tree ring δ18o in southwestern china linked to variations in regional cloud cover and tropical sea surface temperature in this paper we present the first annual oxygen isotope 8180 record 1902 to 2004 from the latewood cellulose of trees growing in a temperate moist forest in southwestern china tree ring delta o 18 ranges from 12 8 to 18 6 parts per thousand and averages 15 2 parts per thousand delta o 18 in the latewood negatively correlates with total cloud cover relative humidity and precipitation during the moist months august to october from 1951 to 2004 and to a lesser extent positively correlates with the temperature in june spatial correlation analysis revealed that tree ring latewood delta o 18 is more strongly related to variability in regional cloud cover and precipitation in autumn tree ring delta o 18 negatively correlates with the indices of the indian summer monsoon 1948 to 2004 the western north pacific monsoon 1948 to 2004 and with the east asian summer monsoon 1902 to 2000 suggesting that these monsoons strongly influence the regional climate under global warming of last century we found a strong inverse correlation between tree ring delta o 18 and the southern oscillation index in different periods indicating a complex association between the el nino southern oscillation and the regional climate which in turn affects tree ring delta o 18 correlation with the global sea surface temperature sst indicates that climatic conditions in the indian ocean might play a dominant role in modulating cloud cover and precipitation over the study region during the monsoon seasons we also found a significant correlation between tree ring delta o 18 and sst over the western north pacific ocean our results suggest strong links between tropical oceans and an enso like climate with the oxygen isotope sources and discrimination for trees in the study region c 2011 elsevier b v all rights reserved

inherited smnd isotope components preserved in monazite inclusions within garnets in leucogneiss from east antarctica and implications for closure temperature studies abstract application of the sm nd dating technique using garnet can be hampered by the presence of minor microscopic to submicroscopic ree rich inclusions in particular monazite and to a lesser extent zircon an acid leaching method using a mixture of hno 3 hcl has been used to tackle the monazite contamination problem with this leaching technique we demonstrate that inherited monazite inclusions have been preserved in garnet formed under high grade metamorphic conditions even very low levels of monazite contamination 0 001 wt have a profound effect on the sm nd system in the garnet analysis of a garnet from a leucogneiss dyke in the northern prince charles mountains eastern antarctica reveals that unleached garnet concentrates and the monazite inclusions as represented by the leachates define an apparent isochron of 1150 30 ma mswd 1 88 which represents a mixing age of inclusions preserving their inherited sm nd isotopic systematics in contrast analyses of the leached garnet concentrates yield much younger ages of 630 to 555 ma model calculations show that the presence of as little as 0 01 wt of monazite inclusions would swamp the sm nd isotope signature of the garnet concentrates this very low level of contamination is beyond the reach of physical purification processes and without leaching contamination is inevitable in inclusion bearing garnets such contamination can lead to older apparent ages than those of garnet formation and thus has profound implications for sm nd as well as u pb garnet chronometry

evidence for inherited sm nd isotopes in granitoid zircons this study presents evidence to show that in addition to preserving u pb isotope systematics refractory zircons also preserve at least in part an inherited sm nd isotope component the zircons analyzed during this study were taken from the strontian granitoid nw scotland the inner intrusion of this composite pluton is known from a previous study to contain substantial u pb zircon inheritance whereas the outer part has only minor inheritance zircons from the inner intrusion were found to have significantly lower end425 values than either their host rock separated apatite or monazite it is argued that this isotopic disequilibrium is due to the presence of an inherited sm nd isotope component rather than being due to a post crystallization disturbance of the zircons the preservation of inherted sm nd isotopes within refractory zircons implies that they remain closed systems with respect to the diffusion of sm and nd and presumably the other ree to temperatures in excess of 700 c the fact that zircons commonly have high sm nd ratios relative to sialic crustal material means that the nd isotopic evolution of inherited zircons will be very different to that of much of the continental crust

tree ring δ18o from southeast china reveals monsoon precipitation and enso variability abstract considerable advances have been made in use of tree ring 18o for climate reconstructions in southeast china the east asian summer monsoon region however the relationships among tree ring cellulose 18o 18ocell local hydroclimate precipitation 18o 18opre and el nino southern oscillation enso have not yet been fully resolved the usual interpretation has been that local hydroclimate influences 18ocell through both the amount effect on 18opre and evaporative enrichment but it cannot fully explain the high inter site correlation of 18ocell chronologies or their response pattern to enso in this study we use a newly developed 18ocell chronology of pinus massoniana from a water stressed site in zhejiang province in combination with another three 18ocell chronologies in southeast china to investigate their climatic implications from a regional perspective the results show that besides local hydroclimate 18opre is also significantly correlated with 18ocell but with different effects spatially homogeneous 18opre variation causes high spatial correlations among 18ocell from different sites analyses show that enso variations are responsible for the large scale common signals in 18ocell by modulating 18opre therefore combining 18ocell chronologies from different locations can enhance enso signals which provides us new opportunities to reconstruct paleo enso activities furthermore eliminating the part of enso signal that is not related to the growing season hydroclimate from 18ocell can increase the explained variance of observed values these findings provide a guide for future optimized enso and local paleoclimate reconstructions using 18ocell

evidence for decreasing south asian summer monsoon in the past 160 years from varved sediment in lake xinluhai tibetan plateau 1 we report glacial varves in the sediment of lake xinluhai tibetan plateau independent data of 137cs and 210pb indicate that these are annually deposited varves varves appear as rhythmic units of light colored silt layer capped by a dark clay layer under microscope varve thickness in lake xinluhai is sensitive to precipitation because sediment accumulation is strongly affected by monsoon rainfall in the area a general decreasing trend can be observed in the varve thickness over the past 160 years spectral analyses of the varve record are dominated by cycles which are similar to enso periodicities it implies that the decreasing trend of the south asia monsoon may be linking with enso spatially the decreasing trend can be observed across different proxy records in the south of the tibetan plateau although arguments still remain for the dynamic mechanisms and spatial rainfall difference the south asian summer monsoon could be weakened due to rising temperatures

is there a low frequency bias in multiproxy reconstructions of tropical pacific sst variability abstract decadal and longer term variability in the tropical pacific has the potential to impact climate worldwide yet paleoclimate observations and climate model simulations disagree on the nature of this variability in this study we investigate whether biases from paleoclimate reconstruction methodology and the currently available proxy network cause reconstructions of enso to overestimate the multidecadal century scale variability of the pacific we build new reconstructions using a variety of commonly employed methods and test the effects of four types of bias on analogous pseudoproxy reconstructions these biases include 1 the number of records used in the reconstruction 2 chronological uncertainty 3 noise in individual proxy records and 4 the geographical distribution of the proxy network we find that each of these biases cause enso reconstructions to overestimate the importance of low frequency variability these biases may partially explain why multiproxy reconstructions of pacific variability have stronger low frequency variability than predicted by historical observations or climate models and why these reconstructions do not have coherent signals over the multidecadal century scale

sm nd dating and cooling history of scourian granulites sutherland the scourian gneisses of the lewisian complex of north west scotland have been the subject of many geochronological investigations sm nd whole rock measurements suggest that the protoliths of the lewisian complex differentiated 2 92 0 05 gyr ago from an approximately chrondritic mantle1 rb sr and pb pb whole rock ages between 2 8 and 2 6 gyr reflect subsequent depletion in rb and u refs 2 3 which has generally been associated with granulite facies metamorphism zircons which are thought to have crystallized during this metamorphism have also given u pb ages of 2 66 gyr ref 4 this granulite facies metamorphism involving pressures in excess of 10 kbar and peak temperatures estimated between 820 50 c ref 5 and 1 250 c refs 6 7 affects a terrain including supracrustal rocks7 and thus implies a major tectonic event we report here the first geochronological data measured on mineral assemblages that have also provided estimates of the conditions of metamorphism such measurements are possible because the major minerals of granulite facies assemblages show an unusually favourable spread in sm nd ratios garnet especially is strongly enriched in sm ref 8 data for three garnetiferous basic gneiss assemblages suggest that closure of the sm nd system occurred significantly later than the peak of the metamorphism

drought reconstructions for the continental united states abstract the development of a 2 lat 3 long grid of summer drought reconstructions for the continental united states estimated from a dense network of annual tree ring chronologies is described the drought metric used is the palmer drought severity index pdsi the number of grid points is 154 and the reconstructions cover the common period 1700 1978 in producing this grid an automated gridpoint regression method called point by point regression was developed and tested in so doing a near optimal global solution was found for its implementation the reconstructions have been thoroughly tested for validity using pdsi data not used in regression modeling in general most of the gridpoint estimates of drought pass the verification tests used in addition the spatial features of drought in the united states have been faithfully recorded in the reconstructions even though the method of reconstruction is not explicitly spatial in its design the drought reconstructions show that the 1930s dust bow

reconstructing enso the influence of method proxy data climate forcing and teleconnections in this study we compare three newly developed independent nino3 4 sea surface temperature sst reconstructions using data from 1 the central pacific corals 2 the texmex region of the usa tree rings and 3 other regions in the tropics corals and an ice core which are teleconnected with central pacific ssts in the 20th century although these three reconstructions are strongly calibrated and well verified inter proxy comparison shows a significant weakening in inter proxycoherenceinthe 19thcentury thisbreakdownin commonsignalcouldberelatedtoinsufficient data dating errors in some of the proxy records or a breakdown in el nino southern oscillation s enso s influence on other regions however spectral analysis indicates that each reconstruction portraysenso likespectralproperties superposedepochanalysisalsoshowsthateachreconstruction shows a generally consistent el nino like response to major volcanic events in the following year while duringyearst 4tot 7 la nina like conditions prevail theseresults suggest thateachofthe series expresses enso like behaviour but this behaviour does not appear to be spatially or temporally consistent this result may reflect published observations that there appear to be distinct types of enso variability depending on location within the tropical pacific future work must address potential dating issues within some proxies i e sampling of multiple coral heads for one location as well as assessing the time stability of local climate relationships with central pacific ssts more emphasis is needed on sampling new and extending old coral proxy records from the crucial central and eastern tropical pacific region copyright 2009 john wiley sons ltd and crown copyright 2009

abundant climatic information in water stable isotope record from a maritime glacier on southeastern tibetan plateau climatic significance of ice core stable isotope record in the himalayas and southern tibetan plateau tp where the climate is alternately influenced by indian summer monsoon and mid latitude westerlies is still debated a newly drilled zuoqiupu ice core from a temperate maritime glacier on the southeastern tp covering 1942 2011 is investigated in terms of the relationships between 18o and climate parameters distinct seasonal variation of 18o is observed due to high precipitation amount in this area thus the monsoon june to september and non monsoon october to may 18o records are reconstructed respectively the temperature effect is identified in the annual 18o record which is predominantly contributed by temperature control on the non monsoon precipitation 18o record conversely the negative correlation between annual 18o record and precipitation amount over part of northeast india is mostly contributed by the monsoon precipitation 18o record the variation of monsoon 18o record is greatly impacted by the indian summer monsoon strength while that of non monsoon 18o record is potentially associated with the mid latitude westerly activity the relationship between zuoqiupu 18o record and sea surface temperature sst is found to be inconsistent before and after the climate shift of 1976 1977 in summer monsoon season the role of sst in the monsoon 18o record is more important in eastern equatorial pacific ocean and tropical indian ocean before and after the shift respectively in non monsoon season however the atlantic multidecadal oscillation has a negative impact before but positive impact after the climate shift on the non monsoon 18o record

nd and sr systematics in an eclogite xenolith from tanzania evidence for frozen mineral equilibria in the continental lithosphere combined isotopic nd sr and petrographic analyses are reported for an eclogitic xenolith from the vissury mine tanzania an exceedingly large difference in measured nd values in garnet and clinopyroxene 200 units suggest a major mineral equilibration at 1 75 0 014 ga nd isotopic heterogeneities are demonstrated in different generations of garnet and zonation in sr and nd isotope compositions is present within the clinopyroxene the variation in measured nd isotope compositions in different generations of garnet corresponds to 16 units exsolution of garnet from clinopyroxene occurred in an essentially closed system with respect to sr and nd petrographically different generations of garnet are present one garnet with rutile inclusions as well as the rims of clinopyroxene are clearly off the isochron features like this can originate either if a system is not closed e g affected by a migrating fluid or if a remanent isotopic heterogeneity survived the homogenisation at 1 75 ga the subsolidus partitioning of sm and nd between garnet and clinopyroxene results in higher fractionation of the smnd ratio in garnet than in the liquid crystal partitioning since the closure temperature for the sm nd exchange between garnet and clinopyroxene may be around 850 c in a dry system many of the lithospheric ultramafic rocks may exhibit frozen mineral equilibria the isotopic data suggest that this eclogite was emplaced at 1 75 ga into the lithosphere mantle at temperatures of about 1040 c and then cooled as a closed system at a rate of 6 50 c my down to 840 c where all the exchange reactions were efficiently frozen in at 1 75 ga ago the coincidence of the emplacement of granites 1 7 1 8 ga into the central part of the tanzanian craton with the age of the eclogite suggests that lower crustal melting was triggered by a thermal event in the upper lithosphere

reduction in himalayan snow accumulation and weakening of the trade winds over the pacific since the 1840s 1 in 1884 blanford suggested that summer rainfall over northwest india was anti correlated with snow cover during the preceding winter and spring in the western himalaya walker elaborated on this suggestion in his seminal work on predictors of the indian summer monsoon a body of work that forms the basis of our understanding of how eurasia influences this monsoonal circulation recently a number of studies have questioned the existence of this relationship or have proposed a more complex coupling between eurasian snow cover including the himalaya and the indian summer monsoon here we present a 196 year record of snow accumulation from a himalayan ice core that contains a decreasing trend in accumulation that began in the 1840s indian summer monsoon rainfall shows no evidence of such a trend and we argue that this reduction in snow accumulation is associated with a long term weakening of the trade winds over the pacific ocean citation zhao h and g w k moore 2006 reduction in himalayan snow accumulation and weakening of the trade winds over the pacific since the 1840s geophys res lett 33 l17709

high resolution geochemical record for the last 1100 yr from lake toson northeastern tibetan plateau and its climatic implications abstract knowledge of the origin of past climatic variations on annual to decadal timescales is important for assessing the likelihood of the occurrence of similar variations in the future here we present a high resolution 82 m element record obtained using synchrotron radiation x ray fluorescence from the sediments of toson lake in the northeastern tibetan plateau the record which spans the last 1100 yr exhibits variability on an annual to decadal scale the results of principal component analysis of the element dataset indicates that the first three principal components reflect variations in detrital inputs via runoff and possibly eolian activity drought conditions and temperature variations respectively spectral analysis of samples scores on these components reveals strong el nino southern oscillation enso like variability at periods of 3 8 years which indicates that the regional climatic variability was effected by enso events over the last 1100 yr on the centennial time scale the element data and toc record suggest a warm and dry climate during the medieval warm period mwp and a cold and wet little ice age lia the early 20th century was a warm interval and drier than the lia but wetter than the mwp

regional hydroclimate and precipitation δ18o revealed in tree ring cellulose δ18o from different tree species in semi arid northern china abstract oxygen isotopic ratios 18o of tree ring cellulose grown from 1954 to 2003 in semi arid northern china demonstrate a common inter annual variability despite coming from three different species in two distinct growth environments an alpine meadow and a rocky ridge the variability was significantly negative correlated with precipitation and relative humidity during the growing season this suggests that the past summer hydroclimate can be inferred from tree ring cellulose 18o from various kinds of trees growing in semi arid northern china in addition we evaluated past changes in 18o of precipitation from the tree ring cellulose 18o and relative humidity using the mechanistic model for tree ring cellulose 18o in roden et al 2000 by fixing the species dependent exchange rate of oxygen between carbohydrate and xylem water for larix principis rupprechtii and picea koraiensis we could also reconstruct the variations in precipitation 18o from the different tree species which are similar to the observed 18o of precipitation during 1985 2002 although the reconstructed 18o of precipitation does not have any significant relation to local temperature or precipitation during 1954 2003 its long term variation pattern is similar to that of the asian summer monsoon indices and 18o of stalagmite in the heshang cave 30 27 n 110 25 e fig 1 suggesting that 18o of precipitation is not controlled by local meteorology but is influenced by large scale atmospheric circulation

tree ring reconstruction of late summer temperatures in northern sikkim eastern himalayas abstract the sikkim region of the himalayas is among one of the most highly sensitive hotspots to climate change due to its fragile mountainous environment and rapidly growing population which exert significant impacts on regional ecosystem factors including biodiversity and hydrology limited observational data coverage in space and time for the high altitude mountainous region impedes our understanding of climate change and its impact on the environment in this paper we develop a 437 year tree ring width index chronology of tsuga dumosa d don eichler in northern sikkim as a climate proxy the substantial dendroclimatic potential of this proxy is evidenced in various statistics computed from the tree ring chronology an analysis of the tree ring chronology indicates a strong negative relationship between late summer mean temperatures july august september jas and tree growth this relationship enables us to reconstruct the jas mean temperature over northern sikkim since 1705 c e the 304 year 1705 2008 c e reconstructed temperature series shows similar warm and cool epochs which have been observed in many other temperature reconstructions in the region and other proxy records of glacial fluctuations an overall steady decreasing trend in the regional surface temperature is observed since 1705 c e while an increasing trend with intermittent short and cool epochs are noticed from 1850 c e to the present prior to the observational period before 1901 c e cold conditions x 1 prevailed during 1816 1819 1831 1837 1856 1859 and 1884 1887 c e with extremely cold conditions x 2 occurring in 1816 1817 1832 1833 1857 1877 1884 and 1885 c e warm conditions x 1 prevailed during 1713 1735 and 1823 1827 c e with extremely warm x 2 conditions occurring in 1724 1823 1824 and 1825 c e global teleconnections of the reconstructed temperature variations indicate the important roles of the pacific decadal oscillation pdo el nino southern oscillation enso and volcanic eruptions as drivers of temperature variations in the sikkim region of the himalayas

may september precipitation in the bhutan himalaya since 1743 as reconstructed from tree ring cellulose δ18o 1 we developed a 50 year tree ring 18o chronology for each of three tree species juniperus indica larix griffithii and picea spinulosa using a total of 12 trees four trees per species from the bhutan himalaya despite originating from different species sampled at two different altitudes the 18o chronologies are highly correlated with one another r 0 76 0 89 response analyses reveal that tree ring 18o values are controlled mainly by summer precipitation irrespective of species based on these results a robust 269 year 18o chronology was established to reconstruct the amount of may september precipitation based on data from four larch trees our tree ring 18o data show significant correlations with those from other regions of the himalaya and the tibetan plateau indicating that common signals related to monsoon activity are recorded in the data however at centennial timescales our data from bhutan show normal conditions during the 20th century whereas records from sites in western nepal and the southern eastern tibetan plateau show weakening trends in monsoon intensity during the last 100 200 years the weakening trends may be the result of a reduction in the meridional sea surface temperature gradient in the indian ocean during this time at continental scales the tree ring records show that areas more from ocean basins are particularly sensitive to reduced monsoon circulation correlation analyses suggest that the el nino southern oscillation enso plays an important role in modulating summer precipitation however the teleconnected relationship disappears during the period 1951 1970 coinciding with a negative phase of the pacific decadal oscillation pdo implying interdecadal modulation of the pdo on the influence of the enso on precipitation in bhutan

spring precipitation variations over the western himalaya india since a d 1731 as deduced from tree rings 1 spring precipitation representative of regional scale features was reconstructed since a d 1731 using 15 site ring width chronologies of himalayan cedar cedrus deodara roxb ex lambert g don prepared from distantly located moisture stressed sites in the western himalayan region this is so far the strongest tree ring based precipitation reconstruction in terms of variance explained in the calibration model a d 1897 1986 from the western himalayan region the twentieth century experienced the driest and wettest years in the whole reconstructed series the 10 and 20 year means also indicate extreme precipitation periods in the twentieth century the increasing precipitation trend noticed in the reconstructed data of the late twentieth century closely matches with instrumental data

oxygen isotope ratios of oak in east england implications for reconstructing the isotopic composition of precipitation annual latewood 18o values from oak quercus robur l are presented for the period 1895 1994 for four trees growing in eastern england we demonstrate using the 18o values of precipitation from wallingford 1982 1994 and the longer time series from groningen 1965 1994 that the 18o values of winter precipitation had the strongest influence on the 18o values of tree ring cellulose the influence of winter precipitation on the spring summer formed latewood may be explained by several factors most soil water is replenished during the winter water may take several months to penetrate the unsaturated zone and oaks may sample water from lower in the profile during times of water stress the 18o values of oak latewood cellulose were also significantly p 0 01 correlated with summer relative humidity therefore although precipitation 18o values may be altered by partial isotopic exchange with xylem water and the influence of stomatal conductance upon evapotranspiration some of the original 18o signature remains

sampling strategy and climatic implications of tree ring stable isotopes on the southeast tibetan plateau we explore the potential of tree ring cellulose d18o and d13c records for reconstructing climate variability in the southeast tibetan plateau our sampling strategy was designed to investigate intra and inter tree variability and the effects of the age of tree on d18o variation we show that intra tree d13c and d18o variability is negligible and inter tree coherence is sufficient to build robust tree ring d18o or d13c chronologies based on only four trees there is no evidence of an age effect regarding d18o in contrast with tree ring width in our warm and moist sampling site young tree d13c is not clearly correlated with monthly mean meteorological data tree ring d18o appears significantly anti correlated with summer precipitation amount regional cloud cover and relative humidity simulations conducted with the orchidee land surface model confirm the observed contribution of relative humidity to tree cellulose d18o and explain the weak correlation of d13c with climate by the non linear integration linked with photosynthesis altogether the tree ring cellulose d18o is shown to be a promising proxy to reconstruct regional summer moisture variability prior to the instrumental period 2010 elsevier b v

stable isotopic variations in west china a consideration of moisture sources 1 in this study individual precipitation samples collected over 2 years at stations in different climatic regions of west china tibetan plateau region tianshan region and altay were analyzed for the stable isotopes of precipitation to improve our understanding of how vapor transport impacts the modern stable isotopic distribution our results identify regional patterns in both 18o and deuterium excess d excess defined as d 8 18o and in particular we have identified the northward maximum extent of the southwest monsoon over the tibetan plateau this demarcation is also the boundary for the fractionation effect of temperature on stable isotopes in precipitation the patterns we have identified are as follows 1 in the southern tibetan plateau along the southern slope of the himalayas our results show a distinct seasonality for both 18o and d excess as a result of the shift of summer monsoon moisture and winter westerly moisture transport the signals of 18o in the western tibetan plateau reveal that the region receives southwest monsoonal moisture in the east of the plateau stable isotopic variation shows alternation between monsoon intrusion and recycling of northern moisture 2 in contrast in tianshan there is an apparent temperature effect in 18o with enriched values occurring in summer and depleted values occurring in winter seasonal d excess values opposite to those observed in the southern tibetan plateau are controlled by differing seasonal evaporation conditions 3 in altay the most northern mountain region the seasonal 18o shows the same variation with that in tianshan region however d excess shows no apparent seasonal variation

accessory phase controls on the geochemistry of crustal melts and restites produced during water undersaturated partial melting the profound geochemical conseqences of accessory phase behaviour during partial melting of highgrade metapelites are demonstrated with reference to two geochemically distinct crustal melts produced by biotite dehydration melting reactions under granulite facies kbar 860 cc conditions these two leucogneiss suites from the brattstrand bluffs coastline eastern antarctica have similar field relations transport distances 10 100 s of metres and major element chemistry type 1 leucogneisses have low zr th and lree positive eu anomalies and zr zr and lreet lreet values less than 1 0 i e less than required to saturate the melt mass balance constraints suggest that these melts have been extracted before equilibration with host melanosomes the dry peraluminous nature of vapour undersaturated melts inhibits monazite and zircon solubility and results in concentration of these phases in the residue melts are consequently depleted in lree and hree melanosomes show complementary enrichment in lree while hree patterns are dominated by residual garnet type 2 leucogneisses in contrast have strongly enriched zr th and lree abundances negative eu anomalies and zr zr and lreet lreet 1 resulting from accessory phase entrainment vapour absent partial melting under moderate 6 8 kbar pressure granulite facies conditions of a pelitic source containing monazite is likely to give disequilibrium melts depleted in lree and hree as monazite and garnet are concentrated in the residue if temperatures are high enough 850 870 c to permit relatively large degrees of partial melting then the feldspar component of the source will be removed almost completely giving melts with large positive eu anomalies melts formed under vapour present conditions are unlikely to show such extreme lree and hree depletion or positive eu anomalies even at high degrees of partial melting disequilibrium melting coupled with source entrainment could fortuitously produce ree and trace element signatures similar to those typical of s type granites and usually ascribed to equilibrium melting conditions

tree ring cellulose δ18o of fokienia hodginsii in northern laos a promising proxy to reconstruct enso 1 a tree ring cellulose 18o chronology of fokienia hodginsii from 1951 to 2002 is established by four cores from four different trees to explore its potential for reconstructing climatic variations in northern laos this chronology is the first tree ring 18o chronology from laos as well as the first for this species we compare variations of tree ring cellulose 18o and ring width between cores the results suggest that the 18o time series are more strongly correlated between different trees than ring width time series are in addition correlation analysis shows a significantly negative correlation between tree ring cellulose 18o and the may october palmer drought severity index pdsi while the tree ring width indices have a poor correlation with pdsi the spatial correlation analysis between tree ring cellulose 18o and global sea surface temperature and the time series correlation analysis between tree ring cellulose 18o and the multivariate el nino southern oscillation enso index mei during the investigated period 1951 2002 reveal that enso has an important effect on tree ring cellulose 18o in laos our results indicate that the tree ring cellulose 18o of fokienia hodginsii is a promising proxy to reconstruct pdsi in southeast asian countries such as laos and to discuss their teleconnections with global atmospheric circulations such as enso

two hundred fifty years of reconstructed and modeled tropical temperatures 1 recent large scale palaeoclimate reconstructions of past temperature have been essentially biased to the extratropics owing to a paucity of proxy data in tropical regions herein we describe the first coral based reconstruction of sea surface temperatures ssts for the whole of the tropics 30 n 30 s it was developed from 14 disparate coral records located in the indian and pacific oceans over the most replicated period the reconstruction explains 57 of the tropical sst variance however the strength of this signal weakens markedly as the number of coral records decreases the reconstruction is robust between 1850 and 1993 but some fidelity is indicated back as far as the mid 18th century these results suggest that ambiguities in the low frequency domain of 18o measurements can be partially overcome by pooling together multiple time series from different locations around the tropics agreement with simulations from two general circulation models indicates that the late 20th century is likely the warmest period in the tropics for the last 250 years and that this recent warming can only be explained by anthropogenic forcing the high frequency variability is dominated by the el nino southern oscillation the reconstruction owing to the small number of coral records is unfortunately restricted both in time and space therefore we hope that this study will spur the palaeoclimate community to develop new and longer proxy series to improve the current meager data base of temperature sensitive series in the tropics

hydroclimatic seasonality recorded by tree ring δ18o signature across a himalayan altitudinal transect abstract water stable isotope ratios of tropical precipitation predominantly reflect moisture source and precipitation intensity trees can incorporate the isotopic signals into annual tree ring cellulose records permitting reconstruction of the temporal changes of hydroclimate over decades to millennia this is especially valuable in the himalayas where the understanding of monsoon dynamics is limited by the lack of a dense and representative observational network we have analyzed tree ring 18 o records from two distinct physiographic sites along the upper kali gandaki valley in the central nepal himalayas representing the wet high himalayas and the trans himalayan dryland to the north empirical correlations and regression analyses were compared to an in situ calibrated oxygen isotope fractionation model exploring the relationships between tree ring 18 o and seasonal mean variability of hydroclimatic forcing at the different locations for this purpose gridded precipitation data from the asian rain gauge dataset aphrodite as well as high resolution onsite observations relative humidity air temperature 18 o of precipitation and radial tree growth were used we found that two distinct sets of meteorological values reflecting pre monsoon and monsoon conditions are needed to reproduce the measured tree ring 18 o values from the high himalayan site but that a single set of monsoonal values performs best for the trans himalayan site we conclude that trans himalayan trees capture long term changes in strength of the indian summer monsoon in contrast high himalayan tree ring 18 o records a more complex hydro climatic signal reflecting both pre monsoon and monsoon seasons with very contrasting isotopic signatures of precipitation this difference in the two hydroclimatic proxy records offers an opportunity to reconstruct first order hydroclimate conditions such as local precipitation rates and to gain new insights into monsoon timing and seasonal water source determination across the himalayan orographic region

the timing of mineral growth across a regional metamorphic sequence if regional metamorphism occurs in response to crustal thickening then low grade rocks are likely to record earlier thermal conditions than will high grade rocks in the same exhumed terrain1 4 at sulitjelma north norway regional metamorphism during the caledonian orogeny created a type sequence of progressive metamorphic zones5 7 garnet and coexisting minerals from the high grade part of this terrain yield precise and concordant sm nd u pb and rb sr ages which relate directly to the pressure temperature conditions of mineral growth8 here we present pressure temperature time p t t information for lower grade rocks occurring at the garnet isograd taken together these data provide a precise estimate of the timing of mineral equilibration across a prograde metamorphic terrain and indicate that peak metamorphic conditions at the garnet isograd at 458 20 c were attained 8 3 3 0myr t sm nd or 8 7 3 2myr t u pb before the peak in the high grade sample at 544 16 c these results clearly illustrate that the exhumed p t array recorded in such terrains cannot be used to deduce any single geotherm that existed during metamorphism

tree ring density inferred late summer temperature variability over the past three centuries in the gaoligong mountains southeastern tibetan plateau long and high resolution proxy records are still sparse in the southeastern tibetan plateau tp hampering our understanding of past climatic variability from a long term perspective in this study we developed a regional maximum latewood density mxd chronology of larix speciosa stretching up to 523 years based on 72 tree ring cores 44 trees collected from three sites close to the tree line in the gaoligong mountains southeastern tp this chronology responded well to temperatures during august through september and was thus used to reconstruct late summer august september temperature over the period a d 1690 2008 the reconstruction explains 40 9 of the total temperature variance during the calibration phase cold conditions prevailed during the periods 1695 1702 1806 1821 the 1850s 1882 1889 the 1900s and the 1960s warm phases occurred in 1734 1745 the 1770s 1824 1840 the 1890s 1927 1936 the 1940s 1950s and 2002 2008 spatial correlation with the gridded temperature data set showed that our reconstruction captures large scale regional temperature variations for the southeastern and southern tp comparison with other tree ring inferred temperature time series in the surrounding areas glacier fluctuations and historical documental records imply a high degree of confidence for our reconstruction c 2015 elsevier b v all rights reserved

t phase observations in northern california acoustic to seismic coupling at a weakly elastic boundary plans for a hydroacoustic network intended to monitor compliance with the ctbt call for the inclusion of five t phase stations situated at optimal locations for the detection of seismic phases converted from ocean borne t phases we examine factors affecting the sensitivity of land based stations to the seismic t phase the acoustic to seismic coupling phenomenon is described by upslope propagation of an acoustic ray impinging at a sloping elastic wedge we examine acoustic to seismic coupling characteristics for two cases the first in which the shear velocity of the bottom is greater than the compressional velocity of the fluid i e vp vs vw the second is a weakly elastic solid in which vs vw vw we show that acoustic energy couples primarily to shear wave energy except at very high slope angles we show that the weakly elastic solid i e vs vw behaves nearly like a fluid bottom with acoustic energy coupling to both p and s waves even at low slope angles

temperature signals in tree ring oxygen isotope series from the northern slope of the himalaya abstract oxygen isotope ratios 18 o are the most commonly used parameters recorded in paleoclimate archives since they link different natural archives via the water cycle tree ring 18 o 18 otr has been widely used for hydroclimate reconstructions in the himalaya however few of them record temperature signals which are dominant in himalaya ice core 18 o we hypothesize that the precipitation amount effect due to the south asian summer monsoon sasm may overprint temperature signals in 18 otr series the purpose of this study is to investigate whether temperature signals could be found in the 18 otr in locations where the influence of sasm is weak we developed a 105 yr 18 otr chronology from the northern slope of the western himalaya which greatly blocks the sasm our 18 otr clearly shows stronger correlations with temperature dominant winter and weak summer than summer precipitation signals it also agrees well with summer soil moisture 18 o simulated by the global isotope model lmdz4 r 0 72 1979 2010 in lmdz4 low winter temperature was found to increase winter snowfall and subsequent snow melt and thus to increase the contribution of winter snowfall to soil moisture in summer at the expense of summer precipitation since winter snowfall is more depleted than summer precipitation this leads to lower summer soil moisture 18 o the temperature signals found in our 18 otr series are consistent with those found in the dasuopu ice core 18 o this implies that 18 otr series from the southwest tibetan plateau tp with a weak monsoon hold great potential to capture temperature signals climate interpretations of 18 o proxies in the himalaya largely depend on the influence of seasonal water from the dominant atmosphere circulation systems of the westerlies or monsoon the 18 o proxies from the monsoon affected region have a higher potential for the reconstruction of boreal summer hydroclimate whereas 18 o proxies from westerly affected sites have a higher potential for temperature reconstructions

rare earth element distributions among minerals in a granodiorite and their petrogenetic implications a study of the distribution of lanthanide rare earths in a granodiorite from the eastern peninsular ranges batholith southern california reveals that a large fraction of the ree in this rock resides in the accessory phases sphene and allanite the minerals plagioclase alkali feldspar biotite epidote and apatite each contribute approximately 1 or less of each ree to the whole rock with the exception of eu for which plagioclase contributes 7 sphene and allanite together contain 80 to 95 of each ree each of these phases is zoned in ree concentration with substantial decreases from core to margin textural observations argue for relatively early saturation and precipitation of sphene and allanite in the magma ree zoning trends in sphene and allanite and unexpectedly low ree concentrations in largely later crystallizing minerals such as feldspar indicate that the precipitation of sphene and allanite significantly reduced ree concentrations in residual melts these results illustrate the potential that sphene and allanite have for controlling the behavior of ree in granitic magmas available information collectively suggest that the sampled granodiorite existed as a complete melt that the ree contained in the assemblage of phases were derived by direct crystallization from the melt and that the melt behaved essentially as a closed system once crystallization of the phases now present began close correspondences between the major and trace element chemistries of the granodiorite and phenocryst poor lavas from similar tectonic settings support these conclusions the ree pattern of the granodiorite melt appears to have originated at depth and is characteristic of its source regions and derivation mechanism the high liquidus temperature of a granodiorite melt 1000 c indicates the importance of mantle derived components within the sources of batholithic magmas in the peninsular ranges

are pooled tree ring δ13c and δ18o series reliable climate archives a case study of pinus nigra spp laricio corsica france abstract stable carbon and oxygen isotopes in tree rings are considered as reliable climate archives as they provide past environmental information with high resolution however recent studies have shown that isotope chronologies may reveal a long term age trend and be influenced by non climatic factors as other tree ring parameters as well these trends can only be identified in chronologies measured on individual trees but not on pooled sample chronologies consisting of several trees in order to test whether pooled chronologies from pine trees from the island of corsica mediterranean france can be used for climatic reconstructions we compared calculated mean values from 5 individual trees with pooled chronologies from the same 5 individuals carbon and oxygen isotope chronologies for a 50 year interval with annual resolution and 400 years with decadal resolution were analysed in order to document secular changes in inter tree variability and to test for age related trends in the isotope ratios pooled carbon and oxygen isotope series correspond well to chronologies based on mean values calculated from analyses of individual trees inter tree variability in oxygen isotope ratios is higher than in carbon isotope ratios but remains relatively constant over time similarities between the isotope series of individual trees are stronger over the 400 year time scale documenting a common long term signal in the isotope values no long term age related trends are observed oxygen isotope values of the juvenile phase are characterised by a remarkable decrease over 40 50 years interpreted to be related to the less developed root system of the young trees this age effect can be avoided by not considering the first 50 years from the chronologies our results confirm that pooled carbon and oxygen isotope chronologies from pinus nigra can be used for environmental reconstructions without statistical detrending

southern tibetan plateau ice core δ18o reflects abrupt shifts in atmospheric circulation in the late 1970s ice cores from the tibetan plateau provide high resolution records of changes in the snow and ice isotopic composition in the monsoon sector of southern tibetan plateau their climatic interpretation has been controversial here we present a new high resolution 18o record obtained from 2206 measurements performed at 2 3 cm depth resolution along a 55 1 m depth ice core retrieved from the noijinkansang glacier nk 5950 m a s l that spans the period from 1864 to 2006 ad the data are characterized by high 18o values in the nineteenth century 1910s and 1960s followed by a drop in the late 1970s and a recent increasing trend the comparison with regional meteorological data and with a simulation performed with the lmdziso general circulation model leads to the attribution of the abrupt shift in the late 1970s predominantly to changes in regional atmospheric circulation together with the impact of atmospheric temperature change correlation analyses suggest that the large scale modes of variability pdo and enso i e pacific decadal oscillation and el nino southern oscillation play important roles in modulating nk 18o changes the nk 18o minimum at the end of the 1970s coincides with a pdo phase shift an inflexion point of the zonal index representing the overall intensity of the surface westerly anomalies over middle latitudes as well as enso implying interdecadal modulation of the influence of the pdo enso on the indian monsoon on southern tp precipitation 18o while convective activity above north india controls the intra seasonal variability of precipitation 18o in southern tp other processes associated with changes in large scale atmospheric circulation act at the inter annual scale

a modern pollen climate dataset from the darjeeling area eastern himalaya assessing its potential for past climate reconstruction abstract relying on the ability of pollen assemblages to differentiate among elevationally stratified vegetation zones we assess the potential of a modern pollen climate dataset from the darjeeling area eastern himalaya in past climate reconstructions the dataset includes 73 surface samples from 25 sites collected from a c 130 3600 m a s l elevation gradient along a horizontal distance of c 150 km and 124 terrestrial pollen taxa which are analysed with respect to various climatic and environmental variables such as mean annual temperature mat mean annual precipitation map mean temperature of coldest quarter mtcq mean temperature of warmest quarter mtwq mean precipitation of driest quarter mpdq mean precipitation of wettest quarter mpwq aet actual evapotranspiration and mi moisture index to check the reliability of the modern pollen climate relationships different ordination methods are employed and subsequently tested with huisman olff fresco hof models a series of pollen climate parameter transfer functions using weighted averaging regression and calibration partial least squares wa pls models are developed to reconstruct past climate changes from modern pollen data and have been cross validated results indicate that three of the environmental variables i e mtcq mpdq and mi have strong potential for past climate reconstruction based on the available surface pollen dataset the potential of the present modern pollen climate relationship for regional quantitative paleoclimate reconstruction is further tested on a late quaternary fossil pollen profile from the darjeeling foothill region with previously reconstructed and quantified climate the good agreement with existing data allows for new insights in the hydroclimatic conditions during the last glacial maxima lgm with winter temperature being the dominant controlling factor for glacial changes during the lgm in the eastern himalaya

monazite controlled sm nd fractionation in leucogranites an ion microprobe study of garnet phenocrysts rare earth element ree abundances in four garnet phenocrysts from two monazite bearing leucogranites from southern british columbia have been measured with an ion microprobe this study examines the effect of monazite crystallization on the lrees by using garnet as a monitor of elemental variations in the liquid this approach virtually eliminates uncertainties associated with source induced lree fractionation the garnets examined are spessartine rich alm70 75sps18 22pyp3 4grs3 4 phenocrysts that show primary igneous zoning and lack monazite inclusions garnet rims have zoning profiles i e eu to ce that are depleted by factors of five to ten relative to cores of the three models investigated to constrain processes controlling lree zoning in garnet 1 1 variations in the garnet melt distribution coefficients 2 2 liquid diffusion controlled partitioning and 3 3 crystal diffusion controlled partitioning the latter model best explains the observed zoning this model is consistent with experimental studies suggesting that monazite has a low solubility in granitic melts these results suggest that nd model ages calculated using measured 147sm144nd in leucogranites should be viewed with caution as is demonstrated by neodymium isotopic data from southern british columbia and the central nepalese himalaya

a metamorphic history from micron scale 207pb 206pb chronometry of archean monazite ion microprobe measurements of pb isotope ratios in monazites have been obtained in situ from thin sections using the cambridge isolab 120 molecular interferences are sufficiently resolved at an rp of 6500 to allow 2 7pb z 6pb dating of monazite with precisions as low as 4 5 ma 2 r the results presented here provide important information on the chronological history of the late archean metamorphism of the wind river range wyoming usa matrix monazites and monazite inclusions in garnets from a metapelite from the northern wind river range have been analysed by sims in a previous study peak metamorphic conditions t 800 c p 8 1 kb were estimated using inclusion assemblages in garnets from this same sample isolated monazite inclusions in garnet yield 2 7pb z 6pb age estimates of 2781 6 to 2809 10 ma those along fractures yield lower ages 2603 2687 ma which are similar to tims and sims ages of matrix monazites a single large 500 xm monazite grain locally preserves growth zoning but has a recrystallised core and a resorbed recrystallised rim age estimates for these three regions are 2788 9 ma 2663 4 and 2523 6 ma respectively thus the inclusion assemblages of sharp and essene may record peak metamorphic conditions at ca 2 8 ga and indicate a phase of metamorphism that predates by over 100 ma the emplacement of the bridget batholith the major lithologic component of the northern wind river range the analysed monazite grains appear to preserve ca 300 ma history even within a single grain monazite inclusions in garnet that are fully armoured may provide estimates for the time of garnet growth even in high grade terranes where most chronometers are reset the age pattern preserved by the large monazite grain cannot be simply related to diffusion controlled closure instead a chronology is preserved which can be related to the petrographic setting of individual grains through in situ analysis

on the weakening relationship between the indian monsoon and enso analysis of the 140 year historical record suggests that the inverse relationship between the el nino southern oscillation enso and the indian summer monsoon weak monsoon arising from warm enso event has broken down in recent decades two possible reasons emerge from the analyses a southeastward shift in the walker circulation anomalies associated with enso events may lead to a reduced subsidence over the indian region thus favoring normal monsoon conditions additionally increased surface temperatures over eurasia in winter and spring which are a part of the midlatitude continental warming trend may favor the enhanced land ocean thermal gradient conducive to a strong monsoon these observations raise the possibility that the eurasian warming in recent decades helps to sustain the monsoon rainfall at a normal level despite strong enso events