upper ocean variability between iceland and newfoundland 1993 1998 we investigate the variability of upper ocean temperature and surface salinity between iceland and newfoundland along world ocean circulation experiment line ax2 in 1993 1998 north of 54 n as well as close to newfoundland deviations from the seasonal cycle indicate upper ocean warming from 1994 to 1998 with largest anomalous warming during late 1995 early 1996 and during the winter 1997 1998 north of 54 n surface salinity increases after mid 1996 the winter of 1995 1996 is the first winter of weak westerlies after more than 20 years of strong westerly conditions in the subarctic gyre and the ocean loses less heat during that winter than during a normal year the magnitude of upper ocean heat content change is at least twice as large as what results from the change in air sea fluxes which indicates a complementary contribution to heat content change by advection altimetric sea level data indicate also an increase of sea level of the order of 6 5 cm during that year out of which more than 4 cm is contributed by the steric change associated with the temperature increase a principal component analysis of the sea level data suggests that the increase sensed along line ax2 west of the reykjanes ridge is found in most of the subpolar gyre although to a lesser extent in most other areas

continuous marine radiocarbon reservoir calibration and the 13c suess effect in the irish sea results from the first multi centennial shell based marine master chronology abstract the identification in various proxy records of periods of rapid decadal scale climate change over recent millennia together with the possibility that feedback mechanisms may amplify climate system responses to increasing atmospheric co2 highlights the importance of a detailed understanding at high spatial and temporal resolutions of forcings and feedbacks within the system such an understanding has hitherto been limited because the temperate marine environment has lacked an absolute timescale of the kind provided by tree rings for the terrestrial environment and by corals for the tropical marine environment here we present the first annually resolved multi centennial 489 year absolutely dated shell based marine master chronology the chronology has been constructed by detrending and averaging annual growth increment widths in the shells of multiple specimens of the very long lived bivalve mollusc arctica islandica collected from sites to the south and west of the isle of man in the irish sea the strength of the common environmental signal expressed in the chronology is fully comparable with equivalent statistics for tree ring chronologies analysis of the 14c signal in the shells shows no trend in the marine radiocarbon reservoir correction r although it may be more variable before 1750 the 13c signal shows a very significant r2 0 456 p

north atlantic nordic seas exchanges abstract the northeastern part of the north atlantic is unique in the sense that it is much warmer in the surface than other ocean areas at similar latitudes the main reason for this is the large northward transport of heat that extends to high latitudes and crosses the greenland scotland ridge to enter the nordic seas and the arctic there the warm atlantic water is converted to colder water masses that return southwards over the ridge partly as surface outflows and partly as overflows through the deep passages across the ridge in this paper the state of knowledge on the exchanges especially across the eastern part of the greenland scotland ridge is reviewed based on results from the ices nansen north atlantic norwegian sea exchanges project from the nordic woce project and from other sources the accumulated evidence allows us to describe the exchanges in fair detail the origins of the waters the patterns of their flow towards and over the ridge and their ultimate fate there is also increasing information on temporal variations of the exchanges although dynamical changes are still not well understood quantitative estimates for the volume transport of most of the overflow branches seem reasonably well established and transport measurements of the atlantic inflows to the nordic seas are approaching acceptable levels of confidence which allows preliminary budgets to be presented the deep overflows are driven by pressure gradients set up by the formation of deep and intermediate water the dominance of deep overflows over surface outflows in the water budget argues that this thermohaline forcing also dominates over direct wind stress and estuarine forcing in driving the atlantic water inflow across the greenland scotland ridge while wind stress seems to influence the characteristics and distribution of the atlantic water north of the ridge

marine radiocarbon reservoir corrections for the midto late holocene in the eastern subpolar north atlantic the time dependency of the regional difference r in the marine radiocarbon reservoir correction is an important issue for the calibration of marine radiocarbon ages and also provides information about past ocean circulation changes few measurements of holocene reservoir corrections are available for the climatically important north atlantic we determined r for intervals during the past 6100 years before present bp by comparing radiocarbon ages of 31 marine and terrestrial sample pairs from 14 archaeological sites from the coast of ireland scotland and the orkney islands we find that while a time dependency in r for this region cannot be ruled out within the error of the determinations the r appears to have been constant for at least the last 2000 and possibly the last 6000 years this work results in a recommendation for r of 33 93 for the region

life on the edge microbial biomineralization in an arsenic and lead rich deep sea hydrothermal vent abstract unravelling complex microbial activity in modern hydrothermal vents can provide crucial insights into the evolution of ancient life on earth it is well established that microorganisms in hydrothermal vents have a significant impact on the cycling of metals and mineral formation however the detailed roles played by microorganisms in driving sulfide deposition and cycling of toxic metals like arsenic as and lead pb in high temperature deep sea hydrothermal vents remain unknown the understanding of these mechanisms in extreme environments is of particular importance as as has been postulated as a driver of microbial activities on the early earth here we present the first geologic evidence of pb as rich microbial filamentous clusters observed in a modern high temperature black smoker from the manus back arc basin papua new guinea the clusters occur as net like structures on the surface of barite and sulfides and are composed of multiple filaments and fine grained pb as sulfosalt each of the filaments includes an as pb rich sulfosalt core and organic rich shell structure with elevated carbon nitrogen and phosphorus further synchrotron x ray absorption near edge structure analysis shows that the clusters contain a mixture of as ii and as iii additionally those filaments show a close association with realgar as4s4 by penetrating and dissolving this as sulfide mineral we interpret the filaments to be a result of as related microbial activity in as and pb enriched hydrothermal environments the findings show possible processes through which extremophiles live in pb and as rich environments during chimney growth in addition as hydrothermal vents are regarded as modern analogs of ancient volcanogenic massive sulfide deposits the observed biominerals present the potential to be used as proxies to trace the signatures of early life in ancient geological systems

environmental controls on the stable isotopic composition of mercenaria mercenaria potential application to paleoenvironmental studies 1 we have investigated the environmental controls of seasonally resolved records of oxygen and carbon isotopes of modern mercenaria mercenaria bivalves collected live from five coastal sites along the east coast of north america seasonal profiles of 18o and 13c obtained by subsampling the incremental growth layers of aragonite were compared with in situ historical records of temperature and salinity we show that m mercenaria 18o profiles track accurately the seasonal variations of water temperature and that variations in growth rates do not affect the shell 18o values growth rates are strongly reduced or interrupted below water temperatures ranging from 8 to 10 c implying that only bivalves sampled in tropical areas track the full amplitude of seasonal variations although further measurements of water 18o and a better understanding of seasonal variations of the water 18o salinity relationships are necessary mercenaria mercenaria bivalves appear to precipitate their shell close to isotopic equilibrium whereas the amplitude of the seasonal profiles of 18o reflects variations in water temperature the annual average 18o decreases with latitude reflecting the trend of rainfall and riverwater 18o with latitude over the northern american continent

marine 14c reservoir ages for 19th century whales and molluscs from the north atlantic abstract in order to compare radiocarbon dates on marine and terrestrial samples the former have to be corrected for a reservoir age we present reservoir ages from dating 21 whales collected 1860 1901 and recalculating dates of 23 molluscs collected 1857 1926 most of the whales were caught along the coast of norway but one is from france and one from iceland we assume the former mainly lived in the north and equatorial atlantic and in the norwegian sea whales feed only on pelagic organisms and will provide the reservoir age for the open ocean surface water however they travel long distances and will integrate the reservoir ages of the different water masses along their way molluscs dated from norway spitsbergen and arctic canada are stationary and monitor the sea water passing their dwelling site but some also take up carbon from particulate food or sediment pore water coastal water also often contains some continental carbon we present two different views on how to analyze and interpret the data mangerud recommends to use reservoir ages based on a combination of the whale and mollusc dates i e 380 30 and 360 30 yr relative to intcal04 and british oak respectively and a r value of 20 30 for the surface water in the n atlantic and norwegian sea bondevik and gulliksen maintain that the reservoir age and r along the norwegian coast is latitude dependant with r values increasing from 3 22 in the south to 105 24 at spitsbergen whales reflecting north atlantic open ocean surface water have lower r 7 11 than most molluscs

and ratios in skeletal calcite of mytilus trossulus covariation with metabolic rate salinity and carbon isotopic composition of seawater minor element and isotopic compositions of marine bivalve calcite are frequently used as proxy records of seawater temperature and salinity although molluscan calcite is secreted at or near oxygen isotope equilibrium the influence of metabolic activity i e vital effects on skeletal srca ratios and 13c values is not well known we present measurements of skeletal chemistry from a consecutive samples milled in chronological order from the organism s final year of growth and b adjacent samples within three separate growth bands of the marine mussel mytilus trossulus to investigate chemical disequilibrium effects among different parts of the shell seawater temperature and salinity were monitored for one year at squirrel cove british columbia at the end of the year a young rapidly growing mussel mussel a and an old slowly growing mussel mussel b were harvested from this site growth bands within the shells were sampled to provide a chronological record of shell carbonate chemistry results from consecutive samples show 1 a significantly higher average srca ratio in mussel a than that in mussel b and 2 13c values that correlate well with salinity in mussel a but not in mussel b results from time equivalent adjacent samples show 1 higher srca and 13c values near the ventral margin than at time equivalent regions on lateral margins of the shell and 2 little or no variation in 18o values these observations suggest that skeletal chemistry srca and 13c is primarily controlled by rate of mantle metabolic activity and secondarily modified by variation in seawater salinity because metabolic activity in the mantle at the site of carbonate precipitation varies with shell curvature the composition of calcite secreted along lateral margins is influenced to a greater extent by metabolic activity than calcite secreted coevally at the central margin of the shell hence the chemistry of calcite secreted at the ventral margin is precipitated in near equilibrium with seawater and allows accurate estimation of seawater srca ratios and carbon isotopic composition in contrast shell precipitation along lateral margins is dominantly controlled by metabolic activity and calcite chemistry is not in equilibrium with ambient seawater in this context we present a biomineralization model where variations in skeletal srca and 13c values are explained in the context of mantle metabolic activity and seawater salinity

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

decade time scale variability of ventilation in the north atlantic high precision measurements of bomb radiocarbon in banded corals the first high precision radiocarbon measurements for the upper ocean are presented for banded corals from two sites in the north atlantic ocean the striking dissimilarities between the post 1950 records at bermuda in the sargasso sea and the florida straits in the gulf stream illustrate the different mixing processes in the upper ocean at each site convective overturn associated with 18 degree water formation during late winter in the northern sargasso sea facilitates storage of considerable quantities of bomb radiocarbon at depth which accounts for the damping of the 14c signal at bermuda during the 1960s a multibox isopycnal mixing model is used to estimate the ventilation rate of the upper 700 m of the water column in the sargasso sea from 1950 to 1983 an inverse model is used that is the water mass renewal rate was calculated for the post bomb period in order to satisfy the bomb radiocarbon time history in the corals sea water radiocarbon measurements made during the geosecs 1972 1973 and transient tracers in the ocean 1980 1981 surveys are used to constrain the subsurface radiocarbon values calculated by the model results show that the rate of water mass renewal in the sargasso sea was high during 1963 1964 decreased during the late 1960s and remained low during most of the 1970s the 14c derived record of water mass renewal precedes by about 4 years that derived from isopycnal salinity in the sargasso sea jenkins 1982 illustrating that the coral 14c record is controlled to a large extent by changes in ocean circulation rather than by atmospheric exchange of co2

the shell of the queen scallop aequipecten opercularis l as a promising tool for palaeoenvironmental reconstruction evidence and reasons for equilibrium stable isotope incorporation abstract the queen scallop aequipecten opercularis has been an important part of the marine fauna of the northeast atlantic region since the miocene and is a suitable candidate for palaeoenvironmental studies using stable isotopes modern shells were investigated to determine if carbonate is precipitated in isotopic equilibrium in this species and to confirm that growth continues through the year specimens of a opercularis were cultured under monitored semi natural conditions over an autumn winter period and the analyses of these specimens were supplemented with isotope data from preserved indigenous north sea specimens the results indicated that the cultured specimens grew in relatively low temperatures that oxygen isotopes of shell exterior carbonate were precipitated in isotopic equilibrium and that a large proportion of the ambient temperature range was recorded in shell carbonate the indigenous north sea specimens exhibited a good correspondence to predicted oxygen isotope values for summer the isotopic record related to winter was however somewhat truncated due to growth decelerations in the specimens carbon isotopes of shell exterior carbonate were calculated as being derived primarily from external sources and showed comparatively little influence from metabolically derived carbon this suggests that carbon isotopes were at least close to equilibrium with ambient waters the limited incorporation of metabolic products suggests that a opercularis would be a good monitor of changing carbon isotope ratios in seawater dissolved inorganic carbon the occurrence of equilibrium shell precipitation is explained using a pteriomorph shell calcification model which proposes that transport of ions through the periostracum caused the composition of the extrapallial fluid to be effectively the same as seawater carbonate secretion is therefore not influenced significantly by biological vital effects

stable isotope aspects of modern molluscs brachiopods and marine cements from cool water carbonates lacepede shelf south australia the isotopic composition of some modern gastropods bivalves and brachiopods from the lacepede shelf of south australia were investigated to determine the isotopic equilibrium and dis equilibrium states of biogenic and non biogenic inorganic carbonates and to understand the kinetic and metabolic isotopic effects on precipitating carbonates and the isotopic fractionation between these different carbonates and dissolved bicarbonate seawater and high mg calcite hmc marine cements from different depths were also analyzed to determine equilibrium isotopic composition this study shows that the shells of some cool water gastropods and bivalves precipitate in isotopic equilibrium with their ambient waters while brachiopod shells show 18o values heavier than equilibrium values and coralline algae and ahermatypic corals exhibit significant metabolic and kinetic effects the isotopic equilibrium precipitation seen in these biogenic carbonates results from lower precipitation rates that are in turn caused by the lower bottom temperatures in this area

the great salinity anomaly in the northern north atlantic 1968 1982 the widespread freshening of the upper 500 800m layer of the northern north atlantic which this paper describes represents one of the most persistent and extreme variations in global ocean climate yet observed in this century though a range of explanations have been advanced to explain this event including in situ changes in the surface moisture flux this paper describes the great salinity anomaly as largely though not entirely an advective event traceable around the atlantic subpolar gyre for over 14 years from its origins north of iceland in the mid to late 1960s until its return to the greenland sea in 1981 1982 the overall propagation speed around this subpolar gyre is estimated at about 3cm s 1 of the total salt deficit associated with the anomaly as it passed south along the labrador coast in 1971 1973 about 72 109 tonnes a deficit equivalent to about two thirds of this figure 47 109 tonnes ultimately passed through the faroe shetland channel to the barents sea arctic ocean and greenland sea during the mid 1970s possible effects on deep water formation and on the representativeness of historical section data are discussed

influence of the atlantic subpolar gyre on the thermohaline circulation during the past decade record high salinities have been observed in the atlantic inflow to the nordic seas and the arctic ocean which feeds the north atlantic thermohaline circulation thc this may counteract the observed long term increase in freshwater supply to the area and tend to stabilize the north atlantic thc here we show that the salinity of the atlantic inflow is tightly linked to the dynamics of the north atlantic subpolar gyre circulation therefore when assessing the future of the north atlantic thc it is essential that the dynamics of the subpolar gyre and its influence on the salinity are taken into account

late holocene radiocarbon variability in northwest atlantic slope waters abstract deep sea gorgonian corals secrete a 2 part skeleton of calcite derived from dissolved inorganic carbon at depth and gorgonin derived from recently fixed and exported particulate organic matter radiocarbon contents of the calcite and gorgonin provide direct measures of seawater radiocarbon at depth and in the overlying surface waters respectively using specimens collected from northwest atlantic slope waters we generated radiocarbon records for surface and upper intermediate water layers spanning the pre and post bomb 14 c eras in labrador slope water lsw convective mixing homogenizes the pre bomb 14 c signature 67 4 to at least 1000 m depth surface water bomb 14 c signals were lagged and damped peaking at 45 in the early 1980s relative to other regions of the northwest atlantic and intermediate water signals were damped further off southwest nova scotia the vertical gradient in 14 c is much stronger in surface water pre bomb 14 c averaged 75 5 at 250 475 m depth pre bomb 14 c oscillated quasi decadally between 80 and 100 likely reflecting interannual variability in the presence of labrador slope water vs warm slope water wsw finally subfossil corals reveal no systematic changes in vertical 14 c gradients over the last 1200 yr

the subpolar mode water of the north atlantic ocean abstract the warm waters of the subtropical and subpolar basins of the north atlantic have tight regional temperature salinity relationships and are conventionally called the regional central waters a volumetric census of the temperature salinity characteristics of the north atlantic by wright and worthington 1970 shows that waters characterized by certain segments of the t s relationships have large volumes compared to those of other segments volumetric mode waters such mode waters appear as layers with increased vertical separation between isopycnals pycnostads the present study reports on the existence of pycnostads in the central and eastern north atlantic these subpolar mode waters are formed by deep winter convection in the subpolar north atlantic and participate in the upper water circulation of the northern north atlantic the seasonal outcropping of the pycnostads occurs within and adjacent to the north atlantic current the irminger current the east and west greenland currents and

on the radiocarbon record in banded corals exchange parameters and net transport of 14co2 between atmosphere and surface ocean we have made radiocarbon measurements of banded hermatypic corals from florida belize and the galapagos islands interpretation is presented here of these previously reported results these measurements represent the 14c 12c ratios in dissolved inorganic carbon dioc in the surface ocean waters of the gulf stream and the peru current at the time of coral ring formation a depletion in radiocarbon concentration was observed in coral rings that grew from a d 1900 1952 it was caused by dilution of existing 14c levels with dead co2 from fossil fuel burning the suess effect or se the observed depletion of radiocarbon was greater in corals from the gulf stream 11 than in corals from the peru current 6 a similar trend was observed in the distribution of bomb produced 14c in corals that had grown during the years following a d 1952 the concentration of bomb produced radiocarbon was much higher in corals from temperate regions florida belize hawaiian islands than in corals from tropical regions galapagos islands and canton island a linear relationship appears to exist between the preanthropogenic 14c values and the se values measured in the individual corals because the 14c in corals is derived from two different carbon reservoirs 1 the atmosphere and 2 the subsurface ocean a linear relationship is also observed between the preanthropogenic 14c values and the concentration of bomb produced 14c in the individual corals during a d 1973 the apparent radiocarbon ages of the surface waters in temperate and tropical oceans during the preanthropogenic period range from about 280 to 520 years b p 40 to 69 at all investigated locations it is likely that waters at subsurface depths have the same apparent radiocarbon age of about 670 years b p from the change of oceanic 14c in the surface ocean during post bomb times the approximate annual rate of net input of 14co2 to the ocean waters is calculated to be about 8 of the prevailing 14c difference between atmosphere and ocean from this input and from preanthropogenic 14c values found at each location it can be seen that vertical mixing of water in the peru current is about 3 times greater than that in the gulf stream

variability of the northeast atlantic sea surface δ14c and marine reservoir age and the north atlantic oscillation nao abstract we compiled new 14 c analyses of mollusc shells bivalves and gastropods of known age from the collection of the museum national d histoire naturelle de paris and previously published data to investigate changes in the sea surface 14 c and reservoir age in the northeast atlantic sector nea between 1823 and 1952 ad the mollusc shells are mainly located off the atlantic margin between 45 n and 60 n downstream of the north atlantic current nac we show that the temporal variability of the nea 14 c is independent of the mollusc species depth habitat diet and latitudinal distribution the quasi null difference between mollusc 14 c and the marine model indicate that the mollusc 14 c reflects the 14 c values of open marine conditions between 1823 and 1850 ad the pre anthropogenic mean of 14 c is 45 5 corresponding to a reservoir age of 380 60 years and a r value of 7 50 years in agreement with previous estimates the 14 c values show a significant long term decrease of 12 from 1823 to 1952 ad attributed to changes in 14 c production between 1823 and 1900 ad and the suess effect between 1900 and 1952 ad between 1885 and 1950 ad 14 c fluctuations of 10 up to 18 occurred in the northeast atlantic corresponding to reservoir age variations of 90 years up to 170 years these fluctuations are very similar to changes of 14 c in the southern norwegian sea spectral analyses of the nea 14 c exhibit quasi periodic cycles of about 7 4 years almost equivalent to the quasi periodic cycles of the winter index of the north atlantic oscillation nao with a period around 6 5 years we find that changes of nea 14 c cannot be attributed to changes in river runoff or the precipitation evaporation budget the 14 c lows or high reservoir ages correspond to the more intense phase of the winter nao with a time lag of 1 3 years such a time lag may reflect the eastward transit time of upstream changes originating in the labrador sea then entrained within the nac along with the subpolar gyre into the northeast atlantic sector during these events we estimate that about 70 of the total transport in the nac was due to water originating in the labrador sea

stable carbon isotopes in marine porewaters abstract we present centimeter scale porewater 13 c profiles from four sites in the central equatorial pacific ocean which reveal steep porewater 13 c gradients up to 1 0 cm 1 at the deep sea sediment water interface we describe the processes controlling porewater carbon isotopic composition and incorporate them into a model of the deep sea benthic carbon cycle our measured 13 c profiles are then used to estimate carbon rain rates at two of these sites manop sites c and s the 13 c data yield organic carbon rain rates of 10 mol c cm 2 yr 1 at site c and 3 mol c cm 2 yr 1 at site s these carbon rain rates agree with recent carbon rain estimates based on sediment trap data and porewater nitrate profiles but are a factor of 2 lower than estimates based on millimeter scale porewater oxygen profiles our model results indicate that changes of the same magnitude in organic carbon rain rate and bottom water composition o 2 co 2 and 13 c have comparable effects on the carbon isotopic composition of surficial porewaters this suggests the need to consider the effects of benthic carbon cycling on the stable carbon isotope record preserved in deep sea benthic foraminifera tests

regional variation of total microbial biomass in sediments of the deep arabian sea eight different sites from 2300 to 4420 m water depth in the arabian sea were sampled for a biochemical quantification of phospholipid concentrations in the sediments this method serves as a measure of microbial biomass in marine sediments comprising all small sized organisms including bacteria fungi protozoa and metazoa phospholipid concentrations can be converted to carbon units as an estimate of total microbial biomass in the sediments the average phospholipid concentrations in the surface sediments 0 1 cm of the 4 abyssal sites ranged from 7 nmol cm 3 at the southern site sast 10 n 65 e 4425 m to 29 nmol cm 3 at the western site wast 16 n 60 e 4045 m the high values detected at the abyssal station wast exceeded those in the literature for other abyssal sites and were comparable to values from the upper continental slope of the ne atlantic and the arctic at the four continental slope sites in the arabian sea average phospholipid concentrations ranged from 9 to 53 nmol cm 3 with the maximum values at stations a 2314 m and d 3142 m close to the omani coast records of particulate organic carbon flux to the deep sea are available for four of the investigated locations allowing a test of the hypothesis that the standing stock of benthic microorganisms in the deep sea is controlled by substrate availability i e particle sedimentation total microbial biomass in the surface sediments of the arabian sea was positively correlated with sedimentation rates consistent with previous studies of other oceans the use of the measurement of phospholipid concentrations as a proxy for input of particulate organic matter is discussed

hydrography and through flow in the north eastern north atlantic ocean the nansen project abstract the circulation and hydrography of the north eastern north atlantic has been studied with an emphasis on the upper layers and the deep water types which take part in the thermohaline overturning of the oceanic conveyor belt over 900 hydrographic stations were used for this study mainly from the 1987 1991 period the hydrographic properties of subpolar mode water in the upper layer which is transported towards the norwegian sea showed large regional variation the deep water mass was dominated by the cold inflow of deep water from the norwegian sea and by a cyclonic recirculation of lower deep water with a high antarctic bottom water content at intermediate levels the dominating water type was labrador sea water with only minor influence of mediterranean sea water in the permanent pycnocline traces of antarctic intermediate water were found geostrophic transports have been estimated and these agreed in order of magnitude with the local heat budget with current measurements with data from surface drifters and with the observed water mass modification a total of 23 sv of surface water entered the region of which 20 sv originated from the north atlantic current while 3 sv entered via an eastern boundary current of this total 13 sv of surface water left the area across the reykjanes ridge and 7 sv entered the norwegian sea while 3 sv was entrained by the cold overflow across the iceland scotland ridge approximately 1 4 sv of norwegian sea deep water was involved in the overflow into the iceland basin which with about 1 1 sv of entrained water and 1 1 sv recirculating lower deep water formed a deep northern boundary current in the iceland basin at intermediate depths where labrador sea water formed the dominant water type about 2 sv of entrained surface water contributed to a saline water mass which was transported westwards along the south icelandic slope