reconstruction of past precipitation δ18o using tree ring cellulose δ18o and δ13c a calibration study near lac d annecy france abstract two sets of living oaks quercus r growing under different hydrological situations were sampled near lac d annecy france the stable isotope composition of the latewood cellulose was analysed in terms of oxygen and carbon isotopic composition for the period 1971 2001 and compared to the nearby monthly meteorological temperature relative humidity and isotopic composition of precipitation records a linear regression shows that 60 of the cellulose oxygen isotopic composition inter annual variations are due to changes in precipitation isotopic composition and relative humidity the small slope between cellulose versus precipitation oxygen isotopic composition suggests a significant contribution of local continental recycling and questions the common assumption that vapour oxygen isotopic composition is at equilibrium with precipitation isotopic composition in europe during the growing season finally the combined use of tree ring oxygen and carbon isotopic composition records enables to account for leaf water enrichment due to stomata stress and to provide a reconstruction r 2 0 64 of the summer precipitation isotopic composition

geomorphic and hydrologic aspects of monsoon floods on the narmada and tapi rivers in central india abstract high magnitude floods during the monsoon season are considered to be india s recurring and leading natural disaster such large flood are extremely important events not only in terms of human impact but also from the standpoint of geomorphic effectiveness and geomorphic work the narmada and tapi rivers in central india are characterized by one of the most intense flood regimes in the seasonal tropics modern historical and palaeoflood records indicate that large floods are relatively common hydrologic and geomorphic events on the narmada and tapi rivers a catastrophic flood on tapi in july 1991 that occurred from heavy rains and a dam break represents one of the highest unit discharges yet recorded in any part of central india flood competence studies indicate that the flood power of the two rivers is comparable with some of the largest historic and prehistoric floods reported from other parts of the world the rivers have preserved geomorphic and sedimentologic records of palaeofloods for the last two millennium and in choral river a 5000 year old record has been located examination of the synoptic conditions associated with the flood generating low pressure systems reveals that all but a few of them are the result of bay of bengal depressions the flooding in such large rivers profoundly challenges flood hazard management because of limited instrumental records and large spatio temporal variation it is therefore imperative that the design engineering community in india incorporates the geomorphic sedimentologic and botanic information in the planning and design of water resource development projects

seasonal incursion of indian monsoon humidity and precipitation into the southeastern qinghai tibetan plateau inferred from tree ring δo18 values with intra seasonal resolution abstract incursion of the indian monsoon flow onto the qinghai tibetan plateau is an important regional moisture delivery mechanism but the causes of intra seasonal and longer term variations are poorly understood we observed a clear intra seasonal cycle in the oxygen isotope composition 18o of smith fir abies forrestii var georgei growing at two different altitudes high elevation site 29 39 n 94 42 e 4200 m a s l low elevation site 29 39 n 94 43 e 3800 m a s l on a se facing slope in the sygera mountains southeastern qinghai tibetan plateau mechanistic modeling suggests that 18o of precipitation which in turn depends on relative humidity and precipitation amount is important in controlling the intra seasonal tree ring isotopic cycle and we speculate that the same controls also operate on interannual and longer time scales if so multi century 18o records with intra seasonal resolution may enable us to infer long term variations in the incursion of the indian monsoon onto the qinghai tibetan plateau

petrology and geochemistry of the paliza canyon formation and the bearhead rhyolite keres group jemez mountains new mexico basaltic andesite andesite dacite and rhyodacite of the paliza canyon formation 9 1 to 8 5 m y and the bearhead rhyolite 7 1 to 6 5 m y belong to a high k calc alkaline association in the southern jemez mountains new mexico the majority of the rocks of the paliza canyon formation contain augite hypersthene and plagioclase phenocrysts olivine is an important phenocryst in the basaltic andesite but it is absent in the other rock types in the rhyodacite hornblende is a major phenocryst at the expense of the pyroxenes characteristically a very restricted range in the fe mg composition is found for the pyroxenes augite from 0 33 0 29 and hornblende 0 41 0 47 throughout the whole range of rock types from basaltic andesite 56 sio 2 to rhyodacite 67 sio 2 on the other hand the bearhead rhyolite lacks pyroxene and it has two feldspars sanidine and plagioclase and bipyramidal quartz and biotite its sio 2 content ranges between 76 5 and 77 3 the bearhead rhyolite lies on the two feldspar surface or below it in the sanidine field the paliza canyon rocks plot within the plagioclase volume of the granite system both major and trace element trends in the paliza canyon formation do not project to the bearhead rhyolite composition major and trace element modeling suggests that the sequence from basaltic andesite to rhyodacite in the paliza canyon formation can be formed by simple fractional crystallization the bearhead rhyolite cannot be formed from the paliza canyon rhyodacite by this process however removal of the observed phenocrysts found in the rhyodacite would form a rhyolite enriched in ba hf th u and light rare earth elements lree and depleted in v and sc the bearhead rhyolite however is depleted in the former group and enriched in the latter these conclusions are supported by initial 87 sr 86 sr ratios three samples of bearhead rhyolite have initial ratios of 0 7056 0 7073 and 0 7076 two samples of paliza canyon basaltic andesite on the other hand have ratios of 0 7041 and 0 7044 the most likely source for the bearhead rhyolite is lower crustal material which may have been fused partially from the heat provided by the andesitic magmas of the paliza canyon formation

model evaluation for reconstructing the oxygen isotopic composition in precipitation from tree ring cellulose over the last century the oxygen isotope composition of tree rings is controlled by many factors including temperature amount of precipitation and changes in relative humidity in this study we present a modified leaf water model from dongmann et al radiation and environmental biophysics 11 1974 41 that can be used to calculate the isotopic composition of the source water and thus of precipitation that a tree used during the growing season the calibration of the model was accomplished by comparing a previously measured oxygen isotope tree ring chronology from central switzerland with the swiss network for isotopes in the hydrologic cycle station at bern from 1971 to 1995 and integrating temperature relative humidity data and ring width in particular our efforts focused on understanding the significance of the dampening factor f which we relate to changes in humidity and its variability over both the calibration period 1971 to 1995 and the study period 1913 to 1995 our results indicate that f ranging between 0 27 to 0 49 is variable based on correlation with relative humidity average daily temperature and ring width index using this model we have constructed a record of the oxygen isotope composition of precipitation during the growing season may through september for the last century in central western europe this approach can be potentially used in other locations where isotopic and meteorological data are available to extend records of the isotopic composition of precipitation back in time beyond observational records

variability of southwest indian summer monsoon precipitation during the bolling allerod we have generated a high resolution 20 yr 2 3 0 th dated stalagmite oxygen isotope record from timta cave in the western himalaya in india that documents southwest indian summer monsoon ism precipitation variations during the bolling allerod interstadial from 15 2 to 11 7 ka compared with the glacial and younger dryas ism precipitation was enhanced during the bolling allerod ism precipitation was apparently coupled to variations in the east asian monsoon and north atlantic climate on millennial and multicentennial time scales during the deglaciation analyses of a high growth rate interval 2 5 yr resolution encompassing the late bolling early alterod suggest that multidecadal monsoon variability was an important aspect of ism behavior at that time the frequency spectrum of ism precipitation during this time interval is similar to that of the 1 4 c record and other ism precipitation records during the latest holocene this raises the hypothesis that multidecadal climate dynamics during the late boiling early allerod may have been similar to those that operated during the last several millennia even though the boundary conditions of these two time intervals were very different

strong coherence between solar variability and the monsoon in oman between 9 and 6 kyr ago variations in the amount of solar radiation reaching the earth are thought to influence climate but the extent of this influence on timescales of millennia to decades is unclear a number of climate records show correlations between solar cycles and climate1 but the absolute changes in solar intensity over the range of decades to millennia are small2 and the influence of solar flux on climate is not well established the formation of stalagmites in northern oman has recorded past northward shifts of the intertropical convergence zone3 whose northward migration stops near the southern shoreline of arabia in the present climate4 here we present a high resolution record of oxygen isotope variations for the period from 9 6 to 6 1 kyr before present in a th u dated stalagmite from oman the 18o record from the stalagmite which serves as a proxy for variations in the tropical circulation and monsoon rainfall allows us to make a direct comparison of the 18o record with the 14c record from tree rings5 which largely reflects changes in solar activity6 7 the excellent correlation between the two records suggests that one of the primary controls on centennial to decadal scale changes in tropical rainfall and monsoon intensity during this time are variations in solar radiation

asymmetric sea floor spreading caused by ridge plume interactions crustal accretion at mid ocean ridges is generally modelled as a symmetric process regional analyses however often show either small scale asymmetries which vary rapidly between individual spreading corridors or large scale asymmetries represented by consistent excess accretion on one of the two separating plates over geological time spans1 2 3 4 5 6 in neither case is the origin of the asymmetry well understood here we present a comprehensive analysis of the asymmetry of crustal accretion over the past 83 myr based on a set of self consistent digital isochrons7 and models of absolute plate motion8 9 we find that deficits in crustal accretion occur mainly on ridge flanks overlying one or several hotspots we therefore propose that asymmetric accretion is caused by ridge propagation towards mantle plumes or minor ridge jumps sustained by asthenospheric flow10 11 between ridges and plumes quantifying the asymmetry of crustal accretion provides a complementary approach to that based on geochemical12 and other geophysical data13 14 in helping to unravel how mantle plumes and mid ocean ridges are linked through mantle convection processes

semiautomatic fracture zone tracking oceanic fracture zone traces are widely used in studies of seafloor morphology and plate kinematics satellite altimetry missions have resulted in high resolution gravity maps in which all major fracture zones and other tectonic fabric can be identified and numerous scientists have digitized such lineaments we have initiated a community effort to maintain low cost infrastructure that allows seafloor fabric lineaments to be stored accessed and updated a key improvement over past efforts is our processing software released as a gmt5 supplement that allows for semiautomatic corrections to previously digitized fracture zone traces given improved gridded data sets here we report on our seafloor fabric processing tools which complement our database of seafloor fabric lineations magnetic anomaly identifications and plate kinematic models

monsoon precipitation variation recorded by tree ring δ18o in arid northwest china since ad 1878 abstract the east asian summer monsoon easm precipitation from may to august over the helan mountains located in the northwest margin of the easm has been investigated through tree ring 18o for the last 120 years the dry and wet intervals derived from the 18o series can be verified by the tree ring width based may july precipitation reconstruction most of the time the 18o series and ring width derived precipitation reconstruction vary synchronously at low frequency high values of 18o correspond to high precipitation periods and vice versa since the 1970s the east asian summer monsoon precipitation has been increasing which was confirmed by other records and documents our results show that tree ring 18o can serve as an indicator of the strength of the east asian summer monsoon variation in the past we also found that tree ring 18o varies inversely to 13c in the study area

ocean basin evolution and global scale plate reorganization events since pangea breakup we present a revised global plate motion model with continuously closing plate boundaries ranging from the triassic at 230 ma to the present day assess differences among alternative absolute plate motion models and review global tectonic events relatively high mean absolute plate motion rates of approximately 9 10 cm yr 1 between 140 and 120 ma may be related to transient plate motion accelerations driven by the successive emplacement of a sequence of large igneous provinces during that time an event at 100 ma is most clearly expressed in the indian ocean and may reflect the initiation of andean style subduction along southern continental eurasia whereas an acceleration at 80 ma of mean rates from 6 to 8 cm yr 1 reflects the initial northward acceleration of india and simultaneous speedups of plates in the pacific an event at 50 ma expressed in relative and some absolute plate motion changes around the globe and in a reduction of global mean plate speeds from about 6 to 4 5 cm yr 1 indicates that an increase in collisional forces such as the india eurasia collision and ridge subduction events in the pacific such as the izanagi pacific ridge play a significant role in modulating plate velocities

strong influence of water vapor source dynamics on stable isotopes in precipitation observed in southern meghalaya ne india to calibrate 18o time series from speleothems in the eastern indian summer monsoon ism region of india and to understand the moisture regime over the northern bay of bengal bob we analyze the 18o and d of rainwater collected in 2007 and 2008 near cherrapunji india d values range from 18 5 to 144 4 while 18o varies between 0 8 and 18 8 the local meteoric water line lmwl is found to be indistinguishable from the global meteoric water line gmwl late ism september october rainfall exhibits lowest 18o and d values with little relationship to the local precipitation amount there is a trend to lighter isotope values over the course of the ism but it does not correlate with the patterns of temperature and rainfall amount 18o and d time series have to be interpreted with caution in terms of the amount effect in this subtropical region we find that the temporal trend in 18o reflects increasing transport distance during the ism isotopic changes in the northern bob surface waters during late ism and vapor re equilibration with rain droplets using an isotope box model for surface ocean waters we quantify the potential influence of river runoff on the isotopic composition of the seasonal freshwater plume in the northern bob temporal variations in this source can contribute up to 25 of the observed changes in stable isotopes of precipitation in ne india to delineate other moisture sources we use backward trajectory computations and find a strong correlation between source region and isotopic composition palaeoclimatic stable isotope time series from northeast indian speleothems likely reflect changes in moisture source and transport pathway as well as the isotopic composition of the bob surface water all of which in turn reflect ism strength stalagmite records from the region can therefore be interpreted as integrated measures of the ism strength

organization of the tectonic plates in the last 200 myr the present tessellation of the earth s surface into tectonic plates displays a remarkably regular plate size distribution described by either one sornette and pisarenko 2003 or two bird 2003 statistically distinct groups characterised by large and small plate size a unique distribution implies a hierarchical structure from the largest to the smallest plate alternatively two distributions indicate distinct evolutionary laws for large and small plates the first tied to mantle flow the second determined by a hierarchical fragmentation process we analyse detailed reconstructions of plate boundaries during the last 200 myr and find that i large and small plates display distinct statistical distributions ii the small plates display little organisational change since 60 ma and iii the large plates oscillate between heterogeneous 200 170 myr and 65 50 ma and homogeneous 120 100 ma plate tessellations on a timescale of about 100 myr heterogeneous states are reached more rapidly while the plate configuration decays into homogeneous states following a slower asymptotic curve suggesting that heterogeneous configurations are excited states while homogeneous tessellations are equilibrium states we explain this evolution by proposing a model that alternates between bottom and top driven earth dynamics physically described by fluid dynamic analogies the rayleigh benard and benard marangoni convection respectively we discuss the implications for true polar wander tpw global kinematic reorganisations 50 and 100 ma and the earth s magnetic field inversion frequency

low frequency of southern asian monsoon variability using a 295 year record from the dasuopu ice core in the central himalayas 1 a better understanding of the spatial and temporal variability of rainfall in the himalayas should be extremely important to improve our understanding of asian monsoon dynamics there is little that is understood about rainfall variability at the high himalayas with elevation over 7000 m a s l here a high resolution snow accumulation record from a well dated dasuopu ice core from central himalayas reflects low frequency variability of monsoon precipitation over the last 295 year multidecadal to centennial variations in the dasuopu snow accumulation dsa are in phase out of phase with that in monsoon rainfall of northeast indian nepal and bangladesh southern india over the period 1901 1995 the record shows the monsoon in central himalayas had weakened in 18th century and strengthened throughout much of 19th and early 20th century and then weakening again from early 1920s to the present

the breakup of east gondwana assimilating constraints from cretaceous ocean basins around india into a best fit tectonic model published models for the cretaceous sea oor spreading history of east gondwana result in unlikely tectonic scenarios for at least one of the plate boundaries involved and or violate particular constraints from at least one of the associated ocean basins we link east gondwana spreading corridors by integrating magnetic and gravity anomaly data from the enderby basin off east antarctica within a regional plate kinematic framework to identify a conjugate series of east west trending magnetic anomalies m4 to m0 126 7 120 4 ma the mid ocean ridge that separated greater india from australia antarctica propagated from north to south starting at 136ma northwest of australia and reached the southern tip of india at 126 ma sea oor spreading in the enderby basin was abandoned at 115 ma when a ridge jump transferred the elan bank and south kerguelen plateau to the antarctic plate our revised plate kinematic model helps resolve the problem of successive two way strike slip motion between madagascar and india seen in many previously published reconstructions and also suggests that sea oor spreading between them progressed from south to north from 94 to 84 ma this timing is essential for tectonic ow lines to match the curved fracture zones of the wharton and enderby basins as greater india gradually began to unzip from madagascar from 100 ma in our model the 85 east ridge and kerguelen fracture zone formed as conjugate anks of a leaky transform fault following the 100ma spreading reorganization our model also identi es the afanasy nikitin seamounts as products of the conrad rise hotspot

climatic significance of tree ring δ18o in the qilian mountains northwestern china and its relationship to atmospheric circulation patterns it is important to understand the history and dynamics of climate in a transitional region between areas with different atmospheric circulation patterns where the vegetation and ecosystems are vulnerable to environmental change we investigated variations in the long term oxygen isotope composition delta 18 o in tree rings of qinghai spruce picea crassifolia and their relationships to climatic parameters in the and qilian mountains of northwestern china from 1870 to 2006 we found that the mean temperature from the previous november to the current february was significantly and positively correlated with the tree ring delta 18 o values the temperature effect the positive relationship between the temperature and the precipitation delta 18 o value can explain the connection between temperature and the tree ring delta 18 o values due to pooling of the earlywood and latewood into yearly tree ring samples it appears that the cellulose delta 18 o may be influenced by isotopically nonhomogeneous water sources and climatic conditions during the previous and current growing seasons subtle shifts and amplitude deviations in cellulose delta 18 o which abruptly became more positive around 1977 1978 may be attributed to the shifting climatic regime in china and to temperature variations respectively our results illustrated the potential for investigating climatic or atmospheric circulation patterns based on oxygen isotope records in tree rings in regions near the interface between different large scale synoptic circulations c 2009 elsevier b v all rights reserved

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

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

deep crustal structure in the eastern gulf of mexico we use air gun data recorded by ocean bottom seismometers to constrain the velocity structure along gulf of mexico basin opening line 4 a profile extending from the northwestern florida peninsula across the florida escarpment to the central gulf of mexico moderately thinned continental crust with a moho depth of 32 33 km average sediment thickness of 6 km and an average crustal thickness of 27 km is interpreted on the northeast end of the profile offshore florida thinned and intruded continental crust is identified over a horizontal distance of 225 km where the crustal layer thins from 25 km to 6 7 km mean seismic velocities of the crust in this region increase from 6 55 km s to 6 95 km s from northeast to southwest and are evidence for increased magmatic input as rifting developed oceanic crust with an average thickness of 5 6 5 7 km is observed over a distance of 175 km on the southwest end of the profile with an extinct spreading ridge with an axial valley morphology imaged on a coincident seismic reflection profile anomalously high upper oceanic crust velocities of 6 0 6 7 km s are interpreted as massive basalt flows and could reflect increased temperatures during emplacement integrating well seismic reflection and our seismic refraction data allow us to estimate a full spreading rate of 2 2 cm yr for seafloor spreading along the profile this indicates that oceanic crust was emplaced at a slow spreading center

indian monsoon precipitation isotopes linked with high level cloud cover at local and regional scales abstract precipitation stable isotopes preserve historic changes of evaporation in the source regions and precipitation processes therefore they can be used to reveal regional hydrological cycle dynamics and paleoclimate reconstructions in monsoon regions strong inverse impacts of convection on precipitation isotope ratios have created a debate regarding the interpretation of isotope records as local climate proxies the proportions of stratiform to convective precipitation on water isotopes together with the influence mechanisms on seasonal and interannual scales remain highly uncertain to further address the influence of precipitation patterns on water isotopes we used 10 yrs of precipitation isotope data from the southern tibetan plateau tp to explore the effects of large scale cloud cover and local climate on precipitation isotopes correlation analysis performed between local precipitation 18 o values and different level cloud data indicated significant negative correlations between precipitation isotopes and high level cloud cover on both seasonal and interannual time scales this result suggests that high level convection in the upper moisture transport stream is a main control on precipitation isotopes in the southern tp the clear and coherent variations of precipitation isotopes with the southern oscillation index and outgoing longwave radiation confirmed that strong convection activity in the moisture source region and during transport significantly depleted heavy isotopes in vapor producing substantially decreased precipitation 18 o in the study region these results agree with earlier findings of tree ring cellulose isotope records that correlate with cloud cover but we emphasized the important role of larger scale regional cloud cover we also delineated different maximum correlation zones for seasonal and interannual time scales likely due to different mechanisms these findings further improve the interpretation of paleoisotope records from the indian summer monsoon region

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

community infrastructure and repository for marine magnetic identifications magnetic anomaly identifications underpin plate tectonic reconstructions and form the primary data set from which the age of the oceanic lithosphere and seafloor spreading regimes in the ocean basins can be determined although these identifications are an invaluable resource their usefulness to the wider scientific community has been limited due to the lack of a central community infrastructure to organize host and update these interpretations we have developed an open source community driven online infrastructure as a repository for quality checked magnetic anomaly identifications from all ocean basins we provide a global sample data set that comprises 96 733 individually picked magnetic anomaly identifications organized by ocean basin and publication reference and provide accompanying hellingerformat files where available our infrastructure is designed to facilitate research in plate tectonic reconstructions or research that relies on an assessment of plate reconstructions for both experts and nonexperts alike to further enhance the existing repository and strengthen its value we encourage others in the community to contribute to this effort

reducing uncertainties in δ13c analysis of tree rings pooling milling and cellulose extraction recent developments of on line methods have provided another boost to the determination of stable isotope ratios in organic material along with a significant increase in sample throughput the sample sizes decrease both of which are necessary conditions to acquire long time series from limited wood amounts in view of this new technique we reconsidered the most important factors influencing the measured isotopic signature which are 1 pooling 2 homogeneity and 3 cellulose extraction in most cases pooling i e mixing wood of the same year from different trees can be made in a simple way by mixing the whole wood available because mass weighted and unweighted isotope measurements were the same within the error more attention must be paid in homogenizing the sample theoretical considerations underpinned by experimental results suggest a fineness of 0 15 mm 115 mesh if cellulose is extracted and 0 1 mm 165 mesh for direct wood analysis many of previous studies did not achieve this fineness we find that wood is as good a climate proxy as cellulose this is shown by comparing correlations of wood and corresponding cellulose isotope values with meteorological data which are identical within the uncertainty

tree ring isotopic pooling without regard to mass no difference from averaging δ13c values of each tree abstract pooling of growth rings from several trees before subsequent isotopic analysis of the mixture may offer the advantage of obtaining representative isotopic values fairly rapidly in principle however unless equal masses are taken from the individuals to make the composite sample the measured isotope value will be biased by the relative mass contribution of the trees each of which likely has a different isotopic composition although biasing associated with direct pooling without regard to mass may happen this study provides evidence at least for stable carbon isotope composition from three sites in the u s midwest and southwest that the error probably more appropriately called difference is negligible with respect to error of preparation and analysis and variability of isotopic composition within and among trees at a site

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

bayesian noise reduction in arabia somalia and nubia arabia finite rotations since 20 ma implications for nubia somalia relative motion knowledge of nubia somalia relative motion since the early neogene is of particular importance in the earth sciences because it i impacts on inferences on african dynamic topography and ii allows us to link plate kinematics within the indian realm with those within the atlantic basin the contemporary nubia somalia motion is well known from geodetic observations precise estimates of the past 3 2 myr average motion are also available from paleo magnetic observations however little is known of the nubia somalia motion prior to 3 2 ma chiefly because the southwest indian ridge spread slowly posing a challenge to precisely identify magnetic lineations this also makes the few observations available particularly prone to noise here we reconstruct nubia somalia relative motions since 20 ma from the alternative plate circuit nubia arabia somalia we resort to trans dimensional hierarchical bayesian inference which has proved effective in reducing finite rotation noise to unravel the arabia somalia and arabia nubia motions we combine the resulting kinematics to reconstruct the nubia somalia relative motion since 20 ma we verify the validity of the approach by comparing our reconstruction with the available record for the past 3 2 myr obtained through antarctica results indicate that prior to 11 ma the total motion between nubia and somalia was faster than today furthermore it featured a significant strike slip component along the nubia somalia boundary it is only since 11 ma that nubia diverges away from somalia at slower rates comparable to the present day one kinematic changes of some 20 might have occurred in the period leading to the present day but plate motion steadiness is also warranted within the uncertainties

are the oxygen isotopic compositions of fitzroya cupressoides and nothofagus pumilio cellulose promising proxies for climate reconstructions in northern patagonia tree ring 18o chronologies from two native species fitzroya cupressoides and nothofagus pumilio in northern patagonia were developed to assess their potential for paleoclimate reconstructions the five annually resolved cellulose 18o chronologies two for f cupressoides and three for n pumilio are located on the andes along the steep west to east precipitation gradient over the common 60 years long interval the five site 18ocell chronologies exhibit a strong common signal as indicated by the significant mean intercorrelation r 0 61 p 0 05 and the high percentage 65 of total variance explained by the first empirical orthogonal function although correlation analyses reveal that the two mean species 18ocell chronologies are mainly modulated by december may temperature the n pumilio chronology shows a greater sensitivity to record temperature variations r 0 57 p 0 05 the 18ocell of n pumilio contains a regional temperature signal representative of a large area in southern south america under the influence of the southern annular mode this study indicates that 18ocell in n pumilio is a promising proxy to reconstruct past variations in temperature in south america south of 38 s

high resolution absolute dated indian monsoon record between 53 and 36 ka from xiaobailong cave southwestern china the oxygen isotopic record of stalagmite xbl 1 from southwestern china reveals millennial scale variability of the indian monsoon between 53 and 36 ka synchronous with changes in the east asian monsoon recorded at hulu cave and similar to dansgaard oeschger cycles recorded in greenland ice our record in general confirms the chronology of hulu cave if our correlations between greenland and the xiaobailong cave record are correct both the greenland ice sheet project 2 and greenland ice core project ss09sea chronologies are accurate within quoted errors a dry interval that we correlate with heinrich event 5 h5 and the greenland stadial preceding greenland interstadial 12 gis 12 is centered ca 48 0 ka and a shift to drier conditions correlated to the end of gis 12 is ca 43 5 ka overall the variability of the indian monsoon from xbl 1 data on millennial scales is similar to and correlated with high latitude ice core rec ords from the northern hemisphere however some indian monsoon characteristics more closely resemble but are anticorrelated with features in the antarctic record suggesting some link to climate of the high southern latitudes in addition to the clear link to the climate of the high northern latitudes

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

enso variability reflected in precipitation oxygen isotopes across the asian summer monsoon region abstract oxygen isotope signals 18 o from paleo archives are important proxies for past asian summer monsoon asm climate reconstruction however causes of interannual variation in the 18 o values of modern precipitation across the asm region remain in argument we report interannual 18 o variation in southern tibetan plateau precipitation based on long term observations at lhasa these data together with precipitation 18 o records from five global network of isotopes in precipitation gnip stations and two ice core 18 o records were used to define a regional metric of asm precipitation 18 o asmoi back trajectory analyses for rainy season precipitation events indicate that moisture sources vary little between years with relatively high and low 18 o values a result that is consistent for the south lhasa southeast bangkok and east asm regions hong kong in contrast 18 o values at these three locations are significantly correlated with convection in the estimated source regions and along transport paths these results suggest that upstream convection rather than moisture source change causes interannual variation in asm precipitation 18 o values contrasting values of the asmoi in el nino and la nina years reveal a positive isotope el nino southern oscillation enso response e g high values corresponding to warm phases which we interpret as a response to changes in regional convection we show that the isotope enso response is amplified at high elevation sites and during la nina years these findings should improve interpretations of paleo 18 o data as a proxy for past asm variation and provide new opportunities to use data from this region to study paleo enso activity

rapid south atlantic spreading changes and coeval vertical motion in surrounding continents evidence for temporal changes of pressure driven upper mantle flow the south atlantic region displays 1 a topographic gradient across the basin with africa elevated relative to south america 2 a bimodal spreading history with fast spreading rates in late cretaceous and eo oligocene and 3 episodic regional uplift events in the adjacent continents concentrated in late cretaceous and oligocene here we show that these observations can be linked by dynamic processes within earth s mantle through temporal changes in asthenosphere flow beneath the region the topographic gradient implies westward pressure driven mantle flow beneath the basin while the rapid spreading rate changes on order 10 million years require significant decoupling of regional plate motion from the large scale mantle buoyancy distribution through a mechanically weak asthenosphere andean topographic growth in late miocene can explain the most recent south atlantic spreading velocity reduction arising from increased plate boundary forcing associated with the newly elevated topography but this mechanism is unlikely to explain the late cretaceous tertiary spreading variations as changes in andean paleoelevation at the time are small we propose an unsteady pressure driven flow component in the asthenosphere beneath the south atlantic region to explain the late cretaceous tertiary spreading rate variations temporal changes in mantle flow due to temporal changes in regional mantle pressure gradients imply a correlation of horizontal and vertical motions we find that this prediction from our models agrees with geologic and geophysical observations of the south atlantic region including episodes of passive margin uplift regional basin reactivation and magmatic activity

indian ocean climate and an absolute chronology over dansgaard oeschger events 9 to 13 oxygen isotope ratios of a stalagmite from socotra island in the indian ocean provide a record of changes in monsoon precipitation and climate for the time period from 42 to 55 thousand years before the present the pattern of precipitation bears a striking resemblance to the oxygen isotope record from greenland ice cores with increased tropical precipitation associated with warm periods in the high northern latitudes the largest change at the onset of interstadial 12 occurred very rapidly in about 25 years the chronology of the events found in our record requires a reevaluation of previously published time scales for climate events during this period

δ 18 o records in water vapor and an ice core from the eastern pamir plateau implications for paleoclimate reconstructions this study is the first to examine 18o in daily water vapor at taxkorgan on the eastern pamir plateau the results show that changes in observed and simulated 18o values in water vapor precipitation at the event scale using a lmdz iso model were mainly affected by temperature the influences of humidity precipitation amount and different moisture sources such as the westerlies local evaporated moisture and polar air masses on 18o values are comparatively weak the combination of the 18o record from the muztagata ice core 58 km away from the study area and the lmdz iso simulated annual 18o pattern in precipitation at taxkorgan also demonstrated that temperature and particularly the temperature of the regions over which the southern branch of the westerlies flows is the most important factor controlling 18o variations the results from this study area which is dominated by the westerlies throughout the year are markedly different from those derived from parts of the tibetan plateau that are dominated by the combined influences of the westerlies in winter and the indian monsoon in summer the results suggested that the eastern pamir plateau is an ideal location to reconstruct past temperature variations and that the 18o records preserved in ice cores from the region are a suitable and robust proxy for temperature

full fit palinspastic reconstruction of the conjugate australian antarctic margins 1 despite decades of study the prerift configuration and early rifting history between australia and antarctica is not well established the plate boundary system during the cretaceous includes the evolving kerguelen broken ridge large igneous province in the west as well as the conjugate passive and transform margin segments of the australian and antarctic continents previous rigid plate reconstruction models have highlighted the difficulty in satisfying all the available observations within a single coherent reconstruction history we investigate a range of scenarios for the early rifting history of these plates by developing a deforming plate model for this conjugate margin pair potential field data are used to define the boundaries of stretched continental crust on a regional scale integrating crustal thickness along tectonic flow lines provides an estimate of the prerift location of the continental plate boundary we then use the prerift plate boundary positions along with additional constraints from geological structures and large igneous provinces within the same australian and antarctic plate system to compute full fit poles of rotation for australia relative to antarctica our preferred model implies that the leeuwin and vincennes fracture zones are conjugate features within gondwana but that the direction of initial opening between australia and antarctica does not follow the orientation of these features rather the geometry of these features is likely related to the earlier rifting of india away from australia antarctica previous full fit reconstructions based on qualitative estimates of continental margin overlaps generally yield a tighter fit than our preferred reconstruction based on palinspastic margin restoration

a 900 year 600 to 1500 a d record of the indian summer monsoon precipitation from the core monsoon zone of india 1 we present a near annually resolved record of the indian summer monsoon ism rainfall variations for the core monsoon region of india that spans from 600 to 1500 a d from a 230th dated stalagmite oxygen isotope record from dandak cave our rainfall reconstruction which spans the medieval warm period mwp and the earliest portion of the little ice age lia indicates that the short instrumental record of ism underestimates the magnitude of monsoon rainfall variability periods of severe drought lasting decades occurred during the 14th and mid 15th centuries and coincided with several of india s most devastating famines

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

lower mantle structure from paleogeographically constrained dynamic earth models seismic tomography reveals two large low shear velocity provinces llsvps beneath africa and the pacific ocean these structures may have existed for several 100 myr and are likely compositionally distinct based on observed seismic characteristics interpreted in light of geodynamic models and mineral physics constraints we investigate the dynamics of the llsvps through the use of evolutionary models of thermochemical convection from 250 ma to present day we use a spherical convection model in which the anomalous structures have a high bulk modulus consistent with seismic interpretation a new progressive assimilation method incorporates constraints from paleogeography using a refined plate history model with 1 myr time spacing to guide the thermal structure of the lithosphere and steer the thermal evolution of slabs in the uppermost mantle the thermochemical structures deform and migrate along the core mantle boundary cmb through coupling to plate motions and in response to slab stresses the models produce a ridge like anomaly beneath africa and a rounded pile beneath the pacific ocean which at present day agrees with tomography waveform modeling and other geodynamic studies plumes emanate from the margins of the domes and ridges of thickened boundary layer between the domes dense and viscous slabs can undermine the stability of high bulk modulus structures at the cmb high bulk modulus structures are not necessarily required to satisfy dynamic constraints on the llsvps

a high resolution absolute dated holocene and deglacial asian monsoon record from dongge cave china abstract we present a continuous record of the asian monsoon over the last 16 ka from 18o measurements of stalagmite calcite over 900 oxygen isotopic measurements providing information on shifts in monsoon precipitation are combined with a chronology from 45 precise 230th dates 18o and therefore asian monsoon intensity generally follows changes in insolation although changes in 18o are generally accommodated in abrupt shifts in contrast to smoothly varying insolation indicating that threshold effects may be important 18o decreased dramatically 3 at the start of the holocene 11 5 ka and remained low for 6 ka four positive 18o events centered at 11225 97 yr bp 1 05 10880 117 yr bp 1 15 9165 75 yr bp 1 4 and a double event centered at 8260 64 yr bp 1 1 and 8080 74 yr bp 1 0 punctuated this period of high monsoon intensity all four events correlate within error with climate changes in greenland ice cores thus the relationship between the asian monsoon and the north atlantic observed during the glacial period appears to continue into the early holocene in addition three of the four events correlate within error with outburst events from lake agassiz the decline of monsoon intensity in the mid late holocene is characterized by an abrupt positive shift in 18o which occurs at 3550 59 yr bp 1 1 in 100 yr in addition the holocene is punctuated by numerous centennial and multi decadal scale events amplitudes 0 5 to 1 up to half the amplitude of the glacial interstadial events seen in the last glacial period thus holocene centennial and multi decadal scale monsoon variability is significant although not as large as glacial millennial scale variability the monsoon shows a strong connection with northern south american hydrological changes related by changes in itcz position spectral analysis of the 18o record shows significant peaks at solar periodicities of 208 yr and 86 yr suggesting variation is influenced by solar forcing however there are numerous other significant peaks including peaks at el nino frequencies observed for high resolution portions of the record between 8110 and 8250 yr which suggest that changes in oceanic and atmospheric circulation patterns in addition to those forced by solar changes are important in controlling holocene monsoon climate in addition for this high resolution portion we observe a distinctive biennial oscillation of the asian monsoon which has been associated with the tropospheric biennial oscillation tbo

asian monsoon oscillations in the northeastern qinghai tibet plateau since the late glacial as interpreted from visible reflectance of qinghai lake sediments abstract qinghai lake is a large saline lake on the qinghai tibetan plateau of central asia that is effected by both the indian and asian monsoons we used reflectance spectroscopy to characterize the sediments in a 795 cm long core taken from the southeastern part of the lake sediment redness which is related to iron oxide content seems to monitor paleoclimatic changes in the core iron oxides appear to be eroded from nearby red beds or loess deposits and are transported by fluvial means into the lake thus redness increases at times of increased precipitation that is as monsoon strength increases our redness monsoon proxy shows climate changes on several times scales on a millennial scale it records humid conditions during the early and mid holocene from about 4200 to 2300 yr bp low redness values suggest a two millennial long dry period which in the late holocene is followed by a more humid period on a centennial scale the redness proxy records not only the little ice age but also the medieval warm period the dark ages cool period and the roman warm period time series analysis of the redness record indicates a 200 yr frequency which corresponds to the de vries solar cycle suggesting that in addition to insolation changes resulting from orbital variations solar forcing also results from cyclic changes in the sun s luminosity

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

holocene forcing of the indian monsoon recorded in a stalagmite from southern oman a high resolution oxygen isotope record from a thorium uranium dated stalagmite from southern oman reflects variations in the amount of monsoon precipitation for the periods from 10 3 to 2 7 and 1 4 to 0 4 thousand years before the present ky b p between 10 3 and 8 ky b p decadal to centennial variations in monsoon precipitation are in phase with temperature fluctuations recorded in greenland ice cores indicating that early holocene monsoon intensity is largely controlled by glacial boundary conditions after approximately 8 ky b p monsoon precipitation decreases gradually in response to changing northern hemisphere summer solar insolation with decadal to multidecadal variations in monsoon precipitation being linked to solar activity

δ18o and δd of streamwaters across the himalaya and tibetan plateau implications for moisture sources and paleoelevation reconstructions abstract this study presents new 18o and d data from 191 streams across the himalaya and tibetan plateau to better constrain the spatial variability of stable isotopes in modern precipitation over this region moisture penetrating into the southeastern tibetan plateau is predominantly derived from monsoonal airmasses originating from the bay of bengal and transported into the eastern himalayan syntaxis along the brahmaputra river progressive rainout during orographic lifting and cooling results in clear relationships between 18o and d and catchment hypsometric elevation on the plateau margin however monsoonal derived moisture is progressively mixed with central asian airmasses in more western and northern parts of the tibetan plateau as a result predicted isotope elevation relationships that are based on empirical lapse rates or thermodynamic models of the isotopic evolution of an airmass produce large 1 3 km misfits between measured and predicted catchment elevations for much of the tibetan plateau including some areas directly north of the central himalayan crest this suggests that changes in the 18o or d of paleoprecipitation on the central and southwestern tibetan plateau may reflect surface uplift along moisture transport pathways or changes in the penetration of monsoonally derived moisture rather than regional surface uplift histories

δ18o of tree ring cellulose in two species spruce and oak as proxies of precipitation amount and relative humidity in northern japan abstract relationships between climatic factors and 18o values of tree rings in two species with different root systems were investigated in the northern area in hokkaido island northern japan this region has a heavy snow cover in winter and has a humid climate throughout the year in the case of spruce picea jezoensis which has shallow roots the 18o values are negatively correlated with precipitation in july and august probably due to higher relative humidity in summer and lower 18o of summer precipitation in a year of higher summer precipitation which is governed by the precipitation amount effect thus the 18o value of tree ring cellulose in spruce must be valuable as a proxy of summer precipitation in this area on the other hand the 18o value in oak quercus crispula which has deeper roots than spruce is not very sensitive to summer precipitation but is negatively correlated mainly with relative humidity in july and august this can be attributed to the smaller 18o enrichment in leaf water in the summer of higher relative humidity our results indicate that 18o values of tree rings in two species with different root systems from the same forest have the potential to reconstruct the two different climate factors

the uncertainties of finite rotations in plate tectonics incomplete knowledge of the pattern of magnetic lineations and fossil transform faults represented by sea floor spreading data on two plates generated by the same spreading center leads to uncertainties in a reconstruction of the past relative configuration of the plates a reconstruction may be represented by the finite rotation that describes one configuration relative to another in this paper a method of reconstruction is provided that reflects the uncertainties in the data the method minimizes a weighted least squares measure of fit as a function of the rotation parameters for a given rotation the measure of fit represents the sum of squares of the weighted distances of fixed and rotated data points representing corresponding former plate margin segments from a common plate margin the common margin is estimated from the locations of both fixed and rotated data points the estimated margin consists of a set of great circle arcs it is shown how the method of reconstruction may be utilized to obtain an uncertainty region for the pole and angle of rotation that characterize the finite rotation these techniques are then used to study the uncertainties of reconstructions in the south pacific for the times of anomalies 13 and 18 the best fit reconstructions and the uncertainty region for the anomaly 18 pole are in good agreement with previous work however the uncertainties in the anomaly 13 pole were substantially underestimated by previous investigators

tibetan plateau summer monsoon northward extent revealed by measurements of water stable isotopes a program of individual precipitation events and river water sampling and of water isotopic measurements d 18o was carried out during summer 1996 along a northeast southwest transect of the tibetan plateau the spatial distribution of both 18o and deuterium excess d d 8 18o of the precipitation reveals three distinct regions simulations with a simple isotopic model and seasonal isotopic variations measured at two extreme south and north locations support our interpretation in terms of different summer moisture origins 1 south of the himalayan mountains the moisture provided by the indian monsoon has been recycled over the indian peninsula 2 between the himalayas and the tanggula mountains the oceanic moisture is directly transported from the bay of bengal along the brahmaptra river valley 3 north of the tanggula mountains the moisture is not provided by the monsoon anymore but by continental water recycling

tree ring δ18o inferred spring drought variability over the past 200 years in the hengduan mountains southwest china abstract in this study we developed a tree ring 18o chronology of abies delavayi from diancangshan 25 41 n 100 06 e in the hengduan mountains of southwest china spanning 205 years 1810 2014 ce tree ring 18o from abies delavayi showed the highest negative correlation with relative humidity in the spring r 0 59 p

signature and hydrologic consequences of climate change within the upper middle brahmaputra basin a prevailing perception is that the glaciers and perennial snow and ice covered areas scap or in the himalayan region are fast contracting however systematic studies providing the quantitative estimates of scap as a function of time within individual river basins are lacking the importance of meltwater in river flows varies greatly from one river basin to another yet the actual estimates of those contributions are largely unknown this study bridges such knowledge gaps for the upper middle brahmaputra basin by using best available digital cartographic and remotely sensed snow cover data we find that when the entire basin is considered scap decreased from 7637 764 in 1980 to 4298 1422 km2 in 1992 however it has increased to 7160 2248 km2 in 2000 from 2000 to 2010 the scap has remained nearly constant around a mean of 10 052 1468 km2 the same trend is observed within individual physiographic zones of the basin such increase in scap is due to the increase in the precipitation over the middle brahmaputra basin and the nyainquentanglha mountains as observed in station records the incursion of moist air through the brahmaputra valley to the higher elevations within the nyainquentanglha mountains causes snowfall during pre monsoonal and post monsoonal seasons and an expansion of the scap glacial expansions in the nyainquentanglha mountains have also been observed in other recent studies in addition to the increase in precipitation and scap another manifestation of climate change observed in this basin is the increasing temperature with a mean annual trend of 0 28 c decade the hydrologic consequences of the observed effects of climate change are expected to be an insignificant change in streamflows in the watersheds drained by the upper brahmaputra river but a perceptible increase in river discharges in the watersheds drained by the middle brahmaputra river and its tributaries particularly within the upper and lower catchments of the middle brahmaputra basin copyright 2012 john wiley sons ltd