mid holocene el nino southern oscillation enso attenuation revealed by individual foraminifera in eastern tropical pacific sediments holocene reconstructions of the el nino southern oscillation enso provide valuable perspective on its recent evolution and can be important for assessing its future optimal assessment of past enso variability requires observations from its center of action in the eastern equatorial pacific but these are limited due to paucity of high resolution paleoceanographic archives e g corals here we use a new approach to quantify past enso variance based on the oxygen isotopic composition 18 o of individual foraminifera globigerinoides ruber from deep sea sediments in the enso source region individual g ruber foraminifera behave as monthly recorders of sea surface conditions including enso extremes circumventing the lack of annual resolution in the sediments intrapopulation 18 o distributions derived with this method from a core near the galapagos islands reveal mid holocene reductions in variance of 50 requiring drastic attenuation of the enso amplitude furthermore mg ca thermometry indicates that mid holocene background conditions were accompanied by a stronger zonal temperature gradient that coincided with a northward displaced intertropical convergence zone itcz the results suggest that the position of the itcz is an important factor in the low frequency modulation of enso and could influence its future evolution

winter time dissolved iron and nutrient distributions in the subantarctic zone from 40 52s 155 160e 1 in hnlc oceanic regions iron fe controls phytoplankton productivity yet large gaps remain in our understanding of iron s biogeochemical cycle here we present the first comprehensive winter dataset for dissolved fe dfe and nitrate no3 distributions 0 1000 m depth between 40s 52s which transects the subantarctic zone saz west of new zealand surface concentrations 0 2 nmol fe kg 1 were conspicuously low i e probably biologically limiting even at winter reserve levels at frontal zones between 43s subtropical front and 51s subantarctic front a fivefold range in fe no3 molar ratios was observed along the transect with subtropical waters where blooms occur having the highest ratios in subsurface waters the major wintertime supply of dfe in the saz is from ekman advection of waters from the south but calculated source water dfe is 0 2 nmol fe kg 1 suggesting that mixed layer dfe concentration is controlled by how long these southern waters remain at the surface 3 years

reduction of oceanic temperature gradients in the early eocene southwest pacific ocean abstract we present a southwest pacific ocean paleothermometry transect using new and existing foraminiferal mg ca data from six eocene locations from eastern new zealand to southwestern campbell plateau spanning 10 of paleolatitude 43 to 53 s sea surface and seafloor temperatures sst and sft have been calculated taking into account the partition coefficients of calcite and paleogene mg ca sw ratios and used to determine values for the power component h of this relationship in foraminiferal calcite from paired proxy 18 o and mg ca records from canterbury basin this study presents the first eocene paleotemperature record for the east coast basin and in so doing shows the absence of a meridional temperature gradient over 10 of latitude during the early eocene climatic optimum eeco and provides evidence for a very weak to absent gradient from the equatorial pacific to 53 s at this time of extreme global warmth the application of a new subsurface tex 86 calibration correlates remarkably well with mg ca seafloor temperature trends from the continental slope setting 86 is recording an upper ocean subsurface temperature record rather than simply sst values sst sft gradients demonstrate a notable reduction decreasing to 3 5 c across the eeco the comparable ocean temperatures of the east coast basin canterbury basin and dsdp site 277 during this time support the intensification of a proto east australian current eac explaining the distribution of tropical sea temperatures extending into the high latitude southwest pacific ocean during the eeco seafloor temperatures 1000 m paleodepth likely correspond to a northern intermediate water source during the early eocene before switching to a cooler southern derived source in the middle to late eocene

glacial interglacial ocean climate variability from planktonic foraminifera during the mid pleistocene transition in the temperate southwest pacific odp site 1123 abstract planktonic foraminiferal assemblages and artificial neural network estimates of sea surface temperature sst at odp site 1123 41 47 2 s 171 29 9 w 3290 m deep east of new zealand reveal a high resolution history of glacial interglacial g i variability at the subtropical front stf for the last 1 2 million years including the mid pleistocene climate transition mpt most g i cycles of 100 kyr duration have short periods of cold glacial and warm deglacial climate centred on glacial terminations followed by long temperate interglacial periods during glacial deglacial transitions maximum abundances of subantarctic and subtropical taxa coincide with sst minima and maxima and lead ice volume by up to 8 kyrs such relationships reflect the competing influence of subantarctic and subtropical surface inflows during glacial and deglacial periods respectively suggesting alternate polar and tropical forcing of southern mid latitude ocean climate the lead of ssts and subtropical inflow over ice volume points to tropical forcing of southern mid latitude ocean climate during deglacial warming this contrasts with the established hypothesis that southern hemisphere ocean climate is driven by the influence of continental glaciations based on wholesale changes in subantarctic and subtropical faunas the last 1 2 million years are subdivided into 4 distinct periods of ocean climate 1 the pre mpt 1185 870 ka has high amplitude 41 kyr fluctuations in sst superimposed on a general cooling trend and heightened productivity reflecting long term strengthening of subantarctic inflow under an invigorated antarctic circumpolar current 2 the early mpt 870 620 ka is marked by abrupt warming during mis 21 followed by a period of unstable periodicities within the 40 100 kyr orbital bands decreasing sst amplitudes and long intervals of temperate interglacial climate punctuated by short glacial and deglacial phases reflecting lower meridional temperature gradients 3 the late mpt 620 435 ka encompasses an abrupt decrease in the subantarctic inflow during mis 15 followed by a period of warm equable climate poorly defined low amplitude g i variations in ssts during this interval are consistent with a relatively stable stf and evenly balanced subantarctic and subtropical inflows possibly in response to smaller less dynamic polar icesheets 4 the post mpt 435 0 ka is marked by a major climatic deterioration during mis 12 and a return to higher amplitude 100 kyr frequency sst variations superimposed on a long term trend towards cooler ssts and increased mixed layer productivity as the subantarctic inflow strengthened and polar icesheets expanded

long term sea surface temperature and climate change in the australian new zealand region 1 we compile and compare data for the last 150 000 years from four deep sea cores in the midlatitude zone of the southern hemisphere we recalculate sea surface temperature estimates derived from foraminifera and compare these with estimates derived from alkenones and magnesium calcium ratios in foraminiferal carbonate and with accompanying sedimentological and pollen records on a common absolute timescale using a stack of the highest resolution records we find that first order climate change occurs in concert with changes in insolation in the northern hemisphere glacier extent and inferred vegetation changes in australia and new zealand vary in tandem with sea surface temperatures signifying close links between oceanic and terrestrial temperature in the southern ocean rapid temperature change of the order of 6 c occurs within a few centuries and appears to have played an important role in midlatitude climate change sea surface temperature changes over longer periods closely match proxy temperature records from antarctic ice cores warm events correlate with antarctic events a1 a4 and appear to occur just before dansgaard oeschger events 8 12 14 and 17 in greenland

southern ocean seasonal temperature and subtropical front movement on the south tasman rise in the late quaternary 1 the subtropical front stf marking the northern boundary of the southern ocean has a steep gradient in sea surface temperature sst of approximately 4c over 0 5 of latitude presently in the region south of tasmania the stf lies nominally at 47s in the summer and 45s in the winter we present here sst reconstructions in a latitudinal transect of cores across the south tasman rise southeast of australia during the late quaternary sst reconstructions are based on two paleotemperature proxies alkenones and faunal assemblages which are used to assess past changes in sst in spring and summer the north south alignment in core locations allows reconstruction of movement of the stf over the last 100 ka surface water temperatures during the last glaciation in this region were 4c colder than today additional temperature changes greater in magnitude than 4c seen in individual cores can be attributed to changes in the water mass overlying the core site caused by the movement of the front across that location during the penultimate interglacial sst was 2c warmer and the stf was largely positioned south of 47s movement of the stf to the north occurred during cool climate periods such as the last marine isotope stages 3 and 4 in the last glaciation the front was at its farthest north position becoming pinned against the tasmanian landmass it moved south by 4 latitude to 47s in summer during the deglaciation but remained north of 45s in spring throughout the early deglaciation after 11 ka b p inferred invigoration of the east australia current appears to have pushed the stf seasonally south of the east tasman plateau until after 6 ka b p when it achieved its present configuration

a source to sink perspective of the waipaoa river margin abstract a fundamental goal of the earth science community is to understand how perturbations on earth s surface are preserved in the stratigraphic record recent source to sink s2s studies of the waipaoa sedimentary system wss new zealand are synthesized herein to provide a holistic perspective of the processes that generate transport and preserve sedimentary strata and organic carbon on the waipaoa margin in the late quaternary rapid uplift associated with subduction processes and weak sedimentary units have conspired to generate rapid rates of incision and erosion in the waipaoa catchment since the last glacial maximum lgm we show that although much of the sediment exported offshore during this time interval originated from valley excavation a substantial portion emanated from hillslopes mostly through deep seated landslide and earthflow processes that were vigorous during periods of rapid fluvial incision just prior to the pleistocene holocene transition lacustrine sediments deposited in naturally dammed 7 ky old lake tutira provide a record of holocene environmental controls on upper catchment sedimentation in the wss with 1400 storms identified storm frequency is modulated by the waxing and waning of atmospheric teleconnections between the tropics and antarctica furthermore clear long term changes in sediment yield are evident from the lake tutira record following human settlement as conversion to pasture is accompanied by a 3 fold increase in the long term lake sediment accumulation rate whereas there is ample evidence that waipaoa river flood deposits are routinely deposited offshore in the sheltered confines of poverty bay over the longer term waves and currents subsequently resuspend and transport these deposits both landward sandy fraction and seaward finer fraction thus the timing of sediment supply to areas of net sediment accumulation is more often driven by wave events that are not associated with river flooding therefore we conclude that asynchronicity of river sediment delivery and of wave resuspension in most instances precludes the direct preservation of flood events in the stratigraphic record of the waipaoa shelf over the longer term the sediment package preserved on the shelf and slope since the lgm can be explained in large measure by sequence stratigraphic models forced by varying sea level and ongoing tectonic deformation of the margin as sea level rose sediment supply to the slope was reduced by about a factor of 5 due to shelf trapping despite this reduction turbidites are found at similar frequency throughout the lgm present as the dominant trigger appears to be subduction earthquakes with large ones having a return interval of about 200 100 years sediment budget exercises that consider both modern river discharge versus centennial accumulation rates and post lgm terrestrial production versus offshore isopachs mass balances indicate that about half of the total sediment production from the waipaoa escapes the study area moreover a coupled sediment transport hydrodynamic model and observations of textural trends on the shelf indicate that a large fraction of the sediment is carried outside the study area along the shelf to the northeast by the river plume or by combined current wave activity therefore we conclude that the wss is an open system with sediment escape from the present day through the lgm the organic matter associated with sediment as it moves from upland source to marine sink is a product of particle history and provides a record of materials that have cycled over timescales of days to millions of years the ubiquity of fossil organic carbon oc in both the terrestrial and marine realms of the waipaoa attests both to the chronic nature of its source crumbling mudstones further destabilized by land use and its biogeochemical recalcitrance modern oc persists by virtue of its continual production along the s2s transit and is buried and preserved within the adjacent marine depocenters the waipaoa contrasts with dispersal systems on wide energetic shelves e g the amazon and fly rivers where sediment is extensively refluxed in oxygenated overlying water resulting in the biogeochemical incineration of particulate oc the waipaoa like other small mountainous rivers on active margins exhibits a high riverine oc preservation efficiency 50 in its marine depocenters because of the relatively rapid event driven accumulation of sediment

a paleo perspective on ocean heat content lessons from the holocene and common era abstract the ocean constitutes the largest heat reservoir in the earth s energy budget and thus exerts a major influence on its climate instrumental observations show an increase in ocean heat content ohc associated with the increase in greenhouse emissions here we review proxy records of intermediate water temperatures from sediment cores and corals in the equatorial pacific and northeastern atlantic oceans spanning 10 000 years beyond the instrumental record these records suggests that intermediate waters were 1 5 2 c warmer during the holocene thermal maximum than in the last century intermediate water masses cooled by 0 9 c from the medieval climate anomaly to the little ice age these changes are significantly larger than the temperature anomalies documented in the instrumental record the implied large perturbations in ohc and earth s energy budget are at odds with very small radiative forcing anomalies throughout the holocene and common era we suggest that even very small radiative perturbations can change the latitudinal temperature gradient and strongly affect prevailing atmospheric wind systems and hence air sea heat exchange these dynamic processes provide an efficient mechanism to amplify small changes in insolation into relatively large changes in ohc over long time periods the ocean s interior acts like a capacitor and builds up large positive and negative heat anomalies that can mitigate or amplify small radiative perturbations as seen in the holocene trend and common era anomalies respectively evidently the ocean s interior is more sensitive to small external forcings than the global surface ocean because of the high sensitivity of heat exchange in the high latitudes to climate variations

340 000 year centennial scale marine record of southern hemisphere climatic oscillation in order to investigate rapid climatic changes at mid southern latitudes we have developed centennial scale paleoceanographic records from the southwest pacific that enable detailed comparison with antarctic ice core records these records suggest close coupling of mid southern latitudes with antarctic climate during deglacial and interglacial periods glacial sections display higher variability than is seen in antarctic ice cores which implies climatic decoupling between mid and high southern latitudes due to enhanced circum antarctic circulation structural and temporal similarity with the greenland ice core record is evident in glacial sections and suggests a degree of interhemispheric synchroneity not predicted from bipolar ice core correlations

ba ca in neogloboquadrina pachyderma as an indicator of deglacial meltwater discharge into the western arctic ocean 1 down core samples of the planktonic foraminifer neogloboquadrina pachyderma sinistral from the mendeleyev ridge in the western arctic ocean have been analyzed for ba ca and 18o the apparent distribution coefficient for n pachyderma sin is estimated at dba 0 22 0 02 a meltwater event is identified at around 11 8 14c kyr bp and is coincident with elevated ba ca ratios the barium enrichment is believed to be the result of enhanced weathering and erosion following glaciation additionally barium may have desorbed from shelf sediments as sea level rose changes in ba ca correlate with the retreat of the laurentide ice sheet and the evolution of the mackenzie river drainage basin therefore maximum ba ca in arctic surface waters at 11 8 ka may be indicative of an increase in the export of freshwater from the arctic to the north atlantic potentially contributing to the onset of the younger dryas this work suggests that ba ca in planktonic foraminifera may be a useful indicator of the timing and processes associated with deglaciation

changes in the position of the subtropical front south of new zealand since the last glacial period this study fills an important gap in our understanding of past changes in the southern subtropical front s stf in the southwest pacific ocean paleo sea surface temperatures sst were estimated from planktic foraminiferal census counts from cores straddling the modern s stf in the solander trough south of new zealand the estimated sst were compared for 6 time slices glacial period 25 21 ka last glacial maximum lgm 21 18 ka early deglaciation 18 16 ka late deglacial early holocene period 14 8 ka mid holocene period 8 4 ka and late holocene period 4 0 ka the position of the s stf was determined by two methods 1 the location of the 10 degrees c isotherm and 2 the location of the highest sst gradients these new results suggest that the s stf was not continuous between east and west of new zealand during the glacial period steep sst gradients indicate that a strong s stf rapidly shifted south during the lgm and early deglaciation during the late deglacial and holocene periods the position of the s stf differs between the two methods with reduced sst gradients suggesting amore diffuse s stf in the solander trough at this time the glacial sst data suggest that the s stf shifted north to the west of new zealand while to the east there was a stronger sst gradient across the front this was possibly the result of an increased wind stress curl which could have been caused by stronger or more northerly southern hemisphere westerly winds shww or a merging of the shww split jet in this region

is there evidence for solar forcing of climate in the gisp2 oxygen isotope record abstract changes in solar constant over an 11 yr cycle suggest a certain but limited degree of solar forcing of climate the high resolution climate oxygen isotope record of the greenland gisp2 greenland ice sheet project 2 ice core has been analyzed for solar and volcanic influences the atmospheric14c record is used as a proxy of solar change and compared to the oxygen isotope profile in the gisp2 ice core an annual oxygen isotope profile is derived from centimeter scale isotope measurements available for the post a d 818 interval associated extreme summer and winter isotope ratios were found to yield similar climate information over the last millennium the detailed record of volcanic aerosols converted to optical depth and volcanic explosivity change was also compared to the isotope record and the oxygen isotope response calibrated to short term volcanic influences on climate this calibration shows that century scale volcanic modulation of the gisp2 oxygen isotope record can be neglected in our analysis of solar forcing the timing estimated order of temperature change and phase lag of several maxima in14c and minima in18o are suggestive of a solar component to the forcing of greenland climate over the current millennium the fractional climate response of the cold interval associated with the maunder sunspot minimum and14c maximum as well as the medieval warm period and little ice age temperature trend of the past millennium are compatible with solar climate forcing with an order of magnitude of solar constant change of 0 3 even though solar forcing of climate for the current millennium is a reasonable hypothesis for the rest of the holocene the century scale events are more frequent in the oxygen isotope record than in the14c record and a significant correlation is absent for this interval oceanic atmospheric circulation forcing of climate may dominate solar forcing during the surprisingly strong 1470 yr climate cycle of the 11 000 75 000 yr b p interval is rather hypothetical

southwest pacific modulation of abrupt climate change during the antarctic cold reversal younger dryas abstract the giant piston core md97 2121 2314 m water depth collected north of the subtropical front new zealand provides a well dated stable isotopic record of subtropical and sub antarctic influences on the surface and deep ocean over the last deglaciation especially during the antarctic cold reversal acr 14 1 12 4 ka and younger dryas yd 13 0 11 5 ka after the last glacial maximum benthic foraminiferal 18ob changed in phase with antarctica the acr being represented by a pause in the 18ob deglacial trend in contrast surface waters as represented by the stable isotopes of 3 planktic foraminifers from 3 different depth zones and alkenone based sea surface temperatures showed no immediate response to the acr it was not until the reversal was at its coldest starting 13 5 ka that the surface ocean responded it became less warm its fertility reduced sharply and its surface structure changed as shown by the merger of the 18opl planktic profiles onshore these changes were accompanied by an expansion of cool climate vegetation an advancement of alpine glaciers and a likely pause in the post glacial transgression these onshore and offshore changes which continued well into yd time probably resulted from modification of polar conditions by subtropical influences the acr caused cooler temperatures weakened seasonality and stronger winds however its onset and impact were ameliorated by a strengthened inflow of subtropical water although acr driven atmospheric conditions prevailed by comparison south of the subtropical front where subtropical influences are weak and water masses have direct links with antarctica the surface waters cooled in phase with the acr

eight glacial cycles from an antarctic ice core the antarctic vostok ice core provided compelling evidence of the nature of climate and of climate feedbacks over the past 420 000 years marine records suggest that the amplitude of climate variability was smaller before that time but such records are often poorly resolved moreover it is not possible to infer the abundance of greenhouse gases in the atmosphere from marine records here we report the recovery of a deep ice core from dome c antarctica that provides a climate record for the past 740 000 years for the four most recent glacial cycles the data agree well with the record from vostok the earlier period between 740 000 and 430 000 years ago was characterized by less pronounced warmth in interglacial periods in antarctica but a higher proportion of each cycle was spent in the warm mode the transition from glacial to interglacial conditions about 430 000 years ago termination v resembles the transition into the present interglacial period in terms of the magnitude of change in temperatures and greenhouse gases but there are significant differences in the patterns of change the interglacial stage following termination v was exceptionally long 28 000 years compared to for example the 12 000 years recorded so far in the present interglacial period given the similarities between this earlier warm period and today our results may imply that without human intervention a climate similar to the present one would extend well into the future

planktic foraminifers as recorders of seawater ba ca abstract recent studies have used the ba ca ratio of planktic foraminifer shells as a proxy for river run off at oceanic sites near estuaries such studies assume that the ba ca ratio in planktic foraminifer shells is primarily controlled by the ba ca concentration of seawater and that other parameters such as salinity temperature and ph do not compromise the primary ba concentration relationship here we provide new insights from culture experiments and review published studies to confirm that environmental parameters including ph temperature salinity and symbiont photosynthesis do not affect ba substitution into planktic foraminiferal calcite the partition coefficient for ba in spinose planktic foraminifers is estimated as d ba 0 15 0 05 95 confidence limits the same factor also seems applicable to the non spinose genus neogloboquadrina but not to specimens of the non spinose genus globorotalia

little ice age cold interval in west antarctica evidence from borehole temperature at the west antarctic ice sheet wais divide 1 the largest climate anomaly of the last 1000 years in the northern hemisphere was the little ice age lia from 1400 1850 c e but little is known about the signature of this event in the southern hemisphere especially in antarctica we present temperature data from a 300 m borehole at the west antarctic ice sheet wais divide results show that wais divide was colder than the last 1000 year average from 1300 to 1800 c e the temperature in the time period 1400 1800 c e was on average 0 52 0 28 c colder than the last 100 year average this amplitude is about half of that seen at greenland summit grip this result is consistent with the idea that the lia was a global event probably caused by a change in solar and volcanic forcing and was not simply a seesaw type redistribution of heat between the hemispheres as would be predicted by some ocean circulation hypotheses the difference in the magnitude of the lia between greenland and west antarctica suggests that the feedbacks amplifying the radiative forcing may not operate in the same way in both regions

southwest pacific ocean response to a warming world using mg ca zn ca and mn ca in foraminifera to track surface ocean water masses during the last deglaciation in situ measurements of mg ca zn ca mn ca and ba ca in globigerinoides bulloides and globigerina ruber from southwest pacific core top sites and plankton tow are reported and their potential as paleoproxies is explored the modern samples cover 20 degrees of latitude from 34 degrees s to 54 degrees s 7 19 degrees c water temperature and variable influence of subantarctic saw and subtropical stw surface waters trace element signatures recorded in core top and plankton tow planktic foraminifera are examined in the context of the chemistry and nutrient profiles of their modern water masses our observations suggest that zn ca and mn ca may have the potential to trace saw and stw intraspecies and interspecies offsets identified by in situ measurements of mg ca and zn ca indicate that these ratios may also record changes in thermal and nutrient stratification in the upper ocean we apply these potential proxies to fossilized foraminifera from the high resolution core md97 2121 at the last glacial maximum surface water mg ca temperature estimates indicate that temperatures were approximately 6 7 degrees c lower than those of the present accompanied by low levels of mn ca and zn ca and minimal thermal and nutrient stratification this is consistent with regional dominance of saw and reduced stw inflow associated with a reduced south pacific gyre spg upper ocean thermal and nutrient stratification collapsed during the antarctic cold reversal before poleward migration of the zonal winds and ocean fronts invigorated the spg and increased stw inflow in the early holocene together with reduced winds this favored a stratified upper ocean from circa 10ka to the present

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

export production in the new zealand region since the last glacial maximum increased export production ep in the subantarctic zone saz of the southern ocean due to iron fertilisation has been proposed as a key mechanism for explaining carbon drawdown during the last glacial maximum lgm this work reconstructs marine ep since the lgm at four sites around new zealand for the first time in this region 230 thorium normalised fluxes of biogenic opal carbonate excess barium and organic carbon are presented in subtropical waters and the saz these flux variations show that ep has not changed markedly since the lgm the only exception is a site currently north of the subtropical front here we suggest the subtropical front shifted over the core site between 18 and 12ka driving increased ep to understand why ep remained mostly low and constant elsewhere lithogenic fluxes at the four sites were measured to investigate changes in dust deposition at all sites lithogenic fluxes were greater during the lgm compared to the holocene the positive temporal correlation between the antarctic dust record and lithogenic flux at a site in the tasman sea shows that regionally increased dust deposition contributed to the high glacial lithogenic fluxes additionally it is inferred that lithogenic material from erosion and glacier melting deposited on the campbell plateau during the deglaciation 18 12ka from these observations it is proposed that even though increased glacial dust deposition may have relieved iron limitation within the saz around new zealand the availability of silicic acid limited diatom growth and thus any resultant increase in carbon export during the lgm therefore silicic acid concentrations have remained low since the lgm this result suggests that both silicic acid and iron co limit ep in the saz around new zealand consistent with modern process studies

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

orbital and millennial antarctic climate variability over the past 800 000 years a high resolution deuterium profile is now available along the entire european project for ice coring in antarctica dome c ice core extending this climate record back to marine isotope stage 20 2 800 000 years ago experiments performed with an atmospheric general circulation model including water isotopes support its temperature interpretation we assessed the general correspondence between dansgaard oeschger events and their smoothed antarctic counterparts for this dome c record which reveals the presence of such features with similar amplitudes during previous glacial periods we suggest that the interplay between obliquity and precession accounts for the variable intensity of interglacial periods in ice core records

authigenic uranium in foraminiferal coatings a proxy for ocean redox chemistry the rate of uranium accumulation in oceanic sediments from seawater is controlled by bottom water oxygen concentrations and organic carbon fluxes two parameters that are linked to deep ocean storage of co2 to investigate glacial interglacial changes in what is known as authigenic u we have developed a rapid method for its determination as a simple addition to a procedure for foraminiferal trace element analysis foraminiferal calcite acts as a low u substrate u ca 15 nmol mol upon which authigenic u accumulates in reducing sediments we measured a downcore record of foraminiferal u ca from odp site 1090 in the south atlantic and found that u ca ratios increase by 70 320 nmol mol during glacial intervals there is a significant correlation between u ca records of benthic and planktonic foraminiferal species and between u ca and bulk sediment authigenic u these results indicate that elevated u ca ratios are attributable to the accumulation of authigenic u coatings in sediments foraminiferal mn ca ratios were lower during the glacial intervals suggesting that the observed u accumulation on the shells is not directly linked to u incorporation into secondary manganese phases thus foraminiferal u ca ratios may provide useful information on past changes in sediment redox conditions

global ocean response to orbital forcing in the holocene 1 global upper ocean evolution in the holocene is studied in two coupled ocean atmosphere models under orbital forcing conditions at 3 6 8 and 11 ka the annual mean sea surface temperature sst changes in the early to mid holocene are found to be forced mainly by the annual mean insolation forcing with an overall symmetric response of colder equator 1 c in the arctic this sst change is consistent with a synthesis of mid holocene paleo sst records in contrast the temperature response in the thermocline is dominated by an antisymmetric pattern with a cooling warming in the northern southern hemisphere midlatitudes the thermocline response is determined predominantly by surface water subduction and ultimately the insolation forcing in local late winter

last glacial jetting of cold waters through the subtropical convergence zone in the southwest pacific off eastern new zealand and some geological implications recent evidence suggests that the subtropical convergence stc zone east of new zealand shifted little from its modern position along chatham rise during the last glaciation and that offshore surface waters north of the stc zone cooled only slightly however at nearshore core site p69 2195 m depth 115 km off the east coast of north island and ca 300 km north of the modern stc zone planktonic foraminiferal species transfer function data and stable oxygen and carbon isotope records suggest that surface waters were colder by up to 6 c during the late last glacial period compared to the holocene and included a strong upwelling signature presently site p69 is bathed by south flowing subtropical waters in the east cape current the nearshore western end of chatham rise supports a major bathymetric depression the mernoo saddle through which some exchange between northern subtropical and southern subantarctic water presently occurs it is proposed that as a result of much intensified current flows south of the rise during the last glaciation a consequence of more compressed subantarctic water masses lowered sea level and an expanded and stronger westerly wind system there was accelerated leakage northwards of both australasian subantarctic water and upwelled antarctic intermediate water over mernoo saddle in a modified and intensified southland current the expanded cold water masses displaced the south flowing warm east cape current off southeastern north island and offshore divergence was accompanied by wind assisted upwelling of nutrient rich waters in the vicinity of p69 a comparable kind of inshore cold water jetting possibly characterised most glacial periods since the latest miocene and may account for the occasional occurrence of subantarctic marine fossils in onland late cenozoic deposits north of the stc zone rather than invoking wholesale major oscillations of the oceanic stc itself

palaeocirculation across new zealand during the last glacial maximum at 21 ka abstract what circulation pattern drove southern alps glacial advances at 21 ka late 20th century glacial advances in new zealand are commonly attributed to a dual precipitation increase and cooler than normal temperatures associated with enhanced westerly flow that occur under synoptic pressure patterns termed zonal regimes kidson 2000 but was the circulation pattern that supported major southern alps glacial advances during the global lgm similar to the modern analog here a regional climate regime classification rcrc time slice was used to infer past circulation for new zealand during the lgm at 21 ka palaeoclimate information that supported the construction of the 21 ka time slice was derived from the nz intimate climate event stratigraphy ces one new auckland maar proxy record and additional low resolution data sourced from the literature the terrestrial evidence at 21 ka implicates several possibilities for past circulation depending on how interpretations for some proxies are made the interpretation considered most tenable for the lgm based on the agreement between terrestrial evidence marine reconstructions and palaeoclimate model results is an anticyclonic zonal circulation regime characterized by increased influences from blocking highs over the south island during winter and an increase in zonal and trough synoptic types with southerly to westerly quarter wind flow during summer these seasonal circulation traits would have generated lower mean annual temperatures cooler than normal summer temperatures and overall lower mean annual precipitation for new zealand particularly in the western south island at 21 ka the anticyclonic zonal time slice reconstruction presented in this study has different spatial traits than the late 20th century and the early little ice age signatures suggesting more than one type of regional circulation pattern can drive southern alps glacial activity this finding lends support to the hypothesis that temperature over precipitation change is more important as the primary modulator of southern alps ice advances the rcrc approach also demonstrates some subtle advantages of integrating multi proxy data within a palaeocirculation context for new zealand notably because this reconstruction technique enables direct comparisons to coarsely resolved palaeoclimate model outputs that do not have downscaled information

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

biogeochemical iron budgets of the southern ocean south of australia decoupling of iron and nutrient cycles in the subantarctic zone by the summertime supply 1 climate change is projected to significantly alter the delivery stratification boundary currents aridification of landmasses glacial melt of iron to the southern ocean we report the most comprehensive suite of biogeochemical iron budgets to date for three contrasting sites in subantarctic and polar frontal waters south of australia distinct regional environments were responsible for differences in the mode and strength of iron supply mechanisms with higher iron stocks and fluxes observed in surface northern subantarctic waters where atmospheric iron fluxes were greater subsurface waters southeast of tasmania were also enriched with particulate iron manganese and aluminum indicative of a strong advective source from shelf sediments subantarctic phytoplankton blooms are thus driven by both seasonal iron supply from southward advection of subtropical waters and by wind blown dust deposition resulting in a strong decoupling of iron and nutrient cycles we discuss the broader global significance our iron budgets for other ocean regions sensitive to climate driven changes in iron supply

155 000 years of west african monsoon and ocean thermal evolution a detailed reconstruction of west african monsoon hydrology over the past 155 000 years suggests a close linkage to northern high latitude climate oscillations ba ca ratio and oxygen isotope composition of planktonic foraminifera in a marine sediment core from the gulf of guinea in the eastern equatorial atlantic eea reveal centennial scale variations of riverine freshwater input that are synchronous with northern high latitude stadials and interstadials of the penultimate interglacial and the last deglaciation eea mg ca based sea surface temperatures ssts were decoupled from northern high latitude millennial scale fluctuation and primarily responded to changes in atmospheric greenhouse gases and low latitude solar insolation the onset of enhanced monsoon precipitation lags behind the changes in eea ssts by up to 7000 years during glacial interglacial transitions this study demonstrates that the stadial interstadial and deglacial climate instability of the northern high latitudes exerts dominant control on the west african monsoon dynamics through an atmospheric linkage

modulation and daily banding of mg ca in orbulina universa tests by symbiont photosynthesis and respiration a complication for seawater thermometry the mg ca composition of calcium carbonate tests shells secreted by planktonic foraminifera is increasingly being employed to estimate past seawater temperatures and reconstruct paleocean and climate records spanning hundreds of thousands of years we show using two high resolution microanalysis techniques that the final chamber of the planktonic foraminifera orbulina universa typically comprises between three and six paired low and high mg growth bands the number and spacing of these bands is consistent with a diurnal origin modulated by changing ph within the foraminiferal microenvironment due to the day night photosynthesis respiration cycle of algal symbionts the amplitude of mg ca variation within individual tests and across many daily growth bands cannot be accounted for by seawater temperature in the shallow euphotic zone habitat of o universa our results indicate the mg ca composition of calcite precipitated by o universa in nature is strongly influenced by diurnal changes in the biological activity of algal symbionts and the host foraminifer this brings into question the fundamental premise often made in applying mg ca palaeoseawater thermometry that the mg ca composition of foraminiferal calcite is determined by seawater temperature and whether the mg ca composition of other planktonic species that are more widely used for palaeoseawater thermometry are subject to similar influences 2004 elsevier b v all rights reserved

the stratigraphic interpretation of a highly deformed proterozoic region in central bushmanland south africa first correlation of structurally separated metasediments of the aggeneys subgroup abstract it is demonstrated that highly deformed and structurally separated proterozoic metasediments which have previously defied stratigraphic and sedimentological classification may be correlated and characterised this is done by using a multidisciplinary approach including stratigraphic and structural mapping and sedimentological interpretation developed during the geodynamics programme in western namaqualand 1975 1980 the metasediments under consideration belong to the economically important aggeneys subgroup which hosts stratabound massive sulphide deposits at aggeneys and gamsberg gams four isolated areas are considered and it is shown that the dabenoris kabas and pella formations and the lower part of the achab formation are equivalent to the lower part of the wortel formation and that the upper part of the stratigraphic column is composed of the upper units of the achab formation the gams formation and the blomhoek formation the zuurwater formation is for the most part equivalent to the lower portion of the wortel formation but the uppermost strata are correlated with the blomhoek formation these results illustrate that it is possible to obtain the information necessary for a palaeobasin analysis from even the most complex proterozoic regions

the mean and variability of ocean circulation past northern new zealand determining the representativeness of hydrographic climatologies eastward flow in the tasman sea from the separated east australia current reattaches to the shelf break near north cape new zealand and then continues alongshore to the southeast as the east auckland current a series of three permanent warm core eddies occurs along the offshore side the mean transport of the east auckland current is about 9 sv with an additional 10 sv or more of circulation in the eddies an extensive hydrographic data set archived broad scale expendable bathythermograph xbt data two repeating high resolution xbt transects neutrally buoyant float trajectories and topex altimetric data are used to estimate the temperature and absolute flow fields and to characterize variability the aim is to examine the usefulness of time series information and absolute velocity measurements in the interpretation of hydrographic snapshots and climatologies as well as to describe a region having intrinsic oceanographic interest and complexity issues of representativeness of the hydrographic data of the magnitude and scales of the underlying variability of the existence of permanent fine scale features and of the appropriateness of deep reference levels are addressed directly the relatively well sampled hydrographic climatology is shown to contain the equivalent of as many as 10 independent realizations temperature errors relative to the true mean are typically a few tenths of a degree significant seasonal bias is identified in the surface layer and interannual bias is seen in the position of an eddy near north cape the dynamic height field at 1000 dbar relative to 2000 dbar is similar to estimates based on float trajectories and the assumption of geostrophic dynamics this study underlines the value of time series data in the interpretation of a hydrographic climatology in quantifying the errors in the estimated mean field as well as determining the magnitude and nature of variability it also highlights the fact that the mean circulation of the oceans contains significant mesoscale structure unnoticed in coarsely smoothed climatologies

mean annual temperature in new zealand during the last glacial maximum derived from dissolved noble gases in groundwater abstract this study presents a reconstruction of mean annual surface temperature in new zealand over the last glacial period using groundwater noble gas paleothermometry low resolution 14c derived mean recharge ages of groundwater from the deep moutere deep wairau and taranaki aquifers range from roughly 41 500 yr to present including the last glacial maximum lgm modeled noble gas temperatures of probable glacial age samples range from roughly 3 7 6 2 c cooler than present we present an error weighted mean cooling of 4 6 0 5 c relative to present during last glacial period the screened depth intervals of some wells sampled in this study allow for a degree of mixing during extraction between groundwater layers of different recharge age mixing with modern groundwater may slightly elevate the noble gas temperatures ngts of glacial age samples while making them appear substantially younger given the uncertainty in dating we cannot rule out a larger lgm temperature depression of up to 6 c the 4 6 c cooling estimate agrees with a number of terrestrial paleoclimate reconstructions near the study area as well as the majority of nearby paleoceanographic temperature studies

white island new zealand volcanic hydrothermal system represents the geochemical environment of high sulfidation cu and au ore deposition the white island volcanic hydrothermal system new zealand is thought to closely represent the chemical conditions that lead to the formation of high sulfidation cu au ore deposits the amounts of cu and au produced over a 10 ka period of activity largely from degassing magma are calculated to be 106 and 45 t respectively altered andesite blocks ejected from recent vents contain alunite anhydrite and pyrite their s isotopic composition indicates vein filling at 380 c at this temperature cu and au are highly soluble in acid solutions which may explain the depletion of cu and absence of au in the ejecta mass balance calculations however suggest that cu and au are precipitated in cooler zones before the acid solutions discharge at the surface

high resolution record of northern hemisphere climate extending into the last interglacial period high resolution record of northern hemisphere climate extending into the last interglacial period

a high resolution transect of dissolved barium in the southern ocean 1 the dissolved barium bad distribution in the whole water column was examined along the woce sr3 line in the southern ocean australian sector late winter spring 2001 the high sampling resolution offered an excellent opportunity to relate the bad distribution to frontal structures and the water masses such a high resolution was not achieved in previous southern ocean studies and showed the tight overprinting of the frontal zones by bad gradients hydrodynamic control on bad is evident in the case of antarctic bottom water formation westward flow of tasman sea waters and return flow of an eddy of the subantarctic front however biogeochemical processes are also acting as witnessed by enhanced bad contents in deep waters of the subantarctic front zone and by a local mesopelagic minimum in the inter polar front zone these features are respectively ascribed to the dissolution of ba rich phases and ba transfer from solution to particles

trace element proxies for surface ocean conditions a synthesis of culture calibrations with planktic foraminifera abstract the trace element composition of planktic foraminiferal calcite provides a useful means of determining past surface ocean conditions we have assembled the results of culture experiments for three species of symbiont bearing planktic foraminifera globigerinoides ruber globigerinoides sacculifer and orbulina universa and one symbiont barren species globigerina bulloides to evaluate their responses to temperature salinity ph carbonate ion and dissolved inorganic carbon dic growth conditions trace element ratios li ca b ca mg ca sr ca mn ca cd ca ba ca na ca and u ca were measured simultaneously on samples grown with the same culture techniques which provides robust relatable calibrations that may be used together in multi proxy paleoceanographic studies our data confirm that temperature is the dominant control on foraminiferal mg ca under the ranges of conditions studied and that the potential effects of salinity and co32 on mg ca of these tropical species across late pleistocene glacial cycles are relatively small carbonate system experiments suggest that sr ca may be useful for reconstructing large dic changes na ca increases with salinity in g ruber pink but not in g sacculifer as these emerging proxy relationships become more firmly established the synthesis of multiple trace element ratios may help paleoceanographers isolate the effects of different environmental parameters in paleo records calcification rates g day vary among species and do not respond consistently to any experimental parameter comparison of our calcification rates with those observed in inorganic calcite precipitation experiments suggest that foraminifera calcify 100 more slowly than inorganic calcites grown in similar solutions we suggest that calcification rate does not typically exert a dominant control on trace element partitioning in planktic foraminiferal calcite though it may play a role for some elements under certain circumstances differences in average growth rate cannot explain composition differences among species pointing to alternative controls that may be biological in origin

antarctic deglacial pattern in a 30 kyr record of sea surface temperature offshore south australia 1 comparison of ice cores from greenland and antarctica shows an asynchronous two step warming at these high latitudes during the last termination however the question whether this asynchrony extends to lower latitudes is unclear mainly due to the scarcity of paleorecords from the southern hemisphere new data from a marine core collected off south australia 36s allows a detailed reconstruction of sea surface temperatures over the last termination this confirms the existence of an antarctic type deglacial pattern and shows no indication of cooling associated with the northern hemisphere yd event the sst record also provides a new comparison with the more extensive paleoclimatic data available from continental australia this shows a strong climatic link between onshore and offshore records for australia and to southern hemisphere paleorecords we also show a progressive sst drop over the last 6 5 kyr not seen before for the australian region citation calvo e c pelejero p de deckker and g a logan 2007 antarctic deglacial pattern in a 30 kyr record of sea surface temperature offshore south australia geophys res lett 34 l13707 doi 10 1029 2007gl029937

petrochemical evidence on the probable origin of ferriferous metasediments in western bushmanland the mineralized proterozoic metasediments of bushmanland are characterized by the presence of ferriferous rocks this includes banded and unbanded iron formations and various types of gossans these units are not laterally extensive and occur in different stratigraphic levels the prevalent minerals in the ferriferous rocks are hematite magnetite quartz garnet muscovite biotite and sillimanite but less common occurrences of graphite alunite plumbojarosite gahnite and dufrenite have been noted the chemical variation wt is extensive total fe2o3 1 3 93 5 sio2 4 93 al2o3 0 2 14 0 cao 0 02 20 7 mno 0 0 14 3 mgo 0 0 5 7 tio2 0 0 4 4 na2o 0 0 2 0 k2o 0 0 1 5 and p2o5 0 1 7 0 the preliminary nature of the data set precludes however firm conclusions regarding stratigraphic control of the chemical composition the trace element contents ppm extend over several orders of magnitude zn 0 7 000 ba 0 5 200 cu 0 1 400 pb 0 1 070 and ni 6 540 collectively the data indicate that most of the ferriferous rocks represent highly metamorphosed sediments

cadmium zinc copper and barium in foraminifera tests the concentrations of cadmium zinc copper and barium have been determined on 2 mg samples of single species foraminifera populations cleaning techniques were tested using north atlantic core tops and followed by a detailed downcore study for the last 30 000 years in south atlantic core v22 174 raw foram tests cleaned by crushing followed by ultrasonic removal of fine grained material and dissolved in a ph 5 5 acetate buffer contain appreciable amounts of trace elements associated with ferromanganese and alumino silicate contaminants a reductive complexing cleaning treatment reduces ferromanganese contamination by 1 2 orders of magnitude acetate buffers at ph 5 5 complex iron and raise the solubility of ferromanganese oxides these buffers are unsuitable for separating carbonate lattice bound trace elements from the fraction associated with ferromanganese phases improved mechanical and ultrasonic reductive cleaning combined with a mild dissolution in distilled water under 1 atm pco2 reduces contaminant levels another order of magnitude the cd and zn concentrations order 10 8 mole cd mole ca and 10 5 mole zn mole ca of species with low surface area show an increase with decreasing isotopic temperatures this increase is consistent with the increasing concentrations of these metals from low values in surface waters to higher values at depth the variance of cd and zn over the last 30 000 years in the central south atlantic is consistent with the probable variability of the dissolved trace elements at the calcification levels of the species analyzed cu and ba are irreproducible and probably sensitive to residual contaminant phases the trace element content of the tests differs from levels observed in a recent coprecipitation study foraminifera may be a significant vector in zinc cycling in the ocean

reduced north atlantic central water formation in response to early holocene ice sheet melting central waters of the north atlantic are fundamentalfor ventilation of the upper ocean and are also linked tothe strength of the atlantic meridional overturning circula tion amoc here weshowbasedonbenthic foraminiferalmg ca ratios that during times of enhanced melting fromthe laurentide ice sheet lis between 9 0 8 5 thousandyears before present ka the production of central watersweakened the upper amoc resulting in a cooling overthenorthernhemisphere centeredat8 54 0 2kaand8 24 0 1 ka our dataset records two 150 year coolingevents in response to the drainage of lake agassiz ojibway indicating early slow down of the upper amoc in responseto the initial freshwater flux into the subpolar gyre spg followed by a more severe weakening of both the upperand lower branches of the amoc at 8 2 ka these resultshighlight the sensitivity of regional north atlantic climatechange to the strength of central water overturning andexemplify the impact of both gradual and abrupt freshwaterfluxes on eastern spg surface water convection in light ofthe possible future increase in greenland ice sheet meltingdue to global warming these findings may help us to betterconstrain and possibly predict future north atlantic climatechange

composition age and tectonic setting of amphibolites in the central bushmanland group western namaqua province southern africa abstract the western namaqua province wnp of southern africa is composed of several supracrustal assemblages and intrusive granitoid suites that were formed during the mid proterozoic 2 0 1 0 ga ago the bushmanland group bg has been the subject of intense study recently because of its considerable strategic metal potential hosting several giant stratiform base metal deposits e g gamsberg and aggeneys the bg contains amphibolites which represent metamorphosed tholeiitic basalts with mgo 9 4 and enriched in ni relative to modern basalts a feature reminiscent of archaean tholeiites post depositional mobility of elements is probably widespread and hampers recognition of parental magma composition and source region characteristics however the amphibolites have yielded a sm nd isochron age of 1649 90 ma nd t 0 48 0 89 which is interpreted as the time of extrusion of the basalt precursors and by inference a minimum sedimentation age for the underlying metalliferous bg sequence it follows that the bg sequence evolved during an intermediate period in the history of the namaqua province after major crustal stabilisation around 2 0 1 9 ga and before the last major tectonothermal event around 1 2 1 1 ga results of a parallel rb sr and u th pb study of the bg amphibolites indicate strong metamorphic resetting 1 2 1 1 ga ago thereby confirming earlier work on the wnp characteristics of the source region to the bg basalts have been inspected with morb normalised trace element abundances with the salient result being the bg basalts require derivation from a source that experienced variable geochemical modification similar to that proposed for the mantle wedge overlying modern subduction zones such a process is currently preferred over crustal contamination since the sm nd isochron for the bg amphibolites is remarkably linear but independent confirmation of the sm nd age is still required before this alternative model can be discounted to reconcile the requirement of subduction related metasomatism in the source to tholeiitic basalts erupted within what appears to be a cratonic sedimentary basin we suggest that back are continental extension could provide a satisfactory tectonic setting as such an environment is intrinsically linked to subduction

the last glacial termination a major puzzle of paleoclimatology is why after a long interval of cooling climate each late quaternary ice age ended with a relatively short warming leg called a termination we here offer a comprehensive hypothesis of how earth emerged from the last global ice age a prerequisite was the growth of very large northern hemisphere ice sheets whose subsequent collapse created stadial conditions that disrupted global patterns of ocean and atmospheric circulation the southern hemisphere westerlies shifted poleward during each northern stadial producing pulses of ocean upwelling and warming that together accounted for much of the termination in the southern ocean and antarctica rising atmospheric co2 during southern upwelling pulses augmented warming during the last termination in both polar hemispheres

uncertainties in seawater thermometry deriving from intratest and intertest mg ca variability in globigerinoides ruber intertest mg ca variability within these deep sea core top samples is a source of significant uncertainty in mg ca seawater temperature estimates and is notable for being site specific our results indicate that widely assumed uncertainties in mg ca thermometry may be underestimated we show that statistical power analysis can be used to evaluate the number of tests needed to achieve a target level of uncertainty on a sample by sample case a varying bias also arises from the presence and varying mix of two morphotypes g ruber ruber and g ruber pyramidalis which have different mean mg ca values estimated calcification temperature differences between these morphotypes range up to 5c and are notable for correlating with the seasonal range in seawater temperature at different sites

sea surface temperature estimates from the southwest pacific based on planktonic foraminifera and oxygen isotopes planktonic foraminiferal census data were collected on 34 surficial sediment samples from east of new zealand sea surface temperature estimates were derived from the data using the modern analogue technique mat and compared to data from climap s fa 20 equation they were also computed from oxygen isotope analyses of globigerina bulloides the temperature estimates compared well between the three methods and were found to correlate closely with the appropriate seasonal sea surface temperature as measured by satellite the foraminiferal assemblages and derivative temperatures clearly identify the major watermasses and oceanic fronts in the region and thus can be applied to palaeoceanographic analysis of southwest pacific sediments

late quaternary palaeoceanography near tasmania southern australia abstract this study of the palaeoceanographic record south of australia is based on two cores taken from lower circumpolar deep water depths core e27 30 located south of tasmania in water depth of 3552 m to the north of the present location of the subtropical convergence and core e55 6 from the continental margin off victoria at 2346 m depth in a region of very low surface productivity a preliminary examination of planktonic foraminiferal faunas in core e27 30 located south of tasmania provides a record of movement of the subtropical convergence through the late quaternary that is consistent with records elsewhere in the southeast indian ocean the convergence has been located equatorward of its present position through much of the late quaternary with poleward excursions in the holocene and at oxygen isotope stage 5e benthic foraminiferal faunas contrast strongly in the two cores despite their location at similar depths within the same water mass core e55 6 is largely dominated by deep infaunal taxa while core e27 30 has a high proportion throughout of epifaunal taxa the benthic foraminiferal fauna in core e27 30 is dominated by epistominella exigua known to feed directly on phytoplankton detritus in the modern deep sea abundances of that species coincide with the presence of the subtropical convergence at or near the site indicating that surface phytoplankton production has had a major influence on benthic productivity dissolution records in the two cores also differ markedly core e55 6 records a strong dissolution event in oxygen isotope stage 4 the cause of the event is not clear although it appears to be associated with increased productivity levels this pronounced dissolution event is not evident in core e27 30 suggesting either the event is localised or that the record in core e27 30 has been overprinted by the convergence the extent to which the records in the two cores vary emphasises the influence of frontal structures on core records in this region and the need to take this into account when investigating southern ocean history

evidence for a holocene climatic optimum in the southwest pacific a multiproxy study the early holocene sea surface temperature sst gradient across the subtropical front stf to the east of new zealand was 2 c measured between core sites md97 2121 and md97 2120 considerably less than the 6 c modern gradient between the two core sites we document the surface ocean temperatures east and south of new zealand during the early and middle holocene to test and expand upon this reconstruction this new study samples a latitudinal transect of seven sediment cores from 37 s to 60 s in the southwest pacific from subtropical waters north of new zealand to polar waters in the southern ocean our compilation of sst proxies consists of 525 sst estimates from five different methods and includes 243 new data points we confirm that an early holocene warm peak in this region was mostly restricted to the area immediately south of the stf which resulted in a lower temperature gradient across the stf than in modern times however there is no change in holocene sst south of the polar front faunal assemblages suggest an early holocene meridional expansion of fauna characteristic of the modern subtropical front in the bounty gyre we suggest that such an expansion could be achieved by a reduced inflow of subantarctic surface water into the bounty gyre results from a modern analog matching platform called the past interpretation of climate tool pict suggest that the early holocene sst is most consistent with reduced westerly winds in the new zealand sector of the southern ocean

holocene and eemian sea surface temperature trends as revealed by alkenone and mg ca paleothermometry in this study we review a global set of alkenone and foraminiferal mg ca derived sea surface temperatures sst records from the holocene and compare them with a suite of published eemian sst records based on the same approach for the holocene the alkenone sst records belong to the actualized ghost database kim j h schneider r r 2004 ghost global database for alkenone derived holocene sea surface temperature records available from http www pangaea de projects ghost while the mg ca derived sst database represents a new compilation the actualized ghost database not only confirms the sst changes previously described but also documents the holocene temperature evolution in new oceanic regions such as the northwestern atlantic the eastern equatorial pacific and the southern ocean a comparison of holocene sst records stemming front the two commonly applied paleothermometry methods reveals contrasting sometimes divergent sst evolution particularly at low latitudes where sst records are abundant enough to infer systematic discrepancies at a regional scale opposite sst trends at particular locations could be explained by out of phase trends in seasonal insolation during the holocene this hypothesis assumes that a strong contrast in the ecological responses of coccolithophores and planktonic foraminifera to winter and summer oceanographic conditions is the ultimate reason for seasonal differences in the origin of the temperature signal provided by these organisms as a simple test for this hypothesis eemian sst records are considered because the holocene and eemian time periods experienced comparable changes in orbital configurations but had a higher magnitude in insolation variance during the eemian for several regions sst changes during both interglacials were of a similar sign but with higher magnitudes during the eemian as compared to the holocene this observation suggests that the ecological mechanism shaping sst trends during the holocene was comparable during the penultimate interglacial period although this ecology hypothesis fails to explain all of the available results we argue that any other mechanism would fail to satisfactorily explain the observed sst discrepancies among proxies c 2010 elsevier ltd all rights reserved

glacial interglacial sea surface temperature changes across the subtropical front east of new zealand based on alkenone unsaturation ratios and foraminiferal assemblages 0 are compared to those derived from foraminiferal assemblages using the modern analog technique in two of these cores reconstructions of sst in core tops and holocene sediments agree well with modern average summer temperatures of 18 c in subtropical waters and 14 c in subpolar waters with a 4 5 c gradient across the front down core u37 k 0 sst estimates indicate that the regional summer sst was 4 5 c cooler during the last glaciation with an sst of 10 c in subpolar waters and an sst of 14 c in subtropical waters temperature reconstructions from foraminiferal assemblages agree with those derived from alkenones for the holocene in subtropical waters reconstructions also agree with a glacial cooling of 4 to 14 c in contrast reconstructions for subantarctic pre holocene waters indicate a cooling of 8 c with glacial age warm season water temperatures of 6 c thus the alkenones suggest the glacial temperature gradient across the front was the same or reduced slightly to 3 5 4 c whereas foraminiferal reconstructions suggest it doubled to 8 c our results support previous work indicating that the stf remained fixed over the chatham rise during the last glacial maximum however the differing results from the two techniques require additional explanation a change in euphotic zone temperature profiles seasonality of growth or preferred growth depth must have affected the temperatures recorded by these biologically based proxies regardless of the specific reason a differential response to the environmental changes between the two climate regimes by the organisms on which the estimates are based suggests increased upwelling associated with increased winds and or a shallowing of the thermocline associated with increased stratification of the surface layer in the last glaciation index terms 4267 oceanography general paleoceanography 4850 oceanography biological and chemical organic marine chemistry 1050 geochemistry marine geochemistry 4835 4850 1055 geochemistry organic geochemistry keywords paleoceanography sea surface temperature alkenones southern ocean last glacial maximum

last glacial holocene climate variability in the atlantic sector of the southern ocean abstract the southern ocean plays a major role in the glacial interglacial global carbon cycle however there is a substantial lack of information from its antarctic zone south of the polar front pf to understand key climate processes e g sea ice variability productivity changes co2 source region shifts of the southern westerly wind active in this region during the glacial interglacial transition due to the limited high resolution sediment records from this area to close this gap we investigated high resolution diatom records from a series of sediment cores from the atlantic and western indian sectors of the southern ocean between the modern pf and the winter sea ice wsi edge summer sea surface temperature ssst and sea ice information spanning the past 30 thousand years were derived from diatom transfer functions and indicators which augment comprehensive information on past surface ocean conditions and related ocean and atmospheric circulation as well as opal deposition these complementary lines of evidences also provide important environmental boundary conditions for climate simulations understanding the past climate development in the high latitudes southern ocean our reconstructions show that the last glacial lg sssts south of the modern pf are 1 3 c colder than modern conditions wsi expanded to the modern pf our data suggests effective carbon export in the antarctic zone during the lg deglacial two steps of warming support the bipolar seesaw mechanism antarctic zone is an important source region for the co2 deglacial increase the warming was more suppressed towards south due to continuous ice discharge from antarctica the sssts exceeded modern values during the early holocene optimum when wsi extent probably retreated south of its modern position the southern boundary of maximum opal deposition zone may have shifted to south of 55 s in the bouvet island area at this time the mid late holocene cooling with wsi re expanding to the bouvet island area probably related to enhanced cold water export by the weddell gyre from the developing cavity under the west antarctic ice shelf the cooling also suggests a northward shift of the southern westerly wind at least its southern boundary

a 70 kyr sea surface temperature record off southern chile ocean drilling program site 1233 1 we present the first high resolution alkenone derived sea surface temperature sst reconstruction in the southeast pacific ocean drilling program site 1233 covering the major part of the last glacial period and the holocene the record shows a clear millennial scale pattern that is very similar to climate fluctuations observed in antarctic ice cores suggesting that the southern hemisphere high latitude climate changes extended into the midlatitudes involving simultaneous changes in air temperatures over antarctica sea ice extent extension of the antarctic circumpolar current and westerly atmospheric circulation a comparison to other midlatitude surface ocean records suggests that this antarctic millennial scale pattern was probably a hemisphere wide phenomenon in addition we performed sst gradient reconstructions over the complete latitudinal range of the pacific eastern boundary current system for different time intervals during the last 70 kyr the main results suggest an equatorward displaced subtropical gyre circulation during marine isotope stages 2 and 4

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

southwest pacific subtropics responded to last deglacial warming with changes in shallow water sources this study examined sources of mixed layer and shallow subsurface waters in the subtropical bay of plenty new zealand across the last deglaciation 30 5 ka 18o and 13c from planktonic foraminifera globgerinoides bulloides and globorotalia inflata in four sediment cores were used to reconstruct surface mixed layer thickness 18o of seawater 18osw and differentiate between high and low latitude water provenance during the last glaciation depleted planktonic 18osw and enriched 13c 0 4 0 1 indicate surface waters had southern ocean sources a rapid 13c depletion of 1 in g bulloides between 20 and 19 ka indicates an early permanent shift in source to a more distal tropical component likely with an equatorial pacific contribution that persisted into the holocene at 18 ka a smaller but similar shift in g inflata 13c depletion of 0 3 suggests that deeper subsurface waters had a delayed reaction to changing conditions during the deglaciation this contrasts with the isotopic records from nearby hawke bay to the east of the north island of new zealand which exhibited several changes in thermocline depth indicating switches between distal subtropical and proximal subantarctic influences during the early deglaciation ending only after the antarctic cold reversal our results identify the midlatitude subtropics such as the area around the north island of new zealand as a key region to decipher high versus low latitude influences in southern hemisphere shallow water masses

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

response of surface water masses and circulation to late quaternary climate change east of new zealand a series of cores from east of new zealand have been examined to determine the paleoceanographic history of the late quaternary in the sw pacific using planktonic foraminiferal data distinct shifts of species can be seen between glacial and interglacial times especially south of chatham rise east of south island foraminiferal fragmentation ratios and benthic planktonic foraminiferal ratios both show increased dissolution during glacials especially isotope stage 2 to the south of chatham rise the present day subtropical convergence appears to be tied to the chatham rise at 44 s but during glacial times this rise separated cold water to the south from much warmer water to the north with an associated strong thermal gradient across the rise we estimate that this gradient could have presented as much as an 8 c temperature change across 4 of latitude during the maximum of the last ice age there is only weak evidence of the younger dryas cool event but there is a clear climatic optimum between 8 and 6 4 ka with temperatures 1 2 c higher than the present day the marine changes compare well with vegetational changes on both south and north island

oceanographic variability on the west antarctic peninsula during the holocene and the influence of upper circumpolar deep water recent intensification of wind driven upwelling of warm upper circumpolar deep water ucdw has been linked to accelerated melting of west antarctic ice shelves and glaciers to better assess the long term relationship between ucdw upwelling and the stability of the west antarctic ice sheet we present a multi proxy reconstruction of surface and bottom water conditions in marguerite bay west antarctic peninsula wap through the holocene a combination of sedimentological diatom and foraminiferal records are for the first time presented together to infer a decline in ucdw influence within marguerite bay through the early to mid holocene and the dominance of cyclic forcing in the late holocene extensive glacial melt limited sea ice and enhanced primary productivity between 9 7 and 7 0 ka bp is considered to be most consistent with persistent incursions of ucdw through marguerite trough from 7 0 ka bp sea ice seasons increased and productivity decreased suggesting that ucdw influence within marguerite bay waned coincident with the equatorward migration of the southern hemisphere westerly winds sww ucdw influence continued through the mid holocene and by 4 2 ka bp lengthy sea ice seasons persisted within marguerite bay intermittent melting and reforming of this sea ice within the late holocene may be indicative of episodic incursions of ucdw into marguerite bay during this period the cyclical changes in the oceanography within marguerite bay during the late holocene is consistent with enhanced sensitively to enso forcing as opposed to the sww forcing that appears to have dominated the early to mid holocene current measurements of the oceanography of the wap continental shelf suggest that the system has now returned to the early holocene like oceanographic configuration reported here which in both cases has been associated with rapid deglaciation

sea surface temperatures of southern midlatitudes 0 160 kyr b p 1 late quaternary climate fluctuated between extremes of glaciations lasting 90 kyr on average and interglacial episodes lasting 10 kyr still largely unknown are the spatial and temporal evolution of these global climate states with vigorous debate still underway on the mechanisms responsible for glacial inceptions and terminations though it is widely believed that the southern hemisphere oceans play a central role in global climate changes few paleoclimate records exist from there here we present three new alkenone derived sst records from the midlatitude southern hemisphere spanning the last 160 kyr a full glacial interglacial cycle our subtropical sst records from the last glacial period are characterized by 1 warming 47 23 kyr b p when high latitudes in both hemispheres cooled and 2 milder temperatures during the penultimate glacial period than during the last glacial interval these sst features are found to be of tropical to subtropical wide extent implying increased thermal gradients at times of high latitude ice sheet growth this has implications for the vigor of atmospheric and upper ocean circulation and the transport of heat and moisture to the poles that may have been instrumental in the growth and maintenance of polar ice sheets during glacial periods

glacial interglacial control of terrigenous and biogenic fluxes in the deep ocean off a high input collisional margin a 139 kyr record from new zealand abstract sediment input to the deep ocean off the new zealand collisional plate boundary is large and variable as revealed by a 139 kyr old record from the 34 92 m long core md97 2121 mass accumulation rates mars were derived for terrigenous and biogenic carbonate and silica sedimentary components with temporal control from a stable isotope age model verified by tephra and radiocarbon ages terrigenous mars changed in phase with glacio eustatic fluctuations of sea level highest rates 30 g cm 2 kyr coincided with the late regressive lowstand early transgressive phase of marine isotope stage mis 2 when rivers discharged at or near the shelf edge lesser but still high terrigenous rates 20 30 g cm 2 kyr characterized peak warm phases of early mis 5 and 1 when a strengthened subtropical inflow probably introduced sediment from fluvial and seabed sources to the north of md97 2121 however during prolonged highstands the flux declined as more sediment was retained on a tectonically subsiding shelf with a shore parallel current paradoxically the lowest mars 10 5 g cm 2 kyr occurred in mis 4 either sea level was too high to allow much sediment to escape off shelf or the fluvial input was modest or both these factors despite the terrigenous dominance biogenic mars are high and are 2 4 times larger than sw pacific ocean rates mars were lowest during mis 4 and 3 possibly due to reduced marine production under a lowered input of fluvial micronutrients in contrast mars increased irregularly though glacial maxima to peak at 5 6 g cm 2 kyr carbonate and 2 2 5 g cm 2 kyr silica in early mid mis 5 and 1 such rates reflected the interaction of macronutrient rich subantarctic waters sourced from the south with local micronutrient rich subtropical waters production also responded to warmer temperatures elevated nutrient runoff and a more stratified surface ocean later in mis 5 and 1 fluxes reduced as less productive subtropical waters prevailed that biogenic and aeolian mar profiles are out of phase suggests fe fertilization by aerosolic dust was not a major influence

manganese carbonate overgrowths on foraminifera tests below the zone where manganese is remobilized as mn2 aq reductively cleaned foraminifera in deep sea sediments have much higher mnca than those in core tops and sediment traps mnca ranges from less than 20 10 6 in and above the mno2 maximum to as high as 700 10 6 in reducing panama basin sediments the most plausible explanation for this enrichment is that the tests are coated with mn carbonate overgrowths these coatings can account for a significant proportion of the mn in reduced deep sea sediments uptake of manganous ion by carbonate may explain the absence of mn nodules in areas of high carbonate accumulation extreme degrees of overgrowth can alter foram trace element values but this artifact can be avoided by avoiding foraminifera with high mn ca

observational evidence for a southern hemisphere oceanic supergyre 1 a high resolution hydrographic atlas resolves the narrow boundary flow of the western pacific gyre and its pathway around tasmania southern australia and into the indian ocean basin this confirms recent model descriptions of a southern hemisphere supergyre a nested system of subtropical gyres the observations show that the gyre flow is squeezed into a narrow band between tasmania and the antarctic circumpolar current the residue of east australian current transport turns westward around tasmania and leaks into the indian ocean while there is also a limited form of gyre connection between the indian and atlantic systems south of africa with a mean outflow of agulhas current water into the atlantic basin these gyre circulations remain far more discrete the gyre coupling and the east australian current in particular provide the mechanism by which sub antarctic mode water and antarctic intermediate water are distributed between the ocean basins

the southern hemisphere westerlies in the australasian sector over the last glacial cycle a synthesis abstract the southern hemisphere westerlies in the southwest pacific are known to have waxed and waned numerous times during the last two glacial cycles though even semi continuous histories of the westerlies extend back no more than about 20 000 years we have good evidence for at least three scales of events a westerly maximum occurs at the last glacial maximum there is less conclusive evidence for another westerly maximum in the late holocene and for a minimum at ca 11 ka it is too early to ascribe even a cycle to these data but there are grounds to suggest that milankovitch precessional forcing may underlie the observed pattern there is also a quasi 2600 year cycle present in antarctic ice cores that appears to correlate to variation in westerly flow there is strong centennial scale variability in historical times the little ice age lia ca 1400 1850 was associated with a poleward shift in the circumpolar trough in the southern ocean strengthened westerly circulation over tasmania and a strengthening of southwesterly circulation and neoglaciation in southern new zealand while the preceding period 800 1400 ad was less certainly marked by reduced westerly flow from modern records we know that decadal and inter annual variability is important e g pacific decadal oscillation high latitude mode also known as the antarctic oscillation el nino southern oscillation only a minority of the proxies examined can identify changes on these temporal scales but data from tree rings ice cores and laminated lake sediments do indicate systematic changes in these phenomena through time rossby wave patterns are shown to play a critical role in long duration events as well as at the synoptic scale we conclude that westerly circulation is as strong now as at any time in the last glacial cycle in addition changes in latitudinal boundaries in the westerlies may be nearly as large in inter annual zonal shifts ca 2 maximum as in glaciation interglaciation movements ca 3 4 there is however reasonable evidence of strengthening weakening across much of the westerly belt at westerly maxima minima such as the lia early holocene

enso sam interactions during the middle and late holocene a new chronology of large magnitude rainfall events derived from the continuous high resolution lake tutira storm sediment record covers the last 6800 years and provides the first insight into changes in el nino southern oscillation enso teleconnections to the higher southern latitudes to be obtained from new zealand synthesis with independent paleoclimate records from the tropical pacific and antarctica also reveals a millennial scale waxing and waning of the teleconnections that were not visible in the narrow historical window previously used to view interactions between enso and the southern annular mode sam consistent with modern enso behaviour we find teleconnections to the southwest pacific varied throughout the middle and late holocene depending on the strength and phase of enso and the phase of the sam we suggest that precession driven changes in the seasonal cycle of solar radiation exert a first order control on the interaction between the two climate modes consequently their present

barium in planktonic foraminifera abstract reconstructions of ba distributions in ancient oceanic surface waters could provide new insight into paleoceanographic change calcite shells of planktonic foraminifera potentially provide a means of reconstructing such paleo ba distributions if lattice bound ba can be determined on shells recovered from deep sea cores planktonic foraminifera shells from a series of cores were purified of non lattice bound ba associated with organic or sedimentary phases by a combination of physical agitation oxidative reductive steps acid leaches and a novel alkaline dtpa step to dissolve barite a sequential dissolution of a large sample of cleaned shells of the planktonic foraminifer globigerinoides conglobatus indicates homogeneous distribution of ba in the shell material comparison of shells from sediments sediment traps and plankton tows indicates no significant differences in the ba content of the purified shells cleaned samples of the planktonic foraminifera globigerinoides sacculifera g ruber g conglobatus orbulina spp and globoquadrina dutertrei from the equatorial pacific north atlantic and mediterranean sea have ba ca ratios between 0 6 and 1 0 mol mol 0 8 to 1 4 ppm variation in foraminiferal ba contents between the three basins is consistent with the trend in surface seawater ba the calculated distribution coefficient for ba incorporation in these five species based on these data is 0 19 0 05 several species of the non spinose planktonic foraminifera globorotalia have ba ca ratios ranging from 2 to 13 mol mol these high ba contents might be explained by differences in the way these foraminifera precipitate their shells a temporal record of ba ca in samples of globigerinoides and orbulina from a core in the northwest atlantic suggests that the ba concentration of surface waters at this site has not changed by more than 20 over the last 14 kyr

foraminiferal reconstruction of barium distributions in water masses of the glacial oceans foraminiferal ba can be used to reconstruct the distribution of deeply regenerated chemical components in past oceans the ba contents of benthic foraminifera recovered from cores in the atlantic ocean indicate that waters deeper than 2900 m had 30 60 higher ba during the last glacial maximum lgm these changes are consistent with previously observed glacial nutrient enrichments based on foraminiferal cd and 13c increases in deepwater nutrient contents in the atlantic can be explained by reductions in north atlantic deep water formation during the lgm ba ca of benthic foraminifera from the glacial sections of intermediate depth atlantic cores are equal to or lower than holocene values this ba evidence argues against the mediterranean as a greatly increased source to atlantic intermediate waters during the lgm since the mediterranean is enriched in ba today and apparently remained enriched during the lgm benthic foraminiferal ba from the glacial sections of cores from the eastern equatorial pacific suggest that deep waters of the glacial pacific were about 25 lower in ba at 3000 m taken together the foraminiferal evidence indicates that the ba content of deep waters of the atlantic antarctic and pacific were similar at the lgm since foraminiferal cd distributions indicate that cd remained significantly lower in the deep atlantic relative to the pacific at the last glacial maximum a seven box ocean model is used to explore several scenarios for reconciling lgm ba and cd distributions while the changed distribution of both tracers suggests diminishment in the flux of nutrient depleted waters to the deep atlantic during the lgm increased atlantic upwelling rates and consequently enhanced ba particle fluxes can account for the the lack of ba fractionation between the deep atlantic and pacific the model suggests that ba can be transferred efficiently to the deep atlantic by enhanced upwelling because the vast majority of the ba is regenerated in the deep atlantic box

southern ocean contributions to the eastern equatorial pacific heat content during the holocene abstract temperature reconstructions from a shallow core 375 m from the peru margin are used to test the influence of subantarctic mode water samw on the eastern equatorial pacific eep thermostad and thus the effect of southern high latitude climate on interior ocean heat content ohc temperature estimates based on mg ca measurements of planktonic and benthic foraminifera neogloboquadrina dutertrei and uvigerina spp respectively show higher temperatures in the early holocene a cooling of 2 by 8 kyr b p and after relatively stable temperatures to the present the temperature signal is similar in direction and timing to a rather robust holocene climate signal from the southern high latitudes suggesting it originated there and was advected to the core site in the eep based on the n dutertrei and uvigerina mg ca temperature and 13c records we conclude that samw acted as a conduit transporting the southern high latitude climate to the interior of the equatorial pacific we propose that the early holocene warmth is related to a southward migration of the subtropical front which enhanced the influence of warm subtropical water in the region of samw formation and was then transported to the eep thermostad the early holocene warmth recorded in the eep thermostad has a muted sea surface temperature expression indicating this mechanism is important for sequestering heat in the ocean interior

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

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

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

a new chronostratigraphic paradigm for the age and tectonic history of the mesoproterozoic bushmanland ore district south africa a discussion sir the authors are to be congratulated for their contribution to the greater understanding of the aggeneys gamsberg district and bushmanland group through the addition of new detrital zircon age data we trust that these data will ultimately contribute to a better understanding of the depositional age of the bushmanland group as well as the tectonic evolution for this portion of the namaqualand metamorphic province fig 1 while we concur with the authors interpretation that deposition of the bushmanland group and associated base metal sulfide deposits of the aggeneys gamsberg district must be younger than 1650 ma as previously concluded by mcclung 2006 and bailie 2007b we would like to raise some fundamental objections to the contribution by cornell et al 2009 our objections center on the poor and possibly erroneous lithostratigraphic position of the samples analyzed by the authors much of this uncertainty is due to the absence of proper geologic descriptions or convincing evidence to support the assumed stratigraphic position uncritical use of an inadequate lithostratigraphic column for the bushmanland group and the lack of appropriate referencing of recent contributions relevant to this region of the na maquland metamorphic province our most important objection to the communication by cornell et al 2009 relates to the stratigraphic column endorsed the authors present a modified version of the stratigraphic column that was originally described and proposed by praekelt et al 1997 and reiterated in several subsequent publications by the same group of authors e g colliston and schoch 1998 2002 2003 2006 colliston et al 2008 this stratigraphic column is however not widely accepted as it is in direct conflict with the results of regional and local field based investigations of the lithostratigraphy of the bushmanland group fig 2 joubert 1974 1986 rozendaal

holocene shifts of the subtropical shelf front off southeastern south america controlled by high and low latitude atmospheric forcings over the uruguayan shelf and uppermost slope the coalescence of northward flowing subantarctic shelf water and southward flowing subtropical shelf water forms a distinct thermohaline front termed the subtropical shelf front stsf running in a sw direction diagonally across the shelf from the coastal waters at 32 s toward the shelf break at ca 36 s the stsf represents the shelfward extension of the brazil malvinas confluence zone this study reconstructs latitudinal stsf shifts during the holocene based on benthic foraminifera 18o and 13c total organic carbon carbonate contents ti ca and grain size distribution from a high accumulation sedimentary record located at an uppermost continental slope terrace our data provide direct evidence for 1 a southern stsf position to the south of the core site at the beginning of the early holocene 9 4 cal ka bp linked to a more southerly position of the southern westerly winds in combination with restricted shelf circulation intensity due to lower sea level 2 a gradual stsf northward migration bypassing the core site toward the north primarily forced by the northward migration of the southern westerly winds from 9 4 cal ka bp onward 3 a relatively stable position of the front in the interval between 7 2 and 4 0 cal ka bp 4 millennial scale latitudinal oscillations close to 36 s of the stsf after 4 0 cal ka bp probably linked to the intensification in el nino southern oscillation and 5 a southward migration of the stsf during the last 200 years possibly linked to anthropogenic influences on the atmosphere

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