current variability near the southeast newfoundland ridge abstract a cooperative moored array experiment to measure currents and temperatures in the vicinity of the southeast newfoundland ridge was carried out over a 14 manth period starting september 1979 and ending december 1980 measurements were obtained from an incoherent exploratory army of nine moorings instrumented at 500 800 1500 and 4000 m levels the objectives were to explore the amplitude spatial variability and time scales of the eddy field in the decay region of the gulf stream an additional experiment and mooring to examine the influx of norwegian sea overflow water into the western north atlantic basin was imbedded in the array supplementary ctd and xbt profiles and a single current profile were taken during deployment and recovery cruises to aid in interpretation of the moored measurements and identification of water masses a description of the array experiment and preliminary results are reported mean velocities were weak compared with rms eddy velocities and were not determined with st

volume heat and freshwater divergences in the subpolar north atlantic suggest the nordic seas as key to the state of the meridional overturning circulation the meridional overturning circulation moc decreases rapidly in subpolar and nordic regions where the warm upper layer loses its buoyancy due to intense heat loss sinks and flows south the maj

tracing the migration of mantle co2 in gas fields and mineral water springs in south east australia using noble gas and stable isotopes abstract geochemical monitoring of co2 storage requires understanding of both innate and introduced fluids in the crust as well as the subsurface processes that can change the geochemical fingerprint of co2 during injection storage and any subsequent migration here we analyse a natural analogue of co2 storage migration and leakage to the atmosphere using noble gas and stable isotopes to constrain the effect of these processes on the geochemical fingerprint of the co2 we present the most comprehensive evidence to date for mantle sourced co2 in south east australia including well gas and co2 rich mineral spring samples from the otway basin and central victorian highlands cvh 3he 4he ratios in well gases and co2 springs range from 1 21 to 3 07 ra and 1 23 3 65 rc ra respectively we present chemical fractionation models to explain the observed range of 3he 4he ratios he ne ar kr xe concentrations and 13c co2 values in the springs and the well gases the variability of 3he 4he in the well gases is controlled by the gas residence time in the reservoir and associated radiogenic 4he accumulation 3he 4he in co2 springs decrease away from the main mantle fluid supply conduit we identify one main pathway for co2 supply to the surface in the cvh located near a major fault zone solubility fractionation during phase separation is proposed to explain the range in noble gas concentrations and 13c co2 values measured in the mineral spring samples this process is also responsible for low 3he concentrations and associated high co2 3he which are commonly interpreted as evidence for mixing with crustal co2 the elevated co2 3he can be explained solely by solubility fractionation without the need to invoke other co2 sources the noble gases in the springs and well gases can be traced back to a single end member which has suffered varying degrees of radiogenic helium accumulation and late stage degassing this work shows that combined stable and noble gas isotopes in natural gases provide a robust tool for identifying the migration of injected co2 to the shallow subsurface

mesoscale variability transition from the western to the eastern atlantic along 48 n abstract the north atlantic low frequency variability along 48 n is described from 76 year long velocity temperature records obtained as part of the topogulf project whose main objective was to document the effects of the mid atlantic ridge upon the circulation the eddy energy is thermocline intensified and shows a fivefold decrease eastward from 35 to 10 w west of the ridge it penetrates more easily to the ocean floor between 1500 and 2500 m sudden energetic bursts are observed and we argue that they are associated with the passage of sub mesoscale concave cyclonic lenses depleted of labrador sea water at nearly all locations a negative zonal momentum flux u v is observed which may be linked to an energy transfer from the north atlantic current eddy heat fluxes are also obtained and are directed up down the mean gradient west east of the ridge crest

noble gases in formation fluids from deep sedimentary basins a review abstract atmospheric ne ar kr and xe are observed in fluids occurring in deep basins modifications of their abundance patterns reveal modes of recharge and brine formation phase separations during boiling and association of natural gas with water or oil radiogenic 4 he and 40 ar serve as age indicators of entrapped fluids effective over a significant portion of the geological time scale simultaneous application of 13 c atmospheric noble gases and radiogenic 4 he and 40 ar is recommended to identify a recent bacterial natural gas formation not accompanied by oil and b natural gas formed along with oil in a mature source rock

widespread distribution of ascending fluids transporting mantle helium in the fore arc region and their upwelling processes noble gas and major element composition of deep groundwater in the kii peninsula southwest japan abstract chemical and isotopic studies including analyses of noble gases were comprehensively conducted on the groundwater of the entire kii peninsula which is located in the fore arc region of southwest japan groundwater of na cl hco3 na hco3 cl and na cl types was shown to be distributed across the whole area groundwater in the inland central part of the peninsula shows relatively low salinity whereas groundwater from the area along the ene trending median tectonic line mtl on the north side of the peninsula shows high salinity up to 18 800 mg l of cl and the presence of unusual heavy oxygen isotopes this trend is similar to that documented in saline waters from the arima region the so called arima type thermal water high 3he 4he ratios relative to the atmospheric value up to 6 7 ra were recorded throughout the kii peninsula covering a wider area than documented previously the saline groundwater is also strongly depleted in 20ne and heavy noble gases from the wide distribution of high 3he 4he values and the associated 20ne and cl concentrations we infer that aqueous fluids derived from dehydration of the subducting slab are present at depth beneath almost the entire kii peninsula these aqueous fluids may ascend along the major north dipping boundary faults the isotopic composition of groundwater from the southern part of the peninsula suggests that the contribution from these dehydration derived fluids is relatively small in this region however volatile components e g noble gases and co2 in the groundwater of this area may originate from the dehydration derived fluids upwelling of arima type thermal water of the na cl hco3 type is expected to undergo a phase separation of volatile species due to decompression as the fluid ascends the variety of water types documented may be due to this water gas separation and the subsequent incorporation of gaseous species into shallow meteoric groundwater the observed high 3he 4he ratios in the absence of a mantle wedge below the southern part of the kii peninsula may reflect the oblique ascent of these fluids along north dipping boundary faults

spreading of denmark strait overflow water in the western subpolar north atlantic insights from eddy resolving simulations with a passive tracer abstractthe oceanic deep circulation is shared between concentrated deep western boundary currents dwbcs and broader interior pathways a process that is sensitive to seafloor topography this study investigates the spreading and deepening of denmark strait overflow water dsow in the western subpolar north atlantic using two eddy resolving atlantic simulations including a passive tracer injected into the dsow the deepest layers of dsow transit from a narrow dwbc in the southern irminger sea into widespread westward flow across the central labrador sea which remerges along the labrador coast this abyssal circulation in contrast to the upper levels of overflow water that remain as a boundary current blankets the deep labrador sea with dsow farther downstream after being steered around the abrupt topography of orphan knoll dsow again leaves the boundary forming cyclonic recirculation cells in the deep newfoundland basin the deep recirculation mostly driven by the meandering pathway of the up

noble gases in crude oils from the paris basin france implications for the origin of fluids and constraints on oil water gas interactions in order to investigate the potential of noble gases to trace the dynamics of oil reservoirs we have analysed the abundance and isotopic composition of all noble gases he ne ar kr and xe in crude oils from the paris basin france using a new extraction and purification procedure the main oil reservoirs are presently located in the jurassic dogger limestone and in the triassic keuper sandstone but hydrocarbons originated from a common source rock formation located in the interbedded liassic sequence despite this common origin the abundance and isotopic ratios of the noble gases differ between the dogger and the keuper the isotopic compositions of kr and xe are indistinguishable from that of air 3he 4he ratios higher than those predicted from radiogenic production in the sediments or in the crust are attributed to the occurrence of mantle derived 3he in the basin each sedimentary sequence is characterised by well defined and homogeneous 21ne 22ne and 40ar 36ar ratios which average 0 0306 0 0008 and 312 10 for the dogger and 0 0367 0 0012 and 664 30 for the keuper respectively the main source of radiogenic noble gases appears to be the continental crust underlying the basin with possible regional contributions of noble gas isotopes produced in the sediments the helium and argon isotopic ratios of the dogger oils are very similar to those observed in geothermal waters flowing in the dogger aquifer throughout the basin demonstrating that noble gases in oils derive from associated groundwaters oil reservoirs in the paris basin therefore accumulate noble gases from wide regions of the continental crust through cross formational flow of groundwaters and subsequent partitioning into oil this observation implies that noble gases cannot be directly used to date oils but can provide time constraints if 1 water oil interactions are quantified and 2 the residence time as well as the noble gas characteristics of associated groundwaters are known oil water gas partitioning processes are well recorded in the fractionation of noble gas elemental abundance two distinct processes have been identified 1 accumulation of atmosphere derived ang and radiogenic noble gases both initially dissolved in groundwaters resulting in a positive correlation between absolute amount of ang and the extent of heavy noble gas fractionation and 2 subsequent fractional degassing resulting in a negative correlation between ang abundance and heavy noble gas fractionation degassing is particularly evident for the keuper oils and might have occurred in the reservoirs following hydrodynamic gas stripping the ang abundance in the dogger reservoirs requires that about one order of magnitude more water than presently observed has interacted with the oil given current estimates of the residence time for groundwaters in the dogger aquifer the duration of oil water interaction is in qualitative agreement with a palaeocene oligocene age for the major episode of secondary oil migration in the paris basin high xenon contents in keuper reservoirs suggest that they have experienced hydrodynamic interactions between flowing waters and oils for long time and that the trias might have reached hydrostatic condition only recently

observations inferences and mechanisms of the atlantic meridional overturning circulation a review this is a review about the atlantic meridional overturning circulation amoc its mean structure temporal variability controlling mechanisms and role in the coupled climate system the amoc plays a central role in climate through its heat and freshwater transports northward ocean heat transport achieved by the amoc is responsible for the relative warmth of the northern hemisphere compared to the southern hemisphere and is thought to play a role in setting the mean position of the intertropical convergence zone north of the equator the amoc is a key means by which heat anomalies are sequestered into the ocean s interior and thus modulates the trajectory of climate change fluctuations in the amoc have been linked to low frequency variability of atlantic sea surface temperatures with a host of implications for climate variability over surrounding landmasses on intra annual timescales variability in amoc is large and primarily reflects the response to local wind forcing meridional coherence of anomalies is limited to that of the wind field on interannual to decadal timescales amoc changes are primarily geostrophic and related to buoyancy anomalies on the western boundary a pacemaker region for decadal amoc changes is located in a western transition zone along the boundary between the subtropical and subpolar gyres decadal amoc anomalies are communicated meridionally from this region amoc observations as well as the expanded ocean observational network provided by the argo array and satellite altimetry are inspiring efforts to develop decadal predictability systems using coupled atmosphere ocean models initialized by ocean data

directly measured mid depth circulation in the northeastern north atlantic ocean the circulation of water masses in the northeastern north atlantic ocean has a strong influence on global climate owing to the northward transport of warm subtropical water to high latitudes but the ocean circulation at depths below the reach of satellite observations is difficult to measure and only recently have comprehensive direct observations of whole ocean basins been possible here we present quantitative maps of the absolute velocities at two levels in the northeastern north atlantic as obtained from acoustically tracked floats we find that most of the mean flow transported northward by the gulf stream system at the thermocline level about 600 m depth remains within the subpolar region and only relatively little enters the rockall trough or the nordic seas contrary to previous work our data indicate that warm saline water from the mediterranean sea reaches the high latitudes through a combination of narrow slope currents and mixing processes at both depths under investigation currents cross the mid atlantic ridge preferentially over deep gaps in the ridge demonstrating that sea floor topography can constrain even upper ocean circulation patterns

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

velocity probability density functions for oceanic floats probability density functions pdfs of daily velocities from subsurface floats deployed in the north atlantic and equatorial atlantic oceans are examined in general the pdfs are approximately gaussian for small velocities but with significant exponential tails for large velocities correspondingly the kurtoses of the distributions are greater than three similar pdfs are found in both western and eastern regions above and below 1000 m depth with more significant non gaussianity in the north atlantic than at the equator analogously lagrangian statistics in decaying two dimensional turbulence also display non gaussian velocity pdfs with approximately exponential tails in the limit of large reynolds number

assimilation of altimetric data and mean sea surface height into an eddy permitting model of the north atlantic this paper shows that the mean flow of an eddy permitting model can be altered by assimilation of surface height variability providing that information about the mean sea surface is included using an adaption of a statistical dynamical method devised by oschlies and willebrand we show that for a restricted depth range about 1000 m dynamical knowledge can make up for the null space present in surface data whose temporal extent may be too short to distinguish between vertical modes the lack of an accurate geoid has meant that most assimilation methods while representing variability well have been unable to modify the mean flow to any extent however we show that by including several approximate forms for the mean sea surface the mean interior flow in the upper kilometer can be rapidly adjusted towards reality by the assimilation with the location of major current systems moved by hundreds of kilometers

dating ultra deep mine waters with noble gases and 36cl witwatersrand basin south africa abstract concentrations and isotopic ratios of dissolved noble gases 36cl d and 18o in water samples from the ultra deep gold mines 0 718 to 3 3 km below the surface in the witwatersrand basin south africa were investigated to quantify the dynamics of these ultra deep crustal fluids the mining activity has a significant impact on the concentrations of dissolved gases as the associated pressure release causes the degassing of the fissure water the observed under saturation of the atmospheric noble gases in the fissure water samples 70 98 normalized to asw at 20 c and 1013 mbar is reproduced by a model that considers diffusive degassing and solubility equilibration with a gas phase at sampling temperature corrections for degassing result in 4he concentrations as high as 1 55 10 1cm3stp4he g 1 40ar 36ar ranging between 806 and 10331 and 134xe 132xe and 136xe 132xe ratios above 0 46 and 0 44 respectively corrected 134 136 xe 132xe and 134 136 xe 4he ratios are consistent with their production ratios whereas the nucleogenic 4he 40ar and 134 136 xe 40ar ratios generally indicate that these gases are produced in an environment with an average u th k content 2 3 times above that of crustal average in two scenarios one considering only accumulation of in situ produced noble gases the other additionally crustal flux components the model ages for 14 individual water samples range from 13 to 168 ma and from 1 to 23 ma respectively the low 36cl ratios of 4 37 10 15 and comparatively high 36cl concentrations of 8 350 10 15 atoms 36cl l 1 reflect subsurface production in secular equilibrium indicating an age in excess of 1 5 ma or 5 times the half life of 36cl in combination the results suggest residence times of the fluids in fissures in this region up to 3 3 km depth are of the order of 1 100 ma we cannot exclude the possibility of mixing and that small quantities of younger water have been mixed with the very old bulk

fingerprinting coal derived gases from the uk abstract the large scale extraction of unconventional hydrocarbons in the united states has led to fears of methane contamination of shallow groundwaters differentiating between the deep gas released during extraction shale gas coal bed methane and underground coal gasification and natural shallow sourced methane is imperative for the monitoring and managing of environmental risks related to the extraction process here for the first time we present measurements of the major gas and stable and noble gas isotope composition of coal bed methane cbm from central scotland and coal mine methane cmm from central england uk the molecular c1 c2 c3 21 to 121 and stable isotope compositions 13cch4 39 5 to 51 1 dch4 163 to 238 indicate a thermogenic origin for the methane they are distinct from the majority of shallow sourced gases in uk both sample suites exhibit high he concentrations 338 to 2980 ppmv that are considerably above atmospheric and groundwater levels simple modelling shows that these high 4he concentrations cannot be solely derived from in situ production since coal deposition and hence the majority is derived from the surrounding crust the scottish cbm contains a resolvable mantle he ne and ar contribution that may originate from melts in the deep crust demonstrating the uk coals have acted as a store for deep volatiles for 10s of millions of years the high 4he in the coal derived gases has the potential to be used as a novel diagnostic fingerprint to track fugitive release of deep methane from future unconventional gas extraction operations in the uk

multiple atmospheric noble gas components in hydrocarbon reservoirs a study of the northwest shelf delaware basin se new mexico the northwest shelf of the delaware basin se new mexico is the site of several large and productive oil and gas fields the most productive reservoirs are located in the late pennsylvanian morrow and early permian abo formations production from the latter more important play is predominately from fluvial abo red beds of the pecos slope field the oxidizing conditions implied by the reddish color of the formation require an external hydrocarbon source to test the existing migration model for the region and constrain the location of potential hydrocarbon sources we measured the elemental and isotopic composition of noble gases produced along with the hydrocarbons we found the hydrocarbons to be highly enriched in radiogenic 4he 40 ar and nucleogenic 21 ne f 4he 44 000 250 000 40ar 36ar 400 3145 21ne 22ne 0 044 0 071 the greatest enrichments occur in the pecos slope gas fields the hydrocarbons also contain three independent nonradiogenic noble gas components each with an atmospheric isotopic composition one component is most likely air saturated water asw the second component is enriched in the heavy noble gases f 130xe 8 5 and is derived from the hydrocarbon sources the third component is enriched in ne f 20ne 0 8 that we believe is degassed from sources within the reservoirs this component is correlated with but decoupled from the dominant source of radiogenic 4he and 40 ar very high concentrations of 4he up to 1 by volume in the pecos slope reservoirs require a source external to the reservoirs such as the underlying precambrian basement granites and sedimentary equivalents structural buckles cutting through the pecos field may act as high flux vertical pathways for the radiogenic 4he if the hydrocarbons in the pecos slope fields have migrated northward from the deeper delaware basin as suggested by compositional trends then perhaps the buckles also play an important role in the distribution and filling of the pecos slope reservoirs

evidence for bacterially generated hydrocarbon gas in canadian shield and fennoscandian shield rocks hydrocarbon rich gases found in crystalline rocks on the canadian and fennoscandian shields are isotopically and compositionally similar suggesting that such gases are a characteristic feature of precambrian shield rocks gases occure in association with saline groundwaters and brines in pressurized pockets formed by sealed fracture systems within the host rocks when released by drilling activities gas pressures as high as 5000 kpa have been recorded typical gas flow rates for individual boreholes range from 0 25 l min to 4 l min the highest concentrations of ch4 are found in the deepest levels of the boreholes associated with ca na cl and na ca cl brines n2 is the second major component of the gases and with ch4 accounts for up to 80 to 90 vol higher hydrocarbon c2 concentrations range from 1 to 10 vol with c1 c2 c3 ratios from 10 1000 isotopically the gases show a wide range of values overall 13c 57 5 to 41 1 d 245 to 470 but a relatively tight cluster of values within each sampling locality the enonkoski mine methanes are unique with 13c values between 65 4 and 67 3 and d values between 297 and 347 the shield gases are not readily reconcilable with conventional theories of methanogenesis the range of c1 c2 c3 ratios for the shield gases is too low to be consistent with an entirely bacterial origin in addition dch4 values are in general too depleted in the heavy isotope to be produced by thermogenic methanogenesis or by secondary alteration processes such as bacterial oxidation or migration however isotopic and compositional evidence indicates that bacterially derived gas can account for a significant component of the gas at all shield sites conventional bacterial gas accounts for 75 94 vol of the occurrences at enonkoski mine in finland at each of the other shield sites bacterial gas can account for up to 30 50 vol of the total gas accumulation this study and other recent evidence of active bacterial communities in deep hydrogeological environments emphasize the need for more comprehensive investigation of the role of microorganisms in the deep subsurface

interaction of the north atlantic current with the deep charlie gibbs fracture zone throughflow the charlie gibbs fracture zone cgfz a passage of 3600 m sill depth through the mid atlantic ridge near 52 n is a known gateway for the passage of deep waters from the northeast atlantic into the western basin during a shipboard survey of august 1997 deep current profiling yielded eastward deep flow through the passage while geostrophy calculated against an intermediate reference level resulted in westward relative deep transport the reason was an unusual and deep reaching northward excursion of the north atlantic current nac inspection of historical data showed that such interference of the nac with the cgfz regime occured occasionally in the past relocation of surface circulation patterns by decadal ocean climate anomalies may thus be of significance also for the deep circulation

on variations in static stability along lagrangian trajectories abstract by causing an isopycnal float to rise and sink to neighboring density surfaces one can measure layer thickness along a float trajectory and thus variations in static stability we report here on layer thickness measurements that were obtained from the nearly 100 isopycnal floats that were deployed in the 1993 1995 lagrangian study of the north atlantic current layer thickness variations depend significantly upon location and process in the high velocity core of the meandering north atlantic current layer thickness changes correlate with curvature of the flow stretching in troughs compression in crests but this correlation fails in unsteady flows or outside the high velocity center of the current floats also register significant changes in stratification when they cross between the warm waters in the newfoundland basin and the cold waters from the labrador sea as floats enter and exit what appear to be coherent eddy structures significant but not necessarily predictable changes in layer thickness can occur while the technology to measure layer thickness variations performed as well and reliably as we had hoped for the presence of ubiquitous small scale features in the density field together with the fact that the thickness measurements sampled only o 100 m of the total water column limited our ability to isolate and identify the cause of thickness variations to only relatively energetic features

regional groundwater focusing of nitrogen and noble gases into the hugoton panhandle giant gas field usa the hugoton panhandle giant gas field located across sw kansas and the texas and oklahoma panhandles in the usa is the case type example of high nitrogen concentrations in a natural gas being linked with high helium concentrations we collected 31 samples from producing wells in a north south traverse of the 350 km long field the samples reflect the previously observed north south change in 4he n2 with values changing from 0 020 to 0 049 respectively 3he 4he 21ne 22ne and 40ar 36ar vary between 0 14 0 25 ra 0 0373 0 0508 and 818 1156 respectively and are caused by quantifiable contributions from mantle crustal and atmosphere derived sources the atmosphere derived 20ne 36ar ratios are indistinguishable from groundwater values the crustal 4he 21ne and 4he 40ar ratios show a 60 excess of 4he compared to predicted production ratios in the crust and are typical of noble gases released from the shallow crust the mantle 3he n2 and groundwater recharge 36ar n2 ratios enable us to rule out significant magmatic or atmosphere contributions to the gas field n2 which is dominantly crustal in origin correlated 20ne n2 and 4he n2 shows mixing between two distinct crustal n2 components one n2 component n2 is associated with the crustal 4he and groundwater derived 20ne and the other with no resolvable noble gas contribution measured 15nn2 values vary from 2 7 to 9 4 the n2 and non he associated n2 endmembers are inferred to have 15nn2 3 and 13 and contribute from between 25 60 and 75 40 of the nitrogen respectively the non he associated nitrogen is probably derived from relatively mature organic matter in the sedimentary column the 15nn2 value is not compatible with a crystalline or high grade metamorphic source and similar to the 4he is inferred to be from a shallow or low metamorphic grade source rock 4he mass balance requires a regional crustal source its association with significant magmatic 3he pointing to a tectonically active source to the west of the hugoton system the volume of groundwater required to source the 20ne in the gas field demonstrates the viability of the groundwater system in providing the collection transport and focusing mechanism for the 4he and n2 the n2 20ne ratio shows that the n2 transport must be in the aqueous phase and that the degassing mechanism is probably contact between the regional groundwater system and the preexisting reservoir hydrocarbon gas phase

natural gas association with water and oil as depicted by atmospheric noble gases case studies from the southeastern mediterranean coastal plain a model for the equilibrium distribution of atmospheric noble gases ang between natural gas and water phases was extended to include the gas oil relationship the basic assumption is that the ang are introduced into hydrocarbon systems via recharge or seawater theoretical ang patterns of natural gas at equilibrium with water fall between the air pattern and that of air saturated water theoretical ang patterns of natural gas degassed from oil which had previously equilibrated with a water phase cover a wide range including the range calculated for gas water equilibration ang patterns in natural gas which fall outside the overlapping range may thus indicate association of the gas with oil the model was tested in the case of hydrocarbon systems of the southeastern mediterranean coastal plain other geochemical evidence indicates that the ashdod sadot shallow gas wells are not related to oil the relative ang abundances in gas samples from these wells lie within the range predicted for gas water association the relative ang abundances in samples degassed from oils of the helez kokhav oilfield are similar to specific patterns predicted for the degassing of oil which was previously associated with water published and new analyses of methane dominated natural gas samples from california japan and northern israel also reveal ang patterns of the type predicted by the model the results of the case studies support our hypothesis that water is responsible for transport of atmospheric noble gases into subsurface hydrocarbon systems this forms the basis for identification of oil associated natural gases via ang study

uncertainty of north atlantic current observations from altimetry floats moorings and xbt abstract large scale geostrophic flow across an oceanographic section can be computed from in situ density profiles and satellite borne sea level anomaly measurements at the section endpoints here uncertainties are estimated and compared for observations that span the north atlantic current out of multi year mooring records from two sites porcupine abyssal plain and central irminger sea 16 months from the 2002 2005 period are available that have sufficient data coverage to observe this current transport and uncertainty estimates from these moorings are compared to results from argo floats and expendable bathythermographs the latter have longer data sets and provide decadal time series with semiannual resolution in time typical uncertainties which take sensor errors and sub sampling the eddy field into account are below 2 sv of volume transport for the mooring and float based estimates and just below 3 sv for the expendable bathythermographs peak to peak variability occurs on decadal time scales and is about 11 sv well above the observational uncertainty we can therefore have confidence that the observed signal reflects true changes in the ocean the time series is further extended to 25 years duration using solely the altimetry data by proxy the aim of this study is to add value to such time series by understanding and quantifying the uncertainties and consistency between methods the methodology is applicable at other locations as well

coupled use of carbon isotopes and noble gas isotopes in the potiguar basin brazil fluids migration and mantle influence abstract we used the carbon isotope ratios of hydrocarbons and co 2 and the proportions of noble gas isotopes of associated gases from several geological provinces of the potiguar basin brazil for gas source rock correlation and to determine maturity post genetic processes migration leakage biodegradation and to assess the possible interactions between hydrocarbons and surrounding waters barriers of permeability at the basin scale the amount of water interacting with the accumulated hydrocarbons proportion of meteoric water and contamination of the fluids by the mantle were quantified for the distinct petroleum systems defined in this basin four hydrocarbon provinces have been defined in the potiguar basin the first is located in the southern part of the basin and the other three are in the northern part with offshore pods of generation migration occurred along ne sw horst and grabben structures all gases are mainly thermogenic 13 c of methane between 49 and 34 except for biodegraded gases with isotopically lighter methane generated in the oil window and only two fields from one of the trends seem to have been significantly biodegraded 13 c of propane up to 5 8 per mil the source rocks were lacustrine for the gases from the southwest of the basin and mixed marine lacustrine for two trends the third trend as well as an offshore field appears to have a lacustrine source rock and the hydrocarbon generation and accumulation are older than for the other fields each of the three trends is generally isolated in terms of fluid migration except in one location where noble gas isotopes indicate that the guamare trend is invaded by fluids of the macau trend an important contamination by mantle fluids has been confirmed for all the hydrocarbon fields close to the shore 3 he 4 he ratios up to 1 6 times the atmospheric ratio the mantle contribution as high as 20 of total helium decreases inland the mantle contribution provides some chronological constraints for the hydrocarbon accumulations and may have had an influence in hydrocarbon generation due to an igneous activity associated influence in the hydrocarbon generation pod

the north atlantic current and surrounding waters at the crossroads the north atlantic current is a well defined western boundary current that flows north along the east side of the grand banks from 40 to 51 n where it turns sharply to the east and begins its journey across the ocean the current is unique in transporting warm tropical waters to much higher latitudes than any other western boundary current and thus plays a crucial role in ameliorating the climate of the european subcontinent the north atlantic current originates in the gulf stream when the latter curves north around the southeast newfoundland rise a major submarine ridge that stretches se from the grand banks a well defined front delineates the path of the current as long as it flows north as a western boundary current after the current turns east in the north it broadens into a widening band of eastward drift without a sharp or permanent front in the sense of the eastward flowing gulf stream after it separates from cape hatteras the north atlantic current transports more than 40 sv 1 sv 106 m s 1 in the south and about 20 sv by the time it flows east across the mid atlantic ridge the currents along the northward flowing front are quite swift with typical maximum average speeds in the upper 300 m near 1 m s 1 2 knots the current meanders almost as wildly as a snaking river but unlike steep meanders in the gulf stream these meanders appear to be stable and with one exception have not been observed to break off to form pools of warm and or cold waters as frequently occurs in the gulf stream the meanders appear to be induced by major topographic features along the path of the current namely the southeast newfoundland rise the newfoundland seamounts and flemish cap strong recirculations develop on the concave side of the meanders one of these the mann eddy at the first meander crest of the north atlantic current should be regarded as a permanent feature of the north atlantic circulation other meanders also contain recirculations that can persist for months under certain conditions these can merge together to form an extended sw flow recirculation just east of the north atlantic current

identifying and quantifying natural co2 sequestration processes over geological timescales the jackson dome co2 deposit usa co2 sources sinks and migration mechanisms in natural co2 gas fields provide critical analogues for developing the safe application of anthropogenic co2 sequestration technologies here we use noble gas and carbon isotopes together with other gases to identify and quantify the origin transport and trapping mechanisms of co2 in the late cretaceous jackson dome co2 gas deposit 98 75 to 99 38 co2 located in central mississippi usa and producing from 5000 m it is one of the deepest commercial co2 gas fields in the world 10 gas samples from producing wells were determined for their noble gas chemical and stable carbon isotope composition he 3 he 4 ratios range between 4 27r a and 5 01r a where r a is the atmospheric value of 1 4 x 10 6 indicating a strong mantle signature similar to co2 deposits worldwide co2 he 3 decreases with increasing groundwater derived ne 20 and he 4 we model several different processes that could account for the jackson dome data and conclude that similar to other co2 dominated deposits a groundwater gas stripping and re dissolution ggs r process best accounts for observed ne 20 ar 36 kr 84 ar 36 co2 he 3 delta c 13 co2 he 4 ne 20 and ar 36 in this context crustal and magmatic co2 components contribute 57 and 43 respectively changes in co2 he 3 across the field show that groundwater contact is responsible for up to 75 loss of original emplaced co2 delta c 13 co2 variance limits the degree of precipitation to be less than 27 with the remaining co2 loss being accounted for by dissolution only a higher degree of dissolution gas loss and evidence for water contact at the reservoir crest compared to the reservoir flanks is used to argue that co2 in this system has not undergone subsequent loss to either dissolution or precipitation since shortly after reservoir filling at over 60 ma c 2012 elsevier ltd all rights reserved

rare gas isotopic compositions in natural gases of japan isotopic and elemental compositions of rare gases in various types of gas samples collected in the japanese islands were investigated excess3he was found in most samples many samples showed a regionally uniform high3he 4he ratio of about 7 times the atmospheric ratio the he concentrations varied from 0 6 to 1800 ppm and they were low in co2 rich gases and high in n2 rich gases ne isotopic deviations from the atmospheric ne were detected in most volcanic gases the deviations and the elemental abundance patterns in volcanic gases can be explained by a mixing between two components one is mass fractionated rare gases and the other is isotopically atmospheric and is enriched in heavy rare gas elements ar was a mixture of mass fractionated ar atmospheric ar and radiogenic ar and the contribution of radiogenic40ar was small in all samples except for he elemental abundance patterns were progressively enriched in the heavier rare gases relative to the atmosphere several samples were highly enriched in kr and xe relative to the abundance pattern of dissolution equilibrium of atmospheric rare gases in water the component which is highly enriched in heavy rare gases may be released from sedimentary materials in the crust

the north atlantic current based on trajectories of satellite tracked buoys and hydrographic sections both dietrich s and worthington s schemes of the north atlantic current are reconsidered ninety satellite tracked buoys have been analyzed in order to distinguish between these schemes neither could be confirmed the north atlantic current appears as a superposition of a broad west wind drift and a frontal jet in the western part of the north atlantic north of 40 n which becomes independent from the subtropical gyre neither a permanent branching suggested by dietrich nor a confinement of the subpolar gyre to the east of newfoundland per worthington can be found the north atlantic current extends over the entire north atlantic carrying more than 20 sverdrups sv toward the north this northward transport is mainly due to the northward flow around flemish cap and a sudden turn of the north atlantic current east of the mid atlantic ridge the buoy tracks have been used to determine speed and direction in the upper layers 100 m we combine these results with hydrographic data in order to obtain an estimate of the mass transport transport across the mid atlantic ridge is based on recent sections fahrbach et al 1985 while transport in the northeastern north atlantic has been derived from the erika dan sections at 53 5 n and 59 5 n according to these two sections the return flow occurs mainly below 1000 m after water mass conversion in the northern areas the results imply that about 7 sv of atlantic water are transformed into deep water in the area between 53 5 n and 60 n

spatial scales of mesoscale variability in the north atlantic as deduced from geosat data two years of geosat data were used to systematically investigate the mesoscale variability and spatial scales of the north atlantic we first calculated sea surface height variability and eddy kinetic energy these compare well with the eddy kinetic energy obtained with surface drifters then the spatial scales of mesoscale variability were characterized in 10 latitude 10 longitude areas by their wave number spectra and autocorrelation functions comparison with existing in situ data shows good agreement and it is believed that the total error budget is globally below that of the oceanic signal the wave number spectra show significant differences as a function of latitude and longitude and these can be related to different types of forcing instability of a mean current or fluctuating wind scales typically decrease from west to east and south to north simple proportionality with respect to the first internal rossby radii does not apply everywhere

the climatology of the north atlantic abstract data from approximately 144 000 hydrographic stations in the north atlantic have been retrieved from the national oceanic data centre and analysed to produce maps of mean pressure temperature salinity and oxygen on selected potential density surfaces for the domain bounded by 0 85 w and 0 65 n the data span the period from 1904 to 1990 with the majority of the data from the last four decades the data set for this region is 60 larger than that used in the production of levitus climatological world atlas this increase in stations coupled with smoothing scales specific to the north atlantic rather than the global ocean considerably improves the resolution of the basin s features the mean property fields and their associated standard deviations are resolved on a one degree grid with little smoothing contrasting with the levitus atlas where properties although presented on a one degree grid have been smoothed on the order of 1000km another important feature of this database is the process by which irregularly spaced data are averaged onto a regular grid in a significant departure from the levitus analysis which averaged on depth surfaces these data were averaged on potential density surfaces thus eliminating an artificial mixing of water mass properties the database is used to describe the baroclinicity of well known features such as the gulf stream the north atlantic current and the deep western boundary current and to elucidate the recirculations associated with these currents it additionally resolves several new features in the intermediate and deep north atlantic these features include the signature of a large scale deep recirculation that extends southwestward from the eastward extension of the north atlantic current to the separation point of the gulf stream near cape hatteras this recirculation which spans approximately 2000m of the water column encompasses more local recirculations and potentially mixes subpolar and subtropical waters furthermore in the upper thermocline this database reveals a coherent azores current that stretches from the gulf stream system south of the tail of the grand banks to madeira this flow is marked by divergences to the south and convergences from the north such that its downstream transport is not much changed

on the movements of the north atlantic subpolar front in the preinstrumental past abstractthree sediment records of sea surface temperature sst are analyzed that originate from distant locations in the north atlantic have centennial to multicentennial resolution are based on the same reconstruction method and chronological assumptions and span the past 15 000 yr using recursive least squares techniques an estimate of the time dependent north atlantic sst field over the last 15 kyr is sought that is consistent with both the sst records and a surface ocean circulation model given estimates of their respective error co variances under the authors assumptions about data and model errors it is found that the 10 c mixed layer isotherm which approximately traces the modern subpolar front would have moved by 15 of latitude southward northward in the eastern north atlantic at the onset termination of the younger dryas cold interval yd a result significant at the level of two standard deviations in the isotherm position in contrast meridional movements of the isotherm in

sea surface conditions in the southern nordic seas during the holocene based on dinoflagellate cyst assemblages dinoflagellate cyst dinocyst records from the southern nordic seas were compiled in order to evaluate the evolution of upper ocean conditions on a millennial timescale and supported by a highly resolved record from the voring plateau after the transitional phase from the last deglaciation three main phases define the holocene the early holocene 7 5 ka bp features important numbers of cool temperate species dominated by nematosphaeropsis labyrinthus and impagidinium pallidum in the west the assemblage composition changes drastically at the transition from the early to the mid holocene from when on operculodinium centrocarpum dominates the changeover is dated between 6 1 and 7 5 ka bp perhaps earlier closer to the iceland scotland ridge and appears to be linked to the onset of a modern type of surface circulation warmest assemblages occur at the voring plateau shortly after the transition when atlantic waters also appear to have spread farthest westward the recurrence of colder elements can be linked to cooling from 2 4 ka bp at the voring plateau and presumably earlier in the west but is difficult to date there because of the low sedimentation rates this is a general issue in many areas of the nordic seas and appears to have an important effect on cyst concentrations and assemblage composition with the possible loss of oxygenation sensitive cysts in the older parts of the cores comparing dinocyst based quantitative reconstructions with those retrieved from other plankton reveals a significantly different trend between proxies linked to a differing autecological response to seasonal changes at their respective depth habitats

fossil brines preserved in the st lawrence lowlands quebec canada as revealed by their chemistry and noble gas isotopes abstract brines in cambrian sandstones and ordovician dolostones of the st lawrence lowlands at becancour quebec canada were sampled for analysis of all stable noble gases in order to trace their origin and migration path in addition to quantifying their residence time major ion chemistry indicates that the brines are of na ca cl type possibly derived from halite dissolution 87 sr 86 sr ratios and ca excess indicate prolonged interactions with silicate rocks of the proterozoic grenville basement or the cambrian potsdam sandstone the brines constrain a 2 3 contribution of mantle 3 he and large amounts of nucleogenic 21 ne and 38 ar and radiogenic 4 he and 40 ar 4 he 40 ar and 21 ne 40 ar ratios corrected for mass fractionation during incomplete brine degassing are identical to their production ratios in rocks the source of salinity halite dissolution plus the occurrence of large amounts of 40 ar in brines constrain the residence time of becancour brines as being older than the cretaceous evaporites in the st lawrence lowlands likely existed only during devonian silurian time brines might result from infiltration of devonian water leaching halite penetrating into or below the deeper cambrian ordovician aquifers during the devonian the basin reached temperatures higher than 250 c allowing for thermal maturation of local gas prone source rocks utica shales and possibly facilitating the release of radiogenic 40 ar into the brines the last thermal event that could have facilitated the liberation of 40 ar into fluids and contributed to mantle 3 he is the cretaceous monteregian hills magmatic episode for residence times younger than the cretaceous it is difficult to find an appropriate source of salinity and of nucleogenic radiogenic gases to the becancour brines

gulf stream intensification after the early pliocene shoaling of the central american seaway abstract the shoaling of the central american seaway cas around 4 6 ma million years ago is thought to have enhanced the gulf stream strengthening the atlantic meridional overturning circulation and potentially influencing the evolution of pliocene climate paleoclimate records indicate a buildup of heat and salt in the caribbean and changes in the formation of north atlantic deep water nadw associated with a major step in the shoaling of the cas at 4 6 ma however so far direct evidence supporting an intensification of the gulf stream is scarce here we report new north atlantic early pliocene 5 3 3 9 ma records of sea surface temperature sst reconstructed using the u 37 k and tex86 paleotemperature indices based on new sediment trap measurements near the study site we suggest that in this particular region the two paleothermometers record sst during different seasons spring for u k 37 and summer for tex86 at 4 6 and 4 2 ma our results indicate substantial increases in sst and salinity during summer but not spring pointing to a significant intensification of the gulf stream and its extension the north atlantic current after the shoaling of the cas the divergence of the u 37 k and tex86 temperature trends in those intervals suggests that the gulf stream intensification contributed to the strong north atlantic seasonality that is observed today

export of labrador sea water from the subpolar north atlantic a lagrangian perspective abstract results from 59 acoustically tracked rafos floats obtained during 2003 2008 are analyzed here to study the spreading pathways of labrador sea water lsw from the subpolar to subtropical north atlantic an earlier paper based on a subset of these float data presented evidence of a potentially important interior pathway for the southward spreading of lsw here those results are reinforced with the full data set and new information on lsw pathways around the grand banks is presented about 70 of the rafos floats were expelled into the ocean interior east of the grand banks and meandered slowly eastward toward the mid atlantic ridge a pathway observed previously with profiling floats less than 10 was advected continuously around the grand banks by the deep western boundary current dwbc a larger fraction 17 drifted into the subtropical interior from the tail of the grand banks suggesting that this pathway is at least if not more important than the dwbc pathway for the export of lsw to the subtropics rafos floats released closest to the continental slope at 700 m depth were more likely to rapidly reach subtropical latitudes mainly because they drifted through flemish pass a 1100 m deep channel between the grand banks and the flemish cap which protects fluid parcels from being swept off the continental slope by meanders of the north atlantic current a statistical comparison of the rafos trajectories with more than 5000 simulated floats obtained from the family of linked atlantic models experiment flame high resolution ocean general circulation model reveals a similar pattern of lsw spreading the rafos and simulated floats are also used to show that contrary to a previous modeling study the isobaric rafos floats do not underestimate the amount of lsw that continuously follows the dwbc around the grand banks compared to isopycnal floats these results have implications for the connectivity of the deep limb of the atlantic meridional overturning circulation between the subpolar and the subtropical north atlantic

observations in the northwest corner of the north atlantic current abstract the north atlantic current a northern branch of the gulf stream flows in a northerly direction to the east of the grand banks of newfoundland and turns sharply to the right north of flemish cap in the northwest corner the currents and water masses in and near this turn are described using data from batfish satellite tracked drifters ctds and current meters drifter trajectories and water mass properties indicate that the northward current toward the northwest corner is sometimes well defined narrow converging and accelerating at other times it is poorly defined weaker less coherent and diverging when it is well defined the current turns sharply eastward between 51 and 52 n but rather than continuing east it forms 100 km anticyclonic eddies which persist for at least 1 2 months records from 16 current meters placed on four moorings across the current show the flow direction to be variable in time but nearly constant throughout the water column speed is also constant with depth

seasonal variations of snow chemistry at neem greenland we conducted a pit study in july 2009 at the neem north greenland eemian ice drilling deep ice coring site in northwest greenland to examine the seasonal variations of snow chemistry and characteristics of the drill site we collected snow firn samples from the wall of a 2 m deep pit at intervals of 0 03 m and analyzed them for electric conductivity ph cl no3 so 4 2 ch 3 so 3 msa na k mg 2 ca 2 and stable isotopes of water 18 o and d pronounced seasonal variations in the stable isotopes of water were observed which indicated that the snow had accumulated regularly during the past 4 years concentrations of na cl and mg 2 which largely originate from sea salt peaked in winter to early spring while ca 2 which mainly originates from mineral dust peaked in late winter to spring slightly later than na cl and mg 2 concentrations of no 3 showed double peaks one in summer and the other in winter to spring whereas those of so 4 2 peaked in winter to spring the winter to spring concentrations of no 3 and so 4 2 seem to have been strongly influenced by anthropogenic inputs concentrations of msa showed double peaks one in spring and the other in late summer to autumn our study confirms that the neem deep ice core can be absolutely dated to a certain depth by counting annual layers using the seasonal variations of stable isotopes of water and those of ions we calculated the annual surface mass balance for the years 2006 08 the mean annual balance was 176 mm w e and the balances for winter to summer and summer to winter halves of the year were 98 and 78 mm respectively snow deposition during the winter to summer half of the year was greater than that during the summer to winter half by 10 20 mm for all three years covered by this study

release of gas bubbles from lake sediment traced by noble gas isotopes in the sediment pore water abstract the release of gas bubbles from lacustrine or oceanic sediments into the overlying water ebullition is a major mechanism for the discharge of biogenic or geogenic gases into the water body ebullition of methane or carbon dioxide for instance contributes considerably to the release of these potent greenhouse gases through the sediment water interface depending on the rate of ebullition the pore water will show a depletion in dissolved atmospheric noble gases because the poorly soluble noble gases escape from the pore water into the gas bubbles in this study the depletion of dissolved noble gases in sediment pore water was analyzed for the first time to study bubble formation and ebullition in sediments the noble gases in the pore water of the sediments of soppensee switzerland show a distinct depletion due to ebullition of biologically produced methane this depletion is lowest in the deep sediment and increases towards the sediment surface the noble gas isotope ratios in the pore water indicate that vertical diffusion barely affects the observed noble gas profiles the isotope ratios further show that the methane bubbles remain long enough in the sediment to attain noble gas solubility equilibrium before escaping into the overlying water the volume of gas released from the sediment by ebullition can therefore be reconstructed from the extent of the noble gas depletion in the pore water using a simple gas equilibration model the noble gas profiles in the sediment indicate that ebullition increased in soppensee during the holocene and that ebullition contributed strongly to the release of methane from the sediment our case study thus illustrates that noble gases are sensitive proxies for the release of gas from lacustrine and marine sediments or similar aquatic environments

carbon helium neon and argon isotopes in a po basin northern italy natural gas field the abundance and isotopic composition of he ne and ar have been determined in 19 gas samples taken from the dosso degli angeli hydrocarbon gas field between 3000 and 3750 m depth in the po basin carbon isotope ratios in these samples vary between 13c ch4 67 5 and 73 4 indicating a predominantly biogenic source for the methane c2 c2h6 c3h8 concentrations increase systematically from 0 04 to 0 17 by volume with depth suggesting that there is a small additional thermogenic or diagenetic hydrocarbon contribution to these gases ch4 36ar ratios in the dosso degli angeli gases are in the range predicted for a groundwater which has derived its rare gas by equilibration with the atmosphere and is ch4 saturated under reservoir conditions there is also up to 10 excess of ch4 which is not associated with the groundwater these results are consistent with 90 of the ch4 in the dosso degli angeli reservoir originating from ch4 saturated groundwater measured 20ne 36ar ratios depart from the predicted ratio in air equilibrated groundwater this fractionation is consistent with water gas phase equilibration under reservoir conditions and is similar to that observed in gas reservoirs in the vienna and pannonian basins austria and hungary respectively the he in the dosso degli angeli gases is almost entirely radiogenic and derived from the crust the concentration of 4he in the reservoir gases requires that he is mostly sourced from outside the reservoir volume radiogenic 4he 40ar ratios input into the reservoir gas must be much higher than averaged crustal production ratios as no shift from the atmospheric 40ar 36ar ratio is observed preferential release of 4he over 40ar from the sites of their production is the preferred explanation this observation contrasts with previous studies from active extensional basins in which radiogenic 4he and 40ar appear to have been stored released and transported at near production ratio on a regional scale the most obvious difference between these studies is the comparatively low thermal gradient of the po basin

air xe enrichments in elk hills oil field gases role of water in migration and storage hydrocarbons from the elk hills naval petroleum reserve npr 1 bakersfield ca are enriched in heavy noble gases the 132xe 36ar ratios are as high as 576 times the ratio in air and represent the largest relative xe enrichments ever observed in terrestrial fluids the xe isotopic composition is indistinguishable from air we show that these samples cannot be explained by equilibration of oil with air saturated water and secondary enrichment via a rayleigh distillation gas stripping process based on laboratory studies of others with potential petroleum source rocks we believe the source of this enriched heavy noble gas component was adsorbed air initially trapped in on the source rocks that was expelled and mixed with the hydrocarbons during expulsion and primary migration kr and xe enrichments decrease with increasing 36ar concentration we propose a model in which an initial kr xe enriched hydrocarbon becomes diluted with noble gases extracted from air saturated groundwater during expulsion migration and storage the model generates an integrated water hydrocarbon ratio for the production fluid which indicates a minimal role for water in hydrocarbon expulsion and migration the results are interpreted to provide time geometrical constraints on the mechanisms by which hydrocarbons can migrate as a separate phase

a simple kinematic mechanism for mixing fluid parcels across a meandering jet abstract recent observations of fluid parcel pathways in the gulf stream using isopycnal rafos floats revealed a striking pattern of cross stream and vertical motion associated with meanders bower and rossby 1989 in an attempt to explain the observed pattern a two dimensional kinematic model of a meandering jet has been developed which enables examination of the relationship between streamfunction patterns and fluid parcel trajectories the streamfunction fields are displayed in a reference frame moving with the wave pattern so motions of fluid parcels relative to the jet can be seen more easily the results suggest that the observed pattern of cross stream motion results primarily from the downstream phase propagation of meanders the model successfully reproduces several of the most distinctive features of the float observations 1 entrainment of fluid into the gulf stream occurs at the leading edges of meander extrema while detrainment takes place at the trailing edges 2 exchange between the gu

isopycnal rafos floats as roving hydrographers in the north atlantic current region the properties measured by isopycnal floats can be compiled to provide hydrographic information about the sampled surfaces the height and temperature of two specific volume anomaly surfaces reported by 84 rafos floats deployed in the north atlantic current nac region are compared here with the climatological hydrographic database the mean pathway of the nac and other prominent features of the region are similar in float derived and climatological surfaces the most striking difference between floats and climatology an extended trough in the nac path at 44 n in the float derived surface reflects the sampling time scales the baroclinic transport of the nac estimated from rafos floats using the observed climatological relationship between the potential energy anomaly and the height of the specific volume anomaly surfaces was 42 sv at 42 n and 24 sv at 47 n in reasonable agreement with climatological estimates

near surface mean circulation and kinetic energy in the central north atlantic from drifter data an analysis of a large drifting buoy data set is presented the objective is to obtain a self contained description of the properties of the near surface circulation drogue depth 100 m in the central north atlantic ocean independent of hydrographic data a necessary preanalysis step was the removal of all data from undrogued buoys from the data set the physical parameters of the circulation were deduced by averaging the remaining data in 2 3 boxes the minimum amount of data which is necessary to get statistically stable results was determined by an empirical quality criterion all important mean currents in the investigation area are reproduced by the near surface mean velocity field a separation of the mean velocity field into a nondivergent and an irrational part shows that the flow field is almost nondivergent the distribution of eddy kinetic energy is concentrated along the mean currents and provides the largest part of the total kinetic energy but there are regional variations energy from inertial movements dominates the high frequency part of the kinetic energy its distribution is very patchy the analysis of the reynolds stress terms shows an energy transfer from the eddy field to the mean circulation in the vicinity of the north atlantic current

basin scale natural gas source migration and trapping traced by noble gases and major elements the pakistan indus basin he ne and ar concentrations he and ar isotopic ratios carbon isotopic ratios and chemical compositions of hydrocarbon gases were measured in natural gas samples from gas producing wells in the indus basin pakistan where no oil has ever been found 3he 4he ratios are in the range 0 01 0 06 ra ra is the atmospheric value of 1 38 10 6 indicating the absence of mantle derived helium despite the trias extension 40ar 36ar ratios range from 296 to 800 consistent with variable additions of radiogenic argon to atmospheric groundwater derived argon rare gas concentrations show large variations from 6 10 5 to 1 10 3 mol mol for 4he and from 3 10 7 to 3 10 5 mol mol for 36ar in general 36ar concentrations are high compared to literature data for natural gas co2 and n2 concentrations are variable ranging up to 70 and 20 respectively mantle derived he is not observed therefore co2 and n2 are not mantle derived either hydrocarbon gas maturity is high but accumulation efficiency is small suggesting that early produced hydrocarbons including oil were lost as well as mantle helium this is consistent with the generally late pliocene trap formation and explains the high n2 concentrations since n2 is the final species generated at the end of organic matter maturation based on 13c data co2 originates from carbonate decomposition very elevated 20ne 36ar ratios are found reaching a maximum of 1 3 compared to 0 1 0 2 for air saturated water and 0 5 for air and these high values are related to the lowest rare gas concentrations we suggest that this highly fractionated signature is the trace of the past presence of oil in the basin and appeared in groundwater we propose a model where oil water contact is followed by gas water contact both with rayleigh distillation for rare gas abundance ratios thereby generating the fractionated 20ne 36ar signature in groundwater first and transferring it to gas later assuming the gas water contact occurred shallower than present reservoir depths this model explains the generally high 36ar concentrations and low ch4 36ar ratios compared to other studies on younger basins it thus provides a historical perspective on fluid transfer in a sedimentary basin where a gas accumulation may have been buried to greater depth since formation rare gas and major element data point to mixing between two gas pulses produced successively the very co2 n2 rich gases are terminal products of organic matter maturation which have been trapped after important migration this gas was followed by a more typical thermogenic gas which mixed with it

the isopycnal swallow float a simple device for tracking water parcels in the ocean abstract a standard swallow float can be converted into a passive isopycnal follower by the addition of a compressee a spring backed piston in a cylinder designed to give the float the compressibility of seawater thus no archimedian buoyancy is created due to changes in depth in addition the float must have a coefficient of thermal expansion significantly smaller than that of seawater an instrument meeting these requirements ballasted to a chosen isopycnal will approximately follow that isopycnal on time scales longer than the local buoyancy period two preliminary field experiments were conducted in the upper main thermocline near the north wall of the gulf stream during august 1981 a spherical glass float was deployed 200 km downstream from cape hatteras and was tracked for approximately 100 km neutrally buoyant in the oxygen minimum near 380 m the float tracked the t 27 12 0 01 as determined from ctd data during its passage through a mini meander during september 1982 a cylindrical float was tracked for approximately 100 km east of cape hatteras deployed in the gulf stream near the 250 m level the float tracked the t 26 74 0 01 isopyncal surface during a gradual descent and cross stream motion over the 24 hr sampling period thus the floats tracked nearly isopycnally in both field tests clusters of these instruments used in concert with hydrographic surveys have the potential for unique studies of mixing entrainment and topographic effects

currents and mixing in the irminger sea and in the iceland basin on the basis of a hydrographic section from the faeroe islands toward greenland along 62m 0n and the deployment of about 20 satellite tracked buoys it is shown that the irminger current branches at the reykjanes ridge its total transport amounts to 17 18 sv the eastern branch of the irminger current 8 sv turns east and enters the norwegian sea both through the faeroe shetland channel 3 sv and by passing northeast of the faeroe islands maximum speeds of 70 cm s 1 are reached at the outer edge of the east and west greenland current very intensive mixing is observed between the four water masses that flow into the irminger basin stirring by eddies plays a dominant role for strong interleaving subsequent salt fingering and double diffusive layering conditions for these processes are optimal nearly everywhere in the irminger sea

a magnus opus helium neon and argon isotopes in a north sea oilfield this study of the magnus oilfield located in the east shetland basin northern north sea represents the most detailed investigation of noble gas isotope systematics in a liquid hydrocarbon reservoir yet undertaken samples from nine producing wells across this middle jurassic field were taken and the helium neon and argon isotopic ratios and abundances in the oil were determined both the helium and the neon isotope systematics require a contribution from a mantle source if the mantle endmember is modeled using mid ocean ridge mor values 2 3 4 5 of the 4he and 4 3 6 2 of the 21ne is mantle derived the remainder of the 4he and 9 0 12 0 of the 21ne is crustal radiogenic and the remaining 21ne is atmosphere derived the resolved mantle derived he ne ratio is quite distinct from upper mantle values estimated from mor samples but indistinguishable from values resolved in other regions of continental extension this result provides strong evidence that the subcontinental lithospheric mantle not only has a different noble gas inventory to the convecting mantle under mors but also has a near uniform composition the quantity of radiogenic noble gas associated with the magnus oil groundwater system can only be accounted for by production predominantly from outside the volume of the magnus sandstone aquifer reservoir drainage area and the associated kimmeridge clay source rock formation and together with the mantle derived noble gases provides strong evidence for cross formational communication with deeper regions of the crust the 20ne and 36ar must have been input into the oil phase by interaction with an air equilibrated groundwater noble gas partitioning between a seawater derived groundwater and the oil phase at the average magnus sandstone aquifer temperature requires a subsurface seawater oil volume ratio of 110 40 to account for both the 20ne and 36ar concentrations in the central and southern magnus samples the volume of groundwater which has equilibrated with the magnus oil is indistinguishable from the static volume of water estimated to be in the down dip magnus aquifer reservoir drainage volume this suggests that the magnus oil has obtained complete equilibrium with the groundwater in the reservoir drainage volume probably during secondary migration and further suggests that concurrent cementation of the magnus sandstone aquifer has occurred with little or no large scale movement of air equilibrated groundwater through the aquifer system higher concentrations of 20ne and 36ar in the n magnus oil cannot be accounted for by equilibration with a seawater derived groundwater this is qualitatively consistent with the earlier and more mature oil in this section equilibrating with freshwater which is known to have been trapped in the crest of the reservoir structure

impact of late spring siberian snow on summer rainfall in south central china located in the yangtze river valley and surrounded by mountains south central china scc frequently suffered from natural disasters such as torrential precipitation landslide and debris flow here we provide corroborative evidence for a link between the late spring may snow water equivalent swe over siberia and the summer july august abbr ja rainfall in scc we show that in may anomalously low swe over siberia is robustly related to a large warming from the surface to the mid troposphere and to a stationary rossby wave train from siberia eastward toward the north atlantic on the one hand over the north atlantic there exhibits a tripole pattern response of sea surface temperature anomalies in may it persists to some extent in ja and in turn triggers a wave train propagating downstream across eurasia and along the asian jet as the so called silk road pattern srp on the other hand over northern siberia the drier soil occurs in ja accompanied by an overlying anomalous anticyclone through the positive feedback this anomalous anticyclone favors the tropospheric cooling over southern siberia and the meridional northward displacement of the asian jet jmd due to the change in the meridional temperature gradient the combination of the srp and the jmd facilitates less water vapor transport from the tropical oceans and anomalous descending motion over scc and thus suppresses the precipitation these findings indicate that may siberian swe can be exploited for seasonal predictability of scc precipitation

eastward jets over diverging isobaths with applications to the gulf stream past the grand banks a three dimensional primitive equation model is employed to investigate how an initially eastward jet responds to isobaths that diverge eastward this problem is investigated using first a barotropic model and then a baroclinic model in the barotropic regime the diverging isobaths force an initially supercritical jet to widen and become subcritical after a hydraulic jump increasing eastward advection of vorticity moves the diverging point eastward and narrows the jet locally but widens the jet farther downstream the incoming jet axis is fixed at a preferred latitude due to the steep meridional bottom slope upstream in the baroclinic regime the eastward divergence of the jet becomes much more pronounced this strong divergence leads to the bifurcation of the jet downstream the northern branch flows northeastward and the main branch continues eastward the former is a western boundary current along the northeastward continental slope the bifurcation of baroclinic jets is caused by hydraulic jumps reinforced by instabilities of the baroclinic current system among possible applications the model is particularly relevant to the bifurcation of the gulf stream to the south of the grand banks where the essentially zonal isobaths begin to bifurcate eastward

halogens and noble gases in sedimentary formation waters and zn pb deposits a case study from the lennard shelf australia abstract halogen ratios br cl and i cl and concentrations provide important information about how sedimentary formation waters acquire their salinity but the possible influence of organic br derived from sedimentary wall rocks is rarely quantified here it is demonstrated that br cl versus i cl mixing diagrams can be used to deconvolve organic br contributions that organic matter has a limited range of br i ratios and that organic br is a more significant component in zn pb deposit ore fluids than previously recognised the significance of these findings is illustrated for the lennard shelf zn pb deposits of western australia fluid inclusions related to lennard shelf zn pb mineralisation have variable salinity and hydrocarbon contents the halogen data from these fluid inclusions require mixing of three fluid end members 1 an evaporated seawater bittern brine 30 wt nacl equiv with greater than seawater br cl ratio 2 a lower salinity pore fluid 5 wt nacl equiv with moderately elevated br cl and i cl and 3 fluids with br cl ratios of 5 times seawater and extremely elevated i cl ratios of 11 500 times seawater the first two fluids have 40 ar 36 ar of 300 400 and greater than air saturated water 36 ar concentrations that are typical of fluid inclusions related to zn pb mineralisation the third organic rich fluid has the highest 40 ar 36 ar ratio of up to 1500 and a depleted 36 ar concentration mineralisation is interpreted to have resulted from mixing of zn rich evaporitic brines and h 2 s present in hydrocarbons it is suggested that aqueous fluids acquired organic br and i from hydrocarbons and that hydrocarbons exsolving from the aqueous fluid removed noble gases from solution interaction of variably saline brines and hydrocarbons could account for the variable br cl and i cl composition and 36 ar concentrations recorded by lennard shelf fluid inclusions the distinct 40 ar 36 ar signature of the fluid with the highest i cl ratio suggests the hydrocarbons and brines were sourced independently from different parts of the sedimentary basin these data indicate the complementary nature of halogen and noble gas analysis and provide new constraints on important mixing processes during sediment hosted zn pb mineralisation

lagrangian studies of fluid exchange between the gulf stream and surrounding waters abstract between spring of 1988 and winter of 1990 75 rafos floats were released east of cape hatteras near the center of the gulf stream on the 26 8 t surface o 15 c the purpose of this sequential deployment was to investigate the spatial and temporal characteristics of the meandering stream and the lagrangian properties of fluid motion in the upper thermocline these new observations were also intended to provide a database for comparative studies of fluid motion in the upper thermocline with similar observations made earlier 1984 85 in the middle and lower thermocline sixty one of the 75 rafos float trajectories in the 13 16 c layers have been analyzed from both a lagrangian and eulerian point of view the results reconfirm the strong baroclinic structure of the gulf stream established earlier and reveal enhanced cross stream motion with increasing depth and over the new england seamounts float trajectories tend to be more convoluted east of the seamounts reflecting the large amplitude meand

temperature flux carried by individual eddies across 47 n in the atlantic ocean surface geostrophic velocity fields derived from satellite altimetry between january 1993 and april 2014 are used to detect and investigate eddies in the north atlantic between 40 55 n and 60 10 w focus is on a zonal section along 47 n roughly at the boundary between the subpolar and the subtropical gyres sea surface temperature data are used to quantify the temperature anomalies associated with eddies and the respective surface temperature fluxes related to these eddies identified eddy pathways across 47 n are related to the mean background velocity from full depth ship observations carried out on 11 cruises between 2003 and 2014 the analysis is repeated in two model simulations with 1 4 and 1 12 horizontal resolution respectively for the period 2002 2013 the analysis reveals almost 37000 altimeter derived eddies with a lifetime longer than one week in the area the highest number of eddies is found along the pathway of the north atlantic current roughly following the 4000 m isobath and on the grand banks of newfoundland time series of temperature fluxes by eddies crossing 47 n reveal that single isolated eddies with large sst signatures contribute 25 to the surface temperature flux relating the observed eddies to the observed top to bottom velocity distribution at 47 n points to the existence of eddy pathways across 47 the highest temperature fluxes are linked to the fastest and most pronounced current branches in the western newfoundland basin while there are fewer eddies in both model simulations the key findings are consistent between the observations and the two model simulations this article is protected by copyright all rights reserved

mean circulation and eddy kinetic energy in the eastern north atlantic sixty two satellite tracked buoys have been released in the northern part of the western and central north atlantic during 1981 and 1982 by the institut fur meereskunde universitat kiel federal republic of germany additionally six buoys deployed in spring 1980 by the bedford institute have been taken over mean values and variances about the mean have been calculated for 3 by 3 areas the mean velocities confirm the large scale gyre circulation as deduced from hydrographie data and numerical models the center of the gyre is located at about 33 n eddy kinetic energy decreases east and southward and is concentrated along the north atlantic current it appears that the north atlantic current polar front is the main source of eddy kinetic energy for the northern north atlantic whereas the mid atlantic ridge is no source of eddy energy eddy kinetic energy along the north atlantic current decreases from about 1000 cm2 s 2 near newfoundland to 300 cm2 s 2 west of scotland a homogeneous pool of low eddy kinetic energy less than 100 cm2 s 2 appears in the central north atlantic east of the mid atlantic ridge the level increases towards the european and african shelf where the mean southward flow also becomes stronger the results concern the upper ocean

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

thermal constraints on crustal rare gas release and migration evidence from alpine fluid inclusions the palfris marl of the helvetic alpine nappes contains four distinct vein fill generations ch4 rich gas is found in abundant fluid inclusions within these carbonate veins while free ch4 gas has also been produced from exploratory boreholes through this formation the stable isotope and helium neon and argon isotopic composition of these fluids has been determined a constant radiogenic 40ar concentration of 1 25 0 13 1 ppm in these differently sited fluids requires an intimate association between the 40arrad source and the hydrocarbon phase this can only be reasonably explained if the 40arrad was input into the hydrocarbon phase during hydrocarbon generation migration or storage prior to entrapment in the fluid inclusions stable isotope results constrain the maturity of hydrocarbon production while fluid inclusion formation pressures and temperatures record values of up to 2 5 kbars and 250 c these values place limits on the range of thermal conditions in which the hydrocarbon 40arrad relationship was established all fluids within inclusions also contain radiogenic 4he40ar values at predicted crustal production ratios these observations provide the first evidence that both 4herad and 40arrad can be quantitatively released on a regional scale bounded by the thermal conditions required to produce the hydrocarbon phase and the conditions under which the fluid inclusions were formed t 190 250 c these results require that negligible quantities of excess 40arrad decoupled from 4herad have been released into this system given the wide array of mechanisms which can potentially cause decoupling of these two species this result provides an important constraint on the role of these processes within the sedimentary fluid regime in contrast the free borehole gas contains excess radiogenic 4he and 21ne relative to 40arrad in proportions which can be accounted for by local production and subsequent diffusion from the surrounding marl the latter pattern is consistent with rare gas migration in lower temperature environments a conceptual model which considers both diffusional and metamorphic release of helium and argon and the ability of the surrounding fluid regime to transport the rare gases from their respective mineral production sites is consistent with both these results and data from regional rare gas studies

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

historical position of the north atlantic current the path of the north atlantic current nac within the newfoundland basin is determined from the historical hydrographic database 1910 1988 horizontal probability distributions for dynamical and property front locations on specific volume anomaly surfaces are derived from an analysis of all available hydrographic stations in the basin these probability distributions indicate where the fronts were most likely to have been observed in the past they are observed to exhibit a pattern of stationary meanders with troughs located over the southcast newfoundland rise over the newfoundland seamounts and to the east of the flemish cap the width of the nac s envelope varies from 300 km over the southeast newfoundland rise temporal subsamples of the historical data indicate that the path and meander patterns are persistent features for all seasons and for the four decades between 1950 and 1990

the origin of helium in deep sedimentary aquifers and the problem of dating very old groundwaters noble gases inert elements having isotopes produced by the decay of long half life radionuclides offer a powerful approach for tracing fluid circulation and dating groundwaters the u th 4he water ages calculated from the accumulation rate in water of radiogenic 4he produced by decay of u and th contained in the aquifer rocks is frequently higher than the hydrological ages this discrepancy is generally interpreted by two contrasting models i heterogeneities of the aquifers which allow water stagnation and accumulation of large amounts of radiogenic 4he or ii addition of 4he produced in deeper regions of the continental crust in this contribution we propose that the apparent contrast between u th 4he ages and hydrological ages in the paris basin reflects the mixing of different types of water having different residence times we show using the helium isotopic signatures of waters that this mixing occurs between three aquifers the middle jurassic the triassic and the palaeozoic basement which have contrasting helium contents and heterogeneous chemical compositions and permeabilities the difference of radiogenic 4he 4 ratios between the aquifers of triassic and middle jurassic strongly suggests that a significant fraction of helium is produced in the aquifer rocks this implies residence times for groundwaters circulating in the middle jurassic carbonate aquifer much longer than those obtained from hydrological studies independent fluid age estimates based on the ground palaeotemperatures recorded in the same groundwaters by the atmospherederived noble gases seem to confirm the presence of very old groundwaters in the paris basin the estimation of the residence time of ancient groundwaters is the most challenging problem in basin hydrology e g chapman 1987 typical water residence times of 104 108 years outreach the range of half lives of most of the geochronometers available in hydrology e g 3h 14c and prolonged water rock interactions alter the chemical and isotopic signature of water preventing the identification of the fluid sources on the other hand hydrological modelling faces serious problems of estimating space and time variations of critical parameters such as the permeability due to the petro physical heterogeneities of the aquifers and fluid velocity estimates can be valid only on a local scale e g alexander et al 1987 because noble gases are inert and have isotopes produced by natural decay of long halflife radionuclides these elements have received increasing attention as tracers of groundwater movements in deep aquifers e g marine 1979 andrews et al 1982 1985 bottomley et at 1984 1990 torgersen clarke 1985 zaikowski et al 1987 ballentine et al 1991 stute et al 1992 marty et al 1993 o nions ballentine 1993 groundwaters contain noble gases derived from the atmosphere the crust and the mantle fig 1 studies on water dating are focused mainly on the crustal derived radiogenic noble gas component for obvious reasons although the mantle derived component has the capacity of tracing fluid sources oxburgh et al 1986 and the atmosphere derived component can provide independent estimates on the water residence times pinti et al 1997 in continental environments mantle derived noble gases are generally observed in regions of active volcanism or extensional tectonics ballentine et al 1991 the source is probably sub continental magma intrusion and underplating with successive episodic and tectonically controlled advective transport in the crust torgersen 1993 mantle derived helium can be easily identified from its isotopic signature indeed the mantle is enriched in primordial 3he as indicated by 3he 4he ratios greater than 10 5 whereas the atmospheric ratio is l a x 10 6 and crustalderived radiogenic helium has 3he 4he ratios in the range of 10 8 consequently the geographical distribution of the 3he 4he ratios in sedimentary fluids can be used to identify the fluids pinti d l marty b 1998 the origin of helium in deep sedimentary aquifers and the problem of dating very old groundwaters in parnell j ed 1998 dating and duration of fluid flow and fluid rock interaction geological society london special publications 144 53 68 by guest on january 5 2014 http sp lyellcollection org downloaded from

on the origin of the azores current the azores current south of the azores archipelago is part of the subtropical north atlantic gyre using an international hydrographic data set we analyze mean and seasonal geostrophic transport fields in the upper 800 m of the ocean in order to determine the origin of the azores current in the western basin and seasonal changes in the related flow geostrophic currents are obtained by using the method applied by stramma 1984 in the eastern basin the azores current is found to originate in the area of the southwest newfoundland rise figure 10 in winter an almost uniform current connects this region of origin with the azores current while a branching into two current bands is observed in summer with the southern band forming a marked cyclonic loop within the upper 800 m all of the transport in the northern band and about 70 of the transport in the southern band recirculates in the eastern basin additionally expendable bathythermograph data from the azores current region indicate an increase of eddy potential energy from winter to summer

deep water formation the subpolar gyre and the meridional overturning circulation in the subpolar north atlantic on interannual to decadal times scales model simulations suggest a strong relationship between anomalies in the deep water formation rate the strength of the subpolar gyre and the meridional overturning circulation in the north atlantic whether this is valid can only be confirmed by continuous long observational time series several measurement components are already in place but crucial arrays to obtain time series of the meridional volume and heat transport in the subpolar north atlantic are still missing here we summarize the recent developments of the deep water formation rates and the subpolar gyre transports we discuss how existing observational components in the subpolar north atlantic could be supplemented to provide long term monitoring of the meridional heat and volume transport through a combined analysis of observations and model results the temporal and spatial scales that had to be covered with instruments are discussed together with the key regions with the highest variability in the velocity and temperature fields

the water masses of the central north atlantic in 1983 84 abstract hydrographic surveys carried out in 1983 84 along both sides of the mid atlantic ridge between 24 and 53 n provide a detailed description of the well known north atlantic water masses with particular emphasis on their meridional distribution and zonal dissymetry in the upper layers the dense horizontal sampling resolves the several narrow gulf stream extensions into the ocean interior giving the image in the central water density range of a mosaic of mode waters separated by fronts at intermediate depths a vertical shear in the distributions of the mediterranean water and labrador sea water stands out both water masses having their lower part displaced southwards relative to their upper parts bottom waters containing nearly 20 percent of pure antarctic bottom water are observed at 50 n in the eastern basin in contrast with the western basin where proportions greater than 10 percent were found only south of 36 n along our section this water mass analysis also gives indications that stron

warm water pathways transports and transformations in the northwestern north atlantic and their modification by cold air outbreaks 1 this paper presents a numerical study of the warm water pathways transports and water mass transformation in the newfoundland basin region and an investigation of the rectification effects of a series of cold air outbreaks caos on the above processes an initial mean state simulation was compared with observations and showed good agreement then repeated cao events were explicitly included in the surface fluxes and illustrated the following rectification effects the thermal regime of the entire baroclinic layer was impacted as the thermocline deepened and the temperature anomaly was noticeable down to 500 m different mechanisms were responsible for the propagation of the temperature anomaly at different stages during the onset of the cao vertical diffusion propagated the temperature anomaly downward near the surface then vertical advection further propagated the anomaly downward between cao events to about 500 m depth with caos the north atlantic current carried more warm water and its pathway in the northwest corner shifted towards the southeast the volume averaged mean and eddy kinetic energy increased by 30 and 20 respectively and the water mass transformation rate in the newfoundland basin was doubled the gulf stream carried more heat but heat transport to the eastern basin decreased owing to the increase in heat release to the atmosphere

sampling of volcanic gases the role of noble gas measurements a case study of vulcano south italy abstract collection of volcanic gases during a workshop at vulcano south italy revealed that the atmospheric noble gases are sensitive monitors to air contamination whereas indigenous deep seated compounds such as he co 2 hcl and h 2 s are insensitive to such contaminations fumaroles at the vulcano crater contained high concentrations of he 1 3 10 3 cm 3 stp g h 2 o and he ne equaled 1000 in the least contaminated sample compared to 0 2 in air saturated water 40 ar 36 ar was up to 692 radiogenic 40 ar was 11 10 4 cm 3 stp g h 2 o and radiogenic 4 he 40 ar equaled 1 2 these characteristics resemble those of steam separated from boiling geothermal fluids occurrences of vigorous bubbling drowned fumaroles were studied at the vulcano beach and at the adjacent hippopotamus pond he ne was 20 40 indicating the presence of some radiogenic he accompanied by no significant radiogenic ar the ratio of atmospheric noble gases to dry gas was 10 times higher in the drowned fumaroles at the beach than in the crater fumaroles the water of the hippopotamus pond contained 9690 mg 1 1 cl 11 800 mg 1 1 so 2 4 the ph measured in the laboratory was 1 2 these characteristics indicate that the fumaroles loose reactive gases co 2 h 2 s hcl while passing shallow water

physical oceanography of the azores front abstract there is a considerable body of evidence for the existence of a permanent front sw of the azores surveys in the summer of 1981 show the structure to penetrate to a depth of 2 000 m and suggest that its meandering is related to the alignment of the atlantis gt meteor seamount chain the total volume transport above 2 000 m is between 10 and 12 106 m3 s 1 towards the east the main water mass contrasts across the front are confined to the upper 400 m of the water column only a small change in mediterranean water strength was seen across the front satellite tracked drogued buoys seeded into the front showed surface speeds of up to 40 cm sec 1 and revealed the formation of a closed cold core eddy some 100 115 km in diameter which propagated westward at 2 2 km day 1 over a 200 day period sea surface temperature contrasts across the frontal boundary are small and together with frequent cloud cover prevent the detection of the front and associated eddies by satellite infra red imagery the front apparently marks the eastward extension of the southern branch of the gulf stream recirculation and the northern limit of the 18 c water mass eddies formed at the front could propagate westward into the interior of the sargasso sea but have not yet been observed to cross the mid atlantic ridge

observations of an intense anticyclonic warm eddy in the newfoundland basin an intense anticyclonic warm eddy was sampled in february 1997 in the newfoundland basin its presence detected during a hydrographic survey was further corroborated through ers topex sea surface height anomaly and satellite tracked drifters this 120 km wide eddy was very homogeneous in temperature and salinity down to 800 m and its transport 15 1800 dbar reached 27 sv its location 49 n 40 w in the warm and saline waters of the northwest corner the northernmost position reached by the north atlantic current is clearly exceptional although intense anticyclonic eddies have previously been observed with satellite tracked buoys and rafos floats this is the first eddy to our knowledge ever documented at such a high latitude in the north atlantic current system its formation is discussed in term of thermohaline processes

genetic characterization of natural gases natural gases can be characterized genetically using four properties c2 concentration carbon and hydrogen isotope variations in methane and carbon isotope variation in ethane three diagrams for genetic characterization of gases have been designed in which the carbon isotopic composition of methane is correlated with the other parameters in these diagrams compositional fields have been defined for primary gases biogenic thermogenic associated and thermogenic nonassociated and for gases which result from mixing of these gases these fields are strictly empirical and comprise compositional variations found in about 500 natural gases the isotopic and compositional variations in natural gases can be described in terms of 1 processes during formation of the gases such as bacterial fermentation or maturation of organic matter and 2 processes during secondary migration mixing of primary gases is an important and common process migration of gases predominantly affects the c2 concentration whereas the isotopic properties of gaseous hydrocarbons primarily remain unchanged allowing an assessment of the origin of migrated gases and properties of their source rocks the formation of gas from humic organic matter and coals is not yet clear from published data the diagrams use data from various basins and areas interstitial gases from the gulf of california are entirely of bacterial origin traces of thermogenic gases are formed only in the vicinity of dolerite sills gases in the south german molasse basin and in the vienna basin are of bacterial mixed and thermogenic origins data from the north italian po basin provide examples for genetic characterization of migrated gases

the noble gas isotope record of hydrocarbon field formation time scales abstract noble gases may be considered as the most prominent tracers of natural fluids including hydrocarbons the atmosphere is the only source of 20ne 36ar 84kr 130xe in subsurface environments and their concentrations in pore waters after recharge are known from the solubility data this allows modelling of noble gas partitioning between coexisting gas oil and water phases in the course of hydrocarbon formation migration and storage radiogenic isotopes 4he 21ne 40ar 136xe after being released from source rocks are mixed with air derived noble gases already present in the pore space concentrations of radiogenic species in the pore space of typical hydrocarbon fields are generally so high that they can hardly be accumulated in situ and thus indicate noble gas transfer from ground waters the time bearing ratios 4he 20ne 21ne 20ne 4he 40arair 40ar 40arair in hydrocarbon fields are thus proportional to the time interval between the ground water recharge and noble gases partitioning into the hydrocarbon phase s the recharge partition interval the largest available data set allows the recharge partition intervals to be constrained for a large number of hydrocarbon fields situated in different tectonic settings ancient plates young plates mobile belts these intervals increase systematically with the ages of hydrocarbon source and trap lithologies and are comparable with these ages this important feature valid in general for different hydrocarbon fields implies i local sources of radiogenic noble gas isotopes in ground waters ii relatively recent formation of hydrocarbon fields and iii their short formation time scales in some cases the duration of formation of a hydrocarbon field can be constrained for example nearly constant 21ne 20ne 40ar 40arair ratios measured in samples from the magnus oil field north sea give an accumulation time scale 10 ma it should be emphasized that the above noble gas isotope ratios give the time estimates which are independent of geological reconstructions sometimes the noble gas inventory in a hydrocarbon field and ground waters allows characterization of the source rock volume involved in formation of the field generally this volume exceeds that of the hydrocarbon field rocks by orders of magnitude

eddy kinetic energy in the north atlantic from surface drifters one hundred ten satellite tracked freely drifting buoys measured velocities and trajectories of the near surface currents in the north atlantic mean velocity values and the velocity variance about the mean were calculated for different regions a horizontal map of eddy kinetic energy was prepared on a 2 2 grid between latitudes 20 and 55 n maximum eddy energy 3000 cm2 s 2 coincides with the high speed gulf stream jet where it begins large amplitude meanders near 37 n 67 w a tongue of high eddy energy coincides with the stream s path eastward and around the grand banks into the newfoundland basin where values of 1000 cm2 s 2 are found a weaker tongue extends eastward across the mid atlantic ridge near 45 n a second weak extension reaches southeastward from the stream and crosses the mid atlantic ridge between 30 and 35 n north and south of the stream eddy energy diminishes rapidly reaching an e folding at 300 km from the axis values of 200 cm2 s 2 were observed in the mid gyre region and 100 cm2 s 2 in the eastern north atlantic and north equatorial current although the gross distribution of eddy energy is similar to that determined from ship drift measurements there are significant differences eddy energy from drifters amounts to about twice the value measured by ship drift in the gulf stream and one half the ship drift values in the mid gyre it is suggested that these differences are due to the horizontal averaging of mesoscale motion and the errors in navigation both of which are problems with the ship drift technique

determining fluid migration and isolation times in multiphase crustal domains using noble gases geochemical characteristics in subsurface fluid systems provide a wealth of information about fluid sources migration and storage conditions determining the extent of fluid interaction aquifer hydrocarbon connectivity is important for oil and gas production and waste storage applications but is not tractable using traditional seismic methods furthermore the residence time of fluids is critical in such systems and can vary from tens of thousands to billions of years our understanding of the transport length scales in multiphase systems while equally important is more limited noble gas data from the rotliegend natural gas field northern germany are used here to determine the length scale and isolation age of the combined water gas system we show that geologically bound volume estimates i e gas to water volume ratios match closed system noble gas model predictions suggesting that the rotliegend system has remained isolated as a closed system since hydrocarbon formation radiogenic helium data show that fluid isolation occurred 63 129 m y after rock and or groundwater deposition ca 300 ma which is consistent with known hydrocarbon generation from 250 to 140 ma thus corroborating long term geologic isolation it is critical that we have the ability to distinguish between fluid systems that despite phase separation have remained closed to fluid loss from those that have lost oil or gas phases these findings are the first to demonstrate that such systems remain isolated and fully gas retentive on time scales 100 m y over 10 km length scales and have broad implications for saline aquifer co2 disposal site viability and hydrocarbon resource prediction which both require an understanding of the length and time scales of crustal fluid transport pathways

assessing variability in the size and strength of the north atlantic subpolar gyre recent studies on the size and strength of the north atlantic subpolar gyre spg offer contrasting assessments of the gyre s temporal variability studies that use empirical orthogonal function eof analyses of satellite sea surface height ssh report a rapid decline in spg size and strength since 1992 20 per decade while concurrent in situ observations report either no trend or a slight decline here we investigate this discrepancy by analyzing the size and strength of the spg with satellite ssh from 1993 to 2015 with two separate methods indirectly via eof analysis and more directly through measurements of the gyre center and boundary we define the boundary of the gyre as the largest closed contour of ssh the center as the minimum ssh and the strength as the difference between the ssh at the boundary and the center we identify a linear decline over the study period in the spg strength 5 1 per decade but find no statistically significant trend in the spg area the trend in the gyre strength is weaker than the eof based trend and is most likely below the level of detection of the in situ measurements we conclude that the variability previously identified as a sharp decline in spg circulation can be more appropriately attributed to basin wide sea level rise during the satellite altimetry period in addition we find that the properties of the eastern spg do not co vary with the spg size suggesting that spg dynamics do not control the strength of the inter gyre throughput

noble gases solubility models of hydrocarbon charge mechanism in the sleipner vest gas field abstract noble gases are chemically inert and variably soluble in crustal fluids they are primarily introduced into hydrocarbon reservoirs through exchange with formation waters and can be used to assess migration pathways and mechanisms as well as reservoir storage conditions of particular interest is the role groundwater plays in hydrocarbon transport which is reflected in hydrocarbon water volume ratios here we present compositional stable isotope and noble gas isotope and abundance data from the sleipner vest field in the norwegian north sea sleipner vest gases are generated from primary cracking of kerogen and the thermal cracking of oil gas was emplaced into the sleipner vest from the south and subsequently migrated to the east filling and spilling into the sleipner ost fields gases principally consist of hydrocarbons 83 93 co2 5 4 15 3 and n2 0 6 0 9 as well as trace concentrations of noble gases helium isotopes 3he 4he are predominantly radiogenic and range from 0 065 to 0 116 ra reported relative to air ra 1 4 10 6 clarke et al 1976 sano et al 1988 showing predominantly 98 crustal contributions consistent with ne 20ne 22ne from 9 70 to 9 91 21ne 22ne from 0 0290 to 0 0344 and ar isotopes 40ar 36ar from 315 to 489 air derived noble gas isotopes 20ne 36ar 84kr 132xe are introduced into the hydrocarbon system by direct exchange with air saturated water asw the distribution of air derived noble gas species are controlled by phase partitioning processes in that they preferentially partition into the gas i e methane phase due to their low solubilities in fluids therefore the extent of exchange between hydrocarbon phases and formation waters that have previously equilibrated with the atmosphere can be determined by investigating air derived noble gas species we utilize both elemental ratios to address process i e open vs closed system and concentrations to quantify the extent of hydrocarbon water exchange i e volumetric gas water ratios these data are discussed within the framework of several conceptual models i total gas stripping model which assumes all noble gases have been stripped from the water phase thus defining the minimum volume of water to have interacted with the hydrocarbon phase ii equilibrium model which assumes equilibration between groundwater and hydrocarbon phase at reservoir p t and salinity and iii open and closed system gas stripping models using concentrations and elemental ratios by applying these models to ne ar data from sleipner we estimate volumetric gas water ratios v g v w between 0 02 and 0 07 which are lower than standard geologic gas water estimates of 0 24 estimated by combining gas in place estimates with groundwater porosity estimates sleipner vest data can be best approximated by an open system model which predicts more than an order of magnitude more groundwater interaction during migration than geologic estimates indicating a dynamic aquifer system and or a hydrous migration pathway in an open system the extent of gas loss can be estimated to be between 8 and 10 reservoir volumes which have passed through the system and been lost i e filled and spilled

the noble gas geochemistry of natural co2 gas reservoirs from the colorado plateau and rocky mountain provinces usa identification of the source of co2 in natural reservoirs and development of physical models to account for the migration and interaction of this co2 with the groundwater is essential for developing a quantitative understanding of the long term storage potential of co2 in the subsurface we present the results of 57 noble gas determinations in co2 rich fields 82 from three natural reservoirs to the east of the colorado plateau uplift province usa bravo dome nm sheep mountain co and mccallum dome co and from two reservoirs from within the uplift area st john s dome az and mcelmo dome co we demonstrate that all fields have co2 3he ratios consistent with a dominantly magmatic source the most recent volcanics in the province date from 8 to 10 ka and are associated with the bravo dome field the oldest magmatic activity dates from 42 to 70 ma and is associated with the mcelmo dome field located in the tectonically stable centre of the colorado plateau co2 can be stored within the subsurface on a millennia timescale the manner and extent of contact of the co2 phase with the groundwater system is a critical parameter in using these systems as natural analogues for geological storage of anthropogenic co2 we show that coherent fractionation of groundwater 20ne 36ar with crustal radiogenic noble gases 4he 21ne 40ar is explained by a two stage re dissolution model stage 1 magmatic co2 injection into the groundwater system strips dissolved air derived noble gases asw and accumulated crustal radiogenic noble gas by co2 water phase partitioning the co2 containing the groundwater stripped gases provides the first reservoir fluid charge subsequent charges of co2 provide no more asw or crustal noble gases and serve only to dilute the original asw and crustal noble gas rich co2 reservoir scale preservation of concentration gradients in asw derived noble gases thus provide co2 filling direction this is seen in the bravo dome and st john s dome fields stage 2 the noble gases re dissolve into any available gas stripped groundwater this is modeled as a rayleigh distillation process and enables us to quantify for each sample 1 the volume of groundwater originally stripped on reservoir filling and 2 the volume of groundwater involved in subsequent interaction the original water volume that is gas stripped varies from as low as 0 0005 cm3 groundwater cm3 gas stp in one bravo dome sample to 2 56 cm3 groundwater cm3 gas stp in a st john s dome sample subsequent gas groundwater equilibration varies within all fields each showing a similar range from zero to 100 cm3 water cm3 gas at reservoir pressure and temperature

on the mixing enhancement in a meandering jet due to the interaction with an eddy abstract the interaction between a simple meandering jet such as the gulf stream and an eddy is shown to greatly enhance the mixing and dispersal of fluid parcels in the jet this enhanced mixing is quantified by calculating the rate of increase of the root mean square pair separation of lagrangian particles e g floats launched in the jet s immediate vicinity in the presence of an eddy particles can escape from the regions in which they were initially launched comparisons with observations show a markedly improved qualitative agreement when the eddy is allowed to interact with the meandering jet

the branching of the gulf stream southeast of the grand banks during march april 1987 101 hydrographic stations were occupied on three sections spanning a triangle between the azores faial the southern tip of the grand banks of newfoundland and bermuda information on the near surface processes in the interior of the triangle were obtained from 32 satellite tracked buoys deployed during the cruise and a composite infrared image based on cloud free noaa 9 data during april 1987 the data were combined to analyze the eddy field and the branching of the gulf stream into the north atlantic current and the azores current calculations of mass transports through the legs of the triangle gave a total of 46 sv supplied by the gulf stream 31 sv of which left the area as the north atlantic current and westwind drift north of the azores the remaining 14 sv continued towards east southeast as the azores current and southern recirculation additional conductivity temperature depth stations from a cruise in april 1986 into the same area allowed also study of the large scale circulation within that triangle in deeper layers the azores current appears as a baroclinic stream which reaches down to approximately 1000 m intensive mixing was observed at the continental slope of newfoundland between water of the labrador current and the gulf stream mixed water owing to cabbeling and consecutive convective mixing this water penetrates down to 2000 m depth and creates horizontal density gradients to the surrounding gulf stream water which intensifies the north atlantic current this process is considered to be an important energy source for this current

meandering of the subtropical front south east of the azores a subtropical front was observed in the area south and southeast of the azores during cruises of fs meteor and fs poseidon in early 1982 the front has a basically west east extension with considerable meandering observed meso scale eddies are found on both sides the overall flow pattern corresponds to earlier results on geopotential differences in the upper northeast atlantic but the baroclinic transport of the order of 107 m3 s 1 is found to be concentrated in a 60 km wide jet we suggest here that the current band is part of the gyre circulation resulting from a branching of the north atlantic current

gulf stream structure transport and recirculation near 68 w an analysis of the structure and transport of the gulf stream is undertaken using direct current meter observations from a 13 mooring array deployed near 68 w from june 1988 to august 1990 the analysis is based on a stream coordinate approach in which velocities are rotated into a local downstream coordinate frame and averaged according to their relative cross stream location within the current the picture so obtained represents the average synoptic structure of the gulf stream rather than the eulerian averaged structure in which the current is weakened and broadened by lateral meandering of the current and adjacent recirculations many familiar features of the gulf stream are reproduced in the analysis including an asymmetric velocity profile with larger shear on the cyclonic shoreward side of the current an offshore displacement of the velocity core with depth and a subsurface velocity maximum on the offshore side of the current westward recirculations are also seen on both sides of the gulf stream maximum downstream speeds at the axis of the gulf stream reach approximately 2 0 m s at the surface and 0 7 m s at 1000 m roughly twice the corresponding eulerian averaged values the analysis also reveals a deep extension of the gulf stream at 3500 m depth with a width of 130 km and average speeds of 3 4 cm s the transport of the gulf stream in the stream coordinate frame is 113 8 sv approximately 30 larger than the eulerian averaged transport of 88 sv on the basis of these results and other recent studies the downstream transport increase of the gulf stream and the inflow structure to the gulf stream are reconsidered it is concluded that approximately 30 sv or over half of the transport increase between cape hatteras and 68 w is fed by inflow from the northern side of the gulf stream and that this inflow is concentrated near cape hatteras and 68 w where the gulf stream flows steeply across isobaths converging from the north