statistical properties of the surface velocity field in the northern gulf of mexico sampled by glad drifters the grand lagrangian deployment glad used multiscale sampling and gps technology to observe time series of drifter positions with initial drifter separation of o 100 m to o 10 km and nominal 5 min sampling during the summer and fall of 2012 in the northern gulf of mexico histograms of the velocity field and its statistical parameters are non gaussian most are multimodal the dominant periods for the surface velocity field are 1 2 days due to inertial oscillations tides and the sea breeze 5 6 days due to wind forcing and submesoscale eddies 9 10 days and two weeks or longer periods due to wind forcing and mesoscale variability including the period of eddy rotation the temporal e folding scales of a fitted drifter velocity autocorrelation function are bimodal with time scales 0 25 0 50 days and 0 9 1 4 days and are the same order as the temporal e folding scales of observed winds from nearby moored national data buoy center stations the lagrangian integral time scales increase from coastal values of 8 h to offshore values of approximately 2 days with peak values of 3 4 days the velocity variance is large o 1 m2 s2 the surface velocity statistics are more anisotropic and increased dispersion is observed at flow bifurcations horizontal diffusivity estimates are o 103 m2 s in coastal regions with weaker flow to o 105 m2 s in flow bifurcations a strong jet and during the passage of hurricane isaac the gulf of mexico surface velocity statistics sampled by the glad drifters are a strong function of the feature sampled topography and wind forcing

mineralogical and stable isotopic characterization of authigenic carbonate from a hydrocarbon seep site gulf of mexico slope possible relation to crude oil degradation abstract one of the characteristic features on the cold deep seafloor on atwater valley at block 425 1930 m water depth in the gulf of mexico is the occurrence of seepage of crude oil and hydrocarbon gases associated with thermogenic gas hydrate and authigenic carbonate deposits mineralogical petrographic and isotopic analyses revealed that the precipitation of these carbonates was related to the microbial oxidation of hydrocarbons carbonate deposits are composed of heavily oil stained small nodules to large cobbles of dense limestones of fine grained textures other carbonate fragments are composed of small intraclasts pellets and some bivalve shell fragments cemented together by aragonite cement xrd analysis and petrographic investigations revealed that the authigenic carbonate is predominantly composed of aragonite that occurs as microcrystalline matrix and cement microcrystalline sparitic and botryoidal acicular aragonite crystals are observed as void filling cement the 18o values of the authigenic carbonate 3 80 to 4 16 v pdb suggest that the precipitating fluid has equilibrated with the cold bottom seawater the calculated 18o values 0 18 to 0 54 smow of the precipitating fluid show subtle deviation from the values reported for the present bottom seawater this is attributed possibly to the precipitation from pore water with temperature ranged from 3 3 to 1 7 c which is less than the measured bottom seawater 4 c however the mixing of the marine pore water with some deep hydrocarbon rich brines or hydrate water would provide a source of 18o enrichment fluid for the precipitation of the authigenic carbonates based on the predominance of aragonite with botryoidal and clotted fabric the occurrence of pyrite and from the oxygen isotopic data it is plausible that the authigenic carbonates may have formed near the sediment water interface in an oxygen depleted environment with low temperature the narrow range of the 13c values of the authigenic carbonate 23 88 to 28 62 v pdb suggests that a single source of carbon is predominant based on the moderately low 13c values and the occurrence of spots of crude oil coatings of the carbonate samples in addition to the application of a carbon isotope mass balance model the carbon involving in the formation of the carbonates of the at 425 seep site could be mainly derived from microbial degradation of crude oil microbial oxidation of non methane thermogenic hydrocarbon gases such as ethane propane and isobutane would play some role as a source of carbonate carbon

eddy diffusivities estimated from observations in the labrador sea eddy diffusivities in the labrador sea ls are estimated from deep eddy resolving float trajectories moored current meter records and satellite altimetry a mean residence time of 248 days in the central ls is observed with several floats staying for more than 2 years by applying a simple random walk diffusion model the observed distribution of float residence times in the central ls could be explained by a mean eddy diffusivity of about 300 m2 s 1 estimates from float trajectories themselves and from moored current meter records yield significantly higher eddy diffusivities in the central ls of 950 1100 m2 s 1 this discrepancy can be explained by an inhomogeneity of the eddy diffusivity at middepth with high low values in the central ls region between central ls and deep labrador current which could be conjectured from the mean altimetric eddy kinetic energy eke distribution the different diffusivities explain both 1 a fast lateral homogenization of water masses in the central ls and 2 a weak exchange between central ls and boundary current the mean lagrangian length scale of 11 5 0 7 km as estimated from deep float trajectories is only slightly larger than the mean rossby radius of deformation 8 8 km largest eddy diffusivities within the central ls are associated with strong eddy drifts rather than with large swirl velocities and associated large eke between central ls and deep labrador current which could be conjectured from the mean altimetric eddy kinetic energy eke distribution the different diffusivities explain both 1 a fast lateral homogenization of water masses in the central ls and 2 a weak exchange between central ls and boundary current the mean lagrangian length scale of 11 5 0 7 km as estimated from deep float trajectories is only slightly larger than the mean rossby radius of deformation 8 8 km largest eddy diffusivities within the central ls are associated with strong eddy drifts rather than with large swirl velocities and associated large eke

archaeal lipid biomarkers and isotopic evidence of anaerobic methane oxidation associated with gas hydrates in the gulf of mexico abstract anaerobic oxidation of methane aom occurs in the gulf of mexico gas hydrate systems here we show lipid biomarker and isotopic evidence that archaea are involved in aom the estimated abundance of total archaeal lipids ranges from 44 8 to 60 4 g g dry sediment in hydrate bearing samples but is below detection limit in the hydrate free sample the 13c values of archaeal lipids range from 69 to 99 in hydrate bearing samples these results suggest that biomass of archaea is significantly enhanced through aom at the gas hydrate deposits these data also support a currently acknowledged mechanism of aom mediated by a consortium of sulfate reducing bacteria and archaea observed in a variety of methane rich marine settings anaerobic oxidation of oil hydrocarbons also occurs in the gulf of mexico gas hydrate systems as shown by degradation of n alkanes c15 in the anoxic sediments these processes convert hydrocarbons to carbon dioxide and increase pore water alkalinity which promote the precipitation of enormous volumes of authigenic carbonate rock depleted in 13c this long term geologic sequestration of carbon may affect models of global climate change

origin distribution and alteration of asphalts at chapopote knoll southern gulf of mexico abstract following the discovery of asphalt volcanism in the campeche knolls a research cruise was carried out in 2006 to unravel the nature of the asphalt deposits at chapopote the novel results support the concept that the asphalt deposits at the seafloor in 3000 m of water depth originate from the seepage of heavy petroleum with a density slightly greater than water the released petroleum forms characteristic flow structures at the seafloor with surfaces that are ropy or rough similar to magmatic lava flows the surface structures indicate that the viscosity of the heavy petroleum rapidly increases after extrusion due to loss of volatiles consequently the heavy petroleum forms the observed asphalt deposit and solidifies detailed survey with a remotely operated vehicle revealed that the asphalts are subject to sequential alterations e g volume reduction leading to the formation of visible cracks in the asphalt surface followed by fragmentation of the entire deposit while relatively fresh asphalt samples were gooey and sticky older fragmented pieces were found to be brittle without residual stickiness furthermore there is evidence for petroleum seepage from below the asphalt deposits leading to local up doming and sometimes to whip shaped extrusions extensive mapping by tv guided tools of chapopote asphalt volcano indicates that the main asphalt deposits occur at the south western rim that borders a central crater like depression the most recent asphalt deposit at chapopote is the main asphalt field covering an area of 2000 m2 asphalt volcanism is distinct from oil and gas seepage previously described in the gulf of mexico and elsewhere because it is characterized by episodic intrusions of semi solid hydrocarbons that spread laterally over a substantial area and produce structures with significant vertical relief as chapopote occurs at the crest of a salt structure it is inferred that asphalt volcanism is a secondary result of salt tectonism

decomposition of surface drifter observations in the atlantic ocean 1 surface drifter observations are decomposed into mean seasonal annual and semiannual and eddy components via gauss markov estimation this approach helps separate seasonal fluctuations and mean values in the observationally sparse tropical and south atlantic where monthly mean values cannot be calculated at the spatial scale of the major currents in some regions large differences are found between these means and those obtained by simple binned averaging the differences are attributed to inhomogeneous sampling of seasonal variability and to the inherent bias of lagrangian observations towards periods of low velocity the analysis reveals strong seasonal variations of some surface currents including a significant late spring reversal of the western north equatorial counter current

the anaerobic oxidation of methane and sulfate reduction in sediments from gulf of mexico cold seeps we determined the geochemical characteristics of sediments and measured rates of the anaerobic oxidation of methane aom and sulfate reduction sr in samples collected near thermogenic structure ii gas hydrate mounds and in areas lacking hydrates along the continental slope in the gulf of mexico we used radiotracer c 14 and s 35 techniques to determine rates of aom and sr over depth in sediment cores abundant mats of white and orange beggiatoa spp were common in areas of active seepage and these sediments were enriched in hydrogen sulfide and methane in cores collected from areas without beggiatoa or hydrate concentrations of redox metabolites showed little variation over depth and these sites were inferred to be areas of low seepage integrated aom rates were low in beggiatoa free cores 0 05 mmol m 2 day 1 and averaged 2 8 4 6 mmol m 2 day 1 in seep cores that contained beggiatoa or gas hydrate integrated sr rates were also low in beggiatoa free cores 1 mmol m 2 day 1 and averaged 54 94 mmol m 2 day 1 in cores with beggiatoa or hydrate rates of sr generally exceeded rates of aom and the two processes were loosely coupled suggesting that the majority of sr at gulf of mexico hydrocarbon seep sites is likely fueled by the oxidation of other organic matter possibly other hydrocarbons and oil rather than by aom

eulerian and lagrangian statistics in the bluelink numerical model and aviso altimetry validation of model eddy kinetics 1 we compare eulerian and lagrangian timescales velocity autocorrelations and spectra from 14 years of hindcast ocean model and satellite velocities with direct observations our main aim is to determine how well the model bluelink version bran 2 1 and satellite derived currents archiving validation and interpretation of satellite oceanographic data aviso simulate mesoscale eddy variability which is important in mixing heat salinity and momentum and in controlling dispersion ocean eulerian observations are from topex poseidon t p crossover velocities and lagrangian observations are from global drifter program gdp surface drifters eulerian spectra from bluelink are similar to eulerian spectra from crossover velocities over the range of common frequencies the 10 day sampling from t p limits the comparison to low frequencies and eulerian timescales from bluelink are slightly shorter than from the observations part of this difference may be an effect of the t p sampling rate in contrast lagrangian spectra from bluelink are considerably steeper than spectra from gdp drifters and consequently lagrangian timescales from bluelink are longer than from the observations both eulerian and lagrangian spectra from aviso are steeper than from observations so that both eulerian and lagrangian aviso timescales are longer than observed the real ocean is an ocean where the eulerian lagrangian relationship described by middleton 1985 is followed the tasman sea averaged ratio of lagrangian to eulerian timescales is about 0 1 zonally and 0 15 meridionally however the eulerian lagrangian relationship described by middleton 1985 is not obeyed by bluelink and we believe that this behavior in bluelink reflects a loss of short wavelength eddies in the model

circulation and stirring in the southeast pacific ocean and the scotia sea sectors of the antarctic circumpolar currenta abstractthe large scale middepth circulation and eddy diffusivities in the southeast pacific ocean and scotia sea sectors between 110 and 45 w of the antarctic circumpolar current acc are described based on a subsurface quasi isobaric rafos float based lagrangian dataset these rafos float data were collected during the diapycnal and isopycnal mixing experiment in the southern ocean dimes the mean flow adjusted to a common 1400 m depth shows the presence of jets in the time averaged sense with speeds of 6 cm s 1 in the southeast pacific ocean and upward of 13 cm s 1 in the scotia sea these jets appear to be locked to topography in the scotia sea but aside from negotiating a seamount chain are mostly free of local topographic constraints in the southeast pacific ocean the eddy kinetic energy eke is higher than the mean kinetic energy everywhere in the sampled domain by about 50 the magnitude of the eke increases drastically by a factor of 2 or more as the current crosses over the hero and

california undercurrent variability and eddy transport estimated from rafos float observations 1 rafos float observations collected between 1992 and 2002 were analyzed to identify the seasonal variability of circulation in four geographical boxes which extended along the central and northern california coast and were successively located farther offshore the mean pressure of the floats was 375 dbar poleward flow associated with the california undercurrent dominated the two boxes closest to shore extending from the 400 m isobath to a distance of 190 km offshore for the box closest to shore the monthly mean alongshore velocity was maximum minimum 5 4 cm s 1 7 cm s in may june february while the eddy kinetic energy eke was minimum was 33 cm2 s2 21 cm2 s2 in september december february the mean eke in the coastal region was 28 cm2 s2 increasing to 50 cm2 s2 for the region farthest offshore a distance of about 400 km for that region farthest offshore eke had a broad maximum from june to november and a minimum in april lagrangian correlation and dispersion tensors were estimated for floats that left the coastal region three different dispersive regimes of float motion were identified as ballistic transport normal diffusion and anomalous sub diffusion westward sub diffusion was induced by rossby wave like structures with a periodicity of 100 120 days

application of the ce anomaly as a paleoredox indicator the ground rules much attention has been paid in recent years to the potential application of the ce anomaly measured in various marine phases as a paleoceanographic indicator of widespread marine anoxia in this paper we present and discuss results from recent studies of present day rare earth element ree distributions and hence ce anomaly distributions in the marine environment which are particularly pertinent to paleoceanography subsequently we review and discuss the validity of the recent literature in which ce anomalies have been employed as paleoredox indicators

a conceptual model for hydrocarbon accumulation and seepage processes around chapopote asphalt site southern gulf of mexico from high resolution seismic point of view 1 as part of the german r v meteor m67 2 expedition in 2006 to the southern gulf of mexico a set of 2d high resolution seismic profiles was acquired across the chapopote knoll to study seafloor asphalt occurrences on the basis of regional seismostratigraphic studies and dsdp drilling a more highly reflective coarse grained sediment unit of late miocene age is identified as a potential shallow hydrocarbon reservoir although a unit of that age would typically be buried by pliocene and pleistocene sediment cover at chapopote local salt tectonism has highly elevated the structure since the late miocene and the miocene reservoir is locally above present day regional datum the elevation resulted in a thin 100 200 m fine grained sediment cover on the crest of the knoll above the reservoir because oil and gas production can be expected at depth in jurassic cretaceous and tertiary source rocks the presence of high amplitude reflector packages within the reservoir unit is interpreted as an evidence of hydrocarbons this is variously supported by observations of crosscutting reflectors polarity reversal and drops in instantaneous frequency the thin seal above the reservoir unit facilitates leakage of trapped hydrocarbons hydrocarbons apparently invaded into the seal sediments in the wider vicinity around the crest of the knoll even extending beyond the area where seafloor asphalt is known the asphalt site thus may be a currently active spot while the rest of the crest may be temporarily sealed by solid phase hydrocarbons we propose that a shallow large reservoir with deeply sourced relatively heavy petroleum is principally responsible for the formation of asphalts on the seafloor

estimating suppression of eddy mixing by mean flows particle and tracer based estimates of lateral diffusivities are used to estimate the suppression of eddy mixingacrossstrongcurrents particlesandtracersare advectedusingavelocityfieldderivedfromseasurface height measurements from the south pacific in a region west of drake passage this velocity field has been used in a companion paper to show that both particle and tracer based estimates of eddy diffusivities are equivalent despite recent claims to the contrary these estimates of eddy diffusivities are here analyzed to show 1 that the degree of suppression of mixing across the strong antarctic circumpolar current is correctly predicted by mixing length theory modified to include eddy propagation along the mean flow and 2 that the suppressioncan beinferredfromparticletrajectoriesby studyingthestructureofthe autocorrelationfunction of the particle velocities beyond the first zero crossing these results are then used to discuss how to compute lateral and vertical variations in eddy diffusivities using floats and drifters in the real ocean

statistical analysis of the surface circulation of the california current we use a set of mixed layer drifting buoy trajectories from the california current 20 n 40 n during 1985 1990 to obtain statistically reliable estimates of the mean currents the mean variance field and the geographically varying diffusivity integral timescales and integral space scales typical values for the diffusivity are 1 1 8 7 107 cm2 s 1 while the timescales and space scales are 2 1 7 1 days and 16 59 km respectively the variance field displays a strong westward gradient out to 125 w and diffusivity shows a tendency to decrease toward the southwest part of the domain significant anisotropy is found in the variance field near the coastal boundary and at 30 n 130 w which is the region where the subarctic and northern subtropical fronts approach the california current the antisymmetric component of the diffusivity tensor indicates that cyclonic eddies dominate the mesoscale signature of drifters in this region we seek simple parameterizations to relate the scales of motion of the random velocity field to the diffusivity by testing least squares fits to u02t and u0l where u02 is the velocity variance we found no cases for which these two hypotheses could be distinguished for the meridional component the linear regressions are not successful which suggests that the meridional departure velocities result from a flow regime that is significantly organized by for example waves or coherent structures a subset of the drifters measured temperature along their tracks and we use the resultant data to produce the first direct estimates of the horizontal eddy heat flux divergence based on lagrangian estimates in addition we separately compute the eddy diffusivity parameterization of the eddy heat flux divergence u using our diffusivity estimates and a sea surface temperature climatology the two independent terms agree well which provides a measure of reassurance about the diffusivity estimates the eddy heat flux divergence in the california current is very small 5 w m 2 and does not appear to be significant in the long term heat budget of the upper ocean in this region

raman spectra of carbonaceous material in metasediments a new geothermometer metasedimentary rocks generally contain carbonaceous material cm deriving from the evolution of organic matter originally present in the host sedimentary rock during metamorphic processes this organic matter is progressively transformed into graphite s s and the degree of organisation of cm is known as a reliable indicator of metamorphic grade in this study the degree of organisation of cm was systematically characterised by raman microspectroscopy across several mesozoic and cenozoic reference metamorphic belts this degree of organisation including within sample heterogeneity was quantified by the relative area of the defect band r2 ratio the results from the schistes lustres western alps and sanbagawa japan cross sections show that 1 even through simple visual inspection changes in the cm raman spectrum appear sensitive to variations of metamorphic grade 2 there is an excellent agreement between the r2 values calculated for the two sections when considering samples with an equivalent metamorphic grade and 3 the evolution of the r2 ratio with metamorphic grade is controlled by temperature t along the tinos cross section greece which is characterised by a strong gradient of greenschist facies overprint on eclogite facies rocks the r2 ratio is nearly constant consequently the degree of organisation of cm is not affected by the retrogression and records peak metamorphic conditions more generally analysis of 54 samples representative of high temperature low pressure to high pressure low temperature metamorphic gradients shows that there is a linear correlation between the r2 ratio and the peak temperature t c 445 r2 641 whatever the metamorphic gradient and probably the organic precursor the raman spectrum of cm can therefore be used as a geothermometer of the maximum temperature conditions reached during regional metamorphism temperature can be estimated to 50 c in the range 330 650 c a few technical indications are given for optimal application

fluid flow methane fluxes carbonate precipitation and biogeochemical turnover in gas hydrate bearing sediments at hydrate ridge cascadia margin numerical modeling and mass balances a numerical model was applied to investigate and to quantify biogeochemical processes and methane turnover in gas hydrate bearing surface sediments from a cold vent site situated at hydrate ridge an accretionary structure located in the cascadia margin subduction zone steady state simulations were carried out to obtain a comprehensive overview on the activity in these sediments which are covered with bacterial mats and are affected by strong fluid flow from below the model results underline the dominance of advective fluid flow that forces a large inflow of methane from below 869 mumol cm 2 a 1 inducing high oxidation rates in the surface layers anaerobic methane oxidation is the major process proceeding at a depth integrated rate of 870 mumol cm 2 a 1 a significant fraction 14 of bicarbonate produced by anaerobic methane oxidation is removed from the fluids by precipitation of authigenic aragonite and calcite the total rate of carbonate precipitation 120 mumol cm 2 a 1 allows for the build up of a massive carbonate layer with a thickness of i m over a period of 20 000 years aragonite is the major carbonate mineral formed by anaerobic methane oxidation if the flow velocity of methane charge fluids is high enough greater than or equal to10 cm a 1 to maintain super saturation with respect to this highly soluble carbonate phase it precipitates much faster within the studied surface sediments than previously observed in abiotic laboratory experiments suggesting microbial catalysis the investigated station is characterized by high carbon and oxygen turnover rates approximate to1000 mumol cm 2 a 1 that are well beyond the rates observed at other continental slope sites not affected by fluid venting this underlines the strong impact of fluid venting on the benthic system even though the flow velocity of 10 cm a 1 derived by the model is relative low compared to fluid flow rates found at other cold vent sites non steady state simulations using measured fluid flow velocities as forcing demonstrate a rapid respond of the sediments within a few days to changes in advective flow moreover they reveal that efficient methane oxidation in these sediments prevents methane outflow into the bottom water over a wide range of fluid flow velocities 80 cm a 1 only at flow rates exceeding approximately 100 cm a 1 does dissolved methane break through the sediment surface to induce large fluxes of up to 5000 mumol ch4 cm 2 a 1 into the overlying bottom water

a statistical description of the mean circulation and eddy variability in the northwestern atlantic using sofar floats abstract velocity data obtained from trajectories of sofar floats launched as part of several experiments carried out in the northwest atlantic during the last two decades are used to give a statistical description of the mean gulf stream and its recirculation the distribution of eddy variability in the region is also presented a mean gulf stream which bifurcates between 55 and 45 w to feed the north atlantic current and a southern recirculation can be clearly identified a weak interior sverdrup flow is also suggested the spatial distribution of eddy variability is consistent with previous descriptions showing a maximum near the gulf stream

on too fast baroclinic planetary waves in the general circulation abstract recent altimetric observations of the ocean surface reveal signatures of long planetary waves near the annual frequency band comparisons of the observed wave speeds and those predicted by standard linear theory suggest that the latter is inadequate as it yields different westward speeds than those measured in the extratropical latitudes the predicted speeds are typically slower than the observations here the problem of long baroclinic wave propagation in a forced stratified ocean is considered theoretically with a view toward explaining these observations of too fast planetary waves from a quasigeostrophic analysis it is argued that baroclinic waves in a sheared environment are accelerated to the west via their interactions with both the mean advective field and the mean potential vorticity field conditions under which the ratio of actual to linear phase speeds matches the observed ratio are computed and found to be typical of the open ocean extensions of these ideas to continuously st

marine cold seeps and their manifestations geological control biogeochemical criteria and environmental conditions characteristics of cold seeps at different geologic settings are the subject of this review primarily based on results of the research consortium sfb 574 criteria are drawn from examples on the erosive convergent margin off costa rica the accretionary margin off chile supplemented by examples from the transform margin of the golf of cadiz and the convergent hikurangi margin off new zealand others are from well studied passive margins of the black sea the golf of mexico the eastern mediterranean sea and the south china sea seeps at all settings transport water and dissolved compounds to the ocean through the seafloor by different forcing mechanism and from different depths of the submerged geosphere 10s of meters to 10s of km the compounds sustain oasis type ecosystems by providing bioactive reductants sulfide methane and hydrogen hereby the interaction between fluid composition flux rates and biota results in a diagnostic hydrocarbon metazoan microbe carbonate association currently well over 100 active sites are known the single most important reaction is microbially mediated anaerobic oxidation of methane with secondary reactions involving s biogeochemistry and carbonate mineral precipitation seep fluids and their seafloor manifestations provide clues as to source depth fluid sediment rock interaction during ascent lifetime and cyclicity of seepage events but less so on the magnitude of return flow at erosive margins cl depleted and b enriched fluids from clay dehydration provide criteria for source depth and temperature the upward material flow generates mud volcanoes at the seafloor above the projected location of dehydration at depth at accretionary margins fluids are derived from more shallow depths by compaction of sediments as they ride on the incoming oceanic plate they are emitted through thrust faults at highly sedimented margins organic rich and evaporite containing strata when present determine the final fluid composition by emitting characteristically gas hydrate derived methane brine associated non methane hydrocarbons or leached elements and their isotopes li 7li b ba from host sediments smectite illite transformation and associated cl depletion from release of interlayer water is a pervasive process at these margins rare earth element pattern in conjunction with redox sensitive metals retained in seep carbonates indicate whether or not they precipitated in contact with oxic bottom water or suboxic fluids clear environmental characterization though currently remains inconclusive more deeply sourced fluids as in transform margins may be characterized by their 87sr 86sr ratios from interaction with oceanic crustal rocks below quantification of flow and reliable estimates of total volatile output from fore arcs remain a challenge to seep research as does understanding the role of geologically derived methane in the global methane cycle

pattern formation at the ocean surface sargassum distribution and the role of the eddy field positively buoyant organisms such as the macroalga sargassum and the cyanobacterium trichodesmium often form surface accumulations visible in satellite imagery that have lateral scale separation of tens of kilometers and cannot be explained by langmuir circulation here we discuss the accumulation of floating materials in the ocean in presence of meso and submesoscale activity using high resolution simulations of the ocean mesoscale in both idealized a 3 dimensional box where coherent eddies are forced by small scale winds and realistic domains western gulf of mexico where extensive concentrations of floating sargassum have been recorded in satellite images we show that the distribution of tracers at the ocean surface departs rapidly from that observed a few tens of meters below it such distribution does not resemble that observed for passive tracers in quasi geostrophic turbulence the strong divergence and convergence zones generated at the surface by ageostrophic processes in the submesoscale range are responsible for the creation of areas where the floating material accumulates floating particles are expelled from the core of mesoscale eddies and concentrate in convergence regions in patterns comparable to the ones observed through the satellite images in light of those results sargassum and or trichodesmium may provide a useful proxy to track convergence divergence processes resulting from ageostrophic processes at the ocean surface

statistical analysis of the surface circulation in the california current system using satellite tracked drifters abstract a kinematic description of the surface circulation in the southern california current system is presented using the statistics of the 7 11 month long trajectories of 29 satellite tracked mixed layer drifters the drifters were released north of 30 n and traveled southward at an average speed of 3 4 cm s 1 along baja california through an inhomogeneous field of mesoscale eddies of 15 cm s 1 rms variability lagrangian and eulerian statistics of the variations about this mean southward drift are computed the drifter ensemble mean lagrangian decorrelation time scale is 4 5 days and the lagrangian decorrelation space scale is 40 50 km the computation of dispersion of single particles about the mean drift shows that the theory of diffusion by homogeneous random motion taylor s theory describes these dispersive motions well ensemble mean diffusivities of about 4 107 cm2 s 1 are found on a 200 200 km2 spatial average single partial diffusivities are found to be proportional to the kinetic ene

near surface circulation in the northern north atlantic as inferred from lagrangian drifters variability from the mesoscale to interannual 1 the near surface circulation of the nordic seas is basically cyclonic and consists of jets and recirculation cells which are tightly linked to the bottom topography variable forcing by the large scale rotation of the wind leads to a modulation in the strength of the gyres and their interconnecting jets this is seen in drifter and altimeter data currents are stronger during winter and during phases of high north atlantic oscillation index the exchanges between the north atlantic and the nordic seas do not seem to be directly affected by this variable forcing the narrow boundary currents and the intergyre jets are subject to instability causing mesoscale current fluctuations which contribute to the stirring and mixing of polar and atlantic water masses

spatial variations of stirring in the surface ocean a case study of the tasman sea abstract stirring in the tasman sea is examined using surface geostrophic currents derived from satellite altimeter measurements calculations of the distribution of finite time lyapunov exponents ftles indicate that the stirring in this region is not uniform and stretching rates over 15 days vary from less than 0 02 day 1 to over 0 3 day 1 these variations occur at both small 10 km and large 1000 km scales and in both cases are linked to dynamical features of the flow the small scale variations are related to the characteristics of coherent vortex structures and there are low ftles inside vortices and filaments of high ftles in strain dominated regions surrounding these vortices regional variations in the stirring are closely related to variations in mesoscale activity and eddy kinetic energy eke high values of mean ftle occur in regions of high eke highest mean values of around 0 2 day 1 occur in the east australia current separation region whereas small values occur in regions with low

eulerian and lagrangian velocity distributions in the north atlantic velocity probability density functions pdfs are calculated using data from subsurface current meters in the western north atlantic ocean the pdfs are weakly but significantly non gaussian they deviate from normality because of an excess of energetic events and there are evidently more such events in the main thermocline than in the deep ocean the pdfs are also compared with those obtained from subsurface floats in the same region the pdfs are statistically indistinguishable so long as the float data are averaged in appropriately sized bins taking too small bins yields overly gaussian float pdfs and taking too large bins yields too non gaussian pdfs with this caveat the lagrangian and eulerian pdfs agree consistent with expectations from theory and previous numerical simulations

eulerian and lagrangian eddy statistics of the tasman sea and southwest pacific ocean 1 ocean eddy variability dominates many important processes in the ocean at a range of length and timescales we describe the eddy statistics in the tasman sea new zealand region using drifter data from the global drifter program gdp to derive lagrangian statistics and topex poseidon t p satellite data to derive eulerian statistics the ratio of the lagrangian to eulerian timescales is also a measure of length scales in the ocean when is high lagrangian length scales are short compared with eulerian length scales and vice versa we compute both in the time domain from temporal autocorrelations of drifter and satellite data and in the frequency domain from drifter and satellite velocity spectra the zonal component of this ratio appears to be constant in the tasman sea whereas the meridional component shows a latitudinal dependence we argue that if is known all eulerian and lagrangian timescales can be determined from relatively easy measurements of the eulerian timescale and eddy kinetic velocity

global surface eddy diffusivities derived from satellite altimetry 1 velocities derived from aviso sea surface height observations adjusted to be nondivergent are used to simulate the evolution of passive tracers at the ocean surface eddy mixing rates are derived from the tracer fields in two ways first the method of nakamura is applied to a sector in the east pacific second the osborn cox diffusivity is calculated globally to yield estimates of diffusivity in two dimensions the results from the east pacific show weak meridional mixing at the surface in the southern ocean 1000 m2 s 1 consistent with previous results but higher mixing rates 3000 5000 m2 s 1 in the tropical ocean the osborn cox diagnostic provides a global picture of mixing rates and agrees reasonably well with the results from the east pacific it also shows extremely high mixing rates 104 m2 s 1 in western boundary current regions the osborn cox diffusivity is sensitive to the tracer initialization which we attribute to the presence of anisotropic mixing processes the mixing rates are strongly influenced by the presence of a mean flow nearly everywhere as shown by comparison with an eddy only calculation with the mean flow absent finally results are compared with other recent estimates of mixing rates using lagrangian and inverse methods

tracing the composition and origin of fluids at an ancient hydrocarbon seep hollard mound middle devonian morocco a nd ree and stable isotope study abstract for the first time nd isotope signatures combined with rare earth element ree concentrations were used in investigations of ancient seep carbonates the study was performed on the fossil hydrocarbon seep deposit of the middle devonian hollard mound eastern anti atlas morocco where nd isotopes ree concentrations and carbon and oxygen isotope ratios were measured to investigate the origin former migration pathways and composition of fluids relatively high end values compared to local eifelian seawater as well as consistently appearing positive eu anomalies in mree enriched shale normalized ree patterns of the seep carbonates provided evidence for interaction between the seeping fluids and the lower devonian basaltic volcaniclastics underlying the studied seep deposit strongly reducing conditions and increased temperature of methane formation could have constituted an additional factor in the eu enrichment of the investigated carbonate phases the presence of exclusively negative ce anomalies in these carbonates is in line with observations of other workers that seep limestones may not necessarily display positive ce anomalies indicative of precipitation under anoxic conditions the negative ce anomalies are attributed here to mixing between anoxic pore waters and oxic ce depleted seawater necessary to enable carbonate precipitation at seeps the methane rich fluids ascended most likely from below the volcaniclastic unit and inherited the enriched end signatures and positive eu anomalies due to fluid rock interactions during their seepage to the seafloor the carbon isotope data are most consistent with thermogenic origin of methane although contribution of abiotic and biogenic methane sources cannot be excluded our results indicate that neodymium isotope and rare earth element analyses constitute one of the most valuable tools for reconstructing former fluid migration patterns the study shows also that nd isotopes and eu anomalies can serve as sensitive tracers of fluid rock interactions at submarine springs

observed and modeled global ocean turbulence regimes as deduced from surface trajectory data a large scale tool for systematic analyses of the dispersal and turbulent properties of ocean currents and the subsequent separation of dynamical regimes according to the prevailing trajectories taxonomy in a certain area was proposed by rupolo in the present study this methodology has been extended to the analysis of model trajectories obtained by analytical computations of the particle advection equation using the lagrangian open source software package tracing the water masses of the north atlantic and the mediterranean tracmass and intercomparisons have been made between the surface velocity fields from three different configurations of the global nucleus for european modelling of the ocean nemo ocean sea ice general circulation model lagrangian time scales of the observed and synthetic trajectory datasets have been calculated by means of inverse lagrangian stochastic modeling and the influence of the model field spatial and temporal resolution on the analyses has been investigated in global scale ocean modeling compromises are frequently made in terms of grid resolution and time averaging of the output fields because high resolution data require considerable amounts of storage space here the implications of such approximations on the modeled velocity fields and consequently on the particle dispersion have been assessed through validation against observed drifter tracks this study aims moreover to shed some light on the relatively unknown turbulent properties of near surface ocean dynamics and their representation in numerical models globally and in a number of key regions these results could be of interest for other studies within the field of turbulent eddy diffusion parameterization in ocean models or ocean circulation studies involving long term coarse grid model experiments

observing surf zone dispersion with drifters abstract surf zone dispersion is studied using drifter observations collected within about 200 m of the shoreline at depths of less than about 5 m on a beach with approximately alongshore uniform bathymetry and waves there were about 70 individual drifter releases each 10 20 min in duration on two consecutive days on the first day the sea swell significant wave height hs was equal to 0 5 m and mean alongshore currents were moderate 0 1 m s 1 on the second day the obliquely incident waves were larger with hs equal to 1 4 m and at some surf zone locations was greater than 0 5 m s 1 the one particle diffusivity was larger with larger waves and stronger currents on both days the one particle diffusivity tensor is nonisotropic and time dependent the major axis is initially parallel to the cross shore direction but after a few wave periods it is aligned with the alongshore direction in both the along and cross shore directions the asymptotic diffusivity is reached sooner within r

rare earth elements in seep carbonates as tracers of variable redox conditions at ancient hydrocarbon seeps marine hydrocarbon seeps are dynamic systems which are typically reflected in complex lithologies of limestones forming at these sites in order to test if seep limestones with their multiple generations of carbonate phases reflect variable redox conditions the rare earth element ree patterns of limestones from five ancient hydrocarbon seep localities hollard mound middle devonian iberg mississippian beauvoisin oxfordian canyon and satsop river oligocene and marmorito miocene have been investigated the total ree contents vary widely 0 3 43 7 p p m early microcrystalline phases tend to show higher contents than spatially associated later phases microspar sparite and blocky cement the shale normalized ree patterns of the carbonates show both negative and positive ce anomalies even for individual deposits suggesting that the redox conditions varied significantly it is apparent that in addition to anoxic conditions oxic conditions were common in some ancient seep environments intermittent oxygenation is presumed to have resulted from abrupt changes in fluid flow

estimating lagrangian transport blending drifters with hf radar data and models results from the tosca experiment in the ligurian current north western mediterranean sea abstract lagrangian transport estimates are investigated using results from hf radar model and drifter data during a dedicated experiment in the ligurian current in the toulon area north western mediterranean sea uncertainty estimates on particle position d t are computed and compared to absolute dispersion d 0 t that provides an indication of the uncertainty in case of zero prior knowledge in agreement with previous studies radar results show that d t 1 2 d 0 t i e 6 km after 24 h model results are less reliable as it can be expected in highly nonlinear coastal flows without local data assimilation the central result of this paper is that when drifters are promptly deployed in an area of interest their data can be used to significantly improve transport estimates using the lagrangian blending algorithm lava with velocity fields from models or radar uncertainty can be reduced to 1 6 d 0 t i e 2 km after 24 h for both radar and model implying a much reduced search range in case of operational applications the method is also found to have some forecasting skills with uncertainty 1 2 d 0 t during the first 6 h sensitivity tests provide indications on relevant time and space scales of predictability and provide suggestions for appropriate drifter sampling strategies

zonal structure of the mean flow and eddies in the azores current system 1 the surface circulation and eddy field from the azores current system are studied here by analyzing surface drifters records and altimetry maps collected over more than 16 years clear differences in mean flow and eddy characteristics allow for a classification of the azores current in three zonal sectors west of 30 w between the mid atlantic ridge and the hyeres atlantis seamount system between 30 w and the longitude of madeira and east of madeira a detailed and quantitative characterization of each sector is given the transition between the western and central parts is controlled by the hyeres atlantis ridge in the transition to the eastern sector there is a change in the dynamics and the flow is forced by the cyclonic recirculation driven by the mediterranean outflow there is no clear expression of a continuous surface northern counterflow but three distinct westward flows are seen one along the southeastern border of the azores plateau another one southwest of madeira and a third one along 31 n west of the hyeres seamount no clear tilt in the axis of the azores current is found in the calculated mean surface flow from surface drifters observations from both drifters and altimetry data show that anticyclonic features dominate in the northern region whereas cyclonic ones dominate in the southern region overall cyclones are more numerous constituting 60 of large eddies the eddy features detected in the west tend to be larger than those in the east both in size and sea level anomaly there is indication of different mean propagation speeds east and west of 25 w 30 w with the mean speeds consistently increasing by 25 45 in the west estimates for the rate of formation of strong eddies range from 1 4 to 2 4 year 1 for cyclones and 1 2 to 1 7 year 1 for anticyclones

a lagrangian based approach for determining trajectories taxonomy and turbulence regimes abstract the use of the ratio between the acceleration and velocity time scales y ta t to separate lagrangian trajectories in homogeneous classes is proposed in fact when analyzing subsurface floats data in the atlantic ocean and surface drifters data in the world s ocean basins it is observed that trajectories having different values of y are characterized by different shapes correlation and dispersal properties in particular trajectories having similar values of the acceleration and velocity time scales clearly show the influence of eddies and are characterized by an oscillating velocity correlation function it is shown here that this trajectory screening is a useful procedure to rationalize the analysis of real lagrangian trajectories and to avoid a mixture of different regimes when averaging quantities the mean statistical quantities computed averaging on quasi homogeneous datasets put in evidence the role of the coherent structures in the dispersion properties both in time and in the ma

variability of the norwegian atlantic current and associated eddy field from surface drifters the norwegian atlantic current nwac and its eddy field are examined using data from surface drifters the data set used spans nearly 20 years from june 1991 to december 2009 the results are largely consistent with previous estimates which were based on data from the first decade only with our new data set statistical analysis of the mean fields can be calculated with larger confidence the two branches of the nwac one over the continental slope and a second further offshore are clearly captured the norwegian coastal current is also resolved in addition we observe a semipermanent anticylonic eddy in the lofoten basin a feature seen previously in hydrography and in models the eddy kinetic energy eke is intensified along the path of the nwac with the largest values occurring in the lofoten basin the strongest currents exceeding 100 cm s 1 occur west of lofoten lateral diffusivities were computed in five domains and ranged from 1 5 107 cm2 s 1 the lagrangian integral time and space scales are 1 2 days and 7 23 km respectively the data set allows studies of seasonal and interannual variations as well the strongest seasonal signal is in the nwac itself as the mean flow strengthens by approximately 20 in winter the eke and diffusivities on the other hand do not exhibit consistent seasonality in the sampled regions there are no consistent indications of changes in either the mean or fluctuating surface velocities between the 1990s and 2000s

paleoredox variations in ancient oceans recorded by rare earth elements in fossil apatite abstract rare earth element concentrations in biogenic apatite of conodonts fish debris and inarticulate brachiopods were determined in over 200 samples from cambrian to modern sediments tests for experimental bias caused by the chemicals used to separate fossils from the rock matrix and for interlaboratory interexperiment or interspecies related variations clearly show that no resolvable fractionation of ree occurs incorporation of ree in biogenic apatite of recent fish debris occurs near the sediment water interface soon after deposition and reflects characteristics of seawater the original ree signature apparently survives subsequent burial and diagenesis cerium variations in fish debris from modern environments are controlled by redox potential ce is fractionated by co precipitation with metallic oxides under oxidizing conditions this fractionation produces a negative ce anomaly ce anom in seawater that is reflected in the sedimented fish debris conversely no fractionation of ce occurs under reducing conditions resulting in ce concentrations that are normal to enriched in anoxic seawater and fish debris deposited under local or basinwide anoxic conditions extrapolation of observations of the redox control of ce anom in modern oceans to fossil apatite indicates that anoxic conditions were prevalent in lower paleozoic and lower triassic oceans whereas in the upper paleozoic the world ocean was generally oxidizing

eulerian and lagrangian statistics in the south china sea as deduced from surface drifters abstracteulerian and lagrangian statistics of the surface flows over the south china sea scs are investigated based on observations of satellite tracked lagrangian drifters of the surface velocity program although the dataset contains the most recent observations up to 2011 the spatial and temporal distributions of the data are quite inhomogeneous the luzon strait as well as the northern and western parts of the scs are heavily sampled by drifters whereas the internal scs is less sampled the overall eulerian mean circulation derived from all drifter observations resembles the wintertime circulations because of the seasonal sampling bias toward wintertime it is found that the calculation of the diffusivity may be misled by the low frequency temporal variabilities such as annual cycle which could be removed using the gauss markov decomposition in the regions around luzon strait typical values of diffusivity time scale and length scale are 3 7 11 9 107 cm2 s 1 0 8 1 9 days and 16 4 44 4 km r

the effect of diagenesis and fluid migration on rare earth element distribution in pore fluids of the northern cascadia accretionary margin analytical challenges in obtaining high quality measurements of rare earth elements rees from small pore fluid volumes have limited the application of rees as deep fluid geochemical tracers using a recently developed analytical technique we analyzed rees from pore fluids collected from sites u1325 and u1329 drilled on the northern cascadia margin during the integrated ocean drilling program iodp expedition 311 to investigate the ree behavior during diagenesis and their utility as tracers of deep fluid migration these sites were selected because they represent contrasting settings on an accretionary margin a ponded basin at the toe of the margin and the landward tofino basin near the shelf s edge ree concentrations of pore fluid in the methanogenic zone at sites u1325 and u1329 correlate positively with concentrations of dissolved organic carbon doc and alkalinity fractionations across the ree series are driven by preferential complexation of the heavy rees simultaneous enrichment of diagenetic indicators doc and alkalinity and of rees in particular the heavy elements ho to lu suggests that the heavy rees are released during particulate organic carbon poc degradation and are subsequently chelated by doc ree concentrations are greater at site u1325 a site where shorter residence times of poc in sulfate bearing redox zones may enhance ree burial efficiency within sulfidic and methanogenic sediment zones where ree release ensues cross plots of la concentrations versus cl li and sr delineate a distinct field for the deep fluids z 75 mbsf at site u1329 and indicate the presence of a fluid not observed at the other sites drilled on the cascadia margin changes in ree patterns the presence of a positive eu anomaly and other available geochemical data for this site suggest a complex hydrology and possible interaction with the igneous crescent terrane located east of the drilled transect

natural oil seep detection in the santa barbara channel california with shuttle imaging radar natural submarine oil seeps in the santa barbara channel california were detected by the first shuttle imaging radar sir a oil slicks on the ocean are seen in radar imagery as areas of decreased radar signal return that result from a damping of surface roughness orbital radar imagery shows promise as an effective and efficient means of mapping submarine oil seeps as sources of naturally occurring oil slicks

lagrangian eddy scales in the northern atlantic ocean eddy time and length scales are calculated from surface drifter and subsurface float observations in the northern atlantic ocean outside the energetic gulf stream subsurface timescales are relatively constant at depths from 700 m to 2000 m length scale and the characteristic eddy speed decrease with increasing depth below 700 m but length scale stays relatively constant in the upper several hundred meters of the gulf stream it is suggested that this behavior is due to the lagrangian sampling of the mesoscale field in limits set by the eulerian eddy scales and the eddy kinetic energy in high energy regions of the surface and near surface north atlantic the eddy field is in the frozen field lagrangian sampling regime for which the lagrangian and eulerian length scales are proportional however throughout much of the deep ocean interior the eddy field may be in the fixed float regime for which the lagrangian and eulerian timescales are nearly equal this does not necessarily imply that the deep interior is nearly linear as fixed float sampling is possible in a flow field of o 1 nonlinearity

methane discharge into the black sea and the global ocean via fluid flow through submarine mud volcanoes during the margasch cruise m52 1 in 2001 with rv meteor we sampled surface sediments from three stations in the crater of the dvurechenskii mud volcano dmv located in the sorokin trough of the black sea and one reference station situated 15 km to the northeast of the dmv we analysed the pore water for sulphide methane alkalinity sulphate and chloride concentrations and determined the concentrations of particulate organic carbon carbonate and sulphur in surface sediments rates of anaerobic oxidation of methane aom were determined using a radiotracer 14ch4 incubation method numerical transport reaction models were applied to derive the velocity of upward fluid flow through the quiescently dewatering dmv to calculate rates of aom in surface sediments and to determine methane fluxes into the overlying water column according to the model aom consumes 79 of the average methane flux from depth 8 9 10 6 mol a 1 such that the resulting dissolved methane emission from the volcano into the overlying bottom water can be determined as 1 9 10 6 mol a 1 if it is assumed that all submarine mud volcanoes smvs in the black sea are at an activity level like the dmv the resulting seepage represents less than 0 1 of the total methane flux into this anoxic marginal sea the new data from the dmv and previously published studies indicate that an average smv emits about 2 0 10 6 mol a 1 into the ocean via quiescent dewatering the global flux of dissolved methane from smvs into the ocean is estimated to fall into the order of 10 10 mol a 1 additional methane fluxes arise during periods of active mud expulsion and gas bubbling occurring episodically at the dmv and other smvs

lagrangian observations of the middepth and deep velocity fields of the northeastern atlantic ocean the circulation of the northeastern atlantic ocean at intermediate depths is characterized by watermass transformation processes that involve iceland scotland overflow water isow from the northeast labrador sea water lsw from the west and mediterranean water from the south field observations were carried out with 89 eddy resolving floats rafos and marvor types the data coverage achieved is remarkably high and enables a comprehensive study of the eastern basins between iceland and the azores the trajectories show typical pathways of the water masses involved and the role that the complex bottom topography plays in defining them the isow paths tend to lean against the slopes of the reykjanes ridge and rockall plateau westward escapes through multiple gaps in the ridge are possible superimposed on a sustained southward flow in the eastern basin along the mid atlantic ridge lsw pathways leading to the eastern basins are subject to high variability in flow direction and eddy activity in addition to a selection of characteristic trajectories maps of the horizontal distributions of lagrangian eddy kinetic energy and integral time scales are presented these reveal distinct areas of intensified mixing in the iceland basin as well as the sharp contrast between the subpolar and subtropical dynamics a self contained eddy detection scheme is applied to obtain statistics on individual eddy properties and their abundance it is suggested that much of the intensified mixing can be related to cyclonic activity particularly in the subpolar region

variational analysis of drifter positions and model outputs for the reconstruction of surface currents in the central adriatic during fall 2002 1 in this paper we present an application of a variational method for the reconstruction of the velocity field in a coastal flow in the central adriatic sea using in situ data from surface drifters and outputs from the roms circulation model the variational approach previously developed and tested for mesoscale open ocean flows has been improved and adapted to account for inhomogeneities on boundary current dynamics over complex bathymetry and coastline and for weak lagrangian persistence in coastal flows the velocity reconstruction is performed using nine drifter trajectories over 45 d and a hierarchy of indirect tests is introduced to evaluate the results as the real ocean state is not known for internal consistency and impact of the analysis three diagnostics characterizing the particle prediction and transport in terms of residence times in various zones and export rates from the boundary current toward the interior show that the reconstruction is quite effective a qualitative comparison with sea color data from the modis satellite images shows that the reconstruction significantly improves the description of the boundary current with respect to the roms model first guess capturing its main features and its exchanges with the interior when sampled by the drifters

rare earth elements in cold seep carbonates from the niger delta abstract the circulation of methane rich fluids at cold seeps often leads to precipitation of authigenic carbonates mediated by microbial activity which can be used as archives of fluid seepage on continental margins in this study we have investigated the potential of using rare earth element ree concentrations in authigenic carbonates for tracing fluid sources and providing information on associated biogeochemical processes at cold seeps we have examined various chemical procedures for the analysis of ree in authigenic carbonates and present a robust method using dilute acetic acid solution that allows the extraction of ree from carbonate phases with reduced contamination from fe mn oxides and detrital minerals using this method we analysed a series of carbonate samples collected at various deep sea sites of active fluid seepage on the niger delta for their ree and trace element concentrations 13c and 18o values and 87sr 86sr isotope compositions we show that the ree composition of cold seep carbonates is controlled primarily by that of the fluid from which they have precipitated our results also suggest that significant ree fractionation can occur during carbonate precipitation which can be related to various degrees of ree complexation by organic versus carbonate ligands in response to changing pore water chemical composition for parameters such as carbonate alkalinity

estimates and implications of surface eddy diffusivity in the southern ocean derived from tracer transport abstract near surface effective diffusivities associated with geostrophic eddies in the southern ocean are estimated by numerically monitoring the lengthening of idealized tracer contours as they are strained by surface geostrophic flow observed by satellite altimetry the resulting surface diffusivities show considerable spatial variability and are large 2000 m2 s 1 on the equatorward flank of the antarctic circumpolar current and are small 500 m2 s 1 at the jet axis regions of high and low effective diffusivity are shown to be collocated with regions of respectively weak and strong isentropic potential vorticity gradients the maps of diffusivity are used along with climatological estimates of surface wind stress and air sea buoyancy flux to estimate surface meridional residual flows and the relative importance of eulerian and eddy induced circulation in the streamwise averaged dynamics of the antarctic circumpolar current

lagrangian time scales and eddy diffusivity at 1000 m compared to the surface in the south pacific and indian oceans abstractargo floats cannot be regarded as true lagrangian drifters because they periodically rise to the surface hence previous estimates of eddy diffusivity at depth using single particle statistics have been limited to one submerged cycle however unless the lagrangian time scale is significantly shorter than the argo cycle time this single particle calculation can have a large bias here eddy diffusivity computed from single particle statistics using argo data is compared to that computed by assuming that eulerian scales at depth are the same as at the surface and that the relationship between lagrangian and eulerian time scales derived by middleton is valid if the methods provide the same answer one can have confidence in both methods eddy diffusivity calculated from the single particle statistics shows the same spatial structure as that computed from inferred time scale but is smaller by a factor of about 2 it is suggested that this is because the deep lagrangian time scale over much of th

formation of carbonate chimneys in the mediterranean sea linked to deep water oxygen depletion marine sediments at ocean margins vent substantial amounts of methane1 2 microbial oxidation of the methane released can trigger the precipitation of carbonate within sediments and support a broad diversity of seafloor ecosystems3 4 the factors controlling microbial activity and carbonate precipitation associated with the seepage of submarine fluid over geological time remain poorly constrained here we characterize the petrology and geochemistry of rocks sampled from metre size build ups of methane derived carbonate chimneys located at the amon mud volcano on the nile deep sea fan we find that these carbonates comprise porous structures composed of aggregated spherules of aragonite and closely resemble microbial carbonate reefs forming at present in the anoxic bottom waters of the black sea5 using u series dating we show that the amon carbonate build ups formed between 12 and 7 thousand years ago contemporaneous with the deposition of organic rich sediments in the eastern mediterranean the so called sapropel layer s1 we propose that the onset of deep water suboxic or anoxic conditions associated with sapropel formation resulted in the development of intense anaerobic microbial activity at the sea floor and thus the formation of carbonate chimneys

year long float trajectories in the labrador sea water of the eastern north atlantic ocean abstract year long lagrangian trajectories within the labrador sea water of the eastern north atlantic ocean are analysed for basic flow statistics root mean square velocities at 1750 m depth are about 2 cm s except within the north atlantic current where they are twice as large these values are consistent with previous eulerian measurements and extend those results to a much larger domain of the eastern basin mean flow estimates in boxes large enough to contain about 1 float year of data indicate that labrador sea water having crossed the mid atlantic ridge not resolved near 50 55 n presumably with the north atlantic current partially recirculates to the north in the subpolar gyre as well as entering the subtropical gyre and continuing south and west the circulation of this water mass as defined by the 1 yr average velocities is stronger than traditional models of deep circulation would suggest with an interior flow of roughly 1 cm s mean speeds up to 3 cm s were observed with the highest values near the azores plateau north of 45 n 55 n mean eastward speeds closer to 0 2 cm s were observed wind generated barotropic fluctuations may be responsible for some part of the transport at this depth

anisotropic material transport by eddies and eddy driven currents in a model of the north atlantic this study analyzes anisotropic properties of the material transport by eddies and eddy driven zonal jets in a general circulation model of the north atlantic through the analysis of lagrangian particle trajectories spreading rates defined here as half the rate of change in the particle dispersion in the zonal direction systematically exceed the meridional rates by an order of magnitude area averaged values for the upperocean zonal and meridional spreading rates are approximately 8100 and 1400 m 2 s 21 respectively and in the deep ocean they are 2400 and 200 m 2 s 21 the results demonstrate that this anisotropy is mainly due to the actionofthetransienteddiesandnotto thesheardispersionassociated withthetime meanjets thisproperty is consistent with the fact that eddies in this study have zonally elongated shapes with the exception of the upper ocean subpolar gyre eddies also cause the superdiffusive zonal spreading significant variations in the spreading rate in the vertical and meridional directions and the difference between the westward and eastward spreading

north atlantic surface circulation during the 1990 s observed with satellite tracked drifters a new compilation of lagrangian velocity observations describes the state of the north atlantic surface circulation during the 1990s gridded fields of velocity and eddy kinetic energy eke are constructed from trajectories of more than 1500 15 m drogued satellite tracked surface drifters in service between january 1990 and december 1999 this time period overlaps a coordinated field study of circulation and variability in the north atlantic completed between 1996 2000 as part of the world ocean circulation experiment we describe the construction of a self consistent drifter climatology present decadal mean quasi eulerian velocity and eke fields computed on a 1 grid and compare these results with contemporary satellite measurements detailed discussion of the inferred surface circulation is focused on three regions 1 the gulf stream and north atlantic current 2 the labrador sea and subpolar gyre and 3 the caribbean sea the swiftest drifter motions were found in the equatorial region and along the tropical subtropical and subpolar western boundaries the maximum instantaneous speed determined from a single quality controlled and filtered drifter observation was 273 cm s 1 in the gulf stream southeast of cape cod the highest eke value in the north atlantic 2790 cm2 s 2 was found in the gulf stream just downstream of the new england seamounts over most of the atlantic basin drifter derived eke values were found to be o 100 cm2 s 2 higher than corresponding values derived from satellite altimetry in the labrador sea a region of sharply elevated eke appears to be geographically related to the localized ejection of drifters and by extension mass and kinetic energy from the energetic west greenland current between 60 and 62 n when compared to drifter measurements made in the late 1970s our results suggest but do not statistically confirm an enhancement and slight northward shift of the zonal gulf stream extension such a shift is consistent in sign with expectations based on observed interdecadal variations in wind stress and subtropical gyre potential energy associated with the north atlantic oscillation

surface drifter pair spreading in the north atlantic 1 this study examines spreading of surface drifter pairs deployed as part of the clivar mode water dynamic experiment climode project in the gulf stream region the spreading is resolved at hourly resolution and quantified by relative dispersion and finite scale lyapunov exponents at scales from 1 3 km to 300 500 km the dispersion follows richardson s law indicating stirring by eddies comparable in scale to the pair separation distance at larger scales the spreading becomes a random walk described by a constant diffusivity the behavior from 1 3 km to the local deformation radius is inconsistent with the enstrophy cascade of 2 d quasigeostrophic turbulence to test various hypotheses for this result drifter pair spreading is examined for pairs that were not launched together pairs deployed in the eastern subtropical north atlantic and climode pairs subsampled to daily temporal resolution our results indicate the presence of significant energy at the submesoscale in the gulf stream region which flattens the wave number spectrum and dominates surface stirring at this scale range results in the less energetic subtropical eastern atlantic are more equivocal

an eddy permitting model of the atlantic circulation evaluating open boundary conditions as part of the french clipper project an eddy permitting model of the atlantic circulation has been run for 22 years the domain has open boundaries at drake passage and at 30 e from africa to antarctica the simulated mean circulation as well as the eddy activity is satisfactory for a 1 3 model resolution and the meridional heat transport at 30 s is within the range estimated from observations we use the mixed open boundary algorithm of barnier et al 1998 which has both a radiation condition and a relaxation to climatology the climatological boundary forcing strongly constrains the solution in the whole domain the model heat balance adjusts through the surface heat flux retroaction term more than the open boundaries the radiation phase velocities calculated within the algorithm are analyzed this shows quite surprisingly that both the eastern and western boundaries have a similar behavior regardless of the preferred directions for advection mainly eastward and wave propagation mainly westward our results confirm that open boundary algorithms behave differently according to the dynamics of the region considered the passive boundary condition that penduff et al 2000 applied successfully in the north eastern atlantic does not work in the present south atlantic model we emphasize the need for a careful prescription of the climatology at the open boundary for which a new approach based on synoptic sections is implemented

biogeochemical controls on authigenic carbonate formation at the chapopote asphalt volcano bay of campeche abstract the campeche knolls in the bay of campeche southern gulf of mexico were investigated through detailed seafloor mapping rov surveys and sediment and pore water sampling the knolls are elongated submarine hills created by salt tectonics with a positive relief of up to 800 m above the surrounding seafloor several of the knolls are associated with sea surface oil slicks identified from satellite data indicating the presence of hydrocarbon seeps on the seafloor one of the knolls named chapopote was studied in detail during two international research expeditions so174 2 and m67 2 and is characterized by extensive hydrocarbon seepage including large asphalt flows oil and gas seeps and seafloor gas hydrate deposits chemosymbiotic biological communities and authigenic carbonate deposits are associated with the seeps and are the result of both biogeochemical turnover and the interaction between downward diffusing seawater and hydrocarbon rich pore fluids at shallow sediment depth authigenic carbonates are characterized by aragonite exhibit a porous texture and are cemented by a matrix of microsparitic to sparitic aragonite macropores of the carbonates were completely filled with liquid oil carbonate microfabrics include peloidal or clotted fabrics that may indicate the existence of microenvironments resulting from microbial metabolism banded botryoidal aragonite cements line the intra and bioclasts and incompletely fill the pore spaces the stable carbon isotopic composition of authigenic aragonite varies between 28 6 and 17 9 pdb identifying oil oxidation as the primary source of carbon to the dic pool while lipid biomarker data demonstrate the concurrent existence of microbial communities responsible for anaerobic oxidation of methane aom these observations indicate the presence of additional aom independent reactions responsible for carbon sequestration at hydrocarbon seeps and demonstrate the complexity of biogeochemical processes at seep sites in the gulf of mexico basin oxygen isotope data of authigenic aragonite vary from 2 5 to 3 8 pdb indicating carbonate precipitation in slight disequilibrium with the surrounding pore fluids

robustness of an effective diffusivity diagnostic in oceanic flows the robustness of nakamura s effective diffusivity diagnostic for quantifying eddy diffusivities of tracers within a streamwise average framework is carefully examined in an oceanographic context and the limits of its applicability are detailed the near surface southern ocean geostrophic flow obtained from altimetric observations is chosen for particular examination since it exhibits strong eddy activity careful analysis indicates that the effective diffusivity calculation is not strongly sensitive to the resolution of the velocity field or to the tracer initial conditions after a spinup time of 3 months and that a numerical diffusivity of 50 m 2 s 21 is appropriate to resolve the batchelor scale at a computational resolution of 1 208 the spatial variability of the effective diffusivity is examined and shown to be related to the eddy kinetic energy eke mean zonal current u and phase speed of the eddies c following the streamwise averge of eke u 2 c 2 in agreement with linear baroclinic instability theory the temporal variability of the effective diffusivity over the period 1996 2001 indicates significant variability on seasonal time scales with a magnitude of 610 215 interannual variations are investigated and discussed in the context of changes in the wind stress associated with the southern annular mode

eulerian and lagrangian isopycnal eddy diffusivities in the southern ocean of an eddying model abstractlagrangian isopycnal diffusivities quantify the along isopycnal mixing of any tracer with mean gradients along isopycnal surfaces they are studied in the southern ocean of the 1 10 parallel ocean program pop model using more than 50 000 float trajectories concurrent eulerian isopycnal diffusivities are estimated directly from the eddy fluxes and mean tracer gradients consistency spatial variation and relation to mean jets are evaluated the diffusivities are calculated in bins large enough to reduce contributions from the rotational components that do not lead to net tracer mixing because the mean jets are nonzonal and nonparallel meridional dispersion includes standing eddies and is significantly different from cross stream dispersion with the subtraction of the local eulerian mean the full lagrangian diffusivity tensor can be estimated along stream diffusivities are about 6 times larger than cross stream diffusivities along streamline averages of eulerian and lagrangian isopycnal d

a comprehensive approach to the study of methane seep deposits from the lincoln creek formation western washington state usa a comprehensive approach using palaeontology petrography stable isotope geochemistry and biomarker analyses was applied to the study of seven small methane seep carbonate deposits these deposits are in the oligocene part of the lincoln creek formation exposed along the canyon and satsop rivers in western washington each deposit preserves invertebrate fossils many representing typical seep biota authigenic carbonates with 1 3 c values as low as 51 pdb reveal that the carbon is predominately methane derived carbonates contain the irregular isoprenoid hydrocarbons 2 6 11 15 tetramethylhexadecane crocetane and 2 6 10 15 19 pentamethylicosane pmi lipid biomarkers diagnostic for archaea these lipids are strongly depleted in 1 3 c 1 3 c values as low as 120 pdb indicating that archaea were involved in the anaerobic oxidation of methane small filaments preserved in the carbonate may represent methanotrophic archaea archaeal methanogenesis induced the formation of a late diagenetic phase brownish calcite consisting of dumbbell shaped crystal aggregates that exhibit 1 3 c values as high as 7 pdb clotted microfabrics of primary origin point to microbial mediation of carbonate precipitation downward directed carbonate aggregation in the seeps produced inverted stromatactoid cavities large filaments interpreted as green algae based on their size shape arrangement and biomarkers imply that deposition occurred in places in water no deeper than 210 m

eddies observed by argo floats part i eddy transport in the upper 1000 dbar abstractargo floats measure horizontal current velocities at the parking depth and vertical profiles of temperature and salinity the data are sufficient for simultaneous estimates of velocities and vertical displacements of isopycnal surfaces more than 980 000 pairs of observations of current velocity and water column stratification were used to calculate eddy transport above 1000 dbar and its uncertainty based on the temporal residual mean framework eddy transports larger than 1 0 m2 s 1 were found in the north atlantic western north pacific and southern oceans the eddy transport t had components perpendicular and parallel to the density contours at 1000 dbar in the midlatitude oceans eddy transport was weaker 0 5 m2 s 1 mostly perpendicular to the density contours and equatorward a large area of northward was found in the south indian ocean analysis of velocity and thickness perturbations suggested that this transport was a northward intrusion of antarctic intermediate water in the midla

the mediterranean outflow splitting a comparison between theoretical models and canigo data abstract the mediterranean outflow in the atlantic is vertically subdivided into two main cores that are identified by temperature and salinity maxima hydrological data collected west of the strait of gibraltar and off the south and south west coasts of portugal in september 1997 have been used in two different models to shed some light on the mechanisms that cause a splitting of the mediterranean outflow these models are i a steady one dimensional streamtube model and ii a local time dependent model that includes cross stream variations the streamtube model applied at the northern respectively the southern part of the outflow appears capable of reproducing the observed density difference between the two cores the vertical separation however was underestimated the results from the local model suggest that a bump in the bottom topography may be a determining factor for the splitting tendency of the flow

raman spectrum of carbonaceous material a possible metamorphic grade indicator for low grade metamorphic rocks raman spectral analyses of carbonaceous material cm extracted from pelitic samples along two sections traversing the metamorphic belt of taiwan were carried out in the present study the results show similar spectral variations of cm with metamorphic grade as those documented in the literature however continuous sampling from zeolite facies through prehnite pumpellyite facies to greenschist facies metamorphic rocks in the present study does reveal some interesting features on the raman spectra of cm that were not noted before both the raman d disordered o ordered peak area i e integrated intensity ratio and the d o peak width i e full width at half maximum fwhm ratio of the cm decrease with progressive metamorphism but the most prominent change in the d o peak area ratio occurs in samples of lower greenschist facies metamorphic grade while the most significant decrease in the d o peak width ratio occurs in samples near the boundary of prehnite pumpellyite facies and greenschist facies this phenomenon is interpreted as a result of the decoupling of the changing rates of in plane crystallite size and degree of defects of cm with progressive metamorphism it is postulated that the raman spectrum of cm can serve as a metamorphic grade indicator to distinguish samples of prehnite pumpellyite facies metamorphic grade from those of greenschist facies metamorphic grade

does the potential vorticity distribution constrain the spreading of floats in the north atlantic float trajectories are compared with the distribution of climatological potential vorticity q on approximate isentropic surfaces for intermediate waters in the north atlantic the time mean displacement and eddy dispersion are calculated for clusters of floats in terms of their movement along and across q contours for float clusters with significant mean velocities the mean flow crosses q contours at an angle of typically less than 208 308 in magnitude in the ocean interior the implied peclet number in the ocean interior ranges from 1 to 19 with a weighted mean value of 4 4 this mean peclet number suggests that there is significant eddy mixing in the ocean interior tracers should only be quasi conserved along mean streamlines over a subbasin scale rather than over an entire basin the mean flow also strongly crosses q contours near the western boundary in the tropics where the implied peclet number is 0 7 this value may be a lower bound as q contours are assumed to be zonal and relative vorticity is ignored float clusters with a lifetime greater than 200 days show anisotropic dispersion with greater dispersion along q contours than across them float clusters with shorter lifetimes are ambiguous this anisotropic dispersion along q contours cannot generally be distinguished from enhanced dispersion along latitude circles since q contours are generally zonal for these cases however for the null case of uniform q for the gulf stream at 2000 m there is strong isotropic dispersion rather than enhanced zonal dispersion in summary diagnostics suggest that floats preferentially spread along q contours over a subbasin scale and imply that passive tracers should likewise preferentially spread along q contours in the ocean interior

isopycnal diffusivities in the antarctic circumpolar current inferred from lagrangian floats in an eddying model average 750 250 m 2 s 1 around the polar frontal zone the results imply that parameterizations that only use eddy kinetic energy to parameterize the diffusivities are incomplete we suggest that dominant correlations of lagrangian eddy diffusivities with eddy kinetic energy found in previous studies may have been due to the use of too short time lags in the integration of the velocity autocovariance used to infer the diffusivities we find evidence that strong mean flow inhibits cross stream mixing within the acc but there are also areas where cross stream diffusivities are large in spite of strong mean flows for example in regions close to topographic obstacles such as the kerguelen plateau

rare earth elements in authigenic methane seep carbonates as tracers for fluid composition during early diagenesis abstract authigenic carbonates forming at an active methane seep on the makran accretionary prism mainly consist of aragonite in the form of microcrystalline cryptocrystalline and botryoidal phases the 13 c carbonate values are very negative 49 0 to 44 0 v pdb agreeing with microbial methane as dominant carbon source the 18 o carbonate values are exclusively positive 3 0 to 4 5 v pdb and indicate precipitation in equilibrium with seawater at bottom water temperatures the content of rare earth elements and yttrium ree y determined by laser ablation inductively coupled plasma mass spectrometry la icp ms and solution icp ms varies for each aragonite variety with early microcrystalline aragonite yielding the highest cryptocrystalline aragonite intermediate and later botryoidal aragonite the lowest ree y concentrations shale normalised ree y patterns of different types of authigenic carbonate reflect distinct pore fluid compositions during precipitation microcrystalline aragonite shows high contents of middle rare earth elements mree reflecting ree patterns ascribed to anoxic pore water cryptocrystalline aragonite exhibits a seawater like ree y pattern at elevated total ree y concentrations indicating higher concentrations of rees in pore waters which were influenced by seawater botryoidal aragonite is characterised by seawater like ree y patterns at initial growth stages followed by an increase of light rare earth elements lree with advancing crystal growth reflecting changing pore fluid composition during precipitation of this cement conventional sample preparation involving micro drilling of carbonate phases and subsequent solution icp ms does not allow to recognise such subtle changes in the ree y composition of individual carbonate phases to be able to reconstruct the evolution of pore water composition during early diagenesis an analytical approach is required that allows to track the changing elemental composition in a paragenetic sequence as well as in individual phases high resolution analysis of seep carbonates from the makran accretionary prism by la icp ms reveals that pore fluid composition not only evolved in the course of the formation of different phases but also changed during the precipitation of individual phases

characteristics of the near surface currents in the indian ocean as deduced from satellite tracked surface drifters part i pseudo eulerian statistics using the 1985 2013 record of near surface currents from satellite tracked drifters the pseudo eulerian statistics of the near surface circulation in the indian ocean io are analyzed it is found that the distributions of the current velocities and mean kinetic energy mke in the io are extremely inhomogeneous in space and nonstationary in time the most energetic regions with climatologic mean velocity over 50cms 21 and mke over 500cm 2 s 22 are found off the eastern coast of somalia with maxima of over 100cms 21 and 1500cm 2 s 22 and the equatorial io associated with the strong annually reversing somalia current and the twice a year eastward equatorial jets high eddy kinetic energy eke is found in regions of the equatorial io western boundary currents and agulhas return current with a maximum of over 3000cm 2 s 22 off the eastern coast of somalia the lowest eke 500cm 2 s 22 occurs in the south subtropical gyre between 308 and 408s and the central eastern arabian sea annual and semiannual variability is a significant fraction of the total eke off the eastern coast of somalia and in the central eastern equatorial io in general both the mke and eke estimated in the present study are qualitatively in agreement with but quantitatively larger than estimates from previous studies these pseudo eulerian mke and eke fields based on the most extensivedrifterdatasettodate arethemostpreciseinsituestimatestodateandcanbeusedtovalidatesatellite and numerical results

general circulation of the western subtropical north atlantic observed using profiling floats 1 the general circulation of the subtropical western north atlantic is described using hydrography and subsurface velocity measured simultaneously by 71 profiling floats during the period july 1997 to december 2002 subsurface trajectories of the floats revealed a strong topographic influence and depth dependence of the gulf stream its recirculation gyres and the north atlantic current we discuss eddy like and nonsteady flows in several subregions especially near the major topographic features the seasonal cycle of volume transport estimated using the absolute geostrophic velocity in the upper 900 m was shown to be a maximum in winter and minimum in summer the eddy kinetic energy and eddy diffusivity derived from the float data and mapped over the subtopical gyre show seasonal variability in the vicinity of the gulf stream with a maximum in spring and minimum in winter for both quantities

in situ estimates of submesoscale horizontal eddy diffusivity across an ocean front in the last decade the rapid advancements in computational power have favored the development of high resolution numerical models capable of directly resolving small scale structures such as fronts and filaments such models have greatly improved our understanding of submesoscale dynamics at the same time the small dimensions and short duration of these structures still pose major challenges for small scale dedicated field experiments for this reason submesoscale studies from in situ observations are still relatively scarce and quantitative estimates of key physical parameters for high resolution numerical models such as horizontal eddy diffusivity are still lacking this study presents a novel approach for computing in situ horizontal eddy diffusivity associated with frontal structures by combining cross front widths derived from surface thermosalinograph sections with stirring rates estimated from lagrangian drifter trajectories the method is applied to the measurements collected across a frontal structure observed in the western part of the gulf of lion during the latex10 campaign lagrangian transport experiment 1 24 september 2010 a total of 76 estimates of eddy diffusivity were obtained for strain rates of 0 70 and 1 21 day 1 and front widths horizontal scales ranging between 1 and 4 km the estimates are log normally distributed with 70 of the values ranging between 0 4 and 5 m 2 s 1 further analysis based on high resolution simulations and remote sensed observations as well as dedicated field experiments will help to assess the robustness of some of the assumptions at the base of the proposed approach and to extend the results to different ocean regions

why does the deep western boundary current leak around flemish cap abstractthe southward flowing deep limb of the atlantic meridional overturning circulation is comprised of both the deep western boundary current dwbc and interior pathways the latter are fed by

year to year reoutcropping of eighteen degree water in an eddy resolving ocean simulation abstractwinter outcropping of the eighteen degree water edw and its subsequent dispersion are studied using a eddy resolving simulation of the family of linked atlantic modeling experiments flame outcropped edw columns in the model simulations are detected in each winter from 1990 to 1999 and particles are deployed in the center of each outcropped edw column subsequently the trajectories of these particles are calculated for the following 5 yr the particles slowly spread away from the outcropping region into the nonoutcropping subducted edw region south of 30 n and eventually to the non edw region in the greater subtropical gyre approximately 30 of the particles are found in non edw waters 1 yr after deployment after 5 yr only 25 of the particles are found within edw the reoutcropping time is defined as the number of years between when a particle is originally deployed in an outcropping edw column and when that particle is next found in an outcropping edw column of the particles 66 ar

kinematics of the pacific equatorial undercurrent an eulerian and lagrangian approach from gcm results abstract three dimensional monthly velocity fields from an ocean general circulation model are used to study the annual mean mass balance of the pacific equatorial undercurrent euc eulerian diagnostics are used to evaluate the various meridional vertical and zonal mass fluxes related to the euc there are several distinct regimes along the equator showing clear asymmetries between the western and eastern parts of the basin and between the northern and southern edges of the euc meridional fluxes are decomposed into pure ekman divergence and geostrophic convergence and it is shown that the asymmetries are mainly related to the spatial structure of the ekman divergence and thus to that of the trade winds lagrangian calculations are used to evaluate accurately the mass transfers between various sections of the euc and between the euc domain and the tropics the authors show that geostrophic convergence only ventilates the upper layers of the euc and that the euc really is a tongue of water flowing

temporal changes in ocean eddy transports abstract new estimates from 11 yr of altimetric data are made of the global time average variability kinetic energy and its decadal scale variability making the approximation that the variability reflects primarily eddy motions a time mean but spatially varying eddy mixing coefficient is then estimated along with its changes over the last decade with a record length more than 2 times that previously available the time mean variability kinetic energy ke is statistically more reliable and smoother in its spatial pattern minimum values of ke are present in the subpolar north pacific ocean and in the eastern south pacific both less than 100 cm2 s 2 in contrast to the north pacific the subpolar north atlantic ocean shows relatively enhanced ke eddy kinetic energy and eddy mixing appear to have declined during the last decade over large parts of the western pacific ocean in some regions by as much as 50 of the time mean value increased eddy variability can be found in the kuroshio and gulf stream

eddy induced particle dispersion in the near surface north atlantic abstractthis study investigates the anisotropic properties of the eddy induced material transport in the near surface north atlantic from two independent datasets one simulated from the sea surface height altimetry and one derived from real ocean surface drifters and systematically examines the interactions between the mean and eddy induced material transport in the region the lagrangian particle dispersion which is widely used to characterize the eddy induced tracer fluxes is quantified by constructing the spreading ellipses the analysis consistently demonstrates that this dispersion is spatially inhomogeneous and strongly anisotropic the spreading is larger and more anisotropic in the subtropical than in the subpolar gyre and the largest ellipses occur in the gulf stream vicinity even at times longer than half a year the spreading exhibits significant nondiffusive behavior in some parts of the domain the eddies in this study are defined as deviations from the long term time mean the contr

direct observation of subtropical mode water circulation in the western north atlantic ocean abstract eighteen degree water edw is the dominant subtropical mode water of the north atlantic subtropical gyre and is hypothesized as an interannual reservoir of anomalous heat nutrients and co2 although isolated beneath the stratified upper ocean at the end of each winter edw may re emerge in subsequent years to influence mixed layer properties and consequently air sea interaction and primary productivity here we report on recent quasi lagrangian measurements of edw circulation and stratification in the western subtropical gyre using an array of acoustically tracked isotherm following bobbing profiling floats programmed to track and intensively sample the vertically homogenized edw layer and directly measure velocity on the 18 5 c isothermal surface the majority of the clivar mode water dynamics experiment climode bobbers drifted within the subtropical gyre for 2 5 3 5 years many exhibiting complex looping patterns indicative of an energetic eddy field bobber derived lagrangian integral time and length scales 3 days 68 km associated with motion on 18 5 c were consistent with previous measurements in the gulf stream extension region and fall between previous estimates at the ocean surface and thermocline depth several bobbers provided evidence of long lived submesoscale coherent vortices associated with substantial edw thickness while the relative importance of such vortices remains to be determined our observations indicate that these features can have a profound effect on edw distribution edw thickness defined using a vertical temperature gradient criterion exhibits seasonal changes in opposition to a layer bounded by the 17 c and 19 c isotherms in particular edw thickness is generally greatest in winter as a result of buoyancy forced convection while the 17 19 c layer is thickest in summer consistent with seasonal ekman pumping contrary to previous hypotheses the bobber data suggest that a substantial fraction of subducted edw is isolated from the atmosphere for periods of less than 24 months seasonal to biennial re emergence principally within the recirculation region south of the gulf stream appears to be a common scenario which should be considered when assessing the climatic and biogeochemical consequences of edw

deep currents obtained from argo float trajectories in the japan east sea abstract the deep currents at 700 800 m depths from argo float trajectories including pre argo floats have been compiled from 1999 to 2010 in the japan east sea jes more than 14 000 velocities from the dataset provides the first view of interbasin scale dependency in deep currents of the jes such as mean circulation and eddy variability especially with an emphasis on their topographic steering characteristics the observational findings in this study are 1 the argo observation exhibits dominance of cyclonic mean circulation in the entire jes yet with a distinct interbasin variability of its magnitude the mean circulation is strongest in the eastern japan basin jb while overall currents in the ulleung basin ub are weaker than that in the eastern japan basin and western yamato basin yb by a factor of two to three 2 the eddy kinetic energy eke is maximum in the western japan basin where strong dipole structure of wind stress curl in winter is located the interior of each basin the eastern jb ub and yb has local maxima of the eke a factor of four to five smaller than that in the western jb 3 cyclonic bottom following characteristics prevail in the bin averaged velocities however the individual deep flows presumably containing temporal variability have a preference to follow topography not only with cyclonic flows shallow depth to the right but also anticyclonic flows shallow depth to the left especially when flows are highly energetic occurrence of anticyclonic flows is proportional to the local eke level relative to mean kinetic energy implying that such flows could exist only in a transient manner such as topographic rossby waves the argo observations may demonstrate an asymmetry of stable cyclonic and unstable anticyclonic circulation in the marginal seas of the northern hemisphere as the previous theoretical modeling studies suggested

organically bound metals and biomarkers in the monterey formation of the santa maria basin california abstract systematic variations in metal concentration ratios and biomarker ratios are observed with depth in cores of the monterey formation of the union leroy 51 18 well in the santa maria basin california specific metal ratios v v ni and mo mo cr correlate between kerogen and extractable organic matter further the organic matter in the two predominant lithofacies siliceous shales vs phosphatic shales can be distinguished based upon metal concentration ratios e g v v ni and certain biomarker characteristics e g sterane terpane mono triaromatic steroid hydrocarbon ratios maximum 28 30 bisnorhopane hopane ratios occur over a narrow range of v v ni ratios in kerogen concentrates and extractable organic matter this suggests that metal ratios in kerogen concentrates and eom may be useful for oil source rock correlation studies in the monterey further while kerogen parameters metals are discontinuous at the lithofacies boundary extract parameters biomarkers are gradational at this boundary suggesting about 30 ft 9 m of vertical hydrocarbon migration across the lithofacies contact

natural oil seepage at kobuleti ridge eastern black sea abstract analysis of advanced synthetic aperture radar satellite images in combination with water column and seafloor investigations documented natural oil seepage from pechori mound and colkheti seep in 1000 1200 m water depth in the eastern black sea offshore georgia hydroacoustic imaging of the water column using multibeam echosounder evidenced numerous gas emissions from both structures gas bubbles rose as high as 45 m below sea surface it is proposed that oil coatings around gas bubbles hamper their dissolution allowing them to reach the sea surface where widespread oil slicks are formed slow rise velocities 14 1 cm s 1 of bubbles with radii of 2 6 0 3 mm n 101 derived from video data obtained with the remotely operated vehicle marum quest4000 corroborate the assumption that bubbles are oil coated high resolution seafloor mapping with the autonomous underwater vehicle marum seal5000 at colkheti seep revealed a crater strewn morphology whose formation is explained by frequent rafting of shallow gas hydrate deposits satellite imaging of oil slicks on the sea surface above both sites indicates that oil seepage is rather persistent since 2003 an order of magnitude estimation of minimum oil seepage rates suggests discharge rates of 40 liters per hour from both sites the data presented are the first comprehensive description of oil seepage in the black sea

discriminating stromatolite formation modes using rare earth element geochemistry trapping and binding versus in situ precipitation of stromatolites from the neoproterozoic bitter springs formation northern territory australia stromatolites consist primarily of trapped and bound ambient sediment and or authigenic mineral precipitates but discrimination of the two constituents is difficult where stromatolites have a fine texture we used laser ablation inductively coupled plasma mass spectrometry to measure trace element rare earth element ree y and th concentrations in both stromatolites domical and branched and closely associated particulate carbonate sediment in interspaces spaces between columns or branches from bioherms within the neoproterozoic bitter springs formation central australia our high resolution sampling allows discrimination of shale normalised ree patterns between carbonate in stromatolites and immediately adjacent fine grained ambient particulate carbonate sediment from interspaces whereas all samples show similar negative la and ce anomalies positive gd anomalies and chondritic y ho ratios the stromatolites and non stromatolite sediment are distinguishable on the basis of consistently elevated light rees lrees in the stromatolitic laminae and relatively depleted lrees in the particulate sediment samples additionally concentrations of the lithophile element th are higher in ambient sediment samples than in stromatolites consistent with accumulation of some fine siliciclastic detrital material in the ambient sediment but a near absence in the stromatolites these findings are consistent with the stromatolites consisting dominantly of in situ carbonate precipitates rather than trapped and bound ambient sediment hence high resolution trace element ree y th geochemistry can discriminate fine grained carbonates in these stromatolites from coeval non stromatolitic carbonate sediment and demonstrates that the sampled stromatolites formed primarily from in situ precipitation presumably within microbial mats biofilms rather than by trapping and binding of ambient sediment identification of the source of fine carbonate in stromatolites is significant because if it is not too heavily contaminated by trapped ambient sediment it may contain geochemical biosignatures and or direct evidence of the local water chemistry in which the precipitates formed

a lagrangian stochastic model of surf zone drifter dispersion 1 drifter derived cross shore and alongshore surf zone diffusivities were previously estimated on an alongshore uniform beach over 1000 s for five huntington beach california 2006 hb06 experiment release days the cross shore diffusivity kx had a nonmonotonic time dependence potentially due to the shoreline or to weaker diffusivity seaward of the surf zone the alongshore diffusivities ky were qualitatively consistent with shear dispersion but differed from the classic taylor laminar theory here modeled and analytic diffusivities for the five release days are derived from a lagrangian stochastic model lsm that uses the drifter derived bulk cross shore averaged velocity variance and cross shore dependent mean alongshore current the lsm modeled and analytic cross shore diffusivities are nonmonotonic due to the shoreline and strongly suggest that the observed cross shore diffusivity is shoreline affected the lsm typically reproduce well the observed kx with lagrangian time scale between 75 and 200 s consistent with surf zone eddy time scales hb06 drifter trajectories were too short to observe the analytic long time kx limit and weaker diffusivity seaward of the surf zone may be important at longer times 1000 s on all release days the lsm model and analytic alongshore diffusivity reproduce well the observed ky with alongshore lagrangian time scales between 95 and 155 s the isolated shear induced diffusivity is very well represented by an analytic theory which incorporates a nonzero lagrangian time scale many of the stochastic model parameters can be specified a priori with reasonable assumptions to predict surf zone dispersion of an initial value problem pollution spill

chemoherms on hydrate ridge unique microbially mediated carbonate build ups growing into the water column two active chemoherm build ups growing freely up into the oceanic water column the pinnacle and the south east knoll chemoherms have been discovered at hydrate ridge on the cascadia continental margin these microbially mediated carbonate formations rise above the seafloor by several tens of meters and display a pinnacle shaped morphology with steep flanks the recovered rocks are pure carbonates dominated by aragonite based on fabric and mineralogic composition different varieties of authigenic aragonite can be distinguished detailed visual and petrographic investigations unambiguously reveal the involvement of microbes during the formation of the carbonates the fabric of the cryptocrystalline and fibrous aragonite can be described as thrombolitic fossilized microbial filaments in the microcrystalline aragonite indicate the intimate relationship between microbes and carbonates the strongly 13c depleted carbon isotope values of the samples as low as 48 1 pdb are characteristic of methane as the major carbon source for the carbonate formation the methane rich fluids from which the carbonates are precipitated originate most probably from a gas reservoir below the bottom simulating reflector bsr and rise through fault systems the 18o values of the aragonitic chemoherm carbonates are substantially higher as high as 5 0 pdb than the expected equilibrium value for an aragonite forming from ambient seawater 3 5 pdb as a first approximation this indicates formation from glacial ocean water but other factors are considered as well a conceptual model is presented for the precipitation of these chemoherm carbonates based on in situ observations and the detailed petrographic investigation of the carbonates this model explains the function of the consortium of archaea and sulfate reducing bacteria that grows on the carbonates performing anaerobic oxidation of methane aom and enabling the precipitation of the chemoherms above the seafloor surrounded by oxic seawater beggiatoa mats growing on the surface of the chemoherms oxidize the sulfide provided by sulfate dependent anaerobic oxidation of methane within an oxic environment the contact between beggiatoa and the underlying microbial consortium represents the interface between the overlying oxic water column and an anoxic micro environment where carbonate formation takes place