the strontium magnesium and sodium composition of recent scleractinian coral skeletons as standards for palaeoenvironmental analysis to establish standards for the palaeoenvironmental interpretation of scleractinian coral bearing strata the geochemistry of the three major trace element constituents of living scleractinian coral skeletons is discussed in relation to possible controls on their concentrations experiments were conducted in which the sr ca and mg ca ratios of the seawater were altered and the resultant change in skeletal composition monitored the partition coefficient of strontium ksr was shown to be linear ranging from approximately half to over ten times the normal seawater sr ca ratio increases in the magnesium concentration of seawater decreased ksr growth rates were increased through the addition of calcium and strontium but decreased by magnesium the sodium and magnesium contents of the skeleton were unaffected by their seawater concentrations relative to calcium or strontium magnesium however was affected by growth while sodium by salinity

regional primitive equation studies of the gulf stream meander and ring formation region abstract primitive equation and quasi geostrophic eddy resolving open ocean models are used for hindcast studies in the gulf stream meander and ring formation region a feature model approach is used to initialize the models based on one month of observations during november to december 1984 flat bottom and topographic calculations are carried out using an initial gulf stream velocity profile based on the pegasus dataset all of the major events observed in the upper thermocline are reproduced by both numerical models the addition of bottom topography is shown to significantly alter the character of the deep velocity fields large basin scale circulations found near the bottom in both flat bottom calculations were replaced by energetic jets and eddies associated with the dominant spatial scales of the bottom topography use of the quasi geostrophic model to dynamically adjust the initial conditions for the primitive equation model is shown to reduce the growth of large scale meanders on time scales o

circulation of tritium in the pacific ocean abstract the input of bomb tritium into the high latitude northern hemisphere waters has demonstrated the spread of a tracer in three dimensions in the north pacific ocean subsurface tritium maxima in middle and low latitudes clearly show the importance of lateral mixing along isopycnals in the upper waters the tritium pattern as mapped on isopycnal surfaces puts definite time bounds on the exchange between the subtropical anticyclonic gyre of the north pacific and both the subarctic cyclonic gyre and the system of zonal flows in the equatorial region the penetration of bomb tritium to depths below 1000 m in the western north pacific ocean shows that these waters have been ventilated at least partially in the past 17 years of the post bomb era from the tritium pattern the upper waters of the north pacific can be divided into three regions a mixed layer that exchanges rapidly with the atmosphere a laterally ventilated intermediate region between the mixed layer and at most the winter outcrop isopy

anomalous levels of 90sr and 239 240pu in florida corals evidence of coastal processes abstract strontium 90 a radionuclide whose primary source is fallout from nuclear weapons testing serves as a tritium like tracer of ocean circulation the historical record of 90 sr activities in the annual bands of island corals have been shown by other investigators to reflect the 90 sr concentration in surface waters at those site strontium 90 activities measured in annual bands in montastrea annularis from the florida keys are 30 120 higher than those in corresponding peak activity years 1960 1965 of a bermuda coral diploria the bermuda 90 sr activity record reflects the fallout source only whereas the additional 90 sr activity in the florida keys is expected to reflect a coastal runoff source as well as the fallout the coastal circulation patterns off the northern and western edge of the florida current further act to concentrate and prolong the exposure of the runoff 90 sr to the corals six measured 239 240 pu activities in the florida coral are 30 of 239 240 pu activities in island coral records previously reported since pu is expected to be scavenged by particles in coastal waters this decrease in 239 240 pu substantiates the importance of coastal influences in the florida 90 sr record strontium 90 activities measured in subannual coral bands from 1973 to 1974 reflect seasonal changes in the 90 sr concentrations in the surface layer of the coastal waters this may reflect loop current intrusion events the seasonal and long term coral 90 sr data presented in this paper suggests that coastal 90 sr coral time series may be very useful for documenting coastal circulation patterns

a census of eddy activities in the south china sea during 1993 2007 1 numerous mesoscale eddies occur each year in the south china sea scs but their statistical characteristics are still not well documented a pacific basin wide three dimensional physical biogeochemical model has been developed and the result in the scs subdomain is used to quantify the eddy activities during the period of 1993 2007 the modeled results are compared with a merged and gridded satellite product of sea level anomaly by using the same eddy identification and tracking method on average there are about 32 9 2 4 eddies predicted by the model and 32 8 3 4 eddies observed by satellite each year and about 52 of them are cyclonic eddies the radius of these eddies ranges from about 46 5 to 223 5 km with a mean value of 87 4 km more than 70 of the eddies have a radius smaller than 100 km the mean area covered by these eddies each year is around 160 170 km2 equivalent to 9 8 of the scs area with water depths greater than 1000 m linear relationships are found between eddy lifetime and eddy magnitude and between eddy vertical extent and eddy magnitude showing that strong eddies usually last longer and penetrate deeper than weak ones interannual variations in eddy numbers and the total eddy occupied area indicate that eddy activities in the scs do not directly correspond to the el nino southern oscillation events the wind stress curls are thought to be an important but not the only mechanism of eddy genesis in the scs

ocean quahogs arctica islandica and atlantic surfclams spisula solidissima on the mid atlantic bight continental shelf and georges bank the death assemblage as a recorder of climate change and the reorganization of the continental shelf benthos abstract the degree to which evidence of range shifts in shelf biomass dominants atlantic surfclams and ocean quahogs as a function of climate change is examined by comparing the dissimilarity in distribution of the living community and the record of habitation ensconced in the death assemblage comparison of the distribution of live animals and dead shells reveals for both species that live animals are rarely found where dead shells were not collected but dead shells were collected at a substantively larger number of sites than where live animals were found the geographic footprint resolved by the dead shells was much broader than that of live animals extensive spatially coherent regions exist inshore and offshore of the present day habitat of occupation where evidence of previous occupation exists sites where ocean quahog shells were found without live ocean quahogs included a portion of the continental shelf inshore of the present day habitable range an area only habitable under colder climatic conditions than observed today surfclam shells were found offshore of the present day habitable region in deeper water additional warming of bottom waters offshore would be necessary for surfclams to occupy the region now occupied solely by dead shells the death assemblage shows that these biomass dominants have repositioned themselves across the continental shelf during the past and this repositioning certainly is driven by changes in bottom water temperature moreover the distribution of surfclam shells indicates that the death assemblage may provide a possible window into the future as movement of the present day population is towards these deeper water previously occupied regions overall the death assemblage may provide an important source of information on range shifts sparing the need to carry out extensive and frequent benthic surveys and may permit reconstruction of ongoing shifts in community composition as a product of climate change when adequate survey data are not available

influence of a gulf stream warm core ring on water mass and chlorophyll distributions along the southern flank of georges bank during late spring 1997 a gulf stream warm core ring wcr strongly in uenced water mass and chlorophyll distributions along the southern ank of georges bank entrainment of georges bank shelf water by the wcr centered at the central southern ank persisted through may by late may shelf water encircled nearly the entire wcr and horizontal convergence toward the central southern ank was evident scotian shelf water ssw extended across northeast channel onto georges bank near the northeast peak and along the southern ank between the 60 m isobath and the shelfbreak front ssw extended furthest southwest along the southern ank shelfbreak satellite imagery from the ocean color and temperature sensor octs showed that by late may in addition to the high chlorophyll concentrations within the entrained shelf water encircling the wcr pigment rich bands of chlorophyll developed along the 60 and 100 m isobaths where this biological enhancement developed along 100 km of the shelfbreak 100 m isobath shelf waters extended furthest seaward due to entrainment by the wcr the enhanced shelfbreak chlorophyll was sampled in situ along two transects separated by 40 km along shelf along both transects the enhanced chlorophyll coincided with divergent cross shelf ow maximum along shelf ow and minimum surface temperature coincidence of the highest surface chlorophyll and lowest surface temperature with divergent cross shelf ow is consistent with upwelling coincidence with along shelf jets and their associated vertical shear is consistent with turbulent vertical mixing the importance of turbulent vertical mixing was supported maximum velocity at the shelfbreak coincided with the subsurface temperature minimum of ssw near 30 m depth estimated gradient richardson numbers ri above the ssw were below critical 0 25 within the shelfbreak chlorophyll maximum along both transects and surface chlorophyll was signi cantly inversely correlated with ri along the southern ank wcr entrainment of shelf water continued into june as

multi scale modeling of the north pacific ocean assessment and analysis of simulated basin scale variability 1996 2003 1 a primitive equation ocean general circulation model is used to investigate climate impacts in the north pacific ocean in the 1996 to 2003 period the objective is to assess the model ability to reproduce observed modes of variability and study their impact in the northeast pacific this work is done within the framework of the u s global ecosystem globec northeast pacific program studying the links between climate variability and ecosystem dynamics three large scale events are considered the 1997 1998 el nino the 1999 regime shift and the 2002 cold fresh subsurface anomalous water mass that was observed in the gulf of alaska and off the coast of oregon the circulation model is shown to generate the correct seasonal to interannual large scale variability and is able to represent the climatic signals of interest in the eastern pacific we show that the influence of the 1997 1998 el nino reached the coastal gulf of alaska and induced an increase in the upper ocean heat content along the coast of north america an analysis of the sea surface temperature for the model years shows agreement between model and data in the representation of the 1999 shift to a cold phase in the eastern and northern north pacific finally using the model results we speculate that the origin of the 2002 cold fresh anomaly in the northeast pacific was due to enhanced mixing during the preceding winter in the center of the alaska gyre owing to anomalous changes in the density structure of the upper ocean this water was able to move geostrophically toward the coast and it persisted in the northeast pacific below the mixed layer the following year

on the cross shelf exchange driven by frontal eddies along a western boundary current during austral winter 2007 western boundary currents are characterized by high mesoscale eddy activity including that of cyclonic frontal eddies cfes these form frequently adjacent to the shelf break export coastal water and affect biological productivity here we study the physical properties of eddies identified within the intensification zone of the east australian current eac through the analysis of remotely sensed data the application of an ocean circulation model and the evaluation of lagrangian simulations during austral winter 2007 we examine the spatial and temporal evolution of identified eddies investigate their formation mechanism and quantify the contribution made to cross shelf exchanges the mesoscale eddies are tracked from generation to decay using an eddy detection and tracking method in this case study we identify two cfes referred to as c1 and c2 with lifetimes of 11 and 38 days and radii of 45 and 70 km respectively and one anticyclonic eddy ace with a lifetime of 62 days and a radius of 60 km both cfes interact with the ace leading to quasi stationary dipole eddies located in the vicinity of the shelf this is the first time dipole eddies are reported for the intensification zone of the eac the location of cfes characterised by negative sea surface height anomaly ssha and clockwise rotation coincides with remotely sensed sea surface temperature sst and chlorophyll a chl a anomalies cfes c1 and c2 appear to contribute in different ways to the cross shelf transport along the shelf break cfe c1 drives a stronger onshore transport while cfe c2 appears to enhance the offshore transport the estimated daily cross shelf export of shelf water associated with cfe c2 is estimated with about 1 23 sv 106 km3 day 1 it renews the regional shelf water in about 7 days the lifetime of cfe c2 is about 38 days thus the eddy had the potential to flush the shelf at least five times the transient cfes were found for the first time to intensify the cross shelf exchange that is due to the wind driven cyclonic circulation of the fraser gyre this seasonally occurring gyre dominates the local shelf during austral autumn and winter the results from this study demonstrate the importance of cfes in exporting cooler and chl a enriched shelf water into the warmer and oligotrophic waters of the southward flowing eac

current meter observations on the continental slope at two sites in the eastern gulf of mexico abstract current meter observations obtained at two sites on the continental slope of the eastern gulf of mexico at nominal positions of 29 n 88 w the mobile site and 27 5 n 85 5 w the tampa site are presented data were collected at three levels at mobile 90 190 and 980 m from july 1977 through august 1978 and at four levels at tampa 150 250 550 and 950 m from june 1978 through june 1979 at 90 and 190 m the flow at mobile was on the average to the east sustained periods of flow to the west were observed during the summer 1977 and spring 1978 during the periods of eastward flow the wind was generally out of the north and during the periods of westward flow the wind was out of the east the flow at the top meter at tampa was on the average to the west in the same direction as the average wind at both sites the motions are perturbed by events associated with the loop current these events make it difficult to define any seasonal variability in the upper layers the flow at the bottom m

the geochemistry of plutonium in fresh and marine water environments abstract the chemical behaviour of plutonium in the hydrosphere is a subject of both great practical and intrinsic importance the production and eventual disposal of pu and other artificial radionuclides dictates that this be the case the main objective of this paper is to provide a synthesis and critical examination of currently published data and interpretations on the geochemistry of pu in natural waters and sediments where appropriate an attempt is made to reinterpret published data with the aim of establishing the relationships between geochemical and biological processes and the distribution concentration and speciation of pu particular attention is paid to the question of the potential for the chemical remobilization of pu from the solid to the aqueous phase approximately one third of the text deals with freshwaters mostly lakes while two thirds discusses the estuarine coastal and open ocean environments

decade time scale variability of ventilation in the north atlantic high precision measurements of bomb radiocarbon in banded corals the first high precision radiocarbon measurements for the upper ocean are presented for banded corals from two sites in the north atlantic ocean the striking dissimilarities between the post 1950 records at bermuda in the sargasso sea and the florida straits in the gulf stream illustrate the different mixing processes in the upper ocean at each site convective overturn associated with 18 degree water formation during late winter in the northern sargasso sea facilitates storage of considerable quantities of bomb radiocarbon at depth which accounts for the damping of the 14c signal at bermuda during the 1960s a multibox isopycnal mixing model is used to estimate the ventilation rate of the upper 700 m of the water column in the sargasso sea from 1950 to 1983 an inverse model is used that is the water mass renewal rate was calculated for the post bomb period in order to satisfy the bomb radiocarbon time history in the corals sea water radiocarbon measurements made during the geosecs 1972 1973 and transient tracers in the ocean 1980 1981 surveys are used to constrain the subsurface radiocarbon values calculated by the model results show that the rate of water mass renewal in the sargasso sea was high during 1963 1964 decreased during the late 1960s and remained low during most of the 1970s the 14c derived record of water mass renewal precedes by about 4 years that derived from isopycnal salinity in the sargasso sea jenkins 1982 illustrating that the coral 14c record is controlled to a large extent by changes in ocean circulation rather than by atmospheric exchange of co2

thermohaline structure transport and evolution of the black sea eddies from hydrological and satellite data abstract combination of altimetry based method of eddy identification and historical hydrological measurements for 1992 2015 is used to analyze the thermohaline and dynamic structure of the black sea eddies and its relation with eddy intensity eddy age and season of a year anticyclonic eddies aes are characterized by negative salinity anomalies which can reach 1 7 psu at the depth of the main halocline the temperature anomalies are positive in their upper layers and negative in the deeper layers because of the vertical displacement of the waters of the cold intermediate layer cil cyclonic eddies ces have the opposite structure with increased salinity colder upper layers and warmer deeper layers thermohaline anomalies in the eddies of both signs are maximal in summer while in winter they are shallowest and minimal the displacement of pycnocline in eddies causes the decrease increase of stratification in the upper layer of aes ces and opposite increase decrease in their deeper layers it also causes the deepening uplift of the layer of maximum geostrophic vertical shear in aes ces the latter is the probable reason of the observed higher intensity and deeper penetration of orbital velocities in aes than in ces the changes of isopycnals positions during the eddies lifetime are used to quantify the evolution of vertical velocity in aes and ces in the beginning of aes life during intensification phase vertical velocity is directed downward while during the decaying phase it change its sign and is directed upward the opposite is observed in ces vertical velocity is maximal at the pycnocline depth of 100 110 m with values changing from 8 to 8 10 6 m s in aes and from 5 to 25 10 6 m s in ces eddies thermohaline structure and altimetry derived orbital velocity is tightly related this relation obtained in the study and altimetry derived data on the distribution of eddy frequency translational speed and orbital velocity is used to quantify eddies salt heat content and transport in the basin the transport velocity of water in the eddies core 2 4 cm s is significantly smaller than the average velocity of the large scale currents 10 40 cm s such slowing causes the relative transport of eddies against the mean flow direction this effect leads to the accumulation of brackish and cold water in the deep layers of east black sea and maintain the observed east west asymmetry of the basin thermohaline fields

average circulation seasonal cycle and mesoscale dynamics of the peru current system a modeling approach h isolines the pccc appears to be directly forced by the cyclonic wind stress curl the model is able to produce the upwelling front the cold water tongue which extends toward the equator and the equatorial front as described in the literature model seasonal changes in sst and ssh are compared to measurements for the central pcs model eke is 10 to 30 lower than the observations the model eddy diameters follow a strong equatorward increase the injection length scales derived from the energy spectra strongly correlate to the rossby radius of deformation confirming the predominant role of baroclinic instability at 3 s the model solution appears to switch from a turbulent oceanic regime to an equatorial regime dominated by zonal currents

wind influence on the mesoscale activity along the gulf stream and the north atlantic currents two independent data sets are used to diagnose the wind effect on the mesoscale activity in the north atlantic ocean the oceanic surface variability is described with topex poseidon sea surface height measurements from october 1992 to september 1997 spatial extensions and temporal variations of high mesoscale activity are compared with the zonal and meridional components of the ers 1 wind stress the ekman pumping and the zonal sverdrupian velocity regions with high mesoscale surface variability seem to be correlated to regions with eastward sverdrupian velocities when the sverdrupian velocity is eastward and increases with time the mesoscale activity is intensified indicating a growth of instability rates theoretical and numerical results based on the interplay of barotropic eastward sverdrup flows and westward propagation of long rossby waves suggest that the wind controls western regions where baroclinic instability is favored interactions between the eddy field and the mean circulation are therefore analyzed to try to extract the instability mechanism responsible for the growth of the mesoscale activity along the gulf stream and the north atlantic current our results seem to suggest that the seasonal changes of mesoscale activity associated with eastward currents are linked to seasonal changes of the eastward sverdrupian velocity

intrusion of loop current waters onto the west florida continental shelf an intrusion of loop current water up desoto canyon and onto the west florida continental shelf to within 8 km of the shore occurred in february 1977 boat aircraft and satellite data collected in the area for another purpose were used to estimate the space and time scales of the intrusion and the ultimate fate of the intruded waters the duration of the event was 18 days oceanic waters advanced across the shelf at speeds of 20 cm s sup 1 at maximum intrusion 6650 km sup 2 of shelf were affected approximately half the intruded water receded off the shelf and half appears to have been modified in situ

seasonal and interannual changes in the north atlantic subpolar gyre from geosat and topex poseidon altimetry sea surface slopes from the altimetric satellites geosat and topex poseidon are used to calculate eddy kinetic energy of the north atlantic subpolar gyre 40 65 n 60 5 w using two years of data from each satellite december 1986 to december 1988 and october 1992 to september 1994 respectively interannual differences in the north atlantic current nac are revealed in regions of strong currents the eddies are driven by baroclinic instability of the mean flow are not seasonally varying and may therefore be used as a surrogate for the mean flow itself wind stress curl fields for the same periods show that the northward and southward shifts in the current branches across the mid atlantic ridge are related to interannual differences in the winter wind stress curl pattern when the zero in wind stress curl is well defined and wind stress is at a maximum outside the nac the eddies are driven primarily by wind stress indicated by a significant seasonality time series of eddy kinetic energy and wind stress are generated for the 4 years and the magnitude phase and significance of annual and semiannual signals are determined interannual changes in the timing of the maximum eddy kinetic energy are associated with that of the maximum wind stress with each being shifted by a month or two later or earlier throughout much of the northern north atlantic a significant annual signal in eddy kinetic energy is observed lagging the wind stress by on average 6 weeks a negligible lag is found in the region of the east greenland current and irminger sea whereas the greatest lag about 2 months is found in the labrador sea

spatial and temporal melt variability at helheim glacier east greenland and its effect on ice dynamics this is the publisher s version also available electronically from http onlinelibrary wiley com

global observations of large oceanic eddies 1 ten years of sea surface height ssh fields constructed from the merged topex poseidon t p and ers 1 2 altimeter datasets are analyzed to investigate mesoscale variability in the global ocean the higher resolution of the merged dataset reveals that more than 50 of the variability over much of the world ocean is accounted for by eddies with amplitudes of 5 25 cm and diameters of 100 200 km these eddies propagate nearly due west at approximately the phase speed of nondispersive baroclinic rossby waves with preferences for slight poleward and equatorward deflection of cyclonic and anticyclonic eddies respectively the vast majority of the eddies are found to be nonlinear

gulf stream path analysis near the new england seamounts as part of the naval ocean research and development activity s regional energetics experiment 12 inverted echo sounders iess were deployed from june 1985 to july 1986 in two arrays across the historical mean path of the gulf stream near 67 w and 58 w slightly upstream and downstream of the new england seamount chain gulf stream positions and directions were computed at half day intervals for adjacent ies pairs levels of variability at the two array locations were similar but the characteristics of the meanders in terms of propagation and current direction were quite different evidence was found for a quasi stationary meander near 58 w features deduced from ies measurements are compared with concurrent infrared air dropped expendable bathythermograph and geosat altimetry observations

fallout plutonium and natural radionuclides in annual bands of the coral montastrea annularis st croix u s virgin islands abstract we have investigated the banded coral montastrea annularis as a recorder of the history of fallout pu in surface seawater thirty annual growth bands representing growth during coral years 1951 1980 were subsampled from m annularis collected at st croix u s virgin islands coral years begin and end in late summer early autumn and are designated for the calendar year in which they end 239 240 pu was finite in coral years 1954 1980 and the coral pu record is very simply related to the fallout history of 90 sr peaks in coral pu in coral years 1959 and 1964 correspond to fallout peaks in 1959 and 1963 respectively peak broadening and time lags in the coral pu record as compared to the 90 sr fallout record are consistent with retention of fallout pu in surface seawater for about two years characteristic removal time during the period of major fallout and possibly longer thereafter the simplicity of the coral pu record and its close correspondence with fallout history suggest that 239 240 pu was incorporated into the coral skeleton with constant discrimination relative to ca the effects of speciation and oxidation state upon pu incorporation are presently unknown to aid the pu interpretation ca mg sr na and natural radionuclides 238 u 228 ra 232 th and 210 pb were also determined in the annual bands in small samples 0 5 g ca mg and na show correlated variations which could be due to seasonal variability in uptake the 238 u and 228 ra records were generally consistent with uptake at constant discrimination from surface water reservoirs of nearly constant concentration although one sample showed probable diagenetic addition of u 232 th was not detected with certainty this implies that terrigenous particles were not consistently entrapped within the coral skeleton interpretation of 210 pb was difficult because 226 ra was not measured montastrea annularis preserves a record of fallout pu to make this record useful it must be considered in the broadest possible geochemical context

energetics of eddy mean flow interactions in the gulf stream region a detailed energetics analysis of the gulf stream gs and associated eddies is performed using a highresolution multidecadal regional ocean model simulation the energy equations for the time mean and timevaryingflowsarederivedasatheoreticalframeworkfortheanalysis theeddy meanflowenergycomponents and their conversions show complex spatial distributions in the along coast region the cross stream and cross bump variations are seen in the eddy mean flow energy conversions whereas in the off coast region a mixed positive negative conversion pattern is observed the local variations of the eddy mean flow interaction are influenced by the varying bottom topography when considering the domain averaged energetics theeddy meanflowinteractionshowssignificantalong streamvariability upstreamofcapehatteras the energy is mainly transferred from the mean flow to the eddy field through barotropic and baroclinic instabilities upon separating from the coast the gs becomes highly unstable and both energy conversions intensify when the gs flows into the off coast region an inverse conversion from the eddy field to the mean flow dominates the power transfer for the entire gs region the mean current is intrinsically unstable and transfers 28 26gw of kinetic energy and 26 80gw of available potential energy to the eddy field the mesoscaleeddykineticenergyisgeneratedbymixedbarotropicandbaroclinicinstabilities contributing28 26 and 9 15gw respectively beyond directly supplying the barotropic pathway mean kinetic energy also provides 11 55gw of power to mean available potential energy and subsequently facilitates the baroclinic instability pathway

eddies in the western arctic ocean from spaceborne sar observations over open ocean and marginal ice zones the western arctic ocean is a host to major ocean circulation systems many of which generate eddies that can transport water masses and corresponding tracers over long distances from their formation sites however comprehensive observations of critical eddy characteristics are currently not available and are limited to spatially and temporally sparse in situ observations here we use high resolution spaceborne synthetic aperture radar measurements to detect eddies from their surface imprints in ice free sea surface roughness and in sea ice patterns throughout marginal ice zones we provide the first estimate of eddy characteristics extending over the seasonally ice free and marginal ice zone regions of the western arctic ocean including their locations diameters and monthly distribution using available synthetic aperture radar data we identified over 4 000 open ocean eddies as well as over 3 500 eddies in marginal ice zones from june to october in 2007 2011 and 2016 eddies range in size between 0 5 and 100 km and are frequently found over the shelf and near continental slopes but also present in the deep canada basin and over the chukchi plateau we find that cyclonic eddies are twice more frequent compared to anticyclonic eddies at the surface distinct from the dominating anticyclonic eddies observed at depth by in situ moorings and ice tethered profilers our study supports the notion that eddies are ubiquitous in the western arctic ocean even in the presence of sea ice and emphasizes the need for improved ocean observations and modeling at eddy scales

trace metals and radium in the gulf of mexico an evaluation of river and continental shelf sources abstract several studies have provided evidence for the enrichment of trace elements in coastal waters particularly for copper these enrichments have been attributed to diffusion from continental shelf sediments and to an influx of river water we attempted to resolve between these sources by undertaking an extensive suite of measurements of trace metals cu ni cd 226 ra and 228 ra in the surface waters of the gulf of mexico along with trace metal profiles at 6 stations april 1981 and december 1982 these data establish that enrichments of copper nickel and cadmium occur in the shallow waters of the gulf of mexico on the mississippi continental shelf high trace element concentrations cu ni 9 nmol kg cd 200 pmol kg in lower salinity waters 26 are similar to those observed in the mississippi plume at the same salinity this evidence suggests a river water source on the other hand trace element enrichments are also observed in the northern gulf cu 0 4 nmol kg ni 0 5 nmol kg cd 20 pmol kg which coincide with an increase in 228 ra but are not accompanied by decreased salinity the excess of evaporation over precipitation in this region makes it possible that this water could be evaporated estuarine water therefore hydrographic observations cannot distinguish readily between river and shelf sources a regional flux balance shows that most of the excess copper in the surface waters of the florida current can be supplied by the river borne dissolved copper flux within the uncertainties of such calculations the continental shelf copper flux must be less than or equal to the river flux

mesoscale eddies off peru in altimeter records identification algorithms and eddy spatio temporal patterns relatively little is known about coherent vortices in the eastern south pacific along the peruvian coast even with regard to basic facts about their frequency of occurrence longevity and structure this study addresses these issues with nearly 15 years of relatively high resolution satellite altimetry measurements we first compare two distinct automated methods for eddy identification the objective validation protocol shows that the rarely used geometrical or winding angle method based on the curvature of the streamline functions is more accurate than the commonly used okubo weiss algorithm which defines a vortex as a simple connected region with values of okubo weiss parameter weaker than a given threshold we then investigate vortices off peru using more than 20 000 mesoscale eddies identified by the winding angle method coherent eddies characterized by a high ratio of vorticity to deformation rate are typically formed along the coast and propagate westward at 3 6 cm s 1 the vortices have a mean radius of 80 km increasing northward and are most frequently observed off of chimbote 9s and south of san juan 15s the mean eddy lifetime is about 1 month but if eddies survive at least 2 months the probability for surviving an additional week or month is constant at 90 or 67 anticyclonic eddies tend to propagate northwestward whereas cyclonic vortices migrate southwestward in general cyclones and anticyclones are similar except for eddies surviving at least 6 months in this case after a similar 3 4 months of radius and amplitude growth amplitudes or sizes decay particularly rapidly for anticyclonic or cyclonic eddies in terms of intensity cyclonic eddies show a rapid decay during the first 3 months before arriving at a quasi constant value whereas anticyclones exhibit steady decline finally eddy temporal variations were examined at seasonal and interannual scales in the coastal region favorable to the formation of energetic mesoscale structures on seasonal scales eddy activity is maximal in fall and minimum in spring at interannual scales the eddy activity index was maximal during the strong el nino of 1997 1998 but another strong maximum of eddy activity also occurred late in 2004 these temporal variations are probably associated with the intensification of the upwelling thermal front and with the passage of coastal trapped waves which generate baroclinic instabilities further investigation of the mechanisms involved on the eddy genesis is needed

eddy characteristics in the eastern south pacific 1 the main eddy characteristics length scales rotation period swirl and translation velocities are determined in the eastern south pacific region 10 35 s and 70 100 w based on surface drifter measurements satellite altimetry and hydrographic data from the woce p19 section the chile peru current eddies have a typical diameter of order of 30 km smaller than the typical rossby radii observed in the region they are principally formed near the south american coast and propagate seaward with a translation velocity varying from 3 cm s 1 in the southern part of the study domain to 6 cm s 1 north of 15 s long lived anticyclonic eddies propagate northwestward with a mean angle of around 333 t whereas cyclonic vortices propagate westward consistent with the vortices propagation theory on a plane the radial distribution of the swirl velocity shows that the chile peru current eddies have a maximum diameter of order 200 km with a swirl velocity of around 14 cm s 1 and a rotation period of 50 days hydrographic data reveal a vertical extent down to around 2000 m for energetic eddies no significant difference is observed between the tangential velocities of cyclonic and anticyclonic eddies geostrophic balance can be considered for large radii whereas ageostrophic dynamics may play an important role near the eddy centers

gulf stream eddy characteristics in a high resolution ocean model 1 a detailed statistical study of the mesoscale eddy activity in the gulf stream gs region is performed based on a high resolution multidecadal regional ocean model hindcast an eddy detection and tracking method that can be used to capture eddy features from large datasets is presented this method is applied to the 50 year model hindcast within a domain with the most energetic eddy activity along the gs detection results are then analyzed to investigate the kinematic properties and temporal variability of gs mesoscale eddies the studied kinematic properties include the eddy size duration intensity propagation and spatial distribution on average cyclonic eddies are smaller in size but more energetic and remain coherent longer than anticyclonic ones cyclonic eddies generally travel further from the generation sites and have a strong tendency for westward propagation with a small equatorward deflection anticyclonic eddies remain near their generation locations and tend to propagate northward the temporal evolution of eddy properties for long lived eddies lifetime 90 days is also examined for both cyclonic and anticyclonic eddies the size increases rapidly to their maximum value within the first 20 days at which point they begin to slowly decay in terms of intensity cyclonic eddies show a quasi linear decay while the anticyclonic ones reach a quasi steady state after 3 4 months of a more rapid decay finally the seasonal variability of the gs mesoscale eddies is explored in autumn and winter both types of eddies are more numerous and larger but less intense while in spring they are more intense but less numerous and generally smaller several possible mechanisms including the wind stress thermal forcing and topographic influence are considered to explain the seasonal cycle of eddy variability

numerical modeling of an estuary a comprehensive skill assessment i numerical simulations of the hudson river estuary using a terrain following three dimensional model regional ocean modeling system roms are compared with an extensive set of time series and spatially resolved measurements over a 43 day period with large variations in tidal forcing and river discharge the model is particularly effective at reproducing the observed temporal variations in both the salinity and current structure including tidal spring neap and river discharge induced variability large observed variations in stratification between neap and spring tides are captured qualitatively and quantitatively by the model the observed structure and variations of the longitudinal salinity gradient are also well reproduced the most notable discrepancy between the model and the data is in the vertical salinity structure while the surface to bottom salinity difference is well reproduced the stratification in the model tends to extend all the way to the water surface whereas the observations indicate a distinct pycnocline and a surface mixed layer because the southern boundary condition is located near the mouth the estuary the salinity within the domain is particularly sensitive to the specification of salinity at the boundary a boundary condition for the horizontal salinity gradient based on the local value of salinity is developed to incorporate physical processes beyond the open boundary not resolved by the model model results are sensitive to the specification of the bottom roughness length and vertical stability functions insofar as they influence the intensity of vertical mixing the results only varied slightly between different turbulence closure methods of k e k and k kl

divergent pathways of cyclonic and anti cyclonic ocean eddies satellite altimetry is used to study the propagation pathways of warm and cold ocean eddies in different ocean basins we consider eddies that have a life span longer than 3 months and we present three regional studies in the southeast indian the southeast atlantic and the northeast pacific oceans the case studies show that simple theories for vortex propagation on a plane work in regions where energetic eddies propagate though a weak background flow under these conditions anticyclonic cyclonic eddies propagate westward and equatorward poleward this divergence in the eddy pathways implies a net equatorward eddy heat flux and has implications for the meridional transport of freshwater carbon nutrients etc