stress state in the cuu long and nam con son basins offshore vietnam abstract the results presented in this paper are the first published estimates of the complete stress tensor in the cuu long and nam con son basins offshore vietnam we analysed in situ stress and pore pressure fields in the sedimentary formations using data from petroleum exploration and production wells to evaluate the stress state in these basins the data were obtained from the seafloor to 4300 m burial depth and include both hydrostatic and overpressured sections minimum horizontal stresses were obtained from extended leak off tests and mini fracture tests maximum horizontal stresses were estimated from drilling induced fracture parameters and borehole breakout widths in twelve wells using rock properties measured in the laboratory or estimated empirically from wireline logs seven data points are located in sediments and seventeen data points in igneous basement rocks at depths greater than 3000 m the estimated magnitudes of h are 70 110 of the v magnitudes considering the errors in the stress magnitude estimates their relative magnitudes suggest that a borderline normal strike slip stress regime presently exists in normally pressured sequences of the nam con son and cuu long basins of the twenty four data points twenty have effective stress ratios at a critical stress state for faulting on the assumption that there are faults present that are optimally oriented for failure with friction coefficients of 0 5 the results suggest that the stress state in these basins is generally critical

radiogenic and stable sr isotope ratios 87 sr 86 sr δ 88 86 sr as tracers of riverine cation sources and biogeochemical cycling in the milford sound region of fiordland new zealand this study reports radiogenic sr isotope ratios 87sr 86sr stable sr isotope ratios 88 86sr and major ion concentrations for river rock sediment soil and plant samples collected from the cleddau and hollyford catchments in the milford sound region of fiordland new zealand the catchments primarily drain gabbro but some tributaries access limestone and volcanogenic sediments the goal of the study was to understand controls on riverine 88 86sr values in a landscape with multiple factors that may influence chemical weathering including dense vegetation high rainfall and abundant freshly eroded holocene fluvio glacial and landslide debris rivers draining gabbro have higher 88 86sr values than bedrock by as much as 0 14 and the 88 86sr values strongly correlate with molar ca sr ratios r2 0 69 leaching of rocks and sediment reveals no evidence for the preferential dissolution of minerals having high 88 86sr values and ca sr ratios in stream sr isotope fractionation seems unlikely because comparison against 87sr 86sr and ca sr ratios demonstrates that riverine 88 86sr values conservatively trace water mass mixing the riverine data are best explained by the input of soil water which is distinct from potential bedrock end members i e silicates and carbonates based on 88 86sr but indistinguishable in terms of ca sr and 87sr 86sr while strontium isotope fractionation during secondary mineral formation and pedogenesis is possible clay mineral formation is minor and most soils are poorly developed instead soil water 88 86sr values more likely reflect plant uptake plant samples yielded a wide range of 88 86sr values but on average they are lower than those for bedrock consistent with the expectation that plants preferentially incorporate lighter sr isotopes mass balance constraints together with 87sr 86sr ratios indicate that soil water 88 86sr values are 0 30 higher than bedrock 88 86sr values and mixing calculations show that the plant fractionated soil water pool contributes 27 of the riverine sr for tributaries accessing limestone and volcanogenic sediments ca sr and 87sr 86sr ratios appear consistent with two component mixing between silicate and carbonate weathering but 88 86sr values reveal a third contribution from soil water inputs similar to gabbro catchments the results of this study suggest that sr isotopes behave conservatively during water mass mixing and stream transport but non conservatively in soil where plant uptake can elevate soil water 88 86sr values relative to bedrock plant uptake or related biogeochemical processes such as ion exchange on organic matter surfaces also appear to modify soil water ca sr ratios many studies use 87sr 86sr and ca sr ratios to apportion riverine solutes between silicate and carbonate weathering but ca sr ratios may be non conservative in densely vegetated areas the stable sr isotope tracer shows promise for resolving riverine cation sources as well as effects from biological cycling

an updated view on water masses on the pan west greenland continental shelf and their link to proglacial fjords the accelerated melt of the greenland ice sheet has been linked to a sudden increase in the presence of warm subsurface coastal water in west greenland yet pathways of warm coastal water along the entire west greenland coast have remained largely unstudied here we present the first near synoptic hydrographic observations at both the continental slope and fjord entrances of the west greenland coastal system from cape farewell 59 n to melville bay 75 n in summer 2016 we observed a distinct north south division in the water mass distribution in west greenland approximately partitioned by the northern part of davis strait and a division between the continental slope and fjord entrances waters from the regional southern freshwater source with origin in the east greenland current that rounds cape farewell are not observed to enter baffin bay the regional heat source transported by the west greenland current is blocked by southwest greenland coastal water in the south but the deep connections in the north allow warm deep subpolar mode water to enter fjords furthermore we observed cold and relative saline baffin bay polar water over the inner part of the banks periodically reaching as far south as 64 n suggesting the presence of an undescribed southward current at the southwest greenland continental shelf

outside influences on the water column of cumberland sound baffin island cumberland sound host to a commercially viable fish population in the deepest depths is a large embayment on the southeast coast of baffin island that opens to davis strait conductivity temperature and depth profiles were collected during three summer field seasons 2011 2013 and two moorings were deployed during 2011 2012 within the sound salinity increases with increasing depth while water temperature cools reaching a minimum of 1 49 c at roughly 100 m below 100 m the water becomes both warmer and saltier temperature salinity curves for each year followed a similar pattern but the entire water column in cumberland sound cooled from 2011 to 2012 and then warmed through the summer of 2013 even though the sound s maximum depth is over a kilometer deeper than its sill water in the entire sound is well oxygenated a comparison of water masses within the sound and in davis strait shows that above the sill the sound is flooded with cold baffin island current water following an intermittent geostrophic flow pattern entering the sound along the north coast and leaving along the south below the sill replenishment is infrequent and includes water from both the baffin island current and the west greenland current deep water replenishment occurred more frequently on spring tides especially in the fall of 2011 although the sound s circulation is controlled by outside currents internal water modifying processes occur such as estuarine flow and wind driven mixing

organic walled microfossils and geochemical tracers sedimentary indicators of productivity changes in the north water and northern baffin bay during the last centuries analyses performed on 26 surface sediment samples collected with a box corer at 17 stations throughout the north water and northern baffin bay 75 791n 68 801w revealed abundantorganic walled microfossils most ly dinoflagellate cysts 10 3 10 4 cysts g 1 and organic linings of benthic foraminifers 10 2 10 3 ol g 1 as well as high organic carbon concentrations 0 87 2 81 dry weight these data indicate high productivity in both the pelagic and benthic environments of the north water and slightly lower productivity in northern baffin bay the data also showed calcium carbonate and biogenic silica dissolution throughout the study area the dinocyst assemblages were relatively uniform in the north water and dominated by heterotrophic taxa algidasphaeridium minutum and brigantedinium spp whereas northern baffin bay assemblages were dominated by autotrophic taxa notably operculodinium centrocarpum and spiniferites elongatus the difference between these two assemblages may be related to higher diatomaceous primary production in the north water than in northern baffin bay since diatoms constitute the principal food source of heterotrophic dinoflagellates the biogeographical boundary between the north water and northern baffin bay has been maintained for at least the last few centuries as shown by analyses of microfossils and geochemical tracers in two sediment cores one taken in the southeastern part of the north water 76117 0 n 72102 0 w and the other in northeastern baffin bay 75135 0 n 70148 0 w the analyses of the north water core revealed relatively uniform microfossil assemblages and organic carbon fluxes ranging from 1 1 to 1 5 mg corg cm 2 yr 1 for the last few centuries which corresponded to 4 6 of the present annual primary production in the euphotic zone these data suggest high productivity and relatively stable conditions in the polynya on a decadal time scale in the northeastern baffin bay core the analyses indicated generally lower organic carbon fluxes ranging from 0 3 to 0 6 mg corg cm 2 yr 1 and from the microfossil data significant variations in sea surface conditions at this lower latitude over the last centuries r 2002 elsevier science ltd all rights reserved

modeling wind driven circulation and landfast ice edge processes during polynya events in northern baffin bay abstract a high resolution sea ice ocean numerical model of the north water polynya has been developed to study the wind driven circulation during polynya events an idealized three layer stratified ocean is used to initialize the model to characterize the baroclinic response to realistic wind and ice conditions the model general circulation pattern is mainly forced by an along channel sea level gradient between the arctic ocean and baffin bay which determines the magnitude of the southward baffin current and by an across channel sea level gradient in baffin bay which drives the northward west greenland current wgc these two currents are found to be anticorrelated to each other in the smith sound area during strong northerly wind events occurring quite frequently in the winter spring period in the polynya nutrient rich baffin bay waters transported by the wgc are forced toward the greenland shelf coinciding with upwelling events along the greenland coast whenever an ice bridge is present i e

establishment of modern circulation pattern at c 6000 cal a bp in disko bugt central west greenland opening of the vaigat strait variations in the holocene circulation of the west greenland current wgc in the disko bugt region have been reconstructed from a suite of sediment cores palaeoceanographic proxies include magnetic susceptibility ms and x ray fluorescence titanium counts which document a major shift in circulation at c 6000 cal a bp before this date sediments in southern disko bugt were characterized by high terrigeneous and basaltic input suggesting widespread influence of meltwater plumes our data show that the wgc re circulated in the southern disko bugt area because a potential northern pathway the narrow vaigat strait was blocked by icebergs that calved from marine outlet glaciers in eastern disko bugt sediments in southern disko bugt deposited after c 6000 cal a bp have significantly lower terrestrial and basaltic sediment input which coincides with minimum holocene ice sheet extent the reduced meltwater and iceberg discharge to the embayment caused the vaigat strait to become free of blocking icebergs and terrigenous input was partly diverted to the outer shelf thus the modern circulation pattern of the wgc was established in the disko bugt region through the opening of the vaigat strait c 6000 cal a bp

nares strait hydrography and salinity field from a 3 year moored array 1 nares strait to the west of greenland facilitates the exchange of heat and freshwater between the arctic and atlantic oceans this study focuses on salinity temperature and density measurements from nares strait from a mooring array deployed from 2003 to 2006 innovative moorings requiring novel analysis methods measured seawater properties near 80 5 n at spacing sufficient to resolve the internal rossby deformation radius the 3 year mean geostrophic velocity has a surface intensified southward flow of 0 20 m s 1 against the western side of the strait and a secondary core flowing southward at 0 14 m s 1 in the middle of the strait data show warm salty water on the greenland side and cold fresher water on the ellesmere island side especially in the top layers there was a clear difference in hydrographic structure between times when sea ice was drifting and when it was land fast ice was drifting in late summer fall and early winter with a strong surface intensified geostrophic flow in the middle of the strait ice was land fast in late winter spring and early summer when there was a subsurface core of strong geostrophic flow adjacent to the western side of the strait salinity variations of about 2 psu in time and space reflect a variable freshwater outflow from the arctic ocean one particularly strong pulse occurred at the end of july 2005 for several days steeply sloping isohalines indicated strong geostrophic flow down the middle of the strait coinciding with an amplified ice export from the arctic due to strong southward winds

mechanical characterization of limestone from sound velocity measurement the aim of this research was to establish correlations between different physical properties sound velocity vp bulk density and open porosity p0 and mechanical properties compressive strength rc tensile strength rt static elasticity modulus e0 and poisson s ratio i i of limestones the first step of the work consisted in an experimental campaign on limestone cores drilled from a gothic building in paris eight cores were extracted from the monument and tested in the laboratory secondly the experimental results were added to those proposed by 14 authors in the international scientific literature and all of these data were analyzed using the generalized least squares method so that correlation curves could be suggested seven correlations are proposed rc vp rc vp p0 e0 rc i i vp rt rc finally the dispersion of the results led to an estimated confidence level of 90 according to statistical considerations highlights we carried out an experimental physical and mechanical campaign on limestones cores correlations between different physical and mechanical properties are established dispersion of results led to an estimated confidence level according to statistical considerations

87sr 86sr chemostratigraphy of neoproterozoic dalradian carbonates below the port askaig glaciogenic formation scotland abstract the neoproterozoic cambrian dalradian supergroup of scotland contains three glaciogenic sedimentary units the port askaig formation the stralinchy reelan formation and the loch na cille boulder bed in ascending order although the idea that relatively cold climates occurred during the latest proterozoic is widely accepted the cause of the onset of glaciation is still controversial we use new carbonate 87 sr 86 sr data to better constrain this environmental change some dalradian limestones have high strontium contents 1000 ppm low manganese contents and mn sr ratios 87 sr 86 sr values of paleoseawater in the neoproterozoic the 87 sr 86 sr values of limestones of the islay formation ca 0 7067 sampled on the island of islay are similar to the values of previous studies however the 87 sr 86 sr values of limestones just below the port askaig formation ca 0 7064 collected on the island of garbh eileach have the lowest values recorded in the dalradian supergroup comparing these 87 sr 86 sr values with coeval 87 sr 86 sr values of other regions in the world such low 87 sr 86 sr i87 sr 86 sr ratio from the tonian through the cryogenian and ediacaran to the earliest cambrian the results show that the 87 sr 86 sr ratio of seawater decreased just before the older cryogenian glaciation that it increased by two steps in the early and middle ediacaran and that there were at least two abrupt positive excursions in the middle ediacaran and at the precambrian cambrian boundary the decline of the 87 sr 86 sr ratio of seawater just before the older cryogenian sturtian glaciation suggests that enhancement of weathering related to break up of the rodinia supercontinent and continental flood basalt volcanism was a likely driver for generating global cooling for the snowball earth conditions godderis et al 2003 donnadieu et al 2004

the freshwater budget and under ice spreading of mackenzie river water in the canadian beaufort sea based on salinity and 18o 16o measurements in water and ice observations of salinity and oxygen isotope composition 18o were made for the beaufort shelf mackenzie estuary waters in september 1990 just prior to ice formation and for both the water column and ice in april may 1991 at the end of winter these measurements are used to determine the apportioning of fresh water in the estuary between its two main sources runoff and sea ice melt changes in disposition of water between seasons and amounts frozen into the growing ice sheet are also derived two domains are considered in order to construct a freshwater budget for the mackenzie shelf the nearshore within which landfast ice grows in winter and the outer shelf most of the winter inflow from the mackenzie river appears to remain impounded as liquid under the ice within the landfast zone at the end of winter and about 15 of it is incorporated into the landfast ice oxygen isotopes 18o in ice cores collected from across the shelf record the progress beneath the ice of new mackenzie inflow as it invades the nearshore throughout winter rates of spreading are about 0 2 cm s 1 away from the coast and 1 3 cm s 1 along the coast as this inflow spreads across the shelf it progressively shuts off convection driven by brine production at locations within the landfast ice salinity and 18o in the offshore water column suggest that about 3 m of sea ice was formed in the outer shelf domain since both brine and newly formed sea ice can be advected off the shelf a complete budget for brine or sea ice production cannot be established without first measuring the advection of one of these two components

centennial scale benthic foraminiferal record of late holocene oceanographic variability in disko bugt west greenland a new centennial scale benthic foraminiferal record of late holocene climate variability and oceanographic changes off west greenland disko bugt highlights substantial subsurface water mass changes e g temperature and salinity of the west greenland current wgc over the past 3 6 ka bp benthic foraminifera reveal a long term late holocene cooling trend which may be attributed to increased advection of cold low salinity water masses derived from the east greenland current egc cooling becomes most pronounced from c 1 7 ka bp onwards at this point the calcareous atlantic benthic foraminiferal fauna decrease significantly and is replaced by an agglutinated arctic fauna superimposed on this cooling trend centennial scale variability in the wgc reveals a marked cold phase at c 2 5 ka bp which may correspond to the 2 7 ka bp cooling event recorded in marine and terrestrial archives elsewhere in the north atlantic region a warm phase recognized at c 1 8 ka bp is likely to correspond to the roman warm period and represents the warmest bottom water conditions during the time period of the medieval climate anomaly we observe only a slight warming of the wgc a progressively more dominant cold water contribution from the egc on the wgc is documented by the prominent rise in abundance of agglutinated arctic water species from 0 9 ka bp onwards this cooling event culminates at c 0 3 ka bp and represents the coldest episode of the little ice age gradually increased influence of cold low salinity water masses derived from the egc may be linked to enhanced advection of polar and arctic water by the egc these changes are possibly associated with a reported shift in the large scale north atlantic oscillation atmospheric circulation pattern towards a more frequent negative north atlantic oscillation mode during the late holocene

structure and mixing across an arctic atlantic front in northern baffin bay 1 a front forms in northern baffin bay 75 25 n between atlantic derived water carried by the west greenland current and arctic derived waters exiting southward through nares strait and jones sound via the baffin current subsurface waters e g below 100 m of the west greenland current are as much as 2 c warmer than those of the baffin current confluence of these waters leads to a frontal transition between 100 500 m wherein cross frontal gradients of potential temperature l 0 06 0 07 c km 1 and salinity s l 0 005 0 007 psu km 1 are largely density compensating l 0 001 km 1 subsequent thermohaline interleaving establishes conditions conducive to mixing via cabelling and double diffusion the front s location would allow it to play a contributing role in the formation of baffin current water structure and eventual export of freshwater to the north atlantic

water column structure and circulation under the north water during spring transition april july 1998 abstract the north water is a large recurring polynya in northern baffin bay over 400 hydrographic ctd profiles taken over a grid of stations between april and july 1998 were analysed to understand the water column structures underlying the polynya during spring transition in the north water imported and dissimilar water masses converge over a complex bathymetry northern assembly na waters are derived from inflows through nares strait and jones sound southern assembly sa waters are derived from a northern moving branch of the west greenland current wgc na and sa waters mix primarily over the north south smith sound canyon between 76 5 n and 77 n latitude to form a distinct relatively thick halocline layer termed north water assembly nwa characterised by density compensating thermohaline intrusions in the southern portion of the north water a sharp front between nwa waters and sa waters roughly aligns with the 500 m isobath flow patterns deduced from potential temperature vs salinity s diagrams and from minima in stability frequency n profiles indicate that this front results from the convergence of nwa waters and a branch of the wgc that is cyclonically re directed as it approaches smith sound canyon not all sa waters are immediately re directed south towards the front as a second branch follows the greenland coast toward smith sound while s signatures show some evidence of upwelling along the greenland coast e g outcropping of isopycnal surfaces no surfacing of warm atlantic derived water was observed during the sampling period 1998 suggesting that mechanical removal of ice by winds and currents is the primary mechanism by which the north water forms some sensible heat exchange associated with brine rejection and penetrative convection may occur but only during periods of active ice formation

physical and geochemical properties across the atlantic pacific water mass front in the southern canadian basin temperature salinity nutrients oxygen and halocarbon data collected in the arctic ocean reveal a frontal structure previously unrecognized in the hydrography of the canadian basin samples were collected on a 1300 km section extending from the beaufort sea in the canada basin to the east siberian sea in the makarov basin these data collected in 1993 aboard the ccgs henry larsen reveal a lateral boundary between water masses of atlantic and pacific origin the term water mass assembly is introduced to describe the basic arrangement or vertical stacking of water masses found in the arctic ocean recognizing that water mass components within each assembly may differ from basin to basin using historical data two primary water mass assemblies are defined each consisting of three layers an upper layer an atlantic layer and a deep layer these two assemblies are marked by important differences one assembly here defined as the western arctic wa assembly is characterized by an upper layer of relatively fresh high nutrient water of pacific origin below this by an atlantic layer with a core temperature generally below 0 5 c and finally by a deep layer of higher salinities and colder temperatures about 0 5 c than found in the overlying atlantic layer the second assembly here defined as eastern arctic ea assembly is characterized by the absence of pacific water in the upper layer below this by an atlantic layer core as warm as 2 to 3 c and by a colder about 0 9 c deep layer because the presence or absence of pacific origin water is a key characteristic distinguishing the two assemblies we will refer to the water mass boundary between the two assemblies as the atlantic pacific front earlier research indicated that water masses in the arctic ocean were separated by a front above the lomonosov ridge into the canadian and eurasian basins although all larsen 93 stations from the canada basin a1 d1 display classic wa assembly characteristics the makarov basin station e1 shows ea assembly characteristics in the upper and atlantic layers and a wa assembly deep layer this suggests a relocation in the position of the atlantic pacific boundary away from the lomonosov ridge further larsen 93 data show the transition region between the atlantic and deep layers is fresher in the makarov basin than corresponding water in either the canada or eurasian basins implying a source of cold low salinity water perhaps from the laptev and east siberian shelves the front separating these two assemblies lies above the mendeleyev ridge and is marked by large lateral gradients in all measured properties in particular the penetration of anthropogenic halocarbons is 2 to 3 times deeper in the makarov basin than in the canada basin implying enhanced rates of ventilation this suggests that direct exchange between the canadian and eurasian basins has occurred recently near the perimeter and that physical and chemical properties including contaminants may have been transported by boundary currents more quickly from one basin to the other

potential vorticity distribution in the north pacific abstract vertical sections and maps of potential vorticity 1f z for the north pacific are presented on shallow isopycnals high potential vorticity is found in the tropics subpolar gyre and along the eastern boundary of the subtropical gyre all associated with ekman upwelling low potential vorticity is found in the western subtropical gyre subtropical mode water in a separate patch near the sea surface in the eastern subtropical gyre and extending around the gyre and near sea surface outcrops in the subpolar gyre the last is analogous to the subpolar mode water of the north atlantic and southern ocean meridional gradients of potential vorticity are high between the subtropical and subpolar gyres at densities which outcrop only in the subpolar gyre lateral gradients of potential vorticity are low in large regions of the subtropical gyre on these isopycnals on slightly denser isopycnals which do not outcrop in the north pacific there are large regions of low potential vorticity gradients

distribution and circulation of labrador sea water abstract labrador sea water is the final product of the cyclonic circulation of subpolar mode water in the open northern north atlantic mccartney and talley 1982 the temperature and salinity of the convectively formed subpolar mode water decrease from 14 7 c 36 08 to 3 4 c 34 88 on account of the cumulative effects of excess precipitation and cooling the coldest mode water is labrador sea water which spreads at mid depths and is found throughout the north atlantic ocean north of 40 n and along its western boundary to 18 n a vertical minimum in potential vorticity is used as the primary tracer for labrador sea water labrador sea water is advected in three main directions out of the labrador sea 1 northeastward into the irminger sea 2 southeastward across the atlantic beneath the north atlantic current and 3 southward past newfoundland with the labrador current and thence westward into the slope water region crossing under the gulf stream off cape hatteras the labrador sea water core is

a nonlinear steady state model of the north water polynya baffin bay abstract a nonlinear steady state model of the north water now the arctic s largest polynya is presented the model follows in the spirit of the recently developed latent and sensible heat polynya model of mysak and huang but extends it in several important ways finite amplitude displacements of the upper layer thickness are allowed the channel walls diverge to the south the sensible heat flux from the lower layer is physically well defined in terms of a vertical entrainment velocity and the free drifting frazil ice to the north of the now ice edge is allowed to move to the right of the northerly winds an important result found here is that with the exception of late spring the asymptotic southern ice edge position of the now can be simulated in terms of a latent heat model alone in this case the observed equatorward curvature of the ice edge in the region adjacent to the west greenland coast can be produced by a combination of a channel that widens in the equatorward direction together wit

a latent and sensible heat polynya model for the north water northern baffin bay abstract the pease latent heat polynya model is coupled to a reduced gravity coastal upwelling model in order to simulate the formation and maintenance of the north water now the arctic s largest polynya located in northern beffin bay in this region strong northerly winds during winter and spring drive ice southward as fast as it is produced locally the pease mechanism for polynya formation and also produce upwelling of warm subsurface water along the west coast of greenland this upwelling provides an upward heat flux that melts ice near the coast a sensible host mechanism for polynya formation this combined latent and sensible heat polynya model is formulated as an initial boundary value problem with uniform winds its solution gives the tide evolution of the upper layer velocity and depth and also the polynya width as measured southward from the northern boundary of the polynya there are two fundamental time scales in the problem a fast one of the order of days that characterizes the

impact of the large scale arctic circulation and the north water polynya on nutrient inventories in baffin bay 1 the distributions of nitrate phosphate and silicate in northern baffin bay were determined from 90 bottle casts taken between april 11 and july 21 1998 during late spring low salinity arctic water entered northern smith sound and mixed with baffin bay water bbw within the north water polynya the arctic water originated from the bering sea and contained high concentrations of phosphate and silicate referred to as silicate rich arctic water sraw the distribution of the two water masses was established using a new tracer siex which showed moderate penetration of sraw into smith sound during april and a very strong incursion in may and june consistent with the intensification of southward current velocities biological depletion of macronutrients in bbw began in april and continued until nitrate was exhausted from the upper mixed layer in early june beneath the polynya the deep waters 450 m showed a marked increase in nutrient concentration toward the bottom which was most pronounced in the south and much stronger for silicate than nitrate and phosphate the silicate enrichment was consistent with dissolution of diatom derived biogenic silica in deep waters the results indicate that the north water acts as a silicate trap in which the biota differentially transports surface silicate to depth thereby influencing local and downstream nutrient signatures

a model for the influence of wind and oceanic currents on the size of a steady state latent heat coastal polynya abstract this paper presents a model for determining the size and shape of a steady state latent heat coastal polynya in terms of the following free parameters 1 the frazil ice production rate f 2 the wind stress 3 the surface ocean velocity field u 4 the offshore consolidated thin ice transport t 5 the coastline shape and 6 the intersection of the polynya ice edge with the coastline all of which must be prescribed frazil ice trajectories are determined via the free drift ice momentum balance analytical solutions for the polynya shape are derived for a straight coastline in the special case when u t and are uniform in the alongshore direction and the rotation of the earth is neglected when the latter constraint is relaxed an expression for the asymptotic uniform polynya width is obtained an expression for the alongshore adjustment length scale of the polynya associated with alongshore variations in the coastline shape u t and is derived with rotation of the earth incl

strontium stable isotopes fractionate in the soil environments abstract this study shows that the stable isotopic composition of strontium the 88sr 86sr ratio expressed as 88 86sr value relative to the nbs987 standard varies significantly in sedimentary terrestrial environments the abundances of 86sr 88sr isotopes were analyzed by mc icp ms nu plasma all studied rocks and waters show 88 86sr values that are distinctly different from the measured nbs987 standard yielding 0 01 0 05 all errors are reported as 2 modern corals from the northern gulf of aqaba red sea yielded significantly different value than seawater 88 86sr 0 22 0 07 compared to 0 35 0 06 respectively in an excellent correlation with the 88 86sr analyses reported by fietzke and eisenhauer fietzke j eisenhauer a 2006 determination of temperature dependent stable strontium isotopes 88sr 86sr fractionation via bracketing standard mc icp ms geochm geophys geosyst 7 no 8 on other coral samples all carbonate samples that originated in the marine environment corals porites and acropora from the northern gulf of aqaba cretaceous limestone and runoff from the judea mountains as well as lacustrine evaporitic aragonite dead sea and red sea and atlantic seawater yield an average 88 86sr value of 0 26 0 1 on the other hand secondary materials products of chemical weathering from the terrestrial environment of the judea mountain such as terra rossa soil and speleothem calcite that derives its sr from the above lying soil yielded significantly lower 88 86sr value of 0 17 0 06 this indicates that strontium isotopes fractionate in the soil environment calling for a possible development of strontium isotopes as a tracer for processes of chemical weathering and pedogenesis

surface and sub surface multi proxy reconstruction of middle to late holocene palaeoceanographic changes in disko bugt west greenland we present new surface water proxy records of meltwater production alkenone derived relative sea surface temperature diatom alkenones and sea ice diatoms changes from the disko bugt area off central west greenland we combine these new surface water reconstructions with published proxy records benthic foraminifera bottom water proxy dinocyst assemblages surface water proxy along with atmospheric temperature from greenland ice core and greenland lake records this multi proxy approach allows us to reconstruct centennial scale middle to late holocene palaeoenvironmental evolution of disko bugt and the western greenland coastal region with more detail than previously available combining surface and bottom water proxies identifies the coupling between ocean circulation west greenland current conditions the atmosphere and the greenland ice sheet centennial to millennial scale changes in the wider north atlantic region were accompanied by variations in the west greenland current wgc during periods of relatively warm wgc increased surface air temperature over western greenland led to ice sheet retreat and significant meltwater flux in contrast during periods of cold wgc atmospheric cooling resulted in glacier advances we also identify potential linkages between the palaeoceanography of the disko bugt region and key changes in the history of human occupation cooler oceanographic conditions at 3 5 ka bp support the view that the saqqaq culture left disko bugt due to deteriorating climatic conditions the cause of the disappearance of the dorset culture is unclear but the new data presented here indicate that it may be linked to a significant increase in meltwater flux which caused cold and unstable coastal conditions at ca 2 ka bp the subsequent settlement of the norse occurred at the same time as climatic amelioration during the medieval climate anomaly and their disappearance may be related to harsher conditions at the beginning of the little ice age

sediment properties and benthic pelagic coupling in the north water abstract measurements of sediment oxygen consumption were made during spring and summer in the north water the polynya that forms between greenland and ellesmere island and used in conjunction with sediment trap data to assess benthic pelagic coupling in this system bottom sediments ranged from cobble in the north to soft muds in the southern part of the sampling grid muddy sediments were often pelletized as shown by disaggregation sediment photopigments were generally lower in coarse sediment stations to the north than in finer sediments stations to the south shipboard incubation of intact cores provided rates of 0 07 0 17 mmol o 2 m 2 h 1 with significantly greater oxygen consumption in summer than in spring additional incubation of macrofauna free sediment aliquots in vials demonstrated significantly lower oxygen consumption in summer than in spring partitioning of benthic metabolism via these selective exclusion experiments showed a seasonal change in the response of the benthos to pelagic input with meio microbenthos dominating oxygen consumption in spring and macrofauna dominating in summer increased oxygen demand in the western polynya is suggested to coincide with the highest rates of carbon input measured by sediment traps and highest levels of sediment pigments this region is an advective sink for particles produced in the east and subsequently transported by net polynya circulation although the benthos of the north water does not display enhanced rates of carbon processing compared to other arctic sediments including other polynyas the protracted production season of north water provides a longer period over which the benthos can receive and mineralize organic carbon

high temperature strontium stable isotope behaviour in the early solar system and planetary bodies abstract this study presents comprehensive strontium stable isotope 88sr 86sr data measured by multiple collector inductively coupled plasma mass spectrometry mc icp ms for a suite of carbonaceous chondrites differentiated meteorites lunar martian and terrestrial samples carbonaceous chondrites comprise a mixture of refractory inclusions and chondrules that have light 88sr values between 0 35 to 0 05 and matrix material that possesses a heavy 88sr composition of 0 65 confirming the results of earlier studies consequently bulk carbonaceous chondrites are relatively heterogeneous in composition ranging from 0 12 to 0 35 most likely reflecting clast matrix variability the light 88sr compositions of the refractory inclusions are consistent with mass dependent fractionation of other refractory elements ca and eu and are most likely produced by non equilibrium fractionation undercooling in the nebula gas during condensation of hibonite from the solar nebula simon and depaolo 2010 stable calcium isotopic composition of meteorites and rocky planets earth planet sci lett 289 457 466 carbonaceous chondrites angrites and martian meteorites have indistinguishable compositions at the level of analytical uncertainty of this study however statistical analysis indicates that melts derived from the earth s mantle have heavier 88sr values than bulk carbonaceous chondrites and martian meteorites but compositions indistinguishable from eucrites 88sr 0 26 0 12 moreover terrestrial basalts and andesites have restricted 88sr values 0 30 0 07 suggesting that mantle melting delivers rather homogenous melts to the earth s surface with respect to 88sr in contrast glasses from evolved terrestrial rocks and lunar basalts extend to very light 88sr values 0 20 the sr stable isotope composition covaries with europium anomaly eu eu as an index of plagioclase fractionation and 88sr can be successfully modelled by the heavy isotopes of sr being preferentially partitioned into plagioclase with a fractionation factor of 1 0007 for 88sr 86sr our results demonstrate that sr stable isotopes may be significantly fractionated at high temperatures and their measurement can provide insights into planetary evolution and magmatic processes

holocene palaeoceanographic evolution off west greenland benthic foraminiferal assemblages from a core southwest of disko bugt provide a holocene perspective last 7 ka bp on ice sheet ocean interactions between the west greenland current wgc and the west greenland ice sheet changes in the fauna reveal significant variations in the water mass properties temperature and salinity of the wgc through time from 7 3 to 6 2 ka bp a relatively warm strong wgc influences ice sheet melt in disko bugt and causes enhanced meltwater production resulting in low surface water productivity the most favourable oceanographic conditions occur from 5 5 to 3 5 ka bp associated with thermal optimum like conditions encompassing minimum ice sheet extent in the disko bugt area these conditions are attributed to 1 reduced meltwater influence as the ice sheet is land based and 2 enhanced contribution of warm saline water masses from the irminger current to the wgc the transition into the late holocene last 3 5 ka bp is characterized by a cooling of oceanographic conditions caused by increased advection of cold low salinity water masses from the east greenland current a longer term late holocene cooling trend within the wgc is attributed to the onset of neoglacial cooling within the north atlantic region superimposed on this cooling trend multicentennial scale variability within the wgc matches reconstructions from a nearby coring site in disko bugt as follows 1 cooling at 2 5 ka bp linked to the 2 7 ka bp cooling event 2 a warm phase centred at 1 8 ka bp associated with the roman warm period 3 slight warming between 1 4 and 0 9 ka bp linked to the medieval climate anomaly 4 severe cooling of the wgc after 0 9 ka bp culminating at 0 3 ka bp during the little ice age we show that multicentennial scale palaeoceanography variability along the west greenland margin is driven by ocean forcing i e variations in the relative contribution of atlantic irminger current and polar east greenland current water masses to the wgc during the last 7 ka bp influencing ice sheet dynamics

micromechanical modeling of the effective elastic properties of oolitic limestone a new micromechanical approach to analytical modeling of oolitic limestone is proposed limestone is modeled as a multiphase composite consisting of sparry calcite matrix spherical oolitic inhomogeneities oblate spheroidal pores of aspect ratio 0 2 and concave pores in the shape of superspheres the concavity factor is the key parameter affecting overall properties maxwell s homogenization scheme is used to calculate effective bulk and shear moduli of this multiphase composite as functions of total porosities the results are in good agreement with experimental data available in the literature

determination of the main hydraulic and poro elastic properties of a limestone from bourgogne france this study is a part of a large experimental program intended to characterise the effects of increasing temperature upon the hydraulic and poro mechanical behaviour of a limestone from anstrude france methods of measurement as well as experimental devices designed by our laboratory are presented and commented on permeability values measured on six different samples either with gas or ethanol clearly show that the results obtained with the two fluids are virtually identical as soon as the gas measurements are corrected for the klinkenberg effect as the permeability is not very sensitive to confining pressure variation it can be assumed that the intact rock is slightly cracked this is confirmed with microscopic observations as well as poro elastic property measurements concerning the latter various ways of obtaining their values are presented and compared they include drained and undrained bulk modulus biot and skempton coefficients and biot modulus the consistency between these parameters is finally highlighted and demonstrates that the classical theory of poro elasticity hold very well for such a rock which is almost monomineralic with quite a high porosity

baffin island and west greenland current systems in northern baffin bay abstract temperature salinity and direct velocity observations from northern baffin bay are presented from a summer 2003 survey the data reveal interactions between fresh and cold arctic waters advected southward along baffin island and salty and warm atlantic waters advected northward along western greenland geostrophic currents estimated from hydrography are compared to measured ocean currents above 600 m depth the baffin island current is well constrained by the geostrophic thermal wind relation but the west greenland current is not furthermore both currents are better described as current systems that contain multiple velocity cores and eddies we describe a surface intensified baffin island current seaward of the continental slope off canada and a bottom intensified west greenland current over the continental slope off greenland acoustic doppler current profiler observations suggest that the west greenland current system advected about 3 8 0 27 sv sv 10 6 m 3 s 1 towards the north west at this time the most prominent features were a surface intensified coastal current advecting 0 5 sv and a bottom intensified slope current advecting about 2 5 sv in the same direction most of this north westward circulation turned southward in the baffin island current system the baffin island system was transporting 5 1 0 24 sv to the south east at the time that includes additional contributions from nares strait to the north 1 0 0 2 sv and lancaster sound to the east 1 0 0 2 sv net freshwater fluxes were 72 and 187 msv for the west greenland and baffin island currents respectively empirical uncertainty arises from unknown temporal variations at weekly time scales and pertubations introduced by unresolved eddies eddies with 10 km horizontal and 400 m vertical scales were common and recirculated up to 1 sv our 2003 observations represent conditions when the north atlantic oscillation index nao was close to zero analysis of historical hydrographic data averaged along isobaths during nao positive years reveals a baroclinic circulation in baffin bay more intense than 2003 with stronger southward flow of fresher arctic waters along baffin island and stronger northward inflow of saltier atlantic waters along greenland during negative nao years this cyclonic circulation weakens as evidenced by a 1979 synoptic survey of the hydrography along baffin island

absorption and fluorescence of dissolved organic matter in the waters of the canadian arctic archipelago baffin bay and the labrador sea the optical properties of dissolved organic matter dom were investigated for the first time in the canadian arctic archipelago caa baffin bay bb and labrador sea ls as part of the international polar year canada s three oceans project c3o the dynamics and composition of absorbing dom i e colored dom or cdom and fluorescent dom fdom were evaluated in several distinct water masses occupying the three regions surface waters arctic outflow waters west greenland intermediate waters wgiw upper labrador sea waters ulsw and bottom baffin deep water bbdw four fluorescent components were identified by applying parallel factor analysis parafac to 522 excitation emission matrix eem spectra three humic like and one protein like the fdom in surface waters of the caa and bb differed considerably in character from those of the ls with higher fluorescence intensity in the former the fluorescence intensities of the two terrestrial humic like components c1 and c3 were linearly correlated with apparent oxygen utilization aou in the caa arctic outflow and the wgiw whereas only humic like c3 was significantly correlated with aou in ulsw these findings suggest that the humic like components were produced in situ as organic matter was bio oxidized the slopes of the linear relationship between humic like intensity and aou were significantly greater in the wgiw relative to the arctic outflow waters which implies that fdom in the arctic derived deeper layer was less prone to mineralization

an overview of physical processes in the north water the presence of a polynya strongly affects biological processes by influencing underwater light levels water column stratification the upwelling of nutrients and the timing of production cycles an overview of the existing literature on the oceanography meteorology and sea ice conditions of the north water a large recurring polynya in northern baffin bay is presented the north water is influenced by a cold inflow of arctic ocean water from the north and in some areas a warmer inflow of atlantic water from the south earlier observations and modeling studies suggested that both wind and ocean advection of sea ice as well as heat input to the surface waters by either upwelling or mixing were responsible for the formation and maintenance of the polynya recent data indicate the north water to be primarily generated by the southward drift of ice by winds and currents as opposed to melting ice by sensible heat input over large areas localized sensible heat effects occur in fall winter and spring along the greenland side of the polynya

warming and freshening of baffin bay 1916 2003 1 regression analysis of historical hydrographic data is used to determine changes in temperature and salinity in baffin bay for the time period from 1916 to 2003 we find two distinct sets of changes in the baffin first areas affected by the atlantic inflow to baffin bay show substantial and statistically significant warming trends in the more than 2000 m deep basin the warming peaks at 0 11 0 06 c decade at 700 m depth below the 640 m sill depth of davis strait connecting baffin bay to the north atlantic ocean a vertical heat flux divergence of 0 25 w m2 is required to warm baffin bay below 900 m by the amount observed the required heat appears to be advected from the shelf and slope regions of the eastern labrador sea via davis strait along the west greenland shelf break and diffuses vertically and horizontally into the deep central basin the north atlantic oscillation index accounts for about 30 of the interannual variance of temperature fluctuations below the davis strait sill depth second areas affected by arctic inflow to baffin bay show a marginally significant freshening of up to about 0 086 0 039 psu decade this freshening trend extends along the western margin of baffin island to davis strait and into the labrador sea the freshening in the northern reaches of baffin bay is similar in size to that at its southern reaches temporal variability of annual composites between these locations appears to be in phase suggesting a swift transition of arctic waters at 76 n to labrador sea waters at 62 n

change at the margin of the north water polynya baffin bay inferred from organic matter records in dated sediment cores abstract the north water polynya now is one of the most productive marine environments in the arctic with arctic sea ice cover a prominent control in the production of marine organic matter om polynyas are likely to be sentinels of the effects of recent change in ice climate we collected six sediment cores from the now dated them using 210pb corroborated with 137cs where possible and analysed down core profiles of om kerogen rock eval 6 analysis total organic carbon toc total organic nitrogen ton 13c and 15n the down core records were examined for evidence of recent past 150 years change sediment om bulk concentrations toc and ton displayed exponential decreases with water depth reflecting water column remineralization processes using a model to account for sedimentation rate and sediment surface mixing we found that cores from the interior of the now showed no significant change between pre 1900 sediments and post 1900 sediments and little variance among cores in contrast a core from the northwest boundary of the region showed evidence of increased marine organic carbon input and two cores from the southeast boundary showed evidence of decreased terrigenous carbon input in addition the cores at the southeast boundary on the slope off greenland witnessed a significant decline in sedimentation rate during the same time interval we interpret the change in om in the boundary cores in the context of change in regional ice climate and runoff our results suggest that the margin of this polynya is more vulnerable to change than the interior and thus is a better location to seek evidence of change furthermore the diversity of settings within now indicates that change must be understood at sub regional scales