strontium and carbon isotope constraints on carbonate solution interactions and inter aquifer mixing in groundwaters of the semi arid murray basin australia abstract strontium and carbon isotopes are used to study the effect of carbonate mineral dissolution and inter aquifer mixing on the chemical evolution of groundwater from the murray group limestone aquifer in semi arid se australia the 87 sr 86 sr ratio of groundwater evolves from 0 7097 at the basin margin to a less radiogenic value of 0 7084 about 250 km down gradient which is similar to the 87 sr 86 sr ratio of the aquifer carbonate matrix the concomitant increase in 13 c dic sr ca and mg ca ratios in the groundwater along a 250 km transect suggests that incongruent dissolution of high mg calcite controls the carbonate geochemistry in this aquifer further down gradient the groundwater is characterized by a relatively more radiogenic 87 sr 86 sr ratio caused by upward leakage and mixing with more radiogenic groundwater from the renmark group sand aquifer a mixing model using 87 sr 86 sr ratio suggests that the fraction of water that contribute to the murray group aquifer through upward leakage from underlying renmark group aquifer ranges from 15 to 85

arid zone groundwater recharge and salinisation processes an example from the lake eyre basin australia in arid central australia the 1 14 m km2 endorheic lake eyre basin leb experiences sporadic floods and contains saline shallow groundwater in this basin where on ground physical and chemical data are very sparse new observations of major ion chemistry stable isotopes 2h 18o 13c radiogenic isotopes 3h 14c and remote sensing modis data were used to investigate groundwater recharge and salinisation processes in 2006 2007 in january 2007 there was a large and intense local rainfall event followed by flooding to the normally dry lake eyre resulting from heavy rainfall in the northern leb that took 2 months to arrive at lake eyre groundwater chemistry from this study show no evidence of recharge from the floodwaters or the local rainfall however this does not preclude the process low transit times and low infiltrating volumes may mean that the recharge event has not yet been detected over the longer term the stable isotope chemistry indicates that groundwater is predominantly diffusely recharged during heavy local rainfall events 100 150 mm month and radiogenic isotopes reflect an older shallow groundwater efficiently mixing with recent decadal recharge the high total dissolved solids tds of regional shallow groundwater up to 52 5 g l is intrinsically linked with these recharge processes where infiltrating diffuse rainfall is evaporated and heavy rainfall events transport saline pore water saline due to evaporation in the unsaturated zone to the groundwater system the high tds of shallow groundwater beneath the dry lake eyre bed up to 322 g l is also controlled by evaporation however although evaporite minerals are prolific in the lake area the non conservative behaviour of br in pore water limits analysis of the role of halite mineral dissolution and precipitation reactions controlling groundwater salinity evaporation driven salinisation of shallow groundwater in arid central australia is distinct from the transpiration driven salinisation of groundwater in the australian murray basin located in a semi arid climate and results in relatively high groundwater salinity values compared with many other large arid zone endorheic basins across the world

estimating groundwater recharge in fractured rock from environmental 3h and 36cl clare valley south australia 1 vertical profiles of 3h and 36cl concentrations are obtained from piezometer nests installed in fractured metasedimentary aquifers in the clare valley south australia because 3h is lost during evapotranspiration with negligible fractionation while 36cl is retained within the soil comparison of 3h and 36cl concentrations allows estimation of the aquifer recharge rate an analytical solution for the transport of 3h and 36cl through planar parallel fractures is used to investigate the effect of variations in matrix porosity tortuosity fracture aperture fracture spacing and aquifer recharge rate on tracer profiles and then to reproduce observed profiles within piezometer nests while the measured distributions of these tracers are not able to constrain most model parameters they are able to tightly constrain the aquifer recharge rate the broad nature of the 36cl and 3h peaks measured at our sites is simulated using a constant fracture spacing lognormal distributions of fracture apertures and mean recharge rates of 60 75 mm yr 1

the effect of north pacific sea surface temperature anomalies on the january climate of a general circulation model abstract four perpetual january integrations of an atmospheric general circulation model have been performed in each of which a different sea surface temperature sst anomaly was specified in the north pacific the observed sst anomaly for the 1976 77 winter was chosen as the basic anomaly and 1200 day runs were carded out in which this anomaly was multiplied by 1 and 2 a fifth run was performed which combined the basic midlatitude sst anomaly from 1976 77 with a tropical pacific sst anomaly representative of the mature phase of a warm el nino southern oscillation enso episode an ensemble of eight independent 90 day averaged realizations was extracted from each simulation maps of ensemble mean differences from the model climatology are presented in this paper together with estimates of the statistical significance of some of the features which appear on these maps the model response to the basic sst anomaly and to twice the basic sst anomaly is a midiatitude teleconnection pattern the pacifi

groundwater recharge and discharge dynamics in an arid zone ephemeral lake system australia the coongie lakes are a series of ephemeral freshwater lakes on the lower reaches of cooper creek a large intermittent river of the arid lake eyre basin australia hydrogeological chemical and isotopic observations in conjunction with numerical modeling of groundwater responses to lake inundation events have been used to identify the dominant processes linking shallow unconfined groundwater with the hydrology of the lakes during wet and dry periods the lakes are predominantly zones of net groundwater recharge during inundation events however soil profile data suggests that drying of some of these lakes allows evaporative groundwater discharge to occur through the soil profile of the dry lake beds resulting in salinization of the soil profile of the more ephemeral lakes the occurrence of young high salinity groundwater is best explained by variations in soil profile flushing in response to wet and dry interannual periods of river discharge during interannual drier phases when filling of previously dry lakes is more common recharge is mostly via macropore flow during the rising stage of the inundation increased salinization of the lake bed sediments occurs during longer dry periods due to transport of solutes to the near surface from lake bed evaporation and limited flushing of the soil profile because of the macropore dominated flow during recharge during wet periods recharge is more likely dominated by matrix flow that results in leaching of the soil profile and increased export of solutes into the alluvial aquifer

decadal variability of the pacific subtropical cells and its relevance to the sea surface height in the western tropical pacific during recent decades decadal variability of the pacific subtropical cells stcs and associated sea surface height ssh in the western tropical pacific during recent decades are examined by using an historical ogcm simulation the model represents decadal variations of the stcs concurrent with tropical pacific thermal anomalies the eastern tropical pacific is warmer when the stcs are weaker and cooler when they are stronger the spatial patterns of the ssh in the western tropical pacific show different features depending on events associated with decadal variability during the warm phase 1977 1987 the ssh anomalies exhibit deviations from a meridionally symmetric distribution with weakly positive strongly negative anomalies in the western tropical north south pacific analysis of the heat budget in the upper tropical pacific indicates that the termination of the warm phase around 1985 results from a poleward heat transport anomaly that is induced by a horizontal gyre associated with the ssh anomalies during the cold phase 1996 2006 in contrast the ssh anomalies are nearly meridionally symmetric with positive anomalies in both hemispheres enhanced easterly wind anomalies contribute to the development of the cold phase after the late 1990s

groundwater flow regime within the gambier embayment of the otway basin australia evidence from hydraulics and hydrochemistry a conceptual groundwater flow model for the cainozoic sequence of the gambier embayment of the otway basin south australia is developed using hydraulic head distribution environmental isotopes and hydrochemical data local flow cells occur within the upper sequence of the gambier unconfined aquifer and are recognised by local relief of the water table and as rapid lateral variations in chloride 14c 2h and 18o concentrations indicating that regional flow is not dominant in the upper portion of the unconfined aquifer these localised systems are topographically controlled and have developed in response to undulating stranded coastal dune ridges of the bridgewater formation recharge areas correspond to dune highs while discharge is focused towards the lower lying interdunal regions total dissolved solids concentrations are controlled by evapotranspiration processes during recharge and ion ratios are modified by water rock interactions within the groundwater system groundwaters are more dilute in the southern section of the basin where the surplus of precipitation over evapotranspiration in the winter months is greater than that in the northern section of the basin a regional flow system with interaquifer mixing has developed within the confined dilwyn aquifer system recharge to the dilwyn aquifer has been identified downgradient from the basin margin via downward leakage from an intermediate flow system within the gambier unconfined aquifer to the deeper regional flow system of the confined dilwyn aquifer interaquifer mixing appears to be geologically controlled in the south by the elevated gambier axis and in the north by the kanawinka fault downgradient of the zero head difference line lateral flow appears to be the dominant transport mechanism within the dilwyn aquifer as indicated by constant chloride concentrations monotonic decrease in radiocarbon concentration and more negative 2 and 18 o composition

physical hydrogeology and environmental isotopes to constrain the age origins and stability of a low salinity groundwater lens formed by periodic river recharge murray basin australia summary a low salinity total dissolved solids tds 25 000 mg l is marked by a hectometer to kilometer scale transition in tds concentrations that is not stratigraphically controlled rather this boundary represents a mixing zone with the regional groundwater the position of which is controlled by the rate of recharge from the river the lens is part of an active and dynamic hydrogeological system that responds over years to decades to changes in river levels the lens has shrunk during the drought of the late 1990s to the mid 2000s and it will continue to shrink unless regular high flows in the murray river are re established over longer timescales the rise of the regional water table due to land clearing will increase the hydraulic gradient between the regional groundwater and the groundwater in the lens which will also cause it to degrade replacement of low salinity groundwater in the lens with saline groundwater will ultimately increase the salinity of the murray river reducing its utility for water supply and impacting riverine ecosystems

renewal rate estimation of groundwater based on radioactive tracers 3h 14c in an unconfined aquifer in a semi arid area iullemeden basin niger abstract estimation of groundwater recharge in arid and semi arid areas is difficult due to the low amount and variability of recharge a combination of radiotracers investigation based on simple mixing models allows direct investigation of relatively long term renewal rates of an aquifer the recharge process of the shallow continental terminal aquifer in the iullemeden basin niger was investigated using a geochemical and isotopic approach this study investigates the area in the one degree square of nianey 13 14 n 2 3 e in this area recharge is highly heterogeneous and mainly occurs through a drainage system of temporary streams and pools during the rainy season heterogeneity of the recharge is reflected through the wide variation in electrical conductivity and oxygen 18 content of the groundwater the carbon 14 activity range for most of the groundwater falls between 69 and 126 pmc showing pre and post aerial thermonuclear test recharge two renewal rate models have been investigated the first one models a well mixed reservoir and the second one is derived from a piston flow model in which mixing is in equal proportions major ions in tritium data analyses allow exclusion of non representative samples and confirm the carbon 14 renewal rate estimations both models give similar results for the relatively low renewal rate investigated in the area using carbon 14 the mean annual rates of groundwater renewal range from 3 to 0 03 of the aquifer volume with a median of 0 1 assuming the median is representative of the overall renewal rate of the area the recharge rate is in the order of 5 mm a 1 the shallow aquifer recharge extends from the last small humid period around 4000 a up to now high recharge rates are found in depressions whereas low recharge occurs below the plateaux

the modeled atmospheric response to midlatitude sst anomalies and its dependence on background circulation states abstract the atmospheric response to a midlatitude sst anomaly in the north pacific and its dependence on background flow are examined in a gcm experiments are conducted using the same warm sst anomalies but two different model states perpetual january and perpetual february the atmospheric responses to the sst anomalies are statistically significant in both january and february but are completely different the anomalous circulation in january is characterized by a trough decaying with height immediately downstream of the sst anomalies in february the anomalous circulation is dominated by a downstream ridge growing with height the patterns of the anomalous heights in the two months are nearly orthogonal vorticity and thermodynamic budgets are diagnosed to illustrate how the anomalous circulations are maintained over the sst anomalies low level convergence and ascent are observed in both months in january the anomalous convergence is balanced by a residual due primarily to the forcing by submont

carbon 14 and stable isotope data for an area in the murray basin its use in estimating recharge measurements of the carbon 14 concentration of water in 33 boreholes in a saline unconfined aquifer in southern australia have been interpreted to show that local recharge under natural conditions has a mean annual value which falls between 0 1 and 0 2 mm yr 1 the chloride concentration of groundwater is log normally distributed suggesting that its source is rainfall the estimate of mean annual recharge to the aquifer made using chloride is 0 25 mm yr 1

geochemistry of ground waters from the great artesian basin australia herczeg a l torgersen t chivas a r and habermehl m a 1991 geochemistry of ground waters from the great artesian basin australia j hydrol 126 225 245 ground waters from the confined lower cretaceous jurassic aquifer of the great artesian basin australia gab are characterised by na hco 3 type waters throughout the eastern and central parts of the basin and na sq c1 type waters in the western part sodium and bicarbonate increase in concentration from the northeastern margins to the southwestern discharge areas along the regional groundwater flowlines a mass balance and equilibrium model for major dissolved species and stable carbon isotopes of dissolved inorganic carbon show that the chemical trends observed are caused by mass transfer reactions involving cation exchange of na for ca mg carbonate dissolution and reactions between na and kaolinite to form na smectite the stable carbon isotopic composition of dissolved inorganic carbon dic increases from values of about 15 o near the basin margins to 6 o in the interior of the basin an inverse relationship exists between 6 3c and dic indicating addition of enriched carbon as the ground waters move basinwards a t2c 3c mass balance indicates that the trend toward heavier 6 3c values in the interior of the basin results from bacterial reduction of carbon dioxide to produce methane rather than dissolution of and equilibration with carbonate minerals the gab aquifer system is apparently open to co which is the product of in situ anaerobic fermentation producing co 2 enriched in t3c the chemical evolution of the major dissolved species and carbon isotope distribution in the eastern and central parts of the gab can then be envisaged as an initial pco 2 up to several orders of magnitude above atmospheric level is acquired within the recharge area by plant respiration and oxidation of organic matter in the soil zone initially silicate and carbonate minerals may dissolve at least in some parts of the basin resulting in increased alkalinity higher ca and mg concentrations and a 6 3c concentration of the dic of around 12 0 processes such as cation exchange of na for ca and mg in addition to the removal of some na by reverse weathering which produces a na smectite dominate in the interior of the gab the chemistry of ground waters derived from the western recharge areas is controlled by evaporite dissolution as indicated by very high ci br ratios

a survey of groundwater levels and hydrogeochemistry in irrigated fields in the karamay agricultural development area northwest china implications for soil and groundwater salinity resulting from surface water transfer for irrigation analysis of the water budget along with hydrochemistry and stable isotopes in shallow groundwater were carried out in the karamay agricultural development area kada in order to assess the impact of transfer of irrigation water from the irtysh river in particular in relation to the mechanisms of salinization and the nature of the water table regime in terms of aquifer dynamics the addition of the irrigation water without any groundwater abstraction has caused a sharp rise in the water table is and the development of serious soil salinity together with an almost complete attenuation of inter seasonal water table oscillations the mean rise in the groundwater table from september 1997 to october 2009 was 6 9 m representing an accumulated total water storage change of close to 150 million cubic meters the analysis of aquifer water budget shows that infiltration of irrigation water occupied over 90 of the total recharge of the groundwater in the kada sources of groundwater recharge and mechanisms of salinization in the kada were also investigated using geochemical and isotopic techniques the groundwater is characterized by cl so 4 na type generally becoming more na and cl dominated with increasing salinity the total dissolved solids tds content of the groundwater ranges from 0 5 g l to over 65 g l with greater tds values in areas of low topographic relief and shallow water tables where the sediments are more permeable e g due to the presence of palaeochannels tds values are generally lower and the seasonal water table fluctuations greater the ratios of k cl ca cl na cl and mg cl decrease with increasing cl concentrations especially in the shallow groundwater from 10 to 15 m depth indicating hydrogeochemical evolution via minor water rock interaction feldspar weathering and significant evaporation the stable isotopic compositions show a characteristic evaporation effect in the shallow groundwater and confirm that direct infiltration of precipitation is generally not a volumetrically important source of recharge to the shallow aquifer preferential recharge of river water after irrigation events and or precipitation from rare heavy rain events is likely responsible for the depleted 2 h and 18 o values in some of the groundwater samples the negative relationship between deuterium excess and 18 o values indicates that even in groundwater with relatively depleted 2 h and 18 o values evaporation has occurred to a significant degree careful management of water quantity and quality and implementation of salinity management strategies are considered necessary in order to reduce the risk of further salt accumulation and damage to farming and local ecosystems

using hydrogeochemistry to understand inter aquifer mixing in the on shore part of the gippsland basin southeast australia groundwater in the latrobe valley in the gippsland basin of southeast australia is important for domestic agricultural and industrial uses this sedimentary basin contains a number of aquifers that are used for water supply dewatered for open pit coal mining and which are potentially influenced by off shore oil and gas production major ion chemistry together with stable and sr isotope data imply that the main hydrogeochemical processes are evapotranspiration with minor silicate and carbonate weathering methanogenesis and so4 reduction in reduced groundwater associated with coal deposits have also occurred groundwater has estimated 14c ages of up to 36ka and is largely 3h free carbon 14 ages are irregularly distributed and poorly correlated with depth and distance from the basin margins the observations that the geochemistry of groundwater in aquifers with different mineralogies are similar and the distribution of 14c ages is irregular implies that the aquifers are hydraulically connected and horizontal as well as vertical inter aquifer mixing occurs the connection of shallow and deeper aquifers poses a risk for the groundwater resources in gippsland as contaminants can migrate across aquifers and dewatering of shallow units may impact deeper parts of the groundwater system

the general circulation model response to a north pacific sst anomaly dependence on time scale and pattern polarity abstract a general circulation model was integrated with perpetual january conditions and prescribed sea surface temperature sst anomalies in the north pacific a characteristic pattern with a warm region centered northeast of hawaii and a cold region along the western seaboard of north america was alternately added to and subtracted from the climatological sst field long 1350 day runs as well as short 180 day runs each starting from different initial conditions were performed the results were compared to a control integration with climatological ssts the model s quasi stationary response does not exhibit a simple linear relationship with the polarity of the prescribed sst anomaly in the short runs with a negative sst anomaly over the central ocean a large negative height anomaly with an equivalent barotropic vertical structure occurs over the gulf of alaska for the same sst forcing the long run yields a different response pattern in which an anomalous high prevails over northern canada and

geochemistry of halogens in the milk river aquifer alberta canada abstract analytical data are presented for cl br and i on a regional scale for the milk river aquifer the three halides show strikingly similar spatial distributions and are highly correlated concentrations are low in the freshwater portions of the aquifer but increase by as much as two orders of magnitude along the margins however halide ratios reach nearly constant values moving down gradient suggesting the dominance of a common subsurface source for these ions ratios of cl i and cl br are less than those of seawater and fit an origin derived from the diagenesis of organic matter in the sediments halide ratios rule out leakage and or diffusion from the underlying colorado group as a major influence on the chemistry the favored hypothesis is altered connate seawater diffusing from low permeability units within the milk river formation as the primary source of salts this hypothesis of an internal source has important implications for solute sources in other aquifers affected by saline waters because it does not require the importation of a distant fluid the129i i ratio has a meteoric value in groundwater collected near the recharge area but ratios for downflow waters are only 8 70 of this value due to the 16 ma half life of129i these data indicate that most of the increase in dissolved i cannot derive from concentration of a meteoric source by ion filtration but must have a subsurface origin concentrations of129i producedin situ by spontaneous fission of238u attain measurable levels only in the oldest waters sampled ages 105a in which it may account for nearly 90 of the total dissolved129i concentration water ages based upon36cl cl data range up to 2 ma if uncorrected for any dilution by subsurface sources of dead cl if one assumes that the subsurface contributions of cl contribute at least 90 of total cl in the distal portion then the36cl based ages are reduced to 1ma somewhat greater than those estimated by hydrodynamic modeling

simulated response to recent freshwater flux change over the gulf stream and its extension coupled ocean atmosphere adjustment and atlantic pacific teleconnection abstractrecent observation has shown that the dominant mode of the net freshwater flux variations over the north atlantic ocean is the significant trend of freshwater loss over the gulf stream region and its extension in this paper the coupled ocean atmosphere response to this freshwater flux change is investigated based on a series of the fast ocean atmosphere model coupled model experiments the model demonstrates that the freshwater loss over the gulf stream and its extension region directly forces an anomalous cyclonic gyre and triggers a sst dipole with cooling in the western subtropical and warming in the eastern subpolar north atlantic the freshwater loss also forces a significant response in the atmosphere with a negative nao like response in early winter and a basin scale ridge resembling the eastern atlantic mode eam in late winter the salinification also strengthens the atlantic meridional overturning circulation and thus the poleward heat transport leading to tropical cooling the freshw

recharge history and controls on groundwater quality in the yuncheng basin north china environmental isotopes and water quality indicators e g tds and no 3 contents were used to characterize the age recharge history and controls on the quality of groundwater resources in the yuncheng basin north china where extensive extraction occurs for agriculture and domestic supply delta 18 o and delta 2 h values as low as 10 6 and 73 parts per thousand respectively together with low radiocarbon activities 70 pmc indicating a significant component of modern post 1950s recharge the shallow groundwater has higher delta 18 o and delta 2 h values up to 8 1 and 54 parts per thousand that are similar to those in modern summer monsoon rainfall indicating that current recharge is via direct infiltration and or leakage of ephemeral streams during heavy rain events historic recharge rates estimated using radiocarbon ages are between 1 and 10 mm year corresponding to 20 mg l in some deep wells 180 m preferential leakage has occurred near the linyi fault in the northern sushui river basin salinisation nitrate contamination and excessive drawdown of deep groundwater are major concerns for the future of the groundwater resources in this region c 2010 elsevier b v all rights reserved

dynamics and mechanisms of decadal variability of the pacific south america mode over the 20th century in this paper decadal variability of the pacific south america psa mode is examined from year 1871 to 2008 based on the newly developed ocean and atmosphere reanalysis products the psa mode mirroring the pacific north america mode in the northern hemisphere emerges as the second eof mode of 500 mb geopotential height anomalies the mode displays substantial interannual decadal variability with distinct timescales between 3 8 and 10 18 years respectively the decadal variability of the psa mode is found to be associated with the coupled ocean atmosphere interaction over the subtropical south and tropical pacific the subduction of the subtropical temperature anomalies in the south pacific in conjunction with the tropical subtropical atmospheric teleconnection plays important role in the decadal variability of the psa mode

constraining groundwater recharge and the rate of geochemical processes using tritium and major ion geochemistry ovens catchment southeast australia summary constraining recharge is essential for understanding and managing groundwater systems this study uses high precision tritium 3 h concentrations together with major ion and environmental isotope sr c o h geochemistry to constrain rates of recharge and geochemical processes in the ovens catchment of the southeast murray basin australia 3 h concentrations of groundwater in the ovens catchment decline with depth but not with position in the catchment implying that recharge occurs over broad areas recharge rates calculated using an exponential piston flow model are 120 180 mm yr in the coarse grained alluvial gravels of the upper and middle ovens and 30 45 mm yr in the finer grained sediments of lower ovens these recharge rates are similar to those calculated from the response of shallow bore hydrographs to rainfall the geochemistry of groundwater with low 60 160 mg l total dissolved solids tds from the upper and middle ovens indicates that dissolution of both silicate minerals and calcite has occurred major ion geochemistry 87 sr 86 sr ratios and 13 c values in the upper and middle ovens groundwater are correlated with groundwater residence times and constrain the progress of mineral reactions dissolution of silicates with high 87 sr 86 sr ratios biotite and k feldspar occurs prior to dissolution of silicates with low 87 sr 86 sr ratios plagioclase and calcite mineral dissolution mainly occurs in the upper 20 m of the aquifer system with relatively little change in geochemistry deeper in the flow system groundwater from the lower ovens has higher tds contents 600 9600 mg l due to higher degrees of evapotranspiration although a correlation between tds and groundwater residence times exists it is more likely to reflect differential recharge rates and not the rate of evapotranspiration the conclusion that recharge occurs across the ovens catchment indicates that protection of groundwater from surface contamination is dependent on the protection and management of large areas

the hydrogeology hydrochemistry and environmental isotopes of the campaspe river aquifer system north central victoria australia the campaspe river hydrogeological system of north central victoria consists of two major units 1 the tertiary deep lead aquifer a combination of the renmark group and calivil formation which forms the major aquifer of the region and 2 the plio pleistocene shepparton formation which forms a complex aquitard aquifer system on top of the deep lead recharge to the deep lead aquifer is twofold 1 a major component of recharge occurs along the southern reaches of the campaspe river where the overlying shepparton formation is thin and becomes more permeable and 2 recharge occurs by vertical downward movement of water from the shepparton formation whose heads are everywhere higher than those of the deep lead natural discharge from the system occurs further to the northwest beyond the murray river salinity gradually increases down gradient in the deep lead with an abrupt increase to greater than 6000 mg l 1 total dissolved solids close to the murray river except in the goornong area in the south which appears to be separated from the main deep lead system this increase is characterised by a certain hydrochemical evolution of the water wherein very fresh recharge with a mnacl 1 0 changes to an oceanic type composition while still in the low salinity range this is due largely to concentration of the original solutes in the system and is the consequence of salt remobilisation within the catchment the shepparton formation waters on the other hand are characterised by disorder namely fresh to saline water juxtaposed both horizontally and vertically heads in both the shepparton formation and the deep lead had been increasing at the rate of about 15 20 cm yr 1 for at least several decades the advent of large scale withdrawal from the deep lead in the early 1980s has arrested this trend in the northern and central portions of the area a decline in aquifer pressures is evident this decline will induce increased leakage from the shepparton formation down into the deeper aquifer and such leakage could possibly result in a degradation of its water quality stable isotope data indicate that under the existing hydrologic regime little irrigation drainage water has penetrated to the deep system

interannual to decadal variations of tropical subtropical exchange in the pacific ocean boundary versus interior pycnocline transports abstract interannual to decadal variations of tropical subtropical mass exchange in the pacific ocean are investigated using a near global ocean general circulation model along with satellite observations of sea level and wind and a data assimilation product the analysis focuses on the variability of pycnocline transports through the western boundary and interior near 10 n and 10 s in contrast to time mean exchange where boundary and interior pycnocline transports are both equatorward the variations of boundary and interior pycnocline transports are found to be generally anticorrelated to each other moreover the variation of the boundary pycnocline transport is smaller than that of the interior again different from time mean exchange where the boundary transport at 10 n is substantially larger than that through the interior interannual variations of the boundary and interior transports are consistent with near surface geostrophic flow inferred from sea level data interior pycnocline flow into th

groundwater recharge assessment in an upland sandstone aquifer of southern california abstract the chloride mass balance cmb method was used to obtain long term recharge values for the santa susana field laboratory ssfl site which features a groundwater flow system beneath an upland ridge formed of sandstone and shale beds in the simi hills ventura county southern california this application relied on the availability of on site measurements of bulk atmospheric chloride deposition comprised of dry fallout and wet concentration a large number of groundwater samples 1490 collected over three decades from 206 wells spanning a depth range from 10 to 360 m and measurements of chloride in surface runoff during rain events the use of the cmb method is suited to the assessment of recharge for the study area because the mean chloride values in groundwater show minimal spatial trends indicating no sources other than atmospheric in addition the cl br ratio was used to exclude wells with possible anthropogenic chloride the site wide average recharge ranges between 1 8 and 9 5 of the mean annual precipitation 455 mm with a mean value of 4 2 the measured surface runoff varies from 2 3 to 10 2 with mean value of 6 1 28 mm and therefore the volume of water lost to evapotranspiration is between 95 9 and 80 3 with a mean value of 89 6 408 mm the long term recharge calculated using the cmb method is consistent with tritium distribution based on a subset of groundwater monitoring wells and with an analysis of steady flow in the groundwater mound beneath the ssfl furthermore the recharge value matches those in the literature for sandstone aquifers in arid and semi arid climates this recharge estimate has important relevance for site characterization in terms of constraining the volumetric groundwater flow rates and water balance and understanding the mechanisms of transport towards the water table moreover this is the first application of the cmb in an upland area of california hence the method is demonstrated to be robust and applicable to many upland bedrock areas in southern california and similar regions around the world and can be used to quantify groundwater flow rates and supplies relevant to water resource management

using 3h and 14c to constrain the degree of closed system dissolution of calcite in groundwater abstract this study uses 3h concentrations 14c activities a14c 87sr 86sr ratios and 13c values to constrain calcite dissolution in groundwater from the ovens catchment se australia taken in isolation the 13c values of dissolved organic c dic and 87sr 86sr ratios in the ovens groundwater imply that there has been significant calcite dissolution however the covariance of 3h and 14c and the calculated initial 14c activities a014c imply that most groundwater cannot have dissolved more than 20 of 14c free calcite under closed system conditions rather calcite dissolution must have been partially an open system process allowing 13c and 14c to re equilibrate with co2 in the unsaturated zone recognising that open system calcite dissolution has occurred is important for dating deeper groundwater that is removed from its recharge area in this and other basins the study is one of the first to use 14c and 3h to constrain the degree of calcite dissolution and illustrates that it is a valuable tool for assessing geochemical processes in recharge areas

island groundwater resources impacts of abstraction and a drying climate rottnest island western australia abstract coastal aquifers provide a source of water for more than one billion people with island freshwater lenses being some of the most vulnerable coastal groundwater systems due to their susceptibility to saltwater intrusion basic hydrogeological and hydrochemical knowledge regarding the recharge and salinisation processes of freshwater lenses is important to ensure sustainable utilisation especially considering possible climate change effects this paper makes an assessment of the fate of a freshwater lens in a drying climate through a comparison of current and historic hydrochemical data which to the author s knowledge is unique to this study fresh groundwater stable isotope signatures 18 o 2 h reflect local amount weighted rainfall signatures 18 o 3 8 2 h 15 1 and confirm rainfall as the origin of fresh groundwater 18 o 4 47 to 3 82 2 h 20 0 to 16 6 mixing with seawater was identified through enriched groundwater 18 o and 2 h signatures maximum values of 0 36 and 1 4 respectively compared to local rainfall and higher salinity maximum 29 267 mg l total dissolved solids tds in a number of monitoring wells around the freshwater lens enhanced seawater intrusion detected in the northern section of the lens area was identified through significantly increased tds values over the last 20 40 years with increases of up to 3000 observed between 1990 and 2014 a reduction in the extent of freshwater by approximately 1 km 2 was identified since 1977 which was found to be primarily caused by a reduction in recharge to the freshwater lens due to a 20 decline in winter rainfall in the south west western australian region since the mid 1960s groundwater abstraction was found to equate to between 5 and 9 of the estimated recharge for the island and is not a significant factor in the reduction of the lens extent compared to the observed decline in rainfall recharge interestingly seawater intrusion into the fresh water lens was found to occur by older seawater 0 03 0 09 tu in regions of the lens that were previously fresh or slightly brackish while one sample 0 67 tu suggests either modern seawater intrusion or mixing of older saline groundwaters 60 years with rainfall recharge the use of tritium dating in this island aquifer was essential in identifying older seawater that was previously unidentified until now the isotopic and hydrochemical tools used in this paper quantify the effects of groundwater abstraction and climate variability on the freshwater lens and have implications for the sustainable management of the groundwater resource on rottnest island and elsewhere

observed influence of north pacific sst anomalies on the atmospheric circulation abstract a lagged maximum covariance analysis mca of monthly anomaly data from the ncep ncar reanalysis shows significant relations between the large scale atmospheric circulation in two seasons and prior north pacific sea surface temperature sst anomalies independent from the teleconnections associated with the enso phenomenon regression analysis based on the sst anomaly centers of action confirms these findings in late summer a hemispheric atmospheric signal that is primarily equivalent barotropic except over the western subtropical pacific is significantly correlated with an sst anomaly mode up to at least 5 months earlier although the relation is most significant in the upper troposphere significant temperature anomalies are found in the lower troposphere over north america the north atlantic europe and asia the sst anomaly is largest in the kuroshio extension region and along the subtropical frontal zone resembling the main mode of north pacific sst anomaly variability in late winter

factors affecting groundwater recharge following clearing in the south western murray basin abstract data from 18 field studies in the south western murray basin australia and a simple water balance model were used to study the importance of factors which affect diffuse recharge in that area generally as the texture of the soil became heavier the recharge decreased under cropped land as the clay content in the top 2 m of the soil profile increased from 0 to 20 recharge decreased by one order of magnitude from about 30 to about 3 mm year 1 for a mean annual rainfall of 310 380 mm as mean annual rainfall increased the mean annual recharge also increased sites with an average clay content of about 10 in the top 2 m and a mean annual rainfall of 270 mm had an estimated recharge of about half that of sites with a mean annual rainfall of 310 380 mm data from land which was grazed but not cropped showed similar relationships however the data set did not allow a detailed analysis of the effect of land use on recharge

estimating recharge in fractured aquifers of a temperate humid to semiarid volcanic island jeju korea from water table fluctuations and cl cfc 12 and 3h chemistry summary groundwater table fluctuations wtf chloride mass balance cmb apparent groundwater chlorofluorocarbon cfc 12 ages and tritium 3 h mean residence times were used to assess recharge rates on jeju island korea where groundwater is the main source of potable water given the limitations of various techniques and the respective data the methods yield median values of 687 mm yr wtf 429 mm yr cmb 423 mm yr cfc 12 and 394 mm yr 3 h which are lower than the multi annual 1993 2002 average value calculated using the soil water budget swb method 911 mm yr these underestimates are mainly due to most groundwater samples used for the analyses being located in the more arid lowland areas of the island all methods yield highest recharge rates in the southern and eastern districts of jeju implying a strong control of rainfall on the spatial recharge distribution the spatial variability of recharge at the catchment scale is caused by spatially and temporally variable rainfall and evapotranspiration as well as the wide range in effective porosity and specific yield values of the aquifer lithologies the wtf method yields reliable results in the coastal regions where low hydraulic gradients prevail the cmb technique underestimates the recharge values of the swb in all geographic districts probably as a result of anthropogenic cl additions to groundwater and unaccounted for atmospheric cl dry deposition median recharge estimates from the cfc 12 and 3 h data show the lowest spatial correlation with those from the swb mainly as a result of vertical anisotropies and uncertainties in the determination of effective aquifer thicknesses particularly in the perched high level areas the here applied methods are useful for local calibration and validation of swb estimates in lower parabasal regions where thin unsaturated zones prevail however due to their inability to predict recharge in the more remote upslope areas from which as of yet no groundwater data could be obtained they cannot be applied to predict average recharge values representative for the whole island

the brigalow catchment study revisited effects of land development on deep drainage determined from non steady chloride profiles summary a large area of woodland in the brigalow bioregion in semi arid central queensland was cleared for agriculture from the 1960s to the 1980s to assess the risk of salinity associated with land clearing soil chloride cl was monitored at the brigalow catchment study bcs in brigalow acacia harpophylla scrub a cropped catchment and a pasture catchment before and after clearing in 1982 the monitoring sites include three landscape positions two on clay soils and one on a sodic duplex sodosol within each catchment an earlier report of deep drainage using the early soil cl profiles and steady state and transient chloride sodics mass balance was revisited after a further 13 yr and four more sampling times profile cl mass changed little in 18 4 yr at scrub sites justifying the use of native vegetation sites to represent pre clearing cl for paired cleared sites steady state cl mass balance cmb gave deep drainage of 0 13 0 34 mm yr for nine pre clearing scrub sites large losses of soil cl occurred under cropping and smaller losses occurred under pasture transient cmb gave average deep drainage of 59 and 32 mm yr for crop and pasture catchments respectively during the development phase 1981 1983 when the land was bare following clearing of native vegetation and prior to establishment of crops or pastures in the 16 7 yr following establishment of agricultural land uses 1983 2000 transient cmb gave average deep drainage of 19 8 range 3 3 50 and 0 16 2 2 to 1 4 mm yr respectively in crop and pasture catchments the drainage rate under pasture was similar to that under brigalow scrub in the cropped catchment drainage for modern farming systems less tillage more summer opportunity crops was about half that of older farming systems wheat summer fallow more tillage less stubble retention drainage was greater for the sodosol than for the clay soils under cropping deep drainage occurred under cropping even though the soils are considered to have low permeability and the climate is semi arid with potential evaporation exceeding rainfall on average in all months increased drainage at cropped sites has driven a clear exponential loss of soil cl as predicted by the transient cmb theory one cropped site is at or near a new steady state and the others will reach a new steady state 50 200 yr after clearing the leachate is saline with an average cl concentration of 7000 mg l and would salinised any groundwater it entered the salinity risk associated with the drainage is not well understood as yet and will depend on local hydrogeological conditions which are poorly mapped in the fitzroy effects of these losses of salts on sodicity soil structure and permeability should also be investigated

constraining modern and historical recharge from bore hydrographs 3h 14c and chloride concentrations applications to dual porosity aquifers in dryland salinity areas murray basin australia summary water table fluctuations and renewal rates based on 3h and 14c concentrations in bores screened within 5 m of the water table were used to estimate recharge rates in five dryland salinity areas in northern victoria australia given the resolution of each technique both methods yield broadly similar results of 4 90 mm yr up to 14 of modern rainfall that reflect the recharge rates following land clearing over the last 200 years deeper bores show mixing of modern recharge with older water flowing laterally through the aquifers recharge estimates based on cl concentrations are up to two orders of magnitude lower

the differences between early and midwinter atmospheric responses to sea surface temperature anomalies in the northwest atlantic abstract using an atmospheric global spectral model it is shown that the winter atmosphere in the midlatitudes is capable of reacting to prescribed sea surface temperature sst anomalies in the northwest atlantic with two very different responses the nature of the response is determined by the climatological conditions of the winter regime experiments are performed using either the perpetual november or january conditions with or without the prescribed sst anomalies warm sst anomalies in november result in a highly significant anomalous ridge downstream over the atlantic with a nearly equivalent barotropic structure in january the response is a statistically less significant trough the presence of the sst anomalies also causes a northward southward shift of the atlantic storm track in the november january cases a diagnostic analysis of the anomalous heat advection in the simulations reveals that in the january cases the surface heating is offset primarily by the strong horizontal cold advect

hydrogeochemical and isotopic constraints on the origins of dryland salinity murray basin victoria australia abstract combined hydrogeological and hydrogeochemical data allow flow systems and the origins of solutes in the honeysuckle creek area of the southeastern murray basin which is an area affected by dryland salinity to be constrained recharge occurs both on the uplands that are composed of fractured violet town volcanic rocks and the riverine plain that comprises sediments of the shepparton and coonambidgal formations groundwater from the violet town volcanics has low salinity 20 mmol l groundwater has intermediate cl br ratios 600 1000 which indicate that the high salinities do not simply result from halite dissolution rather mixing of groundwater homogenises cl br ratios and evaporation as a consequence of a shallow water table is the dominant process that increases salinity oxygen and h isotopes also indicate that mixing and evaporation have occurred these results indicate that land use over the whole region not just the uplands needs to be considered in any salinity management plans additionally future development of salinity is controlled by depth to the water table on the plains and the efficiency of recharge rather than by salt stores halite or brines in the unsaturated zone

decoupling of solutes and water in regional groundwater systems the murray basin australia documenting the origins residence times and movement of groundwater and the solutes that it contains is critical to understanding hydrogeological systems this study uses cl mass balance to determine the cl accession time i e the time required for cl to accumulate and cl to estimate the residence times of cl in the victorian portion of the murray basin southeast australia much of the murray basin contains saline groundwater with total dissolved solids tds concentrations commonly 14 000 mg l and locally up to 300 000 mg l the total mass of cl stored in the victorian portion of the basin is estimated as between 12 400 and 47 100 mt using present day rainfall totals and cl concentrations in rainfall the cl accession time is 170 to 650 ka aquifer thicknesses and groundwater salinity both increase westwards in this part of the murray basin consequently the cl accession times increase westward from 0 1 0 6 ka to 286 1080 ka by contrast c activities of the majority of the groundwater are 2 pmc and commonly much higher notwithstanding the difficulty in correcting c residence times the widespread occurrence of groundwater with above background c activities implies that groundwater residence times are generally 30 ka which is substantially shorter than the cl accession times rcl the ratio of cl to total cl 10 values of the groundwater are between 20 and 230 and are uncorrelated with cl concentrations while it is difficult to determine precise cl residence times the observation that the rcl values are significantly higher than those that represent secular equilibrium with the aquifer matrix rcl of 5 to 10 indicates that they are up to a few hundred thousand years and similar to the cl accession times the rcl values together with the geology of the aquifers stable isotope ratios and major ion geochemistry precludes halite dissolution incorporation of connate water or the long term diffusion of cl from clays as mechanisms of producing the elevated cl concentrations rather it is most likely that the high cl concentrations result from recycling of solutes in saline lakes and playas or repeated cycles of evapotranspiration in the unsaturated zone

constraining groundwater flow residence times inter aquifer mixing and aquifer properties using environmental isotopes in the southeast murray basin australia environmental isotopes particularly d 18 o d 2 h and d 13 c values 87 sr 86 sr ratios and a 14 c constrain geochemical processes recharge distribution and rates and inter aquifer mixing in the riverine province of the southern murray basin due to methanogenesis and the variable d 13 c values of matrix calcite d 13 c

distribution of alteration zones in the upper oceanic crust aging of the upper oceanic crust produces alteration zones that have distinct mineralogical and geochemical characteristics five zones are recognized in the troodos ophiolite and in situ oceanic crust 1 a sea floor weathering zone swz 2 a low temperature zone ltz 3 a transition zone tz 4 an upper dike zone udz and 5 a mineralized zone mz the mz may be overlain by the swz ltz or tz but in the known examples it is always underlain by the udz the development of the swz is dependent upon the duration of cold seawater circulation which is dependent upon seafloor topography and the rate and nature of sedimentation the boundary between the low and high temperature zones is largely controlled by permeability contrasts lateral variation in the depth of this boundary indicates that the thermal gradient is not uniform within the crust this along with the evidence for disequilibrium assemblages implies that regional metamorphic zones are not appropriate to describe the distribution of alteration effects

planetary wave modes in the thermocline non doppler shift mode advective mode and green mode a quasi geostrophic theory is proposed for planetary waves in the extratropical thermocline it is shown that planetary wave propagation structure and stability can be affected significantly by the mean thermocline flow one major planetary wave mode is the non doppler shift mode which resembles the first baroclinic mode and has a strong signature in both the sea surface height and the bottom of the thermocline this mode propagates westward regardless of the mean flow however consistent with recent works the westward propagation speed can be modestly enhanced by the mean flow another major planetary wave mode is the advective mode which bears some resemblance to the second baroclinic mode and has a strong signature in the upper thermocline temperature field in the region of strong westward thermocline flow and shear such as the south western part of the north pacific subtropical gyre an unstable green mode is produced by the coupling of the non doppler shift mode and the advective mode this unstable green mode may have e folding times of a few years for a wave hundreds of kilometers in length the structure of the green mode contains the features of the second baroclinic mode with a strong signature in the upper thermocline the green mode always propagates westward finally we discuss the relevance of our theory to recent observations

the importance of silicate weathering of a sedimentary aquifer in arid central australia indicated by very high 87sr 86sr ratios with the exception of brine systems and crystalline rock aquifers groundwater 87sr 86sr ratios rarely differ by more than 0 01 from the phanerozoic seawater value of 0 70923 groundwater 87sr 86sr ratios from central australia 0 72562 0 76248 are the highest ever recorded for a low salinity sedimentary aquifer we propose a model for the evolution of these 87sr 86sr ratios and demonstrate how the lowest 87sr 86sr ratios reflect water rock interactions with predominantly carbonate minerals while the highest 87sr 86sr ratios are ultimately controlled by weathering of old primary silicate minerals detailed analysis of aquifer core material identified albite and microcline as the most prevalent primary silicates and where these minerals were abundant relatively high rb concentrations were measured high rb combined with long time scales since deposition has produced very high 87sr 86sr ratios in the rocks and subsequently the groundwater therefore strontium isotopes can provide further constraints for chemical models of arid zone groundwater systems particularly when silicate hydrolysis is believed to significantly contribute to dissolved solute compositions

uncertainties around modelling of steady state phreatic evaporation with field soil profiles of δ18o and chloride summary the application of the general advection diffusion equation to model phreatic evaporation flux rates from solute concentration soil profiles has been applied to a variety of arid zone locations but the effects of heterogeneous and uncertain field data on modelling performance are rarely described we revisit and extend the model by accounting for the effects of variable water content and sediment type on the impedance factor and in turn effective diffusion coefficient we explore the local sensitivity of the extended model to its major assumptions and parameter values the mean diffusion coefficient of the soil profile data is most sensitive to the volumetric water content close to the evaporation front and so modelled evaporation results can be very sensitive to uncertainty around the position of the evaporation front the uncertainty in the position of the groundwater reservoir and its concentration has little effect where the lower part of the profile shows an asymptotic trend towards a representative value of groundwater concentration but can vary substantially with different values of groundwater depth and concentration if this is not the case field data from the southern margin of the great artesian basin are shown to exhibit considerable uncertainty around the boundary conditions of the advection diffusion model e g position of evaporation front depth and concentration of lower groundwater boundary condition resulting phreatic evaporation flux estimates show a wide range that needs to be considered when using these data in water balance studies of groundwater systems

paleohydrologic implications of some deep soilwater chloride profiles murray basin south australia abstract a chloride mass balance approach to estimating soilwater ages and paleorecharge rates was tested in an area where considerable paleoclimatic data were available for comparison application of the method to data from four cores of the unsaturated zone taken in the western murray basin showed that the soil water at the base of the chloride build up or bulge associated with the root zone of the native mallee vegetation was emplaced during the last glacial interval at least 20 000 years bp furthermore recharge rates at this time were very low these observations agree with independent paleoclimate evidence that suggest that this time was colder windier and drier results are consistent with the notion that the root zone chloride bulge so typical of the murray mallee region developed in response to aridity that peaked during the last full glacial interval in australia the chloride method is a useful tool in paleohydrology especially when used in concert with other evidence

a new chloride leaching approach to the estimation of diffuse recharge following a change in land use abstract a new approach has been developed to estimate the increase in groundwater recharge following land use modification the approach uses the degree of leaching of chloride to quantify soilwater drainage below the root zone which ultimately leads to groundwater recharge it is more general than similar previously reported techniques for analysing transient chloride profiles to infer recharge rates and hence has wider application we have applied the technique to a field situation in southern australia where clearing of native vegetation for agricultural production leads to large increases in groundwater recharge the examples serve to demonstrate the technique and some of the practical difficulties in the application of solutes techniques to recharge estimation

linkage between the pacific decadal oscillation and the low frequency variability of the pacific subtropical cell the decadal variability of pacific subtropical cell stc and its linkages with the pacific decadal oscillation pdo are investigated in the present study based on a simple ocean data assimilation soda 2 2 4 it is found that on decadal time scales the western boundary and interior pycnocline transports are anticorrelated and the variation of the interior component is more significant which is consistent with previous studies the decadal variability of stc in the northern hemisphere is found to be strongly associated with pdo associated with a positive negative phase of pdo the relaxation acceleration of the northeast trades slows down spins up the stc within a few years through baroclinic adjustment in conjunction with the subduction of the cold warm mixed layer anomalies in the extratropics the cold warm water is then injected into the thermocline and advected further southwestward to the tropics along the isopycnal surfaces leading to the slowdown spin up of stc due to zonal pressure gradient change at low latitude along with the stc weakening strengthening a significant warming cold anomaly appears in the tropics and it is advected to the midlatitude by the kuroshio and north pacific currents thus feeding back to the atmosphere over the north pacific in contrast to the northern hemisphere it is found the stc in the south only passively responds to the pdo the mechanism found here highlights the role of the stc advection of extratropical anomalies to the tropics and horizontal gyre advection of the tropical anomalies to the extratropics in decadal variability of the stc and pdo

pacific ocean circulation rebounds 1 recent observations indicate that the shallow meridional overturning circulation in the tropical pacific ocean has rebounded since 1998 following 25 years of significantly weaker flow convergence of cold interior ocean pycnocline water towards the equator increased to 24 1 1 8 106 m3 s 1 during 1998 2003 from a low of 13 4 1 6 106 m3 s 1 during 1992 98 intensified circulation led to the development of anomalously cool tropical pacific sea surface temperatures which may have affected pacific marine ecosystems and global climate the abruptness of the rebound also obscures presumed anthropogenic warming trends in the instrumental temperature record of the tropical pacific

cl br ratios and environmental isotopes as indicators of recharge variability and groundwater flow an example from the southeast murray basin australia abstract systematic variations in cl br ratios together with r 36 cl values 14 c activities and 18 o values reflect differences in groundwater recharge and define groundwater flow paths in the riverine province of the southeast murray basin in groundwater from the shallowest shepparton formation homogenisation of cl br and 18 o values and a decline in 14 c activities with depth imply that vertical flow dominates the 14 c activities define variations in pre land clearing recharge in the palaeovalleys of present day rivers deep leads which contain sandier sediments higher recharge 0 5 to 1 4 mm year produced relatively fresh groundwater tds 36 cl values in groundwater from the goulburn subcatchment zones of groundwater with variable cl br ratios in the deeper calivil renmark aquifer also allow the detection of rapid leakage from the surface that has the potential to compromise groundwater resources

the evaporation path of seawater and the coprecipitation of br and k with halite brines and salt were sampled at the morton bahamas solar salt production facility on great inagua island in the bahamas the brines were analyzed by ion chromatography to define more precisely than heretofore the evaporation path of seawater to the end of the halite facies at inagua calcium carbonate begins to precipitate at a brine concentration factor of 1 8 times that of seawater gypsum begins to precipitate at a brine concentration of 3 8 times seawater and halite at a concentration factor of 10 6 three of the most concentrated brines from inagua 40 times seawater were evaporated further in the laboratory magnesium sulfate first precipitated at brine concentrations about 70 times those of seawater and potassium bearing phases began to precipitate for these brines at concentrations greater than 90 times those of seawater the distribution of coefficients of br and k between brines and halite were determined by combining analytical data for the inagua brines with measurements of the br and k content of halites from inagua and of halite which had precipitated from inagua brines during storage the observed average value of dbr is 0 032 in good agreement with some of the previous measurements the measured values of dk are highly variable 0 001 to 0 021 dk for halite precipitated early in the halite facies is in the vicinity of 0 015

el nino variability in simple ocean data assimilation soda 1871 2008 1 a new ocean reanalysis that covers the period from 1871 to 2008 is used to explore the time evolving characteristics of el nino the new reanalysis assimilates all available hydrographic and sea surface temperature data into a model of the global ocean forced with surface boundary conditions from an atmospheric reanalysis that also covers the period from 1871 through 2008 using traditional measures of el nino our reanalysis shows that the timing of el nino events is in agreement with sea surface temperature reconstructions but el nino in the reanalysis is stronger particularly from 1871 to 1920 a new index based on the first moment of the temperature anomaly is introduced the new index is used to characterize the strength and location of el nino events and has the advantage that it is independent of the location of el nino using the new index el nino in the reanalysis shows prominent decadal variability of strength but relatively little long term trend el nino events were strong in the last part of the 19th century and first part of the 20th century and again in the latter part of the 20th century with weak el nino events in the middle of the 20th century the location of el nino also varies considerably ranging from the western to the eastern pacific near the coast of south america however the null hypothesis that the location of el nino can be represented as a random distribution about a central longitude of about 140 w cannot be rejected

equilibrium atmospheric response to north atlantic sst anomalies abstract the equilibrium general circulation model gcm response to sea surface temperature sst anomalies in the western north atlantic region is studied a coarse resolution gcm with realistic lower boundary conditions including topography and climatological sst distribution is integrated in perpetual january and perpetual october modes distinguished from one another by the strength of the midlatitude westerlies an sst anomaly with a maximum of 4 c is added to the climatological sst distribution of the model with both positive and negative polarity these anomaly runs are compared to one another and to a control integration to determine the atmospheric response in all cases warming cooling of the midlatitude ocean surface yields a warming cooling of the atmosphere over and to the east of the sst anomaly center the atmospheric temperature change is largest near the surface and decreases upward consistent with this simple thermal response the geopotential height field displays a baroclinic

distribution et comportement du bore dans la croute oceanique the behaviour of boron involved in alteration of oceanic crust by sea water was investigated by means of prompt gamma neutron activation analysis of basalt and serpentinite samples from in situ oceanic crust and ophiolites the samples were grouped in the following categories fresh basalts low temperature altered basalts high temperature altered basalts and serpentinites the average b content in fresh basalts is 2 2 0 6 ppm the low temperature altered basalts and the serpentinites are 2 24 times richer in b than the fresh basalts the alteration of the crust at low temperature and its serpentinization imply b extraction from sea water the rate of b removal for this specific low temperature alteration of basalts is estimated to be 10 5 1010 g year on the basis of the development of altered zones in the crust and of the b contents of these zones before and after their alteration the high temperature altered basalts having a low water rock ratio show an average b content 2 3 0 7 ppm similar to

mechanisms of recharge in a fractured porous rock aquifer in a semi arid region abstract eleven porewater profiles in rock core from an upland exposed sandstone vadose zone in southern california with thickness varying between 10 and 62 m were analyzed for chloride cl concentration to examine recharge mechanisms estimate travel times in the vadose zone assess spatial and temporal variability of recharge and determine effects of land use changes on recharge as a function of their location and the local terrain the profiles were classified into four groups reflecting the range of site characteristics century to millennium average recharge varied from 4 to 23 mm y 1 corresponding to 1 moreover the temporal variability of recharge was estimated and along each profile past recharge rates calculated based on the sequence of cl concentrations in the vadose zone recharge rates increased at specific times coincident with historical changes in land use the consistency between the timing of land use modifications and changes in cl concentration and the match between observed and simulated cl concentration values in the vadose zone provide confidence in porewater age estimates travel times recharge estimates and reconstruction of recharge histories this study represents an advancement of the application of the chloride mass balance method to simultaneously determine recharge mechanisms and reconstruct location specific recharge histories in fractured porous rock aquifers the proposed approach can be applied worldwide at sites with similar climatic and geologic characteristics

half precessional cycle of thermocline temperature in the western equatorial pacific and its bihemispheric dynamics the el nino southern oscillation enso which is tightly coupled to the equatorial thermocline in the pacific is the dominant source of interannual climate variability but its long term evolution in response to climate change remains highly uncertain this study uses mg ca in planktonic foraminiferal shells to reconstruct sea surface and thermocline water temperatures sst and twt for the past 142 ky in a western equatorial pacific wep core md01 2386 unlike the dominant 100 ky glacial interglacial cycle recorded by sst and 18o which echoes the pattern seen in other wep sites the upper ocean thermal gradient shows a clear half precessional 9 4 ky or 12 7 ky cycle as indicated by the reconstructed and simulated temperature t and 18o differences between the surface and thermocline waters this phenomenon is attributed to the interplay of subtropical to tropical thermocline anomalies forced by the antiphased meridional insolation gradients in the two hemispheres at the precessional band in particular the twt shows greater variability than sst and dominates the t changes which couple with the west east sst difference in the equatorial pacific at the half precessional band implying a decisive role of the tropical thermocline in orbital scale climate change

a modelling and observational study of the relationship between sea surface temperature in the north west atlantic and the atmospheric general circulation results from four pairs of 50 day wintertime integrations of the meteorological office s 5 level general circulation model with warm and cold sea surface temperature s s t anomalies of about 3 k in the northwest atlantic are described difference fields between the warm and cold integrations are statistically significant at the 1 level with positive geopotential height over the central north atlantic and weaker negative height over europe the storm track over the atlantic is displaced from its normal position results from four further pairs of integrations with halved s s t anomalies are also described the response is approximately linear with systematic differences in 500 mb geopotential height over the atlantic parts of which are just significant at the 10 level with half the full s s t anomaly overall however the model s response is weaker than could be obtained with tropical s s t anomalies of the same magnitude results from the model integrations are compared with results from an observational study of the relationship between wintertime s s t in the north west atlantic and mean sea level pressure and 500mb height two independent 30 year periods were chosen for study thus minimizing the influence of long term trends in s s t over the atlantic and europe the model results compared well with the observations with s s t data lagging the atmosphere by one month the observational study appears to show that the s s t anomalies are initially forced by perturbations in the atmospheric circulation with s s t data leading the atmosphere by one month results show that atmospheric and s s t anomalies are most persistent in the period october to december throughout the winter these lagged relationships are much weaker and not statistically significant diagnostics of e vector divergence from the gcm experiments are used to suggest that anomalous baroclinic wave activity over the atlantic is important as a momentum forcing for the anomalous time mean flow pattern on the other hand the role of thermal forcing provided by anomalous diabatic heating and transient eddy heat flux convergence may be important to substantiate this statement a simple linear steadystate two layer model of the response to extratropical thermal forcing is described with a suitable basic state flow and a mid tropospheric heat source given mainly by the transient eddy heat flux convergence the response is shown to be equivalent barotropic with a downstream ridge and ascent over the thermal source conversely results from an ocean mixed layer model are discussed which suggest that warm s s t anomalies could be maintained by a positive surface pressure perturbation positioned downstream of the anomaly through anomalous northward advection of warm ocean water by ekman drift currents this northward advection would balance the sensible and latent heat loss into the atmosphere over the s s t anomaly hence it is possible that some positive ocean atmosphere feedback may account for the persistence of such atmospheric and oceanic anomalies

coupled ocean atmosphere responses to recent freshwater flux changes over the kuroshio oyashio extension region abstract observations have indicated a trend of freshwater loss in the global western boundary current extension regions over several recent decades in this paper the coupled ocean atmosphere response to the observed freshwater flux trend defined as evaporation minus precipitation emp over the kuroshio oyashio extension koe region is studied in a series of coupled model experiments the model explicitly demonstrates that the positive emp forcing in the koe region can set up a cyclonic gyre straddling the subtropical and the subpolar gyre which induces anomalous southward cold advection in the west and northward warm advection in the interior this leads to the formation of a temperature dipole in the midlatitudes with a cooling in the west and a warming in the east with the positive emp forcing in the koe the response of the extratropical atmospheric circulation in the north pacific sector is characterized by an equivalent barotropic low originating primarily from the western tropical pacific c