physical oceanographic conditions in the deepwater gulf of mexico in summer 2000 2002 abstract the circulation and distribution of water properties in the water column of the gulf of mexico influence the flux of carbon to the benthic environment the eddy field of the upper 1000 m creates environmental conditions that are favorable for biological productivity in an otherwise oligotrophic subtropical ocean this eddy field results in the transport of nutrients and organic matter into the photic zone through cross margin flow of shelf waters upwelling in cyclones and uplift from the interaction of anticyclones with bathymetry these conditions then allow the productivity that becomes a possible source of carbon to the benthos data from four cruises during summers of 2000 2002 are used to describe the currents and water property distributions in the deepwater gulf of mexico which consists of water depths greater than 400 m comparisons are made to historical data sets to provide an understanding of the persistence of the characteristics of the gulf and the processes that occur there the currents in the gulf are surface intensified have minimum in 800 1000 m depths and also exhibit bottom intensification especially near sloping topography historical time series records show current speeds near bottom reach 50 100 cm s 1 at basin scales these currents tend to flow cyclonically counter clockwise along the bathymetry these near bottom episodic high speed currents provide a mechanism for the transport of organic material in both large and small particle sizes from one benthic area to another the distributions of temperature salinity nutrients and dissolved oxygen during the study appear to be unchanged from historical findings the source waters for the deep gulf are the water masses brought into the gulf by the loop current system the properties in the upper 100 200 m are the most variable of the water column consistent with their proximity to wind mixing river discharge mixing and atmospheric influences below 1500 m there are no major horizontal variations in these water properties

gulf of mexico circulation within a high resolution numerical simulation of the north atlantic ocean 1 the gulf of mexico circulation is examined from the results of a high resolution 1 12 north atlantic simulation using the miami isopycnic coordinate ocean model the motivation for this paper is twofold first we validate the model s performance in the gulf of mexico by comparing the model fields to past and recent observations and second given the good agreement with the observed gulf of mexico surface circulation and loop current variability we expand the discussion and analysis of the model circulation to areas that have not been extensively observed analyzed such as the vertical structure of the loop current and associated eddies especially the deep circulation below 1500 m the interval between successive model eddy sheddings is 3 to 15 months the eddy diameters range between 140 and 500 km the life span is about 1 year and the translational speeds are 2 3 km d 1 in good agreement with observations areas of high cyclonic eddy occurrence in the model are southwest of florida the loop current boundary and the western campeche bay area the cyclonic eddy diameters range between 50 and 375 km the orbital speeds range between 1 and 55 cm s 1 the translational speeds range between 0 5 and 14 km d 1 and the eddy life spans range between 1 and 3 months the vertical structure of the temperature and salinity of each modeled eddy from the moment it is shed until it disintegrates in the western gulf of mexico is in agreement with the few available observations below 1500 m deep cyclonic eddies are associated with the surface loop current anticyclones the eddy variability is consistent with rossby waves propagating westward and there is bottom intensification of the flow close to steep topography overall we show that this very high horizontal resolution isopycnic coordinate ocean model which is able to produce a quite realistic surface circulation for the north and equatorial atlantic is also able to reproduce well the smaller scale basin wide intricate dynamics such as the gulf of mexico variability

indications of a link between seismotectonics and ch4 release from seeps off costa rica measurements of ch4 concentrations in the bottom water during two discrete sampling periods in subsequent years above different cold seeps at the pacific margin off costa rica indicate large scale variations of ch4 release ch4 is emitted from mud extrusions and a slide scar at 1000 2300 m water depth maximum ch4 concentrations were found to be lower above all investigated sites in autumn 2003 than in autumn 2002 although seep sites are up to 300 km apart tidal and current changes were observed but found to apply only to individual seep sites increased seismic activity connected to the moment magnitude m w 6 4 earthquake offshore costa rica in june 2002 could have had an impact on all seep sites and thereby caused an increase in ch4 emission this is supported by the largest variations of ch4 concentration found above mud extrusions located above faults likely more strongly affected by tectonic movements even though our data indicate a relation between seismicity and ch4 seepage the relation is not proven and future work is needed to comprehensively test this hypothesis

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

observations of gulf stream ring 83 e and their interpretation using feature models analysis techniques were developed to track and estimate the propagation velocity size shape orientation and swirl velocity of gulf stream warm core rings the methods involve fitting idealized warm core ring feature models to observed surface fronts in the satellite imagery to expendable bathythermograph survey data and to satellite tracked drifting buoy data the ring feature models are analytic structure functions with adjustable parameters in this case the ring is modeled as an isolated translating elliptic paraboloid with a swirl velocity that increases linearly with distance from the center use of the feature models is illustrated with data collected from warm core ring 83 e gradient currents based on the bathythermograph survey of ring 83 e and the feature model agree well with currents measured by expendable current profilers a comparison of the time series of ring 83 e feature model parameters indicates that not only is the feature model analysis of the buoy track an effective method for tracking and monitoring the evolution of gulf stream rings it also provides useful forecasts of ring locations based simply on a persisted propagation velocity these techniques were used to provide real time support for exploratory deepwater drilling operations off the u s east coast

evolution of a warm core ring in the gulf of mexico lagrangian observations during 1985 and 1986 a gulf of mexico ring shed by the loop current was observed to migrate toward the western gulf of mexico this movement across the gulf was well documented by observations that included drifter data within and outside the ring sea surface temperature at weekly intervals expendable bathythermograph surveys at various times one major hydrographic cruise when the ring was in the northwestern gulf and currents from moorings over which the ring passed the drifter data were used to infer the movement of the ring center as well as the eccentricity and orientation of the major axes the data from the drifters bridge the gaps between detailed surveys to the extent that a daily history of the position and shape of the ring can be constructed the synthesis of these diverse but complimentary data sources provides a detailed description of how the ring interacted with the bathymetry of the northern gulf of mexico as well as with previously and subsequently shed rings

simulating the dynamics and intensification of cyclonic loop current frontal eddies in the gulf of mexico 1 the dynamics associated with the loop current lc variability in the gulf of mexico gom are studied using a 5 year free running numerical simulation with the hybrid coordinate ocean model hycom the dynamics of major gom circulation features are represented the extension of the lc and the associated anticyclonic warm core loop current eddies lces and cyclonic loop current frontal eddies lcfes the study focuses on the dynamics of the lcfes and their role during the lces shedding which dramatically affects the gom circulation we analyze several characteristics of the lc frontal dynamics modeled lcfes have a coherent vertical structure which extends to the deep layers of the gom they may split in two separate upper and lower layer eddies deep and surface remnants from different frontal eddies are able to align to form new coherent structures lcfes intensify along the extended lc northern edge when flowing over the deep northern gom shelf slope that forms the mississippi fan through a promontory effect in which the incoming cyclone aggregates positive potential vorticity anomalies in lower layers leading to the intensification of the whole vortex structure lcfes may also expand further along the lc path by horizontal vortex merging when they are blocked between the lc and the northeast corner of the continental shelf in the gom the intensification and merging due to topographic effects explain the enlarged frontal eddies observed on the eastern side of the loop current these larger eddies further migrate along the lc front and may play a role in the shedding sequence

an exercise in forecasting loop current and eddy frontal positions in the gulf of mexico 1 as part of a model evaluation exercise to forecast loop current and loop current eddy frontal positions in the gulf of mexico the princeton regional ocean forecast system profs is tested to forecast 14 4 week periods aug 25 99 sep 20 00 during which a powerful eddy eddy juggernaut eddy j separated from the loop current and propagated southwestward to initialize each forecast profs assimilates satellite sea surface height ssh anomaly and temperature sst by projecting them into subsurface density using a surface subsurface correlation that is a function of the satellite ssh anomaly the closest distances of the forecast fronts from seven fixed stations in the northern gulf over a 4 week forecast horizon are then compared against frontal observations derived primarily from drifters model forecasts beat persistence and the major source of error is found to be due to the initial hindcast fields

aspects of warm rings in the gulf of mexico various aspects of warm rings in the gulf of mexico were derived from satellite infrared data and ship of opportunity data after the warm rings separate from the loop current they move into the western gulf of mexico it was shown from 12 years of data 1973 through 1984 that there are three characteristic paths of movements of the rings a northern path a mid gulf path and a path that takes the rings into the southern extremities of the western gulf of mexico it was shown that all three paths eventually lead the ring to a region in the northwestern portion of the western gulf of mexico the area defined by 25 n to 28 n and 93 w to 96 w as the rings move from the eastern gulf to the western gulf the speed of the ring was observed to oscillate the oscillation is over a speed range from 1 to 8 km per day on the average and the period varies from 40 to 100 days the average speed of the ring was 5 km per day after the ring separates from the loop current the surface area of the ring decreases to about 55 percent of its initial size in approximately 150 days and to about 31 percent of its initial size in about 300 days

coseimic massive methane release from a submarine mud volcano abstract we report here the discovery of two methane enriched plumes in a water column above the kumano knoll 5 submarine mud volcano kk 5 in nankai trough during 2004 a slight methane enrichment was observed in this region in 2000 and 2010 the deeper of the two plumes spread horizontally at depths near the top of kk 5 whereas a shallow plume spread at a height of 300 m from the top of kk 5 the end member 13 c values of methane in both plumes 46 1 4 8 and 51 4 5 8 in the deep and shallow plumes respectively and methane extracted from sediment in kk 5 52 2 are statistically indistinguishable we conclude that the plumes were created by massive release of methane from kk 5 and that this event probably occurred in response to the large earthquakes m w 7 5 that occurred shortly before our observation in 2004 the discharge rates from submarine mud volcanoes smvs in subduction zones may be highly variable in response to major earthquakes

mean and near inertial ocean current response to hurricane gilbert abstract the three dimensional hurricane induced ocean response is determined from velocity and temperature profiles acquired in the western gulf of mexico between 14 and 19 september 1988 during the passage of hurricane gilbert the asymmetric wind structure of gilbert indicated a wind stress of 4 2 n m 2 at a radius of maximum winds rmax of 60 km using observed temperature profiles and climatological temperature salinity relationships the background and storm induced geostrophic currents re 750 m were 0 1 m s 1 and 0 2 m s 1 respectively a loop current warm core ring lcwcr was also located to the right of the storm track at 4 5 rmax where anticyclonically rotating near surface and 100 m currents decreased from 0 9 m s 1 to 0 6 m s 1 at depth the relative vorticity in the lcwcr was shifted below the local coriolis parameter by about 6 in a storm based coordinate system alongtrack residual velocity profiles from 0 to 4 rmax were fit to a dynamical model by least squares to isolate the near

verification of geosat altimetry for operational use in the gulf of mexico geosat altimetry is well suited for locating large eddies shed by the loop current in the gulf of mexico we have compared the altimeter data with in situ data obtained during a survey of eddy murphy in june 1988 since there is no significant mean circulation in the central gulf we used the mean sea surface from the first year of altimeter data as a geoid estimate the dynamic height change due to the eddy closely matched the altimeter data although the eddy moved about one third of a degree between the survey and the satellite pass the motion of the eddy was confirmed by the track of an argos buoy

some observations of ring topography and ring ring interactions in the gulf of mexico the movement and interactions of loop current rings are studied using trajectory and sea surface temperature sst data from the gulf of mexico the movements of three rings as determiend by drifters seeded in the rings are compared the data show the rings moving west through the deepest portion of the gulf and then northward after impacting with the mexican coast the trajectory data indicate a ring life span of at least 9 13 months with two of the rings persisting off the mexican coast for at least 3 5 months the trajectory of a fourth drifter not seeded in a ring still shows strong anticyclonic motion the sst data for the period that this last drifter was deployed show the interaction of three anticyclones in the western gulf the drifter circles all three anticyclones and shows along with the sst data the coalescing of two of the anticyclones

observations of layering under a warm core ring in the gulf of mexico abstracttwo glider transects in the gulf of mexico reveal fine vertical scale thermohaline structures within a loop current eddy lce partially compensating temperature and salinity anomalies are

evolution and kinematics of a loop current eddy in the gulf of mexico during 1985 the large eddy that broke off from the loop current in july 1985 was the most extensively studied eddy ever to appear in the gulf of mexico other investigators have described its early evolution based on lagrangian drifters and its later evolution using moored current meters in the western gulf this paper provides additional insight on the early evolution of the eddy using results from air dropped expendable bathythermographs and air dropped expendable current profilers in early may a hydrographic ship survey in mid july and a detailed ship survey in august using expendable bathythermographs and a current profiler the may survey established a center of circulation at about 26 n but showed that the eddy had not separated from the loop current a maximum velocity of 171 cm s was observed near the northern edge of the feature the evidence suggests that a large elongated eddy then separated from the loop current and later split into two smaller eddies the july hydrographic cruise showed a clear separation of the large eddy from the loop current to the southeast two weeks later the august survey showed an asymmetric eddy with the maximum surface current 178 cm s south of the center of circulation and 132 cm s to the north a western eddy named ghost eddy then separated from an eastern eddy named fast eddy using the current profiles and data from the drifters we constructed a simple kinematic feature model for eddies in the gulf of mexico

the annual cycle of the western boundary current in the gulf of mexico it has been known for decades that the mean circulation in the western gulf of mexico is a large anticyclone this flow is driven both by wind stress curl and detached rings from the loop current this paper is an attempt to examine their relative importance by focusing on the annual cycle of the observed flow a new compilation of ship drift data shows that the flow along the western boundary is strongest in july and weakest in october it appears physically plausible that the annual variation of this western boundary current is driven by the annual variation in wind curl augmented by ekman pumping over the western gulf because the maximum in wind curl is so close to the western boundary the phase delay between the annual cycles of curl and current is only approximately 1 month the magnitudes of the curl and resulting current seem physically plausible the response is baroclinic and penetrates to 1000 m the bottom of the main thermocline the change in velocity at the sea surface is consistent with the cross stream pressure gradient as determined by the changes in sea level at the coast and dynamic height changes offshore the annual cycle is relatively large at the annual minimum the flow is only approximately 25 of the maximum the data suggest that this flow could be driven by wind curl but the uncertainty is high consequently the contribution of loop current rings turns out to be relatively small the reason for this is that when rings reach the western wall the steep bottom topography intersects the sloping fluid contours of the rings the rings decay slowly by normal deepwater processes until they reach the edge of the continental shelf and then they decay more rapidly by loss of fluid once the rings have reached the western boundary the decay time scale is found to be only 70 days

the mean upper layer flow in the central gulf of mexico by a new method abstractprevious studies have found a puzzling disagreement between two large datasets and the results of numerical models in the central gulf of mexico the observations suggest an upper layer mean flow to the west of order 10 cm s 1 while the numerical models find no such mean flow a new technique is used here using 23 yr of satellite derived sea surface height data to estimate the mean flow this third independent set of data yields the same westward flow found in previous studies these findings require that there be sinking in the western gulf the details of the return flow remain an intriguing problem

submesoscale impacts on horizontal and vertical transport in the gulf of mexico 1 impacts of submesoscale processes on transport are investigated numerically in an energetic mesoscale flow with an ocean model run at two horizontal resolutions 1 and 5 km the focus is the northwestern gulf of mexico where the loop current eddies are surrounded by smaller vortices by increasing the horizontal resolution the number and strength of submesoscale eddies and vorticity filaments within the mixed layer increase dramatically and with them the vertical velocities inside the coherent eddies and at their peripheries increased vertical velocities for increasing resolution are associated to near inertial motions and they are not limited to the mixed layer but are found at all depths horizontal velocities on the contrary are similar lagrangian isobaric tracers are deployed close to the surface and at 100 m and three dimensional neutrally buoyant particles are released close to the surface at the base of the mixed layer and at 100 m the modeled horizontal dispersion curves for each deployment depth are independent of the kind of particles and of horizontal resolution close to the ocean surface however convergence zones generated by submesoscale ageostrophic motions and resolved at 1 km resolution influence the details of the tracer distributions vertical dispersion increases by several folds for increasing resolution at all depths explored with the largest differences found close to the surface therefore submesoscales processes play a fundamental role in driving vertical transport in eddy dominated flows both within and below the mixed layer for times comparable to the eulerian time scale

a model for the analysis of drifter data with an application to a warm core ring in the gulf of mexico a model developed primarily for the analysis of drifter data is discussed the model is based on a parametric representation of the drifter velocity in terms of monge potentials two of which are constants following the motion of the fluid in the application presented here one of the potentials is taken as the frequency of rotation about a ring by a parcel a more restricted interpretation of the velocity gradient in variant for horizontal flow is also discussed the other potential is taken as the streamline of a parcel that is locally approximated as a conic section for the restricted interpretation solutions to the model equations are critically dependent on the relative sizes of the squares of the vertical vorticity and the total deformation rate this model differs from drifter cluster models in that each drifter provides independent estimates of the vorticity and deformation rates application is made to path data from three drifters that were seeded in a warm core ring in the gulf of mexico in november 1980 the model provided estimates of the ring translation and swirl velocities along with the ring geometry the analysis showed that the ring was persistently elliptical with the major axis aligned in the east west direction a satellite infrared photo on january 21 1981 confirmed this orientation

the 1982 eruptions of el chichon volcano mexico 3 physical properties of pyroclastic surges two major pyroclastic surges generated during the 4 april 1982 eruption of el chichon devastated an area of 153 km2 with a quasi radial distribution around the volcano the hot surge clouds carbonized wood throughout their extent and were too hot to allow accretionary lapilli formation by vapor condensation field evidence indicates voidage fraction of 0 99 in the surge cloud with extensive entrainment of air thermal calculations indicate that heat content of pyroclasts can heat entrained air and maintain high temperatures in the surge cloud the dominant bed form of the surge deposits are sand waves shaped in dune forms with vertical form index of 10 20 characterized by stoss side erosion and lee side deposition of 1 10 cm reversely graded laminae a systematic decrease in maximum lithic diameter with distance from source is accompanied by decrease in wavelength and amplitude modal analysis indicates fractionation of glass and pumice from the surge cloud relative to crystals resulting in loss of at least 10 25 of the cloud mass due to winnowing out of fines during surge emplacement greatest fractionation from the 1 0 0 0 grain sizes reflects relatively lower pumice particle density in this range and segregation in the formative stages of the surge cloud extensive pumice rounding indicates abrasion during bed load transport flow of pyroclastic debris in the turbulent surge cloud was by combination of bed load and suspended load transport the surges are viewed as expanding pyroclastic gravity flows which entrain and mix with air during transport the balance between sedimentation at the base of the surge cloud and expansion due to entrainment of air contributed to low cloud density and internal turbulence which persisted to the distal edge of the surge zone

hydrography of the gulf of mexico using autonomous floats abstractfourteen autonomous profiling floats equipped with ctds were deployed in the deep eastern and western basins of the gulf of mexico over a four year interval july 2011 august 2015 produ

observations of recurrent mesoscale eddies in the eastern mediterranean a mediterranean sea observation program conducted in the early 1990s by the naval oceanographic office included temperature aerial surveys the deployment of satellite tracked drifting buoys and the real time analysis of satellite infrared imagery over 4 years of weekly front and eddy analyses generated from the satellite imagery and over 100 drifting buoy trajectories were examined here for recurrent eddies in the eastern mediterranean five recurrent mesoscale eddies found in the satellite imagery remained relatively stationary with the standard deviation of the eddy center locations comparable to the mean eddy diameter three of the recurrent eddies were seeded with satellite tracked drifting buoys one buoy circulated within each of two anticyclones for several weeks allowing application of a kinematic feature model to the buoy trajectories for the extraction of propagation and circulation characteristics the ierapetra anticyclone remained southwest of the mean satellite derived center rotating slowly clockwise about 1 2 d 1 with a swirl velocity that increased linearly with distance from the center nearly to its outer edge the pelops anticyclone exhibited a slight westward propagation tendency its major axis rotated clockwise about 4 d 1 and the swirl velocity had a broad maximum well inside the eddy that was nearly independent of radius inertial waves were observed in two of the buoy trajectories with the differences in the observed inertial periods consistent with the effects of eddy circulation on near inertial waves

on the structure and motions of cyclones in the northern gulf of mexico 1 the eddy field on the northern slope of the gulf of mexico has been investigated using high resolution axbt and axcp aircraft surveys and argos tracked drifters a number of vigorous cyclones were mapped their vertical structures showed solid body rotation with radii of 50 75 km with a subsurface maximum 40 cm s 1 at the outer edge at about 150 m flows had little shear in the upper 400 m and only weak currents below depths of 800 to 1000 m cyclones were observed to move on and off the slope under the influence of swirl velocities of larger warm core eddies including loop current lc anticyclones rotational periods range from about 7 to 18 days the mapped eddy fields contained both cyclones and anticyclones with a range of diameters from about 40 to 150 km the presence of many relatively small scale features along the upper slope strongly affects features of the shelf break velocity field that were measured by a moored current meter array the directions and vertical shears of the moored currents were consistent with flows caused by the northern edges of cyclones and anticyclones these eddies can cause persistent events and strong cross isobath fluctuations of the currents counterrotating pairs of eddies on the upper slope seem to be a mechanism for the transport of material on and off the louisiana and east texas shelves coherences between moorings 74 km apart were generally not significant as might be expected when the currents are dominated by small scale eddies however an eof analysis of the shelf break array indicates that about 40 of the along slope current variances could be attributed to westward propagating continental shelf waves

tropical instability vortices in the atlantic ocean 1 this paper examines the physical characteristics and dynamics of atlantic tropical instability vortices based on observational data from 1997 to 2000 and a high resolution numerical model simulation most prominent during boreal summer the vortices are characterized by 400 km spatial scales westward translation at 0 40 cm s 1 anticyclonic circumferential velocities of 30 110 cm s 1 and sstanomalies that decrease from 2 ci n midbasin to 0 5 c or less near the western boundary in contrast the sea level anomalies grow as the vortices progress westward reaching maximum amplitudes of 14 cm near 40 w the large circumferential velocities leading to relative vorticities of 4 10 6 s 1 and rossby numbers of 0 5 indicate that centrifugal effects may play an important role in the vortices vorticity balance we address the vortices vertical structure and vorticity dynamics by examination of a high resolution numerical model there is a reasonably good agreement between the model and observations simulated vortices are confined mostly to the mixed layer which increases westward in depth from 30 to 100 m near the western boundary in the eastern basin potential vorticity within the vortices is not conserved but decreases because of wind stress forcing in contrast in the western basin decreases in potential vorticity are due mostly to the vortices acquisition of southern hemisphere water we estimate an annualized cross equatorial transport of up to 1 2 sv associated with the vortices which is eventually contributed to the north brazil current system index terms 4231 oceanography general equatorial oceanography 4520 oceanography physical eddies and mesoscale processes 4528 oceanography physical fronts and jets keywords tropics instability atlantic

on the circulation of the western gulf of mexico with observations from april 1978 in april 1978 the circulation pattern in the western gulf of mexico was dominated by a cyclonic circulation feature centered near 25 20 n 95 20 w and an anticyclonic circulation feature centered near 23 30 n 95 50 w the north south scales of both gyres are approximately 225 km while the east west scales are greater than 450 km an eastward geostrophic transport of 29 7 106 m3 s is found between the centers of the cyclone and the anticyclone we believe that both the anticyclone and the cyclone migrated to the western gulf from the loop current region of the eastern gulf the anticyclone is probably supplemented by a wind driven circulation as described by blaha and sturges and an eastward extension of the wind driven current which flows to the south along the lower texas shelf may intensify the cyclone and or anticyclone also this extension of the texas shelf current may tend to confine the anticyclone to the south and the cyclone to the north of the current s location

drifting buoy observations of a loop current anticyclonic eddy the loop current penetrated deep into the gulf of mexico in early 1989 after several eddy formation and reattachment cycles a southwestward propagating anticyclonic eddy was formed during the summer the loop current and subsequent eddy produced strong currents over widespread areas on the louisiana continental slope prompting a series of current measurement programs because of the lack of satellite infrared coverage in the gulf of mexico during the summer the trajectories of 53 argos tracked drifting buoys deployed in the gulf of mexico in 1989 were assembled to determine the synoptic history of the loop current and anticyclonic eddy during this event ten of the most critical summertime buoy trajectories are discussed here in addition the trajectories of three of the buoys simultaneously deployed at different radii in the eddy were chosen for analysis with a kinematic feature model the model assumes the looping buoy motion is generated by an elliptical orbit around a translating eddy center the buoy trajectories were used to determine time series of the feature model parameters including eddy center shape and circulation characteristics the time series results indicate that the eddy actually propagated in a series of short sprints separated by longer stalls during the sprints the eddy propagated as an elliptical but otherwise symmetric solid body during the stalls significant asymmetries developed the asymmetries are consistent with attachment to the loop current during the first stall the effects of topographic rossby wave dispersion during the second and the effects of planetary rossby wave dispersion during the third the results provide both a framework for the interpretation of in situ observations and a detailed evolutionary history for numerical modelers

genesis of a gulf of mexico ring as determined from kinematic analyses the kinematics of the loop current are studied using trajectories of drifters in the gulf of mexico during mid june through september 1985 one of the drifters was in the loop current proper while other drifters were in two recently shed loop current rings the drifter in the loop current showed strong anticyclonic motion during the study period this loop current anticyclone first began off the northwest coast of cuba it rapidly moved northward into the gulf of mexico as a ring pinched off from the loop current analysis of the loop current drifter motion showed that the anticyclone became an integral part of the loop current taking on many of the characteristics of the most recently shed ring the results of the analysis suggest a process by which loop current rings can be generated apparently this mechanism can cause the loop current to become reconfigured in 2 3 months for beginning the process of ring separation

velocity and hydrographic structure of two gulf of mexico warm core rings results from an extensive survey of two gulf of mexico warm core rings are presented the data were taken during a 1 week period in december 1983 using a shipboard acoustic doppler current profiler adcp expendable current probes xcp expendable bathythermographs xbt and a ctd two rings were observed an older one in the western gulf adjacent to the west texas shelf and one just separated from the loop current the western ring was of order 200 km in diameter with peak currents of 1 m s 1 at the 100 m level water properties were uniform and characteristic of the high salinity caribbean subtropical underwater the eastern ring was of order 300 km in diameter with peak currents of near 2 m s 1 at the 100 m level water below 200 m is of caribbean origin while the surface waters show more variability suggesting some inflow of gulf of mexico common water the evolution of the rings is also described based on the cruise measurements satellite avhrr and other observations of opportunity

monitoring aseismic tectonic processes via hydrologic responses an analysis of log periodic fluid flow events at the costa rica outer rise a log periodic series of fluid inflow events from the outer rise off the nicoya peninsula costa rica was recorded on a flow meter deployed at the sediment surface similar periodic series have been seen in many failure processes in laboratory and field research including seismic and chemical records preceding earthquakes each cycle has the appearance of an impulse and subsequent decay the hypothesis that the recorded flow pattern is a result of a series of relatively small strain events resulting from aseismic extensional faulting of the outer rise basement is explored and analytical results supporting this hypothesis are presented

the vertical structure of a loop current eddy the vertical structure of a recently detached loop current eddy lce is studied using in situ data collected with an underwater glider from august to november 2016 altimetry and argo data are analysed to discuss the context of the eddy shedding and evolution as well as the origin and transformation of its thermohaline properties the lce appeared as a large body of nearly homogeneous water between 50 and 250 m confined between the seasonal and main thermoclines a temperature anomaly relative to surrounding gulf s water of up to 9 7 c was observed within the eddy core the salinity structure had a double core pattern the subsurface fresh core had a negative anomaly of 0 27 psu while the deeper saline core s positive anomaly reached 1 22 psu both temperature and salinity maxima were stronger than previously reported the saline core of caribbean origin was well conserved during its journey from the yucatan basin to the loop current and at least 7 months after eddy detachment the fresher homogeneous core resulted from surface diabatic transformations including surface heat fluxes and mixing within the top 200 m during the winter preceding eddy detachment heat and salt excess carried by the lce were large and require important negative heat fluxes and positive fresh water input to be balanced the geostrophic velocity structure had the form of a subsurface intensified vortex ring

a geostrophic vortex over a slope abstract nonlinear quasigeostrophic f plane vortices in two layers over a topographic slope are considered scaling arguments suggest two parameters that dictate the effective strength of the slope the first indicates the likelihood of dispersion at depth and the second relates to baroclinic stability if the deep flow is only weakly dispersive weak slopes an initially barotropic vortex can translate barotropically across the isobaths provided the vortex scale exceeds the deformation scale over stronger slopes the vortex separates into topographic waves and a stationary surface trapped vortex an initially surface trapped vortex larger than deformation scale becomes unstable over a weak slope as it does over a flat bottom however a strong slope can stabilize the vortex to small perturbations despite the large vortex scale the effective slope parameters depend not only on topographic grade but on vortex strength and size and on the ambient stratification parameters obtained with represen