atmospheric and depositional environments traced from unique chemical compositions of the snow over an inland high plateau antarctica surface snow samples from the inland high plateau east queen maud land antarctica show unique chemical characteristics they are characterized by high acidity accompanying the high electrical conductivity so that the hydrogen ion is the dominant ion coupling with chloride and nitrate ions the chemical composition differs sharply from sea salts these characteristics appear more clearly than previously reported in antarctica and are most strongly developed in snow samples from the high region the tritium content increases in the inland high area especially in the region higher than 3600 m asl above sea level which corresponds to the region where the effects of katabatic wind have vanished in the glaciological observations the highest tritium content occurs in the vertical profile at a snow pit 3761 m asl 77 00 s 35 00 e which corresponds to the snow deposition in 1966 the concentration is the highest ever reported in antarctica and is almost as high as the one observed in the precipitation in the inland region of north america which is the highest value ever reported in the world all the results suggest that most of the ions contained in snow samples from the inland high plateau especially higher than 3600 m asl are not brought directly through the troposphere from the sea around antarctica but from the higher atmosphere and that they are under the influence of the physicochemical reactions occurring there

na2so4 and mgso4 salts during the holocene period derived by high resolution depth analysis of a dome fuji ice core we analyzed the profiles of ionic chemical species in three 500 mm sections of an ice core from dome fuji antarctica dated 3 0 8 9 and 13 3 kyr bp before present and compared the profiles to those in the surface snow the 3 0 and 8 9 kyr sections are from the holocene and the 13 3 kyr section slightly predates the holocene the analyses were done on 2 mm thick slices within each section at each depth the primary ionic species were na h cl and so 4 2 a the so 4 2 na and mg 2 levels varied with depth in each section over distances ranging from several millimeters to several centimeters also the correlation coefficients between na and so 4 and between mg 2 and so 4 2 for each depth were 0 90 or greater in contrast to the value of 0 59 or less in the surface snow defined here as 0 3 4 m from the surface these results suggest that almost all na and mg 2 in the holocene ice exists as na 2 so 4 and mgso 4 salts and the formation of these salts occurs not only in the atmosphere during transport but also in the firn layer

past and recent tritium levels in arctic and antarctic polar caps tritium concentration was measured in snow deposited at the grip site central greenland and at the vostok station east antarctica from snow pits covering the period 1980 1990 the objective of the study was to investigate tritium concentrations in polar regions several decades after the bomb peak of the sixties and to put them in the context of available data for environmental tritium in the arctic and the antarctic over the last five decades the tritium content of the samples was measured by mass spectrometry using the helium 3 regrowth method in antarctica the tritium concentrations are in the range 70 110 tu the comparison of the bomb tritium history at different locations show that tritium levels increase moving inland where vapour pressure becomes extremely low and therefore more sensitive to the intrusion of stratospheric air masses highly enriched in tritium although most tritium fallout occurred in the northern hemisphere the tritium levels in central greenland in the 80 s in the range 10 40 tu are significantly lower than at vostok unlike antarctica no such continental effect is observed in greenland due to the higher water vapour content of the air masses as evidenced by the much higher snow accumulation rate whereas tritium fallout in antarctica appears to occur as a result of direct injections of stratospheric tritium during winter arctic fallout are the result of the dominant spring injection of stratospheric air at mid latitude in line with the deposition of other stratospheric tracers

glaciochemistry of polar ice cores a review human activities have already modified the chemical composition of the natural atmosphere even in very remote regions of the world the study of chemical parameters stored in solid precipitation and accumulated on polar ice sheets over the last several hundred thousand years provides a unique tool for obtaining information on the composition of the preindustrial atmosphere and its natural variability over the past this paper deals with the chemistry of polar ice focused on the soluble mineral na nh4 k ca mg h f cl no3 so4 and h2o2 and organic methanesulfonate ch3so3 formate hcoo acetate ch3coo and formaldehyde hcho species and their interpretation in terms of past atmospheric composition aerosols and water soluble gaseous species we discuss ice core dating the difficulties connected with trace measurements and the significance of the ionic composition of snow we examine temporal from the last decades back to the last climatic cycle and spatial including examples from coastal as well as central areas of greenland and antarctica variations in the ionic budget of the precipitation and evaluate ice core studies in terms of the chemical composition of our past atmosphere we review 1 how greenland and antarctic ice cores that span the last few centuries have provided information on the impact of human activities and 2 how the chemistry of deep ice cores provides information on various past natural phenomena such as climatic variations glacial interglacial changes el nino volcanic eruptions and large boreal forest fires

densification of layered firn in the ice sheet at dome fuji antarctica in order to better understand the densification of polar firn firn cores from the three sites within 10 km of dome fuji antarctica were investigated using surrogates of density dielectric permittivities e v and e h at microwave frequencies with electrical fields in the vertical and horizontal planes respectively dielectric anisotropy e e v e h was then examined as a surrogate of the anisotropic geometry of firn we find that layered densification is explained as a result of complex effects of two phenomena that commonly occur at the three sites basically layers with initially smaller density and smaller geometrical anisotropy deform preferentially throughout the densification process due to textural effects second layers having a higher concentration of cl ions deform preferentially during a limited period from the near surface depths until smoothing out of layered cl ions by diffusion we hypothesize that cl ions dissociated from sea salts soften firn due to modulation of dislocation movement moreover firn differs markedly across the three sites in terms of strength of geometrical anisotropy mean rate of densification and density fluctuation we hypothesize that these differences are caused by textural effects resulting from differences in depositional conditions within various spatial scales

metamorphism of stratified firn at dome fuji antarctica a mechanism for local insolation modulation of gas transport conditions during bubble close off 1 the evolution of the structure of a 112 59 m long firn core recovered at dome fuji east antarctica was investigated in order to improve understanding of firn densification and bubble formation processes which are important for interpreting local insolation proxies used for astronomical dating of deep ice cores using selected samples we measured physical properties including 1 the relative dielectric permittivities in both the vertical and horizontal planes 2 the bulk density at a resolution of millimeters 3 the three dimensional geometric structure of pore space and 4 crystal orientation fabrics we found that the firn at dome fuji contains horizontal strata with thicknesses of several centimeters near the surface of the ice sheet these strata are characterized by contrasting bulk density earlier field studies suggest that summer insolation causes densification of surface firn down to 30 m density maxima exhibited a clear positive correlation with the strength of structural anisotropy and c axis clustering around the vertical in contrast the correlation is negative in deeper firn confirming previous findings that initially less dense firn became denser than initially dense firn in addition numerous examples of textures indicating that deformation preferentially occurred in weaker layers were found moreover the initially dense firn layers were more permeable for air near the bottom of firn we propose a model linking firn properties with conditions for the gas transport processes near the bottom of firn the model explains how stronger insolation can lead to bulk ice with a lower o2 n2 ratio and smaller total gas content

chemical and isotopic changes in the hydrology of the tauhara geothermal field due to exploitation at wairakei abstract depressurisation of the tauhara field due to massive withdrawal of deep chloride water from the adjacent wairakei field for geothermal power has caused considerably hydrological and chemical changes at tauhara in the undisturbed state 1962 deep chloride water discharged as hot and boiling dilute chloride springs on the east and west flanks of the field the terrace and spa areas respectively while steam from the two phase zone of the deep system produced by absorption into near surface groundwater steam heated sulphatebicarbonate waters and by mixing with chloride water chloride sulphate waters by 1978 1981 the chloride waters had stopped discharging on the western flank the steam flow towards the surface had greatly increased by 5 10 fold increasing the volume and temperature of the steam heated waters but the dilute chloride waters of the terrace area had changed very little silica concentrations in the near surface waters appear to be controlled by the solubility of amorphous silica which is present in the surface zone rocks e g taupo pumice breccias the increased steam flow led to enrichment in the 13 o and d contents of the steam heated waters by loss of secondary steam and enlargement of the area and intensity of steaming ground the latter accompanied by hydrothermal eruptions in 1974 and 1981 generation of the steam heated waters has been modelled using mass heat and isotope balances the model is consistent with observed heat and cold groundwater flows and requires that a large proportion of the heat from adsorbed primary steam is released as secondary steam tritium contents show that the steam heated waters have a mean residence time of 50 100 years in the future invasion of the deep system by cooler surface waters may reduce steam flow and lower surface aquifer temperatures

acidity decline in antarctic ice cores during the little ice age linked to changes in atmospheric nitrate and sea salt concentrations acidity is an important chemical variable that impacts atmospheric and snowpack chemistry here we describe composite time series and the spatial pattern of acidity concentration acy h hco3 during the last 2000 years across the dronning maud land region of the east antarctic plateau using measurements in seven ice cores coregistered measurements of the major ion species show that sulfuric acid h2so4 nitric acid hno3 and hydrochloric acid hcl determine greater than 98 of the acidity value the latter also described as excess chloride excl is shown mostly to be derived from postdepositional diffusion of chloride with little net gain or loss from the snowpack a strong inverse linear relationship between nitrate concentration and inverse accumulation rate provides evidence of spatially homogenous fresh snow concentrations and reemission rates of nitrate from the snowpack across the study area a decline in acidity during the little ice age lia 1500 1900 common era is observed and is linked to declines in hno3 and excl during that time the nitrate decline is found to correlate well with published methane isotope data from antarctica 13ch4 indicating that it is caused by a decline in biomass burning the decrease in excl concentration during the lia is well correlated to published sea surface temperature reconstructions in the atlantic ocean which suggests increased sea salt aerosol production associated with greater sea ice extent

a chemical and isotopic study of the tokaanu waihi geothermal area new zealand abstract the tokaanu waihi geothermal area lies on the northeast flanks of the tongariro volcanic centre an andesitic massif which forms part of the taupo volcanic zone arc subduction system geothermal activity consists of hot springs pools a geyser and an area of steaming ground fumaroles and acidic springs at tokaanu the near neutral ph boiling waters are notable for a high mineral content 3000 mg kg cl relative to other taupo volcanic zone geothermal systems a high b cl ratio and high li alkali ratio the waihi waters and bore waters are lower in mineral content but higher in hco3 so4 mg and ca and represent mixing of deep hot waters with steam heated groundwaters and dilution with cold surface water the sulphate water geothermometer indicates that the deep hot water is at 250 c higher temperatures 350 400 c are indicated for greater depths by the h2s so4 s isotope ratios and the ch4 co2 carbon isotope measurements a minimum residence time of 0 25 ma for co2 and ch4 below the reservoir is proposed but h2s and so4 in the reservoir cannot have coexisted for more than 200 a isotopic analyses of the tokaanu hot spring waters show a significant 180 shift up to 4 from the local meteoric waters some samples show further 180 d and cl enrichment as a result of steam loss at depth and surface evaporation

the rare alkalies in hydrothermal alteration at wairakei and broadlands geothermal fields n z abstract drillcores and waters from wairakei and broadlands geothermal areas new zealand have been analyzed for li rb cs na k mg ca al ti mn and be the drillcores were altered to various degrees at temperatures below 300 c in slightly alkaline chloride water probably derived from rock water interaction in untapped horizons at higher temperature it changes its composition as it leaches ca and na from the rock and adds k rb cs and li evaluation of these changes in relation to the dimensions of the altered zone under observation suggests that a high mass ratio of water to rock e g 100 and a period of up to 1 million years are responsible for the present stage of alteration increase of k and rb in the altered rocks is a result of the formation of abundant adularia in addition to illite the k rb ratio of the rock decreases during alteration but remains higher than that of the fluid only clay materials and zeolites that preferentially absorb rb give slightly lower k rb ratios than the fluid the mineral phases responsible for the uptake of lithium during alteration are chlorite 300 ppm li and quartz up to 430 ppm li li uptake in quartz is considered to be the mechanism by which al rich quartz crystallises from alumino silicates li al atomic ratios of 0 3 0 57 and al concentrations up to 3000 ppm have been observed relatively small concentrations of cs are found in potassic minerals e g 10 ppm cs in adularia 44 ppm cs in illite however 240 ppm cs are found in wairakite from wairakei equilibrated at 235 c lower equilibration temperatures may lead to higher cesium concentrations this effect in conjunction with a more concentrated hydrothermal fluid could explain a content of 4500 ppm cs in wairakite extracted from a drillcore taken in the el tatio geothermal field in chile

the rates of sea salt sulfatization in the atmosphere and surface snow of inland antarctica 1 most of the aerosol particles present in the surface snow and ice of inland antarctica come from primary sea salt sodium chloride and marine biological activity methansulfonic and sulfuric acids melted water from surface snow firn and holocene ice contains mainly sodium chloride and sulfate ions although it is well known that sea salt aerosols react rapidly with sulfuric acid a process known as sulfatization it is not known when this process takes place in this research we undertake to measure the proportion of sea salt aerosols that undergo sulfatization in the atmosphere and surface snow as opposed to deeper ice in order to understand the suitability of sea salt aerosols as a proxy for past climates in deep ice cores we directly measure the sulfatization rates in recently fallen snow 0 4 m in depth collected at the dome fuji station using x ray dispersion spectroscopy to determine the constituent elements of soluble particles and computing the molar ratios of sodium chloride and sodium sulfate we estimate that about 90 of the initial sea salt aerosols sulfatize as they are taken up by precipitation over dome fuji or in the snowpack within one year after being deposited on the ice sheet

ion concentrations in ice wedges an innovative approach to reconstruct past climate variability abstract for atmospheric gases and aerosols snow and ice provide a useful archive of paleoenvironmental history in the northern hemisphere this archive has been largely limited to greenland ice but promising pioneering work has been done recently using chronology of an ice wedge in barrow northern alaska here we investigate past aerosols at the same ice wedge sampling site reconstructing the sea ice fluctuations in the adjacent beaufort sea during the bolling allerod ba and younger dryas yd periods we confirm the integrity of methanesulfonate ion ms concentrations in the biws as marine proxies and then find that the ice wedge has a high ms concentration through the beginning coldest yd periods the high ms concentration indicates that even during the coldest yd periods 12 900 12 700 yrbp the near shore region in the alaskan beaufort sea near barrow may not have been completely filled by permanent sea ice

comparison of holocene electrical records from dome c and vostok antarctica as part of the european project for ice coring in antarctica a new deep ice core is being drilled at dome c two electrical methods have been used on the core drilled so far a new design of electrical conductivity method ecm instrument and a traditional dielectric profiler the two profiles are very similar in both peaks and background consistent with acidity being the dominant influence on both in this part of the record the dome c records have been compared to ecm records from vostok and a tentative match has been made between them this suggests a long term average ratio of accumulation rate of 1 36 between this dome c core and vostok and that the dome c core analyzed so far to 358 m probably includes the very end of the glacial holocene transition

dust and sea salt variability in central east antarctica dome c over the last 45 kyrs and its implications for southern high latitude climate a detailed record of non sea salt calcium a proxy for dust and sea salt sodium a proxy for sea salt covering the last 45 kyr is presented it shows that in the first part of the transition from the last glacial period to the holocene 18 15 kyr bp the changes in dust flux mainly reflect changes at the dust source namely vegetation cover and local climate the changes in the later part of the transition 12 11 kyr bp are similar in extent to the changes seen in sea salt and most likely reflect a reorganization of the atmospheric circulation during the last glacial period considerable variation of dust but not of sea salt is observed pointing to climatic changes in patagonia the main dust source for dome c a comparison of the glacial records from dome c and taylor dome suggests that similar influences controlled aerosol input at both sites during this period

a high altitude snow chemistry record from amundsenisen dronning maud land antarctica in this paper a detailed record of major ions from a 20 m deep firn core from amundsenisen western dronning maud land antarctica is presented the core was drilled at 75 s 2 e 2900 m a s l during austral summer 1991 92 the following ions were measured at 3 cm resolution na mg 2 ca 2 cl no 3 so 4 2 and ch 3 so 3 h msa the core was dated back to 1865 using a combination of chemical records and volcanic reference horizons the volcanic eruptions identified in this core are mount ngauruhoe new zealand 1974 75 mount agung indonesia 1963 azul argentina 1932 and a broad peak that corresponds in time totarawera new zealand 1886 falcon island south shetlands southern ocean 1885 and krakatau indonesia 1883 there are no trends in any of the ion records but the annual to decadal changes are large the mean concentrations of the measured ions are in agreement with those from other high altitude cores from the antarctic plateau at this core site there may be a correspondence between peaks in the msa record and major el nino southern oscillation events

homogeneous climate variability across east antarctica over the past three glacial cycles recent ice core studies have raised the disturbing possibility that glacial interglacial climate changes may be non uniform across antarctica1 2 these findings have been confined to records from the ross sea sector of the continent but significant deviations in other areas would call into question the widely assumed validity of the climate record obtained from vostok east antarctica on large spatial scales3 here we present an isotopic profile from a core drilled at dome fuji4 5 situated 1 500 km from vostok in a different sector of east antarctica the two records show remarkable similarities over the past three glacial cycles the extent of the dome fuji record in both large amplitude changes such as terminations interglacials and interstadials and more subtle glacial events even when the origin of precipitation is accounted for our results indicate that antarctic climate is essentially homogeneous at the scale of the east antarctic plateau possibly as a consequence of the symmetry of the plateau and the adjacent ocean

effect of accumulation rate on water stable isotopes of near surface snow in inland antarctica 1 postdepositional changes in water stable isotopes in polar firn were investigated at three sites characterized by different accumulation rates along the east antarctic ice divide near dome fuji water stable isotopes major ion concentrations and tritium contents of three 2 4 m deep pits were measured at high resolution 2 cm temporally the snow pits cover the past 50 years with snow accumulation rates in the range of 29 41 kg m 2 a 1 around dome fuji oxygen isotopic profiles in the three pits do not show annual fluctuations but instead exhibit multiyear cycles these multiyear cycles are lower in frequency at dome fuji as compared with the other two sites peaks of water stable isotopes in the multiyear cycles correspond to some ion concentration minima in the pits although such relationships are not observed in coastal regions we propose that the extremely low accumulation environment keeps the snow layer at the near surface which result in postdepositional modifications of isotopic signals by processes such as ventilation and vapor condensation sublimation we estimate that oxygen isotopic ratios could be modified by 10 and that the original seasonal cycle could be completely overprinted under the accumulation conditions at dome fuji moreover stake measurements at dome fuji suggest that the large variability in snow accumulation rate is the cause of the multiyear cycles

a tentative chronology for the epica dome concordia ice core a tentative age scale edc1 for the last 45 kyr is established for the new 788 m epica dome c ice core using a simple ice flow model the age of volcanic eruptions the end of the younger dryas event and the estimated depth and age of elevated 10be about 41 kyr ago were used to calibrate the model parameters the uncertainty of edc1 is estimated to 10 yr for 0 to 700 yr bp up to 200 yr back to 10 kyr bp and up to 2 kyr back to 41 kyr bp the age of the air in the bubbles is calculated with a firn densification model in the holocene the air is about 2000 yr younger than the ice and about 5500 yr during the last glacial maximum

interannual variations of snow accumulation on the greenland ice sheet 1985 1996 new observations versus model predictions newly measured time series of net water equivalent accumulation from ice cores are reported for 11 sites located near the 2000 m contour of the greenland ice sheet many of these sites are located in regions where accumulation has not been previously measured we compared these new time series of annual accumulation with previously reported modeled precipitation covering the same time range because ice core accumulation records include both regional and local accumulation components we used adjacent ice core records at six multiple core sites to estimate the local component and extrapolated these results to the five single core sites we investigated the impact of this short scale spatial variability in accumulation on statistical comparisons between the observed accumulation and model precipitation although sealers were required to match the 12 year mean modeled precipitation to the mean observed accumulation a high degree of correspondence between observed interannual accumulation and scaled modeled precipitation was found at 7 of 11 locations the need for scaling and the low correspondence between model simulations and observations at some sites clearly indicate that model improvements are needed although very encouraging a more spatially distributed array of ice core accumulation measurements spanning the same time period as the precipitation modeling is necessary for continued model improvement and validation in agreement with earlier studies the large temporal variability in snow accumulation predicted by modeling and confirmed by ice cores indicates that the ice sheet elevation varies by tens of centimeters from year to year simply because of changing accumulation

a relationship between ion balance and the chemical compounds of salt inclusions found in the greenland ice core project and dome fuji ice cores 1 we have proposed a method of deducing the chemical compounds found in deep polar ice cores by analyzing the balance between six major ions cl no3 so42 na mg2 and ca2 the method is demonstrated for the holocene and last glacial maximum regions of the dome fuji and grip ice cores the dominant compounds depend only on the ion balance and the sequence of chemical reactions in priority order the principle salts are calcium sulfate other sulfates nitrate chloride and carbonate the chemical abundances deduced by this method agree well with the results of raman spectroscopy on individual salt inclusions the abundances in the ice cores are shown to reflect differences in climatic periods the acidic environment of the holocene versus the reductive environment of the last glacial maximum and regional conditions the marine environment of antarctica versus the continental environment of greenland

vapor transport grain growth and depth hoar development in the subarctic snow measurements from the subarctic snowpack are used to explore the relationship between grain growth and vapor flow the fundamental processes of dry snow metamorphism due to extreme temperature gradients the subarctic pack undergoes extensive depth hoar metamorphism by the end of the winter a five layered structure with a pronounced weak layer near the base of the snow evolves grain size increases by a factor of 2 3 while the number of grains per unit mass decreases by a factor of 10 observed growth rates require significant net inter particle vapor fluxes stable isotope ratios show that there are also significant net layer to layer vapor fluxes soil moisture enters the base of the pack and mixes with the bottom 10 cm of snow while isotopically light water vapor fractionates from the basal layer and is deposited up to 50 cm higher in the pack end of winter density profiles for snow on the ground compared with snow on tables indicate the net layer to layer vapor flux averages 6 x 10 7 kg m 2 s 1 though detailed measurements show the net flux is episodic and varies with time and height in the pack with peak net fluxes ten times higher than average a model driven by observed temperature profiles reproduces the layer to layer flux pattern and predicts the observed weak layer at the base of the snow calculated layer to layer vapor fluxes are ten times higher than inter particle fluxes which implies that depth hoar grain growth is limited by factors other than the vapor supply this finding suggests that gain and loss of water molecules due to sublimation from grains takes place at a rate many times higher than the rate at which grains grow and it explains why grains can metamorphose into different forms so readily

limited migration of soluble ionic species in a siple dome antarctica ice core high resolution 10 samples a i glaciochemical analyses covering the last 110 years from a siple dome antarctica ice core reveal limited migration of certain soluble ionic species methane sulfonic acid n03 and mg2 the observed chemical m igration m ay be due in part to seasonal alternation between less acidic winter from h igh sea salt concentrations and m ore acidic summer from high m arine biogenic acid concentrations layers common at coastal sites such as siple dome exact mechanisms to explain the migration are unclear although simple diffusion and gravitational movement are unlikely since new peaks are formed where none previously existed in each case initial migration of each species is both sh allower and earlier at siple dome than at other sites in antarctica where similar phenomena have been observed which may be related to the relatively low accumulation rate at siple dome 13 3 cm ice a i migration appears to be limited to either the preceding or fol lowing seasonal layer for each species suggest ing that paleoclimatic interpretations based on data with lower than annual resolution are not likely to be affected

antarctic aerosol and snowfall chemistry implications for deep antarctic ice core chemistry in this paper we first summarise major findings of recent atmospheric studies of nitrogen and sulphur species present in the boundary layer of coastal antarctic regions we then discuss the implications of such atmospheric data for the interpretation of nitrate ammonium methanesulphonate and sulphate records in deep ice cores extracted from central antarctica in terms of past atmospheric chemistry changes

alteration of the oceanic crust implications for geochemical cycles of lithium and boron abstract fresh tholeiitic basalt glass has been reacted with seawater at 150 c water rock mass ratio of 10 and fresh diabase has been reacted with a na k ca cl fluid at 375 c water rock mass ratios of 1 2 and 5 to understand better the role of temperature basalt composition and water rock mass ratio on the direction and magnitude of b and li exchange during basalt alteration at 150 c slight but nevertheless significant amounts of b and li were removed from seawater and incorporated into a dominantly smectite alteration phase at 375 c however b and li were leached from basalt b behaved as a soluble element and attained concentrations in solution limited only by the b concentration in basalt and the water rock mass ratio li however was less mobile for example at water rock mass ratios of 1 2 and 5 the percent of li leached from basalt was 58 70 and 92 respectively this suggests some mineralogic control on li mobility during hydrothermal alteration of basalt especially at low water rock mass ratios in general these results as well as those for b are consistent with the temperature dependent chemistry of altered seafloor basalt and the chemistry of ridge crest hydrothermal fluids based on the distribution and chemistry of products of seafloor weathering low 150 c and high temperature hydrothermal alteration of basalt and the chemistry of ridge crest hydrothermal fluids it was estimated that alteration of the oceanic crust is a li source for seawater this is not true for b however since the hot spring flux estimated for b is balanced by low temperature basalt alteration these data coupled with b and li flux estimates for other processes e g continental weathering clay mineral adsorption authigenic silicate formation and formation of siliceous skeletal material yield new insight into the b and li geochemical cycles calculations performed here indicate relatively good agreement between the magnitude of b and li sources and sinks the geochemical cycle of b however may be affected by serpentinization of mantle derived peridotite in oceanic fracture zones serpentinites are conspicuously enriched in b and if the b source for these rocks is seawater then an additional b sink exists which must be integrated into the b geochemical cycle however until more data are available in terms of areal extent of serpentinization serpentite chemistry and isotopic composition the importance of b in these rocks with respect to the b geochemical cycle remains speculative at best

antarctic sea ice extent during the holocene reconstructed from inland ice core evidence 1 interannual fluctuations in the antarctic sea ice extent sie affect the global albedo and heat balance and they may affect global co2 levels we found that the annual trend of sodium ion fluxes in the snowpack in the dome fuji region of east antarctica can serve as a proxy for the present day sie in the southern indian ocean and weddell sea sectors we then used sodium ion profiles obtained from the dome fuji ice core to reconstruct the sie during the holocene we observed that 1 the beginnings of both the climatic optimum 12 0 ka bp and neoglaciation 5 4 ka bp in the southern ocean indicated by siliceous microfossil records are consistent with decreases 11 8 ka bp and increases 5 4 ka bp in the sodium ion fluxes in the dome fuji ice core and 2 the interannual fluctuation in the sie during some periods of the neoglaciation was greater than the interannual fluctuation during the climatic optimum

the pinatubo eruption in south pole snow and its potential value to ice core paleovolcanic records snow samples collected in the 1996 austral summer at south pole show that sulfate concentrations in snow and by inference sulfur aerosol concentrations in the antarctic atmosphere were elevated from the end of 1991 to mid 1994 over a stable non volcanic background the new data support earlier findings that the june 1991 pinatubo eruption and the hudson eruption in the same year deposited volcanic sulfate and tephra in south pole snow and provide strong evidence of the global distribution of volcanic materials from the pinatubo eruption in this study snow samples were taken in six snow pits spatially distributed around the south pole station in order to evaluate the local spatial variability of volcanic signals due to glaciological variables such as snow accumulation rates and snow redistribution by wind after initial deposition the results indicate that pinatubo sulfate flux varies by as much as 20 throughout a 400 km2 area centered around the south pole station this glaciological variability probably represents the likely range of volcanic signals due to variations in snow deposition and post depositional changes the pinatubo eruption provides an unprecedented opportunity to estimate aerosol mass loadings by explosive volcanic eruptions found in antarctic ice cores via a quantitative relationship between aerosol mass loadings and sulfate flux in antarctic snow here the satellite estimated pinatubo so2 emission and the measured volcanic sulfate flux in snow with an assumed linearly quantitative relationship are used to calculate so2 loadings for several well known volcanic eruptions in the past 300 years covered by a shallow 42 m south pole firn core drilled in 1996 the errors for the calculated mass loadings are estimated by means of the glaciological variability associated with pinatubo volcanic flux

so42 minimum in summer snow layer at dome fuji antarctica and the probable mechanism 1 by chemically analyzing snow samples at dome fuji antarctica we found that the snowdrift deposited just after snowfall and the snow layer down to 3 4 m have summer minima in the non sea salt nss so42 and na concentrations and summer maxima of cl na such a summer nss so42 minimum in either snowdrift or the snow layer has not been reported at any other site in antarctica and arises in spite of the known maximum in the nss so42 concentration in aerosol at dome fuji in summer we then did laboratory experiments to better understand the phenomenon the results supported the following mechanism for the summer nss so42 minimum in the snowdrift and snow layer in summer water vapor sublimates from within the snow in the daytime and condenses on the surface as frost in the nighttime resulting in a dilution of the nss so42 concentration this sublimation condensation process likely occurs at other cold inland regions in addition the results might be useful for obtaining a high resolution dating method for dome fuji deep ice cores by counting the number of layers with low nss so42 concentration

geometry and kinematics of the arlar strike slip fault sw qaidam basin china new insights from 3 d seismic data abstract the right stepping en echelon kunbei fault system consisting of the hongliuquan arlar xiii and kunbei faults features importantly in the tectonic evolution of the southwest qaidam basin the 3d seismic cross section interpretation and key horizon similarity attribute analysis show that the nww striking arlar fault is composed of two steeply dipping faults f1 and f2 in cross sectional view and branches eastward into two west dipping faults f5 and f6 in map view the fact that the strata above t 2 the base of the early miocene xiayoushashan formation become dramatically thinner toward the high points of the arlar fault suggests an early miocene initiation ca 22 0 ma for this fault as indicated by the windowed amplitude related attribute maps the arlar fault and f5 one branch of the arlar fault have cumulative sinistral offsets of 8 6 8 7 km and 5 2 5 4 km respectively these considerably greater strike slip components in conjunction with the respective maximum true dip slip displacements of