calibrating the end permian mass extinction the end permian mass extinction was the most severe biodiversity crisis in earth history to better constrain the timing and ultimately the causes of this event we collected a suite of geochronologic isotopic and biostratigraphic data on several well preserved sedimentary sections in south china high precision u pb dating reveals that the extinction peak occurred just before 252 28 0 08 million years ago after a decline of 2 per mil in 13c over 90 000 years and coincided with a 13c excursion of 5 that is estimated to have lasted 20 000 years the extinction interval was less than 200 000 years and synchronous in marine and terrestrial realms associated charcoal rich and soot bearing layers indicate widespread wildfires on land a massive release of thermogenic carbon dioxide and or methane may have caused the catastrophic extinction

oxygen and hydrogen isotope ratios in tree rings how well do models predict observed values we have measured annual oxygen and hydrogen isotope ratios in the cellulose of the latewood of oak quercus robur l growing on well drained ground in norfolk uk we compare the observed values of isotope ratios with those calculated using equations that allow for isotopic fractionation during the transfer of oxygen and hydrogen from source water taken by the tree to cellulose laid down in the cambium the equations constitute a model in which isotopic fractionation occurs during evaporative enrichment within the leaf and during isotopic change between carbohydrates and water in the trunk during cellulose synthesis from the relationship between isotope ratios in precipitation and cellulose we deduce that the source water used by the tree comprises a constant mixture of groundwater and precipitation chiefly from the months of may june and july of the growth year by selection of isotopic fractionation factors and the degree of isotope exchange within the trunk we are able to model the observed annual values of oxygen isotope ratios of cellulose to a significant level r 0 77 p 0 01 when we apply the same model to hydrogen isotope ratios however we find that although we can predict the average value over the time series we can no longer predict the year to year variation we suggest that this loss of environmental signal in the hydrogen isotopes is caused by differences in the kinetic isotope effects of the biochemical reactions involved in the fixation of hydrogen in different positions of the glucose molecule owing to these effects the hydrogen isotope ratios of cellulose can vary in a way not anticipated in current models and hence may induce non climatic noise in the hydrogen isotope time series

pedogenic carbonate proxies for amount and seasonality of precipitation in paleosols the depth to carbonate nodular bk horizon in soils d in cm is correlated with mean annual precipitation p in mm so that bk horizons are deep in subhumid regions but shallow in semiarid regions previous quantifications of this relationship are unchanged by this new compilation of 807 soils p 137 24 6 45 d 0 013 d 2 where r 2 0 52 and standard error s e 147 mm in most north american postglacial soils the bk horizon is thin and well defined whereas in monsoonal tropical soils of pakistan and kenya the bk horizon is thick and diffuse data from 675 modern soils define the relationship between the thickness of soil with nodules t in cm and mean annual range of precipitation m in mm difference between monthly means of wettest and driest months m 0 79 t 13 71 where r 2 0 58 and s e 22 mm the relationship between carbonate nodule size s in cm and soil age a in ka is quantified by 9 radiocarbon dated soils from las cruces new mexico a 3 92 s 0 34 where r 2 0 57 and s e 1 8 k y these transfer functions are applied to reconstructing paleoclimatic change from paleocene eocene paleosols of the north horn formation and flagstaff limestone of axhandle canyon utah the terminal paleocene spike of warmth recorded by fossil plants in nearby wyoming was coincident with a brief peak in both mean annual precipitation and mean annual range of precipitation in utah

robotic micromilling of tree rings a new tool for obtaining subseasonal environmental isotope records high resolution intra ring 18 o d and 13 c values of modern tree species picea glauca larix laricina and populus grandidentata were obtained using a robotic micromill the micromilling apparatus permits accurate mapping and sampling of growth bands at a resolution of a few m producing a fine homogenous powder that facilitates chemical processing and analyses of very small aliquots of cellulose and cellulose nitrate 100 g considerable intra ring isotope variability observed in tree samples in this study correlates with temperature and precipitation data indicating that intra ring variability in 18 o 13 c and d has great potential for reconstructing high resolution variation in meteorological

the coexistence approach a method for quantitative reconstructions of tertiary terrestrial palaeoclimate data using plant fossils abstract the coexistence approach is introduced as a method for quantitative terrestrial palaeoclimate reconstructions in the tertiary it is based on the assumption that tertiary plant taxa have similar climatic requirements to their nearest living relatives the aim of the coexistence approach is to find for a given fossil flora and a given climate parameter the climatic interval in which all nearest living relatives of the fossil flora can coexist for this purpose we have developed a data base climbot containing for over 800 tertiary plant taxa the nearest living relatives and their climatic requirements and an algorithm for analysis climst for all types of fossil floras the coexistence approach thus allows the rapid quantitative reconstruction of 10 different climate parameters including the mean annual temperature temperature of the warmest month temperature of the coldest month mean annual precipitation maximum monthly precipitation minimum monthly precipitation precipitation of the warmest month relative humidity potential evaporation as well as the ratio of mean annual precipitation over potential evaporation the reliability and resolution of the coexistence approach are tested with various techniques and proved to be reasonably good for instance the resolution with respect to the mean annual temperature can be up to 1 c applications to various modern and fossil floras are illustrated and the advantages and disadvantages of the coexistence approach are discussed

climatologic and hydrologic influences on the oxygen isotope ratio of tree cellulose in coastal southern california during the late 20th century 1 the oxygen isotope ratio 18o of precipitation in continental midlatitude regions is a complex measure of atmospheric dynamics and regional climate variability and can be preserved in geologic archives however continuous modern observations of precipitation 18o in many midlatitude regions particularly in the coastal western united states are sparse here tree ring cellulose 18o from southern california is used to assess the potential of this proxy as an indicator of long term hydroclimate and atmospheric variability from 1954 to 2004 we observed that cellulose 18o was well replicated within a single stand of blue oak quercus douglasii on interannual and decadal time scales by using a forward mechanistic model we demonstrate that cellulose 18o is not driven solely by the oxygen isotope composition of precipitation at the site nor any other single hydroclimate variable instead the interannual variability in cellulose 18o prior to 1979 is positively correlated with growing season soil water 18o and after 1979 is negatively correlated with relative humidity in addition 2 years 1983 and 1998 of anomalously low cellulose 18o coincided with the wettest years in california and the strongest el nino events of the late 20th century for these years decreased near surface evaporation and or increased upper level condensation could account for the more depleted cellulose 18o values while blue oak cellulose 18o is sensitive to atmospheric and hydroclimate variability the varying temporal correlation between the cellulose 18o and different environmental variables complicates any attempt to use the cellulose oxygen isotopes for reconstructions of climate variability beyond the calibration period

winter precipitation isotope slopes of the contiguous usa and their relationship to the pacific north american pna pattern this study compares the synoptic dynamic relationship between two phases of the pacific north american pna pattern and winter precipitation isotopes at 73 sites across the contiguous usa we use the spatial pattern of isotope slope the rate of changes in precipitation isotope ratios with distance to identify features in the seasonal precipitation isotope fields related to climatic patterns pna positive and pna negative our results show relationships between zones of high isotope slopes and the spatial position of the polar jet stream and juxtaposition of air masses associated with the pna pattern during a positive pna winter zones of high isotope slope in the eastern usa shift southward this change is coincident with a southward displacement of the polar jet stream in this region which leads to a greater frequency of polar air masses and 18o depleted isotope values of precipitation in the region in the western usa zones of high slope shift eastward during the positive pna winter associated with more frequent penetration of tropical air masses that bring 18o enriched precipitation to the region differences in 18o temperature relationships between the pna positive and negative winters and contrasting 18o temperature behaviors in the eastern and western usa provide support for the role of variation in moisture source and transport as a control on the isotopic patterns these findings highlight the importance of synoptic climate driven by pna pattern in determining the spatial patterns of precipitation isotopes and provide constraints on paleo water isotope interpretation and modern isotope hydrological processes

seasonal temperature and precipitation recorded in the intra annual oxygen isotope pattern of meteoric water and tree ring cellulose abstract modern and ancient wood is a valuable terrestrial record of carbon ultimately derived from the atmosphere and oxygen inherited from local meteoric water many modern and fossil wood specimens display rings sufficiently thick for intra annual sampling and analytical techniques are rapidly improving to allow for precise carbon and oxygen isotope measurements on very small samples yielding unprecedented resolution of seasonal isotope records however the interpretation of these records across diverse environments has been problematic because a unifying model for the quantitative interpretation of seasonal climate parameters from oxygen isotopes in wood is lacking towards such a model we compiled a dataset of intra ring oxygen isotope measurements on modern wood cellulose 18ocell from 33 globally distributed sites five of these sites represent original data produced for this study while the data for the other 28 sites were taken from the literature we defined the intra annual change in oxygen isotope value of wood cellulose 18ocell as the difference between the maximum and minimum 18ocell values determined within the ring then using the monthly resolved dataset of the oxygen isotope composition of meteoric water 18omw provided by the global network of isotopes in precipitation database we quantified the empirical relationship between the intra annual change in meteoric water 18omw and 18ocell we then used monthly resolved datasets of temperature and precipitation to develop a global relationship between 18omw and maximum minimum monthly temperatures and winter summer precipitation amounts by combining these relationships we produced a single equation that explains much of the variability in the intra ring 18ocell signal through only changes in seasonal temperature and precipitation amount r2 0 82 we show how our recent model that quantifies seasonal precipitation from intra ring carbon isotope profiles can be incorporated into the oxygen model above in order to separately quantify both seasonal temperature and seasonal precipitation determination of seasonal climate variation using high resolution isotopes in tree ring records makes possible a new understanding of the seasonal fluctuations that control the environmental conditions to which organisms are subject both during recent history and in the geologic past

how wet was the arctic eocene rain forest estimates of precipitation from paleogene arctic macrofloras the eocene was the warmest part of the cenozoic when warm climates extended into the arctic and substantive paleobotanical evidence indicates broadleaf and coniferous polar forests paleontological temperature proxies provide a basis for understanding arctic early paleogene climates however there is a lack of corresponding proxy data on precipitation both leaf physiognomic analysis and quantitative analysis of nearest living relatives of an arctic macroflora indicate upper microthermal to lower mesothermal moist climates mean annual temperature 13 15 c cold month mean temperature 4 c mean annual precipitation 120 cm yr for axel heiberg island in the middle eocene leaf size analysis of paleocene and eocene arctic floras demonstrates high precipitation for the paleogene western and eastern arctic the predicted enormous volume of freshwater entering the arctic ocean as a result of northward drainage of a significant region of the northern hemisphere under a high precipitation regime would have strongly affected arctic ocean salinity potentially supporting arctic ocean azolla blooms high paleogene precipitation around the arctic basin is consistent with high atmospheric humidity which would have contributed significantly to polar and global eocene warming

lessons learned from oxygen isotopes in modern precipitation applied to interpretation of speleothem records of paleoclimate from eastern asia abstract variability in oxygen isotope ratios collected from speleothems in chinese caves is often interpreted as a proxy for variability of precipitation summer precipitation seasonality of precipitation and or the proportion of 18o to 16o of annual total rainfall that is related to a strengthening or weakening of the east asian monsoon and in some cases to the indian monsoon we use modern reanalysis and station data to test whether precipitation and temperature variability over china can be related to changes in climate in these distant locales we find that annual and rainy season precipitation totals in each of central china south china and east india have correlation length scales of 500 km shorter than the distance between many speleothem records that share similar long term time variations in 18o values thus the short distances of correlation do not support though by themselves cannot refute the idea that apparently synchronous variations in 18o values at widely spaced 500 km caves in china are due to variations in annual precipitation amounts we also evaluate connections between climate variables and 18o values using available instrumental measurements of 18o values in precipitation these data from stations in the global network of isotopes in precipitation gnip show that monthly 18o values generally do not correlate well with either local precipitation amount or local temperature and the degree to which monthly 18o values do correlate with them varies from station to station for the few locations that do show significant correlations between 18o values and precipitation amount we estimate the differences in precipitation amount that would be required to account for peak to peak differences in 18o values in the speleothems from hulu and dongge caves assuming that 18o scales with the monthly amount of precipitation or with seasonal differences in precipitation insofar as the present day relationship between 18o values and monthly precipitation amounts can be applied to past conditions differences of at least 50 in mean annual precipitation would be required to explain the 18o variations on orbital time scales which are implausibly large and inconsistent with published gcm results similarly plausible amplitudes of seasonal cycles in amounts or in seasonal variations in 18o values can account for less than half of the 4 5 difference between glacial and interglacial 18o values from speleothems in china if seasonal cycles in precipitation account for the amplitudes of 18o values on paleoclimate timescales they might do so by extending or contracting the durations of seasons a frequency modulation of the annual cycle but not by simply varying the amplitudes of the monthly rainfall amounts or monthly average 18o values amplitude modulation allowing that several processes can affect seasonal variability in isotopic content we explore the possibility that one or more of the following processes contribute to variations in 18o values in chinese cave speleothems different source regions of the precipitation which bring different values of 18o in vapor different pathways between the moisture source and the paleorecord site along which exchange of 18o between vapor surface water and condensate might differ a different mix of processes involving condensation and evaporation within the atmosphere or different types of precipitation each may account for part of the range of 18o values revealed by speleothems and each might contribute to seasonal differences between past and present that do not scale with monthly or even seasonal precipitation amounts

humidity estimate for the middle eocene arctic rain forest the exquisite preservation of fossilized metasequoia trees that grew near 808n latitude during the middle eocene ca 45 ma in nunavut canada allowed for dd and d 18 o analyses of cellulose techniques previously restricted to wood 30 000 yr old from the isotopic results we determined that the middle eocene arctic atmosphere contained 23 the water found in the region s atmosphere today this water vapor contributed to a middle eocene greenhouse effect that insulated the polar region during dark polar winters

fossil biotas from the okanagan highlands southern british columbia and northeastern washington state climates and ecosystems across an eocene landscape the late early to early middle eocene okanagan highlands fossil sites spanning 1000 km north south northeastern washington state southern british columbia provide an opportunity to reconstruct biotic communities across a broad upland landscape during the warmest part of the cenozoic plant taxa from these fossil sites are characteristic of the modern eastern north american deciduous forest zone principally the mixed mesophytic forest but also include extinct taxa taxa known only from eastern asian mesothermal forests and a small number of taxa restricted to the present day north american west coast coniferous biome in this preliminary report paleoclimates and forest types are reconstructed using collections from republic in washington state usa and princeton quilchena falkland mcabee hat creek horsefly and driftwood canyon in british columbia canada both leaf margin analysis lma and quantitative bioclimatic analysis of identified nearest living relatives of megaflora indicated uppe

annually resolved temperature reconstructions from a late pliocene early pleistocene polar forest on bylot island canada abstract here we use 18o ratios measured in tree rings of crossdated sub fossil wood to reconstruct an annually resolved record of temperature and 18o of meteoric water for an interglacial late pliocene early pleistocene fossil forest found on bylot island nunavut canada our record represents the first crossdated record of pliocene wood mean annual temperatures determined in this study average 3 4 3 8 c which is 11 4 4 4 c warmer than present day bylot island 14 8 2 2 c june july temperatures average 13 5 1 1 c approximately 12 6 1 6 c warmer than present day meteoric water 18o values average 15 5 2 9 2 6 more enriched than present values of precipitation 18o our temperatures are comparable to mid pliocene modeled temperatures for the arctic 3 5 c warmer than present suggesting that interglacial warm periods in the late pliocene early pleistocene may have been as warm as the mid pliocene warm period that both the bylot island forest deposit and the kap kobenhavn deposit represent the remains of northern tree line vegetation that lived during warm interglacial periods within the overall cool plio pleistocene suggests that forest deposits in the arctic capture a snapshot of interglacial conditions during the plio pleistocene rather than the average pliocene climate and may not be suitable records to study pliocene cooling

resolving seasonality in tropical trees multi decade high resolution oxygen and carbon isotope records from indonesia and thailand abstract dendrochronological techniques have found limited applications in the tropics because of invisible or indistinct banding in wood the seasonal cycles of rainfall and relative humidity in these regions while not sufficient to produce distinct visible rings may still generate seasonal signals in the oxygen isotopic composition of tree cellulose which can be used for climate reconstruction and chronology we explore this approach using trees from indonesia and thailand from three different families multi decade 18o records from javanese cross dated teak rings and bomb radiocarbon dated suar wood lacking visible rings demonstrate the reproducibility of the signal between trees grown at the same locality as well as from wider geographical regions these results confirm predictions that the trees oxygen isotopic signatures reflect an external climatic forcing high resolution 18o records reveal large seasonal cycles up to 4 for javanese suar samples and up to 18 for a thai podocarpus sample we show that the six 18o and 13c cycles measured on a podocarpus match the number of growth years for the period spanning the time of wounding and cutting of the wedge section this result demonstrates that the isotopic cycles found in this tree with indistinct annual rings are indeed seasonal and could be used for chronology we present evidence that stable isotope chronologies of tropical trees also contain insights in tropical tree physiology and growth dynamics

oxygen isotope ratios in fossil wood cellulose isotopic composition of eocene to holocene aged cellulose abstract we measured the 18 o of cellulose 18 o cel extracted from fossil wood collected at 9 sites in the northern and southern hemispheres as a potential source of information about precipitation 18 o 18 o ppt in the past and paleotemperatures the samples had been buried in fluvial sediments for periods of time ranging from ca 45 million to 250 years at the oldest localities high latitude eocene through pliocene age sites in canada and russia mean annual temperature mat estimates derived from the modern relationship between mat and 18 o cel are 6 16 c lower than the mat estimates derived from other biological proxies estimates of pleistocene and holocene mean annual temperatures are close to the modern values at those sites these results are consistent with other recent findings that the mat 18 o ppt relationship across north america was not constant throughout the cenozoic paleo 18 o ppt estimates derived from fossil cellulose and the modern north american relationship between 18 o cel and 18 o ppt are within the current annual range of 18 o ppt values at all locations the middle eocene 18 o ppt we determined from arctic cellulose samples 21 9 is consistent with river water 18 o determined in two other studies 19 1 to 22 these findings provide some evidence that a precipitation 18 o signal may be retained in wood cellulose during millions of years of burial and that latitudinal patterns in 18 o ppt may not have changed much during the past 45 ma these interpretations depend of course on the assumption that the isotopic composition of the cellulose has not changed during burial an assumption for which it is difficult to gather direct evidence xrd analysis shows that the crystalline form of the fossil cellulose we used to estimate paleoprecipitation 18 o and paleo mat is the same as that of modern cellulose and that the samples are free of quartz and iron oxide contaminants that result in negative errors in measured 18 o cel

quantifying the isotopic continental effect since the establishment of the iaea wmo precipitation monitoring network in 1961 it has been observed that isotope ratios in precipitation h2 and o18 generally decrease from coastal to inland locations an observation described as the continental effect while discussed frequently in the literature there have been few attempts to quantify the variables controlling this effect despite the fact that isotopic gradients over continents can vary by orders of magnitude in a number of studies traditional rayleigh fractionation has proven inadequate in describing the global variability of isotopic gradients due to its simplified treatment of moisture transport and its lack of moisture recycling processes in this study we use a one dimensional idealized model of water vapor transport along a storm track to investigate the dominant variables controlling isotopic gradients in precipitation across terrestrial environments we find that the sensitivity of these gradients to progressive rainout is controlled by a combination of the amount of evapotranspiration and the ratio of transport by advection to transport by eddy diffusion with these variables becoming increasingly important with decreasing length scales of specific humidity a comparison of modeled gradients with global precipitation isotope data indicates that these variables can account for the majority of variability in observed isotopic gradients between coastal and inland locations furthermore the dependence of the continental effect on moisture recycling allows for the quantification of evapotranspiration fluxes from measured isotopic gradients with implications for both paleoclimate reconstructions and large scale monitoring efforts in the context of global warming and a changing hydrologic cycle

predicting the orientation of joints from fold shape results of pseudo three dimensional modeling and curvature analysis we treat layers of sedimentary rock as elastic plates and predict the orientations of joints by assuming that they open parallel to the maximum instantaneous stretch of a layer because the direction of maximum instantaneous stretch is parallel to the maximum curvature of a surface we hypothesize that joints will trend parallel to the minimum curvature of an elastically deformed layer after constructing pseudo three dimensional trishear models of laramide style uplifts that grow self similarly we calculated the direction of minimum curvature axes during the evolution of the fold our analysis of minimum curvature axes in evolving folds suggests several important characteristics for fold related joint sets 1 joints that are neither parallel nor perpendicular to the fold axis may be induced by local fold related strains 2 at any time during folding joint orientations may vary according to the structural position on a fold 3 at any location on a fold joint orientation may depend on when a joint forms during the evolution of the fold and 4 joint patterns in trishear folds may vary with stratigraphic position natural folds that evolve along simple geometric pathways may develop fold related joint sets the orientation dominance abutting relationships spacing and continuity of which will vary systematically throughout the structure this variation in joint system architecture may reflect the history of fold growth

annual patterns within tree rings of the arctic middle eocene ca 45 ma isotopic signatures of precipitation relative humidity and deciduousness the spectacular preservation of middle eocene ca 45 ma wood allows for intra season sampling of stable carbon oxygen and hydrogen in order to reconstruct the paleoseasonal environment of this arctic forest paleolatitude 78 6 1 6 n present latitude 80 n carbon isotopes in bulk organics and cellulose reveal striking annual patterns interpreted as the seasonal switchover from stored to actively acquired carbon associated with deciduous growth in these unusual conifers oxygen and hydrogen stable isotopes of cellulose and cellulose nitrate allow for the calculation of changes in relative humidity and in the isotopic value of plant available water clear annual patterns of increasing relative humidity resulting from tissue growth and concomitant transpiration are apparent as is the systematic increase in the reconstructed oxygen isotope value of environmental water refl ecting progressively increasing temperatures during the growing season

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

modeled and observed intra ring δ18o cycles within late holocene bristlecone pine tree samples abstract the oxygen isotope ratio of alpha cellulose produced by bristlecone pine trees from the white mountains of california was measured for three different 10 year tree ring sections at near weekly resolution to investigate how the growing season climate cycle influences the annual to inter annual isotopic variability of whole ring samples we selected sections of wood that grew under periods of generally reduced 155 172 bc and increased ad 1106 1122 ad 1827 1834 growth to assess whether or not the environmental parameters that are responsible for ring width variability including water availability also influence the intra annual cellulosic isotope variability each annual ring is characterized by a parabolic function of intraseasonal 18 o change that reflects humidity and temperature dependent fractionations of h 2 18 o utilized by the tree during the growth period subtle shifts in the shape and amplitude of the seasonal 18 o cycle are attributed to changing growing season length but the differences are not large enough to bias a whole ring isotopic value we model the isotope fractionations based on growing season climate variables and tree physiology and find that the measured 18 o is in close agreement with the model predicted values the model retains no information on previous winter conditions and thus confirms that these trees draw upon an isotopically homogenized water source the intraseasonal 18 o cycle arises entirely from fractionations due to summer season temperature and humidity a persistent issue with dendroclimatic reconstructions is addressing seasonal biases in the record we find that in this environment where growth and precipitation are separated by many months we are able to capture distinct information on both seasons by coupling average annual values with information on sub seasonal variability

quantifying and understanding the uncertainty of atmospheric co2 concentrations determined from calcic paleosols 1 a computer program pbuq that uses monte carlo simulations to propagate uncertainty through regression equations and the equation for the paleosol carbonate co2 paleobarometer is presented pbuq includes options for all of the common approaches to determining values for input variables and incorporates several recent advancements relevant to determining values for soil respired co2 concentrations 13c values of respired co2 13c values of atmospheric co2 and temperatures of soil carbonate formation pbuq is intended to improve confidence in paleoatmospheric co2 research by helping researchers draw statistically significant conclusions pbuq can also be used to attribute and partition error among various sources and thereby advance this technique sensitivity analysis indicates that s z is the largest source of uncertainty for most paleosols and that uncertainty is minimized for soils in which co2 is an evenly balanced mixture between soil derived and atmospheric components evenly balanced mixtures are most likely for paleosols formed in deserts and for weakly developed paleosols development of proxies for soil respired co2 concentrations and 13c values of soil respired co2 specifically for such soils is perhaps the most crucial next step for improving this technique currently calcic paleosols are best used to test the significance of trends and or differences among time slices in paleoatmospheric co2 concentration application to quantifying earth system sensitivity will require large scale averaging of determinations from individual paleosols and or reduced uncertainty associated with input variables

crustal stress map of iran insight from seismic and geodetic computations we used the focal mechanisms of crustal earthquakes depth 40 km in the period 1909 2012 and the available gps velocities derived from the data collected between 1999 to 2011 to estimate the magnitude and directions of maximum principal stress and strain rates in iran the pearson product moment correlation was used to find the correlation between the stress field obtained from the focal mechanism stress inversion and that obtained using the seismic and geodetic strain rates our assumption is that stresses in a continuum are produced by tectonic forces and the consequent deformation on the crustal scale therefore the direction of the stress and strain or strain rate are ideally to be the same our results show a strong correlation between the directions of the principal components of stress and strain rate obtained using the different data methods using weighted average analysis we present a new stress map for iran

seasonally resolved stable isotope chronologies from northern thailand deciduous trees abstract despite the existence of a number of climate proxies the terrestrial expression of tropical climate variability over the past few centuries remains poorly resolved we explore the applicability of stable isotope dendroclimatology as a tool for chronology and paleo hydrology reconstruction on deciduous trees from monsoonal northern thailand analysis of 11 trees coming from 4 different regions of northern thailand yielded 7 records with varying degrees of 18 o and 13 c seasonality we develop age models for trees lacking visible rings based on the seasonality of the 18 o and find agreement to within 3 years with radiocarbon age estimates we use the isotopic age models to reconstruct estimates of growth rates and find a significant positive correlation between growth and amplitude of the oxygen and carbon seasonal isotopic signals a comparison of a reconstructed dendro isotopic index from pangmapa with regional rainfall records indicates significant correlations consistent with the locally derived patterns but with decreased representation of the variance individual isotopic chronologies stemming from different tree species share common trends which are also consistent with patterns of rainfall variability we see an increase in the amplitude of the seasonal 18 o cycle along with an increase in 18 o max over the past few decades suggesting a tracking of the recent drying trend of thailand s monsoon

the role of soil processes in δ18o terrestrial climate proxies a paleoclimate interpretation of a terrestrial hydrologic proxy such as the 18o of tree cellulose or speleothem calcite may be biased or misinterpreted if the isotopic composition of the soil water from which the proxy originated undergoes isotopic exchange or fractionation in this study we use a global isotope enabled land surface model to investigate how the 18o of precipitation may be altered in a soil column due to evaporation and vertical moisture transport in order to assess how precipitation and evaporation contribute to the soil water isotopic variability we compare seasonal and interannual changes in simulated xylem water 18o within a control simulation and in a suite of sensitivity experiments where the effects of precipitation 18o water vapor 18o and soil water evaporation are independently removed the simulations carried out for the period 1979 to 2004 reveal that in semiarid regions such as the southwest united states the seasonal cycle in xylem water 18o is strongly affected by evaporative loss during the dry season and evaporation can also constitute as much as 50 of the interannual 18o variance additional simulations including soil water tagging experiments indicate that upward fluxes of soil water occur during drier periods for soil water 18o profiles that are isotopically more depleted in 18o at depth this imparts a low isotopic signature to xylem water 18o during such dry intervals hence without taking into account vertical moisture transport in the soils low 18o years could be misinterpreted as wet conditions due to decreased evaporative enrichment when instead drier conditions are equally as likely

twentieth century summer temperature variability in the southern altai mountains a carbon and oxygen isotope study of tree rings the altai mountains southern siberia represent an area of significant scientific interest and exceptional palaeoecological potential to assess the influence of climate on the stable isotopic composition of tree ring cellulose and the potential of this record as a palaeoclimate proxy replicated stable oxygen and carbon isotope time series were developed for the twentieth century from four siberian pine pinus sibirica du tour trees growing near the settlement of aktash russian altai mountains southern siberia bootstrapped calibrations for the local instrumental period ad 1954 2000 reveal strong correlations between summer july august growing season temperatures and tree ring oxygen r2 0 55 and carbon r2 0 30 isotopes covariance observed between both carbon and oxygen isotope data suggest a common stomatal control the resulting empirical model was used to reconstruct regional summer temperatures for the twentieth century no divergence is observed between the non detrended tree ring isot

an investigation of the common signal in tree ring stable isotope chronologies at temperate sites we observed a strong common high frequency interannual signal for thed 13 c chronologies whereas the low frequency decadal scale signal was more similar among thed 18 o chronologies for both carbon and oxygen isotopes we found significant positive relationships with annual and growing season temperatures and negative relationships with precipitation again of similar magnitude for all species except forfraxinus which contained only minor climatic information averaging of all chronologies resulted in an increase in the climatic signal of the mean chronology the combinedd 18 o record reflected decadal scale temperature variations remarkably well r 0 72 however the relationship between climate and carbon isotopes declined over the last 3 decades of the 20th century probably related to the steep increase in atmospheric co 2 concentrations resulting in strongly divergingd 13 c trends of the different chronologies our study indicates that combining chronologies from different species enhances the potential of isotope studies for extending climate reconstructions into areas of temperate climate

the correlation between 18o 16o ratios of meteoric water and surface temperature its use in investigating terrestrial climate change over geologic time abstract correlations between mean annual temperature mat and the weighted average oxygen isotope composition of yearly precipitation 18opt are well known but the utility of modern relations to make reliable estimates of temperature change over geological time is uncertain this question has been addressed by using seasonal subsets of the global data base of temperature and isotopic measurements to represent two different climate modes a comparison of middle to high latitude 18opt temperature relations for each climate mode reveals 1 a significant offset between them and 2 a difference in the strength of their correlations the offset in relations is due to differences in temperature and water vapor budget in the tropics and can lead to serious underestimates of temperature change differences in the strength of correlations arise from the influence of climate mode specific non temperature factors on 18opt the overall result is that no single relation can be used in all cases to make unambiguous temperature estimates using a temporal record of 18opt values one way to overcome these problems is to reconstruct 18opt temperature relations for the time periods being investigated if an appropriate proxy for 18opt is available it may also be possible to estimate temperature without relying on 18opt temperature relations a promising alternative to these options is to use records of 18opt to test predictions of global climate models an approach that may allow a reliable and more complete reconstruction to be made of climate change over geologic time

stable isotope records of hydrologic change and paleotemperature from smectite in cenozoic western north america abstract the oxygen and hydrogen isotopic composition of soil water 18ow and dw hereafter reflect the history of water through processes such as source evaporation precipitation and vapor recycling temperature humidity evaporation and post condensation processes can affect 18ow and dw as such isotope proxy records are often limited in their ability to constrain paleoclimate paleoecology or paleoelevation without independently corroborating data smectite preserves both the hydrogen and oxygen isotope signature of parent water and therefore provides critical insight into meteoric water line relationships and paleotemperature here we use in situ pedogenic smectite 18o and d records to characterize the evolution of the hydrologic cycle in cenozoic western north america we incorporate 192 samples 119 of which are previously unpublished from 11 cenozoic basins representing a range of environments in the basin and range rocky mountains and great plains our results indicate that the processes controlling smectite isotopic compositions vary both regionally and temporally in some localities such as oligocene to pleistocene western nebraska change in temperature is the primary control on smectite isotopic composition in other basins such as in miocene trapper creek id isotope values lie along the meteoric water line suggesting change in meteoric water composition is responsible for the variation in most basins especially those in the neogene basin and range smectite line slope suggests either evaporation of previously meteoric water or a combination of change in paleotemperature and meteoric water composition smectite geothermometry suggests mineral formation temperatures of 30 40 c in the middle miocene in the rocky mountains great plains and basin and range and a decrease of 10 15 c since the middle miocene climatic optimum consistent with clumped isotope and paleofloral temperature estimates

using fossil leaves as paleoprecipitation indicators an eocene example estimates of past precipitation are of broad interest for many areas of inquiry including reconstructions of past environments and topography climate modeling and ocean circulation studies the shapes and sizes of living leaves are highly sensitive to moisture conditions and assemblages of fossil leaves of flowering plants have great potential as paleoprecipitation indicators most quantitative estimates of paleoprecipitation have been based on a multivariate data set of morphological leaf characters measured from samples of living vegetation tied to climate stations however when tested on extant forests this method has consistently overestimated precipitation we present a simpler approach that uses only the mean leaf area of a vegetation sample as a predictor variable but incorporates a broad range of annual precipitation and geographic coverage into the predictor set the significant relationship that results in addition to having value for paleoclimatic reconstruction refines understanding of the long observed positive relationship between leaf area and precipitation seven precipitation estimates for the eocene of the western united states are revised as lower than previously published but remain far wetter than the same areas today abundant moisture may have been an important factor in maintaining warm frost free conditions in the eocene because of the major role of water vapor in retaining and transporting atmospheric heat

micro scale analysis of tree ring δ18o and δ13c on α cellulose spline reveals high resolution intra annual climate variability and tropical cyclone activity high resolution analysis of stable carbon and oxygen isotopic composition 13c and 18o of tree ring cellulose has been increasingly in demand for the study of climate seasonality droughts and tropical cyclone hurricane activity the peeling grinding method commonly used for tree ring cellulose preparation is both time consuming and labor intensive and often results in cross tracheid sampling that masks high frequency intra annual climate signals and short term climate events here we present a new method by extracting tree ring cellulose directly from wholewood spline that omits the peeling grinding step and allows for micro scale 13c and 18o analysis that facilitates high resolution seasonal climate study this ultrasound assisted non destructive extraction method has significantly increased the output of tree ring cellulose preparation while retaining the wood cell fabric wood cell wall fibers collected from the cellulose spline were directly loaded into pre weighed silver or tin capsules and packed after oven drying for stable oxygen or carbon isotope analysis a 3 045 mm annual ring subdivided over 26 sections for 13c and 18o analysis revealed remarkable intra annual isotopic variations 1 62 for 13c and 5 85 for 18o the intra annual 13c values inversely covary with the seasonal precipitation pattern suggesting moisture regulation on tree ring 13c variations the high resolution 18o analysis unravels tropical cyclone activities hurricanes frances and ivan in 2004 that are characterized by an abrupt decline in 18o values by 2 6 with a v shape pattern in tree ring latewood an algorithm is developed for establishing regional patterns of tree ring seasonal 13c and 18o for the study of the mean state of climate seasonality and its anomalies