evidence of bottom trapped currents in the kuroshio extension region as partof thekuroshioextensionsystemstudy observations fromfivecurrentmetermoorings revealthat the abyssal currents are weakly bottom intensified in the framework of linear quasigeostrophic flow the best fittedverticaltrappingdepthsrangefrom8to15 kmintheabsenceofsteeptopography butonemooringnear an isolated seamount exhibited vertical trapping that was more pronounced and energetic with a vertical trapping depth of 5 km the ratios of current speeds and geostrophic pressure streamfunctions at the sea surface compared to the bottom are 88 in the absence of steep topography 63 near an isolated seamount and overall on average 83 of their value at a reference depth of 5300 m it is hypothesized that weakly depth dependent eddies impinging upon topographic features introduce to the flow the horizontal length scales of the topography and these smaller lateral scales are subject to bottom intensification

ree mobility in groundwater proximate to the natural fission reactor at bangombe gabon the natural nuclear fission reactor at bangombe is located at a depth of approximately 12 m and has undergone supergene weathering and chemical exchange with groundwater under moderately oxidizing conditions this reactor has been studied as an analogue for the migration of radionuclides in a geologic repository five water samples were taken from a drill hole in the reactor zone and from drill holes that are situated along the direction of the groundwater flow dissolution of phosphates in the weathering profile provided an important mechanism for the mobilization of phosphorous and ree this phosphorous allowed the formation of secondary minerals e g phosphatian coffinites and fe uranyl phosphate hydroxide hydrates the filtered groundwaters dissolved phase obtained directly from the reactor zone had anomalous 143nd 146nd 145nd 146nd and 149sm 147sm isotope ratios of 0 7235 0 4933 and 0 843 respectively confirming mixing between a fissiogenic and normal ree component in this dissoved phase a small fraction of the nd 2 3 at is of fissiogenic origin the suspended loads filtered particulates of the same groundwater from within the reactor show similar isotopic anomalies with a fissiogenic nd contribution of 3 2 at similar fissiogenic nd contributions are observable for groundwater samples from outside the reactor zone 3 m distance both dissolved and suspended load samples from the more distant well 25 m have normal isotopic ratios thus the prevailing physico chemical conditions within this groundwater system allow the migration of the fissiogenic ree over at least 3 m but less than 25 m although ree phases are abundant in the reactor zone the ree concentrations of the water in contact with the sediments of this zone are very low 17 ppt the most important lanthanide and actinide bearing phases are uraninite coffinites and fe uranyl phosphate hydroxide hydrate the presence of all of these phases retards the mobility of the fissiogenic lanthanides and actinides

mobility and fractionation of rare earth elements during supergene weathering and gossan formation and chemical modification of massive sulfide gossan primary massive sulfide gossans msg in the bathurst mining camp bmc new brunswick canada are characterized by relative enrichment of au sb and as formation of jarosite group minerals jarosite plumbojarosite and argentojarosite and little or no fractionation in the rare earth elements ree including preservation of large positive eu anomalies average eu eu nasc 4 14 in msg 6 61 in massive sulfide mineralization 0 60 in host rocks the chemical and mineralogical characteristics of msg e g halfmile lake deposit imply low ph 3 and relatively oxidizing conditions during gossan formation oxidation of a volcanogenic massive sulfide body comprising pyrite pyrrhotite sphalerite galena and chalcopyrite with a falling water table the lack of light ree or heavy ree fractionation and preservation of positive eu anomalies characteristic of the original 465 ma hydrothermal fluid is consistent with relatively large water rock ratios during massive sulfide mineralization oxidation and removal of the ree predominantly as sulfate complexes lnso4 ln so4 2 low ph groundwaters recovered from past producing mines in the bmc display ree patterns reflecting those inferred to have occurred during gossan formation gossan at the restigouche deposit in contrast to the halfmile lake deposit displays mineralogical and chemical evidence for having been chemically reworked since primary gossan formation evidence for chemical reworking includes loss of primary massive sulfide mineralization textures replacement of plumbojarosite with anglesite almost complete removal of jarosite minerals loss of au sb and as and apparent preferential removal of eu resulting in loss of positive eu anomalies for most samples average eu eu nasc 1 21 in the gossan with many displaying strong negative anomalies 3 65 in massive sulfide mineralization 0 54 in host rocks based on geochemical modeling conditions inferred for the chemical reworking of the restigouche deposit include near neutral conditions and either relatively oxidizing conditions with eu2 hosted in a preferentially weathered mineral host possibly through substitution for pb in plumbojarosite and beudantite or cycling between reduced and oxidized conditions during gossan reworking

a numerical study of the propagation of topographic rossby waves abstract the propagation of linear barotropic rossby waves is investiaged numerically over a one dimensional topography similar to the continental rise and slope a point source is used to generate waves with periods from 4 to 36 days the resulting distribution of streamfunction and kinetic energy density is examined the result show that the propagating of tropographic rossby waves depends on the wave period over the continental rise waves are generated mainly by low frequency disturbances at periods of about a month in addition the continental slope is a good insulator to these waves therefore deep ocean circulation will not influence motions on the continental shelf at 36 and 15 days the steep continental slope is a wave guide and regions of high energy density generated by local sources may be found energy of 36 day waves over the continental shelf cannot penetrate the steep slope although waves of periods shorter than a week may reach the lower slope these waves are trapped by the coast

xenon geochronology of schwarzwald pitchblendes the uranium fission xenon systems in eleven samples selected from three occurrences in the schwarz wald were investigated menzenschwand wittichen mullenbach relationships between mineralogical properties xe release profiles and xe xe age spectra provide criteria for sample suitability for u xe and xe xe dating and interpretation of the xe xe age spectra u leaching from pitchblendes was demonstrated for three of the wittichen samples indicating also disturbed u pb relations the results show that the u xe isotopic system is a valuable geochronological tool for studying uranium minerals in samples of two deposits fission xe was well preserved and allowed us to determine xe xe plateau ages 301 11 304 9 and 279 10 ma for menzenschwand and 244 9 ma for wittichen pitchblendes these ages show the closure times of the u xe isotope systems and most probably correspond to the formation of these pitchblendes they are in accord with published u pb data four other samples of these two deposits had very irregular spectra an attempt was made to interpret integrated xe xe ages u xe ages in these samples in terms of alteration events little fission xe was found in material from mullenbach there is a large time gap between the formation of the hosting granites and the u ore depositions about 30 and 90 ma respectively in menzenschwand and wittichen

observations of the vertical structure of the eddy field in the kuroshio extension normalized kinetic energy frequency distributions at a site in the kuroshio extension along 152 e are independent of depth as a good first approximation the lowest frequencies are strongly vertically coherent from 350 to 6000 m depths nominal none of the other vertical sets of time series previously examined possess these characteristics to such a degree coherence being typically much lower between the thermocline and abyssal depths with spectral shape changing significantly as well the vertical distributions of eddy kinetic energy at this kuroshio extension site and for the gulf stream along 55 w are very similar if a depth independent contribution of approximately 100 cm2 s 2 be added to the former the latter observation suggests the existence of a more energetic weakly depth dependent component for the eddy field in the north atlantic than for the north pacific at special locations in the vicinity of their mid latitude jets possibly a signature of distinct instability mechanisms

multi stage ag bi co ni u and cu bi vein mineralization at wittichen schwarzwald sw germany geological setting ore mineralogy and fluid evolution the wittichen co ag bi u mining area schwarzwald ore district sw germany hosts several unconformity related vein type mineralizations within variscan leucogranite and permian to triassic redbeds the multistage mineralization formed at the intersection of two fault systems in the last 250 ma a permo triassic ore stage i with minor u bi quartz fluorite mineralization is followed by a jurassic to cretaceous ore stage ii with the main ag and co mineralization consisting of several generations of gangue minerals that host the sub stages of u bi bi ag ni as bi and co as bi important ore minerals are native elements co and ni arsenides and pitchblende sulphides are absent the miocene ore stage iii comprises barite with the cu bi sulfosalts emplectite wittichenite and aikinite and the sulphides anilite and djurleite besides native bi chalcopyrite sphalerite galena and tennantite the mineral forming fluid system changed from low salinity 5 wt nacl at high temperature around 300 c in permian to highly saline around 25 wt nacl cacl2 at lower temperatures 50 150 c in triassic to cretaceous times thermodynamic calculations and comparison with similar mineralizations worldwide show that the mesozoic ore forming fluid was alkaline with redox conditions above the hematite magnetite buffer we suggest that the precipitation mechanism for native elements pitchblende and arsenides is a decrease in ph during fluid mixing processes ree patterns in fluorite and the occurrence of bi in all stages suggest a granitic source of some ore forming elements whereas e g ag co and ni probably have been leached from the redbeds the greater importance of cu and isotope data indicates that the miocene ore stage iii is more influenced by fluids from the overlying redbeds and limestones than the earlier mineralization stages

hydrochemical characteristics of shallow groundwater in aquifer containing uranyl phosphate minerals in the koprubasi manisa area turkey the concentrations of uranium iron and the major constituents were determined in groundwater samples from aquifer containing uranyl phosphate minerals meta autunite meta torbernite and torbernite in the koprubasi area groundwater samples from wells located at shallow depths 0 5 6 m show usually near neutral ph values 6 2 7 1 and oxidizing conditions eh 119 275 mv electrical conductivity ec values of samples are between 87 and 329 s cm 1 they are mostly characterized by mixed cationic ca dominating bicarbonate types the main hydrogeochemical process is weathering of the silicates in the shallow groundwater system all groundwater in the study area are considered undersaturated with respect to torbernite and autunite phreeqc predicted uo2 hpo4 22 as the unique species the excellent positive correlation coefficient r 0 99 between u and po4 indicates the dissolved uranium in groundwater would be associated with the dissolution of uranyl phosphate minerals the groundwater show u content in the range 1 71 70 45 g l but they are mostly lower than us epa 2003 maximum contaminant level of 30 g l this low u concentrations in oxic groundwater samples is attributed to the low solubility of u vi phosphate minerals under near neutral ph and low bicarbonate conditions iron closely associated with studied sediments were also detected in groundwater the maximum concentration of fe in groundwater samples was 2837 g l while the drinking water guidelines of turkish tse 1997 and us epa 2003 were suggested 200 and 300 g l respectively furthermore iron and uranium showed a significant correlation to each other with a correlation coefficient r of 0 94 this high correlation is probably related to the iron rich sediments which contain also significant amounts of uranium mineralization in addition to ph and bicarbonate controlling dissolution of uranyl phosphates association of uranyl phosphates with iron hydr oxides seems to play important role in the amount of dissolved u in shallow groundwater

direct observations of seasonal exchange through the bab el mandab strait the exchange flow between the red sea and the gulf of aden indian ocean through the bab el mandab strait was measured continuously for 10 months june 1995 march 1996 adcp and temperature salinity chain moorings allow an unprecedented look at the magnitude and seasonal evolution of the inflow layer from the gulf of aden and the high salinity outflow layer from the red sea the timing structure and evolution of the summer season mid depth intrusion of cold low salinity water into the red sea from the gulf of aden is measured for the complete intrusion cycle of 1995 we unexpectedly find the deep outflow still strong in june 1995 with speeds of 0 6 m sec and transport of 0 4 sv 1 sv 106 m sec from july to mid september the deep outflow persists but is attenuated to speeds of 0 2 m sec and transport of 0 05 sv the dominant summer feature the cold low salinity intermediate layer intrusion persists for 3 months occupies 70 of the water column in the strait and carries approximately 1 7 1012 m of cold nutrient rich water into the red sea the winter regime begins in mid september is fully developed by early november and continues to the end of our first observation interval in march 1996 speeds in the lower layer are 0 8 1 0 m sec and 0 4 0 6 m sec in the upper layer at maximum exchange in mid february outflow transport reaches 0 7 sv ubiquitous oscillations in current and salinity at synoptic and intraseasonal periods appear closely related to fluctuations in the along channel wind forcing and perhaps to coastally trapped waves

rare earth patterns with positive cerium anomaly in alkaline waters from lake van turkey abstract the distribution of rare earth elements has been studied for aerobic alkaline ph 9 6 carbonate rich waters from lake van turkey shale normalized ree ree sn patterns display an almost linear increase from the light to the heavy rees and strong positive ce sn anomalies there exist neither positive nor negative gd sn anomalies the ree sn patterns are consistent with domination of ree speciation in solution by poly carbonato complexes generating enrichment of the heavy rees that is even more pronounced than that seen in seawater this is the first report of positive ce sn anomalies observed in ree sn patterns of aerobic natural waters these anomalies apparently result from stabilization of penta carbonato ce iv complexes in solution leading to enhanced abundances of ce in comparison with its trivalent ree neighbours thus in remarkable contrast to seawater positive ce sn anomalies may be general features of alkaline carbonate rich and aerobic lake waters

loop current frontal eddies formation along the campeche bank and impact of coastally trapped waves abstractvelocity data from a mooring array deployed northeast of the campeche bank cb show the presence of subinertial high frequency below 15 days velocity fluctuations within the core of the northward flowing loop current these fluctuations are associated with the presence of surface intensified loop current frontal eddies lcfes with cyclonic vorticity and diameter 30 days that have been linked to caribbean eddies and the lc separation process model results show that wind variability associated with winter cold surges are responsible for the emergence

the krunkelbach uranium deposit schwarzwald germany correlation of radiometric ages u pb u xe kr k ar 230 th 234 u pitchblendes and secondary uranium minerals from the krunkelbach vein type uranium deposit in southwest germany were investigated by the u xe kr u pb and 234 u 230 th methods and by microprobe analysis both u pb and u xe kr results indicate a late carboniferous formation age of 295 or 7 ma for all veins of the deposit and an episodic pb loss during the tertiary 50 or 8 ma 234 u 230 th dating yields quaternary formation ages of 250 to 350 ka kiloyears for five secondary u minerals u pb isotope investigations on three of these samples show a strong component of inherited radiogenic pb which means that during the quaternary pitchblende oxidation pb was not completely separated from u the three isotopically dated events probably correlate with three generations of fluid inclusions the carboniferous hydrothermal veins were formed from low salinity solutions at temperatures of 100 degrees to 300 degrees c uranium probably was derived from leaching of magmatic uraninite in the brhalde granite by near surface oxidizing ground waters and later precipitated due to mixing with hot strongly reducing solutions or by reaction with a previously deposited reduced ore assemblage a gap of 30 to 40 m g between granite emplacement and pitchblende formation indicates that circulation of hydrothermal fluids in the late carboniferous early permian probably was caused by a high regional heat flow rather than by magmatic heat during the formation of the rhinegraben in the early tertiary barite fluorite and calcite but not ore minerals were deposited from highly saline na ca cl brines of 150 degrees to 200 degrees c these brines leached radiogenic and fissiogenic uranium daughters from the pitchblendes and there are indications of minor uranium remobilization eight illite samples from hydrothermally altered wall rocks yield k ar ages of 119 to 208 ma these values are interpreted as mixing ages of the u pb and u xe kr documented carboniferous and tertiary events although a mesozoic event not recorded in the other isotopic systems cannot be ruled out with certainty in the late tertiary early quaternary the present hydrological conditions were installed with infiltration of oxygen rich meteoric waters causing uranium remobilization and precipitation of secondary uranyl minerals i e phosphates arsenates silicates and tungstates yielding 230 th 234 u ages of at least 250 ka

global energy dissipation rate of deep ocean low frequency flows by quadratic bottom boundary layer drag computations from current meter data the global energy dissipation rate of deep ocean low frequency flows by quadratic bottom boundary layer drag is estimated in three ways first an average over the dissipations computed from the near bottom velocities recorded by 290 moored current meters is multiplied by the world ocean area second near global maps of surface velocities derived from satellite altimetry data are used to estimate the bias due to the sparse spatial coverage of the moorings third a relationship between bottom and surface flows computed over the mooring locations is used to estimate global maps of bottom flows from the surface data all three methods suggest that at least 0 2 tw of the wind power input into geostrophic flows is dissipated in deep water by quadratic bottom drag implications for the oceanic overturning circulation and for oceanic mesoscale eddy dynamics are briefly discussed

investigating reservoir sediment and watershed erosion using a geographical information system most economic developments may have been at the expense of soil conservation soil erosion results in impacts on reservoir sediment crop yield and water quality this study introduces the procedure of using a geographical information system for investigating reservoir sediments and soil erosion of the corresponding watershed first the bathymetric surface of a reservoir is surveyed using two real time kinematic global position systems and a sonar based depth gauge using the on board computer receivers and sonar bathymetric readings are recorded three times a second to establish actual coordinates and depth measurements data are then converted using a digital terrain model to obtain the current image bathymetric surface the image of original bathymetric surfaces when constructed can be obtained by digitizing the existing map the subtraction of these two images is used to estimate the amount of sediment deposits next parameters of rainfall runoff erosivity factor soil erodibility factor slope length factor slope steepness factor cover management factor and support practice factor are evaluated for each grid of the corresponding watershed the average annual soil loss from each grid is estimated by the revised universal soil loss equation to obtain the total amount of the soil loss for the watershed using the example of charles mill lake ohio usa the estimated average amount of sediment deposits in the lake was about 2 44 x 10 4 m 3 year 1 on the other hand the estimated soil erosion from the corresponding watershed was about 4 22 x 10 8 kg year 1 or 1 56 x 10 5 m 3 year 1 hence it can be concluded that about 15 6 of the soils eroded from the watershed have been deposited in the lake

planetary wave response to surface forcing and instability in the presence of mean flow and topography the local response of an ocean with slowly varying mean flow stratification and topography to two sources of disturbance is examined concentrating on whether the resulting surface elevations are observable the first is the ocean response to surface forcing ekman pumping or buoyancy forcing for typical amplitudes of random forcing while much of the ocean response is small surface elevations less than 1 mm there are sufficient near resonances or pseudoresonances involving a critical layer to produce elevations of 1 cm or more in much of the ocean the second source is baroclinic instability the fastest linear growth rate as well as those for specific wavelengths is computed globally almost all of the ocean is baroclinically unstable and the most unstable waves are found to possess a small wavelength often less than 10 km with a disturbance concentrated near the surface e folding times o 20 days are frequently found however the phase speed for the disturbances is almost everywhere slower westward than free planetary waves with mean flow and topography since the free waves propagate at speeds similar to observations instability may be a good source of variability but is probably not responsible directly for observed wave propagation

rare earth elements as geochemical tracers of regional groundwater mixing abstract the rare earth elements ree were analyzed in a groundwater system from south central nevada i e ash meadows national wildlife refuge the spring mountains pahranagat national wildlife refuge and the nevada test site in order to investigate their potential use as tracers of regional groundwater flow previous investigations using conservative tracers e g deuterium and uranium isotopes identified recharge in local mountains as the primary source 60 70 of total discharge for the springs in the regional discharge zone i e ash meadows with the remaining contribution being interbasin flow from the northeast initial mixing calculations for these groundwaters using shale normalized ree patterns agreed well with the previous studies however because the rees are not expected to behave conservatively in natural waters the effect of both solution complexation which acts to enhance the stability of the rees in solution as well as surface complexation responsible for the particle reactive behavior of the rees were examined in subsequent mixing calculations in order to assess the roles of solution and surface complexation relative partitioning coefficients were estimated for each ree in each groundwater by evaluating the ratio of the ionic strength corrected co 3 1 ree co 3 2 ree and co 3 2 f to the first hydrolysis binding constants for the rees the relative partitioning coefficients were then used to calculate ree patterns expected to develop and persist in solution as a consequence of solution and surface complexation the calculated ree values closely resembled the actual measured ree concentrations suggesting that the rees are in fact controlled by solution and surface complexation in these groundwaters the calculated ree concentrations were subsequently used to determine mixing ratios the results of which coincided with the initial calculations as well as the previous studies the results of this study suggest that solution complexation of the rees is sufficient to overcome to a certain degree the affinity of the rees to be adsorbed onto surface sites in the aquifers such that distinctive ree signatures develop and persist in solution in groundwaters from different aquifers the ability of solution complexation to overcome surface complexation is likely related to the formation of the negatively charged dicarbonato complex i e ln co 3 2 where ln is any ree which accounts for significant fractions of each ree in these groundwaters

weathering of bi bearing tennantite abstract the tennantite tetrahedrite solid solution series called fahlore cu ag 6cu4 fe zn cu hg cd 2 sb as bi te 4 s se 13 is widespread in many geological environments since it incorporates heavy metals and toxic elements a better understanding of its weathering behaviour and details of its weathering process is important to evaluate environmental risks emerging mainly from the mobilization of as sb bi and local and global metal fluxes in stream waters and oceans in this study weathering of bi rich members of this mineral group was investigated using microscopy empa sem tem la icp ms raman xrd and mla observations reveal a succession of four distinct stages of weathering during stage 1 irregular tubes within fahlore show an assemblage of nm to m sized romeite group minerals tripuhyite crystalline cu oxides and cu sulfides stage 1 textures and secondary sulfides indicate a low redox potential and a low fluid rock ratio typical of cementation zones mass balance calculations show that during this stage all zn and the majority of as and s are released to the weathering fluids bismuth is immobile in this stage and sb and fe are immobile if bi is sufficiently available from fahlore but both are partly released if the fahlore did not contain sufficient bi during stage 2 amorphous and nano crystalline arsenates replace fahlore as weathering fronts such assemblages indicate a higher redox potential than in stage 1 typical for oxidation zones mass balance calculations reveal that zn sb s and partially cu are lost arsenic and bi are immobile stage 3 occurs only locally dissolving former weathering stages and or precipitating amorphous cu arsenates silicates reflecting processes in micro compartments not characteristic for the general weathering process stage 4 is characterized by the formation of crystalline bi cu ba ca or al bearing arsenates and cu carbonates spatially independent of the precursor fahlore copper and as originate from older weathering assemblages whereas many other elements are derived externally ca ba al this stage reflects the increasing importance of the local host rock and gangue mineralogy as it is typical in near surface environments of oxidation zones or on mine dumps where elements are highly mobile and a high fluid rock ratio prevails gossan mineralization the temporal evolution of fahlore weathering textures reflects the transition from fresh ore to cementation zone oxidation zone and gossan assemblages in one hand specimen thus one fahlore grain can record the uplift and erosion and the increasing fluid rock interaction of a weathered ore deposit with time tube like textures similar to the ones observed in stage 1 have been reported from other weathering environments and from a variety of element oxide arsenide and sulfide phases they also were produced during experimental work in ilmenite this is clear evidence that the diffusive process during the first contact with alteration fluids is a basic physical process and that it is not only valid for fahlore the importance of bi to stabilize sb bearing supergene phases and thereby for the immobilization of toxic sb shown in the present work may stimulate further investigations on the environmental immobilization of toxic elements by companion metals during weathering processes

particle fluxes induced by benthic storms during the 2012 dense shelf water cascading and open sea convection period in the northwestern mediterranean basin abstract the effects of deep dense shelf water cascading and open sea convection on the sediment dynamics of the northwestern mediterranean basin were studied by near bottom moored instruments recording trapped particle fluxes suspended particle fluxes water properties and hydrodynamics from november 2011 to july 2012 during this period near bottom currents induced by winter dense water formation generated benthic storms that caused resuspension at 2450 m water depth increasing by more than one order of magnitude the ambient suspended sediment concentrations the trapped particle fluxes and the suspended sediment fluxes during the preconditioning phase of the open sea convection from december 2011 to mid february 2012 currents 1 10 cm s 1 suspended sediment concentrations

deep water properties near 35 n 143 e observed during the kuroshio extension regional experiment deep water measurements were obtained from a closely spaced conductivity temperature depth hydrographic section that crossed the japan trench and the kuroshio in the vicinity of the kashima 1 seamount near 35 n 143 e vertical sections of temperature salinity density oxygen and nutrients are discussed for water below 1000 m at the northwestern extreme of the section the existence of a southward flowing deep western boundary current is suggested by the silica distribution as well as by geostrophic calculations in the vicinity of the seamount hydrographic properties are perturbed and contrasting variabilities are found in the deep water characteristics along the section the measurements also suggest a deep northward flow associated with the trench current meter observations hallock and teague 1996 along the section lend credence to these interpretations these observations help piece together an overall picture of the deep and abyssal circulation of the northwest pacific

deep current measurements at 38 n east of japan 1 deep currents east of japan were investigated using direct current measurements and hydrographic observations current data recorded for 9 months along 38 n showed a pair of currents one southward and the other northward flowing along local isobaths above the western and eastern flanks respectively of the japan trench geostrophic velocities calculated from conductivity temperature depth ctd data showed a similar velocity pattern to the current measurements the transports referring to the mean current velocities were estimated below 2000 m the deep transports above the trench were southward 5 5 sv and northward 13 5 sv and the boundary was at the deepest point of the trench the mean current measured above the abyssal plain to the east of the trench was westward at 38 n since the bottom water properties above the eastern flank of the trench were colder and more saline than those on the abyssal plain the westward current does not enter the trench but rather is expected to turn northward just east of the trench its northward transport was estimated to be 6 2 sv and the total northward transport was estimated to be 19 7 sv at 38 n a pair of oppositely flowing deep currents is confirmed in the japan trench while the transports were similar to those of the izu ogasawara and kuril kamchatka trenches whose ends connect with the japan trench the current structure resembles that at the izu ogasawara trench rather than that at the kuril kamchatka trench

a modified law of the wall applied to oceanic bottom boundary layers 1 near the bottom the velocity profile in the bottom boundary layer over the continental shelf exhibits a characteristic law of the wall that is consistent with local estimates of friction velocity from near bottom turbulence measurements farther from the bottom the velocity profile exhibits a deviation from the law of the wall here the velocity gradient continues to decrease with height but at a rate greater than that predicted by the law of thewall with the local friction velocity we argue that the shape of the velocity profile is made consistent with the local friction velocity by the introduction of a new length scale that near the boundary asymptotes to a value that varies linearly from the bottom farther from the boundary this length scale is consistent with the suppression of velocity fluctuations either by stratification in the upper part of the boundary layer or by proximity to the free surface the resultant modified law of the wall provides a good representation of velocity profiles observed over the continental shelf when a local estimate of the friction velocity from coincident turbulence observations is used the modified law ofthe wall is then tested on two very different sets of observations from a shallow tidal channel and from the bottom of the mediterranean outflow plume in both cases it is argued that the observed velocity profile is consistent with the modified law of the wall implicit in the modified law of the wall is a new scaling for turbulent kinetic energy dissipation rate this new scaling diverges from the law of the wall prediction above 0 2d where d is the thickness of the bottom boundary layer and agrees with observed profiles to 0 6d

interaction of the gulf stream and deep western boundary current where they cross the long timescale variability of the deep western boundary current dwbc where it crosses under the gulf stream is analyzed using a 3 year array of bottom current meters and inverted echo sounders the relationship of this variability to fluctuations in the upper layer gulf stream is specifically addressed at periods shorter than a year the dwbc variability shows no relationship to the local gulf stream 100 day fluctuations show a pulsing of the dwbc transport whereas longer period fluctuations are indicative of a meandering type variability by contrast on timescales greater than a year variations in the orientation and transport of the dwbc are directly related to such fluctuations in the local gulf stream the coupling reveals that the dwbc is forced by changes in the gulf stream rather than causing such variations which is in contrast to earlier modeling results

direct observation of tetravalent cerium in ferromanganese nodules and crusts by x ray absorption near edge structure xanes abstract x ray absorption near edge structure xanes was successfully applied for the direct determination of ce valence in hydrogenetic ferromanganese nodules two samples and crust one sample rare earth element ree patterns of the hydrogenetic ferromanganese nodules and crust recovered from the pacific ocean show large positive ce anomalies especially when normalized to seawater despite some disadvantages in the spectroscopic analysis of ce in natural samples e g low concentration and interference from other elements intense synchrotron radiation and measurement of fluorescent xanes with semiconductor detectors having high energy resolution enabled us to detect xanes at ce l iii edge in the ferromanganese nodule or crust in the xanes spectra of the nodule or crust large double peaks were observed showing that the oxidation state of ce in the nodule or crust is predominantly tetravalent with little contribution from ce iii this is the first in situ quantitative analysis of ce iv among total ce in natural samples as a trace element as far as we know the results obtained by xanes seem to be consistent with the percentage of ce iv estimated from seawater normalized ree patterns suggesting that seawater is a precursor of ree in the marine deposits the present results also confirm that ce enrichment relative to other rees in hydrogenetic ferromanganese deposits is due to oxidative removal of ce from seawater to the ferromanganese nodules and crust in the marine environment comparison of xanes spectra of ce sorbed on synthetic manganese oxide and ceo 2 vs those of the ferromanganese nodules and crust suggests that the initial reaction of ce with the ferromanganese nodules and crust is the sorption of dissolved ce iii to the manganese oxide surface

low frequency eddy kinetic energy spectrum in the deep western north pacific the frequency spectrum for the low frequency eddy kinetic energy is estimated from a long term current meter record obtained in a deep layer in the western north pacific the eddy field is characterized by three time scales an annual scale with zonal dominance of eddy motions a temporal mesoscale with meridional dominance and a monthly scale with horizontal isotropy about two thirds of the eddy kinetic energy is contained in the temporal mesoscale

erosion and sediment characteristics of cultivated forest soils as affected by the mechanical stability of aggregates abstract information on erosion and size distribution of soil and sediment is useful in developing effective soil conservation techniques in farms the size distribution and mechanical stability of soil may influence the size distribution of sediment due to erosion in this study erosion and sediment characteristics were measured in simulated rainfall experiments for three forest soils of contrasting physical properties four erosion treatments combined varying slope and kinetic energy of rainfall to provide three effective levels of energy from rain and runoff a comparison of soil loss and size distribution quantified as mean weight diameter mwd of the uneroded soils with size distribution of sediment indicated soil loss to be greatest and sediment finest for the soil which was most susceptible to wetting in contrast soil loss was low and sediment was coarse for the strongly aggregated soil indices of relative mechanical stability have been developed which will assist interpretation of sediment quality and erosion for a range of soils

circulation of the pacific ocean seen in a global ocean model ocean circulation and climate advanced modelling project occam this paper compares observations made in the pacific ocean and the 8 12 year climatology of a global numerical model meridional mass and heat transports and their divergences are calculated and zonal averages compared with the air sea exchange values of doney et al 1998 with mixed success the large scale distribution of sea surface height and near surface currents are shown to be well reproduced by the model but their variance is underestimated severely so in areas of weak variability synoptic wind forcing enhances the latter though only slightly while higher model resolution improves agreement in areas of strong variability model mean transports in the east australian current in the vitiaz strait and in the kuroshio exceed measurements by 10 0 18 sv respectively and variability is underestimated by factors between 2 and 4 near 1000 m and in strong currents the flow is overestimated but over most of the ocean model output does not match either the magnitude or the spatial variability of the observations in contrast the inflow of bottom water and its spreading path throughout both south and north pacific is well described good agreement is found with measured transport through the samoan passage but at 32 s east of the tonga kermadec ridge the model yields only 60 of the observed value the sverdrup balance is shown to hold widely in the model interior utilizing the complete depth integrated vorticity equation it is found that bottom pressure torques balance the advection of planetary vorticity in both surface and bottom intensified western boundary currents

observed oceanic response over the upper continental slope and outer shelf during hurricane ivan abstract hurricane ivan passed directly over an array of 14 acoustic doppler current profilers deployed along the outer continental shelf and upper slope in the northeastern gulf of mexico currents in excess of 200 cm s 1 were generated during this hurricane shelf currents followed ekman dynamics with overlapping surface and bottom layers during ivan s approach and transitioned to a dominant surface boundary layer as the wind stress peaked slope currents at the onset of ivan were wind driven near the surface but deeper in the water column they were dominated during and after the passage of ivan by subinertial waves with a period of 2 5 days that had several characteristics of topographic rossby waves currents on the slope at 50 m and greater depths commonly exceeded 50 cm s 1 surprisingly the strongest currents were present to the left of the storm track on the shelf while more energetic currents were to the right of the hurricane path on the slope during the forced stage near inertial motion last

alteration adsorption and nucleation processes on clay water interfaces mechanisms for the retention of uranium by altered clay surfaces on the nanometer scale abstract nano scale processes on the solid water interface of clay minerals control the mobility of metals in the environment these processes can occur in confined pore spaces of clay buffers and barriers as well as in contaminated sediments and involve a combination of alteration adsorption and nucleation processes of multiple species and phases this study characterizes nano scale processes on the interface between clay minerals and uranyl bearing solution near neutral ph samples of clay minerals with a contact ph of 6 7 are collected from a u mill and mine tailings at key lake saskatchewan canada the tailings material contains cu as co mo ni se bearing polymetallic phases and has been deposited with a surplus of ca oh 2 and na2co3 slaked lime small volumes of mill process solutions containing sulfuric acid and u are occasionally discharged onto the surface of the tailings and are neutralized after discharge by reactions with the slaked lime transmission electron microscopy tem in combination with the focused ion beam fib technique and other analytical methods sem xrd xrf and icp oes are used to characterize the chemical and mineralogical composition of phases within confined pore spaces of the clay minerals montmorillonite and kaolinite and in the surrounding tailings material alteration zones around the clay minerals are characterized by different generations of secondary silicates containing variable proportions of adsorbed uranyl and arsenate species and by the intergrowth of the silicates with the uranyl minerals cuprosklodowskite cu uo2 2 sio3oh 2 h2o 6 and metazeunerite cu uo2 aso4 2 h2o 8 the majority of alteration phases such as illite illite smectite kaolinite and vermiculite have been most likely formed in the sedimentary basin of the u ore deposit and contain low amounts of fe 10 at formed most likely in the limed tailings at high contact ph 10 5 and their structure is characterized by a low degree of long range order adsorption of u and nucleation of metazeunerite and cuprosklodowskite are strongly controlled by the presence of the adsorbed oxy anion species arsenate and silica on the fe enriched silicates heterogeneous nucleation of nano crystals of the uranyl minerals occurs most likely on adsorption sites of binary uranyl arsenate and silica complexes as well as on ternary uranyl arsenate or uranyl silicate complexes the uranyl minerals occur as aggregates of misoriented nano size crystals and are the result of supersaturated solutions and a high number of nucleation sites that prevented the formation of larger crystals through oswald ripening the results of this study provide an understanding of interfacial nano scale processes between uranyl species and altered clay buffers in a potential nuclear waste repository as similar alteration conditions of clays may occur in a multi barrier system

ree systematics in hydrothermal fluorite abstract ree patterns of fluorite from 63 post variscan hydrothermal veins of the schwarzwald area germany can be divided into two major groups type a fluorite shows roof shaped paas normalized patterns with enriched mree the turning point of the curvature is at ho or er position all patterns of type a show a distinct positive eu anomaly type b fluorite shows roof shaped patterns with enriched mree and strongly depleted hree and a characteristic steep slope between nd and sm the turning point of the curvature is at gd to dy all patterns of type b show negative or no eu anomalies laser ablation icp ms traverses through single grains combined with cathodoluminescence imagery revealed either i identical ree patterns and total ree concentrations from core to rim ii identical ree patterns but concentration gradients or iii variable ree patterns and concentration gradients from core to rim these features are explained by different degrees of supersaturation or different fluid fluorite ratios during crystallization and by complexly controlled precipitation processes under closed system conditions petrographically late fluorites from several deposits show the characteristics of new fluid batches rather than the expected remobilization features lree enrichment close to the crystal faces in some grains may result from the copreciptiation of a submicrometer sized lree enriched phase or from lree clustering in late cool fluids by comparison with literature data on natural waters from gneissic and granitic aquifers and of leachates of granites and gneisses we show that the hydrothermal vein fluorite preserves the characteristic source related ree feature of the hydrothermal fluid that migrated through either gneissic type a or granitic type b host rocks the immediate host rocks of the veins however are not the source rocks of the ree which indicates large scale fluid convection in the basement gneiss related type a fluorite shows tb ca tb la trends of primary hydrothermal crystallization whereas granite related type b fluorite indicates remobilization of possibly pegmatitic or variscan fluorite

deep eddy energy and topographic rossby waves in the gulf of mexico abstract observations suggest the hypothesis that deep eddy kinetic energy eke in the gulf of mexico can be accounted for by topographic rossby waves trws it is presumed that the trws are forced by loop current lc pulsation loop current eddy lce shedding and perhaps also by lce itself although the hypothesis is supported by model results such as those presented in oey the existence of trws in the model and how they can be forced by larger scale lc and lces with longer period vacillations have not been clarified in this paper results from a 10 yr simulation of lc and lces with double the resolution of that used by oey are analyzed to isolate the trws it is shown that along an east to west band across the gulf approximately over the 3000 m isobath significant eke that accounts for over one half of the total spectrum is contained in the 20 100 day periods bottom energy intensification exists in this east west band with vertical decay scales of about 600 300 m decreasing westward the de

global rate and spectral characteristics of internal gravity wave generation by geostrophic flow over topography the rate of generation of internal gravity waves in the lee of small length scale topography by geostrophic flow in the world ocean was estimated using linear theory with corrections for finite amplitude topography several global data sets were combined for the calculation including an ocean circulation model for the near bottom geostrophic flow statistics over 500 abyssal current meter records historical climatological data for the buoyancy frequency and two independent estimates of the small scale topographic statistical properties the first topography estimate was based on an empirically derived relationship between paleo spreading rates and abyssal hill roughness with corrections for sedimentation the second estimate was based on small scale 100 km roughness of satellite altimetry derived gravity field using upward continuation relationships to derive estimates of abyssal hill roughness at the seafloor at scales less than approximately 20 km the lee wave generation rate was found to be between 0 34 to 0 49 tw the southern hemisphere produced 92 of the lee wave energy with the southern ocean dominating strength of the bottom flow was the most important factor in producing the global pattern of generation rate except in the indian ocean where extremely rough topography produced strong lee wave generation despite only moderate bottom flows the results imply about one half of the mechanical power input to the ocean general circulation from the extra equatorial wind stress of the world ocean results from abyssal lee wave generation topographic length scales between 176 m and 2 5 km horizontal wavelengths between 1 and 16 km accounted for 90 of the globally integrated generation

the effect of slope length on the amount and size distribution of eroded silt loam soils short slope laboratory experiments on interrill erosion abstract the data of rainfall simulation experiments on a sandy loam and a loamy sand were compared to assess the effect of slope length on the soil loss from short slopes between 0 3 and 0 9 m the total soil loss and the aggregate size distribution in the total soil loss were determined after 90 min of rainfall with rainfall intensities between 22 0 and 78 5 m h 1 the experimental results indicated that the slope length effect is different for the two soils although for both soils the total soil loss increased with increasing slope length the soil loss per unit slope length increased with increasing slope length only for the sandy loam soil 1 and decreased with increasing slope length for the loamy sand soil 2 the difference in slope length effect between the two soils was also reflected in the aggregate size distribution in the soil loss the different aggregate sizes displayed different relationships between soil loss and slope length for the loamy sand the slope length effect was less for the large aggregate sizes which contained more sand than the original soil for both soils the slope length effect was most pronounced for the aggregate sizes smaller than 0 05 mm

remobilization of u and ree and the formation of secondary minerals in oxidized u deposits the hydrothermal uranium vein type deposits of menzenschwand and wittichen in the schwarzwald in southwestern germany have been investigated with regards to their primary and secondary mineralization primary magmatic uraninite i from the host granite of menzenschwand primary hydrothermal uraninite ii and secondary supergene uranyl silicates uranophane and cuprosklodowskite uranyl phosphates torbernite and uranocircite and uranyl arsenates zeunerite heinrichite novacekite walpurgite and uranospinite were analyzed for their ree contents by la icp ms together with uraninite ii samples from other known schwarzwald uraninite ii occurrences for comparison water samples were taken from drillings and abandoned mines and were analyzed for their major and trace element composition including u and ree the ree patterns of uraninite show significant eu anomaly variations negative eu anomalies are related to granitic host rocks whereas positive eu anomalies imply a gneissic ree source this is in agreement with the observation of eu anomalies in granite and gneiss derived waters which display negative and positive eu anomalies respectively rare earth element distributions in the secondary uranyl minerals provide information about the sequence of mineral precipitation and the degree of remobilization of u cerium anomalies or their absence imply that uranyl silicates formed during an earlier stage of weathering under more reduced conditions than the uranyl arsenates and phosphates the ree patterns of the uranyl silicates in wittichen are similar to those of uraninite ii suggesting a very local redistribution on the millimeter to centimeter scale in contrast the ree patterns of uranyl arsenates and phosphates are different from uraninite ii patterns and resemble those of the waters this shows that the uranyl phosphates and arsenates are formed not only by redistribution of u in the hydrothermal veins but are influenced by waters from the host rock implying that u was probably transported over a greater distance these conclusions are supported by field observations where uranyl silicates are often found in the vicinity of uraninite ii whereas uranyl phosphates and arsenates are commonly found on fissures in the host rock to explain specific features in the sulfide rich pyrite chalcopyrite menzenschwand deposit we conducted thermodynamic reaction modeling using the phreeqc computer code sulfide oxidation was modeled by reaction of a u rich water in equilibrium with atmospheric oxygen with fes2 and cufes2 a water that initially precipitates uranophane gradually evolves to more acidic ph values thereby reaching torbernite saturation this is in agreement with observed paragenetic sequences ongoing reaction results in a further decrease of ph and in the destabilization of uranophane and torbernite since goethite precipitates even at low ph values these calculations can explain observed pseudomorphs of goethite after both uranophane and torbernite which are frequently observed at menzenschwand if the reaction proceeds and f o2 in the system is buffered by the surrounding minerals u6 can be reduced to u4 and uraninite can form and replace pyrite and earlier formed secondary uranium minerals such as ianthinite also these textures have been observed we show that the combination of ree geochemistry careful paragenetic observations and thermodynamic modeling allows to reconstruct the formation and weathering of uranium deposits in great detail

two year moored instrument results along 152 e results from a 2 year nominal deployment of a moored array along 152 e from 28 n to 41 n are presented with emphasis on similarities and differences between settings approximately year to year ten moorings and 38 instruments were involved from the fall of 1980 to 1982 current temperature meters spanned the water column from 500 to 4000 m depths with occasional instruments in the vicinity of 300 m and near the bottom 6000 m upper level features located in the center of the array near 35 36 n were generally stable relative to the axis of the kuroshio extension varying from deployment to deployment with meanders in this flow regime some properties of the abyssal 4000 m currents were comparatively more variable with these changes not connected to meandering of the kuroshio extension in an obvious way the vertical structure and frequency distributions of eddy kinetic energy were similar in shape and to some extent in amplitude from deployment to deployment especially relative to meanders of the kuroshio extension but translated in the opposite direction

ree fractionation during granite weathering and removal by waters and suspended loads sr and nd isotopic evidence very few studies deal with ree rare earth element mobility within the system soil soil solution streamwater in this article we try to characterize the fractionation and the migration of the ree in a granite derived soil system located in a small catchment of the vosges mountains icp ms and tims measurements were performed on both solid samples fresh granite soil and suspended load of the stream and waters soil solutions springwater and streamwater to determine their respective ree concentrations and sr and nd isotopic compositions the paas normalized ree pattern of the bedrock is characterized by a strong depletion in hree heavy ree and a negative eu anomaly 0 46 similarly the granite normalized ree distribution patterns of the soil samples show hree depletions that become more important with decreasing depth the correlative behavior between p2o5 th and ree with depth indicates that besides apatite other phosphate minerals such as monazite are the most important phases controlling the th and ree budget in the soil profile on the other hand at greater depth zircon seems to be another important mineral phase controlling especially the hree enrichment as shown by the positive relationship between zr content and the yb ho ratio different grain size fractions show similar ree distribution patterns and are only weakly fractionated compared with bulk soil sample however the finest fraction 0 20 m is more enriched in sr and ree suggesting a stronger concentration of ree carrying minerals in this fraction the suspended and dissolved load of the stream show as a whole an enrichment in hree if compared with the granite or with the different soil samples however compared with the uppermost soil samples the suspended load is significantly more enriched in hree its ree distribution pattern is more similar to that of the finest fraction of the deeper soil sample and to the fresh granite thus most probably the ree of the suspended load originated from a source with ree characteristics found in the deep soil horizons this source might have been situated in the uppermost soil profile which is actually ree depleted the weathering process can be compared with a leaching experiment where the waters correspond to the leachate and the soil to the residual phase of the granite the sr isotope data indicate that the suspended load originates from the finest soil fraction the sr and nd isotopic data of the suspended load suggest that it contains up to 3 sr and nd from apatite and up to 97 from feldspar most of the sr and nd in the waters originate from apatite leaching or dissolution

evolution and structure of the upper rhine graben insights from three dimensional thermomechanical modelling the evolution and geometry of the tertiary upper rhine graben were controlled by a continually changing stress field and the reactivation of pre existing crustal discontinuities a period of wnw ese extension in the late eocene and oligocene was followed by lateral translation from the early miocene onwards this study utilizes 3d finite element techniques to simulate extension and lateral translation on a lithospheric scale brittle and creep behaviour of lithospheric rocks are represented by elastoplasticity and thermally activated power law viscoplasticity respectively contact elements allocated with cohesion and frictional coefficients are used to describe pre existing zones of weakness in the elastic brittle field our results suggest that 1 extension is accommodated along listric border faults to midcrustal depth of 15 16 km beneath pure shear stretching occurs without a need for localized shear zones in lower crust and upper mantle 2 ductile flow at midcrustal depth across the graben accounts for the pronounced halfgraben morphology thereby the shape of the border faults their frictional coefficients and sedimentary loads have profound effects on the rate of ductile flow across the graben 3 horizontal extension of 8 8 5 km and sinistral displacement across the rift of 3 4 km are needed to accommodate the observed sediment thickness

deep currents in the central subarctic pacific ocean abstract sections of closely spaced ctd stations along longs 165 w 175 w and 175 e in combination with 14 month current records from the central longitude define two deep nearly zonal currants with speed increasing upward in the subarctic pacific one flows eastward above the aleutian rise and aleutian trench and appears to be a concentration of geostrophic flow forced by the bottom topography the other flows westward along the aleutian island arc and is the northern boundary current predicted by deep circulation theory both currents reach to the sea surface the boundary current being simply the deep part of the alaskan stream the current records were too few to permit better than rough estimates of volume transports but to the extent that they could be combined with thermal wind calculations they suggest at 175 w 1 a transport of 28 106 m3 s 1 for the alaskan stream of whch 5 106 m3 s 1 was found below 1500 m and 2 a transport of around 20 1o6 m3 s 1 for the eastward jet of wh

biweekly periodic deep flow variability on the slope inshore of the kuril kamchatka trench abstract five long term current records are analyzed to investigate the temporal variability for deep flows from a single mooring fitted with two current meters on the slope inshore of the southern end of the kuril kamchatka trench southeast of cape erimo where the oyashio and a deep western boundary current are considered to flow southwestward together at 3000 m the spectral peaks of eddy kinetic energy were found at about 2 weeks in all current records the flow variability with period of 2 weeks at 3000 m was more energetic than that at 1000 m by applying topographic rossby wave theory this variability is thought to be due to bottom trapped topographic rossby waves

length scales of eddy generation and nonlinear evolution of the seasonally modulated south pacific subtropical countercurrent the dynamical processes behind the seasonal modulation of the two dimensional eddy kinetic energy eke wavenumber spectrum in the subtropical countercurrent region of the south pacific are investigated with 14 yr of satellite altimeter data and climatological hydrographic data the authors find a seasonally modulated generation of eke via baroclinic instability in modes with larger meridional length scales subsequent nonlinear eddy eddy interactions redistribute the eke to larger total horizontal length scales and larger zonal scales in particular this is confirmed by diagnosing the spectral transfer of eke in the surface geostrophic flow which is found to drive an anisotropic inverse cascade being redirected in the sense consistent with the effect as predicted by geostrophic turbulence theory on the plane because of the seasonal renewal of meridionally elongated anomalies by baroclinic instability and possibly because of the barotropization process however the net outcome for the formation of surface zonal flows is observed to be limited

deep current variability near the sigsbee escarpment in the gulf of mexico abstract observations of deep currents from a closely spaced array deployed at the base of the sigsbee escarpment south of the mississippi delta are dominated by energetic short period 10 days topographic rossby waves over a 2 yr interval distinct trains of waves occurred with differing characteristic periods wavelengths and horizontal energy distribution usually initiated with a burst of large amplitude current fluctuations that slowly decay over the next 2 3 months two of the wave trains were associated with the shedding and westward passage of major loop current anticyclones however one event occurred when upper layer currents were quiescent this latter wave train showed that bottom trapped topographic wave motions can be traced to within 300 m of the surface in a 2000 m water column ray tracing showed that a likely source region of the short period waves was the west side of an extended loop current the data and ray paths suggest that through refraction and reflection the steep es

hydrographic section aeross the kuroshio near 35 n 143 e a closely spaced conductivity temperature depth hydrographic section was conducted off the east coast of japan in july 1992 the southeastward section crossed the japan trench and the kuroshio in the vicinity of the kashima 1 seamount vertical sections of temperature salinity density oxygen and nutrients are discussed in conjunction with the movement and interleaving of water masses complicated vertical and horizontal mixings of water masses are inferred from the temperature and salinity relationships mixing processes are patchy and not continuous beneath the front warm salty water found beneath the kuroshio may result from upward mixing of water from intermediate depths the main axis of the kuroshio indicated by the 14 c isotherm at 200 m is at 35 7 n 142 6 e about 20 km from the north wall surface thermal front geostrophic speeds exceed 170 cm s 1 at the surface volume transport through the section is 81 106 m3 s 1

rapid development of negative ce anomalies in surface waters and contrasting ree patterns in groundwaters associated with zn pb massive sulphide deposits ground and surface waters collected from two undisturbed zn pb massive sulphide deposits the halfmile lake and restigouche deposits and active mines in the bathurst mining camp bmc nb canada were analysed for the rare earth elements ree ree contents are highly variable in waters of the bmc with higher contents typical of waters with higher fe and lower ph there are significant differences between ground and surface waters and between groundwaters from different deposits the ree contents of surface waters are broadly similar within and between deposit areas although there are spatial variations reflecting differences in ph and redox conditions surface waters are characterised by strong negative ce anomalies ce ce nasc as low as 0 08 produced by oxidation of ce3 to ce4 and preferential removal of ce4 from solution upon leaving the shallow groundwater environment groundwaters and seeps typically lack significant ce anomalies reflecting generally more reducing conditions in the subsurface environment and indicating that ce oxidation is a rapid process in the surface waters deeper groundwaters at the halfmile lake deposit are characterised by ree patterns that are similar to the host lithologies whereas most groundwaters at the restigouche deposit have lree depleted patterns compared to nasc halfmile lake deposit groundwaters have generally lower ph values whereas restigouche deposit groundwaters show greater heavy ree complexation by carbonate ions shallow waters at the halfmile lake and stratmat main zone deposits have unusual patterns which reflect either the adsorption of light ree onto colloids and fracture zone minerals and or precipitation of ree phosphate minerals middle ree enrichment is typical for ground and surface waters and is highest for neutral ph waters the labile portion of stream sediments are generally more middle ree enriched than total sediment and surface waters indicating that the ree are removed from solution by adsorption to fe and mn oxyhydroxides in the order middle ree light ree heavy ree

slope dependent friction in a barotropic model 1 an evaluation of different bottom friction parameterizations has been performed with a nonlinear barotropic shallow water model the model was set up for the baltic sea and forced with meteorological data during 1 year the simulations were validated using hourly observations from 38 tide gauge stations around the baltic a new parameterization with friction proportional to the scalar product between the flow velocity and the bottom slope was tested and compared with parameterizations using rayleigh friction ekman friction laplacian viscosity or quadratic bottom friction the new parameterization consistently gave both a smaller error and a better correlation with the observations the average error with slope friction was 5 0 cm as compared with 5 2 cm using quadratic bottom friction the best of the other parameterizations the correlation using slope friction was 0 92 as compared with 0 91 using quadratic bottom friction the results were slightly improved by combining slope friction and rayleigh friction

weathering of galena mineralogical processes hydrogeochemical fluid path modeling and estimation of the growth rate of pyromorphite in many natural and anthropogenically affected environments alteration of galena produces thermodynamically more stable secondary lead phases these secondary minerals control the mobility of the toxic heavy metal lead in water these textural paragenetic and stability relations have not been investigated in detail in the literature yet an extensive petrographic study of 41 thin sections of weathered zoned galena and adjacent country rock from the schwarzwald mining area southwest germany is presented the observed textures were evaluated using phreeqc fluid path modeling and sequences of stable secondary mineral assemblages were predicted the most common secondary supergene lead minerals of interest here are cerussite anglesite and pyromorphite group minerals pygm pyromorphite mimetite and vanadinite these lead phases show a spatially well ordered zoned texture around the preexisting relic galena cerussite and anglesite commonly occur either as in situ replacement of galena and or as euhedral crystals in cavities of former partially dissolved galena the pygm are present either as crusts around the margin of the former relic galena or are common as infiltration products into the host rock gangue during progressive weathering anglesite typically disappears first followed by cerussite finally only the highly insoluble pygm persist as a perimorphose hence a spatially and temporally zoning texture is formed thermodynamic models of various fluid evolution paths using phreeqc show the influence of temperature ph variable p co2 phosphorous contents and or different mineral reactions on the sequence of formation and stability of the secondary lead phases already small changes in one or more of these parameters can lead to different mineral assemblages or sequences of secondary lead minerals over almost the whole relevant ph range pygm are the most stable lead phases precipitating at very low ion activities explaining their textural position whether cerussite or anglesite forms depends mainly on the ph value of the supergene fluids which is affected by the quite variable fluid pathways furthermore a solubility diagram for a typical near surface fluid was calculated showing that anglesite is the most soluble phase followed by cerussite and pygm this again reflects the microscopic observations as a further step the time span for the formation of a natural millimeter thick pyromorphite crust was evaluated using subsoil phosphorous fluxes from the literature the calculation indicates that millimeter thick pyromorphite crusts can be formed in few tens to about hundred years which is in agreement with observations in the nature in this study a framework for predicting stable secondary lead mineral assemblages and textures by fluid path modeling is given these models are potentially important for predicting the retention and mobilization of lead in systems around contaminated sites or natural ore deposits

subinertial slope trapped waves in the northeastern gulf of mexico abstract current velocity from moored arrays of acoustic doppler current profilers adcps deployed on the outer shelf and slope south of mobile bay in the northeastern gulf of mexico shows evidence of alongslope generally westward propagating subinertial baroclinic kelvin waves with periods of about 16 and 21 days amplitudes of 5 10 cm s 1 and wavelengths of about 500 km the observed waves were highly coherent over the slope between about 200 and 500 m and accounted for a significant amount of the current variability below 200 m the source of the waves could be attributed to effects of the loop current on the west florida slope but is more likely due to direct forcing by loop current generated eddies impacting the experimental area

major and trace element compositions including ree of mineral thermal mine and surface waters in sw germany and implications for water rock interaction abstract the near surface water cycle in a geologically complex area comprises very different sources including meteoric metamorphic and magmatic ones fluids from these sources can react with sedimentary magmatic and or metamorphic rocks at various depths the current study reports a large number of major minor and trace element analyses of meteoric mineral thermal and mine waters from a geologically well known and variable area of about 200 150 km in sw germany the geology of this area comprises a variscan granitic and gneissic basement overlain in parts by triassic and jurassic shales sandstones and limestones in both the basement and the sedimentary rocks hydrothermal mineralization occurs including pb cu as zn u co and many others which were mined in former times mineral waters thermal waters and meteoric waters flowing through abandoned mines mine waters are distributed throughout the area although the mine waters concentrate in and around the schwarzwald the present analyses show that the major element composition of a particular water is determined by the type of surrounding rock e g crystalline or sedimentary rocks and the depth from which the water originates for waters from crystalline rocks it is the origin of the water that determines whether the sample is na cl dominant deeper origin or ca hco3 dominant shallow origin in contrast compositions of waters from sedimentary rocks are determined by the availability of easily soluble minerals like calcite ca hco3 dominant halite na cl dominant or gypsum ca so4 dominant major element data alone cannot therefore be used to trace the origin of a water however the combination of major element composition with trace element data can provide further information with respect to flow paths and fluid rock interaction processes accordingly trace element analyses showed that ce anomalies can be used as an indicator for the origin of a water whereas surface waters have negative or strongly negative ce anomalies waters originating from greater depths show no or only weak negative ce anomalies eu anomalies can be used to differentiate between host rocks waters from gneisses display positive eu anomalies whereas waters from granites have negative ones waters from sedimentary rocks do not display any eu anomalies rb and cs can also be indicators for the rock with which the fluid interacted rb and cs correlate positively in most waters with rb cs ratios of 2 which suggests that these waters are in equilibrium with the clay minerals in the rocks rb cs ratios 5 indicate reaction of a water with existing clay minerals whereas rb cs ratios the chemical compositions of carbonate precipitates from thermal waters indicate that rare earth elements rees rb and cs concentrations in the minerals are controlled by the incorporation of clay particles that adsorb these elements

near surface currents in desoto canyon 1997 99 comparison of current meters satellite observation and model simulation this study evaluates a data assimilated model simulation of near surface circulation in desoto canyon dsc gulf of mexico with emphasis on analyzing moored current meter observations and comparing them with satellite data and model results the study period is for two years from april 1997 to april 1999 the model results are from a high resolution gulf of mexico model forced by analyzed wind and surface heat flux two types of data are used to deduce near surface circulation moored current meters at 13 locations in the dsc and satellite sea level anomaly the moored currents are mapped through multivariate objective analysis to produce surface currents and surface geopotentials against which satellite and model derived sea surface heights and geostrophic currents are compared coupled patterns between the observations model results and satellite data are obtained using the singular value decomposition svd analysis there are two dominant modes a single eddy mode in which currents are concentrated at the foot of the canyon and an eddy pair mode in which one eddy is at the foot of the canyon and the other a counterrotating eddy is over the head of canyon mode 1 appears to be associated with the mesoscale eddy traveling around the loop current crest and trough and mode 2 is associated with the intrusion of loop current crest and trough over the west florida shelf the observed and model currents are in good agreement about the means and variances the model currents also appear to be well constrained by the steep topography however the model velocity field contains only the first mode the satellite derived velocity field on the other hand contains both the first and second modes though the satellite field does not adequately resolve the velocity structures over the slope

lead isotopes in north pacific deep water implications for past changes in input sources and circulation patterns the sources of non anthropogenic pb in seawater have been the subject of debate here we present pb isotope time series that indicate that the non anthropogenic pb budget of the northernmost pacific ocean has been governed by ocean circulation and riverine inputs which in turn have ultimately been controlled by tectonic processes despite the fact that the investigated locations are situated within the asian dust plume and proximal to extensive arc volcanism eolian contributions have had little impact we have obtained the first high resolution and high precision pb isotope time series of north pacific deep water from two ferromanganese crusts from the gulf of alaska in the ne pacific ocean and from the detroit seamount in the nw pacific ocean both crusts were dated applying 10be 9be ratios and yield continuous time series for the past 13 5 and 9 6 myr respectively lead isotopes show a monotonic evolution in 206pb 204pb from low values in the miocene 18 57 to high values at present day 18 84 in both crusts even though they are separated by more than 3000 km along the aleutian arc the variation exceeds the amplitude found in equatorial pacific deep water records by about three fold there also is a striking similarity in 207pb 204pb and 208pb 204pb ratios of the two crusts indicating the existence of a local circulation cell in the sub polar north pacific where efficient lateral mixing has taken place but only limited exchange in terms of pb with deep water from the equatorial pacific has occurred both crusts display well defined trends with age in pb pb isotope mixing plots which require the involvement of at least four distinct pb sources for north pacific deep water the pb isotope time series reveal that eolian supplies volcanic ash and continent derived loess have only been of minor importance for the dissolved pb budget of marginal sites in the deep north pacific over the past 6 myr the two predominant sources have been young volcanic arcs one located in the northeastern part and one located in the northwestern part of the pacific margin from where material has been eroded and delivered to the ocean most likely via riverine pathways

bottom dissipation of subinertial currents at the atlantic zonal boundaries 1 estimates of the dissipation of subinertial currents due to bottom boundary layer drag at the eastern and western boundaries of the north atlantic ocean between 15 n and 60 n are computed using data from the world s largest archive of ocean current meter time series we show from these data that a significant proportion of such loss in this region is due to dissipation at the western boundary ocean floor via quadratic bottom boundary layer drag with an estimated 40 60 31 47 gw of the wind input power across the whole basin dissipated by this method we further show that the majority of this dissipation occurs at shallow depths 500 m this has significant implications for the power available for abyssal mixing

deep current structure above the izu ogasawara trench above the izu ogasawara trench south of japan direct current measurements were made at 34 n from 1987 to 1996 and hydrographic observations were carried out at 34 and 30 n in 1995 the geostrophic shears calculated from the conductivity temperature depth data were consistent with the shears calculated from the current data it is found that there are opposing currents that flow southward on the western flank and northward on the eastern flank along the isobaths in the cross trench direction the magnitude of the mean velocity tended to increase with the distance from the deepest point of the trench and exceeded 10 cm s 1 on the eastern flank in the vertical direction the mean velocity increased with depth but it decreased just above the bottom probably because of friction the southward transport above the western flank was estimated to be 5 8 sv both at 34 and 30 n however the northward transport above the eastern flank increased from 5 sv at 30 n to 22 sv at 34 n suggesting a large inflow from the west

radiation and dissipation of internal waves generated by geostrophic motions impinging on small scale topography theory abstract observations and inverse models suggest that small scale turbulent mixing is enhanced in the southern ocean in regions above rough topography the enhancement extends o 1 km above the topography suggesting that mixing is supported by the breaking of gravity waves radiated from the ocean bottom in this study it is shown that the observed mixing rates can be sustained by internal waves generated by geostrophic motions flowing over bottom topography weakly nonlinear theory is used to describe the internal wave generation and the feedback of the waves on the zonally averaged flow vigorous inertial oscillations are driven at the ocean bottom by waves generated at steep topography the wave radiation and dissipation at equilibrium is therefore the result of both geostrophic flow and inertial oscillations differing substantially from the classical lee wave problem the theoretical predictions are tested versus two dimensional high resolution numerical simulations with parameters representative of

evidence for a north pacific deep western boundary current four current meter moorings arrayed across the japan trench near 35 n yielded 2 years of deep current velocities in the vicinity of the kuroshio where it separates from the japanese coast one and 2 year means are interpreted in the context of other observations including concurrent hydrography as well as the results of earlier investigations principal findings are as follows the presence of a persistent southward deep western boundary current 1 2 cm s 1 along the slope 2000 4000 m inshore of the japan trench a generally northward deep flow 4 cm s 1 over the trench beneath the kuroshio and southward and eastward deep flows farther southeast of the kuroshio separation these deep mean flows particularly the one inshore of the japan trench may be partly of thermohaline origin eddy driven local recirculations and bottom intensification are also likely

characteristics of deep currents along trenches in the northwest pacific in the deep sea area of the japan trench located about 150 km east from northern honshu one observes southward flow on the landward slope and the northward flow on the oceanward slope in 1994 and 1995 moorings were deployed on the japan trench landward slope around 40 n one mooring was deployed for 275 days at about 5800 m and another mooring was deployed for 20 days at 4200 m depth results showed the following 1 a deep western boundary current flows south southwest on the landward slope of the japan trench with mean speed of 3 7 cm sec and maximum speed of 15 20 cm s 2 current changes depend mainly on the m2 tide 3 previous measurements as well as inferences from observed benthic fauna imply oppositely directed flow along the oceanward slope of the trench forming a trench countercurrent

some preliminary results concerning deep northern boundary currents in the north pacific abstract fourteen month velocity records from five moorings along long 175 w in combination with ctd and nutrient data distinguish two pronounced quite steady deep zonal currents near the northern margin of the north pacific one flows westward at speeds of 1 3 cm s 1 along the slope of the aleutian island arc and appears to be the northern boundary current required by deep circulation theory the other flows eastward at about 1 2 cm s 1 just to the south above the aleutian trench and upper aleutian rise and carries water that is slightly lower in temperature and dissolved silica and slightly higher in salinity and dissolved oxygen than that to the north or south we believe that this eastward jet represents an extreme distortion of a level bottom interior flow pattern as forced by the meridional variation in bottom slope on the southern flank of the aleutian rise which imposes a varying effective beta on the system a simple model of this effect is discussed

sustained in situ measurements of dissolved oxygen methane and water transport processes in the benthic boundary layer at mc118 northern gulf of mexico abstract within months of the bp macondo wellhead blowout elevated methane concentrations within the water column revealed a significant retention of light hydrocarbons in deep waters plus corresponding dissolved oxygen do deficits however chemical plume tracking efforts were hindered by a lack of in situ monitoring capabilities here we describe results from in situ time series lander based investigations of physical and biogeochemical processes controlling dissolved oxygen and methane at mississippi canyon lease block 118 18 km from the oil spill conducted shortly after the blowout through april 2012 multiple sensor arrays plus open cylinder flux chambers chimneys deployed from a benthic lander collected oxygen methane pressure and current speed and direction data within one meter of the seafloor the rovard lander system was deployed for an initial 21 day test experiment 9 13 2010 10 04 2010 at 882 m depth before a longer 160 day deployment 10 24 2011 4 01 2012 at 884 m depth temporal variability in current directions and velocities and water temperatures revealed strong influences of bathymetrically steered currents and overlying along shelf flows on local and regional water transport processes do concentrations and temperature were inversely correlated as a result of water mass mixing processes flux chamber measurements during the 160 day deployment revealed total oxygen utilization tou averaging 11 6 mmol m2 day chimney do concentrations measured during the 21 day deployment exhibited quasi daily variations apparently resulting from an interaction between near inertial waves and the steep topography of an elevated scarp immediately adjacent to the 21 day deployment site that modulated currents at the top of the chimney variability in dissolved methane concentrations suggested significant temporal variability in gas release from nearby hydrocarbon seeps and or delivery by local water transport processes free vehicle lander monitoring over time scales of months to years utilizing in situ sensors can provide an understanding of processes controlling water transport respiration and the fate and impacts of accidental and natural gas and oil releases

on the driving processes of the atlantic meridional overturning circulation because of its relevance for the global climate the atlantic meridional overturning circulation amoc has been a major research focus for many years yet the question of which physical mechanisms ultimately drive the amoc in the sense of providing its energy supply remains a matter of controversy here we review both observational data and model results concerning the two main candidates vertical mixing processes in the ocean s interior and wind induced ekman upwelling in the southern ocean in distinction to the energy source we also discuss the role of surface heat and freshwater fluxes which influence the volume transport of the meridional overturning circulation and shape its spatial circulation pattern without actually supplying energy to the overturning itself in steady state we conclude that both wind driven upwelling and vertical mixing are likely contributing to driving the observed circulation to quantify their respective contributions future research needs to address some open questions which we outline

geostrophic volume transport in high eddy energy areas of the kuroshio extension and gulf stream abstract three new deep hydrographic sections taken in july 1980 may 1981 and may 1982 between 29 41 n along 152 e across the high eddy energy area of the kuroshio extension are used to compute the relative geostrophic transport as a function of depth the mean eastward geostrophic transport relative to the bottom through this section is 57 106 m3 s 1 57 sv these sections were occupied across an array of ten moorings deployed from mid 1980 to mid 1982 using the 22 month average directly measured currents at 1200 and 4000 m depth for reference levels in the least square sense the absolute transport during the 1980 82 period is estimated to be 31 16 108 m3 s 1 to the west this lower bound on the uncertainty of the net transport estimate is based on the uncertainty of the measured mean currents at 55 w we use july 1976 and july 1977 deep hydrographic sections to compute the bottom relative geostrophic transport across the high eddy energy area of the gulf stream between 42 and 32 n it is 32 s

field evidence for uranium nanocrystallization and its implications for uranium transport abstract high resolution transmission and scanning electron microscopies hrtem and sem both equipped with energy dispersive x ray spectrometers eds have been used to determine the chemical form of u vi in rocks and to examine u uptake mechanisms at low u concentrations 10 8 10 7 mol l in the downgradient of the koongarra u ore deposit in australia uranium was concentrated in fe hydr oxide nodules and veins that consisted mainly of goethite and hematite nanocrystals 20 100 nm in size of uranyl phosphates such as metatorbernite cu uo2 2 po4 2 8h2o were scattered between and firmly attached to nanocrystals 2 50 nm of goethite and hematite the environment where the nanocrystallization occurred was probably isolated from the koongarra groundwaters undersaturated with respect to the uranyl phosphates chemical analyses by eds showed that the uranyl phosphate nanocrystals contribute more to the u uptake than adsorbed u the presence of the uranyl phosphate nanocrystals between fe hydr oxides explains the u distribution previously studied in the macro and micro scale in koongarra our hrtem and sem observations suggest that during crystallization of goethite and hematite from ferrihydrite u p and cu or mg adsorbed onto ferrihydrite are released from ferrihydrite accumulated on the surface of forming goethite and hematite and finally form nanocrystals of uranyl phosphates thus uranyl phosphate nanocrystallization though initiated by adsorption is a dominating mechanism of the u uptake and controls long term u transport at low u concentrations

how mineralogy and slope aspect affect ree release and fractionation during shale weathering in the susquehanna shale hills critical zone observatory abstract to understand the factors that control rare earth elements ree release and fractionation during shale weathering we investigate the ree contents in solid bedrock regolith stream sediments and natural waters stream and pore waters from a first order catchment developed entirely on gray shales in central pennsylvania usa up to 65 of the ree relative to parent bedrock is depleted from the weathering profiles in the acidic and organic rich soils due to chemical leaching in addition newly formed fine particles were also lost along with the down slope movement of soil waters weathering profiles on the south facing slope show less depletion of ree than those on the north facing slope 33 vs 45 on average we hypothesize that the different degrees of ree depletion on the two transects reflect a history of different chemical weathering rates and possible different surface erosion rates controlled by contrasting slope aspect induced microclimate conditions in addition weathering profiles natural waters and sequential extractions all show a preferential removal of middle ree up to 22 more relative to light ree and heavy ree during shale weathering due to preferential release of mree from rhabdophane furthermore the long term phosphate mineral dissolution rates e g rhabdophane were estimated at 10 15 to 10 14 mol m 2 s 1 under field conditions based on ree depletion profiles strong positive ce anomalies average ce ce n value 1 79 observed in the regolith stream sediments and regolith extractions point to the fractionation and preferential precipitation of ce as compared to other ree due to the generally oxidizing conditions during release transport and redistribution of ree in the surface and subsurface environments positive eu anomalies average eu eu n value 1 30 observed in the natural waters of the catchment are attributed to weathering of plagioclases in the shale bedrock this study highlights the use of ree as natural tracers for low temperature geochemical processes

mobility of uranium during weathering mineralogical and geochemical mechanisms of u fixation under oxidizing conditions in the vicinity of the secondary u ore deposit at koongarra australia were examined using transmission and scanning electron microscopy and thermodynamic calculations the formation of saleeite mg uo 2 2 po 4 2 1oh 2 o is the predominant mechanism for u fixation upstream from the deposit where saleeite replaces sklodowskite and granular apatite within the deposit and further downstream u is fixed in microcrystals 10 50 nm of saleeite and meta torbernite scattered within veins of fine grained 2 50 nm fe super 3 minerals primarily goethite and hematite thermodynamic calculations indicate the groundwater is undersaturated with respect to saleeite and metatorbernite and that these minerals should precipitate at higher u or p concentrations than observed this suggests that the upstream saleeite precipitated at the reaction interfaces of dissolving sklodowskite and apatite under local saturation conditions observed textural relationships of saleeite and meta torbernite microcrystals with the fe minerals combined with thermodynamic calculations suggest surface precipitation as the formation mechanism for saleeite and meta torbernite microcrystals within and downstream from the secondary ore deposit phosphorous released during the aging of ferrihydrite and u adsorbed onto fe minerals are probably the sources of the major components of the microcrystals downstream the microcrystals exist where groundwater u concentrations are as low as 10 30 mu g l once released from the ore deposit u is fixed in uranyl phosphates even where measured groundwater is undersaturated with respect to uranyl phosphates the surface precipitation is an important example of long term post adsorption u fixation in a natural system the fully crystalline and radiation damaged microstructures of saleeite indicate uranyl phosphates have formed continuously or intermittently for the last few million years

global observations of ocean bottom subinertial current dissipation quadratic bottom boundary layer drag is a potentially significant source of energy dissipation in the deep ocean this study presents a new estimate of the energy dissipated by this process using results from the world s largest archive of ocean current meter time series and focusing strongly upon the potential uncertainties in this calculation two methods are used one based on a simple division of the world ocean into a series of regular grids and the other based on a more sophisticated analysis using a hierarchical clustering mechanism assisted by estimates from the hybrid coordinate ocean model hycom model from these analyses the authors estimate a globally integrated bottom boundary layer dissipation of 0 65 6 0 15 statistical uncertainty 6 0 15 methodological uncertainty tw

western ross sea continental slope gravity currents antarctic bottom water of the world ocean is derived from dense shelf water that is carried downslope by gravity currents at specific sites along the antarctic margins data gathered by the anslope and clima programs reveal the presence of energetic gravity currents that are formed over the western continental slope of the ross sea when high salinity shelf water exits the shelf through drygalski trough joides trough immediately to the east offers an additional escape route for less saline shelf water while the glomar challenger trough still farther east is a major pathway for export of the once supercooled low salinity ice shelf water that forms under the ross ice shelf the drygalski trough gravity currents increase in thickness from 100 to 400 m on proceeding downslope from 600 m the shelf break to 1200 m upper slope sea floor depth while turning sharply to the west in response to the coriolis force during their descent the mean current pathway trends 35 downslope from isobaths benthic layer current and thickness are correlated with the bottom water salinity which exerts the primary control over the benthic layer density a 1 year time series of bottom water current and hydrographic properties obtained on the slope near the 1000 m isobath indicates episodic pulses of shelf water export through drygalski trough these cold 34 75 pulses correlate with strong downslope bottom flow extreme examples occurred during austral summer fall 2003 comprising concentrated high salinity shelf water 1 9 c 34 79 and approaching 1 5 m s 1 at descent angles as large as 60 relative to the isobaths such events were most common during november may consistent with a northward shift in position of the dense shelf water during austral summer the coldest saltiest bottom water was measured from mid april to mid may 2003 the summer fall export of high salinity shelf water observed in 2004 was less than that seen in 2003 this difference if real may reflect the influence of the large iceberg c 19 over drygalski trough until its departure in mid may 2003 when there was a marked decrease in the coldest saltiest gravity current adjacent to drygalski trough northward transport of cold saline recently ventilated antarctic bottom water observed in march 2004 off cape adare was 1 7 sv including 0 4 sv of high salinity shelf water