a cool anomaly off northern california an investigation using ir imagery and in situ data satellite ir imagery and in situ hydrographie data are used to understand better the mesoscale variability of the california current system and to explore the relation of its surface and subsurface thermal structures in august 1982 one of the cool filaments commonly seen in satellite ir images during summer off northern california was sampled hydrographically during an optoma ocean prediction through observation modeling and analysis cruise based on the cool anomaly seen in a series of ir images and the in situ hydrographie data and based on geostrophic calculations a jet entrained upwelled coastal water and advected it rapidly through the warmer waters offshore providing an important cross shore transfer process the anomaly was about 50 km wide and extended vertically to about 40 m the temperature patterns at the surface were well correlated with those to about 30 m below 50 m the surface temperature was better correlated with horizontal temperature gradients i e the thermal wind consistent with strong horizontal advection by the geostrophic jet the cool anomaly was also relatively dense based on investigation of the t s properties the coastal water had been diluted through mixing with columbia river plume water on the northern edge of the anomaly near the temperature front in the shoreward sampled portion of the anomaly and just south of the anomaly interleaving occurred there was also a surface saline anomaly embedded in the cool anomaly near the temperature front the location of the temperature front in the in situ data and in the ir imagery corresponded well the temperature front was tracked in a series of ir images over 2 weeks the reorientation of the seaward extremity of the anomaly from westward to northwestward and the southwestward displacement of its southern boundary at speeds of 2 to 5 km d were consistent with the propagation of mesoscale features evident in successive quasi synoptic surface dynamic topography maps the southwestward displacement was probably also related to surface ekman transport

mesoscale features along the first oyashio intrusion satellite and hydrographic observations obtained during may 1981 are used to examine the sea surface and subsurface temperature structures within a portion of the tohoku area 38 43 n extending east of japan to 149 e longitude these data delineate the oyashio front and the evolution of mesoscale features dominating the surface layer circulation east of northern honshu and hokkaido a perturbation on the first oyashio intrusion generated eddies adjacent to the oyashio front and contributed to a jetlike feature with associated paired vortices that intruded into what has been defined as the perturbed area 39 42 n southeastward from the vicinity of the tsugara strait noaa6 satellite advanced very high resolution radiometer infrared images and sea surface temperature distributions identified specific eddies and fronts that also appeared as banded warm and cold regions within xbt expendable bathythermograph sections the satellite data helped define the lateral extent of the features while the sections provided estimates of their vertical extent a new procedure for the determination of satellite sea surface temperatures was used to produce a composite temperature distribution over a portion of the tohoku area the satellite derived temperature estimates exhibited a 0 8 c rms scatter about a 0 6 c warm bias relative to the xbt data this map displays the intense mesoscale sea surface temperature variability in the region along the oyashio front and within the subarctic regime

transient pulse test and morphological analysis of single rock fractures abstract transient pulse tests were performed on single rock fractures at different confining pressures a new data analysis method based on polynomial fitting was introduced to investigate the relationship between flow velocity and hydraulic gradient 3d laser scanning was used to quantify the morphological changes of the fracture surface after the transient pulse test or under the hydro mechanical coupling effect the results show that the flow velocity versus hydraulic gradient data gradient shows a nonlinear relationship at very low hydraulic possibly due to strong solid water interaction but becomes approximately linear after the hydraulic gradient is high enough the permeability of a single fracture is sensitive to the confining pressure as the confining pressure increases the permeability first remarkably decreases when the confining pressure is lower than a certain value and then decreases at a much lower speed when the confining pressure is higher than that value both mechanical and hydraulic apertures decrease at a decreasing rate with the increase in confining pressure the effect of fracture roughness on the permeability is related to the magnitude of the confining pressure rougher fractures have lower permeability at low confining pressures but the opposite can be true when the confining pressure is high enough roughness is no longer critical to permeability when the confining pressure is over a certain value

the tectonostratigraphic history of the proterozoic northern lawn hill platform australia an integrated intracontinental basin analysis abstract the northern lawn hill platform nlhp comprises an area of approximately 16 000 km2 in north central australia thick packages of proterozoic strata outcrop in the region although large areas are also covered by younger strata the packages contain basin sediments and igneous rocks that span 400 m y we present a regional synthesis of approximately 150 m y of the tectonostratigraphic history of the area which hosts several world class base metals deposits the interpretation is based primarily on a sequence stratigraphic and structural interpretation of seismic data a common approach in the petroleum resource sector but rare in analyses of mineral resources models of subsurface geology and a basement template are provided using observed geopotential data that are iteratively calibrated with other data geochronological palaeomagnetic geochemical and sequence stratigraphic investigations on outcrop and drill core also are integrated into the history the seismic data allow separated outcrop belts to be confidently correlated for the first time geochronological data control the basin history delineated by this interpretation palaeomagnetic data allow the results presented here to be extrapolated regionally and globally although considered to be deposited on entirely intracontinental lithosphere the basin phases record significant fluctuations in the volume and geometry of accommodation space for sedimentation multiple pulses of deformation are recorded by changing depositional geometries we propose a history of re activation of a basement template and speculate on geodynamical mechanisms for accommodation space fluctuations and geometric variability the detailed understanding of the basin evolution of the nlhp gained by integrated basin analysis provides a powerful tool for predictive fluid flow models as an aid to resource exploration it should also provide a useful analogy in understanding tectonic processes and basin evolution of other similar aged intracontinental basins

moored observations of the current and temperature structure over the continental slope off central california 2 the energetics of the flow off point sur the data from two current meter moorings off point sur california were analyzed to examine the energy transfers over the continental slope in the california current system ccs the method used was to calculate terms in the heat equation at intermediate depths between instruments using the thermal wind relation to estimate the horizontal temperature gradients from the vertical shear time series of u v and t were collected for 17 months may 1989 to october 1990 at site p2 on the 800 m isobath and for 12 months may 1990 to may 1991 at site p3 25 km farther offshore on the 1800 m isobath instrument depths were 100 350 and 500 m at both moorings plus 1000 m at site p3 mean values of the energy conversion terms were computed at sites p2 and p3 at 225 m depth and at site p2 at 425 m depth the local change of eddy potential energy epe was approximately balanced epe t 0 for each case but the dynamics were quite different at p2 225 the sources of epe were advection by the mean flow and baroclinic instability which converted mean potential energy mpe to epe the losses came from eddy advection out of the region and the vertical eddy heat flux vehf which converted epe to eddy kinetic energy eke at p2 425 baroclinic instability provided the major source of epe this plus a small positive contribution from the vehf was balanced by advection of epe out of the region by both the mean flow and the eddies at p3 225 mean advection and baroclinic instability were negligible and the downward eddy heat flux vehf was balanced by advection of heat out of the region by the eddies time series of terms in the epe equation were used to examine high energy transfer events at both moorings events at p2 involved both horizontal and vertical processes and had longer timescales several days to weeks than those at p3 which had much shorter timescales 2 5 days and were dominated by vertical processes compared to the gulf stream the mean baroclinic instability at p2 both depths was smaller by at least a factor of 10 a term by term comparison between the mean values off point sur and the kuroshio extension showed different processes with the eddies gaining strength at the expense of the mean flow off point sur and the opposite occurring in the kuroshio extension

physical description of an upwelling filament west of cape st vincent in late october 2004 1 the present paper describes the physical characteristics of an upwelling filament off cape st vincent southern iberia in october 2004 based on remote sensing hydrographic adcp and wind data it was associated with a meandering jet similar to eastern pacific or canary filaments though its dynamical features were weaker as a result of the surface trapped top 100 m and weak horizontal density gradients the filament transported 0 9 sv of coastal water offshore of which 8 was due to ekman transport it formed following the destabilization of an alongshore equatorward upwelling jet close to the cape the filament was structurally asymmetric with anticyclonic geostrophic vorticity to the north and more strongly cyclonic to the south as a result of the meanders and existing eddies the filament comprised a sequence of cold submesoscale 30 km diameter cyclones vertical velocities of 15 m d 1 were associated with meanders of the jet the surface and subsurface circulation was coupled at middepths 90 150 m anticyclonic recirculation of northern water seemed associated with a separated older upwelling jet mediterranean water mw was present below 350 dbar as a topographically steered undercurrent and a meddy cyclone dipole these undercurrents contributed to the formation of the october filament through baroclinic instability associated with the enhanced vertical shear

wind driven circulation in a shelf valley part i mechanism of the asymmetrical response to along shelf winds in opposite directions abstractmotivated by observations in hudson shelf valley showing stronger onshore than offshore flows this study investigates wind driven flows in idealized shallow shelf valleys this first part of a two part sequence focuses on the mechanism of the asymmetrical flow response in a valley to along shelf winds of opposite directions model simulations show that i when the wind is in the opposite direction to coastal trapped wave ctw phase propagation the shelf flow turns onshore in the valley and generates strong up valley transport and a standing meander on the upstream side in the sense of ctw phase propagation of the valley and ii when the wind is in the same direction as ctw phase propagation the flow forms a symmetric onshore detour pattern over the valley with negligible down valley transport comparison of the modeled upstream meanders in the first scenario with ctw characteristics confirms that the up valley flow results from ctws being arrested by the wind driven shelf flow establishin

ocean climate of the south east atlantic observed from satellite data and wind models the near coastal south east atlantic ocean off africa is a unique and highly dynamic environment comprising the cool benguela current warm angola current and warm agulhas current strong coastal upwelling and the congo river strongly influence primary production much of the present knowledge of the south east atlantic has been derived from ship borne measurements and in situ sensors which cannot generally provide extensive spatial and temporal coverage similarly previous satellite studies of the region have often focused on small spatial areas and limited time periods this paper provides an improved understanding of seasonal and interannual variability in ocean dynamics along the south east atlantic coast of africa using time series of satellite and model derived data products eighteen years of satellite sea surface temperature data are complimented by 7 years of sea level data three years of chlorophyll a data illustrate the seasonal biological response but the time series is not of sufficient length for investigating interannual variability in chlorophyll biomass modelled wind fields are used to describe atmospheric forcing of the surface ocean this is the first synoptic scale description of the south east atlantic from a suite of large spatial coverage long time series products previous studies of seasonal and interannual variability in the region are reviewed and used to interpret key oceanographic features and processes identified in the satellite data key findings of this study are 1 descriptions of seasonal and interannual variability from these data show climate forcing of the south east atlantic coast of africa from both the northern and southern boundaries bimodal seasonal signals of equatorial origin propagate poleward along the angolan coast while the trade winds and events in the agulhas region dominate the agulhas bank and southern benguela the northern benguela is a mixed regime under the influence of forcing from both directions 2 the benguela nino years of 1984 and 1995 are clearly observed in sea surface temperature and sea level anomalies and correspond to anomalously weak southerly winds at the equator these conditions were also observed in 1999 suggesting this too may have been a benguela nino year 3 consideration of putative nino type events in the equatorial atlantic from this and other studies suggests that the frequency of these events is much higher than previously estimated and may be similar to the frequency of el nino southern oscillation enso events in the pacific ocean furthermore years of anomalously strong southerly winds at the equator occur during pacific enso years c 2003 elsevier ltd all rights reserved

an offshore eddy in the california current system part ii surface manifestation abstract ship and satellite observations taken over the last thirty years show that mesoscale patterns of sea surface temperature sst in the california current system are consistently found throughout the year and usually occur in approximately the same geographical locations typically these patterns are more pronounced in fall winter than in spring summer the temporal and spatial characteristics of these persistent feature were examined with satellite infrared ir measurements during winter 1980 1981 in january 1981 a ship surveyed the vertical structure of several physical chemical and biological parameters beneath one of these sst features centered near 32 n 124 w the surface ir pattern had a length scale of 200 km and a time scale of about 100 days it disintegrated following the first two storms of the winter season motion studies of the pattern in late october indicated an anticyclonic rotation with maximum velocities of 50 cm s 1 at 50 km from the axis of rotation as a unit the pattern advected southward with an average speed of 1 cm s 1 thermal fronts determined from the satellite imagery were strongest 0 4 c km 1 along the rim of the pattern and were advected anticyclonically with the pattern their length scales were 20 30 km in the along front direction and less than 10 km wide the hydrographic data revealed a three layer structure beneath the surface pattern a 75 m deep surface layer a cold core region from 75 to 200 m depth and a warm core eddy extending from 250 to 1450 m the anticyclonic motion of the surface layer was caused by a geostrophic adjustment to the surface dynamic height anomaly produced by the subsurface warm core eddy the ir pattern observed from space reflects the horizontal structure of the surface layer and is consistent with a theoretical model of a mean horizontal sst gradient perturbed by a subsurface density anomaly ship of opportunity sst observations collected by the national marine fisheries are shown to resolve mesoscale patterns for december 1980 the sst pattern near 32 n 124 w represented a 2 c warm anomaly compared with the 20 year mean monthly sst pattern

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

the subtropical front satellite observations during fronts 80 satellite derived sea surface temperature in situ hydrography data and satellite tracked drifter data collected during winter 1979 1980 as part of the fronts 80 experiment are used to describe the spatial structure of the north pacific subtropical front northeast of hawaii the satellite observations reveal a deformation scale meander 85 km 32 km in association with the front having an evolution time scale of 60 days the satellite measurements of the change in sea surface temperature across the front are typically 1 c within a distance of 10 km the correlation coefficients between the satellite data and the in situ hydrographic data were computed and found to be significantly nonzero above 800 m the high correlation at deep levels indicates that the satellite was viewing a feature with sizable vertical extent not just a surface phenomenon additionally the hydrographic data and drifter trajectories were combined with the satellite derived sea surface temperature data together they demonstrate that the feature observed by the satellite was nearly stationary during the experiment period in addition they also indicate that the flow along the front was nearly in geostrophic balance

demographics of mesoscale eddies in the california current 1 demographics and variability of persistent mesoscale eddies in the california current have been investigated in a systematic manner using a decade 1995 2004 of merged satellite altimeter data the number of persistent eddies formed each year varied almost 3 fold 4 fold for cyclones anticyclones and was strongly modulated by the 1997 1998 el nino event over the 10 year period cyclone formation was maximum in both winter and summer while maximum anticyclone formation occurred only in winter the majority of long lived eddies 70 day lifespan originated seaward of the 1000 m isobath and with the exception of 2 anticyclones did not form between 45 and 50 n maximum westward propagation of long lived eddies was almost 800 km with similar mean propagation speeds for cyclones and anticyclones

genetic tracers of zooplankton transport in coastal filaments off northern california genetic markers were used to describe the transport of the calanoid copepod metridia pacifica in a cool filament off point arena california in july 1986 the markers used were genetic variants of enzymes allozymes individual copepods were assayed for allozymic variability at nine enzyme encoding genes loci by polyacrylamide gel electrophoresis zooplankton samples were collected in a 300 km by 170 km domain maps of surface dynamic height in this domain showed an offshore jet with strong cross shore transport in the presence of a cool anomaly comprising multiple fronts and filaments the genetic data sorted the samples into two heterogeneous groups according to maximum likelihood analysis one comprising samples near the coast and at the head of the filament and the other comprising offshore samples the groups themselves were heterogeneous revealing smaller scale patterns of transport and mixing the genetic spatial structure of the calanoid copepod metridia pacifica collected in the flow field was used to infer patterns of transport in the filament flow field patterns of transport inferred from genetic differences between zooplankton samples were compared with expected particle transport based on models which consider physical geostrophic advection ekman drift and mixing transport plus vertical migration behavior according to both the flow models and the genetic data transport of zooplankton occurred primarily along paths of geostrophic flow there was little cross jet exchange and almost no exchange between samples in the filament and samples in a cyclonic eddy to the south of the jet the genetic data further indicated that copepod populations at the coastal source of the filament were genetically heterogeneous advection in the filament thus resulted in the juxtaposition of genetically distinct zooplankton populations in the jet axis the genetic structure of zooplankton in the filament resulted from advection of previous distant populations not because of the time scales of the processes from changes in the genetic character of samples during transport the presence of multiple fronts and filaments within the cool anomaly prevented homogenization of the plankton assemblages during transport thus samples collected less than 10 km apart across the jet axis were genetically different these findings indicated that plankton populations in complex flow fields may show patchiness in biological biochemical and or genetic character at small time space scales

the missing dimension in magsat and pogo anomaly studies the development of a comprehensive model of the near earth magnetic field in terms of sources in the core ionosphere and magnetosphere has allowed the isolation of heretofore unknown north south trending anomalies of lithospheric origin previously along track filtering of satellite magnetic field data had been necessary in order to remove unmodeled magnetospheric and ionospheric magnetic fields these fields change between adjacent passes by tens of nanoteslas and have wavelengths which overlap the crustal spectrum an example from australia illustrates the additional information that can be extracted from the magsat data set when this missing dimension is included a north south trending low covers most of eastern australia in agreement with the aeromagnetic map of australia this feature is seen in both the dawn and dusk subsets collected from magsat the center of this low is roughly coincident with the eromanga basin but extends for almost 2000 km in a n s direction the low corresponds to a region of almost featureless magnetic field on the aeromagnetic map it is also consistent with an elevated geotherm previously proposed from studies of xenoliths in southeastern australia filtering the new map in a north south direction reproduces the previous best estimate of the australian satellite anomaly field we expect that this comprehensive model will provide a new window into the magnetic field of the earth s lithosphere the model continues to be enhanced

a laboratory model of thermocline depth and exchange fluxes across circumpolar fronts a laboratory experiment has been constructed to investigate the possibility that the equilibrium depth of a circumpolar front is set by a balance between the rate at which potential energy is created by mechanical and buoyancy forcing and the rate at which it is released by eddies in a rotating cylindrical tank the combined action of mechanical and buoyancy forcing builds a stratification creating a large scale front at equilibrium the depth of penetration and strength of the current are then determined by the balance between eddy transport and sources and sinks associated with imposed patterns of ekman pumping and buoyancy fluxes it is found that the depth of penetration and transport of the front scale like l and wel2 respectively where fw g9 e we is the ekman pumping g9 is the reduced gravity across the front f is the coriolis parameter and l is the width scale of the front last the implications of this study for understanding those processes that set the stratification and transport of the antarctic circumpolar current acc are discussed if the laboratory results scale up to the acc they suggest a maximum thermocline depth of approximately h 5 2 km a zonal current velocity of 4 6 cm s 21 and a transport t 5 150 sv 1 sv 106 m3 s 21 not dissimilar to what is observed

the shear convergence and thermohaline structure of a front abstract with the objective of measuring convergence directly to confirm previous observations of frontal subduction a seaward upwelling jet off central california was studied using satellite infrared images hydrographic sections ship drift and clusters of surface drifters the cyclonic front of the jet was sharper than 1 km resulting in a shear several times larger than f a cross frontal convergence of 7 cm s 1 over the width of the front equivalent to 0 8f was visible as a 20 m wide accumulation of debris the sharpness of the front lasted at least for a day away from the cyclonic front the divergence of the flow was small and the shear was less than 0 6f thermohaline layers originating at the front were interleaving along isopycnals suggesting water subduction it is proposed that the asymetry between anticyclonic and cyclonic sides of the jet and the strong convergence at the cyclonicfront resulted from a frictionally driven ageostrophic secondary circulation superimposed on the geostr

the role of nearshore slope on cross shore surface transport during a coastal upwelling event in gulf of finland baltic sea abstract the wind induced coastal upwelling process often contains a mid phase that involves coherent long living cross shore surface jets of cooler water these jets extend to 40 45 km from the coast and tend to start from particular coastal locations we develop a simple method for evaluating the depth in the water column from where the upwelled water originates we also test the hypothesis that the development of cross shore surface jets may be triggered by some permanent characteristics such as the bathymetry or the slope of the nearshore seabed the analysis is performed for a strong and well documented upwelling in the gulf of finland the baltic sea using high resolution bathymetry data satellite derived sea surface temperature surface currents measured by in situ drifters and properties of water masses in two sampling locations the results indicate that the cross shore jets originate exclusively from the shore sections with much steeper slopes 0 0075 than in the rest of the study area the cooler water most likely origins from intermediate water masses at depths between 15 and 30 m the resulting identification of the source depth of the upwelled water and its spatial location assists in understanding the flux of nutrients during upwelling events and their link to the onset of cyanobacteria blooms

reconstruction and geostatistical analysis of multiscale fracture apertures in a large block of welded tuff reconstruction of fracture apertures in a block of welded tuff has revealed two scales of autocorrelation one on the order of millimeters the other on the order of tens of centimeters the spatial and frequency distributions of apertures changed drastically as a result of minor nondestructive shear

recurrent patterns in surface thermal fronts associated with cold filaments along the west coast of north america abstract previous studies indicate that cold filaments off northern california have sharp southern s type and diffuse northern d type thermal boundaries in this study 44 avhrr satellite images taken from three coastal regions in the california current system northern central and baja california over a period of 10 years were used to examine the regional variation in surface frontal structure associated with cold filaments the images were specifically chose from months where past mean wind conditions indicated upwelling occurred because cold filaments appear to be more abundant during the upwelling season the images also were chosen to provide independent realizations of filament structure distributions of average gradient magnitude as a function of gradient angle were used to provide a more compact representation of the frontal information contained in each image an analysis of these distributions shows that the sharp diffuse boundary structure associated with cold filaments observed in shipboard data dominates the total surface frontal structure found in satellite data for two of the three regions studied the recurrent ubiquitous patterns found in the satellite determined frontal structure are discussed in terms of their potential effects on acoustic propagation and regional implications on ecological community structure in the california current system

sea surface flow estimation from advanced very high resolution radiometer and coastal zone color scanner satellite imagery a verification study a refined technique for estimating surface currents from the displacement of features in sequential advanced very high resolution radiometer avhrr and coastal zone color scanner czcs images is presented it is used to calculate flow fields in two regions along the california coast and the results are compared to concurrent drifter drogue observations there is overall agreement to within approximately 6 cm s with somewhat better agreement at velocities less than 40 cm s the poorer performance of the technique at high velocities was due to difficulties in identifying and tracking features in areas of rapid flow the accuracy of the measurements is primarily affected by the analyst s precision in tracking each feature which in turn depends on how well the 2 to 6 km features preserve their identity from one image to the next a 12 to 24 hour interval yielded the best results in this study the directional component of the satellite derived flow field was representative of subsurface flow patterns down to at least 100 m although velocities obtained from avhrr infrared and czcs visible images may not always represent flow at the same depth the measurements were practically identical with the data used

dewarping the composite aeromagnetic anomaly map of australia using control traverses and base stations the composite aeromagnetic anomaly map of australia like similar maps of other continent size regions contains spurious trends warps and base level shifts these arise from the arbitrary nature of aeromagnetic data processing methods and edge matching of disparate surveys corrections have been applied to the australian map based on long aeromagnetic control traverses flown around the country in january and february 1990 the control traverses were timed to coincide with a continent wide magnetometer array study thus enabling accurate corrections to be made for transient diurnal variations of the geomagnetic field magnetic observatory data spanning several months each side of the traverse interval were used to correct for long term displacement of the total field from its normal value the transient contribution to total field was modeled as a set of one minute time slices over the whole country and then used to reduce the control traverse data to normal values absolute anomaly values were generated along traverses by subtraction of igrf 1990 then compared with corresponding anomalies given by the uncorrected composite map the resulting anomaly difference values were interpolated and extrapolated over the whole country and used to relevel the composite magnetic anomaly map the corrections applied range typically between 200 and 200 nt with a maximum of about 400 nt in the far western region and a minimum of about 450 nt in south australia these corrections are smaller than expected but are still large compared with the amplitude of long wavelength magnetic anomalies

an offshore eddy in the california current system part i interior dynamics abstract from january 9 to 17 1981 detailed observations of the horizontal and vertical structure beneath one of the quasi permanent semi stationary mesoscale offshore eddy signatures in the california current system ccs discussed by bernstein breaker and whritner 1977 burkov and pavlova 1980 and simpson 1982 were made the vertical sections of temperature and density show the presence of three layer system a subsurface warm core eddy whose diameter is about 150 km at the 7 c isotherm is the dominant feature a warm surface layer which extends to a depth of 75 m lies over the eddy between the warm surface layer and the subsurface warm core eddy there is a cold core region which extends to a depth of about 200 m there is a high degree of symmetry about the vertical axis of rotation vertical sections of salinity and dissolved oxygen are entirely different from sections of temperature and density diagrams of water mass characteristics confirm that the core of the eddy found between 250 600 m consists of inshore water from the california undercurrent cu below about 700 m local waters from the deep poleward flow dpf have been incorporated into the eddy the observed distributions of properties t s o 2 are inconsistent with a single local generation process for the eddy system radial distributions of angular velocity normalized gradient velocity and relative vorticity support the use of a gaussian radial height field as an initial condition in eddy models possible reasons why ccs eddies may differ dynamically from gulf stream rings are given in the text at the time the observations were made the system as a whole was in near geostrophic balance local geostrophic balance however cannot explain the observed distribution of properties and structure the observed symmetry in the structure of the eddy system chemical evidence simpson 1984 biological distributions haury 1984 and satellite images of the cc koblinsky simpson and dickey 1984 suggest that lateral entrainment of warm oceanic and cold coastal water into the upper two layers of the three layer system by the subsurface eddy is a likely generation mechanism for the cold core region the coastal origin of the frontal structure along the northeastern quadrant and the oceanic origin of the frontal structure along the southwestern quadrant of the eddy system further support lateral entrainment as a generation mechanism for the cold core this entrainment makes the ccs eddy system different from cold core rings in the gulf stream and rather similar to some warm core eddies found in the east australian current the presence of cu water in the core of this eddy raises the question of how cu water was transported from the continental slope eddy generation mechanisms other than baroclinic instability of the cc may be required to explain the distribution persistence and core composition of offshore mesoscale eddies in the ccs there is evidence that barotropic in addition to baroclinic processes may be important

satellite observations and modeling of meanders in the california current system off oregon and northern california abstract infrared satellite images from the west coasts of oregon and northern california are used to identify meander patterns in sea surface temperature which appear as large cold tongues extending offshore two relatively long series of images from 1982 and a few examples from 1980 and 1983 demonstrate the evolution of the cold tongues from an initial variety of scales 60 200 km to the fastest growing waves 110 130 km and then finally to tongues with longer wavelengths 400 km this is observed to occur over periods of about three months in summer and fall when the coastal circulation is composed of a southward surface current over a northward undercurrent the initial shorter scale features are believed to be excited by the interaction between the mean current and the coastal topography baroclinic instability associated with the vertical shear between the surface current and the undercurrent is found to be responsible for the growth of the features observed in the satellite imagery a nonlinear

possible sources driving the potential vorticity structure and long wave instability of coastal upwelling and downwelling currents it is well known that upwelling and downwelling currents are unstable to perturbations less is however known about the physical mechanism responsible for the observed and modeled instabilities it is shown that the origin of the long wave barotropic baroclinic instability observed on upwelling currents has to be sought among diabatic or thermobaric mechanisms in particular the role of mixing associated with kelvin helmholtz instability and of wind forcing is investigated low richardson numbers occur when the pycnocline outcrops at the sea surface the criterion for instability ri 1 4 can be reached in a narrow region close to the upwelling front permitting kelvin helmholtz instability and mixing this can precondition the current for long wave instability by transforming the current s potential vorticity a constant wind can likewise modify the potential vorticity the resulting potential vorticity anomaly is always negative for both upwelling and downwelling currents and this anomaly interacts with the outcropped front destabilizing it examples are provided via numerical calculations using an idealized front a wind stress is an effective means of inducing the negative pv necessary for instability with wind kelvin helmholz instability when present merely modifies the instability characteristics in addition upwelling fronts are always less stable than comparable downwelling fronts

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

application of satellite visible band data to high latitude oceans abstract remote sensing of high latitude oceans differs from oceans of tropical and subtropical latitudes because of the decoupling of the water s temperature structure from the flow dynamics at low water temperatures sea surface thermal patterns are useful here as tracers of the flow only without a direct link to the circulation dynamics oceanic flow responds to water density contrasts and at high latitudes the density is controlled by salinity distributions though density contrasts are not ordinarily detectable with remote sensors freshwater discharge in the northeast pacific contains very fine sediments glacial flour that can be detected using landsat thematic mapper tm and multi spectral scanner mss imagery from the tm data we have discovered several new coastal circulation features in the northern gulf of alaska flow around a coastal island produces a myriad of dipole eddies which are important to the cross shelf transport of salt and heat they also serve as sites to test numerical models to allow a better understanding of coastal flows and eddy formation elsewhere detection of these dipole eddies from their sediment distributions has allowed the comparison of different spectral bands from six imaging satellite sensors for their abilities to describe these features we conclude that in addition to the tm sensor s capability the sediments can be detected with the mss and coastal zone color scanner czcs sensors but not with avhrr or defense meteorological satellite program dmsp as a consequence of this comparison of satellite visible data we have confirmed that the dipole eddies here exist under low flow conditions 3 s

horizontal transport and the distribution of nutrients in the coastal transition zone off northern california effects on primary production phytoplankton biomass and species composition conductivity temperature depth surveys during 1988 encountered strong baroclinic jets that were evident in acoustic doppler current profiler and hydrographic data during june and july 1988 a filament with high surface nitrate high chlorophyll abundant populations of neritic centric diatoms and higher rates of primary production was evident perpendicular to the coast between point arena and point reyes however the high nutrient and phytoplankton regions were not in the baroclinic jets but were south and inshore of them surface water transported offshore by the strong baroclinic jets was found to have relatively low nutrient content suggesting that the jets themselves do not carry significant levels of coastally upwelled high nutrient water to the ocean interior the low nutrient and salinity content of the jet suggests that the water originated several hundred kilometers upstream although the jets themselves do not appear to transport significant levels of nutrients directly from the coastal regime to the oceanic regime dynamic processes associated with a meandering jet are likely responsible for high surface nutrients found several hundred kilometers offshore processes such as upwelling along the southern edge of the seaward jet result in significant enrichment of the coastal transition zone and in large blooms of neritic diatoms during 1988 the high nutrient high phytoplankton filament was present when the survey sequence began but then decayed after a month the surface and subsurface nitrate fields were coherent with the dynamic topography field throughout the survey sequence however the surface and integrated chlorophyll fields were coherent only through the first two surveys a decrease in phytoplankton biomass began during the third survey coincident with physical changes which occurred in that time frame 1 an intensification of the undercurrent and 2 changes in the surface circulation from predominantly offshore to predominantly longshore understanding the processes responsible for the uncoupling between biology and physics is paramount for realistic biological models of this region

coastal upwelling in the california current system abstract coastal upwelling in the california current system has been the subject of large scale studies off california and baja california and of small scale studies off oregon recent studies of the winds along the entire coast from 25 n to 50 n indicate that there are significant along shore variations in the strength of coastal upwelling which are reflected in the observed temperature distribution active upwelling appears to be restricted to a narrow coastal band about 10 25 km wide along the entire coast but the region influenced by coastal upwelling may be much wider intensive observations of the upwelling zone during summer off oregon show the presence of a southward coastal jet at the surface a mean vertical shear a poleward undercurrent along the bottom and persistently sloping isopycnals over the continental shelf most of the upwelling there occurs during relatively short periods several days long of upwelling favorable winds during the upwelling season off oregon the offshore ekman transport is carried by the surface ekman layer and the onshore return flow occurs through a quasi geostrophic interior it is not known whether the structure and dynamics observed off oregon are typical of the upwelling zone along the entire coast though some of the same features have been observed off baja california current and future research will eventually show whether the oregon results are also applicable in the region of persistently strong upwelling favorable winds off northern california and in the region of complex bathymetry off central and southern california

mesoscale to submesoscale transition in the california current system part ii frontal processes this is the second of three papers investigating the regime transition that occurs in numerical simulations for an idealized equilibrium subtropical eastern boundary upwelling current system similar to the california current the emergent upper ocean submesoscale fronts are analyzed from phenomenological and dynamical perspectives using a combination of composite averaging and separation of distinctive subregions of the flow the initiating dynamical process for the transition is near surface frontogenesis the frontal behavior is similar to both observed meteorological surface fronts and solutions of the approximate dynamical model called surface dynamics i e uniform interior potential vorticity q and diagnostic force balance in the intensification of surface density gradients and secondary circulations in response to a mesoscale strain field however there are significant behavioral differences compared to the surface dynamics model wind stress acts on fronts through nonlinear ekman transport and creation and destruction of potential vorticity the strain induced frontogenesis is disrupted by vigorous submesoscale frontal instabilities that in turn lead to secondary frontogenesis events submesoscale vortices and excitation of even smaller scale flows intermittent submesoscale breakdown of geostrophic and gradient wind force balance occurs during the intense frontogenesis and frontal instability events

numerical simulation of coastal upwelling and inerfacial instability of a rotaion and stratified fluid the evolution of the coastal upwelling and interfacial instability of a stratified and rotating fluid is studied numerically by using large eddy simulation upwelling is generated near the sidewall of a rotating annulus by the shear at the top the fluid initially consists of a stably stratified two layer structure with a narrow interface separating the two layers the large scale motion of the flow is simulated by solving the time dependent non hydrostatic incompressible navier stokes and scalar transport equations while the small scale motion is represented by a dynamic subgrid scale model the upwelling process contains both stable and unstable stratification the vertical structure of upwelling consists of a persistent primary front a trailing mixing zone on the shore side of the front and a temporary secondary front which leads a top inversion layer the longshore velocity profile has two maxima which occur at the edge of the sidewall boundary layer and at the density front the upwelled density front is unstable to azimuthal perturbations and baroclinic waves develop and grow to large amplitude pairs of cyclonic and anticyclonic waves appear at the front which form jet streams the secondary front is unstable to azimuthal perturbations its instability and the associated drop of the top inversion layer take the form of radial bands which subsequently break up into isolated patches and eventually sink the computed values of various upwelling time and length scales are compared to and are in good agreement with past experimental data

a real time dynamical forecast of ocean synoptic mesoscale eddies energetic eddy currents are the oceanic analogue of atmospheric weather and have time scales of days to weeks and space scales of tens to hundreds of kilometres1 we have predicted their evolution in time by internal dynamical processes for the forecasts we transferred initialization data from ship to shore based computers during two 2 week periods in june and july of 1983 from an approximately 150 km 2 region in the deep north east pacific off california this is to the best of our knowledge the first such real time forecast at sea the results were substantially successful the dynamics predicted a prominent zonal jet absent in the initial flow also the model forecast revealed a strong eddy merger event otherwise obscured in the data prospects are encouraging for future forecasting which should have important implications for research and practical operations at sea2

comparison of basin scale acoustic transmissions with rays and further evidence for a structured thermal field in the northeast pacific from may to september of 1987 250 hz 16 ms resolution acoustic signals were transmitted between four sources and nine receivers in the northeast pacific this paper examines the acoustic transmissions across nine of the sections within this group with path lengths ranging from approximately 1700 to 3300 km acoustic multipaths are tracked in the data and ray theory is successfully used to identify the multipaths where the spring and summer levitus climatological databases are used to determine the sound speeds the observed multipaths arrive on the order of 1 s later than the predicted rays travel time differences greater than 0 15 s are due to temperature errors in levitus climatology within the ocean s upper 1 km the resulting corrections to levitus spring and summer oceans are 0 2 and 0 3 c respectively the upper turning depths for all rays are found to vary by less than 50 m from spring to summer variations in the measured travel times over the four month period are about 0 5 s some s

two layer model of shear driven coastal upwelling in the presence of bottom topography a stratified two layer fluid is brought to solid body counterclockwise rotation inside a cylindrical tank having a conical bottom with a radial topographic ridge a stress is then applied to the top surface by means of a clockwise differentially rotating disk the resulting ekman layer flux causes the top layer to spin down and the interface to rise near the wall and to descend a t the centre of the tank as this process continues the interface front between the two layers intersects the disk surface and after that migrates away from the wall and allows the bottom fluid to contact the disk directly the migration of the front continues until a steady state is reached the front becomes stationary and the system is in geostrophic balance the first sign of upwelled flow at the surface always occurs as a high speed jet like plume at the bottom topography and only at a later time does a uniform upwelled flow appear a t the surface upstream of the topography this plume which always forms near the downstream edge of the topography migrates in advance of the upstream front to produce an upwelling maximum at the bottom topography the final width of the upstream flow in steady state conditions is estimated by a simple theoretical model which is in good agreement with the experimental results we have an experimental criterion to predict the occurrence of travelling baroclinic waves on the upstream front on the downstream side of the ridge large standing waves are observed with significant upwelling within them under some circumstances cyclones pinch off from the upstream front the plume on the ridge and the crests of the large downstream standing waves we present criteria to predict the occurrence of these pinch off processes

merging airborne magnetic surveys into continental scale compilations regional compilations of airborne magnetic data are becoming more common as national databases grow grids of the magnetic survey data are joined together to form geological province scale or even continental scale compilations the advantage of these compilations is that large tectonic features and geological provinces can be better mapped and interpreted we take a holistic approach to the joining of survey grids the leveling of the grids into a regional compilation is treated as a single inverse problem we use the weighted least squares method to find the best adjustment for each survey grid such that the data value differences in the grid overlap areas are minimized the method spreads any inconsistencies between grids among all of the grid overlap areas and minimizes the introduction of long wavelength errors into the composite grid this is an improvement on the conventional approach of joining grids sequentially a comparison of leveled data over western australia with diurnally corrected long aero

surface patterns in temperature flow phytoplankton biomass and species composition in the coastal transition zone off northern california satellite thermal imagery and in situ biological and physical data are presented that describe the spatial variability of phytoplankton biomass and species composition in relation to the physical structure at the sea surface during persistent upwelling off northern california surface patterns in temperature geostrophic velocity chlorophyll and particle size structure show that the coastal zone was dominated by two water masses separated by a well defined physical boundary this boundary is apparent in satellite thermal imagery as a cold front and in dynamic height as a meandering jet in the california current on the landward side of the front jet we observed cold coastal water that was relatively enriched in phytoplankton biomass due to the presence of large diatoms on the seaward side of the front jet we observed relatively warm water where the phytoplankton biomass was low and the diatoms were largely absent broad tongues and narrow filaments of cold chlorophyll rich water that extended over 100 km offshore were present in our study area these features were bounded by the meandering coastal jet the coldest most chlorophyll rich water in these tongues and filaments was located between the onshore and offshore flows in relatively slow moving water but entraimnent of coastal water into the jet was apparent

basin scale wind forced dynamics of the seasonal southern south china sea gyre 1 using observed wind forcing the seasonal development and disappearance of the near surface anticyclonic gyre in the southern south china sea is modeled along with associated dynamic features forced by monsoon winds the ocean circulation in the south china sea alternates between a single cyclonic gyre during the winter northeast monsoon and a double gyre cyclonic anticyclonic in the northern southern south china sea during the summer southwest monsoon reversing the western boundary current along vietnam with each shift of the monsoon regime during the summer southwest monsoon the poleward western boundary current converges with the equatorward western boundary current of the northern gyre turning offshore to create an eastward jet and flanking dipole recirculation near 13 n the development and timing of the eastward jet and recirculations are consistent with large scale basin dynamics the subsequent transition to the winter northeast monsoon regime destroys the recirculation cells and eastward jet employing high resolution 1 5 layer and 2 0 layer numerical models we demonstrate the applicability of large scale dynamics to the deeper central basin of the south china sea specifically showing that the gyre scale circulation governs the development of the eastward jet and dipole recirculations the destruction of the recirculations by the monsoon winds each autumn is also modeled this effort highlights the dominance of monsoon wind forcing in the south china sea s basin scale dynamics

mesoscale variability in current meter measurements in the california current system off northern california current meter data from a triad of moorings located on the continental rise offshore of point reyes point arena and from a mooring site located about 250 km offshore and to the northwest of the array are analyzed the continental rise moorings were deployed from october 1984 to july 1985 and each had five meters at depths from about 150 to about 3560 m the offshore mooring was deployed from september 1982 to august 1983 with six meters positioned from about 150 to 3800 m velocity components were highly vertically coherent in the upper 600 m and were in phase for periods longer than about 10 days temperature tended to be less coherent there was some horizontal coherence in the continental rise array coherence at 9 13 days between the deep temperature t at about 3200 m measurements at m1 and m2 located about 120 km offshore and separated by about 100 km coincided with very high in phase coherence in the northward velocity component v although there was no coherence between the first baroclinic modal components at m1 and m2 the eastward barotropic velocity component was coherent at periods of 9 11 days and the northward barotropic velocity component was coherent at 8 15 days and 4 5 6 days the triad provided a complete data set only at 350 m the highest coherence was between out of phase v components and also t at m2 and m3 about 100 km seaward of m2 at periods of 45 90 days with the dominant time domain empirical orthogonal function eof representing strong horizontal shear between m2 and m3 at periods of 9 13 days there was bottom and surface intensification in the nearshore kinetic energy spectra suggestive of a superposition of a barotropic mode with the first two baroclinic modes and partially consistent with the presence of topographic rossby waves the vertical structure at m2 differed from that at w10 the offshore mooring where the deep about 3000 m flow tended to be stronger than that near the continental slope and rotary behavior was apparent at 3000 m the barotropic modal energy was higher at w10 than at m2 but the first baroclinic modal energy was comparable at the two sites at m2 when they were coherent the barotropic and first baroclinic modes enhanced each other in the upper water column and led to reduced flow at deeper levels at w10 these modes were mainly out of phase and so enhanced the flow at deeper levels these differences which may be spatial rather than temporal increase the complications of initialization of predictive models from mass field data alone there are some indications of current and temperature variability due to fluctuating winds for example the northward components of wind stress and barotropic current were coherent at all locations at periods of 8 9 days at w10 there was also coherence between the eastward components of barotropic current and wind stress at 16 19 days on the basis of frequency domain eofs some of the current variability was forced by large scale i e about 1000 km wind stress at periods of between 5 and 10 days however less than half the current variability was demonstrably related to the wind stress at m2 and m3 at 150 m large amplitude about 1 c temperature variations which are sustained for several weeks are influenced by alongshore flow convergence and offshore jets coherence between t at 350 m and wind stress curl is suggestive of ekman pumping at m3 but the temperature was also related to alongshore convergence and offshore flow

flow through fractures flow through fractures is often idealized as flow between two parallel plates plane poiseuille flow the opening or aperture between parallel plates is unambiguous and its relation to flowrate is well known however fractures in rock have uneven walls and a variable aperture a model for flow in a fracture is proposed wherein the fracture is represented by a set of parallel plate openings with different apertures the model leads to a modified poiseuille equation for flow which includes an aperture frequency distribution for the fracture any arbitrary aperture distribution can be used in order to simplify computation and demonstrate the properties of the model a log normal form of distribution is assumed even when an analytical form of the distribution is assumed two parameters rather than a single value representing aperture size are required to determine flowrate models of aperture change for a fracture undergoing compression fracture walls deforming and extension fracture walls separating are developed which constrain the additional parameter and allow calculation of flowrate as a function of mean aperture the theoretical relationships developed between mean aperture and flowrate can be used to interpret published laboratory data for single fractures

roughness decomposition and nonlinear fluid flow in a single rock fracture abstract the objective of this paper is to investigate the effects of wall surface roughness on fluid flow through rock fractures a wavelet analysis technique was developed to define a mathematical criterion for decomposing the original wall surface roughness profiles of a fracture into a high frequency secondary roughness profile and a low frequency primary roughness profile in order to examine their impacts on fluid flow by solving the navier stokes equations nse without linearization using a self developed 2d finite volume method fvm code the results indicate that the high frequency secondary roughness is the main cause for dynamic evolution of eddy flow regions in the fracture flow field besides the reynolds number re in the original fracture model with the high frequency secondary roughness our results show that fluid flow fields are not only generally non linear but also with non stop generation and motions of eddies in the boundary layer regions of rough fractures when the re 1000 in this study which will affect the solute transport processes in fractured rock masses the complete nse were solved without removing acceleration and inertial terms so that the impacts of surface roughness on the nonlinear and dynamic flow behavior of rock fractures were calculated and visualized more accurately which is important for modeling mass and energy transport processes in fractures and fractured rock masses

extending comprehensive models of the earth s magnetic field with orsted and champ data summary a new model of the quiet time near earth magnetic field has been derived using a comprehensive approach which includes not only pogo and magsat satellite data but also data from the orsted and champ satellites the resulting model shows great improvement over its predecessors in terms of completeness of sources time span and noise reduction in parameters with its well separated fields and extended time domain of 1960 to mid 2002 the model is able to detect the known sequence of geomagnetic jerks within this frame and gives evidence for an event of interest around 1997 because all sources are coestimated in a comprehensive approach intriguing north south features typically filtered out with other methods are being discovered in the lithospheric representation of the model such as the s atlantic spreading ridge and andean subduction zone lineations in addition this lithospheric field exhibits significantly less noise than previous models as a result of improved data selection the f region currents through which the satellites pass are now treated as lying within meridional planes as opposed to being purely radial results are consistent with those found previously for magsat but an analysis at orsted altitude shows exciting evidence that the meridional currents associated with the equatorial electrojet likely close beneath the satellite besides the model a new analysis technique has been developed to infer the portion of a model parameter state resolved by a particular data subset this has proven very useful in diagnosing the cause of peculiar artefacts in the magsat vector data which seem to suggest the presence of a small misalignment bias in the vector magnetometer

use of simulated drifter tracks to investigate general transport patterns and residence times in the coastal transition zone general transport patterns and residence times in the upper 100 m of the coastal transition zone ctz were studied using simulated lagrangian drifter experiments the circulation fields used for the drifter experiments were obtained from a regional primitive equation model that incorporates coastal geometry and bottom topography that is representative of the ctz region the simulated circulation fields show velocity patterns that are consistent with those associated with the filaments and jets observed in the ctz region drifters were released at 880 points in the model domain in a pattern that bracketed both horizontally and vertically the region in which offshore flowing filaments were observed to form at each location drifters were released at depths of 30 60 90 m and tracked for 30 days the depth of these drifters varied along their trajectories in response to the vertical velocities experienced by the drifters an additional set of drifters was released at 30 m and was constrained to remain at this depth the composite drifter trajectories show that transport patterns and residence times in the upper 100 m are determined by the proximity of the drifter release point to the offshore flowing filament drifters released inshore of the filament are transported southward with the mean flow of the model california current drifters released near the region in which the filament originates are transported rapidly offshore the point at which this difference in drifter fate occurs is approximately 100 km offshore the time required for a drifter to be transported from the nearshore region to the outer boundary of the area covered in the ctz model domain is approximately 20 days comparison of the free floating drifters with the 30 m fixed depth drifters shows that the deeper drifters are displaced southward as they are transported offshore in the jet the magnitude of the southward displacement for the 90 m drifters is about 15 km implying substantial cross jet exchange comparison of the simulated drifter trajectories with the trajectory followed by a drifter released during the 1988 ctz field sampling program support the hypothesis that the deepening of the abundance maxima observed in the distributions of dolioletta gegenbauri juvenile forms of euphausia pacifica and eucalanus californicus resulted from these populations being downwelled as they were transported offshore by the flow associated with the filament observed in 1988

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

selective withdrawal and spin up of a rotating stratified fluid we present an experimental study demonstrating that rotation has a pronounced effect on currents induced by selective withdrawal of fluid from a density stratified reservoir our observations show that initiating outflow from the reservoir generates kelvin shear waves these waves propagate cyclonically around the perimeter of the reservoir establishing an anticyclonic withdrawal layer flow this flow accelerates owing to the production of relative vorticity by compression of planetary vorticity the withdrawal layer thickness as shown by vertical profiles of the horizontal velocity grows with time separation of the side wall boundary layers in the corners of the tank causes the spun up flow to eventually break up into a series of counterrotating gyres we also present a model that describes many features of the spin up process observed before onset of separation and subsequent gyre formation the model shows that vertical diffusion of vorticity plays an important role in the spin up process leading us to conclude that apparent thickening of the withdrawal layer over time as seen in changes in the velocity profile is associated with the vertical diffusion of the spun up vorticity