validating earth and ocean tide models using tidal gravity measurements summary o1 and m2 observations from well calibrated spring gravimeters and superconducting gravimeters from the global geodynamics project ggp are used to test models of the earth s body tide and 10 ocean tide models it is shown that some of the ocean tide models give anomalous results in various parts of the world for example the schwiderski ocean tide model gives discrepancies in several areas and the fes series of ocean tide models have problems in the western pacific china japan and australia the majority of the high quality tidal gravity measurements in europe are in close agreement with the dehant defraigne and wahr ddw elastic and inelastic body tide models the gravimetric factors for the ddw elastic and inelastic models only differ by 0 12 per cent and the present calibration accuracy does not allow us to distinguish between these models but does reduce the previous upper bound on inelastic gravimetric factors the european observations give a phase lag of a few hundredths of a degree for the o1 body gravity tide which is consistent with the mathews inelastic body tide model at some european and worldwide stations the gravimetric factors differ by up to 0 3 per cent from the ddw model and it is suggested that further checks on the gravimeter calibrations are required accurate determinations of instrumental phase lags are now easier to achieve and the imaginary out of phase component of tidal gravity can be used for accurate tests of this component of ocean tide models

alkane terpene and polycyclic aromatic hydrocarbon geochemistry of the mackenzie river and mackenzie shelf riverine contributions to beaufort sea coastal sediment abstract to study the largest source of river sediment to the arctic ocean we have collected suspended particulates from the mackenzie river in all seasons and sediments from the mackenzie shelf between the river mouth and the shelf edge these samples have been analyzed for alkanes triterpenes and polycyclic aromatic hydrocarbons pahs we found that naturally occurring hydrocarbons predominate in the river and on the shelf these hydrocarbons include biogenic alkanes and triterpenes with a higher plant peat origin diagenetic pahs from peat and plant detritus petrogenic alkanes triterpenes and pahs from oil seeps and or bitumens and combustion pahs that are likely relict in peat deposits because these components vary independently the season is found to strongly influence the concentration and composition of hydrocarbons in the mackenzie river while essentially the same pattern of alkanes diagenetic hopanes and alkyl pahs is observed in all river and most shelf sediment samples alkane and triterpene concentration variations are strongly linked to the relative amount of higher plant peat material polycyclic aromatic hydrocarbon molecular mass profiles also appear to be tied primarily to varying proportions of peat with an additional petrogenic component which is most likely associated with lithic material mobilized by the mackenzie river at freshet consistent with the general lack of alkyl pahs in peat the higher pahs found in the river are probably derived from forest and tundra fires a few anthropogenic pyrogenic compounds are manifest only at the shelf edge probably due to a weakening of the river influence we take this observation of pyrogenic pahs and the pronounced source differences between two sediment samples collected at the shelf edge as evidence of a transition from dominance by the mackenzie river to the geochemistry prevalent in arctic regions far removed from major rivers

the tidal spectrum underneath antarctic ice shelves a year long tidal record has been obtained from beneath the george vi ice shelf antarctica an unusual feature of the record is a significant response in tidal species 3 to 7 these harmonics are practically absent from records further north on the west coast of the antarctic peninsula but are present in all tidal height records from george vi sound a strong ter diurnal signal also exists in the tidal currents under the ice shelf nonlinearity also occurs in the tidal motion of the ronne and ekstrom ice shelves but has not been reported from the ross ice shelf the tidal dynamics of several antarctic ice shelves have therefore been modified by a region of strong nonlinear response to tidal forcing if nonlinear tides in the semidiurnal band are present on the ross ice shelf they could account for difficulties in modeling the area s weak semidiurnal tides an anelastic component in the deformation of the ice at the grounding line is tentatively proposed as the mechanism responsible the positioning of recording pressure sensors in pairs on the seafloor and at the ice shelf base will allow this hypothesis to be tested and also provide a value for the power dissipated by tidally induced flexure at the grounding line

low temperature hydrothermal maturation of organic matter in sediments from the atlantis ii deep red sea abstract hydrocarbons and bulk organic matter of two sediment cores no 84 and 126 chain 61 cruise located within the atlantis ii deep have been analyzed although the brines overlying the coring areas were reported to be sterile microbial inputs and minor terrestrial sources represent the major sedimentary organic material this input is derived from the upper water column above the brines both steroid and triterpenoid hydrocarbons show that extensive acid catalyzed reactions are occurring in the sediments in comparison with other hydrothermal guaymas basin or intrusive systems cape verde rise the atlantis ii deep exhibits a lower degree of thermal maturation this is easily deduced from the elemental composition of the kerogens and the absence of polynuclear aromatic hydrocarbons of a pyrolytic origin in the bitumen the lack of carbon number preference among the n alkanes suggests especially in the case of the long chain homologs that the organic matter of atlantis ii deep sediments has undergone some degree of catagenesis however the yields of hydrocarbons are much lower than those observed in other hydrothermal areas the effect of lower temperature and poor source rock characteristics appear to be responsible for the differences

diploptene in antarctic sediments abstract the presence of diploptene 17 h 21 h hop 22 29 ene in sediment cores from bransfield strait and mcmurdo sound antarctica is reported the organic geochemical data for these sediments provide evidence for the authigenic marine origin of this hopene

distribution and transport of hydrocarbons in surface sediments of the alaskan outer continental shelf abstract surface sediments from the outer continental shelf of alaska were analyzed for hydrocarbons as part of an environmental survey sponsored by noaa blm sediments were collected from the proposed oil lease areas of beaufort sea southeastern bering sea norton sound navarin basin gulf of alaska kodiak shelf and lower cook inlet data on normal and branched alkanes and di and triterpenoids from capillary gas chromatography gc and gas chromatography mass spectrometry gc ms indicate that the area displays little evidence of petroleum hydrocarbons i e seeps except at a few isolated stations beaufort sea sediments have the highest hydrocarbon budget whereas kodiak shelf sediments have the lowest the molecular markers of the hydrocarbons are of a mixed marine autochthonous and terrestrial allochthonous origin norton sound and cook inlet sediments contain the highest levels of terrigenous lipids and kodiak shelf the lowest the abundance of alkenes implies that relatively low oxidizing conditions exist in some of the depositional areas studied suggesting that extraneous petroleum hydrocarbons introduced into these sediments would be expected to have a relatively long residence time the distribution of polynuclear aromatic hydrocarbons pah is complex and shows a pyrolytic origin the data on perylene strongly favor the hypothesis that it is performed from terrigenous precursors and transported into the marine environment with no apparent in situ generation polynuclear aromatic hydrocarbons of diagenetic origin are probably dominant in gulf of alaska and kodiak shelf sediments two stations north of kalgin island in lower cook inlet and one in southeastern bering sea show typical weathered petroleum distribution of n alkanes and triterpenoids probable pathways of transport and fate of petroleum hydrocarbons in case of an oil spill are also briefly discussed

ocean tide model obtained from topex poseidon altimetry data tidal corrections are very important for oceanographic study of altimetry because tidal signals contaminate the low frequency part of raw altimetric signals accurate tidal predictions are also necessary for geophysical research such as with the superconducting gravimeter scg which needs to distinguish very weak signals from the overwhelming tidal signals the aim of this paper is to derive accurate global ocean tide models from the topex poseidon sea surface height data of 5 cm accuracy more accurate than any other previous altimeter data topex geophysical data records of cycles 9 94 were processed and analyzed we describe response analysis of tidal waves at crossover points and application of hydrodynamical interpolation the tidal solutions with 0 5 grid system are obtained for eight major constituents i e m2 s2 n2 k2 k1 o1 p1 and q1 and compared with the schwiderski 1980a b c model the cartwright and ray 1991 model and the eight constituent version of the egbert et al 1994 model or tpxo 2 the accuracy of the models is checked using island and bottom tide gauge data in open ocean and using scg data in antarctica and japan

hydrocarbon geochemistry of the puget sound region iii polycyclic aromatic hydrocarbons in sediments abstract polycyclic aromatic hydrocarbon pah distributions and sources are characterized in 96 sediment samples from 24 210 pb dated cores collected at locations in the greater puget sound the highest pah concentrations are found within a few kilometers of several sources including industrial facilities in northern puget sound urban areas in central puget sound and river systems draining coal bearing strata regional patterns of combustion derived pah in surficial sediments indicate little atmospheric or waterborne exchange of pah between different regions of the sound significant subsurface maxima in combustion derived pah concentrations 210 pb dated at the 1950s occur only in sediment cores collected near urban centers perylene apparently derives from erosion of a terrestrial source with little or no evidence of in situ production at depth in sediment cores coal fragments are carriers of a characteristic suite of alkylated phenanthrene chrysene and picene derivatives concentrated near river mouths in central and southern puget sound

the ocean tide gravimetric loading reconsidered in 1994 95 a set of new global ocean tide models computed by different teams was made available to the scientific community these models were derived from the analysis of satellite altimetric data numerical hydrodynamics or a combination of both the task is now to evaluate their relative accuracy in particular with independent data the data bank prepared by the international center for earth tides icet melchior 1994 gives us a unique opportunity to compare the tidal models by testing their capability to predict the induced gravimetric loading effects the more recent versions released in 1995 of the models by ma et al 1994 and by schrama and ray 1994 both completed at high latitudes by the le provost et al 1994 fes94 1 model have the best scores for the semidiurnal m2 wave with a standard deviation sd of the gravimetric data residues less than 0 540 gal schwiderski 1980 and egbert et al 1994 models give the smallest residual sd about 0 370 gal for the diurnal o1 component however the ordering of the models may change when we focus on some particular regions of the globe

intercomparison of recent ocean tide models one of the tremendous achievements of the topex poseidon t p satellite mission is the release of 12 new global ocean tide models during 1994 virtually all of these models are based on the high precision altimetry obtainable from the t p satellite and all of the models are superior to both the cartwright and ray 1990 1991 model as well as to the schwiderski 1980a b model when compared to tide gauges in the present intercomparison only global ocean tide models released during 1994 have been tested as t p continues to operate new ocean tide models will continue to be released and existing ocean models will be updated hence this intercomparison can only present a snapshot of the state of the art within ocean tide modeling however the intercomparison demonstrates the high accuracy and consistency of all these recent ocean tide models from a comparison with a common 104 tide gauge data set compiled by le provost and others unpublished data the general result is that six of the new ocean tide models have rms agreement better than 3 cm the obtainable accuracy with different tide gauge types raises the question about the accuracy of ground truth as ocean tide models become increasingly more accurate the accuracy of the harmonic constants derived from the tide gauge recordings becomes significant generally the rms agreement between models based on 2 years of t p altimetry is significantly better than the agreement between models based on 1 year of t p altimetry for models based on two years of t p altimetry the rms agreement has values around 2 0 1 4 1 0 and 0 7 cm for the m2 s2 k1 and o1 constituents respectively as a preliminary evaluation these values might be taken as a measure of the consistency of ocean tides estimated from the first part of the t p mission which is extremely promising for future ocean tide models derived from t p altimetry using 3 or more years of data this also suggests that further improvement using 3 or more years of data will only be marginal the differences arise when studying the ocean tides on continental shelves surrounding the ocean major differences are seen especially on the patagonian shelf as the continental shelves are critical for tidal dissipation it will be very important to improve tide models on the shelves in future global ocean tide models

source apportionment of the hydrocarbon background in sediment cores from hecate strait a pristine sea on the west coast of british columbia canada abstract significant reserves of oil and gas have been predicted for hecate strait a pristine semi enclosed sea on the continental shelf adjacent to british columbia on the west coast of canada to establish a baseline for the natural background of hydrocarbons in sediment prior to any further offshore oil and gas development or increase in oil tanker traffic in the hecate strait region three sediment box cores were collected along a west to east transect across southern hecate strait in september 2003 210 pb measurements established that the bottom sections date to 1920 pre 1800 and 1870 respectively which predate any significant industrial development on the coast alkane and polycyclic aromatic hydrocarbon pah concentrations are low in most sediment samples and both the concentrations and fluxes differ little between surface and bottom core sections pah profiles exhibit a dominance of alkyl pahs for each alkyl pah homologous series with varying amounts of parent unsubstituted pahs while alkane chromatograms show no unresolved complex mixture ucm and there is little change in composition between present day and pre 1800 sediments for most parameters principal components analysis pca models and pah and biomarker ratios indicate that composition patterns are consistent with low and varying natural petrogenic and pyrogenic inputs with little or no anthropogenic input the most likely primary source of petrogenic pahs to the sediments is cenozoic lignites from the skonun formation which outcrops on haida gwai and underlies most of hecate strait two subsurface sections deposited in 1990 and 1930 in the core from milbanke sound on the east side of the transect have elevated concentrations for the alkyl phenanthrene anthracenes and dibenzothiophenes with no ucm and most likely also have a source in immature coal this study suggests that the hecate strait environment has low hydrocarbon concentrations with an apparent minor role for oil seeps and a likelihood that most of the petrogenic pah sources are shales or immature coals with limited pah bioavailability if these characteristics are representative of hecate strait sediments overlying the queen charlotte basin it may mean that biota are likely unadapted to the presence of oil and thus would be more sensitive to exposure to oil from an oil spill than those in a more impacted environment

the diagenetic fate of taraxer 14 ene and oleanene isomers abstract the extractable organic matter in holocene to early miocene deep sea sediments from site 645 odp leg 105 in baffin bay contains almost exclusively biological markers of terrigenous origin pentacyclic triterpenoids of the ursene and amyrin oleanene type often occur as the most abundant compounds in the aliphatic hydrocarbon ketone and alcohol fractions of the sediment extract a specific diagenetic reaction involves the conversion of taraxer 14 ene into olean 12 ene in the upper 700 metres of the sedimentary sequence the taraxerene to oleanene conversion is complete before the onset of isomerisation of diasterenes at c 20 in the sediment as well as in laboratory simulation experiments olean 12 ene further isomerises to olean 13 18 ene and olean 18 ene the latter of which may be the direct precursor of 18 h and 18 h oleanane found in sediments containing more mature organic matter and in crude oils the subsurface interconversion of these triterpenoid skeletons indicate that oleanane does not necessarily start life as an oleanoid

inter monsoonal changes in the t s properties of the near surface waters of the northern arabian sea the arabian sea experiences extremes in atmospheric forcing that lead to the greatest seasonal variability in any ocean during 1995 6 cruises were carried out within the northern arabian sea the data collected represent the first consistent dataset covering an entire monsoonal cycle ocean soundings of temperature and salinity from these cruises are used to characterize variability of water masses in the surface layers associated with monsoonal forcing this paper documents the role of advection versus local water mass modification on seasonal extremes in t s in near surface waters of the arabian sea seasonal changes are associated with seasonal heating advection of waters from the oman upwelling zone varying of mixed layer depth due to ekman pumping in the central basin and mixing of high salinity waters from persian gulf

accuracy assessment of recent ocean tide models over 20 global ocean tide models have been developed since 1994 primarily as a consequence of analysis of the precise altimetric measurements from topex poseidon and as a result of parallel developments in numerical tidal modeling and data assimilation this paper provides an accuracy assessment of 10 such tide models and discusses their benefits in many fields including geodesy oceanography and geophysics a variety of tests indicate that all these tide models agree within 2 3 cm in the deep ocean and they represent a significant improvement over the classical schwiderski 1980 model by approximately 5 cm rms as a result two tide models were selected for the reprocessing of topex poseidon geophysical data records in late 1995 current ocean tide models allow an improved observation of deep ocean surface dynamic topography using satellite altimetry other significant contributions include theft applications in an improved orbit computation for topex poseidon and other geodetic satellites to yield accurate predictions of earth rotation excitations and improved estimates of ocean loading corrections for geodetic observatories and to allow better separation of astronomical tides from phenomena with meteorological and geophysical origins the largest differences between these tide models occur in shallow waters indicating that the current models are still problematic in these areas future improvement of global tide models is anticipated with additional high quality altimeter data and with advances in numerical techniques to assimilate data into high resolution hydrodynamic models

seasonal variation of hydrographic and nutrient fields during the us jgofs arabian sea process study abstract between september 1994 and december 1995 the us jgofs arabian sea process experiment collected extensive high quality hydrographic data temperature salinity dissolved oxygen and nutrients during all seasons in the northern arabian sea an analysis of this unique data suite suggests the presence of many features that are described in the canonical literature but these new data provided the following insights 1 although the seasonal evolution of mixed layer depths was in general agreement with previous descriptions the deepest mixed layer depths in our data occurred during the late ne monsoon instead of the sw monsoon 2 the region exhibits considerable mesoscale variability resulting in extremely variable temperature salinity ts distributions in the upper 1000 db this mesoscale variability is readily observed in satellite imaging in the high resolution data taken by a companion onr funded project and in underway adcp data 3 the densest water reaching the sea surface during coastal upwelling appeared to have maximum offshore depths of 150 m and s close to the core value 25 for the saline arabian sea water asw but salinities in these upwelling waters were relatively low the densest water found at the sea surface during late ne monsoon conditions has s 24 8 and relatively high salinities suggesting that they are a source for the asw salinity maximum 4 persian gulf water pgw with a core of 26 6 forms a widespread salinity maximum despite the considerable extent of this feature persian gulf outflow water with a salinity 4 of 39 at its source can only be a minor contributor within the standard us jgofs sampling grid maximum salinities on this surface are 36 8 at stations near the gulf falling to values as low as 35 3 at the stations farthest removed from its influence even at our standard stations closest to the gulf n 1 and n 2 the high salinity low nutrient persian gulf water has only a modest direct effect on nutrient concentrations this pgw salinity maximum is associated with the suboxic portions of the arabian sea s oxygen minimum zone 5 the salinity maximum associated with red sea water rsw core 27 2 in the jgofs study region is clearly evident at the southermost sampling site at 10 n s 15 elsewhere this signal is weak or absent and salinity on the 27 2 surface tends to increase towards the persian gulf suggesting that the disappearance of this salinity maximum is due at least in part to the influence of the persian gulf outflow 6 inorganic nitrogen to phosphate ratios were lower frequently much lower than the standard redfield ratio of 15 1 16 1 by atoms at all times and all depths suggesting that inorganic nitrogen was more important than phosphate as a limiting nutrient for phytoplankton growth and that the effects of denitrification dominated the effects of nitrogen fixation 7 the water upwelling off the omani coast during the sw monsoon has inorganic nitrogen to silicate ratios that were higher 2 1 than the 1 1 ratio often assumed as the ratio of uptake during diatom growth 8 the temporal evolution of inorganic nitrogen to silicate ratios suggests major alteration by diatom uptake only during the late sw monsoon cruise tn050 in august september 1995 9 widespread moderate surface layer nutrient concentrations occurred during the late ne monsoon 10 a zone of high offshore nutrient concentrations was encountered during the sw monsoon but instead of being associated with offshore upwelling it may represent offshore advection from the coastal upwelling zone the influence of an eddy or both 11 although our data do not contradict previous suggestions that the volume of subtoxic water may be reduced the sw monsoon they suggest a weaker re oxygenation than indicated by some previous work similarly they do not confirm results suggesting that secondary nitrite maxima may be common in waters with oxygen concentrations 5 m

tidal parameters for an inelastic earth abstract the gravimetric factors for an elliptical uniformly rotating earth are computed according to a new definition with respect to wahr s results and considering the mantle inelasticity the love numbers h and k are defined in the elliptical earth case to correspond to the love spherical definition they become latitude dependent the tidal parameters discussed in this paper are computed for an inelastic earth s mantle the numerical results show an increase of 0 4 of the gravimetric factors with respect to the wahr s values the love numbers h and k increase by 1 4 to 3 with respect to the elastic case

a comparison of tidal ocean loading models using superconducting gravimeter data 1 errors in global ocean models have been shown to be larger than the accuracy of surface gravity measurements baker and bos 2001 and also new space gravity missions ray et al 2001 in this paper we compare the tidal loading estimated using 10 different ocean tide models to the surface gravity variations observed with 12 superconducting gravimeters sg belonging to the global geodynamics project crossley et al 1999 worldwide network ocean tidal gravity variations are shown to be mostly dependent on tidal sea height variations within a radius of 5000 km precise surface gravity measurements are therefore another tool for validating ocean tidal models from short to long wavelengths in addition for example to tide gauge data in this study we also compute the tidal loading using several different available computer codes as for ocean tidal models we show that the differences between tidal loading programs are frequently larger than the error estimates of sg measurements compared to previous models both recent hydrodynamical and topex poseidon derived tidal models allow a significant reduction of discrepancies between ocean tidal observations using sg and tidal loading estimates there still remains however a nonnegligible in phase discrepancy between ocean tidal loading estimates and surface gravity observations whereas the out of phase component is much smaller we have shown that the in phase disagreement does not seem to be caused by an inaccurate determination of the sg calibration

spreading of red sea overflow waters in the indian ocean as a result of its remarkably high salinity and despite its small volume input remnants of red sea water rsw have been identified in the agulhas current over 6000 km distant of their source this provided the motivation to investigate the long term mean spreading of rsw throughout the indian ocean using a comprehensive set of observations taken from the national oceanographic data center archives and from the world ocean circulation experiment hydrographic program for the indian ocean after emerging from the gulf of aden into the arabian sea rsw spreads predominantly southwestward along the african continental slope as indicated by strongly inclined isohalines across the arabian sea there is some monsoon variability so that during the winter monsoon there is more rsw present in the gulf of aden and an intensification of southward spreading along the western boundary between 12 and 5 n elsewhere the intermediate depth salinity field of the indian ocean appears relatively stationary between 5 and 10 s in the region of the south equatorial current isohalines of the rsw layer become quasi zonal across the width of the indian ocean only dipping southward toward the western boundary west of 50 e south of here there is a strong tongue of rsw spreading southward through the mozambique channel and into the agulhas current these conclusions concur with previous localized investigations of intermediate water properties using a simple mixing model the percentage of rsw throughout the indian ocean was quantified it was found that the flux of salt into the gulf of aden from the red sea is similar to that estimated to cross 32 s in the agulhas current this result implies that all the rsw which is mixed into the interior of the indian ocean may eventually be exported at the western boundary furthermore it implies that rsw is the dominant component of the salt budget for the intermediate layer and that input from the indonesian seas and via diapycnic processes are small

formation and spreading of arabian sea high salinity water mass the formation and seasonal spreading of the arabian sea high salinity water ashsw mass were studied based on the monthly mean climatology of temperature and salinity in the arabian sea north of the equator and west of 80 e on a 2 2 grid the ashsw forms in the northern arabian sea during winter and spreads southward along a 24 sigma t surface against the prevailing weak zonal currents the eastern extent of the core is limited by the strong northward coastal current flowing along the west coast of india during the southwest monsoon the northern part of the core shoals under the influence of the findlater jet while the southern part deepens throughout the year the southward extent of the ashsw is inhibited by the equatorial currents the atmospheric forcing that leads to the formation of ashsw was delineated using the monthly mean climatology of heat and freshwater fluxes monsoon winds dominate all the flux fields during summer june september while latent heat release during the relative calm of the winter november february monsoon driven by cool dry continental air from the north results in an increased density of the surface layer thus excess evaporation over precipitation and turbulent heat loss exceeding the radiative heat gain cool the surface waters of the northern arabian sea during winter and drive convective formation of ashsw

global charts of ocean tide loading effects global ocean tide loading charts of the radial displacement the potential divided by g gravity acceleration and the gravity effect have been computed using the 11 constituents m2 s2 n2 k2 k1 o1 p1 q1 mf mm ssa of schwiderski s tidal model these new charts have a resolution of 1 1 on the continents as well as on the oceanic area a description of farrell s convolution method to compute the loading effects is given and an estimate of the numerical errors leads to the conclusion that these global charts have a precision better than 2 5 independent of the accuracy of schwiderski s maps the current approximation of the loading effects by a proportionality relation with the local oceanic tides is also compared with farrell s convolution method departures of several centimeters systematically appear in particular over the continental shelves we then show that the maps of the oceanic tides deduced from satellite altimetry could be corrected for the loading effect by an iterative computational procedure based on our algorithm of farrell s convolution

hydrocarbons in phosphatized and non phosphatized sediments from the phosphate basin of gafsa abstract the sedimentary layers in the phosphate basin of gafsa show interlayering of phosphatized and less phosphatized beds shales marls limestone and cherts 1 1 the n alkane distribution of the chloroform extracts and the pyrochromatograms obtained from the related kerogens are very similar in all the strata suggesting that the organic matter which accumulated in these strata had a similar origin marine planktonic 2 2 the occurrence of some significant fossil molecules in poorly phosphatized sediments chert including c ring monoaromatic steroids and benzohopanoids confirms the autochthonous marine origin and the immature character of the organic matter and reflects intensive bacterial anaerobic activity the lack of these fossil molecules in phosphorites is essentially due to the more oxidative conditions occurring during phosphatogenesis in contrast the presence of these fossil molecules in humic acid fractions from phosphorites reflects a specific property of humic substances to incorporate hydrocarbons from petrological studies humic acids and incorporated fossil molecules are thought to be preserved because they were trapped inside phosphorite pellets or ooids at an early stage of diagenesis 3 3 the chromatograms of hydrocarbons and pyrochromatograms for the humic compounds which can be extracted from each of the strata are very similar to those of the non humic organic matter of the same samples this suggests that hydrocarbons have been incorporated by the humic acids at an early stage of diagenesis the amount of such humic associated hydrocarbons can reach 20 of the humic acid weight 4 4 the amount of hydrocarbons in the bulk sediment confirms that the conditions favourable or not favourable to phosphate concentrations are a result of variation in eh during deposition and not variation in organic matter type

a numerical investigation of circulation in the arabian gulf a three dimensional hydrodynamic model is developed to study the circulation in the arabian gulf the model contains realistic basin geometries and bathymetries of the arabian gulf and a good portion of the gulf of oman and is driven by monthly climatological winds evaporation and net ocean heat gain in both gulfs and the shatt al arab discharge it is found that the cyclonic circulation in the southern portion of the gulf is primarily driven by the evaporation induced freshening from the strait of hormuz in the northwestern corner of the gulf the shatt al arab discharge maintains the cyclonic circulation which would otherwise be anticyclonic the northwestward intrusion of fresher water along the iranian coast is weakened by northwesterly winds in winter but strengthens and extends almost to the head of the gulf in summer owing to the warming of the gulf of oman waters the development of the summer thermocline in the arabian gulf and diminishing winds the southward coastal current along the arabian coast is most prominent between the head of the gulf and qatar the model also predicts a strong southward coastal jet east of qatar which is primarily wind driven no similar coastal jet can be developed in the gulf of salwa west of qatar

hydrocarbons in the sediments of port valdez alaska consequences of five years permitted discharge abstract hydrocarbons have been investigated in the sediments of port valdez alaska after three to five years of oil terminal operation with a routine daily discharge of 170 kg of petroleum residue in an otherwise undeveloped area surficial benthic sediments 0 5 cm and core segments down to 30 cm have been analyzed information about total hydrocarbons unresolved complex mixture normal alkanes pristane phytane hopanes and polycyclic aromatic hydrocarbons indicates that petroleum biogenic hydrocarbons and combustion derived aromatic hydrocarbons are present in sediments around the terminal at concentrations up to 218 g g 1 dry sediment the vertical horizontal and temporal distributions of anthropogenic hydrocarbons indicate that most of the sedimentary hydrocarbon accumulation has occurred within 1 km of the terminal a simple calculation suggests that less than 3 of the total oil discharged during routine operations of the terminal has entered the sediments of port valdez for comparison sediment hydrocarbon accumulation associated with a nearby small boat harbor was also examined

observations of load tides at the south pole abstract the use of tidal observations to study the nearly diurnal free wobble mode of the earth is possible if oceanic effects in the tidal record are accurately removed we have analyzed vertical gravity data from the south pole to determine the amplitude and phase of the small daily and semidaily tides observed at the pole since these signals at the pole are most probably caused by oceanic tides our observations provide an excellent target for the oceanic models a comparison with the best models of the oceans now available indicates the need for improvement in measuring and modeling the southern oceans

a prolonged high salinity event in the northern arabian sea during 2014 17 abstracta prolonged high salinity event in the northern arabian sea to the east of the gulf of oman during 2014 17 was identified based on argo datasets the prolonged event was manifested as enh

hydrocarbon geochemistry in surface sediments of alaskan outer continental shelf part 1 c15 hydrocarbons the c15 hydrocarbons in 220 surface sediments from the outer continental shelf of alaska were analyzed as part of an environmental survey supervised by national oceanic and atmospheric administration and bureau of land management gas chromatography and gas chromatography mass spectrometry were employed for the identification of organic compounds in the bitumen extracts surface sediments from one station in southeastern bering sea and two stations in lower cook inlet display n alkanes and triterpenoid distribution typical of weathered petroleum major faulting in the vicinity of the southeastern bering sea station may account for the leakage of petroleum from subsurface reservoir rocks oil production in upper cook inlet or a hitherto unrecorded seep in the rea could contribute petroleum hydrocarbons to the sediments from the two stations in lower cook inlet apart from these stations there is little evidence of near surface petroleum seeps in the sites investigated

latitudinal change of normal paraffin composition in the northwest pacific sediments abstract we analyzed normal saturated paraffins n paraffins in 70 surface sediments in the northwest pacific to examine the spatial distribution of organic materials all sediments show bimodal n paraffin abundance patterns against carbon number with maxima at c 16 and c 31 indicating that n paraffins in marine sediments are a mixture of long chain n paraffins from land based higher plant waxes and short ones from marine organisms we observed in this study a significant change of carbon preference index cpi from 2 5 in low latitudes to 4 5 in mid high latitudes around 19 25 n the following influences are discussed as the cause of cpi offset between low and mid high latitudes 1 meteorological conditions 2 n paraffin composition of higher land plants 3 contribution of petroleum components and 4 mixing ratio of higher land plants and marine organisms however none of them can be the possible cause of the cpi offset because n paraffin content and composition vary significantly according to the species of a bacterium difference of the species of bacterial communities between low and mid high latitudes may be a possible reason for the cpi offset found in sediment from the northwest pacific

a discussion of world wide measurements of tidal gravity with respect to oceanic interactions lithosphere heterogeneities earth s flattening and inertial forces abstract by the end of 1981 the international center of earth tides icet had collected and evaluated a considerable amount of data from 180 stations including those of the trans world profile which ensure for the first time a world wide distribution including the tropical areas and the southern hemisphere in 1979 80 new oceanic cotidal maps of high quality established by schwiderski became available these maps fit on land tidal gravity measurements quite successfully a new theoretical approach developed by wahr in 1981 has resulted in a set of theoretical formulae establishing the latitude dependence of the classical elastic amplitude factors for tidal deformations we calculate here for six tidal waves the correlations between the observed gravity variations and those resulting from a calculation based upon the schwiderski maps these correlations are highly significant after subtraction of these oceanic effects we calculate the latitude dependences of the experimentally determined amplitude factors which are found to fit wahr s theoretical formulae there remains however a serious discrepancy in the constant terms of the various formulae the effects of heterogeneities in the lithosphere on tidal deformations are also clearly identified

hydrocarbon geochemistry of the puget sound region ii sedimentary diterpenoid steroid and triterpenoid hydrocarbons cyclic components of the aliphatic hydrocarbon mixtures extracted from puget sound sediment cores include a suite of c19 and c20 diterpenoid hydrocarbons of which fichtelite sandaracopimaradiene and isopimaradiene have been identified although apparently also derived from vascular plants these diterpenoid hydrocarbons have relative abundances distinctly different from the co existing plant wax n alkane suite five c27 c28 and c29 diasteranes and four c29 c30 and c31 17 h 21 h hopanes occur in relatively constant proportion as components of a highly weathered fossil hydrocarbon assemblage these chromatographically resolved cycloalkanes along with the strongly covarying unresolved complex mixture have been introduced to puget sound sediments from adjacent urban centres at increasing levels over the last 100 yr in the absence of any major oil spill naturally occurring triterpenoid hydrocarbons including hop 22 29 ene diploptene are also present a new group of c30 polyenes has been detected which contains compounds apparently structurally related to a co existing bicyclic c25 diene and to c20 and c25 acyclic multibranched hydrocarbons described in a previous paper barrick et al 1980

a continuing discussion about the correlation of tidal gravity anomalies and heat flow densities on the basis of several objections rydelek et al phys earth planet inter 68 215 219 1991 hereafter noted rzh denied the existence of a correlation between residuals of tidal gravity r and heat flow h suggested by other workers to re examine the whole matter on safe grounds we previously revised and reanalysed all the original tidal data from 300 stations taking care of the rzh objections by eliminating what they considered as the important sources of errors in the data essentially calibration errors of the instruments in amplitude and phase using this new data base we meet here one by one the other criticisms not related to the original tidal measurements and show that most of them are not valid in particular those concerning oceanic load and attraction corrections the findings are as follows 1 no correlation between diurnal tide and semi diurnal tide residuals is normal 2 distance from the sea is not a valid criterion for elimination of several excellent stations 3 unexpected residues at the south pole are not due to imperfections of the cotidal schwiderski maps but to ice shelf tides not considered by rzh 4 the correlation of the tidal gravity residues with the age of tectonic provinces is proposed as an alternative to the correlation with heat flow the data used in 1991 having been corrected are recalculated for comparison with 1986 1991 statistics the correlation is confirmed with the same degree of probability also new tidal gravity data obtained since 1990 with nullified instruments as recommended by rzh in africa 31 stations and latin america 34 stations are included in new statistics which also confirm the correlation the global result obtained from 174 revised and new stations on all continents gives a correlation coefficient k 0 691 with a linear regression r 0 0201 h 57 0 063 0 0013 where r is in microgals and h is in mw m 2 as there is at present no practical or theoretical means to take into account the role of fluids lubrication and stress corrosion owing to deep seated saline waters or fluids in crustal processes such as tidal deformations such small tidal gravity anomalies cannot be correctly calculated the use of a correlation technique therefore remains the only way to treat unexplained residues even if this does not constitute an unequivocal proof other arguments have to be found to deny the existence of this correlation

alkane and pah biomarkers as tracers of terrigenous organic carbon in arctic ocean sediments abstract we present the first sedimentary biomarker study encompassing the entire arctic ocean a large data set of organic markers for terrigenous petroleum and combustion inputs alkanes hopanes and steranes parent and alkyl polycyclic aromatic hydrocarbons pahs is examined for patterns in space and time using principal components analysis pca and partial least squares pls biomarker patterns reveal the central arctic ocean basin sediments to be compositionally distinct from those of the mackenzie river beaufort sea and barents sea but similar to those of the laptev sea pah distributions reflected in pah ratios and pca projections demonstrate that arctic ocean sediment is dominated by natural inputs to the extent that anthropogenic combustion pahs are not significant we find only modest changes between the glacial and post glacial sediments for atmospherically transported hydrocarbon biomarkers while particle associated biomarkers were captured strongly at basin edges during the glacial period and much more evenly transported across basins during the post glacial period the orders of magnitude decreases in particle associated petrogenic alkanes and pahs in central basins during glacial times coupled with the uniformity of most petrogenic biomarker parameters for most basin and shelf locations reflect a massive reduction in ice transport that makes the margins the most likely source of petrogenic material for the pleistocene holocene central arctic basins the proximity of large coal deposits of various maturity levels along the lena river the overlap in pah and biomarker composition of the laptev sea and surficial sediments from the central arctic ocean and the location of the laptev sea at the origin of the main transpolar drift all point to eroded coals from the lena river laptev sea as the likely source of petrogenic hydrocarbons to the central arctic ocean the ubiquitous presence of allochthonous coal in arctic ocean surface sediments provides a major constraint on the use of petrogenic biomarkers to infer the presence of subsurface petroleum reserves

comparative study of sterols in shelf and slope sediments off northeastern taiwan abstract bottom sediments and suspended matter from the shelf and slope areas off northeastern taiwan were analyzed for sterol n alkanol and n alkane compositions the algal sterols cholesterol ratios mean 1 were 1 00 0 31 n 7 for the shelf sediments 3 29 0 61 n 7 for the slope sediments and 1 54 0 19 n 3 for the suspended matter the much higher proportion of cholesterol in the shelf sediments is most likely derived from mollusks in the relict sediments an additional sterol source for the shelf sediments probably is suspended matter in the water column although the shelf has no apparent sedimentation results from phytol and n alkanols suggest recent inputs of lipids from the water column to the shelf the stanol stenol ratios are lower for the older shelf sediments than for the younger slope sediments

organic geochemistry of marine sediments in antarctic region marine lipids in mcmurdo sound abstract the compositions of resolvable lipid components from four sediment cores 0 90 cm of mcmurdo sound ross sea have been examined the various lipid components occur in the following order of abundance sterols fatty acids n alcohols n alkanes pah the data indicate that the organic matter is mainly derived from recycled kerogen mixed with modern marine input the distribution of lipids and lignin analyses indicate that there is little recognizable higher plant debris in the sediments the sediments contain unaltered biogenic triterpenoids and there is no evidence for natural and or anthropogenic petroleum influx in the region aeolian transport of organic carbon from the continents appears to be negligible the dominance of labile alkenes c 25 compounds and hopenes and the presence of unsaturated fatty acids down to a depth of 90 cm reflect a very early diagenetic stage the persistent cold climate has probably helped in the better preservation of these labile lipids in the water column and in the young sediments diploptene 17 h 21 h hop 22 29 ene appeats to originate from autochthonous marine productivity in mcmurdo sound

a new data bank for tidal gravity measurements db 92 abstract tidal gravity parameters are now available in 352 permanent or temporary stations all over the world previous tentative interpretations of these data were made on the basis of a data bank created in 1980 1982 which contained all available results without any discrimination which could have appeared as arbitrary these interpretations were criticized on the basis of the different qualities of instruments null instruments or not data calibration and necessary corrections for ocean continent interactions as we agree that a careful re examination of the basic data is needed before any geophysical discussion we have built this new data bank which contains only those 211 stations where rigid control of every step in the observations calibrations and reduction could be made either because the original data are stored in the world data center c or because the published results give enough information to permit checks and revisions as a result the scattering in the tidal parameters is reduced by a factor of 2 with respect to the previous data while the mean values of the amplitude factors of the two main waves o 1 diurnal m 2 semi diurnal calculated continent by continent agree with the best available earth model it is expected that this new data bank will be used for renewed discussions of the results

hydrocarbon geochemistry in surface sediments of alaskan outer continental shelf part 2 distribution of hydrocarbon gases the distribution of c1 to c4 hydrocarbon gases in surficial sediments from the alaskan continental shelf was determined as part of a regional environmental survey sponsored by national oceanic and atmospheric administration and bureau of land management noaa blm methane ethane ethene propane propene n butane and iso butane were observed in low concentrations 0 1 10 ppb as weight gas to dry weight sediment in nearly all of the 190 sediment samples examined with methane exceeding c2 to c4 hydrocarbons in abundance by about a factor of 10 no gasoline range c5 to c8 hydrocarbons were detected above blank levels ethene was found generally to be more abundant than ethane while propane was slightl more abundant than propene the correlation between these hydrocarbons suggests a common possibly biogenic origin sediments from norton sound have anomalously high methane concentrations probably as a result of biological methanogenesis in subsurface organic rich peat layers most of the regions sampled showed median values of the c1 c2 c3 ratio of 20 the generally low c1 concentrations probably resulted from the selective loss of c1 by biologic oxidation or ebullition from the surface sediments no major c2 to c4 hydrocarbon anomalies were discovered however at some stations in kachemak bay kodiak shelf and norton sound anomalously high c3 c3 1 ratios indicated the poss ble presence of thermogenic gases at depth

geochemistry and fluxes of hydrocarbons to the beaufort sea shelf a multivariate comparison of fluvial inputs and coastal erosion of peat using principal components analysis abstract the allochthonous inputs of hydrocarbon to the canadian beaufort shelf were studied by applying principal components analysis pca to well validated and rigorously blank corrected samples incorporation of a wide range of perdeuterated n alkanes and pah into the analysis scheme ensured that only reliably quantified variables were used to interpret the hydrocarbon geochemistry application of pca to mackenzie river samples demonstrated a homogeneous system from which we infer coupling or equilibrium between the river particulate hydrocarbons and the dissolved fraction particulate particle size 0 7 m hydrocarbon flux from the mackenzie river is by far the most important terrestrially derived source of hydrocarbons to the beaufort sea the mackenzie river particulates have a distinct n alkane signature which can be used to identify the riverine influence on the hydrocarbon geochemistry of the beaufort sea shelf based on one year s data the flux of total alkanes is 440 94 tonne a and pah is 49 8 tonne a uncertainties are one standard deviation of the sampling and analytical variation the particulate flux exceeds the accompanying dissolved hydrocarbon flux by two orders of magnitude and has a strong seasonal cycle winter contributes less than an estimated 0 6 of total annual flux deltaic silt from the western mackenzie delta and the smaller amounts of detritus from coastal erosion of peat are minor hydrocarbon sources and contribute in total less than 10 to the budget for most alkanes an important exception with regard to shelf geochemistry is the significant quantity of peat derived higher plant n alkanes

testing recent global ocean tide models with loading gravimetric data as soon as altimetric data from topex poseidon satellite were available several ocean tide models were able to be constructed by different teams in response to the scientific community request here we present a complement to a first comparison study made with ten tidal models llubes and mazzega 1996 we use five more models of which some are updated versions computed using longer time series of altimetric data the loading tide effects predicted by these models are compared to a data base of 228 gravimetric stations provided by the international center for earth tides melchior 1994 global statistical tests provide us with the relative performances of the models merging the five new models with the ten previous models allows us to make more general conclusions csr3 0 eanes 1994 remains the best of the fifteen models for the m2 constituent standard deviation of 0 425 gal for the o1 constituent schwiderski schwiderski 1980 with a standard deviation of 0 298 gal gives the best results when considering only regional subsets of gravimetric data no ocean tide model systematically performs better than any other

normal paraffins in shales as an indicator of depositional environment abstract normal paraffin compositions were determined for marine sediments from coastal and pelagic environments and for shales in the jurassic cretaceous bedded chert sequence from the franciscan terrane western north america the pelagic sediments and shales from a lower horizon of the bedded chert sequence are characterized by short chained n paraffins the coastal sediments and shales from the upper horizon show high abundance of n paraffins especially for long chained ones and a strong odd carbon predominence the comparison of n paraffin compositions of shales with those of marine sediments suggests that the bedded chert sequence had deposited in continuous environments from pelagic to coastal this inference is in harmony with that based on the major minor and rare earth element compositions the result suggests that shales in the franciscan bedded chert sequence preserve well the normal paraffin signals acquired at the deposition and demonstrates that the normal paraffin composition can be a useful indicator of sedimentary environment

lignin geochemistry of north american coastal and continental shelf sediments abstract the concentrations and composition of lignin in coastal and shelf sediments at five locations along the north american continent georges bank north atlantic shelf northwestern gulf of mexico southern california norton sound and nearshore beaufort sea have been characterized using alkaline cuo oxidation lignin concentrations are generally highest at close proximity to the mouth of major rivers indicating that deposition of river borne vascular plant debris is the principal source of lignin to the offshore sediments arctic sediments contain the highest concentrations presumably as a result of an abundant supply of terrestrial organic material and the prevalence of frigid temperatures and surface ice cover during much of the year concentrations are lowest in the georges bank north atlantic sediments where a dynamic physical environment persists over much of the year and the supply of terrestrial organic matter to the offshore in the form of major rivers is lacking stable carbon isotopic compositions show that sediments containing the highest lignin concentrations also contain isotopically lighter organic matter consistent with a terrestrial source input vanillyl syringyl and cinnamyl phenol distributions in these offshore sediments are consistent with primary contributions from gymnosperm predominant and angiosperm woods and secondary contributions from nonwoody tissues these estimates may be subject to some uncertainty due to diagenetic alteration of individual lignin phenols in contrast p hydroxyl phenol yields are not strongly correlated with those of the other lignin derived phenols suggesting generation from both lignin and non lignin sources elevated acid aldehyde ratios relative to undegraded plant tissues suggest that the lignin transported to these offshore sediments has undergone some biodegradative oxidation

origins of hydrocarbons in bering sea sediments i aliphatic hydrocarbons and fluorescence abstract sixty three samples from thirteen gravity cores were analyzed by gc fid qualitative gc ms and fluorescence spectroscopy to determine the concentration distribution and sources of hydrocarbons in bering sea sediments aliphatic hydrocarbons and fluorescence associated with aromatic compounds were detected in sediments at all locations the sediments contain variable amounts of marine biological debris terrigenous plant biowaxes recycled continental material petroleum and combustion derived hydrocarbons hydrocarbon concentrations were low and similar to previous reports from the alaskan outer continental shelf average ucm and total n alkanes varied from 10 7 to 73 3 and 2 6 to 4 6 g g respectively olefins of a presumed biological origin were widely distributed throughout bering sea sediments the presence of a complete suite of normal alkanes isoprenoids an unresolved complex mixture alkylated pahs and mature biological markers suggest that locations in the western and southern bering sea are contaminated with petroleum this petroleum may be derived from natural seepage recycled mature continental material autochthonous exposed immature mature sediments and or deposition of water column tarballs the petroleum at one southern bering sea location is typical of a condensate and is significantly different from that observed at western bering sea locations vertical distributions and the presence of significant amounts of volatile hydrocarbons suggest that petroleum seepage is a likely source of contamination at these locations

early diagenesis of lipid biomarker compounds in north atlantic sediments near surface sediments 0 45 mm depth interval from the iceland basin 59 n 21 w 3070 m water depth and biscay abyssal plain 48 n 17 w 4105 m water depth were sectioned at millimeter scale resolution to assess alterations in key lipid biomarkers during early diagenesis inventories g cm 2 in the topmost 45 mm of biomarkers from presumed terrestrial sources c20 linear n alkanes n alkanoic acids n alkanols and from phytoplankton sources phytosterols long chain alkenones and alkenoates were 1 5 4 times more abundant in the iceland basin core than in the biscay abyssal plain core indicating greater sedimentary inputs and or preservation at the iceland basin site biomarker concentrations varied significantly over millimeter scale depth intervals pronounced subsurface concentration maxima were present at both sites at the biscay abyssal plain site steep concentration gradients in the uppermost few mm of the sediment column indicate extensive diagenetic losses at or near the sediment water interface strong covariance was seen in the concentrations of various compounds within each class e g long chain n alkanes n alkanols n alkanoic acids and long chain alkenones and alkyl alkenoates indicating that individual compounds within each class are associated with the same organic matrix and have similar degradation and mixing rates thus biomarker indices for assessment of land derived inputs cpi c29 c31 acl and sea surface temperature ipt remain largely unaltered by early diagenetic processes in oxic abyssal sediments in spite of extensive bioturbation and degradative losses within the uppermost few centimeters of the sediment column

saturated and olefinic hydrocarbons in recent sediments from the baltic sea abstract saturated and olefinic hydrocarbons in the top sections of contemporary sediments from four stations in the baltic sea teili 1 f 81 eb 1 and xv 1 were analysed by capillary gas chromatography and gc ms techniques the 0 2 2 4 4 5 and 10 11 cm sections showed a small unresolved complex mixture ucm however in all these sections a strong predominance of odd over even carbon numbered compounds exists indicating an insignificant petroleum hydrocarbon input in the areas studied the resolved hydrocarbons are of mixed marine autochthonous and terrigenous origin the 0 5 cm sections contained the highest proportions of short chain and branched chain hydrocarbons derived mostly from algae and bacteria in general an increase was observed in the ratios of saturated to unsaturated and of longer chain to short chain hydrocarbons with increasing depth because of the facile diagenesis of unsaturated components and faster biodegradation of short chain hydrocarbons in addition between one and seven hydrocarbons the exact structure of which could not be assigned were detected in the samples most of these components were cyclic and unsaturated and a number were triterpenes

a study of the organic matter in tunisian phosphates series relevance to phosphorite genesis in the gafsa basin tunisia abstract in the gafsa basin tunisia peloidal fracolite is interbedded with shales limestones and rocks of intermediate lithology the rocks were deposited in an epicontinental sea and have been buried no more than 500 m the organic matter they contain is therefore thermally immature and in all units derived mainly from marine plankton particularly dinoflagellates the organic matter in the phosphorite units is composed predominantly of humic acids ha which are essentially located within the pellets these pellets are surrounded by an outer matrix in which the organic matter is similar to the kerogen comprised in the shally strata alternating with the phosphorite and limestone beds during weathering the content of the organic matter assocciated with the matrix decreases more rapidly than that of the organic matter entrapped within the pellets geochemical and palynological study of the organic matter in interbedded rocks of different lithology shale limestone phosphorite suggest that the shales were deposited in a reducing environment the limestones in one that was oxic whilst the phosphorites were formed in a redox environment inermediate between the two the interpretation of the data presented in this paper is that the genesis of shales phosphate and some carbonate beds excluding coquinas did not result from the deposition of initially sharply differentiated sediments but resulted from differences in diagenesis of sediments initially containing planktonic organic matter associated with clay and carbonate minerals

chemical evidence of differential particle dispersal in the southern washington coastal environment aliphatic hydrocarbons cupric oxide oxidation products of lignin and polycyclic aromatic hydrocarbons pah were analyzed by capillary gas chromatography in sediments from the southern washington continental shelf and slope the concentration of diploptene relative to plantwax n alkanes increased systematically in surface sediments with distance offshore along east west transects of the study area and remained constant in surface sediments along the midshelf silt deposit analogous trends were also observed for the concentration of cinnamyl phenols relative to vanillyl phenols and total methylphenanthrenes relative to phenanthrene these changes in sedimentary composition are evidence that diploptene from some terrestrial source lignin characteristic of non woody vascular plant tissue and a fossil organic material contained within weathered rock debris disperse across the washington continental shelf and slope in geographic patterns distinct from that for other river derived chemically related materials the compositional variations are explained by the particulate associations of the land derived chemicals and differential hydraulic dispersion of their respective carrier particles after discharge at the mouth of the columbia river

hydrology and circulation in the strait of hormuz and the gulf of oman results from the gogp99 experiment 1 strait of hormuz in october and early november 1999 the gogp99 experiment collected hydrological currentmeter tide recorder thermistor and drifting buoy data near the strait of hormuz data analysis provides the water mass structure in the strait persian gulf water pgw core is banked against the omani coast while indian ocean surface water iosw lies near the iranian coast these water masses are most often covered by a homogeneous surface layer thermohaline characteristics of the pgw core decrease substantially downstream from the persian arabian gulf to the gulf of oman pgw and iosw thermohaline characteristics and distribution also exhibit notable changes at periods shorter than a month as shown by repeated hydrological sections the tidal signal measured south of the strait by moored adcp and thermistor chains has predominant semi diurnal m2 and s2 and diurnal k1 components and possesses a complex vertical structure tidal intensification near the surface pycnocline is associated with noticeable internal waves at subtidal timescale mooring recordings confirm the water mass variability observed in the repeated hydrological sections the mixed layer also deepens substantially during the 1 month period finally trajectories of surface buoys drogued at 15 m exhibit reversals over periods characteristic of changes in wind direction

modeling of circulation in the arabian gulf and the sea of oman skill assessment and seasonal thermohaline structure hindcast simulations of the arabian gulf and the sea of oman using the regional ocean modeling system roms are quantitatively evaluated with basin wide hydrographic data and time series measurements the model shows comparable skill in reproducing moored observations of current velocities structure in upper and bottom depths the skill in simulating observed temperature is higher of 0 93 scale 0 1 in upper depths compared to 0 52 in bottom depths model results are sensitive to parameterization of water clarity a lower sensitivity was noticed to kpp gls and my2 5 turbulence closures when coastal turbid water parameterization is used accuracy of the model in reproducing seasonal and spatial variations of temperature and salinity increased by 25 compared to the clear water case whereas only 10 increase was noticed when applying kpp turbulent closure the model reproduces well anticlockwise circulation in the gulf a stronger surface inflow of fresher water to the arabian gulf through the strait of hormuz is simulated in summer compared to winter conditions mainly due to upper layer horizontal gradient of density between the arabian gulf and the sea of oman less seasonal variability of outflow between 0 15 and 0 20 m s 1 at 50 m to bottom depth around the strait of hormuz was noticed in the model results modeled surface layer stratification is stronger in summer than winter and varies spatially in the arabian gulf with highest stratification near the strait of hormuz overall the stratification in shallow water area of the arabian gulf remains low throughout the year

overview of the recent sediment hydrocarbon geochemistry of atlantic and gulf coast outer continental shelf environments abstract an overview of the hydrocarbon geochemistry of recent marine sediments from the u s atlantic and gulf of mexico outer continental shelf ocs regions is presented hydrocarbon levels along the atlantic ocs are fairly uniform ranging between in the north atlantic eastern gulf south texas gulf and coastal louisiana sediments a linear relationship exists between total hydrocarbon and total organic carbon concentrations indicating that each area consists of a geochemical province defined by a source input or depositional regime specific to the region the use of trace parameter bulk parameter ratios such as total hydrocarbon or individual pah concentrations total organic carbon content in defining such provinces and thus in serving as a basis for evaluating variations in source inputs as part of future surveys is demonstrated this approach views the hydrocarbon content and composition of atlantic and gulf coast ocs sediments as points on a spectrum defined by input types sources and deposition patterns sedimentation and erosion which conceptually link all the regions into a unified system

an evaluation of petrogenic hydrocarbons in northern gulf of alaska continental shelf sediments the role of coastal oil seep inputs abstract we compared hydrocarbons in water suspended particulate matter spm and riparian sediment collected from coastal watersheds along the yakataga foreland with corresponding hydrocarbons in gulf of alaska benthic sediments this comparison allows an evaluation of hydrocarbon contributions to marine sediments from natural oil seeps coal and organic matter e g kerogen associated with eroding siliciclastic rocks the samples from oil seeps show extensive loss of low molecular weight n alkanes n c 14 and the presence of large bimodal unresolved complex mixtures ucms in contrast to the hydrocarbon fingerprints on the spm and riparian sediment samples collected upstream from the oil seeps after entering the fluvial systems hydrocarbons from seep oils are rapidly diluted and associate with the spm phase as oil mineral aggregates oma johnston creek the watershed containing the most prolific seep conveys detectable seep derived hydrocarbons to the gulf of alaska but overall seep inputs are largely attenuated by the non seep petrogenic hydrocarbon content of the high spm loads in contrast to the geochemical signature of seep oil gulf of alaska benthic sediments are characterized by abundant alkylated naphthalene homologues relatively smooth n alkane envelopes n c 9 through n c 34 but with elevated levels of n c 27 n c 29 and n c 31 and small ucms further hydrocarbons in benthic sediments are highly intercorrelated taken together these characteristics indicate that seep oil is a negligible petrogenic hydrocarbon source to the gulf of alaska continental shelf coaly material separated from the benthic sediment samples using a dense liquid 2 00 g cm 3 also accounted for a minor portion of the total pah 1 6 and total n alkanes 0 4 2 in the benthic samples most of the hydrocarbon burden in the sediments is found in the denser sediment fraction and likely derives from organic matter contributed by denudation of siliciclastic formations in the yakutat terrane we therefore conclude that previous investigations relying on source allocation models have considerably overestimated oil seeps as a hydrocarbon source to the gulf of alaska

impact of anthropogenic pb and ocean circulation on the recent distribution of pb isotopes in the indian ocean abstract pb and pb isotope ratios in the modern ocean have been altered significantly by anthropogenic pb inputs over the past century most studies of anthropogenic pb in the ocean have focused on the north atlantic and north pacific oceans and the impact of anthropogenic pb inputs to the indian ocean and processes controlling the distribution of pb in the indian ocean are poorly known this study presents the pb and pb isotopic composition 206 pb 207 pb 208 pb 207 pb of 11 deep stations from the indian ocean japanese geotraces cruise kh 09 5 from the bay of bengal and arabian sea to the southern ocean 62 s the pb isotope ratios of the indian ocean range 1 140 1 190 for 206 pb 207 pb and 2 417 2 468 for 208 pb 207 pb with lower ratios appearing in the shallow waters of the northern indian ocean and higher ratios appearing in the deep layers of the southern ocean this result agrees with a previous study on pb concentrations echegoyen et al 2014 showing that the indian ocean particularly its northern part is largely perturbed by anthropogenic pb inputs 206 pb 207 pb and 208 pb 207 pb of the indian sector southern ocean are still lower than natural pb showing this region was also affected by anthropogenic pb anomalously low or high 206 pb 207 pb and 208 pb 207 pb were observed in the thermocline and shallow waters of the southern indian ocean and the arabian sea which are ascribed to water mass distribution e g subantarctic mode water and evolving pb isotope ratios of this region as dominant anthropogenic pb sources change 206 pb 207 pb and 208 pb 207 pb in the bay of bengal are higher than those in the arabian sea which might be the result of the anthropogenic pb inputs from different provenance or seawater exchanging pb isotopes with natural particles derived from rivers and or sediments at the basin boundaries

injection of oxygenated persian gulf water into the southern bay of bengal persian gulf water pgw is an oxygenated high salinity water mass that has recently been detected in the bay of bengal bob however little is known about the transport pathways of pgw into the bob ocean glider observations presented here demonstrate the presence of pgw in the southwestern bob output from an ocean reanalysis product shows that this pgw signal is associated with a northward flowing filament of high salinity water particle tracking experiments reveal two pathways one in the eastern arabian sea that takes a minimum of 2 years and another in the western arabian sea that takes a minimum of 3 years the western pathway connects to the bob via equatorial currents the greatest influx of pgw occurs between 82 and 87 e during the southwest monsoon we propose that injection of pgw to the bob oxygen minimum zone omz contributes to keeping oxygen concentrations in the bob above the level at which denitrification occurs

a hycom modeling study of the persian gulf 2 formation and export of persian gulf water 1 the circulation and water mass transformation processes in the persian gulf and the water exchange with the indian ocean through the strait of hormuz are studied using the hybrid coordinate ocean model hycom model results suggest that intruding indian ocean surface water iosw is transformed into hypersaline waters with salinity 41 practical salinity unit by the fresh water loss in the northern end of the gulf and in the southern shallow banks during wintertime intense heat loss from sea to air leads to the formation of cold and saline waters both in the northern gulf and in the southern gulf dense waters formed in the southern gulf have higher salinity and spill into the axial deep trough of the gulf as a sporadic bottom outflow in winter which leads to high salinity pulses in the strait as observed whereas in summer their buoyancy is increased due to heating and they are exported as a warm yet salty intermediate depth flow through the strait dense waters formed in the northern gulf propagate toward the strait along the axial trough throughout the year correspondingly there are two branches of seasonal overturning circulation in density classes the northern branch peaking in august with strength of 0 13 sv and the southern branch peaking in february and december with strength of 0 08 sv these two branches outflow together feed a seasonally varying deep outflow through the strait with an annual mean volume transport of 0 12 sv

dynamics of the indian ocean oxygen minimum zones abstract in the indian ocean mid depth oxygen minimum zones omzs occur in the arabian sea and the bay of bengal the lower part of the arabian sea omz asomz below 400 m intensifies northward across the basin in contrast its upper part above 400 m is located in the central eastern basin well east of the most productive regions along the western boundary the bay of bengal omz bbomz although strong is weaker than the asomz to investigate the processes that maintain the indian ocean omzs we obtain a suite of solutions to a coupled biological physical model its physical component is a variable density 6 1 2 layer model in which each layer corresponds to a distinct dynamical regime or water mass type its biological component has six compartments nutrients phytoplankton zooplankton two size classes of detritus and oxygen because the model grid is non eddy resolving 0 5 the biological model also includes a parameterization of enhanced mixing based on the eddy kinetic energy derived from satellite observations to explore further the impact of local processes on omzs we also obtain analytic solutions to a one dimensional simplified version of the biological model our control run is able to simulate basic features of the oxygen nutrient and phytoplankton fields throughout the indian ocean the model omzs result from a balance or lack thereof between a sink of oxygen by remineralization and subsurface oxygen sources due primarily to northward spreading of oxygenated water from the southern hemisphere with a contribution from persian gulf water in the northern arabian sea the northward intensification of the lower asomz results mostly from horizontal mixing since advection is weak in its depth range the eastward shift of the upper asomz is due primarily to enhanced advection and vertical eddy mixing in the western arabian sea which spread oxygenated waters both horizontally and vertically advection carries small detritus from the western boundary into the central eastern arabian sea where it provides an additional source of remineralization that drives the asomz to suboxic levels the model bbomz is weaker than the asomz because the bay lacks a remote source of detritus from the western boundary although detritus has a prominent annual cycle the model omzs do not because there is not enough time for significant remineralization to occur

ocean load tides at the south pole a validation of recent ocean tide models small diurnal and semidiurnal gravity tides are seen at the south pole because of the loading by and attraction of the ocean tides these data provide a check on the quality of ocean tide models especially in the southernmost ocean which has historically been the most lacking in tidal data ocean tide models developed in the 1980 s did not predict the gravity tides at this location very well recently developed models based on the topex poseidon altimetric data and improved hydrodynamical modeling agree much better with the observations provided that the tides beneath the ice shelves are included the level of agreement at this remote location suggests that loads from very local tides aside the new generation of ocean tide models can predict the loading tides to very high accuracy

character and dynamics of the red sea and persian gulf outflows historical hydrographic data and a numerical plume model are used to investigate the initial transformation dynamics and spreading pathways of red sea and persian gulf outflow waters where they enter the indian ocean the annual mean transport of these outflows is relatively small 0 4 sv but they have a major impact on the hydrographic properties of the indian ocean at the thermocline level because of their high salinity they are different from other outflows in that they flow over very shallow sills depth 200 m into a highly stratified upper ocean environment and they are located at relatively low latitudes 12 n and 26 n furthermore the red sea outflow exhibits strong seasonal variability in transport the four main results of this study are as follows first on the basis of observed temperature salinity t s characteristics of the outflow source and product waters we estimate that the red sea and persian gulf outflows are diluted by factors of 2 5 and 4 respectively as they descend from sill depth to their depth of neutral buoyancy the high dilution factor for the persian gulf outflow results from the combined effects of large initial density difference between the outflow source water and oceanic water and low outflow transport second the combination of low latitude and low outflow transport and associated low outflow thickness results in ekman numbers for both outflows that are o 1 this indicates that they should be thought of as frictional density currents modified by rotation rather than geostrophic density currents modified by friction third different mixing histories along the two channels that direct red sea outflow water into the open ocean result in product waters with significantly different densities which probably contributes to the multilayered structure of the red sea product waters in both outflows seasonal variations in source water and oceanic properties have some effect on the t s of the product waters but they have only a minor impact on equilibrium depth fourth product waters from both outflows are advected away from the sill region in narrow boundary currents at least during part of the year at other times the product water appears more in isolated patches

global ocean tides from ers 1 and topex poseidon altimetry ocean tide models representing all major diurnal and semidiurnal tidal constituents with a spatial resolution of 0 75 0 75 have been estimated using the first 1 5 years of ers 1 and topex poseidon altimetry the ocean tide model was derived from the combined use of ers 1 and topex poseidon data by using a modified orthotide formulation that simultaneously solves for all diurnal and semidiurnal constituents as well as the annual signal an additional adjustment of the solar semidiurnal harmonic of the gravitational potential was applied in order to account for radiational forcing particularly in the s2 constituent topex poseidon provides excellent ocean tide estimates in the open ocean however especially in coastal regions the track spacing of topex poseidon 315 km at the equator is too coarse to determine large parts of the ocean tide signal for these regions the inclusion of data from the ers 1 35 day repeat mission provides a valuable supplement as the ers 1 satellite has a track spacing which is around 3 6 times better than that of the topex poseidon satellite the combined ers 1 and topex poseidon ocean tide solution exhibits distinct sectoral geographical pattern of highs and lows when compared with the cartwright and ray 1990 1991 ocean tide model this indicates the presence of small but fundamental orbit errors present in the cartwright and ray ocean tide solution compared with a new set of 104 tide gauge readings compiled by le provost the rms differences of the combined ers 1 and topex solution are 2 51 1 67 1 58 and 1 13 cm for the m2 s2 k1 and o1 constituents respectively the increased spatial resolution of the combined ers 1 and topex model as compared to a topex alone model is seen to reduce rms differences from 37 to 22 cm for the m2 constituent when compared to a selection of 90 pelagic and coastal tide gauges in the northwest european shelf region

glacial to postglacial transformation of organic input pathways in arctic ocean basins 1 the arctic ocean is undergoing rapid loss in ice cover with yet unknown consequences for the cycling of organic material here we examine persistent terrigenous land based alkane and polycyclic aromatic hydrocarbons with vascular plant combustion and petrogenic sources in seven cores collected from all major basins of the arctic ocean for insight as to how organic cycling at the last glacial maximum compares to the present day we find only modest changes between the glacial and postglacial sediments for atmospherically transported hydrocarbon biomarkers demonstrating that glacial sea ice was not a barrier to atmospheric inputs in stark contrast particle associated biomarkers were captured strongly at basin edges during the glacial period and much more evenly transported across basins during the postglacial period evidently the capture of organic matter shifted from the slopes to the shelves as the latter flooded during the holocene and the transpolar drift and beaufort gyre evolved from minor carriers of plant detritus from the glacial ocean margins to major modern transporters of shelf sediment to the basins this suggests that changes in organic transport currently accompanying the loss of sea ice are likely to be very different from those that occurred at the end of the last glacial period

sediment cores representative of contrasting environments in salt flats of the moknine continental sabkha eastern tunisia sedimentology bulk features of organic matter alkane sources and alteration the moknine continental sabkha exhibits particularly contrasting situations in terms of inundation silting up evaporite deposition vegetation and detrital material input following extensive preliminary studies eight representative cores were selected marked differences in sedimentology were observed between the cores they are accounted for by the present and past position of the core in the sabkha the depth of the zone and the extent of detrital material input from oueds examination of 58 sections from the cores showed conspicuous differences in organic matter abundance and aliphaticity not related to the nature of the facies and also in the abundance of the total lipid extracts and aliphatic hydrocarbons alkane distributions in the 58 sections and their variations reflect the complex and variable interrelationships in the contrasting environments of the sabkha between the i nature of the different types of sources bacteria cyanobacteria microalgae and higher plants ii composition of these different sources and iii extent of bacterial degradation of the alkanes from primary sources

organic molecular evidence of seafloor hydrocarbon seepage in sedimentary intervals down a core in the northern south china sea abstract the hydrocarbons in sedimentary organic matter om at site 4b in the pearl river mouth basin prmb northern south china sea scs were analyzed the odd even predominance oep of long chain n alkanes n c24 with cpi carbon preference index values from 1 62 to 3 80 and n c29 n c31 being the two most abundant in most of the samples are strongly indicative of a terrestrial higher plant source and the even odd predominance eop distribution of mid chain n alkanes n c16 22 suggests a marine bacterial input probably chemical autotrophic bacteria however the biomarker distributions at the 65 70 cm 80 85 cm and 85 90 cm intervals show a similar to those of crude oils which were characterized by a dominance of an unresolved complex mixture ucm in the n c20 region low cpi values 9 of total tricyclic terpanes c30 hopane these features are typical characteristics of mature om that has experienced catagenesis and metagenesis suggesting that outside hydrocarbons migrated into these three intervals in terms of petroleum systems developed in the prmb hydrocarbon seepage from deep source rocks via a diaper structure and fault system is proposed to be responsible for the occurrence of this mature om

spring evolution of arabian sea high in the indian ocean the seasonal formation of a large anticyclonic circulation pattern southern arabian sea high sah appears in the southern arabian sea during the northeast monsoon sah is studied on the basis of the recent observations that include the world ocean circulation experiment woce tropical ocean global atmosphere toga experiment drifting buoys along with topex ers 2 satellite altimeter data in conjunction with the climatological hydrography observations the sah forms west of the laccadive high lh first appears in january and grows rapidly in situ to form a well developed anticyclonic eddy extending across the southern arabian sea by march the center of the eddy is 65 e 5 n the sah is bounded by a strong eastward current to the north and a weak southward flow between 65 and 70 e which separates sah from the lh the westward flowing north equatorial current nec is on the southern flank a strong northward flow along 55 e during january and february marks the western boundary sah propagates westward as a rossby wave between march and april the arrival of sah in the western boundary in april is accompanied by intensification of current along the coast of somalia in may part of the sah has subsequently moved northward to form an anticyclonic eddy with an apparent center 13 n 53 e in the vicinity of the gulf of aden gulf of aden eddy gae the gae extends horizontally nearly 600 km along 13 and is vertically extended down through the upper main thermocline to 250 m comparisons of hydrography buoy and altimetry reveal a good agreement in eddy size location and time of appearance of the gae

tidal loading in south western europe a test area the gravity attraction and loading effects computed on the basis of recent ocean tide models still present non negligible discrepancies for the principal tidal lunar wave m2 the installation of new tidal gravity stations in these regions would be useful to assess the accuracy of these new ocean tide models in particular for the atlantic ocean this investigation clearly proves that there is a real scientific interest to set up a new earth tides gravity profile along the coasts from belgium to portugal

heat production and seismic velocity of crustal rocks heat production of the continental crust can be determined from the seismic velocity structure there is however a significant scatter in the determination partly caused by the quality of geothermal data and partly by the fact that seismic velocity and radiogenic heat production are not uniquely related to each other by the chemical composition of rocks

tidal gravity and ocean tide loading in europe b the results are presented from tidal gravity measurements at five sites in europe using lacoste and romberg et gravimeters improvements that we have made to the accuracies of these gravimeters are discussed it is shown that the standard calibration of the international center for earth tides used for worldwide tidal gravity profiles is 1 2 per cent too high the m2 and o1 observations are compared with model calculations of the earth s body tide and ocean tide loading and it is shown that there is a very significant improvement in the agreement between observations and models compared to that obtained with previous tidal gravity measurements for o1 where the ocean tide loading and attraction in central europe is only 0 4 per cent of the body tide our measurements verify that the dehant wahr anelastic body tide model gravimetric factor is accurate to 0 2 per cent it is also shown that the effects of lateral heterogeneities in earth structure on tidal gravity are too small to explain the large anomalies in previously published tidal gravity amplitudes the observations clearly show the importance of conserving tidal mass in the schwiderski ocean tide model for sites in central europe the m2 and o1 observations and the models are in agreement at the 0 1 gal 10 9 m s 2 level and tidal corrections to this accuracy can now be made to absolute gravity measurements

upper mantle properties of the tuscan tyrrhenian area a framework for its recent tectonic evolution abstract within the alpine mediterranean deformational system several interesting features in the physical properties of the upper mantle have been recognized through the regional analysis of surface wave dispersion a large upper mantle anomaly uma here called the tuscan uma has been identified in the area northeast of corsica which includes part of the northern tyrrhenian sea and part of the north central apennines this anomalous upper mantle area together with the upper mantle characteristics of the tyrrhenian sea located further to the south provides a natural framework for comprehensive interpretation of the large data set of geological and geophysical observations such as land and marine geology volcanism gravity magnetic data seismic data and seismology deep temperatures and surface heat flow

organic matter sources and early diagenetic alterations in arctic surface sediments lena river delta and laptev sea eastern siberia ii molecular and isotopic studies of hydrocarbons abstract the hydrocarbons extracted from three surface sediment samples from the delta of the lena river and adjacent areas of the laptev sea were examined to derive information on their source s natural vs anthropogenic terrestrial vs marine the abundance nature distribution and individual stable carbon isotope ratios of these hydrocarbons were determined it thus appeared that the laptev samples are characterized by i a negligible level of oil pollution due to anthropogenic and or natural petrogenic inputs ii an almost exclusive occurrence of long chain predominantly odd carbon numbered n alkanes and iii some differences in the level of bacterial alteration with a relatively higher degradation of the n alkanes in the seaward sediment a non terrestrial origin is proposed for these n alkanes based on the present results and on previous observations on carboxylic acid moieties and the pyrolysis products of the three surface sediments such hydrocarbons are probably not derived from the epicuticular waxes of higher plants but chiefly correspond to autochthonous products likely of algal origin these observations added to recent results on samples from other types of marine environments stress that an abundance of long chain predominantly odd n alkanes in extracts should not be systematically considered alone as evidence for a major contribution of higher plant waxes the relatively low contribution of terrestrial n alkanes in the laptev sediments should result from the combination of i a major dilution of the terrestrial input due to high primary productivity in summer promoted both by a large influx of nutrients provided by the lena river and by the specific conditions in such an arctic environment and ii the high level of degradation of the organic material transported by the lena river thus the latter probably provided a low input of lipids from terrestrial sources to the laptev samples

hydrology and circulation in the strait of hormuz and the gulf of oman results from the gogp99 experiment 2 gulf of oman art no c12038 hydrological adcp and drifting buoy data obtained during the gogp99 experiment in october and early november 1999 are analyzed to describe the persian gulf water pgw core and the regional circulation in the gulf of oman the warm and salty pgw core flows out of the strait of hormuz heading southeastward unto 25degrees20 n 57degreese approximately from there it cascades down the continental slope veers southwestward and joins the omani coast near 24degrees50 n 56degrees50 e to form a slope current this pgw current has then thermohaline maxima on isopycnal sigma 0 26 5 near 220 m depth its thermohaline characteristics decrease along its progression to ra s al hadd and then offshore into the arabian sea but maintain a sharp contrast with surrounding waters outflow variability at the strait of hormuz can be related to downstream fluctuations of the thermohaline maxima in the pgw core at gulf scale and over a 2 to 3 week period moreover several mechanisms baroclinic instability flow intermittency cape effects are examined to explain the widening of this pgw core upstream and downstream of ra s al hamra in the eastern part of the gulf of oman the regional circulation is a cyclonic gyre the circulation in the western part of the gulf is more complex with the outflow of pgw and southeastward currents in the upper 250 m near the omani coast and a recirculation of upwelled waters near ra s jagin on the iranian coast the large cyclonic gyre occupies at least the upper 300 m of the water column and undergoes little variation over a month the pgw outflow in the northern arabian sea is southward and located 50 100 km from the coast it borders a shallower northward current located offshore

evidence for the existence of persian gulf water and red sea water in the bay of bengal the high salinity water masses that originate in the north indian ocean are arabian sea high salinity water ashsw persian gulf water pgw and red sea water rsw among them only ashsw has been shown to exist in the bay of bengal we use ctd data from recent cruises to show that pgw and rsw also exist in the bay the presence of rsw is marked by a deviation of the salinity vertical profile from a fitted curve at depths ranging from 500 to 1000 m this deviation though small of the order of similar to 0 005 psu and therefore comparable to the ctd accuracy of 0 003 psu is an order of magnitude larger than the similar to 0 0003 psu fluctuations associated with the background turbulence or instrument noise in this depth regime allowing us to infer the existence of rsw throughout the bay pgw is marked by the presence of a salinity maximum at 200 450 m in the southwestern bay pgw can be distinguished from the salinity maximum due to ashsw because of the intervening arabian sea salinity minimum this salinity minimum and the maximum associated with ashsw disappear east and north of the south central bay 85a degrees e 8a degrees n owing to mixing between the fresher surface waters that are native to the bay bay of bengal water or bbw with the high salinity ashsw hence ashsw is not seen as a distinct water mass in the northern and eastern bay and the maximum salinity over most of the bay is associated with pgw the surface water over most of the bay is therefore a mixture of ashsw and the low salinity bbw as a corollary we can also infer that the weak oxygen peak seen within the oxygen minimum zone in the bay at a depth of 250 400 m is associated with pgw the hydrographic data also show that these three high salinity water masses are advected into the bay by the summer monsoon current which is seen to be a deep current extending to 1000 m these deep currents extend into the northern bay as well providing a mechanism for spreading ashsw pgw and rsw throughout the bay

seasonal spreading of the persian gulf water mass in the arabian sea the characteristics of the subsurface salinity maximum associated with the persian gulf water mass pgw are used to quantify the spreading and mixing of pgw in the thermocline of the arabian sea based on a bimonthly climatology of temperature and salinity examination of the seasonal cycles of heat and freshwater fluxes in the persian gulf region indicates that pgw forms as a result of elevated evaporative cooling in conjunction with reduced insolation during winter maps are presented of the distributions of depth salinity and geostrophic flow on 26 5 which nearly coincides with the core of the pgw after intense mixing in the strait of hormuz the property fields suggest that warm 17 c and high salinity 36 2 psu pgw enters the arabian sea to form a subsurface salinity extremum between 200 and 300 m we have found variability in the distribution of pgw in the arabian sea associated with monsoonal changes in the arabian sea circulation during the winter monsoon there is southward spreading of pgw along the western boundary during summer it is not present lateral mixing with low salinity water from the bay of bengal in the region south of 10 n and along the west coast of india during winter accounts for changes in the characteristics of pgw along these paths associated with the findlater jet during summer the entire thermohaline structure is vertically displaced along the coasts of somalia and arabia ekman convergence in the central arabian sea accounts for deepening of the pgw either lateral or vertical mixing would cause changes in pgw properties in these regions during this time pgw spreads predominantly southward along the central arabian sea as indicated by a tongue of high salinity

c25 and c30 biogenic alkenes in sediments and detritus of a new england salt marsh as part of a geochemical study of c25 and c30 biogenic alkenes in estuarine environments distributions of these compounds in detritus and sediments collected from a new england salt marsh round swamp on conanicut island in narragansett bay rhode island have been determined the alkene assemblages detected consisting primarily of four acyclic c25 dienes and trienes and a c30 bicyclic diene qualitatively resemble those previously reported for other sediments in which anoxic conditions were prevalent these similarities exist despite significant differences in the principal sources of sedimentary organic matter suggesting that the occurrence of these specific alkenes is more likely associated with an in situ process common to anoxic environments than with a direct input from a specific source size fractionation 840 m and 840 m to 1 2 m of marsh detritus revealed that the larger size fraction consisting primarily of decaying spartina debris contains significant amounts of alkenes this result together with alkene subsurface profiles which show high surface concentrations decreasing to near background levels by 20 cm suggest that anaerobic bacteria are mediating in situ production of these compounds previous studies of bacterial hydrocarbons have not reported the presence of these c25 and c30 alkenes although similar compounds have been isolated from several species of methanogenic bacteria however attempts to induce alkene synthesis by decomposing spartina anaerobically in the laboratory were unsuccessful in light of this result the exact source of alkenes in marsh sediments remains uncertain the absence from marsh sediments of other c25 alkenes whose sedimentary distributions had been previously correlated with the presence of marine planktonic organic matter implies the existence of different origins for structurally related constituents of this hydrocarbon series

impact of water mass mixing and dust deposition on nd concentration and e nd of the arabian sea water column abstract the concentration and isotopic composition e nd of dissolved nd have been measured in the sub oxic denitrifying water column of the eastern arabian sea to explore the impact of water mass mixing and release from particles dissolved nd in the north eastern arabian sea is more radiogenic e nd 7 to 10 compared to its south eastern part e nd 11 to 15 suggesting contribution of nd from the bay of bengal bob the vertical profile of nd typically show higher values in surface waters 15 8 27 8 pmol kg followed by minima 12 18 pmol kg in the subsurface waters 200 300 m and a gradual increase with depth thereafter the nd concentration does not seem to show any changes in the sub oxic layers suggesting no impact of the sub oxic denitrifying conditions in this oceanic region on the biogeochemistry of nd the enrichment of nd in surface waters can be explained either by supply from high nd low salinity waters from the bob to the arabian sea via the east india coastal current eicc or alternatively the nd surface excess can be result of release from aeolian dust depositing over the sea surface inverse modeling computations suggest that in addition to nd contributed from water mass mixing some additional excess nd nd xs is required to balance the nd inventory in the water column there is significant nd xs in the surface waters of the north eastern arabian sea with e nd 6 similar to that of dust depositing over the arabian sea the fractional solubility of nd released from the aeolian dust was estimated to be varying from 3 to 17 for excess nd inventory per unit area nd xs of 20 g m 2 with nd ranging from 1 to 3 years this study highlights the significance of aeolian dust deposition in controlling the abundance and distribution of nd in the arabian sea the western arm of the northern indian ocean lying in the proximity to the arid landmass and characterized by high lithogenic aeolian dust deposition

qualitative comparisons of global ocean tide models by analysis of intersatellite ranging data 1 four global ocean tide models are compared in terms of their contribution to gravity recovery and climate experiment grace satellite to satellite tracking residuals the residuals are computed relative to a comprehensive model of earth s time varying gravity including allowance for mass motions in the atmosphere ocean terrestrial hydrology and mantle in addition to tides for each analyzed tide model 4 years of grace range rate data are processed range and range acceleration residuals are tidally analyzed by geographic location all four global tide models are shown to be error prone in various ways leaving tidally coherent residuals especially in polar regions but also in some lower latitude regions considerable power in the solar semidiurnal s2 tide in low latitudes suggests errors in our adopted model of atmospheric tides which is based on 3 hourly european centre for medium range weather forecasts operational analyses anomalies in the 2 tidal constituent over some shallow seas suggest the presence of unmodeled nonlinear compound tides in this case 2ms2 similarly anomalies in the nonlinear m4 tide are seen if this constituent is omitted from the models errors in assumed seawater density may be contributing to some residuals

a new test of earth tide models in central europe new improved ocean tide models allow a corresponding improvement in ocean tide loading computations during recent years various groups have made more accurate tidal gravity observations in central europe using gravimeters carefully calibrated on various calibration lines this progress with tidal gravity measurements and ocean loading corrections now allows a more comprehensive test of body tide models than was possible previously it is shown that the o1 and m2 gravimetric factors corrected using the latest ocean tide models are very consistent between the sites despite the different instruments and gravity calibration lines that have been used these observations allow constraints to be put on the anelasticity of the earth at tidal frequencies the corrected gravimetric factors are consistent with recent model results for both the elastic prem model and with 0 09 for an anelastic prem model with the q for dissipation in shear varying as frequency to the power

formation and circulation of dense water in the persian arabian gulf 1 the nature and circulation of water masses in the persian arabian gulf hereinafter referred to as the gulf is investigated by examination of a historic database of hydrographic observations the densest water forms in winter at the northern end of the gulf rather than along the warmer southern and western coasts with the exception of small amounts of water directly above the seafloor most water flowing out of the gulf mixes across a density front that separates gulf deep water within the gulf from the indian ocean surface water iosw contrary to previous inferences the seasonally variable incursion of iosw into the gulf peaks in late spring this timing may be due to seasonal changes in sea surface slope driven by variations in evaporation rate in order to explain mooring results published elsewhere that show relatively small seasonal changes in the volume flux through the strait of hormuz hereinafter referred to as the strait we suggest that this flux is driven by the difference between the density of gulf deep water in the interior of the basin and water at comparable depths outside the gulf this density difference varies less than 15 during the year high rates of vertical mixing in the strait extend about 200 km westward in response to topographic constriction of tidal flows by islands and shoals

validation of ocean tide models around antarctica using onshore gps and gravity data 1 ocean tide models around antarctica are presently only sparsely tested against independent data ocean tide modeling errors along with subsequent ocean tide loading otl displacement modeling errors alias into altimetry and time variable gravity e g gravity recovery and climate experiment grace time series for example to validate various ocean tide models around antarctica gps data from 15 sites have been used to derive three dimensional displacement estimates at eight diurnal and semidiurnal tidal frequencies using hundreds of days of gps data harmonic parameters were estimated on a daily basis then combined these were then compared with otl displacement estimates derived from global and regional ocean tide models in east antarctica where the tides are well defined submillimeter differences are demonstrated in each coordinate component with the lunar n2 and q1 constituents in closest agreement as found in other studies k1 and especially k2 agree less well the spatial variation in the misfits for these two constituents indicates a site dependency with the k2 errors also suggesting an interaction with satellite dependent effects in west antarctica where sites are nearer the largest ice shelves agreement with the older models csr3 and tpxo 2 and nao 99b is poor for all constituents modeled tidal gravity variations were also compared with gravity measurements at the south pole overall the gps and gravity data agree best with newer tide models namely tpxo 6 cada00 10 fes99 and cats02 01 however validation data are lacking at the southern extents of the large ice shelves and hence some uncertainty still exists in all ocean tide models in these regions