annual biogenic particle fluxes to the interior of the north atlantic ocean studied at 34 n 21 w and 48 n 21 w abstract in order to clarify the annual quality quantity and export processes of biogenic particles from the euphotic zone to the deep ocean interior an array of automated time series sediment traps were deployed for 1 year from 4 april 1989 to 17 april 1990 at 34 n 21 w and 48 n 21 w as part of the joint global ocean flux program jgofs north atlantic bloom experiment nabe three sediment traps with 13 time series sediment collectors were placed at both stations approximately 1 and 2 km below the surface and 0 7 km above the bottom they collected settling particles during 26 14 day intervals for 376 days with an 20 day hiatus in september october 1989 for changeover of the trap moorings the collection periods of the six traps were synchronized forming a spatio temporal matrix of 156 samples the annual mass flux at about 2 km deep during this experiment was 22 and 27 g m 2 y 1 at the 34 and 48 n stations consisting of biogenic particles with traceable quantities of lithogenic particle flux the spring particle bloom characterized by the sedimentation of particles relatively enriched by norg began in january at the 34 n station and in march at the 48 n station the bloom continued for 4 5 and 3 months and provided 62 and 50 of the annual biogenic particle mass flux at 2 km at the 34 and 48 n stations the surface bloom penetrated to the ocean interior within a few weeks with apparently accelerated settling speed at deeper layers the order of susceptibility of biogenic elements to mineralization while settling in the 0 7 1 km a b water column was from least to most resistant p norg corg si and ca the c n p ratio at 0 7 km a b was 154 18 1 at the 34 n station and 148 18 1 at the 48 n station

erosion of the laurentide region of north america by glacial and glaciofluvial processes collection of seismic reflection data from continental margins and ocean basins surrounding north america makes it possible to estimate the amount of material eroded from the area formerly covered by laurentide ice sheets since major glaciation began in north america a minimum estimate is made of 1 62 106 km3 or an average 120 m of rock physically eroded from the laurentide region this figure is an order of magnitude higher than earlier estimates based on the volume of glacial drift cenozoic marine sediments and modern sediment loads of rivers most of the sediment produced during laurentide glaciation has already been transported to the oceans the importance of continental glaciation as a geomorphic agency in north america may have to be reevaluated evidence from sedimentation rates in ocean basins surrounding greenland and antarctica suggests that sediment production sediment transport and possibly denudation by permanent ice caps may be substantially lower than by periodic ice caps such as the laurentide low rates of sediment survival from the time of the permo carboniferous and precambrian glaciations suggest that predominance of marine deposition during some glacial epochs results in shorter lived sediment because of preferential tectonism and cycling of oceanic crust versus continental crust

solute provenance transport and denudation in a high arctic glacierized catchment recent understanding of chemical weathering in glacierized catchments has been focused on mid latitude alpine catchments comparable studies from the high latitudes are currently lacking this paper attempts to address this deficiency by examining solute provenance transport and denudation in a glacierized catchment at 78 n in the svalbard high arctic archipelago representative samples of snow glacier ice winter proglacial icing and glacier meltwater were obtained from the catchment during spring and summer 1993 and analysed for major ion chemistry seasonal variations in the composition of glacier meltwater occur and are influenced by proglacial solute acquisition from the icing at the very start of the melt season and subsequently by a period of discharge of concentrated snowmelt caused by snowpack elution weathering within the ice marginal channels that drain the glacier particularly carbonation reactions continues to furnish solute to meltwater when suspended sediment concentrations increase later in the melt season partitioning the solute flux into its various components sea salt crustal aerosol and atmospheric sources shows that c 25 of the total flux is sea salt derived consistent with the maritime location of the glacier and c 71 is crustally derived estimated chemical denudation 160 meq m 2 a 1 sea salt corrected cation equivalent weathering rate is somewhat low compared with other studied glacierized catchments estimates in the range 450 1000 meq m 2 a 1 which is probably attributable to the relatively short melt season and low specific runoff in the high arctic a positive relationship was identified between discharge and co 2 drawdown owing to carbonation reactions in turbid meltwater

particulate organic carbon fluxes to the ocean interior and factors controlling the biological pump a synthesis of global sediment trap programs since 1983 particulate organic carbon poc is vertically transported to the oceanic interior by aggregates and their ballasts mainly caco3 and biogenic opal with a smaller role for lithogenic aerosols through the mesopelagic zone diel migrating zooplankton communities effect vertical transport and remineralization of poc in the upper layers of the ocean below 1 5 km the presence of zooplankton is reduced and thus the aggregates travel mainly by gravitational transport we normalized the fluxes of poc caco3 and biogenic opal from data published on samples collected at 134 globally distributed bottom tethered time series sediment trap ts trap stations to annual mole fluxes at the mesopelagic bathypelagic boundary m b at 2 km and defined them as fm bcorg fm bcinorg and fm bsibio using this global data set we investigated 1 the geographic contrasts of poc export at m b and 2 the supply rate of co2 to the world mesopelagic water column fm bcorg varies from 25 pacific warm pool to 605 divergent arabian sea mmolc m 2 yr 1 fm bcinorg varies from 8 high latitude polar oceans or 15 pacific warm pool to 459 divergent arabian sea mmolc m 2 yr 1 and fm bsibio the most spatially temporally variable flux ranges from 6 north atlantic drift to 1118 pacific subarctic gyre mmolsi m 2 yr 1 the oceanic region exhibiting the highest poc flux over a significantly large region is the area of the north pacific boreal gyres where the average fm bcorg 213 fm bcinorg 126 and fm bsibio 578 mmol m 2 yr 1 fm bcorg and fm bcinorg are particularly high in large upwelling margins including the divergent arabian sea and off cape verde one of the data sets showing the lowest flux over a significant region basin is fm bcorg 39 fm bcinorg 69 and fm bsibio 22 mmol m 2 yr 1 in the north pacific subtropical tropical gyres pan atlantic average fluxes are similar except fm bsibio fluxes are even lower where corg cinorg and sibio cinorg are 1 defines the carbonate ocean and where these ratios are 1 defines the silica ocean the carbonate ocean occupies about 80 of the present world pelagic ocean between the two major oceanographic fronts the north pacific polar front and the antarctic polar front and the silica ocean is found on the polar sides of these fronts the total global annual fluxes of fm bcorg fm bcinorg and fm bsibio at m b calculated by parameterizations of the export flux data from 134 stations are surprisingly similar 36 2 33 8 and 34 6 teramol yr 1 120 112 and 114 mmol m 2 yr 1 respectively resulting in a near uniform binary ratio between the above three elements of about one the global ternary ratios estimated from 152 ts trap samples of the three elements are 35 32 33 from our global fm bcorg and a published model estimate of the global export production we estimate the regeneration rate of co2 through the mesopelagic zone by the biological pump is 441 teramolc yr 1 based on our global fm bcinorg and recently estimated global primary production of pic 36 86 teramolc yr 1 of pic is assumed to be dissolved within the upper 2 km of the water column

the long term hydrographic record at bermuda abstract a long by oceanographic standards time series of hydrographic observations at bermuda was begun in 1954 and continues to the present analysis of this dataset has shown the temperature and salinity variations on interannual timescales to be largely independent in the surface layer 0 200 dbar where integral timescales for salinity are 50 longer than for temperature and surface salinity changes are correlated with decadal changes in the 18 c water production temperature salinity anomalies are highly correlated in the thermocline where the interannual variability at that level is accountable to either vertical oscillations of the thermocline with amplitudes of 50 m or meridional oscillations of the horizontal gradient set up at the southern edge of the recirculation gyre of 300 kim salinity changes in the deepest layer observed at bermuda station s 1500 2500 dbar are uncorrelated with temperature masked by measurement errors in the early years of the time series inclusion of earlier

late quaternary sediment yield from the high arctic svalbard area late quaternary sediment yields from the isfjorden drainage area 7327 km 2 a high arctic region on svalbard characterized by an alpine landscape have been reconstructed by using seismic stratigraphy supported by sediment core analysis the sediments that accumulated in the fjord during and since deglaciation can be divided into three stratigraphic units the volumes of these units were determined and converted into sediment yield rates averaged over the drainage basin during deglaciation 13 to 10 ka the sediment yield was sim 860 tons t cdot km 2 cdot yr 1 in the early holocene it decreased to 190 t cdot km 2 cdot yr 1 and then increased to 390 t cdot km 2 cdot yr 1 during the late holocene little ice age when normalized to the approximate glacierized area these rates correspond to a sediment yield of sim 800 t cdot km 2 cdot yr 1 sediment yield from non glacierized parts of the drainage is estimated to be 35 t cdot km 2 cdot yr

quaternary sedimentary processes and budgets in orphan basin southwestern labrador sea abstract the continental slope in orphan basin northeast of newfoundland is underlain by several seaward thinning debris flow wedges alternating with acoustically stratified regionally extensive mainly hemipelagic sediments 18o stratigraphy and volcanic ash layers in a 11 67 m core indicate that the uppermost debris flow wedge formed during the last of several sea level lowstands in isotopic stages 2 4 similarly seismic reflection correlation of dated levels at dsdp site 111 with the orphan basin succession suggests that two deeper debris flow wedges were deposited during oxygen isotopic stages 6 and 8 the oldest of the debris flow deposits in at least three of the wedges formed well into the corresponding glacial cycle after ice sheets had reached the edge of the continental shelf slower deposition by hemipelagic processes and ice rafting formed the acoustically stratified units including heinrich layers the youngest three debris flow wedges each have volumes of 1300 1650 km3 approximately two thirds of this material is attributed to glacial erosion of mesozoic and tertiary strata beneath the northeast newfoundland shelf the remainder is believed to have been derived by glacial erosion of older bedrock that now forms the island of newfoundland the observed sediment volumes and the inferred basal and upper ages of the debris flow wedges imply an average glacial denudation rate of about 0 13 mm yr for this older bedrock and an average of about 60 m of glacial bedrock erosion since oxygen isotope stage 22 this denudation rate is similar to estimates from the barents sea region off norway

use of digital elevation models to understand and map glacial landforms the case of the canigou massif eastern pyrenees france abstract this paper presents an improved geomorphological methodology that uses remotely sensed data a geographical information system and a brief field campaign to allow rapid yet precise mapping as well as interpretation and analysis of glacial earth surface morphology in high mountain areas the study area consists of the quaternary glaciated part of the coumelade valley canigou massif eastern pyrenees france which ranges between 1450 and 2731 m a s l a topographical map derived digital elevation model was used for analyzing glacial landforms by extracting the slope gradient valley profiles and the slope aspect the results were gradually refined from the interpretations of aerial photograph and the field investigation glacial landforms are present above 1500 m a s l and include glacial and nivation cirques cirque and latero frontal moraines 7 7 106 m and micro scale landforms such as chattermarks crescent grooves and polished surfaces the geomorphological investigation reveals that the quaternary glaciation of the coumelade valley remained limited resulting in a low denudation rate of 0 011 mm yr 1 over the last glacial cycle

effects of sinking velocities and microbial respiration rates on the attenuation of particulate carbon fluxes through the mesopelagic zone the attenuation of sinking particle fluxes through the mesopelagic zone is an important process that controls the sequestration of carbon and the distribution of other elements throughout the oceans case studies at two contrasting sites the oligotrophic regime of the bermuda atlantic time series study bats and the mesotrophic waters of the west antarctic peninsula wap sector of the southern ocean revealed large differences in the rates of particle attached microbial respiration and the average sinking velocities of marine particles two parameters that affect the transfer efficiency of particulate matter from the base of the euphotic zone into the deep ocean rapid average sinking velocities of 270 150 m d 1 were observed along the wap whereas the average velocity was 49 25 m d 1 at the bats site respiration rates of particle attached microbes were measured using novel respire respiration of sinking particles in the subsurface ocean sediment traps that first intercepts sinking particles then incubates them in situ respire experiments yielded flux normalized respiration rates of 0 4 0 1 day 1 at bats when excluding an outlier of 1 52 day 1 while these rates were undetectable along the wap 0 01 0 02 day 1 at bats flux normalized respiration rates decreased exponentially with respect to depth below the euphotic zone with a 75 reduction between the 150 and 500 m depths these findings provide quantitative and mechanistic insights into the processes that control the transfer efficiency of particle flux through the mesopelagic and its variability throughout the global oceans

upper ocean temperature response to hurricane felix as measured by the bermuda testbed mooring hurricane felix passed over the bermuda testbed mooring on 15 august 1995 providing a unique opportunity to observe the response of the upper ocean to a hurricane in the vicinity of bermuda felix was a particularly large hurricane with hurricane force winds over a diameter of about 300 400 km and tropical storm force winds over a diameter of about 650 800 km felix moved northwestward at about 25 km h21 with the eye passing about 65 km southwest of the mooring on 15 august peak winds reached about 135 km h21 at the mooring complementary satellite sea surface temperature maps show that a swath of cooler water by about 3 58 4 08c was left in the wake of felix with the mooring in the center of the wake prior to the passage of felix the mooring site was undergoing strong heating and stratification however this trend was dramatically interrupted by the passage of the hurricane as felix passed the mooring large inertial currents speeds of 100 cm s 21 at 25 m were generated within the upper layer the e folding decay timescale of the inertial currents was about 9 days the mixed layer depth was about 15 m before the arrival of felix and deepened to about 45 m within three days after felix s passage the temperature at 25 m decreased by approximately 3 5 8 4 08c large amplitude temperature oscillations 1 58c near the inertial period inertial pumping effect were set up by the hurricane in the seasonal thermocline resulting in vertical displacements of isotherms of approximately 15 m at 60 70 m comparative scale analyses of the upper ocean responses to hurricane felix and hurricane gloria 1985 indicate that they have several similarities

cirques have growth spurts during deglacial and interglacial periods evidence from 10be and 26al nuclide inventories in the central and eastern pyrenees cirques are emblematic landforms of alpine landscapes the statistical distribution of cirque floor elevations is used to infer glacial equilibrium line altitude and the age of their frontal moraines for reconstructing glacial chronologies very few studies however have sought to measure cirque floor and supraglacial ridgetop bedrock downwearing rates in order to confront these denudation estimates with theoretical models of quaternary mountain landscape evolution here we use 10 be nuclide samples n 36 from moraines bedrock steps and supraglacial ridgetops among a population of cirques in the east central pyrenees in order to quantify denudation in the landscape and detect whether the mountain topography bears any relevance to the glacial buzzsaw hypothesis minimum exposure ages meas obtained for a succession of moraines spanning the oldest dryas to the holocene produced a deglaciation chronology for three different pyrenean ranges maladeta bassies and carlit based on a series of corrections calibrations and chronostratigraphic tuning procedures meas on ice polished bedrock exposures were further used to model denudation depths at nested timescales during the wurm the younger dryas and the holocene results show that subglacial cirque floor denudation was lower during glacial periods wurm 10 mm ka than during deglacial and interglacial periods tens to hundreds of mm ka the relative inefficiency of glacial denudation in the cirque zone during the wurm would have resulted from i cold based and or ii low gradient glaciers situated in the upper reaches of the icefield and or from iii glacier load starvation because of arrested clast supply from supraglacial rockslopes situated in the permafrost zone denudation peaked during the younger dryas and holocene glacial advances a time when cirque glaciers became steeper warmer based and when frost cracking weakened supraglacial ridgetops thus enhancing sub glacial erosion by providing debris to the sliding glacier base cirques therefore grow faster during more temperate periods of cirque glaciation than under full glacial conditions another key finding was the very low rates of ridgetop lowering averaged over the wurm and holocene 10 25 mm ka a comparison of the denudation rates obtained from the cirque zone with regional estimates of crustal uplift indicates that the alpine topography is not in a steady state the low intensity of glacial denudation failed to bring the topography to a buzzsaw equilibrium state

evaluation of the biogeochemical controls on b ca of globigerinoides ruber white from the oceanic flux program bermuda a b s t r a c t boron to calcium b ca ratios in planktonic foraminifera is suggested to be a proxy for the surface oceanic carbonate system the reliability of the proxy has been questioned due to conflicting reports from culture and sediment calibrations on the influence of temperature on b ca to assess this issue b ca and mg ca ratios and 18 ow ere measured in tests of the symbiont bearing surface dwelling planktonic foraminifer globigerinoides ruber white collected by the oceanic flux program ofp time series sediment traps located approximately 75 km se of bermuda b ca ratios in the 300 400 m size fraction of g ruber were approximately 10 20 higher than those in the 200 300 m size fraction in contrast mg ca ratios and 18 ov alues do not exhibit any relationship to test size which indicates that the size effect observed for b ca is not due to differences in depth habitat but to vital effects seasonal variation in the b ca ratio was similar in both size fractions and ranged by 20 30 mol mol this range is larger than that predicted by seasonal variations in seawater b oh hco the proposed boron species incorporated into planktonic foraminiferal calcite and indicates that b ca in g ruber is influenced by an additional variable s the seasonal cycle of b ca in g ruber white was more strongly correlated with light intensity than with temperature both observations suggest that the presence of symbionts in g ruber and seasonal variability in their photosynthetic activity act to modify the internal ph during calcification by up to 0 2u nits relative to ambient seawater 2014 elsevier b v all rights reserved

association of sinking organic matter with various types of mineral ballast in the deep sea implications for the rain ratio 1 we compiled and standardized sediment trap data below 1000 m depth from 52 locations around the globe to infer the implications of the armstrong et al 2002 ballast model to the ratio of organic carbon to calcium carbonate in the deep sea the rain ratio we distinguished three forms of mineral ballast calcium carbonate opal and lithogenic material we concur with armstrong et al 2002 that organic carbon sinking fluxes correlate tightly with mineral fluxes based on the correlations seen in the trap data we conclude that most of the organic carbon rain in the deep sea is carried by calcium carbonate because it is denser than opal and more abundant than terrigenous material this analysis explains the constancy of the organic carbon to calcium carbonate rain ratio in the deep sea today and argues against large changes in the mean value of this ratio in the past however sediment trap data show variability in the ratio in areas of high relative calcium carbonate export mass caco3 mass ratio 0 4 unexplainable by the model leaving open the possibility of regional variations in the rain ratio in the past

effective diffusivities within oceanic thermohaline staircases a scale for the thickness of layers in regular diffusive type thermohaline staircases derived from dimensional analysis is found to collapse oceanic data combining this scale with laboratory derived double diffusive flux laws we formulate effective diffusivities for salt heat and density the diffusivities depend on the turner number r but are independent of the brunt vaisala frequency for r near 1 the diffusivities for salt and heat are approximately equal 10 4 m2 s 1 they decrease roughly as r 4 and r 2 respectively over the oceanic range 1 r 10

biogeochemistry of dissolved arsenic in the temperate to tropical north atlantic ocean abstract the biogeochemical cycle of arsenic was examined in the water column across the north atlantic from 39 to 17 n as part of the us geotraces north atlantic study geotraces section ga03 results show limited nutrient like distribution of as5 and upper ocean maxima in as3 and methylated as as found in many other studies in the oligotrophic water masses microbial communities i e phytoplankton appear to favor the reduction to as3 instead of methylation as detoxification of as5 taken up during phosphorus p limitation due to their chemical similarities the depth integrated average concentrations in the mixed layer depth of as3 in the western and eastern atlantic ocean were 1 30 1 14 nmol l 1 n 4 and 0 65 n 2 respectively and rose to 3 30 nmol l 1 n 2 in the central atlantic ocean no pattern was observed for as5 15 7 2 8 nmol l 1 n 8 and methylated species were detected occasionally below 0 41 nmol l 1 in the mixed layer based on significant correlations between phosphate alkaline phosphate activity apa a conventional proxy for p limitation and as3 we conclude that as3 is a good proxy for p limitation within the upper water column similar to our earlier evaluation of surface data mass balances for the mixed layer show that atmospheric inputs of as5 can compensate for the losses via export fluxes and microbial reduction to as3 the cycling of as3 is more complex with sources from as5 reduction and losses due to photochemical and microbial induced oxidation the resulting residence time of as3 with respect to these processes can be as short as 0 7 3 days unlike as5 atmospheric inputs of as3 cannot balance the oxidative losses and the short residence time further limits horizontal and vertical advective diffusive inputs it appears that reduction of as5 coupled with detoxification and general microbial reduction are the sources of as3 in the oceanic mixed layer while as3 production during as5 detoxification has been well studied the generic microbial reduction of as5 to as3 requires a more thorough investigation

a comparison of atmospheric inputs and deep ocean particle fluxes for the sargasso sea trace metal distributions in ocean waters are dominated by internal recycling processes however fluxes out of the water column must balance inputs if steady state is to be maintained we use deep sea particle fluxes at 3200 m in the sargasso sea as measured by sediment traps to define the flux to the sediments beneath the sargasso sea and compare this flux to the atmospheric input for a group of trace metals despite the uncertainties associated with the comparison several important features are revealed for elements predominantly associated with crustal particles al mn fe and v lateral advection provides a significant part of the deep sea particle flux for cd cu ni pb and zn this lateral component is minor and atmospheric inputs to the sargasso sea exceed deep sea particle fluxes these excesses appear to be consistent with calculations of the export of these metals from the sargasso sea arising from ocean boundary scavenging pb and release from decomposing organic matter in the southward flowing north atlantic deep water cd cu ni and zn in the atmospheric deposition itself wet deposition exceeds dry deposition for cd cu mn ni pb and zn while wet and dry deposition are of similar magnitudes for v fe and al

nitrogen isotopic composition of planktonic foraminifera from the modern ocean and recent sediments we investigated the controls on the 15n values of shell bound organic matter of planktonic foraminifera foraminifera bound 15n or fb 15n the bulk biomass 15n of live foraminifera collected from plankton tows at sta s in the sargasso sea is within 1 of the fb 15n of the same species picked from surface sediments from the low latitude north atlantic the fb 15n value in the surface sediments is strongly correlated with the 15n of thermocline nitrate the dominant source of new n to the euphotic zone the three euphotic zone dwelling symbiotic spinose species globigerinoides ruber globigerinoides sacculifer and orbulina universa have a fb 15n similar to or slightly higher than that of the nitrate supply to the euphotic zone whereas the deeper dwelling non spinose and or asymbiotic forms have higher 15n in the cariaco basin sediment trap samples the fb 15n of o universa varies substantially 1 2 between the lowest and highest value in some cases in step with 15n changes in the bulk sinking n while the subeuphotic zone dwelling asymbiotic and or non spinose species are generally higher in fb 15n and less variable through the time series the higher and less temporally variable fb 15n values of the deeper dwellers are consistent with their partial reliance on subsurface suspended particulate nitrogen the 15n of which is elevated and relatively stable over time as an alternative possibly additional explanation for the lower fb 15n of the euphotic zone dwellers despite their likely tendency to feed on high 15n zooplankton the dinoflagellate symbionts may reduce the 15n elevation of a foraminifera s biomass relative to its diet by reducing the efflux of low 15n ammonium

seasonal changes in species composition numbers mass size and isotopic composition of planktonic foraminifera settling into the deep sargasso sea abstract planktonic foraminifera recovered from six successive sediment trap samples collected over fourteen months at a depth of 3200 m near bermuda show varied responses to seasonal changes in the near surface hydrography these include changes in species composition and within species changes in number of individuals collected per unit time average size and weight of individuals and in oxygen and carbon isotopic composition a total of seventeen species were identified and eleven were sufficiently abundant for isotopic analysis in at least some of the samples the accumulations on the sea floor of some of these species can be expected to contain a strong seasonal component in their oxygen isotopic composition which may be utilized in paleoclimatic and paleo oceanographic reconstructions best suited to this purpose are those species which form their tests in isotopic equilibrium with surface water and whose abundance is confined to a portion of the year only the best examples are pulleniatina o bliguiloculata globigerinoides conglobatus and neogloboquadrina dutertrei globigerinoides ruber is a good estimator of the average surface water temperature because it occurs in rather even abundance throughout the year hastigerina pelagica though very abundant in surface water is practically eliminated even before arrival on the sea floor by partial resorption and structural weakening of the tests during gametogenesis orbulina universa globorotalia truncaltulinoides and globorotalia hirsuta show morphological and istopic evidence for contibnued calcification in deeper water after initial test formation near ther surface globigerina bulloides represents the most striking example of oxygen isotopic disequilibrium with sea water

seasonal and interannual variability in deep ocean particle fluxes at the oceanic flux program ofp bermuda atlantic time series bats site in the western sargasso sea near bermuda abstract since 1978 the oceanic flux program ofp time series sediment traps have measured particle fluxes in the deep sargasso sea near bermuda there is currently a 20 yr flux record at 3200 m depth a 12 yr flux at 1500 m depth and a 9 yr record at 500 m depth strong seasonality is observed in mass flux at all depths with a flux maximum in february march and a smaller maximum in december january there is also significant interannual variability in the flux especially with respect to the presence absence of the december january flux maximum and in the duration of the high flux period in the spring the flux records at the three depths are surprisingly coherent with no statistically significant temporal lag between 500 and 3200 m fluxes at our biweekly sample resolution bulk compositional data indicate an extremely rapid decrease in the flux of organic constituents with depth between 500 and 1500 m and a smaller decrease with depth between 1500 and 3200 m depth in contrast carbonate flux is uniform or increases slightly between 500 and 1500 m possibly reflecting deep secondary calcification by foraminifera the lithogenic flux increases by over 50 between 500 and 3200 m depth indicating strong deep water scavenging repackaging of suspended lithogenic material concurrent with the rapid changes in flux composition there is a marked reduction in the heterogeneity of the sinking particle pool with depth especially within the mesopelagic zone by 3200 m depth the bulk composition of the sinking particle pool is strikingly uniform both seasonally and over variations in mass flux of more than an order of magnitude these ofp results provide strong indirect evidence for the intensity of reprocessing of the particle pool by resident zooplankton within mesopelagic and bathypelagic waters the rapid loss of organic components the marked reduction in the heterogeneity of the bulk composition of the flux and the increase in terrigenous fluxes with depth are most consistent with a model of rapid particle turnover and material scavenging from the suspended pool during new particle formation we suggest that much of the deep mass flux is generated in situ by deep dwelling zooplankton and that mass flux as well as scavenging of suspended materials from the deep water column varies in proportion to changes in grazer activity labile very rapidly sinking aggregates e g salp fecal material arriving in the bathypelagic zone within days of their upper ocean production may act to stimulate zooplankton grazing rates and increase large particle production and deep mass flux days to weeks in advance of the arrival of bulk of surface produced material this process could reconcile mean particle sinking rate estimates with the phase coherence observed between upper and deep ocean mass fluxes

late pleistocene detrital sediment yield of the jura glacier france abstract measures of present day glacial erosion vary widely with the technique employed this paper quantifies the glacial material trapped in a proglacial lake during the wurm glacial period the combe d ain site was occupied by a meltwater lake where all the detrital material entering it from the jura glacier accumulated sediment yield is computed from three factors 1 the size of the sediment source area 2 the length of time the system operated and 3 the volume of sediment trapped the sediment budget of the lake system suggests a detrital sediment yield of 4400 1700 metric tons per square kilometer and per calendar year this represents a denudation rate of 1 6 0 6 mm per year illustrating that mechanical erosion by the jura glacier is more intensive than other processes of erosion

role of large particles in the transport of elements and organic compounds through the oceanic water column abstract during the past decade data from a variety of sources have been obtained which show conclusively that the relatively rare large particles sinking through the water column are responsible for the majority of the downward vertical mass flux in the sea this finding has important implications for understanding the transfer distribution and fate of elements and organic compounds in marine waters the large 100 m detrital particles responsible for vertical flux are primarily biogenic and range in size and composition from small discrete fecal pellets and plankton hard parts to large amorphous aggregates or snow which contain both organic and inorganic constituents depending on size shape and density these particles sink at rates ranging from 1000 m day 1 several methods have been developed for sampling these particles of which in situ sediment trapping has probably furnished the most comprehensive qualitative and quantitative information on the role large particles play in material transport flux studies have highlighted the importance of marine heterotrophs in packaging fine suspended particulate matter into large rapidly sinking particles which accelerate the movement of incorporated materials to depth large particle production via biological packaging is not restricted to the euphotic zone but can occur at all depths and information is now accruing on rates of production of large particles in the water column chemical analyses of sedimenting particles collected in sediment traps and those sampled by other means have allowed quantifying vertical fluxes and residence times of elements radionuclides and organic compounds natural and anthropogenic in various oceanic regimes pertinent studies dealing with the above aspects are reviewed and several areas for future research are suggested

denudation rates in the arctic estimated from lake sediments on spitsbergen svalbard a mean holocene denudation rate of 15 mm 1000 yr is calculated for the high arctic valley linnedalen western svalbard based on estimates of the total volume of lacustrine sediments deposited in lake linnevatnet thirty six sub bottom sediment profiles and 16 sediment cores have been used to map the postglacial sediments stored in the lake these reveal a lower marine unit overlain by lacustrine sediments the base and top of the marine sediments were radiocarbon dated to around 12 300 and 9600 yr b p respectively from isopach maps of the lacustrine unit and the total sediment thickness we calculated 0 9 10 2 km3 of holocene lacustrine sediments and 20 1 10 2 km3 of marine sediments a denudation rate of 15 mm 1000 yr is calculated from the volume of the lacustrine sediments this demonstrates that fluvial erosion does not contribute significantly to the lowering of the landscape in the present climate in contrast glacial erosion rates in nearby areas on svalbard are much higher indicating that glacial erosion by warm based valley glaciers is the most important geomorphic process in the present climate three km of tertiary sediments are postulated to have been removed from central parts of svalbard our denudation rates suggest that this could not have occurred in the present interglacial type of climate we suggest that most of that was removed either in a warmer climate or by glaciers

a flow line model for calculating the surface profile and the velocity strain rate and stress fields in an ice sheet a flow line model is presented for calculating the surface profile and the velocity strain rate and stress fields in an ice sheet with given base elevation profile ice thickness at the dome divide flow law parameters mass balance distribution and convergence divergence conditions along the flow line the model which is based on a quasi similarity hypothesis as regards the horizontal velocity depth profiles accounts for changes along the flow line in the depth distributions of temperature normal stress deviators and possible enhanced flow of deep ice of wisconsin origin a curvilinear coordinate system is applied with horizontal axes along flow lines and surface elevation contours respectively the flow equations are reduced to two differential equations one for the surface elevation profile and the other for a profile function that determines the depth distributions of velocities and strain rates the two equations are coupled through a profile parameter that communicates the influence of velocity profile changes to the surface profile equation it is shown that the variation along the flow line of this parameter should also be considered when deriving flow law parameters from ice sheet flow line data for a symmetric dome explicit expressions are derived for the depth distributions of the vertical velocity strain rates and stresses the strain rate profiles display an inflection about half way down the ice sheet and in the case of isothermal ice have surface values 2 2 times their depth averaged values the depth distribution of the vertical velocity indicates that a relatively thick layer of almost stagnant ice is present at the ice sheet base below a dome

230th normalization an essential tool for interpreting sedimentary fluxes during the late quaternary there is increasing evidence indicating that syndepositional redistribution of sediment on the seafloor by bottom currents is common and can significantly affect sediment mass accumulation rates notwithstanding its common incidence this process generally referred to as sediment focusing is often difficult to recognize if redistribution is near synchronous to deposition the stratigraphy of the sediment is not disturbed and sediment focusing can easily be overlooked ignoring it however can lead to serious misinterpretations of sedimentary fluxes particularly when past changes in export flux from the overlying water are inferred in many instances this problem can be resolved at least for sediments deposited during the late quaternary by normalizing to the flux of 230th scavenged from seawater which is nearly constant and equivalent to the known rate of production of 230th from the decay of dissolved 234u we review the principle advantages and limitations of this method notwithstanding its limitations it is clear that 230th normalization does provide a means of achieving more accurate interpretations of sedimentary fluxes and eliminates the risk of serious misinterpretations of sediment mass accumulation rates

turbulence in an oceanic convective mixed layer the first direct measurements of turbulence in an oceanic convective mixed layer were obtained during a cold air outbreak the uniformity of the turbulent dissipation rate and its relation to the surface buoyancy flux are similar to observations of convection in the atmosphere

sediment thicknesses and holocene glacial marine sedimentation rates in three east greenland fjords ca 68 n we compared measured and estimated sediment budgets in heavily glaciated fjords in east greenland mass balance calculations and regional glacio climatic conditions suggest that the sediment flux to the seafloor in kangerdlugssuaq and nansen fjords should be dominated by iceberg rafting and not by the rain out of suspended particulates in meltwater as the glacier calving flux is estimated at 15 and 2 km 3 yr compared to meltwater volumes of 4 4 and 1 7 km 3 yr respectively gravity cores in the three fjords indicate that the uppermost 1 2 5 m of sediment consists of diamictons or fine grained laminated muds ams radiocarbon dates on calcareous foramininfera or shells 16 total indicate sedimentation rates of 110 to 340 cm ka within the fjords over the last 1 ka and 10 20 cm ka during the holecene on the inner and middle shelf annual sediment discharge is around 0 67 times 10 6 tonnes yr within the kangerdlugssuaq fjord and trough system which translates into an average basin wide rate

temperature fine structure patches near an upper ocean density front measurements with a towed thermistor chain have been used to map temperature fine structure variability along vertical sections through a frontal shear zone in the seasonal thermocline of the sargasso sea fine structure levels with 1 3 m horizontal wavelengths were normalized with local values of the vertical fine scale stratification to give values of normalized fine structure variance patches of increased levels of normalized variance were found to occur throughout the thermocline but were most extensive in the frontal zone where richardson numbers 7 m by 450 m averages were lowest 1 the largest patches were 5 10 m in vertical extent and horizontally coherent over distances of several kilometers away from the frontal zone patches tended to be smaller and were fewer in number simultaneous microstructure measurements along two depths were spatially correlated with the fine structure patches implying that many patches were areas of increased mixing intensity no consistent relationship was found between the patches and features in the vertical stratification such as inversion zones or sheets and layers internal wave overturns on the scale of a few meters high by 10 m in the horizontal were found within the larger patches suggesting that wave breaking perhaps enhanced by the background shear may be an ingredient in the formation or maintenance of some patches

turbulent dissipation and shear in thermohaline intrusions laterally coherent patches of turbulence were discovered on the upper and lower boundaries of thermohaline intrusions the ratio jb is used to compare the relative importance of turbulence produced by reynolds stress and that produced by the buoyancy flux of double diffusion velocity profiles show near inertial motions through the intrusions

seasonality of surface water properties and particle flux along a productivity gradient off nw africa abstract three stations along a productivity gradient north of the canary islands were investigated for surface water properties particle flux and composition biogenic and lithogenic components and stable nitrogen isotope composition 15n and export production investigation sites along the east west transect off the nw african upwelling margin included the european station for time series in the ocean canary islands estoc one location contiguous to the nw african upwelling zone in the eastern boundary current ebc and one station north of the island la palma lp the seasonality of surface water properties along the transect was mainly influenced by the winter cooling and simultaneous phytoplankton maximum and in addition at ebc by nearby upwelling accordingly particle flux and composition along the transect were closely linked to the winter bloom sedimentation and upwelling related enhanced plankton biomass stemming from the primary upwelling and the cape yubi filament at ebc during all seasons particle flux was highest at ebc and had the highest contribution of biogenic opal and lithogenic components and the lowest 15n compared to the offshore stations but contrary to what would be expected from the productivity gradient particle flux did not decrease from estoc to lp below the upper several hundred meters particle flux was enhanced by additional particle input along the entire transect manifested by an increase of flux with depth and lower 15n values we offer a scenario in which intermediate nepheloid layers originating from the primary upwelling as well as particle dispersion from upwelling filaments mainly the cape ghir filament impact on the trap stations as far as 700 km into the open ocean this study contributes to our understanding of the poorly resolved biogeochemical transition between the productive shelf and subtropical gyre provinces

the alkenone temperature signal in western north atlantic surface waters abstract haptophyte algae derived long chain c 37 c 39 alkenones and alkyl alkenoates were analyzed in euphotic zone particulate matter collected over a 7 yr period at the oceanic flux program bermuda atlantic time series ofp bats site in the western sargasso sea surface water temperatures at the site range annually from 19 to 29 c alkenone concentrations ranged from 1 in summer to 100 ng l 1 following the passage of storms highest seasonal concentrations occurred during the late winter and spring under stratified conditions alkenone concentrations in the surface mixed layer 0 20 m were generally 2 to 4 times higher than in the deep fluorescent maximum 75 110 m consistent with emiliania huxleyi concentration profiles haidar and thierstein 2001 and indicated that alkenone production primarily occurs within the upper euphotic zone in this region alkenone compound distributions and the temperature calibrations of c 37 and c 38 methyl and ethyl alkenone unsaturation u 37 k u 38me k and u 38et k respectively were remarkably similar to that observed in an e huxleyi strain previously isolated from the same area conte et al 1998 providing strong evidence that e huxleyi is the predominant alkenone synthesizer and that characteristics exhibited by randomly isolated clones in culture are in many cases consistent with those of populations in the region of origin the bermuda calibration of u 37 k vs water temperature u 37 k 1 9835 0 2004t 0 0034t 2 r 2 0 95 n 91 is nonlinear and falls along the same trendline as euphotic zone particulates from warm 15 c waters of the eastern north atlantic conte and eglinton 1993 and mediterranean ternois et al 1997 the combined north atlantic temperature calibration u 37 k 1 1365 0 1257t 0 0018t 2 r 2 0 963 n 134 differs significantly from published coretop sediment calibrations rosell mele et al 1995 muller et al 1998 based on sea surface temperature maps levitus and boyer 1994 having a steeper slope at temperatures 24 c the reasons are not clearly apparent and manifest a need for detailed studies linking production patterns in surface waters with the signal arriving at the seafloor to fully understand the generation of the sedimentary signal

direct measurements of diapycnal mixing in a fjord reach puget sound s main basin abstract in the spring of 1988 time series of microstructure and adcp current profiles were collected at four locations in the north main basin of puget sound washington depth and time averages of diapycnal diffusivity k at the four stations 1 8 67 0 10 4 m 2 s 1 were one to three decades above typical open ocean thermocline levels the buoyancy frequency squared n2 was near open ocean levels but unlike the open ocean where n2 s2 finescale shear squared s2 was three to six times n2 over significant portions of the water column at two of the stations the time and space mean of all measurements k 3 6 10 3 m 2 s 1 is close to inferred vertical eddy diffusivity from a primitive equation model for puget sound k z 3 10 3 m 2 s 1 j geophys res 96 1991 16779 large time and space variability of k was found with differences of inter station depth time means over one decade a simple scaling argument using the observed k suggests significant exchange of mass between the layers of the subtidal flow over the basin s residence time additionally measurements show that local mixing may be comparable to volume weighted sill mixing in modifying the main basin s stratification both are contrary to the advective reach simplification of fjord dynamics the mixing levels were dominated by the passage of a mid depth southward flowing density intrusion and what we interpret as a strongly advected non linear internal tide these mechanisms elevated profile averaged k by more than 10 times background levels with sustained patches of k 1 10 2 m 2 s 1 critical 8 m gradient richardson numbers ri8 20 m and strong turbulence suggest that shear instabilities dominated the turbulence production though there was support for double diffusive convection in the warm core of the density intrusion

vertical heat transfer in the arctic ocean the role of double diffusive mixing 1 microstructure profiles collected in the central amundsen basin are analyzed in order to quantify the role of double diffusive mixing for vertical heat transfer from the atlantic layer in the profiles a persistent but laterally incoherent thermohaline staircase structure is identified in the 200 260 m depth range the staircase contains homogeneous layers with average height of 1 3 m and thin high gradient interfaces with average temperature and salinity jumps of about 0 065 c and 0 015 respectively when inferred from a commonly used diffusive convection parameterization the average vertical heat flux within the staircase is 0 6 w m 2 this is one order of magnitude larger than the molecular diffusion alone and of the same order as the overall heat loss from the atlantic layer in the deep basins of the arctic ocean the parameterization is evaluated using observed turbulent heat fluxes and is found to overestimate diffusive convective fluxes with up to an order of magnitude especially for weak thermal forcing small temperature jumps in staircase staircases coexist with thermohaline intrusions in the vertical temperature and salinity profiles lomonosov ridge is identified as a potential region for formation of intrusions it is found that salt fingering is the dominant process during intrusion growth whereas diffusive convection is the dominant process in maintaining the intrusions at steady state in the deep basins

western arabian sea sst during the penultimate interglacial a comparison of u37k and mg ca paleothermometry millennial scale records of planktonic foraminiferal mg ca bulk sediment u37 k and planktonic foraminiferal 18o are presented across the last two deglaciations in sediment core niop929 from the arabian sea mg ca derived temperature variability during the penultimate and last deglacial periods falls within the range of modern day arabian sea temperatures which are influenced by monsoon driven upwelling the u37 k derived temperatures in mis 5e are similar to modern intermonsoon values and are on average 3 5 c higher than the mg ca temperatures in the same period mis 5e u37 k and mg ca temperatures are 1 5 c warmer than during the holocene while the u37 k mg ca temperature difference was about twice as large during mis 5e this is surprising as nowadays both proxy carriers have a very similar seasonal and depth distribution partial explanations for the mis 5e u37 k mg ca temperature offset include carbonate dissolution the change in dominant alkenone producing species and possibly lateral advection of alkenone bearing material and a change in seasonal or depth distribution of proxy carriers our findings suggest that 1 mg ca of g ruber documents seawater temperature in the same way during both studied deglaciations as in the present with respect to e g season and depth and 2 u37 k based temperatures from mis 5 or older represent neither upwelling sst nor annual average sst as it does in the present and the holocene but a higher temperature despite alkenone production mainly occurring in the upwelling season further we report that at the onset of the deglacial warming the mg ca record leads the u37 k record by 4 ka of which a maximum of 2 ka may be explained by postdepositional processes deglacial warming in both temperature records leads the deglacial decrease in the 18o profile and mg ca based temperature returns to lower values before 18o has reached minimum interglacial values this indicates a substantial lead in arabian sea warming relative to global ice melting

thermohaline intrusions in the frontal zones of a warm core ring observed by batfish hydrographic data collected with a towed depth cycling instrument batfish in the frontal regions of warm core ring 82h during and immediately after its formation were analyzed to study small scale structure and processes the frontal and slope water regions are characterized by a complex water mass structure resulting from mixing of the shelf the slope and the sargasso sea waters thermohaline intrusions along constant density surfaces are frequently observed two forms of thermohaline intrusions are studied in detail subsurface tonguelike intrusions and cold filaments a subsurface tongue of shelf water origin was found in the slope water region outside the frontal zone at 70 m depth it had a width of 4 km a thickness of 20 m and a length of at least 40 km and moved in a southeast direction toward the front alongside the subsurface tongue a cold filament 10 km wide extending from the surface to 120 m depth was observed as the subsurface tongue and the filament moved toward the frontal zone their orientation became more and more aligned with the front when they reached the front the strong frontal current carried them downstream and hence prevented further intrusion into the ring mixing in the form of interleaving then became the most important process for cross front mixing interleaving occurs along the side walls of the subsurface tongue and filament with more intense interleaving associated with stronger intrusions this suggests a double diffusive generation mechanism of the interleaving

short term sedimentation pulses recorded with a fluorescence sensor and sediment traps at 9 m depth in the canary basin we observed short term peaks in pigment fluorescence and backscattering using optical sensors combined with time series sediment traps at 900 m depth at an oligotrophic site in the canary island region these events were observed in late winter to early spring and lasted only a few hours to a few days the events generally coincided with late winter to early spring flux maxima recorded by the traps surprisingly microscopic analyses showed no evidence of sedimentation of intact phytoplankton cells during the fluorescence peaks however we observed well preserved zooplankton fecal pellets containing densely packed coccoliths and presumably large amounts of chlorophyll derived pigments

relationship between coccolith sr ca ratios and coccolithophore production and export in the arabian sea and sargasso sea coccolithophore caco3 production can account for 20 80 of biogenic carbonate exported from the photic zone and coccoliths are a dominant biogenic carbonate in many deep sea sediments a new method for picking individual coccoliths from sediment traps and sediments for analysis using secondary ion mass spectrometry ion probe allows us to make precise sr ca and mg ca determinations on coccoliths from single species even in samples where material is limited there are large biological effects in sr ca partitioning in coccoliths that have been related to variations in coccolithophore productivity in sediment traps from the sargasso sea at bermuda and arabian sea in the somali basin we can identify sr ca variations in several species that are consistent with inferred seasonal variations in coccolithophore productivity in surface waters in the arabian sea coccolith sr ca ratios in calcidiscus leptoporus and helicosphaera carteri are lowest during the nonproductive intermonsoon they are highest during the upwelling of southwest monsoon and during the nutrient entrainment from strong winds of the northeast monsoon these sr ca variations match seasonal trends in coccolith export flux furthermore sr ca variations in c leptoporus are larger and this species also has the greater variation in export flux between southwest monsoon and intermonsoon seasons at bermuda a 1996 fall bloom driven by passage of a warm mode water eddy induced a large increase in sr ca of c leptoporus coincident with an increase of c leptoporus export over an annual series for 2004 highest sr ca ratios of c leptoporus in the summer months match the typical summer peak in surface standing stock of this species and the stimulation of its productivity by mesoscale cyclonic eddies and eddy eddy interactions high sr ca did not coincide with the highest export of c leptoporus coccoliths likely because cyclonic eddies unlike mode water eddies are dominated by small phytoplankton with low export efficiency these data confirm a relationship between coccolith sr ca ratios and productivity sr ca ratios of the smaller and more slowly sinking emiliania huxleyi at bermuda show very small o4 seasonal sr ca variations in contrast nutrientlimited culture experiments for this species reveal significant 435 increases in sr ca with nitrate stimulated growth

temporal variations of particle fluxes in the deep subtropical and tropical north atlantic eulerian versus lagrangian effects the flux of particles measured by sediment traps in the deep water of the sargasso sea and western tropical north atlantic undergoes pronounced temporal variation in the sargasso sea the variability is largely due to seasonal changes in mixed layer depth and attendant changes in primary productivity affecting a wide region by contrast the variability in the western tropical atlantic appears to be caused by patches of elevated nutrient and pigment concentrations which have their origin in the plumes of the amazon and orinoco rivers coastal zone color scanner scenes demonstrate the great seasonal and interannual differences in the direction and dispersal patterns of the plumes the river plumes break up into irregular patches which may pass through the catchment area of a sediment trap at varying rates thereby creating the impression of almost random temporal flux variability at a fixed trap site

spatial and temporal patterns of small scale mixing in drake passage temperature and salinity profiles obtained with expendable ctd probes throughout drake passage between february 2002 and july 2005 are analyzed to estimate turbulent diapycnal eddy diffusivities to a depth of 1000 m diffusivity values are inferred from density temperature inversions and internal wave vertical strain both methods reveal the same pattern of spatial variability across drake passage diffusivity estimates from inversions exceed those from vertical strain by a factor of 3 over most of drake passage the polar front pf separates two dynamically different regions strong thermohaline intrusions characterize profiles obtained north of the pf south of the pf stratification is determined largely by salinity and temperature is typically unstably stratified between 100 and 600 m depth in the upper 400 m turbulent diapycnal diffusivities are o 10 3 m2 s 1 north of the pf but decrease to o 10 4 m2 s 1 or smaller south of the pf below 400 m diffusivities typically exceed 10 4 m 2 s 1 diffusivities decay weakly with depth north of the pf whereas diffusivities increase with depth and peak near the local temperature maximum south of the pf the meridional pattern in near surface mixing corresponds to local maxima and minima of both wind stress and wind stress variance near surface diffusivities are also found to be larger during winter months north of the pf wind driven near inertial waves strong mesoscale eddy activity and double diffusive convection are suggested as possible factors contributing to observed mixing patterns

models of glaciomarine sedimentation and their application to the interpretation of ancient glacial sequences abstract this paper argues that glaciomarine environments can be regarded as special glacially influenced types of continental margin environments e g continental shelf slope rise and basin plain knowledge of the stratigraphic architecture and typical sedimentary sequences of non glacial margins is becoming well known but remains limited for those that have been glacially modified the principal influences on sedimentation in these environments relate to the glacial sediment input controlled by relief of basin margin glacier thermal regime and ice flow dynamics and depositional environments influence of traction currents substrate relief and proximity to nearby ice margins typical ranges of sedimentation rates can be established for glacially influenced continental margin environments and these may provide a framework for ancient sequences starvation of sediment supply to glacially influenced continental margins is common the nature of sub ice shelf sedimentation a model that has been applied to many ancient glacial sequences is critically reviewed the significance of such sedimentation in the rock record has probably been exaggerated because of oversimplistic interpretations of diamictite sequences existing process models of glaciomarine sedimentation derived from study of modern environments are sometimes difficult to employ in investigation of ancient sedimentary sequences because simple lithofacies criteria and typical vertical profiles are not available to aid in interpretation in addition compositional data emphasized by many workers for distinguishing glaciomarine from continental glacial diamict ite s frequently fingerprint sediment source and not mode of deposition the importance of facies analysis methods for isolating depositional environments is illustrated by three examples of ancient glaciomarine sequences these are the early proterozoic gowganda formation 2 3 ga of northern ontario canada the late proterozoic port askaig formation 670 ma of scotland and ireland and the late cenozoic yakataga formation 20 ma to recent of the gulf of alaska these examples illustrate the significance of detailed genetic studies of ancient glacial rocks in the interpretation of palaeogeographic and tectonic settings diamictite units in ancient glaciomarine sequences cannot be easily interpreted in terms of climatic or ice advance retreat cycles because of the varied controls on diamict accumulation and diamictite preservation in marine basins

the elemental composition of the deep particle flux in the sargasso sea abstract the elemental composition of the deep particle flux at 500 m 1500 m and 3200 m was measured at the oceanic flux program ofp time series site in the northern sargasso sea from september 2000 to march 2015 the results clearly show that the deep particle flux is sourced from two components an extrinsic flux component that is derived from and temporally coupled with recent surface export fluxes and an intrinsic flux component that is derived from chemical scavenging and suspended particle aggregation within the deep water column elemental fluxes show a seasonal cycle that is closely tied to the overlying cycle in primary production fluxes of biogenic minerals and nutrient elements peak during the late winter spring maximum in overlying primary production a small late winter spring peak in fluxes of non biogenic elements suggests that intrinsic flux generation within the deep water column also covaries with overlying production and the extrinsic flux flux elemental composition also shows a marked seasonal cycle that reflects dilution of the intrinsic flux in the late winter and spring with fresh biogenic materials sourced from recent overlying production factor of four increases in lithogenic element fluxes and lithogenic element ratios indicate that the source of the deep lithogenic flux is not saharan dust but north american margin sediments that have been resuspended and advected to the region via gulf stream recirculation high rates of authigenic mineral precipitation accompany organic matter degradation in mesopelagic waters the excess mn flux i e flux not supported by lithogenic minerals increases by an order of magnitude between 500 m and 1500 m and the excess ba flux increases by a factor of three there is a major reorganization of element associations with flux carrier phases with increasing depth in particular the geochemical behavior and flux of p becomes increasingly independent of organic carrier phases and the geochemical behavior of fe co ni cu and to a lesser extent v and pb becomes increasingly controlled by manganese oxide scavenging this article is part of a special issue entitled cycles of trace elements and isotopes in the ocean geotraces and beyond edited by tim m conway tristan horner yves plancherel and aridane g gonzalez

particulate organic carbon fluxes along upwelling dominated continental margins rates and mechanisms 1 time series sediment trap samples were used to examine the rates and mechanisms of particulate organic carbon poc flux at three continental margin locations santa barbara basin cariaco basin and guaymas basin marked by seasonal upwelling and high primary production the mean poc flux in santa barbara basin 0 096 g m 2 d 1 is nearly twice that of cariaco basin and 4 times higher than that in guaymas basin with all three sites having poc fluxes significantly higher than the open ocean average 0 007 g m 2 d 1 in cariaco basin the only site with available primary production numbers there is no significant relationship between poc flux and monthly primary production rather poc fluxes in all three areas strongly correlate with mineral carbonate opal and lithogenic material fluxes this supports the mineral ballast hypothesis where it has been suggested that higher density minerals enhance the flux of organic matter to the deep ocean on the basis of multiple regression analysis the three mineral components explain 72 of the total variance in poc fluxes at the three study sites with biogenic carbonate particles being the most effective transport mineral

factors controlling the flux of organic carbon to the bathypelagic zone of the ocean 1 particle fluxes measured with time series sediment traps deployed below 2000 m at 68 sites in the world ocean are combined with satellite derived estimates of export production from the overlying water to assess the factors affecting the transfer of particulate organic matter from surface to deep water multiple linear regression is used to derive an algorithm suggesting that the transfer efficiency of organic carbon defined as the settling flux of organic carbon normalized to export production increases with the flux of carbonate and decreases with water depth and seasonality the algorithm predicts 80 of the organic carbon transfer efficiency variability in diverse oceanic regions the influence of the carbonate flux suggests that the ballasting effect of this biogenic mineral may be an important factor promoting export of organic carbon to the deep sea by increasing the density of settling particles however the lack of a similar effect for biogenic opal suggests that factors other than particle density also play a role the adverse effect of increasing seasonality on the transfer efficiency of carbon to the deep sea is tentatively attributed to greater biodegradability of organic matter exported during bloom events in high latitude opal dominated regions with high f ratios and seasonality while a higher fraction of net production is exported a higher fraction of the exported organic matter is remineralized before reaching bathypelagic depths on the other hand in warm low latitude carbonate dominated regions with low f ratios and seasonality a higher fraction of the exported organic matter sinks to the deep sea

latitudinal change of remineralization ratios in the oceans and its implication for nutrient cycles 1 a new three end member mixing model is introduced to obtain remineralization ratios of organic matter in the water column remineralization ratios p n corg o2 of organic matter in the deep water column change systematically from the northern atlantic to the southern oceans then to the equatorial indian and the northern pacific oceans more or less along the global ocean circulation route of deep water average remineralization ratios of organic matter for the northern atlantic ocean are p n corg o2 1 16 1 73 8 137 7 and for the southern oceans p n corg o2 1 15 1 80 3 133 5 those values are similar to the traditional redfield ratios of p n corg o2 1 16 106 138 for marine plankton except for the low corg p ratio average remineralization ratios for the equatorial indian ocean are p n corg o2 1 10 1 94 5 130 7 and for the northern pacific ocean p n corg o2 1 13 1 124 11 162 11 the apparent low n p ratio for both ocean basins suggests that organic nitrogen was converted partly into gaseous n2o and n2 by bacteria through nitrification denitrification processes in a low oxygen or reducing microenvironment of organic matter throughout the oxygenated water column the actual n p ratio of remineralized organic matter is probably around 15 1 the o2 corg ratio of remineralized organic matter also decreases systematically along the global ocean circulation route of deep water indicating changes in relative proportions of biomolecules such as lipids proteins nucleic acids and carbohydrates no temporal trends of remineralization ratios are detected when comparing the results obtained by geosecs and woce data sets

scavenging and fractionation of thorium vs protactinium in the ocean as determined from particle water partitioning experiments with sediment trap material from the gulf of mexico and sargasso sea abstract particle water partition coefficients kd for thorium th and protactinium pa were calculated for sediment trap material collected from the gulf of mexico gom in the upper 140 m and archived sediment trap material collected in the mesopelagic and bathypelagic sargasso sea 500 1500 and 3200 m sediment trap samples from the oceanic flux program ofp site off bermuda results showed that kd values for th were generally greater than for pa when values were smaller but converging to a 1 1 line at higher values furthermore results showed that though the contents of polysaccharides and calcium carbonate are significantly correlated for all samples log kd of th and pa values are correlated with the polysaccharide content while no correlation is apparent with caco 3 mn and fe since polysaccharides are not generally regarded as strongly chelating agents for actinides we hypothesize that other co occurring organic phases originating from the matrix of carbohydrate rich extracellular polymeric substances eps could be responsible for binding the actinides these data provide for the first time direct evidence for the role of carbohydrate rich eps being responsible for the differential scavenging of these two radioisotopes i e their fractionation

fine structure and mixing at the edge of a warm core ring observations of temperature and salinity fine structure near the edge of a newly formed gulf stream warm core ring are presented a thermohaline front and a cold tongue of shelf water were tracked for about 16 km in a series of crossings by a depth cycling ctd the core was observed to become warmer saltier and more dense in the downstream direction leading to estimates of eddy diffusivities larger than 10 3 m2 s it is concluded that fluxes this large cannot be due to double diffusive processes either lateral or vertical shear driven turbulence can account satisfactorily for the mixing of the core but it would require that the richardson number be near 1 4 which is much smaller than that estimated from thermal wind

missing records and depositional breaks in french late pleistocene cave sediments abstract cave entrance and rock shelter infillings are positioned within the pleistocene chronology for three areas of france northern alps franche comte and perigord despite minor local variations it is possible to identify regional types with a consistent depositional record over long intervals of time the interregional variability relates to the frequency and position of the gaps within the infillings sites in the northern alps have not yielded any artifacts older than the upper paleolithic magdalenian and dated sedimentary sequences do not go back beyond the older dryas more complete sequences in franche comte contain mousterian industries two major gaps occur here one lasting about 50 000 yr during the lower glacial and lower pleniglacial periods and the other lasting some 10 000 yr during the upper pleniglacial the sequences are more complete in the perigord where all major climatic phases have been identified with no significant sedimentary gaps differences in sedimentary records can be explained by variations in regional conditions during the last interglacial glacial cycle and especially by the distance from the maximum advance of ice daring glaciation

the role of double diffusion in a gulf stream frontal intrusion double diffusive convection is possible where large vertical gradients in temperature and salinity tend to compensate in density frontal intrusions have these large gradients and can provide the possibility for a salt finger interface at one boundary and a diffusive interface at the other but large vertical gradients of velocity are present at the boundaries of intrusions which cause mechanical stirring and turbulent mixing as well in the exceptionally active intrusions at the gulf stream front near 38 n 69 w a convective process resulting from incomplete mechanical mixing was observed photographically on both intrusive boundaries

heavy metals in sinking particles and bottom sediments from the eastern turkish coast of the black sea concentrations of cd cu cr co ni zn fe mn pb as and sb were determined in sediment trap and bottom sediment samples collected seasonally from a station on the eastern turkish coast of the black sea cd pb and mn concentrations were highest in the sediment trap samples except during the summer period whereas co ni zn and fe levels were much lower than corresponding levels found in the surface sediments cu cr as and sb levels showed no definite trend with sediment type in general with the exception of cr relatively lower metal concentrations in the sediment trap material were determined in the summer period the highest mass flux 56 5 g m 2 day 1 was measured during autumn the highest flux of heavy metals also occurred during autumn and was strongly dependent on particle mass flux based on these results we suggest that the downward vertical transport of particulate heavy metals in this region is related to the high degree of land erosion and the resultant particulate flux dynamics which occur here it was noteworthy that the highest concentrations of cd cu co zn fe and sb in particles were measured during winter a finding which suggests that enhanced fossil fuel combustion which occurs during this period in adjacent urban and industrial areas plays an important role in the metal composition of sinking particles in nearshore waters 2008 elsevier ltd all rights reserved

observations and analyses of upper ocean responses to tropical storms and hurricanes in the vicinity of bermuda 1 a circular region within a radius of 400 km of bermuda has been struck by 188 tropical storms or hurricanes from 1851 through 2005 and by 20 since 1995 here we describe new direct and remote sensing observations and analyses of recent events near the bermuda testbed mooring including hurricane fabian 2003 tropical storm harvey 2005 and hurricane nate 2005 the most impressive upper ocean response of the recent events was produced by hurricane fabian when sst cooling exceeded 3 5 c vertical mixing occurred to a depth of greater than 130 m and upper ocean currents reached 100 cm s 1 fabian also triggered an ocean color event visible in seawifs satellite images related implications include improved estimates of the roles of tropical cyclones in driving meridional overturning circulation moc and testing of hypotheses concerning warming of the tropical oceans which could cause more intense tropical storms and hurricanes

spatial and temporal variability of downward particle fluxes on a continental slope lessons from an 8 yr experiment in the gulf of lions nw mediterranean abstract a long term experiment of downward particle fluxes and currents has been initiated in 1993 on the continental slope of the gulf of lions nw mediterranean and pursued within the frame of several french and european projects pnec euromarge nb mtp ii mater eurostrataform sediment traps and current meters were deployed at several locations on this slope deeply incised by numerous canyons with an extensive spatial coverage for the first 2 years canyons at the entrance middle and exit of the gulf with respect to the general along slope circulation head and mid canyon depths adjacent open slope from late 1995 onwards this design was reduced to the two mid canyon moorings at the entrance and exit of the gulf monthly fluxes and hourly temperatures and currents were recorded at 500 m 30 m above bottom mab in the canyon heads at 500 and 1000 m respectively 530 and 30 mab nominal depths at the mid canyon sites and at 750 m 30 mab open slope this study aims at describing the spatial seasonal and interannual variability of flux intensity and composition of settling particles and at analyzing the role of diverse forcings in the control of particle exchange across the margin results from the first 8 years 1993 2001 show that total mass fluxes in the 101 104 mg m 2 d 1 range increase along slope particularly for the near bottom traps between the ne planier canyon and the sw lacaze duthiers canyon limits of the gulf of lions indicating an increased shelf export of particulate matter in the western part of the system bulk chemical composition organic matter carbonate opal and lithogenic fraction remained rather stable during the course of the experiment tending towards values typical of superficial shelf sediments at higher mass fluxes first order calculations using a simple two component mixing model suggest a decreasing contribution of primary particles settling out of the overlying waters to the total flux from the entrance towards the exit of the system particulate material transferred to the deeper slope in the southwestern part of the gulf of lions appears therefore to predominantly originate in resuspended shelf and or upper slope sediment downward particle fluxes and potential forcing parameters exhibit a high seasonal variability with higher values from late autumn to early spring furthermore unprecedented winter flux peaks observed in 1999 dominated the interannual differences which otherwise were quite limited correlations between sources of particulate material on the shelf i e river and atmospheric inputs phytoplankton biomass and sediment resuspension cross slope exchange mechanisms derived from in situ temperature and current records and flux data indicate a predominant effect of dense cold water cascading on the exchange of particulate matter between the shelf and the slope

oceanic thermohaline intrusions observations intrusions are commonly observed in the upper deep and coastal oceans and are closely linked to lateral fluxes of heat salt and momentum this is a review of observations of intrusions and the results of comparisons of properties such as scale slopes microstructure activity and fluxes with theoretical models a summary of estimates of lateral heat fluxes indicates a wide range of lateral diffusivities we conclude by noting that our present knowledge is insufficient to predict the structure length scales and lateral fluxes of thermohaline intrusions with confidence and list a number of unresolved questions suggestions are made for compilation of existing data into a database for exploratory analysis and testing of theoretical hypotheses an outline is given of a potential collaborative field experiment using ctd fluorescent dye and microstructure observations

228ra 226ra and 226ra ba ratios to track barite formation and transport in the water column abstract we measured 228 ra ex 226 ra ex and 226 ra ex ba ex ratios in suspended and sinking particles collected at the oceanic flux program ofp time series site in the western sargasso sea and compared them to seawater ratios to provide information on the origin and transport of barite baso 4 in the water column the 228 ra ex 226 ra ex ratios of the suspended particles down to 2000 m are nearly identical to those of seawater at the same water depth these ratios are much lower than expected if suspended barite was produced in surface waters and indicate that barite is produced throughout the mesopelagic layer the 228 ra ex 226 ra ex activity ratios of sinking particles collected at 1500 and 3200 m varied mostly between 0 1 and 0 2 which is intermediate between the seawater ratio at these depths ex ba total ba lithogenic considered to be mainly barite present in the sinking flux is a mixture of crystals formed recently in the upper water column formed several years earlier in the upper water column or formed recently in deeper waters we observe a sizeable temporal variability in the 228 ra ex 226 ra ex ratios of sinking particles which indicates temporal variability in the relative proportion of barite crystals originating from surface with a high 228 ra ex 226 ra ex ratio and mesopelagic with a low 228 ra ex 226 ra ex ratio sources however we could not discern a clear pattern that would elucidate the factors that control this variability the 226 ra ba ratios measured in seawater are consistent with the value reported from the geosecs expeditions 2 3 dpm mol 1 below 500 m depth but are significantly lower in the upper 500 m high 226 ra ex ba ex ratios and elevated sr concentrations in suspended particles from the upper water column suggest preferential uptake of 226 ra over ba during formation of srso 4 skeletons by acantharians which must contribute to barite formation in shallow waters deeper in the water column the 226 ra ex ba ex ratios of suspended particles are lower than those of seawater since 228 ra ex 226 ra ex ratios demonstrate that suspended barite at these depths has been produced recently and in situ their low 226 ra ex ba ex ratios indicate preferential uptake of ba over ra in barite formed in mesopelagic water

chemical weathering in glacial environments do glaciers enhance or inhibit chemical weathering rates relative to other environments the importance of glaciers in the global carbon cycle and climate change hinges on the answer we show that catchments occupied by active alpine glaciers yield cation denudation rates greater than the global mean rate but do not exceed rates in nonglacial catchments with similar water discharge silica denudation rates are distinctly lower in glacier covered catchments than in their nonglacial counterparts because sediment yields are high from glaciers this suggests that water flux rather than physical erosion exerts the primary control on chemical erosion by glaciers potassium and calcium concentrations are high relative to other cations in glacial water probably due to dissolution of soluble trace phases such as carbonates exposed by comminution and cation leaching from biotite preferential weathering of biotite may result in higher 87 sr 86 sr in glacial runoff than expected from whole rock compositions thus although glaciers do not influence total chemical denudation rates at a given runoff they may yield compositionally distinctive chemical fluxes to the oceans disruption of mineral lattices by grinding increases dissolution rates this and high surface area should make glacial sediments exceptionally weatherable weathering of glacial erosion products in environments beyond the glacier margin deserves attention because it may figure prominently in global chemical cycles

sediment yield from glacio lacustrine calcareous deposits during the postglacial period in the combe d ain jura france the middle valley of the river ain jura cuts through glacio lacustrine deposits laid down in an ice dammed lake during the most recent glacial advance the total volume eroded is about 6 21 10 8 m 3 for a surface area of 3 7 10 7 m 2 erosion occurred between 18 ka bp and 6 ka bp i e over a duration of some 12 ka sediment yield from the area was of the order of 2500 t km 2 a 1 which is comparable with modern day sediment yield from nw african badlands these high values are ascribed to the amenability of glacio lacustrine deposits to mechanical weathering and to the rapid geomorphological changes that affected glacial and paraglacial sedimentary cover after the retreat of the ice the valley slopes were destabilized by mass wasting earthflow and mudflow which was the predominant erosional process the slopes are currently stabilized or very exceptionally active 1998 john wiley sons ltd

rates of chemical denudation and co2 drawdown in a glacier covered alpine catchment solute fluxes from a glacier covered alpine catchment are partitioned into components derived from sea salt acid aerosol dissolution of atmospheric co2 and crustal weathering the bulk of solute is crustally derived coupled sulfide oxidation and carbonate dissolution so cd and carbonation of carbonate minerals generate approximately equal amounts of solute chemical denudation constitutes 1 5 of solid denudation but is significantly higher than the continental average co2 drawdown by weathering reactions varies directly with discharge and suspended sediment load and inversely with meltwater p co2 if it is generally true that flushing rates control co2 drawdown in glacier covered catchments then glacially driven chemical weathering could be a significant factor in carbon cycling and climate change on glacial interglacial time scales