a record of holocene climate change in the guanzhong basin china based on optical dating of a loess palaeosol sequence optical dating was used to obtain a chronology for a loess palaeosol sequence in the guanzhong basin on the loess plateau in china the sedimentary sequence recorded two dry episodes 3 7 2 4 ka and 1 2 0 8 ka ago in the holocene as shown by the presence of two layers of loess within the holocene deposits these two arid events are consistent with records of global climate change in the holocene and also coincident with major historic events in china this finding suggests that loess paleosol sequences in china can record global climate changes and implies that rapid climate change affected the progress of human civilization in addition changes in the sedimentation rate through the section suggest that agricultural expansion may have accelerated the rate of dust accumulation

anthropogenic influences on changes in the sediment load of the yellow river china during the holocene using data on formation of the loess plateau of central china loess palaeosol sequences pollen analysis historical geography and long term experimentation on rates of soil erosion it is demonstrated that current serious erosion on the loess plateau is mainly due to human destruction of the natural vegetation and irrational land use these two modifications greatly reduce soil infiltration capacity and resistance of the soil to erosion the increase of soil erosion began ca 5000 bp at which time a hunting and pastoral life began to change gradually to a sedentary life centred around cultivation using the volume of holocene loessic sediments on the continental shelf of the bohai yellow and east china seas it is estimated that the present sediment load of the lower yellow river is at least three times greater than it was during the holocene although human induced soil erosion in the loess plateau began earlier it was not until the tang dynasty about 1000 bp that it began to increase rapidly ac

tree ring evidence of little ice age glacier advances in southern tibet the history of late holocene glacier fluctuations in eastern tibet was studied by determining the ages of trees growing on glacier deposits maximum tree ages yield minimum ages of ad 1760 and 1780 for moraine formation at the maximum extent of the little ice age glacier advances in two glacier forefields subsequent moraines could be dated to the beginning of the nineteenth and the beginning of the twentieth century larch trees from a third glacier forefield in southeastern tibet show evidence of glacier activity from 1580 to 1590 from the end of the eighteenth to the beginning of the nineteenth century and from 1860 to 1880 one glacier at mt gyalaperi recently advanced in both 1951 and 1987 periods of glacier advances can partly be correlated with periods of growth reductions in chronologies of total ring width and maximum latewood density derived from trees growing on slopes above the glacier valleys correlation functions with meteorological data suggest that maximum latewood density of subalpin

neotectonics of the thakkhola graben and implications for recent activity on the south tibetan fault system in the central nepal himalaya the thakkhola graben is one of many north trending rifts that define the neogene structural pattern of the southern tibetan plateau lying at the southern margin of the plateau and extending to the crest of the himalaya the graben provides an opportunity to evaluate the kinematic relationships between east west extensional strain in southern tibet and north south extensional strain in the himalaya neotectonic and structural mapping of the dangardzong fault along the western margin of the graben reveals a southward decreasing component of normal slip coupled with a southward increasing component of right lateral slip that affects pleistocene basin fill sediments we present 14c ages for river terraces in the thakkhola graben that provide a ca 17 2 ka minimum age on the latest stage of dangardzong fault movement near the southern termination of the graben the dangardzong fault apparently offsets the annapurna detachment an early miocene strand of the east striking south tibetan fault system however the dangardzong fault itself terminates against a young i e younger than ca 17 2 ka strand of the south tibetan fault system the dhumpu detachment structural relationships among the dangardzong annapurna and dhumpu faults suggest that the dangardzong structure is a tear fault in the south tibetan allochthon that accommodates differential amounts and rates of displacement along the south tibetan fault system thus although the south tibetan fault system first developed as part of the structural architecture of the himalaya in miocene time at least some strands have been active as recently as the pleistocene in a regional context the south tibetan fault system serves to accommodate the strain gradient between extension in tibet and shortening in the himalaya

pollen and diatom inferred climatic and hydrological changes in sumxi co basin western tibet since 13 000 yr b p although the tibetan plateau greatly influences the atmospheric circulation of the nortbern hemisphere few continuous paleoclimatic records are available from the plateau a 13 000 yr pollen and diatom record from the sumxi longmu co basin in western tibet gives information on major changes both in regional vegetation and in local hydrology after the basin first filled ca 13 000 yr b p a dry spell occurred about 10 500 yr b p within the interval spanned by the european younger dryas chronozone a major environmental change occurred suddenly at 10 000 yr b p with the establishment of wet conditions and was followed by a long term trend toward maximum aridity which lasted approximately 6000 yr short term oscillations are superimposed on this general climatic change with a major reversal event about 8000 yr b p and a second wet pulse leading to a maximum lake volume ca 7500 6000 yr b p maximum aridity occurred 4300 yr b p the major environmental fluctuations recorded at sumxi longmu co appear in phase with climatic changes recognized in north tropical africa suggesting that the 8000 to 7000 yr b p event was caused by an abrupt disequilibrium in the climatic system as was the younger dryas and possibly the 4300 yr b p event

the impact of environmental change and human land use on alluvial valleys in the loess plateau of china during the middle holocene abstract in recent years a growing number of studies have reported proxy evidence for holocene climatic and environmental change on the loess plateau of north central china pollen from lake cores and sediment analyses from loess sections firmly point to a warm moist mid holocene climatic optimum archaeological evidence indicates that at the same time human agricultural settlements expanded into this area during the middle neolithic period a geoarchaeological study of sediment sections from several valleys within the catchment of the yiluo river henan province indicates a sequence beginning with a stable landscape soil development and high water tables in the early mid holocene which was exploited by early neolithic millet farmers in the peiligang period subsequently there was a rapid shift to episodes of hillslope erosion and increased valley alluviation in the later mid holocene the resulting alluvial sediments dating from 5300 5010 cal bc through 2130 1870 cal bc represent clay rich water logged deposits that contain sediment and phytolith evidence for the first rice paddy farming in this region this coincides with the first migration of neolithic rice farmers to the area in the yangshao period ca 5500 cal bc these fills temporally and stratigraphically linked to archaeological sites and human land use practices suggest that they originated as a direct result of human impact on the landscape after ca 2000 cal bc holocene valley incision in this catchment led to narrowing floodplains the disappearance of the valley wetland deposits and a reduction in land available for paddy farming

the holocene salinity history of bosten lake xinjiang china inferred from ostracod species assemblages and shell chemistry possible palaeoclimatic implications abstract a sediment core from bosten lake the largest freshwater lake in the tianshan mountains and in the northwesternmost province of china provided a high resolution record of environmental change covering the last 8500 cal a bp higher salinity levels of bosten lake were reconstructed from assemblages the stable isotope composition and sr ca and mg ca ratios of ostracod shells between 7800 and 5600 cal a bp a period of low and moderate salinities between 5600 and 4900 cal a bp was followed by the re establishment of higher salinities between 4900 and 4300 cal a bp since then bosten lake has recorded fluctuating conditions with a number of multi centennial phases of low and moderate salinities although the salinity lake level relationship of bosten lake is not fully understood a higher salinity at the core site seems to correspond to periods of higher lake levels this contradictory interpretation is explained tentatively by the changing distance of the core site to the freshwater providing river mouth with changing lake levels and potentially resulting lateral shifts of the salinity distribution pattern within the lake assuming this explanation is correct the record from bosten lake reflects higher moisture availability and a strong climatic influence of the indian monsoon in the early mid holocene until about 4000 cal a bp and more unstable drier conditions susceptible to minor changes in the regional circulation patterns and temperature variations afterwards

the role of the indian summer monsoon and the mid latitude westerlies in himalayan glaciation review and speculative discussion new dates for late quaternary glaciations in the himalayas show that during the last glacial cycle glaciations were not synchronous throughout the region rather in some areas glaciers reached their maxima at the global glacial maximum of c 18 20 ka bp whereas in others glaciers were most extensive at c 60 30 ka bp comparison of these data with palaeoclimatic records from adjacent regions suggest that on millennial timescales himalayan glacier fluctuations are controlled by variations in both the south asian monsoon and the mid latitude westerlies

holocene glacier fluctuations a global overview of glacier advances and retreats grouped by regions and by millennia for the holocene is compiled from previous studies the reconstructions of glacier fluctuations are based on 1 mapping and dating moraines defined by 14 c tcn osl lichenometry and tree rings discontinuous records time series and 2 sediments from proglacial lakes and speleothems continuous records time series using 189 continuous and discontinuous time series the long term trends and centennial fluctuations of glaciers were compared to trends in the recession of northern and mountain tree lines and with orbital solar and volcanic studies to examine the likely forcing factors that drove the changes recorded a general trend of increasing glacier size from the earlyemid holocene to the late holocene in the extra tropical areas of the northern hemisphere nh is related to overall summer temperature forced by orbitally controlled insolation the glaciers in new zealand and in the tropical andes also appear to follow the orbital trend i e they were decreasing from the early holocene to the present in contrast glacier fluctuations in some monsoonal areas of asia and southern south america generally did not follow the orbital trends but fluctuated at a higher frequency possibly triggered by distinct teleconnections patterns during the neoglacial advances clustered at 4 4e4 2 ka 3 8e3 4 ka 3 3e2 8 ka 2 6 ka 2 3e2 1 ka 1 5e1 4 ka 1 2e1 0 ka 0 7e0 5 ka corresponding to general cooling periods in the north atlantic some of these episodes coincide with multidecadal periods of low solar activity but it is unclear what mechanism might link small changes in irradiance to widespread glacier fluctuations explosive volcanism may have played a role in some periods of glacier advances such as around 1 7e1 6 ka coinciding with the taupo volcanic eruption at 232 5 ce but the record of explosive volcanism is poorly known through the holocene the compilation of ages suggests that there is no single mechanism driving glacier fluctuations on a global scale multidecadal variations of solar and volcanic activity supported by positive feedbacks in the climate system may have played a critical role in holocene glaciation but further research on such linkages is needed the rate and the global character of glacier retreat in the 20th through early 21st centuries appears unusual in the context of holocene glaciation though the retreating glaciers in most parts of the northern hemisphere are still larger today than they were in the early and or mid holocene the current retreat

a late pleistocene holocene lacustrine record from lake manas zunggar northern xinjiang western china information on the late quaternary palaeoclimate in the zunggar desert northern xinjiang is deduced from the study of three 5 m long cores taken from lake manas analyses including the mineralogical composition of bulk sediments stable isotope contents of carbonates organic matter pollen and diatoms were performed to help reconstruct the environmental evolution of the area the chronology is provided by 9 ams 14c dates done on carbonates or organic matter the record suggests a late pleistocene humid episode radiocarbon dated at 37 000 32 000 yr b p this episode is followed by a period of extreme aridity attributed to the last glacial maximum the early mid holocene record indicates conditions generally wetter than today as previously established for western china however our results show that the holocene period is rather complex after a minor wet warm pulse estimated to be around 12 000 yr b p the most important environmental change is recorded at 10 000 yr b p it led to the establishment of a steppic vegetation cover in the catchment and of a permanent lake which lasted 4000 years fluvial sedimentation took place between about 6000 and 4500 yr b p and it coincided with a decrease in moisture availability for vegetation growth a second lacustrine episode is recorded from about 4500 to 2500 yr b p although the pollen record and a sudden influx in detrital organic matter suggest a short term dry event around 3800 3500 yr b p the last 2500 years show climate unstability and the step wise establishment of hypersaline conditions in lake manas the major post glacial environmental changes appear to be roughly in phase with those observed in tibet

holocene environmental changes in bangong co basin western tibet part 4 discussion and conclusions abstract a 12 4 m core taken in lake bangong provides a continuous holocene climatic record we summarize information on changes in stable isotope and radiocarbon balances in the lake hydrobiology and vegetal cover in the catchment deduced from detailed analytical results given in the three preceding papers the bangong record is then compared with the environmental history of the neighbouring lake sumxi also constructed from multidisciplinary analyses the two records show a major environmental change at 10 9 5 ka b p attributed to a rapid strengthening of the summer monsoonal circulation which led to wet warm conditions this event was followed by a long term trend toward aridity which culminated around 4 3 ka b p in western tibet maximum monsoon rainfall seems to have occurred from 9 5 to 8 7 ka b p and from 7 2 to 6 3 ka b p as two wet pulses separated by a reversal event centered on 8 0 7 7 ka b p our results broadly agree with the records from lake seling in central tibet and lake qinghai at the plateau s northeastern margin and with palaeoclimatic studies in western china which document conditions wetter and warmer than those of today during the early middle holocene the environmental fluctuations recorded in western tibet appear in phase with climatic changes recognized in tropical north africa suggesting that the 8 0 7 7 ka b p and the 4 0 3 0 ka b p dry events were caused by abrupt disequilibrium in the climatic system

palaeoenvironmental implications of a holocene sequence of lacustrine peat sediments from the desert loess transitional zone in northern china abstract a high resolution lacustrine peat record from the desert loess transitional zone in northern china was obtained to reconstruct holocene environmental change in the region ams 14c dates are used to provide a chronology the results indicate that the site was a desert environment before 12 2 cal kyr bp and was then occupied by a paleolake which started to shrink with a wetland occurring from 6 2 to 3 0 cal kyr bp subsequently the site became a seasonally water filled depression based on the lithology and measurements of grain size and total organic carbon content the climate changed from arid to humid at 12 2 cal kyr bp and became more humid after 8 3 cal kyr bp from 6 2 to 3 0 cal kyr bp precipitation decreased but the climate remained at an optimum after 3 0 cal kyr bp the climate was dry overall but with several humid intervals a comparison of paleoclimatic records from lacustrine and aeolian deposits from the region reveals a discrepancy about the nature of the early holocene climate and we conclude that this is because lacustrine sediments responded more sensitively to precipitation than aeolian deposits when the temperature was low the environmental evolution of the region was synchronous with changes in the asian summer monsoon asm but temperature also played a key role in the early holocene

environmental change during the holocene in western china on a millennial timescale recent data on the evolution of the inland lakes loess palaeosol sequences and glacier variations in western china are briefly reviewed the lake history shows three distinct stages in the holocene i e low water levels before 7500 bp a stage of expansion during the climatic optimum between 7500 and 3500 bp and contraction after 3500 bp three stages wooded grassland mixed woodland wooded grassland becoming steppe also appear indicated by the holocene loess palaeosol sequence in the lanzhou region the optimal period for soil development being between 7500 and 3500 bp there were seven periods of glacier advance the continental glaciers advanced at about 8300 5700 4000 and 400 bp in northwestern china and the maritime glaciers advanced at about 3000 2000 1000 and 200 bp it is suggested that the climatic changes show two periodicities during the holocene namely at intervals of about 2500 and 1000 years

a persistent holocene wetting trend in arid central asia with wettest conditions in the late holocene revealed by multi proxy analyses of loess paleosol sequences in xinjiang china abstract there are significant differences in the interpretation of the moisture precipitation history of arid central asia aca during the holocene as inferred on one hand from speleothem oxygen isotope records and on the other from lake sediments here we present the results of measurements of climatically sensitive magnetic properties and soil color from four well dated loess paleosol sequences from the northern slopes of the tienshan mountains and the yili river valley xinjiang china in the core area of aca our results demonstrate that the characteristic holocene paleosol indicating relatively moist conditions generally formed after 6 ka 1 ka 1000 cal yr bp in the study region and that the accumulation of unweathered loess prevailed during the early holocene indicating a dry climate at that time the magnetic proxies further reveal a trend of generally increasing moisture since the last glacial maximum with the wettest climate occurring during the late holocene this trend of increasing moisture during the holocene is representative of the xinjiang region and possibly of the whole of the core area of aca and is in marked contrast both to the mid holocene moisture maximum observed in the east asian summer monsoon region and to the general decrease in the strength of the indian summer monsoon since the early holocene our findings are supported by the results of a climate simulation which indicate a trend of increasing summer and winter precipitation during the holocene in the core area of aca caused mainly by an increase in the strength of the westerlies effected by an increasing latitudinal insolation gradient and by a negative trend of the arctic oscillation ao or north atlantic oscillation nao

lateglacial and holocene variation in aeolian sediment flux over the northeastern tibetan plateau recorded by laminated sediments of a saline meromictic lake predominantly laminated lake sediments from a saline closed basin lake on the northeastern tibetan plateau were investigated using a multi proxy approach 14c accelerator mass spectrometry dating smear slide analysis loss on ignition grain size x ray diffraction elemental concentration ostracod assemblages stable isotopes of ostracod shells to trace the regional environmental and climatic history in the lateglacial and holocene before about 15 cal ka bp small saline water bodies probably filled the basin under unstable cold and harsh environmental conditions soon after about 14 9 cal ka bp a relatively deep saline lake was established probably as a result of runoff from melting snow ice and frozen ground in the lake s catchment large changes in flux of aeolian material to the lake were recorded during this initial period of formation of lake kuhai highest lake levels a low sediment accumulation rate and less saline conditions were maintained between about 12 8 and 7 1 cal ka bp when the aeolian influx diminished significantly after about 7 1 cal ka bp the aeolian influx remained at a moderate level apart from a strongly increased dust delivery to the lake between about 6 1 and 5 4 cal ka bp and a minor short lived period of slightly enhanced aeolian influx at about 2 7 cal ka bp the strongly enhanced dust input to the lake between 6 1 and 5 4 cal ka bp represented the largest influx of aeolian material to lake kuhai during the entire holocene however evidence for climatic deterioration during this period is not seen at most other palaeoclimate sites on the tibetan plateau but instead a significant increase in aridity has been recorded at numerous sites in the northern foreland of the tibetan plateau and on the chinese loess plateau the large dust input to lake kuhai between 6 1 and 5 4 cal ka bp probably did not result from a severe climate deterioration on the tibetan plateau itself but from the pronounced aridity in its northern and eastern foreland in contrast the increase in dust influx about 2 7 cal ka bp seems to correspond to a brief warming spell recorded at other sites on the tibetan plateau too a slight increase in lake level and decrease in salinity after about 0 6 cal ka bp suggests a slightly higher effective moisture during the final lake stage accompanied by a somewhat larger dust influx this apparent contradiction possibly results from enhanced human activities on the northeastern tibetan plateau during the last 600 years copyright 2009 john wiley sons ltd

nature and timing of quaternary glaciation in the himalayan tibetan orogen abstract much effort has been made in recent years to define the timing and extent of quaternary glaciation throughout the himalayan tibetan orogen these studies are challenging because of the logistical and political inaccessibility of the region and the inherent problems associated with the application of numerical dating techniques nevertheless the studies are providing abundant evidence for significant glacial advances throughout the last several glacial cycles and are beginning to accurately define the extent and timing of glaciation in selected regions studies are showing that himalayan tibetan glaciers in arid regions during the last glacial cycle reached their maximum extent early in the cycle and that global last glacial maximum glacier advances were significantly less extensive however along the more monsoonal influenced greater himalaya there is increasing evidence to suggest that glaciation was more extensive later in the last glacial cycle but this has yet to be fully assessed in addition the new studies are showing that throughout most himalayan tibetan regions significant glacier advances occurred during the lateglacial and early holocene with minor advances in some regions during the mid holocene the still relatively poor chronological control in the himalayan tibetan orogen however makes it difficult to construct correlations across the region and with regions elsewhere in the world this in turn makes it hard to assess the relative importance of the different climatic mechanisms that force glaciation across the himalayan tibetan orogen and to quantify paleoclimate change in this high altitude subtropical region the lateglacial and holocene glacial records however are particularly well preserved in several himalayan tibetan regions glacial successions such as these have the greatest potential to be examined in detail using newly developing numerical dating and geomorphic and sedimentologic methods to derive high resolution terrestrial records of glaciation that will help in paleoclimatic reconstruction for high altitude subtropical regions

a synthesis of abrupt changes in the asian summer monsoon since the last deglaciation we have compiled 36 previously published palaeoclimate records to determine the timing and spatial pattern of century scale abrupt changes in asian monsoon precipitation since the last deglaciation we identify abrupt events from 1 the interpretations of the authors of these records and 2 the more objective moving t test calculation our results indicate that abrupt climatic changes occurred at 11 5 cal ka 4 5 5 0 cal ka and ad 1300 at the start of the holocene 11 5 cal ka asian monsoon precipitation increased dramatically this climatic change is synchronous with an abrupt warming in the north atlantic during the middle holocene there was a time of preferred and widespread weakening in monsoon strength 4 5 5 0 cal ka this result contradicts previous notions of either a gradual trend towards drier conditions or a series of abrupt events that occurred in an unorganized fashion across space and time the middle holocene abrupt event could have been synchronous with an abrupt cooling event in the north atlantic as well as a warming and intensie cation of internannual variability in the tropical pacie c in contrast to previous periods precipitation changes at ad 1300 have a heterogeneous spatial pattern we e nd no conclusive evidence for a change in the asian monsoon at 8 2 cal ka as suggested by several previous studies more high resolution data may be needed to observe this short lived event overall our results attest to the potential for rapid and major shifts in asian monsoon precipitation that may be triggered by variations in other components of the climatic system

structure and origin of holocene cold events abstract the present interglacial the holocene spans the period of the last 11 700 years it has sustained the growth and development of modern society the millennial scale decreasing solar insolation in the northern hemisphere summer lead to northern hemisphere cooling a southern shift of the intertropical convergence zone itcz and a weakening of the northern hemisphere summer monsoon systems on the multidecadal to multicentury scale periods of more stable and warmer climate were interrupted by several cold relapses at least in the northern hemisphere extra tropical area based on carefully selected 10 000 year long time series of temperature and humidity precipitation as well as reconstructions of glacier advances the spatiotemporal pattern of six cold relapses during the last 10 000 years was analysed and presented in form of a holocene climate atlas hoclat see http www oeschger unibe ch research projects holocene atlas a clear cyclicity was not found and the spatiotemporal variability of temperature and humidity precipitation during the six specific cold events 8200 6300 4700 2700 1550 and 550 years bp was very high different dynamical processes such as meltwater flux into the north atlantic low solar activity explosive volcanic eruptions and fluctuations of the thermohaline circulation likely played a major role in addition internal dynamics in the north atlantic and pacific area including their complex interaction were likely involved

mineral formation and redox sensitive trace elements in a near surface hydrothermal alteration system a recent hydrothermal mudpool at the southwestern slope of the rincon de la vieja volcano in northwest costa rica exhibits an argillic alteration system formed by intense interaction of sulfuric acidic fluids with wall rock materials detailed mineralogical analysis revealed an assemblage with kaolinite alunite and opal c as the major mineral phases electron paramagnetic resonance spectroscopy epr showed 3 different redox sensitive cations associated with the mineral phases cu sup is structure bound in opal c whereas vo sup 2 and fe sup 3 are located in the kaolinite structure the location of the redox sensitive cations in different minerals of the assemblage is indicative of different chemical conditions the formation of the alteration products can be described schematically as a 2 step process in a first step alunite and opal c were precipitated in a fluid with slightly reducing conditions and a low chloride availability the second step is characterized by a decrease in k sup activity and subsequent formation of kaolinite under weakly oxidizing to oxidizing redox conditions as indicated by structure bound vo sup 2 and fe sup 3 the detection of paramagnetic trace elements structure bound in mineral phases by epr provide direct information about the prevailing redox conditions during alteration and can therefore be used as additionalmore insight into the genesis of the hydrothermal near surface system less

late holocene glacier variations in the frontal and inner ranges of the tian shan central asia evidence for the timing and extent of late holocene glacial advances in the tian shan mountains central asia is based on lichenometric and radiocarbon dating of end moraines three phases of glacial advance occurred at 1700 2100 and 1100 1300 lichenometric l years ago and then during the little ice age 150 700 l years ago differences in the pattern of glacier variations between the northwestern frontal and inner areas of the tian shan are reflected in the equilibrium line altitude ela depression of 23 glaciers studied at nine selected sites the peripheral glaciers appear to have been significantly more extensive during late holocene advances than the glaciers of the inner areas this difference seems to be explained by regional differences in humidification in the northwestern periphery of the tian shan the cold periods of the late holocene were more humid than the warm period of the mid holocene whereas in the inner areas the pattern of climate changes was the opposite a warm and hu

late quaternary climatic changes in the eastern kumaun himalaya india as deduced from multi proxy studies abstract an event of neotectonic activity on an ne sw trending subsidiary fault in the zone of e w running intracrustal boundary thrust south almora thrust in the champawat district of eastern kumaun himalaya resulted in creation of a lake at ca 21 5 bp the lake drained in the late holocene leaving behind a 5 0 m thick sedimentary sequence of mostly black and carbonaceous mud with a minor magnetic reversal between 20 5 and 19 7 ka bp at the base the profile studied by using multi proxies e g carbon isotopes pollen analysis palaeo and mineral magnetism and clay minerals has recorded globally well established abrupt climatic events in the last 20 000 years such as the lgm older dryas od younger dryas yd holocene warming 8 2 ka and 4 2 ka events most events estimated assuming a constant rate of sediment accumulation for similar lithologies may be related to the rapid changes in the local climate and albedo structure the itcz may have played a key role in controlling the behavior of the southwest monsoon from the lgm

holocene glacier fluctuations and climate changes in the southeastern part of the russian altai south siberia based on a radiocarbon chronology abstract this study investigates glacier dynamic and climatic variations in the southeastern part of the russian altai se altai during the last 7000 years recent glacier retreats and ice melting in moraines has led to exhumation of organic material allowing the possibility of radiocarbon dating we report here 57 new radiocarbon dates from wood remains buried by moraines and from proglacial forefields from peat layers and lacustrine sediments that cover moraines from dead trees at the upper tree limit and from rock glaciers on trough slopes from six glacial valleys in the north chuya range se altai such a numerous dataset for the vast but unified in neotectonic and climatic conditions area is presented for the first time the history of research in the altai together with 62 previously published radiocarbon ages mainly of fossil soils and peat layers in the foot of the ranges in se altai they form the basis for understanding the relative magnitudes and timing of the most important glacial and climatic events of se altai new data refute the traditional concept of the russian altai holocene glaciations as a consecutive retreat of the late wurm glaciers and argue their complete degradation at the head of trough valleys at least 7000 cal years bp moraine complexes of three holocene glacial stages are morphologically expressed in trough valleys of the north chuya range they correlate with three identified periods of glacial advances from 4900 to 4200 cal years bp akkem stage from 2300 to 1700 cal years bp historical stage and in the 13th 19th centuries little ice age lia or aktru stage the coincident extremes of lowering temperature and increasing precipitation during the akkem stage led to abrupt glacier advances and forming of the most remote moraine complexes downstream in the valleys following glacier advances had distinctly smaller magnitudes in addition to the radiocarbon data the time limits of the historical stage were defined more precisely using dendrochronological and archaeological data from scythian burials of pazyryk culture in se altai repeated forest regrowth in the presently glaciatiated area indicates significant retreat or even complete glacier degradation during interstage warming the decreases of glacier length in the following stages argues for intensification of aridity in the se altai during the second half of the holocene the thermal minimum in the middle of 19th century the greatest in the last millennium did not positively influence the mass balance of glaciers which also supports this conclusion

the onset of neoglaciation 6000 years ago in western mongolia revealed by an ice core from the tsambagarav mountain range glacier highstands since the last glacial maximum are well documented for many regions but little is known about glacier fluctuations and lowstands during the holocene this is because the traces of minimum extents are difficult to identify and at many places are still ice covered limiting the access to sample material here we report a new approach to assess minimal glacier extent using a 72 m long surface to bedrock ice core drilled on khukh nuru uul a glacier in the tsambagarav mountain range of the mongolian altai 4130 m asl 48 39 338 n 90 50 826 e the small ice cap has low ice temperatures and flat bedrock topography at the drill site this indicates minimal lateral glacier flow and thereby preserved climate signals the upper two thirds of the ice core contain 200 years of climate information with annual resolution whereas the lower third is subject to strong thinning of the annual layers with a basal ice age of approximately 6000 years before present bp we interpret the basal ice age as indicative of ice free conditions in the tsambagarav mountain range at 4100 m asl prior to 6000 years bp this age marks the onset of the neoglaciation and the end of the holocene climate optimum the ice free conditions allow for adjusting the equilibrium line altitude ela and derive the glacier extent in the mongolian altai during the holocene climate optimum based on the ela shift we conclude that most of the glaciers are not remnants of the last glacial maximum but were formed during the second part of the holocene the ice core derived accumulation reconstruction suggests important changes in the precipitation pattern over the last 6000 years during formation of the glacier more humid conditions than presently prevailed followed by a long dry period from 5000 years bp until 250 years ago present conditions are more humid than during the past millennia this is consistent with precipitation evolution derived from lake sediment studies in the altai

timing of glacier fluctuations and trigger mechanisms in eastern qinghai tibetan plateau during the late quaternary abstract it is highly debated whether glacial advances on the qinghai tibetan plateau qtp occurred as a response to temperature cooling or whether they were forced by an increase in moisture brought by the intensive indian summer monsoon we here report a case study investigating this issue multiple moraine series in the yingpu valley queer shan ranges of the hengduan mountains and eastern qtp provide an excellent archive for examining the timing and trigger mechanism of glacier fluctuations twenty seven optically stimulated luminescence osl samples of glacial sediments were collected from this valley the quartz osl ages show that the moraine series of y 1 i m and o were formed during the late holocene late glacial the global last glacial maximum lgm and marine oxygen isotope stage mis 3 likely mid mis 3 the youngest y 2 moraines probably formed during the little ice age lia the oldest h moraines formed before mis 3 we found that glacial advances during the late quaternary at the yingpu valley responded to cold stages or cold events rather than episodes of enhanced summer monsoon and moisture as a result glaciers in the monsoonal hengduan mountains were mainly triggered by changes in temperature millennial time scale temperature oscillations might have caused the multiple glacial advances

mineral magnetic record of environment in late pleistocene and holocene sediments lake manas xinjiang china a study of magnetic parameters was carried out on a late pleistocene and holocene sedimentary sequence 5 m from lake manas northern xinjiang china that has already been ana lysed for bulk sediment mineralogy stables isotopes from carbon ates and biogenic material magnetic minerals confirm major changes in palaeoenvironmental and palaeohydrological conditions that were deduced from other methods they also provide complementary information on changes in the lake system during the early and middle holocene the most important mineral mag netic change results from the authigenic formation of ferrimagnetic greigite fe3s 4 during the lacustrine episodes dated from 8 7 kyr b p to 5 5 kyr b p 380 335 cm and from 4 5 kyr b p to 3 5 kyr b p 320 285 cm respectively our data also indicate an abrupt break in sedimentary conditions which coincides with a short term retmxtowards dry climatic conditions around 3 5 kyr b p which was only suggested from other proxy data

toward a late holocene glacial chronology for the eastern nyainqentanglha range southeastern tibet abstract monsoonal affected temperate glaciers in the eastern nyainqentanglha range southeastern tibet are highly sensitive to climate change knowledge about their late holocene dynamics is still however widely lacking the few studies on glacial chronology which are available for this region tend to mainly focus on dating results without sufficiently considering the geomorphological setting often leading to misinterpretations in this complex high mountain environment in this study two selected glacier forelands are investigated using a multi proxy approach encompassing detailed geomorphological mapping dendrochronology sedimentology and optically stimulated luminescence as well as radiocarbon dating the starting point was the creation of a consistent morphosequence which was validated by remote sensing of further glacier forelands from the wider region similarities and differences between the investigated settings were analyzed in detail to identify the relevant morphological and topoclimatic forcing mechanisms we found evidence of climatic events affecting the whole region during the little ice age resulting in similar configurations and numbers of moraines the geomorphological settings of the glacier forelands are however remarkably different making investigations of the landform and sediment configuration an indispensable condition for their interpretation subsequently constraints from different methods of relative and numerical dating were evaluated critically and included into a conceptual chronosequence if applicable our results suggest that the late holocene maximum glacier advance comprised several successive advances from mid 17th to mid 18th century none of our observations supports an earlier neoglacial advance reaching further than the lia maximum after the lia maximum continued retreat that was only interrupted by short phases of stability followed as evidenced by 2 3 recessional moraines in the investigated settings

holocene climatic and environmental changes in the arid and semi arid areas of china a review this paper reviews recently published literature most of which was published in chinese and searches for regional patterns of holocene changes useful in depicting global patterns the holocene in the xinjiang region can be divided into three stages a warming and dry early stage from 11 similar to 10 to 8 similar to 7 ka bp a warm and wet middle stage from 8 similar to 7 to 4 5 similar to 3 ka bp and a fluctuating cool and dry late stage since 4 5 similar to 3 ka bp the holocene in the northern tibetan plateau can also be divided into three stages a warming and wet stage from 10 5 similar to 10 to 5 similar to 4 ka bp followed by a variable drying and probably warm stage 5 similar to 4 to 3 ka bp and ending with a cool and dry stage since 3 ka bp in the inner mongolian plateau the early holocene from 10 5 similar to 9 5 to 8 similar to 7 5 ka bp was warming and dry and a warm and wet climate occurred from 7 5 to 3 5 during which the best time was 6 3 3 8 ka bp the climate has been variably drying and probably cooling since 3 5 ka bp in the northwestern part of the loess plateau several holocene palaeosols have been identified 10 9 7 5 5 4 3 and 2 7 2 ka bp with the 7 5 5 ka bp palaeosol being most strongly expressed the best developed palaeosol equivalent in major valleys is a swamp wetland facies deposited between 8885 and 3805 c 14 yr bp under an extremely wet regime the climate has fluctuated significantly at least three times around a dry and probably cool regime after the swamp wetland facies depositional period our summary shows that the holocene climatic optimum occurred nearly contemporaneously 8 5 ka bp at all sites in the xinjiang region in the inner mongolian plateau and in the northwestern part of the loess plateau a warming and wet early holocene 10 8 ka bp in the northern tibetan plateau is most likely related to high effective soil moisture resulting from snow and ice melting we propose here that the middle holocene climatic optimum 8 5 ka bp in arid to semi arid china was primarily a delayed response of the low latitude oceans to high latitude peak insolation 9 8 ka bp

quaternary glaciation of tibet the geological evidence the question of the number and extent of pleistocene glaciations on the qinghai xizang tibet plateau remains contentious there has been considerable research activity in tibet by chinese scientists since the late 1950s and their principal findings including data on glacial and periglacial geomorphology sedimentology tectonics stratigraphy and lake history have been used to reconstruct ice margins and palaeosnowlines three and in places four distinct glaciations have been recognised the most extensive occurring in the later middle pleistocene valley and piedmont glacial systems with some mountain ice caps and a small ice sheet on the upper reaches of the huang he have been recognised but there is no evidence of a single tibetan ice sheet as the plateau and the himalaya karakoram underwent accelerating uplift through the quaternary there occurred progressive desiccation in the interior as the influx of indian ocean moisture was constrained equilibrium line elevations in the last glacial maximum were 4000 m in the south east and northeast plateau margins rising to 5500 m in the northwest interior the heat island provided by the plateau the progressive reduction in precipitation most marked during the glacials and the strong southeast to northwest precipitation gradients produced a glacier distribution pattern dominated by the trans tibetan mountain ranges tectonics and periglacial including aeolian processes have played an equal role with glaciation in generating the plateau s quaternary sedimentary succession

holocene vegetation variations and the associated environmental changes in the western part of the chinese loess plateau abstract the western part of the chinese loess plateau has experienced a series of environmental changes during the holocene a desert steppe of late glacial was succeeded by a forest steppe from 8850 to 7540 14 c years bp and a pinus dominated forest occupied the landscape from 7540 to 6560 14 c years bp a deciduous forest of high density and diversity existed from 6560 to 5790 14 c years bp afterwards the vegetation changed to a pinus dominated forest steppe 5790 4950 14 c years bp and then to an ulmus dominated forest steppe 4950 to 4000 14 c years bp the vegetation subsequently changed to a steppe from 4000 to 3120 14 c years bp and further to a desert steppe from 3120 to 2900 14 c years bp after a period of vegetation improvement steppe from 2900 to 2460 14 c years bp a desert steppe resumed 2460 2020 14 c years bp steppe vegetation was re established around 2020 14 c years bp and seems to have then deteriorated again around 1000 14 c years bp the general trend of aforementioned climatic changes is proposed here to have been modulated by the insolation changes specifically the insolation started to increase around 15 000 years bp and peaked around 9000 years bp when the obliquity driven seasonality reached a maximum with the summer insolation being about 8 more than the present as a result tropical holocene sst increased steadily from 10 000 to 6 000 years bp thus effectively strengthening the east asian summer monsoon in addition the documented high temperatures from 10 000 to 4000 years bp in high northern latitudes might have weakened the strength of the winter monsoon and thus enhanced the strength of the summer monsoon probably via lengthening of the rainy season directly contributing to the megahumid climate between 10 000 and 4000 years bp in the western part of the chinese loess plateau

holocene environmental change inferred from a high resolution pollen record lake zhuyeze arid china a high resolution pollen record c 50 yr sample from terminal lake sediments in the shiyang river drainage basin on the present margin of the summer monsoon was used to reconstruct vegetation and climate history during the holocene forest trees from mountainous areas of the drainage including sabina picea and pinus dominated pollen assemblages in the early holocene 11 6 7 1 cal ka in the mid holocene 7 1 3 8 cal ka desert and steppe shrubs and herbs around the lake including nitraria poaceae compositae and artemisia were dominant the late holocene 3 8 0 cal ka was again dominated by alternation of pinus sabina tree pollen and desert steppe pollen the early holocene forest expansion in the mountains and subsequent increase in the river transport of tree pollen corresponds with maximum precipitation during the east asian summer monsoon maximum the timing of these changes in our record from arid china is different from that of east china where the holocene monsoon maximum appeared in

reconstructing glacier retreat since the little ice age in se tibet by glacier mapping and equilibrium line altitude calculation abstract temperate glaciers in the eastern nyainqentanglha range southeastern tibet are highly sensitive to climate change and therefore of particular high interest for research on late holocene changes of the monsoonal climate in high asia however because of the remoteness of the area the scarcity of empirical data and the challenges to remote sensing work posed by cloud and snow cover knowledge about the glacier dynamics and changes in this region is still very limited in this study we applied a remote sensing approach in which 1964 glaciers were mapped from a landsat etm scene and subsequently parameterized by dem supported measurements geomorphological evidence i e trimlines and latero frontal moraines were used to obtain quantitative data on the glaciers morphological characteristics and the changes since the little ice age lia maximum glacier advance statistical analysis of glacier length change revealed an average retreat of 27 and a trend toward stronger retreat for smaller glaciers an evaluation of different methods to calculate equilibrium line altitudes elas indicates that an optimized toe to ridge altitude method tram is more suitable than other methods in settings with complex topography and a lack of mass balance measurements a large number of glacier measurements are crucial for high quality of tram results and special attention has to be paid to different glacier characteristics in order to determine the best fitting tram ratio value and to test the quality of the calculated elas a remote sensing approach was applied for each investigated glacier the altitudes of transient snowlines visible in the late summer landsat scene were measured from the dem and compared to tram results the interpolated ela results show a se nw gradient ranging from 4400 to 5600 m asl and an average ela rise of 136 m since the lia because of the high spatial resolution of measurements the ela distribution reveals topographic effects down to the catchment scale specifically orographic rainfall and leeward shielding the interpretation of these patterns reveals that the eastern nyainqentanglha range is influenced by both the indian ism and east asian summer monsoon easm however the easm does not reach the western part of the study area the results indicate that the monsoonal temperate glaciers high sensitivity to climate change is driven by two double forcings owing to the coincidence of accumulation and ablation phases

holocene climatic change and the nomadic anthropocene in eastern tibet palynological and geomorphological results from the nianbaoyeze mountains abstract our study provides detailed information on the lateglacial landscape and vegetation development of tibet based on a suite of geomorphological and palynological proxy data from the nianbaoyeze shan on the eastern margin of the tibetan plateau 33 n 101 e 3300 4500 m asl we reconstruct the current state as a function of climate history and the longevity of human influence study results constrain several major phases of aeolian sedimentation between 50 15 ka and various glacier advances during the late pleistocene the holocene and the little ice age increased aeolian deposition was primarily associated with periods of more extensive glacial ice extent fluvial and alluvial sediment pulses document an increase of erosion starting at 3926 79 cal yr b p coinciding with cooling neoglacial and a growing anthropo zoogenic influence evidence for periglacial mass movements indicate that the late holocene cooling started at around 2000 cal yr b p demonstrating increased surface activity under the combined effects of human influence and climate deterioration the onset of peat growth generally depended on local conditions that include relief meso climate and in more recent times also on soil compaction due to animal trampling we distinguish three initiation periods of peat growth 12 700 10 400 cal yr b p for flat basins inside last glacial terminal moraines 7000 5000 cal yr b p for the main valley floors and 3000 1000 cal yr b p for the higher terrace surfaces the holocene vegetation history started with an open landscape dominated by pioneer shrubs along braided rivers picea juniperus abies and betula trees accompanied by a successive closing of the vegetation cover by poaceae cyperaceae and herbs 9800 8300 cal yr b p first signs of nomadic presence appear as early as 7200 cal yr b p when temperatures were up to 2 c warmer than today forest remained very patchy with strong local contrasts during the following cooling phase 5900 2750 cal yr b p the natural vegetation was transformed by nomadic grazing to bistorta rich kobresia pygmaea pastures modern nomadic migration routes were established at least 2200 years ago overgrazing and trampling led to the shrinking of bistorta and the spreading of annual weeds short lived cold events 8000 6200 3500 cal yr b p impacted on the vegetation only temporarily as the transformation of the natural poaceae rich vegetation into kobresia pastures modified the influence of the tibetan plateau hot plate on the monsoon system our data even point to an early start of a nomadic anthropocene nearly 6000 years ago against the background of a very long grazing history modern tibet must be seen as a cultural landscape