response of the chydorid faunas to rapid climatic changes in four alpine lakes at different altitudes abstract the subfossil assemblages of chydoridae from late glacial preboreal sediments of four sites from 603 m to 2290 m asl were analysed to trace the community response to rapid climatic warming that occurred at this period of time in each site distinct signals at the younger dryas preboreal boundary were recorded by density of remains species diversity or community composition however responses varied considerably among the sites this variation was attributed to the situation that the chydorid community structure is determined not only by temporal younger dryas preboreal boundary and spatial among the sites temperature gradients but also by the specific local ecological conditions at the sites in some species the classification with respect to cold tolerance should be reconsidered

lateglacial vegetation dynamics in the eastern baltic region between 14 500 and 11 400 cal yr bp a complete record since the bolling gi 1e to the holocene abstract this paper discusses a complete record of vegetation history since the bolling gi 1e warming 14 500 cal yr bp up to the holocene in latvia to date this is the only complete record of such age in the eastern baltic area and the northernmost area for which bolling records are present combining pollen evidence pollen accumulation rates par and plant macrofossil data we assess the local and regional vegetation development and we attempt to separate the true lateglacial vegetation signal by removing the obviously redeposited thermophilous pollen however we remove not only their signal we discuss the possibilities of separating the redeposition signal of the so called local lateglacial trees pine and birch by looking at their corrosion and degradation the results show that the bolling warming in the eastern baltic area was a treeless tundra community consisting of the shrubs betula nana dryas octopetala and salix polaris the older dryas cold spell is clearly recognised as a decline in the total concentration of plant macrofossils and pars at between 14 200 and 13 500 cal yr bp at 13 460 cal yr bp the b nana macrofossils disappear and tree birch betula sect albae appears marking the start of tree birch forest the presence of pine forest is confirmed by a variety of macrofossils including bark wood needles and seeds since 13 400 cal yr bp at the same time at which pine stomata are found the first identified pine stomata finds are associated with a pinus par over 3000 grains cm 2 yr 1 and pine macrofossil finds with a pinus par over 4000 grains cm 2 yr 1 during the warmest period of the gi 1a allerod at 13 000 12 700 cal yr bp a pine forest with deciduous trees birch betula pendula and aspen populus tremula developed in the study area the younger dryas gs 1 cooling strongly affected the floral composition in eastern latvia the par of the tree taxa declined abruptly from a maximum value at 12 700 to below 1000 grains cm 2 yr 1 at 12 600 cal yr bp the response time for the pine forest to collapse was 100 years according to the par data pine macrofossils disappear simultaneously with the pollen signal at 12 600 cal yr bp yet occasional pinus stomata are recorded throughout the younger dryas gs 1 the landscape was treeless shrub tundra again with d octopetala s polaris b nana and juniperus present picea is introduced in the region within the cold younger dryas and is represented by stomata 12 400 12 200 cal yr bp needles seeds and wood since 12 050 cal yr bp up to the holocene the pleistocene holocene boundary at 11 650 cal yr bp is marked by changes both in vegetation composition and sediment type the organic rich gyttja accumulated instead of silts and clays and the start of the holocene warm period permitted forest re expansion in eastern latvia

timing of lateglacial vegetation dynamics and respective palaeoenvironmental conditions in southern estonia evidence from the sediment record of lake nakri this paper investigates a detailed well dated lateglacial floristic colonisation in the eastern baltic area ca 14 000 9000 cal a bp using palynological macrofossil loss on ignition and 14c data during 14 000 13 400 cal a bp primarily treeless pioneer tundra vegetation existed tree birch betula sect albae macro remains and a high tree pollen accumulation rate indicate the presence of forest tundra with birch and possibly pine pinus sylvestris l trees during 13 400 12 850 cal a bp palaeobotanical data indicate that the colonisation and development of forested areas were very rapid arising within a period of less than 50 years thus far there are no indications of conifer macrofossils in estonia to support the presence of coniferous forests in the lateglacial period signs of greenland interstadial 1b cooling during 13 100 cal a bp are distinguishable biostratigraphic evidence indicates that the vegetation was again mostly treeless tundra during the final colder episode of the lateglacial period associated with greenland stadial 1 approximately 12 850 11 650 cal a bp this was followed by onset of the holocene vegetation with the expansion of boreal forests in response to rapid climatic warming copyright 2011 john wiley sons ltd

multi proxy speleothem record of climate instability during the early last interglacial in southern turkey abstract a stalagmite from dim cave in southern turkey contains a climate record documenting rapid and significant changes in amounts of precipitation between 132 ka and 128 ka during the penultimate glacial interglacial transition some u th dates have been compromised by carbonate dissolution but rigorous selection and tuning to 18o records from other speleothems has generated a robust age model growth rate was initially very slow but a rapid increase at 129 ka was accompanied by strong negative trends in 18o and 13c a combination implying the onset of much wetter conditions isotopic values at 129 ka suggest that groundwater recharge rates and biogenic activity in the soil zone exceeded those of the early holocene a significant isotopic enrichment event at 128 ka during which there was alternating aragonite and calcite deposition documents a strong drying event with a duration of 200 years a concurrent decrease in 87sr 86sr ratios indicates increased groundwater residence times and the cumulative evidence suggests amounts of rainfall fell from well above to slightly below present day levels similar 18o enrichment events are present in coeval speleothem records from southwest france and the northern alps and these together with pollen evidence from italy greece and the iberian margin of drier conditions at this time imply that a climate anomaly extended across the northern mediterranean borderlands the timing duration and structure of this episode are consistent with marine evidence of strong north atlantic cooling early in the last interglacial and there is a resemblance to the holocene 8 2 ka event recorded globally in many proxy climate archives

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

an abrupt change in the african monsoon at the end of the younger dryas 1 high resolution studies of variations in the elemental and stable carbon and nitrogen isotope composition of organic matter in cores from lakes malawi tanganyika and bosumtwi tropical africa indicate an abrupt change in the wind driven circulation of these lakes that within the limits of available chronologies was contemporaneous with the end of the younger dryas in the northern hemisphere the change was also coincident with shifts in surface winds recorded in cores from off the west and northeast coasts of africa a range of other proxies indicate that these changes in wind regime were accompanied by a marked increase in precipitation in the northern tropics africa south of 5 10 s on the other hand initially suffered drought conditions together the evidence suggests an abrupt northward translation of the african monsoon system at circa 11 5 0 25 ka b p the data assembled here contribute to a growing body of work showing that the younger dryas was a major climatic excursion in tropical africa furthermore they add substance to recent suggestions that climatic events in the southern hemisphere may have played a significant role in the abrupt demise of the younger dryas

quantification of biotic responses to rapid climatic changes around the younger dryas a synthesis to assess the presence or absence of lags in biotic responses to rapid climatic changes we 1 assume that the 18o in biogenically precipitated carbonates record global or hemispheric climatic change at the beginning and at the end of the younger dryas without any lag at our two study sites of gerzensee and leysin switzerland 2 derive a time scale by correlating the 18o record from these two sites with the 18o record of the grip ice core 3 measure 18o records in ostracods and molluscs to check the record in the bulk samples and to detect possible hydrological changes 4 analyse at gerzensee and leysin as well as at two additional sites that lack carbonates and hence a 18o record pollen plant macrofossils chironomids beetles and other insects and cladocera 5 estimate our sampling resolution using the grip time scale for the isotope stratigraphies and the biostratigraphies and 6 summarise the major patterns of compositional change in the biostratigraphies by principal component analysis or correspondence analysis we conclude that at the major climatic shifts at the beginning and end of the younger dryas hardly any biotic lags occur within the sampling resolution of 8 30 years and that upland vegetation responded as fast as aquatic invertebrates we suggest that the minor climatic changes associated with the gerzensee and preboreal oscillations were weakly recorded in the biostratigraphies at the lowland site but were more distinct at higher altitudes individualistic responses of plant and animal species to climatic change may reflect processes in individuals e g productivity and phenology in populations e g population dynamics in spatial distributions e g migrations and in ecosystems e g trophic state we suggest that biotic responses may be telescoped together into relatively short periods 50 to 150 years perhaps disrupting functional interactions among species and thus destabilising ecosystems

younger dryas and allerod summer temperatures at gerzensee switzerland inferred from fossil pollen and cladoceran assemblages linear and unimodal based inference models for mean summer temperatures partial least squares weighted averaging and weighted averaging partial least squares models were applied to a high resolution pollen and cladoceran stratigraphy from gerzensee switzerland the time window of investigation included the allerod the younger dryas and the preboreal characteristic major and minor oscillations in the oxygen isotope stratigraphy such as the gerzensee oscillation the onset and end of the younger dryas stadial and the preboreal oscillation were identified by isotope analysis of bulk sediment carbonates of the same core and were used as independent indicators for hemispheric or global scale climatic change in general the pollen inferred mean summer temperature reconstruction using all three inference models follows the oxygen isotope curve more closely than the cladoceran curve the cladoceran inferred reconstruction suggests generally warmer summers than the pollen based reconstructions which may be an effect of terrestrial vegetation not being in equilibrium with climate due to migrational lags during the late glacial and early holocene allerod summer temperatures range between 11 and 12 c based on pollen whereas the cladoceran inferred temperatures lie between 11 and 13 c pollen and cladocera inferred reconstructions both suggest a drop to 9 10 c at the beginning of the younger dryas although the allerod younger dryas transition lasted 150 160 years in the oxygen isotope stratigraphy the pollen inferred cooling took 180 190 years and the cladoceran inferred cooling lasted 250 260 years the pollen inferred summer temperature rise to 11 5 12 c at the transition from the younger dryas to the preboreal preceded the oxygen isotope signal by several decades whereas the cladoceran inferred warming lagged major discrepancies between the pollen and cladoceran inference models are observed for the preboreal where the cladoceran inference model suggests mean summer temperatures of up to 14 15 c both pollen and cladoceran inferred reconstructions suggest a cooling that may be related to the gerzensee oscillation but there is no evidence for a cooling synchronous with the preboreal oscillation as recorded in the oxygen isotope record for the gerzensee oscillation the inferred cooling was ca 1 and 0 5 c based on pollen and cladocera respectively which lies well within the inherent prediction errors of the inference models

the amphi atlantic distribution of the younger dryas paleoclimatic oscillation abstract interest in significant climatic fluctuations affecting large geographic areas but having a time range that is too brief to adduce the milankovitch radiation cycles has focused on the allerod younger dryas event which is a well established phenomenon of western europe manifested by glacial and vegetational reconstructions it is also shown by the foraminiferal evidence for shifts in the polar front in the north atlantic recent pollen and lithostratigraphic investigations in the maritime provinces of eastern canada and in the till plains of west central ohio on opposite sides of the late glacial spruce forest indicate that the event also left a record in eastern north america experiments with an atmospheric general circulation model with the temperature of north atlantic surface waters depressed to full glacial levels lowered summer temperatures in upwind periglacial eastern north america by 2 c just as far inland as they did downwind in western europe where the paleoecological record of cooling is clear a leading hypothesis for the cause for the younger dryas cooling appeals to the influx of tabular icebergs released from arctic ice shelves around the wasting scandinavian and siberian ice sheets during the allerod warming the resulting cooling of the north atlantic waters during the younger dryas could be facilitated or precipitated by the abrupt influx of glacial meltwater derived from almost the entire southern margin of the laurentide ice sheet and emerging from the gulf of st lawrence as brought about by a major shift in drainage direction from the mississippi river to the st lawrence river about 10 8 ka bp a supplemental influx of fresh water may have come from the contemporaneous drainage of the baltic ice lake the diversion of laurentide meltwater to the atlantic was caused by retreat of an ice lobe in northwestern ontario north of minnesota allowing the huge glacial lake agassiz in saskatchewan and manitoba to drain into the great lakes and more than double the inflow of meltwaters in the north atlantic thereby diverting the gulf stream and permitting the influx of icebergs from the north to cool the ocean surface minor readvance of the ice lobe about 10 ka bp temporarily diverted the lake agassiz drainage to the south with the final retreat of the ice the drainage again went to the east but by this time the ice sheets were much diminished and the regional climate had warmed enough so that the effects of the meltwater flux on the gulf stream were muted and the ice sheets bordering the north atlantic had retreated onto the land and no longer delivered enough icebergs to cool the surface waters the younger dryas interval thus was terminated and the warming manifested in the allerod was renewed

a late glacial chironomid record from hawes water northwest england this paper presents the results of a high resolution late glacial chironomid stratigraphy from hawes water a small carbonate lake in northern lancashire the samples were from a core taken from the terrestrialised margin of the present lake which represents an intermediate depth between the true littoral and the profundal the chironomid assemblage showed a high degree of sensitivity to both broad scale and short term temperature changes comparison with an existing proxy temperature record 18o for the site confirmed the presence of four temperature inversions within the late glacial interstadial a mean july air temperature inference model derived from acid soft water lakes in norway and svalbard was applied to the data despite the absence of carbonate lakes within the norwegian training set there was a close similarity between trends in estimated july air temperature and the 18o trace with a particularly strong correspondence in the periods of clay deposition this suggests that this model is highly robust the inferred maximum interstadial temperature was 13 4 c dropping initially to 7 5 c in the loch lomond stadial temperatures reach a maximum of nearly 10 c in this period cool for a short period before rising rapidly to 13 2 c at the start of the holocene these temperatures are similar to but slightly higher than those estimated for whitrig bog southeast scotland and lower than those inferred from coleopteran based models for sites in south wales

quantifying species environment relationships in non marine ostracoda for ecological and palaeoecological studies examples using iberian data abstract with current concerns over issues such as global warming the use of palaeoecological data to reconstruct past environments has gained a special significance but much of the work on ostracod ecology and paleoecology has been qualitative in nature or on a site specific rather than integrated regional basis furthermore ostracod ecological relationships are complex with each species occupying a multidimensional niche and a range of statistical techniques can be employed to establish the significance of different environmental variables on species distribution we employ logistic regression lr and canonical correspondence analysis cca to define ostracod species niches and assemblage response to environmental gradients using a modern dataset of 465 ostracod samples from the eastern iberian peninsula in addition to these ecological analyses we develop ostracod based transfer functions for the quantitative reconstruction of past environmental change from a modern regional data set of non marine ostracod and limnological data by means of weighted averaging wa regression and calibration examples cited are primarily from modern and fossil ostracod samples from iberian water bodies our results suggest that water chemistry solute composition and concentration and temperature are the factors to which non marine ostracod species respond in a more clear and consistent way species environment relationships modelled using the transfer function approach of wa are strong for the above mentioned variables and therefore these models may be of great help in palaeoenvironmental reconstructions

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

the amphi atlantic oscillation a proposed late glacial climatic event a contribution to the north atlantic seaboard programme of igcp 253 termination of the pleistocene abstract numerous palaeoclimatic records from europe greenland and the north atlantic ocean provide evidence for a short term cooling event which preceded the younger dryas stadial of ca 11 10 ka bp the discovery of a similar event in eastern north america the killarney oscillation ko raised the possibility of a single pre younger dryas cooling event that affected the entire north atlantic seaboard this paper reviews evidence for the ko and other pre younger dryas events and discusses the basis for their correlation the informal name amphi atlantic oscillation is proposed as a collective term for the ko and events that correlate with it

a tex86 lake record suggests simultaneous shifts in temperature in central europe and greenland during the last deglaciation high resolution quantitative temperature records from continents covering glacial to interglacial transitions are scarce but important for understanding the climate system we present the first decadal resolution record of continental temperatures in central europe during the last deglaciation similar to 14 60010 600cal yrb p based on the organic geochemical palaeothermometer tex86 the tex86 inferred temperature record from lake lucerne vierwaldstattersee switzerland reveals typical oscillations during the late glacial interstadial followed by an abrupt cooling of 2 degrees c at the onset of younger dryas and a rapid warming of 4 degrees c at the onset of the holocene within less than 350years the remarkable resemblance with the greenland and regional stable oxygen isotope records suggests that temperature changes in continental europe were dominated by large scale reorganizations in the northern hemispheric climate system

late glacial and holocene history of former salziger see central germany and its climatic and environmental implications an 8 40 m long sediment sequence from the salziger see basin central germany was investigated by a multi disciplinary approach including chronological sedimentological geo and biogeochemical methods radiocarbon dating conducted on ten samples of aquatic and terrestrial fossil remains and the occurrence of the laacher see tephra lst reveal that the sediment sequence comprises the late glacial and holocene lake history since ca 13 800 cal year bp this onset of lacustrine sedimentation is almost 7 000 years earlier as assumed so far the geo and biogeochemical data indicate distinct variations throughout the late glacial which can be correlated with cold and warm periods such as the oldest dryas the bolling the allerod and the younger dryas during most of the holocene minor variations in the geo and biogeochemical data and a high carbonate content due to the formation and precipitation of autochthonous carbonate in the lake indicate relatively stable lacustrine conditions a slight change in the sedimentary conditions between 6 700 and 4 000 cal year bp with lower deposition of carbonate and fine material can be traced back to enhanced subrosion in the basin increased deposition of coarser sediments and a high accumulation of heavy metals document intensive human activity in the region during the past ca 1 000 years

effects of within lake variability of fossil assemblages on quantitative chironomid inferred temperature reconstruction abstract we studied the effects of within lake variation of subfossil chironomid assemblages on chironomid inferred temperatures in five lakes in southern norway in each lake six replicate surface sediment samples in the deepest part of the lake basin and two transects of seven samples each towards the littoral were analysed for subfossil chironomid assemblages a quantitative chironomid july air temperature inference model applied to the subfossil assemblages inferred temperatures with a standard deviation of 0 35 0 54 c for the six mid lake samples and of 0 38 0 59 c for all 20 sediment samples this variation seems high when compared with the cross validated root mean square error of prediction rmsep of the model of 1 04 c however we show that the variability of the replicate mid lake samples can only account for a maximum of 15 of the model prediction error if the rmsep is decomposed into a component due to uncertainties associated with sampling the chironomid assemblage of a lake and into a residual error component thus according to our results analysing multiple samples in the model lakes to obtain better estimates of their subfossil assemblage composition may only slightly reduce the model prediction error it was difficult to detect a clear pattern of chironomid inferred temperatures with respect to water depth in any single lake due to the high variability of inferred values however a comparison of all five study lakes revealed that relative to the mid lake samples cooler temperatures were inferred at intermediate depths and warmer temperatures in the shallowest parts of the lakes although two shallow water samples with very low inferred temperatures were exceptions in this respect this depth related bias of inferred temperatures in our relatively shallow study lakes indicates that chironomid temperature models calibrated on mid lake samples should only be applied with caution to near shore sediments and that a systematic offset in the inferred temperatures may occur

the response of flood plain ecosystems to the late glacial and early holocene hydrological changes a case study from a small central european river valley abstract we use a range of environmental variables to explore the possible drivers influencing the biota especially the composition of aquatic invertebrates during the younger dryas yd and early holocene eh in different river valley sites a well developed meandering river and the confluence zone of headwater streams using pollen macrofossil cladoceran and chironomid as well as geochemical and lithological data as proxies for environmental factors i e water depth and temperature we attempt to show that these different sites display similar hydroclimatic signals especially floods the geochemical records in the studied valley are correlated with environmental factors such as the evolution of the vegetation the intensification phase of slope processes and fluvial activities cladocerans and chironomids potentially play important roles in the recognition of flood episodes in the study sites and any shift in their diversity and especially the co occurrence of planktonic sediment associated cladocerans with rheophilic chironomids could be valuable indicators of floods and flow episodes the variable changes in water levels at the sites reconstructed by the cladoceran based water depth model were positively associated with changes in lithophilic elements k na al mg and ti sio2 biog ter and fe mn and our estimates of the paleohydraulic parameters for the study sites are generally consistent with changes in the composition of aquatic invertebrates the recorded yd floods appear to be synchronous regardless of the size and the different geological and geomorphological settings of each part of the river catchment our investigation demonstrates that flood magnitude increases in the downstream direction along the valley the common increases in the water level at all study sites from the grabia river valley are significant from 12 400 to 12 200 and from 11 900 to 11 800 cal bp and are comparable with those from elsewhere in poland and europe

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

the lateglacial quercus expansion in the southern european alps rapid vegetation response to a late allerod climate warming a pollen inferred vegetation shift from pioneer birch pine woodland to mixed pine summergreen oak forests in the southern alpine forelands is commonly attributed to a centennial scale warming that occurred between the gerzensee oscillation go and the younger dryas two microtephra layers bracketing the younger dryas onset the laacher see tephra and the vedde ash improve the chronology at lago piccolo di avigliana northern italy and allowed accurate correlation with central european records where the go is clearly detected we used pollen percentages pollen accumulation rates pars and plant macrofossils to assess the population dynamics of quercus and leaf cuticle analysis for a better taxonomic identification of quercus our results indicate that the species that was locally present was probably quercus robur pars suggest that the population expansion started as early as the bolling and followed an exponential increase through time we attribute this gradual shift to increasing summer temperatures and longer growing seasons which contrast with a gradually decreasing temperature trend as recorded in greenland ice cores and in central europe breaks or set backs in the par record may indicate the biotic response to minor lateglacial cooling events of different life history stages in the quercus population copyright 2011 john wiley sons ltd

vegetational response to climatic changes recorded in swiss late glacial lake sediments abstract high resolution pollen analysis at five lakes on an altitudinal transect in switzerland gerzensee 603 m leysin 1230 m regenmoos 1260 m zeneggen 1510 m heremence 2290 m focused on the vegetational response to the rapid climatic changes at the end and beginning of the younger dryas and to the minor gerzensee and preboreal climatic oscillations an absolute time scale transferred from the greenland grip ice core to the gerzensee and leysin records by wiggle matching the oxygen isotope stratigraphies facilitates the estimation of pollen influx and rates of change the climatic warming at the end of the younger dryas indicated by increases in oxygen isotope values and or the beginning of organic sedimentation in the lakes was immediately reflected in the vegetation at all the sites investigated the time lags at sites situated above the timberline during the younger dryas are considered to be migrational lags at the onset of the younger dryas a time lag of several decades occurred between the oxygen isotope record of climatic cooling and the major response of the vegetation whereas minor vegetation changes occurred with or without short time lags betula reacted earlier to the new environmental conditions within about 40 50 yr at gerzensee and within less than 36 yr at leysin than pinus and artemisia about 170 yr suggesting that time lags are due to the ecological requirements of the different taxa for the gerzensee and preboreal oscillations little or no change can be observed in the pollen record from gerzensee whereas at leysin both climatic oscillations produced a statistically significant vegetational response to both climatic oscillations generally the vegetation responses to climatic changes are more pronounced near vegetation ecotones at medium and higher altitudes than in the lowlands

high resolution lacustrine record of the late glacial holocene transition in central europe abstract in this paper we present the high resolution record of proxy climatic data in central europe during the final stages of the last deglaciation derived from the annually laminated sediments of lake go ciaz central poland the isotopic palynological and other microfossil data confirm sudden changes of climate at the onset and termination of the younger dryas completed within 150 and 70 years respectively in close agreement with the previous estimates derived from the polar ice cores and marine sediments in the upper yd some amelioration of climate took place already about 600 years before the main yd preboreal transition counting of annual varves in the lake sediments allows a direct estimate of the duration of the younger sdryas in central europe it lasted approximately 1640 years substantially longer than suggested by previous estimates derived from laminated lake sediments and glacial varves but agreeing with the radiocarbon calibration data obtained for barbados corals the calendar ages of the boundaries of the yd 12 920 and 11 280 cal bp are tentatively set

the wurmian late glacial in lowland switzerland a synthesis is provided of late glacial 14 9 ka bp environmental changes in lowland switzerland the swiss plateau the chronology of deglaciation and subsequent developments in vegetation cov

calibration of the climatic signal in a new pollen sequence from la grande pile a new core gpxx from la grande pile vosges france has enabled a more precise evaluation of pollen data concerning the last climatic cycle at this site and has enabled reconstruction of the monthly temperature and precipitation this paper shows that the various components of the reconstructed climatic signal are clearly separated and that they are coherent with the vegetation dynamics the eemian interglacial was influenced first by an oceanic climate and second by a more continental one the two interstadials st germain i and ii were mainly continental these three temperate periods ended with a cool and humid transition period dominated by boreal forests which may have been favourable to ice accretion the dansgaard oeschger oscillations from 55 to 25 kyr bp are not significantly recorded in la grande pile

chironomid δ18o as a proxy for past lake water δ18o a lateglacial record from rotsee switzerland abstract we explored whether the stable oxygen isotope composition 18o of fossil chironomid remains can be used to reconstruct past variations in lake water 18o from lateglacial and early holocene sediments from rotsee switzerland a sediment core from the former littoral zone of the lake was examined since it contained both high concentrations of chironomid remains and abundant authigenic carbonates and therefore allowed a direct comparison of chironomid 18o with values measured on bulk carbonates since carbonate particles adhering to chironomid remains potentially affect 18o measurements we tested two methods to chemically remove residual carbonates trials with isotopically heavy and light acid solutions indicated that treatment with hydrochloric acid promoted oxygen exchange between chironomid remains and the water used during pretreatment in contrast a buffered 2 m ammonium chloride nh4cl solution did not seem to affect chironomid 18o to a significant extent fossil chironomid 18o was analyzed for the rotsee record both using standard palaeoecological methods and after pretreatment with nh4cl samples prepared using standard techniques showed a poor correlation with 18o of bulk carbonate r2 0 14 suggesting that carbonate contamination of the chironomid samples obscured the chironomid 18o signature samples pretreated with nh4cl correlated well with bulk carbonate 18o r2 0 67 and successfully tracked the well known lateglacial changes in 18o chironomid 18o indicated depleted lake water 18o during the oldest dryas period the aegelsee and gerzensee oscillations and the younger dryas whereas enriched 18o values were associated with sediments deposited during the lateglacial interstadial and the early holocene differences in the amplitude of variations in bulk carbonate and chironomid 18o are attributed to differential temperature effects on oxygen isotope fractionation during the formation of carbonates and chironomid head capsules or seasonal changes of lake water 18o potentially affecting 18o of these two substances to a different extent our results indicate that chironomid 18o can successfully reconstruct centennial to millennial scale changes in lake water 18o and that the method can be applied to carbonate rich records provided that care is taken to eliminate carbonate contamination from the samples

pollen inferred late glacial and holocene climate in southern balkans lake maliq abstract high temporal resolution analysis of pollen records from lake maliq albania provides quantitative estimates of monthly temperature and precipitation changes since the last deglaciation the climate parameters were estimated using the best modern analogue technique with an updated modern pollen climate database composed of 2748 surface samples the record shows two main cooling phases in the maliq area the oldest and younger dryas and a cooling event around 8200 years which suggests that the forcing factors driving climate variations in the north atlantic area since the last glacial period also extended their influence into the mediterranean area the oldest and younger dryas are also characterized by an arid climate and a change in the seasonality of precipitation the summer precipitation tends to be greater during the cooling phases than during the temperate periods the holocene climate is relatively stable and the values of each parameter reach their modern levels except for an arid event between 8300 and 8100 cal bp

holocene tree immigration and the chironomid fauna of a small swiss subalpine lake hinterburgsee 1515 m asl early holocene reforestation by stone pine pinus cembra and tree birch betula pubescens took place ca 500 years after the end of the younger dryas at hinterburgsee a small subalpine lake in the northern swiss alps during the next ca 3000 years the local vegetation consisted of open woodlands with many pioneer dwarf shrubs and herbs the expansion of silver fir abies alba at ca 7400 calibrated radiocarbon years before present cal bp and norway spruce picea abies at ca 6000 cal bp in hinterburgsee s catchment led to a closing of the local forests with a successive decrease in erosion and a distinct change in hinterburgsee s sediment composition first signs of probably human induced openings of the catchment forest are apparent at ca 2500 cal bp but it is not until the past ca 800 years that pollen analysis suggests strong local and regional anthropogenic activity the strongest and most abrupt changes in the holocene development of hinterburgsee s chironomid fauna took place at ca 11 500 cal bp and at ca 10 000 cal bp when parts of the alpine taxa that were dominant during the younger dryas disappeared from the lake the first change is most likely related to the increasing temperatures after the end of the younger dryas the second possibly to decreasing lake depth and increasing summer insolation in the early holocene that may have led to warmer bottom water temperatures in the lake no clear relationship between the changes in catchment vegetation and the development of the chironomid fauna was found possibly the increase in sediment organic matter associated with the denser catchment forests was responsible for a succession in the chironomid stratigraphy between 7000 and 4500 cal bp however due to the high sedimentation rates in hinterburgsee this trend could also be a consequence of or be promoted by the sediment infilling of the lake basin this conjecture is supported by the increasing importance of tanytarsus lugens type a chironomid taxon dominant in the extant chironomid assemblages of shallow mountain lakes in switzerland the only shift in the chironomid fauna that clearly parallels a change in catchment vegetation is found during the past ca 800 years we discuss possible reasons for the comparatively weak influence of catchment vegetation on the chironomid fauna of hinterburgsee and the implications of our results for multi proxy studies on past climate involving both palaeobotanical and chironomid based reconstructions 2002 elsevier science b v all rights reserved

sensitivity and response time of natural systems to climatic change in the late quaternary abstract although the leading theory for the cause of climatic change the milankovitch perturbations in insolation indicates variable rates of change at different latitudes any discussion of the sensitivity and response time of different natural systems is most practical when the climatic change is considered to be relatively abrupt and global rather than gradual and regional the oxygen isotope record in glacial ice should have the swiftest response time but the stratigraphic record in ice sheets at particular localities may be obscured or confused if the glacier flow is irregular the oxygen isotope stratigraphy of ocean sediment cores is a sensitive reflection primarily of contemporaneous ice volume and to a lesser extent ocean temperature ocean temperature however is recorded more specifically by microfossils in ocean sediments and may reflect global insolation directly except that in the north atlantic the influence of glacial meltwater and various feedbacks may override the insolation factor the differential lags in the response of isotopes and faunas to insolational change are apparent in the ocean sediment stratigraphy ice sheets themselves at their terminus may respond to climatic change only slowly if a change in snow accumulation is the factor because of the time involved in building a thickness sufficient for flow to great distances but if wastage near the margin is the factor then the response may be more rapid some glaciers however may advance rapidly without regard to climatic change as in the case of surging or they may retreat just as rapidly if they terminate in deep water through iceberg formation world sea level is depressed with glacial growth and thus reflects the volume of ice sheets but isostatic changes in the crust complicate the sea level response not only locally beneath the ice load but elsewhere as well the pluvial lakes of the american southwest correlated in their high levels with intervals of glaciation show a direct response to climatic patterns resulting from the expansion of the north american ice sheets and thus may lag with respect to the primary climatic change that causes ice sheet growth north african lakes on the other hand respond to the intensity of monsoonal circulation which is controlled directly by insolational shifts the response of plants and insects to deglaciation can be immediate in the case of pioneers on newly exposed terrain although the deglaciation itself may lag behind climatic change succession can follow rapidly but then more slowly as other plants immigrate from great distances it is heare where the more realistic assumption of continuing climatic change may be necessary to explain the dynamics of long range vegetational change following the last deglaciation the distribution and abundance of vertebrate populations reflect primarily their food resources and the disharmonious faunas of the last glacial period in north america with components that no longer have overlapping ranges perhaps may be explained by vegetational associations that likewise may have no modern analogues the cause may be a different climatic seasonality wastage of the ice sheet itself lagging behind the climatic change may have changed the seasonal climatic patterns sufficiently to bring about the precipitous extinction of many vertebrate species

late glacial chironomid based temperature reconstructions for lago piccolo di avigliana in the southwestern alps italy chironomid headcapsules were used to reconstruct late glacial and early holocene summer temperatures at lago piccolo di avigliana lpa two training sets northern sweden north america were used to infer temperatures the reconstructed patterns of temperature change agreed well with the grip and ngrip 18o records inferred temperatures were high during the bolling ca 19 c slowly decreased to ca 17 5 c during the allerod reached lowest temperatures ca 16 c during the younger dryas and increased to ca 18 5 c during the preboreal the amplitudes of change at climate transitions i e oldest dryas bolling 3 c allerod younger dryas 1 5 c and younger dryas preboreal 2 5 c were smaller than in the northern alps but similar to those recorded at another site in northeastern italy our results suggest that 1 allerod temperatures were higher in the southern alps and 2 higher during the preboreal 1 c than during the allerod these differences might provide an explanation for the different responses of terrestrial vegetation to late glacial and early holocene climatic changes in the two regions other sites on both sides of the alps should be studied to confirm these two hypotheses

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

mean july temperatures during the younger dryas in northwestern and central europe as inferred from climate indicator plant species abstract we estimated minimum mean july temperatures in northwestern and central europe during the younger dryas 10 950 10 15014c yr b p from distributions of climate indicator plant species which were reconstructed from 140 pollen and plant macrofossil diagrams paleobotanical records mainly from the central and eastern part of the study area show that the coldest conditions occurred early in the younger dryas before 10 55014c yr b p for this phase mean july temperatures at sea level of around 10 c are suggested for the northern part of the british isles and for ice free scandinavia we estimated a mean july temperature of 12 c for central england the netherlands and northern germany the 13 c mean july isotherm largely based on the modern distribution oftypha latifolia was most probably located in southern england belgium central germany and poland the reappearance of thermophilous elements in the records after 10 55014c yr b p suggests a summer warming at least temporarily of 1 to 2 c in the study area the reconstructed temperatures are comparable with temperature estimates based on beetle data however they appear rather high when compared with estimates based on glaciological evidence

synchronized terrestrial atmospheric deglacial records around the north atlantic on the basis of synchronization of three carbon 14 c 14 dated lacustrine sequences from sweden with tree ring and ice core records the absolute age of the younger dryas preboreal climatic shift was determined to be 11 450 to 11 390 80 years before the present a 150 year long cooling in the early preboreal associated with rising delta 14 c values is evident in all records and indicates an ocean ventilation change this cooling is similar to earlier deglacial coolings and box model calculations suggest that they all may have been the result of increased freshwater forcing that inhibited the strength of the north atlantic heat conveyor although the younger dryas may have begun as an anomalous meltwater event

reconciling divergent trends and millennial variations in holocene temperatures cooling during most of the past two millennia has been widely recognized and has been inferred to be the dominant global temperature trend of the past 11 700 years the holocene epoch however long term cooling has been difficult to reconcile with global forcing and climate models consistently simulate long term warming the divergence between simulations and reconstructions emerges primarily for northern mid latitudes for which pronounced cooling has been inferred from marine and coastal records using multiple approaches here we show that temperatures reconstructed from sub fossil pollen from 642 sites across north america and europe closely match simulations and that long term warming not cooling defined the holocene until around 2 000 years ago the reconstructions indicate that evidence of long term cooling was limited to north atlantic records early holocene temperatures on the continents were more than two degrees celsius below those of the past two millennia consistent with the simulated effects of remnant ice sheets in the climate model community climate system model 3 ccsm3 ccsm3 simulates increases in growing degree days a measure of the accumulated warmth above five degrees celsius per year of more than 300 kelvin days over the holocene consistent with inferences from the pollen data it also simulates a decrease in mean summer temperatures of more than two degrees celsius which correlates with reconstructed marine trends and highlights the potential importance of the different subseasonal sensitivities of the records despite the differing trends pollen and marine based reconstructions are correlated at millennial to centennial scales probably in response to ice sheet and meltwater dynamics and to stochastic dynamics similar to the temperature variations produced by ccsm3 although our results depend on a single source of palaeoclimatic data pollen and a single climate model simulation they reinforce the notion that climate models can adequately simulate climates for periods other than the present day they also demonstrate that amplified warming in recent decades increased temperatures above the mean of any century during the past 11 000 years

evolution of sedimentary mode since pleistocene in the central south yellow sea china based on seismic stratigraphy analysis abstract in order to investigate the distribution development and evolution of the strata in the south yellow sea basin sysb seismic and core data were analyzed fourteen 14 reflecting interfaces and 13 seismic units are identified and a stratigraphic framework since 1 81 ma b p is established the deposition rate has changed since 126 ka b p the stratigraphic model shows that the sysb responded to sea level changes during the same period 126 ka b p which suggests a model change of the development of regional strata between 1 81 ma b p and 126 ka b p the zhejiang minnan uplift zmu obstructed the intrusion of seawater into the sysb which is the main factor responsible for the development of regional strata while the sea level fluctuation and fluvial material input have dominated the formation of the strata since 126 ka b p

noble gas based temperature reconstruction on a swiss stalagmite from the last glacial interglacial transition and its comparison with other climate records abstract here we present the results of a first application of a combined vacuum crushing and sieving cvcs system to determine past cave soil temperatures from dissolved noble gas concentrations in stalagmite samples grown under cold climatic conditions e g close to freezing point of water during the last glacial interglacial transition to establish noble gas temperatures ngts also for stalagmites grown in cold regions we applied the cvcs system to samples from stalagmite m2 precipitated in the milandre cave located in the swiss jura mountains the investigated stalagmite m2 covers the allerod younger dryas holocene transitions noble gas temperatures are determined by using a new algorithm based on noble gas and water abundances and not from concentrations noble gas results indicate annual mean temperatures in the milandre cave were 2 2 1 8 c during the late stages of the allerod then dropping to 0 2 6 c at the onset of the younger dryas such temperatures indicate conditions near to the freezing point of water during the first part of the younger dryas during the last part of the younger dryas the temperature increased to 6 3 2 3 c no early holocene temperature could be determined due the non detectable water abundances in these samples however one late holocene sample indicates a cave temperature of 8 7 2 7 c which is close to the present day annual mean temperature ngts estimated for the allerod younger dryas holocene are in good agreement with paleo temperature reconstructions from geochemical and biological proxies in lake sediments the observed deviations between the different paleo temperature reconstructions are minor if the according temperatures are rescaled to annual mean temperatures and are primarily attributed to the chronological tuning of the different records as in other stalagmites ngt reconstructions of the recently precipitated stalagmite young samples again are biased most likely due to diffusive gas loss during sample processing we speculate that a reduced retentivity of noble gases during experimental sample processing is a general feature of recently precipitated stalagmite fabrics therefore the recently precipitated stalagmite samples do not allow the reliable ngt determination given the currently available experimental methods nevertheless this study makes the case that noble gas thermometry can be applied to stalagmites for paleo temperature reconstruction based on a physical method including stalagmites that grew during cold climatic conditions

fido prototype mars rover field trials black rock summit nevada as test of the ability of robotic mobility systems to conduct field science 1 the field integration design and operations fido prototype mars rover was deployed and operated remotely for 2 weeks in may 2000 in the black rock summit area of nevada the blind science operation trials were designed to evaluate the extent to which fido class rovers can be used to conduct traverse science and collect samples fido based instruments included stereo cameras for navigation and imaging an infrared point spectrometer a color microscopic imager for characterization of rocks and soils and a rock drill for core acquisition body mounted belly cameras aided drill deployment and front and rear hazard cameras enabled terrain hazard avoidance airborne visible and infrared imaging spectrometer aviris data a high spatial resolution ikonos orbital image and a suite of descent images were used to provide regional and local scale terrain and rock type information from which hypotheses were developed for testing during operations the rover visited three sites traversed 30 m and acquired 1 3 gigabytes of data the relatively small traverse distance resulted from a geologically rich site in which materials identified on a regional scale from remote sensing data could be identified on a local scale using rover based data results demonstrate the synergy of mapping terrain from orbit and during descent using imaging and spectroscopy followed by a rover mission to test inferences and to make discoveries that can be accomplished only with surface mobility systems

stacking of discontinuous regional palaeoclimate records chironomid based summer temperatures from the alpine region since multi site reconstructions are less affected by site specific climatic effects and artefacts regional palaeotemperature reconstructions based on a number of sites can provide more robust estimates of centennial to millennial scale temperature trends than individual site specific records furthermore reconstructions based on multiple records are necessary for developing continuous climate records over time scales longer than covered by individual sequences here we present a procedure for developing such reconstructions based on relatively short centuries to millennia discontinuously sampled records as are typically developed when using biotic proxies in lake sediments for temperature reconstruction the approach includes an altitudinal correction of temperatures an interpolation of individual records to equal time intervals a stacking procedure for sections of the interval of interest that have the same records available as well as a splicing procedure to link the individual stacked records into a continuous reconstruction variations in the final stacked and spliced reconstruction are driven by variations in the individual records whereas the absolute temperature values are determined by the stacked segment based on the largest number of records with numerical simulations based on the ngrip 18o record we demonstrate that the interpolation and stacking procedure provides an approximation of a smoothed palaeoclimate record if based on a sufficient number of discontinuously sampled records finally we provide an example of a stacked and spliced palaeotemperature reconstruction 15000 90 calibrated 14c yr bp based on six chironomid records from the northern and central swiss alps and eastern france to discuss the potential and limitations of this approach

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

macrofossils as records of plant responses to rapid late glacial climatic changes at three sites in the swiss alps plant macrofossils from the end of the younger dryas were analysed at three sites gerzensee 603 m asl leysin 1230 m asl and zeneggen 1510 m asl for the first two sites an oxygen isotope record is also available that was used to develop a time scale schwander et al this volume dates refer therefore to calibrated years according to the grip time scale around gerzensee a pine forest with some tree birches grew during the younger dryas with the onset of the isotopic shift initiating the rapid warming about 11 535 cal years before 1950 the pine forest became more productive and denser at leysin no trees except some juniper scrub grew during the younger dryas tree birches pine and poplar immigrated from lower altitudes and arrived after the end of the isotopic shift about 11 487 b p i e at the beginning of the preboreal at about 11 420 b p zeneggen is situated somewhat higher than leysin but single tree birches and pines survived the younger dryas at the site at the beginning of the preboreal their productivity and population densities increased simultaneously shifts from nitella to chara and from silt to gyttja are recorded all indicating rapidly warming conditions and higher nutrient levels of the lake water and probably of the soils in the catchment at gerzensee the beginning of the younger dryas was also analysed the beginning of the isotopic shift correlates within one sample about 15 years to rapid decreases of macrofossils of pines and tree birches

high resolution late glacial chronology for the gerzensee lake record switzerland δ18o correlation between a gerzensee stack and ngrip oxygen isotope variations were analyzed on bulk samples of shallow water lake marl from gerzensee switzerland in order to evaluate major and minor climatic oscillations during the late glacial to highlight the overall signature of the gerzensee 18o record 18o records of four parallel sediment cores were first correlated by synchronizing major isotope shifts and pollen abundances then the records were stacked with a weighting depending on the differing sampling resolution to develop a precise chronology the 18o stack was then correlated with the ngrip 18o record applying a monte carlo simulation relying on the assumption that the shifts in 18o were climate driven and synchronous in both archives the established chronology on the gicc05 time scale is the basis for 1 comparing the 18o changes recorded in gerzensee with observed climatic and environmental fluctuations over the whole north atlantic region and 2 comparing sedimentological and biological changes during the rapid warming with smaller climatic variations during the bolling allerod period the 18o record of gerzensee is characterized by two major isotope shifts at the onset and at the termination of the bolling allerod warm period as well as four intervening negative shifts labeled gi 1e2 d c2 and b which show a shift of one third to one fourth of the major 18o shifts at the beginning and end of the bolling allerod despite some inconsistency in terminology these oscillations can be observed in various climatic proxies over wide regions in the north atlantic region especially in reconstructed colder temperatures and they seem to be caused by hemispheric climatic variations

10be cosmic ray exposure dating of moraines and rock avalanches in the upper romanche valley french alps evidence of two glacial advances during the late glacial holocene transition abstract cosmic ray exposure cre dating of moraines allow glacier fluctuations and past climate change reconstructions in the french alps there is a lack of moraine dating for the late glacial holocene transition period here we present a chronology of glacier advances in the upper romanche valley french alps massif des ecrins based on 10 be cre dating cre ages of moraines of 13 0 1 1 ka and 12 4 1 5 ka provide evidence for two stages of glacial advance or standstill at the end of the late glacial the cre dating of a rock avalanche deposit at 12 2 1 5 ka is attributed to post glacial debuttressing and reveals rapid deglaciation at the end of the late glacial a cre age of 7 1 0 7 ka of a second mass wasting whose triggering factor is unidentified so far indicates that up to an altitude of 2300 m a s l the valley was ice free as of 7 kyr at the latest the re evaluation of 21 moraine 10 be cre ages from nine glacial valleys across the alps shows multiple glacial advances occurring at the late glacial holocene transition these results lead to a re evaluation of the importance of cooling events during the allerod and the younger dryas in the alps

a regional tephrostratigraphic framework for central and southern european climate archives during the last glacial to interglacial transition comparisons north and south of the alps abstract this paper summarises the results of tephrochronological investigations into a suite of central and southern european records which include rotmeer southern germany soppensee and rotsee central swiss plateau lago di lavarone and lago piccolo di avigliana italian southern alpine foreland these sites provide records of palaeoenvironmental changes for the last glacial to interglacial transition lgit at the boundary between north atlantic and mediterranean climatic influences chemical characterisation of glass shards in volcanic ash layers indicates that multiple volcanic sources have contributed to the central european tephra record amongst other volcanic markers the laacher see tephra originating from the eifel region of germany c 12 9 0 1 ka and the vedde ash from iceland c 12 1 0 1 ka are found co located within the sediments of rotmeer soppensee rotsee and lago piccolo di avigliana these key horizons which bracket the onset of the younger dryas stadial provide precise calendrically dated tie points around which a detailed picture of the timing of local and regional environmental transitions can be constructed using the co located tephra layers the re colonisation of northern italian catchment areas by quercus is shown to occur just prior to the deposition of the laacher see tephra layer whereas to the north of the alps quercus and other thermophilous trees do not reappear until several centuries after the deposition of the vedde ash furthermore the discovery of the vedde ash in lago piccolo di avigliana and lago di lavarone is indicative of atmospheric transport of polar air into southern europe during the younger dryas stadial matching evidence proposed for such transport of polar air during the last glacial maximum lgm

the response of a shallow lake and its catchment to late glacial climate changes a case study from eastern poland in this study we investigate how climate fluctuation in the late glacial period influenced the development of a lake and its catchment located in the east european plain we analyzed the sediments of the lake for pollen subfossil cladocera macrofossils and chemical composition we aimed at disentangling 1 the climate changes and their limno ecological responses 2 temperature dynamics with the use of cladocera based transfer function mjt and macrofossil based reconstruction of mean minimum july temperature mmjt 3 timing of the response of different proxies to environmental changes the results of multiproxy analyses explicitly suggest that the main driver for changes in aquatic and terrestrial ecosystems as well as geomorphological processes in the catchment was climate reconstructed temperatures generally follow the known trends showing the increase at the beginning of the allerod and decrease at the beginning of the younger dryas however there are some discrepancies between the two reconstructions as well as between the generally accepted temperature trends in late glacial the timing of the proxy response to climate change differs the aquatic proxies responding first

a high mountain pollen altitude calibration set for palaeoclimatic use in the tropical andes the numerical relationship between modem pollen assemblages and altitude in high mountain environments from the northern andes is analysed in order to found inference models that allow estimating palaeoaltitudes and palaeotemperatures from past pollen records the calibration set dm consists of a 50 sample altitudinal transect between 2300 and 4600 m altitude the overall and individual pollen responses to altitude were tested by correspondence analysis ca generalized linear regression hof and weighted averaging wa transfer functions were derived by weighted averaging partial least squares wa pls regression overall altitude is the main controlling factor for the composition of pollen assemblages as shown by the high correlation between altitude and the first ca component r 0 88 individually around 35 of the 82 pollen taxa show a significant response to altitude through monotonic or unimodal functions the best transfer function obtained has a good statistical performance as shown b

novel insights from coleopteran and pollen evidence into the lateglacial holocene transition in aubrac french massif central the aim of this study is to describe the environmental and climate changes that occurred in the mountains of aubrac at the transition between the lateglacial and the holocene from a comparative analysis of fossil coleoptera and pollen and a series of 23 c 14 dates the changes affecting the ecological categories of coleoptera lead to a division of the sequence into 5 beetle assemblage zones baz the lowermost baz a is characterized by extremely poor assemblages periglacial environment baz b oldest dryas and lateglacial interstadial is marked by regular occurrences of taxa associated with open environments aquatic taxa associated with running and highly oxygenated water and cold adapted taxa with relatively low numbers baz c younger dryas corresponds to two important events a particular abundance of cold adapted taxa and a marked decrease of running water taxa beetles associated with herbaceous vegetation and open environments are also well represented baz d early holocene corresponds to the total disappearance of cold adapted taxa the transition baz c baz d is marked also by a dramatic peak of running water taxa the uppermost baz e early mid holocene is marked by a total absence of running water taxa which are replaced by standing water or taxa tolerant of a range of water conditions a particular abundance of wetland taxa and taxa associated with herbaceous vegetation and open environments beetle and pollen data suggest that the harsh climatic conditions prevailing in the aubrac mountains did not allow warm dependent fauna and trees to establish during the lateglacial interstadial at least in the roustieres region and that wide open landscapes occupied the plateau at that time the older dryas a cold spell previously recorded at la taphanel cantal is not visible in the roustieres record probably because of the higher altitude at roustieres whereas the younger dryas is strongly expressed during the holocene concordant beetles and pollen data enable to reconstruct the rapid recolonization of the plateau by mesophilous trees ulmus quercus suggesting the possible presence of refugia to the southern slopes of the aubrac plateau insect pollen comparisons provide evidence for hydrological changes in the former lake of roustieres and suggest that lacustrine water level changes often used as indicator of precipitation regime changes should be taken with caution c 2016 elsevier b v all rights reserved

a precisely dated climate record for the last 9 kyr from three high alpine stalagmites spannagel cave austria 1 here we use the 18o time series of three stalagmites from the high alpine spannagel cave austria which grew in small distance from each other to construct a precisely dated continuous 18o curve for the last 9 kyr comnispa this speleothem record is not influenced by effects of kinetic isotope fractionation due to the low temperatures in the cave thus the variations in 18o can be interpreted in terms of past climate change comnispa exhibits several oscillations within the holocene and their timing and duration is in agreement with that documented by other alpine archives

a compilation of western european terrestrial records 60 8 ka bp towards an understanding of latitudinal climatic gradients terrestrial records of past climatic conditions such as lake sediments and speleothems provide data of great importance for understanding environmental changes however unlike marine and ice core records terrestrial palaeodata are often not available in databases or in a format that is easily accessible to the non specialist as a consequence many excellent terrestrial records are unknown to the broader palaeoclimate community and are not included in compilations comparisons or modelling exercises here we present a compilation of western european terrestrial palaeo records covering entirely or partially the 60 8 ka intimate time period the compilation contains 56 natural archives including lake records speleothems ice cores and terrestrial proxies in marine records the compilation is limited to include records of high temporal resolution and or records that provide climate proxies or quantitative reconstructions of environmental parameters such as temperature or precipitation and that are of relevance and interest to a broader community we briefly review the different types of terrestrial archives their respective proxies their interpretation and their application for palaeoclimatic reconstructions we also discuss the importance of independent chronologies and the issue of record synchronization the aim of this exercise is to provide the wider palaeo community with a consistent compilation of high quality terrestrial records to facilitate model data comparisons and to identify key areas of interest for future investigations we use the compilation to investigate western european latitudinal climate gradients during the deglacial period and despite of poorly constrained chronologies for the older records we summarize the main results obtained from nw and sw european terrestrial records before the lgm

lateglacial and early holocene insect assemblages from sites at different altitudes in the swiss alps implications on climate and environment insect analyses from four sites at differentaltitudes in the swissalps are presented the dominant insect group considered here is coleoptera beetles though other insect orders are also recorded

elevational transects of modern pollen samples site specific temperatures as a tool for palaeoclimate reconstructions in the alps the potential of quantitatively reconstructing climate from modern pollen assemblages from high mountain environments has been widely debated but seldom tested we analysed the pollen deposition in

oxygen isotopes of lake marl at gerzensee and leysin switzerland covering the younger dryas and two minor oscillations and their correlation to the grip ice core the ratio of oxygen isotopes is a temperature proxy both in precipitation and in the calcite of lacustrine sediments the very similar oxygen isotope records from greenland ice cores and european lake sediments during the last glacial termination suggest that the drastic climatic changes occurred quasi simultaneously on an extra regional probably hemispheric scale in order to study temporal relations of the different parameters recorded in lake sediments for example biotic response times to rapid climatic changes a precise chronology is required in unlaminated lake sediments there is not yet available a method to provide a high resolution chronology especially for periods with radiocarbon plateaux alternatively an indirect time scale can be constructed by linking the lake stratigraphy with other well dated climate records new oxygen isotope records from gerzensee and leysin with an estimated sampling resolution of between 15 and 40 years match the greenlandic isotope record in many details under the assumption that the main variations in temperature and thus in oxygen isotopes occurred about simultaneously in greenland and switzerland we have assigned a time scale to the lake sediments of gerzensee and leysin by wiggle matching their stable isotope records with those of greenland ice cores which are among the best dated climatic archives we estimate a precision of 20 to 100 years during the last glacial termination

isotope signature of the younger dryas and two minor oscillations at gerzensee switzerland palaeoclimatic and palaeolimnologic interpretation based on bulk and biogenic carbonates oxygen and carbon isotope ratios in the carbonate of benthic ostracodes pseudocandona marchica and molluscs pisidium ssp were measured across the transitions bordering the younger dryas chronozone in littoral lacustrine cores from gerzensee switzerland the specific biogenic carbonate records confirm the major shifts already visible in the continuous bulk carbonate oxygen isotope record 18occ if corrected for their vital offsets oxygen isotope ratios of pisidium and juvenile p marchica both formed in summer are almost identical to 18occ this bulk carbonate is mainly composed of encrustations of benthic macrophythes chara ssp also mainly produced during summer adult p marchica which calcify in winter show consistently higher 18o larger shifts across both transitions and short positive excursions compared with the summer forms especially during early preboreal despite such complexity the 18o of adult p marchica probably reflects more accurately the variations of the 18o of former lake water because during winter calcification temperatures are less variable and the water column isotopically uniform the difference between normalised 18o of calcite precipitated in winter to that formed in summer can be used to estimate the minimum difference between summer and winter water temperatures in general the results indicate warmer summers during the late allerod and early preboreal compared with the younger dryas altogether the isotopic composition of lake water 18ol and of the dissolved inorganic carbonate 13cdic reconstructed from adult pseudocandona marchica as well as the seasonal water temperature contrasts indicate that the major shifts in the 18o of local precipitation at gerzensee were augmented by changes of the lake s water balance with relatively higher evaporative loss occurring during the allerod compared with the younger dryas it is possible that during the early preboreal the lake might even have been hydrologically closed for a short period we speculate that such hydrologic changes reflect a combination of varying evapotranspiration and a rearrangement of groundwater recharge during those climatic shifts

chronology and paleoenvironment of marine isotope stage 3 from two high elevation speleothems austrian alps abstract a new high resolution stable isotope record from the alpine kleegruben cave 2165 m central alps is presented this record largely duplicates a previously reported speleothem record from this site high precision u series thermal ionization mass spectrometry dates constrain the growth history of this new sample 56 48 ka to the marine isotope stage mis 3 both stalagmites reveal highly similar variations in o isotopes that can be directly compared to o isotope variability associated with dansgaard oeschger interstadials recorded in the greenland ice cores greenland interstadials gis based on the new record we refine our previous age assignments of the gis during this time interval i e gis 15b at 55 7 ka gis 15a at 55 3 ka onset mid point of the prominent gis 14 at 54 5 yr and onset of gis 12 at 48 ka the overall uncertainties associated with these ages are 0 1 0 3 ka the timing of these dansgaard oeschger interstadials is within 0 2 ka of the newly proposed grip sfcp04 timescale the age data for both kleegruben stalagmites demonstrate that liquid water was at least seasonally present in the shallow sub surface allowing calcite precipitation to continue even during stadials of mis 3 given the present day low temperature 2 4 c we propose that these unusual speleothems formed in a karst system overlain by a warm based glacier

very fast environmental changes at the pleistocene holocene boundary recorded in laminated sediments of lake gościz poland abstract this paper presents a reconstruction of the climatic changes at the pleistocene holocene transition recorded in the annually laminated sediments of lake go ci a z poland this reconstruction is based on pollen stable isotope mineralogical and chemical analyses of sediments made with a time resolution of 1 4 yr it reveals a sequence of abrupt climatic changes which preceded and followed the major warming around 11 500 cal bp our data show that the warming period was preceded by a 30 yr long phase of increased winter and decreased summer precipitation 11 550 11 520 cal bp about 11 520 cal bp a very brief period of wetter conditions occurred simultaneously with the beginning of the major warming however most of the first phase of the major warming 11 520 11 500 cal bp was characterised by a generally dry climate presumably due to lowered winter precipitation our records suggest that in this phase the warming concerned winter seasons mostly in the second phase 11 500 11 460 cal bp the warming also concerned summer seasons also a distinct increase of humidity is noted in this period which caused moistening of soils and despite enhanced evaporation and evapotranspiration inhibited the process of lake level drop the following 70 years 11 460 11 390 cal bp were rather dry which caused a distinct lowering of the lake and probably also of groundwater level in this period maximum biological productivity per unit area in the lake is noted the whole sequence of phases of rather different climates was completed within a time interval 160 years spanning two human lifes only one should stress that the transitions between the consecutive phases were rather abrupt lasting no longer than 10 years

seasonality in the north sea during the allerod and late medieval climate optimum using bivalve sclerochronology seasonal temperature patterns may have changed through time in response to current global warming however the temporal resolution of available proxy records is not sufficient to quantify paleotemperature seasonality prior to anthropogenic forcing of the climate in the present study we reconstructed seasonal and inter annual temperature patterns of the north sea during the last 140 years the allerod interglacial and the late medieval climate optimum using sclerochronological and 18oaragonite data from bivalve shells arctica islandica on average the climate during 1278 1353 ad was ca 1 1 c colder and seasonality was ca 60 less than today during the allerod long term temperatures remained about 3 2 c below present values and absolute summer and winter anomalies were ca 4 and 2 7 c respectively however seasonality was statistically indistinguishable from today long term average temperatures compare well with existing data for the late medieval and allerod but detailed information on seasonality during the studied time intervals has never been presented before our data also demonstrated that annual instrumental and 18oaragonite derived temperatures did not always match this difference is explained by 1 nao driven salinity changes which influence the temperature estimation from 18oaragonite and 2 food driven changes in growth rates portions of the shell that formed more rapidly are overrepresented in carbonate samples our study indicated that individual bivalve shells can open discrete near century long ultra high resolution windows into the climate past such information can be vital for testing and verifying numerical climate models

pollen inferred palaeoclimate reconstruction in the alps during the lateglacial and the early holocene how to estimate the effect of elevation and local parameters the modern analogue technique mat was applied to six pollen sequences from the belledonne massif northwestern french alps to estimate the effect of altitude and local parameters on pollen based climate reconstruction during the lateglacial and the early holocene the six sites le vivier 345 m a s l les etelles 700 m a s l la coche 980 m a s l montendry 1330 m a s l le grand leyat 1660 m a s l la gouille 1800 m a s l are located in different vegetation belts mixed deciduous woods conifer woods alpine pastures with maple the main vegetation changes in the past are recorded at each site the evolution of four climate parameters coldest month temperature warmest month temperature mean annual temperature annual precipitation was quantitatively inferred from pollen data using mat the curves obtained were compared to the les etelles site which was the least affected by non local pollen transport the results show consistent trends for the climate parameters reconstructed at the different sites however the reconstruction does not indicate a decrease in temperature values related to the increasing elevation difficulties in reconstructing the altitudinal variations of climate parameters from pollen data during the periods studied are discussed and perspectives for improvement are considered copyright 2009 john wiley sons ltd