major pathways of atlantic water in the northern north atlantic and nordic seas toward arctic 1 the major pathways of near surface atlantic water in the northern north atlantic and nordic seas are identified as current speeds above 30 cm s using 1014 lagrangian drifters combined with previously published hydrography the inflow over the scotland greenland ridge and establishment of the two branch norwegian atlantic current nwac are described in light of the circulation in the northern north atlantic the western branch of the nwac appears as a jet in the polar front topographically guided from the iceland faroe front through the nordic seas toward fram strait the eastern branch starts as a shelf edge current above the irish scottish continental shelf and after passing through the faroe shetland channel it continues northward along the norwegian shelf edge toward the arctic with a branch bifurcating into the barents sea the nwac appears to maintain its two branch structure throughout the nordic seas with the atlantic water confined to a 200 600 km wide wedge

modelling the non linear deformation properties of stiff geomaterials the modelling of non linear stifaffess based on elastic characteristic moduli for stiff geomaterials is proposed on the basis of the results of a large number of triaxial compression tests on sedimentary soft rocks tuff weathered granite cement treated soils densely compacted gravels and sands axial strains from less than 0 001 to about 1 were measured by using a local gauge while elastic young s moduli e sbp e were obtained by applying a series of small unload reload cycles of axial stress during each monotonic loading test strain increments less than about 0 001 were nearly recoverable and strain rate independent for sedimentary soft rocks and cement treated soils the elastic young s moduli e e from laboratory tests using high quality undisturbed samples were very similar to the equivalent values obtained from field seismic surveys the dependence of e e on stress state is summarized and the effects of geomaterial type are analysed the non linearity during shear deformation is regarded

horizontal and vertical copepod distribution and abundance on the mid atlantic ridge in june 2004 abstract copepod composition abundance and distribution were studied in june 2004 on the mid atlantic ridge along a transect extending from iceland 60 n to the azores 41 n the samples were depth stratified from the surface down to a maximum depth of 2500 m the transect covered relatively warm and relatively saline modified north atlantic water mnaw on the reykjanes ridge in the northern part colder and less saline sub arctic intermediate water saiw further south to the charlie gibbs fracture zone cgfz and warm high salinity north atlantic central water nacw in the southern part in total 68 copepod genera and 117 species were identified calanoid copepods dominated the generic richness with 57 genera there was a clear increase in the number of genera southwards from 30 in the northern region to 57 in the south the total copepod number was variable between stations ranging from 45 000 to 178 000 m 2 however the variability did not show any clear north south trend and the lowest abundance was observed close to the sub polar front located near the cgfz cluster analysis divided the transect into three main regions as based on copepod community structure one in the northern part containing mnaw and saiw where calanus finmarchicus and pareuchaea tonsa characterized the region one in the frontal region saiw nacw where c hyperboreus was more abundant than in the other two regions and one southern region containing nacw characterized by several species e g calanus helgolandicus mecynocera clausi and pleuromamma gracialis vertically the copepods mainly occurred in the upper part of the water column in total 53 of the individuals occurred above 100 m and 75 above 500 m depth below 1000 m depth only low numbers were recorded 10 of the total copepod abundance there were large differences in vertical distribution between genera species with m clausi acartia spp and pseudocalanus spp showing the shallowest distribution and oncaea spp pleuromamma spp and microcalanus spp the deepest distribution depth distribution however was also affected by hydrographic differences between stations in the deepest samples there was a tendency for a higher total abundance close to the bottom than at greater distances from bottom

frontal surveys with a towed profiling conductivity temperature depth measurement package seasoar in april 1986 rv oceanus participated in the frontal air sea interaction experiment fasinex1 in the region 27 29 n 68 71 w the objective was to survey a pronounced oceanic front2 4 and its effect on the oceanic and atmospheric boundary layers although moorings have yet to be recovered and much of the data analysis is as yet only preliminary it is possible to report here the typical density structure of a front as derived from seasoar5 6 fig 1a observations which were analysed within a few hours of collection previously unreported detail is revealed including subducted pycnostads areas of weak vertical density gradient with anomalous temperature salinity signature splitting of the frontal jet and three dimensional structure not apparent in the surface temperature field

variability along the atlantic water pathway in the forced norwegian earth system model the growing attention on mechanisms that can provide predictability on interannual to decadal time scales makes it necessary to identify how well climate models represent such mechanisms in this study we use a high 0 25 horizontal grid and a medium 1 resolution version of a forced global ocean sea ice model utilising the norwegian earth system model to assess the impact of increased ocean resolution our target is the simulation of temperature and salinity anomalies along the pathway of warm atlantic water in the subpolar north atlantic and the nordic seas although the high resolution version has larger biases in general at the ocean surface the poleward propagation of thermohaline anomalies is better resolved in this version i e the time for an anomaly to travel northward is more similar to observation based estimates the extent of these anomalies can be rather large in both model versions as also seen in observations e g stretching from scotland to northern norway the easternmost branch into the nordic and barents seas carrying warm atlantic water is also improved by higher resolution both in terms of mean heat transport and variability in thermohaline properties a more detailed assessment of the link between the north atlantic ocean circulation and the thermohaline anomalies at the entrance of the nordic seas reveals that the high resolution is more consistent with mechanisms that are previously published this suggests better dynamics and variability in the subpolar region and the nordic seas in the high resolution compared to the medium resolution this is most likely due a better representation of the mean circulation in the studied region when using higher resolution as the poleward propagation of ocean heat anomalies is considered to be a key source of climate predictability we recommend that similar methodology presented herein should be performed on coupled climate models that are used for climate prediction

large bio geographical shifts in the north eastern atlantic ocean from the subpolar gyre via plankton to blue whiting and pilot whales pronounced changes in fauna extending from the english channel in the south to the barents sea in the north east and off greenland in the north west have occurred in the late 1920s the late 1960s and again in the late 1990s we attribute these events to exchanges of subarctic and subtropical water masses in the north eastern north atlantic ocean associated with changes in the strength and extent of the subpolar gyre these exchanges lead to variations in the influence exerted by the subarctic or lusitanian biomes on the intermediate faunistic zone in the north eastern atlantic this strong and persistent bottom up bio physical link is demonstrated using a numerical ocean general circulation model and data on four trophically connected levels in the food chain phytoplankton zooplankton blue whiting and pilot whales the plankton data give a unique basin scale depiction of these changes and a long pilot whale record from the faroe islands offers an exceptional temporal perspective over three centuries recent advances in simulating the dynamics of the subpolar gyre suggests a potential for predicting the distribution of the main faunistic zones in the north eastern atlantic a few years into the future which might facilitate a more rational management of the commercially important fisheries in this region

directly measured mid depth circulation in the northeastern north atlantic ocean the circulation of water masses in the northeastern north atlantic ocean has a strong influence on global climate owing to the northward transport of warm subtropical water to high latitudes but the ocean circulation at depths below the reach of satellite observations is difficult to measure and only recently have comprehensive direct observations of whole ocean basins been possible here we present quantitative maps of the absolute velocities at two levels in the northeastern north atlantic as obtained from acoustically tracked floats we find that most of the mean flow transported northward by the gulf stream system at the thermocline level about 600 m depth remains within the subpolar region and only relatively little enters the rockall trough or the nordic seas contrary to previous work our data indicate that warm saline water from the mediterranean sea reaches the high latitudes through a combination of narrow slope currents and mixing processes at both depths under investigation currents cross the mid atlantic ridge preferentially over deep gaps in the ridge demonstrating that sea floor topography can constrain even upper ocean circulation patterns

north atlantic nordic seas exchanges abstract the northeastern part of the north atlantic is unique in the sense that it is much warmer in the surface than other ocean areas at similar latitudes the main reason for this is the large northward transport of heat that extends to high latitudes and crosses the greenland scotland ridge to enter the nordic seas and the arctic there the warm atlantic water is converted to colder water masses that return southwards over the ridge partly as surface outflows and partly as overflows through the deep passages across the ridge in this paper the state of knowledge on the exchanges especially across the eastern part of the greenland scotland ridge is reviewed based on results from the ices nansen north atlantic norwegian sea exchanges project from the nordic woce project and from other sources the accumulated evidence allows us to describe the exchanges in fair detail the origins of the waters the patterns of their flow towards and over the ridge and their ultimate fate there is also increasing information on temporal variations of the exchanges although dynamical changes are still not well understood quantitative estimates for the volume transport of most of the overflow branches seem reasonably well established and transport measurements of the atlantic inflows to the nordic seas are approaching acceptable levels of confidence which allows preliminary budgets to be presented the deep overflows are driven by pressure gradients set up by the formation of deep and intermediate water the dominance of deep overflows over surface outflows in the water budget argues that this thermohaline forcing also dominates over direct wind stress and estuarine forcing in driving the atlantic water inflow across the greenland scotland ridge while wind stress seems to influence the characteristics and distribution of the atlantic water north of the ridge

interannual thermohaline changes in the northern north atlantic 1991 1996 abstract in the period 1991 1996 the woce hydrographic section a1e ar7e between greenland and ireland was repeated five times the observed thermohaline changes altered the baroclinic structure along the eastern margin of the subpolar gyre significantly between june 1995 and august 1996 an overall increase of the temperature and thickness and a decrease of the density of the subpolar mode water spmw layer were observed accompanied by an increase of its salinity east of the reykjanes ridge and a decrease of its salinity in the irminger sea the changes were most pronounced in the iceland basin where the subarctic front retreated westwards coinciding with a strong weakening of the westerlies as determined by the north atlantic oscillation they are related to a local reduction of the ekman upwelling and the ocean to atmosphere heat flux on the one hand and to the advection of anomalies from the subtropics on the other hand the eastward spreading of the different labrador sea water lsw vintages led to a corresponding cooling of the lsw in the irminger sea and in the iceland basin in the period 1991 1996 the renewal of the lsw in the rockall trough occurred more sporadically indicating that the north atlantic current nac impedes the southward spreading of lsw in the eastern atlantic the changes in 1996 seem to have also counteracted this spreading

a triaxial investigation of kinematic yielding in sand the elastic plastic behaviour of a reconstituted sand is considered under triaxial conditions covering a wide range of strains monotonic probing tests are used to identify two types of kinematic yield surface for samples with loose and dense initial states under drained and undrained conditions and after different patterns of consolidation plastic strain development and global stiffness degradation are found to be closely interrelated and the interpretation involves decoupling the elastic and plastic strain components the sizes and the shapes of the loci are strongly affected by effective stress states and histories including any periods allowed for creep and ageing a tentative qualitative micromechanical explanation is offered for the phenomena observed

the interplay between subduction and lateral extrusion a case study for the european eastern alps based on analogue models a series of analogue experiments simulating intra continental subduction contemporaneous with lateral extrusion of the upper plate are performed to study the interference between these two processes at crustal levels and in the lithospheric mantle the models demonstrate that intra continental subduction and coeval lateral extrusion of the upper plate are compatible processes leading to similar deformation structures within the extruding region as compared to the classical setup lithosphere scale indentation strong coupling across the subduction boundary allows for the transfer of stresses to the upper plate where strain regimes are characterized by crustal thickening near a confined margin and dominated by lateral displacement of material near a weak lateral confinement the strain regimes propagate laterally during ongoing convergence creating an area of overlap characterized by transpression when subduction is oblique to the convergence direction the upper plate is less deformed and as a consequence the amount of lateral extrusion decreases in addition strain is partitioned along the oblique plate boundary resulting in less subduction in expense of right lateral displacement close to the weak lateral confinement both oblique and orthogonal subduction models have a strong resemblance to lateral extrusion tectonics of the eastern alps europe where subduction of the adjacent adriatic plate beneath the eastern alps is debated our results imply that subduction of adria is a valid mechanisms to induce extrusion type deformation within the eastern alps lithosphere furthermore our findings suggest that the oligocene to late miocene structural evolution of the eastern alps reflects a phase of oblique subduction followed by a later stage of orthogonal subduction conform a miocene shift in the plate motion of adria oblique subduction also provides a viable mechanism to explain the rapid decrease in slab length of the adriatic plate beneath the eastern alps towards the pannonian basin

decadal water mass variations along 20 w in the northeastern atlantic ocean abstract water mass variations in the northeastern atlantic ocean along 20 w are analyzed with pentadal resolution over the past 15 years using data from four repeat occupations of a meridional hydrographic section running south from iceland the section was sampled in 1988 1993 1998 and 2003 the results are interpreted in the context of changes in air sea forcing ocean circulation and water properties associated with the north atlantic oscillation nao the nao index oscillated around zero from 1984 to 1988 was strongly positive from 1989 to 1995 after which it shifted to lower positive and occasionally negative values from 1996 to 2003 previously published studies suggest that after the 1995 1996 shift of the nao the subpolar gyre largely retreated to the northwest in the northeastern atlantic ocean resulting in an increasingly southeastern character of local water masses with time water property changes extending from the subpolar mode water spmw just below the seasonal pycnocline through the density range shared by mediterranean outflow water and subarctic intermediate water saiw along 20 w are consistent with changes in wind driven ocean circulation and air sea heat flux associated with shifts in the nao especially after accounting for ocean memory after periods of lower nao index the spmw is warmer saltier and lighter at these same times large increases of apparent oxygen utilization aou and potential vorticity are found at the spmw base consistent with spmw ventilation to lighter densities during lower nao index periods deeper and denser in the water column the cold fresh and dense saiw signature within the permanent pycnocline that was most strongly present in 1993 near the culmination of a period of high nao index is much reduced in 1988 and 1998 in 2003 after a prolonged period of lower nao index increasing influence of warmer saltier subtropical waters is clear within the permanent pycnocline the deep penetration of the changes implies that they are caused primarily by circulation changes resulting from nao associated wind shifts but changes in air sea heat flux could also have played a role

the physical oceanographic conditions along the mid atlantic ridge north of the azores in june july 2004 abstract during the mar eco expedition in june and july 2004 39 deep ctd stations were occupied with uneven spacing along the mid atlantic ridge mar between 41 n and 61 n the ctd stations coincided with the biological sampling stations and thus gave a detailed vertical description of the water properties at these locations many different water masses were identified however using the predominant water mass in the upper 500 m four different hydrographic regions were identified stations in the vicinity of the reykjanes ridge north of 57 n were dominated by modified north atlantic water mnaw stations south of 56 30 n and north of the sub polar front spf were dominated by sub arctic intermediate water saiw ctd data combined with along track continuous surface temperature and salinity measurements satellite sea level anomaly data and sea surface temperature sst and along track current data adcp data showed that the position of the spf was at about 52 n at the southern edge of the charlie gibbs fracture zone cgfz south of the spf a frontal region with both north atlantic central water nacw and saiw present was observed and south of about 50 n the predominant water mass in the upper 500 m was nacw a ship mounted rdi 75 khz adcp was operated during the cruise and yielded high quality data during the first leg the currents showed large variations over short distances and were strongly affected by topography the adcp data was be used to describe the mesoscale eddy field along the mar and to detect three jets in the north atlantic current nac data from a current meter mooring left for 10 months after the cruise at a seamount just to the south of cgfz showed the dominance of the tidal currents in the area typical spring tidal currents were about 0 15 m s 1 and the mean flow an order of magnitude smaller about 0 03 m s 1 a short term mooring on a seamount farther south showed tidal currents of 0 3 m s 1 binned 8 day 4 km sst satellite imagery were collected and processed for 2004 the sst data were analysed and showed characteristic frontal structures in the mar eco region

elastic shear modulus of bangkok clay during undrained triaxial compression introduction the elastic stiffness is one of the main parameters in performing elastic plastic analysis when compared with the effort given to formulating the complicated plasticity partner its importance is generally ignored by treating it as a constant throughout the analysis elastic stiffness is known to be a function of several factors including effective stress level anisotropy stress condition plasticity index and overconsolidation ratio abundant literature can be found on this topic e g hardin drnevich 1972 roesler 1979 yu richart 1984 yan byrne 1991 tatsuoka shibuya 1992 however information on the variation of elastic stiffness during shearing has been limited yu richart 1984 tanizawa et al 1994 kohata et al 1997 rampello et al 1997 the elastic shear modulus is generally expressed as a function of the effective stresses the most common stress component adopted is the effective mean stress p9 1 4 9 1 9 2 9 3 3 g 1 4 c p9 1

north atlantic surface circulation during the 1990 s observed with satellite tracked drifters a new compilation of lagrangian velocity observations describes the state of the north atlantic surface circulation during the 1990s gridded fields of velocity and eddy kinetic energy eke are constructed from trajectories of more than 1500 15 m drogued satellite tracked surface drifters in service between january 1990 and december 1999 this time period overlaps a coordinated field study of circulation and variability in the north atlantic completed between 1996 2000 as part of the world ocean circulation experiment we describe the construction of a self consistent drifter climatology present decadal mean quasi eulerian velocity and eke fields computed on a 1 grid and compare these results with contemporary satellite measurements detailed discussion of the inferred surface circulation is focused on three regions 1 the gulf stream and north atlantic current 2 the labrador sea and subpolar gyre and 3 the caribbean sea the swiftest drifter motions were found in the equatorial region and along the tropical subtropical and subpolar western boundaries the maximum instantaneous speed determined from a single quality controlled and filtered drifter observation was 273 cm s 1 in the gulf stream southeast of cape cod the highest eke value in the north atlantic 2790 cm2 s 2 was found in the gulf stream just downstream of the new england seamounts over most of the atlantic basin drifter derived eke values were found to be o 100 cm2 s 2 higher than corresponding values derived from satellite altimetry in the labrador sea a region of sharply elevated eke appears to be geographically related to the localized ejection of drifters and by extension mass and kinetic energy from the energetic west greenland current between 60 and 62 n when compared to drifter measurements made in the late 1970s our results suggest but do not statistically confirm an enhancement and slight northward shift of the zonal gulf stream extension such a shift is consistent in sign with expectations based on observed interdecadal variations in wind stress and subtropical gyre potential energy associated with the north atlantic oscillation

structure transports and transformations of the water masses in the atlantic subpolar gyre we discuss the distributions and transports of the main water masses in the north atlantic subpolar gyre naspg for the mean of the period 2002 2010 ovide sections 2002 2010 every other year as well as the inter annual variability of the water mass structure from 1997 4x and meteor sections to 2010 the water mass structure of the naspg quantitatively assessed by means of an optimum multiparameter analysis with 14 water masses was combined with the velocity fields resulting from previous studies using inverse models to obtain the water mass volume transports we also evaluate the relative contribution to the atlantic meridional overturning circulation amoc of the main water masses characterizing the naspg identifying the water masses that contribute to the amoc variability the reduction of the magnitude of the upper limb of the amoc between 1997 and the 2000s is associated with the reduction in the northward transport of the central waters this reduction of the northward flow of the amoc is partially compensated by the reduction of the southward flow of the lower limb of the amoc associated with the decrease in the transports of polar intermediate water and subpolar mode water spmw in the irminger basin we also decompose the flow over the reykjanes ridge from the east north atlantic basin to the irminger basin 9 4 4 7 sv into the contributions of the central waters 2 1 1 8 sv labrador sea water lsw 2 4 2 0 sv subarctic intermediate water saiw 4 0 0 5 sv and iceland scotland overflow water isow 0 9 0 9 sv once lsw and isow cross over the reykjanes ridge favoured by the strong mixing around it they leave the irminger basin through the deep to bottom levels the results also give insights into the water mass transformations within the naspg such as the contribution of the central waters and saiw to the formation of the different varieties of spmw due to air sea interaction

late holocene 0 2 4 ka bp surface water temperature and salinity variability feni drift ne atlantic ocean abstract planktonic foraminiferal mg ca ratios and oxygen isotopic compositions of a spliced sediment record from feni drift ne atlantic ocean box core m200309 and piston core enam9606 trace late holocene sea surface temperature sst and salinity changes over the past 2400 years at this location the variability of sst and oxygen isotopic composition of seawater 18 o w reflects variable northward advection of warm and saline surface waters which appears linked to climate variability over the adjacent european continent our records reveal a general long term cooling trend superimposed on this overall trend partly higher temperatures and salinities from 180 to 560 ad and 750 to 1160 ad may be ascribed to the roman and medieval warm periods respectively subsequently our record displays highly variable surface water conditions the main little ice age sst minimum is restricted to the 15th and 16th centuries ad pervasive multidecadal to centennial scale variability throughout the sedimentary proxy records can be partly attributed to solar forcing and or variable heat extraction from the surface ocean caused by shifts in the prevailing state of the north atlantic oscillation nao high salinities in the 17th and 18th centuries are considered to reflect tropical anomalies linked to a southward shift of the intertropical convergence zone propagating across the north atlantic ocean

vivaldi 1991 a study of the formation circulation and ventilation of eastern north atlantic central water abstract a synoptic hydrographic data set comprising 32 full depth ctd casts and 2500 ctd seasoar profiles to 500 m is used to describe the s properties and circulation of central water east of the mid atlantic ridge and between 39 n and 54 n eastward transport of 20 10 6 m 3 s 1 in the north atlantic current turns entirely northwards to the west of 54 n 20 w this transport consists in the upper layers of western north atlantic water freshened at temperatures below 10 c by mixing with subarctic intermediate water northern and southern branches of the north atlantic current are well defined and both turn northwards west of 20 w a further 10 10 6 m 3 s 1 of eastern north atlantic water forms and recirculates anticyclonically to the west of spain south of the north atlantic current and north of 40 n eastern north atlantic water is most weakly stratified east of 20 w and there is clear correlation between weakly stratified pycnostads and positive salinity anomalies relative to western north atlantic water thus eastern north atlantic water is a winter mode water in which strong winter cooling has increased the density and hence also the salinity anomaly at a given temperature near the southern entrance to the rockall trough there is evidence that salinities are also increased by mediterranean water influence circulation south of the north atlantic current is complex there is no evidence for direct ventilation southwards across 40 n where water properties s potential vorticity and cfc 113 and historical data all indicate westward ventilation east of 24 w with weak southward ventilation occurring further west in the vicinity of the azores the circulation pattern suggested is remarkably similar to that proposed by helland hansen and nansen in 1926 the eastern north atlantic geophysiske publicajoner 4 1 76 with anticyclonic circulation of colder eastern north atlantic water north of 40 n meeting warmer water from south of 40 n circulating cyclonically north of the azores current the distribution of pycnostads and s properties between 20 w and 35 w north of the azores indicates alternate bands of western and eastern north atlantic water moving eastward and westward respectively including evidence for westward motion immediately south of the southern branch of the north atlantic current possibly by westward propagation of anticyclonic eddies containing deep pycnostads

water masses and circulation pathways through the iceland basin during vivaldi 1996 quasi synoptic data from late 1996 spanning the subpolar north atlantic have been used to determine the major pathways of the north atlantic current nac at that time high spatial resolution allows fronts to be accurately positioned on each seasoar section a clearly defined front of the nac the southern branch turns north at around 25 w and continues through the middle of the iceland basin as far as 60 n 20 w a second branch the northern branch or subarctic front turns north around 30 w and retroflects westward north of 54 n to re enter the irminger basin and become part of the irminger current up the western side of the reykjanes ridge a third eastward branch turns sharply northwest at the mouth of the rockall trough to skirt the southwestern margin of hatton bank this branch carries a tongue of saline eastern north atlantic water enaw over hatton bank and in consequence enaw covers the whole of the hatton and rockall banks as well as the rockall trough bounded in the west by the southern branch the most saline water found in rockall trough spills out into the northern iceland basin between rockall and lousy banks this saline weakly stratified tongue can be traced westward to the south of iceland continuing southwestward along the eastern flank of the reykjanes ridge subarctic intermediate water is carried into the iceland basin creating a fresh tongue bounded east and west by the more saline enaw over hatton bank and the eastern flank of the reykjanes ridge respectively

observed variability of the north atlantic current in the rockall trough from 4 years of mooring measurements the rockall trough is one of the main conduits for warm atlantic water to the nordic seas ocean heat anomalies originating from the eastern subpolar gyre are known to influence arctic sea ice ex

the great salinity anomaly in the northern north atlantic 1968 1982 the widespread freshening of the upper 500 800m layer of the northern north atlantic which this paper describes represents one of the most persistent and extreme variations in global ocean climate yet observed in this century though a range of explanations have been advanced to explain this event including in situ changes in the surface moisture flux this paper describes the great salinity anomaly as largely though not entirely an advective event traceable around the atlantic subpolar gyre for over 14 years from its origins north of iceland in the mid to late 1960s until its return to the greenland sea in 1981 1982 the overall propagation speed around this subpolar gyre is estimated at about 3cm s 1 of the total salt deficit associated with the anomaly as it passed south along the labrador coast in 1971 1973 about 72 109 tonnes a deficit equivalent to about two thirds of this figure 47 109 tonnes ultimately passed through the faroe shetland channel to the barents sea arctic ocean and greenland sea during the mid 1970s possible effects on deep water formation and on the representativeness of historical section data are discussed

north atlantic oscillation induced changes of the upper layer circulation in the northern north atlantic ocean 1 hydrographic data of the 1990s along world ocean circulation experiment sections a1e greenland ireland and a2 newfoundland france indicate a redistribution of cold low saline subarctic waters and warm saline subtropical waters in the upper layer of the northern north atlantic within about 2 years after the north atlantic oscillation had turned from a period with strong westerlies until 1995 to a period with weak westerlies in 1996 and 1997 in the latter period subarctic waters spread preferably southward along the continental slope east of newfoundland rather than eastward with the north atlantic current nac into the irminger iceland and west european basins as a consequence the subarctic front and the associated nac shifted eastward in the newfoundland basin where subarctic waters accumulate and westward in the iceland basin where a large warm and saline anomaly was found in 1996 and 1997 indicating a contraction of the subpolar gyre in the irminger basin the anomaly occurred in 1998 and 1999 whereas the cyclonic circulation in the irminger and iceland basins weakened it intensified in the newfoundland basin where a strengthened labrador current retroflection joined the nac this and the increased anticyclonic recirculation of subtropical waters in the newfoundland and west european basins caused a considerable reduction of the northward heat transport across 47 n in the upper layer in 1997 the anticyclonic circulation occurring in the west european basin suggested a northward expansion of the subtropical gyre

evolution of subpolar north atlantic surface circulation since the early holocene inferred from planktic foraminifera faunal and stable isotope records abstract past changes in the surface flow regime of two main eastern north atlantic warm water pathways toward the nordic seas were reconstructed based on faunal analyses in combination with carbon and oxygen stable isotope measurements in planktic foraminifera the investigated sites in the surroundings of the faroe islands are located in the transitional area where surface waters of subpolar and subtropical origin mix before entering the arctic mediterranean in these areas large amplitude millennial variability in the characteristics of the upper water column appears modulated by changes in the intensity of the subpolar gyre circulation from 7 8 to 6 ka bp faunal records indicate a deep mixed layer which in conjunction with lighter 18 o values suggest that the inflowing atlantic waters were dominated by a relatively cooler and fresher water mass reflecting a strengthening of the subpolar gyre under conditions of enhanced positive nao like forcing and reduced meltwater input a shift in the hydrographic conditions occurred during the mid holocene centered at 5 ka bp at this time increasing upper water column stratification and the incipient differentiation of the stable isotopic signal of the iceland faroe and faroe shetland surface water masses suggest increasing influx of warmer more saline surface waters from the subtropical gyre as subpolar gyre circulation weakened the mid holocene decline in subpolar gyre strength is presumably related to a shift toward a low state of the nao like forcing associated with decreased solar irradiance later in the holocene from 4 ka bp to present the increased frequency and reduced amplitude of the surface hydrographic changes reflect corresponding fluctuations in subpolar gyre circulation these high frequency oscillations in subpolar gyre strength suggest increased surface circulation sensitivity to moderate freshwater fluxes to the labrador irminger sea basin highlighting the importance of the salinity balance in modulating subpolar gyre dynamics particularly under conditions of low nao atmospheric forcing

the water masses of the central north atlantic in 1983 84 abstract hydrographic surveys carried out in 1983 84 along both sides of the mid atlantic ridge between 24 and 53 n provide a detailed description of the well known north atlantic water masses with particular emphasis on their meridional distribution and zonal dissymetry in the upper layers the dense horizontal sampling resolves the several narrow gulf stream extensions into the ocean interior giving the image in the central water density range of a mosaic of mode waters separated by fronts at intermediate depths a vertical shear in the distributions of the mediterranean water and labrador sea water stands out both water masses having their lower part displaced southwards relative to their upper parts bottom waters containing nearly 20 percent of pure antarctic bottom water are observed at 50 n in the eastern basin in contrast with the western basin where proportions greater than 10 percent were found only south of 36 n along our section this water mass analysis also gives indications that stron

the flux of dense cold overflow water southeast of iceland abstract from the period commencing midsummer 1990 and lasting for 13 months 13 current meters were deployed on seven moorings at depths between 1000 and 2300 m southeast of iceland 63 09 n 17 18 w to 61 44 n 15 24 w the purpose of the array designated woce acm8 was to measure the overflow of dense water downstream of the source in the faeroe bank channel and downstream of any sources on the iceland faeroe ridge in the depth range 1300 2100 m three of the moorings showed a bottom intensified current that was persistent and directed to the southwest at the other moorings the current was erratic and weak the records were combined to form a transport time series for water denser than 0 27 8 kg m 3 in the direction 240 a mean value of 3 2 0 5 sv was found with considerable variability near a period of seven days but there was no convincing evidence for a seasonal signal the amount of pure norwegian sea water present in the overflow was estimated at 1 6 0 15 sv close to previous determina

interannual variability of the subpolar mode water properties over the reykjanes ridge during 1990 2006 combining hydrographic data from the ovide observatoire de la variabilite interannuelle a decennale observatory of the interannual to decadal variability section greenland portugal with argo and historical ctd data over the period 1990 2006 we estimate the variability of the core properties of a variety of subpolar mode water spmw observed on the eastern flank of the reykjanes ridge this spmw acquires its core properties in the winter mixed layer along the eastern side of the reykjanes ridge we find that the february sea surface temperature along the ridge is a proxy for its core temperature the sources of this mode water are water masses advected by the mean cyclonic circulation in the iceland basin a density compensated tendency for cooling and freshening of the spmw core properties is observed in the early 1990s it stops in 1996 and is followed by an increase in temperature and salinity 1 41 c and 0 11 psu and a decrease in density 0 12 kg m 3 until at least 2003 during the entire period the data do not show any significant modification in the depth of the mode water core while they suggest that the thickness of the layer shrank the variability of the local air sea freshwater and heat fluxes cannot explain the observed salinity and temperature variations they are most likely related to the modifications of the properties of the spmw sources due to the recently evidenced changes driven by the north atlantic oscillation in the relative contributions of subtropical waters and subpolar waters in the iceland basin

vertical distribution 0 1000 m of macrozooplankton estimated using the underwater video profiler in different hydrographic regimes along the northern portion of the mid atlantic ridge abstract the vertical distribution 0 1000 m depth of macrozooplankton along the northern portion of the mid atlantic ridge 59 58n 25 53w to 41 29n 28 19w was investigated during the mar eco program june and july 2004 using the underwater video profiler uvp twelve relatively large 1 cm groups were selected from the recorded images sarcodines with two sub groups crustaceans excluding copepods chaetognaths ctenophores with two sub groups cydippids and lobates siphonophores medusae with three sub groups aeginura grimaldii aglantha spp and all other medusae appendicularians and thaliaceans the numerically dominant groups over the whole area were crustaceans 26 medusae 20 and appendicularians 17 the gelatinous fauna were consistently most numerous at 400 900 m appendicularians ctenophores and aeginura grimaldii occurred mostly below 300 m maximum concentrations of 75 58 and 30 individuals 100 m 3 respectively siphonophores aglantha spp and the other medusae were more uniformly distributed in the water column maxima of 42 42 and 300 individuals 100 m 3 respectively the macrozooplankton community below 200 m varied with the spatial distribution of the water masses suggesting that the sub polar front restricts the mixing of macrozooplankton communities down to 1000 m depth

a simplified nonlinear settlement prediction model for foundations on sand this paper presents a simple method for predicting the settlement of spread foundations on sand operating under typical working loads the method accounts for the well known effects on soil stiffness of strain stress level and density dependence but adopts the simplifying assumption that the stress distribution beneath a loaded foundation can be obtained from boussinesq s equations for an elastic half space despite this simplification the method is shown to predict foundation responses that closely match those computed using more sophisticated finite element fe analyses and those measured in laboratory footing tests where the stiffness characteristics in triaxial compression were well defined the method is also seen to predict general variations of foundation settlement with bearing pressure foundation width and degree of preloading that are entirely consistent with empirically observed trends it is concluded that satisfactory settlement predictions for shallow foundations on cohesionless soil may be obtained using boussinesq s equations if the soil s vertical stiffness characteristics as inferred from triaxial compression data can be specified with some degree of precision

hydrography and through flow in the north eastern north atlantic ocean the nansen project abstract the circulation and hydrography of the north eastern north atlantic has been studied with an emphasis on the upper layers and the deep water types which take part in the thermohaline overturning of the oceanic conveyor belt over 900 hydrographic stations were used for this study mainly from the 1987 1991 period the hydrographic properties of subpolar mode water in the upper layer which is transported towards the norwegian sea showed large regional variation the deep water mass was dominated by the cold inflow of deep water from the norwegian sea and by a cyclonic recirculation of lower deep water with a high antarctic bottom water content at intermediate levels the dominating water type was labrador sea water with only minor influence of mediterranean sea water in the permanent pycnocline traces of antarctic intermediate water were found geostrophic transports have been estimated and these agreed in order of magnitude with the local heat budget with current measurements with data from surface drifters and with the observed water mass modification a total of 23 sv of surface water entered the region of which 20 sv originated from the north atlantic current while 3 sv entered via an eastern boundary current of this total 13 sv of surface water left the area across the reykjanes ridge and 7 sv entered the norwegian sea while 3 sv was entrained by the cold overflow across the iceland scotland ridge approximately 1 4 sv of norwegian sea deep water was involved in the overflow into the iceland basin which with about 1 1 sv of entrained water and 1 1 sv recirculating lower deep water formed a deep northern boundary current in the iceland basin at intermediate depths where labrador sea water formed the dominant water type about 2 sv of entrained surface water contributed to a saline water mass which was transported westwards along the south icelandic slope