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

geographic and seasonal distributions of brunt vaisala frequency and rossby radii in the north pacific and north atlantic abstract long term mean temperature and salinity profiles computed from an edited set of historical hydrographic data have been used to calculate mean profiles of density and brunt vaisala seasonal variations in internal rossby radii are everywhere surprisingly small

changing atmospheric δ14c and the record of deep water paleoventilation ages we propose a new calculation method to better estimate the deep water ventilation age from benthic planktonic foraminifera 14 c ages our study is motivated by the fact that changes in atmospheric 14 c through time can cause contemporary benthic and planktonic foraminifera to have different initial 14 c values this effect can cause spurious ventilation age changes to be interpreted from the geologic data using a new calculation method 14 c projection ages we recalculate the data from the pacific ocean contrary to previous results we find that the pacific intermediate and deep waters were about 600 years older than today at the last glacial maximum in addition there are possible signals of ventilation age change prior to ice sheet melting and at the younger dryas however the data are still too sparse to constrain these ventilation transients

the nappe structure of the central northern calcareous alps and its disintegration during miocene tectonic extrusion a contribution to understanding the orogenic evolution of the eastern alps the classical concept of the nappe structure of the central northern calcareous alps nca is in contradiction with modern stratigraphic structural metamorphic and geochronological data we first perform a palinspastic restoration for the time before miocene lateral tectonic extrusion which shows good continuity of structures facies and diagenetic metamorphic zones we present a new nappe concept in which the tirolic unit practically takes the whole area of the central nca and is divided into three subunits nappes lower and upper tirolic subunit separated by the upper jurassic trattberg thrust and the metamorphic ultra tirolic unit the hallstatt iuvavic nappe s formed the highest unit but were completely destroyed by erosion after nappe stacking remnants of the hallstatt nappes are only represented by components of up to 1 km in size in middle upper jurassic radiolaritic wildflysch sediments hallstatt melange belonging to the tirolic unit destruction of the continental margin started in middle to upper jurassic time and prograded from the oceanic side towards the shelf the original substratum of the external nappes bavaric units of the nca was largely the austroalpine crystalline basement of the internal nappes tirolic units the weakly metamorphosed palaeozoic sequences greywacke zone and equivalents eocene movements caused limited internal deformation in the tirolic unit

a new mechanistic model for organic carbon fluxes in the ocean based on the quantitative association of poc with ballast minerals abstract in simulation studies of the ocean s role in the global carbon cycle predicting the depth distribution for remineralization of particulate organic carbon poc is of particular importance following sarmiento et al global biogeochemical cycles 7 1993 417 most simulation models have the power law curve of martin et al deep sea research 34 1987 267 for this purpose the martin et al curve is an empirical fit to data most of which is from shallow floating sediment traps using such a fit implies that all the information necessary for prediction is contained in the carbon flux itself so that the organic carbon flux f oc z at any depth z can be predicted from the flux of organic carbon f oc z 0 at some near surface depth z 0 here we challenge this basic premise arguing that fluxes of ballast minerals silicate and carbonate biominerals and dust determine deep water poc fluxes so that a mechanism based model of poc flux must simultaneously predict fluxes of both poc and ballast minerals this assertion is based on the empirical observation that poc fluxes are tightly linked quantitatively to fluxes of ballast minerals in the deep ocean here we develop a model structure that incorporates this observation and fit this model to us jgofs eqpac data this model structure plus the preliminary parameter estimates we have obtained can be used to explore the implications of our model in studies of the ocean carbon cycle

a heton model of the spreading phase of open ocean deep convection abstract a point vortex heton model of the lateral dispersion of cold water formed in open ocean deep convection is developed and studied as an idealized representation of the sinking and spreading phase of open ocean deep convection the overturning and geostrophic adjustment of dense fluid on and below the radius of deformation scale formed by cooling on the large scale are parameterized in the model by introducing paired discrete point vortices hetons of cyclonic sense in the surface layer anticyclonic below driving a cold baroclinic vortex the convection site is imagined to be made up of many such baroclinic vortices each with a vertically homogeneous core carrying cold convectively tainted waters the point vortices are introduced at a rate that depends on the large scale cooling and the intensity assumed for each vortex the interaction of many cold baroclinic vortices making up a cloud is studied using point vortex green s function techniques the current solenoids of the individual ele

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

atmospheric patterns forcing two regimes of arctic circulation a return to anticyclonic conditions atmospheric sea level pressure slp patterns associated with two regimes of ice ocean circulation are identified by sorting the data into bins depending on whether modeled arctic ocean circulation was anticyclonic or cyclonic the transition between regimes is a zonally symmetric slp cell with maximum amplitude at the north pole from 1946 to 1997 four anticyclonic and four cyclonic regimes track the arctic ocean slp oscillation recent slp data suggest that the ocean atmosphere system will shift or has already shifted to an anticyclonic state

greenland sea convection in the winter of 1987 1988 during february 1988 a layer of almost uniform temperature and salinity between 100 and 1250 m depth was observed in the central greenland sea this feature indicative of previous deep convection is explained in terms of a conceptual penetrative convection model

new evidence for block and thrust sheet rotations in the central northern calcareous alps deduced from two pervasive remagnetization events 1 we present 81 paleomagnetic sites early triassic to early cretaceous from the central sector of the northern calcareous alps nca eastern alps austria and germany stepwise thermal demagnetization defines three magnetic directions mostly carried by low unblocking temperature and low coercivity minerals j3 350 j2 500 j1 575 and 680 j3 and j2 show positive inclinations whereas j1 very seldom is of dual polarity the fold tests show that a j3 can be interpreted as a postfolding and posttilting remagnetization and j2 as a postfolding and pre syn tilting j1 can be considered as primary because of the occurrence of two polarities and evidence presented by other authors in the area all three components show a systematic and significant clockwise rotation after comparing with the expected european references j2 or j1 are marked by higher rotation values than j3 j2 shows different inclinations depending on the structural position north or southward dips considering the structural evolution and the observed inclinations the first postfolding and pretilting remagnetization event j2 could have taken place between late cretaceous and eocene times but certainly before the thrusting of the nca over the rhenodanubian flysch and northward tilting caused by the stacking of the lower austroalpine nappes the second postfolding and posttilting remagnetization j3 would have been acquired after the final thrusting of the nca over penninic units from then the nca behaved as a set of rigid blocks recording the main stage of vertical axis clockwise rotation 65 in average associated with the continental collision the variable degree of rotation in the different positions from 40 to 134 can be explained by individual vertical axis rotation in a block system trying to adjust to space problems the constant declination differences between j2 and j3 25 in average would reflect the rotation related with the lateral differences of shortening during the oblique thrust of the austroalpine units over the penninic units

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

geographical seasonal and depth variation in sinking particle speeds in the north atlantic particle sinking velocity is considered to be a controlling factor for carbon transport to the deep sea and thus carbon sequestration in the oceans the velocities of the material exported to depth are considered to be high in high latitude productive systems and low in oligotrophic distributions we use a recently developed method based on the measurement of the radioactive pair 210po 210pb to calculate particle sinking velocities in the temperate and oligotrophic north atlantic during different bloom stages our estimates of average sinking velocities asvs show that slowly sinking particles 100 m d 1 contribute significantly to carbon flux at all the locations except in the temperate regions during the bloom asvs appear to vary strongly with season which we propose is caused by changes in the epipelagic community structure our results are the first field data to confirm the long standing theory that particle sinking velocities increase with depth with increases of up to 90 between 50 and 150 m depth

the development of the odden ice tongue in the greenland sea during winter 1993 from remote sensing and field observations the odden ice tongue in the central greenland sea believed to be associated with midgyre convection developed prominently during the winter of 1993 january april during this period it was studied by a succession of cruises which formed part of the european subpolar ocean programme and which included direct sampling and measurement of the frazil and pancake ice which constituted the material of the ice tongue as well as studies of the ocean structure passive microwave imagery was used to determine the evolution of odden through the winter and when combined with ers 1 synthetic aperture radar studies and the field data yielded estimates of ice extent and thickness through the winter from these studies it was possible to estimate the salt flux into the ocean originating from brine release from sea ice during the growth phases of odden

glacial interglacial co2 change the iron hypothesis several explanations for the 200 to 280 ppm glacial interglacial change in atmospheric co2 concentrations deal with variations in southern ocean phytoplankton productivity and the related use or nonuse of major plant nutrients an hypothesis is presented herein in which arguments are made that new productivity in today s southern ocean 7 4 1013g yr 1 is limited by iron deficiency and hence the phytoplankton are unable to take advantage of the excess surface nitrate phosphate that if used could result in total southern ocean new production of 2 3 1015 g c yr 1 as a consequence of fe limited new productivity holocene interglacial co2 levels preindustrial are as high as they were during the last interglacial 280 ppm in contrast atmospheric dust fe supplies were 50 times higher during the last glacial maximum lgm because of this fe enrichment phytoplankton growth may have been greatly enhanced larger amounts of upwelled nutrients may have been used and the resulting stimulation of new productivity may have contributed to the lgm drawdown of atmospheric co2 to levels of less than 200 ppm background information and arguments in support of this hypothesis are presented

annular modes in the extratropical circulation part i month to month variability the leading modes of variability of the extratropical circulation in both hemispheres are characterized by deep zonally symmetric or annular structures with geopotential height perturbations of opposing signs in the polar cap region and in the surrounding zonal ring centered near 458 latitude the structure and dynamics of the southern hemisphere sh annular mode have been extensively documented whereas the existence of a northern hemisphere nh mode herein referred to as the arctic oscillation ao has only recently been recognized like the sh mode the ao can be defined as the leading empirical orthogonal function of the sea level pressure field or of the zonally symmetric geopotential height or zonal wind fields in this paper the structure and seasonality of the nh and sh modes are compared based on data from the national centers for environmental prediction national center for atmospheric research reanalysis and supplementary datasets the structures of the nh and sh annular modes are shown to be remarkably similar not only in the zonally averaged geopotential height and zonal wind fields but in the mean meridional circulations as well both exist year round in the troposphere but they amplify with height upward into the stratosphere during those seasons in which the strength of the zonal flow is conducive to strong planetary wave mean flow interaction midwinter in the nh and late spring in the sh during these active seasons the annular modes modulate the strength of the lagrangian mean circulation in the lower stratosphere total column ozone and tropopause height over mid and high latitudes and the strength of the trade winds of their respective hemispheres the nh mode also contains an embedded planetary wave signature with expressions in surface air temperature precipitation total column ozone and tropopause height it is argued that the horizontal temperature advection by the perturbed zonal mean zonal wind field in the lower troposphere is instrumental in forcing this pattern a companion paper documents the striking resemblance between the structure of the annular modes and observed climate trends over the past few decades

in situ measurement of mesopelagic particle sinking rates and the control of carbon transfer to the ocean interior during the vertical flux in the global ocean vertigo voyages in the north pacific abstract among the parameters affecting carbon transfer to the ocean interior particle sinking rates vary three orders of magnitude and thus more than primary production f ratios or particle carbon contents e g boyd p w trull t w 2006 understanding the export of marine biogenic particles is there consensus progress in oceanography 4 276 312 doi 10 1016 j pocean 2006 10 007 very few data have been obtained from the mesopelagic zone where the majority of carbon remineralization occurs and the attenuation of the sinking flux is determined here we report sinking rates from 300 m depth for the subtropical station aloha june 2004 and subarctic station k2 july 2005 north pacific ocean obtained from short 6 5 day deployments of an indented rotating sphere irs sediment trap operating as an in situ settling column peterson m l wakeham s g lee c askea m a miquel j c 2005 novel techniques for collection of sinking particles in the ocean and determining their settling rates limnology and oceanography methods 3 520 532 to separate the flux into 11 sinking rate fractions ranging from 820 to 2 m d 1 that are collected by a carousel for further analysis functioning of the irs trap was tested using a novel programming sequence to check that all particles have cleared the settling column prior to the next delivery of particles by the 6 hourly rotation cycle of the irs there was some evidence from the flux distribution among the cups and photomicroscopy of the collected particles that very slow sinking particles may have been under collected because they were unable to penetrate the brine filled collection cups but good evidence for appropriate collection of fast settling fractions approximately 50 of the particulate organic carbon poc flux was sinking at greater than 100 m d 1 at both stations at aloha more than 15 of the poc flux sank at 820 m d 1 but low fluxes make this uncertain and precluded resolution of particles sinking slower than 137 m d 1 at k2 less than 1 of the poc flux sank at 820 m d 1 but a large fraction 15 45 of the flux was contributed by other fast sinking classes 410 and 205 m d 1 pic and bsi minerals were not present in higher proportions in the faster sinking fractions but the observations were too limited to rule out a ballasting contribution to the control of sinking rates photographic evidence for a wide range of particle types within individual sinking rate fractions suggests that biological processes that set the porosity and shape of particles are also important and may mask the role of minerals comparing the spectrum of sinking rates observed at k2 with the power law profile of flux attenuation with depth obtained from other vertigo sediment traps deployed at multiple depths buesseler k o lamborg c h boyd p w lam p j trull t w bidigare r r bishop j k b casciotti k l dehairs f elskens m honda m karl d m siegel d silver m steinberg d valdes j van mooy b wilson s e 2007b revisiting carbon flux through the ocean s twilight zone science 316 5824 567 570 doi 10 1126 science 1137959 emphasizes the importance of particle transformations within the mesopelagic zone in the control of carbon transport to the ocean interior

stress induced changes in plate density vail sequences epeirogeny and short lived global sea level fluctuations the stratigraphic record contains clear evidence that broad regions have experienced rapid changes in sea level unrelated to changes in glacial ice volume e g third and higher order vail sea level variations continental foundering we propose that many of these changes can be caused by stress induced changes in plate density stress changes produce significant changes in the density of the crust and lithosphere a point missed in previous investigations and propagate across even the largest plates in less than 30 000 years lithospheric plates interacting at existing boundaries can produce stress related density changes sufficient to cause several meters change in plate elevation these may account for many of the regressions and transgressions seen in the stratigraphic record the creation of new rifts could increase plate compression enough to cause 50 m of plate subsidence plate elevation changes of up to 200 m could result from increased plate compression during continental collisions a particularly enigmatic kind of rapid nonglacial global ngg sea level change is a coupled 50 m sea level fall regression and roughly equal rise transgression occurring in less than 106 years these couplets associated with black shales and marine extinctions can be explained by the elastic snapback attending the rapid formation of a new rift isostatic disequilibria along the new rift depresses the seafloor sufficiently to cause a 50 m fall in sea level mantle flow restores isostatic equilibrium along the rift axis and erases the fall in 60 000 years unusually intense hydrothermal circulation along the new rift during the snapback promotes anoxic bottom water conditions and deposition of black shales a rapid drop in global sea levels reduces the area of ocean bottom within the photic zone causing overpopulation food exhaustion and extinctions the connections between changes in plate stress and density have many implications perhaps the most far reaching is that tectonic events on the 3 4 of the globe that is covered by oceans as well as the 1 4 that is subaerial are recorded in sedimentary strata

high export via small particles before the onset of the north atlantic spring bloom sinking organic matter in the north atlantic ocean transfers 1 3 gt carbon year 1 from the surface ocean to the interior the majority of this exported material is thought to be in form of large rapidly sinking particles that aggregate during or after the spring phytoplankton bloom however recent work has suggested that intermittent water column stratification resulting in the termination of deep convection can isolate phytoplankton from the euphotic zone leading to export of small particles we present depth profiles of large 0 1mm equivalent spherical diameter esd and small 300m depth leading to deep mixing of particles as deep as 600m subsequent re stratification could trap these particles at depth and lead to high particle fluxes at depth without the need for aggregation mixed layer pump overall we suggest that pre bloom fluxes to the mesopelagic are significant and the role of small sinking particles requires careful consideration this article is protected by copyright all rights reserved

synrift sedimentation on the northern tethys margin an example from the ligurian alps upper triassic to lower cretaceous prepiedmont domain italy the prepiedmont domain succession of the ligurian alps is formed by a thick mesozoic sedimentary cover tectonically detached from its substratum the arnasco castelbianco unit preserves the most complete record of the ligurian prepiedmont although completely overturned and deformed due to alpine tectonics it is composed of carbonate and clastic rocks deposited during the upper triassic to lower cretaceous interval this paper is focused on the stratigraphy of the jurassic series and its relationships to the tethyan rifting each term of the sedimentary record is seen as a witness of the several phases through which the rifting took place an early rifting phase late hettangian to early sinemurian brought to the formation of a normal fault system affecting the carbonate platform and favoured the development of condensed sedimentation on pelagic highs the rapid transition from open platform carbonates to slope basin cherty limestones testifies the increased subsidence of the margin in the late sinemurian during which moderate fault activity is recorded intraformational breccia horizons until the early pliensbachian a tectonic pause brought to the sedimentation of a succession of pelagic carbonates occasionally interrupted by clastic flows during the late pliensbachian to toarcian the rifting phase followed evidenced by the large amount of clastics and generated by renewed fault activity clastics flowed down into the basin as fluxoturbidites first and then passed to breccias during the maximum tectonic pulse in the late toarcian to aalenian the thermal uplift of the brianconnais shoulder generated a basin fill of fine clastics the following thermal subsidence aalenian to tithonian favoured the restoration of quiet basinal conditions evidenced by the deposition of radiolarites

breccias of the adnet formation indicators of a mid liassic tectonic event in the northern calcareous alps salzburg austria stratigraphy lithology and depositional structures of liassic red limestone breccias of the adnet formation including the adnet scheck were studied at several outcrops of the northern calcareous alps nca south east of salzburg a four fold lithostratigraphic division is proposed for the adnet formation of the osterhorn mountains the hemipelagic schmiedwirt sinemurian and kehlbach carixian members are separated from the pelagic saubach member toarcian by a layer of amalgamated breccias scheck member probably domerian to early toarcian several other breccia beds occur locally from the base of the kehlbach member up to the lower saubach member although the sediments overlying the scheck member breccias are of coeval age the ages of the underlying strata are very different this can be explained by submarine liassic erosion during a period of resedimentation from the middle carixian until the early toarcian at least 10 15 m of partly lithified sediments were eroded by gravity flows the entire kehlbach member and up to two thirds of the schmiedwirt member were removed at adnet the breccias originated from submarine debris flows repeated flows over a long period and the depositional setting exclude a triggering by sea level fluctuations most probably they arose from tectonically triggered slumps and slides of superficial sediments the scheck was initiated on the steep upper slope of the drowned triassic adnet reef and flowed to the north east the pliensbachian to early toarcian period of tectonic activity indicated by the breccias was the most important during the liassic in the osterhorn mountains and other parts of the nca from the large scale regional distribution of the breccias and in accord with published data a roughly northeast trending strike slip fault zone is proposed crossing the nca south of the osterhorn block with a peaking activity during the pliensbachian to early toarcian as the cause of the tectonic movements

extensional detachment faulting in the evolution of a tethys passive continental margin eastern alps switzerland the austroalpine nappes of switzerland represent an exhumed and tectonically imbricated segment of the passive continental margin of the jurassic tethys within one of these nappes err nappe part of an upper crustal extensional detachment is preserved indicating that the thinning of the crust was achieved by non uniform extension the mesozoic age of the detachment is shown by comparison between its associated cataclasites and identical cataclasites that are found as redeposited components in middle jurassic sedimentary breccias this low angle detachment within the basement was kinematically linked to synsedimentary high angle normal faults at the surface the area of the err nappe belongs in terms of jurassic paleogeography to the most distal part of the continental margin where both low and high angle normal faults dipped oceanward that is west to northwest in present day coordinates in the more proximal part of the margin however the high angle normal faults dipped eastward toward the continent ammonite stratigraphy within the sediment prisms adjacent to the faults gives evidence for an early jurassic age of the faulting in the proximal part of the margin whereas in the distal part faulting occurred during latest early to middle jurassic time we therefore propose that the jurassic extension of the crust which finally led to the opening of the piemont ligurian ocean was achieved by two fault systems which differ in geometry fault orientation and age these fault systems were composed of a basal low angle detachment with high angle normal faults above the orientation of the older eastward dipping detachment was prone for reactivation during early alpine crustal shortening the present day thrust contact between the two major tectonic units of the area the lower austroalpine and the central austroalpine nappe complex therefore might correspond to an eastward dipping jurassic low angle normal fault

deciphering of the complex depositional and diagenetic history of a scarp limestone breccia middle jurassic krasin breccia pieniny klippen belt western carpathians abstract the pieniny klippen belt boundary between the central and outer western carpathians is a tectonic melange of various mesozoic sedimentary units in the shallowest unit a czorsztyn succession syntectonic middle jurassic bajocian sedimentary breccia to megabreccia was discovered it resulted from extensional tectonic movements tied to jurassic neotethys rifting the breccia was investigated by standard petrographic methods cathodoluminescence microfacies analysis and isotope analysis c o it represents the whole spectrum from crackled breccia through mosaic breccia to mixed rubble breccia all of them consist mostly of crinoidal limestone clasts the crackled breccias are penetrated by a network of radiaxial fibrous calcite the mosaic breccias have interstitial pores mostly filled with a younger generation of crinoidal limestone the rubble breccia usually possesses the most complex filling as a rule the clasts are coated by at least one generation of stromatolite and then cemented by radiaxial fibrous calcite the stromatolites may appear at various levels of the breccia diagenesis most of them are cryptic stromatolites the remaining void filling starts with the crinoidal detritus which indicates that the breccia was formed due to synsedimentary tectonics occurring during the deposition of crinoidal limestones bajocian the rest was filled by micritic limestone with filamentous microfacies bathonian callovian which also contained local planktonic foraminifers globuligerina sp the latest sedimentary filling is represented by sterile micrite containing a few allochems and fauna of cavity dwelling ostracods pokornyopsis sp the latest cement is represented by clear blocky calcite filling veinlets cutting the whole rock numerous instances of disturbance resedimentation and recementation are evident in the breccia the isotope composition of some early generations of stromatolites local etching of the clasts and early cements together with some earlier generations of blocky calcite veinlets possibly indicate a presence of fresh water diagenesis

sedimentation fracturing and sliding on a pelagic plateau margin the middle jurassic to lower cretaceous succession of rocca busambra western sicily italy the jurassic succession of rocca busambra consists of two lithostratigraphic units a pile of peritidal limestones several hundreds of metres thick inici formation hettangian to sinemurian and a 2 to 15 m thick sequence of rosso ammonitico type pelagic limestones toarcian to lowermost berriasian an extensive interval of non deposition is evidenced by a thick fe mn oxide crust on the bounding disconformity and is recorded partially in the material contained within a complex network of neptunian dykes and sills seven lithofacies are distinguished in the rosso ammonitico these lithofacies show that the rosso ammonitico limestones differ from most analogues both in sicily and elsewhere sediments are mostly grain supported and non nodular obviously bottom currents were important during deposition of these sediments these currents were pulsating at different frequencies and induced winnowing intraclast production and early cement precipitation other rosso ammonitico lithosomes of late jurassic to earliest cretaceous age usually decimetre thick and discontinuous overlie the inici formation without any fe mn crust their anomalous stratigraphical and geometrical relationships show that they were deposited on an inclined stepped erosional surface incised in the sub horizontal inici formation this ancient escarpment is interpreted as the result of a mainly gravitational collapse of the margin of a pelagic plateau such mass wasting was probably due to the backstepping of the tectonic plateau basin margin that is not observable directly but may be inferred from circumstantial evidence this observation clearly shows that tectonic activity affected the rocca busambra sector of the west tethys continental margins a few tens of millions of years after the end of the rifting stage the anomalous rosso ammonitico sediments are the only indication of the escarpment and their occurrence in the stratigraphic record is probably more widespread than reported in the literature more accurate palaeoenvironmental and palaeogeographic reconstructions may depend on the identification of these sediments

haq et al eustatic sea level curve implications for sequestered water volumes the eustatic sea level curve of haq and co workers differentiates a long and a short term signal the mechanism that controls the long term curve is primarily variation in the volume of the ocean basins while the short term curve reflects changes in ocean water volume only glacial eustasy operates at the frequency and with sufficient magnitude to control the short term curve at each increment of time the volume of water sequestered from the ocean basins to account for the difference between the long and short term curves is computed incorporating both hypsometric and water loading factors an amount equivalent to that of present day antarctica was sequestered at an approximately 5 ma frequency since 145 ma but direct geological evidence of late jurassic to early tertiary continental ice of this equivalent magnitude is lacking because the existing ice coverage of antarctica inhibits direct observation we use the known fractionation affects of sequestration of water on the oxygen isotopic composition

from rifting to drifting tectonic evolution of the south alpine upper crust from the triassic to the early cretaceous abstract the tectonic evolution of the south alpine rifted margin is discussed on the base of four palinspastic upper crustal profiles extension related to the movements between adria and europe began in the norian after variscan orogeny late carboniferous to middle permian orogenic collapse and continental scale wrenching from the late triassic to the early liassic stretching was mostly limited to the lombardian basin during this time extension was mainly controlled by four major listric faults symmetrically centred around the late carboniferous early permian collio grabens smaller faults which also started in the norian were progressively de activated during the late triassic after the middle liassic faulting in the lombardian basin gradually ceased and the site of extension shifted westwards i e towards the future site of crustal separation extension was then controlled by a set of west dipping normal faults oceanic crust was formed not later than 157 ma the overall extension along the profile which had a final length of 290 km was 52 km which corresponds to a stretching factor of 1 22 for the whole length of the preserved margin the strain rate is ca 1 10 16 s the sedimentation history suggests that the extension of the south alpine margin was a continuous process from the norian to the middle jurassic the changes in tectonic pattern are related to progressive hardening of the lithospheric segment undergoing slow extension

on the temporal character and regionality of the arctic oscillation decadal differences between the 1990s and 1980s in winter jfm sea level pressure and 300 mb zonal winds have an arctic centered character with nearly equal contributions from the atlantic and pacific sectors in contrast the differences between positive and negative arctic oscillation ao composites defined from monthly values of principal components from the same period have similar magnitudes in the pacific and arctic but have an additional large north atlantic oscillation nao signature in the atlantic sector thus arctic changes on decadal scales are more symmetric with the pole than suggested by the standard ao index definition change point analysis of the ao shows that a shift in value near 1989 is an alternate hypothesis to a linear trend analysis of zonal and meridional winds by longitudinal sectors shows the importance of the standing wave pattern in interpreting the ao which supplements the view of the ao as a simple zonal average annular mode

the role of subduction and gravitational sinking in particle export carbon sequestration and the remineralization length scale in the california current ecosystem particles and aggregates created in the surface layers of the ocean are transported not only by gravity but also by the horizontal and vertical advection of the surrounding water subduction in particular can transport organic matter from the surface ocean to the mesopelagic in a manner that is not likely to be detected by typical in situ carbon export measurements e g sediment traps and 238u 234th disequilibrium to assess the importance of subduction to the biological pump we combined in situ sediment trap thorium primary productivity and particulate organic carbon poc measurements with a data assimilative physical circulation model and a lagrangian particle tracking model we develop a simple parameterization of two alternative particle sinking processes phytoplankton fecal pellet pfp and aggregation using results from 13 extensively sampled water parcels in the california current ecosystem both parameterizations suggested that subduction is an important at times dominant mechanism of poc vertical export in the region median 44 and 23 contribution to total poc export for pfp and aggregate parameterizations at the 100 m depth horizon the percentage contribution of subduction was highly variable across water parcels ranging from 7 to 90 with subduction typically more important in offshore oligotrophic regions on average the fate of particles that are passively transported out of the surface layer by advection is different from that of particles that sink across the 100 m depth horizon subducted particles were predominantly remineralized shallower than 150 m while approximately 50 of gravitationally exported poc was remineralized at depths 500 m

open ocean convection observations theory and models we review what is known about the convective process in the open ocean in which the properties of large volumes of water are changed by intermittent deep reaching convection triggered by winter storms observational laboratory and modeling studies reveal a fascinating and complex interplay of convective and geostrophic scales the large scale circulation of the ocean and the prevailing meteorology two aspects make ocean convection interesting from a theoretical point of view first the timescales of the convective process in the ocean are sufficiently long that it may be modified by the earth s rotation second the convective process is localized in space so that vertical buoyancy transfer by upright convection can give way to slantwise transfer by baroclinic instability moreover the convective and geostrophic scales are not very disparate from one another detailed observations of the process in the labrador greenland and mediterranean seas are described which were made possible by new observing technology when interpreted in terms of underlying dynamics and theory and the context provided by laboratory and numerical experiments of rotating convection great progress in our description and understanding of the processes at work is being made

mesozoic paleogeography of the northern calcareous alps evidence from paleomagnetism and facies analysis the northern calcareous alps are generally thought to have been part of the same southern tethyan continental margin as the southern alps during late jurassic and early cretaceous time contrasting liassic paleomagnetic data from the northern calcareous alps and the southern alps can be explained by large scale clockwise rotation during late cretaceous and tertiary tectonic emplacement of the northern calcareous alps onto the european continental margin alternatively the data can be reconciled by postulating that the northern calcareous alps did not undergo the african mesozoic rotational history seen in the southern alps and were separated from the southern alps by a short lived branch of jurassic ocean facies analysis in the karwendel thiersee syncline of the northern calcareous alps indicates that the jurassic basin sediments in this area were deposited in an east west oriented sinistral strike slip fault system in the southern alps and central austroalpine complex coeval basin sedimentation was controlled by north south oriented normal faults this contrasting basin evolution and evidence for a source of ophiolitic detritus south of the northern calcareous alps argue for a short lived ocean basin south of the northern calcareous alps that was closed by early cretaceous time

meteorological forcing of sea ice concentrations in the southern beaufort sea over the period 1979 to 2000 1 northern hemisphere sea ice areal extent and perhaps thickness have shown a detectable reduction over the past several decades this situation is particularly apparent in the southern beaufort sea the region encompassing the mackenzie shelf the cape bathurst polynya and the canada basin mobile pack ice all occur in a region referred to here as the canadian arctic shelf exchange study area cases in this paper we present results from an analysis of atmosphere sea ice and ocean coupling over the period 1979 to 2000 as a means of setting a physical science context for the cases research network operating over the period 2001 2005 results show that the cape bathurst polynya complex can be considered as a recurrent polynya particularly the flaw leads associated with the early opening of the polynya the polynya appears to be a consequence of the beaufort sea gyre acting like an ice bridge and a series of flaw leads creating conditions conducive to oceanic upwelling the sea ice average areal extent has been decreasing in this region over the period 1979 to 2000 large regional reductions are found i north of the yukon and alaska coasts in the region between the canada basin pack ice and the landfast sea ice and 2 at the eastern limit of the cape bathurst polynya in amundsen gulf the meteorological forcing of sea ice anomalies occurs through a full range of timescales and space scales at hemispheric scales a statistical cross correlation analysis between weekly sea ice concentration anomalies and the arctic oscillation accounts for a maximum of about 25 percent of the explained variance and show a surprising spatial coherence in correlation magnitudes both within the study area and northward along the canadian archipelago coast at local scales positive and negative concentration anomaly periods can be explained through local scale advective processes associated with regional scale sea level pressure 500 hpa geopotential heights and surface temperature anomalies

evidence for jurassic subduction from the northern calcareous alps berchtesgaden austroalpine germany the closure of the western part of the neotethys ocean started in late early jurassic the middle to early late jurassic contraction is documented in the berchtesgaden alps by the migration of trench like basins formed in front of a propagating thrust belt due to ophiolite obduction these basins propagated from the outer shelf area hallstatt realm to the interior continent hauptdolomit dachstein platform realm the basins were separated by nappe fronts forming structural highs this scenario mirrors syn orogenic erosion and deposition in an evolving thrust belt active basin formation and nappe thrusting ended around the oxfordian kimmeridgian boundary followed by the onset of carbonate platforms on structural highs starved basins remained between the platforms rapid deepening around the early late tithonian boundary was induced by extension due to mountain uplift and resulted in the reconfiguration of the platforms and basins erosion of the uplifted nappe stack including obducted ophiolites resulted in increased sediment supply into the basins and final drowning and demise of the platforms in the berriasian the remaining early cretaceous foreland basins were filled up by sediments including siliciclastics the described jurassic to early cretaceous history of the northern calcareous alps accords with the history of the western carpathians the dinarides and the albanides where 1 age dating of the metamorphic soles prove late early to middle jurassic inneroceanic thrusting followed by late middle to early late jurassic ophiolite obduction 2 kimmeridgian to tithonian shallow water platforms formed on top of the obducted ophiolites and 3 latest jurassic to early cretaceous sediments show postorogenic character

the interpretation of cyclic successions of the middle and upper triassic of the northern and southern alps abstract theories regarding the formation of sedimentary cycles in the 3rd 4th and 5th order bands are reviewed with reference to the middle and upper triassic of the northern calcareous alps nca and southern alps milankovitch autocyclic and tectonic theories are discussed together with an evaluation of concepts of chaotic sedimentation and a case example from the nca concerning eustasy 3rd 4th and 5th order sea level fluctuations were probably a low amplitude low rate phenomenon caused by fluctuations in the volume of mountain glaciers and ocean water during the triassic the mid and late triassic was a non glacial interval in which polar regions may have been ice free so glacio eustasy can not be expected eustatic sea level variations in the 3rd 4th and 5th order bands seem to have left no useful imprint on cyclic successions in the region whatever record there may be is inextricably mixed with two other signals tectonic activity and autocycles the review shows how sedimentation in the triassic of the area was strongly influenced by tectonic activity this is as true for the middle and late triassic of the nca as it is for the southern alps tectonic activity may be responsible for large scale cyclicity 4th to 3rd order scale although seismogenic structures have yet to be identified and described in carbonate successions of the alps candidates do exist slumped and microfaulted layers in laminated sediments of the seefeld basin upper triassic nca have been described as the products of fault movements the sedimentary record from the nca and southern alps also leaves little doubt that autocyclic processes were important in all environments except perhaps the deep sediment starved basins most small scale platform cycles 5th order scale in the region can be related to autocyclic processes and in shallow basinal successions to events such as storms previous workers have not been consistent in their interpretation of cyclic successions in the area applying diverse theories to similar successions so far the steinplatte hochkonig platform with attached kossen basin is the only example interpreted with reference to tectonics and autocyclicity eustasy was probably not the most important factor in cycle generation in the triassic of the nca and southern alps such an approach could prove useful in future studies

carbonate debris flows cow head group western newfoundland abstract the cow head group is an allochthonous cambro ordovician sequence of deep water limestone conglomerates mudstones to grainstones minor quartz sandstones siltstones and shales platy clast conglomerates and boulder rich megaconglomerates as much as 100 m thick exhibit features similar to those described for subaerial debris flows that is flat sharp bases with only minor evidence for erosion poorly developed clast fabric with tilting of platy clasts at right angles to the flow direction boulders floating within flows or projecting above the tops of flows irregular flow tops indicating primary relief above the sea floor and tapered flow margins snouts snout geometry and the extent of boulder projection both allow calculation of debris static strength these results combined with measured flow thickness permit calculation of minimum and maximum paleoslope gradients original debris static strengths were in the range of 103 to 105 dynes cm2 similar to the observed range in subaerial flows calculations yield bottom gradients of l l 8 but independent field data suggest that the paleoslope dip was on the order of only a few degrees this constraint suggests that debris strength was substantially reduced during flow probably by excess pore fluid pressures thus permitting flow on very gentle slopes the paleoslope orientations used in this study are substantially different from those previously published by hubert et at 1977

anachronistic facies from a drowned lower triassic carbonate platform lower member of the alwa formation ba id exotic oman mountains abstract the lower member of the alwa formation lower olenekian found within the ba id exotic in the oman mountains sultanate of oman consists of ammonoid bearing pelagic limestones that were deposited on an isolated drowned carbonate platform on the neotethyan gondwana margin the strata contain a variety of unusual carbonate textures and features including thrombolites frutexites bearing microbialites that contain synsedimentary cements matrix free breccias surrounded by isopachous calcite cement and fissures and cavities filled with large botryoidal cements thrombolites are found throughout the study interval and occur as 0 5 1 0 m thick lenses or beds that contain laterally laterally linked stromatactis cavities the frutexites bearing microbialites occur less frequently and also form lenses or beds up to 30 cm thick the microbialites may be laminated and often developed on hardgrounds in addition the frutexites bearing microbialites also contain synsedimentary calcite cement crusts and botryoids typically frutexites bearing microbialites low level of calcium carbonate supersaturation associated with anoxic conditions and deposition below a stable chemocline formed the results of this study point to continued environmental stress in the region during the early triassic that likely contributed to the uneven recovery from the permian triassic mass extinction

shelf derived iron inputs drive biological productivity in the southern drake passage water entrainment while fe 228 ra ratios were used to calculate the fe flux in the summer of 2006 we found rapid mixing and significant lateral iron export namely a dissolved iron flux of 1 1 10 5 mol d 1 and total acid leachable iron flux of 1 1 10 6 mol d 1 all of which is transported in the mixed layer from the shelf region offshore this dissolved iron flux is significant especially considering that the bloom observed in the offshore region 0 5 2 mg chl a m 3 had an iron demand of 1 1 to 4 10 5 mol fe net vertical export fluxes of particulate fe derived from 234 th 238 u disequilibrium and fe 234 th ratios accounted for only about 25 of the dissolved iron flux on the other hand vertical upward mixing of iron rich deeper waters provided only 7 of the lateral dissolved iron flux we found that similarly to other studies in iron fertilized regions of the southern ocean lateral fluxes overwhelm vertical inputs and vertical export from the water column and support significant phytoplankton blooms in the offshore regions of the drake passage

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

paleomagnetism and paleogeography of the northern calcareous alps austria prefolding magnetization components have been resolved at 38 sites of liassic adnet limestones in the central northern calcareous alps nca and at one site in the drauzug the site mean directions are northeasterly and down and are closer to coeval european directions than to southern alpine african directions the western end of both the nca and of the drauzug yield different site mean directions and negative fold tests indicating remagnetization the sampling localities have been rotated relative to one another during thrusting however comparison of paleomagnetic poles with the european apparent polar wander path implies an average clockwise rotation of about 30 for the nca relative to europe larger scale clockwise rotations in excess of 80 relative to the southern alps are implied by comparison with the southern alpine african polar wander path facies analysis of jurassic and lower cretaceous basinal sediments in the central part of the nca suggests that liassic subsidence was related to presently e w sinistral strike slip faults whereas malm berriasian subsidence was controlled by presently e w south dipping normal faults both paleomagnetic and facies data tend to indicate that the nca did not undergo the african rotation seen in southern alpine paleomagnetic data this implies the existence of a short lived tract of triassic jurassic ocean floor between the nca and the southern alps which linked the pindos ocean to the ligurian trough and allowed adria to rotate independently from the nca during the late jurassic eo alpine deformation and metamorphism are associated with the early cretaceous closure of this hallstatt trough

zinc and nickel isotopes in seawater from the indian sector of the southern ocean the impact of natural iron fertilization versus southern ocean hydrography and biogeochemistry abstract the southern ocean is the site of 20 of global ocean carbon export and the origin of water masses that significantly impact the chemistry of the global ocean much of the southern ocean is a high nutrient low chlorophyll hnlc region iron is the primary limiting nutrient for phytoplankton growth and may also be an important control on the biogeochemistry of the water masses emanating from the southern ocean here we investigate the response of zn and ni and their isotopes to natural fe fertilization from southern ocean islands using samples collected during the keops 2 oct nov 2011 program in the early austral spring near the kerguelen plateau indian sector of the southern ocean zinc and ni concentrations show depth distributions and relationships to major nutrients that are very similar to published data from the atlantic sector of the southern ocean away from island fertilization as in the atlantic sector and other regions outside the southern ocean there is a slight minimum in 66zn at about 100 150 m depth and a slightly heavier value at the surface at the keops 2 sites the light sub surface zn isotopes occur at the depth level where measured chl a has declined to near zero the heaviest zn isotope values in either the atlantic or indian sectors occur in bottom waters are associated with samples that show high dissolved si relative to zn these latter represent possible evidence for a heavy input directly to deep water or from sediment and the zn si 66zn systematics are consistent with a source in diatom opal nickel concentrations show much less variation than those of zn with the most depleted surface value only 15 20 lower than those in upwelled deep water in the southern ocean these small variations in ni concentration are associated with no significant variability in ni isotopes as also previously observed in the atlantic sector overall the key feature of the dataset is the apparent absence of any significant impact of natural fe fertilization on the distribution of zn and ni with the dominant control being the station location relative to the polar front in both the atlantic and indian sectors zinc and ni isotopes are invariant in surface waters whether inside or outside the fertilized zone and whether south or north of the polar front 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

on the horizontal extent of the canada basin thermohaline steps abstract microstructure profiles of temperatures through the diffusive thermohaline staircase above the atlantic layer core in the canada basin of the arctic ocean are used to investigate the horizontal scales of layers daily profiles during two periods 23 march 3 april and 17 26 april 1985 show that diffusive steps are present throughout the 200 km drift track a 20 hour series on 22 april sampled at about 5 profiles per hour indicates that particular diffusive layers can be traced for at least 600 m the temperature of some layers varies by up to 0 01 c h 1 30 m lateral motion therefore we cannot reliably trace steps in this location if the sampling distance is larger than about 15 m analysis of a longer time series with variable spacing from 0 4 to 5 km indicates that layers can rarely be traced between profiles more than 1 km apart

observation of a deep convection regime with acoustic tomography in the winter of 1991 1992 a convection experiment was conducted in the western mediterranean gulf of lions combining a variety of observational techniques an essential component was an acoustic tomography array consisting of six moorings designed to observe the time evolution of the large scale processes believed to be relevant in a convection regime here two dimensional slice inversions in three directions from the central mooring are used to estimate the volume of convected water and the mean convection depth and to observe the preconditioning and restratification processes before and after the convection the near surface layer is well sampled by the acoustics which show cooling and subsequent entrainment of the warmer levantine intermediate water liw from below in agreement with mixedlayer calculations during the 2 months prior to the main convection event the total heat loss of the large scale field is in approximate agreement with the surface heat fluxes showing that little net warm water advection takes place from outside the convection region the implied confinement of water by the local circulation should be an important factor in setting the location and extent of the deep convection patch the volume of water modified by convection in this winter is estimated to correspond to an area of order 60 km radius and 1500 m depth it is argued that the homogenized area implies an annual mean deep water replenishment of 0 3 sv the restratification by the return of less dense water in the surface and liw layers occurs first by rapid capping in the near surface region thereafter the southern and eastern parts of the region restratify in the deeper layers on a 40 day timescale while a dense core of 50 60 km diameter remains in the northwest until the end of the experiment

buoyancy driven circulation in an ocean basin with isopycnals intersecting the sloping boundary abstract the dynamics that govern the spreading of a convectively formed water mass in an ocean with sloping boundaries are examined using an isopycnal model that permits the interface between the layers to intersect the sloping boundaries the simulations presented here use a two layer configuration to demonstrate some of the pronounced differences in a baroclinically forced flow between the response in a basin with a flat bottom and vertical walls and a more realistic basin bounded by a sloping bottom each layer has a directly forced signal that propagates away from the forcing along the potential vorticity pv contours of that layer paired opposed boundary currents are generated by refracted topographic rossby waves rather than kelvin waves it is impossible to decompose the flow into globally independent baroclinic and barotropic modes topography causes the barotropic i e depth averaged response to buoyancy forcing to be just as strong as the baroclinic response because layer pv contours di

attenuation of particulate organic carbon flux in the scotia sea southern ocean is controlled by zooplankton fecal pellets the southern ocean so is an important co2 reservoir some of which enters via the production sinking and remineralization of organic matter recent work suggests that the fraction of production that sinks is inversely related to production in the so a suggestion that we confirm from 20 stations in the scotia sea the efficiency with which exported material is transferred to depth transfer efficiency is believed to be low in high latitude systems however our estimates of transfer efficiency are bimodal with stations in the seasonal ice zone showing intense losses and others displaying increases in flux with depth zooplankton fecal pellets dominated the organic carbon flux and at stations with transfer efficiency 100 fecal pellets were brown indicative of fresh phytodetritus we suggest that active flux mediated by zooplankton vertical migration and the presence of sea ice regulates the transfer of organic carbon into the oceans interior in the southern ocean

kilometre scale palaeoescarpments as evidence for cretaceous synsedimentary tectonics in the external brianconnais domain ligurian alps italy abstract in the central part of the external ligurian brianconnais in the ligurian alps nw italy a large and diverse set of stratigraphic sedimentologic and petrographic data provides evidence for the occurrence of cretaceous kilometre scale palaeoescarpments these palaeoescarpments consist of irregular erosional surfaces more or less deeply incising a stratigraphic succession that ranges from upper jurassic limestones down to permian volcano sedimentary rocks at present they are partly exposed and partly covered by upper cretaceous upper eocene sediments and patchily encrusted by authigenic minerals palaeoescarpments resulted from the remodelling of palaeofault planes by gravity driven rock fall processes whose products are represented by breccias and metre to tens of metres sized blocks of upper jurassic limestones either lying directly over the surfaces or embedded within onlapping sediments palaeofault related tensional stresses are also documented by the occurrence of subvertical sedimentary neptunian dykes and tabular breccia bodies interpreted as fault rocks and locally bearing evidence of the uprise of hot overpressured fluids fault activity started during the aptian with most of the displacement which locally reached several hundred metres accomplished during the late cretaceous resulting in deep morpho structural depressions that by eocene times were not yet levelled out two systems of kilometre long palaeoescarpments are recognized and mapped suggesting the existence of a cretaceous kilometre sized fault bounded basin limited to the north and south by two main transcurrent zones presently striking e w and internally partitioned by n s oriented east dipping normal faults this type of setting could be consistent with the western tethys tectonic context in which the ligurian brianconnais domain close to the early late cretaceous boundary was located at the easternmost end of a transcurrent belt connecting the bay of biscay to the valais and ligurian piedmont oceans

the arctic oscillation signature in the wintertime geopotential height and temperature fields the leading empirical orthogonal function of the wintertime sea level pressure field is more strongly coupled to surface air temperature fluctuations over the eurasian continent than the north atlantic oscillation nao it resembles the nao in many respects but its primary center of action covers more of the arctic giving it a more zonally symmetric appearance coupled to strong fluctuations at the 50 hpa level on the intraseasonal interannual and interdecadal time scales this arctic oscillation ao can be interpreted as the surface signature of modulations in the strength of the polar vortex aloft it is proposed that the zonally asymmetric surface air temperature and mid tropospheric circulation anomalies observed in association with the ao may be secondary baroclinic features induced by the land sea contrasts the same modal structure is mirrored in the pronounced trends in winter and springtime surface air temperature sea level pressure and 50 hpa height over the past 30 years parts of eurasia have warmed by as much as several k sea level pressure over parts of the arctic has fallen by 4 hpa and the core of the lower stratospheric polar vortex has cooled by several k these trends can be interpreted as the development of a systematic bias in one of the atmosphere s dominant naturally occurring modes of variability

synsedimentary slides and bedding formation in apennine pelagic limestones abstract jurassic to lower tertiary pelagic carbonates in the umbria marches apennines of northern peninsular italy are well bedded and synsedimentary submarine slide deposits are common bedding planes were formed by pressure solution during compaction where original rhythmic alternations in clay content were present bedding formed along the clay rich horizons where the original sediments were uniform stylolitic pseudobedding approximately marks paleohorizontal even where true bedding departs from paleohorizontal because of the presence of soft sediment folds deformational facies observed in synsedimentary slides are compared to a conceptual model of a bedding plane glide with a longitudinal sequence of four deformational facies 1 the slide scar where section is missing may be identified if biostratigraphic or magnetostratigraphic zones are missing 2 the stretched rear of the slide is thinned and shows extensional shear joints and sedimentary boudinage 3 the transported but undeformed main body of the slide may be identified paleomagnetically if it has been rotated and the basal shear surface may show deformational structures 4 the shortened front of the slide commonly shows on a small scale the ramp thrusts and folds typical of foreland fold and thrust belts the state of induration of the sediments at the time of movemen is shown by their theological behavior in areas of major subsea relief slides may have moved far enough for the distal parts to lose their coherence and all the transitional stages from a slide to a pebbly mudstone can be identified

physical and biogeochemical controls on the variability in surface ph and calcium carbonate saturation states in the atlantic sectors of the arctic and southern oceans polar oceans are particularly vulnerable to ocean acidification due to their low temperatures and reduced buffering capacity and are expected to experience extensive low ph conditions and reduced carbonate mineral saturations states in the near future however the impact of anthropogenic co2 on ph and will vary regionally between and across the arctic and southern oceans here we investigate the carbonate chemistry in the atlantic sector of two polar oceans the nordic seas and barents sea in the arctic ocean and the scotia and weddell seas in the southern ocean to determine the physical and biogeochemical processes that control surface ph and high resolution observations showed large gradients in surface ph 0 10 to 0 30 and aragonite saturation state ar 0 2 to 1 0 over small spatial scales and these were particularly strong in sea ice covered areas up to 0 45 in ph and 2 0 in ar in the arctic sea ice melt facilitated bloom initiation in light limited and iron replete dfe 0 2 nm regions such as the fram strait resulting in high ph 8 45 and ar 3 0 along the sea ice edge in contrast accumulation of dissolved inorganic carbon derived from organic carbon mineralisation under the ice resulted in low ph 8 05 and ar 1 1 in areas where thick ice persisted in the southern ocean sea ice retreat resulted in bloom formation only where terrestrial inputs supplied sufficient iron dfe 0 2 nm such as in the vicinity of the south sandwich islands where enhanced ph 8 3 and ar 2 3 were primarily due to biological production in contrast in the adjacent weddell sea weak biological uptake of co2 due to low iron concentrations dfe 0 2 nm resulted in low ph 8 1 and ar 1 6 the large spatial variability in both polar oceans highlights the need for spatially resolved surface data of carbonate chemistry variables but also nutrients including iron in order to accurately elucidate the large gradients experienced by marine organisms and to understand their response to increased co2 in the future

pre oceanic rifting in the alps abstract a review of mesozoic mainly earliest jurassic to mid jurassic rifting in the western and central alps normal faults with throws up to a few kilometers are moderately inclined and involve rotation of crustal blocks the amount of stretching and thinning of the crust by jurassic rifting is discussed the rifting 200 165 m y pre dates the opening of the alpine oceans by spreading and transform movements 165 110 m y

the flux of bio and lithogenic material associated with sinking particles in the mesopelagic twilight zone of the northwest and north central pacific ocean abstract as part of the vertigo program we collected and analyzed sinking particles using tethered and neutrally buoyant sediment traps at three depths in the oceanic mesopelagic zone and at two biogeochemically contrasting sites n central pacific at aloha n pacific western subarctic gyre at k2 this effort represented the first large scale use of neutrally buoyant traps and represents a significant step forward in the study of the marine biological pump in this paper we present the results of mass macronutrient biominerals and phytoplankton pigment determinations made on these samples the impact of a variety of potential collection biases were examined including those from in trap particle degradation zooplankton swimmers and poisons though these factors have been observed to affect results in other programs we found them to have relatively little impact on measured fluxes in this study there was evidence however that the neutrally buoyant traps performed better than the tethered traps in terms of flux accuracy during one deployment possibly because of improved large particle collection efficiency fluxes of material exhibited three different patterns through the mesopelagic increasing decreasing and constant with depth decreasing fluxes with depth were observed for all biogenic material formed in the euphotic zone the attenuation of flux with depth was not the same for all components however with phytoplankton pigments exhibiting the greatest degradation with depth and particulate inorganic carbon the least organic carbon and nitrogen showed a very high correlation in these samples with little evidence of different attenuation length scales increasing fluxes with depth were observed for particulate ba at both sites and al at k2 the increases in ba are attributed to the formation of barite in degrading particles while increasing al at k2 was the result of lateral inputs from a continental shelf slope constant fluxes with depth were observed for al at aloha where fluxes appeared to be in steady state with atmospheric dust deposition the mesopelagic zone at k2 was observed to attenuate particle flux less than at aloha and with a higher poc pic rain ratio these two factors combine to imply that the subarctic province had a much more efficient biological pump than had the subtropical gyre during our occupations this could be the result of either faster sinking particles generated from grazing by large zooplankton or inherently slower particle degradation rates

high biomass low export regimes in the southern ocean high biomass low export regimes in the southern ocean phoebe j lam 1 2 and james k b bishop 1 earth sciences division lawrence berkeley national laboratory 1 cyclotron road berkeley ca 94720 usa department of earth and planetary science university of california berkeley berkeley ca 94720 usa now at department of marine chemistry and geochemistry woods hole oceanographic institution woods hole ma 02543 submitted january 27 2006 to deep sea research ii special topics in oceanography special volume on the role of marine organic carbon and calcite fluxes in driving climate change past and future revised version accepted june 28 2006 keywords ballast remineralization poc twilight zone mesopelagic southern ocean mulvfs opal carbonate phosphorus

surface area control of organic carbon accumulation in continental shelf sediments the relationship between organic carbon oc and grain size found in most continental shelf sediments is here reinterpreted in terms of the surface area of the sediments cores from many north american shelf environments show downcore decreases in oc to similar refractory background concentrations if expressed relative to the surface area of the sediments this consistent concentration is 0 86 mg oc m 2 which is equivalent in concentration to a monolayer of organic matter coating all mineral surfaces a more global collection of sediment water interface samples show that this relationship is even more extensive with exceptions occurring in areas of very high riverine sediment input organic pollution or low oxygen water columns density separations indicate that organic matter is largely adsorbed to mineral grains the microtopography of surfaces was examined with n2 sorption and most surface area was found to be inside pores of 10 nm width these data lead to a hypothesis that organic matter is protected by its location inside pores too small to allow functioning of the hydrolytic enzymes necessary for organic matter decay such protection would likely work in concert with other protection mechanisms such as humification this consistent surface area correlation with oc concentration may explain control of spatial and temporal variations in oc burial rates by sedimentation rates the pore protection hypothesis provides a causal mechanism for this observed control

on the proportion of ballast versus non ballast associated carbon export in the surface ocean the role of biominerals in driving carbon export from the surface ocean is unclear we compiled surface particulate organic carbon poc and mineral ballast export fluxes from 55 different locations in the atlantic and southern oceans substantial surface poc export accompanied by negligible mineral export was recorded implying that association with mineral phases is not a precondition for organic export to occur the proportion of non mineral associated sinking poc ranged from 0 to 80 and was highest in areas previously shown to be dominated by diatoms this is consistent with previous estimates showing that transfer efficiency in such regions is low however we propose that rather than the low transfer efficiency arising from diatom blooms being inherently characterized by poorly packaged aggregates which are efficiently exported but which disintegrate readily in mid water it is due to such environments having very high levels of unballasted organic c export