stable isotope compositions of waters in the great basin united states 3 comparison of groundwaters with modern precipitation 1 groundwater samples from wells and springs scattered over most of the great basin province were collected and analyzed for their isotopic makeup they were augmented by previously published isotopic data on groundwaters from southeast california and by several hundred unpublished isotopic analyses the ratio of 2h deuterium d to 1h in water samples from valleys in parts of california idaho nevada oregon and utah are here compared with the winter summer and annual isotopic compositions of precipitation falling in or near the sampled areas the main goal of this study was to identify basins where the groundwaters have isotopic compositions that are lighter depleted in the heavier isotope d relative to modern winter precipitation where these basins do not adjoin substantially higher terrain we consider those light groundwaters to be of pleistocene age and thus more than 10 000 years old where the groundwater is 10 to 19 lighter than local winter precipitation we consider it to be possibly an indication of pleistocene water where the d makeup is 20 lighter we consider it to be probably pleistocene water more than 80 sites underlain by waters of possible or probable pleistocene age were identified

integrated seismic studies of the baltic shield using data in the gulf of bothnia region in the autumn of 1989 a co operative experiment involving 12 research institutions in northwestern europe collected 2268 km of deep seismic reflection profiles in the gulf of bothnia and the baltic

light stable isotope systematics of large scale hydrologic regimes in california and nevada surface waters shallow groundwaters and precipitation samples were collected along three traverses which begin at the california coast and are oriented in an east west manner roughly parallel to the atmospheric flow path of meteoric water the hydrogen isotope compositions from short term precipitation records varied as much as 40 at one location and were not representative of the average annual isotopic composition of precipitation the hydrogen isotope ratios of surface waters and shallow groundwaters distinguish segments with isotopic variations that correlate with measured vertical fluxes of meteoric water one coastal segment appears to closely approximate an open system in which precipitation dominates over evapotranspiration most segments are described by rather regular variations in d 3 45 per 100 km which represent different degrees of closure of the hydrologic system caused by variable partitioning of precipitation between runoff and evapotranspiration all partially closed systems imply terrestrial recycling of water a simple model estimates this amount to be about 20 across northern and central california three segments representing the great basin show virtually no geographic variation and appear to represent isotopically closed systems

paleoclimatic significance of δd and δ13c values in pinon pine needles from packrat middens spanning the last 40 000 years we compared two approaches to interpreting dd of cellulose nitrate in pinon pine needles pinus edulis preserved in packrat middens from central new mexico usa one approach was based on linear regression between modern dd values and climate parameters and the other on a deterministic isotope model modified from craig and gordon s terminal lake evaporation model that assumes steady state conditions and constant isotope effects one such effect the net biochemical fractionation factor was determined for a new species pinon pine regressions showed thatdd values in cellulose nitrate from annual cohorts of needles 1989 1996 were strongly correlated with growing season may august precipitation amount and d 13 c values in the same samples were correlated with june relative humidity the deterministic model reconstructed dd values of meteoric water used by plants after constraining relative humidity effects with d 13 c values growing season temperatures were estimated via modern correlations with dd values of meteoric water variations of this modeling approach have been applied to tree ring cellulose before but not to macrofossil cellulose and comparisons to empirical relationships have not been provided results from fossil pinon needles spanning the last40 000 years showed no significant trend in dd values of cellulose nitrate suggesting either no change in the amount of summer precipitation based on the transfer function or dd values of meteoric water or temperature based on the deterministic model however there were significant differences in d 13 c values and therefore relative humidity between pleistocene and holocene published by elsevier science b v

identification of blind geothermal resources in surprise valley ca using publicly available groundwater well water quality data abstract geothermal resource exploration is generally limited to areas with surface expressions of thermal activity fumaroles and hot springs or relies on expensive geophysical exploration techniques in this study the hidden subsurface distribution of geothermal fluids has been identified using a free and publicly available water quality dataset from agricultural and domestic water wells in surprise valley northeastern california thermally evolved waters in surprise valley have element ratios that vary in response to ca carbonate and mg silicate mineral precipitation and have elevated total dissolved solids tds the arid climate in surprise valley leads to surface water evaporation in a closed basin producing high tds na cl co3 so4 brines in three ephemeral alkali lakes and in shallow groundwater under elevated soil co2 conditions evaporated fluids in surprise valley follow a chemical divide that leads to ca carbonate and mg silicate mineral precipitation plots of dissolved element ratios can be used to distinguish groundwater affected by evaporation from water affected by thermal water rock interaction however it is challenging to select components for plotting that best illustrate different fluid evolution mechanisms here we use a principal component analysis of centered log ratio transformed data coupled with geochemical models of fluid evaporation and thermal mixing pathways to identify components to plot that distinguish between groundwater samples influenced by evaporation from those influenced by thermal processes we find that groundwater samples with a thermal signature come from wells that define a coherent linear geographical distribution that closely matches the location of known and inferred faults modification of the general approach employed here provides promise for identifying blind geothermal resources in other locations by applying low cost geochemical modeling and statistical techniques to areas where large groundwater quality geochemical datasets are available

climatological significance of δ18 o in precipitation and ice cores a case study at the head of the urumqi river tien shan china stable oxygen isotope ratios 18 o of precipitation and ice core samples collected from the headwaters of the urumqi river tien shan china were used to test the relationship between 18 o and contemporaneous surface air temperature t a a strong temporal relationship is found between 18 o in precipitation and t a particularly for the monthly averages which remove synoptic scale influences such as changes in condensation level condensation temperature and moisture sources yao and others 1996 linear fits as high as 0 95 c for precipitation events and 1 23 c for monthly averages are found although the 18 o amplitude in ice cores drilled at the nearby urumqi glacier no 1 2 km from the precipitation sampling site decreased dramatically compared to the precipitation samples the ice core records of annually averaged 18 o are still positively correlated with contemporaneous air temperature especially summer air temperature at the nearby daxigou meteorological station nevertheless the relationship between the ice core 18 o records and contemporaneous air temperature is less significant than that for the precipitation samples due to depositional and post depositional modification processes which are highlighted by the successive snow pit 18 o profiles from the urumqi glacier no 1 our results might extend the application of high altitude and subtropical ice core 18 o t a records for palcoclimate reconstruction

comparison of the crustal structures of the barents sea and the baltic shield from seismic data abstract a compilation of the available seismic refraction and wide angle reflection data from the barents sea and the baltic shield and a comparison of the crustal structures of both areas are presented seismic cross sections and velocity depth models of the crust have been analyzed six areas differing in crustal structure are revealed and outlined in the barents sea region as a result of the velocity depth models analysis three main layers are distinguished in the central area the upper layer with an average velocity of 3 5 km s overlies two layers with velocities of 5 5 and 6 8 km s the average thickness of the crust is 33 km the crustal structure in the area is anomalous as compared to the marginal areas of the sea and is distinguished by the absence of the 6 2 km s velocity layer combined seismic cross sections for the coastal and marine seismic profiles show that the main seismic boundaries with velocities of 6 2 6 5 6 8 7 2 and 8 0 8 2 km s can be confidently interpolated from the northern part of the baltic shield to the southern part of the barents sea the junction of their crusts is marked by a deepening of the crystalline basement with a seismic velocity of 6 2 km s the sedimentary cover thickness increases to 15 20 km and the total thickness of the crust is reduced northward from 40 60 to 28 30 km a comparison of the models shows that the barents sea basin and the baltic shield appreciably differ in the total thickness of the earth s crust under the basin it is just about 10 km less than on the shield both regions have an important similarity seismic velocities in the lower crystalline crust 7 0 km s are similar their fundamental difference is that the upper part of the crystalline crust with a seismic velocity of 6 0 6 5 km s characteristic of the baltic shield is absent in the central barents sea basin and a thick sedimentary layer with velocities to 5 8 km s exists instead of it the anomalous crustal structure in the central part of the barents sea is assumed to be of a riftogenic nature

the crustal structure along the polar profile from seismic refraction investigations abstract seismic refraction investigations along a 440 km long profije on the northern baltic shield have resolved the crustal structure in this area of archaean to early proterozoic lithosphere formation the profile called the polar profile extends approximately along a sw ne oriented line from the karelian province in northern finland across the lapland granulite belt and the kola peninsula province to the varanger peninsula in northeastern norway at six shotpoints large explosions 200 1680 kg and at three shotpoints small explosions 80 kg were detonated and recorded at an average station spacing of 2 km providing high quality record sections a two dimensional cross section of the crust was obtained by forward modelling using ray tracing techniques high velocity bodies are found in the upper crust related to the karasjok kittila greenstone belt and the lapland granulite belt they extend to a depth of 6 13 km in the karelian province in the southwest a low velocity zone was found between the depths of 8 and 14 km the middle crust shows a slight increase in the average velocities from the southwest to the northeast and a small velocity jump is found along a mid crustal boundary between 18 and 21 km the thickness of the middle crust varies between 16 and 18 km the lower crust and the crust mantle boundary moho show considerable lateral variation the top of the lower crust lies between 26 and 33 km while its thickness decreases from 21 km in the southwest to 10 14 km beneath the lapland granulite belt and the inari terrain reaching 20 km again in the extreme northeast the velocities also change laterally the thin lower crust is characterized by rather low velocities 6 8 6 9 km s whereas in the southwest and northeast the velocities 6 9 7 3 km s resemble more typical shield structures the moho is found at 47 km in the karelian province rises to 40 km beneath the lapland granulite belt and descends to 46 km in the northeastern part of the kola peninsula province the upper mantle velocities at the moho range from 8 1 km s in the region of the thin crust to 8 5 km s and more beneath the karelian province it is tempting to suggest that the anomalous lower crust underlying the lapland granulite belt and the inari terrain may represent the remnants of an early proterozoic back arc basin that was active prior to the 2 0 to 1 9 ga plate convergence event during which the lapland granulite belt was thrust onto the archaean basement of the karelian province another explanation is to assume that the velocity reduction in the anomalous lower crust was caused by a rather pronounced uplift of this region following the 1 9 ga collision event

stable isotopic evidence for a pre middle miocene rain shadow in the western basin and range implications for the paleotopography of the sierra nevada 1 a recently proposed method for approximating the paleorelief of mountain belts makes use of the predictable relationship between the isotopic depletion of precipitation and the net elevation of an orographic barrier over which an air mass rises this rain shadow effect often creates desert regions on the lee side of mountain belts in which precipitation is isotopically light changes in the isotopic composition of precipitation can be estimated from the isotopic composition of authigenic or pedogenic minerals which can then be used to infer both the development of relief during orogenesis as well as the stability of a rain shadow formed by developing mountains the 18o of smectites formed from the weathering of middle miocene to late pliocene volcanic ashes currently exposed in the rain shadow of the modern sierra nevada of california show no indication of large scale late cenozoic surface uplift of the sierra and corresponding regional rain shadow development rather smectite isotope data tentatively suggest that elevations may have decreased over this time by as much as 2000 m toward the southern end of the range and 700 m in regions farther north this suggests that the modern rain shadow cast over the western basin and range has been in existence since pre middle miocene and that the sierra nevada have been a prominent orographic barrier since before this time these interpretations are in accord with several recent studies also suggesting a possible cenozoic elevation loss of an already developed sierra nevada mountain range

reflection seismic measurements across the granulite belt of the polar profile in the northern baltic shield northern finland abstract reflection seismic measurements were carried out in 1985 on the central part of the polar refraction seismic profile in northern finland the survey was planned and executed jointly by the universities of helsinki uppsala and hamburg using digital equipment with a total of 144 channels by repeating the shots and moving the geophone spreads every day we were able to observe a 42 50 km recording spread referred to reflection elements a line of 84 km total length through the source receiver midpoints was recorded we processed the results up to normal moveout corrected time sections a number of reflectors dipping 8 15 to the northeast were recorded in the lapland granulite belt range these represent a system of sheared granulites which were observed on the surface in the southern part of the profile from gravity modelling the bottom of the dipping layers coincides with the lower boundary of the granulites between the depths of 22 and 35 km the crust in this area seems to be transparent to seismic signals this leads to the assumption that the middle part of the crust is characterized by gentle velocity and density gradients the crust mantle boundary seems to be a layered moho with good reflectors lying at depths between 40 and 44 km

crustal structure of the baltic shield based on off fennolora refraction data abstract since the early 1960s deep seismic sounding experiments have been carried out on the baltic shield in this study we will mainly concentrate on the results obtained from two international profiles sveka and baltic carried out in finland in 1981 and 1982 results from these profiles are shown and discussed and compared with those obtained from the fennolora and from the other recent refraction profiles of the baltic shield in fennoscandia according to the results from sveka and baltic and average crustal velocity is 6 6 6 7 km s which is rather high several distinct reflection boundaries have been found within the crust in the lower part of the crust a high velocity layer with a p wave velocity of 7 0 7 5 km s has been found in some cases in addition the results indicate that the crustal structure has a clear block like character different blocks being separated from each other by deep fractures the crustal thickness in the baltic shield is about 45 km on average whereas around the ladoga bothnian bay zone in central finland it is about 10 km thicker than this thus there is a large scale depression in the moho boundary in the central part of the baltic shield

isotope ratios of nonexchangeable hydrogen in soils from different climate zones abstract the fractionation of h isotopes in global precipitation leads to a continuous decrease in 2 h concentrations of precipitation with increasing latitude altitude and continentality thus the local precipitation soil and ground water used by plants for photosynthesis or consumed during neoformation of pedogenic clay minerals often have a spatially diagnostic 2 h value we hypothesize that the 2 h value of isotopically nonexchangeable h in bulk soil composed of c bonded h in soil organic matter som and the nonexchangeable fraction of o bonded h in pedogenic clay minerals is correlated with the mean 2 h value of local precipitation water at the place and time of biomass production and clay mineral neoformation respectively we equilibrated soil samples with water of known isotopic composition prior to 2 h analysis with an elemental analyzer isotope ratio mass spectrometer ea irms to determine the 2 h value of isotopically nonexchangeable h in soil we analyzed 12 topsoil samples from different climate zones temperate zone subarctic zone and tropics the 2 h values of nonexchangeable h in soil ranged from 75 to 167 the 2 h values of nonexchangeable h in soil were highly correlated with predicted average annual 2 h values of local precipitation at the sampling sites r 0 89 p 2 h values of nonexchangeable h in soils from siberia were up to 80 depleted in 2 h compared to soils from central europe which directly corresponds to the difference in average annual 2 h values of precipitation from central europe and siberia our study supports the hypothesis that the average h isotope composition of local precipitation is the primary control of the isotopic composition of nonexchangeable h in bulk soils since 2 h values of nonexchangeable h in som and pedogenic clay minerals are both primarily determined by 2 h values of global precipitation 2 h analyses of bulk soil samples are meaningful irrespective of the precise fractions of som and clay minerals in soil

isotope characteristics of meteoric water and groundwater in the sahelo sudanese zone the stable isotopic concentration 18o and 2h of water in phreatic aquifers in the sahelo sudanese zone of africa is representative of the original mean rainfall contributing to ground water recharge the isotopic decrease of 18o in the rainwater and groundwater 0 084 100 km 1 showed an east west gradient this suggests a supply of water vapor transported by the zonal flows east african jet tropical easterly jet and easterly waves thus increasing the contribution from the evaporating surfaces of the indian ocean in relation to that of the guinean monsoon the gradient also indicates the importance of atmospheric recycling of continental water through evapotranspiration a model of conservation of the isotopic masses is presented which takes into account the return of continental vapor toward the rain giving clouds the remaining fraction of water vapor during the east west transit between djibouti and dakar is thus determined by evapotranspiration

stable isotope composition of precipitation across the southern patagonian andes 1 a surface water and precipitation transect across the southern patagonian andes at 47 48 s was conducted to assess how mountains affect the isotopic composition of precipitation this westerly wind region derives its moisture that falls as precipitation from the pacific orographic uplift of air over the andes causes pseudoadiabatic cooling and orographic precipitation on the western side and a strong rain shadow on the eastern side of the mountains these processes also produce a profound isotopic rain shadow with 18o values 4 lower in the east compared to the west on the windward western side of the andes the isotope values of precipitation and surface waters show weak although systematic trends with elevation but a pronounced correlation with distance from the main source of moisture pacific ocean a rayleigh simulation of precipitation 18o values as a function of condensation altitude matches our data well suggesting that other processes such as mixing of water sources and postcondensation evaporation are negligible and that topography is the dominant control on the isotope ratio of precipitation in contrast isotope ratios of waters on the leeward eastern side of the southern patagonian andes vary neither with elevation nor with distance from the mountains consistent with much of the precipitation on the leeward side being derived from precipitation carried over the andes by winds thus paleoprecipitation isotopic composition on the leeward side of orogens in similar climatic settings single moisture source and cool climate yield useful estimates of the elevation of these orogens but not local elevation

predicting paleoelevation of tibet and the himalaya from δ18o vs altitude gradients in meteoric water across the nepal himalaya the 18o value of meteoric water varies with elevation providing a means to reconstruct paleoelevation if the 18o values of paleowater are known in this study we determined the 18o values of water 18omw from small tributaries along the seti river and kali gandaki in the nepal himalaya we found that 18omw values decrease with increasing altitude for both transects 18omw vs altitude along the kali gandaki in west central nepal fit a second order polynomial curve consistent with increasing depletion of 18o with increasing elevation as predicted by a rayleigh type fractionation process this modern 18omw vs altitude relationship can be used to constrain paleoelevation from the 18o values of miocene pliocene carbonate 18oc deposited in the thakkhola graben in the southern tibetan plateau paleoelevations of 3800 480 m to 5900 350 are predicted for the older tetang formation and 4500 430 m to 6300 330 m for the younger thakkhola formation these paleoelevation estimates suggest that by 11 ma the southern tibetan plateau was at a similar elevation to modern

hydrogen isotope study of large scale meteoric water transport in northern california and nevada abstract the depletion of deuterium in surface and shallow groundwaters along a traverse through northern california and nevada is used to model the local hydrologic balance as controlled by the eastward flux of meteoric water in a way not possible by conventional methods when plotted against distance from the pacific ocean our data indicate three hydrologic provinces which differ in their relative degree of openness isotopic variations of groundwater in the first province are governed by rayleigh distillation from the eastward moving storm clouds some 40 of the storm water vapor precipitates out before reaching the california coast and another 16 in the first 55 km across the continent the isotopic depletion in the second hydrologic province is linear with distance and this suggests extensive recycling of terrestrial water the third province constitutes the great basin characterized by the lack of significant hydrogen isotope variation of groundwater is thought to be an isotopically closed system the quantity of water crossing the coast calculated from a model that incorporates the rayleigh distillation equation is approximately equal to the quantity of precipitation along the northern california part of the transect studied this illustrates the importance of evapotranspiration in the terrestrial water budget as well as the dependency of inland areas on the eastward flux of recycled terrestrial water

a conceptual geochemical model of the geothermal system at surprise valley ca abstract characterizing the geothermal system at surprise valley sv northeastern california is important for determining the sustainability of the energy resource and mitigating hazards associated with hydrothermal eruptions that last occurred in 1951 previous geochemical studies of the area attempted to reconcile different hot spring compositions on the western and eastern sides of the valley using scenarios of dilution equilibration at low temperatures surface evaporation and differences in rock type along flow paths these models were primarily supported using classical geothermometry methods and generally assumed that fluids in the lake city mud volcano area on the western side of the valley best reflect the composition of a deep geothermal fluid in this contribution we address controls on hot spring compositions using a different suite of geochemical tools including optimized multicomponent geochemistry geot models hot spring fluid major and trace element measurements mineralogical observations and stable isotope measurements of hot spring fluids and precipitated carbonates we synthesize the results into a conceptual geochemical model of the surprise valley geothermal system and show that high temperature quartz na k na k ca classical geothermometers fail to predict maximum subsurface temperatures because fluids re equilibrated at progressively lower temperatures during outflow including in the lake city area we propose a model where hot spring fluids originate as a mixture between a deep thermal brine and modern meteoric fluids with a seasonally variable mixing ratio the deep brine has deuterium values at least 3 to 4 lighter than any known groundwater or high elevation snow previously measured in and adjacent to sv suggesting it was recharged during the pleistocene when meteoric fluids had lower deuterium values the deuterium values and compositional characteristics of the deep brine have only been identified in thermal springs and groundwater samples collected in proximity to structures that transmit thermal fluids suggesting the brine may be thermal in nature on the western side of the valley at the lake city mud volcano the deep brine meteoric water mixture subsequently boils in the shallow subsurface precipitates calcite and re equilibrates at about 130 c on the eastern side of the valley meteoric fluid mixes to a greater extent with the deep brine cools conductively without boiling and the composition is modified as dissolved elements are sequestered by secondary minerals that form along the cooling and outflow path at temperatures

a lagrangian approach to modelling stable isotopes in precipitation over mountainous terrain a lagrangian rayleigh distillation model is used to track the evolution of stable isotopes in precipitation over mountainous terrain from the pacific coast of canada to two alpine field sites in the canadian rocky mountains precipitation 18o at vancouver constrains the model and air mass back trajectories provide the water vapour pathway for 10 winter storm events isotopic values along storm pathways are modelled with a classical rayleigh model that prescribes a linear decrease in temperature and pressure from initial to final conditions and two models that account directly for orographic precipitation processes by i applying an orographic rainfall model and ii using north american regional reanalysis data to calculate the change in vapour content along storm pathways all models are significant predictors of snowpack 18o but the orographic model provides the best fit to precipitation weighted 18o for each storm the improvement in modelled 18o by accounting for terrain along storm trajectories illustrates the need to account for orographically driven moisture loss when modelling vapour transport to ice core sites with mountainous upwind terrain this finding is also applicable to isotopic studies of paleoaltimetry and source areas of groundwater recharge copyright 2011 john wiley sons ltd

the polar profile revisited combined p and s wave interpretation abstract the polar profile project studied the crustal structure in a 440 km long swath extending across the northern baltic shield in a southwest northeasterly direction the obtained seismic data comprise p waves and very clear s waves the results of forward modelling using the raytracing technique together with synthetic seismograms for the s waves necessitated slight modification of a previously published velocity model obtained from p waves only the profile crosses the lapland granulite belt with granulite facies rocks at the surface the lapland granulite belt and a part of the karasjok kittila greenstone belt are recognized as high velocity bodies in the upper crust both for p and s waves the v p v s ratio and poisson ratio respectively seems to be slightly lower than that in the surrounding archaean gneisses which also prevail in the middle crust down to a depth of about 30 km the lower crust 30 45 km is marked by a pronounced velocity contrast of the p waves in respect to the middle crust but only a small velocity contrast for the s waves is seen in the southwestern part of the profile unusually high velocities 8 6 8 7 km s are found in the upper mantle at depths of 46 to 50 km

the relation between the 18o and deuterium contents of rain water in the negev desert and air mass trajectories abstract sampling of rain water was carried out in the negev israel from 1978 till 1981 by means of a self sealing sampler which enables the sampling of each separate rain storm as well as parts of each storm the relation between the isotopic composition and various synoptic parameters is discussed based on deuterium excess values the rain samples can be separated into three groups the majority of the samples have a deuterium excess between 10 and 22 these samples have different histories from the meteorological point of view however there are two extreme groups one has deuterium excess values above 22 and the other has values less than 10 it was found that the rains which are most depleted with regard to deuterium and with the lowest deuterium excess values are associated with air masses that reach the region concerned from the southwest rains with a deuterium excess of more than 22 are associated with air masses which come mainly from northeastern europe and reach the considered region from west to northwest following intense interaction with the central eastern mediterranean sea

a study of historic earthquakes of the prince william sound alaska region we have investigated the character of seismicity that occurred in the prince william sound cook inlet region during 40 years prior to the 1964 great alaskan earthquake we have relocated all events of magnitude 5 5 focal mechanisms have been determined from body waveform modeling and first motion analysis for the larger generally magnitude 6 3 events the results suggest a number of similarities and differences between pre and post 1964 mainshock seismicity similarities include the persistence of normal faulting at depths of 40 to 60 km within the subducted slab in both the tazlina glacier and columbia bay regions north of prince william sound and among deeper events within northern cook inlet differences include a higher level of shallow seismicity 40 km depth in the upper cook inlet region and north of cook inlet prior to 1964 higher levels of seismicity within the subducting plate in the south central and eastern kenai peninsula prior to 1964 and a lower level of seismicity in the offshore prince william sound region prior to 1964 much of the lower plate seismicity for the past 70 years appears to cluster immediately downdip of the 1964 asperity two of the events in this study caused notable damage modified mercalli intensity vii to viii in the anchorage area the first in 1933 m w 6 9 appears to have occurred at 9 km depth along a strike slip fault within northern cook inlet the second in 1954 m w 6 7 occurred within the subducting plate at 60 km depth beneath the northern kenai peninsula analysis of these events as well as smaller events we have studied will greatly improve models of seismic hazard for the anchorage region manuscript received 18 september 2000

stable isotope paleoaltimetry a critical review stable isotope paleoaltimetry makes use of systematic trends in the distribution and isotopic composition of modern precipitation with climate and topography and of the potential to estimate the isotopic composition of paleoprecipitation from authigenic in situ formed minerals to illustrate the usefulness as well as potential limitations of this method we review 1 processes controlling the isotopic composition of modern precipitation 2 stable isotope data from modern precipitation across regions of high topography and 3 stable isotope data from authigenic minerals that have been used to infer paleotopography from this we conclude that stable isotope studies of authigenic minerals can permit useful inferences on paleotopography with uncertainties that critically depend on a detailed understanding of local to global scale paleoclimate during the time interval of interest

crustal structure of the fennoscandian shield a traveltime interpretation of the long range fennolora seismic refraction profile abstract the 1979 fennoscandian long range project fennolora was aimed at the determination of the detailed structure in the earth s mantle down to a depth of about 400 km observation distances reached almost 2000 km within scandinavia between shotpoints off the north cape and the southern coast of sweden to achieve an unbiased regarding the upper mantle structure a careful crustal survey was carried out along the entire profile at the same time beneath the fennoscandian shield i e the central section of the profile the crust is characterized by quite a smooth increase in p wave velocity down to the moho which lies at a depth of about 50 km in the southern half of the shield and at about 45 km further north the mean crustal velocity is 6 6 6 7 km s at the base of the crust the velocity increases gradually from about 7 km s to 8 0 8 4 km s in a 5 10 km thick crust mantle transition zone both in the south and in the north the relatively homogeneous crust of the baltic shield borders on areas with a more differentiated velocity structure first order discontinuities at shallower depth characterize the crust mantle boundary near the southeastern tip of sweden 38 km and under the caledonides in the north 43 km

stable isotope composition of waters in the great basin united states 1 air mass trajectories 1 isentropic trajectories calculated using the noaa climate monitoring and diagnostics laboratory s isentropic transport model were used to determine air parcel origins and the influence of air mass trajectories on the isotopic composition of precipitation events that occurred between october 1991 and september 1993 at cedar city utah and winnemucca nevada examination of trajectories that trace the position of air parcels backward in time for 10 days indicated five distinct regions of water vapor origin 1 gulf of alaska and north pacific 2 central pacific 3 tropical pacific 4 gulf of mexico and 5 continental land mass deuterium d and oxygen 18 18o analyses were made of precipitation representing 99 of all cedar city events similar analyses were made on precipitation representing 66 of the precipitation falling at winnemucca during the same period the average isotopic composition of precipitation derived from each water vapor source was determined more than half of the precipitation that fell at both sites during the study period originated in the tropical pacific and traveled northeast to the great basin only a small proportion traversed the sierra nevada the isotopic composition of precipitation is determined by air mass origin and its track to the collection station mechanism of droplet formation reequilibration within clouds and evaporation during its passage from cloud to ground the rayleigh distillation model can explain the changes in isotopic composition of precipitation as an air mass is cooled pseudo adiabatically during uplift however the complicated processes that take place in the rapidly convecting environment of cumulonimbus and other clouds that are common in the great basin especially in summer require modification of this model because raindrops that form in the lower portion of those clouds undergo isotopic change as they are elevated to upper levels of the clouds from where they eventually drop to the ground

tracking regional and global teleconnections recorded by western north american speleothem records abstract speleothem proxy records are useful for interrogating past climates in the low and mid latitudes given their ability to provide continuous high resolution and long lived records that can be dated with high precision several speleothem oxygen isotope records from western north america have recently been developed that highlight the importance of this archive in documenting past changes in atmospheric circulation taken individually these records hint at teleconnections between western north american hydroclimate and climate changes in the high northern latitudes and tropics however there has been no systematic investigation of global climate teleconnections to this region that draws upon the body of north american speleothem records as a whole here we review the dominant controls on precipitation oxygen isotopes across the region and conduct statistical comparisons and network visualizations of high resolution speleothem oxygen isotope records from western north america to investigate the regional response to pronounced climate changes of the last deglaciation and to determine the pattern of global teleconnections to this region we find that most western north american speleothem oxygen isotope records demonstrate a robust and consistent response to the events of the last deglaciation despite differing controls on the oxygen isotope ratio of precipitation across the region one record that receives a strong influence from the gulf of mexico exhibits a contrasting pattern in oxygen isotopes relative to most of the other records which are dominated by westerly storms generated in the pacific during the studied interval major shifts in western north american speleothem records appear broadly synchronous at least within the uncertainty of age models we also find strong statistical linkages between western north american speleothem records and speleothem records of asian monsoon variability and other records from regions directly influenced by movement of the intertropical convergence zone demonstrating that nearly synchronous changes in atmospheric circulation measurably altered precipitation dynamics in these regions during the last deglaciation further multi proxy investigations are needed to determine how such changes in atmospheric circulation recorded by speleothem oxygen isotope ratios influenced precipitation amounts in drought prone western north america