salinity change in the subtropical atlantic secular increase and teleconnections to the north atlantic oscillation 1 recent studies comparing shipboard data between the 1950 s and the 1990 s have shown significant heterogeneous adjustments of the temperature salinity structure of the n atlantic ocean here we present proxy records of temperature and salinity from aragonite sclerosponge skeletons extending existing records of the salinity maximum waters smw of the n atlantic back to 1890 these proxy records show secular temperature increases of 1 6 2 0 c higher than published global averages and salinity increases of 0 35 0 5 psu smaller than short term secular trends recently measured salinity reconstructions vary more significantly on the decadal scale showing changes that are related to low frequency variations of the north atlantic oscillation nao on both secular and decadal time scales the records indicate significant thermohaline changes in the smw either via forcing at the surface or increasing depths of density surfaces in the bahamas

effect of drilling fluids on coal permeability impact on horizontal wellbore stability the objective of this study was to evaluate a series of mud systems and additives typically used in coalbed methane drilling in terms of formation of an instantaneous filter cake ability of the coal reservoir to rid itself of the filter cake during production and overall impact on coal permeability to achieve this a series of laboratory tests were conducted initially using artificially cleated gypstone rock to simulate coal this was followed by the use of large diameter coal cores which unfortunately did not allow for the tests to be done under in situ confining stress conditions the three mud systems tested against coal xantham gum hec and na cmc did not have a negative impact on coal permeability in contrast to previous laboratory data that showed large decreases two fluid loss control additives which have been used successfully in drilling clastic and carbonate rocks were also tested using a non ionic polymer mud system during simulated drilling these additives flc 2000 and q stop were very effective in building a thin filter cake on the coal surface almost instantaneously to the point that no solids were detected in the downstream fluid accumulator during simulated production a small pressure drop was sufficient to remove the filter cake coal permeability to water returned to its original pre test value which suggested that there was no permanent permeability damage caused by the two additives when coal derived fines were added to the drilling mud in another experiment using the same coal the near wellbore coal permeability was reduced by 87 5 indicating severe damage to the cleat system and in agreement with previously reported laboratory data following the very good performance of flc 2000 and q stop in the laboratory tests these two additives were then used in field applications their presence in the drilling fluid resulted in the successful drilling of 953 m and 1400 m of total horizontal length in the deep mannville coals in alberta at true vertical depth of 1400 m and 1150 m respectively no borehole instability problems were encountered during drilling of the two horizontal wellbores the monitored mud losses were low in both cases with the horizontal well 2 experiencing lower mud loss possibly as a result of the absence of large fractures encountered along the horizontal path horizontal well 1 remained stable which allowed sufficient time to insert a production liner

does stommel s mixed layer demon work abstract stommel argued that the seasonal cycle leads to a bias in the coupling between the surface mixed layer and the main thermocline of the ocean he suggested that a demon operated that effectively only allowed fluid at the end of winter to pass from the mixed layer into the main thermocline in this study stommel s hypothesis is examined using diagnostics from a time dependent coupled mixed layer primitive equation model of the north atlantic cme the influence of the seasonal cycle on the properties of the main thermocline is investigated using two methods in the first the rate and timing of subduction into the main thermocline is diagnosed using kinematic methods from the 1 resolution cme fields in the second tracer diagnostics of the cme and idealized experiments using a date tracer identifying the timing of subduction are performed over the subtropical gyre both approaches generally support stommel s hypothesis that fluid is only transferred from the mixed layer into the main therm

inferring the subduction rate and period over the north atlantic abstract the annual rate at which mixed layer fluid is transferred into the permanent thermocline that is the annual subduction rate sann and the effective subduction period x1d4af eff is inferred from climatological data in the north atlantic from its kinematic definition sann is obtained by summing the vertical velocity at the base of the winter mixed layer with the lateral induction of fluid through the sloping base of the winter mixed layer geostrophic velocity fields computed from the levitus climatology assuming a level of no motion at 2 5 km are used the vertical velocity at the base of the mixed layer is deduced from observed surface ekman pumping velocities and linear vorticity balance a plausible pattern of sann is obtained with subduction rates over the subtropical gyre approaching 100 m yr twice the maximum rate of ekman pumping the subduction period x1d4af eff is found by viewing subduction as a transformation process converting mixed layer fluid into stratified thermocline fluid the effective

salinity changes along the upper limb of the atlantic thermohaline circulation lagrangian analyses of a global ocean circulation model quantify the salinity changes experienced by the warm limb of the thermohaline circulation during the northward flow to the atlantic deep convection regions 6 sv out of the estimated 10 sv transfer from 45 s to 47 n flow through regions of prevailing surface evaporation the southern and northern formation regions of salinity maximum water and the gulf of cadiz mediterranean sea domain the remaining transport gains salinity through mixing with adjacent waters as much as 6 sv flow through the low salinity surface mixed layer at the latitudes of the itcz whose effect annihilates that of the southern region of salinity maximum water most of the salinity increase corresponds to the transformation of south to north atlantic central water with strong diapycnal transfers for the water that intersects the high and low salinity regions and nearly isopycnal modifications for the water that avoids these regions

generation mechanism of spiciness anomalies an ogcm analysis in the north atlantic subtropical gyre oceanic teleconnections between the low and midlatitudes are a key mechanism to understanding the climate variability spiciness anomalies density compensated anomalies have been shown to transport temperature and salinity signals when propagating along current streamlines in the subtropical gyres of the atlantic and pacific oceans the generation mechanism of spiciness anomalies in the north atlantic subtropical gyre is investigated using an analytical model based on the late winter subduction of salinity and temperatureanomalies along isopycnal surfaces the keystone ofthis approachisthe change ofthe coordinates frame from isobaric to isopycnic surfaces suited for subduction problems the isopycnal nature of spiciness anomalies and the use of a linear density equation allows for the analytical model to depend only upon surface temperature and salinity anomalies the mean thermocline currents and the surface density ratio this model clarifies and above all quantifies the mechanism by which surface temperature and salinity anomalies are modulated by density ratios to produce fully different isopycnal temperature and salinity anomalies

formation of salinity maximum water and its contribution to the overturning circulation in the north atlantic as revealed by a global general circulation model 1 the formation of salinity maximum water in the north atlantic is investigated using a simulated passive tracer and its adjoint the results reveal that most salinity maximum water in the north atlantic comes from the northwestern part of the subtropical gyre and direct contribution from the evaporation precipitation maximum region via the surface ekman current is minor water originating from the evaporation precipitation maximum region has to recirculate in the subtropical gyre before entering the sea surface salinity maximum region from the northwest once subducted some portion 10 of the salinity maximum water enters the equatorial region in the shallow subtropical cell but most 70 of it appears to turn northward to join the north atlantic deep water the latter pathway involves a three dimensional circulation when the warm fresh surface water flows northward along the western boundary it turns eastward in the northern subtropical gyre as a result of the large excess of evaporation over precipitation this water gradually gains its salinity on the route until it reaches the sea surface salinity maximum region in the central subtropical gyre from there the salinity maximum water is subducted and flows back to the western boundary in the depth range of the thermocline with its high salinity nature a major portion of this water penetrates into the subpolar region and directly contributes to the deep thermohaline circulation

seasonal changes in beach topography and beach volume in delaware abstract a beach study was conducted along a shore segment of the delaware coast from march 1982 through to april 1983 results indicate that beach topography and beach volume varied with changes in wave climatic regimes the regimes in turn were generally in phase with the winter and summer seasons because both the magnitude and frequency of storm waves were higher during winter than in summer the winter beach shape was concave upward following the winter storms of 1981 1982 swells rebuilt the beach in two stages from march through to august 1982 in the first stage the beach vertically accreted aggraded and in the second it laterally accreted prograded the aggrading stage involved the welding of a swash bar to the foreshore thereafter swash overtopping caused deposition on and landward of the bar in time the swash bar attained a berm and swale topography the prograding stage started when the swash could no longer overtop the berm crest which confined deposition to the foreshore this stage occurred following a minor or moderate storm event that shifted the berm crest upward and landward or during a neap tidal stage that occurred after the construction of a spring tide berm between march and the end of august 1982 60 m 3 of sediments per 1 m of beach were deposited on the shore of this value 67 was attributed to aggradational processes while the remaining 33 was attributed to progradational processes swells as well as storm waves caused vertical accretion storm waves contributed 20 of the total sediment volume deposited on the beach when the shore was at its maximum sediment volume for 1982 the beach topography was convex upward an inverse relationship existed between the mean monthly sediment volume and the mean monthly surge variability the surge level was used as an index of wave conditions high surge levels were associated with large waves while low surge levels were associated with small waves when surge variability was high during the winter sediment volume on the beach was low and conversely when surge variability was low in summer sediment volume was high correlation analysis showed that 80 of the variance of the mean monthly sediment volume was explained by the mean monthly surge variability

a simple model of the mass exchange between the subtropical and tropical ocean abstract a simple ventilated thermocline model is used to study the subtropical tropical mass exchange it is found that the water subducted in the western subtropical gyre recirculating window tends to recirculate within the subtropical gyre while the water subducted in the eastern part exchange window tends to penetrate equatorward the exchange window expands with an increased easterly wind or basin width on the southern boundary of the subtropical gyre but shrinks with an increased wind curl within the subtropical gyre furthermore the total exchange transport increases with the easterly wind or the width of the basin on the southern boundary of the subtropical gyre but it is independent of subtropical wind the ventilation mechanism is important in supporting the exchange transport for wind with realistic strength at the southern boundary the reduction of the exchange transport is about 15 30 of the ekman transport finally relative to the exchange transport in the interior of the ocean

crossing of the equator by the deep western boundary current in the western atlantic ocean abstract property distributions and geostrophic shear from a hydrographic section near 37 w in the atlantic ocean show the deep western boundary current dwbc in the north atlantic deep water nadw established against the western boundary of the brazil basin immediately south of the equator between 2 and 5 s the dwbc thus has directly crossed the equator to the south atlantic following the east southeast trend of the continental slope isobaths the estimated dwbc transport of nadw is 35 106 m3 s 1 similar to other estimates from the tropics discussed here these large dwbc transports are opposed by flow of deep water to the north atlantic immediately offshore of the dwbc with as much as two thirds of the dwbc transport being returned as these recirculations one recirculation center is the guiana basin north of the equator but extends at least a few hundred kilometers south of the equator another is visible at 11 s in the brazil basin the degree of connection of these two observed recirculatio

seasonal variation of mid foreshore sediments at a delaware beach abstract from march 1982 through april 1983 at a delaware beach there was a modest but significant relation between the first three moments of mid foreshore sediment distributions and surge variability based on monthly averages as surge variability increased from summer to winter that is as the magnitude and frequency of storm waves increased the mean grain size increased sorting improved and skewness became more positive the reverse was also noted from winter to summer the results of stepwise regression analysis showed that mean particle size was highly influenced by the percentage of fine sands between 2 25 and 2 75 fines which was relatively high in summer and low in winter sorting was most sensitive to the extent of the coarse tail in a sediment sample as this tail was extended sorting became poorer the extent of the coarse tail and the percentage of fines explained most the variance of skewness as the coarse end of a sediment sample was extended and as the percentage of fines increased skewness became more negative

3h and 3he in the beta triangle observations of gyre ventilation and oxygen utilization rates abstract isopycnal maps of 3h 3he age with about 100 km resolution have been obtained for a 1000 km scale area in the eastern subtropical north atlantic the midscale texture of the maps is consistent with isopycnal diffusivities of order 500 m 2 s 1 analysis of the distributions within the context of advection diffusion equations reveals that the larger scale 3h 3he age gradients observed within the area are not seriously affected by mixing on those surfaces that outcrop in the region of ekman downwelling thus isopycnal velocities can be estimated from 1 but record only the velocity component normal to the outcrop the velocities thus obtained agree well with geostrophic estimates although the comparison is flawed by the fundamental mismatch in timescales between the two techniques backward extrapolation of the maps to zero age outcrop positions indicate that the contribution of unventilated older recirculated water to the gyre flow above 600 m depth is small in this area no more than 20

a lagrangian numerical investigation of the origins and fates of the salinity maximum water in the atlantic the origins and fates of the atlantic salinity maximum water smw formed through excess evaporation in the tropics and subtropics of both hemispheres are studied using monthly mean outputs of a numerical simulation of the world ocean climatological circulation after defining formation domains from the surface salinity field and the vertical stratification a lagrangian technique is used to estimate the formation rates and main pathways in each hemisphere and the role of this water in the framework of the warm water return flow of the meridional overturning cell formation rates around 9 and 11 sv are found in the southern and northern hemispheres respectively while the export of the southern smw from its formation area is realized by the western boundary currents that of the northern smw mainly results from interior subduction equatorward of the formation regions a fraction of each smw variety is entrained in the subtropical cells that connect the subtropics to the equatorial region poleward of them both varieties are seen to feed the regions of subtropical mode water stmw formation around 35 of latitude in both hemispheres the bulk of the transport associated with each variety eventually turns northward this amounts to 6 sv of southern smw gathered in the north brazil undercurrent nbuc and 10 sv of northern smw found in the gulf stream at 35 n of which 8 sv have gone through the caribbean sea of the 13 4 sv northward transport of the meridional overturning cell estimated by the model at 47 n more than 50 6 9 sv is found to have transited through at least one of the smw regions this gives an indication of the likely important role of smw formation in the observed northward salinity increase of the upper atlantic ocean

behavior of grain size characteristics on reflective and dissipative foreshores broken bay australia abstract beach morphology wave current dynamics or sediment attributes such as grain size changes and sorting processes intrinsically characterize each other the extreme cases of the morphological spectrum include reflective beaches which are steep and devoid of inshore topographic expression or surf zone circulation and dissipative beaches which are flat and have inshore barred topography with attendant longshore currents and rips for a study of four beaches in broken bay australia representing these morphological extremes four facts become obvious first reflective beaches have rapid variaiton in foreshore grain size alongshore mean settling velocity changes greater than 0 3 log10 cm sec km grain size changes greater than 0 2 mm km whereas dissipative beaches have weak r variation mean settling velocity changes approximate 0 1 log10 cm sec km grain size changes less than 0 1 mm km second the pattern on reflective foreshores remains fixed over time whereas the pattern on dissipative foreshores varies to the point that size gradients can reverse direction within one year third this temporal variation reflects the directional width of the incoming wave spectra and not changes in the level of wave power reflective beaches have waves approaching almost shore normal because of the nullification of deep water variation by wave refraction or by the sheltering effects of headlands wave approach on dissipative beaches varies daily and the beach planform and sediment must respond over time to this variation fourth grain size changes fit one of two postulates the energy postulate states that grain size and sorting increase along a foreshore as energy increases the drift postulate states that grain size increases downdrift the energy postulate is more appropriate on reflective beaches whereas the drift postulate accounts for the difference in the magnitude of grain size changes alongshore between reflective and dissipative beaches on reflective foreshores coarse material is naturally concentration at the base of the swash zone because of gravity effects or shear sorting in backwash larger grains here move faster alongshore than finer ones near the top of the foreshore because longshore currents at the base of the swash are stronger than the zigzag motion of swash drift further up the beach face this drift sorti g produces strong longshore size gradings on the foreshore this effect is negated on dissipative beaches by swash bore transport of coarse grains upslope by dilution with inshore sediment that has undergone preferential movement of fines alongshore in suspension and by locally reversed longshore currents near rips

an interpretation of trends in grain size measures abstract the mean grain size sorting and skewness of a sedimentary deposit are dependent on the sediment grain size distribution of its source and the sedimentary processes of i winnowing erosion ii selective deposition of the grain size distribution in transport and iii total deposition of the sediment in transport if a source sediment undergoes erosion and the resultant sediment in transport is deposited completely the deposit must be finer better sorted and more negatively skewed than the source this trend is referred to as case i the lag remaining after erosion on the other hand must be coarser better sorted and more positively skewed case ii if sediment in transport undergoes selective deposition the resultant deposit can either be finer case iiia or coarser cas iiib than the source but the sorting will be better and the skew more positive although exceptions to these trends may occur they suggest that comparison of one sediment must be made with another for the proper identification of the sedimentary process and therefore it is not possible for a single grain size distribution to identify the depositional environment the trends also suggest that the skewness of a grain size distribution has been widely misinterpreted and implies neither the truncation of one of the tails nor the mixing of more than one mode rather a skewed sediment is the natural result of the sedimentary process in a system of related environments these trends can be used to identify both the probable source and the probable deposit and by inference the net sediment transport paths among sedimentary deposits such an analysis provides a rapid understanding of the sedimentary processes identifies patterns of erosion and accretion and may suggest transport processes

evidence for calcification depth change of globorotalia truncatulinoides between deglaciation and holocene in the western atlantic ocean abstract measurements of the 18o in tests of planktonic and benthic foraminifera in the florida straits are used to reconstruct the properties of the water column through time over the last 12 ka lynch stieglitz et al in press the isotopic composition of the foraminifera largely reflects the vertical density gradient we use this reconstruction and 18o measurements on globorotalia truncatulinoides in a nearby core to track the depth habitat of this species from the last deglaciation to 1 6 ka b p around 9 ka g truncatulinoides was calcifying in much shallower water than during the late holocene the downward migration toward its modern habitat is a regional phenomenon over the western tropical atlantic continental slope the cause is still unclear but we hypothesize that the shallower calcification depth may be a response to the presence of glacial melt water or to circulation changes this study points to the value of further study of the ecology life cycle and calcification depth for g truncatulinoides and other planktonic foraminifera that are used to reconstruct the history of the thermocline and upper water column structure

north atlantic subtropical underwater and its year to year variability in annual subduction rate during the argo period abstractsubtropical underwater stuw and its year to year variability in annual subduction rate are investigated using recently available argo data in the north atlantic for the period of observation 2002 14 the mean annual subduction rate of the stuw is 7 3 1 2 sv 1 sv 106 m3 s 1 within the density range between 25 0 and 26 0 kg m 3 once subducted the stuw spreads in the subtropical gyre as a vertical salinity maximum in the mean the spatial changes in temperature and salinity of the stuw tend to compensate each other and the density of the water mass remains rather stable near 25 5 kg m 3 in the southwestern part of the subtropical gyre the annual subduction rate of the stuw varies from year to year and most of this variability is due to lateral induction which in turn is directly linked to the variability of the winter mixed layer depth through modulation of surface buoyancy wind anomalies associated with the north atlantic oscillation are primarily responsible for this variability

thorium distributions in high and low dust regions and the significance for iron supply thorium and uranium isotopes 232th 230th 238u and 234u were investigated to refine their use for estimating mineral dust deposition and fe delivery to the ocean u concentrations and isotope ratios were consistent with conservative behavior and can safely be described using published u salinity relationships and global average seawater isotopic composition near barbados waters affected by the amazon outflow contained elevated 232th this signals one region where the thorium dust method is inaccurate because of a confounding continental input dissolved 232th fluxes in this region suggest that amazonian fe supply to the adjacent open ocean is much larger than local atmospheric deposition the colloidal content of dissolved th south of bermuda was found to be quite small 2 6 similar to that found north of hawaii despite the order of magnitude higher dust deposition in the atlantic this finding supports the assumption that dissolved 232th and 230th are scavenged at the same rate despite their different sources and also sheds light on the increase of dissolved 232th fluxes with integrated depth outside the region influenced by amazon river waters dissolved 232th fluxes are compared with bermudan aerosol fe deposition to estimate that fractional th solubility is around 20 in this region finally new dissolved and soluble fe mn and cr data from the subtropical north pacific support the idea that fe concentrations in the remote ocean are highly buffered whereas 232th has a larger dynamic range between high and low dust regions

observation of spiciness interannual variability in the pacific pycnocline monthly gridded fields predominantly based on global argo in situ temperature and salinity data are used to analyze the density compensated anomaly of salinity spiciness anomaly in the pycnocline of the subtropical and tropical pacific ocean between 2004 and 2011 interannual variability in the formation propagation and fate of spiciness anomalies are investigated the spiciness anomalies propagate on the isopycnal surface sq 25 5 along the subtropical tropical pycnocline advected by the mean currents they reach the pacific western tropics in about 5 6 years in the southern hemisphere and about 7 8 years in the northern hemisphere their amplitude strongly diminishes along the way and only very weak spiciness anomalies seem to reach the equator in the western tropics a complex eof analysis of interannual salinity anomalies on sq 25 5 highlights two dominant modes of variability at interannual scale i the former shows a variability of 5 7 years predominant in the northern hemisphere and ii the latter displays an interannual variability of 2 to 3 years more marked in the southern hemisphere the significant correlation of this second mode with enso index suggests that spiciness formation in the southeastern pacific sep is affected by enso tropical interannual variability a diagnosis of the mechanisms governing the interannual generation of spiciness in the sep region leads the authors to suggest that the spiciness interannual variability in the sub surface is linked to the equatorward migration of the isopycnal outcrop line sq 25 5 into the area of maximum salinity quantitative analysis based on turner angle reveals the dominance of the spiciness injection mechanism occurring through convective mixing at the base of mixed layer

the subpolar mode water of the north atlantic ocean abstract the warm waters of the subtropical and subpolar basins of the north atlantic have tight regional temperature salinity relationships and are conventionally called the regional central waters a volumetric census of the temperature salinity characteristics of the north atlantic by wright and worthington 1970 shows that waters characterized by certain segments of the t s relationships have large volumes compared to those of other segments volumetric mode waters such mode waters appear as layers with increased vertical separation between isopycnals pycnostads the present study reports on the existence of pycnostads in the central and eastern north atlantic these subpolar mode waters are formed by deep winter convection in the subpolar north atlantic and participate in the upper water circulation of the northern north atlantic the seasonal outcropping of the pycnostads occurs within and adjacent to the north atlantic current the irminger current the east and west greenland currents and

ventilation of the north atlantic and north pacific subduction versus obduction abstract ventilation in the north atlantic and north pacific is examined by analyzing the levitus climatological data and the hellerman and rosenstein wind stress data ventilation between the permanent pycnocline and the overlying seasonal pycnocline and mixed layer consists of two physical processes subduction and obduction subduction takes place mainly in the subtropical basin where surface water is irreversibly transferred into the permanent pycnocline below obduction takes place in the subpolar basin where water from the permanent pycnocline is irreversibly transferred into the mixed layer above veatilation in the north atlantic and north pacific can be clarified into four physically different regions the subductive region the obductive region the ambiductive region where both subduction and obduction take place and the insulated region where neither subduction nor obduction occurs although the total subduction rates in these two oceans are comparable the total obduction rates are considera

kinematics of the pacific equatorial undercurrent an eulerian and lagrangian approach from gcm results abstract three dimensional monthly velocity fields from an ocean general circulation model are used to study the annual mean mass balance of the pacific equatorial undercurrent euc eulerian diagnostics are used to evaluate the various meridional vertical and zonal mass fluxes related to the euc there are several distinct regimes along the equator showing clear asymmetries between the western and eastern parts of the basin and between the northern and southern edges of the euc meridional fluxes are decomposed into pure ekman divergence and geostrophic convergence and it is shown that the asymmetries are mainly related to the spatial structure of the ekman divergence and thus to that of the trade winds lagrangian calculations are used to evaluate accurately the mass transfers between various sections of the euc and between the euc domain and the tropics the authors show that geostrophic convergence only ventilates the upper layers of the euc and that the euc really is a tongue of water flowing

the water masses along the western boundary of the south and equatorial atlantic a quasi meridional hydrographic section located offshore from south america from 50 s to 10 n and three shorter transverse lines to the continental slope are used for a descriptive study of the water masses along the western boundary of the south and equatorial atlantic at the upper and intermediate levels the tracer analysis provides geographical limits of the wind driven circulation regimes and a comparison of the tracer values at the continental slope and along the meridional section shows where the boundary currents originate at depths shallower than about 200 m the subdivision of the subtropical gyre into two cells separated by the subtropical countercurrent near 28 s that was pointed out in a previous study is corroborated south of this front a warm variety 18 c of subtropical mode water in the inner recirculation of the brazil current appears despite its limited extent as a southern counterpart of the north atlantic 18 c water at the deep levels the upper circumpolar water and upper north atlantic deep water enter the south atlantic in a significantly overlapping density range the ensuing lateral encounter of both water masses occurs at 26 s near the western boundary where most of the boundary flow of the latter water is stopped and deflected seaward by the base of the subtropical gyre other tracer anomalies signal significant eastward escapes of north atlantic deep water within two jets at about two degrees of latitude on either side of the equator in another narrow current at 10 s and at 34 s the latter latitude marks the confluence and eastward deflection of the opposite boundary currents of lower north atlantic deep water and lower circumpolar water near the bottom of the argentine basin the weddell sea deep water that flows westward north of the zapiola ridge is more recently ventilated than the water carried by the boundary current near the falkland escarpment while a part of it flows anticyclonically around the ridge another part turns equatorward and enhances the southern property signatures of the water farther north

evidence of multidecadal salinity variability in the eastern tropical north atlantic 1 ocean circulation and global climate are strongly influenced by seawater density which is itself controlled by salinity and temperature although adequate instrumental sea surface temperature sst records exist for most of the surface oceans over the past 100 150 years records of salinity really only exist for the last 40 50 years here we show that longer proxy records from corals siderastrea radians in the eastern tropical north atlantic are dominated by multidecadal variations in salinity which are correlated with the relationship between sst and the north atlantic oscillation nao over the course of the 20th century the data reveal an increase in eastern tropical north atlantic salinity of 0 5 practical salinity units psu between about 1950 and 1990 rather than a monotonic secular increase as indicated by some instrumental records the preinstrumental coral proxy records presented here suggest that salinity in the tropical north atlantic is periodic on a decadal to multidecadal scale

water masses and circulation in the surface layers of the caribbean at 66 w a meridional hydrographic section was made in august september 1997 at 66 w from the coast of venezuela to woods hole aboard the r v knorr in this report we concentrate on near surface measurements in the caribbean the data show two distinct water masses with different origins from approximately 14 n to puerto rico caribbean surface water and subtropical under water with their source in the north atlantic are found as previously observed from venezuela to approximately 13 n a less saline water mass with its source in the tropics and south atlantic is found within the southern portion of the section two different velocity patterns are observed namely an eastward flow with a subsurface maximum near the coast of venezuela and a surface intensified westward jet with velocities of 130 cm s 1 in midbasin

poleward propagation of spiciness anomalies in the north atlantic ocean 1 recent modelling results suggest that subsurface salinity anomalies propagating from the tropics can reach and precondition the deep water formation regions thus modulating the thc variability the forcing and propagative aspects of this mechanism are presented in the north atlantic ocean over 1948 2002 using an ogcm density compensated salinity anomalies of 0 1 up to 0 35 psu along s 26 kg m 3 are generated in the salinity maximum region at interannual to decadal frequency the relation between subsurface conditions and late winter sea surface salinity variability supports the subduction mechanism they circulate over isopycnals ranging from 25 6s to 26 2s at current speed between 150 m and 250 m depth toward cape hatteras via the gulf of mexico on a typical 6 year transit although mixing along the pathway reduces the amplitude of salinity anomalies by about 66 they largely determine the subsurface spiciness of the gulf stream up to 30 n upstream of the outcrop region citation laurian a a lazar g reverdin k rodgers and p terray 2006 poleward propagation of spiciness anomalies in the north atlantic ocean geophys res lett 33 l13603

origin formation and variability of the subpolar mode water located over the reykjanes ridge the origin and formation of the subpolar mode water spmw located over the reykjanes ridge in the north atlantic ocean and the variability of its properties over the period 1966 2004 are investigated through the use of a global eddy permitting 1 4 degrees ocean sea ice model and a lagrangian analysis tool the spmw is fed by subtropical and subpolar waters advected by the branches of the north atlantic current the spmw acquires its properties when its source waters enter the winter mixed layer in the iceland basin the spmw temperature variability is mainly explained by variations of the relative contributions of the subtropical and subpolar water transports to the total transport compared to the 1966 2004 mean lower higher subtropical water relative transport contribution leads to colder warmer spmw in the early 1990s in the late 1960s and late 1990s the intensity of the winter convection in the iceland basin also influences the spmw temperature through the amount of relatively cold intermediate waters of subtropical origin integrated in the spmw layer strong convection partly explains the cold spmw of the early 1990s the large increase in the spmw temperature in the late 1990s is due to both a decrease in the winter convection and an increase in the relative transport of the subtropical waters

barrier layers in the tropical south atlantic mean dynamics and submesoscale effects abstractbarrier layers are generated when the surface mixed layer is shallower than the layer where temperature is well mixed in geographical regions where salinity plays a key role in setting up upper ocean density stratification in the tropical oceans thick barrier layers are also found in a latitude range where spiraling trajectories from surface in situ drifters suggest the presence of predominantly cyclonic submesoscale like vortices the authors explore these dynamical processes and their interplay in the present paper focusing on the tropical south atlantic ocean and using a high resolution modeling approach the objective is threefold to investigate the mean dynamics contributing to barrier layer formation in this region to study the distribution and seasonality of submesoscale features and to verify whether and how the submesoscale impacts barrier layer thickness the model used is the regional ocean modeling system roms in its adaptive grid refinement in fortran agrif online nested co

on the pathways of the equatorial subsurface currents in the eastern equatorial pacific and their contributions to the peru chile undercurrent 1 theconnections between theequatorial currentsystem andtheperu currentsystem in the eastern tropical pacific etp are examined with a primitive equations eddy resolving regional model the quasi equilibrium solutions reproduce three eastward equatorial subsurface currents of interest the equatorial undercurrent euc located between 1 n and 1 s the primary southern subsurface countercurrent psscc between 3 and 4 s and farther south the secondary southern subsurface countercurrent ssscc between 7 and 8 s using a lagrangian tracking procedure the fate of these currents in the etp and their contribution to the peru chile undercurrent pcuc are studied lagrangian diagnostics show that for the most part the euc water contributes to westward flows including the south equatorial current and deeper flows below it and strikingly only a very little fraction feeds the pcuc while a significant part of both ssccs contribute substantially mesoscale eddies are shown to exert an effect on these connections in addition about 30 of the pcuc is fed by the three subsurface equatorial flows euc psscc ssscc the remaining part of the pcuc comes from an alongshore recirculation associated with flows below it and from the southern part of the domain south of 9 s