oceanography in the kattegat and skagerrak over the past 8000 years in the kattegat between sweden and denmark a large number of cores containing holocene seafloor deposits were investigated stratigraphically sedimentological biostratigraphical and chronostratigraphical variables were especially emphasized palynological and foraminiferal analyses indicate several changes in the oceanographic circulation system in the skagerrak kattegat during the holocene radiocarbon datings and pollen analyses suggest that these changes occurred at 8000 4000 2000 between 1000 and 500 and 300 years b p compilation of stratigraphical data from the region suggests that at about 8000 years b p the english channel opened and the southern jutland current was formed this had a major influence on the skagerrak but only a marginal effect can be traced in the kattegat the major components of the present circulation system in the kattegat skagerrak were established about 4000 years b p and the subsequent changes in the circulation pattern and the inflow outflow system that developed at approximately 2000 500 and 300 years b p are variants of these

intermediate to felsic middle crust in the accreted talkeetna arc the alaska peninsula and kodiak island alaska an analogue for low velocity middle crust in modern arcs 1 seismic profiles of several modern arcs have identified thick low velocity midcrustal layers vp 6 0 6 5 km s that are interpreted to represent intermediate to felsic plutonic crust the presence of this silicic crust is surprising given the mafic composition of most primitive mantle melts and could have important implications for the chemical evolution and bulk composition of arcs however direct studies of the middle crust are limited by the restricted plutonic exposures in modern arcs the accreted talkeetna arc south central alaska exposes a faulted crustal section from residual subarc mantle to subaerial volcanic rocks of a jurassic intraoceanic arc and is an ideal place to study the intrusive middle crust previous research on the arc which has provided insight into a range of arc processes has principally focused on western exposures of the arc in the chugach mountains we present new u pb zircon dates radiogenic isotope data and whole rock geochemical analyses that provide the first high precision data on large intermediate to felsic plutonic exposures on kodiak island and the alaska peninsula a single chemical abrasion thermal ionization mass spectrometry analysis from the afognak pluton yielded an age of 212 87 0 19 ma indicating that the plutonic exposures on kodiak island represent the earliest preserved record of talkeetna arc magmatism nine new dates from the extensive jurassic batholith on the alaska peninsula range from 183 5 to 164 1 ma and require a northward shift in the talkeetna arc magmatic axis following initial emplacement of the kodiak plutons paralleling the development of arc magmatism in the chugach and talkeetna mountains radiogenic isotope data from the alaska peninsula and the kodiak archipelago range from nd t 5 2 to 9 0 and 87sr 86srint 0 703515 to 0 703947 and are similar to age corrected data from modern intraoceanic arcs suggesting that the evolved alaska peninsula plutons formed by extensive differentiation of arc basalts with little or no involvement of preexisting crustal material the whole rock geochemical data and calculated seismic velocities suggest that the alaska peninsula represents an analogue for the low velocity middle crust observed in modern arcs the continuous temporal record and extensive exposure of intermediate to felsic plutonic rocks in the talkeetna arc indicate that evolved magmas are generated by repetitive or steady state processes and play a fundamental role in the growth and evolution of intraoceanic arcs

northern europe climate variations during late holocene evidence from marine skagerrak abstract granulometric and stable oxygen isotope analyses of four sediment cores from two high accumulation areas in the skagerrak ne north sea were carried out in order to reconstruct climate fluctuations and to evaluate climate impact during the upper holocene extremely high sedimentation rates especially in the eastern skagerrak are explained by increased current activity which is responsible for the transport and deposition of high quantities of suspension load during periods of stormy zonal atmospheric circulation patterns these were most frequent during colder periods while warmer phases are characterized by calmer meridional to zonal atmospheric circulation patterns while the subatlantic climate deterioration and the subboreal climate optimum left only indistinct traces in the sediments the roman climate optimum and a colder period between ca 400 and 700 ad are well documented the following medieval warm period is characterized by a clear temperature increase of the waterbody in connection with less frequent advances of atlantic water masses into the skagerak deep and a decrease in bottom current strength a mode of sedimentation prevails similar to that of recent summer conditions suggesting short and mild winters during that period the onset of the little ice age around 1350 ad however shows an intensified bottom current circulation most probably due to amplifying westerly winds and a decrease in water temperatures in connection with more frequent advances of higher saline atlantic waters the little ice age can be divided into 3 phases a stormy zonal onset a calm meridional maximum and a stormy zonal end the stormy phases are characterized by a sedimentation mode similar to that of recent winter conditions while the little ice age maximum shows conditions comparable to exceptional cold modern winters from 1900 ad at the onset of the modern climate optimum the winter type sedimentation decreases and conditions change again to a level comparable to the medieval warm period

estimating wind speed and direction using wave spectra compact wave buoys are increasingly used to provide monitoring of coastal and oceanic conditions by measuring surface waves in real time due to their relatively compact size they are generally not suited to measure wind directly however since the wave field is intrinsically coupled to the wind field wave measurements can serve as a proxy observation of ocean surface winds in this study we use spectral wave observations to estimate wind speed and direction based on the assumption of a universal shape of the wave energy spectrum in the equilibrium range and the presence of a logarithmic wind speed profile above the ocean surface the wind speed and direction were estimated between 2014 and 2017 at more than a 100 coastal sites with colocated wave and wind observations estimates of wind speed and direction based on wave measurements have a root mean square error of 2 m s for wind speeds between 3 and 12 m s and a relative error of 17 for wind speeds between 10 and 20 m s and up to 20 for wind speeds between 10 and 20 m s the accuracy of proxy measurements of wind depends on fetch wave steepness wave age directional alignment between wind and dominant waves and temporal variability of the wind further we show that estimates of wind speed and direction improve considerably as the size of the buoy is reduced

stable isotope fractionation in benthic foraminifera from the peruvian continental margin abstract stable isotope ratios of the carbonate tests of benthic foraminifera are now widely used to reconstruct past changes in ocean circulation and chemistry such studies depend on the accuracy with which changing environmental conditions are recorded and preserved in the tests of foraminifera found in deep sea deposits assessment of this aspect of the method is best accomplished through rigorous study of modern core tops collected from a wide range of depths and bottom water temperatures stable isotope analyses of eighteen taxa of benthic foraminifera from surface sediments of the peru continental margin indicate that most foraminifera are slightly depleted in 18o relative to the benthic foram uvigerina peregrina for at least five taxa we observed subparallel 18 o temperature relationships with slopes nearly equal to that predicted by shackleton 1974 for uvigerina for seven taxa isotopic analysis of six size fractions in the range 210 590 mm reveals that with the exception of u peregrina variation between different size classes for each species is small for 18 o and for 13 c a slight inverse correlation between foraminiferal 18o and 13c content implies a complex interplay of biological and environmental factors which control isotopic composition

organic matter rain rates oxygen availability and vital effects from benthic foraminiferal δ13c in the historic skagerrak north sea abstract the sediment cores 225514 and 225510 were recovered from 420 and 285 m water depth respectively they were investigated for their benthic foraminiferal 13c during the last 500 years both cores were recovered from the southern flank of the skagerrak the 13c values of uvigerina mediterranea and other shallow infaunal species in both cores indicate that organic matter rain rates to the seafloor varied around a mean value until approximately ad 1950 after which they increased this increase might result from changes in the north atlantic current system and a co occurring persistently high north atlantic oscillation index state in the 1980s to 1990s rather than from anthropogenic eutrophication using 13c mean values of multiple species we reconstruct 13c gradients of dissolved inorganic carbon dic within pore waters for the time periods ad 1500 to 1950 and ad 1950 to 2000 the calculated 13cdic ranges interpreted as indicating total organic matter remineralization due to respiration are generally bigger in core 225514 than in core 225510 since mean 13c values of u mediterranea suggest that organic matter rain rates were similar at both locations differences in total organic matter remineralization are attributed to differing oxygen availability however oxygen concentrations in the overlying bottom water masses are not likely to have differed significantly thus we suggest that organic matter remineralization was controlled by oxygen availability within the sediments reflecting strong differences in sedimentation rates at the two investigated core sites based on the assumptions that tests of benthic foraminiferal species inhabiting the same microhabitat depth should show equal 13c values unless they are affected by vital effects and that globobulimina turgida records pore water 13cdic we estimate microhabitat corrected vital effects for several species with respect to g turgida 0 7 for cassidulina laevigata 1 3 for hyalinea balthica and 0 7 for melonis barleeanus melonis zaandami seems to closely record pore water 13cdic

tangential stress beneath wind driven air water interfaces the detailed structure of the aqueous surface sublayer flow immediately adjacent to the wind driven air water interface is investigated in a laboratory wind wave flume using particle image velocimetry piv techniques the goal is to investigate quantitatively the character of the flow in this crucial very thin region which is often disrupted by microscale breaking events in this study we also examine critically the conclusions of okuda kawai toba 1977 who argued that for very short strongly forced wind wave conditions shear stress is the dominant mechanism for transmitting the atmospheric wind stress into the water motion waves and surface drift currents in strong contrast other authors have more recently observed very substantial normal stress contributions on the air side the availability of piv and associated image technology now permits a timely re examination of the results of okuda et al which have been influential in shaping present perceptions of the physics of this dynamically important region the piv technique used in the present study overcomes many of the inherent shortcomings of the hydrogen bubble measurements and allows reliable determination of the fluid velocity and shear within 200 m of the instantaneous wind driven air water interface the results obtained in this study are not in accord with the conclusions of okuda et al that the tangential stress component dominates the wind stress it is found that prior to the formation of wind waves the tangential stress contributes the entire wind stress as expected with increasing distance downwind the mean tangential stress level decreases marginally but as the wave field develops the total wind stress increases significantly thus the wave form drag represented by the difference between the total wind stress and the mean tangential stress also increases systematically with wave development and provides the major proportion of the wind stress once the waves have developed beyond their early growth stage this scenario reconciles the question of relative importance of normal and tangential stresses at an air water interface finally consideration is given to the extrapolation of these detailed laboratory results to the field where the present findings suggest that the sea surface is unlikely to become fully aerodynamically rough at least for moderate to strong winds

sediment transport pathways in the skagerrak and kattegat as indicated by sediment chernobyl radioactivity and heavy metal concentrations abstract the concentration of the heavy metals hg cu pb and zn as well as chernobyl cs 137 radioactivity was determined in surface sediments from the skagerrak and kattegat sediment samples from adjacent swedish fjords were analysed as well the sampling was carried out between spring 1988 and autumn 1990 highest concentrations of heavy metals and largest cs 137 activities occur in fine grained organic rich 62 2 c org sediment from swedish inshore waters and locally also in the kattegat regional trends of relative enrichment of the various heavy metals and chernobyl cs 137 with respect to organic carbon was used to determine transport patterns of material enriched with respective elements it can be proven that deposition of fine grained material transported from the southern north sea by the jutland current is the main mechanism determining the regional accumulation of lead and chernobyl derived cs 137 this mechanism principally controlls the areal distribution of mercury enriched material as well but it is regionally of less importance as far as the accumulation of cu and zn concerns the chernobyl cs 137 data show that a large proportion of the fine grained material transported by the jutland current originally is river borne suspension load from central western europe the areal enrichment pattern of copper and on a smaller scale those of mercury and zinc too points to westerly directed suspension load transport across the kattegat material enriched with these elements apparently is being discharged from swedish industrial and urban centers in particular the goteborg area

multispecies stable isotopes of benthic foraminifers reveal past changes of organic matter decomposition and deepwater oxygenation in the arabian sea 1 the stable isotope composition of one epifaunal and three infaunal benthic foraminiferal species of a sediment core from 1800 m water depth of the western arabian sea was determined to evaluate deepwater oxygenation organic matter remineralization and early diagenetic processes during the past 190 000 years the 18o records reveal species specific metabolic effects susceptibility to changes in carbonate ion concentration and supralysoclinal calcite dissolution the foraminiferal 13c records reveal changes in the stable carbon isotope gradients of pore water dissolved inorganic carbon 13cdic and in the microhabitat depth of infaunal species maximum 13cdic offsets between bottom and pore waters ranged between mean values of 0 8 and 1 2 corresponding to estimates of deepwater oxygen concentration between approximately 1 and 2 7 ml l 1 intervals of improved deepwater oxygenation coincided with high benthic foraminiferal diversity and indicate the admixture of well oxygenated deepwater masses during interglacials during interglacial maxima the 13c difference between epifauna and shallow infauna indicates highest organic matter remineralization rates at times of maximum organic matter fluxes

living stained benthic foraminifera within surficial sediments of the skagerrak abstract an analysis of living stained benthic foraminifera within four box cores raised from water depths of 74 to 621 m in the skagerrak shows that faunal patterns at different water depths are strikingly different within this relatively shallow organicrich marginal sea environment although some genera show vertical stratification within the sediments a number of taxa are found over wide intervals or have different patterns between cores the vertical distributional data are compared with deep sea data from the eastern margin of north america benthic foraminifera from a deep core at 530 m in the skagerrak have similar faunal patterns within the surficial sediments as found in the deep sea but shallow cores at 74 and 212 m have more complex patterns this difference between shallow and deep cores within the skagerrak and the north atlantic is attributed to higher biological activity in the shallow environments which creates a greater amount of heterogeneity within the shallow water sediments than is found in deeper environments the faunal data suggest that the use of benthic foraminifera for paleoenvironmental reconstructions in shallow organicrich regions will be complicated in future studies the ecology of individual species is difficult to assess because of the complex faunal patterns observed within the surficial sediments geochemical studies for estimating bottom water oxygen or organic carbon flux will also be difficult since these studies assume that taxa occupy particular microhabitats within the surficial sediments

benthic stable isotope variability in the trondheimsfjord during the last 50 years proxy records of mixing dynamics related to nao abstract benthic stable isotopes 18 o c and 13 c c in the trondheimsfjord reliably reflect the prevailing hydrological conditions with regard to the distance to the fjord entrance and the local topography at the fjord entrance the 18 o c and 13 c c variabilities record changes in the temperature of the north atlantic current nac and in the delivery of terrigenous organic matter by the norwegian coastal current ncc and the fjord estuarine circulation respectively in the inner fjord basins the benthic stable isotope compositions are predominantly controlled by hydrological characteristics linked to internal mixing and the prevailing wind pattern the fjord deep basins are relatively sheltered from erosion and both land and marine derived sediments accumulate at very high rates indicating past regional climate and associated driving parameters in the present study we discuss the recent variability last 55 years of the stable isotope compositions oxygen and carbon measured in calcite shells of the benthic foraminiferan melonis barleeanus with regard to the changing influence of marine versus fresh water inputs and of the prevailing wind patterns the relative influence of marine versus continental waters were analysed as well as the complex topography and the related hydrology of the trondheimsfjord using sediment cores collected in three different settings along the fjord axis the variability the of stable isotope compositions obtained from the sedimentary archives is compared with in situ instrumental measurements over the investigated time interval

response of anaerobic methanotrophs and benthic foraminifera to 20 years of methane emission from a gas blowout in the north sea highlights high abundance of active anaerobic methanotrophs in sediments of the blowout crater suggests adaptation to methane seepage within at most two decades fast exchange processes in permeable surface sediments prevent sulfate depletion and probably methane derived carbonate precipitation methane seepage impacts isotopic and assemblage composition of benthic foraminifera abstract methane emissions from marine sediments are partly controlled by microbial anaerobic oxidation of methane aom aom provides a long term sink for carbon through precipitation of methane derived authigenic carbonates mdac estimates on the adaptation time of this benthic methane filter as well as on the establishment of related processes and communities after an onset of methane seepage are rare in the north sea considerable amounts of methane have been released since 20 years from a man made gas blowout offering an ideal natural laboratory to study the effects of methane seepage on initially pristine sediment sediment cores were taken from the blowout crater and a reference site 50 m distance in 2011 and 2012 respectively to investigate porewater chemistry the aom community and activity the presence of authigenic carbonates and benthic foraminiferal assemblages potential aom activity up to 3060 nmol cm 3 sediment d 1 or 375 mmol m 2 d 1 was detected only in the blowout crater up to the maximum sampling depth of 18 cm card fish analyzes suggest that monospecific anme 2 aggregates were the only type of aom organisms present showing densities up to 2 2 107 aggregates cm 3 similar to established methane seeps no evidence for recent mdac formation was found using stable isotope analyzes 13c and 18o in contrast the carbon isotopic signature of methane was recorded by the epibenthic foraminifer cibicides lobatulus 13c 0 66 surprisingly the foraminiferal assemblage in the blowout crater was dominated by cibicides and other species commonly found in the norwegian channel and fjords indicating that these organisms have responded sensitively to the specific environmental conditions at the blowout the high activity and abundance of aom organisms only at the blowout site suggests adaptation to a strong increase in methane flux in the order of at most two decades high gas discharge dynamics in permeable surface sediments facilitate fast sulfate replenishing and stimulation of aom the accompanied prevention of total alkalinity build up in the porewater thereby appears to inhibit the formation of substantial methane derived authigenic carbonate at least within the given time window

the relationship between pore water carbon isotopic composition and bottom water oxygen concentration abstract we present pore water 13c profiles from the western north atlantic and the eastern pacific oceans and interpret them using a stoichiometric model of the relationship between carbon isotopic composition and oxygen concentration pore water 13c at the depth in the sediments where oxygen approaches zero is largely determined by the oxygen concentration of the overlying bottom water although sulfate reduction adds a significant amount of isotopically light carbon at some locations the 13c difference between bottom water and pore water at o2 0 13c increases from 1 in sediments of three low bottom water oxygen basins in the southern california borderlands to 4 in sediments underlying well oxygenated water in the western north atlantic we suggest that the relationship between bottom water oxygen and 13c could form the basis for a new way to use the benthic foraminifera 13c record to estimate bottom water oxygen concentration paleo oxygen values derived from a pair of benthic foraminifera species which record the bottom water pore water o2 0 13c difference will be independent of the preformed 13c of the deep water mass

calcium isotope ratios in calcitic tests of benthic foraminifers abstract we analysed ca isotope ratios of the infaunal foraminiferal species cassidulina laevigata elphidium spp gyroidinoides spp and uvigerina peregrina as well as the epifaunal cibicidoides wuellerstorfi over a depth temperature gradient the calcium isotope ratios of the benthic foraminifers tests show a distinct anomaly around 4 c this anomaly is observed in both epi and infaunal species but there are also characteristic differences between both the 44 40 ca characteristics of benthic foraminifers may be explained by the interference of temperature and carbonate chemistry of the fluid on ca isotope fractionation we suggest that ca isotope composition of benthic foraminifer tests is dominantly controlled by temperature at temperatures higher than 5 c while in the temperature range below 5 c calcite saturation cc becomes an increasingly important controlling factor due to the non linear shape of the cc 44 40 ca relation of actively transported calcium the potential applicability of ca isotope ratios in benthic foraminifers for reconstruction of either temperatures or 44 40 ca sw is limited by the complex fractionation pattern below 5 c however due to the minor temperature dependence in the temperature range above 5 c benthic foraminifers might provide a possible alternative archive for 44 ca sw avoiding some uncertainties associated with planktic records relocation habitat calcification depth short time climate variability as long as a defined bottom water temperature above 5 c can be secured

δ13c values of miocene pacific benthic foraminifera correlations with sea level and biological productivity 13 c 12 c ratios of miocene benthic foraminifera from 22 pacific ocean sites vary with time but are similar at almost all sites in any restricted interval 13 c values are correlated with sea levels inferred from onlap offlap curves reflecting the deposition of greater amounts of organic matter on the continental shelves during transgressions differences in 13 c between sites are correlated with local differences in biological productivity in the overlying surface waters 13 c 12 c values of benthic foraminifera show promise as indicators of marine paleoproductivity

the influence of microhabitats on the carbon isotopic composition of deep sea benthic foraminifera we report 13c and 18o values for rose bengal stained benthic foraminifera from a set of box cores from continental margin environments in the atlantic and pacific oceans these isotopic results are compared with foraminiferal distribution data and pore water 13c profiles to evaluate the importance of environmental microhabitat effects on the carbon isotopic composition of benthic foraminifera the 13c values of infaunal taxa are consistently lower than those of epifaunal taxa suggesting that microhabitat effects on test composition do exist the 13c differences between foraminiferal carbonate and bottom water dissolved inorganic carbon are not correlated with the 18o differences between benthic foraminifera tests and equilibrium calcite but they do correlate with variations in the chemistry of sediment pore waters however interspecific 18o differences as well as 13c differences between species with similar vertical distributions in the sediments indicate that taxon specific vital effects also influence test composition

13c record of benthic foraminifera in the last interglacial ocean implications for the carbon cycle and the global deep water circulation the 13c 12c ratios of upper holocene benthic foraminiferal tests genera cibicides and uvigerina of deep sea cores from the various world ocean basins have been compared with those of the modern total carbon dioxide tco2 measured during the geosecs program the 13c difference between benthic foraminifera and tco2 is 0 07 0 04 for cibicides and 0 83 0 07 for uvigerina at the 95 confidence level 13c analyses of the benthic foraminifera that lived during the last interglaciation isotopic substage 5e about 120 000 yr ago show that the bulk of the tco2 in the world ocean had a 13c value 0 15 0 12 lower than the modern one at the 95 confidence level reflecting a depletion compared to the present value of the global organic carbon reservoir regional differences in 13c between the various oceanic basins are explained by a pattern of deep water circulation different from the modern one the antarctic bottom water production was higher than today during the last interglaciation but the eastward transport in the circumpolar deep water was lower

application of aeromagnetic data to mineral potential evaluation in minnesota aeromagnetic ground magnetic and gravity data together with all available drillhole data and physical property measurements were used to map the precambrian geology of an area in minnesota that is virtually devoid of outcrop the work was done for purposes of land use planning and to encourage minerals exploration and mostly consisted of the analysis of profiles of aeromagnetic data to map magnetic lithologic contacts to infer structure and to determine thickness of overburden cover two greenstone belts were resolved they comprise higher density rocks separated by nonmagnetic metasedimentary intervals the belts are deformed into synclinal structures that according to modeling range from 1 km to as much as 5 km in depth lithologic predictions were confirmed in five out of six holes drilled on completion of the magnetic interpretation in over 40 of the area precambrian rocks are apparently mantled by less than 50 m of overburden and in 50 of the area there is between 50 and 100 m of overburden cover in the remaining 10 the magnetic basement is overlain by a thick blanket of nonmagnetic precambrian sedimentary rocks over 200 m thick basement depth determinations were subsequently tested at six holes depth determinations at all drill sites were found to lie within the 20 error expectation of the method of depth determination thirty seven sites were resolved from the aeromagnetic data as targets for basemetal sulfide copper zinc as well as precious metal gold mineralization thirteen magnetic anomalies were identified as possible kimberlite pipes

microhabitat preferences and stable carbon isotopes of endobenthic foraminifera clue to quantitative reconstruction of oceanic new production seventeen surface sediment samples from the north atlantic ocean off ne greenland between 76 and 81 n and nine samples from the south atlantic ocean close to bouvet island between 48 and 55 s were taken with the aid of a multiple corer and investigated for their live rose bengal stained benthic foraminiferal content within the upper 15 cm of sediment preferentially endobenthic melonis barleeanum m zaandami and bulimina aculeata as well as preferentially epibenthic lobatula lobatula were counted from 1 cm thick sediment slices each and analyzed for stable carbon and oxygen isotopic compositions of their calcareous tests live and dead specimens were counted and measured separately the carbon isotopic composition of the foraminifera was compared to that of the dissolved inorganic carbon dic of simultaneously sampled bottom water during a period of one month one station off ne greenland was replicately sampled once every week and samples were processed as above live specimens of lobatula lobatula are confined to the uppermost two centimeters of sediment live specimens of melonis spp are found down to eight centimeters within the sediment but with a distinct sub surface maximum between two and five centimeters the down core distribution of live bulimina aculeata shows a distinct surface maximum in the top centimeter and constant but low numbers down to 11 cm subbottom depth the average stable carbon isotopic composition d13c per mil vpdb of live l lobatula off ne greenland is by 0 4 0 1 per mil higher than the d13cdic of the ambient bottom water at the time of sampling there is evidence that this species calcify before the ice free season when bottom water d13cdic is supposed to be higher this would reconfirm the one to one relationship between d13c of ambient water dic and cibicids widely used by paleoceanographers live m barleeanum show a negative offset from bottom water dic of 1 7 0 6 per mil in the uppermost sediment and of 2 2 0 5 per mil in three to four centimeters subbottom depth all d13c values of live melonis spp decrease within the upper four centimeters regardless of the time of sampling and site investigated the offset of live b aculeata from bottom water d13cdic values of eight stations rather constantly amounts 0 6 0 1 per mil no matter what subbottom depth the specimens are from at one station however where is strong indication of elevated organic carbon flux the negative offset averaged over all sub bottom depths increases to 1 5 0 2 per mil buliminids actively move within the sediment and by this either record an average isotope signal of the pore water or the signal of one specific calcification depth the recorded signal however depends on the organic carbon flux and reflects general but site specific pore water d13cdic values if compared with epibenthic d13c values from the same site not influenced by pore water and related phytodetritus layer effects bulimina d13c values bear some potential as a paleoproductivity proxy specimens of melonis spp seem to prefer a more static way of life and calcify at different but individually fix depths within the sediment although live specimens thus record a stratified pore water d13c signal there is no means yet to correct for bioturbational and early diagenetic effects in fossil faunas

environmental and biological effects on the stable isotope composition of recent deep sea benthic foraminifera from the western mediterranean sea abstract the influence of microhabitat organic matter flux and metabolism on the stable oxygen and carbon isotope composition of live rose bengal stained and dead empty tests deep sea benthic foraminifera from the gulf of lions western mediterranean sea have been studied the total range of observed foraminiferal isotope values exceeds 1 0 for 18o and 2 2 for 13c demonstrating a wide range of coexisting disequilibria relative to 18o of equilibrium calcite 18oeq and 13c of bottom water dissolved inorganic carbon 13cdic the mean 18o values reveal strongest disequilibria for the studied epifaunal to shallow infaunal species cibicidoides pachydermus uvigerina mediterranea uvigerina peregrina while values approach equilibrium in deep infaunal species globobulimina affinis globobulimina pseudospinescens the mean 13c values decrease with increasing average living depths of the different species thus reflecting a dominant microhabitat pore water signal at the axis of the lacaze duthier canyon a minimum 13cdic pore water gradient of approximately 2 1 is assessed for the upper 6 cm of the surface sediment although live individuals of u mediterranea were found in different depth intervals their mean 13c values are consistent with calcification at an average living depth around 1 cm the deep infaunal occurrence of u mediterranea specimens suggests association with macrofaunal burrows creating a microenvironment with geochemical characteristics similar to the topmost centimeter this also explains the excellent agreement between stable isotope signals of live and dead individuals the ontogenetic enrichment in both 18o and 13c values of u mediterranea suggests a slow down of metabolic rates during test growth similar to that previously observed in planktic foraminifera enhanced organic carbon fluxes and higher proportion of resuspended terrestrial organic material at the canyon axis are reflected by 13c values of u mediterranea on average 0 58 lower than those from the open slope these results demonstrate the general applicability of the 13c signal of this species for the reconstruction of past organic matter fluxes in the mediterranean sea further studies on live specimens are needed for a more quantitative paleoceanographic approach

the southern kahiltna terrane implications for the tectonic evolution of southwestern alaska regionally extensive and highly deformed jurassic to cretaceous basinal turbidite deposits occur along most of the inboard boundary of the talkeetna superterrane in southern alaska and western canada the southern kahiltna terrane of southwestern alaska consists largely of such basinal deposits regional and detailed studies in and adjacent to this terrane suggest several new conclusions regarding the origin of the basin and its role in the tectonic evolution of southwestern alaska stratigraphic sedimentologic compositional and structural evidence suggests that the upper jurassic to lower cretaceous strata of the southern kahiltna terrane were derived from and deposited on rocks of the adjacent talkeetna superterrane deposition of these clastic rocks apparently postdated arc magmatism in the talkeetna superterrane suggesting deposition in a basin developed on the suture between the talkeetna superterrane and north america if true this observation implies that collision of the talkeetna superterrane with north america began prior to latest jurassic time probably at a more southerly location the superterrane has since been translated northward probably by coast parallel strike slip displacement to its present location where it was structurally juxtaposed with middle to upper creteceous rocks of the kuskokwim group a magmatic overprint indicates that the talkeetna superterrane was in approximately its present location by latest cretaceous to paleocene time

benthic foraminiferal distribution and abundance changes in skagerrak surface sediments 1937 hoglund and 1992 1993 data compared both living stained and dead unstained foraminiferal assemblages from surface sediments 0 2 cm in the northwestern part of the skagerrak have been studied in order to 1 define and characterize the distribution of various modern benthic environments and 2 by comparing these findings with surface samples collected 40 60 years ago to document possible faunal changes that might have occurred the investigated area is physiographically divided into the norwegian slope the skagerrak basin and the danish slope the latter is under the influence of the jutland current while the basin and the investigated parts of the norwegian slope are bathed in atlantic water all areas have bottom waters with a high oxygen concentration three living stained and three dead unstained assemblages occupy the three physiographic areas only one assemblage on the norwegian slope is common to both the living and dead assemblages but the boundaries between them lie at comparable depths the higher standing crops are found on the fertile danish slope while the lower ones are in the deep basin where the diversity is at a maximum in the dead assemblages the relative abundance of agglutinated tests increases with depth comparison with data collected 40 to 60 years ago shows increases in absolute numbers of tests especially in the deep basin there are changes in assemblage compositions in all areas the dominant species found in 1937 are different from those of 1992 1993 there is a major change in the basin where one agglutinated species has changed its depth distribution downslope and two present day abundant species are new arrivals these faunal events are probably linked to environmental changes

evolution of backarc rifting mariana trough 20 24 n the mariana trough is an actively opening backarc basin in the western pacific the trough formed by extension which longitudinally split an earlier arc massif creating a crescent shaped basin between the remnant west mariana ridge and eastern active volcanoes of the mariana arc opening increases southward from the volcano islands near 24 n where the two arcs join at 18 n in the central mariana trough the basin is widest and may be opening primarily by seafloor spreading we present a synthesis of closely spaced shipboard gravity magnetic and bathymetry measurements from the northern basin 20 24 n an area that undergoes a significant progressive southward increase in extension we have identified three stages in the evolution of rifting in this area 1 asymmetric rifting from 24 n to 22 15 n where faulting and magmatism have migrated laterally to remain near the active volcanic arc side of the basin 2 a localization of rifting from 22 15 n to 21 n where the primary zone of rifting separates from the active volcanic arc and 3 a further concentration of rifting from 21 n to 20 n leading to the formation of deep tectonic grabens near the center of the basin this last stage may be a precursor to or incipient seafloor spreading we describe a new type of magnetic lineation resolved in a three dimensional seafloor magnetization inversion of the trough between 20 and 24 n the detailed character of these lineations their association with tectonic structures and other geophysical observations indicate that they are not seafloor spreading lineations but rather result from magnetic intrusions and volcanism emplaced within preexisting less magnetic rifted arc crust the development of these well defined magnetization bands indicates that the zone of magmatism remains relatively narrow at any one time throughout the opening of the trough although tectonic deformation appears to be more widely distributed in addition the geometry of the magnetization bands with respect to the remnant arc border faults indicates that rifting propagated rapidly northward

stable isotope fractionation in live benthic foraminifera from the southern california borderland live specimens of benthic foraminifera have been analyzed from surface sediment samples collected from 108 to 1134 m depth in the southern california borderland the temperature and isotopic composition of the ambient water and dissolved inorganic carbon have also been measured to permit comparison of foraminiferal compositions to expected equilibrium values the species analyzed break down into four groups which reflect the influence of mineralogy aragonite vs calcite biological fractionation vital effect and microhabitat effects on isotopic composition the aragonitic hoeglundina elegans show an enrichment in 18o relative to equilibrium calcite of 0 41 0 in shallower water increasing to at least 1 06 0 in deeper water the 13c enrichment of h elegans relative to the dissolved inorganic carbon dic is also depth dependent increasing from 1 27 0 at 108 m to 2 13 0 at 940 m this depth dependence results from the change in composition of the dic the 13c composition of h elegans remains constant with depth for some unknown reason one possible explanation is that the change in composition of the dic is balanced by an increase in hoeglundina hco 3 fractionation with decreased temperature the 13c values of the cassidulina species are almost identical to those of the ambient dissolved inorganic carbon dic and reflect the decrease in the 13c of the dic with depth the 13c values of species not in 18o equilibrium vary independently of the changing composition of the dic there is a correlation between 13c and 18o among coeval species consistent with the model which explains vital effect as the result of incorporation of isotopically light metabolic co2 into the shell the magnitude of disequilibrium is relatively constant for 18o but not for 13c suggesting that in isotopic stratigraphy studies it may be difficult to calibrate the 13c of different species as has been done with 18o there appears to be a relationship between taxonomic group and vital effect the foraminifera in approximate 18o equilibrium with the water including species of cassidulina bolivina uvigerina and globobulimina are members of the family cassidulinidae or superfamily buliminacea those not in 18o equilibrium including species of pyrgo quinqueloculina triloculina and lenticulina belong to the families miliolidae and vaginulinidae no disequilibrium species have been found as yet in the low oxygen environments of the borderland this observation and published findings on the ultrastructure of benthic foraminifera suggest that isotopic behavior may be related to a foraminifer s ability to exchange gases rapidly with its ambient water

mineral magnetic and textural interpretations of sedimentation in the skagerrak eastern north sea abstract the mineral magnetic properties of surface sediments in the northern skagerrak show systematic trends which allow the identification of sediment provinces and the interpretation of transport pathways this application is especially valuable considering the importance and difficulty of environmental analyses involving fine grained deposits magnetic susceptibility and saturation isothermal remanent magnetisation sirm have different geographic patterns but their individual trends are consistent in the skagerrak muds clay content 25 60 over the entire studied area the values correlate positively with general trends in particle size whereas sirm does not show particle size dependency the present study confirms that the majority of sediments accumulating in the northern skagerrak are supplied from the south the mineral magnetic parameters facilitate detailed tracking of the counterclockwise transport of sediments around and into the norwegian trench

spatial and temporal organic carbon burial along a fjord to coast transect a case study from western norway we investigated spatial and temporal changes in accumulation rate and source of organic carbon on a gradient along the lysefjord and the more coastal hogsfjord western norway this was achieved th

mineralogy and geochemistry of a core from the skagerrak kattegat boundary abstract sedimentological and geochemical analyses have been carried out on samples from a sediment core taken at 183 m water depth in the eastern skagerrak the results suggest uniform sedimentation in this region over approximately the last 1000 years with the exception of calcium carbonate all parameters investigated showed the highest concentrations at the core top rapidly decreasing within the upper 10 cm to more or less constant values calculation of paleoproductivities and comparison with contemporaneous production suggests 50 to 75 of the sedimentary organic carbon to be of refractory or allochthonous origin

sea state dependence of the wind stress over the ocean under hurricane winds 1 the impact of the surface wave field sea state on the wind stress over the ocean is investigated with fetch dependent seas under uniform wind and with complex seas under idealized tropical cyclone winds two different approaches are employed to calculate the wind stress and the mean wind profile the near peak frequency range of the surface wave field is simulated using the wavewatch iii model the high frequency part of the surface wave field is empirically determined using a range of different tail levels the results suggest that the drag coefficient magnitude is very sensitive to the spectral tail level but is not as sensitive to the drag coefficient calculation methods the drag coefficients at 40 m s vary from 1 10 3 to 4 10 3 depending on the saturation level the misalignment angle between the wind stress vector and the wind vector is sensitive to the stress calculation method used in particular if the cross wind swell is allowed to contribute to the wind stress it tends to increase the misalignment angle our results predict enhanced sea state dependence of the drag coefficient for a fast moving tropical cyclone than for a slow moving storm or for simple fetch dependent seas this may be attributed to swell that is significantly misaligned with local wind

deep water renewal in the skagerrak during the last 1200 years triggered by the north atlantic oscillation evidence from benthic foraminiferal δ8o benthic foraminiferal tests of a sediment core from southwestern skagerrak northeastern north sea 420 m water depth were investigated for their ratio of stable oxygen isotopes during modern times sudden drops in temperature and salinity of skagerrak deep waters point to advection induced cascades of colder and denser central north sea waters entering the skagerrak these temperature drops which are recorded in benthic foraminiferal tests via the stable oxygen isotopic composition were used to reconstruct deep water renewal in the skagerrak in a second step we will show that at least during the last 1200 years skagerrak deep water renewal is triggered by the negative phase of the north atlantic oscillation nao the nao exerts a strong influence on the climate of northwestern europe it is currently under debate if the long term variability of the nao is capable of influencing northern hemisphere climate on long timescales the data presented here cannot reinforce these speculations our data sho

holocene sedimentation in the skagerrak a review abstract stratigraphic sedimentological geochemical and micropaleontological aspects of holocene sedimentation processes in the skagerrak are reviewed published data show the skagerrak to be the main depositional basin of the north sea with additional inputs from the north atlantic the baltic and the scandinavian mainland as this area is a highly dynamic and complex environment it is difficult to define overall controlling factors and processes from a consideration of available and lacking approaches and data suggestions are made for future research

reconstructing benthic carbon oxidation rates using δ13c of benthic foraminifers abstract in non bioturbated organic rich marine sediments the concentration and carbon isotope gradient of total dissolved carbon dioxide co2 primarily reflects the rate of carbon oxidation and co2 diffusion within the sediment pore waters here we investigate whether the calcium carbonate secreted by benthic foraminifers that inhabit discrete depths within the sediments record the pore water 13c co2 gradient and hence can be used as proxies to reconstruct a history of carbon oxidation change the distribution and live abundance of bolivina argentea s l bolivina subadvena s l and buliminella tenuata inhabiting the dysoxic marine sediments along the california margin is similar among sites that differ in co2 gradient by up to a factor of three bolivina argentea inhabits the sediments at the sediment water interface whereas b subadvena s l is most abundant at depths of between 2 and 4 mm buliminella tenuata is most abundant at deeper depths of between 4 and 6 mm the 13c of calcite precipitated by these species matches the 13c of the pore water co2 at the depth of their maximum live abundance indicating that each species has a preferred depth for calcification the 13c difference between the species increases as the rate of carbon oxidation increases these results indicate the carbon isotopic difference between these species in fossil assemblages can be used to estimate changes in the rate of carbon oxidation

reconstruction of mid to late holocene winter temperatures in the skagerrak region using benthic foraminiferal mg ca and δ18o reconstruction of skagerrak deep water renewal is used to assess regional changes in winter thermal conditions over the past 6800 years changes in winter climate conditions from the skagerrak region are in turn linked to shifts in holocene large scale atmospheric circulation patterns prevailing over northern europe we use melonis barleeanus mg ca from two sediment cores in the central skagerrak to reconstruct temperature of skagerrak intermediate water representing the warm season temperature variability and deep water for monitoring skagerrak deep water renewal reflecting the winter temperature variability in addition m barleeanus 18o is used from the deeper core to reconstruct salinity also monitoring the deep water renewal our results show that the skagerrak deep water experienced phases of particularly enhanced renewal during the mid holocene reflecting severe winter conditions followed by a general shift to reduced renewal as a consequence of milder winter conditions over the north sea a

coastal dysoxia accompanies early miocene warming based on benthic foraminiferal and sedimentary records from oregon abstract the newport member of the astoria formation exposed on the central oregon coast was deposited at shallow marine depths during the early miocene global warming that led to the middle miocene climate optimum this record thus provides the opportunity to examine a coastal environment over past warming and ask if the low oxygen conditions observed in recent years on the modern oregon shelf is a recent phenomenon or a repeated symptom of global warming although 18o variation can be influenced by freshwater flux if due to temperature 18o values suggest 2 4 4 5 c of local warming during deposition of the newport member species of buliminacea fursenkoina and nonionella abundant in organic rich low oxygen sediments in modern seas increased in proportional abundance after warming began in addition the offset in 13c values between epifaunal to shallow infaunal taxa and a deeper infaunal species is greater in sediments with higher abundances of these taxa further supporting increased organic carbon flux an increase in laminated sediments coincident with these faunal and geochemical changes suggests dysoxic conditions accompanied the increase in organic carbon taken together this multiproxy record suggests that high organic low oxygen environments developed in shallow waters during early miocene warming perhaps driven by similar upwelling mechanisms thought to drive hypoxia on the modern oregon coast

mineral potential mapping in an accreted island arc setting using aeromagnetic data an example from southwest alaska the distribution of volcanogenic massive sulfide vms porphyry epithermal alaska type ultramafic mafic complexes intrusion related au and granitoid sn w ore deposits in southwest alaska supports current metallogenic models linking the formation of these deposit types to the emplacement of different suites of igneous rocks during the evolution of this convergent plate margin regional scale aeromagnetic data provide a continuous set of observations over the deposits and show contrasting patterns over the igneous rock suites hosting the various deposit types combined with surface geologic data and regional metallogenic constraints aeromagnetic data filtered to enhance the anomalous magnetic field and map magnetic domains were used to produce a mineral potential map across this accreted island arc setting the reduced to pole upward continuation and total horizontal gradient transform maps show anomalies that could represent porphyry epithermal deposits within the intraoceanic and continental arc terranes the tilt derivative transform highlights lineaments within the back arc that may represent zones with potential for vms deposits the truncations of tilt derivative lineaments outline a major magnetic domain boundary between the back arc and craton margin which is prospective for granitoid sn w deposits annular tilt derivative highs outline granitoids that could be associated with intrusion related au deposits within the craton margin shallow magnetite rich alaska type ultramafic mafic complexes are mapped by their short wavelength high amplitude anomalies successful mineral potential mapping across southwestern alaska as performed in the present study suggests that filtered aeromagnetic data can be effectively used in mineral exploration in convergent continental margin settings

wave follower field measurements of the wind input spectral function part ii parameterization of the wind input abstract nearly all of the momentum transferred from wind to waves comes about through wave induced pressure acting on the slopes of waves known as form drag direct field measurements of the wave induced pressure in airflow over water waves are difficult and consequently rare those that have been reported are for deep water conditions and conditions in which the level of forcing measured by the ratio of wind speed to the speed of the dominant spectral peak waves is quite weak u10 cp 3 the data reported here were obtained over a large shallow lake during the australian shallow water experiment auswex the propagation speeds of the dominant waves were limited by depth and the waves were correspondingly steep this wider range of forcing and concomitant wave steepness revealed some new aspects of the rate of wave amplification by wind the so called wind input source function in the energy balance equation for wind driven water waves it was found that the exponential growth rate parameter fra

geological analysis of aeromagnetic data from southwestern alaska implications for exploration in the area of the pebble porphyry cu au mo deposit aeromagnetic data are used to better understand the geology and mineral resources near the late cretaceous pebble porphyry cu au mo deposit in southwestern alaska the reduced to pole rtp transformation of regional scale aeromagnetic data shows that the pebble deposit is within a cluster of magnetic anomaly highs similar to pebble the iliamna kijik and neacola porphyry copper occurrences are in magnetic highs that trend northeast along the crustal scale lake clark fault a high amplitude short to moderate wavelength anomaly is centered over the kemuk occurrence an alaska type ultramafic complex similar anomalies are found west and north of kemuk a moderate amplitude moderate wavelength magnetic low surrounded by a moderate amplitude short wavelength magnetic high is associated with the gold bearing shotgun intrusive complex the rtp transformation of the district scale aeromagnetic data acquired over pebble permits differentiation of a variety of jurassic to tertiary magmatic rock suites jurassic cretaceous basalt and gabbro units and late cretaceous biotite pyroxenite and granodiorite rocks produce magnetic highs tertiary basalt units also produce magnetic highs but appear to be volumetrically minor eocene monzonite units have associated magnetic lows the rtp data do not suggest a magnetite rich hydrothermal system at the pebble deposit the 10 km upward continuation transformation of the regional scale data shows a linear northeast trend of magnetic anomaly highs these anomalies are spatially correlated with late cretaceous igneous rocks and in the pebble district are centered over the granodiorite rocks genetically related to porphyry copper systems the spacing of these anomalies is similar to patterns shown by the numerous porphyry copper deposits in northern chile these anomalies are interpreted to reflect a late cretaceous magmatic arc that is favorable for additional discoveries of late cretaceous porphyry copper systems in southwestern alaska

stable oxygen and carbon isotopes of live benthic foraminifera from the bay of biscay microhabitat impact and seasonal variability we determined the stable oxygen and carbon isotopic composition of live rose bengal stained benthic foraminifera n150 am size fraction of seven taxa sampled along a downslope transect between 140 to 2000 m water depth in the bay of biscay at the five stations hoeglundina elegans cibicidoides pachydermus uvigerina peregrina uvigerina mediterranea preferentially occupy shallow infaunal niches whereas melonis barleeanus and uvigerina elongatastriata occupy an intermediate infaunal microhabitat and globobulimina spp live in a deep infaunal niche close to the zero oxygen boundary when compared with d 18 o values of calcite formed in equilibrium with bottom waters u peregrina forms its test in close equilibrium with bottom water d 18 o all other foraminiferal taxa calcify with a constant offset to calculated equilibrium calcite there is no systematic relationship between the foraminiferal microhabitat depth and the dd 18 o between foraminiferal and equilibrium calcite we calculated correcting factors for the various taxa which are needed for constructing multispecies based oxygen isotope records in paleoceanographic studies of the study area the d 13 c values of foraminiferal taxa investigated in this study do neither record bottom water d 13 cdic in a 1 1 relationship nor with a constant offset but appear to be mainly controlled by microhabitat effects the increase of d 13 c values of shallow infaunal taxa with increasing water depth reflects the decrease of the exported flux of organic carbon along the bathymetric transect and early diagenetic processes in the surface sediment this is particularly the case for the shallow infaunal u peregrina the d 13 c values of deep infaunal globobulimina spp are much less dependent on the exported organic matter flux we suggest that the dd 13 c between u peregrina and globobulimina spp can shed light on the various pathways of past degradation of organic detritus in the benthic environments at a station in 550 m water depth where periodic eutrophication of sediment surface niches was demonstrated previously we performed a two year seasonal survey of the isotopic composition of foraminiferal faunas no marked seasonal changes of the stable carbon isotopic composition of shallow intermediate and deep infaunal foraminiferal taxa were observed thus the d 13 c values of foraminiferal individuals belonging to the n150 am fraction may result from rather long term calcification processes lasting for several weeks or months which limit the impact of ephemeral 12 c enrichment of shallow infaunal niches on the isotope chemistry of adult individuals during eutrophic periods only highly opportunistic taxa reproducing or calcifying during

late pliocene variations in the carbon isotope values of north atlantic benthic foraminifera biotic control of the isotopic record abstract analyses of benthic foraminifera carbon isotope values were made in 172 samples from the late pliocene at dsdp site 548 which is located in the northeast atlantic on the continental slope southwest of ireland 1253 m water depth the carbon isotope record is quite stable from about 3 4 to 2 5 ma and contrasts with the record at site 552a in the north atlantic 2311 m water depth which is much more variable for this time period the carbon record at site 548 is also consistently more negative than that of site 552a after 2 5 ma the benthic carbon isotope record of uvigerina at site 548 becomes extremely variable with large negative deviations these isotopic variations might be associated with paleoceanic circulation changes caused by glaciation between 2 5 and 2 ma however paired analyses of uvigerina and cibicidoides species for 38 samples within the glacial interval yield carbon isotopic records which are quite different from one another the uvigerina record contains larger negative deviations than does the cibicidoides record also the isotopic difference between uvigerina and cibicidoides increases during glaciations and in a long term trend from 2 5 to 2 0 ma the lack of covariance between the uvigerina and cibicidoides carbon isotope records indicates that after 2 5 ma at site 548 biotic factors influenced the benthic isotopic record

late holocene productivity and hydrographic variability in the eastern mediterranean inferred from benthic foraminiferal stable isotopes 1 the paleoproductivity paleo oxygenation and paleohydrographic configuration of the southeastern mediterranean during the late holocene was reconstructed on the basis of the isotopic composition of the epibenthic heterolepa floridana shallow endobenthic uvigerina mediterranea and the deeper endobenthic bulimina inflata from two high resolution cores ga 112 470 m and ga 110 670 m the 13c between h floridana and u mediterranea reveals four intervals of enhanced productivity from 3 3 2 6 2 3 1 9 1 5 1 1 and 0 8 0 4 kyr bp coinciding with increased nutrient supply by the nile river the entire basin was well aerated with oxygen consumption varying between 1 0 and 3 5 ml o2 l oxygen consumption increases toward present day probably because of higher accumulation of total organic carbon at 1 7 kyr bp coinciding with the appearance of the mesotropic benthic species the hydrographic configuration of the basin has changed during the course of the last 3 75 kyr the levantine intermediate water liw deepens below 470 m between 3 3 and 2 0 kyr and especially between 2 5 and 2 0 kyr during the last 1 5 kyr the liw becomes shallower than 470 m similar to the present day the change in the hydrographic configuration reflects changes in evaporation precipitation ratio and in temperature

low δ13c in tests of live epibenthic and endobenthic foraminifera at a site of active methane seepage 1 to investigate the use of benthic foraminifera as a means to document ancient methane release we determined the stable isotopic composition of tests of live rose bengal stained and dead specimens of epibenthic fontbotia wuellerstorfi preferentially used in paleoceanographic reconstructions and of endobenthic high latitude cassidulina neoteretis and cassidulina reniforme from a cold methane venting seep off northern norway we collected foraminiferal tests from three push cores and nine multiple cores obtained with a remotely operated vehicle and a video guided multiple corer respectively all sampled sites except one control site are situated at the hakon mosby mud volcano hmmv on the barents sea continental slope in 1250 m water depth at the hmmv in areas densely populated by pogonophoran tube worms 13c values of cytoplasm containing epibenthic f wuellerstorfi are by up to 4 4 lower than at control site thus representing the lowest values hitherto reported for this species live c neoteretis and c reniforme reach 13c values of 7 5 and 5 5 vienna pee dee belemnite vpdb respectively whereas 13c values of their empty tests are higher by 4 and 3 however 13c values of empty tests are never lower than those of stained specimens although they are still lower than empty tests from the control site this indicates that authigenic calcite precipitates at or below the sediment surface are not significantly influencing the stable isotopic composition of foraminiferal shells the comparatively high 13c results rather from upward convection of pore water and fluid mud during active methane venting phases at these sites these processes mingle tests just recently calcified with older ones secreted at intermittent times of less or no methane discharge since cytoplasm containing specimens of suspension feeder f wuellerstorfi are almost exclusively found attached to pogonophores which protrude up to 3 cm above the sediment and 13c values of bottom water dissolved inorganic carbon dic are not significantly depleted we conclude that low test 13c values of f wuellerstorfi are the result of incorporation of heavily 13c depleted methanotrophic biomass that these specimens feed on rather than because of low bottom water 13cdic alternatively the pogonophores which are rooted at depth in the upper sediment column may serve as a conduit for depleted 13cdic that ultimately influences the calcification process of f wuellerstorfi attached to the pogonophoran tube well above the sediment water interface the lowest 13c of live specimens of the endobenthic c neoteretis and c reniforme are within the range of pore water 13cdic values which exceed those that could be due to organic matter decomposition and thus in fact document active methane release in the sediment

wave follower field measurements of the wind input spectral function part iii parameterization of the wind input enhancement due to wave breaking abstract this is the third in a series of papers describing wave follower observations of the aerodynamic coupling between wind and waves on a large shallow lake during the australian shallow water experiment auswex it focuses on the long standing problem of the aerodynamic consequences of wave breaking on the wind wave coupling direct field measurements are reported of the influence of wave breaking on the wave induced pressure in the airflow over water waves and hence the energy flux to the waves the level of forcing measured by the ratio of wind speed to the speed of the dominant spectral peak waves covered the range of 3 7 the propagation speeds of the dominant waves were limited by the water depth and the waves were correspondingly steep these measurements allowed an assessment of the magnitude of any breaking induced enhancement operative for these field conditions and provided a basis for parameterizing the effect overall appreciable levels of wave breaking occurred for the strong win

origin distribution and accumulation of organic carbon in the skagerrak abstract organic carbon contents have been determined in grain size fractions of sediments from the skagerrak southern slope and basin c org concentrations were generally inversely related to grain size the 62 63 m fraction in surface sediments from deeper waters had higher contents attributable to agglutination of fine material by tube forming benthic organisms especially in the clay and fine silt fractions c org increased with increasing fraction content presumably as a result of higher grazing pressure on fine material in coarse sediments a comparison of high resolution age 210 pb porosity and grain size composition profiles indicates that deviations in the 210 pb curves are due both to bioturbation and sedimentation events porosity profiles also show high regional variability on a small scale when primary production c org vertical fluxes and accumulation rates are compared an excess of organic carbon stored in skagerrak sediments becomes apparent potential sources for this carbon such as river input dumping or sea floor erosion are examined

variations in organic carbon flux and stagnation periods during the last 2400 years in a skagerrak fjord basin inferred from benthic foraminiferal δ13c

changes in the distribution of δ13c of deep water σco2 between the last glaciation and the holocene carbon isotopic measurements on the benthic foraminiferal genus cibicidoides document that mean deep ocean 13c values were 0 46 lower during the last glacial maximum than during the late holocene the geographic distribution of 13c was altered by changes in the production rate of nutrient depleted deep water in the north atlantic during the late holocene north atlantic deep water with high 13c values and low nutrient values can be found throughout the atlantic ocean and its effects can be traced into the southern ocean where it mixes with recirculated pacific deep water during the glaciation decreased production of north atlantic deep water allowed southern ocean deep water to penetrate farther into the north atlantic and across low latitude fracture zones into the eastern atlantic mean southern ocean 13c values during the glaciation are lower than both north atlantic and pacific 13c values suggesting that production of nutrient depleted water occurred in both oceans during the glaciation enriched 13c values in shallow cores within the atlantic ocean indicate the existence of a nutrient depleted water mass above 2000 m in this ocean

bathymetry and magnetic anomalies in the havre trough and southern lau basin from rifting to spreading in back arc basins abstract the havre trough and lau basin are active back arc basins related to pacific australian plate convergence these back arc basins provide insight into the evolution of rifting through various stages including a final stage of oceanic spreading we carried out a swath bathymetry and magnetic anomaly survey focused on the less studied havre trough and southern lau basin the western portion of the whole havre trough is deeper and more thickly sedimented whereas shallow bathymetry and volcanic edifices are dominant in the east we suggest that crustal rifting progresses asymmetrically with respect to the trough axis the active tectono magmatic zone migrates trenchward during ongoing widening rifting along normal faults trending in the longitudinal trough strike occurs in the southern havre trough volcanism is restricted to a line along the normal faults circular or elongated knolls in the northern havre trough indicate that en echelon type segmented rifting of short strike length and successive volcanic intrusion takes place volcanism in this area is dominated by diapir like magma intrusion into an extended and thinned arc crust the southernmost tip of the spreading center of lau basin is defined by the deep graben striking at n20 e located at 24 00 s 177 10 w

core top evaluation of benthic foraminiferal isotopic ratios for paleo oceanographic interpretations abstract the benthic foraminifera cibicides wuellerstrofi oridforsalis tener and pyrgo rotalaria from twelve core tops in the norwegian greenland sea and c wuellerstorfi o tener and o umbonatus from four core tops on the rio grande rise were analysed for oxygen and carbon isotopes the norwegian greenland sea data yield statistically discrete means for both 18o and 13c for each species the interregional comparison of our data to published data from the east pacific rise shows that c wuellerstorfi 18o and 13c variations reflect oceanographic differences between sites whereas the data on oridorsalis and pyrgo do not we conclude that c wuellerstorfi is a reliable sensor of bottom water conditions whereas other taxa are of unproven utility supportive biological studies and the lack of positive covariance of 18o to 13c among deep sea benthic taxa lead us to reject models calling for incorporation of metabolic co2 to explain the isotopic variation among deep sea benthic foraminifera we propose a within sediment microhabitat hypothesis to explain the 13c variations among taxa

the δ13c in benthic foraminiferal tests of fontbotia wuellerstorfi schwager relative to the δ13c of dissolved inorganic carbon in southern ocean deep water implications for glacial ocean circulation models on a transect between 20 and 70 s in the eastern atlantic ocean and weddell sea water samples from 19 hydrographic stations and bottom water from 55 surface sediment samples taken with a multiple corer were investigated for the stable carbon isotopic composition of the total dissolved inorganic carbon 13c co2 these measurements were compared to 13c values determined on live specimens of the benthic foraminifer fontbotia wuellerstorfi and closely related genera from the same stations in addition at 16 stations the stable carbon isotope composition of sedimentary organic carbon was measured general deepwater and bottom water mass circulation patterns as inferred from the 13c co2 are in close agreement with those known from other nonconservative tracers very low 13c values of upper circumpolar deep water 0 3 pee dee belemnite pdb in the polar front region and the eastern limb of the weddell gyre coincide with nutrient maxima however a significant decoupling of the dissolved phosphate signal from the 13c co2 signal is indicated in the abyssal weddell sea we attribute this to temperature dependent fractionation processes during gas exchange of surface waters with the atmosphere at sites of bottom water formation multiple corer water from the sediment water interface is slightly 13c depleted relative to deepwater and bottom water 13 co2 the surface sediment organic carbon 13c is 3 to 4 lower south of the polar front than north of it and the 13corg in freshly accumulated phytodetritus is 3 to 4 lower than surface sediment organic carbon 13c comparison of live f wuellerstorfi 13c and related genera with bottom water 13c co2 exhibits at most stations between the subtropical front 41 s and the southern boundary of the antarctic circumpolar current 55 s a significant lowering of foraminiferal 13c values compilation of a mean last glacial interglacial 13c amplitude 13c from six published southern ocean cores results in a shift of 0 99 0 13 pdb this shift is greater than that in all other regions however all of these cores are from positions close to recent oceanic fronts thus for these peripheral areas of the southern ocean we suggest about half of the glacial interglacial shift can be explained by varying frontal zone positions and widths accompanied by a change in mode and height of export production

stable carbon isotopes in marine porewaters abstract we present centimeter scale porewater 13 c profiles from four sites in the central equatorial pacific ocean which reveal steep porewater 13 c gradients up to 1 0 cm 1 at the deep sea sediment water interface we describe the processes controlling porewater carbon isotopic composition and incorporate them into a model of the deep sea benthic carbon cycle our measured 13 c profiles are then used to estimate carbon rain rates at two of these sites manop sites c and s the 13 c data yield organic carbon rain rates of 10 mol c cm 2 yr 1 at site c and 3 mol c cm 2 yr 1 at site s these carbon rain rates agree with recent carbon rain estimates based on sediment trap data and porewater nitrate profiles but are a factor of 2 lower than estimates based on millimeter scale porewater oxygen profiles our model results indicate that changes of the same magnitude in organic carbon rain rate and bottom water composition o 2 co 2 and 13 c have comparable effects on the carbon isotopic composition of surficial porewaters this suggests the need to consider the effects of benthic carbon cycling on the stable carbon isotope record preserved in deep sea benthic foraminifera tests

productivity and organic carbon rain to the california margin seafloor modern and paleoceanographic perspectives 1 we have developed a proxy measurement for the determination of organic carbon corg oxidation rates cox on the seafloor utilizing the 13c values of two benthic foraminifera bolivina argentea a near surface dwelling species and buliminella tenuata an infaunal species the 13c isotopic composition of these tests preserve a record of the 13co2 pore water gradient which is directly related to cox on the seafloor of santa monica basin cox has fluctuated between 0 6 and 2 5 mmolc m 2 d 1 and generally increased from 1600 to 1980 ad between 1920 and 1970 cox increased from 1 to 2 mmolc m 2 d 1 and then decreased into the 1980s by adding cox to a high resolution record of corg burial rate we have derived the pattern of corg rain to the seafloor which fluctuated between 2 9 and 3 8 mmolc m 2 d 1 over the last 80 years the ratio of corg rain at 900 m to primary productivity is constant at 10 1 over a 40 change in mean annual primary productivity sediments in santa monica basin accumulate 50 of the corg raining to the seafloor however there is a trend toward lower burial efficiency with higher productivity and rain rate

effects of wind trend and gustiness on the sea drag lake george study 1 the air sea coupling is usually parameterized in terms of the drag coefficient cd but the scatter of experimental data around such dependences is very significant and has not improved noticeably over some 30 years in the paper which is meant to be the first in a series a complex approach to the problem is suggested multiple mechanisms contributing into the sea drag are to be singled out studied separately evaluated and then reunited in a joint parameterization for cd dependences of the drag coefficient on the wind speed and sea state and effects of wind trends and gustiness are investigated in detail gustiness is found to be responsible for the most distant outliers our approach also combines an experimental lake george study with theoretical investigations conducted by means of the wowc wind over waves coupling model overall agreement of the model with measured wind stresses is quite good within 20 for the bulk of the data lower envelopes of the drag dependences are an important result of the paper they provide some lake george ideal relationships for the sea drag almost any deviation from such conditions causes the drag to increase it is suggested that decrease of the drag with respect to the ideal conditions which exhibits itself in a number of known open ocean data sets would be caused by a momentum flux back from the waves to the wind due to long waves outrunning the wind behavior of the charnock parameter in terms of wave age is also considered

observation based source terms in the third generation wave model wavewatch iii updates and verification abstractthe observation based source terms available in the third generation wave model wavewatch iii i e the st6 package for parameterizations of wind input wave breaking and swell dissipatio

numerical investigation of spectral evolution of wind waves part i wind input source function abstract this paper is dedicated to the investigation and calibration of the parameterized form for the wind input source term sin proposed earlier on the basis of field observations at lake george australia the main objective of this study was to obtain spectral forms for the wind input source function sin which incorporates the novel observation based features and at the same time satisfies the important physical constraint that the total integrated wind input must agree with independently observed magnitudes of the wind stress within this approach a new methodology a dynamic self adjusting routine was developed for correction of the wind input source function sin this correction involves a frequency dependent adjustment to the growth rate f based on extrapolations from field data the model results also show that light winds require higher rate adjustments of the wind input than strong winds

benthic foraminiferal δ13c and accumulation rates of organic carbon uvigerina peregrina group and cibicidoides wuellerstorfi the glacial to interglacial 13c records of the benthic foraminifera cibicidoides wuellerstorfi and the uvigerina peregrina group from deep sea cores cannot be adjusted by a generally valid constant the 13c values of the u peregrina group largely correlate with the accumulation rates of organic carbon suggesting a local habitat effect those of c wuellerstorfi vary independently with respect to the carbon flux and record fluctuations in the 13c of the ambient bottom water isotopic composition