holocene oceanographic changes in sw labrador sea off newfoundland benthic foraminiferal assemblages supported by selected geochemical data from three marine sediment cores collected in placentia bay se newfoundland are used to construct an 13 000 year long rec

correlation scales objective mapping and absolute geostrophic flow in the california current the spatial covariances of the time dependent density and geostrophic velocity fields off southern california are determined from a unique set of repeated hydrographic observations 44 cruises made by the california cooperative oceanic fisheries investigations from 1984 to 1994 the covariances and objective analysis are used to combine direct velocity observations from shipboard acoustic doppler current profiler adcp measurements made on a recent survey october 1993 with hydrographic observations the analysis reduces ageostrophic noise in the adcp velocities by smoothing and enforcing horizontal nondivergence additionally the velocities are mapped over scales that are dynamically consistent with the hydrography maximum surface geostrophic flow in the california current in october 1993 is about 35 cm s 1 50 larger than that estimated assuming a 500 m level of no motion absolute flow at 500 m is o 10 cm s 1 and indicates that the surface eddy field penetrates through the thermocline uncertainty in the geostrophic reference calculated from the adcp measurements is of o 4 cm s 1 the velocity residual objectively analyzed minus raw adcp estimates exhibits smaller correlation scales than the geostrophic flow

ekman transport along the galician coast northwest spain calculated from forecasted winds 1 ekman transport is studied close to the galician coast by means of forecasted winds provided by meteogalicia from november 2001 to october 2004 three different coastal zones are identified western coast from mino river to cape finisterre middle coast from cape finisterre to cape ortegal and northern coast from cape ortegal to cape penas in addition to existence of long term variations the periodicity of the transport signal is characterized by an annual component 365 days a seasonal fluctuation 50 to 80 days and a timescale related to passing storms 15 20 days although the periodicity of the signal is similar at the three zones owing to external meteorological forcing the ekman transport is modulated by the presence of the coast in such a way that seasonal patterns vary in intensity and direction along the coast thus the autumn winter pattern is characterized by high transport at the northern and middle coast pointing landward perpendicular to the shoreline and moderate values at the western coast pointing landward and oblique to the shoreline on the other hand the spring summer pattern is characterized by high transport at the western coast pointing seaward perpendicular to the shoreline the same orientation is observed at the middle coast although with a lower magnitude finally ekman transport at the northern coast points landward and oblique to the shoreline the different transport orientations are shown to be responsible for the upwelling probability variation along the coast

decadal variability of subpolar gyre transport and its reverberation in the north atlantic overturning 1 analyses of sea surface height ssh records based on satellite altimeter data and hydrographic properties have suggested a considerable weakening of the north atlantic subpolar gyre during the 1990s here we report hindcast simulations with high resolution ocean circulation models that demonstrate a close correspondence of the ssh changes with the volume transport of the boundary current system in the labrador sea the 1990s decline of about 15 of the long term mean appears as part of a decadal variability of the gyre transport driven by changes in both heat flux and wind stress associated with the north atlantic oscillation nao the changes in the subpolar gyre as manifested in the deep western boundary current off labrador reverberate in the strength of the meridional overturning circulation moc in the subtropical north atlantic suggesting the potential of a subpolar transport index as an element of a moc monitoring system

dynamics of decadal variability in the atlantic subpolar gyre a stochastically forced oscillator internal variability of the atlantic subpolar gyre is investigated in a 600 years control simulation of a comprehensive coupled climate model the subpolar gyre shows irregular oscillations of decadal time scale with most spectral power between 15 and 20 years positive and negative feedback mechanisms act successively on the circulation leading to an internal oscillation this involves periodically enhanced deep convection in the subpolar gyre center and intermittently enhanced air sea thermal coupling as a result anomalies of the large scale atmospheric circulation can be transferred to the ocean on the ocean s intrinsic time scale exciting the oscillator stochastically a detailed understanding of oscillatory mechanisms of the ocean and their sensitivity to atmospheric forcing holds considerable potential for decadal predictions as well as for the interpretation of proxy data records

contribution of icelandic ice caps to sea level rise trends and variability since the little ice age 1 in total icelandic ice caps contain 3600 km3 of ice which if melted would raise sea level by 1 cm here we present an overview of mass changes of icelandic ice masses since the end of the 19th century they have both gained and lost mass during this period changes in ice volume have been estimated both through surface mass balance measurements performed annually since 1990 and differencing of digital elevation models derived from various satellite and airborne observations while the glaciers showed little mass loss as the 20th century began losses increased rapidly after 1925 peaked in the 1930s and 1940s and remained significant until the 1960s after being near zero or even positive during the 1980s and early 1990s glacier mass budgets declined considerably and have since the mid 1990s shown an average annual loss of 9 5 1 5 gt a 1 contributing 0 03 mm a 1 to sea level rise since 1995 interannual variability in mass loss is high ranging from 2 7 to 25 3 1 5 gt a 1 corresponding to surface mass balances of 0 2 to 2 2 0 15 m we a 1 this variability is driven by climate fluctuations and also by transient reduction of albedo due to volcanic eruptions

salinity driven thermocline transients in a wind and thermohaline forced isopycnic coordinate model of the north atlantic abstract an isopycnic coordinate oceanic circulation model formulated with the aim of simulating thermodynamically and mechanically driven flow in realistic basins is presented special emphasis is placed on the handling of diabatic surface processes and on thermocline ventilation the model performance is illustrated by a 30 year spinup run with coarse horizontal resolution 2 mesh in a domain with north atlantic topography extending from 10 to 60 n latitude the vertical structure encompasses 10 isopycnic layers in steps of 0 2 units capped by a thermodynamically active mixed layer from an initially isohaline state with isopycnals prescribed by zonally averaged climatology the model is forced by seasonally varying wind stress radiative and freshwater fluxes and by a thermal relaxation process at the surface after a mechanical spinup time of about 15 years a quasi stationary pattern of mean circulation and annual variability ensues characterized by pronounced subtropical mode water formation

foraminiferal radiocarbon record of northeast pacific decadal subsurface variability 1 the decadal dynamics of the subsurface north pacific ocean are largely inaccessible beyond sparse instrumental observations spanning the last 20 years here we present a 200 year long record of benthic foraminiferal radiocarbon 14c extracted at biennial resolution from the annually laminated sediments at the santa barbara basin sbb depocenter 600 m the close match between core top benthic foraminiferal 14c values and the 14c of seawater dissolved inorganic carbon dic suggests that benthic foraminifera faithfully capture the bottom water radiocarbon concentrations as opposed to that of the deeper 0 5 cm sediment porewater zone the full time series of benthic foraminiferal 14c displays significant variability on decadal timescales with excursions on the order of 40 these excursions are overprinted by a unidirectional trend over the late 20th century that likely reflects the sedimentary incorporation of bomb radiocarbon via remineralized particulate organic carbon we isolate this trend by means of a one dimensional oxidation model which considers the possible contribution of remineralized particles to the total ambient carbon pool this oxidation model also considers the possible influence of carbon with a variety of sources ages though variable oxidation of preaged carbon could exert a strong influence on benthic foraminiferal radiocarbon variability the totality of evidence points to the vertical density structure along the southern california margin scm as the primary driver of the sbb benthic foraminiferal 14c record for example intervals characterized by significantly lower 14c values correspond to periods of enhanced upwelling and subsurface equatorward flow along the scm

holocene development of the river lippe valley germany a case study of anthropogenic influence the characteristics of the holocene valley floor of the river lippe germany are atypical for a river in central europe the valley floor consists of three terrace levels which are not always clearly separated from each other analysis of the sediments making up the terraces indicates that they accumulated during the course of the entire holocene although there is insufficient information available to allow detailed determination of phases of fluvial change and stability responsible for terrace formation two of the terraces exist only in the lower reaches of the valley where they converge and diverge with the third the lowest terrace consists only of a narrow strip running parallel to the river channel the configuration of the valley floor may be explained by a series of anthropogenic influences the earliest human impact probably occurred about 2000 years ago when during their campaign against german tribes the romans built a towpath and may have changed the channel planform from its natural anabranching pattern to a meandering form by building small dams on local distributary forks implementation of artificial meander cut offs to improve navigation on the river began in medieval times the morphological response to these human interventions was primarily degradational in the 19th century artificial lateral fill was used to narrow the channel and the towpath was renewed several times the trace of the most recent towpath is still discernible as a narrow strip parallel to the river channel and it constitutes the lowest terrace level comparison between the bankfull discharge of a 4000 year old abandoned channel and the formative flow for the modern channel supports the premise that prior to anthropomorphic influence the natural planform was anabranched copyright 2000 john wiley sons ltd

a wind driven isopycnic coordinate model of the north and equatorial atlantic ocean 1 model development and supporting experiments numerical approximations to the dynamic equations are given which allow basin size ocean circulation models formulated in isopycnic coordinates to accommodate variable bottom topography and irregular coastlines emphasis is placed on computational economy through the use of a split explicit time integration scheme on the proper formulation of the advection and coriolis terms in the momentum equation in case of strongly varying layer thickness and on the correct estimation of the horizontal pressure gradient force in grid boxes truncated by steep bottom slopes the algorithms are tested in a series of two and three layer double gyre experiments in cases of steady forcing leading to a steady circulation we are able to reproduce the expected motionless final state in coordinate layers that are below the direct influence of the wind forcing this includes layers intersecting topographic obstacles a long term 25 30 year vacillation tentatively associated with the outcropping of isopycnals along the edge of the cyclonic gyre in a steadily forced model is documented the paper forms the basis for a subsequent study in which circulation features obtained in a realistic north atlantic setting will be discussed

the 8 2 ka event abrupt transition of the subpolar gyre toward a modern north atlantic circulation 1 climate model simulations of the 8 2 ka event show an abrupt strengthening of the atlantic subpolar gyre that allows us to connect two major but apparently contradictory climate events of the early holocene the freshwater outburst from proglacial lakes and the onset of labrador sea water formation the 8 2 ka event is the largest climatic signal of our present interglacial with a widespread cooling in the north atlantic region about 8200 years before present it coincides with a meltwater outburst from north american proglacial lakes that is believed to have weakened the atlantic meridional overturning circulation and northward heat transport followed by a recovery of the deep ocean circulation and rising temperatures after a few centuries marine proxy data however date the onset of deep water formation in labrador sea to the same time the subsequent strengthening of the slope current system created a regional signal recorded as an abrupt and persistent surface temperature decrease although similarities in timing are compelling a mechanism to reconcile these apparently contradictory events was missing our simulations show that an abrupt and persistent strengthening of the atlantic subpolar gyre provides a plausible explanation the intense freshwater pulse triggered a transition of the gyre circulation into a different mode of operation stabilized by internal feedbacks and persistent after the cessation of the perturbation as a direct consequence deep water formation around its center intensifies this corresponds to the modern flow regime and stabilizes the meridional overturning circulation possibly contributing to the holocene s climatic stability

fine scale variability of isopycnal salinity in the california current system this paper examines the finescale structure and seasonal fluctuations of the isopycnal salinity of the california current system from 2007 to 2013 using temperature and salinity profiles obtained from a series of underwater glider surveys the seasonal mean distributions of the spectral power of the isopycnal salinity gradient averaged over submesoscale 12 30 km and mesoscale 30 60 km ranges along three survey lines off monterey bay point conception and dana point were obtained from 298 transects the mesoscale and submesoscale variance increased as coastal upwelling caused the isopycnal salinity gradient to steepen areas of elevated variance were clearly observed around the salinity front during the summer then spread offshore through the fall and winter the high finescale variances were observed typically above 25 8 kg m 3 and decreased with depth to a minimum at around 26 3 kg m 3 the mean spectral slope of the isopycnal salinity gradient with respect to wavenumber was 0 19 0 27 over the horizontal scale of 12 60 km and 31 to 35 of the spectra had significantly positive slopes in contrast the spectral slope over 12 30 km was mostly flat with mean values of 0 025 0 32 an increase in submesoscale variability accompanying the steepening of the spectral slope was often observed in inshore areas e g off monterey bay in winter where a sharp front developed between the california current and the california under current and the lower layers of the southern california bight where vigorous interaction between a synoptic current and bottom topography is to be expected

a damped decadal oscillation in the north atlantic climate system a simple stochastic atmosphere model is coupled to a realistic model of the north atlantic ocean a north south sst dipole with its zero line centered along the subpolar front influences the atmosphere model which in turn forces the ocean model by surface fluxes related to the north atlantic oscillation the coupled system exhibits a damped decadal oscillation associated with the adjustment through the ocean model to the changing surface forcing the oscillation consists of a fast wind driven positive feedback of the ocean and a delayed negative feedback orchestrated by overturning circulation anomalies the positive feedback turns out to be necessary to distinguish the coupled oscillation from that in a model without any influence from the ocean to the atmosphere using a novel diagnosing technique it is possible to rule out the importance of baroclinic wave processes for determining the period of the oscillation and to show the important role played by anomalous geostrophic advection in sustaining the oscillation

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

the california current system in the southern california bight and the santa barbara channel recent observations in the santa barbara channel and over the california cooperative oceanic fisheries investigations calcofi southern california grid are used to examine seasonal circulation patterns in and near the southern california bight defined as the region east of the santa rosa ridge and including the santa barbara channel poleward flow relative to 500 m is found throughout the bight in all seasons except for spring and all subregions except the western part of the santa barbara channel in spring there is equatorward flow throughout the bight at all depths to 500 m though it tends to be surface or midcolumn intensified equatorward flow offshore of the bight present in all seasons narrows and accelerates into a jet like feature and simultaneously moves close to the santa rosa ridge in summer current meter data from the eastern entrance to the santa barbara channel are consistent with the seasonal results from the calcofi data and further show an upward propagation of phase at annual period with a phase speed of 1 to 2 m d 1 comparison with the calcofi ship winds suggests that poleward flow in the bight may be the result of positive wind stress curl through a sverdrup balance though the observed transport is only about 75 of that expected from the curl amplitude equatorward flow in the bight may be the result of coastal upwelling though the transport is larger than expected from the relatively weak winds in the bight and the offshore extent of the equatorward flow is about 10 rossby radii farther than might be expected for linearized coastal upwelling equatorward flow outside the bight cannot be explained as a sverdrup flow because the wind stress curl is positive throughout most of the region upward propagation of phase and downward propagation of energy may be indicative of forcing by remote wind equatorward of the bight given the complexity of possible forcing mechanisms for circulation in and near the bight a model that includes effects of remote wind forcing ekman pumping and topography is needed to explain the observations in a satisfactory way

simulated variability of the atlantic meridional overturning circulation to examine the multi annual to decadal scale variability of the atlantic meridional overturning circulation amoc we conducted a four member ensemble with a daily reanalysis forced medium resolution global version of the isopycnic coordinate ocean model micom and a 300 years integration with the fully coupled bergen climate model bcm the simulations of the amoc with both model systems yield a long term mean value of 18 sv and decadal variability with an amplitude of 1 3 sv the power spectrum of the inter annual to decadal scale variability of the amoc in bcm generally follows the theoretical red noise spectrum with indications of increased power near the 20 years period comparison with observational proxy indices for the amoc e g the thickness of the labrador sea water the strength of the baroclinic gyre circulation in the north atlantic ocean and the surface temperature anomalies along the mean path of the gulf stream shows similar trends and phasing of the variability indicating that the simulated amoc variability is robust and real mixing indices have been constructed for the labrador the irminger and the greenland iceland norwegian gin seas while convective mixing in the labrador and the gin seas are in opposite phase and linked to the nao as observations suggest the convective mixing in the irminger sea is in phase with or leads the labrador sea newly formed deep water is seen as a slow anomalous cold and fresh plume flowing southward along the western continental slope of the atlantic ocean with a return flow of warm and saline water on the surface in addition fast travelling topographically trapped waves propagate southward along the continental slope towards equator where they go east and continue along the eastern rim of the atlantic for both types of experiments the northern hemisphere sea level pressure and 2 m temperature anomaly patterns computed based on the difference between climate states with strong and weak amoc yields a nao like pattern with intensified icelandic low and azores high and a warming of 0 25 0 5 c of the central north atlantic sea surface temperature sst the reanalysis forced simulations indicate a coupling between the labrador sea water production rate and an equatorial atlantic sst index in accordance with observations this coupling is not identified in the coupled simulation

response of the north atlantic subpolar gyre to persistent north atlantic oscillation like forcing the response of the north atlantic subpolar gyre spg to a persistent positive or negative phase of the north atlantic oscillation nao is investigated using an ocean general circulation model forced with idealized atmospheric reanalysis fields the integrations are analyzed with reference to a base line integration for which the model is forced with idealized fields representing a neutral state of the nao in the positive nao case the results suggest that the well known cooling and strengthening of the spg are after about 10 years replaced by a warming and subsequent weakening of the spg the latter changes are caused by the advection of warm water from the subtropical gyre stg region driven by a spin up of the atlantic meridional overturning circulation amoc and the effect of an anomalous wind stress curl in the northeastern north atlantic which counteracts the local buoyancy forcing of the spg in the negative nao case however the spg response does not involve a sign reversal but rather shows a gradual weakening throughout the integration the asymmetric spg response to the sign of persistent nao like forcing and the different time scales involved demonstrate strong non linearity in the north atlantic ocean circulation response to atmospheric forcing the latter finding indicates that analysis based on the arithmetic difference between the two nao states e g nao minus nao may hide important aspects of the ocean response to atmospheric forcing

response of north atlantic ocean circulation to atmospheric weather regimes a new framework is proposed for investigating the atmospheric forcing of north atlantic ocean circulation instead of using classical modes of variability such as the north atlantic oscillation nao or the east atlantic pattern the weather regimes paradigm was used using this framework helped avoid problems associated with the assumptions of orthogonality and symmetry that are particular to modal analysis and known to be unsuitable for the nao using ocean only historical and sensitivity experiments the impacts of the four winter weather regimes on horizontal and overturning circulations were investigated the results suggest that the atlantic ridge ar negative nao nao and positive nao nao regimes induce a fast monthly to interannual time scales adjustment of the gyres via topographic sverdrup dynamics and of the meridional overturning circulation via anomalous ekman transport the wind anomalies associated with the scandinavian blocking regime sbl are ineffective in driving a fast wind driven oceanic adjustment the response of both gyre and overturning circulations to persistent regime conditions was also estimated ar causes a strong wind driven reduction in the strengths of the subtropical and subpolar gyres while nao causes a strengthening of the subtropical gyre via wind stress curl anomalies and of the subpolar gyre via heat flux anomalies nao induces a southward shift of the gyres through the southward displacement of the wind stress curl the sbl is found to impact the subpolar gyre only via anomalous heat fluxes the overturning circulation is shown to spin up following persistent sbl and nao and to spin down following persistent ar and nao conditions these responses are driven by changes in deep water formation in the labrador sea

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

decline of subpolar north atlantic circulation during the 1990s observations of sea surface height reveal that substantial changes have occurred over the past decade in the mid to high latitude north atlantic ocean topex poseidon altimeter data show that subpolar sea surface height increased during the 1990s and the geostrophic velocity derived from altimeter data exhibits declining subpolar gyre circulation combining the data from earlier satellites we find that subpolar circulation may have been weaker in the late 1990s than in the late 1970s and 1980s direct current meter observations in the boundary current of the labrador sea support the weakening circulation trend of the 1990s and together with hydrographic data show that the mid to late 1990s decline extends deep in the water column analysis of the local surface forcing suggests that the 1990s buoyancy forcing has a dynamic effect consistent with altimetric and hydrographic observations a weak thermohaline forcing allows the decay of the domed structure of subpolar isopycnals and weakening of circulation

poleward flows in the southern california current system glider observations and numerical simulation 1 three years of continuous spray glider observations in the southern california current system ccs are combined with a numerical simulation to describe the mean and variability of poleward flows in the southern ccs gliders provide upper ocean observations with good across shore and temporal resolution along two across shore survey lines while the numerical simulation provides a dynamically consistent estimate of the ocean state persistent poleward flows are observed in three areas within 100 km of the coast at point conception within the southern california bight scb and offshore of the scb and the santa rosa ridge srr poleward transport by the flows within the scb and offshore of the srr exceeds the poleward transport off point conception suggesting that the poleward flows are not continuous over the 225 km between observation lines the numerical simulation shows offshore transport between the survey lines that is consistent with some of the poleward flow turning offshore before reaching point conception the poleward current offshore of the srr is unique in that it is strongest at depths greater than 350 m and it is observed to migrate westward away from the coast this westward propagation is tied to westward propagating density anomalies originating in the scb during the spring summer upwelling season when wind stress curl is most strongly positive the across shore wave number frequency and phase speed of the westward propagation and the lack of across shore transport of salinity along isopycnals are consistent with first mode baroclinic rossby dynamics

observations inferences and mechanisms of the atlantic meridional overturning circulation a review this is a review about the atlantic meridional overturning circulation amoc its mean structure temporal variability controlling mechanisms and role in the coupled climate system the amoc plays a central role in climate through its heat and freshwater transports northward ocean heat transport achieved by the amoc is responsible for the relative warmth of the northern hemisphere compared to the southern hemisphere and is thought to play a role in setting the mean position of the intertropical convergence zone north of the equator the amoc is a key means by which heat anomalies are sequestered into the ocean s interior and thus modulates the trajectory of climate change fluctuations in the amoc have been linked to low frequency variability of atlantic sea surface temperatures with a host of implications for climate variability over surrounding landmasses on intra annual timescales variability in amoc is large and primarily reflects the response to local wind forcing meridional coherence of anomalies is limited to that of the wind field on interannual to decadal timescales amoc changes are primarily geostrophic and related to buoyancy anomalies on the western boundary a pacemaker region for decadal amoc changes is located in a western transition zone along the boundary between the subtropical and subpolar gyres decadal amoc anomalies are communicated meridionally from this region amoc observations as well as the expanded ocean observational network provided by the argo array and satellite altimetry are inspiring efforts to develop decadal predictability systems using coupled atmosphere ocean models initialized by ocean data

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

characteristics of recessional moraines at a temperate glacier in se iceland insights into patterns rates and drivers of glacier retreat icelandic glaciers are sensitive to climate variability on short term timescales owing to their north atlantic maritime setting and have been undergoing ice marginal retreat since the mid 1990s recent patterns rates and drivers of ice frontal retreat at skalafellsjokull se iceland are examined using small scale recessional moraines as a geomorphological proxy these small scale recessional moraines exhibit distinctive sawtooth planform geometries and are constructed by a range of genetic processes associated with minor ice margin re advance including i combined push squeeze mechanisms ii bulldozing of pre existing proglacial material and iii submarginal freeze on remote sensing investigations and lichenometric dating highlight sequences of annually formed recessional moraines on the northern and central parts of the foreland conversely moraines are forming on a sub annual timescale at the southeastern skalafellsjokull margin using annual moraine spacing as a proxy for annual ice margin retreat rates imrrs we demonstrate that prominent periods of glacier retreat at skalafellsjokull are coincident with those at other icelandic outlet glaciers as well as those identified at greenlandic outlet glaciers analysis of imrrs and climate data suggests summer air temperature sea surface temperature and the north atlantic oscillation have an influence on imrrs at skalafellsjokull with the glacier appearing to be most sensitive to summer air temperature on the basis of further climate data analyses we hypothesise that sea surface temperature may drive air temperature changes in the north atlantic region which in turn forces imrrs the increase in sea surface temperature over recent decades may link to atmospheric driven variations in north atlantic subpolar gyre dynamics

the pattern and variability of winter kuroshio intrusion northeast of taiwan the variations of the kuroshio path and velocity northeast of taiwan are analyzed based on along track satellite altimeter data as well as high resolution model experiments observations reveal that in winter the kuroshio intrusion into the east china sea ecs at this location is manifested by a secondary maximum current core smcc shoreward of the kuroshio s main path the smcc varies significantly on interannual time scale and its variability is strikingly out of phase with that of the kuroshio entering the ecs meaning that the stronger the kuroshio the weaker the smcc and vice versa model experiments corroborate the observational results and more importantly indicate that the kuroshio intrusion here follows two primary routes a large anticyclonic loop that separates from the kuroshio at the northern end of taiwan and moves forward to form the smcc and a straight northward path onto the shelf when the kuroshio turns sharply eastward along the continental slope of the ecs the intrusion is controlled by both local forcing and remote effect with its pattern and variability depending mostly on the local heat flux and the inertia of the kuroshio current

santa barbara basin diatom and silicoflagellate response to global climate anomalies during the past 2200 years santa barbara basin sbb diatom and silicoflagellate assemblages are quantified from a box core record spanning ad 1940 2001 and an ocean drilling program hole 893a record from 220 bc to ad 1880 the combined relative abundance of the diatoms fragilariopsis doliolus and nitzschia interrupteseriata from continuous two year sampling intervals in the box core varies with sea surface temperature sst suggesting its utility in sst reconstruction the assemblage data from the odp 893a record indicate a broad interval of generally cooler ssts between ad 800 and 1350 which corresponds to the medieval climate anomaly mca a period of generally warmer temperatures across other regions of the northern hemisphere the assemblages also indicate an interval of generally warmer ssts between ad 1400 and 1800 a period of otherwise global cooling referred to as the little ice age lia the changes in assemblages of diatoms and silicoflagellates support the hypothesis that the widespread droughts of the medieval climate anomaly in the western us were associated with cooler eastern north pacific sst the box core assemblages have higher percentages of tropical and subtropical compared to temperate and subpolar species than the odp samples reflecting a response of phytoplankton communities to an unusual 20th century warming pseudonitzschia australis a diatom linked with domoic acid production begins to become more common 3 of the diatom assemblage in the box core only after ad 1985 suggesting a link to anthropogenic activity

relaxation from upwelling the effect on dissolved oxygen on the continental shelf 1 continental shelves in upwelling regimes are subject to sequences of upwelling and relaxation events each on timescales of order 1 week typically these episodes have pronounced impacts on the temperature and density structure on the shelves and also on the along shore and cross shore flow regimes it had previously been demonstrated that relaxation phases advect warm water along shore poleward from regions of less intense upwelling thus adding to the heat balance in upwelling locations and providing a rectification of oscillating heat fluxes in the current paper it is shown that relaxations also modify the dissolved oxygen do budget of the lower layers on a narrow shelf this provides enhanced do values due to near surface exposure while on a wide shelf decreased do concentrations are created due to oxygen consumption on the inner shelf the resulting variations along the coast can lead to along shore advection of high or low do during a relaxation event observations are presented from moorings off san diego and del mar which show large departures from density correlated do values during relaxations and which support the proposed mechanisms

effects of nao variability on the north atlantic ocean circulation 1 the ocean response to an idealised north atlantic oscillation like wind stress is evaluated as a function of the atmospheric forcing frequency in order to elucidate the relationship between internal and forced variability the nao is modulated with two specific timescales 10 and 50 years which characterise the spectrum of the system s internal variability different timescales of atmospheric variability select distinct sea surface temperature sst and large scale circulation patterns under a 50 year nao forcing period a lagged sst response is excited in the gulf stream extension region which is consistent with the spin up of the gyre circulation the thermohaline circulation varies in phase with the nao and shows a strong sensitivity to the forcing frequency a dipole mode of the overturning is excited by a 10 year modulation of the nao while an enhanced overturning response emerges under a 50 year nao with low enough lateral mixing the ocean exhibits an irregular response to a regular nao like forcing

interdecadal variations of the thermohaline circulation in a coupled ocean atmosphere model abstract a fully coupled ocean atmosphere model is shown to have irregular oscillations of the thermohaline circulation in the north atlantic ocean with a time scale of approximately 50 years the irregular oscillation appears to be driven by density anomalies in the sinking region of the thermohaline circulation approximately 52 n to 72 n combined with much smaller density anomalies of opposite sign in the broad rising region the spatial pattern of see surface temperature anomalies associated with this irregular oscillation bears an encouraging resemblance to a pattern of observed interdecadal variability in the north atlantic the anomalies of sea surface temperature induce model surface air temperature anomalies over the northern north atlantic arctic and northwestern europe

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

mud re distribution in epicontinental basins exploring likely processes abstract fine grained clastic sediments are very common in the interior deposits of ancient epicontinental seas not only do they make up the gross lithology in these basins but they can also be traced for more than 1000 km offshore from basin margins given that epicontinental seas were overall shallow and in many parts most likely less than 100 m deep basin floor slopes can safely be expected to be in the 0 01 to 0 001 range for much of depositional history known processes that bring muds to the basin margin and beyond are hypopycnal river plumes hyperpycnal fluvial discharge events storm setup relaxation flows and gravity driven fluidized muds with the exception of river plumes all of these processes require the presence of sufficient slope for sustained movement due to that constraint these processes combined might in the majority of situations have been able to move muddy sediments on the order of 100 km offshore whereas this is sufficient to distribute mud across marginal shelf seas it becomes problematic in the case of much larger epicontinental seas for example those of upper devonian or upper cretaceous times extended in places for thousands of kilometers and thus a process is needed that can move muddy sediments the rest of the way flume studies of the bedload transport of mud combined with observations from the rock record suggest that wind or tide induced bottom current circulation was most likely essential for moving muddy sediments from the periphery of epicontiental seas to their interiors remobilization of seafloor muds during frequently recurring lowering of sea level is likely to have aided in this process

an ocean model s response to north atlantic oscillation like wind forcing the response of the atlantic ocean to north atlantic oscillation nao like wind forcing was investigated using an ocean only general circulation model coupled to an atmospheric boundary layer model a series of idealized experiments was performed to investigate the interannual to multi decadal frequency response of the ocean to a winter wind anomaly pattern overall the strength of the sst response increased slightly with longer forcing periods in the subpolar gyre however the model showed a broad response maximum in the decadal band 12 16 years

biogeochemical anomalies at two southern california current system moorings during the 2014 2016 warm anomaly el nino sequence author s lilly le send u lankhorst m martz tr feely ra sutton aj ohman md abstract 2019 american geophysical union all rights reserved we analyzed impacts of the 2014 2015 pacific warm anomaly and 2015 2016 el nino on physical and biogeochemical variables at two southern california current system moorings cce2 nearshore upwelling off point conception cce1 offshore california current nitrate and chl a fluorescence were l1 m and l1 standardized fluorescence unit respectively at cce2 for the entire durations of the warm anomaly and el nino the two longest periods of such low values in our time series negative nitrate and chl a anomalies at cce2 were interrupted briefly by upwelling conditions in spring 2015 near surface temperature anomalies appeared simultaneously at both moorings in spring 2014 indicating region wide onset of warm anomaly temperatures although sustained negative nitrate and chl a anomalies only occurred offshore at cce1 during el nino summer 2015 to spring 2016 warm anomaly temperature changes were expressed more strongly in near surface l40 m than subsurface 75 m waters at both moorings while el nino produced comparable temperature anomalies at near surface and subsurface depths nearshore aragonite at 76 m showed notably fewer undersaturation events during both warm periods suggesting an environment more conducive to calcifying organisms planktonic calcifying molluscs pteropods and heteropods increased markedly in springs 2014 and 2016 and remained modestly elevated in spring 2015 moorings provide high frequency measurements essential for resolving the onset timing of anomalous conditions and frequency and duration of short term days to weeks perturbations reduced nitrate and aragonite undersaturation events that can affect marine organisms

variability of the simulated meridional heat transport in the north atlantic for the period 1951 1993 a 43 year ocean model simulation for the period 1951 1993 is analyzed with a focus on the meridional heat transport mht as a proxy for the strength of meridional overturning cell moc at 25 n the surface heat flux forcing associated with the north atlantic oscillation nao pattern is related to the variability in mht both on interannual and longer timescales the manifestation of the interannual and decadal oceanic response to nao is nonlocal as evidenced by the concentrated heat content and sea level variability at the gulf stream and north atlantic current regions and shown by the comparison of the model sea level variability to the altimeter data between low mht years in mid 1980s and high mht years in early 1990s the same area is singled out by empirical orthogonal function analysis in the leading mode of the sea level mht and time series of the leading sea level mode are highly correlated which reflects the importance of the moc in determining the variability of the heat content of the whole basin also the model suggests that the mht moc has entered a very strong phase since the mid 1980s and this trend has continued up to the end of 1993 this behavior follows the general trend in the nao index

a study of the interaction of the north atlantic oscillation with ocean circulation observed patterns of wind stress curl and air sea heat flux associated with the north atlantic oscillation nao are used to discuss the response of ocean gyres and thermohaline circulation to nao forcing and their possible feedback on the nao the observations motivate and are interpreted in the framework of a simple mathematical model that couples ekman layers ocean gyres and thermohaline circulation to the atmospheric jet stream meridional shifts in the zero wind stress curl line are invoked to drive anomalies in ocean gyres and north south dipoles in air sea flux drive anomalous thermohaline circulation both gyres and thermohaline circulation play a role in modulating sea surface temperature anomalies and hence through air sea interaction the overlying jet stream the model which can be expressed in the form of a delayed oscillator with ocean gyres and or thermohaline circulation providing the delay identifies key nondimensional parameters that control whether the ocean responds passively to nao forcing or actively couples it suggests that both thermohaline circulation and ocean gyres can play a role in coupled interactions on decadal timescales

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

dissolved iron and macronutrient distributions in the southern california current system 1 the distribution of dissolved iron in the southern california current system sccs is presented from seven research cruises between 2002 and 2006 dissolved iron concentrations were generally low in most of the study area 0 5 nm although high mixed layer and water column dissolved iron concentrations up to 8 nm were found to be associated with coastal upwelling both along the continental margin and some island platforms a significant supply of iron was probably not from a deep remineralized source but rather from the continental shelf and bottom boundary layer as identified in previous studies along the central and northern california coast with distance offshore dissolved iron decreased more rapidly relative to nitrate in a transition zone 10 250 km offshore during spring and summer resulting in relatively high ratios of nitrate dissolved iron higher nitrate dissolved iron ratios could be the result of utilization and scavenging in addition to an overall lower supply of iron relative to nitrate in the offshore transition zones the low supply of iron leads to phytoplankton iron limitation and a depletion in silicic acid relative to nitrate in the coastal upwelling and transition zones of the sccs

near surface dynamics of a separated jet in the coastal transition zone off oregon 1 three dimensional circulation in the coastal transition zone ctz off oregon is studied using a 3 km resolution model based on the regional ocean modeling system the study period is spring and summer 2002 when extensive observations were available from the northeastern pacific component of the global ocean ecosystems dynamics project our main focus is on near surface transports particularly in an area off cape blanco where an energetic coastal current is separated in the ctz comparisons with available observations velocities from midshelf moorings surface velocities from high frequency radars satellite sea surface temperature maps along track sea surface height altimetry and seasoar hydrography show that the model reproduces qualitatively correctly the flow structure and variability in the study area the near surface flow behavior during 26 july to 21 august a late summer time period of strong time variable southward winds is examined during that period the coastal jet separates from the continental shelf around cape blanco 43 n the energetic separated jet continues to flow southward in a near coastal region between 42 2 n and 43 n it subsequently turns around 42 n to flow westward offshore past 127 w relatively vigorous up and downwelling is found concentrated in the region of the separated jet frontogenesis secondary circulation nonlinear effects of the relative vorticity on the ageostrophic ekman transport and submesoscale instabilities contribute to the vertical circulation within the jet vertical velocities are found to reach 50 m d 1 in the offshore part of the jet and 100 m d 1 in the near coastal part where the jet is aligned with the wind direction

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

the california current system in relation to the northeast pacific ocean circulation abstract the california current system is described in its regional setting using two modern datasets argo provides a broadscale view of the entire eastern north pacific ocean for the period 2004 2010 and the high resolution xbt network includes transects from honolulu to san francisco 1991 2010 and to los angeles 2008 2010 together these datasets describe a california current of 500 800 km width extending along the coast from 43 n to 23 n the mean southward transport of the california current is about 5 sv off central and southern california with about 2 5 sv of northward flow on its inshore side interannual variations are 50 or more of the mean transports the salinity minimum in the core of the california current is supplied by the north pacific current and by freshwater from the northern continental shelf and modified by alongshore geostrophic and across shore ekman advection as well as eddy fluxes and air sea exchange the heat and freshwater content of the california current vary in response to the fluctuating strength of the alongshore geostrophic flow on its offshore side the california current is influenced by north pacific intermediate waters at its deepest levels and by eastern subtropical mode waters on shallower density surfaces in total the sources of the california current its alongshore advection and its strong interactions with the inshore upwelling region and the offshore gyre interior combine to make this a rich and diverse ecosystem the present work reviews previous contributions to the regional oceanography and uses the new datasets to paint a spatially and temporally more comprehensive description than was possible previously

response of the northern north atlantic and arctic oceans to a sudden change of the north atlantic oscillation 1 the influence of a switch from a long time high north atlantic oscillation nao state to an enduring nao situation is investigated with a coupled sea ice ocean model we compare the response to a sustained shift to nao conditions with that to a short lived transition to nao and back to nao forcing observed changes in sea ice and oceanic variables between high and low nao states are well captured in the model response the ocean circulation adjustment includes a fast barotropic anomaly accompanied by an enhancement of the meridional overturning and the northward heat transport at 48 n the slow response contains a substantial decrease of the northward heat transport which is caused by a reduction of the transport of subpolar and subtropical gyres after a delay of around 2 years the oceanic heat transport reacts to counteract the meridional temperature gradient imposed by the surface forcing the propagation time of baroclinic rossby waves is irrelevant for the delay between the forcing and the oceanic response rather the strength of the subpolar gyres is determined by the rapid spin up of a topographic sverdrup circulation and the subsequent slower changes through the jebar joint effect of baroclinicity and relief in an experiment where only the wind stress is changed to nao conditions the adjustment is dampened strongly by the nao thermohaline forcing the gyres decrease slower than in the nao case comparison with an experiment where only the wind stress is changed to nao conditions indicates that the thermohaline forcing is most important the heat fluxes counteract the wind stress forcing such that the meridional overturning and the northward heat transport decrease only slightly compared to the control run

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

a forcing mechanism for the poleward flow off the southern california coast it is shown that when the wind distribution along a coast is anisotropic such that its cross shore scale is smaller than its alongshore scale the coastal sea level or the upper layer anomoly a of an ocean forced by both wind and wind curl is governed by a modified nondimensionalized kelvin wave equation a t a y k0 0 y t k1 y dtl where k0 and k1 are wind stress and wind stress curl at the coast respectively y is the alongshore distance and t is the time numerical experiments from a simple reduced gravity type with idealized forcing and coastline to a three dimensional primitive equation model with a realistic coastline bottom topography of the southern california bight and the santa barbara channel and observed wind stresses were carried out to show that the observed near coast near surface poleward flow in the region is primarily forced by the equatorward weakening of the wind curl k1 y 0 in the bight beta provides natural damping by weakening and widening the current through westward propagating rossby waves and causes the current to lead the coastal pressure field by 1 2 months which improves the agreement with observations of the phasing of the modeled currents but is otherwise not required in forcing the poleward flow

formation and propagation of great salinity anomalies north atlantic arctic ocean and sea ice variability for the period 1948 2001 is studied using a global ocean general circulation model coupled to a dynamic thermodynamic sea ice model forced by daily ncep ncar reanalysis data kalnay et al 1996 variability of arctic sea ice properties is analysed in particular the formation and propagation of sea ice thickness anomalies that are communicated via fram strait into the north atlantic these export events led to the great salinity anomalies gsa of the 1970s 1980s and 1990s in the labrador sea ls all gsas were found to be remotely excited in the arctic rather than by local atmospheric forcing over the ls sea ice and fresh water exports through the canadian archipelago caa are found to be only of minor importance except for the 1990s gsa part of the anomalies are tracked to the newfoundland basin where they enter the north atlantic current the experiments indicate only a minor impact of a single gsa event on the strength of the north atlantic thermohaline circulation thc

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

modelling the generation of haida eddies abstract a numerical model forced with average annual cycles of climatological winds surface heat flux and temperature and salinity along the open boundaries is used to demonstrate that haida eddies are typically generated each winter off cape st james at the southern tip of the queen charlotte islands of western canada annual cycles of sea surface elevation measured at coastal tide gauges and topex poseidon crossover locations are reproduced with reasonable accuracy model sensitivity studies show that haida eddies are baroclinic in nature and are generated by the merging of several smaller eddies that have been formed to the west of cape st james the generation mechanism does not require the existence of instability processes and is associated with the mean advection of warmer and fresher water masses around the cape from hecate strait and from the southeast these advected water masses generate plumes of buoyant flow which intensify and sustain small patches of anticyclonic circulation immediately to the northwest of the cape when the flow is stronger several of these smaller eddies can merge to generate a larger eddy the haida eddy similar to observations a typical generation shedding cycle for larger haida eddies in the model is 3 4 months consistent with previous in situ water property measurements these experiments show that the eddies are generally comprised of mixed layer water from hecate strait queen charlotte sound and the continental shelves off northern vancouver island their vertical extent during the mature stage is roughly 1000 m

a possible mechanism for the strong weakening of the north atlantic subpolar gyre in the mid 1990s 1 the extent and strength of the north atlantic subpolar gyre spg changed rapidly in the mid 1990s going from large and strong in 1995 to substantially weakened in the following years the abrupt change in the intensity of the spg is commonly linked to the reversal of the north atlantic oscillation nao index changing from strong positive to negative values in the winter 1995 96 in this study we investigate the impact of the initial spg state on the subsequent behavior of the spg by means of an ocean general circulation model driven by ncep ncar reanalysis fields our sensitivity integrations suggest that the weakening of the spg cannot be explained by the change in the atmospheric forcing alone rather for the time period around 1995 the spg was about to weaken irrespective of the actual atmospheric forcing due to the ocean state governed by the persistently strong positive nao during the preceding seven years 1989 1995 our analysis indicates that it was this preconditioning of the ocean in combination with the sudden drop in the nao in 1995 96 that lead to the strong and rapid weakening of the spg in the second half of the 1990s this hypothesis explains the diverging evolution of the strength of the spg and the atmospheric forcing winter nao after 1995 as has been suggested recently

impact of greenland orography on the atlantic meridional overturning circulation we show that the absence of the greenland ice sheet would have important consequences on the north atlantic ocean circulation even without taking into account the effect of the freshwater input to the ocean from ice melting these effects are investigated in a 600year long coupled ocean atmosphere simulation with the high resolution global climate model ec earth 3 0 1 once a new equilibrium is established a cooling of eurasia and of the north atlantic and a poleward shift of the subtropical jet are observed these hemispheric changes are ascribed to a weakening of the atlantic meridional overturning circulation amoc by about 12 we attribute this slowdown to a reduction in salinity of the arctic basin and to the related change of the mass and salt transport through the fram strait a consequence of the new surface wind pattern over the lower orography this idealized experiment illustrates the sensitivity of the amoc to local surface 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

particulate δ15n in laminated marine sediments as a proxy for mixing between the california undercurrent and the california current a proof of concept the measurements of particulate 15n in coastal marine laminated sediments provide a high resolution proxy for fluctuations in the intensity of denitrification in the water column in the eastern tropical north pacific oxygen minimum zone this denitrification signal is transported northward by the california undercurrent thus serving as a tracer of ocean circulation this is verified through comparisons between salinity in the thermocline off southern california santa monica basin and the difference between 15nsed within age equivalent sediments from a southern pescadero slope and northern santa monica basin site trends in this parameter 15nsed relate to pacific decadal oscillation pdo phase changes between 1900 and 1990 we hypothesize that the decline in 15nsed during warm pdo phases is due to a strengthening of the california undercurrent transporting 15n enriched nitrate from the eastern tropical north pacific northward the deviation from this trend after 1990 suggests recent changes in circulation and or california current water nutrient biogeochemistry

forcing of low frequency ocean variability in the northeast pacific abstract an ocean model is used to examine and compare the forcing mechanisms and underlying ocean dynamics of two dominant modes of ocean variability in the northeast pacific nep the first mode is identified with the pacific decadal oscillation pdo and accounts for the most variance in model sea surface temperatures ssts and sea surface heights sshs it is characterized by a monopole structure with a strong coherent signature along the coast the second mode of variability is termed the north pacific gyre oscillation npgo this mode accounts for the most variance in sea surface salinities ssss in the model and in long term observations while the npgo is related to the second eof of the north pacific sst anomalies the victoria mode it is defined here in terms of ssh anomalies the npgo is characterized by a pronounced dipole structure corresponding to variations in the strengths of the eastern and central branches of the subpolar and subtropical gyres in the north pacific it is found tha

multicentennial variability of the sea surface temperature gradient across the subpolar north atlantic over the last 2 8 kyr a 2800 year long august sea surface temperature asst record based on fossil diatom assemblages is generated from a marine sediment core from the northern subpolar north atlantic the record is compared with the asst record from the norwegian sea to explore the variability of the asst gradient between these areas during the late holocene the asst records demonstrate the opposite climate tendencies towards a persistent warming in the core site in the subpolar north atlantic and cooling in the norwegian sea at the multicentennial scale of asst variability of 600 900 years the records are nearly in anti phase with warmer colder periods in the subpolar north atlantic corresponding to the colder warmer periods in the norwegian sea at the shorter time scale of 200 450 years the records display a phase locked behaviour with a tendency for the positive asst anomalies in the norwegian sea to lead by 30 years the negative asst anomalies in the subpolar north atlantic this apparent asst seesaw might have an effect on two major anomalies of the european climate of the past millennium medieval warm period mwp and the little ice age lia during the mwp warming of the sea surface in the norwegian sea occurred in parallel with cooling in the northern subpolar north atlantic whereas the opposite pattern emerged during the lia the results suggest that the observed asst seesaw between the subpolar north atlantic and the norwegian sea could be a surface expression of the variability of the eastern and western branches of the atlantic meridional circulation amoc with a possible amplification through atmospheric feedback

heat budget in the north atlantic subpolar gyre impacts of atmospheric weather regimes on the 1995 warming event abstract in the mid 1990s the north atlantic subpolar gyre has shown a dramatic warming event that has been thoroughly investigated from observations and numerical simulations some studies suggest that it was due to an interannual wind driven weakening and shrinking of the gyre that facilitated the penetration of warm atlantic water the weakening of the gyre being attributed to changes in the north atlantic oscillation nao and in the east atlantic pattern which are the two dominant modes of atmospheric variability in the north atlantic however other studies suggest that the warming event was due to a decadal buoyancy driven strengthening of the meridional overturning circulation and subsequent intensification of the poleward heat transport in response to the positive nao conditions of 1988 1995 to reconcile this discrepancy the heat budget in the north atlantic subpolar gyre is reconstructed from four ocean hindcast simulations sharing the same modelling platform but using different settings the novelty of this work is the decomposition of the subpolar gyre into a western and an eastern subregion which is motivated by water mass distribution around reykjanes ridge and by the fact that deep convection only occurs in the western subpolar gyre in the western subpolar gyre the 1995 warming event is the decadal baroclinic ocean response to positive nao conditions from 1988 to 1995 the latter induced increased surface heat loss in the labrador sea that intensified deep convection hence strengthened the meridional overturning circulation and the associated poleward heat transport in the eastern subregion a concomittant warming is induced by an interannual barotropic adjustment of the gyre circulation to an abrupt switch from positive nao conditions in winter 1995 to negative nao conditions in winter 1996 indeed the gyre response to negative nao conditions is a cyclonic intergyre gyre that increases northward volume and heat transports at the southeastern limit of the subpolar gyre therefore the discrepancies found in the literature about the 1995 warming event of the north atlantic subpolar gyre are reconciled in the present work which suggests that the atmospheric drivers the mechanisms at stake and the associated timescales are different to the east and to the west of reykjanes ridge

effects of the 2013 2016 northeast pacific warm anomaly on physical and biogeochemical variables off northwestern baja california derived from a numerical npzd ocean model abstract interannual climatic anomalies have important physical and biological consequences for the southern part of the california current system ccs two examples of these anomalies are the blob and el nino phenomena the blob was an anomalously warm water mass that formed in the gulf of alaska during fall 2013 and then affected most of the eastern north pacific including the waters off baja california mexico in this work we use a biogeochemical nutrient phytoplankton zooplankton detritus npzd model coupled to a three dimensional hydrodynamic model which allowed the simulation of some of the physical and biological consequences of the anomalous warm 2013 2016 period the blob was observed in 2014 and el nino by mid 2015 a model observation comparison showed that in some cases the model solution deviates substantially from the observed vertical thermal structure but the temporal evolution of the spatially averaged variables diagnosed by the model shows good agreement with the observations except for the period from late 2015 to mid 2016 when the sea surface temperature sst is underestimated and the model failed to reproduce the correct sign of the surface chlorophyll a schl anomalies an eof analysis of the 15 year 2003 2017 record of monthly mean modeled variables allowed the identification of two main contributions to the model variability one mode mostly correlated with the multivariate el nino southern oscillation enso index mei explaining 50 of the variance of temperature t and dissolved nitrogen n and 10 of the variance of chlorophyll a chl and another mode mostly correlated with the coastal upwelling index cui anomaly explaining 50 70 of variance of chl and only 10 20 of variance of t and n in the 2013 2016 period an el nino signal diagnosed by the mei induced a remarkable warming off northwestern baja california as a consequence the thermocline and the nutricline deepened during this period and caused a deepening and weakening of the subsurface chl maximum scm around the southern region of the study area near punta baja these effects were more intense at the surface over the shelf but in the northern region south of southern california bight the effects were more intense subsurface seaward of the shelf break this enso modulated subsurface warming tends to weaken the southern california eddy during el nino events and intensify it during la nina episodes during the 2013 2015 period there was also a weakening of the upwelling favorable winds which caused a prolonged negative anomaly of the wind forcing reducing the nutrient flux and causing negative chl anomalies finally in addition to the partial relation between the enso and the warming observed along the baja california coast the anomalies were observed in this area 4 6 months before the onset of the el nino conditions mei 0 5 period when the blob was affecting the southern part of the ccs

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

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

high resolution paleoclimatology of the santa barbara basin during the medieval climate anomaly and early little ice age based on diatom and silicoflagellate assemblages in kasten core spr0901 02kc abstract diatom and silicoflagellate assemblages documented in a high resolution time series spanning 800 to 1600 ad in varved sediment recovered in kasten core spr0901 02kc 34 16 845 n 120 02 332 w water depth 588 m from the santa barbara basin sbb reveal that sbb surface water conditions during the medieval climate anomaly mca and the early part of the little ice age lia were not extreme by modern standards mostly falling within one standard deviation of mean conditions during the pre anthropogenic interval of 1748 1900 no clear differences between the character of mca and the early lia conditions are apparent during intervals of extreme droughts identified by terrigenous proxy scanning xrf analyses diatom and silicoflagellate proxies for coastal upwelling typically exceed one standard deviation above mean values for 1748 1900 supporting the hypothesis that droughts in southern california are associated with cooler or la nina like sea surface temperatures ssts increased percentages of diatoms transported downslope generally coincide with intervals of increased siliciclastic flux to the sbb identified by scanning xrf analyses diatom assemblages suggest only two intervals of the mca at 897 to 922 and 1151 1167 when proxy ssts exceeded one standard deviation above mean values for 1748 to 1900 conversely silicoflagellates imply extreme warm water events only at 830 to 860 early mca and 1360 to 1370 early lia that are not supported by the diatom data silicoflagellates appear to be more suitable for characterizing average climate during the 5 to 11 year long sample intervals studied in the spr0901 02kc core than diatoms probably because diatom relative abundances may be dominated by seasonal blooms of a particular year

influence of the atlantic subpolar gyre on the thermohaline circulation during the past decade record high salinities have been observed in the atlantic inflow to the nordic seas and the arctic ocean which feeds the north atlantic thermohaline circulation thc this may counteract the observed long term increase in freshwater supply to the area and tend to stabilize the north atlantic thc here we show that the salinity of the atlantic inflow is tightly linked to the dynamics of the north atlantic subpolar gyre circulation therefore when assessing the future of the north atlantic thc it is essential that the dynamics of the subpolar gyre and its influence on the salinity are taken into account

development of the california current during the past 12 000 yr based on diatoms and silicoflagellates detailed diatom and silicoflagellates records in three cores from the offshore region of southern oregon to central california reveal the evolution of the northern part of the california current during the past 12 000 yr the early holocene prior to 9 ka was characterizedbyrelativelywarmseasurfacetemperatures sst owingtoenhancednortherlyflowofthesubtropicalwaterscomparable tothemoderndavidsoncurrent progressivestrengtheningof thenorthpacifichighleadtointensificationofthesouthwardflowofthe california current at 8 ka resulting in increased coastal upwelling and relatively cooler sst which persisted until 5 ka reduced southward flow of the california current between 4 8 ka and 3 6 ka may have been responsible for a period of decreased upwelling modern seasonal oceanographic cycles as evidenced by increased spring early summer coastal upwelling and warming of early fall sst evolved between 3 5 and 3 2 ka widespread occurrence of paleoceanographic and paleoclimatic change between 3 5 3 0 ka along the eastern margins of the north pacific was likely a response to increasing enso variability in the tropical pacific published by elsevier b v

ocean gyre circulation changes associated with the north atlantic oscillation abstract observational evidence is presented for interannual to interdecadal variability in the intensity of the north atlantic gyre circulation related to the atmospheric north atlantic oscillation nao patterns a two point baroclinic pressure difference between the subtropical and subpolar gyre centers an oceanic analogue to the much used sea level pressure slp based atmospheric nao indices is constructed from time series of potential energy anomaly pea derived from hydrographic measurements in the labrador basin and at station s near bermuda representing the upper 2000 db eastward baroclinic mass transport between the two centers the transport index indicates a gulf stream and north atlantic current that gradually weakened during the low nao period of the 1960s and then intensified in the subsequent 25 years of persistently high nao to a record peak in the 1990s the peak to peak amplitude difference was 15 20 megatons per second mt s 1 with a 43 yr mean of about 60 mt s 1 a change of 25 33

gulf stream variability in five oceanic general circulation models five non eddy resolving oceanic general circulation models driven by atmospheric fluxes derived from the ncep reanalysis are used to investigate the link between the gulf stream gs variability the atmospheric circulation and the atlantic meridional overturning circulation amoc despite the limited model resolution the temperature at the 200 m depth along the mean gs axis behaves similarly in most models to that observed and it is also well correlated with the north atlantic oscillation nao indicating that a northward southward gs shift lags a positive negative nao phase by 0 2 yr the northward shift is accompanied by an increase in the gs transport and conversely the southward shift with a decrease in the gs transport two dominant time scales appear in the response of the gs transport to the nao forcing a fast time scale less than 1 month for the barotropic component and a slower one about 2 yr for the baroclinic component in addition the two components are weakly coupled the gs response seems broadly consistent with a linear adjustment to the changes in the wind stress curl and evidence for baroclinic rossby wave propagation is found in the southern part of the subtropical gyre however the gs shifts are also affected by basin scale changes in the oceanic conditions and they are well correlated in most models with the changes in the amoc a larger amoc is found when the gs is stronger and displaced northward and a higher correlation is found when the observed changes of the gs position are used in the comparison the relation between the gs and the amoc could be explained by the inherent coupling between the thermohaline and the wind driven circulation or by the nao variability driving them on similar time scales in the models

north atlantic interdecadal variability oceanic response to the north atlantic oscillation 1865 1997 abstract in contrast to the atmosphere knowledge about interdecadal variability of the north atlantic circulation is relatively restricted it is the objective of this study to contribute to understanding how the north atlantic circulation responds to a forcing by the north atlantic oscillation nao on interdecadal timescales for this purpose the authors analyze observed atmospheric and sea surface temperature sst data along with the response of an ocean general circulation model to a realistic monthly surface flux forcing that is solely associated with the nao for the period 1865 1997 in agreement with previous studies it is shown that the relationship between the local forcing by the nao and observed sst anomalies on interdecadal timescales points toward the importance of oceanic dynamics in generating sst anomalies a comparison between observed and modeled sst anomalies reveals that the model results can be used to assess interdecadal variability of the north atlantic circulation the observed

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

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

modeling the generation of the juan de fuca eddy 1 numerical simulations with the regional ocean modeling system are used to study the generation of the cyclonic juan de fuca eddy located off the entrance of juan de fuca strait in summer an initial simulation forced with average summer upwelling favorable winds tides and buoyancy boundary conditions that maintain an estuarine flow in juan de fuca strait produces an eddy and currents that are in reasonable agreement with observations sensitivity studies are then carried out to explore the importance of these three forcing mechanisms the relative proximity of dense water in the bottom estuarine flow entering the strait is shown to lead to enhanced upwelling off cape flattery when either wind or tidal forcing is applied this upwelled water then mixes with the estuarine outflow and is advected offshore the tidal upwelling arises through three mechanisms m2 vertical excursions of nearly 20 m at 50 m depth west of the cape on the flood tide strong tidally rectified vertical velocities west of the cape and the spilling of denser bottom water over the western wall of juan de fuca canyon on the ebb tide the cyclonic eddy is a consequence of geostrophic adjustment to the doming isopycnals that arise from the upwelling these model simulations refute an earlier hypothesis that the eddy is generated when california undercurrent water is drawn up tully canyon and onto the vancouver island shelf suggesting instead that these canyon dynamics play only a secondary role in maintaining the eddy once it is formed

three dimensional oceanic eddy analysis in the southern california bight from a numerical product with eight islands complex coastlines and bottom topography strong wind curls and frequent upwelling fronts the southern california bight scb is an area with strong eddy activity by applying an automated eddy detection scheme to a 12 year high resolution numerical product of the oceanic circulation in the scb a three dimensional eddy data set is developed it includes information for each eddy s location polarity intensity size boundary and moving path at nine vertical levels through a series of statistical analyses applied to the eddy data set three dimensional statistical characteristics of mesoscale and submeoscale eddy variations in the scb are elucidated these shed light on how eddies are generated evolve and terminate a significant percentage of eddies is found to be generated around islands and headlands along the coastline which indicates that islands in the scb play a vital role in eddy generation three types of eddies based on shape are identified from the numerical product bowl lens and cone a dynamic analysis shows that some submesoscale eddies with finite local rossby numbers tend to be ageostrophic balanced while mesoscale eddies are in geostrophic balance the present research results are useful for the interpretation of data sets obtained during the interdisciplinary santa barbara channel radiance in a dynamic ocean radyo field experiment conducted on september 3 25 2008