propagation of signals in basin scale ocean bottom pressure from a barotropic model 1 the exchange of atmospheric plus oceanic mass between ocean basins is investigated using a global barotropic ocean model we find two particular cases of exchange between two basins at periods of 4 6 days the exchange is between the atlantic and pacific basins and represents a known oscillation forced by atmospheric pressure this mode represents a failure of the inverse barometer relationship due to the large scale and high frequency of atmospheric forcing and the presence of continents significant exchange between atlantic and pacific also occurs at longer periods the second case is most prominent at periods longer than 30 days strongest at periods longer than 100 days and represents a mass exchange between the southern ocean and the pacific the southern ocean part of this exchange is clearly related to the southern mode of fluctuations in antarctic circumpolar transport forced by southern ocean wind stress the reason for the exchange being with the pacific rather than other basins is explored and is found to be related to the balance of wind stress by form stress in drake passage exchange with the atlantic and indian oceans becomes dominant if drake passage topography is removed while recognizing the limitations of a barotropic model we contend that it is necessary to understand the barotropic adjustment process in order to make sense of longer timescale processes accordingly we end with speculation on the possible importance of the barotropic results for global sea level and tropical dynamics

sea ice atmosphere and upper ocean variability in the weddell sea antarctica a frequency domain singular value decomposition is performed on 20 years 1979 1998 of monthly sea ice concentration sea ice drift and sea level pressure data in the weddell sea antarctica interannual oscillations with periods of around 3 4 years are found to dominate the variability in this region anomalous atmospheric patterns periodically reach the weddell sea from the west and perturb the sea ice circulation and distribution in the weddell gyre through changes in the intensity and direction of the climatological winds sea ice accumulates in the southeastern weddell sea every 3 4 years owing to two atmospherically driven processes 1 weak ice export to the north due to a weak northward branch of the gyre driven by weak southerly winds and 2 large ice import from the east due to a strong east wind drift driven by strong easterly winds along the coast the opposite situation gives rise to a depletion of sea ice in the same region half a cycle later sea ice anomalies are then advected north northeastward before turning eastward in the gyre circulation the eastward propagation of ice anomalies along the ice margin accounts for the passage of the antarctic circumpolar wave through the atlantic sector of the southern ocean a low frequency signal is also detected in the weddell sea variations albeit rather speculatively in this 20 year long record sea ice variability on this timescale appears to be associated with a change in the shape and characteristics of the weddell gyre circulation around 1990 this mode of variability implicates feedbacks between the gyre and weddell deep water temperature variations whose impact is observed near the maud rise topographic feature

can the equatorial ocean quickly respond to antarctic sea ice salinity anomalies 1 el nino southern oscillation enso plays a critical role in many of the extremes or anomalies of climate causing floods droughts and the collapse of fisheries recent studies have revealed a statistically significant link between equatorial processes and sea ice anomalies in the southern ocean the generally accepted view is that the primary interaction of the equatorial and polar oceans takes place via the atmosphere indeed the lag in these processes is usually of the order of a few months and is much too quick to be connected with ocean currents the question is can climate anomaly signals effectively and rapidly propagate by another oceanic mechanism it is demonstrated that signals generated by anomalies in the antarctic sea ice cover salinity distribution can propagate in a wave like manner in the form of fast moving barotropic rossby waves such waves propagates from the drake passage to the western pacific in only few days this signal is reflected at the western boundary of the pacific and generates an coastally trapped kelvin wave moving equatorwards the resulting temperature anomaly propagates northwards along the western coastline to the vicinity of the equator and increases in amplitude in time the anomaly in the western edge of the equatorial pacific then begins to move eastward along the equator as a trapped equatorial wave after about 2 3 months this wave reaches the eastern coast this process is suggested as one possible direct mechanism by which the extra tropical ocean can induce anomalies in the equatorial ocean

investigation of the geochemical evolution of groundwater under agricultural land a case study in northeastern mexico summary zona citricola is an important area for mexico due to its citriculture activity situated in a sub humid to humid climate adjacent to the sierra madre oriental this valley hosts an aquifer system that represents sequences of shales marls conglomerates and alluvial deposits groundwater flows from mountainous recharge areas to the basin fill deposits and provides base flows to supply drinking water to the adjacent metropolitan area of monterrey recent studies examining the groundwater quality of the study area urge the mitigation of groundwater pollution the objective of this study was to characterize the physical and chemical properties of the groundwater and to assess the processes controlling the groundwater s chemistry correlation was used to identify associations among various geochemical constituents factor analysis was applied to identify the water s chemical characteristics that were responsible for generating most of the variability within the dataset hierarchical cluster analysis was employed in combination with a post hoc analysis of variance to partition the water samples into hydrochemical water groups recharge waters ca hco 3 transition zone waters ca hco 3 so 4 to ca so 4 hco 3 and discharge waters ca so 4 inverse geochemical models of these groups were developed and constrained using phreeqc to elucidate the chemical reactions controlling the water s chemistry between an initial recharge and final water the primary reactions contributing to salinity were the following 1 water rock interactions including the weathering of evaporitic rocks and dedolomitization 2 dissolution of soil gas carbon dioxide and 3 input from animal human wastewater and manure in combination with by denitrification processes contributions from silicate weathering to salinity ranged from less important to insignificant the findings suggest that it may not be cost effective to regulate manure application to mitigate groundwater pollution

assessment of shallow groundwater in lake nyos catchment cameroon central africa implications for hydrogeochemical controls and uses in 1986 carbon dioxide gas exploded from lake nyos and killed about 1 800 people after that disaster various administrative and research activities have been conducted to mitigate subsequent disasters however none of those endeavors have characterized the groundwater chemistry to identify hydrogeochemical processes that control the water chemistry and the quality of the water for domestic and agricultural uses that support the lives of un official resettlers around lake nyos conventional hydrochemical techniques coupled with statistical and graphical analysis were therefore employed to establish the baseline hydrochemical conditions assess processes controlling solutes distribution in shallow groundwater in the lake nyos catchment and explore its usability groundwater samples were analyzed for their physical and chemical properties the wide ranges of electrical conductivity and total dissolved solid values reveal the heterogeneous distribution of groundwater within the watershed the relative abundance of major dissolved species was ca mg na k for cations and hco3 cl so4 no3 for anions piper diagram classified almost all water samples into mixed camg hco3 water type major ion geochemistry reveals that in addition to silicates weathering water rock interaction ion exchange processes regulate the groundwater chemistry principal component analysis supports the occurrence of water rock interaction hierarchical cluster analysis showed that the chemistry of groundwater in the study area is controlled by three main factors and suggests no hydraulic connectivity between deep lake water and groundwater in the catchment the quality assessment of the groundwater showed that groundwater parameters are within the acceptable limit of the world health organization and nigeria guidelines for drinking and domestic uses and water found to be good for irrigation

modeling of groundwater processes in a karstic aquifer of sierra madre oriental mexico abstract the sierra madre oriental smo is composed of ranges with important regional geological structures in highly fractured carbonate rocks abra formation which facilitate the recharge of aquifers at the regional scale recharge occurs in the western smo and locally in ranges such as palmillas la colmena and abra while the regional discharge is to the east in the huasteca zone intermountain valleys such as el salto are located near the regional discharge zone three end members were identified in these regions one related to local flow another to intermediate and a third to regional flow these flows define ternary mixing processes in groundwater in this paper the evolution of groundwater is studied which is important for learning the system performance and hydrogeochemical processes through vishmod virtual samples in hydrochemical modeling methodology the mixing model for the intermountain valleys indicates that many recharges occur for which local flow contributes 68 3 intermediate flow 12 3 and regional flow 19 4 the inverse modeling shows that the water rock interaction precipitation and or dissolution of calcite gypsum and dolomite are the main processes occurring in the aquifer system of the intermountain valleys

response of the intertropical convergence zone to antarctic ice sheet melt past cooling events in the northern hemisphere have been shown to impact the location of the intertropical convergence zone itcz and therewith induce a southward shift of tropical precipitation here we use high resolution coupled ocean atmosphere simulations to show that reasonable past melt rates of the antarctic ice sheet can similarly have led to shifts of the itcz albeit in opposite direction through large scale surface air temperature changes over the southern ocean through sensitivity experiments employing slightly negative to large positive meltwater fluxes we deduce that meridional shifts of the hadley cell and therewith the itcz are to a first order a linear response to southern hemisphere high latitude surface air temperature changes and antarctic ice sheet melt rates this highlights the possibility to use past episodes of anomalous melt rates to better constrain a possible future response of low latitude precipitation to continued global warming and a shrinking antarctic ice sheet

identifying the roles of the ocean and atmosphere in creating a rapid equatorial response to a southern ocean anomaly recent research has identified a rapid ocean response mechanism to salinity anomalies in the southern ocean using an idealised ocean model here we examine the relative importance of the ocean and atmosphere in creating an equatorial response to a southern ocean anomaly using a coupled climate model with realistic bottom topography and land relief two rapid teleconnections are produced from a high latitude anomaly an equatorial ocean response can be seen after 30 days the mechanism producing this response is shown to rely on barotropic and baroclinic oceanic wave propagation a second atmospheric response is seen in the northern hemisphere nh high latitudes driven by atmospheric rossby waves the ocean quickly responds to the atmospheric signal above it resulting in sea surface temperature anomalies at nh high latitudes

the dynamics of the antarctic circumpolar current abstract the dynamics of the antarctic circumpolar current acc in a near eddy resolving model of the southern ocean fram are investigated a streamwise coordinate system is used rather than a more conventional approach of considering zonally averaged quantities the motivation for this approach is the large deviation from a purely zonal flow made by the current comparisons are made with a zonal mean analysis of the same model it is found that the topographic form drag is the main sink of the momentum that is input by the wind however in contrast to a zonal mean analysis other terms namely horizontal mixing bottom friction and advection of momentum are no longer negligible the total effect of transient eddies is to produce a drag on the mean flow again in contrast to the zonally averaged case the vertical penetration of stress is considered a generalized formula is derived for the interfacial form stress averaged along a convoluted path and that includes nonquasigeostrophic effects the i

geochemical and isotopic evidence of shallow groundwater salinization in a reclaimed coastal zone the yellow river delta china this paper aims to improve the current knowledge of groundwater salinization processes of a young coastal aquifer in the yellow river delta yrd and to assess the impact of both the transfer of irrigation water from the yellow river and seawater intrusion using a combination of hydrochemical isotopic measurements the major ion cl ratios generally closely follow the mixing line between freshwater end member the yellow river and saline water end members salt groundwater or seawater indicating the importance of mixing under natural and anthropogenic influences the examination of stable isotope in groundwater ranging from 9 0 to 3 5 for 18o and from 73 to 29 for d respectively and chloride concentrations 2 to 629 meq l confirms that the saline end member is associated with saltwater rather than present seawater and most groundwater samples are plotted on mixing lines between the yellow river and saltwater the similar range in stable isotopes 18o and d and cl compositions between saltwater and confined aquifer supports the hypothesis that upward seepage of confined saline water intruded the shallow aquifer moreover the deviations in some cases from mixing line imply water rock interaction is also important in dominant control on groundwater chemistry such as cation exchange so4 2 reduction and nacl solution the brackish water was characterized by slight excess of na and deficit of ca2 compared to non reactive mixing line this indicates that the coastal aquifer is generally freshening with respect to extensive irrigation network as well as the transfer from the yellow river for ecological recharge into wetland

groundwater chemistry and mass transfers in the independence aquifer central mexico by using multivariate statistics and mass balance models in the light of progressive depletion of groundwater reservoir and water quality deterioration of the independence aquifer an investigation on chemical data of dissolved major and minor constituents in 246 recent groundwater samples was performed the main objective was the detection of processes responsible for the geochemical evolution and mineralization throughout the area multivariate techniques revealed different sources of solutes a dissolution of calcium and magnesium carbonate minerals b weathering of acid volcanic minerals c alteration of manganese containing alkaline silicates d leaching of halite deposits of meteoric origin e contamination from agricultural and urban wastewaters and f evaporative effects due to intensive irrigation although nitrate contamination is associated with pollution from intensive cultivated areas natural contamination plays an important role in the study area the investigation reveals that weathering of acid volcanic rocks rhyolite and oxidation of arsenic bearing sulfide minerals are the responsible processes for high fluorine up to 16 mg l and arsenic up to 0 12 mg l contents respectively exceeding the mexican maximum admissible concentration for drinking water except for kaolinite all recharge processes are dissolution oriented co2 calcite dolomite k feldspar plagioclase silicate precipitation amorphous silica and chalcedony is of growing importance in discharge zones cation exchange is not an important issue in the whole study area

hydrologic and geologic factors controlling surface and groundwater chemistry in indian wells owens valley area southeastern california usa the indian wells owens valley area is located in the semi arid basin and range province which is characterized by alternating mountains and alluvial basins surface water resources are limited in this arid region and water demand is mainly met by groundwater pumpage in a classic basin and range groundwater system water flows from recharge areas in the mountains to discharge areas in adjacent valleys discharge areas are generally occupied by playas where large amounts of salt deposition occur due to evaporating groundwater hydrochemical data from a total of 1368 spring surface and well water samples collected over an 80 year period were used to evaluate water quality and to determine processes that control water chemistry q mode hierarchical cluster analysis hca was employed for partitioning the water samples into hydrochemical facies also known as water groups or water types five major water groups resulted from the hca analysis the samples from the area were classified as recharge area waters ca na hco3 water and na ca hco3 water transition zone waters na hco3 cl water and discharge area waters na cl water and more concentrated na cl water spatial plots of the major statistical groups show that the samples that belong to the same group are located in close proximity to one another suggesting the same processes and or flowpaths inverse geochemical models of the statistical groups were developed using phreeqc to elucidate the chemical reactions controlling water chemistry the inverse geochemical modeling demonstrated that relatively few phases are required to derive water chemistry in the area in a broad sense the reactions responsible for the hydrochemical evolution in the area fall into four categories 1 silicate weathering reactions 2 dissolution of salts 3 precipitation of calcite amorphous silica and clay minerals and 4 ion exchange

rapid ocean wave teleconnections linking antarctic salinity anomalies to the equatorial ocean atmosphere system the coupled climate model forte is used to investigate rapid ocean teleconnections between the southern ocean and equatorial pacific ocean salinity anomalies located throughout the southern ocean generate barotropic signals that propagate along submerged topographic features and result in the growth of baroclinic energy anomalies around indonesia and the tropical pacific anomalies in the ross bellingshausen and amundsen seas exchange the most barotropic kinetic energy between high and low latitudes in the equatorial pacific baroclinic kelvin waves are excited which propagate eastwards along the thermocline resulting in sst anomalies in the central and eastern pacific sst anomalies are subsequently amplified to magnitudes of 1 25 c by air sea interaction which could potentially influence other coupled pacific phenomena

an antarctic circumpolar wave in surface pressure wind temperature and sea ice extent the southern ocean is the only oceanic domain encircling the globe it contains the strong eastward flow of the antarctic circumpolar current and is the unifying link for exchanges of water masses at all depths between the world s major ocean basins1 as these exchanges are an important control on mean global climate the southern ocean is expected to play an important role in transmitting climate anomalies around the globe interannual variability has been often observed at high southern latitudes and observations of sea ice extent suggest that such features propagate eastwards around the southern ocean2 3 here we use data from a variety of observational techniques to identify significant interannual variations in the atmospheric pressure at sea level wind stress sea surface temperature and sea ice extent over the southern ocean these anomalies propagate eastward with the circumpolar flow with a period of 4 5 years and taking 8 10 years to encircle the pole this system of coupled anomalies which we call the antarctic circumpolar wave is likely to play an important role in climate regulation and dynamics both within and beyond the southern ocean

assessment of geochemical processes in the unconfined and confined aquifers in the eastern ganges basin a geochemical approach groundwater quality is gaining more importance in groundwater management due to rapid growth in population agriculture and industrial sectors worldwide the goal of the present study is to evaluate the groundwater chemistry and to identify the geochemical processes governing the water chemistry in the shallow unconfined and deeper confined aquifers in the eastern ganges basin using geochemical methods groundwater samples were analysed for major ions and metals fe mn zn cu pb and as shallow wells are found to have high ph ec tds ca mg cl and so4 and low hco3 cl ratio compared to the deep wells however the average concentration of na hco3 no3 po4 f and mn is not significantly varied with depth which indicates that the variation in the water chemistry between unconfined and confined aquifers is not only due to the natural processes but also indicates that surface contamination sources could have affected the water chemistry in the unconfined aquifer in the unconfined aquifer processes like wastewater infiltration denitrification reverse ion exchange and mineral weathering govern the water chemistry the water chemistry in the confined aquifer is regulated by weathering of silicate and carbonate minerals and regional flow

a quick response of the equatorial ocean to antarctic sea ice salinity anomalies the potential mechanisms for a quick response of the equatorial ocean to processes occurring in the high latitude southern ocean have been investigated in the southern ocean at the drake passage latitudes there is an zonally unbounded channel the antarctic circumpolar current belt accb it is demonstrated that in a multiconnected domain such as the accb signals generated by anomalies in the southern ocean sea ice cover salinity distribution can propagate in a wave like manner in the form of fast moving barotropic rossby waves a disturbance induced near the drake passage is demonstrated to generate a rossby wave that propagates across the pacific in only a few days this signal is reflected at the western boundary of the pacific and generates an equatorward propagating coastally trapped kelvin wave the resulting temperature anomaly moves northward along the western coastline up to the vicinity of the equator and increases in amplitude over time the anomaly in the western edge of equatorial pacific then begins to propagate eastward along the equator as a trapped equatorial wave after about 2 3 months this wave reaches the eastern coast reflects and generates the coastal trapped wave which propagates north and south along the coastline in both hemispheres this process is suggested as one possible direct mechanism by which the extratropical ocean can induce anomalies in the equatorial ocean

slow oceanic teleconnections linking the antarctic circumpolar wave with the tropical el nino southern oscillation a case study for the period 1982 1994 shows that a major source for the antarctic circumpolar wave is in the western subtropical south pacific where interannual anomalies in sea surface temperature sst and precipitable water prwat form once established these interannual anomalies in tandem with anomalies in sea level pressure slp move south toward the southern ocean the system then migrates east around the globe through a combination of oceanic advection with the antarctic circumpolar current and ocean atmosphere coupling the coincidence of interannual anomalies in sst slp and prwat indicates the extratropical ocean and atmosphere are tightly linked on these timescales large portions of the interannual sst anomalies branch advectively northward into the south atlantic and indian oceans ultimately reaching the tropics in each basin some 6 8 years after appearing in the low latitude pacific this constitutes a slow oceanic teleconnection that is unique in climate dynamics made possible by the continuity of earth s oceans via the southern ocean in the tropical indian ocean these interannual anomalies move east and arrive at the indo pacific transition in advance of the trans pacific propagation of the respective el nino southern oscillation enso phases the interannual sst and prwat anomalies that appear in the subtropical south pacific are directly linked with the enso cycle on the equator through anomalous vertical convection and a regional overturning cell in the troposphere the same cell that initiates fast planetary waves in the atmosphere that carry enso signals around the southern hemisphere on much shorter timescales

geochemical modeling of the madison aquifer in parts of montana wyoming and south dakota stable isotope data for dissolved carbonate sulfate and sulfide are combined with water compo sition data to construct geochemical reaction models along eight flow paths in the madison aquifer in parts of wyoming montana and south dakota the sulfur isotope data are treated as an isotope dilution problem whereas the carbon isotope data are treated as rayleigh distillations all reaction models reproduce the observed chemical and carbon and sulfur isotopic composition of the final waters and are partially validated by predicting the observed carbon and sulfur isotopic compositions of dolomite and anhydrite from the madison limestone the geochemical reaction models indicate that the dominant groundwater reaction in the madison aquifer is dedolomitization calcite precipita tion and dolomite dissolution driven by anhydrite dissolution sulfate reduction ca mg2 ina cation exchange and halite dissolution are locally important particularly in central montana the groundwater system is treated as closed to c02 gas from external sources such as the soil zone or cross formational leakage but open to c02 from oxidation of organic matter coupled with sulfate reduction and other redox processes occurring within the aquifer the computed mineral mass transfers and modeled sulfur isotopic composition of madison anhydrites are mapped throughout the study area carbon 14 groundwater ages adjusted for the modeled carbon mass transfer range from modem to about 23 000 years b p and indicate flow velocities of 7 7 ftlyr 2 1 26 5 rnlyr most horizontal hydraulic conductivities calculated from darcy s law using the average 14 c flow velocities are within a factor of 5 of those based on digital simulation the calculated mineral mass transfer and adjusted 14 c groundwater ages permit determination of apparent rates of reaction in the aquifer the apparent rate of organic matter oxidation is typically 0 12 jlidol uyr sulfate and to a lesser extent ferric iron are the predominant electron acceptors the kinetic biochemical fractionation of 34 s between sulfate and hydrogen sulfide is approximately 44 o at 25 c with a temperature variation of

two way cluster analysis of geochemical data to constrain spring source waters abstract the purpose of the study was to use geochemical characteristics and apparent ages of sampled groundwaters to determine which of the two regionally extensive bedrock aquifers the lower bedrock aquifer or the upper bedrock aquifer is a more likely source of water discharging to springs in the nine springs watershed the use of summary statistics and our knowledge of the regional hydrostratigraphy resulted in the identification of three groups of monitoring points that are representative of groundwaters with distinct geochemical characteristics two way cluster analysis of the geochemical data supports these groupings and further identifies subtle geochemical characteristics of the groups one spring which is representative of smaller springs and seeps found in the watershed belongs to a group that is characterized by variable nitrate and chloride concentrations water discharging from this spring has a groundwater residence time of approximately 8 years based on the tritium helium 3 dating method the water discharging to this small spring is thought to have traveled primarily through the unlithified aquifer as opposed to either of the major bedrock aquifers most of the springs in the watershed belong to a group that is characterized by elevated but consistent nitrate sodium and chloride concentrations in addition cluster analysis revealed that potassium and alkalinity concentrations are somewhat low apparent groundwater ages for this group range from 10 to 15 years the water discharging from the majority of the springs in the watershed is thought to have traveled primarily through the unlithified aquifer and the upper bedrock aquifer before discharging into the former glacial lakebed wetland complex due to the relatively short groundwater residence times spring water quality and flow in the nine springs watershed are likely to be vulnerable to the rapid urban expansion occurring within the watershed

influence of detrital composition on the diagenetic history of tight sandstones with implications for reservoir quality examples from the permian xiashihezi formation and carboniferous taiyuan formation daniudi gas field ordos basin china abstract tight gas reservoirs characterized by low porosity and low permeability are widely considered to be the product of post depositional diagenetic processes associated with progressive burial this study utilizes a combination of thin section petrography scanning electron microscopy microprobe and back scatter electron analysis stable isotope geochemistry and fluid inclusion analysis to compare the diagenetic history including porosity formation within sandstones of the second member of carboniferous taiyuan formation c3t2 and the first member of permian xiashihezi formation p1x1 in the ordos basin in central china in the p1x1 member relatively high abundances of metamorphic rock fragments coupled with a braided river and lacustrine delta environment of deposition produced more smectite for transformation to illite 50 120 c this reaction was driven by dissolution of unstable minerals k feldspar and rock fragments during the early to middle stages of mesodiagenesis and consumed all k feldspar abundant intragranular porosity average values of 2 8 and microporosity in kaolinite average values of 1 5 formed at these burial depths with chlorite and calcite developed as by products in the c3t2 member relatively low abundances of metamorphic rock fragments coupled with an incised valley coastal plain environment of deposition resulted in less smectite for transformation to illite high k h ratios in the early pore waters related to a marine sedimentary environment of deposition promoted this reaction under these conditions k feldspar was partially preserved during the middle to late stages of mesodiagenesis k feldspar breakdown produced secondary intragranular average values of 1 4 and intergranular pores average values of 1 2 release of k ions promoted illitization of kaolinite with quartz overgrowths and ferrous carbonates developed as by products this study has demonstrated that whereas both members are typical tight gas sandstones they are characterized by quite different diagenetic histories controlled by the primary detrital composition especially during mesodiagenesis types of secondary porosity vary between the two members and developed at different stages of progressive burial the content of unstable detrital components notably feldspar was the key factor that determined the abundance of secondary porosity

hydrogeochemical controls on shallow alluvial groundwater under agricultural land case study in central portugal a hydrogeochemical study employing graphical multivariate statistical and modeling tools was conducted in an area of alluvial deposits in the mondego river basin to determine the factors and processes controlling the shallow groundwater chemistry groundwater was collected from 29 observation wells in six sampling campaigns between march 2001 and september 2002 samples were analyzed for basic physicochemical parameters major ions and some minor ions hierarchical cluster analysis was applied to the data set including both the spatial and temporal monitoring data and resulted in the definition of eight distinct water types with the aid of hydrochemical and physicochemical scatter plots it was possible to identify the main processes controlling the groundwater chemistry 1 evapotranspiration and recharge 2 calcium and magnesium carbonate and co2 dissolution 3 nitrate leaching from agriculture 4 oxidation and reduction and 5 cation exchange these processes are frequently common to more than one water type but unique in combination and or extent in space and or time geochemical modeling of the water types using phreeqc allowed the validation and to a certain extent quantification of the processes that affect the shallow groundwater evolution these tools can provide an essential support for the assessment of groundwater vulnerability to contamination and for the elaboration of groundwater resource management strategies

age stratigraphy and deposition of near k t siliciclastic deposits in mexico relation to bolide impact examination of 10 k t boundary sections in northeastern and east central mexico and new data presented from 7 sections permit the following conclusions 1 the globally recognized k t boundary and mass extinction in planktic foraminifera is stratigraphically above and separated by a thin marl layer of maastrichtian age from the siliciclastic deposit that is commonly interpreted as a short term hours to days k t impact generated tsunami deposit a similar relationship between the k t boundary and siliciclastic or breccia deposits is observed at brazos river in texas beloc in haiti and poty quarry in brazil 2 stratigraphic control indicates that deposition of the siliciclastic member occurred sometime during the last 150 k y of the maastrichtian and ended at least several thousand years prior to the k t boundary 3 at least four discrete horizons of bioturbation have been observed within the siliciclastic deposit that indicate episodic colonization by invertebrates over an extended time period 4 the glass and spherule rich unit which has been linked to the haiti spherule layer and the chicxulub structure is at the base of the siliciclastic deposit and thus significantly predates the k t boundary event the stratigraphic separation of the k t boundary and siliciclastic deposits and the evidence of long term deposition between them suggests the presence of two events 1 a globally recognized k t boundary impact event marked by ir anomaly and the mass extinction and 2 a caribbean event impact or volcanic and probably linked to the chicxulub structure that predates the k t boundary and is marked by glass and siliciclastic or breccia deposits

diagenesis of a tight gas formation jurassic cotton valley sandstone east texas basin abstract the upper jurassic cotton valley sandstone is a thick siliciclastic unit in the east texas basin sandstones and shales of this unit were deposited in shallow marine and fluvial deltaic environments and exhibit progradational successions of facies along the eastern flank of the basin natural gas is produced from cotton valley reservoirs characterized by low porosity and permeability which have been stimulated by massive hydraulic fracturing

a theory for the surface atlantic response to thermohaline variability abstract the response of the upper warm limb of the thermohaline circulation in the north atlantic to a rapid change in deep water formation at high latitudes is investigated using a reduced gravity ocean model changes in deep water formation rate initiate kelvin waves that propagate along the western boundary to the equator on a timescale of months the response in the north atlantic is therefore rapid the southern hemisphere response is much slower limited by a mechanism here termed the ldquo uatorial buffer since to leading order the flow is in geostrophic balance the pressure anomaly decreases in magnitude as the kelvin wave moves equatorward where the coriolis parameter is lower together with the lack of sustained pressure gradients along the eastern boundary this limits the size of the pressure field response in the southern hemisphere interior adjustment is by the westward propagation of rossby waves but only a small fraction of the change in thermohaline circulation strength is commun

global teleconnections in response to freshening over the antarctic ocean abstract in this paper coupled ocean atmosphere responses to freshening over the antarctic ocean are investigated in a fully coupled model with a series of sensitivity experiments in the model 1 0 sv 1 sv 106 m3 s 1 of freshwater flux is uniformly imposed over the antarctic ocean for 400 yr while the ocean and atmosphere remain fully coupled both locally and elsewhere the model explicitly demonstrates that a freshening of the antarctic ocean can induce a significant local cooling coupled with an intensification of the westerly winds and expansion of sea ice furthermore the cooling can extend to the entire southern extratropical and tropical oceans coupled with an intensification of southeasterly trades and the equatorial trade winds some modest warm anomalies also occur in the northern extratropical oceans forming a sharp interhemispheric sst contrast a series of sensitivity experiments are conducted to understand the mechanisms responsible for transmitting the southern high latitude cooling

isotope signatures and hydrochemistry as tools in assessing groundwater occurrence and dynamics in a coastal arid aquifer groundwater from the la paz arid coastal aquifer in baja california mexico is essentially the only source of drinking water for the local population and tourists as well as irrigation water for agricultural needs the intensive exploitation of the aquifer and water cycling has resulted in groundwater abatement up to 10 m and high salinity up to 5800 mg l 1 a study using hydrochemistry isotopic deuterium oxygen 18 and carbon 14 and gaseous tracers chlorofluorocarbons cfc 11 cfc 12 cfc 113 as well as multivariate statistics was developed to elucidate groundwater composition flow and occurrence groundwater is of meteoric origin and a large proportion is subject to evaporation the primary natural recharge is generated in the el novillo and las cruces ranges and groundwater subsequently flows in a se nw direction toward the coast the initial water type is the result of discordant dissolution of silicate minerals and ion exchange on soils in the lower plain portion the aquifer system is recharged from irrigation return flow and seawater intrusion which significantly affects groundwater chemistry nitrate and chloride concentrations indicate that groundwater is highly affected by an overuse of fertilizers in agricultural activities but there is little effect from urban activities seawater intrusion has progressed rapidly during the past decade and the impact currently extends 13 km inland radiocarbon residence time calculations suggest that groundwater is modern with the exception of chametla and el centerario sites in the central and western lowlands with ages of up to 5000 years these waters indicate an additional recharge source for the upconing of fossil groundwater or regional flow

modeling of geochemical processes and multivariate statistical analysis for hydrochemical assessment of spring water of the outer himalaya india water resources in the himalayan region are under stress because of the changes in land use and land cover pattern and climate in the recent past the region has encountered extreme events such as cloud burst and widespread flooding in this reference this study was conducted on the spring water resources in the outer himalayan region to assess their quality and quantity the main geochemical processes and the impact of anthropogenic forcing on water chemistry were deciphered using geochemical modeling tools multivariate statistical analysis and graphic plots the hierarchical cluster analyses were used to categorize the springs in two clusters based on their chemical characteristics the principal component analysis was used to evaluate the effective loading of spring water hydrochemical data ionic ratios and geochemical modeling using phreeqc were used to confirm the processes that govern the chemistry of the spring water the results indicate that silicate weathering and anthropogenic activities are the dominant processes controlling the chemical evolution of spring water in the region this study will provide a better insight for understanding the spring water resources and their sustainable management in the himalayan region