physical dynamics and biological implications of a mesoscale eddy in the lee of hawai i cyclone opal observations during e flux iii abstract e flux iii march 10 28 2005 was the third and last field experiment of the e flux project the main goal of the project was to investigate the physical biological and chemical characteristics of mesoscale eddies that form in the lee of maui and the island of hawai i focusing on the physical biogeochemical interactions the primary focus of e flux iii was the cyclonic cold core eddy opal which first appeared in the noaa goes sea surface temperature sst imagery during the second half of february 2005 during the experiment cyclone opal moved over 160 km generally southward thus the sampling design had to be constantly adjusted in order to obtain quasi synoptic observations of the eddy analyses of ship transect depth profiles of ctd optical and acoustic doppler current profiler adcp data revealed a well developed feature characterized by a fairly symmetric circular shape with a radius of about 80 km depth profiles of temperature salinity and density were characterized by an intense doming of isothermal isohaline and isopycnal surfaces isopleths of nutrient concentrations were roughly parallel to isopycnals indicating the upwelling of deep nutrient rich water the deep chlorophyll maximum layer dcml shoaled from a depth of about 130 m in the outer regions of the eddy to about 60 m in the center chlorophyll concentrations reached their maximum values in opal s core region about 40 km in diameter where nutrients were upwelled into the euphotic layer adcp velocity data clearly showed the cyclonic circulation associated with opal vertical sections of tangential velocities were characterized by values that increased linearly with radial distance from near zero close to the center to a maximum of about 60 cm s 1 at roughly 25 km from the center and then slowly decayed the vertical extent of the cyclonic circulation was primarily limited to the upper mixed layer as tangential velocities decayed quite rapidly within a depth range of 90 130 m potential vorticity analysis suggests that only a relatively small about 50 km in diameter and shallow to a depth of approximately 70 m portion of the eddy is isolated from the surrounding waters radial movements of water can occur between the center of the eddy and the outer regions along density surfaces within an isopycnal range of t 23 6 t 23 6 kg m 3 and t 24 4 t 24 4 kg m 3 thus the biogeochemistry of the system might have been greatly influenced by these lateral exchanges of water at depth especially during opal s southward migration while the eddy was translating deep water in front of the eddy might have been upwelled into the core region leading to an additional injection of nutrients into the euphotic zone at the same time part of the chlorophyll rich waters in the core region might have remained behind the translating eddy and thus contributed to the formation of an eddy wake characterized by relatively high chlorophyll concentrations

theoretical and experimental studies of coupled seepage pipe flow to a horizontal well abstract this study proposes a new approach which describes a finite diameter horizontal well and flow inside the pumping well jointly this approach utilizes a new treatment for in well hydraulics thus eliminating the flux or head based boundary condition along the horizontal well an equivalent hydraulic conductivity concept is applied for treating the horizontal wellbore this conceptual model is more general than previous models that describe the horizontal wellbore the description of in well hydraulics depends on the reynolds number a sample case of horizontal well pumping underneath a river is first used to illustrate the solution of the proposed approach a physical laboratory model was constructed and hydraulic heads and the well flow rate were carefully monitored and compared with the numerically calculated results using the proposed model the experimental data agree well with the numerical solution

an empirical orthogonal function analysis of remotely sensed sea surface temperature variability and its relation to interior oceanic processes off baja california abstract empirical orthogonal function eof analysis was applied to a 4 6 year sequence of avhrr images off baja california centered near punta eugenia to examine large and mesoscale processes in this region of the california current system ccs the mean structure found in the image sequence describes the seasonal cycle in sea surface temperature sst and the large scale north south oceanic sst gradient of the region the first eof amplitude pair also describes the seasonal cycle in sst both results are consistent with long term large scale mean shipboard data for the region the second eof amplitude pair defines two distinct regions paralleling the coast the inshore region coincides with the coastal zone of lynn and simpson 1987 and the adjacent region farther offshore is identical to their transition zone the third through fifth eof amplitude pairs primarily represent meandering of the california current and anticyclonic mesoscale eddy occurrences in the region these results also are consonant with a large number of shipboard observations the eof results provide independent satellite derived evidence for the existence of a transition zone off baja california which is similar to that found off central and southern california moreover the agreement between the satellite based results and the shipboard observations indicates that satellite data can be used successfully to study other current systems e g peru current where in situ observations ships buoys are less abundant

multi level slug tests in highly permeable formations 1 modification of the springer gelhar sg model a multi level slug test model and a method for the evaluation of vertical profiles of hydraulic conductivity in highly permeable formations are developed a double packer system is employed to estimate local hydraulic conductivity depending on the formation and double packer system parameters the water level recovery in the tested well can exhibit a monotonic or oscillatory response to discern information on aquifer properties from artifacts introduced by the measurement system the theory of flow in an aquifer and a double packer system is developed the mathematical model incorporates features of the springer and gelhar 1991 model and reduces to the bouwer and rice 1976 model in a special case the model involves equations of momentum and mass conservation for the double packer system with quasi steady well aquifer interaction equations the method is uniformly applicable for both monotonic and oscillatory well responses and can produce profiles of hydraulic conductivity for the tested well the criterion is given to determine the type of well response for given slug test conditions

evaluation and interpretation of thirteen official van telegrams for the period september 10 1986 to april 28 1988 abstract all the thirteen official earthquake prediction telegrams sent by van researchers during september 10th 1985 to april 28th 1988 based on seismic electric signals ses observations were examined against seismic data the first four telegrams pertaining to the m s 6 0 kalamata earthquake and its aftershocks were all failures of the remaining nine telegrams five were complete failures because there was no earthquakes with m 4 in the candidate areas within 11 d after the telegram even when some events occured after the telegram correlation with prediction was either non unique or the error in magnitude was too large in seven cases earthquakes with a magnitude comparable to that of predicted events took place in the candidate areas just before the related telegrams without any ses contrary to van s assertion of one to one correspondence between ses and earthquakes

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

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

balances of heat and momentum at 33 5 n 127 w in the upper ocean during the mixed layer dynamics experiment the balances of momentum and heat were studied for an 18 day period in october november 1983 during the mixed layer dynamics experiment at a site 650 km off central california data were collected from a drifting platform from which surface winds air temperature and ocean currents from a string of vector measuring current meters were measured the position of the unattended drifter was determined by loran c on the platform currents in the surface layers were partially wind driven and partially coherent with low frequency currents at deeper levels the latter currents though coherent were sheared turned significantly with depth and were presumably nearly geostrophically balanced vertically differencing velocity in the mixed layer improved the balance between wind and current by removing a portion of the geostrophic flow the complex correlation coefficient between wind stress and current integrated to 38 m was 0 76 for current relative to 38 m yet only 0 36 for the undifferenced case surface heat flux magnitudes were not clearly reflected in the heat content of the near surface layers although variability was over the first 13 days of the experiment the correlation coefficient between daily averaged heat flux and heat content change was 0 89 but average net surface heating was 60 w m 2 while the average heat content change in the top 38 m was only 10 w m 2 heat balance must have been restored by advection vertical advection was rejected as an explanation because heat content changes in layers defined by isotherm depths showed similar imbalances with regard to surface heating horizontal advection was estimated by two methods 1 by using sparse thermistor chain tows around the current meter drifter to construct a history of horizontal temperature gradients and 2 by using current profiles at moderate depths to estimate pressure gradients essentially through geostrophy hence buoyancy gradients by the hydrostatic relation hence temperature gradients the two methods gave very different estimates though both tended to redress the imbalance between surface heat flux and local heat storage

three dimensional model of modern channel bend deposits 1 we present a three dimensional model of heterogeneous modern channel bend deposits developed through purely structure imitating interpolation kriging of hydraulic properties this model augmented with ground penetrating radar data and directional variograms agrees with detailed observations in similar modern environments and leads to a process based interpretation of the presented hydraulic conductivity structure integration of all available information permitted delineation and characterization of the modern streambed as a distinct hydrostratigraphic unit without coring or outcrop studies our results imply that the modern streambed is commonly oversimplified in available analytical and numerical models of groundwater surface water interactions where it is assumed to be homogeneous and isotropic and characterized by a constant width and thickness this three dimensional approach that integrates concepts and principles developed in sedimentology hydrogeology geophysics and geostatistics has potential implications on model development of stream aquifer systems

analysis of slug tests in bypassed wells in berlin many wells are constructed with an additional small diameter bypass tube flanged on to the large diameter casing and running parallel to the later upward to the surface the response to a slug test conducted in such a well is usually characterised by significant water level oscillations developing inside the branched pipe system in the present paper a general non linear model is developed for the analysis of slug tests performed in bypassed wells the model includes skin effects non linear head losses due to internal well bore fluid friction minor losses originating at radius changes along the flow path inside the well and inertial effects of the water columns contained within the primary casing and the bypass pipe flow inside the branched tubing system is described by the one dimensional conservation law of the mechanical energy of the well bore fluid aquifer flow is quantified by a convolution type approach the coupled well aquifer system is governed by an integro differential equation representing the mean mechanical energy of the total well bore fluid and coupled to it by a non linear ordinary differential equation which accounts for mechanical energy fluctuations between the water columns inside the main casing and the bypass both equations are solved by finite difference approximations coupled to point iterative numerical techniques an application of the model to field data suggests that non linear hydraulic head losses originating inside the well bore may cause the measured head responses to depend on the initial displacement a packer used to initiate a slug test can induce these non linear distortions through the combined effect of minor losses originating at the inlet and the outlet of a small diameter packer flow through tube and internal fluid friction potentially developing inside that packer passage as classical linear theories do not allow for the analysis of such phenomena a model accounting for these non linear processes should be used if field data show significant dependencies on the initial slug height

global statistical space time scales of oceanic variability estimated from the topex poseidon altimeter data four years of the topex poseidon altimeter data are used to produce estimates of statistical space time scales of ocean variabilities for the sea surface height a three dimensional space time correlation function with an anisotropic directional dependence is assumed the function has gaussian distributions in radial directions in the space time coordinates and ellipsoidal contour surfaces the function can reveal the space time scales and propagations of the variabilities and statistical errors in the altimeter data we evaluated the space time scales using the best fit correlation function to the altimeter data the scales show geographical differences this means that dominant variabilities depend on regions we show an optimum interpolation oi method as an example of the application of the fitted correlation function the oi is applied to the altimeter data in the space time domain to make grid point data with higher accuracy than those obtained from a usual spatial two dimensional oi 2 d oi the values of the correlation function are used for the correlation coefficients of the first guess error in the oi a propagation diagram obtained from the space time oi 3 d oi shows clear propagations of planetary disturbances with larger amplitude the grid point values from the 3 d oi show better correspondences with sea levels from tide gauges than those from the 2 d oi the advantage is due to the data of the different cycles being additionally adopted and the correlation function reflecting propagation of the ocean variabilities

some thoughts on fine grained sediment transport and deposition abstract fine sediments are receiving greater emphasis due to economic significance as source rocks for petroleum the often nearly continuous record of depositional histories and the volumetric importance in the geologic record distribution of these particulates is driven primarily by ocean circulation deposition is primarily controlled by planktic biologic filtering aggregation and reworking early diagenesis is controlled by bacterial processes with consequent changes in bulk and chemical properties most fine particulates are initially deposited in the continental margins and then move to deep ocean floors by mass wasting and high concentration flows stability of these fine deposits even on slopes of gentle gradient is controlled primarily by water content which in turn is a function of sedimentation rate and texture of the supply mass transport can occur in a variety of forms from slow creep to catastrophic failures of large scale a sequence of morphologies can result from the various forms of movement most of the fine grained stratigraphic record urgently needs reevaluation and restudy models of paleogeographic reconstructions on a large scale need to include the results of physical and biological oceanographers since the older simpler scenarios of locations of zones of high bioproductivity and of the patterns of major ocean currents have been greatly modified in recent years biological oceanographers have contributed models for contemporary upwelling systems that have changed the thinking of paleobiologists and biostratigraphers working with biogenically dominated fine sedimentary rocks

a pressure packer system for conducting rising head tests in water table wells abstract the pressure system developed for fully saturated well screens has been modified for conducting rising head tests in water table wells installed in highly permeable aquifers the pressure system consists of a compressed air source and 1 inch diameter pvc piping with a packer attached at the end the pressure system was evaluated in a series of rising head tests conducted in a well at a superfund site in new england the well was tested with slugs and with the pressure system within each technique estimates of hydraulic conductivity showed no difference comparison of hydraulic conductivity estimates between techniques slug test vs pressure test showed differences due to stratigraphy the interval tested using slug tests crossed two stratigraphic units the pressure system tested only one of these units we conclude that the pressure system may be used to characterize the vertical hydraulic conductivity distribution in a series of successive tests by changing the packer position and the screened interval tested

cross borehole slug test analysis in a fractured limestone aquifer summary this work proposes new semi analytical solutions for the interpretation of cross borehole slug tests in fractured media our model is an extension of a previous work by barker barker j a 1988 a generalized radial flow model for hydraulic tests in fractured rock water resources research 24 10 1796 1804 butler jr j j zhan x 2004 hydraulic tests in highly permeable aquifers water resources research 40 w12402 doi 10 1029 2003 wr002998 it includes inertial effects at both test and observation wells and a fractional flow dimension in the aquifer the model has five fitting parameters flow dimension n hydraulic conductivity k specific storage coefficient ss and effective lengths of test well le and of observation well leo the results of a sensitivity analysis show that the most sensitive parameter is the flow dimension n the model sensitivity to other parameters may be ranked as follows k le leo ss the sensitivity to aquifer storage remains one or two orders of magnitude lower than that to other parameters the model has been coupled to an automatic inversion algorithm for facilitating the interpretation of real field data this inversion algorithm is based on a gauss newton optimization procedure conditioned by re scaled sensitivities it has been used to interpret successfully cross borehole slug test data from the hydrogeological experimental site hes of poitiers france consisting of fractured and karstic limestones hes data provide flow dimension values ranging between 1 6 and 2 5 and hydraulic conductivity values ranging between 4 4 10 5 and 7 7 10 4 m s 1 these values are consistent with previous interpretations of single well slug tests the results of the sensitivity analysis are confirmed by calculations of relative errors on parameter estimates which show that accuracy on n and k is below 20 and that on ss is about one order of magnitude the k values interpreted from cross borehole slug tests are one order of magnitude higher than those previously interpreted from interference pumping tests these findings suggest that cross borehole slug tests focus on preferential flowpath networks made by fractures and karstic channels i e the head perturbation induced by a slug test propagates only through those flowpaths with the lowest hydraulic resistance as a result cross borehole slug tests are expected to identify the hydrodynamic properties of karstic channels and fracture flowpaths and may be considered as complementary to pumping tests which more likely provide bulk properties of the whole fracture karstic channel matrix system

an offshore eddy in the california current system part iii chemical structure abstract from january 9 to 17 1981 detailed physical chemical and biological measurements were made through the historical surface signature berstein breaker and whritner 1977 burkov and pavlova 1980 simpson 1982 of a warm core eddy in the california current system the data show a three layer system surface layer to 75 m intermediate cold core region to about 200 m and the physically dominant subsurface warm core eddy to about 1400 m the chemical structure simultaneously possesses characteristics of both warm and cold core eddies this structure results from a complex interplay among non local eddy generation processes at the time the three layer system was formed and a continuous set of interactions within the three layer system both inshore cold and offshore warm waters of the california current and coastal and local biological processes e g this california current system eddy is not an isolated structure like some gulf stream rings the dominant biological chemical process in the euphotic zone is phytoplankton photosynthesis photosynthetic alteration of the chemical structure below 100 m is much reduced the effects of heterotrophic activity on the deeper lying chemical structure however are not as significant as those of autotrophs on the chemical structure of the euphotic zone hence below 100 m the distribution and structure of chemical properties is controlled primarily by physical processes the continuous set of interactions of the three layer system with coastal and oceanic waters of the california current make this offshore eddy in the california current system fundamentally different chemically and biologically from cold core gulf stream rings and rather similar to some of the warm core eddies found in the east australian current

measurements of total carbon dioxide and alkalinity by potentiometric titration in the geosecs program abstract approximately 6000 determinations of the alkalinity and total carbon dioxide content of seawater have now been made in the atlantic pacific and indian oceans as part of the geosecs program by a computer controlled potentiometric titration technique the equations used to locate the equivalence points of the carbonic acid system on this titration curve were developed in 1971 but have not previously been published these functions may be represented by f 1 v 2 v v 0 n h k 1 c v 0 v v 0 h h s o 4 h f b o h 4 1 h k 1 c f 2 v 0 v v 0 h h s o 4 h f h c o 3 upon inspection these functions are analogous to the modified gran functions of hansson and jagner 25 with the omission of the contributions of oh and co 3 2 and with the contribution of b oh 4 being assessed at a chlorinity of 19 for all samples reprocessing the original titration e m f volume data with appropriate corrections and modified gran functions reveals an error of about 12 mol kg in the geosecs total carbon dioxide data in addition the protonation of dissolved phosphate species during the titration results in a contribution to measured total carbon dioxide equal to the total phosphate concentration differences in the application of the geosecs functions between the atlantic and the pacific indian oceans expeditions are also to be found so that the error deriving from this source for the atlantic expedition was only 5 mol kg the application of the correct functions increases precision enabling smaller differences such as those attributable to fossil fuel carbon dioxide potentially to be observed and increases accuracy so that the error in titrator total carbon dioxide previously diagnosed by takahashi 14 can be logically accounted for

estimation of hydraulic conductivity from borehole flowmeter tests considering head losses abstract recent numerical studies have demonstrated that the conventional interpretation of the borehole flowmeter test bft may lead to considerable errors in estimates of the horizontal hydraulic conductivity k r due to neglect of head loss across the electromagnetic borehole flowmeter ebf even in uniform aquifers the conventional interpretation underestimates k r at the base and overestimates k r at the top of the aquifer in this paper we derive exact analytical solutions for hydraulic head and streamlines induced by the bft in a confined homogeneous aquifer the solutions explicitly consider head loss across the ebf the derived analytical solutions for head distribution in the vicinity of the pumping well and for volumetric flux to the well sections above and below the ebf can be used to interpret field bft data in uniform aquifers this approach can be applied to obtain estimates of k r from the conventional interpretation applications of this approach to the bft field data set from a highly heterogeneous aquifer indicate that the constraint of aquifer homogeneity limits the applicability of this approach but it can provide useful insights into the mechanism of flux redistribution near the borehole during the bft

monitoring of a quasi stationary eddy in the bay of biscay by means of satellite in situ and model results the presence of a quasi stationary anticyclonic eddy within the southeastern bay of biscay centred around 44 30 n 4 w has been reported on various occasions in the bibliography the analysis made in this study for the period 2003 2010 by using in situ and remote sensing measurements and model results shows that this mesoscale coherent structure is present almost every year from the end of winter beginning of spring to the beginning of fall during this period it remains in an area limited to the east by the landes plateau to the west by le danois bank and torrelavega canyon and to the northwest by the jovellanos seamount all the observations and analysis made in this contribution suggest that this structure is generated between capbreton and torrelavega canyons detailed monitoring from in situ and remote sensing data of an anticyclonic quasi stationary eddy in 2008 shows the origin of this structure from a warm water current located around 43 42 n 3 30 w in mid january this coherent structure is monitored until august around the same area where it has a marked influence on the sea level anomaly sea surface temperature and surface chlorophyll a concentration an eddy tracking method applied to the outputs of a numerical model shows that the model is able to reproduce this type of eddy with similar 2d characteristics and lifetimes to that suggested by the observations and previous works this is the case for instance of the simulated may04 eddy which was generated in may 2004 around torrelavega canyon and remained quasi stationary in the area for 4 months the diameter of this eddy ranged from 40 to 60 km its azimuthal velocity was less than 20 cm s 1 its vertical extension reached 3000 3500 m depth during april and may and it was observed to interact with other coherent structures

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

an offshore study in the california current system preface l etude d un tourbillon de mesoechelle quasi permanent et quasi stationnaire dans le systeme du courant de californie comprend quatre parties dynamique au sein du systeme manifestations a la surface structure chimique et distribution du plancton

the application of the magnetotelluric impedance tensor to earthquake prediction research in greece continuous short period 0 1 3600 s measurements of the magnetotelluric field components were conducted simultaneously at two sites in greece for a period of 5 weeks the estimation of the impedance tensor elements from 8 hr windows of recorded data at each station is found to describe the local electromagnetic induction with great accuracy the computation of the residual electric field obtained as the difference between the observed and estimated inductive part of the electric fields clearly improves the detection of any local electric field anomaly this method was used in an attempt to detect precursory sci smic electrical signals ses that have been reported to precede earthquakes in greece the results indicate the success of this method in resolving ambiguities about the nature of the reported ses i e whether it has an external or internal source although during the recording period no large earthquake occurred five with a magnitude of between ml 4 0 and ml 4 3 occurred within a radius of 150 km from one of the stations the magnetotelluric recordings and the computed residual electric fields for the time intervals reported to contain the ses precursors to these events were analysed in some detail in two of the cases it was found that the sources could not be related to earthquake processes in the other three cases the nature of the source of the suspected ses although electric could not be established with certainty these results indicate that for earthquakes of small magnitude ml 4 3 or of large epicentral distance r 100 km the detection of a ses is extremely difficult

equatorial pacific 13 c water eddies in the eastern subtropical south pacific ocean abstract argo float profile data are used to analyze warm salty weakly stratified subthermocline eddies of tropical origin in the eastern subtropical south pacific ocean these eddies contain anomalous signatures of the equatorial pacific 13 c water that is carried poleward within the peru chile undercurrent pcu as it flows along the west coast of south america from their source along the chilean coast between 29 and 39 s the eddies spread westward and slightly northward likely at least partly advected by the subtropical gyre the eddy water properties contrast strongly with the colder fresher more strongly stratified waters of subantarctic origin being carried northward then westward by the gyre near the eddy source about 6 of argo profiles sample eddies that are above selected thresholds for both salinity and potential vorticity anomalies relative to maps of the mean distributions of these properties on and around the core isopycnal for the eddies the proportion of such profiles dimini

a method to estimate hydraulic conductivity while drilling abstract a field test and analysis method has been developed to estimate the vertical distribution of hydraulic conductivity in shallow unconsolidated aquifers the field method uses fluid injection ports and pressure transducers in a hollow auger that measure the hydraulic head outside the auger at several distances from the injection point a constant injection rate is maintained for a duration time sufficient for the system to become steady state exploiting the analogy between electrical resistivity in geophysics and hydraulic flow two methods are used to estimate conductivity with depth a half space model based on spherical flow from a point injection at each measurement site and a one dimensional inversion of an entire dataset the injection methodology conducted in three separate drilling operations was investigated for repeatability reproducibility linearity and for different injection sources repeatability tests conducted at 10 levels demonstrated standard deviations of generally less than 10 reproducibility tests conducted in three closely spaced drilling operations generally showed a standard deviation of less than 20 which is probably due to lateral variations in hydraulic conductivity linearity tests made to determine dependency on flow rates showed no indication of a flow rate bias in order to obtain estimates of the hydraulic conductivity by an independent means a series of measurements were made by injecting water through screens installed at two separate depths in a monitoring pipe near the measurement site these estimates differed from the corresponding estimates obtained by injection in the hollow auger by a factor of less than 3 5 which can be attributed to variations in geology and the inaccurate estimates of the distance between the measurement and the injection sites at depth

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

multi level slug tests in highly permeable formations 2 hydraulic conductivity identification method verification and field applications abstract using the developed theory and modified springer gelhar sg model an identification method is proposed for estimating hydraulic conductivity from multi level slug tests the computerized algorithm calculates hydraulic conductivity from both monotonic and oscillatory well responses obtained using a double packer system field verification of the method was performed at a specially designed fully penetrating well of 0 1 m diameter with a 10 m screen in a sand and gravel alluvial aquifer msea site shelton nebraska during well installation disturbed core samples were collected every 0 6 m using a split spoon sampler vertical profiles of hydraulic conductivity were produced on the basis of grain size analysis of the disturbed core samples these results closely correlate with the vertical profile of horizontal hydraulic conductivity obtained by interpreting multi level slug test responses using the modified sg model the identification method was applied to interpret the response from 474 slug tests in 156 locations at the msea site more than 60 of responses were oscillatory the method produced a good match to experimental data for both oscillatory and monotonic responses using an automated curve matching procedure the proposed method allowed us to drastically increase the efficiency of each well used for aquifer characterization and to process massive arrays of field data recommendations generalizing this experience to massive application of the proposed method are developed

global observations of submesoscale coherent vortices in the ocean abstract subsurface intensified anticyclones are ubiquitous in the ocean yet their impact on the large scale transport of heat salt and chemical tracers is poorly understood these submesoscale coherent vortices scvs can trap and advect waters thousands of kilometers away from the formation region providing a transport pathway that is unresolved by low resolution earth system models however knowledge of the importance of these eddies for the large scale circulation is hindered by the lack of systematic observations here we take advantage of the global network of argo floats to identify occurrences of these eddies which appear as weakly stratified anomalous water masses with gaussian shaped vertical structures we develop a general algorithm to detect subsurface eddies that have propagated away from their source region and apply it to the database of argo float profiles resulting in roughly 4000 detections from more than 20 years of observations we further group detections into regional populations to identify hot spots of generation and mechanisms of formation analysis of regional scv statistics reveals important sites of scv generation in eastern boundary upwelling systems marginal sea overflows and mode water formation regions along major open ocean fronts because of the heat and salt anomaly contained within their cores scv could leave a significant imprint on the hydrographic properties of water masses in regions of high scv density

physical properties of the variations of the electric field of the earth preceding earthquakes ii determination of epicenter and magnitude abstract as reported in the preceding paper a transient change of the electric field of the earth seismic electric signal hereafter called ses appears many hours before an earthquake eq by measuring this change in a given direction and dividing it with a suitable relative effective resistivity one obtains a quantity that reflects the current density in this direction measurements in two directions e w and n s give the relative signal intensity jrel at the station under consideration by measuring jrel at a number of stations and considering that it attenuates according to a 1 r law the epicenter can be determined with an accuracy usually around 100 km once the epicenter has been determined the product jrel r can be evaluated so that the magnitude m can be estimated by resorting to an empirical log jrel r versus m plot the uncertainty of m is around 0 5 units following sobolev 1975 and for the statistics to be beyond any doubt predictions were officially documented before the eq occurrence for 23 earthquakes with a magnitude equal or greater than ms 5 0 two events were missed the present method is compared to other electrical methods used in china japan and soviet union a number of problems concerning the origin of the effect its directivity and the attenuation with distance remain open for further studies

eddies and an extreme water mass anomaly observed in the eastern south pacific at the stratus mooring in the tropical eastern south pacific the stratus ocean reference station ors 20 s 85 5 w is located in the transition zone between the oxygen minimum zone omz and the well oxygenated subtropical gyre in february march 2012 extremely anomalous water mass properties were observed in the thermocline at the stratus ors the available eddy oxygen anomaly was 10 5 1016 mol this anomalous water was contained in an anticyclonic mode water eddy crossing the mooring site this eddy was absorbed at that time by an anticyclonic feature located south of the stratus mooring this was the largest water property anomaly observed at the mooring during the 13 5 month deployment period the sea surface height anomaly ssha of the strong mode water eddy in february march 2012 was weak and while the lowest and highest ssha were related to weak eddies ssha is found not to be sufficient to specify the eddy strength for subsurface intensified eddies still the anticyclonic eddy and its related water mass characteristics could be tracked backward in time in ssha satellite data to a formation region in april 2011 off the chilean coast the resulting mean westward propagation velocity was 5 5 cm s 1 this extremely long lived eddy carried the water characteristics from the near coastal chilean water to the open ocean the water mass stayed isolated during the 11 month travel time due to high rotational speed of about 20 cm s 1 leading to almost zero oxygen in the subsurface layer of the anticyclonic mode water eddy with indications of high primary production just below the mixed layer

intermittent existence of a southern californian upwelling cell during submillennial climate change of the last 60 kyr 1 application of a high resolution multiproxy approach to a sedimentary section drilled at ocean drilling program site 1017 located under a highly active upwelling cell off point conception california provides clear evidence for surface ocean productivity shifts on submillennial timescales during the last 60 kyr the proxies include bulk sediment major and minor elements organic carbon and carbonate concentrations 15n and planktonic foraminiferal species assemblage and carbon isotope determinations the collective results demonstrate that marine productivity in this area was not simply linearly related to cold and warm cycles except during the millennial scale climate oscillations of marine isotope stage mis 3 during that interval the upwelling cell and resulting high productivity were active during warm interstadial events and were largely inactive during cool stadial events however the last glacial maximum was also relatively productive productivity increased dramatically during the bolling warm interval while the allerod and younger dryas were much less productive high coccolithophorid abundance commenced during the earliest holocene after 10 ka the complexity of the productivity response was probably related to interplay between local winds as well as california undercurrent strength

temperature plant pigment optical relations in a recurrent offshore mesoscale eddy near point conception california the temperature plant pigment optical structure of a mesoscale anticyclonic eddy consistently found in shipboard surveys and satellite sensed data several hundred kilometers southwest of point conception california is described on three different time scales 100 day mesoscale annual and several year the satellite coastal zone color scanner czcs ocean color imagery detected the near surface chlorophyll structure of the eddy but in situ optical and plant pigment data suggest that such imagery does not provide a good estimate of the integrated chlorophyll field of the eddy the temperature and plant pigment boundaries of the eddy as determined from two dimensional gradients of advanced very high resolution radiometer avhrr and czcs imagery do not coincide spatially this and in situ temperature plant pigment and optical structure provide additional evidence that some eddy systems in the california current are not isolated vortex systems but rather continuously entrain waters of nonlocal origin laterally into their upper layers within the california current a ratio of avhrr czcs data is useful for separating inshore from oceanic water masses and following their surface entrainment by offshore vortices the historical 28 year california cooperative oceanic fisheries investigations data for the point conception region of the california current and remotely sensed data over this region show that the point conception eddy is a recurrent feature in the offshore california current moreover the available data provide evidence that a large number of warm core mesoscale eddies occur simultaneously in a transition zone between coastal and oceanic regimes that these features recur at preferred locations within the transition zone and that this family of eddies should impose a significant offshore boundary condition on the flow of the california current

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

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

measurement of anisotropic hydraulic conductivity in unconsolidated sands a case study from a shoreface deposit oyster virginia in this study an integrated field and laboratory method which can be used to evaluate the magnitude and distribution of anisotropic hydraulic conductivity at the scale of bedding structures in unconsolidated sediment is demonstrated undisturbed sediment cores 10 16 cm in diameter and 18 25 cm long are obtained using a split barrel core sampler two undisturbed 5 72 cm diameter 7 90 cm long subcores oriented parallel and perpendicular to the primary bedding structures are then obtained from each field core the hydraulic conductivities of the subcores are then measured with a constant head permeameter the sampling and experimental procedures are designed to minimize potential sources of error sixty four 10 16 cm cores were sampled in a coastal sand outcrop located 300 m from a subsurface injection experiment near oyster virginia four distinct lithologies were sampled in horizontal transects with a spacing of 0 5 m between core locations in addition iron oxide bands which were prevalent throughout the exposure were sampled from both ends of the outcrop the average hydraulic conductivity values are consistent with the observable geologic features grain size sorting and iron oxide banding hydraulic conductivity is greater in the parallel oriented subcore for 90 of the core pairs and mean hydraulic conductivity ratios of parallel to perpendicular oriented subcores k k for the different lithologies ranged from 1 33 to 1 57 the major control on the anisotropy in this sediment is interpreted to be preferential grain orientations resulting from depositional processes with additional influences from the prominence of the bedding structures and secondary features such as hydrous iron oxide banding

complementary use of glider data altimetry and model for exploring mesoscale eddies in the tropical pacific solomon sea mesoscale activity is an important component of the solomon sea circulation that interacts with the energetic low latitude western boundary currents of the south tropical pacific ocean carrying waters of subtropical origin before joining the equatorial pacific mixing associated with mesoscale activity could explain water mass transformation observed in the solomon sea that likely impacts el nino southern oscillation dynamics this study makes synergetic use of glider data altimetry and high resolution model for exploring mesoscale eddies especially their vertical structures and their role on the solomon sea circulation the description of individual eddies observed by altimetry and gliders provides the first elements to characterize the 3d structure of these tropical eddies and confirms the usefulness of the model to access a more universal view of such eddies mesoscale eddies appear to have a vertical extension limited to the surface waters sw and the upper thermocline water utw i e the first 140 150 m depth most of the eddies are nonlinear meaning that eddies can trap and transport water properties but they weakly interact with the deep new guinea coastal undercurrent that is a key piece of the equatorial circulation anticylonic eddies are particularly efficient to advect salty and warm sw coming from the intrusion of equatorial pacific waters at solomon strait and to impact the characteristics of the new guinea coastal current cyclonic eddies are particularly efficient to transport south pacific tropical water sptw anomalies from the north vanuatu jet and to erode by diapycnal mixing the high sptw salinity

a note on the prediction of the september 13 1986 strong earthquake in kalamata southwest peloponnesus greece abstract a comparison between the observed focal parameters of the september 13 1986 kalamata greece strong shock and the predicted ones shows that the prediction was quite successful as far as time of occurrence location and focal depth are concerned the discrepancy between the observed m s 6 2 and predicted m s 6 5 7 6 magnitude is attributed to the use of old seismological information and the lack of systematic observation of non seismic earthquake precursors precursors of this type observed by local people before some recent greek shocks including the kalamata earthquake indicate that their systematic monitoring could substantially contribute toward earthquake prediction in greece assuming the random model the probability that the kalamata earthquake occurred in the specified target area by chance is 0 65

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

historical and modern distributions of benthic foraminifers on the continental shelf of monterey bay california historical early 1930s and modern samples provide a detailed account of the spatial distribution of benthic foraminifers on the continental shelf of monterey bay california ten species among a total of 110 present dominated the 110 samples investigated in the historical study a cluster analysis of the foraminiferal abundances in the historical study identified five assemblages inner shelf middle shelf outer shelf southeastern shelf and southwestern shelf specimens with calcareous tests were most prevalent in all the assemblages a cluster analysis of the modern foraminiferal frequencies from 95 samples also defined five assemblages inner shelf middle shelf middle outer shelf arenaceous outer shelf and southern shelf although arenaceous taxa dominate much of the modern fauna the spatial distribution of the modern assemblages is similar to that of the historical record when presumably unrecognized taxa are eliminated from the data both the historical and to a greater degree the modern foraminiferal assemblages exhibit a strong correlation with the sediment grain size distribution

eddy properties in the california current system 1 eddy detection and tracking algorithms are applied to both satellite altimetry and a high resolution dx 5 km climatological model solution of the u s west coast to study the properties of surface and undercurrent eddies in the california current system eddy properties show remarkable similarity in space and time and even somewhat in polarity summer and fall are the most active seasons for undercurrent eddy generation while there is less seasonal variation at surface most of the eddies have radii in the range of 25 100 km sea level anomaly amplitudes of 1 4 cm and vorticity normalized by f amplitudes of 0 025 0 2 many of the eddies formed near the coast travel considerable distance westward with speeds about 2 km day consistent with the effect anticyclones and cyclones show equatorward and poleward displacements respectively long lived surface eddies show a cyclonic dominance the subsurface california undercurrent generates more long lived anticyclones than cyclones through instabilities and topographic coastline effects in contrast surface eddies and subsurface cyclones have much more widely distributed birth sites the majority of the identified eddies have lifetimes less than a season eddies extend to 800 1500 m depth and have distinctive vertical structures for cyclones and anticyclones eddies show high nonlinearity rotation speed higher than propagation speed and hence can be efficient in transporting materials offshore

the relationship between downward irradiance and upper ocean structure abstract the relationship between downward irradiance and upper ocean structure has been studied using a numerical model two general classes of irradiance parameterizations were utilized the first case i employed a single attenuation length while the second cast ii involved two attenuation lengths the latter formulation provided for enhanced absorbance in the upper few meters wind speeds of 0 1 2 3 4 5 10 and 20 m s 1 were used for the simulations in order to characterize heat versus wind dominated regimes a one dimensional second moment turbulent closure model was selected for the study so that heat could be treated differentially with depth the case ii results indicated warmer surface temperatures shallower mixed layers and more intense thermoclines than case i for wind speeds 10 m s 1 results converged for higher wind speeds there was considerably greater sensitivity to wind speed for case ii when compared with case i mean horizontal velocity as well as thermal structure was sensi

an offshore eddy in the california current system part iv plankton distributions abstract the distribution of plankton across a warm core eddy system in the california current 400 km off point conception california was studied in january 1981 the eddy system about 150 km in diameter at the 7 c isotherm was made up of a 75 m thick surface layer a cold core region extending from 75 m to about 200 m and a warm core eddy below 200 m extending to at least 1450 m casts for the vertical distribution of chlorophyll phaeophytin and integrating zooplankton net tows were taken at 37 stations located about 20 km apart on two orthogonal transects across the eddy system vertical distributions of microplankton were determined on one section from the eddy center to beyond the eastern edge integrated chlorophyll phaeophytin values were highest to the north and east of the eddy system across the system itself there was only a small increase of values near the center asymmetrical distributions of maximum concen current water was being entrained into the center of the eddy system from the northeast dinoflagellates were numerically the most important member of the microplankton especially in the deep chlorophyll maximum zooplankton distributions indicated the intermingling of warm and cool water species throughout at least the upper 200 m of the eddy system some cold water species were as abundant inside the system as outside to the north and east their numbers were much reduced in a band surrounding the system where warm water species were most abundant the presence of species characteristic of different water types throughout the region of the eddy system provides an indication of the mixing that had occurred since the system originally formed the biological data together with the physical and chemical results indicate the importance of frontal boundary processes and lateral entrainment of surrounding water into the eddy system in determining the character and productivity of such systems

physical dynamics and biological implications of cyclone noah in the lee of hawai i during e flux i abstract quasi synoptic observations of the horizontal and vertical structure of a cold core cyclonic mesoscale eddy feature cyclone noah were conducted in the lee of hawai i from november 4 22 2004 as part of the e flux interdisciplinary collaborative research program cyclone noah appears to have spun up to the southwest of the alenuihaha channel between maui and hawai i as a result of strong and persistent northeasterly trade winds through the channel shipboard hydrographic surveys 2 5 months later suggest that noah weakened and was in a hypothesized spin down phase of its life cycle although the initial surface expression of noah was limited in scale to 40 km in diameter and as evidenced by surface temperatures 2 3 c cooler than the surrounding waters depth profiles revealed a fully developed semi elliptical shallow feature 200 m 144 km long and 90 km wide based on sigma t 23 kg m 3 with tangential speeds of 40 80 cm s 1 and substantial isopycnal doming potential vorticity distribution of noah suggests that radial horizontal flow of the core water was inhibited from the surface to depths of 75 m with high vorticity confined above the sigma t 23 5 kg m 3 isopycnal surface upward displacements of isopycnal surfaces in the eddy s center 50 m were congruent with enhanced pigment concentrations 0 50 mg m 3 comparisons of the results obtained for e flux i noah and e flux iii opal suggest that translation characteristics of cyclonic hawaiian lee eddies may be important in establishing the biogeochemical and biological responses of the oligotrophic ocean to cyclonic eddies

the influence of a mature cyclonic eddy on particle export in the lee of hawaii abstract mesoscale eddies may enhance primary production pp in the open ocean by bringing nutrient rich deep waters into the euphotic zone potentially leading to increased transport of particles to depth this hypothesis remains controversial however due to a paucity of direct particle export measurements in this study we investigated particle dynamics using 234 th 238 u disequilibria within a mesoscale cold core eddy cyclone opal which formed in the lee of the hawaiian islands 234 th samples were collected along two transects across cyclone opal as well as during a time series within the eddy core during a decaying diatom bloom particulate carbon pc particulate nitrogen pn and biogenic silica bsio 2 fluxes at 150 m varied spatially and temporally within the eddy and strongly depended on the 234 th model formulation used e g steady state versus non steady state inclusion of upwelling etc particle fluxes estimated from a steady state model assuming an upwelling rate of 2 m day 1 yielded the best fit to sediment trap data these 234 th derived particle fluxes ranged from 332 14 to 1719 53 mol c m 2 day 1 27 3 to 114 12 mol n m 2 day 1 and 33 20 to 309 73 mol si m 2 day 1 although pp rates within cyclone opal were elevated by a factor of 2 3 pc and pn fluxes were the same within error inside and outside of cyclone opal the ratio of pc export to pp remained surprisingly low at 2 fluxes within the eddy core were three times higher detailed analyses of 234 th depth profiles consistently showed excess 234 th at 100 175 m associated with the remineralization and possible accumulation of suspended and dissolved organic matter from the surface we suggest that strong microzooplankton grazing facilitated particulate organic matter recycling and resulted in the export of empty diatom frustules thus while eddies may increase pp they do not necessarily increase pc and pn export to deep waters this may be a general characteristic of wind driven cyclonic eddies of the north pacific subtropical gyre and suggests that eddies may preferentially act as a silica pump thereby playing an important role in promoting silicic acid limitation in the region

main eddy vertical structures observed in the four major eastern boundary upwelling systems in the four major eastern boundary upwelling systems ebus mesoscale eddies are known to modulate the biological productivity and transport near coastal seawater properties toward the offshore ocean however little is known about their main characteristics and vertical structure this study combines 10 years of satellite altimetry data and argo float profiles of temperature and salinity and our main goals are i to describe the main surface characteristics of long lived eddies formed in each ebus and their evolution and ii to depict the main vertical structure of the eddy types that coexist in these regions a clustering analysis of the argo profiles surfacing within the long lived eddies of each ebus allows us to determine the proportion of surface and subsurface intensified eddies in each region and to describe their vertical structure in terms of temperature salinity and dynamic height anomalies in the peru chile upwelling system 55 of the sampled anticyclonic eddies aes have subsurface intensified maximum temperature and salinity anomalies below the seasonal pycnocline whereas 88 of the cyclonic eddies ces are surface intensified in the california upwelling system only 30 of the aes are subsurface intensified and all of the ces show maximum anomalies above the pycnocline in the canary upwelling system 40 of the aes and 60 of the ces are subsurface intensified with maximum anomalies extending down to 800 m depth finally the benguela upwelling system tends to generate 40 50 of weak surface intensified eddies and 50 60 of much stronger subsurface intensified eddies with a clear geographical distribution the mechanisms involved in the observed eddy vertical shapes are discussed

subtraction of the telluric inductive component from van measurements abstract in order to understand the role of electrical properties in the vicinity of van stations that have already been found to be appropriate for the collection of seismic electric signals ses a magnetotelluric mt investigation was carried out over of the entire van network we present preliminary mt results for two stations of the van telemetric network in continental greece a procedure was developed by which a real time subtraction of the telluric inductive component from the electric measurements can be made the resulting real time recording of the residual electric field allows a better identification of the ses such an example is presented for an ses that preceded a 5 5 magnitude earthquake in western greece

new chemical bio optical and physical observations of upper ocean response to the passage of a mesoscale eddy off bermuda a mesoscale eddy advected across the bermuda testbed mooring site over a 30 day period centered on july 14 1995 temperature and current measurements along with biogeochemical measurements were used to characterize the biological response of the upper ocean associated with the introduction of nitrate into the euphotic layer due to the doming of isotherms associated with the eddy complementary shipboard data showed an anomalous water mass which extended from a depth of 50 to 1000 m manifesting as a cold surface expression and warm anomaly at depth although mesoscale eddies are frequently observed in the sargasso sea the present observations are particularly unique because of the high temporal resolution measurements of the new instrumentation deployed on the mooring analyzers that measure nitrate plus nitrite were placed at depths of 80 and 200 m and bio optical sensors were located at depths of 20 35 45 71 and 86 m peak nitrate values of nearly 3 0 mm at 80 m and chlorophyll a values of 1 4 mg m 23 at 71 m were observed as well as a 25 to 30 meter shoaling of the 1 light level depth a doppler shift from the inertial period 22 8 hours to 25 2 hours was observed in several time series records due to the movement of the eddy across the mooring inertial pumping brought cold nutrient rich waters farther into the euphotic zone than would occur solely by isothermal lifting silicic acid was depleted to undetectable levels owing to the growth of diatoms within the eddy the chlorophyll a values associated with the eddy appear to be the largest recorded during the 8 years of the ongoing u s jgofs bermuda atlantic time series study bats program

influence of a quasi geostrophic flow on the deepening of the wind mixed layer the presence of a mean flow vorticity field is found to affect significantly mixed layer deepening

do upwelling filaments result in predictable biological distributions in coastal upwelling ecosystems abstract we used satellite sea surface temperature sst images and in situ zooplankton data collected in four summers of field sampling in the northern california current to address the question can the physical variables that indicate advective mesoscale circulation features e g upwelling filaments be used to infer biological distributions transects were selected from research cruises conducted when upwelling filaments were present in our study region and compared to transects occupied when filaments were not present the hydrography and distribution of several indicator species of copepods were examined along each transect sst in filaments ranged from 1 5 c to 3 0 c lower than the surrounding ocean water distributions of coastal and oceanic taxa reflected the sst patterns coastal taxa occurred offshore in higher abundances in cold upwelling filaments than in the surrounding warm ocean water in contrast species with oceanic and sub tropical affinities were most abundant where warm surface water was present biomass and species abundances varied substantially among cruises and locations and so could not be quantitatively predicted by sst patterns however upwelling filaments consistently expanded the across shelf region in which high zooplankton biomass occurred spreading the biomass from the continental shelf into offshore regions of the upwelling system we conclude with a discussion of the sampling strategies necessary to capture ecosystem variability caused by these dynamic circulation features

field study of dispersion in a heterogeneous aquifer 3 geostatistical analysis of hydraulic conductivity observations of the spatial variability of hydraulic conductivity at a tracer test site located at columbus air force base in mississippi are presented direct measurements of hydraulic conductivity of the heterogeneous alluvial aquifer at the site were made using borehole flowmeter logging slug tests and a laboratory permeameter to test undisturbed soil cores indirect methods estimating hydraulic conductivity were also evaluated including soil grain size analyses surface geophysical surveys and mapping of sediment facies the spatial covariance of the 2187 hydraulic conductivity values obtained with the borehole flowmeter method was examined the log hydraulic conductivity variance ln2k and the horizontal and vertical correlation scales h and v of 4 5 12 8 m and 1 6 m respectively were estimated assuming second order stationarity of the conductivity field the covariance parameters are uncertain with bounding values that are 24 76 above or below the estimate covariance parameters estimated with more limited nonflowmeter data were within the same magnitude as those obtained using the extensive flowmeter data suggesting that data from a variety of methods may be used to provide approximate values of the autocovariance parameters nonstationarity of the ln k field was examined by removing three dimensional polynomial trend surfaces and calculating variograms of the residuals significantly lower estimates for ln2k h and v of 2 7 4 8 m and 0 8 m respectively were obtained from the third order log conductivity residuals after trend removal the bounding parameter values differ 15 44 from the estimated values accounting for unsteady flow and the uncertainty in the covariance parameters of the third order log conductivity residuals the calculated longitudinal and horizontal transverse macrodispersivities ranged from 1 5 m to 1 8 m and 0 3 m to 0 6 m respectively

1 fα fluctuations in geoelectrical signals observed in a seismic area of southern italy abstract recent studies have shown that many natural systems display temporal fluctuations with long range power law correlations suggesting a fractal geometry of the underlying dynamical system four geoelectrical time series measured in a seismic area of southern italy are investigated by means of spectral tools in order to evidence the existence of power law correlations results show the scaling behaviour for all the signals recorded pointing to the presence of fractal features expressing a long term correlation with scaling exponents which indicate stabilizing mechanisms furthermore our findings suggest an observational evidence of correlations between the variation of parameters describing the temporal fluctuations of geoelectrical signals and earthquakes that occurred in the area investigated

the carbon dioxide system and net community production within a cyclonic eddy in the lee of hawaii abstract the dynamics of dissolved inorganic carbon dic and processes controlling net community production ncp were investigated within a mature cyclonic eddy cyclone opal which formed in the lee of the main hawaiian islands in the subtropical north pacific gyre within the eddy core physical and biogeochemical properties suggested that nutrient and dic rich deep waters were uplifted by 80 m relative to surrounding waters enhancing biological production a salt budget indicates that the eddy core was a mixture of deep water 68 and surface water 32 ncp was estimated from mass balances of dic nitrate nitrite total organic carbon and dissolved organic nitrogen making rational inferences about the unobserved initial conditions at the time of eddy formation results consistently suggest that ncp in the center of the eddy was substantially enhanced relative to the surrounding waters ranging from 14 1 10 6 0 110 m within the euphotic zone to 14 2 9 2 0 50 m within the mixed layer to 18 5 10 7 0 75 m within the deep chlorophyll maximum layer mmol c m 2 d 1 depending on the depth of integration ncp in the ambient waters outside the eddy averaged about 2 37 4 24 mmol c m 2 d 1 in the mixed layer 0 95 m most of the enhanced ncp inside the eddy appears to have accumulated as dissolved organic carbon doc rather than exported as particulate organic carbon poc to the mesopelagic our results also suggest that the upper euphotic zone 0 75 m above the deep chlorophyll maximum is characterized by positive ncp while ncp in the lower layer 75 m is close to zero or negative

remote reference magnetotellurics equipment and procedures during the past 3 years major advances in the magnetotelluric technique have improved the quality of magnetotelluric data to the point where random errors in the impedance tensor and tipper are generally smaller than the uncertainty in their interpretation the major factor in this improvement has been the introduction of the remote reference technique although the use of ultrasensitive magnetometers and minicomputers for in field data processing has also been important after a review of the remote reference technique this paper describes the equipment and procedures used for remote reference magnetotellurics by the authors magnetometers using d c superconducting quantum interference devices typically have a sensitivity of 10 14 t hz 1 2 a dynamic range of 10 7 in a 1 hz bandwidth and a slewing rate of 3 10 5 t s 1 at 10 khz the electric field measurements use conventional cu cuso 4 electrodes the remote magnetic reference signals are transmitted to the base station using fm analog telemetry the data are collected and processed by a minicomputer based on an lsi 11 microprocessor the essential results for example the apparent resistivities and the tipper components with their probable errors are available in the field practical details are given of the handling of superconducting devices low temperature cryostats and liquid helium in the field various spurious noise sources are mentioned and techniques for minimizing their effects are described

the distribution of methane in the upper waters of the southern california bight profiles of dissolved methane in the upper 300 m of a 190 000 km2 area of southern californian waters were determined during november 1989 and march 1990 methane in near surface waters ranged from 1 to 1416 nmol l 1 the lowest concentrations were at depths 200 m the highest levels were found along the coast especially in the region extending from point conception to santa barbara vertical profiles of methane are characterized by maxima in supersaturation within a narrow density band located within the pycnocline this layer is continuous over a large geographic area offshore stations exhibiting elevated levels of methane are spatially coincident with mesoscale eddies of the california current system interpretation of hydrographic and chemical data suggests that ch4 rich waters are upwelled from relatively shallow areas that are characterized by numerous hydrocarbon seeps the data are consistent with a nearshore source of methane presumably submarine seeps subsurface maxima in offshore waters are likely maintained by lateral transport of allochthonous ch4 along density surfaces from coastal waters and autochthonous microbial production

biological consequences of a recurrent eddy off point conception california the biological effects on three different time scales 100 day mesoscale annual and several year of a mesoscale anticyclonic eddy consistently found in shipboard surveys and satellite sensed data several hundred kilometers southwest of point conception california are described a detailed shipboard study of the eddy in january 1981 found a complex system of fronts in surface chlorophyll at the northern edge of the eddy microplankton and zooplankton distributions were strongly affected by entrainment processes at the surface and apparently at depth concurrent satellite coastal zone color scanner ocean color images show agreement with the general surface characteristics of the eddy chlorophyll field but do not reflect features deeper than about 25 m including the contribution of the deep chlorophyll maximum to the integrated chlorophyll values satellite data for the period october 1980 through october 1981 and shipboard data from california cooperative oceanic fisheries investigations calcofi for december 1980 to july 1981 show the continued presence of the eddy in the sea surface temperature and color field and in the distributions of surface chlorophyll and zooplankton displacement volume a review of the calcofi survey results from 1949 to the present time demonstrates the recurrent nature of the eddy system on a year to year basis the eddy system appears to have a significant effect on the distribution of both oceanic and nearshore organisms offshore transport of coastal species occurs in the form of large entrained plumes or filaments

the flow of the undercurrent over the continental borderland off southern california 1 iniroduction 2 background the bottom topography off southern california has been the cc a slow had equatornard flow is the eastern limb of termed a continental borderland to distinguish it from the ordinary the large scale anticyclonic gyre of the temperate north pacific shelf slope morphology found along most continental margins ocean the cc carries relatively cool low salinity waters of shepard and emuy 19411 islands shallow banks basins and subarctic origin to lower latitudes on average the core of the cc troughs form a complex bathymetric region extending from the has velocities of 0 10 to 0 15 m s and traces a path roughly coast to 200 lon offshore the southern california coastline has a parallel to the california baja california coastline localized concave curvature between the headland at point conception to measurements of flow can exceed 0 5 m s davis 19851 an the u s mexican border as a whole this region is referred to as instantaneous realization of the cc includes a tangle of meanders the california bight the geographic bathymetric dguration eddies and narrow jetlike flows and counterllows the cc lies at of the bight exm a pronounced influence upon the local circula varying distances off the coast and at the latitude of the tion patterns and heme upon the distributions of physical e u s mexican border there is a strong shoreward component to sverdrup and fleming 19411 and biological quantities e g the flow in most seasons especially summa the flow splits one allen 1945 owen 19801 during 1985 we conducted an oceano branch turns and flows northward into the california bight graphic survey off southern california the sampling grid was becoming the eastern limb of a cyclonic eddy centered about the designed to reveal the mumce of the geographic bathymetric offshore banks seasonally fall and winter a weak inshore features upon the circulation of the california current system countercurrent ic develops at the surface along various portion6 ccs especially the flow of the california undercurrent cu of the coastline reid et d 19581 at depth the cu cdes the survey grid also includes station lines mss the core of the waters of subtropical origin poleward along the continental slope california current cc and transects an offshore dipole eddy these waters are relatively warm and saline and have low mm simpson and lym this issue the station grid of this study trations of dissolved oxygen the cu also demonstrates a welldiffers considerably from that used by the california cooperative defined seasonality and at times opposes the overlying dace oceanic fisheries investigations calcofi surveys in both its flow maps and sections of the long term seasonal means of relaspatial resolution and depth of sampling the objectives of thic tive geostrophic velocity and distributions of ocean characteristics report are 1 to examine the spatial continuity of the cu through for the ccs are available in calcofi atlas 30 lym et d 19821 the complex bathymeny of the bight 2 to trace the poleward for a comprehensive review of the long term seasonal large scale paths and offshore spread of waters of southern origin transported description of the ccs the readex is referred to recent papas by by the cu 3 to contrast this subsurface flow with the surface hickey 1979 chelton 19841 and lynn andslnpsm 19871 and flow and 4 to compare these results with the long term calcofi to important references of pioneering work given therein mean conditions

theory of dipole flow in uniform anisotropic aquifers a theory of dipole flow is developed to model flow induced by a vertical circulation well consisting of injection and extraction chambers in a single borehole included in the theory are an analytical description of the kinematic flow structure around a vertical circulation well and the drawdown in the well chambers using stokes stream function simple criteria are derived to determine the region of intensive recirculation this region extends from the dipole center approximately five distances between chamber centers in the radial direction and two distances between chamber centers in both vertical directions the vertical scale does not depend on anisotropy of hydraulic conductivity and the radial scale is corrected for anisotropic aquifers based on these estimates criteria are given for the selection of the appropriate aquifer model to employ in five settings including infinite semi infinite confined semi infinite unconfined finite confined and finite unconfined aquifers applications of dipole flow theory are given for analytical estimation of the capture zone for recirculation wells and for simultaneous measurement of horizontal and vertical hydraulic conductivity in uniform anisotropic aquifers using steady state measurements of drawdown in the well chambers

observed evolution of a california undercurrent eddy abstracta california undercurrent eddy cuddy was repeatedly surveyed using multiple seagliders for over three months found and tracked off of the washington vancouver island coasts this cuddy t

correlation of marine and coastal terrestrial records of central california response to paleoceanographic and paleoclimatic change during the past 19 000 years new benthic foraminiferal census data combined with previously published planktic foraminiferal and pollen data from the continental margin off central california provide a unique opportunity to document concurrent paleoceanographic and paleoclimatic changes in the region during the late quaternary all three datasets were evaluated in gravity core s3 15g collected at a depth of 3491 on the western levy of the monterey fan 36 23 53 n 123 20 52 w accelerator mass spectrometry radiocarbon dates and the ratio of the planktic foraminiferal species neogloboquardrina pachyderma ehrenberg to neogloboquadrina incompta cifelli provide a good age depth model for the last 19 000 years covering the last glacial bolling allerod younger dryas and holocene intervals separate q mode cluster analyses of the hemipelagic as well as mixed combined hemipelagic and turbiditic mud samples grouped the benthic foraminiferal fauna into two clusters reflecting faunal adaptation to changing climatic conditions during the pleistocene and holocene r mode cluster analysis also differentiated glacial uvigerina senticosa and globobulimina auriculata and interglacial melonis pompilioides and gyroidina planulata faunas a general trend of slightly increasing oxygen in the deep sea is suggested from the pleistocene to holocene based on the reduction in abundance of g auriculata and increased frequency of m pompilioides q mode cluster analysis of the planktic foraminifera illustrates a change in the surface water from a glacial subpolar fauna in the pleistocene to a transitional fauna in the holocene whereas the pollen record separated into three clusters two of pleistocene age glacial and transitional and one in the holocene interglacial reflecting the terrestrial floral adaptation in the california coast ranges of central california to the warmer climate in the holocene decoupling is evident between the benthic and planktic foraminiferal and terrestrial floral responses to changing oceanographic and climatic conditions the floral response leads the surface dwelling fauna by several millennia and is followed by the deep dwelling benthic foraminiferal fauna a millennium later

the coalescence of two east australian current warm core eddies two warm core eddies coalesced in about 20 days as their centers rotated around a point on the contracting line that joined them in the process of forming the new eddy the subsurface isothermal isohaline signature layer of one eddy was uplifted and somewhat depleted while that of the other was depressed

a concept of maximum stream depletion rate for leaky aquifers in alluvial valleys 1 existing analytical models for evaluating stream depletion by wells in alluvial aquifers are based on the assumption that stream depletion supplies 100 of groundwater withdrawals analysis of specific hydrostratigraphic conditions in leaky aquifers indicates that stream depletion may range from 0 to 100 a new concept of maximum stream depletion rate msdr is introduced and defined as a maximum fraction of the pumping rate contributed by the stream depletion several new analytical solutions indicate that the msdr is determined by aquifer hydrostratigraphic conditions geometry of recharge and discharge zones and locations of pumping wells

surface manifestations of subsurface thermal structure in the california current remote sensing is useful for studying certain oceanographic problems only if the signal obtained from the sea surface contains information about subsurface structure historical bottle temperature data from the california current were analyzed for surface manifestations of vertical structure and subsurface mesoscale structure results showed that surface temperature is useful in predicting thermocline strength over a large area south of point conception the error of a regression estimate is 20 30 less than the error of the seasonal mean however surface temperature gives little useful information about mixed layer depth mesoscale patterns of temperature at the surface and at depth caused by eddies meanders and up welling are coherent r2 0 50 to a depth below the mixed layer only off central california and point conception and along the coast of baja california coherence is most likely to extend below the mixed layer during summer when the water column is strongly stratified and the mixed layer is most shallow thus some aspects of subsurface structure within limited regions of the california current have surface manifestations potentially detectable by satellite sensors

a mini slug test method for determination of a local hydraulic conductivity of an unconfined sandy aquifer abstract a new and efficient mini slug test method for the determination of local hydraulic conductivities in unconfined sandy aquifers is developed the slug test is performed in a small diameter 1 inch driven well with a 0 25 m screen just above the drive point the screened drive point can be driven from level to level and thereby establish vertical profiles of the hydraulic conductivity the head data from the test well are recorded with a 10 mm pressure transducer and the initial head difference required is established by a small vacuum pump the method described has provided 274 spatially distributed measurements of a local hydraulic conductivity at a tracer test site at vejen denmark the mini slug test results calculated by a modified dax slug test analysing method applying the elastic storativity in the dax equations instead of the specific yield are in good accordance with the results from two natural gradient tracer experiments performed at the test site the original dax the bouwer and rice and the chirlin analysing methods all led to an underestimation of the effective hydraulic conductivity by a factor of more than 2 when compared with the tracer tests in contrast the spherical flow model of karasaki et al overestimated the results of the tracer tests by approximately a factor 1 4 the dax and the cooper et al methods assuming only radial flow to the partially screened well yielded a better approximation of the horizontal hydraulic conductivity than the chirlin method which also considers axial flow this fact is suggested to be a result of aquifer anisotropy as a significant higher horizontal than vertical hydraulic conductivity may suppress the significance of the axial flow component

enhancement of seismic electric signals using magnetotellurics abstract during two field studies carried out in greece in 1986 and 1987 1988 electric precursors superimposed on the telluric field and the time dependence of the magnetotelluric apparent resistivity were studied using the magnetotelluric method applied in the frequency band of 0 00028 0 5 hz the recognition of any transient electric signal in the telluric field was improved by reducing the main part of the magnetotelluric induction by making use of a residual electric field the residual field is defined as the difference between the measured electric field and the field which is calculated by multiplying the measured magnetic field with the magnetotelluric impedance tensor in concordance with a previous study this method is shown to be rather effective one conclusion from our study is that it is practical to employ the residual field method in a continuous daily analysis within an earthquake prediction research experiment we have demonstrated that suspected electric transients are revealed as anomalies of non magnetic origin after a careful analysis in three cases significant transient electric signals were classified as suspected seismic electric signals they were clearly resolved on the residual field and all correlated well in time with three earthquakes occurring close to the stations during the time of recording

physical properties of the variations of the electric field of the earth preceding earthquakes i abstract in an earlier paper we described the physical properties of the preseismic transient variations in the electrotelluric field the present letter clarifies a few points that were not properly emphasized in our previous publications furthermore recent results like that of the destructive kalamata earthquake on september 13 1986 indicate that the duration of a preseismic electric signal may reach considerably high values lasting up to several hours

an investigation into axisymmetrization of a vortex embedded in horizontal shearing currents 1 the problem of tropical cyclogenesis in a triple scale coexisting system which includes a subtropical high ridge a preexisting cyclonic circulation with the initial maximum tangential wind vbmax of 5 m s 1 and single double or four cluster anomalies is examined in this paper using a shallow water primitive equation swpe model this work validates the recent results concerning the upscale cascade mechanism suggested for tropical cyclogenesis in the double scale coexisting system containing the basic state vortex and anomalies and it is shown that for the double cluster anomaly the mean azimuthal maximum tangential wind of the final vortex is increased and the radius of the maximum tangential wind rmw is contracted in the case of 1 388 kut 0 0 in which kut usmax vbmax with usmax being the maximum of the easterlies south of the initial subtropical ridge which demonstrates an amplification of the vortex within this range of parameter for the single cluster anomaly of large amplitude the anomaly will become a master vortex and for the four cluster one the spin up of the initial basic state vortex will be decreased compared with the case of still environmental currents introducing the subtropical ridge will have the following impact on axisymmetrization in horizontal shearing currents 1 the interaction of a single cluster anomaly with the basic state vortex will occur in the environmental currents with cyclonic vorticity when the anomaly is located initially in the sw se quadrant of the basic state vortex the interaction between the anomaly and the basic state vortex makes the spin up double that in the case of still environmental currents 2 although axisymmetrization of vortex configuration may occur it is mainly limited to the inner region of the vortex with a distinct new nonaxisymmetry in its outer region and there exist a series of cells of smaller scales in the northeastern quadrant of the outer region 3 the total kinetic energy for the inner region of the vortex in the mean increases but fluctuates with time unlike the still environmental currents case in which it increases monotonically

large scale natural gradient tracer test in sand and gravel cape cod massachusetts 3 hydraulic conductivity variability and calculated macrodispersivities hydraulic conductivity k variability in a sand and gravel aquifer on cape cod massachusetts was measured and subsequently used in stochastic transport theories to estimate macrodispersivities nearly 1500 k measurements were obtained by borehole flowmeter tests and permeameter analyses of cores the geometric mean for the flowmeter tests 0 11 cm s is similar to that estimated from other field tests the mean for the permeameter tests 0 035 cm s is significantly lower possibly because of compaction of the cores the variance for the flowmeter 0 24 is also greater than that for the permeameter 0 14 geostatistical analyses applying negative exponential models with and without nuggets reveal similar spatial correlation structures for the two data sets estimated correlation scales range from 2 9 to 8 m in the horizontal and from 0 18 to 0 38 m in the vertical estimates of asymptotic longitudinal dispersivity b 35 0 78 m are similar in magnitude to that observed in the natural gradient tracer test 0 96 m previously conducted at this site

long term evolution and dynamics of a persistent warm core eddy in the eastern mediterranean sea abstract shipboard data from seven cruises covering april 1988 october 1990 are analyzed to follow the dynamical evolution of a persistent warm core eddy located to the southeast of cyprus the eddt is characterized by an isothermal isohaline lens of water wedged between the seasonal and permanent thermoclines in the winter this thermostad extends from the surface to a depth of nearly 400 m while in other seasons it lies in the layer from 200 to 400 m the data indicate that the temperature and salinity of the core of the eddy remained constant throughout most of 1989 and then increased abruptly with a slight increase in in the winter of 1989 1990 the velocity jet usually appears between the surface and 200 m at a mean distance of 35 km from the center of the eddy speeds in the jets typically exceed 25 cm s 1 and occasionally reach 50 cm s 1 during 1989 the eddy spins down as indicated by a loss of kinetic energy this weakening permits an abrupt renewal or exchange of core water during the winter of 1989 1990 the remnants of the previous core are apparently forced to sink into the permanent thermocline where the water may be free to spread laterally if the cross isopycnal gradient of potential vorticity is weak this process could explain the cycle of levantine intermediate water formation in the centers of warm core eddies and its eventual lateral spreading finally the eddy slowly begins to spin up again in 1990

extracting the internal tide from data methods and observations from the mixed layer dynamics experiment several methods are developed for analyzing data containing a highly variable internal tide in particular the methods are aimed at the analysis of moored observations with relatively few measurements in the vertical the analysis depends upon an elliptical decomposition that is a generalization of the familiar rotary decomposition the technique is applied to velocity and temperature observations in the upper ocean made during the mixed layer dynamics experiment mildex in the northeast pacific ocean about 700 km west of santa barbara california during october november 1983 the observed propagation direction and amplitude of the internal tide was highly variable in time it was anticipated that the wave could be propagating from the continental shelf where it is presumed to be generated however most of the time the internal tide appears to be propagating parallel to the coast this result suggests the importance of density and velocity structure at mesoscale and frontal scale in affecting the propagation of the internal tide

revisiting the circulation of the east australian current its path separation and eddy field abstract the traditional view of the east australian current eac as depicted in many schematics is of a continuous boundary current that flows along the shelf off eastern australia between approximately 18 s and about 32 5 s where it separates from the coast and continues either towards new zealand along the tasman front or towards tasmania as the eac extension additionally it is widely recognised that eddies are prevalent in the eac region particularly south of the eac separation we revisit this long standing paradigm and suggest that the eac is perhaps better viewed as a continuous meandering stream flowing adjacent to the coast that feeds a field of mesoscale eddies observations show that eac eddies are prevalent over a broad region of the western tasman sea as far north as 25 s typically with maximum intensity between 30 and 35 s at any instant in time the eac jet is usually evident as a poleward stream adjacent to the continental shelf edge other commonly accepted components of the eac system including the tasman front and eac extension are rarely seen as distinct identifiable features rather these features are evident only in time mean fields when the eddy variability is filtered out it is also common for the eac to be spatially discontinuous due to the presence of eddies often with multiple short streams that sometimes separate and re attach to the coast recognition of the eac as an eddy dominated current system has seen many recent studies focus on various aspects of eddies in the eac system providing new insights into mesoscale ocean dynamics recent studies of individual eddies have shown that the circulation within eddies including tilting and vertical motion is more complex than previously understood a summary of these studies along with a review of the eac system particularly its path separation and eddy field is presented here