agulhas eddy fluxes in a 1 6 atlantic model a 1 6 resolution primitive equation model of the atlantic circulation is analyzed in the agulhas region the model has a realistic level of eddy kinetic energy and produces anticyclonic agulhas rings as well as cyclonic structures in the model as well as in the data ring trajectories undergo a transition between a turbulent character in the cape basin and a steady propagation in the rest of the south atlantic the topography of the walvis ridge does not seem to play a part in generating this contrast in the model the model shows that cyclones are primarily generated from the negative shear vorticity side of the agulhas current as it leaves the coast and they are most of the time paired with anticyclones in dipolar or tripolar structures contribution of agulhas rings to the transports has been estimated by two methods either focussing on the amount of water trapped inside the eddies and carried with them or as a perturbation to the time mean flow the second estimate always produces smaller mass fluxes than the first even so the transient eddy flux 2 sv of warm water over the agulhas ridge is very large when compared to parameterizations of eddy fluxes used in low resolution climate models

distribution of anthropogenic co2 in the pacific ocean 1 this work presents an estimate of anthropogenic co2 in the pacific ocean based on measurements from the woce jgofs oaces global co2 survey these estimates used a modified version of the c technique modifications include a revised preformed alkalinity term a correction for denitrification and an evaluation of the disequilibrium terms using an optimum multiparameter analysis the total anthropogenic co2 inventory over an area from 120 e to 70 w and 70 s to 65 n excluding the south china sea the yellow sea the japan east sea and the sea of okhotsk was 44 5 5 pg c in 1994 approximately 28 pg c was located in the southern hemisphere and 16 5 pg c was located north of the equator the deepest penetration of anthropogenic co2 is found at about 50 s the shallowest penetration is found just north of the equator very shallow anthropogenic co2 penetration is also generally observed in the high latitude southern ocean one exception to this is found in the far southwestern pacific where there is evidence of anthropogenic co2 in the northward moving bottom waters in the north pacific a strong zonal gradient is observed in the anthropogenic co2 penetration depth with the deepest penetration in the western pacific the pacific has the largest total inventory in all of the southern latitudes despite the fact that it generally has the lowest average inventory when normalized to a unit area the lack of deep and bottom water formation in the north pacific means that the north pacific inventories are smaller than the north atlantic

comparison of imbrie kipp transfer function and modern analog temperature estimates using sediment trap and core top foraminiferal faunas we evaluate the reliability of statistical estimates of sea surface temperature sst derived from planktonic foraminiferal faunas using the modem analog method and the imbrie kipp method global core top faunas provide a calibration data set while modem sediment trap faunas are used for validation linear regression of core top predicted sst against atlas sst generated slopes close to one for both methods however the imbrie kipp transfer function temperature estimates had an intercept 1 3oc warmer than modem analog estimates and 1 7oc warmer than recorded atlas sst the rms error for the core top data set using the modem analog method 1 5oc was smaller than that of the imbrie kipp method 1 9oc sst errors for the sediment trap faunas were not statistically different from those of the core top data set regardless of method developing imbrie kipp transfer functions for limited regions reduced the rms variability but introduced residual structure not present in the global imbrie kipp transfer function dissolution simulations with the sediment trap sample which generated the warmest sst residual for both methods suggests that the loss of delicate warm water foraminifera from midlatitude sediments may be the cause of this thermal error we conclude that 1 the fauna structure of sediment trap and core top assemblages are similar 2 both methods estimate sst reliably for modem foraminifera flux assemblages but the modem analog method exhibits less bias and 3 both methods are relatively robust to samples with low communality but sensitive to selective faunal dissolution

estimation of the agulhas ring impacts on meridional heat fluxes and transport using argo floats and satellite data 1 a method that combines vertical profiles from the argo floats program and satellite sea surface height ssh data is used to reconstruct the vertical structure of the agulhas rings all eddies shed by the agulhas retroflection in the period between january 2005 and december 2008 were successfully reconstructed the velocity structures obtained are tilted and phase shifted in relation to the temperature anomalies resulting in an annual mean eddy meridional heat flux across the ring paths of 0 062 0 012 pw northward a first order estimate indicates 0 07 pw entering the atlantic from the indian ocean through agulhas rings the volume transport by agulhas rings is believed to play a central role in the overturning circulation being the main process responsible for the leakage of indian ocean waters to the atlantic the new estimates of the time mean ring volume transport of 9 8 sv from the indian to the atlantic ocean fall in the range obtained by previous works these estimates include a better representation of the trapped water region in the eddies a large inter annual variability in the volume transport was observed with a maximum of 11 21 sv in 2007 this variability is related to the number of structures shed by the agulhas retroflexion per year the ring shapes play a secondary though important role

oceanic cooling recorded in shells spanning the medieval climate anomaly in the subtropical eastern north atlantic ocean abstract the medieval climate anomaly mca 900 1300 ad was the most recent period of pre industrial climatic warming in the northern hemisphere and thus estimations of mca signals can illuminate possible impacts of anthropogenic climate change current high resolution mca climate signals are restricted to mid and high latitude regions which confounds inferences of how the mca impacted some global hemispheric climate mechanisms e g north atlantic oscillation nao to address this knowledge gap we estimate seasonally resolved sea surface temperatures ssts from the oxygen isotope composition 18o of serially sampled phorcus atratus shells from archaeological sites spanning the mca in the canary islands twelve archaeological and six modern p atratus shells were analyzed and archaeological shells were dated using carbonate target radiocarbon dating ssts were estimated using the published aragonite water equilibrium fractionation equation modern shells showed a mean sst of 20 0 1 5 c with a seasonal amplitude of 5 3 0 9 c archaeological shells exhibited a mean sst of 18 2 0 7 c with a mean seasonal amplitude of 5 5 1 0 c thus shells that span the mca in the canary islands recorded ssts that were significantly cooler than the modern p

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

persisting maximum agulhas leakage during mis 14 indicated by massive ethmodiscus oozes in the subtropical south atlantic 1 the glacial marine isotope stage 14 mis 14 appears in many climate records as an unusually warm glacial during this period an almost monospecific up to 1 5 m thick laminated layer of the giant diatom ethmodiscus rex has been deposited below the south atlantic subtropical gyre this oligotrophic region is today less favorable for diatom growth with sediments typically consisting of calcareous nannofossil oozes we have reconstructed temperatures and the stable oxygen isotopic compositions of sea surface and thermocline water 18ow from planktonic foraminiferal globigerinoides ruber and globorotalia inflata mg ca and stable oxygen isotopes to test whether perturbations in surface ocean conditions contributed to the deposition of the diatom layer at 530 kyr b p temperatures and 18ow values reconstructed from this diatom ooze interval are highly variable with maxima similar to interglacial values since the area of the ethmodiscus oozes resembles the region where agulhas rings are present we interpret these hydrographic changes to reflect the varying influence of warm and saline water of indian ocean origin that entered the subtropical gyre trapped in agulhas rings the formation of the ethmodiscus oozes is associated with a period of maximum agulhas leakage and a maximum frequency of agulhas ring formation caused by a termination type position of the subtropical front during the unusual warm mis 14 the input of silica through the agulhas rings enabled the shift in primary production from calcareous nannoplankton to diatoms leading to the deposition of the massive diatom oozes

palaeoceanographic implications of genetic variation in living north atlantic neogloboquadrina pachyderma the shells of the planktonic foraminifer neogloboquadrina pachyderma have become a classical tool for reconstructing glacial interglacial climate conditions in the north atlantic ocean1 2 3 palaeoceanographers utilize its left and right coiling variants which exhibit a distinctive reciprocal temperature and water mass related shift in faunal abundance both at present and in late quaternary sediments1 2 4 5 recently discovered cryptic genetic diversity in planktonic foraminifers6 7 8 now poses significant questions for these studies here we report genetic evidence demonstrating that the apparent single species shell based records of right coiling n pachyderma used in palaeoceanographic reconstructions contain an alternation in species as environmental factors change this is reflected in a species dependent incremental shift in right coiling n pachyderma shell calcite 18o between the last glacial maximum and full holocene conditions guided by the percentage dextral coiling ratio our findings enhance the use of 18o records of right coiling n pachyderma for future study they also highlight the need to genetically investigate other important morphospecies to refine their accuracy and reliability as palaeoceanographic proxies

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

moored sediment trap measurements of carbon export in the subantarctic and polar frontal zones of the southern ocean south of australia sediment trap moorings were deployed from september 21 1997 through february 21 1998 at three locations south of australia along 140 e at 47 s in the central subantarctic zone saz with traps at 1060 2050 and 3850 m depth at 51 s in the subantarctic front with one trap at 3080 m and at 54 s in the polar frontal zone pfz with traps at 830 and 1580 m particle fluxes were high at all the sites 18 32 g m 2 yr 1 total mass and 0 5 1 4 g organic carbon m 2 yr 1 at 1000 m assuming minimal flux outside the sampled summer period these values are similar to other southern ocean results and to the median estimated for the global ocean by lampitt and antia 1997 and emphasize that the southern ocean exports considerable carbon to the deep sea despite its high nutrient low chlorophyll characteristics the saz site was dominated by carbonate 50 of total mass and the pfz site by biogenic silica 50 of total mass both sites exhibited high export in spring and late summer with an intervening low flux period in december for the 153 day collection period particulate organic carbon export was somewhat higher in all the traps in the saz range 0 57 0 84 gc m 2 than in the pfz range 0 31 0 53 with an intermediate value observed at the saf 0 60 the fraction of surface organic carbon export estimated from seasonal nutrient depletion lourey and trull 2001 reaching 1000 m was indistinguishable in the saz and pfz despite different algal communities

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

sea surface temperatures of the southwest pacific ocean during the last glacial maximum the southwest pacific ocean covers a broad range of surface water conditions ranging from warm salty water in the subtropical east australian current to fresher cold water in the circumpolar current using a new database of planktonic foraminifera assemblages ausmat f2 we demonstrate that the modern analog technique can be used to accurately reconstruct the magnitude of sea surfacetemperature sst in this region we apply this technique to data from 29 deep sea cores along a meridional transect of the southwest pacific ocean to estimate the magnitude of sst cooling during the last glacial maximum we find minimal cooling in the tropics 0 2 c moderate cooling in the subtropical midlatitudes 2 6 c and maximum cooling to the southeast of new zealand 6 10 c the magnitude of cooling at the sea surface from the tropics to the temperate latitudes is found to generally be less than cooling at the surface of adjacent land masses

core top calibration of δ18o and δ13c of g ruber white and u mediterranea along the southern adriatic coast of italy we carried out an extensive survey of the oxygen and carbon isotope composition of the planktic species g ruber white and of the benthic species u mediterranea along the southern italian coast of the adriatic sea and in the gulf of taranto comparison with seasonal satellite based sea surface temperature maps and water column profiles as well as with several sets of water samples allows estimation of the effect of salinity and different nutrient supply on the 18o and 13c of foraminifera the results indicate that g ruber white while being highly affected by different salinity and nutrient distributions related to circulation patterns of major water masses dominantly record summer temperature conditions u mediterranea reflect the recent environmental conditions such as nutrient supply and bottom water temperature characteristics along the southern italian coast and clearly show the transition from a near coastal eutrophic system to an offshore oligotrophic system

carbon isotopic disequilibrium in polar planktonic foraminifera and its impact on modern and last glacial maximum reconstructions calibration studies of neogloboquadrina pachyderma sinistral coiling hereinafter referred to as n pachyderma s in the south atlantic raise questions about the interpretation of this species carbon isotope composition as a paleoceanographic tracer of southern ocean surface nutrient contents carbon isotope disequilibrium between 13c of total co2 tco2 of seawater and 13c of n pachyderma s increases systematically between 70 and 40 s several effects could cause the observed carbon isotope disequilibrium including a combination of foraminiferal diet calcification temperature and carbonate ion chemistry combining these corrections to the 13c of n pachyderma s improves the reconstruction of the 13c of seawater tco2 between 0 and 200 m in the modern south atlantic with these corrections applied the 13c for equilibrium calcite reconstructed from n pachyderma s at the last glacial maximum is very similar to preindustrial values suggesting that one cannot rule out the possibility that surface nutrient concentrations in the south atlantic ocean were comparable to today however the magnitude of the uncertainties associated with these corrections make it difficult to assess absolute paleonutrient concentrations with much confidence

eddy train encounters with a continental boundary a south atlantic case study satellite altimetry suggests that large anticyclonic eddies rings originating from the agulhas current retroflection occasionally make their way across the entire south atlantic ocean what happens when these rings encounter a western boundary current in this work interactions between a train of nonlinear lenslike eddies and a southern hemisphere continental boundary are investigated analytically and numerically on a b plane the train of eddies is modeled as a steady double frontal zonal current with the same vorticity and transport as the eddies themselves the continental boundary is represented by a vertical wall which is purely meridional in one case and is tilted with respect to the north in another case it is demonstrated analytically that the eddy wall encounter produces an equatorward flow parallel to the continental wall thus suggesting a weakening of the transport of the associated poleward flowing western boundary current upstream of the encounter zone and unchanged transport downstream a large stationary eddy is established in thecontactzonebecauseitsb inducedforceisnecessarytobalancetheotherforcesalongthewall thesizeof this eddy is directly proportional to the transport of the eddy train and the meridional tilt of the wall these scenarios are in good agreement with results obtained numerically using an isopycnal bleck and boudra model

seasonal changes in the isotopic composition of planktonic foraminifera collected in panama basin sediment traps abstract isotopic analyses have been made on five species of planktonic foraminifera collected in two deployments of parflux mark ii time series sediment traps in the panama basin the automated sampling system on the traps provided 4 one month samples from 29 july to 16 november 1979 and 6 two month samples from december 1979 to november 1980 the 18o values of globigerinoides ruber and globigerinoides sacculifer in this region are primarily affected by a low salinity surface layer that forms during the early winter these species each show a 1 total range in 18o the 18o values of the colder water species globorotalia menardii neogloboquadrina dutertrei and globorotalia theyeri show smaller seasonal changes in 18o the 13c values of g ruber and g sacculifer exhibit small seasonal changes 0 35 and 0 4 respectively despite large seasonal changes in surface water productivity the colder water species exhibit only slightly larger changes in 13c up to 0 55 throughout the year all colder water species exhibit minimum or near minimum 13c values during february and march which is the period of maximum upwelling and primary productivity seasonal variations in the flux of foraminifera in the water column at this location will have only a small effect on the isotopic composition of the sediment assemblage extreme values of 18o and 13c do not occur during the periods which are associated with the high flux of foraminiferal tests

merging and migration of two meddies in this study a scenario is developed of two adjacent mediterranean water eddies meddies as they were observed merging and drifting through the iberian basin observations are based on four rafos floats at 850 1050 dbar two hydrographic surveys centered roughly at 38 n 24 w and trajectories of surface drifters drogued at 100 m in april 1991 the meddy a was identified and labeled by surface drifters during the revisit one month later two meddies were encountered b1 and b2 in the vicinity of the former meddy a the coalescence of b1 subsequently identified as a one month older and b2 is inferred from a simple kinematic model describing the observed movement of the rafos floats for up to three months after the second ctd survey the deduced vorticity front radius 15 km within b1 was of insufficient strength to keep the core waters of b1 isolated and prevent the absorption of b1 by b2 the resulting meddy b1 b2 showed a clear near surface dynamical signal its deep root 1800 m could explain the expulsion from the meddy of the remaining rafos float and surface drifter at the time of the meddy s collision with the josephine seamount for the first time a set of lagrangian and hydrographic observations give direct evidence that neighboring meddies can merge as predicted by theoretical considerations

a kinematic analysis of the indian atlantic interocean exchange we analyze the indian atlantic interocean exchanges in an eddy permitting numerical simulation focusing on the cape basin a region of the southeastern atlantic bounded on the northwest by the walvis ridge and on the south by the agulhas ridge near 40 s to quantify the relative importance of the different dynamical mechanisms involved in the interocean exchange we separated the climatological mean circulation from the transients the analysis indicates that agulhas eddies influence not only the transient but also fluxes associated with the mean circulation eddy fluxes for example supply most of the energy of the benguela current a distinctive characteristic of the eddy variability within the cape basin is the co existence of cyclonic and anticyclonic vortices in dipole structures that resemble the heton model of hogg and stommel proc r soc london a 397 1985 1 anticyclones are surface intensified vortices that in spite of their baroclinic structure reach to deep layers cyclones are bottom intensified vortices with dominant barotropic structure that projects into the upper layer the propagation of both cyclones and anticyclones is strongly affected by the bottom topography our analysis shows that the walvis ridge and the vema seamount block the passage of bottom intensified cyclones and changes the trajectories of the upper intensified anticyclones although most anticyclones are able to escape the basin the deep compensation generated by the ridge generates an energy loss of approximately 30 and a change of the eddy trajectory to a more westward direction

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

controls on the carbon isotopic composition of southern ocean phytoplankton carbon isotopic compositions of suspended organic matter and biomarker compounds were determined for 59 samples filtered from southern ocean surface waters in january 1994 along two north south transects woce sr3 from tasmania to antarctica and across the princess elizabeth trough pet east of prydz bay antarctica along the sr3 line bulk organic matter show generally decreasing 13c contents southward which are well correlated with increasing dissolved molecular carbon dioxide concentrations co2 aq this relationship does not hold along the pet transect using concentrations and isotopic compositions of molecular compounds we evaluate the relative roles of several factors affecting the 13c of southern ocean suspended particulate organic matter along the woce sr3 transect the concentration of co2 aq plays an important role it is well described by a supply versus demand model for the extent of cellular co2 utilization and its associated linear dependence of isotopic fractionation ep on the reciprocal of co2 aq an equally important factor appears to be changes in algal assemblages along the sr3 transect with their contribution to isotopic fractionation also well described by the supply and demand model when formulated to include the cell surface volume control of supply changes in microalgal growth rates appear to have a minor effect on ep along the pet transect algal assemblage changes and possibly changes in microalgal growth rates appear to strongly affect the carbon isotopic variations of suspended organic matter these results can be used to improve the formulation of modern carbon cycle models that include phytoplankton carbon isotopic fractionation

origins and variability of the benguela current a subset of the benguela sources and transports best 1992 1993 data is analyzed to study the magnitude and variability of the large scale transports in the area the data consist of inverted echo sounder series and conductivity temperature depth stations the mean 16 month transport values for the upper 1000 m indicate that of the 13 sv northward transport within the benguela current 50 is derived from the central atlantic which from geometry may be chiefly south atlantic water 25 comes from the indian ocean which may be chiefly agulhas water and the remaining 25 may be a blend of agulhas and tropical atlantic water a simple schematic of the transport pattern with a somewhat restricted corridor for agulhas eddies translation is envisioned to the west of the eddy corridor flows the south atlantic source for the benguela current to the east is the agulhas indian ocean source the corridor is breached by south atlantic and indian water as the transient eddy field stirs these water masses

the influence of air sea exchange on the isotopic composition of oceanic carbon observations and modeling although the carbon isotropic composition of ocean waters after they leave the surface ocean is determined by biological cycling air sea exchange affects the carbon isotopic composition of surface waters in two ways the equilibrium fractionation between oceanic and atmospheric carbon increases with decreasing temperature in southern ocean surface waters this isotopic equilibrium enriches delta sup 13 c relative to the delta sup 13 c expected from uptake and release of carbon by biological processes alone similarly surface waters in the subtropical gyres are depleted in delta sup 13 c due to extensive air sea exchange at warm temperatures countering the tendency toward isotopic equilibration with the atmosphere a relatively slow process are the effects of the equilibration of co sub 2 itself a much faster process in regions where there is a net transfer of isotopically light co sub 2 from the ocean to the atmosphere e g the equator surface waters become enriched in sup 13 c whereas in regions where isotopically light co sub 2 is entering the ocean e g the north atlantic surface waters become depleted in sup 13 c a compilation of high quality oceanic delta sup 13 c measurements along with experiments performed using a zonally averaged three basin dynamic ocean model are used to explore these processes 40 refs 14more figs 1 tab less

characteristics and evolution of an agulhas ring a south atlantic ring is studied through remote sensing altimetry hydrographic stations and drifters trajectories the ring s core was characterized by warmer and saltier indian ocean waters at the time of the cruise the ring s signature extended out 110 km and down to 2000 m and its core absolute dynamic topography adt exceeded the surrounding atlantic ocean waters in 0 4 m the geostrophic velocities were anticyclonic with maximum velocities about 35 cm s 1 at 100 m and reaching negligible values near 4500 m the rotational transport inside the ring was 33 sv in the thermocline and intermediate layers the drifters data distinguishes a 30 km core revolving as a solid body with periodicity near 5 days and a transitional band that revolves with constant tangential velocity resembling a rankine vortex the adt data identifies the ring s track showing that it was shed by the agulhas current retroflection in november 2009 and propagated northwest rapidly during the first two months mean speed ca 10 cm s 1 but slowed down substantially 3 4 cm s 1 between march and july 2010 when it was last detected the altimetry data also outlines the evolution of the ring s core adt radius vorticity and through a simple calibration with the cruise data rotational transport in particular the ring surface and mean vorticity decay with time scales of 373 and 230 days respectively indicating that most of the property anomalies contained by the ring are diffused out to the subtropical gyre before it reaches the western boundary current system

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

climatic evolution in the australian region over the last 94 ka spanning human occupancy and unveiling the last glacial maximum abstract the quaternary is well known for being a period of the geological record that saw significant and alternating climatic fluctuations here we concentrate on the last 94 millennia that saw australia and its surrounding seas undergo significant environmental changes importantly also it is during that this period of time includes the arrival and settlement of humans in australia following on from marine isotopic stage 4 mis4 that saw over the period of 71 59 ka bp a significant eustatic sea level drop 100 m low sea surface temperatures as well as glacial conditions on land australia experienced wet conditions again but eventually progressively entered into a glacial phase by then humans had arrived on this large continent and later the megafauna progressively became extinct this paper describes in detail the climate over this period based principally on the high resolution record of two marine sediment cores located offshore of the southern australian margin and that are then compared with known events on land as well as other deep sea cores particular emphasis is placed on the period that spans the last glacial maximum lgm the extent of which thus far had been poorly defined in the australian region emphasis is placed on the period from 34 to 14 ka to demonstrate that 1 the lgm defined here as the period 24 to 18 ka was not always extremely dry and cold and 2 that people were able to live in inland australia as water existed in places despite generally cold conditions we also show using a series of ten maps at 2 ka intervals over the 34 14 ka period the waxing and waning of oceanic fronts such as the subtropical and subantarctic fronts link sea surface temperatures sst with periods of glacial expansion in the australian alps and tasmania as well as the south island of new zealand and the extent of the leeuwin current down to south of australia aeolian dust was transported at sea over the main core site from 26 to 18 ka period pointing to arid conditions in australia but this period was punctuated by two significant reductions in dust transport to both core sites coinciding with a retreat of the subantarctic front away from the australian southern coastline and slight sst shifts for a few centuries at 24 and 22 21 ka bp at the peak of the cold phase from 23 to 18 4 ka summer sst were of the order of 9 c below that experienced during the middle of the holocene at about 6 ka bp a similar temperature drop was also experienced offshore the northwestern corner of western australia periglacial activity dates for the australian mainland and tasmania pool around 22 ka on either side of the 24 ka event the chain of lakes in the willandra lakes retained water and human activity was registered in the area elsewhere in australia water was present to sustain human populations during the cold and dry times it is postulated here that northern australia was at times quite wet especially during mis4 the cessation of the lgm is set on 18 4 ka from offshore southern australia as confirmed for the deep sea cores by several proxies and more likely at 18 ka inland finally we document that it took two millennia for glacial conditions to end in the australian region as registered in our deep sea core records well after the lowest global sea level 20 6 and 20 ka respectively started to rise there is also evidence of another very cold period determined on the australian mainland tasmania and the south island of new zealand centred around 27 ka after which time warmer conditions occurred before the start of the lgm this is matched with our deep sea records with very cold conditions and changes in oceanographic conditions

seasonal associations of phytoplankton and planktic foraminifera in an upwelling region and their contribution to the seafloor abstract seasonal occurrences of both phytoplankton and zooplankton are closely associated with upwelling and stabilization in waters overlying the san pedro basin this region is situated within the southern california bight and is affected by variations in the general southward flowing california current and variable intrusion of oceanic waters increased northerly wind stress in spring and early summer results in upwelling of deeper nutrient rich waters into the photic zone a seven month time series sediment trap experiment revealed clear patterns in seasonal succession of both phytoplankton and planktic foraminifera several distinct high and low flux periods occurred over the study period some of which can be related to rapid changes in the hydrographic environment caused by upwelling and subsequent surface water stratification factor analysis of relative abundances of combined phytoplankton and foraminiferal taxa defines seven assemblages reflecting seven stages of production which range in duration from two to five weeks factor scores describe phytoplankton and foraminiferal taxa indicative of specific production stages periods of high flux of the more abundant diatoms and planktic foraminifera also illustrate preferred production stages and compare well with percentage based results a comparison of the sediment trap assemblage with local sediment from an oxygenated portion of the basin suggests that long term phytoplankton accumulation in this region is dominated by taxa associated with winter bloom and post upwelling bloom production implying that brief but massive episodic events overwhelm and dominate the annually averaged diatom species assemblage found in the sediments foraminifera however are modified by dissolution to the extent that the high production periods of late spring and during upwelling are poorly represented rather species indicative of early spring and post upwelling conditions dominate the planktic foraminiferal sedimentary assemblage

anticyclonic and cyclonic eddies of subtropical origin in the subantarctic zone south of africa two eddies one anticyclonic and the other cyclonic intersected in the subantarctic zone south of south africa during a hydrographic transect are described using a large set of measurements including full depth hydrography acoustic doppler current profiler velocities biogeochemical tracers air sea fluxes and altimetric sea surface height both eddies have a subtropical origin the anticyclone is an agulhas ring with convected core water of similar to 12 degrees c and swirl velocities of 1 m s 1 it was 9 5 months old when sampled and had crossed the agulhas ridge though sampled in summer it was releasing similar to 200 w m 2 sensible plus latent heat flux to the atmosphere it was observed adjacent to the subantarctic front illustrating the usual encounters of such structures with this front the cyclone marked by pronounced low oxygen and cfc anomalies revealing an origin at the continental slope was 4 5 months old it had swirl speeds of 0 3 m s 1 and was coupled with the anticyclone when observed from their kinematics and water mass properties both structures were found to transport subtropical water down to similar to 900 m the water trapped below this depth being either from the northern subantarctic zone or local water the two structures illustrate the capacity of eddies in the region to transfer subtropical and alongslope water properties into the subantarctic zone

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

the imprint of anthropogenic co2 in the arctic ocean evidence from planktic δ13c data from watercolumn and sediment surfaces 13c values of n pachyderma sin from the water column and from core top sediments are compared in order to determine the 13c decrease caused by the addition of anthropogenic co2 to the atmosphere this effect which is referred to as the surface ocean suess effect is estimated to be about 0 9 0 2 within the arctic ocean halocline waters and to about 0 6 0 1 in the atlantic derived waters of the southern nansen basin this means that the area where the arctic ocean halocline waters are formed the arctic shelf regions are relatively well ventilated with respect to co2 nevertheless 13c of dissolved inorganic carbon 13cdic in the arctic ocean halocline waters is far from isotopic equilibrium absolute values of 13c of n pachyderma sin covary with the surface ocean suess effect and we interprete changes in both parameters as a reflection of the degree of ventilation of the waters on the shelf sea measurements of 13c of n pachyderma sin in the arctic ocean from plankton tows reveal a vital effect of about 2 significantly different from other published values a first order estimate of the total anthropogenic carbon inventory shows that despite of its permanent sea ice cover the arctic ocean with 2 of the global ocean area is responsible for about 4 6 of the global ocean s co2 uptake

carbon isotope composition of caribbean sea surface waters response to the uptake of anthropogenic co2 1 the burning of fossil fuels and deforestation have significantly increased atmospheric co2 levels from 280 ppm prior to the industrial revolution to the present value of 390 ppm suess 1955 was the first to show that the carbon isotopic composition of the atmosphere is changing in response to the anthropogenic input of radiocarbon dead 13c depleted co2 from fossil fuel combustion here we report a high resolution planktonic foraminiferal 13c record from the caribbean sea for the last 300 years that clearly resolves the timing and magnitude of the marine 13c suess effect associated with the oceanic uptake of anthropogenically derived co2 cariaco basin sediment trap and upper most box core sediment 13c match both the trend and magnitude of observed 13c changes in atmospheric co2 over the last 15 years the longer sediment record suggests the marine suess effect to be 0 75 from pre industrial values with most of the change occurring since 1950 coincident with the rapid rise in atmospheric co2 noted in ice core and instrumental data if the current anthropogenic co2 emission trend continues extrapolating our marine 13c rate curve into the future suggests that the rate of marine 13c change caused by anthropogenic co2 will increase to 0 10 yr 1 by the end of this century an increase of more than an order of magnitude from 1950 values

three agulhas rings observed during the benguela current experiment a field program to study the circulation of the benguela current and its extension into the southeastern atlantic ocean has completed the survey and instrument deployment phase we report here new observations of three agulhas rings north and west of cape town south africa three mesoscale anticyclonic rings initially identified by means of topex poseidon altimetry were surveyed with expendable bathythermographs conductivity temperature depth oxygen profiles direct current measurements from a lowered acoustic doppler current profiler a hull mounted acoustic doppler current profiler and satellite tracked surface drifters characteristics of the rings are presented and their origins are discussed two are typical agulhas rings surveyed at different times after their generation the third agulhas ring has an anomalous water mass structure whose most likely origin is the subtropical front

petrogenetic linkages among martian basalts implications based on trace element chemistry of olivine the shergottites exhibit a range of major and trace element compositions crystallization ages and initial sr nd hf and pb isotopic compositions to constrain the physical mechanisms by which shergottites obtain their compositional characteristics we examined the major and trace element record preserved in olivine in the more primitive shergottites based on such characteristics as the mg v zoning calculated dni co the olivine in y 980459 are most likely phenocrysts many of these same characteristics indicate that the olivines in other shergottites are not in equilibrium with the adjacent melt however in most cases they are not xenocrystic but additions of olivine from the same basaltic system elephant moraine eet a79001 may be an exception with the olivine data suggesting that it is xenocrystic in this case the olivine crystallized from a reduced and lreedepleted melt and was incorporated into an oxidized and enriched basalt vanadium and cao in olivine appear to record the appearance of spinel and pyroxene on the liquidus of most of the shergottites most of the olivine shergottites represent basalts produced by melting of reduced iw to iw 1 depleted mantle sources olivine data indicate that many of the primary melts derived from this source had similar ni co and mn shergottites such as northwest africa nwa 1110 1068 and perhaps roberts massif rbt 04261 that appear to be derived from more enriched sources have distinctly different olivine in the case of nwa 1110 1068 the olivine data suggests that the enriched component was added to system prior to olivine crystallization

oceanic fluxes on the woce a11 section abstract the most southerly woce one time section in the south atlantic designated a11 was occupied in january 1993 the cruise track lay across the cool subantarctic zone of the circumpolar current in the west and the warm subtropical gyre in the east in this paper estimates of the flux of heat salt oxygen and other tracers across the section are presented a brief description of the distribution of physical and chemical properties is followed by a determination of the flux in the surface ekman layer direct measurements of current shear made from a shipborne adcp and estimates from cruise wind data and climatological data all yield a flux of 5 1 sv sv 106 m3 s 1 equatorward when combined with geostrophic estimates relative to a level near 3500 dbar or the bottom where shallower an initial guess for the flow field is derived this initial guess is combined with absolute currents derived from the adcp when the ship is underway unrealistic aspects of the circulation are found and we conclu

late holocene dynamics of sea surface temperature and terrestrial hydrology in southwestern africa southwest africa is an important region for paleo climatic studies being influenced by both tropical and temperate climate systems and thus reflecting the interplay of variable controls the aim of this study was to unravel the interaction of sea surface temperature sst changes in the southernmost benguela upwelling system with precipitation changes in south africa s winter rainfall zone wrz during the late holocene therefore a marine sediment core from the southernmost benguela upwelling system was investigated to reconstruct climate changes in this region for the past 2000 years grain size and geochemical analyses were conducted to reconstruct changes in fluvial sediment discharge and weathering intensity while sst changes were estimated using alkenone paleo thermometry results show that the southernmost benguela behaves distinctly in comparison with the rest of the benguela system reflecting amplified sst changes decreasing ssts accompanied increasing river discharge during times of increas

carbon isotopes and habitat of polar planktic foraminifera in the okhotsk sea the carbonate ion effect under natural conditions the upper 500 or 1000 m of the water column in the okhotsk sea was sampled for living planktic foraminifera the polar species neogloboquadrina pachyderma sinistral strongly dominates the foraminiferal assemblage the subpolar to temperate species globigerina bulloides accounts for 10 25 other species account for up to 3 only the shell 18o and 13c values of the species n pachyderma sin are compared to water 18o values and 13c values of dissolved inorganic carbon dic the strong gradient in 18o composition and temperature in the upper water column is reflected in the 18o of n pachyderma sin relative to the values expected for inorganic calcite precipitated under equilibrium conditions n pachyderma sin displays a vital effect of about 1 in 18o the 13c composition of n pachyderma sin is about constant with water depth and the reflection of 13cdic in the foraminiferal shell seems to be masked by other effects most foraminifera are found above or slightly below the thermocline and can be assumed to calcify in the upper 200 m of the water column the gradient of 13cdic extends well below this depth therefore the lack of correlation can partly be attributed to this fact the remaining discrepancy between 13c of n pachyderma sin and 13cdic correlates with the carbonate ion concentration in the water column this leads to the conclusion that the carbonate ion effect cie which has been derived from culturing experiments for other species spero et al 1997 nature 390 497 500 is found here under natural conditions when the magnitude of the cie derived for g bulloides is applied to n pachyderma sin cie corrected 13c of n pachyderma sin is a direct reflection of 13cdic in the water column with a constant offset of 1 2

coastal zone color scanner pigment concentrations in the southern ocean and relationships to geophysical surface features the spatial and seasonal distributions of phytoplankton pigment concentration over the entire southern ocean have been studied for the first time using the coastal zone color scanner historical data set from october 1978 through june 1986 enhanced pigment concentrations are observed between 35 s and 55 s throughout the year with such enhanced regions being more confined to the south in the austral summer and extending further north in the winter north and south of the polar front phytoplankton blooms 1 mg m3 are not uniformly distributed around the circumpolar region instead blooms appear to be located in regions of ice retreat or high melt areas such as the scotia sea and the ross sea in relatively shallow areas e g the patagonian and the new zealand shelves in some regions of ekman upwelling like the tasman sea and near areas of high eddy kinetic energy such as the agulhas retroflection among all features examined by regression analysis bathymetry appears to be the one most consistently correlated with pigments correlation coefficient being about 0 3 for the entire region the cause of negative correlation with bathymetry is unknown but is consistent with the observed abundance of iron in shallow areas in the antarctic region it is also consistent with resuspension of phytoplankton cells by wind induced mixing especially in shallow waters on the other hand in the deep ocean especially at latitudes 30 in average pigment concentration over the entire region during different seasons indicates possible influence of time dependent parameters

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

main eddy vertical structures observed in the four major eastern boundary upwelling systems in the four major eastern boundary upwelling systems ebus mesoscale eddies are known to modulate the biological productivity and transport near coastal seawater properties toward the offshore ocean however little is known about their main characteristics and vertical structure this study combines 10 years of satellite altimetry data and argo float profiles of temperature and salinity and our main goals are i to describe the main surface characteristics of long lived eddies formed in each ebus and their evolution and ii to depict the main vertical structure of the eddy types that coexist in these regions a clustering analysis of the argo profiles surfacing within the long lived eddies of each ebus allows us to determine the proportion of surface and subsurface intensified eddies in each region and to describe their vertical structure in terms of temperature salinity and dynamic height anomalies in the peru chile upwelling system 55 of the sampled anticyclonic eddies aes have subsurface intensified maximum temperature and salinity anomalies below the seasonal pycnocline whereas 88 of the cyclonic eddies ces are surface intensified in the california upwelling system only 30 of the aes are subsurface intensified and all of the ces show maximum anomalies above the pycnocline in the canary upwelling system 40 of the aes and 60 of the ces are subsurface intensified with maximum anomalies extending down to 800 m depth finally the benguela upwelling system tends to generate 40 50 of weak surface intensified eddies and 50 60 of much stronger subsurface intensified eddies with a clear geographical distribution the mechanisms involved in the observed eddy vertical shapes are discussed

erosion of a surface vortex by a seamount on the β plane abstract this paper investigates the behavior of a surface intensified anticyclone encountering a seamount on the plane in a stratified ocean the eddy may be strongly eroded and sometimes subdivided provided that it gets close enough to the seamount in case of subdivision the detached part has a vertical structure different from that of the initial eddy and a subsurface vortex may result the basic erosion mechanism previously observed with f plane experiments is still active on the plane deep fluid motions induced by the initial vortex across the isobaths generate topographic vortices whose upper parts exert a shear strain on the initial eddy causing its filamentation on the plane this process is further complicated by the presence of additional eddies created by fluid motion across the planetary vorticity gradient experiments without any topography show that these eddies by themselves can erode the initial vortex in particular a deep positive potential vorticity pole influences the ne

seasonal variability of δ18o and δ13c of planktic foraminifera in the bering sea and central subarctic pacific during 1990 2000 we evaluated a 10 year time series of 18o and 13c records from three planktic foraminifers neogloboquadrina pachyderma globigerina umbilicata and globigerinita glutinata in the bering sea and central subarctic pacific with a focus on their responses to environmental changes foraminiferal 18o followed the equilibrium equation for inorganic calcite with species specific equilibrium offsets ranging from nearly zero 0 02 for n pachyderma and 0 01 for g umbilicata to 0 16 g glutinata equilibrium offsets in our sediment trap samples were smaller than those from plankton tow studies implying that foraminiferal 18o was modified by encrustation during settling habitat calcification depths varied from 35 55 m n pachyderma and g umbilicata or 25 45 m g glutinata during warm stratified seasons to around 100 m during winter when the mixed layer depth increases unlike 18o foraminiferal 13c showed species specific responses to environmental changes we found a dependency of 13c in g umbilicata on co32 concentrations in ambient seawater that agreed reasonably well with published laboratory results suggesting that 13c of g umbilicata is subject to vital effects in contrast 13c of n pachyderma and g glutinata are likely affected by other species specific biological activities seasonal flux patterns reveal that fossil records of n pachyderma and g glutinata represent annual mean conditions whereas that of g umbilicata most likely indicates those of a specific season because none of these three taxa was abundant from december to february their fossil records likely do not reflect isotope signals from cold seasons

using species specific paleotemperature equations with foraminifera a case study in the southern california bight abstract species specific paleotemperature equations were used to reconstruct a record of temperature from foraminiferal 18 o values over the last 25 kyr in the southern california bight the equations yield similar temperatures for the 18 o values of globigerina bulloides and neogloboquadrina pachyderma in contrast applying a single paleotemperature equation to g bulloides and n pachyderma 18 o yields different temperatures which has been used to suggest that these species record the surface to thermocline temperature gradient in santa barbara basin an isotopically distinct morphotype of g bulloides dominates during glacial intervals and yields temperatures that appear too cold when using a paleotemperature equation calibrated for the morphotype common today when a more appropriate paleotemperature equation is used for glacial g bulloides we obtain more realistic glacial temperatures glacial interglacial temperature differences g i t calculated in the present study indicate significant cooling 8 10 c throughout the southern california bight during the last glacial maximum lgm the magnitude of glacial cooling varies from 8 c near the middle of the southern california bight tanner basin and san nicolas basin to 9 c in the north santa barbara basin and 9 5 10 c in the south velero basin and no name basin our temperature calculations agree well with previous estimates based on the modern analog technique in contrast studies using n pachyderma coiling ratios u k 37 indices and transfer functions estimate considerably warmer lgm temperatures and smaller g i t

characteristics of intermediate water flow in the benguela current as measured with rafos floats abstract seven floats not launched in rings crossed over the mid atlantic ridge in the benguela extension with a mean westward velocity of around 2 cm s between 22s and 35s two agulhas rings crossed over the mid atlantic ridge with a mean velocity of 5 7 cm s toward 285 this implies they translated at around 3 8 cm s through the background velocity field near 750 m the boundaries of the benguela current extension were clearly defined from the observations at 750 m the benguela extension was bounded on the south by 35s and the north by an eastward current located between 18s and 21s other recent float measurements suggest that this eastward current originates near the trindade ridge close to the western boundary and extends across most of the south atlantic limiting the benguela extension from flowing north of around 20s the westward transport of the benguela extension was estimated to be 15 sv by integrating the mean westward velocities from 22s to 35s and multiplying by the 500 m estimated thickness of intermediate water roughly 1 5 sv of this are transported by the 3 agulhas rings that cross the mid atlantic ridge each year as observed with altimetry this value of the benguela extension transport is the first one to have been obtained from long term two year observations and across the full width of the benguela extension

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

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

subduction of a surface vortex under an outcropping front the possibility for a preexisting surface intensified anticyclone to subduct beneath a surface front is investigated using an isopycnal numerical model subduction occurs for strong coherent vortices and is usually accompanied by strong dissipation two main mechanisms cause the erosion of the vortex core the first one is induced by the velocity shear associated with the front it results in the peeling of the vortex potential vorticity pv core sometimes leading to its complete disappearance the second mechanism occurs after the vortex has subducted entrainment of high positive pv fluid parcels from the front above the vortex low negative pv core modifies the stability properties of the latter meanders are observed to grow at the rim of the structure which favors the formation of pv filaments the erosion rates caused by each mechanism are discussed in relation to the jet and vortex characteristics and to the background stratification the trapping of high pv fluid parcels above the vortex is also shown to be partly responsible for the decrease and eventual loss of the eddy altimetric signal after it has subducted

does carbon 13 track anthropogenic co2 in the southern ocean a multiparametric linear regression technique was used for waters in the southern ocean to estimate the change in both 13 c dic 13 c dic and dissolved inorganic carbon dic dic between 1978 and 1998 due to the accumulation of anthropogenic co 2 the observed decrease in 13 c dic at the surface the suess effect was 0 015 0 003 yr 1 in the sub antarctic zone and 0 005 0 003 yr 1 in the antarctic zone similar to values reported for the southern indian ocean gruber et al 1999 sonnerup et al 2000 to compare the 13 c dic with adic we used the ratio of these two anomalies rc 13 c dic dic mol kg 1 1 along the section arc ranged from 0 015 0 005 at 42 s to 0 007 0 005 mol kg 1 1 at 54 s the spatial variability in arc in the southern ocean reflects different timescales for processes controlling the uptake of 13 c from those controlling the uptake of 12 c and indicates that 13 c dic decouples from adic poleward of the sub antarctic zone the variations of arc along the section suggest that the 13 c dic anomaly is not a good predictor of the anthropogenic co 2 inventory in the southern ocean some methods for determining anthropogenic co 2 uptake both on the global and regional scale assume the penetration depths of 13 c dic to be the same as adic which implies a constant value for arc in the ocean at 0 016 mol kg 1 1 heimann and maier reimer 1996 ortiz et al 2000 bauch et al 2000 the use of a constant arc and the observed 13 c dic to estimate anthropogenic co 2 could lead to an underestimate in the inventory of anthropogenic co 2 for the southern ocean by 50

agulhas eddies a synoptic view using geosat erm data abstract warm core rings formed in the agulhas retroflection transfer water from the indian ocean to the south atlantic in an attempt to measure the strength of this exchange a combination of satellite altimeter and hydrographic data are used to examine agulhas eddy paths and decay rates in the south atlantic because the surface dynamic height of a warm core eddy is higher than surrounding waters the rings are visible in satellite altimeter measurements over 20 agulhas eddies have been tracked from maps of anomalous sea surface height ssh derived from the geosat exact repeat mission erm dataset the correlation r2 of dynamic height referenced to 2000 dbar and anomaly ssh for one coincidentally sampled area is 97 within an agulhas eddy dropping to a fraction of that outside of it indicating that the ssh anomaly signal is a reliable measure for strong features like agulhas eddies the sizes and distribution of the agulhas eddies in the erm record compare favorably with those in recent hydrogr

the influence of air and sea exchange on the carbon isotope distribution in the sea we explore here the influence of the temperature dependence of isotope fractionation between atmospheric co2and ocean co2 on the distribution of carbon isotopes in the ocean this is accomplished by an analysis of departures from the expected redfield tie between po4 and 13c we find that for the surface ocean the temperature influence largely compensates for the biologic influence in the deep ocean the temperature influence imprinted at the sites of deepwater formation reduces somewhat the biologically induced difference between the carbon isotope ratios for deep waters produced in the northern atlantic and in the antarctic these same features are reproduced in the hamburg ocean model in order to assess the impact of changes in the ratio of ocean mixing rate to wind speed we have made a model run in which co2 exchange rates between air and sea were everywhere doubled as expected the influence of the thermodynamic effect on the oceanic carbon isotope distribution is magnified

tropical instability vortices in the atlantic ocean 1 this paper examines the physical characteristics and dynamics of atlantic tropical instability vortices based on observational data from 1997 to 2000 and a high resolution numerical model simulation most prominent during boreal summer the vortices are characterized by 400 km spatial scales westward translation at 0 40 cm s 1 anticyclonic circumferential velocities of 30 110 cm s 1 and sstanomalies that decrease from 2 ci n midbasin to 0 5 c or less near the western boundary in contrast the sea level anomalies grow as the vortices progress westward reaching maximum amplitudes of 14 cm near 40 w the large circumferential velocities leading to relative vorticities of 4 10 6 s 1 and rossby numbers of 0 5 indicate that centrifugal effects may play an important role in the vortices vorticity balance we address the vortices vertical structure and vorticity dynamics by examination of a high resolution numerical model there is a reasonably good agreement between the model and observations simulated vortices are confined mostly to the mixed layer which increases westward in depth from 30 to 100 m near the western boundary in the eastern basin potential vorticity within the vortices is not conserved but decreases because of wind stress forcing in contrast in the western basin decreases in potential vorticity are due mostly to the vortices acquisition of southern hemisphere water we estimate an annualized cross equatorial transport of up to 1 2 sv associated with the vortices which is eventually contributed to the north brazil current system index terms 4231 oceanography general equatorial oceanography 4520 oceanography physical eddies and mesoscale processes 4528 oceanography physical fronts and jets keywords tropics instability atlantic

rings in the ocean certain robust long lived eddy features in t he world s ocean have come to be k nown as rings the nomenclature stems from fuglister 1 1972 who c oined t he name based on the c ircle or ring of gulf stream waters t hat surrounded a class of eddies formed from t he g ulf stream through the pinch off of meanders here it s uffices to define rings as intense eddies or vortices that represent a wrapped up piece of a major ocean c urrent they t ranslate over space scales of hundreds to thousands of k ilometers and exist for periods lasting from months to years rings move t hrough the ocean carrying anomalies s imilar to the contrasts in physical biological and chemical properties observed across the major ocean c urrents while the term ring is t ied to fuglister t he existence ofthese features was evident at least as early as t he 1930s when iselin 2 1936 1940 encountered strong cold anomalies in the region south of the gulf stream that we would identify as c old corc cyclonic rings today iselin fully rec ognized these features as part of the highly time dependent eddy motion in the ocean later iselin fuglister 1948 were the first to survey what is now k nown as a warm core anticyc lonic ring there are tw o types of rings cold core rings are made up of w aters from the poleward s ide of c urrents like the gulf stream that are introduced to

ferric iron in catio3 perovskite as an oxygen barometer for kimberlite magmas ii applications we apply an oxygen barometer based on the fe content of catio3 perovskite to estimate the oxygen fugacity fo2 during the crystallization and emplacement of kimberlites in different eruptive phases of a single pipe or between different pipes clusters or provinces mineral chemical data for perovskite were compiled from the literature and obtained in our detailed study of perovskites from 11 kimberlites at somerset island and lac de gras canada perovskite compositions in kimberlites record a range in fo2 of many orders of magnitude from nno 5 to nno 6 where log fo2 is given relative to the nickel nickel oxide nno buffer the range of fo2 recorded by different parageneses of perovskite within a single pipe can vary up to three orders of magnitude with trends toward both oxidation and reduction during crystallization kimberlites record some of the greatest ranges and the highest known fo2 conditions for any terrestrial magma this is attributed to the presence of deep and oxidized source regions and the variable interplay of ferric ferrous vs carbon fluid equilibria during ascent of kimberlite magmas three kimberlite pipes from the lac de gras field show that higher fo2 values correlate with higher proportions of more resorbed diamonds suggesting that this variable has a measurable effect on the physical properties of diamonds in a pipe

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

carbon isotopic disequilibrium between seawater and air in the coastal northern south china sea over the past century six coastal sediment cores collected from the northern south china sea were dated by 210 pb and analyzed for stable carbon and oxygen isotope composition of planktonic foraminifer globigerinoides ruber d 13 cgr and d 18 ogr three of these cores were located east of hainan island and the other three off the pearl river estuary pre surface seawater d 18 o and dissolved inorganic carbon dic d 13 c were identified as the dominant factors controlling downcore variations of d 18 ogr and d 13 cgr respectively results of d 13 cgr were then used to study surface water d 13 cdic and its relation to d 13 c of atmospheric co2 d 13 catm over the past century downcore records showed rather constant d 13 cgr in cores off hainan island but moderate decreases of d 13 cgr at rates between 0 006 and 0 009 per year in cores off the pre isotopic disequilibrium between d 13 cdic and d 13 catm was observed with d 13 cdic apparently higher than expected at equilibrium with d 13 catm except at the site closest to the pre the relatively steady d 13 cgr values east of hainan island were explained by balanced vertical mixing and biological pump whereas the moderate d 13 cgr decreases with time off the pre were attributable to fluvial input of

crustal reworking at convergent margins traced by fe isotopes in i type intrusions from the gangdese arc tibetan plateau abstract voluminous magmatism at active continental margins and collision zones is marked by i type intrusions paleocene eocene intrusions exposed in the lhasa terrane of the tibetan plateau are part of the gangdese arc that operated during neo tethyan ocean subduction and subsequent india asia collision arc like geochemical trace element signatures and radiogenic isotope systematics are indicative of juvenile i type magmatism with variable silica contents consequent to igneous differentiation here we present the first fe isotope data for this fossil arc terrane which have highly variable 57fe values relative to irmm 014 of 0 05 to 0 57 the data show no obvious correlations with major and trace element systematics except for highly evolved rocks with 70 wt sio2 based on trace element systematics deuteric fluid exsolution is excluded as a cause for the isotope variations in less evolved rocks furthermore there is no apparent relation between fe isotope values and the established tectonic evolution from syn to post collisional magmatism comparison with i type granites of the australian lachlan fold belt and cordilleran snake river plain reveals an on average lighter 57fe in the gangdese suite in primitive lavas yet distinctively heavier than intra oceanic arcs the heavier 57fe values for primitive lachlan fold belt and snake river plain rocks are interpreted here as crustal contribution in the form of s type magmas derived from crustal anatexis which are absent in the gangdese arc gangdese belt data yield an average 57fe of 0 13 0 02 2 which is proposed as the best estimate for juvenile crust at active continental margins rhyolite melts modelling suggests that the gangdese belt data can be reproduced through fractional crystallization along a liquid line of descent at oxygen fugacity between fmq 0 to 2 typical for arc related melts crucially the majority of data is coherent with partial melts of existing mafic crust as the major contributor to the juvenile component in the intrusions with minor mantle derived melts evidenced through heavier primitive fe isotopes this indicates that for the gangdese belt samples the primitive parental melts are derived from lower crustal successions through predominantly crustal reworking with only subordinate crustal growth hence the fe isotope data indicates a two step evolution with melting of underplated mafic material sometime in the geologic past although juvenile in nature these successions are part of the existing crust supporting scenarios in which crustal reworking in convergent margin intrusions is an important process in evolved magma generation

observations of mesoscale eddies in the south atlantic cape basin baroclinic and deep barotropic eddy variability 1 anticyclones and cyclones in the eastern south atlantic are characterized based on data collected during january 2003 to march 2005 along a jason 1 satellite altimeter ground track as part of the agulhas south atlantic thermohaline transport experiment large and small cyclones and anticyclones were ubiquitous in the deep ocean of the eastern south atlantic as well as in the upper ocean eddy structures jointly corotating in the upper and deep water column were common most of the time 94 these were not axially aligned as they copropagated the agulhas rings and cyclones that populate the region generally carry both a steric component baroclinic and a mass loading component deep barotropic structure average translation speeds were 7 5 cm s 1 for baroclinic eddies and twice as fast for barotropic eddies irrespective of polarity translation speeds were higher than advection by the mean background flow field in addition large mixed baroclinic barotropic rings crashed into the agulhas ridge and nearby seamounts and split into two or more parts some ring parts were also observed to fuse together deep cyclones as well as interactions with topography were observed to play a role in the fission process of agulhas rings these processes can increase the population of agulhas rings and their remnant eddies which took three pathways from the agulhas and into the cape basin 1 a deep pathway between the continental slope and erica seamount 2 a shallower pathway over or near the agulhas ridge and schmitt otto seamount and 3 a deep seaward pathway around the agulhas ridge

seasonal nutrient depletion and carbon export in the subantarctic and polar frontal zones of the southern ocean south of australia seasonal surface water nitrate and phosphate depletions were calculated for the subantarctic zone saz and polar frontal zone pfz of the southern ocean along the world ocean circulation experiment sr3 repeat section south of tasmania australia and three other transects slightly to the west the depletions were calculated between a single winter july section and eight other sections from october to march in the years 1991 1998 and corrected for frontal movements and changes in water masses between the cruises using observed quasi linear nutrient salinity relationships arranged in a seasonal progression depletion began in approximately october and continued through march in good agreement with satellite biomass based estimates of production nitrate depletion in the saz 510 mmol n m 2 was approximately twice that of the pfz 250 mmol n m 2 but phosphate depletions were similar 29 and 24 mmol p m 2 for the saz and pfz respectively the saz exhibited a redfield n p depletion ratio 15 1 2 3 but the pfz ratio was much lower 8 3 5 4 while the saz exhibits greater seasonal nutrient depletion the relative magnitudes of export in the two zones remain uncertain because supply of nutrients from south of the polar front may lower the observed nutrient depletions in the pfz however comparisons with sediment trap and production measurements for the region south of australia suggest the saz and pfz differences derive from differences in production assuming a redfield c n ratio 6 6 carbon export for the longest period examined july march averaged 3400 430 mmol c m 2 in the saz with a range between 2700 and 3900 mmol c m 2 depending on latitude in the pfz carbon export averaged 1600 350 mmol c m 2 with a range of 1100 to 2000 mmol c m 2 these averages represent minimum annual export production estimates because neither resupply nor export outside the july march observational period is included

the coalescence of two east australian current warm core eddies two warm core eddies coalesced in about 20 days as their centers rotated around a point on the contracting line that joined them in the process of forming the new eddy the subsurface isothermal isohaline signature layer of one eddy was uplifted and somewhat depleted while that of the other was depressed

particle fluxes to the interior of the southern ocean in the western pacific sector along 170 w abstract an array of five bottom tethered moorings with 19 parflux time series sediment trap at three depths 1 and 2 km below the surface and 0 7 km above the sea floor was deployed in the western pacific sector of the southern ocean along 170 w the five stations were selected to sample settling particles in the main hydrological zones of the southern ocean the sampling period spanned 425 days november 28 1996 january 23 1998 and was divided into 13 or 21 synchronized time intervals a total of 174 sequential samples were recovered and analyzed to estimate fluxes of total mass tmf organic carbon carbonate biogenic silica and lithogenic particles the fluxes of biogenic material were higher than anticipated challenging the notion that the southern ocean is a low productivity region organic carbon fluxes at 1 km depth within the polar frontal zone and the antarctic zone were relatively uniform 1 7 2 3 g m 2 yr 1 and about twice the estimated ocean wide average ca 1 g m 2 yr 1 carbonate fluxes were also high and uniform between the subantarctic front and ca 64 s 11 13 g m 2 yr 1 a large fraction of the carbonate flux in the antarctic zone was due to the presence of pteropod shells coccoliths were found only to the north of the polar front and calcium carbonate became the dominant phase in the subantarctic zone in contrast carbonate particles were nearly absent near 64 s latitudinal variations in biogenic silica fluxes were substantial the large opal flux 57 g m 2 yr 1 measured in the antarctic zone suggests that opal productivity in this region has been previously underestimated and helps to explain the high sedimentary opal accumulation often found south of the polar front unlike biogenic material fluxes of lithogenic particles were among the lowest measured in the open ocean 0 12 0 05 g m 2 yr 1 reflecting a very low dust input

planktonic foraminiferal fluxes in the santa barbara basin response to seasonal and interannual hydrographic changes results of a three year time series sediment trap experiment in the santa barbara basin indicate linkages between water column dynamics and variations in plankton fluxes on both seasonal and interannual time scales the two week collection interval utilized for this study allows evaluation of high frequency changes in the production and flux of planktonic foraminifera which are compared to those of siliceous microorganisms diatoms radiolaria and silicoflagellates annual hydrographic conditions in santa barbara basin are influenced by seasonal changes in insolation the wind field and source waters this study includes periods of weak to moderate el nino conditions followed by a transitional period to a non el nino state planktonic foraminiferal fluxes and species turnover are related to seasonal and interannual changes in source waters and water column conditions globigerina bulloides g quinqueloba and neogloboquadrina pachyderma dextral dominate the planktonic foraminiferal population in this location and are present throughout the year globigerina bulloides and g quinqueloba have similar flux patterns and highest fluxes occur in association with diatom blooms the flux patterns of g bulloides and g quinqueloba in general are inversely related to that of n pachyderma dextral globigerina quinqueloba seems to respond earlier to the onset of upwelling than g bulloides three temperature limited species neogloboquadrina dutertrei orbulina universa and globigerinoides ruber are present in lower numbers and show more restricted seasonal ranges in the thermal regime of the santa barbara basin n dutertrei like o universa disappears during upwelling neogloboquadrina dutertrei occurs in highest abundance when the water column is thermally stratified and there is a well developed deep chlorophyll maximum increased fluxes of globigerinoi ruber the most thermally restricted of the dominant species in the basin are associated with the presence of warm oceanic diatoms and warm water radiolarians total planktonic foraminiferal fluxes were lower in 1995 than during the previous two years which were characterized by el nino conditions

late quaternary palaeoceanography of the circumpolar deep water from the south tasman rise we use sediment cores from the south tasman rise str to reconstruct deepwater circulation in the southwest pacific sector of the southern ocean sediment cores md972106 45 09 s 146 17 e 3310 m water depth and gc34 45 06 s 147 45 e 4002 m water depth preserve records covering the last 160 k yr with chronology controlled by calibrated accelerator mass spectrometry radiocarbon dates and benthic foraminiferal 18o tied to specmap the stir benthic foraminiferal 13c records provide new 13c values for southern ocean deep water spanning the last 160 kyr at sites unlikely to be affected by variations in productivity the records establish that glacial benthic foraminifera cibicidoides spp 13c values are lower relative to interglacial values and are comparable to previous glacial benthic 13c records in the indian and pacific sectors of the southern ocean comparisons of the benthic foraminiferal 13c time series at the str are made with the equatorial pacific v19 30 and site 846 and the equatorial atlantic geob1115 the similarity of benthic 13c records at the str to the equatorial pacific suggest the southern ocean deep water mass closely tracked those of the deep pacific and the presence of a 13c gradient between the str and the equatorial atlantic suggests there was continual production of northern source deep water over the past 160 k yr

planktonic foraminiferal δ13c records from southern ocean sediment traps new estimates of the oceanic suess effect the carbon isotopic composition is measured for three species of planktonic foraminifera globigerina bulloides globorotalia inflata and neogloboquadrina pachyderma s from southern ocean sediment traps the sediment traps represent the annual flux of foraminifera in subtropical to polar frontal environments from the western pacific southern australia sector comparison between the seasonal 13c composition of the foraminifera and estimated 13c of dissolved inorganic carbon dic allows disequilibrium effects to be determined disequilibrium exhibits a latitudinal trend with greatest offsets from equilibrium at lower latitudes this effect causes a north to south increase in foraminiferal 13c while the 13cdic displays a decrease across these latitudes disequilibrium in g bulloides can be accounted for by changes in temperature the relationship between disequilibrium and temperature which we derive in this field study is consistent with the laboratory relationship of bemis et al 2000 corrected 13c for g bulloides is closely correlated to seasonal changes in nutrients at each site indicating the utility of g bulloides 13c as a nutrient tracer in southern ocean environments comparison between flux weighted sediment trap values and nearby core tops indicates a modern depletion in 13c which we attribute to the oceanic suess effect the imprint of this effect on the foraminiferal isotopes provides further evidence for the equilibration between surface waters and the atmosphere in the subantarctic zone

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

planktic foraminiferal and sea surface temperature record during the last 1 myr across the subtropical front southwest pacific planktic foraminiferal faunas and modern analogue technique estimates of sea surface temperature sst for the last 1 million years myr are compared between core sites to the north odp 1125 178 faunas and south dsdp 594 374 faunas of the present location of the subtropical front stf east of new zealand faunas beneath cool subtropical water stw north of the stf are dominated by dextral neogloboquadrina pachyderma globorotalia inflata and globigerina bulloides whereas faunas to the south are strongly dominated by sinistral n pachyderma 80 95 in glacials with increased g bulloides 20 50 and dextral n pachyderma 15 50 in interglacials beneath subantarctic water or saw canonical correspondence analysis indicates that at both sites sst and related factors were the most important environmental influences on faunal composition greater climate related faunal fluctuations occur in the south significant faunal changes occur through time at both sites particularly towards the end of the mid pleistocene climate transition mis18 15 e g decline of globorotalia crassula in stw disappearance of globorotalia puncticulata in saw and during mis8 5 interglacial sst estimates in the north are similar to the present day throughout the last 1 myr to the south interglacial ssts are more variable with peaks 4 7 c cooler than present through much of the early and middle pleistocene but in mis11 mis5 5 and early mis1 peaks are estimated to have been 2 4 c warmer than present these high temperatures are attributed to southward spread of the stf across the submarine chatham rise along which the stf appears to have been dynamically positioned throughout most of the last 1 myr for much of the last 1 myr glacial sst estimates in the north were only 1 2 c cooler than the present interglacial except in mis16 mis8 mis6 and mis4 2 when estimates are 4 7 c cooler these cooler temperatures are attributed to jetting of saw through the mernoo saddle across the chatham rise and or waning of the stw current to the south glacial sst estimates were consistently 10 11 c cooler than present similar to temperatures and faunas currently found in the vicinity of the polar front one interpretation is that these cold temperatures reflect thermocline changes and increased circumpolar surface water spinning off the subantarctic front as an enhanced bounty gyre along the south side of the chatham rise for most of the last 1 myr the temperature gradient across the stf has been considerably greater than the present 4 c during glacial episodes the stf in this region did not migrate northwards but instead there was an intensification of the temperature gradient across it interglacials 4 11 c glacials 8 14 c

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

valence state partitioning of vanadium between olivine liquid estimates of the oxygen fugacity of y980459 and application to other olivine phyric martian basalts the valence state of vanadium v2 v3 v4 and v5 is highly sensitive to variations in redox conditions of basaltic magmas differences in valence state will influence its partitioning behavior between minerals and basaltic liquid using partitioning behavior of v between olivine and basaltic liquid precisely calibrated for martian basalts we determined the oxidation state of a primitive olivine rich high mg no martian basalt y980459 near its liquidus the behavior of v in the olivine from other martian olivine phyric basalts sau005 dag476 and nwa1110 was documented the combination of oxidation state and incompatible element characteristics determined from early olivine indicates that correlations among geochemical characteristics such as f o2 lree hree initial 87sr 86sr and initial end observed in many martian basalts is also a fundamental characteristic of these primitive magmas these observations are interpreted as indicating that the mantle sources for these magmas have a limited variation in f o2 from iw to iw 1 and are incompatible element depleted moreover these mantle derived magmas assimilated a more oxidizing iw 3 incompatible element enriched lower crustal component as they ponded at the base of the martian crust

isotopic composition and morphology of living globorotalia scitula a new proxy of sub intermediate ocean carbonate chemistry abundance isotopic composition and morphological imprints of the planktonic foraminifera globorotalia scitula brady were closely examined for possible use as a novel reconstruction tool of chemical environments in sub intermediate depth seawater in the past based on the mocnes plankton tow observation of dwelling depths of g scitula and the isotopic compositions together with hydrochemistry data the empirical relations between isotopic disequilibria in carbon 13c 13cg scitula 13cdic and oxygen 18o 18og scitula 18ow isotopes in the carbonate tests and the seawater 18o and 13c of dissolved inorganic carbon dic respectively are introduced the morphological information such as pore density and porosity is also examined for significant relations to carbonate chemistry shell porosity is strongly correlated saturation state of calcite the dissolution of living g scitula tests may promote the observed isotopic differences as well as the increases in porosity 18o of g scitula is found effectively to be linear function of both water temperature and calcite saturation state and thereby temperature equation for g scitula is provided while 13c of g scitula is a linear function of only calcite saturation state the equation was validated by using globorotalia scitula collected by a sediment trap in intermediate water depths satisfactory agreements were found between observed and calculated 18o from the empirical equations based on temperature and hydrochemistry data at sediment trap deployment site indicating that the equation may be useful in paleo environmental reconstruction of sub intermediate water the sediment trap observation further suggests that the abundance of g scitula does not necessarily correspond to surface water productivity and to poc flux but instead it correlates well with the supply of fine organic matter which appears to be a result of water convection thus g scitula may be an unambiguous and excellent paleo environmental recorder for carbonate chemistry and for fine organic matter transport to the depths if isotopic and morphological observations are combined