insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

isotope calibrated greenland temperature record over marine isotope stage 3 and its relation to ch4 large temperature variations on millennial time scales in greenland characterised the last ice age abrupt warmings known as dansgaard oeschger do events can be traced in the 18oice record of greenland ice cores however it has been shown that 18oice is not a direct temperature proxy measurements of the isotopic composition of gases trapped in the ice can be used to calibrate the paleothermometer here we present a continuous temperature record based on high resolution 15n measurements and firn model studies it covers a sequence of 9 do events 9 17 during the time period from 38 to 64 kyr bp for which temperature changes of 8 to 15 c were estimated the difference between the modern and the glacial 18oice t relationship can be explained by a combination of source temperature changes and changes in the annual distribution of precipitation a detailed comparison of the temperature evolution with reconstructions of the atmospheric methane ch4 concentration shows that ch4 rises lag temperature increases at the onset of do events by 25 to 70 yr within data resolution the strong correlation between greenland temperature and ch4 on millennial and submillennial time scales suggests that variations on these time scales were probably of hemispheric extent

abrupt environmental oscillations during the early weichselian recorded at lago grande di monticchio southern italy abstract this study presents multi proxy data from a new core from lago grande di monticchio italy extending back to about 100 000 calendar years bp the time scale of this record is independent from deep sea and ice core chronologies and has been established from a combination of varve counts and high resolution sedimentation rate calculations based on microscopic sediment investigation this paper focuses on environmental variability between 100 000 and 65 000 calendar years bp several abrupt cold periods have been recognised and correlated to other terrestrial as well as to ice core and deep sea records the longest of the monticchio cold phases corresponds to marine isotopic stage 5b and lasted from ca 87 000 to 84 000 calendar years bp two shorter events about 1000 years long occurred during the transition from interstadial to full glacial conditions between 79 000 and 75 000 calendar years bp the increased frequency of cold events during this time interval probably indicates a higher degree of climatic instability in periods of major changes dating discrepancies between monticchio grip and deep sea chronologies range between a few hundred to a few thousand years however these differences in dating are not constant but vary significantly for different sections of the records nevertheless the good match of environmental fluctuations at monticchio with atmospheric variability at the greenland summit as well as variations in the oceanic circulation pattern suggests a close link of the mediterranean to the atlantic climate regime

testing theoretically predicted stalagmite growth rate with recent annually laminated samples implications for past stalagmite deposition annually laminated stalagmites deposited over the last 30 160 years are analysed to determine their growth rate three natural and artificial cave sites in england france and belgium were chosen for their wide range of variability in growth rate determining variables and multiple samples were taken from each site the annual nature of laminae deposition within the stalagmite calcite was confirmed by comparison to the date of cave void opening 14c analyses or by using dated event horizons measured stalagmite growth rate was determined from annual laminae thickness measurements and compared to that theoretically predicted from the chemical kinetics of the calcite precipitation reaction a good agreement is observed between empirical observations and theoretical predictions although two complicating factors variations in calcite porosity and seasonal cessation of the water supply to the samples both affect the growth rate implications for the extraction of palaeoclimate information from stalagmite growth rate are discussed

prediction of glossosoma biomass spatial distribution in valley creek by field measurements and a three dimensional turbulent open channel flow model the fluid flow environment associated with high glossosoma abundance is predicted by large eddy simulation of a natural turbulent open channel flow the spatial distribution of glossosoma was depicted by high resolution physical variables described by fluid flow and streambed topography variogram analysis of the streambed topography revealed a characteristic length scale of the streambed of the order 0 2 m over which bed roughness height was correlated flow simulation output was spatially and temporally averaged over the streambed characteristic length scale and linked to glossosoma spatial density a dimensionless scaling relationship between glossosoma spatial distribution and streamwise velocity averaged in the longitudinal and transverse direction spatial velocity fluctuation and spanwise vorticity from the computational fluid dynamics simulation output explained 79 of the variation in observed dimensionless glossosoma spatial density the analysis demonstrated that computational fluid mechanics and high resolution bed topography could be instrumental in predicting benthic macroinvertebrate spatial distribution in streams and rivers

rapid environmental changes in southern europe during the last glacial period oxygen isotope records from greenland ice cores1 2 indicate numerous rapid climate fluctuations during the last glacial period north atlantic marine sediment cores show comparable variability in sea surface temperature and the deposition of ice rafted debris3 4 5 in contrast very few continental records of this time period provide the temporal resolution and environmental sensitivity necessary to reveal the extent and effects of these environmental fluctuations on the continents here we present high resolution geochemical physical and pollen data from lake sediments in italy and from a mediterranean sediment core linked by a common tephrochronology our lacustrine sequence extends to the past 102 000 years many of its features correlate well with the greenland ice core records demonstrating that the closely coupled ocean atmosphere system of the northern hemisphere during the last glacial4 extended its influence at least as far as the central mediterranean region numerous vegetation changes were rapid frequently occurring in less than 200 years showing that the terrestrial biosphere participated fully in last glacial climate variability earlier than 65 000 years ago our record shows more climate fluctuations than are apparent in the greenland ice cores together the multi proxy data from the continental and marine records reveal differences in the seasonal character of climate during successive interstadials and provide a step towards determining the underlying mechanisms of the centennial millennial scale variability

controls on trace element sr mg compositions of carbonate cave waters implications for speleothem climatic records abstract at two caves clamouse s france and ernesto ne italy cave drip and pool waters were collected and sampled at intervals over a 2 3 year period mg ca and sr ca concentration ratios corrected for marine aerosols are compared with those of bedrocks and in some cases aqueous leachates of soils and weathered bedrocks cave waters do not lie along mixing lines between calcite and dolomite of bedrock carbonate but typically show enhanced and covarying mg ca and sr ca four factors are considered as controlling processes 1 the much faster dissolution rate of calcite than dolomite allows for the possibility of increase of mg ca if water rock contact times are increased during drier conditions a theoretical model is shown to be comparable to experimental leachates 2 prior calcite precipitation along a flow path is a powerful mechanism for generating enhanced and covarying mg ca and sr ca ratios this mechanism requires the solution to lose co 2 into pores or caverns 3 incongruent dolomite dissolution has only limited potential and is best regarded as two separate processes of dolomite dissolution and calcite precipitation 4 selective leaching of mg and sr with respect to ca is shown to be important in leachates from ernesto where it appears to be a phenomenon of calcite dissolution in general selective leaching can occur whenever ca is sequestered into precipitates due to freezing or drying of soils or if there is derivation of excess sr and mg from non carbonate species the ernesto cave has abundant water supply which in the main chamber is derived from a reservoir with year round constant p co 2 of around 10 2 4 and no evidence of calcite precipitation in the karst above the cave two distinct but overlying trends of enhanced and covarying mg ca and sr ca away from the locus of bedrock compositions are due to calcite precipitation within the cave and at a variable drip site due to enhanced selective leaching at slow drip rates mg enhancement in the first chamber is due to a more dolomitic bedrock and longer residence times the clamouse site has a less abundant water supply and presents geochemical evidence of prior calcite precipitation both in the cave and in overlying porous dolomite dedolomitized limestone bedrock initial p co 2 values as high as 10 1 are inferred experimental incubations of clamouse soils which generated enhanced p co 2 and precipitated caco 3 had compositions similar to the karst waters calcite precipitation is inferred to be enhanced in drier conditions hydrological controls on cave water chemistry imply that the trace element chemistry of speleothems may be interpretable in palaeohydrological terms drier conditions tends to promote not only longer mean residence times enhancing dolomite dissolution and hence mg ca but also enhances degassing and calcite precipitation leading to increased mg ca and sr ca

orbital and sub orbital scale climate impacts on vegetation of the western mediterranean basin over the last 48 000 yr article i nfo high resolution pollen analysis of alboran sea core md95 2043 provides a 48 ka continuous vegetation record that can be directly correlated with sea surface and deep water changes the reliability of this record is supported by comparison with that of padul sierra nevada spain marine isotope stage mis 3 was characterised by fluctuations in quercus forest cover in response to dansgaard oeschger climate variability mis 2 was characterised by the dominance of semi desert vegetation despite overall dry and cold conditions during mis 2 heinrich events hes 2 and 1 were distinguished from the last glacial maximum by more intensely arid conditions taxon specific vegetation responses to a tripartite climatic structure within the hes are observed in mis 1 the bolling allerod was marked by rapid afforestation while a re expansion of semi desert environments occurred during the younger dryas the maximum development of mixed quercus forest occurred between 11 7 and 5 4 cal ka bp with forest decline since 5 4 cal ka bp on orbital timescales a long term expansion of semi desert vegetation from mis 3 into mis 2 reflects global ice volume trends while holocene arboreal decline reflects summer insolation decrease the influence of precession on the amplitude of forest development and vegetation composition is also detected

phase relationships between millennial scale events 64 000 24 000 years ago a core recovered on the iberian margin off southern portugal can be correlated with greenland ice cores using oxygen isotope variability in planktonic foraminifera which closely matches the ice core records of temperature over greenland our age model identifies the base of every interstadial between 64 000 and 24 000 years ago and uses the greenland ice core project grip timescale the oxygen isotope signal in benthic foraminifera on this grip based timescale is quite different from the planktonic record and resembles the temperature record over antarctica when this is synchronized with greenland using the record of methane in the atmospheric air in the polar ice cores we interpret the benthic record as indicating significant fluctuations in ice volume during millennial events and we suggest that antarctic temperature changed as a function of ice volume

synchroneity between marine and terrestrial responses to millennial scale climatic variability during the last glacial period in the mediterranean region land sea climatic proxies have been obtained from the last glacial section of images core md95 2043 western mediterranean sea vegetation and alkenone derived sst curves indicate rapid 150 years and synchronous terrestrial and marine climatic changes paralleling the dansgaard oeschger d o climatic variability over greenland this frequency of climate change can be related to shifts between the two modes of operation of the north atlantic oscillation nao transfer functions applied to the pollen data indicate that there was an amplification of the climatic signal during heinrich events hes in comparison with other d o stadials the development and persistence of both scandinavian and atlantic mobile polar highs over southwestern europe may explain the extreme cooling 10 c and dryness 400 mm during heinrich events 5 and 4 in the mediterranean region comparison of the results of core md95 2043 with similar climatic data from images core md95 2042 located off portugal indicates that thermal and precipitation gradients occurred between the mediterranean and the atlantic sides of iberia within hes hes 4 and 5 are associated with more humid conditions in the atlantic by 200 mm than in the mediterranean site as is the case at the present time this comparison also illustrates the different behaviour of these areas during the d o stadials in contrast with the mediterranean site the atlantic site shows similar precipitation and temperature drops for all the d o stadials including those related to the hes here we propose the operation of different mobile polar highs mph as the driving mechanism for this difference in behaviour between the atlantic and mediterranean sides of iberia hes are related to a stronger influence of the scandinavian mph forcing a severe aridification and cooling of the full iberian peninsula the atlantic mph may have been dominant during the other stadials which would preferentially affect southwestern iberia

sensitivity of a greenland ice sheet model to ice flow and ablation parameters consequences for the evolution through the last climatic cycle sensitivity experiments are conducted to test the influence of poorly known model parameters on the simulation of the greenland ice sheet by means of a three dimensional numerical model including the mechanical and thermal processes within the ice two types of experiments are performed steady state climatic conditions and simulations over the last climatic cycle with a climatic forcing derived from the grip record the experiments show that the maximum altitude of the ice sheet depends on the ice flow parameters deformation and sliding law coefficients geothermal flux and that it is low when the ice flow is fast on the other hand the maximum altitude is not sensitive to the ablation strength and consequently during the climatic cycle it is driven by changes in accumulation rate the ice sheet extension shows the opposite sensitivity it is barely affected by ice flow velocity and the ice covered area is smaller for large ablation coefficients for colder climates when there is no ablation the ice sheet extension depends on the sea level an interesting result is that the variations with time of the altitude at the ice divide summit do not depend on the parameters we tested the present modelled ice sheets resulting from the climatic cycle experiments are compared with the present measured ice sheet in order to find the set of parameters that gives the best fit between modelled and measured geometry it seems that compared to the parameter set most commonly used higher ablation rate coefficents must be used

high resolution record of northern hemisphere climate extending into the last interglacial period high resolution record of northern hemisphere climate extending into the last interglacial period

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

new constraints on the timing of sea level fluctuations during early to middle marine isotope stage 3 1 to settle debate on the timing of sea level fluctuations during marine isotope stage mis 3 we present records of 18oruber sea level proxy and magnetic susceptibility from the same samples within the single sediment archive i e coregistered of central red sea core geotu kl11 core scanning x ray fluorescence and environmental magnetic data establish the suitability of magnetic susceptibility as a proxy for eolian dust content in red sea sediments the eolian dust data record similar variability as greenland 18oice during early to middle mis 3 in agreement with previous observations that regional arabian sea climate fluctuated with a timing similar to that of greenland climate variations in contrast the sea level record fluctuates with a timing similar to that of antarctic style climate variations the coregistered nature of the two records in core kl11 unambiguously reveals a distinct offset in the phase relationship between sea level and eolian dust fluctuations the results confirm that sea level rises indicated by shifts in red sea 18oruber to lighter values occurred during cold episodes in greenland during early to middle mis 3 this indicates that the amplitudes of the reconstructed mis 3 sea level fluctuations would not be reduced by inclusion of regional climate fluctuations in the red sea sea level method our analysis comprehensively supports our earlier conclusions of large amplitude sea level variations during mis 3 with a timing that is strongly similar to antarctic style climate variations

glacial abrupt climate changes and dansgaard oeschger oscillations in a coupled climate model 1 there are three fundamental features which characterize large glacial millennial dansgaard oeschger oscillations 1 the climatic transitions were abrupt and large 2 the lengths of both interstadials and stadials and the period of dansgaard oeschger oscillations were not uniform and 3 there were no large millennial oscillations during an early stage of a glacial period and a peak glacial period in this modeling study we offer a consistent explanation for these three features by employing an earth system model of intermediate complexity we demonstrate that a moderate global cooling forces the atlantic meridional overturning circulation moc into an unstable state and hence causes the flip flop of the atlantic moc between a strong mode and a weak mode the durations of both interstadials and stadials associated with these millennial oscillations are modulated by the changing background climate in qualitative agreement with the observations in a warm climate the atlantic moc is strong and stable with the deep water formed mainly by intense heat loss to the atmosphere in a cold climate the atlantic moc is weak and stable and this mode is largely maintained by the process of sea ice brine rejection since the dansgaard oeschger oscillations result from an alternation between these two moc states during an intermediate phase climate we conclude that brine rejection plays a necessary role in the oscillations confirming a hypothesis suggested in some proxy data studies

the climate in western europe during the last glacial interglacial cycle derived from pollen and insect remains using the pollen sequence of la grande pile xx france we review problems with the application of transfer functions in paleoclimatic reconstructions one of them is to find modern analogues for the herbaceous vegetation of the cold periods we propose a method to distinguish between steppes and tundra vegetations for which the moderns are only partial analogues of the glacial periods another method to solve these problems is based on constraining by insect remains the two methods provide coherent reconstructions the results are also compared with other paleodata there is a good correlation with the six cold heinrich events between 70 and 15 ka b p a cooling event during the eemian period marked by high percentages of taxas at about 125 ka b p needs still to be correlated with high resolution ocean and ice cores

h4 abrupt event and late neanderthal presence in iberia heinrich event 4 h4 is well documented in the north atlantic ocean and the adjacent continents as a cooling event 39 000 yr before present bp to quantify the impact of this event with respect to climate and vegetation over the iberian peninsula we perform numerical experiments using a high resolution general circulation model forced by sea surface temperatures before and during h4 our model simulates an expansion of aridity over the peninsula during h4 a desertification of the south and a replacement of arboreal by herbaceous plants in the north all of which are in agreement with contemporaneous pollen sequences from marine cores located off the iberian peninsula our simulations demonstrate that the h4 marine event imprinted drastic changes over southern iberia which would not have favoured its occupation by anatomically modern humans therefore providing a plausible explanation for the delayed extinction of neanderthals in this region inferred from the archaeological record

contrasting intrainterstadial climatic evolution between high and middle north atlantic latitudes a close up of greenland interstadials 8 and 12 1 three highly resolved pollen and sea surface temperature records from the iberian margin 36 42 n reveal the local evolution of vegetation and climate associated with the rapid climatic variability of marine isotope stage 3 the comparison of the climate at these midlatitudes with d and d excess from greenland ice cores shows that the north south climatic gradient underwent strong variations during the long greenland interstadials gis 8 and 12 after the northern hemispheric rapid warming at the greenland stadial gs gi transition the trend during the first part of the gi is a greenland cooling and an iberian warming this increase of the north atlantic climatic gradient led to moisture transportation to greenland from midlatitudes lightest d excess and to a drying episode in iberia the subsequent temperature decrease in greenland and iberia associated with the precipitation increase in the latter region occurred when the major source of greenland precipitation shifted to lower latitudes d excess increase

isotopic characterization of rapid climatic events during ois3 and ois4 in villars cave stalagmites sw france and correlation with atlantic and mediterranean pollen records abstract we present a new mid latitude speleothem record of millennial scale climatic variability during ois3 from the villars cave that combined with former published contemporaneous samples from the same cave gives a coherent image of the climate variability in sw france between 55 ka and 30 ka the 0 82 m long stalagmite vil stm27 was dated with 26 tims u th analyses and its growth curve displays variations that are linked with the stable isotopes both controlled by the climatic conditions it consists in a higher resolved replicate of the previously published vil stm9 and vil stm14 stalagmites where dansgaard oeschger do events have been observed the good consistency between these three stalagmites and the comparison with other palaoeclimatic reconstructions especially high resolution pollen records odp 976 from the alboran sea monticchio lake record from southern italy and the nearby md04 2845 atlantic ocean record permits to draw a specific climatic pattern in sw france during the ois3 and to see regional differences between these sites main features of this period are 1 warm events corresponding to greenland interstadials gis that are characterized by low speleothem 13 c high temperate pollen percentages warm temperatures and high humidity among these events gis 12 is the most pronounced one at villars characterized by an abrupt onset at 46 6 ka and a duration of about 2 5 ka the other well individualized warm event coincides with gis 8 which is however much less pronounced and occurred during a cooler period as shown by a lower growth rate and a higher 13 c 2 cold events corresponding to greenland stadials gs that are clearly characterized by high speleothem 13 c low temperate pollen abundance low temperature and enhanced dryness particularly well expressed during gs coinciding with heinrich events h5 and h4 the main feature of the villars record is a general cooling trend between the do 12 event 45 5 ka and the synchronous stop of the three stalagmites at 30 ka 1 with a first well marked climatic threshold at 41 ka after which the growth rate and the diameter of all stalagmites slows down significantly this climatic evolution differs from that shown at southern mediterranean sites where this trend is not observed the 30 ka age marks the second climatic threshold after which low temperatures and low rainfalls prevent speleothem growth in the villars area until the lateglacial warming that occurred at 16 5 0 5 ka this 15 ka long hiatus as the older villars growth hiatus that occurred between 67 4 and 61 ka are linked to low sea levels reduced ocean circulation and a southward shift of the polar front that likely provoked local permafrost formation these cold periods coincide with both low summer 65 n insolation low atmospheric co 2 concentration and large ice sheets development especially the fennoscandian

a minimum thermodynamic model for the bipolar seesaw 1 the simplest possible model is proposed to explain a large fraction of the millennial climate variability measured in the isotopic composition of antarctic ice cores the model results from the classic bipolar seesaw by coupling it to a heat reservoir in this thermal bipolar seesaw the heat reservoir convolves northern time signals with a characteristic timescale applying the model to the data of grip and byrd we demonstrate that maximum correlation can be obtained using a timescale of about 1000 1500 years higher correlations are obtained by first filtering out the long term variability which is due to astronomical and greenhouse gas forcing and not part of the thermal bipolar seesaw the model resolves the apparent confusion whether northern and southern climate records are in or out of phase synchronous or time lagged

irregular glacial interstadials recorded in a new greenland ice core the greenland ice sheet offers the most favourable conditions in the northern hemisphere for obtaining high resolution continuous time series of climate related parameters profiles of 18o 16o ratio along three previous deep greenland ice cores1 3 seemed to reveal irregular but well defined episodes of relatively mild climate conditions interstadials during the mid and late parts of the last glaciation but there has been some doubt as to whether the shifts in oxygen isotope ratio were genuine representations of changes in climate rather than artefacts due to disturbed stratification here we present results from a new deep ice core drilled at the summit of the greenland ice sheet where the depositional environ ment and the flow pattern of the ice are close to ideal for core recovery and analysis the results reproduce the previous findings to such a degree that the existence of the interstadial episodes can no longer be in doubt according to a preliminary timescale based on stratigraphic studies the interstadials lasted from 500 to 2 000 years and their irregular occurrence suggests complexity in the behaviour of the north atlantic ocean circulation

quantitative interpretation of fossil pollen spectra dissimilarity coefficients and the method of modern analogs abstract dissimilarity coefficients measure the difference between multivariate samples and provide a quantitative aid to the identification of modern analogs for fossil pollen samples how eight coefficients responded to differences among modern pollen samples from eastern north america was tested these coefficients represent three different classes 1 unweighted coefficients that are most strongly influenced by large valued pollen types 2 equal weight coefficients that weight all pollen types equally but can be too sensitive to variations among rare types and 3 signal0to noise coefficients that are intermediate in their weighting of pollen types the studies with modern pollen allowed definition of critical values for each coefficient which when not exceeded indicate that two pollen samples originate from the same vegetation region dissimilarity coefficients were used to compare modern and fossil pollen samples and modern samples so similar to fossil samples were found that most of three late quaternary pollen diagrams could be reconstructed by substituting modern samples for fossil samples when the coefficients indicated that the fossil spectra had no modern analogs then the reconstructed diagrams did not match all aspects of the originals no modern analogs existed for samples from before 9300 yr b p at kirchner marsh minnesota and from before 11 000 yr b p at wintergreen lake michigan but modern analogs existed for almost all holocene samples from these two sites and brandreth bog new york

connection between south mediterranean climate and north african atmospheric circulation during the last 50 000 yr bp north atlantic cold events abstract high resolution clay mineralogical analyses were performed on sediment deposited during the last 50 000 yr in the alboran sea odp site 976 the clay mineral record is compared with pollen assemblages and with annual precipitation pann and mean temperatures of the coldest month mtco reconstructed with the modern analog technique mat enhanced contribution of palygorskite a typical wind blown clay mineral characterizes the north atlantic cold climatic events coeval development of the semi arid vegetation artemisia rich associated with a drastic fall of reconstructed precipitations and temperatures suggest cold and arid continental conditions in the west mediterranean area during north atlantic cold events the clay mineral association especially the palygorskite content and the illite to kaolinite ratio indicate western morocco as one of the major source of the clay size fraction during the north atlantic cold events the maximum abundance of artemisia associated with the presence of argania pollen both indicate morocco as the main origin for pollen during these cold periods the comparison of these pollen and clay mineral specific features allows us to pinpoint western morocco as the dominant source of wind blown particles during north atlantic cold events these specific mineralogical composition and palynological assemblages reveal enhanced aridity over north africa and intensification of winds favouring dust erosion and transport from north africa toward the alboran sea during the north atlantic cold events according to atmospheric models such a meridian transport 1 likely results from the development of strong and stable anticyclonic conditions over the tropical atlantic and north africa similar to today s summer meteorological configuration and 2 implies a northward position of the westerly winds during north atlantic cold events finally the synoptic situation over the west mediterranean during the north atlantic cold events is compared with the north atlantic oscillation nao suggesting that during the cold atlantic events weather regimes over europe and north africa may have been systematically shifted towards a positive nao situation

from blunt to cutting distinguishing alternating method flakes in early stages on rounded blanks abstract two main knapping strategies can be used to start bifacial reduction on a lithic cobble or nodule the alternate strategy in which first one face is knapped and then the other and the alternating strategy in which both faces are removed in the same sequence interspersing core about turns between strikes flaking reduction of spherical and elliptical blanks cobbles or nodules is a common knapping process documented in many archaeological records rounded and thick edges require different fracture parameters and give rise to constraints in terms of viable knapping methods when analysing abandoned cores it is only possible to see the last strikes so it is important to know how they were shaped or exploited in the earlier knapping stages in order to understand the entire reduction process as cortical flakes are the direct evidence of the first reduction phases we undertook an experimental programme for the purpose of comparing the first flakes generated using the alternate and alternating knapping strategies we have focused our efforts on identifying and diagnosing distinctive features produced by each strategy in the first or cortical flakes our study indicates that several platform attributes can be considered as diagnostic features to differentiate between the alternate and alternating knapping strategies and that this kind of analysis can be translated to archaeological assemblages

mediterranean vegetation lake levels and palaeoclimate at the last glacial maximum the apparent conflict between pollen evidence for widespread artemisia steppe1 6 implying semi arid conditions and geomorphological evidence for high lake levels4 7 11 has produced controversy about the ice age palaeoclimate of the mediterranean region here we use a water balance model12 to predict catchment runoff and a biome model13 to predict vegetation type to reconstruct the palaeoenvironment around lake loannina a type locality for the northern mediterranean region we show that both sets of evidence are compatible with a summer dry winter wet regime with seasonal temperature anomalies similar to those predicted by atmospheric model simulations of the last glacial maximum14 18 the drying effect of the cold north atlantic ocean may have been counteracted in winter by increased storm frequency under a southward shifted jet stream as shown by several atmospheric models16 18

climatic changes in eurasia and africa at the last glacial maximum and mid holocene reconstruction from pollen data using inverse vegetation modelling in order to improve the reliability of climate reconstruction especially the climatologies outside the modern observed climate space an improved inverse vegetation model using a recent version of biome4 has been designed to quantitatively reconstruct past climates based on pollen biome scores from the biome6000 project the method has been validated with surface pollen spectra from eurasia and africa and applied to palaeoclimate reconstruction at 6 cal ka bp calendar years the climate was generally wetter than today in southern europe and northern africa especially in the summer winter temperatures were higher 1 5 c than present in southern scandinavia northeastern europe and southern africa but cooler in southern eurasia and in tropical africa especially in mediterranean regions summer temperatures were generally higher than today in most of eurasia and africa with a significant warming from 3 to 5 c over northwestern and southern europe southern africa and eastern africa in contrast summers were 1 3 c cooler than present in the mediterranean lowlands and in a band from the eastern black sea to siberia at 21 cal ka bp a marked hydrological change can be seen in the tropical zone where annual precipitation was 200 1 000 mm year lower than today in equatorial east africa compared to the present a robust inverse relationship is shown between precipitation change and elevation in africa this relationship indicates that precipitation likely had an important role in controlling equilibrium line altitudes ela changes in the tropics during the lgm period in eurasia hydrological decreases follow a longitudinal gradient from europe to siberia winter temperatures were 10 17 c lower than today in eurasia with a more significant decrease in northern regions in africa winter temperature was 10 15 c lower than present in the south while it was only reduced by 0 3 c in the tropical zone comparison of palaeoclimate reconstructions using lgm and modern co2 concentrations reveals that the effect of co2 on pollen based lgm reconstructions differs by vegetation type reconstructions for pollen sites in steppic vegetation in europe show warmer winter temperatures under lgm co2 concentrations than under modern concentrations and reconstructions for sites in xerophytic woods scrub in tropical high altitude regions of africa are wetter for lgm co2 concentrations than for modern concentrations because our reconstructions account for decreased plant water use efficiency

the technology and significance of the acheulian giant cores of gesher benot ya aqov israel abstract the presence of very large lithic artifacts at the acheulian site of gesher benot ya aqov is one of the site s most distinctive and enlightening features basalt giant cores and their products modified by a variety of core methods and found in association with different hominin activities occur throughout the stratigraphic sequence of the site in this paper we describe the giant artifacts of gesher benot ya aqov together with their reduction sequence from the nature and acquisition of the raw material through the shaping of the cores to the discarded cores and their typical waste products we then discuss the significance of these finds and their implications for understanding the site and its varied activities as well as for acheulian cognitive abilities and behavior during the early middle pleistocene on the margins of the paleo lake hula

what attributes are important for the measurement of assemblage reduction intensity results from an experimental stone artefact assemblage with relevance to the hoabinhian of mainland southeast asia abstract our understanding of variation in the technology of flaked stone artefacts from mainland southeast asia during the terminal pleistocene and holocene periods has improved little since they were originally labelled hoabinhian in 1932 chronological and geographical variation has been described in terms of typological differences but there are few anthropological explanations of lithic diversity and change an analysis of an experimentally produced hoabinhian assemblage is undertaken here to show which flake variables are significant indicators of assemblage reduction intensity the results show that recording the presence of overhang removal interior platform angle and percentage of dorsal cortex will provide robust data on the extent of assemblage reduction a new method for detecting assemblage variation based on the location of dorsal cortex on flakes is also presented and experimentally verified these methods are designed to take advantage of the typical geometry and reduction patterns of hoabinhian assemblages these findings provide another tool to build anthropological explanations of hoabinhian archaeology

the world s oldest stone artefacts from gona ethiopia their implications for understanding stone technology and patterns of human evolution between 2 6 1 5 million years ago the systematic archaeological and geological survey and excavations at gona between 1992 1994 led to the discovery of well flaked stone artefacts which are currently the oldest known from anywhere in the world more than 3000 surface and excavated artefacts were recovered at 15 localities documented east and west of the kada gona river based on radioisotopic dating 40 ar 39 ar and magnetostratigraphy the artefacts are dated between 2 6 2 5 million years ago ma eg10 and eg12 from east gona are the most informative with the highest density providing the best opportunity for characterizing the oldest assemblages and for understanding the stone working capability of the earliest tool makers slightly younger artefact occurrences dated to 2 4 2 3 ma are known from hadar and omo in ethiopia and from lokalalei in kenya cut marked bones dated to 2 5 ma from bouri in ethiopia are now providing important clues on the function of these artefacts in addition australopithecus garhi known from contemporary deposits at bouri may be the best candidate responsible for the oldest artefacts surprisingly the makers of the gona artefacts had a sophisticated understanding of stone fracture mechanics and control similar to what is observed for oldowan assemblages dated between 2 0 1 5 ma this observation was corroborated by the recent archaeological discoveries made at lokalalei because of the similarities seen in the techniques of artefact manufacture during the late pliocene early pleistocene it is argued here that the stone assemblages dated between 2 6 1 5 ma group into the oldowan industry the similarity and simplicity of the artefacts from this time interval suggests a technological stasis in the oldowan 2000 academic press

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

evidence for general instability of past climate from a 250 kyr ice core record recent results1 2 from two ice cores drilled in central greenland have revealed large abrupt climate changes of at least regional extent during the late stages of the last glaciation suggesting that climate in the north atlantic region is able to reorganize itself rapidly perhaps even within a few decades here we present a detailed stable isotope record for the full length of the greenland ice core project summit ice core extending over the past 250 kyr according to a calculated timescale we find that climate instability was not confined to the last glaciation but appears also to have been marked during the last interglacial as explored more fully in a companion paper3 and during the previous saale holstein glacial cycle this is in contrast with the extreme stability of the holocene suggesting that recent climate stability may be the exception rather than the rule the last interglacial seems to have lasted longer than is implied by the deep sea specmap record4 in agreement with other land based observations5 6 we suggest that climate instability in the early part of the last interglacial may have delayed the melting of the saalean ice sheets in america and eurasia perhaps accounting for this discrepancy

examining stage and continuum models of flake debris analysis an experimental approach abstract flake debris produced from a number of flintknapping experiments is used to explore stage and continuum models of lithic reduction using metric attributes flakes produced during core reduction are separated from those produced during tool production theoretically this should allow the utilization of continuum approaches in the analysis of archaeological assemblages that represent a mix of reduction strategies i e core reduction and tool production further continuum based analyses are refined by providing a standardized scale although this work demonstrates the potential utility of a continuum based model for analysing archaeological lithic assemblages stage analyses retain utility and can be fruitfully used in conjunction with the refined continuum model developed here

oldowan reduction sequences methodological considerations abstract transport of resources is a major feature of oldowan hominin technological adaptations comparisons between different oldowan localities often employ measures of transport that are based on artefact attributes as proxies for the intensity of raw material utilization the technological flake category system toth n 1985 oldowan reassessed a close look at early stone artifacts journal of archaeological science 12 pp 101 120 has been used extensively to infer the relative intensity of lithic reduction within oldowan assemblages here we use a large experimental sample to test the relationship between a flake s stage in a reduction sequence and various quantitative attributes we demonstrate how many previously described attributes are affected by initial core size we then develop a multiple linear regression model that incorporates several variables to predict the placement of a flake within a generalized reduction sequence the model is then applied to oldowan assemblages in the koobi fora formation which explores the strengths and weaknesses of different methods of investigating reduction intensity on an assemblage level

european climatic response to millennial scale changes in the atmosphere ocean system during the last glacial period abstract pollen foraminifer dinocyst and coarse lithic high resolution analyses and 18 o measurements have been carried out for the last glacial section of marine core md95 2042 located near the southwestern margin of the iberian peninsula the pollen data indicate a high frequency of vegetational changes on the adjacent continent during this period suggesting a climatic variability very similar to that of the dansgaard oeschger cycles recorded by the greenland ice cores the detailed direct correlation of the terrestrial and marine proxy data from core md95 2042 indicates a three phase pattern of heinrich events in land and ocean environments the first and last phases of the h5 and h4 events are characterized by a mild and humid climate in southwestern europe probably associated with the european origin of the ice rafted detritus the middle phase exhibits a cold and dry climate in iberia linked with the maximum input of ice rafted detritus this phase seems to correspond with the laurentide ice sheet surges between the heinrich events several cold and dry periods on land are correlated with stades of the dansgaard oeschger cycles the impact of the dansgaard oeschger stades in southwestern europe seems to be preferentially connected to the cold winter air masses reaching this mid latitude region

constraints on the duration and freshwater release of heinrich event 4 through isotope modelling heinrich events1 abrupt climate cooling events due to ice sheet instability that occurred during the last glacial period are recorded in sediment cores throughout the north atlantic ocean2 3 modelling studies have described likely physical mechanisms4 5 6 for these events but the quantitative characteristics of heinrich events are less well known here we use a climate model of intermediate complexity7 that explicitly calculates the distribution of oxygen isotopes in the oceans to simulate heinrich event 4 at about 40 000 yr ago we compare an ensemble of scenarios for this heinrich event with oxygen isotope data measured in foraminiferal calcite of a comprehensive set of sediment cores8 9 from this comparison we obtain a duration of 250 150 yr and an ice release of 2 1 m sea level equivalent for heinrich event 4 significantly reducing the uncertainties in both values compared to earlier estimates5 10 11 12 13 14 of up to 2 000 yr and 15 m of sea level equivalent ice release respectively our results indicate that the consequences of heinrich events may have been less severe than previously assumed at least with respect to greenland climate and sea level