reconstructing high resolution climate using ct scanning of unsectioned stalagmites a case study identifying the mid holocene onset of the mediterranean climate in southern iberia the forcing mechanisms responsible for the mid holocene onset of the mediterranean type climate in south western europe are currently unclear but understanding these is critical for accurate climate projections under future greenhouse gas warming additionally regional studies that present conflicting patterns for the onset and advancement of mediterranean climatic conditions complicate definitively ascribing causality here we use a new high resolution stalagmite density record obtained non destructively using computed tomography ct scanning to reconstruct southern iberian climate between 9 3 and 2 9 ka bp we suggest that stalagmite density can be used as a water excess proxy with lower densities associated with more variable drip rates possibly reflecting increased seasonality consistent with expectations from previous studies of speleothem textures and crystal fabrics our results reveal an early holocene humid interval and mid holocene year round aridity that preceded the onset of mediterranean climate at 5 3 ka bp in southern iberia using this new dataset combined with previously published results we link the gradual advancement of the mediterranean climate to the southward migration of the north atlantic subtropical high induced by an orbitally driven decrease in northern hemisphere insolation future anthropogenic warming could result in a reversal of this trend a northward migration of the north atlantic subtropical high and a return to year round aridity in south western europe

regulation of the monsoon climate by two different orbital rhythms and forcing mechanisms the east asian monsoon is responsible for transferring huge amounts of heat and moisture between the land and the adjacent ocean significant changes in its capacity to do this will have direct impacts on regional climatic gradients and global atmospheric circulation determining the mechanisms that force long term variation in monsoon behavior is therefore important for understanding global climate change competing theories vary in the degree of importance attached to glacial forcing other orbital rhythms and internal feedback mechanisms as primary drivers of change there is however no convincing explanation as to why different proxy records from closely neighboring regions are tuned to different orbital rhythms here we present quantitative climatic reconstructions for the past 450 k y based on a long pollen record from lake biwa in japan the data suggest that continental and oceanic air mass temperatures respond predominantly to the 100 k y orbital rhythm whereas the land ocean temperature gradient and monsoon vigor oscillate mainly at the 23 k y insolation cycle we suggest that the mechanisms for this behavior lie in the differential response of land and ocean to solar forcing and conclude that the 100 k y signal dominates monsoon intensity only when the amplitude of solar forcing falls below a threshold level

middle bronze age humidity and temperature variations and societal changes in east central europe abstract archaeological evidence points to substantial changes in bronze age societies in the european mediterranean region isotope geochemical proxies have been compiled to provide independent ancillary data to improve the paleoenvironmental history for the period of interest and support the interpretation of the archaeological observations in addition to published compositions in this study we gathered new h isotope data from fluid inclusion hosted water from a stalagmite of the trio cave southern hungary and compared the h isotope data with existing stable isotope and trace element compositions reported for the stalagmite additionally animal bones and freshwater bivalve shells unio sp were collected from bronze age archaeological excavations around lake balaton and their stable c and o isotope compositions were measured in order to investigate climate changes and lake evolution processes during this period the data indicate warm and humid conditions with elevated summer precipitation around 3 7 cal ka bp before present where present is 1950 ce followed by a short term deterioration in environmental conditions at about 3 5 cal ka bp the environment became humid and cold with winter precipitation dominance around 3 5 to 3 4 cal ka bp then gradually changed to drier conditions at 3 2 cal ka bp significant cultural changes have been inferred for this period on the basis of observations during archaeological excavations the most straightforward consequences of environmental variations have been found in changes of settlement structure the paleoclimatological picture is well in line with other east central european climate records indicating that the climate fluctuations took place on a regional scale

the rhone glacier was smaller than today for most of the holocene we present the development and application of the novel in situ cosmogenic 14 c 10 be chronometer to recently exposed proglacial bedrock of the rhone glacier switzerland results show that during the holocene the glacier was smaller than today for 6500 2000 yr and larger than today for 4500 2000 yr this pattern is consistent with limited data from other techniques for glaciers in the alps and scandinavia but in contrast to glaciers from the southern alps of new zealand emphasizing the high sensitivity of large mountain glaciers to small climate changes the 14 c 10 be chronometer also shows that abrasion rates beneath the rhone glacier increased with ice speed

chironomids can be reliable proxies for holocene temperatures a comment on velle et al 2010 velle et al 2010 discussed discrepancies between scandinavian holocene chironomid inferred temperature estimates which they attribute to the response of chironomids to environmental variables other than temperature and to taxonomic shortcomings they suggest ways in which the reliability of chironomid based paleotemperature reconstructions could be improved by taking into account ecological complexity while we agree with many of their recommendations based on the results of other work we think their paper is unnecessarily pessimistic regarding the ability of existing chironomid based temperature inference models to provide reliable estimates of past temperature we offer a critique of the main points discussed by velle et al 2010 and provide evidence that chironomid based temperature inference models can reliably reconstruct mean july air temperature in the lateglacial and holocene over millennial and centennial timescales

holocene warming in western continental eurasia driven by glacial retreat and greenhouse forcing the global temperature evolution during the holocene is poorly known whereas proxy data suggest that warm conditions prevailed in the early to mid holocene with subsequent cooling model reconstructions show long term warming associated with ice sheet retreat and rising greenhouse gas concentrations one reason for this contradiction could be the under representation of indicators for winter climate in current global proxy reconstructions here we present records of carbon and oxygen isotopes from two u th dated stalagmites from kinderlinskaya cave in the southern ural mountains that document warming during the winter season from 11 700 years ago to the present our data are in line with the global holocene temperature evolution reconstructed from transient model simulations we interpret eurasian winter warming during the holocene as a response to the retreat of northern hemisphere ice sheets until about 7 000 years ago and to rising atmospheric greenhouse gas concentrations and winter insolation thereafter we attribute negative 18o anomalies 11 000 and 8 200 years ago to enhanced meltwater forcing of north atlantic ocean circulation and a rapid decline of 13c during the early holocene with stabilization after about 10 000 years ago to afforestation at our study site we conclude that winter climate dynamics dominated holocene temperature evolution in the continental interior of eurasia in contrast to regions more proximal to the ocean models and proxy data diverge on the global temperature evolution of the holocene perhaps due to representation of the seasons isotopic analyses of stalagmites from the ural mountains suggest that winter climate dominated in the eurasian interior

orbitally driven insolation forcing on holocene climate trends evidence from alkenone data and climate modeling a global spatial pattern of long term sea surface temperature sst trends over the last 7000 years is explored using a comparison of alkenone derived sst records with transient ensemble climate simulations with a coupled atmosphere ocean circulation model under orbitally driven insolation forcing the spatial trend pattern both in paleo sst data and in model results shows pronounced global heterogeneity generally the extratropics cooled while the tropics experienced a warming during the middle to late holocene we attribute these divergent holocene climate trends to seasonally opposing insolation changes furthermore climate mode changes similar to the arctic north atlantic oscillation are superimposed on the prevalent pattern it is concluded that nonlinear changes in the entire seasonal cycle of insolation played a dominant role for the temporal evolution of holocene surface temperatures for understanding of marine proxy data apart from the dominance of summer insolation in high latitudes a notable shift in the maximum insolation of the year in low latitudes has to be taken into account which may influence timing of phytoplankton production and thus alters the seasonal origin of temperature signals recorded in the proxies

a mid european decadal isotope climate record from 15 500 to 5000 years b p oxygen isotope ratios of precipitation delta18op inferred from deep lake ostracods from the ammersee southern germany provide a climate record with decadal resolution the record in detail shows many of the rapid climate shifts seen in central greenland ice cores between 15 000 and 5000 years before the present b p negative excursions in the estimated delta18op from both of these records likely reflect short weakenings of the thermohaline circulation caused by episodic discharges of continental freshwater into the north atlantic deviating millennial scale trends however indicate that climate gradients between europe and greenland changed systematically reflecting a gradual rearrangement of north atlantic circulation during deglaciation

pollen based continental climate reconstructions at 6 and 21 ka a global synthesis subfossil pollen and plant macrofossil data derived from 14c dated sediment profiles can provide quantitative information on glacial and interglacial climates the data allow climate variables related to growing season warmth winter cold and plant available moisture to be reconstructed continental scale reconstructions have been made for the mid holocene mh around 6 ka and last glacial maximum lgm around 21 ka allowing comparison with palaeoclimate simulations currently being carried out as part of the fifth assessment report ar5 of the intergovernmental panel on climate change the synthesis of the available mh and lgm climate reconstructions and their uncertainties obtained using modern analogue regression and model inversion techniques is presented for four temperature variables and two moisture variables reconstructions of the same variables based on surface pollen assemblages are shown to be accurate and unbiased reconstructed lgm and mh climate anomaly patterns are coherent consistent between variables and robust with respect to the choice of technique they support a conceptual model of the controls of late quaternary climate change whereby the first order effects of orbital variations and greenhouse forcing on the seasonal cycle of temperature are predictably modified by responses of the atmospheric circulation and surface energy balance

climatic reconstruction in europe for 18 000 yr b p from pollen data an improved concept of the best analogs method is used to reconstruct the climate of the last glacial maximum from pollen data in europe in order to deal with the lack of perfect analogs of fossil assemblages and therefore to obtain a more accurate climate reconstruction we used a combination of pollen types grouped according to plant phenology and present climate constraints rather than pollen percentages for each individual taxon the distribution of pollen taxa into plant functional types pfts is aimed to reflect the vegetation in terms of biomes which have a wider distribution than a species the climatic variables are then calibrated on these pfts using an artificial neural network technique the use of pfts allowed us to deal with situations where pollen assemblages have only partial modern analogs the method is applied to the glacial steppic vegetation in europe using 15 pollen records north of the pyrenees alps line the reconstructed temperatures were lower than today 30 10 degrees c for the temperature of the coldest month t c and 12 3 degrees c far the annual mean t ann south of that line t c and t ann anomalies were respectively 15 5 degrees c and 10 5 degrees c the available moisture index and annual precipitation were also lower than present 60 20 north of mediterranean sea 800 100 mm for precipitation in italy and greece the available moisture was 20 lower with a precipitation anomaly of ca 600 200 mm southward the moisture index was close to that at present 20 and precipitation was lower 300 300 mm c 1998 university of washington

beginnings of olive cultivation in eastern spain in relation to holocene bioclimatic changes morphometric analyses show quantitative differences in anatomical characters of wood and charcoal between wild and cultivated olive samples from modern olive wood in eastern spain levante provide five distinctive anatomical criteria growth width ring vessel surface number of vessels per group vessel density and vulnerability ratio multivariate analysis shows that growth ring width and number of vessels per group are both significant criteria for discriminating between wild and cultivated olive moreover bioclimatic environments of wild olive thermomediterranean and mesomediterranean stages are distinguished by vessel density ancient olive charcoal from archaeological sites at valencia and alicante implies increasing aridification from the cardial neolithic to the roman period this pattern may reflect the onset of a mediterranean climate and human deforestation charcoal from cultivated specimens of early neolithic age shows that the olive tree is the earliest cultivated temperate fruit

the disturbance regime of an early holocene swamp forest in the czech republic as revealed by dendroecological pollen and macrofossil data abstract a unique remnant of forest dating back to the period 9733 7897 yr bc and consisting of hundreds of tree bases was discovered in the czech republic we aimed to reveal the complex disturbance history of this sub fossil forest using dendrochronology and to describe its detailed plant species composition changes using palaeobotanical techniques analysing such early holocene forest dynamics should help us understand the ability of the forest community to actively adapt to climate change and generally to understand the role of dynamic instability in ecosystem evolution we anatomically identified woody species in 488 samples and determined the ages growth suppressions releases and fire scars in 116 well preserved tree ring series using a modern boundary line approach this image of the forest structure and dynamics was supplemented with analyses of pollen spectra and plant macrofossils in excavated profiles in order to achieve accurate dating we dated 87 samples using 14c and synchronized tree ring series and compared them with an existing pinus sylvestris chronology the developmental trajectory of the forest was unique and did not match the general trend of postglacial pine growth in central europe palaeobotanical proxies indicated that during the circa 2000 years the forest persisted this early holocene ecosystem passed through several phases reflected in the species composition of the vegetation as well as in habitat conditions nevertheless the dominance of pine and the complex fine scale disturbance regime were relatively robust and did not change fundamentally low severity fires and short term changes in soil moisture regime were crucial disturbance agents in the ecosystem stand replacing disturbances were not found up to the gradual collapse of the forest around 8300 yr bc replaced by a swamp community the disturbance regime was relatively stable suggesting a mitigating effect of changing climate due to the predominance of pine in the forest

quantitative palaeotemperature records inferred from fossil pollen and chironomid assemblages from lake gilltjarnen northern central sweden palaeotemperature reconstructions based on radiocarbon dated fossil pollen and chironomid stratigraphies obtained from lake gilltjarnen provide evidence of climate changes during the last 11 000 years in the boreal zone of northern central sweden the records show consistent trends during the early and mid holocene indicating low temperatures at 11 000 10 000 cal yr bp followed by a rising trend and a period of maximum values from about 7000 to 4000 cal yr bp at 3000 cal yr bp the chironomid inferred temperature values rise abruptly deviating from the late holocene cooling trend indicated by the pollen based reconstruction and most of the other palaeotemperature records from central scandinavia probably as a result of local limnological changes in lake gilltjarnen and its catchment comparison of the present results with a lake level reconstruction from lake ljustjarnen ca 100 km southwest of lake gilltjarnen shows that the low early holocene temperatures were associated with high lake levels at 10 500 8500 cal yr bp whereas low lake levels and dry conditions prevailed during the period of high temperatures at between 7500 and 5000 cal yr bp probably due to high summer evapotranspiration and lower precipitation copyright 2006 john wiley sons ltd

holocene valley incision in the southern bukk foreland climate human environment interferences in northern hungary abstract prehistoric human settlement activities in northern hungary have been well studied for several decades recent studies from the great hungarian plain provide evidence of human impact starting as early as in the neolithic c 8200 cal bp archaeological records suggest that with establishment of the baden culture c 5500 cal bp settlements were moved from tisza river towards the northern mountainous area although quaternary landscape development of the bukk mountains is well studied holocene human environment interactions in particular have not been focused on so far here we present holocene landscape history around bogacs in the southern bukk mountain foreland sediment records were sampled from fans of secondary tributaries in the middle course of the hor valley morphology of the tributary valleys suggests different incision phases with older forms and less human impact in the northern part of the studied valley section type 1 and younger forms and stronger human impact in the southern part type 2 however 14c dates from the fan of a type 2 valley in the southern part suggest initial incision between 9000 and 8000 cal bp whereas human activity is not reflected in the sediments in the fan sediments of a type 1 tributary in the northern part of the studied valley section daub was found in the context of deposits dated to 3000 cal bp here thickness of holocene sediments suggest significant soil erosion it can be summarised that post pleistocene valley incision was restricted to short periods of extreme climate conditions during the early to mid holocene human activities did not contribute to initial valley incision nevertheless human activities seem to have enhanced soil erosion in the catchments of type 1 tributaries

exploring holocene continentality changes in fennoscandia using present and past tree distributions with global warming the distribution of warmth through the year is likely to change in the future and comparable changes may have occurred over the course of the holocene its effect on vegetation composition and species distribution can be compared to that of a continental versus an oceanic climate the distribution of five major tree species along a continentality gradient was studied in fennoscandia based on distribution maps and on their proportions of pollen in surface sediment samples both analyses indicate that the five arboreal species show similar patterns of response to a continentality index in the order ulmus glabra corylus avellana quercus robur tilia cordata and picea abies from the most oceanic to most continental continentality growing degree days above 5 degrees c and january temperature were reconstructed quantitatively from four pollen diagrams using transfer functions based on a combined fennoscandian pollen surface sample data set quantitative reconstructions indicate that the climate in fennoscandia has become increasingly more continental over the last 7000 years and this is largely an effect of winter cooling early holocene vegetation composition has poor analogues to the present vegetation in fennoscandia which hampers quantitative reconstructions qualitative reconstructions suggest that the early holocene in fennoscandia was the most oceanic period but probably with a high variability in temperature c 2008 elsevier ltd all rights reserved

early holocene humidity patterns in the iberian peninsula reconstructed from lake pollen and speleothem records abstract comparison of selected well dated lacustrine speleothem and terrestrial pollen records spanning the holocene onset and the early holocene ca 11 7 8 cal kyrs bp in the iberian peninsula shows large hydrological fluctuations and landscape changes with a complex regional pattern in timing and intensity marine pollen records from alboran the mediterranean and off shore atlantic sites show a step wise increase in moisture and forest during this transition however available continental records point to two main patterns of spatial and temporal hydrological variability i atlantic influenced sites located at the northwestern areas enol sanabria lucenza prd 4 characterized by a gradual increase in humidity from the end of the younger dryas to the mid holocene similarly to most north atlantic records and ii continental and mediterranean influenced sites laguna grande villarquemado fuentillejo padul estanya banyoles salines with prolonged arid conditions of variable temporal extension after the younger dryas followed by an abrupt increase in moisture at 10 9 cal kyrs bp different local climate conditions influenced by topography or the variable sensitivity gradual versus threshold values of the proxies analyzed in each case are evaluated vegetation composition conifers versus mesothermophilous taxa and resilience would explain a subdued response of vegetation in central continental areas while in mediterranean sites insufficient summer moisture availability could not maintain high lake levels and promote mesophyte forest in contrast to atlantic influenced areas comparison with available climate models greenland ice cores north atlantic marine sequences and continental records from central and northern europe and the whole mediterranean region underlines the distinctive character of the hydrological changes occurred in inner iberia throughout the early holocene the persistent arid conditions might be explained by the intensification of the summer drought due to the high seasonality contrast at these latitudes caused by the orbital induced summer insolation maximum new records particularly from western and southernmost iberia and palaeoclimate models with higher spatial resolution would help to constrain these hypotheses

centennial climate variability in the british isles during the mid late holocene abstract multi millennial climate changes were relatively minor over the mid late holocene in the british isles because orbitally forced insolation changes were smaller than those at higher latitudes centennial climate variability is thus likely to have exerted a greater influence on the environment and human society of the region proxy climate records from the british isles covering the last 4500 years are assembled and re evaluated with the aim of identifying centennial climate variability reflected by multi proxy indicators the proxies include bog oak populations peatland surface wetness flooding episodes from fluvial deposits speleothem annual band width and oxygen isotopes chironomids from lake sediments and sand and dune deposition most proxies reflect water balance rather than temperature alone and records predominantly reflect warm season climate a series of 12 key periods of enhanced precipitation evaporation p e are identified by their presence in two or more proxy records variability in p e is much greater than that shown by temperature proxies and there is no necessary association between warm cool and dry wet periods although the data for temperature are less robust than those for p e a series of key temperature changes are proposed based on speleothem 18o and chironomid inferred july temperature records relatively cool before c 3100 years bp warmer 3100 2000 years bp cool 2000 1250 cal years bp warm 1250 650 cal years bp and cool 650 cal years bp onwards some key increases in p e 2750 1650 550 cal years bp show a strong correspondence with bond cycles in ocean proxy records for increased ice rafted debris decreased summer sea surface temperatures and sometimes decreased north atlantic deep water circulation other higher frequency changes in p e are also strongly related to sst variability whilst some of the main changes to cooler ssts and increased p e are approximately coincident with reduced solar output most are not and thus must be the result of the internal dynamics of the ocean and atmosphere future work should concentrate on firmly establishing the pattern of temperature change improving chronological accuracy and precision in existing records and improving process based understanding of proxies

holocene and late pleistocene climate in the sub mediterranean continental environment a speleothem record from poleva cave southern carpathians romania the pp10 stalagmite from poleva cave provides a late pleistocene and holocene isotopic record characteristic for the sw of romania a sub mediterranean climatic region the speleothem was dated by eight tims and one alpha u series dates which showed that it was precipitated between 75 ka and 2 ka with at least two hiatuses the basal sector of the stalagmite showed a slow growing regime of 0 26 cm ka while the upper one grew relatively fast with about 5 cm ka the temporal resolution for the isotopic sampling is thus 2 ka sample for the lower sector and 150 years sample for the upper one the relationship between 18 o and temperature was found positive the isotopic record of the lower sector shows two marked cold intervals during 67 and 58 ka and 40 35 ka respectively which correlate well with the villars and soreq records the upper sector record is so far the most detailed holocene isotopic record in romania and the only one available for the regions located at the exterior of the carpathians range the signal shows a gradual warming after the gs1 event punctuated by several cold events at 8 7 2 and 4 2 ka and also by warm oscillations centered at about 5 2 and 3 3 ka the results seem to indicate that if the north atlantic firstorder signals may extend well to the south eastern europe their amplitude and general trend may be diminished by the interferences with the mediterranean circulation

glacier fluctuations equilibrium line altitudes and palaeoclimate in lyngen northern norway during the lateglacial and holocene based on lacustrine and morpho stratigraphical evidence from lyngen in troms northern norway 13 marginal moraines have been mapped in front of lenangsbreene in strupskardet moraines m1 m13 are inferred to represent glacier halts or advance readvance taking place during the lateglacial and holocene the presence of collapse depressions suggests that some of them were ice cored m1 m3 a chronological framework taking into account a combination of former shorelines and related glacier meltwater channels lichenometry and ams radiocarbon dated lacustrine sediments spanning the last 20 000 cal yr bp has been established the distal glacier fed lake aspvatnet was isolated from the sea c 10 300 cal yr bp and the lacustrine sediments have been investigated by use of loss on ignition loi magnetic susceptibility water content wet and dry bulk density dbd and the magnetic parameters anhysteretic remanent magnetization arm and saturation remanent magnetization sirm there is in general good agr

detrital events and hydroclimate variability in the romanian carpathians during the mid to late holocene the romanian carpathians are located at the confluence of three major atmospheric pressure fields the north atlantic the mediterranean and the siberian despite its importance for understanding past human impact and climate change high resolution palaeoenvironmental reconstructions of holocene hydroclimate variability and in particular records of extreme precipitation events in the area are rare here we present a 7500 year long high resolution record of past climatic change and human impact recorded in a peatbog from the southern carpathians integrating palynological geochemical and sedimentological proxies natural climate fluctuations appear to be dominant until 4500 years before present yr bp followed by increasing importance of human impact sedimentological and geochemical analyses document regular minerogenic deposition within the bog linked to periods of high precipitation such minerogenic depositional events began 4000 yr bp with increased depositional rates during the medieval warm period mwp the little ice age lia and during periods of societal upheaval e g the roman conquest of dacia the timing of minerogenic events appears to indicate a teleconnection between major shifts in north atlantic oscillation nao and hydroclimate variability in southeastern europe with increased minerogenic deposition correlating to low nao index values by linking the minerogenic deposition to precipitation variability we state that this link persists throughout the mid to late holocene

holocene environmental changes as recorded in the geochemistry of glacial lake sediments from retezat mountains south carpathians abstract sediment cores obtained from two deep 15 m glacial lakes were analyzed in context of terrestrial vegetation development and in lake processes from the retezat mountains southern carpathians romania only the holocene parts were chosen for study for testing what is the connection between geochemical changes and biotas around and in the lakes the lakes are situated at slightly different altitudes on the northern lake gales 1990 m a s l and southern slope lake bucura 2040 m a s l respectively changes in geochemical composition were relatively low amplitude during the studied period 10 300 1790 and 10 300 695 cal yr bp in both lakes but the applicability of enrichment factor ef for geochemical elements and diatom ecological traits guilds in paleoecological reconstruction were demonstrated in this paper the main changes have been observed at ca 10 670 9000 6500 and 3100 cal yr bp in geochemistry vegetation and siliceous algal assemblages catchment soil stabilization was apparent from 9000 cal yr bp onwards in lake and terrestrial productivity was the highest between 9000 and 6500 cal yr bp and human impact became the dominant driver in both terrestrial vegetation and sediment geochemical changes and in lake processes over the last 3400 years in both lakes the geochemical record displayed frequent erosional events within the holocene the strongest soil erosions clustered around 6500 7400 and 3200 900 cal yr bp

orbital forcing and role of the latitudinal insolation temperature gradient orbital forcing of the climate system is clearly shown in the earths record of glacial interglacial cycles but the mechanism underlying this forcing is poorly understood traditional milankovitch theory suggests that these cycles are driven by changes in high latitude summer insolation yet this forcing is dominated by precession and cannot account for the importance of obliquity in the ice age record here we investigate an alternative forcing based on the latitudinal insolation gradient lig which is dominated by both obliquity in summer and precession in winter the insolation gradient acts on the climate system through differential solar heating which creates the earths latitudinal temperature gradient ltg that drives the atmospheric and ocean circulation a new pollen based reconstruction of the ltg during the holocene is used to demonstrate that the ltg may be much more sensitive to changes in the lig than previously thought from this it is shown how lig forcing of the ltg may help explain the propagation of orbital signatures throughout the climate system including the monsoon arctic oscillation and ocean circulation these relationships are validated over the last eemian interglacial which occurred under a different orbital configuration to the holocene we conclude that lig forcing of the ltg explains many criticisms of classic milankovitch theory while being poorly represented in climate models

holocene vegetation history and quantitative climate reconstructions in a high elevation oceanic district of the italian alps evidence for a middle to late holocene precipitation increase abstract we reconstructed the vegetation and climate history during the last 10 ka in a high elevation sedimentary record armentarga peat bog 2345 m asl on the southern flank of the european alps through the study of paleoecological and sedimentary proxies we included a specific elevational transect of modern pollen accumulation rates for timberline forming trees and shrubs alnus viridis pinus sylvestris mugo pinus cembra quantitative reconstructions of july temperature and annual precipitation were obtained by applying numerical transfer functions built on an extensive pollen climate calibration set from the european alps changes in elevational vegetation arrangement were primarily driven by phases of precipitation increase and to a lesser extent by millennial scale temperature changes already known from glacier timberline chironomids and speleothem records at alpine scale changes in pollen inferred annual precipitation occurred in three main steps an early holocene moderately humid phase is mirrored by the early spread of alnus viridis dwarf forests precipitation started to increase at 6 2 ka cal bp a further prominent step forward at the middle to late holocene transition led to the high values of snowfall and runoff characterizing today s oceanic elevational climates of the outer italian alps this change led to timberline depression and grassland expansion locally human impact was weak at the late neolithic bronze age transition this event correlates with lake level oscillations in the northern mediterranean borderlands suggesting intensification of southern air masses conveyed by tyrrhenian cyclones towards windward districts

testing solar forcing of pervasive holocene climate cycles the temporal and spatial extent of holocene climate change is an area of considerable uncertainty with solar forcing recently proposed to be the origin of cycles identified in the north atlantic region to address these issues we have developed an annually resolved record of changes in irish bog tree populations over the last 7468 years which together with radiocarbon dated bog and lake edge populations extend the dataset back to 9000 yr ago the irish trees underpin the internationally accepted radiocarbon calibration curve used to derive a proxy of solar activity and allow us to test solar forcing of holocene climate change tree populations and age structures provide unambiguous evidence of major shifts in holocene surface moisture with a dominant cyclicity of 800 yr similar to marine cycles in the north atlantic indicating significant changes in the latitude and intensity of zonal atmospheric circulation across the region the cycles however are not coherent with changes in solar activity both being on the same absolute timescale indicating that holocene north atlantic climate variability at the millennial and centennial scale is not driven by a linear response to changes in solar activity copyright 2005 john wiley sons ltd

sea surface temperatures around the australian margin and indian ocean during the last glacial maximum abstract we present new last glacial maximum lgm sea surface temperature sst maps for the oceans around australia based on planktonic foraminifera assemblages to provide the most reliable sst estimates we use the modern analog technique the revised analog method and artificial neural networks in conjunction with an expanded modern core top database all three methods produce similar quality predictions and the root mean squared error of the consensus prediction the average of the three under cross validation is only 0 77 c we determine lgm sst using data from 165 cores most of which have good age control from oxygen isotope stratigraphy and radiocarbon dates the coldest sst occurred at 20 500 1400 cal yr bp predating the maximum in oxygen isotope records at 18 200 1500 cal yr bp during the lgm interval we observe cooling within the tropics of up to 4 c in the eastern indian ocean and mostly between 0 and 3 c elsewhere along the equator the high latitudes cooled by the greatest degree a maximum of 7 9 c in the southwest pacific ocean our maps improve substantially on previous attempts by making higher quality temperature estimates using more cores and improving age control

palaeolimnological and sedimentary responses to holocene forest retreat in the scandes mountains west central sweden a suite of analyses was performed on sediments accumulated duringthe last 10 700 years in lake spaime a small hydrologically open water body in the modern alpine tundra zone of the scandes moun tains west central sweden the study aimed to evaluate 1 the nature of climate changes that forced the late holocene loweringof altitudinal tree limit in the region the timingof which is known from prior stu dies based on radiocarbon dating of subfossil wood and 2 the impact of these vegetational changes on an aquatic ecosystem arboreal pollen and plant macrofossil data confirm the persistence of trees in the lake catchment at least from c 9700 cal bp until c 3700 cal bp although growing season temperature is com monly believed to be the dominant factor drivingboreal forest tree limit variations in the reg ion a chir onomid based reconstruction of mean july air temperature suggests that local deforestation during the late holocene was not accompanied by a significant cooling the tree limit retreat was more likely caused by increasing effective moisture and declining length of the growing season the ecohydrological response of lake spaime to this combination of climate and vegetational changes included a decline in primary pro ductivity as indicated by an abrupt decrease in sediment organic matter content while associated increases in organic d 13 c d 15 n and c n point to diminished fluxes and altered balance of catchment derived nutrients followingdeforestation the decline in aquatic productivity is also marked by a distinct change in the mineral magnetic properties from a high magnetic concentration assemblage dominated by fine grained magnetite of biogenic origin to one dominated by background levels of coarse grained detrital magnetite

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

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

the oxfordian stable isotope record δ18o δ13c of belemnites brachiopods and oysters from the kachchh basin western india and its potential for palaeoecologic palaeoclimatic and palaeogeographic reconstructions abstract the study combines the results of stable isotope 13c 18o analyses of 187 belemnites brachiopods and oysters from the middle to upper jurassic upper callovian to kimmeridgian of the kachchh basin in western india generally belemnites show lower 13c and higher 18o ratios than the benthic fauna it is proposed that this discrepancy is caused by different life habitats of both groups with belemnites spending major parts of their life in deeper water outside the kachchh basin and entering shallow areas only occasionally e g during seasonal migrations to spawning grounds a mode of life as fast swimming nektonic predators similar to many modern squid species seems plausible the study emphasises that results of stable isotope analyses should be evaluated separately for each fossil group in addition to the influence of diagenetic alteration weathering salinity changes and sea level fluctuations the ecology of the analysed fossil taxa has to be considered temperatures calculated from 18o ratios point to relatively warm conditions around the middle to late jurassic transition with no evidence for a glacial phase which had been proposed for this boundary a distinct fall in temperatures is observed during the middle oxfordian reaching a minimum in the early late oxfordian it is tempting to connect this event with the break up of gondwana causing stronger upwelling in the northwestern tethys or alternatively the influx of polar water by the opening of the transgondwanan seaway however such connections cannot be verified without further data preferably from localities in the southern malagasy gulf e g madagascar and from younger horizons kimmeridgian tithonian

the climate of europe 6000 years ago palaeoclimates across europe for 6000 y bp were estimated from pollen data using the modern pollen analogue technique constrained with lake level data the constraint consists of restricting the set of modern pollen samples considered as analogues of the fossil samples to those locations where the implied change in annual precipitation minus evapotranspiration p e is consistent with the regional change in moisture balance as indicated by lakes an artificial neural network was used for the spatial interpolation of lake level changes to the pollen sites and for mapping palaeoclimate anomalies the climate variables reconstructed were mean temperature of the coldest month tc growing degree days above 5 c gdd moisture availability expressed as the ratio of actual to equilibrium evapotranspiration and p e the constraint improved the spatial coherency of the reconstructed palaeoclimate anomalies especially for p e the reconstructions indicate clear spatial and seasonal patterns of holocene climate change which can provide a quantitative benchmark for the evaluation of palaeoclimate model simulations winter temperatures tc were 1 3 k greater than present in the far n and ne of europe but 2 4 k less than present in the mediterranean region summer warmth gdd was greater than present in nw europe by 400 800 k day at the highest elevations and in the alps but 400 k day less than present at lower elevations in s europe p e was 50 250 mm less than present in nw europe and the alps but was 10 15 greater than present in s europe and p e was 50 200 mm greater than present in s and e europe

climate dynamics in the borderlands of the aegean sea during formation of sapropel s1 deduced from a marine pollen record abstract to unravel the climatic and environmental dynamics in the borderlands of the aegean sea during the early and middle holocene and notably for the interval of sapropel s1 s1 formation we have analysed terrestrial palynomorphs from a marine core in the northern aegean sea the qualitative results were complemented by quantitative pollen based climate reconstructions a land sea correlation was established based on pollen data and sediment lightness measurements from the same core and previously published benthic foraminifer data from a nearby core the borderlands of the aegean sea underwent a transition from an open vegetation to oak dominated woodlands between 10 4 and 9 5 ka cal bp a coeval increase in winter precipitation suggests that moisture availability was the main factor controlling holocene reforestation the 50 higher winter precipitation during s1 formation relative to pre sapropelic conditions suggests a strong contribution from the borderlands of the aegean sea to the freshwater surplus during s1 formation the humid and mild winter conditions during s1 formation were repeatedly punctuated by short term climatic events that caused a partial deforestation and a reorganisation within the broad leaved arboreal vegetation in the marine realm these events are documented by improved benthic oxygenation the strongest event represents the regional expression of the 8 2 ka cold event and led to an interruption in s1 formation except for the interval of s1 formation the pollen derived winter temperatures correlate with the smoothed gisp2 k series they support the previously published marine based concept that the intensity of the siberian high strongly controlled the winter climate in the aegean region during s1 formation in the aegean sea however climate conditions in the borderlands were more strongly affected by the monsoonally influenced climate system of the lower latitudes

high resolution palaeohydrological reconstruction of central italy during the holocene the endorheic nature of lake trasimeno in combination with its position in central italy makes it a relevant site to better constrain spatial differences in holocene climatic variability in the med

the spatial and temporal complexity of the holocene thermal maximum the holocene thermal maximum a period of relatively warm climate between 11 000 and 5 000 years ago1 2 is most clearly recorded in the middle and high latitudes2 3 of the northern hemisphere where it is generally associated with the local orbitally forced summer insolation maximum however proxy based reconstructions have shown that both the timing and magnitude of the warming vary substantially between different regions2 3 4 suggesting the involvement of extra feedbacks and forcings here we simulate the holocene thermal maximum in a coupled global ocean atmosphere vegetation model we find that before 7 000 years ago summers were substantially cooler over regions directly influenced by the presence of the laurentide ice sheet whereas other regions of the northern hemisphere were dominated by orbital forcing our simulations suggest that the cool conditions arose from a combination of the inhibition of labrador sea deep convection by the flux of meltwater from the ice sheet which weakened northward heat transport by the ocean and the high surface albedo of the ice sheet we thus conclude that interglacial climate is highly sensitive to relatively small changes in ice sheet configuration

termination of the last glaciation in the iberian peninsula inferred from the pollen sequence of quintanar de la sierra abstract a 4 5 m thick late glacial pollen sequence supported by 17 ams14c dates has been investigated at the quintanar de la sierra marshland iberian cordillera north central spain pollen zones were defined that correspond to successive phases in vegetation history during the end of the late wurm late glacial interstade and younger dryas periods a transfer function approach has been adopted to derive quantitative climate estimates from the pollen assemblage data a first expansion ofjuniperusandhippophae about 13 50014c yr b p indicates the beginning of the late glacial interstade which is characterized by ajuniperus betula pinussuccession that suggests higher temperatures and moisture than during full glacial time the younger dryas interval is recorded by a 120 cm thick sediment unit that is dominated by herbaceous pollen transfer function estimates suggest that the climate during this period was cold with low precipitation during most of the year although not in summer the holocene arboreal recolonization in the area started about 10 00014c yr b p with a renewedjuniperus betula pinussuccession related to a strong increase in annual temperature and precipitation the start of this process was synchronous with mean sea surface temperature changes as recorded from the nearby su 81 18 marine core the strong affinity with other european late glacial pollen sequences demonstrates that the pattern of climatic changes during the last glacial interglacial transition was similar in both northwestern and southwestern europe

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

comparison of north american pollen based temperature and global lake status with cccma agcm2 output at 6 ka abstract we present new paleoclimate reconstructions for the time period of 6000 yr bp 6 ka that permit a quantitative comparison to corresponding mapped patterns of the newest version of the canadian cccma agcm2 climate model july temperature reconstructions were estimated using the modern analog technique employing fossil pollen records from the north american pollen database we present a new method of optimizing critical choices within the application of the mat through modern calibration the pattern of 6 ka temperature anomalies generated by the cccma agcm2 generally agree with those of the pollen based reconstruction particularly in the presence of a band of positive temperature anomalies across the continent from the yukon through the great lakes region and along the st lawrence this agreement suggests that both the model and data are reconstructing a contraction in the polar vortex over north america at 6 ka major areas of disagreement between the pollen based reconstruction and model simulation are also areas where the data are sparse and edge effects produce less reliable reconstructions the cccma agcm2 simulates drier conditions in a west east band stretching from alaska through the canadian prairies and midwest united states in agreement with low lake level observations at 6 ka simulated and reconstructed precipitation evaporation are also in agreement over the southwest united states with the exception of north central africa the cccma agcm2 fails to capture the northward and eastern extension of the afro asian monsoon belt at 6 ka general agreement between cccma agcm2 p e anomalies and lake status change is found throughout europe at 6 ka

north american paleoclimate reconstructions for the last glacial maximum using an inverse modeling through iterative forward modeling approach applied to pollen data the inverse modeling through iterative forward modeling imifm approach was used to reconstruct last glacial maximum lgm climates from north american fossil pollen data the approach was validated using modern pollen data and observed climate data while the large scale lgm temperature imifm reconstructions are similar to those calculated using conventional statistical approaches the reconstructions of moisture variables differ between the two approaches we used two vegetation models biome4 and biome5 beta with the imifm approach to evaluate the effects on the lgm climate reconstruction of differences in water use efficiency carbon use efficiency and atmospheric co2 concentrations although lower atmospheric co2 concentrations influence pollen based lgm moisture reconstructions they do not significantly affect temperature reconstructions over most of north america this study implies that the lgm climate was very cold but not very much drier than present over north america which is inconsistent with previous studies

pronounced northward shift of the westerlies during mis 17 leading to the strong 100 kyr ice age cycles abstract the mis 17 interglacial 715 675 ka marks the end of the mid pleistocene transition as intensified long and asymmetrical 100 kyr ice age cycles became eminently established increasing arrival of moisture to the northern hemisphere high latitudes resulting from the northwestward migration of the subpolar front and the intensification of the norwegian greenland seas ngs convection has been put forward to explain the emergence of this quasi periodic 100 kyr cycle however testing this hypothesis is problematic with the available north atlantic precipitation data here we present new pollen based quantitative seasonal climate reconstructions from the southwestern iberian margin that track changes in the position and intensity of the westerlies our data compared to changes in north atlantic deep and surface water conditions show that mis 17 interglacial was marked by three major changes in the direction and strength of the westerlies tightly linked to oceanographic changes in particular we report here for the first time a drastic two steps northward shift of the westerlies centered at 693 ka that ended up with the sustained precipitation over southern european this atmospheric reorganization was associated with northwestward migration of the subpolar front strengthening of the ngs deep water formation and cooling of the western north atlantic region this finding points to the substantial arrival of moisture to the northern hemisphere high latitudes at the time of the decrease in summer energy and insolation contributing to the establishment of strong 100 kyr cycles

a spatio temporal reconstruction of holocene temperature change in southern scandinavia holocene mean july tjul and mean january tjan temperatures were reconstructed at lake trehorningen in southwest sweden using pollen climate calibration functions and converted into anomalies re

eemian and early weichselian temperature and precipitation variability in northern germany abstract dramatic changes in european vegetation occurred during the transition from the eemian interglacial to weichselian glacial climates correlative with major changes in global ice core and marine records quantitative knowledge of climate change is important for understanding of the climate system and for climate modelling for which reconstructions of this transitional period are of special interest however it has been difficult to quantify the climatic changes involved in the eemian to early weichselian transition from terrestrial archives due to the lack of modern vegetation analogues to circumvent this problem we applied a suitable multivariate probabilistic approach to pollen and plant macrofossil assemblages to reconstruct temperature and precipitation for this transition in central europe our reconstructions span the interval from the beginning of the eemian marine isotope stage mis 5e to the odderade interstadial mis 5a they indicate a relatively stable eemian with increasing precipitation reducing the continentality of the climate with time during the transition from the eemian to the herning stadial mean july and january temperatures decreased by 4 c and by as much as 20 c respectively temperatures remained high enough to support forests during the stadials and we infer that the reconstructed decrease of precipitation below 500 mm per year caused the extirpation of forests during these periods thus we conclude that precipitation although difficult to reconstruct is of vital importance for explaining vegetation change during the eemian and eemian early weichselian transition

the holocene sea level story since 7500 bp lessons from the eastern mediterranean the black and the azov seas abstract this paper addresses the obvious controversy between the so far published sea level curves of the black sea and the mediterranean it starts with a discussion of the methods of reconstructing sea level curves the evaluation of sea level indicators and the application of the radiocarbon dating method at least since 7500 bp when the black sea and the mediterranean were connected both water bodies must have reacted synchronously on glacio eustatic changes it is documented that none of the mediterranean sea level curves shows the major wiggles postulated for the black sea which are supposed to reflect trans and regression cycles the very shallow bathymetric condition of the azov sea and the northern black sea should have led to considerable and traceable shoreline displacements there is neither archaeological nor historical evidence of mid and late holocene regressions of several meters the tectonic setting of the black and azov seas implicates that the tectonic signal often overrides the eustatic one therefore only local sea level curves can be established in this paper based on vibracores a locally valid sea level curve for the taman peninsula is demonstrated layers of paralic peat were used as sea level indicators and for 14 c dating the shape of this curve follows the one known from the mediterranean this study also revealed that the present peninsula of taman evolved out of a former archipelago

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

closure of the budget of global sea level rise over the grace era the importance and magnitudes of the required corrections for global glacial isostatic adjustment abstract the budget of global sea level rise includes contributions from several distinct factors including thermosteric effects the wasting of small ice sheets and glaciers and the loss of mass by the great polar ice sheets and by the continents due to desiccation since the former contribution may be estimated on the basis of both hydrographic survey data and more recently using argo float data the second may be estimated on the basis of mass balance measurements on existing ice fields and the latter on the basis of modern grace based time dependent gravity field measurements the inputs to the globally averaged rate of sea level rise may be directly constrained since grace also provides a measurement of the rate at which mass is being added to the oceans we are now in a position to ask whether this rate of mass addition to the oceans matches the rate at which mass is being removed from the continents as demonstrated herein the mass component of the budget of global sea level is closed within the observational errors when the mass derived contribution is added to the thermosteric contribution it is furthermore shown that the inference of the net rate of global sea level rise by the altimetric satellites topex poseidon and jason 1 is also reconcilable over the grace era it is noted those individual terms in the budget especially the contribution from small ice sheets and glaciers remains insufficiently accurate it is demonstrated that the lingering influence of the late quaternary ice age upon sea level is profound and that closure of the budget requires an accurate model of its impact

early holocene climate variability and the timing and extent of the holocene thermal maximum htm in northern iceland the magnitude and timing of holocene maximum warmth in the arctic and sub arctic has been the subject of considerable recent interest particularly in the context of future climate change although lying at a crucial location in the north atlantic close to significant atmospheric and oceanic boundaries terrestrial holocene climatic data from iceland are few and predominantly derive from glacial and palaeoecological evidence here we present new datasets from trollaskagi based on chironomid inferred temperatures ci t using sub fossil chironomids from the same lake sediments supplemented by pollen data july air temperatures have been derived using an icelandic training set and the data suggest optimal temperatures at sea level up to 1 5 c above current levels around 8 k cal yr bp a time when birch woodland was well developed in trollaskagi but when woodland had still not fully developed in the more isolated nw peninsula our data thus suggest that optimal summer warmth did not occur in iceland until 8 kcal yr bp at the earliest possibly lasting until 6 7 kcal yr bp the amount of warming for july was therefore at least 1 5 c but possibly up to 2 3 c higher than the 1961 1990 average on the basis of the tree line data comparison with data from elsewhere in adjacent arctic regions greenland and eastern arctic canada show peak warmth to be later in iceland and less pronounced it also appears that there were enhanced temperature gradients during the first half of the holocene between the two study areas trollaskagi and the nw peninsula and that they influenced patterns of vegetation colonisation with current spatial temperature patterns only developing as holocene climate deteriorated after around 6 kcal yr bp

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

a chironomid based holocene summer air temperature reconstruction from the swiss alps we developed a quantitative chironomid july air temperature inference model based on surface sediments from 81 swiss lakes and applied it to the holocene subfossil chironomid record of hinterburgsee a small subalpine lake in the northern swiss alps present day mean july air temperature of 11 3 c after smoothing to reduce the high between sample variability of inferred temperatures the reconstruction indicates july air temperatures of 10 4 10 9 c at the end of the younger dryas of 11 9 12 8 c during the early and mid holocene 11500 4000 cal bp and slightly lower temperatures of 11 5 12 0 c during the late holocene 3500 1000 cal bp a warming trend inferred for the past millennium is most likely an artifact of human impact on hinterburgsee s chironomid fauna rather than a genuine temperature signal the most prominent climatological events during the holocene were two periods of lower temperatures at c 10700 10500 cal bp and 8200 7700 cal bp and an abrupt shift to a cooler late holocene cl

the holocene history of the ne black sea and surrounding areas an integrated record of marine and terrestrial palaeoenvironmental change here we present an almost complete and integrated holocene record of marine and terrestrial palaeoenvironmental change from the ne shelf of the black sea a dinoflagellate cyst record used to recon

quantitative precipitation estimates for the northeastern qinghai tibetan plateau over the last 18 000 years quantitative information regarding the long term variability of precipitation and vegetation during the period covering both the lateglacial and the holocene on the qinghai tibetan plateau qtp is scarce herein we provide new and numerical reconstructions for annual mean precipitation pann and vegetation history over the last 18 000 years using high resolution pollen data from lakes dalianhai and qinghai on the northeastern qtp hitherto five calibration techniques including weighted averaging wa weighted average partial least squares regression wa pls modern analogue technique mat locally weighted weighted averaging regression lwwa and maximum likelihood ml were firstly employed to construct robust inference models and to produce reliable pann estimates on the qtp the biomization method was applied for reconstructing the vegetation dynamics the study area was dominated by steppe and characterized with a highly variable relatively dry climate at 18 000 11 000 cal a b p pann increased since the early holocene obtained a maximum at 8000 3000 cal a b p with coniferous temperate mixed forest as the dominant biome and thereafter declined to present the pann reconstructions are broadly consistent with other proxy based paleoclimatic records from the northeastern qtp and the northern region of monsoonal china the possible mechanisms behind the precipitation changes may be tentatively attributed to the internal feedback processes of higher latitude e g north atlantic and lower latitude e g subtropical monsoon competing climatic regimes which are primarily modulated by solar energy output as the external driving force these findings may provide important insights into understanding the future asian precipitation dynamics under the projected global warming

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

paleoclimate reconstruction in the levant region from the geochemistry of a holocene stalagmite from the jeita cave lebanon dated oxygen and carbon isotopic profiles from a holocene stalagmite 11 9 1 1 ka from the jeita cave lebanon are compared to variations in crystallographic habit stalagmite diameter and growth rate the profiles show generally high 18o and 13c values during the late glacial period low values during the early holocene and again high values after 5 8 ka on the basis of the good correlation between the morphological and crystallographic aspect of the stalagmite and its isotopic records as well as the isotopic response of speleothems from central and northern israel we relate high 18o and 13c values to drier conditions between 6 5 and 5 8 ka an increase in isotopic values a decrease in growth rate and stalagmite diameter suggest a transition from wet conditions in the early holocene towards drier conditions in the mid holocene the transition occurred in two steps first a progressive change to drier conditions started at 6 5 ka but was interrupted by a short 100 years return to wetter conditions followed by an equally rapid 200 years change to drier conditions

holocene glacier history from alpine speleothems milchbach cave switzerland abstract mountain glaciers and their sediments are prominent witnesses of climate change responding sensitively to even small modifications in meteorological parameters even in such a classical and thoroughly studied area as the european alps the record of holocene glacier mass balance is only incompletely known here we explore a novel and continuous archive of glacier fluctuations in a cave system adjacent to the upper grindelwald glacier in the swiss alps milchbach cave became partly ice free only recently and hosts holocene speleothems four coeval stalagmites show consistent petrographic and stable isotopic changes between 9 2 and 2 0 ka which can be tied to abrupt modifications in the cave environment as a result of the closing and opening of multiple cave entrances by the waxing and waning of the nearby glacier during periods of holocene glacier advances columnar calcite fabric is characterized by 18 o values of about 8 0 indicative of speleothem growth under quasi equilibrium conditions i e little affected by kinetic effect related to forced degassing or biological processes in contrast fabrics formed during periods of glacier minima are typical of bacterially mediated calcite precipitation within caves overlain by an alpine soil cover moreover 18 o values of the bacterially mediated calcite fabrics are consistent with a ventilated cave system fostering kinetic fractionation these data suggest that glacier retreats occurred repeatedly before 5 8 ka and that the amplitudes of glacier retreats became substantially smaller afterwards our reconstruction of the upper grindelwald glacier fluctuations agrees well with paleoglaciological studies from other sites in the alps and provides a higher temporal resolution compared to traditional analyses of peat and wood remains found in glacier forefields

seasonal resolution of eastern mediterranean climate change since 34 ka from a soreq cave speleothem the combination of ion microprobe analysis of d 18 o and confocal laser fluorescent microscope imaging of annual growth bands in a soreq cave speleothem provides sub annual scale climate information between 34 and 4 ka this high resolution methodology is ideal both for comparing seasonal climate patterns across broad windows of time and examining rapid climate events such as the younger dryas termination in detail the sub annual d 18 o gradients we report represent a combination of seasonal variability in rainfall amount and air temperature a distinct change in both the pattern of fluorescent banding and the gradient of d 18 o measured in situ across single annual growth bands indicates a change in seasonal climate patterns of the eastern mediterranean region following heinrich event 1 and again after the younger dryas throughout the holocene wet winters and dry summers characterized regional climate during the younger dryas we find that regional climate may have been more arid than in the holocene but the fluorescent banding pattern indicates that the supply of dripwater to the cave was more consistent year round we suggest that a reduced gradient of seasonal precipitation occasional snowfall and vegetation differences may have all contributed to the isotope and fluorescent banding patterns observed during heinrich event 1 and the last glacial stadial detailed investigation of the younger dryas termination reveals a rapid onset of regional environmental change fluorescent band counting indicates that the younger dryas termination as recorded by rainfall in the

holocene carbon cycle dynamics based on co2 trapped in ice at taylor dome antarctica a high resolution ice core record of atmospheric co2 concentration over the holocene epoch shows that the global carbon cycle has not been in steady state during the past 11 000 years analysis of the co2 concentration and carbon stable isotope records using a one dimensional carbon cycle model uggests that changes in terrestrial biomass and sea surface temperature were largely responsible for the observed millennial scale changes of atmospheric co2 concentrations

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

lusitanian mediterranean ostracods in the holocene of denmark implications for the interpretation of winter temperatures during the postglacial temperature maximum two species of lusitanian mediterranean ostracods aurila arborescens and callistocythere badia are reported from middle holocene atlantic chronozone localities in northern jutland denmark the two species occur in gyttja rich sandy deposits in association with shallow water euryhaline mollusc and ostracod faunas they are found in sediments from the atlantic chronozone dated between 6790 75 bp and 5900 110 bp a arborescens is essentially a mediterranean species with only two documented live occurrences outside the mediterranean it lives in shallow water with coldest month temperatures of at least 6 c and warmest month temperatures of at least 15 16 c c badia occurs in littoral marine environments in the eastern mediterranean and along the southern and western coasts of the british isles it is suggested that coldest month sea surface temperatures in northern denmark between 6800 bp and 5900 bp were more than 5 6 c above present values the temperature maximum of the atlantic chronozone in s

chrysophyte cysts from lake sediments reveal the submillennial winter spring climate variability in the northwestern mediterranean region throughout the holocene in the last decade much effort was dedicated to the reconstruction of past climate at high temporal resolution here we show the suitability of chrysophyte cysts from lake sediments for revealing continental climate variability when used in sensitive sites such as those in high mountains we demonstrate that altitude is a main factor influencing the present distribution of chrysophytes and develop a transfer function to evaluate the local altitude anomaly on a lake site throughout time based on our knowledge of chrysophyte ecology the altitude anomalies are interpreted as winter spring climate signatures the method was applied to a holocene record from a lake in the pyrenees showing submillennial climatic variability in this northwestern mediterranean zone a warming trend was present from the early holocene to 4 kyear bp comparison with pollen based reconstructions of summer temperatures denoted a contrasting decrease in continentality between the two parts of the holocene oscillations of 1 cycle per ca 2 000 years appeared throughout the record the warmest holocene winters were recorded during the medieval warm period at ca ad 900 and 450 and the roman warm period 2 7 2 4 kyear bp winters in the period ad 1 050 1 175 were inferred to be as cold as in the little ice age the period between 3 and 7 kyear bp showed lower intensity in the fluctuations than in early and late holocene the cold event 8 200 years ago appeared embedded in a warm fluctuation another cold fluctuation was recorded around 9 kyear bp which is in agreement with irish and greenland records

global characterization of the holocene thermal maximum we analyze the global variations in the timing and magnitude of the holocene thermal maximum htm and their dependence on various forcings in transient simulations covering the last 9000 years 9 ka performed with a global atmosphere ocean vegetation model in these experiments we consider the influence of variations in orbital parameters and atmospheric greenhouse gases and the early holocene deglaciation of the laurentide ice sheet lis considering the lis deglaciation we quantify separately the impacts of the background melt water fluxes and the changes in topography and surface albedo in the analysis we focus on the intensity of the maximum temperature deviation relative to the preindustrial level its timing in the holocene and the seasonal expression in the model the warmest htm conditions are found at high latitudes in both hemispheres reaching 5 c above the preindustrial level while the smallest htm signal is seen over tropical oceans less than 0 5 c this latitudinal contrast is mostly related to the nature of the orbitally forced insolation forcing which is also largest at high latitudes and further enhanced by the polar amplification the holocene timing of the htm is earliest before 8 ka bp in regions not affected by the remnant lis particularly nw north america e asia n africa n south america the middle east ne siberia and australia compared to the early holocene insolation maximum the htm was delayed by 2 3 ka over ne north america and regions directly downwind from the lis a similar delay is simulated over the southern ocean while an intermediate lag of about 1 ka is found over most other continents and oceans the seasonal timing of the htm over continents generally occurs in the same month as the maximum insolation anomaly whereas over oceans the htm is delayed by 2 3 months exceptions are the oceans covered by sea ice and north africa were additional feedbacks results in a different seasonal timing the simulated timing and magnitude of the htm are generally consistent with global proxy evidence with some notable exceptions in the mediterranean region sw north america and eastern eurasia 2012 elsevier ltd

physiological significance of low atmospheric co2 for plant climate interactions abstract methods of palaeoclimate reconstruction from pollen are built upon the assumption that plant climate interactions remain the same through time or that these interactions are independent of changes in atmospheric co 2 the latter may be problematic because air trapped in polar ice caps indicates that atmospheric co 2 has fluctuated significantly over at least the past 400 000 yr and likely the last 1 6 million yr three other points indicate potential biases for vegetation based climate proxies first c 3 plant physiological research shows that the processes that determine growth optima in plants photosynthesis mitochondrial respiration photorespiration are all highly co 2 dependent and thus were likely affected by the lower co 2 levels of the last glacial maximum second the ratio of carbon assimilation per unit transpiration called water use efficiency is sensitive to changes in atmospheric co 2 through effects on stomatal conductance and may have altered c 3 plant responses to drought third leaf gas exchange experiments indicate that the response of plants to carbon depleting environmental stresses are strengthened under low co 2 relative to today this paper reviews the scope of research addressing the consequences of low atmospheric co 2 for plant and ecosystem processes and highlights why consideration of the physiological effects of low atmospheric co 2 on plant function is recommended for any future refinements to pollen based palaeoclimatic reconstructions

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

holocene temperature evolution in the northern hemisphere high latitudes model data comparisons abstract heterogeneous holocene climate evolutions in the northern hemisphere high latitudes are primarily determined by orbital scale insolation variations and melting ice sheets previous inter model comparisons have revealed that multi simulation consistencies vary spatially we therefore compared multiple model results with proxy based reconstructions in fennoscandia greenland north canada alaska and siberia our model data comparisons reveal that data and models generally agree in fennoscandia greenland and canada with the early holocene warming and subsequent gradual decrease to 0 ka bp hereinafter referred as ka in fennoscandia simulations and pollen data suggest a 2 c warming by 8 ka but this is less expressed in chironomid data in canada a strong early holocene warming is suggested by both the simulations and pollen results in greenland the magnitude of early holocene warming ranges from 6 c in simulations to 8 c in 18 o based temperatures simulated and reconstructed temperatures are mismatched in alaska pollen data suggest strong early holocene warming while the simulations indicate constant holocene cooling and chironomid data show a stable trend meanwhile a high frequency of alaskan peatland initiation before 9 ka can reflect a either high temperature high soil moisture or large seasonality in high latitude siberia although simulations and proxy data depict high holocene temperatures these signals are noisy owing to a large spread in the simulations and between pollen and chironomid results on the whole the holocene climate evolutions in most regions fennoscandia greenland and canada are well established and understood but important questions regarding the holocene temperature trend and mechanisms remain for alaska and siberia

rapid holocene sea level changes along the iranian caspian coast abstract the caspian sea is well known for its rapid sea level change during 1929 1995 a full sea level cycle was observed first the sea level dropped 3 m with a lowstand in 1977 followed by a 3 m rise to 1995 after which the sea level has been relatively stable these oscillations are a specific feature of the caspian sea and its sedimentary record the main purpose of this study is to reconstruct the sea level curve in the holocene by using sedimentological and biostratigraphic analysis and radiocarbon dating along the iranian part of the caspian shore remote sensing images and historical maps show that two lagoons totally emerged and the gorgan delta prograded rapidly at a rate of around 160 m y 1 until the 1975 lowstand gorgan bay was reduced in size considerably and the connection to the sea was blocked due to growth of a spit and change in base level when sea level started to rise again the coastal morphology rapidly changed and the gorgan delta retrograded at the rate of around 140 m y 1 these sedimentary dynamics can be recognized in the preserved deposits in addition to the recent dynamics core data from the southeastern lowlands show four earlier highstands using characteristic barrier lagoon deposits early holocene sea level rose until a highstand was reached of ca 34 m this phase was followed by fluvial deposition in the gorgan delta associated with a base level fall there is also an evidence of sea level rise between 5000 and 2300 bp at ca 27 7 m on top of these deposits there is evidence of a highstand between 2700 and 2300 bp at ca 23 5 m the fourth highstand from the core data is dated to the little ice age at ca 24 m data from these last two highstands correspond well with other observations from the caspian region

reservoir theory for studying the geochemical evolution of soils 1 linking mineral weathering rates measured in the laboratory to those measured at the landscape scale is problematic in laboratory studies collections of minerals are exposed to the same weathering environment over a fixed amount of time in natural soils minerals enter are mixed within and leave the soil via erosion and dissolution leaching over the course of soil formation the key to correctly comparing mineral weathering studies from laboratory experiments and field soils is to consistently define time to do so we have used reservoir theory residence time of a mineral as defined by reservoir theory describes the time length between the moment that a mineral enters via soil production and leaves via erosion and dissolution leaching the soil age of a mineral in a soil describes how long the mineral has been present in the soil turnover time describes the time needed to deplete a species of minerals in the soil by sediment efflux from the soil these measures of time are found to be sensitive to not only sediment flux which controls the mineral fluxes in and out of a soil but also internal soil mixing that controls the probability that a mineral survives erosion when these measures of time are combined with published data suggesting that a mineral s dissolution reaction rate decreases during the course of weathering we find that internal soil mixing by partially controlling the age distribution of minerals within a soil might significantly alter the soil s mass loss rate via chemical weathering

a multi proxy study of lake development in response to catchment changes during the holocene at lochnagar north east scotland abstract this paper describes a multi core lake sediment study using pollen diatoms and chironomids together with magnetics and sediment biogeochemistry as biotic and abiotic proxies to infer lake development in response to environmental change during the holocene at lochnagar in the eastern highlands of scotland diatoms are used to infer ph chironomids to infer temperature with pollen and plant megafossils acting as an independent proxy to validate these records and to provide insights into changes in catchment vegetation and soils lipid biomarkers are explored for their potential to provide additional information on lake productivity the results indicate highly distinctive fluctuations in the loss on ignition loi record which are in phase with changes in some biotic chironomid head capsule concentration and abiotic coarse silt particle size fraction and lipid and chlorine fractions variables catchment driven changes due to the development and degredation of soils and the natural succession and human intervention on terrestrial catchment vegetation have the strongest influence on the diatom and chironomid assemblages these catchment processes resulted in the natural acidification of the lake water post industrial acidification of the lake was also influential on the lake biota climate driven temperature change appears to have had only a weak influence on the biota with declines in cold stenothermic chironomid taxa in response to early holocene warming and declines in thermophilic chironomids in response to cooling at about 2600 cal yr bp

multi proxy records of quaternary fluvio lacustrine sediments around lakes eymir and mogan ankara central anatolia turkey this paper presents the mineralogical geochemical palynological and stable isotopic compositions of the late pleistocene holocene fluvio lacustrine sediments around lakes eymir and mogan ankara central anatolia it is based on the interpretation of the multi proxy records in conjunction with the geochronological data in eight different sections the comparison between the increase decrease in the abundances of carbonates and total clay assemblages is correlated with the changing abundance of coniferous forests and herbaceous plants mainly asteraceae and chenopodiaceae 13c and 18o values and molecular weathering ratios of the sediments revealing the hydrolysis evaporation and leaching together with chemical index of alteration cia provide insight into the climatic changes in the study area between 11 899 and 1428 cal year bp relatively higher total clay amount 18o of around 8 and higher cia 40 with higher hydrolysis suggest humid conditions during 11 899 6448 cal year bp between 6448 and 5763 cal year bp sediments show oscillations between high and relatively low values of the proxy data implying intercalation of dry and wet seasons the last period recorded between 5763 and 1428 cal year bp is realized with high calcite precipitation low total clay and low cia and relatively higher salinization which directly characterize aridity

the temperature of europe during the holocene reconstructed from pollen data we present the first area average time series reconstructions of warmest month coldest month and mean annual surface air temperatures across europe during the last 12 000 years these series are based on quantitative pollen climate reconstructions from over 500 pollen sites assimilated using an innovative four dimensional gridding procedure this approach combines three dimensional spatial gridding with a fourth dimension represented by time allowing data from irregular time series to be focussed onto a regular time step we provide six regional reconstructed temperature time series as well as summary time series for the whole of europe the results suggest major spatial and seasonal differences in holocene temperature trends within a remarkably balanced regional and annual energy budget the traditional mid holocene thermal maximum is observed only over northern europe and principally during the summer this warming was balanced by a mid holocene cooling over southern europe whilst central europe occupied an intermediary position changes in annual mean temperatures for europe as a whole suggest an almost linear increase in thermal budget up to 7800 bp followed by stable conditions for the remainder of the holocene this early holocene warming and later equilibrium has been mainly modulated by increasing winter temperatures in the west which have continued to rise at a progressively decreasing rate up to the present day

the climate of europe during the holocene a gridded pollen based reconstruction and its multi proxy evaluation we present a new gridded climate reconstruction for europe for the last 12 000 years based on pollen data the reconstruction is an update of davis et al 2003 using the same methodology but with a greatly expanded fossil and surface sample dataset and more rigorous quality control the modern pollen dataset has been increased by more than 80 and the fossil pollen dataset by more than 50 representing almost 60 000 individual pollen samples the climate parameters reconstructed include summer winter and annual temperatures and precipitation as well as a measure of moisture balance and growing degree days above 5 degrees c confidence limits were established for the reconstruction based on transfer function and interpolation uncertainties the reconstruction takes account of post glacial isostatic readjustment which resulted in a potential warming bias of up to 1 2 degrees c for parts of fennoscandia in the early holocene as well as changes in palaeogeography resulting from decaying ice sheets and rising post glacial sea levels this new dataset has been evaluated against previously published independent quantitative climate reconstructions from a variety of archives on a site by site basis across europe the results of this comparison are generally very good only chironomid based reconstructions showed substantial differences with our values our reconstruction is available for download as gridded maps throughout the holocene on a 1000 year time step the gridded format makes our reconstructions suitable for comparison with climate model output and for other applications such as vegetation and land use modelling our new climate reconstruction suggests that warming in europe during the mid holocene was greater in winter than in summer an apparent paradox that is not consistent with current climate model simulations and traditional interpretations of milankovitch theory c 2015 elsevier ltd all rights reserved

reconstruction of holocene precipitation patterns in europe using pollen and lake level data abstract lake level data can be used to refine palaeoclimate reconstructions based on pollen data this approach is illustrated for the european holocene estimates of p pet precipitation minus potential evapotranspiration were first inferred from modern pollen analogues the pollen based estimates were then compared with the status of lakes within a 5 radius analogues with p pet anomalies inconsistent with the lake level changes were rejected the constrained sets of analogues were used to estimate continental scale patterns of annual mean temperature and annual precipitation at 3000 yr intervals estimated temperature anomalies differed only slightly from the unconstrained reconstructions estimated precipitation anomalies however showed improved spatial coherence and increased regional contrast and were occasionally reversed in sign the effect of the constraint was to impose a rational selection among almost equally similar modern pollen analogues with similar temperatures but widely varying moisture regimes the resulting maps showed clear spatially coherent patterns of change in precipitation as well as temperature suitable for comparison with climate model results further improvement of these maps will become possible as a more extensive coverage of lake level data is obtained

holocene seasonality changes in the central mediterranean region reconstructed from the pollen sequences of lake accesa italy and tenaghi philippon greece this study presents pollen based climate reconstructions of holocene temperature and precipitation seasonality for two high resolution pollen sequences from the central lake accesa central italy and eastern mediterranean tenaghi philippon greece regions the quantitative climate reconstruction uses multiple methods to provide an improved assessment of the uncertainties involved in palaeoclimate reconstructions the multimethod approach comprises partial least squares regression weighted average partial least squares regression the modern analogues technique and the non metric multidimensional scaling generalized additive model method we find two distinct climate intervals during the holocene the first is a moist period from 9500 to 7800 cal bp characterised by wet winters and dry summers resulting in a strongly seasonal hydrological contrast stronger than today that is interrupted by a short lived event around 8200 cal bp this event is characterised by wet winters and summers at accesa wh

a multiproxy study of younger dryas and early holocene climatic conditions from the grabia river paleo oxbow lake central poland abstract a multi proxy reconstruction of water depth temperature and precipitation inferred from cladocera chironomidae and pollen assemblages has been obtained from wierczyna paleo oxbow central poland during the younger dryas yd and early holocene results suggest that the yd was relatively cold and comprised two main phases the first ca 12 500 12 000 cal yrs bp is characterized by a continental climatic regime and a decrease in winter temperatures and precipitation but an increase in spring summer precipitation the second phase ca 12 000 11 500 cal yrs bp was more mild with a variable continental climate an increase in summer and winter temperature a lengthening of the growing season and increased annual precipitation the reconstructed water level generally follows changes in spring and summer precipitation and length of growing season the frequency and timing of hydroclimatic oscillations at wierczyna show strong similarities to records from other sites in europe this confirms that oxbows and valley mire ecosystems respond to rapid climate change during the yd and early holocene this study therefore brings new insights into the effects of climate changes on river environments especially during the yd we also discuss the limitations of water depth temperature and precipitation reconstructions inferred from the studied biotic assemblages

geomorphologic and paleoclimatic evidence of holocene glaciation on mount olympus greece this study investigates the possibility of holocene glaciation on mount olympus greece with a respective local temperature precipitation equilibrium line altitude tp ela at c 2200m a s l based on geomorphologic and paleoclimatic evidence at present the local tp ela is situated above the mountain s summit c 2918 m a s l but permanent snowfields and ice bodies survive within megala kazania cirque between c 2400 and c 2300 m a s l because of the cirque s maritime setting that results from its close proximity c 18km to the aegean sea and of the local topographical controls the snow and ice bodies occupied a considerably larger area and attained a stabilization phase between ad 1960 and 1980 also manifested from aerial photographs a period characterized by increased winter precipitation pw with subsequent tp ela depression to c 2410m a s l mid to late 20th century pw and tp ela variations exhibit negative correlations with the winter north atlantic oscillation index naow at annual and multidecadal 30 years timescales late holocene ad 1680 1860 reconstructed summer mean temperatures were lower by ts 1 1 c in relation to the reference period between ad 1960 and 1980 and were also superimposed to negative naow phases thus bracketing this time interval as a favorable one to glacial formation and or advance millennial scale annual precipitation reconstructions at the hypothesized tp ela c 2200m a s l point the period between 8 and 4 kyr bp as another glacier friendly candidate the mid holocene rather simplistic sequence of potential glacial advance phase was disturbed by short lived cold climatic deteriorations well documented over the northern aegean region that may partly explain the multicrested shape of the highest c 2200 m a s l morainic complex of megala kazania cirque

global glacial isostasy and the surface of the ice age earth the ice 5g vm2 model and grace abstract the 100 kyr quasiperiodic variation of continental ice cover which has been a persistent feature of climate system evolution throughout the most recent 900 kyr of earth history has occurred as a consequence of changes in the seasonal insolation regime forced by the influence of gravitational n body effects in the solar system on the geometry of earth s orbit around the sun the impacts of the changing surface ice load upon both earth s shape and gravitational field as well as upon sea level history have come to be measurable using a variety of geological and geophysical techniques these observations are invertible to obtain useful information on both the internal viscoelastic structure of the solid earth and on the detailed spatiotemporal characteristics of glaciation history this review focuses upon the most recent advances that have been achieved in each of these areas advances that have proven to be central to the construction of the refined model of the global process of glacial isos

holocene mean july temperature and winter precipitation in western norway inferred from palynological and glaciological lake sediment proxies reconstructions of mean july temperature tjul and winter precipitation pw for the last 11 500 years on the folgefonna peninsula are presented tjul was reconstructed using pollen climate transfer functions and pw was reconstructed based on the exponential relationship between mean solid winter precipitation and ablation season temperature at the equilibrium line altitude ela with a reconstructed former ela using tjul as the proxy for ablation season temperature the reconstructions from the folgefonna peninsula suggest that the early holocene was relatively cool and dry until c 8000 cal yr bp followed by a warm and humid mid holocene until c 4000 cal yr bp with inferred tjul above 128c and pw reaching as high as 225 of the present day subsequent to c 4000 cal yr bp a reduction is seen in both inferred tjul and pw with large fluctuations during the last 500 years in addition new calculations of pw from two glaciers hardangerjokulen and jostedalsbreen in southern norway are presented the results show that pw varied in phase at all glaciers probably as a response to the same climate forcing factor during the early holocene a major shift is suggested between winds from the west and the east

climatic and environmental controls on speleothem oxygen isotope values variations in speleothem oxygen isotope values d 18 o result from a complicated interplay of environmental controls and processes in the ocean atmosphere soil zone epikarst and cave system as such the controls on speleothem d 18 o values are extremely complex an understanding of the processes that control equilibrium and kinetic fractionation of oxygen isotopes in water and carbonate species is essential for the proper interpretation of speleothem d 18 o as paleoclimate and paleoenvironmental proxies and is best complemented by study of site specific cave processes such as infiltration flow routing drip seasonality and saturation state and cave microclimate among others this review is a process based summary of the multiple controls on d 18 o in the atmosphere soil epikarst and speleothem calcite illustrated with case studies primary controls of d 18 o in the atmosphere include temperature and relative humidity through their role in the multiple isotope effects variability and modifications of water d 18 o values in the soil and epikarst zones are dominated by evaporation mixing and infiltration of source waters the isotopically effective recharge into a cave system consists of those waters that participate in precipitation of caco3 resulting in calcite deposition rates which may be biased to time periods with optimal dripwater saturation state recent modeling experimental and observational data yield insight into the significance of kinetic fractionation between dissolved carbonate phases and solid caco3 and have implications for the hendy test to assist interpretation of speleothem d 18 o time series quantitative and semi quantitative d 18 o climate calibrations are discussed with an emphasis on some of the difficulties inherent in using modern spatial and temporal isotope gradients to interpret speleothems as paleoclimate proxy records finally several case studies of globally significant speleothem paleoclimate records are discussed that show the utility of d 18 o to reconstruct past climate

forest history peatland development and mid to late holocene environmental change in the southern taiga forest of central european russia understanding the long term ecological dynamics of boreal forests is essential for assessment of the possible responses and feedbacks of forest ecosystems to climate change new data on past forest dynamics and peatland development were obtained from a peat sequence in the southern valdai hills european russia based on pollen plant macrofossil micro charcoal peat humification and testate amoeba analyses in terms of vegetation history the results demonstrate a dominance of broadleaved forests in the study area from 7000 4000 cal yr bp picea was initially a minor component of this forest but increased in cover rapidly with climatic cooling beginning at 4000 cal yr bp becoming the dominant species broadleaved species persisted until 900 cal yr with evidence for intensified felling and forest management over recent centuries over the last four hundred years there is evidence for widespread paludification and the establishment of picea sphagnum forests these data demonstrate how modern wet woodlands have been shaped by a combination of climatic and anthropogenic factors over several millennia the results also demonstrate the value of a multiproxy approach in understanding long term forest ecology