comment on paleoclimatic inference from stable isotope profiles of accretionary biogenic hardparts a quantitative approach to the evaluation of incomplete data by wilkinson b h ivany l c 2002 palaeogeogr palaeocl palaeoecol 185 95 114 the time base reconstruction method proposed by wilkinson and ivany paleoclimatic inference from stable isotope profiles of accretionary biogenic hardparts a quantitative approach to the evaluation of incomplete data palaeogeogr palaeocl palaeoecol 185 2002 95 114 can be further refined they have shown that variations in accretion rate can be reconstructed from variations in the period of the measured signal here it is shown that such variations influence not only the period but also the phase of the signal so a refined estimator for the time base is constructed which takes both period and phase variations into account

high resolution record of environmental changes and tephrochronological markers of the last glacial holocene transition at lake lautrey jura france this paper presents the results of a multiproxy investigation including volume magnetic susceptibility mineral and pollen analyses of late glacial sediments from lake lautrey jura france small scale lithological variations have been identified with high stratigraphic resolution in order to establish lithostratigraphic correlations between cores measurements combined with mineralogical analyses provide information on past sedimentary processes this combined approach reflects major changes in terrestrial habitats and soil processes which may relate to the climatic events characterising the late glacial climatic warming and cooling phases during warm intervals the record indicates increased lake productivity via carbonate precipitation and decreased input of detrital material in contrast cooler intervals show reduced lake productivity catchment area instability and increased detrital inputs several short interruptions in reforestation and in soil stabilisation can be identified and linked with abrupt colder events occurring through the bolling a general trend of warming is recorded from the coldest part of the younger dryas three tephra layers were also detected the mineral composition analyses show that the upper tephra layer corresponds to the laacher see eruption eifel germany while the lower ones may relate to the volcanic activity of the chaine des puys massif central france around 13 000 cal yr bp these two events recognised for the first time outside the massif central region may provide additional chronostratigraphic markers for the late glacial sedimentary records of the jura mountains and northern alps copyright 2004 john wiley sons ltd

the influence of changing orbital parameters and surface boundary conditions on climate simulations for the past 18 000 years abstract general circulation model experiments at 3000 year intervals for the past 18 000 years were made to estimate the magnitude timing and pattern of the climatic response to prescribed changes of orbital parameters date of perihelion axial tilt eccentricity and glacial age lower boundary conditions ice sheets land albedo sea ice and sea surface temperature the experiments used the community climate model ccm of the national center for atmospheric research ncar the response of monsoon circulations and tropical precipitation to the orbitally produced solar radiation changes was much larger than the response to changes of glacial age boundary conditions the continental interior of eurasia was 2 4 k warmer in summer and summer monsoon precipitation of north africa south asia was increased by 10 20 between 12 000 and 6000 yr bp before present when perihelion occurred during northern summer rather than in winter as now and the earth s axial tilt was larger than now southern hemisphe

numerical evaluation of land subsidence induced by groundwater pumping in shanghai to predict the future behavior of land subsidence in shanghai due to pumping of groundwater a numerical model is established in the proposed model groundwater flow in three dimensional conditions and soil deformation in one dimen sional conditions are calculated the model takes into account the multi aquifer aquitard hydrogeological condition of the soft deposit of shanghai the variation of the coefficient of compressibility and coefficient of hydraulic conductivity of the soils with the consolidation process are simulated relationships among land subsidence groundwater withdrawal volume and groundwater level are analyzed comparison between the measured value and calculated value shows that the model simulates the measured value fairly well the future of land subsidence behavior due to groundwater withdrawal is predicted and discussed via consideration of the variation of the following parameters in the future 30 years net withdrawn volume of groundwater pumping layer and pumping region resume un modele numerique est propose afin de predire le comportement futur d un affaissement de sol cause par le pompage de l eau souterraine a shanghai dans le modele propose l ecoulement de l eau souterraine en trois dimensions et la deformation du sol en une dimension sont calcules le modele considere la condition hydrogeologique multi aquifere aquitard du depot mou de shanghai les variations du coefficient de compressibilite et du coefficient de conductivite hy draulique des sols lors du processus de consolidation sont simulees les relations entre l affaissement du sol le volume de retrait de l eau souterraine et le niveau phreatique sont analysees des comparaisons entre les valeurs mesurees et calculees montrent que le modele peut simuler les valeurs mesurees relativement bien le comportement futur du sol en affaissement cause par le retrait de l eau souterraine est predit et discute en considerant les variations pour les prochains 30 ans pour les parametres suivants le volume net d eau souterraine retire la couche de pompage et la region de pompage mots cles pompage de l eau souterraine affaissement du sol ecoulement de l eau souterraine en trois dimensions consoli dation en une dimension prediction traduit par la redaction

late glacial climatic changes in eastern france lake lautrey from pollen lake levels and chironomids high temporal resolution analyses of pollen chironomid and lake level records from lake lautrey provide multi proxy quantitative estimates of climatic change during the late glacial period in eastern france past temperature and moisture parameters were estimated using modern analogues and plant functional types transfer function methods for three pollen records obtained from different localities within the paleolake basin the comparison of these methods shows that they provide generally similar climate signals with the exception of the bolling comparison of pollen and chironomid based temperature of the warmest month reconstructions generally agree except during the bolling major abrupt changes associated with the oldest dryas bolling allerod younger dryas and the younger dryas preboreal transitions were quantified as well as other minor fluctuations related to the cold events e g preboreal oscillation the temperature of the warmest month increased by not vert similar5 c at the start of bolling and by 1 5 3 c at the onset of the holocene while it fell by ca 3 to 4 c at the beginning of younger dryas the comparative analysis of the results based on the three lautrey cores have highlighted significant differences in the climate reconstructions related to the location of each core underlining the caution that is needed when studying single cores not taken from deepest part of lake basins

experimental investigation on the creep behavior of an unsaturated clay to better understand the long term deformation of landslides with consideration of the influence of water content variation a series of triaxial creep tests with suction control was conducted on clay specimens taken from one large scale landslide in the three gorges reservoir area in china results indicate that in the double logarithmic coordinates the axial strain increases linearly and the axial strain rate decreases linearly with the elapsed time the axial strain and strain rate increase with increasing deviator stress levels and decreasing matric suction for theoretical analysis based on the simulation of the test results by an empirical creep model developed for saturated soils a linear relationship was established between suction and one of the parameters of the model then a revised model with consideration of suction effects was developed in the revised model a power function was adopted for the description of the strain time relationship and a hyperbolic function was employed for the stress strain relationship verification indicated that the calculated results were in good agreement with the experimental ones

decoding nonlinear growth rates in biogenic environmental archives 1 the record of an environmental proxy along a growth axis in biogenic carbonates can reflect changing environmental conditions experienced during the lifetime of the organism when a chronology of the growth axis is not available a method based on anchor points is commonly used to introduce a time grid between these anchor points a constant growth rate is generally assumed despite the fact that growth rates change during life in most organisms here we present a method which refines the constant growth rate assumption at least in situations where the environmental proxy has a periodic component in its signal a nonlinear growth rate can then be estimated enabling the construction of a more realistic time base the anchor point method and the method proposed here are first compared on a synthetic record it is shown that the choice of the anchor points which is always a subjective one is largely influenced by the stochastic noise on the data record this results in biased growth rate profiles and biased time grids next we apply the method on the mg record in the bivalve isognomon ephippium on three samples of the clam saxidomus giganteus from washington state and on the vanuatu coral stable isotope record the method developed is applicable to a wide range of proxy records which are measured along an indirect time grid and are complicated by nonlinear accretion rates furthermore this method which takes variable growth rates into account opens perspectives on quantitative modeling of the relationship between environmental proxies recorded by accretive archives and the instrumental record like temperature or salinity

a 15 000 year isotopic record from lake zurich of deglaciation and climatic change in switzerland abstract ostracod and pelecypod carbonate preserved since the latest pleistocene in the bottom sediments of lake zurich was probably formed under constant temperature conditions temporal shifts in the oxygen isotype ratios for those carbonates therefore correspond to shifts in the isotopic character of the net lake inflow alpine deglaciation which released isotopically light meltwaters commenced prior to ca 15 000 yr b p and was essentially completed in northern switzerland by 12 4000 250 yr b p well before substantially increased atmospheric heat was available from either increased insolation or an increased atmospheric co 2 content the early holocene climate for the region was characterized by minor short term fluctuations in mean annual air temperatures and an overall amelioration of up to 2 c contemporaneously precipitated authigenic and biogenic carbonates have recorded partitioning of carbon isotopes between surface and bottom waters during photosynthetic production and subsequent oxidation of organic matter in the lake the degree of that partitioning provides an index of the relative production rates which were low in the late pleistocene meltwater lake but considerably enhanced during the holocene

patterns of variation in late glacial pollen stratigraphy along a northwest southeast transect through switzerland a numerical analysis palynological data from seven late glacial sites on a transect from the swiss plateau through the north and central alps to the south alps are analysed numerically constrained classification procedures were used to derive local pollen assemblage zones for each site detrended correspondence analysis was used to compare pollen stratigraphical similarities and differences within and between sites and to estimate the amount of palynological change at each site canonical correspondence analysis was used to display graphically patterns of variation between local zones within the sites and between the seven sites and to partition the total palynological variance into within site temporal variation and between site spatial variation the numerical results suggest that no two sites have identical late glacial pollen stratigraphies that the south alps site has a very different pollen stratigraphy compared with the other sites that the major spatial patterns of variation correspond to site location and thus that there was considerable variation in late glacial pollen rain along the transect just as there is today the total palynological variance is partitioned into 73 temporal variance 13 2 spatial variance and 13 8 unexplained variance the younger dryas event is poorly reflected in the south alps but is well reflected as a palynological revertence towards pre allerod assemblages at mid and high elevation sites in the north and central alps it is also well reflected as changes in pollen composition at one site on the swiss plateau but is poorly reflected at a nearby site on the swiss plateau

paleoclimatic inference from stable isotope profiles of accretionary biogenic hardparts a quantitative approach to the evaluation of incomplete data abstract variation in 18o of invertebrate and vertebrate skeletons has been widely employed to estimate annual means and seasonal ranges of temperature from many geologic settings among incertitudes encountered in employing this approach is the influence of unconstrained noise in environmental signals cessation of hardpart accretion during reproduction and or seasonal temperature extremes biasing of calculated mean temperatures toward seasons of maximum growth rate and dependence on the most extreme 18o values observed for estimating annual temperature range to better constrain paleoclimatic interpretations we describe several applications of a computational approach that address many of these uncertainties it is predicated on the presumption that annual variation in isotope composition across an accretionary skeleton represents sinusoidal variation in temperature and or the composition of ambient fluids the analysis resolves a best fit sinusoid for any portion of the data output consists of determinations of mean annual 18o seasonal range in 18o and sine period which reflects hardpart growth rate the procedure can be employed over some window of values within any data series and can be reiterated to arrive at solutions for all possible windows the technique allows for quantitative interpretation of mean values and annual amplitudes of 18o variation for every window regardless of whether or not that window actually spans a seasonal isotope extreme moreover it affords equal interpretational weight for every analysis in the data set in that mean annual and seasonal variation values estimated for each window are derived from every analysis in the data set it is therefore not necessary to estimate mean annual 18o as simply the arithmetic mean of all analyses and estimates of seasonality can be derived from data within any window rather than depending only on those several analyses that fall at compositional extremes in order to demonstrate the utility this methodology to the interpretation of paleoclimatological data we have applied it to published temperature data from several modern climatological data sets and to published 18o data from a paleogene gulf coast fish otolith a modern arabian sea coral a miocene texan equine tooth and an eocene bivalve from england each yields robust estimates of mean annual temperatures or isotopic compositions and of seasonal ranges in these values in addition unique features of data from each of these examples illustrate the power of this method to shed light on climatological and or biological phenomena that are also unique to each system

radiocarbon dating the devensian lateglacial in britain new evidence from llanilid south wales radiocarbon dates are described from a section through lateglacial and early flandrian sediments at llanilid mid glamorgan south wales comparisons between age determinations on the alkali soluble humic and alkali insoluble humin organic fractions from 12 biostratigraphic horizons reveal the extent of contamination by both older and younger carbon residues the llanilid time scale suggests that for the lateglacial the earliest organic sediments date from around 13 200 yr bp the early interstadial juniperus maximum occurred at ca 12 400 12 500 yr bp with a marked decline some 200 years later the main betula phase lasted only from ca 11 700 to 11 400 yr bp and the end of the interstadial occurred around 11 100 yr bp the beginning of the flandrian dates from ca 10 000 yr bp the juniperus maximum occurred approximately 200 years later the expansion of birch woodland began around 9600 yr bp while the first hazel arrived in the area at ca 9300 yr bp these age determinations are discussed in the context of radiocarbon dates from comparable biostratigraphic horizons in western britain and the dating of lateglacial events in the ocean core records from the north atlantic

the chronology of the last termination a review of radiocarbon dated high resolution terrestrial stratigraphies abstract the last termination is traditionally subdivided into the oldest dryas bolling older dryas allerod younger dryas and preboreal chronozones this paper briefly summarizes the history of the late weichselian chronostratigraphic system and gives an overview of recent developments in radiocarbon dating terrestrial records between 15 000 and 10 000 14 c years bp problems inherent in the traditional chronostratigraphy are discussed in the light of new and more advanced dating possibilities including accelerator mass spectrometry ams measurements on terrestrial macrofossils new results obtained using ams 14 c dated varve sequences are compared with each other and with the marine u th coral record in addition the importance of time synchronous marker horizons as a tool for long distance correlation between different archives is illustrated

environmental and climatic changes in the jura mountains eastern france during the lateglacial holocene transition a multi proxy record from lake lautrey this paper presents a multi proxy reconstruction of the climatic and environmental changes during the last glacial interglacial transition as recorded by a sediment sequence from lake lautrey jura eastern france this reconstruction is based on analysis of pollen chironomid organic matter oxygen isotope mineralogical magnetic susceptibility and inferred lake level data at a high temporal resolution the chronology is derived using ams radiocarbon dates the position of the laacher see tephra lst and of correlation between the lautrey and grip oxygen isotope records this data set reveals a detailed sequence of environmental changes in the jura mountains from greenland stadial 2a to the early holocene biotic and abiotic indicators allow the recognition of major abrupt changes associated with the gs 2a gi 1e gi 1a gs 1 and gs 1 preboreal transitions and other minor fluctuations related to the cold events gi 1d gi 1b and the preboreal oscillation pbo they also suggest additional cooling spells at ca 14 550 and 14 350 cal yr bp intra bolling cold periods at ca 13 500 and ca 12 700 cal yr bp just before the gs 1 onset and at ca 11 350 cal yr bp just before the pbo as well as an intriguing brief warming episode within gs 1 at ca 12 080 cal yr bp summer temperature increased by ca 5 c at the start of gi 1e and by 1 5 3 c at the holocene onset while it decreased by ca 3 4 c at the beginning of gs 1 major changes in local hydrology and in seasonality appear to be also associated with the gs 2a gi 1e gi 1a gs 1 and gs 1 preboreal transitions pollen and abiotic indicators suggest a greater sensitivity of the vegetation cover to climatic oscillations during the first part of the lateglacial interstadial than during the second part after ca 13 700 cal yr bp when a closed forest had been restored in this area by contrast the restoration of forest cover took less than 300 yr after the end of gs 1 at the beginning of gi 1e and gs 1 no lag occurs within the sampling resolution of 20 50 yr in the responses of aquatic chironomids and terrestrial pollen ecosystems while at the onset of the holocene the response of the vegetation appears slightly delayed in comparison with that of the chironomid community finally the recognition of two successive tephra layers which were deposited just before the lst at ca 12 950 cal yr bp and which originated from le puy de la nugere massif central france provides an additional tephrochronological tool for correlation between lateglacial european sequences

clamr a statistical evaluation of isotopic and temperature records in sclerochronologic studies abstract isotope sclerochronology has been widely used to reconstruct paleoclimate from the hard part remains of a broad range of taxa from many different environmental settings and geological and cultural contexts oxygen isotope 18o time series derived from these ultra high resolution daily seasonal annual records have been used to estimate annual averages seasonal ranges and seasonal extremes these time series however inherently include uncertainties such as unconstrained environmental noise changes in seasonal growth rates resulting in weighting annual temperature estimates toward seasons of maximum growth growth cessation and reliance on the most extreme 18o values in the time series to estimate seasonal temperature range etc to better quantify uncertainties in paleoclimate reconstructions using sclerochronologic data we developed an open source r package clamr the clamr evaluation tool improves upon the previous best fit sinusoid approach by introducing additional statistical computation and analysis including discrete fourier transform to initialize parameters for the sinusoidal function nelder mead method to optimize parameters jackknife error estimation and window size calculation for sinusoidal smoothing it can automatically calculate and plot statistical errors for oxygen isotope or temperature data series and provide statistical estimation of temperature and isotopic variables such as annual averages seasonal ranges and seasonal extremes moreover it allows evaluation of the influence of environmental and or physiological noise added to the climate signal therefore clamr enables more comprehensive and justified comparison between paleoclimate reconstructions and modern instrument records and ultimately advances our interpretation of seasonal isotope records from biogenic hard parts

variations of atmospheric 14 c concentrations over the allerood younger dryas transition highly variable atmospheric radiocarbon concentrations are a distinct feature during the last deglaciation the synchronisation of two high resolution ams 14c dated records lake go ci z and a floating late weichselian glacial varve chronology at the allerod younger dryas transition allowed us to assess in detail atmospheric 14c changes between late allerod and early preboreal the combined data set shows a drastic rise in 14c during the first 200 years or so of younger dryas and the two following about 500 year long 14c plateaux model experiments which included variations in the geomagnetic field atmospheric co2 variations and a drastic reduction in north atlantic deep water flux at the onset of younger dryas allowed to reproduce the distinct rise in 14c during the first 200 years of younger dryas fairly well also the drop in 14c at the younger dryas holocene boundary seems reasonably explained by changes in north atlantic deep water circulation however the reason behind the anomalous behaviour of the 14c signal in the middle of younger dryas remains an open question

late glacial climatic oscillations as recorded in swiss lake sediments regional pollen assemblage zones for the late glacial period of the swiss plateau are introduced and defined they include four major zones artemisia juniperus hippophae betula pinus paz with several subzones pollen and oxygen isotope analyses on lacustrine sediments from several lakes in the area reveal four distinct phases of climatic oscillation in the time period of 13 000 9500 yr bp the first oscillation termed the aegelsee fluctuation occurs shortly before 12 000 yr bp and varve counts suggest its duration was ca 100 yr it is characterised by a short decrease in the oxygen isotopes as well as a short increase in nap associated with a depression in birch pollen values the second oscillation which occurs in the 18o record shortly before the deposition of the laacher see tephra ca 11 000 yr bp is termed the gerzensee fluctuation it occurs during a pine dominated phase and its vegetational effects cannot be determined palynologically the most prominent regressive phase is the younger dryas biozone ca 10 700 10 000 yr bp characterised by an increase in heliophilous nap and low 18o values the younger dryas biozone can often be subdivided palynologically into two parts a first part rich in grasses and juniper and a second part with higher filipendula and birch values during the preboreal biozone another distinct oscillation is evidenced only in the oxygen isotope ratios comparison of the swiss oxygen isotope profiles with the greenland dye 3 record suggests that not only the three major shifts in the 18o curves but also the minor ones are closely comparable suggesting some common climatic control

climatic solar oceanic and geomagnetic influences on late glacial and holocene atmospheric 14c 12c change late glacial and holocene 14c12c ratios of atmospheric co2 vary in magnitude from a few per mil for annual decadal pertubations to more than 10 for events lasting millennia a data set illuminating 10 to 104 yr variability refines our understanding of oceanic climatic versus geomagnetic or solar forcing of atmospheric 14c12c ratios most of the variance in the holocene atmospheric 14c12c record can be attributed to the geomagnetic millennia time scale and solar century time scale influence on the flux of primary cosmic rays entering the atmosphere attributing the observed atmospheric 14c12c changes to climate alone leads to ocean circulation and or global wind speed changes incompatible with proxy records climate ocean related 14c redistribution between carbon reservoirs while evidently playing a minor role during the holocene may have perturbed atmospheric 14c12c ratios measurably during the late glacial younger dryas event first order corrections to the radiocarbon time scale 12 000 30 000 14c yr b p are calculated from adjusted lake sediment and tree ring records and from geomagnetically defined model 14c histories paleosunspot numbers 100 9700 cal yr b p are derived from the relationship of model 14c production rates to sunspot observations the spectral interpretation of the 14c12c atmospheric record favors higher than average solar activity levels for the next century minimal evidence was found for a sun weather relationship

lateglacial cryptotephra detected within clay varves in ostergotland south east sweden here we present a 710 year long floating varve record from south east sweden tephra analyses confirm the presence of the rhyolitic vedde ash preserved within two consecutive varve years confirming the younger dryas age of the varve series this permits for the first time direct correlation of swedish varved clay with other records of equivalent resolution which also preserve the vedde ash and demonstrates that the potential exists to independently date the swedish timescale this discovery will allow direct comparison of rates timing and duration of key climatic events across europe and the north atlantic region in records of equivalent resolution

characteristics of groundwater seepage with cut off wall in gravel aquifer i field observations1 this paper presents a case history of the leakage behavior during dewatering tests in the gravel strata of an excavation pit of a metro station in hangzhou china the groundwater system at the tes

interpretation of increased deformation rate in aquifer iv due to groundwater pumping in shanghai shanghai is a typical example of a region in china suffering from severe land subsidence previous investigations have shown that land subsidence is strongly related to groundwater pumping in both the temporal and spatial domains a series of field investigations shows that the deformation rate of aquifer iv aqiv has increased contributing significantly to the total subsidence in shanghai to predict the deformation behavior of aqiv in shanghai due to groundwater pumping four different models have been applied in this study i a model based on groundwater flow theory ii an elastic model based on cauchy mechanics iii a creep model incorporated into cauchy mechanics and iv a recently proposed land subsidence model by budhu based on cosserat mechanics based on a number of assumptions budhu s concept was extended to consider the time dependent behavior of groundwater potential in aquifers and the consolidation behavior of overburdened aquitards the calculated results of aqiv s deformation we

chronology of the last glacial cycle in the european alps chronological data for glacier advances in the european alps between the last interglacial eemian and the holocene are summarised 115 to 11 ka during this time glaciers were most extensive extending tens of kilometres out onto the forelands between 30 and 18 ka that is synchronous with the global ice volume maximum of marine isotope stage mis 2 evidence for ice expanding to just past the mountain front for an earlier major glacier advance comes from swiss sites where advances have been luminescence dated to mis 5d 100 ka and mis 4 70 ka up to now no such evidence has been found in the eastern alps by 18 ka more than 80 of the late wurmian ice volume had gone subsequently glaciers readvanced reaching into the upper reaches of the main valleys during the lateglacial gschnitz stadial which likely occurred around 17 ka with final moraine stabilisation no later than 15 4 ka the link of the egesen stadial with the younger dryas climate deterioration is supported by exposure ages from four sites as well as minimum limiting radiocarbon dates from bogs within former glacier tongue areas key questions on the spatial and temporal variability of ice extents throughout the last glacial cycle have yet to be answered copyright 2008 john wiley sons ltd

rates of change and chronological problems during the late glacial period results of high resolution ams 14c dating of terrestrial plant macrofossils from late glacial and early holocene lake deposits in switzerland show three periods with constant radiocarbon ages these plateaux of constant age occur at 12700 10000 and 9500 y bp a comparison of this radiocarbon chronology with a varve chronology documents discrepancies between the sidereal and the radiocarbon time scale for the late glacial period the age plateaux and the time scale discrepancies have a significant impact on the estimation of rates of change during this period estimates of rates of change can be very misleading if calculated on the basis of radiocarbon ages this is illustrated by an example of estimated rates of late glacial and early holocene palynological change in switzerland

linear simulation of the stationary eddies in a gcm part ii the mountain model abstract the validity of linear stationary wave theory in accounting for the zonal asymmetries of the winter averaged tropospheric circulation obtained in a general circulation model gcm is ascertained the steady linear primitive equation model used towards this end has the same vertical and zonal resolution as the spectral gcm but is finite differenced in the meridional direction it is linearized about a zonally symmetric basic state and forced by topography and 3 dimensional diabatic heating and transient flux convergence fields all of which are taken from the gcm as in part i in which we studied a gcm with a flat lower boundary we obtained the best correspondence between the gcm and the linear solutions when strong rayleigh friction is included in the linear model not only near the surface but in the interior of the tropical troposphere as well there is sufficient quantitative correspondence between the gcm and the linear solution to justify decomposing the linear simulation into parts for

the life and time of clams derivation of intra annual growth rates from high resolution oxygen isotope profiles abstract the paired analysis of subannual microincrements and serially sampled oxygen isotope data affords insights into the physiological and environmental conditions controlling bivalve growth however daily microincrements are faint or absent in many taxa difficult or ambiguous to count under the best conditions and are often constrained to the earliest years of ontogeny limiting the practicality of intra annual comparisons between growth rate and environmental parameters we present a computational approach to derive growth rates using only serially sampled oxygen isotope data thereby allowing for broader application of bivalve growth rate studies variation in the isotopic composition of shell carbonate along an ontogenetic sampling profile reflects temporal variation in ambient water temperatures while variation in the position of isotope values in the distance domain reflects intra annual variation in rates of shell accretion thus the shape of the isotope profile in distance space over a given year records the concomitant influence of subannual variation in temperature y axis and growth rate x axis presumption that annual variation in temperature is sinusoidal allows for the determination of an intra annual growth rate function that best approximates observed 18ocarb data the fidelity of the approach is affirmed using synthetically generated isotope datasets and previously published isotope profiles the method offers a variety of applications to sclerochronologic studies using only oxygen isotope values determined along an ontogenetic trajectory the approach can be used to quantify spatial and temporal patterns of intra annual accretion within populations additionally the model can be applied to long time series such that year to year variations in the growth profiles can be used to identify ontogenetic and climatic trends while we focus here on isotope distance records from bivalve shell carbonate this method is equally applicable to similar data from other accretionary biogenic skeletal materials

characteristics of groundwater seepage with cut off wall in gravel aquifer ii numerical analysis this paper presents a numerical investigation into the leakage behavior of cut off walls in gravel strata due to dewatering in a deep excavation pit the calculated values of the groundwater head and surface settlement using a model agree well with the measured values values of the hydraulic conductivity k and storage coefficient ss of each soil layer are obtained from the test results when the cut off wall is 43 m deep the leakage through the cut off wall in gravel is analyzed by considering a variation in hydraulic conductivity in different sections of the cut off wall the simulated results show that a significant leakage occurred in the 54 m deep cut off wall although leakage did occur in the full cut off wall in the confined aquifer the full cut off wall is still more efficient in preventing groundwater seepage than the partial cut off wall the relative depths of the cut off wall and of the wells have a significant effect on ground surface settlement during the withdrawal of groundwater the

environment and climate in southwestern switzerland during the last termination 15 10 ka bp abstract various records from sites ranging in altitude between 372 and 2290 m along a nw se transect through sw switzerland were compiled and correlated within well defined chrono and biostratigraphic units deglaciation of lowland areas is estimated at ca 15 000 14 000 bp minimum age while the lower part of the rhone valley and the jura mountains may have become ice free later a significant climatic warming is clearly indicated by several palaeoecological records at ca 12 600 bp the compiled data give no clear evidence of a cooler phase between 12 200 12 000 bp oxygen isotope data point to a slight and progressive decrease in the 18 o values between ca 12 500 11 000 bp which is followed by a marked drop at 11 000 bp a very distinct change in lithology rock glacier development and in mollusc and vegetation records characterises many low and high altitude sites ca 300 years later at 10 700 bp between 11 000 and 10 000 bp oxygen isotope records seem to respond more rapidly to the climatic shifts than the biostratigraphical records possible explanations for these time lags are discussed our compilation shows that further multidisciplinary research in key sites would provide more precise palaeoclimatological information both qualitatively and quantitatively higher time resolution and quantitative estimates of climatic parameters are needed to evaluate in detail the mechanisms and consequences of these rapid climatic changes in sw switzerland

the impact of cold north atlantic sea surface temperatures on climate implications for the younger dryas cooling 11 10 k the sensitivity of global climate to colder north atlantic sea surface temperatures is in vestigated with the use of the giss general circulation model north atlantic ocean temperatures 18 000 b p resembling those prevalent during the younger dryas were incorporated into the model of the present climate and also into an experiment using orbital parameters and land ice characteristic of 11 000 b p the results show that with both 11 000 b p and present conditions the colder ocean temperatures produce cooling over western and central europe in good agreement with younger dryas paleoclimatic evidence cooling also occurs over extreme eastern north america although the precise magnitude and location depends upon the specification of ocean temperature change in the western atlantic despite the presence of increased land ice and colder ocean temperatures the younger dryas summer air temperatures at northern hemisphere midlatitudes in the model are warmer than those of today due to changes in the orbital parameters chiefly precession and atmospheric subsidence at the perimeter of the ice sheets

biogeochemical and micro facial fingerprints of ecosystem response to rapid late glacial climatic changes in varved sediments of meerfelder maar germany the response of a lacustrine ecosystem to climatic changes from 13 500 to 10 800 bp was studied in a varve dated sediment profile of lake meerfelder maar western germany bulk biogeochemical parameters stable carbon and nitrogen isotopes of sedimentary organic matter and micro facies analysis are used for a detailed investigation of the lake s development from the allerod interstadial al to the younger dryas stadial yd and into the early holocene preboreal varve micro facies reveal rapid changes in composition and seasonal structure of the depositional environment mainly in temporal accordance with changes of terrestrial biozones the respective responses of bulk proxy parameters bi decadal resolution indicate different sensitivities to diverse climatic changes a prominent transition took place within two decades at the al yd boundary 12 690 12 670 bp increased flux of nutrients released from redeposited littoral sediments and shorter yd summer seasons led to an acceleration and concentration of lacustrine primary production with reduced discrimination against 13c high lacustrine primary production was further favored by relatively warm yd summer temperatures at 12 240 varve years bp from 1 year to the next a regular deposition of detrital layers in spring set in which is related to local hydrologic threshold processes amplifying the response to increased snowmelt discharge this distinct change in the middle of the yd is clearly detected by varve micro facies but not equally recorded in organic bulk proxy data especially carbon isotope ratios remain constant and indicate a negligible effect of this process on the productivity of lacustrine algae the yd preboreal transition 11 645 11 585 bp is marked by a characteristic change in micro facies throughout this transition stable carbon isotope ratios strongly decline while the accumulation of opal and organic matter om remained constant this is seen as an increasing importance of spring and autumn for gross primary production at the onset of the holocene

orographically forced planetary waves in the northern hemisphere winter steady state model with wave coupled lower boundary formulation abstract a planetary wave model has been developed in which the orographic forcing at the lower boundary arising from the kinematically induced vertical motion is due to the total flow impinging on the mountains rather than just the zonal mean basic state component of the flow over the mountains used in previous models consequently the effects of the vertical motions produced by the eddies at the lower boundary are included and are found to be as large if not larger than the zonal mean component the model remains linear mathematically but all the planetary waves become coupled through the lower boundary condition lbc and the model wave equations have to be solved for simultaneously a contrast is drawn between the wave coupled solutions and the solutions using the traditional lower boundary formulation in which the planetary waves are decoupled the model is symmetric about the equator and uses the linear balance set of equations on the sphere with full spherical geometry and spherical harmonic f

sudden changes in north atlantic circulation during the last deglaciation sudden changes in the flow of warm atlantic surface waters into the norwegian sea occurred frequently during the last deglaciation typically involving shifts in sea surface temperature of 5 c in fewer than 40 years these led to equally large and rapid changes in atmospheric temperatures and to shifts in atlantic deep thermo haline circulation and ice sheet melting rates

environmental responses to lateglacial climatic fluctuations recorded in the sediments of pre alpine lake mondsee northeastern alps investigation of the sedimentary record of pre alpine lake mondsee upper austria focused on the environmental reaction to rapid lateglacial climatic changes results of this study reveal complex proxy responses that are variable in time and influenced by the long term evolution of the lake and its catchment a new field sampling approach facilitated continuous and precisely controlled parallel sampling at decadal to sub annual resolution for mu xrf element scanning carbon geochemistry stable isotope measurements on ostracods pollen analyses and large scale thin sections for microfacies analysis the holocene chronology is established through microscopic varve counting and supported by accelerator mass spectrometric 14 c dating of terrestrial plant macrofossils whereas the lateglacial age model is based on delta 18 o wiggle matching with the greenland ngrip record using the gicc05 chronology microfacies analysis enables the detection of subtle salimentological changes proving that depositional processes even in rather large lake systems are highly sensitive to climate forcing comparing periods of major warming at the onset of the lateglacial and holocene and of major cooling at the onset of the younger dryas reveals differences in proxy responses reflecting threshold effects and ecosystem inertia temperature increase vegetation recovery decrease of detrital flux and intensification of biochemical calcite precipitation at the onset of the holocene took place with only decadal leads and lags over a ca 100 a period whereas the spread of woodlands and the reduction of detrital flux lagged the warming at the onset of the lateglacial interstadial by ca 500 750a cooling at the onset of the younger dryas is reflected by the simultaneous reaction of delta 18 o and vegetation but sedimentological changes reduction of endogenic calcite content increase in detrital flux were delayed by about 150 300 a three short term lateglacial cold intervals corresponding to greenland isotope substages gl 1d gl 1c2 and gl 1b also show complex proxy responses that vary in time copyright c 2011 john wiley sons ltd

decoding the oxygen isotope signal for seasonal growth patterns in arctic bivalves abstract chemical and physical variations in skeletal structures of marine organisms can reflect environmental variability forming the basis for reconstructing the conditions in which the organism lived the successful use of these bio archives for reconstructing seasonal environmental conditions is dependent on understanding intra annual growth patterns and timing of their deposition within skeletal structures we studied intra annual shell growth patterns as well as the timing and environmental processes associated with winter growth line deposition in two circumpolar bivalve mollusks serripes groenlandicus and ciliatocardium ciliatum shell growth deposited during a 1 year deployment on oceanographic moorings in kongsfjorden and rijpfjorden svalbard was analyzed in situ for 18 o values using high spatial resolution secondary ion mass spectrometry sims a new digital method was developed to measure the location of sims spots along chronologically deposited shell material dynamic time warping algorithms were adapted to align sims determined 18 o values with 18 o values predicted from continuous mooring instrument recordings of seawater temperature and salinity in order to derive intra annual shell growth models the resulting growth models indicated that the prominent winter growth band was formed during a slow shell growth period lasting from december until may in kongsfjorden and from november until mid june in rijpfjorden the length of the slow growth period was most likely controlled by food availability shell growth rate during the growing season was significantly explained by temperature marginal r 2 0 29 p

a long lacustrine record from the pianico sellere basin middle late pleistocene northern italy abstract the stratigraphical succession of the pianico sellere basin northern italy represents an exceptionally well preserved sedimentary assemblage which formed in a closed lake basin during the middle upper pleistocene these deposits are grouped into the hereby proposed pianico formation this includes four lacustrine fine grained laminated lithostratigraphical units containing a 10 5 m thick interval of well preserved varved carbonates the lacustrine units are coeval and laterally heteropic to lake marginal talus cone fan delta debris flow deposits accumulated within the lake the stratigraphical study and sedimentary facies analysis throughout the lacustrine succession combined with a preliminary pollen and microstratigraphical investigation provide evidence of a complex environmental and climatic evolution which occurred during the lacustrine deposition the pianico formation shows multiple changes in sedimentary processes which indicate a transition from a peri proglacial to a temperate lacustrine environment within forested phases a complex evolution is evident main changes in vegetational patterns from conifer to broad leaved warm temperate forests correspond to changes in sediment composition from distal sand silt turbidites to a regular continuous succession of endogenic calcite rich annual varves an increased rate of erosional processes on the surrounding slopes is also indicated by debris flow deposits stratigraphically their frequency within the fine grained basinal sediments increases upwards which would indicate increasing subaerial erosion processes at the end of the sedimentation of the pianico formation these data highlight the sensitivity of the pianico sellere basin sedimentation in recording minor climatic fluctuations and related environmental changes which occurred before the last glacial maximum probably during oxygen isotope stage 5 7 or 9

centennial scale lake level lowstand at lake uddelermeer the netherlands indicates changes in moisture source region prior to the 2 8 kyr event the uddelermeer is a unique lake for the netherlands containing a sediment record that continuously registered environmental and climatic change from the late pleistocene on to the present a 15 6 m long sediment record was retrieved from the deepest part of the sedimentary basin and an age depth model was developed using radiocarbon dating 210pb dating and bayesian modeling lake level change was reconstructed using a novel combination of high resolution palaeoecological proxies e g pollen non pollen palynomorphs chironomids quantitative determinations of lake level change ground penetrating radar and estimates of changes in precipitation lipid biomarker stable isotopes we conclude that lake levels were at least as high as present day water levels from the late glacial to 3150 cal yr bp with the exception of at least one lake level lowstand during the preboreal period lake levels were ca 2 5 m lower than at present between 3150 and 2800 cal yr bp which might have been the result of a change in moisture source region prior to the so called 2 8 kyr event increasing precipitation amounts around 2800 cal yr bp resulted in a lake level rise of about 3 5 4 m to levels that were 1 1 5 m higher than at present in line with increased precipitation levels as inferred for the 2 8 kyr event from nearby raised bog areas as well as with reconstructions of higher lake levels in the french alps all of which have been previously attributed to a phase of decreased solar activity lake levels decreased to their present level only during recent times although the exact timing of the drop in lake levels is unclear the author s 2016

late glacial and early holocene palaeoenvironmental changes in geneva bay lake geneva switzerland abstract detailed interdisciplinary investigations demonstrate that geneva bay lake geneva sediments clearly record important palaeoenvironmental and palaeoclimatic changes occurred during the late glacial and early holocene sediments are in fact differentiated by changes in texture mineralogical and geochemical composition distal turbidite and glacial rhythmite deposition associated with wind transported sediment supply dominate during the oldest dryas these were replaced during the allerod by detrital settling of sediment from turbid water and by endogenic calcite precipitation the younger dryas climate reversal for the first time in lake geneva well documented by a pollen record was characterized by an increase in detrital supply owing to increased run off from the bay slopes surrounding and within the catchment area caused by thinning of vegetation cover a brief pause in endogenic precipitation related to decreased productivity also occurs at this time endogenic carbonate sedimentation abruptly resumed at the start of the preboreal biozone in response to the rapid global climatic warming in the middle preboreal renewed detrital sedimentation is interpreted as the sedimentological response to increased erosion in high altitude regions of the catchment area caused by a minor early holocene cooling phase preboreal oscillation and interrupts the trend towards increasing endogenic calcite precipitation favourable limnic conditions are reached during the late preboreal when diatom calcite rhythmites begin to form stable isotope analysis 18 o 13 c in bulk carbonate highlight the transition from clastic dominated to endogenic dominated sedimentation endogenic calcite deposition continues during the boreal biozone occasionally interrupted by local high energy sedimentary processes wave induced erosion and reworking of littoral deposits enhanced by progressive lake level lowering during the older atlantic biozone sedimentation was mainly dominated by low energy deposition creating enhanced conditions for the development of benthic fauna we will discuss the factors that make geneva bay an important site for recording the late glacial holocene climate and environmental changes the comparison with other swiss plateau lacustrine systems allowed us to emphasize the role played by the particular geographical and morphological setting of the site investigated and links with climate sensitive regions in the catchment area

stationary waves of the ice age climate abstract a linearized steady state primitive equation model is used to simulate the climatological zonal asymmetries stationary eddies in the wind and temperature fields of the 18 000 ybp climate during winter we compare these results with the eddies simulated in the ice age experiments of broccoli and manabe who used climap boundary conditions and reduced atmospheric co2 in an atmospheric general circulation model gcm coupled with a static mixed layer ocean model the agreement between the models is good indicating that the linear model can be used to evaluate the relative influences of orography diabatic heating and transient eddy heat and momentum transports in generating stationary waves we find that orographic forcing dominates in the ice age climate the mechanical influence of the continental ice sheets on the atmosphere is responsible for most of the changes between the present day and ice age stationary eddies this concept of the ice age climate is complicated by the sensitivity of t

late weichselian environmental history in southeastern sweden during the deglaciation of the scandinavian ice sheet abstract late weichselian litho bio and chronostratigraphy 14 c and varves in southeastern sweden provide a detailed picture of the deglaciation pattern and dynamics shore displacement late glacial sedimentation and history of the landscape vegetation and climate two plausible glacial models were tested against lithologic chronologic and climatic data permafrost at and outside the ice margin and topographic conditions beneath the ice apparently caused inward spread of frozen glacier bed conditions this led to a buildup of a large zone of debris rich basal ice a climatic amelioration about 12 700 yr b p changed the temperature profile in the ice sheet deposition of basal melt out till began at the previously frozen glacier bed and a rapid recession of the clean ice set in thin exposed debris rich basal ice which was separated from the active ice margin about 150 yr later in this zone of stagnant ice there followed a 200 300 yr period marked by subglacial and supraglacial melt out and resedimentation forming a large hummocky transverse moraine the mild climate favored rapid plant immigration and a park tundra was established the gradual closing of the landscape was interrupted by a 100 to 150 yr period of tundra vegetation and a cool dry climate with local vegetational differences caused by differences in soil moisture about 12 000 yr b p a second climatic amelioration set in and during the next 1000 yr a birch and pine woodland gradually developed soils stabilized and empetrum heaths became abundant as the climate gradually deteriorated at the end of this period by 11 000 yr b p the area had become a tundra again with scattered birch stands dominated by herbs such as artemisia chenopodiaceae grasses and sedges some 500 yr later a birch pine woodland again succeeded and within about 500 yr the vegetation changed to a rather closed woodland as the climate ameliorated further however the time lag between climatic and vegetation change was considerable

gradients in seasonality and seawater oxygen isotopic composition along the early permian gondwanan coast se australia abstract oxygen isotope compositions of marine carbonates are commonly employed for understanding ancient temperatures but this approach is complicated in the very distant past due to uncertainties about the effects of diagenesis and the isotopic composition of seawater both locally and globally microsampled accretionary calcite from two species of the fossil bivalve eurydesma sowerby and morris 1845 collected from sediments of cisuralian age in high latitude marine sediments along the se coast of australia records cyclic seasonal fluctuations in shell 18 o values during growth demonstrating the primary nature of the isotope signal and thus allowing investigation of early permian seawater isotopic composition and water temperature in the high southern latitudes the mean and seasonal range of 18 o carb decreases poleward across about 10 of paleolatitude 67 s 77 s the presence of co occurring dropstones and stratigraphically associated glendonites constrains winter temperatures across the region to near freezing thus permitting calculation of realistic estimates of water composition and summer temperatures summer 18 o carb values indicate water temperatures between 5 c and 12 c with warmer values at lower latitudes the decrease in both mean sea surface temperature and seasonal amplitude with increasing latitude on the gondwanan coast is much like that observed along high latitude coastlines today calculated 18 o water decreases toward the pole likely associated with an increasing contribution of isotopically light fresh water derived from summer snow melt the gradient in 18 o water is similar to that documented over a similar span of latitude on the modern se greenland coast we infer the presence of a north flowing coastal current of cold o 18 depleted water that entrains progressively greater amounts of more typical seawater as it moves away from the pole 18 o values in se australia however are about 3 lower than those off greenland suggesting comparatively lower salinity water or more o 18 depleted glacial ice runoff in the permian gondwanan high latitudes perhaps augmented by more depleted negative global average seawater conditions in southeastern australia during the largest of the permian deglaciations were warmer than present day antarctica at similar latitudes but may approximate those of early mid miocene antarctica with frozen winters but summers closer to 10 c