trace element signatures of chilean upwelling sediments at 36 s abstract with this contribution we continue the discussion on trace element te cycling in chilean upwelling sediments from within and below the oxygen minimum zone omz boning et al 2005 marine geology 220 1 21 low authigenic i e non lithogenic contents of te ag cd mo re and se were interpreted to result from the distinct seasonality in productivity induced organic flux bottom water oxygenation as well as dilution by terrigenous matter while all sediments were reducing enough to become depleted in mn highest enrichments in mo cd and re occur in sediments in contact with the omz here for a meaningful discussion total contents of as bi co cr cu ni pb sb tl v u and zn were corrected for the lithogenic background by determining te al ratios from local river samples the latter showed significantly lower te al ratios than average shale crust or andesite which are classically used for background correction hence the precise assessment of the lithogenic te contribution for the calculation of authigenic te contents allows to examine the source sink relationship of individual authigenic te for chilean sediments four te groups may be distinguished i mo re u and sb likely originate from sea water and accumulate via diffusive supply across the swi ii cd cr cu ni and zn require biologically induced pre concentration within biogenic material iii ag as se tl and v show an intermediate behaviour and iv bi and pb are contributed by anthropogenic activity highest enrichments in ni cu u as and v occur in sediments in contact with the omz the distinct depletion in co along with mn indicates the overall reducing but non sulfidic character of the chilean omz the degree of sedimentary sulfate reduction seems to be the most important control on chilean and peruvian near coastal enrichment of cd mo and u

historical evolution and extreme climate events during the last 400years on the rhone prodelta nw mediterranean abstract the rhone river is the most important source of freshwater and sediment to the western mediterranean sea deltaic lobes and littoral prisms compose the sedimentary units that make up the whole rhone subaqueous delta which reaches up to 50 m in thickness individual lobes that accompanied the retreat of the rhone during sea level rise and the subsequent westward then eastward shift of the main outlet display averaged sedimentation rates in excess of 1 cm yr 1 containing both continental and marine material during the industrial period most of the river flow was delivered through the pegoulier and roustan distributary channels which evolved under human influence within the prodeltas associated to these distributaries very expanded sedimentation rates 10 cm yr 1 allow the documentation of historical extreme climate events a 7 71 m long piston core rhs ks57 was retrieved from the distal prodelta 79 m water depth a multi proxy study was carried out using microfossil assemblages ostracods benthic foraminifera and coccoliths in combination with sedimentological and geochemical proxies our results show that 1 four different intervals i iv spanning a time range comprised between 1600 ad and present day have been differentiated from this multi proxy analysis they correspond to a different position of distributary channels each interval correlates with the different phases of channel avulsion induced by climate events or by human activity 2 the signature of extreme floods that can be identified by the punctuated occurrence of freshwater continental ostracods e g candona spp ilyocypris sp correlating with increases in grain size and or organic carbon content they correspond to decadal scale increased runoffs reported in historical archives our study demonstrates the relevance of benthic microfossil studies for reconstructing paleoenvironmental changes in transitional marine continental settings

cadmium diagenesis in laurentian trough sediments the depth distributions of cd mn and fe in pore water and sediment were determined on three replicate box cores collected at a 325 m deep station in the laurentian trough the results reveal a surface layer in which the content of solid phase cd first decreases but then increases sharply with depth in contrast mn decreases regularly over the same depth interval in the oxygenated zone of this layer cd probably associated with organic matter is released to the pore water resulting in concentrations that are more than an order of magnitude higher than in the overlying water column some of the dissolved cd is returned to the water column and some migrates downward and is precipitated at depth this part of the cd cycle is virtually complete within the surface layer the base of which corresponds to the base of the zone of mn enrichment in the subsurface layer solid phase cd and mn show little or no concentration change however dissolved cd which reaches often non detectable concentrations 0 05 nm in this layer increases once again deep within the anaerobic zone and attains concentrations even higher than in the surface layer the presence of dissolved cd complexes revealed by 1 5 to 8 fold increases in electrochemically active cd in pore water following uv treatment as well as inconsistent distributions of dissolved and solid phase cd indicate complexities in diagenesis that merit further investigation

origin and accumulation of trace elements in sediments of the northwestern mediterranean margin continental margins receive natural and anthropogenic trace elements tes from direct atmospheric deposition of aerosols onto the sea surface and from advection of riverine suspended particles and or resuspended sediments from the continental shelf slope when the margin is incised by submarine canyons as for example in the northwestern mediterranean sea most of these particles are preferentially transferred via these topographic features towards their final repositories in the abyssal plain the gulf of lions gol shelf receives the largest particulate riverine input to the western mediterranean with its associated chemical contaminants originating from the industrialized and urbanized rhone valley sediments samples grabs cores and moored traps collected in the cap de creus cdc canyon and its adjacent areas at the southwestern exit of the gol were analyzed to explore the origin dispersion transfer and accumulation of a suite of tes ag cd co cr cu ni pb zn and v from the gol shelf to the adjacent continental rise distributions of cu cr ni pb zn and v in the surface sediments of the shelf confirm their terrigenous origin in association with clay minerals whereas ag and cd are more associated with organic matter om all these tes are anthropogenically enriched in the rhone prodelta sediments anthropogenic influence remains clearly discernible in the gol shelf surface sediments for ag pb and zn hydrodynamical resuspension and sorting of shelf sediments occur at the head of the cdc canyon during dense shelf water cascading events during these events the material collected in moored sediment traps contains a higher coarse carbonate fraction slightly impoverished in tes compared to the clays of the nepheloid layer and the organically rich particles deposited before and at the end of the cascading period upper and middle canyon sediments are characterized by high sedimentation rates 0 2 cm yr 1 of fine clay material conversely sediments from the lower continental slope and rise exhibit low sedimentation rates 0 06 cm yr 1 and receive carbonaceous planktonic detritus from the water column at the lower continental slope coarse material includes foraminifers and pteropods whereas at the continental rise finer planktonic derived material is more abundant both in the cdc canyon and in its adjacent lower continental slope rise sediments co cu cr ni and v are associated with clay whereas ag cu and pb are preferentially associated with om cadmium cr and zn are also associated with om in canyon sediments carbonaceous plankton appears to be especially efficient for scavenging ag

thick bottom nepheloid layers in the western mediterranean generated by deep dense shelf water cascading the analysis of a compilation of deep ctd casts conducted in the western mediterranean from 1998 to 2011 has documented the role that dense water formation and particularly deep dense shelf water cascading off the gulf of lions plays in transporting suspended particulate matter from the coastal regions down to the basin deep ctd casts reveal that after the 1999 and 2005 2006 deep cascading events the western mediterranean deep water wmdw was characterized by the presence of a thick bottom nepheloid layer bnl that corresponded in thickness with a thermohaline anomaly generated by the mixture of dense waters formed by deep convection in the open sea and by deep cascading this bnl can be hundreds of meters thick and in the central part of the basin usually exhibits suspended sediment concentrations of 1 mg l after winter 1999 the bnl spread from the gulf of lions and the catalan margin over the northwestern mediterranean basin reaching west of the balearic islands and the ligurian sea while after winters 2005 2006 the bnl covered the entire western mediterranean basin thickness and concentration of the bnl tend to diminish with time but this trend is highly dependent on the volume of dense water generated both by convection and cascading after winter 1999 the bnl signal vanished in one year but after winters 2005 2006 it lasted for longer and the turbidity signal can still be distinguished at present 2011 particle size distribution in the bnl reveals the presence of large aggregates up to 1 mm in size formed by a mixture of single particles with the same bimodal grain size distribution as the surface sediments found in the northwestern mediterranean slope and basin results presented in this paper highlight the fact that the wmdw can be periodically affected by the arrival of new dense waters loaded with suspended particles mainly introduced by resuspension processes during major cascading events being a key process that could ultimately affect deep sea biogeochemical cycles in the western mediterranean

a walk down the cap de creus canyon northwestern mediterranean sea recent processes inferred from morphology and sediment bedforms the cap de creus canyon northwestern mediterranean sea belongs to a complex network of submarine canyons cutting the western gulf of lion continental shelf and opening into the larger sete canyon swath bathymetry data mak 1m deep towed side scan sonar imagery and 5 khz high resolution seismic reflection profiles show striking morphologies in the cap de creus canyon floor and walls as a consequence of the canyon head and the upper reach severe incision the continental shelf dramatically narrows in front of the creus cape promontory the upper canyon has a flat bottomed thalweg incised in a mega scale sediment furrow field displaying hyperbolic seismic facies the tens of kilometres long linear furrows extend also over the middle canyon down to 1400 m of water depth the furrows on either side of the canyon are not parallel but oblique and display varying degrees of excavation mid channel sediment bars are locally present in the thalweg which is made of sandy lag deposits as revealed by its acoustic response and verified by sediment samples the middle canyon is linear and steep with an up to 700 m high southern wall contrasting with the sinuous smooth lower canyon which is controlled by flowage of the underlying messinian evaporites large sections of the canyon are affected by sediment instability processes the lower cap de creus canyon hangs up to 260 m over its distalmost reach and the sete canyon through a narrow less than 1 km wide gorge numerous scours up to 10 m deep suggesting bed load transport occupy the lower sete canyon immediately downstream of the cap de creus canyon mouth the data set provides the first complete very high resolution imaging of a submarine canyon from its upper part down to its distalmost reach the observations evidence a wide set of erosion transport and deposition processes along the cap de creus canyon including sediment entrapment at the canyon head furrow generating dense water cascading through the southern wall along channel currents strong enough to excavate specific sections of the channel floor and bed load sediment transport as demonstrated by the presence of mega ripples crescent scours and grooves in the lower canyon

210pb manganese and carbon indicators of focusing processes on the northwestern mediterranean continental margin abstract organic carbon contents 210 pb data and organic and oxidised forms of manganese in sediments are used for reconstructing the shelf and deep sea transport of particulate matter and for evaluating early diagenesis conditions the latter are used as indicators of focusing processes on the northwestern mediterranean continental margin twelve different physiographical sites were sampled between 400 and 2000 m in the pyrenean and golfe du lion canyon axes and on their open slopes in the canyon axes which indent the pyrenean slope 210 pb activities show a regular exponential decrease with sediment depth computed sedimentation rates range from 170 to 198 cm 10 3 yr for an identical regular exponential decrease in the golfe du lion canyon the sedimentation rate is lower 119 cm 10 3 yr on the lower open slopes and deep sea fans rapid deposition turbidites and surficial sliding occurs onto sediments that were deposited regularly at a rate of about 175 cm 10 3 yr a deposit enriched in organic carbon is identified at mid slope between 500 and 1300 m in this area surface sediments of the canyon axes are richer in organic carbon than at the adjacent open slope sites 0 9 against 0 6 dry weight canyon axes are more active than open slopes as channels for organic matter transfer in the axial channel of the pyrenean canyon organic carbon decreases exponentially in the uppermost 12 cm in the golfe du lion canyons only the upper 2 cm of sediment are enriched in organic carbon this is related to lower sedimentation rates in the golfe du lion area as compared to the pyrenean area on the upper and lower open slopes the organic carbon contents decrease rapidly within 1 2 cm of sediment there is no exponential evolution profile and the residence times at the sediment water interface are longer than in the canyons the highest surface mn concentrations are also found in the middle of the continental slope the average is 64 g g 1 for mn associated with the organic phase mn org and 1400 g g 1 for mn ox as for organic carbon contents canyons are areas of high concentrations the lowest values 4 g g 1 for mn org and 495 g g 1 for mn ox are found for the lower open slope 1200 1700 m where there is active surficial remobilisation and gravity mass movements moreover the vertical distribution of mn has allowed us to identify sites located at depths of about 1000 m where the redox discontinuity is located in the first few centimetres and where the mn ox and the mn org profiles display a positive gradient from the deepest layers to the sediment water interface the distribution of the various parameters was caused by three different mechanisms 1 bottom advection of particulate matter transferred from the continental shelf deposits to the slope along the canyon axes 2 scavenging of the dissolved phases of metals and 3 sedimentary focusing of the particles in a favoured area of the continental slope a mid slope depocenter these data contribute to our knowledge of the role of continental margins in the global recycling of carbon and other materials

the influence of tropical instability waves on phytoplankton blooms in the wake of the marquesas islands during 1998 and on the currents observed during the drift of the kon tiki in 1947 1 during 1998 five episodes of elevated chlorophyll concentration are observed in the pacific around the marquesas islands 140 w 10 s in seawifs ocean color observations daily positions of geostationary satellite sea surface temperature fronts reveal the influence of the westward propagating tropical instability waves as narrow temperature fronts that extend far to the south of the equator and intersect the nutrient rich waters of the marquesas because the upwelled equatorial waters are rich in iron phytoplankton blooms are produced and are advected downstream by the south equatorial current previous studies attributed the blooms to local sources of iron and the interaction of the marquesas with the south equatorial current the satellite observations suggest that the currents that produced the phytoplankton blooms may have diverted the kon tiki southward in 1947 as described by thor heyerdahl

sediment dynamics during wet and dry storm events on the tet inner shelf sw gulf of lions abstract the importance of short term processes such as floods and storms on sediment delivery and reworking on the tet inner shelf was investigated the tet inner shelf is a small event dominated system located in the south western part of the gulf of lions the expected sedimentary scenario in this environment is that fluvial sediment should be deposited on the prodelta and later dispersed around the shelf and slope by wave and current reworking during storms this paper investigates differences in inner shelf sediment dynamics between storm events occurring during usual river discharges and those occurring during river floods waves current velocities near bottom water turbidity bottom sediment grain size and sea floor erosion accretion were concurrently measured at 28 m water depth on the tet inner shelf from november 2003 to march 2004 two major storms took place on 4 december 2003 and 21 february 2004 and two moderate storms occurred on 8 december 2003 and 14 march 2004 the two major storms displayed similar wave characteristics maximum significant wave height h s 7 m peak period t p 12 s and wave direction around 90 the main environmental differences during the two major storm events correspond to the amount of sediment discharged from the tet river about 2 10 4 t of sediment was delivered by the river during the 4 december flood wet storm and less than 5 10 2 t during the 21 february storm dry storm sediment dynamics were quite similar during the storm events resuspension caused by waves and sediment advection towards the southeast due to near bottom shelf currents were the dominant sedimentary processes the result was a bottom sediment erosion of several centimetres at the study site during both the wet and dry events the main differences between the wet and dry events arose after the storm immediately after the peak of the wet storm sediment supplied by the tet river and probably from other rivers was deposited around the river mouth a few days later during a moderate storm this unconsolidated sediment was resuspended transported offshore and deposited on the inner shelf in contrast a moderate storm which occurred some days after the dry february storm caused bottom erosion on the inner shelf because no fresh sediment was available on the shallower area the results from this study indicate that the tet inner shelf at 28 m water depth is mainly a bypass zone for sediment that is transported s se towards the middle outer shelf and slope although ephemeral sediment deposits may be favoured by the sediment supplied from flood events sediment transport across the shelf from the river to the slope follows a complex multi step pattern that needs to be addressed using a multi event approach

observed features of the halmahera and mindanao eddies 1 the structure and variability of the halmahera and mindanao eddies he and me which are thought to be quasi stationary eddies are described based on onboard and time series observations in the gateway region of the indonesian throughflow itf the he was found to have a clear anticyclonic eddy structure during all cruises it tilted northward and or westward with increasing depth the he mixes waters from the northern and southern hemispheres and transfers this mixed water to the eastern route of the itf the he shifted northwestward in the boreal summer and the cold phase of enso el nino and southern oscillation and southeastward in the boreal winter and the warm phase of enso in contrast the me with its cyclonic eddy structure was observed only once and seems not to be a quasi stationary eddy it appears in the mean field and is confined above the thermocline the stationary northward undercurrent the mindanao undercurrent was also not found at 7 n east of mindanao but the northern tip of the he was found at this latitude

transport and depositional process of soil organic matter during wet and dry storms on the tet inner shelf nw mediterranean article i nfo river floods and storm waves are major processes for the dispersal and deposition of terrestrial organic matter om in river dominated coastal areas a wet storm is connected to a flood with a high river discharge while a dry storm is not associated with a flood to better understand the sedimentation dynamics of terrestrial om especially soil om at the land ocean interface during wet and dry storms we studied sediment trap and core material collected on the tet inner shelf nw mediterranean using multiple organic proxies in combination with hydrodynamic parameters the proportion of soil om to the total om in the trap material calculated based on the bit branched and isoprenoid tetraether index was higher during both wet 40 and dry 30 storms than during non storm periods 10 however only surface sediments 1 cm thick layers recovered after december wet and moderate storms in 2003 showed enhanced soil om percentages compared to the deeper sediments deposited during the last century given that the wet storm eroded 4 cm of seabed at the study site flood induced fresh soil om was not deposited on the tet inner shelf during the wet storm however the following moderate storm caused resuspension of flood associated soil om which was previously trapped nearshore accordingly soil om was transported to the tet inner shelf and stored there until the dry storm occurred

diagenesis of oxyanions v u re and mo in pore waters and sediments from a continental margin this research tests the hypothesis that trace metals respond to the extent of reducing conditions in a predictable way we describe pore water and sediment measurements of iron fe manganese mn vanadium v uranium u rhenium re and molybdenum mo along a transect off washington state usa sediments become less reducing away from the continent and the stations have a range of oxygen penetration depths depth to unmeasurable o2 concentration varying from a few millimeters to five centi meters when oxygen penetrates 1 cm or less fe is reduced in the pore waters but reoxidized near the sediment water interface preventing a flux of fe 2 to overlying waters whereas mn oxides are reduced and mn 2 diffuses to overlying waters both re and u authigenically accumulate in sediments only at the most reducing location where the oxygen penetrates 0 3 cm below the sediment water interface does the surface 30 cm of sediments become reducing enough to authigenically accumulate mo stations in close proximity to the juan de fuca ridge crest are enriched in mn and fe from hydrothermal plume processes both v and mo clearly associate with mn cycling whereas u may be associating with either mn oxides and or fe oxyhydroxides rhenium is uncomplicated by adsorption to mn oxides and or fe oxyhydroxides and re accumulation in sediments appears to be due solely to the extent of reducing conditions therefore authigenic sediment re enrichment appears to be the best indicator for intermediate reducing conditions where oxygen penetrates less than 1 cm below the sediment water interface when coupled with negligible authigenic mo enrichment copyright 2005 elsevier ltd 1 introduction oceanic and atmospheric carbon cycles are strongly coupled with the ocean reservoir of dissolved inorganic carbon being 60 times larger than that of the atmosphere broecker and peng 1987 models that couple both ocean and atmosphere have been used to investigate why atmospheric carbon dioxide pco2 atm was reduced during the last glacial age and thus may be useful in predicting the environmental impact of future changes in pco2 atm some of these models require a large increase in organic carbon export through the more efficient use of nutrients to predict the lower pco2 atm observed during

the provenance of sediments in the gulf of lions western mediterranean sea in this study we undertook a reconnaissance study of sediments provenance in the gulf of lions focusing over the last 16 ka we used geochemical and isotopic tracers to determine the source of sediments and give insight into the weathering conditions prevailing sediments samples were selected both onshore and offshore from the western eastern and central part of the gulf of lions we analyzed bulk sediments coarse and fine silt and clay fractions elemental and nd isotope compositions appeared to differ from one grain size fraction to another one these are interpreted in terms of zircon addition in the coarse silt fraction for the elemental concentrations and variable sources influences for the nd isotope compositions our results indicate that sediments in the gulf of lions mainly originated from the rhone river watershed although a contribution of saharan dust is seen in one sample influence of pyrenean small rivers is minor in these samples some sr isotope compositions shifts are interpreted as reflecting variable amounts of chemical weathering that are consistent with published paleoclimatic reconstructions

input of particulate heavy metals from rivers and associated sedimentary deposits on the gulf of lion continental shelf abstract fluxes of the heavy metals chromium cr cobalt co nickel ni copper cu lead pb cadmium cd and zinc zn delivered by rivers to the gulf of lion nw mediterranean sea were estimated over a three year study of the river rhone and its smaller tributaries most of the particulate metal fluxes 80 90 delivered by these rivers occurred within a very short period of time less than 12 a typical trend for the mediterranean environment where highly contrasting hydrological regimes were observed over the year temporal and spatial variations in the fluxes of these particulate metals were driven by the fluxes in both water discharge and suspended particulate matter load on the shelf these particulate metal fluxes largely arising from the rhone watershed were two to ten times more important than those resulting from atmospheric deposition co cr and ni in the rivers and on the shelf surface sediments were mainly natural and associated with the finest particles cd and phosphorus appeared to be associated with the silt fraction and to be enriched in the prodelta areas pb zn and cu were more closely associated with the organic matter content and also showed enrichment in the organic rich prodeltaic sediments anthropogenic influences diminished offshore except for pb and zn which could be supplied from the atmosphere by man made aerosols although most of the metals tended to be enriched in the prodelta areas these did not constitute a permanent sink due to resuspension processes affecting these shallow depths a resuspension experiment conducted on sediment cores from the rhone prodelta demonstrated that metal deposited on the surface layer especially those associated with the organic matter may be resuspended this should be taken into account for a complete understanding of the biogeochemical cycle of these metals

mo total organic carbon covariation in modern anoxic marine environments implications for analysis of paleoredox and paleohydrographic conditions 1 sedimentary molybdenum mo s has been widely used as a proxy for benthic redox potential owing to its generally strong enrichment in organic rich marine facies deposited under oxygen depleted conditions a detailed analysis of mo s total organic carbon toc covariation in modern anoxic marine environments and its relationship to ambient water chemistry suggests that 1 mo s while useful in distinguishing oxic from anoxic facies is not related in a simple manner to dissolved sulfide concentrations within euxinic environments and 2 patterns of mo s toc covariation can provide information about paleohydrographic conditions especially the degree of restriction of the subchemoclinal water mass and temporal changes thereof related to deepwater renewal these inferences are based on data from four anoxic silled basins the black sea framvaren fjord cariaco basin and saanich inlet and one upwelling zone the namibian shelf representing a spectrum of aqueous chemical conditions related to water mass restriction in the silled basin environments increasing restriction is correlated with a systematic decrease in mo s toc ratios from 45 5 for saanich inlet to 4 5 1 for the black sea this variation reflects control of mo s by mo aq which becomes depleted in stagnant basins through removal to the sediment without adequate resupply by deepwater renewal the basin reservoir effect the temporal dynamics of this process are revealed by high resolution chemostratigraphic data from framvaren fjord and cariaco basin sediment cores which exhibit long term trends toward lower mo s toc ratios following development of water column stratification and deepwater anoxia mo burial fluxes peak in weakly sulfidic environments such as saanich inlet owing to a combination of greater mo aq availability and enhanced mo transport to the sediment water interface via fe mn redox cycling and are lower in strongly sulfidic environments such as the black sea and framvaren fjord these observations demonstrate that at timescales associated with deepwater renewal in anoxic silled basins decreased sedimentary mo concentrations and burial fluxes are associated with lower benthic redox potentials i e more sulfidic conditions these conclusions apply only to anoxic marine environments exhibiting some degree of water mass restriction e g silled basins and are not valid for low oxygen facies in open marine settings such as continent margin upwelling systems

fluxes and budget of on the continental margin of the bay of biscay northeastern atlantic abstract as part of the ecofer experiment ecomarge program jgofs france concentrations of the natural radionuclide 210 pb were measured in particulate matter collected by sediment traps deployed for a 14 month period june 1990 august 1991 on two mooring lines within the cap ferret canyon on the french continental slope of the bay of biscay northeastern atlantic 210 pb concentrations range 63 218 dpm g 1 and fluxes range 0 1 11 2 dpm cm 2 yr 1 displayed typical gradients increasing with depth at both mooring sites also at equivalent trap depths 210 pb activities were systematically higher on the deep slope mooring 3000 m compared to the shallow one 2300 m fluxes of 210 pb generally decreased seaward and exhibited temporal variations but with no marked seasonal trend essentially matching variations in total mass flux various correlations between 210 pb activities and major constituents of trapped particles were examined 210 pb activities were independent of the particle composition indicating that in this area scavenging of this nuclide from the water column was not directly tied to the quality of settling particles the 210 pb budget as determined by the balance of local supply flux and fluxes to sediment traps and sediments implies important lateral inputs to both mooring sites 65 89 of the flux measured by traps a feature typical of continental margin environments on the basis of annual mean 210 pb activity in traps of the two mooring sites two particle sources are hypothesized the first source located in shallow waters of the shelf and upper slope supplies the entire slope region the second source probably composed of resuspended particles from upper slope sediments feeds essentially the upper and intermediate slope region maximum sedimentation rates determined on seven box cores decreased with bottom depth from 0 3 to 0 4 cm yr 1 at the canyon heads down to 0 06 cm yr 1 at 3000 m a good agreement was observed at both mooring sites between 210 pb fluxes registered by the near bottom traps and excess 210 pb inventories within the underlying sediments suggesting that nuclide fluxes measured by traps during this experiment are representative of fluxes on a longer time scale 10 100 yr nevertheless total mass fluxes measured by traps were 3 4 times lower than 210 pb determined sediment accumulation rates a discrepancy that may be more apparent than real given the possible errors in the latter due to bioturbation

observed horizontal temperature advection by tropical instability waves 1 velocity data from moored current meters is combined with satellite sea surface temperature sst to compute oceanic mixed layer temperature advection by tropical instability waves tiws for the years 2002 to 2005 it is found that this process heats the equatorial mixed layer at an annual mean rate of 0 8 c month at 0 n 140 w and 2 8 c month at 0 n 110 w at 0 n 110 w approximately 25 of the heating is contributed by zonal temperature advection a process that has often been assumed to be negligible from a nine month segment of data may 2004 february 2005 the zonal temperature advection at 2 n 140 w has been estimated to be approximately 0 7 c month much larger than the equatorial value for the same time period thus the data supports a recent hypothesis that tropical instability waves contribute a significant mean zonal temperature advection with off equatorial maxima to the equatorial mixed layer heat budget comparisons with numerical model results suggest that current ocean general circulation models can realistically simulate important aspects of tropical eddy mixed layer interactions

natural and anthropogenic trace metals in sediments of the ligurian sea northwestern mediterranean abstract the magnitude and the chronology of anthropogenic impregnation by hg and other trace metals of environmental concern v cr ni cu zn ag cd and pb including its stable isotopes in the sediments are determined at the dyfamed station a site in the ligurian sea northwestern mediterranean chosen for its supposed open sea characteristics the dyfamed site vd is located on the right levee of the var canyon turbidite system at the end of the middle valley in order to trace the influence of the gravity current coming from the canyon on trace metal distribution in the sediment we studied an additional sediment core va from a terrace of the var canyon and material collected in sediment traps at the both sites at 20 m above sea bottom the patterns of hg and other trace element distribution profiles are interpreted using stable pb isotope ratios as proxies for its sources taking into account the sedimentary context turbidites redox conditions and sedimentation rates major element distributions coupled with the stratigraphic examination of the sediment cores point out the high heterogeneity of the deposits at va and major turbiditic events at both sites at the dyfamed site we observed direct anthropogenic influence in the upper sediment layer according to the 210pbxs derived sedimentation rate at the dyfamed site 0 4 mm yr 1 the hg enriched layer of the top core corresponds to the sediment accumulation of the last 50 years which is the period of the highest increase in hg deposition on a global scale with the hypothesis of the absence of significant post depositional redistribution of hg the hg corg ratio changes between the surface and below are used to estimate the anthropogenic contribution to the hg flux accumulated in the sediment the hg enrichment from pre industrial to the present time is calculated to be around 60 consistent with estimations of global hg models however based on the chemical composition of the trapped material collected in sediment traps we calculated that epibenthic mobilization of hg would reach 73 conversely the cd corg ratio decreases in the upper 5 cm which may reflect the recent decrease of atmospheric cd inputs or losses due to diagenetic processes

global ocean surface velocities from drifters mean variance el nino southern oscillation response and seasonal cycle 1 global near surface currents are calculated from satellite tracked drogued drifter velocities on a 0 5 0 5 latitude longitude grid using a new methodology data used at each grid point lie within a centered bin of set area with a shape defined by the variance ellipse of current fluctuations within that bin the time mean current its annual harmonic semiannual harmonic correlation with the southern oscillation index soi spatial gradients and residuals are estimated along with formal error bars for each component the time mean field resolves the major surface current systems of the world the magnitude of the variance reveals enhanced eddy kinetic energy in the western boundary current systems in equatorial regions and along the antarctic circumpolar current as well as three large eddy deserts two in the pacific and one in the atlantic the soi component is largest in the western and central tropical pacific but can also be seen in the indian ocean seasonal variations reveal details such as the gyre scale shifts in the convergence centers of the subtropical gyres and the seasonal evolution of tropical currents and eddies in the western tropical pacific ocean the results of this study are available as a monthly climatology

long term observations of tropical instability waves abstract reynolds sea surface temperature sst data showing tropical instability waves tiws in the tropical pacific are analyzed along with current measurements from the tropical atmosphere ocean tao buoy array and wind speeds from the european remote sensing satellite ers 1 and 2 scatterometers tiws are visible as undulations in the sst cold fronts that delineate the northern and southern boundaries of the cold tongue in the equatorial pacific the sst pattern results from advection of the sst front by instabilities in the near surface equatorial currents although the waves are seen on both sides of the pacific cold tongue and north of the equator in the atlantic they are most intense and thereby most observable in the north equatorial pacific the combination of data used in this analysis provides information about these waves the factors controlling them and their coupling to the atmosphere on annual and interannual timescales on annual timescales the tiws generally establish a strong

anthropogenic trace metals in the sedimentary record of the llobregat continental shelf and adjacent foix submarine canyon northwestern mediterranean abstract anthropogenic trace metal concentrations and inventories were studied on the llobregat continental margin from the llobregat river mouth to the foix submarine canyon a prodelta sedimentary depocentre was identified along with a previously known canyon depocentre significant upward increases in trace metal contents were detected in sediment cores of the prodelta and upper part of the canyon down to 860 m depth metal enrichment factors ranged between 1 8 and 10 on the continental shelf and between 1 2 and 2 7 in the submarine canyon these metal enrichments occurred during the 20th century and can be correlated with the period of maximum increase of population and industrial activities in the barcelona area and the consequent anthropogenic metal inputs maximum trace metal enrichments are located in the prodelta depocentre and significant enrichments were also measured in the southern prodelta and in the foix upper canyon as a consequence of efficient shelf canyon sediment and metal transfer deeper in the canyon at 1370 m depth no metal enrichments were detected probably because of particle dispersion and dilution with uncontaminated sediment within the canyon this study shows that in some mediterranean sedimentation systems anthropogenic trace metal contamination is affecting not only the littoral and the continental shelf but also the adjacent continental slope sediments through submarine canyons

last millennia sedimentary record on a micro tidal low accumulation prodelta tet nw mediterranean statistical sequential analysis was performed on a series of sediment cores collected from the tet prodelta in the gulf of lions northwestern mediterranean sea between october 2003 and october 2004 seabed changes during that period were correlated to hydrodynamic conditions waves and currents and river discharge low sediment supply prevents full preservation of new sediment strata on this low accumulation prodelta located on a microtidal storm dominated inner shelf severe meteorological events caused a rapid succession of erosion and deposition phases for example the december 2003 flood and storm produced a flood layer deposit that persisted for 2 months with only slight transformations due to early diagenesis and or bioturbation until a new storm event eroded this layer a typical sedimentary sequence was observed for the secular deposits composed of a 10 cm thick sandy layer overlaying siltyclayey layers these characteristic features were used to analyse the last millennia sedimentary record of the tet prodelta the low preservation of freshly deposited sediments and variable sedimentation rates during the last millennia period yield a sedimentary sequence formed by the outcropping of muddy prodeltaic units intersected by heterogeneous siltysandy units similar to those formed under present day hydrodynamic conditions no flood layer was found related to catastrophic flooding of the last century in the sedimentary record the little ice age 1550 1850 ad probably favoured the formation of a well developed muddy prodelta in the mouth of the tet river later on the decrease of sediment supply by rivers due to climate change and or human activities damming irrigation and the increase of the number of high energy storms reaching the coast induced a coarsening of the top sediment layer on this prodelta this modern change of the substrate is also observed in the composition of benthic biota found in the substrate

comparative geochemistry of cadmium rhenium uranium and molybdenum in continental margin sediments the concentrations of authigenic phases of cd re u and mo increase with depth in four 45 cm long sediment box cores collected along the axis of the laurentian trough gulf of st lawrence average authigenic accumulation rates estimated from element inventories are similar to rates in other continental margin environments strong regional variations in sediment accumulation rate and sulfide concentration have little influence on the accumulation rates of cd and re this suggests that slow precipitation kinetics controls the accumulation of cd and re in these sediments the accumulation rate of authigenic u is more variable it may be tied to the kinetics of microbially mediated u reduction and be controlled by the availability of reactive organic matter authigenic mo is distinguished by a sharp subsurface concentration minimum above which mo cycles with manganese mo released to pore water upon reduction of mn oxides diffuses downward and enriches the subsurface sediment mo accumulates most rapidly in the sediment with the highest sulfide content slow conversion of molybdate to thiomolybdate may explain the much slower mo accumulation rate in the less sulfidic sediments a component of authigenic mo accumulates with pyrite in an approximately constant mo fe ratio the accumulation rate of pyrite and associated mo is insensitive to avs abundance pyrite formation may be limited by the reactivity of iron oxide minerals

diagenetic separation of cadmium and manganese in suboxic continental margin sediments abstract the vertical distribution of cd differs from that of mn in sediment cores taken from the continental margins of the arctic and atlantic oceans the oxic surface sediment is depleted in cd and enriched in mn whereas the subsurface sediment is enriched in cd and depleted in mn in some cores the distributions of solid phase and dissolved mn are offset the porewater profiles indicate that mn is being precipitated relatively deep in the sediment whereas the solid phase distributions indicate that mn has been precipitated very close to the sediment surface in the recent past at one deep site located near the base of the continental slope 3000 m the offset may be caused by a relatively recent decrease in ocean productivity a corresponding decrease in the organic carbon flux to the sediment and a subsequent migration of the redox boundary deeper into the sediment however at a site where the upper sediment layers have accumulated during the last few decades this explanation cannot account for the offset distributions we propose that a fluctuating input of organic matter to the sediment on seasonal or decadal timescales causes the position of the redox boundary to fluctuate the fluctuating redox boundary pumps dissolved mn upward and concentrates it as mn oxide in a distinct layer at the upper limit of the redox excursion at the same time it pumps cd downward and concentrates it in a distinct layer at the lower limit of the redox excursion the net result of a fluctuating redox boundary is to increase the spatial separation of cd and mn during the early diagenesis of suboxic sediments

chronology and sources of trace elements accumulation in the rhone pro delta sediments northwestern mediterranean during the last 400years abstract the rhone pro delta sediments receive the particulate inputs from the rhone river the largest freshwater discharge of the western mediterranean sea trace element tes ag cd co cr cu ni pb and zn concentrations and stable pb isotope ratios were determined along a 7 7 m long sediment core collected from the rhone prodeltaic lobe archiving the deposits of the last 400 years trace element mean concentrations during the pre industrialized era before 1850 ce were no different from the average composition of earth s upper crust except for cr principal component analysis performed on tes and tracers suggests three origins for tes that we identified as i marine biogenic material ag cd ii ultramafic rocks li cr ni and iii other clay minerals co cu pb and zn during the pre industrial period several changes in the te al ratios coincided with flood events or and modifications in the channelization of the rhone river mouth some frequencies in the tes temporal variations allow us to hypothesize some influence of climate variation sediments deposited after 1850 ce exhibited concentrations of certain tes exceeding 1 3 3 5 times the concentrations of the pre industrial era ag cd pb cu zn principal component analysis performed on post 1850 ce data allows to distinguish pristine and anthropogenically impacted tes pristine tes such as co cr and ni are linked with clay markers al li and fe co and ni are associated with mn enrichment whereas cr is correlated with fe anthropogenically impacted elements consist of ag cd cu pb and zn vertical profiles show that te contamination has increased dramatically after the iind world war and reached a maximum between 1970 and 1980 consistently with anthropogenic atmospheric emissions changes sediment deposited on the rhone prodelta at the beginning of xviith century have 206 207pb ratios close to values of natural pb 1 200 whereas sediments deposited after 1850 ce are clearly contaminated by european gasoline and industrial pb pools

recent sediment transport and deposition in the nazare canyon portuguese continental margin processes pathways and fluxes of sediment transport and deposition in the nazare submarine canyon portuguese continental margin were investigated by water column profiling of suspended particulate matter recording of near bottom currents and suspended particulate matter fluxes with benthic landers and by analysis of surface sediment cores the results show that fine grained suspended sediment from the adjacent shelf is captured in the upper canyon and actively transported through the canyon to the abyssal plain under influence of tidal currents and intermittent sediment gravity flows tidal currents are actively resuspending and transporting sediment in the upper to middle canyon as reflected by high concentration of suspended particles in bottom waters high horizontal and vertical sediment fluxes in the bottom water layer and high sediment accumulation rate on the seabed diminishing strength of tidal currents leads to focussed sediment deposition in the middle canyon further transport of sediments toward the lower canyon takes place predominantly by sediment gravity flows occurring on yearly or longer timescale turbidity currents strong enough to transport sand sized material to the lower canyon occur only on centennial or longer timescales

historical levels of heavy metals and artificial radionuclides reconstructed from overbank sediment records in lower rhone river south east france trace metals cu cd cr ni pb zn hg and artificial radionuclides cs 137 am 241 pu 238 and pu239 240 were investigated in overbank sediments located in inter embankment areas of the lower rhone river enrichment factors ef and anthropogenic factors af were calculated to estimate the level of contamination in these sediment storages the results show that in the studied sites co ni and sc display low ef values and are mainly from lithogenic origin for the other studied trace metals a great variability of sedimentary record is observed significant anthropogenic enrichment was highlighted at a particular site that undergoes fluvial inputs occurring in the last 50 years lead is the element with the highest ef values ef 13 followed by cd ef 11 cu ef 5 hg ef 7 and zn ef 2 temporal variations of pb cd and hg show a maximum in the 1960 s and a decreasing trend afterward maximum enrichment of artificial radionuclides were observed in sediment deposit during the period 1960 1990 when maximum liquid releases from nuclear activities occurred these results indicate that despite the high energy conditions and the generally sandy nature of the riverbank sediments significant anthropogenic enrichments were observed in some areas of sediment accumulation in the lower rhone river these enrichments are however relatively low compared to some other rivers in france and europe due to the important suspended sediment discharge in this river in particular during strong floods which dilutes the anthropogenic inputs of contaminant c 2011 elsevier ltd all rights reserved

210pb sedimentation rates from the northwestern mediterranean margin abstract a total of 83 cores were collected in the gulf of lions continental margins and analysed for 210 pb xs excess 210 pb in order to understand sedimentation patterns apparent sedimentation rates asr range from 0 65 cm year 1 in the vicinity of the rhone river mouth to 0 01 cm year 1 in the deep basin except for the prodelta area rates decrease with depth linearly with the water depth on the slope asr do not differ between canyons and open slope except for the western area where the rates are slightly higher in the lacaze duthiers canyon compared to its adjacent open slope in the canyon and open slope areas mass accumulation rates determined from 210 pb xs profiles 0 10 and 0 08 g cm 2 year 1 respectively are in good agreement with particulate fluxes calculated from 5 years of near bottom sediment trap data even when the trap particle fluxes and the apparent accumulation rates are overestimated in response to resuspension and bioturbation effects however differences in sediment trap data between west and east portion of the slope are not observed in the sedimentation rates calculated with 210 pb xs the outer shelf area may have an important role in trapping sediment but it is not sufficiently documented sediment surface mixed layer depths decrease with water depth with a mean value for the whole margin of 8 6 cm 210 pb xs inventories in the sediment are systematically higher than the net 210 pb export flux estimated from the above water column over the margin the ratio between accumulated 210 pb and available 210 pb is about 3 suggesting boundary scavenging effects and advective transport

trace element behavior and redox facies in core shales of upper pennsylvanian kansas type cyclothems the black shale submember of core shales of pennsylvanian kansas type cyclothems is highly enriched in redox sensitive trace elements tes relative to the overlying gray shale submember as well as to many other modern and ancient organic rich deposits controls on trace element behavior in the black shale can be inferred from trace element enrichment factors efs relative to gray shale and the relationship of tes to total organic carbon toc most tes conformed to one of two patterns 1 mo u v zn and pb exhibited moderate efs and strong covariation with toc in samples having 10 wt toc and 2 cu ni cr and co exhibited low efs and moderate to strong covariation with toc in all samples these patterns are inferred to represent different responses to benthic redox conditions the first pattern is characteristic of tes of strong euxinic affinity i e those taken up in solid solution by fe sulfide or involved in other reactions catalyzed by free h2s and resident mainly in authigenic phases whereas the second pattern is characteristic of tes of weak euxinic affinity i e those not strongly influenced by the presence of free h2s and resident mainly in the organic carbon or detrital fractions of the sediment these inferences allowed development of a multiproxy technique for assessing redox facies in black shale samples euxinic conditions were considered to have existed if at least two of four redox indicator trace elements mo u v zn showed euxinic levels of enrichment and nonsulfidic anoxic conditions were inferred otherwise the validity of the procedure is indicated by 1 agreement among all four redox indicators for a large majority of samples 69 of 185 2 among samples yielding a mixed redox signal a systematic sequence of te enrichment v zn mo u and 3 for tes of weak euxinic affinity reduced variance among samples representing each redox facies sequential enrichment may be a response to differential redox thresholds for accumulation e g v or postdepositional remobilization of trace elements e g u and may provide a basis for finer assessment of redox conditions in low oxygen paleoenvironments than permitted by simple classification schemes the multiproxy procedure for redox facies analysis developed in this study is likely to be more reliable than widely used single proxy indicators based on trace elements e g mo authigenic u or v v ni or c s fe systematics e g s toc or dop d 2004 elsevier b v all rights reserved

sedimentary trace element records over the last 200 kyr from within and below the northern arabian sea oxygen minimum zone two piston cores pcs containing two full glacial cycles were retrieved at murray ridge one core pc463 contains sediment deposited at 920 mbsl within the other pc464 has sediment deposited at 1470 mbsl below the current oxygen minimum zone omz o2 2 m variations in the organic carbon oc content correlate well between the two cores high oc contents correspond with periods of high insolation and are accompanied by a stable and intensive omz the lithogenic fractions are similar and have a rather constant composition the v mn co cu se zn and sb contents in these fractions are in fair agreement with the values in standard shales ss the nicontent of the lithogenic fraction ishigherthanin ssdue to its high content in the regional eolian input andthe mo re andu contents are higher as a result ofsyngenetic and or diagenetic overprints in both cores mn and cohavea negative the other elements a positive correlation with oc four processes contributing to sedimentary enrichment in trace elements can be envisaged

lateral advection of organic matter in cascading dominated submarine canyons in the gulf of lions gol dense water overflowing off the shelf occurs seasonally and represents the main mechanism affecting the shelf slope exchange of particulate organic matter om most of the dense water export takes place in the south western gol and in particular through cap de creus cdc submarine canyon here benthic instruments were deployed to collect down canyon particulate fluxes whereas surface sediments were taken after the cascading event along the sediment dispersal system on the shelf in cdc canyon and in the nearby lacaze duthiers ld canyon the chemical composition of the suspended material and surface sediments were investigated using several proxies including organic and inorganic carbon total nitrogen biogenic silica 13c 14c and alkaline cuo oxidation products thermohaline anomalies and high current speed events were measured in cdc canyon since december 2004 until mid april 2005 indicating a marked off shelf export of dense water trough the canyon during the cascading mud and relatively coarse shelf and upper canyon sediments were the major component of the mass flux conversely advection of fine material via nepheloid layers dominated down slope fluxes during pre and post cascading the resulting change in grain size affected the flux of mineral bound terrigenous oc indicating that the down canyon transport of land derived om did not occur as bulk but rather its composition is driven by sediment sorting associated with different transport mechanisms both surface sediments and sediment trap samples indicated that cdc canyon is well connected to the gol terrigenous dispersal system conversely our results suggest an overall limited influence of land derived om in ld canyon in spite of the reduced fluvial nutrient supply a significant pulsed input of modern marine om was observed in april 2005 at the end of the cascading period both intense mixing and lack of strong water column stratification likely played a key role allowing for both diffusion of nutrients rich waters into the euphotic zone and efficient vertical sink of marine oc on its way toward the seafloor this fresh pool of oc interacted with the dense plume overflowing off the shelf becoming part of the material laterally advected to the slope

the geochemistry of redox sensitive trace metals in sediments abstract we analyzed the redox sensitive elements v mo u re and cd in surface sediments from the northwest african margin the u s northwest margin and the arabian sea to determine their response under a range of redox conditions where oxygen penetrates 1 cm or less into the sediments mo and v diffuse to the overlying water as mn is reduced and remobilized authigenic enrichments of u re and cd are evident under these redox conditions with the onset of sulfate reduction all of the metals accumulate authigenically with re being by far the most enriched general trends in authigenic metal accumulation are described by calculating authigenic fluxes for the 3 main redox regimes oxic reducing where oxygen penetrates 1 cm and anoxic conditions using a simple diagenesis model and global estimates of organic carbon rain rate and bottom water oxygen concentrations we calculate the area of sediments below 1000 m water depth in which oxygen penetration is 1 cm to be 4 of the ocean floor we conclude that sediments where oxygen penetrates 1 cm release mn v and mo to seawater at rates of 140 260 60 150 and 5 10 of their respective riverine fluxes using the authigenic metal concentrations and accumulation rates from this work and other literature these sediments are sinks for re cd and u with burial fluxes of 70 140 30 80 and 20 40 respectively of their dissolved riverine inputs we modeled the sensitivity of the response of seawater re cd and v concentrations to changes in the area of reducing sediments where oxygen penetrates 1 cm our analysis suggests a negligible change in seawater re concentration whereas seawater concentrations of cd and v could have decreased and increased respectively by 5 10 over 20 kyr if the area of reducing sediments increased by a factor of 2 and by 10 20 if the area increased by a factor of 3 the concentration variations for a factor of 2 increase in the area of reducing sediments are at about the level of uncertainty of cd ca and v ca ratios observed in foraminifera shells over the last 40 kyr this implies that the area of reducing sediments in the ocean deeper than 1000 m 4 has not been greater than twice the present value in the recent past

suspended particle movement in and around quinault submarine canyon abstract time and space dependent light transmission temperature salinity and velocity data obtained during two winter experiments in the vicinity of quinault submarine canyon are used to examine processes controlling subtidal cpd fluctuations in suspended particulate concentration in the region in particular local resuspension of particles by waves and currents horizontal advection and vertical advection data include time series from four to eight mooring locations as many as 16 current meters and 10 transmissometers on the shelf over the open slope and in the canyon during each experiment spatial distributions from five ctd transmission surveys and gravity wave information particle concentration in the bottom boundary layer at the shelf edge was dominated by resuspension events the mechanism for resuspension had a large inter annual variation in the first year wave induced resuspension dominated whereas in the second year current induced resuspension dominated the cut off depth for storm related resuspension was generally m subtidal advection across isobaths upwelling downwelling accounted for 20 of the variance in concentration fluctuations at the shelf edge in the bottom boundary layer horizontal advection of material suspended in the bottom nepheloid layer on the shelf resulted in the formation of shelf break depth intermediate nepheloid layers over the canyon in regions where the flow crosses isobaths the existence strength onshore offshore extent and vertical structure of such nepheloid layers at a given time in this asymmetrical canyon appear to be a function of the direction of flow over the outer shelf and over the upper slope in the canyon whether active resuspension is occurring over the shelf and the maximum resuspension depth and magnitude of the active resuspension event the frequency timing and magnitude of previous resuspension events spatial and temporal continuity magnitude and direction of flow over the open slope north and south of the canyon vertical settling and upwelling or downwelling related to the along isobath flow over the upper slope fluctuations in particle concentration below the shelf break depth over the canyon slope were controlled by vertical rather than horizontal advection vertical excursions by the water mass of 100 m occurred both as a result of isopycnal adjustment to the quasi geostrophic along isobath flow and as a result of semidiurnal tidal oscillations when an overhead nepheloid layer was present such water mass excursions produced concentration fluctuations at depths below the maximum depth of storm related local resuspension in open slope regions where strong inls intermediate depth nepheloid layers were absent the portion of concentration variance that could be explained by advective models with constant spatial gradients was almost negligible only one resuspension event was documented in the bottom boundary layer within the deep canyon bottom depth 1000 m suggesting that advection must account for the observed variance in particle concentration however the large scale gradients at these depths are sufficiently weak cf the smaller scale gradients or noise that advective control could only be demonstrated during the second winter experiment when velocities along the canyon axis were relatively large finally the data demonstrate that subtidal concentration fluctuations within 50 m of the canyon floor are correlated to those at the shelf edge this correlation reflects a correlation in the velocity field rather than a transfer of particles as might occur with a turbidity current

spatial and temporal variability of downward particle fluxes on a continental slope lessons from an 8 yr experiment in the gulf of lions nw mediterranean abstract a long term experiment of downward particle fluxes and currents has been initiated in 1993 on the continental slope of the gulf of lions nw mediterranean and pursued within the frame of several french and european projects pnec euromarge nb mtp ii mater eurostrataform sediment traps and current meters were deployed at several locations on this slope deeply incised by numerous canyons with an extensive spatial coverage for the first 2 years canyons at the entrance middle and exit of the gulf with respect to the general along slope circulation head and mid canyon depths adjacent open slope from late 1995 onwards this design was reduced to the two mid canyon moorings at the entrance and exit of the gulf monthly fluxes and hourly temperatures and currents were recorded at 500 m 30 m above bottom mab in the canyon heads at 500 and 1000 m respectively 530 and 30 mab nominal depths at the mid canyon sites and at 750 m 30 mab open slope this study aims at describing the spatial seasonal and interannual variability of flux intensity and composition of settling particles and at analyzing the role of diverse forcings in the control of particle exchange across the margin results from the first 8 years 1993 2001 show that total mass fluxes in the 101 104 mg m 2 d 1 range increase along slope particularly for the near bottom traps between the ne planier canyon and the sw lacaze duthiers canyon limits of the gulf of lions indicating an increased shelf export of particulate matter in the western part of the system bulk chemical composition organic matter carbonate opal and lithogenic fraction remained rather stable during the course of the experiment tending towards values typical of superficial shelf sediments at higher mass fluxes first order calculations using a simple two component mixing model suggest a decreasing contribution of primary particles settling out of the overlying waters to the total flux from the entrance towards the exit of the system particulate material transferred to the deeper slope in the southwestern part of the gulf of lions appears therefore to predominantly originate in resuspended shelf and or upper slope sediment downward particle fluxes and potential forcing parameters exhibit a high seasonal variability with higher values from late autumn to early spring furthermore unprecedented winter flux peaks observed in 1999 dominated the interannual differences which otherwise were quite limited correlations between sources of particulate material on the shelf i e river and atmospheric inputs phytoplankton biomass and sediment resuspension cross slope exchange mechanisms derived from in situ temperature and current records and flux data indicate a predominant effect of dense cold water cascading on the exchange of particulate matter between the shelf and the slope

determination of the copper isotope composition of seawater revisited a case study from the mediterranean sea abstract a new technique for the determination of dissolved copper isotope composition 65cu of seawater was applied to examine copper sources and internal cycling in the mediterranean sea along the geotraces ga04n transect a succession of chelating resin with nitrilotriacetic acid functional groups and strong base anion exchange resin together with optimization of the multi collector inductively coupled plasma mass spectrometry set up allowed to isolate copper from seawater matrix and to measure the 65cu 63cu ratios in seawater with an external precision of 0 06 2 s d this method was first applied for inter comparison measurements to surface and deep waters sampled at the bermuda atlantic time series station bats in the north atlantic ocean during the geotraces intercalibration cruise 1 disparities in 65cu reported here and in the literature over these samples showed a need to investigate whether a new inter comparison sample should be decided upon or whether the use of uv oxidation can also affect the measurement of 65cu we also measured total dissolved cu concentration dcu t and 65cu for 12 stations in the mediterranean sea the 65cu distribution showed significant variations in the euphotic zone at the chl a maximum and at bottom depths copper isotope ratios ranged from 0 21 to 0 76 0 06 2 s d yielding an average of 0 51 0 20 2 s d n 96 for the mediterranean sea a strong zonation between natural aerosol deposition to the south and anthropogenic aerosol deposition to the north was seen in the sample set dulaquais et al 2017 gerringa et al 2017 rolison et al 2015 natural dust deposits seemed to draw 65cu toward lower values and deeper in the euphotic zone whereas the impact of anthropogenic aerosols seemed restricted to an increase in dcu t at the chl a maximum 65cu showed significant increase which we attributed to scavenging on and or uptake by phytoplankton the isotope signature of cu sources to the mediterranean sea was also investigated and we inferred a significant source of isotopically heavy cu in the gibraltar area potentially originating from a release of cu sulfide leached in the mining area of southern spain i e iberian pyrite belt in rivers and transported to the mediterranean sea in surface by seasonal water mass circulation conversely marine sediments appear to be a source of isotopically light cu to deep waters this study provides new hints on the use of copper isotopes to study sources and sinks of cu in seawater this article is part of a special issue entitled cycles of trace elements and isotopes in the ocean geotraces and beyond edited by tim m conway tristan horner yves plancherel and aridane g gonzalez

mobility of authigenic rhenium silver and selenium during postdepositional oxidation in marine sediments sedimentary records of redox sensitive trace elements hold significant potential as indicators of paleoceanographic environmental conditions records of re can reveal the intensity of past reducing conditions in sediments at the time of deposition whereas records of ag may record the magnitude of past diatom fluxes to the seafloor confidence in paleoenvironmental reconstruction from records of either metal however requires it to have experienced negligible redistribution since deposition this study examines diagenetic rearrangements of re and ag that occur in response to exposure to bottom water o2 in environments of low sedimentation rate including madeira abyssal plain turbidites and eastern mediterranean basin sapropels authigenic re was remobilized quantitatively by oxidation but poorly retained by the underlying sediments all records are consistent with previous work demonstrating that only a limited reimmobilization of re occurs preferentially in corg rich reducing sediments silver was also mobilized quantitatively by oxidation but it was subsequently immobilized more efficiently in all cases as sharp peaks immediately into anoxic conditions below active oxidation fronts and these peaks remain immobile in anoxic conditions during long term burial comparison of ag s and se records from various cores suggests that ag is likely to have been immobilized as a selenide a mechanism previously proposed for hg in similar situations mercone et al 1999 coexisting narrow peaks of ag and hg with se offer a means of assessing whether oxidative burndown has ever occurred at the top of corg and sulfide rich sedimentary units although these results suggest that caution must be used when inferring paleoenvironmental information from records of ag and re in cores with low sediment accumulation rates 5 cm ka 1 they should not affect the promise that authigenic ag and re records hold for paleoenvironmental reconstruction in sediments with higher accumulation rates and where anoxic conditions have been maintained continuously

a biomineralization model for the incorporation of trace elements into foraminiferal calcium carbonate measurements of srca of benthic foraminifera show a linear decrease with water depth which is superimposed upon significant variability identified by analyses of individual foraminifera new data for cdca support previous work in defining a contrast between waters shallower and deeper than 2500 m measured element partition coefficients in foraminiferal calcium carbonate relative to sea water d have been described by means of a one box model in which elements are extracted by rayleigh distillation from a biomineralization reservoir that serves for calcification with a constant fractionation factor such that d 1 f 1 f where f is the proportion of ca remaining after precipitation a modification to the model recognises differences in element speciation the model is consistent with differences between dsr dba and dcd in benthic but not planktonic foraminifera depth variations in d for sr and ba are consistent with the model as are differences in depth variation of dcd in calcitic and aragonitic benthic foraminifera the shallower depth variations may reflect increasing calcification rates with increasing water depth to an optimum of about 2500 m observations of unusually lower dcd for some deep waters not accompanied by similar dsr or dba may be because of dissolution or a calcification response to a lower carbonate saturation state

trace elements from the central pacific mexican shelf geochemical associations and anthropogenic influences baselines for major and trace elements were determined from surface sediment samples from sites located along the central pacific mexican shelf cpms 16 7 20 45 n this study area is next to the biggest harbours in mexico for example touristic puerto vallarta and acapulco touristic and industrial manzanillo and industrial harbours lazaro cardenas the industrial harbours have been expanding transporting tonnes of materials to asia and north and south america oceanographic campaigns were conducted to obtain sediment from depths ranging from 56 to 159 m the grain size was predominately fine fraction 63 m mean 56 m 30 more than 50 elements were analysed and methods were validated with certified reference materials the results extracted the iron ore signal enrichment and the association between fe and co cr cu mg mn mo ni v and zn were determined for the sediments arsenic is enriched in the cpms the normalized enrichment factor average nefav for as is nefav 8 7 however the ratio between as and cs indicates a natural origin in the most of the sites cadmium mo and ag were significantly correlated with corg enhanced precipitation of sulfide reactive metals moreover an anthropogenic influence was detected for hg nefav 4 3 1 5 and ag nefav 8 5 2 6 in the shelf near the heavily industrialized harbour of lazaro cardenas

sediment transport to the deep canyons and open slope of the western gulf of lions during the 2006 intense cascading and open sea convection period an array of mooring lines deployed between 300 and 1900 m depth along the lacaze duthiers and cap de creus canyons and in the adjacent southern open slope was used to study the water and sediment transport on the western gulf of lions margin during the 2006 intense cascading period deep reaching cascading pulses occurred in early january in late january and from early march to mid april dense water and sediment transport to the deep environments occurred not only through submarine canyons but also along the southern open slope during the deep cascading pulses temporary upper and mid canyon and open slope deposits were an important source of sediment to the deep margin significant sediment transport events at the canyon head only occurred in early january because of higher sediment availability on the shelf after the stratified and calm season and in late february because of the interaction of dense shelf water cascading with a strong e se storm during the january deep cascading pulses increases in suspended sediment concentration within the canyon were greater and earlier at 1000 m depth than at 300 m depth whereas during the march april deep cascading pulses sediment concentration only increased below 300 m depth indicating resuspension and redistribution of sediments previously deposited at upper and mid canyon depths deeper than 1000 m depth net fluxes show that most of the suspended sediment left the canyon and flowed along the southern open slope towards the catalan margin whereas a small part flowed down canyon and was exported basinward additionally on the mid and lower continental slope there was an increase in the near bottom currents induced by deep open sea convection processes and the propagation of eddies this combined with the arrival of deep cascading pulses also generated moderate suspended sediment transport events in the deeper slope regions

annual and interannual variability of the tropical instability vortices in the equatorial eastern pacific observed from lagrangian surface drifters abstractthis study documents the spatial distributions and temporal variations of anticyclonic eddies with identified radii 100 km in the equatorial eastern tropical pacific ocean viz tropical instability vortices tivs using lagrangian surface drifters the tivs identified from lagrangian surface drifters are distributed in a band along 5 n and are closely associated with latitudinal barotropically unstable shear between the westward south equatorial current sec and the eastward north equatorial countercurrent necc fewer tivs are identified from february to june when the shear between the sec and necc is weak whereas more tivs are found from july to january when the shear is enhanced the number of identified tivs also exhibits substantial interannual variability with fewer tivs identified during el nino events and more tivs found during la nina events this relationship is likely associated with the interannual variations of the zonal circulation in the equatorial pacific modulated by el ni