stabilization of the coupled oxygen and phosphorus cycles by the evolution of bioturbation animal burrowing and sediment mixing bioturbation began during the run up to the ediacaran cambrian boundary1 2 3 initiating a transition4 5 between the stratified precambrian6 and more well mixed phanerozoic7 sedimentary records against the backdrop of a variable8 9 global oxygen reservoir probably smaller in size than present10 11 phosphorus is the long term12 limiting nutrient for oxygen production via burial of organic carbon13 and its retention relative to carbon within organic matter in marine sediments is enhanced by bioturbation14 15 16 17 18 here we explore the biogeochemical implications of a bioturbation induced organic phosphorus sink in a simple model we show that increased bioturbation robustly triggers a net decrease in the size of the global oxygen reservoir the magnitude of which is contingent upon the prescribed difference in carbon to phosphorus ratios between bioturbated and laminated sediments bioturbation also reduces steady state marine phosphate levels but this effect is offset by the decline in iron adsorbed phosphate burial that results from a decrease in oxygen concentrations the introduction of oxygen sensitive bioturbation to dynamical model runs is sufficient to trigger a negative feedback loop the intensity of bioturbation is limited by the oxygen decrease it initially causes the onset of this feedback is consistent with redox variations observed during the early cambrian rise of bioturbation leading us to suggest that bioturbation helped to regulate early oxygen and phosphorus cycles

zone of metal driven anaerobic oxidation of methane is an important sink for phosphorus in the taixinan basin south china sea abstract phosphorus p is an important nutrient and has an important impact on global primary productivity presently the dynamics of the p cycle in low sulfate anoxic settings are largely unknown in this study the adsorption desorption behavior of fe bound p organic p loosely bund p detrital apatite p and refractory p was described in the sulfate and methane transition zone smtz at site 973 4 in the cold seep area of the taixinan basin south china sea results showed that the fe bound p and organic p were influenced by sulfate driven anaerobic oxidation of methane sd aom and metal driven anaerobic oxidation of methane md aom and subsequently the fe bound p and organic p were released as hpo42 into the pore water meanwhile significant increases were detected in authigenic carbonate fluorapatite pcfa and vivianite within the md aom zone which indicate that this zone is an important p sink area the md aom plays an important role in the formation of pcfa and vivianite because md aom provide the necessary hpo42 and fe2 for the formation of these minerals our findings have major implications for understanding the p cycle in low sulfate anoxic settings and are important for understanding the influence of md aom on the phosphate cycle

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

carbon to phosphorus ratios in sediments implications for nutrient cycling defining the transformations of phosphorus p in sediments is critical to assessing the geochemical behavior of sedimentary p and the behavior of reactive p preactive poxide associated pauthigenic porganic relative to organic carbon corganic this study includes the determination of p components and corganic concentrations on samples from sites in the california current region ocean drilling program odp leg 167 sites 1010 1011 1012 1014 1016 and 1021 in the benguela current region odp leg 175 sites 1082 1084 and 1085 and on blake nose in the western atlantic odp leg 17 1b sites 1050 and 1052 sample depths range up to 650 m and ages range up to 65 ma our data demonstrate the transformation of labile forms of p porganic and poxide associated to pauthigenic throughout the sediment column in all redox states and at all sedimentation rates investigated until a substantial portion of reactive p is in the authigenic form 80 c p organic ratios are always greater than or equal to the redfield ratio in all of the sediments we studied sediments with corganic concentrations 2 wt have corganic preactive ratios less than the redfield ratio and corganic preactive ratios increase linearly with corganic consistent with degradation of corganic with age in general corganic preactive ratios for sediments with corganic concentrations 2 wt from a variety of redox states and sedimentation rates center around the redfield ratio although some ratios are as high as 3 times the redfield ratio however corganic preactive ratios up to 400 do not approach the high ratios observed for c p organic ratios up to 4500 because of the efficient transfer of labile forms of p to pauthigenic corganic preactive ratios better describe the geochemical behavior of sedimentary p

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

subgrade reaction and load settlement characteristics of gravelly cobble deposits by plate load tests this paper presents the result of plate load tests conducted on a gravelly cobble deposit in taichung basin taiwan the geologic formation of the gravelly cobble deposit makes it very difficult to

vivianite is a key sink for phosphorus in sediments of the landsort deep an intermittently anoxic deep basin in the baltic sea phosphorus p is an essential nutrient for marine organisms its burial in hypoxic and anoxic marine basins is still incompletely understood recent studies suggest that p can be sequestered in sediments of such basins as reduced iron fe p but the exact phase and the underlying mechanisms that lead to its formation are unknown in this study we investigated sediments from the deepest basin in the baltic sea the landsort deep site m0063 that were retrieved during the integrated ocean drilling project iodp baltic sea paleoenvironment expedition 347 the record comprises the whole brackish marine littorina sea stage including past intervals of extensive hypoxia in the baltic sea that occurred during the holocene thermal maximum htmhi and the medieval climate anomaly mca1hi and mca2hi various redox proxies e g the presence of laminations and high mo contents suggest almost permanent bottom water hypoxia during the littorina sea stage in the landsort deep the bottom waters were likely even seasonally anoxic or sulfidic during the mca1hi and mca2hi and permanently sulfidic during the htmhi with the use of micro analysis of sieved minerals sem eds xrd and synchrotron based xas we show that mn and mg rich vivianite crystals are present at various depths in the littorina sea sediments we also have indications for vivianite in the mca1hi mca2hi and htmhi deposits the formation of vivianite thus likely explains the high fe bound p fraction throughout the whole littorina sea stage shuttling of fe and mn from the shelves into the basin and high inputs of p in settling organic matter are likely key drivers for vivianite formation our study shows that vivianite can likely form in near surface sediments under a broad range of bottom water redox conditions varying from hypoxic and anoxic to sulfidic

dense water production on the northern okhotsk shelves comparison of ship based spring summer observations for 1996 and 1997 with satellite observations for the northern okhotsk sea polynyas five russian ctd surveys taken during 1995 to 1997 are used to examine the evolution of the polynya dense water the surveys show that consistent with other investigations the largest potential densities are 26 99 and the densest water occurs in sakhalin and shelikhov bays the surveys also suggest that the shelikhov water drains directly into the deep okhotsk while on the northern shelves gravity currents transport the dense water west to sakhalin bay for comparison determination of the polynya sizes and ice production from satellite passive microwave and meteorological observations shows that polynyas occur on the northwest shelf nws between ayan and okhotsk city on the northern shelf between okhotsk city and magadan and in shelikhov bay in contrast the observations show that sakhalin bay is a region of land fast ice with no polynyas so that the dense water observed here cannot form locally for all polynyas the satellite observations show that the nws contributes 60 to 70 of the total ice production and due to the warmer 1997 air temperatures the 1996 production is about 1 5 times the 1997 value an estimate of the ice production from the surveys shows a similar regional distribution and enhancement of the 1996 production with the satellite and ship estimates in agreement within their error bars finally analysis of the dense water outflow shows that the upper okhotsk sea mode water has a renewal time of about 4 years the lower part about 14 years

iron and manganese shuttles control the formation of authigenic phosphorus minerals in the euxinic basins of the baltic sea microanalysis of epoxy resin embedded sediments is used to demonstrate the presence of authigenic iron fe ii phosphates and manganese mn calcium ca carbonate phosphates in the deep euxinic basins of the baltic sea these minerals constitute major burial phases of phosphorus p in this area elevating the total p burial rate above that expected for a euxinic depositional environment particle shuttles of fe and mn oxides into the deep euxinic basins act as drivers for p bearing mineral authigenesis while fe ii phosphates are formed continuously in the upper sediments following the sulfidization of fe oxyhydroxides and release of associated p mn ca carbonate phosphates are formed intermittently following inflow events of oxygenated north sea water into the deep basins the mechanism of fe ii phosphate formation differs from previously reported occurrences of vivianite formation in marine sediments by occurring within rather than below the sulfate methane transition zone the spatial distribution of both authigenic phases in baltic sediments varies in accordance with the periodic expansion of anoxia on centennial to millennial timescales the results highlight the potential importance of authigenic p bearing minerals other than carbonate fluorapatite for total p burial in euxinic basins

transport and modification processes of dense shelf water revealed by long term moorings off sakhalin in the sea of okhotsk 1 the region off the east coast of sakhalin is thought of as an important pathway of dense shelf water dsw from its production region in the northwestern okhotsk sea to the southern okhotsk sea from july 1998 to june 2000 the first long term mooring experiment was carried out in this region to observe the southward flowing east sakhalin current esc and dsw moored and associated hydrographic data show considerable modification of cold dense water via mixing with warm offshore water in the slope region off northern sakhalin significant onshore eddy heat flux was observed at the northernmost mooring 54 9 n which suggests the occurrence of baroclinic instability the eddy heat flux was not significant farther south at moorings along 53 n cold anticyclonic eddies were identified that were consistent with isolated eddies seen in the hydrographic data the three years of hydrographic data also showed large differences in extent and properties of dsw furthermore the mooring data show that seasonal variability of dsw was quite different in the two years the average dsw transport for 26 7 evaluated using the moored data at 53 n for 1 year 1998 1999 was 0 21 sv 106 m3 s 1 this value is at the lower end of the previous indirect estimates along with the dsw modification this transport estimate indicates that dsw was not only carried southward by the esc but was spread offshore by eddies off northern sakhalin

sequential extraction of iron manganese and related elements in s1 sapropel sediments eastern mediterranean a detailed sequential extraction scheme mesex was developed to distinguish fe and mn phases in eastern mediterranean sediments after calibration and validation using single natural minerals and a mixed mineral standard mesex was applied to holocene eastern mediterranean sediments from 1 a former brine basin and 2 a normal setting including the organic rich sapropel s1 in both sediments the mn ii mn iii iv redox boundary is clearly distinguished with carbonate related mn being enriched below and mn oxides occurring only above it a clear fe ii fe iii redox boundary is present in the normal eastern mediterranean sediments and is located just below the mn ii mn iii iv redox boundary the fe ii fe iii boundary closely coincides with the visible boundary between the lower unoxidised and the upper oxidised burned down part of the original sapropel s1 interval pyrite is only present within the unoxidised interval whereas fe oxides are abundant above it the fe ii fe iii redox boundary in the former brine sediments resides on top of the organic enriched sediments as deduced from the distribution of fe oxides and pyrite as a result of burn down of the sapropel s1 unit in the normal sediments a vanadium peak has been formed below the oxidation front whereas no such v peak was observed in the former brine sediments this together with the location of the mn ii mn iii iv redox boundary well above the organic enriched sediments suggests that no burn down has taken place into the sapropelic sediments of the former brine basin resulting in the preservation of the relationships of trace metal to organic carbon or pyrite in these latter sediments mn and co appear to be associated with pyrite whereas ni cu and zn as well as v are more related to organic matter on the basis of mesex variations have also been detected in the terrigenous component i e aluminosilicates fe al clay mg al clay and several trace metal to al ratios are higher in sapropelic than in non sapropelic sediments these results indicate that sources of terrestrial material have been different during sapropel times compared to the period immediately after it on the other hand the fairly constant k alclay ratio suggests that no major changes may have occurred in the relative illite contribution

chlorofluorocarbons in the sea of okhotsk ventilation of the intermediate water 1 ventilation of the intermediate layer in the sea of okhotsk is studied with regard to the ventilation of north pacific intermediate water npiw measurements of chlorofluorocarbons cfcs from 1998 to 2000 reveal that the okhotsk intermediate water is ventilated in two ways the first consists of dense water formation in the polynyas that form on the northern shelves during winter measurements show that on the northwestern shelf because of atmospheric cooling and brine rejection the cold water that forms is dense enough to enter the intermediate layer the cfc concentration in this dense shelf water dsw is high and almost saturated with respect to atmospheric cfcs indicating that the dsw experiences active air water gas exchange during its formation away from the shelves the cfc distribution shows that the dsw directly ventilates the upper level of the okhotsk sea intermediate water osiw the second ventilation process is driven by the strong tidal mixing around the bussol strait the observed distribution of cfcs at the 27 4 level suggest that diapycnal mixing around the strait transports cfcs from the surface to this deeper layer ventilating the osiw combination of both processes means that the osiw is more ventilated than pacific water at the same density levels

multiple sulfur isotopic evidence for the origin of elemental sulfur in an iron dominated gas hydrate bearing sedimentary environment abstract elemental sulfur is commonly regarded as the product of oxidative sulfur cycling in the sediment however reports on the occurrence of elemental sulfur in seepage areas are few and thus its origin and mechanisms controlling its distribution are insufficiently understood here we analyzed the multiple sulfur isotopic compositions for elemental sulfur and pyrite from an iron dominated gas hydrate bearing sedimentary environment of the south china sea to unravel the impact of sulfate driven anaerobic oxidation of methane so4 aom on the formation of elemental sulfur the multiple sulfur isotopes reveal variable ranges for both elemental sulfur and pyrite 34s between 15 7 and 23 3 for elemental sulfur and between 35 3 and 34 4 for pyrite 33s between 0 08 and 0 06 for elemental sulfur and between 0 03 and 0 15 for pyrite the enrichment of 34s in pyrite throughout the sediment core suggests pronounced so4 aom in paleo sulfate methane transition zones smtz in addition the occurrence of seep carbonates with very negative 13c values as low as 57 v pdb coincides with the inferred paleo smtzs and agrees with formerly locally pronounced so4 aom interestingly the multiple sulfur isotopic composition of elemental sulfur reveals a different pattern from that of pyrite derived from organoclastic sulfate reduction i e with low 34s and high 33s values for the latter in comparison to coexisting pyrite most of the elemental sulfur reveals higher 34s values as much as 28 9 which is best explained by an enrichment of 34s in the residual pool of dissolved sulfide generated by so4 aom as an intermediate sulfur phase elemental sulfur can form via sulfide oxidation coupled to iron reduction but it can only persist in the absence of free sulfide therefore the occurrence of 34s enriched elemental sulfur is likely to represent an oxidative product after hydrogen sulfide had vanished due to vertical displacement of the smtz our observations suggest that elemental sulfur may serve as a useful recorder for reconstructing the dynamics of sulfur cycling in modern and possibly ancient seepage areas

authigenesis of vivianite as influenced by methane induced sulfidization in cold seep sediments off southwestern taiwan abstract authigenesis of iron rich phosphate nodules occurs in iron rich cold seep sediments md052911 core at yung an ridge offshore southwestern taiwan raman ftir and quantitative x ray energy dispersive spectroscopic analyses indicate that the phosphate mineral is vivianite or baricite and shows fe mg molar ratios spanning from ca 0 6 to 4 0 and a general down core trend of increasing fe mg ratios the formation of vivianite is limited to a depth interval of 13 17 mbsf meters below seafloor and is most prominent at 16 mbsf in association with high dissolved iron concentrations and depleted dissolved sulfide below a peak sulfidization zone enriched in mackinawite and greigite alternate growths of vivianite and iron monosulfides and compositional zoning with mg enriched towards the peripheries of individual nodules occur in the transition from the zone of vivianite mineralization to the sulfidization zone the crystallization of vivianite below the sulfidization front could have been favored by scavenging of downward diffusive dissolved sulfide from pore waters in the sulfidization zone alternate growths and overlapping of the zones of iron monosulfides and vivianite can be attributed to fluctuations of the sulfidization front and methane flux the discovery of vivianite in the yung an ridge sediments implies that authigenic vivianite can be an important sink for phosphorus burial in cold seep sediments that have high reactive iron contents and high sedimentation rates

shear modulus and damping ratio characteristics of gravelly deposits in this paper the results of an experimental investigation of dynamic characteristics of gravelly cobble deposits such as shear modulus g and damping ratio d are presented the gravelly cobble deposits are very common in the taichung metropolitan area of taiwan where there is an urgent need to determine g and d for dynamic analysis and design of structures the test program includes measurements of shear wave velocity by the downhole method and large scale dynamic triaxial tests and resonant column tests special consideration is given to preparing samples of gravelly cobble deposits for laboratory tests the equal weight replacement method to scale down the real gravelly deposits to cell diameters is used for the preparation of samples this method is found to be satisfactory as consistent and reasonable results are obtained the results of the present study show that the shear modulus shear strain g relationship for this gravelly deposit does not follow exactly those reported in the lite

structure and seasonal variability of the east sakhalin current abstract in order to clarify the structure and seasonal variability of the flow field near the western boundary of the sea of okhotsk long term mooring measurements were carried out from 1998 to 2000 in this region in most of the mooring period a persistent southward flow the east sakhalin current was observed which extends from the surface to a depth around 1000 m the speed of this southward flow clearly changed seasonally the peak monthly mean speed along 53 n at a depth of 200 m attained a maximum of 37 9 cm s 1 in january and a minimum of 10 8 cm s 1 in july three different cores of intense flow were identified in the southward flow the first core was centered over the continental slope and had rather large vertical extent reaching the bottom on the slope the second core was trapped over the shelf near the surface and was observed from october to november this core was associated with less saline surface water affected by the amur river discharge the third core was intensified toward

phosphorus recycling and burial in baltic sea sediments with contrasting redox conditions in this study redox dependent phosphorus p recycling and burial at 6 sites in the baltic sea is investigated using a combination of porewater and sediment analyses and sediment age dating pb 21

increase and decrease of sea ice area in the sea of okhotsk ice production in coastal polynyas and dynamic thickening in convergence zones 1 this paper examines the production and reduction of sea ice area in the sea of okhotsk analyses were carried out for 10 winters december april from 1991 1992 to 2000 2001 using daily data of sea ice velocity and concentration derived from images of the defense meteorological satellite program dmsp special sensor microwave imager ssm i first we mapped sea ice divergence which was calculated from the daily ice velocity field in the case of offshore winds high divergence was observed along the coastline while there existed a broad convergence area with inshore winds next we examined local changes in an area of sea ice as in the case of ice divergence ice production and reduction are strongly controlled by wind direction we found that a large amount of sea ice was produced in coastal areas under offshore wind conditions the geographical distribution of the ice production area agrees well with that of the well known coastal polynya areas our estimation shows that 8 7 105 km2 yr 1 of sea ice is produced in the northern coastal area and 3 7 105 km2 yr 1 in the sakhalin coastal area in contrast 7 4 105 km2 yr 1 of the ice area disappeared in shantarskiy bay this reduction of ice area is mainly caused by dynamic deformation of existing ice forming rafted ice or pressure ridges this dynamic deformation plays an important role not only in the reduction of okhotsk sea ice area but also in the thickening of ice

authigenic apatite formation and burial in sediments from non upwelling continental margin environments abstract evidence for precipitation of authigenic carbonate fluorapatite cfa in long island sound and mississippi delta sediments suggests that formation of cfa is not restricted to environments of active coastal upwelling we present porewater data suggestive of cfa formation in both these areas application of a sequential leaching procedure designed specifically to separate authigenic carbonate fluorapatite from other phosphorus containing phases including detrital apatite of igneous or metamorphic origin provides strong supporting evidence for authigenic apatite formation in these sediments the size of the authigenic apatite reservoir increases with depth indicating continued formation of cfa during early diagenesis this depth increase is mirrored by a decrease in solid phase organic p at both sites suggesting that cfa is forming at the expense of organic p mass balance considerations application of diagenetic models to interstitial water nutrient data and the saturation state of the interstitial water are consistent with this interpretation diagenetic redistribution of phosphorus among the different solid phase reservoirs is observed at both sites and results in near perfect retention of p by these sediments over the depth intervals sampled formation of cfa in continental margins which do not conform to the classically defined regions of phosphorite formation renders cfa a quantitatively more important sink than has previously been recognized including this reservoir as a newly identified sink for reactive p in the ocean the residence time of p in the modern ocean must be revised downward the implication for ancient oceans of cfa formation in continental margin sediments other than phosphorites is that phosphorite formation may be less a representation of episodicity in removal of reactive p from the oceans than of localized concentration of cfa in phosphatic sediments by secondary physical processes

phosphorus distribution c n p ratios and δ13coc in arctic temperate and tropical coastal sediments tools for characterizing bulk sedimentary organic matter abstract onshore offshore trends in phosphorus p organic carbon oc and total nitrogen tn concentration p distribution elemental organic c n p ratios and stable carbon isotopic composition of oc 13 c oc of surficial sediments are presented from three river dominated coastal regimes the mackenzie river beaufort shelf in the canadian arctic the mississippi delta and louisiana shelf in the temperate gulf of mexico and the tropical amazon shelf these parameters measured in surficial sediments from the three sites are used to assess changes in the importance of terrestrial and marine organic matter sources to sediments as a function of distance from the locus of riverine discharge trends in elemental ratio data from the arctic transect and a portion of the gulf of mexico transects can be explained in terms of a two end member mixture of terrestrial and marine phytodetritus in the arctic transect covariation of organic c p ratios with 13 c oc is consistent with a two end member mixture of terrestrial and marine organic matter a similar relationship between c p ratios and 13 c oc is not evident in gulf of mexico or amazon shelf sediments at these sites the two end member model fails to explain the data adequately the most striking feature of the onshore offshore trends in elemental oc op and oc tn ratios is the occurrence of low ratios in sediments from deep water stations in the gulf of mexico and all stations on the amazon shelf resulting from p and n enrichments exceeding the redfield ratio for marine plankton three explanations are discussed to account for these low ratios 1 the dominance of refractory op and on compounds in the residuum of degraded organic matter 2 differential sorption of op and n compounds regardless of lability on the surfaces of the fine grained sediments characteristic of these sites and 3 a dominance of bacterial biomass or components derived from bacterial biomass elemental ratios and 13 c oc signatures indicate that differential sorption may be most important in the deep water gulf of mexico sites in contrast elemental ratios and 13 c oc on the amazon shelf are most consistent with a sedimentary organic matter pool dominated by bacterial biomass or derivative substances

tidally induced diapycnal mixing in the kuril straits and its role in water transformation and transport a three dimensional nonhydrostatic model experiment 1 baroclinic processes generated by the k1 tidal flow around the kuril straits and their role in the linkage between the okhotsk sea and the north pacific are investigated using a three dimensional nonhydrostatic model large amplitude unsteady lee waves are generated around sill tops all along the kuril island chain and induce significant density inversions from the sea surface down to the 27 6 density layer along with this wave breaking a large flow of energy takes place from the swift tidal flow regions to greater depths as a result of the clockwise propagation of both the topographically trapped waves around the islands and the remaining unsteady lee waves such wave generation and energy exchange eventually cause intense diapycnal mixing over the shallow topographic features and near the bottom leading to a maximum diapycnal diffusivity of over 103 cm2 s 1 even in the deep bussol strait which is thought to be the main exit of the okhotsk sea water considerable mixing corresponding to diapycnal diffusivity values of between 10 50 cm2 s 1 occurs vigorous mixing in the shallow regions produces low potential vorticity pv water in the upper layer and high pv water below accordingly pv fronts are formed along the island chain and sustain instabilities that in turn release baroclinic eddies with low core pv values these features are indicated in recent satellite imagery and in situ observations suggesting that the tide is the controlling factor in the formation of fronts observed in the kuril straits tidally induced mean transport across the straits is estimated to reach 26 sv 1 sv 106 m3 s 1 which is much larger than in the barotropic case however most of the exchanged water tends to circulate around the islands due to the effect of bottom topography whereas eddies pinched off from the tidal fronts carry the exchanged water offshore the amount of eddy driven offshore transport away from the islands reaches 14 sv with roughly half being directed to the north pacific this significant offshore transport spreads the effect of the diapycnal mixing taking place in the straits over wider areas of the north pacific and the okhotsk sea for example the pv values generated in the eddies differ by 30 40 from the ambient water on average whereas sea surface salinity within the eddies is 0 1 psu higher than the surroundings corresponding to the density increase of 0 08 thus the eddy transport provides significant pv and salinity fluxes to both the north pacific and the okhotsk sea hence we infer that a combination of tidally driven processes taking place at the passages leads to the formation of eddies that play a central role in water transport and transformation and are an essential aspect of the physical interplay between the okhotsk sea and the north pacific

diagenetic changes of magnetic and geochemical signals by anaerobic methane oxidation in sediments of the zambezi deep sea fan sw indian ocean abstract the zambezi deep sea fan the largest of its kind along the east african continental margin is poorly studied to date despite its potential to record marine and terrestrial climate signals in the southwest indian ocean therefore gravity core geob 9309 1 retrieved from 1219 m water depth was investigated for various geophysical magnetic susceptibility porosity colour reflectance and geochemical pore water and sediment geochemistry fe and p speciation properties onboard and onshore data documented a sulphate methane transition smt zone at 450 530 cm sediment depth where the simultaneous consumption of pore water sulphate and methane liberates hydrogen sulphide and bi carbonate into the pore space this leads to characteristic changes in the sediment and pore water chemistry as the reduction of primary fe oxyhydr oxides the precipitation of fe sulphides and the mobilization of fe oxyhydr oxide bound p these chemical processes also lead to a marked decrease in magnetic susceptibility below the smt we find a reduction of porosity possibly due to pore space cementation by authigenic minerals formation of the observed geochemical magnetic and mineralogical patterns requires a fixation of the smt at this distinct sediment depth for a considerable time which we calculated to be 10 000 years assuming steady state conditions following a period of rapid upward migration towards this interval we postulate that the worldwide sea level rise at the last glacial interglacial transition 10 000 years b p most probably caused the fixation of the smt at its present position through drastically reduced sediment delivery to the deep sea fan in addition we report an internal redistribution of p occurring around the smt closely linked to the de coupling of sedimentary fe and p and leaving a characteristic pattern in the solid p record by phosphate re adsorption onto fe oxyhydr oxides above and formation of authigenic p minerals e g vivianite below the smt deep sea fan deposits may potentially act as long term sinks for p

coupled pyrite concentration and sulfur isotopic insight into the paleo sulfate methane transition zone smtz in the northern south china sea abstract the sulfate methane transition zone smtz is an important diagenetic redox boundary within marine sediments where the anaerobic oxidation of methane aom coupled with bacterial sulfate reduction can promote sulfur isotopic enrichments in several solid phase minerals including pyrite fes2 authigenic pyrite can form in concentrated abundances within the smtz and as such can be used as a proxy to identify paleo smtzs this study uses enrichments in 34s and anomalously high abundances of authigenic pyrites in 287 samples from the northern south china sea scs to determine the paleo smtz the pyrite samples were collected from sediment cores acquired at three sites each of which are known to be located in natural gas hydrate bearing regions we assess the relative abundances of authigenic pyrites the types of pyrite morphologies recovered in the cored sediments and the sulfur isotopic values of recovered pyrite samples using two methods 1 handpicked sample analysis using a binocular microscope and 2 the chromium reduction method our results show that pyrite concentrations and sulfur isotopic compositions exhibit synchronous fluctuations particularly from 6 8 m below seafloor mbsf to 8 4 mbsf at all three study sites there is a significant increase in the occurrence of rod like pyrite morphology within this key interval we define the position of the paleo smtz by the presence of anomalously high accumulations of pyrites at greater than 5 0 wt using the handpicking method or greater than 0 5 wt via the chromium reduction method along with positive 34s excursions greater than 10 0 vcdt we discovered a regional paleo smtz that is shallower than the modern smtz suggesting a previous period of elevated methane flux from depth possibly related to widespread gas hydrate dissociation

deepwater circulation variation in the south china sea since the last glacial maximum deepwater circulation plays a central role in global climate compared with the atlantic the pacific deepwater circulation s history remains unclear the luzon overflow a branch of the north pacific deep water determines the ventilation rate of the south china sea scs basin sedimentary magnetic properties in the scs reflect millennial scale fluctuations in deep current intensity and orientation the data suggest a slightly stronger current at the last glacial maximum compared to the holocene but the most striking increase in deep current occurred during heinrich stadial 1 h1 and to a lesser extent during the younger dryas yd results of a transient deglacial experiment suggest that the northeastern current strengthening at the entrance of the scs during h1 and the yd times of weak north atlantic deep water formation could be linked to enhanced formation of north pacific deep water

dense shelf water formation process in the sea of okhotsk based on an ice ocean coupled model 1 formation process of the dense shelf water dsw in the sea of okhotsk was investigated with an ice ocean coupled model the hindcast through 1998 2000 modeled the anomalous ice productions being controlled by air temperature and mean ice speed over the coastal area ice production was larger by 30 in 1998 1999 while less developed ice cover in 1999 2000 allowed larger heat loss from the ocean the compensating heat loss sustained the similar production of the dsw for 26 75sin 1998 1999 however ice production thickened up the density constitution of the dsw which was significantly denser in 1998 1999 an experiment without brine rejection suggested such modification of the density constitution plays a rather more important role in brine rejection for the dsw property than an increase of the volumetric production the signal of brine rejection reached the 27slayer farther south in the kuril basin the model also showed that when winter outflow of the dsw from the continental shelf was neglected as is the case in observational estimations the annual production was underestimated by 20 compared with actual productions in 1998 2000 ice production was increased as the air ice drag coefficient cdai increased and as the ice water drag coefficient cdiw decreased because of the intensified polynya activity in contrast the density constitution of the dsw was lightened with the increased cdai as a linear balance of dominantly intensified advection and slight increase of ice production consequently the dsw property seemed insensitive to cdai and cdiw compared with the anomalous air conditions year by year

fault rock injections record paleo earthquakes fault rocks such as pseudotachylyte melt or granular gouge are sometimes injected into cracks off a fault surface the width to height ratio of the injection veins is a direct measure of the shear strain in the wall rock required to accommodate the injection so the aspect ratios preserve a record of the overpressure opening the cracks and injecting melt or fluidized granular material from the fault zone we measured the aspect ratios for 201 pseudotachylyte injections and 29 granular injections they have aspect ratios of 0 2 0 177 0 025 and 0 227 0 077 respectively within 99 confidence these are significantly proportionally wider than the aspect ratios of ordinary dikes from 10 4 to 10 3 the injection aspect ratios exceed the usual limit of elastic strain in the wallrock 1 so we infer that the injection veins were accommodated by permanent deformation by microcracking and slip on foliation surfaces in the host rock which is difficult to detect observationally the fully elastic model therefore offers an upper bound on the stress required to open these injection veins 10 8 210 10 pa with higher pressures in stiffer host rock lithologies these overpressures cannot be achieved by expansion of the fault rock fluids during melting or gouge fluidization mechanisms as the pressure along the fault is limited to 10 7

compositions of foraminifera rich turbidite sediments from the shenhu area on the northern slope of the south china sea implication for the presence of deep water bottom currents abstract the sediments in gravity core dh 1 collected from shenhu area on the northern slope of the south china sea are composed of two dark grey clay silt layers a1 and a3 and two foraminifera rich layers a2 and a4 a1 is the top layer and a4 is the bottom layer major and trace metal contents along with grain size and mineralogic data suggest that these silt layers represent background hemipelagic sedimentation unlike silt layers the intervening foraminifera rich layera4 exhibits a fining upward trend is distal turbidite grain size cm diagram and the sharp contacts between the foraminifera rich layer a2 and the upper and lower layers suggest layer a2 is the result of depositional interaction between turbidite and bottom currents ams 14c dating of planktonic foraminifera indicate the age of the turbidite in a2 is between15 3 ka and 22 6 ka we hypothesize that turbidite formation in this period was related to the increase supply of terrigenous matter since the last glacial maximum the rapid deposition of each turbidite led to reduced rates of oxygen diffusion into the sediment allowing anoxic conditions develop in sediments and fostering u enrichment 3 1 g g in foraminifera rich layer a4b in contrast decrease concentration of u and u mo ratios in foraminifera rich layera2 which is possibly due to u remobilization as a consequence of downward penetration of the oxidation front from the oxygen rich bottom currents these new data suggest that authigenic u was quite sensitive to the inflow of bottom currents and u mo ratios may indicate the depositional environmental change in relation to the bottom current action on the turbidite

vivianite is a major sink for phosphorus in methanogenic coastal surface sediments abstract studies of authigenic phosphorus p minerals in marine sediments typically focus on authigenic carbonate fluorapatite which is considered to be the major sink for p in marine sediments and can easily be semi quantitatively extracted with the sedex sequential extraction method the role of other potentially important authigenic p phases such as the reduced iron fe phosphate mineral vivianite fe ii 3 po4 8h2o has so far largely been ignored in marine systems this is in part likely due to the fact that the sedex method does not distinguish between vivianite and p associated with fe oxides here we show that vivianite can be quantified in marine sediments by combining the sedex method with microscopic and spectroscopic techniques such as micro x ray fluorescence xrf elemental mapping of resin embedded sediments as well as scanning electron microscope energy dispersive spectroscopy sem eds and powder x ray diffraction xrd we further demonstrate that resin embedding of vertically intact sediment sub cores enables the use of synchrotron based microanalysis x ray absorption near edge structure xanes spectroscopy to differentiate between different p burial phases in aquatic sediments our results reveal that vivianite represents a major burial sink for p below a shallow sulfate methane transition zone in bothnian sea sediments accounting for 40 50 of total p burial we further show that anaerobic oxidation of methane aom drives a sink switching from fe oxide bound p to vivianite by driving the release of both phosphate aom with sulfate and fe oxides and ferrous fe aom with fe oxides to the pore water allowing supersaturation with respect to vivianite to be reached the vivianite in the sediment contains significant amounts of manganese 4 8 wt similar to vivianite obtained from freshwater sediments our results indicate that methane dynamics play a key role in providing conditions that allow for vivianite authigenesis in coastal surface sediments we suggest that vivianite may act as an important burial sink for p in brackish coastal environments worldwide

distribution and formation of okhotsk sea intermediate water an analysis of isopycnal climatological data 1 in order to clarify the distribution and formation of okhotsk sea intermediate water osiw an isopycnal climatological data set based on all of the available historical observations is developed and examined the isopycnal maps clearly show that there are two direct ventilation sources for osiw dense shelf water dsw with cold and fresh properties influenced by sea ice formation in the northwest shelf region and forerunner of soya warm current water fscw which has warm and saline properties originating in the japan sea the cold and fresh water extends southward from the northwest shelf to the shelf slope off sakhalin island it suggests that dsw is transported southward by the east sakhalin current the dsw enters the kuril basin and mixes with fscw and western subarctic water wsaw originating from the north pacific to form osiw the annual mean production rate of dsw estimated from the total volume of dsw over the shelf in spring and summer is 0 67 sv 1 sv 106 m3 s the annual mean volume transport of fscw is estimated to be 0 08 sv on the basis of its cross section area and the current speed assumption of isopycnal mixing yields a mixing ratio of 1 1 0 1 among dsw wsaw and fscw to form osiw we estimate the annual production rate of osiw to be 1 4 sv the corresponding osiw s renewal time is 7 years continued assumption of isopycnal mixing yields a mixing ratio of 0 6 0 4 between wsaw and osiw to form oyashio intermediate water oyiw

distribution formation and seasonal variability of okhotsk sea mode water 1 russian historical data and recently completed conductivity temperature depth surveys are used to examine the formation and spread in the deep ohkotsk sea of dense shelf water dsw produced in the okhotsk sea polynyas isopycnal analysis indicates that all of the main polynyas contribute to the ventilation at 27 1 vigorous tidal mixing leads to outflow of water with a density of only about 26 7 in the western okhotsk sea the east sakhalin current rapidly transports modified dense shelf water along the eastern sakhalin slope to the kuril basin where it is subject to further mixing because of the large anticyclonic eddies and tides most of the dense water flows off the shelves in spring their average flux does not exceed 0 2 sv in summer and fall the shelf water transport and water exchange with the north pacific cause large seasonal variations of temperature at densities of 26 7 27 0 depths of 150 500 m in the kuril basin where the average temperature minimum occurs in april may and the average temperature maximum occurs in september with a range of 0 2 0 7 c the average seasonal variations of salinity are quite small and do not exceed 0 05 psu the soya water mixed by winter convection penetrating to depths greater than 200 m in the southern kuril basin also produces freezing water with density greater than 26 7 using a simple isopycnal box model and seasonal observations the osmw production rate is seen to increase in summer up to 2 2 1 7 sv mainly because of increased north pacific inflow and drops in winter to 0 2 0 1 sv a compensating decrease in temperature in the kuril basin implies a dsw volume transport of 1 4 1 1 sv from february through may the residence time of the osmw in the kuril basin is 2 1 7 years

phosphorus dynamics around the sulphate methane transition in continental margin sediments authigenic apatite and fe ii phosphates abstract the formation of authigenic phosphate minerals in marine sediments is an important process for the burial and long term storage of the bio essential nutrient phosphorus p in this context we report the composition of pore waters bulk sediments and the speciation of p in four sediment cores recovered on the continental margins off the amazon rio de la plata and zambezi rivers here pronounced sulphate methane transitions smts occur between 4 5 and 6 5 m sediment depth where sulphate is consumed by the anaerobic oxidation of methane and free hydrogen sulphide builds up in the pore waters this leads to the reductive dissolution of primary fe oxyhydr oxides feox by hydrogen sulphide and the subsequent liberation of feox adsorbed phosphate into pore waters at the smt the released phosphate builds up to significant concentrations making it available for the precipitation of authigenic minerals within and below the smt using a sequential p extraction we find consistently high contributions of carbonate fluorapatite cfa to the total p pool within the smt where it likely precipitates due to high local phosphate concentrations high alkalinity and abundant dissolved ca in the pore waters phreeqc calculations confirm these results with highest saturation states with respect to authigenic apatite calculated at all smts cfa authigenesis however is insufficient to completely consume pore water phosphate leading to diffusive loss of phosphate from the smt while the upward decrease in phosphate above the smt is relatively gentle the significantly steeper phosphate gradient into underlying sediments suggests the formation of another authigenic mineral phase sequential p extraction and phreeqc results clearly show that the dominant authigenic phase below the smt is not cfa instead geochemical conditions below the sulphidic zone at all four sites are favourable for the precipitation of fe ii phosphate minerals e g vivianite these conditions are summarized as the absence of sulphate and free hydrogen sulphide but the presence of fe 2 and phosphate in pore waters and low calcium carbonate contents in the sediment while we did not directly detect or quantify fe ii phosphate minerals fe bound p clearly increases in the sediments below the sulphidic zones at all studied sites and this is where highest pore water saturation states with respect to vivianite are calculated with phreeqc in addition geochemical inverse models performed in phreeqc show that vivianite formation is an important geochemical process controlling the observed patterns of dissolved p and fe ph and redox potential of the pore waters analysed below the smt we therefore argue that fe ii phosphate minerals are formed in these ocean margin sediments on a large scale and pore water and sediment data indicate that this fe bound p largely originates from feox adsorbed phosphate liberated within the sulphidic smt this study suggests that under specific but not unusual depositional conditions smts are hotspots for biogeochemical p cycling in marginal marine sediments worldwide with cfa precipitating within the smt and fe ii phosphates forming below it it also adds to the growing evidence that fe ii phosphates may contribute significantly to the long term burial of reactive p phases in fe rich methanic marine sediments and thus act as a previously underestimated sedimentary p sink