climate instability during the last interglacial period recorded in the grip ice core isotope and chemical analyses of the grip ice core from summit central greenland reveal that climate in greenland during the last interglacial period was characterized by a series of severe cold periods which began extremely rapidly and lasted from decades to centuries as the last interglacial seems to have been slightly warmer than the present one its unstable climate raises questions about the effects of future global warming

absolute calibration of the greenland time scale implications for antarctic time scales and for δ14c abstract we propose a new age scale for the two ice cores grip and gisp2 that were drilled at greenland summit based on accelerator mass spectrometry 14c dating of foraminifera in core md95 2042 paleoceanography 15 2000 565 calibrated by means of recently obtained paired 14c and 230th measurements on pristine corals marine radiocarbon calibration curve spanning 10 500 to 50 000 years bp thousand years before present based on paired 230th 234u 238u and 14c dates on pristine corals geological society of america bulletin 2003 submitted for publication the record of core md95 2042 can be correlated very precisely to the greenland ice cores between 30 and 40 ka bp our scale is 1 4 ka older than the grip ss09sea time scale journal of quaternary science 16 2001 299 at the older end of marine isotope stage 3 we use published 230th dates from speleothems to calibrate the record using this scale we show a 14c record that is broadly consistent with the modelled record earth planet sci lett 200 2002 177 and with the data of hughen et al science 303 2004 202 but not consistent with the high values obtained by beck et al science 292 2001 2453 or by voelker et al radiocarbon 40 1998 517 we show how a set of age scales for the antarctic ice cores can be derived that are both fully consistent with the greenland scale and glaciologically reasonable

seasonal variability in the origin of recent atmospheric mineral dust at northgrip greenland abstract isotopic sr and nd and mineralogical analyses of dust extracted from snow deposits from the last decade at the northgrip greenland ice camp 75 1 n 042 3 w confirm the eastern asian source for greenland dust and extend it to the present day the 1998 and 1999 samples which represent a 2 4 month resolution of dust deposition show that there are at least two east asian sources for the greenland dust that vary seasonally the provenance of dust during the major spring summer deposition is the takla makan desert of northwest china

atmospheric radiocarbon calibration to 45 000 yr b p late glacial fluctuations and cosmogenic isotope production more than 250 carbon 14 accelerator mass spectrometry dates of terrestrial macrofossils from annually laminated sediments from lake suigetsu japan provide a first atmospheric calibration for almost the total range of the radiocarbon method 45 000 years before the present the results confirm the recently revised floating german pine chronology and are consistent with data from european and marine varved sediments and combined uranium thorium and carbon 14 dating of corals up to the last glacial maximum the data during the glacial show large fluctuations in the atmospheric carbon 14 content related to changes in global environment and in cosmogenic isotope production

last glacial maximum in poland abstract the last glacial maximum lgm in poland is represented by the leszno phase and occurred after 21 ka radiocarbon years in turn the deglacial poznan phase is estimated at 18 4 ka the pomeranian phase at 15 2 ka the gardno phase at about 14 0 13 8 ka the slupsk bank phase at 13 5 13 2 ka and the southern middle bank phase at 12 7 12 5 ka bp the ice sheet limit at lgm was not synchronous everywhere in poland but occurred as several major and minor ice lobes that reflected a stream like structure of the ice body that radiated southwards from the baltic basin meltwater runoff during the lgm created a complex system of sandur trains and ice marginal spillways with numerous intervening proglacial lakes

integration of ice core marine and terrestrial records intimate refining the record of the last glacial interglacial transition integration of ice core marine and terrestrial records intimate is a core project of the inqua palaeoclimate commission the primary goal of which is to synchronise records of the last glacial interglacial transition lgit through a series of international workshops intimate has encouraged direct collaboration between scientists with interests and expertise in a wide range of palaeoenvironmental approaches the workshops have focused on the dissemination of good practice in the dating correlation and synthesis of diverse palaeoenvironmental records that span the lgit this special issue of quaternary science reviews presents some of the outcomes of the 8th intimate international workshop held in iceland in september 2005 and focuses on four themes considered vital to intimate s long term strategy 1 an event stratigraphy approach which uses the greenland oxygen isotope record as a stratotype sequence lies at the core of intimate s operations a revised event stratigraphy scheme for application to north atlantic lgit records is presented which is based on the new gicc05 greenland ice core chronology 2 new tree ring data from switzerland and the application of bayesian based procedures in the analysis of comprehensive radiocarbon data sets provide much potential for reducing the uncertainties in radiocarbon based age models 3 three of the contributions present new evidence that helps to refine the tephrostratigraphy of the lgit in the ne atlantic and new zealand regions 4 establishing the precise order and synchroneity of events during the lgit is vital to understand the causes and effects of abrupt climate change data are presented from the baltic region and alaska which vary in degree of compatibility with north atlantic records two final papers consider the roles of dansgaard oeschger events on thermokarst during the middle weichselian and of solar activity variations during the mid holocene both illustrate how the intimate event stratigraphy approach can apply to the study of other time intervals

rapid and cyclic aeolian deposition during the last glacial in european loess a high resolution record from nussloch germany abstract this paper reports the results of an investigation of the weichselian upper pleniglacial loess sequences of nussloch rhine valley germany based on stratigraphy palaeopedology sedimentology palynology malacology and geochemistry 13 c supported by radiocarbon tl and osl dating grain size and magnetic susceptibility records are taken at 5 cm intervals from the upper pleniglacial upg loess the data indicate cyclic variations in loess deposition between ca 34 and 17 ka when the sedimentation rate is especially high 1 0 1 2 m per ka for more than 10 m the grain size index gsi ratio of coarse silt versus fine silt and clay shows variations which are assumed to be an indirect measurement of wind intensity the sedimentation rate interpreted from the profiles indicates high values in loess loess events le 1 to le 7 and low or negligible values in tundra gley horizons g1 to g8 osl ages from the loess and 14 c dates from organic matter in the loess show that loess deposition was rapid but was interrupted by shorter periods of reduced aeolian sedimentation comparison between the data from nussloch and other european sequences demonstrates a progressive coarsening of the loess deposits between ca 30 and 22 ka this coarsening trend ends with a short but major grain size decrease and is followed by an increase to a new maximum at 20 2 ka w shape correlation between the loess gsi and the greenland ice core dust records suggests a global connection between north atlantic and western european global atmospheric circulation and wind regimes in addition the typical upper pleniglacial loess deposition begins at ca 30 31 ka close to heinrich event he 3 and the main period of loess sedimentation at about 25 2 ka is coeval to he 2 correlation of magnetic susceptibility and grain size records shows that the periods characterised by high gsi coincide with an increase in the amount of ferromagnetic minerals reworked from the rhine alluvial plain they suggest enhancement in the frequency of the storms from n nw these results are integrated within a palaeogeographical model of dust transport and deposition in western europe for the weichselian upper pleniglacial or late pleniglacial

what is what in the ice and the ocean recently released data from the north greenland ice core project ngrip document several rapid abrupt climate changes affecting the northern hemisphere in the last 110 000 years in particular the new core shows high resolution succession of expressed warm and cold episodes which occurred during substages of marine isotope stage mis 5 some of these variations were reported earlier from the gisp2 and grip ice cores in the ngrip core following the intimate group recommendations the oscillations were given labels which are in part the same as in the isotope system of deep sea sediments although to some extent they are not coeval here we recommend honoring the originally published marine designations wherever possible but distinguishing them by a prefix referring to their recognition in the ice

loess in europe mass accumulation rates during the last glacial period abstract upper pleistocene loess palaeosol sequences provide excellent high resolution terrestrial archives of climate forcing due to improvements in numerical age determinations especially in luminescence dating methods a more reliable time based reconstruction of the past climate and environmental change has become available for the loess record in europe chronological information was collected from 43 sites along a northwest to southeast transect in europe thirty three of these sites had sufficient age information to allow estimation of mass accumulation rates and it was possible to isolate the mass accumulation rates of primary loess during the last glacial period 28 13 ka bp at 21 of these locations these sites fall along a coarse climatic gradient from the relatively coastal climate of belgium and france to the drier more continental climate of central europe interpreting mass accumulation rates of loess in terms of this climatic gradient is not straightforward as these deposits are dominated by sources in floodplains and large river systems thus accumulation rates are influenced strongly by regional wind and precipitation patterns but mostly by the availability of glacially derived material from the alps and the periglacial terrains that characterized european fluvial systems during and immediately following glaciation

ice core evidence for a very tight link between north atlantic and east asian glacial climate 1 corresponding millennial scale climate changes have been reported from the north atlantic region and from east asia for the last glacial period on independent timescales only to assess their degree of synchrony we suggest interpreting greenland ice core dust parameters as proxies for the east asian monsoon systems this allows comparing north atlantic and east asian climate on the same timescale in high resolution ice core data without relative dating uncertainties we find that during dansgaard oeschger events north atlantic region temperature and east asian storminess were tightly coupled and changed synchronously within 5 10 years with no systematic lead or lag thus providing instantaneous climatic feedback the tight link between north atlantic and east asian glacial climate could have amplified changes in the northern polar cell to larger scales we further find evidence for an early onset of a younger dryas like event in continental asia which gives

rapid climatic events as recorded in middle weichselian thermokarst lake sediments from a middle weichselian sediment sequence in the opencast brown coal mine of reichwalde eastern germany a 40 cm thick thermokarst gyttja deposit has been sampled the ams 14c dates although at the limit of detection indicate an early middle weichselian age of the gyttja pollen botanical and zoological e g chironomids macroremains have been analyzed botanical and chironomid taxa indicate warm climatic conditions in the bottom part of the sequence for this lower part the botanical data suggest a minimum mean july temperature of 12 14 c following this a cooling is indicated coinciding with an increased clastic deposition in the lake a return to permafrost conditions is reconstructed for the upper part of the sequence the combined evidence strongly suggests a degradation of permafrost due to increased warming in response to a d o event as a forcing factor for the thermokarst lake formation

middle eocene to early oligocene paleoceanography of the antarctic ocean maud rise odp leg 113 site 689 change from a low to a high productivity ocean the sediment record from the middle eocene about 45 ma to the early oligocene about 33 ma on maud rise site 689 weddell sea paleodepth 1400 1650 m has been studied by means of a coarse fraction analysis in order to reconstruct variations in surface water productivity and bottom water masses productivity has been estimated using carbonate dissolution and accumulation rates of radiolaria diatoms benthonic and planktonic foraminifers sponge debris ostracods and echinoids accumulation rates of bolboforma spp vary parallel to these proxies productivity increased with time three episodes were found in which productivity increased sharply and productivity varied cyclically with a period of 430 ky the middle eocene ca 45 44 37 26 ma was a period of generally low productivity no opal was deposited and carbonate preservation was excellent during periods of a slight increase in productivity accumulation rates of benthonic and planktonic foraminifers ostracods and echinoids increased in spite of an increase in carbonate dissolution in the period ca 41 62 43 07 ma productivity rose in three distinct pulses clinoptilolite formed from biogenous opal is a common mineral in these sediments these three productivity maxima coincide with a mica rich unit mica probably originated from erosion on antarctica and was transported by an intermediate water depth current in the late eocene ca 36 9 34 95 ma productivity increased considerably and opal skeletons were deposited carbonate dissolution increased but planktonic foraminifer accumulation rates were not markedly decreased in periods of higher productivity because productivity increase exceeded or equalled rises in dissolution rates increasing opal accumulation rates coincided with increases in the rates for benthonic foraminifers sponge debris ostracods and echinoids in the late eocene early oligocene period 34 95 33 05 ma a further increase in productivity led to a strong dissolution of planktonic foraminifers in high productivity periods the productivity increase is probably due to the increasing pole equator temperature gradient which led to stronger atmospheric and oceanic turnover and mixing in the oceans in the uppermost late eocene two unusual layers suggest changes in bottom water masses affecting the seafloor at site 689 a sediment interval with especially well preserved carbonate microfossils underlies an interval that has poor carbonate preservation despite evidence of low productivity these intervals suggest a change in bottom water conditions from warm saline deep water wsdw which favors carbonate preservation to antarctic bottom water aabw which promotes carbonate dissolution cooling of surface waters over a period of 300 ky led to a thickening of the deep aabw layer and an upward shift of the overlying wsdw until the aabw finally reached the top of the maud rise in the area of site 689 this period of aabw influence on top of the maud rise lasted 200 ky

abrupt increase in greenland snow accumulation at the end of the younger dryas event the warming at the end of the last glaciation was characterized by a series of abrupt returns to glacial climate the best known of which is the younger dryas event1 despite much study of the causes of this event and the mechanisms by which it ended many questions remain unresolved1 oxygen isotope data from greenland ice cores2 4 suggest that the younger dryas ended abruptly over a period of about 50 years dust concentrations2 4 in these cores show an even more rapid transition 20 years this extremely short timescale places severe constraints on the mechanisms underlying the transition but dust concentrations can reflect subtle changes in atmospheric circulation which need not be associated with a large change in climate here we present results from a new greenland ice core gisp2 showing that snow accumulation doubled rapidly from the younger dryas event to the subsequent preboreal interval possibly in one to three years we also find that the accumulation rate change from the oldest dryas to the bo11ing allerod warm period was large and abrupt the extreme rapidity of these changes in a variable that directly represents regional climate implies that the events at the end of the last glaciation may have been responses to some kind of threshold or trigger in the north atlantic climate system

175 years of loess research in germany long records and unconformities abstract loess research in germany has a long tradition dating back to the early works of von leonhard von leonhard k c 1823 1824 charakteristik der felsarten 3 bde 772 s heidelberg j engelmann and his contemporary geoscientists ever since that time german researchers and loess research within germany have provided important contributions to the international state of the art to date however perceptual unconformities have existed in both the continuity of loess research in germany and the interpretation of the loess record in both the palaeoecological and the stratigraphic sense this paper briefly highlights some relevant periods of loess research in germany and the approaches adopted from the early days to the present the development of a refined stratigraphy of the last glacial loess in germany during the second half of the 20th century is reviewed in the contribution by a semmel fundamental contributions were first published by schonhals freising and brunnacker in the course of the subsequent work of the loess commission of the international union for quaternary research inqua the stratigraphy of the wurmian loess has since been refined in almost all loess regions of germany and schemes consistent in their fundamental features have been published in recent years contributions have focussed on age determination in particular those based on luminescence dating techniques

high resolution chronologies for loess comparing ams 14c and optical dating results the nuxloch loess section in south west germany is famous in central europe for its thick deposits from the last glacial maximum it has therefore been intensively studied during the past few years and offers an excellent opportunity to compare the performance of different dating techniques covering the period 15 45 ka here we present results fromoptical and ams 14 c dating the silt sized polymineral fraction of the clastic sediments and a multiple aliquot approach was used for ir osl dating 14 c dating was carried out on organic macro remnants and humin fractions extracted fromthe sedim ents with the exception of samples taken from the uppermost 1 5 m of the section ir osl and calibrated 14 c ams ages are consistent over the entire period the inconsistencies in the upper meters are thought to be due to disturbances during soil formation in the holocene the good agreement obtained on the remaining sequence demonstrates the high accuracy of both methods when studying loess sections for the ir osl ages no significant age underestimations are obvious the results clearly document that accurate chronologies can be developed for such continental sedimentary sequences this gives access to archives that can now be studied with a high temporal resolution and allows the establishment of new paleoclimatic proxies for the study of terrestrial responses to past climatic changes r 2003 elsevier science ltd all rights reserved

field experiment provides ground truth for surface nuclear magnetic resonance measurement a field experiment was conducted in the high plains aquifer central united states to explore the mechanisms governing the non invasive surface nmr snmr technology we acquired both snmr data and logging nmr data at a field site along with lithology information from drill cuttings this allowed us to directly compare the nmr relaxation parameter measured during logging t2 to the relaxation parameter t2 measured using the snmr method the latter can be affected by inhomogeneity in the magnetic field thus obscuring the link between the nmr relaxation parameter and the hydraulic conductivity of the geologic material when the logging t 2 data were transformed to pseudo t2 data by accounting for inhomogeneity in the magnetic field and instrument dead time we found good agreement with t 2 obtained from the snmr measurement these results combined with the additional information about lithology at the site allowed us to delineate the physical mechanisms governing the snmr measurement such understanding is a critical step in developing snmr as a reliable geophysical method for the assessment of groundwater resources citation knight r e grunewald t irons k dlubac y song h n bachman b grau d walsh j d abraham and j cannia 2012 field experiment provides ground truth for surface nuclear magnetic resonance measurement geophys res lett 39 l03304

reconstruction of the late quaternary paleoenvironments of the nussloch loess paleosol sequence germany using n alkane biomarkers abstract this study contributes to the paleoenvironmental reconstruction of the loess paleosol sequence of nussloch germany by using n alkanes as plant leaf wax derived lipid biomarkers we found that n alkane patterns and concentrations in the saalian loess and the last interglacial eemian paleosol of nussloch point to very strong degradation and prevailing deciduous vegetation degradation effects in the overlying paleosols and loess layers are less pronounced and allow for the application of an end member mixing model to estimate vegetation changes semi quantitatively our findings highlight the potential for the interpretation of degradation corrected n alkane ratios n alkane modelling results for loess layers paleosols and an in filled paleochannel dated to 60 32 ka suggest that up to 50 of the n alkanes were derived from deciduous trees or shrubs this finding is in agreement with the abundant occurrence of wood fragments and indicates a highly variable and dynamic landscape dominated by tundra shrubland on the other hand deciduous trees or shrubs did not contribute significantly to the soil organic matter in the late weichselian loess layers and the intercalated gelic gleysols 32 18 ka

towards a revised chronostratigraphy of loess in austria with respect to key sections in the czech republic and in hungary abstract the stratigraphic ages of some well known and characteristic paleosols in austrian and hungarian loess sections have been questioned by several workers since the mid 1970s in particular a generally accepted correlation of austrian and hungarian loess stratigraphies with the well established czech loess stratigraphy has not been put forward this paper presents 41 new thermoluminescence tl dates and the first results from amino acid chronology of key sections in these areas the results are in agreement and suggest a new interregional correlation of loess paleosol sequences for loess older than the last interglacial quartz and feldspar inclusions yield more reliable tl ages than the polymineralic fine grain fraction

the last climatic cycles in western europe a comparison between long continuous lacustrine sequences from france and other terrestrial records abstract during the last two decades numerous studies applied to various continental deposits have highly improved the knowledge of environmental changes in western europe during the last climatic cycles here we review a set of available data and try to correlate and compare the three long lacustrine sequences from france la grande pile les echets and le velay with other west european discontinuous limnic deposits fluvial systems and l ss accumulations limnic sequences provide the best records of the last interglacial and early glacial ca 125 75 kyr allowing a clear picture of environmental changes during this interval nevertheless there are divergent interpretations on the timing and climate regime of the last interglacial during the last glacial in the north atlantic deep sea cores and greenland ice cores short term abrupt climatic fluctuations bond events dansgaard oeschger events which are poorly or partly reflected on the continent have been recognised the classical subdivision in a lower ca 75 55 kyr very cold middle ca 55 29 kyr cold and upper pleniglacial ca 29 15 kyr very cold is confirmed both by limnic and terrestrial sequences in the rhine valley north eastern france belgium and the netherlands subcontinuous l ss accumulation river systems and associated periglacial features provide quantitative climate reconstructions that are compared with those obtained from limnic sequences interstadial events may be correlated with the major warm oscillations of the grip core during the upper pleniglacial no clear vegetation changes are apparent from lacustrine pollen sequences whereas thick l ss accumulations have registered a succession of climatic changes the timing of the lateglacial warming is now well documented from rare annually laminated lake sediments

oxygen isotope and palaeotemperature records from six greenland ice core stations camp century dye 3 grip gisp2 renland and northgrip oxygen isotope variations spanning the last glacial cycle and the holocene derived from ice core records for six sites in greenland camp century dye 3 grip gisp2 renland and northgrip show strong similarities this suggests that the dominant influence on oxygen isotope variations reflected in the ice sheet records was regional climatic change differences in detail between the records probably reflect the effects of basal deformation in the ice as well as geographical gradients in atmospheric isotope ratios palaeotemperature estimates have been obtained from the records using three approaches i inferences based on the measured relationship between mean annual 18o of snow and of mean annual surface temperature over greenland ii modelled inversion of the borehole temperature profile constrained either by the dated isotopic profile or iii by using monte carlo simulation techniques the third of these approaches was adopted to reconstruct holocene temperature variations for the dye 3 and grip temperature profiles which yields remarkably compatible results a new record of holocene isotope variations obtained from the northgrip ice core matches the grip short term isotope record and also shows similar long term trends to the dye 3 and grip inverted temperature data the northgrip isotope record reflects i a generally stronger isotopic signal than is found in the grip record ii several short lived temperature fluctuations during the first 1500 yr of the holocene iii a marked cold event at ca 8 2 ka the 8 2 ka event iv optimum temperatures for the holocene between ca 8 6 and 4 3 ka a signal that is 0 6 stronger than for the grip profile v a clear signal for the little ice age and vi a clear signal of climate warming during the last century these data suggest that the northgrip stable isotope record responded in a sensitive manner to temperature fluctuations during the holocene copyright 2001 john wiley sons ltd

14c activity and global carbon cycle changes over the past 50 000 years a series of 14c measurements in ocean drilling program cores from the tropical cariaco basin which have been correlated to the annual layer counted chronology for the greenland ice sheet project 2 gisp2 ice core provides a high resolution calibration of the radiocarbon time scale back to 50 000 years before the present independent radiometric dating of events correlated to gisp2 suggests that the calibration is accurate reconstructed 14c activities varied substantially during the last glacial period including sharp peaks synchronous with the laschamp and mono lake geomagnetic field intensity minimal and cosmogenic nuclide peaks in ice cores and marine sediments simulations with a geochemical box model suggest that much of the variability can be explained by geomagnetically modulated changes in 14c production rate together with plausible changes in deep ocean ventilation and the global carbon cycle during glaciation

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

a 135 000 year vostok specmap common temporal framework the object of the present study is to introduce a means of comparing the vostok and marine chronologies our strategy has been to use the 18o of atmospheric o2 denoted 18oatm from the vostok ice core as a proxy for the 18o of seawater denoted 18osw our underlying premise in using 18oatm as a proxy for 18osw is that past variations in 18osw an indicator of continental ice volume have been transmitted to the atmospheric o2 reservoir by photosynthesizing organisms in the surface waters of the world s oceans we compare our record of 18oatm to the 18osw record which has been developed from studies of the isotopic composition of biogenic calcite 18oforam in deep sea cores we have tied our 18oatm record from vostok to the specmap timescale throughout the last 135 kyr by correlating 18oatm with a 18osw record from v19 30 results of the correlation indicate that 77 of the variance is shared between these two records we observed differences between the 18oatm and the 18osw records during the coldest periods which indicate that there have been subtle changes in the factors which regulate 18oatm other than 18osw our use of 18oatm as a proxy for 18osw must therefore be considered tentative especially during these periods by correlating 18oatm with 18osw we provide a common temporal framework for comparing phase relationships between atmospheric records from ice cores and oceanographic records constructed from deep sea cores our correlated age depth relation for the vostok core should not be considered an absolute vostok timescale we consider it to be the preferred timescale for comparing vostok climate records with marine climate records which have been placed on the specmap timescale we have examined the fidelity of this common temporal framework by comparing sea surface temperature sst records from sediment cores with an antarctic temperature record from the vostok ice core we have demonstrated that when the southern ocean sst and antarctic temperature records are compared on this common temporal framework they show a high degree of similarity we interpret this result as supporting our use of the common temporal framework for comparing other climate records from the vostok ice core with any climate record that has been correlated into the specmap chronology

a simple model for the prediction of the deflation threshold shear velocity of dry loose particles abstract a very important parameter in aeolian equations is the de ation thresholdshear velocity which quanti es the instant of particle motion in this paper asimple model is presented for the prediction of the threshold shear velocity ofdry loose particles it has the same functional form as the widely used modelsof bagnold 1941 and greeley iversen 1985 but differs in its treatment ofthe so called threshold parameter as the new expression was based on themoment balance equation used by greeley iversen it includes a function forthe aerodynamic forces including the drag force the lift force and theaerodynamic moment force and a function for the interparticle forces theeffect of gravitation is incorporated in both functions however rather thanusing an implicit function for the effect of the aerodynamic forces as in thegreeley iversen model a constant aerodynamic coef cient was introduced from consideration of the van der waals force between two particles it wasalso shown that the function for the interparticle cohesion force is inverselyproportional to the particle diameter squared the model was calibrated ondata reported by iversen white 1982 the new expression compared atleast for terrestrial conditions very well with the greeley iversen model although it is much simpler it was nally validated with data from wind tunnel experiments on different fractions of dune sand and sandy loam soilaggregates the soil aggregates were treated as individual particles with adensity equal to their bulk density the good agreement between observationsand predictions means that when predicting mass transport of particles abovea given soil minimally dispersed particle size distributions should beconsidered rather than the granulometric composition of the soil keywords de ation threshold wind erosion wind tunnel introductionde ation is the blowing away of soil particles bywind particles start to move only if the aerody namic destabilizing forces exceed the stabilizingforces that keep the particles together once thewind erosion process has started particles willalso be detached as a result of impact forcescaused by the collisions that occur when settlingparticles hit the surface the initiation of particlemovement is generally quanti ed by means of thethreshold shear velocity u

the impact of dansgaard oeschger cycles on the loessic environment and malacofauna of nussloch germany during the upper weichselian abstract a loess sequence has been sampled continuously at high resolution in nussloch rhine valley germany for malacological and grain size analyses between ca 34 and 20 ka molluscan abundance and richness percentage in hygrophilous species and grain size index show cyclical variations related to the lithological loess gley alternation major molluscan abundance maxima were triggered by temperature increases through an enhancement of the reproduction cycle whereas cyclical richness fluctuations and percentage in hygrophilous species reflect variations in local humidity and changes in the environmental mosaic malacological parameters allow the distinction of four environmental phases organised in cyclical successions correlated with most of the loess gley doublets the correlation of the grain size index of the nussloch loess sequence with the dust content of the grip ice core demonstrates the synchronicity of major molluscan abundance maxima and 18 o increases characterising temperature increases during dansgaard oeschger interstades a schematic model is proposed to link the north atlantic dansgaard oeschger climatic oscillations with local environmental changes indicated by both malacofauna and pedostratigraphy this malacological study of the nussloch loess sequence thus provides new information about the response of terrestrial loessic palaeoenvironments to millennial timescale climatic fluctuations during the upper weichselian marine isotope stage 2 mis 2 and end of mis 3

palaeoprecipitation reconstruction by inverse modelling using the isotopic signal of loess organic matter application to the nusloch loess sequence rhine valley germany a modified version of the biome4 vegetation model for simulation of the mean 13c of plant communities is presented and used to reconstruct palaeoprecipitation we treat all fractionations by c3 and c4 plants in all coexistent plant functional types weighted by their respective net primary production we constrain the range of variation in the intracellular versus atmospheric co2 concentration by fixing a lower limit finally we replace some constant parameters by functions of external forcing to account for their responses to environmental variation the new version of biome4 was applied as an inverse model and tested on three modern data sets the fit between observations and simulations is very close to the 1 1 relationship with respective slopes of 0 90 0 02 r2 0 98 n 29 for 13c and 0 97 0 06 r2 0 90 n 29 for precipitation inverse modelling was applied using the metropolis hastings algorithm to the nusloch loess sequence over the last glaciation simulated palaeoprecipitation varies between 240 mm year 1 and 400 mm year 1 this study clearly demonstrates atmospheric teleconnections with the greenland ice sheet extension by matching dansgaard oeschger events with precipitation increase of ca 100 200 mm year 1

synchronization of the ngrip grip and gisp2 ice cores across mis 2 and palaeoclimatic implications abstract we here present a synchronization of the ngrip grip and gisp2 ice cores based mainly on volcanic events over the period 14 9 32 45 ka b2k before ad 2000 corresponding to marine isotope stage 2 mis 2 and the end of mis 3 the matching provides a basis for applying the recent ngrip based greenland ice core chronology 2005 gicc05 time scale to the grip and gisp2 ice cores thereby making it possible to compare the synchronized palaeoclimate profiles of the cores in detail and to identify relative accumulation differences between the cores based on the matching a period of anomalous high accumulation rates in the gisp2 ice core is detected within the period 16 5 18 3 ka b2k the 18 o and ca 2 profiles of the three cores are presented on the common gicc05 time scale and generally show excellent agreement across the stadial interstadial transitions and across the two characteristic dust events in greenland stadial 3 however large differences between the 18 o and ca 2 profiles of the three cores are seen in the same period as the 7 9 increase in the gisp2 accumulation rate we conclude that changes of the atmospheric circulation are likely to have occurred in this period altering the spatial gradients in greenland and resulting in larger variations between the records

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

luminescence dating indicates radiocarbon age underestimation in late pleistocene fluvial deposits from eastern england robust geochronological control is crucial for interpreting and correlating the environmental record from fragmentary terrestrial sequences from the last glacial period traditional terrestrial stratigraphies are typically reliant on radiocarbon dating although estimates of antiquity for samples older than 40 ka may be unreliable optically stimulated luminescence osl dating of sediments is an alternative for dating the whole of the last glacial period and also provides the opportunity to independently test radiocarbon based chronologies this paper presents a set of nine directly comparable paired osl and accelerator mass spectrometry ams radiocarbon ages from multiple sites within devensian fluvial sediments in lowland britain and shows that it is possible to obtain robust osl age estimates throughout this time period the two techniques agree well for ages younger than ca 29 14c ka bp ca 35 cal ka bp but disagree beyond ca 35 14c ka bp ca 40 cal ka bp this is thought to be due to radiocarbon ages on older organic material having been contaminated by low levels of modern carbon it is therefore suggested that all conventionally pre treated radiocarbon ages greater than 35 14c ka bp should be treated with extreme caution copyright 2009 john wiley sons ltd

abrupt millennial climatic changes from nussloch germany upper weichselian eolian records during the last glaciation abstract increasing attention has been focussed on the massive iceberg discharges in the north atlantic heinrich events during the last glaciation and their worldwide terrestrial counterparts however these events are particular episodes among more regular cyclic events named dansgaard oeschger events in ice cores or bond cycles in marine cores here we examine grain size 13c and magnetic susceptibility data from nussloch one of the most complete west european eolian sequence examined so far these indices indicate that during the 31 19 kyr interval using chronology provided by radiocarbon osl and tl dates millennial scale variations occurred affecting both precipitation and vegetation furthermore these are associated with oscillations in the wind strength matching the dust deposition rate in greenland as recorded in the grip ice core our study shows that the abrupt climatic changes the dansgaard oeschger events are also recorded in the west european loess sequences this implies an atmospheric mechanism linking dust deposition over greenland and europe which is probably connected to global climatic events during the last glaciation

δ13c of loess organic matter as a potential proxy for paleoprecipitation paleoprecipitation reconstructions on the basis of pollen are well known but they do not provide high temporal resolution for glacial periods high resolution paleoprecipitation reconstructions for the last glaciation based on the isotopic record organic matter in loess from nussloch rhine valley germany are consistent with paleoprecipitation inferred from peat in the same area using an independant method thus 13c of loess organic matter can be used as a proxy for paleoprecipitation

seismic imaging of the puritan batholith wisconsin using split array cross correlator processing a seismic data set was collected in northern wisconsin in the summers of 1980 1981 the study area overlies a less heterogeneous portion of the precambrian puritan batholith a body which has been intruded and otherwise deformed since its emplacement high velocity bedrock lies beneath a thin glacial till layer other than a shallow penetration first arrival there was no evidence of refractors or reflectors in the upper few kilometers the data contain an abundance of energy and our goal was to determine the source of that energy a processing technique based on the split array cross correlator jacobsen 1957 doll 1983 was developed for locating diffractors with a sparse data set the technique is similar to those used in underwater acoustics and radio astronomy for locating point sources it assumes an acoustic medium with known velocity structure in which inhomogeneities may be treated as point diffractors the output is the windowed cross correlation of two stacks of delayed traces the delays are determined by ray tracing for each source to grid point and grid point to receiver path the cross correlations are calculated over a two dimensional array of grid points the method is useful when data are sparse and conventional linear methods fail to image subsurface structure our images show reflections and diffractions from a dipping interface at about 6 8 km depth as well as other features associated with the puritan batholith

nitrate in greenland and antarctic ice cores a detailed description of post depositional processes a compilation of nitrate no 3 data from greenland has shown that recent no 3 concentrations reveal a temperature dependence similar to that seen in antarctica except for sites with very low accumulation rates lower temperatures tend to lead to higher no 3 concentrations preserved in the ice accumulation rate which is closely linked to temperature might influence the concentrations preserved in snow as well but its effect cannot be separated from the temperature imprint processes involved in no 3 deposition are discussed and shown to be temperature and or accumulation rate dependent apart from scavenging of nitric acid hno 3 during formation of precipitation uptake of hno 3 onto the ice crystal s surface during and after precipitation seems to contribute further to the no 3 concentrations found in surface snow post depositional loss of no 3 from the top snow layers is caused by release of hno 3 and by photolysis of no 3 it is suggested that photolysis accounts for considerable losses at sites with very low accumulation rates depending on the site characteristic and given that the temperature and accumulation rate dependence is quantified it should be possible to infer changes in atmospheric hno 3 concentrations

debates over palaeolithic chronology the reliability of 14c is confirmed abstract the debate about the complex issues of human development during the middle to upper palaeolithic transition period 45 35 ka bp has been hampered by concerns about the reliability of the radiocarbon dating method large 14 c anomalies were postulated and radiocarbon dating was considered flawed we show here that these issues are no longer relevant because the large anomalies are artefacts beyond plausible physical limits for their magnitude previous inconsistencies between 14 c radiocarbon datasets have been resolved and a new radiocarbon calibration curve intcal09 reimer et al 2009 was created improved procedures for bone collagen extraction and charcoal pre treatment generally result in older ages consistent with independently dated time markers

climatic reconstruction of the weichselian pleniglacial in northwestern and central europe a multiproxy approach is applied to reconstructing accurately the weichselian pleniglacial climate 72 13 ka in northwestern and central europe standardised translations are used to transform proxy data into climate parameter values for six characteristic time windows quantitative reconstructions of the temperature regime are derived from periglacial coleoptera and botanical evidence while aeolian and fluvial evidence provide qualitative information on wind activity and precipitation respectively the early pleniglacial 74 59 ka the cold period between 41 38 ka and the late pleniglacial 27 13 ka are characterised by a strong north to south climatic gradient over northwestern europe during the last glacial maximum discontinuous permafrost was established in northern france whereas the continuous permafrost zone extended from the uk belgium the netherlands germany and poland to the nordic ice sheets prominent wind activity and a relatively low precipitation typify these periods in contrast an indistinct west to east climate gradient was present in the relatively more temperate intervals e g 50 41 ka seasonally frozen ground conditions prevailed in northwestern europe whereas discontinuous permafrost may be suggested for central germany it appears that the climate conditions in northwest and central europe were controlled by three major factors the scandinavian ice sheet the north atlantic surface water circulation and the russian continent 1998 john wiley sons ltd

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 chronological position of the lohne soil in the nussloch loess section re evaluation for a european loess marker horizon abstract the loess section of nussloch in southwestern germany is a key profile for the reconstruction of the terrestrial palaeo environment of central europe at the time of the last glacial and interglacial recently the significance of the site for palaeo environmental and geoarchaeological research increased additionally with the discovery of unique palaeolithic cultural remains from anatomically and culturally modern humans that invaded southwestern germany during the weichselian wurmian pleniglacial period at nussloch a chrono stratigraphical key position is taken by a middle pleniglacial cambisol remain which under the designation lohne soil serves as an important pedostratigraphic marker horizon for the greater area repeatedly greenland interstadial gis 8 was suggested as a likely period of soil formation for the lohne soil this interpretation is yet not justified on the basis of published chronometric data critical assessment of the data points to a later period of soil formation likely during gis7 to gis5 this conclusion is supported by a new set of radiocarbon ages for the nussloch site which are presented here for the first time consequences of a revised chronology for correlations of pleniglacial cryosols below and above the lohne soil with greenland interstadials are discussed the implications are important for european loess research as the nussloch section serves as a reference base for loess sections throughout europe

the greenland ice core chronology 2005 15 42 ka part 2 comparison to other records a new greenland ice core chronology gicc05 based on multi parameter counting of annual layers has been obtained for the last 42 ka here we compare the glacial part of the new time scale which is based entirely on records from the northgrip ice core to existing time scales and reference horizons covering the same period these include the grip and northgrip modelled time scales the meese sowers gisp2 counted time scale the shackleton fairbanks grip time scale sfcp04 based on 14c calibration of a marine core the hulu cave record three volcanic reference horizons and the laschamp geomagnetic excursion event occurring around greenland interstadial 10 gicc05 is generally in good long term agreement with the existing greenland ice core chronologies and with the hulu cave record but on shorter time scales there are significant discrepancies around the last glacial maximum there is a more than 1 ka age difference between gicc05 and sfcp04 and a more than 0 5 ka discrepancy in the same direction between gicc05 and the age of a recently identified tephra layer in the northgrip ice core both sfcp04 and the tephra age are based on 14c dated marine cores and fixed marine reservoir ages for the laschamp event gicc05 agrees with a recent independent dating within the uncertainties

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

contrasting ocean changes between the subpolar and polar north atlantic during the past 135 ka variations in the poleward directed atlantic heat transfer was investigated over the past 135 ka with special emphasis on the last and present interglacial climate development eemian and holocene both interglacials exhibited very similar climatic oscillations during each preceding glacial terminations deglacial ti and tii like ti also tii has pronounced cold warm cold changes akin to events such as h1 bolling allerod and the younger dryas but unlike ti the cold events in tii were associated with intermittent southerly invasions of an atlantic faunal component which underscores quite a different water mass evolution in the nordic seas within the eemian interglaciation proper peak warming intervals were antiphased between the nordic seas and north atlantic moreover inferred temperatures for the nordic seas were generally colder in the eemian than in the holocene and vice versa for the north atlantic a reduced intensity of atlantic ocean heat transfer to the arctic therefore characterized the eemian requiring a reassessment of the actual role of the ocean atmosphere system behind interglacial but also glacial climate changes key points reduced amoc during the eemian ba yd type warming cooling in termination 1 and 2 comparison of glacial inceptions reveals present climate status

saltation threshold on earth mars and venus new formulations valid for wide ranges of particle diameter and density and gas density are presented for prediction of saltation threshold speed for small particles a low air density wind tunnel was used to extend the range of previous investigations and to separate the effects of reynolds number and interparticle forces of cohesion the new formulations are used to predict saltation threshold for atmospheric conditions on the surface of the earth mars and venus

new data for the last glacial maximum in great britain and ireland abstract understanding the history of the british and irish ice sheet biis at the last glacial maximum lgm has been advanced by new approaches in particular by cosmogenic nuclide surface exposure dating aminostratigraphy of shelly glacial deposits ams radiocarbon dating and the evidence from continental margin marine cores all of which supersede the previously weak geochronologic control it was formerly believed that great britain and ireland was largely ice free between the last interglacial oxygen isotope sub stage 5e and the late devensian when the lgm occurred as such the biis was effectively out of phase with laurentide and scandinavian ice sheets as well as inferences of ice volume from oxygen isotope stratigraphy the biis during the late devensian maximum was also perceived as having been relatively stationary new evidence shows that the lgm was an important event during the evolution of an earlier biis when the extent of ice was greater repeated iceberg rafting events over the past 50 ka are shown by marine cores while the derivative inference of numerous corresponding glacial advances is supported by several clusters of 36 cl ages on glaciated surfaces and glacial boulders that are indicative of deglacial events between 40 and 12 ka these appear to be associated with heinrich events the earliest being inferred as heinrich 4 at about 40 ka during this advance the biis and scandinavian ice sheet sis were in contact and all of ireland was glaciated the ice sheet appears to have fluctuated several times between 40 and 25 ka although evidence for this is poorly preserved but the 36 cl and 14 c evidence is clear that the biis reached its lgm maximum size about 22 ka soon after heinrich event 2 when the biis and sis were not in contact one cluster of 36 cl and 14 c ages at 21 4 1 3 ka records an initial pulse of deglaciation that was followed by extensive deglaciation about 17 4 0 4 ka just before heinrich event 1 when the ice sheet readvanced contrary to previous views the biis probably existed throughout much of devensian time as a mobile and sensitive ice sheet during which the lgm advance was but one important event in places glacial deposits of the earlier devensian glaciation have previously been incorrectly identified as products of the later lgm glaciation

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

thermoluminescence dating applied to paleosols abstract thermoluminescence tl dating of quaternary sediments has developed rapidly in the last few years as paleosols often prove to be useful stratigraphic marker horizons it is of great interest to obtain absolute ages for them a technique is proposed which increases the range of tl dating of loess to some 300 ka special problems associated with paleosol tl dating such as sampling and dose rate evaluation are discussed three examples for paleosols from west german loess regions are presented the intra wurmian lohner boden soil 28 30 ka lower wurmian chernozem like soils ca 70 ka and the penultimate interglacial soil karlich interglacial between 230 and 170 ka

holocene relief and soil changes in loess covered areas of south western germany the pedosedimentary archives of bretten bauerbach kraichgau based on infrared stimulated luminescence irsl dating of loess borne sediments a chronometry of holocene landscape evolution is established for a representative study site in the early settled kraichgau area in south western germany the results show that the gently rolling relief is due essentially to soil erosion and colluvial deposition triggered by humans cultivating the loess soils since the onset of agriculture in the neolithic period levelling of relief is accompanied by alterations in soil type patterns from haplic luvisols before the impact of humans over variably truncated luvisols with bt horizons prevailing at the slope surfaces in the middle ages to calcaric regosols characterizing both sites of erosion and accumulation since then the tremendous changes show that the effects of human activities have been recorded over thousands of years indicating an early anthropocene in a geomorphological and pedological sense most landscapes are probably more modified by humans than thought at first sight as the results show this recognition requires considering that current geomorphological and soil forming processes might work at different frequencies or magnitudes e g by changes of internal system thresholds such as increased erodibility following the complete erosion of a more resistant bt horizon and or in a different direction e g accumulation instead of erosion or sediment transport due to slope angles decreased by former deposition of colluvium than they would in the absence of a human controlled pre history

a high resolution absolute dated late pleistocene monsoon record from hulu cave china oxygen isotope records of five stalagmites from hulu cave near nanjing bear a remarkable resemblance to oxygen isotope records from greenland ice cores suggesting that east asian monsoon intensity changed in concert with greenland temperature between 11 000 and 75 000 years before the present yr b p between 11 000 and 30 000 yr b p the timing of changes in the monsoon as established with 230th dates generally agrees with the timing of temperature changes from the greenland ice sheet project two gisp2 core which supports gisp2 s chronology in this interval our record links north atlantic climate with the meridional transport of heat and moisture from the warmest part of the ocean where the summer east asian monsoon originates

continuous record of microparticle concentration and size distribution in the central greenland ngrip ice core during the last glacial period 1 a novel laser microparticle detector used in conjunction with continuous sample melting has provided a more than 1500 m long record of particle concentration and size distribution of the ngrip ice core covering continuously the period approximately from 9 5 100 kyr before present measurements were at 1 65 m depth resolution corresponding to approximately 35 200 yr particle concentration increased by a factor of 100 in the last glacial maximum lgm compared to the preboreal and sharp variations of concentration occurred synchronously with rapid changes in the 18o temperature proxy the lognormal mode of the volume distribution shows clear systematic variations with smaller modes during warmer climates and coarser modes during colder periods we find 1 7 m diameter during lgm and 1 3 m during the preboreal on timescales below several 100 years and the particle concentration exhibit a certain degree of independence present especially during warm periods when generally is more variable using highly simplifying considerations for atmospheric transport and deposition of particles we infer that 1 the observed changes of in the ice largely reflect changes in the size of airborne particles above the ice sheet and 2 changes of are indicative of changes in long range atmospheric transport time from the observed size changes we estimate shorter transit times by roughly 25 during lgm compared to the preboreal the associated particle concentration increase from more efficient long range transport is estimated to less than one order of magnitude

timing of the last glacial maximum from observed sea level minima during the last glacial maximum ice sheets covered large areas in northern latitudes and global temperatures were significantly lower than today but few direct estimates exist of the volume of the ice sheets or the timing and rates of change during their advance and retreat here we analyze four distinct sediment facies in the shallow tectonically stable bonaparte gulf australia each of which is characteristic of a distinct range in sea level to estimate the maximum volume of land based ice during the last glaciation and the timing of the initial melting phase we use faunal assemblages and preservation status of the sediments to distinguish open marine shallow marine marginal marine and brackish conditions and estimate the timing and the mass of the ice sheets using radiocarbon dating and glacio hydroisostatic modelling our results indicate that from at least 22 000 to 19 000 calendar years before present land based ice volume was at its maximum exceeding today s grounded ice sheets by 52 5 x 10 exp 6 cu km a rapid decrease in ice volume by about 10 percent within a few hundred years terminated the last glacial maximum at 19 000 250 years

an event stratigraphy for the last termination in the north atlantic region based on the greenland ice core record a proposal by the intimate group it is suggested that the grip greenland ice core should constitute the stratotype for the last termination based on the oxygen isotope signal in that core a new event stratigraphy spanning the time interval from ca 22 0 to 11 5 k grip yr bp ca 19 0 10 0 k 14 c yr bp is proposed for the north atlantic region this covers the period from the last glacial maximum through termination 1 of the deep ocean record to the pleistocene holocene boundary and encompasses the last glacial late glacial of the traditional northwest european stratigraphy the isotopic record for this period is divided into two stadial episodes greenland stadials 1 gs 1 and 2 gs 2 and two interstadial events greenland interstadials 1 gi 1 and 2 gi 2 in addition gi 1 and gs 2 are further subdivided into shorter episodes the event stratigraphy is equally applicable to ice core marine and terrestrial records and is considered to be a more appropriate classificatory scheme than the terrestrially based radiocarbon dated chronostratigraphy that has been used hitherto 1998 john wiley sons ltd

the greenland ice core chronology 2005 15 42 ka part 1 constructing the time scale the greenland ice core chronology 2005 gicc05 is extended back to 42 ka b2k before 2000 ad i e to the end of greenland stadial 11 the chronology is based on independent multi parameter counting of annual layers using comprehensive high resolution measurements available from the north greenland ice core project ngrip these are measurements of visual stratigraphy conductivity of the solid ice electrolytical melt water conductivity and the concentration of na c a 2 s o 4 n o 3 n h 4 a n uncertainty estimate of the time scale is obtained from identification of uncertain annual layers which are counted as 0 570 5 years the sum of the uncertain annual layers the so called maximum counting error of the presented chronology ranges from 4 in the warm interstadial periods to 7 in the cold stadials the annual accumulation rates of the stadials and interstadials are on average one third and half of the present day values respectively and the onset of the greenland interstadials 2 3 and 8 based on 20 year averaged d 18 o

radiocarbon calibration curve spanning 0 to 50 000 years bp based on paired 230 th 234 u 238 u and 14 c dates on pristine corals abstract radiocarbon dating is the most widely used dating technique in the world recent advances in accelerator mass spectrometry ams and sample preparation techniques have reduced the sample size requirements by a factor of 1000 and decreased the measurement time from weeks to minutes today it is estimated that more than 90 percent of all measurements made on accelerator mass spectrometers are for radiocarbon age dates the production of 14 c in the atmosphere varies through time due to changes in the earth s geomagnetic field intensity and in its concentration which is regulated by the carbon cycle as a result of these two variables a radiocarbon age is not equivalent to a calendar age four decades of joint research by the dendrochronology and radiocarbon communities have produced a radiocarbon calibration data set of remarkable precision and accuracy extending from the present to approximately 12 000 calendar years before present this paper presents high precision paired 230 th 234 u 238 u and 14 c age determinations on pristine coral samples that enable us to extend the radiocarbon calibration curve from 12 000 to 50 000 years before present we developed a statistical model to properly estimate sample age conversion from radiocarbon years to calendar years taking full account of combined errors in input ages and calibration uncertainties our radiocarbon calibration program is publicly accessible at http www radiocarbon ldeo columbia edu along with full documentation of the samples data and our statistical calibration model

dust deposition and climate in the carpathian basin over an independently dated last glacial interglacial cycle dust deposition and climate in the carpathian basin over an independently dated last glacial interglacial cycle

link between european and north atlantic abrupt climate changes over the last glaciation 1 sub millennial timescale climate variations correlated with those in the north atlantic area are identified in the loess sequence from nussloch germany exceptionally developed over the interval between about 38 000 and 18 000 years ago the dansgaard oeschger do events 8 to 2 as well as some less pronounced warming episodes recorded in the greenland ice have their counterpart in the nussloch loess stratigraphy and in the variations of the loess grain size index gsi the north atlantic heinrich events 3 and 2 are expressed at nussloch as maxima of the gsi record the similarity of the fine variations in the nussloch loess and the greenland ice records points to an intimate link of climate changes in western europe with those in the north atlantic