time variations of δ15n of organic nitrogen in deep western subarctic pacific sediment over the last 145 ka we present 15n data of organic nitrogen 15non from a deep western subarctic pacific wsap sediment core over the last 145 ka to remove the effect of inorganic nitrogen in on bulk nitrogen bn we used the contents of in and bn and the isotopic ratios of in 15nin and bn 15nbn the contribution of in to bn was largest 59 and 15nin had lower values than 15nbn however the large contributions of in to bn and the distinct isotopic values did not largely change any variability associated with 15non in the 15nbn thus it is possible to use 15nbn in carrying out paleoceanographic research with 15n at least in the open wsap the 15non values have been affected by long term diagenesis making the values lower with depth in the sediment but the values during less productive colder periods were generally lower compared to those during neighboring productive warmer periods the results might indicate that 15non during the less productive colder periods i e glacial periods were lower than that during the productive warmer periods i e interglacial periods previous studies have reported that the biological production in wsap where it is limited by iron at present during glacial periods was at more reduced level than during interglacials despite there being more eolian dust supply during glacial periods this indicates that the increase of biological production with enhanced iron supply derived from eolian dust during the glacial periods did not occur if this is the case and alternatively the iron input from the subsurface layer to the surface mixed layer by ventilation process is more important as suggested by recent works the variations in 15non would be explained by the variations in the fe no3 ratio in the upwelled water although 15non has been affected by long term diagenesis in the sediment the usage of this isotopic ratio provides new implication regarding the past ocean circulation in the open wsap

impact processes permafrost dynamics and climate and environmental variability in the terrestrial arctic as inferred from the unique 3 6 myr record of lake el gygytgyn far east russia a review lake el gygytgyn in far east russia is a 3 6 myr old impact crater lake located in an area that has never been affected by cenozoic glaciations nor desiccation the unique sediment record of the l

influence of stratification on residual tidal currents in the yellow sea the m 2 tide and residual current generation in the yellow sea are examined using the blumberg and mellor 1987 numerical coastal ocean circulation model with no stratification the model tide and tidal currents show good agreement with the observed tide and tidal currents coherent residual currents are predicted around the southwest of korea flowing northward as a strong jet with a maximum speed of 8cm s 1 and around yangtze bank flowing southeastward as a weak broad current with initial stratification tidal mixing occurs in the bottom boundary layer which leads to surface tidal fronts around yangtze bank and the southwest of korea and our model experiments reproduce successfully the basic water property structure in these regions the resulting stratified tidal rectification intensifies the residual currents at the front and at the top of the bottom boundary layer over the sloping bottom so that the vertical structure of the residual currents is modified the strong residual currents in the top of the bottom mixed layer around yangtze bank support the interpretation of kim et al 1991 for the southeastward movement of yellow sea bottom cold water in summer the residual currents in the surface layer reach 40 of the mean currents observed by beardsley et al 1992 using satellite tracked drifters deployed in the yellow sea in summer these results suggest that stratified tidal rectification is an important process in driving the summertime subtidal flow in the yellow sea

the tidally averaged momentum balance in a partially and periodically stratified estuary abstract observations of turbulent stresses and mean velocities over an entire spring neap cycle are used to evaluate the dynamics of tidally averaged flows in a partially stratified estuarine channel in a depth averaged sense the net flow in this channel is up estuary due to interaction of tidal forcing with the geometry of the larger basin the depth variable tidally averaged flow has the form of an estuarine exchange flow downstream at the surface upstream at depth and varies in response to the neap spring transition the weakening of the tidally averaged exchange during the spring tides appears to be a result of decreased stratification on the tidal time scale rather than changes in bed stress the dynamics of the estuarine exchange flow are defined by a balance between the vertical divergence of the tidally averaged turbulent stress and the tidally averaged pressure gradient in the lower water column in the upper water column tidal stresses are important contributors particularly during the n

dynamics of surface currents over qingdao coastal waters in august 2008 1 surface currents measured by high frequency hf radar are used to investigate the dynamics in the coastal waters of qingdao china on the western coast of the yellow sea different factors affecting the surface currents are revealed by dynamical analysis harmonic tidal analysis shows that the coastal tidal currents are barotropic and their temporal evolution is mainly influenced by the semidiurnal tidal constitutes topography and geometry it is also found that their horizontal distribution represents the effect of local topography at sub tidal frequencies the high correlation between winds and the sub tidal surface currents indicates a crucial role of wind forcing in driving the currents varying wind direction coupled with small scale features of the coastal geometry results in complicated sub mesoscale circulation in addition the monthly coastal circulation is characterized by an eddy structure and is primarily determined by the outflow which is closely associated with the sea level slope along the coast the variability of the residual currents is studied by analyzing the cross shore momentum equation with wind stress sea level records and hf radar currents it is shown that both the barotropic pressure gradient and the nonlinear tidal stress contribute to the variations of the residual currents near the bay mouth and further govern the coastal monthly circulation in august 2008

patterns of deglacial warming in the pacific ocean a review with emphasis on the time interval of heinrich event 1 abstract based on a compilation of currently available records of past sea surface temperature sst variability estimated from a variety of different proxies the regional scale deglacial sst development in the pacific ocean is tentatively classified into four endmember types the subtropical and tropical pacific is characterized by a continuous deglacial warming without marked interruption during the time interval of heinrich event 1 h1 whereas the subarctic north pacific exhibits centennial scale warm cold oscillations during this time interval sst records from marginal seas of the pacific show a deglacial warming interrupted by a cooling event coeval with h1 followed by a marked bolling sst increase a single sst record from the southwestern subantarctic pacific displays a continuous deglacial warming across h1 followed by an antarctic cold reversal type cooling during the allerod thus in contrast to the deglacial sst development in the atlantic which has been inferred to be overwhelmingly driven by the redistribution of heat through changes in the meridional overturning circulation moc none of the open oceanic pacific sst records reviewed here displays any obvious and or dominant response to the reduction of the moc and or the reorganization of atmospheric circulation during h1 within the limits of absolute chronologies all tropical and subtropical pacific sst records show an onset of deglacial warming at 19 1 ka coeval with the onset of the deglacial rise in sea level

glacial interglacial changes in subarctic north pacific stratification since the first evidence of low algal productivity during ice ages in the antarctic zone of the southern ocean was discovered there has been debate as to whether it was associated with increased polar ocean stratification or with sea ice cover shortening the productive season the sediment concentration of biogenic barium at ocean drilling program site 882 indicates low algal productivity during ice ages in the subarctic north pacific as well site 882 is located southeast of the summer sea ice extent even during glacial maxima ruling out sea ice driven light limitation and supporting stratification as the explanation with implications for the glacial cycles of atmospheric carbon dioxide concentration

evidence from diatom bound nitrogen isotopes for subarctic pacific stratification during the last ice age and a link to north pacific denitrification changes higher diatom bound d 15 n 70 wt lower opal content and 1200 ppm lower biogenic barium taken together and with constraints on sediment accumulation rate these results suggest a reduced supply of nitrate to the surface due to stronger stratification of the upper water column of the bering sea during glacial times with more complete nitrate consumption resulting from continued iron supply through atmospheric deposition this finding extends the body of evidence for a pervasive link between cold climates and polar ocean stratification in addition we hypothesize that more complete nutrient consumption in the glacial age subarctic pacific contributed to the previously observed ice age reduction in suboxia and denitrification in the eastern tropical north pacific by lowering the nutrient content of the intermediate depth water formed in the subpolar north pacific in the deglacial interval of the bering sea record two apparent peaks in export productivity are associated with maxima in diatom bound and bulk sediment d 15 n the high d 15 n in these intervals may have resulted from greater surface nutrient consumption during this period however the synchroneity of the deglacial peaks in the bering sea with similar bulk sediment d 15 n changes in the eastern pacific margin and the presence of sediment lamination within the bering sea during the deposition of the productivity peaks raise the possibility that both regional and local denitrification worked to raise the d 15 n of the nitrate feeding bering sea surface waters at these times

a surface velocity spiral observed with adcp and hf radar in the tsushima strait 1 the structure of a wind driven flow in the tsushima strait is investigated with moored acoustic doppler current profiler adcp and hf radar two adcps of high and low acoustic frequencies are simultaneously used to measure velocities in both the surface boundary layer and the interior with high resolutions the velocity relative to an interior flow in the surface boundary layer is estimated by subtracting the reference velocity estimated from velocities at greater depths from a velocity in the surface layer and complex principal component analysis pca of the lagged wind stress and the relative velocity is performed despite a short 2 weeks observation period of relatively calm and variable wind a clockwise velocity spiral similar to a theoretical ekman spiral is detected as the first mode of pca ekman transport estimated from the relative velocities of the first mode agrees best with ekman transport expected from wind stress of the first mode with 11 13 hours time lag for which the explained variance of the first mode is also largest this indicates that a wind driven flow is balanced with wind stress after 11 13 hours half of the inertial period at this latitude eddy viscosity is also inferred from wind stress and the relative velocities of the first mode it is found to increase from o 10 3 m 2 s 1 at greater depth to o 10 2 m 2 s 1 near the sea surface

refining the alkenone pco2 method i lessons from the quaternary glacial cycles abstract the alkenone pco2 method is one of the most widely used approaches to reconstruct atmospheric co2 in the cenozoic the method depends upon fractionation of stable carbon isotopes during algal photosynthesis expressed as ep37 2 and a physiological scaling parameter b that accounts for biological factors such as growth rate cell size and membrane permeability alkenone derived co2 records for the late pleistocene however are poorly correlated with ice core co2 challenging the classic model that considers most of the co2 used for coccolithophore photosynthesis to be acquired through simple diffusion in this study we investigate the nature of the b term and the underlying patterns of the sensitivity of ep37 2 to pco2 changes we generated two new ep37 2 records from the south china sea md01 2392 and tropical atlantic ocean odp 668b and compiled other published ep37 2 records over glacial interglacial cycles using the ep37 2 data ocean temperature estimates and ice core co2 we were able to back calculate the corresponding values of b at all locations b varies over glacial cycles the highest values of b correspond to peak interglacial stages indicating that the phytoplankton growth rate is faster or cell size is smaller during interglacials than during glacial periods we further show that the range of ep37 2 between glacial and interglacial conditions ep37 2 scales with growth conditions consistent with the predictions of the carbon isotope fractionation model based on co2 diffusion in other words the sensitivity of ep37 2 to pco2 changes increases where the modern b values are large contradicting the recommendations that oligotrophic sites are the best for alkenone co2 applications because of the presumed stability of b using the average back calculated b value for each site the composite pco2 estimates from md01 2392 and odp 668b the two sites with adequate ep37 2 sensitivity show broad agreement with the ice core co2 record

empirical cotidal charts of the bohai yellow and east china seas from 10 years of topex poseidon altimetry 1 harmonic analysis of 10 years of topex poseidon tp along track altimetry is performed to derive the semidiurnal diurnal long period and quarter diurnal tides in the bohai yellow and east china seas the tp solutions are evaluated through intercomparison for crossover points and comparison with the ground truth showing that the accuracy of tp solutions in the study area has achieved levels of 2 4 cm in amplitudes and 5degrees in phase lags for principal constituents m 2 s 2 k 1 o 1 and s a the tp derived s a amplitudes have a systematic bias of about 10 as compared with the ground truth indicating the possible importance of loading effect of this constituent in the study area which is generally not considered in geodetic surveys the tidal harmonics from tp altimetry and at coastal and island stations are used to give a new set of empirical cotidal charts for principal constituents m 2 s 2 k 1 o 1 and s a the accuracy of these new charts is believed to be significantly higher than the previous charts for the offshore area

similar glacial and interglacial export bioproductivity in the atlantic sector of the southern ocean multiproxy evidence and implications for glacial atmospheric co2 we present time series of export productivity proxy data including 230thex normalized deposition rates rain rates of 10be dissolution corrected biogenic ba and biogenic opal as well as authigenic u concentrations which are complemented by rain rates of total detrital fe and sea ice indicating diatom abundances from five sediment cores across the atlantic sector of the southern ocean covering the past 150 000 years the results suggest that 10be rain rates and authigenic u concentration cannot serve as quantitative paleoproductivity proxies because they have also been influenced by detrital particle fluxes in the case of 10be and bulk sedimentation rates sediment focussing and deep water oxygenation in the case of u the combined results of the remaining productivity proxies of this study rain rates of biogenic opal and biogenic ba in those sections without authigenic u and other previously published proxy data from the southern ocean 231pa 230th and nitrogen isotopes suggest that a combination of sea ice cover shallow remineralization depth and stratification of the glacial water column south of the present position of the antarctic polar front and possibly fe fertilization north of it have been the main controlling factors of export paleoproductivity in the southern ocean over the last 150 000 years an overall glacial increase of export paleoproductivity is not supported by the data implying that bioproductivity variations in the southern ocean are unlikely to have contributed to the major glacial atmospheric co2 drawdown observed in ice cores

heavy metal trends in floodplain sediments and valley fill river lahn germany abstract sampling along the river lahn a major tributary to the river rhine that flows through an agrarian region of west central germany reveals that heavy metal pollution occurs outside major industrial regions and mined landscapes along a 60 km reach of the river between marburg and wetzlar mean concentrations of cu pb and zn at depths of 5 and 15 cm in four floodplain transects were greater than background levels concentrations declined sharply between 15 and 25 cm laterally concentrations peaked at the bank top and in the near channel zone of the floodplain beyond the near channel zone generally up to 100 m from the channel concentrations were much less and fairly uniform to the valley wall the clustering of metals close to the channel suggests that they are a fluvial rather than an eolian deposit during floods of a moderate magnitude sediments and attached metals are deposited soon after the river overtops its banks although the overall store of metals in the valley is less than that along the rhine near channel metal concentrations are similar to those along rivers draining major industrial and mined areas

expansion of subarctic water masses in the north atlantic and pacific oceans and implications for mid pleistocene ice sheet growth 1 past surface ocean circulation changes associated with the mid pleistocene transition 0 9 0 6 ma were reconstructed in the northern north atlantic odp 983 and the northwest pacific odp 882 using proxies for subarctic subpolar water mass distributions c37 4 alkenone and sea surface temperature u37 both sites experienced a secular expansion of subarctic waters from 1 15 ma spanning both glacial and interglacial intervals after 0 9 ma low c37 4 at site 983 records a northward retreat of subarctic waters during interglacials in the atlantic while continued high glacial c37 4 indicate extensive subarctic waters during glacial maxima associated with the development of the larger late pleistocene ice sheets in contrast a secular decline in c37 4 occurred at site 882 from 0 9 to 0 5 ma marking a more gradual retreat of subarctic conditions in the pacific it is proposed that the expansion of subarctic waters between 1 15 and 0 9 ma exerted negative feedbacks to the moisture supply to the ice sheet source regions and may account for the apparent delayed ice sheet response to atmosphere ocean circulation changes associated with the mid pleistocene transition that began as early as 1 2 ma

combined oxygen and silicon isotope analysis of diatom silica from a deglacial subarctic pacific record we present an sif4 separation line coupled to a laser fluorination system which allows for an efficient combined silica d18o and d30si analysis 50 min per sample the required sample weight of 1 5 2 0mg allows for high resolution isotope studies on biogenic opal besides analytical tests the new instrumentation set up was used to analyse two marine diatom fractions 63 mm 10 20mm with different diatom species compositions extracted from a bolling allerod holocene core section md01 2416 north west nw pacific to evaluate the palaeoceanographic significance of the diatom isotopic signals and to address isotopic effects related to contamination and species related isotope effects vital and environmental effects while d30si offsets between the two fractions were not discernible supporting the absence of species related silicon isotope effects systematic offsets occur between the d18o records although small these offsets point to species related isotope effects as bias by contamination can be discarded the new records strengthen the palaeoceanographic history during the last deglaciation in the nw pacific characterized by a sequence of events with varying surface water structure and biological productivity with such palaeoceanographic evolution it becomes unlikely that the observed systematic d18o offsets signal seasonal temperature variability this calls for reconsideration of vital effects generally excluded to affect d18o measurements

remotely sensed surface currents in monterey bay from shore based hf radar coastal ocean dynamics application radar near surface currents in monterey bay derived from a network of shore based hf radars are presented for august december 1994 and compared with those from april to september 1992 focus is placed on the low frequency 2 to 30 day period motions in the remotely sensed data and on comparison of radar derived currents with moored current and wind observations ship based acoustic doppler current profiler observations satellite based surface temperature imagery and surface drifter velocities the radar derived picture of the late summer mean flow is very similar in the two realizations and is consistent with historical data flow is equatorward in the outer part of the bay poleward in a narrow band nearshore and very sluggish in the middle of the bay low pass filtered time series of radar derived currents are highly correlated with moored current observations and with winds in the outer part of the bay the vector time series are also coherent across a broad frequency band with currents typically in phase between 1 and 9 m depths and with 1 m currents typically 40 60 to the right of the wind overall these results confirm the utility of coastal ocean dynamics applications radar codar type hf radars for the study of coastal surface currents out to ranges 50 km from shore particularly for highly averaged fields data variability and comparison with in situ observations for high frequency 1 to 48 hour period motions point to the need to better characterize and minimize sources of error in the radar observations

dynamics of the last four glacial terminations recorded in lake van turkey abstract a well dated suite of lake van climate proxy data covering the last 360 ka documents environmental changes over 4 glacial interglacial cycles in eastern anatolia turkey the picture of cold and dry glacials and warm and wet interglacials emerging from pollen organic carbon authigenic carbonate content elemental profiling by xrf and lithological analyses is inconsistent with classical interpretation of oxygen isotopic composition of carbonates pointing to a more complex pattern in lake van region detailed analysis of glacial terminations allows for the constraining of a depositional model explaining different patterns observed in all the proxies we hypothesize that variations in relative contribution of rainfall snowmelt and glacier meltwater recharging the basin have a very important role for all sedimentary processes in lake van lake level of glacial lake van predominantly fed by snowmelt was low the water column was oxic and carbonates precipitating in the epilimnion recorded the light isotopic signature of inflow during terminations increasing rainfall and significant supply of mountain glaciers meltwater contributed to lake level rise increased rainfall enhanced density gradients in the water column and hindered mixing leading to development of bottom water anoxia carbonates precipitating during terminations show large fluctuations in their isotopic composition full interglacial conditions in lake van are characterized by high or slowly falling lake level rainfall and snowmelt feed the lake but due to re established mixing the isotopic composition of authigenic carbonates is heavier and closer to that of evaporation influenced lake water than that of runoff representing snowmelt and atmospheric precipitation

palaeoproductivity at the antarctic continental margin opal and barium records for the last 400 ka abstract records of biogenic opal and barium were measured in sediment cores at the antarctic continental margin in the area of the weddell lazarev and cosmonaut seas these records provide a qualitative and quantitative tool to estimate changes in palaeoproductivity over the last 400 ka the stratigraphy of the investigated cores is calibrated to a lithostratigraphy adjusted to a stable isotope record from the eastern weddell sea which is supported by a th dating method we present evidence that interglacial productivity along the antarctic continental margin is twice as high compared to subantarctic sites near south orkney a glacial interglacial pattern with high productivity during peak warm stages can be observed back to 400 ka high interglacial productivity is linked to a reduced sea ice coverage which is regulated by the heat flux introduced by north atlantic deep water nadw to the antarctic ocean generally good correlations between the barium and opal records of the sediment cores indicate that dissolution of opal in the water column and the sediment does not obscure the surface productivity signal therefore in this area biogenic opal in combination with other proxies can be used for palaeoproductivity estimates palaeoproductivity is also assessed quantitatively from the barium record using the approaches of dymond et al dymond j suess e lyle m 1992 barium in deep sea sediments a geochemical proxy for paleoproductivity paleoceanography 7 163 181 and francois et al francois r honjo s manganini s j ravizza g e 1995 biogenic barium fluxes to the deep sea implications for paleoproductivity reconstructions glob biochem cycles 9 2 289 303 palaeoproductivity rates obtained by both methods show a good temporal correspondence in peak warm stages higher values are computed with the approach of dymond et al 1992 though some barium may be provided by lateral advection of material as indicated by th data near south orkney both methods provide values which are representative of a high productivity area they are drastically reduced during glacial times the extent and duration of sea ice coverage and the persistence of coastal polynyas is considered to be of primary importance in controlling the flux of biogenic material to sediments of the antarctic continental margin

three dimensional residual tidal circulation in an elongated rotating basin abstract the three dimensional residual circulation driven by tides in an elongated basin of arbitrary depth is described with a small amplitude constant density model on the f plane the inclusion of rotation fundamentally alters the residual flow with rotation fluid is drawn into the basin on the right side of an observer looking toward the closed end in the northern hemisphere and the return flow is on the opposite side a lateral circulation is superposed on the axial flow with upwelling over the deeper part of each section and downwelling near the sides the residual flow is driven by a combination of advective terms including the lateral advection of axial momentum associated with the coriolis acceleration and stokes forcing tidally averaged fluid parcel trajectories are determined by integrating the lagrangian mean velocities with or without rotation these trajectories vary considerably depending on small differences in initial position as well as on basin shape and other parameters of the

pore fluid constraints on the temperature and oxygen isotopic composition of the glacial ocean pore fluids from the upper 60 meters of sediment 3000 meters below the surface of the tropical atlantic indicate that the oxygen isotopic composition 18 o of seawater at this site during the last glacial maximum was 0 8 0 1 per mil higher than it is today combined with the 18 o change in benthic foraminifera from this region the elevated ratio indicates that the temperature of deep water in the tropical atlantic ocean was 4 c colder during the last glacial maximum extrapolation from this site to a global average suggests that the ice volume contribution to the change in 18 o of foraminifera is 1 0 per mil which partially reconciles the foraminiferal oxygen isotope record of tropical sea surface temperatures with estimates from barbados corals and terrestrial climate proxies

polar stratification a critical view from the southern ocean oceanic stratification represents an effective mechanism to reduce vertical mixing of the water column thereby locking up carbon dioxide co2 in the deep sea and preventing air sea exchange of co2 it has been proposed that enhanced stratification of the upper water column in polar oceans during late cenozoic cooling episodes limited the upwelling of co2 rich deep waters and thus co2 release to the atmosphere resulting in a net global drawdown of atmospheric co2 increased stratification in the subarctic northwest pacific during both the onset of northern hemisphere glaciation at 2 73 ma and late quaternary glacial periods has been recently linked to enhanced ocean stratification south of the antarctic polar front apf in the pacific and atlantic sectors of the southern ocean increased stratification of southern ocean surface waters was mainly deduced from a reduction of biological production during these cooling episodes manifested by the decrease of geochemical proxies for productivity such as biogenic opal and barium in the marine sediment records however the records chosen from the southern ocean do not provide evidence for a more stratified upper water column rather the observed decrease in biological productivity is likely to have resulted from an expansion of annual sea ice coverage the sediment records suggest that south of the apf in the pacific and atlantic sectors of the southern ocean extensive sea ice may have contributed to the global co2 drawdown during glacial periods with hypothetical glacial increase of stratification in today s permanent open ocean zone merely being an add on caused by this expansion

influence of the water content on x ray fluorescence core scanning measurements in soft marine sediments the x ray fluorescence xrf core scanner provides bulk sediment chemistry data measured nondestructively at the split core sediment surface although this method is widely accepted there is little known about the effects of physical properties such as density and water content on xrf core scanner data comparison of xrf scanner measurements from the sediment surface and dry powder samples of sediment core geob7920 indicates strongly reduced element intensities for the lighter elements al and si we relate the lower element intensities of the measurements taken at the sediment surface to the amount of water in the sample volume analyzed by the xrf core scanner the heavier elements k ca ti and fe remain relatively unaffected by the variation of any physical property within sediment core geob7920 additionally we successfully use the elemental intensity of cl as a proxy for the seawater content in the sample volume analyzed by the xrf core scanner this enables the establishment of a correction function for the elements al and si that corrects for the radiation absorption of the water content in sediment core geob7920 off cape blanc nw africa

residual circulation in shallow estuaries 2 weakly stratified and partially mixed narrow estuaries long wave theory is used herein to analyze circulation in weakly stratified and partially mixed estuaries unlike the highly stratified systems considered in part 1 the flows considered here have only a minimal tidal frequency internal wave component these estuaries may therefore be modeled as the sum of weakly interacting barotropic and baroclinic modes the dominant factors driving the residual flow are finite amplitude barotropic effects in weakly stratified estuaries and a combination of barotropic effects and steady horizontal density gradient forcing in partially mixed estuaries the dominant vertical exchange mechanism in the weakly stratified case is bottom boundary induced turbulence and that in partially mixed estuaries is believed to be random internal wave interactions a model of the columbia river estuary under weakly stratified conditions accurately predicts the observed residual velocity and salinity fields and the tidal amplitude at which a transition to a highly stratified state takes place the partially mixed state is unstable in the columbia river estuary because the tides and buoyancy input are both too strong

calibration of xrf core scanners for quantitative geochemical logging of sediment cores theory and application abstract on line analysis of split sediment cores by xrf core scanners has become increasingly popular in the past decade because it allows nondestructive extraction of near continuous records of element intensities from sediment cores with a minimum of analytical effort a disadvantage of xrf core scanning relative to conventional geochemical analysis is the problematic conversion of core scanner output to element concentrations the main reason for this long standing problem is the poorly constrained measurement geometry attributable to inhomogeneity of the specimens e g variable water content and grain size distribution irregularities of the split core surface and in some setups spatial variations in thickness of an adhesive pore water film which forms directly below a protective foil covering the core surface we propose a log ratio calibration model for xrf core scanners derived from a combination of xrf spectrometry theory principles of compositional data analysis and empirical evidence the log ratio calibration model provides accurate and precise predictions of sediment composition element concentrations from xrf core scanner output with a limited number of parameters namely 2 d 1 where d equals the number of chemical elements whose concentrations are to be estimated the model can accommodate the inherent non linearity of the relation between relative intensities and concentrations which is apparent from the fact that it provides unbiased estimates an immediate corollary of our results is that log ratios of element intensities which are related to log ratios of element abundances by a simple linear transformation provide the most easily interpretable signals of relative changes in chemical composition consistent use of log ratios of element intensities or concentrations should minimise the risk of drawing erroneous conclusions from geochemical proxies the relative standard deviation precision of predicted element concentrations in core geob7920 is less than 2 stochastic simulations indicate that this level of precision can be attained with 40 randomly selected calibration specimens improved control over input errors and development of robust goodness of fit statistics allows xrf core scanning to be developed into a rigorous quantitative measurement technology the log ratio calibration equation derived in this study may be adapted to inter laboratory and inter instrument calibration as well

early diagenetic greigite as an indicator of paleosalinity changes in the middle miocene paratethys sea of central europe the miocene epicontinental paratethys sea of central eurasia has experienced multiple restriction and reconnection events to the open ocean magnetostratigraphy is an important dating tool to better understand the temporal and spatial paleoenvironmental variations associated with these changes magnetostratigraphy in the paratethys domain however is complicated by the presence of greigite fe3s4 here we report rock magnetic and x ray fluorescence data of the tisa section romania which was previously magnetostratigraphically dated at the middle miocene base at 12 8 ma and top at 12 2 ma this section comprises the badenian sarmatian extinction event bsee which is marked by a major salinity change from marine to brackish environments related to the opening of the connection between the central and the eastern paratethys basins in the marine badenian sediments below the bsee the pyritization process is shown to be complete because of abundant sulfate supply in the brackish sarmatian deposits four intervals with early diagenetic greigite are observed and linked to insufficient sulfate in the water column these four greigite intervals appear to correspond to maxima in the 100 kyr eccentricity cycle we propose that increased fresh water from the eastern paratethys basin during eccentricity maxima restricted the sulfate availability in the tisa area leading to a reduced hs production and enhanced greigite preservation the early diagenetic formation of greigite enables a quasi syn depositional recording of the paleomagnetic field which allows reliable paleomagnetic dating in this section our results further suggest greigite as a potential indicator for salinity changes during marine brackish transitions

marine radiocarbon evidence for the mechanism of deglacial atmospheric co2 rise we reconstructed the radiocarbon activity of intermediate waters in the eastern north pacific over the past 38 000 years radiocarbon activity paralleled that of the atmosphere except during deglaciation when intermediate water values fell by more than 300 per mil such a large decrease requires a deglacial injection of very old waters from a deep ocean carbon reservoir that was previously well isolated from the atmosphere the timing of intermediate water radiocarbon depletion closely matches that of atmospheric carbon dioxide rise and effectively traces the redistribution of carbon from the deep ocean to the atmosphere during deglaciation

paleonutrient and productivity records from the subarctic north pacific for pleistocene glacial terminations i to v our study addresses fundamental questions of the mode and timing of orbital and millennial scale changes in the meridional overturning circulation moc of the subarctic north pacific particular concerns are the vertical mixing the present and past abundance of nutrients in surface waters despite strong stratification and the north pacific north atlantic seesaw of oscillations in sea surface temperature sst we do this by generating and interpreting multiple records for glacial terminations i v down two long piston cores one each from the western and eastern subarctic pacific chlorins and biogenic opal are proxies for surface water productivity delta 13 c of epibenthic foraminifera is a record of deepwater ventilation and the delta 13 c of n pachyderma sin is a tracer of nutrients in subsurface waters that extend up to the sea surface during times of vertical mixing the degree of mixing is traced by pairing sst and delta 18 o records of planktic surface and subsurface pycnocline dwellers tight age control is deduced from a suite of age calibrated 14 c plateau boundaries for termination i and benthic delta 18 o and geomagnetic events for the last 800 ka carbon 14 paleoreservoir ages record the ages of surface and deep waters to uncover short term changes in moc over termination i we have defined a standard sequence of short term productivity events for termination i also evident during terminations ii to v and subsequent interglacials over the last 450 ka the peak glacial regime of stable stratification and low productivity terminated together with the end of ice rafting and melting near 17 ka similar to 2000 years after the onset of termination i pulses of vertical mixing and incursion of warm surface waters from the subtropics followed convected young water masses finally penetrated down to 3600 m water depth at 17 0 to less than 14 5 ka significantly improving bottom water ventilation through the late deglacial and earliest interglacial mixing with upwelled nutrients from the pycnocline induced short term maxima in algal production of chlorins and biogenic opal near 17 15 and 15 12 ka respectively deglacial meltwater incursions in the aleutian current and silica input from north american rivers also promoted east pacific productivity after 15 5 ka productivity decreased during the late deglacial and early interglacial coeval with an exceptional peak in caco 3 preservation caused by both low organic flux and well ventilated deepwater subsequently low salinity and cool surface waters and in turn stratification were gradually restored a second opal dominated productivity maximum marked the ends of interglacials the deglacial pulses of vertical mixing around 17 11 ka imply an important contribution of the north pacific to the coeval release of oceanic co 2 into the atmosphere and support the east west seesaw model of climate change

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

southern ocean control on the extent of denitrification in the southeast pacific over the last 70 ka abstract temporal changes in oceanic denitrification the bacterial reduction of nitrate under suboxic conditions highlight the potential importance of n inventory changes and the production of n 2 o on the climate system at the same time the cause of the globally observed variation in denitrification remains unclear high resolution benthic foraminiferal oxygen isotope and bulk sediment nitrogen isotope records from odp site 1234 on the chile margin record integrated denitrification changes within the peru chile upwelling system over the last 70 ka denitrification changes in the southeast pacific are coherent with antarctic climate changes recorded by the byrd ice core 18 o record and lead northern hemisphere climate events the southern hemisphere character of the chile margin 15 n record suggests that episodes of reduced denitrification in the se pacific represent times when more oxygen was supplied as the result of changes in the ventilation and preformed nutrient content of subantarctic mode water samw which forms in the subantarctic zone of the southern ocean and feeds into the low latitude thermocline

glacial to interglacial surface nutrient variations of bering deep basins recorded by δ13c and δ15n of sedimentary organic matter stable carbon and nitrogen isotopic ratios 13c and 15n of organic matter were measured in three sediment cores from deep basins of the bering sea to investigate past changes in surface nutrient conditions for surface water reconstructions hemipelagic layers in the cores were distinguished from turbidite layers on the basis of their sedimentary structures and 14c ages and analyzed for isotopic studies although 13c profiles may have been affected by diagenesis both 15n and 13c values showed common positive anomalies during the last deglaciation we explain these anomalies as reflecting suppressed vertical mixing and low nutrient concentrations in surface waters caused by injection of meltwater from alpine glaciers around the bering sea appendix tables are available with entire article on microfiche order from american geophysical union 2000 florida avenue n w washington dc 20009 document p95 003 2 50 payment must accompany order

glacial interglacial changes in nutrient supply and stratification in the western subarctic north pacific since the penultimate glacial maximum abstract in piston cores from the open subarctic pacific and the okhotsk sea diatom bound 15n 15ndb biogenic opal calcium carbonate and barium were measured from coretop to the previous glacial maximum mis 6 glacial intervals are generally characterized by high 15ndb 8 and low productivity whereas interglacial intervals have a lower 15ndb 5 7 6 3 and indicate high biogenic productivity these data extend the regional swath of evidence for nearly complete surface nutrient utilization during glacial maxima consistent with stronger upper water column stratification throughout the subarctic region during colder intervals an early deglacial decline in 15ndb of 2 at 17 5 ka previously observed in the bering sea is found here in the open subarctic pacific record and arguably also in the okhotsk and a case can be made that a similar decrease in 15ndb occurred in both regions at the previous deglaciation as well the early deglacial 15ndb decrease best explained by a decrease in surface nutrient utilization appears synchronous with southern hemisphere associated deglacial changes and with the heinrich 1 event in the north atlantic this 15ndb decrease may signal the initial deglacial weakening in subarctic north pacific stratification and or a deglacial increase in shallow subsurface nitrate concentration if the former it would be the north pacific analogue to the increase in vertical exchange inferred for the southern ocean at the time of heinrich event 1 in either case the lack of any clear change in paleoproductivity proxies during this interval would seem to require an early deglacial decrease in the iron to nitrate ratio of subsurface nutrient supply or the predominance of light limitation of phytoplankton growth during the deglaciation prior to bolling allerod warming

mid holocene origin of the sea surface salinity low in the subarctic north pacific images core md01 2416 511n 1681e provides the first centennial scale multiproxy record of holocene variation in north pacific sea surface temperature sst salinity and biogenic productivity our results reveal a gradual decrease in subarctic sst by 3 51c from 11 1 to 4 2 ka and a stepwise long term decrease in sea surface salinity sss by 2 3 p s u early holocene sss were as high as in the modern subtropical pacific the steep halocline and stratification that is characteristic of the present day subarctic northpacific surface ocean is a fairly recent feature developed as a product of mid holocene environmental ch ange highsss matched a salient productivity maximum of biogenic opal during bolling to early holocene times reaching levels similar to those observed during preglacial times in the warm mid pliocene prior to 2 73 ma similar productivity spikes marked every preceding glacial termination of the last 800 ka indicating recurrent short term events of mid pliocene style intense upwelling of nutrient rich pacific deepwater in the pleistocene such events led to a repeated exposure of co2 richdeepwater at the ocean surface facilitating a transient co2 release to the atmosphere but the timing and duration of these events repudiate a long term influence of the subarctic northpacific on global atmosph eric co 2 concentration r 2004 elsevier ltd all rights reserved

hydrological changes and paleoproductivity in the gulf of california during middle and late holocene and their relationship with itcz and north american monsoon variability abstract this study investigates changes in precipitation patterns and variations in paleoproductivity in the tropical pacific region associated with the north american monsoon intertropical convergence zone itcz latitudinal migration and changes in insolation during the middle and late holocene major and trace element records al ba c k si and ti and zr al and ba al ratios in a core from alfonso basin southern gulf of california are used as proxies of terrigenous input and bio productivity records reveal an increase in precipitation and low bio productivity ca 6200 to 2400 cal yr bp associated with the strengthening of monsoonal precipitation and northward shift of the itcz mean position in the eastern tropical pacific a multi centennial drought from ca 2400 to 1900 cal yr bp and a dry and cold interval ca 700 and 500 cal yr bp are characterized by strong aeolian input and enhanced productivity associated with diminution of the summer monsoonal precipitation and reduced insolation in the northern hemisphere and more southerly itcz position correlation of alfonso basin records with other records in the gulf of california and the pigmy and cariaco basins in the gulf of mexico and central atlantic provides constraints on nam itcz migration and insolation driven changes

nutrient leakage from the north pacific to the bering sea iodp site u1341 following the onset of northern hemispheric glaciation 1 intergrated ocean drilling program expedition 323 recovered a sediment record covering the last 4 3 ma from the bering sea integrated ocean drilling program site u1341 bowers ridge 2177 m water depth to resolve pliocene pleistocene paleoenvironmental changes in this marginal basin 190 sediment samples were analyzed for their bulk element composition aluminium contents in bowers ridge sediments are variable but overall higher toward younger sediments probably related to the intensification of the northern hemispheric glaciation and increasing sea ice transport in the bering sea the gradual increase of terrigenous input is mirrored by decreasing sio2 and excess si sixs contents but the overall si enrichment of the deposits reflects continuous opal deposition since the pliocene at bowers ridge unlike in the north pacific the sixs record at site u1341 does not support a dramatic decrease in opal export following the onset of the northern hemispheric glaciation around 2 7 ma but sio2xs have higher accumulation rates up to 8 g cm2 ka between 2 6 and 1 8 ma bp during this period the major oceanic opal deposition centers shifted globally from open marine high latitude regions to upwelling areas we here discuss how the onset of north pacific stratification at 2 7 ma bp may have caused leakage of nutrient rich deep intermediate north pacific water into the bering sea via the deep kamtchatka strait leading to increased opal deposition and likely reactive organic matter export at bowers ridge as a result magnetic and geochemical records were overprinted by intensified diagenesis significantly affecting their applications as paleoceanographic proxies

hf radar observations of surface circulation off bodega bay northern california usa 1 two high frequency radar stations codar were installed along the northern california coast in may 2001 comparisons of radar data with acoustic doppler current profiler adcp current data and near surface drifter tracks indicate considerable agreement with minimum rms differences of order 0 05 0 15 m s and average drifter hf radar track separation rates of 5 3 km d radar data resolve the three main sources of intraseasonal current variability in the area 1 upwelling relaxation dynamics 2 tidal and diurnal forcing and 3 inertial currents subtidal fluctuations are the largest component of variability accounting for 45 75 of the variance wind driven dynamics are the dominant source of this subtidal variability 67 of subtidal variability both upwelling and relaxation periods exhibit consistent patterns of surface velocity with nearshore currents being slower and more poleward than offshore currents which are strongly equatorward analysis of tidal and inertial variability indicate that current fluctuations are polarized toward clockwise rotation and are generally weaker and more linearly polarized near the coast m2 tidal current ellipses switch direction of rotation at the shelf break suggesting the presence of internal tidal waves currents in all frequency bands are deflected and accelerated around pt reyes and there are indications of increased current variability and changes in flow direction near cordell bank the presence of considerable cross shore and alongshore gradients in the strength and direction of surface flow patterns and in particular weak poleward currents over the inner shelf could have important consequences for plankton retention in the area

barium accumulation in the atlantic sector of the southern ocean results from 190 000 year records extensive investigations of sedimentary barium were performed in the southern south atlantic in order to assess the reliability of the barium signal in antarctic sediments as a proxy for paleoproductivity maximum accumulation rates of excess barium were calculated for the antarctic zone south of the polar front where silica accumulates at high rates the correspondence between barium and opal supports the applicability of barium as a proxy for productivity within the antarctic zone north of today s average sea ice maximum interglacial vertical rain rates of excess barium are high with a maximum occurring during the last deglaciation and early holocene and during oxygen isotope chronozone 5 5 during these periods the maximum silica accumulation was supposedly located south of the polar front glacial paleoproductivity instead was low within the antarctic zone north of the polar front significantly higher barium accumulation occurs during glacial times the vertical rain rates however are as high as in the glacial antarctic zone therefore there was no evidence for an increased productivity in the glacial southern ocean

coefficients for sea surface wind stress heat flux and wind profiles as a function of wind speed and temperature surface layer coefficients for wind profiles wind stress and heat flux in typical open sea conditions are briefly reviewed businger dyer flux gradient relationships and a charnock wind stress formula fit the empirical data and are dimensionally consistent these have been solved by an iterative method and the results are presented in a tabular form suitable for climatological calculations from marine wind and temperature data

three dimensional structure of the summertime circulation in the yellow sea from a wave tide circulation coupled model 1 the three dimensional structure of the summertime circulation of the yellow sea hereafter ys is studied by using a prognostic wave tide circulation coupled model based on the princeton ocean model pom and a surface wave model the simulated tidal harmonic constants and temperature structure agree with the observations well the patterns of the simulated salinity generally agree also with the observations the simulated results show that the horizontal circulation has a three layer structure in the surface layer 0 4 m the prevailing current direction is northeastward in the upper layer 4 40 m it is dominated by a basin scale anticlockwise cyclonic gyre in the bottom layer below 40 m the water diverges from the center area and there exists a weak southward current along the ys trough the stream function of the ys shows that the net circulation of the ys is an anticlockwise cyclonic one and the net transport is about 0 1 sv diagnostic analysis of the momentum balance and sensitivity show that the cyclonic circulation in the upper layers is mainly a quasi geostrophic flow along tidal induced temperature front and it is also strengthened by the tide residual currents the tidal residual current and the compensation for northward surface layer wind transport contribute to the formation of southward flow in the bottom layer the vertical circulations vary along different sections a circulation cell is found in the frontal area near the korean coast and an upwelling is found along the slope

the evolution of hypoxia off the changjiang estuary in the last 3000 years evidence from benthic foraminifera and elemental geochemistry abstract estuarine hypoxia has exerted great influence on the ecological system and fishery production in the past decades consequently attracting intensive concern in this study the upper 18 0 m of core yd0902 retrieved from the hypoxic area off the changjiang estuary was dated by ams 14c method and analyzed with lithology grain size benthic foraminifera and geochemical elements to decipher the paleoenvironmental change and hypoxic history in the last 3000 years the core location was in the neritic to prodelta transitional environment during 3000 2160 cal yr bp and the delta front environment after 2160 cal yr bp no hypoxia occurred during 3000 2600 cal yr bp potentially related to the contemporary occurrence of a rapid cold climate event in the northern hemisphere hypoxia has likely existed persistently since 2600 cal yr bp the period 2600 600 cal yr bp characterizes persistently severe hypoxia mainly linked with the warm climate strong east asian summer monsoon easm and rainfall intensified taiwan warm current intrusion and upwelling and high primary production lessened hypoxia followed in the period 600 260 cal yr bp because of the cold climate weak easm and minor precipitation the recent period post 260 cal yr bp was not disclosed by the core due to lost sediments in the top 4 5 m and could only be surmised to have severe hypoxia because of climate factors similar to the period 2600 600 cal yr bp our findings shed new light on long term hypoxic evolution and controlling factors in mega river estuaries

global deep sea burial rate of calcium carbonate during the last glacial maximum global databases concentrations rates in holocene and last glacial of calcium carbonate and mass accumulation maximum sediments were used to estimate the deep sea sedimentary calcium carbonate burial rate during these two time intervals sparse calcite mass accumulation rate data were extrapolated across regions of varying calcium carbonate concentration using a gridded map of calcium carbonate concentrations and the assumption that accumulation of noncarbonate material is uncorrelated with calcite concentration within some geographical region mean noncarbonate accumulation rates were estimated within each of nine regions determined by the distribution and nature of the accumulation rate data for core top sediments data coverage 67 of the high calcite the regions of reasonable encompass 75 sediments globally and within these regions we estimate an accumulation rate of 55 9 3 6x1011 mol yr 1 the same regions cover 48 of glacial high caco3 sediments the smaller fraction is due to a shift of calcite deposition to the poorly sampled south pacific and total 44 1 6 0x1011 mol yr 1 projecting to 100 coverage south and total 44 1 6 0x1011 both estimates yields accumulation estimates of 8 3x1012 mol yr 1 today and 9 2x1012 mol yr 1 during glacial time this is little better than a guess given the incomplete data coverage but it suggests that glacial deep sea calcite burial rate was probably not considerably faster than today in spite of a presumed decreasein shallow water burial during glacial time

on the vertical structure of wind driven sea currents abstract the vertical structure of wind driven sea surface currents and the role of wind wave breaking in its formation are investigated by means of both field experiments and modeling analysis of drifter measurements of surface currents in the uppermost 5 m layer at wind speeds from 3 to 15 m s 1 is the experimental starting point of this study the velocity gradients beneath the surface are found to be 2 to 5 times weaker than in the wall boundary layer surface wind drift identified via drift of an artificial slick with respect to 0 5 m depths is about 0 7 which is even less than the velocity defect over the molecular sublayer in the wall boundary layer at a smooth surface to interpret the data a semiempirical model describing the effect of wave breaking on wind driven surface currents and subsurface turbulence is proposed the model elaborates on the idea of direct injection of momentum and energy from wave breaking including microscale breaking into the water body momentum and energy tran