modeling study of turbulent mixing over the continental shelf comparison of turbulent closure schemes limitation is imposed during upwelling favorable winds the majority of turbulent mixing occurs in the top and the bottom boundary layers and in the vicinity of the vertically and horizontally sheared coastal jet turbulent mixing in the coastal jet is primarily driven by shear production the near surface flow on the inner shelf becomes convectively unstable as wind stress forces the upwelled water to flow offshore in the surface layer during downwelling favorable winds the strongest mixing occurs in the vicinity of the downwelling front the largest turbulent kinetic energy and dissipation are found near the bottom of the front turbulence in the bottom boundary layer offshore of the front is concentrated between recirculation cells which are generated as a result of symmetric instabilities in the boundary layer flow index terms 4219 oceanography general continental shelf processes 4568 oceanography physical turbulence diffusion and mixing processes 4255 oceanography general numerical modeling 4279 oceanography general upwelling and convergences

volcanic plutonic parity and the differentiation of the continental crust the continental crust is central to the biological and geological history of earth however crustal heterogeneity has prevented a thorough geochemical comparison of its primary igneous building blocks volcanic and plutonic rocks and the processes by which they differentiate to felsic compositions our analysis of a comprehensive global data set of volcanic and plutonic whole rock geochemistry shows that differentiation trends from primitive basaltic to felsic compositions for volcanic versus plutonic samples are generally indistinguishable in subduction zone settings but are divergent in continental rifts offsets in major and trace element differentiation patterns in rift settings suggest higher water content in plutonic magmas and reduced eruptibility of hydrous silicate magmas relative to dry rift volcanics in both tectonic settings our results indicate that fractional crystallization rather than crustal melting is predominantly responsible for the production of intermediate and felsic magmas emphasizing the role of mafic cumulates as a residue of crustal differentiation a global geochemical data set of volcanic and plutonic rocks indicates that differentiation trends from primitive basaltic to felsic compositions for volcanic versus plutonic samples are generally indistinguishable in subduction zone settings but are divergent in continental rifts brenhin keller and co authors present a global geochemical dataset of the two fundamental building blocks of the continental crust volcanic externally erupted and plutonic internally solidified rocks their results indicate that differentiation trends from primitive basaltic to felsic compositions for volcanic versus plutonic samples are generally indistinguishable in subduction zone settings but divergent in continental rifts offsets in major and trace element differentiation patterns in rift settings suggest higher water content in plutonic magmas and reduced eruptibility of hydrous silicate magmas relative to dry rift volcanics this work indicates that in both tectonic settings fractional crystallization rather than crustal melting is predominantly responsible for the production of intermediate and felsic magmas

weathering and the mobility of phosphorus in the catchments and forefields of the rhone and oberaar glaciers central switzerland implications for the global phosphorus cycle on glacial interglacial timescales abstract in this study we evaluate the dynamics of the biophile element phosphorus p in the catchment and proglacial areas of the rhone and oberaar glaciers central switzerland we analysed erosion and dissolution rates of p containing minerals in the subglacial environment by sampling water and suspended sediment in glacier outlets during three ablation and two accumulation seasons we also quantified biogeochemical weathering rates of detrital p in proglacial sedimentary deposits using two chronosequences of samples of fresh suspended material obtained from the oberaar and rhone water outlets little ice age lia moraines and younger dryas yd tills in each catchment subglacial p weathering is mainly a physical process and detrital p represents more than 99 of the precipitation corrected total p denudation flux 234 and 540 kg km 2 yr 1 for the rhone and oberaar catchments respectively the calculated detrital p flux rates are three to almost five times higher than the world average flux the precipitation corrected soluble reactive p srp flux corresponds to 1 88 1 99 kg km 2 yr 1 rhone and 2 12 2 44 kg km 2 yr 1 oberaar respectively these fluxes are comparable to those of tropical rivers draining transport limited tectonically inactive weathering areas in order to evaluate the efficiency of detrital p weathering in the rhone and oberaar proglacial areas we systematically graded apatite grains extracted from the chronosequence in each catchment relative to weathering induced changes in their surface morphologies grades 1 4 fresh apatite grains are heavily indented and dissolution rounded grade 1 lia grains from two 0 10 cm deep moraine samples show extensive dissolution etching similar to surface grains from the yd profile mean grades 2 7 3 5 and 3 5 respectively in these proglacial deposits the weathering front deepens progressively as a function of time due to biocorrosion in the evolving acidic pedosphere with mechanical indentations on grains acting as sites of preferential dissolution we also measured iron bound organic and detrital p concentrations in the chronosequence and show that organic and iron bound p has almost completely replaced detrital p in the top layers of the yd profiles detrital p weathering rates are calculated as 310 and 280 kg km 2 yr 1 for lia moraines and 10 kg km 2 yr 1 for yd tills during the first 300 years of glacial sediment exposure p dissolution rates are shown to be approximately 70 times higher than the mean global dissolved p flux from ice free continents after 11 6 kyr the flux is 2 5 times the global mean these data strengthen the argument for substantial changes in the global dissolved p flux on glacial interglacial timescales a crude extrapolation from the data described here suggests that the global dissolved p flux may increase by 40 45 during the first few hundred years of a deglaciation phase

chemical stability of the atmosphere and ocean abstract the earth system processes most of the chemical components of its atmosphere and oceans in geologically short periods of time it does this in a regulated way one that maintains a remarkably constant surface environment this we know primarily from the fossil record of uninterrupted complex life on earth that extends over the last billion years we are only beginning to understand the feedbacks that control the chemistry of the oceans and atmosphere numerical models of biogeochemical cycles are most stable when there is feedback between the amount of a chemical component in the ocean or atmosphere and its transfer to or from that reservoir coupling of subsystem especially of those operating on different time scales enhances stability an example of the role of feedback in stabilizing earth s chemical environment is the mechanism of control of atmospheric oxygen there appears to be no strong relationship between oxygen level and oxygen consumption however oxygen production may be a function of oxygen level the burial rate of organic carbon oxygen production in marine sediments may be sensitive to bottom water oxygenation levels also combustion may be an effective mechanism of transferring nutrients namely phosphorus from efficient terrestrial ecosystems to less efficient marine ecosystems when o2 rises fires become more frequent and p is transferred to the ocean stimulating marine organic carbon burial but depressing global burial rates global o2 production rates decline as does the o2 level a negative feedback models of ocean chemical composition are presently incapable of reproducingthe temporal constancy indiated by geological observations these models do not incorporate ion exchange equilibria as important processes in marine geochemical cycles when included these equilibria significantly damp the fluctuations in ion ratios calculated by the extant models

did a katian large igneous province trigger the late ordovician glaciation a hypothesis tested with a carbon cycle model abstract the ordovician is known as a period with high temperatures and high sea levels and a cooling event at the end of the period leading to the hirnantian glaciation and the first of the big five mass extinctions of marine life the cause of this cooling event remains unclear several authors correlate it with a drop in atmospheric p co 2 to a threshold permitting the ice accumulation on the gondwana supercontinent however what are the reasons of the atmospheric p co 2 decrease here we follow the hypothesis initiated by barnes 2004 that an ordovician superplume event occurred during the middle to late ordovician such an event would not only have a large impact on the ordovician biodiversification barnes 2004 but it would also be responsible for the climatic upheaval during the late ordovician by the emplacement of a low latitudinal continental basaltic province that had an impact on the atmospheric p co 2 there is no direct evidence of a superplume event or of basaltic traps and the present study is therefore a hypothetical modelling approach where we demonstrate with a numerical box model including carbon alkalinity and phosphorus cycles coupled with a 1d climate model energy balance model ebm francois and walker 1992 that such a scenario allows to explain both the mid ashgill katian global warming event known as the boda event fortey and cocks 2005 and the subsequent late ordovician hirnantian glaciation because silicate weathering is enhanced upon warm and wet climate we try to constrain the size and the latitudinal emplacement of the basaltic province leading to a sufficient consumption of atmospheric p co 2 to the threshold proposed by herrmann et al 2004 a b to initiate a glaciation on gondwana

solubilities of some hydrous ree phosphates with implications for diagenesis and sea water concentrations abstract solubility product determinations suggest that the hydrous phosphates of the rare earths repo4 xh 2 o are important in controlling the sea water ree concentrations two of these solids rhabdophane p6222 and hydrous xenotime 141 amd have been synthesized at 100 c via the acid hydrolysis of the respective ree pyrophosphate the solubility products at infinite dilution were determined to be pk 0 24 5 la at 25 c 26 0 pr at 100 c 25 7 nd at 100 c and 25 5 er at 100 c on the basis of calculations involving the reaction of re3 with apatite to form the hydrous phosphate the lanthanum concentration in sea water is predicted to be about 140 pmol l laboratory experiments support the hypothesis that apatite is a substrate for reactions with dissolved ree

modeling phosphorus cycling and carbon burial during cretaceous oceanic anoxic events article i nfo in the greenhouse world of the cretaceous there were episodes of oxygen depletion in the deep ocean associated with enhanced organic carbon burial in sediments black shale formation in this study we use a box model of the oceanic phosphorus p organic carbon orgc and oxygen cycles to explore the hypothesis that variations in marine p availability control deep ocean oxygen depletion anoxia and the formation of black shales under cretaceous ocean conditions we find that for the cretaceous ocean with large continental shelves slow oceanic overturning and high sea surface temperatures oceanic anoxic events oaes can be triggered by enhanced p supply from land and that the system is particularly sensitive to oceanic mixing in our baseline scenario the deep sea becomes completely anoxic while the shelves attain only partial anoxia sedimentary burial differs between the shelves and open ocean while organic carbon burial is enhanced in both regions deep sea reactive p burial decreases dramatically under anoxia but not on the shelves where oxygen depletion is not complete furthermore our model results imply that oaes can be sustained by p recycling from sediments under low oxygen conditions ultimately however the feedbacks which result in the accumulation of atmospheric oxygen terminate the anoxic event atmospheric oxygen is modulated by land processes such as forest fires and oxidative weathering which limit the rise of atmospheric o2 our model findings are corroborated by p burial data from the geological record for oae2 approximately 94 myr bp through a sensitivity analysis we identify two necessary criteria for oaes low mixing of surface and deep waters poor ocean ventilation and enhanced sedimentary p recycling under low oxygen conditions when these criteria are met ocean anoxia is a robust result to a mild increase of continental supply of phosphorus under a wide range of environmental conditions

development of a modified sedex phosphorus speciation method for ancient rocks and modern iron rich sediments abstract we report the development of a modified method for evaluating different reservoirs of sedimentary phosphorus p in ancient marine sedimentary rocks and in modern fe rich sediments utilising the existing sedex scheme for p partitioning in modern sediments we initially demonstrate limitations in the application of the original scheme to sediments and rocks containing crystalline hematite and magnetite we tested additional extractions for these crystalline fe phases using both synthetic minerals and modern and ancient sediments the addition of 6 h oxalate and 6 h citrate dithionate acetate extractions considerably enhanced the total recovery of synthetic magnetite and hematite to 88 7 1 1 and 76 9 3 8 respectively in addition application of the 6 h oxalate extraction to synthetic p containing magnetite recovered 93 9 1 7 of the fe present and 88 2 12 8 of the co precipitated p based upon these results we developed a modified sedex extraction scheme the modified scheme was applied to modern fe rich sediments from golfo dulce costa rica which resulted in 16 higher fe bound p recovery application of the scheme to a variety of ancient marine rocks increased the recovery of fe bound p by up to 22 we also highlight the potential for authigenic carbonate fluorapatite to convert to more crystalline apatite in ancient rocks during deep burial and metamorphism we suggest that in such systems minimum and maximum estimates of the total reactive p pool may be calculated with and without the inclusion of crystalline p it is noted that the application of the revised method may have important implications for understanding the cycling of p in ancient marine environments

atmospheric co2 content in the last 120 000 years the phosphate extraction model broecker 1982 has proposed that during the retreat of the wisconsin ice sheets atmospheric co2 increased because of the extraction of phosphorus from the ocean as sea level rose using a time dependent box model we examine the consequences of the phosphate extraction hypothesis over the last 120 000 years assuming that 18o change in core v28 238 is analogous to sea level variation the model takes into account the total co2 and alkalinity balance in the deep sea and in an upper reservoir consisting of the surface ocean and atmosphere which are assumed to be in equilibrium dissolution of deep sea calcium carbonate sediment is assumed to respond to the supply of particulate carbonate from the upper box and to the dissolved carbonate ion concentration of the deep sea assuming 1015 mole of phosphorus and 1017 mole of carbon were extracted during deglaciation the predicted increase in pco2 is 54 ppm variation of pco2 follows the ice volume forcing function with a 1000 yr lag which is the input residence time of water in the deep sea the accumulation supply minus dissolution of caco3 and the percent preservation accumulation over supply follow the derivative of the ice volume function both are similar to the solution index and percent fragments of core v28 238 in addition unusually good preservation is predicted during deglaciation due to carbon extraction if phosphorus but not carbon is assumed to be extracted the accumulation of caco3 varies little remaining near a value equivalent to the river input

paleoenvironmental changes during the valanginian new insights from variations in phosphorus contents and bulk and clay mineralogies in the western tethys paleoenvironmental and paleoclimatic changes during the valanginian carbon isotopic excursion cie have been investigated in the western tethys for this purpose bulk rock and clay mineralogies as well as phosphorus p contents were evaluated in a selection of five sections located in the vocontian basin angles se france alvier e switzerland malleval e france and the lombardian basin capriolo n italy breggia s switzerland within the cie interval bulk rock and clay mineralogies are inferred to reflect mostly climate change the onset of the cie busnardoites campylotoxus ammonite zone is characterized by higher detrital index di sum of the detrital minerals divided by calcite contents values and the presence of kaolinite in their clay mineral assemblages in the late valanginian from the saynoceras verrucosum zone up to the end of the valanginian the samples show relatively variable di and lower values or the absence of kaolinite the variation in the mineralogical composition is interpreted as reflecting a change from a climate characterized by optimal weathering conditions associated with an increase in terrigenous input on the southern european margin during the cie towards an overall unstable climate associated with drier conditions in the late valanginian this is contrasted by a dissymmetry proximal vs distal along the studied transect the northern tethyan margin being more sensitive to changes in continental input compared to the distal environments p accumulation rates par present similar features in the vocontian basin p content variations are associated with changes in terrigenous influx whereas in the lombardian basin i e capriolo and breggia par values are less well correlated this is mainly because the deeper part of the tethys was less sensitive to changes in continental inputs the onset of the cie top of the b campylotoxus zone records a general increase in par suggesting an increase in marine nutrient levels this is linked to higher continental weathering rates and the enhanced influx of nutrients into the ocean in the period corresponding to the shift itself p contents show a dissymmetry between the vocontian and lombardian basins proximal vs distal for the sections of malleval alvier and angles a decrease in p concentrations associated to a decrease in detrital input is observed in capriolo and breggia par show maximum values during the plateau indicating a more complex interaction between different p sources the time interval including the top of s verrucosum zone up to the end of the valanginian is characterized by variable par values suggesting variable nutrient influxes these changes are in agreement with an evolution towards seasonally contrasted conditions in the late valanginian

early diagenetic processes in deep labrador sea sediments reactive and nonreactive iron and phosphorus a sequential extraction procedure was applied to separate the oxides and lithogenous phases of iron and manganese and the organic and inorganic phosphorus phases in four box cores and one piston core from the slopes and rises of the labrador sea sedimentation rate rather than the location in the basin appears as a master variable of the diagenetic transformations of fe mn and p high sedimentation rate characteristic of two of the box cores led to the creation of zones near the redox boundary of partial reprecipitation of dissolved fe mn and p released in the deeper reducing portions of the sediments in contrast surficial sediments from box cores with 10 times lower sedimentation rate only have sufficient reductive capacity to remobilize mn hydroxides while leaving the fe oxyhydroxides intact under these conditions there is evidence for a redistribution of reactive inorganic p leading to the crystallization of carbonate fluorapatite in the top 30 cm of the cores gradual transformation of bur

phosphorus in foraminiferal sediments from north atlantic ridge cores and in pure limestones samples of foraminiferal ooze from two north atlantic cores were cleaned and progressively dissolved most of the p fe and mn was released during the first of two reductive cleaning steps most of the remainder of these elements and most of the ca were released during the final acid dissolution step the p in these samples is present largely in fe and mn rich coatings not as a constituent of the foraminiferal shells themselves our results are consistent with those of earlier studies the concentration of p in carbonate oozes in which it is clearly associated with coatings is similar to that of modern calcareous sediments in general and with that of reasonably pure limestones of all ages phosphorus is apparently associated with fe mn oxide coatings in many carbonate sediments the rate of removal of p from the oceans as a constituent of such sediments depends on the rate of formation of fe mn coatings not on the rate of incorporation of p into calcium carbonate

on the origin of a phosphate enriched interval in the chattanooga shale upper devonian of tennessee a combined sedimentologic petrographic and geochemical study abstract the devonian chattanooga shale contains an uppermost black shale interval with dispersed phosphate nodules this interval extends from tennessee to correlative strata in kentucky indiana and ohio and represents a significant period of marine phosphate fixation during the late devonian of north america it overlies black shales that lack phosphate nodules but otherwise look very similar in outcrop the purpose of this study is to examine what sets these two shales apart and what this difference tells us about the sedimentary history of the uppermost chattanooga shale in thin section the lower black shales pbs show pyrite enriched laminae and compositional banding the overlying phosphatic black shales phbs are characterized by phosbioclasts have a general banded to homogenized texture with reworked layers and show well defined horizons of phosphate nodules that are reworked and transported in the phbs up to 8000 particles of p debris per cm2 occur in reworked beds whereas the background black shale shows between 37 88 particles per cm2 in the pbs the shale matrix contains between 8 16 phosphatic particles per cm2 the shale matrix in the phbs contains 5 6 inertinite whereas just 1 inertinite occurs in the pbs the shale matrix in both units is characterized by flat ree patterns shale normalized whereas phosbioclast rich layers in the phbs show high concentrations of rees and enrichment of mrees negative ce anomalies are common to all samples but are best developed in association with phosbioclasts redox sensitive elements co u mo are more strongly enriched in the pbs when compared to the phbs trace elements associated with organic matter cu zn cd ni show an inverse trend of enrichment deposited atop a sequence boundary that separates the two shale units the phbs unit represents a transgressive systems tract and probably was deposited in shallower water than the underlying pbs interval the higher phosphate content in the phbs is interpreted as the result of a combination of lower sedimentation rates with reworking winnowing episodes three types of phosphatic beds that reflect different degrees of reworking intensity are observed strong negative ce anomalies and abundant secondary marcasite formation in the phbs suggests improved aeration of the water column and improved downward diffusion of oxygen into the sediment the associated oxidation of previously formed pyrite resulted in a lowering of pore water ph and forced dissolution of biogenic phosphate phosphate dissolution was followed by formation of secondary marcasite and phosphate repeated episodic reworking caused repetitive cycles of phosphatic dissolution and reprecipitation enriching mrees in reprecipitated apatite a generally deeper seated redox boundary favored p remineralization within the sediment matrix and multiple repeats of this process in combination with wave and current reworking at the seabed led to the formation of larger phosphatic aggregates and concentration of phosphate nodules in discrete horizons

diagenetic evolution of the upper devonian phosphorites alborz mountain range northern iran abstract the upper devonian mixed siliciclastic carbonate stratigraphic succession of the geirud formation in the alborz mountain range north of iran hosts numerous phosphorites and phosphatic rocks these phosphorites which represent one of the most globally important deposits in the devonian have gained little attention regarding their genesis and diagenetic evolution this study focuses mainly on the post depositional changes that occurred during shallow to deep burial diagenetic evolution and subaerial weathering of the geirud phosphorites the phosphorites consist of phosphatic massive mudclasts detritus rich lithoclasts bioclasts and bones formed by several stages of phosphogenesis and erosion reworking winnowing and condensation associated with famennian sea level changes the phosphatic clasts consist of early diagenetic poorly crystalline carbonate fluorapatite cfa and pyrite cementing detrital quartz illite muscovite rutile and zircon phosphatic clasts are intensely compacted with sutured grain contacts along which dissolution and reprecipitation of chemically refined well crystalline cfa with a bright blue cathodoluminescence and illite occurred during deep burial diagenesis similarly quartz shows deformation planar features overgrowth cement was developed as a result of pressure dissolution in phosphatic sandstones followed by precipitation of ferroan dolomite ankerite and chlorite in secondary porosity subaerial weathering led to oxidation of pyrite and generation of acidic ph condition under which ca and p from phosphates fe and s from pyrite fe ca mg and mn from ferroan carbonates and al and si from aluminosilicates were released to form goethite psilomelane calcite gypsum and crandallite the paas normalized rare earth elements rees show bell shaped patterns with middle rees enrichment positive eu anomaly and a weak negative ce anomaly this implies recrystallization of cfa in phosphorites and phosphatic rocks during deep burial diagenesis deviating from the modern seawater like ree patterns in this regard deep burial diagenesis affecting the upper devonian geirud phosphorites is possibly a common process in the proterozoic paleozoic phosphorites in northern iran and elsewhere in the world

intensification of ocean fronts by down front winds abstract many ocean fronts experience strong local atmospheric forcing by down front winds that is winds blowing in the direction of the frontal jet an analytic theory and nonhydrostatic numerical simulations are used to demonstrate the mechanism by which down front winds lead to frontogenesis when a wind blows down a front cross front advection of density by ekman flow results in a destabilizing wind driven buoyancy flux wdbf equal to the product of the ekman transport with the surface lateral buoyancy gradient destabilization of the water column results in convection that is localized to the front and that has a buoyancy flux that is scaled by the wdbf mixing of buoyancy by convection and ekman pumping suction resulting from the cross front contrast in vertical vorticity of the frontal jet drive frontogenetic ageostrophic secondary circulations ascs for mixed layers with negative potential vorticity the most frontogenetic ascs select a preferred cross front width and do not translate with

apatite weathering and the phanerozoic phosphorus cycle despite widespread debate in the literature there is still considerable uncertainty concerning which nutrient ultimately controls marine net ecosystem production nep over geologic time geochemical arguments suggest that phosphorus is the culprit the weathering of apatite the primary phosphorus sink in earth s exosphere controls long term phosphorus availability if phosphorus is the ultimate controlling nutrient over geologic time scales then long term marine nep is coupled to the release of phosphorus from apatite weathering the most abundant apatite compositions found in nature are igneous fluorapatite and marine sedimentary carbonate fluorapatite sparse data exist on how these compositions dissolve under earth s surface conditions to demonstrate a need for these data and their application we present a kinetic treatment of existing data augmented by new results we then use these results in a weathering model designed to illustrate the control exerted by temperature via activation energy and surface area on the phosphorus flux from apatite dissolution during the phanerozoic our conclusion is that activation energy and hence temperature and apatite surface area are important parameters governing the phosphorus flux from apatite weathering and therefore marine nep during phanerozoic time

landslide susceptibility mapping of vicinity of yaka landslide gelendost turkey using conditional probability approach in gis on 19 february 2007 a landslide occurred on the alaardic slope located 1 6 km south of the town of yaka gelendost turkey subsequently the displaced materials transformed into a mud flow in eglence creek and continued 750 m downstream towards the town of yaka the mass poised for motion in the yaka landslide source area and its vicinity which would be triggered to a kinetic state by trigger factors such as heavy or sustained rainfall and or snowmelt poise a danger in the form of loss of life and property to yaka with its population of 3 000 this study was undertaken to construct a susceptibility mapping of the vicinity of the yaka landslide s source area and to relate it to movement of the landslide mass with the goal of prevention or mitigation of loss of life and property the landslide susceptibility map was formulated by designating the relationship of the effecting factors that cause landslides such as lithology gradient slope aspect elevation topographical moisture index and stream power index to the landslide map as determined by analysis of the terrain through the implementation of the conditional probability method it was determined that the surface area of the goksogut formation which has attained lithological characteristics of clayey limestone with a broken and separated base and where area landslides occur possesses an elevation of 1 100 1 300 m a slope gradient of 15 35 and a slope aspect between 0 67 5 and 157 247 loss of life and property may be avoided by the construction of structures to check the debris mass in eglence creek the cleaning of the canal which passes through yaka the broadening of the canal s base area elevating the protective edges along the canal and the establishment of a protective zone at least 10 m wide on each side of the canal to deter against damage from probable landslide occurrence and mud flow

impact of oceanic reorganizations on the ocean carbon cycle and atmospheric carbon dioxide content a zonally averaged circulation biogeochemical ocean model is used to explore how the distribution of po4 and 13c in the major basins and the atmospheric pco2 respond to rapid changes in the thermohaline circulation thc different evolutions of the atlantic thc are simulated by applying surface freshwater pulses typical for example of heinrich events and the last deglaciation in the model when the thc completely collapses po4 increases 0 5 mmol m 3 and 13c decreases 1 because of a longer residence time of waters at the surface these surface anomalies are propagated to the bottom north atlantic when the thc resumes when the thermohaline overturning is only partly reduced and at shallower depths changes in bottom waters are accompanied by a po4 decrease and 13c increase at intermediate levels in the mid latitude atlantic this results in enhanced vertical gradients of these properties consistent with chemical and isotopic reconstructions for the last glacial maximum finally the atmospheric pco2 increases during the cold period in the north atlantic when the thc is reduced with an amplitude 7 30 atm and timescale 10 to 1 2 10 yr depending on the intensity of the thc change this is qualitatively consistent with recent data from an antarctic ice core documenting a pco2 increase during the younger dryas and after heinrich events 4 and 5

dynamics of the summer shelf circulation and transient upwelling off ningaloo reef western australia received 19 july 2012 revised 21 january 2013 accepted 25 january 2013 published 11 march 2013 1 the shelf circulation off ningaloo reef near the north west cape of western australia is driven by complex interactions between the southward flowing leeuwin current and wind driven currents that episodically reverse the coastal flow toward the north the presence of these northward equatorward wind driven currents is thought to make this section of coast one of the few locations along western australia to experience periodic coastal upwelling we used a combination of field observations and numerical modeling to investigate the summer circulation and upwelling dynamics along ningaloo reef we analyzed current and temperature profiles from moorings at four sites across the shelf and used two regional ocean modeling system roms sub models 1 a coarser model of northwestern australia forced by a global ocean model and 2 a nested fine scale model of the ningaloo region this nesting significantly improved model skill as it included the offshore mesoscale dynamics that strongly influenced the shelf circulation off ningaloo the field observations revealed several northward flow reversals accompanied by cooling of the coastal waters adjacent to ningaloo which were associated with strong northward wind events analysis of the coastal heat budget revealed that cooling events were primarily driven by upwelling whereas warming of coastal waters during relaxation events resulted mostly from along shelf advection of warm water from the north due to the combined effects of its relatively steep 1 50 slope shelf and strong summer stratification upwelled water was sourced from the interior of the water column likely influencing the sources and fluxes of nutrients to ningaloo reef

an intermediate complexity model for simulating marine biogeochemistry in deep time validation against the modern global ocean we present a new high resolution 1 d intermediate complexity box model icbm of ocean biogeochemical processes for paleoceanographic applications the model contains 79 reservoirs in three regions that should be generally applicable throughout much of earth history 1 a stratified gyre region 2 a high latitude convective region and 3 an upwelling region analogous to those found associated with eastern boundary currents transport processes are modeled as exchange fluxes between boxes and by eddy diffusion terms significant improvement in the representation of middepth oxygen budgets was achieved by implementing nonlocal mixing between the high latitude surface and gyre thermocline reservoirs the biogeochemical submodel simulates coupled c n p o and s systematics with explicit representation of microbial populations using a process based approach primary production follows redfield stoichiometry while water column remineralization is depth and redox couple dependent settling particulate organic matter is incorporated into a benthic submodel that accounts for burial and remineralization the c p ratio of burial depends on bottom water oxygen denitrification takes place both by classical and anammox pathways the icbm was tested against modern oceanographic observations from the global ocean data analysis project joint global ocean flux study and other databases comparisons of model output with circulation tracers including salinity cfc 12 and radiocarbon permit a test of the physical exchange scheme vertical profiles of biogeochemically reactive components in each of the three regions are in good agreement with observations under modern conditions the upwelling zone displays a pronounced oxygen minimum zone and water column denitrification while these are not present in the high latitude or gyre regions model generated global fluxes also compare well to independent estimates of primary production burial and phosphorous and nitrogen cycling the icbm appears to adequately simulate the long term kyr evolution of several biogeochemical cycles and improves on previous box models in several important ways in a companion paper the model s performance under euxinic conditions is tested against modern black sea data the simple and adaptable structure of the model should make it applicable to a wide range of paleoceanographic problems the model source code is available in matlabtm 7 m files provided as auxiliary material

fluxes to sediments underlying the rainbow hydrothermal plume at 36 14 n on the mid atlantic ridge abstract a geochemical investigation has been conducted of a suite of four sediment cores collected from directly beneath the hydrothermal plume at distances of 2 to 25 km from the rainbow hydrothermal field as well as a large biogenic component 80 caco3 these sediments record clear enrichments of the elements fe cu mn v p and as from hydrothermal plume fallout but only minor detrital background material systematic variations in the abundances of hydrothermal elements are observed at increasing distance from the vent site consistent with chemical evolution of the dispersing plume further pronounced ni and cr enrichments at specific levels within each of the two cores collected from closest to the vent site are indicative of discrete episodes of additional input of ultrabasic material at these two near field locations radiocarbon dating reveals mean holocene accumulation rates for all four cores of 2 7 to 3 7 cm kyr 1 with surface mixed layers 7 to 10 cm thick from which a history of deposition from the rainbow hydrothermal plume can be deduced deposition from the plume supplies elements to the underlying sediments that are either directly hydrothermally sourced e g fe mn cu or scavenged from seawater via the hydrothermal plume e g v p as holocene fluxes into to the cores surface mixed layers are presented which typically are an order of magnitude greater than background authigenic fluxes from the open north atlantic one core collected closest to the vent site indicates that both the concentration and flux of hydrothermally derived material increased significantly at some point between 8 and 12 14c kyr ago the preferred explanation is that this variation reflects the initiation intensification of hydrothermal venting at the rainbow hydrothermal field at this time perhaps linked to some specific tectonic event in this fault controlled hydrothermal setting

oceanic phosphorus imbalance magnitude of the mid ocean ridge flank hydrothermal sink 10 10 mol p yr 1 this value is larger 130 than the riverine dissolvedfluxofinorganicphosphateandisasmuchas35 of the sedimentary p sink the concordant seawater flux 2 1 10 16 kg yr 1 is 65 of the riverine fluid flux and circulates a fluidvolumeequivalenttotheentireoceaninabout70 000yr additional sampling of seafloor springs is required to further constrain the range of calculated phosphate fluxes nevertheless the modern phosphorus budget is clearly unbalanced with total sinks outpacing sources index terms 1045 geochemistry low temperature geochemistry 1050 geochemistry marine geochemistry 4835 4850 3015 marine geology and geophysics heat flow benthic and hydrothermal processes 4805 oceanography biological and chemical biogeochemical cycles 1615 4845 oceanography biological and chemical nutrients and nutrient cycling keywords ridge flank hydrothermal phosphate ocean drilling program geochemical cycles citation wheat c g j mcmanus m j mottl and e giambalvo oceanic phosphorus imbalance magnitude of the mid ocean ridge flank hydrothermal sink geophys res lett 30 17 1895 doi 10 1029 2003gl017318 2003

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

geochemistry of modern carbonaceous sediments overlain by a water mass showing photic zone anoxia in the saline meromictic lake kai ike southwest japan i early diagenesis of organic carbon nitrogen and phosphorus abstract the early diagenetic effects of organic matter om decomposition in carbonaceous sediments overlain by an anoxic water body were investigated using a sediment core kai4 from the saline meromictic lake kai ike in southwest japan lake kai ike a current model for past anoxic ocean environments is characterized by development of photic zone anoxia and a bacterial plate which create permanent density stratification in the water over the last 40 years rapid decreases in organic carbon corg 55 nitrogen 60 and reactive phosphorus p 85 contents accompanied by 1 increase positive shift in the stable isotope compositions of corg 13corg which is attributed to a preferential loss of low 13corg components during early diagenesis are reflected with increasing depth of the sediments the molar corg p and n p ratios increase with depth from initial values that are very close to those of the redfield ratio during the early diagenesis of om degradation the decomposition rate of p is much faster than that of corg and n in contrast the molar corg n ratios are rather insensitive to various biogeochemical reactions confirming their utility as a proxy for source om although the stable isotope compositions of nitrogen 15n in sedimentary om are useful indicators of om sources correlations to the above mentioned parameters for the kai4 core remain unclear we emphasize that the om present in ancient carbonaceous sediments or sedimentary rocks was most likely subject to very rapid

on the temporal memory of coastal upwelling off nw africa we use a combination of satellite in situ and numerical data to provide a comprehensive view of the seasonal coastal upwelling cycle off nw africa in terms of both wind forcing and sea surface temperature sst response wind forcing is expressed in terms of both instantaneous local and time integrated nonlocal indices and the ocean response is expressed as the sst difference between coastal and offshore waters the classical local index the cross shore ekman transport reproduces reasonably well the time latitude distribution of sst differences but with significant time lags at latitudes higher than cape blanc two nonlocal indices are examined one of them a cumulative index calculated as the backward averaged ekman transport that provides the highest correlation with sst differences reproduces well the timing of the sst differences at all latitudes except near cape blanc the corresponding time lags are close to zero south of cape blanc and range between 2 and 4 months at latitudes between cape blanc and the southern gulf of cadiz the results are interpreted based on calculations of spatial and temporal auto and cross correlations for wind forcing and sst differences at temporal scales of 2 3 weeks the alongshore advection of alongshore momentum compensates for interfacial friction allowing the upwelling jet and associated frontal system to remain active we conclude that the coastal jet plays a key role in maintaining the structure of coastal upwelling even at times of relaxed winds by introducing a seasonal memory to the system in accordance with the atmospheric forcing annual cycle

the role of nearshore slope on cross shore surface transport during a coastal upwelling event in gulf of finland baltic sea abstract the wind induced coastal upwelling process often contains a mid phase that involves coherent long living cross shore surface jets of cooler water these jets extend to 40 45 km from the coast and tend to start from particular coastal locations we develop a simple method for evaluating the depth in the water column from where the upwelled water originates we also test the hypothesis that the development of cross shore surface jets may be triggered by some permanent characteristics such as the bathymetry or the slope of the nearshore seabed the analysis is performed for a strong and well documented upwelling in the gulf of finland the baltic sea using high resolution bathymetry data satellite derived sea surface temperature surface currents measured by in situ drifters and properties of water masses in two sampling locations the results indicate that the cross shore jets originate exclusively from the shore sections with much steeper slopes 0 0075 than in the rest of the study area the cooler water most likely origins from intermediate water masses at depths between 15 and 30 m the resulting identification of the source depth of the upwelled water and its spatial location assists in understanding the flux of nutrients during upwelling events and their link to the onset of cyanobacteria blooms

phosphorus speciation and sedimentary phosphorus release from the gulf of mexico sediments implication for hypoxia abstract phosphorus p is an important macronutrient that can limit primary productivity in coastal marine ecosystems this study provides a quantitative determination of abundance and chemical speciation of p and potential anaerobic p release rates from northern gulf of mexico gom sediments seven sediment cores were collected from shelf slope and deep sea sediments in the northern gom a sequential extraction method was used to operationally separate p pools into readily available p fe al p alkali extractable organic p ca mg p and residual p ca mg p was the most abundant form of sediment p 79 0 9 4 of tp northern gom sediments were found to release 0 02 4 4 mg kg 1 d 1 of bioavailable p under anoxic sediment condition p release rate had significant positive correlation p 0 001 with the fe al p fraction indicating this relatively small pool of tp 0 4 10 2 is primarily releasing available p to the water column during hypoxia events the findings of this study suggest that the internal sedimentary p loading contributes substantial bioavailable p to the p limited water column which leads to increased primary production in the northern gom creating a positive feedback mechanism for hypoxia therefore the action plan to reduce the gom hypoxia zone needs to take internal sediment p loading into account when managing for watershed nutrient loading

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

co diagenesis of iron and phosphorus in hydrothermal sediments from the southern east pacific rise implications for the evaluation of paleoseawater phosphate concentrations abstract we present a detailed study of the co diagenesis of fe and p in hydrothermal plume fallout sediments from 19 s on the southern east pacific rise three distal sediment cores from 340 1130 km from the ridge crest collected during dsdp leg 92 were analysed for solid phase fe and p associations using sequential chemical extraction techniques the sediments at all sites are enriched in hydrothermal fe oxyhydr oxides but during diagenesis a large proportion of the primary ferrihydrite precipitates are transformed to the more stable mineral form of goethite and to a lesser extent to clay minerals resulting in the release to solution of scavenged p however a significant proportion of this p is retained within the sediment by incorporation into secondary goethite by precipitation as authigenic apatite and by readsorption to fe oxyhydr oxides molar p fe ratios for these sediments are significantly lower than those measured in plume particles from more northern localities along the southern east pacific rise and show a distinct downcore decrease to a depth of 12 m molar p fe ratios are then relatively constant to a depth of 35 m the fe and p speciation data indicate that diagenetic modification of the sediments is largely complete by a depth of 2 5 m and thus depth trends in molar p fe ratios can not solely be explained by losses of p from the sediment by diffusion to the overlying water column during early diagenesis instead these sediments are likely recording changes in dissolved p concentrations off the sepr possibly as a result of redistribution of nutrients in response to changes in oceanic circulation over the last 10 million years furthermore the relatively low molar p fe ratios observed throughout these sediments are not necessarily solely due to losses of scavenged p by diffusion to the overlying water column during diagenesis but may also reflect post depositional oxidation of pyrite originating from the volatile rich vents of the southern east pacific rise this study suggests that the molar p fe ratio of oxic fe rich sediments may serve as a proxy of relative changes in paleoseawater phosphate concentrations particularly if fe sulfide minerals are not an important component during transport and deposition

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

226ra in phosphate nodules from the peru chile seafloor abstract 226ra and other uranium series radionuclides have been measured in a suite of marine phosphorite samples from the upwelling area off peru chile by gamma ray spectrometry and radiochemical techniques our results lead to the following conclusions 1 phosphorite nodules typically show unidirectional growth at rates of 1 to 10 mm kyr 2 very young samples less than a few thousand years contain slight excess amounts of 226ra probably derived from pore fluids and 3 slow but persistent leakage of 226ra out of phosphate nodules occurs resulting in systematically lower 226ra ages compared to 230th ages for samples older than about twenty thousand years radium fluxes from these phosphate nodules appear to be 1 to 3 orders of magnitude less than those calculated for deep sea sediments and ferromanganese nodules

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

drifter behavior on the oregon washington shelf during downwelling favorable winds abstract drifters released offshore of oregon during predominantly downwelling favorable alongshore winds during three different deployments october 1994 january 1998 and september 1998 display similar behavior after being advected around in the offshore eddy field they move onshore to a particular isobath and are advected poleward alongshore without coming ashore numerical modeling results suggest that this may be due to downwelling circulation creating a marginally stable density gradient on the shelf inshore of the downwelling front thereby increasing the vertical eddy diffusivity which reduces the effective cross shelf ekman transport to nearly zero the downwelling front itself is accompanied by a poleward jet which carries drifters rapidly to the north this behavior is consistent with previous modeling results

carbon and nutrient geochemistry of the surface sediments of the gulf of riga baltic sea abstract the distribution of different forms of carbon nitrogen and phosphorus and standard physical sediment parameters of the surface sediments of the gulf of riga a shallow semi enclosed brackish bay of the baltic sea has been examined several measured parameters were highly correlated this is valid almost irrespectively of differences in depth below seafloor and sediment characteristics as well as location and extent of burial diagenesis preferential release of nitrogen n relative to carbon during organic matter decomposition seems to occur during halmyrolysis and or almost instantaneously upon settling at the sediment surface because the c org n org ratio is uniform 10 2 within all types of sediment preferential release of phosphorus p relative to both c and n also occurs and organic matter decomposition appears independent of the amount of c and n inorganic c and n in sediments normally constitute only a small proportion of the total c and n concentrations the amount of inorganically bound nitrogen depends to a great deal on the surface area of the adsorbing species and the clay mineral composition inorganic p usually constitutes more than 50 of the total amounts of p irrespective of physical and chemical differences between samples concerning early diagenesis the amount of inorganic p is controlled mainly by the release fixation on species prone to oxidation reduction reactions an estimate of the total amount of annually sequestered c n and p in the accumulation sediments suggests 44 000 5800 and 1100 ton year respectively for n and p this sequestering constitutes around 6 and 40 of the total annual load

phosphorus speciation in the sediment and mass balance for the central region of the great barrier reef continental shelf australia abstract solid phase p speciation has been determined in sediments from a transect across the central section of the continental shelf and slope of the great barrier reef gbr lagoon this region is characterized by a gradient of riverine aluminosilicate clay and silt nearshore seawards of which biogenic carbonate sediment predominates phosphorus speciation results show large variations along this transect organic p and authigenic apatite p are the major chemical forms of phosphorus in the central gbr continental shelf sediments post depositional reorganization of p was also observed converting organic p and iron bound p fe p to authigenic apatite p phosphorus burial rate was estimated from measurements of total p concentration and excess 210pb sediment mass accumulation rates burial efficiency varies significantly over the shelf inshore areas showed significant p remobilization from sediments to the water column up to 50 the mid and the outer shelf showed little evidence for remobilization except for coral reef platform sediments with more of the sediment p being in the less reactive authigenic apatite phases an appreciable fraction of this non labile authigenic apatite phase was identified as fish bone p sources and sinks over the central part of the gbr shelf were quantified using a mass balance approach this showed that coral sea shelf edge upwelling events are essential to satisfy the large p nutrient demand of the whole gbr lagoon p inputs due to upwelling events were greater than those contributed by local rivers over an average year

decoupling of p and corg burial following early cretaceous valanginian hauterivian platform drowning along the nw tethyan margin during the hauterivian three important phases of platform drowning phosphogenesis and mesotrophic carbonate deposition along the northern margin of the tethys are not mirrored by positive n 13 ccarb excursions such as during the valanginian and aptian but rather by decreasing to stable trends the aim of this study is to understand the decoupling of organic carbon and phosphorus burial during the hauterivian for this purpose po4 concentrations were determined from biogenic limestones from eight sections along a platform to basin transect integration with a previously obtained dataset for the valanginian leads to a biostratigraphically calibrated high resolution phosphorus accumulation rate mg cm 2 kyr curve based on 575 data points from the late valanginian to early hauterivian phosphorus accumulation rates increased nearly threefold from 0 75 mg cm 2 kyr to 2 1 mg cm 2 kyr the phosphorus accumulation rate increase obtained in this study correlates well with a compilation based on odp and dsdp records indicating that phosphorus accumulation rates along the northern margin of the tethys reflect global changes in p in and output a global rise in continental p input is thought to have resulted from intensified greenhouse climate conditions leading to increased riverine runoff coeval sea level rise led to re arrangement of circulation and oxygenation of bottom waters which meant that p was increasingly well retained by means of fe and mnoxyhydroxides furthermore the nw margin of the tethys may have been especially susceptible to phosphogenesis as it was influenced by cold water exchange with the boreal realm and prone to coastal upwelling the late hauterivian witnessed sea level fall more sluggish circulation along the nw tethyan margin and also globally lower weathering and erosion rates leading to generally lower phosphorus accumulation rates increased regeneration of phosphorus might have occurred as circulation stagnated and bottom water oxygen levels decreased increased phosphorus input into early hauterivian oceans did not lead to the production of organic carbon rich rocks but rather to increased carbonate carbon burial also seen in a decoupling between the n 13 ccarb record decreasing and phosphorus accumulation rates increasing decoupling of these records reflects the ecological recovery of the carbonate system after a prolonged phase of reef destruction during the late early and late valanginian carbonate production in the

pyrite and organic matter in normal marine sediments of middle cambrian age southern georgina basin australia normal marine sedimentary rocks of middle cambrian floran undillan age from the southern georgina basin have pyrite sorganic c ratios with a mean value of 0 65 and show a significant positive correlation with an extension of the line of best fit through zero the sc ratio of 0 65 determined in this study is close to the mean ratio for all cambrian sediments of 0 7 but differs markedly from the recently reported sc ratio of 2 for normal marine early palaeozoic rocks mainly from the united kingdom the variations shown by these figures indicate that if the oxidation state of the crust ocean atmosphere over geological time is to be fully understood and related to possible world wide trends further assessment of early palaeozoic sulfur and carbon burial rates is needed furthermore as sc burial rates are known to vary the ages of the sediments being analysed need to be more precisely known

exact solutions of wind driven coastal upwelling and downwelling over sloping topography abstractthe dynamics of wind driven coastal upwelling and downwelling are studied using a simplified dynamical model exact solutions are examined as a function of time and over a family of sloping topographies assumptions in the two dimensional model include a frictionless ocean interior below the surface ekman layer and no along slope dependence of the variables however dependence in the cross slope and vertical directions is retained density and the along slope component of momentum are advected by the cross slope velocity with thermal wind balance maintained at all times the time dependent initial value problem is solved with constant initial stratification and no initial along slope flow previously this model has been used to study upwelling over flat bottomed ocean but the novel features in this work are the study of exact solutions for a family of sloping topographic profiles for both upwelling and downwelling the exact solutions are compared to numerical solutions from a primitive equat

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

wind forced downwelling slope currents a numerical study abstract a study is made of the dynamics of slope currents that arise from a steady constant alongshore wind over a uniform shelf over the first 10 20 days the evolution of the downwelled system on an f plane is qualitatively described by linear coastal trapped wave dynamics after this time the thermal wind shear associated with the bottom mixed layer becomes important in the evolution of the undercurrent uc which is shown to be driven by the alongshore pressure gradient due to sea level as the uc over the slope evolves the bottom ekman transport becomes small and negative leading to the detachment of flow near the shelf break localized spreading of isopycnals and further intensification of the uc in contrast to results obtained without bottom drag bottom friction and boundary layer transport are shown to lead to a two to threefold increase in cross shelf interior transport downwelling and thermal wind shear by day 60 the resultant uc has speeds of up to 15 cm s 1 and a net transport of

the phosphorus cycle phosphogenesis and marine phosphate rich deposits abstract phosphorus in the form of phosphate is an essential nutrient and energy carrier on many different levels of life and a key element in mediating between living and lifeless parts of the biosphere one of the most important aspects of the phosphorus cycle is its vital role in governing productivity thereby interacting with the exogenic part of the carbon cycle which in turn is important in regulating earth s climate phosphorus is a prime element to be traced in earth s history because it allows for the reconstruction of long term feedback mechanisms between climate environment and ecology and of global change as such marine sedimentary phosphate deposits are particularly suited to study aspects of the phosphorus cycle because in the case of ubiquity their origin may result from a general acceleration of the global phosphorus cycle sources of sedimentary phosphate are microbial breakdown of buried organic matter and redox driven phosphate desorption from iron and manganese oxyhydroxides dissolved sea water phosphate represents an additional source which may become important in the formation of phosphatic hardgrounds the main locus of phosphogenesis is near the sediment water interface but phosphogenesis also occurs at greater sediment depths current induced winnowing and transport processes along the sea floor concentrate phosphate precipitates into deposits which exhibit internal stratification patterns typical for the prevailing hydraulic energy regime in a sequence stratigraphic context phosphate deposits preferentially occur along marine or maximum flooding surfaces consequent sedimentary reworking may result in the transfer of phosphates to highstand or lowstand deposits bio chemical weathering on continents represents the most significant source of bioavailable phosphorus this implies that long term changes in marine phosphorus levels and with these changes in marine ecology productivity rates and ratios of exported carbonate carbon and organic carbon are a response to changes in continental weathering rates a compilation of marine sedimentary phosphorus burial rates for the last 160 myr suggests that natural variations have occurred that span one order of magnitude for the late jurassic cretaceous and most of the paleogene the phosphorus cycle appears to have been accelerated in times of climate warming which was most likely due to the spreading of zones of humid climate and more intense continental weathering in the neogene the phosphorus cycle appears to have responded to changes in glacially induced weathering this suggests that uniform interpretations with respect to the emplacement of major phosphorite deposits should be treated with caution integrated analyses of the sedimentary and biogeochemical context of phosphorite occurrences may help to identify paleoenvironmental conditions as well as to improve our understanding of periods of enhanced phosphate accumulation periods which were usually characterized by steep gradients in the development of climate and environment with regard to the complexity of feedback mechanisms between the phosphorus cycle and the biosphere the present day input rates of phosphate into the world s oceans should be of great concern they are more than doubled by anthropogenic means and affect ecological systems on a rapidly increasing scale

the inner shelf response to wind driven upwelling and downwelling abstract a two dimensional numerical model is used to study the response to upwelling and downwelling favorable winds on a shelf with a strong pycnocline during upwelling or downwelling the pycnocline intersects the surface or bottom forming a front that moves offshore the characteristics of the front and of the inner shelf inshore of the front are quite different for upwelling and downwelling for a constant wind stress the upwelling front moves offshore at roughly a constant rate while the offshore displacement of the downwelling front scales as t because the thickness of the bottom layer increases as the front moves offshore the geostrophic alongshelf transport in the front is larger during downwelling than upwelling for the same wind stress magnitude because the geostrophic shear is near the bottom in downwelling as opposed to near the surface in upwelling during upwelling weak stratification is maintained over the inner shelf by the onshore flux of denser near bottom water this weak stratif

glacial interglacial variations in marine phosphorus cycling implications for ocean productivity 1 using a box model of organic carbon c and phosphorus p cycling in the global ocean we assess the effects of changes in the continental supply of reactive p oceanic mixing and sea level on the marine p cycle on glacial interglacial timescales our model results suggest that mixing is a dominant forcing during early glaciation causing retention of p in the deep ocean thereby lowering primary production and associated organic c and p burial sea level fall is the dominant forcing during late glaciation when reduced coastal trapping of reactive p enhances its transfer to the open ocean restoring primary production and p burial during postglacial periods changes in circulation and weathering dominate open ocean processes and oceanic primary production peaks as primary production is reduced upon glaciation changes in the marine p cycle are unlikely to drive enhanced primary production and co2 drawdown during glaciation

distribution of phosphorus in sediments from tomales bay california abstract the distribution of phosphorus among six sequentially extracted fractions was determined in suspended load and bottom sediments from lagunitas creek and tomales bay california the sequential extraction scheme was a modification of the sedex scheme of ruttenberg 1992 using the surfactant sodium dodecyl sulfate sds to extract organic phosphorus sds effectively removed organic phosphorus from sediments with little interference from inorganic phosphorus containing phases the distribution of phosphorus in the sequentially extracted fractions was similar in suspended load and bottom sediments collected from lagunitas creek and the bay the concentration of phosphorus in cdb extractable iron oxide phases was below detection in all samples most of the phosphorus 70 80 contained in these sediments was found in the organic and residual phases porewaters from sediment cores were analyzed for dissolved inorganic carbon ammonium phosphate sulfate iron calcium and fluoride within bay sediments porewaters were depleted in phosphate relative to dissolved inorganic carbon and ammonium suggesting that phosphate released from organic matter decomposition is being removed from the porewaters sequential extraction results suggest that approximately 15 of the phosphate released from organic matter decomposition could be removed from the porewaters by adsorption into the exchangeable phosphorus fraction and an additional 3 may be precipitated as authigenic phosphate minerals the remaining phosphate 82 released from organic matter decomposition must be either taken up within the sediment mixed layer 0 40 cm or escapes to the overlying water column

preservation efficiencies and accumulation rates for biogenic silica and organic c n and p in high latitude sediments the ross sea rates of biogenic sediment accumulation biogenic silica and organic c n and p and pore water flux have been established for a variety of depositional environments in the ross sea on the basis of 14c measurements in kasten cores sediment accumulation rates ranged from 250 cm kyr 1 in the coastal basin of granite harbor to 1 2 cm kyr 1 in the shelf and slope environments of the northern and eastern ross sea burial of biogenic material was most rapid in the southwestern ross sea where biogenic silica accumulation rates ranged from 2 to 31 g cm 2 kyr 1 and organic carbon accumulation rates ranged from 0 05 to 1 4 g cm 2 kyr 1 in the northern and eastern ross sea biogenic silica and organic carbon accumulation rates typically equaled 0 02 0 03 g sio2 cm 2 kyr 1 and 0 002 0 004 g c cm 2 kyr 1 flux core measurements were used to estimate seabed regeneration rates for biogenic silica organic carbon and phosphorus pore water fluxes in general showed much less variability across the ross sea than did the biogenic accumulation rates pore water silicate fluxes in the study area ranged from 0 6 to 5 3 g sio2 cm 2 kyr 1 whereas carbon fluxes ranged from 0 1 to 1 2 g c cm 2 kyr 1 and phosphate fluxes varied from 0 006 to 0 012 g p cm 2 kyr 1 seabed preservation efficiencies were calculated for biogenic silica organic carbon and phosphorus by combining the solid phase and pore water data the seabed preservation efficiencies for biogenic silica 1 86 were greater than for organic carbon 1 71 at all nine stations examined the preferential preservation of biogenic silica relative to organic carbon also was apparent in ross sea sediments because the biogenic silica organic carbon ratio in the material buried in the seabed generally was 2 times greater than the ratio in sediment particles arriving at the sediment water interface sediment accumulation rate correlated strongly with both the biogenic silica and the organic carbon preservation efficiency data p preservation efficiencies remained relatively high 24 65 even when the accumulation rates were low 1 2 cm kyr 1 because of the near zero phosphate fluxes out of the seabed of the total p in the seabed 0 04 0 09 wt approximately 25 existed in the form of organic p the total amount of biogenic silica accumulating on the ross sea shelf is 2 3 1012 g sio2 yr 1 which is approximately an order of magnitude less than the ledford hoffman et al 1986 estimate that was based on 210pb chronologies biogenic silica accumulation rates in the southern central and western ross sea increased during the mid and late holocene reaching their maximum values during the past 500 to 1000 years

tertiary paleoceanic chemical variability unintended consequences of simple geochemical models five lines of concrete quantitative evidence about oceanic chemical composition during the past 65 m y can provide insights into the controlling processes and their temporal variations but the system constraints are not yet fully understood the calcium carbonate compensation depth mean carbon isotopic ratio and strontium isotopic ratio have all changed significantly during this time while changes in lithium to calcium and strontium to calcium ratios have been much smaller when these tracers are considered separately simple scenarios of changes in geochemical and geological factors can be used to explain the historical records these factors include 1 increases in continental chemical weathering rates and net continental fluxes to the oceans 2 changes in the isotopic composition of material weathered from continents to the oceans 3 decreases in the proportion of calcium carbonate deposited on continental shelves 4 changes in the deposition or weathering rates of certain types of sediments and 5 changes in hydrothermal circulation because these geochemical cycles are linked to each other and to others such as nutrients and global atmospheric carbon dioxide an explanation invoked for one tracer must satisfy the direction magnitude and timing of the patterns for all the tracers several simple scenarios for geochemical variations have been evaluated for their consequences both intended and unintended and compared to the historical records despite the attractiveness and possible justifications of some simple hypotheses for example decreases in organic carbon burial rates increases in carbonate weathering rates on the continents or increases in all continental weathering rates no one simple scenario appears to be consistent with both the timing and magnitude of the changes observed during the past 65 m y for all tracers considered the contradictions uncovered can be useful in defining what knowledge is crucial to further understanding of oceanic chemical history better knowledge is needed of absolute deep ocean sediment accumulation rates and their temporal variability of the extent and time scale of variability in the net carbon isotope input to the ocean from continental weathering of steady state fluxes for oceanic mass balances and the extent to which these mass balances approach steady state behavior and of the links and interactions between the geochemical cycles of various elements

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

rapid 20th century increase in coastal upwelling off northwest africa near shore waters along the northwest african margin are characterized by coastal upwelling and represent one of the world9s major upwelling regions sea surface temperature sst records from moroccan sediment cores extending back 2500 years reveal anomalous and unprecedented cooling during the 20th century which is consistent with increased upwelling upwelling driven ssts also vary out of phase with millennial scale changes in northern hemisphere temperature anomalies nhtas and show relatively warm conditions during the little ice age and relatively cool conditions during the medieval warm period together these results suggest that coastal upwelling varies with nhtas and that upwelling off northwest africa may continue to intensify as global warming and atmospheric co 2 levels increase

experimental study of igneous and sedimentary apatite dissolution control of ph distance from equilibrium and temperature on dissolution rates apatite dissolution experiments were conducted using both a fluidized bed and stirred tank reactor over a range of ph temperature solution saturation state and on non carbonated and carbonated apatite compositions igneous fluorapatite fap and sedimentary carbonate fluorapatite cfa respectively from 2 8 5 were not possible due to detection limits of the analytical techniques used in this study and the high insolubility of fap for the cfa compositions studied the dissolution rate decreased with increasing ph from 4 ph 7 during early stages of the dissolution reaction for both fap and cfa mineral components were released in non stoichiometric ratios with reacted solution ratios of dissolved ca p and ca f being greater than mineral stoichiometric ratios suggesting that ca was preferentially released compared to p and f from the mineral structure during the early stages of dissolution an increase in reacted solution ph accompanies this early elevated release of ca as the dissolution reaction proceeded to steady state dissolution became congruent when normalized to bet measured surface area fap dissolved faster from 4 ph 7 compared to cfa the apparent arrhenius activation energy ea of fap dissolution over the temperature range of 25 55 c at ph 3 0 i 0 1 and pco2 0 is 8 3 0 2 kcal mol 1 both the apparent exchange of solution h for solid bound ca at low ph in the early stage of dissolution and the ea of dissolution suggest a surface and not a diffusion controlled dissolution reaction for fap and cfa the degree of undersaturation of the solution gr with respect to fap was important in determining the dissolution rate at ph 3 0 i 0 1 and pco2 0 the dissolution rate of fap was 5 greater in the far from equilibrium region compared to the near equilibrium slope region a simple apatite weathering model incorporating the experimental results from this study was constructed and numerical calculations suggest that during the phanerozoic both the surface area of igneous rock available for weathering and the average global temperature were important factors in determining the p weathering flux from apatite dissolution it is possible that elevated global temperatures coupled with relatively high surface area of igneous rock during the early to mid paleozoic resulted in elevated p weathering fluxes which along with climatic evolutionary pressures of the neoproterozoic facilitated the radiation of multicellular organisms large scale phosphorite deposition and abundance of calcium phosphate shelled organisms during the early cambrian

reassessment of the oceanic residence time of phosphorus phosphorus p is an essential nutrient for the growth of all organisms and is believed to limit marine productivity especially on geologic time scales holland 1984 smith 1984 howarth 1988 codispoti 1989 as a result of the link between marine photosynthetic productivity and atmospheric co2 phosphorus along with other nutrients present in short supply in the euphoric zone have been cited as potential players in the ocean s role in climate change this link has been referred to as the nutrient co2 connection broecker 1982 model simulations which aim to quantify the role of oceanic nutrient inventories in promoting or enhancing climate change rely on the most currently formulated element budgets for the ocean in this paper significant modifications to the currently accepted marine phosphorus budget are proposed the modified p budget presented here requires a reassessment of phosphorus residence time in the ocean and a concomitant review of the role of p as a potential player in climate change over glacialinterglacial time scales element budgets constructed for the oceans consist of a mass balance between inputs and outputs for which the simplifying assumption is generally made that the ocean is in steady state with the specific element in question the fluvial p flux constitutes the bulk of the input term for the marine phosphorus budget atmospheric input is 10 of the fluvial input froelich et al 1982 burial with sediments is the mechanism for ultimate removal of p from the oceans for a system at steady state the input flux equals the output flux in the present paper we focus on the output flux burial with sediments for two reasons first the chemistry of phosphorus buried in sediment cores from which p burial fluxes are calculated has not been affected to the same degree as rivers by anthropogenic perturbation it is therefore simpler to quantify the output term of the p budget which can be extrapolated to pre anthropogenic times second detailed p speciation data permit us to quantify the burial flux of reactive p as contrasted with refractory p in sediments this distinction is significant because burial of reactive p constitutes removal of potentially bio available p from the oceans two types of modification to the marine phosphorus budget are proposed here first the locus of p burial is addressed specifically the importance of p burial in the deep sea is contrasted with p burial in continental margins second the burial flux is characterized in terms of reactive potentially bio available p vs refractory p this distinction is made possible by obtaining detailed p speciation data from application of the sedex method ruttenberg 1992 a selective leaching procedure which separates solid phase p into five reservoirs on the basis of chemical reactivity loosely sorbed p ferric iron bound p authigenic apatite biogenic apatite c a c o 3 bound p detrital apatite p and organic p detailed p spe

modeling the carbon and sulfur isotope compositions of marine sediments climate evolution during the devonian abstract a model of global biogeochemical cycles coupled to an energy balance climatic model modified after the combine model godderis y joachimski m m 2004 global change in the late devonian modeling the frasnian famennian short term carbon isotope excursions palaeogeogr palaeoclimatol palaeoecol 202 309 329 is used to calculate the short term evolution of atmospheric p co 2 during the devonian the geochemical cycles for carbon alkalinity phosphorus sulfur and oxygen are included in this model with also 13 c and 34 s cycles high resolution records of 13 c of marine carbonates and 34 s of marine sulfates are used as forcing parameters of the geochemical cycles in an inverse modeling atmospheric p co 2 and p o 2 at the end of the silurian are calculated to have been 3000 ppmv and 0 165 bar 0 75 pal respectively a long term decrease in p co 2 is modeled for almost the entire devonian short term lowering of p co 2 to concentrations around 2000 ppmv is calculated for the silurian devonian transition and the pragian contents around 900 ppmv are modeled for the eifelian givetian givetian frasnian and frasnian famennian boundaries as a consequence of enhanced organic carbon burial during deposition of lochkovian eifelian and frasnian grey and black shales organic carbon burial is enhanced by the increase of phosphorus delivery to the ocean triggered by short term sea level falls the corresponding short term global climatic cooling at the silurian devonian boundary at the end of the pragian and the givetian frasnian as well as frasnian famennian boundaries reached 2 c at the equator the rapid colonization of continental surface by land plants during the middle and late devonian increasing chemical alteration of the continents and co 2 consumption by silicate weathering is assumed to have caused cooling of surface seawater as suggested by the 18 o values of biogenic apatites

an astrobiological perspective on meridiani planum sedimentary rocks exposed in the meridiani planum region of mars record aqueous and eolian deposition in ancient dune and interdune playa like environments that were arid acidic and oxidizing on earth microbial populations have repeatedly adapted to low ph and both episodic and chronic water limitation suggesting that to a first approximation the meridiani plain may have been habitable during at least part of the interval when deposition and early diagenesis took place on the other hand the environmental conditions inferred for meridiani deposition would have posed a challenge for prebiotic chemical reactions thought to have played a role in the origin of life on earth orbital observations suggest that the combination of sulfate minerals and hematite found in meridiani rocks may be unusual on the martian surface however there is reason to believe that acidity aridity and oxidizing conditions were broadly distributed on ancient mars when these conditions were established and how much environmental heterogeneity existed on early mars remain to be determined because sulfates and iron oxides can preserve detailed geochemical records of environmental history as well as chemical textural and microfossil signatures of biological activity meridiani planum is an attractive candidate for mars sample return

upper cretaceous campanian phosphorites in jordan implications for the formation of a south tethyan phosphorite giant a record of sedimentary authigenic and biological processes are preserved within the upper cretaceous campanian alhisa phosphorite formation ap in central and northern jordan the ap formed near the eastern extremity of the south tethyan phosphorite province stpp a carbonate dominated upper cretaceous to eocene phosphorite giant that extends from colombia north africa to the middle east multidisciplinary research of the ap and associated cherts chalks and oyster buildups indicate that phosphatic strata formed on a highly productive storm dominated east west trending epeiric platform along the south tethyan margin the onset of phosphogenesis and the accumulation of economic phosphorite coincided with a rise in relative sea level that onlapped peritidal carbonates of the ajlun group pristine phosphates are associated with well developed micrite concretionary horizons and contain abundant non keeled spiral planktic foraminifera and a low diversity benthic assemblage of buliminacean foraminifera suggesting that pristine phosphates are a condensed facies and phosphogenesis was stimulated by the effects of a highly productive surface ocean and the suboxic diagenesis of sedimentary organic matter the bulk sediment composition and absence of fe bearing authigenic phases such as glauconite pyrite including pyrite molds siderite and goethite within pristine phosphates suggests that deposition and authigenesis occurred under conditions of detrital starvation and that iron pumping played a minimal role in phosphogenesis authigenic precipitation of phosphate occurred in a broad array of sedimentary environments herein termed a phosphorite nursery that spanned the entire platform this is a non uniformitarian phenomenon reflecting precipitation of sedimentary apatite across a wide depositional spectrum in a variety of depositional settings wherever the conditions were suitable for phosphogenesis sedimentologic data indicate that pristine phosphates were concentrated into phosphatic grainstones through storm wave winnowing and storm generated shelf parallel geostrophic currents economic phosphorites formed through the amalgamation of storm induced event beds stratigraphic packaging of phosphatic strata indicates that temporal variations in storm frequency were a prerequisite for the formation of economic phosphorite syndepositional phosphogenesis reworking and amalgamation to form phosphorites contrasts sharply with the principles of baturin cycling a transgressive systems tract coupled with high surface productivity created detritally starved settings favourable for phosphogenesis storm reworking of pristine

topographically induced upwelling off eastern australia abstract a high resolution numerical study of an idealized western boundary current flow over variable topography is presented with application to the east australian current eac the results indicate that alongshelf topographic variations off australia s east coast cause the eac to accelerate over the narrowing continental shelf near cape byron this acceleration is sufficient to hinder the geostrophic adjustment in the bottom boundary layer bbl which would usually cause the eac driven bbl to shut down consequently a region of persistent high bottom stress was established off cape byron which was responsible for driving an upwelling bbl it is shown that the enhanced vertical mixing associated with a low richardson number flow beneath the eac reduced the local stratification consequently the burger number is decreased resulting in a long shutdown timescale of the bbl which enables a nearshore thermal to be established and maintained such fronts are commonly observed in the region as a p

biogeochemical phosphorus mass balance for lake baikal southeastern siberia russia abstract extensive data for lake baikal have been synthesized into a geochemical mass balance for phosphorus p some of the p budget and internal cycling terms for baikal have been compared to similar terms for oligotrophic lake superior mesotrophic lake michigan and the baltic sea and the ocean lake baikal has a large external source of fluvial p compared to the laurentian upper great lakes and the ocean the major tributary to lake baikal has experienced substantial increases in organic p loading during the past 25 years this coupled with potential p inputs from possible phosphorite mining may threaten baikal s oligotrophic status in the future water column remineralization of particulate organic p is substantially greater in lake baikal than in the laurentian great lakes this is probably due to the great water depths of lake baikal there is a gradient in p burial efficiency with very high values 80 for lake baikal and lake superior lower values 50 for lake michigan and the baltic sea and a low value 13 for the ocean the accumulation rate of p in lake baikal sediments is somewhat greater than that in the laurentian upper great lakes and the baltic sea and much greater than in the ocean benthic regeneration rates are surprisingly similar for large lacustrine and marine environments and supply less than 10 of the p utilized for primary production in these aquatic environments

three dimensional flow in a shallow coastal upwelling zone alongshore convergence and divergence on the new jersey shelf alongshore flow field divergence is investigated on the inner shelf off the coast of new jersey during the summer upwelling season of 1996 velocities obtained from an array of moorings are used to examine the flow field empirical orthogonal function eof analyses are employed to extract those features of the flow field that are resolved by the moorings and to construct a measure of alongshore divergence multi input single output linear systems analysis is used to examine the role of buoyancy intrusions and wind stress in determining alongshore divergence or convergence of the flow field and to construct a proxy for divergence derived from a time series of stratification gradients and wind stress alongshore divergence on this shallow shelf 25 m depth is shown to be a function of both wind stress and buoyancy intrusions the latter originate in the hudson river outflow and produce downshelf flow i e in the direction of kelvin wave propagation examination of the first eof mode containing 67 of the variance reveals that the largest resolved fluctuations are oriented alongshore and are characterized by strong counterclockwise veering with depth momentum balances demonstrate that the depth averaged flow fields are governed by wind stress bottom stress and the across shore pressure gradient the second eof mode describes significantly less variance 8 however it represents the across and alongshore variations of the flow field composing the bulk of the alongshore divergence the production of alongshore divergence by a combination of wind stress and buoyancy intrusions is a likely outcome in upwelling regimes downshelf of a major buoyancy source

geochemistry and time series analyses of orbitally forced upper cretaceous marl limestone rhythmites lehrte west syncline northern germany a cyclic marl limestone succession of middle late campanian age has been investigated with respect to a milankovitch controlled origin of geochemical data in general the major element geochemistry of the marl limestone rhythmites can be explained by a simple two component mixing model with the end members calcium carbonate and average shale like material carbonate content varies from 55 to 90 non carbonate components are clay minerals illite smectite and biogenic silica from sponge spicules as well as authigenically formed zeolites strontian heulandite and quartz the redox potential suggests oxidizing conditions throughout the section trace element and stable isotopic data as well as sem investigations show that the carbonate mud is mostly composed of low magnesium calcitic tests of planktic coccolithophorids and calcareous dinoflagellate cysts calcispheres diagenetic overprint results in a decrease of 2 18 o and an increase in mn of up to 250 ppm however the sediment seems to preserve most of its high sr content compared to the primary low magnesium calcite of co occurring belemnite rostra the periodicity of geochemical cycles is dominated by 413 ka and weak signals between 51 and 22 5 ka attributable to orbital forcing accumulation rates within these cycles vary between 40 and 50 m ma the resulting cyclic sedimentary sequence is the product of a changes in primary production of low magnesium calcitic biogenic material in surface waters within the long eccentricity and the precession demonstrated by the caco 3 content and the mg al mn al and sr al ratios and b fluctuations in climate and continental weathering which changed the quality of supplied clay minerals the illite smectite ratio demonstrated by the k al ratio high carbonate productivity correlates with smectite favouring weathering semi arid conditions conspicuously dry and moist seasonal changes in warmer climates ti as the proxy indicator for the detrital terrigenous influx as well as rb si zr and na shows only low frequency signals indicating nearly constant rates of supply throughout the more or less pure pelagic carbonate deposition of the long lasting third order middle upper campanian sedimentary cycle

sedimentary environments and chemical composition of pacific pelagic sediments abstract the chemical compositions of 140 deep sea sediment samples collected in the pacific ocean were determined by inaa and icp oes methods in order to study the relationship between elemental abundances and the environment of their sedimentation in particular we observed horizontal changes along the longitude of 170 w across the pacific in calcareous ooze there is a positive relationship between ca content and sr content however the mg content is influenced more by basic rock detritus than by biogenic carbonate our observations of red clays suggest 1 the ti al ratio is a good indicator of the contribution of mafic rock detritus 2 the hydrogenous component of pelagic sediments is characterized by high co and mn content but not high v content fe content is influenced primary by basic rock detritus 3 there is a good correlation between p content and cu content high p and cu contents are characteristic of the high primary production zones in pelagic areas for example the equatorial zone the mn content is also considered to be influenced by the primary productivity of overlying surface water

factors controlling the concentrations of soluble phosphorus in the mississippi estuary1 sediments from the mississippi river estuary were suspended in solutions with a range of salinities and various initial concentrations of phosphate after 42 days the suspensions had nearly uniform values for the ion activity product of calcium times biphosphate ca2 hp0 2 x 10e9 m2 similar values were observed for this ion product in the mississippi river and in the upper estuary suggesting that the concentration of soluble phosphorus nlay be controlled by an equilibrium with sedimentary material the data are consistent with a inechanism where soluble phosphorus is controlled by hydrolysis on the surface of hydroxyapatize particles ca po oh 6h2o z 4 ca hpo oh 2ca2 2hpod2 phosphorus levels in the lower estuary are controlled primarily by tlilution with low nutrient waters from the gulf of mexico

a new solution of a nonlinear model of upwelling abstract a two dimensional frictionless nonlinear model of coastal upwelling is reexamined the model has been solved previously at steady state and as an initial value problem the previous solution to the initial value problem is inconsistent with the steady state solution a new solution to the spinup problem is presented that approaches the existing steady state solution in the new solution a surface equatorward jet develops more rapidly than a poleward undercurrent but the surface jet is of limited strength so that the undercurrent velocity eventually surpasses that of the surface flow consideration of dimensional scales implies that the magnitude of the wind stress determines how quickly steady state is approached but does not affect the steady state fields exact solutions found with an arbitrary alongshore pressure gradient imply that there is no poleward flow without a poleward pressure gradient

al to oxide and ti to organic linkages in biogenic sediment relationships to paleo export production and bulk al ti abstract to increase our understanding of the mechanisms that control the distribution of al and ti within marine sediment we performed sequential extractions targeting the chemical signatures of the loosely bound exchangeable carbonate oxide organic opal and residual fraction of sediment from a carbonate dominated regime equatorial pacific and from a mixed opal terrigenous regime west antarctic peninsula we observe a systematic partitioning of al and ti between sediment phases that is related to bulk al ti we show that where we can quantify an alexcess component the dissolved al is preferentially affiliated with the oxide fraction resulting in al ti molar ratios of 500 3000 this is interpreted as the result of surface complexation in the water column of dissolved al onto oxyhydroxides we also observe a previously undetected tiexcess with as much as 80 of the total ti in the organic fraction which is most likely a function of metal organic colloidal removal from the water column in samples where the excess metals are obscured by the detrital load the al and ti are almost exclusively found in the residual phase this argues for the paired removal of al preferentially by the oxide component and ti preferentially by the organic component from the water column by settling particulate matter this research builds upon earlier work that shows changes in the bulk ratio of al to ti in carbonate sediment from the central equatorial pacific that coincide with changes in the sedimentary bulk accumulation rate bar the ratios that are observed are as much as three times higher than typical shale values and were interpreted as the result of scavenging of dissolved al onto particles settling in the water column because this non terrigenous alexcess accounts for up to 50 of the total sedimentary al inventory and correlates best with bar the bulk al ti may be a sensitive tracer of particle flux and therefore export production because we show that the excess metals are the result of scavenging processes the bulk al ti may be considered a sensitive proxy for this region