nebular and asteroidal modification of the iron isotope composition of chondritic components abstract the fe isotope signatures 56feirmm and 57feirmm of twelve chondrules three ca al rich inclusions cais and multiple matrix aliquots from two type 3 chondrites allende cv3 and chainpur ll3 were measured by mc icp ms the mass fractionation line for these samples is 57feirmm 1 45 0 05 56feirmm 0 01 0 02 with r2 0 9995 two processes appear to affect the fe isotope composition of these chondritic components initially short lived high temperature events within the solar nebula drove isotopic signatures towards isotopically heavier compositions subsequently metasomatism shifted isotopic signatures of chondrules and cais towards bulk like compositions the fe isotope composition of allende matrix 56feirmm 0 07 0 02 n 6 is similar to that of bulk allende 56feirmm 0 05 0 05 the range of chainpur matrix compositions is 0 03 56feirmm 0 02 this relatively homogeneous matrix composition appears to be governed by metasomatic exchange of iron although the possibility that matrix is heterogeneous on a scale smaller than the sample size cannot be ruled out cais from allende in which iron has been metasomatically introduced from the matrix are mainly unfractionated with respect to the bulk composition of allende the least altered cai which contains minor bulk feo 0 4 wt is isotopically lighter 56feirmm 0 16 with respect to bulk allende this signature may reflect condensation of isotopically light iron in the nebula or preferential incorporation of the lighter iron isotopes contained within the matrix chondrule fe isotope compositions 1 33 56feirmm 0 65 are driven by both high temperature nebular events and subsequent metasomatic exchange the relationship between compositional and isotopic signatures clearly points to an evaporation origin for type i chondrules which are isotopically heavier than type ii chondrules subsequent metasomatic exchange with matrix iron has driven some chondrules most notably the smaller chondrules towards a bulk like fe isotopic signature

isotopic fractionation of cu in tektites tektites are terrestrial natural glasses of up to a few centimeters in size that were produced during hypervelocity impacts on the earth s surface it is well established that the chemical and isotopic composition of tektites is generally identical to that of the upper terrestrial continental crust tektites typically have very low water content which has generally been explained by volatilization at high temperature however the exact mechanism is still debated because volatilization can fractionate isotopes comparing the isotopic composition of volatile elements in tektites with those of their source rocks may help to understand the physical conditions during tektite formation interestingly volatile chalcophile elements e g cd and zn seem to be the only elements for which isotopic fractionation is known so far in tektites here we extend this study to cu another volatile chalcophile element we have measured the cu isotopic composition for 20 tektite samples from the four known different strewn fields all of the tektites except the muong nong types are enriched in the heavy isotopes of cu 1 98 delta 61 cu 6 99 in comparison to the terrestrial crust delta 65 cu approximate to 0 with no clear distinction between the different groups the muong nong type tektites and a libyan desert glass sample are not fractionated delta 65 cu approximate to 0 in comparison to the terrestrial crust to refine the cu isotopic composition of the terrestrial crust we also present data for three geological reference materials delta 65 cu approximate to 0 an increase of delta 65 cu with decreasing cu abundance probably reflects that the isotopic fractionation occurred by evaporation during heating a simple rayleigh distillation cannot explain the cu isotopic data and we suggest that the isotopic fractionation is governed by a diffusion limited regime copper is isotopically more fractionated than the more volatile element zn delta 66 64 zn up to 2 49 parts per thousand this difference of behavior between cu and zn is predicted in a diffusion limited regime where the magnitude of the isotopic fractionation is regulated by the competition between the evaporative flux and the diffusive flux at the diffusion boundary layer due to the difference of ionic charge in silicates zn 2 vs cu cu has a diffusion coefficient that is larger than that of zn by at least two orders of magnitude therefore the larger isotopic fractionation in cu than in zn in tektites is due to the significant difference in their respective chemical diffusivity c 2009 elsevier ltd all rights reserved

comparative stable isotope geochemistry of ni cu zn and fe in chondrites and iron meteorites high precision ni isotopic variations are reported for the metal phase of equilibrated and unequilibrated ordinary chondrites carbonaceous chondrites iron meteorites mesosiderites and pallasites we also report new zn and cu isotopic data for some of these samples and combine them with literature fe cu and zn isotope data to constrain the fractionation history of metals during nebular vapor solid and planetary metal sulfide silicate phase changes the observed variations of the 62ni 58ni 61ni 58ni and 60ni 58ni ratios vary linearly with mass difference and define isotope fractionation lines in common with terrestrial samples this implies that ni was derived from a single homogeneous reservoir while no 60ni anomaly is detected within the analytical uncertainties ni isotopic fractionation up to 0 45 per mass difference unit is observed the isotope compositions of ni and zn in chondrites are positively correlated we suggest that in ordinary chondrites exchange between solid phases in particular metal and silicates and vapor followed by mineral sorting during accretion are the main processes controlling these isotopic variations the positive correlation between ni and zn isotope compositions contrasts with a negative correlation between ni and zn and cu isotope compositions which when taken together do not favor a simple kinetic interpretation the observed transition element similarities between different groups of chondrites and iron meteorites are consistent with the genetic relationships inferred from oxygen isotopes iiia pallasites and iva l chondrites copper is an exception which we suggest may be related to separate processing of sulfides either in the vapor or during core formation

implications for post comminution processes in subglacial suspended sediment using coupled radiogenic strontium and neodymium isotopes abstract enhanced physical weathering rates in subglacial systems promote high levels of comminution transport and deposition of fine grained sediment within the subglacial drainage network the impact of shifts in sediment loads from variations in meltwater flux and their effects on downstream ecosystems remains poorly quantified and places a fundamental importance on our ability to characterize subglacial depositional environments here for the first time we assess the seasonal evolution of the subglacial suspended sediment using coupled radiogenic strontium 87 sr 86 sr and neodymium 143 nd 144 nd isotopic ratios with elemental ratios and in situ measurements weathering rates in fluvial and riverine systems have been traditionally assessed using radiogenic isotopic tracers 143 nd 144 nd ratios relate to the crustal age whereas 87 sr 86 sr ratios relate to age and preferential mineral dissolution thus relative shifts in these ratios will allow us to characterize distinct sediment transport networks we apply this technique to the lemon creek glacier lcg alaska usa and to the athabasca glacier ag alberta ca at the lcg the 143 nd 144 nd values range from e nd of 4 6 0 9 to 8 7 0 2 which suggests a poorly mixed sediment flux however the greatest period of variability may correlate with the drainage of a supraglacial lake and suggests caution should be exerted in time scale 143 nd 144 nd provenance studies that may be affected by climatic disturbances in contrast limited variation is observed within the ag 143 nd 144 nd seasonal record a consistent direct relation between the rb sr elemental ratio and the 87 sr 86 sr ratio proves interesting as it enables us to unravel incongruent weathering trends in the radiogenic sr record correlation between the 87 sr 86 sr and total discharge suggests that the process is partially controlled by mantling of the bedrock which can be detected using post comminution ages while the subglacial structure may be enabled by the subglacial till beneath the ag our study supports the use of sr nd as a new proxy in the subglacial environment

iron isotope differences between earth moon mars and vesta as possible records of contrasted accretion mechanisms the iron isotope compositions of shergotty nakhla chassigny snc meteorites thought to come from mars eucrites and diogenites assumed to sample asteroid 4 vesta and rocks from the moon and earth have been measured using high precision plasma source mass spectrometry the means of eight samples from mars and nine samples from vesta are within error identical despite a range of rock types they are lighter by 0 1 in 57fe 54fe compared to the average of 13 terrestrial mantle derived rocks the latter value is identical within uncertainty with a previously published mean of 46 igneous rocks from the earth the average for 14 lunar basalts and highland plutonic rocks covering a broad spectrum of major element composition is heavier by 0 1 in 57fe 54fe relative to our estimate for the earth s mantle and therefore 0 2 heavier than the eucrites diogenites and snc meteorites however the data scatter somewhat and the apollo 15 green glass and apollo 17 orange glass are identical to samples from mars and vesta there is no clear relationship between petrological characteristics and fe isotope composition despite a wide spectrum of samples instead contrasted planetary isotopic signatures are clearly resolved statistically after evaluating alternative scenario it appears that the most plausible explanation for the heavier fe in the earth and moon is that both objects grew via processes that involved partial vaporisation leading to kinetic iron isotope fractionation followed by minor loss this is consistent with the theory in which the moon is thought to have originated from a giant impact between the proto earth and another planet combined with numerical simulations fe isotope data can offer the potential to provide constraints on the processes that occurred in planetary accretion

an fe isotope study of ordinary chondrites the fe isotope composition of ordinary chondrites and their constituent chondrules metal and sulphide grains have been systematically investigated bulk chondrites fall within a restricted isotopic range of 1 0 84 to 0 21 relative to the irmm 14 fe standard fe isotope compositions do not vary systematically with the very large differences in total fe concentration or oxidation state of the h l and ll chondrite classes similarly the fe isotope compositions of chondrules do not appear to be determined by the h l or ll classification of their host chondrite this may support an origin of the three ordinary chondrite groups from variable accretion of identical fe bearing precursors a close relationship between isotopic composition and redistribution of fe during metamorphism on ordinary chondrite parent bodies was identified the largest variations in chondrule compositions were found in chondrites of the lowest petrologic types the clear link between element redistribution and isotopic composition has implications for many other non traditional isotope systems e g mg si ca cr isotopic compositions of chondrules may also be determined by their melting history porphyritic chondrules exhibit a wide range in isotope compositions whereas barred olivine and radial pyroxene chondrules are generally isotopically heavier than the ordinary chondrite mean very large chondrules preserve the greatest heterogeneity of fe isotopes the mean fe isotope composition of bulk ordinary chondrites was found to be 0 06 0 12 2 sd this is isotopically lighter than the terrestrial mean composition and all other published non chondritic meteorite suites e g lunar and martian samples eucrites pallasites and irons ordinary chondrites though the most common meteorites found on earth today were not the sole building blocks of the terrestrial planets

the isotopic composition of magnesium in mantle olivine records of depletion and metasomatism we have investigated detailed mg isotopic variations in the lithospheric mantle by analysing olivine in mantle derived peridotite xenoliths and megacrysts high precision in situ analyses of mg 26 mg 24 and mg 25 m 24 g are made using a laser ablation microprobe and mc icpms measurements are done using a standard sample bracketing technique with an in house olivine standard replicate analyses of this standard give a precision of 0 20 parts per thousand 2sd for delta mg 26 mg 26 mg 24 sample mg 26 mg 24 standard 1 x 1000 and 0 12 parts per thousand 2sd for delta mg 25 the analysed olivine grains represent the lithospheric mantle beneath archean cratons siberia kaapvaal slave and phanerozoic fold belts se australia results from olivines show significant heterogeneity in the lithospheric mantle delta mg 26 ranges from 3 01 parts per thousand to 1 03 parts per thousand and delta mg 25 from 1 59 parts per thousand to 0 51 parts per thousand relative to the magnesium isotopic standard dsm 3 there is a broad trend from lighter mg isotopic compositions in depleted xenoliths from archean mantle to heavier mg in the less depleted phanerozoic samples samples with petrographic evidence of refertilisation including modal metasomatism show large ranges in delta mg values within samples sheared peridotite xenoliths from the kaapvaal and slave cratons show a shift to higher delta mg associated with the introduction of fluids with an asthenospheric signature olivine in the least metasomatised peridotites from se australia has isotopically light mg whereas olivine in cryptically and modally metasomatised peridotites amphibole apatite bearing becomes progressively heavier both absolutely and relative to pyroxene and amphibole with increasing degrees of metasomatism the heterogeneity measured in individual samples suggests that mg isotopic fractionations produced by processes of mantle metasomatism are preserved on the intra grain scale and the magnitude of the observed fractionations indicates that diffusion related kinetic processes are important in controlling isotope fractionation at high temperatures the in situ measurement of mg isotopes provides a powerful new method for investigating processes in the mantle c 2005 elsevier b v all rights reserved

the causation and sensitivity of the northern winter planetary waves abstract we have made high resolution calculations of the wintertime stationary atmospheric response to planetary scale topographic and thermal forcings a numerical model has been used that solves the spherical primitive equations linearized about observed zonal wind and temperature fields the model s lid is placed high enough so that spurious reflections do not affect the results considerable attention has been paid to numerical accuracy the model s response to realistic forcing is in general agreement with observational analysis of van loon et al we find that in middle latitudes the response to topographic forcing strongly dominates the response to thermal forcing in the midlatitude troposphere the topographic response is insensitive to changes in the zonal wind the interannual variability of the tropospheric waves is due more to the heating response the 500 mb amplitude of the interannual variability due to the sum of both forcings is as indicated by our model and as measured at the himalaya

formation process of the kuroshio large meander in 2004 1 formation process of the 2004 kuroshio large meander has been examined using a data assimilation and prediction system the small meander southeast of kyushu that occurred in december 2003 remains stationary until the next spring the vorticity analysis indicates that this small meander is maintained by a balance between the advection and the bottom pressure torque on the continental slope this balance is achieved as a result of reducing the advection by a westward propagating negative temperature anomaly originating in the wind stress field the small meander starts moving eastward around may 2004 when an anticyclonic eddy east of the tokara strait is intensified by coalescing of two anticyclonic eddies at that time a deep anticyclonic eddy is generated below the kuroshio by a cross frontal flow the deep anticyclonic eddy grows up during its eastward propagation then a southward flow in the eastern part of the eddy carries the kuroshio path offshore bringing about the large meander the eddy energetic analysis indicates that baroclinic instability is essentially responsible for this large meander formation the sensitivity analysis reveals that the small meander and the intensified anticyclonic eddy significantly affect the phase speed and the amplitude of the meander respectively it is also revealed that a slow phase speed and a large amplitude of the meander are regarded as conditions for the stationary large meander which is also applicable to the past large meanders in the 2004 large meander these conditions coexist by the stationary small meander staying until the intensified anticyclonic eddy triggers baroclinic instability

evidence for stable sr isotope fractionation by silicate weathering in a small sedimentary watershed in southwestern taiwan abstract radiogenic sr isotopes 87 sr 86 sr are robust for provenance identification in hydrology affected mainly by the age of background lithologies and the degree of chemical weathering however there is limited knowledge concerning the fractionation mechanism of stable sr isotopes 88 sr 86 sr in rivers in this study river water was collected on a weekly to monthly basis throughout dry and wet seasons furthermore to study the variations of radiogenic and stable sr isotopes during intense weathering a major flooding event 2000 mm precipitation in three days typhoon morakot water was captured within a small drainage catchment system 161 km 2 along the hou ku river in southwestern taiwan for a better constraint on the end member compositions bedload sediments suspended particles and several host rocks were sampled for a systematic investigation the carbonate and silicate phases of these solids were chemically separated dissolved major elements indicate that the watersheds were predominated by silicate weathering stable sr isotopes show no significant variation 88 sr 0 24 0 31 temporally and spatially with an average of 0 28 additionally all solids showed lower 88 sr values than the river water while the host rocks had higher 88 sr values 88 sr 0 20 0 26 than the residual weathering products 88 sr 0 08 0 22 indicating preferential leaching of heavy sr into the hydrosphere and leaving light sr in the residual solids results of laboratory acid leaching experiments reveal that dissolution of high 88 sr value minerals occurred at an early stage of weathering the variation of weathering intensity does not alter stable sr isotopes in silicate weathering dominated river water which contains higher stable sr isotopes than the associated sediments the silicatic sedimentary rocks preferentially released higher stable sr isotopes into the hydrosphere during chemical weathering thus leaving lower stable sr isotopes in the residual solids

effects of large scale wind on the kuroshio path south of japan in a 60 year historical ogcm simulation the effects of large scale wind forcing on the bimodality of the kuroshio path south of japan the large meander lm and non large meander nlm were studied by using a historical simulation 1948 2007 with a high resolution ocean general circulation models ogcm the kuroshio in this simulation spent much time in the nlm state and reproduced several aspects of its long term path variability for the first time in historical ogcm simulation presumably because the eddy kinetic energy was kept at a moderate level by using the simulated fields the relationships between wind forcing or kuroshio transport and path variation proposed by past studies were tested and specific roles of eddies in those variations were investigated the long term variation of the simulated net kuroshio transport south of japan was largely explained by the linear baroclinic rossby wave adjustment to wind forcing in the simulated lm events a triggering meander originated from the interaction of a wind induced positive sea surface height ssh anomaly with the upstream kuroshio and was enlarged by cyclonic eddies from the recirculation gyre the cyclonic eddy of the trigger meander was followed by a sizable anticyclonic eddy on the upstream side subsequently a weak strong kuroshio favored the lm nlm the lm tended to be maintained when the kuroshio transport off southern japan was small and increasing kuroshio transport promoted decay of an existing lm the supply of disturbances from upstream which is related to the wind induced ssh variability at low latitudes contributed to the maintenance of an existing lm

equilibrium high temperature fe isotope fractionation between fayalite and magnetite an experimental calibration abstract the iron isotopic fractionation factor between magnetite and fayalite was measured at high temperature in a piston cylinder apparatus for the first time the three isotope method matsuhisa j goldsmith j r and clayton r n 1978 mechanisms of hydrothermal crystallisation of quartz at 250 c and 15 kbar geochim cosmochim acta 42 173 182 has been used to determine equilibrium fractionation between two minerals directly the experimentally determined temperature dependent iron isotope fractionation between fayalite and magnetite is described by 10 3 ln 57 mag fa 57 fe mag fa 0 30 0 024 10 6 t 2 the equation predicts measurable fractionation at magmatic temperatures our work bears on the magnitude of fe isotope fractionation attending differentiation in magmatic systems and provides a new isotope thermometer for co existing fayalite and magnetite

ensemble forecast of the kuroshio meandering 1 focusing on predictability of the kuroshio meandering we have done an ensemble forecast experiment the application of the method to the problem addressed seems to be the first comprehensive attempt in the community of physical oceanography by assimilating sea surface height anomaly into an ocean general circulation model in the preceding 40 day period the observed kuroshio meandering manifested south of japan in november 1999 was successfully predicted 2 months before the event the experiment yields a forecasting skill of the kuroshio meander position for 60 days in the sense that the rms error does not exceed the magnitude of the model climatic variation and those obtained from the non assimilated simulation and persistence in addition to a single trajectory forecast experiment ensemble forecasts were conducted using 10 perturbed initial states generated by the breeding method the predicted states realized as the ensemble members of the 80 day forecast are classified into two categories large and non large meander it is found that the intensity of an anticyclonic eddy in the initial state seems to play a key role in selecting one of the two states

tropospheric response to stratospheric sudden warmings in a simple global circulation model abstract a composite analysis is made of 132 stratospheric sudden warming ssw events obtained in a 10 000 day integration with a simple global circulation model under a perpetual winter condition the analysis confirms general features of the ssws such as enhanced upward propagation of planetary wave activity from the troposphere to the stratosphere before the ssws and downward propagation of warming signals to the lower stratosphere after the events a further dynamical diagnosis shows that the tropospheric circulation is quite different between pre ssw and post ssw periods in terms of the zonal mean zonal wind planetary wave and synoptic scale waves in the pre ssw period the planetary wave is more active than normal in relation to the tropospheric westerly jet that shifts poleward in the post ssw period on the other hand the planetary wave is less active while the mean zonal wind is close to the climatology synoptic scale waves also exhibit anomalous features in both periods corresponding to

on the validity of downgradient eddy closures in ocean models results are presented from an eddy resolving primitive equation ocean model to test the hypothesis that geostrophic eddies can be parameterized through a variety of downgradient closures time mean eddy fluxes of temperature isopycnic thickness and quasi geostrophic potential vorticity are diagnosed on level surfaces from 5 years of model data and are spatially correlated with the corresponding time mean gradients we find no discernible correlation between the absolute eddy fluxes and mean gradients however after decomposing the eddy fluxes into rotational and divergent components we find a positive correlation between the divergent eddy fluxes and the mean gradients although the overall correlation coefficients remain small typically o 0 2 the correlation between the eddy temperature fluxes and mean temperature gradients is positive only over the upper 2 km and is negative at depth suggesting that the abyssal temperature fluxes are upgradient in contrast the correlations between eddy fluxes and mean gradients of isopycnic thickness and potential vorticity are positive over the most of the fluid column the overall correlations are similar for both thickness and potential vorticity closures we further decompose the divergent component of the eddy fluxes into components directed perpendicular and parallel to mean contours we find that both the perpendicular and the parallel components are similar in magnitude

chemical and isotopic kinship of iron in the earth and moon deduced from the lunar mg suite abstract the moon and the earth s mantle share many chemical and isotopic traits leading to the prevailing theory that they were formed from similar material iron is one element that shows apparent differences between the two bodies with models for the composition of the moon having 1 5 times more feo 12 14 wt relative to the earth s mantle 8 wt this difference is mirrored in their isotope compositions where lunar mare basalts have 57fe per mille deviation of the 57fe 54fe ratio from the irmm 014 standard 0 1 0 2 higher than peridotitic rocks representative of earth s mantle a feature initially attributed to loss of isotopically light fe following a giant impact however whether basaltic rocks are suitable analogues for the moon s composition is debatable in the light of their distinct source regions that reflect the extensive lithological stratification of the lunar mantle here we evaluate the iron isotope composition of the bulk moon through the study of igneous cumulate rocks of the lunar highlands magnesium suite mg suite the 57fe of mg suite rocks spans a limited range from 0 05 to 0 10 with an average 0 07 0 02 that overlaps with earth s mantle 0 05 0 01 similarities that extend to their mg s where both reach 0 9 numerical modelling of iron isotope fractionation during lunar magma ocean crystallisation shows that the mg suite should accurately reflect the composition of the bulk moon which is therefore 0 07 0 02 indistinguishable from earth s mantle but heavier than chondrites 0 01 0 01 iron thus behaves coherently with other elements that condense at temperatures higher than li in showing no isotopic difference between the earth and moon suggesting element depletion on the moon affected only the more volatile elements therefore there is no cosmochemical basis for iron enrichment or depletion in the bulk moon relative to the earth s mantle whose composition is an analogue for that of the moon

determination of temperature dependent stable strontium isotope 88sr 86sr fractionation via bracketing standard mc icp ms stable strontium isotopes here 88sr 86sr are introduced as a new member of the nontraditional stable isotopes we have developed a bracketing standard method for the determination of 88 86sr using an axiom mc icp ms and normalizing to strontium srm nbs987 for individual measurements the external reproducibility is better than about 25 ppm 1 rsd for the iapso seawater standard a 88 86sr value of 0 381 0 010 2sem was determined for the first time a temperature dependent strontium isotope fractionation during calcium carbonate precipitation could be shown aragonite samples inorganically precipitated under temperature control between 10 and 50 c revealed a 88 86sr temperature dependency of 0 0054 5 c r2 0 987 in contrast for natural coral samples pavona clavus from a proxy calibration study 23 to 27 c we did determine 0 033 5 c r2 0 955 the processes causing this sixfold stronger temperature dependency for the natural coral samples have to be studied in more detail in future studies in a first approach the different slopes can be interpreted as effects of kinetic fractionation of strontium ions with or without a hydrate shell of 22 to 29 water molecules

high precision sulfur isotope composition of enstatite meteorites and implications of the formation and evolution of their parent bodies abstract in order to better understand the formation and evolution of their parent bodies the three isotope ratios of sulfur were analyzed in 33 enstatite meteorites 24 enstatite chondrites and 9 aubrites the results show that on average all enstatite chondrite groups are enriched in the lightest isotopes compared to other chondrite groups with means of 34 s of 0 28 0 22 for eh3 4 0 16 0 16 for eh5 0 32 0 15 for el3 0 67 0 16 for el6 and 0 64 0 00 for el7 all 1 aubrites show a larger isotope variability in their composition with a 34 s varying from 1 350 to 0 154 contrary to previously published results our data show a distinct composition for el6 compared to other enstatite chondrites this could be related to an impact induced loss of isotopically heavy oldhamite 34 s by 3 62 3 02 1 on the el parent body although the bulk sulfur in both enstatite meteorites and aubrites does not show any significant 33 s and 36 s the oldhamite fraction shows clear evidence of mass independent fractionation on the 36 s 32 s ratio in 3 out of 9 analyzes 36 s up to 2 2 a signal that is not correlated to any 33 s 32 s anomaly in 1 out of 9 analyzes 33 s down to 0 085 though a nebular or photochemical origin cannot be ruled out the most plausible mechanism to produce such isolated non mass dependent 36 s 32 s anomalies would be a contribution of fecl 2 containing excesses of 36 s due to the decay of 36 cl to the leached oldhamite fraction even though the sulfur isotopic composition measured in enstatite meteorites is distinct from the bulk silicate earth bse the isotopically lightest samples of el6 el7 and aubrites are approaching the isotopic composition of the bse and enstatite meteorites remain the meteorites with the sulfur isotopic composition the closest to the terrestrial one

variations of current path velocity and volume transport of the kuroshio in relation with the large meander abstract the variations of the kuroshio current path and their relations with current velocity volume transport and upstream position of the kuroshio are examined using sea level data after the long time non large meander nlm path during 1963 75 the kuroshio takes a large meander lm path during most of 1975 91 1975 80 1981 84 1986 88 and 1989 91 the study of these meanders confirms the description of the path of the kuroshio based on the three typical paths and the transitions between them with an exception being the 1981 84 lm path the formation and decay of the large meander are associated with velocity and position of the kuroshio in the tokara strait south of kyushu a small meander precursor of the large meander seems to be formed southeast of kyushu in relation with a temporary increase of kuroshio velocity and a northward shift of the kuroshio in the tokara strait an eastward propagation of the small meander leading to the lm formation is associated with remaining in the northe

a note on orbital control of equator pole heat fluxes we note that orbital milankovitch variations in particular the precession of the equinoxes can lead to profound variations in the flux of heat from the tropics to higher latitudes the mechanism involves changing the intensity of the hadley circulation by varying the maximum displacement from the equator of the zonally averaged surface temperature maximum in summer the precession of the equinoxes causes this quantity to vary by more than a factor of 2 the intensity of the hadley circulation has a major influence on the heat fluxes in the winter hemisphere summer heat fluxes are generally small although the precession cycle is characterized by periods in the neighborhood of 20000 years the variations are modulated by the eccentricity whose variation is dominated by periods in the neighborhood of 100000 years and 400000 years we show how the fact that both small and large heat fluxes lead to low snowfall and hence small glacial accumulation causes the demodulation of the heat flux leading to dominant eccentricity periods in the resulting glaciation

contributors to chromium isotope variation of meteorites we report the results of a comprehensive high precision survey of the cr isotopic compositions of primitive chondrites along with some differentiated meteorites to ensure complete dissolution of our samples they were first fused with lithium borate tetraborate at 1050 1000 c relative to the nist cr standard srm 3112a carbonaceous chondrites exhibit excesses in 54cr 52cr from 0 4 to 1 6e 1e 1 part in 10 000 and ordinary chondrites display a common 54cr 52cr deficit of 0 4e analyses of acid digestion residues of chondrites show that carbonaceous and ordinary chondrites share a common 54cr enriched carrier which is characterized by a large excess in 54cr 52cr up to 200e associated with a very small deficit in 53cr 52cr 2e we did not find 54cr anomalies in either bulk enstatite chondrites or in leachates of their acid digestion residues this either requires that the enstatite chondrite parent bodies did not incorporate the 54cr anomaly carrier phase during their accretion or the phase was destroyed by parent body metamorphism chromium in the terrestrial rocks and lunar samples analyzed here show no deviation from the nist srm 3112a cr standard the eucrite and martian meteorites studied exhibit small deficits in 54cr 52cr the 54cr 52cr variations among different meteorite classes suggest that there was a spatial and or temporal heterogeneity in the distribution of a 54cr rich component in the inner solar system we confirm the correlated excesses in 54cr 52cr and 53cr 52cr for bulk carbonaceous chondrites but the new data yield a steeper slope 6 6 than that reported in shukolyukov and lugmair 2006 the correlated excesses may affect the use of the mn cr chronometer in carbonaceous chondrites we could not confirm the bulk carbonaceous chondrite mn cr isochron reported by shukolyukov and lugmair 2006 and moynier et al 2007 mostly because we find much smaller total variations in e53cr 0 2 all bulk chondrites have small e53cr excesses up to 0 3 relative to the earth most likely reflecting the sub chondritic mn cr ratio of the earth the e53cr variations in chondrites do seem to grossly correlate with mn cr and yield an initial solar system 53mn 55mn value of 5 4 2 4 10 6 corresponding to an absolute age of 4566 4 2 2 ma nuclear interactions with cosmic rays result in coupled excesses in e54cr and e53cr with a 4 1 ratio in phases with high fe cr these are most dramatically demonstrated in the iron meteorite carbo showing excesses in e54cr of up to 140e these new results show that the mn cr chronometer should be used with caution in samples minerals with high fe cr and long cosmic ray exposure ages

26 al 26 mg and 207 pb 206 pb systematics of allende cais canonical solar initial 26 al 27 al ratio reinstated abstract the precise knowledge of the initial 26 al 27 al ratio 26 al 27 al 0 is crucial if we are to use the very first solid objects formed in our solar system calcium aluminum rich inclusions cais as the time zero age anchor and guide future work with other short lived radio chronometers in the early solar system as well as determining the inventory of heat budgets from radioactivities for early planetary differentiation new high precision multi collector inductively coupled plasma mass spectrometry mc icp ms measurements of 27 al 24 mg ratios and mg isotopic compositions of nine whole rock cais six mineralogically characterized fragments and three micro drilled inclusions from the cv carbonaceous chondrite allende yield a well defined 26 al 26 mg fossil isochron with an 26 al 27 al 0 of 5 23 0 13 10 5 internal mineral isochrons obtained for three of these cais a44a ajef and a43 are consistent with the whole rock cai isochron the mineral isochron of ajef with 26 al 27 al 0 4 96 0 25 10 5 anchored to our precisely determined absolute 207 pb 206 pb age of 4567 60 0 36 ma for the same mineral separates reinstate the canonical 26 al 27 al 0 of 5 10 5 for the early solar system the uncertainty in 26 al 27 al 0 corresponds to a maximum time span of 20 ka thousand years suggesting that the allende cai formation events were culminated within this time span although all allende cais studied experienced multistage formation history including melting and evaporation in the solar nebula and post crystallization alteration likely on the asteroidal parent body the 26 al 26 mg and u pb isotopic systematics of the mineral separates and bulk cais behaved largely as closed system since their formation our data do not support the supra canonical 26 al 27 al ratio of individual minerals or their mixtures in cv cais suggesting that the supra canonical 26 al 27 al ratio in the cv cais may have resulted from post crystallization inter mineral redistribution of mg isotopes within an individual inclusion this redistribution must be volumetrically minor in order to satisfy the mass balance of the precisely defined bulk cai and bulk mineral data obtained by mc icp ms the radiogenic 208 pb 206 pb ratio obtained as a by product from the pb pb age dating is used to estimate time integrated 232 th 238 u ratio value of cais limited variations among the minerals within a single cai contrasted by much larger variations among the bulk cais suggest th u fractionation occurred prior to crystallization of igneous cais if interpreted as primordial heterogeneity the value can be used to calculate the mean age of the interstellar dust from which the cais condensed

evidence for mo isotope fractionation in the solar nebula and during planetary differentiation abstract mass dependent mo isotope fractionation has been investigated for a wide range of meteorites including chondrites enstatite ordinary and carbonaceous chondrites iron meteorites and achondrites eucrites angrites and martian meteorites as well as for lunar and terrestrial samples magmatic iron meteorites together with enstatite ordinary and most carbonaceous chondrites define a common 98 95 mo value of 0 16 0 02 relative to the nist srm 3134 mo standard which is interpreted to reflect the mo isotope composition of bulk planetary bodies in the inner solar system heavy mo isotope compositions for iab iron meteorites most likely reflect impact induced evaporative losses of mo from these meteorites carbonaceous chondrites define an inverse correlation between 98 95 mo and metal content and a positive correlation between 98 95 mo and matrix abundance these correlations are mainly defined by cm and ck chondrites and may reflect the heterogeneous distribution of an isotopically light metal and or an isotopically heavy matrix component in the formation region of carbonaceous chondrites alternatively the elevated 98 95 mo of the cm and ck chondrites could result from the loss of volatile isotopically light mo oxides that formed under oxidized conditions typical for the formation of these chondrites the mo isotope compositions of samples derived from the silicate portion of differentiated planetary bodies are heavy compared to the mean composition of chondrites and iron meteorites this difference is qualitatively consistent with experimental evidence for mo isotope fractionation between metal and silicate the common 98 95 mo values of 0 05 0 03 of lunar samples derived from different geochemical reservoirs indicate the absence of significant mo isotope fractionation by silicate differentiation or impact metamorphism volatilization on the moon the most straightforward interpretation of the mo isotope composition of the lunar mantle corresponds to the formation of a lunar core at a metal silicate equilibration temperature of 1800 200 c the investigated martian meteorites angrites and eucrites exhibit more variable mo isotope compositions which for several samples extend to values above the maximum 98 95 mo 0 14 that can be associated with core formation for these samples post core formation processes such as partial melting metamorphism and in the case of meteorite finds terrestrial weathering must have resulted in mo isotope fractionation estimates of the metal silicate equilibration temperatures for mars 2490 770 c and the angrite parent body 1790 230 c are thus more uncertain than that derived for the moon although the mo isotope composition of the bulk silicate earth has not been determined as part of this study a value of 0 16 98 95 mo 0 can be predicted based on the chondrite and iron meteorite data and by assuming a reasonable temperature range for core formation in the earth this estimate is in agreement with four analyzed basalt standards 0 10 0 10 improved application of mass dependent mo isotope fractionation to investigate core formation most of all requires an improved understanding of potential mo isotope fractionation during processes not related to metal silicate differentiation

stable calcium isotopic composition of meteorites and rocky planets abstract new measurements of mass dependent calcium isotope effects in meteorites lunar and terrestrial samples show that earth moon mars and differentiated asteroids e g 4 vesta and the angrite and aubrite parent bodies are indistinguishable from primitive ordinary chondritic meteorites at our current analytical resolution 0 07 sd for the 44 ca 40 ca ratio in contrast enstatite chondritic meteorites are slightly enriched in heavier calcium isotopes ca 0 5 and primitive carbonaceous chondritic meteorites are depleted in heavier calcium isotopes ca 0 5 the calcium isotope effects cannot be easily ascribed to evaporation or intraplanetary differentiation processes the isotopic variations probably survive from the earliest stages of nebular condensation and indicate that condensation occurred under non equilibrium undercooled nebular gas conditions some of this early high temperature calcium isotope heterogeneity is recorded by refractory inclusions niederer and papanastassiou 1984 and survived in planetesimals but virtually none of it survived through terrestrial planet accretion the new calcium isotope data suggest that ordinary chondrites are representative of the bulk of the refractory materials that formed the terrestrial planets enstatite and carbonaceous chondrites are not the enrichment of light calcium isotopes in bulk carbonaceous chondrites implies that their compositions are not fully representative of the solar nebula condensable fraction

the phanerozoic δ88 86sr record of seawater new constraints on past changes in oceanic carbonate fluxes the isotopic composition of phanerozoic marine sediments provides important information about changes in seawater chemistry in particular the radiogenic strontium isotope 87sr 86sr system is a powerful tool for constraining plate tectonic processes and their influence on atmospheric co2 concentrations however the 87sr 86sr isotope ratio of seawater is not sensitive to temporal changes in the marine strontium sr output flux which is primarily controlled by the burial of calcium carbonate caco3 at the ocean floor the sr budget of the phanerozoic ocean including the associated changes in the amount of caco3 burial is therefore only poorly constrained here we present the first stable isotope record of sr for phanerozoic skeletal carbonates and by inference for phanerozoic seawater 88 86srsw which we find to be sensitive to imbalances in the sr input and output fluxes this 88 86srsw record varies from 0 25 to 0 60 vs srm987 with a mean of 0 37 the fractionation factor between modern seawater and skeletal calcite 88 86srcc sw based on the analysis of 13 modern brachiopods mean 88 86sr of 0 176 0 016 2 standard deviations s d is 0 21 and was found to be independent of species water temperature and habitat location overall the phanerozoic 88 86srsw record is positively correlated with the ca isotope record 44 40casw but not with the radiogenic sr isotope record 87sr 86sr sw a new numerical modeling approach which considers both 88 86srsw and 87sr 86sr sw yields improved estimates for phanerozoic fluxes and concentrations for seawater sr the oceanic net carbonate flux of sr f sr carb varied between an output of 4 7x1010mol myr and an input of 2 3x1010mol myr with a mean of 1 6x1010mol myr on time scales in excess of 100myrs the f sr carb is proposed to have been controlled by the relative importance of calcium carbonate precipitates during the aragonite and calcite sea episodes on time scales less than 20myrs the f sr carb seems to be controlled by variable combinations of carbonate burial rate shelf carbonate weathering and recrystallization ocean acidification and ocean anoxia in particular the permian triassic transition is marked by a prominent positive 88 86srsw peak that reflects a significantly enhanced burial flux of sr and carbonate likely driven by bacterial sulfate reduction bsr and the related alkalinity production in deeper anoxic waters we also argue that the residence time of sr in the phanerozoic ocean ranged from 1myrs to 20myrs

the nonlinear optimal triggering perturbation of the kuroshio large meander and its evolution in a regional ocean model abstractbased on the regional ocean modeling system roms and the conditional nonlinear optimal perturbation cnop method we explore the nonlinear optimal triggering perturbation of the kuroshio

rapid perturbation growth on spatially and temporally varying oceanic flows determined using an adjoint method application to the gulf stream abstract the stability of the gulf stream flow predicted by a nonlinear quasigeostrophic model is examined by employing an iterative method which uses both the tangent linear equations and the adjoint tangent linear equations of the quasigeostrophic model the basic state flow is the model s representation of the gulf stream as observed during january and february 1988 the growth of perturbation energy is examined as a measure of disturbance growth and linear perturbations are found that are optimal in the sense that they maximize the growth of perturbation energy the structures of optimal perturbations are compared with the structure of the normal modes the optimal perturbations are found to be mere localized and to grow much more rapidly than the normal modes optimal perturbations are of interest because they can be used to plan tight constructive upper bounds on the growth of perturbations to ocean currents such as the gulf stream and they provide valuable information about the predictability of

sr stable isotope composition of earth the moon mars vesta and meteorites abstract high precision stable sr isotopic variations 88 sr 86 sr are reported in a variety of terrestrial samples martian and lunar meteorites hed undifferentiated primitive meteorites chondrules and refractory inclusions almost all the whole rock samples are isotopically indistinguishable at a 50 parts per million ppm level the exceptions are cv and co chondrites which are isotopically light and for which we believe that their isotopic composition is controlled by the proportion of refractory material five separated chondrules and one refractory inclusion from allende are isotopically light with 88 86 sr fractionations up to 1 73 whereas the matrix is enriched in the heavy isotopes 88 86 sr 0 66 the depletion in heavy isotopes observed in chondrules and refractory inclusions could be attributed to the condensation of a material already depleted in sr however in that case more than 60 of the original material would be unaccounted we propose instead that isotopic fractionation by electromagnetic sorting of ionized heavy sr from neutral sr in the early solar system for the origin of the fractionation observed in refractory inclusions and redistribution of sr by aqueous alteration for the origin of the fractionation observed in chondrules and matrix we conclude that cv and co chondrites are not the primary building blocks for earth and mars

coupled 63cu and 16o excesses in chondrites abstract recent developments in multiple collector magnetic sector icp ms inductively coupled plasma mass spectrometry have permitted the relative abundances of the two isotopes 63 and 65 of copper to be measured with unprecedented precision 40 ppm here we report cu isotopic variations among eight carbonaceous chondrites ccs from the ci cm co and cv groups and the presently ungrouped tagish lake and 10 ordinary chondrites ocs from the h l and ll groups the widest isotopic range of 0 8 per a m u is observed for the carbonaceous chondrites copper in carbonaceous chondrites becomes isotopically lighter with petrologic type in the order 1 to 3 but seems extremely homogeneous for each type the cu isotopic composition of tagish lake confirms its other characteristics that are intermediate between ci and cm in three of the groups ci cm co as well as for tagish lake 63 cu excess over terrestrial mantle abundances correlates well with 16 o excess for all four groups 63 cu excess also correlates remarkably well with elemental refractory volatile ratios e g ca mn for ordinary chondrites small differences exist between the h l and ll groups with cu becoming isotopically heavier in that order equilibrated and unequilibrated samples however exhibit the same cu isotopic signature within each group although the range of cu isotopic compositions in ordinary chondrites is smaller than in carbonaceous chondrites 63 cu excesses still correlate with 16 o excesses the observed trends of isotopic variation seem incompatible with a single stage fractionation process by either volatilization or low temperature metamorphism the correlations between 63 cu excesses and 16 o excesses suggest the presence of at least two and perhaps three isotopically distinct cu reservoirs in the early solar system 1 an earth like reservoir common to the ci and ll probably representing the main cu stock of the inner solar system 2 a reservoir present in all carbonaceous chondrites but most abundant in cv with large 63 cu and 16 o excesses this reservoir is probably hosted in refractory material and 3 possibly a third reservoir present in ordinary chondrites the oc trend may also be explained as a mixture of the first two cu reservoirs if its oxygen was first equilibrated with nebular gas the coexistence of 63 cu and 16 o excesses in the same component raises the issue of how volatile cu was preserved in refractory material a strong correlation between 63 cu 65 cu and ni cu ratios suggests that 63 cu excess may have originated as more refractory 63 ni t 1 2 100 yr upon irradiation of refractory grains by electromagnetic flares and particle bursts during the t tauri phase of the sun

controls on the solute geochemistry of subglacial discharge from the russell glacier greenland ice sheet determined by radiogenic and stable sr isotope ratios abstract we used radiogenic and stable sr isotope ratios 87sr 86sr and 88 86sr to examine controls on solute acquisition in subglacial discharge from the russell glacier a land terminating lobe of the greenland ice sheet gris located in western greenland the study focused on two melt seasons in 2014 and 2015 subglacial discharge 87sr 86sr ratios are 13 000 ppm higher than those measured for bedload and suspended sediment digests and are more similar to those of bedload sediment leachates these results point to the preferential dissolution of minerals with high 87sr 86sr ratios analyses of mineral separates from bulk rocks demonstrate that biotite chlorite hornblende and k feldspar have relatively high 87sr 86sr ratios subglacial discharge 88 86sr values are 0 10 higher than those for bedload and suspended sediment digests isotope fractionation during secondary mineral formation and or adsorption cannot account for the difference between subglacial discharge and bedrock 88 86sr values as suspended and bedload sediment leachates and digests produced similar 88 86sr values and are within the range for bulk silicate earth consistent with the interpretation of 87sr 86sr ratios we attribute the difference to the preferential dissolution of minerals with high 88 86sr values mineral separates display a wide range of 88 86sr values 0 40 those having high 88 86sr values include hornblende and k feldspar as well as apatite and titanite taken together the preferential weathering of predominately silicate minerals explains the sr isotope geochemistry of subglacial discharge subglacial discharge from the russell glacier feeds the proglacial akuliarusiarsuup kuua river akr along a 32 km transect of the akr from the gris margin toward the coast riverine 87sr 86sr ratios increase from 0 722 to 0 747 in an approximately step wise pattern that corresponds to point source inputs of additional subglacial discharge major cation concentrations and 87sr 86sr ratios minimally vary along lengths of the transect with no hydrological inputs this suggests that proglacial chemical weathering is negligible and likely does not contribute significantly to gris solute fluxes in general this study supports the recent contention that silicate mineral weathering dominates the solute geochemistry of gris subglacial discharge in contrast to valley glaciers which typically show substantial contributions from carbonate and sulfide weathering regardless of primary bedrock composition ice sheet subglacial chemical weathering may therefore have a greater impact on long term atmospheric co2 drawdown than previously realized

development of a four dimensional variational assimilation system for coastal data assimilation around japan abstractthe authors have developed an assimilation system toward coastal data assimilation around japan which consists of a four dimensional variational 4dvar assimilation scheme with an eddy resolving model in the western north pacific move 4dvar wnp and a fine resolution coastal model covering the western part of the japanese coastal region around the seto inland sea move seto the 4dvar scheme is developed as a natural extension of the 3dvar scheme used in the meteorological research institute multivariate ocean variational estimation move system an initialization scheme of incremental analysis update iau is incorporated into move 4dvar wnp to filter out high frequency noises during the backward integration of the adjoint model it works as an incremental digital filtering move seto which is nested within move 4dvar wnp also employs iau to initialize the interior of the coastal model using move 4dvar wnp analysis fields the authors conducted an assimilation experiment using move 4dvar

samarium neodymium chronology and rubidium strontium systematics of an allende calcium aluminum rich inclusion with implications for 146sm half life abstract calcium aluminum rich inclusions cais are primitive objects that formed within the protoplanetary disk surrounding the young sun recent pb pb chronologic studies have demonstrated that cais are the oldest solar system solids crystallizing 4567 ma ago amelin et al 2002 connelly et al 2012 the isotope systematics of cais therefore provide critical insight into the earliest history of the solar system although sm nd and rb sr geochronometers are highly effective tools for investigating cosmochemical evolution in the early solar system previous studies of cais have revealed evidence for isotopically disturbed systems here we report new age data for allende cai al3s4 derived from both the long lived 147sm 143nd and short lived 146sm 142nd isotopic systems the 147sm 143nd chronometer yields an age of 4560 34 ma that is concordant with 207pb 206pb ages for cais and indicates that the sm nd system was not significantly disturbed by secondary alteration or nucleosynthetic processes the slope of the 146sm 142nd isochron defines the solar system initial 146sm 144sm of 0 00828 0 00044 this value is significantly different from the value of 0 0094 determined by kinoshita et al 2012 ages recalculated from all published 146sm 142nd isochron data using the traditional 103 ma half life and the initial 146sm 144sm value determined here closely match pb pb and 147sm 143nd ages determined on the same samples in contrast ages recalculated using the 68 ma half life determined by kinoshita et al 2012 and either of the initial 146sm 144sm values are often anomalously old this is particularly true for the youngest samples with 146sm 142nd isochron ages that are most sensitive to the choice of 146sm half life used in the age calculation in contrast to the sm nd isotope system the rb sr system is affected by alteration but yields an apparent isochron with a slope corresponding to a much younger age of 4247 110 ma although the rb sr system in cais appears to be disturbed the initial 87sr 86sr value determined from the isochron is 0 698942 0 000008 and closely approximates estimates of the initial solar system value although this isochron may be a mixing line it might also record alteration on the allende parent body in which rb was added to the al3s4 cai that was initially largely devoid of rb

the first large scale bioavailable sr isotope map of china and its implication for provenance studies abstract strontium isotope ratio 87sr 86sr has been widely used to trace human migrations across geologically distinct landscapes in archaeological and forensic sciences 87sr 86sr based provenance studies require a detailed strontium reference map to make valid interpretations of mobility patterns for a given region in this study we first review the previous development for 87sr 86sr isoscapes relevant to research on migration and then present the first map of bioavailable 87sr 86sr ratios for china based on 1935 measurements on biosphere samples collated from published research and supplemented by our targeted collection strategy the results show that 87sr 86sr ratios in china span a large range and exhibit regional patterns largely dependent on the divergent geological conditions of each of china s tectonic blocks we further combine river water 87sr 86sr ratios with lithology integrated elemental data and chemical weathering rates to determine which dominant weathering patterns e g silicate carbonate or evaporite have the most significant influence on 87sr 86sr ratios the low ranges of 87sr 86sr ratios 0 7125 appear in the cathaysia block as well as some orogenic belts and the southeastern margin of the tibetan plateau likely due to the influence of the metamorphic rocks and granitoid sources additionally topography differential weathering among lithologies and eolian deposits e g loess are also significant factors that influence 87sr 86sr ratios in china our study reveals that the large variation of 87sr 86sr ratios across china is predominately driven by geological conditions revealing that future sr isotope provenance studies can shed on ancient and historical migrations in china

the effect of the hadley circulation on the meridional propagation of stationary waves the effect on the meridional propagation of stationary planetary waves of the inclusion of the zonal mean hadley circulation in linearized models of the atmosphere is examined in a forced barotropic vorticity equation model a meridional wind in the basic state enables wave propagation through tropical easterlies in the direction of the wind this is shown to be consistent with the wkb solution in a multi level linearized steady primitive equation model with an idealized meridional circulation tropical forcing can still produce response through easterlies although propagation from one mid latitude to the other is much less than in the barotropic result this is explained through wkb and wave tracing methods for a simplified three dimensional vorticity equation the near non divergence of the unforced tropical motion permits a wave to travel largely within a layer of favourable winds in a twelve level model using observed january and july zonal mean conditions the hadley circulation changes the response to earth topographic forcing mainly in the subtropics however tropical heat forcing can now produce a large mid latitude response in the winter hemisphere especially the resulting subtropical jets suggest a mechanism for the maintenance of those observed over australia during the northern monsoon season and adjacent to the anomalous forcing of the 1983 el nino

the moon a personal recollection and memorial for professor lawrence a taylor an apollo stalwart abstract the first geochemical analysis of lunar samples returned by the apollo 11 mission revealed that the moon was highly differentiated and depleted in volatile elements stable isotope compositions show that earth and moon are closely related but they have evolved in totally dissimilar ways probably related to the deficiency of water in the moon as well as the vast differences in size currently available lunar samples come from cumulate source regions making the establishment of a bulk planetary composition more reliant on geophysical rather than geochemical properties

isotopic composition of zinc copper and iron in lunar samples abstract we determined by icp ms the concentrations and isotopic ratios of fe cu and zn in the ti rich lunar basalt 74275 in the lunar orange glass 74220 and in up to 10 lunar soils namely 14163 15231 64501 66041 68841 69941 70011 72501 75081 and 76501 two analyses of zinc in lunar basalt 74275 give 66 zn 0 17 and 0 75 values within the range of those measured in terrestrial basalts copper in lunar basalt 74275 has 65 cu 1 4 which is isotopically heavier than values observed in terrestrial basalts in the orange glass we measured 56 fe 0 24 65 cu 0 42 and 66 zn 3 6 these values of are more negative than those obtained for 74275 and for typical lunar basalts but for cu comparable to those observed in terrestrial sulfides and meteorites in lunar soils we found 0 11 56 fe 0 51 2 6 65 cu 4 5 and 2 2 66 zn 6 4 insofar as we can generalize from a small sample set s fe cu zn and cd show similar trends in isotopic fractionation on the moon lunar basalts have nearly terrestrial isotopic ratios relative to the lunar basalt 74275 the pyroclastic glass 74220 is enriched in the lighter isotopes of fe cu and zn and the soils are enriched in the heavier isotopes of fe cu and zn the patterns in the basalts are likely inherited from the source material the light isotope enrichments seen in the orange glass originated during lava fountaining or less probably during partial condensation of vapor and the heavy isotope enrichments in the lunar soils were likely created by a combination of processes that included micrometeorite vaporization and sputtering in the orange glass the light isotope enrichments relative to lunar basalts of zn are larger than those of cu if these enrichments reflect accurately the isotopic composition of the gas they suggest that cu is more volatile than zn in the liquid from which the gas derived a simple model built on the known flux of micrometeorites to the lunar surface and a published estimate that micrometeorites generate 10 times their own mass of vapor predicts heavy isotope enrichments comparable to those observed in soils but only if the regolith gardening rate is set at about one twentieth of the generally accepted value of 1 cm my this discrepancy may reflect the difference in the time constants for micrometeorite milling and decimeter scale gardening or the importance of sputtering

magnesium isotopic fractionation of silicates produced in condensation experiments isotopic mass fractionations of magnesium have been studied for silicates produced in condensation experiments for the purpose of studying the evaporation condensation process in the early solar nebula in connection with the isotopic data observed in various primitive materials the silicate gas which is evaporated from forsterite was fractionated to produce condensates at various temperatures below 1350 c down to room temperature and the amount of isotopic mass fractionation varied considerably with the condensation temperature tc the variation in the 26mg 24mg ratio with respect to the initial evaporation source 26 varies from 8 to 30 astc changes from 1350 c to room temperature the obtained 26 tc relationship is explained in terms of the rayleigh fractionation model and the relationship indicates that the condensates fractionate isotopically toward the heavy mass with respect to the gas phase at temperatures from 700 c to 1350 c the obtained data show that the condensates can be fractionated both toward the heavy and light isotopes with respect to the initial source according to the fraction of the residual gas phase tc the evaluation of mass fractionation between the condensed phase and the residual gas phase is essential for the analysis of various isotopic data on primitive materials

low frequency variability in regions of the kuroshio extension and the gulf stream using sea surface height data collected by the topex poseidon altimeter we studied the low frequency variability in the kuroshio extension and gulf stream the most significant signals are the basin wide background seasonal cycle and low frequency wave activity generated over major bottom bathymetry and subsequent westward propagation in both regions the spatial structures of the seasonal cycle in the two regions are quite different in the kuroshio extension the seasonal cycle has a northeast southwest orientation and lies closer to the western boundary whereas it has an east west orientation and lies more offshore in the gulf stream the close relationship between the low frequency wave activity and major bottom bathymetry features is discussed through both empirical orthogonal functional eof analysis and calculation of eddy kinetic energy and reynolds stress the spatial structures of these eddy statistics are fundamentally different from those of high frequency mesoscale variability they are not in the proximity of maximum time mean flow but rather they lie mostly to the west of major bottom bathymetry the close association of the clusters of local maximum eddy properties with major bottom topographic features in both regions wave generation over the major bottom topographic features and subsequent westward propagation and difference of the eddy statistics from that associated with high frequency mesoscale variability all suggest that unlike in the case with high frequency mesoscale variability generation in which internal dynamics of the background mean flow such as nonlinear instability plays a fundamental role external forcing through bottom topography must play a fundamental role in generating the low frequency wave activity

oxygen isotopic compositions of enstatite chondrites and aubrites oxygen isotopic compositions have been measured for ten eh chondrites eight el chondrites and nine aubrites the mean 18o and 17o values are 5 31 and 2 74 5 57 and 2 96 5 24 and 2 70 respectively within the eh group more equilibrated meteorites are fractionated toward higher heavy isotope abundances than the less equilibrated meteorites small departures of individual meteorites from a common mass fractionation occur for some of the eh samples the aubrites may be genetically related to either the eh or el group or to both almost all of the measured isotopic compositions are indistinguishable from the terrestrial oxygen isotope fractionation line suggesting a genetic relationship among the earth the moon and the enstatite the meteorites

radiogenic and stable strontium isotopes in provenance studies a review and first results on archaeological wood from shipwrecks abstract different approaches are used to study wood provenance but most of them are based on tracers in wood that are generally controlled by climatic factors the strontium isotopic ratio 87 sr 86 sr in trees and soils is related to the signature of the local bedrock despite being used in diverse archaeological studies sr isotopes have rarely been used to trace the provenance of archaeological wood and especially wood from shipwrecks in addition recent analytical advances have allowed the detection of mass dependent fractionation of sr isotopes during biogeochemical processes as reflected in the variation of 88 86 sr values between different environmental materials the 88 86 sr values could be used in conjunction with the 87 sr 86 sr isotope ratio to improve constraints on the sources of sr in the archaeological materials being studied this paper discusses the potential and limitations of using both of these sr isotope ratios to trace the provenance of wood from shipwrecks we review the 87 sr 86 sr and 88 86 sr variations in rocks waters soils plants and other living organisms and discuss how to determine the local sr isotopic signature of potential sites we also compile a list of known wood post mortem modifications in seawater possible implications in terms of the modification of the original sr isotope ratios of wood during storage in seawater are illustrated through preliminary observations this paper points out some limitations and perspectives for using sr isotopes in provenancing wood from shipwrecks and suggests future research to test and apply this approach for tracing the origin of archaeological wood

vertical structure physical properties and energy exchange of the east asian trough in boreal winter the relation between the intensity of the east asian trough and the strength of the east asian winter monsoon is documented a prominent dipole of the available potential energy of the zonal mean flow can be observed over the midlatitudes and polar regions and is related to temperature anomalies variation in the intensity of the east asian trough is caused by variation in the energy conversion from the available potential energy of the zonal mean flow to the east asian trough the in phase relation between the intensities of the east asian jet and east asian trough is illustrated by the relation between the potential energy and kinetic energy of stationary eddies the dipole of height anomalies over the midlatitude and polar regions develops in late autumn and decays in early spring we investigate the effect of both stationary and transient eddy forcing on the evolution of the dipole the combined forcing of the two types of eddy makes an important contribution to the development maintenance and decay of the dipole

eddy mean flow interaction in the gulf stream at 68 w part i eddy energetics abstract from june 1988 to august 1990 twelve tall high performance current meter moorings measured the gulf stream s velocity and temperature fields at nominal depths of 400 m 700 m 1000 m and 3500 m along three lines centered at 68 w the overall eddy variability during the 26 month experiment was dominated by six large amplitude trough formation events with each event lasting approximately one month to determine the source s of energy for this eddy variability the eddy energy budget is evaluated traditionally the baroclinic conversion of mean potential energy to eddy potential energy is defined as a downgradient heat flux however because a nondivergent heat flux can be downgradient even under conditions in which there is no barolinic conversion occurring a better more dynamically correct definition of a baroclinic conversion rate is a downgradient horizontally divergent heat flux the horizontally divergent heat flux component is estimated to be approximately half the full horizontal hea

roles of mesoscale eddies in the kuroshio paths a high resolution ocean general circulation model is developed to simulate connections between the kuroshio path variations and mesoscale eddy activities as realistically as possible the climatological mean of the modeled kuroshio takes a nearshore nonlarge meander path it is found that the model is capable of simulating two types of nonlarge meander state and a possible version of the large meander state the offshore nonlarge meander is generated through interaction between the kuroshio and an anticyclonic eddy the large meander occurs just after significant intensification of the anticyclonic kuroshio recirculation successive intrusion of anticyclonic eddies from the upstream region is responsible for this process those anticyclonic eddies are advected by the kuroshio from the region northeast of luzon island and increase the upstream kuroshio volume transport on an interannual time scale the cyclonic eddies propagating from the kuroshio extension region on the other hand weaken the kuroshio meander after the merger the kuroshio path variations south of japan thus seem to be closely related to eddy activities in the subtropical gyre system

astrophysics of cai formation as revealed by silicon isotope la mc icpms of an igneous cai silicon isotope ratios of a typical cai from the leoville carbonaceous chondrite obtained in situ by laser ablation mc icpms together with existing 25 mg 24 mg data reveal a detailed picture of the astrophysical setting of cai melting and subsequent heating models for the chemical and isotopic effects of evaporation of the molten cai are used to produce a univariant relationship between ph2 and time during melting the result shows that this cai was molten for a cumulative time of no more than 70 days and probably less than 15 days depending on temperature the object could have been molten for an integrated time of just a few hours if isotope ratio zoning was eliminated after melting by high subsolidus temperatures e g n1300 k for 500 yr in all cases subsolidus heating sufficient to produce diffusion limited isotope fractionation at the margin of the solidified cai is required these stable isotope data point to a two stage history for this igneous cai involving melting for a cumulative timescale of hours to months followed by subsolidus heating for years to hundreds of years the thermobarometric history deduced from combining si and mg isotope ratio data implicates thermal processing in the disk perhaps by passage through shockwaves following melting this study underscores the direct link between the meaning of stable isotope ratio zoning or lack thereof and the inferred astrophysical setting of melting and subsequent processing of cais 2007 elsevier b v all rights reserved

a nebula setting as the origin for bulk chondrule fe isotope variations in cv chondrites abstract we combined micro computer tomography with fe and si isotope measurements of mokoia allende and grosnaja chondrules ten mokoia chondrules contain 0 9 to 11 8 vol opaque phases metal sulfide and 6 allende chondrules contain 0 0 to 6 6 vol opaque phases hence the fe isotope composition of many chondrules is dominated by the fe isotope composition of their opaque phases we studied fe isotopes of 35 bulk chondrules the range is different for each of the three meteorites studied and largest for allende with 56 fe ranging from 0 82 to 0 37 six out of seven chondrules analysed for their si isotope composition in mokoia and grosnaja have similar 29 si of around 0 12 one anomalous chondrule in mokoia has a 29 si of 0 58 we exclude isotopically heterogeneous chondrule precursors and different isotopic chondrule reservoirs as the source of the observed fe isotope variation among bulk chondrules we conclude that the observed bulk chondrule fe isotope variation is the result of evaporation and re condensation processes in a nebula setting with high dust densities required to explain the comparatively low isotope fractionations subsequent parent body alteration slightly overprinted this pre accretionary fe isotope variation

europium isotopic variations in allende cais and the nature of mass dependent fractionation in the solar nebula we measured the 153eu 151eu ratio by mc icp ms for a terrestrial basalt two terrestrial soils and four meteorites whole rocks and or chondrules of bjurbo le forest city murchison and allende and found no isotopic variations by contrast two cai separates from two different pieces of allende show a 153eu deficit of up to one per mil such a shortage in the heavy isotopes which had also been identified in allende cais for sr patchett p j 1980b sr isotopic fractionation in allende chondrules a reflection of solar nebular processes earth planet sci lett 50 181 188 cannot reflect evaporative fractionation the lack of sm isotope fractionation in the same samples further makes fractionation by purely kinetic processes an unlikely cause of the anomalous eu isotopic composition an alternative interpretation is condensation from a vapor already significantly depleted in eu but in such a scenario the fate of the missing material is unclear we therefore prefer yet another interpretation based on the low ionization potential of eu and sr in which electromagnetic separation of the ionized gas preferentially depletes the nebular gas in heavy isotopes

effects of koshu seamount on the development of baroclinic instability leading to the kuroshio large meander abstractthe kuroshio south of japan shows bimodal path fluctuations between the large meander lm path and the nonlarge meander nlm path the transition from the nlm path to the lm path is triggered by a small meander generated off southwestern japan the small meander first propagates eastward downstream along the kuroshio and then rapidly amplifies over koshu seamount located about 200 km south of japan leading to the formation of the lm path of the kuroshio although koshu seamount is essential for the rapid amplification of the small meander the underlying physical mechanism is not fully understood in this study the role of koshu seamount is revisited using a two layer quasi geostrophic model that takes into account the effects of bottom topography numerical experiments show that the transition from the nlm path to the lm path can be successfully reproduced only when bottom topography mimicking koshu seamount is incorporated in this case the upper layer meander trough is rapidly amplified

simulations of temperature and turbulence structure of the oceanic boundary layer with the improved near surface process an improved model for the oceanic boundary layer is presented in view of the recent observation of the microstructure of the upper ocean including the high dissipation rate near the sea surface in the new model the surface boundary conditions for both the turbulent kinetic energy flux and the roughness length scale are modified the parameterization of stratification effects on turbulence is improved and the convective process is reformulated on the basis of the observation of uniform temperature and velocity profiles within the convective mixed layer evolutions of the profiles of both the dissipation rate and temperature of the observation data patches experiment as well as the time series of the sea surface temperature over the observation days are successfully simulated during a diurnal cycle for the first time it is also shown that the model reproduces various important features of the oceanic boundary layer for example the formation of a diurnal thermocline the profiles of buoyancy flux and the magnitudes of the buoyancy gradients both within the mixed layer and at the diurnal thermocline performance of the model is compared with that of the widely used mellor yamada model

weathering processes catchment geology and river management impacts on radiogenic 87sr 86sr and stable δ88 86sr strontium isotope compositions of canadian boreal rivers abstract radiogenic 87sr 86sr and stable 88 86sr strontium isotope compositions spanning a calendar year are reported for rivers from across subarctic canada that drain contrasting lithologies ranging from precambrian bedrock koksoak great whale and la grande rivers of northern quebec to carbonate and clastic phanerozoic sedimentary rocks of the western interior platform nelson river of central and western canada the 87sr 86sr isotopic compositions of the river waters reflect the underlying geology with rivers draining the precambrian shield having higher 87sr 86sr ratios 0 727 0 734 than the phanerozoic dominated nelson river 0 713 the stable strontium isotope values 88 86sr range from 0 26 to 0 39 with the values for the nelson river overlapping those of the other three rivers that have not been developed for hydroelectric power show a seasonal variation in the 87sr 86sr ratios whereas those that have been diverted or dammed show little or no seasonal variation due to increased residence time of their water in hydroelectric reservoirs the three rivers from northern quebec show discrete ranges in their 87sr 86sr and 88 86sr isotope compositions that correlate with the ca sr and na sr ratios of the river water these correlations are interpreted to reflect differential chemical weathering of felsic versus mafic source rocks and or of surficial sediment vs bedrock sources

manganese chromium isotope systematics of carbonaceous chondrites abstract in this article we present the results of cr isotope investigations of different types of carbonaceous chondrites and of the pallasite eagle station the 53 cr 52 cr ratios in the bulk samples of carbonaceous chondrites are correlated with 55 mn 52 cr ratios the slope of the correlation line yields a 53 mn 55 mn ratio of 8 5 1 5 10 6 at the time of mn cr fractionation mapping this ratio onto an absolute time scale yields a time for this event of 4568 1 0 8 1 1 ma ago this time is very similar to the formation age of efremovka cais of 4567 2 0 6 ma y amelin a n krot i d hutcheon a a ulyanov lead isotopic ages of chondrules and calcium aluminum rich inclusions science 297 2002 1678 1683 to a time of the chondrule formation of 4568 1 ma ago l e nyquist d lindstrom d mittlefehldt c y shih h wiesmann s wentworth r martinez manganese chromium formation intervals for chondrules from the bishunpur and chainpur meteorites meteorit planet sci 36 2001 911 938 which most likely constrains early global high temperature mn cr fractionation in a nebular setting the bulk samples of carbonaceous chondrites exhibit clear 54 cr excesses 54 cr that are correlated with the 53 cr excesses 53 cr and also with mn cr ratios one possible explanation of this correlation is that 54 cr is also radiogenic like 53 cr and was formed by the decay of the short lived parent radionuclide 54 mn the very short half life of 54 mn of 312 days would require that both short lived radionuclides 53 mn and 54 mn were generated locally in spallation reactions during the early period of an active sun the alternative and possibly more plausible explanation is the heterogeneous addition of presolar material the presolar component enriched in 54 cr is mostly contained in the matrix of carbonaceous chondrites the relative amount of matrix decreases in the sequence ci cm co cv a large proportion of mn is associated with the matrix while cr preferentially resides in the chondrules thus the mn cr ratio also follows the sequence ci cm co cv and is correlated with 54 cr the acid resistant residues of carbonaceous chondrites are characterized by relatively large excesses of 54 cr and moderate deficits of 53 cr the magnitude of these excesses and deficits decreases in the sequence ci cm cv and may imply that cr in the cm and cv residues is increasingly more equilibrated with cr from the rest of the meteorites the 53 cr 52 cr and 54 cr 52 cr ratios in the residues are anti correlated indicating that there are at least two cr components of possibly presolar origin all residues have large excesses of the most neutron rich ti isotope 50 ti the pattern of 50 ti does not exactly follow that observed for 54 cr but it is generally similar the cr isotope systematic of the pallasite eagle station indicates that the precursor of this meteorite was a cv type material the 53 mn 53 cr system indicates that the cr isotopes equilibrated in this meteorite 4557 5 0 6 ma ago

strontium isotopes trace biological activity in the critical zone along a climate and vegetation gradient abstract weathering and ecosystem nutrition are intimately linked through the supply of fresh mineral nutrients from regolith and bedrock the geogenic nutrient pathway however the prominence of this link is dependent on the efficiency of nutrient recycling from plant litter the organic nutrient cycle isotope ratios of strontium sr an element that behaves similarly to ca in ecosystems confer two types of information radiogenic sr isotopes inform as to the sources of sr and the degree of weathering while stable sr isotopes constrain partitioning between compartments of the critical zone bedrock water secondary solids and plants to date however neither the reactions nor the mass balance between compartments that fractionate sr isotopes nor the fractionation factors involved are well understood here we present geochemical budgets of sr using radiogenic and stable sr isotopes and ca sr ratios at four sites along a substantial climate and primary production gradient in the coastal mountains of chile we found that sr release through weathering is isotopically congruent and released sr is not strongly isotopically fractionated either during secondary mineral formation or transfer into the exchangeable pool despite this the 88sr 86sr ratio of bio available sr which should reflect the ratio of dissolved sr is higher than that of rock and regolith we propose that this offset is caused by plants while 88sr 86sr in plant organs at the four study sites systematically increased from roots towards their leaves whole plant sr isotope compositions indicate preferential uptake of light sr into plants with a fractionation of up to 0 3 relative to the bio available pool despite this strong biological fractionation 88sr 86sr ratios in bio available sr do not covary with biomass production across our study sites because with greater plant growth sr is recycled more times after release by weathering an isotope neutral process rather the loss of sr from the ecosystem in solid organic material sets the isotope ratio of dissolved or bio available sr organic solids thus appear to constitute a significant export path of elements released during weathering with the removal of solid plant debris reducing the recycling factor of sr and possibly that of other mineral nutrients too

insights into combined radiogenic and stable strontium isotopes as tracers for weathering processes in subglacial environments this study reports stable and radiogenic strontium isotope behaviour in the dissolved load and suspended sediments from the subglacial outflow of the lemon creek glacier juneau ice field alaska over a single melt season in situ measurements discharge total alkalinity ph and conductivity are combined with elemental concentrations x ray diffraction xrd analysis and radiogenic strontium isotope measurements to interpret the variations observed in stable strontium isotopic ratios the stable sr isotope composition 88sr 86sr ratio expressed as 88 86sr of the dissolved load averages 0 31 0 05 and is heavier than both the suspended sediment 0 18 0 03 as well as local bedrocks 0 20 to 0 26 we attribute the enrichment of heavier isotopes in the dissolved load to the uptake of lighter sr isotopes by secondary weathering minerals driving the dissolved load to heavier values x ray diffraction xrd analysis confirms the presence of clays in the suspended sediments and thermodynamic modelling suggests the presence of iron oxy hydroxide phases although it is not possible to completely rule out the effect of dissolution of primary minerals in controlling sr isotopic compositions of the dissolved load our data indicate that the extent of secondary mineral formation likely plays a significant role the preferential weathering of minerals such as biotite consistent with the mineralogical assemblages found in the suspended sediments as well as the potential presence of radiogenic calcites from metacarbonates derived from the yukon tanana terrain may be driving the small seasonal shifts in 87sr 86sr of the dissolved load to more radiogenic compositions from 87sr 86sr dl 0 71048 to 0 710647 using the combination of stable and radiogenic strontium isotopes to investigate weathering processes shows that radiogenic sr isotopes provide information regarding weathering of primary phases while the stable sr isotope data appear to record information regarding the extent of secondary mineral formation where secondary minerals incorporate the light isotopes driving the dissolved load to heavy values

lithium systematics in howardite eucrite diogenite meteorites implications for crust mantle evolution of planetary embryos we present lithium li abundances and isotope compositions in a suite of howardites eucrites and diogenites heds these meteorites most likely originated from asteroid vesta and were delivered to earth by a series of independent impact events the li concentrations show striking differences between li poor diogenites plus cumulate eucrites and li enriched eucrites whilst howardites have li abundances intermediate between eucrites and diogenites contrary to li elemental inter group differences li isotope compositions are irresolvable among these individual groups of hed meteorites despite their wildly distinct petrography attesting to insignificant li isotope fractionation during formation of a thick basaltic crust by melting of the vestan mantle the mean li isotope composition of bulk silicate vesta is estimated at 3 7 0 6 1 intermediate to that of the earth versus mars and moon but identical with these terrestrial bodies within uncertainty this further validates largely homogeneous inner solar system solids from the li isotope perspective and supports the lack of loss of moderately volatile elements from planetary embryos during their magmatic histories because li does not follow depletion trends inferred from more volatile elements pasamonte eucrite has the same li isotope composition as other eucrites although it may not be directly linked to vesta these observations are also important for generating li elemental and isotope signatures in juvenile basaltic crusts of large terrestrial planets and numerous planetary embryos in the early solar system a combination of cv l chondrites may be less suitable for building vesta from li perspective but this may face sampling bias of available data and only further analyses may resolve this issue alternatively significant shift of 1 towards heavier li isotope compositions must have occurred during thermal processing of cv l 2 2 2 8 mixture in order to account for the observed li isotope systematics in hed meteorites no correlation is observed between li versus zn fe or si isotopes respectively implying unrelated processes of forming stable isotope variations observed in hed meteorites

dynamics of kuroshio path variations in a high resolution general circulation model 1 a long lived 2 year typical large meander lm path of the kuroshio is reproduced in a high resolution general circulation model gcm simulation with realistic topography and the life cycle formation maintenance and disappearance of the lm is studied the formation of the lm is triggered by a pair of upper layer anticyclonic and cyclonic eddies on the kuroshio with the cyclonic one on the downstream side upon reaching the western side of the shikoku basin south of japan these anomalies induce a lower layer anticyclonic eddy they enhance each other while they are carried eastward by the kuroshio specifically the southward flow on the eastern side of the lower anticyclonic eddy carries the upper cold cyclonic eddy offshore resulting in the southward deflection of the kuroshio path large meander these processes can be understood as a growth of baroclinic instability a stationary lm is established when the westward tendency caused by the beta effect owing to the large meridional displacement counterbalances the eastward tendency caused by the combination of advection and vortex induction owing to the curvature of the kuroshio path large scale disturbances from the upstream tend to strengthen the lm through baroclinic energy conversion in contrast small scale disturbances from the upstream grow locally along the meandering kuroshio front through baroclinic energy conversion they extract cold waters from the cold cyclonic eddy of the lm as they flow away to the east the horizontal extent of the cold cyclonic eddy is reduced and the meander is carried eastward since the advection effect dominates over the beta effect that weakens as a result of the smaller meridional extent

application of singular vector analysis to the kuroshio large meander 1 singular vector analysis is applied to the formation of the kuroshio large meander south of japan we use a simulation run of an ocean general circulation model ogcm in which a large meander occurs as the background state singular vectors are calculated by the lanczos method in which the tangent linear and adjoint models of the ogcm are used we apply an incremental correction approach for setting up the initial perturbation and averaging for the final norm in order to get modes reflecting nonlinear physics by filtering out high frequency variations the perturbation extracted as the leading right singular vector affects the formation of the large meander most if it is set to the background state two months before when the perturbation is added it enhances an anticyclonic eddy southeast of kyushu in the upper layer which induces downwelling north of it and develops an anticyclonic eddy in the deep layer the anticyclonic eddy produces a cold anomaly at the downstream edge and produces baroclinic instability there resulting in further development of the large meander in contrast the anticyclonic eddy in the deep layer is weakened when the perturbation is subtracted the development of the cold anomaly in the deep layer is delayed and consequently the meander is not so well developed thus singular vector analysis reveals the role of the anticyclonic eddy approaching southeast of kyushu in the upper layer and indicates the importance of the anticyclonic eddy in the deep layer

fractionation of oxygen and iron isotopes by partial melting processes implications for the interpretation of stable isotope signatures in mafic rocks abstract recycling of oceanic crust into the deep mantle via subduction is a widely accepted mechanism for creating compositional heterogeneity in the upper mantle and for explaining the distinct geochemistry of mantle plumes the oxygen isotope ratios 18o of some ocean island basalts oib span values both above and below that of unmetasomatised upper mantle 5 5 0 4 and provide support for this hypothesis as it is widely assumed that most variations in 18o are produced by near surface low temperature processes here we show a significant linear relationship between 18o and stable iron isotope ratios 57fe in a suite of pristine eclogite xenoliths the 18o values of both bulk samples and garnets range from values within error of normal mantle to significantly lighter values the observed range and correlation between 18o and 57fe is unlikely to be inherited from oceanic crust as 57fe values determined for samples of hydrothermally altered oceanic crust do not differ significantly from the mantle value and show no correlation with 18o it is proposed that the correlated 57fe and 18o variations in this particular eclogite suite are predominantly related to isotopic fractionation by disequilibrium partial melting although modification by melt percolation processes cannot be ruled out fractionation of fe and o isotopes by removal of partial melt enriched in isotopically heavy fe and o is supported by negative correlations between bulk sample 57fe and cr content and bulk sample and garnet 18o and sc contents as cr and sc are elements that become enriched in garnet and pyroxene bearing melt residues melt extraction could take place either during subduction where the eclogites represent the residues of melted oceanic lithosphere or could take place during long term residence within the lithospheric mantle in which case the protoliths of the eclogites could be of either crustal or mantle origin this modification of both 57fe and 18o by melting processes and specifically the production of low 18o signatures in mafic rocks implies that some of the isotopically light 18o values observed in oib and eclogite xenoliths may not necessarily reflect near surface processes or components

the cold core eddy and strong upwelling off the coast of new south wales in early 2007 abstract during the austral summer of 2006 07 a series of extreme oceanic events occurred in the tasman sea following a series of strong wind driven upwelling events an intense cold core eddy developed off sydney australia a data assimilating eddy resolving ocean model is used to create a three dimensional time varying reanalysis of these events the reanalysis indicates that the cold anomalies associated with the upwellings were in excess of 5 c near the coast where sea level decreased by as much as 0 2 m the reanalysed three dimensional structure of the cold core eddy shows the eddy leaning to the west north west in towards the continental shelf the diameter of the eddy is about 100 km and the sea level anomaly at the eddy centre peaks at around 1 m with an associated sub surface temperature anomaly in excess of 8 c at 200 m depth corresponding to an upward isotherm excursion of 600 m the circulation around the cyclonic eddy is ageostrophic with upwelling in the southern sector of the eddy where flow is onshore and climbing the continental slope and downwelling in the northern sector where flow is descending off the slope three dimensional trajectories of water parcels around the eddy involve 50 100 m vertical excursions based on the reanalysed circulation and composite satellite images of chlorophyll a we hypothesise that the circulation around the eddy led to significant nutrient enrichment in the euphotic zone around the perimeter of the eddy

the dynamics of error growth and predictability in a model of the gulf stream part i singular vector analysis abstract the recently developed ideas of generalized linear stability theory for dynamical systems are applied to time evolving flows of the gulf stream using a quasigeostrophic numerical model the potential for the growth of perturbations arising from errors and uncertainties in forecasts of the gulf stream is investigated by computing the singular vectors or so called optimal perturbations of time evolving flows using a linearized model and its adjoint the authors calculations reveal that the potential for rapid perturbation growth is greatest in regions of developing straining and shearing flows such regions include developing meanders and regions where eddies form and where existing eddies interact with the main gulf stream it is found that the optimal perturbations of the gulf stream share many features in common with those of the jet streams in the atmosphere the ideas and techniques developed in this paper have been applied to the problem of ensemble prediction of the gulf stream in part ii

isotopic fractionation of zinc in tektites abstract tektites are terrestrial natural glasses produced during a hypervelocity impact of an extraterrestrial projectile onto the earth s surface the similarity between the chemical and isotopic compositions of tektites and terrestrial upper continental crust implies that the tektites formed by fusion of such target rock tektites are among the driest rocks on earth although volatilization at high temperature may have caused this extreme dryness the exact mechanism of the water loss and the behavior of other volatile species during tektite formation are still debated volatilization can fractionate isotopes therefore comparing the isotope composition of volatile elements in tektites with that of their source rocks may help to understand the physical conditions during tektite formation for this study we have measured the zn isotopic composition of 20 tektites from four different strewn fields almost all samples are enriched in heavy isotopes of zn compared to the upper continental crust on average the different groups of tektites are isotopically distinct listed from the isotopically lightest to the heaviest muong nong type indochinites 66 64 zn 0 61 0 30 north american bediasites 66 64 zn 1 61 0 49 ivory coast tektites 66 64 zn 1 66 0 18 the australasian tektites others than the muong nong type indochinites 66 64 zn 1 84 0 42 and central european moldavites 66 64 zn 2 04 0 19 these results are contrasted with a narrow range of 66 64 zn 0 0 7 for a diverse spectrum of upper continental crust materials the elemental abundance of zn is negatively correlated with 66 64 zn which may reflect that isotopic fractionation occurred by evaporation during the heating event upon tektite formation simple rayleigh distillation predicts isotopic fractionations much larger than what is actually observed therefore such a model cannot account for the observed zn isotope fractionation in tektites we have developed a more realistic model of evaporation of zn from a molten sphere during its hypervelocity trajectory the molten surface of the tektite will be entrained by viscous coupling with air that will then induce a velocity field inside the molten sphere this velocity field induces significant radial chemical mixing within the tektite that accelerates the evaporation process our model albeit parameter dependent shows that both the isotopic composition and the chemical abundances measured in tektites can be produced by evaporation in a diffusion limited regime

magnesium isotopic fractionation in chondrules from the murchison and murray cm2 carbonaceous chondrites we present high precision measurements of the mg isotopic compositions of a suite of types i and ii chondrules separated from the murchison and murray cm2 carbonaceous chondrites these chondrules are olivine and pyroxene rich and have low 27 al 24 mg ratios 0 012 0 316 the mg isotopic compositions of murray chondrules are on average lighter d 26 mg ranging from 0 95 to 0 15 relative to the dsm 3 standard than those of murchison d 26 mg ranging from 1 27 to 0 77 taken together the cm2 chondrules exhibit a narrower range of mg isotopic compositions than those from cv and cb chondrites studied previously the least altered cm2 chondrules are on average lighter average d 26 mg 0 39 0 30 2se than the moderately to heavily altered cm2 chondrules average d 26 mg 0 11 0 21 2se the compositions of cm2 chondrules are consistent with isotopic fractionation toward heavy mg being associated with the formation of secondary silicate phases on the cm2 parent body but were also probably affected by volatilization and recondensation processes involved in their original formation the low al cm2 chondrules analyzed here do not exhibit any mass independent variations in 26 mg from the decay of 26 al with the exception of two chondrules that show only small variations just outside of the analytical error in the case of the chondrule with the highest al mg ratio a type iab chondrule from murchison the lack of resolvable 26 mg excess suggests that it either formed 1 ma after calcium aluminum rich inclusions or that its al mg isotope systematics were reset by secondary alteration processes on the cm2 chondrite parent body after the decay of 26 al

isotopic composition of silicon in meteorites abstract samples of bulk meteorites show only mass dependent fractionation of silicon isotopes no isotopic anomalies were found the variation of the ratios 29 si 28 si and 30 si 28 si over the meteorite classes is small 1 per mass unit difference the average si isotopic composition for each class of meteorites is identical within analytical uncertainties this is quite unlike o whose anomalous isotopic abundances in bulk samples differentiate among the classes of meteorites the overlapping abundance ranges of si isotopes among many classes of meteorites suggest closed system behavior for this element prior to meteorite accretion and allow calculation of an average solar system si isotope composition

a reassessment of the iron isotope composition of the moon and its implications for the accretion and differentiation of terrestrial planets abstract the fe isotope composition of planetary bodies may provide constraints on their accretion modes and or differentiation processes but to do so the fe isotope systematics of key planetary reservoirs needs to be determined to investigate this for the moon we measured the fe isotope compositions for a suite of 33 bulk lunar mare basalts and highland rocks combined with published data a compendium of 73 different lunar bulk rocks reveals a statistically significant fe isotope difference between low ti and high ti mare basalts yielding average 57fe 0 127 0 012 2se n 27 and 57fe 0 274 0 020 2 se n 25 respectively relative to the irmm 14 isotopic reference material as lunar basalts are thought to reflect the fe isotope composition of their respective mantle sources the estimated relative proportion of the low ti and high ti source mantle suggests that the lunar upper mantle 57fe value should be close to 0 142 0 026 whilst the composition of highland rocks ferroan anorthosites and mg suite rocks should provide a more global view of the moon the calculation of the mean 57fe value of 15 available highland rock analyses yields 57fe 0 078 0 124 such a value is not defined precisely enough to be of critical use for comparative planetology ferroan anorthosites and mg suite rocks also give unresolvable means it appears that fe isotope heterogeneity among the lunar highland rocks is caused by non representatively too small sample aliquots of coarse grained rocks it can also be the result of mixed lithologies for some when the kinetic effect of olivine tending towards low 57fe and feldspar with predominantly high 57fe is cancelled a more precise 57fe value of 0 094 0 035 is calculated it is indistinguishable from the mean 57fe of impact melts and is also similar to the upper lunar mantle estimate obtained from mare basalts collectively this newly determined fe isotope composition of the bulk moon is indistinguishable from that of the earth and heavier than those reported for other planetary bodies this planetary isotope relationship is only observed for silicon given the currently available mass dependent stable isotope database because both iron and silicon reside in the earth s metallic core in significant quantities this may point to the involvement of metallic cores of the earth and moon in the interplanetary fe and si isotope fractionation rather than via high pressure metal silicate fractionation at the core mantle boundary this would more likely be achieved by partial vaporization of the liquid outer metallic core in the aftermath of a moon forming giant impact

evidence for mass dependent isotopic fractionation of strontium in a glaciated granitic watershed abstract the stable isotope composition of strontium expressed as 88 86sr may provide important constraints on the global exogenic strontium cycle here we present 88 86sr values and 87sr 86sr ratios for granitoid rocks a 150 yr soil chronosequence formed from these rocks surface waters and plants in a small glaciated watershed in the central swiss alps incipient chemical weathering in this young system whether of inorganic or biological origin has no resolvable effect on the 87sr 86sr ratios and 88 86sr values of bulk soils which remain indistinguishable from bedrock in terms of sr isotopic composition although due in part to the chemical heterogeneity of the forefield the lack of a resolvable difference between soil and bedrock isotopic composition indicates that these soils have thus far witnessed minimal net loss of sr a low degree of chemical weathering is also implied by bulk soil chemistry the isotopic composition of sr in streamwater is more radiogenic than median soil reflecting the preferential weathering of biotite in the catchment streamwater 88 86sr values however are indistinguishable from bulk soil 88 86sr values implying that no resolvable fractionation of sr isotopes takes place during release to the weathering flux in the damma forefield analyses of plant tissue reveal that plants rhododendron and vaccinium preferentially assimilate the lighter isotopes of sr such that their 88 86sr values are significantly lower than those of the soils in which they grow additionally 88 86sr values of foliar and floral tissues are lower than those of roots contrary to observations for ca for which sr is often used as an analogue in weathering studies we suggest that processes that discriminate against sr in favour of ca due to the different nutritional requirement of plants for these two elements are responsible for the observed contrast

non chondritic magnesium and the origins of the inner terrestrial planets abstract high precision magnesium mg isotope data obtained using a large geometry high resolution mc icpms are reported for 9 carbonaceous and ordinary chondrites 9 eucrites and diogenites generally considered to originate from asteroid 4 vesta together with 4 martian meteorites and a variety of terrestrial and lunar materials the variation in mg isotopic composition found for mafic and ultramafic rocks mafic minerals and chondrites is smaller than reported previously the range of 26mg and 25mg of 0 6 and 0 3 defines a single mass dependent fractionation line consistent with a homogeneous mix of nucleosynthetic components data for the earth mars and vesta display no systematic mg isotopic differences despite large variations in the level of depletion in moderately volatile elements lunar mare basalts exhibit a significant range in 26mg 0 53 to 0 05 and 25mg 0 27 to 0 02 attributable to magmatic differentiation in the lunar magma ocean lmo lunar basalts derived from early segregated cumulates and thought to be the most primitive are on average slightly 0 17 26mg heavy relative to basalts from the earth mars and vesta however the difference is not well resolved more strikingly all differentiated planets and planetesimals as sampled have mg that is on average isotopically heavy compared with most chondrites analyzed thus far chondrules and cais also are generally heavy in terms of mg so this might reflect sorting of material in the proto planetary disk such an explanation would be similar to one previously proposed hewins r h and herzberg c t 1996 earth planet sci lett 144 1 7 to explain the non chondritic si mg of the earth in this model chondrule like objects separate from volatile rich planetary dust by accumulation in stagnant regions between eddies in the solar nebula small 1 km planetesimals formed by accumulation of such molten material then develop into planetary embryos and thence to larger terrestrial planets by combinations of runaway growth and collisions as such accumulation of molten chondrule like droplets provides an explanation that obviates some of the dynamic difficulties associated with the onset of planetary accretion the non chondritic mg isotopic composition of the earth is consistent with data for li and has important implications for earth s bulk composition and putative hidden reservoirs

seasonal changes in the radiogenic and stable strontium isotopic composition of xijiang river water implications for chemical weathering seasonal changes in strontium sr isotopic systematics in large rivers can effectively track temporal variations in regional chemical weathering and help to better constrain the sr isotopic budget of global oceans however such records are scarce here we present a year long time series of both radiogenic and stable sr isotope measurements 87sr 86sr and 88sr from river water at guiping in the middle reaches of the xijiang river south china temporal changes in chemical weathering in the drainage basin were investigated by recording seasonal changes in the composition of both sr isotopes and major ions in the river water river water 87sr 86sr values range from 0 708487 to 0 710336 with most values being 0 7092 are generally accompanied by high rb sr ratios and low ph and 13c of dissolved inorganic carbo dic and occur during periods of large river flux this indicates that the contribution to the chemistry of river water from the weathering of silicate rocks is enhanced during rainy seasons seasonal variation in river water 88sr is large from 0 147 to 0 661 with higher 88sr values generally corresponding to higher 87sr 86sr values again low 88sr values 0 3 suggest a dominant contribution from the weathering of carbonate rocks whereas the high 88sr values may represent a contribution from intensive weathering of silicate rocks using the time series data we estimated the flux weighted averages of sr concentration 87sr 86sr and 88sr for the xijiang river to be 1 00 mol l 0 70960 and 0 38 respectively the sr concentration and 87sr 86sr results are close to previous estimates while the 88sr value is amongst the highest recorded for the large rivers of the world and is close to that of seawater our results indicate that large rivers draining through tropical sub tropical regions could play an important role in regulating the stable sr isotopic budget of global oceans

pathways of the north pacific intermediate water identified through the tangent linear and adjoint models of an ocean general circulation model 1 this study develops a strategy for tracing a target water mass and applies it to analyzing the pathway of the north pacific intermediate water npiw from the subarctic gyre to the northwestern part of the subtropical gyre south of japan in a simulation of an ocean general circulation model this strategy estimates the pathway of the water mass that travels from an origin to a destination area during a specific period using a conservation property concerning tangent linear and adjoint models in our analysis a large fraction of the low salinity origin water mass of npiw initially comes from the okhotsk or bering sea flows through the southeastern side of the kuril islands and is advected to the mixed water region mwr by the oyashio current it then enters the kuroshio extension ke at the first ke ridge and is advected eastward by the ke current however it deviates southward from the ke axis around 158 e over the shatsky rise or around 170 e on the western side of the emperor seamount chain and enters the subtropical gyre it is finally transported westward by the recirculation flow this pathway corresponds well to the shortcut route of npiw from mwr to the region south of japan inferred from analysis of the long term freshening trend of npiw observation copyright 2013 john wiley sons ltd

the neodymium stable isotope composition of the silicate earth and chondrites abstract the non chondritic neodymium nd 142nd 144nd ratio of the silicate earth potentially provides a key constraint on the accretion and early evolution of the earth yet it is debated whether this offset is due to the earth being formed from material enriched in s process nd isotopes or results from an early differentiation process such as the segregation of a late sulfide matte during core formation collisional erosion or a some combination of these processes neodymium stable isotopes are potentially sensitive to early sulfide segregation into earth s core a process that cannot be resolved using their radiogenic counterparts this study presents the first comprehensive nd stable isotope data for chondritic meteorites and terrestrial rocks stable nd measurements were made using a double spike technique coupled with thermal ionisation mass spectrometry all three of the major classes of chondritic meteorites carbonaceous enstatite and ordinary chondrites have broadly similar isotopic compositions allowing calculation of a chondritic mean of 146 144nd 0 025 0 025 2 s d n 39 enstatite chondrites yield the most uniform stable isotope composition 146 144nd 26 ppm with considerably more variability observed within ordinary 146 144nd 72 ppm and carbonaceous meteorites 146 144nd 143 ppm terrestrial weathering nucleosynthetic variations and parent body thermal metamorphism appear to have little measurable effect on 146 144nd in chondrites the small variations observed between ordinary chondrite groups most likely reflect inherited compositional differences between parent bodies with the larger variations observed in carbonaceous chondrites being linked to varying modal proportions of calcium aluminium rich inclusions the terrestrial samples analysed here include rocks ranging from basaltic to rhyolitic in composition morb glasses and residual mantle lithologies all of these terrestrial rocks possess a broadly similar nd isotope composition giving an average composition for the bulk silicate earth of 146 144nd 0 022 0 034 n 30 in the samples here magmatic differentiation appears to only have an effect on stable nd in highly evolved magmas with heavier 146 144nd values observed in samples with 70 wt sio2 the average stable nd isotope composition of chondrites and the bulk silicate earth are indistinguishable at the 95 confidence level however mantle samples do possess variable stable nd isotope compositions 146 144nd 75 ppm with an average 146 144 nd value of 0 008 if these heavier values represent the true composition of pristine mantle then it is not possible to completely rule out some role for core formation in accounting for some of the offset between the mantle and chondrites overall these results indicate that the mismatch of 142nd between the earth and chondrites is best explained by a higher proportion of s process nd in the earth rather than partitioning into sulfide or s rich metal in the core

stationary waves of the ice age climate abstract a linearized steady state primitive equation model is used to simulate the climatological zonal asymmetries stationary eddies in the wind and temperature fields of the 18 000 ybp climate during winter we compare these results with the eddies simulated in the ice age experiments of broccoli and manabe who used climap boundary conditions and reduced atmospheric co2 in an atmospheric general circulation model gcm coupled with a static mixed layer ocean model the agreement between the models is good indicating that the linear model can be used to evaluate the relative influences of orography diabatic heating and transient eddy heat and momentum transports in generating stationary waves we find that orographic forcing dominates in the ice age climate the mechanical influence of the continental ice sheets on the atmosphere is responsible for most of the changes between the present day and ice age stationary eddies this concept of the ice age climate is complicated by the sensitivity of t

nickel isotope heterogeneity in the early solar system article i nfo ni of bulk iron and chondritic meteorites carbonaceous chondrites have variable positive e 62 ni 0 05 to 0 25 whereas ordinary chondrites have negative e 62 ni 0 04 to 0 09 the ni isotope compositions of iron meteorites overlap with those of chondrites and define an array with negative slope in the e 60 ni versus e 62 ni diagram the ni isotope compositions of the volatile depleted group ivb irons are similar to those of the refractory co cv carbonaceous chondrites whereas the other common magmatic iron groups have ni isotope compositions similar to ordinary chondrites only enstatite chondrites have identical ni isotope compositions to earth and so appear to represent the most appropriate terrestrial building material differences in e 62 ni reflect distinct nucleosynthetic components in precursor solids that have been variably mixed but some of the e 60 ni variability could reflect a radiogenic component from the decay of 60 fe comparison of the e 60 ni of iron and chondritic meteorites with the same e 62 ni allows us to place upper limits on the 60 fe 56 fe of planetesimals during core segregation we estimate that carbonaceous