense water over the shelf during the midspring and summer upwelling season when the winds temporarily weaken the upwelling flows between point reyes and point arena relax becoming strongly poleward over the shelf analytical and numerical models are used to describe the effect of alongshore variability of winds bathymetry and basin scale pressure gradients on the strength of upwelling and its relaxation alongshore winds weaken to the south of point reyes and the shelf becomes narrower from point reyes to monterey bay both of these lead to reduced upwelling at and to the north of point reyes causing an alongshore gradient of temperature and density on the shelf these alongshore gradients lead to an along isobath pressure gradient over the shelf that drive the relaxation flows a simple analytical model is used to explain the dynamics magnitude and structure of the relaxation flows the modeling also suggests that the depth of origin of the upwelled waters and thus their temperature is controlled by the along isobath pressure gradient that exists over the continental slope this along slope pressure gradient is also responsible for the california undercurrent in this region this pressure gradient is not generated in a model of the californian coast extending from 32 n to 42 n and integrated for several months suggesting it is caused by dynamics whose spatial or temporal scales are larger than the californian coast and or longer than several months

impact of nearshore wind stress curl on coastal circulation and primary productivity in the peru upwelling system 1 coastal upwelling dynamics are strongly affected by alongshore wind stress and nearshore wind stress curl a coupled physical biogeochemical regional model and lagrangian diagnostics are used in the peru current system to determine how the upwelling of nutrients and the primary productivity are impacted by the spatial structure of the nearshore wind stress three wind stress products derived from the ers and quikscat scatterometers and a smoothed quikscat field mainly differing in nearshore wind stress curl patterns were used simulations are found to produce significantly different mean surface chlorophyll distributions and show that strong upwelling favorable nearshore wind stress curl may locally induce a wide coastal productive zone through upwelling of nutrient replete waters brought by a shoaling coastal undercurrent using wind stress products with realistic nearshore patterns is therefore crucial for the modeling of coupled physical biogeochemical coastal processes

mesoscale to submesoscale transition in the california current system part i flow structure eddy flux and observational tests in computational simulations of an idealized subtropical eastern boundary upwelling current system similar to the california current a submesoscale transition occurs in the eddy variability as the horizontal grid scale is reduced to o 1 km this first paper in a series of three describes the transition in terms of the emergent flow structure and the associated time averaged eddy fluxes in addition to the mesoscale eddies that arise from a primary instability of the alongshore wind driven currents significant energy is transferred into submesoscale fronts and vortices in the upper ocean the submesoscale arises through surface frontogenesis growing off upwelled cold filaments that are pulled offshore and strained in between the mesoscale eddy centers in turn some submesoscale fronts become unstable and develop submesoscale meanders and fragment into roll up vortices associated with this phenomenon are a large vertical vorticity and rossby number a large vertical velocity relatively flat horizontal spectra contrary to the prevailing view of mesoscale dynamics a large vertical buoyancy flux acting to restratify the upper ocean a submesoscale energy conversion from potential to kinetic a significant spatial and temporal intermittency in the upper ocean and material exchanges between the surface boundary layer and pycnocline comparison with available observations indicates that submesoscale fronts and instabilities occur widely in the upper ocean with characteristics similar to the simulations

spatial and temporal characteristics of the mesoscale circulation of the california current from eddy resolving moored and shipboard measurements moored observations of currents and temperatures made in the upper 600 rn on eddy resolving scales over a 2 year period are used to examine the spatial and temporal characteristics of the california current mesoscale circulation the observations were made at three principal longitudes 124ow 126ow and 128ow in the vicinity of point arena they bracket the 600 km wide band of high mesoscale variability found along the eastern boundary of the north pacific at all locations the mesoscale variability was larger than the mean flow and the spatial modes of variability as determined from empirical orthogonal function analysis consisted of an alongshore mode a cross shore mode and a rotational mode observations made near the continental slope 124ow were dominated by the poleward flowing california undercurrent with mesoscale eddies and meanders superposed the nearshore eddy kinetic energy peaked in a band centered around 60 days observations made at 128ow near the offshore boundary between the energetic mesoscale band and the eddy desert of the northeast pacific were characterized by small means fewer eddy events and a peak in eddy kinetic energy at 120 180 days the good horizontal resolution of the current meter arrays allowed us to estimate the relative vorticity horizontal divergence and rossby number and therefore to evaluate the relative strength and occurrence of anticyclones and cyclones we found the mesoscale eddy field to be strongly nonlinear with rossby numbers ranging from 0 1 to 0 5 all of the eddies observed at the offshore site were nonlinear deep warm anticyclones shipboard hydrography revealed the origin of one of these anticyclones to be the california undercurrent and this eddy retained its strong anomalies after several months and several hundred kilometers of propagation despite the lower incidence of eddies as one moves west from the coast the eddies that we observed offshore provide evidence for propagation and transport of properties from the coast to the central north pacific across the california current system

wind driven coastal generation of annual mesoscale eddy activity in the california current abstract two candidate sources for the generation of mesoscale eddy activity in the california current are local baroclinic instability and or the wind stress adjacent to the coast the latter constitutes remote forcing with eddy activity propagating westward from the coast into the california current via rossby wave dynamics in this study two wind driven models are utilized to test the relative significance of these two sources one is an eddy resolving quasigeostrophic qg model with the ability to represent baroclinic instability but not the coastal response to winds the other is a 1 layer primitive equation pe model with the ability to represent the coastal response to winds but not baroclinic instability both models have the same spatial grid i e approximately 20 km and are driven by the same coarse grid wind stress forcing fields over the same one year time period i e january 1987 to december 1987 this period is chosen because of the availability of geosat altimetric sea level obs

an index to distinguish surface and subsurface intensified vortices from surface observations in this study the authors first show that it is difficult to reconstruct the vertical structure of vortices using only surface observations in particular they show that the recent surface quasigeostrophy sqg and interior and surface quasigeostrophy isqg methods systematically lead to surface intensified vortices and those subsurface intensified vortices are thus not correctly modeled the authors then investigate the possibility of distinguishing between surface and subsurface intensified eddies from surface data only using the sea surface height and the sea surface temperature available from satellite observations a simple index based on the ratio of the sea surface temperature anomaly and the sea level anomaly is proposed while the index is expected to give perfect results for isolated vortices the authors show that in a complex environment errors can be expected in particular when strong currents exist in the vicinity of the vortex the validity of the index is then analyzed using results from a realistic regional circulation model of the peru chile upwelling system where both surface and subsurface eddies coexist the authors find that errors are mostly associated with double core eddies aligned surface and subsurface cores and that the index can be useful to determine the nature of mesoscale eddies surface or subsurface intensified from surface satellite observations however the errors reach 24 and some possible improvements of the index calculations are discussed

seasonal dynamics of the surface circulation in the southern california current system abstract the seasonal dynamics of the southern california current scc is investigated using a primitive equation ocean model with real coastlines and topography the model is tested with different wind forcing and the resulting flow fields are compared to the mean and seasonal circulation inferred from long term in situ observations california cooperative oceanic fisheries investigation calcofi the model integration forced with the output winds of a regional atmospheric model rsm best captures the statistics of the observed circulation with a 0 9 correlation coefficient for the streamlines and 0 5 for the velocity fields the model integrations reveal a pronounced linear response of the flow field to changes in winds on the shelf region a dynamical feature inferred from calcofi hydrography also suggested in topex ers maps is an annually recurrent westward propagation of ssh anomalies originated in the southern california bight scb during the upwelling season the rsm integration is the only one to capture the correct timing and spatial evolution of this process we therefore use this model integration for guidance in constructing a dynamical framework to interpret the observed circulation and its variability during the upwelling season in spring there is an upward tilt of the isopycnals along the coast directly forced by the winds in the bight as the spring transitions to the summer the upwelling winds relax in the bight but are still strong in the region offshore approximately in correspondence of the continental slope positive wind stress curl condition anomalous denser waters in the location of the southern california eddy are maintained and reinforced by the combined interaction of the coastal islands geometry and the wind stress curl through ekman dynamics the adjustment process to the denser water initiates a westward propagation of ocean density anomaly through rossby waves and reinforces the cyclonic gyre like circulation of the sce increasing positive vorticity surface poleward flow maintained by the positive wind stress curl is also reinforced in proximity of point conception as a consequence of the adjustment during the summer the cyclonic gyre becomes increasingly unstable as the core of the ocean anomalies crosses the continental slope instability processes within the cyclonic region characterized by a sharp increase in eke shed eddies that leave the region either drifting to the west or interacting with existing eddies in the region offshore the eke reaches a seasonal maximum at the end the summer in the cyclonic region and in late fall further offshore where the eddies are fully developed the shedding of eddies cannot be directly seen in the calcofi observations because of the sampling aliasing for this point we rely on the strong suggestion of the model which we assume is able to capture the leading order dynamics additional integrations with a linearized version of the model are also presented to reinforce our interpretation of the westward propagation of the isopycnal anomalous displacement associated with rossby wave dynamics

filaments on the western iberian margin a modeling study coastal upwelling filaments off the western iberian margin detected in avhrr satellite imagery and in a realistic roms simulation of sea surface temperature were studied in the upwelling seasons may october of 2001 2010 sea surface temperature data were retrieved from avhrr satellite imagery and from a realistic roms numerical simulation the development and variability of the observed filaments were characterized and analyzed during each upwelling season of the 10 year period filaments were generally found anchored to the main bathymetric and coastal features but off the more regular northern coast of the western iberian margin their locations were more variable the results from the modeling analysis reproduced well the general features of filament development moreover results of model and observation showed very similar characteristics as those found in the earlier study of haynes et al 1993 the model output was used to relate filament patterns eddy activity and wind forcing there was a clear relation between upwelling favorable wind strength and number and length of filaments although the relation was weaker in the north of the region model filaments were clearly related to eddies only during periods of weak winds the filament detection method was also applied to a climatologically forced roms simulation which reproduced only gross features of the observed and interannually forced model filament development this suggests that direct wind forcing and its spatial structure are highly important

seasonal variability of alongshore geostrophic velocity off central california seasonal variability of alongshore geostrophic velocity relative to 500 dbar is examined from 23 years of hydrographic data along two sections off central california one off point sur and the other off point conception the seasonal cycles are determined by least square fits of the gappy data records to harmonics with annual and semiannual periods attention is focused on variability over the outer continental slope geostrophic flow in the upper 100 m along both sections is coherent and predominantly annual with equatorward flow from february to september and poleward flow from october to january the flow deeper than 100 m is distinctly different along the two sections the nearshore deep flow is predominantly semiannual off point conception notably different from surface flow and poleward all year with maxima in december and june this semiannual variability at depth is a prevalent feature of the california current system the nearshore deep flow off point sur is unusual in that it is predominantly annual with maximum poleward flow in december and weak equatorward flow from march to may the seasonal variations over the continental slope compare favorably with existing models of eastern boundary current systems in two respects 1 the surface flow leads the predominantly annual wind forcing in this region by about one month and 2 the deep poleward counterflow is coherent with the local poleward barotropic pressure gradient at both locations with a phase lag of approximately 2 months however contrary to the results of existing dynamical models the semiannual poleward pressure gradient and undercurrent off point conception appear to be unrelated to the wind forcing which is predominantly annual in this region these semiannual variations are highly coupled to the semiannual flow throughout the water column inside the southern california bight suggesting that they may be topographically generated

an analysis of sst gradients off the peruvian coast the impact of going to higher resolution abstract the peruvian coastal upwelling system pcus is one of the most productive fisheries in the world upwelling events are associated with changes in the magnitude and location of frontal structures sst gradients from four different data sets ncdc remss ostia and mur are compared in two test areas off the pcus paita 5 s and pisco 14 s in both areas gradients derived from the mur data set show greater magnitudes as well as larger seasonal cycles off pisco the magnitude of the seasonal cycle of 2 2 c 100 km in mur is larger than the one derived from the lower resolution data sets all data sets at pisco exhibit a seasonal cycle that peaks in late austral summer and early fall hovmoller diagrams calculated at 5 5 s 10 5 s and 14 5 s show clearly defined offshore maxima in the cross shore gradients for all the data sets upwelling scales determined by the distance to the first maxima vary depending on the data set used at 5 5 s upwelling scales vary from 10 km for mur to 50 km for ncdc at 14 5 s the scales vary from 20 km for mur to 40 km for ostia all four data sets show similar large scale structures associated with the peruvian upwelling however mur shows finer scale structures that are most likely due to submesoscale to mesoscale eddies sub sampled mur 1 km data at the 25 km 9 km and 4 km resolutions compare well in magnitude and phase with the lower resolution products agreement in gradient magnitude between the lower resolution data sets and the mur sub sampled at their respective resolutions implies that the pixel to pixel analysis noise in mur is at a similar level as the other data sets

frontal dynamics in a california current system shallow front 1 frontal processes and tracer structure 1 the three dimensional dynamics in a shallow front are examined using density and current data from two surveys 100 km offshore of monterey bay california survey 1 is forced by down front winds and both surveys have considerable cross front density gradients and flow curvature the maximum rossby numbers on the dense side reached maxima of 0 60 in survey 1 and 0 45 in survey 2 downwelling occurs in regions of confluence frontogenesis associated with potential vorticity pv change and thermal wind imbalance streamers of particulate matter and pv are advected southeastward by the frontal jet and downward nonlinear ekman currents advect dense water over light water in the presence of down front winds which leads to upwelling along the front and downwelling on the light side of the front at sites of active ageostrophic secondary circulation asc induced by frontogenesis or ekman effects the observed cross front ageostrophic velocity is consistent with the diagnosed vertical velocity furthermore in survey 2 ageostrophic divergence may play an important role at the curved front presumably counteracting quasi geostrophic frontogenesis due to isopycnal confluence downward frictional vertical pv flux below the surface extracts pv from the pycnocline and reinforces the frontogenetic vertical pv flux pv destruction at the surface is inferred from a low pv anomaly below the mixed layer in survey 2 since the magnitude of the frontogenetic asc is only twice the magnitude of ekman suction external forcing may have a considerable impact on the vertical heat and pv fluxes

coastal trapped waves alongshore pressure gradients and the california undercurrent abstractthe california undercurrent cuc a poleward flowing feature over the continental slope is a key transport pathway along the west coast of north america and an important component of regional upwelling dynamics this study examines the poleward undercurrent and alongshore pressure gradients in the northern california current system ccs where local wind stress forcing is relatively weak the dynamics of the undercurrent are compared in the primitive equation navy coastal ocean model and a linear coastal trapped wave model both models are validated using hydrographic data and current meter observations in the core of the undercurrent in the northern ccs in the linear model variability in the predominantly equatorward wind stress along the u s west coast produces episodic reversals to poleward flow over the northern ccs slope during summer however reproducing the persistence of the undercurrent during late summer requires additional incoming energy from sea level variability applied south

mesoscale dynamics in the arabian sea and a focus on the great whirl life cycle a numerical investigation using roms the great whirl gw is a persistent anticyclonic mesoscale eddy that is observed seasonally in the arabian sea during a period embedding the 3 months of the southwest monsoon june july august at a quasi steady location its dynamics remain unclear despite it being one of the largest coherent vortices in the world ocean realistic regional numerical experiments using roms are performed to investigate the life cycle of the gw which is not well resolved by sparse available in situ measurements in the region using a set of sensitivity experiments and an accurate temporal characterization of the eddy properties including position radius depth and vorticity we i confirm the role of basin scale downwelling rossby waves in the gw generation ii clarify the role of the monsoonal strong anticyclonic wind in its maintenance and barotropization and iii suggest a connection between basin scale rossby wave dynamics and gw collapse

generation of low frequency spiciness variability in the thermocline abstract the generation of variance by anomalous advection of a passive tracer in the thermocline is investigated using the example of density compensated temperature and salinity anomalies or spiciness a coupled markov model is developed in which wind stress curl forces the large scale baroclinic ocean pressure that in turn controls the anomalous geostrophic advection of spiciness the double integration of white noise atmospheric forcing by this markov model results in a frequency spectrum of large scale spiciness proportional to 4 so that spiciness variability is concentrated at low frequencies an eddy permitting regional model hindcast of the northeast pacific 1950 2007 confirms that time series of large scale spiciness variability are exceptionally smooth with frequency spectra 4 for frequencies greater than 0 2 cpy at shorter spatial scales wavelengths less than 500 km the spiciness frequency spectrum is whitened by mesoscale eddies but this eddy forced variability can be fi

variability of the near surface eddy kinetic energy in the california current based on altimetric drifter and moored current data low pass filtered velocities obtained from world ocean circulation experiment woce surface drifters deployed in the california current off northern california during 1993 1995 have been compared with surface geostrophic velocity estimates made along subtracks of the topex poseidon altimeter and with moored acoustic doppler current profiler adcp data to obtain absolute geostrophic velocities a mean sea surface height ssh field was estimated using the mean drifter velocities and historical hydrographic data and was added to the altimetric ssh anomalies the correlation between collocated drifter and altimetric velocities is 0 73 significant at the 95 level the component of the drifter velocity which was uncorrelated with the altimetric velocity was correlated with the wind in the ekman transport sense monthly averages of eddy kinetic energy eke estimated using all drifter and altimeter data within the domain 124 132 w 33 40 5 n show energy levels for the drifters that are about 13 greater than those for the altimeter drifter altimeter and adcp measurements all exhibit similar seasonal cycles in eke with the altimeter data reaching maximum values of about 0 03 m 2 s 2 in late summer fall wavenumber spectra of the altimeter velocity indicate that the velocity fluctuations were dominated by features with wavelengths of 240 370 km while the adcp data suggest that the temporal scales of these fluctuations are at least several months between 36 and 40 5 n the region of monthly maximum eke migrates westward to about 128 w on a seasonal timescale this region of maximum eke coincides with the maximum zonal ssh gradient with increased eke associated with increased southward flow a simple model shows that much of the seasonal cycle of the ssh anomalies can be produced by linear processes forced by the curl of the wind stress although the model cannot explain the offshore movement of the front

geostrophic and ageostrophic circulation of a shallow anticyclonic eddy off cape bojador a shallow mesoscale anticyclonic eddy observed south of the canary islands with satellite altimetry has been intensively studied with multiparametric sampling hydrographic data from a ctd installed on an undulating nu shuttle platform reveal the presence of a mesoscale anticyclonic eddy of 125 km diameter the difference in sea level anomaly sla between the interior and the edge of the eddy as determined from altimetry is 15 cm which compares well with the maximum dynamic height differences as inferred using a very shallow reference level 130 m further the associated surface geostrophic velocities of about 35 cm s 1 in the northeast and southwest edges of the eddy are in good agreement with direct velocity measurements from the ship deep rosette ctd casts confirm that the structure is a shallow eddy extending no deeper than 250 m before the fusion with another anticyclone the sla tendency temporal rate of change of sea surface height indicates a clear northwestward migration during the two first weeks of november 2008 applying an eddy ssh based tracker the eddy s velocity propagation is estimated as 4 km d 1 use of the qg omega equation diagnoses maximum downward upward velocities of about 2 m d 1 the instability of the canary coastal jet appears to be the mechanism responsible for the generation of the shallow anticyclonic eddy

high resolution real time modeling of the marine atmospheric boundary layer in support of the aosn ii field campaign abstract the navy s coamps atmospheric model has been used to provide twice daily real time forecasts of 72 h duration in support of the aosn ii field campaign during august 2003 the model was configured with four grid meshes with a minimum horizontal grid increment of 3 km a statistical analysis of the model forecasts using available buoy observations demonstrates the skill of the atmospheric model predictions with characteristic wind speed rms and bias errors of 1 3 m s 1 and less than 0 5 1 0 m s 1 respectively and temperature rms errors of 1 2 c and biases typically less than 1 0 c the highest resolution mesh provides more accurate wind speed variances during the upwelling periods in the nearshore region where the wind speed gradients and diurnal variations are the largest persistent and strong low level winds from a northwesterly direction were associated with a mid tropospheric trough and jet stream that was substantially stronger than the overall mean monthly conditions during the relaxation periods which were relatively infrequent during august 2003 the trough was weaker than the mean conditions with a closed low west of the coast that resulted in southerlies near the coast during upwelling favorable conditions the mean marine inversion was substantially stronger than during the relaxation periods with the surface stress field exhibiting maxima in the lee of prominent coastal capes and topography particularly during the periods of strong larger scale low level flow the persistent mean stress pattern that is topographically locked yields maxima in the stress curl pattern that induce favorable regions of coastal upwelling near and downwind of the coastal promontories and headlands

the benguela a laboratory for comparative modeling studies abstract equilibrium dynamics of the benguela system is investigated using the holistic nature of the spatially and temporally cohesive output of a numerical model the regional ocean modeling system roms is used to simulate the benguela system in its entirety it successfully simulates the cool coastal upwelling regime and its division into seven distinctly separate cells as well as the large scale offshore regime and the respective seasonal fluctuations it does however present a cool bias at the coast due to an underestimation of the coastal wind drop off as well as a warm bias offshore in the southern benguela due to the overestimation of agulhas current input the benguela can be divided into northern and southern regimes based on dynamic as well as topographic differences topographically the division between the northern and southern regimes coincides with an abrupt narrowing of the continental shelf toward the north at 28 s the large scale depth integrated flow to the north of this feature is weak but distinctly poleward while to the south the flow regime is governed by the meandering nature of the equatorward benguela current and is the pathway for eddies that originate at the agulhas retroflection the poleward flowing regime of the northern benguela is tied to the sverdrup relation which links meridional transport with wind stress curl the luderitz upwelling cell at 27 s experiences the most vigorous upwelling throughout the year and as a result offshore volume fluxes in this region are extremely large this upwelling cell divides the northern and southern benguela coastal upwelling systems into separate regimes based on the fact that their seasonal signals are out of phase the offshore gradient of eddy kinetic energy eke is generally strong in the benguela system and exceptionally so in the southern benguela due to vigorous mesoscale activity offshore of the shelf edge originating from the agulhas retroflection area the juxtaposition between the steep offshore eke gradients in the south and much weaker offshore gradients of eke in the northern benguela has different implications for cross shore exchanges

continuity of the poleward undercurrent along the eastern boundary of the mid latitude north pacific abstract several recent data sets improve our view of the poleward undercurrent of the california current system as part of a triennial national marine fisheries service nmfs survey of pacific whiting a series of 105 shipboard acoustic doppler current profiler adcp velocity sections across the shelf break from 33 to 51 n at about 18 km meridional spacing were collected from july to august 1995 significant 0 05 m s 1 subsurface poleward flow occurred in 91 of the sections a mean cross shelf section using the entire data set has statistical significance revealing an undercurrent core 0 1 m s 1 from 200 275 m depth 20 25 km off the shelf break the mean poleward volume transport in a 125 325 m layer is 0 8 0 2 10 6 m 3 s 1 we focus particular attention on the cape blanco to cape mendocino region and the nmfs results are compared with shipboard adcp three weeks later from a study of coastal upwelling processes near cape blanco adcp streamfunction maps are derived and strongly suggest that one portion of flow is continuous over the 440 km meridional extent of the analysis region other portions of the flow show evidence of offshore turning separation and the formation of anti cyclonic eddies we also note that isopycnic potential vorticity from alongslope ctd stations during the nmfs survey appears to be a tracer for the poleward flow