preservation of extraterrestrial 3he in 480 ma old marine limestones we have measured the helium abundance and isotopic composition of a suite of lower ordovician marine limestones and associated fossil meteorites from kinnekulle sweden limestone 3he 4he ratios as high as 11 5 times the atmospheric value in fused samples and up to 23 times atmospheric in a single step heat fraction indicate the presence of extraterrestrial helium and demonstrate that at least a fraction of the extraterrestrial 3he carried by interplanetary dust particles must be retained against diffusive and diagenetic losses for up to 480 ma the carrier phase has not been identified but is not magnetic extrapolation of high temperature 3he diffusivities in these sediments is consistent with strong retention of extraterrestrial 3he under ambient earth surface conditions combination of the observed helium concentrations with sedimentation rates estimated from conodont biostratigraphy suggest that the flux of extraterrestrial 3he in the early ordovician was about 0 5 10 12 cm 3 stp cm 2 ka 1 ignoring potential post deposition helium loss this value is indistinguishable from the average 3he flux estimated for the cenozoic era in contrast previous studies of fossil meteorites ir abundances and os isotopic ratios in the limestone suggest that the total accretion rate of extraterrestrial material during the studied interval was at least an order of magnitude higher than the cenozoic average this disparity may reflect significant post depositional loss of 3he from idps within these old limestones if so the match between the ordovician flux and the cenozoic average would be fortuitous alternatively the size distribution of infalling objects during the early ordovician may have been enriched only in extraterrestrial material too large to retain 3he during atmospheric entry heating 30 m the fossil meteorites themselves also preserve extraterrestrial helium meteorite 3he concentrations of 2 to 9 10 12 cm 3 stp g 1 are several orders of magnitude lower than found in most modern meteorites suggesting very substantial helium loss probably 99 9 from these chemically altered objects the meteorites carry 3he concentrations only a factor of a few higher than the host limestones the meteorites themselves cannot be the source of the extraterrestrial 3he observed in the limestones

interferometer studies of equatorial f region irregularities and drifts a radar interferometer technique developed at jicamarca peru and first used to study electrojet irregularities has now been used successfully to study plasma turbulence in the equatorial f region our first results have shown that the most turbulent echoes appear to come from a region that extends for tens of kilometers in altitude but for only a kilometer or less in the east west direction this slab may very well be the wall of a depleted region a plasma bubble sometimes the irregularities can be tracked as they move eastward or westward velocity profiles for the evening period obtained in this way show a strong shear with westward velocities at the lowest altitudes observed and eastward velocities above a plausible explanation for this shear is that the westward drifts are driven by electric fields produced by westward e region winds and mapped up along magnetic field lines while at higher heights where the electron density is greater the drifts are controlled by the f region dynamo driven by eastward winds

mixed layer simulation of buoy observations taken during hurricane eloise a one dimensional mixed layer model is used to simulate observations made by a noaa buoy in the gulf of mexico during hurricane eloise the model predicted sst mixed layer depth and inertial current agree favorably with the observations in addition model experiments demonstrate the importance of the veering of the wind vector during the passage of the eye to the amplitude of the inertial current generated by the wind and the extent of vertical mixing

isotope data from ice station weddell implications for deep water formation in the weddell sea helium isotope data 3he 4he ratios and 4he concentrations and h218o h216o ratios obtained from stations occupied during the drift of ice station weddell february to june 1992 are used together with hydrographic data to study formation of deep and bottom water in the western weddell sea the data indicate deep and bottom water formation along the entire track of the ice station 71 4 to 65 8 s 53 w ice shelf water isw seems to contribute significantly to the formation of weddell sea deep water wsdw and weddell sea bottom water wsbw in the southern part of the drift track toward the north the fraction of isw contained in wsdw wsbw decreases this trend is overlaid by high isw fractions in the deep and bottom waters found in the vicinity of the larsen ice shelf the fraction of western shelf water wsw in wsbw shows the opposite trend increasing from south to north the combined fraction of isw and wsw in waters with potential temperatures below 0 c is about 20 corresponding to a roughly 200 m thick layer overall wsw seems to contribute approximately 2 to 3 times more water than isw to the water column below the 0 c isotherm using the estimated flow of isw over the sill north of the filchner depression of 1 sv foldvik et al 1985a together with the ratio of wsw plus winter water ww to isw we calculate a value of about 5 sv for the formation rate of wsbw with a potential temperature of 0 7 c about one third of this flux represents near surface waters wsw ww which have recently been equilibrated with the atmosphere whereas pure isw contributes about 10

search for the origin of exotic helium in deep sea sediments merrihue1 first observed helium with a very high 3he 4he isotope ratio 10 4 here termed exotic helium in a magnetic separate of a deep ocean sediment and attributed it to input of extraterrestrial material krylov et al 2 subsequently reported the existence of exotic he in several deep sea sediments while tilles3 measured argon isotope ratios in magnetic separates of two ocean sediments observing that the 3he 4he ratio is inversely correlated with the sedimentation rate ozima et al 4 concluded that the exotic he is carried by interplanetary dust particles idps we have now examined other deep sea sediments to characterize the exotic he and to identify its carrier and have confirmed that the exotic he resides mainly in a strongly magnetic fraction stepwise degassing experiments suggest that the exotic he consists of a single component the carrier of the he is likely to be chondritic idps the higher level of exotic he in magnetic fractions of sediments can be explained by secondarily produced magnetite in idps as a result of thermal shock during atmospheric entry

discovery of an anoxic basin within the strabo trench eastern mediterranean we report here the discovery of a basin which we call the tyro basin in the eastern mediterranean in which anoxic conditions exist and organic rich sediments are accumulating bottom water samples show extremely high salt concentrations a horizontal midwater sound reflector about 70 m above the basin floor was observed in a seismic reflection profile across the basin from shipboard observations we conclude that dissolution of messinian evaporites exposed by faulting in the sides of the basin causes stagnant bottom conditions this basin provides an opportunity to test some of the hypotheses concerning the formation of sapropels present in cores collected from the same area cores taken in an adjacent similar basin for which we propose the name kretheus basin indicate a recent change from anoxic to oxygenated conditions which was probably caused by tectonic activity associated with the strabo trench

on the importance of surface forcing in conceptual models of the deep ocean in the major ocean basins diapycnal mixing upwells dense antarctic bottom water which returns southward and closes the deepest cell of the meridional overturning circulation moc this cell ventilates the deep ocean and regulates the partitioning of co2 between the atmosphere and the ocean the oceanographic community s conceptual understanding of the deep stratification and moc has evolved from classic abyssal recipes arguments to a more recent appreciation of along isopycnal upwelling in the southern ocean consistent with a weakly mixed ocean interior both the deep stratification and the deep moc are shown here to be sensitive to the form of the surface buoyancy forcing in a two dimensional model that includes a circumpolar channel and northern basin for a fixed surface buoyancy condition the deep stratification is essentially prescribed whereas for a fixed surface buoyancy flux the deep stratification varies by orders of magnitude over the range of diapycnal diffusivity observed in the ocean these cases also produce different scalings for the deep moc with in both weak and strong regimes in addition these scalings are shown to be sensitive not only to the type of surface boundary condition but also to the latitudinal structure of the surface fluxes this latter point is crucial as buoyancy budgets and dynamical features of the circulation are poorly constrained along the antarctic margins this study emphasizes the need for caution in the interpretation of simple conceptual models that while useful may not include all mechanisms that contribute to the moc s strength and structure

gas exchange and co2 flux in the tropical atlantic ocean determined from 222rn and pco2 measurements measurements of sup 222 rn vertical profiles and pco sub 2 in the surface water and the atmosphere were made simultaneously in the tropical atlantic ocean as part of the tto tas program the gas exchange rate or piston velocity was determined from the sup 222 rn profiles and the delta pco sub 2 between the surface ocean and the atmosphere was determined from the pco sub 2 measurements the net flux of co sub 2 across the sea air interface was calculated from these two data sets the piston velocity ranged from 1 4 to 6 9 m d and was correlated with wind speed the slope of piston velocity versus wind speed was estimated to be between 0 3 and 1 1 m d m s the delta pco sub 2 ranged from minus 35 mu atm at 15 degree n 55 degree w to 64 mu atm at 5 degree s 28 degree w with the zero delta pco sub 2 isopleth located at about 10 degree n the high delta pco sub 2 values can be explained by lateral advection of surface water from the east with heating and biological consumption of co sub 2 and alkalinity during transit the net flux of co sub 2 was into the ocean north of 10 degree n latitude with values reaching a maximum of 1 4 mol m sup minus 2 yr sup minus 1 at 15 degree n 50 degree w south of 10 degree n more the net flux was out of the ocean reaching a maximum value of 2 7 mol m sup minus 2 yr sup minus 1 at 8 degree s 28 degree w the average net flux from 10 degree n to 10 degree s was 1 3 mol m sup minus 2 yr sup minus 1 out of the ocean which is equivalent to 0 15 gigatons of carbon per year if the flux determined applied throughout the year 56 refs 16 figs 4 tabs ss less

extraterrestrial 3 he as a tracer of marine sediment transport and accumulation the deposition rate of deep sea sediments and their focused redeposition by deep sea currents can be evaluated from analyses of sedimentary 230th with a temporal resolution limited only by bioturbation6 7 10 11 230th is produced uniformly throughout the ocean by radioactive decay of dissolved 234u and is removed sufficiently fast by sorption onto sinking particles to act as a constant flux tracer of sedimentation rates but the half life of 230th 75 kyr limits its use for this purpose to the past 200 250 kyr here we explore the use of extraterrestrial 3he from interplanetary dust particles1 4 idps as a constant flux proxy that is free from this limitation a comparison of 3he with 230th in two cores from the equatorial pacific ocean indicates that the variability in the mean flux of idps over the past 200 kyr is less than 75 but in contrast to this relatively constant rate of supply of 3he to the deep sea the local burial rates of 3he and 230th have varied by a factor of five over the past 450 and 200 kyr respect ively we interpret this variability as reflecting sediment focusing with a temporal pattern that suggests regular cycles of climate driven reorganization of near bottom currents in the deep pacific ocean

impact of meridional winds on equatorial spread f revisited 1 the impact of meridional winds on the onset and evolution of equatorial spread f esf is studied using the nrl ionosphere model sami3 esf the prevailing belief is that meridional winds have a stabilizing effect on the onset of esf in this letter it is shown that this is not necessarily the case and that meridional winds can be destabilizing we find that a wind profile with a positive gradient as a function of latitude v m 0 is a stabilizing influence on the generalized rayleigh taylor instability a wind profile with a negative gradient v m 0 is a destabilizing influence here a northward wind is positive and increases in the northward direction it is suggested that meridional wind profiles may account for in part the longitudinal and day to day variability of esf

a short duration of the cretaceous tertiary boundary event evidence from extraterrestrial helium 3 analyses of marine carbonates through the interval 63 9 to 65 4 million years ago indicate a near constant flux of extraterrestrial helium 3 a tracer of the accretion rate of interplanetary dust to earth this observation indicates that the bolide associated with the cretaceous tertiary k t extinction event was not accompanied by enhanced solar system dustiness and so could not have been a member of a comet shower the use of helium 3 as a constant flux proxy of sedimentation rate implies deposition of the k t boundary clay in 10 2 10 3 years precluding the possibility of a long hiatus at the boundary and requiring extremely rapid faunal turnover

mid 1980s distribution of tritium 3he 14c and 39ar in the greenland norwegian seas and the nansen basin of the arctic ocean abstract the distributions of tritium 3 he 14c and 39ar observed in the period between 1985 and 1987 in the greenland norwegian seas and the nansen basin of the arctic ocean are presented the data are used to outline aspects of the large scale circulation and the exchange of deep water between the greenland norwegian seas and the nansen basin additionally semi quantitative estimates of mean ages of the main water masses found in these regions are obtained apparent tritium 3 he ages of the upper waters depth 1 500m depth of the greenland norwegian seas show apparent tritium 3 he ages between about 17 years in the greenland sea and 30 years in the norwegian sea 39ar based estimates of the nansen basin intermediate deep and bottom water ages are 91 26 23 161 50 44 and 277 33 31 years for arctic intermediate water aiw eurasian basin deep water ebdw and eurasian basin bottom water ebbw respectively within the errors age estimates of ebdw and ebbw based on 14 c tritium correlations are consistent with those derived from 39ar 163 to 287 years for ebdw and 244 to 368 years for ebbw a quantitative evaluation of the data in terms of deep water formation and exchange rates based on box model calculations is presented in an accompanying paper

terrigenous helium in deep sea sediments abstract we have measured the isotope ratios of helium contained in various terrigenous materials that contribute to deep sea sediments these materials include ice rafted debris from the north atlantic chinese loess and sediment collected at or near the mouths of three large rivers the amazon the ganges and the yangtze we observe terrigenous 3he 4he ratios that vary from 1 8 10 9 to 4 6 10 7 i e values that are higher than the theoretically derived range of 10 9 to 10 8 atlantic and pacific deep sea sediment 3he 4he ratios can be explained by mixing of helium from similar extraterrestrial but different terrigenous sources terrigenous sources for north atlantic and north pacific sediments are characterized by 3he and 4he contents that are higher and 3he 4he ratios that are lower than those for central and eastern equatorial pacific sediments this is consistent with the supply to the north atlantic and north pacific oceans of older cratonic continental material that contains high amounts of in situ produced nucleogenic and radiogenic helium terrigenous material transported to central and eastern equatorial pacific sediments contains lower amounts of 3he and 4he and higher 3he 4he ratios indicative of supply from a more juvenile andean source in the equatorial atlantic core v31 135 we have used previously published 230th data to determine an extraterrestrial 3he flux of 1 16 0 15 10 12 cm3stp cm 2 ka 1 within error of that previously determined in sediments from the equatorial pacific ocean 0 78 0 29 10 13 cm3stp cm 2 ka 1 marcantonio et al 1996

helium a new tracer in antarctic oceanography the abyssal characteristics of the world oceans are strongly influenced by the northward propagation of antarctic bottom water aabw an important source of aabw is weddell sea bottom water wsbw which is formed in part on the continental slope of the southern weddell sea1 3 the formation of wsbw on the continental slope is related to the floating ice shelves of the southern weddell sea filchner ronne ice shelves western shelf water wsw is modified under the ice shelves by cooling and admixture of melt water to form ice shelf water isw and a substantial part of the isw flows over the sill that separates the filchner depression from the weddell sea and participates in the formation of wsbw4 5 the data reported here demonstrate that the water ice interaction leads to a strong 4he supersaturation of the isw due to dissolution of air entrapped in the ice shelf melt water the 4he supersaturation of the isw can be used as a tracer of this water mass and also influences the 4he balance of the wsbw

simultaneous presence of orbital inclination and eccentricity in proxy climate records from ocean drilling program site 806 ocean drilling program site 806 in the western pacific shows evidence of a remarkably constant average sedimentation rate this feature allows us to analyze ancient climate proxies without the need for orbital tuning a standard procedure in prior work but one that can lead to biased results spectral analysis of stable oxygen isotope ratios at this site a proxy for global ice volume shows a single narrow peak with a period 100 k y a result that supports our model which links glacial cycles to variations in the inclination of the earth s orbit in contrast spectral analysis of the coarse component fraction of the sediment primarily foraminifera shows a structure characteristic of standard milankovitch theory with a triplet of peaks with periods near those expected from the earth s eccentricity 95 125 and 400 k y bispectral analysis confirms these linkages but suggests that orbital inclination also plays some role in the coarse fraction from the clear presence of both signals in different proxies at the same site we conclude that although eccentricity affected the local climate it is orbital inclination that drove the variations in the global ice volume for the past million years

measurements of air sea gas transfer during an open ocean algal bloom measurements of air sea gas transfer were made during the development of a large algal bloom that immediately followed in situ iron enrichment in the equatorial pacific ocean gas transfer rates were determined from changes in the ratio of the deliberately released tracers sulphur hexafluoride and helium 3 this first application of the dual tracer technique in the open ocean produced estimates of the gas transfer rate that were similar in magnitude to those obtained previously from measurements in shelf seas we found no evidence that gas transfer rates declined during the development of the algal bloom incorporation of the new open ocean measurements with other published dual tracer data gives a relationship between transfer velocity and wind speed that explains 82 of the total variance in the dataset

geochemical evidence for a comet shower in the late eocene analyses of pelagic limestones indicate that the flux of extraterrestrial helium 3 to earth was increased for a 2 5 million year my period in the late eocene the enhancement began 1 my before and ended 1 5 my after the major impact events that produced the large popigai and chesapeake bay craters 36 million years ago the correlation between increased concentrations of helium 3 a tracer of fine grained interplanetary dust and large impacts indicates that the abundance of earth crossing objects and dustiness in the inner solar system were simultaneously but only briefly enhanced these observations provide evidence for a comet shower triggered by an impulsive perturbation of the oort cloud

temporal variation of 3he 4he ratio recorded in deep sea sediment cores he isotopic composition was measured for 72 deep sea sediments from 16 sites in the pacific and atlantic oceans and the japan sea 3he content ranges from less than 10 12 cm3 stp g to about 6 10 11 cm3 stp g and 3he 4he from about 10 8 to 1 67 10 4 the he isotopic data lie fairly well on a mixing curve in a 3he 4he 3he diagram where the end members of the mixing curve are extraterrestrial he in interplanetary dust particles idp s and terrestrial he in ocean sediments this confirms the view that there are significant amounts of extraterrestrial he in ocean sediments from global fallout of idp s into deep sea sediments 3he flux estimated for two long cores gives a value of about 1 5 1 0 10 15 cm3 stp cm2 yr over a time span of 40 m y which corresponds to an annual fallout rate of idp s size 10 m of about 400 t in one of the cores we observe a 3he spike which is associated with anomalously high ir content 1 86 0 56 ppb this may be due to meteorite debris

ventilation of the deep western boundary current and abyssal western north atlantic estimates from tritium and 3he distributions abstract the tritium and excess 3he data from the 1981 tto nas program are used to study the time scales for the ventilation of the deep western basin by recently formed north atlantic deep water nadw the large scale distributions of tritium and 3he in the deep north atlantic are presented and tracer inventories are computed for individual deep water basins the bulk of the bomb tritium and thus new nadw resided in 1981 in the deep labrador sea and western subpolar gyre with a slightly smaller amount in the deep western subtropical gyre the maximum excess 3he values were located south of the overflows in the labrador sea the result of competition between ventilation and in situ tritium decay the subpolar gyre was also the site of the strongest increase in decay corrected tritium 120 and excess 3he 100 between the 1972 geosecs survey and the 1981 tto nas program the observed deep water tritium inventory is in reasonable agreement with model tracer inputs computed for the combined overflow

climatology of postsunset equatorial spread f over jicamarca 1 we use radar observations from 1996 to 2006 to study the climatology of postsunset equatorial 3 m spread f irregularities over jicamarca during all seasons we show that the spread f onset times do not change with solar flux and that their onset heights which occur near the altitude of the evening f region velocity vortex increase linearly from about 260 to 400 km from solar minimum to solar maximum higher onset heights generally lead to stronger radar echoes during the equinox spread f onset occurs near vertical drift evening reversal times while during the december solstice they occur near the drift reversal times close to solar minimum and near the time of the prereversal velocity peak for high solar flux conditions on average radar plume onset occurs earlier with increasing solar flux in all seasons plume onset and peak altitudes increase with solar activity and the peak heights are generally highest during the equinox the f region upward drift velocities that precede spread f onset increase from solar minimum to solar maximum and are approximately proportional to the maximum prereversal drift peak velocities

excess helium and argon of radiogenic origin in mediterranean brine basins extraordinary helium and argon signatures were observed in a recently discovered brine lake district in the eastern mediterranean sea at water depths of 3500 m in the urania basin 4he concentrations are enriched by a factor of up to 32000 compared to normal seawater low 3he 4he ratios of 1 10 7 and high 40ar 36ar ratios of up to 470 indicate a radiogenic source these data represent by far the highest radiogenic supersaturations ever observed in an oceanic environment we propose a new conceptional model assuming that the urania basin is fed by advective transport from a deep fluid reservoir below the messinian evaporite sequence the evaporite seal provides the unique condition for accumulating the extraordinary high amounts of radiogenic helium from deep sedimentary strata injection of radiogenic helium from brine pools like the urania basin may contribute significantly to the inventory of terrigenic helium in the deep waters of the eastern mediterranean

radar and satellite global equatorial f region vertical drift model we present the first global empirical model for the quiet time f region equatorial vertical drifts based on combined incoherent scatter radar observations at jicamarca and ion drift meter observations on board the atmospheric explorer e satellite this analytical model based on products of cubic b splines and with nearly conservative electric fields describes the diurnal and seasonal variations of the equatorial vertical drifts for a continuous range of all longitudes and solar flux values our results indicate that during solar minimum the evening prereversal velocity enhancement exhibits only small longitudinal variations during equinox with amplitudes of about 15 20 m s is observed only in the american sector during december solstice with amplitudes of about 5 10 m s and is absent at all longitudes during june solstice the solar minimum evening reversal times are fairly independent of longitude except during december solstice during solar maximum the evening upward vertical drifts and reversal times exhibit large longitudinal variations particularly during the solstices in this case for a solar flux index of 180 the june solstice evening peak drifts maximize in the pacific region with drift amplitudes of up to 35 m s whereas the december solstice velocities maximize in the american sector with comparable magnitudes the equinoctial peak velocities vary between about 35 and 45 m s the morning reversal times and the daytime drifts exhibit only small variations with the phase of the solar cycle the daytime drifts have largest amplitudes between about 0900 and 1100 lt with typical values of 25 30 m s we also show that our model results are in good agreement with other equatorial ground based observations over india brazil and kwajalein

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

deep water formation and exchange rates in the greenland norwegian seas and the eurasian basin of the arctic ocean derived from tracer balances abstract multi tracer data sets collected in the greenland norwegian seas and the eurasian basin of the arctic ocean in the 1970s and 1980s are used together with temperature and salinity to 1 constrain box model calculations of the deep water formation rates in the greenland sea and the eurasian basin of the arctic ocean and 2 estimate the exchange rates of deep waters depth 1 500m between the greenland norwegian seas and the eurasian basin we obtain deep water formation rates of 0 1sv since 1980 to 0 47sv from at least 1965 to 1980 for the greenland sea and 0 3sv for the eurasian basin of the arctic ocean the southward flux of eurasian basin deep water through fram strait is estimated to be about 1sv about 0 12sv of this flux are transported into the greenland sea about 0 37sv reach the deep norwegian sea through the jan mayen fracture zone and about 0 39sv leave the arctic ocean through a shallower core which more or less directly feeds into the iceland sea and after modification eventually ends up in the overflow waters the outflow of eurasian basin deep water is balanced by deep water formation in the arctic ocean and by inflow of norwegian sea deep water about 0 77sv of deep water formed in the greenland sea and the eurasian basin contribute to the formation of north atlantic deep water uncertainties of the fluxes are estimated to be roughly 20 to 30