on the 1470 year pacing of dansgaard oeschger warm events 1 the oxygen isotope record from the greenland ice sheet project 2 gisp2 ice core was reanalyzed in the frequency and time domains the prominent 1470 year spectral peak which has been associated with the occurrence of dansgaard oeschger interstadial events is solely caused by dansgaard oeschger events 5 6 and 7 this result emphasizes the nonstationary character of the oxygen isotope time series nevertheless a fundamental pacing period of 1470 years seems to control the timing of the onset of the dansgaard oeschger events a trapezoidal time series model is introduced which provides a template for the pacing of the dansgaard oeschger events statistical analysis indicates only a 3 probability that the number of matches between observed and template derived onsets of dansgaard oeschger events between 13 and 46 kyr b p resulted by chance during this interval the spacing of the dansgaard oeschger onsets varied by 20 around the fundamental 1470 year period and multiples thereof the pacing seems unaffected by variations in the strength of north atlantic deep water formation suggesting that the thermohaline circulation was not the primary controlling factor of the pacing period

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

methodology of the last climatic cycle reconstruction in france from pollen data abstract a numerical method has been devised to reconstruct the climate of the last climatic cycle from pollen data reliable annual reconstructions have been published recently for the two french long sequences of la grande pile and les echets covering the last 140 millennia this paper gives more details on the method used it proposes new reconstructions based on an extended modern pollen data base these reconstructions are consistent with the previous ones especially detailed information is obtained on the seasonal characteristics of climate computations of gcm on the climate variations from 125 kyr to 115 kyr b p are confirmed for western europe the insolation variations have induced at that time a decrease of seasonality accompanied by an increased cyclonic activity in winter this has been the beginning of the first ice growth after the last interglacial other glacier growth phases are detected at the end of substage 5c and particularly at the end of substage 5a

imf sector effects on the polar geomagnetic field in winter imf sector effects on the polar geomagnetic field particularly in winter are examined with a use of the geomagnetic data from 13 northern and 6 southern high latitude geomagnetic stations detailed behavior of the winter reversal of the sector effects near 70 invariant latitude is investigated a method to improve the sector estimation from geomagnetic data is suggested and formation of the winter reversal is briefly discussed taking electric field propagations along field lines from the summer hemisphere as well as upward and downward field aligned electric current effects into consideration

eolian quartz flux to lake biwa central japan over the past 145 000 years abstract eolian quartz flux eqf g cm 2 103yr 1 to lake biwa central japan provides direct information on variations of the east asian winter monsoon lake biwa sediments spanning the past ca 145 000 yr are characterized by two main periods when eqf values were significantly greater than 5 50 g cm 2 103yr 1 and two main intervals during which eqf values were lower two periods with eqf values 5 50 g cm 2 103yr 1occurred from ca 145 000 to 125 000 and 73 000 to 13 000 yr b p while times of lower eqf values occurred from ca 125 000 to 73 000 yr b p and around ca 5500 yr b p between ca 125 000 and 73 000 yr b p three minimum eqf values and two intervening peaks of slightly higher eqf values are recorded eqf increased markedly from ca 73 000 to 13 000 yr b p whereas between ca 53 000 and 20 000 yr b p the values recorded were relatively lower than those recorded during either the preceding or the subsequent episodes the data imply that the east asian winter monsoon strengthened during the periods when eqf values were high and weakened during the intervals with low eqf values the eqf record of lake biwa can be correlated with the grain size record of the quartz fraction in chinese loess and with the specmap marine 18o record however the eqf record apparently lags ca 5000 yr behind the loess and 18o records during stage 6 5 and 2 1 transitions and ca 10 000 yr during stage 5 4 transition these apparent lags could be due to problems with the chronology alternatively they may imply that the eolian quartz flux depended more on the extent of dust source regions than on wind intensity during these transitions

electromagnetic induction studies recent developments in electromagnetic induction studies of the lithosphere and the asthenosphere are reviewed attention is given to geoelectrical studies of active tectonic areas in terms of the major zones of crustal extension the basin and range province along western regions of north america and the rio grande rift studies have also been performed of tectonic activity around iceland the salton trough and cerro prieto and the subduction zones of the cascade mountains volcanic belt where magnetotelluric and geomagnetic variation studies have been done geomagnetic variations experiments have been reported in the central appalachians and submarine electromagnetic studies along the juan de fuca ridge controlled source electromagnetic and dc resistivity investigations have been carried out in nevada hawaii and in the adirondacks mountains laboratory examinations on the conductivity of representative materials over a broad range of temperature pressure and chemistry are described

biological and environmental changes in lake baikal during the late quaternary inferred from carbon nitrogen and sulfur isotopes abstract an 8 m continuous sediment core approximately 250 ky old at the bottom from academician ridge in lake baikal has been analyzed for the stable isotopes of carbon nitrogen and sulfur in order to study the paleoclimatic and paleobiological changes that occurred in the eurasian continental interior these isotopic changes are closely related to changes in vertical lake water circulation between glacial and interglacial periods sedimentary organic carbon in cool periods is more enriched in 13 c 23 8 on average than that in warm periods 27 0 on average the 13 c enrichment of organic carbon suggests a decrease of land derived organic matter influx to the lake less precipitation and loss of terrestrial vegetation around lake baikal in cool periods pyrite in high total sulfur total organic carbon ts toc layers shows strong depletion in 34 s 20 8 to 32 4 during climate transitions from glacial to interglacial periods at the beginning of oxygen isotope stages ois 1 5 and 7 the 34 s depleted pyrite indicates augmentation of dissimilatory sulfate reduction by sulfate reducing bacteria srb at the sediment water interface enhancement of aqueous sulfate concentrations and limitation of oxygen circulation to the surface sediments might also occur in the climate transition periods the 15 n values of total nitrogen increase abruptly by 2 just after the 34 s negative peaks which may result from low nutrient concentrations in the euphotic zone associated with water circulation changes in lake baikal

orbital scale stratigraphy and high resolution analysis of biogenic components and deep water oxygenation conditions in the japan sea during the last 640 kyr abstract paleoceanographic conditions in the japan sea changed drastically during the late quaternary in association with orbital and suborbital cycles and glacio eustatic sea level changes however few studies have examined long term sediment records older than 160 ka because of the lack of long and continuous cores and the difficulty in constructing high resolution age models in this study we first constructed an orbital scale stratigraphy of the sediments covering the last 640 kyr by comparing the specmap 18o curve and the 18o curve of planktonic foraminifera 18opf in the japan sea together with the combination zones of dominant planktonic foraminifera species then we reconstructed temporal variations in biogenic silica biosil and biogenic carbonate biocarb contents calculated from high resolution major element analysis data determined by an xrf microscanner in order to evaluate the deep water oxygenation conditions we also defined excess s as the difference between the content of s in the sediments and that for normal marine sediments calculated from the organic carbon content corg estimated from lightness l by assuming a total sulfur content stotal corg ratio of 0 36 and examined its variability biosil shows orbital scale variation and is generally low except during interglacial maxima when global sea level was high enough to allow a strong influx of the tsushima warm current biocarb shows orbital and suborbital scale variations and tends to be higher in dark layers deposited during glacial stages whereas the relationship is reversed during interglacial stages the low biocarb in dark layers deposited during interglacial stages is probably due to dissolution of biogenic carbonate caused by the increase in surface productivity as a result of the strong influx of nutrient rich east china sea coastal water and consequent increase in surface productivity and decomposition rate of organic matter in the intermediate water excess s tends to be higher in thicker dark layers deposited during glacial maxima when the sea level dropped below 90 m compared to adjacent light layers suggesting development of euxinic deep water conditions during these periods the results demonstrated the presence of orbital and suborbital scale variations in biosil and biocarb and their association with dark and light layers in the japan sea that reflect variations in the nature and strength of inflow through the tsushima strait controlled by both climatic and sea level changes whereas higher excess s reflects the development of euxinic deep water condition during glacial maxima in association with glacio eustatic sea level drops below 90 m during the last 640 kyr

quantitative reconstruction of paleoclimate in central japan for the past 158 000 years based on a modern analogue technique of pollen composition abstract in this study quantitative climate information for central japan for the past 158 ka is reconstructed on the basis of pollen composition data of nj88 core from lake nojiri and those of tkn 2004 core from the lacustrine takano formation using a modern analogue technique reconstructed values at the sites around 36 6 n and 700 m altitude are as follows in marine isotope stage mis 6 the average annual mean temperature was about 2 1 c with a coldest month temperature of 11 8 c which suggest very cold climate conditions the climates of mis 4 and 2 were similarly cold and the precipitation was low with 1050 mm for mean annual precipitations during these cold periods in contrast the annual mean temperatures of mis 5e and mis 1 among the warmest periods averaged about 5 5 c and 9 1 c respectively the annual mean temperature of mis 5e was significantly lower than that of the holocene we estimate that an intensely cold winter controlled the vegetation which resulted in the lower temperature reconstruction for mis 5e the annual mean temperatures of intermediately warm periods such as mis 5c and 5a were a slightly high with averages of 4 4 c and 5 1 c respectively annual precipitations increased up to 1400 mm on average in these warmer periods annual mean temperatures of mis 5d and 5b were low with averages of about 3 0 c annual mean temperatures reconstructed for mis 3 fluctuated over short periodicities that correspond to dansgaard oeschger cycles for example the annual mean temperature of the interstadial gi 8 greenland interstadial 8 38 39 cal ka bp calendar ka before 1950 ce was about 4 0 c and that of the stadial he 4 heinrich event 4 in 42 43 cal ka bp was about 2 6 c from 14 to 12 cal ka bp annual mean temperature increased significantly in a relatively short period from 1 3 to 9 5 c and annual precipitation also increased from 1040 to 1380 mm a cool event corresponding to the younger dryas was identified in this deglaciation process but its intensity was much weaker than that in the north atlantic region the climate in the holocene mis 1 was warm with an average annual mean temperature of 9 0 c with wide variation by a maximum of about 2 c which suggests temporal change of the arctic polar front situated in mid latitude regions

identification and correlation of visible tephras in the lake suigetsu sg06 sedimentary archive japan chronostratigraphic markers for synchronising of east asian west pacific palaeoclimatic records across the last 150 ka abstract the lake suigetsu sg06 sedimentary archive from honshu island central japan provides a high resolution palaeoenvironmental record including a detailed record of explosive volcanism from japan and south korea thirty visible tephra are recorded within the 73 m long sg06 core which spans the last 150 ka here we describe and characterise these tephras based on major element glass composition which is useful for the identification and correlation of these tephras and the age models of the records in which they are found utilising the large number of radiocarbon measurements n 600 from terrestrial plant macrofossils in the lake suigetsu sg06 record we are able to provide precise and accurate ages for the tephras from eruptions within the last 50 ka glass compositional data of some of the largest eruptions from japan k ah at aso 4 aso a aso d and ata sampled at proximal outcrops are also presented these data show that the major element glass chemistry is distinctive for many of the visible sg06 tephra units and allows some of the layers to be correlated to known eruptions from volcanoes in japan and south korea namely k ah sg06 0967 u oki sg06 1288 at sg06 2650 aso 4 sg06 4963 sg06 4979 k tz sg06 5181 aso abcd sg06 5287 and ata sg06 5181 the following ages were obtained for the sg06 tephra units 3 966 4 064 cal ka bp 95 4 probability range for the sg06 0588 tephra 10 242 10 329 cal ka bp 95 4 probability range for sg06 1293 19 487 112 sg06 2012 ka bp 2 for sg06 1965 28 425 194 sg06 2012 ka bp 2 for sg06 2504 28 848 196 sg06 2012 ka bp 2 for sg06 2534 29 765 190 sg06 2012 ka bp 2 for sg06 2601 29 775 191 sg06 2012 ka bp 2 for sg06 2602 43 713 156 sg06 2012 ka bp 2 for sg06 3485 46 364 202 sg06 2012 ka bp 2 for sg06 3668 49 974 337 sg06 2012 ka bp 2 for sg06 3912 50 929 378 sg06 2012 ka bp 2 for sg06 3974 and improved ages for two of the most important tephra markers across japan the k ah 7 165 7 303 cal ka bp at 95 4 probability range sg06 0967 and at tephra 30 009 189 sg06 2012 ka bp at 2 sg06 2650

paleolithic cultures of mis 3 to mis 1 in relation to climate changes in the central japanese islands abstract the pattern of latest pleistocene climate changes reconstructed on the basis of sediment cores from lake nojiri is one of the most detailed and reliable reconstructions in japan the climate changes over the last 72 ka can be compared directly with those recorded at upper paleolithic and incipient jomon sites on the basis of a revised age model for the lake nojiri sediment cores and the revised 14c dates calibrated after intcal09 fossil bones of megafauna from the tategahana site beside the lake have been placed ca 53 37 ka cal bp in the relatively warm temperate climate of the early mis 3 part of the tategahana site was interpreted as a kill and butchery site although the presence of the big game hunters is still uncertain as so far there is no reliable archaeological evidence in the japanese archipelago dating back to the middle paleolithic the number of paleolithic sites increased suddenly after 38 ka cal bp around lake nojiri this seems to coincide with the timing of the migration of homo sapiens into the japanese archipelago the climate had been gradually cooling toward the last glacial maximum lgm however the area around lake nojiri in the late mis 3 seems to have been a suitable place for the subsistence of hunter gatherers backed blade industries ca 29 20 ka cal bp point tool industries ca 22 19 ka cal bp and microblade industries 20 16 ka cal bp were characteristic of the late upper paleolithic the number of sites around lake nojiri decreased significantly during the lgm at the end of the lgm an abrupt change of vegetation from subarctic conifer forest to deciduous broadleaf forest had occurred around 14 ka and human activities became prominent around lake nojiri as shown by the linear relief pottery group ca 15 13 ka cal bp the number of sites seems to have decreased slightly during the younger dyras cooling event patterns of human occupation around lake nojiri show the influence of global and local climate changes

inferred quasi steady ionospheric neutral winds and electrical currents at 79 south latitude in austral summer conditions an analysis of the range of geomagnetic variations as measured at arrival heights and south pole stations in the antarctic over an 8 year interval during the present solar cycle shows that there are quasi dc level shifts in some of the magnetic components during austral summer conditions when referenced to austral winter the most dramatic of these level shifts in the signals occurs in the d component west east magnetic component at arrival heights geomagnetic latitude 79 s the onsets of the d component shifts occur during a period that lasts one to several days in late austral spring such geomagnetic variations would not appear to arise from magnetosphere processes coupling to the ionospheric e region the inferred quasi steady ionospheric current is estimated to be of the order of 105 amps above arrival heights it is speculated that neutral wind dynamics with quasi steady e region 110 115 km neutral wind speeds of 10 m sec directed east to west above ah are responsible for generating the austral summer electrical currents in the e 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

fluctuations in the east asian monsoon over the last 144ka in the northwest pacific based on a high resolution pollen analysis of images core md01 2421 abstract a high resolution pollen analysis of images core md01 2421 45 83 m from the northwest pacific off central japan was used to clarify the vegetation history of central japan over the past 144 ka an age model was constructed using the oxygen isotope stratigraphy of benthic foraminifera 12 accelerator mass spectrometry ams 14c datings and two tephra layers with known eruption ages the pollen temperature index t p 1 0 0 t w t c t w where tw is the sum of temperate taxa and tc the sum of subalpine taxa values were high during 129 119 115 100 82 76 53 49 and 15 0 ka cool temperate broad leaved forests developed during the high tp periods and subalpine conifer forests grew during the low tp periods the tp fluctuated synchronously with summer insolation at 36 n where the core was collected during periods with abundant cryptomeria or sciadopitys 120 118 115 89 78 70 and 4 0 3 ka the east asian summer monsoon was stronger and the annual precipitation was greater in central japan than at present 2000 vs 1500 mm fluctuations in the sea surface temperature sst calculated from the oxygen isotopes of foraminifera in core md01 2421 and changes in the strength of the summer monsoon were synchronous the sst was determined by the currents passing over the core site rather than by the strength of summer insolation northward movement high sst of the kuroshio current which is under the influence of the summer okhotsk high pressure was strong near the summer insolation minima when precipitation was high particularly around 116 94 and 71 ka thus the strengths of both summer insolation and the east asian summer monsoon have determined the vegetation history of central japan for the last 144 ka

pollen event stratigraphy of the varved sediment of lake suigetsu central japan from 15 701 to 10 217 sg vyr bp suigetsu varve years before present description interpretation and correlation with other regions high resolution pollen data average interval between samples 15 years are reported on part of a varved sediment core from lake suigetsu japan spanning the interval 15 701 to 10 217 sg vyr bp suigetsu varve years before present this new record is compared with a previously proposed event stratigraphy based on pollen based reconstructed changes of mean annual temperature the deglacial climate history reconstructed at lake suigetsu resembles that observed in the north atlantic although the major boundaries of pollen zones are asynchronous with those in the north atlantic event stratigraphy by several centuries the onset of the late glacial interstadial occurred earlier in japan than in the north atlantic this demonstrates that the climate in japan was closely linked to the low latitude pacific sea surface temperatures that first reacted to orbital forcing conversely the onset of the subsequent cold reversal phase in japan lagged that of the north atlantic younger dryas by several centuries the duration of this cold phase was about the same as the younger dryas event but the amplitude was much reduced 4 2 c in mean annual temperature these findings support the hypothesis that this pan hemispheric cooling event was triggered by north atlantic forcing most probably by a meltwater pulse and an associated change in the north atlantic thermohaline circulation however the mechanism which transmitted the change in the north atlantic to the far east is unknown

seasonally specific responses of the east asian monsoon to deglacial climate changes the deglacial meltwater pulse in the north atlantic that induced the younger dryas event also prompted climate cooling in east asian monsoon regions such as japan and coastal mid latitude china however very little is understood about the mechanism that can transmit changes in the north atlantic to the far east here we show that the shutdown of the north atlantic thermohaline circulation brought about significantly lower temperatures and higher precipitation in the japanese winter whereas the change in the japanese summer climate was considerably smaller the cooling of the siberian air mass seems to have caused an increased pressure gradient between siberia and the west pacific in winter intensifying the winter monsoon the mongolian high pressure system and the westerly jet stream played an important role in the teleconnection in contrast the warming at the onset of the late glacial interstadial gi 1 bolling allerod in the west pacific did not have season specific features implying that the principal driving mechanism of this warming event may lie in a pan hemispheric or global factor such as insolation changes

imf sector behavior estimated from geomagnetic data at south pole imf sector behavior which has previously been estimated from the geomagnetic data at godhavn is confirmed by study of the data at south pole for 1959 1970 with the same estimation technique taking the difference between northern and southern hemispheres into consideration a method to improve about 18 the agreement between assigned and actual sector structures by study of the data at the two stations is suggested geomagnetic disturbance effects on sector estimation are discussed and reversed sector effects in winter are given special emphasis

grain size of quartz as an indicator of winter monsoon strength on the loess plateau of central china during the last 130 000 yr the chinese loess paleosol sequence constitutes an important record of variations in asian monsoon climate over the past 2 4 myr magnetic susceptibility of loess and paleosols has been used as a proxy for summer monsoon intensity while median grain size has been regarded as a measure of the strength of winter monsoon winds that were responsible for most of the dust transport however median grain size is only an approximate index of winter monsoon strength because both paleosols and loess have been modified to various degrees by weathering processes that have produced pedogenic clay the quartz component of loess and paleosols is largely unaffected by weathering processes and therefore constitutes a more reliable proxy index of monsoon wind strength median grain size qmd and maximum grain size qmax values of monomineralic quartz isolated from the loess paleosol section at luochuan in the central loess plateau are characterized by two main intervals during the last ca 130 000 yr when these parameters were significantly greater than 9 and 85 m respectively and three main intervals when they were lower the data imply that the winter monsoon weakened during the intervals with low qmd and qmax values which coincide with marine oxygen isotope stages 5 3 and 1 and was strongest ca 67 000 and 20 000 yr ago during isotope stages 4 and 2 however both quartz grainsize records display second order high frequency high amplitude variations which are lacking in the magnetic susceptibility record that imply rapid and significant changes in atmospheric conditions that affect dust transport and deposition

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

a diatom record for the past 400 ka from lake biwa in japan correlates with global paleoclimatic trends abstract detailed diatom records from a 140 m sediment core with a time resolution of approximately 1000 1500 yr were obtained from lake biwa to examine possible correlations between diatom concentrations and paleoclimatic changes during the last approximately 400 ka in the sediments the diatom assemblages are generally dominated by planktonic diatoms the diatom stratigraphy is characterized by four zones with distinctly higher concentration values and 12 horizons with low concentration values diatom records from the 140 m core and another core indicate that these changes were not local phenomena but occurred throughout the lake basin comparison of diatom concentration records with pollen records from lake biwa sediments indicates that higher diatom concentrations represent warmer and wetter climatic conditions and that lower concentrations represent colder and drier climatic conditions comparison of diatom records from lake biwa with marine oxygen isotopic records shows that the number of peaks and their relative amplitudes are similar in both profiles therefore peaks and drops in diatom concentration profile might correlate with most oxygen isotopic events this finding indicates that during approximately the last 400 ka the changes in diatom concentration represented as diatom productivity in lake biwa correlate closely with global paleoclimatic changes at the scale of the milankovitch cycle precession cycles of 23 and 19 ka and that diatom concentration was higher during warm events and lower during cold or cooling events

climate changes for the past 52 ka clarified by total organic carbon concentrations and pollen composition in lake biwa japan total organic carbon toc and total nitrogen tn analyses have been performed for three core samples obtained recently from lake biwa which include biw07 5 biw07 6 and biw08 b cores the toc and tn data from these cores show similar stratigraphic changes and can be regarded as reliable records of biological productivity occurring in the lake during the past 52 ka pollen analysis data are also used to determine climate change during the past 40 ka by reconstructing meteorological parameters such as annual temperature and precipitation temporal changes in toc concentration show detailed climate changes in tens year intervals climate change of orbital scale are well recognized demonstrating the change from mis 3 to 1 associated with severe cold periods known as heinrich events 1 to 5 and warm periods known as greenland interstadials gis 1 13 these climate events in millennial time scale are also well supported by pollen characteristics and by modern analogue analysis the good concordance of climate change between north atlantic region and japan is explained by a hypothesis that the intensity of the arctic air mass controls the climate in both the north atlantic and east asia regions through the migration of the arctic polar front although the average annual mean temperature in mis 3 was 8 2 0 8 2 c it varied largely and frequently among its substages for example 9 4 2 0 c was detected in a warm interstadial gis 8 and 6 3 1 5 c indicated in a cold stadial heinrich event 4 the average annual temperature was 4 5 0 3 c in mis 2 when the average temperature of the coldest month was 7 3 0 2 c and that of the warmest month was 16 8 0 2 c through termination 1 the annual mean temperature suddenly increased more than 5 c and the annual mean temperature became 11 2 0 8 c in early mis 1 which is much lower than that of the present temperature this low temperature estimation is attributed to the delay in expansion of evergreen broadleaf trees the annual mean temperature in the late mis 1 was as same as that of present meteorological observation

orbital and millennial scale variations in asian dust transport path to the japan sea abstract orbital and millennial scale variations in the asian monsoon and its probable association with the dansgaard oeschger d o cycles have been demonstrated by previous studies however the origin and nature of such variations are poorly understood the japan sea is located down wind of the arid areas of the eurasian continent and thus receives significant amounts of aeolian dust consequently the hemipelagic sediments of the japan sea are expected to record a continuous aeolian dust accumulation which may provide information about the past variations in asian monsoon grain size flux and provenance of aeolian dust in the sediments were examined using two sediment cores obtained from the northern and southern parts of the japan sea in order to understand the spatial variability of asian monsoon since the silt fraction of the detrital materials in hemipelagic sediments of the japan sea is composed predominantly of aeolian dust the grain size flux and provenance of the silt fraction were examined the taklimakan desert loess plateau and siberia northeast china areas were identified as possible source areas of aeolian dust in the sediments of the japan sea based on the electron spin resonance esr signal intensity and crystallinity of quartz moreover the relative contribution of aeolian dust from each source area was estimated based on the esr signal intensity and crystallinity of quartz aeolian dust fluxes from the two source areas at the southern site were then estimated grain size and flux of eolian dust at the northern site and fluxes of aeolian dust from two source areas at the southern site show orbital scale variations in harmony with the insolation change at 30 n in june these results indicate orbital scale changes in the extent of the arid area and or frequency of dust storms in the taklimakan desert loess plateau and siberia northeast china areas and suggest that southward northward shifts of the westerly jet axis occurred together with either intensified weakened winter monsoon decreased increased winter precipitation in the siberia northeast china area or southeastward northwestward shifts of summer monsoon limit during periods of smaller larger insolation at 30 n in june in addition to these orbital scale variations millennial scale variations possibly associated with the d o cycles are observed in the grain size record of aeolian dust at the two sites based on analogy with orbital scale variations these millennial scale variations are considered to reflect millennial scale changes in the position of the westerly jet axis together with the changes either in winter monsoon intensity winter precipitation or position of summer monsoon limit our results suggest n s oscillations in the westerly jet and summer monsoon limit and changes in the intensity of the winter monsoon on orbital and millennial timescales

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

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 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

numerical simulation of the evolution and propagation of aeolian dune fields toward a desert oasis zone abstract in this study the evolution and propagation of aeolian dune fields toward a desert oasis transitional zone are numerically investigated through considering the spatial variation of wind speed and the influence of vegetation on sand erosion and transportation etc the propagation speed at the edge of desertified land and the influence of a straw checkerboard are quantitatively analyzed results show that evolution time wind speed and sand diameter have obvious impacts on the propagation of desert and desertified land a formula describing the propagation speed of desertified land with respect to wind speed and vegetation coverage is given in addition when considering the effects of straw checkerboards the propagation speed of the downwind desertified land is found to be related to the length of and distance from the checkerboard area

land ocean linkages over orbital and millennial timescales recorded in late quaternary sediments of the japan sea late quaternary sediments of the japan sea are characterized by centimeter to meter scale alternations of dark and light layers which are synchronous basinwide high resolution analyses of the sediments from ocean drilling program site 797 reveal that deposition of the meter scale alternations reflect variations in paleoceanographic conditions which were closely associated with glacio eustatic sea level changes through the modulation of the volume and character of the influx to the sea through the tsushima strait the centimeter to decimeter scale alternations reflect millennial scale variations which are possibly associated with dansgaard oeschger d o cycles with each dark layer appearing to correspond to an interstadial this variability is attributed to the development of a humid climate in central to eastern asia and the consequent increase in discharge from the huanghe and changjiang rivers during interstadials this caused expansion of the east china sea coastal water ecscw which penetrated more strongly into the japan sea the increased influence of the lower salinity nutrient enriched ecscw reduced deep water ventilation and enhanced the surface productivity leading to the development of anoxic bottom waters and deposition of the dark layers thus the centimeter to decimeter scale alternations of the dark and light layers record wet and dry cycles in central to eastern asia possibly associated with d o cycles

quantitative pollen based climate reconstruction in central japan application to surface and late quaternary spectra abstract climate reconstruction in japan by the best modern analogues method was tested with 285 surface pollen spectra and then applied to the 47 000 years pollen profile from lake mikata central japan both pollen taxa percentages and plant functional type affinity scores were used in the reconstruction of six climate variables the reconstructed values were compared with the estimated modern climate at each surface pollen site in order to evaluate the accuracy of the pollen based reconstruction the reconstruction of thermal parameters is very reliable correlation coefficient r between 0 86 and 0 89 the reconstruction of annual precipitation is less accurate r 0 7 we also proposed a new technique to calibrate reconstructed values into both probability distribution and or confidence regions of observed values the specialized programs for this calibration polcalib and polhist are available at qsr website http www elsevier nl locate quascirev the reconstruction of the late quaternary climate changes around lake mikata shows that the summer and winter temperatures were 5 c lower than present around 40 uncal kyr bp reached a minimum around 20 uncal kyr bp 10 c lower than present and became similar to present day at 8 uncal kyr bp the estimates for annual precipitation show that it was driest around 20 uncal kyr bp

correlation between climate events in the north atlantic and china during the last glaciation episodes of massive iceberg release heinrich events 1 3 into the north atlantic ocean during the last glaciation were associated with recurring episodes of unusually cold north atlantic surface water bond cycles 4 and cold air temperatures over greenland dansgaard oeschger events 5 6 four of the youngest of these cold events have also been reported in climate records from sites outside the north atlantic region7 but until now the entire suite has been identified only in north atlantic marine sediments greenland ice core records and tentatively in french lake sediments8 here we examine grain size data from chinese loess and intercalated accretionary palaeosols of last glacial age for evidence of similar climate signals remote from the north atlantic region we see grain size maxima with ages that match those of the last six heinrich events which we interpret as an indication of the changing strength of the east asian winter monsoon which largely controls the transport and deposition of central asian aeolian dust thus it seems that these heinrich events have left their signature in the chinese loess record this is consistent with simulations of the glacial climate9 which imply that the climates of the north atlantic and china were linked by the effect of westerly winds

sg06 a fully continuous and varved sediment core from lake suigetsu japan stratigraphy and potential for improving the radiocarbon calibration model and understanding of late quaternary climate changes abstract the high potential of the varved sediments of lake suigetsu central japan to provide a purely terrestrial radiocarbon calibration model and a chronology of palaeoclimatic changes has been widely recognised for the last two decades however this potential has not been fully realised since the only available long sediment core from the lake sg93 was extracted from a single bore hole and was therefore interrupted by gaps of unknown duration between successive core sections in the summer of 2006 a new sediment core sg06 was recovered from the lake four separate boreholes were drilled and the parallel sets of cores recovered were found to overlap completely without gaps between segments this new record provides the ability to test existing atmospheric radiocarbon calibration models as well as to assess the scale of inter regional leads and lags in palaeoclimatic changes over the last glacial interglacial cycle multi disciplinary analyses from sg06 are still ongoing but a reliable description of the sedimentary sequence needs to be provided to the wider science community before major outputs from the project are released thereby allowing fully informed critical evaluation of all subsequent releases of data based on the sg06 record in this paper we report key litho stratigraphic information concerning the sg06 sediment core highlighting changes in the clarity of annual laminations varves with depth and possible implications for the mechanism of the climate change we also discuss the potential of the sg06 record to meet the fundamental goals of the inqua intimate project