hydrographic structure of the convection regime in the gulf of lions winter 1987 abstract deep winter convection in the northwestern mediterranean gulf of lions and the subsequent formation of mediterranean deep water were observed using advanced oceanographic instrumentation during a six week long experiment in 1987 the severe 1987 european winter forced an intense outbreak of the mistral a cold dry wind blowing down the rhone valley in mid january surface cooling and evaporation were of sufficient intensity to cause an initial episode of deep convection shortly before the experiment described here began however several more mistral events took place during the experiment during several cruises into the area ctd and absolute horizontal velocity profiles were measured in the mixed area over the rhone fan as well as across the southern front of this region in addition continuous records of shipboard meteorological and oceanographic parameters air temperature surface salinity etc were made an early february mistral apparently did not produce enough surface cooling to

dense shelf water cascading in the northwestern mediterranean during the cold winter 2005 quantification of the export through the gulf of lion and the catalan margin dense shelf water cascading in the northwestern mediterranean sea during winter 2005 which was shown to cause large erosion in the canyons and to influence deep benthic ecosystem was investigated using numerical modeling validated with temperature and current observations intense dense water formation took place on the gulf of lion and catalan shelves dense shelf water was transferred to the deep basin through three pathways the cap de creus canyon in the western gulf of lion already identified as a huge pathway was shown to export about 1000 km3 of dense water during two months the palamos and blanes canyons located on the catalan margin were shown to be important pathways for water formed locally and for water transiting from the gulf of lion after the cascading period dense shelf water was transported mostly toward the balearic sea

decadal accumulation of anthropogenic co2 in the southern ocean a comparison of cfc age derived estimates to multiple linear regression estimates 1 the decadal accumulation of anthropogenic co2 from 1968 to 1996 was estimated from cfc ages along three woce sections sr3 p14 p15 in the southern ocean we explore the validity of the method in the southern ocean by directly comparing the cfc age derived estimates to values obtained using a multiparametric linear regression method over the same period the agreement in anthropogenic co2 accumulation between the two independent methods was very good less than 8 for waters younger than 30 years we found waters older than 30 years to significantly overestimate the decadal accumulation when using the cfc age method this is mainly due to significant mixing biases when using cfcs to infer ages for these older waters sonnerup 2001 the cfc age method assumes a steady state circulation cfc 11 variations on interannual timescales have been found to be relatively large doney et al 1998 to test the biases from interannual variations we compare cfc data on the sr3 section for two different years 1991 and 1994 although we found large differences in the estimated cfc 11 ages 8 years from the two cruises these differences had little impact on the decadal accumulation of anthropogenic co2 estimated by the cfc age method we found the cfc age method to be insensitive to interannual variations or non ideal age biases sonnerup 2001 haine and hall 2002 because of the similar atmospheric histories of cfc 11 and co2 from about 1965 to 1993 our study validates the use of transient tracer ages to infer decadal anthropogenic co2 accumulations in the southern ocean during the 1970s 1980s and 1990s the application of other transient tracers to determine ages will be needed to improve the estimates of anthropogenic co2 accumulation and uptake by the southern ocean for both now and into the future

ploughing the deep sea floor bottom trawling is a fishing technique whereby heavy nets and gear scrape along the sea bed and is shown here to disturb sediment fluxes and modify the sea floor morphology over large spatial scales the direct impact of bottom trawling on local fish populations has received much attention but trawling also affects other aspects of the ocean environment this paper shows that bottom trawling a commercial practice in which heavy nets and gear are dragged along the ocean floor induces sediment reworking and erosion causing the gradient of the sea floor to become smoother over time this reduces the morphological complexity of deep sea environments the authors draw parallels between the effects of bottom trawling at sea and intensive agriculture on land with the important difference that on land ploughing takes place once or twice a year whereas at sea bottom trawling can be a frequent occurrence bottom trawling is a non selective commercial fishing technique whereby heavy nets and gear are pulled along the sea floor the direct impact of this technique on fish populations1 2 and benthic communities3 4 has received much attention but trawling can also modify the physical properties of seafloor sediments water sediment chemical exchanges and sediment fluxes5 6 most of the studies addressing the physical disturbances of trawl gear on the seabed have been undertaken in coastal and shelf environments7 8 however where the capacity of trawling to modify the seafloor morphology coexists with high energy natural processes driving sediment erosion transport and deposition9 here we show that on upper continental slopes the reworking of the deep sea floor by trawling gradually modifies the shape of the submarine landscape over large spatial scales we found that trawling induced sediment displacement and removal from fishing grounds causes the morphology of the deep sea floor to become smoother over time reducing its original complexity as shown by high resolution seafloor relief maps our results suggest that in recent decades following the industrialization of fishing fleets bottom trawling has become an important driver of deep seascape evolution given the global dimension of this type of fishery we anticipate that the morphology of the upper continental slope in many parts of the world s oceans could be altered by intensive bottom trawling producing comparable effects on the deep sea floor to those generated by agricultural ploughing on land

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

depth distributions of alkalinity tco2 and δ13ctco2 at seats time series site in the northern south china sea abstract in this study measurements of titration alkalinity ta total dissolved carbon dioxide tco2 and 13c of tco2 13 c tco 2 throughout the water column at the southeast asian time series study seats site were investigated in order to understand better the fundamental processes controlling their vertical distributions in the south china sea scs the linear correlations between ta and salinity in the shallow waters as identified by the mixing line between the surface water and salinity maximum water suggested the predominant control of physical mixing on the variability of ta in contrast tco2 and 13 c tco 2 showed the non conservative behavior in the respective tco2 and 13 c tco 2 vs salinity plot due to the effect of biological production a stoichiometric model further showed that the depth profile of nta ta salinity 35 largely reflects the increase of preformed nta in the shallow waters whereas carbonate dissolution was responsible for the continuous increase of nta in the deep waters a one dimensional diffusion advection model further revealed that the carbonate dissolution could account for 28 of ntco2 tco2 salinity 35 increase in deep waters and the remaining 72 of ntco2 was from organic decomposition calculation of excess ta further showed that it emerged well above the aragonite and calcite saturation depths at 600 and 2500 m respectively indicating that some biologically chemically and physically mediated processes must be involved to provide excess ta into the shallow waters the decrease in 13 c tco 2 with depth primarily resulted from organic decomposition the influence of anthropogenic co2 throughout the water column was assessed with the carbon chemistry and the isotope based approach in this study both methods obtained nearly the same results in which the signal of anthropogenic co2 decreased exponentially with depth and its penetration depth were found to be at 1000 m the inventory of anthropogenic co2 in the water column was estimated to be 16 6 mol c m 2 which was less than that reported in the northwest pacific at the same latitude presumably due to the enhanced upwelling in the scs such an anthropogenic co2 penetration had led to decreases of the saturation levels of aragonite and calcite by 17 and 14 respectively in the surface water and an upward migration of aragonite saturation depth by 100 m since industrial revolution

the geomorphic evolution and sediment balance of the lower rhone river southern france over the last 130 years hydropower dams versus other control factors article i nfo atthe end of thelittleice age lia agriculturalpractices and successive phasesof channel management involv ing embankments and dams however the respective roles of these various control factors in modifying sedi ment storage and channel stability are often difficult to identify the aim of this paper is to determine the main factors that have driven morphological changes over the past 130 years on the 120 km long downstream reach of the rhone river a gis based analysis of maps and aerial photographs available since 1860 coupled with chrono stratigraphic data on the river s alluvial deposits has enabled quantification of sediment storage and erosion in different morphological units changes measured include riverbed incision narrowing of the main channel in relation with accumulation of fine sediments along the channel margins and reduction of sed iment input at the mouth on the basis of local and reach scale sediment balances we show that these changes are synchronous with engineering works carried out at the end of the nineteenth century and beginning of the twentieth century a period that coincided with a decline in river sediment inputs largely generated by human activities the early stabilisation of mountain slopesresulting from a decline inrural agriculture rural exodus re forestation and engineered torrent control has had a much greater impact in geomorphically transforming the rhone than dams and gravel mining the major identified causes of river destabilisation in the world this calls for caution in the all too common and wholesale attribution of declining sediment budgets of european rivers

anthropogenic carbon accumulation in the subtropical north atlantic 1 recent data suggest the accumulation of anthropogenic carbon dioxide canth in the subtropical north atlantic is not occurring at a steady rate throughout the water column carbon measurements from three transatlantic cruises along 24 5 n in 1992 1998 and 2004 were investigated for changes in canth using both a back calculation shortcut technique and extended multiple linear regression for three time periods 1992 1998 1998 2004 and 1992 2004 we observed spatial and vertical changes in canth storage along with a general increase in total concentration in the surface layers total dissolved inorganic carbon tco2 and canth concentrations increased in line with atmospheric co2 levels tco2 8 8 0 5 mol kg 1 for 1992 1998 and 8 6 0 5 mol kg 1 for 1998 2004 and canth 8 0 0 2 mol kg 1 for 1992 1998 and 6 8 0 3 mol kg 1 for 1998 2004 in deeper waters canth was significantly different than zero for all depths above 5000 dbar between 1992 and 2004 while on a subdecadal timescale significant variability was observed for canth at a depth range of 800 1000 dbar evidence is presented for the arrival at 24 5 n at depth of freshly ventilated labrador sea water from the subpolar north atlantic between 1992 and 1998 as well as consistent smaller canth signals alongside the mid atlantic ridge this is in addition to low level stable increases identified in the deep eastern basin between 1992 and 2004 the first time that canth has been detected and confirmed by new measurements of carbon tetrachloride and cfc 11 from 2004 these results highlight the importance of the subtropics as a site for long term canth storage away from the surface

harrison canyon debris flows of 1980 this article describes predictable events and geological mechanisms that led to a disastrous flood and mudflow which affected a housing development below the harrison canyon debris basin located in san bernardino county california u s a factors that contributed to the disaster included fires topography geology hydrology climatology and design and location of the harrison canyon debris basin if all of these factors had been taken into consideration during planning and approval of the housing development known as tract 6206 this disaster could have been averted

megafauna distribution along active submarine canyons of the central mediterranean relationships with environmental variables abstract the tectonically controlled margins off southern italy are carved by several shelf indenting submarine canyons that are periodically flushed by sedimentary gravity flows in this study the distribution of benthic and demersal megafauna within the thalweg of some of these canyons i e the gioia petrace and caulonia marina canyons in the tyrrhenian and the ionian calabrian margins respectively and the sant agata san gregorio tremestieri and messina canyons in the messina strait was studied using remotely operated vehicle video transects the relationships between fauna distribution and environmental conditions i e seafloor type depth slope aspect and canyon system extracted from video footage and bathymetric data were assessed to identify the main physical drivers influencing the megafaunal assemblages within active submarine canyons these latter have their heads in shallow water so representing highly dynamic environments affected by present day sediment transport hierarchical cluster analysis allowed to distinguish seven different assemblages occurring in the study areas permanova analysis showed significant differences among species groups associated to different seafloor types depth ranges and canyon systems distance based linear modeling distlm identified the canyon system as the main factor explaining the variability of the megafaunal assemblages across the study areas in the gioia and petrace canyons both characterized by homogenous fine grained sediment the assemblages were mainly dominated by polychaeta sabellidae and ceriantharia the almost total absence of sessile fauna at the canyons head was interpreted as an effect of a strong physical disturbance due to the impact of sedimentary flows in the canyons of the messina strait the presence of more varied seafloor encompassing fine and coarse sediment along with an higher spatial heterogeneity of physical disturbance determined more diversified faunal assemblages featuring species associated with hard and soft substrates more in detail in the sant agata san gregorio and messina canyons the colonization of cobbles and boulders by slow growing species vulnerable to physical disturbance such as the gorgonians acanthogorgia hirsuta and swiftia dubia was recorded for the tremestieri canyons a stronger impact by sedimentary flows was reflected both by a very high abundance of land based litter and the lowest values of species richness interactions between megafauna and marine litter whose widespread occurrence was recorded on the floor of all these canyons have been also presented and discussed although in several cases litter caused entanglement of benthic species the anthropogenic debris was also used as growing substrate or shelter by some invertebrates and fishes suggesting complex fauna litter interactions that should be better explored overall the large variability in morphology and seafloor characteristics across the studied canyons is reflected on the variability of megafauna assemblages suggesting a strong influence of the physical conditions specific of each canyon in controlling fauna distribution

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

frequency magnitude distribution of debris flows compiled from global data and comparison with post fire debris flows in the western u s abstract forecasting debris flow hazard is challenging due to the episodic occurrence of debris flows in response to stochastic precipitation and in some areas wildfires in order to facilitate hazard assessment we have gathered available records of debris flow volumes into the first comprehensive global catalog of debris flows n 988 we also present results of field collection of recent debris flows n 77 in the northern rocky mountains where debris flow frequency increases following wildfire as a first step in parameterizing hazard models we use frequency magnitude distributions and empirical cumulative distribution functions ecdfs to compare volumes of post fire debris flows to non fire related debris flows the ecdf of post fire debris flow volumes is significantly different at 95 confidence from that of non fire related debris flows suggesting that the post fire distribution is composed of a higher proportion of small events than that of non fire related debris flows the slope of the frequency magnitude distribution of post fire debris flows is steeper than that of non fire related debris flows corroborating evidence that small post fire debris flows occur with a higher relative frequency than non fire related debris flows taken together the statistical analyses suggest that post fire debris flows come from a different population than non fire related debris flows and their hazard must be modeled separately we propose two possible non exclusive explanations for the fact that the post fire environment produces a higher proportion of small debris flows 1 following fires smaller storms or effective drainage areas can trigger debris flows due to increased runoff and or decreases in root strength resulting in smaller volumes and increased probability of failure and 2 fire increases the probability and frequency of debris flows causing their distribution to shift toward smaller events due to limitations in sediment supply

the influence of air sea exchange on the isotopic composition of oceanic carbon observations and modeling although the carbon isotropic composition of ocean waters after they leave the surface ocean is determined by biological cycling air sea exchange affects the carbon isotopic composition of surface waters in two ways the equilibrium fractionation between oceanic and atmospheric carbon increases with decreasing temperature in southern ocean surface waters this isotopic equilibrium enriches delta sup 13 c relative to the delta sup 13 c expected from uptake and release of carbon by biological processes alone similarly surface waters in the subtropical gyres are depleted in delta sup 13 c due to extensive air sea exchange at warm temperatures countering the tendency toward isotopic equilibration with the atmosphere a relatively slow process are the effects of the equilibration of co sub 2 itself a much faster process in regions where there is a net transfer of isotopically light co sub 2 from the ocean to the atmosphere e g the equator surface waters become enriched in sup 13 c whereas in regions where isotopically light co sub 2 is entering the ocean e g the north atlantic surface waters become depleted in sup 13 c a compilation of high quality oceanic delta sup 13 c measurements along with experiments performed using a zonally averaged three basin dynamic ocean model are used to explore these processes 40 refs 14more figs 1 tab less

abundance of litter on condor seamount azores portugal northeast atlantic abstract marine litter is an emerging problem for the world s ocean health but little is known on its distribution and abundance on seamounts and how it affects deep sea ecosystems the scientific underwater laboratory set up on condor seamount offered an ideal case study for the first documentation of litter distribution on a shallow seamount with historical fishing a total of 48 video transects deployed on the summit n 45 and the northern flank n 3 covered an area of 0 031 and 0 025 km 2 respectively revealing 55 litter items litter density on the summit was 1439 litter items km 2 whilst on the deeper northern flank estimates indicate densities of 397 litter items km 2 lost fishing line was the dominant litter item encountered on both areas 73 of total litter on the summit and 50 on northern flank all being entirely or partly entangled in the locally abundant gorgonians dentomuricea cf meteor and viminella flagellum other items included lost weights anchors and glass bottles the predominance of lost fishing gear identifies the source of litter on condor seamount as exclusively ocean based and related to fishing activities abundance of litter on the condor seamount was much lower than that reported from other locations closer to populated areas

reconstructing the oceanic 13c suess effect the anthropogenic 13c change for the time period 1968 to 1991 was determined based on calculations of the preformed 13c 12c of dissolved inorganic carbon dic distributions on isopycnal surfaces in the main thermocline of the pacific north atlantic and south indian oceans the time rate of change of preformed 13c the 13c suess effect along isopycnals was calculated using cfc derived water ages and yields a time history of the surface water 13c change at the isopycnal outcrop location the surface ocean suess effect recorded on isopycnals decreased with increasing outcrop latitude from approximately 0 2 decade 1 within the subtropics to around 0 1 decade 1 in the subpolar oceans in the pacific ocean these surface 13c change rate reconstructions agree both in magnitude and meridional trend with direct observations of surface ocean 13c changes reported from time series measurements and from comparisons of surface water 13c of dic measurements in 1970 and 1993 a global ocean average surface 13c rate of change of 0 15 0 04 decade 1 is determined which is slightly smaller than a previous time series data and model based estimate 0 171 decade 1 bacastow etal 1996 depth integrations of the 13c reconstructions in the pacific indian and atlantic oceans when combined with these previous individual depth profile comparisons and geochemical ocean sections study bomb 14c inventories quay et al 1992 imply a global depth integrated 13c change rate of 9 7 2 4 m yr 1 over the time period 1970 1990 these results imply a net oceanic co2 uptake rate of 1 9 0 9 gt c yr 1 over the time period 1970 1990 when applied to an atmospheric 13co2 and 12co2 budget

the imprint of anthropogenic co2 in the arctic ocean evidence from planktic δ13c data from watercolumn and sediment surfaces 13c values of n pachyderma sin from the water column and from core top sediments are compared in order to determine the 13c decrease caused by the addition of anthropogenic co2 to the atmosphere this effect which is referred to as the surface ocean suess effect is estimated to be about 0 9 0 2 within the arctic ocean halocline waters and to about 0 6 0 1 in the atlantic derived waters of the southern nansen basin this means that the area where the arctic ocean halocline waters are formed the arctic shelf regions are relatively well ventilated with respect to co2 nevertheless 13c of dissolved inorganic carbon 13cdic in the arctic ocean halocline waters is far from isotopic equilibrium absolute values of 13c of n pachyderma sin covary with the surface ocean suess effect and we interprete changes in both parameters as a reflection of the degree of ventilation of the waters on the shelf sea measurements of 13c of n pachyderma sin in the arctic ocean from plankton tows reveal a vital effect of about 2 significantly different from other published values a first order estimate of the total anthropogenic carbon inventory shows that despite of its permanent sea ice cover the arctic ocean with 2 of the global ocean area is responsible for about 4 6 of the global ocean s co2 uptake

morphology and sediment dynamics of the northern catalan continental shelf northwestern mediterranean sea abstract the northern catalan continental shelf in the northwestern mediterranean sea extends along 200 km from the cap de creus submarine canyon to the llobregat delta in the vicinity of the city of barcelona in this paper we present the results of a systematic investigation of this area by means of very high resolution multibeam bathymetry to fully assess its morphological variability the causative factors and processes determining such variability are subsequently interpreted the shelf is divided in three segments by two prominent submarine canyons the northernmost roses shelf is separated from the intermediate la planassa shelf by the la fonera canyon while the boundary between the la planassa shelf and the southernmost barcelona shelf is marked by the blanes canyon these two canyons are deeply incised in the continental margin with their heads located at only 0 8 and 5 km from the shore respectively the seafloor character reflects the influence of external controlling factors on the geomorphology and sediment dynamics of the northern continental shelf of catalonia these factors are the geological setting the volume and nature of sediment input and the type and characteristics of processes leading to sediment redistribution such as dense shelf water cascading dswc and eastern storms the interaction of all these factors determines sediment dynamics and allows subdividing the northern catalan continental shelf into three segments the erosional depositional roses shelf to the north the non depositional la planassa shelf in the middle and the depositional barcelona shelf to the south erosional features off the cap de creus peninsula and an along shelf subdued channel in the outer shelf illustrate prevailing sediment dynamics in the roses segment which is dominated by erosional processes local sediment accumulations and the southward bypass of sediment the rocky character of the seafloor immediately north of the blanes canyon head demonstrates that neither significant sediment inputs from the tordera river nor from the northern sources reach the southern part of the la planassa shelf palaeo shorelines depict a number of paleodeltas with steep delta fronts on the drowned barcelona shelf

decadal 1994 2008 change in the carbon isotope ratio in the eastern south pacific ocean we determined the 14 year change in the anthropogenic co2 inventory in the eastern south pacific ocean along the 110 w meridian from 67 s to 21 n using seawater 13c data sets collected in 1994 and 2008 the vertical integral of the 14 year 13c change was assessed in five latitude bands and found to be greatest 14 7 m yr 1 in the subpolar band 38 s 55 s and smallest 3 0 m yr 1 in the tropical band 21 n 18 s the 13c change in each of the latitudinal bands was primarily caused by inputs of anthropogenic co2 via air sea exchange and transport more than 50 of the total anthropogenic co2 was added to the subpolar band via the northward movement of antarctic intermediate water aaiw from the south and the remaining 50 was added via air sea exchange we also calculated the ratio of the temporal change in 13c to the change in dissolved inorganic carbon which is a measure of the efficiency of oceanic uptake of anthropogenic co2 the ratio for aaiw in 1994 0 017 mol kg 1 1 was greater than that in 2008 0 010 mol kg 1 1 based on the change in preformed 13c and dissolved inorganic carbon dic indicating reduced efficiency of co2 uptake by the southern ocean in 2008 relative to that in 1994 aaiw remained at the surface for a shorter period in 2008 relative to 1994 and thus would have taken up less atmospheric co2 prior to subduction the projected reduction in this ratio indicates a weakening of co2 uptake by the southern ocean in the future

sediment dynamics and post glacial evolution of the continental shelf around the blanes submarine canyon head nw mediterranean abstract the blanes submarine canyon bc deeply incises the catalan continental shelf in the nw mediterranean sea as a consequence of the closeness only 4 km of its head to the coastline and the mouth of the tordera river the canyon has a direct influence on the shelf dispersal system as it collects large amounts of sediment mainly during high energy events multibeam bathymetry backscatter imagery and very high resolution seismic reflection profiles have allowed characterizing the morphology of the continental shelf around the canyon head also identifying sediment sources and transport pathways into the canyon the morphological data have also been used to reconstruct the evolution of the continental shelf during the last sea level transgression so that the current understanding of shelf to canyon sediment exchanges through time could be improved the continental shelf surrounding the bc consists of both depositional and erosional or non depositional areas depositional areas display prominent sediment bodies a generally smooth bathymetry and variable backscatter these include i an area of modern coarse grained sediment accumulation that comprises the inner shelf ii a modern fine grained sedimentation area on the middle shelf offshore tossa de mar and iii a modern sediment depleted area that covers most of the middle and outer shelf to the west of the canyon head erosional and non depositional areas display a rough topography and high backscatter and occur primarily to the east of the canyon head where the arrival of river fed inputs is very small in agreement with this pattern the continental shelf north and west of the canyon head likely is the main source of shelf sediment into the canyon to the north a pattern of very high backscatter extends from the coastline to the canyon head suggesting the remobilization and off shelf export of fines additionally relict near shore sand bodies developed over the barcelona shelf that extend to the canyon head rim constitute a source of coarse sediment high energy processes namely river floods and coastal storms are the main controls over the river shelf canyon sediment exchange river floods increase the delivery of terrigenous particles to the coastal system storms mainly from the east remobilize the sediment temporarily accumulated on the shelf towards the canyon head so that the finer fractions are preferentially removed and a coarse lag is normally left on the shelf floor exceptionally very strong storms also remove the coarse fractions from the shelf drive them into the canyon processes like dense shelf water cascading which is much more intense in canyons to the north of bc and the northern current also contribute to the transport of suspended sediment from far distant northern sources during the last post glacial transgression the bc had a strong influence on the evolution of the inner continental margin as it interrupted the shelf sediment dispersal system by isolating the shelves to its north and south named la planassa and barcelona shelves respectively

understanding sediment dynamics of two large submarine valleys from seafloor data blanes and la fonera canyons northwestern mediterranean sea abstract the studied area appears as a major place for dense shelf water dsw formation and export towards the deep basin with blanes and la fonera canyons as most efficient pathways these two canyons are so deeply indented on the continental shelf and slope of the northern catalan margin western mediterranean sea that their heads significantly reduce the width of the shelf and interfere with coast and contour parallel sediment transport patterns this study presents the results of the analysis of swath bathymetry data and parametric seismic reflection profiles showing the detailed morphology and uppermost sedimentary structure of blanes and la fonera canyons with the focus on their heads and adjacent upper courses and shelf the main aim is to understand their functioning and assess how they influence and respond to the hydrosedimentary processes active in the study area the n s oriented blanes canyon head whose shortest distance to shore is only 4 km extends along 21 7 km from 70 to 1300 m water depth with an average rim to rim width of 8 km and a canyon floor width up to 750 m la fonera canyon head extends along 28 km from 60 to 1700 m water depth rim to rim and canyon floor widths are up to 7 km and up to 700 m respectively the canyon head follows a general wnw ese trending course in its deeper part but trends n s in its shallower course formed by cap begur branch south of it the illa negra branch trends nw se and its tip located at 60 m water depth and 800 m from the coastline intersects the littoral sedimentary prism backscatter data show high reflectivity into both blanes and la fonera canyon floors as well as on tributary gullies which at these locations is indicative of coarse sediment the seafloor and subseafloor observations here presented are explained and best understood from the sedimentological viewpoint by the interplay of event driven dsw flows permanent mesoscale circulation and storm action while dsw flows from the gulf of lion and the shelf area around the studied canyons are the most dynamic agent in terms of sediment transport and seafloor shaping the northern current ensures background sedimentation of fines and coastal storms promote episodic entries through canyon heads and upper course rims canyon wall morphology and sediment draping respond to the currentward or leeward position of each wall with respect to the main southward moving water flows in the area either episodic or permanent that are dsw and the northern current other relevant morphosedimentary features such as a 40 km long southbound subdued channel on the roses outer shelf that originates off cap de creus promontory to finally feed cap begur branch of la fonera canyon and a contouritic ridge and moat attached to the northern wall of the canyon are interpreted in terms of dsw flows a comprehensive model of the sedimentary functioning of the canyoned north catalan margin that integrates seafloor information and background data on dynamic processes is presented which could be of application to other continental margins worldwide such an integrative view is eased by the enormous unprecedented multidisciplinary research effort carried out in the study area over the last three decades

changes in dissolved oxygen in the southern ocean with climate change 1 climate models predict that increasing greenhouse gases in the atmosphere will change our climate however the range of observations available to assess these model predictions is limited we have utilized an ocean biogeochemical model to project the impact of climate change on the oxygen cycle in the ocean and the air sea exchange of oxygen with climate change our model predicts an outgassing of oxygen from the ocean in the model the southern ocean is the region that displays the largest change in the air sea exchange of oxygen with climate change the reduced oxygen uptake in the southern ocean is dominated by a reduction in convective mixing and in the subduction rate of bottom water which decreases the amount of dissolved oxygen in the southern ocean our model results suggest that dissolved oxygen is sensitive to changes in southern ocean circulation revealing the potential to use dissolved oxygen to test model predictions of climate change from southern ocean observations collected 28 years a part we observed a decrease in dissolved oxygen that was consistent with model climate change simulation this provides credibility to the climate model predictions additional analysis and observations of dissolved oxygen are needed to substantiate our climate model simulations

cascades of dense water around the world ocean dense water overflow off continental shelves cascading is one of the contributing processes of shelf deep ocean exchange and of topical interest to climate studies and nutrient fluxes dense water originating from cooling evaporation freezing and salinization on a shallow shelf spills over the shelf edge and may develop as near bottom gravity current or an intermediate depth intrusion it is difficult to observe in nature due to its intermittent character this paper provides an extensive inventory of observed cases of water cascades around the world ocean summarises their locations and individual properties and provides statistics of the identified cases the search for cascading was carried out using oceanographic databases and a literature review this study identified 61 confirmed cases world wide including 25 cases in the arctic seas 12 at mid latitudes seven in sub tropical and tropical regions and 17 off the antarctic shelves eighteen cascades had not been reported before we analyze a set of numerical parameters of dense water cascades allowing us to quantify compare and contrast the properties of water cascades the overall average density contrast between the confirmed cascades and ambient water is 0 37 kg m3 it can be as much as 2 kg m3 on some arctic shelves frequently initiated by strong cooling at the surface cascades often remain colder through the descent thus supplying the deep ocean with colder and fresher water in non dimensional variables the data from all climate zones fit well to a unique curve which represents a relationship between a cascade s internal structure and the parameters describing its forcing on average the down slope volumetric flux provided by dense water cascades is estimated as 0 05 to 0 08 sv per 100 km of shelf edge regional terms arctic antarctic north atlantic ocean barents sea mediterranean sea skagerrak tasman sea sea of okhotsk

interaction of dense shelf water cascading and open sea convection in the northwestern mediterranean during winter 2012 the winter of 2012 experienced peculiar atmospheric conditions that triggered a massive formation of dense water on the continental shelf and in the deep basin of the gulf of lions multiplatforms observations enabled a synoptic view of dense water formation and spreading at basin scale five months after its formation the dense water of coastal origin created a distinct bottom layer up to a few hundreds of meters thick over the central part of the nw mediterranean basin which was overlaid by a layer of newly formed deep water produced by open sea convection these new observations highlight the role of intense episodes of both dense shelf water cascading and open sea convection to the progressive modification of the nw mediterranean deep waters

open ocean convection observations theory and models we review what is known about the convective process in the open ocean in which the properties of large volumes of water are changed by intermittent deep reaching convection triggered by winter storms observational laboratory and modeling studies reveal a fascinating and complex interplay of convective and geostrophic scales the large scale circulation of the ocean and the prevailing meteorology two aspects make ocean convection interesting from a theoretical point of view first the timescales of the convective process in the ocean are sufficiently long that it may be modified by the earth s rotation second the convective process is localized in space so that vertical buoyancy transfer by upright convection can give way to slantwise transfer by baroclinic instability moreover the convective and geostrophic scales are not very disparate from one another detailed observations of the process in the labrador greenland and mediterranean seas are described which were made possible by new observing technology when interpreted in terms of underlying dynamics and theory and the context provided by laboratory and numerical experiments of rotating convection great progress in our description and understanding of the processes at work is being made

comments on cascades of dense water around the world ocean abstract evidences of temperature controlled dense water cascading off the gulf of lion shelf in the northwestern mediterranean and several aegean shelves in the northeastern mediterranean are reported together with the adiatic shelf already listed by ivanov shapiro huthnance aleynik golovin 2004 these zones represent the major coastal areas of the mediterranean sea where dense water is produced

megabenthic assemblages at the hudson canyon head nw atlantic margin habitat faunal relationships abstract the distribution of megabenthic communities at the head of hudson canyon and adjacent continental shelf was studied by means of underwater video transects and still photo imagery collected using a towed camera system the goal was to explore the relationships between faunal distribution and physical seafloor conditions and to test the hypothesis that increased seafloor heterogeneity in the hudson canyon supports a larger diversity of benthic communities compared with the adjacent continental shelf hierarchical cluster analysis was performed to identify benthic assemblages as defined in imagery the bio env procedure and the canonical correspondence analysis were carried out to elucidate species groupings in relation to terrain variables extracted from bathymetric data species accumulation curves were generated to evaluate species turn over in and out of hudson canyon the results indicate that seafloor morphology is the main physical factor related to benthic community composition and distribution assemblages dominated by sponges zoanthids and cup corals colonized the canyon margins and flanks and were associated with coarse grained sediments while sea pen assemblages were observed along muddy seafloor within the thalweg an assemblage dominated by sea stars occurred on the shelf associated with a sandy seafloor some assemblages were exclusively observed in the canyon area suggesting that the increased variability of seafloor composition together with the oceanographic processes specific to the canyon area enhance beta diversity the colonization by benthic suspension feeders within the canyon in contrast to shelf assemblages mainly composed of carnivores and detritus feeders could be favored the intense hydrodynamics at the canyon head that increase the availability of suspended organic matter from the perspective of management and conservation of marine resources the results obtained support the relevance of hudson canyon as a biodiversity hotspot such results are of particular significance in light of the recent action promoted by the mid atlantic fisheries management council that restricts bottom trawling in most of the submarine canyons of the us atlantic margin including the hudson canyon to protect cold water corals from damage by fishing gear

marine litter on the floor of deep submarine canyons of the northwestern mediterranean sea the role of hydrodynamic processes marine litter represents a widespread type of pollution in the world s oceans this study is based on direct observation of the seafloor by means of remotely operated vehicle rov dives and reports litter abundance type and distribution in three large submarine canyons of the nw mediterranean sea namely cap de creus la fonera and blanes canyons our ultimate objective is establishing the links between active hydrodynamic processes and litter distribution thus going beyond previous essentially descriptive studies litter was monitored using the liropus 2000 rov litter items were identified in 24 of the 26 dives carried out in the study area at depths ranging from 140 to 1731 m relative abundance of litter objects by type size and apparent weight and distribution of litter in relation to depth and canyon environments i e floor and flanks were analysed plastics are the dominant litter component 72 followed by lost fishing gear disregarding their composition 17 and metal objects 8 most of the observed litter seems to be land sourced it reaches the ocean through wind transport river discharge and after direct dumping along the coastline while coastal towns and industrial areas represent a permanent source of litter tourism and associated activities relevantly increase litter production during summer months ready to be transported to the deep sea by extreme events after being lost fishing gear such as nets and long lines has the potential of being harmful for marine life e g by ghost fishing at least for some time but also provides shelter and a substrate on which some species like cold water corals are capable to settle and grow la fonera and cap de creus canyons show the highest mean concentrations of litter ever seen on the deep sea floor with 15 057 and 8090 items km 2 respectively and for a single dive litter observed reached 167 540 items km 2 while most of the largest concentrations were found on the canyon floors at water depths exceeding 1000 m relatively little litter was identified on the canyon walls the finding of litter hotspots i e large accumulations of litter formed by mixtures of land and marine sourced litter items and natural debris such as sea urchin carcasses evidences an efficient transport to the floor of mid and lower canyon reaches at least high energy down canyon near bottom flows are known to occur in the investigated canyons these are associated to seasonal dense shelf water cascading and severe coastal storms which are the most energetic hydrodynamic processes in the study area thus becoming the best candidates as main carriers of debris to the deep the fact that the investigated canyons have their heads at short distance 4 km from the shoreline enhances their ability to trap littoral drift currents and also to convey the signal of the above mentioned high energy events to the deep including their litter load this study contributes to assess the origin and transport mechanisms of litter to the deep sea as well as its potential impact on deep sea ecosystems

mediterranean river systems of andalusia southern spain and associated deltas a source to sink approach abstract the northern shores of the semi isolated mediterranean sea with its low tidal range and a relatively voluminous fluvial supply of sediments constitute an ideal delta forming environment in this paper we examine the present day and multi decadal behaviour of 26 river systems from andalusia southern spain forming deltas in the alboran sea the westernmost basin in the mediterranean sea eastern central and western andalusian watersheds have been defined based on geomorphological climatological and hydrological characteristics a comprehensive data set has been compiled including satellite images aerial photographs a digital elevation model thematic maps time series of precipitation temperature and water discharge and the damming history of individual river basins this data set has been used to analyse basin morphology and hydrology and anthropogenic impact several modelling approaches have been applied to obtain the water budget and mean annual sediment yield of 12 of the 26 studied river systems in addition the periodicities of water discharge events and their possible link with north atlantic oscillation nao fluctuations have been also studied a decreasing trend has been observed in most water discharge time series during the last decades which has been attributed to natural factors although it could have been expected that the diminution of water discharge may have caused a reduction in sediment load calculated sediment discharge time series do not show any significant tendency in general sediment yield shows an opposite relationship with basin area a comparative analysis of spanish mediterranean deltas indicates that in terms of sediment transport andalusian river systems are quite efficient despite the small size of their catchments repetitive flood events and the consequent suspension plumes off river mouths play a major role in the development of deltaic and prodeltaic bodies nowadays 42 of the study area is regulated although to date the effect of dam building is hardly noticeable on river mouths

does carbon 13 track anthropogenic co2 in the southern ocean a multiparametric linear regression technique was used for waters in the southern ocean to estimate the change in both 13 c dic 13 c dic and dissolved inorganic carbon dic dic between 1978 and 1998 due to the accumulation of anthropogenic co 2 the observed decrease in 13 c dic at the surface the suess effect was 0 015 0 003 yr 1 in the sub antarctic zone and 0 005 0 003 yr 1 in the antarctic zone similar to values reported for the southern indian ocean gruber et al 1999 sonnerup et al 2000 to compare the 13 c dic with adic we used the ratio of these two anomalies rc 13 c dic dic mol kg 1 1 along the section arc ranged from 0 015 0 005 at 42 s to 0 007 0 005 mol kg 1 1 at 54 s the spatial variability in arc in the southern ocean reflects different timescales for processes controlling the uptake of 13 c from those controlling the uptake of 12 c and indicates that 13 c dic decouples from adic poleward of the sub antarctic zone the variations of arc along the section suggest that the 13 c dic anomaly is not a good predictor of the anthropogenic co 2 inventory in the southern ocean some methods for determining anthropogenic co 2 uptake both on the global and regional scale assume the penetration depths of 13 c dic to be the same as adic which implies a constant value for arc in the ocean at 0 016 mol kg 1 1 heimann and maier reimer 1996 ortiz et al 2000 bauch et al 2000 the use of a constant arc and the observed 13 c dic to estimate anthropogenic co 2 could lead to an underestimate in the inventory of anthropogenic co 2 for the southern ocean by 50

the effect of wind mixing on the vertical distribution of buoyant plastic debris 1 micro plastic marine debris is widely distributed in vast regions of the subtropical gyres and has emerged as a major open ocean pollutant the fate and transport of plastic marine debris is governed by poorly understood geophysical processes such as ocean mixing within the surface boundary layer based on profile observations and a one dimensional column model we demonstrate that plastic debris is vertically distributed within the upper water column due to wind driven mixing these results suggest that total oceanic plastics concentrations are significantly underestimated by traditional surface measurements requiring a reinterpretation of existing plastic marine debris data sets a geophysical approach must be taken in order to properly quantify and manage this form of marine pollution

near bottom suspended sediment variability caused by storms and near inertial internal waves on the ebro mid continental shelf nw mediterranean abstract near bottom currents and suspended sediment concentrations ssc recorded on the ebro continental shelf at 60 m depth during the transition between fair and stormy weather have revealed some of the major processes controlling the sediment re suspension and transport at mid shelf depths in this nw mediterranean area storm waves were the main contributor to the transport of sediment although they only resuspended surface sediments during extreme wave conditions h s 4 5 m and t s 11 s during the recording period the net suspended sediment flux along the shelf was one order of magnitude higher than the net suspended sediment flux across the shelf and the resultant transport was towards the sw and seaward fluctuations of the near bottom ssc during fair weather showed a periodicity around 17 h and were related to the occurrence of near inertial internal waves caused by wind pulses during storm events the energy propagation of these internal waves reached critical angles at the mid and outer shelf which could favor the development and maintenance of the bottom nepheloid layer on the ebro continental shelf as well as on other mediterranean continental shelves

lost at sea where is all the plastic millions of metric tons of plastic are produced annually countless large items of plastic debris are accumulating in marine habitats worldwide and may persist for centuries 1 1 4 2 here we show that microscopic plastic fragments and fibers fig 1a 3 are also widespread in the

anthropogenic co2 accumulation rates in the north atlantic ocean from changes in the 13c 12c of dissolved inorganic carbon 1 the anthropogenic co2 accumulation rate for the north atlantic ocean was estimated on the basis of the decrease in the 13c of the dissolved inorganic carbon measured between cruises in 1981 transient tracers in the north atlantic 1993 oaces and 2003 repeat hydrography a mean depth integrated 13c change of 15 0 3 8 m yr 1 was estimated by applying a multiple linear regression approach to determine the anthropogenic 13c decrease at 22 stations where 13c depth profiles were compared the largest and deepest anthropogenic 13c decreases occurred in the subpolar ocean and in contrast the smallest and shallowest decreases occurred in the tropical ocean a mean anthropogenic co2 accumulation rate of 0 63 0 16 mol c m 2 yr 1 0 32 0 08 pg c yr 1 in the north atlantic ocean over the last 20 years was determined from the mean depth integrated 13c change and a ratio of anthropogenic 13c to dic change of 0 024 mol kg 1 1 only half of the accumulated anthropogenic co2 in the north atlantic during the last 20 years was the result of air sea co2 uptake based on a comparison of the air sea 13co2 flux to the dic13 inventory change with the other half likely a result of northward advective transport

suspended sediment fluxes and transport processes in the gulf of lions submarine canyons the role of storms and dense water cascading contemporary suspended sediment transport was studied in seven submarine canyons of the gulf of lions gol current meters equipped with turbidity sensors were moored 4 m above bottom at 300 m depth in the canyon axis from november 2003 to may 2004 sediment transport events were monitored and studied in relation to forcing conditions there was a large flood in early december during which discharges from all of the coastal rivers increased by more than one order of magnitude a smaller flood of the rhone river occurred later in mid january followed by a persistent high river discharge that lasted until mid february there were also several e se storm events during the measurement period two of them causing large swell one in early december max hs 8 4 m coinciding with the major river flood andoneinlatefebruary maxhs 7m duringaperiodoflowerriverdischarge mostofthevariabilityindown canyoncurrentspeeds waslinkedtostrongdownwellinginducedbye sestormsandtocascadingofdenseshelfwaterinducedbynandnwwinds theintensity and timing of these processes strongly varied spatially eastern storms generated higher waves and induced stronger downwelling in the western than in the eastern sector of the gol shelf dense water cascading events were enhanced during eastern storms and they were also more intense in the western sector of the gol these events occurred frequently from january to may along the western canyons and from february to april along the eastern canyons from february to april they occurred simultaneously in all the canyons sediment transport was mainly down canyon and mostly concentrated during storm induced downwelling and dense water cascading events during the high river discharge season most of the newly supplied and resuspended sediment remained stored on theshelf however duringthelatefebruarystormandcascadingevent thestoredsedimentwasquicklyresuspendedandtransported mainly through the westernmost submarine canyon cap de creus following a flushing pattern later although minor storms and shelfdensewatercascadinghardlyincreasedsuspendedsedimentconcentrationswithinthecanyons theyinducedstrongnear bottom current velocities increasing down canyon sediment fluxes and generating small but significant sediment transport events most of the shelf canyon transfer took place during the late february storm and cascading event through the cap de creus canyon where the net suspended sediment flux was between one and two orders of magnitude higher than in the other canyons

sedimentary processes of the kusawa lake torrent system yukon canada as revealed by the september 16 1982 flood event abstract the kusawa lake torrent system is located in the northern canadian cordillera of southwestern yukon it is holocene in age and consists of a catchment area gorge and alluvial fan complex the north compartment of the catchment is a third order basin covering an area of 13 2 km 2 it is characterized by active slumping of quaternary glacial deposits that supply sediment for the torrent system the gorge is approximately 800 m long and distinguished by 10 m high vertical walls cut into granitic bedrock the fan complex is semiconical in shape and covers an area of 1 52 km 2 the active part of the fan is plano convex in longitudinal profile covers an area of 0 75 km 2 and is subdivided into an upper middle and lower fan based on the occurrence of seven sedimentary facies that were deposited by a catastrophic flood in 1982 the upper fan is characterized by boulder gravel levees and boulder gravel lobes that were deposited by debris flows it is also characterized by sandy boulder gravel that may represent a transition from debris flow to dominantly hyperconcentrated flow processes the middle fan is distinguished by sandy cobble gravel and sandy pebble gravel that is interbedded with horizontally laminated sand these sediments were deposited by hyperconcentrated flows the lower fan is characterized by horizontally bedded and laminated sand that may represent a transition from hyperconcentrated flow to sheetflood dominant processes and by sand channels that represent rechannelized waning flood discharge the fan displays downfan trends in grain size boulders to sand slope style plano concave and slope value 4 1 typical of sheetflood dominated fans the initiation of sedimentation in the kusawa lake torrent system was due to a combination of rainfall flooding and flooding related to catastrophic slope failure in the catchment area slope failure leads to the formation of a landslide dam and lake and when the dam fails the draining lake results in a flood many times larger than a rainfall flood the frequency of these catastrophic flood events may be once every 200 years although the kusawa lake torrent system is now dormant the potential for further landslide dams and subsequent catastrophic floods is high and could result in further damage to a campground and private property in the area

does sedimentary organic δ13c record variations in quaternary ocean co2 aq ocean surface water co2 aq variations based on glacial interglacial changes in sediment delta 13corg are shown to compare favorably with reconstructions based on ice core co2 in particular an approximate 80 microatmospheres increase in atmospheric pco2 during the last glacial interglacial transition is calculated to correspond to a 3 4 micromolar increase in ocean surface water co2 aq at atmospheric equilibrium a widespread marine delta 13corg decrease of 1 2 accompanied this event and was not preceded by an equivalent isotopic change in surface water total dissolved inorganic carbon these observations support the hypothesis that co2 aq influences photosynthetic isotope fractionation between marine inorganic and organic carbon pools and therefore that plankton sediment delta 13corg may serve as a proxy for surface water co2 aq

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

the indian ocean 13c suess effect the 13c of dissolved inorganic carbon dic decrease the 13c suess effect in the indian ocean was calculated using a multiparameter linear regression comparison of the 1978 geochemical ocean sections study and 1995 world ocean circulation experiment 13c of dic hydrographic and nutrient data the surface ocean 13c decrease rate along 80 and 115 e ranged from approximately 0 1 decade 1 at 55 s to a maximum of approximately 0 18 decade 1 at 35 s and decreased northward to around 0 13 decade 1 at the equator using a global extrapolation based on ocean model results bacastow et al 1996 and previous 13c changes calculated from 1970 to 1993 station reoccupations in the pacific ocean and based on preformed 13c versus chlorofluorocarbon age trends in the indian pacific and atlantic oceans sonnerup et al 1999 an ocean wide average surface ocean 13c rate of change of 0 15 to 0 17 decade 1 was estimated the average depth integrated 13c change rate between 1978 and 1995 along 80 and 115 e was 6 9 0 5 m yr 1 from 58 s to 5 n

impact of end member mixing on depth distributions of δ13c cadmium and nutrients in the n atlantic ocean abstract the po 4 13 c and cd depth distributions measured in the n atlantic ocean during recent geotraces and clivar cruises are a result of biological and circulation processes with in situ uptake and remineralization of organic matter dominating in the upper 300 m and mixing of water masses dominating in the thermocline and deep sea the observed slopes of the no 3 po 4 preindustrial 13 c po 4 and by analogy cd po 4 along isopycnals deviate significantly from that expected from redfield in the thermocline and deep sea and in each case the observed slope is similar to the slopes of the end member water masses being mixed the depth increase in the cd po 4 slope resulting from end member mixing explains the observed kink at 1 m po 4 in the cd po 4 relationship in the n atlantic the observation that the po 4 preindustrial 13 c cd relationship in the modern n atlantic is heavily influenced by end member mixing throughout most of the water column complicates the use of 13 c and cd as proxies of the paleocean s nutrient distribution because changes in the po 4 13 c cd composition of locally and remotely produced end members water masses would change the po 4 13 c and cd depth distributions in the paleo n atlantic ocean

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