shelf response to intense offshore wind this is the accepted version of the following article grifoll m aretxabaleta a espino m shelf response to intense offshore wind journal of geophysical research setembre 2015 vol 120 num 9 p 6564 6580 which has been published in final form at http onlinelibrary wiley com doi 10 1002 2015jc010850 full

upwelling and cyclonic regimes of the near surface circulation in the santa barbara channel the observed near surface circulation in the santa barbara channel indicates in particular two patterns a dominant cyclonic circulation mode and a less frequent upwelling flow mode to explain the dynamics that may govern these two flow regimes momentum balance from a hindcast model of currents in the channel forced by observed hourly winds and hydrographic data was calculated the along channel balance was found to be between wind which was eastward i e equatorward sea level tilt which was westward i e poleward and coriolis which was westward if the wind was 1 intense west and east of the channel and was eastward if the wind was 2 weaker in the east wind condition 1 produced southward cross channel flow in the midchannel connected by eastward currents upstream downstream along the northern southern coast of the channel while wind condition 2 produced northward cross channel flow connected by cyclonic recirculation in the west and westward inflow in the east it is suggested that the former corresponds to the dynamical balance that may occur in the upwelling flow mode while the latter corresponds to the cyclonic circulation mode

characteristic patterns of the circulation in the santa barbara channel the subtidal near surface circulation in the santa barbara channel sbc and on the shelf north of point conception is described based on observations obtained during the 3 year period from 1993 to 1995 near surface currents in the channel are a superposition of a larger than sbc scale flow and a cyclonic circulation of variable intensity located inside the channel on seasonal timescales the larger than sbc scale flow near the surface is equatorward in spring and poleward from summer through winter the increase in equatorward flow in spring occurs concurrently with the increase in equatorward wind stress and the decrease in near surface temperatures and synthetic subsurface pressures ssps the flow reverses in late spring simultaneously with the increase in the along channel ssp difference and months before wind stress has reached its peak the period during which the cyclonic circulation within the sbc is strongest coincides with the period of strongest poleward flow through the eastern entrance a synoptic description of the circulation in the sbc is presented in terms of six characteristic patterns labeled upwelling relaxation cyclonic propagating cyclones flood east and flood west an analysis of the 5 and 45 m currents into empirical orthogonal functions eofs isolates 50 53 of the 5 m 45 m low frequency current variance into three two modes combining these modes with the mean current fields the modes have spatial patterns that correspond to the characteristic flow patterns subjectively deduced from inspection of daily averages of the near surface currents from late spring through fall the two largest 5 m current modes produce a repeating pattern of circulation in which the sequence of four states namely upwelling cyclonic relaxation and quiescent is traversed roughly every 16 days in addition to the large scale cyclonicity in the central sbc smaller cyclonic eddies form frequently in the eastern channel and travel toward the west with an average speed of 0 06 m s 1 the patterns described here develop in response to the wind stress and the along channel ssp gradient

objective maps of near surface flow states near point conception california abstract objective streamfunction and velocity potential maps of three commonly observed flow states near point conception california are derived from moored current meter and drifter observations the states are defined using current meter data drifter data are sorted by flow state and averaged within spatial bins to resolve their spatial structures spatial correlations of drifter data show the along shelf and cross shelf decorrelation distances are approximately 45 and 25 km respectively this information is used to make the objective streamfunction and velocity potential maps the total velocity is represented as the sum of the rotational nondivergent streamfunction component and the irrotational divergent velocity potential component the velocity derived from the streamfunction is much stronger than that derived from the velocity potential the streamfunction is sufficiently well resolved to make meaningful vorticity maps the velocity potential indicates a source term in the western santa bar

diurnal period internal waves near point conception california diurnal period internal waves were observed near point conception california using an array of moorings extending 120 km along the inner shelf the waves have an along shelf coherence scale of at least 50 km and appear to propagate nearly straight onshore wave amplitudes vary over time depending on thermal stratification and the amplitude of the diurnal sea breeze oscillation barotropic tides and vorticity over the mid shelf are not correlated with internal wave amplitude large amplitude internal waves with supercritical froude numbers are observed in mid summer although such waves may drive vertical mixing and cross shelf transport of passive particles there is no significant correlation between wave amplitude and invertebrate settlement in the santa barbara channel

physical oceanography of the western iberia ecosystem latest views and challenges the present review is focused on the mesoscale physical processes recognized in the western iberia ecosystem complementing earlier reviews dedicated to larger scales recent studies support the idea that the mesoscale processes superimposed on the larger scale variability are the major factor controlling the ecosystem functioning in the region a complex structure of interleaved alongshore slope shelf and coastal currents that interact with eddies buoyant plumes upwelling filaments and fronts surface layer expressions of the subsurface circulation and internal waves is revealed by the latest research all of these contribute in different ways to have an effect on the ecosystem the supposedly less variable winter circulation also exhibits significant mesoscale activity in the form of eddy shedding from the poleward slope current intermittent upwelling events and transient nearshore poleward flows the present incomplete knowledge of this complex system presents a number of challenges and questions that must be addressed if we are to arrive at a satisfactory understanding and predictive capability for the system as a whole 2007 elsevier ltd all rights reserved

statistical aspects of surface drifter observations of circulation in the santa barbara channel argos tracked drifters are used to study the near surface circulation in the santa barbara channel the mean consists of a cyclonic cell in the western santa barbara channel with weaker flow in the eastern channel drifter mean velocities agree well with record means from near surface current meters at the eastern entrance to the channel drifter velocities are biased toward outflow eastward velocity conditions drifter variability at synoptic and seasonal scales shows a tendency for upwelling and eastward flow in spring a strong cyclonic circulation in summer poleward relaxation in fall and weak variable circulation in winter drifter estimates of eddy stress divergence indicate advective terms play a secondary role in the mean surface momentum balance lagrangian time and space scales are about 1 day and under 10 km respectively the mismatch between lagrangian and eulerian timescales indicates advective terms are important to the fluctuating circulation

coastal water circulation patterns around the northern channel islands and point conception california abstract the northern channel islands in california host multiple marine protected areas containing kelp forest ecosystems little is known about the water circulation onshore of the 20 m isobath we use water velocity recorded at 21 sites near the 15 m isobath at the islands and mainland during 1999 2012 to describe the water circulation on time scales of days to months the mean circulation is eastward or weak at the islands but poleward along the mainland speeds 0 10 cm s 1 the subinertial frequency along shelf flow is surface intensified and reverses direction on time scales of days in summer the flow becomes more poleward throughout the region the mean cross shelf flow profiles are strikingly similar at most sites with flow speeds 1 2 cm s 1 the mean flow near bottom in the vicinity of the kelp forests is offshore the time varying two layered response to wind is stronger up to 6 cm s 1 the flushing time of the shelf onshore of the 15 m isobath is short at most 2 dy at a few sites exposed to the prevailing wind up to 60 of the velocity variance is predictable from wind measured in the santa barbara channel in the lee of point conception or at the islands however regional wind explains little of the velocity variance during weak winds the velocity at some mainland but not island sites responds to pressure gradients measured along the mainland coast these pressure gradients are associated with local wind relaxations at pt conception not with remotely generated coastal trapped waves

formation of fine sediment deposit from a flash flood river in the mediterranean sea we identify the mechanisms controlling fine deposits on the inner shelf in front of the besos river in the northwestern mediterranean sea this river is characterized by a flash flood regime discharging large amounts of water more than 20 times the mean water discharge and sediment in very short periods lasting from hours to few days numerical model output was compared with bottom sediment observations and used to characterize the multiple spatial and temporal scales involved in offshore sediment deposit formation a high resolution 50 m grid size coupled hydrodynamic wave sediment transport model was applied to the initial stages of the sediment dispersal after a storm related flood event after the flood sediment accumulation was predominantly confined to an area near the coastline as a result of preferential deposition during the final stage of the storm subsequent reworking occurred due to wave induced bottom shear stress that resuspended fine materials with seaward flow exporting them toward the midshelf wave characteristics sediment availability and shelf circulation determined the transport after the reworking and the final sediment deposition location one year simulations of the regional area revealed a prevalent southwestward average flow with increased intensity downstream the circulation pattern was consistent with the observed fine deposit depocenter being shifted southward from the river mouth at the southern edge bathymetry controlled the fine deposition by inducing near bottom flow convergence enhancing bottom shear stress according to the short term and long term analyses a seasonal pattern in the fine deposit formation is expected

osl chronology and palaeoclimatic implications of aeolian sediments in the eastern qaidam basin of the northeastern qinghai tibetan plateau abstract aeolian sediments are widely distributed in the hyper arid qaidam basin and are good palaeoclimatic records due to limited age control aeolian processes and their relevance to palaeoclimatic change are poorly understood in this study we present 28 optically stimulated luminescence osl ages for both loess 14 samples and aeolian sand 14 samples from 8 profiles in eastern qaidam basin eqb in order to provide a detailed chronology for understanding the timing of aeolian processes and associated environmental conditions we reconstructed the history of aeolian activity in the eqb since deglaciation by combining osl chronologies lithologic stratigraphy and grain size analysis the results indicate that 1 aeolian sand underlying the loess accumulated at ca 12 4 11 5 ka and 10 8 ka but not during the last glacial maximum 2 loess accumulation started at 10 ka and lasted to 0 45 ka at least while most of the loess was deposited during 8 4 5 ka 3 palaeoclimates in the eqb are inferred to be arid during 12 4 11 5 ka relatively humid during 10 8 ka humid during 8 4 5 ka and relatively arid during 4 5 0 45 ka and 4 evolution of aeolian sediments were mainly controlled by effective moisture and also affected by local topography

the formation of antitaxial calcite veins with well developed fibres oppaminda creek south australia abstract of the several vein types with elongate crystals we distinguish a class of veins with well developed fibres exposed at oppaminda creek south australia these calcite veins are characterised by very limited competition between growing crystals which leads to the development of fibrous crystals with smooth boundaries and which can attain extreme length width ratios fibres are often curved and track the opening trajectory the veins are also characterised by their outwards antitaxial growth starting from a narrow median zone these median zones contain wall rock inclusions and a distinctly different non fibrous internal microstructure such veins continue growing as long as extension is suitably oriented relative to the vein orientation multiple cross cutting vein sets can thus grow simultaneously and can together track over 90 rotation of the fibre growth direction the veins formed by calcite precipitation on both their outer surfaces we suggest that the term antitaxial should be redefined as applying only to those veins that have two simultaneous growth planes at their outer surfaces antitaxial veins grow without further fracturing which sets them apart from other veins that grew by precipitation inside a crack and which only have one single growth plane at the time the veins at oppaminda creek are about 585 ma in age and therefore formed at an estimated 4 6 km depth scanning electron microscope observations revealed about 1 m sized structures which we interpret as fossils of microbes that lived inside the veins at the time of their formation and which may even have played a role in the vein formation these structures would represent the first finds of fossilised life forms of such a combined age and depth

circulation in the point conception santa barbara channel region during spring and early summer 1983 fifteen current moorings were deployed around the periphery of santa barbara channel and over the continental shelf to the west off point conception data from these moorings have been used to describe the regional circulation and to address problems of wind forcing and the spatial coherency scales for current fluctuations the mean circulation in santa barbara channel was dominated by a westward jet which occupied the northwestern portion of the channel current and temperature fluctuations were generally well correlated among all locations around the channel and time lags suggested cyclonic propagation of events around the channel the time fluctuations were dominated by a relatively few low frequency events it was impossible to determine exactly either the driving mechanisms for these events or their relationships to regional flow the flow regime was considerably different off point conception than in the channel locally wind driven upwelling was observed in both the mean and fluctuating flows and the time scales of current variability i e spectral shapes mimicked those of the local winds a dramatic change in the regime off point conception occurred in late may before the transition currents and sea levels had been well correlated in time with both local and remote winds after late may the relation to fluctuating winds was less clear and the alongshore structure of sea level variability had changed radically

the early appearance of shuidonggou core and blade technology in north china implications for the spread of anatomically modern humans in northeast asia abstract the identification and dating of south temple canyon 1 stc 1 an early upper paleolihic eup site in north central china near shuidonggou sdg helps confirm that sdg is one of the earliest eup sites in northern asia materials from stc 1 bear a strong resemblance to the early sdg core and blade lithic technology that includes flat faced cores and elongate blades we obtained a 14c age estimate of 41 070 890 14c yr bp on the innermost lamina of a calcium carbonate pendant attached to one of the quartzite flakes from the site the purity of the micrite lamina the care taken in obtaining the carbonate sample for processing and dating and the geomorphological setting from which the flake came suggest the age estimate represents a reasonable assessment of an accurate minimum age for stc 1 together with recently derived age estimates of 35 14c ka for the initial eup occupations at sdg 1 and 2 it appears that the eup in the sdg area is as old as any of the handful of eup sites in mongolia and siberia dating to about 40 14c ka and brings into question a postulated north to south spread of the eup lithic technology present at sdg whether or not the dispersal of this technology is associated with the spread of anatomically modern humans remains unknown

characteristic patterns of shelf circulation at the boundary between central and southern california 1 the coastal circulation in the santa barbara channel sbc and the southern central california shelf is described in terms of three characteristic flow patterns the upwelling pattern consists of a prevailing equatorward flow at the surface and at 45 m depth except in the area immediately adjacent to the mainland coast in the sbc where the prevailing cyclonic circulation is strong enough to reverse the equatorward tendency and the flow is toward the west in the surface convergent pattern north of point conception the surface flow is equatorward while the flow at 45 m depth is poleward east of point conception along the mainland coast the flow is westward at all depths and there results a convergence at the surface between point conception and point arguello with offshore transport over a distance on the order of 100 km beneath the surface layer the direction of the flow is consistently poleward the relaxation pattern is almost the reverse of the upwelling pattern with the exception that in the sbc the cyclonic circulation is such that the flow north of the channel islands remains eastward although weak the upwelling pattern is more likely to occur in march and april after the spring transition when the winds first become upwelling favorable and while the surface pressure is uniform the surface convergent pattern tends to occur in summer when the wind is still strong and persistently upwelling favorable and the alongshore variable upwelling has build up alongshore surface pressure gradients the relaxation pattern occurs in late fall and early winter after the end of the period of persistent upwelling favorable winds

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

shipboard acoustic doppler profiler velocity observations near point conception spring 1983 during april 1983 shipboard doppler acoustic log current profiles were collected in an effort to characterize the flow field near points conception and arguello california subsurface velocity maps derived from these profiles have been used to describe spatial flow structures both on and off the shelf and to investigate flow variability as a function of time and of wind stress persistent westward flow out of the northern half of the santa barbara channel and eastward flow into its southern half were observed regardless of the direction of the local wind stress during one well documented upwelling favorable wind event currents responded in the form of an energetic maximum 21 m speeds of 60 cm s 1 offshore squirt of cold water during weak or downwelling favorable winds currents continuous with the santa barbara channel outflow were observed flowing to the northwest following the local isobaths before turning offshore west of point arguello evidence for wind forcing of current fluctuations nearshore between the points and north of point arguello was found lack of a thermal wind balance between directly measured velocity shear and horizontal density gradient was explained by the presence of large accelerations in the momentum equations lack of a consistent relation between velocity and temperature gradient illustrates the difficulty in estimating velocity from temperature information alone in this area

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

the inner shelf response to wind driven upwelling and downwelling abstract a two dimensional numerical model is used to study the response to upwelling and downwelling favorable winds on a shelf with a strong pycnocline during upwelling or downwelling the pycnocline intersects the surface or bottom forming a front that moves offshore the characteristics of the front and of the inner shelf inshore of the front are quite different for upwelling and downwelling for a constant wind stress the upwelling front moves offshore at roughly a constant rate while the offshore displacement of the downwelling front scales as t because the thickness of the bottom layer increases as the front moves offshore the geostrophic alongshelf transport in the front is larger during downwelling than upwelling for the same wind stress magnitude because the geostrophic shear is near the bottom in downwelling as opposed to near the surface in upwelling during upwelling weak stratification is maintained over the inner shelf by the onshore flux of denser near bottom water this weak stratif

seasonal cycles of currents temperatures winds and sea level over the northeast pacific continental shelf 35 n to 48 n seasonal cycles of coastal wind stress adjusted sea level asl shelf currents and water temperatures off the west coast of north america 35 n to 48 n are estimated by fitting annual and semiannual harmonics to data from 1981 1983 longer records 9 34 years of monthly asl indicate that these two harmonics adequately represent the long term monthly average seasonal cycle and that the current measurement period is long enough to estimate the seasonal cycles we characterize the differences between fall winter and spring summer as follows for fall winter monthly mean winds north of 35 n are northward for 3 6 months longer in the north than in the south south of 35 n the mean winds are near zero or weakly southward monthly mean alongshore currents are northward over midshelf and shelf break at all locations sampled at depths of 35 m and deeper and are associated with high coastal sea levels and relatively warm water temperatures for spring summer monthly mean wind stresses are southward at all latitudes for 3 6 months longer in the south than in the north sea levels are low and water temperatures are relatively cool monthly mean currents at 35 m depth over the shelf are southward for 1 6 months longer at the shelf break than over midshelf and longer in the north than in the south while the deeper currents are less southward or northward the magnitudes of the seasonal cycles of all variables are maximum between approximately 38 n and 43 n generally decreasing slightly to the north and greatly to the south at each location the seasonal cycle of the alongshore current from 35 m depth at midshelf leads the sea level slightly and both lead the wind stress and temperatures by 1 2 months the seasonal cycles of all variables show a south to north progression south leads north by 1 2 months at 48 n annual mean currents at 50 m depth over the shelf break oppose the annual mean wind northward wind and southward current similarly at 35 n annual mean currents at 35 m depth over both midshelf and shelf break are opposed to the annual mean wind southward wind and northward current from 35 n to 43 n both summer and winter regimes are dominated by strongly fluctuating currents

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

the propagating response of coastal circulation due to wind relaxations along the central california coast 1 following relaxations of prevailing upwelling favorable winds warm waters from the santa barbara channel propagate poleward around point conception and along the south central california coast we examined characteristics of these relaxation flows including frontal propagation speed and temperature changes during the warm water arrivals by using multiyear time series of currents and temperatures from four moorings along the 15 m isobath surface current observations from high frequency radars and satellite sea surface temperature images propagation speeds of the warm fronts relative to ambient waters ranged from 0 04 to 0 46 m s 1 as the fronts arrived at the moorings temperature increases ranged from 0 7 c to 4 2 c in ensemble averages over many frontal arrivals alongshore flow speeds increased by 0 1 0 2 m s 1 over the water column during arrivals cross shore flows were onshore near the surface and offshore near the bottom with speeds of 0 02 0 05 m s 1 this cross shore flow structure persisted as temperature increased during arrivals and ceased when temperatures stopped increasing frontal propagation speeds were correlated with temperature increases at the moorings consistent with forcing by baroclinic pressure gradients compared to other buoyant flows such as from the chesapeake bay where density contrasts with ambient waters are 2 3k g m 3 these relaxation flows are less buoyant with density contrasts of 0 1 0 9 kg m 3 consequently the propagation of these flows is more affected by bottom friction and the speeds are closer to the slope controlled or bottom advected limit described in theoretical and laboratory work but not well studied in the ocean

the structure and variability of the marine atmosphere around the santa barbara channel the santa barbara channel is a region characterized by coupled interaction between the lower level atmosphere the underlying ocean and the elevated topography of the coastline the nature of these interactions and the resulting weather patterns vary between summer and winter during summer synoptic winds are largely controlled by the combined effect of the north pacific anticyclone and the thermal low located over the southwestern united states resulting in persistent northwesterly winds a well defined marine atmospheric boundary layer mabl with properties distinct from the free atmosphere above is a conspicuous feature during the summer the wind has different characteristics in each of three zones maximum winds occur in the area extending south and east from pt conception zone 1 where they initially increase as they turn to follow the coast then decrease farther east winds are usually weak in zone 2 located in the easternmost part of the channel offshore from the oxnard plain winds are also weak in zone 3 sometimes reversing to easterly at night in a narrow band located along the mainland coast summer air temperature at the surface follows the sst closely and varies significantly with location summer sea level pressure gradients are large with the lowest pressure occurring on the northeast end of the santa barbara channel diurnal variations are strongest in summer although the modulation is weakest in zone 1 the diurnal variation is parallel to the coast in all of zone 3 but the oxnard plain where it is perpendicular to the coast the height of the marine layer varies between 300 m in late afternoon and 350 m in late morning in winter synoptic conditions are driven by traveling cyclones and sometimes accompanied by fronts these are usually preceded by strong southeast winds and followed by strong northwest winds atmospheric parameters are distributed more uniformly than in summer and diurnal variations are greatly reduced sea level air temperature and pressure are more spatially uniform than in the summer spatial variations in the observed fields in the summer are consistent with a hydraulic model of the mabl as a transcritical expansion fan the summertime situation is governed by a coupled interaction between the atmosphere and the underlying water the ocean influences the density of the mabl to the extent that it behaves distinctly from the free atmosphere above resulting in strong winds polarized in the direction parallel to the coast in turn these winds provoke an upwelling response in the coastal ocean which in part determines the surface properties of the water

inner shelf response to cross shelf wind stress the importance of the cross shelf density gradient in an idealized numerical model and field observations this study investigates the effects of horizontal and vertical density gradients on the inner shelf response to cross shelf wind stress by using an idealizednumericalmodel and observations from a mooredarray deployed south of martha s vineyard massachusetts in two dimensional no along shelf variation numerical model runs of an initially stratified shelf a cross shelf wind stress drives vertical mixing that results in a nearly wellmixed inner shelf with a cross shelf density gradient because of the sloping bottom the cross shelf density gradient causes an asymmetric response to on and offshore wind stresses for density increasing offshore an offshore wind stress drives a near surface offshore flow and near bottom onshore flow that slightly enhances the vertical stratification and the cross shelf circulation an onshore wind stress drives the reverse cross shelf circulation reducing the vertical stratification and the cross shelf circulation a horizontal richardson number is shown to be the nondimensional parameter that controls the dependence of the wind driven nondimensional cross shelf transport on the cross shelf density gradient field observations show the same empirical relationship between the horizontal richardson number and transport fraction as the model predicts these results show that it is the cross shelf rather than vertical density gradient that is critical to predicting the inner shelf cross shelf transport driven by a cross shelf wind stress

low frequency waves in the santa barbara channel observed by high frequency radar are antisymmetric with a mean propagation speed of 5k m d 1 and relative vorticity of order 0 1 f complex empirical orthogonal function decomposition in the 10 20 day passband partitions variance into two dominant modes the first mode represents the vortices with an average period of 14 4 days the second mode represents alongshore fluctuations with an average period of 13 3 days amplitude functions of the two modes correlate with in situ current time series at 5 and 45 m depths obtained from moorings at the east and west channel entrances suggesting coupling with the larger scale circulation of the northern southern california bight the observations support interpretation of mode 2 as a coastal trapped wave since the period and alongshore flow are consistent with previous observations and predictions we hypothesize that mode 1 is a resonant response of the santa barbara basin in the form of a trapped topographic rossby mode the spatial mode resembles the predicted pattern based on a simplified analytical model of the fundamental mode the amplitude of mode 1 is consistently large when the frequencies of modes 1 and 2 converge suggesting that the vortices are a basin scale resonant response to coastal trapped waves index terms 4520 oceanography physical eddies and mesoscale processes 4512 oceanography physical currents 4508 oceanography physical coriolis effects 4516 oceanography physical eastern boundary currents 4544 oceanography physical internal and inertial waves keywords propagating eddies santa barbara channel coastal trapped waves citation beckenbach e and l washburn 2004 low frequency waves in the santa barbara channel observed by high frequency radar j geophys res 109 c02010 doi 10 1029 2003jc001999

wind stress curl forcing of the coastal ocean near point conception california near point conception california the atmospheric flow separates from the coast and a large wind stress curl results direct spatial wind field observations from 20 aircraft overflights in the spring of 1983 suggest that ekman pumping of on average 4 m day21 contributes to the local dynamics during strong and persistent upwelling events the curl driven ekman pumping reaches up to 20 m day21 a single complex empirical orthogonal function explains more than 72 of the spatial and temporal wind stress variance it reveals large wind stress curl at the center of the western santa barbara channel entrance this dominant mode correlates strongly r 2 5 0 79 with the wind stress observed at a moored buoy the location of largest ekman pumping in the ocean indicated by this mode coincides with the location of a laterally sheared cyclonic flow cold upwelled waters enter the santa barbara channel along its southern perimeter while warm and thus buoyant waters from the southern california bight exit the channel along its northern perimeter buoy wind stress and lateral current shear at 30 m depth correlate significantly at periods of about 3 5 and 6 days with phase lags of about 0 5 and 2 days respectively hydrographic observations from 1983 do not however indicate effects of ekman pumping on the internal mass field as winds vary in speed and direction at daily timescales this contrasts with 1984 observations that do indicate strong doming of isopycnals over the center of the channel at its western entrance winds prior to and during hydrographic observations in the spring of 1984 were both stronger and more steady than they were in 1983 cyclonic shears reach 0 4 f at the entrance of the santa barbara channel near point conception here f is the planetary vorticity the thermal wind balance explains the lateral shear of the alongchannel surface flow rather well

wind relaxations and poleward flow events in a coastal upwelling system on the central california coast 1 when upwelling favorable winds weaken or relax in coastal upwelling systems prevailing equatorward currents often weaken and then reverse to form propagating poleward currents here the statistics of wind relaxations and poleward flow events along the south central california coast are derived using meteorological and oceanographic times series during 2000 2006 over the 7 year record 169 wind relaxations were observed about 1 every 2 weeks and 127 of these were followed by poleward flow events thermistor moorings and current profilers along the 15 m isobath at alegria point arguello point purisima and point sal recorded the poleward flows the poleward flows propagate northward at 10 30 km d 1 and appear as sequential temperature increases at the moorings wind relaxations occur throughout the year but are most frequent in september and least frequent in april when upwelling winds are strong and persistent poleward flows follow wind relaxations frequently during may through november and rarely in december and january sea level differences between santa monica and port san luis california decreased as winds relaxed consistent with forcing by alongshore pressure gradients temperature distributions at point arguello point purisima and point sal were skewed toward higher values because of the poleward flows the alongshore distance traveled by the poleward flows increased with duration of the wind relaxations and magnitudes of alongshore temperature and sea level differences prior to the relaxations

subtidal inner shelf circulation near point conception california 1 we discuss connections between inner shelf and mid shelf circulation near point conception california as well as the wind forcing of inner shelf circulation point conception marks the southern edge of a major upwelling zone that extends from oregon to central california the coastline makes a sharp eastward turn at point conception and the santa barbara channel to the east is generally assumed to be an upwelling shadow consistent with this regional division inner shelf currents are strongly correlated with wind north of point conception but not in the santa barbara channel one exception to this generalization is a location in the santa barbara channel near a pass that cuts through the coastal mountains where local winds have a dominant cross shore component and directly drive cross shore currents over the inner shelf inner shelf currents in the santa barbara channel when compared with mid shelf currents in that area are weaker but strongly correlated by contrast inner shelf currents north of point conception show a far greater incidence of poleward flow than is seen over the mid shelf in that area poleward flow events lasting 1 5 days transport warm water from the santa barbara channel around point conception to the central california coast these events are associated with relaxation of the generally equatorward wind but not always with mid shelf flow reversals