dynamics of eddy motions in the eastern north atlantic abstract the behavior of the intense anticyclonic eddy observed during the tourbillon experiment september november 1979 is studied within the framework of quasi geostrophic dynamics the nondivergent part of the pressure held is estimated through objective analysis at the times of four quasi synoptic ctd arrays making use as well of velocity data from the current meter mooring array and subsurface acoustic floats maps of relative vorticity vortex stretching and potential vorticity allow identification of the signature of the eddy nearby companion anomalies caused by an intrusion of mediterranean water mw can be singled out and are comparable to those of the main eddy around 1200 m eulerian and lagrangian tests of the conservation of potential vorticity are presented and the close similarities of salinity and potential vorticity as tracers of mesoscale motions are vividly demonstrated computations of advection of vortex stretching and relative vorticity show that the anticyclonic path of the mai

coupling of the surface and near bottom currents in the gulf of mexico coupling between the surface and near bottom currents in the gulf of mexico gom has been reported in many case studies however geographical variations of this coupling need more examination in this study surface geostrophic currents derived from satellite observed sea surface height and subsurface currents from a collection of deep ocean moorings are used to examine the surface and bottom coupling in different parts of the gom the short period 30 90 days fluctuations generated by the loop current lc and the lc eddies lces have a more vertically coherent structure and stronger deep ocean expressions than the long period fluctuations 90 days in addition the strength of the coupling is modulated by the long period variations of the lc and lce sheddings moreover the surface and bottom coupling varies geographically in the lc region the surface fluctuations along the eastern side of the lc are important in causing the bottom current fluctuations through baroclinic instability under the lc and through traveling topographic rossby waves trws north of the lc in the central deep gom the bottom currents are affected by the upper fluctuations of the northern lc through both local baroclinic instability and remote trw propagation in the northwestern gom the bottom current fluctuations are largely related to the remote surface variability from the west side of the lc by trws propagating northwestward this study will help us better understand mechanisms of the bottom current fluctuations that are important for the dispersal of deep ocean materials and properties

observation of internal tides in the east china sea with an underwater sliding vehicle detailed structures of internal tides in the east china sea were observed during autumn from 1986 to 1989 using an underwater sliding vehicle that can measure temperature conductivity and depth continuously sliding up and down along a faired cable a variety of structures were observed and are classified with internal froude numbers of the lowest two modes which depend on the barotropic tidal current velocities and the phase speeds of internal waves i e stratification in the central east china sea the second mode waves are most strongly generated at the shelf break and then propagate shoreward onto the east china sea continental shelf since the barotropic tidal current is faster than the phase speed of the second mode waves on the shelf the generation mechanism is consistent with conventional models on the other hand in the southern east china sea the lowest mode response is dominant although the tidal current velocity is slower than the lowest mode phase speed a nonlinear model is proposed for this response

medium term forecasting of loop current eddy cameron and eddy darwin formation in the gulf of mexico with a divide and conquer machine learning approach

loop current eddy shedding estimated using geosat altimeter data a method for extracting periodic signals from altimeter data is applied in the gulf of mexico using data from the first two years of the geosat exact repeat mission the least squares fitting of selected frequencies of sine and cosine functions to the time series of sea surface height at each point of the geosat ground track is used to estimate the dominant frequency in the gulf for this time period optimal interpolation of the sine and cosine coefficients at the dominant frequency to a uniformly spaced grid allows reconstruction of the time series in the gulf and shows eddies shedding from the loop current with a period of approximately 10 5 months consistent with shedding periods determined from numerical models and analysis of satellite infrared data this technique is a novel method for investigation of periodic signals in geosat altimetry and is not severely affected by the data outages present in the time series

loop current growth and eddy shedding using models and observations analyses of the july 2011 eddy shedding event recent studies suggest that as the trade wind in the caribbeansea weakens from summer to fall conditions become more favorable for the loop current in the gulf of mexico to shed an anticyclonic ring this idea originated with observations showing a preference for more eddies from summer through fall and it was confirmed using multidecadal model experiments here the hypothesis is further tested by studying the dynamics of a specific eddy shedding event in summer 2011 using a model experiment initialized with observation assimilated reanalysis and forced by reanalysis wind from ncep eddy shedding in july 2011 is shown to follow the weakening of the trade wind and yucatan transport in late june the shedding time is significantly earlier than can be explained based on reduced gravity rossby wave dynamics altimetry and model data are analyzed to show that empirical orthogonal function modes 1 1 2 dominate the reducedgravity process while higher modes contain the coupling of the loop current with deep layer underneath the loop s westward expansion at incipient shedding induces a deep cyclonic gyre in the eastern gulf embedded within which are small cyclones caused by the baroclinic instability of the strongly sheared current north of the campeche bank the associated deep upwelling and upper layer divergence from these cyclonic circulations accelerate eddy shedding

instabilities and multiscale interactions underlying the loop current eddy shedding in the gulf of mexico abstracta recently developed tool the multiscale window transform along with the theory of canonical energy transfer is used to investigate the roles of multiscale interactions and instabilities

on the loop current penetration into the gulf of mexico the gulf of mexico loop current generally intrudes some distance into the gulf of mexico before shedding an anticyclonic eddy and retreating back to its more direct entry to exit pathway the control of this aperiodic process remains only partially known here we describe the evolution of the loop current throughout the era of satellite altimetry and offer a mechanistic hypothesis on loop current intrusion as a complement to the known effects of loop current forcing on the west florida shelf circulation we argue that the west florida shelf in turn impacts the loop current evolution a self organizing map analysis shows that anomalous northward penetrations of the loop current into the gulf of mexico occur when the eastern side of loop current is positioned west from the southwest corner of the west florida shelf whereas the more direct inflow to outflow route occurs when the eastern side of the loop current comes in contact with the southwest corner of the west florida shelf in essence we argue that the west florida shelf anchors the loop current in its direct path configuration and that farther northward penetration into the gulf of mexico occurs when such anchoring is released to test of this hypothesis heuristically we estimate that the dissipation and buoyancy work due to known loop current forcing of the west florida shelf circulation when in contact with the southwest corner may exceed the pressure work required for the loop current to advance against the ambient gulf of mexico fluid

loop current and deep eddies abstract in contrast to the loop current and rings much less is known about deep eddies deeper than 1000 m of the gulf of mexico in this paper results from a high resolution numerical model of the gulf are analyzed to explain their origin and how they excite topographic rossby waves trws that disperse energy to the northern slopes of the gulf it is shown that north of campeche bank is a fertile ground for the growth of deep cyclones by baroclinic instability of the loop current the cyclones have horizontal vertical scales of about 100 km 1000 2000 m and swirl speeds 0 3 m s 1 the subsequent development of these cyclones consists of two modes a and b mode a cyclones evolve into the relatively well known frontal eddies that propagate around the loop current mode a cyclone can amplify off the west florida slope and cause the loop current to develop a neck that sometimes leads to shedding of a ring this process is shown to be the loop current s dominant mode of upper to deep variability

characterizing long island sound outflows from hf radar using self organizing maps abstract the surface outflows from the long island sound are examined from one year records of hf radar codar observations synoptic flow patterns are identified using manual classification empirical orthogonal function eof decomposition and self organizing maps som four characteristic flow patterns for the spring summer and fall winter seasons each are obtained through a 2 2 som array the som is confirmed by comparison with manual classification and is shown to be a significant improvement over eof classification it is suggested that the degrees of freedom of the leading eof modes can be used as a constraint on the otherwise arbitrary som dimension the relationship between the flow patterns and the winds also can be conveniently examined in som the outflows are shown to interact strongly with the ambient coastal currents both of which are under the influence of the winds this result challenges the conventional wisdom which often treats the outflows independent of the ambient currents the advantage of using som in synthesizing and interpreting synoptic hf radar observations is clearly demonstrated

anticyclonic rings in the gulf of mexico abstract using the historical data set this study describes the anticyclonic rings that separated from the loop current in the eastern gulf of mexico six quasi synoptic data sets are used to describe the evolving circulation of the gulf of mexico from october 1966 to september 1967 showing the separation and movement into the western gulf of three anticyclonic rings the historical data are used to determine that these rings typically translate to the west at a mean speed of 2 1 km day 1 their length scale as defined by their rms radii is 183 km an estimate of ring life span as defined by an e folding time is one year within the context of the gulf s water property distributions these rings appear as warm salty bodies the heat and salt added by one of these rings after separation are estimated to be 7 109 j m 2 and 17 g cm 2 respectively the heat and salt added by one of these features play an important role in the heat and salt budget of the western gulf the latter indicates that about one r

matched field processing gain degradation caused by tidal flow over continental shelf bathymetry temporally variable range dependent sound speed profiles measured during ebb flow and estimated for slack flow are used to quantify the variability of matched field signal processing gain degradation in shallow water propagation channels controlled by tidally driven stratified flow over variable bathymetry calculations along a 9 3 km range establish phase changes in the acoustic signal as the primary cause of a 3 9 db degradation in the coherent matched field processing output of a full water column vertical array the work indicates that over a tidal cycle acoustic signal properties and matched field processing gain can be expected to change continuously in a shallow water stratified channel that has bathymetry variability acoustic signals propagating in such tidal flow controlled environments may be expected to display repeatable over successive tidal cycles and predictable changes in their phase coherent properties these results suggest that matched field processor replica fields used in the shelf slope propagation environment will have to be updated regularly during a tidal cycle to maintain maximum processor gain

comparisons between a continuous 3 year current meter observation at the sill of the yucatan strait satellite measurements of gulf loop current area and regional sea level from october 1977 through november 1980 a current meter mooring was maintained in the yucatan strait the meter was moored halfway between mexico and cuba 145 m above the sill or in 1895 m of water motions of low frequency 14 1 cycles day are oriented approximately parallel to the isobaths 021 030 true net drift for 3 years is to the ssw at an average velocity of 1 8 cm s sustained southward flows at intervals of 8 months which persisted for several months each have average velocities of 5 cm s with randomly spaced bursts as high as 15 cm s energy in subtidal frequency bands has significant peaks near 38 1 and 19 1 cycles day with a broad band of energy between 300 1 and 200 1 cycles day the latter peak is consistent with the approximately 8 month interval between the southward flow events comparison with weekly areal coverage of the gulf loop current from geostationary operational environmental satellite infrared observations shows little covariation except that 8 months is typical of some anticyclonic eddy generation there is little coherence of sill depth velocities with naples sea level at subtidal frequencies but with miami there is coherence at several frequencies notably 38 1 and 19 1 cycles day in the higher frequencies the principal tidal motions are diurnal and are oriented somewhat across the isobaths toward the northwest 346 349 true with counterrotating o1 and k1 constituents no semidiurnal inertial or fortnightly energy is observed above the background continuum

loop current growth and eddy shedding using models and observations numerical process experiments and satellite altimetry data abstractrecent studies on loop current s variability in the gulf of mexico suggest that the system may behave with some regularity forced by the biannually varying trade winds the process is analyzed here using a reduced gravity model and satellite data the model shows that a biannual signal is produced by vorticity and transport fluctuations in the yucatan channel because of the piling up and retreat of warm water in the northwestern caribbean sea forced by the biannually varying trade wind the loop grows and expands with increased northward velocity and cyclonic vorticity of the yucatan current and eddies are shed when these are near minima satellite sea surface height ssh data from 1993 to 2010 are analyzed these show consistent with the reduced gravity experiments and previous studies a statistically significant asymmetric biannual variation of the growth and wane of loop current strong from summer to fall and weaker from winter to spring the asymmetry being due to the asymmetry that als

ostracoda from inland waterbodies with saline influence in central germany implications for palaeoenvironmental reconstruction abstract as a necessary precursor to reconstructing the palaeoenvironmental conditions likely to be temporarily influenced by salt bearing ground waters modern sites of central germany known from the literature to be continental salt water localities were investigated for their ostracod faunas analysing their associations enables the test of several methods in palaeoenvironmental analysis based on ostracods in total 54 ostracod taxa are documented one species microdarwinula zimmeri is new for the area interesting is the historical occurrence of cyprideis torosa and cytheromorpha fuscata typically regarded as indicators of brackish water the draining of wetlands has led to the disappearance of many former inland salt sites so that only a few of the sampled water bodies still show slightly elevated salinity oligohaline range the most important factors for the distribution of ostracod associations are groundwater influence turbidity and ecological stability whereas the type of dominating ions is of lesser importance because of time averaging using taphocoenoses from surface sediments in our study the relative proportion of ecological groups of ostracods appears to be the best tool for reconstructing past habitat types the newly established ostracod permanence index and ostracod turbulence index allow the recognition of the influx of ground and surface waters perennial habitats and flowing waters a test of the mutual ostracod temperature range motr method demonstrates its capability to reconstruct with a precision of 2 c the mean july and january air temperatures for the time interval 2002 2012 additionally the study contributes to the poorly known recent distribution of ostracods in central germany

mean surface topography of the northwest atlantic comparison of estimates based on satellite terrestrial gravity and oceanographic observations 1 the accuracy of a new mean sea surface topography msst of the northwest atlantic is assessed the msst is estimated from 12 years of altimeter observations referenced with respect to a new regional geoid based on a blend of gravity recovery and climate experiment grace terrestrial and altimeter derived gravity data the new msst is first compared to a recently published mean surface topography calculated using an eddy permitting model of the north atlantic geostropic currents calculated from the grace based msst are next compared to mean surface currents in the northwest atlantic estimated from the motion of near surface drifters corrected for surface ekman effects finally the mean path of the gulf stream is compared to the line of zero skewness of sea level variability which provides a measure of the mean path of unstable intense ocean currents overall the agreement amongst the various estimates of surface topography and circulation is excellent there are however some significant differences that can be separately attributed to problems with the msst and in some cases with the ocean model in particular the ocean climatology to which it was nudged

satellite based prediction of pco2 in coastal waters of the eastern north pacific continental margin carbon cycling is complex highly variable over a range of space and time scales and forced by multiple physical and biogeochemical drivers predictions of globally significant air sea co2 fluxes in these regions have been extrapolated based on very sparse data sets we present here a method for predicting coastal surface water pco2 from remote sensing data based on self organizing maps soms and a nonlinear semi empirical model of surface water carbonate chemistry the model used simple empirical relationships between carbonate chemistry total dissolved carbon dioxide t co2 and alkalinity talk and satellite data sea surface temperature sst and chlorophyll chl surface water co2 partial pressure pco2 was calculated from the empirically predicted t co2 and talk this directly incorporated the inherent nonlinearities of the carbonate system in a completely mechanistic manner the model s empirical coefficients were determined for a target study area of the central north american pacific continental margin 22 50n within 370 km of the coastline by optimally reproducing a set of historical observations paired with satellite data the model predicted pco2 agreed with the highly variable observations with a root mean squared rms deviation of 0 8 r 0 81 r 2 0 66 this level of accuracy is a significant improvement relative to that of simpler models that did not resolve the biogeochemical sub regions or that relied on linear dependences on input parameters air sea fluxes based on these pco2 predictions and satellite based wind speed measurements suggest that the region is a 14 tg c yr 1 sink for atmospheric co2 over the 1997 2005 period with an approximately equivalent uncertainty compared with a 0 5 tg c yr 1 source predicted by a recent bin averaging and interpolation based estimate for the same area

frequency of ring separations from the loop current in the gulf of mexico a revised estimate the most energetic events in the circulation of the gulf of mexico are the separation of large anticyclonic rings from the loop current building on previous work the authors examine all the apparent rings since july 1973 this new dataset includes the satellite altimetry since 1992 providing a set of 34 consecutive ring formations the primary advantage of altimetry is that the data remain available in the summer one finding is that the ambiguity of whether or not a ring has separated is reduced but not eliminated the uncertainty with which separation events can be specified remains approximately 4 weeks even with nearly continuous data primary peaks in the distribution of separation intervals are found at 6 and 11 months with a smaller peak at 9 months if the spectrum is smoothed heavily enough a peak in the distribution can be formed nearer 12 months but this near annual peak is a result more of the smoothing than of the data

did deepwater horizon hydrocarbons transit to the west florida continental shelf abstract hydrocarbons that originated from deepwater horizon were observed at the surface along west florida s northern coastline in june 2010 the farthest eastward advance nearly to cape san blas occurred during the last week of june before the surface oil retreated back westward and dissipated surface oil was not observed on the portion of the west florida continental shelf wfs situated to the southeast of cape san blas nevertheless there were numerous anecdotal occurrences of reef fish caught on the wfs with lesions and other deformities subsequent systematic sampling of wfs reef fish provided additional evidence for damage that extended as far south as the dry tortugas here we examine the possibility that hydrocarbons of deepwater horizon origin transited to the wfs beneath the surface we use a numerical circulation model simulation run for the entirety of 2010 and quantitatively gauged against in situ observations a passive tracer is introduced into the model to mimic the movement of subsurface hydrocarbons either dissolved or of sufficiently small particle size to effectively be dissolved the tracer driven primarily by an anomalously strong and persistent upwelling circulation eventually covered most of the wfs using reasonable estimates of what the initial tracer concentration may have been with respect to hydrocarbons we conclude that the transport of subsurface hydrocarbons to the wfs is both plausible and consistent with the observed distribution of fish lesions fish liver chemistry and other chemical and ecological evidence

west florida shelf upwelling origins and pathways often described as oligotrophic the west florida continental shelf supports abundant fisheries experiences blooms of the harmful alga karenia brevis and exhibits subsurface chlorophyll maxima evident in shipboard and glider surveys renewal of inorganic nutrients by the upwelling of deeper ocean water onto the shelf may account for this but what are the origins and pathways by which such new water may broach the shelf break and advance toward the shoreline we address these questions via numerical model simulations of pseudo lagrangian isopycnic water parcel trajectories focus is on 2010 when the west florida shelf was subjected to an anomalously protracted period of upwelling caused by gulf of mexico loop current interactions with the shelf slope origins and pathways are determined by integrating trajectories over successive 45 day intervals beginning from different locations along the shelf break and at various locations and depths along the shelf slope waters upwelling across the shelf break are found to originate from relatively shallow depths along the shelf slope even for the anomalous 2010 year much of this upwelling occurs from about 150 m and above although waters may broach the shelf break from 300 m depth particularly in the florida panhandle such interannual renewal of west florida shelf waters appears to have profound effects on west florida shelf ecology

climatology of ocean features in the gulf of mexico using satellite remote sensing data a climatology of various ocean features in the gulf of mexico gom was developed using the combination of satellite remote sensing and in situ data that spanned periods as long as 32 years twelve separate statistics were created some of which described characteristics of the loop current while others are involved with warm core rings that separate from the loop current and cold core rings these statistics examined the frequency with which the loop current was found in the gom the orientation of the loop current the frequency of intrusion of loop current water onto the west florida shelf and into the gom common water region ring separation period from the loop current ring dissipation ring speed ring path frequency of ring water in the western gom and the frequency of warm and cold core rings wcrs and ccrs respectively in the gom the results indicate that ccrs were principally responsible for mass and heat redistribution in the eastern gom egom and wcrs are responsible for mass and heat redistribution in the western gom wgom the average period for wcr separation from the loop current was 11 months and the range from 5 to 19 months wcrs moved through the wgom most often using the central path i e their trajectory was found between 24 and 26 n latitude and they decreased to about 55 of their initial size when they reach the western wall of the gom ccrs were most often found in the egom and their frequency of occurrence in the egom surpassed that of wcrs anywhere in the gom

on the global estimates of geostrophic and ekman surface currents surface currents in oceanic environments are of crucial importance because they transport momentum heat salt and tracers over large distances that regulate both the local and large scale climate conditions and because they contribute to the lagrangian displacement of floating material ranging from living resources to marine pollution in recent decades the understanding of surface currents has benefited from the opportunity of observing sea level and wind stress via satellite derived measurements combining these parameters into geostrophic and wind driven components provides an estimate of surface currents with a quarter degree horizontal resolution at a global scale and at a daily time scale in the present study improvements are made on the consideration of the time dependence of the main parameters implied in the determination of the ekman wind driven component and on the treatment of the equatorial singularity the resulting geostrophic and ekman current observatory gekco estimates were validated with independent observations from both lagrangian and eulerian perspectives the statistics of comparison were significant over the globe for the 2000 2008 period the only exception was the estimation of meridional current along the equator which requires further developments of the dynamic model and probably more accurate measurements applications using our gekco surface current estimates in cross disciplinary approaches from physical oceanography to marine ecology are presented and discussed

surface current patterns in the northern adriatic extracted from high frequency radar data using self organizing map analysis 1 a network of high frequency hf radars was installed in the northern adriatic in the second half of 2007 aimed to measure surface currents in the framework of the north adriatic surface current mapping nascum project this study includes a detailed analysis of current measurements from february to august 2008 a period in which three radars were simultaneously operational current patterns and temporal evolutions of different physical processes were extracted by using self organizing map som analysis the analysis focused on subtidal frequency band and extracted 12 different circulation patterns on a 4 3 rectangular som grid the som was also applied on a joint data set that included contemporaneous surface wind data obtained from the operational hydrostatic mesoscale meteorological model aladin hr the strongest currents were recorded during energetic bora episodes being recognized by several current patterns and having the characteristic downwind flow with magnitudes exceeding 35 cm s at some grid points another characteristic wind the sirocco was represented by three current patterns while the remaining current structures were attributed to weak winds and the residual thermohaline circulation a strong resemblance has been found between som patterns extracted from hf radar data only and from combined hf radar and wind data sets revealing the predominant wind influence to the surface circulation structures and their temporal changes in the northern adriatic these results show the som analysis being a valuable tool for extracting characteristic surface current patterns and forcing functions

on the relationship between the decadal oscillations of the northern ionian sea and the salinity distributions in the eastern mediterranean 1 we study the impact of decadal inversions of the ionian upper layer circulation denominated as adriatic ionian bimodal oscillation system on thermohaline properties of the levantine and cretan seas lagrangian drifter data and surface geostrophic currents show that the atlantic water aw flow is well organized and most intense when the ionian circulation is cyclonic during the ionian anticyclonic phase the aw spreading pathway is the longest contributing to its prolonged mixing and higher salinity once it reaches the levantine thus the levantine basin is subject to less dilution by aw during the anticyclonic surface circulation phase empirical orthogonal function analysis of the sea level shows a large amplitude circular feature in the northern ionian which matches the cyclonic anticyclonic gyre obtained from lagrangian measurements furthermore it reveals the out of phase variability of the north ionian gyre and the aegean and levantine sea levels we further show that the surface salinity of the levantine basin variation is out of phase with that of the ionian surface layers salinity variations of the deepwater column in the aegean are out of phase with the ionian surface salinity values owing probably to a fast transfer of the surface salinity changes via winter deep convection the changing of the levantine and cretan seas salinity parallel to the ionian circulation inversions suggests that the preconditioning for the eastern mediterranean transient emt is driven by internal processes as the ionian inversions are cyclical events we conclude that the emt is not an isolated episode but potentially a recurrent phenomenon

high frequency response of wind driven currents measured by drifting buoys and altimetry over the world ocean 1 we investigate the wind driven current response over the world ocean using svp drifting buoys ers 1 and ers 2 and topex altimetry data and ecmwf wind stress fields wind driven ageostrophic currents are estimated from drifting buoys by removing altimetry deduced geostrophic currents from observed drifting velocities removing the geostrophic signal enhances the coherence with wind stress at periods longer than 10 days for superinertial periods lower than 20 days a two parameter i e angle and amplitude model is fitted to the isolated ageostrophic signal to study the upper ocean response to surface wind stress in that frequency band the model which can explain up to 30 of the variance in some areas indicates that the currents spiral to the right left of the wind with depth in the northern southern hemisphere in agreement with the ekman theory the absolute value of the angle parameter is found to exhibit significant spatial and seasonal variability the vertical eddy viscosity and the ekman layer depth as deduced from ekman theory are compared to previous results their seasonal variability is also studied model results are then used to compute the mean and standard deviation of ageostrophic currents in 5 boxes over the world ocean the equatorial divergence and the subpolar and subtropical convergence zones are well reproduced

effect of ocean currents on the performance of a time reversing array in shallow water active acoustic time reversal may be accomplished by recording sounds with an array of transducers a time reversing array tra or time reversal mirror trm and then replaying the recorded and time reversed sounds from the same array to produce back propagating waves that converge at the location s of the remote sound source s future active sonar and underwater communication systems suitable for use in unknown shallow ocean waters may be developed from the automatic spatial and temporal focusing properties of tras however ocean currents affect time reversal because they alter acoustic reciprocity in the environment this paper presents a theoretical and computational investigation into how ocean currents influence tra retrofocusing in shallow ocean environments for various array orientations the case of tra retrofocusing in a three dimensional range independent sound channel with a steady horizontal ocean current is covered here based on a normal mode propagation model valid for low mach number currents the main finding is that in the presence of ocean currents typically 1 m s a tra performs well the associated retrofocus amplitude decay is less than 1 db except that a retrofocus shift up to a few wavelengths at 500 hz at a range of 2 5 km may occur due to the differing interaction between the ocean current profile and each acoustic normal mode in addition tra performance is predicted to depend on the array orientation relative to the ocean current direction especially for horizontal arrays

temporal variability of the antarctic circumpolar current observed from satellite altimetry sea level measurements by the seasat altimeter were used to study the temporal variability of the antarctic circumpolar current between july and october 1978 large scale zonal coherence in the cross stream sea level difference was observed indicating a general increase in the surface geostrophic velocity of the current around the southern ocean the result demonstrates the power of satellite altimetry to monitor the variability of large scale ocean currents

variability in satellite winds over the benguela upwelling system during 1999 2000 1 wind stress variability over the benguela upwelling system is considered using 16 months 01 august 1999 to 29 november 2000 of satellite derived quikscat wind data variability is investigated using a type of artificial neural network the self organizing map som and a wavelet analysis the som and wavelet analysis are applied to an extracted data set to find that the system may be divided into six discrete wind regimes the wavelet power spectra for these wind regions span a range of frequencies from 4 to 64 days with each region appearing to contain distinct periodicities to the north 10 23 5 s the majority of the power occurs during austral winter with a 4 16 day periodicity further investigation of national centers for environmental prediction reanalysis outgoing longwave radiation data indicates that the winter intensification of wind stress off the angolan coast is linked with convective activity over equatorial west africa the summer activity appears to be linked with the intensification of the angolan heat low convective activity over the congo basin appears to impact upon wind stress variability off the angolan coast throughout the year farther south 24 35 s the majority of the power occurs in the summer here a bimodal distribution occurs with peaks of 4 12 and 25 50 days the southernmost regions appear to be forced at higher frequencies by both midlatitude cyclones austral winter and mesoscale coastal lows austral summer at lower frequencies eastward propagating periodic wind events that originate over eastern south america appear to be important to the forcing of wind stress over the southern benguela

combining altimeter and subsurface float data to estimate the time averaged circulation in the upper ocean 1 a new technique is presented for estimating time averaged upper ocean geostrophic velocity from a combination of altimeter data and subsurface float data the technique makes uses of the strong relationship between sea surface height anomaly and anomalous velocity at depth to reduce mesoscale eddy variability in subsurface float displacements the technique is demonstrated on a region in the north atlantic that was well sampled by argo floats the 2004 through 2006 time averaged density field was estimated from the surface to 2000 db by combining altimeter and hydrographic data from the floats in addition a reference velocity field was estimated at 1000 db based on a combination of altimeter data and subsurface float displacements the reference velocity field was combined with geostrophic shear based on the density field to produce a three dimensional estimate of geostrophic velocity from the surface to 2000 db the gulf stream transport in the upper 2000 db is estimated to be 76 sv at 73 w in addition an estimate of the 3 year average dynamic height at the surface was computed by combining the 1000 db reference dynamic height and the time averaged density field

intraseasonal variability associated with wet monsoons in southeast arizona the intraseasonal evolution of the north american monsoon in southeast arizona during the 1980 93 period is investigated using a neural network based nonlinear classification technique known as the self organizing map som the goal of the som algorithm is to discover meaningful low dimensional structures hidden in the high dimensional observations various daily lagged atmospheric fields 850 hpa meridional winds 700 hpa specific humidity 500 hpa geopotential heights and 850 500 hpa thickness for the summer season june july august september of the 1980 93 period are used in the nonlinear classification of monsoon modes special emphasis is given to the wettest monsoon modes the neural network classification successfully captures the multidimensional interaction of the atmospheric variables during the monsoon evolution and shows monsoon bursts and breaks in a given year spectral analysis of daily summer rainfall in the study area reveals a significant peak in the 12 18 day band a secondary and significant peak is also found near 40 days thus monsoon bursts and breaks seem to be modulated by low frequency variability the som nonlinear classification shows that the mature phase of the monsoon is associated with two distinct intraseasonal 10 days wet monsoon modes the signature of the wettest monsoon mode is a zonal three cell anomalous midtropospheric height pattern over the north pacific north american sector suggesting a largescale dynamical mechanism possibly linked to sea surface temperature sst anomalies in the north pacific this zonal mode which is most frequent in july and august is characterized by an enhanced and northeastwarddisplaced monsoon ridge large amounts of midtropospheric moisture over the study area and an out of phase relationship between precipitation in the southwest united states and precipitation in the great plains the zonal mode has been recognized in longer datasets and it is the most typical mode that characterizes the mature phase of the monsoon in the southwest united states in contrast the second wettest intraseasonal monsoon mode does not show a monsoon ridge but a meridional three cell anomalous midtropospheric height pattern along the west coast of north america weak height anomalies over the rest of north america and large amounts of moisture over the study area importantly this meridional mode which is most frequent in august and september does not show out of phase links to great plains precipitation the meridional wet mode also shows an anomalous low level cyclonic circulation off the west coast of central south mexico suggesting that convective activity off the southern mexican coast possibly associated with the intertropical convergence zone may cross over the isthmus of tehuantepec toward the gulf of mexico and the southern united states this would explain the weak link between precipitation in the southwest and precipitation in the great plains during august and september of the 1980 93 period at more regional scales the zonal wet mode is also characterized by a latitudinal gradient of sst anomalies between baja california and southern mexico and reversed low level flow over the gulf of california looking at extreme wet monsoons outside of the study period e g 1955 1959 1999 it is shown that the positive sst anomaly pattern along the pacific coast of baja california which characterized wet events during 1980 93 can be completely reversed during other extreme wet events these contrasting results suggest that interaction between local and remote forcing mechanisms over the study area are complex during extreme events and needs further investigation

mapping of oceanographic properties along a middle adriatic transect using self organising maps abstract this paper examines oceanographic properties along the northern portion of the palagru a sill middle adriatic sea from 1998 to 2011 temperature salinity dissolved oxygen do total inorganic nitrogen tin and orthophosphate concentrations were collected at four stations on a seasonal basis and monthly basis spanning from coastal waters to the deepest part of the sill seasonal profiles and variances were computed exhibiting no strong seasonal variability in either coastal or open adriatic waters except for temperature the transect profiles were analysed using the self organising maps som method which extracted two regimes with several transitional patterns characterized by an anomaly in one or more variables these regimes match the bimodal adriatic ionian oscillation bios regimes in the northern ionian sea which are found to drive decadal oscillations in oceanographic parameters in the adriatic as the transect mainly encompasses the euphotic zone no strong connection was found between bios regimes and do tin and orthophosphate concentrations this suggests that in addition to basin wide circulation other physical and biogeochemical processes are more important for nutrient dynamics in the euphotic zone the use of the som method in ocean coastal studies is discussed

the surface circulation of the caribbean sea and the gulf of mexico as inferred from satellite altimetry the surface circulation of the caribbean sea and gulf of mexico is studied using 13 years of satellite altimetry data variability in the caribbean sea is evident over several time scales at the annual scale sea surface height ssh varies mainly by a seasonal steric effect interannually a longer cycle affects the ssh slope across the current and hence the intensity of the caribbean current this cycle is found to be related to changes in the wind intensity the wind stress curl and el nino southern oscillation at shorter time scales eddies and meanders are observed in the caribbean current and their propagation speed is explained by baroclinic instabilities under the combined effect of vertical shear and the b effect then the loop current lc is considered focusing on the anticyclonic eddies shed by it and the intrusion of the lc into the gulf of mexico through time twelve of the 21 anticyclonic eddies observed to detach from the lc are shed from july to september suggesting a seasonality in the timing of these events also a relation is found between the intrusion of the lc into the gulf of mexico and the size of the eddies shed from it larger intrusions trigger smaller eddies a series of extreme lc intrusions into the gulf of mexico when the lc is observed as far as 928w are described the analyses herein suggest that the frequency of such events has increased in recent years with only one event occurring in 1993 versus three from 2002 to 2006 transport through the straits of florida appears to decrease during these extreme intrusions

late quaternary salinity variation in the lake of siebleben thuringia central germany methods of palaeoenvironmental analysis using ostracoda and pollen we test several methods of ostracod based palaeoenvironmental reconstruction using indicator species approach mutual ecological climatic range methods transfer functions modern analogue techniqu

extreme cooling and dense water formation estimates in open and coastal regions of the adriatic sea during the winter of 2012 generation of dense waters in the adriatic sea during an extreme cooling event in the winter of 2012 including its preconditioning and spreading phases have been investigated using the one way coupled roms and the aladin hr modeling system both climatological and real river fluxes are used in the simulations aside from the convenient dense water formation areas located at the northernmost adriatic shelf we found that a similar amount of dense water with slightly lower density was formed in the eastern and deeper adriatic coastal area which was subjected to extreme heat losses up to 2000 w m2 during peak cooling periods this part of the adriatic has been known for extreme cooling during wintertime bora outbreaks nevertheless no ocean model study has previously reproduced dense water formation in this area the most likely reason for that was an overestimate of river discharges introduced to ocean models from newly available data we estimated that the contribution of eastern adriatic rivers between the neretva river and rijeka bay is more than six times lower than what has been previously documented transport of dense water toward the middle adriatic had a peak value of about 0 6 sv while the speed of initial bottom density current surpassed 40 50 cm s which is several times faster than past events different pathways of the dense water toward the middle and south adriatic depressions have also been documented the contribution of the eastern coastal adriatic area to the overall north adriatic dense water formation has been quantified and discussed for average and low freshwater load conditions indicating that this part of the adriatic is a common place for dense water generation

eddy mean flow interaction in the decadally modulating kuroshio extension system abstract satellite altimeter sea surface height ssh data of the past 16 years are used to investigate the decadal changes of the kuroshio extension ke system that oscillated between a stable and an unstable dynamic state during the stable state of 10 1992 06 1995 and 01 2002 12 2004 the ke jet was intense and had a northerly zonal mean path and a well defined southern recirculation gyre during the unstable state of 07 1995 12 2001 and 01 2005 present the ke jet had a reduced eastward transport and a more southerly flow path transitions between the two dynamic states are caused by the basin scale wind stress curl forcing in the eastern north pacific related to the pacific decadal oscillations pdos or the north pacific gyre oscillations npgos during the positive pdo or negative npgo phase the intensified aleutian low generates negative ssh anomalies in the eastern north pacific through ekman divergence as these wind induced negative ssh anomalies propagate to the west as baroclinic rossby waves they weaken the zonal ke jet and shift its path southward as its path is pushed southward 32 n the deep reaching ke jet has to ride over the shallow shatsky rise generating localized disturbances that lead to their subsequent development along the ke jet west of the shatsky rise the sequence opposite to that listed above occurs when the pdo npgo changes to its negative positive phase after the ke system transitions from a stable to unstable state the enhanced eddy interaction is found to strengthen both the southern recirculation gyre and quasi stationary meanders along the ke s upstream path this nonlinear eddy interaction is important in determining the amplitude of the observed decadal ke variability

large scale ocean circulation from the grace ggm01 geoid 1 the grace gravity model 01 ggm01 computed from 111 days of grace k band ranging kbr data is differenced from a global mean sea surface mss computed from a decade of satellite altimetry to determine a mean dynamic ocean topography dot as a test of the ggm01 gravity model large scale zonal and meridional surface geostrophic currents are computed from the topography and are compared with those derived from a mean hydrographic surface reduction in residual rms between the two by 30 60 and increased correlation indicates that the ggm01 geoid represents a dramatic improvement over older geoid models which were developed from multiple satellite tracking data altimetry and surface gravity measurements for the first time all major current systems are clearly observed in the dot from space based measurements

stationary mesoscale jet like features in the ocean 1 xbt and float data of the world ocean database 2005 are used to validate new stationary jet like features striations recently found in the high resolution mean dynamic ocean topography mdot two study areas were selected in the eastern parts of the north and south pacific subtropical gyres free of any strong currents appropriate horizontal high pass filtering applied to the ensemble mean temperature at 100 m depth revealed the striation signal coherent with mdot the features are also distinct in the data of depth of 12 c isotherm lying close to the thermocline the striations are oriented nearly zonally and coherent vertically at least through 700 m depth their wavelength is approximately 400 km and the azimuth of wavevector is 13 9 in the northern southern domains correspondence between the striations in observations and ofes ogcm for the earth simulator model as well as the nature of the striations are discussed

what can we learn from global altimetry hydrography comparisons differences and complementarities between altimeter and hydrographic data are studied to describe the sea level and ocean circulation variations in terms of steric and non steric contributions altimeter sea level anomalies sla and hydrographic dynamic height anomalies dha agree remarkably well they also reveal however systematic large scale differences in several areas of the pacific and indian oceans that are related to a barotropic sverdrup like response of the ocean to wind forcing in addition the use of the two data sets provides a good estimation of the partition between barotropic and baroclinic modes needed for data synthesis or assimilation studies

dense water formation and bios induced variability in the adriatic sea simulated using an ocean regional circulation model a performance analysis of the nemomed8 ocean regional circulation model was undertaken for the adriatic sea during the period of 1961 2012 focusing on two mechanisms dense water formation dwf and the adriatic ionian bimodal oscillating system bios which drive interannual and decadal variability in the basin the model was verified based on sea surface temperature and sea surface height satellite measurements and long term in situ observations from several key areas the model qualitatively reproduces basin scale processes thermohaline driven cyclonic circulation and freshwater surface outflow along the western adriatic coast dense water dynamics and the inflow of ionian and levantine waters to the adriatic positive temperature and salinity biases are reported the latter are particularly large along the eastern part of the basin presumably because of the inappropriate introduction of eastern adriatic rivers into the model the highest warm temperature biases in the vertical direction were found in dense water collecting depressions in the adriatic indicating either an inappropriate quantification of dwf processes or temperature overestimation of modelled dense water the decadal variability in the thermohaline properties is reproduced better than interannual variability which is considerably underestimated the dwf rates are qualitatively well reproduced by the model being larger when preconditioned by higher basin wide salinities anticyclonic circulation in the northern ionian sea was modelled only during the eastern mediterranean transient no other reversals of circulation that could be linked to bios driven changes were modelled

acoustic propagation under tidally driven stratified flow amplitude and phase variability in acoustic fields are simulated within a canonical shelf break ocean environment using sound speed distributions computed from hydrodynamics the submesoscale description of the space and time varying environment is physically consistent with tidal forcing of stratified flows over variable bathymetry and includes the generation evolution and propagation of internal tides and solibores for selected time periods two dimensional acoustic transmission examples are presented for which signal gain degradation is computed between 200 and 500hz on vertical arrays positioned both on the shelf and beyond the shelf break decorrelation of the field is dominated by the phase contribution and occurs over 2 3min with significant recorrelation often noted for selected frequency subbands detection range is also determined in this frequency band azimuth time variations in the acoustic field are illustrated for 100hz sources by extending the acoustic simulations to three spatial dimen

can internal processes sustain reversals of the ocean upper circulation the ionian sea example 1 in 1997 an inversion in the ionian upper layer circulation was documented and ascribed to a massive inflow of aegean dense waters associated with the eastern mediterranean transient emt and not to the wind stress borzelli et al 2009 here we generalize the concept hypothesizing that such inversions are possible even in the absence of the aegean influence indeed salinity and density data collected in the southern adriatic the main source of the eastern mediterranean deep water show decadal variations coherent with changes in the sea level height in the northern ionian scaling considerations suggest that the redistribution of ionian water masses resulting from changes in the thermohaline properties of waters entering the basin can sustain inversions of the upper layer circulation therefore we propose a feedback mechanism named the adriatic ionian bimodal oscillating system bios between variations in the thermohaline properties of waters formed in the southern adriatic and the ionian circulation

patterns of the loop current system and regions of sea surface height variability in the eastern gulf of mexico revealed by the self organizing maps the self organizing map som an unsupervised learning neural network is employed to extract patterns evinced by the loop current lc system and to identify regions of sea surface height ssh variability in the eastern gulf of mexico gom from 23 years 1993 2015 of altimetry data spatial patterns are characterized as different lc extensions and different stages in the process of lc eddy shedding the temporal evolutions and the frequency of occurrences of these patterns are obtained and the typical trajectories of the lc system progression on the som grid are investigated for an elongated northwest extended or west positioned lc it is common for the lc anticyclonic eddy lce to separate and propagate into the western gom while an initially separated lce in close proximity to the west florida continental slope often reattaches to the lc and develops into an elongated lc or reduces intensity locally before moving westward as a smaller eddy regions of differing ssh variations are also identified using the joint som wavelet analysis along the general axis of the lc ssh exhibits strong variability on time scales of 3 months to 2 years also with energetic intraseasonal variations which is consistent with the joint empirical orthogonal function eof wavelet analysis in the more peripheral regions the ssh has a dominant seasonal variation that also projects across the coastal ocean the som when applied to both space and time domains of the same data provides a powerful tool for diagnosing ocean processes from such different perspectives

dnsc08 mean sea surface and mean dynamic topography models 1 the danish national space center data set dnsc08 mean sea surface mss is a new enhanced mapping of the mean sea surface height of the worlds oceans derived from a combination of 12 years of satellite altimetry from a total of eight different satellites covering the period 1993 2004 it is the first global mss without a polar gap including all of the arctic ocean by including laser altimetry from the icesat mission the mean dynamic topography mdt is the quantity that bridges the geoid and the mean sea surface constraining large scale ocean circulation here we present a new high resolution 1 min global mdt called dnsc08 mdt derived from the slightly smoothed difference between the dnsc08 mss and the egm2008 geoid the derivation and quality control of the new dnsc08 mss and dnsc08 mdt is presented in this paper along with suggestions for time period standardization of the mss and mdt models this way a consistent modeling of the interannual sea level variability is carried out before different mss and mdt models are compared altimetric derived physical mss can be converted into an inverse barometer corrected mss by correcting the altimeter range for the inverse barometer effect of the atmosphere on the sea surface height it is demonstrated that it is important to choose the right version of the mss when comparing with hydrodynamic models and gps measured tide gauges

interaction between the east china sea kuroshio and the ryukyu current as revealed by the self organizing map 1 the self organizing map som is used to study the linkage between the two western boundary currents the kuroshio current and the ryukyu current through the kerama gap four coherent ocean current patterns extracted from a numerical model output for the kerama gap area are used to describe the variability of the kuroshio current axis and the mesoscale eddies in the ryukyu current system the temporal evolution of these four patterns shows a robust cycle with an average period of 120 days the shift of the kuroshio current axis is found to be a dominant factor in determining the water exchange in the kerama gap and the eddies associated with the ryukyu current are also important in affecting the strength of eddies in the kerama gap the interaction between the kuroshio current and the ryukyu current through the kerama gap as revealed by the som provides new insights in understanding the water exchange between the east china sea and the northwest pacific

patterns of ocean current variability on the west florida shelf using the self organizing map 1 patterns of ocean current variability are examined on the west florida shelf by a neural network analysis based on the self organizing map som using time series of moored velocity data that span the interval october 1998 september 2001 three characteristic spatial patterns are extracted in a 3 4 som array spatially coherent southeastward and northwestward flow patterns with strong currents and a transition pattern of weak currents on the synoptic weather timescale the variations of these patterns are coherent with the local winds on the seasonal timescale the variations of the patterns are coherent with both the local winds and complementary sea surface temperature patterns the currents are predominantly southeastward during fall winter months from october to march and northwestward during summer months from june to september the spatial patterns extracted by the nonlinear som method are asymmetric a feature that is not captured by the linear empirical orthogonal function method thus we find for the synoptic weather and longer timescales that 1 southeastward currents are generally stronger than northwestward currents 2 the coastal jet axis is located further offshore for southeastward currents than for northwestward currents and 3 the velocity vector rotations with depth are larger in shallower water when the currents are southeastward relative to when the currents are northwestward

mean mesoscale global ocean currents from geodetic pre goce mdts with a synthesis of the north pacific circulation 1 a new milestone in satellite geodesy is about to be completed with the expected availability of the high resolution data from the already in orbit global ocean circulation explorer goce satellite there are still some open questions related to capability of recovering mean mesoscale 50 km plus geostrophic circulation mgc patterns from observational gravity recovery and climate experiment grace based geodetic mean dynamic topography mdts which we examine here in detail a new set of global geodetic mdts with high grid resolutions was computed 0 1 and 0 25 based on the newest egm08 and grace ggm02 geoid models the high resolution coupled to good mesoscale feature discrimination was derived using efficient filtering procedure based on singular spectrum analysis the new solutions were contrasted with five important mdts including the hybrid and the geodetic mdts through empirical orthogonal functions analysis which permit the determination of the mutual correlation among the mdts and establishment of error bounds the methodology made viable a detailed and robust analysis of the north pacific ocean circulation based on these mgcs including comparisons with known results from other studies we prove the superiority of the geodetic egm08 as opposed to hybrid mdt models by obtaining less noisy and more intense and slender western boundary currents and their recirculations the bifurcations at the shatsky rise and the known mean eddies in the low latitude shear region nec necc

ocean currents and sea surface heights estimated across the west florida shelf abstract the across shelf structures of the ocean circulation and the associated sea surface height ssh variability are examined on the west florida shelf wfs for the 3 yr interval from september 1998 to december 2001 five sets of characteristic circulation patterns are extracted from 2 day low pass filtered data using the self organizing map extreme upwelling and downwelling structures with strong currents asymmetric upwelling and downwelling structures with moderate currents and a set of transitional structures with weak currents the temporal variations of these structures are coherent with the local winds on synoptic weather time scales on seasonal time scales they are related to both the local winds and the water density variations the circulation is predominantly upwelling during autumn to spring months october april and downwelling during summer months june september coastal sea level fluctuations are related to both the dynamical responses of the inner shelf circulation to meteorol

cyclonic activity in the eastern gulf of mexico characterization from along track altimetry and in situ drifter trajectories abstract the shedding sequence of the loop current lc inside the gulf of mexico gom is strongly influenced by cyclonic frontal eddies around its edge along track altimetry data analyzed based on a wavelet decomposition to provide estimates of individual cyclones diameter amplitude and relative vorticity and in situ surface drifter data from the global drifter program are used to investigate the cyclonic activity in the eastern gulf of mexico where the lc extends and retracts by analyzing this 20 year long 1992 2011 combined set of observation data records we were able to complement previous findings to confirm results from modeling studies and to provide new insights on the lc frontal dynamics drifter data indicate for the first time that loop current frontal eddies lcfes are in solid body rotation close to their core this property makes relative vorticity the most robust diagnostic from along track altimetry for characterizing lcfes in the eastern gom based on consistent comparisons with drifter data both data sets are complementary for describing the lcfes regional variability lcfes observed in the deep southeastern gom show intense relative vorticity but they are not frequently observed the study of an unprecedented long drifter trajectory suggests that they are not intensified locally this implies that among lcfes coming from the northern gom only intense ones reach the deep southeastern gom the observation datasets provide for the first time quantitative evidences of processes so far only identified with models lcfes are intensified when they are advected over the mississippi fan in the northern gom a small area north of campeche bank shows intense lcfe activity the altimetry and drifter data confirm and complement results from more limited datasets lcfes forming the tortugas eddies at the entrance of the straits of florida are the most intensely observed lcfes in altimetry coming from the gom interior they can be modified in size and intensity just before or during their stay in the dry tortugas area whereas they were long considered to be modified only after they were advected in the straits of florida a single drifter trajectory illustrates in detail the erosion of a lcfe in the southeastern gom presumably under the influence of the lc which leads to the re arrangement of vorticity and the formation of a distinct lcfe just upstream the dry tortugas area the study also confirms that lcfes have diameters of 80 120 km generally larger east and north of the lc they tend to stay for long periods in the northeastern gom and thus may undergo vortex merging with incoming eddies as previously noted on individual episodes altimetry reveals that the largest lcfes reside in the central eastern gom in a location where they are known to block the lc extension however our long altimetry dataset shows that these large eddies are not always involved in such lc blocking finally this study led to improvements in data treatment for both along track altimetry and drifter trajectories the wavelet approach used to derive eddy characteristics from along track altimetry allows robust estimates of the eddy relative vorticity the drifter dataset has been extended to include data from drifters even after they lost their drogue the latter data treatment can be applied in areas of moderate winds

dynamics of benthic marine communities across the early middle pleistocene boundary in the mediterranean region valle di manche southern italy biotic and stratigraphic implications abstract the valle di manche vdm section calabria southern italy offers the opportunity to investigate the ostracod turnover along a continuous shelf succession straddling the early middle pleistocene boundary and compare it against other paleoenvironmental i e mollusks and paleoclimatic uvigerina peregrina 18o records high resolution ca 1 sample m ostracod fauna quantitative data coupled with gradient analysis detrended correspondence analysis and non metric multi dimensional scaling document a strong relationship between changes in faunal composition and lithofacies vertical stacking patterns the comparison between the mollusk and ostracod derived ordination data demonstrates that the meio and macro faunal turnover is guided by a common complex gradient bathymetry the integrated ostracod mollusk gradient analysis also provides a trend in water depths along the section highlighting to what extent such multivariate approach can improve the paleoenvironmental and sequence stratigraphic interpretation of ancient shallow marine successions when plotted stratigraphically ordination major axis sample scores reveal two increasing decreasing patterns in water depth that fit well with the t r cycles previously identified paleobathymetric estimates combined with the vertical distribution of key ostracod groups i e epiphytic taxa on sandy substrates vs deep sea mud related taxa allow refining depositional trends stratal stacking patterns and position of previously not well resolved sequence stratigraphic surfaces within each t r cycle e g transgressive surface ts indeed two rapid increases in water depth values mark the tss that separate shallowing upward progradational rst from deepening upward retrogradational tst stratal stacking patterns of shelf deposits the tss which underline fine grained successions dominated by deep sea mud lover taxa are invariably constrained to the inception of interglacials marine isotope stages mis 21 and 19 identified within the vdm section by benthic foraminifera 18o values within both the vdm t r cycles the deepest conditions ca 140 m of water depth are invariably identified within the neopycnodonte unit slightly above the lightest 18o intervals the overlying decreasing bathymetric trend coupled with shifts in ostracod ecological groups allows to identify in the bryozoans lithofacies the stillstand falling of the relative sea level also tracked by a progressively heavier 18o record more stable paleobathymetric conditions around 40 45 m of water depth characterize the overlying silt sand deposits dominated by epiphytic species and showing the heaviest 18o values

new cnes cls09 global mean dynamic topography computed from the combination of grace data altimetry and in situ measurements 1 an accurate knowledge of the ocean mean dynamic topography mdt is mandatory for the optimal use of altimetric data including their assimilation into operational ocean forecasting systems a new global 1 4 resolution mdt was computed for the 1993 1999 time period with improved data and methodology compared to the previous rio05 mdt field first a large scale mdt is obtained from the cls01 altimetric mean sea surface and a recent geoid model computed from 4 5 years of grace gravity recovery and climate experiment data altimetric sea level anomalies and in situ measurements are then combined to compute synthetic estimates of the mdt and the corresponding mean currents while the rio05 mdt was based on 10 years of in situ dynamic heights and drifting buoy velocities the new field benefits from an enlarged data set of in situ measurements ranging from 1993 to 2008 and includes all hydrological profiles from the argo array moreover the processing of the in situ data has been updated a new ekman model was developed to extract the geostrophic velocity component from the drifting buoy measurements the handling of hydrologic measurements has also been revisited compared to the previous rio05 solution the new global mdt resolves much stronger gradients in western boundary currents with mean velocities being doubled in some places moreover in comparison to several other recent mdt estimates we find that the new cnes cls09 mdt is in better agreement with independent in situ observations

cyclonic eddies northeast of the campeche bank from altimetry data eight cyclonic eddies were identified near the western edge of the loop current at the northeast shelf break of the campeche bank through topex poseidon sea surface height anomaly data from january 1993 through march 2000 the eddies migration and their lifecycle are described the formation of the eddies appears to be related to the dynamics of the loop current because the timing of their generation corresponds to the last stage of the anticyclone shedding from the loop current the cyclones intensify while moving slightly to the northwest along the shelf break of the campeche bank later some cyclones are observed to move northward toward the mississippi shelf break the cyclones remain next to the campeche bank south of 268n from 1 3 to 9 6 months later some of them move northward and strengthen by merging with other eddies extending their life span the eddies vertical structure is analyzed with hydrographic data and the connection between the formation of the cyclones and the evolution of the loop current is further described using sea surface temperature images

impact of indian ocean dipole on intraseasonal zonal currents at 90 e on the equator as revealed by self organizing map a neural network pattern recognition approach called self organizing map som has been used to examine the impact of the indian ocean dipole iod on intraseasonal zonal currents in the eastern equatorial indian ocean this study shows that during negative iod events the intraseasonal zonal currents are mostly dominated by the first two modes on the other hand contributions from the higher modes to the intraseasonal zonal current significantly increase during positive iod events this is attributed to the change in the background stratification associated with the iod events the sharp pycnocline in the eastern basin during the positive iod events causes the wind forcing to project more onto the higher modes

hurricane isaac storm surges off florida observed by jason 1 and jason 2 satellite altimeters abstract storm surges can cause damage to properties and loss of life in coastal communities thus it is important to enhance our capabilities of observing understanding and forecasting storm surges for mitigating damage and loss previous studies have shown that cross shelf altimetric sea surface height profiles can be used to determine storm surge features in this study we combine satellite altimetry with tide gauge data to study storm surge features off florida in the gulf of mexico during hurricane isaac 2012 satellite observations show a storm surge of about 0 8 m near cedar key and apalachicola decreasing westward and southward in the early morning of august 28 2012 utc consistent with tide gauge measurements our analysis of satellite data reveals that the storm surge propagates northward from naples to cedar key with a phase speed of 14 16 m s and a cross shelf decay scale of 190 220 km in approximate agreement with the estimates from tide gauge data in contrast an analysis of tide gauge data reveals that the storm surge propagates westward from apalachicola to pensacola with a phase speed of 6 7 m s and a cross shelf decay scale of about 85 km it is further shown that the post storm sea level variations at these stations are associated with first mode continental shelf waves the present study shows that along shelf altimetric sea surface height profiles can be useful to observe and understand storm surge features as cross shelf ones demonstrated previously of importance to improvement of storm surge forecasting it suggests that a constellation of altimeter missions especially with wide swath altimetry could be suited to monitor storm surges

evidence for the influence of atlantic ionian stream fluctuations on the tidally induced internal dynamics in the strait of messina abstract on 24 and 25 october 1995 high resolution oceanographic measurements were carried out in the strait of messina by using a towed conductivity temperature depth chain and a vessel mounted acoustic doppler current profiler during the period of investigation the surface water of the tyrrhenian sea north of the strait sill was heavier than the surface water of the ionian sea south of the strait sill as a consequence during northward tidal flow surface water of the ionian sea spread as a surface jet into the tyrrhenian sea whereas during southward tidal flow heavier surface water of the tyrrhenian sea spread after having sunk to a depth of about 100 m as a subsurface jet into the ionian sea both jets had the form of an internal bore which finally developed into trains of internal solitary waves whose amplitudes were larger north than south of the strait sill these measurements represent a detailed picture of the tidally induced internal dynamics in the strait of messina during the period of i