holocene glacial activity and climatic variations in the swiss alps reconstructing a continuous record from proglacial lake sediments cores recovered from proglacial lake silvaplana swiss alps were investigated to examine the influence of holocene glaciers on lacustrine sedimentation during times of glacial activity in the catchment the sedimentation in the lake is dominated by the input of silt and clay sized material delivered by glacial meltwaters the deposition of fine grained material and the formation of varves reflect the existence of glaciers in the catchment and can therefore be used for the reconstruction of glacial history sedimentation rates are up to nine times higher in the varved than in the non varved sediments indicating significantly higher erosion rates under glaciated catchment conditions glacial varves were deposited in lake silvaplana during glacial retreat in the latest pleistocene and early holocene until 9400bp non varved deposits having a higher organic content and coarser grain sizes accumulated at lower rates when glacial activity was absent or negligible within the catchment between 9400 and 3300 bp

holocene climatic and environmental changes inferred from midge records diptera chironomidae chaoboridae ceratopogonidae at lake berkut southern kola peninsula russia a radiocarbon dated sediment sequence from lake berkut in the southern part of the kola peninsula northwest russia was investigated by means of midge analysis in order to reconstruct the holocene climatic and environmental history of the region past mean july air temperatures at the study site and hypolimnetic oxygen contents of the lake water were inferred from chironomid based transfer functions the early holocene c 10 100 8400 cal yr bp is characterized by summer temperatures and hypolimnetic oxygen concentrations broadly similar to present day conditions the midge records give evidence of a lake level fall at c 7000 cal yr bp resulting in weakened thermal stratification of the lake water and improvement of the hypolimnetic oxygen conditions after c 4000 cal yr bp midge assemblages suggest a lake level rise related to increased effective moisture a secondary mid holocene climatic optimum with inferred mean july air temperatures of c 12 1 degrees c was recorded between 6000 and 4400 cal yr bp followed by minimum values c 11 3 degrees c between 3500 and 1500 cal yr bp accompanied by the onset of natural acidification of the lake the late holocene midge assemblages suggest weakly acidic conditions low hypolimnetic oxygen contents and a general warming trend during the last c 1500 years although paludification and natural acidification may have influenced the temperature reconstruction at this stage however the modern chironomid inferred mean july air temperature 12 5 degrees c is consistent with meteorological data from a nearby station in general the midge records reflect relatively warm and moist conditions at lake berkut before c 7000 cal yr bp a relatively warm and dry climate at c 7000 4000 cal yr bp and a shift to cooler and wetter climatic conditions in the region after c 4000 cal yr bp less

characterizing the mesozoic extension direction in the northern iberian plate margin by anisotropy of magnetic susceptibility ams we present the results of anisotropy of magnetic susceptibility ams analyses carried out on weakly deformed triassic red beds jurassic and lower cretaceous limestones sandstones and shales from several northern iberian mesozoic basins located near the northern iberian plate margin santander cabuerniga and polientes basins in the western part of the basque cantabrian basin and bilbao and aralar basins in the central eastern part cameros basin in the northernmost part of the iberian chain a well defined magnetic lineation of tectonic origin is found at most of the sampled sites and is interpreted as the stretching direction resulting from the extensional deformation characterizing this period during the mesozoic the northern margin of the iberian plate underwent two rifting stages the triassic and late jurassic early cretaceous kimmeridgian albian rifting events both the triassic and the period of the late jurassic early cretaceous rifting event with maximum subsidence rates i e until the barremian are characterized by a ne sw extensional direction in the main subsidence areas this indicates that nw se master faults controlled basin subsidence and sedimentation through these periods in the northern iberia plate margin basins conversely during jurassic and aptian times a lower activity of nw se faults together with more important extension along a nw se direction can be inferred from ams analysis this study indicates the power of ams analysis in basin analysis and geodynamic reconstructions even in subsequently inverted basins

palaeolimnological approaches to climate change with special regard to the biological record abstract lakes systems respond physically chemically and biologically to changes in climate and these responses are registered in many various ways in lake sediment records this paper focuses principally on the biological record and describes recent research that aims to reconstruct i past variability in effective moisture and ii past variability in temperature changes in effective moisture are manifested especially by changes in lake water level in closed lake basins water level change can cause significant changes in water salinity that is registered in sediments by changes in the composition of fossil assemblages especially diatoms in open freshwater lake basins changes in water level are best reconstructed from the aquatic macrofossil record and potentially from the ratio of open water to littoral species of cladocera ostracods and diatoms the most promising biological method for reconstructing past temperature is chironomid analysis and a range of new chironomid temperature transfer functions are being developed however biological responses to changing temperature are usually indirect as a result of temperature effects on water column stratification nutrient cycling and alkalinity generation and in most cases a correct interpretation of the climatic significance of changes in the fossil record requires an understanding of the processes that are operating in the water column a multi proxy whole lake approach is advocated as the best way forward not only as a means of reconstructing past climate but also as a means of assessing the impact of climate change on lake systems

holocene climate variability in europe evidence from δ18o textural and extension rate variations in three speleothems time series o isotope profiles for three u th dated stalagmites have revealed that for much of the holocene a site on the atlantic seaboard sw ireland exhibits first order 18o trends that are almost exactly out of phase with coupled 18o curves from two southern european sites se france and nw italy in the irish stalagmite cc3 from crag cave sw ireland low 18o at 10 000 cal yr bp reflects cool conditions by the early to mid holocene 9000 6000 cal yr bp 18o had increased reflecting the onset of warmer conditions on the atlantic seaboard this shift to higher 18o was accompanied by a marked increase in the stalagmite extension rate reinforcing our interpretation that this was a period of relative warmth except for an episode of increased extension rate about 5500 yr ago 18o in the crag stalagmite exhibits a gradual decrease accompanied by declining extension rates between 7800 and 3500 cal yr bp interpreted as a cooling trend there is evidence for increases in both 18o and stalagmite extension rate in the period from 3500 cal yr bp to the present day suggesting a return to warmer conditions on the atlantic seaboard in the stalagmite from nw italy er76 grotta di ernesto trentino province the early holocene c 9200 7800 cal yr bp is characterised by high 18o probably indicative of warm and or dry conditions exceptionally low 18o from 7800 to 6900 cal yr bp at this site reflects a well defined wet phase cerin wet phase in the last three millennia this stalagmite exhibits a shift to lower 18o interpreted as some combination of cooler and or wetter conditions unlike the irish stalagmite the italian sample does not show a correlation between 18o and extension rate instead its extension rate correlates roughly with 13c presumably reflecting a climate driven vegetation change in the early holocene 18o in the french stalagmite cl26 grotte de clamouse herault province se france was low relative to its holocene average for much of the period since c 3500 cal yr bp this stalagmite exhibits higher 18o than in the early holocene suggesting warmer conditions like the irish stalagmite the french sample exhibits a well defined correlation between 18o and extension rate had drip water availability been the dominant control on 18o at this semi arid site then higher 18o would have been accompanied by lower not higher extension rates this suggests strongly that temperature rather than rainfall amount was the dominant control at this site while conclusions regarding the patterns of climate variability on a continent scale must remain tentative because of the limited number of stalagmites studied we argue that early holocene warm conditions on the atlantic seaboard irish site coincided with relatively cool conditions at the clamouse site by c 3500 yr ago the pattern appears to have been reversed

tripartite climate reversal in central europe 5600 5300 years ago abstract the history of variations in water level of lake constance as reconstructed from sediment and pollen analysis of a sediment sequence from the archaeological site of arbon bleiche 3 shows an abrupt rise in lake level dendrochronologically dated to 5375 yr ago 5320 yr relative to ad 1950 this event paralleled by the destruction of the neolithic village by fire provoked the abandonment of this prehistoric lake shore location established in the former shallow bay of arbon bleiche and was the last of a series of three episodes of successively higher lake level the first occurring at 5600 5500 cal yr b p the dendrochronologically dated rise event was synchronous with an abrupt increase in atmospheric 14 c this supports the hypothesis of an abrupt climate change forced by varying solar activity moreover the three successive episodes of higher lake level between 5600 and 5300 cal yr b p at arbon bleiche 3 coincided with climatic cooling and or changes in moisture conditions in various regions of both hemispheres this period corresponds to the mid holocene climate transition onset of the neoglaciation and suggests inter hemispheric linkages for the climate variations recorded at arbon bleiche 3 this mid holocene climate reversal may have resulted from complex interactions between changes in orbital forcing ocean circulation and solar activity finally despite different seasonal hydrological regimes the similarities between lake level records from lake constance and from jurassian lakes over the mid holocene period point to time scale as a crucial factor in considering the possible impact of climate change on environments

holocene thinning of the greenland ice sheet the nature of the response of the greenland ice sheet gis to climate change is a fundamental question in climate science but the details remain unclear during the holocene climate optimum 6 000 to 9 000 years ago for example many locations in the northern hemisphere showed unusual warmth yet changes in greenland appeared inconsistent vinther et al now standardize the previously disparate seeming ice core records of climate history on the gis during the holocene and find consistent evidence for a stronger climate optimum than was previously recognized together with elevation reduction and marginal ice sheet thinning the response of the greenland ice sheet gis to changes in climate remains uncertain during the holocene climatic optimum an unusually warm period from about 9 000 to 6 000 years ago changes in greenland appear inconsistent with the rest of the northern hemisphere here the greenland holocene temperature history and the evolution of gis surface elevation are extracted from four gis locations the results may resolve this disparity on entering an era of global warming the stability of the greenland ice sheet gis is an important concern1 especially in the light of new evidence of rapidly changing flow and melt conditions at the gis margins2 studying the response of the gis to past climatic change may help to advance our understanding of gis dynamics the previous interpretation of evidence from stable isotopes 18o in water from gis ice cores was that holocene climate variability on the gis differed spatially3 and that a consistent holocene climate optimum the unusually warm period from about 9 000 to 6 000 years ago found in many northern latitude palaeoclimate records4 did not exist here we extract both the greenland holocene temperature history and the evolution of gis surface elevation at four gis locations we achieve this by comparing 18o from gis ice cores3 5 with 18o from ice cores from small marginal icecaps contrary to the earlier interpretation of 18o evidence from ice cores3 6 our new temperature history reveals a pronounced holocene climatic optimum in greenland coinciding with maximum thinning near the gis margins our 18o based results are corroborated by the air content of ice cores a proxy for surface elevation7 state of the art ice sheet models are generally found to be underestimating the extent and changes in gis elevation and area our findings may help to improve the ability of models to reproduce the gis response to holocene climate

lateglacial environmental and climatic changes at the maloja pass central swiss alps as recorded by chironomids and pollen abstract chironomids and pollen were studied in a radiocarbon dated sediment sequence obtained from a former lake near the maloja pass in the central swiss alps 1865 m a s l to reconstruct the lateglacial environment pollen assemblages imply a vegetation development around the maloja pass from shrub tundra at the beginning of the allerod to coniferous forest during the early holocene with a lowering of the timberline during the younger dryas chironomid assemblages are characterized by several abrupt shifts in dominant taxa through the lateglacial the occurrence of taxa able to survive hypoxia in the second part of the allerod and during the preboreal and their disappearance at the onset of the younger dryas cold phase suggest summer thermal stratification and unfavourable hypolimnetic oxygen conditions in the palaeo lake during the warmer periods of the lateglacial interstadial and early holocene mean july air temperatures were reconstructed using a chironomid temperature transfer function from the alpine region the pattern of reconstructed temperature changes agrees well with the greenland 18 o record and other lateglacial temperature inferences from central europe the inferred july temperatures of ca 10 0 c during most of the allerod were slightly lower than modern values 10 8 c and increased up to ca 11 7 c i e above present day values at the end of the allerod the first part of the younger dryas was colder ca 8 8 c than the second part ca 9 8 c during most of the preboreal the temperatures persisted within the limits of 13 5 14 5 c i e ca 3 c above present day values the amplitudes of temperature changes at the allerod younger dryas preboreal transitions were ca 3 5 4 0 c the temperature reconstruction also shows three short lived cooling events of ca 1 5 2 0 c which may be attributed to the centennial scale greenland interstadial events gi 1d and gi 1b and the preboreal oscillation

holocene climatic instability a prominent widespread event 8200 yr ago the most prominent holocene climatic event in greenland ice core proxies with approximately half the amplitude of the younger dryas occurred 8000 to 8400 yr ago this holocene event affected regions well beyond the north atlantic basin as shown by synchronous increases in windblown chemical indicators together with a significant decrease in methane widespread proxy records from the tropics to the north polar regions show a short lived cool dry or windy event of similar age the spatial pattern of terrestrial and marine changes is similar to that of the younger dryas event suggesting a role for north atlantic thermohaline circulation possible forcings identified thus far for this holocene event are small consistent with recent model results indicating high sensitivity and strong linkages in the climatic system

hydrological changes in the european midlatitudes associated with freshwater outbursts from lake agassiz during the younger dryas event and the early holocene abstract recent studies of lake level fluctuations during the last deglaciation in eastern france jura mountains and pre alps and on the swiss plateau show distinct phases of higher water level developing at the beginning and during the latter part of greenland stade 1 i e younger dryas event and punctuating the early holocene period at 11 250 11 050 10 300 10 000 9550 9150 8300 8050 and 7550 7250 cal yr b p the phases at 11 250 11 050 and 8300 8050 cal yr b p appear to be related to the cool preboreal oscillation and the 8200 yr event assumed to be associated with deglaciation events a comparison of this mid european lake level record with the outbursts from proglacial lake agassiz in north america suggests that between 13 000 and 8000 cal yr b p phases of positive water balance were the response in west central europe to climate cooling episodes which were induced by perturbation of the thermohaline circulation due to sudden freshwater releases to oceans this probably was in response to a southward migration of the atlantic westerly jet and its associated cyclonic track moreover it is hypothesized that during the early holocene varying solar activity could have been a crucial factor by amplifying or reducing the possible effects of lake agassiz outbursts on the climate

midges as quantitative temperature indicator species lessons for palaeoecology calibration data sets give a unique opportunity to establish patterns of biological existence and their statistical associations with environmental variables by use of calibration data sets environmental variables can be inferred quantitatively the resulting long time series may assist in distinguishing natural environmental variability from human induced variability both in terms of climate change and biotic turnover however the validity of the palaeoenvironmental reconstructions depends on their accuracy precision and sensibility before performing palaeoenvironmental inferences key mechanisms controlling contemporary species distribution abundances and dynamics should be identified and understood an inference model is developed to produce reconstructions a major challenge lies in validating and interpreting the reconstructions calibration data sets involving midges diptera chironomidae suggest that climate has a broad scale regional control over midge existence and abundance often ove

climate and vegetation dynamics in the tundra and forest zone during the late glacial and holocene abstract analysis of palynological successions has enabled reconstruction of climate variations throughout the late glacial and holocene in the tundra and forest zones of northern eurasia statistical analysis allows estimation of mean annual precipitation and mean annual and july temperatures based on palynological assemblages thus the dynamic relationships between climate and vegetation changes can be established throughout the late glacial and holocene climate fluctuations were more dramatic in eastern europe than in siberia primarily as a result of the influence of westerly air masses in contrast the autochthonous climate of siberia dominated by local air masses was less prone to influence from climate changes elsewhere in the northern hemisphere and shows only an attenuated younger dryas signal mid holocene warming characterizes all of northern eurasia although the regions of siberia most influenced by continental climates show less pronounced cooling during the later holocene sharp changes between summer monsoonal and winter anti cyclonic regimes characterize the pacific maritime region

chironomids as a tool for inferring holocene climate an assessment based on six sites in southern scandinavia abstract chironomid subfossil assemblages from six low alpine and sub alpine holocene stratigraphies are presented and compared they are from five lakes in mid southern and western norway and one in central sweden when comparing the chironomid inferred july air temperatures there are many time segments with a poor among lake fit in inferred temperatures possible environmental variables influencing the fossil chironomid assemblages are discussed using a modern norwegian calibration data set to indicate taxon environment relationships these analyses indicate that local changes in ph water chemistry and productivity at times may have overridden the regional temperature signal in addition other causes of poor among site temperature fit are discussed in particular those related to chronological uncertainties holocene temperature inferences from single cores based on chironomids may not always be able to provide a reliable regional temperature signal but can act as a guide from which hypotheses about past environmental conditions can be tested with the aid of chironomid inferred temperatures from several sites and from other environmental proxies we have obtained a regional picture of holocene summer temperature change by developing a consensus reconstruction based on the overall temperature signal from all six sites this consensus is developed by fitting a smoother through all 330 site specific temperature deviations from the holocene mean the consensus temperature deviations vary from 0 8 c at 8800 cal years bp to 0 8 c at 6500 cal years bp

late holocene summer temperature reconstruction from chironomid assemblages of lake anterne northern french alps we present a chironomid based reconstruction of late holocene temperature from lake anterne 2060 m a s l in the northern french alps chironomid assemblages were studied in 49 samples along an 8 m long sediment core covering the last 1800 years july air temperatures were inferred using an inference model based on the distribution of chironomid assemblages in 100 swiss lakes the transfer function has a leave one out cross validated coefficient of determination r of 0 88 a root mean square error of prediction rmsep of 1 40 c despite possible biases induced by methodological aspects and the ecological complexity of the chironomid response to both climate and environmental changes the concordance of the lake anterne temperature reconstruction with other alpine records suggests that the transfer function has successfully reconstructed past summer temperature during the last two millennia the twentieth century is the only section of the record which shows a poor agreement with other climate recons

paleoecological evidence for abrupt cold reversals during peak holocene warmth on baffin island arctic canada a continuous record of insect chironomidae remains preserved in lake sediments is used to infer temperature changes at a small lake in arctic canada through the holocene early holocene summers at the study site were characterized by more thermophilous assemblages and warmer inferred temperatures than today presumably in response to the positive anomaly in northern hemisphere summer insolation peak early holocene warmth was interrupted by two cold reversals between 9 5 and 8 cal ka bp during which multiple cold stenothermous chironomid taxa appeared in the lake the earlier reversal appears to correlate with widespread climate anomalies around 9 2 cal ka bp the age of the younger reversal is equivocal but it may correlate with the 8 2 cal ka bp cold event documented elsewhere widespread abrupt climate shifts in the early holocene illustrate the susceptibility of the climate system to perturbations even during periods of enhanced warmth in the northern hemisphere

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

holocene temperature variations at a high altitude site in the eastern alps a chironomid record from schwarzsee ob solden austria few well dated quantitative holocene temperature reconstructions exist from high altitude sites in the central eastern alps here we present a chironomid based quantitative reconstruction of mean july air temperatures tjuly throughout the holocene for a remote high mountain lake schwarzsee ob solden situated above the treeline at 2796 m a s l in the austrian alps applying a chironomid temperature inference model developed from lakes of the alpine region to a high resolution chironomid record from the lake provides evidence for early holocene ca 10000 8600 cal yr bp tjuly of up to 8 5 c i e 4 c above the modern 1977 2006 mean july temperature the reconstruction reveals the so called 8 2 ka cold event centered at ca 8250 8000 cal yr bp with temperatures ca 3 c below the early holocene thermal maximum rather warm ca 6 c and productive conditions prevailed during ca 7900 4500 cal yr bp the chironomid record suggests a climate transition between ca 5200 and 4500 cal yr bp to cooler tjuly a distinct cooling trend is evident from ca 4500 until ca 2500 cal yr bp thereafter the study site experienced its coldest conditions around 4 c or less throughout the rest of the holocene with the exception of the warming trend during the late 20th century beside other factors the northern hemisphere summer insolation seems to be the major driving force for the long term trends in tjuly at high altitudes in the eastern alps due to the extreme location of the lake and the limited temperature range represented by the applied calibration data set the chironomid based temperature reconstruction fails to track phases of the late holocene climatic history with tjuly cooler than 4 c further chironomid based palaeoclimate model and down core studies are required to address this problem provide more realistic tjuly estimates from undisturbed high altitude lakes in the alps and extract a reliable regional temperature signal

vegetation responses to the 8200 cal bp cold event and to long term climatic changes in the eastern alps possible influence of solar activity and north atlantic freshwater pulses subfossil pollen from two bogs in temperature sensitive high altitude regions were analysed in order to reconstruct early to mid holocene summer temperature fluctuations in the eastern alps the p

petrological geochemical and isotopic constraints on the origin of the harzburg intrusion germany we present mineralogical petrological and geochemical data to two isotopically distinct reservoirs dominates the pb of all samples constrain the origin of the harzburg mafic ultramafic intrusion the ultramafic rocks and the cumulates best reflect the initial isotopic the intrusion is composed mainly of mafic rocks ranging from and geochemical signature of the parent magma magma that gabbronorite to quartz diorite ultramafic rocks are very rare in crystallized in the upper part of the chamber was more strongly surface outcrops dunite is observed only in deeper sections of the affected by assimilated material petrographic geochemical and flora i drill core microgranitic fine grained quartz feldspathic isotope evidence demonstrates that during a late stage of crysveins found in the mafic and ultramafic rocks result from contallization hybrid rocks formed through the mechanical mixing of tamination of the ultramafic magmas by crustal melts in ultramafic early cumulates and melts with strong crustal contamination from and mafic compositions cumulate textures are widespread and filter the upper levels of the magma chamber pressing phenomena are obvious the order of crystallization is olivine pargasite phlogopite spinel plagioclase orthopyroxene plagioclase clinopyroxene hydrous minerals such as phlogopite

high resolution isotope records of early holocene rapid climate change from two coeval stalagmites of katerloch cave austria abstract two coeval stalagmites from katerloch cave show pronounced intervals of low 18o values around 8 2 9 1 and 10 0 kyr all ages are reported before the year 2000 ad and represent an inorganic u th dated climate archive from the southeast of the european alps a region where only very few well dated climate records exist the o isotope curves providing near annual resolution allow a direct comparison to the greenland ice core records as temperature was the primary factor controlling the o isotopic composition of katerloch speleothems the 8 2 kyr climate anomaly lasted about one century from 8196 to 8100 yr with a maximum amplitude of 1 1 at 8175 yr the event is characterized by a rapid onset and a more gradual demise and u th data as well as annual lamina counting support a rapid climate change towards cooler conditions within 10 20 yr there is no strong evidence that the 8 2 kyr anomaly was superimposed on a pronounced longer term cooling episode nor do the new data support two separate cooling events within the 8 2 kyr event as reported by other studies our record also shows a distinct climate anomaly around 9 1 kyr which lasted 70 110 yr and showed a maximum amplitude of 1 0 i e it had a similar duration and amplitude as the central 8 2 kyr event compared to the 8 2 kyr event the 9 1 kyr anomaly shows a more symmetrical structure but onset and demise still occurred within a few decades only the different progression of the 8 2 asymmetrical and 9 1 kyr anomaly symmetrical suggests a fundamental difference in the trigger and or the response of the climate system moreover both stalagmites show evidence of a climate anomaly around 10 0 kyr which was of comparable magnitude to the two subsequent events using a well constrained modern calibration between air temperature and 18o of precipitation for the study area and cave monitoring data confirming speleothem deposition in katerloch reflecting cave air temperature a maximum cooling by ca 3 c can be inferred at 8 2 and 9 1 kyr which is similar to other estimates e g from lake ammersee north of the alps the o isotopic composition of meteoric precipitation however is a complex tracer of the hydrological cycle and these temperature estimates do not take into account additional effects such as changes in the source area or synoptic shifts apart from that the relative thickness of the seasonally controlled lamina types in the katerloch stalagmites remains rather constant across the intervals comprising the isotopic anomalies i e the stalagmite petrography argues against major shifts in seasonality during the early holocene climate excursions

synchronous holocene climatic oscillations recorded on the swiss plateau and at timberline in the alps eight synchronous pre roman cold phases were found at 9600 9200 8600 8150 7550 6900 6600 6200 5350 4900 4600 4400 3500 3200 and 2600 2350 radiocarbon years bp by reconstructing past climate at two sites on the swiss plateau and at timberline in the alps the cooling events during the early and mid holocene represent temperature values similar to today and apparently the onset of cooling events represents a deviation from today s mean annual temperature of about 1 c and is triggered at a 1000 year periodicity at wallisellen langachermoos 440 m a former oligotrophic lake near zurich the correlation between sum mertime lake levels and the seed production of the amphi atlantic aquatic plantnajas flexilis was used to reconstruct lake levels over a 3000 year period during the first part of the holocene at lake seedorf on the western swiss plateau 609 m the sedimentological palynological and macrofossil record revealed fluctuations of lake levels for the complete holocene from lago basso in the

quantitative multiproxy assessment of long term patterns of holocene environmental change from a small lake near abisko northern sweden quantitative reconstructions are made of holocene changes in climatic and environmental conditions from analyses of pollen chironomids and diatoms in identical stratigraphic levels of a sediment c

a 1052 year tree ring proxy for alpine summer temperatures a june august alpine temperature proxy series is developed back to ad 951 using 1 527 ring width measurements from living trees and relict wood the reconstruction is composed of larch data from four alpine valleys in switzerland and pine data from the western austrian alps these regions are situated in high elevation alpine environments where a spatially homogenous summer temperature signal exists in an attempt to capture the full frequency range of summer temperatures over the past millennium from inter annual to multi centennial scales the regional curve standardization technique is applied to the ring width measurements correlations of 0 65 and 0 86 after decadal smoothing with high elevation meteorological stations since 1864 indicate an optimal response of the rcs chronology to june august mean temperatures the proxy record reveals warm conditions from before ad 1000 into the thirteenth century followed by a prolonged cool period reaching minimum values in the 1820s and a warming trend into the twentieth century this latter trend and the higher frequency variations compare well with the actual high elevation temperature record the new central alpine proxy suggests that summer temperatures during the last decade are unprecedented over the past millennium it also reveals significant similarities at inter decadal to multi centennial frequencies with large scale temperature reconstructions however deviating during certain periods from h h lamb s european north atlantic temperature history

lateglacial and holocene climate oscillations in the south western alps an attempt at quantitative reconstruction abstract the high topographic complexity of the alpine region is the origin of important climate differences that characterise the different areas of the alps these differences might have had a strong influence on vegetation and on migrations of human populations in the past based on an improved database containing about 3000 modern pollen samples the standard modern analogue technique has been applied to five pollen sequences from the subalpine belt of the south western italian alps laghi dell orgials 2240 m lago delle fate 2130 m torbiera del biecai 1920 m rifugio mondovi 1760 m pian marchisio 1624 m to provide quantitative climate estimates for the lateglacial and holocene periods consistent climate trends are reconstructed for the different sequences sites recorded in detail the climate variations when they were located at the limit of two ecotones sites above the tree line recorded lower temperature values and less important variations climate was cold and dry during the oldest and younger dryas and close to present day values during the bolling allerod interstadial at the beginning of the holocene climate changed to warmer and moister conditions a high number of climate fluctuations are recorded at several sites a climate optimum is recorded in the atlantic period which caused a development of fir above its present day altitudinal distribution climatic differences recorded at the various sites are discussed taking into account the limits of the method