eastern mediterranean surface water nd during eemian sapropel s5 monitoring northerly mid latitude versus southerly sub tropical freshwater contributions abstract a well developed sapropel s5 was deposited in the eastern mediterranean during the last interglacial eemian 124 119 ka freshwater contributions to the basin at this time can be traced using the isotopic composition of nd in planktonic foraminifera this enables differentiation between radiogenic sources to the south under the influence of the african monsoon and unradiogenic sources to the north relating to the mid latitude westerlies here we compare new nd data from a core in the southeast aegean sea with published data from the ionian and levantine seas shifts towards more radiogenic nd in the lower and middle parts of sapropel s5 are most pronounced in the ionian sea record with nd and 18og ruber co varying more closely here than in the levantine and aegean seas this is consistent with a freshwater source proximal to the ionian sea site likely indicating a substantial reactivation of rivers flowing northward from the central saharan watershed the lack during s5 deposition of a noticeable shift towards more unradiogenic nd in the aegean record would exclude a large influx of water from the northern borders of the eastern mediterranean during sapropel deposition these findings support a scenario whereby the last interglacial eastern mediterranean was influenced strongly by the remote effects of an intensified african monsoon with more local precipitation in the northern borders contributing relatively little to the sea surface composition

balancing rare earth element distributions in the northwestern mediterranean sea abstract elemental concentrations of rare earth elements ree and isotopic compositions of neodymium end have been measured in three water column profiles in the north western mediterranean sea clear enrichments of ree are observed when comparing to adjacent atlantic waters suggesting ree inputs along the circulation in this area for the first time relative proportions of external sources including submarine groundwater discharges sgd have been quantified for the studied area atmospheric deposition is estimated to be the most important external source for all the ree with an average contribution of 44 followed by diffusion from porewaters which provide a 30 dissolved riverine fluxes account for 11 sgd for 10 and dissolution of remobilized surface sediments the remaining 6 mass balances accounting for seawater transport and identified external sources have been delineated for the three main water masses modified atlantic waters levantine intermediate waters and western mediterranean deep waters they show that the balances of ree in this area are dominated by seawater mass mixing superimposed on this hydrography ree vertical profiles are affected by external sources and biogeochemical cycling dissolved ree are correctly balanced in deep waters whereas substantial missing fluxes are identified in the surface and intermediate water masses additional net lree outputs and hree inputs are required in the surface waters while net output fluxes for all the ree are missing at intermediate waters the most likely process suggested here is an active reversible scavenging consistent with a stronger adsorption of lree compared to hree in the particular case of the redox sensitive cerium the most plausible mechanism to explain the net output missing fluxes is ce 3 removal by particle scavenging via oxidation to insoluble ce 4 estimated ce oxidation rates of 0 33 d 1 in surface waters agree well with previously published values exchange fluxes derived from the isotopic nd mass balance indicate higher nd scavenging in surface compared to intermediate waters

rare earth element concentrations and nd isotopes in the southeast pacific ocean 1 three vertical profiles of rare earth element concentrations and nd isotopic compositions have been measured in the remote southeast pacific ocean the three stations represent contrasting environments the oligotrophic center of the gyre station gyr the transition zone east of the south tropical front station egy and the peru chile upwelling marked by a pronounced oxygen minimum station upx rare earth concentrations display nutrient like vertical profiles except at upx where surface waters are enriched at this station nd isotopic compositions are clearly more radiogenic than in the open ocean suggesting that boundary exchange process is releasing lithogenic rare earth element from the volcanic andes unexpected radiogenic values end reaching 3 7 are also observed at 2000 m at station gyr in the upper circumpolar deep water that commonly have end values around 6 exchange processes related to hydrothermal activity are suspected to produce this increase in end in the vicinity of the east pacific rise these results provide some guidance for higher resolution studies planned in this region by the international geotraces program

heat transfer in magma in situ heat transfer rates in a basaltic magma were measured under typical magma chamber conditions and a numerical model of the experiment was used to estimate magma viscosity the results are of value for assessing methods of thermal energy extraction from magma bodies in the upper crust as well as for modeling the evolutionary track of these systems

the hafnium neodymium isotopic composition of atlantic seawater the first full water column hafnium isotopic compositions of atlantic seawater have been obtained at seven locations from the labrador sea to the drake passage despite subpicomolar concentrations in seawater a precision of the hf isotopic measurements of 03 epsilon hf units was achieved an overall epsilon hf range between 3 1 in the labrador sea and 4 4 in antarctic bottom water was determined the distribution of which broadly reflects continental weathering inputs within particular water column profiles significant differences of up to 4 epsilon hf units occur combined with nd isotope data of the same samples it is evident that the hf isotopic composition of seawater is too radiogenic for a given nd isotopic composition and that the largest difference between expected and measured hf isotopic compositions in seawater occurs near the oldest continental crust in the labrador sea this corroborates the previous proposition which was mainly based on ferromanganese crust data that the hf isotopic composition of seawater is controlled by incongruent weathering of continental crust and possibly to some extent by hydrothermal contributions hafnium concentrations in the ocean do not increase along the deep ocean conveyer indicating an oceanic residence time of only a few hundred years which is significantly shorter than previously assumed the hf isotopic composition of past seawater can therefore serve as a proxy for short distance basin scale mixing processes and the regime and intensity of nearby continental weathering processes c 2009 elsevier b v all rights reserved

the hafnium and neodymium isotope composition of seawater in the atlantic sector of the southern ocean we present the first combined dissolved hafnium hf and neodymium nd concentrations and isotope compositions of deep water masses from the atlantic sector of the southern ocean eight full depth profiles were analyzed for hf and twelve for nd hafnium concentrations are generally depleted in the upper few hundred meters ranging between 0 2 pmol kg and 0 4 pmol kg and increase to relatively constant values of around 0 6 pmol kg in the deeper water column at the stations north of the polar front pf nd concentrations increase linearly from about 10 pmol kg at depths of 200 m to up to 31 pmol kg close to the bottom indicating particle scavenging and release within the weddell gyre wg however nd concentrations are essentially constant at 25 pmol kg at depths greater than 1000 m the distributions of both elements show a positive correlation with dissolved silicon implying a close linkage to diatom biogeochemistry hafnium essentially shows invariant isotope compositions with values averaging at ehf 4 6 whereas nd isotopes mark distinct differences between water masses such as modified north atlantic deep water nadw end 11 to 10 and antarctic bottom water aabw end 8 6 to 9 6 but also waters locally advected via the agulhas current can be identified by their unradiogenic nd isotope compositions mixing calculations suggest that a small fraction of nd is removed by particle scavenging during mixing of water masses north of the pf nevertheless the nd isotope composition has apparently not been significantly affected by uptake and release of nd from particles as indicated by mixing calculations a mixing envelope of an approximated north pacific and a north atlantic end member shows that nd isotope and concentration patterns in the lower circumpolar deep water lcdw can be fully explained by 30 70 percentage contributions of these respective end members

rare earth elements and neodymium isotopes in sedimentary organic matter abstract we report rare earth element ree and neodymium nd isotope data for the organic fraction of sediments collected from various depositional environments i e rivers n 25 estuaries n 18 open ocean settings n 15 and cold seeps n 12 sedimentary organic matter som was extracted using a mixed hydrogen peroxide nitric acid solution 20 h2o2 0 02 m hno3 after removal of carbonate and oxy hydroxide phases with dilute hydrochloric acid 0 25 m hcl a series of experimental tests indicate that extraction of sedimentary organic compounds using h2o2 may be complicated occasionally by partial dissolution of sulphide minerals and residual carbonates however this contamination is expected to be minor for ree because measured concentrations in h2o2 leachates are about two orders of magnitude higher than in the above mentioned phases the mean ree concentrations determined in the h2o2 leachates for samples from rivers estuaries coastal seas and open ocean settings yield relatively similar levels with ree 109 86 ppm mean s n 58 the organic fractions leached from cold seep sediments display even higher concentration levels 285 150 ppm mean s n 12 the h2o2 leachates for most sediments exhibit remarkably similar shale normalized ree patterns all characterized by a mid ree enrichment compared to the other ree this suggests that the distribution of ree in leached sedimentary organic phases is controlled primarily by biogeochemical processes rather than by the composition of the source from which they derive e g pore river or sea water the nd isotopic compositions for organic phases leached from river sediments are very similar to those for the corresponding detrital fractions in contrast the som extracted from marine sediments display end values that typically range between the end signatures for terrestrial organic matter inferred from the analysis of the sedimentary detrital fractions and marine organic matter inferred from the analysis of local surface seawater a notable exception is the case of organic matter om fractions leached from cold seep sediment samples which sometimes exhibit end values markedly different from both terrigenous and surface seawater signatures this suggests that a significant fraction of organic compounds in these sediments may be derived from chemosynthetic processes recycling pore water ree characterized by a distinct isotopic composition overall our results confirm that organic matter probably plays an important role in the oceanic ree budget through direct scavenging and remineralization within the water column both the high ree abundances and the shape of shale normalized patterns for leached som also suggest that om degradation in sub surface marine sediments during early diagenesis could control to a large extent the distribution of ree in pore waters benthic fluxes of organic bound ree could hence substantially contribute to the exchange processes between particulates and seawater that take place at ocean margins neodymium isotopes could provide useful information for tracing the origin terrestrial versus marine and geographical provenance of organic matter with potential applications in paleoceanography in particular future studies should further investigate the potential of nd isotopes in organic compounds preserved in sedimentary records for reconstructing past variations of surface ocean circulation

glacially influenced basin plain sedimentation in the southern faeroe shetland channel northwest united kingdom continental margin abstract quaternary sediments at the southwest end of the faeroe shetland channel are preserved as a basin plain succession of variable fill geometry and lithology in high resolution seismic profiles the basin plain succession is characterised by laterally discontinuous and transparent mounded lensoid bodies interbedded with acoustically well layered sediments which display drape and onlapping reflection configurations the lensoid bodies comprise an up to 50 m thick amalgamated package of mass flow deposits consisting primarily of debris flow diamictons they represent resedimented glacigenic deposits derived from the west shetland shelf accumulation of these packages was episodic and related to specific rapid phases of downslope resedimentation most probably concomitant with ice marginal deposition on the west shetland slope the acoustically well layered sediments include glaciomarine hemipelagites and contourites these indicate phases of reduced sediment supply from the adjacent shelf and slope areas and probably represent the more pervasive background sedimentation in the basin although weak bottom current activity may have prevailed throughout the glacial episodes the onset of vigorous bottom current circulation occurred at the changeover from a glacial to an interglacial regime the debris flow packages form about 50 of the basin plain sediments in this part of the faeroe shetland channel thereby forming a significant component of the deep water succession

warming salting and origin of the tyrrhenian deep water 1 data collected from 1996 to 2001 down to 3 500 m in the tyrrhenian sub basin with ship handled and moored instruments show 5 year t and s trends 0 016 c yr 0 008 yr that are the largest ever evidenced in mediterranean deep waters this is not consistent with the usual hypothesis that tyrrhenian deep water tdw is a mixture of eastern water flowing from the sicily channel and western water flowing from the sardinia channel partly since both are reported to encounter lower trends we argue that tdw might result from a dense water formation process occurring within the tyrrhenian itself in a region never reported up to now east of the bonifacio strait whatever the validity of our hypothesis climatic changes are occurring in the whole sea and are efficiently specified with long time series

rare earth elements in the mediterranean sea and mixing in the mediterranean outflow abstract mediterranean surface waters contain elevated levels of the rare earth elements compared to similar nutrient depleted open ocean waters application of a flux balance model shows that the mediterranean is a net sink for ce and a net source for the other ree the abundance pattern of the excess ree required for mass balance is enriched in heavy ree and has a negative ce anomaly this supports a marine possibly coastal source for the ree although the magnitudes of the fluxes involved are consistent with aeolian input an aeolian source would require large scale removal of ce and the light ree within the mediterranean sea a mixing model to compute trace metal anomalies in the mediterranean outflow predicts the observed ree concentrations well this implies that ce behaves conservatively in outflow waters over the calculated one month period for mediterranean water to reach the study site application to other trace metals gives good agreement for al cd and mn

sedimentary fe mn oxyhydroxides as paleoceanographic archives and the role of aeolian flux in regulating oceanic dissolved ree in the marine environment authigenic ferromanganese fe mn oxides precipitate from seawater incorporating many dissolved trace elements such as nd pb whose isotopic composition is a direct proxy for ambient seawater thus isotopic studies of the fe mn oxyhydroxide component leached from sedimentary records can provide information on changes in erosional input or ocean circulation changes such studies may be complicated however by the presence of detrital material containing a fe mn oxide component which may mask the true seawater signal in addition the formation of fe mn oxyhydroxides in the marine environment remains poorly understood in particular the phase carbonates detrital particles that controls the delivery of authigenic fe mn oxides to the sediments has not yet been determined in this study we have analysed the ree and nd isotopic compositions of fe mn oxyhydroxide fractions dispersed in marine sediment cores from the cape and angola basins in the se atlantic cruise images ii for the angola basin deep sea core located at 1000 km south of the congo river mouth both the ree and nd isotopic compositions nd measured in recent fe mn oxyhydroxide fractions are typical of congo river borne fe mn oxides this shows that preformed fe mn oxides associated with detrital fractions can locally contaminate the seawater signal recorded by authigenic oxyhydroxides by contrast examination of ree distributions nd isotope data and mass accumulation rates in cape basin sediments shows paradoxically that the flux of fe mn oxides to sediments is controlled by aeolian particles from the nearby namib desert even though their ree and nd compositions point clearly to an authigenic origin it is proposed that partial dissolution of aeolian dust occurs in the water column releasing into solution its easily leachable fe mn component the dissolved fe2 and mn2 would then fuel the reprecipitation of authigenic fe mn oxyhydroxides scavenging additional dissolved trace elements from the ocean most probably from deep water masses in this case calculations suggest that aeolian deposition acts as a net sink for dissolved nd in the cape basin rather than a source and allows us to estimate the rate of removal of dissolved nd associated with atmospheric deposition yielding a global oceanic residence time for nd nd of between 500 and 1400 years

surface and deep ocean circulation in the subpolar north atlantic during the mid pleistocene revolution 1 we investigated surface and deep ocean variability in the subpolar north atlantic from 1000 to 500 thousand years ago ka based on two ocean drilling program odp sites feni drift site 980 55 29 n 14 42 w and bjorn drift site 984 61 25 n 24 04 w benthic foraminiferal stable isotope data planktic foraminiferal faunas ice rafted debris data and faunally based sea surface temperature estimates help test the hypothesis that oceanographic changes in the north atlantic region were associated with the onset of the 100 kyr world during the mid pleistocene revolution based on percentage of neogloboquadrina pachyderma s records from both sites surface waters during interglacials and glacials were cooler in the mid pleistocene than during marine isotope stages mis 5 and 6 in particular interglaciations at bjorn drift site 984 were significantly cooler faunal evidence suggests that the interglacial arctic front shifted from a position between the two sites to a position northwest of bjorn drift site 984 after ca 610 ka as during the late pleistocene we find faunal evidence for lagging surface warmth at most of the glacial initiations during the mid pleistocene each initiation is associated with high benthic 13c values that are maintained into the succeeding glaciation which we term lagging nadw production these findings indicate that lagging warmth and lagging nadw production are robust features of the regional climate system that persist in the middle to late pleistocene

submarine groundwater discharge is an important net source of light and middle rees to coastal waters of the indian river lagoon florida usa abstract porewater i e groundwater samples were collected from multi level piezometers across the freshwater saltwater seepage face within the indian river lagoon subterranean estuary along florida s usa atlantic coast for analysis of the rare earth elements ree surface water samples for ree analysis were also collected from the water column of the indian river lagoon as well as two local rivers eau gallie river crane creek that flow into the lagoon within the study area concentrations of rees in porewaters from the subterranean estuary are 10 100 times higher than typical seawater values e g nd ranges from 217 to 2409 pmol kg 1 with submarine groundwater discharge sgd at the freshwater saltwater seepage face exhibiting the highest ree concentrations the elevated ree concentrations for sgd at the seepage face are too high to be the result of simple binary mixing between a seawater end member and local terrestrial sgd instead the high ree concentrations indicate that geochemical reactions occurring within the subterranean estuary contribute substantially to the ree cycle a simple mass balance model is used to investigate the cycling of rees in the indian river lagoon and its underlying subterranean estuary mass balance modeling reveals that the indian river lagoon is approximately at steady state with respect to the ree fluxes into and out of the lagoon however the subterranean estuary is not at steady state with respect to the ree fluxes specifically the model suggests that the sgd nd flux for example exported from the subterranean estuary to the overlying lagoon waters exceeds the combined input to the subterranean estuary from terrestrial sgd and recirculating marine sgd by on average 100 mmol day 1 the mass balance model also reveals that the subterranean estuary is a net source of light rees lree and middle rees mree to the overlying lagoon waters but acts as a sink for the heavy rees hree geochemical modeling and statistical analysis further suggests that this fractionation occurs in part due to the coupling between ree cycling and iron redox cycling within the indian river lagoon subterranean estuary the net sgd flux of nd to the indian river lagoon is 7 fold larger than the local effective river flux to these coastal waters this previously unrecognized source of nd to the coastal ocean could conceivably be important to the global oceanic nd budget and help to resolve the oceanic nd paradox by accounting for a substantial fraction of the hypothesized missing nd flux to the ocean

volcanic hot spots on io correlation with low albedo calderas comparison of voyager imaging data with voyager 1 infrared observations iris and with ground based telescopic infrared data demonstrates a strong correlation between hot spots and low albedo features reflectivity 0 3 in all visual wavelengths on io most of these low albedo areas occur on the floors of volcanic calderas and many are associated with active or recent volcanism we use this correlation to identify additional hot spots in regions not observed by iris and to model their temperatures the major features discovered by this method are in a ringlike structure in the south polar region centered at 140 w 75 s and amaterasu patera 307 w 38 n our model temperature for the south polar feature is 280 50 k taking account of the high latitudes of these features the estimated global average heat flow from the hot spots becomes 1 8 0 5 w m 2 most of this heat emanates from just a few very large hot spots the global distribution of hot spots is further evidence that io is a dimorphous body the hemisphere centered on 310 w 30 s is much more volcanically active than the opposite hemisphere the styles of heat transfer in io conductive versus convective may be related to the global distribution of hot spots large eruptive plumes and large scale topographic relief the correlation between hot spots and dark areas is due to 1 the absence of the bright materials such as so2 frost which cover most of the surface and 2 the presence of a low albedo substance spectral properties of the low albedo features extracted from the voyager multispectral data are consistent with a number of candidate materials liquid sulfur boiled sulfur silicate sulfur mixtures zinc sulfide fe sulfate and fe chloride quenched sulfur allotropes on the other hand are redder than the low albedo features on io and are incompatible with the elevated temperatures of the hot spots some of the dark caldera floor materials may be liquid sulfur and or thermally altered boiled sulfur liquid sulfur would tend to collect in the topographic depressions and fractured bedrock of the calderas and this would explain the concentration of low albedo material in the calderas the presence of liquid sulfur is also suggested by the hot spot temperature distribution typically 200 400 k and by morphologies suggestive of lava lakes however the liquid boiled sulfur model does not seem to work for babbar and amaterasu paterae and the evidence for liquid sulfur is not conclusive

distribution and mixing of intermediate water masses in the channel of sicily mediterranean sea 1 the channel of sicily which represents the only connection between the western and the eastern mediterranean sea can be described as a three layer system where fresher water of atlantic origin modified atlantic water flows eastward in the upper layer levantine intermediate water liw leaves the eastern basin at around 250 350 m and an outflow of transitional ionian deep water tidw is identified below the liw synoptic mesoscale plankton experiment data collected during four surveys in the channel of sicily show that liw and tidw are subject to major modifications when crossing the eastern sill a significant bernoulli aspiration is found there and the bottom water at the sill is composed of modified deep ionian waters coming from 800 m an analysis of the water mass composition proves that liw mixes essentially with tidw and that the tidw flow through the channel must be larger than the expected 0 5 sv the presence of a secondary circulation related to the bottom boundary layer is demonstrated to be the primary factor leading to the dilution and cooling of liw

composition and origin of ash zones from marine isotope stages 3 and 2 in the north atlantic abstract the composition and distribution of four north atlantic ash zones from the faroe islands margin is presented including the widespread north atlantic ash zone ii naaz ii 52 53 ka bp and three mainly basaltic ash zones here referred to as the faroe marine ash zones fmaz i ca 15 4 14 c ka bp ii ca 23 14 c ka bp also referred to as the fugloyarbanki tephra and iii ca 33 14 c ka bp one core from the south east labrador sea was also analysed naaz ii was found in all investigated cores indicating very large eruption events in the early marine isotope stage mis 3 detailed investigations of naaz ii in high resolution cores show that two separate layers can be distinguished a lower mixed alkalic basalt and rhyolitic layer and an upper predominantly tholeiitic basalt tephra the main component of the basaltic fmaz ii was found in all cores from the faroe island margin and the labrador sea indicating that this tephra is the most widespread tephra from mis 2 in the north atlantic discovered so far we discuss the possibility to use these tephra layers for exact correlations between marine records and land sections such as the greenland ice cores and terrestrial records on the european mainland

quaternary sedimentation margin architecture and ocean circulation variability around the faroe islands north atlantic abstract the quaternary development offshore the faroe islands has been studied using high resolution seismic and core data from the r v dana 2000 cruise and previous cruises several glacial related features and deposits are observed all bearing witness to former extensive glaciations of the faroe area on the shelves overlaying a mid pleistocene glacial erosional surface glacial and glacimarine deposits form a sheet geometry interrupted by ridges of sediment that are likely to represent ice front deposits an iceberg turbate north of the faroe islands provides evidence of large scale drift of ultra deep draft 600 m icebergs in the nordic seas at pre weichselian glacial stage s marginal and transverse troughs found on the eastern and western shelf are suggested to have formed during the same glacial period s as the iceberg turbate iceberg plough marks and abundant ice rafted material of non faroese origin together with the relict moraine ridges encircling the faroe islands at around the 100 and 200 m water depth contours indicate that the outer shelf was probably ice free during the weichselian ice age on the slopes and basinal parts the formation of fine grained contourites was favoured during weichselian glacial stages when bottom currents were reduced sediment overloading during these glacial stages resulted in repeated slope instability causing mass failures of the contourite deposits

recent changes in deep water formation and spreading in the eastern mediterranean sea a review abstract observations of the last decade testify that the characteristics of the deep thermohaline circulation in the eastern mediterranean sea have changed thoroughly the source of the most dense waters of the basin has moved from the adriatic to the aegean sea this new source has proved to be very efficient since the estimated formation rate for the period 1989 95 was more than 1 sv about three times more than the dense water formation rate of the adriatic sea these new waters with hydrological characteristics that are warmer and more saline have replaced almost 20 of the older deep waters of the basin and have uplifted the deep isopycnals by about 500 m this major event can be attributed to important meteorological anomalies in the eastern mediterranean and to changes of circulation patterns the extended dry period of 1988 93 and the exceptionally cold winters of 1987 and 1992 93 created favorable conditions for increased formation of dense water in the aegean furthermore changes in the circulation patterns in the intermediate water range levantine intermediate water liw and cretan intermediate water themselves possibly linked to meteorological anomalies appear to have played an important role in the redistribution of salt as a result of an interruption to exchanges between the ionian and levantine basin the salinities in the latter started to rise high salinity waters were diverted into the aegean malanotte rizzoli p manca b b ribera dacala m theocharis a 1998 the eastern mediterranean in the 80s and in the 90s the big transition emerged from the poem bc observational evidence rapport du commission international de la mer medittanee 35 174 175 and the westward transport of liw was reduced an additional effect of the deep water discharge from the aegean and the resulting uplifting of mid depth waters was to lower salinities in the liw layer this effect is most strongly felt in the ionian sea a 3 d primitive equation numerical model for the eastern mediterranean with a 20 km grid size is used to simulate the observed changes and understand the basic mechanisms which caused them under appropriate atmospheric forcing the model successfully reproduces the main characteristics of the transient these results indicate that the observed changes can be at least partially explained as a response of the eastern mediterranean and more specifically of the aegean to atmospheric forcing variability

saharan dust inputs to the western mediterranean sea depositional patterns geochemistry and sedimentological implications data are presented for a number of parameters for aerosols and rainwaters collected at a station on sardinia the findings are interpreted with special reference to saharan dusts and are compared to other data on these dusts obtained from a variety of sites around the mediterranean sea at the sardinia site the particle size distribution of the saharan outbreaks exhibits a bimodal structure the two modes being between 2 and 4 m and 15 and 30 m the presence of giant particles strongly affects the deposition velocities of the saharan aerosols source markers for the saharan dusts are palygorskite kaolinite calcite dolomite and rounded quartz grains the input of saharan dust has important effects on the chemistry of the mediterranean aerosols these include i increases in the atmospheric concentrations and sea surface fluxes of crust controlled trace metals e g al fe ii decreases in the efcrust values of non crust controlled trace metals e g cu zn and pb in the aerosols and iii changes in the solid state speciation of cu zn and pb which decrease their solubilities in seawater the saharan dusts also affect the composition of rainwater by raising the ph following the dissolution of calcium and by decreasing the solubility of trace metals such as cu zn and pb wet deposition controls the flux of saharan dust to the mediterranean sea but dry deposition can also be important the dust transport occurs in the form of pulses and the annual dust flux can be controlled by a few episodes of saharan outbreaks e g sometimes a single outbreak can account for 40 80 of the flux saharan dust deposition fluxes range from 2 to 25 g m 2 average 10 in the west mediterranean between 39 and 42 n from 6 to 46 g m 2 average 20 in the east mediterranean and from 0 4 to 1 0 g m 2 over the alps on continental europe the present day saharan dust fluxes 1 mg cm 2 year 1 account for about 10 20 of the recent deep sea sedimentation in the western mediterranean 3 15 mg cm 2 year 1

heat transfer measurements of the 1983 kilauea lava flow convective heat flow measurements of a basaltic lava flow were made during the 1983 eruption of kilauea volcano in hawaii eight field measurements of induced natural convection were made giving heat flux values that ranged from 1 78 to 8 09 kilowatts per square meter at lava temperatures of 1088 and 1128 degrees celsius respectively these field measurements of convective heat flux at subliquidus temperatures agree with previous laboratory measurements in furnace melted samples of molten lava and are useful for predicting heat transfer in magma bodies and for estimating heat extraction rates for magma energy

water mass circulation on demerara rise during the late cretaceous based on nd isotopes abstract circulation in the north atlantic during the late cretaceous has implications for poleward heat transport and nutrient distribution during an extreme greenhouse interval with episodes of ocean anoxia nd isotopes of fossil fish teeth and debris represent one of the few water mass tracers that can be used to reconstruct deep ocean circulation we present nd isotopic data interpreted as bottom water values for 290 samples from three ocean drilling program sites on demerara rise sites 1258 1260 and 1261 along with 102 analyses from four other north atlantic sites cape verde goban spur bermuda rise and blake nose that provide additional geographic and bathymetric control our results confirm the presence of a water mass with low end values 14 to 17 that are believed to be influenced by continental material during local water mass formation at low latitudes this demerara bottom water dbw is the primary water mass in the region from the cenomanian to coniacian and from the late campanian through early maastrichtian following a hiatus of 10 my a positive 8 end unit excursion occurs during ocean anoxic event 2 oae2 that cannot be explained by changes in weathering inputs diagenesis or magmatic sources of nd instead it appears to represent an influx of bottom waters sourced from the tethys or north atlantic this replacement of dbw during oae2 argues for decreased production of dbw or enhanced production of tethys north atlantic waters during peak greenhouse conditions from the late campanian through early maastrichtian dbw becomes the only water mass recorded at demerara rise and it appears to expand to abyssal depths at cape verde in the campanian this water mass is ultimately replaced by waters that appear to be sourced from the north atlantic starting in the late maastrichtian observed variations in circulation in the tropical north atlantic during the late cretaceous can account for extensive deposition of black shales in the region prior to the hiatus as well as local warming during a global cooling event in the maastrichtian

pleistocene glacial history of the nw european continental margin abstract in this paper new and previously published data on the pleistocene glacial impact on the nw european margin from ireland to svalbard between c 48 n 80 n are compiled the morphology of the glaciated part of the european margin strongly reflects repeated occurrence of fast moving ice streams creating numerous glacial troughs channels that are separated by shallow bank areas end moraines have been identified at several locations on the shelf suggesting shelf edge glaciation along the major part of the margin during the last glacial maximum deposition of stacked units of glacigenic debris flows on the continental slope form fans at a number of locations from 55 n and northwards whereas the margin to the south of this is characterised by the presence of submarine canyons glaciation curves based primarily on information from the glacial fed fan systems that depict the pleistocene trends in extent of glaciations along the margin have been compiled these curves suggest that extensive shelf glaciations started around svalbard at 1 6 1 3 ma while repeated periods of shelf edge glaciations on the uk margin started with mis 12 c 0 45 ma the available evidence for mis 2 suggest that shelf edge glaciation for the whole margin was reached between c 28 and 22 14 c ka bp and maximum positions after this were more limited in some regions north sea and lofoten the last glacial advance on the margin has been dated to 15 13 5 14 c ka bp and by c 13 14 c ka bp the shelf areas were completely deglaciated the younger dryas loch lomond advance reached the coastal areas in only a few regions

circulation changes in the eastern mediterranean sea over the past 23 000 years inferred from authigenic nd isotopic ratios the eastern mediterranean sea ems is a key region to study circulation change because of its own thermohaline circulation in this study we focused on intermediate deep water circulation since the last glacial maximum lgm including the sapropel s1 period two cores from the levantine sea and the strait of sicily respectively collected at 1 780 m and 771 m water depth were studied using 143nd 144nd end of foraminiferal tests and leachates as well as benthic foraminiferal stable isotopes 13c 18o this approach allowed the determination of variations in 1 the north atlantic water contribution to the mediterranean basin 2 water exchanges at the strait of sicily and 3 the influence of the nile river over the last 23 000 years during the lgm high benthic foraminiferal 13c values indicate well ventilated intermediate and deep waters in the ems the end values were more radiogenic than at present reflecting a smaller contribution of unradiogenic north atlantic waters to the ems due to reduced exchange at the strait of sicily the sluggish circulation in the ems initiated during deglaciation was further enhanced by increased nile river freshwater inputs between 15 ka bp and the s1 period partial dissolution of nile river particles contributed to an increase in ems end the large end gradient between the ems and the western mediterranean sea observed during lgm and s1 suggests that each basin had a distinct circulation mode decreasing end values at the strait of sicily after s1 reflected improved water exchange between both basins leading to the modern circulation pattern

variable hfsrnd radiogenic isotopic compositions in a saharan dust storm over the atlantic implications for dust flux to oceans ice sheets and the terrestrial biosphere isotopic characterization of aerosol mineral particles atmospheric dust of varying sizes is essential in classifying source areas and for determining the source of dust deposited over oceans and icesheets however the effect of atmospheric transport on radiogenic isotopic compositions is not well constrained making provenance interpretation difficult in order to investigate the isotopic variability of 176hf 177hf 87sr 86sr and 143nd 144nd we analyzed eight airborne dust samples in two size fractions collected along a cross atlantic transect through a dust storm originating in the sahara in late 2002 past measurements of 176hf 177hf 87sr 86sr and 143nd 144nd of dust have focused primarily on coarse sized particles 30 m whereas far field deposition is primarily finer particles 2 m strontium or neodymium isotopic sorting based on distance is not evident in our dataset however the combined isotopic ratios of the dust collected suggest a saharan origin hafnium isotopic compositions show an east to west trend towards more radiogenic compositions across the atlantic suggesting grain and mineral sorting during dust transport along the 4000 km transect transport models with variable dust particle diameter and wind speed demonstrate the preferential depletion of the high density mineral zircon during transport of dust from the source area the transport model combined with a simple two component mixing model show that the hf isotopic composition changes can be explained by the loss of the mineral zircon during transport modeling of this zircon effect with distance from the dust source in the hf isotopic composition of marine terrestrial and glacial dust deposits may reveal additional information concerning dust transport and sources in the geologic past

interbasin deep water exchange in the western mediterranean owing to its nearly enclosed nature the tyrrhenian sea at first sight is expected to have a small impact on the distribution and characteristics of water masses in the other basins of the western mediterranean the first evidence that the tyrrhenian sea might in fact play an important role in the deep and intermediate water circulation of the entire western mediterranean was put forward by hopkins 1988 there an outflow of water from the tyrrhenian sea into the algero provencal basin was postulated in the depth range 700 1000 m to compensate for an observed inflow of deeper water into the tyrrhenian sea however this outflow the tyrrhenian deep water tdw was undetectable since it would have hydrographic characteristics that could also be produced within the algero provencal basin a new data set of hydrographic tracer lowered acoustic doppler current profiler ladcp and deep float observations presented here allows us now to identify and track the tdw in the algero provencal basin and to demonstrate the presence and huge extent of this water mass throughout the western mediterranean it extends from 600 m to 1600 1900 m depth and thus occupies much of the deep water regime the outflow from the tyrrhenian is estimated to be of the order of 0 4 sv sv 10 6 m 3 s 1 based on the tracer balances this transport has the same order of magnitude as the deep water formation rate in the gulf of lions the tyrrhenian sea effectively removes convectively generated deep water western mediterranean deep water wmdw from the algero provencal basin mixes it with levantine intermediate water liw above and reinjects the product into the algero provencal basin at a level between the wmdw and liw thus smoothing the temperature and salinity gradients between these water masses the tracer characteristics of the tdw and the lowered adcp and deep float observations document the expected but weak cyclonic circulation and larger flows in a vigorous eddy regime in the basin interior

the last 18 kyr fluctuations in norwegian sea surface conditions and implications for the magnitude of climatic change evidence from the north sea a combined record of three cores spanning the last 18 kyr from the northern north sea is investigated for content of benthic and planktonic foraminifera and stable oxygen isotopes the paleoenvironmental development through this time period shows an early deglaciation 18 14 4 ka and the younger dryas 12 7 11 5 ka characterized by arctic polar conditions and increased ice rafting in the norwegian channel during the bolling allerod period warm sea surface temperature 9 c conditions similar to present conditions are inferred while bottom waters stayed cold 0 1 c with normal salinity the bolling allerod period is interrupted twice at 13 9 13 6 ka older dryas and at 13 0 12 8 ka inter allerod cooling period by reductions in sea surface temperatures and increased sea ice cover the beginning of the holocene period is marked by increases in surface and bottom water temperature superimposed on the broad climatic changes through the holocene a series of short lived oscillations in the ocean circulation are recorded the amplitude of these holocene events appears larger in the early holocene prior to 8 ka than compared with the remaining part of the holocene this amplification can possibly be attributed to a general increased freshwater budget in the north atlantic at this time during the final stages of the deglaciation of the laurentide and scandinavian ice sheets

the gin sea a synthesis of its physical oceanography and literature review 1972 1985 abstract a synthesis and review of the physical oceanography of the gin sea greenland iceland and norwegian seas is presented an accompanying bibliography is included from 1972 through 1985 some 1986 works are also noted emphasis is placed on describing the gin sea as a major semi enclosed basin that plays a role unique among the world s oceans by providing a strong two way advective exchange between the ice covered polar sea and the north atlantic ocean and at the same time acting as the primary site for northern hemisphere bottom water formation the water masses for the gin sea are defined in a manner as consistent as possible with the literature the large scale oceanographic and meteorological factors influencing the water mass formation and circulation are described a sample calculation of the various horizontal and vertical thermohaline driven exchanges is given

rare earth elements rees in the tropical south atlantic and quantitative deconvolution of their non conservative behavior this study presents new concentration measurements of dissolved rare earth elements drees along a full depth east west section across the tropical south atlantic 12 s and uses these data to investigate the oceanic cycling of the rees enrichment of drees associated with the redox cycling of fe mn oxides is observed in the oxygen minimum zone omz off the african shelf for deeper waters a multi parameter mixing model was developed to deconvolve the relative importance of physical transport i e water mass mixing from biogeochemical controls on the dree distribution in the deep atlantic this approach enables chemical processes involved in ree cycling not apparent from the measurements alone to be distinguished and quantified results show that the measured dree concentrations below 1000 m are dominantly controlled 75 by preformed ree concentrations resulting from water mass mixing this result indicates that the linear correlation between drees and dissolved si observed in atlantic deep waters results from the dominantly conservative behavior of these tracers rather than from similar chemical processes influencing both drees and si minor addition of drees 10 of dnd and 5 of dyb is observed in the deep 4000 m brazil basin resulting from either remineralization of particles in situ or along the flow path greater addition of drees up to 25 for dnd and 20 for dyb is found at 1500 m and below 4000 m in the angola basin near the african continental margin cerium anomalies suggest that different sources are responsible for these dree addition plumes the 1500 m excess is most likely attributed to dree release from fe oxides whereas the 4000 m excess may be due to remineralization of calcite higher particulate fluxes and a more sluggish ocean circulation in the angola basin may explain why the dree excesses in this basin are significantly higher than that observed in the brazil basin hydrothermal venting over the mid atlantic ridge acts as a regional net sink for light rees but has little influence on the net budget of heavy rees the combination of dense ree measurements with water mass deconvolution is shown to provide quantitative assessment of the relative roles of physical and biogeochemical processes in the oceanic cycling of rees

water mass analysis for the u s geotraces ga03 north atlantic sections we present the distributions of hydrographic properties potential temperature salinity dissolved oxygen and micromolar level inorganic macronutrients along two sections occupied in the subtropical north atlantic as part of the first u s geotraces ga03 survey during 2010 and 2011 the purpose of this work is to place subsequent papers in this special issue in a general context and to provide a framework in which the observed distributions of trace elements and isotopes can be interpreted using these hydrographic properties we use a modified optimum multiparameter water mass analysis method to diagnose the relative contributions of various water types along the sections and rationalize their distributions the water mass compositions appear largely consistent with what is understood from previous studies about the large scale circulation and ventilation of the north atlantic with perhaps one exception we found that the north atlantic deep water both east and west of the mid atlantic ridge is more strongly influenced by iceland scotland overflow water relative to denmark straits overflow water about 3 1 than inferred from other tracer studies typically 2 1 it remains unclear whether this is an artifact of our calculation or a real change in deep water composition in the decades between the determinations

an electrical resistivity measurement in molten basalt during the 1983 kilauea eruption during the recent 1983 eruption of kilauea volcano in hawaii a field measurement of electrical resistivity was made in an 1118 c molten lava flow a probe containing a four electrode wenner aray was inserted into the molten basaltic lava flow at a point about 100 m from the erupting vent the probe indicated an electrical resistivity of approximately 40 ohm m for the freshly erupted molten lava this value is consistent with existing but sparce laboratory data for molten rock in this temperature range

convective heat extraction from molten magma the convective heat of molten magma in the upper 10 km of the continental crust represents a significant geothermal energy resource shallow basaltic magmas 10 km near the liquidus 1250 c are predicted to offer heat extraction rates in the range of 15 50 kw m2 20 80 mw well more accessible andesitic and wet rhyolitic magmas are predicted to offer heat extraction rates in the range of 5 25 kw m2 8 40 mw well convective heat transfer correlations are used which include corrections for high prandtl number fluids and cylindrical boundary layers the calculations based on these correlations agree well with laboratory tests using molten basalt at superliquidus temperatures 1450 1650 c at liquidus and subliquidus temperatures an additional correction is developed for the thick solidified crust that forms on the heat exchanger non newtonian rheology is considered and shown to have a possible effect on the initiation of convection in the liquidus and subliquidus temperature range in addition to heat extraction estimates the analysis presented here is also relevant to convective heat loss to walls of magma bodies

deep sea records from the southeast labrador sea ocean circulation changes and ice rafting events during the last 160 000 years 1 results from two deep sea cores from northeast of newfoundland at 1251 and 2527 m water depth respectively indicate that during the time period from 160 000 to 10 000 years bp ice rafting events in the labrador sea were accompanied by rapid variations in deep and surface water circulation twelve ice rafting events occurred each coinciding with high concentrations of detrital carbonate and oxygen isotopic depletion of both surface and bottom waters eleven of these can be correlated with the north atlantic heinrich events h1 h11 the remaining very conspicuous ice rafting event took place early in mis substage 5e at a time when the planktic faunal assemblage suggests marked warming of the sea surface in the shallower core benthic delta 13 c values rise from a minimum during the deglaciation to peak substage 5e values following the last ice rafting event indicating that the ventilation of intermediate depths was renewed after the deglaciation was complete and continued throughout substage 5e the benthic foraminifera suggest that this well ventilated water mass was comparable to the modern labrador sea water lsw the benthic faunas suggest that a relatively warm intermediate water mass entered the se labrador sea during heinrich events generally low benthic delta 13 c values indicate that this water mass was poorly ventilated and rich in inorganic nutrients isotope data and benthic faunal distributions indicate that north atlantic deep water nadw formed in the norwegian greenland sea reached the se labrador sea between the heinrich events

some features of the algerian current an analysis of infrared images leads to a new conception of the dynamics of the atlantic water in the algerian basin in situ current measurements are not yet available but coherent hypotheses are presented with the aim to initiate further experimental and theoretical works the algerian current flows steadily along the coast near 0 and becomes unstable near 1 2 e eddies of both signs are generated that are advected by the mean current but only the anticyclonic eddies increase in size diameter about 100 km as they extract more energy from the mean current they are advected more slowly and they may detach from the coast and drift for several weeks in the algerian basin they grow as deep as 1000m at least and they are able to pull lenses of intermediate water seaward from the sardinian continental slope coastal upwelling cells are generated near 1 2 e between the cyclonic and the anticyclonic eddies they are also advected by the mean current and are definitively not wind induced these turbulent structures create intense mixing between the atlantic and mediterranean waters which account for the large eastward gradient of salinity encountered in the surface layer therefore the algerian basin is characterized by a large mesoscale variability mainly due to the instability of the algerian current it appears to be a reservoir in which the water of atlantic origin is amassed and it forms a buffer zone which disconnects the flow of atlantic water coming in at gibraltar from the flow of hygly modified atlantic water exiting the basin through the strait of sardinia and into the ligurian sea

neodymium isotopic composition and concentration in the western north atlantic ocean results from the geotraces ga02 section the neodymium nd isotopic composition of seawater is commonly used as a proxy to study past changes in the thermohaline circulation the modern database for such reconstructions is however poor and the understanding of the underlying processes is incomplete here we present new observational data for nd isotopes and concentrations from twelve seawater depth profiles which follow the flow path of north atlantic deep water nadw from its formation region in the north atlantic to the northern equatorial atlantic samples were collected during two cruises constituting the northern part of the dutch geotraces transect ga02 in 2010 the results show that the different water masses in the subpolar north atlantic ocean which ultimately constitute nadw have the following nd isotope characteristics upper labrador sea water ulsw end 14 2 0 3 labrador sea water lsw end 13 7 0 9 northeast atlantic deep water neadw end 12 5 0 6 northwest atlantic bottom water nwabw end 11 8 1 4 in the subtropics where these source water masses have mixed to form nadw which is exported to the global ocean upper nadw is characterised by end values of 13 2 1 0 2sd and lower nadw exhibits values of end 12 4 0 4 2sd while both signatures overlap within error the signature for lower nadw is significantly more radiogenic than the traditionally used value for nadw end 13 5 due to the dominance of source waters from the nordic seas nwabw and neadw comparison between the concentration profiles and the corresponding nd isotope profiles with other water mass properties such as salinity silicate concentrations neutral densities and chlorofluorocarbon cfc concentration provides novel insights into the geochemical cycle of nd and reveals that different processes are necessary to account for the observed nd characteristics in the subpolar and subtropical gyres and throughout the vertical water column while our data set provides additional insights into the contribution of boundary exchange in areas of sediment resuspension the results for open ocean seawater demonstrate at an unprecedented level the suitability of nd isotopes to trace modern water masses in the strongly advecting western atlantic ocean

new neodymium isotope data quantify nile involvement in mediterranean anoxic episodes the development of widespread anoxic conditions in the deep oceans is evidenced by the accumulation and preservation of organic carbon rich sediments but its precise cause remains controversial the two most popular hypotheses involve 1 circulation induced increased stratification resulting in reduced oxygenation of deep waters or 2 enhanced productivity in the surface ocean increasing the raining down of organic matter and overwhelming the oxic remineralization potential of the deep ocean in the periodic development of deep water anoxia in the pliocene pleistocene mediterranean sea increased riverine runoff has been implicated both as a source for nutrients that fuel enhanced photic zone productivity and a source of a less dense freshwater cap leading to reduced circulation basin wide stagnation and deep water oxygen starvation monsoon driven increases in nile river discharge and increased regional precipitation due to enhanced westerly activity two mechanisms that represent fundamentally different climatic driving forces have both been suggested as causes of the altered freshwater balance here we present data that confirm a distinctive neodymium nd isotope signature for the nile river relative to the eastern mediterranean providing a new tracer of enhanced nile outflow into the mediterranean in the past we further present nd isotope data for planktonic foraminifera that suggest a clear increase in nile discharge during the central intense period of two recent anoxic events our data also suggest however that other regional freshwater sources were more important at the beginning and end of the anoxic events taken at face value the data appear to imply a temporal link between peaks in nile discharge and enhanced westerly activity

the use of foraminifera as a record of the past neodymium isotope composition of seawater 1 we present new isotopic data for sedimentary planktonic foraminifera as well as for potential water column and sedimentary sources of neodymium nd which confirm that the isotopic composition of the foraminifera is the same as surface seawater and very different from deep water and sedimentary nd the faithfulness with which sedimentary foraminifera record the isotopic signature of surface seawater nd is difficult to explain given their variable and high nd ca ratios ratios that are often sedimentary foraminifera ratios that are often much higher than is plausible for direct incorporation within the calcite structure we present further data that demonstrate a similarly large range in nd ca ratios in plankton tow foraminifera a range that may be controlled by redox conditions in the water column cleaning experiments reveal in common with earlier work that large amounts of nd are released by cleaning with both hydrazine and diethylene triamine penta acetic acid but that the nd released at each step is of surface origin while further detailed studies are required to verify the exact location of the surface isotopic signature and the key controls on foraminiferal nd isotope systematics these new data place the use of planktonic foraminifera as recorders of surface water nd isotope ratios and thus of variations in the past supply of nd to the oceans from the continents via weathering and erosion on a reasonably sure footing

flow and convective cooling in lava tubes tube fed basaltic lava flows with lengths ranging from 10 to 200 km are inferred to exhibit similar amounts of cooling to explain the wide range of implied cooling rates we consider forced convection as a dominant cooling process in lava tubes and present solutions that express mean temperature versus distance down the tube as a function of flow rate and flow cross section our models treat forced convective thermal losses in steady laminar flow through a lava tube with constant temperature walls and constant material properties we explore the effects of different wall temperature and heat flux rate boundary conditions for circular tube and parallel plate flows over a range of tube sizes plate spacings eruption temperatures and volume flow rates results show that nonlinear cooling rates over distance are characteristic of constant wall temperature for a piecewise parallel plate circular tube model this provides the best fit to temperature observations for hawaiian tubes such a model may also provide an explanation for the very low 10 c cooling observed in 10 km long hawaii tube flows and inferred in longer 50 to 150 km tube fed flows in queensland the forced convective cooling model may also explain similar flow morphologies for long tube fed basaltic lava flows in a wide variety of locations since small variations in eruption temperature or flow rate can accommodate the entire range of flow lengths and cooling rates considered our results are consistent with previous suggestions that long basaltic flows may be a reflection of low slopes a particularly steady moderate eruption rate and well insulated flow rather than of high discharge rates

high resolution paleo environmental changes during the sapropel 1 in the north ionian sea central mediterranean high resolution paleoceanographic reconstruction of surface water properties during the most recent sapropel event s1 has been carried out by means of quantitative analyses of planktonic foramini

dense water dynamics along the strait of sicily mediterranean sea abstract hydrographic and current meter data gathered in different periods in the strait of sicily and in the southern tyrrhenian sea allow the outflow characteristics from the eastern toward the western mediterranean basin to be analyzed the evolution through the strait of a deep vein of dense water coming from the eastern mediterranean is described together with the dynamic interaction with overlying layers these data are related to a slightly generalized version of recent density current models such as those of emms and those of baringer and price taking into account the dynamic influence of the overlying currents and in particular their friction and mixing this model explains the path of this deep flow and enables estimates of entrainment and bottom friction to be made with these new data a phenomenon of considerable interest namely the dynamics of density currents crossing and outflowing from a strait is examined and discussed

rare earth elements and nd isotopes as tracers of modern ocean circulation in the central mediterranean sea abstract seawater rare earth element ree concentrations and nd isotopic composition end are increasingly applied as valuable tracers of oceanographic processes such as water mass mixing and lithogenic inputs to seawater however their measurements are basically lacking in the mediterranean sea water column this study analyzes 9 seawater stations around the central mediterranean sea to clarify the relative importance of external sources vertical biogeochemical processes and lateral water mass transport in controlling ree and end distributions concentrations of ree do not show nutrient like profiles with depth likely indicative of relatively young waters with limited accumulation of remineralized ree light ree lree present a non conservative behavior which largely peak at surface waters and rapidly decrease with depth the negative correlation of surface lree enrichment with offshore distance highlights the influence of continental input from the western italian coast to the tyrrhenian surface waters in contrast to other regions with reported boundary exchange this process does not modify the end values here on the other side distributions of dissolved heavy ree hree and end display a conservative behavior that can be explained by mixing of western maw and wmdw and eastern liw and emdw originated waters we test this hypothesis with an optimum multi parameter analysis ompa including hree and end parameters even though the limited data set consistent results of water mass fractions are obtained for the four main water masses although with some particularities while liw takes on major importance when considering hree in the model emdw fractions are preferentially detected with end this latter finding implies a noticeable deep water flux across the sicily strait into the western mediterranean that was not clearly evidenced before

reconstructing deglacial north and south atlantic deep water sourcing using foraminiferal nd isotopes during the last few decades neodymium isotopes have been increasingly used as a paleoceanographic and paleoclimate proxy on million year through millennial time scales the widespread use of the nd isotope proxy depends on whether the nd isotopic composition of past seawater can be reliably extracted from authigenic sediment phases here we show evidence that planktonic foraminifera with authigenic coatings preserve a deep water nd isotopic signature and thus can be used to reconstruct past deep water nd isotopes applying this method downcore on south atlantic deep cape basin core tno57 21 41 1 s 7 9 e 4981 m the nd isotopic composition of the planktonic foraminiferal fe mn oxide coatings is identical with and confirms that of the reductively leached bulk sediment fraction piotrowski et al 2004 2005 2008 as reflecting changes in bottom water sourcing in the case of northeastern north atlantic core bofs 8k 52 5 n 22 1 w 4045 m the planktonic foraminiferal fe mn oxide coatings have different nd isotopes from reductive sediment leaches clearly acid reductive leaching must be tested in more detail we observe that the nd isotopic composition of the deep northeastern atlantic core shifted during the deglaciation from glacial values similar to the south atlantic cape basin towards holocene values similar to the bermuda rise roberts et al 2010 taken as a whole the nd isotope record from foraminiferal authigenic coatings suggests large scale changes in the proportion of northern and southern deep water sources occurred throughout the atlantic ocean with substantial chemical gradients at times during the last deglaciation

rare earth elements and yttrium in seawater icp ms determinations in the east caroline coral sea and south fiji basins of the western south pacific ocean abstract using inductively coupled plasma mass spectrometry icp ms vertical profiles of yttrium and all the rare earth elements rees in seawater were obtained at three locations in the western south pacific the east caroline coral sea and south fiji basins based on the data we have analyzed the inter ree iii relationships and found that ree iii s heavier than dy and particularly close neighbors show strong coherencies in their oceanic behavior considering that the heavy ree iii s are less particle reactive than the light and middle ree iii s and that they have very tight correlations with regressions passing almost through the origin the neighboring element ratios of the heavy ree iii s behave virtually conservatively and are suitable as tracers of water masses the dy ho er system is practically good because its dynamic range signal to noise ratio is large in the ocean the highest ho dy ratios 0 31 are found in intermediate and deep waters throughout the western south pacific which overlie the antarctic bottom water with a low ho dy ratio 0 27 these high ho dy waters are probably formed in the polar and subantarctic frontal zone and advect northward ree iii data provide better insights into the deep water recirculation in the south pacific than those discussed based upon the regular oceanographic properties alone

tracing papua new guinea imprint on the central equatorial pacific ocean using neodymium isotopic compositions and rare earth element patterns abstract the nd isotopic composition ic and rare earth patterns of hydrodynamic structures of the equatorial pacific ocean were characterized along 140 w the nd ic of antarctic intermediate water aaiw and of the lower layer of the equatorial undercurrent euc at 140 w 13 c water are much more radiogenic at the equator than at their origin in the south equatorial current 12 s revealing that these water masses have been in contact with the highly radiogenic papua new guinea png slope in both cases only a small fraction less than 9 of the sediment deposited on the png slope is required to be exchanged or dissolved to explain these nd ic variations whereas the hydrographic properties of the same water masses remain unchanged this confirms the usefulness of this tracer to identify pathways of water masses these results emphasize the importance of jets in transporting lithogenic material into the subsurface layers of remote areas where aeolian inputs are particularly weak and corroborate the previous results on fe and al maximum in this area m l wells g k vallis e a silver nature 398 1999 601 604 the nd ic of the upper layer of the euc contrasts strongly to that of the subpycnocline layer indicating that the equatorial upwelling only affects the surface waters and is not effective between 120 and 150 m we calculate that the nd imprint of the png input is likely to vanish from this surface layer as it traverses the basin due to the replacement of upwelled waters by non radiogenic ones

tyrrhenian sea circulation and water mass fluxes in spring 2004 observations and model results 1 hydrological and current measurements collected in the tyrrhenian sea during may june 2004 are analyzed with an inverse box model ibm to establish the mean circulation patterns of the basin during spring 2004 these patterns are compared with those provided by a high resolution primitive equation model the princeton ocean model or pom implemented over the area to simulate the mean basin circulation during the survey the good agreement between the two circulation fields despite the differences and the respective limitations of the employed methods represents solid evidence for the reliability of the estimated dynamical structures moreover the pom reveals the short spatial variability of the basin not always resolved by ibm because of the low spatial resolution of the in situ measurements the comparative study indicates the tyrrhenian basin as an extremely active region of the mediterranean sea characterized by a rich mesoscale dynamics this work provides for the first time after more than 25 years a novel qualitative assessment of the tyrrhenian sea spring circulation together with a robust quantitative estimation of the water mass stream fluxes inside the basin and of the exchanges with the adjacent regions

sedimentation and climate induced sediments on feni ridge northeast atlantic ocean abstract feni ridge has been studied in detail in the area between 54 and 56 n and 12 and 16 w by using high resolution profiling water column sampling with transmissometer and ctd and by piston and box core sampling the crest of feni ridge is absent in the north of the study area but on passing towards the south it begins to take shape and to increase in height its distance from the rockall slope also increases towards the south on the lower southeastern flank a secondary ridge crest has locally developed and sediment waves along the flanks have amplitudes of up to 45 m the highest and steepest waves are found in the south the waves in the north being somewhat lower bottom nepheloid layers of 175 m near the foot of rockall plateau and 125 m near the crest are attributed to a norwegian sea overflow water current with a core at 2100 m bottom nepheloid layers of 75 100 m on the lower flanks of the ridge are thought to have been caused by northeast atlantic deep water piston cores reflect alternations of glacial and interglacial periods interglacials have a high carbonate and corg content a positive eu anomaly and negative ce anomaly and a low rb la ratio they are dominated by a subpolar and transitional foraminiferal assemblage glacials show a low carbonate and corg content a reduced eu anomaly and a high rb la ratio suggesting increasingly continental sediment sources these deposits are dominated by a polar planktonic foraminiferal assemblage characterized by n pachyderma s and g quinqueloba sedimentation rates reflect differential deposition at crestal station na 87 25 rates are 17 1 cm k y for stage 1 14 6 cm k y for stage 2 3 4 cm k y for stage 3 and 5 4 cm k y for stage 4 stage 5a e has a mean sedimentation rate of 6 1 cm k y over the last 125 k y the development of feni ridge has taken place under a relatively low energy current regime

seasonal variability of the tyrrhenian sea surface geostrophic circulation as assessed by altimeter data abstractnew insights into the structure and variability of the tyrrhenian sea s surface circulation are obtained through the analysis of a very long series of altimetric observations 1993 2010 in late winter and part of spring a consistent mean flow is individuated in the eastern tyrrhenian sea formed by a stream of atlantic water that meanders around four anticyclonic structures located along the italian coast which have smaller cyclonic companions offshore the signatures of these vortices are also found in images of chlorophyll and sea surface temperature as well as in modeling results both from a high resolution operational model of the tyrrhenian sea s circulation and from a dedicated numerical simulation analysis of the energy exchange between eddies and mean flow together with numerical evidence suggests that this winter spring circulation pattern may result from basin scale instability of the atlantic stream in summer the dynamic is dominated by a well known dipole located to the east

another description of the mediterranean sea outflow abstract papers about the outflow in the strait of gibraltar assume that i it is composed of only two mediterranean waters mws the levantine intermediate water liw and the western mediterranean deep water wmdw from the eastern and western basins respectively ii both mws are mixed near 6 w hence producing a homogeneous outflow that is then split into veins due to its cascading along different paths and to different mixing conditions with the atlantic water aw a re analysis of 1985 1986 ctd profiles gibraltar experiment indicates two other mws the winter intermediate water wiw from the western basin and the tyrrhenian dense water tdw basically originated from the eastern basin in the central alboran subbasin these four mws are clearly differentiated roughly lying one above the other in proportions varying from north to south proportions also vary with time so that the outflow can be mostly of either eastern or western origin while progressing westward the mws can still be differentiated and associated isopycnals tilt up southward as much as being in the sill surroundings roughly parallel to the moroccan continental slope where the densest mws are the mws at the sill are thus juxtaposed and they all mix with aw leading to an outflow that is horizontally heterogeneous just after the sill 5 45 w before progressively becoming vertically heterogeneous as soon as 6 15 w there can be little liw and or no wmdw outflowing for a while an analysis of new 2003 2008 time series from two ctds moored ciesm hydro changes programme at the sill 270 m and on the moroccan shelf 80 m confirms the juxtaposition of the mws their individual and generally intense mixing with aw as well as the large temporal variability of the outflow composition only liw and tdw were indicated at the sill while on the shelf only liw tdw sometimes denser there than 200 m below and wmdw were indicated but none of the mws has been permanently outflowing at one or the other place the available data can be analyzed coherently intermediate and deep mws are formed in both basins in amounts that although variable from year to year allow their tracing up to the strait four major mws circulate alongslope counterclockwise as density currents and as long as they are not trapped within a basin which is necessarily the case for the deep mws in the alboran the intermediate mws wiw liw and upper tdw circulate in the north while the deep mws lower tdw and wmdw are uplifted hence relatively motionless and mainly pushed away in the south since both the intermediate and deep mws outflow at the sill they are considered as light and dense mws the light dense mws interface possibly intersecting the aw mws interface in the sill surroundings considering an outflow east of the sill composed of only two light dense homogeneous layers gives significant results across the whole strait the outflow has spatial and temporal variabilities much larger than previously assumed the mws are superposed in the sea and lead at the sill to juxtaposed and vertically stratified suboutflows that will cascade independently before forming superposed veins in the ocean these veins can have similar densities and hydrographic characteristics even if associated with different mws which accounts for the features permanency assumed up to now the outflow structure downstream of the sill depends on its composition upstream and more importantly on that of aw in the sill surroundings where fortnightly and seasonal signals are imposed on the whole outflow

biogeochemical implications from dissolved rare earth element and nd isotope distributions in the gulf of alaska dissolved rare earth element ree concentrations and nd isotope compositions were measured for surface waters and full water column profiles of the gulf of alaska goa and compared to water mass properties and circulation in order to better understand the mechanisms controlling the input and transport of rees in the ocean the rees display a typical open ocean range of concentrations i e la 12 66 pm lu 0 2 2 5 pm and depth distributions i e surface ocean depletion and enrichment with water depth nd isotope signatures are highly radiogenic as expected for the north pacific margin ranging from 3 8 to 0 2 epsilon nd the most radiogenic values were found in the coastal waters but also in the cores of eddies indicating efficient export of rees from the margins and across the mixed layer this is the first time that distinct nd isotope distributions in near surface waters can be directly assigned to offshore eddy transport a distinct mid depth similar to 2200 m nd isotope signal was found that most likely reflects advection of a water mass that formed through past down welling in the northern pacific subsurface nd isotope compositions appear to behave conservatively and can be explained through a ree distribution model proposed here this model is based on multivariate analysis of the rees and invokes two distinct pools of dissolved rees a passive pool complexed by carbonate ions and a bio reactive pool that is microbially manipulated the latter pool is only significant in the upper water column and most likely reflects the indirect effects of microbial cycling of iron our model of the open ocean ree distribution contributes to explaining the conservative nature of nd isotopes and provides a mechanism linking surface ocean and pore water ree dynamics

the geochemical balance of the rare earth elements and neodymium isotopes in the oceans profiles of ree concentrations and neodymium isotope measurements in the western indian ocean are consistent with published data from the other major oceans ree concentrations show a strong hydrographic control the influence of intermediate water masses is particularly significant surface water concentrations vary with salinity paniculate rees are less than 5 of dissolved concentration except for ce where up to 20 of total rees are present as 0 4 m particles in contrast to dissolved profiles concentration profiles of paniculate rees including ce all increase with depth ree concentrations correlate with silica over all but the deepest waters although in detail correlations are complex the neodymium isotopic composition of indian ocean seawater avg nd 0 8 3 is intermediate between that for the atlantic and pacific oceans comparison of ree data from the major oceans shows that the hrees behave more like si than do the lrees sm nd ratios are near constant for all oceans whereas ernd ratios vary between the atlantic indian and pacific oceans the fractionation of the rees in surface seawaters can be explained by fractionation factors relative to silica from 0 12 for la to 0 05 for er use of a seven box model shows that the interoceanic variations in neodymium isotopic compositions and nd concentrations cannot be reconciled unless particle water exchange is invoked the degree of exchange required is consistent with particle residence times of 1 10 yr

additional evidence of liw entrainment across the algerian subbasin by mesoscale eddies and not by a permanent westward flow abstract the circulation of the levantine intermediate water liw in the algerian subbasin western basin of the mediterranean sea has been much debated for more than fifteen years now together with the old circulation diagrams several numerical models claim that a branch of liw is permanently flowing westwards across the algerian subbasin i e directly from the channel of sardinia towards the strait of gibraltar only a few models support the fact that the unique continuous flow of liw is structured as an alongslope counterclockwise vein which is thus directed northwards off sardinia in the algerian subbasin and hence support the diagram published by millot in 1987 millot c 1987a circulation in the western mediterranean oceanologica acta 10 2 143 149 according to this diagram any little mixed liw found in the central subbasin corresponds to fragments which have been pulled away from the vein and entrained there by mesoscale eddies originated from the algerian current the elisa experiment 1997 1998 as a follow up of other ones conducted since about 15 years was designed partly to validate the diagram in addition to about 40 current meters set in place for one year four main campaigns were conducted with a sampling strategy guided in real time by infrared satellite information the data set we present clearly provides additional evidence that the little mixed liw found in the central algerian subbasin has been entrained there by the mesoscale eddies and not by a permanent westward flow

climatic instability ice sheets and ocean dynamics at high northern latitudes during the last glacial period 58 10 ka bp abstract oxygen isotope magnetic susceptibility and foraminiferal distribution data are presented for a high resolution core enam93 21 located at the northeast faeroe margin this core recorded a rapid succession of faunistic sedimentologic and isotopic variations which paralleled the greenland ice core isotopic records with their typical succession of abrupt temperature rises and gradual coolings the dansgaard oeschger cycles the most notable feature was the contemporaneous changes in surface and bottom water conditions and circulation that appeared tightly coupled with the rapid climate fluctuations warm episodes interstadials were appeared with higher sea surface temperatures and thermohaline convection in the norwegian greenland sea the polar front was located north of the enam93 21 site cold episodes stadials were associated with an increase in the input of melting fennoscandian icebergs low sea surface temperature and salinity and no thermohaline convection in the norwegian greenland sea intermediate waters changed to an estuarine mode at the faeroe margin with a reversed flow pattern through the faeroe shetland channel the polar front was located south of the enam93 21 site

neodymium isotopes in the mediterranean sea comparison between seawater and sediment signals nine depth profiles of dissolved nd concentrations and isotopic ratios epsilon nd were obtained in the levantine basin the ionian the aegean the alboran seas and the strait of gibraltar thirteen core top sediments and nile river particle samples were also analyzed leached with 1 n hcl acetic acid or hydroxylamine hydrochloride the seawater epsilon nd values become more radiogenic during the eastward circulation in the mediterranean sea the relationship between salinity and the seawater epsilon nd shows that the nd isotopic signature is more conservative than salinity in the mediterranean sea the water mass with the highest epsilon nd 4 8 is found at about 200 m in the easternmost levantine basin the average epsilon nd value for deep waters is 7 0 in the eastern basin 2 5 epsilon units higher than in the western basin by examining the sensitivity of seawater epsilon nd to nd inputs from the nile we conclude that the most significant radiogenic nd source is partially dissolved nile river particles the nd flux from the nile river water has a minor influence on the mediterranean seawater end except for the easternmost levantine basin the leachate epsilon nd values are consistent with the seawater values in the easternmost levantine basin the leachate end values obtained with hcl leaching are systematically higher than the seawater values the relationship between leachate and residual epsilon nd values indicates that the hcl leaching partially dissolves lithogenic nd so the dissolution of nile river particles is the cause of the observed shift some end values obtained with hydroxylamine hydrochloride leaching are higher than those obtained with hcl leaching although the reason for this shift is not clear sr 87 sr 86 successfully detects the presence of a nonmarine component in the leachate our results suggest that leaching performance may vary with the mineralogy of marine sediments at least in the case of the mediterranean sea copyright c 2004 elsevier ltd

rare earth elements and nd isotopes tracing water mass mixing and particle seawater interactions in the se atlantic abstract distributions of dissolved and particulate rare earth elements rees and seawater neodymium isotopic composition e nd were established in samples from the bonus goodhope bgh ipy geotraces cruise in the se atlantic sector of the southern ocean 36 s 13 e to 57 s 0 feb mar 2008 close to the south african continent in the subtropical domain particulate rees show the highest concentrations and flat paas normalized patterns clearly tracing their lithogenic origin active cerium oxidation onto suspended particles is evidenced by the mirror image relationship of the cerium anomaly between dissolved and particulate phases unradiogenic dissolved neodymium in surface waters e nd 17 1 traces the influence of old sedimentary material brought by the agulhas current and rings to the cape basin area a mass balance calculation suggests that the release of nd from dissolution of lithogenic material corresponds to a remobilization of 154 10 6 t of sediment per year i e 5 of the total sediment delivered to the southeast african coast annually at open ocean stations both dissolved and particulate rees present negative cerium anomalies indicating that particles have acquired a marine signature the increasing ree concentrations with depth and the strong linear correlations of dissolved ree with silica indicate that surface removal and deep re mineralisation of rees are partially related to the biogeochemical cycle of silicate which involves biogenic silica diatoms combined with marine carbonates these authigenic phases could explain the observed ree patterns in suspended particles except for la we suggest that the positive la anomalies in both phases are linked to the oceanic barium cycle and the partial dissolution of barite crystals especially in the polar frontal zone the e nd composition behaves conservatively in intermediate and deep waters while input processes affect the isotopic signal of subtropical surface waters and weddell gyre bottom waters an indian ocean and an atlantic variety of aaiw have been isotopically differentiated e nd 9 3 0 3 and e nd 8 0 0 5 respectively homogeneous signatures characterize circumpolar waters e nd from 8 2 to 8 4 for cdw a binary mixing model has been used to assess the contribution of undiluted nadw reaching southern latitudes

a high resolution study of holocene paleoclimatic and paleoceanographic changes in the nordic seas 1 high resolution records from images core md95 2011 in the eastern norwegian sea provide evidence for relatively large and small scale high latitude climate variability throughout the holocene during the early and mid holocene a situation possibly driven by consistent stronger westerlies increased the eastward influence of arctic intermediate and near surface waters for the late holocene a relaxation of the atmospheric forcing resulted in increased influence of atlantic water the main changes in holocene climate show no obvious connection to changing solar irradiance and spectral analysis reveals no consistent signature for any periodic behavior of holocene climate at millennial or centennial timescales there are however indications of consistent multidecadal variability

neodymium isotopic composition of the mediterranean outflow and the eastern north atlantic the neodymium concentration and isotopic composition of the mediterranean outflow in the strait of gibraltar has been directly determined the outflow has a dissolved nd concentration of 23 pmoles kg with nd 0 9 4 these results are in clear disagreement with previous values inferred for the mediterranean this concentration and nd 0 do not sharply contrast with north atlantic deep water nadw values and can produce isotopic anomalies no larger than 1 unit in the north atlantic a new profile in the eastern north atlantic does not exhibit an nd 0 anomaly at the depth of the mediterranean water core in accordance with the above inferences while concentrations and nd 0 at this site indicate that nd is conservative in the deep eastern north atlantic a previously reported nd 0 anomaly in the eastern north atlantic originally associated with the mediterranean outflow has a different source the direct contribution of the mediterranean outflow to the nadw nd budget is small 10 of the high latitude sources however the outflow plus entrained water supply 30 of the total nd associated with northern latitude deep water sources concentrations of dissolved nd in the outflow are enriched compared to the atlantic inflow which has 16 pmoles kg with nd 0 11 8 the principal source of the excess dissolved nd is inferred to be partial dissolution of detrital particles simple mass balance calculations suggest that 0 6 of the nd associated with detrital river transported sediments and or 3 5 of the nd associated with eolian particles delivered to the mediterranean is mobilized during passage into the marine environment if general these mobilization efficiencies imply that the dissolution of detrital particles is a significant source of dissolved nd and other rare earth elements in seawater

neodymium budget in the modern ocean and paleo oceanographic implications the oceanic nd budget is calculated using a steady state 10 box model and a compilation of field data this is the first attempt to propose consistent estimates of the nd fluxes entering the ocean as well as indicating possible nd sources and the proportion of nd fluxes exchanged between dissolved and particulate fractions with presently available nd data the best estimates give a total nd influx of 9 x 10 9 g yr which leads to an oceanic nd residence time of 500 years from modeling tests we suggest that the authigenic nd scavenged by particulates is 100 remineralized in the deep ocean the total exchanged nd flux may be as high as 2 x 10 10 g yr the epsilon nd 0 values of the influxes are 22 11 1 and 4 for the north atlantic surface atlantic north pacific and surface indo pacific regions respectively atmospheric and riverine nd fluxes are insufficient to explain the magnitude and regional variability of calculated nd influxes and epsilon nd 0 we propose continental margins as an additional source supplying nd to the ocean using the model calibrated for nd we examine the sensitivity of deep water epsilon nd 0 to variations of nd inputs to the ocean deep water nd concentrations and epsilon nd 0 vary with the changes in nd influxes and their epsilon nd 0 as nd sources to the ocean may change during glacial interglacial periods the epsilon nd 0 shifts recorded in ferromanganese nodules and crusts do not necessarily reflect changes in paleoceanic circulation the effects of continental erosion should be considered in reconstructing patterns of ocean circulation using nd isotopes