decadal biogeochemical changes in the subtropical indian ocean associated with subantarctic mode water within the subantarctic mode water samw density level we study temporal changes in salinity nutrients oxygen and ttd transit time distribution ages in the western w and eastern e subtropical gyre of the indian ocean io from 1987 to 2002 additionally changes in total alkalinity ta and dissolved inorganic carbon dic are evaluated between 1995 and 2002 the mechanisms behind the detected changes are discussed along with the results from a hindcast model run community climate system model the increasing salinity and decreasing oxygen trends from 1960 to 1987 reversed from 1987 to 2002 along the gyre in the w io a decreasing trend in ttd ages points to a faster delivery of samw thus less biogenic matter remineralization explaining the oxygen increase and noisier nutrients decrease in the e io samw no change in ttd ages was detected therefore the trends in oxygen and inorganic nutrients relate to changes in the antarctic surface water transported into the e io samw formation area in the w io between 1995 and 2002 the dic increase is equal or even less than the anthropogenic input as the reduction in remineralization contributes to mask the increasing trend in the e io between 1995 and 2002 dic decreases slightly despite the increase in the anthropogenic input differences in the preformed e io samw conditions would explain this behavior trends in the w and e io samw are decoupled and related to different forcing mechanisms in the two main sites of samw formation in the io at 40 s 70 e and 45 s 90 e respectively

textural and stable isotopic evidence for the genesis of the tynagh base metal deposit ireland at the tynagh mine county galway four major stages of mineralization can be recognized that span the diagenetic and postlithification history of the host waulsortian limestones 1 growth of colloform and granular pyrite clots during the early diagenesis of the micritic host 2 rapid geopetal precipitation of microcrystalline sphalerite galena barite and dolomite within a dilatant fracture system that developed as a consequence of the forceful injection of metalliferous fluids into the coherent waulsortian carbonate mudbanks adjacent to the tynagh fault 3 veining and replacement of the host and previously precipitated phases by tennantite chalcopyrite bornite arsenopyrite medium to coarsely crystalline galena and coarse sparry barite and 4 finally precipitation of calcite within veinlets and cavities and dolomitization of large bodies of previously unmineralized waulsortian limestones sulfur isotope ratios indicate that contemporaneous lower carboniferous seawater acted as the source of sulfate for precipitation of barite delta 34 s 21 1 to 17 4ppm stage 1 delta 34 s 3 1 to 15 5ppm and stage 2 delta 34 s 4 1 to 26 0ppm sulfides were precipitated by reduced sulfur generated during open system bacterial reduction of this sea water sulfate source isotopically heavier delta 34 s or 0ppm reduced sulfur of deep seated origin was introduced from the fault zone during stage 3 this mixed with bacteriogenic sulfur migrating into the waulsortian bank limestones to precipitate stage 3 sulfides and sulfosalts delta 34 s 11 1 to 23 0ppm mineralized limestones delta 13 c 2 1 to 4 0ppm delta 18 o 17 6 to 27 1ppm ore stage carbonates delta 13 c 2 8 to 3 4ppm delta 18 o 17 1 to 26 9ppm and postore carbonates delta 13 c 4 0 to 2 6ppm delta 18 o 15 9 to 25 8ppm are depleted in the heavier isotopes of carbon and oxygen with respect to unmineralized limestones delta 13 c 3 1 to 4 1ppm delta 18 o 22 2 to 28 1ppm the depletion in 13 c is attributed to the mixing of host derived carbon with bacterially oxidized carbon and during stage 4 deep seated carbon the 18 o depletion of the mineralized host is a consequence of isotopic exchange with the ore fluids an oxygen isotope fractionation temperature of 200 degrees c and a delta 18 o smow value of 10 5 per mil for the coexisting water is obtained from a single stage 3 quartz albite pair collected from the fault zone if these values are accepted the delta 18 o values of stage 3 carbonates can only be interpreted in terms of mixing of this isotopically heavy water introduced from the fault with isotopically lighter water already present or migrating into the bank limestones

base metal mineralization in the kanmantoo group south australia a regional sulfur isotope study a number of base metal sulfide deposits are hosted by multiply deformed metagraywackes of the kanmantoo group south australia sulfide mineralization is of three main types 1 copper deposits which include the kanmantoo and bremer mines south hill prospect and several minor occurrences 2 lead zinc deposits at the aclare wheal ellen and strathalbyn mines 3 pyrite pyrrhotite mineralization of the nairne pyrite deposit and other pyritic schists within the kanmantoo group copper deposits are discordant and pipelike and contain chalcopyrite pyrrhotite magnetite and pyrite as the major opaque minerals lead zinc deposits lack magnetite and are apparently concordant beds of pyritic schist reach an overall thickness of 100 m and persist for as much as 32 km sulfur isotope ratios for ore shoots from the kanmantoo mine excluding one sample range from 3 5 to 12 4 per mil and average 8 0 or 2 3 per mil average values for individual ore shoots differ by as much as 4 per mil 34 s enrichment is noted at kanmantoo among some low grade sulfide mineralization delta 34 s 16ppm and supergene pyrite from the main orebody delta 34 s 39 6ppm the minor deposits of copper and lead zinc all show a similarity in sulfur isotope composition the delta 34 s values for sulfides range from 4 7 to 6 5 per mil and averages for these deposits lie close to zero per mil the pyritic schists are strongly depleted in 34 s and contain biogenic sulfur formed in an anoxic marine environment individual sulfides range from 19 9 to 11 9 per mil isotopic disequilibrium is a characteristic feature of coexisting sulfide pairs from many of the deposits despite subsequent amphibolite facies metamorphism 3 8 kb and 500 degrees 600 degrees c sphalerite galena pairs at the wheal ellen mine yield consistent calculated temperatures 379 degrees c and may have reequilibrated below the metamorphic peak base metal mineralization is accounted for by subsurface copper and sea floor lead zinc accumulation from hydrothermal fluids circulating to or expelled from depths of at least 3 to 4 km within the sedimentary basin this minimum depth estimate for fluid extraction corresponds to the stratigraphic interval occupied by pyritic schists which underlies the horizon of base metal mineralization sulfur isotope evidence suggests that sulfur was extracted by hydrothermal leaching from the pyritic schists sulfur within the base metal mineralization shows a mixed cambrian seawater and biogenic pyritic schist source variations in mixing proportions of the two forms of sulfur are responsible for differences among ore lenses at the kanmantoo mine and individual deposits within the region

interpentadal variability of temperature and salinity at intermediate depths of the north atlantic ocean 1970 1974 versus 1955 1959 we have composited historical hydrographic observations for the world ocean for two pentads 1955 1959 and 1970 1974 and have objectively analyzed these data for the purpose of studying the temporal variability of temperature and salinity in the north atlantic ocean the subtropical gyre 500 1300 m of the north atlantic was colder and fresher during 1970 1974 compared to 1955 1959 the relatively large changes in temperature and salinity on constant depth surfaces in the subtropical gyre were due to upward displacements of isopycnal surfaces at intermediate depths the eastern portion of the subarctic gyre was also colder and fresher during the 1970 1974 pentad in contrast the western portion of the subarctic gyre exhibited higher temperatures and salinities during 1970 1974 compared to 1955 1959 characteristic differences in temperature and salinity for both gyres were 0 5 c and 0 025 respectively analysis of changes in potential vorticity indicates that in the subtropical gyre potential vorticity increased in all density layers above the 26 5 surface suggesting that convection in this region may have been shallower in 1970 1974 compared to 1955 1959 below the 26 5 surface potential vorticity decreased through the 27 3 surface indicating that deeper than normal convection may have formed the water masses in these layers at 250 m depth relatively large changes in temperature and salinity occurred along the line of maximum climatological mixed layer depth that extends northeast to southwest across the north atlantic ocean

apparent changes in the climatic state of the deep north atlantic ocean determination of any long term changes in the large scale characteristics of the deep ocean circulation would be an important clue in understanding the climatic interactions of the ocean and atmosphere in the summer of 1981 the rv atlantis ii reoccupied two transatlantic sections at nominal latitudes of 24 30 n and 36 16 n with a conductivity temperature depth instrument ctd one purpose of the work was to make a comparison with previous surveys conducted during the international geophysical year igy 1 when sections were obtained in october 1957 and april may 1959 we report here that significant warming occurred in an ocean wide band from 700 m to 3 000 m with a maximum temperature difference of 0 2 c these changes are sufficient to expand the water column by several centimetres the historical temperature salinity curve was apparently unchanged interannual changes in local water mass characteristics have been proposed previously2 3 perhaps it would be most surprising if no changes were seen to occur what remains obscure is the significance of these changes and the extent to which they represent long term climate trends or merely the minor and random fluctuations to be expected in any complex fluid system

a model of sea level rise caused by ocean thermal expansion abstract warming of the atmosphere as a result of an increased concentration of greenhouse gases is expected to lead to a significant rise is global sea level we present estimates of the component of this sea level rise caused by thermal expansion of the ocean these estimates are based on the idea that the upper layers of the main gyres of the ocean are ventilated by the subduction of water at higher latitudes and its subsequent equatorward and downward flow into the main thermocline along surfaces of constant density in this mechanism heat enters the ocean by an advection process rather than by vertical diffusion as in previous estimates of the component of sea level rise that is caused by thermal expansion after the heat initially enters the subtropical gyres by subduction it is then redistributed to preserve gradients of the depth integrated pressure field by an adjustment involving low vertical mode baroclinic waves estimates of historical sea level rise based on this simple ventilation sch

circulation and low frequency variability near the chilean coast remotely forced fluctuations during the 1991 92 el nino results are reported from the first long recording current meter observations over the slope off chile these observations at 308s during the 1991 92 el nino event are analyzed together with observations of currents at a local deep sea site local wind and sea level sea level from the peru and chile coasts and wind temperature and currents from the equatorial pacific mean poleward flow of 12 cm s21 was observed within the peru chile undercurrent over the slope mean flow in the depth range of antarctic intermediate water was not distinguishable from zero in the presence of strong low frequency lf variability which dominated slope currents at all depths the strongest lf fluctuations had periods of about 50 days but periods of 10 and about 5 days were also observed significant local wind forcing of slope currents was only found in the period band 6 10 days and may be related to coastal trapped waves in the atmosphere our analysis shows that free coastal trapped waves in the ocean arriving from the north dominated the lf variability over the shelf and slope off northern and central chile during the 1991 92 el nino event strong 50 day period fluctuations there started their journey about two months earlier and 15 000 km farther up the coastal equatorial waveguide near the date line in the equatorial pacific as equatorial kelvin waves forced by westerly wind events of similar period upon reaching the south american coast these waves forced coastal trapped waves which propagated along the peru coast into the study region likewise a scenario of equatorial trapped waves forcing coastal trapped waves may explain 10 day as well as 6 day and 4 5 day period coastal trapped waves off chile stemming from mixed rossby gravity and inertia gravity waves trapped at the equator since the large 50 day period coastal trapped waves may strongly modify coastal upwelling source water such remotely forced waves may have a significant influence on the pelagic ecosystem off chile at least during el nino events

using a cfc effective age to estimate propagation and storage of climate anomalies in the deep western north atlantic ocean 1 1990s chlorofluorocarbon cfc observations are used to estimate an effective age of 20 years for north atlantic deep water nadw at the equator the effective age is found by subtracting a relic age from pcfc 11 age the effective age is several to 10 years younger at the equator than other methods from the effective age equatorward effective spreading rates of 1 2 cm s are found which are similar for the nadw components effective spreading rates take into account recirculation gyres along equator flow and mixing which slow spreading of climate anomalies from the north atlantic to the southern hemisphere the difference between direct velocities and tracer effective spreading rates suggests that the buffering effect due to storage in the western north atlantic and equatorial region is about 20 years even so warming and freshening due to greenhouse gases will be first felt in the deep waters of the western north atlantic

a moving boundary box model mbbm for oceans in change an application to the east japan sea 1 the east japan sea has undergone dramatic changes during the last 50 60 years as the result of a shift in its ventilation system from bottom water formation to intermediate water formation a moving boundary box model mbbm was developed to quantify these changes the model consists of three boxes for deep waters representing central deep and bottom waters respectively and two boundaries in between which are moving according to the volume changes of these water masses the model calibrated with cfc 11 and tritium distribution shows the bottom water formation of 0 02 sv in magnitude in the past slowed down and came to a complete halt in mid 1980s and late 1990s furthermore this model predicts the bottom water will disappear completely in 2040 as central water penetrates deeper considering the recent observations that many oceans are in change a mbbm could be a valuable tool to investigate the nature of such changes

on the wind driven circulation of the south pacific ocean abstract a layered model of the study circulation in the south pacific ocean is constructed along the lines of luyten pedlosky and stommel and driven by the mean annual wind stress distributions computed by hellerman and rosenatein the results of the model agree quite well with published maps of topography of density surfaces and circulation best agreement is found in the deeper layers the deepest modeled layer of density range 26 90 0 27 30 which contains the core layer of the antarctic intermediate water transports northwards some 14 sv 1 sv 106 m3 s 1 between new zealand and south america of this about three quarters comes from the west in an intense zonal jet that rounds the southern tip of new zealand and quickly fans out from the boundary current along those islands into the anticyclonic gyre some 5 sv returns southwards in the australian boundary current much of the anticyclonic gyre in the western south pacific is taken up by a shadow zone formed in the shelter of new zealand

ore lead and sulphur isotope pattern from the low temperature veins of the catalonian coastal ranges ne spain the lead isotopic composition of galenas from low temperature veins of the catalonian coastal ranges ne spain displays a small but distinct range of values 18 318 206pb 204pb 18 678 15 678 207pb 204pb 15 767 and 38 534 208pb 204pb 39 189 the data define a linear trend in the 208pb 204pb versus 206pb 204pb diagram that can be interpreted in terms of mixing of lead from different reservoirs the lead appears to be derived from a solution that preferentially leached granites of late hercynian age sulphur isotopic compositions of the galenas range from 8 5 to 7 3 but variations in a single deposit are small 1 2 pointing to different sources of sulphur in a 34s versus 206pb 204pb plot no clear correlation trends appear lead isotope data from deposits of similar characteristics situated within the hercynian orogenic belt as the linares la carolina district s spain and the inglesiente sulcis area sardinia show slight differences indicating a source area of similar lead isotopic composition in the ccr and linares la carolina districts the main source of lead is related to the hercynian granites of each area although small contributions from metasediments cannot be ruled out the contribution of lead from metasedimentary rocks is particularly seen in the sardinian hercynian vein type ores

interpentadal variability of temperature and salinity in the deep north atlantic 1970 1974 versus 1955 1959 historical hydrographic observations have been composited and objectively analyzed for the north atlantic ocean for two pentads 1955 59 and 1970 74 for the purpose of studying the temporal variability of the thermohaline structure of the deep north atlantic ocean statistically significant differences between the two pentads are found in the deep ocean at 1750 m depth most of the north atlantic increased in temperature approximately 0 1 c and salinity 0 025 from the earlier to the later period an exception to this was a region in the eastern atlantic between 33 n and 50 n where a cooling 0 1 c and freshening 0 025 occurred changes at other depths as evidenced by difference fields of temperature along 24 5 n and 36 5 n are in agreement with differences found by roemmich and wunsch 1984 who described changes at these latitudes between sections taken in the late 1950 s and sections taken in 1981

recent changes in subsurface temperature and salinity in the canary region 1 based on hydrographic sections carried out during the last decade in the canary region at 29 10 n we show that there has been a statistically significant rise in temperature and salinity on isobars between 1500 and 2300 db the maximum increase found at 1600 db is occurring at a rate of 0 29 c and 0 047 per decade isobaric change decomposition into changes on neutral surfaces and changes due to the vertical displacement of the isoneutrals was performed results reveal that the lower part of north atlantic central water nacw cooled and freshened on neutral surfaces suggesting changes in the freshwater fluxes at the outcropping region however the signal in deep waters 1500 2300 db was principally due to a downward displacement of the isoneutrals although water mass modification is observed in the range of mediterranean water mw influence

climate and antarctic intermediate water coupling during the late holocene little is known about the scale of natural variability of the southern hemisphere upper ocean on decadal to centennial time scales despite its potential importance for influencing regions as distant as the tropical pacific el nino southern oscillation enso or even the north atlantic overturning circulation here we present the first subdecadally sampled reconstruction of variability in the southeast pacific upper intermediate ocean from ca a d 0 1300 using foraminiferal oxygen and carbon isotope records our results reveal large variability in surface ocean physical properties on both decadal and centennial time scales in the southeast pacific as much as 3 c or more in as little as 50 yr on centennial time scales changes in antarctic intermediate water physical properties benthic foraminiferal 18 o covary with those in the surface and are associated with shifts in tropical temperatures thermocline nutrient dynamics and enso suggesting that they are part of a common pacific wide phenomenon our results reveal that natural variability in upper ocean properties is greater than previously appreciated and coherent with changes in the tropical thermocline supporting both theories and models postulating the importance of extratropical tropical teleconnections and the oceanic tunnel in interdecadal to centennial climate variability

decadal changes in water mass characteristics at 24 n in the subtropical north atlantic ocean abstract three transatlantic hydrographic sections across 24 n through the center of the subtropical gyre are analyzed for evidence of decadal changes in water mass characteristics in the main thermocline there has been a steady increase in salinity from 1957 to 1981 to 1992 the salinity at a given potential temperature between 12 c and 17 c has increased at a nearly constant rate of 0 010 per decade at constant potential density salinity and temperature both increased at rates of 0 018 per decade and 0 065 c per decade in the intermediate waters between 800 and 1500 dbar salinity has increased as well on average by as much as 0 025 from 1981 to 1992 either on constant potential temperature or constant density surfaces these changes cannot be due to vertical heaving of a constant water mass structure and they cannot be easily explained in terms of horizontal shifts in the subtropical gyre water mass structure throughout the water column down to 2000 dbar and across the zonal extent of the 24 n

the little ice age and 20th century deep pacific cooling proxy records show that before the onset of modern anthropogenic warming globally coherent cooling occurred from the medieval warm period to the little ice age the long memory of the ocean suggests that these historical surface anomalies are associated with ongoing deep ocean temperature adjustments combining an ocean model with modern and paleoceanographic data leads to a prediction that the deep pacific is still adjusting to the cooling going into the little ice age whereas temperature trends in the surface ocean and deep atlantic reflect modern warming this prediction is corroborated by temperature changes identified between the hms challenger expedition of the 1870s and modern hydrography the implied heat loss in the deep ocean since 1750 ce offsets one fourth of the global heat gain in the upper ocean

temperature and salinity variability in the deep western boundary current abstract a ten year time series 1984 1993 of repeat hydrographic sections from offshore abaco island the bahamas 26 5 n is used to define the mean and time dependent characteristics of the deep western boundary current dwbc the dwbc flow is divided into four vertical layers based on chlorofluorocarbon cfc concentration and formation regions upper layer cfc core 3 9 5 0 c second layer classical labrador sea water 3 2 3 9 c third layer cfc minimum 2 4 3 2 c deepest layer cfc core 1 85 2 4 c time series analysis of mean layer properties and their anomalies showed that the temperature and salinity of each layer did not increase or decrease monotonically with time variations in temperature and salinity were characterized by 2 3 yr period oscillations variability between years is illustrated by subtracting repeat sections of temperature and salinity along levels of both constant pressure and constant potential density to determine an original water mass modificati

an intensification trend of south pacific mode water subduction rates over the 20th century 1 in this paper the trend of the south pacific mode water subduction rate is assessed based on recently developed ocean and atmosphere reanalysis products for the 20th century it is found that the subduction volume of the mode water is intensified in the 20th century the intensification of the mode water in the subtropical gyre of the south pacific is primarily due to the strengthening of the vertical pumping velocity dominated by the enhanced wind stress curl over the past century in contrast the intensification of the south pacific subantarctic mode water samw is mainly caused by a deepening of the mixed layer depths and a strengthening of the advection in warm climate as a result the total subduction volume of the mode water over the south pacific is increased in the 20th century

redox zonation of elements at an oxic post oxic boundary in deep sea sediments abstract deep sea sediments generally provide limited evidence of redox control on the post depositional redistributions of elements this is because only a fraction of any element is reactive and observed elemental distributions are the result of a number of competing processes which are simultaneously active so that redox effects are not dominant a detailed investigation is reported of a core which is unusual in showing unequivocal evidence of direct redox control operating in a homogeneous environment that is relatively free from competing processes a progressive oxidation front has migrated slowly downwards into a uniform turbidite over a long period ca 250 ky the reactive fractions of several redox sensitive elements now show a remarkable degree of organisation around the redox boundary of this front with the different elements exhibiting individual responses solid phase enrichments are not coincident but are arranged in a clear succession of concentration peaks along the redox gradient from oxic to postoxic conditions the succession is mn i fe se and pt cu and pb v zn and sb and u the movement directions of most elements can be inferred from the peak shapes against the homogeneous turbidite background composition the system seems to have been essentially isolated within the sediment for most elements so that no loss or gain can be ascribed to redox processes exceptions are u and v which have been augmented by uptake from ocean bottom waters into the sediments by an efficient redox trap mechanism

north atlantic sea level and circulation summary monthly sea levels from an extensive array of north atlantic tide gauges 26 50 n are examined the spatial scale of the sea level variations and the reasons for them are discussed one application of such a study is clearly in the design of a tide gauge network for monitoring eustatic changes of sea level the spatial scale of the sea level changes is large there is a coherent sealevel signal which can be traced along the eastern boundary of the north atlantic from newlyn 50 n to tenerife 28 n there are also two distinct groupings of tide gauges along the western boundary separated by cape hatteras the contribution of local air pressure and wind stress is quantified at each gauge through multiple regression techniques and the gains are then interpreted in terms of recent theoretical and numerical modelling studies for example the gains suggest that the wind forced boundary current along the nova scotian shelf is trapped to within about 16 km of the coast the influence of local meteorology cannot account for the large scale modes of variability the coherent signal along the eastern boundary is correlated with changes in the sverdrup transport of the north atlantic and hence the large scale wind field the two modes on the western boundary appear to be related to baroclinic boundary current variations the newlyn sea level record is finally corrected for some of the above effects to illustrate the utility of such a residual series in the identification of eustatic changes and vertical crustal movement

climatic warming of atlantic intermediate waters abstract interdecadal temperature variability of the atlantic ocean is investigated by differencing hydrographic sections taken from the 1920s through the 1990s a comprehensive reanalysis of north atlantic sections and the inclusion of south atlantic sections show that warming seen previously in the north atlantic extends to the south atlantic the largest statistically significant changes occur on pressure surfaces between 1000 and 2000 decibars db over this pressure range and for latitudes between 32 s and 36 n temperatures have warmed by 0 5 c century 1 at 48 n a cooling of 3 c century 1 occurred between the 1950s and 1980s these isobaric temperature trends are decomposed into ones along surfaces of constant neutral density and ones due to the vertical movement of neutral surfaces the two components are associated with different processes in the southern north atlantic 8 36 n the subthermocline warming between the 1950s and 1980s appears to be due primarily to downward displacements of n

interannual and decadal temperature variability in the southwest pacific ocean between 1955 and 1988 abstract the spatial and temporal variability of the southwest pacific ocean is examined with the aim of describing the physical processes operating on interannual and decadal timescales the study takes advantage of a new temperature atlas of the upper 450 m of the southwest pacific ocean obtained from 40 000 bathythermograph profiles between 1955 and 1988 rotated principal components analysis was used to filter the important spatial and temporal scales of temperature variability in the data three different analyses are presented they include two intraocean analyses and a joint analysis of subsurface ocean temperature sea level pressure and surface winds the dominant el nino mode describes the large vertical excursions of the thermocline in the western tropical pacific in response to atmospheric forcing at a 3 6 month lag more importantly most of the retained modes outside of the equatorial region have time variations that correlate with el nino one ocean mode with a spatial pattern represen

hydrography of the eastern south pacific ocean results from the sonne 102 cruise may june 1995 abstract full depth conductivity temperature depth hydrographic measurements were taken in may june 1995 along 28 15 35 15 and 43 15 s from the chilean coast to 86 88 w from the r v sonne sections of potential temperature salinity neutral density and oxygen are presented to illustrate the water column structure in this sparsely sampled region a more comprehensive database on all available hydrographic data from the region was compiled these data and available meteorological data are used to help in the interpretation of the sonne results a number of important features found in the sections are discussed including a shallow salinity minimum apparently ventilated from south of 37 s salt fingering as a possible mechanism to transport high salinity subtropical water into the shallow salinity minimum equatorial subsurface water subantarctic mode water and antarctic intermediate water geostrophic calculations of alongshore flow show the poleward peru chile undercurrent at each of the three sections with a poleward descending core and peak velocities of 10 cm s 1 as in earlier works a deep pacific outflow is found near the chilean coast part of a clockwise deep circulation in the chile basin

genesis of late proterozoic copper mineralization copper claim south australia bedded disseminations no evidence for hydrothermal alteration the disseminated sulfides have a delta 34 s range of 17 3 to 15 8 per mil consistent with bacterial reduction of sulfate veinlet sulfides have a similar but smaller delta 34 s range in accord with formation by remobilization of the disseminated sulfides no significant delta 13 c differences between bedded and veinlet carbonates marked variations in delta 18 o values with magnesite values being generally higher than dolomite and the median value for bedded carbonates being around 23 per mil some 3 per mil higher than the median value for veinlet carbonates low temperature oxygen isotope equilibration during early diagenetic carbonate reactions low grade regional metamorphism caused minor recrystallization and formation of additional veinlets but did not extensively overprint the diagenetic isotopic trends isotopic similarities between the cupriferous and the unmineralized lithologies support introduction of the copper during sedimentation and or early diagenesis veinlet carbonates contain small nacl rich fluid inclusions formed at around 300 degrees c and 4 km depth during the metamorphism general trend of increasing mean delta 34 s values with decreasing age of the late proterozoic strata in the adelaide geosyncline and stuart shelf this trend may be the product of local environmental conditions which resulted in sulfate reduction outweighing sulfate replenishment alternatively it could be reflecting global processes which caused major 34 s enrichment of seawater sulfate modified journal abstract

sulphur isotope composition of silurian shale hosted pge ag au zn cu mineralisations of the prades mountains catalonia spain several silurian metamorphosed shale hosted sulphide occurrences have been studied in the prades mountains southern part of the coastal catalonian ranges most of the sulphides are found as stratiform or shale disseminated occurrences pyrrhotite is the most abundant sulphide mineral chalcopyrite and arsenopyrite are less common gold pd bearing lollingite partly replaced by arsenopyrite sperrylite hessite clausthalite altaite galena sphalerite molybdenite scheelite and v cr oxides and silicates are minor components sulphur isotopic analyses were made on three outcrops roca de ponent coma fosca and sant miquel and in the silurian black shales of the sant bernat series in order to determine the origin of the sulphur which formed these deposits the coma fosca and sant miquel outcrops yield a narrow range of 34s values 11 3 to 4 6 whereas the roca de ponent and sant bernat series have a wider range 19 9 to 7 6 in pyrrhotite and up to 36 in pyrite from the top of the sant bernat series in the roca de ponent outcrop the 34s values decrease with increasing stratigraphic height all the deposits have a mean 34s composition close to 9 annealing of pyrrhotite took place during the hercynian metamorphism later during the retrograde metamorphism pyrite replaced pyrrhotite and arsenopyrite replaced lollingite large scale compositional inhomogeneities survived metamorphism from pyroxene to amphibolite facies a hydrothermal source of s has been postulated for the coma fosca and sant miquel outcrops sulphur in these deposits is from leaching of sulphides from the underlying rocks in the roca de ponent outcrop and in the sant bernat series sulphur was derived from a hydrothermal source and from biogenic reduction of seawater sulphate the contribution of the latter source increased with time biogenic reduction of seawater sulphide in a closed or semi closed system for sulphate is considered responsible of the high 34s values of pyrite from the uppermost part of the sant bernat series based on textural and isotopic evidence we propose an exhalative origin for the precious metals cogenetic with the stratiform sulphides

water masses in the humboldt current system properties distribution and the nitrate deficit as a chemical water mass tracer for equatorial subsurface water off chile abstract three sections are used to analyze the physical and chemical characteristics of the water masses in the eastern south pacific and their distributions oceanographic data were taken from the scorpio may june 1967 piquero may june 1969 and krill june 1974 cruises vertical sections of temperature salinity dissolved oxygen nitrate nitrite phosphate and silicate were used to analyze the water column structure five water masses were identified in the zone through t s diagrams subantarctic water subtropical water equatorial subsurface water antarctic intermediate water and pacific deep water their proportions in the sea water mixture are calculated using the mixing triangle method vertical sections were used to describe the geographical distributions of the water mass cores in the upper 1500 m several characteristic oceanographic features in the study area were analyzed the shallow salinity minimum displacement towards the equator the equatorial subsurface salinity maximum associated with a dissolved oxygen minimum zone and a high nutrient content displacement towards the south and the equatorward intermediate antarctic salinity minimum associated with a dissolved oxygen maximum the nitrate deficit generated in the denitrification area off peru and northern chile is proposed as a conservative chemical tracer for the equatorial subsurface waters off the coast of chile south of 25 s

long term hydrographic changes at 52 and 66 w in the north atlantic subtropical gyre caribbean abstract in july september 1997 two hydrographic lines were done in the western n atlantic along longitudes of 52 and 66 w as part of the woce one time hydrographic survey of the oceans each of these two lines approximately repeated earlier ones done during the international geophysical year s igy and the mid 1980s because of this repeated sampling long term hydrographic changes in the water masses can be examined in this report we focus on temperature and salinity changes within the subtropical gyre mainly between latitudes of 20 and 35 n and compare our results to those presented by bryden et al 1996 who examined changes along a zonal line at 24 n most recently occupied in 1992 since this most recent 24 n section in 1992 substantial changes have occurred in the western part of the subtropical gyre at the depths of the labrador sea water lsw in particular we see clear evidence for colder fresher labrador sea water throughout the gyre on our two recent sections that was not yet present in 1992 at similar longitudes along 24 n at shallower depths inhabited by waters that are an admixture of mediterranean mw and antarctic intermediate waters aaiw our recent survey shows an increase in salinity which can only be attributed to changes in water masses on potential temperature or neutral density surfaces furthermore waters above the mw aaiw layer and into the deeper part of the main pycnocline have continued to become saltier and warmer throughout the 40 year period spanned by our sections these latter changes have been dominantly due to a vertical sinking of density surfaces as t s changes in density surfaces are small but depths of individual t s horizons have increased with time the net change since the igy shows a mean temperature increase between 800 and 2500 m depth at a rate of 0 57 c century with a corresponding steric sea level rise of 1 mm yr and a net downward heave with small values near the top and bottom and a maximum rate of 2 7 m yr at 1800 m depth changes in the deep caribbean indicate a warming since the igy due to temperature increases of the inflowing source waters in the subtropical gyre at 1800m depth but no significant change in the deep salinity

temperature and salinity increase in the eastern north atlantic along the 24 5 n in the last ten years 1 the ocean section along the 24 5 n has been one of the most frequently sampled of the world s oceans it has been sampled in 1957 1981 1992 and 1998 previous works showed a progressive warming and salt increase of the thermocline and intermediate waters from around 800 m to 3000 m the maximum warming rate was 0 009 c yr at 1100 m the eastern part of this section was sampled in 2002 the warming of the main thermocline has continued at a higher rate 0 042 yr at 400 m in the last 10 years salinity has also increased along the thermocline conserving the 1992 s relationship from 100 to 1000 db the warming is mainly due to downward displacement of the isopycnals though some cooling along isopycnals is also observed in the upper 350 db

anoxic sediments an important environment for pge an overview anoxic sediments and metasediments have been recently recognized as important host environments for the platinum group elements pge economically significant pge concentrations have been reported from marine metal rich black shales in china yukon canada and poland these ore bearing horizons are characterized by extremely restricted vertical and sometimes larger horizontal extents they are associated with the evolution of intracontinental rifting structures without any magmatic activity suggesting a possible driving mechanism for mineralization processes complex pge associations including a significant relationship of pd and pt with ni bi se y and also with sb cu co au u and f are suggested using the results of a new statistical evaluation of available geochemical data these occurrences show more common features with other hydrothermal pge deposits the rift volcanic related marine metal rich black shales of the czech republic and finland however display lower pge values the mineralized layers are much thicker with a typically limited horizontal extent showing a close association with volcanic centres pd reveals a strong correlation with ni zn au and v pt exhibits a highly significant link with the cu and mo phases low average nicu ratios and pge au chondrite normalized patterns are similar to those of some magmatic pge deposits hosted in mafic and ultramafic rocks it is very likely that organic matter played an important role in the genesis of pge accumulations in metal rich black shales in both rift and rift volcanic related environments

multidecadal variability of north atlantic temperature and salinity during the twentieth century abstract substantial changes occurred in the north atlantic during the twentieth century here the authors demonstrate through the analysis of a vast collection of observational data that multidecadal fluctuations on time scales of 50 80 yr are prevalent in the upper 3000 m of the north atlantic ocean spatially averaged temperature and salinity from the 0 300 and 1000 3000 m layers vary in opposition prolonged periods of cooling and freshening warming and salinification in one layer are generally associated with opposite tendencies in the other layer consistent with the notion of thermohaline overturning circulation in the 1990s widespread cooling and freshening was a dominant feature in the 1000 3000 m layer whereas warming and salinification generally dominated in the upper 300 m except for the subpolar north atlantic where complex exchanges with the arctic ocean occur the single signed basin scale pattern of multidecadal variability is evident from decadal 1000 3000 m temperature and salin

circumpolar deep water circulation and variability in a coupled climate model abstract the natural variability of circumpolar deep water cdw is analyzed using a long term integration of a coupled climate model the variability is decomposed using a standard eof analysis into three separate modes accounting for 68 and 82 of the total variance in the upper and lower cdw layers respectively the first mode exhibits an interbasin scale variability on multicentennial time scales originating in the north atlantic and flowing southward into the southern ocean via north atlantic deep water nadw salinity dipole anomalies appear to propagate around the atlantic meridional overturning circulation on these time scales with the strengthening and weakening of nadw formation the anomaly propagates northward from the midlatitude subsurface of the south atlantic and sinks in the north atlantic before flowing southward along the cdw isopycnal layers this suggests an interhemispheric connection in the generation of the first cdw variability mode the second mode shows a localized s varia

two sulphur isotope provinces deduced from ores in the mount isa eastern succession australia the sulphur isotopic characteristics of ore deposits in the australian mount isa eastern succession are not well known unlike those of the western succession in this study new detailed analyses are provided for recently discovered eastern succession mineralisation such as the starra and osborne bif hosted cu au ores the dugald river sediment hosted pb zn prospect and four vein hosted cloncurry style cu au deposits hampden mt elliot swan mt cobalt and the answer mine all of the deposits of the eastern succession have 34ssulphide between 8 and 9 regardless of their genesis empirically a moderate 34s range averaging close to 0 characterises starra style cu au and pegmont pb zn bif ores whereas shear and vein style cu mineralisation populations are tighter and do not average close to 0 this is a particularly surprising result for dugald river where a larger isotopic variation more typical of stratiform sediment hosted pb zn ores in the region might have been expected by comparison western succession stratiform pb zn and vein style cu deposits span a huge range of 15 to 51 large sulphur isotope ranges typify sulphate evaporite or organic sulphur rich sedimentary successions the lack of such variation in the eastern succession in turn suggests that primary evaporite sequences there were halite dominated but sulphate poor and or contained only limited volumes of organic sulphur rich sediment eastern succession sequences were therefore less likely hosts for giant stratiform pb zn deposits because of their paucity of sulphur although local sulphur sources permitted small deposits such as dugald river to develop sedimentary conditions were more favourable for the development of sulphur poor synsedimentary hydrothermal systems such as starra osborne and pegmont although sulphur isotope evidence is equivocal about the origin of these epigenetic deposits close to the williams batholith mt dore hampden owe their clustering around 0 to their granitic fluid source

decadal water mass variations along 20 w in the northeastern atlantic ocean abstract water mass variations in the northeastern atlantic ocean along 20 w are analyzed with pentadal resolution over the past 15 years using data from four repeat occupations of a meridional hydrographic section running south from iceland the section was sampled in 1988 1993 1998 and 2003 the results are interpreted in the context of changes in air sea forcing ocean circulation and water properties associated with the north atlantic oscillation nao the nao index oscillated around zero from 1984 to 1988 was strongly positive from 1989 to 1995 after which it shifted to lower positive and occasionally negative values from 1996 to 2003 previously published studies suggest that after the 1995 1996 shift of the nao the subpolar gyre largely retreated to the northwest in the northeastern atlantic ocean resulting in an increasingly southeastern character of local water masses with time water property changes extending from the subpolar mode water spmw just below the seasonal pycnocline through the density range shared by mediterranean outflow water and subarctic intermediate water saiw along 20 w are consistent with changes in wind driven ocean circulation and air sea heat flux associated with shifts in the nao especially after accounting for ocean memory after periods of lower nao index the spmw is warmer saltier and lighter at these same times large increases of apparent oxygen utilization aou and potential vorticity are found at the spmw base consistent with spmw ventilation to lighter densities during lower nao index periods deeper and denser in the water column the cold fresh and dense saiw signature within the permanent pycnocline that was most strongly present in 1993 near the culmination of a period of high nao index is much reduced in 1988 and 1998 in 2003 after a prolonged period of lower nao index increasing influence of warmer saltier subtropical waters is clear within the permanent pycnocline the deep penetration of the changes implies that they are caused primarily by circulation changes resulting from nao associated wind shifts but changes in air sea heat flux could also have played a role

global sea level trend in the past century data derived from tide gauge stations throughout the world indicate that the mean sea level rose by about 12 centimeters in the past century the sea level change has a high correlation with the trend of global surface air temperature a large part of the sea level rise can be accounted for in terms of the thermal expansion of the upper layers of the ocean the results also represent weak indirect evidence for a net melting of the continental ice sheets

a twenty year reversal in water mass trends in the subtropical north atlantic temperature and salinity changes have been compared along three repeat sections at 36 n in the north atlantic the principal changes cooling of the upper waters and warming of the intermediate waters observed between 1959 and 1981 were reversed between 1981 and 2005 the controlling mechanisms for the changes over the two time periods differed through the water column neutral density surfaces over the upper 800 m were firstly uplifted and secondly depressed by typically 50 m which is broadly consistent with the changes in thermocline thickness implied by the temporal changes in ekman pumping in contrast the intermediate waters 800 2500 m firstly became warmer and saltier and secondly became cooler and fresher this change in the intermediate waters was controlled by water mass changes along neutral density surfaces suggesting a change in the source waters principally labrador sea water and mediterranean outflow water

warming and circulation change in the eastern south pacific ocean deep ocean temperature salinity and dissolved oxygen observations in the eastern south pacific ocean collected during the late austral fall in 1995 are compared with observations made there 28 years earlier during the same season and similar el nino southern oscillation phase warming observed above 800 m at 43 s reflects the production of warmer subantarctic mode water in recent decades warming observed above 1600 m at 28 s is due to downward isotherm displacement and southward movement of water masses by 100 200 km as revealed by joint analysis of temperature and oxygen data such changes would be expected for a weaker subtropical gyre in the south pacific an observed oxygen decrease between about 1800 m and 2900 m at 28 s may indicate enhanced southward boundary current flow at mid depths off chile

satellite altimetry the marine geoid and the oceanic general circulation for technical reasons the general circulation of the ocean has historically been treated as a steady laminar flow field the recent availability of extremely highaccuracy and high precision satellite altimetry has provided a graphic demonstration that the ocean is actually a rapidly time evolving turbulent flow field to render the observations quantitatively useful for oceanographic purposes has required order of magnitude improvements in a number of fields including orbit dynamics gravity field estimation and atmospheric variability with five years of very high quality data now available the nature of oceanic variability on all space and time scales is emerging including new findings about such diverse and important phenomena as mixing coefficients the frequency wavenumber spectrum and turbulent cascades because the surface elevation is both a cause and consequence of motions deep within the water column oceanographers soon will be able to provide general circulation numerical models tested against and then combined with the altimeter data these will be complete three dimensional timeevolving estimates of the ocean circulation permitting greatly improved estimates of oceanic heat carbon and other property fluxes

a sulphur isotopic study of the bleikvassli zn pb cu deposit nordland northern norway the bleikvassli zn pb cu deposit occurs in the uppermost allochthon in the caledonides of northern norway the orebody is enclosed in amphibolite facies schists and gneisses underlain by amphibolites and it has been classified as a sediment hosted massive sulphide sedex deposit the stratiform ore is dominantly pyritic with a basal layer of pyrrhotitic ore sulphide veins occur in the footwall the orebody generally has a limited range of 34s from 0 3 to 4 5 x 2 4 1 2 1 n 26 the lowest 34s values 0 3 2 3 were found in sulphide veins in the footwall and vent proximal stratiform ore more distal pyritic zn pb ore has heavier average 34s values up to 4 5 the ore sulphides were deposited from a hydrothermal solution with 34s about 2 perhaps with the incorporation of a minor portion of sulphide from the ambient seawater the hydrothermal solution probably acquired most of its sulphide from the underlying mixed lithology notably basaltic rocks sulphide produced by thermochemical reduction of seawater in the deep conduit system may also have been incorporated bacteriogenic sulphide is not likely as a major source of ore sulphur in the massive ore sulphide incorporated in distal pyrite which have 34s from 12 to 10 could have formed either by oxidation of the hydrothermal sulphide or by bacterial reduction of seawater sulphate in the depositional environment exchange of sulphur isotopes probably took place only on a localized scale during caledonian metamorphism the bulk sulphur isotopic composition of the ore being preserved in a hand specimen scale

calculating shoreline erosion potential using nearshore stratigraphy and sediment volume outer banks north carolina 1 despite the acknowledged influence of coastal geological framework on the behavior of beaches and barrier islands and a wealth of geological and bathymetric observations from the inner shelf quantitatively connecting those observations to shoreline behavior has been difficult nearshore geologic and morphologic variability described by recent research is not well represented by conventional geologic parameters such as mean grain size and shoreface slope used in most shoreline change models we propose that total nearshore sediment volume as calculated to a continuous seismic reflection surface provides a flexible and robust metric for use in the prediction of shoreline change this method of determining the volume of sediment in the nearshore accounts for three dimensional sandbar morphologies and heterogeneous seafloor sediments the decadal scale shoreline change rate for northeastern north carolina is significantly correlated to the volume of sediment in the nearshore when a geologically defined base is used in volume determinations suggesting that the shallow stratigraphic framework of transgressive coasts is an important influence on decadal shoreline behavior nearshore sediment volume was overestimated when an arbitrary depth constant baseline was used and was not correlated to decadal shoreline change this implies that a volume metric which accounts for both framework geology and variable seafloor morphology better represents the geologic character of the shoreface and may help to improve existing models of shoreline change an empirical model of regional shoreline erosion potential demonstrates the importance of incorporating nearshore sediment volume shallow framework geology and surface morphology when predicting seasonal to decadal shoreline evolution

southwest pacific ocean water mass changes between 1968 69 and 1990 91 abstract water mass changes are estimated in the southwest pacific ocean by comparing a meridional hydrographic section along 170 w between 60 s and the equator occupied in 1968 69 during the southern cross cruise and again in 1990 during a noaa climate and global change cruise another comparison is made using a hydrographic section along 35 s between the date line and 169 w occupied in 1969 during usns eltanin cruise 40 and again in 1991 during a mapkiwi cruise the most robust change consists of cooling and freshening on isopycnals with peak differences exceeding 1 0 c 0 25 pss at the base of the subtropical thermocline the cooling and freshening starts above the stratification minimum of the subantarctic mode water and persists to below the salinity minimum of the antarctic intermediate water amplitudes are largest at 48 s near where these water masses subduct and decay toward 20 s near the axis of the subtropical gyre this change is likely the result of surface warming and or freshening

influence of glacial isostatic adjustment on tide gauge measurements of secular sea level change modem tide gage records of secular sea level change are strongly contaminated by the ongoing influence of glacial isostatic adjustment in this paper we employ an accurate high resolution model of the glacial isostatic adjustment process to filter this signal from time series consisting of annual mean heights observed on over 500 tide gages from which records of duration longer than 10 years are available these records are all contained in the archive of the permanent service for mean sea level at bidston in the united kingdom prior to removal of the isostatic adjustment contamination from these records the secular sea level change signal is seen to exhibit both rising and falling levels depending upon geographic location with regions of falling level corresponding to those that were ice covered during the last glaciation event of the present ice age after filtering the geographic heterogeneity in rates is considerably reduced so much so that a globally coherent component consisting of a rise of sea level at a rate of 2 4 0 9 mm yr 1 is revealed this could conceivably be driven by the greenhouse effect although no particular mechanism has been unambiguously identified by our analyses we investigate the impact of a number of different variants of the analysis procedure upon the inferred global signal

mar geol erratum to geology of the wrightsville beach north carolina shoreface implications for the concept of shoreface profile of equilibrium 126 1995 271 287

observed property changes in eastern south pacific antarctic intermediate water 1 we compared potential temperature and salinity of antarctic intermediate water along 32 30 s from the coast of chile to the central south pacific ocean between 2003 and 1992 based on two vertically and horizontally high resolution repeat sections each being 6795 km long the temperature of antarctic intermediate water considering the entire body of the water mass along the section increased by 0 048 c and salinity by 0 002 the increase in salinity could be explained by a slight shift in the evaporation precipitation balance of the south pacific ocean

optimal estimation of hydrographic station data and derived fields abstract optimal estimation is applied to contouring and analysis of hydrographic sections measured fields such as temperature and salinity and derived fields such as geostrophic velocity are decomposed into large scale and small scale components first a heavily sampled basin scale field is estimated and subtracted from the data a small scale field barely resolved by the hydrography is then found from the residuals the power and utility of the technique are illustrated by means of examples using a short section from the straits of florida and a transatlantic section along 24 n

ocean warming and sea level rise along the southwest u s coast hydrographic time series data recorded during the past 42 years in the upper 500 meters off the coast of southern california indicate that temperatures have increased by 0 8 c uniformly in the upper 100 meters and that temperatures have risen significantly to depths of about 300 meters the effect of warming the surface layer of the ocean and there by expanding the water column has been to raise sea level by 0 9 0 2 millimeter per year tide gauge records along the coast are coherent with steric height and show upward trends in sea level that vary from about 1 to 3 millimeters per year

recirculating components to the deep boundary current of the northern north atlantic abstract the meridional overturning system of the north atlantic is conventionally thought of as transporting warm water 4 c to high latitudes and covd water to low latitudes the northern cold water sources for this system are dense overflow from the nordic seas and less dense water from the labrador sea lsw the overflow components are carried westward by a deep northern boundary current dnbc that is shown here actually to begin southeast of the overflow regions the dnbc lies along the southern side of a system of islands and submarine ridges that divides the nordic seas from the subpolar basins the overflows act to increase the transport of the dnbc and this transport is further increased through the entrainment of warm waters once inside the labrador sea the dnbc is joined by lsw before continuing south to low latitudes as a cold deep western boundary current dwbc however published transport estimates are larger than can be explained by warm water entrainment alone thus indicating entrainment also of recirculating cold components the subject of this paper their sources are shown to be the lsw and cold abyssal waters originating from the southern hemisphere the lsw is entrained downward into the denser part of the dnbc and laterally into the upper part of the dwbc whereas the cold abyssal waters are supplied by an eastern intensified northward flow in the eastern atlantic that serves as the initial source of the dnbc and by a similar northward flow in the western atlantic the meridional overturning system described includes recirculations and poleward transport of cold water in addition tothe components described by the conventional system the cold abyssal waters in both the eastern and western basins have relatively low levels of oxygen and high concentrations of silicate reflecting their southern origin but their influence in the northwestern atlantic is somewhat obscurred by strong recirculating cyclonic gyres in the newfoundland and labrador basins this influence is detected by a deep silicate maximum extending poleward from the mid latitude western atlantic through the two gyres with eastern concentration and recirculating back diluted toward the south in the dwbc within the respective basins such a maximum also extends northward through the irminger basin into the dnbc but there is an ambiguity as to whether this is a direct extension of the signal from the south in the western basin or if it comes from the mid latitude eastern basin by way of westward flow through the charlie gibbs fracture zone it is perhaps consequence of both estimates of the volume transports of the various recirculating cold components indicate that they supply about as much water to the deep boundary currents as do the combined cold water sources in the north

spin up and breakdown of source driven deep north atlantic flow over realistic bottom topography in this study we examine the time dependent behaviour of the deep north atlantic dynamics we use a 1 layer nonlinear shallow water model with realistic topography and high spatial resolution it is driven by an inflow of deep water from a northern source and by parameterized density exchange processes at the interface the evolving circulation pattern is complex the mid atlantic ridge with the charlie gibbs fracture zone has a fundamental influence on the large scale flow field a reduction of the inflow causes a temporary reversal of the interior currents the perturbation travels along the geostrophic contours the response times of the currents for the spin up and breakdown experiments are of the order of years they differ for different areas of the north atlantic ocean the area which is affected last by the perturbation is the northwesternmost interior corner which is close to the position of the source

preservation of original hydrothermal δ34s values in greenschist to upper amphibolite volcanogenic massive sulfide deposits laser microprobe analysis of sulfide mineral pairs from several volcanogenic massive sulfide vms stockwork feeder zones shows that greenschist to upper amphibolite facies metamorphism will reset sulfur isotope thermometers if the mineral grains are in direct grain to grain contact however discrete monomineralic sulfide grains that are completely encased in quartz matrix and that are not in direct grain to grain contact with one another will preserve their original hydrothermal sulfur isotope compositions because exchange during metamorphism is inhibited by the enclosing quartz calculated temperatures from three separate vms systems range from 170 to 424 c for sulfide pairs that are not in direct grain to grain contact and are consistent with independently determined temperature estimates sulfide pairs that are in direct contact yield unreasonably low temperatures indicative of reequilibration during metamorphism and subsequent slow cooling

water property and current distributions along the whp p9 section 137 142 in the western north pacific the japan meteorological agency carried out full depth high resolution hydrographic measurements in july august 1994 along the 137 142 e line as a contribution to the world ocean circulation experiment the line spans the subtropical and tropical regions of the western north pacific with a full set of water mass and current distributions at 28 n to the south of the kuroshio recirculation there exists an eastward current distinct from the currents associated with the subtropical fronts the eastward current is characterized by the meridional thermal gradient extending down to 1500 m depth deep silicate has a meridional boundary at 25 n forming two cores of the maximum to the north and south of the boundary the northern core centered at 28 n is meridionally coincident with other property extrema indicating an inflow from the northwest pacific basin down to 2000 m depth the southern core centered at 16 n suggests another westward inflow from the east mariana basin to the west mariana basin a broad isopycnal depression at middepths and bottom water properties over the shikoku and west mariana basins indicate a near bottom circulation along which the inflow water through the yap mariana junction at 12 n fills the west mariana basin and then spreads to the shikoku basin and philippine basin successively a part of the bottom water from the south pacific bifurcates around the yap mariana junction and enters the west caroline basin via the yap trench this supports another path of deep water inflow to the philippine basin from the southernmost channel at 4000 m depth

preliminary sulphur isotope data of diagenetic and vein sulphides in the lower palaeozoic strata of ireland and southern scotland implications for zn pb ba mineralization genetic models for many irish lower carboniferous zn pb ore deposits invoke a dual supply of sulphide the dominant source is from the bacteriogenic reduction of lower carboniferous seawater sulphate but a significant minor supply is derived from deep seated sources the 34 s range of the latter component varies among the deposits from the lightest range of 15 to 0 at keel to the heaviest of 4 to 14 4 in the navan tatestown area we hypothesize that such sulphur is leached mainly from diagenetic sulphide minerals in the underlying lower palaeozoic sediments 6 s of pyrite in the silurian ordovician moffat shales 17 1 to 0 6 and of sphalerite and galena in lower palaeozoic hosted veins at salterstown 8 7 to 4 5 and wanlockhead 10 3 to 5 1 are consistent with the hypothesis below the navan ore deposit lower palaeozoic shales containing minor diagenetic pyrite with a very wide range in 34 s have been found 34 s is typically heavy 16 but extreme values up to 62 are encountered the general enrichment in 34 s is in accord with the noticeably heavy isotopic composition of deep seated sulphur in the navan orebody and its tatestown satellite our preliminary results therefore suggest that geographical variations in the 34 s range of lower palaeozoic diagenetic write may have contributed to the isotopic variation in the deep seated sulphur among the irish deposits

micro analysis of sulfur isotope ratios and zonation by laser microprobe the university of wisconsin laser microprobe mass spectrometer system combines high spatial resolution with precise accurate and rapid analysis of sulfur isotope ratios spot sizes of 100 200 m are routine and much higher spatial resolution may be possible analytical precision ranges from 1 0 15 pyrite pyrrhotite sphalerite to 1 0 43 galena chalcopyrite comparison of laser microprobe and conventional combustion analyses indicates that laser 34s values are approximately equal to or lower than combustion values for these minerals and an empirical correction of 0 1 sphalerite to 1 4 pyrrhotite is required variations in 18o of so2 laser power density and burn duration affect the magnitude of this correction thus consistent technique is critical natural samples were analyzed by laser microprobe to evaluate the extent of sulfur isotope ratio zonation coexisting sulfide mineral pairs from the rua cove mine alaska show that isotopic equilibrium exists in the stockwork feeder zone while disequilibrium characterizes coexisting pairs from the overlying more rapidly cooled massive sulfide blanket conventional sulfur isotope extraction data on these samples are not valid due to the fine grained intergrown nature of the sulfide phases which precludes satisfactory mineral separation isotopically homogeneous sphalerite and pyrite crystals were found in samples from the amphibolite facies balmat mine while isotopically heterogeneous pyrite crystals were found in a sample from the upper greenschist facies sullivan mine sulfur isotope zonation up to 2 9 in 200 m was found in banded sphalerite blacksmoker chimney material from the bayda mine oman retrograde sulfides from the marcy anorthosite massif vary by 4 2 over 1 cm and finely disseminated sulfides from an amphibolite granulite facies transition zone sample southern india are in disequilibrium across the 25 cm facies transition these results show that sulfur isotope homogeneity may be attained in the cores of annealed high grade metamorphic minerals while lower temperature retrograde or hydrothermally deposited minerals are often isotopically zoned due to temporal variations in fluid chemistry and temperature

iridium and other platinum group elements as geochemical markers in sedimentary environments iridium anomalies are commonly used as indicators of extraterrestrial processes which caused global extinctions however platinum group element pge anomalies may result from several different processes both syn and postdepositional acting separately or jointly the sources and processes of enrichment involved are extraterrestrial asteroid comet cosmic dust impact ejecta volcanogenic pge rich condensates precipitation from seawater low sedimentation rate anoxic conditions microbial concentration dissolution reprecipitation exhalative hydrothermal leaching transport and precipitation at a redox boundary geochemical characteristics of pge and accompanying elements in sediments can be used to identify the contributions of some specific sources and processes 1 extraterrestrial chondritic ru ir and os ir ratios low 187os 186os ratio high ir compared to pt pd and au 2 volcanogenic high iridium and se as sb and in contents 3 exhalative hydrothermal high au pd and pt relatively low ir contents 4 precipitation from seawater high pt and low pd contents also high cd and ag contents under anoxic conditions and 5 reduction from intermediate and low temperature solutions high pge and cu or mo u ni contents

unaccounted role of mediterranean water in the drawdown of anthropogenic carbon a three sided box medbox comprising the strait of gibraltar 24 41 n east of 22 w was constructed using hydrographic and chemical data from three world ocean circulation experiment cruises in 1997 1998 an extended optimum multiparameter omp analysis resolves the water mass structure in the medbox the mass transport is estimated from data and models warranting mass conservation and no deep water formation within the region combining the mass transport the omp analysis and the spatial distribution of anthropogenic carbon cant some relevant questions about the mediterranean water mw formation transport and role in the global co2 cycle are resolved mw is produced at a rate of 2 7 0 2 sv in the eastern north atlantic it entrains 2 3 sv of central waters during its formation including also remnants of antarctic intermediate water the main advection route of mw is northward close to the iberian margin 2 2 sv while about 0 5 sv are exported into the subtropical eastern north atlantic the eastern north atlantic within the medbox is a strong region of air sea cant uptake 0 7 0 7 mmol m 2 d 1 where cant is accumulated at a rate of 66 21 kmol s 1 0 025 gtc yr 1 17 are taken up through the air sea interface and the rest is advected into the area by the circulation the entrainment of central waters to form mw drives a drawdown of 151 14 kmol s 1 0 06 gtc yr 1 from the surface to intermediate levels and 88 8 kmol s 1 0 03 gtc yr 1 are exported with mw into the north atlantic mainly by the horizontal eddy circulation

a 170 year sr ca and ba ca coral record from the western pacific warm pool 2 a window into variability of the new ireland coastal undercurrent 1 a porites coral from new ireland 2 5 s 150 5 e at the heart of the pacific warm pool records variations of ba ca back to the early 1820s the new ireland coastal undercurrent which flows along the north coast and transports high nutrient thermocline waters is thought to be the main source of the ba enrichment observed in the coral during el nino between the 1850s and the 1960s frequent large ba peaks indicate that nutrients were available during both phases of el nino southern oscillation enso during la nina ba could be advected along the south equatorial current also during this period clusters of ba ca peaks at nearly decadal timescale generally coincide with the return time of a strong el nino in accord with the high decadal variance of nino3 sea surface temperatures ba enrichment in this coral primarily reflects the stratification in the thermocline that controls vertical mixing the coral records long term changes in those properties affecting nutrients in surface waters with reduced ba after the 1960s and even less between 1823 and 1850 these reductions are tentatively attributed to the high rate of warming at the end of the dalton minimum and since the mid 20th century an ensuing weakening of the trade winds may have produced a more stratified equatorial thermocline hindering the transport of ba and nutrients from the undercurrent to the shallow coastal waters north of new ireland

annual and interannual changes on a reef fringed pocket beach kailua bay hawaii abstract historical aerial photographs and topographic survey sheets are used to establish a 70 year shoreline history 1926 1996 for kailua beach oahu hawaiian islands the shoreline has migrated seaward over this period at an average rate of 0 5 m yr with a maximum net accretion along the beach of 58 7 m and a maximum net erosion of 13 2 m net accretion has taken place even while sea levels have risen on the order of 0 1 m semi annual and monthly beach profile surveys 1995 1999 at seven transects reveal short term variations of shoreline position sand volume and beach shape a relationship between beach width and corresponding sand volume fluctuations established from the beach profile data is applied to the historical shoreline change data to establish a history of sand volume fluctuations results show that kailua has experienced a net accretion of 673 000 m3 of sand over the period 1926 1996 with average annual rates of volume change varying between 6 8 m3 m yr and 0 1 m3 m yr the most recent period 1989 1996 shows a net volume increase of 41 000 m3 given the lack of sand inputs at the ends of the beach exchange with offshore deposits is a likely mechanism for long term accretional trends seasonal fluctuations in kailua beach morphology dominate the variability with a response to seasonal wave state that varies along the length of the beach in magnitude and sign at least four alongshore zones are observed with the first and third zones exhibiting high low sand volumes during the summer winter and the second and fourth zones exhibiting opposite behavior with high low volumes during the winter summer although seasonal sand accumulation varies along the beach the overall beach profile is largely maintained moreover changes in sand volume occur in phase over the subaqueous and subaerial sections of the beach this behavior suggests that longshore rather than cross shore sand transport is important at annual time scales a simple seasonal transport pattern is proposed to account for these observed fluctuations which depends in part on the topography of the offshore reef

a simple model for the spatially variable coastal response to hurricanes abstract the vulnerability of a beach to extreme coastal change during a hurricane can be estimated by comparing the relative elevations of storm induced water levels to those of the dune or berm a simple model that defines the coastal response based on these elevations was used to hindcast the potential impact regime along a 50 km stretch of the north carolina coast to the landfalls of hurricane bonnie on august 27 1998 and hurricane floyd on september 16 1999 maximum total water levels at the shoreline were calculated as the sum of modeled storm surge astronomical tide and wave runup estimated from offshore wave conditions and the local beach slope using an empirical parameterization storm surge and wave runup each accounted for 48 of the signal the remaining 4 is attributed to astronomical tides indicating that wave driven process are a significant contributor to hurricane induced water levels expected water levels and lidar derived measures of pre storm dune and berm elevation were used to predict the spatially varying storm impact regime swash collision or overwash predictions were compared to the observed response quantified using a lidar topography survey collected following hurricane landfall the storm averaged mean accuracy of the model in predicting the observed impact regime was 55 4 a significant improvement over the 33 3 accuracy associated with random chance model sensitivity varied between regimes and was highest within the overwash regime where the accuracies were 84 2 and 89 7 for hurricanes bonnie and floyd respectively the model not only allows for prediction of the general coastal response to storms but also provides a framework for examining the longshore variable magnitudes of observed coastal change for hurricane bonnie shoreline and beach volume changes within locations that experienced overwash or dune erosion were two times greater than locations where wave runup was confined to the foreshore swash regime during hurricane floyd this pattern became more pronounced as magnitudes of change were four times greater within the overwash regime than in the swash regime comparisons of pre storm topography to a calm weather survey collected one year after hurricane floyd s landfall show long term beach volume loss at overwash locations here the volume of sand eroded from the beach was balanced by the volume of overwash deposits indicating that the majority of the sand removed from the beach was transported landward across the island rather than being transported offshore in overwash locations sand was removed from the nearshore system and unavailable for later beach recovery resulting in a more permanent response than observed within the other regimes these results support the predictive capabilities of the storm scaling model and illustrate that the impact regimes provide a framework for explaining the longshore variable coastal response to hurricanes

variable bottom water in the western mediterranean basin the deep water of the western mediterranean has long been considered to have practically constant values of s and between 1909 1910 the thor expedition and the 1970 cruise of the jean charcot the deep water at more than 1800 m depth showed very little variation the small changes which appeared through the years could be due in part to changes in instrumentation analysis and methods of sampling in 1972 and 1973 during the medoc cruises a bottom layer of 200 300 m thickness was found its temperature and salinity showed a small gradient producing at the bottom an increase of potential temperature of about 0 01 to 0 02 c and an increase in salinities of about 0 010 00 relative to a minimum of and s in the deep water at 1800 2000 m these minima of and s were found to be homogeneous horizontally at all stations occupied in the medoc area and in the ligurian sea in 1973 interestingly the bottom layer was not present in 1974 however in november 1981 during the cruise mediprod iv the variable bottom water was again present extending from the ligurian sea and medoc areas along the western coasts of corsica and sardinia to the eastern alboran sea in most cases the maximum values of and s were recorded at the bottom and were higher than the 1973 values by about 0 03 c and up to 0 0150 00 but with a rather high spatial variability by february 1982 cruise dyome ii the situation had become more complicated not only was a layer of minimum and s present but it was underlain by a layer of maximum and s below which a decrease appeared producing a new minimum at the very bottom in addition a number of stations displayed higher values of by about 0 05 c and of s by about 0 0150 00 in the layers of minimum and maximum characteristics as well as on the bottom in contrast to the situation in 1973 high spatial variability was found in the deep layering the variability may have been due to patchy deep convention activity possibly in the ligurian sea the phenomenon of variable bottom water and the processes which produce it may be relevant to our understanding of water mass formation

ore depositional process in the navan zn pb deposit ireland the navan zn pb deposit in ireland is hosted by a lower carboniferous carbonate dominated sedimentary sequence in excess of 97 percent of the ore is hosted by a courceyan shallow water succession termed the pale beds the ore occurs as complex strata bound tabular lenses often dislocated by faulting and truncated by a submarine erosional slide structure above this surface unconformity lies the economically minor but genetically important conglomerate group ore hosted by a complex debris flow termed the boulder conglomerate timing constraints on the mineralization can be defined by the relationship to the erosion surface and style of mineralization suggesting a late chadian or early arundian age approximately 345 ma the bulk of the ore formed below the erosion surface in the semilithified to lithified pale beds ore the mineralogy of the economic ores is relatively simple being dominated by sphalerite and galena in a 5 1 ratio pyrite and marcasite are present in subordinate amounts in the majority of the pale beds ore but dominate the conglomerate group ore and the pale beds ore immediately below the erosion surface particularly lens 2 1 gangue minerals are dominated by calcite dolomite and barite the morphology of the mineralization reflects subsea floor emplacement the orebody occurs as numerous strata bound horizons ranging from intense high grade massive sulfides to lower grade sulfide layers separated by barren limestone in all cases there is strong evidence for tectonic disruption during ore deposition sulfides were dominantly deposited as open space growth and replacement of host rock open space textures include dendritic skeletal stalactitic internal sediment geopetal and coarse bladed forms the general absence of coarse euhedral cavity lining textures or substantial collapse brecciation suggests that large cavities were not present prior to mineralization replacement textures range from delicate pseudomorphs of biodasts to more destructive granular styles sulfide sulfur isotope analyses exhibit two dominant groupings of delta 34 s from around 23 to 5 and 0 to 15 per mil respectively and a third minor grouping around 32 to 28 per mil at least two sources of sulfur are invoked values around 23 to 15 per mil are considered to be the result of bacteriogenic reduction of lower carboniferous seawater sulfate approximately 20ppm with a characteristic fractionation around 35 to 45 per mil away from sulfate this is the most common range of delta 34 s in the deposit values around 8 to 15 per mil are interpreted to be hydrothermal sulfide transported with the metal bearing fluid mixing of these two components is inferred from the isotopic data and trends in the mineral paragenesis barite has a mean of delta 34 s 21 or 2 per mil which falls within the range generally recognized for lower carboniferous seawater sulfate we consider that contemporaneous seawater sulfate was the dominant source of sulfur in the barite at navan implying that seawater accessed the pale beds at the time of mineralization

how does underlying geology affect coastline change an initial modeling investigation 1 conceptual geologic framework models predict that areas of the coast underlain by a weak or very fine grained lithology retreat landward faster than adjacent more resistant or coarser grained segments these apparently commonsense predictions seem inconsistent with observations that sandy coastlines underlain by heterogeneous lithology remain fairly smooth we have developed a numerical model to explore the interaction between shoreface lithology effects and alongshore transport processes on scales greater than years and kilometers shoreline indentations or sections of the coast that are slightly landward of adjacent sections tend to form in the model where the shoreface weathers more rapidly or is composed of finer grained material however alongshore transport tends to fill in these indentations slowing the weathering rates there while increasing them in adjacent areas where mobile sediment is preferentially removed over the long term this leads to an alongshore uniform retreat rate subtle shoreline undulations reflecting the heterogeneous geologic framework exist in the model but their amplitude reaches a steady state rather than increasing with time compositional heterogeneities determine the morphology of the coast while weathering rate heterogeneities control the thickness of sediment on the shoreface thus indentations can form in sections composed of harder less erodible rocks if they are finer grained

variability of the meridional overturning in the north atlantic from the 50 year gecco state estimation abstract the german partner of the consortium for estimating the circulation and climate of the ocean gecco provided a dynamically consistent estimate of the time varying ocean circulation over the 50 yr period 1952 2001 the gecco synthesis combines most of the data available during the entire estimation period with the ecco massachusetts institute of technology mit ocean circulation model using its adjoint this gecco estimate is analyzed here for the period 1962 2001 with respect to decadal and longer term changes of the meridional overturning circulation moc of the north atlantic a special focus is on the maximum moc values at 25 n over this period the dynamically self consistent synthesis stays within the error bars of h l bryden et al but reveals a general increase of the moc strength the variability on decadal and longer time scales is decomposed into contributions from different processes changes in the model s moc strength are strongly influenced by the southward communication of d

revision of the global carbon budget due to changing air sea oxygen fluxes 1 carbon budgets inferred from measurements of the atmospheric oxygen to nitrogen ratio o2 n2 are revised considering sea to air fluxes of o2 and n2 in response to global warming and volcanic eruptions observational estimates of changes in ocean heat content are combined with a model derived relationship between changes in atmospheric o2 n2 due to oceanic outgassing and heat fluxes to estimate ocean o2 outgassing the inferred terrestrial carbon sink for the 1990s is reduced by a factor of two compared with the most recent estimate by the intergovernmental panel on climate change ipcc this also improves the agreement between calculated ocean carbon uptake rates and estimates from global carbon cycle models which indicate a higher ocean carbon uptake during the 1990s than the 1980s the simulated decrease in oceanic o2 concentrations is in qualitative agreement with observed trends in oceanic o2 concentrations