the physicochemical habitat of sclerolinum sp at hook ridge hydrothermal vent bransfield strait antarctica at hook ridge hydrothermal vent a new species of sclerolinum monilifera siboglinidae was found at a water depth of 1 045 m on the basis of investigations of multicores and gravity cores the species habitat is characterized sclerolinum does not occur in sediments that are most strongly influenced by hydrothermal fluids probably because of high temperature up to 49 c and precipitation of siliceous crusts about 800 individuals m 2 occur in sediments that are only weakly exposed to hydrothermal flow and have the following characteristics 20 c 15 cm sediment depth to 21 5 c bottom water 18 40 cm yr 1 advection rates ph 5 5 25 mol l 1 methane 170 mol l 1 sulfide and 0 0054 mol m 2 yr 1 sulfide flux comparison with geochemical data from other reducing sediments indicates that the two groups of siboglinidae monilifera and frenulata occur in sediments with low sulfide concentration and flux in contrast sulfurbased chemosynthetic organisms that typically occur at hydrothermal vents and cold seeps e g vestimentifera vesicomyid clams and bacterial mats occur in sediments with higher sulfide availability threshold values are around 500 mol l 1 sulfide and 0 1 mol m 2 yr 1 sulfide fluxes we did not find typical hydrothermal vent species at hook ridge hydrothermal vent which might be explained by the unfavorable physicochemical habitat at sites inhabited by sclerolinum sulfide availability appears to be too low whereas at sites with higher sulfide availability the temperatures might be too high siliceous crust precipitation could preclude their occurrence or both

assessing the reliability of magnesium in foraminiferal calcite as a proxy for water mass temperatures though many studies on the mg contents in the calcitic tests of foraminifers exist the processes controlling its uptake are still a matter of debate laboratory cultures offer an excellent opportunity to reveal these mechanisms the mg concentrations within single chambers of the planktic foraminifer globigerinoides sacculifer brady maintained under controlled laboratory conditions were measured 1 at variable temperatures 19 5 29 5 c and constant salinity and 2 at variable salinity 22 45 and constant temperature the experimental results suggest that under natural conditions temperature is the leading mechanism controlling the mg ca ratio temperature and magnesium are related proportionally a temperature increase of ca 10 c gives rise to an increase of the magnesium concentrations of ca 130 drastic unnatural salinity changes dominate the effects of temperature a 110 change in the mg ca ratio was observed when salinity was elevated or reduced by more than ca 10 specimens which underwent gametogenesis reveal significantly higher mg concentrations than specimens that did not release gametes partition coefficients for mg in foraminiferal calcite are orders of magnitude lower than values from inorganically precipitated calcite when comparing observed mg ca ratios of foraminiferal tests with predicted mg ca ratios calculated according to empirical equations it becomes evident that foraminiferal tests are undersaturated with respect to mg for the water temperature they have experienced apparently foraminifers are capable of controlling their mg concentration the physiological processes presumably responsible for such depressed mg ca ratios appear to be temperature controlled as deduced from the close relationship of the observed mg ca ratios and water temperature this study demonstrates that variations in temperature and salinity are definitely reflected in the mg content of foraminiferal tests magnesium may thus serve as a paleo proxy for past surface water temperatures as long as postdepositional changes and salinity variations are of subordinate importance or can be excluded

the effects of temperature salinity and the carbonate system on mg ca in globigerinoides ruber white a global sediment trap calibration abstract the mg ca of planktic foraminifera globigerinoides ruber white is a widely applied proxy for tropical and sub tropical sea surface temperature the accuracy with which temperature can be reconstructed depends on how accurately relationships between mg ca and temperature and the multiple secondary controls on mg ca are known however these relationships remain poorly quantified under oceanic conditions here we present new calibrations based on 440 sediment trap plankton tow samples from the atlantic pacific and indian oceans including 130 new samples from the bay of bengal arabian sea and the tropical atlantic ocean our results indicate temperature salinity and the carbonate system all significantly influence mg ca in g ruber white we propose two calibration models the first model assumes ph is the controlling carbonate system parameter in this model mg ca has a temperature sensitivity of 6 0 0 8 c 2 a salinity sensitivity of 3 3 2 2 psu and a ph sensitivity of 8 3 7 7 0 1 ph units the second model assumes carbonate ion concentration co 3 2 is the controlling carbonate system parameter in this model mg ca has a temperature sensitivity of 6 7 0 8 c a salinity sensitivity of 5 0 3 0 psu and a co 3 2 sensitivity of 0 24 0 11 mol kg 1 in both models the temperature sensitivity is significantly lower than the widely applied sensitivity of 9 0 0 6 c application of our new calibrations to down core data from the last glacial maximum considering whole ocean changes in salinity and carbonate chemistry indicate a cooling of 2 4 1 6 c in the tropical oceans if ph is the controlling parameter and 1 5 1 4 c if co 3 2 is the controlling parameter

surface and subsurface seawater temperature reconstruction using mg ca microanalysis of planktonic foraminifera globigerinoides ruber globigerinoides sacculifer and pulleniatina obliquiloculata laser ablation inductively coupled plasma mass spectrometry microanalyses of mg ca across individual final chambers of three planktonic foraminifera species globigerinoides ruber g sacculifer and pulleniatina obliquiloculata reveal significant interspecies differences in test mg concentrations whereas these three species have similar mg ca values at low sea surface temperatures similar to 22 degrees c they diverge markedly at high sea surface temperatures similar to 29 degrees c explanations for these differences in species mg ca values based on detailed comparison of species intratest mg ca distributions suggest that compositional variability within tests cannot account for the observed deviation of species mg ca values in warm water equatorial regions multiple regression modeling and delta o 18 analysis of globigerinoides sacculifer tests indicate that interspecies differences in mg ca values result from different depth habitats the average mg ca values of g ruber final chambers reflect the temperature of the surface mixed layer 0 25 m whereas those of g sacculifer and pulleniatina obliquiloculata correlate best with subsurface temperatures at 50 75 m and 100 125 m water depths respectively mg ca calibration to the temperatures at these depths reveals a similar temperature control on mg test composition in all species combining our results with mg ca values from published culturing experiments we derive a generalized equation for the effect of temperature and seawater salinity on foraminiferal mg ca we also show that the mg ca composition of specific calcite layers within foraminiferal tests including the low mg ca layers of globigerinoides ruber and g sacculifer and the cortex layer of pulleniatina obliquiloculata correlates with seawater temperature and can be used as an additional proxy for seawater temperature

comment on the treatment of residual water content in a consistent set of parametric models for the two phase flow of immiscible fluids in the subsurface by l luckner et al

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

uniqueness and stability analysis of hydrogeophysical inversion for time lapse ground penetrating radar estimates of shallow soil hydraulic properties precise measurement of soil hydraulic properties at field scales is one of the prerequisites to simulate subsurface flow and transport processes which is crucial in many research and engineering areas in our study we numerically analyze uniqueness and stability for integrated hydrogeophysical inversion of time lapse off ground ground penetrating radar gpr data in estimating the unsaturated soil hydraulic properties in the inversion hydrodynamic modeling based on the one dimensional 1 d richards equation is used to physically constrain a full waveform radar electromagnetic model synthetic gpr data in terms of 3 d multilayered media green s functions were generated for three different textured soils coarse medium and fine and assuming different infiltration events inversion was performed iteratively to estimate three key soil hydraulic parameters n and ks of the mualem van genuchten model using the global multilevel coordinate search optimization algorithm for the coarse and medium textured soils inversions converged to the actual solution for all scenarios for the fine soil estimation errors occurred mainly because of the higher attenuation of the electromagnetic waves in such a soil high electric conductivity the procedure appeared to be generally stable with respect to possible errors in the hydrodynamic and petrophysical model parameterization however we found that particular attention should be given to an accurate estimation of the saturated water content and infiltration flux for real field applications the results from our numerical experiments suggest that in theory the proposed method is promising for the noninvasive identification of the shallow soil hydraulic properties at the field scale with a high spatial resolution

indo pacific warm pool variability during the holocene and last glacial maximum we measured oxygen isotopes and mg ca ratios in the surface dwelling planktonic foraminifer globigerinoides ruber white s s and the thermocline dweller pulleniatina obliquiloculata to investigate upper ocean spatial variability in the indo pacific warm pool ipwp we focused on three critical time intervals the last glacial maximum lgm 18 21 5 ka the early holocene 8 9 ka and the late holocene 0 2 ka our records from 24 stations in the south china sea timor sea indonesian seas and western pacific indicate overall dry and cool conditions in the ipwp during the lgm with a low thermal gradient between surface and thermocline waters during the early holocene sea surface temperatures increased by similar to 3 degrees c over the entire region indicating intensification of the ipwp however in the eastern indian ocean timor sea the thermocline gradually shoaled from the lgm to early holocene reflecting intensification of the subsurface indonesian throughflow itf increased surface salinity in the south china sea during the holocene appears related to northward displacement of the monsoonal rain belt over the asian continent together with enhanced influx of saltier pacific surface water through the luzon strait and freshwater export through the java sea opening of the freshwater portal through the java sea in the early holocene led to a change in the vertical structure of the itf from surface to thermocline dominated flow and to substantial freshening of timor sea thermocline waters

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

in situ calcium carbonate dissolution in the pacific ocean over the past several years researchers have been working to synthesize the woce jgofs global co2 survey data to better understand carbon cycling processes in the oceans the pacific ocean data set has over 35 000 sample locations with at least two carbon parameters oxygen nutrients cfc tracers and hydrographic parameters in this paper we estimate the in situ caco3 dissolution rates in the pacific ocean water column calcium carbonate dissolution rates ranging from 0 01 1 1 mmol kg1 yr1 are observed in intermediate and deepwater beginning near the aragonite saturation horizon in the north pacific intermediate water between 400 and 800 m caco3 dissolution rates are more than 7 times faster than observed in middle and deep water depths average 0 051 mmol kg1 yr1 the total amount of caco3 that is dissolved within the pacific is determined by integrating excess alkalinity throughout the water column the total inventory of caco3 added by particle dissolution in the pacific ocean north of 40s is 157 pg c this amounts to an average dissolution rate of approximately 0 31 pg c yr1 this estimate is approximately 74 of the export production of caco3 estimated for the pacific ocean these estimates should be considered tomore be upper limits for in situ carbonate dissolution in the pacific ocean since a portion of the alkalinity increase results from inputs from sediments less

glacial holocene biogenic sedimentation patterns in the south china sea productivity variations and surface water pco2 a bathymetric transect of cores in the south china sea extending from 4200 m to less than 1000 m water depth has been examined for glacial interglacial changes in carbonate and organic carbon sedimentation typical pacific carbonate cycles high carbonate content during glacials and low carbonate content during interglacials characterize cores from water depths deeper than 3500 m in contrast atlantic carbonate cycles low carbonate during glacials and high carbonate during interglacials are observed in cores from depths shallower than 3000 m as a result of increased dilution of carbonate by terrigenous material during glacial low stands of sea level glacial interglacial changes in the carbonate chemistry of south china sea intermediate and deep waters resulted in significant changes in the positions of the carbonate compensation depth ccd and the aragonite compensation depth acd during the last glacial the ccd and acd were at least 400 and 1200 m deeper respectively than at present organic carbon accumulation rates in the south china sea were approximately 2 times higher during the last glacial than the holocene carbon isotopic analyses and c n ratios of the organic matter indicate that only a small fraction of the increase in glacial organic carbon accumulation can be attributed to input of terrestrial carbon on the basis of this we conclude that surface water productivity in the south china sea was approximately 2 times higher during the last glacial maximum this is consistent with previous studies which have demonstrated that glacial productivity was higher in low to mid latitude regions of the atlantic and eastern pacific the deglacial decrease in organic carbon accumulation is accompanied by a decrease in 13corg using the relationship between 13corg and co2 aq developed by popp et al 1989 we estimate that surface water pco2 values in the south china sea during the last 25 000 years were very similar to atmospheric co2 concentrations

links between salinity variation in the caribbean and north atlantic thermohaline circulation variations in the strength of the north atlantic ocean thermohaline circulation have been linked to rapid climate changes1 during the last glacial cycle through oscillations in north atlantic deep water formation and northward oceanic heat flux2 3 4 the strength of the thermohaline circulation depends on the supply of warm salty water to the north atlantic which after losing heat to the atmosphere produces the dense water masses that sink to great depths and circulate back south2 here we analyse two caribbean sea sediment cores combining mg ca palaeothermometry with measurements of oxygen isotopes in foraminiferal calcite in order to reconstruct tropical atlantic surface salinity5 6 during the last glacial cycle we find that caribbean salinity oscillated between saltier conditions during the cold oxygen isotope stages 2 4 and 6 and lower salinities during the warm stages 3 and 5 covarying with the strength of north atlantic deep water formation7 at the initiation of the bolling allerod warm interval caribbean surface salinity decreased abruptly suggesting that the advection of salty tropical waters into the north atlantic amplified thermohaline circulation and contributed to high latitude warming

novel observations on biomineralization processes in foraminifera and implications for mg ca ratio in the shells stable isotopes and trace elements in foraminifera shells are important for determining the paleochemistry of the ocean and mg ca ratios and 1 8 o values in foraminifera have recently been used to determine simultaneously the temperature and salinity of past oceans however large variations between species and significant mg intra shell heterogeneity indicate a major role for biological factors in determining the mg ca ratio in foraminifera our novel in vivo observations on the biomineralization process of perforate foraminifera show that their calcareous wall is composed of two different calcite types a thin high mg primary layer and low mg layers that cover the primary layer on both sides the data may suggest that two biomineralization pathways are employed in the formation of the different calcite types a new conceptual framework is provided to explain part of the mg heterogeneity in foraminiferal shells and the variable sensitivity of the mg ca ratio to temperature in different species

depth distributions of alkalinity tco2 and δ13ctco2 at seats time series site in the northern south china sea abstract in this study measurements of titration alkalinity ta total dissolved carbon dioxide tco2 and 13c of tco2 13 c tco 2 throughout the water column at the southeast asian time series study seats site were investigated in order to understand better the fundamental processes controlling their vertical distributions in the south china sea scs the linear correlations between ta and salinity in the shallow waters as identified by the mixing line between the surface water and salinity maximum water suggested the predominant control of physical mixing on the variability of ta in contrast tco2 and 13 c tco 2 showed the non conservative behavior in the respective tco2 and 13 c tco 2 vs salinity plot due to the effect of biological production a stoichiometric model further showed that the depth profile of nta ta salinity 35 largely reflects the increase of preformed nta in the shallow waters whereas carbonate dissolution was responsible for the continuous increase of nta in the deep waters a one dimensional diffusion advection model further revealed that the carbonate dissolution could account for 28 of ntco2 tco2 salinity 35 increase in deep waters and the remaining 72 of ntco2 was from organic decomposition calculation of excess ta further showed that it emerged well above the aragonite and calcite saturation depths at 600 and 2500 m respectively indicating that some biologically chemically and physically mediated processes must be involved to provide excess ta into the shallow waters the decrease in 13 c tco 2 with depth primarily resulted from organic decomposition the influence of anthropogenic co2 throughout the water column was assessed with the carbon chemistry and the isotope based approach in this study both methods obtained nearly the same results in which the signal of anthropogenic co2 decreased exponentially with depth and its penetration depth were found to be at 1000 m the inventory of anthropogenic co2 in the water column was estimated to be 16 6 mol c m 2 which was less than that reported in the northwest pacific at the same latitude presumably due to the enhanced upwelling in the scs such an anthropogenic co2 penetration had led to decreases of the saturation levels of aragonite and calcite by 17 and 14 respectively in the surface water and an upward migration of aragonite saturation depth by 100 m since industrial revolution

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

paleosecular variations of the geomagnetic field during the holocene from eastern asia abstract high resolution paleomagnetic secular variation psv records bear great information of dynamics processes of the earth s geomagnetic field and can be further used for inter profile correlation and for dating sediments however effects of changes in the depositional environment on psv records have not been fully determined this study constructed holocene psv records for the gravity piston core zsqd34 obtained from the northern south china sea rock magnetic and transmission electron microscope tem results indicate that single sd and psd domain magnetites are the main carrier of the natural remanent magnetization comparable to the records derived from the freshwater lakes and the modeling results we observed that direction curves from these two environments of contrasting salinity content are rather consistent the direction curves are independent of the constructed salinity however the gradual increasing trend of relative intensity since about 5 kyr might be related to the decreasing sea surface salinity furthermore on the centennial and millennial time scale the relative intensity and salinity show some positive relation suggesting a potential contribution of salinity to the paleomagnetic relative intensity recording processes

contrasting seasonal fluxes of planktonic foraminifera and impacts on paleothermometry in the mozambique channel upstream of the agulhas current 1 we assess d 18 o and mg ca based paleothermometry in relation to seasonal variations in the shell fluxes of the surface dwelling planktonic foraminifera g ruber and g trilobus using deep moored sediment traps in the mozambique channel upstream of the agulhas current we find a distinct antiphase response to the annual cycle in sea surface temperature sst in g ruber and g trilobus maximum fluxes of g ruber occur in late austral summer february march when sst ranges between 28 7 c and 30 3 c by contrast g trilobus maxima appear in early winter june july at a lower sst between 25 3 c and 27 0 c cross correlation of the 2 5 year time series data confirmed that the g ruber g trilobus ratio r t ratio closely followed the annual cycle in sst as did their paired d 18 o and mg ca in all proxies g ruber showed a 3 week phase lag against sst and g trilobus of 6 weeks consistent with semi lunar population turnover rates in combination with a 1 week settling time to the 2500 m deep ocean floor after correcting for these lags we derived five independent equations for improved paleothermometry in the southwestern indian ocean that specify flux weighted annual mean sst the offset between flux weighted sst of g ruber and g trilobus and annual mean instrumental sst is about 0 8 c despite their strong seasonality in shell export this is far less than the mean difference in instrumental sst between summer and winter of 3 2 c both species therefore closely reflect annual mean sst in sediments within a margin of 0 5 c for g ruber and 0 3 c for g trilobus w e also find that multiple linear regression of the five proxies r t ratio and the d 18 o mg ca of g ruber and g trilobus strongly reduces the effects of fast rotating eddies and improves the correlation coefficient from an r 2 of 0 4 to an r 2 of 0 8

mg ca ratios of two globigerinoides ruber white morphotypes implications for reconstructing past tropical subtropical surface water conditions 1 tests of the planktonic foraminifer globigerinoides ruber white d orbigny have become a standard tool for reconstructing past oceanic environments paleoceanographers often utilize the mg ca ratios of the foraminiferal tests for reconstructing low latitude ocean glacial interglacial changes in sea surface temperatures sst we report herein a comparison of mg ca measurements on sample pairs n 20 of two g ruber white morphotypes g ruber sensu stricto s s and g ruber sensu lato s l from surface and downcore samples of the western pacific and indian oceans g ruber s s refers to specimens with spherical chambers sitting symmetrically over previous sutures with a wide high arched aperture whereas g ruber s l refers to a more compact test with a diminutive final chamber and small aperture the g ruber s s specimens generally show significantly higher mg ca ratios compared to g ruber s l our results from the mg ca ratio analysis suggest that g ruber s l specimens precipitated their shells in slightly colder surface waters than g ruber s s specimens this conclusion is supported by the differences in 18o and 13c values between the two morphotypes although it is still unclear if these two morphotypes represent phenotypic variants or sibling species our findings seem to support the hypothesis of depth and or seasonal allopatry within a single morphospecies

effects of seawater carbonate ion concentration and temperature on shell u mg and sr in cultured planktonic foraminifera we investigate the sensitivity of u ca mg ca and sr ca to changes in seawater co3 and temperature in calcite produced by the two planktonic foraminifera species orbulina universa and globige rina bulloides in laboratory culture experiments our results demonstrate that at constant temperature u ca in o universa decreases by 25 7 per 100 mol co3 k g 1 as seawater co3 increases from 110 to 470 mol kg 1 results from g bulloides suggest a similar relationship but u ca is consistently offset by 40 at the same environmental co3 in o universa u ca is insensitive to temperature between 15 c and 25 c applying the o universa relationship to three u ca records from a related species globigerinoides sacculifer we estimate that caribbean and tropical atlantic co3 was 110 70 mol kg 1 and 80 40 mol kg 1 higher respectively during the last glacial period relative to the holocene this result is consistent with estimates of the glacial interglacial change in surface water co3 based on both modeling and on boron isotope ph estimates in settings where the addition of u by diagenetic processes is not a factor down core records of foraminiferal u ca have potential to provide information about changes in the ocean s carbonate concentration below ambient ph ph 8 2 mg ca decreased by 7 5 o universa t o 16 6 g bulloides per 0 1 unit increase in ph above ambient ph the change in mg ca was not significant for either species this result suggests that mg ca based paleotemperature estimates for the quaternary during which surface ocean ph has been at or above modern levels have not been biased by variations in surface water ph sr ca increased linearly by 1 6 0 4 per 0 1 unit increase in ph shell mg ca increased exponentially with temperature in o universa where mg ca 0 85 exp 0 096 t whereas the change in sr ca with temperature was within the reproducibility of replicate measurements copyright 2004 elsevier ltd

high resolution uk 37 temperature reconstructions in the south china sea over the past 220 kyr past sea surface temperatures sst in the northern and southern areas of the south china sea have been reconstructed for the past 220 kyr using the uk37 alkenone index the sst profiles follow the glacial interglacial pattern exhibiting differences between last glacial maximum and holocene that are 1 3 c larger than those observed at the same latitudes in the atlantic and pacific oceans in termination i both planktonic foraminiferal 18o and sst exhibit well defined bolling allerod and younger dryas events with temperature differences between both periods of 0 8 and 0 4 c in north and south respectively ssts record a constant north south difference of 1 c in the interglacials and nearly 2 5 c in the glacial stages these differences define two distinct climatic and water circulation patterns that correspond with glacial interglacial sea level oscillations which opened and closed water exchange with the tropical indo pacific ocean through the present sunda shelf

accurate estimation of sea surface temperatures using dissolution corrected calibrations for mg ca paleothermometry 1 paired 18o and mg ca measurements on the same foraminiferal shells offer the ability to independently estimate sea surface temperature sst changes and assess their temporal relationship to the growth and decay of continental ice sheets the accuracy of this method is confounded however by the absence of a quantitative method to correct mg ca records for alteration by dissolution here we describe dissolution corrected calibrations for mg ca paleothermometry in which the preexponent constant is a function of size normalized shell weight 1 for g ruber 212 300 m mg ca ruber 0 025 wt 0 11 e0 095t and b for g sacculifer 355 425 m mg ca sacc 0 0032 wt 0 181 e0 095t the new calibrations improve the accuracy of sst estimates and are globally applicable with this correction eastern equatorial atlantic sst during the last glacial maximum is estimated to be 2 9 0 4 c colder than today

shallow depth caco3 dissolution evidence from excess calcium in the south china sea and its export to the pacific ocean national basic research program of china 973 program 2009cb421201 2009cb421206 national science foundation of china nsfc 40821063 90711005 south china sea institute of oceanology the chinese academy of sciences

comparison of atlantic and pacific paleochemical records for the last 215 000 years changes in deep ocean circulation and chemical inventories abstract detailed cd ca and 13 c data have been obtained for benthic foraminifera from western north atlantic and equatorial pacific sediment cores in the modern ocean both tracers are closely linked to nutrient distributions the sedimentary records for both tracers indicate that bottom waters overlying the atlantic site have been nutrient depleted relative to those at the pacific site over the last 215 000 years from this evidence it is reasonable to infer that there has been a continuous net flux of nutrient depleted water from the western north atlantic into the pacific this exchange has undergone significant fluctuations with the export of nutrient depleted atlantic water diminishing by about a factor of two relative to the inflow from southern ocean sources over the last 215 000 years carbon isotope fluctuations in both regions are dominated by variable storage of isotopically light carbon on continents with a lesser contribution from these deep ocean circulation changes the cadmium signal in the north atlantic is dominated by changes in deep ocean circulation patterns cadmium shows less variability in the pacific which may reflect changes in the global average cadmium content or minor changes in deep pacific circulation patterns using these records to estimate global averages it appears that glacial ocean water had 22 more cd and 0 46 less 13 c than the modern ocean these numbers are estimates which may be revised as more data become available although they are not likely to be as much as 20 in error for cd or 0 2 for 13 c relative north atlantic deep water nadw formation rates are modulated with a significant 41 kyr periodicity linked to obliquity induced variations in high latitude insolation nadw lags 8 2 kyr behind insolation however

estimating glacial western pacific sea surface temperature methodological overview and data compilation of surface sediment planktic foraminifer faunas abstract we present a detailed comparison of five transfer function techniques calibrated to reconstruct sea surface temperature sst from planktic foraminifer counts in western pacific surface sediments the techniques include the imbrie kipp method ikm modern analog technique mat modern analog technique with similarity index simmax revised analog method ram and the artificial neural network technique ann the calibration is based on a new database of 694 census counts of planktic foraminifers in coretop samples from the western pacific compiled under a cooperative effort within the margo multiproxy approach for the reconstruction of the glacial ocean surface project all five techniques were used to reconstruct sst variation in a well dated holocene to last glacial maximum interval in core md972151 from the southern south china sea scs to evaluate the magnitude of cooling in the western tropical pacific during the lgm our results suggest that mat simmax ram and ann show a similar level of performance in sst estimation and produce 1 c uncertainties in coretop sst calibrations of the western pacific when applying these techniques to the downcore faunal record the ikm which performed significantly worst in the calibration exercise produced glacial sst estimates similar to present day values whereas the other four techniques all indicated 1 c cooler glacial sst because of their better performance in the calibration dataset and because of the convergence among the techniques in the estimated magnitude of glacial cooling in the studied core we conclude that mat simmax ram and ann provide more robust planktic foraminifer paleo sst estimates than traditional ikm techniques in western pacific paleoceanographic studies

seasonal variation of planktonic foraminiferal isotopic composition from sediment traps in the south china sea abstract the imprint of seasonal hydrographic changes on two widely distributed tropical subtropical planktonic foraminifer species globigerinoides sacculifer without sac and globigerinoides ruber white variety has been investigated using specimens collected in sediment traps deployed in the northern south china sea scs october 2000 october 2002 the faunal assemblage is dominated by g ruber during the warm summer months whereas g sacculifer is consistently present year round at abundances of less than 20 in general the measured 18o and 13c isotopic compositions of g ruber are more depleted than those of g sacculifer and the 18o difference between seasons summer vs winter is comparable to that of the local glacial interglacial cycle ca 1 the lowest 13c values are associated with relatively heavy 18o values in january and march for both species and suggest higher nutrient levels in the surface water that are likely related to the prevailing winter monsoon this speculation is supported by the increase in terrigenous input to the traps brought by the winter monsoon the ratio between 18o and 13c in g ruber is approximately two times that of g sacculifer with a 18o 13c slope of 1 18 vs 0 55 and differs from that in most biogenic carbonates 0 25 0 33 based on culture and field studies which indicate enhanced kinetic fractionation at higher ambient carbonate ion concentrations co3 however similar regression slopes of 18o 13c 0 52 to 0 6 are also derived for g sacculifer collected from plankton tows factors other than the carbonate ion effect hence appear to be responsible for the negative relationship between 18o and 13c in this region

in situ fluxes and zonation of microbial activity in surface sediments of the hakon mosby mud volcano from the hakon mosby mud volcano hmmv on the southwest barents sea shelf gas and fluids are expelled by active mud volcanism we studied the mass transfer phenomena and microbial conversions in the surface layers using in situ microsensor measurements and on retrieved cores the hmmv consists of three concentric habitats a central area with gray mud a surrounding area covered by white mats of big sulfide oxidizing filamentous bacteria beggiatoa and a peripheral area colonized by symbiontic tube worms pogonophora a fourth habitat comprised gray microbial mats near gas seeps the differences between these four methane fueled habitats are best explained by different transport rates of sulfate into the sediments and pore water upflow rates the upflow velocities were estimated by two independent methods at 3 6 m yr21 in the central area and 0 3 1 m yr21 in beggiatoa mats in the central area no sulfide was found indicating that the rapidly rising sulfate free fluids caused sulfate limitation that inhibited anaerobic oxidation of methane aom under beggiatoa mats a steep sulfide peak was found at 2 to 3 cm below the seafloor bsf most likely due to aom all sulfide was oxidized anaerobically possibly through nitrate reduction by beggiatoa the beggiatoa mats were dominated by a single filamentous morphotype with a diameter of 10 mm and abundant sulfur inclusions a high diversity of sulfide oxidizer morphotypes was observed in a grayish microbial mat near gas vents where aerobic sulfide oxidation was important the sediments colonized by pogonophora were influenced by bioventilation allowing sulfate penetration and aom to 70 cm bsf the hmmv is a unique and diverse ecosystem the structure and functioning of which is mainly controlled by pore water flow

mud volcanoes the most important pathway for degassing deeply buried sediments abstract this paper discusses the nature of the phenomenon of mud volcanism with respect to degassing of deeply buried sediments mud volcanoes are defined as geological structures and their main elements are described based on the nature of activity mud volcanoes are grouped in to three main types and the relationship between each type and corresponding morphological expression is discussed the presented up to date data of the world geographical distribution of mud volcanoes show that they approximate to 1800 individuals a detail overview of geological environments in which they occur helps to deduce some necessary conditions for mud volcano formation the basic mechanisms of mud volcano formation are discussed specifically the fluid pressure hypothesis and some triggering events are identified the most common investigation approach and some criteria for recognizing of a submarine mud volcano on side scan sonar records and seismic sections are given mud volcanism in the mediterranean ridge an accretionary complex and black sea abyssal plane a back ark basin with tectonic regime of extension are described as case studies to show variety in morphology and common factors in development of mud volcanoes the manifestation of continuous gas migration through mud volcanoes is clarified and the attempt made to quantify the gas release shows that mud volcanoes are one of the significant natural sources of atmospheric methane emitting a total amount of about 10 3 to 12 6 tg annually

amplitude and timing of sea surface temperature change in the northern south china sea dynamic link to the east asian monsoon magnesium calcium mg ca ratios of foraminiferal shells from a sediment core from the northern south china sea a semi enclosed basin in the western tropical pacific document variations in sea surface temperature sst during the past 145 k y glacial ssts were 4 c colder than interglacial ssts during the last deglaciation most of the warming was accomplished in a single abrupt step after continental ice sheet decay had already begun but warming and ice sheet demise were nearly synchronous during the penultimate deglaciation abrupt sst changes of the past 15 k y were apparently synchronous with events in east asian monsoon rainfall suggesting that variations in monsoon winds and their influence on surface circulation of the western pacific exerted a strong control on northern south china sea ssts we suggest that this link persisted for the previous 130 k y during which time orbital scale 2 3 c sst changes and several small 2 c abrupt sst events occurred in the northern south china sea the similar timing of northern south china sea sst on a benthic 1 8 o time scale to a well dated speleothem record from eastern china suggests that the demise of ice sheets associated with the penultimate deglaciation did not precede northern hemisphere summer insolation increase our results suggest that surface waters had higher 1 8 o values during times of strong summer monsoon than during times of weak monsoon likely reflecting a redistribution of 1 8 o depleted rainfall from land during times of strong summer monsoons to the western pacific during times of weaker summer monsoons

past sea surface temperatures as measured by different proxies a cautionary tale from the late pliocene the paleoclimate community uses a variety of different proxies to reconstruct past sea surface temperatures estimates from different paleothermometers are often used interchangeably despite a scarcity of studies exploring the validity of this practice here we provide an orbital resolution case study from the pliocene using mg ca and alkenone paleothermometry that reinforces results from previous studies showing consistent estimates for some climate parameters and inconsistent results for others we argue that the paleoclimate community should undertake an effort to more systematically evaluate if when and where climate estimates from different paleothermometers can be used interchangeably

incorporation and preservation of mg in globigerinoides sacculifer implications for reconstructing the temperature and 18o 16o of seawater using bathymetric transects of surface sediments underlying similar sea surface temperatures but exposed to increasing dissolution we examined the processes which affect the relationship between foraminiferal mg ca and 18o we found that globigerinoides saccculifer calcifies over a relatively large range of water depth and that this is apparent in their mg content on the seafloor foraminiferal mg ca is substantially altered by dissolution with the degree of alteration increasing with water depth selective dissolution of the chamber calcite formed in surface waters shifts the shell s bulk mg ca and 18o toward the chemistries of the secondary crust acquired in colder thermocline waters the magnitude of this shift depends on both the range of temperatures over which the shell calcified and the degree to which it is subsequently dissolved in spite of this shift the initial relationship between mg ca and 18o determined by their temperature dependence is maintained we conclude that paired measurements of 18o and mg ca can be used for reconstructing 18owater though care must be taken to determine where in the water column the reconstruction applies

planktic foraminifera from the southwestern atlantic 30 60 s species specific patterns in the upper 50 m abstract planktic foraminifers were studied in 96 samples collected in the southwestern atlantic 30 60 s along 53 w in november 1993 mainly from depths between 0 and 50 m very high proportions of juveniles unidentified were present throughout the area especially north of 37 s where they accounted for up to 70 80 of all shells recorded for most species no clear vertical specific stratification was detected in the 0 50 m layer zoogeographic grouping of the 18 species identified allowed the defining of 5 distinct zones along the transect subtropical north of 31 s 80 warm water individuals warm transitional 34 37 s 35 warm water transitional 37 49 s 99 cold water subantarctic 49 55 s 100 cold water and antarctic south of 56 s 100 cold water boundaries between foraminiferal assemblage zones are in good agreement with hydrological fronts described for the area comparison of the present data with planktic collections from the north atlantic show large differences in the proportions of various taxa in the 14 24 c range g bulloides is much more abundant in the northern hemisphere than in the southern one whereas g quinqueloba g inflata and g rubescens show the opposite trend on the other hand temperature related percentage contributions within the 14 24 c range indicate that the preferred thermic regimes of the 9 species considered are remarkably similar in the north and south atlantic collections compared the southernmost planktic distributional ranges of selected warm water taxa are roughly coincident with those established previously on the basis of surface sediments disagreements being chiefly attributable to selective dissolution on the bottom in contrast at the bottom percentages of cold water foraminifers g bulloides g pachyderma are significantly enhanced with respect to their planktic populations and their sedimentary northward limits extend well beyond their maximum ranges in the upper layer plankton it is suggested that submergence of these cold water species and northward displacement at subsurface depths is chiefly responsible for the mismatching patterns observed dissimilar species proportions in both hemispheres and plankton sediment uncoupling can conceivably engender erroneous conclusions when distributional data are used for paleoecologic reconstructions with the aid of numerical analyses such as the imbrie kipp transfer function technique

possible overestimation of shallow depth calcium carbonate dissolution in the ocean 1 we argue that diagnostics of excess dissolved calcium carbonate ta above the saturation horizon cannot be unambiguously interpreted in terms of local in situ dissolution we examine a three dimensional numerical model of global ocean circulation and biogeochemistry with explicit representation of the formation and dissolution of calcium carbonate in particular dissolution is only allowed to occur below the saturation horizon the model qualitatively captures the observed basin and global scale patterns of alkalinity and ta as well as the relationship between ta and chlorofluorocarbon age in the thermocline the existence of ta above the saturation horizon in the model can only be explained in terms of transport subsequent to dissolution the model study does not rule out the possibility of shallow depth calcium carbonate dissolution but suggests that dissolution rates derived from tracer observations have not adequately accounted for the influence of transport

mg ca variation in planktonic foraminifera tests implications for reconstructing palaeo seawater temperature and habitat migration the nature of compositional variability within the tiny calcitic shells tests that are precipitated by planktonic foraminifera has been investigated using laser ablation inductively coupled plasma mass spectrometry la icp ms systematic large and correlated variation of mg ca mn ca ba ca and zn ca but relatively uniform sr ca are observed through the test walls of analysed species globigerinoides sacculifer globigerinoides ruber neogloboquadrina pachyderma and neogloboquadrina dutertrei distinct chamber and chamber wall layer compositions can be resolved within individual tests and mg ca compositional differences observed in sequentially precipitated test components of the different species analysed are consistent with seawater temperature changes occurring with habitat migration during their adult life cycle stages estimated test calcification temperatures are in keeping with available seawater temperature constraints indicating the potential for accurate seawater temperature reconstruction using la icp ms mg rich 1 6 mol mg surface veneers that are also enriched in mn ba and zn have been found on all species and all fossil tests as well as on live sampled tests of g ruber with the latter suggesting a possible biogenic origin these mg rich surfaces bias bulk test compositions toward higher mg ca values by between 5 and 35

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

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

significance of mud volcanism 1 mud volcanism and diapirism have puzzled geoscientists for 2 centuries they have been described onshore and offshore in many places on earth and although they occur in various tectonic settings the majority of the features known to date are located in compressional tectonic scenarios this paper summarizes the main thrusts in mud volcano research as well as the various regions in which mud volcanism has been described mud volcanoes show variable geometry up to tens of kilometers in diameter and several hundred meters in height and a great diversity regarding the origin of the fluid and solid phases gas predominantly methane water and mud may be mobilized at subbottom depth of only a few meters but in places can originate from several kilometers depth with minor crustal or mantle input the possible contribution of mud extrusion to global budgets both from quiescent fluid emission and from the extrusive processes themselves is important in regions where mud volcanoes are abundant such as the collision zones between africa and eurasia fluid flux through mud extrusion exceeds the compaction driven pore fluid expulsion of the accretionary wedge also quiescent degassing of mud volcanoes may contribute significantly to volatile budgets and hence to greenhouse climate

seasonal and interannual variation in santa barbara basin water temperatures observed in sediment trap foraminiferal mg ca 1 we have generated a santa barbara basin sediment trap mg ca record to evaluate culture based calibration equations for the temperate subpolar planktonic foraminiferal species globigerina bulloides and neogloboquadrina pachyderma dextral g bulloides and n pachyderma mg ca are significantly correlated with seasonal variations in temperature of the near surface and subthermocline depths respectively the average deviation between mg based and 18o based temperature estimates is 0 6 c for g bulloides and 0 8 c for n pachyderma differences between mg derived temperatures and instrumental temperatures may be due to cleaning methods environmental factors such as seasonal variations in foraminiferal depth habitats or possible secondary effects on mg ca core top mg ca of both g bulloides and n pachyderma is in excellent agreement with average values from the sediment trap lending strong support for the interpretation of downcore mg ca from these species as annual average near surface and thermoclinal temperatures

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

east asian winter monsoon variability over the last glacial cycle insights from a latitudinal sea surface temperature gradient across the south china sea article i nfo high resolution planktonic foraminifer mg ca sea surface temperature sst and 18 o records of images core md052896 from the southern south china sea scs provide a history of east asian winter monsoon variability over the past 23 kyr specifically we find that the latitudinal sst gradient of the north south scs shows promise as a useful proxy of east asian winter monsoon changes the sst record of core md052896 from the southern scs and odp site 1145 from the northern scs documents several positive anomalies indicating east asia winter monsoon maxima during cold periods of the past 23 kyr including the h1 and younger dryas events the sst record also indicates that after 8 5 ka the east asian winter monsoon strengthened relative to the deglaciation reaching levels of the last glacial period comparison of the scs sst record with stalagmite 18 o records suggests that both the east asian summer and winter monsoons strengthened from the last glacial to the holocene and that summer and winter monsoon strength probably are not anti correlated at least over the last glacial interglacial cycle

comparative characteristics of the black sea and mediterranean ridge mud volcanoes morphological and structural characteristics of the black sea and mediterranean ridge mud volcanoes studied during several unesco esf cruises of the r v gelendzhik 1991 1994 are compared on the basis of single and multi channel seismic and sidescan sonar observations morphologically three types of mud volcanoes were distinguished in the black sea and six types in the mediterranean they differ in size shape and presence of the mud flows some types from both localities are very similar to each other but in any case their deep structure is very distinctive this difference in deep structure is explained by their development in different geological conditions under an extensional regime with high terrigenous input in the black sea and under strong lateral compression on the mediterranean ridge

structural setting and tectonic control of mud volcanoes from the central mediterranean ridge eastern mediterranean based on a recent marine geophysical data set including swath bathymetry acoustic imagery and six channel seismics recorded over a large area of the mediterranean ridge mr in early 1998 during the prismed 2 survey this paper presents a study of the various relationships observed between tectonic features cutting across the central mediterranean ridge accretionary wedge and massive mud expulsions known as mud volcanoes identified over large areas of the ridge regional mapping of two of the mud volcano fields previously only partly investigated olimpi and united nations rise revealed the presence of many new mud expulsion centres and a third new mud volcano field has been identified all the mud features show great variability in morphology size and backscatter strength of their surrounding mud flows based on their contrasting morpho acoustic characteristics we propose a classification into three main groups of mud construction 1 mud volcanoes these consist of subcircular and prominent reliefs often associated with high backscatter mud flows 2 mud domes similar to mud volcano but smaller these occurrences correspond to weakly reflective mud constructions 3 mud plateaus represent a third category which appears as wide often highly reflective and rather flat mud extrusions from all available data an attempt to explain the different mud ascent processes and driving forces is discussed in relation to the initial collision structural setting of the central mediterranean ridge within this area most of the mud constructions have been observed to be associated with tectonic features and in particular with strike slip faulting for the first time as a hypothesis we propose in this paper two different ascent processes to explain the contrasting mud constructions 1 extrusion for the mud volcanoes and plateaus and 2 intrusion for the mud domes connected to two different mud levels controlled by the crustal geometry of this pre collision area and especially the southwards extension of the cretan continental crust below the mediterranean ridge accreted sediments

planktonic foraminifera differential dissolution and the quaternary stable isotope record in the west equatorial pacific differential dissolution affects the isotopic composition of different species of planktonic foraminifera in different ways in the two species studied here in cores from ontong java plateau the less resistant species globigerinoides sacculifer is more readily affected at a shallower depth than the more resistant species pulleniatina obliquiloculata 2 9 versus 3 4 km but shows a smaller and less predictable response to partial dissolution 0 2 to 0 3 per mil versus 0 6 to 0 7 per mil comparison of isotopic values from the last glacial period with those from the late holocene indicates that the apparent dissolution effect is considerably reduced during the last glacial presumably due to reduced dissolution intensity during glacial time a change in the level of the lysocline of about 400 m is suggested in the published isotope records from pacific cores v28 238 and v28 239 the dissolution generated difference in 18o noted previously by shackleton and opdyke 1976 is seen to describe a mid brunhes dissolution maximum between 300 and 500 thousand years ago this mid brunhes dissolution excursion is well known from the pacific and the indian ocean

profiling planktonic foraminiferal crust formation planktonic foraminifera migrate vertically through the water column during their life thereby growing and calcifying over a range of depth associated conditions some species form a calcite veneer crust or cortex at the end of their lifecycle this additional calcite layer may vary in structure composition and thickness potentially accounting for most of their total shell mass and thereby dominating the element and isotope signature of the whole shell here we apply laser ablation icp ms depth profiling to assess variability in thickness and mg ca composition of shell walls of three encrusting species derived from sediment traps compositionally mg ca is significantly lower in the crusts of neogloboquadrina dutertrei and globorotalia scitula as well as in the cortex of pulleniatina obliquiloculata independent of the species specific mg ca of their lamellar calcite shell wall thickness accounts for nearly half of the total thickness in both crustal species and nearly a third in cortical p obliquiloculata regardless of their initial shell wall thickness crust thickness and crustal mg ca decreases toward the younger chambers in n dutertrei and to a lesser extent also in g scitula in contrast the cortex of p obliquiloculata shows a nearly constant thickness and uniform mg ca through the complete chamber wall patterns in thickness and mg ca of the crust indicate that temperature is not the dominant factor controlling crust formation instead we present a depth resolved model explaining compositional differences within individuals and between successive chambers as well as compositional heterogeneity of the crust and lamellar calcite in all three species studied here

climate impact of late quaternary equatorial pacific sea surface temperature variations magnesium calcium data from planktonic foraminifera in equatorial pacific sediment cores demonstrate that tropical pacific sea surface temperatures ssts were 2 8 0 7 c colder than the present at the last glacial maximum glacial interglacial temperature differences as great as 5 c are observed over the last 450 thousand years changes in sst coincide with changes in antarctic air temperature and precede changes in continental ice volume by about 3 thousand years suggesting that tropical cooling played a major role in driving ice age climate comparison of sst estimates from eastern and western sites indicates that the equatorial pacific zonal sst gradient was similar or somewhat larger during glacial episodes extraction of a salinity proxy from the magnesium calcium and oxygen isotope data indicates that transport of water vapor into the western pacific was enhanced during glacial episodes

calcification depths and temperatures of planktonic foraminifera off southwest hainan island and their paleoceanographic implications abstract the east asian monsoon system influences the local oceanographic and climatic conditions of south china sea scs making the habitat depths of planktonic foraminifera pf specific for this region the previous paleo ocean reconstructions of scs have been based on calcification habitat depths derived from other oceans which may have affected the accuracy of interpretations in this study the calcification depths of globigerinoides ruber globigerinoides sacculifer and neogloboquadrina dutertrei from sediment traps deployed at 1000 m depth off southwest hainan island from july 2012 to april 2013 were analyzed with regard to the stable isotopes of oxygen 18o and carbon 13c to calculate their regional apparent calcification depths acds with the overall aim to improve the reconstruction of the upper ocean thermal structure acds and temperature estimated from foraminifera 18o ranged from 0 to 42 m and 25 c for g ruber 30 65 m and 23 3 c for g sacculifer and 75 100 m and 20 3 c for n dutertrei respectively the difference between the thermocline species n dutertrei and mixed layer species g ruber and g sacculifer 18o 18oth ml and the temperature t shows water column stratification the periods of lower and higher t and 18o were in phase with the changes in regional overlying wind speed additionally this study reveals that n dutertrei lives and calcifies its shells within the base of the mixed layer depth mld and upper thermocline depth in scs overall the results from this study provide a new insight to understand the mixed layer and thermocline depth in the northern scs

the amplitude and phasing of climate change during the last deglaciation in the sulu sea western equatorial pacific 1 variations in tropical sea surface temperature patterns and the phasing relative to climate change in higher latitudes provide insight into the mechanisms of climate change on both orbital and shorter time scales here we present well dated high resolution records of planktonic foraminiferal 18o and mg ca based sst spanning the last deglaciation from the sulu sea located in the western equatorial pacific the results indicate that the last glacial maximum was 2 3 0 5 c cooler than present in the sulu sea with a concomitant decrease in sea surface salinity the similarity between variations in surface salinity in the sulu sea the western and eastern equatorial pacific and the greenland ice core record suggests that the observed changes in salinity reflect large scale rearrangement of atmospheric patterns which were coherent and synchronous throughout the northern hemisphere the results suggest that the glacial equatorial pacific climate was strongly influenced by both tropical and extra tropical forcing although it is not clear whether interannual enso variability is a good analogue of glacial interglacial climate change

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

determination of carbonate bound barium in foraminifera and corals by isotope dilution plasma mass spectrometry abstract the trace metal content of biogenic carbonates reflects seawater concentrations only if one can selectively determine the portion of metal bound into the ca lattice site we have developed a procedure to purify benthic foraminifera shells of extraneous sedimentary organic and diagenetic ba the purification procedure involves treatment similar to those developed for the determination of cd in foraminifera shells but with the addition of an alkaline dtpa step to dissolve away sedimentary barite associated with the shells paired sample studies and partial dissolution of benthic foraminifera confirm the effectiveness of this procedure ba ca is determined on the purified shells by measurement of ba by isotope dilution inductively coupled plasma mass spectrometry id icp ms and ca by flame atomic absorption long term precision of the foraminifera ba ca determinations is between 2 and 3 we have also developed a rapid procedure for id icp ms determination of ba in aragonite coral samples with routine precisions of

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

late quaternary paleoceanography of the south china sea glacial interglacial contrasts in an enclosed basin the sea surface paleotemperature of the south china sea scs is estimated quantitatively based on the quantitative analysis of planktonic foraminiferal faunas recovered from piston cores v36 06 3 v36 06 5 and so49 kl8 on the northern continental slope the results lead to a reconstruction of the history of paleocirculation patterns during the last 200 000 years the postglacial and interglacial transbasinal circulation pattern was replaced by a semienclosed basin flow pattern during glacial episodes lowered sea level transformed the scs into a semienclosed basin with the only passageway to the open ocean in its northeastern corner the east asian monsoon which governs circulation patterns in the scs both today and during the late quaternary created both clockwise summer and counterclockwise winter surface gyres during glacials the inflow of tropical surface water masses from both the pacific and indian oceans decreased or was completely cut off from this marginal sea causing a greater decrease in glacial sea surface temperature than in the open ocean of the same latitude inferred increased influence of pacific temperate waters and decreased influence of tropical subtropical waters are confirmed by changes in the planktonic foraminiferal assemblages glacial interglacial fluctuation in sea surface temperature sst 6 8 9 3 c for winter and 2 3 c for summer as well as the seasonality 4 6 c for postglacial and interglacials and 9 10 c for glacials are much greater than the adjacent open western pacific reflecting the amplification of the climatic signal in the marginal sea

changes in intermediate water conditions in the northern south china sea using globorotalia inflata over the last 20 ka intermediate circulation is one of the crucial controls of thermohaline changes in seawater due to the lack of data for some of the more significant indicators there has been little research into past intermediate waters in the south china sea scs in particular little is known of the thermohaline properties of intermediate water here we present paired mg ca and 18o data for the planktonic foraminifera globorotalia inflata from core ghe27l in the northern scs these data provide records of temperature and residual 18oseawater 18oresidual being used as a proxy for salinity to tentatively investigate changes in the intermediate water of the scs over the last 20 ka our results show that g inflata in the scs grew principally within the 200 450 m water depth interval thermohaline changes recorded by g inflata indicate warm and relatively freshening water during the last glacial maximum lgm 20 17 7 ka bp changing to warm and saline waters between 17 7 and 13 6 ka bp in general waters during the 13 6 8 3 ka bp period were characterized by high temperatures and salinity with obvious millennial scale fluctuations after which during the holocene they became cold and fresh we suggest that the temperature and salinity of the intermediate water of the scs recorded by g inflata in core ghe27l were possibly associated with a switch in intermediate water masses during the lgm the intermediate water in the northern scs was mainly impacted by north pacific intermediate water npiw but that subsequently the influence of antarctic intermediate water strengthened during the last deglaciation and pre boreal period 17 7 8 3 ka bp after this period npiw was the principal control of the intermediate water of the scs again

in situ calibration of mg ca ratio in planktonic foraminiferal shell using time series sediment trap a case study of intense dissolution artifact in the south china sea this study examines mg ca temperature equations through the use of planktonic foraminifers collected from continuous time series sediment traps at four water depths in the south china sea this deployment provides an opportunity to refine partial dissolution artifacts and to identify responses of shell chemistry to changes in ambient seawater conditions paired mg ca and 18o measurements on shells are strongly correlated with seasonal variability in terms of temperature at specific habitat depths however partial dissolution can significantly alter mg ca ratios even at depths well above the calcite lysocline or carbonate compensation depth of the three species studied neogloboquadrina dutertrei is the most sensitive species to dissolution relative to the other surface dwelling species globigerinoides ruber and globigerinoides sacculifer differences between the mg derived temperature equation here and those from previously established core top or sediment trap calibrations can be attributed to various degrees of dissolution and lateral advection thus highlighting the need for in situ empirical calibration for different ocean basins

interlaboratory comparison study of mg ca and sr ca measurements in planktonic foraminifera for paleoceanographic research thirteen laboratories from the usa and europe participated in an intercomparison study of mg ca and sr ca measurements in foraminifera the study included five planktonic species from surface sediments from different geographical regions and water depths each of the laboratories followed their own cleaning and analytical procedures and had no specific information about the samples analysis of solutions of known mg ca and sr ca ratios showed that the intralaboratory instrumental precision is better than 0 5 for both mg ca and sr ca measurements regardless whether icp oes or icp ms is used the interlaboratory precision on the analysis of standard solutions was about 1 5 and 0 9 for mg ca and sr ca measurements respectively these are equivalent to mg ca based temperature repeatability and reproducibility on the analysis of solutions of 0 2 c and 0 5 c respectively the analysis of foraminifera suggests an interlaboratory variance of about 8 rsd for mg ca measurements which translates to reproducibility of about 2 3 c the relatively large range in the reproducibility of foraminiferal analysis is primarily due to relatively poor intralaboratory repeatability about 1 2 c and a bias about 1 c due to the application of different cleaning methods by different laboratories improving the consistency of cleaning methods among laboratories will therefore likely lead to better reproducibility even more importantly the results of this study highlight the need for standards calibration among laboratories as a first step toward improving interlaboratory compatibility

unsaturated hydraulic conductivity function based on a soil fragmentation process we present a new two parameter expression for relative hydraulic conductivity rhc of partially saturated soils it is based on the premise of assouline et al 1998 that soil structures evolve from a uniform random fragmentation process this assumption allows us to derive hydraulic properties of soils water retention curves and unsaturated hydraulic conductivity from primary properties such as pore geometry and soil structure we tested our rhc expression against different soil types and found that it fits data better than the widely used models of brooks and corey 1964 and van genuchten 1980

li sr mg and na in foraminiferal calcite shells from laboratory culture sediment traps and sediment cores abstract constant temperature laboratory culture experiments of the planktonic foraminiferal species globigerinoides sacculifer brady suggest that the ratios of li and sr to ca in the shells are a function of these ratios in the culture solutions mg ca and na ca in the shells did not vary with changes of these ratios in the culture solution these are the first direct determinations of the relationship between foraminiferal shell chemistry and solution composition the possibility of temperature dependence for the minor elemental composition of foraminiferal shells was also investigated in the laboratory and by analysis of several planktonic and one benthic foraminiferal species from sediment trap and sediment core samples the sr ca mg ca and na ca ratios in the natural samples roughly correlate with calcification temperature whereas differences in the li ca ratios are small and not systematically related to temperature however laboratory culture experiments at 20 c and 30 c showed no variation in the li ca sr ca mg ca and na ca ratios with calcification temperature for the planktonic foraminifera g sacculifer and orbulina universa therefore observed differences in the sr ca mg ca and na ca ratios for the sediment trap and core foraminiferal samples cannot be ascribed to direct effects of calcification temperature but may be due to some other environmental factor which is correlated with temperature

temperature control on the incorporation of magnesium strontium fluorine and cadmium into benthic foraminiferal shells from little bahama bank prospects for thermocline paleoceanography surface sediments from little bahama bank lbb intersecting the subtropical thermocline were used to assess the influence of temperature on the incorporation of mg sr f and cd into shells of benthic foraminifera samples were obtained from twelve cores along the southern slope of lbb covering a temperature range of 18 4 5 c between 301 and 1585 m we studied the composition of ten calcitic and one aragonitic species which are often used in paleochemical reconstructions mg ca ratios decrease with increasing water depth in all benthic species both with calcitic and aragonitic mineralogy showing a strong correlation with water temperature similar decrease is seen in sr ca but with no correlation with temperature none of the benthic species studied here exhibits a depth or temperature related change in f ca similar trends are observed when using an ocean wide dataset which includes shallow and deep core tops 300 5000 m we suggest that temperature is the primary control on the mg content of benthic foraminifera based on inorganic precipitation experiments and thermodynamic considerations presented here a 30 40 decrease in the mg distribution coefficient in calcite may be expected as a result of a temperature change from 25 c to 5 c which is about half the observed change in lbb a calibration curve applied to c pachyderma data from core tops along the slope of little bahama bank suggests that water temperature may be inferred from mg ca ratios with an uncertainty of about 0 8 c therefore the mg content of benthic foraminifera may provide a new independent temperature proxy for studying shallow waters paleoceanography the linear decrease in sr ca with increasing depth is not correlated with temperature the trend is constant from the ocean surface down to 5 km suggesting that pressure related effects on the calcification process are a more likely explanation than post depositional dissolution mg ca ratios in aragonitic shells of h elegans covary with temperature in accord with recent observations from corals in contrast the sr and f chemistry of h elegans is very different than that of corals and inorganically precipitated aragonites the disparities between the elemental composition of biogenic and inorganic phases and the large intergeneric and interspecific differences observed both in planktonic and benthic foraminifera implicate temperature related physiological processes in regulating the coprecipitation of elements in foraminiferal shells our work demonstrates that cd ca ratios of shallow calcitic species reflect the vertical distribution of nutrients no significant influence of temperature on the partitioning of cd into the shells was found our data extend the previous deep water calibration boyle 1992 thereby allowing for the reconstruction of the nutrient chemistry of shallow thermocline waters

crustal motion in the zone of the 1960 chile earthquake detangling earthquake cycle deformation and forearc sliver translation temporary deformation in great earthquake cycles and permanent shear deformation associated with oblique plate convergence both provide critical clues for understanding geodynamics and earthquake hazard at subduction zones in the region affected by the mw 9 5 great chile earthquake of 1960 we have obtained gps observations that provide information on both types of deformation our velocity solutions for the first time span the entire latitudinal range of the 1960 earthquake the new observations revealed a pattern of opposing roughly arc normal motion of coastal and inland sites consistent with what was reported earlier for the northern part of this region this finding supports the model of prolonged postseismic deformation as a result of viscoelastic stress relaxation in the mantle the new observations also provide the first geodetic evidence for the dextral motion of an intravolcanic arc fault system and the consequent northward translation of a forearc sliver the sliver motion can be modeled using a rate of 6 5 mm a accommodating about 75 of the margin parallel component of nazca south america relative plate motion with the rate diminishing to the north furthermore the new gps observations show a southward decrease in margin normal velocities of the coastal area we prefer explaining the southward decrease in terms of changes in the width or frictional properties of the megathrust seismogenic zone because of the much younger age of the subducting plate and warmer thermal regime in the south the currently locked portion of the plate interface may be narrower using a three dimensional viscoelastic finite element model of postseismic and interseismic deformation following the 1960 earthquake we demonstrate that this explanation although not unique is consistent with the gps observations to the first order

el nino like pattern in ice age tropical pacific sea surface temperature sea surface temperatures ssts in the cold tongue of the eastern equatorial pacific exert powerful controls on global atmospheric circulation patterns we examined climate variability in this region from the last glacial maximum lgm to the present using a sst record reconstructed from magnesium calcium ratios in foraminifera from sea floor sediments near the galapagos islands cold tongue sst varied coherently with precession induced changes in seasonality during the past 30 000 years observed lgm cooling of just 1 2 c implies a relaxation of tropical temperature gradients weakened hadley and walker circulation southward shift of the intertropical convergence zone and a persistent el nino like pattern in the tropical pacific this is contrasted with mid holocene cooling suggestive of a la nina like pattern with enhanced sst gradients and strengthened trade winds our results support a potent role for altered tropical pacific sst gradients in global climate variations

geological geochemical and microbial processes at the hydrate bearing hakon mosby mud volcano a review abstract submarine mud volcanoes are point sources of fluid expulsion and oases of active geological geochemical and microbial processes in the deep ocean the results of multidisciplinary investigations at the hakon mosby mud volcano hmmv in the norwegian sea at 1250 m water depth are reviewed in this paper seafloor morphology lithotypes geochemical and biological processes at the hmmv are concentrically zoned the zonation is controlled by ejection of sediment water and gases mainly methane accompanied by high heat flow in the mud volcano crater a structural gas hydrate accumulation is associated with the hmmv gas hydrate is abundant only in a relatively narrow zone where optimal conditions low temperature and high gas concentration exist for gas hydrate crystallization authigenic minerals bacterial mats and chemosynthetic communities typical of cold seep environments are present rapid anaerobic sulfate dependant oxidation of methane is thought to be mediated by a consortium of methanogens and sulfate reducing bacteria although methane is oxidized in sediments at high rates a significant portion of this gas may escape into the ocean mainly as diffuse flux in the water column methane is rapidly dissolved and oxidized this observation supports the hypothesis that gas flux from deep water mud volcanoes contributes to the oceanic carbon pool but not to the atmosphere the hmmv represents an important natural laboratory and provides insight to processes at the interface of methane rich sediments and cold bottom water in the deep ocean future studies may best focus on accurate direct measurements of gas flux and quantification of the biogeochemical cycling of major chemical elements in shallow sediment

characterization of mg ca distributions in planktonic foraminifera species by electron microprobe mapping 1 the distribution of mg ca within the tests of eight modern planktonic foraminifer species has been characterized using electron microprobe mapping species include several that are commonly used for estimation of past seawater temperatures globigerinoides ruber g sacculifer neogloboquadrina incompta synonym of n pachyderma dex n dutertrei and g truncatulinoides each of the investigated species displays large variations in mg ca composition within individual tests however the pattern of mg ca variation is notably different between symbiont bearing and symbiont free species in symbiotic species cyclic mg ca compositional banding occurs that is characterized by narrow 1 3 m high mg ca typically 8 11 mmol mol bands intercalated between broader low mg ca typically 1 5 mmol mol bands this factor of 2 3 difference equates to an apparent calcification temperature change of 10 c or more such temperature changes are considered highly improbable and suggest vital effects significantly modify the incorporation of mg ca into the tests of symbiont bearing species these vital effects remain poorly understood and demand further careful evaluation as they may need to be accounted for when making reliable reconstructions of past oceanic temperatures symbiont free species typically have fewer and broader compositional bands that may reflect more closely changes in calcification temperature as these species migrate within a water column

environmental versus biological controls on mg ca variability in globigerinoides ruber white from core top and plankton tow samples in the southwest pacific ocean 1 laser ablation inductively coupled plasma mass spectrometry was used to analyze the individual chambers from tests of foraminiferal fossil and plankton tow globigerinoides ruber from the southwest pacific ocean from latitudes 3 s to 42 s the variability of mg ca between chambers of an individual intraindividual and individuals of the same population interindividual is such that when converted to temperature the extent of intra individual and interindividual variability appears to exceed that attributable to either calcification or seasonal temperature variability the pooled mean chamber mg ca from each core top and plankton tow site demonstrates a significant p 0 05 positive correlation with temperature we derive chamber specific calibrations where mg cach f 2 0 798 exp0 070 t mg cach f 1 0 891 exp0 067 t and mg cach f 0 590 exp0 072 t we do not observe any bias between the two morphotypes gs ruber ruber and gs ruber pyramidalis the chamber specific calibrations potentially offset mg ca based temperature reconstructions if used on bulk whole test mg ca or applied to misidentified chambers nevertheless these calibrations can be used to reliably estimate sea surface temperature although there is a general overriding temperature control on mg ca we show that removal of the effect of temperature at each site reveals a lognormal mg ca distribution this suggests that mg ca variability at each site is also affected by biological mechanism s that may control the distribution of interindividual mg ca in addition other te ca data al ca and mn ca from laser ablation trace element depth profiles can be used to identify detrital or diagenetic phases that may bias the trace element ca signal

late quaternary paleoceanography of the south china sea surface circulation and carbonate cycles paleoceanographic information from 34 sediment cores is summarized to investigate the glacial interglacial variations in sea surface circulation and late quaternary carbonate cycles in the south china sea judging from the distribution pattern of deposition rates the enormous terrigenous supply by rivers is responsible for the high rate of hemipelagic sedimentation which was even higher during glacial periods paleotemperature maps based on transfer function temperature estimates have revealed a e w gradient of sst for glacial summer and a s n gradient for glacial winter and this agrees well with the clockwise surface circulation in summer and counterclockwise in winter during glacials as shown by a preliminary computer modelling the high resolution paleotemperature curves of core v36 3 from the northern slope show an abrupt cooling event which may belong to the younger dryas carbonate percentage in sediments and preservation of foraminifers and pteropods are used to study the carbonate cycles in the marginal sea it turns out that two mechanisms are functioning there being a basin with large drainage areas vast amount of river borne terrigenous input dilutes carbonate and its intensification during glacial decreases the glacial cac03 being a basin connected with the pacific the fluctuations of lysocline ccd and acd in the scs are related to those in the pacific ocean and dissolution is strengthened at interglacial thus above the present ccd the dilution factor predominates and the atlantic cycles are produced below the present ccd the dissolution factor prevails resulting in the pacific pattern of carbonate cycles

synchronous tropical south china sea sst change and greenland warming during deglaciation the tropical ocean plays a major role in global climate it is therefore crucial to establish the precise phase between tropical and high latitude climate variability during past abrupt climate events in order to gain insight into the mechanisms of global climate change here we present alkenone sea surface temperature sst records from the tropical south china sea that show an abrupt temperature increase of at least 1 c at the end of the last glacial period within the recognized dating uncertainties this sst increase is synchronous with the bolling warming observed at 14 6 thousand years ago in the greenland ice sheet project 2 ice core

foraminiferal magnesium in globeriginoides sacculifer as a paleotemperature proxy foraminiferal magnesium shows increasing promise as a paleothermometer but the accuracy and precision are limited by biases introduced by partial dissolution salinity variations mg rich gametogenic calcite and contaminant phases we improved cleaning methods and reduced errors introduced by partial dissolution by sampling from well preserved cores in the equatorial atlantic and the caribbean sea with different dissolution histories all cores reveal a synchronous 25 increase in mg ca from the stage 2 3 boundary to the holocene core top indicating that dissolution is not a controlling factor modern temperatures estimated from core top mg ca are 24 5 25 0 c equal to mean annual water temperatures at 50 100 m we estimate that sea surface temperature increased by 2 6 c 1 3 from the last glacial maximum to the holocene holocene values were comparable to those during isotope stage 5e our data indicate that biases from contaminant phases and partial dissolution can be reduced this paleothermometer holds promise if uncertainties introduced by salinity variations and gametogenic calcite can be constrained

tracing deep sea calcite dissolution agreement between the globorotalia menardii fragmentation index and elemental ratios mg ca and mg sr in planktonic foraminifers 1 accurately quantifying deep sea calcite dissolution is crucial for understanding the role of the marine carbonate system in regulating atmospheric pco2 over millennia we compare a foraminifer fragmentation based calcite dissolution proxy globorotalia menardii fragmentation index mfi to mg ca sr ca and mg sr in several species of deep dwelling planktonic foraminifers we conducted microfossil and geochemical analyses on the same core top samples taken at different depths on the ontong java plateau to maximize the dissolution signal and minimize the temperature overprint on our data we also compare elemental ratios from planktonic foraminifer tests to modern bottom water co3 undersaturation and model derived estimates of percent calcite dissolved in deep sea sediments we find clear linear decreases in mg ca or mg sr in g menardii and pulleniatina obliquiloculata with increasing 1 bottom water co3 undersaturation 2 percent calcite dissolved in sediments calculated with biogeochemical modeling 3 mfi and 4 percent calcite dissolved derived from mfi these findings lend further support to mfi as a calcite dissolution proxy for deep sea sediments in contrast we find no significant correlation between sr ca and independent dissolution indicators our results suggest that mg ca and mg sr from deep dwelling foraminifers could potentially be used as calcite dissolution proxies in combination with independent water temperature estimates likewise establishing the relationship between mfi and dissolution induced changes in the mg ca of surface dwelling foraminifers could provide a tool to correct mg ca derived sea surface temperature reconstructions for calcite dissolution

a biomineralization model for the incorporation of trace elements into foraminiferal calcium carbonate measurements of srca of benthic foraminifera show a linear decrease with water depth which is superimposed upon significant variability identified by analyses of individual foraminifera new data for cdca support previous work in defining a contrast between waters shallower and deeper than 2500 m measured element partition coefficients in foraminiferal calcium carbonate relative to sea water d have been described by means of a one box model in which elements are extracted by rayleigh distillation from a biomineralization reservoir that serves for calcification with a constant fractionation factor such that d 1 f 1 f where f is the proportion of ca remaining after precipitation a modification to the model recognises differences in element speciation the model is consistent with differences between dsr dba and dcd in benthic but not planktonic foraminifera depth variations in d for sr and ba are consistent with the model as are differences in depth variation of dcd in calcitic and aragonitic benthic foraminifera the shallower depth variations may reflect increasing calcification rates with increasing water depth to an optimum of about 2500 m observations of unusually lower dcd for some deep waters not accompanied by similar dsr or dba may be because of dissolution or a calcification response to a lower carbonate saturation state

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

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

morphological geochemical and ecological differences of the extant menardiform planktonic foraminifera globorotalia menardii and globorotalia cultrata taxonomic consistency is the prerequisite for any foraminiferal study in particular interpretation of planktonic foraminiferal geochemical data requires consistent selection of monospecific tests due to varying habitats of different species in order to exemplify the impact of slightly varying morphological characteristics on geochemical signatures we investigated three basic shape dimensions test weights stable isotope values and mg ca ratios of globorotalia menardii and globorotalia cultrata which are often grouped or referred to as synonyms along with visual distinction encrusted g menardii is distinguished from shiny g cultrata by its on average doubled test weight when referring to the same maximum diameter more elongated and flattened g cultrata calcifies within the deeper mixed layer which applies also for the initial calcification of g menardii final encrustration of g menardii after vertical migration is suggested to take place close to the bottom of the seasonal thermocline combined mg ca ratios versus calcification temperature calibration provides a reliable tool for monospecific thermal reconstructions for the seasonal thermocline g menardii and the deeper mixed layer g cultrata c 2010 elsevier b v all rights reserved

spatial distribution of mud flows chemoautotrophic communities and biogeochemical habitats at hakon mosby mud volcano marine mud volcanoes are significant source locations contributing to the marine methane cycle enhanced heat flow unique chemoautotrophic communities occurrence of massive gas hydrates and large gas plumes are direct evidences of elevated methane concentrations and the dynamic environment of mud volcanoes related to the high concentrations and large inventories of ch4 in surface sediments only a fraction of the methane is exported to the bottom water this is mainly due to chemoautotrophic communities oxidizing methane and proving a microbial filter reducing ch4 fluxes although these processes were studied for several mud volcanoes still little is known about the spatial pattern and the areas covered by chemoautotrophic communities or by present mud flows for this purposes the hakon mosby mud volcano hmmv which is located at the continental slope of the barents sea was studied by several dives with the remotely operated vehicle victor6000 during these dives a high resolution microbathymetric map with a footprint of 25 25 cm and a vertical resolution of better than 10 cm was derived furthermore video streams of the bottom camera were converted into georeferenced mosaics providing a detailed image about the spatial distribution of seafloor features as bacterial mats pogonophorans both indicating methane oxidation or mud flows based on visual inspection of 2310 georeferenced mosaics covering an area of 46 160 m 2 different biogeochemical habitats were identified and quantified on a m 2 basis by application of geostatistic techniques as indicator kriging the distribution of different biogeochemical habitats was quantified and mapped for the entire hmmv considering the flat and hummocky area of hmmv approximately 16 115 165 m 2 of the flat centre is nearly void of any benthic communities this area is considered as a region of high methane discharge into bottom water an area of 5 38 244 m 2 located in the south eastern part is densely inhabited by beggiatoa the hummocky outer part is colonised dominantly by pogonophoran tube worms 37 3 276 121 m 2 and only occasional by beggiatoa source locations and drainage directions for current mud flows were identified by computation of trend surfaces and consideration of temperature data this suggests that present mud flow ascend close to the northern edge of the flat unit of hmmv and that the drainage pattern of mud flows shifted from a westward to a south south eastern direction 2007 elsevier b v all rights reserved