freeboard and mass extraction of the disintegrated mertz ice tongue with remote sensing and altimetry data abstract in february 2010 the mertz ice tongue mit collapsed and generated a giant iceberg however parameters about this iceberg have not been calculated and published in detail in this study the freeboard map of this iceberg was generated for the first time using a time series icesat glas data methods for producing the freeboard map of this iceberg are suggested field data for ice velocity were used to relocate the footprints collected by different campaigns cross validation was conducted with freeboards extracted from crossovers observed within 30 days of each other the precision of the freeboard extraction is approximately 0 50 m when taking one standard deviation as the precision the freeboard varied from 23 m to 59 m with the mean of 41 m with assumption of hydrostatic equilibrium assuming a snow layer depth of 1 m a snow density of 360 kg m 3 an ice density of 915 kg m 3 and a sea water density of 1024 kg m 3 the minimum maximum and average ice thickness were calculated as 210 m 550 m and 383 m respectively the total ice loss is approximately 8 96 10 11 tons over an area 34 km in width and 75 km in length or approximately 2560 5 km 2 these parameters extracted from remote sensing and altimetry data will provide additional information for studies of the evolution of iceberg especially in iceberg tracking system

geochemistry of dissolved inorganic carbon in a coastal plain aquifer 1 sulfate from confining beds as an oxidant in microbial co2 production a primary source of dissolved inorganic carbon dic in the black creek aquifer of south carolina is carbon dioxide produced by microbially mediated oxidation of sedimentary organic matter groundwater chemistry data indicate however that the available mass of inorganic electron acceptors oxygen fe iii and sulfate and observed methane production is inadequate to account for observed co2 production although sulfate concentrations are low approximately 0 05 0 10 mm in aquifer water throughout the flow system sulfate concentrations are greater in confining bed pore water 0 4 20 mm the distribution of culturable sulfate reducing bacteria in these sediments suggests that this concentration gradient is maintained by greater sulfate reducing activity in sands than in clays calculations based on fick s law indicate that possible rates of sulfate diffusion to aquifer sediments are sufficient to explain observed rates of co2 production about 10 5 mmoll 1 year 1 thus eliminating the apparent electron acceptor deficit furthermore concentrations of dissolved hydrogen in aquifer water are in the range characteristic of sulfate reduction 2 6 nm which provides independent evidence that sulfate reduction is the predominant terminal electron accepting process in this system the observed accumulation of pyrite and calcite cemented sandstones at sand clay interfaces is direct physical evidence that these processes have been continuing over the history of these sediments

potential vorticity structure in the north atlantic western boundary current from underwater glider observations abstractpotential vorticity structure in two segments of the north atlantic s western boundary current is examined using concurrent high resolution measurements of hydrography and velocity from gliders spray gliders occupied 40 transects across the loop current in the gulf of mexico and 11 transects across the gulf stream downstream of cape hatteras cross stream distributions of the ertel potential vorticity and its components are calculated for each transect under the assumptions that all flow is in the direction of measured vertically averaged currents and that the flow is geostrophic mean cross stream distributions of hydrographic properties potential vorticity and alongstream velocity are calculated for both the loop current and the detached gulf stream in both depth and density coordinates differences between these mean transects highlight the downstream changes in western boundary current structure as the current increases its transport downstream upper layer potential vorticity is generall

stable isotopic biogeochemistry of carbon and nitrogen in a perennially ice covered antarctic lake lake hoare 77 degrees 38 s 162 degrees 53 e is an amictic oligotrophic 34 m deep closed basin lake in taylor valley antarctica its perennial ice cover minimizes wind generated currents and reduces light penetration as well as restricts sediment deposition into the lake and the exchange of atmospheric gases between the water column and the atmosphere the biological community of lake hoare consists solely of microorganisms both planktonic populations and benthic microbial mats lake hoare is one of several perennially ice covered lakes in the mcmurdo dry valleys that represent the end member conditions of cold desert and saline lakes the dry valley lakes provide a unique opportunity to examine lacustrine processes that operate at all latitudes but under an extreme set of environmental conditions the dry valley lakes may also offer a valuable record of catchment and global changes in the past and present furthermore these lakes are modern day equivalents of periglacial lakes that are likely to have been common during periods of glacial maxima at temperate latitudes we have analyzed the dissolved inorganic carbon dic of lake hoare for delta 13c and the organic matter of the sediments and sediment trap material for delta 13c and delta 15n the delta 13c of the dic indicates that 12c is differentially removed in the shallow oxic portions of the lake via photosynthesis in the anoxic portions of the lake 27 34 m a net addition of 12c to the dic pool occurs via organic matter decomposition the dissolution of caco3 at depth also contributes to the dic pool except near the canada glacier where a substantial amount of allochthonous organic matter enters the lake the organic carbon being deposited on the lake bottom at different sites is isotopically similar suggesting an autochthonous source for the organic carbon preliminary inorganic carbon flux calculations suggest that a high percentage of the organic carbon fixed in the water column is remineralized as it falls through the water column at nearby lake fryxell the substantial relative to lake hoare glacial meltstream input overprints fryxell s shallow water biological delta 13c signal with delta 13c depleted dic in contrast lake hoare is not significantly affected by surface water input and mixing and therefore the delta 13c patterns observed arise primarily from biological dynamics within the lake organic matter in lake hoare is depleted in 15n which we suggest is partially the result of the addition of relatively light inorganic nitrogen into the lake system from terrestrial sources

biodiversity change after climate induced ice shelf collapse in the antarctic the marine ecosystem on the eastern shelf of the antarctic peninsula was surveyed 5 and 12 years after the climate induced collapse of the larsen a and b ice shelves an impoverished benthic fauna was discovered that included deep sea species presumed to be remnants from ice covered conditions the current structure of various ecosystem components appears to result from extremely different response rates to the change from an oligotrophic sub ice shelf ecosystem to a productive shelf ecosystem meiobenthic communities remained impoverished only inside the embayments on local scales macro and mega epibenthic diversity was generally low with pioneer species and typical antarctic megabenthic shelf species interspersed antarctic minke whales and seals utilised the larsen a b area to feed on presumably newly established krill and pelagic fish biomass ecosystem impacts also extended well beyond the zone of ice shelf collapse with areas of high benthic disturbance resulting from scour by icebergs discharged from the larsen embayments

arsenic concentrations and speciation along a groundwater flow path the carrizo sand aquifer texas usa abstract groundwater samples for arsenic as concentration and speciation analysis were collected from production wells along a flow path in the carrizo sand aquifer in southeastern texas during june 2004 the study was conducted as part of a larger investigation of trace metal and metalloid concentrations speciation and geochemical behavior along a groundwater flow path in the relatively pristine carrizo sand aquifer additional sample aliquots were collected and analyzed for fe ii and fe iii concentrations h 2 s concentrations ph and alkalinity oxidation reduction potential eh and dissolved oxygen concentrations were also monitored in groundwaters at each well head dissolved inorganic as i e as iii and as v species in carrizo sand aquifer groundwater samples were separated during sample collection using anion exchange chromatography arsenic concentrations were subsequently determined by inductively coupled plasma mass spectrometry total dissolved arsenic as t i e as iii as v ranges from 0 37 to 2 5 nmol kg 1 in groundwater from the carrizo sand aquifer arsenate which is the dominant form of as in carrizo groundwaters collected from the first 15 km along the flow path ranges from below the method detection limit 0 36 nmol kg 1 to 2 0 nmol kg 1 arsenite concentrations are relatively constant along the flow path compared to as v ranging from 0 29 to 0 87 nmol kg 1 arsenic concentrations and speciation exhibit systematic changes along the carrizo sand aquifer flow path that correspond to changes in dissolved fe ii and fe iii concentrations dissolved sulfide concentrations ph and alkalinity the data are consistent with a combination of physiochemical reactions and inferred microbial processes e g ferric iron reduction adsorption ph related desorption playing significant roles in speciation mobility and cycling of as in the carrizo sand aquifer

chemical and isotopic evidence for hydrogeochemical processes occurring in the lincolnshire limestone over 150 groundwater samples from the lincolnshire limestone have been analysed for ph major ions and 13c ratios where possible field eh and iodide concentrations were measured and methane concentrations were determined for 12 samples stable isotope ratios were determined for soil and rock carbonate samples a system of zonation allows the division of hydrogeochemical processes occurring in the aquifer the use of hydrochemical and isotope data in modelling exercises enables the re evaluation and possible enhancement of the understanding of hydrogeochemical processes the carbonate chemistry of outcrop groundwaters is explained by calcite saturation being achieved under open system conditions in the soil zone 13c ratios in the range 15 99 to 10 57 may be generated from a stoichiometric reaction with possible additional partial and or simultaneous exchange with soil co2 or carbonate the isotopic composition of soil carbonate shows the effects of precipitation from soil waters the incongruent dissolution of primary depositional limestone carbonate results in increasing magnesium and strontium concentrations and increasing 13c ratios for the groundwaters with flow down the hydraulic gradient as a result of incongruent dissolution secondary calcite may be precipitated onto fissure surfaces significant nitrate and sulphate reduction in non saline groundwaters is not supported by the results of hydrochemical and isotope modelling exercises however sulphate reduction and methane fermentation may be affecting the isotopic and chemical compositions of saline groundwaters sodium calcium ion exchange leads to limited calcite dissolution deep in the aquifer but the evolution of these groundwaters is confused by the uncertain effects of oxidation of organic carbon and mixing with a saline end member solution

equilibration of baroclinic meanders and deep eddies in a gulf stream type jet over a sloping bottom abstract spatiotemporal evolution of a small localized meander on a gulf stream type baroclinically unstable jet over a topographic slope is investigated numerically using a three dimensional primitive equation model an unperturbed jet is prescribed by a potential vorticity front in the upper thermocline overlaying intermediate layers with weak isentropic potential vorticity gradients and a quiscent bottom layer over a positive same sense as isopycnal tilt cross stream continental slope a series of numerical experiments with the same initial conditions over a slope and flat bottom on the plane and on the f plane has been carried out an initially localized meander evolves into a wave packet and generates deep eddies that provide a positive feedback for the meander growth meanders found growing over a flat bottom are able to pinch off resembling warm and cold core rings while in the presence of a weak bottom slope such as 0 002 the maximum amplitudes of meanders and associated deep eddies saturat

propagation of internal tides generated near luzon strait observations from autonomous gliders 1 the vertical isopycnal displacements associated with internal waves generated by the barotropic tidal currents in the vicinity of luzon strait are estimated using measurements collected by autonomous underwater gliders nearly 23 000 profiles from seagliders and spray gliders collected during 29 different missions since 2007 are used to estimate the amplitude and phase of the linear semidiurnal and diurnal internal waves in this energetic region particularly in the previously poorly sampled area near the eastern ridge and on the pacific side of luzon strait the mean and variability of the internal wave field in the upper 1000 m of the water column are described the phase progression of internal waves as they propagate away from their generation sites is captured directly the glider based observations are used to map the mode 1 semidiurnal and diurnal internal wave fields providing the baroclinic energy flux over a roughly 600 km 800 km region based strictly on in situ observations

observations of unusual fast ice conditions in the southwest ross sea antarctica preliminary analysis of iceberg and storminess effects massive tabular icebergs 1000 km 2 surface area 1011 kg mass arrived in the southwest ross sea in early 2001 where they remained relatively immobile for the next 4 years during the period of their presence extensive landfast sea ice fast ice waxed and waned along the victoria land coast with maximum coverage exceeding typical coverage prior to the arrival of the icebergs by a factor of 5 the purposes of this study are to determine 1 whether the extensive iceberg blockade extending from ross island to drygalski ice tongue was indeed as intuition suggests responsible for the unusual fast ice conditions and 2 how storm frequency intensity and seasonal timing may have mitigated the effects of the icebergs our simple analysis of glaciological and atmospheric conditions observed during 2001 05 suggests that iceberg movement alone is not sufficient to explain fast ice variability and in fact it is the detailed interplay between storms and iceberg location that determine this variability

impact of iceberg c 19 on ross sea primary production 1 for the second time in 26 months a large iceberg c 19 calved off the face of the ross ice shelf rather than breaking up as did its predecessor b 15 the iceberg c 19 remained largely intact eventually stopping temporarily near pennell bank before moving out of the southwestern ross sea the presence of c 19 restricted advection of sea ice out of the region resulting in unusually high sea ice cover during the spring and summer consequently phytoplankton blooms in the region were diminished dramatically and primary production was reduced by over 90 relative to normal years calving events over the last two decades indicate that reduced primary productivity may be a typical consequence of large icebergs that drift through the southwestern ross sea during spring and summer

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

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

bacterial metabolism and the δ13c composition of ground water floridan aquifer system south carolina viable bacteria are present 10 5 10 7 cells per gram sediment in the clastic water table and hawthorn aquifers that overlie and recharge the floridan aquifer near hilton head island south carolina incubation of cored sediments shows that indigenous bacteria are capable of producing carbon dioxide co 2 as they metabolize sedimentary organic material estimated in situ co 2 production rates based on dissolved inorganic carbon dic changes and ground water flow rates are in the range of 10 2 mmol l 1 yr 1 two independent lines of evidence 1 isotope balance calculations on dic along ground water flow paths and 2 direct measurement of the isotopic composition of co 2 produced by incubation of hawthorn sediment suggest that bacterially produced co 2 in the hawthorn aquifer is much heavier isotopically 13 c 10 to 15 than associated sedimentary organic material 13 c 21 the relatively heavy 13 c values of dic in water from the floridan aquifer which receives much of its recharge from the overlying hawthorn reflect this source of isotopically heavy co 2

climate patterns and phytoplankton dynamics in antarctic latent heat polynyas 1 seasonal coherence between satellite derived phytoplankton parameters chlorophyllaconcentration chl and phytoplankton bloom initiation time bit environmental variables sea ice concentration surface solar radiation and wind speed and climate patterns el nino 3 4 the southern annular mode the pacific south america pattern the semiannual oscillation and the wave 3 stationary pattern was investigated in four latent heat polynyas amundsen sea western ross sea dumont d urville and prydz bay using data corresponding to 1998 2006 phytoplankton growing seasons in general polynyas in the western sector i e amundsen sea and western ross sea had a greater sea ice cover lower solar radiation levels higher and more variable chl and more variable and delayed i e high bit phytoplankton blooms differences in chl and bit were mainly attributed to differences in water stratification and interannual variability of sea ice concentration caused by ice shelf calving events in the ross sea changes in solar radiation reaching the sea surface played an important role in determining phytoplankton blooms in the western ross sea and prydz bay stronger winds tend to benefit development of phytoplankton blooms in polynyas having more stratified waters sensitivity of phytoplankton to climate variability in polynyas under investigation was highly influenced by the polynya size during summer e g chl in dumont d urville and bit in the western ross sea also the response of chl to the same climate pattern changed with the polynya s location e g correlation between chl and el nino 3 4 in amundsen sea positive and dumont d urville negative

sea ice variability and primary productivity in the ross sea antarctica from methylsulphonate snow record 1 the ross sea contains the most biologically productive continental shelf in antarctica and is a region where the annual formation of sea ice drives substantial amounts of bottom water formation we present snow pit chemistry data from mt erebus saddle that provide a quantitative proxy to reconstruct summer sea ice conditions and rates of marine primary production the methylsulphonate ms record is strongly correlated with changes in the area of open water r2 0 903 p 0 05 caused by differences in atmospheric circulation and the sea ice damming effect of large icebergs b 15 and c 19 which calved from the ross ice shelf in 2000 and 2002 respectively furthermore ms and phytoplankton net primary production correlate significantly r2 0 927 p 0 01 our results demonstrate the potential of the mt erebus saddle ice core to reconstruct sea ice and primary productivity variability in the ross sea beyond the observational record

asymmetry of an equilibrated gulf stream type jet over topographic slope abstract the symmetry properties of the gulf stream type jet equilibrated over topographic slope are investigated in a series of idealized numerical experiments a baroclinically unstable zonal jet equilibrates over a sloping bottom through the process of potential vorticity pv homogenization underneath the main thermocline by the bottom intensified eddy activity associated with the stream meandering potential vorticity homogenization underneath the main thermocline leads to formation of recirculation gyres on both sides of the jet the magnitude of the northern recirculation gyre as measured by its westward transport is larger than the magnitude of the southern recirculation gyre this asymmetry in recirculations is shown to be the result of an asymmetric pv mixing underneath the thermocline produced by an asymmetric jet in particular the lateral shift of the velocity maximum near the surface relative to the velocity maximum at depth is shown to be responsible for the asymmetry the results are re

sources and transport pathways of marine aerosol species into west antarctica sixteen high resolution marine aerosol na so4 records from spatially distributed international trans antarctic scientific expedition itase ice cores spanning the last 200 years from the pine island thwaites and ross drainage systems and the south pole are used to examine sources sea spray and frost flowers and transport pathways of marine aerosols into west antarctica factors contributing to the amount of marine aerosols transported inland include sea ice extent the presence of open water features polynyas leads wind strength and direction and the strength and positioning of low pressure systems analysis of so4 na ratios indicates that frost flowers can contribute significantly 40 to the na budget of antarctic ice cores higher na concentrations in the ross drainage system may result from greater production of marine aerosols related to frost flowers in the ross sea region in association with greater sea ice extent and larger open water areas significant positive correlations of sea ice extent and the na time series exist in some regions of west antarctica higher wind speeds in winter and higher na concentrations when slp is

correction to characterization and isotopic composition of organic and inorganic carbon in the milk river aquifer by ellyn m murphy stanley n davis austin long douglas donahue and a j timothy jull

chemical hydrogeology in natural and contaminated environments abstract chemical hydrogeology including organic and inorganic aspects has contributed to an increased understanding of groundwater flow systems geologic processes and stressed environments most of the basic principles of inorganic chemical hydrogeology were first established by investigations of organic free regional scale systems for which simplifying assumptions could be made the problems of groundwater contamination are causing a shift of emphasis to microscale systems that are dominated by organic chemical reactions and that are providing an impetus for the study of naturally occurring and manmade organic material along with the decrease in scale physical and chemical heterogeneity become major controls current investigations and those selected from the literature demonstrate that heterogeneity increases in importance as the study site decreases from regional scale to macroscale to microscale increased understanding of regional scale flow systems is demonstrated by selection of investigations of carbonate and volcanic aquifers to show how application of present day concepts and techniques can identify controlling chemical reactions and determine their rates identify groundwater flow paths and determine flow velocity and determine aquifer characteristics the role of chemical hydrogeology in understanding geologic processes of macroscale systems is exemplified by selection of investigations in coastal aquifers phenomena associated with the mixing zone generated by encroaching sea water include an increase in heterogeneity of permeability diagenesis of minerals and formation of geomorphic features such as caves lagoons and bays ore deposits of manganese and uranium along with a simulation model of ore forming fluids demonstrate the influence of heterogeneity and of organic compounds on geochemical reactions associated with genesis of mineral deposits in microscale environments importance of heterogeneity and consequences of organic reactions in determining the distributions and concentrations cf constituents are provided by several studies including infiltration of sewage effluent and migration of creosote in coastal plain aquifers these studies show that heterogeneity and the dominance of organically controlled reactions greatly increase the complexity of investigations

high frequency internal waves near the luzon strait observed by underwater gliders 1 tidal flow through the luzon strait produces large internal waves that propagate westward into the south china sea and eastward into the pacific underwater gliders gathered sustained observations of internal waves during seven overlapping missions from april 2007 through july 2008 a particular focus is the high frequency internal waves where the operational definition of high involves periods shorter than a glider profile taking 3 6 h internal wave vertical velocity is estimated from measurements of pressure and glider orientation through two methods 1 use of a model of glider flight balancing buoyancy and drag along the glider path and 2 high pass filtering of the observed glider vertical velocity by combining high frequency vertical velocities from glider flight with low frequency estimates from isopycnal depth variations between dives a spectrum covering five decades of frequency is constructed a map of the standard deviation of vertical velocity over the survey area shows a decay from the luzon strait into the pacific the growth of high frequency vertical velocity with propagation into the south china sea is observed through two 2 week time series stations the largest observed vertical velocities are greater than 0 2 m s 1 and are associated with displacements approaching 200 m the high frequency waves are observed at regular intervals of 1 day as they ride on diurnal tidal internal waves generated in the strait

influence of sea ice cover and icebergs on circulation and water mass formation in a numerical circulation model of the ross sea antarctica 1 satellite imagery shows that there was substantial variability in the sea ice extent in the ross sea during 2001 2003 much of this variability is thought to be due to several large icebergs that moved through the area during that period the effects of these changes in sea ice on circulation and water mass distributions are investigated with a numerical general circulation model it would be difficult to simulate the highly variable sea ice from 2001 to 2003 with a dynamic sea ice model since much of the variability was due to the floating icebergs here sea ice concentration is specified from satellite observations to examine the effects of changes in sea ice due to iceberg c 19 simulations were performed using either climatological ice concentrations or the observed ice for that period the heat balance around the ross sea polynya rsp shows that the dominant term in the surface heat budget is the net exchange with the atmosphere but advection of oceanic warm water is also important the area average annual basal melt rate beneath the ross ice shelf is reduced by 12 in the observed sea ice simulation the observed sea ice simulation also creates more high salinity shelf water another simulation was performed with observed sea ice and a fixed iceberg representing b 15a there is reduced advection of warm surface water during summer from the rsp into mcmurdo sound due to b 15a but a much stronger reduction is due to the late opening of the rsp in early 2003 because of c 19

geochemistry of dissolved inorganic carbon in a coastal plain aquifer 2 modeling carbon sources sinks and δ13c evolution abstract stable isotope data for dissolved inorganic carbon dic carbonate shell material and cements and microbial co2 were combined with organic and inorganic chemical data from aquifer and confining bed pore waters to construct geochemical reaction models along a flowpath in the black creek aquifer of south carolina carbon isotope fractionation between dic and precipitating cements was treated as a rayleigh distillation process organic matter oxidation was coupled to microbial fermentation and sulfate reduction all reaction models reproduced the observed chemical and isotopic compositions of final waters however model 1 in which all sources of carbon and electron acceptors were assumed to be internal to the aquifer was invalidated owing to the large ratio of fermentation co2 to respiration co2 predicted by the model 5 49 compared with measured ratios two or less in model 2 this ratio was reduced by assuming that confining beds adjacent to the aquifer act as sources of dissolved organic carbon and sulfate this assumption was based on measured high concentrations of dissolved organic acids and sulfate in confining bed pore waters 60 100 m and 100 380 m respectively relative to aquifer pore waters from less than 30 m and 2 80 m respectively sodium was chosen as the companion ion to organic acid and sulfate transport from confining beds because it is the predominant cation in confining bed pore waters as a result excessive amounts of na for ca ion exchange and calcite precipitation three to four times more cement than observed in the aquifer were required by model 2 to achieve mass and isotope balance of final water for this reason model 2 was invalidated agreement between model predicted and measured amounts of carbonate cement and ratios of fermentation co2 to respiration co2 were obtained in a reaction model that assumed confining beds act as sources of dic as well as organic acids and sulfate this assumption was supported by measured high concentrations of dic in confining beds 2 6 2 7 mm results from this study show that geochemical models of confined aquifer systems must incorporate the effects of adjacent confining beds to reproduce observed groundwater chemistry accurately

nature and origin of authigenic rhodochrosite and siderite from the paleozoic aquifer northeast mississippi u s a abstract botryoidal rhodochrosite siderite and pyrite are the principal authigenic phases in fractured chert comprising the paleozoic aquifer of northeast mississippi locally alternating bands of near end member composition rhodochrosite and siderite occur in veinlets up to 2 mm wide in the fractured chert carbon isotope data for the carbonates 13c values ranging from 9 6 to 11 3 pdb indicate that both inorganic and organic c were incorporated into the authigenic phases the paleozoic aquifer is hydraulically connected with the overlying upper cretaceous coastal plain strata groundwater in the coastal plain units is undersaturated with respect to calcite and has relatively high fe and mn contents the latter apparently caused by the dissolution of fe mn oxyhydroxides the natural downward recharge of these waters into the paleozoic aquifer causes calcite dissolution in limestone at the base of the chert which in turn leads to the precipitation of rhodochrosite and siderite additionally pyrite is precipitated as so4 reduction occurs in the same zone rhodochrosite has not been previously documented as an authigenic phase in a fresh water aquifer system suggesting that the geochemical environment necessary for its precipitation is not common the alternating bands of rhodochrosite and siderite observed in this study coupled with available thermodynamic data indicate that the groundwater a mn2 afe2 ratio must have fluctuated over time variations in the ratio are best explained by variable eh conditions at the site where fe mn oxyhydroxide dissolution occurs

key role of organic complexation of iron in sustaining phytoplankton blooms in the pine island and amundsen polynyas southern ocean primary productivity in the amundsen sea southern ocean is among the highest in antarctica the summer phytoplankton bloom in 2009 lasted for 470 days in both the pine island and amundsen polynyas such productive blooms require a large supply of nutrients including the trace metal iron fe the organic complexation of dissolved fe was investigated in the amundsen sea during the spring of 2009 to better understand the potential role of ligands in enhancing the local stock of dissolved fe the main sources of fe and ligands to the amundsen sea are thought to be melting sea ice and the circumpolar deep water cdw which is modified mcdw on the continental shelf and upwells beneath the coastal glaciers and ice shelves upwelling of relatively warm mcdw is also responsible for the rapid melting of the pine island glacier pig and surrounding ice shelves resulting in additional release of fe into surface waters at upwelling stations near ice shelves organic ligands were nearly saturated with fe thus enhancing the stock of fe and its availability to the phytoplankton community however ligands had little capacity to buffer additional fe input from glacial melt in these coastal upwelling regions much of the glacial fe supply is lost due to vertical export of fe via scavenging and precipitation conversely within the phytoplankton bloom in the nearby coastal polynyas the uptake of fe combined with the production of organic matter enhanced the abundance of relatively unsaturated organic ligands capable of stabilizing additional fe supplied from glacial melt these unsaturated dissolved organic ligands combined with the continuous input of fe dissolved and particulate from glacial melt appear to favor the solubilization of fe thus increasing the stock of bioavailable fe and fueling the phytoplankton bloom

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

geographical distribution and volume of antarctic icebergs derived from ship observation data information on the occurrence spatial distribution and morphometric characteristics of antarctic icebergs is needed in a large number of applications including navigation heat and freshwater balance calculations biochemistry of the ocean and climatology using over 60 000 ship observations of icebergs in the southern ocean collected since the end of the 1940s we have produced a detailed map of the distribution of antarctic icebergs as well as maps of related statistics including the standard deviation minimum and maximum values of the iceberg concentration and the probability of iceberg free observations the study incorporated small and medium sized icebergs with a length of 2 and 16 893 km 3 with uncertainties of 32 33

record of a mid pleistocene depositional anomaly in west antarctic continental margin sediments an indicator for ice sheet collapse abstract modern global warming is likely to cause future melting of earth s polar ice sheets that may result in dramatic sea level rise a possible collapse of the west antarctic ice sheet wais alone which is considered highly vulnerable as it is mainly based below sea level may raise global sea level by up to 5 6 m despite the importance of the wais for changes in global sea level its response to the glacial interglacial cycles of the quaternary is poorly constrained moreover the geological evidence for the disintegration of the wais at some time within the last ca 750 kyr possibly during marine isotope stage mis 11 424 374 ka is ambiguous here we present physical properties palaeomagnetic geochemical and clay mineralogical data from a glaciomarine sedimentary sequence that was recovered from the west antarctic continental margin in the amundsen sea and spans more than the last 1 myr within the sedimentary sequence proxies for biological productivity such as biogenic opal and the barium aluminum ratio and the supply of lithogenic detritus from the west antarctic hinterland such as ice rafted debris and clay minerals exhibit cyclic fluctuations in accordance with the glacial interglacial cycles of the quaternary a prominent depositional anomaly spans mis 15 mis 13 621 478 ka the proxies for biological productivity and lithogenic sediment supply indicate that this interval has the characteristics of a single prolonged interglacial period even though no proxy suggests environmental conditions much different from today we conclude that if the wais collapsed during the last 800 kyr then mis 15 mis 13 was the most likely time period apparently the duration rather than the strength of interglacial conditions was the crucial factor for the wais drawdown a comparison with various marine and terrestrial climate archives from around the world corroborates that unusual environmental conditions prevailed throughout mis 15 mis 13 some of these anomalies are observed in the pelagic southern ocean and the south atlantic and might originate in major ice sheet drawdown in antarctica but further research is required to test this hypothesis

saturn s northern hemisphere ribbon simulations and comparison with the meandering gulf stream voyager observations of saturn in 1980 81 discovered a wavy feature engirdling the planet at 47 n planetographic latitude its latitude coincides with that of an eastward jet stream which is the second fastest on saturn after the equatorial jet the 47 n jet s wavy morphology is unique among the known atmospheric jets on the gas giant planets since the voyagers it has been seen in every high resolution image of this latitude for over 25 years and has been termed the ribbon the ribbon has been interpreted as a dynamic instability in the jet stream this study tests this interpretation and uses forward modeling to explore the observed zonal wind profile s stability properties unforced initial value numerical experiments are performed to examine the nonlinear evolution of the jet stream parameter variations show that an instability occurs when the 47 n jet causes reversals in the potential vorticity pv gradient which constitutes a violation of the charney stern stability criterion after the initial instability development the simulations demonstrate that the instability s amplitude nonlinearly saturates to a constant when the eddy generation by the instability is balanced by the destruction of the eddies when the instability saturates the zonal wind profile approaches neutral stability according to arnol d s second criterion and the jet s path meanders in a ribbon like manner it is demonstrated that the meandering of the 47 n jet occurs over a range of tropospheric static stability and background wind speed the results here show that a nonlinearly saturated shear instability in the 47 n jet is a viable mechanism to produce the ribbon morphology observations do not yet have the temporal coverage to confirm the creation and destruction of eddies but these simulations predict that this is actively occurring in the ribbon region similarities exist between the behaviors found in this model and the dynamics of pv fronts studied in the context of meandering western boundary currents in earth s oceans in addition the simulations capture the nonlinear aspects of a new feature discovered by the cassini visual and infrared mapping spectrometer vims the string of pearls which resides in the equatorward tip of the 47 n jet the explicit planetary isentropic coordinate epic model is used herein

air sea co2 exchange in the ross sea antarctica although the ross sea is one of the most productive regions in antarctica it is not clear to what extent this region is an atmospheric co2 sink we calculate instantaneous co2 flux rates with in situ pco2 and wind speed data from 20 cruises in the ross sea in addition we estimate annual co2 fluxes into the ross sea with nutrient budgets from a late summer cruise we find that the ross sea is a lesser atmospheric co2 sink 7 5 0 5 tg c yr 1 1 3 0 1 mol c m 2 yr 1 than previously reported 13 tg c yr 1 1 7 to 4 2 mol c m 2 yr 1 one exception is terra nova bay tnb in the western ross sea with co2 flux rates 4 8 0 3 mol c m 2 january march that are 3 4 times greater than the ross sea mean the majority of the co2 flux into tnb occurs during the late summer with instantaneous co2 flux rates up to 246 mmol c m 2 d 1 these extraordinary co2 flux rates are caused by the unique coupling of strong katabatic winds and low surface pco2 values although strong katabatic winds deepen the mixed layer and entrain co2 rich water from below late season net community productivity maintains low surface water pco2 levels while tnb only covers 1 3600 km2 of the ross sea continental shelf extraordinary air to sea co2 fluxes during the late summer may be regular features in many of the major sea ice production polynyas 148 000 km2 combined including antarctic bottom water formation regions

importance of methanogenesis for organic carbon mineralisation in groundwater contaminated by liquid effluent south australia abstract groundwater in the vicinity of a former abattoir and cheese factory in south east south australia has very high concentrations of dissolved inorganic carbon dic total alkalinity alk and organic and inorganic n due to the disposal of organic rich effluent down drainage boreholes directly into a limestone aquifer one of the possible means of reducing potential nitrate contamination of the aquifer is by adding organic carbon as a substrate for inducing bacterial denitrification a mass balance model of alkalinity dissolved inorganic carbon co 3 2 hco 3 co 2 and 13 c was used to evaluate this approach and to determine the fate of organic carbon derived from the waste isotope and chemical data could be used to distinguish the plume of contaminated groundwater and identify regions which are dominated by methanogenesis or those regions where oxidation reactions dominate the model shows that methanogenesis is responsible for degradation of the largest fraction up to 80 of the organic carbon present organic carbon oxidation rather than methanogenesis is a more important mechanism for c org degradation in the less contaminated boreholes farthest from the factory calcite dissolution appears to be unimportant at least on the time scale since disposal of effluent 70 a

recent localised sulphate reduction and pyrite formation in a fissured chalk aquifer reply reduction oxidation reactions in the london basin aquifer system how may they be investigated

estimating 14c groundwater ages in a methanogenic aquifer this paper addresses the problem of 14c age dating of groundwaters in a confined regional aquifer affected by methanogenesis increasing ch4 concentrations along the groundwater flow system and 13c and 14c isotopic data for dissolved inorganic carbon dissolved organic carbon and ch4 clearly show the effect of methanogenesis on groundwater chemistry inverse reaction path modeling using netpath indicates the predominant geochemical reactions controlling the chemical evolution of groundwater in the aquifer are incongruent dissolution of dolomite ion exchange methanogenesis and oxidation of sedimentary organic matter modeling of groundwater 14c ages using netpath indicates that a significant part of groundwater in the alliston aquifer is less than 13 000 years old however older groundwater in the range of 15 000 23 000 years is also present in the aquifer this paper demonstrates that 14c ages calculated using netpath incorporating the effects of methanogenesis on the carbon pools provide reasonable groundwater ages that were not possible by other isotopic methods

potential vorticity structure across the gulf stream observations and a pv gradient model abstract potential vorticity pv structure across a baroclinic front is a property that determines the stability characteristics of that front cross frontal exchange and the behavior of the vortical waves that this front enables hence there has been much interest in estimating pv across the gulf stream gs however pv estimations have typically encountered two problems the horizontal resolution of sampling has been inadequate and noise in measurements gets amplified by differentiation when estimating pv this paper s approach addresses both of these problems the authors have used a unique set of highly resolved simultaneous density and direct velocity measurements across the gulf stream first to calculate the pv structure and then to obtain its idealization within density layers using a pv gradient pvg model the pvg model inverts an input pv in layers to determine the isopycnal depths and velocities in isopycnal layers by comparing the observed and pvg modeled velocities and isopycnal posi

satellite observations of katabatic wind propagation for great distances across the ross ice shelf abstract five winter months april august 1988 of thermal infrared satellite images were examined to investigate the occurrence of dark warm signatures across the ross ice shelf in the antarctic continent these features are inferred to be generated by katabatic winds that descend from southern marie byrd land and then blow horizontally across the ice shelf significant mass is added to this airstream by katabatic winds blowing from the major glaciers that flow through the transantarctic mountains from east antarctica these negatively buoyant katabatic winds can reach the northwestern edge of the shelf a horizontal propagation distance of up to 1000 km 14 of the time where the airstream crosses from the ice shelf to the ice covered ross sea a prominent coastal polynya is formed because the downslope buoyancy force is near zero over the ross ice shelf the northwestward propagation of this katabatic air mass requires pressure gradient support the study shows that the extended horizontal propagat

feature modeling approach to simulating loop current frontal eddies abstract loop current frontal eddies lcfe in the gulf of mexico are simulated with a regional configuration of the princeton ocean model using a feature oriented initialization technique the initialization procedure is based on a prior investigation of stability characteristics of the loop current lc zonal channel experiments conducted with a multi layer intermediate equations model allowed to identify conditions necessary for formation and growth of frontal eddies the simulations were able to reproduce key features of lcfe topography interaction in the desoto canyon region observed during the eddy intrusion study

distribution and isotopic characterization of methane in a confined aquifer in southern ontario canada abstract methane is one of the major carbon pools in the groundwater of the confined alliston aquifer geochemical geological and hydrological tools were used to evaluate the origin and distribution of this hydrocarbon the potential sources for methane were migration of thermocatalytic methane from bedrock units and in situ production by bacteria mediated reactions the distribution of methane in the aquifer excludes the possibility that methane occurrences were controlled by the nature of the underlying bedrock limestone vs shale 13 c and 2 h data in ch 4 from aquifer and bedrock wells indicate that these gases are microbial in origin and they are formed in situ mainly by co 2 reduction chemical and 14 c data in ch 4 and doc support the hypothesis of the existence of carbon sources for in situ microbial production of ch 4 in the aquifer

a 200 year sulfate record from 16 antarctic ice cores and associations with southern ocean sea ice extent chemistry data from 16 50 115m deep sub annually dated ice cores are used to investigate spatial and temporal concentration variability of sea salt ss so4 2 and excess xs so4 2 over west antarctica and the south pole for the last 200 years low elevation ice core sites in western west antarctica contain higher concentrations of so4 2 as a result of cyclogenesis over the ross ice shelf and proximity to the ross sea polynya linear correlation analysis of 15 west antarctic ice core so4 2 time series demonstrates that at several sites concentrations of ssso4 2 are higher when sea ice extent sie is greater and the inverse for xsso4 concentrations of xsso4 2 from the south pole site east antarctica are associated with sie from the weddell region and west antarctic xsso4 2 concentrations are associated with sie from the bellingshausen amundsen ross region the only notable rise of the last 200 years in xsso4 around 1940 is not related to sie fluctuations and is most likely a result of increased xsso4 2 production in the mid low latitudes and or an increase in transport efficiency from the mid low latitudes to central west antarctica these high resolution records show that the source types and source areas of ssso4 2 and xsso4 2 delivered to eastern and western west antarctica and the south pole differ from site to site but can best be resolved using records from spatial ice core arrays such as the international trans antarctic scientific expedition itase

observations of flow and ice ocean interaction beneath the mcmurdo ice shelf antarctica 1 the first oceanographic data from beneath the mcmurdo ice shelf antarctica are presented here with synchronous observations from southern mcmurdo sound multilevel current profiles at three sites over spring tide revealed primarily k1 diurnal tides with net transport from mcmurdo sound into the basin beneath the mcmurdo ice shelf the time series in southern mcmurdo sound captured the 14 day tidal phase shift and showed that transport into the subice shelf cavity was even greater over neap tide with average transport 1 8 sv mcmurdo sound sea ice cover during this period was the heaviest in 25 years of satellite record and was associated with the proximity of two massive icebergs b 15a and c 19 the warmest waters observed beneath the ice shelf were set at the surface freezing temperature probably through recent interaction with this extensive sea ice cover observed ranges of temperature and salinity were narrowed to the extent that neither antarctic surface water nor high salinity shelf water were observed beneath the ice shelf we anticipate that in years with more typical summer sea ice cover surface waters swept beneath the ice shelf will be significantly warmer having even greater potential for basal melt near the ice shelf front our observations also exhibit some of the interactions particular to the subice shelf ocean environment these include occurrence of platelet ice in ice shelf meltwater boundary layer friction effects from the ice cover on the ocean and tidal currents driving enhanced melting near the ice shelf front

introduction to geochemistry of metalliferous black shales 1 metalliferous black shales metalliferous black shales exhibit a wide range of physical and chemical characteristics they can be enriched in many different metals and the metals can be in a variety of geochemical states depositional and geological histories of these shales are diverse some metalliferous black shales contain relatively high concentrations of organic matter whereas others do not because of elevated carbonate contents some are calcareous shales or marlstones metal enrichments can result from redox reactions mediated by bacteria during early diagenesis and also from those associated with hydrothermal processes after deep burial however unifying characteristics of metalliferous black shales are sufficiently well established to justify combining a diverse number of fine grained sedimentary rock types under a common term that reflects enhanced metal content dark color and an inferred association with organic matter e g huyck 1990 moreover the term metalliferous black shales is sufficiently accepted that working group 254 of the international geological correlation program igcp has that title and focus this special issue of chemical geology brings together reports describing characteris