modeling equilibrium dynamics of the benguela current system the regional ocean modeling system roms is used to systematically investigate equilibrium conditions and seasonal variations of the benguela system at a resolution of 9 km including both the large scale offshore flow regime and the economically and ecologically important coastal upwelling regime a shelf edge poleward flow exists in the northern benguela region i e north of 28 s and is driven primarily by the wind stress curl via the sverdrup relation as such it is strongly seasonal and is most intense during spring and summer when the wind stress curl is most negative the poleward flow deepens as it moves southward between 25 and 27 s much of it veers offshore because of the nature of the wind stress curl and its interaction with the northwestward path of the benguela current which is influenced by alongshore topographical variations the benguela current is driven by nonlinear interactions of passing agulhas rings and eddies and does not have a striking seasonal signal in the mean state it is characterized by two streams the more inshore stream is topographically controlled and follows the run of the shelf edge the meandering nature of the offshore stream is a result of the preferential path of agulhas rings the model simulates all seven of the major upwelling cells within its domain the three southernmost cells have the strongest seasonal signal and experience their greatest upwelling during spring and summer months whereas the two northernmost cells have less seasonal variability but nevertheless have increased upwelling from autumn to spring and least upwelling in summer and the central benguela upwelling cells experience year round upwelling the effect of topography on coastal upwelling was investigated by smoothing alongshore coastline and topography variations which showed that in all of the seven major upwelling cells upwelling is enhanced on the downstream side of capes

the present day formation of apatite in mexican continental margin sediments abstract results of pore water and sediment analyses from the western mexican continental margin strongly suggest the present day formation of apatite the interstitial water phosphate and fluoride profiles indicate chemical removal at a depth which corresponds to a large maximum in the phosphorus content of the sediments apatite is identified within this maximum via x ray diffraction but is elsewhere undetectable in the core radioisotopic thorium uranium and radium data support the conclusion that this deposit is modern the present day depositional environment is consistent with those reported by other workers for phosphorite formation with the exception that pore water magnesium is not depleted below its seawater value

distribution of pleuroncodes monodon larvae over the continental shelf of south central chile field and modeling evidence for partial local retention and transport abstract in situ and modeled spatial distribution of squat lobster pleuroncodes monodon larvae over the continental shelf off south central chile 35 37 s was analyzed along with currents and hydrography we aimed to identify the main larval transport retention characteristics in the study area which constitutes the southernmost p monodon fishing grounds embedded in the humboldt current system we hypothesized that the main contribution to population renewal originates in the two persistent adult aggregations close to the nursery ground that occurs over a continental shelf terrace limited by two submarine canyons two extensive bio physical field campaigns were carried out during the main 2001 2002 upwelling season field data indicated that larvae were released from late austral winter to spring from spots to the north and south of the nursery zoea i were found mainly below 50 m depth in southward flowing waters whereas older zoea dominated in northward flowing layers above 50 m larvae were circumscribed between the coast and the shelf break front and pelagic retention areas were identified over the widest shelf area megalopa and juveniles during march were only found over the nursery area individual based simulations coupled to the output of a hydrodynamic model climatological configuration for the studied area showed that the release sites close to the nursery made the largest contribution to recruitment sites further north could also contribute to recruitment if hatching occurred later in the upwelling season the contribution of vertical behavior to larval success was also important as was the former s interaction with the site and time of larval release our results support the relevance of coastal circulation affected by topography on the persistence of p monodon populations off southern chile and the modulation of temporal variability these results might apply to other abundant species in the area

a model for microbial phosphorus cycling in bioturbated marine sediments significance for phosphorus burial in the early paleozoic abstract a diagenetic model is used to simulate the diagenesis and burial of particulate organic carbon c org and phosphorus p in marine sediments underlying anoxic versus oxic bottom waters the latter are physically mixed by animals moving through the surface sediment bioturbation and ventilated by burrowing tube dwelling organisms bioirrigation the model is constrained using an empirical database including burial ratios of c org with respect to organic p c org p org and total reactive p c org p reac burial efficiencies of c org and p org and inorganic carbon to phosphorus regeneration ratios if p org is preferentially mineralized relative to c org during aerobic respiration as many previous studies suggest then the simulated p org pool is found to be completely depleted a modified model that incorporates the redox dependent microbial synthesis of polyphosphates and p org termed the microbial p pump allows preferential mineralization of the bulk p org pool relative to c org during both aerobic and anaerobic respiration and is consistent with the database results with this model show that p burial is strongly enhanced in sediments hosting fauna animals mix highly labile p org away from the aerobic sediment layers where mineralization rates are highest thereby mitigating diffusive po 4 3 fluxes to the bottom water they also expand the redox niche where microbial p uptake occurs the model was applied to a hypothetical shelf setting in the early paleozoic a time of the first radiation of benthic fauna results show that even shallow bioturbation at that time may have had a significant impact on p burial our model provides support for a recent study that proposed that faunal radiation in ocean sediments led to enhanced p burial and possibly a stabilization of atmospheric o 2 levels the results also help to explain c org p org ratios in the geological record and the persistence of p org in ancient marine sediments

a snow transport model for complex terrain as part of the winter environment in middle and high latitude regions the interactions between wind vegetation topography and snowfall produce snow covers of non uniform depth and snow water equivalent distribution a physically based numerical snow transport model snowtran 3d is developed and used to simulate this three dimensional snow depth evolution over topographically variable terrain the mass transport model includes processes related to vegetation snow holding capacity topographic modification of wind speeds snow cover shear strength wind induced surface shear stress snow transport resulting from saltation and suspension snow accumulation and erosion and sublimation of the blowing and drifting snow the model simulates the cold season evolution of snow depth distribution when forced with inputs of vegetation type and topography and atmospheric foreings of air temperature humidity wind speed and direction and precipitation model outputs include the spatial and temporal evolution of snow depth resulting from variations in precipitation saltation and suspension transport and sublimation using 4 years of snow depth distribution observations from the foothills north of the brooks range in arctic alaska the model is found to simulate closely the observed snow depth distribution patterns and the interannual variability

variations of the east asian jet stream and asian pacific american winter climate anomalies in this study the authors apply the ncep ncar reanalysis and other observations to depict the association of the asian pacific american climate with the east asian jet stream eajs with an emphasis on boreal winter seasons and on interannual timescales they analyze the variations of the eajs and their relationships with el nino southern oscillation enso and extratropical north pacific sea surface temperature sst and assess the relative connections of the eajs and enso to the anomalies of atmospheric circulation surface temperature and precipitation in the asian pacific american region it is found that the eajs is coupled to a teleconnection pattern spanning the entire asian pacific american region with the strongest signals over east asia and the western pacific this pattern differs significantly from that associated with enso which influences the earth s climate extensively with a strongest impact on the climate over the central pacific and east a strong eajs is associated with an intensification of the weather and climate systems in asia and over the pacific such as deepening of the east asian trough and the aleutian low and strengthening of the east asian winter monsoon it is linked to colder and drier conditions in east asia and stronger convection over the tropical asia australia sector compared with enso the eajs seems to link to the climate signals of asia and the pacific more strongly an intensified eajs is also associated with anomalies of temperature and precipitation in north america due to the related changes in stationary wave patterns while the eajs does not strongly link to the tropical central eastern pacific sst it is significantly associated with the extratropical north pacific sst more specifically the second most dominant mode of the empirical orthogonal function analysis of the sst in addition a strong weak eajs seems to follow a large small meridional gradient of the western pacific sst associated with warming cooling in the tropics subtropics and cooling warming in the extratropics

rates of formation of modern phosphorite off western mexico abstract phosphorite deposition represents a significant but poorly constrained sink in the marine p cycle this study establishes conclusively that phosphorite forms today throughout a widespread region along the upper continental slope off southern baja california mexico in this region o2 depleted 5 50 m bottomwater overlies the seafloor and a narrow range of suboxic to anoxic redox conditions prevail in the modern 0 18 000 yr old near surface 0 50 cm organic c rich 2 10 wt sediment interstitial gradients of total alkalinity ta and inferred effects of organic matter decay correlate directly with sedimentation rates calculated from 14c dating other porewater and solid phase data indicate that francolite currently precipitates authigenically at each of five study sites moderately high concentrations 20 100 m of dissolved inorganic phosphate dip produced in the upper 5 cm of sediment sustain francolite growth at slightly greater depths while the necessary f diffuses into the sediment from above neither organic matter decay nor fish bone dissolution seem capable of producing the steep near surface gradients of dip measured in this study at some sites dip production coincides spatially with the reversible production of dissolved fe2 but thorough evaluation of the possible link between these processes requires further study the mechanism responsible for the near surface enrichment of interstitial dip thus remains unidentified box cores from each site contain an unreworked sequence of up to six thin 1 3 cm discrete francolite rich horizons several of which qualify as true phosphorite 50 wt francolite estimated diffusional burial fluxes of inorganic p and f range respectively from 2 40 g cm 2 y 1 and 4 12 g cm 2 y 1 or the equivalent in francolite of 16 260 g cm 2 y 1 these present day accumulation rates lie within the range of those determined for several ancient phosphorite deposits and for the extensively studied region of modern phosphorite deposition off peru

1997 1998 el nino off peru a numerical study an eddy resolving numerical simulation for the peru chile system between 1993 and 2000 is analyzed mainly for the 1997 1998 el nino atmospheric and lateral oceanic forcings are realistic and contain a wide range of scales from days to interannual the solution is validated against altimetric observations and the few in situ observations available the simulated 1997 1998 el nino closely resembles the real 1997 1998 el nino in its time sequence of events the two well marked sea level peaks in may june and november december 1997 are reproduced with amplitudes close to those observed other sub periods of the el nino seem to be captured adequately simple dynamical analyses are performed to explain the 1997 1998 evolution of the upwelling in the model the intensity of the upwelling appears to be determined by an interplay between alongshore poleward advection related to coastal trapped waves and wind intensity but also by the cross shore geostrophic flow and distribution of the water masses on a scale of 1000 km or more involving rossby waves westward propagation and advection from equatorial currents in particular the delay of upwelling recovery until fall 1998 i e well after the second el nino peak is partly due to the persistent advection of offshore stratified water toward the coast of peru altimetry data suggest that these interpretations of the numerical solution also apply to the real ocean

tropical atlantic biases in ccsm4 abstractthis paper focuses on diagnosing biases in the seasonal climate of the tropical atlantic in the twentieth century simulation of the community climate system model version 4 ccsm4 the biases appear in both atmospheric and oceanic components mean sea level pressure is erroneously high by a few millibars in the subtropical highs and erroneously low in the polar lows similar to ccsm3 as a result surface winds in the tropics are 1 m s 1 too strong excess winds cause excess cooling and depressed ssts north of the equator however south of the equator sst is erroneously high due to the presence of additional warming effects the region of highest sst bias is close to southern africa near the mean latitude of the angola benguela front abf comparison of ccsm4 to ocean simulations of various resolutions suggests that insufficient horizontal resolution leads to the insufficient northward transport of cool water along this coast and an erroneous southward stretching of the abf a similar proble

rare earth elements in the permian phosphoria formation paleo proxies of ocean geochemistry abstract the geochemistry of deposition of the meade peak member of the phosphoria formation mpm in southeast idaho usa a world class sedimentary phosphate deposit of permian age that extends over 300 000 km2 is ascertained from its rare earth element ree composition ratios of ree al2o3 suggest two sources seawater and terrigenous debris the seawater derived marine fraction identifies bottom water in the phosphoria sea as o2 depleted denitrifying suboxic most of the time and seldom sulfate reducing anoxic this interpretation is supported by earlier research that showed progressively greater ratios in the marine sediment fraction of cr ni v ni mo ni relative to their ratios in seawater for which marine cr v and mo can have a dominantly o2 depleted bottom water source and ni a photic zone largely algal source the water chemistry was maintained by a balance between bacterial oxidation of organic matter settling through the water column determined largely by primary productivity in the photic zone and the flux of oxidants into the bottom water via advection of seawater from the open ocean samples strongly enriched in carbonate fluorapatite the dominant ree host mineral have variable er sm tm sm and yb sm ratios their distribution may represent greater advection of seawater between the phosphoria sea and open ocean during deposition of two ore zones than a center waste and greater upwelling of nutrient enriched water into the photic zone however the mean rate of deposition of marine ni a trace nutrient of algae and po43 a limiting nutrient indicate that primary productivity was probably high throughout the depositional history an alternative interpretation of the variable enrichments of er tm and yb relative to sm is that they may reflect temporally variable carbonate alkalinity of open ocean seawater in permian time a more strongly negative ce anomaly for all phosphatic units than the ce anomaly of modern pelletal phosphate is further indicative of an elevated o2 concentration in the permo carboniferous open ocean as proposed by others in contrast to the depletion of o2 in the bottom water of the phosphoria sea itself the oceanographic conditions under which the deposit accumulated were likely similar to conditions under which many sedimentary phosphate deposits have accumulated and to conditions under which many black shales that are commonly phosphate poor have accumulated a shortcoming of several earlier studies of these deposits has resulted from a failure to examine the marine fraction of elements separate from the terrigenous fraction

controls on phosphorus concentration and accumulation in oceanic sediments understanding phosphorus p sedimentation in the ocean is important both for quantifying outputs in the marine phosphorus cycle and for determining the controls on phosphogenesis the authigenic formation of carbonate fluorapatite and phosphorite deposition large accumulations of p rich sediments on continental margins in this study i have compiled literature data on sedimentary p concentrations and sedimentation rates from continental margins phosphogenic continental margins and open ocean environments i have also calculated p accumulation rates the product of p concentration sediment density and sedimentation rate in these settings sedimentary p concentrations exhibit a similar range in a wide variety of oceanic environments and sedimentation rate conditions for example p concentrations in continental margin sediments range from 8 to 108 mol p g 1 with sedimentation rates from 80 to 8 000 m my 1 in open ocean sediments the p concentration range is similar 7 307 mol p g 1 even though sedimentation rates are generally about 100 times lower 2 50 m my 1 the exception to this are phosphogenic environments where p concentrations are exceptionally high 580 3 700 mol p g 1 while sedimentation rates are relatively low 20 310 m my 1 phosphorus accumulation rates appear to be controlled by sedimentation rate in ocean sediments although p concentrations generally exhibit similar ranges the large difference in sedimentation rates between various environments results in p accumulation rates that are several orders of magnitude higher in continental margins 90 8 000 mol p cm 2 kyr 1 compared to open ocean sediments 2 75 mol p cm 2 kyr 1 in the case of phosphogenic environments low sedimentation rates result in p accumulation rates 80 6 300 mol p cm 2 kyr 1 that are surprisingly similar to those of non phosphogenic continental margin sediments

respective roles of the guinea current and local winds on the coastal upwelling in the northern gulf of guinea abstractthe northern gulf of guinea is a part of the eastern tropical atlantic where oceanic conditions due to the presence of coastal upwelling may influence the regional climate and fisheries the dynamics of this coastal upwelling is still poorly understood a sensitivity experiment based on the regional oceanic modeling system roms is carried out to assess the role of the detachment of the guinea current as a potential mechanism for coastal upwelling this idealized experiment is performed by canceling the inertia terms responsible for the advection of momentum in the equations and comparing with a realistic experiment the results exhibit two major differences first the guinea current is found to be highly sensitive to inertia as it is no longer detached from the coast in the idealized experiment the guinea current adjusts on an inertial boundary layer the inertial terms defining its lateral extension second the upwelling east of cape palmas disappears in absence of the guinea current detach

the phosphorus cycle in coastal marine sediments the concentration of dissolved phosphate in sediment box cores from the laurentian trough in the gulf of st lawrence increased sharply across the sediment water interface from 2 0 mol po4 1 in the bottom water to 6 3 mot po4 1 in the top cm remained almost constant at this value down to 5 15 cm depth and then increased rapidly with further depth in the region of constant concentration phosphate is buffered by sorption equilibria with the sediment the production rate of phosphate the sorption capacity of the sediment and the thickness of the diffusive boundary layer at the sediment water interface appear to control the shape of the pore water profile even though the buffering places an upper limit on the concentration gradient across the sediment water interface and hence on the flux the phosphate flux to the overlying water is controlled by the production rate of phosphate within the sediment a model is proposed to relate sediment chemistry to phosphorus fluxes

similar phosphorus fluxes in ancient phosphorite deposits and a modern phosphogenic environment phosphogenesis is major sink for phosphorus p in the modern ocean and the deposition of ancient phosphorites appears to have been an important sink for p in past oceans to evaluate the importance of p burial we combined published estimates along with our data for one section of the monterey formation california of p inventories areal extents and time intervals of deposition for three well studied major phosphorite deposits to calculate p accumulation and burial rates phosphorus accumulation and burial rates of major phosphorite deposits are comparable to those of the modern peru margin though phosphorite deposition probably requires favorable sedimentological tectonic and or oceanographic conditions it does not appear to be a geochemically anomalous phenomenon when compared to modern oceanic conditions

early diagenetic reactions in interbedded pelagic and turbiditic sediments in the nares abyssal plain western north atlantic consequences for the composition of sediment and interstitial water abstract measured pore water concentrations of iron in interbedded pelagic and turbiditic sediments from the nares abyssal plain are in excellent agreement with sediment colour and measured redox potential the organic carbon content of these sediments appears to define the redox conditions and consequently the porewater and solid phase concentration of constituents that are involved in early diagenetic reactions in the turbiditic sediments the concentration of no 3 generally goes to zero within a sediment depth of 1 m whereas at 8 m in a pelagic core from the same area the concentration of no 3 is still higher than it is in the bottom water the pore water concentration of mn 2 in the turbiditic sediments increases sharply down to a depth of approximately 3 m and from thereon remains nearly constant due to saturation with respect to mn ca co 3 the pore water of the turbiditic sediments is also saturated with respect to calcite the few diagenetic spikes in the pore water concentration of no 3 and mn 2 and the concentration depth profile of dissolved iron h 4 sio 4 and phosphate all clearly demonstrate the inhomogeneous nature of interbedded pelagic and turbiditic sediments the simultaneous occurrence of peaks of dissolved iron silica and of sediment intervals with a relatively high organic carbon content is attributed to enhanced early diagenetic reactions associated with the decomposition of organic matter in these specific intervals linked with these reactions is the irregular pore water concentration of phosphate which is shown to originate partly from the oxidation of organic matter but mainly from the desorption of phosphate from iron oxide potential concentrations of phosphate are calculated from the stoichiometric early diagenetic reactions and compared with measured concentrations due to the unique combination of low porosity and relatively high sedimentation rates the sediments from the nares abyssal plain are an ideal basis for the study of such interbedded sequences of pelagic and turbiditic deposits

organic matter apatite pyrite relationships in the botneheia formation middle triassic of eastern svalbard relevance to the formation of petroleum source rocks in the nw barents sea shelf abstract the middle triassic botneheia formation of eastern svalbard edgeoya and barentsoya comprises an organic carbon rich fine grained clastic succession 100 m thick that makes the best petroleum source rock horizon in the nw barents sea shelf the succession records a transgressive regressive interplay between the prodelta depositional system sourced in the southern barents sea shelf black shale facies of the lower and middle parts of the muen member and the open shelf phosphogenic system related to upwelling and nutrient supply from the panthalassic ocean phosphogenic black shale facies of the upper part of the muen member and the blanknuten member the relationships between organic matter authigenic apatite and pyrite in these facies allow to characterize the relative roles of redox conditions and oceanic productivity in the organic carbon preservation the accumulation of terrestrial and autochthonous marine organic matter in the black shale facies occurred under dominating oxic conditions and increasing upward productivity related to early transgressive phase and retrogradation of the prodelta system the phosphogenic black shale facies deposited in an oxygen minimum zone omz of the open shelf environment during the late transgressive to regressive phases under conditions of high biological productivity suppressed sedimentation rates and changing bottom redox the phosphatic black shales occurring in the lower and upper parts of the phosphogenic succession reveal depositional conditions indicative of the shallower part of omz including high input of autochthonous organic matter into sediment oxic to dysoxic episodically suboxic and or anoxic conditions intense phosphogenesis and recurrent reworking of the seabed the massive phosphatic mudstone occurring in the middle of the phosphogenic succession reflects the development of euxinia in the deeper part of omz during high stand of the sea high input of autochthonous organic matter in this environment was coupled with mineral starvation and intermittent phosphogenesis in mature sections in eastern svalbard the petroleum potential of the botneheia formation rises from moderate to good in the black shale facies and from good to very good in the phosphogenic black shale facies attaining maximum in the massive phosphatic mudstone

the role of the indian summer monsoon and the mid latitude westerlies in himalayan glaciation review and speculative discussion new dates for late quaternary glaciations in the himalayas show that during the last glacial cycle glaciations were not synchronous throughout the region rather in some areas glaciers reached their maxima at the global glacial maximum of c 18 20 ka bp whereas in others glaciers were most extensive at c 60 30 ka bp comparison of these data with palaeoclimatic records from adjacent regions suggest that on millennial timescales himalayan glacier fluctuations are controlled by variations in both the south asian monsoon and the mid latitude westerlies

environmental control on concretion forming processes examples from paleozoic terrigenous sediments of the north gondwana margin armorican massif middle ordovician and middle devonian and sw sardinia late ordovician abstract concretions of various compositions are common in the paleozoic terrigenous successions of the north gondwana margin this study focuses on phosphatic p and siliceous si concretions present in some successions of the armorican massif nw france and sw sardinia w italy it shows that they consist of mudstones fine to very fine grained sandstones or shellbeds with a more or less abundant p cement and form a continuum between a phosphatic end member and a siliceous biogenic end member the p 2 o 5 contents are ranging from 0 26 to 21 5 and are related to apatite the sio 2 contents vary from 25 to 82 and are linked both to a terrigenous phase and to a biogenic silica phase concretions showing the lower p contents p 2 o 5 2 al 2 o 3 5 comparison with the surrounding sediments shows that all the concretions are enriched in chlorite and in middle rare earth elements la s gd s 0 12 0 72 and some of them in y up to 974 ppm rare earth elements more than 300 ppm and sr 260 880 ppm the concretions with highest biogenic silica concentrations are contained in the outer shelf sediments whereas the other concretions are present from the proximal part of the inner shelf to the outer shelf a genetic model in two stages is proposed during early diagenesis the dissolution of shells and degradation of organic matter progressively enrich the pore water in dissolved si ca and p when the suboxic zone is reached p precipitation begins leading to the formation of protoconcretions in shallow environments the relative permeability of sediments and the winnowing or reworking of the upper few centimetres by bottom currents allow for suboxic conditions to be maintained leading to p rich concretion formation in deeper environments the anoxic zone is reached more rapidly thereby preventing extensive phosphogenesis nevertheless in the protoconcretions the early p cement preserves pore spaces from compaction in the presence of biogenic siliceous particles the fluids are enriched in dissolved silica and diffuse towards the protoconcretions silica precipitation can thus occur later in the intergranular spaces

ocean circulation along the southern chile transition region 38 46 s mean seasonal and interannual variability with a focus on 2014 2016 satellite and atmospheric model fields are used to describe the wind forcing surface ocean circulation temperature and chlorophyll a pigment concentrations along the coast of southern chile in the transition region between 38 and 46 s located inshore of the bifurcation of the eastward south pacific current into the equatorward humboldt and the poleward cape horn currents the region also includes the chiloe inner sea and the northern extent of the complex system of fjords islands and canals that stretch south from near 42 s the high resolution satellite data reveal that equatorward currents next to the coast extend as far south as 48 51 s in spring summer they also display detailed distributions of forcing from wind stress and wind stress curl near the coast and within the inner sea between 38 46 s both winds and surface currents during 1993 2016 change directions seasonally from equatorward during summer upwelling to poleward during winter downwelling with cooler sst and greater surface chlorophyll a concentrations next to the coast during upwelling opposite conditions during downwelling over interannual time scales during 1993 2016 there is a strong correlation between equatorial el nino events and sea level and a moderate correlation with alongshore currents looking more closely at the 2014 2016 period we find a marginal el nino during 2014 and a strong el nino during 2015 that connect the region to the tropics through the oceanic pathway with some atmospheric connections through the phenomenon of atmospheric blocking as noted by others the period also includes a harmful algal bloom of the dinoflagellate alexandrium catenella during early 2016 that occurred during a sequence of physical conditions winds currents and temperatures that would favor such a bloom the most anomalous physical condition during this specific bloom is an extreme case of atmospheric blocking that creates a long period of calm in austral autumn after strong upwelling in austral summer the blocking is related to the 2015 2016 el nino and an unusual coincident positive phase of the southern annular mode

a modern vs permian black shale the hydrography primary productivity and water column chemistry of deposition the sediment currently accumulating in the cariaco basin on the continental shelf of venezuela has an elevated organic carbon content of approximately 5 is accumulating under o2 depleted bottom water conditions so42 reduction is composed dominantly of foraminiferal calcite diatomaceous silica clay and silt and is dark greenish gray in color upon lithification it will become a black shale recent studies have established the hydrography of the basin and the level of primary productivity and bottom water redox conditions these properties are used to model accumulation rates of cd cr cu mo ni v and zn on the seafloor the model rates agree closely with measured rates for the uppermost surface sediment the model is applied to the meade peak phosphatic shale member of the phosphoria formation a phosphate deposit of permian age in the northwest united states it too has all of the requisite properties of a black shale although the deposit is a world class phosphorite it is composed mostly of phosphatic mudstone and siltstone chert limestone and dolomite it has organic carbon concentrations of up to 15 is strongly enriched in several trace elements above a terrigenous contribution and is black the trace element accumulation defines a mean primary productivity in the photic zone of the phosphoria basin as moderate at 500 g m 2 year 1 organic carbon comparable to primary productivity in the cariaco basin the source of nutrient enriched water that was imported into the phosphoria basin upwelled into the photic zone and supported primary productivity was an o2 minimum zone of the open ocean the depth range over which the water was imported would have been between approximately 100 and 600 m the mean residence time of bottom water in the basin was approximately 4 years vs 100 years in the cariaco basin the bottom water was o2 depleted but it was denitrifying or no3 reducing rather than so42 reducing

organic carbon cycling and modern phosphorite formation on the east australian continental margin an overview during 1987 the australian bureau of mineral resources conducted a multidisciplinary investigation of the modern phosphorites on the continental margin of southeastern australia between 28 and 32 s the objectives of the work were to examine the processes controlling the cycling of organic carbon and bioactive elements nitrogen phosphorus sulphur and iron in the sediments and to investigate the roles which these processes played in the formation of the modern phosphorites bacterial productivities sulphate reduction rates sedimentary oxygen and pore water concentrations of nitrate ammonia phosphate iron sulphate and fluoride were measured at sea the highest rates of microbial productivity were found in the surficial 0 20 mm sediments of the modern phosphorite zone in 350 460 m water depth these rates were about double those in shallower shelf 300 m sediments and 3 4 fold those rates in mid slope 600 1000 m sediments aerobic and anaerobic oxidation rates of organic matter calculated from sediment oxygen profiles and sulphate reduction rates were highest in the surface sediments in the modern phosphorite zone the recycling of sedimentary iron via reductive dissolution of iron oxyhydroxides and reprecipitation at the oxic anoxic boundary results in a near surface sedimentary trap for iron in the phosphorite zone sediments phosphate released from organic matter in the interfacial sediments and fluoride from seawater are scavenged by iron oxyhydroxides in the top few centimetres of sediment phosphorus in this way is decoupled from organic carbon in the near surface sediments and linked to the redox cycling of iron phosphate and fluoride scavenged onto iron oxyhydroxides and concentrated in the surficial sediments are subsequently released to pore waters in the anoxic sediments when iron oxyhydroxides are buried and dissolve the recycling process releases phosphate and fluoride for incorporation into apatite fluoride is depleted from pore waters at depths 18 cm phosphorite nodules form within anoxic sediments at depths 18 cm and continue to accumulate iron and phosphorus while resident in the mixed layer combinations of rapid sediment mixing rates a slow sedimentation rate and a mixed layer to about 18 cm result in an average particle residence time in the phosphorite zone sediments which is about ten fold that of the mid slope sediments long residence times and rapid mixing promote the oxidation of organic carbon and release of phosphate while the continuous recycling of iron and phosphate concentrates the phosphorus for apatite precipitation and accumulation into phosphorite nodules phosphorite nodules are not found in mid slope sediments probably because of combinations of relatively rapid sedimentation rates ineffective iron phosphorus and fluoride recycling and trapping mechanisms plus dilution and dissemination of any incipient apatite

the marine phosphorus cycle phosphorus introduced to the ocean must ultimately be removed if a steady state is to be maintained over geologic time aeolian input is insignificant and there is evidently no hydrothermal contribution rivers dominate p input to the ocean the fluvial p flux is poorly quantified due to the interactions of two factors 1 man s influence on river nutrient fluxes and 2 inherent complexities in understanding the biological and inorganic associations of p in estuarine and coastal waters our best estimate of the natural or pre man p input flux is about 10 x 10 sup 9 moles p cm sup 2 ocean surface year of the identified flux of phosphorus to the sediments about 90 percent is in the form of biogenic debris or its regeneration products the burial of phosphatic fish debris is negligible p removal by direct reaction of phosphate in seawater with sea floor basalts during mid ocean ridge hydrothermal circulation is insignificant p removal by processes such as sorption on clay surfaces or formation of authigenic fe and al phosphate phases is presently unquantified and remains a serious uncertainty in the phosphorus cycle the identified sources and sinks approximately balance yielding a residence time for p in the oceans of about 10 sup 5 yrs

a kinematic analysis of the indian atlantic interocean exchange we analyze the indian atlantic interocean exchanges in an eddy permitting numerical simulation focusing on the cape basin a region of the southeastern atlantic bounded on the northwest by the walvis ridge and on the south by the agulhas ridge near 40 s to quantify the relative importance of the different dynamical mechanisms involved in the interocean exchange we separated the climatological mean circulation from the transients the analysis indicates that agulhas eddies influence not only the transient but also fluxes associated with the mean circulation eddy fluxes for example supply most of the energy of the benguela current a distinctive characteristic of the eddy variability within the cape basin is the co existence of cyclonic and anticyclonic vortices in dipole structures that resemble the heton model of hogg and stommel proc r soc london a 397 1985 1 anticyclones are surface intensified vortices that in spite of their baroclinic structure reach to deep layers cyclones are bottom intensified vortices with dominant barotropic structure that projects into the upper layer the propagation of both cyclones and anticyclones is strongly affected by the bottom topography our analysis shows that the walvis ridge and the vema seamount block the passage of bottom intensified cyclones and changes the trajectories of the upper intensified anticyclones although most anticyclones are able to escape the basin the deep compensation generated by the ridge generates an energy loss of approximately 30 and a change of the eddy trajectory to a more westward direction

reduction in himalayan snow accumulation and weakening of the trade winds over the pacific since the 1840s 1 in 1884 blanford suggested that summer rainfall over northwest india was anti correlated with snow cover during the preceding winter and spring in the western himalaya walker elaborated on this suggestion in his seminal work on predictors of the indian summer monsoon a body of work that forms the basis of our understanding of how eurasia influences this monsoonal circulation recently a number of studies have questioned the existence of this relationship or have proposed a more complex coupling between eurasian snow cover including the himalaya and the indian summer monsoon here we present a 196 year record of snow accumulation from a himalayan ice core that contains a decreasing trend in accumulation that began in the 1840s indian summer monsoon rainfall shows no evidence of such a trend and we argue that this reduction in snow accumulation is associated with a long term weakening of the trade winds over the pacific ocean citation zhao h and g w k moore 2006 reduction in himalayan snow accumulation and weakening of the trade winds over the pacific since the 1840s geophys res lett 33 l17709

elemental geochemistry of lower cambrian phosphate nodules in guizhou province south china an integrated study by la icp ms mapping and solution icp ms abstract the late ediacaran to early cambrian transition was a critical interval in earth history during which both the environment and life experienced dramatic change relationships between these events however are widely debated this time interval also witnessed the occurrence of massive phosphate deposits studies on the characteristics origins and depositional context of this geochemical archive may provide important insights into not only the ore forming process but also the coevolution of the earth surface system here phosphate nodules from two sections jinsha and songtao are investigated using in situ la icp ms mapping and solution icp ms methods elemental images and factor analyses of the la icp ms dataset show that ca p and sr are evenly distributed and co enriched within the nodule whereas iron related elements fe as and mo are roughly present as concentric layers the paas normalized ree patterns of the jinsha samples exhibit moderately negative ce anomalies and pronounced mree enrichments possibly related to uptake of ree released by iron oxyhydroxides during early diagenesis in contrast the songtao samples are characterized by more seawater like signals with significantly lower ce ce and higher eu eu values these positive eu anomalies are ascribed to active submarine hydrothermal vents along the yangtze platform margin based on a compilation of published ce ce data we suggest that the prominent negative ce anomalies during the ediacaran cambrian phosphogenesis give evidence of possible link between p dynamics and ocean oxygenation

origins and variability of the benguela current a subset of the benguela sources and transports best 1992 1993 data is analyzed to study the magnitude and variability of the large scale transports in the area the data consist of inverted echo sounder series and conductivity temperature depth stations the mean 16 month transport values for the upper 1000 m indicate that of the 13 sv northward transport within the benguela current 50 is derived from the central atlantic which from geometry may be chiefly south atlantic water 25 comes from the indian ocean which may be chiefly agulhas water and the remaining 25 may be a blend of agulhas and tropical atlantic water a simple schematic of the transport pattern with a somewhat restricted corridor for agulhas eddies translation is envisioned to the west of the eddy corridor flows the south atlantic source for the benguela current to the east is the agulhas indian ocean source the corridor is breached by south atlantic and indian water as the transient eddy field stirs these water masses

phosphate regeneration from sediments of the peru continental margin by dissolution of fish debris generally oxidative regeneration of phosphate from anoxic sediments is by microbially mediated sulfate reduction processes stoichiometric modelling of such reactions takes into consideration varying proportions of decomposable organically bound p to account for the ratios among nutrients in depth concentration profiles of near surface sediments new results of interstitial water composition from sediments underlying the water masses influenced by coastal upwelling of the eastern boundary current system off peru indicate that dissolution of phosphatic fish debris represents a mechanism for remineralization of phosphate comparable to or larger in magnitude than that by oxidative regeneration of organically bound p dissolved interstitial phosphate from fish debris is revealed by an excess amount of phosphate over that predicted from a simple stoichiometric oxidative regeneration model and by anomalously high dissolved interstitial fluoride concentrations phosphate flux estimates based on diffusion from the sediment suggest that this mechanism may generate up to 10 of the nutrient pool in the waters of the peru undercurrent partitioning of p among the two sources reveals further that fish debris phosphate is about four times more important than organically bound p in nutrient generation from sediments of the peru continental margin not only does this mechanism of regeneration affect the nutrient cycling but may also control widespread phosphorite formation in this area

phosphogenesis and organic carbon preservation in the miocene monterey formation at naples beach california the monterey hypothesis revisited the middle part of the miocene monterey formation at naples beach west of santa barbara california is predominantly composed of organic rich mudstone interstratified with phosphatic laminae minor lithologies include volcanic ash dolomite porcelanite and chert and condensed phosphatic beds sediments dated as 14 3 13 5 ma have average total organic carbon toc values around 8 5 wt and organic carbon oc accumulation rates are around 565 mg cm2 k y sediments dated as 13 5 13 ma are characterized by average toc values of 12 6 wt and oc accumulation rates of around 1130 mg cm2 k y the interval between 13 and 10 6 ma is marked by condensation average toc values are around 8 6 wt and oc accumulation rates diminished to around 55 mg cm2 k y the last interval studied is dated as 10 6 9 4 ma and average toc values are around 6 wt whereas oc accumulation rates rose again to 320 mg cm2 k y the presence of erosional surfaces angular unconformities and reworked clasts and nodules suggests that bottom current activity and gravity flow deposition have been instrumental in sediment accumulation the phosphatic laminae were precipitated at a very early stage of diagenesis during periods of nonsedimentation they formed less permeable sedimentary lids and may as such have contributed to enhanced oc preservation between 13 and 10 6 ma the thus formed phosphatic laminae were frequently subjected to subsequent sediment winnowing and reworking resulting in the formation of condensed phosphatic beds calculated p c molar ratios suggest that 1 the measured section is highly enriched in phosphorus p relative to oc 2 regeneration of organic p from organic matter decomposition was negligible and 3 the source of p was external likely upwelled bottom water rich in inorganic p in spite of good preservation conditions and correspondingly high toc contents the overall oc accumulation rates are moderate in comparison to those of actual high productivity areas which is mainly due to the episodic character of depositional processes and the intervening long periods of nondeposition and sediment reworking they preclude this section and by extrapolation the monterey formation in general from being an important oc sink during the middle miocene alternatively large oc sinks were probably created on the continent lignite deposits and in sedimentary depocenters which received increasing amounts of detrital sediments due to a combination of climate change spreading of grasslands and the increasing importance of mountain chains such as the himalaya the associated high nutrient fluxes may have been involved in the backstepping and drowning of carbonate platforms and in the generation of widespread phosphat rich deposits during the late early and early middle miocene

phosphorus diagenesis in sediment of the thau lagoon we describe the depth distribution of phosphorus in relation to the distribution of major redox species dissolved o2 n o 3 n h 4 mn and fe and particulate s organic c reactive mn and fe oxides in modern sediments of two stations in the thau lagoon sediments close to the oyster bank zone are enriched in organic carbon and are highly bioturbated while those outside the bank are less bioturbated and organic carbon levels are lower in all sites early diagenesis follows the well accepted depth sequence of redox reactions of organic matter mineralization the upper sediments of the station enriched in organic carbon contain high amounts of reactive particulate organic phosphorus that arrives at the sediment surface through biodeposition only a part of this phosphorus is released to the bottom water after mineralization since more than 50 of total p is buried as an authigenic phosphate mineral in the middle of the lagoon outside the oyster bank zone organic matter seems to be much more refractory but the distribution of the major redox compounds indicates that this organic matter is partially mineralized a portion of the phosphate and ammonium released during mineralization does not escape the sediment since the concentration gradient is close to zero between 1 and 25 cm depth below the sedimentewater interface pore water n and p are likely fixed by biological uptake the characterisation and magnitude of this process require further study 2006 elsevier ltd all rights reserved

atmospheric effects in the angola benguela frontal zone the angola benguela front is the generic border between on the one hand the benguela current and the coastal upwelling regime along the southwest african coastline and on the other hand the warm southward flowing angola current this frontal zone has a variable morphology geographic location and thermal characteristics it has been suggested that this variability may be related to changing wind patterns we have studied the thermal characteristics of the surface expression of the frontal zone for a 74 day period using daily thermal infrared images and compared these to wind patterns from synoptic weather maps there is little correlation between the location of the northern and the southern front that form the envelope for this frontal zone the location of the southern front largely determines the thermal gradient across the entire frontal zone large short term displacements in the geographic location of the frontal zone as well as short term variations in its thermal characteristics are shown to be strongly correlated to the atmospheric pressure gradient of the south atlantic anticyclone with a 1 day lag period this is true irrespective of the latitude changes of the center of the south atlantic anticyclone

oxygen cycling in the northern benguela upwelling system modelling oxygen sources and sinks abstract this paper elucidates the oxygen dynamics in the northern benguela upwelling system by means of process oriented numerical modelling owing to the complex physical biological interaction in this system a coupled hydrodynamic biogeochemical model is required to grasp the various aspects of the oxygen dynamics we used high resolution atmospheric fields derived from observations to force our model available since 1999 the model results represent a 15 years consistent data set of realistic hydrographic and ecosystem variables including oxygen distribution patterns after a concise description of the main aspects of the model we use the model data to analyse the components contributing to the oxygen dynamics namely the ocean circulation the exchange between ocean and atmosphere as well as the local biogeochemical oxygen cycling in the system we thoroughly validate the model with available field observations and remote sensing data the strengths of coastal upwelling which controls the nutrient supply to the euphotic zone as well as the poleward undercurrent that carries oxygen and nutrients to the shelf in the northern benguela upwelling system are well reproduced in the model among the biological oxygen sinks mineralisation in the sediment respiration of zooplankton and nitrification in the water column are important we also found that vertical migration of zooplankton in response to the oxygen conditions provides a regulating feedback which may prevent a complete deoxygenation of suboxic waters as long as oxygen or nitrate are available in the bottom waters the activities of chemolithoautotrophic sulphur bacteria on the sediment surface keep the redoxcline within the sediment and prevent the release of hydrogen sulphide into the water column by horizontal integration of the simulated ocean atmosphere oxygen flux it can be shown that the kunene upwelling cell between 16 s and 18 s is a boundary between the equatorial ocean characterise by weak oxygen release to the atmosphere and the subtropical benguela upwelling system governed by an enhanced and seasonal varying flux furthermore a comparison of oxygen fluxes controlled by physical transport versus biogeochemical processes shows that the physical processes dominate in the northern benguela upwelling system

the effect of hydrothermal processes on midwater phosphorus distributions in the northeast pacific abstract the distributions of dissolved particulate and sedimentary phosphorus were measured in the region of the juan de fuca ridge to determine the impacts of hydrothermal processes on the phosphorus cycle in the oceans significant negative dissolved phosphate anomalies ranging from 0 to 60 nmol l were observed in the water column at depths between 1900 and 2300 db the largest anomalies

the diagenesis of phosphorus in a nearshore marine sediment abstract chemical analyses have been made for total inorganic phosphorus total organic phosphorus and organic carbon in plankton and in anoxic sediments from long island sound u s a when combined with laboratory experiments the measurements of other studies on the same sediments and mathematical modelling the results indicate that 1 1 a large proportion of dissolved phosphate in the upper 10 cm of sediment zone of bioturbation is provided by the release of adsorbed phosphate during the reduction of ferric oxyhydroxides 2 2 below the zone of bioturbation phosphate is liberated to solution solely via organic matter decomposition and the release is stoichiometrically coupled to bacterial sulfate reduction and ammonia formation 3 3 a steady state diagenetic model can be used to predict the profile of organic phosphorus from that of dissolved phosphate at depths below the zone of bioturbation 4 4 the flux of dissolved phosphate out of the sediment must arise largely from phosphate liberation occurring very close 5 5 there is a large preferential loss of phosphorus relative to carbon from organic matter at the time of or prior to burial whereas after burial phosphorus is not lost preferentially at this location

modis terra observed seasonal variations of snow cover over the tibetan plateau 1 seasonal variations of snow cover fraction sfc over the tibet plateau tp are examined using the data acquired from the moderate resolution imaging spectroradiometer modis on the terra spacecraft in this study we first evaluate the accuracy of the modis high resolution snow cover data by comparing the data with in situ chinese snow observations results show that overall accuracy of modis snow data is about 90 over the tp area statistical analysis is then performed over the modis snow data during 2000 2006 it is found that the most persistent snow cover is located in the southern and western edges of the tp within large mountain ridges and western part of yarlung zangbo valley the higher scfs are mostly concentrated in the regions where the elevation is higher than 6000 m the duration for snow persistence varies in different elevation ranges and generally becomes longer with increases in the terrain elevation

pore water fluoride in peru continental margin sediments uptake from seawater abstract fluoride analyses display downward decreasing pore water gradients in peru shelf phosphatic muds that require diffusion from the overlying seawater into the sediment column and removal by reaction within the upper few tens of centimeters presumably by incorporation into carbonate fluorapatite the profiles can be modeled as first order f removal with rate constants of 3 yr 1 and asymptotic f concentrations deep in the cores of 35 45 m almost one half the seawater value the integrated flux of fluoride from seawater into organic rich shelf sediments in coastal upwelling zones phosphatic muds yields a contemporaneous global f burial of 0 54 10 10 mol f yr 1 about one fifth the burial in other sinks mostly carbonates and opal the associated burial flux of phosphorus in shelf phosphorites is about 1 6 10 10 mol p yr 1 comparable to p burial in the deep sea with organic matter 1 4 10 10 mol yr 1 and biogenic carbonates 1 4 10 10 mol yr 1 thus phosphorite formation on the peru shelf is a significant contemporaneous process

relation between sedimentation rate and burial of organic phosphorus and organic carbon in marine sediments organic carbon and organic phosphorus concentrations in marine sediment cores with known sedimentation rates were determined and collected from the literature with the exception of organic rich sediments from upwelling areas organic phosphorus concentrations in marine sediments do not correlate linearly with organic carbon concentrations the c p ratios of organic matter buried in marine sediments vary systematically with sedimentation rate over the range studied 0 0001 to 2 5 cm y low c p ratios 200 atomic occur in sediments with sedimentation rates both less than 0 002 cm y and greater than 1 cm y higher c p ratios up to 600 are found at intermediate sedimentation rates a simple steady state model is developed for the early diagenesis of organic carbon and organic phosphorus in marine sediments the processes included are sediment burial pore water diffusion and bacterial decomposition of organic matter by oxic respiration and sulfate reduction preferential regeneration of phosphorus relative to carbon is assumed to take place during oxic respiration the modeling shows that both organic matter preservation and the degree of elemental fractionation between phosphorus and carbon depend strongly on the overall sedimentation rate very high sedimentation rates coastal deltaic environment result in a good preservation of deposited organic matter with an initial c p ratio close to the redfield value at very slow sedimentation rates pelagic environment the oxidation of the sedimentary organic matter is nearly complete and produces a low c p residual organic material this residual organic matter may represent either refractory detrital organic compounds enriched in phosphorus or in situ synthesized low c p bacterial remains the high c p ratios at intermediate sedimentation rates slope and shelf environment reflect the preferential regeneration of phosphorus during the incomplete decomposition of the metabolizable organic matter

high altitude himalayan climate inferred from glacial ice flux 1 glaciological processes are modeled to investigate precipitation patterns and the resulting mass flux of snow and ice across himalayan topography our model tracks the accumulation and ablation of snow and ice and the transport of snow and ice across the topography by glacier motion we investigate high elevation precipitation on the annapurna massif by comparing the existing ice cover with model simulated glaciers produced by a suite of different precipitation scenarios our results suggest that precipitation reaches a maximum level well below the elevation of the highest peaks further essentially no snow accumulates on the topography above an elevation of 6200 6300 m hence the upper 1000 m of the massif is a high elevation desert with little flux of snow and ice active glaciers are limited to a band of intermediate elevations where a maximum of about 60 of the landscape is covered by moving ice index terms 1863 hydrology snow and ice 1827 3354 meteorology and atmospheric dynamics precipitation 1854 1854 hydrology precipitation 3354 1625 global change geomorphology and weathering 1824 1886 citation harper j t and n f humphrey high altitude himalayan climate inferred from glacial ice flux geophys res lett 30 14 1764 doi 10 1029 2003gl017329 2003

equilibrium structure and dynamics of the california current system this paper addresses the structure and dynamical mechanisms of regional and mesoscale physical variability in the subtropical northeast pacific ocean using the regional oceanic modeling system roms the model is configured with a u s west coast domain that spans the california current system ccs with a mesoscale horizontal resolution up to as fine as 3 5 km its mean seasonal forcing is by momentum heat and water fluxes at the surface and adaptive nudging to gyre scale fields at the open water boundaries its equilibrium solutions show realistic mean and seasonal states and vigorous mesoscale eddies fronts and filaments the level of eddy kinetic energy eke in the model is comparable to drifter and altimeter estimates in the solutions with sufficiently fine resolution because the model lacks nonseasonal transient forcing the authors conclude that the dominant mesoscale variability in the ccs is intrinsic rather than transiently forced the primary eddy generation mechanism is the baroclinic instability of upwelling alongshore currents there is progressive movement of meanseasonal currents and eddy energy offshore and downward into the oceanic interior in an annually recurrent cycle the associated offshore eddy heat fluxes provide the principal balance against nearshore cooling by mean ekman transport and upwelling the currents are highly nonuniform along the coast with important influences by capes and ridges in both maintaining mean standing eddies and launching transient filaments and fronts

the initial gradient of sulfate in gulf of california sediments abstract results of pore waters sulfate analysis from 26 cores from the gulf of california were used to calculate initial gradients of sulfate the values range from 0 05 to 0 72 mm cm 1 the highest values are from the continental shelf the intermediate and lowest values are from deep basins regression analysis between sedimentation rates and sulfate gradients gives an equation of the form w b c x o with an empirical constant b 1 49 this constant differs from that obtained for marine sediments from other areas this difference may be due to the fact that gulf of california sediments apparently contain less reactive organic matter than do other marine sed ments with similar sedimentation rates

early diagenetic redistribution and burial of phosphorus in the sediments of the southwestern east sea japan sea this study was carried out in order to understand the early diagenetic redistribution of phosphorus and relevant mass balance in the sediments of the east sea in two cruises during may 1993 and october 1995 11 box cores were collected in the southwestern part of the east sea dissolved phosphorus and iron were analyzed in the porewater from the cores sediment samples were analyzed for solid phase p species and solid phase fe oxyhydroxide by sequential extraction phosphorus speciation results show that organic p is the major chemical form of phosphorus in young sediments within the upper 50 cm of sediment however the authigenic fraction of total p increases with depth indicating the precipitation of carbonate fluorapatite cfa in the sediments the authigenic cfa ca5 po4 2 6 co3 0 4f was formed and buried at rates of 11 110 mol cm 2 kyr 1 the main source of dissolved phosphorus for the precipitation of cfa is organic p dissolved phosphorus released from the decomposition of organic p diffuses upward to return to bottom water or is sorbed to iron oxides in the oxidized sediments as sedimentation proceeds the iron oxide bound p is released in the reduced layer and enters the dissolved phase which contributes p to the formation of cfa in addition to that contributed by the organic p the burial flux of reactive p iron oxide bound p authigenic p organic p is 0 09 0 53 g p m 2 yr 1 that accounts for 18 58 of the reactive p arriving at the sediment water interface the burial flux of reactive p is high in the upper and lower continental margin sediment the burial flux of reactive p in the ulleung basin sediment is less than those in the continental margin sites by a factor of 6 indicating that the reactive p burial flux is mainly dependent on sedimentation rate

geochemical characteristics of phosphorite and carbonate nodules from the miocene funakawa formation western margin of the yokote basin northeast japan abstract phosphorite nodules were discovered in diatomite and diatomaceous mudstones of the late miocene funakawa formation in dewa height on the western margin of the yokote basin northeast japan they occur as small nodules cemented burrows and small trace fossils in diatom rich sediment that was deposited just above the contact between underlying siliceous shales the underlying shales are essentially devoid of fossils and the overlying bioturbated diatomaceous mudstones are fossil rich the underlying shale is rich in manganese mn calcite nodules and the overlying mudstone is rich in magnesian mg calcite nodules some phosphorite nodules exhibit a zonal structure caused by two phases of mg calcite cementation with or without mn calcite within the pore space of the nodule the phosphorus p content of these nodules exceeded 25 wt in p2o5 the principle phosphate mineral composing the nodules is fluor f carbonate apatite crystals which are a few m in length and cocoon shaped their aggregate includes a small amount of silica aluminum and water si al and h2o respectively the rare earth element ree composition of the phosphorite nodules is characterized by a positive europium eu anomaly and no cerium ce anomaly the biomarker distribution of the phosphorite nodules is characterized by low cpi low carbon number n alkane and high hopenes type hopane and isoprenoid ketone phosphorite nodules originate from the phosphate contained in diatoms the mineralization occurs in the bacterial sulphate reduction zone and bacteria appear to have played an important role in the concentration of p and precipitation of apatite

near coastal circulation in the northern humboldt current system from shipboard adcp data the near coastal circulation of the northern humboldt current system is described analyzing 8700 velocity profiles acquired by a shipboard acoustic doppler current profiler sadcp during 21 surveys realized between 2008 and 2012 along the peruvian coast this data set permits observation of i part of the peru coastal current and the peru oceanic current that flow equatorward in near surface layers close to the coast and farther than 150 km from the coast respectively ii the peru chile undercurrent pcuc flowing poleward in subsurface layers along the outer continental shelf and inner slope iii the near surfacing equatorial undercurrent renamed as ecuador peru coastal current that feeds the pcuc and iv a deep equatorward current referred to as the chile peru deep coastal current flowing below the pcuc a focus in the pcuc core layer shows that this current exhibits typical velocities of 5 10 cm s 1 the pcuc deepens with an increasing thickness poleward consistent with the alongshore conservation of potential vorticity the pcuc mass transport increases from 1 8 sv at 5 s to a maximum value of 5 2 sv at 15 s partly explained by the sverdrup balance the pcuc experiences relatively weak seasonal variability and the confluence of eddy like structures and coastal currents strongly complicates the circulation the pcuc intensity is also affected by the southward propagation of coastally trapped waves as revealed by a strong pcuc intensification in march 2010 coincident with the passage of a downwelling coastal wave associated with a weak el nino event

miocene phosphate accumulation in the cuyama basin southern california abstract middle and upper miocene phosphatic strata in the cuyama basin of southern california contain approximately 6 4 10 9 metric tons 2 1 10 14 mol of phosphorus p that accumulated in slope and shelf strata at rates between 0 9 and 3 8 mol p cm 2 year 1 from 15 5 to 10 8 ma an estimated 63 of all phosphorus lies in a single third order sequence deposited between 14 8 and 13 ma the main impetus for this brief phosphogenic event was a 200 m relative sea level rise that resulted from strike slip faulting immediately east of the basin minor element and petrologic analyses suggest the overall increase in phosphorus accumulation correlates with less reducing conditions in the shallowly buried marine sediments on the slope and the expansion of phosphogenesis to the outer shelf both events were probably related to landward shifts of the pacific oxygen minimum zone and coastal upwelling centers during the relative sea level rise whereas these tectonic events were apparently local the phosphatic deposits of the cuyama basin clearly demonstrate that tectonism can strongly influence phosphate accumulation rates in marginal marine environments

phosphorus speciation and its bioavailability in sediments of the jiaozhou bay abstract phosphorus p is an important macronutrient that can limit primary productivity in coastal marine ecosystems in this study four sediment cores were collected in the jiaozhou bay to study the phosphorus forms and their bioavailability including exchangeable or loosely sorbed p ex p iron bound p fe p authigenic p ca p detrital p de p and organic p op which were separated and quantified using a sequential extraction method sedex the results showed that the concentration of total p tp in core sediments ranged from 6 23 to 10 46 mol g and inorganic p ip was the dominated p form fe p and de p were the main chemical forms of ip in core sediments the profile variation of op presented the most significant among the phosphorus forms whereas the concentrations of ex p fe p and ca p varied slightly with depth indicating that the transformation of ex p fe p ca p and op could occur during sedimentary p burial moreover the distribution of p species was influenced by many factors including terrigenous input biological processes organic matter degradation and increasing human activities high total organic carbon toc op ratio occurred in the jiaozhou bay ranging from 73 to 472 average 180 81 in core sediments which was caused by the increasing terrestrial organic matter the ratio of toc p reactive ranged from 24 to 101 average 46 15 in core sediments lower than the redfield ratio implying a surplus of sedimentary reactive p compared with toc potential bioavailable p bap accounted for about 28 2 60 8 average 47 1 7 4 of tp in core sediments and presented an increasing trend since 1980s which might be responsible for the shift of phytoplankton community composition during these decades

a modeling study of shelf circulation off northern california in the region of the coastal ocean dynamics experiment response to relaxation of upwelling winds 1 a two part modeling study of the wind forced flow on the continental shelf off northern california in the region 37 40 n of the coastal ocean dynamics experiment code is pursued this paper involves a process oriented study with idealized wind stress forcing gan and allen 2002 involves forcing with observed winds and heat flux for april may 1982 and comparison of model results with code observations a characteristic but previously unexplained response observed during code following the weakening or relaxation of southward upwelling favorable winds is the time dependent development of northward currents over the inner shelf next to the coast the presence of northward winds is not necessary for this occurrence the objective in this paper is to investigate the dynamics of the shelf flow response to upwelling wind relaxation events under idealized conditions in the basic case experiment a spatially uniform upwelling favorable southward wind stress of 0 1 pa is applied to the ocean initially at rest the stress is held constant for 10 days and then decreased linearly to zero over 3 days in response to the southward wind stress southward alongshore currents develop on the shelf accompanied by upwelling of cold dense water near the coast considerable spatial variability in the shelf flow clearly related to the alongshore variations in coastline and bottom topography is found the alongshore currents tend to separate from the coast south of capes and the coldest surface water is found at those locations as the winds decrease northward currents similar to those observed develop on the inner shelf next to the coast at many alongshore locations examination of the alongshore momentum balances shows that the northward currents are forced by a northward pressure gradient force associated with negative alongshore pressure gradients these pressure gradients are set up by the interaction of the wind forced flow with the alongshore variations in shelf topography in general negative alongshore pressure gradients intensified off pt reyes and pt arena by the gradient wind balance are found south of capes the negative pressure gradients geostrophically balance onshore flow at depth and upwelling is strengthened in these locations north of capes positive pressure gradients that are primarily in balance with nonlinear advective effects are found after the winds cease the forced across shelf circulation weakens and the resulting unbalanced negative pressure gradients south of the capes accelerate the alongshore currents northward processes with similar dynamics are found embedded in the more complex coastal ocean response to observed time varying winds by gan and allen 2002

snow avalanche formation 1 snow avalanches are a major natural hazard endangering human life and infrastructure in mountainous areas throughout the world in many countries with seasonally snow covered mountains avalanche forecasting services reliably warn the public by issuing occurrence probabilities for a certain region however at present a single avalanche event cannot be predicted in time and space much about the release process remains unknown mainly because of the highly variable layered character of the snowpack a highly porous material that exists close to its melting point the complex interaction between terrain snowpack and meteorological conditions leading to avalanche release is commonly described as avalanche formation it is relevant to hazard mapping and essential to short term forecasting which involves weighting many contributory factors alternatively the release process can be studied and modeled this approach relies heavily on snow mechanics and snow properties including texture while the effect of meteorological conditions or changes on the deformational behavior of snow is known in qualitative or semiquantitative manner the knowledge of the quantitative relation between snow texture and mechanical properties is limited but promising developments are under way fracture mechanical models have been applied to explain the fracture propagation and micromechanical models including the two competing processes damage and sintering have been applied to explain snow failure there are knowledge gaps between the sequence of processes that lead to the release of the snow slab snow deformation and failure damage accumulation fracture initiation and fracture propagation simultaneously the spatial variability that affects damage fracture initiation and fracture propagation has to be considered this review focuses on dry snow slab avalanches and shows that dealing with a highly porous media close to its melting point and processes covering several orders of scale from the size of a bond between snow grains to the size of a mountain slope will continue to be very challenging

particulate iron and manganese in the santa barbara basin california abstract particulate fe and mn may be important trace metal scavengers in the water column as well as being probable indicators of biologically mediated redox processes a study has been made of suspended particulate composition in the santa barbara basin a shallow near shore basin off southern california with sub oxic conditions below sill depth observations have revealed several interesting phenomena relating to the geochemistry of fe and mn most striking is a profound enrichment of particulate fe in samples from the bottom two hundred meters these particulates have a constant fe p mole ratio of about three and may originate at the sediment water interface or may be transported to the basin from local marshes for particulate mn enrichments are observed both in the sub sill waters and near the base of the euphotic zone a consideration of particle removal rates suggests that the sub photic zone enrichment has a biogenic origin in the sub sill waters enrichment in mn is apparently due to the precipitation of dissolved mn diffusing from the anoxic basin sediments a simple mass balance suggests that most of the mn lost from the sediments is transported from the santa barbara basin in dissolved form

mount everest snow plume a case study 1 a plume of snow blowing from the summit of mount everest is one of the most iconic images of the world s highest mountain its presence provides evidence of the strong jet stream winds that can buffet the mountain in january 2004 astronauts onboard the international space station iss observed a 15 to 20 km long snow plume emanating from the summit of mount everest remarkably little is known about these plumes and the role that they play in the redistribution of snow in the high himalaya in this paper we use a variety of meteorological datasets to show that the observed plume was the combination of high winds associated with the east asian jet stream eajs and a heavy snowfall that had occurred over the himalaya during the preceding week a simple model of a blown snow plume is shown to be consistent with the observations made from the iss

short term upwelling events at the western african coast related to synoptic atmospheric structures as derived from satellite observations satellite scatterometers provide continuously valuable surface wind speed and direction estimates over the global ocean on a regular grid both in space and time the level 3 data derived from the advanced scatterometer ascat available at 1 4 spatial resolution hereafter as25 and quick scatterometer quikscat available on 1 2 and 1 4 horizontal grids qs50 and qs25 respectively are studied at regional scales in both the benguela and canary upwelling systems they are compared to the european center for medium range weather forecast surface wind analysis with insight into their intrinsic and actual spatial resolutions in the coastal band the finest spatial patterns are found in the qs25 winds and are o 75 km this demonstrates the sensitivity of the high resolution satellite derived winds to coastal processes related to sea surface temperature sst perturbations and land sea transition next short lived upwelling episodes sues calculated from sst anomalies are defined consistently with the qs25 actual resolution these cold events refer to local short lived perturbations that add to seasonal upwelling variability we characterize concomitant atmospheric synoptic conditions for sues identified at chosen latitudes and highlight two subregions in both upwelling systems with contrasted patterns for the alongshore wind stress component and curl the complexity of the latter patterns is closely linked to local short term sst variability closer to the shore numerical sensitivity experiments show that the imbalance between ekman transport and ekman pumping has an impact on ocean dynamics wind reduction in the coastal qs25 forcing partially induced by orography tends to reduce coastal sst cooling

the benguela upwelling system quantifying the sensitivity to resolution and coastal wind representation in a global climate model abstractof all the major coastal upwelling systems in the world s oceans the benguela located off southwest africa is the one that climate models find hardest to simulate well this paper investigates the sensitivity of upwelling processes and of sea surface temperature sst in this region to resolution of the climate model and to the offshore wind structure the community climate system model version 4 is used here together with the regional ocean modeling system the main result is that a realistic wind stress curl at the eastern boundary and a high resolution ocean model are required to well simulate the benguela upwelling system when the wind stress curl is too broad as with a 1 atmosphere model or coarser a sverdrup balance prevails at the eastern boundary implying southward ocean transport extending as far as 30 s and warm advection higher atmosphere resolution up to 0 5 does bring the atmospheric jet closer to the coast but there can be too strong a wind stress curl the most

phosphogenesis and active phosphorite formation in sediments from the arabian sea oxygen minimum zone in this study porewater chemistry solid phase analysis and microscopic observations were combined to evaluate phosphogenesis in three boxcores located within the intensive oxygen minimum zone of the arabian sea three parameters namely a decrease of the dissolved phosphate and fluoride concentrations with depth saturation with respect to carbonate fluorapatite and the presence of a solid phase ca phosphate mineral all indicate that phosphogenesis is currently taking place at all three sites authigenic apatite precipitation rates vary between 0 076 and 1 04 molp cm 2 yr 1 and are of the same order of magnitude as reported for other high productivity areas precipitation of an intermediate precursor precedes francolite formation in the continental slope sediments on the karachi margin results of a diagenetic p model indicate that phosphogenesis is induced by high rates of organic matter degradation dissolution of fish debris is likely to provide a substantial additional source of phosphate redox iron cycling does not influence phosphogenesis in these environments model results suggest that sediment mixing is essential in promoting early diagenetic phosphogenesis the highest rate of francolite formation was observed in a boxcore taken on the oman margin where it contributes to the formation of a holocene phosphorite deposit this observation contrasts with previous reports of only old phosphorites in this area phosphorites are presently forming on the oman margin as a result of a deposition of older reworked material from the continental shelf which has undergone an earlier phase of phosphogenesis b a high input of reactive p fish debris and degradable organic matter c a relatively low sediment accumulation rate and d the absence of winnowing on this location holocene phosphorite deposits may be less common on the oman margin than in other coastal upwelling areas because of the narrowness of the shelf and the steepness of the slope which limit the area where phosphorite formation may occur

role of a strong oxygen deficient zone in the preservation and degradation of organic matter a carbon budget for the continental margins of northwest mexico and washington state rates of organic carbon oxidation in marine sediments were determined for the continental margins of northwest mexico and washington state with the goal of assessing the role of oxygen in the preservation of organic matter on a margin with a strong oxygen deficient zone and on a typical western continental margin total carbon oxidation rates including rates for individual electron acceptors o2 no3 and so4 were determined at depths ranging from 100 to 3000 m on both margins carbon oxidation rates were generally higher on the washington margin than on the mexican margin the relative importance of the different electron acceptors varied across the two margins and was related primarily to the availability of o2 and no3 from the overlying water the relative contribution of o2 consumption increased in deeper sediments 2000 m as aerobic processes began to dominate the total carbon oxidation rate denitrification rates were highest in washington sediments however denitrification represented a larger fraction of the total carbon oxidation rate in the mexican sediments 40 for mexico vs 30 for washington sulfate reduction accounted for as much as 79 of the total carbon oxidation rate in shallow sediments and less than 20 in deep sediments on both margins the offshore trends in carbon oxidation rate appeared to be related to the organic carbon input rate pore water o2 and no3 penetration depths were shallowest in nearshore stations and increased offshore regeneration ratios of c n p reveal non redfield behavior on both margins carbon budgets for the two margins demonstrate that off mexico a much greater percentage of the organic matter produced in the surface ocean reached the sediments 15 vs 8 for mexico and washington respectively on the mexican margin 8 of the primary production escaped oxidation in the surface sediments to be permanently buried as compared with only 1 2 of the primary production on the washington margin this suggests that oxygen deficient conditions on mexican margin are linked to enhanced carbon preservation

madagascar a pacemaker for the agulhas current system 1 western boundary currents are driven by zonally integrated wind stress curl over the width of subtropical basins this cross basin integration is interrupted in the south indian ocean where madagascar presents a formidable barrier nevertheless a western boundary current has been thought to exist in the mozambique channel the mozambique current recent observations have however shown that no such current exists and that the flow in the channel instead consists of a train of eddies is this western boundary anomaly due to the presence of madagascar we have used a primitive equations model to investigate the flow in the south west indian ocean as if there were no madagascar we show that a normal continuous western boundary current is then formed that constitutes a continuum with the agulhas current the presence of madagascar is shown to affect the frequency of inter ocean exchange events south of africa

oceanic origin of southeast tropical atlantic biases most coupled general circulation models suffer from a prominent warm sea surface temperature bias in the southeast tropical atlantic ocean off the coast of africa the origin of the bias is not understood and remains highly controversial previous studies suggest that the origin of the bias stems from systematic errors of atmospheric models in simulating surface heat flux and coastal wind or poorly simulated coastal upwelling in this study we show using different reanalysis and observational data sets combined with a set of eddy resolving regional ocean model simulations that systematic errors in ocean models also make a significant contribution to the bias problem in particular 1 the strong warm bias at the angola benguela front that is maintained by the local wind and the convergence of angola and benguela currents is caused by an overshooting of the angola current in ocean models and 2 the alongshore warm bias to the south of the front is caused by ocean model deficiencies in simulating the sharp thermocline along the angola coast which is linked to biases in the equatorial thermocline and the complex circulation system within the benguela upwelling zone

phosphorus accumulation in marine sediments and the oceanic phosphorus cycle ideas about key factors in the oceanic mass balance of dissolved reactive phosphate have changed substantially i present an integrated overview of these here with an emphasis on evaluating the burial sinks for p and defining areas needing further research the major source of reactive p to the ocean is river input reactive p is delivered to the oceanic sediment water interface primarily in particulate organic matter p scavenged by hydrothermal iron rich oxyhydroxide particles with uptake in proportion to deep water phosphate concentrations represents a substantially smaller flux to the sediment water interface diagenetic transformations are important influences on the form of reactive p burial in marine sediments p burial occurs with organic carbon burial and as p associated with iron rich oxyhydroxide particles and coatings formation of authigenic p rich phases presumably apatite at the expense of organic p and oxide associated p is significant in open ocean marine sediments the authigenic p sink may represent a substantially larger portion of the sedimentary burial than indicated by previous estimates focused on p burial in organic rich continental margin sediments

uplift of africa as a potential cause for neogene intensification of the benguela upwelling system the benguela current cooled over the past 12 million years numerical modelling suggests that uplift of parts of africa during this time enhanced coastal low level winds and promoted greater upwelling of cool subsurface waters

mesoscale eddy buoyancy flux and eddy induced circulation in eastern boundary currents abstracta dynamical interpretation is made of the mesoscale eddy buoyancy fluxes in the eastern boundary currents off california and peru chile based on regional equilibrium simulations the eddy fluxes are primarily shoreward and upward across a swath several hundred kilometers wide in the upper ocean as such they serve to balance mean offshore air sea heating and coastal upwelling in the stratified interior the eddy fluxes are consistent with the adiabatic hypothesis associated with a mean eddy induced velocity advecting mean buoyancy and tracers furthermore with a suitable gauge choice the horizontal fluxes are almost entirely aligned with the mean horizontal buoyancy gradient consistent with the advective parameterization scheme of gent and mcwilliams the associated diffusivity is surface intensified matching the vertical stratification profile the fluxes span the across shore band of high eddy energy but their alongshore structure is unresolved because of sampling limitations in the sur

hydrographic variability in the st helena bay region of the southern benguela ecosystem cross shelf distributions of temperature salinity water masses and dissolved oxygen in st helena bay revealed substantial vertical and seasonal variations in the surface layers nearshore and offshore temperature and salinity patterns differed with bay scale variability linked to upwelling dynamics and coastal processes while the offshore region was influenced by solar insolation spectral analysis revealed that an annual signal prevailed at most stations and corroborated contrasting patterns between the offshore and nearshore regions with phase differences suggesting shoreward propagation of the offshore temperature signal the shelf was dominated by modified upwelled water muw and subantarctic mode water samw which comprised the primary source of upwelled water clear zonation of muw was evident across the shelf resulting from seasonal variations in locations of the oceanic and bifurcated shelf break fronts dynamics within st helena bay consistently differed from those further offshore due to the influences of the shelf break front cape columbine upwelling plume and cyclonic recirculation which appeared to be associated with an intraannual signal with a periodicity of 3 4 months persistent hypoxia in the bottom waters suggested the occurrence of a permanent reservoir of low oxygen water low seasonal shoreward and offshore expansion of low occurred throughout the upwelling season with maximum extent reached during summer and autumn due to the coupled effects of advection and local phytoplankton decay while wind mixing ventilated the water column at nearshore stations in winter and the onset of upwelling during spring introduced oxygen richer water from further offshore hypoxia persisted in the center of the bay

a model study of the angola benguela frontal zone sensitivity to atmospheric forcing 1 a regional ocean model is applied to the tropical south east atlantic ocean in order to investigate the sensitivity of the intensity and position of the angola benguela frontal zone the results suggest that the position of the angola benguela frontal zone is mainly determined by opposing northward and southward flow within 2 degrees off the coast the windstress curl plays a major role in altering the position of the angola benguela frontal zone as it controls the southeastward flow of the south equatorial counter current the opposing northward flow is mainly the result of geostrophic adjustment to coastal upwelling driven by the meridional windstress the strength of the frontal zone is found to be related to the strength of the southerly windstress that controls the coastal upwelling

trace and rare earth element geochemistry of phosphate nodules from the lower cambrian black shale sequence in the mufu mountain of nanjing jiangsu province china abstract phosphate nodules are abundant in the lowermost section of the lower cambrian black shale sequence along a ne trend belt in the yangtze platform south china in this study we examined the neoproterozoic cambrian mufu mountain section near nanjing of jiangsu province and conducted a detailed trace and rare earth element ree study on the phosphate nodules we employed a step leaching acid dissolution protocol of 1 m hac and 1 m hcl respectively to separate carbonate from phosphate mineral contributions in the nodules both the hac leached and hcl leached fractions of the phosphate nodules show similar symmetrical variations in trace and ree concentrations and ratios the total rees and a number of redox sensitive trace metals such as v cr mo ni abundances show a systematic increase from the core to rim whereas the u and mn abundances decrease from the core to rim in most of the nodules similar trends are also observed for the rb sr u th co ni and v ni ratios but these trends in the hac leached fractions are less pronounced than the hcl leached fractions all of the hcl leached fractions for the nodule cores show seawater like shale normalized ree patterns but the rims of the nodules display slightly mree enriched and hree depleted patterns we suggest that the phosphate nodules may have formed in a basinal setting beneath a stratified water column during early cambrian and the compositional variations of rees and redox sensitive trace elements from the core to rim may record a changing redox condition and fluid mixing during different stages of nodule growth the cores of the nodules preserve more pronounced negative ce anomalies and progressively hree enriched patterns which may retain primary early cambrian seawater chemistry whereas the nodule rims record chemistry consistent with changed redox conditions and or influences from pore fluids such as generated from degradation of organic matter

relationship between phosphogenesis and sequence architecture sequence stratigraphy and biostratigraphy in the middle ordovician of the armorican massif nw france abstract in the armorican massif nw france the middle ordovician formations contain abundant phosphatic p beds associated with terrigenous sediments laid down on a storm dominated shelf facies analysis and sequence stratigraphy carried out on sections located in the crozon peninsula w armorican massif allow us to distinguish four p facies 1 beds with p nodules and crusts contained within sediments laid down on the distal and median parts of the inner shelf 2 amalgamated beds with p nodules and crusts and 3 beds with lingulid brachiopods heavy minerals and p clasts associated with retrogradation phases 4 p clast bearing conglomerates associated with progradation phases the genesis of these facies and their location in the depositional sequences are controlled by the fluctuation of terrigenous inputs during sea level changes sediment volume partitioning we propose a genetic model integrating the superposition of very high frequency vhf and high frequency hf eustatic signals in this model the amalgamated beds and beds with lingulid brachiopods heavy minerals and p clasts result from the superposition of several sea level rise episodes of vhf cycles occurring within the retrogradation phase of a hf cycle the lateral extension of p facies was investigated in the eastern part of the armorican massif benioc domfront les tanneries and st aubin du cormier sections several early darriwilian transgressive events associated with phosphogenesis episodes are dated through high resolution chitinozoan studies some of these transgressive events are at least of regional scale e g ornensis and protocalix transgressive events the topmost calix transgressive event is clearly identified over the northern gondwanan and avalonian domains and may reflect a global eustatic signature

speciation bioavailability and preservation of phosphorus in surface sediments of the changjiang estuary and adjacent east china sea inner shelf abstract the speciation potential bioavailability and preservation of phosphorus p in surface sediments of the changjiang yangtze river estuary and adjacent east china sea ecs inner shelf were investigated through the analyses of p fractions and sediment bulk properties a sequential extraction method sedex was used to separate and quantify the following six sedimentary p reservoirs exchangeable p ex p authigenic p au p detrital p de p organic p or p refractory p re p and fe bound p fe p total p tp in surface sediments ranged from 15 0 to 21 4 mol g 1 and was highest near the changjiang river mouth the average contribution of each form of p to tp was 55 6 de p 17 8 re p 16 1 or p 5 5 au p 2 5 ex p and 2 5 fe p respectively de p showed relatively higher concentrations in the river mouth and the ecs shelf region off the changjiang estuary high concentrations of or p were found mainly in mud areas showing a similar distribution pattern with silt sediment surface area ssa and total organic carbon toc re p was mainly distributed near the estuarine area and the zhe min coast bioavailable p bap accounted for 9 5 32 0 of tp with a mean of 21 2 and showed a similar distribution pattern to that of or p de p ssa and toc ssa loadings both decreased with increasing of ssa while or p ssa loadings varied little with ssa indicating that or p may have reached an adsorption desorption equilibrium on mineral surfaces toc to total organic p top sum of re p and or p ratios less than the redfield ratio 84 in average may have indicated efficient remineralization of organic matter in mobile muds of the changjiang estuary and adjacent ecs inner shelf furthermore the relatively high toc or p ratios 72 422 with a mean of 188 likely suggest a higher degree of preferential regeneration of labile or p over toc in sediments

diagenetic trends of fluorine concentration in negev phosphorites israel implications for carbonate fluorapatite composition during phosphogenesis an electron probe and chemical study of bulk phosphorite samples and separated constituents from various negev deposits was carried out together with xrd ftir spectroscopy and textural analysis the results allow a better understanding of the distribution of fluorine in these upper cretaceous phosphorite sequences and shed light on variations in the composition of the carbonate fluorapatite cfa phase during phosphogenesis two facies are recognized 1 a pristine microbially generated phosphorite facies 2 a recycled peloidal and biodetrital facies fluorine distribution in the negev phosphorites is facies controlled f p2o5 is much lower in the pristine facies 0 090 0 107 than in the recycled facies 0 107 0 120 in addition f p2o5 varies considerably between the various constituents of the phosphate fraction f poor francolites f p2o5 as low as 0 080 co exist with f rich francolites f p2o5 as high as 0 135 in the same phosphorite bulk sample a lower f p2o5 in francolite is associated with higher cd and zn concentrations in the phosphorite an increase in fe rich smectites in the clay fraction and the presence of structural oh in the francolite the lower f p2o5 ratios in the pristine facies are attributed to high organic deposition rates during the formation of these matted sediments leading to rapid burial of the in situ forming cfa this is possibly coupled with diffusion of f from sea water into bottom sediments being hampered by microbial mat coatings these conditions resulted in o2 depleted porefluids inducing the precipitation of cd rich zn sulphides and the formation of fe rich smectites f enrichment probably takes place when the earlier formed f poor primary cfa is relocated close to the sea floor and bathed with interstitial sea water solutions of higher f concentrations oxidation and removal of the sulphide bound cd and zn apparently occurred together with enrichment in f of the francolite combining chemical data with xrd and ftir results suggests a multistage growth for the negev phosphate constituents in shifting formational sites and porefluids of varying f concentrations this multiphase growth is reflected in the patchy distribution of f in the negev constituents and might explain the inverse correlation between mean co2 f and f p2o5 ratios of the analysed phosphorites in the two facies it also suggests that cfa or an amorphous precursor initially formed with some oh groups in the apatite structure which were subsequently substituted by f ions in recycled francolite through re equilibration with porefluids of higher f concentrations

average circulation seasonal cycle and mesoscale dynamics of the peru current system a modeling approach h isolines the pccc appears to be directly forced by the cyclonic wind stress curl the model is able to produce the upwelling front the cold water tongue which extends toward the equator and the equatorial front as described in the literature model seasonal changes in sst and ssh are compared to measurements for the central pcs model eke is 10 to 30 lower than the observations the model eddy diameters follow a strong equatorward increase the injection length scales derived from the energy spectra strongly correlate to the rossby radius of deformation confirming the predominant role of baroclinic instability at 3 s the model solution appears to switch from a turbulent oceanic regime to an equatorial regime dominated by zonal currents

filaments on the western iberian margin a modeling study coastal upwelling filaments off the western iberian margin detected in avhrr satellite imagery and in a realistic roms simulation of sea surface temperature were studied in the upwelling seasons may october of 2001 2010 sea surface temperature data were retrieved from avhrr satellite imagery and from a realistic roms numerical simulation the development and variability of the observed filaments were characterized and analyzed during each upwelling season of the 10 year period filaments were generally found anchored to the main bathymetric and coastal features but off the more regular northern coast of the western iberian margin their locations were more variable the results from the modeling analysis reproduced well the general features of filament development moreover results of model and observation showed very similar characteristics as those found in the earlier study of haynes et al 1993 the model output was used to relate filament patterns eddy activity and wind forcing there was a clear relation between upwelling favorable wind strength and number and length of filaments although the relation was weaker in the north of the region model filaments were clearly related to eddies only during periods of weak winds the filament detection method was also applied to a climatologically forced roms simulation which reproduced only gross features of the observed and interannually forced model filament development this suggests that direct wind forcing and its spatial structure are highly important

the benguela a laboratory for comparative modeling studies abstract equilibrium dynamics of the benguela system is investigated using the holistic nature of the spatially and temporally cohesive output of a numerical model the regional ocean modeling system roms is used to simulate the benguela system in its entirety it successfully simulates the cool coastal upwelling regime and its division into seven distinctly separate cells as well as the large scale offshore regime and the respective seasonal fluctuations it does however present a cool bias at the coast due to an underestimation of the coastal wind drop off as well as a warm bias offshore in the southern benguela due to the overestimation of agulhas current input the benguela can be divided into northern and southern regimes based on dynamic as well as topographic differences topographically the division between the northern and southern regimes coincides with an abrupt narrowing of the continental shelf toward the north at 28 s the large scale depth integrated flow to the north of this feature is weak but distinctly poleward while to the south the flow regime is governed by the meandering nature of the equatorward benguela current and is the pathway for eddies that originate at the agulhas retroflection the poleward flowing regime of the northern benguela is tied to the sverdrup relation which links meridional transport with wind stress curl the luderitz upwelling cell at 27 s experiences the most vigorous upwelling throughout the year and as a result offshore volume fluxes in this region are extremely large this upwelling cell divides the northern and southern benguela coastal upwelling systems into separate regimes based on the fact that their seasonal signals are out of phase the offshore gradient of eddy kinetic energy eke is generally strong in the benguela system and exceptionally so in the southern benguela due to vigorous mesoscale activity offshore of the shelf edge originating from the agulhas retroflection area the juxtaposition between the steep offshore eke gradients in the south and much weaker offshore gradients of eke in the northern benguela has different implications for cross shore exchanges

early diagenesis of organic matter in peru continental margin sediments phosphorite precipitation abstract pore water chemistry total dissolved co 2 nh 4 no 3 no 2 po 4 si oh 4 ca mg fe mn so 4 h 2 s and f and titration alkalinity solid phase chemistry c org p org c tot n tot f si opal and s ii and sediment characteristics porosity dry bulk density and formation factors were determined on a centimeter scale spacing in the upper 20 40 cm of sediments under intense upwelling areas on the peru continental shelf these data demonstrate that carbonate fluorapatite cfa is precipitating from pore waters in the upper few centimeters of a gelatinous mud with high organic carbon content up to 20 c org very high porosity 0 96 ml cm 3 and very low dry bulk density 3 dissolved phosphate concentrations at the sediment water interface range from 20 to 100 m orders of magnitude higher than bottom water concentrations and much higher than predicted from regeneration of organic matter the mechanism of this interfacial phosphate release is unclear but is apparently uncoupled from carbon and nitrogen metabolism and thus may be linked either to dissolution of fish debris or to the presence of a microbial mat in surficial sediments fluoride is incorporated into cfa by diffusion from the overlying seawater and carbonate ions are provided from pore water alkalinity magnesium concentrations in this reaction zone are not significantly different from those of seawater suggesting that magnesium depletion is not a necessary prerequisite for cfa precipitation the environment of precipitation is interface linked rather than driven by organic diagenesis of phosphorus deeper in the sediment most of the cores display a wide range of diagenetic characteristics below the immediate interfacial region but almost all show the precipitation signature near the interface this interface linked early diagenetic porewater environment for the precipitation of cfa explains many of the geochemical characteristics of phosphorites and provides a testable model to compare the modern phosphogenic analog with ancient phosphorite deposits two of the cores display very high solid phase phosphorus and fluoride contents reflecting the presence of apparently modern pelletal apatites