sources and flow patterns of deep ocean waters as deduced from potential temperature salinity and initial phosphate concentration through the deconvolution of ocean chemical data it has been shown that the ratio of o2 utilization to phosphate production in the sea is 175 6 rather than 138 as proposed by redfield et al 1963 we find no evidence that this ratio changes significantly with location or depth in the sea we have used this new ratio to calculate the initial phosphate concentrations for the waters sampled during the geosecs and tto programs the important application of these new results is in constraining the origin and flow patterns of deep waters in the ocean we believe that a strong case can be made that antarctic salinity maximum water i e the common water of montgomery 1958 is produced by the mixing of waters entering the antarctic from mid depths in the indian pacific and atlantic with weddell sea bottom water southern component antarctic common water consists of about 45 weddell sea bottom water 30 intermediate waters from the pacific and indian oceans and 25 deep water originating from the northern atlantic

water column hydrothermal plumes on the juan de fuca ridge hydrographic surveys on the juan de fuca ridge jdfr carried out from 1980 to 1987 show a complex pattern of sup 3 he and mn rich water column plumes produced by venting from several submarine hot spring areas in the vicinity of axial volcano at latitude 46 degree n distinct plumes were detected in 1980 1982 and 1983 with sup 3 he signatures up to delta sup 3 he 64 at approximately 1 500 m depth at distances of approximately 10 km from the seamount summit however the same plumes had no detectable thermal signature a paradox which is attributed to the high sup 3 he heat ratios and low salinities of the fluids venting within the caldera of axial volcano profiles directly over the seamount show hydrothermal sup 3 he in the water column up to 300 m above the caldera floor with the sup 3 he signal increasing with depth to very high and uniform ratios of delta sup 3 he 108 150 below the approximately 1 500 m caldera sill depth another apparent locus of hydrothermal input is helium basin a depression on the northeast flank of axial volcano which had delta sup 3 he 51 when first sampled in 1980 however subsequent hydrocasts into helium basin in 1982 and 1983 yielded lowermore helium enrichments suggesting either a decrease in hydrothermal input or flushing of the basin via a mixing event to the south of axial volcano high delta sup 3 he values of approximately 40 observed over the ridge axis at 45 degree 18 prime n and 45 degree 39 prime n indicate venting on this previously unexplored section of the ridge the water column plumes over the us geological survey vent site at approximately 44 degree 40 prime n on the southern jdfr have very high mn sup 3 he ratios of 4 600 mol cm sup 3 an apparently unique characteristic which can be used to distinguish these plumes from those originating at other jdfr vent fields less

helium transport in sediment pore fluids of the congo angola margin during the zairov2 cruise of the zaiango project 1998 2000 on the passive congo angola margin several gravity cores were analyzed for helium isotopic composition of sedimentary pore waters in two cold fluid seepage zones the astrid slide area and the regab giant pockmark gas concentration and isotopic composition are presented along with thermal data in terms of the origin and circulation of fluids helium isotope data lie on a mixing line between bottom seawater and an almost pure radiogenic helium and temperature vertical profiles are well described by the classic diffusionadvection equation on the basis of he profiles we estimate the advection rate on the rim of the pockmark between 1 2 and 2 3 mm a the he flux derived for a pure diffusive regime 2 4 10 8 mol m 2 a can favorably be compared to literature data and contrasts with the flux computed close to the pockmark center 1 9 10 7 mol m 2 a helium depth profiles turned to be more sensitive to advection rate than temperature profiles are

noble gases in hydrothermal plumes of loihi seamount abstract seawater samples from hydrothermal plumes of loihi seamount show very high 3 he 4 he ratios up to 15 8 10 6 and 4 he 20 ne ratios higher than that of air saturated seawater assw the 3 he 4 he ratio in the source from which the helium is released into the seawater is estimated as 23 1 2 3 10 6 from the correlation plot of 3 he 20 ne vs 4 he 20 ne the 3 he heat ratio at loihi is 5 49 times higher than that at the galapagos rift and at 21 n epr the difference may be attributed to the differences in the structure of the mantle beneath hot spots and the mid ocean ridge the former representing the deeper mantle region and the latter the shallower depleted mantle these observations are consistent with the view that helium in hydrothermal plumes of loihi seamount was derived from a deeper mantle region via a hot spot where more primordial helium is still preserved

a far field hydrothermal plume from loihi seamount an extensive helium plume in the north central pacific emanates from loihi seamount on the flanks of hawaii the maximum helium signal is found at a depth of about 1100 meters the same depth as the near field plume directly above loihi seamount although this helium plume is strongest near hawaii where the 3he 4he ratio at a depth of about 1100 meters reaches values 28 percent above the atmospheric ratio it can be detected quite clearly at latitude 24 n over 400 kilometers to the north excess 3he is also present on the same isopycnal between 15 n and 20 n at 135 w some 2000 kilometers east of the hawaiian islands

helium isotopes at the rainbow hydrothermal site mid atlantic ridge 36 14 n the 3he 4he ratio and helium concentration have been measured in the vent fluids and the dispersing plume of the rainbow hydrothermal site on the mid atlantic ridge mar the 3he 4he ratio 7 51 ra and 3he end member concentration 25 pmol kg are in the range of observed values elsewhere on mid ocean ridges pointing to the relative homogeneity of the upper mantle with respect to helium isotope geochemistry 3he is linearly correlated with methane and manganese throughout the plume with ch4 3he and mn 3he ratios identical to those measured in the hot fluids the bulk residence time of the plume in the rift valley estimated from the plume 3he budget is v20 days the 3he flux transported by the plume calculated from current meter data is 12 3 3 nmol s requiring a flux of 490 kg s of high temperature fluid the scaling of the heat flux emitted by the rainbow site to that of 3he using the 3he heat ratio measured in the hydrothermal fluids 9 3 2u10318 mol j indicates a heat output of 1320 mw with a regional spreading rate of v25 mm year we calculate that the annual 3he flux for this section of the mar is of the order of 0 5 0 2 mmol per kilometre of ridge per millimetre of newly formed crust this figure compares well with the flux calculated for the neighbouring lucky strike segment although the uncertainties remain large both fluxes are v40 50 above the world average 0 33 mmol km mm thus supporting earlier suggestions that the intensity of the hydrothermal activity south of the azores is higher than expected from the regional spreading rate

the isotopic composition of radiogenic helium and its use to study groundwater movement in confined aquifers abstract the 3 he 4 he ratio for radiogenic he is shown to be primarily determined by the abundance of li and neutron absorbing elements in the host formations and is almost independent of the radioelement abundance the 3 he 4 he ratios have been computed for various li contents in rock matrices with average abundances of other elements the 3 he 4 he ratio is specific for each formation and may therefore be used to study crustal diffusion of he it is shown however that both the 3he and 4he contents of continental basements are likely to exceed those of the mantle so that diffusion of mantle he through continental crust is not likely to occur changes in the 3 he 4 he ratio for dissolved he have potential for studying groundwater movement and mixing processes atmospheric he which was dissolved at recharge is progressively diluted by radiogenic he with an isotopic ratio characteristic of the aquifer as the groundwater migrates down dip mixing proportions for formation he and atmospheric he in aquifers for which there is admixture of fracture borne water and interstitially stored water can also be estimated from isotopic measurements these processes are discussed in relation to two aquifers in eastern england

on the use of doppler shift for sea surface wind retrieval from sar the synthetic aperture radar sar doppler centroid has been used to estimate the scatter line of sight radar velocity in weak to moderate ocean surface current environment the sar doppler centroid is dominated by the directionality and strength of wave induced ocean surface displacements in this paper we show how this sea state signature can be used to improve surface wind retrieval from sar doppler shifts of c band radar return signals from the ocean are thoroughly investigated by colocating wind measurements from the ascat scatterometer with doppler centroid anomalies retrieved from envisat asar an empirical geophysical model function cdop is derived predicting doppler shifts at both vv and hh polarization as function of wind speed radar incidence angle and wind direction with respect to radar look direction this function is used into a bayesian inversion scheme in combination with wind from a priori forecast model and the normalized radar cross section nrcs the benefit of doppler for sar wind retrieval is shown in complex meteorological situations such as atmospheric fronts or low pressure systems using in situ information validation reveals that this method helps to improve the wind direction retrieval uncertainty of the calibration of doppler shift from envisat asar hampers the inversion scheme in cases where nrcs and model wind are accurate and in close agreement the method is however very promising with respect of future sar missions in particular sentinel 1 where the doppler centroid anomaly will be more robustly retrieved

deep tracer and dynamical plumes in the tropical pacific ocean anomalous middepth plumes in potential temperature salinity s and buoyancy frequency squared n2 originate east of the east pacific rise crest and decay toward the west conductivity temperature depth ctd data from recent hydrographic sections at 15 s and 10 n are used together with meridional sections at 110 135 and 151 w to map these structures warm salty plumes west of the rise crest have maxima centered at 2700 m 10 s and 8 n and are interrupted by a cold fresh tongue centered at 2900 m 2 s the s anomalies decay to half their peak strength 2800 km to the west of the rise crest 300 km in the meridional and 0 4 km in the vertical vertical n2 minima occur within the plumes regions of reduced vertical gradients in and s these minima are underlain by maxima near the depth of the rise crest about 3200 m the n2 plumes decay more rapidly to the west of the rise crest than do the s plumes the n2 structure is consistent with a pair of stacked gyres in each hemisphere there are at least three possible mechanisms consistent with some aspects of these features first a deep maximum in upwelling somewhere below 2700 m would result in equatorward and westward interior flow at 2700 m advecting these plumes along with it second rapid upwelling of warm salty unstratified water in the eastern basins could result in westward overflows over the rise crest third upwelling and associated entrainment processes owing to hydrothermal venting could result in stacked counter rotating gyres west of the rise crest

evidence of deep and bottom water formation in the western weddell sea abstract during ice station polarstern ispol r v polarstern cruise ant xxii 2 november 2004 january 2005 hydrographic and tracer observations were obtained in the western weddell sea while drifting closely in front of the larsen ice shelf these observations indicate recently formed weddell sea bottom water which contains significant contributions of glacial melt water in its upper part and high salinity shelf water in its lower layer the formation of this bottom water cannot be related to the known sources in the south the filchner ronne ice shelf we show that this bottom water is formed in the western weddell sea most likely in interaction with the larsen c ice shelf by applying an optimum multiparameter analysis omp using temperature salinity and noble gas observations helium isotopes and neon we obtained mean glacial melt water fractions of about 0 1 in the bottom water on sections across the weddell gyre farther north melt water fractions are still on the order of 0 04 using chlorofluorocarbons cfcs as age tracers we deduced a mean transit time between the western source and the bottom water found on the slope toward the north 9 3 years this transit time is larger and the inferred transport rate is small in comparison to previous findings but accounting for a loss of the initially formed bottom water volume due to mixing and renewal of weddell sea deep water a formation rate of 1 1 0 5 sv in the western weddell sea is plausible this implies a basal melt rate of 35 19 gt year or 0 35 0 19 m year at the larsen ice shelf this bottom water is shallow enough that it could leave the weddell basin through the gaps in the south scotia ridge to supply antarctic bottom water these findings emphasize the role of the western weddell sea in deep and bottom water formation particularly in view of changing environmental conditions due to climate variability which might induce enhanced melting or even decay of ice shelves

hydrothermal helium plumes in the pacific ocean hydrothermal activity along the global mid ocean ridge system and at active seamounts introduces a 3 he rich signal into the deep ocean basins which can be used to trace patterns of ocean circulation and mixing this hydrothermal helium signal is especially strong in the pacific ocean where the spreading rate of the ridges is the greatest in several areas of the pacific the hydrothermal activity is of sufficient strength to produce intense helium plumes which clearly define the regional circulation among these are 1 a pair of helium plumes at 2500 m depth which extend westward from the east pacific rise at 10 n and 15 s into the interior of the pacific basin 2 a helium plume at 2000 m depth extending southwest from sources on the juan de fuca ridge in the northeast pacific and 3 a plume at 1100 m depth emanating from loihi seamount at 20 n which extends eastward from hawaii to the coast of mexico the flow field implied by the helium distribution appears to be in reasonable agreement with reid s 1997 steric height analysis for the pacific

component separation of oceanic helium a new procedure to quantify the components of oceanic helium terrigenic 3he and 4he released from the ocean floor and tritiugenic 3he from tritium decay is described terrigenic he and nonatmospheric 3he i e terrigenic and tritiugenic combined are obtained in terms of measured concentrations of the he isotopes and also of neon ne which improves the separation considerably assuming terrigenic he to vanish in the mixed layer for the subsequent separation of terrigenic and tritiugenic 3he additional information is required and 3he due to natural tritium represents a complication the procedure is applied to data from a hydrographic section in the south atlantic 19 s 1991 and one in the eastern mediterranean 1987 the 1 data precisions and a systematic error accounting for uncertainties in mixed layer he are approximately 0 3 sections of the new representations of oceanic he and 3he and comparisons to the nearest classical quantities i e 3he he are presented in the south atlantic the 3he distribution reflects the hydrographic structure east of 20 w the average 3he 4he ratio of terrigenic he below 800 m is 4 5 0 8 times the atmospheric ratio which implies a substantial contribution of crustal he in the upper waters tritiugenic 3he 0 5 tritium units 20 is separated from terrigenic 3he in the eastern mediterranean tritiugenic 3he is quantified throughout the water column in the presence of substantial levels of terrigenic he the release rate of terrigenic he from the sea floor is found to be 3 1 1 2 1010 atoms m 2 s 1 similar to the rate for continental crust with a mantle he contribution of 5 1 2 only recommendations for future work are to reduce the mentioned systematic error and the uncertainty margins of the he and ne solubilities and of 3he due to natural tritium

crustal helium in deep pacific waters we have analyzed deep helium isotope data from world ocean circulation experiment section p17 along 135 w in the pacific ocean combining these data with neon data we have derived the isotopic ratio rt of the nonatmospheric part of helium terrigenic helium the calculated rt values are significantly lower than helium isotope ratios from mid ocean ridge mor sources rmor 8ra ra 3he 4he air which are generally presumed to dominate the isotope characteristics of helium of nonatmospheric origin for the depths most influenced by the southern east pacific rise epr helium plume the isotopic ratio of terrigenic helium is 7 4 ra however both the northern epr plume and the juan de fuca ridge jdfr plume show significantly lower rt values of 6 8 ra we find minimum rt values of 5 6 ra at about 20 n to 30 n from 2000 m depth to the ocean floor we conclude that in addition to the epr and jdfr helium sources having mor isotope characteristics there is a flux of radiogenic 4he out of deep sea sediments and the oceanic crust which causes a significant deviation of rt toward values lower than rmor using our calculated terrigenic 4he concentrations and isotope ratios rt and the helium isotope ratios of the two end members mor helium and crustal helium we derive concentrations and ocean bottom fluxes of crustal 4he 4hecrust maximum concentrations of 4hecrust up to 30 pmol kg 1 are found at about 20 n to 30 n between 2000 m and 4000 m along the p17 section the mean crustal 4he flux is obtained as 1 0 0 4 109 atoms m 2earth s 1

helium and methane measurements in hydrothermal fluids from the mid atlantic ridge the snake pit site at 23 n methane and helium isotopes concentrations have been measured in hydrothermal fluids of black smoker vents at the snake pit area mar 23 n as part of the hydrosnake cruise with the submersible nautile the samples contain large quantities of helium and methane with endmember values of 4 6 10 5 cm3 stp g for helium and 1 38 10 3 cm3 stp g for methane the helium isotopic ratio 3he 4he is 8 4 times the atmospheric ratio these values are strikingly similar to those already obtained on the east pacific rise the ch4 3he ratio is also quite similar ch4 3he 2 6 106 suggesting a non biogenic origin of this gas in the fluids assuming that the range of variation of the 3he concentration data obtained so far from various tectonic settings is close to the genuine range of values encountered on mid ocean ridges the global mass flow involved in the hydrothermal circulation at the ridge s axis is estimated between 1000 and 3000 m3 of water sec leading to a residence time of the global ocean with respect to the hydrothermal circulation between 15 and 45 million years this estimate implies that in addition to the individual vents smokers there is an extensive diffuse circulation of hydrothermal fluids along the ridges in agreement with recent observations concerning heat budgets at hydrothermal sites in the eastern pacific

evaluating earth degassing in subduction zones by measuring helium fluxes from the ocean floor abstract volatiles are lost from the earth s mantle to the atmosphere hydrosphere and the crust through subaerial and submarine volcanism quantifying the volatile sources bears fundamental information on a number of issues in earth sciences from the evolution of the atmosphere and oceans to the nature of chemical heterogeneity of the earth s mantle the primordial noble gas isotope 3he provides an unambiguous measure of the volatile flux from the mantle yet so far in the ocean region it has been only measured at a mid ocean ridge here we present original measurements of the 3he flux at the mid okinawa trough back arc basin the 3he flux was estimated from 3he 20ne vertical profiles measured in deep sea sediment pore water diffusive 3he fluxes vary from 1 6 3he atoms cm 2 s 1 at the hydrothermally active izena cauldron to 0 57 3he atoms cm 2 s 1 at the background site 13 km away these values are about 20 of the 3he flux measured at the east pacific rise supporting the never proven hypothesis that 3he mantle flux from subduction zones is a quarter of that at mor measured ocean floor 4he flux ranges from 3 3 105 to 4 8 105 4he atoms cm 2 s 1 higher than that measured worldwide suggesting that 4he flux at subduction zones might have been previously underestimated

an introduction to saxon fpn the synthetic aperture radar and x band ocean nonlinear it ies saxon forschungsplatform nordsee fpn program was a 3 year effort to investigate radar backscatter from the ocean and synthetic aperture radar sar imagery of the ocean a secondary objective of the program was to explore the relationship between acoustic and microwave scattering from the ocean surface the program was a joint effort between the united states and the federal republic of germany it consisted primarily of a major field experiment phase i in the north sea on and around the german forschungs platform nordsee fpn during november 1990 a second smaller field experiment phase ii on the same platform in november 1991 and a series of four data analysis workshops

an analytical model for the description of the full polarimetric sea surface doppler signature this paper describes an analytical model of the full polarimetric sea surface scattering and doppler signature the model combines the small slope approximation theory at the second order with a weak nonlinear sea surface representation such a model is used to examine the variation of the doppler central frequency bandwidth and of the normalized radar cross section as function of wind speed and direction the results suggest that the model can be a valuable tool for the accurate observation of sea surface currents

helium isotope variations in juan de fuca ridge basalts we have measured he 4he ratios and he and ne concentrations on a suite of 24 basalt glasses from the neovolcanic zone of the juan de fuca ridge jdfr from 44 6 n near the blanco transform up to 48 0 n on the endeavour segment the helium isotope ratios exhibit a clear geographic variation with relatively constant values of 7 8 ra along the southern jdfr increasing to a maximum of 8 8 ra at 46 9 n on the cobb segment and then dropping to values of 8 0 ra at the cobb offset ratios along the endeavour segment further north are somewhat higher averaging 8 2 ra basalts dredged from axial seamount have he 4he 7 9 8 4 ra indicating that the seamount does not have a geochemical or isotopic signature distinct from other portions of the jdfr this confirms that while axial seamount is the locus of excess magma generation it is devoid of any hotspot or ocean island basalt geochemical signature for the whole sample set he 4he ratios show a negative correlation with 87sr 86sr we attribute the geographical variations in he 4he to broad scale heterogeneity in the mantle source region beneath the jdfr beginning at axial seamount and further north he 4he shows a positive correlation with fe8 0 suggesting that melting dynamics in the underlying mantle may exert some control on the helium isotope ratios along part of our survey area

a mass wasting dominated quaternary mountain range the coastal range in eastern taiwan abstract fluvial bedrock incision which creates topographic relief and controls hillslope development has been considered the key medium linking denudation and tectonic uplift of unglaciated mountains this article however shows a different scenario from the coastal range in eastern taiwan this range with the steepness inherited from pre orogenic volcanoes has been subject to mass wasting even before its emergence above sea level no earlier than middle pleistocene numerous terraced alluvial fans fan deltas record the ancient mass movements of the range including rock avalanches multiple radiocarbon dates 1 km 2 alluvial terraces are typically exhibited close to the source ridges of mass movements and strath terraces along the downstream parts of rivers both were created when enormous sediment supply had exceeded or matched the prevailing river transport capacity this process along with the protection by giant boulders from mass movement disturbed the long term incision trend of rivers in response to tectonic uplift as a result the observed holocene bedrock incision at most sites has not kept pace with the tectonic uplift the spatial contrast in mass wasting histories further accounts for the great diversity of the terrace sequences even in areas with similar tectonic and base level conditions

helium isotope fluxes and groundwater ages in the dogger aquifer paris basin the dogger aquifer of the paris basin has been shown to be first order homogeneous in its helium concentration and its helium isotopic ratio although slight differences are noted in relation to specific chemical water types the helium isotopic composition of the dogger aquifer contains a small component of mantle helium that is associated with a magmatic input although the heat accompanying this magma is small constraints on the age of the overlying albien aquifer are used to calculate the flux of helium out of the dogger this constraint allows a calculation of the residence time of waters in the dogger aquifer of 4 myr 50 which is significantly longer than estimates derived from hydrologic models and hydrologic testing it is possible that the hydrologic ages and the helium ages can be reconciled by a vertically layered dogger aquifer with gradients in he salinity and fluid flow vertical profiles of fluid composition helium concentration and permeability are required in the paris basin to resolve this question

comparison of composite bragg theory and quad polarization radar backscatter from radarsat 2 with applications to wave breaking and high wind retrieval 1 depolarized de pol radar backscatter is now produced by many spaceborne satellites analysis of radarsat 2 r2 quad polarization quad pol data with collocated in situ ocean wind measurements reveals that the de pol radar backscatter does not saturate in high winds this is a significant development for radar wind sensing because wind retrieval with copolarized co pol backscatter suffers from problems of incidence and azimuth angle dependent signal saturation and dampening in high winds we present a study comparing satellite quad pol measurements with the composite surface bragg cb theory of radar backscattering from the ocean surface the co pol data are in good agreement with the cb theory de pol data are more sensitive to wind speed compared to theoretical prediction thus retrieval of high winds is more accurate using the de pol return the cubic wind speed dependence of de pol returns in high winds reflects the significant breaking wave contributions the relationship can be used to obtain wave breaking properties from space

advection of pore fluids through sediments in the equatorial east pacific measurements of the ratio of helium 4 to helium 3 and of calcium ion in the pore waters of sediments at two locations in the eastern equatorial pacific indicate that solution advection is occurring through the sediments both the helium ratio and the calcium ion profile yield velocity values for advective flow of about 20 centimeters per year mass balance constraints are also consistent with the interpretation presented flow appears to be occurring thorugh relatively thick sediments on the order of 300 meters

estimation of heat and chemical fluxes from a seafloor hydrothermal vent field using radon measurements the circulation of seawater through newly formed ocean crust at mid ocean ridge spreading centres is important in the oceanic heat and chemical budgets the heat transfer in submarine hydrothermal systems accounts for 25 of the total global heat loss1 the transfer of mass resulting from basaltic alteration affects the geochemistry of seawater2 and is responsible for the formation of ore deposits on and beneath the seafloor3 various geophysical techniques have been employed in efforts to determine the heat output from hydrothermal vent fields4 9 however the magnitudes of the heat and chemical fluxes through these systems remain uncertain here we introduce a geochemical approach for estimating the flux from a vent field based on radon 222rn measurements in the overlying effluent plume this method was applied successfully in september 1986 during a 23 day expedition to an active vent field on the 170 km endeavour segment of the juan de fuca ridge fig la we estimate the heat flux from this site to be l 5 l09 w

hydrothermal heat enhances abyssal mixing in the antarctic circumpolar current upwelling in the world s strongest current the antarctic circumpolar current is thought to be driven by wind stress surface buoyancy flux and mixing generated from the interaction between bottom currents and rough topography however the impact of localized injection of heat by hydrothermal vents where the antarctic circumpolar current interacts with mid ocean ridges remains poorly understood here a circumpolar compilation of helium and physical measurements are used to show that while geothermal heat is transferred to the ocean over a broad area by conduction heat transfer by convection dominates near hydrothermal vents buoyant hydrothermal plumes decrease stratification above the vent source and increase stratification to the south altering the local vertical diffusivity and diapycnal upwelling within 500 m of the sea floor by an order of magnitude both the helium tracer and stratification signals induced by hydrothermal input are advected by the flow and influence properties downstream

noble gases in ocean waters and sediments noble gases are widely used in studies of the basic properties and dynamics of natural systems including the ocean this chapter describes some of the more extensive applications of noble gases mainly helium isotopes to studies of oceanographic problems they include the modern oceanic circulation paleo oceanography hydrothermal and cold brine systems in the deep ocean and ocean atmosphere gas exchange originally oceanic noble gas studies were focused on geochemical problems such as the question of the existence of excess helium in seawater derived from radioactive decay of the elements of the uranium and thorium series in ocean sediments suess and wanke 1965 bieri et al 1966 after the discovery of mantle primordial helium during the 1960s clarke et al 1969 craig and weiss 1971 craig et al 1975 and 3he derived from decay of tritium in the near surface waters of the ocean jenkins and clarke 1976 large programs were developed to exploit helium isotopes frequently in combination with tritium for studies of water mass formation circulation and variability e g jenkins 1987 schlosser et al 1991 more recent studies started to explore the use of helium isotopes to paleoceanographic objectives these studies build upon the discovery of extraterrestrial helium in deep sea sediments in the early 1960s merrihue 1964 this signal is now being systematically examined for its potential as a tool for investigations of sediment accumulation rates on very long time scales millions of years and their correlation with changes in paleoceanography e g farley 1995 farley and patterson 1995 marcantonio et al 1995 1996 2001 soon after the discovery of mantle helium in seawater noble gases were applied to studies of hydrothermal systems originally these studies were focused on the source of the fluids emanating from hydrothermal vents as well as

oxygen 18 and helium as tracers of ice shelf water and water ice interaction in the weddell sea oxygen 18 and helium isotope data from stations located in the filchner depression on the continental slope of the southern weddell sea and in the central weddell sea are presented and discussed the 18o and 4he signals imprinted on the water circulating under the filchner ronne ice shelf ice shelf water or isw due to melting of glacial ice at the base of the ice shelf are traced across the sill separating the filchner depression from the weddell sea low 18o values are correlated with high 4he concentrations in the isw found in the filchner depression minimum 18o values 0 8 maximum 4he concentrations about 4 7 10 8 cm3 stp g 1 the fraction of glacial meltwater contained in the isw found in the filchner depression is estimated to about 6 to 7 the 18o and helium isotope data from the overflowing shelf water component observed on the continental slope confirm the hypothesis that isw contributes significantly to the weddell sea bottom water wsbw on the basis of a inultiparameter water mass analysis it is discussed which fraction of the wsbw originates from isw and which other shelf waters potentially could contribute to wsbw

tracing southwest pacific bottom water using potential vorticity and helium 3 abstractthis study uses potential vorticity and other tracers to identify the pathways of the densest form of circumpolar deep water in the south pacific termed southwest pacific bottom water spbw along the 28 2 kg m 3 surface this study focuses on the potential vorticity signals associated with three major dynamical processes occurring in the vicinity of the pacific antarctic ridge 1 the strong flow of the antarctic circumpolar current acc 2 lateral eddy stirring and 3 heat and stratification changes in bottom waters induced by hydrothermal vents these processes result in southward and downstream advection of low potential vorticity along rising isopycnal surfaces using 3he released from the hydrothermal vents the influence of volcanic activity on the spbw may be traced across the south pacific along the path of the acc to drake passage spbw also flows within the southern limb of the ross gyre reaching the antarctic slope in places and contributes via entrainment to the formation of

a major helium 3 source at 15 s on the east pacific rise an extensive plume of water enriched with helium 3 has been discovered in the deep pacific ocean at latitude 15 s on the east pacific rise in the core of the plume at a depth of 2500 meters over the ridge crest the helium 3 helium 4 ratio is 50 percent higher than the ratio in atmospheric helium indicating a strong injection of mantle or primordial helium at the spreading center axis through local hydrothermal systems the helium 3 plume is completely absent east of the rise but it can be traced over 2000 kilometers to the west above a newly observed physical feature a density discontinuity here caled the ridge crest front the injected plume provides a unique deep sea tracer with an asymmetric distribution which shows that the deep circulation across the rise is from east to west the striking intensity and lateral extent of this helium 3 anomaly compared to observations at known oceanic hydrohrmal sites suggest that the largest hydrothermal fields in the ocean are yet to be discovered and that they will be found near 15 s on the east pacific rise