topography and self gravitation interaction in elastic gravitational modeling changes in gravity due to volcanic loading of the crust are influenced by topography we investigate the relative importance of topography and self gravitation in the interpretation of gravity changes it is shown that modeling of gravity changes can be more precise with the introduction of topographic relief although it is neglected self gravitation of the medium this paper exploits this result by suggesting a mathematical simplification that could be useful in the future development of a numerical technique to accurately include topographic effects in the modeling of deformation and gravity changes finally we perform an inversion of the gravity changes observed at mayon volcano philippines between december 1992 and december 1996 including topographic effects by varying the depth of the source failure to account for topographic influences can bias estimates of source parameters particularly when the lateral extension of the relief is of the same order of magnitude as the source depth

3d multi source model of elastic volcanic ground deformation abstract developments in interferometric synthetic aperture radar insar and gnss global navigation satellite system during the past decades have promoted significant advances in geosciences providing high resolution ground deformation data with dense spatio temporal coverage this large dataset can be exploited to produce accurate assessments of the primary processes occurring in geologically active areas we present a new original methodology to carry out a multi source inversion of ground deformation data to better understand the subsurface causative processes a nonlinear approach permits the determination of location size and three dimensional configuration without any a priori assumption as to the number nature or shape of the potential sources the proposed method identifies a combination of pressure bodies and different types of dislocation sources dip slip strike slip and tensile that represent magmatic sources and other processes such as earthquakes landslides or groundwater induced subsidence through the aggregation of elemental cells this approach has the following features 1 simultaneous inversion of the deformation components and or line of sight los data 2 simultaneous determination of diverse structures such as pressure bodies or dislocation sources representing local and regional effects 3 a fully 3d context and 4 no initial hypothesis about the number geometry or types of the causative sources is necessary this methodology is applied to mt etna southern italy we analyze the ground deformation field derived from a large insar dataset acquired during the january 2009 june 2013 time period the application of the inversion approach models several interesting buried structures as well as processes related to the volcano magmatic plumbing system local subsidence within the valle del bove and seaward motion of eastern flank of the volcano

quantitative reconstruction of mid to late holocene climate in ne china from peat cellulose stable oxygen and carbon isotope records and mechanistic models there has been an increasing need to reconstruct past climate from proxy records quantitatively and mechanistically the inverse proxy modeling method stands out as a novel approach to quantitative palaeoclimate reconstructions through integrating process based models and proxy records representing a major progress in quantitative palaeoclimatology it has been proposed to incorporate multiple proxy records to produce a more robust constraint on the climate parameters sought for estimation and most of the work has been conducted using pollen records in conjunction with vegetation models here i show a worked example of using paired stable oxygen and carbon isotope records of peat cellulose from one single core to infer the climate history in ne china for the last 6000 years through solving a well posed inverse problem using bayesian statistics the quantitative palaeoclimate data obtained in this study may deepen our insight into the dynamics of the east asian summer monsoon mean growing season temper

gravity changes and deformation due to a magmatic intrusion in a two layered crustal model we develop and extend theoretical and computational methods for the calculation of the deformation gravity and potential change due to a point source of magma injection into a multilayered elastic gravitational earth model in our calculations which are based upon the method outlined by rundle two distinct layers overlying a half space may be incorporated the source can be located in either of the layers or the half space the method is quite general and can be readily adapted to calculations in which stresses in either the layers or the half space relax by viscoelastic flow the results obtained indicate that the use of homogeneous half space to represent the earth may in some cases be too simple a model and that variations in elastic moduli have a more significant effect than variation in reference density on both the surface displacements and gravity changes as an example we calculate the displacement and gravity changes due to a subsurface mass injection in a crust mantle model appropriate to the volcanic island of lanzarote which is presently the subject of numerous geophysical experiments both historical and recent data indicate that lanzarote may be subject to some risk of volcanic eruption in the future thus our calculations may be useful in interpreting observations of preemption phenomena the results are discussed in terms of prediction versus measurement capabilities

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

study of volcanic sources at long valley caldera california using gravity data and a genetic algorithm inversion technique we model the source inflation of the long valley caldera california using a genetic algorithm technique and micro gravity data while there have been numerous attempts to model the magma injection at long valley caldera from deformation data this has proven difficult given the complicated spatial and temporal nature of the volcanic source recent work illustrates the effectiveness of considering micro gravity measurements in volcanic areas a genetic algorithm is a problem solving technique which combines genetic and prescribed random information exchange we perform two inversions one for a single spherical point source and another for two sources that might represent a more spatially distributed source the forward model we use to interpret the results is the elastic gravitational earth model which takes into account the source mass and its interaction with the gravity field the results demonstrate the need to incorporate more variations in the model including another source geometry and the faulting mechanism in order to provide better constraints on intrusion volumes future work should include the joint inversion of gravity and deformation data during the same epoch

geodetic methods for detecting volcanic unrest a theoretical approach in this paper we study the application of different geodetic techniques to volcanic activity monitoring using theoretical analysis this methodology is very useful for obtaining an idea of the most appropriate and efficient monitoring method mainly when there are no records of geodetic changes previous to volcanic activity the analysis takes into account the crustal structure of the area its geology and its known volcanic activity to estimate the deformation and gravity changes that might precede eruptions the deformation model used includes the existing gravity field and vertical changes in the crustal properties both factors can have a considerable effect on computed deformation and gravity changes topography should be considered when there is a steep slope greater than 10 the case study of teide stratovolcano tenerife canary islands for which no deformation or gravity changes are available is used as a test to avoid considering topography we worked at the lowest level of las canadas and examined a smaller area than the whole caldera or island therefore the results are only a first approach to the most adequate geodetic monitoring system the methodology can also be applied to active areas where volcanic risk is not associated with a stratovolcano but instead with monogenetic scattered centers especially when sites must be chosen in terms of detection efficiency or existing facilities the canary islands provide a good example of this type of active volcanic areas and we apply our model to the island of lanzarote to evaluate the efficiency of the monitoring system installed at the existing geodynamic station on this island topography is not important the results of our study show clearly that the most appropriate geodetic volcano monitoring system is not the same for all different volcanic zones and types and the particular properties of each volcano zone must be taken into account when designing each system

the inorganic geochemistry of a peat deposit on the eastern qinghai tibetan plateau and insights into changing atmospheric circulation in central asia during the holocene abstract peat records enable the reconstruction of changes in the global biogeochemical mineral dust cycle and the detection of variations in atmospheric circulation patterns during the holocene they can therefore provide a key tool for understanding the relationship between the geochemical dust cycle and past climate change here we present the first detailed study of the inorganic geochemistry of a peat core collected at an altitude of 3500 m from the hongyuan peatland on the eastern qinghai tibetan plateau and test its potential as an archive of atmospheric dust deposition we find that the low accumulation rates of the peat and the presence of the extensive dust sources of northern china in the vicinity of the study site lead to approximately five times higher concentrations of mineral matter compared to temperate ombrotrophic peats a detailed geochemical assessment of the core and surface samples from local and non local dust sources as well as of the hydrology and hydrochemistry of the surrounding waters suggests that external and internal post depositional processes have not affected the record of lithogenic elements including the rare earth elements ree sc y and th changes in ti normalized major element profiles la yb y tb and the eu anomaly identify seven major shifts among the dominant dust sources and therefore potential changes in atmospheric circulation patterns bivariate plots using the ree based tracers la yb y tb la th y er sc la th sc and th ree suggest that the taklamakan desert and the chinese loess plateau in northern china were the dominant non local dust sources to the peat local dust input dominated throughout the early holocene until 4 9 kyr bp increased dust input from the non local sources thereafter suggests an enhanced influence of winds associated with the east asian winter monsoon and the westerly jet throughout most of the late holocene sharp increases in non local dust fluxes between 3 1 2 7 and between 1 3 0 9 kyr bp suggest a particular strengthening of these wind systems during these times in agreement with the organic characteristics of the core our results show that the hongyuan peat is a reliable archive to study dust deposition in central asia and allows the identification of changes in atmospheric circulation patterns and in the larger climatic arrangements of the monsoon system in this region during the holocene

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

viscoelastic modeling of deformation and gravity changes induced by pressurized magmatic sources abstract gravity and height changes which reflect magma accumulation in subsurface chambers are evaluated using analytical and numerical models in order to investigate their relationships and temporal evolutions the analysis focuses mainly on the exploration of the time dependent response of gravity and height changes to the pressurization of ellipsoidal magmatic chambers in viscoelastic media firstly the validation of the numerical finite element results is performed by comparison with analytical solutions which are devised for a simple spherical source embedded in a homogeneous viscoelastic half space medium then the effect of several model parameters on time dependent height and gravity changes is investigated thanks to the flexibility of the numerical method in handling complex configurations both homogeneous and viscoelastic shell models reveal significantly different amplitudes in the ratio between gravity and height changes depending on geometry factors and medium rheology the results show that these factors also influence the relaxation characteristic times of the investigated geophysical changes overall these temporal patterns are compatible with time dependent height and gravity changes observed on etna volcano during the 1994 1997 inflation period by modeling the viscoelastic response of a pressurized prolate magmatic source a general agreement between computed and observed geophysical variations is achieved

development and refinement of proxy climate indicators from peats peat especially from acidic mires bogs is a natural archive of past environmental change reconstructions of past climate from bogs commenced in the 19th century through examination of visible peat stratigraphy and later formed the basis for a postglacial climatic scheme widely used in northwest europe nevertheless misconceptions as to how bogs grow led to a 50 year lacuna in peat climate study before the concept of cyclic regeneration in bogs was refuted in recent decades research using proxy climate indicators from bogs has burgeoned a range of proxies for past hydrological change has been developed as well as use of pollen bog oaks and pines and other data to reconstruct past temperatures most of this proxy climate research has been carried out in northern europe but peat based research in parts of asia and north america has increased particularly during the last decade while research has also been conducted in australia new zealand and south america this paper reviews developments in proxy climate reconstructions from peatlands chronicles use of a range of palaeo proxies such as visible peat stratigraphy plant macrofossils peat humification testate amoebae and non pollen palynomorphs and explains the use of wiggle match radiocarbon dating and relationship to climate shifts it details other techniques being used increasingly such as biomarkers stable isotopes inorganic geochemistry and estimation of dust flux and points to new proxies under development although explicit protocols have been developed recently for research on ombrotrophic mires it must be recognised that not all proxies and techniques have universal applicability owing to differences in species assemblages mire formation topographic controls and geochemical characteristics

the influence of climate hydrology and permafrost on holocene peat accumulation at 3500 m on the eastern qinghai tibetan plateau peatland of the eastern qinghai tibetan plateau lies at the convergence of the east asian and indian monsoon systems in eastern asia to understand the evolution of this peatland and its potential to provide new insights into the holocene evolution of the east asian monsoon a 6 m peat core was collected from the undisturbed central part of a peat deposit near hongyuan the age depth profile was determined using 16 14c ams age dates the peat analysed for a range of environmental variables including carbon nitrogen and hydrogen concentration bulk density 13c and the associated spring water analysed for hydrogen and oxygen isotopes the age depth profile of the recovered peat sequence covers the period from 9 6 to 0 3 kyr bp and is linear indicating that the conditions governing productivity and decay varied little over the holocene using changes in carbon density organic carbon content and its 13c cold dry periods of permafrost characterised by low density and impeded surface drainage were identified the low 18o and d values of the spring water emanating around the peat deposit down to 13 8 and 102 vsmow respectively with an inverse relationship between electrical conductivity and isotopic composition indicate precipitation under colder and drier conditions relative to the present day in view of the current annual mean air temperature of 1 c this suggests conditions in the past have been conducive to permafrost inferred periods of permafrost correspond to independently recognised cold periods in other holocene records from across china at 8 6 8 2 7 8 5 6 4 2 3 1 and 1 8 1 5 kyr bp the transition to a cold dry climate appears to be more rapid than the subsequent recovery and cold dry periods at hongyuan are of longer duration than equivalent cold dry periods over central and eastern china light dark banding peat on a scale of 15 30 years from 9 6 to 5 5 kyr bp may indicate a strong influence of decadal oscillations possibly the pacific decadal oscillation and a potential link between near simultaneous climatic changes in the northwest pacific enso movement of the intertropical convergence zone and the east asian monsoon

intrusive mechanisms at mt etna forerunning the july august 2001 eruption from seismic and ground deformation data in this work we present seismological and ground deformation evidence for the phase preparing the july 18 to august 9 2001 flank eruption at etna the analysis performed through data from the permanent seismic and ground deformation networks highlighted a strong relationship between seismic strain release at depth and surface deformation this joint analysis provided strong constraints on the magma rising mechanisms we show that in the last ten years after the 1991 1993 eruption an overall accumulation of tension has affected the volcano then we investigate the months preceding the 2001 eruption in particular we analyse the strong seismic swarm on april 20 24 2001 comprising more than 200 events mmax 3 6 with prevalent dextral shear fault mechanisms in the western flank the swarm showed a ca ne sw earthquake alignment which in agreement with previous cases can be interpreted as the response of the medium to an intrusive process along the approximately nnw sse volcano genetic trend these mechanisms leading to the july 18 to august 9 2001 flank eruption are analogous to ones observed some months before the 1991 1993 flank eruption and more recently in january 1998 before the february november 1999 summit eruption

hydrogen isotopic ratios of plant wax n alkanes in a peat bog deposited in northeast china during the last 16 kyr abstract based on paleoclimatic reconstructions using various proxies the holocene climate optimum 10 5 6 ka has been characterized as a warmer and wetter period in most of east asia the summer monsoons associated with the east asian monsoon evidently intensified and extended further inland from the pacific ocean a source region of moisture a notable exception to this general pattern exists in northeast china where less wet conditions are recorded we determined molecular compositions of individual plant wax hydrocarbons and their hydrogen isotope compositions d values in a radiocarbon dated peat core recovered from the hani marsh in jilin province china and confirmed that the temperature dependent effective precipitation in northeast china decreased during the holocene climate optimum a combination of p aq an indicator of the relative contribution of aquatic to terrestrial plants and the difference in d between low c 23 c 25 and c 27 and high molecular weight c 31 n alkanes in the hani peat bog indicates a dramatic change in vegetation from the deglaciation to the holocene no significant differences were observed between the d values of low and high molecular weight n alkanes with relatively high d values and low p aq during the early holocene indicating that all n alkanes were produced by evapotranspiration sensitive terrestrial plants during that time however lower d values of mid chain n alkanes c 23 c 25 and c 27 relative to the long chain n alkane c 31 together with higher p aq values during the deglaciation 14 11 ka suggest an increase in the contribution of aquatic plants and a higher water level during the period the study demonstrates that northeast china was under a markedly wetter climate condition during the late deglaciation for the 16 kyr record in the hani peat sequence we infer that moisture delivery by the east asian monsoon was relatively invariable in northeast china but increased evaporation during the warmer holocene climate optimum reduced the effective precipitation defined by the balance between precipitation and evaporation

major features and forcing of high latitude northern hemisphere atmospheric circulation using a 110 000 year long glaciochemical series the greenland ice sheet project 2 glaciochemical series sodium potassium ammonium calcium magnesium sulfate nitrate and chloride provides a unique view of the chemistry of the atmosphere and the history of atmospheric circulation over both the high latitudes and mid low latitudes of the northern hemisphere interpretation of this record reveals a diverse array of environmental signatures that include the documentation of anthropogenically derived pollutants volcanic and biomass burning events storminess over marine surfaces continental aridity and biogenic source strength plus information related to the controls on both high and low frequency climate events of the last 110 000 years climate forcings investigated include changes in insolation of the order of the major orbital cycles that control the long term behavior of atmospheric circulation patterns through changes in ice volume sea level events such as the heinrich events massive discharges of icebergs first identified in the marine record that are found to operate on a 6100 year cycle due largely to the lagged response of ice sheets to changes in insolation and consequent glacier dynamics and rapid climate change events massive reorganizations of atmospheric circulation that are demonstrated to operate on 1450 year cycles changes in insolation and associated positive feedbacks related to ice sheets may assist in explaining favorable time periods and controls on the amplitude of massive rapid climate change events explanation for the exact timing and global synchroneity of these events is however more complicated preliminary evidence points to possible solar variability climate associations for these events and perhaps others that are embedded in our ice core derived atmospheric circulation records

persistent solar influence on north atlantic climate during the holocene surface winds and surface ocean hydrography in the subpolar north atlantic appear to have been influenced by variations in solar output through the entire holocene the evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon 14 and beryllium 10 and centennial to millennial time scale changes in proxies of drift ice measured in deep sea sediment cores a solar forcing mechanism therefore may underlie at least the holocene segment of the north atlantic9s 1500 year cycle the surface hydrographic changes may have affected production of north atlantic deep water potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally

new results at mayon philippines from a joint inversion of gravity and deformation measurements in this paper we detail the combination of the genetic algorithm ga inversion technique with the elastic gravitational model originally developed by rundle and subsequently refined by fernandez and others a sensitivity analysis is performed for the joint inversion of deformation and gravity to each of the model parameters illustrating the importance of proper identification of both the strengths and limitations of any source model inversion and this technique in particular there is a practical comparison of the theoretical results with the inversion of geodetic data observed at the mayon volcano in the philippines where there are gravity changes without significant deformation after the 1993 eruption

numerical inversion of magma chamber pressurization in volcanic areas a case study of changbaishan volcano abstract volcanoes are commonly associated with significant topographic relief however most analytical models of volcanoes consider the earth s surface as flat and use half space solutions finite element method can take into account topography we applied the equivalent body force method to the changbaishan volcanic area to account for the influence of topographic effects on the inversion of magma chamber pressurization and to calculate the influence of the magma induced stresses on the stability of the surrounding faults the influence of surface topography should not be ignored when calculating the surface deformation caused by the magma chamber pressurization in a volcanic area the shallower the burial depth the closer the surface maximum radial displacement ur to the center of the magma chamber when the slope reaches 30 the maximum vertical displacement uz is no longer directly above the magma chamber an ellipsoidal pressurization was used to satisfactorily simulate the gps and leveling measurements at the changbaishan volcanic area from 2002 to 2003 the superposition of the magma induced stresses and the regional tectonic stresses likely cause the present stress directions around the changbaishan volcano which are dominated by the ew direction to the west of tianchi lake and the nw nnw direction to the north of tianchi lake the coulomb failure stress change caused by the magma chamber is conducive to the distribution of the nw trending earthquake swarms that mainly occur to the southwest and northeast of changbaishan crater

a 6000 year record of changes in drought and precipitation in northeastern china based on a δ13c time series from peat cellulose we report a new peat delta c 13 proxy record for humidity or precipitation based on c3 plants from northeastern china the record reveals two times of significant climate shift and eight severe drought periods during the past 6000 years all of which have the nature of widespread global occurrence the variability of precipitation shows periodicities of around 70 80 90 107 110 123 134 141 162 198 205 249 278 324 389 467 584 834 and 1060 years the occurrence and persistent times of drought and periodicities of precipitation show good correspondence with solar variability the remarkable correlations between peat delta c 13 peat delta o 18 and atmospheric delta c 14 suggest that on timescales of decades to centuries the changes in drought and precipitation are likely caused by variations of atmospheric circulation and atmosphere ocean interactions in large scale patterns that seem to be related to solar variability c 2001 elsevier science b v all rights reserved

high resolution unsaturated alkenones sea surface temperature records in the yellow sea during the period of 3500 1300 cal yr bp abstract high resolution sea surface temperature records based on long chain unsaturated alkenones u 37 k sst in the south yellow sea ys during the period of 3500 1300 cal yr bp were reconstructed in sediment core z8 from the shandong mud wedge the sst records show broad variations between 14 3 and 16 9 c 15 6 c on the average with a high sst phase at 3500 2750 cal yr bp a low and intense fluctuating sst period at 2500 2000 cal yr bp and a sharp cooling period at 1750 1300 cal yr bp superimposed on this trend five cooling periods occurred in 3360 3250 cal yr bp 3150 3050 cal yr bp 2750 2650 cal yr bp 2350 2150 cal yr bp and 1750 1300 cal yr bp variation pattern of the sst records is similar to the fluctuations of the kuroshio current kc indicating a close relationship between the yellow sea warm current yswc and the kc the general u 37 k sst curve fluctuates with the local air temperature variations the intensity of the east asia winter monsoon eawm could be a key factor affected the prevailing relationship between the cold coastal current and the warm yswc and dominated the sst variation in core site z8 during 3500 1300 cal yr bp furthermore our temperature records within age uncertainty coincides with the changes of the solar irradiance changes suggesting a possible link between solar forcing and climate variability

temperature responses to quasi 100 yr solar variability during the past 6000 years based on δ18o of peat cellulose in hongyuan eastern qinghai tibet plateau china abstract during the past 6000 years the temperature variation trend inferred from 18o of peat cellulose in a peat core from hongyuan eastern qinghai tibet plateau southwestern china is similar to the atmospheric 14c concentration trend and the modeled solar output trend the general trend of hongyuan 18o during the past millennium also coincides well with the atmospheric 14c concentration trend the 10be concentration trend in an ice core from the south pole the reconstructed total solar irradiance trend as well as the modeled solar output trend in addition temperature events also correspond well to solar perturbations during the past 6000 years therefore the driving force of holocene temperature variations should be properly ascribed to solar activity the spectrum analysis further illustrates that quasi 100 yr fluctuation of solar activity was probably responsible for temperature variations in northeast qinghai tibet plateau during the past 6000 years

correlation between indian ocean summer monsoon and north atlantic climate during the holocene there has been a number of investigations for the correlation between the asia monsoon and the north atlantic climate for the last glacial however little research has been done for the present interglacial the holocene here we present for the first time a high resolution composite proxy record for the indian ocean summer monsoon spanning around 12 000 years based on the 13c time series of both a single plant species carex mulieensis remains cellulose and the total plant assemblage cellulose in the hongyuan peat bog from the tibet plateau the records show that the strength of the indian ocean summer monsoon had abrupt variations during the last 12 000 years the weakest monsoon occurred in the younger dryas period following rapid strengthening from around 11 200 to 10 800 a bp the monsoon kept a generally strong level for around 5300 years from around 5500 a bp onwards the monsoon strength tended to gradual decrease in addition there are a series of abrupt variation events of the monsoon strength on centennial to millennial time scales which superimpose the general tendency of the monsoon variation in every case when the ice rafted debris events in the north atlantic occurred the summer monsoon strength decreased correspondingly these evidences show that teleconnection between the indian ocean summer monsoon and the north atlantic climate is present not only in the last glacial but also in the holocene which may be linked to abrupt reorganizations of the ocean thermohaline circulation leading to redistribution of energy changing temperature and moisture gradient over the southern subtropical indian ocean and eventually controlling the variability of the indian ocean summer monsoon

inversion of temporal gravity changes by the method of local corrections a case study from mayon volcano philippines abstract the 3d inversion method based on local corrections has been introduced by prutkin to invert potential field data it has been applied to gravity data inversion on local regional and global scales here we introduce the application of this method to invert temporal gravity changes the inversion procedure is demonstrated by a case study on gravity changes observed at the mayon stratovolcano between campaigns spanning a period of 1992 1996 residual gravity changes are compiled from the observed ones no significant surface deformation was observed within the accuracy of the campaign gps measurements during the considered period residual gravity changes were first inverted in terms of sources represented by 3d line segments the line segment approximation facilitates the second step of the iterative non linear inversion based on local corrections in the second step the residual gravity changes were inverted in terms of 3d star convex homogenous bodies representing sources of subsurface mass density changes published geological evidence indicates a shallow magma system at mayon the absence of significant deformation accompanying the gravity changes indicates that this system was nearly open during 1992 1996 we hypothesize that the sources of the gravity signal represent mass transport namely injection of magma into voids of the shallow system inversion results for campaign differences 3 1 and 4 1 are presented for both epochs the inversion results in a source located at a depth of about 4 4 km 0 3 km below sea level the mass of injected magma was estimated at 0 35 0 10 mu and 0 12 0 04 mu for the two epochs respectively we also compare our results with previous interpretations of the same data

influence of variations in nao and so on air temperature over the northern tibetan plateau as recorded by δ18o in the malan ice core 1 an isotopic 18o enrichment trend from 1887 to 1998 recorded in the malan ice core from the northern tibetan plateau indicates that temperatures there have warmed in the past century statistical analyses suggest that the annual 18o in this ice core largely reflects air temperature variations in the warm season statistically significant modest to weak correlations were found between the annual 18o and the north atlantic oscillation nao index from may through october and the southern oscillation so index from august through november respectively a multivariate linear regression shows that when combined the nao and so account for 55 of the total variance in 18o over the past century moreover the correlations between 18o and the nao and the so vary over the study period as might be expected due to changes in the strength and amplitude of the nao and so over the past century

environmental influences over the last 16 ka on compound specific δ13c variations of leaf wax n alkanes in the hani peat deposit from northeast china compound specific carbon isotope ratios 13c of leaf wax n alkanes c21 c33 odd carbon numbered n alkanes were measured in the hani peat sequence from northeast china these data were compared with lipid biomarker compositions to assess changes in local vegetation and paleoclimate for the last 16 ka the 13c values of n alkanes range between 36 6 and 30 7 showing that the compounds originate from c3 plants much larger variations 5 4 in the n alkane 13c values than those of atmospheric co2 during the last 16 ka 0 5 indicate that the isotopic values were affected by environmental factors in addition to the postglacial 13c variations in the atmospheric reservoir the stratigraphic records of 13c reveal decoupled fluctuations among the individual n alkanes particularly between 15 5 and 11 4 ka synchronous excursions in the 13c offsets among individual n alkanes 13c and lipid biomarker paleoplant proxies paq and c23 c31 and c27 c31 from 14 9 to 13 2 ka and 12 7 to 11 6 ka suggest that vegetational changes are the most likely causes for the decoupled 13c variations parallel fluctuations of the 13c values of terrestrial higher plant derived c29 and c31n alkanes and the n alkane average chain length acl from 11 to 6 ka indicate that the 13c variations responded to net evaporation changes negative shifts in the n alkane 13c values coinciding with the acl decreases at 10 5 9 3 ka and 8 1 ka indicate the short term onset and fluctuations of the summer monsoon strength in eastern china during the early holocene

lead atmospheric deposition rates and isotopic trends in asian dust during the last 9 5 kyr recorded in an ombrotrophic peat bog on the eastern qinghai tibetan plateau a full understanding of the atmospheric pb cycle in asia during the holocene is key to palaeoclimate studies of past atmospheric circulation patterns as well as to assess the impact of increasing industrial activities in this region however long term records of atmospheric pb isotopic trends in asia are still sparse consequently we study changes in the concentrations fluxes and isotopic signature of deposited pb contained in a 14c dated peat core from the eastern qinghai tibetan plateau dating back to 9 5 kyr bp and present the first peat record of the changing isotopic composition of atmospheric pb in dust in asia during this time lead concentrations and fluxes vary between 2 96 21 58 lg g 1 and 0 06 3 52 mg m 2 y 1 respectively with an average pb baseline of 6 80 4 18 lg g 1 these values agree with other pb studies of lake and peat archives in china but are one order of magnitude larger than early and mid holocene values measured in europe lead isotopic variability throughout the core is small varying between 206pb 207pb 1 190 1 197 206pb 204pb 18 648 18 786 207pb 204pb 15 666 15 694 and 208pb 204pb 38 890 39 090 the application of bayesian trans dimensional changepoint modelling to the pb dataset enabled the identification of eight significant changes in the isotopic composition of the deposited pb such changes mark different phases of atmospheric pb deposition and hence variations in atmospheric circulation patterns and environmental conditions temporal variations in the potential natural and or anthropogenic pb sources are assessed based on the 206pb 207pb 208pb and 204pb isotopic composition and the 1 pb ratio of the peat samples our results suggest that pb deposition throughout the holocene was governed by local deposition and long range input from natural dust sources in northwestern taklamakan desert and qaidam basin and northern china badain jaran and tengger deserts input from the northern sources seems to have been particularly important between 3 1 2 7 kyr bp and 1 7 0 9 kyr bp suggesting a possible strengthening of the east asian winter monsoon in agreement with previous reconstructions in asia based on the pb sc and isotopic composition profiles we do not note any evidence for anthropogenic pb derived from the thriving mining or smelting activities in northern and eastern china in the last few millennia suggesting that atmospheric deposition to this region of the eastern tibetan plateau was dominated by natural pb fluxes these can serve as a true asian background value against which anthropogenic impacts can be quantified our results confirm that the combination of radiogenic isotopes pb and trace elements in peat bogs enables observational reconstructions of changes in past regional atmospheric circulation such records will enable more refined interpretations of marine and terrestrial palaeorecords in asia and the pacific and consequently provide further constraints for changes in ocean and atmospheric circulation and for the testing of palaeoclimate models of circulation patterns

aeolian sediments on the north eastern tibetan plateau abstract aeolian sediments on the tibetan plateau are an important archive of palaeoclimatic information this study presents a detailed analysis of sediments from the donggi cona catchment on the north eastern part of the tibetan plateau long and short distance sediment transport leads to a complex pattern of aeolian sediment deposition that depends on climatic changes as well as on the availability of sediments based on the largest dataset of osl datings 51 from a single catchment on the tibetan plateau so far different periods of increased sediment transport have been reconstructed increased aeolian deposition in this high elevation environment started in the early holocene with the accumulation of sands from around 10 5 to 7 ka loess sediments have been preserved from a period from 10 5 to 7 5 ka both archives are related to the strengthening of the asian summer monsoons characterized by wetter and warmer climate this change in climate supported the trapping of aeolian sediments under full monsoon conditions from around 9 ka onwards fluvial processes resulted in erosion of the aeolian archives and the formation of colluvial sediments until 6 ka a dry and cooler climate resulted in the reactivation of dune sands from 3 ka to present possibly in combination with stronger human influence aeolian sediments on the tibetan plateau therefore indicate two different climatic modes during the early holocene wetter conditions were favourable to retain aeolian sediments the reactivation of sediment in the late holocene due to small scale disturbances in the vegetation cover points to a cooler and drier climate

volcanic eruption prediction magma chamber physics from gravity and deformation measurements one of the greatest remaining problems in modern volcanology is the process by which volcanic eruptions are triggered it is generally accepted that eruptions are preceded by magma intrusion sigurdsson and sparks 1978 the degree of interaction between previously ponded magma in a chamber and newly intruded magma determines the nature and rate of eruption and also the chemistry of erupted lavas and shallow dykes here we investigate the physics of this interaction volcano monitoring at its most effective is a synergy between basic science and risk assessment while hazard mitigation depends on reliable interpretation of eruption precursors the simple and much used mogi model relates ground deformation h to changes in magma chamber volume gravity changes g combined with ground deformation provide information on magma chamber mass changes our new models predict how the g h gradient will evolve as a volcano develops from a state of dormancy through unrest into a state of explosive activity thus by simultaneous measurement of deformation and gravity at a few key stations magma chamber processes can be identified prior to the onset of conventional eruption precursors

spherical and ellipsoidal volcanic sources at long valley caldera california using a genetic algorithm inversion technique abstract we model the second inflation period at long valley caldera california using a genetic algorithm technique and high quality geodetic measurements of elevation changes and baseline extensions we compare two source inversions for both spherical mogi point sources and the finite prolate ellipsoid of yang and davis a sensitivity analysis for the genetic algorithm is performed based upon synthetic data set inversions on similar sources in order to better constrain the areal location orientation and volume of the potential sources the spherical sources are well constrained the larger located at 9 9 km beneath the resurgent dome with a volume of 0 036 km 3 while the second at only 0 008 km 3 is located at a depth of 7 3 km beneath the south moat the depths to the ellipsoidal sources are switched with the larger source at a depth of 9 6 km and the smaller at 11 8 km with volumes of 0 037 and 0 002 km 3 respectively

determining the spatial and temporal patterns of climate changes in china s western interior during the last 15 ka from lacustrine oxygen isotope records china s western interior is a climatologically complex region where climatic conditions are primarily controlled by the westerly jet stream and the asian monsoon system observations reveal that the 18o signatures of these atmospheric elements as expressed in their meteoric waters are different and these differences are reflected in the lacustrine systems that are ultimately fed by the meteoric waters empirical orthogonal function eof decomposition of 17 lacustrine 18o records from this area clearly reveals the spatial and temporal structures of climate changes during the last 15 ka the first eof mode dominated by sites in the nw sector captures the temperature effect on the variability of the 18o dataset we interpret the variations through time in the amplitude of this mode to be indicative of changes in summer air temperature the second eof mode heavily weighted by sites in the se sector reveals the amount effect on 18o and thus its amplitude time series indicates changes in the intensity of the asian summer monsoon our eof based reconstructions of regional climate are generally consistent with the 18o records of ice cores cave speleothems and marine carbonates copyright 2008 john wiley sons ltd

deformation gravity and potential changes due to volcanic loading of the crust a method for calculating deformation gravity and potential changes induced by volcanic loads imposed within and on the earth s crust is presented the method involves application of techniques developed for earthquake loading problems in elastic gravitational earth models by considering the elastic gravitational equilibrium of the layered system the gravitational and displacement response due to intruding masses and to pressurized magma chambers can be computed for applications involving seamount loading variations in the height of sea level can be calculated by requiring that seawater lie along an equipotential in continental loading problems the change in potential can be used to calculate the orthometric height cahnge as distinct from the geometric height change for some plausible loading geometries the difference between these two qunatities can be significant results for various loads and earth structures are shown and discussed in particular a magmatic mass intruding into an elastic gravitational lithosphere overlying a compressible gravitating asthenosphere produces distinct gravity anomalies which depend on the depth of intrusion applications of this result can be made to problems of isostatic compensation the intrusion of a magmatic mass together with the associated pressurization of the magma chamber produces distinctive surface gravity and deformation in the near field gravity gradients more defined as surface gravity divided by uplift vary with distance from the source moreover orthometric elevations can be significantly 25 less than geometric elevations these results have clear application to data from events such as the posteruption deflation of kilauea volcano less

on the relative importance of self gravitation and elasticity in modeling volcanic ground deformation and gravity changes 1 elastic half space models widely used to interpret displacements and gravity data in active volcanic areas usually compute the displacement response to dilatational sources that simulate a change in pressure of the magma chamber elastic gravitational models allow the computation of gravity deformation and gravitational potential changes due to pressurized magma cavities and intruding masses together this type of model takes into account the mass interaction with the self gravitation of the earth through coupling between model equations we perform a dimensional analysis of the elastic gravitational model estimating the magnitude of intrusion mass and coupling effects at the space scale associated with volcano monitoring we show that the intrusion mass cannot be neglected in the interpretation of gravity changes while displacements are primarily caused by pressurization therefore the intrusion of mass together with the associated pressurization of the magma chamber produces distinctive changes in gravity that could be used to interpret gravity changes without ground deformation and vice versa depending on what type of source plays the main role in the intrusion process theoretical experiments indicate that mass and self gravitation could produce changes in the magnitude and pattern of predicted gravity that may be above microgravity accuracy application of the elastic gravitational model to interpret geodetic precursors observed at mayon volcano philippines prior to the eruption of 2001 shows that inversions increase in precision by using this model therefore our elastic gravitational model is a refinement of purely elastic models and can better interpret gravity and deformation changes in active volcanic zones

inflation or deflation new results for mayon volcano applying elastic gravitational modeling volcanic activity produces deformation and gravity changes that many times can be used as precursors of future eruptions applying geodetic techniques to monitoring activity involves interpretation using deformation models usually the observed changes of the deformation and gravity fields are interpreted seperately not in a joint inversion it can be difficult if not impossible to interpret the data coherently or correctly in terms of the characteristics of the intrusion or the deflation derived from the gravity changes with purely elastic models as in the case of mayon volcano phillipines we show that elastic gravitational models can be used to interpret these cases simultaneously leading to a result that is more plausible on the basis of the available information thus we may need to change the philosophy normally used to interpret geodetic observations interpretation as proposed in this work can significantly improve the possibility of predicting future eruptions

evaluation of glycerol dialkyl glycerol tetraether proxies for reconstruction of the paleo environment on the qinghai tibetan plateau the uplift of the qinghai tibetan plateau has a great effect on local and global climate changes here we report the late holocene climate change in the northern plateau by using a 3490 year sediment core record from kusai lake glycerol dialkyl glycerol tetraethers gdgts collected from the core were examined in combination with other paleo environmental proxies the reconstructed mean annual air temperatures maat using branched gdgt membrane lipids of certain bacteria proxies are higher than the measured maat but much closer to measured summer air temperatures suggesting a possibility of a bias of the reconstructed maat towards summer temperatures the ph values derived from a branched gdgt proxy show a negative correlation with toc a lake productivity indicator in arid regions furthermore both cbt ph and toc show temporal cyclic changes which suggest that the branched gdgt derived ph index may be useful in reconstructing paleo ph values in a lacustrine system lastly the composition of isoprenoid gdgts membrane lipids of archaea shows a major shift around 1400 bp which is in line with a large increase in sediment soluble salts at this time but lags behind the onset of salt mineral precipitation by 600 yr suggesting that change in archaeal community composition and salt mineral precipitation may require different threshold values of salinity the results of this study demonstrate that useful paleo climatic and paleo environmental information can be extracted from the gdgts preserved in lake sediments

radar interferometry and its application to changes in the earth s surface geophysical applications of radar interferometry to measure changes in the earth s surface have exploded in the early 1990s this new geodetic technique calculates the interference pattern caused by the difference in phase between two images acquired by a spaceborne synthetic aperture radar at two distinct times the resulting interferogram is a contour map of the change in distance between the ground and the radar instrument these maps provide an unsurpassed spatial sampling density 100 pixels km 2 a competitive precision 1 cm and a useful observation cadence 1 pass month 1 they record movements in the crust perturbations in the atmosphere dielectric modifications in the soil and relief in the topography they are also sensitive to technical effects such as relative variations in the radar s trajectory or variations in its frequency standard we describe how all these phenomena contribute to an interferogram then a practical summary explains the techniques for calculating and manipulating interferograms from various radar instruments including the four satellites currently in orbit ers 1 ers 2 jers 1 and radarsat the next chapter suggests some guidelines for interpreting an interferogram as a geophysical measurement respecting the limits of the technique assessing its uncertainty recognizing artifacts and discriminating different types of signal we then review the geophysical applications published to date most of which study deformation related to earthquakes volcanoes and glaciers using ers 1 data we also show examples of monitoring natural hazards and environmental alterations related to landslides subsidence and agriculture in addition we consider subtler geophysical signals such as postseismic relaxation tidal loading of coastal areas and interseismic strain accumulation we conclude with our perspectives on the future of radar interferometry the objective of the review is for the reader to develop the physical understanding necessary to calculate an interferogram and the geophysical intuition necessary to interpret it

summer monsoon precipitation variations in central china over the past 750 years derived from a high resolution absolute dated stalagmite abstract a 2 3 year resolution record of stalagmite oxygen isotope variations from the south flank of the qinling mountains central china has revealed the asian summer monsoon asm precipitation variations in the investigated area over the past 750 years the summer monsoon precipitation gradually increased since 1249 ad reaching its highest values in the period 1535 1685 ad and then decreased with substantial decadal to centennial scale fluctuations the monsoon precipitation increased again between 1920 and 1970 ad three intervals of high monsoon precipitation were identified 1535 1685 ad 1755 1835 ad and 1920 1970 ad three intervals of low precipitation were inferred in 1249 1325 ad 1390 1420 ad and 1890 1915 ad the 18 o composition and lithological features of the stalagmite coincidently indicate a wetter climate during the little ice age lia which is also confirmed by climate records from chinese historical documents within this area a comparison with other high resolution speleothem records indicates regional differences in monsoon precipitation variability from the south to the north of central china in the last 750 years on decadal to centennial scale power spectrum analysis of the 18 o record shows significant 117 8 34 6 14 10 3 and 6 year periodicities these periodicities are widely observed in the climate records from asm controlled areas of china and are consistent with the gleissburg periodicity br ckner periodicity sunspot periodicity of solar activity and el nino southern oscillation enso periodicity these correlations suggest that both solar activity and enso periodicity may have had important influences on asm precipitation in china over the past 750 years

numerical evidence enabling reconciliation gravity and height changes in volcanic areas s u m m a r y gravity and height changes reflecting magma accumulation in subsurface chambers are evaluated using finite element models in order to resolve controversial relationships observed in some volcanic areas when significant gravity changes occur without any significant deformation or vice versa it is often difficult if not impossible to jointly explain the observations using the popular mogi model here we explore whether these discrepancies can be explained by magma compressibility and source geometry effects compression of resident magma and expansion of the chamber wall act concurrently to accommodate newly added magma gravityheight ratios are found to mainly depend on i geometry of the sources which control the volume expansion of the chamber ii magma compressibility which affects the contraction of the magma resident in the chamber and iii depth of the sources our numerical results show that when magma compressibility and non spherical sources are taken into account significant gravity variations can indeed be successfully reconciled with negligible height changes this may be the case at etna volcano where gravity changes about 40 gal without any significant deformation below 5 cm were observed during the 1994 1995 inflation period the numerical results point to the accumulation of a 1 4 1010 kg mass into an elongated source simulating a shallow storage region supplying the summit craters

spatiotemporal gravity changes on volcanoes assessing the importance of topography 1 mass redistribution and deformation cause spatiotemporal gravity changes in active volcano areas the ability of the gravity measurements to detect subsurface magma movement as a precursor to volcanic eruptions is greatly enhanced if gravity changes are analyzed and modeled jointly with ground deformation data one effective tool for this analysis is provided by the gravity and elevation change ratio the proposed numerical formulation allows to simulate a wide range of pressures and mass loads however the assessment of gravity changes is especially important when they occur without measurable ground deformation in such a case it is very difficult to relate the gravity uplift ratio to changes in subsurface mass movements by using classical models in this work we study the role played by pressure and mass sources in the interpretation of observed gravity uplift ratio when deformation is negligible in volcanic areas associated with rough topographic relief

interpretation of 1992 1994 gravity changes around mayon volcano philippines using point sources significant gravity changes observed around the mayon volcano philippines between 1992 and 1994 at 26 stations are interpreted in terms of an increase of mass and pressure changes at several point sources modelled using a fast inversion process this inversion approach attempts to fit gravity and elevation changes by combining a random search for the positions of the sources and a linear least squares fit for the incremental mass pressure and possible common regional values for gravity or elevation changes some stabilizer terms are included in the misfit function models with one and two sources were tested against the observed changes at mayon models with only one source give a best fit for a shallow source with a positive mass increment horizontally displaced far from the summit the study using two sources gives a best fit that is similar to the one source model but in addition indicates anomalous behavior at stations in the sw neglecting the stations located southward from a local fracture the best fitting model suggests one central positive mass change source which is likely to be an intrusion of about 0 5 mu with a depth of about 5 km beneath the volcano standard deviation for the residuals ranges from 7 8 gal for one source models to 6 7 gal for models with two sources both of the cases are below the error value of 9 4 gal estimated for the gravity data so that it is not possible to discriminate between both possible interpretations without additional information

peatland development and climate changes in the dajiuhu basin central china over the last 14 100 years abstract peatlands are one of the optimal archives for paleoclimate research and their records contain a detailed history of climatic and environmental variations during their formation here we collected a peat profile from the dajiuhu basin in central china and analyzed several geochemical proxies such as total organic carbon toc total nitrogen tn titanium ti and aluminum al to investigate the history of peat development the results show that the peat growth was initiated after around 12 8 cal ka bp at the sampling site and the toc and tn contents kept stable during the holocene except during the periods of 10 5 9 0 cal ka bp and recent 1 5 cal ka bp however compared with other toc records in the dajiuhu basin the history of peat development varied greatly in different sampling sites indicating that the peat development in the dajiuhu basin probably responds to both climate changes and local geological and hydrological conditions investigations of the interactions between climate change and peat development record in this study suggest that peat development presented significant responses to the large and rapid decreases in east asian summer monsoon intensity such as the 9 2 ka monsoon weakening event however the obvious long term decreasing trend of monsoon precipitation during the mid late holocene did not lead to the degradation of the dajiuhu peat probably resulting from relatively stable temperature in addition the sharp decrease of toc and tn values in the surface 15 cm of dajiuhu peat was probably attributed to increased human activity

abnormal positive δ13c values of carbonate in lake caohai southwest china and their possible relation to lower temperature abstract carbon source inputs co 2 exchange between atmosphere and lake water as well as lacustrine productivity are commonly served as the main controls on 13 c values of authigenic carbonates in lake sediments generally 13 c values of recent carbonates in most lakes are lower than 5 all values reported here with respect to the pdb standard and rather few reach up to 13 extreme positive 13 c values up to 23 10 are reported in authigenic carbonate in lake caohai southwest china and some 13 c values are the most positive values in the previously reported surface water carbonate 13 c values in lakes simultaneously there are two intervals of large carbonate 13 c enrichment during the past 500 years namely 1670 1714 ad and 1788 1881 ad on the basis of combination with the oxygen isotopic composition of carbonate and drought flood index proxies d f carbon source inputs co 2 exchange between atmosphere and lake water can not cause this extreme carbonate 13 c enrichment in addition the inconsistent between organic matter content and 13 c values of carbonate lower organic matter 13 c values as well as the weak negative correlation between 13 c values of organic matter and carbonate during these two intervals confirmed that lacustrine productivity is also not the dominant factor that controls abnormal positive carbonate 13 c values temperature variations in lake caohai during the past 500 years were reconstructed from co analysis of 18 o values of carbonate and organic matter cellulose and periods of abnormal positive 13 c values of carbonate correspond well with the lower temperature periods the 1670 1714 ad and 1788 1881 ad cold periods were synchronous with the coldest intervals of little ice age lia and also consistent with the maunder and dalton sunspot minimum respectively considering these geochemical data together although there is no direct effect between temperature and carbonate 13 c values the lower temperature restrains the degradation of organic matter and bacteria have the chance to participate the carbon isotopic fractionation of organic matter thus generating the methane ch 4 gas which has the extreme lower 13 c values up to 60 resulting in the extreme enrichment 13 c in carbonates due to the preferential synthesis of 12 ch 4 the important inputs of bacteria to sedimentary sequence during the periods of 1670 1714 ad and 1788 1881 ad have been further verified by the carbon isotopic fractionation between carbonate and organic matter therefore this mechanism may be responsible for abnormal positive 13 c values in lake caohai abnormal positive 13 c values of carbonate in lake caohai may be indirectly ascribed to the lower temperature and more attention should be paid to the carbon isotopic composition of carbonates in lake caohai in future research particular factors affecting carbonate carbon isotopic composition should be taken into account in order to avoid misinterpreting palaeoclimatic reconstructions

mechanisms of magma eruption and emplacement at mt etna between 1989 and 1992 the present eruption sequence of mt etna began during september 1989 with extensive fracturing and culminated in 1991 93 with the largest lava eruption this century1 here we present measurements of gravity and ground deformation which in conjunction with seismic data provide a detailed record of the processes occurring before and during eruption these reflect a complex interplay between magma injection into the paths of lowest compressive stress through the volcano flanks forcing elastic deformation and fracture growth in response to gravitational stresses we find that after the end of the eruptive activity in 1989 fractures in the south southeast flank of the volcano remained unfilled until some months before the 1991 93 eruption these results indicate the utility of microgravity monitoring as the precursory processes that we identify were largely undetected by seismic and ground deformation monitoring

decadal multi decadal temperature discrepancies along the eastern margin of the tibetan plateau abstract knowledge of the synchronicity and discrepancy of temperature variations along the eastern margin of the tibetan plateau etp is critical in understanding the driving forcing of regional temperature variations in this study we established 15 n timeseries in organic matter and 13 c timeseries in ostracod shells from sediments of lake lugu and attributed their variations to decadal multi decadal temperature variations we compared temperature variations along the etp transect during the past four centuries based on our presently developed and previously developed temperature proxy indices as well as temperature variations reconstructed by other researchers we found that 1 over the north etp area n etp the decadal multi decadal variations in temperature correlate well with each other 2 over the south etp area s etp temperature variations correlate not so well with each other while those at south to west portion of the tibetan plateau are rather local 3 the decadal variations in temperature are generally synchronous with those in precipitation over the n etp area and they are broadly anti phase out of phase with the corresponding ones over the s etp area 4 the long term temperature and precipitation trends are coupling over the n etp but decoupling over the s etp we speculate that because the n etp is located at the frontier of the asian summer monsoon asm region temperature variations there are not as strongly influenced by the asm they are most likely dominated by changes in solar activities and show general similarity to the average of the northern hemisphere over the s etp area decadal temperature variations are obviously influenced by precipitation because the decadal multi decadal precipitation variations are anti phase and or out of phase between the n etp and s etp the decadal multi decadal temperature variations between these two regions are also anti phase and or out of phase

abrupt holocene indian summer monsoon failures a primary response to solar activity knowledge of the millennial abrupt monsoon failures is critical to understanding the related causes here we extracted proxy indices of indian summer monsoon ism intensity during the early to mid holocene from peat deposits at lake xihu in southwestern china there are a series of abrupt millennial scale episodes of ism weakening inferred from the lake xihu records which are generally synchronous with those inferred from other archives over ism areas an important feature is that the ism failures inferred from the lake xihu proxy indices synchronize well with abrupt changes in solar activity we argue that changes in solar activity play a primary role in producing most of these millennial ism failures while some other causes including freshwater outbursts into the north atlantic ocean and changes in sea surface temperatures of the eastern tropical pacific ocean may have also exerted influences on parts of the millennial ism failures

lipid biomarkers in the zoige hongyuan peat deposit indicators of holocene climate changes in west china abstract lipid biomarkers extracted from a peat core obtained from the northeast edge of the tibetan plateau have provided a 13 kyr record of regional climate change a period of warmer climate corresponding to the holocene optimum between 9 ka and 5 ka is evident in greater alteration of n alkanoic acids and n alkanols and in the appearance of biomarkers indicative of greater microbial activity concomitant increases in local precipitation that raised the water level of the peat bog are recorded by increases in the proportions of c23 and c25 n alkanes that are mainly derived from submerged floating plants alternations in submergent and emergent plant n alkane proxies reveal multi decimeter scale rises and falls in the bog water level that relate to variation in precipitation on the tibetan plateau during the holocene major low water level events occurred around 12 6 11 3 10 7 9 4 8 3 6 0 4 5 3 1 2 1 and 1 0 ka these events correlate well with cold dry events recorded in same region from other climatic proxies that reflect millennial scale holocene instability in the asian monsoon system our biomarker results also indicate that peat accumulation and preservation on the tibetan plateau are more sensitive to variability in monsoonal precipitation than in annual temperature

possible solar forcing of century scale drought frequency in the northern great plains a 2100 yr decadal resolution salinity and aridity proxy record of lacustrine ostracode shell mg ca ratios from a closed basin lake in the northern great plains shows statistically significant periodicities of 400 200 130 and 100 yr these periodicities are similar to the three principal solar oscillation periods 420 218 143 yr as inferred from the atmospheric radiocarbon record suggesting strong solar forcing of century scale drought frequency with a fundamental 400 yr period and its 2nd 3rd and 4th harmonics our proxy record correlates visually and statistically cross spectral analysis with the atmospheric 14 c record solar proxy and the gisp2 greenland ice sheet project two 18 o record climate proxy showing that solar minima are in phase with drought periods in the northern great plains and cold periods in greenland this spectral similarity together with phase correlation indicates a possible teleconnection of century scale global climate fluctuations through common solar forcing

a 700 year macrophyte productivity record inferred from isotopes of macrophyte remains and bulk carbonates in lake koucha northeast qinghai tibetan plateau abstract the isotopic composition of total organic carbon toc in lakes has been widely used to interpret paleoclimatic changes and the depositional environments of lake sediments however the main factors that affect the carbon isotopes of toc may vary in different lake sediment records limiting the ability of organic carbon isotopes to explain biogeochemical and environmental changes especially in lakes with a large number of aquatic plants in this study the 13c values of macrophyte remains and bulk carbonate in a sedimentary core from lake koucha were investigated to evaluate their paleoenvironmental implications we found that the bulk carbonate was dominated by authigenic carbonates formed in the lake and that their 18o and 13c values can be used to reconstruct environmental changes in the lake koucha area the macrophyte productivity derived from the carbon isotopic offset between the macrophyte remains and the bulk carbonate eremains bc in the lake koucha area agree well with total solar irradiance tsi records inferred from 10be and temperature records based on tree rings from the qinghai tibetan plateau although the distribution of macrophytes is related to water depth according past studies and our observations in the field our findings suggest that changes in macrophyte productivity may be primarily driven by temperature changes in the lake koucha area

the interpretation of gravity changes and crustal deformation in active volcanic areas simple models like the well known point source of dilation mogi s source in an elastic homogeneous and isotropic half space are widely used to interpret geodetic and gravity data in active volcanic areas this approach appears at odds with the real geology of volcanic regions since the crust is not a homogeneous medium and magma chambers are not spheres in this paper we evaluate several more realistic source models that take into account the influence of self gravitation effects vertical discontinuities in the earth s density and elastic parameters and non spherical source geometries our results indicate that self gravitation effects are second order over the distance and time scales normally associated with volcano monitoring for an elastic model appropriate to long valley caldera we find only minor differences between modeling the 1982 1999 caldera unrest using a point source in elastic homogeneous half spaces or in elasto gravitational layered half spaces a simple experiment of matching deformation and gravity data from an ellipsoidal source using a spherical source shows that the standard approach of fitting a center of dilation to gravity and uplift data only excluding the horizontal displacements may yield estimates of the source parameters that are not reliable the spherical source successfully fits the uplift and gravity changes overestimating the depth and density of the intrusion but is not able to fit the radial displacements

quantitative palaeoclimate reconstruction as an inverse problem a bayesian inference of late holocene climate on the eastern tibetan plateau from a peat cellulose δ18o record there has been a sustained need to quantify past climate changes from proxy records to better understand the driving mechanisms and thus to improve the prediction of the future transfer function is an intuitive and frequently used method in this regard however this method is unable to provide interpretive and predictive results from proxy records because physical processes are not included the inverse proxy modelling method opened up a new avenue for quantitative palaeoclimate reconstructions through the integration of proxy records with deterministic models it is fundamentally different from the statistical approach representing a conceptual advance in quantitative palaeoclimatology here we demonstrate the potential of this method by placing a mechanistic model and a 6000 year long peat cellulose 18o record obtained from the high cold and monsoonal eastern tibetan plateau c 3500 m a s l in a bayesian paradigm in this worked example the marginal posterior probability distributions of palaeo

the history and variability of the east asian paleomonsoon climate abstract changes in the east asian paleomonsoon reflect interactions between the global atmosphere ocean land and ice systems and are also an expression of their combined effect within the boundary conditions imposed by the east asian continent and solar radiation the history of the east asian monsoon is an alternation between dominance by the dry cold winter and warm humid summer monsoons high resolution eolian sequences preserved in the chinese loess plateau reveal that the east asian monsoon may have commenced at least 7 2 ma ago they also provide evidence indicating that the pulsed uplift of the tibetan plateau at about 3 4 and 7 2 ma may have played an important role in inducing climate change the palaeoclimatic records of the last glacial cycle show high frequency variability on time scales of 1000 year or even shorter and instability of the east asian paleomonsoon system the high frequency variability could be due to a non linear response to orbital forcing or a result of the coupling processes between different components of the global system cold air activity in northern high latitudes the trans equatorial air streams from the southern hemisphere and possibly enso may have played an important role in east asian monsoon variability the synchroneity of all the palaeoclimatic events along the polar equator polar pep transect is still an open question correlation of limited palaeoclimatic records for the last 30 kyr obtained from east asia and australia suggests that the trans equatorial air streams driven by the monsoon and trade winds may have had an influence on opposite hemispheres

synchronous climate changes in antarctica and the north atlantic central greenland ice cores provide evidence of abrupt changes in climate over the past 100 000 years many of these changes have also been identified in sedimentary and geochemical signatures in deep sea sediment cores from the north atlantic confirming the link between millennial scale climate variability and ocean thermohaline circulation it is shown here that two of the most prominent north atlantic events the rapid warming that marks the end of the last glacial period and the bolling allerod younger dryas oscillation are also recorded in an ice core from taylor dome in the western ross sea sector of antarctica this result contrasts with evidence from ice cores in other regions of antarctica which show an asynchronous response between the northern and southern hemispheres

quartz veins deformed by diffusion creep accommodated grain boundary sliding during a transient high strain rate event in the southern alps new zealand abstract the crystallographic preferred orientations cpos and microstructures of deformed quartz veins were measured for four samples in the hanging wall of the alpine fault in the southern alps new zealand their deformation and exhumation has occurred since 4 ma the quartz veins have been ductilely sheared to finite shear strains of 5 15 in late cenozoic shear zones at 450 50 c 310 90 mpa and strain rates between 2 10 11 and 2 10 9 s 1 the sheared veins have a polygonal microstructure with few subgrains and an average grain size of 100 m the cpo of the veins is random to very weak within the shear zones we suggest that dislocation creep accommodated initial shear deformation at high stresses and strain rates the deformation must have created a strong cpo and concomitant dynamic recrystallization reduced the grain size significantly dissipation of stresses during initial deformation lead to a stress and strain rate drop required for a switch to diffusion creep accommodated grain boundary sliding gbs continued shearing accommodated by gbs destroyed the cpo post deformational grain growth gave rise to a final polygonal microstructure with a similar grain size in veins and in the wall rocks analysis of existing experimental data suggest that this sequence of events is possible in the time available rates of all processes may have been enhanced by the presence of a water rich fluid within the shear zones these observations of naturally deformed rocks provide a model for the processes that may occur during short lived deformation at transiently high stresses at mid crustal depths or deeper

synchronous climate anomalies in the western north pacific and north atlantic regions during the last 14 000 years abstract a peat cellulose 18 o record spanning around 14 000 years from the hani peat mire in northeastern china reveals several abrupt temperature anomalies in the period from the last deglaciation through the holocene the timing of these anomalies coincides well with the notable cooling events recorded respectively using the gisp2 ice core and ice rafted sediment of the north atlantic ocean such as the older dryas inter allerod younger dryas and the nine ice rafted debris events the results demonstrate that this repeating pattern of abrupt temperature deterioration is not limited to the north atlantic area at high latitude but also exists in the western north pacific region at middle latitude the synchronous temperature anomalies possibly are resulted from the joint effects of meltwater discharge into the north atlantic ocean and reduced solar activity in the period from around 8600 to 8200 cal yrs bp the hani peat record shows a broad 18 o peak that may reflect compound climate signals resulting from the two kinds of forcing factors the temperature drop related to reduced solar activity at around 8600 8250 cal yrs bp and the temperature anomaly attributed to the meltwater effect at around 8220 70 cal yrs bp this result may provide palaeo temperature evidence for existence of the sharp 8 2 k event in the western north pacific region in addition our results have revealed that in the period from the last deglaciation through the holocene the synchronous temperature anomalies before and after the 8 2 k event seem to be related to meltwater outflow and reduced solar activity respectively it is important that the all temperature anomalies whether because of reduced solar activity in the late holocene or from meltwater discharge in the early holocene are accompanied by an abrupt decline in the indian ocean summer monsoon and abrupt strengthening of the east asian summer monsoon it is likely that reduced solar activity and meltwater outflow appear to modulate earth system changes in the same direction the influences could be compounded reduced solar activity and meltwater outburst both appear to act as triggers for occurrence of the el nino phenomenon in the equatorial pacific ocean which may result in broad teleconnections between the temperature anomaly in the northern hemisphere and abrupt variation of the asian monsoon

modern hydrology and late holocene history of lake karakul eastern pamirs tajikistan a reconnaissance study abstract lake karakul in the pamirs tajikistan is a deep brackish water lake in a closed basin at almost 4000 m above sea level water samples from the catchment area and lake karakul and a 104 cm sediment core from its shallow eastern sub basin were investigated and provide a first lake record from the region spanning the last 4200 cal yr bp multi proxy analyses revealed the following a relatively high meltwater inflow from glaciers snow fields and frozen ground in the catchment as a result of relatively warm conditions was reconstructed for the period between 4200 and 3500 cal yr bp the shift to colder climatic conditions around 3500 cal yr bp was probably abrupt total organic carbon values displayed the most dramatic drop for the entire core within less than 40 years in contrast the subsequent re establishment of warmer conditions occurred gradually over several centuries a higher meltwater supply to the lake and warmer conditions were recorded since ca 1900 cal yr bp with two slightly colder intervals between 1200 and 800 cal yr bp and between 400 and 100 cal yr bp the abrupt shift to significantly colder and drier conditions around 3500 cal yr bp in the eastern pamirs is seen also in records from the aral sea and the guliya ice core from the western tibetan plateau however more palaeoclimate studies in this highly continental part of central asia are needed to assess the spatial and temporal patterns of the holocene climate in the region

mayon volcano philippines change of monitoring strategy after microgravity and gps measurements from 1992 to 1996 abstract mayon volcano is part of the bicol volcanic chain on the island luzon philippines during this century there were ten activity periods distributed almost regularly because of the density of population about one million people living in the vicinity of the volcano three seismological observatories are in operation measurements of gravity changes started in 1992 just before the eruption of february march 1993 two profiles at the slope were established connected to a regional network around the volcano in order to enable the determination of mass changes between the campaigns the height control was provided by parallel gps measurements in all the network consists of 26 points which were remeasured with three gravimetres at least three times within one campaign during five campaigns within 4 years the differential gps gives no significant changes of the elevation within 4 cm nevertheless the gravity increased significantly by up to 1500 nm s2 equivalent to 150 gal as no significant change of elevation is observed gps no extended shallow magma chamber system below the volcano can be proved this is in accordance with geochemical results indicating a rather undifferentiated magma the youngest lava which is of interest for the eruption dynamics belongs to the medium k basaltic andesite field of the k2o vs sio2 diagram a rather qualitative check of groundwater level changes reveals that these cannot be the sources for the observed gravity changes thus the increase of gravity after the eruption of february 1993 can be explained by a mass redistribution in the volcanic vent from above the level of the gravity points to below practical conclusions of these results lead to changes in the monitoring strategy deformation measurements did not reveal any volcanic activities at least for the eruption of 1993 no significant deformation was observed gravity could be an indicator for long term changes thus repeated gravity measurements gps at selected points could be used in parallel to seismic monitoring to detect slow mass movements prior to changes in seismicity

the effect of collapse structures on ground deformations in calderas ground deformations related to unrest episodes in calderas are generally interpreted like in other volcanic environments in terms of increased pressure within a magma chamber embedded in a continuous elastic medium in this framework the depth of the pressure source is inferred from the size of the deformed area this scheme works quite well for individual volcanoes for instance hawaiian shields where a good correspondence between inflation events and eruptive episodes has been observed ground deformation in calderas however show unusual features that are difficult to interpret within such a scheme because considerable positive deformation in the order of several meters and microfracturing i e intense seismicity may occur without eruptions altough the estimated depth for the magma source is sometime very shallow less than 1 2 km it has been recently suggested that the contact zones at the border of collapsed calderas could act as stress strain discontinuity zones and thus bias modeling results obtained for continuous elastic media we use both observations and theoretical modeling based on 3 d finite element techniques to show that ground deformations in collapsed calderas are strongly influenced by the caldera structure giving a new perspective in related geological and geophysical observations in such areas

an insar based survey of volcanic deformation in the central andes we extend an earlier interferometric synthetic aperture radar insar survey covering about 900 remote volcanos of the central andes 14 27 s between the years 1992 and 2002 our survey reveals broad 10s of km roughly axisymmetric deformation at 4 volcanic centers two stratovolcanoes are inflating uturuncu bolivia and hualca hualca peru another source of inflation on the border between chile and argentina is not obviously associated with a volcanic edifice here called lazufre and a caldera cerro blanco also called robledo in northwest argentina is subsiding we explore the range of source depths and volumes allowed by our observations using spherical ellipsoidal and crack like source geometries we further examine the effects of local topography upon the deformation field and invert for a spherical point source in both elastic half space and layered space crustal models we use a global search algorithm with gradient search methods used to further constrain best fitting models inferred source depths are model dependent with differences in the assumed source geometry generating a larger range of accepted depths than variations in elastic structure source depths relative to sea level are 8 18 km at hualca hualca 12 25 km for uturuncu 5 13 km for lazufre and 5 10 km at cerro blanco deformation at all four volcanoes seems to be time dependent and only uturuncu and cerro blanco were deforming during the entire time period of observation inflation at hualca hualca stopped in 1997 perhaps related to a large eruption of nearby sabancaya volcano in may 1997 although there is no obvious relation between the rate of deformation and the eruptions of sabancaya we do not observe any deformation associated with eruptions of lascar chile at 16 other volcanoes that had recent small eruptions or fumarolic activity or associated with a short lived thermal anomaly at chiliques volcano we posit a hydrothermal system at cerro blanco to explain the rate of subsidence there for the last decade we calculate the ratio of the volume of magma intruded to extruded is between 1 10 and that the combined rate of intrusion and extrusion is within an order of magnitude of the inferred geologic rate

decrypting stable oxygen isotope variability in modern plants of the dajiuhu peatland from hubei province china implications for palaecology and palaeoenvironments abstract stable oxygen isotopes 18o from cellulose of peatland plants represent a widely used tool for studying ecological processes and palaeoenvironmental evolution however comparison of different regions shows that the climate drivers of 18o from peat cellulose vary by location in addition controversy remains about the parts of plants that are most suitable for analysis in this study 18o from different parts of modern plants in the peatland of dajiuhu hubei province china were determined to better understand the environmental factors that influence 18o in this area and at a seasonal scale results show that 18o values do not significantly differ in different parts of the plants whole sample stem and leaf correlation analyses indicate that the major factor contributing to 18o variability is the 18o value of peatland water under the influence of monsoons in addition significant negative correlations exist between 18o of plants and mean monthly temperature therefore results demonstrate that 18o of plants may preserve the 18o isotopic signatures of the peatland water and mean monthly temperature signals irrespective of the plant organ analysed our findings provide a reference and basis for a modern process that uses cellulose 18o in plants to study palaeoenvironmental changes

holocene climate changes inferred from peat humification a case study from the daiyun mountains southeast china abstract the investigation of two profiles dys1 and dys5 from the daiyun mountains in southeastern china sheds new light on the history of regional climate changes and the variability of the intensity of the east asian summer monsoon easm over the past 10350 years based on the degree of peat humification loss on ignition loi magnetic susceptibility ms and geochemical rb zr and zr rb data the records indicate that three main climatic regimes have occurred over the past 10350 years 1 relatively warm and wet conditions from 10350 to 8800 cal bp 2 a warmer and wetter climate from 8800 to 3000 cal bp that was interrupted by four cold episodes at 7500 6400 5400 and 4400 cal bp and 3 a dry and cool climate after 3000 cal bp these climatic changes were probably associated with a weak easm which was related to the latitudinal movement of the intertropical convergence zone itcz other important influences include solar radiation etc

organic matter geochemical signatures of sediments of lake ngoring qinghai tibetan plateau a record of environmental and climatic changes in the source area of the yellow river for the last 1500 years abstract the climate history of the source area of the yellow river sayr is important to understanding the pacing and processes of climate evolution on the northeastern qinghai tibetan plateau qtp to date results of research in this alpine region are limited herein we provide a first lacustrine record from the largest freshwater lake on the qtp that archives climatic and environmental variations in the sayr for the last 1500 yr the bulk organic carbon and nitrogen isotopic compositions 13corg and 15ntot are combined with atomic carbon nitrogen c n ratios to indicate that the sedimentary organic matter in lake ngoring originates from autochthonous algae and that the terrestrial input is minor comparison of the record of organic carbon isotope values with published records of ice accumulation rate iar of dunde and guliya glaciers from the northern qtp the total solar irradiance tsi 18o variations in the greenland ice core and biologically sensitive indicators c37 4 alkenone crenarchaeol and bgdgt concentrations from lake qinghai indicate that variations in the 13corg values in lake ngoring sediments reflect lake level fluctuations that are associated with variations in the amount of precipitation and glacier meltwater on the sayr high lake level phases indicated by positive shifts of 13corg values correspond to higher values of the north atlantic oscillation index naoi and lower values of the southern oscillation index soipr this relation suggests that the hydrologic history in the sayr is linked to changes in the indian monsoon and the westerlies and that both air masses delivered more moisture to the sayr during high tsi stages in contrast variations in the 15ntot values resemble the multiple paleoclimate proxy records obtained from ice cores peat sequences lake sediments and integrated paleo records from other qtp sites suggesting that the 15ntot values archived in lake ngoring sediments provide a history of past lake water temperature variations that is consistent with the variation history of the temperature dependent parameters from regional paleo climatic studies global climatic events including the dark ages cold period the medieval climate anomaly the little ice age and modern warming in 20th century could be clearly observed in the 15ntot variations in general the 13corg and 15ntot values in lake ngoring sediments appear to be useful indicators for paleo environment and paleo climate reconstructions in alpine oligotrophic freshwater lakes such as this one

paleoenvironmental significance of compound specific δ13c variations in n alkanes in the hongyuan peat sequence from southwest china over the last 13 ka abstract compound specific 13c 12c ratios of the c23 c25 c27 c29 and c31 n alkanes in the hongyuan peat sequence from southwest china were measured to decipher paleoenvironmental information recorded in the 13c variations over the last 13 ka the 13c values of the n alkanes range between 35 4 and 30 5 falling within the range of those from modern c3 peat forming vegetation however the vertical trends do not match with those of the 13c value for the c3 peat forming plant cellulose such a discrepancy between the 13c profiles implies that the n alkane 13c values are unlikely to reflect signals from emerged aquatic plants in the bog because submerged floating aquatic plants are major contributors of mid chain c23 and c25 n alkanes in the sequence the decoupling between the c23 and c25 n alkanes and the peat cellulose likely reflects the situation that these mid chain homologues primarily record the isotopic signals of submerged floating aquatic plants the stratigraphic profile of 13c values of submerged floating aquatic plant n alkanes c23 and c25 reveals two prominent positive excursions 0 8 2 4 during the early to middle holocene the excursions coincide with peat accumulation maxima and stronger indian monsoon activity in southwest china indicating that the 13c variations in submerged floating aquatic plants are closely related to changes in bog primary productivity controlled by the asian monsoon activity

general characteristics of temperature variation in china during the last two millennia three alternate china wide temperature composites covering the last 2000 years were established by combining multiple paleoclimate proxy records obtained from ice cores tree rings lake sediments and historical documents five periods of temperature variation can be identified a warm stage in ad 0 240 a cold interval between ad 240 and 800 a return to warm conditions from ad 800 1400 including the medieval warm period between ad 800 1100 the cool little ice age period between 1400 1920 and the present warm stage since 1920 regional temperature variation is found during ad 800 1100 when warm conditions occurred in eastern china and in the northeastern tibetan plateau and in ad 1150 1380 when the southern tibetan plateau experienced a warm interval in contrast evidence for cool conditions during the lia is more consistent among the proxy records the temperature reconstructions for china and the northern hemisphere show good agreement over the past millennium

proxy climate record for the last 1000 years from irish blanket peat and a possible link to solar variability recent research has shown that ombrotrophic mires can yield a proxy climate signal based on changes in the degree of peat humification 1 2 and that oceanic margin sites show the most sensitive record 3 we compare humification records for the last 1000 yr from two radiocarbon dated blanket peat profiles from western ireland and show several corresponding periods of climatic fluctuations periods favouring reduced peat decomposition suggestive of wetter and or cooler climatic conditions seem to coincide with periods of reduced sunspot activity and atmospheric14c anomalies whilst climatologists have continued to debate a link between solar variability on a century timescale and climate change the exact nature of that link remains elusive 4 7 the results from ireland demonstrate that data derived from mires could be relevant to the debate as to the extent of solar forcing in natural climatic variability and the curves shown provide a continuous record to add to previous evidence for the so called medieval optimum and little ice age 8 the record may imply that during the past millennium climatic change at the oceanic margin of the northeast atlantic largely corresponded to inferred variations in solar output

modeling of stress changes at mayon volcano philippines in this paper we analyze the stress change associated with the inverted volcanic source models at mayon volcano philippines where there are gravity changes without significant deformation after the 1993 eruption we detail the applicable data and the associated inversion techniques and models prior to calculating the appropriate stress changes it is determined that the stress change associated with the central magmatic source produces compressional stress changes at a secondary source to the northwest prompting a change in the local water storage in the underlying fractured rock

chronology of the palmer deep site antarctic peninsula a holocene palaeoenvironmental reference for the circum antarctic palmer deep sediment cores are used to produce the first high resolution continuous late pleistocene to holocene time series from the antarctic marine system the sedimentary record is dated using accelerator mass spectrometer radiocarbon methods on acid insoluble organic matter and foraminiferal calcite fifty four radiocarbon analyses are utilized in the dating which provides a calibrated timescale back to 13 ka bp reliability of resultant ages on organic matter is assured because duplicates produce a standard deviation from the surface age of less than laboratory error i e 50 years in addition surface organic matter ages at the site are in excellent agreement with living calcite ages at the accepted reservoir age of 1260 years for the antarctic peninsula spectral analyses of the magnetic susceptibility record against the age model reveal unusually strong periodicity in the 400 200 and 50 70 year frequency bands similar to other high resolution records from the holocene but so far unique f

holocene peatland development along the eastern margin of the tibetan plateau knowledge of peatland initiation accumulation and decline or cessation is critical in understanding peatland development and the related carbon source sink effect in this study we investigated the development of three peat profiles along the eastern margin of the tibetan plateau etp and compared the results with those of our previous work along this transect our work showed that the initiation over the northern etp is later and the slowdown cessation earlier than in the middle to southern etp the timing of optimum peatland formation over the northern etp lags the holocene climatic optimum these spatio temporal differences are likely to be related to the intensity of asian summer monsoon our work suggests that some peatlands along the etp transect have returned or are now returning their previously captured carbon to the atmosphere and thus act as carbon sources some peatlands still have net accumulation at present but the rates have been reduced concomitant with the decreasing summer monsoon intensity we speculate that more of the previously stored carbon in the etp peatlands will be re emitted to the atmosphere if the aridity continues as might occur under a continuous global warming scenario

the continental margin in iceland a snapshot derived from combined gps networks abstract the tectonical setting in iceland is quite complex due to the interaction of the iceland hot spot and the mid atlantic ridge while in the north of the island one active spreading zone exists the divergent motion in the centre and the south is distributed over at least two volcanic rift zones the spreading rate increases linearly along the western volcanic zone from north to south up to 8 mm yr at the hengill triple junction on the contrary the spreading rate of the parallel eastern volcanic zone decreases from 16 mm yr down to 6 mm yr at the island s southern coast the hreppar microplate between the two predominant rift zones has an independent motion which is distinct from that of the eurasian and north american plates a new detected feature is the spreading activity around the hofsjokull volcanic zone located in the centre of iceland with a significant rate of 6 mm yr during this investigation the coordinate sets of nearly 20 years of gps data acquisition on iceland were combined to get a velocity field for the surface of iceland this velocity field is based on a linear kinematic model with the consideration of local non linear effects like volcano up doming and displacements due to major earthquakes

structural setting of the bicol basin and kinematic analysis of fractures on mayon volcano philippines mayon volcano is located within the bicol basin in the southeastern region of luzon philippines the basin is contained within a releasing bend associated with the curvature of the central segment of the left lateral philippine fault a structural analysis of the faults that traverse the bicol basin was conducted through reviews of existing literature seismic data interpretation and remote sensing in particular those structures that may have influenced the growth and evolution of mayon dynamic analysis of the aforementioned structures reveals a regional transtensional stress regime for the bicol basin field investigation on mayon s slopes revealed the existence of fractures along its western and eastern flanks these structures on mayon have the same geometry as the dominant faults found within the bicol basin interpretation of these fractures indicates a tectonic control over their origin the identification of fractures on mayon s slopes is the first description of such features on its edifice these new data highlight the probable landslide hazards associated with an oversteepened volcano that may have been further destabilized by tectonic activity

genesis and evolution of unrest episodes at campi flegrei caldera the role of thermal fluid dynamical processes in the geothermal system we develop a model for describing water flow in a porous medium under the effect of thermal and pressure gradients the model simulates geothermal systems in calderas given the boundary conditions and the fluid dynamical properties of the medium the model allows computation in fluid dynamical stationary states of parameters characterizing the flow such as flow velocity and temperature and pressure distributions at depth the model is applied to investigate the effects of the local geothermal system on the unrest episodes at campi flegrei caldera using experimentally determined fluid dynamical parameters for the caldera rocks we show that changes of water flow in shallow aquifers under the effect of pressure and or temperature variations within the geothermal system can be very important in the genesis and evolution of unrest crises in particular they can strongly amplify the effect of pressure increase in the magma chamber on ground uplift they can also explain the timescales of evolution of ground movements in terms of transit times of the water front and of the connected temperature fronts due to advective transport on such grounds an integrated mechanic thermal fluid dynamical model was built allowing us to give a semiquantitative global explanation to the genesis and evolution of unrest phenomena results obtained here can be generalized to other similar calderas

postglacial climate change record in biomarker lipid compositions of the hani peat sequence northeastern china abstract the peat sequence at hani in northeastern china accumulated over the past 16 cal kyr in a percolation mire in which rain water and ground water seeped through the peat system the molecular compositions of n alkanes n alkanols and n alkanoic acids extracted from the hani peat sequence reveal different responses to the progressive evolution of climate and changes in the nature of the peat forming vegetation long chain length components that originate from the waxy coatings of subaerial vascular plants dominate the n alkane distributions throughout the hani peat sequence the paleoclimate integrity of these biomarker molecules appears to be well preserved most of the n alkanol distributions are similarly dominated by long chain components that indicate their origins from subaerial plants in contrast n alkanoic acid distributions are dominated by secondary components that record the importance of post depositional microbial activity in this peat sequence which evidently can be extensive in a percolation mire elevated n alkane paq values and c23 c29 ratios which are both molecular proxies for water loving plants record an especially moist local climate in the bolling allerod 14 5 to 12 9 ka younger dryas 12 9 to 11 5 ka and pre boreal 11 5 to 10 5 ka portions of the hani peat sequence depressed paq values and c23 c29 ratios and larger n alkane average chain length values indicate that the holocene climatic optimum 10 5 to 6 ka was a period of warmer climate with lower effective precipitation which contrasts with evidence of wetter climates in most of east asia

gravity changes and internal processes some results obtained from observations at three volcanoes temporal gravity changes provide information about mass and or density variations within and below the volcano edifice three active volcanoes have been under investigation each of them related to a plate boundary mayon luzon philippines merapi java indonesia and galeras colombia the observed gravity changes are smaller than previously expected but significant for the three volcanoes under investigation and within the observation period mainly the increase of gravity is observed ranging from 1 000 nm 2 to 1 600 nms 2 unexpectedly the gravity increase is confined to a rather small area with radii of 5 to 8 km around the summit at mayon and merapi the parallel gps measurements yield no significant elevation changes this is crucial for the interpretation as the internal pressure variations do not lead to significant deformation at the surface thus the classical mogi model for a shallow extending magma reservoir cannot apply to confine the possible models the attraction due to changes of groundwater level or soil moisture is estimated along the slope of merapi exemplarily by 2 d modelling mass redistribution or density changes were evaluated within the vent as well as deeper fluid processes to explain the gravity variations the results are compared to the model incorporating the additional effect of elastic deformation

stable isotopes in bulk carbonates and organic matter in recent sediments of lake qinghai and their climatic implications abstract multi proxy indices on annual decadal scales during the past 600 years were developed from the surface sediments of lake qinghai based on 210pb and 137cs geochronology the 13ccarb 18ocarb and total carbonate content are consistent with one another in trends and their variations have been mainly ascribed to regional temperature it is suggested that the strong evaporation contributes in modifying 18o of lake water and 13c of the dissolved inorganic carbon of the surface water and appears to be responsible for the covariance between 13ccarb and 18ocarb photosynthesis of the aquatic plants appears to have played a significant role in determining 15n of organic matter the discrimination of 14n and 15n during photosynthesis may have triggered a positive linkage between temperatures and 15norg after removal of the stratigraphic trend variations of total organic carbon toc c n ratio and 13corg have been ascribed to local precipitation toc after removal of the stratigraphic trend is positively correlated with the c n ratio r 0 45

proxy value of n alkan 2 ones in the hongyuan peat sequence to reconstruct holocene climate changes on the eastern margin of the tibetan plateau abstract n alkan 2 ones in the hongyuan peat core from the eastern margin of the tibetan plateau were investigated to assess the paleoclimate proxy value of variations in their compositions over the last 13 500 cal years a homologous series of these compounds that ranged from c 19 to c 31 was identified throughout the peat sequence maximizing at c 23 and showing a strong odd over even carbon chain length predominance to help evaluate the possible paleoclimatic value of the n alkan 2 ones in the hongyuan peat core we compared our molecular results with the pollen records from the same sequence results show that past changes in monsoon precipitation amounts as revealed by the ratio of abies cyperaceae firs sedges are also recorded in the n alkan 2 one c 23 c 25 c 27 c 29 c 31 ket ratio and cpi ket carbon preference index value stratigraphic variations of n alkane and n alkanoic acid ratios suggest that changes in the moisture sensitive microbial oxidation of odd chain n alkanes and decarboxylation of even chain length n alkanoic acids is recorded in the abundance of n alkan 2 ones changes in the monsoon rain intensity on millennial scales are also evident in the n alkan 2 one proxies indicating that their variations in the peat sequence are correlative with changes in microbial activity controlled by the asian monsoon