charcoal records from thermokarst deposits in central yakutia eastern siberia implications for forest fire history and thermokarst development abstract macroscopic charcoal records from a thermokarst lake deposit in central yakutia eastern siberia were used to reconstruct the history of forest fires and investigate its relationship to thermokarst initiation high accumulation rates of charcoal and pollen were coincident in the basal deposits of the thermokarst lake which suggests that both were initially deposited on the forest floor and subsequently reworked and accumulated in the thermokarst depression high charcoal and pollen accumulation rates in the basal deposits dating to 11 000 9000 cal yr bp also indicate that the thermokarst topography developed during the early holocene a lower charcoal accumulation rate after ca 9000 cal yr bp suggests that thermokarst development has been inhibited since this time it also indicates that a surface fire regime has been predominant at least since ca 9000 cal yr bp in central yakutia

vanadium in the massive coral porites a potential proxy for historical wood clearing and burning abstract inshore coral reefs are threatened globally by decreased water quality resulting from anthropogenic land clearing and other drivers understanding the timing and rate of past native vegetation clearing and forest firing is critical for improved catchment management to protect reefs and other coastal ecosystems however commonly used coral based sediment proxies e g ba ca and y ca are controlled partly by variable precipitation and discharge rates no current marine proxy provides a temporal record of rates and areas of land clearing itself here we present a high resolution temporal record 1957 2010 of vanadium calcium v ca ratios in a porites coral colony from the southern great barrier reef gbr that correlates uniformly with historical clearance rates of woody vegetation in the local catchment despite discordant stream discharge we found that the v ca record could not be explained by terrestrial flux nutrient flux hydrocarbon pollution or upwelling and propose that the reaction between hot alkaline ash and the upper soil layer under oxidizing conditions during clearing associated burning may favour formation and desorption of soluble anionic vv species e g hvo 4 2 from soil based iron oxyhydroxides containing less mobile viii the newly soluble v components can then mobilise quickly into the earliest surface runoff and reach coastal seawater where they provide a distinct temporal record in corals that record is temporally decoupled from the sediment bound elements such as y and ba which require greater degrees of erosion to mobilise and thus better reflect particulate sediment flux the porites v ca record documented here captured the temporal effects of specific legislations aimed at regulating and conserving vegetation in the local catchment and may provide a means for evaluating catchment management practices elsewhere the new proxy also may provide records of catchment clearing and firing in prehistoric times with implications for both natural and anthropogenic fire regimes in coastal areas

vanadium in foraminiferal calcite evaluation of a method to determine paleo seawater vanadium concentrations we assess the potential of using foraminiferal calcite as a paleoceanographic indicator of seawater v concentrations laboratory culture experiments show that living benthic and planktonic foraminifera incorporate v into their test in direct proportion to seawater concentrations distribution coefficients relative to the culture solution are d 2 1 10 3 and 2 8 10 3 for g calida and a lobifera respectively we use a cleaning procedure that effectively removes most v rich contaminant phases from foraminiferal calcite preserved in the fossil record including organic matter and mn fe oxyhydroxides mnco3 overgrowths cannot be eliminated since v is conservative in the ocean foraminiferal calcite recently accreted and found in surface sediment samples should have the same v content if this tracer accurately reflects seawater concentrations v ca values for the same species of foraminifera are constant for core top samples collected above the foraminiferal lysocline in different ocean basins the mean distribution coefficients relative to seawater are d 5 8 1 0 10 3 10 3 0 7 10 3 and 32 2 5 x 10 3 for g sacculifer g tumida and c wuellerstorfi respectively these differences suggest that v incorporation is species dependent core top analyses along two submarine rises in the equatorial atlantic and pacific oceans indicate significant dissolution effects with increasing depth of deposition and thus more extensive partial dissolution of the test vca decreases by a factor of three in g tumida increases by up to a factor of four in g sacculifer and increases by a factor of two in c wuellerstorfi no exchange between foraminiferal v and detrital v in sediments is observed over an interval of 200 kyr

mechanisms by which extratropical wave forcing in the winter stratosphere induces upwelling in the summer hemisphere observational evidence presented here suggests that zonal body force in the middle and high latitude winter stratosphere can induce an extensive circulation with upwelling spreading into the summer hemisphere numerical model results are used to investigate the nature of the circulation anomaly and the mechanism by which it is produced it is found that nonlinearity is important in allowing cross equatorial flow which connects the upwelling in the summer hemisphere to the wave forcing in the winter hemisphere the connection between the summer and winter hemispheres in our model is through the cross equatorial flow in the upper stratosphere in a region of low angular momentum gradient the existence of an extensive circulation and the required cross equatorial flow is sensitive to the location of the wave forcing in the winter extratropics it requires that the wave forcing be present between 40 and 60 km and extends equatorward of 30 in the winter stratosphere in the real atmosphere planetary waves presumably break predominantly above 40 km and more equatorward in january and february we therefore expect that such an extensive circulation exists in the atmosphere during late winter indeed our model tracer temperature and zonal wind patterns are very similar to those observed with respect to the response of the nearly global circulation to extratropical wave forcing in winter

decadal variations in trace metal concentrations on a coral reef evidence from a 159 year record of mn cu and v in a porites coral from the northern south china sea geochemical cycles of trace metals are important influences on the composition and function of the marine ecosystem although spatial distributions of most trace metals have now been determined in at least some parts of the oceans temporal variations have barely been studied on account of data limitations in this paper we report on a 159 year record of trace metal concentrations from a porites coral from the northern south china sea scs and discuss how oceanic and climatic processes control variations in mn cu and v concentrations in this region our results show that trace metal concentrations in the coral skeleton demonstrate decadal to interdecadal fluctuations and that their variations are controlled by different mechanisms the input of mn to reef water is partly controlled by the pacific decadal oscillation pdo which controls precipitation and river runoff surface water concentrations of the nutrient like element cu are controlled by summer upwelling to the east of hainan island the concentrations of v show complex interrelationships and are linked to riverine input prior to the 1990 and to upwelling after the 1990 our results imply that in the northern scs ocean atmosphere climate fluctuations such as the pdo and the east asian summer monsoon easm are important factors that influence long term variability of mn cu and v concentrations in seawater by controlling precipitation related river runoff and the strength of upwelling systems

climate and vegetation changes around lake baikal during the last 350 000 years abstract we conducted particle size and pollen analyses on two cores extracted from lake baikal to investigate the response of vegetation to climate change and to assess the differences in vegetation changes between the northern and southern regions of lake baikal over the last 350 kyr vegetation changes in the lake baikal region corresponded well to the fluctuations in median particle size which are indicators of the climate changes in this region forest which was mainly composed of pinus and picea spread widely during the interglacials interstadials of mis 9 7 5 and 1 and open forest or desert covered most areas during the glacial stadial substages however the responses of vegetation to climate changes differed between the northern and southern regions generally vegetation expansion was restricted around the northern region during the interglacial substages equivalent to mis 9 3 7 5 and 5 5 forest spread widely around both the northern and southern regions however sparsely vegetated poor desert open forest covered the northern region during mis 5 3 and 5 1 while forest extended around the southern region in these substages moreover during glacial periods open forest composed mainly of artemisia chenopodiaceae amarantaceae betula and alnus covered the southern region while poor desert open forest covered the northern region these different vegetation responses are considered to have been caused by the geographical characteristics of the regions i e the mountains around the northern region and the plains around the selenga river in the southern region

does the holton tan mechanism explain how the quasi biennial oscillation modulates the arctic polar vortex idealized experiments with the whole atmosphere community climate model waccm are used to explore the mechanism s whereby the stratospheric quasi biennial oscillation qbo modulates the northernhemispherewintertimestratosphericpolarvortex overall theeffectofthecriticallineemphasized in the holton tan mechanism is less important than the effect of the mean meridional circulation associated with qbo winds for the polar response to the qbo more specifically the introduction of easterly winds at the equator near 50 hpa 1 causes enhanced synoptic scale eliassen palm flux epf convergence in the subtropics from 150 to 50 hpa which leads to the subtropical critical line moving poleward in the lower stratosphere and2 createsabarriertoplanetarywavepropagationfromsubpolarlatitudestomidlatitudesin the middle andupper stratosphere e g less equatorwardepf near 508n whichleads to enhancedplanetary wave convergence in the polar vortex region these two effects are mechanistically distinct while the former is relatedtothesubtropicalcriticalline thelatterisduetothemeanmeridionalcirculationofthe qbo allof these effects are consistent with linear theory although the evolution of the entire wind distribution is only quasi linear because induced zonal wind changes cause the wave driving to shift and thereby positively feed back on the zonal wind changes finally downward propagation of the qbo in the equatorial stratosphere upper stratospheric equatorial zonal wind and changes in the tropospheric circulation appear to be less important than lower stratospheric easterlies for the polar stratospheric response overall an easterly qbo wind anomaly in the lower stratosphere leads to a weakened stratospheric polar vortex in agreement with previous studies although not because of changes in the subtropical critical line

an alternative to exotic spore or pollen addition in quantitative microfossil studies uncertainties in availability and formulation of exotic microfossils e g lycopodium spp eucalyptus spp to be added to microfossil preparations may be resolved by the use of plastic microspheres 25 0 1 0 m which are unaffected by standard pollen preparative treatments koh hcl hf acetolysis and organic solvents the microspheres are sensitive to strongly oxidizing treatments e g schulze s reagent h2o2 h2so4 reflux for diatom preparation but can be added following digestion of organic material preparation of microsphere suspensions in a suitable electrolyte e g nacl formic acid water permits calibration by coulter counter of suitable dilutions e g 5000 100 ml 1 for delivery by tipet volumetric flasks the uniformity and distinctive appearance of the microspheres not only facilitate recognition but also provide a constant reference for both size 25 m and volume 8180 m3 as well as a reference standard for computerized microfossil scanning the microspheres are inert

early diagenesis of trace metals cd cu co ni u mo and v in the freshwater reaches of a macrotidal estuary vertical profiles from the water column including the maximum turbidity zone mtz to the consolidated sediment were sampled in september 2000 in the freshwater reaches of the gironde estuary during a complete neap tide spring tide cycle the vertical distributions of dissolved major redox parameters and metals mn fe cd cu v co ni mo and u were determined reactive particulate metal fractions were also determined from selective leaching the studied system is characterized by density layers functioning at different time scales consisting of two mobile layers i e the liquid lm and the soft mud sm overlying consolidated sediments cs this results in a three zone diagenetic regime where 1 o2 dynamics are fast enough to show depletion in the rapidly mixed lm sequence tidal time scale 2 denitrification occurs on the weekly time scale mixing sm sequence and 3 the mn fe and sulfate cycling occurs in the cs layer annual time scale the studied trace metals show differential behavior during early diagenesis 1 cd cu and v are released into pore water preferentially from organic matter in the sm 2 co ni and u are released in the cs from mn and fe oxides during reductive dissolution and 3 mo from both processes transient conditions i e oscillations of redox fronts and reoxidation processes due to the dynamics of the mobile layers strongly influence the trace metal distributions as inducing resolubilization cd cu and mo in the cs authigenic metal phases accumulate either by direct precipitation with sulfides cu cd or co precipitation with fe sulfides mo microbially mediated reduction of fe oxides is proposed to control u removal from pore water by reduction of u vi to u iv at depth however a significant fraction of the trace metals is trapped in the sediment in exchangeable forms and therefore is susceptible to be mobilized due to resuspension of estuarine sediment during strong river flood periods and or dredging activities

copper and copper ii porphyrins of the cretaceous tertiary boundary at stevns klint denmark high levels of copper ii cu 2a were found with the major part s 90 of the total cu located in the smectite cu 175 ppm and kerogen cu up to 1000 ppm of the basal black marl of the cretaceous tertiary kt boundary informal type sedimentary rock the fish clay at stevns klint denmark anomalous abundance 4000 ppm of the kerogen cu 2a porphyrins in this marl was detected by electron spin resonance a model is proposed in which the enormous acid rains caused by the kt asteroid impact washed out the humics already enriched with cu 2a cu 2a porphyrins of the top horizon of the nearby oxic soil into the fish clay basin during the kt event fl 2000 elsevier science b v all rights reserved

world wide delivery of river sediment to the oceans new data and new estimates from old data show that rivers with large sediment loads annual discharges greater than about 15 times 10 6 tons contribute about 7 times 10 9 tons of suspended sediment to the ocean yearly extrapolating available data for all drainage basins the total suspended sediment delivered by all rivers to the oceans is about 13 5 times 10 9 tons annually bedload and flood discharges may account for an additional 1 2 times 10 9 tons about 70 of this total is derived from southern asia and the larger islands in the pacific and indian oceans where sediment yields are much greater than for other drainage basins

vanadium and its isotope composition of river water and seawater analytical improvement and implications for vanadium isotope fractionation abstract investigation of redox variations in recent and paleo oceans has been of particular scientific interest to elucidate the rise and variations of the atmospheric oxygen level by analyses of isotopic signatures of redox sensitive elements like fe mo and u vanadium is another redox sensitive metal that has become the target of stable isotope research during the last decade research of the oceanic v cycle revealed a rather complex interplay of riverine v as a major v source to the oceans on one side with v deposition in sediments and at hydrothermal vents as major sinks on the other the balance between these major v pools is sensitive to the ocean water oxygen level and chemistry the current data set of stable v isotope signatures of seawater is still very small but indicates already subtle variation of the v isotope signatures in the marine environment however the v isotopes of marine sediments and particularly the riverine v isotope composition of dissolved and particulate v i e the major source of v in modern marine environments has not been constrained at all so far in this study we present a new method for efficient v separation from seawater that allows multiple analyses of the v isotope composition of a single sample to separate v from large amounts volume 2 l of seawater samples we employ the bio rad chelex 100 resin and conventional cation and anion resins to yield a high v recovery of 90 from an uv irradiated sample non irradiated samples were marked by lower v recovery rates of ca 75 which was also observed in earlier studies further tests however revealed that even such reduced v yields do not incur significant v isotope fractionation within analytical uncertainty our 51vaa value of 0 27 0 14 2s d n 3 for the nass 6 seawater reference solution perfectly matched earlier results in addition seawater collected in the wadden sea at the german north sea coast is marked by a 51vaa signature of around 0 02 0 19 2s d n 17 which is slightly lower than those of the great oceans and may be related to an influx of river water bioactivity or a tide induced v mobilization to characterize the v isotope composition of the major v source to the oceans we determined for the first time v isotope signatures of 13 selected rivers dissolved and particulate fractions of source water tributary rivers and the yangtze river in the yangtze river basin china a large variation of dissolved v ca 0 07 to 6 0 g l and particulate bound v ca 0 03 to 17 g l was found for the sample suite the obtained 51vaa values of the dissolved v pool span a range of 0 76 0 18 2s d to 0 10 0 22 2s d whereas particulate bound v extends to lower 51v signatures between 2 13 0 30 2s d and 0 11 0 11 2s d notably dissolved v from the river sources and small tributaries scatters between ca 0 4 to 0 7 and agrees well with the predicted average 51vaa value of 0 6 0 3 for continental run off for the lower yangtze river however the dissolved 51vaa signatures increase from the three gorges dam towards the estuary from 0 76 to 0 10 suggesting v isotope fractionation due to adsorption to abundant particulate fe oxides but may also reflect an input of anthropogenic v the low 51vaa of particulate v largely follow this trend and thus indicate ongoing v isotope fractionation during riverine v transport to the ocean our first results of stable v isotope investigation of river waters show that v isotope signatures can indeed carry their host rock signature but are also sensitive to adsorption driven fractionation in oxidized environments the latter strongly depends as predicted from earlier theoretical calculations on the presence of particulate fe oxyhydr oxides and highlights gradual v isotope fractionation during riverine v transport to the ocean

long term fire activity under the east asian monsoon responding to spring insolation vegetation type global climate and human impact inferred from charcoal records in lake biwa sediments in central japan abstract records of sedimentary charcoal provide fire histories for assessing the relationship between fires and climate conditions vegetation human impact and other factors we analyzed charcoal particles in sediments from lake biwa in central japan dating back to 150 000 years ago the sediments are well dated homogenous and had a constant sedimentation rate making them ideal for assessing the long term fire history through charcoal concentration analysis low charcoal concentrations in the glacial periods of marine isotope stage mis 2 and 6 indicate that few fires occurred in the periods under the cold climatic conditions variations in the microcharcoal concentration between 40 000 and 130 000 years ago with a periodicity of 21 000 23 000 years correspond to variations in the spring insolation in central japan vegetation type and global climate suggesting that the long term fire activity in central japan was determined mainly by spring insolation and vegetation type under the influence of global climate change this finding suggests that insolation changes induced by precession cycles could influence a long term phenomenon in an area as a direct local effect between 16 000 and 3000 years ago sediments were characterized by an extraordinarily high concentration of large charcoal particles 50 m and the predominance of elongated charcoal particles suggesting that grassland fires presumably anthropogenic occurred frequently in the lakeside area the frequent fire occurrence presumably contributed to the inflow of a large amount of organic materials resulting in changes in the aquatic environment of lake biwa and or its adjacent area

vanadium accumulation in carbonaceous rocks a review of geochemical controls during deposition and diagenesis abstract published data relevant to the geochemistry of vanadium were used to evaluate processes and conditions that control vanadium accumulation in carbonaceous rocks reduction adsorption and complexation of dissolved vanadium favor addition of vanadium to sediments rich in organic carbon dissolved vanadate v v species predominate in oxic seawater and are reduced to vanadyl ion v iv by organic compounds or h 2 s vanadyl ion readily adsorbs to particle surfaces and is added to the sediment as the particles settle the large vanadium concentrations of rocks deposited in marine as compared to lacustrine environments are the result of the relatively large amount of vanadium provided by circulating ocean water compared to terrestrial runoff vanadium rich carbonaceous rocks typically have high contents of organically bound sulfur and are stratigraphically associated with phosphate rich units a correspondence between vanadium content and organically bound sulfur is consistent with high activities of h 2 s during sediment deposition excess h 2 s exited the sediment into bottom waters and favored reduction of dissolved v v to v iv or possibly v iii the stratigraphic association of vanadiferous and phosphatic rocks reflects temporal and spatial shifts in bottom water chemistry from suboxic phosphate concentrated to more reducing euxinic conditions that favor vanadium accumulation during diagenesis some vanadium organic complexes migrate with petroleum out of carbonaceous rocks but significant amounts of vanadium are retained in refractory organic matter or clay minerals as carbon in the rock evolves toward graphite during metamorphism vanadium is incorporated into silicate minerals

vanadium geochemistry along groundwater flow paths in contrasting aquifers of the united states carrizo sand texas and oasis valley nevada aquifers abstract vanadium v concentrations were measured along the flow paths in two contrasting aquifer systems to study how changing solution composition and redox conditions affect v cycling and transport in groundwater flow systems the oasis valley groundwater system in nevada is an unconfined system where groundwaters generally remain oxic along the flow path whereas the carrizo sand aquifer is a deep confined coastal plain aquifer in texas that contains well defined fe iii and so 4 2 reduction zones along the flow path speciation modeling predicts that in groundwaters from the oasis valley v chiefly occurs as the vanadate oxyanion e g h 2 vo 4 hvo 4 2 which is mobile along the entire flow path because of vanadate s solubility in oxic and alkaline waters furthermore the data indicate that v concentrations increase in groundwaters along the flow path suggesting that mineral dissolution and or desorption reactions progressively contribute v to groundwaters of the oasis valley system geochemical modeling is consistent with dissolution of mafic phenocrysts that are common in the local tuffaceous aquifer rocks as a probable source of v to oasis valley groundwaters within the carrizo sand aquifer groundwater v concentrations decrease with flow beyond the recharge zone and into the confined portion of the aquifer thereafter total v concentrations remain low and relatively constant along the remainder of the studied flow path exhibiting no systematic variations across the fe iii and so 4 2 reduction zones groundwaters from the carrizo sand aquifer are generally reducing and as such geochemical modeling suggests that both v v and v iv species occur in carrizo sand groundwaters and furthermore that the proportion of v iv species increases concurrent with the decrease in total v concentrations along the flow path results from sequential extraction experiments on carrizo sand aquifer sediment samples suggest that v adsorption onto fe iii mn iv oxides oxyhydroxides acts to decrease the aqueous v concentrations in carrizo sand groundwater furthermore geochemical modeling is consistent with complexation of v iv with dissolved organic matter dom within the carrizo sand aquifer groundwaters which owing to the low dom concentrations appears to buffer v at low but relatively constant concentrations within the confined and reducing carrizo sand groundwaters these results support previous reports of v iv dom binding and imply that aquifer material maintains an essential role in not only determining the availability of v to enter aqueous solution but also in influencing partitioning between solid and aqueous phases

tracking the onset of phanerozoic style redox sensitive trace metal enrichments new results from basal ediacaran post glacial strata in nw canada abstract a global rise in oxygen levels has been proposed to coincide with the ediacaran to cambrian radiation of animals yet the precise timing and nature of this change remains unresolved one hypothesis is that the ocean atmosphere system became temporarily well oxygenated in the earliest ediacaran directly following the marinoan snowball earth glaciation 635 ma the evidence for oxygenation is based on large enrichments of redox sensitive trace elements in black shale from south china presumably deposited under a euxinic water column these enrichments meet or exceed the bulk concentrations of redox sensitive trace elements found in phanerozoic shale deposited under euxinic water columns here we test the early ediacaran post snowball oxygenation hypothesis with new data from a high resolution multi proxy geochemical and sedimentological study of three stratigraphic sections in the earliest ediacaran sheepbed formation of the mackenzie and wernecke mountains nw canada iron speciation data from all sections suggest that the local water column was dominantly ferruginous with a notable exception of probable euxinic conditions recorded in part of one section redox sensitive elements show no appreciable enrichments in the basal sheepbed formation with maximum concentrations of molybdenum vanadium uranium and chromium only slightly above world average shale values the lack of substantial elemental enrichments within the sheepbed formation is consistent with results from coeval ferruginous strata in svalbard the dominance of local ferruginous conditions in nw canada cannot alone account for the muted redox sensitive element enrichments as v u and cr are thought to be enriched under these conditions and samples deposited under euxinic conditions also lack phanerozoic style enrichments these contrasting results from different localities highlight a need to further investigate the veracity of trace metal enrichments in all localities as representing global redox conditions as the results have important implications for the timing of oxygenation with respect to early animal evolution

arsenic antimony and vanadium in the north atlantic ocean abstract new measurements of arsenic antimony and vanadium in samples from vertical profiles at nine stations between 50 and 70 n in the atlantic ocean are presented antimonate concentrations exhibit little variation with depth and location the average concentration being 1 16 nmol 1 1 the vertical distribution of arsenate is similar to that reported for the south atlantic and pacific ocean with somewhat lower surface concentrations 14 to 18 nmol 1 1 and uniform deep water concentrations mean 19 nmol 1 1 uniform vertical profiles for vanadium with a mean concentration of 32 6 nmol 1 1 are in agreement with data for the central atlantic but differ from profiles in the pacific which exhibit surface water depletion the presented data for as and v have extended the limited basis for comparison so that inter ocean fractionation processes can now be recognized the concentrations of both as and v show regular increases in the ocean deep water as it passes from the north atlantic as 19 0 v 32 6 nmol 1 1 via the south atlantic as 21 1 nmol 1 1 and indian ocean as 22 5 v 35 6 nmol 1 1 to the pacific ocean as 24 0 v 36 4 nmol 1 1 the magnitude of biological recycling for v and as as deduced from interoceanic fractionation is consistent with estimates based on particle or algal compositions

a model study of the influence of the quasi biennial oscillation on trace gas distributions in the middle and upper stratosphere the dominant tracer transport processes in the equatorial and subtropical latitudes of the middle and upper stratosphere are investigated distributions of water vapor in northern hemisphere winter from the microwave limb sounder onboard the upper atmosphere research satellite are employed together with a three dimensional stratosphere mesosphere model that incorporates a representation of the quasi biennial oscillation qbo the model reproduces the observed tracer distributions in particular a staircase feature that is present in northern winter of 1992 easterly qbo phase but not in 1993 westerly qbo phase this feature is highly asymmetric about the equator the model circulation is diagnosed to show that while the induced qbo circulation in the lower stratosphere of the model is relatively symmetric about the equator in the middle and upper stratosphere it is highly asymmetric and in the correct sense to give rise to the staircase feature model experiments are compared in which trajectories are advected by 1 the full three dimensional circulation and 2 the residual mean circulation only thereby removing the local effects of isentropic mixing by planetary waves on the trajectory distributions these confirm the importance of advection by the qbo circulation at equatorial and subtropical latitudes however sharpening of the tracer gradients at the subtropical edge of the surf zone by the action of planetary waves is shown to be important in the formation of a subtropical cliff between 10 and 20 mbar at 20 30 n the model results also suggest that the prominence of the summer subtropical peak in easterly phase years compared with westerly phase years is not entirely due to increased summer upwelling of the large scale global circulation caused by the stronger planetary wave driving the depression of the winter half of the equatorial peak by the local asymmetric qbo circulation is also shown to be important

modulation of northern hemisphere wintertime stationary planetary wave activity east asian climate relationships by the quasi biennial oscillation 1 the modulation of the relationship between the tropospheric stationary planetary wave activity and the east asian winter climate by the tropical quasi biennial oscillation qbo wind in the stratosphere is investigated in the qbo easterly phase a significant warming appears in northeastern asia in the presence of high wave activities this corresponds to a weakened east asian trough at 500 hpa which determines the extent to which cold waves penetrate into east asia however in the qbo westerly phase both the surface warming and the weakening of the east asian trough become insignificant in response to high wave activities the possible mechanism for this qbo modulation on the tropospheric wave activities may be attributed to the indirect influence of the qbo induced polar and extratropical stratospheric circulation changes under the qbo easterly phase conditions the tropospheric wave activity flux divergence in the higher latitude region is enhanced due to enhanced upward eliassen palm ep flux into the stratosphere while the wave flux convergence in the subtropical troposphere is increased due to the decrease in the equatorward flux this leads to an enhanced wave activity difference and thus the associated east asian climate anomalies become larger and robust an opposite effect i e reduced wave activity difference appears in the qbo westerly phase further analyses reveal that the qbo significantly modulates both the zonal wave number 1 and 2 in the sea level pressure field but not for wave number 3 the combination of wave number 1 and 2 patterns leads to the strongest surface temperature anomalies in northern asia

quasi biennial and subbiennial variations of stratospheric trace constituents derived from haloe observations interannual variability of trace constituents in the stratosphere is examined using methane water vapor and ozone data from the halogen occultation experiment aboard the upper atmosphere research satellitein 1992 99 application of rotated principal component analysis to the dataset reveals dominant modes of variability consisting of annual semiannual and quasi biennial oscillations qbos together with subbiennial variations evidently due to nonlinear interaction between the annual cycle and qbo the structure of quasi biennial variability is approximately symmetric about the equator while subbiennial variability with certain exceptions is approximately antisymmetric and confined mostly to the subtropics the vertical structure and downward propagation of the ozone qbo at the equator is described by a pair of symmetric eofs having separate amplitude maxima in the lower and upper stratosphere a second pair of eofs explains the seasonal dependence of subtropical ozone anomalies for each tracer the subtropical anomaly is larger in the northern hemisphere a novel phase diagram illustrates the joint seasonal and qbo dependence of tracer anomalies a pair of principal components are used to define the phase of the dynamical qbo when plotted against the phase of the annual cycle the qbo follows a diagonal trajectory with regular phase progression except for an occasional slowing of easterly shear zone descent near 50 hpa tracer principal components of symmetric and antisymmetric eofs plotted along this trajectory display the distinct signatures of quasi biennial and subbiennial variation tracer anomalies reconstructed using an idealized representation of qbo and subbiennial harmonics display the seasonal synchronization and decadal modulation characteristic of qbo annual cycle interaction

quasi biennial oscillation in vertical velocity inferred from trace gas data in the equatorial lower stratosphere vertical velocity variations associated with the quasi biennial oscillation qbo in the equatorial lower stratosphere are investigated with the halogen occultation experiment haloe data from 1993 to 1998 the vertical velocity is inferred from ascent rates of an annual cycle in total water h2o 2 ch4 profiles around the 20 60 hpa layer over the equator the zonally averaged ascent rates of total water anomalies exhibit qbo related variations with anomalies of 0 10 0 15 mm s 1 between 20 and 40 hpa at the equator whereas there scarcely exists an annual cycle in the ascent rates the qbo variation of the ascent rates shows that its positive anomalies precede negative anomalies of temperature and ozone variations by about 2 3 months at the equator and 30 60 hpa this phase relationship is in conflict with former results from several two dimensional model studies which have reported that vertical velocity variations are almost out of phase with temperature anomalies preceding ozone anomalies by a few months it is supposed that these differences could be caused by the observed large tendency of temperature anomalies which is related to the observed rapid acceleration of the qbo westerly an estimate of vertical advection of zonal momentum expected from the ascent rates suggests that the asymmetric acceleration of the zonal wind qbo can be explained by the qbo induced vertical velocity being asymmetric between the easterly and the westerly shear zones

osmium isotopic variations in metalliferous sediments from the east pacific rise and the bauer basin the osmium concentration and isotopic composition of metalliferous sediments from the east pacific rise epr and bauer basin have been determined 187os186os ratios range from 7 9 to 8 6 with epr samples between 8 4 and 8 6 and bauer basin samples between 7 9 and 8 2 the osmium isotopic composition of epr samples is indistinguishable from the inferred osmium isotopic composition of seawater requiring that nearly all the osmium in these sediments is hydrogenous in origin this result is used to place broad constraints on the behavior of osmium in ridge crest hydrothermal systems while bauer basin samples also contain predominantly hydrogenous osmium an additional source of osmium with low 187os186os is required to account for the lower measured ratios calculation of total osmium burial fluxes in the bauer basin show that the background flux of cosmic osmium is adequate to produce the observed depression in bauer basin 187os186os ratios burial flux calculations also suggest that metalliferous sediment deposition is a significant sink in the marine osmium cycle

a 850 year record climate and vegetation changes in east siberia russia inferred from geochemical and biological proxies of lake sediments east siberia is very sensitive to moisture regimes because it is located in a margin area where moisture from the north atlantic is strongly depleted and the penetration of the east asian monsoon is weak and rare in winter months the siberian anticyclone strongly blocks and reduces the external influences on the region the high latitude of the study area at 52 n is probably sensitive to variation in insolation and solar activity we analysed a 42 cm long sediment record from lake mountain located in east siberia russia for geochemical mineralogical subfossil diatoms chironomids and pollen to provide a reconstruction of the climate history of the area for the last 850 years according to our reconstruction a clear decrease in summer temperatures occurred in east siberia after ca 1400 and we linked this temperature drop with the beginning of the little ice age the coldest summer occurred about ca 1570 1700 and 1830 1900 we assumed that the most significant changes of the lake bio productivity and the catchment area were occurred about ca 1160 1350 1350 1590 1590 1730 1730 1900 and 1940 to the present the most dramatic period with unfavorable climate conditions for lake biota was during 1590 1730

on the distribution of copper nickel and cadmium in the surface waters of the north atlantic and north pacific ocean concentrations of copper nickel and cadmium have been determined for about 250 surface water samples nonupwelling open ocean concentrations of these metals are cu 0 5 1 4 nmol kg ni 1 2 nmol kg and cd less than 10 pmol kg in the equatorial pacific upwelling zone concentrations of ni 3 nmol kg and cd 80 pmol kg are higher than in the open ocean but cu 0 9 nmol kg is not significantly enriched metal concentrations are higher in cool nutrient rich eastern boundary currents cu 1 5 nmol kg ni 3 5 nmol kg and cd 30 50 pmol kg copper is distinctly higher in the coastal waters of the gulf of panama 3 4 nmol kg and also higher in the shelf waters north of the gulf stream 2 5 nmol kg these copper enrichments may be caused by copper remobilized from mildly reducing shelf sediments and maintained by a coastal nutrient trap in the open ocean events of high cu water 1 5 3 5 nmol kg are seen on scales up to 60 km presumably these are due to the advection of coastal water into the oceanic interior the lowest copper concentrations in the north pacific central gyre 0 5 nmol kg bruland 1980 are lower than in the sargasso sea 1 3 nmol kg while for nickel the lowest concentrations are 2 nmol kg in both the north pacific and the north atlantic nickel and cadmium while generally correlated with the nutrients in surface waters show distinct regional changes in their element nutrient correlations the residual concentrations of trace metals in the surface waters of the ocean can be explained if biological discrimination against trace metals relative to phosphorus increases as productivity decreases

interaction of the quasi biennial oscillation and stratopause semiannual oscillation analysis of rawinsonde and rocketsonde data at ascension island 7 6 s 14 4 w and kwajalein 8 7 n 167 e in 1962 1991 suggests that the quasi biennial oscillation qbo in the middle stratosphere is synchronized with the seasonal cycle and that descending westerly phases of the stratopause semiannual oscillation sao are strongly influenced by the underlying qbo the effect of the seasonal cycle on the qbo in the middle stratosphere is revealed in two perhaps unrelated observations first a tendency for deseasonalized qbo westerly maxima to occur in local winter or to avoid local summer second a smooth uninterrupted connection between descending sao westerly shear zones and the formation of a new qbo westerly shear zone aloft the timing of deseasonalized qbo westerly maxima in the middle stratosphere allows a simple composite of 2 and 3 year cycles to be constructed from the data illustrating the effect of the qbo on descending westerly phases of the stratopause sao

quantitative paleoclimate reconstruction based on a 130 ka pollen record from the c9001c core off ne japan abstract although monsoons are an important climatic factor in the indo pacific region the mechanism responsible for monsoon variations is not fully understood particularly at the 10 5 year scale which includes the milankovitch orbital cycles here we provide a palynological result from the c9001c marine core drilled in the nw pacific off the shimokita peninsula eastern japan based on the parallel 18 o record the pollen record covers the past 130 000 years during the interglacial periods mis1 and 5e the c9001c core is dominated by cool temperate pollen of fagus beech and quercus subgenus lepidobalanus deciduous oak that is similar to the present day shimokita vegetation however during the glacial periods mis2 4 the pollen spectra are dominated by subarctic elements of betula birch and picea spruce similar to the vegetation of sakhalin and northern hokkaido these fossil pollen data are converted into quantitative climate variables by using the modern analog technique of the reconstructed paleoclimate variables the mean annual temperature tann correlates with the parallel 18 o record by contrast reconstructed precipitation in the summer psum shows a similar pattern to the northern insolation variations particularly during mis5 though the phase relation between the two curves requires further studies

vegetation response in the southern lake baikal region to abrupt climate events over the past 33calkyr abstract we reconstructed vegetation changes and fire events in the southern lake baikal region over the past 33 cal kyr using a sediment core from the buguldeika saddle southern lake baikal to examine vegetation response to past short term climate variations herbs such as artemisia and asteraceae were dominant just before the last glacial maximum lgm low pollen accumulation rates pars with little herb pollen indicate sparse herbaceous vegetation cover during the lgm picea expanded after the bolling interval suggesting expansion of riparian areas and shrub alnus rapidly increased during the following allerod interval abies and pinus subgen haploxylon began to increase at the beginning of the holocene and pinus subgen diploxylon has been highly dominant since the middle holocene the vegetation change after the lgm is similar to that from other sites in the lake baikal region but the responses to short term climate events are pronounced fluctuations in herb elements and vegetation cover as indicated by the par correspond to the younger dryas yd cooling event the decline in the par and increase in herb taxa were remarkable at the beginning of the yd but larix and picea trees were distributed in river valleys near lake baikal in the latter half the rapid expansion of betula and artemisia following frequent fires in the early holocene may have been in response to the 8 2 cal ka bp cooling event from these findings the southern lake baikal region including the selenga river basin may possibly have been more sensitive than other parts of the region to abrupt climate changes

dissolved vanadium in rivers and estuaries abstract new measurements of dissolved vanadium in a variety of rivers and estuaries are presented here the data indicate that the average concentration of dissolved vanadium in major rivers entering the ocean is 15 nmol kg weathering rate and type of source rock rather than solution chemistry or anthropogenic influences appear to be the important factors in determining fluvial dissolved vanadium concentrations laboratory experiments suggest that in oxic waters vanadium is found predominantly in its most oxidized anionic form v v complexation with organic matter and formation of large colloidal species appear to be unimportant adsorption also appears to be a less important influence for vanadium than for some other trace elements such as zinc in estuaries vanadium behaves as a bioactive element showing a close correspondence with the distribution of phosphate the extent of estuarine vanadium removal is presently uncertain but may be low due to rapid remineralization of this element based on the river flux the oceanic residence time for dissolved vanadium is estimated to be 100 000 years

seasonal asymmetry of the low and middle latitude qbo circulation anomaly abstract it is usually assumed that the circulation anomaly induced directly by the quasi biennial oscillation qbo in the equatorial zonal wind is approximately a seasonally independent two cell structure symmetric about the equator and confined to the tropics it is shown here using a simple two dimensional model that although the two cell structure exists at equinox at solstice the summer cell disappears and the winter cell is greatly strengthened about three times stronger than at equinox and expanded strong cross equatorial flow is induced near the shear zone where the qbo winds are easterly this result may explain why the observed anomalies in trace gases are small in the summer hemisphere and it also reduces the need for a modulation of the planetary wave fluxes at low and middle latitudes in order to explain the modulation of the circulation there at low latitudes the shape of the isopleths of a modeled tracer closely resemble those observed in both easterly and westerly phases of the q

trace metals in lacustrine and marine sediments a case study from the gulf of carpentaria northern australia abstract sediment cores taken from the shallow the data form remarkably linear covariation trends suggesting physical mixing of two sedimentary components as the predominant process controlling the compositions of both lacustrine and marine sediments one component has high ca sr and mn suggestive of biogenic carbonate the other component contributes virtually all of the sedimentary budget of the other elements and is probably terrigenous clay either water borne or aeolian minor contributions from heavy minerals such as zircon may account for the higher values of zr and y for some horizons in the core anomalously high concentrations of zircon may have been brought into the gulf as dust particles during episodes of increased aeolian activity carbonate is most abundant in the marine sediments resulting in the higher observed ca and sr concentrations v and mn seem to be the metallic elements most sensitive to depositional environment and water chemistry environmental conditions had little or no effect on sedimentation of the other metals v and mn were delivered to the lacustrine sediments more efficiently than to the marine sediments probably reflecting changes in solubility as slightly acid lacustrine waters gave way to more neutral oceanic conditions metal organic complexing was not an important process in these oxidised sediments

millennial scale vegetation changes during the last 40 000 yr based on a pollen record from lake biwa japan abstract a high resolution pollen record covering the last 40 000 yr biw95 4 from lake biwa western japan shows regional vegetation responses to millennial scale climate changes from 40 to 30 ka cryptomeria japonica was dominant around the lake among pinaceous conifers and deciduous broad leaved trees during this period fluctuations of c japonica are correlated with dansgaard oeschger d o cycles recognized from the anhysteretic remanent magnetization arm record increases in the abundance of this taxon may have been caused by wetter summer conditions influenced by the east asian monsoon or increased snowfall on the sea of japan side of the japanese archipelago between 29 and 14 ka pinaceous conifer forests mainly composed of pinus subgenus haploxylon tsuga and picea trees developed at approximately 23 ka picea trees increased in abundance as arm values decreased this expansion of picea trees has been correlated with heinrich event he 2 in the north atlantic at about 14 ka the distribution of broad leaved forest mainly composed of deciduous oaks began to expand after d o 1 evidence of significant vegetation change related to the abrupt younger dryas cooling event has not been found

climatology of the equatorial lower stratosphere abstract twenty years of radiosonde data have been analyzed in an attempt to develop a latitudinal structure climatology of winds temperature and geopotential at 30 and 50 mb in the equatorial stratosphere the fine latitudinal resolution provided by the wmo station network reveals several interesting features in the latitudinal structure of the annual and quasi biennial cycles which dominate this region for example the westerly and easterly acceleration phases of the quasi biennial oscillation are markedly different westerly accelerations appear first at the equator spreading outward with time to higher latitude and an more intense on average than the easterly accelerations the easterly accelerations are more uniform in latitude but leer uniform in time sometimes occurring in two stages the quasi biennial wind and temperature oscillations are symmetric about the equator while the annual harmonic in zonal wind is antisymmetric about the equator but is not proportional to the coriolis paramete

dynamical response in the northern hemisphere midlatitude and high latitude winter to the qbo simulated by ccsr nies ccm 1 an analysis of the relationship between zonal wind in the equatorial stratosphere and zonal wind temperature and eliassen and palm e p flux in the northern hemisphere extratropical winter was performed using the ccsr nies chemistry climate model ccm and the japanese 25 year reanalysis jra 25 data the tropical zonal wind of the ccm was forced by observations including the observational equatorial quasi biennial oscillation qbo the influence of the qbo on the northern hemisphere winter was estimated by a composite analysis with statistical significance the analyses suggest that the difference in latitude of the critical line zero value line of zonal wind in the low latitudes around 10 hpa as well as 50 hpa between the easterly and westerly phases is related to the wave propagation and circulation over the whole depth of the stratosphere the circulation anomaly is further related to the temperature anomaly at the northern hemisphere midlatitudes and the zonal wind anomaly at the high latitudes these results suggest a mechanism through which 10 hpa qbo could influence the polar vortex while the mechanism of 50 hpa qbo influence is unclear but the possibility is not ruled out

global qbo in circulation and ozone part 2 a simple mechanistic model abstract although the phenomenon of equatorial quasi biennial oscillation is relatively well understood the problem of how the equatorially confined qbo wave forcing can induce a signal in the extratroics of comparable or larger magnitude remains unsolved a simple mechanistic model is constructed to provide a quantitative test of the hypothesis that the phenomenon of extratropical qbo is mainly caused by an anomalous seasonal circulation induced by an anomalous eliassen palm flux divergence the anomaly in e p flux divergence may be caused in turn by the relative poleward and downward shift of the region of irreversible mixing breaking of the extratropical planetary waves during the easterly phase of the equatorial qbo as compared to its westerly phase the hemispheric nature of the anomaly wave forcing in solstice seasons viz no wave breaking in the summer hemisphere induces a global circulation anomaly that projects predominantly into the first few zonal hough modes of plumb such a global qbo c

late holocene human impact on the vegetation around mizorogaike pond in northern kyoto basin japan a comparison of pollen and charcoal records with archaeological and historical data abstract pollen and macroscopic charcoal analyses of ams radiocarbon dated sediment from mizorogaike pond located near japan s ancient capital established in ad 794 were used along with archaeological and historical data to reconstruct vegetation change in the northern kyoto basin since 7300 cal yr b p between ca 7300 and 3400 cal yr b p early to late jomon period the site was surrounded by warm temperate forest composed of quercus subgenus lepidobalanus and q subgenus cyclobalanopsis with celtis aphananthe trees with the occurrence of fire disturbance q subgenus lepidobalanus increased from ca 3400 to 1400 cal yr b p late jomon to kofun periods in the early seventh century asuka period pinus started to increase coinciding with a significant charcoal peak probably related to the operation of roof tile kilns near the site pinus continued to increase and q subgenus cyclobalanopsis decreased through the seventh to tenth centuries asuka to heian periods further increase of pinus occurred in the eleventh century possibly reflecting the establishment of the manor of kamigamo shrine from the eleventh to seventeenth centuries heian to medieval periods no significant vegetational change or fire disturbance took place in the eighteenth century the landscape became totally open with poor vegetation and sparse pinus woodland the medieval and early modern landscapes reconstructed from the palaeoecological record are rather similar to those described from studies of ancient artwork and historical documents this study demonstrates that late holocene vegetation change in the northern kyoto basin was closely tied to anthropogenic activities such as the pottery industry and fuel wood collection

molybdenum vanadium and uranium weathering in small mountainous rivers and rivers draining high standing islands abstract rivers draining high standing islands hsis and small mountainous rivers smrs are known to have extremely high sediment fluxes and can also have high chemical weathering yields which makes them potentially important contributors to the global riverine elemental flux to the ocean this work reports on the riverine concentrations ocean flux and weathering yields of molybdenum mo vanadium v and uranium u in a large number of small but geochemically important rivers using 338 river samples from ten lithologically diverse regions these redox sensitive elements are used extensively to infer paleo redox conditions in the ocean and mo and v are also important rock derived micronutrients used by microorganisms in nitrogen fixation unlike in large river systems in which dissolved mo has been attributed predominately to pyrite dissolution mo concentrations in these rivers did not correlate with sulfate concentrations v was found to correlate strongly with si in terrains dominated by silicate rocks but this trend was not observed in primarily sedimentary regions many rivers exhibited much higher v si ratios than larger rivers and rivers draining young quaternary volcanic rocks in nicaragua had much higher dissolved v concentrations mean 1306 nm than previously studied rivers u concentrations were generally well below the global average with the exception of rivers draining primarily sedimentary lithologies containing carbonates and shales fluxes of u and mo from igneous terrains of intermediate composition are lower than the global average while fluxes of v from these regions are higher and up to two orders of magnitude higher in the nicaragua rivers weathering yields of mo and v in most regions are above the global mean despite lower than average concentrations measured in some of those systems indicating that the chemical weathering of these elements are higher in these smr watersheds than larger drainages in regions of active boundaries with andesite dacite lithologies rivers draining young pleistocene rocks had higher concentrations than did older miocene pliocene rocks of a similar composition this work shows that weathering yields of mo v and u from smrs are slightly higher than from large rivers and the age of igneous lithologies in these regions exhibits a measurable control on riverine concentrations of these elements

vanadium in foraminiferal calcite as a tracer for changes in the areal extent of reducing sediments we have used the vanadium concentration in cleaned foraminiferal calcite as a tracer of seawater v changes in the past since the benthic flux of vanadium is sensitive to the redox po tential of sediments changes in the vanadium concentration of seawater should be a reflection of changes that control the redox state of sediments v ca in g sacculifer from an eastern equatorial atlantic core eno66 17ggc is 21 6 2 8 nmol v mol ca this value does not change over 35 kyr indicating that there was no measurable change in seawater vanadium levels over this period potential artifacts from partial dissolution are not significant based on low constant values for foraminiferal fragmentation 6 7 in the top 50 cm of the core a minor correction to account for vanadium associated with mn carbonate overgrowths estimated from two caribbean cores where this mixed phase dominates the deeper v ca values has been applied changes in the areal extent of anoxic and suboxic sediments are thus constrained by this constant value and the standard deviation of the measurement 12 based on a mass balance for vanadium where suboxic sedi ments are a source and anoxic sediments are a sink to the ocean suboxic sediments are predicted to have changed by no more than 0 5 1 5 times the current value assuming no changein the areal extent of anoxic sediments this correspondsto 1 3 3 5 of total ocean sediments given a con stant area of suboxic sediments the areal extentof anoxic sediments didonot increase by more than fivefold or 1 5 of the ocean floor over th e past 35 kyr the significant reductions in deep water oxygen levels and consequent changes in sedimen t redox conditions required by polar nutrient de pletion scenarios are not reflected in the foraminiferal vanadium data over the past 35 kyr this suggests that models which call on less or no changes in deep water oxygen are more likely alternatives

the climatology of the stratospheric thin air model an improved two and a half dimensional chemical dynamical radiative model shows remarkably realistic behaviour in a number of respects the stratospheric mesospheric westerly jet slopes equatorwards with height and is split at mid latitudes in the southern hemisphere the parametrized orographic gravity waves exert a mid latitude drag and are important in splitting the jet and are possibly important in pre conditioning the stratosphere for a sudden warming a large easterly drag is required in the winter high latitude mesosphere in order to obtain a tropical mesospheric westerly jet the summer easterly jet maximum lies above the tropospheric jet due to gravity wave absorption in the lower stratosphere very realistic annual and semi annual cycles are produced in the model with a mesospheric semi annual oscillation forced by tidal drag and gravity waves planetary wave temperatures are also modelled well and wave amplitudes are correlated with the westerly jets in the lower stratosphere zonalmean ertel s potential vorticity gradients strongly influence the wave activity horizontal convergence and heating rates with descent being strongest equatorwards of the vortex edge this forms the basis for an explanation of the inter hemispheric asymmetry in the ozone column nitrous oxide distributions indicate too much equatorial ascent but show a double peak connected with the tropical circulation and steep horizontal gradients near the winter vortex edge

dissolved vanadium in rivers effects of silicate weathering new measurements of vanadium in 15 small california catchments as well as some tributaries of the mississippi river are presented here these measurements complement previously published fluvial vanadium data and allow a re examination of prior conclusions about the geochemistry of vanadium in rivers the data suggest a best estimate of the fluvial flux of dissolved vanadium to be 0 52 gmol year 1 though considerable uncertainty remains in this number dissolved vanadium in rivers appears to be derived largely from the weathering of silicate rocks which leads to a general correlation between dissolved v and si in rivers however rock type can modify this basic correlation as can solubility limits on si the nature of the erosional regime may play some role in modifying fluvial v si ratios but the effect is weak enough to be obscured by other factors fluvial vanadium transport is also potentially affected both by organic matter through complexation and reduction and by the effects of oxygen depletion in lakes reservoirs and fresh water sediments however these factors require additional study the development of methodology to determine vanadium redox speciation in the field would aid the further understanding of the processes affecting the transport of this element through the environment

hydrothermal alteration of basalt by seawater under seawater dominated conditions fresh mid ocean ridge basalt glass and diabase have been reacted with seawater at 150 300 c 500 bar and water rock mass ratios of 50 62 and 125 using experimental apparatus which allowed on line sampling of solution to monitor reaction progress these experiments characterize reaction under what we have called seawater dominated conditions of hydrothermal alteration in an experiment at 300 c basalt glass undergoing alteration removed nearly all mg2 from an amount of seawater 50 times its own mass in the process the glass was converted entirely to mixed layer smectite chlorite anhydrite and minor hematite removal of mg from seawater occurred as a mg oh 2 component incorporated into the secondary clay this produced a precipitous drop in solution ph early in the experiment accompanied by a dramatic increase in the concentrations of fe mn and zn in solution as mg removal neared completion and the glass was hydrolyzed ph rose again and heavy metal concentrations dropped at water rock ratios of 62 and 125 and 150 300 c the mineral assemblage produced was similar to that at a water rock ratio of 50 solution chemistry however contrasted with the earlier experiment in that mg concentrations in solution were greater and ph lower this caused significant leaching of heavy metals at 300 c nearly all of the na ca cu zn and co2 and most of the k ba sr and mn were leached from the silicates h2s al si and possibly co were also significantly mobilized whereas v cr and ni were not little or no seawater sulfate was reduced although submarine hot spring solutions sampled to date along mid ocean ridges clearly come from rock dominated hydrothermal systems evidence from ocean floor metabasalts and from heat flow studies indicates that seawater dominated conditions of alteration prevail at least locally both in axial hightemperature systems and in ridge flank systems at lower temperatures

field and laboratory studies of metal uptake and release by hydrothermal precipitates data for suspended particles from hydrothermal plumes on the mid atlantic ridge mar support uptake of dissolved v and as during formation of fe oxides and release of cu and cd during alteration of sulfides to complement these field observations we carried out laboratory time series experiments to determine the stability of v as cu and cd in precipitates from hydrothermal plumes on the mar and juan de fuca ridge for v and as the metal fe ratio in plume particles remained uniform after sampling in contrast to v and as particulate cu and cd values decreased relative to fe over time in laboratory studies using both plume particles and mound derived sulfides the combined field and laboratory results show that scavenging is an important removal mechanism for seawater v and as whereas oxidative dissolution of hydrothermal precipitates in seawater adds cu and cd to the ocean

the geochemistry of redox sensitive trace metals in sediments abstract we analyzed the redox sensitive elements v mo u re and cd in surface sediments from the northwest african margin the u s northwest margin and the arabian sea to determine their response under a range of redox conditions where oxygen penetrates 1 cm or less into the sediments mo and v diffuse to the overlying water as mn is reduced and remobilized authigenic enrichments of u re and cd are evident under these redox conditions with the onset of sulfate reduction all of the metals accumulate authigenically with re being by far the most enriched general trends in authigenic metal accumulation are described by calculating authigenic fluxes for the 3 main redox regimes oxic reducing where oxygen penetrates 1 cm and anoxic conditions using a simple diagenesis model and global estimates of organic carbon rain rate and bottom water oxygen concentrations we calculate the area of sediments below 1000 m water depth in which oxygen penetration is 1 cm to be 4 of the ocean floor we conclude that sediments where oxygen penetrates 1 cm release mn v and mo to seawater at rates of 140 260 60 150 and 5 10 of their respective riverine fluxes using the authigenic metal concentrations and accumulation rates from this work and other literature these sediments are sinks for re cd and u with burial fluxes of 70 140 30 80 and 20 40 respectively of their dissolved riverine inputs we modeled the sensitivity of the response of seawater re cd and v concentrations to changes in the area of reducing sediments where oxygen penetrates 1 cm our analysis suggests a negligible change in seawater re concentration whereas seawater concentrations of cd and v could have decreased and increased respectively by 5 10 over 20 kyr if the area of reducing sediments increased by a factor of 2 and by 10 20 if the area increased by a factor of 3 the concentration variations for a factor of 2 increase in the area of reducing sediments are at about the level of uncertainty of cd ca and v ca ratios observed in foraminifera shells over the last 40 kyr this implies that the area of reducing sediments in the ocean deeper than 1000 m 4 has not been greater than twice the present value in the recent past

geochemistry and lithofacies of permo carboniferous carbonaceous rocks from the southwestern edge of the bohemian massif germany a contribution to facies analysis of continental anoxic environments abstract the permo carboniferous schmidgaden weiden erbendorf and stockheim basins from southern germany host discontinuous seams of high ash coal and carbargillites which were mined for hard coal explored for uranium and only recently have proved their source rock potential for gaseous and fluid hydrocarbons alteration and facies of these carbonaceous beds were geologically and chemically investigated during silicification which is exclusively confined to the carbonaceous interbeds of pyroclastic depositions element depletion prograded except for zn pb u the anoxic environments under consideration may be subdivided into fluvial swamp upper westphalian beds from schmidgaden weiden erbendorf and stockheim and lacustrine depositions upper stephanian and upper autunian carbargillites from erbendorf weiden bechtsrieth sio 2 mgo cao mo and zr have proved to be most suitable for recognition of these environments whereas u k 2 o and notably cu zn are less appropriate in the ternary plots displaying the organic chemistry of extracts of these carbonaceous beds fluvial swamps have low and lacustrine beds high contents of saturated hydrocarbons all samples show a pronounced oep odd even predominance of n alkanes which partly are environment controlled terrestrial origin partly maturity controlled the high iso and cyclo alkanes of schmidgaden and bimodal n alkyl distribution point to a contribution of algal material finally four basin types bearing carbonaceous rocks are discussed with respect to their economic potential and compared with basins elsewhere cerilly lodeve st hippolyte uinta type i intramontane fault bounded basin swamp type ii volcanic depression with steep relief swamps type iii halfgraben lake type iv volcanic depression with smooth relief lake types i and ii are of interest for hard coal organic hosted u deposits and mainly gasprone types iii and iv however show good source rock potential for crude oil

organic matter and trace element rich sapropels and black shales a geochemical comparison a distinct pliocene eastern mediterranean sapropel i 282 recovered from three ocean drilling program odp leg 160 sites has been investigated for its organic and inorganic composition this sapropel is characterized by high organic carbon corg and trace element contents and the presence of isorenieratene derivatives the latter suggests that the base of the photic zone was sulphidic during formation of the sapropel combined with evidence of bottom water anoxia preservation of laminae high redox sensitive trace element contents and the abundance and isotopic composition of pyrite this leads to the tentative conclusion that almost the entire water column may have been anoxic this anoxia resulted from high productivity and not from stagnation because an approximation of the trace element budget during sapropel formation shows that water exchange with the western mediterranean is needed entire water column anoxia has been suggested earlier for several black shales with regard to the depositional environment and the corg content however only the cenomanian turonian boundary event ctbe black shales appear to be comparable to this sapropel the proposed trace element removal mechanism of scavenging and co precipitation in an anoxic water column is thought to be similar for both types of deposits the ultimate trace element source for the sapropel however is seawater whereas it is hydrothermal and fluvial input for ctbe black shales because they have a larger temporal and spatial distribution nonetheless the corg rich eastern mediterranean pliocene sapropel discussed here may be considered to be a younger analogue of ctbe black shales

the influence of the quasi biennial oscillation on global constituent distributions long lived stratospheric constituents observed by the upper atmosphere research satellite are compared between late northern winters 1991 1992 and 1992 1993 the phase of the quasi biennial oscillation qbo was such that the equatorial zonal wind was easterly westerly in the lower stratosphere during the first second winter in the tropics winter to winter differences in the latitude height distribution of zonally averaged n 2 o and h 2 o are associated with differences in large scale upwelling the qbo s mean meridional circulations and lateral mixing by incident extratropical rossby waves in the extratropics significant differences in zonally averaged n 2 o and h 2 o are also found which are believed to represent the extratropical constituent qbo the transport processes creating the extratropical constituent qbo are tentatively identified in the winter extratropics qbo modulation of the residual circulation appears to dominate in the upper stratosphere while qbo modulated rossby wave isentropic mixing dominates below about 10 mbar analysis of rossby waves at low latitudes as deduced from isobaric constituent distribution maps suggests that the meridional distribution of rossby wave breaking depends on the tropical zonal winds easterly qbo winds prevent rossby wave radiation into the tropics so that a strong constituent concentration gradient is generated in the winter subtropics westerly qbo winds allow some wave radiation into the tropics accompanied by isentropic mixing in the winter subtropics cross equatorial propagation and occasional mixing in the summer subtropics these effects depend on altitude and appear to vary in accord with the descending phases of the qbo

late pleistocene and holocene vegetation and climate records from lake kotokel central baikal region abstract climatically driven late pleistocene and holocene vegetation changes were reconstructed based on pollen records from the sediments of lake kotokel and cheremushka bog located on the eastern shore of lake baikal the described paleoenvironmental record has higher resolution than records collected from lake baikal and unites individual events identified in prior studies of bottom and onshore cores remarkable shifts in landscapes and expansions of index plants are as follows forest tundra and or forest steppe landscape with birch spruce artemisia and poaceae prevailed at ca 50 25 14 c kyr bp tundra and or steppe vegetation dominated by artemisia and poaceae was typical for the last glacial maximum the expansion of shrub birch and willow occurred at ca 15 5 14 c kyr bp two peaks of spruce expansion at ca 47 5 42 4 14 c kyr bp karginian time and at ca 14 5 13 ka bolling allerod warm intervals suggest that the condition were more humid than today a slight increase in artemisia at ca 11 10 5 14 c kyr bp 13 12 ka was indicative of the younger dryas event an expansion of birch forests with fir at ca 12 6 4 ka suggests higher humidity the currently dominant scots and siberian pine forests with birch expanded since 6 4 ka

biogeochemical control on the temporal variability of trace element concentrations in the oubangui river central african republic abstract dissolved ba cd co mn mo ni rb sb sr u and v were measured in the oubangui river central african republic during a complete flood period the dissolved concentrations vary by factors ranging from 1 4 to 8 2 as a function of river discharge sr ba rb and mo concentrations decrease with rising stage ni u sb cd v and mn concentrations increase with rising stage these distributions are explained by a mixing of quick flow mostly surface runoff with delayed flow mostly groundwater the dual origin of stream waters is demonstrated by the major element ratios which are close to a silicate end member during the high flow period and trend towards a carbonate end member during the low flow period moreover geological heterogeneities in the oubangui basin may play a role in the variation of concentrations observed at the basin outlet the previously indicated presence of a subsurface carbonate sequence in the lower part of the basin is confirmed cd v mn and co show peak concentrations during decreasing stage we suggest that biological processes such as release from phytoplanktonic material and dissolution of oxides or carbonate phases may explain this maximum

modulation of antarctic vortex composition by the quasi biennial oscillation using a decade of aura microwave limb sounder observations we show distinctly different n2o distributions in southern hemisphere winter that depend on the phase of the quasi biennial oscillation qbo composites of the nitrous oxide n2o anomalies calculated for westerly and easterly phases show that qbo generated variability originating in the subtropical middle stratosphere fills the midlatitude surf zone by late winter after the spring vortex breakup the anomaly is transported to the antarctic where it remains until the next vortex forms in fall trapped in the newly formed vortex the anomaly descends in isolation through fall and winter arriving in the antarctic lower stratosphere in september about 1 year after it formed this transport pathway explains previously reported variability of n2o and inorganic chlorine cly inside the antarctic vortex and demonstrates that the middle stratosphere qbo affects ozone depletion by modulating antarctic cly

forcing mechanism of the seasonally asymmetric quasi biennial oscillation secondary circulation in era 40 and maecham5 1 the seasonality of the quasi biennial oscillation qbo and its secondary circulation is analyzed in the european reanalysis era 40 and middle atmosphere european centre hamburg model maecham5 general circulation model data sets through the multitaper method singular value decomposition mtm svd in agreement with previous studies the results reveal a strong seasonal dependence of the qbo secondary circulation this is characterized by a two cell structure symmetric about the equator during autumn and spring however anomalies strongly weaken in the summer hemisphere and strengthen in the winter hemisphere leading to an asymmetric qbo secondary circulation characterized by a single cell structure displaced into the winter hemisphere during the solstices in era 40 this asymmetry is more pronounced during the northern than during the southern winter these results provide the first observation of the qbo secondary circulation asymmetries in the era 40 reanalysis data set across the full stratosphere and the lower mesosphere up to 0 1 hpa the mtm svd reconstruction of the seasonal qbo signals in the residual circulation and the qbo signals in eliassen palm ep flux divergences suggest a particular mechanism for the seasonal asymmetries of the qbo secondary circulation and its extension across the midlatitudes the analysis shows that the qbo modulates the ep flux in the winter hemispheric surf zone poleward of the qbo jets the zonal wind forcing by ep flux divergence is transformed by the coriolis effect into a meridional wind signal the seasonality in the stratospheric ep flux and the hemispheric differences in planetary wave forcing cause the observed seasonality in the qbo secondary circulation and its hemispheric differences

mixing zone in the tropical stratosphere above 10 mb observations of trace constituents obtained from the upper atmosphere research satellite in late winter 1991 92 reveal a zone of quasi horizontal stirring in the tropical stratosphere above 10 mb equatorward of the subtropical jet this mixing region was separated from the midlatitude surf zone by a strong gradient of potential vorticity and tracer along the jet axis the jet and accompanying gradients are climatological features mixing equatorward of the jet evidently depends on the phase of the quasi biennial oscillation

diel stream geochemistry taylor valley antarctica unlike temperate and polythermal proglacial streams the proglacial streams in taylor valley tv antarctica are derived primarily from glacier surface melt with no subglacial or groundwater additions solute responses to flow reflect only the interaction of glacial meltwater with the valley floor surrounding the stream channel we have investigated the major minor and trace element 24 h variations of two proglacial melt streams andersen creek and canada stream originating from the canada glacier in tv antarctica both streams exhibited diel mid austral summer diurnal flow variation with maximum flow being more than 50 times the minimum flow dissolved 0 4 m major minor and trace solute behaviors through diel periods were strongly controlled by the availability of readily solubilized material on the valley floor and hyporheic biological exchanges anderson creek had generally greater solute concentrations than canada stream because of its greater receipt of eolian sediment andersen creek also acquired greater solute concentrations in the rising limb of the hydrograph than the falling limb because of dissolution of eolian material at the surface of the stream channel coupled with minimal hyporheic biological exchange conversely canada stream had less available eolian sediment but a greater hyporheic biological exchange which preferentially removed trace and major solutes in the rising limb and released them in the falling limb given the dynamic nature of discharge eolian and hyporheic biological processes solute loads in tv streams are difficult to predict copyright 2012 john wiley sons ltd