gulf stream variability during marine isotope stage 3 we have studied ocean drilling program site 1060 on the blake outer ridge which lies beneath the gulf stream we focus on marine isotope stage 3 60 25 thousand years before present ka sea surface temperatures ssts inferred both from foraminiferal fauna and alkenone ratios as well as counts of iceberg melt out debris and benthic stable isotope analyses enable our record to be interpreted in terms of regional hydrographic changes as well as changing thermohaline circulation thc the observed sst record is consistent with the air temperature record from the greenland ice cores however site 1060 exhibits important differences in detail compared with the ice core record and when compared to other sites within the north atlantic significant longitudinal differences emerge at site 1060 in the western atlantic all greenland stadials gs whether associated with heinrich events hes or not show a similar small amplitude of cooling mean faunal based sstaug during gs is only 1 5 c colder than during greenland interstadials gis in addition during gs the coldest ssts are limited to apparently brief events this is in contrast to several eastern atlantic sites where he stadials exhibit coolings that are enhanced by 2 c compared to other gs and where cold conditions are not restricted to cold pulses but cover 2 ka long intervals furthermore site 1060 ssts remained warm right through each interstadial in contrast to the sustained and uniform cooling trend through interstadials that is consistently observed in greenland indicated by measurements of 18o in ice

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

globorotalia truncatulinoides growth and chemistry as probes of the past thermocline 1 shell size this work identifies features of the life history of the deep living planktonic foraminifer globorotalia truncatulinoides that offer possibilities for reconstructing characteristics of the past ocean s main thermocline part 1 considers two aspects of variation in shell size the predictability of growth related size changes which we need to calculate changes in shell chemistry and a model for environmentally forced changes in shell size frequency which suggests how shell size may be a direct source of paleoceanographic information even though size variation among shells of g truncatulinoides at the same stage of growth same number of chambers exceeds the size difference between successive growth stages growth related size changes are predictable because shells tend to grow at the same rate variation in initial shell size is sufficient to account for the large size variation found among shells at the same stage of growth several lines of evidence suggest that g truncatulinoides reproduces at 600 m in the water column and it appears that vertical mixing to that depth is required to return juvenile shells to the surface anything that prevents this such as shallowing of the thermocline can interfere with g truncatulinoides life history in such a way that its shell size frequency distributions are altered among shells falling to the seafloor from a reproducing population are large numbers of both juvenile and adult sizes and if reproduction is inhibited the frequencies of those sizes are reduced and the relative frequency of intermediate sized shells increases a paleoceanographically useful result of this is that the topography of the main thermocline tends to be reflected in the size frequency distribution of g truncatulinoides shells from the underlying sediments in areas where the top of the main thermocline is shallower than 600 m production of juveniles 125 177 m and reproductive adults 425 m is reduced leaving predominantly intermediate sized 212 355 m shells

morphological variation of emiliania huxleyi and sea surface salinity morphometric analysis of coccoliths of various coccolithophore species from core top and culture samples has revealed that the morphology of single placoliths can be affected by environmental parameters such as temperature salinity and productivity in this study we have tested the morphological variations of placoliths of emiliania huxleyi the most common coccolithophore species in the modern ocean with respect to environmental gradients we have investigated especially the potential effect of salinity on the morphology as it is known from culture studies that the growth of e huxleyi placoliths is strongly influenced by varying salinities morphometric analysis of about 2150 placoliths from 37 globally distributed core top and plankton samples revealed that the morphology of e huxleyi varies significantly along a sea surface salinity gradient from 33 to 38 morphological parameters such as the mean size of placoliths are used as explaining variables in multiple regression analysis to reconstruct sea surface salinities sss the best model for mean sss yields an r 2 of 0 88 with a standard error of 0 49 whereas statistical models describing surface water temperature or productivity are less reliable and accurate application of the best model to plankton samples allows the prediction of in situsalinitieswithingivenerrorestimates theapplicationofthebestmodeltofossilassemblagesfromthelgm however ismore puzzling paleosalinity reconstructions in the south atlantic the caribbean sea and the subtropical atlantic are in good agreement with the published values 2007 elsevier b v all rights reserved

response of the tropical atlantic thermocline to late quaternary trade wind changes we applied the modern analog technique to foraminiferal counts from three equatorial atlantic gravity cores to estimate paleothermocline depths in the eastern and western tropical atlantic during the past 250 kyr the eastern equatorial core geob 1105 4 is characterized by variations in the 23 kyr cycle whereas the western sediment cores show a dominant periodicity at the 41 kyr band the phase relationships with respect to insolation and ice volume suggest that thermocline fluctuations in the east are primarily driven by the intensity of the monsoon due to variations in low latitude insolation in contrast changes of the thermocline depth in the western tropical atlantic which lead global ice volume at the 41 kyr band by 3 4 kyr seem to depend on the strength of the se trade winds in response to the meridional temperature gradients in the south atlantic

impacts of storms on recent planktic foraminiferal test production and caco3 flux in the north atlantic at 47 n 20 w jgofs planktic foraminiferal assemblages are well known to vary in accordance with seasonal fluctuations in ocean properties periodic reproduction cycles and variations between water masses here we report that storms also can significantly influence foraminiferal assemblages during the rv meteor cruise 21 to the northeast atlantic ocean biotrans area from march to may 1992 planktic foraminifera were sampled using a multiple opening closing net while sampling two storms with wind forces up to 12 beaufort caused intensified surface layer mixing with shifts in the depth of the upper ocean mixed layer from 20 40 m to 170 240 m subsequently planktic foraminiferal growth rates increased resulting in an elevated quantity of small 100 150 m tests phase 1 when the wind strength increased a second time the mixed layer deepened to a depth below the former position of the pycnocline and again the abundance of small tests increased phase 2 during phase 2 the weight of calcite in specimens of the productive zone reached its maximum in the export zone an associated increase in empty tests occurred with a lag time depending on the test sinking velocity in the upper export zone down to 700 m water depth caco3 flux increased from 9 3 to 49 8 mg caco3 m 2 d 1 after the first storm and from 8 9 to 19 9 mg caco3 m 2d 1 after the second storm in the 700 to 2500 m depth interval the flux increased from 5 1 mg caco3 m 2 d 1 to about 9 2 mg caco m 2 d 1 thus the standing stock of living foraminifera and export of empty tests from the productive zone increased after the storms leading to pulses of caco3 exported from the surface to deep water

enhanced carbon dioxide outgassing from the eastern equatorial atlantic during the last glacial biological productivity and carbon export in the equatorial atlantic are thought to have been dramatically higher during the last glacial period than during the holocene here we reconstruct the ph and co2 content of surface waters from the eastern equatorial atlantic ocean over the past 30 k y using the boron isotope composition of globigerinoides ruber a mixed layer dwelling planktic foraminifera our new record combined with previously published data indicates that during the last glacial in contrast to today a strong west to east gradient existed in the extent of air sea equilibrium with respect to pco2 pco2 with the eastern equatorial atlantic acting as a significant source of co2 100 atm while the western atlantic remained close to equilibrium 25 atm this pattern suggests that a fivefold increase in the upwelling rate of deeper waters drove increased atlantic productivity and large scale regional cooling during the last glacial but the higher than modern pco2 in the east indicates that export production did not keep up with enhanced upwelling of nutrients however the downstream decline of pco2 provides evidence that the unused nutrients from the east were eventually used for biologic carbon export thereby effectively negating the impact of changes in upwelling on atmospheric co2 levels our findings indicate that the equatorial atlantic exerted a minimal role in contributing to lower glacial age atmospheric co2

multiple early eocene benthic foraminiferal assemblage and δ13c fluctuations at dsdp site 401 bay of biscay ne atlantic abstract within the last decade several early eocene hyperthermals have been detected globally these transient warming events have mainly been characterized geochemically using stable isotopes carbonate content measurements or xrf core scanning yet detailed micropaleontological records are sparse limiting our understanding of the driving forces behind hyperthermals and of the contemporaneous paleoceanography here detailed geochemical and quantitative benthic foraminiferal records are presented from lower eocene pelagic sediments of deep sea drilling project site 401 bay of biscay northeast atlantic in calcareous nannofossil zone np11 several clay enriched levels correspond to negative 13c and 18o bulk rock excursions with amplitudes of up to 0 75 suggesting that significant injections of 12c enriched greenhouse gasses and small temperature rises took place coeval with several of these hyperthermal events the benthic foraminiferal record reveals increased relative abundances of oligotrophic taxa e g nuttallides umbonifera and a reduction in the abundance of buliminid species followed by an increase of opportunistic taxa e g globocassidulina subglobosa and gyroidinoides spp these short lived faunal perturbations are thought to be caused by reduced seasonality of productivity resulting in a decreased corg flux to the seafloor moreover the sedimentological record suggests that an enhanced influx of terrigenous material occurred during these events additionally the most intense 13c decline here called level gives rise to a small yet pronounced long term shift in the benthic foraminiferal composition at this site possibly due to the reappraisal of upwelling and the intensification of bottom water currents these observations imply that environmental changes during smaller hyperthermal events are also reflected in the composition of deep sea benthic communities on both short

the reef builder gastropod dendropoma petreaum a proxy of short and long term climatic events in the eastern mediterranean abstract high resolution 18 o and 13 c records obtained from seven cores were drilled from ledges of the reef builder gastropod dendropoma petreaum and used to reconstruct variations in the levantine basin sea surface temperature hydrology and productivity during the past 500 years the 18 o of the aragonite shell of living d petreaum indicate that skeletal deposition occurs under isotopic equilibrium and faithfully record the temperature and surface water 18 o during summer and autumn the mean down core 18 o record clearly captures global and local climatic events such as the little ice age lia and the recent warming of surface waters in the eastern mediterranean comparison to the western mediterranean vermetid 18 o record reveals changes in the freshwater evaporation budgets of the two basins during cold and warm periods the eastern basin had lower surface temperatures and excess evaporation during the lia and experienced a relatively larger warming and or a decrease in freshwater evaporation during the past 70 years the d petraeum 13 c is strongly related to 13 c of dissolved inorganic carbon and to the primary productivity of the surface water the mean down core 13 c record exhibits enrichment during the lia maximum and a strong depletion trend during the last century the lia 13 c enrichment is attributed to an increase in primary production and high nutrient levels which resulted from increased vertical mixing and upwelling the last century 13 c depletion is mostly related to the increased anthropogenic emissions of 13 c depleted carbon dioxide and to a certain decrease in primary production the data indicate that d petraeum isotopic signatures are unique proxies for last 500 years high resolution reconstruction of paleo oceanographic environments in the mediterranean and potentially in the sub tropical atlantic regions

late quaternary variations in sea surface temperatures and their relationship to orbital forcing recorded in the southern ocean atlantic sector late quaternary summer sea surface temperatures ssts have been derived from radiolarian assemblages in the east atlantic sector of the southern ocean in the subantarctic and the polar frontal zone glacial ssts oxygen isotope stages 2 4 6 and 8 were 3 5 c cooler than today indicating northward displacements of the isotherms about 2 4 of latitudes during interglacials ssts almost reached modern levels oxygen isotope stages 7 and 9 or exceeded them by 2 3 c oxygen isotope stages 1 and 5 5 in the subantarctic atlantic ocean changes in sst and calcium carbonate content of the sediment precede variations in global ice volume in the range of the main milankovitch frequencies comparisons with the timing of north atlantic deep water nadw proxy records suggests that this early response in the subantarctic atlantic ocean is not triggered by the flux of nadw to the southern ocean

morphometric response of late aptian planktonic foraminiferal communities to environmental changes a case study of paraticinella rohri at poggio le guaine central italy abstract the aptian albian boundary interval represents a pivotal time of pronounced climate ocean changes associated with oceanic anoxic event 1b oae 1b that seriously influenced marine pelagic ecosystems the sedimentary successions record the first and most significant species turnover in the evolutionary history of planktonic foraminifera consisting of the selective extinction disappearance of large aptian species and resulting in inter specific size reduction the post extinction dwarfing as in the lilliput effect in the earliest albian assemblages in this study we investigate how the planktonic foraminifera respond to crucial environmental stress and if any intra specific decrease in test size predate the extinction pre extinction dwarfing paraticinella rohri was chosen as the most representative of the aptian planktonic foraminiferal taxa and its test size evolution was compared with the high resolution record of redox and productivity geochemical proxies through the uppermost aptian lowermost albian pelagic succession of poggio le guaine central italy our geochemical data document long term fluctuations characteristic of a system with transitions among different states oligotrophic mesotrophic eutrophic and oxic dysoxic anoxic the strong correlation of the large test size changes of pa rohri during its total range with higher productivity increased baexcess concentrations suggests that the trophic regime was the key factor controlling robust abundance and size variability in this taxon the progressive increase in surface water fertility during the late aptian offered optimum ecological conditions for planktonic foraminifera that increased in abundance size and specific diversity after the transient anoxic 113 jacob sub event smaller to dwarfed specimens of pa rohri and depauperate planktonic foraminifera assemblages faced high selective pressures due to more oligotrophic conditions transition to a more eutrophic ocean in the latest aptian irreversibly eroded their resilience and aptian dwarfed k strategist taxa became extinct the planktonic foraminifera turnover has been therefore the result of an irreversible and drastic regime shift toward a more eutrophic ecosystem that promoted the thriving of small sized opportunistic disaster planktonic foraminiferal species and the siliceous radiolaria

foraminiferal variations and stratigraphic implications to the deposition of sapropel s5 in the eastern mediterranean abstract detailed study of the temporal and spatial patterns of planktonic foraminiferal assemblages was performed on seven eastern mediterranean deep sea cores to evaluate differences and similarities in their stratigraphic records during the eemian sapropel s5 interval changes in the succession of planktonic assemblages are very similar in all investigated sapropel s5 sequences analyses carried out on the 63 and 150 m size fractions indicate that during this time interval size does not significantly affect the stratigraphic patterns benthic assemblages were studied at three sites where their succession of changes was concordant but locally different in this framework comparison of s5 sapropels layers from different areas of the eastern mediterranean suggests that the onset of the dark colour does not occur in the same stratigraphic position at a regional scale whereas the absence drastic reduction of benthic foraminifera within sapropel intervals appears to be a time equivalent event and corresponds to the last local occurrence of globorotalia inflata

foraminiferal faunal estimates of paleotemperature circumventing the no analog problem yields cool ice age tropics the sensitivity of the tropics to climate change particularly the amplitude of glacial to interglacial changes in sea surface temperature sst is one of the great controversies in paleoclimatology here we reassess faunal estimates of ice age ssts focusing on the problem of no analog planktonic foraminiferal assemblages in the equatorial oceans that confounds both classical transfer function and modern analog methods a new calibration strategy developed here which uses past variability of species to define robust faunal assemblages solves the no analog problem and reveals ice age cooling of 5 o to 6oc in the equatorial current systems of the atlantic and eastern pacific oceans classical transfer functions underestimated temperature changes in some areas of the tropical oceans because core top assemblages misrepresented the ice age faunal assemblages our finding is consistent with some geochemical estimates and model predictions of greater ice age cooling in the tropics than was inferred by climate long range investigation mapping and prediction climap 1981 and thus may help to resolve a long standing controversy our new foraminiferal transfer function suggests that such cooling was limited to the equatorial current systems however and supports climap s inference of stability of the subtropical gyre centers

shell size variation of the planktonic foraminifer neogloboquadrina pachyderma sin in the norwegian greenland sea during the last 1 3 myrs implications for paleoceanographic reconstructions we present measurements of the maximum diameter of the planktonic foraminifer neogloboquadrina pachyderma sin from six sediment cores ocean drilling program sites 643 644 907 909 985 and 987 from the norwegian greenland sea our data show a distinct net increase in mean shell size of n pachyderma sin at all sites during the last 1 3 ma with largest shell sizes reached after 0 4 ma external factors such as glacial interglacial variability and carbonate dissolution alone cannot account for the observed variation in mean shell size of n pachyderma sin we consider the observed shell size increase to mirror an evolutionary trend towards better adaptation of n pachyderma sin to the cold water environment after 1 1 1 0 ma probably the mid pleistocene climate shift and the associated change of amplitude and frequency of glacial interglacial fluctuations have triggered the evolution of this planktonic foraminifer oxygen and carbon stable isotope analyses of diverent shell size classes indicate that the observed shell size increase could not be explained by the functional concept that larger shells promote increasing sinking velocities during gametogenesis for paleoceanographic reconstructions the evolutionary adaptation of neogloboquadrina pachyderma sin to the cold water habitat has significant implications carbonate sedimentation in highest latitudes is highly dependent on the presence of this species in the norwegian greenland sea carbonate poor intervals before 1 1 ma are therefore not necessarily related to severe glacial conditions they are probably attributed to the absence of this not yet polar adapted species further transfer function and modern analog techniques used for the reconstruction of surface water conditions in high latitudes could therefore contain a large range of errors if they were applied to samples older than 1 1 1 0 myrs 2000 elsevier science b v all rights reserved

atlantic sea surface temperatures estimated from planktonic foraminifera off the iberian margin over the last 40 ka bp abstract sea surface temperatures ssts were reconstructed from planktonic foraminiferal assemblages in two sediment cores off the nw iberian continental margin for the last 40 kyr results of this work were compared with published ssts estimated in six cores from the iberian margin and the 18 o data from ngrip ice core of greenland longitudinal and latitudinal sst changes were identified in several intervals related to alterations in the hydrographic conditions off the iberian peninsula namely the influence of the upwelling system the intensity of paleo portugal and paleo azores currents and the positions of the polar and arctic fronts during the holocene the ssts were quite stable along the west iberian margin when compared with the last glaciation however during the last glacial maximum lgm ssts were not much lower than during the holocene the portugal current as an eastward descending branch of the north atlantic drift should have been quite vigorous in transporting warm water to the west iberian margin which could have moderated the ssts during the lgm however our results suggest a much higher instability during the lgm than previously reported and much lower ssts at 42 n the lowest ssts during the last 40 ka were recorded during the heinrich stadials hs and the younger dryas yd during the hs ssts at the northwest iberian margin were lower than today by about 10 to 16 c as a result of the invasion of cool and low salinity water masses and the increased transport of icebergs from the northern seas the polar front was persistently situated at 42 n for 3 ka during the hs1 and a comparable present day arctic front should have been present up to the latitude of 40 n during the hs2 hs3 and hs4 off the west iberian peninsula the hs were recorded all along the west iberian margin however an overall trend of increasing of mean ssts from north to south of 8 c during the hs1 of 10 c during the hs2b and hs3 of 11 c during the hs2a and of 4 c during the hs4 was recorded these gradients also were present during the yd of 9 c and the lgm of 4 c and may be related to the strong influence of the paleo azores current in southern areas

ice sheet erosion and the stripping of tertiary regolith from baffin island eastern canadian arctic abstract the erosion of glaciated regions and concomitant changes in ice sheet dynamics through the pleistocene are poorly documented the baffin island landscape which has been shaped by the foxe sector of the laurentide ice sheet lis contains a variety of glacial and proximal glaciomarine sedimentary archives spanning the pleistocene we examine these records to better understand when tertiary regolith was stripped from beneath the foxe sector of the lis till on the interior plateaux of the island in areas with scoured bedrock have low chemical index of alteration cia values low meteoric 10 be 10 be met concentrations and clay mineralogy consistent with erosion from an unweathered bedrock source however in some areas in between fiord onset zones more weathered till is present containing considerably higher cia values high 10 be met concentrations and secondary clay mineral weathering products implying that the till has persisted on the landscape and weathered during successive glaciations using these weathering signatures we analyze the coastal glaciogenic deposits of the clyde foreland formation cff at two sites for evidence of tertiary regolith removal from the interior of baffin island by lis erosion provenance indicators within the cff demonstrate that pleistocene lis ice flow lines across baffin island have remained generally constant the oldest cff glaciogenic unit likely representing one of the first if not the first lis advances across baffin island had high 10 be met concentrations at the time of deposition consistent with extensive regolith erosion evidence of notably weathered sediment is absent in all younger units suggesting that tertiary regolith was likely largely stripped from the interior of the island by 1 6 0 2 ma

using foraminiferal test size distribution and other methods to recognise quaternary bathyal turbidites and taphonomically modified faunas abstract the aim of this study was to develop a simple methodology using foraminifera to distinguish between sediment that has been displaced downslope as in a turbidity current and in situ hemipelagic sediment these same methods will also be useful to identify seafloor foraminiferal faunas that have suffered considerable taphonomic modification e g through dissolution winnowing mixing which render them unsuitable as modern analogues for paleoenvironmental reconstructions to help develop this methodology we used late quaternary samples from cores containing identified turbiditic sand mud couplets that had been deposited at lower bathyal to upper abyssal depths 1400 3000 m off the earthquake prone east coast of new zealand comparison of the proportions of the total planktic and benthic foraminiferal tests in each of three size categories 63 125 m 125 250 m 250 m with those in unmodified in situ modern bathyal faunas from off new zealand showed an increased proportion of larger tests in the lower sandy turbidite layers and a slight increase of smaller tests in the upper muddy layers presumably as a result of winnowing processes during deposition a regression formula was used to estimate depositional depths based on the relative abundance of planktics in the quaternary foraminiferal faunas 63 m in all but one of our core samples these depth estimates were considerably shallower than the cores present depth and suggested that most sediment both sand and mud had been transported downslope modern analogue technique mat was used to estimate depths of deposition of the core samples based on a modern benthic foraminiferal dataset 63 m from around new zealand there was no great difference between estimates based on species and on genus some mat depth estimates were inconsistent with those from the other foraminiferal and sedimentological proxy methods that suggested turbiditic displacement because of the inconsistent results and the much greater work required to acquire the species census data we exclude the mat method from our suggested methodology genera were lumped into groups with similar bathymetric range and the relative abundances of these groups in each core sample were used to infer sediment provenance and mixing during downslope transport we recommend a methodology using three elements test size distribution planktic percentage and relative abundance of bathymetric groups of benthic genera the first two require the least amount of work and can reliably identify the majority of displaced and taphonomically modified faunas the third requires some taxonomic skills to identify key genera but gives more information on the provenance depth and amount of mixing in displaced turbiditic sediment although developed using new zealand modern and late quaternary foraminiferal data we contend that these methods should be applicable for use throughout most of the neogene in other temperate and subtropical parts of the world s oceans before use elsewhere studies in the local region may be needed to test recalibrate and tweak the modern analogue data on local test size distribution and planktic percentage our study also suggests that these methods can be useful to identify seafloor foraminiferal faunas that have suffered considerable taphonomic modification e g through dissolution winnowing mixing which render them unsuitable as modern analogues for paleoenvironmental reconstructions

biological and ecological insights into ca isotopes in planktic foraminifers as a palaeotemperature proxy sea surface temperature sst is a critical variable in the earth s climate system since it influences atmospheric circulation the hydrological cycle and via ocean surface density drives ocean circulation a detailed reconstruction of past sst s is therefore a central goal of palaeoceanographic studies although calcium isotopes in foraminiferal carbonate have been introduced as a new proxy for sst reconstruction there is considerable debate about their robustness and general applicability to resolve some of these questions we have investigated the extent to which other environmental parameters e g the calcification temperature depth stratification growth rates and or environmental adaptation may influence the 44ca values of planktic foraminifers in modern and eocene samples geographically distributed data sets are affected by the exchange of cryptic species i e morphologically similar but genetically distinct species and by a mixing of optimal versus less optimal adaptation thus we have compared species within individual samples to evaluate whether the well documented depth stratification of foraminifers is reflected in their calcium isotopes the eocene data set shows a general agreement between 44ca and 18o derived calcification temperatures which supports a temperature effect on ca isotope incorporation the vertical temperature gradient using the different depth habitats of several foraminiferal species indicates a 44ca temperature dependence of 0 034 c 1 similar to inorganic calcite 0 015 c 1 and cultured o universa 0 019 c 1 the gradient resembles the global sediment 44ca compilation but it is significantly smaller than the temperature calibration of 0 22 0 02 c 1 for cultured g sacculifer the modern data set shows a general correlation between 44ca and depth habitat reflecting a similar temperature gradient to the eocene sample set in contrast the lower absolute 44ca values for the eocene foraminifers suggest a lower seawater isotope composition in situ analyses of individual calcite layers reveal large isotopic differences between the different calcite layers of the foraminifers highlighting the strong biological control on 44ca in foraminiferal calcite that may overprint a potential t relationship

glacial north atlantic sea surface conditions reconstructed by glamap 2000 the response of the tropical ocean to global climate change and the extent of sea ice in the glacial nordic seas belong to the great controversies in paleoclimatology our new reconstruction of peak glacial sea surface temperatures ssts in the atlantic is based on census counts of planktic foraminifera using the maximum similarity technique version 28 simmax 28 modern analog technique with 947 modern analog samples and 119 well dated sediment cores our study compares two slightly different scenarios of the last glacial maximum lgm the environmental processes of the ice age land oceans glaciers epilog and glacial atlantic ocean mapping glamap 2000 time slices the comparison shows that the maximum lgm cooling in the southern hemisphere slightly preceeded that in the north in both time slices sea ice was restricted to the north western margin of the nordic seas during glacial northern summer while the central and eastern parts were ice free during northern glacial winter sea ice advanced to the south of iceland and faeroe in the central northern north atlantic an anticyclonic gyre formed between 45degrees and 60degreesn with a cool water mass centered west of ireland where glacial cooling reached a maximum of 12degreesc in the subtropical ocean gyres the new reconstruction supports the glacial to interglacial stability of sst as shown by climap project members climap 1981 the zonal belt of minimum sst seasonality between 2degrees and 6degreesn suggests that the lgm caloric equator occupied the same latitude as today in contrast to the climap reconstruction the glacial cooling of the tropical east atlantic upwelling belt reached up to 6degrees 8degreesc during northern hemisphere summer differences between these simmax based and published u37 k and mg ca based equatorial sst records are ascribed to strong sst seasonalities and sst signals that were produced by different planktic species groups during different seasons

the evolutionary history of size variation of planktic foraminiferal assemblages in the cenozoic abstract the iterative evolutionary radiation of planktic foraminifers is a well documented macroevolutionary process here we document the accompanying size changes in entire planktic foraminiferal assemblages for the past 70 my and their relationship to paleoenvironmental changes after the size decrease at the cretaceous paleogene k p boundary high latitude assemblages remained consistently small size evolution in low latitudes can be divided into three major phases the first is characterized by dwarfs 65 42 ma the second shows moderate size fluctuations 42 14 ma and in the third phase planktic foraminifers have grown to the unprecedented sizes observed today our analyses of size variability with paleoproxy records indicate that periods of size increase coincided with phases of global cooling eocene and neogene these periods were characterized by enhanced latitudinal and vertical temperature gradients in the oceans and high diversity polytaxy in the paleocene and during the oligocene the observed minor size changes of the largely low diversity oligotaxic assemblages seem to correlate with productivity changes however polytaxy per se was not responsible for larger test sizes

response of planktic foraminiferal size to late quaternary climate change 1 geographical size distribution within entire holocene foraminiferal assemblages is related to global environmental gradients such as temperature primary productivity and environmental variability this study demonstrates that these correlations are also recognizable in late quaternary assemblages from three locations in the south atlantic on temporal and latitudinal scales the size response to temporal paleoenvironmental changes during glacial interglacial cycles mimics the geographic holocene size variability the amplitude of size variability is directly related to the amplitude of the climatic fluctuations as shown by the stable size temperature relationship over time the documented changes in the assemblage size are caused by species replacement and intraspecific size variability the relative importance of these processes depends on the environmental setting species have been shown to reach their maximum size and abundance under certain optimum conditions and decrease in size if environmental conditions differ from these optima we confirm that late quaternary species sizes were largest at paleotemperatures identical to holocene ones

controls on shell mg ca and sr ca in cultured planktonic foraminiferan globigerinoides ruber white mg ca and sr ca ratios were determined on a single species of planktonic foraminiferan globigerinoides ruber white collected from the gulf of eilat and cultured in seawater at five different salinities 32 to 44 five temperatures 18 to 30 c and four ph values 7 9 to 8 4 the mg ca temperature calibration of cultured g ruber with an exponential slope of 8 3 c agrees well with previously published calibrations from core tops and sediment traps however the dependence of mg ca on salinity with an exponential slope of 5 3 psu is also significant and should be included in the calibration equation with this purpose we calculated a calibration equation for g ruber dependent on both temperature and salinity within the 95 confidence limits mg ca mmol mol exp 0 06 0 02 s psu 0 08 0 02 t c 2 8 1 0 r2 0 95 the influence of ph on mg ca ratios is negligible at ambient seawater ph 8 1 to 8 3 however we observe a dominating ph control on shell mg ca when the ph of seawater is lower than 8 0 sr ca in g ruber shows a significant positive correlation with average growth rate presumably part of the variability in shell sr ca in the geological record is linked to changes in growth rates of foraminifera as a response to changing environmental conditions

opening the carbon isotope vital effect black box 2 quantitative model for interpreting foraminiferal carbon isotope data interpretation of carbon isotope records from late quaternary planktonic foraminifers are confounded due to the presence of a significant physiological component in the carbon isotopic signal a quantitative carbon isotope qc model is presented which relates the carbon isotopic composition of a foraminiferal shell to the physiological processes of respiration and symbiont photosynthesis and to the 13c value of seawater co2 the qc model is calibrated with physiological and stable isotopic data from laboratory experiments with living planktonic foraminifers model simulations of chamber and shell 13c values with the symbiont bearing foraminifers orbulina universa and globigerinoides sacculifer suggest 1 variations in symbiont density and photosynthetic rate light level or habitat depth are the primary physiological parameters controlling intraspecific carbon isotopic variability in these species 2 respiration has little effect on the 13c of o universa and 3 each chamber in a multichambered foraminiferal test will have a distinct 13c value depending on its position in the test whorl size 13c value relationships reported for g sacculifer from fossil assemblages can be explained as a function of increasing symbiont density during ontogenetic development

pleistocene sea surface temperature evolution early cooling delayed glacial intensification and implications for the mid pleistocene climate transition the mid pleistocene climate transition mpt is defined by the emergence of high amplitude quasi 100 ka glacial interglacial cycles from a prior regime of more subtle 41 ka cycles this change in periodicity and amplitude cannot be explained by a change in external astronomical forcing here we review and integrate published records of sea surface temperatures ssts to assess whether a common global expression of the mpt in the surface ocean can be recognized and examine our findings in light of mechanisms proposed to explain climate system reorganization across the mpt we show that glacial interglacial variability in ssts is superimposed upon a longer term cooling trend in oceanographic systems spanning the low to high latitudes regional variability exists in the timing of the onset and magnitude of cooling but in most cases a long term cooling trend begins or intensifies from 1 2 ma marine isotope stage mis 35 34 the sst cooling accompanies a long term trend towards higher global ice volume as recorded in benthic foraminifera 18o but predates a step like increase in 18o at 0 9 ma mis 24 22 that is argued to reflect expansion of continental ice sheets the strongest expression of pleistocene cooling is found during glacial stages whereas minor or negligible trends in interglacial temperatures are identified however pronounced cooling during both glacial and interglacial maxima is evident at 0 9 ma alongside the long term sst cooling trends quasi 100 ka cycles begin to emerge in both the sst and 18o records at 1 2 ma and become dominant with the expansion of the ice sheets at 0 9 ma we show that the intensified glacial stage cooling is accompanied by evolving pco2 abyssal ocean ventilation atmospheric circulation and or dust inputs to the southern ocean these changes in diverse environmental parameters suggest that glacial climate boundary conditions evolved across the mpt in turn these modified boundary conditions may have altered climate sensitivity to orbital forcing by placing pre existing ice sheets closer to some threshold of climate ice sheet response

biogeography and evolution of body size in marine plankton body size is a central feature of any organism reflecting its physiology ecology and evolutionary history marine microplankton are major contributors to the particulate inorganic carbonate foraminifers and coccolithophorids and opal flux radiolaria and diatoms in the ocean and hence size changes in these organisms can influence global biogeochemical cycles this paper is discussing abiotic influences on micro and macroecological size changes among major marine plankton groups linking these to evolutionary size changes during the neogene we review the patterns and outline the causes of size changes geographically and through time in coccolithophorids foraminifers and radiolarians the main feature of the neogene size record is a dramatic size increase in foraminifers a similarly dramatic reduction in the size range of coccolithophorids and highly variable size patterns in radiolarians we argue that the observed pattern is too complex to be explained by a simple common forcing and propose that speculations on the response of oceanic biomineralisation to global warming have to consider the scales at which marine plankton evolve

drift motions of very high latitude f region irregularities azimuthal doppler analysis since october 1983 a new hf radar facility has been operated from goose bay labrador for the purpose of studying high latitude ionospheric irregularities in this paper we present autocorrelation functions of the backscattered signals from these irregularities and show how these are processed to yield information on the drift velocities of the irregularities since the radar is typically operated in an azimuth scan mode the doppler data derived from the autocorrelation functions may be used to study the two dimensional structure of the irregularity drift a procedure is presented for this analysis and it is shown that the results are reasonably accurate during periods in which the irregularity drift is approximately uniform however if the flow is nonuniform as it is in the vicinity of the cusp and in the midnight local time sector then the procedure leads to erroneous results we consider the implication that these results have on azimuth scan measurements of plasma drift with incoherent scatter radars and we present possible ways in which measurements might be made under nonuniform flow conditions

monsoon upwelling effects on test size of some planktonic foraminiferal species from the oman margin arabian sea variation in upwelling may be monitored using various micropaleontological indices such as the relative abundance or accumulation rate of the planktonic foraminiferal species globigerina bulloides or mass accumulation rate of planktonic foraminifera we have analyzed the relationships between the upwelling history and mean test size variations in the planktonic foraminiferal species globigerinoides ruber globigerinita glutinata g bulloides and neogloboquadrina dutertrei through the last 19 000 years in ocean drilling program hole 723 a from the oman margin arabian sea the study reveals that these species were larger on average between 11 and 5 ka which coincides with a period of strong upwelling on the other hand these species showed smaller mean test sizes during the last glacial period and late holocene when upwelling was weaker mass accumulation rates of these species are linearly proportional to their mean test sizes indicating that both mean size and productivity of individual species are related to the upwelling intensity therefore we propose that the size variations in g ruber g glutinata g bulloides and n dutertrei can be used as an additional micropaleontological index of upwelling intensity in the arabian sea

reconstruction of sea surface temperatures from assemblages of planktonic foraminifera multi technique approach based on geographically constrained calibration data sets and its application to glacial atlantic and pacific oceans abstract we present a conceptual framework for a new approach to environmental calibration of planktonic foraminifer census counts this approach is based on simultaneous application of a variety of transfer function techniques which are trained on geographically constrained calibration data sets it serves to minimise bias associated with the presence of cryptic species of planktonic foraminifera and provides an objective tool for assessing reliability of environmental estimates in fossil samples allowing identification of adverse effects of no analog faunas and technique specific bias we have compiled new calibration data sets for the north n 862 and south n 321 atlantic and the pacific ocean n 1111 we show evidence that these data sets offer adequate coverage of the sea surface temperature sst and faunal variation range and that they are not affected by the presence of pre holocene samples and or calcite dissolution we have applied four transfer function techniques including artificial neural networks revised analog method and simmax with and without distance weighting on faunal counts in a last glacial maximum lgm data set for the atlantic ocean 748 samples in 167 cores based on the glamap 2000 compilation and a new data set for the pacific ocean 265 samples in 82 cores and show that three of these techniques provide adequate degree of independence for the advantage of a multi technique approach to be realised the application of our new approach to the glacial pacific lends support to the contraction and perhaps even a cooling of the western pacific warm pool and a substantial 3 c cooling of the eastern equatorial pacific and the eastern boundary currents our results do not provide conclusive evidence for lgm warming anywhere in the pacific the atlantic reconstruction shows a number of robust patterns including substantial cooling of eastern boundary currents with considerable advection of subpolar waters into the benguela current a cooling of the equatorial atlantic by 5 c and steep sst gradients in the mid latitude north atlantic the transfer function techniques generally agree that subtropical gyre areas in both hemispheres did not change significantly since the lgm although the ann technique produced glacial sst in the southern gyre 1 2 c warmer than today we have revisited the issue of sea ice occurrence in the nordic seas and using the distribution of subpolar species of planktonic foraminifera in glacial samples we conclude that the norwegian sea must have been ice free during the summer

maastrichtian north atlantic warming increasing stratification and foraminiferal paleobiology at three timescales 1 analysis of 944 single specimens of three species of late maastrichtian planktonic foraminifera racemiguembelina fructicosa contusotruncana contusa and rugoglobigerina rugosa from 38 samples spanning the last 3 myr of the cretaceous shows consistent isotopic trends through time consistent isotopic differences among taxa and high within sample isotopic variability throughout within sample variability does not change systematically through time for any taxon but average 18o values decrease by 1 5 and average 13c values diverge up section comparing taxa average 18o values are similar within most samples but average 13c values generally decrease from r fructicosa to r rugosa to c contusa in addition the within sample variability of individual 13c measurements is larger for r fructicosa than for either c contusa or r rugosa an observation which is consistent with a photosymbiotic habitat for r fructicosa in terms of maastrichtian paleoceanography the negative 18o trend of 1 5 corresponds to a temperature increase of 6 c and the divergence of 13c values up section suggests an increasingly stratified water column in the western atlantic through the late maastrichtian we suggest that these trends are best explained by increasing import of south atlantic waters into the north atlantic and an intensification of the northern hemisphere polar front

contribution of seasonal sub antarctic surface water variability to millennial scale changes in atmospheric co2 over the last deglaciation and marine isotope stage 3 the southern ocean is thought to have played a key role in past atmospheric carbon dioxide co2 atm changes three main factors are understood to control the southern ocean s influence on co2 atm via their impact on surface ocean pco2 and therefore regional ocean atmosphere co2 fluxes 1 the efficiency of air sea gas exchange which may be attenuated by seasonal or annual sea ice coverage or the development of a shallow pycnocline 2 the supply of co2 rich water masses from the sub surface and the deep ocean which is associated with turbulent mixing and surface buoyancy and or wind forcing and 3 biological carbon fixation which depends on nutrient availability and is therefore influenced by dust deposition and or upwelling in order to investigate the possible contributions of these processes to millennial scale co2 atm variations during the last glacial and deglacial periods we make use of planktonic foraminifer census counts and stable oxygen and carbon isotope measurements in the planktonic foraminifera globigerina bulloides and neogloboquadrina pachyderma sinistral from marine sediment core md07 3076q in the sub antarctic atlantic these data are interpreted on the basis of a comparison of core top and modern seawater isotope data which permits an assessment of the seasonal biases and geochemical controls on the stable isotopic compositions of g bulloides and n pachyderma s based on a comparison of our down core results with similar data from the southeast atlantic cape basin we infer past basin wide changes in the surface hydrography of the sub antarctic atlantic we find that millennial scale rises in co2 atm over the last 70 ka are consistently linked with evidence for increased spring upwelling and enhanced summer air sea exchange in the sub antarctic atlantic parallel evidence for increased summer export production would suggest that seasonal changes in upwelling and air sea exchange exerted a dominant influence on surface pco2 in the sub antarctic atlantic these results underline the role of southern ocean dynamics in particular their seasonal variations in driving millennial scale variations in co2 atm

trace element variability in crust bearing and non crust bearing neogloboquadrina incompta p d intergrade and globoconella inflata from the southwest pacific ocean potential paleoceanographic implications mg ca and sr ca ratios were measured in the sub surface dwelling planktonic foraminifera neogloboquadrina incompta neogloboquadrina pachyderma neogloboquadrina dutertrei p d intergrades and globoconella inflata from core top dredge and plankton tow material from the southwest pacific ocean the presence of outer crusts on each foraminifera test was determined using a scanning electron microscope after trace element analysis using laser ablation inductively coupled plasma mass spectrometry la icpms our laser ablation profiles allow an arbitrary distinction between crust and inner calcite mg ca values with the former exhibiting consistently lower mg ca by up to 56 depending on both the species and core top location analyzed the lower crust mg ca values suggest that 1 crust formation may be initiated at a specific low temperature or 2 crust calcite no longer follows the mg to ca thermodynamic relationship typically associated with foraminiferal primary calcite for sr ca ratios we did not observe any difference between crust in and inner calcite the thickness of the crust between measured individual chambers varied such that whole test mg ca were affected by variable crustal thickness across all chambers this study shows that increasing ratios of crust to non crust bearing tests in n incompta p d intergrades and g inflata have the potential to lower the bulk composition of mg ca thus resulting in biased cooler temperature reconstructions

the response of the bering sea gateway during the mid pleistocene transition abstract the mid pleistocene transition and the response of sea ice in the subarctic north pacific are examined using a diatom record from the north eastern bering sea slope iodp core u1344a high percentages of diatom sea ice species in the assemblage foster the development of groupings specific to differing ice conditions thalassiosira antarctica var borealis emerges as a key diatom species that delineates the development of thick multiannual sea ice and marks a series of advancements from 0 9 to1 2 ma after which it dominates the assemblage until 0 6 ma the decline of neodenticula seminae indicative of alaskan stream water inflow is in agreement with neighbouring core u1343e confirming the reduction of bering sea circulation after 0 9 ma we propose that during the mpt a stepped advancement of sea ice occurs in the bering sea as a response to increased moisture delivery to the high latitudes an extended period of diatom productivity between 0 75 and 0 65 ma marks major deglacial conditions towards the end of the mpt by 0 6 0 55 ma the work highlights the important role played by sea ice and supports the contention of a colder mpt in the subarctic pacific

the subantarctic and polar fronts in relation to deep water masses through the southwestern atlantic the two principal fronts within the antarctic circumpolar current acc the subantarctic front saf and the polar front pf are investigated with respect to their spatial patterns and relations to deep water masses from the northern drake passage to the western and southern argentine basin observations from four recent cruises in adjoining and overlapping regions are supplemented with satellite infrared imagery and trajectories from surface drifters east of drake passage the width of the polar frontal zone pfz increases rapidly when the saf turns sharply northward as a part of the falkland malvinas current while the pf remains oriented mainly toward the northeast found within this region of the pfz are mesoscale eddies the upper layers of which consist of subantarctic mode water from the pacific the contrasts in upper layer water properties that identify the saf can be traced the entire length of the falkland current to the brazil falkland confluence zone and then southward to the southern argentine basin there the saf turns eastward and later but perhaps not always merges with the pf north of ewing bank to form a single intense current core strongly influenced by bottom topography at times this eastward current loops southward through a gap in the falkland ridge into the georgia basin thereby supplying relatively warm and salty subantarctic water to the antarctic zone east of the gap the two fronts become separated and are once again distinct features in the vicinity of the islas orcadas rise at depth within drake passage and the western scotia sea the saf and pf are not lateral boundaries between distinct water masses but are instead identified by enhanced vertical displacements of property isopleths with the northward turn of the saf east of drake passage a thick layer of circumpolar deep water cdw is advected over the falkland plateau into the argentine basin there it is joined by waters entering the argentine basin via a deep spreading route through the georgia basin denser cdw deep water from the weddell sea and episodically deep water from the southeastern pacific ocean together these waters form a northward flow off the patagonian shelf that extends from the sea surface to the bottom most of which turns back toward the south with the falkland current return also flowing south along the seaward side of the falkland current return well away from the western boundary is the main core of north atlantic deep water nadw detatched masses of nadw are observed within the cdw at the western boundary as well as within the acc south of the saf in the south central argentine basin

arctic ocean during the last glacial maximum atlantic and polar domains of surface water mass distribution and ice cover on the basis of 52 sediment cores analyzed and dated at high resolution the paleoceanography and climate of the last glacial maximum lgm were reconstructed in detail for the fram strait and the eastern and central arctic ocean sediment composition and stable isotope data suggest three distinct paleoenvironments 1 a productive region in the eastern to central fram strait and along the northern barents sea continental margin characterized by atlantic water advection frequent open water conditions and occasional local meltwater supply and iceberg calving from the barents sea ice sheet 2 an intermediate region in the southwestern eurasian basin up to 84 85 n and the western fram strait characterized by subsurface atlantic water advection and recirculation a moderately high planktic productivity and a perennial ice cover that breaks up only occasionally and 3 a central arctic region north of 85 n in the eurasian basin characterized by a low salinity surface water layer and a thick ice cover that strongly reduces bioproduction and bulk sedimentation rates although the total inflow of atlantic water into the arctic ocean may have been reduced during the lgm its impact on ice coverage and halocline structure in the fram strait and southwestern eurasian basin was strong