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

barotropic tides on the north carolina shelf observations from 18 near bottom pressure sensors and 8 current meter moorings provide a characterization of the barotropic tides over the north carolina continental shelf between chesapeake bay and cape hatteras the largest tidal constituents in this region are the m2 sea level amplitude 47 cm n2 11 cm and s2 10 cm semidiurnal tides and the k1 p1 7 cm and o1 5 cm diurnal tides the barotropic tidal currents are small less than 3 cm s21 except for the m2 current which reaches 10 cm s21 at mid shelf cross shelf currents increase linearly from approximately zero near the coast to a maximum over the mid and outer shelf alongshelf currents are nonzero near the coast and increase to roughly twice the coastal value over the mid and outer shelf while bottom friction is weak over most of the shelf in water depths of less than 10 m bottom friction results in a rapid phase decrease toward the coast in the semidiurnal alongshelf velocities this phase difference is not observed in the k1 p1 alongshelf flow possibly because diurnal wind forcing causes an opposing phase increase toward the coast alongshelf variations in tidal amplitudes and phases near the coast are much larger than expected based on variations along the shelf break inferred from basin scale altimeter estimates the shelf width in this region increases from 25 to 100 km over an alongshelf distance of about 150 km results from an analytic flat bottom two dimensional model indicate that widening of the shelf toward the north causes the observed alongshelf increase in the semidiurnal amplitude and phase but does not explain alongshelf variations in the weaker diurnal constituents

internal tides over abrupt topography in the southern california bight observations of diurnal waves poleward of the critical latitude 1 in the ocean a mechanism for baroclinic internal tide generation is through the interaction of barotropic tidal currents with topography velocity profiles from a bottom mounted acoustic doppler current profiler are used to characterize the tidal generation of diurnal and semidiurnal internal modes over a ridge atop an abrupt 30 bathymetric slope in the southern california bight this location is poleward of the critical latitude for diurnal frequency internal waves yet the circulation is dominated by the diurnal internal tide overall the structure of the diurnal internal tide resembles the first baroclinic mode however the mode is topographically distorted in the lower water column where it is amplified and polarized in the cross ridge direction the behavior of the diurnal response is contrasted with the nearly ideal appearance of the semidiurnal response the diurnal baroclinic mode occurs as a persistent response to tidal forcing rather than because of the diurnal sea breeze as has also been suggested as an explanation for internal diurnal tides in other areas of the southern california bight

joint sun glitter and radar imagery of surface slicks a method is proposed to retrieve and interpret fine spatial variations of the sea surface roughness in sun glitter imagery observed sun glitter brightness anomalies are converted using a transfer function determined from the smoothed shape of sun glitter brightness the method is applied to modis and meris sun glitter imagery of natural oil seeps and the catastrophic deepwater horizon oil spill in the gulf of mexico the short scale roughness variations in the presence of mineral oils slicks are consistently extracted and compared to variations associated with the biogenic slicks in doing so the wind speed dependency on the roughness anomalies is also considered a comparison to normalized radar cross section nrcs anomalies taken from the corresponding high resolution asar images is performed and similarities as well as differences are investigated the results document significant benefit from the synergetic use of sun glitter and radar imagery for detection and monitoring of surface slicks

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

measurements of tidal flow around a headland with a shipboard acoustic doppler current profiler a shipboard acoustic doppler current profiler adcp and moored current meters were used to obtain detailed measurements of the spatial structure of the tidal flow around a headland in vineyard sound massachusetts where tidal currents typically range from 50 to 70 cm s 1 eight shipboard surveys were conducted each of which followed one of five trapezoidal tracks in the vicinity of the headland completing 11 12 circuits in the course of the tidal cycle 12 4 hours the measurements from the adcp compare favorably with moored velocity measurements at two locations rms deviations of 3 cm s 1 but the comparison showed more scatter at two other sites rms deviations of 7 cm s 1 the adcp measurements from separate cruises were merged to form a composite spatial representation of the tidal and residual currents providing resolution of the spatial structure of the flow around the headland at scales from several hundred meters to 10 km the semidiurnal tidal flow is relatively uniform in space roughly following the bathymetry around the headland while a residual current field consists of counterrotating eddies on either side of the headland with spatial scales of 5 8 km and velocities as high as 25 cm s 1 the instantaneous current field indicates the formation of transient eddies on the downstream side of the headland during flood and ebb with clear evidence of flow separation near the tip of the headland

momentum balances on the north carolina inner shelf four months of moored current pressure temperature conductivity wave and wind observations on the north carolina shelf indicate three dynamically distinct regions the surf zone the inner shelf between the surf zone and the 13 m isobath and the midshelf in the surf zone the along shelf momentum balance is between the cross shelf gradient of the wave radiation stress and the bottom stress the linear drag coefficient in the surf zone is about 10 times larger than seaward of the surf zone on the inner shelf the along shelf momentum balance is also frictional the along shelf wind stress and pressure gradient are balanced by bottom stress in the cross shelf momentum balance the pressure gradient is the superposition of roughly equal contributions from the coriolis force geostrophy and wave setdown from shoaling unbroken surface gravity waves at midshelf the along shelf momentum balance is less frictional and hence flow accelerations are important the cross shelf momentum balance is predominantly geostrophic because the greater depth and smaller bottom slope at midshelf reduce the importance of wave setdown the cross shelf density gradient is in thermal wind balance with the vertical shear in the along shelf flow in depths as shallow as 10 m the dominant along shelf momentum balances provide a simple estimate of the depth averaged along shelf current in terms of the measured forcing i e wind stress wave radiation stress divergence and along shelf pressure gradient that reproduces accurately the observed cross shelf variation of the depth averaged along shelf current between the surf zone and midshelf

momentum balances on the inner continental shelf at martha s vineyard coastal observatory 1 the subtidal depth average momentum balances in 12 m and 27 m water depth are investigated using observations from 2001 to 2007 of water velocity temperature and density bottom pressure surface gravity waves and wind stress in the fluctuating across shelf momentum budget the dominant terms are surface wind stress pressure gradient and coriolis acceleration the balance is a combination of 1 the geostrophic balance expected at midshelf sites and 2 the coastal setup and setdown balance driven by the across shelf wind stress expected where surface and bottom boundary layers overlap at the 12 m site the estimated wave radiation stress gradient due to surface gravity wave shoaling is also large but is uncorrelated with the observed pressure gradient a simple model suggests the wave radiation stress gradient is balanced by an across shelf pressure gradient with a spatial scale too small to resolve with this mooring array in the fluctuating along shelf momentum balance the dominant terms are surface wind stress pressure gradient and bottom stress at the shallower site but the other estimated terms are not negligible our results support the grant and madsen 1986 formulation for wave induced bottom stress the fluctuating along shelf pressure gradient is mainly a local sea level response to wind forcing not a remotely generated pressure gradient a strong correlation between along shelf velocity and along shelf wind stress at the shallower site is captured by a simple steady model of imbalance between wind stress and pressure gradient balanced by linear bottom drag

implementation and modification of a three dimensional radiation stress formulation for surf zone and rip current applications regional ocean modeling system roms v 3 0 a three dimensional numerical ocean model was previously enhanced for shallow water applications by including wave induced radiation stress forcing provided through coupling to wave propagation models swan ref dif this enhancement made it suitable for surf zone applications as demonstrated using examples of obliquely incident waves on a planar beach and rip current formation in longshore bar trough morphology haas and warner 2009 in this contribution we present an update to the coupled model which implements a wave roller model and also a modified method of the radiation stress term based on mellor 2008 2011a b in press that includes a vertical distribution which better simulates non conservative i e wave breaking processes and appears to be more appropriate for sigma coordinates in very shallow waters where wave breaking conditions dominate the improvements of the modified model are shown through simulations of several cases that include a obliquely incident spectral waves on a planar beach b obliquely incident spectral waves on a natural barred beach duck 94 experiment c alongshore variable offshore wave forcing on a planar beach d alongshore varying bathymetry with constant offshore wave forcing and e nearshore barred morphology with rip channels quantitative and qualitative comparisons to previous analytical numerical laboratory studies and field measurements show that the modified model replicates surf zone recirculation patterns onshore drift at the surface and undertow at the bottom more accurately than previous formulations based on radiation stress haas and warner 2009 the results of the model and test cases are further explored for identifying the forces operating in rip current development and the potential implication for sediment transport and rip channel development also model analysis showed that rip current strength is higher when waves approach at angles of 5 to 10 in comparison to normally incident waves

subinertial currents on the southern califoinia shelf abstract subinertial currents on the southern california shelf are investigated using observations from a current meter array deployed near san diego during the summer fall and winter of 1978 79 this region is characterized by weak winds order 1 2 m s 1 and thus other driving mechanisms for the subinertial currents may be important a simplified depth averaged longshore momentum equation consisting of a balance between current accelerations the adjusted sea level asl gradient and the wind and bottom stress is examined the asl gradient is estimated using sea level and atmospheric pressure observations separated by 350 km a linear parameterization of the bottom stress is used with a drag coefficient of 5 10 4 m s 1 during fall and winter the first order balance of terms in the longshore momentum equation over the inner shelf 15 m depth is between the wind and bottom stress over the outer shelf 60 m the primary balance is between the asl gradient and the bottom stress at midshelf 30 m bo

complex mean circulation over the inner shelf south of martha s vineyard revealed by observations and a high resolution model 1 inner shelf circulation is governed by the interaction between tides baroclinic forcing winds waves and frictional losses the mean circulation ultimately governs exchange between the coast and ocean in some cases oscillatory tidal currents interact with bathymetric features to generate a tidally rectified flow recent observational and modeling efforts in an overlapping domain centered on the martha s vineyard coastal observatory mvco provided an opportunity to investigate the spatial and temporal complexity of circulation on the inner shelf adcp and surface radar observations revealed a mean circulation pattern that was highly variable in the alongshore and cross shore directions nested modeling incrementally improved representation of the mean circulation as grid resolution increased and indicated tidal rectification as the generation mechanism of a counter clockwise gyre near the mvco the loss of model skill with decreasing resolution is attributed to insufficient representation of the bathymetric gradients h h which is important for representing nonlinear interactions between currents and bathymetry the modeled momentum balance was characterized by large spatial variability of the pressure gradient and horizontal advection terms over short distances suggesting that observed inner shelf momentum balances may be confounded given the available observational and modeling data this work defines the spatially variable mean circulation and its formation mechanism tidal rectification and illustrates the importance of model resolution for resolving circulation and constituent exchange near the coast the results of this study have implications for future observational and modeling studies near the mvco and other inner shelf locations with alongshore bathymetric variability

undertow over a barred beach the spatial distribution of the mean cross shore flow undertow over a barred beach is examined with field data obtained on three energetic wave days during the duck94 experiment the vertical structure of the undertow is modeled using a turbulent eddy viscosity closure and includes the important effects of wave breaking described using the roller concept and convective acceleration of the current other than a more realistic description of observed turbulence variations a depth dependent eddy viscosity compared with a constant does not improve the agreement between predicted and observed undertow profiles the effect of using different boundary conditions is investigated by extending the formulations of stive and wind 1986 and svendsen et al 1987 to include random waves by ensemble averaging over the wave height distribution the contribution of breaking wave rollers to the surface mass flux can be of the same order or greater than the contribution associated with the organized wave motion the largest discrepancies between model predictions and observations occur over the sandbar where the mass transport of the breaking waves appears to be underestimated

directional spreading of waves in the nearshore observations of surface gravity waves shoaling between 8 m water depth and the shoreline on a barred beach indicate that breaking results in an increase in the directional spread of wave energy in contrast to the directional narrowing with decreasing depth predicted by refraction theory snell s law during low energy wave conditions when breaking induced wave energy losses over the instrumented transect are small the observed mean propagation direction and spread about the mean both decrease with decreasing depth consistent with the expected effects of refraction nonlinearity causes high frequency components of the spectrum to become directionally aligned with the dominant incident waves during high energy wave conditions with significant wave breaking on the sand bar the observed mean directions still decrease with decreasing depth however the observed directional spreads increase sharply nominally a factor of 2 for values integrated over the swell sea frequency range between the outer edge of the surf zone and the crest of the sand bar followed by a decrease toward the shoreline observations on a nonbarred beach also show directional broadening with spreads increasing monotonically from the outer edge of the surf zone to a maximum value near the shoreline although the mechanism is not understood these spatial patterns of directional broadening suggest that wave breaking causes significant scattering of incident wave energy into obliquely propagating components

boussinesq modelling of transient rip currents the flow on a plane beach with a random directionally spread wave field was simulated with a boussinesq model the random wave spectra were directionally symmetric with their central direction perpendicular to the beach so no constant longshore current was generated variable wave averaged currents were generated because of the spatially variable wave field and sometimes formed offshore directed rip currents that appear in variable longshore locations the rip currents are associated with a vortex pair which is generated within the surfzone and subsequently propagates offshore analysis of the vorticity balance show that the main vorticity input occurs within the inner surfzone three different beach slopes and four different wave spectra are simulated the frequency duration and intensity of the transient rips depend on both the beach slope and the incident wave spectra the results have important engineering implications for the transport of material in the nearshore zone in particular on longshore uniform beaches

alongshore momentum balance analysis on a cuspate foreland 1 nearshore measurements of waves and currents off cape hatteras north carolina u s a are used to investigate depth averaged subtidal circulation and alongshore momentum balances in the surf and inner shelf region around a cuspate foreland data were collected on both sides of the cape representing shorefaces with contrasting shoreline orientation north south vs northwest southeast subjected to the same wind forcing in the nearshore the subtidal flow is aligned with the local coastline orientation while at the cape point the flow is along the existing submerged shoal suggesting that cape associated shoals may act as an extension of the coastline alongshore momentum balance analysis incorporating wave current interaction by including vortex and stokes coriolis forces reveals that in deep waters surface and bottom stress are almost in balance in shallower waters the balance is complex as nonlinear advection and vortex force become important furthermore linearized momentum balance analysis suggests that the vortex force can be of the same order as wind and wave forcing farther southwest of cape hatteras point wind and wave forcing alone fail to fully explain subtidal flow variability and it is shown that alongshore pressure gradient as a response to the wind forcing can close the momentum balance adjacent tide gauge data suggest that the magnitude of pressure gradient depends on the relative orientation of local coastline to the wind vector and in a depth averaged sense the pressure gradient generation due to change in coastline orientation even at km length scale is analogous to the effect of alongshore variable winds on a straight coastline

wave driven inner shelf motions on the oregon coast abstract recent work by s lentz et al documents offshore transport in the inner shelf due to a wave driven return flow associated with the hasselmann wave stress the stokes coriolis force this analysis is extended using observations from the central oregon coast to identify the wave driven return flow present and quantify the potential bias of wind driven across shelf exchange by unresolved wave driven circulation using acoustic doppler current profiler adcp measurements at six stations each in water depths of 13 15 m observed depth averaged across shelf velocities were generally correlated with theoretical estimates of the proposed return flow during times of minimal wind forcing across shelf velocity profiles were vertically sheared with stronger velocities near the top of the measured portion of the water column and increased in magnitude with increasing significant wave height consistent with circulation due to the hasselmann wave stress yet velocity magnitudes and vertical shears wer

observations and a model of undertow over the inner continental shelf abstract onshore volume transport stokes drift due to surface gravity waves propagating toward the beach can result in a compensating eulerian offshore flow in the surf zone referred to as undertow observed offshore flows indicate that wave driven undertow extends well offshore of the surf zone over the inner shelves of martha s vineyard massachusetts and north carolina theoretical estimates of the wave driven offshore transport from linear wave theory and observed wave characteristics account for 50 or more of the observed offshore transport variance in water depths between 5 and 12 m and reproduce the observed dependence on wave height and water depth during weak winds wave driven cross shelf velocity profiles over the inner shelf have maximum offshore flow 1 6 cm s 1 and vertical shear near the surface and weak flow and shear in the lower half of the water column the observed offshore flow profiles do not resemble the parabolic profiles with maximum flow at middepth observed within the su

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

inner shelf intrusions of offshore water in an upwelling system affect coastal connectivity 1 poleward warm water flows around point conception are an important transport mechanism linking biogeographic provinces along central california these flows are initiated by relaxation of upwelling winds the intensity and duration of upwelling is an important driver of how far north warm water penetrates against the prevailing surface currents in this paper we present evidence of offshore surface water intrusions to the inner shelf 130 km north of point conception near cambria california satellite observations show that the intrusions originate as eddies generated offshore along the upwelling front these eddies may form as submesoscale instabilities or by interaction of upwelling centers with offshore waters the intrusions move southern waters to the central california inner shelf further northward than is typical for a coastal relaxation plume and therefore inner shelf connectivity and ecology may be governed over timescales and distances longer than those set by the intermittent relaxation of upwelling winds

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

direct evidence of deep water intrusions onto the continental shelf via surging internal tides 1 near bottom diurnal thermocline shoaling and diurnal baroclinic currents were observed from time series data of water temperature salinity pressure and velocity collected from august 2006 to january 2007 in the nearshore zone off the huntington beach where the local inertial frequency is higher than the diurnal frequency poleward of the diurnal critical latitude during the stratified season the deep offshore cold dense water when shoaled into shallow water along the bottom was often trapped for a few hours and dissipated in the nearshore region water depth of 10 20 m during the ebb phase of the diurnal surface tide it appears that perturbations propagating onshore along the shoaled isopycnals can form an upslope surging front and an internal bolus our data allow the application of theoretical lab criteria for internal hydraulic jumps internal bolus formation and internal wave breaking and all criteria are fulfilled during a part of the tidal shoaling cycle nonlinear advection associated with the internal boluses causes higher close to 3 spectral falloff rate of near bottom temperature with frequency than the canonical garret munk spectra 2 in the range of 0 1 1 0 cph implying strong scattering of tidal energy toward smaller scales we are able to directly calculate the offshore eddy heat flux by cold water intrusion onto the shelf resulting from this process similar impacts and implications are expected for the biogeochemical quantities as well as for the role of subinertial internal waves on turbulent mixing in the immediate proximity of the generating region i e sloping bottom

longshore current and wave height modulation at tidal frequency inside the surf zone data were acquired continuously during the 19 day delilah nearshore experiment with a specific objective of examining variability of the longshore current at tidal frequencies it is hypothesized that breaking wave heights inside the surf zone are strong functions of the depth which are modulated by the tidal variations and since radiation stress is a function of the wave height longshore currents are forced at the tidal frequency inside the surf zone the measured longshore current variations at tidal frequency are the same order of magnitude as the mean longshore current variations for moderate wave height conditions indicating that the tide is a dominant mechanism associated with longshore current variability simulations of the magnitude and phase of the longshore current variability with tide elevation using the model by thornton and guza 1986 are used to explain observations the measured tidal elevation and longshore current are in phase in the inner surf zone and out of phase in the outer surf zone as predicted by the model verifying the hypothesis

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

the ebro river in the 20th century or the ecomorphological transformation of a large and dynamic mediterranean channel in the first decades of the 20th century the ebro river was the iberian channel with the most active fluvial dynamics and the most remarkable spatial temporal evolution its meandering typology the dimensions of its floodplain and the singularities of its flow regime produced an especially interesting set of river functions the largest dynamics of the ebro river are concentrated along the meandering profile of the central sector during the 20th century this sector experienced a large alteration of its geomorphological structure we present here an analysis of this evolution through the cartographic study of a long segment of the river 250 km in 1927 1956 and 2003 the results show a large reduction in bank sinuosity a progressive loss of fluvial territory and a large decrease in channel width these changes are especially clear in the areas previously most ecologically connected with the active channel the fluvial territory of the river in 2003 was approximately half that found during the first decades of the 20th century forest plantations which were non existent in 1927 occupied more than 1500 ha of the study area in the last decade this intense geomorphological transformation becomes ecologically visible in i a 35 reduction of the area occupied by riparian vegetation ii a loss of the heterogeneity of riparian forest spots which were formerly structured in an irregular mosaic far from the river thalweg and iii a modification of the riparian forest structure which is currently linear uniform thin and very close to the river axis the ecomorphological alteration was intensified by the remarkable reduction in bank length 13 and the reduced dynamism of the present river system indicated by an increase in the percentage of fluvial territory occupied by riparian forests and a reduction in the area occupied by the active channel copyright 2002 john wiley sons ltd

local and remote forcing of currents and temperature in the central southern california bight 1 a comprehensive study of the central southern california bight shows that subtidal currents are dominated by relatively long time scales 10 25 days large alongshore scales and significant offshore and upward phase propagation a one dimensional model shows that observed fluctuating poleward propagating speeds 140 260 cm s 1 alongshore pressure gradient disturbances account for a much larger fraction of the alongshore velocity variance than local wind stress at least 40 in both seasons and have the longer periods of the dominant currents with the addition of local wind stress about half the velocity variance can be accounted for and overall about 5 more variance in spring than in summer results are consistent with generation of disturbances by remote wind stress several hundred kilometers equatorward of the bight and alongcoast propagation as low mode coastally trapped waves the large scale remote forcing is also responsible for much of the velocity variance on the adjacent shelf the semienclosed santa monica bay a nonlinear three dimensional model shows that water is pushed into the bay initially as part of a throughflow later becoming an eddy that gradually fills the bay producing counterflow on its shoreward side on the shelf local alongshore wind stress accounts for only 25 of the velocity variance in spring and none in summer the large scale disturbances also produce significant temperature fluctuations throughout the region via lateral advection of the mean alongshore temperature gradient local wind driven coastal upwelling is responsible for temperature fluctuations on the inner shelf during several 2 4 day events in spring but only very near the coastal wall

what shapes mesoscale wind anomalies in coastal upwelling zones observational studies have shown that mesoscale variations in sea surface temperature may induce mesoscale variations in wind in eastern subtropical upwelling regions such as the california coast this mechanism could be of great importance for the mean state and variability of the climate system in coastal regions orography also creates mesoscale variations in wind and the orographic effect may extend more than 100 km offshore the respective roles of sst wind links and coastal orography in shaping mesoscale wind variations in nearshore regions is not clear we address this question in the context of the california upwelling system using a high resolution regional numerical modeling system coupling the wrf atmospheric model to the roms oceanic model as well as additional uncoupled experiments to quantify and separate the effects of sst wind links and coastal orography on mesoscale wind variations after taking into account potential biases in the representation of the strength of sst wind links by the model our results suggest that the magnitude of mesoscale wind variations arising from the orographic effects is roughly twice that of wind variations associated with mesoscale sst anomalies this indicates that even in this region where coastal orography is complex and leaves a strong imprint on coastal winds the role of sst winds links in shaping coastal circulation and climate cannot be neglected

modeling surf zone tracer plumes 1 waves mean currents and low frequency eddies 1 a model that accurately simulates surf zone waves mean currents and low frequency eddies is required to diagnose the mechanisms of surf zone tracer transport and dispersion in this paper a wave resolving time dependent boussinesq model is compared with waves and currents observed during five surf zone dye release experiments in a companion paper clark et al 2011 compare a coupled tracer model to the dye plume observations the boussinesq model uses observed bathymetry and incident random directionally spread waves for all five releases the model generally reproduces the observed cross shore evolution of significant wave height mean wave angle bulk directional spread mean alongshore current and the frequency dependent sea surface elevation spectra and directional moments the largest errors are near the shoreline where the bathymetry is most uncertain the model also reproduces the observed cross shore structure of rotational velocities in the infragravity 0 004 f 0 03 hz and very low frequency vlf 0 001 f 0 004 hz bands although the modeled vlf energy is 2 3 times too large similar to the observations the dominant contributions to the modeled eddy induced momentum flux are in the vlf band these eddies are elliptical near the shoreline and circular in the mid surf zone the model data agreement for sea swell waves low frequency eddies and mean currents suggests that the model is appropriate for simulating surf zone tracer transport and dispersion