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maximum as part of the multi proxy approach for the reconstruction of the glacial ocean margo incentive published and unpublished temperature reconstructions for the last glacial maximum lgm based on planktonic foraminiferal mg ca ratios have been synthesised and made available in an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

calibration of the planktonic foraminiferal mg ca paleothermometer sediment trap results from the guaymas basin gulf of california 1 the mg ca ratio has been measured in two surface dwelling species of planktonic foraminifera globigerinoides ruber and globigerina bulloides from biweekly sediment trap samples collected in guaymas basin gulf of california between august 1992 and november 1997 the guaymas basin experiences significant seasonal changes in sea surface temperature sst 16 33 c and thus is an ideal location for testing the temperature dependence of mg incorporation into foraminiferal calcite the planktonic foraminiferal mg ca ratios are directly compared with concurrent temperature measurements from the study site the results from the sediment trap study reveal a strong positive correlation between sst and the mg ca ratio in both g ruber r2 0 86 and g bulloides r2 0 90 the mg ca ratio increases exponentially by 7 per 1 c change in temperature for g ruber and by 6 for g bulloides these results indicate that the mg ca ratio in g ruber and g bulloides accurately records the measured seasonal surface temperature cycle and interannual variability in the guaymas basin within 1 c the greatest deviation between mg ca estimated sst and observed sst occurs in the spring and fall for both species this variability is attributed to rapidly changing hydrographic conditions and possible offset between the time of calcification and the temperature measurements in addition g ruber and g bulloides exhibit very high mg ca ratios during the strong el nino southern oscillation years of 1992 and 1997 verifying their potential to record sst up to 33 c and 28 c respectively the trace metal data are compared with foraminiferal oxygen isotope and alkenone measurements made on the same suite of sediment trap samples to assess the internal consistency of these temperature proxies strong correlations exist between the 18o and mg ca for g ruber r2 0 86 and g bulloides r2 0 79 similarly sea surface temperature estimates from mg ca ratios are in good agreement with alkenone derived temperature estimates r2 0 89 for g ruber and r2 0 81 for g bulloides

seasonal stratification shell flux and oxygen isotope dynamics of left coiling n pachyderma and t quinqueloba in the western subpolar north atlantic blooms this annual population overturning is marked by a 0 7 increase in d 18 o in both species the shell flux of n pachyderma peaks during the spring bloom and in late summer when stratification is close to its minimum and maximum respectively both export periods contribute about equally and account for 95 of the total annual flux shell fluxes of t quinqueloba show only a single broad pulse in summer thus following the seasonal stratification cycle the d 18 oo fn pachyderma reflects temperatures just below the base of the seasonal sml without offset from isotopic equilibrium the d 18 op attern oft quinqueloba shows a nearly identical amplitude and correlates highly with the d 18 oo fn pachyderma therefore t quinqueloba also reflects temperature near the base of the sml but with a positive offset from isotopic equilibrium these offsets contrast with observations elsewhere and suggest a variable offset from equilibrium calcification for both species in the irminger sea the species consistently show a contrast in their flux timings their flux weighted dd 18 o will thus dominantly be determined by seasonal temperature differences at the base of the sml rather than by differences in their depth habitat consequently their sedimentary dd 18 o may be used to infer the seasonal contrast in temperature at the base of the sml citation jonkers l g j a brummer f j c peeters h m van aken and m f de jong 2010 seasonal stratification shell flux and oxygen isotope dynamics of left coiling n pachyderma and t quinqueloba in the western subpolar north atlantic paleoceanography 25 pa2204 doi 10 1029 2009pa001849

mg ca ratios in the planktonic foraminifer neogloboquadrina pachyderma sinistral in the northern north atlantic nordic seas in core top samples in the nordic seas mg ca ratios of n pachyderma sin are generally consistent with previous high latitude calibration data but do not reflect the modern calcification temperature gradient from 2 c in the northwest to 8 c in the southeast this is because mg ca ratios in foraminiferal shells from the central nordic seas are 0 4 mmol mol higher than expected from calibrations of nurnberg 1995 and elderfield and ganssen 2000 the enhanced mg ca ratios are observed in an area with low sedimentation rates 5 cm kyr possible factors that may cause this include bioturbation holocene variability in old core tops dissolution pore water chemistry occurrence of volcanic ash and other natural variability the enhanced foraminiferal mg ca ratios in areas of the nordic seas and the northern north atlantic may also be linked with secondary factors related to the presence of fresher and colder water masses possibly combined with pore water chemistry in low sedimentation areas differing from high sedimentation areas

planktonic foraminiferal depth habitat and δ18o calibrations plankton tow results from the atlantic sector of the southern ocean varies by several orders of magnitude across a large gradient in sea surface temperature and other hydrographic features demonstrating high sensitivity of foraminiferal populations to regional differences in water properties the depth of maximum abundance for key species such as globigerina bulloides and neogloboquadrina pachyderma is not constant from station to station the pattern suggests that their abundance and shell chemistry are tied to density horizons or other conditions such as food availability that become more sharply defined with depth in the northern subantarctic the consistent observation of globorotalia inflata and globoratalia truncatulinoides as relatively deep dwelling species confirms their utility as indicators of upper thermocline properties in d 18 o all species are observed to be isotopically lighter than predicted from water properties but the species specific offset is fairly uniform at all stations these observations define the utility of multispecies d 18 o for reconstructing temperature and density stratification from past surface oceans index terms 4267 oceanography general paleoceanography 4572 oceanography physical upper ocean processes 4870 oceanography biological and chemical stable isotopes 3030 marine geology and geophysics micropaleontology keywords stratification d 18 o

a study of cleaning procedures used for foraminiferal mg ca paleothermometry the various cleaning steps required for preparation of foraminiferal samples for mg ca and sr ca analysis are evaluated for their relative importance and effects on measured elemental ratios it is shown that the removal of silicate contamination is the most important step for the measurement of mg ca ratios in an example bulk sample mg ca decreases from 10 5 to 2 5 mmol mol 1 during clay removal oxidation of organic material causes a lowering of sample mg ca in the order of 10 or approximately 1 c when converted to temperature use of dilute acid leaching to remove adsorbed contaminants causes partial dissolution of the sample carbonate and a corresponding decrease in mg ca reductive treatment also causes dissolution of the sample and a decrease in the mg ca ratio of up to 10 15 sample preparation for sr ca analysis does not require the same degree of rigor as is necessary for mg ca work the within run reproducibility of the method described here for g ruber in a core top sample from the arabian sea was 1 8 mean sample ratio was 4 72 mmol mol 1 when converted to temperature this becomes 28 0 2 c the equivalent result for sr ca was 0 5 mean ratio 1 44 mmol mol 1

ionic relations a tool for studying hydrogeochemical processes in pampean shallow lakes buenos aires argentina abstract main geochemical processes that determine the chemical composition of shallow lakes in the lower salado river basin were studied the region is characterized by the total lack of slope and the succession of humid and dry climates where the lakes are shallow alkaline and eutrophic ecosystems with circulation pattern corresponding to polymictic lakes gibbs classical diagrams confirmed that weathering of mineral phases and evaporation crystallization were the principal processes involved nevertheless deviations to the basic pattern were observed the study of ionic relations in meq l 1 determined that a cationic exchange process takes place in the pampean loessic sediments influencing the chemical characteristics of both groundwater s and surface waters

tropical cyclone intensity estimated from wide swath sar images due to the relatively small amount of in situ data available for the open oceans remote sensing techniques take an important role in the retrieval of geophysical information particularly during extreme events the work presented here aims at the improvement of prediction of cyclone intensity using synthetic aperture radar sar images a new method to measure the hurricane intensity using sar images in combination with a parametric holland type model of wind speed is presented the algorithm is based on a least square minimization of the difference between the parametric model results and the sar measurement the radius of the maximum wind speed required as input for the minimization procedure is estimated from the sar image using wavelet analysis information on wind direction is extracted from the sar image through analysis of image features caused by boundary layer rolls the root mean square error of the suggested method has been validated to be equal to 3 9 m s the study is based on a data set of wide swath sar images of about 400 km 400 km coverage acquired by the european envisat satellite over tropical cyclones as a case study hurricane katrina is investigated in detail a total of five tropical cyclone images will be used to validate the results of the new algorithm

reevaluation of the oxygen isotopic composition of planktonic foraminifera experimental results and revised paleotemperature equations cultured planktonic foraminifera orbulina universa symbiotic and globigerina bulloides nonsymbiotic are used to reexamine temperature 18o relationships at 15 25 c relationships for both species can be described by linear equations equations for o universa grown under low light ll and high light hl share a slope of 4 80 0 21 c 1 with a hl ll offset of 0 33 due to symbiont photosynthetic activity the effect of co32 on o universa is 0 002 mol 1 kg 1 and is insensitive to temperature for g bulloides ontogenetic effects produce size related trends in temperature 18o whereby larger shells are enriched in 18o relative to smaller specimens the o universa temperature 18o relationships are more accurate than previously published equations for describing plankton tow data our equations do not explain planktonic core top data with the same precision but provide a good fit to benthic cibicidoides data below 10 c temperature 18o relationships for g bulloides provide good agreement with field data for this species from the northeast pacific

direct measurements of ocean surface velocity from space interpretation and validation the median doppler shift of radar echoes is analyzed in measurements by envisat s advanced synthetic aperture radar asar over the ocean this doppler centroid differs from a predicted signal based on the predicted motion of the satellite and earth this anomaly converted to a surface doppler velocity u d appears to be of geophysical origin two wide swath images over the gulf stream around cape hatteras suggest that u d contains high resolution information on surface currents while on a global scale u d is found to vary with the wind speed in the range direction a simple quantitative forward model is proposed based on a practical two scale decomposition of the surface geometry and kinematics the model represents the effect of the wind through the wave spectrum and gives u d u 10 u c with u 10 and u c as the 10 m wind speed and quasi eulerian current in the line of sight of the radar projected on the sea surface respectively and as a coefficient function of the wind speed wave development and radar geometry it is found that for an incidence angle of 23 0 3 for moderate winds and fully developed seas this model is validated with a global data set of asar wave mode observations with colocated model winds acquired over the global ocean during the years 2003 and 2004 the doppler signal therefore provides the signed parameter u d that can be used to reduce the wind direction ambiguity in the inversion of high resolution wind fields from sar imagery a qualitative validation of current effects is shown for the english channel where tidal currents dominate thus it should be possible to combine this previously ignored geophysical doppler signal with traditional information on sea surface roughness in order to provide very high resolution wind and current fields

nutrient cycling in the indian sector of the southern ocean over the last 50 000 years most high southern latitude records of carbon and nitrogen isotopic ratios and elemental ratios are from the antarctic and polar front zones thus hindering a comprehensive view of nutrient cycling in the southern ocean we present for the first time two records from the subantarctic zone and the southern subtropical zone of the indian ocean these records provide a latitudinal transect covering the main oceanographic systems of the southern ocean carbon and nitrogen content of the diatom bound organic matter increases during the last glacial in the antarctic and subantarctic zones but does not show a clear climate related signal in the subtropical zone comparison of these records with sea surface temperatures reconstructed at the core locations and record of dust deposition over antarctica suggests that eolian iron input possibly switched diatom physiology toward higher carbon to silica and nitrogen to silica uptake and storage south of the subantarctic front due to the dependency of photosynthesis on iron concentration levels conversely the northernmost core was too remote from any iron source over the last 50 000 years antarctic diatoms therefore have the sole potential to change the nutrient content of the waters escaping from the southern ocean hence providing partial support to the silicic leakage hypothesis as a potential cause of lower glacial atmospheric co 2

boron isotope based seasonal paleo ph reconstruction for the southeast atlantic a multispecies approach using habitat preference of planktonic foraminifera abstract the boron isotopic composition of planktonic foraminiferal shell calcite 11 b cc provides valuable information on the ph of ambient water at the time of calcification hence 11 b cc of fossil surface dwelling planktonic foraminifera can be used to reconstruct ancient aqueous p co 2 if information on a second carbonate system parameter temperature and salinity is available however ph and p co 2 of surface waters may vary seasonally largely due to changes in temperature dic and alkalinity as also the shell fluxes of planktonic foraminifera show species specific seasonal patterns that are linked to intra annual changes in temperature it is obvious that 11 b cc of a certain species reflects the ph and thus p co 2 biased towards a specific time period within a year this is important to consider for the interpretation of fossil 11 b cc records that may mirror seasonal ph signals here we present new multi collector inductively coupled mass spectrometry mc icpms 11 b cc coretop data for the planktonic foraminifera species globigerina bulloides globigerinoides ruber trilobatus sacculifer and orbulina universa and compare them with 11 b borate derived from seasonally resolved carbonate system parameters we show that the inferred season adjusted 11 b cc 11 b borate relationships are similar to existing calibrations and can be combined with published 11 b cc field and culture data to augment paleo ph calibrations to test the applicability of these calibrations we used a core drilled on the walvis ridge in the southeast atlantic spanning the last 330 000 years to reconstruct changes in surface water p co 2 the reconstruction based on g bulloides which reflects the austral spring season was shown to yield values that closely resemble the vostok ice core data indicating that surface water p co 2 was close to equilibrium with the atmosphere during the cooler spring season in contrast p co 2 estimated from 11 b cc of o universa t sacculifer and g ruber that predominantly lived during the warmer seasons exhibits up to 50 ppmv higher values than the vostok ice core data this is probably due to the higher austral summer and fall temperatures as shown by mg ca to be on average 4 c higher than during the cooler spring season accounting for an increase in p co 2 of 4 per 1 c our results demonstrate that paleo ph estimates based on 11 b cc contain a significant seasonal signal reflecting the habitat preference of the recording foraminifera species

effects of temperature on mg ca in neogloboquadrinid shells determined by live culturing 1 new culturing protocols allowed the development of a mg ca temperature calibration equation for neogloboquadrina pachyderma d when cultured between 9 c and 19 2 c mg ca in n pachyderma d shell calcite exhibits a clear dependence on temperature shell calcite mg ca increased exponentially with temperature mg ca 0 51 0 15 0 23 exp 0 10 0 02 t limited data suggest n dutertrei exhibit similar elemental temperature relationships to n pachyderma d we applied the temperature relationship established by culturing to mg ca in neogloboquadrinid shells collected using plankton tows compared to measured sst the calculated temperatures were within 2 c for mg ca 95 ci multiple samples from single tows generally had calculated temperatures that ranged from near surface values to temperatures consistent with calcification depths down to 70 m our work indicates that mg ca temperature calibration equations for temperate and polar foraminiferal species have a similar exponential constant but a higher pre exponential constant than those for surface dwelling tropical species therefore accurate paleotemperature reconstructions from temperate and polar species require the use of an equation distinct from those used for tropical species

surface water temperature changes in the high latitudes of the southern hemisphere over the last glacial interglacial cycle a set of numerical equations is developed to estimate past sea surface temperatures sst from fossil antarctic diatoms these equations take into account both the biogeographic distribution and experimentally derived silica dissolution the data represent a revision and expansion of a floral data base used previously and includes samples resulting from progressive opal dissolution experiments factor analysis of 166 samples 124 holocene core top and 42 artificial samples resolved four factors three of these factors depend on the water mass distribution one subantarctic and two antarctic assemblages factor 4 corresponds to a dissolution assemblage inclusion of this factor in the data analysis minimizes the effect of opal dissolution on the assemblages and gives accurate estimates of sst over a wide range of biosiliceous dissolution a transfer function dtf 166 34 4 is derived from the distribution of these factors versus summer sst its standard error is 1 c in the 1 to 10 c summer temperature range this transfer function is used to estimate sst changes in two southern ocean cores 43 s and 55 s which cover the last climatic cycle the time scale is derived from the changes in foraminiferal oxygen and carbon isotopic ratios the reconstructed sst records present strong analogies with the air temperature record over antarctica at the vostok site derived from changes in the isotopic ratio of the ice this similarity may be used to compare the oceanic isotope stratigraphy and the vostok time scale derived from ice flow model the oceanic time scale if taken at face value would indicate that large changes in ice accumulation rates occurred between warm and cold periods

paleo sea surface temperature calculations in the equatorial east atlantic from mg ca ratios in planktic foraminifera a comparison to sea surface temperature estimates from u37k oxygen isotopes and foraminiferal transfer function we present two 270 kyr paleo sea surface temperature sst records from the equatorial divergence and the south equatorial current derived from mg ca ratios in the planktic foraminifer globigerinoides sacculifer the present study suggests that the magnesium signature of g sacculifer provides a seasonal sst estimate from the upper 50 m of the water column generated during upwelling in austral low latitude fall winter common to both down core records is a glacial interglacial amplitude of 3 3 5 c for the last climatic changes and lower holocene and glacial oxygen isotope stage 2 temperatures compared with interglacial stage 5 5 and glacial stage 6 temperatures respectively the comparison to published sst estimates from alkenones oxygen isotopes and foraminiferal transfer function from the same core material pinpoints discrepancies and conformities between methods

multiproxy approach for the reconstruction of the glacial ocean surface margo michal kucera antoni rosell mele ralph schneider claire waelbroeck mara weinelt department of geology royal holloway university of london egham tw20 0ex uk icrea and institute of environmental science and technology universitat autonoma de barcelona 08193 bellaterra catalonia spain departement de geologie et oceanographie umr5805 epoc cnrs universite de bordeaux1 33405 talence cedex france laboratoire des sciences du climat et de l environnement laboratoire mixte cnrs cea f 91198 gif sur yvette france institute for geosciences university of kiel olshausen strasse 40 d 24098 kiel germany

strontium isotope characterization and major ion geochemistry of karst water flow shentou northern china summary karst water is the most important source of water supply for shanxi province northern china the shentou springs are representative of the 19 major karst springs at shanxi the total area of the shentou karst water system is 5316 km 2 the middle ordovician limestone being its major karst aquifer in this study data about the strontium isotope geochemistry and major ion hydrochemistry were analyzed to understand the flow patterns and hydrogeochemical processes of karst water at shentou the contour map of tds value of karst water and that of sr concentration are similar showing the general tendency of increase from the northern western and southern boundary to the discharge area the average values of 87 sr 86 sr ratios of karst water decrease from recharge 0 7107 to discharge area 0 7102 evolving towards those of limestone hostrocks comparison of 87 sr 86 sr ratios with sr content suggests that isotopic compositions of some karst water samples from the recharge and flow through area should be the result of interaction between aquifer limestone matrix and strontium poor recharge waters of meteoric origin however for samples from the discharge area that are plotted above the mixing line mixing with groundwater in the quaternary aquifers with high 87 sr 86 sr ratios may be another factor controlling sr isotope chemistry two major groundwater flow paths were discerned from hydrogeological and geochemical data along both flow paths the 87 sr 86 sr ratios of karst water show a general tendency of decrease geochemical modeling of the major ion geochemistry of karst water using phreeqc also indicates that the chemistry of springs should be affected by the incorporation of groundwater in quaternary aquifer the effect of the mixing action on the spring hydrochemistry in flow path 1 is more remarkable than that in flow path 2 according to different mixing ratios in both paths 30 in flow path 1 and 5 in flow path 2

mg ca and sr ca ratios in planktonic foraminifera proxies for upper water column temperature reconstruction reliable temperature estimates from both surface and subsurface ocean waters are needed to reconstructpast upper water column temperature gradients and past oceanic heat content this work examines therelationships between trace element ratios in fossil shells and seawater temperature for surface dwellingforaminifera species globigerinoides ruber white and globigerina bulloides and deep dwelling species globorotalia inflata globorotalia truncatulinoides dextral and sinistral and pulleniatina obliquiloculata mg ca and sr ca ratios in shells picked in 29 modern core tops from the north atlantic ocean are calibratedusing calculated isotopic temperatures mg ca ratios on g ruber and g bulloides agree with published dataand relationships for deep dwelling species mg ca calibration follows the equation mg ca 0 78 0 04 exp 0 051 0 003 t with a significant correlation coefficient of r

an intensity ratio calibration method for the accurate determination of mg ca and sr ca of marine carbonates by icp aes an inductively coupled plasma atomic emission spectroscopy icp aes method for the accurate and precise simultaneous measurement of the mg ca and sr ca content of carbonates was established while a precision of 0 3 1 standard deviation sd is easily obtainable for both mg ca and sr ca analysis a ca matrix effect complicates achieving similar levels of accuracy with conventional calibration procedures an alternative ratio calibration procedure is proposed which overcomes the ca matrix effects and ensures the accuracy of the mg ca and sr ca analysis of marine carbonates to 0 3 almost an order of magnitude better than conventional calibration methods the longer term precision is 0 1 if the batch run average values are corrected for longer term drift the method is suitable for analysis of foraminiferal calcite and coral aragonite and can easily be adjusted for the analysis of other carbonates or microsamples

reassessing mg ca temperature calibrations of neogloboquadrina pachyderma sinistral using paired δ44 40ca and mg ca measurements the mg ca temperature calibration of the polar to subpolar planktonic foraminifera neogloboquadrina pachyderma sinistral sinistral indicates left coiling was refined by a multiproxy approach combining hydrographic temperature and salinity data with mg ca delta ca 44 40 and delta o 18 values from holocene nordic seas core top samples reliable mg ca based temperature estimates are limited to foraminiferal tests that calcified in water masses with temperatures above similar to 3 degrees c at habitat depth in these samples mg ca and delta ca 44 40 values are positively correlated mg ca mmol mol 0 77 0 22 x delta ca 44 40 parts per thousand srm 915a 0 52 0 12 n 20 r 2 0 76 both mg ca and delta ca 44 40 derived temperatures projected onto their corresponding depth intervals reveal that the apparent calcification depth of n pachyderma sinistral averaging the specimens whole life cycle is bound to an isopycnal layer defined by water densities sigma t between 27 7 and 27 8 this implies that n pachyderma sinistral prefers gradually deeper habitats with increasing sea surface temperatures thus counterbalancing absolute temperature variations consequently the total temperature range recorded in this foraminiferal species is restricted and only partly reflects environmental changes on the basis of the new mg ca delta ca 44 40 and delta o 18 multiproxy data set we propose a linear mg ca temperature relation for high latitude n pachyderma sinistral mg ca mmol mol 0 13 0 037 t degrees c 0 35 0 17 t 3 degrees c in core top samples from polar waters with peak summer temperatures below similar to 3 degrees c the temperature response in the mg ca and delta ca 44 40 proxy signal is inversed and poorly correlated both mg ca and delta ca 44 40 derived temperature estimates pretend significantly higher calcification temperatures than maximum summer sea surface temperatures of these water masses

millennial scale fluctuations in north atlantic heat flux during the last 150 000 years abstract surface water and deep ocean palaeoclimate records obtained from north atlantic core su90 03 40 n 32 w exhibit pronounced fluctuations at sub orbital time scales surface temperature variability in the mid latitude atlantic over the last 150 kyr is dominated by forcing at precession 21 kyr and semi precession harmonics 11 kyr abrupt changes in sea surface temperatures show that the northward transport of heat by the north atlantic current was curtailed during ice rafting events sea surface temperatures were about 12 c colder than modern values during the most intense cooling episodes associated with major ice rafting events heinrich events 1 4 6 and 11 and 10 c below modern values during the later part of isotope stage 3 40 30 ka during these cold intervals the north atlantic current was displaced to south of 40 n as the cold meltwaters penetrated southwards into what is now the subtropical ocean these changes in surface ocean heat exchange were most probably allied to a latitudinal migration and increase in zonality of atmospheric circulation patterns concurrent shifts in ird concentration sea surface temperatures and benthic 13 c values provide evidence of coupling between sea surface processes and the deep water circulation and suggest that decreases in surface temperature and salinity during ice rafting events culminated in a significant reorganisation of north atlantic deep water production

ecological and temperature controls on mg ca ratios of globigerina bulloides from the southwest pacific ocean we present mg ca data for globigerina bulloides from 10 core top sites in the southwest pacific ocean analyzed by laser ablation inductively coupled plasma mass spectrometry la icpms mg ca values in g bulloides correlate with observed ocean temperatures 7 degrees c 19 degrees c and when combined with previously published data an integrated mg ca temperature calibration for 7 degrees c 31 degrees c is derived where mg ca mmol mol 0 955 x e 0 068 x t r 2 0 95 significant variability of mg ca values 20 30 was found for the four visible chambers of g bulloides with the final chamber consistently recording the lowest mg ca and is interpreted in part to reflect changes in the depth habitat with ontogeny incipient and variable dissolution of the thin and fragile final chamber and outermost layer concomitantly added to all chambers caused by different cleaning techniques prior to solution based icpms analyses may explain the minor differences in previously published mg ca temperature calibrations for this species if the lower mg ca of the final chamber reflects changes in depth habitat then la icpms of the penultimate or older chambers will most sensitively record past changes in near surface ocean temperatures mean size normalized g bulloides test weights correlate negatively with ocean temperature t 31 8 x e 30 5xwtn r 2 0 90 suggesting that in the southwest pacific ocean temperature is a prominent control on shell weight in addition to carbonate ion levels

determination of groundwater flow through regimes of shallow lakes and wetlands from numerical analysis of stable isotope and chloride tracer distribution patterns a numerical model previously developed to systematically examine groundwater flow in vertical section near shallow surface water bodies such as lakes wetlands and ponds is further developed to include simulation of the distribution patterns of hydrogeochemical and stable isotopic tracers in relation to the surface water body and the geometry of distribution patterns of the tracers in the groundwater release zone of the lake many different possible flow regimes are identified however in this paper attention is focused on flow through water bodies as these are the flow regimes observed in field validation two shallow lakes on the swan coastal plain of south west western australia are the subject of field studies where hydrogeochemical and stable isotopes are used to validate the flow through groundwater flow regime predicted by the modelling confirming the validity of the approach the flow regime transition diagrams introduced in earlier papers are extended to include consideration of the hydrogeochemical and stable isotopic indices cl l cl and 1000 l 1000 these ratios are introduced as an additional two of nine non dimensional ratios that are necessary to analyse the problem the ratios represent the chloride and isotopic composition ci l and l respectively in the groundwater release zones of the lakes relative to these parameters in the groundwater capture zone cl and for the lake field data from the case studies plotted on appropriately configured transition diagrams demonstrates the overall validity of the modelling approach and its underlying assumptions it is concluded that isotopic and hydrogeochemical data are invaluable in interpreting the interaction between lakes or wetlands and regional aquifers as it is very difficult to make physical or hydraulic measurements in the field that allow an understanding of lake aquifer interaction the tools and concepts developed that are summarized in the presented transition diagrams are invaluable starting points for the consideration and analysis of other case specific examples of groundwater surface water interaction and will improve the scientific basis of decision making concerning lake and wetland management and groundwater interaction by water resource and environmental managers

constraining ecological and biological bias in planktonic foraminiferal mg ca and δ18occ a multispecies approach to proxy calibration testing 1 parallel stable isotope 18occ and mg ca measurements performed in three planktonic foraminifer species provide multiple perspectives on past temperature change and thus allow published calibrations for these geochemical proxies to be tested against each other the comparison of simultaneous temperature records as recorded by both the 18occ and mg ca signature of each species reveals very clearly the nonpassive character of foraminifera as proxy carriers and allows the systematic temperature response of 18occ and mg ca in different foraminifer species to be explored on the basis of their mg ca signatures neogloboquadrina pachyderma right globigerina bulloides and globigerinoides ruber white are each found to exhibit a specific and narrow range of temperature variability however the interspecies offsets in optimum temperature habitat that are suggested in this way are not expressed by similarly scaled 18occ offsets hence it is demonstrated that the temperature modes variations that are recorded by each species cannot be calibrated to mg ca and 18occ variations via a single pair of calibrations for all three species species specific 18occ and or mg ca temperature calibrations are required on the basis of the average 18occ and mg ca offsets observed between the three species it appears that many of the temperature calibrations that are currently proposed for both of these proxies are inconsistent the data presented here cannot provide species specific mg ca and 18occ temperature calibrations however they do provide a simple method for testing our calibrations in application and clearly indicate that further calibration work using paired mg ca and 18occ is required before the full potential of these proxies may be realized

controls on stable isotope and trace metal uptake in neogloboquadrina pachyderma sinistral from an antarctic sea ice environment article the polar foraminifera neogloboquadrina pachyderma sinistral dominates assemblages from the high latitude southern ocean which plays a key role in determining past climate due to the tight linkage between antarctic temperature and atmospheric co2 here we use n pachyderma s harvested from sediment traps off the west antarctic peninsula to construct a seasonal time series for the calibration of calcite proxies in a high latitude seasonal sea ice environment where temperature is decoupled from other environmental parameters we have used a combination of 18 ocaco3 and 13 ccaco3 to decipher the calcification temperature and salinity which reflect that n pachyderma s live in surface waters throughout the year and at the ice water interface in austral winter further our results demonstrate that the uptake of trace metals into n pachyderma s calcite is influenced by secondary environmental conditions in addition to temperature during periods of sea ice cover we propose an elevated carbonate ion concentration at the ice water interface resulting from biological utilisation of co2 could influence calcification in foraminifera our calculations suggest that for n pachyderma s mg ca sr ca ratios and li ca ratios are linear functions of calcification temperature and co3 2 n pachyderma s mg ca ratios exhibit temperature sensitivity similar to previous studies 10 20 c and a sensitivity to co3 2 of 1 mol kg 1 sr ca ratios are less sensitive to environmental parameters exhibiting 5 increase c and 0 5 10 mol kg 1 the relationship between li ca ratios and both temperature and co3 2 is less significant with 10 increase in li ca ratio c and 10 mol kg 1 we show how a multi proxy approach could be used to constrain past high latitude surface

mid latitude southern indian ocean response to northern hemisphere heinrich events abstract the lack of temporal resolution and accurate chronology of southern ocean marine cores has hampered comparison of glacial millennial scale oscillations between the southern ocean antarctic ice and other records from both hemispheres in this study glacial climate variability is investigated over the last 50 ka using a multi proxy approach a precise chrono stratigraphy was developed on the high sedimentation rate core md94 103 indian southern ocean 45 35 s 86 31 e 3560 m water depth by geomagnetic synchronization between the later core and napis75 and 14c dates high resolution time series of 18o in planktonic foraminifera globigerina bulloides and neogloboquadrina pachyderma and sea surface temperatures ssts estimated from the alkenone uk 37 index and foraminifera assemblages have been generated temporal evolution of the two temperature proxy records is notably different during the last glacial period while foraminifera data indicate a consistent cooling towards the last glacial maximum anomalous warm glacial alkenone temperatures suggest a strong advection of warm detrital alkenones by surface waters of the agulhas current superimposed to this general trend during heinrich events foraminiferal ssts point to warmer surface waters while concurrent alkenone ssts exhibit apparent coolings probably caused by enhanced local alkenone production by analogy to modern observations possible influence of enso like conditions on the subantarctic southern ocean ssts is discussed

modelling co 2 brine rock interactions in the upper paleozoic formations of ordos basin used for co 2 sequestration subsurface immobilization and conversion of co2 into solid mineral phases in deep siliciclastic saline formations containing silicate minerals commonly known as mineral trapping is gaining research attention as a significant option to reduce co2 emissions in the atmosphere although mineral trapping of co2 is a long term process a combination of short term results from both laboratory experiments and numerical simulations can lead to some general understanding of the required long term co2 sequestration mechanisms this is a 100 year preliminary batch simulation study of four sandstone samples under co2 saturated water at 75 c from the upper permian formations in the ordos basin using the toughreact eco2n module to simulate the co2 brine rock interaction processes in deep siliciclastic multilayered saline aquifers the samples approximately correspond to the four target saline formations selected by the shenhua group for a co2 sequestration field demonstration project in the ordos basin pr china preliminary simulation results show that the initial salinity of formation brine plays a significant role in determining the amount of co2 that will be sequestered by solubility or mineral trapping in a deep saline aquifer minimal differences between experimental results and numerical calculation occur in low salinity waters and significantly larger differences in high salinity waters which is still under the maximum acceptable difference between experimental and computed data 10 the upper liujiagou formation with the highest level of salinity ca 88 7 g l tds and lowest level of co2 solubility offers the highest mineral trapping capacity with a maximum carbonate mineral storage of ca 0 7 kg m3 of bulk rock over a 100 year period regardless of the initial acidity or alkalinity of the aquifer brine injection of co2 will inflict a sudden drop in ph of the brine to acidity levels in a range of 3 0 4 6 the subsequent amount of dissolved and precipitated minerals arising from the co2 brine rock interaction is site specific and mainly dependent on initial aquifer mineralogy and brine composition

quaternary lakes of argentina abstract the quaternary lakes of argentina are grouped into eight main environments swamps and playas of the hernandaries formation middle quaternary of northeastern argentina pampean swamps chaco swamps swamps and shallow lakes of the parana system salt lakes of the puna northwestern salt lakes and playas glacial lakes of the southern cordillera and patagonian closed depressions

variations in mg ca and sr ca ratios of planktonic foraminifera caused by postdepositional dissolution evidence of shallow mg dependent dissolution a comparative study has been made of two species of planktonic foraminifera g tumida and g sacculifer in a depth transect on the ontong java plateau western equatorial pacific g tumida tests from core top sediments showed decreasing mg ca 2 65 1 25 mmol mol and sr ca 1 50 1 16 mmol mol ratios with increasing water depth 1600 4400 m while no such variation was found in g sacculifer tests in excess of 355 m average mg ca 3 6 mmol mol sr ca 1 4 mmol mol artificial dissolution of g tumida tests led to a decrease in both mg ca and sr ca but in g sacculifer there was no significant change in the ratios analyses by electron microprobe revealed that mg ca of the inner chamber calcite in g tumida tests was much higher than that of the calcite crust keel whereas sr ca was only slightly elevated there were no consistent spatial differences in either mg ca or sr ca for g sacculifer tests dissolution in the oceans gives rise to the removal of the chamber calcite in g tumida about 30 of the total calcite leaving the keel calcite although g tumida is thought of as a dissolution resistant form the majority of mg ca and sr ca depletion and chamber loss occurs above the lysocline it is also possible that much of the mg enriched gametogenic calcite has been lost by dissolution from g sacculifer above 1600 m mg content has a significant effect on the dissolution susceptibility of planktonic foraminifera calculations show that the saturation horizon for mg rich parts of tests may be elevated by several hundred meters compared with normal calcite

constraints on sst estimates for the northern north atlantic nordic seas during the lgm abstract a map of estimated calcification temperatures of the planktic foraminifer neogloboquadrina pachyderma sinistral tnps for the nordic seas and the northern north atlantic for the last glacial maximum was produced from oxygen isotopes with support of mg ca ratios to arrive at the reconstruction several constraints concerning the plausible salinity and 18 o fields were employed the reconstruction indicates inflow of temperate waters in a wedge along the eastern border of the nordic seas and at least seasonally ice free waters the reconstruction from oxygen isotopes shows similarities with mg ca based paleotemperatures in the southern and southeastern sector while unrealistically high mg ca values in the central nordic seas prevent the application of the method in this area the oxygen isotope based reconstruction shows some agreement with temperature reconstructions based on the modern analogue technique but with somewhat lower temperatures and a stronger internal gradient inside the nordic seas all told our results suggest a much more ice free and dynamic high latitude ocean than the climap reconstruction

asymmetric response of the subtropical western south atlantic thermocline to the dansgaard oeschger events of marine isotope stages 5 and 3 abstract the last glacial period 116 11 7 ka bp was an interval characterized by a sequence of abrupt millennial scale events well documented in greenland and antarctica ice cores throughout this period greenland cold stadials were accompanied by warm conditions in the thermocline to intermediate waters of the atlantic ocean that may have played a role in both the basal melting of ice shelves and the rapid atmospheric warming during the onset of warm interstadials climate model simulations indicated an accentuated response of the subtropical western south atlantic thermocline to the disturbances in the atlantic circulation such works encourage investigations upon thermocline deep dwelling planktic foraminifera in this region however a study with this aim was not performed here we present a paleoceanographic reconstruction from the subtropical western south atlantic based on the thermocline planktic foraminifera globorotalia inflata our high resolution 18o record for the last glacial period presents a millennial scale variability that strongly resembles the structure of the greenland dansgaard oeschger cycles during marine isotope stage mis 5 during mis 3 this millennial scale variability is absent or considerably dampened mg ca derived temperature and seawater 18o corrected for ice volume for the mis 5 interval demonstrate that the region was warmer and saltier colder and fresher during early glacial stadials interstadials our data suggest a reorganization of the northward heat transport throughout the last glacial in which regions as far south as 24 s acted as heat reservoirs in periods of weakened atlantic meridional overturning circulation during mis 5 but not necessarily or only marginally during mis 3

on the use of doppler shift for sea surface wind retrieval from sar the synthetic aperture radar sar doppler centroid has been used to estimate the scatter line of sight radar velocity in weak to moderate ocean surface current environment the sar doppler centroid is dominated by the directionality and strength of wave induced ocean surface displacements in this paper we show how this sea state signature can be used to improve surface wind retrieval from sar doppler shifts of c band radar return signals from the ocean are thoroughly investigated by colocating wind measurements from the ascat scatterometer with doppler centroid anomalies retrieved from envisat asar an empirical geophysical model function cdop is derived predicting doppler shifts at both vv and hh polarization as function of wind speed radar incidence angle and wind direction with respect to radar look direction this function is used into a bayesian inversion scheme in combination with wind from a priori forecast model and the normalized radar cross section nrcs the benefit of doppler for sar wind retrieval is shown in complex meteorological situations such as atmospheric fronts or low pressure systems using in situ information validation reveals that this method helps to improve the wind direction retrieval uncertainty of the calibration of doppler shift from envisat asar hampers the inversion scheme in cases where nrcs and model wind are accurate and in close agreement the method is however very promising with respect of future sar missions in particular sentinel 1 where the doppler centroid anomaly will be more robustly retrieved

seasonal mg ca variability of n pachyderma s and g bulloides implications for seawater temperature reconstruction given the importance of high latitude areas in the ocean climate system there is need for a paleothermometer that is reliable at low temperatures here we assess the applicability of the mg ca temperature proxy in colder waters 5 10 c by comparing for the first time the seasonal mg ca and 18o cycles of n pachyderma s and g bulloides using a sediment trap time series from the northern north atlantic while both species show indistinguishable seasonal 18o patterns that clearly track the near surface temperature cycle their mg ca are very different g bulloides mg ca is high 2 0 3 1 mmol mol but varies in concert with the seasonal temperature cycle the mg ca of n pachyderma s on the other hand is low 1 1 1 5 mmol mol and shows only a very weak seasonal cycle the 18o patterns indicate that both species calcify in the same depth zone consequently depth habitat differences cannot explain the contrasting mg ca patterns the elevated mg ca in pristine g bulloides might be due to the presence of high mg phases that are not preserved in fossil shells the contrasting absence of a seasonal trend in the mg ca of n pachyderma s confirms other studies where calcification temperatures were less well constrained the reason for this absence is not fully known but may include species specific vital effects the very different seasonal patterns of both species mg ca underscore the importance of parameters other than temperature in controlling planktonic foraminiferal mg ca our results therefore lend further caution in the interpretation of mg ca temperature reconstructions from high northern latitudes

core top calibration of mg ca in tropical foraminifera refining paleotemperature estimation 1 optimal use of mg ca as a paleotemperature proxy requires establishing calibrations for different species of foraminifera and quantifying the influence of dissolution to achieve this goal we have measured mg ca and 18o in a series of tropical and subtropical core tops including four depth transects the ceara rise the sierra leone rise and the rio grande plateau in the atlantic and the ontong java plateau in the pacific focusing on spinose mixed layer dwelling species globigerinoides ruber and globigerinoides sacculifer and nonspinose thermocline dwelling neogloboquadrina dutertrei shell mg ca in g sacculifer is 5 15 lower than in g ruber while n dutertrei mg ca is 49 55 lower than in g ruber this statistically significant offset has allowed us to establish different calibrations for each species multilinear regression analysis was used to develop calibration equations that include a correction term for the dissolution effect on mg ca in foraminiferal calcite presented in this paper are two sets of calibrations one set using core depth as a dissolution correction and another using co32 as a dissolution parameter the calibrations suggest that g ruber is the most accurate recorder of surface temperature while g sacculifer records temperatures below the surface at 20 30 m the depth habitat of n dutertrei is more uncertain owing to the wide range in habitat depths depending on hydrographic conditions but on average mg ca and 18o data suggest it is at 50 m of the three species n dutertrei is the most sensitive to dissolution up to 23 decrease in shell mg ca per km while g sacculifer is the most resistant

assessing the effect of dissolution on planktonic foraminiferal mg ca ratios evidence from caribbean core tops in order to assess the dissolution effect on foraminiferal mg ca ratios we analyzed mg ca of seven planktonic foraminiferal species and four of their varieties from caribbean core tops from 900 4700 m water depth depending on the foraminiferal species and variety mg ca start to decline linearly below co32 levels of 18 26 mol kg by 0 04 0 11 mmol mol per 1 mol kg co32 similar to decreases of 0 5 0 8 mmol mol per kilometer below 2500 3000 m water depth above these species specific critical levels mg ca remains stable with higher intraspecific mg ca variability than below we developed routines to correct mg ca from below these critical thresholds for dissolution effects which reduce the overall intraspecific variability by 24 64 and provide dissolution corrected mg ca appropriate to calculate holocene paleotemperatures when taking into account only dissolution unaffected mg ca from 2000 m the systematic succession of foraminiferal species according to their mg ca reflects expected calcification depths

hydrogeochemistry and isotope techniques to determine water interactions in groundwater dependent shallow lakes wet pampa plain argentina this paper gives an account of the implementation of hydrochemical and isotopic techniques to identify and explain the processes that govern solute exchange in two groundwater dependent shallow lakes in the southeastern pampa plain of argentina water samples lakes streams spring water and groundwater for hydrochemical and stable isotopic determination were collected and the main physical chemical parameters were measured the combination of stable isotope data with hydrogeochemical techniques was used for the identification of sources and preferential recharge areas to these aquatic ecosystems which allowed the explanation of the lake water origin the hydrochemical processes which explain los padres lake water chemistry are evaporation from groundwater co2 input calcite dissolution na release by ca2 and mg2 exchange and sulfate reduction the model that best aligns with la brava lake hydrochemical constraints includes mixing co2 and calcite dissolution cationic exchange with na release and mg2 adsorption and to a lesser extent ca na exchange this model suggests that the fractured aquifer contribution to this water body is greater than 50 an isotopic specific fingerprint for each lake was identified finding a higher evaporation rate for la brava lake compared to los padres lake isotopic data demonstrate the importance of these shallow lakes as recharge areas to the regional aquifer becoming areas of high groundwater vulnerability the tandilia range system considered in many hydrogeological studies as the impermeable bedrock of the pampean aquifer acts as a fissured aquifer in this area contributing to low salinity waters and with a fingerprint similar to groundwater isotopic composition

crystallinity of foraminifera shells a proxy to reconstruct past bottom water co3 changes 1 the reconstruction of past changes in bottom water co3 is central to evaluating competing oceanic scenarios that deal with long term variations in atmospheric pco2 in search of a quantitative bottom water co3 proxy we analyzed the variations of calcite crystallinity of planktonic foraminifera globigerinoides ruber shells picked from core top samples along three depth transects ontong java plateau and the northeast margin of irian jaya in the western equatorial pacific and the sierra leone rise in the eastern tropical atlantic the strong empirical relationship between calcite crystallinity inferred from the full width at half maximum fwhm of calcite 104 x ray diffraction peak and bottom water saturation relative to calcite co3 shows that foraminifera calcite crystallinity could be a promising proxy for the reconstruction of upper pleistocene bottom water carbonate ion concentration

mg ca in the planktonic foraminifera globorotalia inflata and globigerinoides bulloides from western mediterranean plankton tow and core top samples abstract due to its strong gradient in salinity and small temperature gradient the mediterranean provides an ideal setting to study the impact of salinity on the incorporation of mg into foraminiferal tests we have investigated tests of globorotalia inflata and globigerina bulloides in plankton tow and core top samples from the western mediterranean using icp oes for bulk analyses and la icp ms for analyses of individual chambers in single specimens mg ca observed in g inflata are consistent with existing calibrations whereas g bulloides had significantly higher mg ca than predicted particularly in core top samples from the easterly stations scanning electron microscopy and laser ablation icp ms revealed secondary overgrowths on some tests which could explain the observed high core top mg ca we suggest that the mediterranean intermediate and deep water supersaturated with respect to calcite cause these overgrowths and therefore increased bulk mg ca however the different species are influenced by diagenesis to different degrees probably due to different test morphologies our results provide new perspectives on reported anomalously high mg ca in sedimentary foraminifera and the applicability of the mg ca paleothermometry in high salinity settings by showing that 1 part of the signal is generated by precipitation of inorganic calcite on the foraminifer test due to increased calcite saturation state of the water and 2 species with high surface to volume shell surfaces are potentially more affected by secondary mg rich calcite encrustation

doppler velocity characteristics during tropical cyclones observed using scansar raw data doppler velocity can be derived by calculating doppler shift anomalies between predicted and estimated doppler centroids the predicted doppler centroid is calculated based on a geometric model of satellite assuming that the target is not moving the estimated doppler centroid can be directly extracted from the raw sar signal data by applying the average cross correlation coefficient method it is known that wind generated ocean waves can significantly contribute to doppler velocity due to the correlation between orbital motions of the waves and tilt and hydrodynamic modulated radar cross sections in addition to what sea surface current contributes in this study the characteristics of doppler velocities under hurricane conditions were investigated using radarsat 1 scansar raw data five different hurricanes hurricane dean hurricane ivan hurricane kyle hurricane lili and typhoon xangsane and sequential acquisitions of two hurricanes hurricane kyle and hurricane lili were selected to study the contribution of wind induced waves to doppler velocities and compared with in situ measurements of drifting buoys the results show that hurricane generated seas and associated winds and waves appear to be different from ordinary sea state this leads to lower estimates of doppler velocities than expected and much closer to sea surface current velocities

ventilation of the deep southern ocean and deglacial co2 rise past glacial interglacial increases in the concentration of atmospheric carbon dioxide co2 are thought to arise from the rapid release of co2 sequestered in the deep sea primarily via the southern ocean here we present radiocarbon evidence from the atlantic sector of the southern ocean that strongly supports this hypothesis we show that during the last glacial period deep water circulating around antarctica was more than two times older than today relative to the atmosphere during deglaciation the dissipation of this old and presumably co2 enriched deep water played an important role in the pulsed rise of atmospheric co2 through its variable influence on the upwelling branch of the antarctic overturning circulation

paired δ18o signals of neogloboquadrina pachyderma s and turborotalita quinqueloba show thermal stratification structure in nordic seas abstract the vertical density gradients in the nordic seas are crucial for the preconditioning of the surface water to thermohaline sinking in winter these gradients can be reconstructed from paired oxygen isotope data in tests of different species of planktonic foraminifera the isotopic signatures of which represent different calcification depths in the water column comparison of 18 o values from foraminiferal tests in plankton hauls sediment traps and nearby core top samples with the calculated 18 o calcite profile of the water column revealed species specific 18 o vital effects and the role of bioturbational admixture of subfossil specimens into the surface sediment on the basis of core top samples obtained along a west east transect across various hydrographic regions of the nordic seas 18 o values of turborotalita quinqueloba document apparent calcification depths within the pycnocline at 25 75 m water depth the isotopic signatures of neogloboquadrina pachyderma s reflect water masses near and well below the pycnocline between 70 and 250 m off norway where the atlantic inflow leads to thermal stratification here temperatures in the calcification depth of n pachyderma s differ from sea surface temperature by approximately 2 5 c in contrast n pachyderma s calcifies very close to the sea surface 20 50 m in the arctic domain of the western nordic seas however further west n pachyderma s prefers somewhat deeper more saline water at 70 130 m well below the halocline that confines the low saline east greenland current this implies that the 18 o values of n pachyderma s do not fully reflect the freshwater proportion in surface water and that any reconstruction of past meltwater plumes based on 18 o is too conservative because it overestimates sea surface salinity minimum 18 o differences n pachyderma s and t quinqueloba may serve as proxy for sea regions with dominant haline and absent thermal stratification whereas thermal stratification leads to 18 o differences of 0 4 to 1 5

coupled southern ocean cooling and antarctic ice sheet expansion during the middle miocene the middle miocene climate transition 14 million years ago was characterized by a dramatic increase in the volume of the antarctic ice sheet the driving mechanism of this transition remains under discussion with hypotheses including circulation changes declining carbon dioxide in the atmosphere and orbital forcing southern ocean records of planktic foraminiferal mg ca have previously been interpreted to indicate a cooling of 6 7 c and a decrease in salinity that preceded antarctic cryosphere expansion by up to 300 000 years this interpretation has led to the hypothesis that changes in meridional heat and vapour transport along with an early thermal isolation of antarctica from extrapolar climates played a fundamental role in triggering ice growth here we revisit the middle miocene southern ocean temperature evolution using clumped isotope and lipid biomarker temperature proxies our records indicate that the southern ocean cooling and the associated salinity decrease occurred in phase with the expansion of the antarctic ice sheet we demonstrate that the timing and magnitude of the southern ocean temperature change seen in previous reconstructions can be explained if we consider ph as an additional non thermal control on foraminiferal mg ca ratios therefore our new dataset challenges the view of a thermal isolation of antarctica preceding ice sheet expansion and suggests a strong coupling between southern ocean conditions and antarctic ice volume in times of declining atmospheric carbon dioxide antarctic ice volume expansion in the middle miocene coincides with southern ocean cooling according to biomarker and clumped isotope temperature records from south of tasmania

ocean surface features and currents measured with synthetic aperture radar interferometry and hf radar this paper describes the results of the first quantitative comparison between high resolution ocean surface current fields extracted from interferometric synthetic aperture radar insar measurements and those from a high frequency hf ocean surface current radar oscr system data from each of these radar systems along with supporting measurements from shipboard and buoy mounted sensors were collected during the high resolution remote sensing experiment high res on june 20 1993 on the continental shelf off the coast of cape hatteras north carolina both components of the surface current were obtained from the insar system at roughly 10 m resolution from two orthogonal flight legs over the region separated in time by about 30 min the oscr system measured two dimensional surface current vectors at about 1 km resolution over this same region while the usns bartlett was collecting hydrographic samples and near surface current measurements two dimensional wave spectra as well as meteorological and additional current measurements were collected at two buoys within the experimental area we discuss in the paper two techniques for eliminating the effect of surface wave motion on the insar current estimates one method relies on some knowledge of the local wind and wave field and the use of a microwave scattering model the other method makes use of a few in situ current measurements spaced at different range locations across the insar image using either of these techniques we find that the agreement between the insar and oscr current estimates is generally very good furthermore the insar current and magnitude imagery show the presence of undulating surface features where abrupt changes in the current speed and direction occurred the ship surveys indicate that these features were caused by the collision of water masses of different density we show for the first time in this paper a high resolution area extensive vector surface current map derived from the insar of the two dimensional flow in the vicinity of these features our results demonstrate convincingly that high resolution oceanic surface current vectors can be derived from insar current measurements and that these measurements may be very beneficial for detailed studies of the dynamics of small scale surface features in regions of strong current divergences or shears

relationships between temperature ph and crusting on mg ca ratios in laboratory grown neogloboquadrina foraminifera author s davis cv fehrenbacher js hill tm russell ad spero hj abstract 2017 american geophysical union all rights reserved mg ca ratio paleothermometry in foraminifera is an important tool for the reconstruction and interpretation of past environments however existing mg ca temperature relationships for planktic species inhabiting middle and high latitude environments are limited by a lack of information about the development and impact of low mg ca ratio crusts and the influence of the carbonate system on mg ca ratios in these groups to address this we cultured individual specimens of neogloboquadrina incompta and neogloboquadrina pachyderma in seawater across a range of temperature 6 12 c and ph 7 4 8 2 we found by laser ablation inductively couple mass spectrometry analyses of shells that culture grown crust calcite in n incompta had a lower mg ca ratio than ontogenetic calcite formed at the same temperature suggesting that temperature is not responsible for the low mg ca ratio of neogloboquadrinid crusts the mg ca temperature relationship for ontogenetic calcite in n incompta was consistent with the previously published culture based relationship and no significant relationship was found between mg ca ratios and ph in this species however the mg ca ratio in laboratory cultured n pachyderma was much higher than that reported in previous core top and sediment trap samples due to lack of crust formation in culture application of our ontogenetic calcite specific mg ca temperature relationships to fossil n pachyderma and n incompta from five intervals in cores from the santa barbara basin and the bering sea shows that excluding crust calcite in fossil specimens may improve mg ca based temperature estimates

neogloboquadrina pachyderma dex and sin mg ca and δ18o records from the norwegian sea magnesium calcium mg ca records based on n pachyderma dex and n pachyderma sin from the last 1200 years have been retrieved from high resolution cores in the norwegian sea comparing temperatures inferred from mg ca and the oxygen isotopic composition of calcite 18oc with instrumental temperature records from ocean weather ship mike suggests that n pachyderma calcifies during the summer season with an offset to oxygen isotope equilibrium of 0 6 in this region summer temperatures below the thermocline are related to the winter season ventilation and breakdown of the seasonal thermocline hence the deeper dwelling n pachyderma sin provides a winter season signal down core n pachyderma dex mg ca temperatures display larger variance than observed in 18oc temperatures record derived from the same morphotype the smaller variance in the 18ocn pachyderma dex temperatures is probably linked to salinity changes in the upper 50 m of the water column the mg ca temperature and 18oc records are used to reconstruct changes in the oxygen isotopic composition of water 18ow during the last 1200 years the reconstructed 18ow records show variation within a realistic range allowing the influence of other water masses than those present at the site today and suggest that the mg ca signal in morphotypes of n pachyderma in the norwegian sea responds to changes in climatic parameters

the residence time of southern ocean surface waters and the 100 000 year ice age cycle from 1 25 million to 700 000 years ago the ice age cycle deepened and lengthened from 41 000 to 100 000 year periodicity a transition that remains unexplained using surface and bottom dwelling foraminifera from the antarctic zone of the southern ocean to reconstruct the deep to surface supply of water during the ice ages of the past 1 5 million years we found that a reduction in deep water supply and a concomitant freshening of the surface ocean coincided with the emergence of the high amplitude 100 000 year glacial cycle we propose that this slowing of deep to surface circulation i e a longer residence time for antarctic surface waters prolonged ice ages by allowing the antarctic halocline to strengthen which increased the resistance of the antarctic upper water column to orbitally paced drivers of carbon dioxide release

refining globigerinoides ruber mg ca paleothermometry in the atlantic ocean abstract the mg ca ratio of the planktonic foraminifera globigerinoides ruber white has become a widely used proxy for reconstructing sea surface temperature sst as numerous studies have shown that temperature is the primary control on mg ca ratios in foraminiferal calcite however a recent study of core top sediments across an atlantic meridional transect suggests that salinity might have a stronger control on foraminiferal mg ca ratios than previously thought by analyzing mg ca ratios and o 18 values in g ruber white arbuszewski et al 2010 found a 27 increase in g ruber mg ca ratios per 1 salinity unit increase for seawater salinities above 35 5 here we use shell weight analyses and sem images from a subset of the core tops used in the arbuszewski et al 2010 study across a narrow depth range 3197 3733 m to show that g ruber shells from the equatorial region are highly dissolved compared to those from the subtropical north and south atlantic gyres significantly impacting their mg ca ssts shell weights from the higher productivity equatorial region of the atlantic are on average 20 and 15 lower than those from the oligotrophic north and south atlantic gyres respectively given the large preservation gradient along the transect studied by arbuszewski et al 2010 application of a single dissolution corrected mg ca sst calibration equation dekens et al 2002 on cores from the subtropical gyres and the equatorial region is not appropriate when regional differences in preservation are considered as well as realistic habitat depths and calcification seasons for g ruber in temperate latitudes we find a strong correlation between observational ssts and calculated g ruber mg ca ssts in core top samples spanning 43 n to 25 s in the atlantic in addition our re calibrated mg ca ssts are more strongly correlated with isotopic calcification temperatures across the transect than originally reported by arbuszewski et al 2010 this study provides evidence that regional differences in preservation rather than salinity significantly affects g ruber mg ca ssts in the atlantic and supports culturing experiments that found salinity only has a minor influence on foraminiferal mg ca ratios

global dissolution effects on planktonic foraminiferal mg ca ratios controlled by the calcite saturation state of bottom waters mg ca ratios of planktonic foraminiferal tests are important tools for reconstructing past ocean temperatures at different levels of the upper water column yet numerous studies suggest a significant influence of calcite dissolution on mg ca ratios lowering their initial signal recorded within a planktonic foraminiferal habitat to determine the effect of dissolution this study presents mg ca ratios of eight planktonic foraminiferal species from the south china sea sediment surface continuously decreasing with increasing water depth the mg ca ratios also decrease with calcite saturation states close to and below saturation bottom water delta co32 40 mu mol kg 1 this preservation pattern compares well with examples of mg ca dissolution from the tropical atlantic ocean and is independent of the foraminiferal species merging a global data set by separate normalization of 79 mg ca data sets from the pacific atlantic and indian oceans which removes thermal differences between the ocean regions and foraminiferal species enabled us to quantify a global decrease in planktonic foraminiferal mg ca ratios of 0 054 0 019 mu mol mol 1 per mol kg 1 below a critical threshold for dissolution of 21 3 6 6 mu mol kg 1 the absolute decline in mg ca ratios which is similar for all species affects temperature estimates from sub thermocline species more strongly than those from shallow dwellers the water depth of this critical threshold in the global oceans shoals from 3 5 km in the north atlantic to 0 5 km in the north pacific based on calculations of the global calcite saturation state from 6321 hydrographic stations above this critical threshold mg ca ratios are well preserved and paleotemperature estimates are broadly unaffected by dissolution

mg ca in foraminifera from plankton tows evaluation of proxy controls and comparison with core tops abstract calibrations and validations of the mg ca paleothermometer in planktic foraminifera have traditionally been performed by means of core tops sediment trap samples and culture experiments in this study mg ca ratios have been measured in 8 species of planktic foraminifera non globorotaliids globigerina bulloides neogloboquadrina incompta orbulina universa globigerinoides ruber white and g sacculifer and globorotaliids globorotalia inflata g hirsuta and g truncatulinoides collected live from the north atlantic the southeast atlantic the northeast pacific and the norwegian sea mg ca ratios for n incompta o universa g ruber g sacculifer and g truncatulinoides are similar to available north atlantic core top studies and consistent with previous calibration equations in contrast some g bulloides g inflata and g hirsuta mg ca ratios are higher than predicted based on 18 o values and exhibit considerable scatter this elevation may be in part related to the impact of potential isotopic disequilibrium effects on 18 o derived temperatures which the mg ca ratios are compared to another factor that may affect mg ca ratios in some plankton samples is the lack of low mg test components e g final chambers or gametogenic calcite because of the incompleteness of the life cycle at the time of collection n incompta mg ca ratios are correlated with salinity with mg ca changing about 16 per salinity unit suggesting that salinity may have an important influence on mg ca of some species even in non extreme salinity environments this is the first extensive multispecific plankton tow mg ca data set from different oceanographic regions which has been used to test the mg ca temperature proxy in the context of published calibration data highlighting the complex physiological ecological controls on the acquisition of the proxy signal

calibration of mg ca thermometry in planktonic foraminifera from a sediment trap time series 1 paired mg ca and 18o measurements on planktonic foraminiferal species g ruber white g ruber pink g sacculifer g conglobatus g aequilateralis o universa n dutertrei p obliquiloculata g inflata g truncatulinoides g hirsuta and g crassaformis from a 6 year sediment trap time series in the sargasso sea were used to define the sensitivity of foraminiferal mg ca to calcification temperature habitat depths and calcification temperatures were estimated from comparison of 18o of foraminifera with equilibrium calcite based on historical temperature and salinity data when considered together mg ca mmol mol of all species except two show a significant r 0 93 relationship with temperature t c of the form mg ca 0 38 0 02 exp 0 090 0 003 t equivalent to a 9 0 0 3 change in mg ca for a 1 c change in temperature small differences exist in calibrations between species and between different size fractions of the same species o universa and g aequilateralis have higher mg ca than other species and in general data can be best described with the same temperature sensitivity for all species and pre exponential constants in the sequence o universa g aequilateralis g bulloides g ruber g sacculifer other species this approach gives an accuracy of 1 2 c in the estimation of calcification temperature the 9 sensitivity to temperature is similar to published studies from culture and core top calibrations but differences exist from some literature values of pre exponential constants different cleaning methodologies and artefacts of core top dissolution are probably implicated and perhaps environmental factors yet understood planktonic foraminiferal mg ca temperature estimates can be used for reconstructing surface temperatures and mixed and thermocline temperatures using g ruber pink g ruber white g sacculifer n dutertrei p obliquiloculata etc the existence of a single mg thermometry equation is valuable for extinct species although use of species specific equations will where statistically significant provide more accurate evaluation of mg ca paleotemperature

impact of biomineralization processes on the mg content of foraminiferal shells a biological perspective the mg ca ratio in foraminiferal shells is widely used as a proxy for paleotemperatures nevertheless it seems that the basic mg content of foraminifera is determined by biological factors as can be concluded from the large inter species and intrashell variability and the frequent deviations from inorganic behavior this paper discusses three possible ways by which foraminifera can control or modify the mg content in their shell 1 involvement of organic matrix in the precipitation process that may alter the partition coefficient of mg in biogenic calcite 2 controlled conversion of transient amorphous phases to calcite and 3 modification of the mg concentration in the parent solution from which the crystals precipitate the first two mechanisms are probably responsible for the precipitation of high mg calcite phases whole shell or sublayers while the third mechanism leads to the formation of low mg calcite phases we propose a model adapted from epithelial cells that allows massive mg2 removal from the biomineralization site this model is especially relevant to the planktonic and deep benthic low mg foraminifera that are frequently used for paleotemperature reconstructions we discuss the possible biological roles of mg in the shell in terms of the calcite polymorph conservation the in vivo chemical stability of the shell the functions of mg as a stabilizer of transient phases and as a controlling agent of the precipitation process several temperature sensitive biological processes that may influence the mg ca ratio of the shell are suggested and a model that combines biogenic and inorganic considerations is presented the model uses mg heterogeneity in the shell together with temperature response biologic and inorganic of biomineralization processes to account for the deviation of planktonic foraminifera from inorganic calcite at equilibrium with seawater

planktonic foraminiferal flux seasonality in subantarctic sediment traps a test for paleoclimate reconstructions sediment trap moorings deployed during 1997 and 1998 in the subantarctic to polar frontal regions of the southern ocean reveal distinct seasonality in foraminiferal flux foraminiferal assemblages vary between each site yet major species exhibit very similar patterns of seasonal succession which can be associated with changes in mixed layer depth enhanced foraminiferal productivity is also associated with periods of high biogenic silica and particulate organic carbon flux on a broader scale foraminiferal assemblages are strongly delineated by temperature temperature estimates derived from the assemblages using the modern analog technique mat are mostly within 2 5 c of the satellite advanced very high resolution radiometer temperatures observed during the deployment period this indicates that core top sediments included in the mat database do reflect modern observed conditions at the sea surface providing a robust technique for estimating past temperature change from foraminiferal assemblages in southern ocean environments

a high resolution record of late quaternary upwelling along the oman margin arabian sea based on planktonic foraminifera planktonic foraminiferal abundances fluxes test sizes and coiling properties are influenced in various ways by the southwest monsoon winds and associated upwelling in the western arabian sea to determine the short term changes in the southwest monsoon we have carried out a high resolution time series analysis of three upwelling indices total flux of planktonic foraminiferal tests and flux and relative abundance of the planktonic foraminiferal species globigerina bulloides from ocean drilling program odp site 723a oman margin western arabian sea spanning the last 19 kyr in addition we have determined the relationships between upwelling intensity and the relative abundance fluxes and shell concentrations of various planktonic foraminiferal species upwelling indices suggest that from 19 to 16 ka 22 to 18 2 cal kyr b p the sw monsoon was relatively strong compared to the period 15 8 to 12 5 ka 17 8 to 13 8 cal kyr b p the intensification of the sw monsoon took place at 12 ka 13 1 cal kyr b p and reached a peak between 10 and 5 ka 10 6 and 4 8 cal kyr b p the high resolution data further demonstrate that the sw monsoon has started weakening from 5 ka 4 8 cal kyr b p and the weakest phase was in place at 3 5 ka 3 cal kyr b p which coincides with evidence of an arid climate in western tibet fluxes and shell concentrations of many of the planktonic foraminiferal species increased between 12 and 5 ka in response to the intensification of the sw monsoon winds after the last glacial period globigerina bulloides shows a fivefold to tenfold increase in flux during this period of intense upwelling the other species whose fluxes are influenced by this upwelling change are in order from strongest to weakest response globigerinita glutinata globigerinoides ruber neogloboquadrina dutertrei globigerinella aequilateralis globigerina falconensis and globigerinoides sacculifer the relative abundances of g bulloides and g ruber increased during intense upwelling whereas the relative abundances of g glutinata n dutertrei g falconensis and g sacculifer did not increase during this period which might be due to differences in the productivity of various species in relation to upwelling change therefore the fluxes and shell concentrations provide better and more reliable information about the changes in the monsoon system in the arabian sea than relative abundance data

hydrochemistry of pampasic ponds in the lower stream bed of salado river drainage basin argentina chemical analyses of major ions were performed in some of the pampasic ponds in the lower stream bed of salado river drainage basin results indicated that total dissolved solids had a mean value of 1341 mg l where sodium was the most abundant of the cations 80 2 and chloride 44 2 and bicarbonate 37 4 were the predominant anions saturation index showed oversaturation with respect to calcite and dolomite since groundwater is the main source of surface water high sodium concentration in the ponds may be explained by a cation exchange process in the loessic sediments of the basin where calcium is replaced by sodium

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

current measurements by sar along track interferometry from a space shuttle we present one of the first studies on ocean current retrievals from interferometric synthetic aperture radar insar data acquired during the shuttle radar topography mission srtm in february 2000 the insar system of srtm was designed for high resolution topographic mapping of the earth s land surfaces using two sar antennas on a space shuttle with a cross track separation of 60 m an additional along track antenna separation of 7 m resulted in an effective time lag of about 0 5 ms between the two images which could theoretically be exploited for target velocity retrievals however the feasibility of ocean current measurements with srtm has been questionable since the time lag was much shorter than the theoretical optimum about 3 ms at x band and the signal to noise ratio over water was quite low nevertheless some x band insar images of coastal areas exhibit clear signatures of tidal flow patterns as an example we discuss an image of the dutch wadden sea we convert the insar data into a line of sight current field which is then compared with results of the numerical circulation model kustwad for tidal phases close to the conditions at the time of the srtm overpass we obtain correlation coefficients of up to 0 6 and rms differences on the order of 0 2 m s furthermore we find that srtm resolves current variations down to spatial scales on the order of 1 km this is consistent with predictions of a numerical insar imaging model remaining differences between srtm and kustwad derived currents can be attributed mainly to residual motion errors in the srtm data as well as to a limited representation of the conditions at the time of the srtm overpass in the available kustwad results

neogene dinoflagellate cysts and acritarchs from the high northern latitudes and their relation to sea surface temperature organic walled dinoflagellate cysts and acritarchs are a vital tool for reconstructing past environmental change in particular in the neogene of the high northern latitudes where marine deposits are virtually barren of traditionally used calcareous microfossils yet only little is known about the paleoenvironmental value of fossil assemblages that do not have modern analogues so that reconstructions remain qualitative thus extracting their paleoecological signals still poses a major challenge in particular on pre quaternary timescales here we unravel the relationship between species relative abundance and sea surface temperature for extinct dinoflagellate cyst and acritarch taxa from the neogene of the iceland sea using palynological assemblages and organic geochemical alkenone data generated from the same set of samples the reconstructed temperatures for the miocene to pliocene sequence of ocean drilling program site 907 range from 3 to 26 c and our database consists of 68 dinoflagellate cyst and acritarch samples calibrated to alkenone data the temperature range of five extant species co occurring in the fossil assemblage agrees well with their present day distribution providing confidence to inferred temperature ranges for extinct taxa the 14 extinct dinoflagellate cyst and acritarch species clearly exhibit a temperature dependency in their occurrence throughout the analysed section the dinoflagellate cyst species batiacasphaera hirsuta labyrinthodinium truncatum cerebrocysta irregulare cordosphaeridium minimum impagidinium elongatum and operculodinium centrocarpum s s and the acritarch lavradosphaera elongatum which are confined to the miocene have highest relative abundances and restricted temperature ranges at the warm end of the reconstructed temperature spectrum the latter five species disappear when iceland sea surface temperatures permanently drop below 20 c thus indicating a distinct threshold on their occurrence in contrast species occurring in both the miocene and pliocene interval batiacasphaera micropapillata habibacysta tectata reticulatosphaera actinocoronata cymatiosphaera invaginata show a broader temperature range and a tolerance towards cooler conditions operculodinium eirikianum may have a lower limit on its occurrence at around 10 c the calibration of species relative abundance versus reconstructed sea surface temperature provides a quantitative assessment of temperature ranges for extinct miocene to pliocene species indicating that temperature is a decisive ecological factor for regional extinctions that may explain the frequently observed asynchronous highest occurrences across different ocean basins it demonstrates that qualitative assessments of ecological preferences solely based on paleo biogeographic distribution should be treated with caution in addition to enhancing knowledge on marine palynomorph paleoecology this study ultimately improves the application of palynomorphs for paleoenvironmental reconstructions in the neogene of the arctic and subarctic seas a region essential for understanding past global climate

glacial differences of southern ocean intermediate waters in the central south pacific abstract southern ocean intermediate waters soiws such as antarctic intermediate water and subantarctic mode water play a key role in modulating the global climate on glacial interglacial time scales they link the southern ocean and the tropics via mechanisms such as oceanic tunneling that transport climatic signals across latitudes despite their importance the past evolution of the soiws in the central south pacific is largely unknown here we compare paired mg ca temperature stable carbon 13c and oxygen 18o isotope records from surface dwelling and deep dwelling planktic foraminifera to infer changes in the water column structure for the last 260 ka in the central south pacific 54 s our study focuses on the subsurface oceanographic variability controlled by soiws which are subducted at the subantarctic front our data show that the subsurface ocean in the central south pacific was colder and fresher during glacial stages than during the holocene 0 10 ka bp suggesting a general glacial enhanced presence of antarctic intermediate water in agreement with previous studies from the eastern equatorial pacific and the southeast pacific however the subsurface ocean salinity differs for both glacial stages with fresher condition during the last glacial maximum lgm 26 5 19 ka bp and more saline condition during the penultimate glacial maximum pgm 155 140 ka bp the 13c data also show contrasting conditions for both glacial time windows in the upper water column with a large depletion of 0 37 in 13c from the lgm values suggests a larger contribution of old low 13c deep waters at intermediate depths at the study site during the pgm plausibly due to stronger upwelling in high southern latitudes the dissimilar scenarios between the lgm and the pgm may have been caused by processes that are analogous to the phase switch in modern day southern annular mode

distribution of living planktonic foraminifera in the ross sea and the pacific sector of the southern ocean antarctica abstract in order to determine the factors controlling the distribution of planktonic foraminifera as a proxy for reconstruction of paleoenvironments we present data on live assemblages collected in the southern ocean plankton tows and hydrographic measurements were taken in the upper 400 m of the water column at different sites in the ross sea site b and at the polar front of the pacific ocean site o during austral summers from 1998 to 2003 based on qualitative micropaleontological observations we discriminated between neogloboquadrina pachyderma dextral dex and n pachyderma sinistral sin in addition for n pachyderma sin we distinguished four morphs the first one 1 has a thickened test and depressed sutures the second morph 2 is represented by specimens characterized by a subspheric and heavily encrusted test the third morph 3 has a thin and lobate walled test the fourth one 4 represent the juvenile stage of n pachyderma sin and is characterized by a smaller average size the microfauna collected in the ross sea site b is characterized by the dominance of n pachyderma sin morphs 1 and 2 whereas low occurrences of turborotalia quinqueloba n pachyderma dex and neogloboquadrina dutertrei were noted in the first 50 m of the water column the water column at this station is characterized by a marked and shallow stratification and a marked thermocline during the sampling season at the ocean station site o the assemblage shows increasing diversification t quinqueloba g bulloides n pachyderma dex and few specimens of globigerinita uvula characterize the planktonic microfauna there is a predominance of non encrusted morphs and juvenile specimens 3 and 4 at this station the mixed surface layer is deeper than in the ross sea 60 70 m the pycnocline and the thermocline less marked the depth and the intensity of the deep chlorophyll maximum dcm influence foraminiferal distribution n pachyderma sin shows abundance peaks at or just below the dcm while g bulloides peaks above the dcm coiling direction of n pachyderma seems to be not controlled exclusively by sea surface temperature sst probably the two coiling types are genetically different results document that diversity of planktonic foraminifera number of specimens and variations in test morphology are related to regional differences in water properties temperature salinity and dcm depth

direct ocean surface velocity measurements from space improved quantitative interpretation of envisat asar observations previous analysis of advanced synthetic aperture radar asar signals collected by esa s envisat has demonstrated a very valuable source of high resolution information namely the line of sight velocity of the moving ocean surface this velocity is estimated from a doppler frequency shift consistently extracted within the asar scenes the doppler shift results from the combined action of near surface wind on shorter waves longer wave motion wave breaking and surface current both kinematic and dynamic properties of the moving ocean surface roughness can therefore be derived from the asar observations the observations are compared to simulations using a radar imaging model extended to include a doppler shift module the results are promising comparisons to coincident altimetry data suggest that regular account of this combined information would advance the use of sar in quantitative studies of ocean currents

mg ca thermometry in planktic foraminifera improving paleotemperature estimations for g bulloides and n pachyderma left planktic foraminiferal mg ca ratios have become a fundamental seawater temperature proxy in past climate reconstructions due to the temperature dependence of mg uptake into foraminiferal calcite however empirical calibrations for single species from methodologically consistent data are still lacking here we present species specific calibrations of mg ca versus calcification temperature for two commonly used species of planktic foraminifera globigerina bulloides and neogloboquadrina pachyderma left based on a series of southern ocean and north atlantic core tops combining these new data with previously published data we derive an integrated g bulloides mg ca temperature calibration for mid and high latitudes of both hemispheres between 2 and 18 c where mg ca 1 006 0 032 e0 065 0 003 tiso r2 0 82 g bulloides is found to calcify deeper in the southern ocean 200 m than in the north atlantic top 50 m we also propose a mg ca temperature calibration to describe the temperature response in n pachyderma left that calcified away from the influence of sea ice in the southern ocean valid between 1 and 9 c of the form mg ca 0 580 0 016 e0 084 0 006 tiso r2 0 70 these calibrations account for uncertainties on mg ca measurements and calcification temperature that were carefully estimated and propagated using monte carlo iterations the 1 propagated error in mg ca derived temperatures is 1 1 c for g bulloides and 0 9 c for n pachyderma left for the presented data sets geographical extension of genotypes must be assessed when choosing to develop regional or global calibrations

mg ca of globorotalia inflata as a recorder of permanent thermocline temperatures in the south atlantic 1 we present a species specific mg ca calcification temperature calibration for globorotalia inflata from a suite of 38 core top samples from the south atlantic from 8 s to 49 s g inflata is a deep dwelling planktonic foraminifer commonly occurring in subtropical to subpolar conditions which qualifies it for reconstructions of the permanent thermocline apparent calcification depths and calcification temperatures were determined by comparing measured 18o with equilibrium 18o of calcite based on water column properties based on our core top samples g inflata apparent calcification depth is constant throughout the south atlantic midlatitudes with a depth of 350 400 m within the permanent thermocline the resulting mg ca calcification temperature calibration is mg ca 0 72 0 045 0 042 exp 0 076 0 006 calcification temperature r2 0 81 and covers the temperature range 3 1 c 16 5 c we applied our mg ca calibration to gravity core ps2495 3 from the mid atlantic ridge at 41 s to test its validity by reconstructing a low resolution record covering the last two glacial interglacial cycles our paleotemperature record reveals large changes in temperature for terminations i and ii when permanent thermocline temperature increased by as much as 8 c the g inflata paleotemperature record suggests that oceanic fronts repeatedly migrated over the location of core ps2495 3 during the last 160 kyr this study shows the potential of g inflata mg ca to reconstruct paleotemperatures in the permanent thermocline

temporal and spatial structure of multi millennial temperature changes at high latitudes during the last interglacial the last interglacial lig 129e116 thousand of years bp ka represents a test bed for climate model feedbacks in warmer than present high latitude regions however mainly because aligning different palaeoclimatic archives and from different parts of the world is not trivial a spatio temporal picture of lig temperature changes is difficult to obtain here we have selected 47 polar ice core and sub polar marine sediment records and developed a strategy to align them onto the recent aicc2012 ice core chronology we provide the first compilation of high latitude temperature changes across the lig associated with a coherent temporal framework built between ice core and marine sediment records our new data synthesis highlights non synchronous maximum temperature changes between the two hemispheres with the southern ocean and antarctica records showing an early warming compared to north atlantic records we also observe warmer than present day conditions that occur for a longer time period in southern high latitudes than in northern high latitudes finally the amplitude of temperature changes at high northern latitudes is larger compared to high southern latitude temperature changes recorded at the onset and the demise of the lig we have also compiled four data based time slices with temperature anomalies compared to present day conditions at 115 ka 120 ka 125 ka and 130 ka and quantitatively estimated temperature uncertainties that include relative dating errors this provides an improved benchmark for performing more robust model data comparison the surface temperature simulated by two general circulation models ccsm3 and hadcm3 for 130 ka and 125 ka is compared to the corresponding time slice data synthesis this comparison shows that the models predict warmer than present conditions earlier than documented in the north atlantic while neither model is able to produce the reconstructed early southern ocean and antarctic warming our results highlight the importance of producing a sequence of time slices rather than one single time slice averaging the lig climate conditions

radar derived interferometric surface currents and their relationship to subsurface current structure radar derived ocean surface currents are analyzed in conjunction with in situ acoustic doppler current profiler adcp measurements the interferometric measurements were collected by an x band imaging doppler radar in a manner analogous to those of along track interferometric synthetic aperture radar ati sar while the advent of ati sar has provided a new potentially powerful technique for current mapping the relationship between surface currents and interferometric velocity measurements is not yet clearly understood this paper presents comparisons between radar derived and in situ current measurements to develop a precise method for estimating the surface current from interferometric measurements the influence of long wave orbital velocities and the influence of bragg resonant waves are studied we find that coupling between the orbital velocity and backscattered power i e the modulation transfer function can bias surface current estimates potentially by up to 20 cm s 1 in an upwind viewing orientation furthermore experimental observations verify a cos 2n 0 2 analytical model for the directional spreading of bragg resonant waves extending our analysis to include subsurface currents case studies are presented under varying environmental conditions for which the vertical current structure changes considerably analysis of radar imagery yields both radial surface currents and vector subsurface current estimates derived from long wave dispersion characteristics combining these with coincident adcp measurements yields a vertical profile of current using these measurement techniques we make several observations within the upper meter of the ocean these profiles reveal the sensitivity of x band interferometric measurements to wind drift and the near surface current structure

glacial interglacial changes in subantarctic sea surface temperature and δ18o water using foraminiferal mg laboratory culturing experiments with living globigerina bulloides indicate that mg ca is primarily a function of seawater temperature and suggest that mg ca of fossil specimens is an effective paleotemperature proxy using culturing results and a core top neogloboquadrina pachyderma calibration we have estimated glacial interglacial changes in sea surface temperature sst using planktonic mg ca records from core rc11 120 in the subantarctic indian ocean 43 s 80 e and core e11 2 in the subantarctic pacific ocean 56 s 115 w our results suggest that glacial sst was about 4 c cooler in the subantarctic indian ocean and 2 5 c cooler in the subantarctic pacific comparison of sst and planktonic 18o records indicates that changes in sst lead changes in 18o by on average 1 3 kyr the glacial interglacial temperature change indicated by the subantarctic mg ca records suggests that temperature accounts for 40 60 of the foraminiferal 18o change we have used the mg ca based sst estimates and 18o determinations to generate site specific seawater 18o records which suggest that seawater 18o was on average 1 more positive during glacial episodes compared with interglacial episodes

interlaboratory comparison study of calibration standards for foraminiferal mg ca thermometry an interlaboratory study of mg ca and sr ca ratios in three commercially available carbonate reference materials bam rs3 cmsi 1767 and ecrm 752 1 was performed with the participation of 25 laboratories that determine foraminiferal mg ca ratios worldwide these reference materials containing mg ca in the range of foraminiferal calcite 0 8 mmol mol to 6 mmol mol were circulated with a dissolution protocol for analysis participants were asked to make replicate dissolutions of the powdered samples and to analyze them using the instruments and calibration standards routinely used in their laboratories statistical analysis was performed in accordance with the international standardization organization standard 5725 which is based on the analysis of variance anova technique repeatability rsdr an indicator of intralaboratory precision for mg ca determinations in solutions after centrifuging increased with decreasing mg ca ranging from 0 78 at mg ca 5 56 mmol mol to 1 15 at mg ca 0 79 mmol mol reproducibility rsdr an indicator of the interlaboratory method precision for mg ca determinations in centrifuged solutions was noticeably worse than repeatability ranging from 4 5 at mg ca 5 56 mmol mol to 8 7 at mg ca 0 79 mmol mol results of this study show that interlaboratory variability is dominated by inconsistencies among instrument calibrations and highlight the need to improve interlaboratory compatibility additionally the study confirmed the suitability of these solid standards as reference materials for foraminiferal mg ca and sr ca determinations provided that appropriate procedures are adopted to minimize and to monitor possible contamination from silicate mineral phases

δ18o seasonality of planktonic foraminifera from southern ocean sediment traps latitudinal gradients and implications for paleoclimate reconstructions abstract the oxygen isotopic record obtained from globigerina bulloides globorotalia inflata and neogloboquadrina pachyderma s was analysed for 5 sediment traps moored in the southern ocean and southwest pacific the traps extend from subtropical to the polar frontal environments providing the first analysis of seasonal foraminiferal 18 o records from these latitudes comparison between the foraminiferal records and various equations for predicted 18 o of calcite reveals that the predicted 18 o is best captured by the equations of epstein et al 1953 epstein s buchsbaum r lowenstam h a urey h c 1953 revised carbonate water isotopic temperature scale geological society of america bulletin 64 1315 1326 and kim and o neil 1997 kim s t o neil j r 1997 equilibrium and non equilibrium oxygen isotope effects in synthetic carbonates geochimica et cosmochimica acta 61 3461 3475 the epstein equation shows a constant offset from the 18 o of g bulloides and n pachyderma s across the full range of latitudes the seasonal range in 18 o values for these two species implies a near surface habitat across all sites while g inflata most likely dwells at 50 m depth a significant finding in this study was that offsets from predicted 18 o for g bulloides do not correlate to changes in the carbonate ion concentration this suggests that co 3 2 in and of itself may not capture the full range of carbonate chemistry conditions in the marine system this sediment trap deployment also reveals distinct seasonal flux patterns for each species comparison between flux weighted isotopic values calculated from the sediment traps and the isotopic composition of nearby surface sediments indicates that the sedimentary records retain this seasonal imprint at the 51 s site g bulloides has a spring flux peak while n pachyderma s is dominated by summer production the imprint of these differing seasonal production patterns on the flux weighted 18 o values results in more depleted 18 o for n pachyderma s than for g bulloides interpretations of n pachyderma s isotopic composition as a record of subsurface conditions may therefore need to be refined with implications for interpretation of depleted glacial 13 c for this species sigman boyle 2000 sigman d m boyle e a 2000 glacial interglacial variations in atmospheric carbon dioxide nature 407 859 869

determination of the mg mn ratio in foraminiferal coatings an approach to correct mg ca temperatures for mn rich contaminant phases the occurrence of manganese rich coatings on foraminifera can have a significant effect on their bulk mg ca ratios thereby biasing seawater temperature reconstructions the removal of this mn phase requires a reductive cleaning step but this has been suggested to preferentially dissolve mg rich biogenic carbonate potentially introducing an analytical bias in paleotemperature estimates in this study the geochemical composition of foraminifera tests from mn rich sediments from the antarctic southern ocean odp site 1094 was investigated using solution based and laser ablation icp ms in order to determine the amount of mg incorporated into the coatings the analysis of planktonic and benthic foraminifera revealed a nearly constant mg mn ratio in the mn coating of 0 2 mol mol consequently the coating mg mn ratio can be used to correct for the mg incorporated into the mn phase by using the down core mn ca values of samples that have not been reductively cleaned the consistency of the coating mg mn ratio obtained in this study as well as that found in samples from the panama basin suggests that spatial variation of mg mn in foraminiferal mn overgrowths may be smaller than expected from mn nodules and mn ca carbonates however a site specific assessment of the mg mn ratio in foraminiferal coatings is recommended to improve the accuracy of the correction