proposed re dating of the european ice core chronology by seven years prior to the 7th century ad 1 progress in the study of past climate change requires integration of historical documentation tree ring data and ice core chemistry larsen et al 2008 re evaluate volcanic acid signals in the dye 3 grip and ngrip ice cores and identify large eruptions at 529 2 and 533 534 2 the latter claimed to cause the dry fog of 536 537 and environmental consequences to 550 this conflicts with previous suggestions of a two stage environmental event one in 536 the second c 540 understanding the full range of natural hazards requires critical evaluation of the happenings in the mid 6th century this paper will show that 4 spaced tree ring responses to extreme environmental conditions in the 6th century can be used to re locate 4 key ice acid dates moving the ice core chronology forward 7 years places two large volcanoes in 536 and 541 explaining the extended duration of the 536 550 effects and anchoring the ice chronology

the topology of evolving rift fault networks single phase vs multi phase rifts rift fault networks can be complex particularly those developed by multiple periods of non coaxial extension comprising non colinear faults with many interactions thus topology rather than simple geometry is required to characterise such networks as it provides a way to describe the arrangement of individual faults in the network topology is analysed here in terms of nodes isolated i nodes or connected y or x nodes and branches i i i c c c branches in map view the relative proportions of these parameters vary in natural single and multi phase rift fault networks and in scaled physical models at different stages of development and strain interactions in single phase rifting are limited to fault splays and along strike fault linkage i node and i i or i c branch dominated networks whereas in multi phase rifting the topology evolves towards y node and c c branch dominated networks with the degree of connectivity increasing with greater strain the changes in topology and network connectivity have significant implications for fluid flow and reservoir compartmentalisation studies furthermore topology helps to distinguish single and multiple phase extension i e tectonic histories and thus provide constraints on the geodynamic context of sedimentary basins

the holocene indian monsoon variability over the southern tibetan plateau and its teleconnections abstract a high resolution stalagmite oxygen isotope record from tianmen cave located in the south central tibetan plateau characterizes detailed climatic variations between 8 7 and 4 3 ka bp on centennial and decadal time scales with a temporal resolution of 3 to 7 years the tianmen record is in good agreement with speleothem records from asian monsoon regions i e dongge cave dykoski et al 2005 wang et al 2005 qunf cave fleitmann et al 2003 upwelling records from the arabian sea gupta et al 2003 gupta et al 2005 and peat bog records from southeast tibetan plateau hong et al 2003 indicating that the indian summer monsoon ism gradually weakened as northern hemisphere summer insolation declined during the early mid holocene and that ism intensity rather than temperature dominates the precipitation 18o on centennial to decadal time scales in the southern tp on centennial to decadal time scales the detrended tianmen record correlates well with the greenland ice core record further confirming the mechanistic connection between the ism and high northern latitude temperature changes meanwhile the tianmen record bears significant solar activity cycles suggesting that the solar output changes may affect the variability of the ism and likely the position of the intertropical convergence zone itcz as well moreover due to joint effects of changes in monsoon precipitation moisture source and temperature the tianmen 18o record shows much larger amplitude changes than speleothem 18o records from low elevation asian monsoon regions which is similar to the previously reported marine isotope stage mis 5 record cai et al 2010 suggesting heightened sensitivity of precipitation isotope composition to climate changes over the high elevation regions and further demonstrating that the stable isotope lapse rate may change under different climatic conditions

comment on a synchronized dating of three greenland ice cores throughout the holocene by b m vinther et al no minoan tephra in the 1642 b c layer of the grip ice core denton j s pearce n j g 2008 comment on a synchronized dating of three greenland ice cores throughout the holocene by b m vinther et al no minoan tephra in the 1642 b c layer of the grip ice core journal of geophysical research 113 d04303 7 pp

reconstruction of the east asian summer monsoon rainfall distribution at centennial scale during the last glacial maximum abstract the last glacial maximum lgm defined as the period between 23 and 19 ka is considered a key climatic period with conditions in great contrast to the present study of this period may reveal aspects of global ice sheet sensitivity to regional and global climate change which is critical in understanding climate teleconnections and feedback mechanisms a stalagmite record from linglong cave central china in combination with other high resolution stalagmite records from southwest china and east china existing on the same moisture transport pathway allows a reconstruction of rainfall patterns during the lgm by making use of the 18o differences between stalagmite records the rainfall around both southwest and central east china show a prominent change centered at 24 ka corresponding to the h2 event one of the heinrich events related to north atlantic ice rafting also in central east china around the periods at 22 and 20 ka the rainfall is lower than the average during the whole lgm while around 23 21 and 19 ka the rainfall is higher than the average which is opposite to the rainfall variation in southwest china this apparent dipole rainfall pattern during the lgm is similar to the modern east asian summer monsoon easm rainfall distribution observed during weak monsoon periods suggesting a much weaker easm with its front moving less far north during the lgm than at present which may link to north atlantic climate and shifting of the intertropical convergence zone itcz power spectral analysis reveals that the rainfall variations in southwest china are mainly controlled by a cycle of 1000 yr while in central east china it is mainly controlled by cycles of 1800 yr and 1300 yr which are all possible solar activity cycles suggesting that the easm rainfall on long term scales is dominated by external forces

holocene tephrostratigraphy of varved sediment records from lakes tiefer see ne germany and czechowskie n poland a detailed holocene tephrostratigraphic framework has been developed for two predominately varved lake sediment sequences from ne germany lake tiefer see and central n poland lake czechowskie a total of thirteen tephras and cryptotephras of icelandic provenance were detected and chemically fingerprinted in order to define correlatives and to integrate known tephra ages into the sediment chronologies out of these three cryptotephras askja ad1875 askja s and h asseldalen were identified in both records thus allowing a detailed synchronization of developing high resolution palaeoenvironmental proxy data the early holocene saksunarvatn ash layer and the middle holocene lairg b and hekla 4 cryptotephras in lake tiefer see are further important anchor points for the comparison with other high resolution palaeoclimate records in central and northern europe tentative correlations of cryptotephras have been made with a historical basaltic grimsv otn eruption ad890 e ad856 and three late holocene rhyolitic eruptions including the 2 1 ka glen garry and two unknown high silicic cryptotephras of probably icelandic provenance 1 9 cal ka bp

identification of aniakchak alaska tephra in greenland ice core challenges the 1645 bc date for minoan eruption of santorini pearce nicholas westgate j a eastwood w j preece s j 2006 identification of aniakchak alaska tephra in greenland ice core challenges the 1645 bc date for minoan eruption of santorini geochemistry geophysics and geosystems 5 pp q03005 rae2008

on the common solar signal in different cosmogenic isotope data sets 1 in this article we aim to determine frequency ranges and intervals of time in which the solar signal dominates in different cosmogenic isotope data from a 14c based reconstruction of cosmic ray intensity over the last millennia we computed expected 10be variations in two antarctic sites dom fuji and south pole and two greenland sites dye 3 and gisp 2 and compared them with the actually measured 10be abundance at the sites by applying different methods of analysis such as bivariate correlation conventional fft coherence and wavelet coherence we found the following 1 the modeled series on the basis of 14c data are in good agreement with the measured 10be data sets on different timescales and at different locations confirming the existence of a common solar signal in both isotope data 2 the 10be data are driven by the solar signal on timescales from about 100 years up to 1000 years or even to multimillennial scales at the longer scales paleomagnetism plays an increasingly important role 3 the local climate dominates the 10be data mostly on short 100 years timescales but the solar signal becomes important even at short scales during periods of grand minima of solar activity 4 there is an indication of a possible systematic uncertainty in the early holocene likely due to a not perfectly stable thermohaline circulation which requires additional studies we have shown that both 14c and 10be based records are consistent with each other over a wide range of timescales and time intervals they form a robust basis for quantitative reconstructions of solar activity variations in the past

a new greenland deep ice core the polar ice sheets are rich sources of information on past atmospheric conditions including paleoclimates a new deep ice core has been drilled in south greenland comparison of the oxygen isotopic profile with that from camp century and with a deep sea foraminifera record indicates that the new core reaches back to about 90 000 years before present in a continuous sequence the details in the wisconsin part of the ice core records seem to be climatically significant and the general trends reveal all of the relevant emiliani stages recorded in deep sea cores the redated camp century record suggests a dramatic termination of the eem sangamon interglacial

stratigraphic analysis of an ice core from the prince of wales icefield ellesmere island arctic canada using digital image analysis high resolution density past summer warmth reconstruction and melt effect on ice core solid conductivity 1 high resolution 1 mm stratigraphic information was derived from digital image analysis of an ice core from the prince of wales pow icefield central ellesmere island canada following careful image processing a profile of ice core transmitted light was derived from the greyscale images and used to reconstruct high resolution density variations for the unfractured sections of the core images were further classified into infiltration and glacier ice using an automatic thresholding procedure and were converted to a high resolution melt percentage index the mean annual melt percentage over the last 580 years was 9 and melting occurred in 8 years out of 10 melting obliterated most of the original depositional sequence and seasonal density cycles were mostly unrecognizable the ice core solid conductivity was greater and more variable in melt features than in glacier ice owing to washout of strong acids by meltwater elution and chemical enrichment upon refreezing this hindered the identification of acid volcanic layers and further compromised dating by annual layer counting comparison of the melt record with those from other arctic ice caps shows that the melt temperature relationship on pow icefield is site specific we speculate that this is due to the peculiar position of the icefield which rests on the periphery of the baffin bay maritime climate zone and to the proximity of the north open water polynya which controls snow accumulation variability on the icefield and affects the melt percentage index

abrupt cooling repeatedly punctuated early holocene climate in eastern north america climate proxy records and general circulation models suggest that atlantic meridional overturning circulation amoc plays a key role for global climate changes paleoceanographic data document mul

deduction of surface accumulation history from ice core age depth data ice core data are the only source of ice response on timescales of hundreds to thousands of years which is necessary to describe polar ice sheet flows and their interaction with changing climatic conditions ice properties such as a grain growth relation require knowledge of each ice particle s history since first deposited at the surface and not simply the present core state this study is an analysis of 11 present ice cores using their age depth data and present accumulation to infer their past accumulation and mean strain rate and in turn the strain at each level of the core these are the ingredients necessary to determine the particle paths and associated evolution of properties the conventional assumptions of a purely vertical velocity distribution with a uniform compressive strain rate in the core are made but unlike an earlier analysis which allowed independent surface accumulation and strain rate histories it is now assumed that the strain rate is proportional to the accumulation determination of the past accumulation and proportionality factor is accomplished by correlation with the present age depth data and while good correlations are obtained a consistent solution other close correlations can yield quite different accumulation histories and corresponding proportional strain rate histories

reconciliation of hydroclimate sequences from the chinese loess plateau and low latitude east asian summer monsoon regions over the past 14 500years we discuss replicated stalagmite 18o records with interannual to multidecadal resolution from lianhua cave on the chinese loess plateau to illustrate the precipitation history of the east asian summer monsoon easm region over the last 14 5 thousand years ka bp before 1950 ce hereafter and to re evaluate the inconsistency in the proxy inferred palaeoclimate time series in northern china agreement between the stalagmite 18o from lianhua and other caves from central southern china indicates that regional climate changes after the last glacial were concurrent across mainland china indicating that insolation was the primary factor controlling the evolution of the asian summer monsoon asm the stalagmite 18o enrichment of 2 5 in the younger dryas and 1 7 during the 8 2 ka bp event in lianhua were larger than those in caves from central and southern china the evidence suggests that different meridional responses of weak precipitation conditions in the asm realm occurred during these two abrupt events driven by high latitude forcing in the northern hemisphere the heterogeneous hydroclimate sequences in northern china inferred from different natural archives are most likely attributable to the complexity of the formations and or some chronological uncertainty

eemian interglacial reconstructed from a greenland folded ice core efforts to extract a greenland ice core with a complete record of the eemian interglacial 130 000 to 115 000 years ago have until now been unsuccessful the response of the greenland ice sheet to the warmer than present climate of the eemian has thus remained unclear here we present the new north greenland eemian ice drilling neem ice core and show only a modest ice sheet response to the strong warming in the early eemian we reconstructed the eemian record from folded ice using globally homogeneous parameters known from dated greenland and antarctic ice core records on the basis of water stable isotopes neem surface temperatures after the onset of the eemian 126 000 years ago peaked at 8 4 degrees celsius above the mean of the past millennium followed by a gradual cooling that was probably driven by the decreasing summer insolation between 128 000 and 122 000 years ago the thickness of the northwest greenland ice sheet decreased by 400 250 metres reaching surface elevations 122 000 years ago of 130 300 metres lower than the present extensive surface melt occurred at the neem site during the eemian a phenomenon witnessed when melt layers formed again at neem during the exceptional heat of july 2012 with additional warming surface melt might become more common in the future

nao signal recorded in the stable isotopes of greenland ice cores 1 the winter 18o signal is extracted from 7 greenland ice cores covering the past 700 years to filter out noise and local variations in the 7 isotope records a principal component analysis is carried out on the ice core data a comparison between the time series of the first principal component pc1 with 67 years of winter december to march temperature measurements from 3 southern greenland synoptic stations shows highly significant correlations southern greenland winter temperatures are known to be greatly influenced by the north atlantic oscillation nao a good proxy for southern greenland temperatures is therefore expected to reveal at least parts of the nao signal it is shown that the pc1 time series indeed is significantly correlated to the nao during the winter months the inclusion of ice core winter season 18o time series in future multiproxy nao reconstructions is therefore recommended

air hydrate inclusions in fresh ice core one of the characteristic features of polar glacier ice is the abundance of air bubbles1 3 with increasing depth from the surface of the ice sheet the size of the bubbles generally decreases in response to the change of overburden pressure below a certain depth the bubbles start to shrink faster than expected and finally become invisible although not visible to the naked eye unit mass of the bubble free clear ice includes almost the same volume of air as unit mass of bubbly ice4 5 it is hypothesized that the air exists in the ice structure probably in the form of clathrate hydrates as suggested by miller6 7 but until now the location of the air has been unknown direct observations of air hydrate inclusions were carried out for the first time in fresh ice cores from dye 3 greenland when the ice structure surrounding air hydrate was melted an explosive transition occurred releasing a gas bubble into the melt cavity

multifractal detrended fluctuation analysis of the δ 18 o record of ngrip ice core the multifractal properties and scaling behaviors of the long term and recent 2000 year 18o records of ngrip ice core are investigated by the multifractal detrended fluctuation analysis method the generalized hurst exponents multifractal scaling exponents and singularity spectrums of two 18o records are derived to verify the multifractiality of two records and the multifractal behaviors of two records are obviously different which may reflect the climate change of the recent 2000 year time is quite different from one of the long term time in addition the probability distribution analysis of two 18o records is presented to manifest the different multifractality between two 18o records of ngrip ice core our results will be helpful to research the climate change

a model of crystal size evolution in polar ice masses in the deep ice cores drilled at the grip ngrip and gisp2 sites in greenland and at byrd station and the summit of law dome in antarctica the mean crystal size increases with depth in the shallow subsurface and reaches steady values at intermediate depth this behaviour has been attributed to the competition between grain boundary migration driven crystal growth and crystal polygonization but the effects of changing crystal dislocation density and non equiaxed crystal shape in this competition are uncertain we study these effects with a simple model it describes how the mean height and width of crystals evolve as they flatten under vertical compression and as crystal growth and polygonization compete the polygonization rate is assumed to be proportional to the mean dislocation density across crystals migration recrystallization which can affect crystal growth via strain induced grain boundary migration but whose impact on the mean crystal size is difficult to quantify for ice at present is not accounted for when applied to the five ice core sites the model simulates the observed crystal size profiles well down to the bottom of their steady regions although the match for law dome is less satisfactory polygonization rate factors retrieved for the sites range from 10 5 to 10 2 a 1 we conclude that since crystal size and dislocation density evolve in a strongly coupled manner consistent modelling requires multiple differential equations to track both of these variables future ice core analysis should also determine crystal size in all three principal directions

downcore variations of sedimentary detrital 238 u 232 th ratio implications on the use of 230 th xs and 231 pa xs to reconstruct sediment flux and ocean circulation excess 231 pa and 230 th 231 pa xs and 230 th xs can be used to reconstruct past oceanic sedimenta tion 230 th normalized flux and circulation changes 231 pa 230 th xs 0 hereafter pa th these quantities are determined by computing the detrital and authigenic contributions from bulk sediment measurement the method relies on the use of a chosen constant value of the detrital 238 u 232 th activity ratio hereafter u th det in this study we have extracted the detrital fraction of the sediments from north atlantic deep sea core su90 08 43803 0 1n 30802 0 5w 3 080 m and determined its u th det value over the last 40 ky we find that u th det varied significantly through time with a minimum value of 0 4 during the holocene and a maximum value of 0 7 during the last glacial maximum lgm the sensitivity of sedimentary 230 th normalized flux and pa th is tested for our study site and for other north atlantic sites we show that the sensitivity is highly dependent on the core location and its terrigenous material supply the 230 th normalized flux and pa th signals are very robust in cores with low detrital contributions whereas they are very sensitive to u th det changes in cores with higher detrital contribution in the latter case changes in 230 th normalized flux and pa th due to the choice of a constant u th det can largely exceed the uncertainty on the 230 th normalized flux and pa th inducing potential biases in the amplitude and temporal variability of reconstructed sedimentation and ocean circulation changes

towards radiocarbon dating of ice cores a recently developed dating method for glacier ice based on the analysis of radiocarbon in carbonaceous aerosol particles is thoroughly investigated we discuss the potential of this method to achieve a reliable dating using examples from a mid and a low latitude ice core two series of samples from colle gnifetti 4450 m a s l swiss alps and nevado illimani 6300 m a s l bolivian andes demonstrate that the 14c ages deduced from the water insoluble organic carbon fraction represent the age of the ice sample sizes ranged between 7 and 100 g carbon for validation we compare our results with those from independent dating this new method is thought to have major implications for dating non polar ice cores in the future as it provides complementary age information for time periods not accessible with common dating techniques

latest pleistocene and holocene glaciation of baffin island arctic canada key patterns and chronologies abstract melting glaciers and ice caps on baffin island contribute roughly half of the sea level rise from all ice in arctic canada although they comprise only one fourth of the total ice in the region the uncertain future response of arctic glaciers and ice caps to climate change motivates the use of paleodata to evaluate the sensitivity of glaciers to past warm intervals and to constrain mechanisms that drive glacier change we review the key patterns and chronologies of latest pleistocene and holocene glaciation on baffin island the deglaciation by the laurentide ice sheet occurred generally slowly and steadily throughout the holocene to its present margin barnes ice cap except for two periods of rapid retreat an early interval 12 to 10 ka when outlet glaciers retreated rapidly through deep fiords and sounds and a later interval 7 ka when ice over foxe basin collapsed in coastal settings alpine glaciers were smaller during the younger dryas period than during the little ice age at least some alpine glaciers apparently survived the early holocene thermal maximum which was several degrees warmer than today although data on glacier extent during the early holocene is extremely sparse following the early holocene thermal maximum glaciers advanced during neoglaciation beginning in some places as early as 6 ka although most sites do not record near little ice age positions until 3 5 to 2 5 ka alpine glaciers reached their largest holocene extents during the little ice age when temperatures were 1 1 5 c cooler than during the late 20th century synchronous advances across baffin island throughout neoglaciation indicate sub milankovitch controls on glaciation that could involve major volcanic eruptions and solar variability future work should further elucidate the state of glaciers and ice caps during the early holocene thermal maximum and glacier response to climate forcing mechanisms

late quaternary carbon cycling responses to environmental change revealed by multi proxy analyses of a sediment core from an upland lake in southwest china stable carbon isotope 13c values of organic matter in lacustrine sediments are commonly used to trace past changes in terrestrial and aquatic carbon cycles here we use a high resolution well dated 13c record from lake tengchongqinghai tcqh in southwestern china together with other proxy indices to reconstruct the paleolimnological history over the past 18 5 ka organic matter in the sediments of lake tcqh is derived predominately from aquatic macrophytes the lacustrine primary productivity is closely linked with lake level changes affected by variations in the strength of the asian summer monsoon and modified by evapotranspiration similar to lake sediments world wide a ca 3 shift occurred in the 13c values of lake tcqh in response to the significant increase in atmospheric co2 concentration during the last deglaciation in the holocene the availability of dissolved co2 in the lake water of lake tcqh was determined by variations in hydraulic energy low water turbulence creates a thick stagnant boundary layer around aquatic plants which will restrict the rate of co2 diffusion and result in more positive 13c values of aquatic plants in contrast significant water turbulence dramatically reduces the boundary layer thickness leading to more negative 13c values of aquatic plants

visual stratigraphic dating of the gisp2 ice core basis reproducibility and application annual layers are visible in the greenland ice sheet project 2 ice core from central greenland allowing rapid dating of the core changes in bubble and grain structure caused by near surface primarily summertime formation of hoar complexes provide the main visible annual marker in the holocene and changes in cloudiness of the ice correlated with dustiness mark wisconsinan annual cycles both markers are evident and have been intercalibrated in early holocene ice layer counts are reproducible between different workers and for one worker at different times with 1 error over century length times in the holocene reproducibility is typically 5 in wisconsinan ice age ice and decreases with increasing age and depth cumulative ages from visible stratigraphy are not significantly different from independent ages of prominent events for ice older than the historical record and younger than approximately 50 000 years visible observations are not greatly degraded by brittle ice or many other core quality problems allowing construction of long consistently sampled time series high accuracy requires careful study of the core by dedicated observers

characterizing atmospheric circulation signals in greenland ice cores insights from a weather regime approach greenland ice cores offer seasonal to annual records of 18o a proxy for precipitation weighted temperature over the last few centuries to millennia here we investigate the regional footprints of the north atlantic weather regimes on greenland isotope and climate variability using a compilation of 22 different shallow ice cores and the atmospheric pressure conditions from the twentieth century reanalysis 20cr as a first step we have verified that the leading modes of winter and annual 18o are well correlated with oceanic atlantic multidecadal oscillation and atmospheric north atlantic oscillation nao indices respectively and also marginally with external forcings thus confirming earlier studies the link between weather regimes and greenland precipitation precipitation weighted temperature and 18o is further explored by using an isotope simulation from the lmdz iso model where the 3 dimensional wind fields are nudged to those of 20cr in winter the nao and nao regimes in lmdz iso produce the largest isotopic changes over the entire greenland region with maximum anomalies in the south likewise the scandinavian blocking and the atlantic ridge also show remarkable imprints on isotopic composition over the region to assess the robustness and model dependency of our findings a second isotope simulation from the isotopic model is also explored the percentage of greenland 18o variance explained by the ensemble of weather regimes is increased by a factor near two in both lmdz iso and isogsm when compared to the contribution of the nao index only similarly weather regimes provide a net gain in the 18o variance explained of similar magnitude for the whole set of ice core records greenland 18o also appears to be locally affected by the low frequency variations in the centres of action of the weather regimes with clearer imprints in the lmdz iso simulation this study opens the possibility for reconstructing past changes in the frequencies of occurrence of the weather regimes which would rely on the sensitive regions identified here and the use of additional proxies over the north atlantic region

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

fragmented reduction processes middle palaeolithic technical behaviour in the abri du maras shelter southeastern france new excavations at the abri du maras located in the southeast of france have yielded middle palaeolithic assemblages with evidence of rock shelter occupations in a cold climatic context contemporaneous with mis 4 few mis 4 sites are known in this part of france and especially in this state of preservation the paper is focused on one sedimentological layer divided into two archaeological levels sub levels 4 1 and 4 2 our goal was to examine the middle palaeolithic lithic assemblage of these two levels by interdisciplinary approaches technology origin of flint and functional analysis of stone tools in order to identify the technical strategies and the land use patterns in a specific environmental context the two occupations do not show differences in behaviours the technical strategies applied to flint and other stones indicate a fragmentation of the reduction processes in a local and semi local perimeter around the site the main core technology is levallois generally on flint cortical cores on flakes flint flakes blades and points are the main components of the series and the technological aims of the debitage due to the small size of the flakes used for flaking large flint flakes blades levallois or cortical and levallois points were produced elsewhere to the north and south of the site up to 20 30 km according to the geological study and then brought to the shelter flakes in other lithic materials quartz quartzite were also knapped elsewhere before being transported to the shelter some of the large flint flakes but also nodules and fragments of slabs were then used for onsite flaking flake tools are very rare evidence of impact fractures and tcsa tcsps values of the corpus of unretouched levallois points suggest that some points brought or prepared on the site could have been used as projectile tips the lithics attest to management of local and semi local stones in a perimeter of 30 km around the site possibly more due to some unidentified flint and an anticipation of domestic needs in relation to reindeer hunting the predominant activity imported artefacts and artefacts made on the site were used for the same diversity of activities and materials butchery plant and woodworking the technological strategies and the type of management differ slightly from those from cave assemblages in the same area located in valleys and on low plateaux near the rhone corridor possibly due to the type of the site a vast shelter data from the abri du maras are compared to data from the other middle palaeolithic sites of the region and the role of the topographic aspect of the site on the type of occupations is discussed

lateglacial changes in river morphologies of northwestern europe an example of a smooth response to climate forcing cher river france climatic oscillations occurring during the pleniglacial and lateglacial periods are generally associated with several changes in fluvial morphology and processes this study investigated two reaches of the cher river basin noyers sur cher and thenioux regarding morphological adjustments during the lateglacial period and the early holocene transitions from the pleniglacial to the lateglacial and from the lateglacial to the early holocene ca 14 700 11 500 cal bp are considered as interesting study cases because it consists of rapid and abrupt climate oscillations generally clearly recorded in current floodplains the sites studied are located in the cher river floodplain which is one of the main tributaries of the loire river several investigations have been conducted in the main valley but few of them specifically focused on geomorphological evolutions of medium sized catchments such as tributaries of the loire river therefore we examined this specific period through investigations recently conducted in the middle valley of the cher river this study aimed to 1 provide a geomorphological approach to fluvial adjustments during the lateglacial from cases located in lowland areas of a medium sized basin and 2 analyse the spatio temporal variability of fluvial responses assessment of geomorphological trajectories of the two reaches studied highlights that fluvial metamorphosis occurring during the lateglacial and early holocene seems to be characterised by lateral readjustments and a low signal of morphological instability shallow incision and aggradation processes slow and progressive change in channel morphology this observation is enhanced by the comparison with known geomorphological evolution patterns of adjacent basins the intrinsic components of the cher basin such as slope and valley width were considered as explanatory factors for the lack of morphogenetic processes in addition the geographical location of the reaches studied may also have led to a moderated expression of climate forcing indeed the elevation as well as the north south and east west gradients may contribute to the low level of geomorphological adjustments in response to these climatic oscillations this gradient could also have support this the fluvial response because of the weakly developed loess cover which may have limited the fine sediment supply and the aggradation of the valley bottom

lake highstands on the altiplano tropical andes contemporaneous with heinrich 1 and the younger dryas new insights from 14 c u th dating and δ 18 o of carbonates this study provides new geochronological and stable isotope constraints on late pleistocene fluctuations in lake level that occurred in the closed watershed of the central altiplano between 25 and 12 ka u series isochrons and 14 c ages from carbonates are used to confirm and refine the previous chronology published placzek et al 2006b our new data support three successive lake highstands during the late pleistocene i the lake sajsi cycle from 25 to 19 ka that culminated at 3670 m at about 22 ka almost synchronously with the global last glacial maximum ii the lake tauca cycle that lasted from 18 to 14 5 ka and was characterized by the highest water level reached at least 3770 m from 16 5 to 15 ka iii the lake coipasa cycle from 12 5 to 11 9 ka that reached an elevation of 3700 m 42 m above the elevation of the salar de uyuni 3658 m these high amplitude lake level fluctuations are in phase with the cold warm oscillations that occurred in the north atlantic and greenland during the late pleistocene heinrich 1 bolling allerod younger dryas such temporal coincidence supports the hypothesis that wet events recorded in the central altiplano are controlled by the northesouth displacement of the inter tropical convergence zone resulting from changes in the meridional temperature gradient finally the oxygen isotope ratios measured in these lacustrine carbonates allows for calculation of the 18 o value of paleolake waters estimates of water 18 o v smow are 2 8 0 7 for lake tauca and 1 6 0 9 for lake coipasa these data are used to constrain changes in lake hydrology and can be interpreted to indicate that the proportion of precipitation arising from local water recycling was less than 50

non linear holocene climate evolution in the north atlantic a high resolution multi proxy record of glacier activity and environmental change from hvitarvatn central iceland abstract iceland is well situated to monitor north atlantic holocene climate variability terrestrial sites there offer the potential for well dated high resolution continuous records of environmental change and or glacier activity laminated sediments from the proglacial lake hvitarvatn provide a continuous record of environmental change and the development of the adjacent langjokull ice cap for the past 10 2 ka replicate lake sediment cores collected from multiple locations in the basin are placed in a secure geochronology by splicing a varve chronology for the past 3 ka with a tephra constrained paleomagnetic secular variation derived chronology for older sediments multiple proxies including sedimentation rate bulk density ice rafted debris sediment organic matter biogenic silica and diatom abundance allow annual to multi decadal resolution and reveal a dynamic holocene terrestrial climate following regional deglaciation of the main iceland ice sheet summer temperatures were high enough that mountain ice caps had already melted or were contributing insignificant sediment to the lake pronounced increases in sedimentation rate sediment density and the influx of terrestrial organic matter between 8 7 and 7 9 ka suggest early holocene warmth was interrupted by two distinct pulses of cold summers leading to widespread landscape destabilization and possibly glacier growth the holocene thermal maximum htm 7 9 to 5 5 ka was characterized by high within lake productivity and ice free conditions in the watershed neoglaciation is recorded as a non linear transition toward cooler summers landscape destabilization and the inception and expansion of langjokull beginning ca 5 5 ka with notable increases in ice cap size and landscape instability at 4 2 and 3 0 ka the past two millennia are characterized by the abrupt onset of sustained cold periods at ca 550 and 1250 ad separated by an interval of relative warmth from ca 950 to 1150 ad the greatest holocene extent of langjokull occurred in the nineteenth century and is coincident with peak landscape instability followed by ice recession throughout the twentieth century

a detailed framework of marine isotope stages 4 and 5 volcanic events recorded in two greenland ice cores sulphate records from greenland ice cores indicate that marine isotope stages 4 and 5 were charactensed by a higher incidence of large volcanic eruptions than other periods during the last glacial

bed conditions of pine island glacier west antarctica although 90 of antarctica s discharge occurs via its fast flowing ice streams our ability to project future ice sheet response has been limited by poor observational constraints on the ice bed conditions used in numerical models to determine basal slip we have helped address this observational deficit by acquiring and analyzing a series of seismic reflection profiles to determine basal conditions beneath the main trunk and tributaries of pine island glacier pig west antarctica seismic profiles indicate large scale sedimentary deposits combined with seismic reflection images measured acoustic impedance values indicate relatively uniform bed conditions directly beneath the main trunk and tributaries comprising a widespread reworked sediment layer with a dilated sediment lid of minimum thickness 1 5 0 4 m beneath a slow moving intertributary region a discrete low porosity sediment layer of 7 3 m thickness is imaged despite considerable basal topography seismic observations indicate that a till layer at the ice base is ubiquitous beneath pig which requires a highly mobile sediment body to maintain an abundant supply these results are compatible with existing ice sheet models used to invert for basal shear stress existing basal conditions upstream will not inhibit further rapid retreat of pig if the high friction region currently restraining flow directly upstream of the grounding line is breached however small changes in the pressure regime at the bed as a result of stress reorganization following retreat may result in a less readily deformable bed and conditions which are less likely to maintain high ice flow rates

a new greenland ice core chronology for the last glacial termination 1 we present a new common stratigraphic timescale for the north greenland ice core project ngrip and grip ice cores the timescale covers the period 7 9 14 8 kyr before present and includes the bolling allerod younger dryas and early holocene periods we use a combination of new and previously published data the most prominent being new high resolution continuous flow analysis cfa impurity records from the ngrip ice core several investigators have identified and counted annual layers using a multiparameter approach and the maximum counting error is estimated to be up to 2 in the holocene part and about 3 for the older parts these counting error estimates reflect the number of annual layers that were hard to interpret but not a possible bias in the set of rules used for annual layer identification as the grip and ngrip ice cores are not optimal for annual layer counting in the middle and late holocene the timescale is tied to a prominent volcanic event inside the 8 2 kyr cold event recently dated in the dye 3 ice core to 8236 years before a d 2000 b2k with a maximum counting error of 47 years the new timescale dates the younger dryas preboreal transition to 11 703 b2k which is 100 150 years older than according to the present grip and ngrip timescales the age of the transition matches the gisp2 timescale within a few years but viewed over the entire 7 9 14 8 kyr section there are significant differences between the new timescale and the gisp2 timescale the transition from the glacial into the bolling interstadial is dated to 14 692 b2k the presented timescale is a part of a new greenland ice core chronology common to the dye 3 grip and ngrip ice cores named the greenland ice core chronology 2005 gicc05 the annual layer thicknesses are observed to be log normally distributed with good approximation and compared to the early holocene the mean accumulation rates in the younger dryas and bolling periods are found to be 47 2 and 88 2 respectively

the greenland ice sheet project 2 depth age scale methods and results the greenland ice sheet project 2 gisp2 depth age scale is presented based on a multiparameter continuous count approach to a depth of 2800 m using a systematic combination of parameters that have never been used to this extent before the ice at 2800 m is dated at 110 000 years b p with an estimated error ranging from 1 to 10 in the top 2500 m of the core and averaging 20 between 2500 and 2800 m parameters used to date the core include visual stratigraphy oxygen isotopic ratios of the ice electrical conductivity measurements laser light scattering from dust volcanic signals and major ion chemistry gisp2 ages for major climatic events agree with independent ages based on varve chronologies calibrated radiocarbon dates and other techniques within the combined uncertainties good agreement also is obtained with greenland ice core project ice core dates and with the specmap marine timescale after correlation through the 18 o of o 2 although the core is deformed below 2800 m and the continuity of the record is unclear we attempted to date this section of the core on the basis of the laser light scattering of dust in the ice

the δ18o record along the greenland ice core project deep ice core and the problem of possible eemian climatic instability over 70 000 samples from the 3029 m long greenland ice core project grip ice core drilled on the top of the greenland ice sheet summit have been analyzed for 8o a highly detailed and continuous 8o profile has thus been obtained and is discussed in terms of past temperatures in greenland we also discuss a three core stacked annual 8o profile for the past 917 years the short term 50 years variability of the annual 8o signal is found to be 1 in the holocene and estimates for the coldest parts of the last glacial are 3 or higher these data also provide insights into possible disturbances of the stratigraphic layering in the core which seems to be sound down to the onset of the eemian spectral analysis of highly detailed sequences of the profile helps determine the smoothing of the 8o signal which for the holocene ice is found to be considerably stronger than expected we suggest this is due to a process involving diffusion of water molecules along crystal boundaries in the recrystallizing ice matrix deconvolution techniques were employed for restoring with great confidence the highly attenuated annual 8o signal in the holocene we confirm earlier findings of dramatic temperature changes in greenland during the last glacial cycle abrupt and strong climatic shifts are also found within the eem sangamon interglaciation which is normally recorded as a period of warm and stable climate in lower latitudes the stratigraphic continuity of the eemian layers is consequently discussed in section 3 of this paper in terms of all pertinent data which we are not able to reconcile

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

a comparison of the volcanic records over the past 4000 years from the greenland ice core project and dye 3 greenland ice cores since 1980 the electrical conductivity method ecm has been used to infer volcanic acid signals in greenland ice cores the method reveals the great majority of major volcanic eruptions including several known from historic records subsequent ion chromatographic analyses of the acid volcanic layers show the chemical composition i e the concentration of the volcanic acids h2so4 hci and hf plus e g the nonvolcanically derived hno3 while ecm data are available from a large number of shallow depth greenland ice cores covering the past 500 1500 years only the greenland ice core project grip greenland ice sheet project 2 gisp2 and dye 3 deep ice cores exist for a detailed comparative study of volcanic signals in greenland ice cores representing several thousand years comparison of the volcanic signals registered in the grip and gisp2 cores will be presented elsewhere the latter cores were augered 30 km apart and essentially represent the same atmospheric conditions such as temperature snow accumulation and chemical composition of the air here we present a comparison between the major volcanic signals over the past 4000 years in the grip core from central greenland and the dye 3 core from se greenland in order to investigate the depositional differences many of the major signals are detected in both cores but some of the differences in the records can be used to infer the latitudinal band of some eruption sites furthermore the influence of the amount of annual precipitation and glaciological postdepositional processes on the volcanic signals is discussed

centennial scale east asian summer monsoon intensity based on δ18o values in ostracode shells and its relationship to land ocean air temperature gradients over the past 1700 years centennial scale variations in the east asian summer monsoon easm remain ambiguous in the present study the 18o of shells from the ostracode bicornucythere bisanensis from lake nakaumi japan were examined to identify the bottom salinity changes caused by easm variations over the past 1700 yr four weak easm periods were identified in lake nakaumi at a d 600 1000 1350 and 1900 we detected discordance among the centennial scale easm variations in japan and the 18o of stalagmites 18ostalagmite in southern china furthermore both total solar irradiance and atmospheric 14c concentration which were previously considered to be linked with the centennial scale easm variations were asynchronous with the easm variations conversely we observed significant positive and negative correlations between the easm from japan and the 18ostalagmite in north central china and the relationship was associated with the asia pacific oscillation apo index centennial scale easm periods dominated during the high apo period these synchronous variations imply that the strength of the easm variations is tied to temperature gradients between east china and the north central pacific ocean

a review of climate reconstructions from terrestrial climate archives covering the first millennium ad in northwestern europe large changes in landscape vegetation and culture in northwestern nw europe during the first millennium ad seem concurrent with climatic shifts understanding of this relation requires high resolution palaeoclimate reconstructions therefore we compiled available climate reconstructions from sites across nw europe extent research area 10 w 20 e 45 60 n through review of literature and the underlying data to identify supraregional climatic changes in this region all reconstructions cover the period from ad 1 to 1000 and have a temporal resolution of 50 yr this resulted in 22 climate reconstructions proxy records based on different palaeoclimate archives chironomids 1 pollen 6 sphagnum mosses 1 stalagmites 8 testate amoebae 4 and tree rings 2 comparing all temperature reconstructions we conclude that summer temperatures between ad 1 and 250 were relatively high and the period between ad 250 and 700 was characterised by colder summer conditions the period from ad 700 to 1000 was again characterised by warmer summers these temperature shifts occurred in the whole of nw europe in contrast the compilation of precipitation reconstructions does not show a common pattern across nw europe either as a result of a heterogeneous precipitation pattern or the lack of suitable and consistent precipitation proxies

a synchronized dating of three greenland ice cores throughout the holocene as part of the effort to create the new greenland ice core chronology 2005 gicc05 a synchronized stratigraphical timescale for the holocene parts of the dye 3 grip and ngrip ice cores is made by using volcanic reference horizons in electri cal conductivity measurements to match the cores the main annual layer counting is carried out on the most suited records only exploit ing that the three ice cores have been drilled at locations with different climatic con ditions and differences in ice flow however supplemental counting on data from all cores has been performed between each set of reference horizons in order to verify the valid ity of the match after the verification the main dating is transferred to all records us ing the volcanic reference horizons as tie points an assessment of the mean annual layer thickness in each core section confirms that the new synchronized dating is consistent for all three cores the data used for the main annual layer counting of the past 7900 years are the dye 3 grip and ngrip stable isotope records as the high accumulation rate at the dye 3 drill site makes the seasonal cycle in the dye 3 stable isotopes very resistant to firn diffusion an effort has been made to extend the dye 3 holocene record the new syn chronized dating relies heavily on this record of 75 000 stable isotope samples the dat ing of the early holocene consists of an already established part of gicc05 for grip and ngrip which has now been transferred to the dye 3 core gicc05 dates the younger dryas termination as defined from deuterium excess to 11 703 b2k 130 years earlier than the previous grip dating

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

controls on the east asian monsoon during the last glacial cycle based on comparison between hulu cave and polar ice core records previous studies have suggested a sound chronological correlation between the hulu cave record east asian monsoon and greenland ice core records which implies a dominant control of northern hemisphere climate processes on monsoon intensity we present an objective straightforward statistical evaluation that challenges this generally accepted paradigm for sub orbital variability we propose a more flexible global interpretation which takes into account a broad range of variability in the signal structures in the hulu cave and polar ice core records rather than a limited number of major transitions our analysis employs the layer counted greenland ice core chronology 2005 gicc05 which was developed for greenland records and has since been applied via methane synchronisation to the high resolution 18oice series from epica dronning maud land edml the gicc05 chronology allows these ice core records to be compared to the u th dated hulu cave record within relatively narrow 3 bounds of age uncertainty following previous suggestions our proposed interpretation suggests that the east asian monsoon is influenced by a combination of northern hemisphere pull which is more intense during boreal warm periods and southern hemisphere push which is more intense monsoon during austral cold periods our analysis strongly suggests a dominant control on millennial scale monsoon variability by southern hemisphere climate changes during glacial times when the monsoon is weak overall and control by northern hemisphere climate changes during deglacial and interglacial times when the monsoon is strong the deduced temporally variable relationship with southern hemisphere climate records offers a statistically more plausible reason for the apparent coincidence of major east asian monsoon transitions with northern hemisphere dansgaard oeschger do climate events during glacial times than the traditional a priori interpretation of strict northern hemisphere control

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

a stratigraphic framework for abrupt climatic changes during the last glacial period based on three synchronized greenland ice core records refining and extending the intimate event stratigraphy due to their outstanding resolution and well constrained chronologies greenland ice core records provide a master record of past climatic changes throughout the last interglacial glacial cycle in the north atlantic region as part of the intimate integration of ice core marine and terrestrial records project protocols have been proposed to ensure consistent and robust correlation between different records of past climate a key element of these protocols has been the formal definition and ordinal numbering of the sequence of greenland stadials gs and greenland interstadials gi within the most recent glacial period the gs and gi periods are the greenland expressions of the characteristic dansgaard oeschger events that represent cold and warm phases of the north atlantic region respectively we present here a more detailed and extended gs gi template for the whole of the last glacial period it is based on a synchronization of the ngrip grip and gisp2 ice core records that allows the parallel analysis of all three records on a common time scale the boundaries of the gs and gi periods are defined based on a combination of stable oxygen isotope ratios of the ice 18o reflecting mainly local temperature and calcium ion concentrations reflecting mainly atmospheric dust loading measured in the ice the data not only resolve the well known sequence of dansgaard oeschger events that were first defined and numbered in the ice core records more than two decades ago but also better resolve a number of short lived climatic oscillations some defined here for the first time using this revised scheme we propose a consistent approach for discriminating and naming all the significant abrupt climatic events of the last glacial period that are represented in the greenland ice records the final product constitutes an extended and better resolved greenland stratotype sequence against which other proxy records can be compared and correlated it also provides a more secure basis for investigating the dynamics and fundamental causes of these climatic perturbations

subdividing the holocene series epoch formalization of stages ages and subseries subepochs and designation of gssps and auxiliary stratotypes the holocene which currently spans 11 700 years is the shortest series epoch within the geological time scale gts yet it contains a rich archive of evidence in stratigraphical contexts that are frequently continuous and often preserved at high levels of resolution on 14 june 2018 the executive committee of the international union of geological sciences formally ratified a proposal to subdivide the holocene into three stages ages along with their equivalent subseries subepochs each anchored by a global boundary stratotype section and point gssp the new stages are the greenlandian lower early holocene subseries subepoch with its gssp in the greenland ngrip2 ice core and dated at 11 700 a b2k before 2000 ce the northgrippian middle holocene subseries subepoch with its gssp in the greenland ngrip1 ice core and dated at 8236 a b2k and the meghalayan upper late holocene subseries subepoch with its gssp in a speleothem from mawmluh cave north eastern india with a date of 4250 a b2k we explain the nomenclature of the new divisions describe the procedures involved in the ratification process designate auxiliary stratotypes to support the gssps and consider the implications of the subdivision for defining the anthropocene as a new unit within the gts less

climate forcing due to the 8200 cal yr bp event observed at early neolithic sites in the eastern mediterranean we explore the hypothesis that the abrupt drainage of laurentide lakes and associated rapid switch of the north atlantic thermohaline circulation 8200 yr ago had a catastrophic influence on neolithic civilisation in large parts of southeastern europe anatolia cyprus and the near east the event at 8200 cal yr bp is observed in a large number of high resolution climate proxies in the northern hemisphere and in many cases corresponds to markedly cold and arid conditions we identify the relevant archaeological levels of major neolithic settlements in central anatolia cyprus greece and bulgaria and examine published stratigraphic architectural cultural and geoarchaeological studies for these sites the specific archaeological events and processes we observe at a number of these sites during the study interval 8400 8000 cal yr bp lead us to refine some previously established neolithisation models the introduction of farming to south east europe occurs in all study regions thrace macedonia thessaly bulgaria near 8200 cal yr bp we observe major disruptions of neolithic cultures in the levant north syria south east anatolia central anatolia and cyprus at the same time we conclude that the 8200 cal yr bp aridity event triggered the spread of early farmers by different routes out of west asia and the near east into greece and bulgaria

resolving climate change in the period 15 23 ka in greenland ice cores a new application of spectral trend analysis northern hemisphere climate history through and following the last glacial maximum is recorded in detail in ice cores from greenland however the period between greenland interstadials 1 and 2 15 23 ka i e the period of deglaciation following the last major glaciation has been difficult to resolve in great detail we here offer a new subdivision of this in the ngrip grip and gisp2 ice cores by newly introducing spectral trend analysis to the study of climate related data series from ice cores this analysis reveals patterns of change and discontinuity in the waveform properties of a data series relating to the environmental including climatic history of accumulation of the rock or ice record the application allows high resolution correlation between the ice cores and a greatly improved subdivision of the study interval nine climatic phases are recognized within which more identifiable events can also be correlated between the three locations

the case for significant numbers of extraterrestrial impacts through the late holocene when astronomers tell us that there should have been numerous impacts from space during the last five millennia when impact craters exist on land and more impacts can be assumed over the oceans why are historians archaeologists and palaeoecologists not diligently seeking evidence for these impacts and their effects this article reviews just some of the relevant evidence for impacts in turn this suggests that ablation material background material from space and micro tektites should all be present in ocean cores ice cores peat and lake sediments it seems that almost no efforts have been made to find evidence that might link to the known crater fields or to identify and date periods of enhanced cosmic activity the question must be why copyright 2007 john wiley sons ltd

a high resolution stalagmite record of the holocene east asian monsoon from mt shennongjia central china high resolution oxygen isotope 18o profiles of six stalagmites from sanbao cave in hubei province central china established with 1413 oxygen isotope data and 65 230th ages provide a continuous history of east asian summer monsoon easm intensity for the period from 13 0 2 thousand years before present ky bp relative to ad 1950 the 18o record includes four distinct stages in the evolution of the easm 1 an abrupt transition 11 5 ky bp into the holocene 2 a period of gradual increase in monsoon intensity 11 5 9 5 ky bp 3 the maximum humid period 9 5 6 5 ky bp and 4 a period of gradual decline in monsoon intensity 6 5 0 2 ky bp comparison of sanbao with regional records of comparable resolution reveals that the timing of the beginning and end of the holocene optimum as defined by the minimum in 18 o was similar in the indian and east asian monsoon systems this supports the idea that shifts in the monsoon tied to shifts in the mean position of the inter tropical convergen

speleothems as sensitive recorders of volcanic eruptions the bronze age minoan eruption recorded in a stalagmite from turkey mounting evidence exists that variations in sulphur content in stalagmites are closely linked to changes in volcanic or anthropogenic atmospheric sulphur the strong dependency of sulphur on soil ph and ecosystem storage however can result in a delay of several years to decades in the registration of volcanic eruptions and anthropogenic emissions by stalagmites here we present synchrotron radiation based trace element analysis performed on a precisely dated section of a stalagmite from sofular cave in northern turkey as this section covers the time interval of the intensively studied minoan volcanic eruption between 1600 and 1650 bc we can test whether this vigorous eruption can be traced in a stalagmite of all measured trace elements only bromine shows a clear short lived peak at 1621 251621 25 bc whereas sulphur and molybdenum show peaks later at 1617 251617 25 and 1589 251589 25 respectively we suggest that all trace element peaks are related to the minoan eruption whereas the observed phasing of bromine molybdenum and sulphur is related to differences in their retention rates in the soil above sofular cave for the first time we can show that bromine appears to be an ideal volcanic tracer in stalagmites as it is a prominent volatile component in volcanic eruptions can be easily leached in soils and rapidly transferred from the atmosphere through the soil and bedrock into the cave and stalagmite respectively highly resolved oxygen and carbon isotope profiles indicate that the minoan eruption had no detectable climatic and environmental impact in northern turkey

atmospheric circulation variability associated with shallow core seasonal isotopic extremes near summit greenland seasonal back diffused 18o time series reconstructed for nine shallow firn cores from the greenland summit for 1959 1987 are evaluated in terms of 1 their spatial and temporal variability and 2 their association to the atmospheric circulation rotated principal component analysis evaluates spatial and temporal patterns of organization in the back diffused 18o ice core time series mean sea level pressure and 500 hpa height fields are obtained for winter and summer seasons that fall in the isotopically warmest and coldest thirds of the seasonal data the winter back diffused 18o data indicate that some degree of longitudinal separation takes place between isotopic records from western and eastern greenland in agreement with coastal station climatic data temporal variability is linked with statistical significance to the variability of the atmospheric circulation over the denmark strait as well as over the norwegian and barents seas the north atlantic oscillation nao and the mean icelandic low in the denmark strait affect isotopic variability over the cores west of the ice divide just as they have been shown to prominently affect west coast air temperature records isotopic variability at some ice cores east of the divide is influenced by pressure variability over the norwegian and barents seas although statistical significance is lower the nao appears insignificant in summer isotopic variability as the circulation in that season is very much localized and dominated by either ridging warm cases or troughs cold cases over eastern greenland and the arctic ocean results suggest that long term winter 18o variability can potentially be linked to climate variation over europe especially from the mediterranean basin northward to about 55 n and as far east as central siberia