spreading of greenland meltwaters in the ocean revealed by noble gases we present the first noble gas observations in a proglacial fjord in greenland providing an unprecedented view of surface and submarine melt pathways into the ocean using optimum multiparameter analysis noble gas concentrations remove large uncertainties inherent in previous studies of meltwater in greenland fjords we find glacially modified waters with submarine melt concentrations up to 0 66 0 09 and runoff 3 9 0 29 radiogenic enrichment of helium enables identification of ice sheet near bed melt 0 48 0 08 we identify distinct regions of meltwater export reflecting heterogeneous melt processes a surface layer of both runoff and submarine melt and an intermediate layer composed primarily of submarine melt intermediate ocean waters carry the majority of heat to the fjords glaciers and warmer deep waters are isolated from the ice edge the average entrainment ratio implies that ocean water masses are upwelled at a rate 30 times the combined glacial meltwater volume flux

on the intermediate water masses of the faroe bank channel overflow a review of available hydrographic data from the faroe bank channel indicates that north icelandic arctic intermediate water masses are present in the passage to a larger extent than was previously believed the presently compiled statistics including results on the seasonality are discussed in relation to previous investigations finally a high quality subset of the hydrographic data is used for an analysis of the alongchannel mixing of the intermediate water masses

glacial meltwater identification in the amundsen sea abstractpine island ice shelf in the amundsen sea is losing mass because of warm ocean waters melting the ice from below tracing meltwater pathways from ice shelves is important for identifying the regions most affected by the increased input of this water type here optimum multiparameter analysis is used to deduce glacial meltwater fractions from water mass characteristics temperature salinity and dissolved oxygen concentrations collected during a ship based campaign in the eastern amundsen sea in february march 2014 using a one dimensional ocean model processes such as variability in the characteristics of the source water masses on shelf and biological productivity respiration are shown to affect the calculated apparent meltwater fractions these processes can result in a false meltwater signature creating misleading apparent glacial meltwater pathways an alternative glacial meltwater calculation is suggested using a pseudo circumpolar deep water endpoint and using an artificial increase

identification of diapycnal mixing through optimum multiparameter analysis 2 evidence for unidirectional diapycnal mixing in the front between north and south atlantic central water optimum multiparameter omp analysis is used to analyze mixing in the central water boundary of the tropical north atlantic ocean diapycnal mixing is found to be prevalent in the frontal region omp analysis shows that the mixing is unidirectional south atlantic central water is always mixed upward into north atlantic central water but cannot identify the process responsible for the observed diapycnal mixing a histogram of stability ratios r for all mixing lines shows r values between unity and the value found in the parent water masses it is suggested that this may indicate competition between isopycnal mixing and double diffusion double diffusive fluxes are likely to make a recognizable and significant contribution to diapycnal mixing between the central waters

evolution of the deep atlantic water masses since the last glacial maximum based on a transient run of ncar ccsm3 during the last deglaciation from approximately 21 to 11 thousand years ago the high latitudes of the atlantic ocean underwent major changes besides the continuous warming the polar and subpolar ocean surface received a large amount of meltwater from the retracting ice sheets these changes in temperature and salinity affected deep waters such as the antarctic bottom water aabw and the north atlantic deep water nadw which are formed in the southern ocean and in the northern north atlantic respectively in this study we present the evolution of the physical properties and distribution of the aabw and the nadw since the last glacial maximum using the results of a transient simulation with ncar ccsm3 in this particular model scenario with a schematic freshwater forcing we find that modern nadw with its characteristic salinity maximum at depth was absent in the beginning of the deglaciation while its intermediate version glacial north atlantic intermediate water gnaiw was being formed gnaiw was a cold and relatively fresh water mass that dominated intermediate depths between 60 and 20 n at this time most of the deep and abyssal atlantic basin was dominated by aabw within the onset of the bolling allerod period at nearly 15 thousand years ago ka gnaiw expanded southwards when the simulated meridional overturning circulation overshoots the transition between gnaiw and nadw ocurred after that when aabw was fresh enough to allow nadw to sink deeper in the water column when the nadw appears 11 ka aabw retracts and is constrained to lie near the bottom

optimal multiparameter analysis of source water distributions in the southern drake passage in order to evaluate the effects of horizontal advection on iron supply in the vicinity of the shackleton transverse ridge str in the southern drake passage the water composition in the region is estimated along the isopycnal containing the subsurface iron peak optimal multiparameter omp analysis of temperature salinity oxygen and nutrient data is used to estimate the water composition at ctd stations sampled in summer 2004 and winter 2006 the highest iron concentrations in the ona basin are found below the mixed layer both in summer and in winter the water composition derived from the omp analysis is consistent with a scenario in which iron rich shelf waters from the south shetland islands and the antarctic peninsula are advected northward on the eastern side of the str where they interact with the low iron waters of the antarctic circumpolar current acc in the ona basin the shelf waters and the acc waters appear to interact through a stirring process without fully mixing resulting in a filamented distribution that has also been inferred from the satellite data to the west of the str the shelf waters are primarily confined to the continental shelf and do not extend northwards this source of water distribution is consistent with the idea that iron enters the ona basin from the continental shelf through advection along an isopycnal resulting in an iron concentration peak occurring below the winter mixed layer in the ona basin

where and how long ago was water in the western north atlantic ventilated maximum entropy inversions of bottle data from woce line a20 1 a maximum entropy me method is used to deconvolve tracer data for the joint distribution of locations and times since last ventilation the deconvolutions utilize world ocean circulation experiment line a20 repeat hydrography for cfc 11 potential temperature salinity oxygen and phosphate as well as global ocean data analysis project glodap radiocarbon data combined with surface boundary conditions derived from the atmospheric history of cfc 11 and the world ocean atlas 2005 and glodap databases because of the limited number of available tracers the deconvolutions are highly underdetermined leading to large entropic uncertainties which are quantified using the information entropy of relative to a prior distribution additional uncertainties resulting from data sparsity are estimated using a monte carlo approach and found to be of secondary importance the me deconvolutions objectively identify key water mass formation regions and quantify the local fraction of water of age or older last ventilated in each region ideal mean age and radiocarbon age are also estimated but found to have large entropic uncertainties that can be attributed to uncertainties in the partitioning of a given water parcel according to where it was last ventilated labrador irminger seawater l water is determined to be mostly less than 40 a old in the vicinity of the deep western boundary current dwbc at the northern end of a20 but several decades older where the dwbc recrosses the section further south pointing to the importance of mixing via a multitude of eddy diffusive paths overflow water lies primarily below l water with young waters 40 a at middepth in the northern part of a20 and waters as old as 600 a below 3500 m

rare earth element distributions in the west pacific trace element sources and conservative vs non conservative behavior abstract recent studies suggest that transport and water mass mixing may play a dominant role in controlling the distribution of dissolved rare earth element concentrations ree at least in parts of the north and south atlantic and the pacific southern ocean here we report vertically and spatially high resolution profiles of dissolved ree concentrations ree along a nw se transect in the west pacific and examine the processes affecting the ree distributions in this area surface water ree patterns reveal sources of trace element te input near south korea and in the tropical equatorial west pacific positive europium anomalies and middle ree enrichments in surface and subsurface waters are indicative of te input from volcanic islands and fingerprint in detail small scale equatorial zonal eastward transport of tes to the iron limited tropical east pacific the low ree of north and south pacific tropical waters and antarctic intermediate water are a long range i e preformed laterally advected signal whereas increasing ree with depth within north pacific intermediate water result from release from particles optimum multiparameter analysis of deep to bottom waters indicates a dominant control of lateral transport and mixing on ree at the depth of lower circumpolar deep water 3000 m water depth 75 100 explained by water mass mixing allowing the northward tracing of lcdw to 28 n in the northwest pacific in contrast scavenging in the hydrothermal plumes of the lau basin and tonga fiji area at 1500 2000 m water depth leads to ree deficits 40 60 removal and marked ree fractionation in the tropical west pacific overall our data provide evidence for active trace element input both near south korea and papua new guinea and for a strong lateral transport component in the distribution of dissolved rees in large parts of the west pacific

geochemistry of a soil catena developed from loess deposits in a semiarid environment sierra chica de cordoba central argentina abstract a catenary sequence of soils formed on reworked loess under semiarid climatic conditions was studied four soil profiles located on the piedmont of sierra chica de cordoba central argentina were described classified and geochemically analyzed all soils developed on summit shoulder backslope and toeslope positions were classified as mollisols decarbonatation carbonatation melanization and argilluviation are the main pedogenic processes recognized in these soils which appear to control the differentiation of genetic horizons along the catena different geochemical approaches indicate that there are not substantial variations in the chemical composition of the studied soils along the catena with the exception of the soil in the toeslope position which exhibits slightly differences in general all profiles show weak depletions of mobile elements ca na mg sr u in the upper continental crust ucc normalized diagrams which are attributed to a slight chemical alteration other elements such as fe cr co and ni also exhibit depletions compared to ucc which can be explained by the alteration of ferromagnesian silicates but can also be an inherited feature from the parent material the significant enrichment in as compared to ucc evident in all profiles along the catena is also a typical feature of the pampean plains loess of argentina so the chemical differences in the profile located on the toeslope are mainly attributed to the supply of materials from local sources i e crystalline basement and sedimentary rocks due to its position in the catena statistical correlations and multivariate cluster analyses reinforce the assumption that the geochemistry of the studied soils is inherited from the parent material in addition chemical indices cia icv elemental ratios ba sr rb sr and the a cn k ternary diagram indicate an incipient degree of chemical alteration for these soils compatible with the weathering regime prevailing in the region thus the differentiation of genetic horizons along the catena is the result of weak weathering and pedogenic processes which have not been strong enough to mask the chemical imprint of the parent material

optimum multiparameter analysis of mixing in the thermocline of the eastern indian ocean a method of water mass analysis is developed which optimizes the use of all information contained in a hydrographic data set by solving an overdetermined linear set of mixing equations it requires representation of water masses by a finite number of water types and observations from at least as many oceanographic parameters as water types the procedure to establish the water types find the correct weights for the parameters and solve the mixing equations through minimization of the residuals is described in detail the method is applied to a data set from the eastern indian ocean where indian central water and australasian mediterranean water meet to produce a strong front in the thermocline it is shown that although most of the water from the indonesian archipelago is carried westward north of 11 s contributions from the australasian mediterranean water are found as far south as 25 s particularly along the australian shelf as a result of advection with the leeuwin current

dissolved aluminium cycling in the northern equatorial and subtropical gyre region of the indian ocean abstract dissolved aluminium hereafter dal concentrations have been determined on 34 full vertical water column profiles sampled along the two separate geotraces india transects gi 01 and gi 06 to understand the biogeochemical controls on dal distribution in the northern the bay of bengal the andaman sea and the arabian sea equatorial and subtropical gyre region of the indian ocean al released due to the partial dissolution of and or al desorption from the suspended lithogenic sediments supplied in a huge amount to the bay of bengal bob waters by the ganga brahmaputra g b river system indian peninsular rivers and sediment resuspension from the continental shelf and slope predominantly controls the dal distribution in the bob and results in an overall increase in the dal concentrations throughout the water column towards the northern bob and the eastern coast of india considering the steady state balance between the dal input from the lithogenic sediment flux in the upper water column and first order scavenging removal of dal the fractional solubility of al from the lithogenic sediments in the bob surface waters is estimated to be in the range of 1 1 4 7 advection of indonesian sea surface waters through the strait of malacca and dal input from the partial dissolution of resuspended terrigenous sediments sourced from the insular shelf of the nicobar islands set major controls on the dal distribution in the surface and upper thermocline waters of the southern andaman sea and the southern bob region near the nicobar islands rapid renewal of and vertical mixing in the deeper waters 1000 m relative to scavenging removal of dal results in near uniform dal concentrations 3 7 nm in the deeper waters at the center of the southern andaman sea in the south eastern arabian sea the continental outflow of mineral dust and advection of dal enriched bay of bengal surface waters control the dal distribution in the surface water layer dal in the surface waters of the equatorial indian ocean during the late winter sampling period of the gi 06 cruise is predominantly determined by the mixing between dal rich surface waters of the southern bob and relatively dal depleted surface waters of the southern arabian sea under the influence of the northeast monsoon current the scavenging residence time of dal in the deep waters of the equatorial indian ocean is estimated using a 1 d scavenging advection diffusion model and found to be in the range of 92 141 years deposition of australian dust and advection of indonesian throughflow water translates to the dal enrichment in the upper water column 3500 m advects across the ninety east ridge from the western australian basin to bring the dal rich waters to the northern end of the central indian ocean basin

the mean age of ocean waters inferred from radiocarbon observations sensitivity to surface sources and accounting for mixing histories a number of previous observational studies have found that the waters of the deep pacific ocean have an age or elapsed time since contact with the surface of 700 1000 yr numerical models suggest ages twice as old here the authors present an inverse framework to determine the mean age and its upper and lower bounds givenglobaloceandataanalysisproject glodap radiocarbonobservations andthey show that the potential range of ages increases with the number of constituents or sources that are included in the analysis the inversion requires decomposing the world ocean into source waters which is obtained here using the total matrix intercomparison tmi method at up to 2 83 28 horizontal resolution with 11 113 surface sources the authors find that the north pacific at 2500 m depth can be no younger than 1100 yr old which is older than some previous observational estimates accounting for the broadness of surface regions where waters originate leads to a reservoir age correction of almost 100 yr smaller than would be estimated with a two or three water mass decomposition and explains some of the discrepancy with previous observational studies a best estimate of mean age is also presented using the mixing history along circulation pathways subject to the caveats that inference of the mixing history would benefit from further observations and that radiocarbon cannot rule out the presence of extremely old waters from exotic sources the deep north pacific waters are 1200 1500 yr old which is more in line with existing numerical model results

anthropogenic co2 estimates in the southern ocean storage partitioning in the different water masses the research leading to these results was supported through eu fp7 project carbochange changes in carbon uptake and emissions by oceans in a changing climate which received funding form the european commission s seventh framework under grant agreement no 264879 and by the spanish ministry of sciences and innovation and was co founded by the fondo europeo de desarrollo regional 2007 2012 feder through the catarina project ctm2010 17141 mar

oxygen in the deep strait of georgia 1951 2009 the roles of mixing deep water renewal and remineralization of organic carbon the concentration of oxygen in the deep strait of georgia has declined at a rate of 0 45 1 3 mmol l21 yr21 since 1971 and now seasonally approaches thresholds of biological tolerance the decline has resulted principally from the increasing hypoxia of upwelled pacific ocean water local anthropogenic loadings have little potential to reduce bottom water oxygen concentrations hypoxic upwelled water mixes vigorously with surface water in the tidal passages of haro strait before entering the deep strait of georgia during a series of deep water renewal events in late spring and late summer remineralization of at least 22 mmol l21 yr21 together with diffusive mixing reduces the bottom water oxygen concentration to a winter minimum of 90 110 mmol l21 linear extrapolation of the long term trend indicates that parts of the strait could become episodically hypoxic 62 5 mmol l21 1 4 ml l21 as early as 2042 however water mass modeling shows that the mixing with surface water in haro strait limits the potential of the shelf water to reduce the oxygen concentration in the deep strait even should the shelf water become completely anoxic the concentration of oxygen in bottom waters would level off just above 90 mmol l21 after 3 yr increasing surface water temperature will reduce the solubility of oxygen but this effect is projected to cause a further decline of only 2 2 mmol l21 over the next 25 yr despite its restricted circulation the deep strait of georgia is less threatened by hypoxia than are many other coastal areas because of the combination of light limited primary production and intense tidal mixing in the approaches which replenishes the deep water oxygen annually

an analysis of mixing in the frontal zone of south and north atlantic central water off north west africa abstract multi parameter mixing analysis is applied to 26 stations of auftrieb 75 a joint expedition of r r s discovery and fs meteor north atlantic central water nacw and south atlantic central water sacw are represented by two water types each and phosphate silicate and nitrate are all used as an additional parameter with temperature and salinity yielding three sets of independent solutions solutions from different parameters show similar vertical distributions but can differ considerably in absolute terms this is believed to be caused by insufficient knowledge of nutrient values of pure nacw and sacw and by low range precision ratios of nutrient determination it is shown that isopycnal mixing analysis correctly describes the water mass distribution to lowest order i e there is agreement between results from isopycnal and multi parameter analysis at most stations within the error bounds which are inherent in the method and which are presently very high significant non isopycnal mixing could be confirmed for only one station situated on the continental slope in the area of the undercurrent of the canary current upwelling regime and may be caused by active upwelling increased lateral and vertical shear in the under current or internal waves interacting with the bottom five stations do not yield oceanographically acceptable solutions and an attempt is made to include a coastal water mass in the analysis in order to improve the result for these stations i e three parameter analysis for nacw and sacw is replaced by four parameter analysis for nacw sacw and coastal water by combining temperature and salinity with phosphate and silicate or with nitrate and silicate simultaneously the combination phosphate and nitrate is degenerate because both nutrients are linearly correlated this indeed improves the results indicating the presence of coastal water at those stations but accumulation of errors inhibits quantitative conclusions

dianeutral mixing and transformation of antarctic intermediate water in the indian ocean transformation of antarctic intermediate water aaiw is achieved through one or more processes of epineutral advection epineutral diffusion dianeutral advection and dianeutral diffusion this paper points to the importance of dianeutral mixing in achieving the aaiw water mass transformation in the indian ocean six neutral surfaces were mapped to span the intermediate water of the indian ocean between 580 and 1500 m at the reference cast south of the antarctic frontal zone aaiw shows a diffusive tongue in the meridional turner angle after j stewart turner sections on its equatorward transition the transformed aaiw is characterized by a tongue of doubly stable conditions extending a great distance to as far as about 5 s a maximum downwelling dianeutral velocity of 2 10 7 m s 1 due to cabbeling is found in the antarctic frontal zone which is 3 orders larger than that in the subtropical gyre thermobaricity acts similarly to cabbeling in the antarctic frontal zone and contributes a maximum downwelling dianeutral velocity of 1 10 7 m s 1 but mainly arises in upwelling north of the frontal zone a strong downwelling dianeutral velocity of 2 10 7 m s 1 contributed by vertical turbulent mixing occurs on the upper two neutral surfaces south of the frontal zone with assumed constant epineutral diffusivity k of 103 m2 s 1 and dianeutral diffusivity d of 10 5 m2 s 1 an area mean net dianeutral upwelling velocity of 0 11 10 7 m s 1 is found north of 32 s across the lowermost neutral surface 27 66 it means a net upward volume transport of 0 6 sv 1 sv 106 m3 s 1 this weak but net upwelling transport roughly corresponds to a net 0 5 sv transported downward with a downwelling dianeutral velocity of 0 25 10 7 m s 1 across the same neutral surface south of 45 s toward the core of aaiw the net dianeutral velocity increases to 0 15 10 7 m s 1 across the 27 37 neutral surface the corresponding net dianeutral transport increases to 0 8 sv you 1996 has estimated a net dianeutral upwelling transport of 1 4 sv across the lower thermocline north of 32 s which suggests about the same amount of volume transport upward across the upper intermediate layer however south of 45 s a much stronger area mean net downwelling dianeutral velocity of 2 63 10 7 m s 1 is found across the uppermost neutral surface 27 1 indicative of a net 5 4 sv transported downward that the downwelling transport across the uppermost surface is 10 times larger than that across the lowermost surface south of 45 s has a strong implication for the equatorward advection of aaiw between the uppermost and lowermost neutral surfaces when both the epineutral and dianeutral diffusivities are increased by 1 order of magnitude to k 104 m2 s 1 and d 10 4 m2 s 1 the above estimated integrated total dianeutral velocity and transport would increase by almost 10 times however when the diffusivities are decreased by 1 order of magnitude to k 102 m2 s 1 and d 10 6 m2 s 1 the integrated total dianeutral velocity and transport would decrease by only less than one time

implications of the deep circulation and ventilation of the indian ocean on the renewal mechanism of north atlantic deep water in the indian ocean sector of the great ocean conveyor scheme the north atlantic deep water nadw replacement is realized by the transformation of the sinking circumpolar deep water cdw from the southern ocean to a prevailingly upward flow in the northern indian ocean this water mass transformation scenario has been studied by using hydrographie data including potential temperature salinity dissolved oxygen and nutrients in a water mass mixing model and by calculation of dianeutral velocity the model comprises a mixing system of three major deep water masses nadw cdw and north indian deep water this third water mass is introduced as a virtual water mass to represent the aged cdw the assumption is feasible as the artificial water mass can be eliminated on the deepest n 28 12 neutral surface characterized by isopycnal mixing the experiment is fulfilled when a conservative variable initial phosphate po40 is introduced and all conservative parameters are used in the mixing scheme the n 28 12 surface provides a major isopycnal transition path of cdw to the northern indian ocean and thus cdw is transformed to an upward flow dominant dianeutral up welling is detected on all four neutral surfaces north of 30 s showing increasingly strong dianeutral velocity toward shallower surfaces with the water mass mixing pattern and spreading path dianeutral circulation and dynamical information of the acceleration potential 10 m2 s 2 mapped on neutral surfaces a schematic of deep water circulation and ventilation of the indian ocean emerges from this study the contribution of nadw is largely limited to the southwest indian ocean the northward cdw is found mainly in two paths one in the western indian ocean apparent between 2000 and 3000 m through the western crozet and madagascar basins and farther north into the somali basin and arabian basin and another in the central indian basin apparent below 3000 m where ridge blocking becomes effective in the west and nadw salinity reaches a maximum while the major path switches from west to the central basin in the deeper layer 3000 3500 m the flow in the western indian ocean reverses southward north of the southeast indian ridge the deep path bifurcates from which point the eastern branch feeds the deep western boundary flow in the west australian basin except for part of the transformed cdw which is contributed to the upward flow in the north the return flow of cdw is found on the eastern side of these basins

least squares multiple tracer analysis of water mass composition we present an inverse method that uses measurements of the concentration of several tracer variables to find the mixture of source water types that best describes in a weighted least squares sense the composition of the water sample the solution includes two physically realistic constraints first that all sources together must sum to 100 and second that no source is present in negative amounts these constraints improve the statistical stability of the solution the method is particularly valuable in regions involving strong mixing among a relatively large number of source water types in contrast to conventional ts analysis more water types can be considered the assumption of mixing along isopycnals is unnecessary and sensitivity to errors in individual tracer measurements is reduced by averaging the influence of a larger number of tracers we demonstrate the method using data from two oceanographic regions analysis of summer data from the continental margin off vancouver island british columbia canada confirms and quantifies the importance of deep upwelling of california undercurrent water onto the continental shelf it also identifies localized outer shelf filaments of low salinity water originating from the vancouver island coastal current finally we reanalyze the north african data of tomczak and confirm his interpretation of diapycnal mixing at the frontal boundary between north atlantic central water and south atlantic central water masses

evidence of deep and bottom water formation in the western weddell sea abstract during ice station polarstern ispol r v polarstern cruise ant xxii 2 november 2004 january 2005 hydrographic and tracer observations were obtained in the western weddell sea while drifting closely in front of the larsen ice shelf these observations indicate recently formed weddell sea bottom water which contains significant contributions of glacial melt water in its upper part and high salinity shelf water in its lower layer the formation of this bottom water cannot be related to the known sources in the south the filchner ronne ice shelf we show that this bottom water is formed in the western weddell sea most likely in interaction with the larsen c ice shelf by applying an optimum multiparameter analysis omp using temperature salinity and noble gas observations helium isotopes and neon we obtained mean glacial melt water fractions of about 0 1 in the bottom water on sections across the weddell gyre farther north melt water fractions are still on the order of 0 04 using chlorofluorocarbons cfcs as age tracers we deduced a mean transit time between the western source and the bottom water found on the slope toward the north 9 3 years this transit time is larger and the inferred transport rate is small in comparison to previous findings but accounting for a loss of the initially formed bottom water volume due to mixing and renewal of weddell sea deep water a formation rate of 1 1 0 5 sv in the western weddell sea is plausible this implies a basal melt rate of 35 19 gt year or 0 35 0 19 m year at the larsen ice shelf this bottom water is shallow enough that it could leave the weddell basin through the gaps in the south scotia ridge to supply antarctic bottom water these findings emphasize the role of the western weddell sea in deep and bottom water formation particularly in view of changing environmental conditions due to climate variability which might induce enhanced melting or even decay of ice shelves

ventilation of the deep ocean constrained with tracer observations and implications for radiocarbon estimates of ideal mean age abstract ocean ventilation is the process that transports water and climatically important trace gases such as carbon dioxide from the surface mixed layer into the ocean interior quantifying the dominant source regions and time scales remains a major challenge in oceanography a mathematically rigorous approach that accounts for the multiplicity of transport pathways and transit times characteristic of an eddy diffusive flow such as the ocean is to quantify ventilation in terms of a probability distribution that partitions fluid parcels according to the time and location of their last surface contact here we use globally gridded radiocarbon data in combination with other transient cfcs and hydrographic temperature salinity phosphate and oxygen tracer data to estimate the joint distribution of age and surface origin of deep ocean waters our results show that 40 and 26 of the global ocean was last in contact with the southern ocean and north atlantic respectively some 80 of the global deep ocean below 1500 m is ventilated from these high latitude regions however contrary to the classical description of the deep ocean as a roughly equal mixture of northern and southern source waters we find a significantly higher contribution from the southern ocean relative to the north atlantic we estimate the mean transit time from the surface to the deep north pacific at 1360 350 y intermediate between two widely used radiocarbon based estimates to reconcile our estimate of the ideal mean age with ventilation age estimates based on radiocarbon we apply the estimated distribution function to construct a 3 dimensional distribution of the water mass fraction weighted surface initial radiocarbon concentration that can serve as an accurate reservoir age radiocarbon ages corrected for this initial reservoir age are found to be in good agreement within 5 with our ideal age estimate demonstrating that it is essential to take into account the spatially variable surface radiocarbon field when computing ventilation ages using radiocarbon a wide spectrum of ages contributes to the mean age providing evidence for the fundamentally eddy diffusive nature of the large scale general circulation of the ocean

characteristics of meltwater export from jakobshavn isbrae and ilulissat icefjord jakobshavn isbrae which terminates in ilulissat icefjord has undergone rapid retreat and is currently the largest contributor to ice sheet mass loss among greenland s marine terminating glaciers accelerating mass loss is increasing fresh water discharge to the ocean which can feed back on ice melt impact marine ecosystems and potentially modify regional and larger scale ocean circulation here we present hydrographic observations including inert geochemical tracers that allow the first quantitative description of the glacially modified waters exported from the jakobshavn icefjord system observations within the fjord suggest a deep reaching overturning cell driven by glacial buoyancy forcing modified waters containing submarine meltwater up to 2 5 0 12 subglacial discharge up to 6 0 37 and large portions of entrained ocean waters are seen to exit the fjord and flow north the exported meltwaters form a buoyant coastal gravity current reaching to 100 m depth and extending 10 km offshore

short term variations of deep water masses in drake passage revealed by a multiparametric analysis of the ant xxiii 3 bottle data short term variations of deep water masses in drake passage revealed by a multiparametric analysis of the ant xxiii 3 bottle data j sudre v garcon c provost n sennechael o huhn and m lacombe doi 10 1016 j dsr2 2011 01 005 a multiparametric analysis is applied on the ant xxiii 3 bottle data to determine the spreading and mixing of water masses across drake passage during january february 2006 focusing our interest on the flow of the deep water masses mixing proportions are quantified along both the southward and northward journeys between the tip of south america and the antarctic peninsula the method is sensitive enough to detect a marked variability in the flow pathways of the circumpolar deep water the southeast pacific deep water spdw and the weddell sea deep water at the intersection of the shackleton fracture zone sfz and the west scotia ridge wsr between the southward and northward journeys indeed the presence of a sharp meander of the southern branch of the polar front pfs together with the displacement of the northern branch of the southern antarctic circumpolar current front saccfn above the complex bathymetric structure of the wsr induced a strong perturbation in the deep flow field during the southward journey the height of the sfz crests clearly sets the lower limit of the spdw in the ona basin an enhanced 3 he signature is confined to the north of the polar front between 55 5 s and 56 5 s in the 1500 2200 m depth range it clearly indicates the signature of the core of the southeast pacific deep slope water the entry pathway in the acc of the spdsw during ant xxiii 3 was farther to the south off the continental slope of south america than it was during the woce a21 expedition in 1990 probably due to the sharp changes in the slope orientation at the extreme tip of the south america

changes in the properties and distribution of the intermediate and deep waters in the fram strait abstract the fram strait is the only deep connection between the arctic ocean and the nordic seas greenland iceland and norwegian seas with a sill depth of approximately 2600 m consequently observations from this area reflect changes in the deep waters of the arctic mediterranean possible changes in the properties and distribution of the intermediate and deep water masses passing through the fram strait have been studied for the period from 1982 to 2008 at a zonal section at 79 n with special emphasis on the period from 1997 to 2008 the temperature of the arctic intermediate water shows large interannual variability where the period from 2002 to 2004 was especially cold indicating a strong winter convection in the nordic seas prior to those years the deep water originating from the norwegian sea has become warmer by about 0 10 c during the study period the changes in the properties of the norwegian sea deep water are caused by changes in its composition i e an increasing fraction of the eurasian basin deep water and a decreasing fraction of the greenland sea deep water each year if this trend continues the norwegian sea deep water will have similar characteristics as the eurasian basin deep water in about 15 years a prominent feature seen in the s diagrams from the deep fram strait is the disappearance of water with the characteristics of greenland sea deep water this very cold water temperature below 1 1 c was not observed after 1997 and the minimum temperature in the strait increased by 0 24 c between 1982 and 2008 in the fram strait the fraction of intermediate waters has increased while the fraction of deep waters from the nordic seas has decreased the fraction of deep waters originating from the arctic ocean shows no trend

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

water mass properties and dynamic conditions of the eastern mediterranean in june 2007 abstract five locations in the eastern mediterranean situated in the ionian sea cretan passage and levantine basin were characterized for their physical and biogeochemical properties on the basis of the data collected during an oceanographic cruise in june 2007 basinwide subbasin and mesoscale surface dynamic features are described in terms of absolute dynamic topography of the sea surface sea surface temperature and chlorophyll a distribution additional information along the ship s track was acquired via the vessel mounted thermosalinograph and the acoustic doppler current profiler providing data on temperature salinity and marine current the latter helped identify the depth penetration

isow spreading and mixing as revealed by deep argo floats launched in the charlie gibbs fracture zone to improve our understanding of deep circulation we deployed five deep argo floats 0 4 000 m in the charlie gibbs fracture zone cgfz which channels the flow of iceland scotland overflow water isow a dense water mass of the north atlantic ocean the floats were programed to drift at 2 750 dbar in the isow layer the floats mainly moved westward in the cgfz although some of them followed different routes for few cycles depending on northward intrusions of the north atlantic current over the cgfz one float revealed a direct route for isow from cgfz to the deep western boundary current at flemish cap in the cgfz oxygen data acquired by the floats revealed that the isow layer characterized by salinity higher than 34 94 and density greater than 27 8 kg m was mainly composed of the highly oxygenated isow and the less oxygenated north east atlantic deep water neadw a complex water mass from the east atlantic in the isow layer the relative contribution of isow was generally larger in the northern valley than in the southern valley of cgfz northward intrusions of the north atlantic current above the cgfz increased the relative contribution of neadw in the northern valley and favors mixing between isow and neadw the isow neadw signal flowing westward from the cgfz toward the deep western boundary current was progressively diluted by labrador sea water and denmark strait overflow water oxygen measurements from deep argo floats are essential for a better understanding and characterization of the mixing and spreading of deep water masses

ventilation processes and water mass ages in the thermocline of the southeast indian ocean indian central water icw and subantarctic mode water samw are the two major sources for the ventilation of the permanent thermocline in the indian ocean icw is formed by subduction in the region of negative wind stress curl while samw is formed by convective overturning at the subantarctic front samw contributes to the depth range of icw but is not easily identified because most hydrographic properties temperature salinity and nutrients of samw do not differ much from those of icw this study identifies icw and samw in a zonal section near 32 s and evaluates the relative importance of convection vs subduction for the ventilation process oxygen and nutrient data from the eastern part 50 114 e of woce section 15 are used with temperature and salinity to determine water mass fractions of subducted icw and of samw from water mass mixing analysis the individual age fields of the two water mass components are then derived from a combination of the fractions obtained with a linear oxygen cfc mixing model unlike earlier studies which derive an uncalibrated apparent age our results express water mass age in true units of time years the core of the samw near 114 e is about 5 years old while the core of the subducted icw at 60 80 e shows an increase of age with depth in agreement with the subduction process icw moves eastward with the south indian current reaching an age of 35 years at 114 e samw spreads westward against the mean flow through turbulent diffusion reaching an age of 25 years at 50 e

sources to the east greenland current and its contribution to the denmark strait overflow data from the east greenland current in 2002 are evaluated using optimum multiparameter analysis the current is followed from north of fram strait to the denmark strait sill and the contributions of different source waters in mass fractions are deduced from the results it can be concluded that at least in spring 2002 the east greenland current was the main source for the waters found at the denmark strait sill contributing to the overflow into the north atlantic the east greenland current carried water masses from different source regions in the arctic ocean the west spitsbergen current and the greenland sea the results agree well with the known circulation of the western nordic seas but also add knowledge both to the quantification and to the mixing processes showing the importance of the locally formed greenland sea arctic intermediate water for the east greenland current and the denmark strait

dissolved rare earth elements distribution in the solomon sea abstract trace elements and isotopes teis were measured as part of the geotraces pandora cruise july august 2012 r v l atalante among them rare earth elements rees as pertinent tracers of land ocean inputs and water mass transformations this work discusses results of 19 dissolved ree dree profiles measured using a trispike method in the coral sea and inside and at the exits of the solomon sea a semi enclosed sea with complex topography and straits overall drees except the insoluble ce show nutrient like profiles i e depleted at the surface and enriched at depth illustrative nd concentrations range from 5 pmol kg at the surface to 25 pmol kg at 5000 m depth however local dree enrichments are observed mostly in the straits indispensable solomon and vitiaz straits and along the island coasts a box model allows calculating and discussing the fate of the drees in the different water layers flowing through the solomon sea finally subtle variations revealed by la ce eu anomalies and the normalized light versus heavy ree ratio expressed as ndn ybn allows the identification of specific mechanisms affecting the distribution of the different drees the positive eu anomaly observed in the surface layers reflects the basaltic origin of external inputs consistent with the intensive weathering and or volcanic activity affecting the surrounding islands these data also confirm that the distributions of heavy drees like yb are better correlated to the dsi concentrations than that of the other rees this article is part of a special issue entitled cycles of trace elements and isotopes in the ocean geotraces and beyond edited by tim m conway tristan horner yves plancherel and aridane g gonzalez

quantifying antarctic bottom water and north atlantic deep water volumes 1 a near global census of antarctic bottom water aabw and north atlantic deep water nadw is essayed through a nonnegative least squares analysis of conservative and quasi conservative seawater properties aabw thickness generally decreases from south to north modulated by ocean bathymetry likewise nadw thickness generally decreases from north to south in the atlantic ocean nadw dominates below the thermocline of the atlantic ocean at least as far south as the subtropical gyre of the south atlantic with a lesser but still significant influence around the entire antarctic circumpolar current in the indian ocean and in the pacific ocean however in the pacific and indian oceans aabw dominates below the thermocline in addition measurable quantities of aabw reach into the abyssal north atlantic on both sides of the mid atlantic ridge the census results suggest that aabw occupies roughly twice the volume of nadw in the three main oceans and that aabw is in contact with roughly twice the area of the deep main ocean floor compared with nadw however these results are somewhat sensitive to choices of water masses their values of seawater properties and the weightings of the seawater properties used in the analysis

on the mediterranean water composition abstractthe mediterranean outflow water mow spills from the mediterranean sea east north atlantic basin west off the strait of gibraltar as mow outflows it entrains eastern north atlantic central waters enacw and intermediate waters to form the neutrally buoyant mediterranean water mw that can be traced over the entire north atlantic basin its high salinity content influences the thermohaline properties of the intermediate deep water column in the north atlantic and its dynamics here the composition of mw in its source region the gulf of cadiz west off strait of gibraltar is investigated on the basis of an optimum multiparameter analysis the results obtained indicate that mixing of mow 34 1 0 3 occurs mainly with overlying enacw 57 1 0 8 in a process broadly known as central water entrainment a diluted form 80 of dilution of the antarctic intermediate water aaiw reaches the region and also takes part in mw formation 8 3 0 5 finally the underlying labrador sea wat

the freshwater system west of the antarctic peninsula spatial and temporal changes climate change west of the antarctic peninsula is the most rapid of anywhere in the southern hemisphere with associated changes in the rates and distributions of freshwater inputs to the ocean here results from the firstcomprehensivesurveyofoxygenisotopesinseawaterinthisregionareusedtoquantifyspatialpatternsof meteoric water glacial discharge and precipitation separately from sea ice melt high levels of meteoric water are found close to the coast due to orographic effects on precipitation and strong glacial discharge concentrations decrease offshore driving significant southward geostrophic flows up to 30 cm s 21 these produce high meteoric water concentrations at the southern end of the sampling grid where collapse of the wilkins ice shelf may also have contributed sea ice melt concentrations are lower than meteoric water and patchier because of the mobile nature of the sea ice itself nonetheless net sea ice production in the northern part of the sampling grid is inferred combined with net sea ice melt in the south this indicates an overall southwardicemotion thesurveyiscontextualizedtemporallyusingadecade longseriesofisotopedatafrom a coastal antarctic peninsula site this shows a temporal decline in meteoric water in the upper ocean contrary to expectations based on increasing precipitation and accelerating deglaciation this is driven by the increasingoccurrenceofdeeperwintermixedlayersandhaspotentialimplications forconcentrations oftrace metals supplied to the euphotic zone by glacial discharge as the regional freshwater system evolves the continuing isotope monitoring described here will elucidate the ongoing impacts on climate and the ecosystem

mixing and water mass formation in the australian subantarctic abstract a cruise south of eastern australia confirmed the formation of a subantarctic mode water type in late winter on the equatorward side of the subantarctic front this water type mixed with the winter surface waters farther north would form the t s relation observed in the tasman sea intermediate waters a subsurface formation of antarctic intermediate water is supported by data collected in the polar frontal zone a matrix method for analyzing mixing indicates that the antarctic intermediate water is formed from a mixture of circumpolar deep water and antarctic surface water with effectively no input from the subantarctic mode water the nutrient data were found to add very little information on the mixing once the temperatures and salinities are known

a generalized transport theory water mass composition and age abstract a general theory to describe and understand advective and diffusive ocean transport is reported it allows any passive tracer field with an atmospheric source to be constructed by superposing sea surface contributions with a generalized green s function called the boundary propagator of the passive tracer equation the boundary propagator has the interpretation of the joint water mass and transit time distribution from the sea surface the theory thus includes the classical oceanographic idea of water mass analysis and extends it to allow for a distribution of transit times from the sea surface the joint water mass and transit time distribution contains complete information about the transport processes in the flow it captures this information in a more accessible way than using velocity and diffusivity fields however at least for the case of sequestration and transport of dissolved material by the ocean circulation the boundary propagator is thus the natural quantity to consider when discus

multidecadal freshening and lightening in the deep waters of the bransfield strait antarctica the deep waters of the bransfield strait receive considerable amounts of water from the weddell sea continental shelf the restricted connections to the surrounding ocean and relatively easier access makes the bransfield strait an important proxy region for monitoring changes in the dense weddell sea shelf water masses which are an important precursor of antarctic bottom water aabw long term hydrographic data from the period 1960s 2010s showed freshening and lightening of the deep water masses of the bransfield strait which was likely caused by large freshwater inputs originating from the western shelf of the weddell sea the rates of freshening and lightening were 0 0010 0 0005 yr 1 and 0 0016 0 0014 kg m 3 yr 1 for the central basin respectively and 0 0010 0 0006 yr 1 and 0 0029 0 0013 kg m 3 yr 1 for the eastern basin respectively the deep waters showed a high degree of interannual thermohaline variability which appeared to be caused by changes in the proportions of source water mass mixing between the years statistically significant negative correlations between salinity neutral density fields and the southern annular mode sam were observed 0 56 and 0 62 for the central basin respectively and 0 58 and 0 68 for the eastern basin respectively between 1980 and 2014 during sam positive phases communication between the weddell sea and the bransfield strait is reduced which leads to less saline and lighter water masses in the bransfield strait however the opposite trends are observed during sam negative phases

how much did glacial north atlantic water shoal observations of 13c and cd ca from benthic foraminifera have been interpreted to reflect a shoaling of northern source waters by about 1000 m during the last glacial maximum with the degree of shoaling being significant enough for the water mass to be renamed glacial north atlantic intermediate water these nutrient tracers however may not solely reflect changes in water mass distributions to quantify the distribution of glacial north atlantic water we perform a glacial water mass decomposition where the sparsity of data geometrical constraints and nonconservative tracer effects are taken into account and the extrapolation for the unknown water mass end members is guided by the modern day circulation under the assumption that the glacial sources of remineralized material are similar to that of the modern day we find a steady solution consistent with 241 13c 87 cd ca and 174 18o observations and their respective uncertainties the water mass decomposition indicates that the core of glacial north atlantic water shoals and southern source water extends in greater quantities into the abyssal north atlantic as previously inferred the depth of the deep northern southern water mass interface and the volume of north atlantic water however are not grossly different from that of the modern day under this scenario the vertical structure of glacial 13c and cd ca is primarily due to the greater accumulation of nutrients in lower north atlantic water which may be a signal of the hoarding of excess carbon from the atmosphere by the glacial atlantic

on the temporal variability of intermediate and deep waters in the western basin of the bransfield strait abstract the western basin wb of the bransfield strait has a complex water mass structure derived from a variety of sources and is located next to the antarctic region most affected by climate change the wb is one of the three bransfield strait deep basins and the one most directly influenced by the waters from the bellingshausen sea and drake passage the objective of this paper is to study the variability of the inflow of water masses to the wb and to detect the possible impact of regional climate change we focus on the modified circumpolar deep water mcdw that enters the wb through the northwestern passages to achieve this goal this study uses historical hydrographic data collected between 1960 and 2014 warming 0 0161 0 0079 c yr 1 and lightening 0 0023 0 0010 kg m 3 yr 1 of the mcdw core n 27 85 28 27 kg m 3 are observed in the wb between 1960 and 2013 the waters within the 27 85 28 kg m 3 n range presented warming and salinization waters deeper than 500 m showed cooling and freshening between the 1960s and 1990s however warming and lightening are observed if 1981 2013 is considered these trends appear to be associated with the positive sam trend observed since the mid 20th century statistically significant negative correlations between s and of the mcdw core with enso were found between 1980 and 2014 during la nina phases the mcdw core extended along the southern slope of the south shetland islands while during el nino phases it was present in patches or was totally absent since the 2000s the mcdw core extends southward within the wb possibly associated to positive sam phases statistically significant negative correlations between and s of the wb deeper waters with enso and sam were found these waters were in general more saline and denser during negative enso and sam phases positive sam phases with la nina events suggest the increase decrease of mcdw weddell sea shelf waters contribution to the deep wb during the 2000s thus high interannual variability in the thermohaline properties within the wb seem to be linked to the effect of these modes of climate variability on the source water masses

anthropogenic co2 in the southern ocean distribution and inventory at the indian atlantic boundary world ocean circulation experiment line i6 1 the southern ocean where various water masses are formed mode intermediate deep and bottom waters has a high potential to absorb anthropogenic co2 cant however most data based and model estimates indicate low cant inventories south of 50 s in order to investigate this paradox the distribution of cant is estimated between south africa and antarctica world ocean circulation experiment woce line i6 based on a back calculation technique previously used in the north atlantic kortzinger et al 1998 and adapted here for application in the southern ocean at midlatitudes 30 50 s formation and spreading of mode and intermediate waters results in a deep penetration of cant down to 2000 m south of 50 s significant concentrations of cant were estimated in circumpolar deep water 10 mol kg and antarctic bottom water aabw 20 25 mol kg higher concentrations are detected along the continental slope in aabw presumably formed in prydz bay compared to aabw of weddell sea origin the distribution of cant obtained north of 50 s compares well with previous data based and model estimates but large disagreements are found in the south however although transient tracers are not used in the back calculation technique employed here the distribution of cant is remarkably well correlated with cfcs we reevaluated the column inventories of cant for the southern ocean and found higher values at high latitudes 70 90 mol m2 compared to the subtropical subantarctic region 40 80 mol m2 these results support the idea that deep and bottom water formation in the southern ocean is a key process in the natural sequestration of anthropogenic co2