planktonic foraminiferal mg ca as a proxy for past oceanic temperatures a methodological overview and data compilation for the last glacial maximum as part of the multi proxy approach for the reconstruction of the glacial ocean margo incentive published and unpublished temperature reconstructions for the last glacial maximum lgm based on planktonic foraminiferal mg ca ratios have been synthesised and made available in an online database development and applications of mg ca thermometry are described in order to illustrate the current state of the method various attempts to calibrate foraminiferal mg ca ratios with temperature including culture trap and core top approaches have given very consistent results although differences in methodological techniques can produce offsets between laboratories which need to be assessed and accounted for where possible dissolution of foraminiferal calcite at the sea floor generally causes a lowering of mg ca ratios this effect requires further study in order to account and potentially correct for it if dissolution has occurred mg ca thermometry has advantages over other paleotemperature proxies including its use to investigate changes in the oxygen isotopic composition of seawater and the ability to reconstruct changes in the thermal structure of the water column by use of multiple species from different depth and or seasonal habitats presently available data are somewhat limited to low latitudes where they give fairly consistent values for the temperature difference between late holocene and the lgm 2 3 5 c data from higher latitudes are more sparse and suggest there may be complicating factors when comparing between multi proxy reconstructions

terrestrial freshwater lenses unexplored subterranean oases freshwater lenses are lenticular bodies of fresh tds 1000 mg l groundwater that develop above more saline groundwater within the same host aquifer due in part to buoyancy in contrast to the widely studied situation of freshwater lenses in coastal aquifers the formation location and persistence of freshwater lenses in terrestrial settings are poorly understood this is despite inland aquifers commonly containing saline groundwater particularly in arid and semi arid climates and the local occurrences of freshwater being critical for ecosystems and human endeavour we identify and classify known terrestrial freshwater lenses tfls using four formation categories namely topography geology groundwater surface water interaction and recharge mechanisms the resulting typology highlights the importance of buoyancy in the formation of tfls in otherwise unlikely situations implying that tfls may be more prevalent than previously thought tfls represent some of the most vulnerable and precious freshwater resources on earth that require considerably more research into mechanisms of formation and threats to their existence

the influence of changing orbital parameters and surface boundary conditions on climate simulations for the past 18 000 years abstract general circulation model experiments at 3000 year intervals for the past 18 000 years were made to estimate the magnitude timing and pattern of the climatic response to prescribed changes of orbital parameters date of perihelion axial tilt eccentricity and glacial age lower boundary conditions ice sheets land albedo sea ice and sea surface temperature the experiments used the community climate model ccm of the national center for atmospheric research ncar the response of monsoon circulations and tropical precipitation to the orbitally produced solar radiation changes was much larger than the response to changes of glacial age boundary conditions the continental interior of eurasia was 2 4 k warmer in summer and summer monsoon precipitation of north africa south asia was increased by 10 20 between 12 000 and 6000 yr bp before present when perihelion occurred during northern summer rather than in winter as now and the earth s axial tilt was larger than now southern hemisphe

variability in tropical thermocline nutrient chemistry on the glacial interglacial timescale abstract the organic carbon to calcite rain ratio in the tropical ocean may play a role in regulating global climate through its influence on co 2 draw down in the upper ocean the rain ratio may be altered by changes in the nutrient chemistry of the thermocline such changes in the tropical pacific are revealed by the carbon isotope values of thermocline dwelling planktonic foraminifera neogloboquadrina dutertrei the tropical pacific record over the last 30 kyr in the region south or along the equator which is fed by upwelling of deeper equatorial undercurrent water euc shows a carbon isotope signal distinct from any other in global mixed layer or benthic environments this unique record is consistent across the pacific unlike carbon isotope data from other basins and oceanic habitats the tropical pacific thermocline tracer shows last glacial values more positive than those of post glacial times the isotopic shift occurs in the early deglacial 20 17 kyr and leads to a deglacial carbon isotope minimum whose timing differs from that seen elsewhere the deglacial record of the pacific seems best interpreted as the progressive development of the modern nutrient rich thermocline under high nutrient low chlorophyll hnlc conditions the eastern tropical atlantic also has a unique glacial to modern carbon isotope record that is essentially opposite to that seen in the pacific strongly negative values in glacial times differ from those of the standard stratified ocean indicating higher nutrient concentrations a large shift to more positive values occurs rapidly at about 13 14 kyr this indicates a marked reduction in thermocline nutrients the implication is that nutrient flow to the tropics from the deep ocean via sub antarctic sources was stronger for the atlantic during the glacial but was weaker in the pacific transformation to modern conditions occurred in two steps at 17 18 and 13 14 kyr a timing that matches shifts in atmospheric co 2 concentrations and which would be compatible with driving those concentrations higher over deglacial time the mechanism could be an inherent difference in production regimes between the tropical pacific and atlantic

mapping climatological seasonal variations of surface currents in the tropical atlantic using ship drifts the seasonal variability of current velocities in the tropical atlantic was studied by grouping ship drift velocity observations into 2 5 boxes and calculating monthly mean velocity values these values were used to calculate and map the annual mean velocity the seasonal variation about the mean the annual and semiannual harmonics and the first two empirical orthogonal functions eofs the seasonal variation is primarily zonal in the equatorial band and in the north equatorial countercurrent necc and primarily alongshore near the coast of south america maxima of seasonal variation of 23 cm s are centered in the necc near 6 n 42 5 w and in the gulf of guinea near 2 n 7 5 w most 80 of the variance in the necc and along the western boundary of the area studied has an annual period most of the variance along the equator in the mid atlantic has a semiannual period over the whole region 49 of the seasonal variance is explained by the annual harmonic and 69 is explained by a combination of the annual and semiannual harmonics the second eof contains 29 of the variance of the data set and shows a simultaneous speeding slowing of the major equatorial currents the south equatorial current sec the north brazil current the necc and the guinea current along their principal axes of variation with a concurrent slowing speeding of the guyana current and the brazil current the pattern of variation resembles a large equatorial gyre centered along 4 n that flows clockwise from may to september and counterclockwise most of the rest of the year the first eof accounts for 35 of the variance and shows a simultaneous speeding slowing of eastward velocity from 5 s to 10 n except in the western sec the western end of the north brazil current and the guinea current the out of phase fluctuations apparent in the western sec near the equator are explained by the slowing and reversal of the south equatorial current near 2 n 40 w between april and june this slowing of the sec is associated with the start up of the necc which accelerates eastward in may june and july and flows eastward across the atlantic from july through december the sec divides seasonally near the eastern tip of brazil where residual alongshore velocities are northward for half the year peaking during may and june and southward for the other half of the year a second division can be seen north of the amazon where the north brazil current continues up the coast into the guyana current during the first half of the year but partially retroflects into the necc during the last half of the year a fast eastward flow in the necc coincides with below average velocities in the guyana current and above average velocities in the western sections of the north brazil current and the sec north of the equator

field examination of the oceanic carbonate ion effect on stable isotopes in planktonic foraminifera we determined the 18o and 13c of individual globigerinoides ruber and pulleniatina obliquiloculata from sediment traps located from 5 n to 12 s along 140 w in the pacific ocean to evaluate the effects of varying co3 on shell 18o and 13c variations in the offset between shell 13c and 13cdic 13cs dic are attributed to differences in co3 temperature and shell size between sample sites when 13cs dic of g ruber was corrected for variations in co3 using the experimental slope of bijma et al 1998 the residual 13cs dic was correlated with mixed layer temperature 0 10 0 04 c 1 the slope of this temperature effect is consistent with experimental results in p obliquiloculata 13cs dic and temperature were strongly anticorrelated 0 14 0 03 c 1 we are unable to separate the influences of co3 and temperature in this species without independent experimental data correcting for co3 variability on 18os of g ruber improves the accuracy of estimated sea surface temperatures

southwest atlantic water mass evolution during the last deglaciation the rise in atmospheric co2 during heinrich stadial 1 hs1 14 5 17 5 kyr b p may have been driven by the release of carbon from the abyssal ocean model simulations suggest that wind driven upwelling in the southern ocean can liberate 13c depleted carbon from the abyss causing atmospheric co2 to increase and the 13c of co2 to decrease one prediction of the southern ocean hypothesis is that water mass tracers in the deep south atlantic should register a circulation response early in the deglaciation here we test this idea using a depth transect of 12 cores from the brazil margin we show that records below 2300 m remained 13c depleted until 15 kyr b p or later indicating that the abyssal south atlantic was an unlikely source of light carbon to the atmosphere during hs1 benthic 18o results are consistent with abyssal south atlantic isolation until 15 kyr b p in contrast to shallower sites the depth dependent timing of the 18o signal suggests that correcting 18o for ice volume is problematic on glacial terminations new data from 2700 to 3000 m show that the deep sw atlantic was isotopically distinct from the abyss during hs1 as a result we find that mid depth 13c minima were most likely driven by an abrupt drop in 13c of northern component water low 13c at the brazil margin also coincided with an 80 decrease in 14c our results are consistent with a weakening of the atlantic meridional overturning circulation and point toward a northern hemisphere trigger for the initial rise in atmospheric co2 during hs1

factors controlling the fluoride content of planktonic foraminifera an evaluation of its paleoceanographic applicability abstract this work is an assessment of the effects of seawater salinity and temperature on the incorporation of fluoride into calcitic shells of planktonic foraminifera and of the subsequent modification of shell chemistry by postdepositional dissolution a strong correlation between the fluoride content of most planktonic species and their calcification depth was observed deeper calcifying foraminifera have lower fluoride content and heavier 18o composition perhaps suggesting a temperature control on the partition coefficient however species deviations from this general trend and the absence of correlation between fluoride and sea surface temperature within an individual species suggest that the coprecipitation of fluoride in foraminiferal calcite is more strongly controlled by biological processes rather than by simple chemical relationships foraminiferal fluoride shows weak or no correlation with sea surface salinity core top planktonic foraminifera from the eastern equatorial atlantic sierra leone rise show a substantial decrease of fluoride and to a lesser extent mg content with increasing water depth 2931 5104 m these decreasing trends with depth are attributed to selective dissolution i e removal of the more dissolution susceptible fraction with a different chemical composition than the residual a process which previously has been suggested to account for variations in the isotopic composition of planktonic foraminifera these findings indicate that foraminiferal fluoride cannot serve as a reliable tracer of oceanic paleo temperature or salinity it is possible however that fluoride may be useful for the study of dissolution in deep sea sediments

thermodynamic influences on the marine carbon isotope record air sea exchange represents an important controlling factor for the distribution of carbon isotopes in the modern ocean even below the surface mixed layer here we show that this thermodynamic influence varies between water masses with a magnitude which is large relative to the amplitude of typical deep sea sediment 13c records thus changes in air sea exchange processes must be regarded as a significant source of variability for any marine 13c signal

geologic and hydrologic settings for development of freshwater lenses in arid lands satellite observations were used to test the validity of previously identified favourable conditions for the formation of freshwater lenses identify additional potential occurrences and model modern potential recharge in the raudhatain watershed 3696 in northern kuwait favourable conditions include infrequent yet intensive precipitation events drainage depressions to collect the limited runoff and presence of conditions e g high infiltration capacity that promote groundwater recharge and preservation e g underlying saline aquifer of infiltrating groundwater as freshwater lenses floating over saline aquifer water due to differences in density specifically the following field and satellite based observations were noted for the raudhatain watershed 1 over 30 precipitation events were identified from the tropical rainfall measuring mission precipitation data 1998 2009 2 slope is gentle 2 m km and the surface is largely 80 covered by alluvial deposits with high infiltration capacities up to 9 m day 3 no flows and long term ponding were reported at the watershed outlet or detected from landsat thematic mapper images 4 infiltration is high based on increases in soil moisture content from an advanced microwave scanning radiometer and vegetation index following large precipitation events and 5 freshwater lenses that overlie highly saline total dissolved solids tds 35 000 unconfined aquifers underlying the watershed are absent in the southern regions where infiltrating fresh water mixes with the less saline groundwater tds 10 000 twenty potential locations size 1 to 75 km2 for freshwater lens development were identified in northern kuwait and continuous rainfall runoff models soil water and assessment tool were applied to provide a first order estimation of the average annual recharge in the watershed 127 106 m3 and freshwater lenses 8 17 106 m3 results demonstrate the settings for enhanced opportunities for groundwater recharge outline the amounts of and preservation conditions for the groundwater feeding the freshwater lenses and highlight potential applications and locations of freshwater lenses in similar settings elsewhere in the arabian peninsula and beyond copyright 2013 john wiley sons ltd

deepwater source variations during the last climatic cycle and their impact on the global deepwater circulation the degree of similarity of the 13c records of the planktonic foraminiferal species n pachyderma and of the benthic foraminiferal genus cibicides in the high latitude basins of the world ocean is used as an indicator of the presence of deepwater sources during the last climatic cycle whereas continuous formation of deep water is recognized in the southern ocean the norwegian sea stopped acting as a sink for surface water during isotope stage 4 and the remainder of the last glaciation however deep water formed in the north atlantic south of the norwegian sea during the last climatic cycle as early as isotope substage 5d and this area was also the only active northern source during stages 4 2 a detailed reconstruction of the geographic distribution of 13c in benthic foraminifera in the atlantic ocean during the last glacial maximum shows that the most important deepwater mass originated from the southern ocean whereas the glacial north atlantic deep water cannot be traced south of 40 n at shallower depth an oxygenated 13c rich intermediate water mass extended from 45 n to 15 s in the pacific ocean a ventilation higher than the modern one was also found in open ocean in the depth range 700 2600 m and is best explained by stronger formation of intermediate water in high northern latitudes

seasonal stable isotopic variations in living planktonic foraminifera from bermuda plankton tows abstract seasonal variations in surface water temperature and the 18o 16o ratios of calcite tests of living planktonic foraminifera collected in the upper 10 mare are coincident in the sargasso sea off bermuda the 18o of seasonally restricted globorotalia truncatulinoides and globigerinoides ruber pink and white may be used to determine the seasonal temperature contrast of the oceans in the past a preliminary model based on yearly absolute abundance and isotopic composition of these two species is able to approximate the composite 18o of fossil specimens of these species carbon and oxygen isotopic compositions of most species are size dependent with the largest differences occuring in 13c as a function of size the calcite tests of all living species were depleted in 13c relative to the 13c of total dissolved co2 at 0 and 50 m with no seasonal pattern in 13c being discernible in any species in almost all cases fossil specimens from box core sediments are significantly enriched in 13c and slightly enriched in 18o relative to their counterparts in the living fauna because the sediment populations are generally composed of larger sized specimens compares to the plankton of larger size specimens compared to the plankton

cadmium chemical tracer of deepwater paleoceanography the oceanic distribution of cadmium resembles that of phosphorus because the cadmium content of foraminiferal shells is governed by the cadmium content of seawater planktonic and benthic fossil shells can be used to infer nutrient distributions within ancient oceans empirical studies demonstrate that cadmium in benthic foraminiferal shells is related to the bottom water composition through a proportionality constant d 2 9 this constant is the same for each of the species studied cibicidoides wuellerstorfi cibicidoides kullenbergi nuttallides umbonifera and uvigerina spp downcore cadmium data from high quality pacific and atlantic sediment cores suggest that the cadmium inventory of the ocean did not change significantly between the most recent glacial maximum and the present hence changes in the cadmium content of fossils at a site directly reflect changes in nutrient distributions due to altered oceanic circulation patterns studies of cadmium in pleistocene sediments show that deep ocean circulation patterns were significantly different during the most recent glacial maximum in the western north atlantic ocean the nutrient content of waters from 2500 to 3500 m was twice as high during glacials as during interglacial periods signifying an increase in the proportion of waters of antarctic origin in this depth interval and a decrease but not a cessation in the flux of north atlantic deep waters through this depth range below 3500 m the nutrient increase was greater indicating a higher proportion of antarctic bottom water above 2500 m the nutrient content was lower during glacial periods than it has been during interglacial times the cd content of high latitude north atlantic and southern ocean surface waters does not show a significant glacial interglacial change which argues against theories for changes atmospheric carbon dioxide that require changes in high latitude nutrient concentrations

changes in the water column structure and paleoproductivity in the western south atlantic ocean since the middle pleistocene evidence from benthic and planktonic foraminifera abstract based on an integrated approach planktonic and benthic foraminifera and stable isotopes carried out in two cores collected on continental slope of santos basin central brazil the paleoceanographic oscillations of the last 570 ka are documented benthic foraminiferal isotopic records coupled with foraminiferal assemblages analyses show 100 ky long term oscillation in the superficial productivity along the middle pleistocene these long term oscillations are interrupted by 30 ky short term changes that mark the transition periods of higher productivity 425 400 ka and 190 160 ka and lower 290 260 ka the planktonic foraminifera species allowed the recognition of changes in the water column structure and in the superficial productivity observed in the area those changes in the superficial waters promoting different organic matter export to the sea floor might have resulted in changes on the more abundant and phytodetritus opportunist benthic taxa epistominella exigua and alabaminella weddellensis

global climate instability reflected by eastern mediterranean marine records during the late holocene abstract extremely high sediment accumulation rates in the southeastern se mediterranean off israel make this region ideal for high resolution paleoceanographic reconstructions two cores were examined and foraminiferal oxygen and carbon isotope composition as well as physical and geochemical properties of the sediments were used to reconstruct the climatic and environmental changes of the se mediterranean basin during the late holocene 3 6 ka the 18o values of globigerinoides ruber suggest that the freshwater balance changed several times during this time interval humid phases took place between 3 5 3 0 ka bp and 1 7 1 0 ka bp the later was accompanied by enhanced preservation of terrestrial organic matter within the sediment ors event relatively more arid conditions prevailed in this area between 3 0 and 1 7 ka bp during the last millennia at ca 0 8 and 0 27 ka two climatic events occurred which are probably correlative to both the medieval warm period and the cooling global event known as the little ice age respectively a long term slight increase in planktonic foraminiferal 18o values occurs together with a gradual decrease in the 13c values of both g ruber and the benthic foraminifera uvigerina mediterranea this trend is associated with an increase in sedimentation rates ti al ratio magnetic susceptibility and color index of the sediments we suggest that this trend shown by various independent proxies seems to be related to the aridification process that started ca 7 0 ka in the mid low latitude desert belt and the se mediterranean region and continuous until the present the long term 13c decrease shown by surface and bottom water foraminifera reflects a gradual change in the 13c of the dissolved co2 of the entire se mediterranean water column this follows the global co2 rise in the late holocene as a result of the terrestrial biomass destruction during the aridification process moreover the gradual reduction of the vegetation cover in east africa led to an increased erratic flood related sediment flux via the nile river up to the present this is reflected by the general change in the local sediment composition at 3 6 ka the saharan eolian input reached 65 whereas at about 0 3 ka 70 of the se mediterranean sediment was composed of nile particulate matter

seasonal variability in the δ18o and δ13c of planktonic foraminifera from an upwelling environment sediment trap results from the san pedro basin southern california bight stable isotopic analyses 18o and 13crpar on four species of planktonic foraminifera collected from high resolution time series sediment trap sampling indicate that rapid and significant seasonal variability occurred in response to rapid changes in both the hydrographic environment and the isotopic composition of ambient seawater specimens were collected at a depth of 500 m for 28 consecutive 1 week periods in the san pedro basin within the southern california bight a region seasonally influenced by upwelling hydrographic monitoring of the study area revealed a 6 week period late april to mid june during which pulses of upwelling occurred causing significant increases in the oxygen isotopic composition of surrounding waters while decreasing the carbon isotopic composition analyses of globigerina bulloides orbulina universa neogloboquadrina dutertrei and neogloboquadrina pachyderma right coiling indicate that during the upwelling period these species live respectively at the surface in the surface mixed layer within the thermocline and below the thermocline globigerina bulloides ascends from well below the thermocline to the surface at the onset of upwelling and increases production to its maximum simultaneously as its morphology changes to less calcified open forms both n dutertrei and n pachyderma follow isothermal ranges migrating to shallower waters during upwelling and subsequently descending after upwelling ceases neogloboquadrina dutertrei appears to inhabit the region associated with both the thermocline base and chlorophyll maximum when it is most abundant following upwelling orbulina universa increases its depth habitat as solar irradiance increases but this species decreases in abundance during upwelling the 18o signal of o universa appears to be a useful indicator of seasonal temperature variations above the thermocline whereas the 18o of g bulloides documents near surface temperatures during upwelling the 13c signal of both n dutertrei and n pachyderma appears to record the 13c of equilibrium calcite for the regions of the thermocline and just below the thermocline respectively due to the relative preservation potentials of the four species analyzed only n dutertrei and n pachyderma are likely to be preserved in the sedimentary record in regions of oxygenated bottom waters thus an actual record of hydrographic conditions during upwelling as would be found in tests of g bulloides is not preserved instead conditions before n pachyderma and just after n dutertrei are more likely recorded

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

ecological controls on the shell geochemistry of pink and white globigerinoides ruber in the northern gulf of mexico implications for paleoceanographic reconstruction abstract we evaluate the relationship between foraminiferal test size and shell geochemistry 13c 18o and mg ca for two of the most commonly used planktonic foraminifers for paleoceanographic reconstruction in the subtropical atlantic ocean the pink and white varieties of globigerinoides ruber geochemical analyses were performed on foraminifera from modern core top samples of high accumulation rate basins in the northern gulf of mexico mg ca analysis indicates a positive relationship with test size increasing by 1 1 mmol mol 2 5 c from the smallest 150 212 m to largest 500 m size fractions of g ruber pink but with no significant relationship in g ruber white in comparison oxygen isotope data indicate a negative relationship with test size decreasing by 0 6 across the size range of both pink and white g ruber the observed increase in mg ca and decrease in 18o are consistent with an increase in calcification temperature of 0 7 c per 100 m increase in test size suggesting differences in the seasonal and or depth distribution among size fractions overall these results stress the necessity for using a consistent size fraction in downcore paleoceanographic studies in addition we compare downcore records of 18o and mg ca from pink and white g ruber in a decadal resolution 1000 year sedimentary record from the pigmy basin based on this comparison we conclude that pink g ruber is calcifying in warmer waters than co occurring white g ruber suggesting differences in the relative seasonal distribution and depth habitat of the two varieties

the late pleistocene history of surface water δ13c in the sulu sea possible relationship to pacific deepwater δ13c changes a reconstruction of late pleistocene surface water carbon isotopic 13c variability is presented from ocean drilling program odp site 769 in the sulu sea in the western tropical pacific the sulu sea is a shallowly silled back arc basin with a maximum sill depth of 420 m site 769 was drilled on a bathymetric high in 3643 m of water and has average late pleistocene sedimentation rates of 8 5 cm kyr the oxygen isotope record 18o of globigerinoides ruber at site 769 shows a strong correlation with the specmap stacked 18o record attesting to the continuity of sediment archive at the site surface 13c displays consistent glacial interglacial variability which averages 0 9 and has varied from 0 75 to 1 1 over the last 800 kyr comparison to surface water 13c records in the south china sea and western tropical pacific suggests that the glacial interglacial surface 13c variability is regional in scale planktonic 13c data from odp site 677 in the eastern pacific is also coherent with the site 769 additionally we have found that the site 769 surface 13c record is coherent at periods of 100 and 41 kyr with deepwater 13c records from the pacific the highest correlation occurs with the deep eastern pacific where benthic 13c data from cores rc13 110 and odp site 677 closely match the sulu sea surface water record we evaluate several possible controls of surface water 13c in the sulu sea that may explain the coherent timing with pacific deepwater 13c records these include variations in terrestrial organic matter flux to the basin the upwelling of subsurface water and productivity changes and the influx of western pacific intermediate water to the sulu sea our preferred explanation involves a region of upper intermediate water upwelling in the far western pacific which has been shown to outgas co2 from subsurface waters into surface waters upwelling also occurs in the area of panama basin site 677 these equatorial upwelling zones could potentially provide a route by which pacific intermediate water can modulate the 13c composition of certain pacific surface water locations future reconstructions of late pleistocene surface water 13c variability in the western pacific and indonesian seas will be required to further evaluate the source of the glacial interglacial surface water 13c change

thermal isolation of campbell plateau new zealand by the antarctic circumpolar current over the past 130 kyr 1 campbell plateau occupies a key position in the southwest pacific sector of the southern ocean the plateau confines and steers the antarctic circumpolar current acc along its flanks isolating the subantarctic plateau from cold polar waters oxygen and carbon isotope records from campbell plateau cores provide new records of water mass stratification for the past 130 kyr during glacial climes strengthening of the subantarctic front saf caused waters over the plateau flanks to be deeply mixed and 3 c cooler waters of the plateau interior remained stratified and isolated from the cold southern waters in the west waters cooled markedly 4 c owing to reduced entrainment of tasman sea water marked cooling also occurred north of campbell plateau under increased entrainment of polar water by a branch of the saf the acc remained along the flanks of campbell plateau during the last interglacial when interior waters were stratified and warmer by 1 c than now

oxygen minimum expansion in the sulu sea western equatorial pacific during the last glacial low stand of sea level the sulu sea in the western equatorial pacific is presently a shallowly silled dysaerobic deep marine basin deep waters in the sulu sea are ventilated through a single sill at 420 m depth which connects it to the china sea benthic and planktonic foraminiferal oxygen and carbon isotope records benthic and planktonic foraminiferal census data and total organic carbon measurements have been used to evaluate changes in water mass conditions in the sulu sea between the last glacial maximum 18 000 yrs b p and the present day an increase in the abundance of the planktonic foraminiferaneogloboquadrina dutertrei and relatively light planktonic foraminiferal 18o values suggest that during the last glacial maximum surface water salinities were reduced in the sulu sea enhanced isolation of the basin due to glacio eustatic lowering of sea level and reduced surface salinities resulted in stagnation of deep water and an expansion of the mid water oxygen minimum layer increased organic carbon preservation at mid water depths occurs at this time benthic carbon isotope data and an increase in the abundance of benthic foraminiferal species considered to prefer low oxygen environments support the conclusion of an oxygen minimum expansion at mid water depths during the last glacial maximum at water depths greater than 4000 m bottom waters appear to have maintained some degree of oxygenation during the last glacial maximum stronger pacific ocean trade winds at this time may have caused the influx of denser celebes sea surface water into the southern part of the sulu sea the slow sinking of this water would have then ventilated bottom waters in this part of the basin at the transition from glacial to interglacial conditions rising sea level caused denser water to flow over the deepest sill into the sulu sea vertical circulation increased resulting in a greater downward flux of oxygen and a dissipation of the oxygen minimum continued post glacial sea level rise caused periodic ventilation of deep water until the present dysaerobic conditions were established

reconstructing the depth of the permanent thermocline through the morphology and geochemistry of the deep dwelling planktonic foraminifer globorotalia truncatulinoides geochemical and morphological characteristics of globorotalia truncatulinoides a deep dwelling planktonic foraminifer have been used since the mid 1950s to infer paleo oceanographic conditions of the upper ocean the coiling ratio has been linked to different water masses and stable oxygen isotope signal of this species to changes in depth habitat and or season here we show that the isotopic composition of single specimens covering termination iii of multiple size fractions of north atlantic g truncatulinoidessinistral is indicative of a deeper calcification depth in the water column compared to g truncatulinoidesdextral as previously indirectly inferred in a plankton tow study furthermore the change in coiling ratio from dominantly g truncatulinoidesdextral 95 to brief episodes of dominantly g truncatulinoidessinistral 80 gives a strong indication of deepening of the permanent thermocline during periods in which g truncatulinoidessinistral was dominant the position of the permanent thermocline during marine isotope stages 8 and 7 echoes the relative strength of the atlantic meridional overturning circulation amoc dominated by interglacial glacial dynamics we demonstrate that glacial heinrich ice rafted debris events appear to proceed a permanent thermocline shoaling whereas interglacial heinrich events follow the shoaling of the permanent thermocline likely a result of a weakened amoc

barium anomaly preceding k t boundary possible causes and implications on end cretaceous events of k t sections in cauvery basin india israel ne mexico and guatemala maastrichtian danian strata of the cauvery basin as well as selected sections of ne mexico guatemala and israel record ba anomalies away from the cretaceous tertiary boundary ktb in addition to common occurrences of geochemical and stable isotopic anomalies across the ktb ba anomalies were recorded in monotonous shallow marine sandstones of the cauvery basin south india which contain minor amounts of ba orthoclase barium anomalies were observed also in shallow marine carbonates in sections of israel ne mexico and guatemala calculation of excess ba with reference to paas post archaen average australian shale comparison of coeval geochemical anomalies depositional pattern and associated petrographic and mineralogical features of the cauvery basin revealed that while a first ba peak was related to detrital influx the second ba peak was coincident with sea level fall which in turn may have been influenced by emission of volatile hydrocarbons and resultant climatic changes in view of intrinsic involvement of ba in various geochemical processes and occurrence of ba anomalies in k t sites distributed around the world ne mexico guatemala and israel it is suggested that probable causes of such widespread ba anomalies should be taken into consideration while analyzing end cretaceous events these observations support the views espoused by many workers who have stated that the k t boundary was also accompanied by many non catastrophic events that might have contributed to environmental stress on marine fauna as a result of which selective multi stage extinctions occurred

a 900 year stable isotope record of interdecadal and centennial change from the california current this paper describes the development of a high resolution record of interdecadal and centennial variability of ocean climate of the california current from continuous 5 year sampling intervals based on varve counts from santa barbara basin sediments we show the importance of the choice of species and size fraction as well as the practice of making multiple measurements per interval to obtain a clear environmental signal capable of resolving interdecadal change changes in temperature and salinity from oceanographic surveys of the past 50 years indicate that thermal variability dominates the 18o signal a 18o record from neogloboquadrina dutertrei spanning 1030 1905 a d contains interdecadal thermal fluctuations within the upper thermocline that are centered around periods of roughly 55 70 and 90 years the interdecadal changes comprise the major share of total variability compared to a low amplitude mode of underlying multicentennial variability corresponding to the medieval warm period and the little ice age

pliocene pleistocene stable isotope and paleoceanographic changes in the northern south china sea abstract based on the stable isotopic analysis of planktonic and benthic foraminifers from ocean drilling program core 1148 of the northern south china sea scs pliocene pleistocene isotope stratigraphy and events have been reconstructed the benthic foraminiferal 18o record shows that the pacific intermediate water had a greater influence upon the scs or the pacific deep water above 2600 m was warmer before 3 2 ma than at present after that the benthic 18o conspicuously increased during the 3 2 2 5 ma period in correspondence to the formation of the northern hemisphere ice sheet whereas the planktonic 18o signal suggests a stepwise overall decrease of sea surface temperature during the 2 2 0 9 ma period compared to the equatorial pacific records the decrease in planktonic globigerinoides ruber 13c during the 3 2 2 2 ma period is particularly striking suggesting that fertility of surface water increased noticeably according to the modern 13c distribution of g ruber in the northern scs it is inferred that the east asian winter monsoon strengthened during this interval afterwards there were several conspicuous decreases of g ruber 13c at 1 7 1 3 0 9 0 45 and 0 15 ma bp that is about every 0 4 ma suggesting that the east asian winter monsoon became episodically stronger this is confirmed by changes in relative abundance of planktonic foraminifer species neogloboquadrina dutertrei a typical east asian winter monsoon proxy the deep water 13c of the scs is close to that of the pacific but lighter than that of the atlantic implying that the pattern of deep water originating mainly from the atlantic and through the pacific entering the scs existed at least since the early pliocene after 1 4 ma the benthic 13c signal decreased conspicuously but with a periodicity of 100 ka suggesting that the deep water ventilation of the scs was reduced probably corresponding to a decrease of the north atlantic deep water and or further isolation of the scs deep basin from the pacific during glaciations

comparison between radiocarbon ages obtained on coexisting planktonic foraminifera as a test of the reliability of paleocean ventilation rates reconstructed from radiocarbon age differences between planktonic and benthic foraminifera measurements have been made on coexisting species of planktonic foraminifera while ideally no differences should exist we do find them in this paper we discuss the possible causes for these differences and attempt to evaluate their impact on the interpretation of benthic planktonic age differences

13c record of benthic foraminifera in the last interglacial ocean implications for the carbon cycle and the global deep water circulation the 13c 12c ratios of upper holocene benthic foraminiferal tests genera cibicides and uvigerina of deep sea cores from the various world ocean basins have been compared with those of the modern total carbon dioxide tco2 measured during the geosecs program the 13c difference between benthic foraminifera and tco2 is 0 07 0 04 for cibicides and 0 83 0 07 for uvigerina at the 95 confidence level 13c analyses of the benthic foraminifera that lived during the last interglaciation isotopic substage 5e about 120 000 yr ago show that the bulk of the tco2 in the world ocean had a 13c value 0 15 0 12 lower than the modern one at the 95 confidence level reflecting a depletion compared to the present value of the global organic carbon reservoir regional differences in 13c between the various oceanic basins are explained by a pattern of deep water circulation different from the modern one the antarctic bottom water production was higher than today during the last interglaciation but the eastward transport in the circumpolar deep water was lower

paired carbon isotope and cadmium data from benthic foraminifera implications for changes in oceanic phosphorus oceanic circulation and atmospheric carbon dioxide abstract the carbon isotope and cadmium content of foraminiferal shells from oceanic sediments provides information on past chemical distributions in the ocean starting from reasonable assumptions it can be shown that paired data on both tracers provides more information than does either separately the slope of paired isochronous 13c and cd ca data from fossil benthic foraminifera depends on oceanic p cd and gd 13c p ratios the zero cd ca intercept of this line depends on mean oceanic 13c p and the 13c p ratio given data sufficient to define oceanic mean 13c and cd contents it is possible to place quantitative constraints on the product of the c p redfield ratio and mean oceanic phosphorus and to estimate a circulation parameter which is independent of changes in ocean chemical inventories with the limited available data no significant changes in oceanic p cd can be detected between the holocene and most recent glacial maximum if this data is taken to be representative of the whole ocean then the p and cd contents of the ocean were about 17 higher during the last glacial maximum than at present ocean box models indicate that this change in oceanic p and a 2 c deep ocean cooling during glacials would cause a 47 ppmv reduction in atmospheric pco2 during glacial intervals

signature of the brazil malvinas confluence argentine basin in the isotopic composition of planktonic foraminifera from surface sediments we explored the potential to use the stable isotopic compositions of planktonic foraminifera as a proxy for the position of the brazil malvinas confluence bmc in the argentine basin for this purpose we measured the oxygen and carbon isotopic compositions of globigerinoides ruber pink and white varieties measured separately globigerinoides trilobus globigerina bulloides globorotalia inflata and globorotalia truncatulinoides left and right coiling forms measured separately from a latitudinal transect of 56 surface sediment samples from the continental slope off brazil uruguay and argentina between 20 and 48 s lowest oxygen isotopes values were found in g ruber pink followed by g ruber white and g trilobus reflecting the highly stratified near surface water conditions north of the bmc globigerina bulloides was present mainly south of the bmc and records subsurface conditions supporting earlier plankton tow studies globorotalia inflata and g truncatulinoides left and right were both available over the whole transect and calcify in the depth level with the steepest temperature change across the bmc accordingly the 18 o of these species depict a sharp gradient of 2 at the confluence with remarkably stable values north and south of the bmc our data show that the oxygen isotopic composition of g inflata and g truncatulinoides left and right are the most reliable indicators for the present position of the bmc and can therefore be used to define the past migration of the front if appropriate cores are available

environmental and biological effects on the stable isotope composition of recent deep sea benthic foraminifera from the western mediterranean sea abstract the influence of microhabitat organic matter flux and metabolism on the stable oxygen and carbon isotope composition of live rose bengal stained and dead empty tests deep sea benthic foraminifera from the gulf of lions western mediterranean sea have been studied the total range of observed foraminiferal isotope values exceeds 1 0 for 18o and 2 2 for 13c demonstrating a wide range of coexisting disequilibria relative to 18o of equilibrium calcite 18oeq and 13c of bottom water dissolved inorganic carbon 13cdic the mean 18o values reveal strongest disequilibria for the studied epifaunal to shallow infaunal species cibicidoides pachydermus uvigerina mediterranea uvigerina peregrina while values approach equilibrium in deep infaunal species globobulimina affinis globobulimina pseudospinescens the mean 13c values decrease with increasing average living depths of the different species thus reflecting a dominant microhabitat pore water signal at the axis of the lacaze duthier canyon a minimum 13cdic pore water gradient of approximately 2 1 is assessed for the upper 6 cm of the surface sediment although live individuals of u mediterranea were found in different depth intervals their mean 13c values are consistent with calcification at an average living depth around 1 cm the deep infaunal occurrence of u mediterranea specimens suggests association with macrofaunal burrows creating a microenvironment with geochemical characteristics similar to the topmost centimeter this also explains the excellent agreement between stable isotope signals of live and dead individuals the ontogenetic enrichment in both 18o and 13c values of u mediterranea suggests a slow down of metabolic rates during test growth similar to that previously observed in planktic foraminifera enhanced organic carbon fluxes and higher proportion of resuspended terrestrial organic material at the canyon axis are reflected by 13c values of u mediterranea on average 0 58 lower than those from the open slope these results demonstrate the general applicability of the 13c signal of this species for the reconstruction of past organic matter fluxes in the mediterranean sea further studies on live specimens are needed for a more quantitative paleoceanographic approach

temperature dependent ocean atmosphere equilibration of carbon isotopes in surface and intermediate waters over the deglaciation abstract high resolution and precise records of the carbon isotopic composition of atmospheric carbon dioxide from ice cores are now providing a valuable constraint on the origin of the rise in co2 over the last deglaciation previous studies using isotopic measurements on the tests of planktonic foraminifera from marine sediments had shown a deglacial minimum in the carbon isotopic composition of seawater carbon in the surface and thermocline waters of the southern hemisphere and the tropics a feature also seen in the atmospheric record here we show that this deglacial minimum also can be clearly seen in carbon isotope measurements on planktonic foraminifera from sediment cores in the north atlantic there are also new high resolution and precise records of the carbon isotopic composition of intermediate and mode waters generated using benthic foraminifera which show a history of change that is strikingly similar to that in the atmosphere similarities in these new highly resolved deglacial records suggest that air sea exchange can effectively globalize the isotopic signature of a release of carbon from the deep ocean this limits the utility of carbon isotopes for constraining the precise location and mechanism of carbon release indicating that more direct nutrient tracers are needed however given that the equilibrium partitioning of carbon isotopes between the atmosphere and ocean is temperature dependent the difference between the atmosphere and upper ocean values could potentially provide an independent estimate of sea surface temperature change

carbon isotope composition of tropical surface water during the past 22 000 years carbon isotope values of many species of planktonic foraminifera are size dependant values of 13c of individual size fractions are therefore an integration of low 13c values of calcite precipitated in the juvenile growth stage and high values precipitated in later stages in general the selection of a particular size fraction for downcore studies has been subjective analysis of different size fractions of planktonic foraminifera however yields different time series in downcore studies by measuring the 13c of many size fractions the 13c precipitated throughout the growth of the foraminifera can be calculated time series of the 13c of calcite precipitated in the late growth stages of planktonic foraminifera from two nearby cores from the caribbean sea result in a better correlation than time series of constant size fractions these 13c records indicate similar 13c values during the last glaciation and the late holocene and a broad deglacial minimum approximately synchronous with a minimum in the 13c records of benthic foraminifera from intermediate depth atlantic cores the deglacial minimum may be a reflection of the isotopic composition of the underlying intermediate water which may be affected by circulation changes or changes in preformed 13c values and or of the flux of water upwelled into the surface layer the small 0 2 to 0 0 glacial interglacial 13c difference in tropical surface water is also believed to be affected by the chemistry of the underlying source water

seasonal cycle of velocity in the atlantic north equatorial countercurrent as measured by surface drifters current meters and ship drifts this report describes the general circulation and seasonal variation of currents in the equatorial atlantic concentrating on the north equatorial countercurrent necc using data collected as part of the seasonal response of the equatorial atlantic and programme francais ocean et climat dans l atlantique equatorial experiments plus historical ship drifts during 1983 1985 the lagrangian circulation was studied by launching and tracking 30 freely drifting drogued buoys in the north equatorial countercurrent and 23 in the south equatorial current sec in addition continuously recording current meters were moored for 20 months at depths from 20 to 300 m near the center of the necc at 6 n 28 w these measurements are the longest series ever obtained in this current and provide information about its seasonal and interannual variations and zonal meridional and vertical structure the seasonal cycle of the necc is very regular from year to year each year the necc starts up in may june it flows eastward across the atlantic with surface speeds of up to 143 cm s in the west extending down to 350 m at 28 w and flowing into both the guinea current and north equatorial current it disappears or reverses from about january june west of 18 w some near surface water of the necc is inferred to downwell and flow equatorward toward the equatorial undercurrent the sec flows into the north brazil current which during spring continues up the coast into the caribbean during fall however the whole north brazil current retroflects or turns back on itself between 45 and 50 w forming the western necc the retroflection establishes a meander pattern in the necc that slowly propagates westward during fall at a speed of 4 cm s the meanders have a displacement of about 300 km in latitude a wavelength of 900 km and meridional velocity fluctuations of up to 100 cm s the swift currents and time dependent meanders in the western necc cause a high eddy kinetic energy 2400 cm2 s2 equivalent to that of the energetic part of the gulf stream

vertical distribution and isotopic fractionation of living planktonic foraminifera from the panama basin a model1 2 which explains the vertical and seasonal distribution of planktonic foraminifera was developed using data from the western north atlantic and is comprised of three tenets 1 the conditions in the photic zone upper 80 100 m exclusively dictate planktonic foraminifera species composition and abundance throughout the water column 2 species are vertically stratified within the photic zone according to their temperature preference depth distribution according to temperature preference has been proposed by several authors3 based on isotope analyses of sediments due to seasonal temperature variations seasonal variations in the 18o composition of seawater and species specific isotope fractionation rigorous proof of this hypothesis cannot be provided from sediment analyses alone 3 the chlorophyll maximum is a major food source zone which is preferentially exploited by foraminifera our data from the panama basin which are presented here are confirmation of this model the panama basin in the eastern equatorial pacific which has a shallow and steep thermocline was sampled for living planktonic foraminifera a multiple opening closing net and environmental sensing system mocness 4 was used to collect 13 sets of eight vertically stratified oblique samples we report here the quantitative distribution and stable isotopic composition of planktonic foraminifera from four mocness tows taken over 5 days during august 1979 rv knorr cruise 73 at 5 20 n 8 50 w each tow consisted of eight samples which integrated 12 5 m intervals from 0 to 100 m for moc 126 25 m intervals from 0 to 200 m for moc 127 100 150 m intervals from 0 to 1 000 m on moc 128 and 250 m intervals from 0 to 2 000 m on moc 131

geochemical and 222rn constraints on baseflow to the murray river australia and timescales for the decay of low salinity groundwater lenses the distribution of 222rn activities and major ion concentrations show that during low river flows characteristic of the recent drought conditions the middle reaches of the murray river northern victoria were a predominantly gaining system at low river levels may 2009 may 2010 and were variably gaining and losing at higher river levels november 2009 the location of gaining and losing reaches are partially governed by the position of the river with respect to the edge of its floodplain gaining reaches occur where the floodplain narrows or where the river is adjacent to the steep slopes at the floodplain margin cumulative inflows along this 350km stretch of the river estimated from 222rn activities were 320 1500m 3 day in november 2009 and 560 4300m 3 day in may 2010 the relatively large uncertainty reflects the heterogeneous and poorly constrained groundwater 222rn activities major ion variations notably cl concentrations and na ca ratios correlate with 222rn activities and may be used as indicators of groundwater inflows baseflow contributed 1 of the total water to this part of the river and consequently has little impact on river water quality nevertheless the groundwater inflows remove water from low salinity groundwater lenses that underlie the river and during the drought conditions these lenses were degrading these reaches of the river murray are an example of a system that transitioned from being dominantly losing to being variably gaining due to diminishing surface water flows

strong deglacial minimum in the δ13c record from planktonic foraminifera in the benguela upwelling region palaeoceanographic signal or early diagenetic imprint

the δ13c of equatorial atlantic surface waters implications for ice age pco2 levels carbon isotopic records of nutrient depleted surface water place constraints on the past fertility of the oceans and on past atmospheric pco2 levels the best records of nutrient depleted 13c are obtained from planktonic foraminifera living in the thick mixed layers of the western equatorial and tropical atlantic ocean we have produced a composite stacked globigerinoides sacculifer 13c record from the equatorial atlantic which exhibits significant spectral power at the 100 000 and 41 000 year milankovitch periods but no power at the 23 000 year period similar to the record presented by shackleton and pisias 1985 surface deep ocean 13c produced with the g sacculifer record leads the 18o ice volume record however the glacial interglacial amplitudes of 13c differ between our record and shackleton and pisias 1985 record although large changes in 13c occur in the equatorial atlantic during early stages of the last three glacial cycles surface deep 13c at glacial maxima 18o stage 2 late stage 6 and late stage 8 was only about 0 2 greater than during the subsequent interglacial our results imply that nutrient driven pco2 changes account for about one third of the pco2 decrease observed in ice cores and consequently 13c should not be used as a proxy pco2 index enough variance in the ice core pco2 records remains to be explained that conclusions about pco2 and ice volume phase relationships should also be reexamined as much as 40 ppm pco2 change still has not been accounted for by models of past physics and chemistry of the ocean

analytic solutions for fresh groundwater lenses floating on saline water under desert dunes the kunin van der veer legacy revisited abstract a fully saturated lens of steady fresh groundwater floating in a homogeneous and isotropic desert sandy aquifer is analytically studied based on a hydrological model by kunin and interface solution by van der veer a static saline groundwater is beneath the lens a phreatic surface of moving fresh water inside the lens is partially recharged either naturally or by managed aquifer recharge from the vadose zone and partially exfiltrates to it a spatially focused recharge and intensive evapotranspiration preserve a steady downward upward topology of fresh water motion in terms of the 1 d dupuit forchheimer approximation in a horizontal in lens saturated flow a boundary value problem bvp for an ode for the strack potential is solved the shape of the water table and based on the ghijben herzberg assumption the interface are found the total volume of the positive pore pressure water flowing within the lens is evaluated constant infiltration and evaporation rates as well as evaporation linearly decreasing with depth of the water table counted from the ground surface are considered the case of 2 d flow is tackled by the toth model a triangular analytic element approximates a half of the flow domain and consists of an isobaric side and two no flow sides conformal mapping of this triangle onto a reference plane and solution of the dirichlet bvp in a half plane deliver the distribution of infiltration exfiltration intensity along the water table total flow rate and locus of the hinge point a mathematically more cumbersome approximation of the flow domain assumes the water table to be a tilted straight line but the interface to be found as a free boundary solution of the corresponding bvp uses a curvilinear triangle in the hodograph plane

downslope migrating sandwaves and platform margin clinoforms in a current dominated distally steepened temperate carbonate ramp guadix basin southern spain during the late tortonian platform margin prograding clinoforms developed at the south western margin of the guadix basin large scale wedge shaped deposits here comprise 26 rhythms of mixed carbonate siliciclastic bedset packages and marl beds these sediments were deposited on a shallow water temperate carbonate distally steepened ramp a downslope migrating sandwave field developed in this ramp with sandwaves moving progressively down the ramp to the ramp slope where they destabilized folded and occasionally collapsed downslope sandwave migration was induced by currents flowing basinwards during the late tortonian the guadix basin was open north to the atlantic ocean via the dehesas de guadix strait and connected east to the mediterranean sea through the almanzora corridor according to the proposed current circulation model for the guadix basin for this time surface marine currents from the atlantic entered the basin from the northern seaway these currents moved counter clockwise and shifted the sediment on the ramp forming sandwaves that migrated downslope the development of platform margin prograding clinoforms by the basinward sediment transport mechanisms inferred here is known relatively poorly in the ancient sedimentary record moreover these wedge shaped geometries are similar to those found in some shelves in the western mediterranean sea and could represent an outcrop analogue to sub recent platform margin clinoforms revealed by high resolution seismic studies

groundwater lens dynamics of atoll islands a variable density groundwater model is used to analyze the effects of various controls on the size of the freshwater lens the structure of the transition zone and the propagation of tidal fluctuations in a two layer atoll island groundwater system modeling results indicate that mixing of fresh water and saltwater occurs primarily as a result of oscillating vertical flow due to tidal fluctuations and depends to a lesser extent on transverse dispersion along the dominantly horizontal recharge discharge path of flow the controls on the amount of mixing are 1 the accumulated vertical distance which increases with tidal range and is restricted by vertical permeabilities and 2 vertical longitudinal dispersion comparison of cross sectional simulations of atoll islands using nontidal and tidal models shows that the nontidal model must use artificially high values of transverse dispersivity to compensate for the lack of tidally driven vertical mixing processes although the tidal model has high computational requirements it can be used to calibrate vertical permeabilities and is best suited for problems dealing with groundwater resource evaluations hydrologic events and hydrologic processes the limitations of the nontidal model are that it cannot be used for calibration of vertical permeabilities and will not realistically simulate those cases in which transition zones are thick or recharge low

influence of test size water depth and ecology on mg ca sr ca δ18o and δ13c in nine modern species of planktic foraminifers abstract mg ca palaeothermometry in foraminiferal calcite is a widely applied tool in palaeoceanography however our understanding of the effects of planktic foraminiferal ecology and early diagenesis on test calcite mg ca is limited here we report results of a study designed to shed new light on ecological size related and very early water column diagenetic controls on mg ca in planktic foraminiferal calcite we analysed mg ca and stable isotopes of nine modern planktic foraminiferal species across fourteen mostly 50 m window sieve fractions in a core top sample from the north atlantic ocean we also analysed mg ca in four of these nine species from plankton tow samples collected from 0 to 2500 m water depth in the north atlantic ocean and arabian sea our core top study confirms that sensitivity of mg ca to change in test size is species specific but reveals an overall decrease in mg ca with increasing test size in all but one species orbulina universa for which mg ca increases with size these findings are broadly consistent with known ecological behaviour suggesting that the size related signal is largely environmentally rather than calcification rate controlled our results underscore the need to undertake mg ca palaeothermometry on narrow size fractions of planktic foraminifers particularly for shallow dwelling species such as g bulloides and g ruber where mg ca is most sensitive to test size across the size range of 200 350 m our plankton tow data from the arabian sea are in agreement with in situ temperatures in contrast our data from the north atlantic ocean reveal large variability and marked offsets to warmer values from in situ temperatures that are interpreted to reflect lateral advection from the south storm induced vertical mixing of the water column and or the influence of surface water salinity on the mg ca signal none of our plankton tow mg ca data shows any evidence of test dissolution in the water column our study provides important verification that the mg ca signal recorded during calcification does not undergo diagenetic degradation during test transport to the sea floor thereby satisfying an important precondition of its palaeo proxy utility

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

stable isotope composition of late cretaceous benthic foraminifera from the southern south atlantic biological and environmental effects abstract the stable carbon and oxygen isotope composition of different benthic foraminiferal species of the latest campanian and earliest maastrichtian from ocean drilling project hole 690c weddell sea southern south atlantic 1800 m paleowater depth have been investigated the total range of measured isotope values of all samples exceeds 4 for 13c and 1 1 for 18o carbon isotope values of proposed deep infaunal species are generally similar or only slightly lower when compared to proposed epifaunal to shallow infaunal species interspecific differences vary between samples probably reflecting temporal changes in organic carbon fluxes to the sea floor constantly lower 13c values for pullenia marssoni and pullenia reussi suggest the deepest habitat for these species the strong depletion of 13c values by up to 3 within lenticulinids may be attributed to a deep infaunal microhabitat strong vital effects or different feeding strategy when compared to other species or modern lenticulinids the mean 18o values reveal a strong separation of epifaunal to shallow infaunal and deep infaunal species epifaunal to shallow infaunal species are characterized by low 18o values deep infaunal species by higher values this result possibly reflects lower metabolic rates and longer life cycles of deep infaunal species or the operating of a pore water co32 effect on the benthic foraminiferal stable isotopes pyramidina szajnochae shows an enrichment of oxygen isotopes with test size comprising a total of 0 6 between 250 and 1250 m shell size although 13c lacks a corresponding trend these data likely represent the presence of changes in metabolic rates during ontogenesis these results demonstrate the general applicability of multi species stable isotope measurements of pristine cretaceous benthic foraminifera to reconstruct past microhabitats and to evaluate biological and environmental effects on the stable isotope composition

carbon isotopes in recent planktonic foraminifera a record of anthropogenic co2 invasion of the surface ocean abstract the release of isotopically light anthropogenic co 2 into the ocean atmosphere carbon reservoir has resulted in a decrease in the carbon isotopic composition of the surface ocean in this paper we examine differences between the carbon isotope composition of planktonic foraminifera from sediment traps with older late holocene material to estimate the change in 13 c 13 c in eastern atlantic surface waters as a result of the invasion of anthropogenic co 2 using stable oxygen isotopes we demonstrate that average trap values for a variety of species are more or less identical to core top values suggesting that foraminifera recovered in sediment traps are representitive of foraminifera deposited in the sediments however carbon isotopes recorded in planktonic foraminifera from recent trap material reveal a decrease in the 13 c composition of all species relative to the core top samples although the magnitude of the decrease varies significantly between species surface dwelling foraminifera g ruber g bulloides show 13 c values of 0 53 to 0 62 which is similar to other estimates from shallow water coral and sponge records for the decrease in the 13 c composition of dissolved organic carbon in surface waters which has taken place since the start of the anthropogenic emissions the magnitude of decrease in the 13 c of surface waters suggested by these records is also close to that predicted by global carbon cycle models deeper thermocline dwelling foraminifera such as g inflata however show 13 c values 0 2 which are substantially lower than their surface dwelling counterparts this reduction in 13 c with increasing depth habitat within the mixed layer may be related to limited vertical penetration of anthropogenic co 2 as a result of the strong upwelling which is observed in the eastern atlantic along the northwest african margin

regional differences in quaternary subantarctic nutrient cycling link to intermediate and deep water ventilation several fundamental issues regarding carbon cycling in the glacial oceans rest on the development of reliable descriptions of high southern latitude surface waters here we compare new subantarctic planktonic foraminiferal 13c records with previously published records to demonstrate two distinct regional patterns over glacial cycles 1 a low amplitude signal 0 7 previously observed in the indian primarily in globigerina bulloides that also dominates the pacific and 2 a higher amplitude signal previously observed in neogloboquadrina pachyderma that is confined to the atlantic and western indian sectors the new observations from the southeast pacific a primary region of antarctic intermediate water aaiw formation strengthen the suggestion that intermediate water acted as a conduit for transferring 13c variability to low latitudes because the timing and amplitude of the indo pacific low amplitude 13c changes are similar to those observed in planktonic records from the tropical pacific and atlantic a new benthic foraminiferal 13c record from intermediate depths in the south atlantic is also similar to the southeast pacific surface water records further demonstrating that this link between high and low latitude surface waters might be maintained the widespread indo pacific subantarctic surface water signal is obscured in records from the atlantic sector by the large glacial interglacial 13c signal 1 0 that is most likely the result of nutrient changes related to variable north atlantic deep water nadw production we find that the large change found uniformly in atlantic n pachyderma 13c records is not matched in a new g bulloides 13c record the confined regional extent of the high amplitude signal and the discrepancy between the two species suggest that most of the excess nutrients in the glacial atlantic inferred from 13c may be removed seasonally by increased production in the subantarctic

ontogenetic effects on stable carbon and oxygen isotopes in tests of live rose bengal stained benthic foraminifera from the pakistan continental margin abstract we determined the stable oxygen and carbon isotopic composition of live rose bengal stained tests belonging to different size classes of two benthic foraminiferal species from the pakistan continental margin samples were taken at two sites with water depths of about 135 and 275 m corresponding to the upper boundary and upper part of the core region of the oxygen minimum zone omz for uvigerina ex gr uvigerina semiornata and bolivina aff bolivina dilatata 13c and 18o values increased significantly with increasing test size in the case of uvigerina ex gr u semiornata 13c increased linearly by about 0 105 for each 100 m increment in test size whereas 18o increased by 0 02 to 0 06 per 100 m increment for bolivina aff b dilatata the relationship between test size and stable isotopic composition is better described by logarithmic equations a strong positive linear correlation is observed between 18o and 13c values of both taxa with a constant ratio of 18o and 13c values close to 2 1 this suggests that the strong ontogenetic effect is mainly caused by kinetic isotope fractionation during co2 uptake our data underline the necessity to base longer 18o and 13c isotope records derived from benthic foraminifera on size windows of 100 m or less this is already common practice in down core isotopic studies of planktonic foraminifera

changes in the oceanic 13c 12c ratio during the last 140 000 years high latitude surface water records detailed records of the carbon and oxygen isotopic ratios of neogloboquadrina pachyderma are compared between nine high latitude sediment cores from the northern and southern hemispheres covering the last 140 000 yrs the strong analogies between the 13c records permit to define a 13c stratigraphic scale with three clear cut transitions simultaneous with the oxygen isotopic transitions 65 125 kyrs 54 65 kyrs and 21 13 kyrs the 13c records of n pachyderma in the high latitude cores which follow the changes in 13c of the surface water tco2 near areas of deep water formation present trends similar to the benthic foraminifera 13c records in cores v19 30 and m12 392 although amplitudes of the isotopic shifts are different this implies that a large part of the observed variations represents global changes in the carbon distribution between biosphere and ocean the 13c12c ratios of n pachyderma in the north atlantic cores display larger regional variations at 18 kyrs b p than at present to explain these differences we have plotted the 18 kyrs b p 13c values of n pachyderma from 17 cores distributed n of 40 n comparison with published surface water temperature distribution at 18 kyrs b p indicates that a strong divergent cyclonic cell centered approximatively 55 n and 15 w was active during most of the last ice age maximum this hydrology analogous to the present weddell sea explains the published evidences of bottom water formation if located on the northern flank of the gyre and the strong polar front on the southern flank probable location of intermediate water formation

benthic isotope evidence for changes of the mediterranean outflow during the late quaternary a suit of sediment cores close to and south of the strait of gibraltar 12 36 n 500 2800 m water depth were analyzed for stable isotopes in epibenthic foraminifers cibicidoides wuellerstorfi and planulina ariminensis during peak glacial times the data exhibit higher 13c values of up to 1 6 at intermediate depths near the strait of gibraltar 36 n the values decrease to the south as evidenced by our data but also to the north as revealed by data of intermediate depth cores north of 38 n in duplessy et al 1987 thus the distribution pattern of 13c provides crucial evidence for an increased influence of nutrient depleted mediterranean outflow water mow on the glacial northeast atlantic hydrography during oxygen isotope terminations i and ii the meridional carbon isotope gradient indicates a significantly decreased but still active mow as deduced from the 18o fluctuations the temperatures of the mow in the atlantic were lower during glacial times by as much as 5 c during glacial times and during termination i the maximum 13c values of the mow correlate with minimum values of the north atlantic deep water nadw and vice versa this inverse response to climatic change of the carbon isotope signals of both water masses indicates that the supply of saline mow to the north atlantic may be less important for the formation of nadw than previously assumed

paleo megalake and paleo megafan in southern africa the near juxtaposition of the makgadikgadi basin botswana the world s largest saltpan complex with the okavango delta one of the planet s largest inland deltas technically an alluvial megafan has intrigued explorers and scientists since the middle of the 19th century it was clear from early observations that the makgadikgadi basin once contained a huge lake paleo lake makgadikgadi several authors have since speculated that this lake also covered wide regions to the north and west of the makgadikgadi basin our interpretation of unusually high quality helicopter time domain electromagnetic htem data indicates that paleo lake makgadikgadi extended northwestward at least into the region presently occupied by the okavango delta the total area of paleo lake makgadikgadi exceeded 90 000 km2 larger than earth s most extensive freshwater body today lake superior north america our htem data constrained by ground based geophysical and borehole information also provide evidence for a paleo megafan underlying paleo lake makgadikgadi sediments

late quaternary paleoproductivity changes off the congo deduced from stable carbon isotopes of planktonic foraminifera a detailed record 2 kyr intervals of the difference in stable carbon isotopes 13c between globigerina bulloides and globigerinoides ruber pink is used to reconstruct changes in upwelling intensity off the congo river for the last 190 000 yr comparisons of the oxygen and carbon isotope data from this core with records from the niger fan and from pelagic cores in the eastern equatorial south atlantic indicate that the congo fan isotope records do not contain a strong freshwater signal as is described off other major rivers the temporal pattern of the 13c signal correlates with the marine organic carbon record from the congo fan thus the planktonic 13c record reflecting past changes in upwelling intensity and nutrient content corroborates the signal provided by sedimentary organic carbon which is presumed to indicate changes in the amount of biological productivity and export flux to the seafloor the planktonic 13c signal is characterized by a dominant 23 kyr periodicity which provides evidence for a strong response of upwelling fluctuations off the congo to precessional forcing minima in the 13c record are aligned with periods of minimum boreal summer insolation over central africa reflecting an increase of upwelling and biological productivity off the congo at periods of enhanced zonal intensity of southeast trades and corresponding weak southeast monsoon over the eastern south atlantic a strong response to changes in river discharge probably did not occur indicating that fertilization by river derived nutrients has played only a minor role with respect to late quaternary changes in the total amount of primary productivity off the congo

groundwater salinity as a control on development of eolian landscape an example from the white sands of new mexico abstract the white sands of southern new mexico form the largest field of gypsum dunes in the world the juxtaposition of several different types of dunes within the field has long been recognized and has generally been attributed to changes in the rate of sand transport across the dune field however steven fryberger fryberger s g 2003 geology of white sands national monument web page www2 nature nps gov geology parks whsa recently hypothesized however that a primary control is groundwater salinity the white sands dune field is underlain by saline waters fryberger proposed that parabolic dunes could form in topographic highs that accumulated a lens of fresher water derived from precipitation water with lower salinity allowed vegetation to grow and stabilized the sand except for the active noses of the parabolic dunes this study is a test of that hypothesis a study transect was established across the boundary between parabolic and barchan dunes groundwater and soil at six sites were sampled during december 2004 and march may and june of 2005 two sites were established in the parabolic field two in the barchans and two in the transition zone between them groundwater was found to be three times more saline in the barchan area conductivity and chloride decreased across the transition zone a gps topographic survey revealed two abrupt topographic steps one at the boundary between the barchans and the transition zone and a second at the edge of the parabolic field a second larger topographic step was found outside the study area defining a higher parabolic dune field these data indicate that fryberger s 2003 hypothesis is correct and groundwater is controlling the dune field morphology the dune field did not begin to form until the mid holocene 6500 years ago a compilation of dates shows that the parabolic dune field has probably been stable for the last 3500 years in contrast the barchan area has been recently deflated and exposed 2000 year old sediment near the surface

neogloboquadrina pachyderma sinistral coiling as paleoceanographic tracers in polar oceans evidence from northeast water polynya plankton tows sediment traps and surface sediments the abundance and chemistry of the planktonic foraminifera neogloboquadrina pachyderma sinistral coiling have long been used as tools for monitoring polar surface ocean changes and for correlating these changes to atmospheric and thermohaline circulation fluctuations however due to its remote habitat very little is known about how modern n pachyderma s respond to changing environmental conditions in the polar seas modern samples of n pachyderma s from the northeast water polynya provide a means for studying how environmental conditions affect the vertical distribution and chemistry of this species highest abundances of n pachyderma s were associated with the chlorophyll maximum in the surface 20 80 m where they are exploiting their primary food source evidence suggests that the addition of a calcite crust modifies the calcite tests of some n pachyderma s between 50 and 200 m increasing shell density and modifying shell chemistry the shell mass of encrusted forms is 3 4 times greater than the nonencrusted forms between 50 and 200 m the oxygen isotope composition of n pachyderma s shells increase by 1 5 in response to local water column gradients the 13c values of n pachyderma s are basically invariant with depth in this region are consistently 1 0 depleted in comparison with the 13c for equilibrium calcite and remain basically constant during the shell thickening process mass balance calculations suggest that encrustation occurs at all depths but abundance counts suggest that the process occurs mostly at the depth of the main pycnocline sediment fluxes of n pachyderma s occur during a 2 week bloom event and decrease to almost zero below complete ice cover the decoupling of the processes controlling abundances and shell chemistry explain the discrepancies between transfer function and isotopically derived paleotemperature estimates of surface conditions in some oceanic settings the ability of 18o to record surface ocean conditions will depend on vertical water column gradients as evidenced by the differences in core top calibrations between the north and south atlantic

interspecies variation in stable isotopic signals of maastrichtian planktonic foraminifera we measured stable isotopic signals of the largest specimens of all abundant species of planktonic foraminifera in late maastrichtian samples from three atlantic mid latitude and high latitude sites each sample is marked by a relatively small interspecies range of 18o values 1 2 to 0 8 each also exhibits an interspecies range of 13c values that resembles those of modern assemblages at similar latitudes 2 8 to 0 9 with greater ranges at lower latitudes these results indicate that late cretaceous planktonic foraminifera inhabited water masses characterized by a relatively narrow range of temperatures but may have occupied an array of niches as ecologically diverse as that of modern taxa maastrichtian taxa exhibit more complex relationships between skeletal morphology and vertical and seasonal paleohabitat affinities than previous paleoecologic models have assumed for example keeled taxa were not limited to cold or deep habitats and serial taxa appear to have occupied both warm near surface niches and the coolest or most saline habitats the isotopic differences between species indicate that apparent variation in maastrichtian stable isotopic signals strongly depends on the taxa analyzed narrowly constrained size fractions of rugoglobigerina species may provide a good estimate of relative variation in isotopic equilibria of near surface summer paleoconditions at low and middle latitudes gublerina species laeviheterohelix species and planoglobulina multicamerata appear the likeliest candidates for consistently tracking relative variation in isotopic equilibria of the coldest or most saline paleohabitats of maastrichtian planktonic foraminifera these isotopic results suggest that upper water column thermal gradients may have been only 3 to 5 c in mid latitude and high latitude regions they also suggest that the western and central atlantic mid latitude summer seasurface may have been much cooler or saltier in the maastrichtian than it is today finally they corroborate previous estimates of 10 c surface water at southern high latitudes

kuwaiti dolocrete petrology geochemistry and groundwater origin abstract near surface sediments in southern kuwait show extensive development of duricrusts the host materials are siliciclastic sandstones of the post eocene kuwait group inland the duricrusts are dominantly pedogenic calcrete with some silcrete and gypcrete whereas within 10 20 km of the coast dolomite is the dominant duricrust mineral both these dolocretes and the inland calcretes display a similar maturation sequence in which carbonate rich nodules develop and coalesce carbonate progressively replacing and displacing detrital grains the dolomite of the dolocretes forms mosaics of crystals typically 10 70 m in size varying from simple rhombs to spherulites an intermediate morphology named artichoke dolomite from its appearance in sem is particularly abundant authigenic palygorskite is associated with the dolomite dissolution of cores or zones within dolomite crystals has occurred calcite is present as sparry crystals always post dating dolomite and is the expected precipitate from present day soil and groundwaters chemical analyses of dolomite show highly negative values of 13 c to 10 7 pdb and 18 o varying from 0 6 to 3 3 pdb the oxygen isotope values are interpreted as reflecting evaporation of a marine based fluid manganese values of around 1000 ppm show that this fluid was reducing strontium data show variability reflecting mineral fluid reactions the general absence of metastable carbonates and presence of zoning in dolomite crystals suggests that meteoric dilution of seawater also occurred given that the duricrusts lack biogenic features the light carbon isotope values are taken to indicate oxidation of seeping hydrocarbons the dolocretes are interpreted as groundwater precipitates near the water table of a brackish water body formed at a time of higher relative sea level than today

glacial deep water geometry south atlantic benthic foraminiferal cd ca and δ13c evidence a depth transect of cores from 1268 to 3909 m water depth in the western south atlantic are ideally situated to monitor the interocean exchange of deep water and variations in the relative strength of northern and southern sources of deep water production benthic foraminiferal cd ca and 13c data suggest that glacial north atlantic intermediate water gnaiw extended at least as far south as 28 s in the western south atlantic the core of nutrient depleted water was situated at 1500 m above and below water masses with higher nutrient concentrations when examined in conjunction with published paired cd ca and 13c from intermediate depth cores from other basins it appears that the extent of gnaiw influence on the intermediate waters of the world s oceans was less than suggested previously differentiating among possible pathways for the glacial deep ocean 3 km requires a better understanding of the controls on cd ca and 13c values of benthic foraminifera

deep circulation of the north atlantic over the last 200 000 years geochemical evidence variations in the cadmium calcium ratio of north atlantic deep water are recorded in the fossil shells of benthic foraminifera the oceanic distribution of cadmium is similar to that of the nutrients hence the cadmium calcium ratio in shells records temporal variations in nutrient distributions data from a north atlantic sediment core show that over the past 200 000 years there has been a continuous supply of nutrient depleted waters into the deep north atlantic the intensity of this source relative to nutrient enriched southern waters diminished by about a factor of 2 during severe glaciations this evidence combined with carbon isotope data indicates that the continental carbon inventory may have been less variable than previously suggested

north atlantic thermohaline circulation during the past 20 000 years linked to high latitude surface temperature during a surface cooling event 10 000 to 12 000 years ago higher cd ca and lower 13c 12c ratios are observed in benthic foraminifera shells from rapidly accumulating western north atlantic sediments data from sediment cores show that marked nutrient depletion of intermediate waters occurs in association with reduced glacial north atlantic deep water flux it is proposed that cold high latitude sea surface temperatures enhance intermediate water formation at the expense of deep water formation

palaeoceanographic change in the northeastern south china sea during the last 15000 years the sedimentary succession of piston core rc26 16 dated by 14 c accelerator mass spectrometry provides a nearly continuous palaeoceanographic record of the northeastern south china sea for the last 15 000 yr planktic foraminiferal assemblages indicate that winter sea surface temperatures ssts rose from 18 c to about 24 c from the last glacial to the holocene a short lived cooling of 1 c in winter temperature centred at about 11 000 14 cy r ago may reflect the younger dryas cooling event in this area summer ssts have remained between 27 c and 29 c throughout the record the temperature difference between summer and winter was about ca 9 c during the last glacial much higher than the holocene value of ca 5 c during the late holocene a short lived cooling event occurred at about 4000 14 cy r ago oxygen and carbon isotopic gradients between surface 0 50 m and subsurface 50 100 m waters were smaller during the last glacial than those in the holocene the fluctuation in the isotopic gradients are caused most likely by changes in upwelling intensity smaller gradients indicate stronger upwelling during the glacial winter monsoon the fauna derived estimates of nutrient content of the surface waters indicate that the upwelling induced higher fertility and biological productivity during the glacial the winter monsoon became weaker during the holocene the carbonate compensation depth and foraminiferal lysocline were shallower during the holocene except for a short lived deepening at about 5000 14 c yr ago a preservation peak of planktic foraminifera and calcium carbonate occurred between 13400 and 12 000 14 c

a pleistocene paleoceanographic record from the north slope of the spratly islands southern south china sea abstract a 1 4 my paleoceanographic history for offshore north central spratly islands southern south china sea is reconstructed using stable isotope carbonate content coarse fraction and planktonic foraminifera census data from gravity core so95 17957 2 the chronological framework for so95 17957 2 is based on stable oxygen isotope correlation with open ocean records and constrained with ams 14c dates floral and faunal bioevents and a pleistocene microtektite event stable oxygen isotope composition of surface water reflects mainly changes in high latitude ice volume but also riverine water influx from surrounding land stable carbon isotope record suggests that surface water 13c in the southern south china sea has been modulated primarily by global changes in atmospheric co2 since the early pleistocene dissimilarities between 18o patterns in so95 17957 2 and those in various cores from the rest of the south china sea indicate that between 60 and 120 ka surface water chemistry at offshore north central spratly islands may be affected by different mechanisms those differences likely reflect unknown hydrological conditions during stages 4 and 5 carbonate content is lower during the interglacial periods than during the glacial deglacial periods which are opposite to the general trend in the shallow south china sea areas during the same period faunal composition rsp and various dissolution indices suggest that productivity is the most important factor controlling carbonate preservation dissolution above the lysocline may modify the productivity signal but cannot reverse the entire pattern faunal composition and carbonate flux suggests productivity is higher during glacial deglacial than during interglacial stronger glacial winter monsoon induces stronger upwelling and deep mixing and enhances nutrient cycling in the surface ocean which in turn increases productivity estimated summer sea surface temperature sst based on transfer function fp 12e agrees with 18o and is consistently between 28 and 29 c during most of the last 1 4 my winter sst reflects geographic location and changes in surface hydrology and fluctuates between 25 and 28 c during the last glacial period disconnection of the south china sea from the indian ocean and the influx of temperate water through the bashi channel allowed winter ssts to vary by as much as 3 5 c comparison of modern and estimated sst and sst estimates based on different methods suggest that g bulloides and g menardii are probably overweighed in transfer function fp 12e which cause discrepancies in sst estimation

changes in the distribution of δ13c of deep water σco2 between the last glaciation and the holocene carbon isotopic measurements on the benthic foraminiferal genus cibicidoides document that mean deep ocean 13c values were 0 46 lower during the last glacial maximum than during the late holocene the geographic distribution of 13c was altered by changes in the production rate of nutrient depleted deep water in the north atlantic during the late holocene north atlantic deep water with high 13c values and low nutrient values can be found throughout the atlantic ocean and its effects can be traced into the southern ocean where it mixes with recirculated pacific deep water during the glaciation decreased production of north atlantic deep water allowed southern ocean deep water to penetrate farther into the north atlantic and across low latitude fracture zones into the eastern atlantic mean southern ocean 13c values during the glaciation are lower than both north atlantic and pacific 13c values suggesting that production of nutrient depleted water occurred in both oceans during the glaciation enriched 13c values in shallow cores within the atlantic ocean indicate the existence of a nutrient depleted water mass above 2000 m in this ocean

the flooding of sundaland during the last deglaciation imprints in hemipelagic sediments from the southern south china sea abstract during the last 30 ka the south china sea scs experienced pronounced palaeogeographic changes associated with the postglacial sea level rise which significantly modified the hydrography of this marginal sea the most crucial effects in the southern part of the basin were the submergence of sundaland and the opening of the southern channels connecting the scs to the tropical indo pacific isotopic sedimentological and organic geochemical parameters determined in two sediment cores from the southern scs one in the open sea and the other close to the continental shelf sites 17961 and 17964 respectively show that the main hydrographical changes during this period were related to critical thresholds in sea level rise the main changes occurred at about 15 13 5 ky bp coincident with meltwater pulse mwp ia when sea surface temperatures ssts at both sites experienced a rapid 1 5 c rise and the clay content and n nonacosane concentrations dropped significantly both trends reflect a rapid retreat of the coastline and an initial flooding of sundaland at that time a second important change starting with the beginning of mwp ib at about 11 5 ky bp and culminating at 10 ky bp involved the establishment of modern hydrographic conditions this is evident from the rapid convergence of the foraminiferal oxygen isotope records and the establishment of holocene sst values these results highlight the need to include the flooding emergence of sundaland as an important boundary condition in future modelling studies of asian palaeomonsoons

variability in the deep and intermediate water circulation of the atlantic ocean during the past 25 000 years northern hemisphere modulation of the southern ocean the relative flux of north atlantic deep water nadw out of the atlantic can be monitored in the southern ocean where high 13c nadw mixes rapidly with low 13c recirculated pacific water before forming antarctic bottom water aabw by using 13c measured in benthic foraminifera as a water mass tracer it is shown that the southern ocean was dominated by pacific water with little nadw contribution during the last glaciation these tracer results document the direct physical connection between insolation controlled northern hemisphere oscillations and changes in the chemical and physical properties of southern ocean water the 13c records from the deep tropical atlantic document the transition from an atlantic dominated by southern ocean water during the last glaciation to an atlantic dominated by nadw during the holocene with more southern ocean water in the deep atlantic during the last glaciation the boundary between nadw and southern ocean water was north of its modern position allowing more southern ocean water to enter the eastern atlantic through the romanche fracture zone carbon isotope records from the caribbean and mediterranean seas suggest that the influence of mediterranean overflow water mow extended to the caribbean during the last glaciation and therefore was a volumetrically much more important water mass in the intermediate depth atlantic than it is today

constraining foraminiferal calcification depths in the western pacific warm pool highlights first apparent calcification depth assessment of living foraminifera in the se wpwp deep surface mixed layer causes deep apparent calcification depths deep dwelling g hexagonus traces nutrient conditions in equatorial water masses abstract insight into past changes of upper ocean stratification circulation and nutrient signatures rely on our knowledge of the apparent calcification depth acd and ecology of planktonic foraminifera which serve as archives for paleoceanographic relevant geochemical signals the acd of different species varies strongly between ocean basins but also regionally we constrained foraminiferal acds in the western pacific warm pool manihiki plateau by comparing stable oxygen and carbon isotopes 18ocalite 13ccalcite as well as mg ca ratios from living planktonic foraminifera to in situ physical and chemical water mass properties temperature salinity 18oseawater 13cdic our analyses point to globigerinoides ruber as the shallowest dweller followed by globigerinoides sacculifer neogloboquadrina dutertrei pulleniatina obliquiloculata and globorotaloides hexagonus inhabiting increasing greater depths these findings are consistent with other ocean basins however absolute acds differ from other studies the uppermost mixed layer species g ruber and g sacculifer denote mean calcification depths of 95 m and 120 m respectively these western pacific acds are much deeper than in most other studies and most likely relate to the thick surface mixed layer and the deep chlorophyll maximum in this region our results indicate that n dutertrei appears to be influenced by mixing waters from the pacific equatorial divergence while p obliquiloculata with an acd of 160 m is more suitable for thermocline reconstructions acds of g hexagonus reveal a deep calcification depth of 450 m in oxygen depleted but nutrient rich water masses consistent to other studies as the 13c of g hexagonus is in near equilibrium with ambient seawater we suggest this species is suitable for tracing nutrient conditions in equatorial water masses originating in extra topical regions

hydrogeochemical evidence for surface water recharge to a shallow regional aquifer in northern victoria australia abstract the third middle and reedy lakes system in northern victoria is a series of interconnected lakes in which groundwater discharge and recharge occur under seasonal climatic and artificial influences at high lake levels there is a pronounced mounding effect which tends to cause localised perturbation of flow systems and recharge into the uppermost aquifer three hydrostratigraphic units referred to as lower middle and upper are identified beneath the lakes an upward hydraulic gradient exists in the region under the present hydrologic regime despite this hydrochemical and isotopic evidence has demonstrated a fresh water lens beneath reedy lake in the middle and lower aquifers these waters have similar characteristics to the present day water table which is being recharged from the lakes suggesting that the lens represents lake water recharge under a prior hydrologic regime when regional water tables were lower the recognition of this lens has important implications for future management strategies in that it may be possible to implement a more natural wetting drying cycle without the intrusion of saline water into this ecologically sensitive area

decoupling of δ13cσco 2 and phosphate in recent weddell sea deep and bottom water implications for glacial southern ocean paleoceanography

a global compilation of late holocene planktonic foraminiferal δ18o relationship between surface water temperature and δ18o we review the different sources of uncertainty affecting the oxygen isotopic composition of planktonic foraminifera and present a global planktonic foraminifera oxygen isotope data set that has been assembled within the margo project for the late holocene time slice the data set consists of over 2100 data from recent sediment with thorough age control that have been checked for internal consistency we further examine how the oxygen isotopic composition of fossil foraminifera is related to hydrological conditions based on published results on living foraminifera from plankton tows and cultures oxygen isotopic values 18o of margo recent fossil foraminifera are 0 2 0 8 higher than those of living foraminifera our results show that this discrepancy is related to the stratification of the upper water mass and generally increases at low latitudes therefore as stratification of surface waters and seasonality depends on climatic conditions the relationship between temperature and 18o established on fossil foraminifera from recent sediment must be used with caution in paleoceanographic studies before models predicting seasonal flux abundance and 18o composition of a foraminiferal population in the sediment are available we recommend studying relative changes in isotopic composition of fossil planktonic foraminifera these changes primarily record variations in temperature and oxygen isotopic composition of sea water although part of the changes might reflect modifications of planktonic foraminifera seasonality or depth habitat

the relationship between shell size and mg ca sr ca δ18o and δ13c of species of planktonic foraminifera the relationship between shell size and mg ca sr ca 18o and 13c of planktonic foraminiferal calcite has been investigated using seventeen species in six different size fractions mg ca increases and sr ca decreases with increasing size except for two globorotaliid species which show the opposite trend the changes in mg ca broadly follow 18o calcification temperatures except that surface and near surface dwelling species show larger changes in mg ca than can be accounted for by differences in calcification temperature derived from 18o the increases in mg ca and decreases in sr ca vary linearly with the well established increase in 13c with size this is consistent with smaller individuals calcifying faster than larger individuals and larger individuals forming calcite that more closely reflects seawater temperature and composition it appears that variations in calcification rate affect mg and sr shell chemistry the observations may account for part of the temporal variability in foraminiferal sr ca within a single size fraction that has been attributed to changes in seawater sr ca

freshwater recharge into a shallow saline groundwater system cooper creek floodplain queensland australia freshwater lenses have been identified as having penetrated the shallow regional saline groundwater beneath the cooper creek floodplain near ballera south west queensland piezometers were installed to evaluate the major element chemistry along a floodplain transect from a major waterhole goonbabinna to a smaller waterhole chookoo associated with a sand dune complex the floodplain consists of 2 7m of impermeable mud underlain by unconsolidated fluvial sands with a saline watertable waterholes have in places scoured into the floodplain the transect reveals that groundwater recharge takes place through the base of the waterholes at times of flood scour but not through the floodplain mud total dissolved solids rise with distance from the waterhole and independently of the presence of sand dunes stable water isotopes 2h and 18o confirm that recharge is consistent with and dependant on monsoonal flooding events following floods the waterholes self seal and retain water for extended periods with sulfate 34s and 18o isotopes suggesting bacterial reduction processes within the hyporheic zone and limited interaction between the surface water and groundwater during no flow conditions the area occupied by the freshwater lenses tds 5000 mg l is locally asymmetrical with respect to the channel flow direction extending down gradient along distances of 300 m

ground truthing the boron isotope paleo ph proxy in planktonic foraminifera shells partial dissolution and shell size effects 1 sediment samples from the ontong java plateau in the pacific and the 90 east ridge in the indian ocean were used to investigate whether shell size and early diagenesis affect 11b of the symbiont bearing planktonic foraminifer globigerinoides sacculifer in pristine shells from both study locations we found a systematic increase of 11b and mg ca with shell size shells in the sieve size class 515 865 m revealed 11b values 2 1 to 2 3 higher than shells in the 250 380 m class this pattern is most likely due to differences in symbiont photosynthetic activity and its integrated effect on the ph of the foraminiferal microenvironment we therefore suggest smaller individuals must live at approximately 50 100 m water depth where ambient light levels are lower using the empirical calibration curve for 11b in g sacculifer only shells larger than 425 m reflect surface seawater ph partial dissolution of shells derived from deeper sediment cores was determined by shell weight analyses and investigation of the shell surface microstructure by scanning electron microscopy the 11b in partially dissolved shells is up to 2 lower relative to pristine shells of the same size class in agreement with a relatively higher weight loss in smaller shells samples from the ontong java plateau show a more pronounced dissolution effect than larger shells on the basis of the primary size effect and potential postdepositional dissolution effects we recommend the use of shells that are visually pristine and in the case of g sacculifer larger than 500 m for paleoreconstructions