holocene thermal optimal and climate variability of east asian monsoon inferred from forest reconstruction of a subalpine pollen sequence taiwan the east asian monsoon holocene optimal period has been debated both about duration and whether conditions were a maximum in thermal conditions or in precipitation in this study we show holocene climate variability inferred by a forest reconstruction of a subalpine pollen sequence from peat bog deposits in central taiwan based on modern analogues of various altitudinal biomes in the region a warmer interval occurred between 8 and 4 ka bp calibrated 14 c years when the subtropical forests were more extensive the holocene thermal optimum is represented by an altitudinal tropical forest at 6 1 5 9 ka bp and 6 9 ka bp and only the latter was accompanied by wet conditions indicating decoupling of thermal and precipitation mechanism in the middle holocene abrupt and relative severe cold phases shown by biome changes occurred at about 11 2 11 0 ka bp 7 5 ka bp 7 2 ka bp 7 1 ka bp 5 2 ka bp 5 0 ka bp and 4 9 ka bp a spectral analysis of pollen of a relatively cold taxon salix reveals that the time series is dominated by a 1500 yr periodicity and similar to the cold cycle reported in the marine records of indian and western pacific oceans the cold warm conditions inferred by the change of forests show close relationship to solar energy in comparison with the production rate of be 10

late quaternary mass wasting records in the actively uplifting pa chang catchment southwestern taiwan abstract although dominated by erosion over long term the tectonically active mountains of taiwan commonly contain thick landslide and debris flow gravels capping hillslopes or forming alluvial terraces these deposits and their associated landforms serve to study ancient mass wasting histories and their controls on fluvial processes this study focuses on the pa chang river draining the 50 mm yr 1 are detected further downstream after the recent gravel mining the fact that the obtained bedrock incision rates and patterns are decoupled with the tectonic uplift advises caution in using short term erosion data to interpret the tectonics of the taiwan s mountains

weak monsoon event at 4 2 ka recorded in sediment from lake rara himalayas abstract the strength of the indian summer monsoon varied significantly on centennial to millennial timescales during the holocene among these variations a weak summer monsoon event occurred approximately at 4 ka the so called 4 2 ka event this event is considered to have been a relatively sustained and widespread phenomenon at regional scales across southern asia to eastern africa however little is known about the impact of such variations in the himalayas a key location for understanding the monsoon system here we present a record of changes in summer monsoon strength during the holocene from lake rara western nepal using redox sensitive elements mn ti and mn fe measured by x ray fluorescence xrf core scanner in addition organic matter properties toc 13c and c n and changes in the 14c age offset between bulk organic matter and leaf matter namely the old carbon offset are used to augment the environmental reconstruction collectively the data indicate a period of prolonged weak monsoon interval at around 4 ka the timing of onset and recovery from the event observed at lake rara exhibits particular similarity with changes in the indus river discharge this is the first record of the 4 2 ka event from the himalayas based on a relatively well constructed age model using 14c dates that are not influenced by reservoir effects these findings provide an important step towards better understanding the spatial and temporal variability in the holocene indian monsoon

quantification of holocene asian monsoon rainfall from spatially separated cave records abstract a reconstruction of holocene rainfall is presented for southwest china an area prone to drought and flooding due to variability in the east asian monsoon the reconstruction is derived by comparing a new high resolution stalagmite 18 o record with an existing record from the same moisture transport pathway the new record is from heshang cave 30 27 n 110 25 e 294 m and shows no sign of kinetic or evaporative effects so can be reliably interpreted as a record of local rainfall composition and temperature heshang lies 600 km downwind from dongge cave which has a published high resolution 18 o record wang y j cheng h edwards r l he y q kong x g an z s wu j y kelly m j dykoski c a li x d 2005 the holocene asian monsoon links to solar changes and north atlantic climate science 308 854 857 by differencing co eval 18 o values for the two caves secondary controls on 18 o e g moisture source moisture transport non local rainfall temperature are circumvented and the resulting 18 o signal is controlled directly by the amount of rain falling between the two sites this is confirmed by comparison with rainfall data from the instrumental record which also allows a calibration of the 18 o proxy the calibrated 18 o record provides a quantitative history of rainfall in southwest china which demonstrates that rainfall was 8 higher than today during the holocene climatic optimum 6 ka but only 3 higher during the early holocene significant multi centennial variability also occurred with notable dry periods at 8 2 ka 4 8 4 1 ka 3 7 3 1 ka 1 4 1 0 ka and during the little ice age this holocene rainfall record provides a good target with which to test climate models the approach used here of combining stalagmite records from more than one location will also allow quantification of rainfall patterns for past times in other regions

evidence for sea level and monsoonally driven variations in terrigenous input to the northern east china sea during the last 24 3 ka geochemical and sedimentological analyses of core pc 1 recovered from the northern east china sea ecs provide insights into variations in terrigenous input associated with sea level and climate changes over the past 24 3 ka based on high resolution multiproxy records our results suggest that the competing processes of sea level and monsoonally driven precipitation determined terrigenous input to the northern ecs dominance of terrigenous material along with relatively light globigerinoides ruber 18o indicates that the last glacial maximum lgm lowstand of sea level has occurred during the period 21 5 19 6 ka not suggesting an early slow rise but supporting the conventional lgm age of 21 ka this lgm lowstand was terminated by the rapid sea level rise of 19 ka meltwater pulse mwp which is well expressed by the nearly synchronous decreases in both terrigenous detritus and mean grain size from 19 6 to 18 9 ka mwp 1a is clearly marked in our records by a sharp reduction in terrigenous input and pronounced maxima of g ruber 18o at 15 3 14 8 ka given the considerable age uncertainties of deglacial marine radiocarbon samples a slightly increasing input of terrigenous matter is noted after 13 4 ka potentially pointing to a sea level fall following the inter allerod cooling period which was seldom reported previously although mwp 1b did not leave robust signatures in terrigenous input it is explicitly captured by the heavy 18o of g ruber and decline in mean grain size at 11 5 10 9 ka mwp 1c probably occurred in a broad millennial interval with multiple peaks which are robustly marked by the abrupt variations in terrigenous input and marine organic matter at 9 7 9 3 and 9 1 ka respectively during the late holocene the effect of continuously weakening monsoon precipitation overwhelmed that of stable sea level resulting in a uniform increase in the proportion of marine derived organic matter after 5 5 ka

late holocene asian monsoon variations recorded in lake rara sediment western nepal the himalayas are a key location for understanding centennial to millennial scale variations in the asian monsoon yet few studies of the late holocene have been conducted in this sensitive area direct evidence for shifts in monsoonal wind strength is often limited to marine proxy records while terrestrial reconstructions e g lake levels and spleothems focus on precipitation here we present the first evidence of terrestrial summer monsoon wind strength changes from lake rara western nepal based on mn ti ratios a proxy for lake stratification these data indicate a link between the arabian sea and the himalayas suggesting that centennial to millennial scale changes in wind strength occurred synchronously distinct similarity is also observed between lake rara and the southern part of china which may support previous suggestions that the southern part of china is influenced by indian summer monsoon copyright 2012 john wiley sons ltd

rising social complexity agricultural intensification and the earliest rice paddies on the loess plateau of northern china geoarchaeological studies of landscapes immediately adjacent to archaeological sites can contribute information on the direct impact of small scale societies on their associated landscapes this direct connection allows us to understand aspects of the motivations economic decision making and agricultural strategies and how they affected local site catchments the origin and spreading of farming communities onto the loess plateau of northern china provides a good example of this we recorded sediment profiles that were immediately adjacent to the site of huizui in the yiluo river basin here we identified evidence for human land use beginning with the early mid holocene deposits which are consistent with stable hillslope soils indicating that the first mixed forager millet farmers of the peiligang neolithic had a very light ecological footprint on the landscape this is in contrast to the later middle neolithic yangshao period farmers sediments from the yangshao period revealed paleolandscape and phytolith evidence for the earliest neolithic paddy farming well outside of the natural habitat of wild rice in addition to evidence for massive deforestation and soil erosion a 15 m deep sediment sequence containing sets of gravels beginning ca 7200 cal bp and gleyed soils dating from ca 6600 cal bp contained rice phytoliths archaeological waste suggesting manuring and micromorphological data indicating trampling these signs of intensive landscape management go hand in hand with rapidly increasing social complexity

variability of southwest indian summer monsoon precipitation during the bolling allerod we have generated a high resolution 20 yr 2 3 0 th dated stalagmite oxygen isotope record from timta cave in the western himalaya in india that documents southwest indian summer monsoon ism precipitation variations during the bolling allerod interstadial from 15 2 to 11 7 ka compared with the glacial and younger dryas ism precipitation was enhanced during the bolling allerod ism precipitation was apparently coupled to variations in the east asian monsoon and north atlantic climate on millennial and multicentennial time scales during the deglaciation analyses of a high growth rate interval 2 5 yr resolution encompassing the late bolling early alterod suggest that multidecadal monsoon variability was an important aspect of ism behavior at that time the frequency spectrum of ism precipitation during this time interval is similar to that of the 1 4 c record and other ism precipitation records during the latest holocene this raises the hypothesis that multidecadal climate dynamics during the late boiling early allerod may have been similar to those that operated during the last several millennia even though the boundary conditions of these two time intervals were very different

holocene climate change in henan area a synthesis of proxy records abstract henan area is climatologically situated in the transition between northern and southern china and the transition is reported to be highly sensitive to climate changes during the holocene to better understand the holocene climatic and environmental changes in henan area where high quality data are lacking this paper first reviewed those published palaeoenvironmental records in attempt to provide a low resolution framework of the holocene environmental changes in henan area and then synthesized the moisture proxy records from the surrounding areas in attempt to define a high resolution trend of the holocene moisture variation for our target site i e zhengzhou within henan area two major conclusions can be drawn first the high resolution holocene moisture curve for our target site well follows the general moisture trend of china and the curve is well corroborated by two recently reported data sets one from mangshan loess palaeosol sequence and another from laomu dongshiya cave second our synthesis supports an earlier notion stating that the holocene moisture optimum in china was a delayed response to the oceanic holocene thermal optimum the latter might in turn be a delayed response to the summer insolation peak

early middle holocene ecological change and its influence on human subsistence strategies in the luoyang basin north central china in north central china subsistence practices transitioned from hunting and gathering to millet based agriculture between the early and middle holocene to better understand how ancient environmental changes influenced this shift in subsistence strategies and human activities at regional to local levels we conducted palynological and lithologic analyses on radiocarbon dated sediment cores from the luoyang basin western henan province our palynological results suggest that vegetation shifted from broad leaved deciduous forest 9230 8850 cal yr bp to steppe meadow vegetation 8850 7550 cal yr bp and then to steppe with sparse trees 7550 6920 cal yr bp lithologic analyses also indicate that the stabilization of the luoyang basin s floodplain after similar to 8370 cal yr bp might have attracted people to move into the basin promoting the emergence of millet based agriculture during the peiligang culture period 8500 7000 cal yr bp once agricultural practices emerged the climatic optimum after similar to 7550 cal yr bp likely facilitated the expansion of the yangshao culture 7000 5000 cal yr bp in north central china as agriculture intensified pollen taxa related to human disturbance such as urtica increased in abundance

moisture variations in lacustrine eolian sequence from the hunshandake sandy land associated with the east asian summer monsoon changes since the late pleistocene abstract paleoclimate records currently lack sufficient geographic detail to understand the spatiotemporal evolution of east asian summer monsoon easm rain belt since the late pleistocene in particular there is no consensus on whether the easm rain belt reached its modern northern limit by the early holocene here we present inferred moisture variations from a multi parameter absolute dated lacustrine eolian sequence from northern china that date back to the late pleistocene 14 ka bp or thousand years ago we observed a sharp transition towards wet conditions at the onset of the holocene epoch maximum wet climate occurred here during 11 3 8 5 ka the climate remained predominantly wet until 4 2 ka then it became progressively drier we observed alternating organic rich fine grained lake deposits and organic depleted coarse grained eolian sand layers during 14 7 ka these layers correspond to sedimentation associated with the allerod younger dryas yd post yd warming pre boreal oscillation pbo early holocene and 8 2 ka event we interpreted the orbital scale moisture variation at our study site to the changes in insolation assigning these abrupt and short lived changes during the late pleistocene holocene transition to a persistent teleconnection between the north atlantic and east asian climate zones

late holocene high frequency east asia winter monsoon variability inferred from the environmentally sensitive grain size component in the distal shelf mud area east china sea the b2 b2g and i4 sediment cores recovered from the centre of the distal mud area of the east china sea ecs were analysed for grain size distribution proxies for environmentally sensitive grai

deglacial sea level record from tahiti corals and the timing of global meltwater discharge the timing of the last deglaciation is important to our understanding of the dynamics of large ice sheets1 and their effects on the earth s surface2 3 moreover the disappearance of the glacial ice sheets was responsible for dramatic increases in freshwater fluxes to the oceans which probably disturbed the ocean s thermohaline circulation and hence global climate4 7 sea level increases bear witness to the melting of continental ice sheets but only two such records from barbados8 9 and new guinea10 11 corals have been accurately dated but these corals overlie active subduction zones where tectonic movements are large and often discontinuous especially in new guinea so the apparent sea level records may be contaminated by a complex tectonic component here we date fossil corals from tahiti which is far from plate boundaries and thus is likely to be tectonically relatively stable and remote from the locations of large former ice sheets the resulting record indicates a large sea level jump shortly before 13 800 calendar years bp which corresponds to meltwater pulse 1a in the barbados coral records8 9 the timing of this event is more accurately constrained in the tahiti record revealing that the meltwater pulse coincides with a short and intense climate cooling event12 15 that followed the initiation of the bolling allerod warm period12 16 but preceded the younger dryas cold event by about 1 000 years

correlation between indian ocean summer monsoon and north atlantic climate during the holocene there has been a number of investigations for the correlation between the asia monsoon and the north atlantic climate for the last glacial however little research has been done for the present interglacial the holocene here we present for the first time a high resolution composite proxy record for the indian ocean summer monsoon spanning around 12 000 years based on the 13c time series of both a single plant species carex mulieensis remains cellulose and the total plant assemblage cellulose in the hongyuan peat bog from the tibet plateau the records show that the strength of the indian ocean summer monsoon had abrupt variations during the last 12 000 years the weakest monsoon occurred in the younger dryas period following rapid strengthening from around 11 200 to 10 800 a bp the monsoon kept a generally strong level for around 5300 years from around 5500 a bp onwards the monsoon strength tended to gradual decrease in addition there are a series of abrupt variation events of the monsoon strength on centennial to millennial time scales which superimpose the general tendency of the monsoon variation in every case when the ice rafted debris events in the north atlantic occurred the summer monsoon strength decreased correspondingly these evidences show that teleconnection between the indian ocean summer monsoon and the north atlantic climate is present not only in the last glacial but also in the holocene which may be linked to abrupt reorganizations of the ocean thermohaline circulation leading to redistribution of energy changing temperature and moisture gradient over the southern subtropical indian ocean and eventually controlling the variability of the indian ocean summer monsoon

anthropocene archaeology of the yellow river china 5000 2000 bp in this paper we use geoarchaeological and paleoenvironmental data from three localities in the yellow river valley china taosi sanyangzhuang and the yiluo valley to argue that human activi

climate and anthropogenic controls on the carbon cycle of xingyun lake china abstract the organic and inorganic carbon cycles in lakes are responsive to both natural climate variability and human induced environmental changes here we present an 8600 year sediment record from xingyun lake in yunnan china that provides insight into carbon cycling and lake primary productivity using stable isotope measurements of organic carbon and nitrogen carbon to nitrogen ratio inorganic carbon isotopes and mass accumulation rates of carbon nitrogen and calcite the early to middle holocene is characterized by relative stability in most proxies although some variation in organic carbon isotopes reflects fluctuating terrestrial organic matter inputs the middle to late holocene from 5300 to 3300 years bp is marked by amplified variability in nearly all proxies and suggests either increased c4 vegetation or increased primary productivity these changes are coincident with declining lake levels and increased aridity throughout the indian summer monsoon region after 3300 years bp the greatest variability is in nitrogen isotopes and coincides closely with human settlement in the region these changes are accompanied by further indications of increased primary productivity suggesting eutrophic lake conditions while we cannot definitively link human activity to these changes the balance of evidence suggests that other mechanisms are unlikely this study supports previous work that anthropogenic activities began measurably impacting the landscape in southwestern china within the last few millennia

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

strong coherence between solar variability and the monsoon in oman between 9 and 6 kyr ago variations in the amount of solar radiation reaching the earth are thought to influence climate but the extent of this influence on timescales of millennia to decades is unclear a number of climate records show correlations between solar cycles and climate1 but the absolute changes in solar intensity over the range of decades to millennia are small2 and the influence of solar flux on climate is not well established the formation of stalagmites in northern oman has recorded past northward shifts of the intertropical convergence zone3 whose northward migration stops near the southern shoreline of arabia in the present climate4 here we present a high resolution record of oxygen isotope variations for the period from 9 6 to 6 1 kyr before present in a th u dated stalagmite from oman the 18o record from the stalagmite which serves as a proxy for variations in the tropical circulation and monsoon rainfall allows us to make a direct comparison of the 18o record with the 14c record from tree rings5 which largely reflects changes in solar activity6 7 the excellent correlation between the two records suggests that one of the primary controls on centennial to decadal scale changes in tropical rainfall and monsoon intensity during this time are variations in solar radiation

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

east asian summer monsoon precipitation variations in china over the last 9500 years a comparison of pollen based reconstructions and model simulations to better understand the long term changes of the east asian summer monsoon precipitation p jja quantitative reconstructions and model simulations are needed here we develop continental scale pollen based transfer functions for p jja with weighted averaging partial least squares wa pls regression and a bayesian multinomial regression method we apply these transfer functions to a set of fossil pollen data from monsoonal china for quantitatively reconstructing the p jja changes over the last 9500 years we compare the reconstructions with p jja simulations from a coupled atmosphere ocean sea ice general circulation model the kiel climate model kcm the results of cross validation tests for the transfer functions show that both the wapls model r2 0 83 root mean square error of prediction rmsep 112 11 mm and the bayesian model r2 0 86 rmsep 107 67 mm exhibit good predictive performance we stack all p jja reconstructions from northern china to a summary curve the stacked record reveals that p jja increased since 9500 cal yr bp attained its highest level during the holocene summer monsoon maximum hsmm at similar to 7000 4000 cal yr bp and declined to present the kcm output and the reconstructions differ in the early holocene similar to 9500 7000 cal yr bp where the model suggests higher p jja than the reconstructions moreover during the hsmm the amplitude of the p jja changes similar to 20 60 mm above present in simulations is lower than the reconstructed changes similar to 70 110 mm above present the rising declining p jja patterns in reconstructions before after the hsmm are more pronounced and fluctuating than in simulations other palaeohydrological data such as lake level reconstructions indicate substantial monsoon precipitation changes throughout the holocene our results therefore show that the kcm underestimates the overall amplitude of the holocene monsoon precipitation changes

orbital and suborbital scale changes in the east asian summer monsoon since the last deglaciation the variability of the east asian summer monsoon easm has far reaching effects on the global climate system and the environment and full understanding of the variability and dynamics of the easm contributes to predictions of its future behavior here we present a well dated mineralogical and total organic carbon record from a saline inland lake in northern china which provides a robust archive of the easm evolution since 16 0 cal ka bp our record reveals a series of rapid and frequent millennial scale climatic fluctuations during the last deglaciation these fluctuations are documented by changes in the abundances of mirabilite bloedite and gypsum which appear to record the oldest dryas the bolling allerod warm period and the younger dryas the peak easm moisture occurred in the early and middle holocene which was punctuated by a prominent and abrupt weak monsoon interval that occurred synchronously with the 8 2 cal ka bp cold event this moisture maximum was terminated at 6 9 5 9 cal ka bp

shell and gravel layers caused by storm induced rip currents during the medieval warm period and little ice age in south korea abstract five shell gravel layers 2 2 2 9 m in elevation 70 cm in thickness formed by storm induced rip currents along the southern coast of the korean peninsula over the past 1300 years are described the three radiocarbon dates s1 s3 and the two optically stimulated luminescence s4 and s5 dates correspond well with the succession of the five shell gravel layers the age of s1 ce 720 60 corresponds to the early medieval warm period mwp the dates of the three overlying layers s2 s4 ce 880 110 950 70 and 995 120 respectively coincide with the middle mwp the fifth date of the uppermost shell gravel layer s5 ce 1535 40 coincides with the little ice age lia of western europe the characteristics of shell habitats based on 16 shell species from each layer suggest that the first four layers formed in a slightly erosional to dominantly depositional environment during the mwp whereas the youngest layer formed in a dominantly erosional environment during the lia analyses of grain size distribution magnetic susceptibility and geochemistry of the sediments and gravel morphology indicate that storm activity at this site during the mwp and lia occurred within active storm periods in the western north atlantic wna comparison of the five storm events and related climatic factors suggests that although the typhoon track type at the site is similar to recurving tracks typical for el nino conditions in north china and japan tracks during the mwp and lia were likely shifted not only by changes in el nino conditions but by other climatic factors such as sea surface temperature the north pacific high and the westerly jet stream however storm energy under el nino years during the middle mwp was likely stronger than that produced in normal years during the early mwp

the first radiocarbon dated steppe polecat mustela eversmanii from the pleistocene of poland the mandible of a steppe polecat was found during excavation in deszczowa cave czestochowa upland southern poland in 2011 direct radiocarbon dating gave an age of 21 920 150 bp not calibrated indicating the earliest part of the last glacial maximum mis 3 mis 2 the association of the steppe polecat with other steppe and tundra taxa from the same layer confirms that this species was an element of the widespread steppe tundra ecosystem in east europe during late pleistocene there is no evidence of sousliks in the layer with the steppe polecat fossil

asynchronous holocene climatic change across china a review of holocene climatic variations in different parts of china shows that they were asynchronous proxy data from ice cores pollen loess lacustrine sediments and changes of sea and lake levels demonstrate that many warm and cold oscillations have occurred in china during the holocene including a most important climatic event known as the holocene optimum a milder and wetter period and that the duration and amplitude of the optimum period as well as its start and end times differed in different parts of china uplift of the tibetan plateau over the past millions of years led to the development of the monsoon climate and to complex atmospheric circulation over continental china during the holocene as a result the holocene optimum began and terminated earlier in high altitude regions of western china than at lower elevations in eastern china and the amplitude of the variations was lower in the east this suggests that the western higher altitude areas were more sensitive to climatic change than were the eastern lower altitude areas holocene climatic records in the dunde and guliya ice cores do not correspond inverse 18o variations between the two cores indicate that the effects of climate and atmospheric processes on the stable isotopes at the two sites differed the correlation between the isotopic composition of carbonates in lake deposits in western china and climatic variations is similar to that in the ice cores the climatic resolution in ice cores and lake sediments is higher than that in other media the lack of precise correspondence of climatic records constructed on the basis of proxy data from different parts of china is a result of the different locations and elevations of the sampling sites the different resolutions of the source material and the varied climatic conditions within china further work is needed to confirm both the conclusions and the inferences presented here

interhemispheric anti phasing of rainfall during the last glacial period abstract we have obtained a high resolution oxygen isotopic record of cave calcite from caverna botuvera 27 13 s 49 09 w southern brazil which covers most of the last 36 thousand years ka with an average resolution of a few to several decades the chronology was determined with 46 u th ages from two stalagmites tests for equilibrium conditions show that oxygen isotopic variations are primarily caused by climate change we interpret our record in terms of meteoric precipitation changes hence the variability of south american monsoon sam intensity the oxygen isotopic profile broadly follows local insolation changes and shows clear millennial scale variations during the last glacial period with amplitudes as large as 3 but with smaller centennial scale shifts 1 during the holocene the overall record is strikingly similar to but strongly anti correlated with a number of records from the northern hemisphere we compared our record to other precisely dated contemporaneous records from hulu cave eastern china minima in 18o wet periods intense sam at our site are synchronous with maxima in 18o dry periods weak east asian monsoon eam in eastern china within precise dating errors and vice versa this anti phased precipitation relationship between two low latitude locations may be interhemispheric in extent based on comparison with records from other sites precipitation anti phasing may be related to north south shifts in the mean position of the intertropical convergence zone itcz and asymmetry in hadley circulation in two hemispheres associated not with seasonal changes as observed today but with millennial scale climate shifts the millennial scale atmospheric see saw patterns that we observe could have important controls and feedbacks on climate within hemispheres because of water vapor s greenhouse properties

proxy based temperature reconstruction in china for the holocene abstract the temperature variation in china is closely related to the dynamics of global climate change in order to reveal its possible connections with global climate during the holocene we present a nationwide temperature reconstruction in china for the past 12 000 years based on multiple proxies with three statistical methods including empirical orthogonal function composite plus scale and simple arithmetic average our reconstruction shows that the late 20th century temperature in china is the highest at least over the past millennium although the low temperature in the period of 10 000 12 000 yr bp was mainly related to the north atlantic cool conditions the reconstructed china s temperature followed solar forcing variations more closely than climatic influence from the north atlantic the asian monsoon was also closely connected to temperature change in china over the holocene

the preboreal like asian monsoon climate in the early last interglacial period recorded from the dark cave southwest china abstract transitions of glacial interglacial cycles are critical periods for quaternary climate shifts here we present new decadal resolution asian summer monsoon asm record from three stalagmites obtained from the dark cave in southwestern china over 130 114 thousand years ago ka before ce 1950 chronology was anchored by 28 230th dates with typical uncertainties of 0 3 1 0 kyr allowing an assessment of timing and transition of climate changes during the onset and end of the last interglacial an agreement between this new and previous stalagmite 18o records supports that summer insolation predominates orbital scale asm evolution a 2 3 kyr long gradually increasing asm period analogous to the classical preboreal episode in the early holocene follows the termination of a weak monsoon interval at 129 0 0 8 ka this finding suggests a strong influence of high latitude ice sheet dynamics on asian monsoonal conditions during the early interglacial period an abrupt end of the marine isotope stage 5e at 118 8 0 6 ka was probably caused by the internal climate system threshold effects

speleothem evidence from oman for continental pluvial events during interglacial periods growth periods and stable isotope analyses of speleothems from hoti cave in northern oman provide a record of continental pluvial periods extending back over the past four of earth s glacial interglacial cycles rapid speleothem growth occurred during the early to middle holocene 6 10 5 ka b p 78 82 ka b p 120 135 ka b p 180 200 ka b p and 300 325 ka b p the speleothem calcite deposited during each of these episodes is highly depleted in 18 o compared to modern speleothems the d 18 o values for calcite deposited within pluvial periods generally fall in the range of 24 to 28 relative to the vienna peedee belemnite standard whereas modern speleothems range from 21 to 23 the growth and isotopic records indicate that during peak interglacial periods the limit of the monsoon rainfall was shifted far north of its present location and each pluvial period was coincident with an interglacial stage of the marine oxygen isotope record the association of continental pluvial periods with peak interglacial conditions suggests that glacial boundary conditions and not changes in solar radiation are the primary control on continental wetness on glacial interglacial time scales

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

asian summer monsoon variability during the late glacial and holocene inferred from the stable carbon isotope record of black carbon in the sediments of muge co southeastern tibetan plateau china a sediment core from an alpine lake muge co from the southeastern margin of the tibetan plateau was analyzed for sediment grain size distribution and the carbon isotopic composition of black carb

early holocene monsoonal fluctuations in the garhwal higher himalaya as inferred from multi proxy data from the malari paleolake abstract a 4 9 m thick lake sequence formed due to the landslide damming of a stream in the semiarid garhwal himalaya was studied to understand past monsoonal variations in the region the optically stimulated luminescence osl chronology indicates that the lake existed between 12 and 7 ka ago chronologically constrained trends of sand percent organic phosphorus op apatite inorganic phosphorus aip and parameters of environmental magnetism were measured in the paleolake profile measured proxies indicate that the indian summer monsoon ameliorated in the early holocene after 12 ka cooling and it appears that all the proxies from the lake have captured this globally recognized early holocene warming four phases of wet conditions intensified monsoon are recognized at 11 5 ka 11 10 5 ka 10 9 ka and 8 7 ka with maximum uncertainties of 1000 years the wet phases are characterized by high magnetic susceptibility increased op and reduced aip in an attempt to understand the primary forcing of the sharp fluctuations in monsoonal activity in the region we show that changes in magnetic susceptibility match variations of residual atmospheric 14c suggesting a role for solar variability as an explanation of climatic variability

abrupt early to mid holocene climatic transition registered at the equator and the poles paleoclimatic records from equatorial east africa antarctica and greenland reveal that atmospheric circulation changed abruptly at the early to mid holocene transition to full postglacial conditions a climatic reorganization occurred at all three sites between 8200 and 7800 years ago that lasted 200 years or less and appears to have been related to abrupt transitions in both marine and terrestrial records around the world

reconstruction of climate and vegetation changes of lake bayanchagan inner mongolia holocene variability of the east asian monsoon a high resolution pollen and pediastrum record spanning 12 500 yr is presented for lake bayanchagan 115 21 e 41 65 n and 1355 m a s l southern inner mongolia individual pollen taxa pt mat and the pft affinity scores pft mat were used for quantitative climatic reconstruction from pollen and algal data both techniques indicate that a cold and dry climate similar to that of today prevailed before 10 500 cal yr b p the wettest climate occurred between 10 500 and 6500 cal yr b p at which time annual precipitation was up to 30 60 higher than today the early holocene increases in temperature and precipitation occurred simultaneously but mid holocene cooling started at approximately 8000 cal yr b p 1500 yr earlier than the drying vegetation reconstruction was based on the objective assignment of pollen taxa to the plant functional type the results suggest that this region was dominated by steppe vegetation throughout the holocene except for the period 9200 to 6700 cal yr b p when forest patches were relatively common inner mongolia is situated at the limit of the present east asian monsoon and patterns of vegetation and climate changes in that region during the holocene probably reflect fluctuations in the monsoon s response to solar insolation variations the early to middle holocene monsoon undoubtedly extended to more northern latitudes than at present

paleotemperature variability in central china during the last 13 ka recorded by a novel microbial lipid proxy in the dajiuhu peat deposit the asian summer monsoon is a very important climatic component affecting the land ecosystem on the eastern asian continent here we assess microbe derived lipid biomarker evidence from a well date

synchronous holocene sea surface temperature and rainfall variations in the asian monsoon system abstract an increasing number of high resolution paleoclimate records show substantial natural variation during the holocene in order to improve climate projections on human lifetime the processes that potentially control teleconnections between different parts of the climate system need to be understood a highly suitable area to study these processes is the asian monsoon system as it is one of the most dynamic climate systems on earth and largely controls climate in asia and the indo w pacific realm here we present a holocene stable o isotope record from the summer dwelling planktic foraminifer g bulloides in core 905 off somalia initially dated by the radiocarbon method the record was tuned to atmospheric 14 c variations without violating the radiocarbon dates the o isotope variations in core 905 imply monsoon controlled holocene average summer sea surface temperature variations of up to 2 2 5 c within decades to centuries other proxy records from marine and continental settings representing key locations in the asian monsoon system were compared with the record of core 905 within the resolution of the individual age models holocene monsoonal records vary in concert for the arabian sea continental china and the south china sea and imply simultaneous warm wet and cool dry alternations in the asian monsoon within centuries to decades two potential scenarios are discussed to explain the coherent monsoonal records scenario one involves trade wind induced temperature variations in the w pacific warm pool as the driving force the second scenario advocates the controlling process to synchronous variations in trade wind strength simultaneously occurring over the pacific and indian ocean

regional and global benthic δ18o stacks for the last glacial cycle although detailed age models exist for some marine sediment records of the last glacial cycle 0 150 ka age models for many cores rely on the stratigraphic correlation of benthic 18o which measures ice volume and deep ocean temperature change the large amount of data available for the last glacial cycle offers the opportunity to improve upon previous benthic 18o compilations such as the lr04 global stack not only are the age constraints for the lr04 stack now outdated but a single global alignment target neglects regional differences of several thousand years in the timing of benthic 18o change during glacial terminations here we present regional stacks that characterize mean benthic 18o change for 8 ocean regions and a volume weighted global stack of data from 263 cores age models for these stacks are based on radiocarbon data from 0 to 40 ka correlation to a layer counted greenland ice core from 40 to 56 ka and correlation to radiometrically dated speleothems from 56 to 150 ka the regional 18o stacks offer better stratigraphic alignment targets than the lr04 global stack and furthermore suggest that the lr04 stack is biased 1 2 kyr too young throughout the pleistocene finally we compare global and regional benthic 18o responses with sea level estimates for the last glacial cycle

timing and duration of the east asian summer monsoon maximum during the holocene based on stalagmite data from north china we present a continuous c o isotope series that shows the detailed variability of east asian summer monsoon easm since 11 0 ka bp the series is based on two stalagmites namely dsy1 and lm2 wh

palaeoclimatic interpretation of high resolution oxygen isotope profiles derived from annually laminated speleothems from southern oman high resolution stable isotope profiles of three contemporaneously deposited stalagmites from a shallow cave in southern oman provide an annually resolved record of indian ocean monsoon rainfall variability for the past 780 years uranium series age dating and counts of annual growth bands enable an excellent age calibration although modern speleothems do not grow in perfect isotopic equilibrium oxygen isotope ratios 18o are a proxy for the amount of monsoon rainfall this is supported by the statistically significant correlation between 18o and the thickness of annual bands whereas 18o is inversely correlated with annual band thickness additionally overlapping 18o profiles are very similar in pattern and range indicating that sample specific noise did not blur the climatic signal the longest oxygen isotope profile derived from stalagmite s3 clearly shows the transition at 1320 ad from a generally wetter medieval warm period to a drier little ice age that lasted from approximately ad 1320 1660 in southern oman the decrease in monsoon rainfall since the 1960s is also obvious in meteorological records from northern africa and india indicating that our speleothem based rainfall records do not only reflect local monsoon rainfall variability

holocene itcz and indian monsoon dynamics recorded in stalagmites from oman and yemen socotra abstract high resolution oxygen isotope 18o profiles of holocene stalagmites from four caves in northern and southern oman and yemen socotra provide detailed information on fluctuations in precipitation along a latitudinal transect from 12 n to 23 n 18o values reflect the amount of precipitation which is primarily controlled by the mean latitudinal position of the itcz and dynamics of the indian summer monsoon ism during the early holocene rapidly decreasing 18o values indicate a rapid northward displacement in the mean latitudinal position of the summer itcz and the associated ism rainfall belt with decadal to centennial scale changes in monsoon precipitation correlating well with high latitude temperature variations recorded in greenland ice cores during the middle to late holocene the summer itcz continuously migrated southward and monsoon precipitation decreased gradually in response to decreasing solar insolation a trend which is also recorded in other monsoon records from the indian and east asian monsoon domains importantly there is no evidence for an abrupt middle holocene weakening in monsoon precipitation although abrupt monsoon events are apparent in all monsoon records they are short lived and clearly superimposed on the long term trend of decreasing monsoon precipitation for the late holocene there is an anti correlation between ism precipitation in oman and inter monsoon spring autumn precipitation on socotra revealing a possible long term change in the duration of the summer monsoon season since at least 4 5 ka bp together with the progressive shortening of the ism season gradual southward retreat of the mean summer itcz and weakening of the ism the total amount of precipitation decreased in those areas located at the northern fringe of the indian and asian monsoon domains but increased in areas closer to the equator

high resolution absolute dated indian monsoon record between 53 and 36 ka from xiaobailong cave southwestern china the oxygen isotopic record of stalagmite xbl 1 from southwestern china reveals millennial scale variability of the indian monsoon between 53 and 36 ka synchronous with changes in the east asian monsoon recorded at hulu cave and similar to dansgaard oeschger cycles recorded in greenland ice our record in general confirms the chronology of hulu cave if our correlations between greenland and the xiaobailong cave record are correct both the greenland ice sheet project 2 and greenland ice core project ss09sea chronologies are accurate within quoted errors a dry interval that we correlate with heinrich event 5 h5 and the greenland stadial preceding greenland interstadial 12 gis 12 is centered ca 48 0 ka and a shift to drier conditions correlated to the end of gis 12 is ca 43 5 ka overall the variability of the indian monsoon from xbl 1 data on millennial scales is similar to and correlated with high latitude ice core rec ords from the northern hemisphere however some indian monsoon characteristics more closely resemble but are anticorrelated with features in the antarctic record suggesting some link to climate of the high southern latitudes in addition to the clear link to the climate of the high northern latitudes

investigating the long term palaeoclimatic controls on the δd and δ18o of precipitation during the holocene in the indian and east asian monsoonal regions abstract this paper aims to achieve an improved understanding of the long term change trends of precipitation d and 18 o values d p and 18 o p in the asian monsoonal region and their relationship with the corresponding humidity trends during the holocene to do this we first review the observed modern spatial pattern of summer precipitation distribution in the east asian summer monsoon easm region under different easm intensities and the relationship between modern observed 18 o p values and corresponding precipitation amounts on monthly and inter annual timescales in the easm and indian summer monsoon ism regions second we compare holocene lacustrine and marine compound specific hydrogen isotopic records of n alkanes n alkanoic acid d n lacustrine authigenic carbonate and cave stalagmite oxygen isotopic records 18 o c and 18 o s from the asian monsoonal region all of which are closely related to d p and 18 o p variations the results demonstrate that in both the ism and easm regions all of these isotopic records exhibit roughly similar long term characteristics i e they were all more negative during the early holocene and early mid holocene ca 11 6 ka b p b p means before present present 1950 ad and then became more positive towards the late holocene third we compare representative paleo humidity records from the asian monsoonal region the results confirm that in the ism region a humid interval occurred in the early holocene and early mid holocene ca 11 6 ka b p and subsequently the climate became more arid towards the late holocene this indicates an enhanced ism during the early holocene and early mid holocene ca 11 6 ka b p and an ism of decreasing intensity towards the late holocene on a holocene orbital scale both 18 o p and d p appear to be controlled by an amount effect in the ism region consistent with the region s inter annual modern 18 o p data this evidence indicates that both 18 o p and d p paleo records are significantly related to paleo humidity in the ism region in contrast holocene humidity variations in the easm region exhibit clear spatial differences a humid mid holocene interval ca 8 3 ka b p occurred in southern and northern china but an arid interval from ca 7 3 ka b p occurred in central china in the middle reaches of the yangtze river based on precipitation distribution patterns under different easm intensities in the easm region over the past few decades we conclude that easm intensity was enhanced during the mid holocene ca 8 3 ka b p relative to the ism intensity the response of easm intensity to summer insolation was relatively slow in the easm region the relationship between climate and 18 o p and d p is more complex consistent with analyses of regional inter annual modern 18 o p data this evidence demonstrates that both 18 o p and d p paleo records cannot be used directly as paleo humidity i e precipitation amount or easm intensity indicators in the easm region further comparison and analyses demonstrate that the coupled variations in west east equatorial pacific temperature gradients and the west pacific subtropical high wpsh played an important role in determining easm intensity during the holocene

the 7 2 ka climate event evidence from high resolution stable isotopes and trace element records of stalagmite in shuiming cave chongqing china speleothem records have radically changed our understanding of the paleo asian monsoon am but explanations for asian summer monsoon asm variations in the holocene period are usually based on s

asynchronous holocene optimum of the east asian monsoon abstract the spatial and temporal distribution of summer monsoon precipitation or effective moisture during the holocene has been reconstructed on the basis of geological data including lake levels pollen profiles and loess paleosol records in addition the summer july precipitation increment effective precipitation and monsoon strength index have been obtained from numerical modeling experiments both geological data and numerical modeling indicate that the holocene optimum as defined by peak east asian summer monsoon precipitation was asynchronous in central and eastern china reaching a maximum at different times in different regions e g ca 10 000 8000 yr ago in northeastern china 10 000 7000 yr ago in north central and northern east central china ca 7000 5000 yr ago in the middle and lower reaches of the yangtze river and ca 3000 yr ago in southern china in southwestern china the maximum appeared ca 11 000 yr ago but probably was related to the maximum landward extension of the indian summer monsoon the regional shift in the maximum precipitation belt from northwest to southeast over the past 10 000 yr is interpreted as a response to changing seasonality related to orbital forcing of the climate the southeastward shift of the east asian summer monsoon maximum is consistent with the progressive weakening of the summer monsoon as the summer solar radiation anomaly decreased progressively through the holocene and the east asian monsoon index declined while the early maximum in southwestern china matches the maximum of the indian monsoon index

abrupt changes in the asian southwest monsoon during the holocene and their links to the north atlantic ocean during the last ice age the indian ocean southwest monsoon exhibited abrupt changes that were closely correlated with millennial scale climate events in the north atlantic region1 2 3 suggesting a mechanistic link in the holocene epoch which had a more stable climate the amplitude of abrupt changes in north atlantic climate was much smaller and it has been unclear whether these changes are related to monsoon variability here we present a continuous record of centennial scale monsoon variability throughout the holocene from rapidly accumulating and minimally bioturbated sediments in the anoxic arabian sea our monsoon proxy record reveals several intervals of weak summer monsoon that coincide with cold periods documented in the north atlantic region4 including the most recent climate changes from the medieval warm period to the little ice age and then to the present we therefore suggest that the link between north atlantic climate and the asian monsoon is a persistent aspect of global climate

archaeology of the anthropocene in the yellow river region china 8000 2000 cal bp although archaeological analysis emphasizes the importance of climatic events as a driver of historical processes we use a variety of environmental and archaeological data to show that human modif

sea surface temperature variability in southern okinawa trough during last 2700 years 1 most of the temperature reconstructions for the past two millennia are based on proxy data from various sites on land here we present a bidecadal resolution record of sea surface temperature sst in southern okinawa trough for the past ca 2700 years by analyzing tetraether lipids of planktonic archaea in the odp hole 1202b a site under the strong influence of kuroshio current and east asian monsoon the reconstructed sst anomalies generally coincided with previously reported late holocene climate events including the roman warm period sui tang dynasty warm period medieval warm period current warm period dark age cold period and little ice age however the medieval warm period usually thought to be a historical analogue for the current warm period has a mean sst of 0 6 0 8 c lower than that of the roman warm period and sui tang dynasty warm period despite an increase since 1850 ad the mean sst in the 20th century is still within the range of natural variability during the past 2700 years a close correlation of sst in southern okinawa trough with air temperature in east china intensity of east asian monsoon and the el nino southern oscillation index has been attributed to the fluctuations in solar output and oceanic atmospheric circulation

indian ocean climate and an absolute chronology over dansgaard oeschger events 9 to 13 oxygen isotope ratios of a stalagmite from socotra island in the indian ocean provide a record of changes in monsoon precipitation and climate for the time period from 42 to 55 thousand years before the present the pattern of precipitation bears a striking resemblance to the oxygen isotope record from greenland ice cores with increased tropical precipitation associated with warm periods in the high northern latitudes the largest change at the onset of interstadial 12 occurred very rapidly in about 25 years the chronology of the events found in our record requires a reevaluation of previously published time scales for climate events during this period

centennial to decadal scale monsoon precipitation variations in the upper hanjiang river region china over the past 6650 years abstract the upper hanjiang river region is the recharge area of the middle route of south to north water transfer project the region is under construction of the hanjiang weihe river water transfer project in china monsoon precipitation variations in this region are critical to water resource and security of china in this study high resolution monsoon precipitation variations were reconstructed in the upper hanjiang river region over the past 6650 years from 18 o and 13 c records of four stalagmites in xianglong cave the long term increasing trend of stalagmite 18 o record since the middle holocene is consistent with other speleothem records from monsoonal china this trend follows the gradually decreasing northern hemisphere summer insolation which indicates that solar insolation may control the orbital scale east asian summer monsoon easm variations despite the declined easm intensity since the middle holocene local precipitation may not have decreased remarkably as revealed by the 13 c records a series of centennial to decadal scale cyclicity was observed with quasi millennium quasi century 57 36 and 22 year cycles by removing the long term trend of stalagmite 18 o record increased monsoon precipitation during periods of 4390 3800 a bp 3590 2960 a bp 2050 1670 a bp and 1110 790 a bp had caused four super floods in the upper reach of hanjiang river dramatically dry climate existed in this region during the 5 0 ka and 2 8 ka events coinciding with notable droughts in other regions of monsoonal china remarkably intensified and southward westerly jet together with weakened summer monsoon may delay the onset of rainy seasons resulting in synchronous decreasing of monsoon precipitation in china during the two events during the 4 2 ka event and the little ice age the upper hanjiang river region was wet which was similar to the climate conditions in central and southern china but was the opposite of drought observed in northern china we propose that weakened summer monsoon and less strengthened or normal westerly jet may cause rain belt stay longer in the southward region which reduced rainfall in northern china but enhanced it in central and southern china

spatial and temporal variability of holocene temperature in the north atlantic region the early holocene climate of the north atlantic region was influenced by two boundary conditions that were fundamentally different from the present the presence of the decaying laurentide ice sheet lis and higher than present summer solar insolation in order to assess spatial and temporal patterns of holocene climate evolution across this region we collated quantitative paleotemperature records at sub millennial resolution and synthesized their temporal variability using principal components analysis pca the analysis reveals considerable spatial variability most notably in the time transgressive expression of the holocene thermal maximum htm most of the region but especially areas peripheral to the labrador sea and hence closest to the locus of lis disintegration experienced maximum holocene temperatures that lagged peak summer insolation by 1000 3000 years many sites from the northeastern north atlantic sector including the nordic seas and scandinavia either warmed in phase with maximum summer insolation 11 000 9000 years ago or were less strongly lagged than the baffin bay labrador sea region these spatially complex patterns of holocene climate development which are defined by the pca resulted from the interplay between final decay of the lis and solar insolation forcing

holocene east asian summer monsoon records in northern china and their inconsistency with chinese stalagmite δ18o records abstract monsoon precipitation over china exhibits large spatial differences it has been found that a significantly enhanced east asian summer monsoon easm is characterized by increased rainfall in northern china and by reduced rainfall in southern china and this relationship occurs on different time scales during the holocene this study presents results from a diverse range of proxy paleoclimatic records from northern china where precipitation variability is traditionally considered as an easm proxy our aim is to evaluate the evolution of the easm during the holocene and to compare it with all of the published stalagmite 18 o records from the asian monsoon region in order to explore the potential mechanism s controlling the chinese stalagmite 18 o we found that the intensity of the easm during the holocene recorded by the traditional easm proxy of moisture or precipitation records from northern china is significantly different from the chinese stalagmite 18 o records the easm maximum occurred during the mid holocene challenging the prevailing view of an early holocene easm maximum mainly inferred from stalagmite 18 o records in eastern china in addition all of the well dated holocene stalagmite 18 o records covering a broad geographical region exhibit a remarkably similar trend of variation and are statistically well correlated on different time scales thus indicating a common signal however in contrast with the clear consistency in the 18 o values in all of the cave records both instrumental and paleoclimatic records exhibit significant spatial variations in rainfall on decadal to centennial time scales over eastern china in addition both paleoclimatic records and modeling results suggest that holocene east asian summer monsoon precipitation reached a maximum at different periods in different regions of china thus the stalagmite 18 o records from the easm region should not be regarded as a reliable indicator of the strength of the east asian summer monsoon furthermore modern observations indicate that the moisture for precipitation in the east asian monsoon region is mainly derived from the indian ocean the moisture transport route from the indian ocean to the east asian monsoon region during the holocene is almost identical to that of modern precipitation therefore the strong correlation of 18 o records in the easm and indian summer monsoon ism regions and the similarity of the pattern of latitudinal changes in 18 o values in stalagmites and in modern meteoric precipitation along the water vapor transport route further suggests that the stalagmite 18 o records from the easm region are essentially a signal of the isotopic composition of precipitation which is determined mainly by changes in the 18 o of atmospheric vapor in the upstream source region over the indian ocean and indian monsoon region via the upstream depletion mechanism finally the main trends of the stalagmite 18 o records are strongly correlated with the known evolution of the ism and therefore these records reflect the history of the ism rather than that of the easm our findings support the conclusion that easm variability is mainly controlled by northern hemisphere summer insolation and was strongly modulated by ice volume during the last deglaciation and early holocene which delayed the response of the easm maximum to peak insolation forcing

a high resolution absolute dated deglacial speleothem record of indian ocean climate from socotra island yemen abstract stalagmite m1 5 from socotra island yemen in the northwest indian ocean provides a robust high resolution paleoclimate record from 27 4 11 1 ka based on 717 stable isotope and 28 230 th measurements variations in m1 5 oxygen isotope ratios 18 o are interpreted to be primarily driven by an amount effect related to changes in the mean position and or intensity of convection of the intertropical convergence zone the island s only source of precipitation the m1 5 18 o time series is strongly correlated to the greenland ice cores similar to an older socotra speleothem deposited from 53 40 ka s j burns d fleitmann a matter j kramers a al subbary indian ocean climate and an absolute chronology over dansgaard oeschger events 9 to 13 science 301 2003 1365 1367 indicating that a north atlantic indian ocean cold dry warm wet teleconnection persisted through the end of the last glacial period peak aridification occurred at 23 ka and a gradual increase in moisture thereafter was interrupted by an abrupt drying event at 16 4 ka perhaps related to heinrich event 1 indian ocean rainfall increased dramatically during the bolling period and then decreased continuously and gradually through the allerod and younger dryas the holocene began abruptly with increased precipitation at 11 4 ka and was followed by a major but short lived drying during the preboreal oscillation at 11 2 ka m1 5 is highly correlated to the dongge cave record from 15 5 11 ka suggesting much of the indian ocean monsoon region responded similarly to the major climate changes of the last deglaciation the transitions into the younger dryas and to a lesser extent the bolling are remarkably gradual in m1 5 as they are in all other asian speleothem records occurring over several centuries these gradual transitions are in striking contrast to high resolution records from around the north atlantic basin where the transitions are extremely abrupt and generally occur in under a century this spatially variable pattern of climate change is consistent with an atlantic origin for these deglacial climate events

east asian hydroclimate modulated by the position of the westerlies during termination i speleothem oxygen isotope records have revolutionized our understanding of the paleo east asian monsoon yet there is fundamental disagreement on what they represent in terms of the hydroclimate changes we report a multiproxy speleothem record of monsoon evolution during the last deglaciation from the middle yangtze region which indicates a wetter central eastern china during north atlantic cooling episodes despite the oxygen isotopic record suggesting a weaker monsoon we show that this apparent contradiction can be resolved if the changes are interpreted as a lengthening of the meiyu rains and shortened post meiyu stage in accordance with a recent hypothesis model simulations support this interpretation and further reveal the role of the westerlies in communicating the north atlantic influence to the east asian climate

the southwest indian monsoon over the last 18 000 years previously published results suggest that the strength of the sw indian monsoon can vary significantly on century to millenium time scales an observation that has important implications for assessments of future climate and hydrologic change over densely populated portions of asia we present new well dated multi proxy records of past monsoon variation from three separate arabian sea sediment cores that span the last glacial maximum to late holocene to a large extent these records confirm earlier published suggestions that the monsoon strengthened in a series of abrupt events over the last deglaciation however our data provide a somewhat refined picture of when these events took place and suggest the primacy of two abrupt increases in monsoon intensity one between 13 and 12 5 ka and the other between 10 and 9 5 ka this conclusion is supported by the comparisons between our new marine data and published paleoclimatic records throughout the african asian monsoon region the comparison of data sets further supports the assertion that maximum monsoon intensity lagged peak insolation forcing by about 3000 years and extended from about 9 5 to 5 5 ka the episodes of rapid monsoon intensification coincided with major shifts in north atlantic european surface temperatures and ice sheet extent this coincidence coupled with new climate model experiments suggests that the large land sea thermal gradient needed to drive strong monsoons developed only after glacial conditions upstream of and on the tibetan plateau receded cold north atlantic sea surface temperatures european ice sheets and extensive asian snow cover it is likely that abrupt changes in seasonal soil hydrology were as important to past monsoon forcing as were abrupt snow related changes in regional albedo our analysis suggests that the monsoon responded more linearly to insolation forcing after the disappearance of glacial boundary conditions decreasing gradually after about 6 ka our data also support the possibility that significant century scale decreases in monsoon intensity took place during the early to mid holocene period of enhanced monsoon strength further highlighting the need to understand paleomonsoon dynamics before accurate assessments of future monsoon strength can be made

replicated stalagmite inferred centennial to decadal scale monsoon precipitation variability in southwest china since the mid holocene a lack of agreement between stalagmite records of the centennial to decadal scale asian summer monsoon asm variability since the mid holocene limited our understanding of forcings and the possible impacts on culture evolution here we present replicated high resolution stalagmite 18o profiles from dark cave in guizhou province southwest china established with 512 oxygen isotope data and 28 230th ages providing a continuous history of the asm precipitation from 6100 to 300 years before present yr bp before ad 1950 consistency of stalagmite 18o inferred long term decreasing asm trends since the mid holocene between caves at this site and others in the indian and east asian monsoon realms on orbital timescales supports the effect of primary orbital solar forcings on monsoonal precipitation the dark cave records display significant centennial to decadal scale variations more evident than previous stalagmite records spectral analysis of the dark cave 18o time series yields periodicities of 731

east asian summer monsoon variations in the past 12 5 ka high resolution delta o 18 record from a precisely dated aragonite stalagmite in central china due to possible aragonite to calcite transformation resulting in alteration in isotopic signatures and a bias in age dating aragonite speleothems are often excluded from paleoclimatic archives however aragonite stalagmites contain ppm level uranium content making them much easier to date achieving higher age dating precisions than calcite stalagmites in this regard provided aragonite to calcite transformation did not occur aragonite stalagmites are potentially well suited for holocene climate research given their climate proxies can be placed into a better constrained chronological framework in this paper we present high precision u th dates and o isotopic time series for a 82 cm long continuous growth aragonite stalagmite lh2 from lianhua cave hunan province china and discuss east asian summer monsoon easm variability for the last 12 5 ka bp before present the u th dated delta o 18 sequence with a mean 16 year resolution and the growth rate pattern of lh2 show that easm experienced a strengthening stage a strong stage and a weakening stage during the last 12 5 ka during the yd 12 5 11 5 ka bp heavy delta o 18 values and low growth rate indicate a weak monsoon period during the preboreal from similar to 11 5 to 10 6 ka bp delta o 18 values decreased dramatically similar to 1 94 parts per thousand reflecting abrupt strengthening of the monsoon from 10 6 to 4 2 ka bp the record is characterized by the lightest delta o 18 values and high growth rates suggesting a strong monsoon period the summer monsoon weakened substantially after 4 2 ka bp as inferred from gradually increasing delta o 18 values and decreasing growth rate overall the intensity of the easm is regulated by summer insolation at 30 degrees n during the last 12 5 ka although oxygen isotope fractionation is different between aragonite h2o and calcite h2o because of rayleigh fractionation law the overall temporal pattern of delta o 18 values from aragonite stalagmite lh2 is concordant with other high resolution holocene calcite stalagmite records from south china the comparison among these records shows that the holocene optimum was synchronous across asian continental region influenced by the easm and indian summer monsoon ism lasting from similar to 10 6 to 4 2 ka bp as reflected by consistently lighter delta 18 ovalues among all these records regardless of their latitudinal difference these records do not support previously reported asynchronism between easm and ism in details the long term delta o 18 trend in lh2 is punctuated by a number of centennial fluctuations for instance two weak monsoon events occurred at 9232 57 yr bp and 8137 21 yr bp correlating in time with cooling events in greenland ice cores the latest weak monsoon event centered at 302 8 yr bp which is related to the little ice age lia in addition the monsoon intensity derived from our record also shows a strong connection with latitudinal migration of the inter tropical convergence zone itcz as recorded in the cariaco basin sediments spectral analysis of delta o 18 values shows that significant peaks match with solar periodicities of 208 yr de vries cycle 86 yr gleissberg cycle or related to delta c 14 production suggesting shorter term monsoon variations are forced by solar radiation overall our study suggests that the delta o 18 record in the aragonite stalagmite is highly consistent with those derived from calcite stalagmites suggesting that aragonite stalagmites are suitable for palaeoclimate reconstruction especially for the holocene period as aragonite calcite transformation has not occurred c 2013 elsevier ltd all rights reserved

a geochemical record of the link between chemical weathering and the east asian summer monsoon during the late holocene preserved in lacustrine sediments from poyang lake central china abstract this paper presents relatively high resolution geochemical records spanning the past 4000 cal yr bp obtained from the lacustrine sediments of poyang lake in central china the variations in the intensity of the east asian summer monsoon easm are traced using the k na ti na al k kaolinite illite and clay feldspar ratios together with the chemical index of alteration cia as indicators of chemical weathering during the last 4000 years the proxy records of chemical weathering from poyang lake exhibit an overall enhanced trend consistent with regional hydrological changes in previous independent records further comparisons and analyses demonstrate that regional moisture variations in central china is inversely correlated with the easm intensity with weak easm generating high precipitation in central china our data reveal three intervals of dramatically dry climatic conditions i e ca 4000 3200 cal yr bp ca 2800 2400 cal yr bp and ca 500 200 cal yr bp a period of weak chemical weathering related to cold and dry climatic conditions occurred during the little ice age lia whereas more intense chemical weathering reflecting warm and humid climatic conditions was recorded during the medieval warm period mwp besides an intensification of chemical weathering in poyang lake during the late holocene agrees well with strong enso activity suggesting that moisture variations in central china may be predominantly driven by enso variability

a large drop in atmospheric 14c 12c and reduced melting in the younger dryas documented with 230th ages of corals paired carbon 14 14 c and thorium 230 230 th ages were determined on fossil corals from the huon peninsula papua new guinea the ages were used to calibrate part of the 14 c time scale and to estimate rates of sea level rise during the last deglaciation an abrupt offset between the 14 c and 230 th ages suggests that the atmospheric 14 c 12 c ratio dropped by 15 percent during the latter part of and after the younger dryas yd this prominent drop coincides with greatly reduced rates of sea level rise reduction of melting because of cooler conditions during the yd may have caused an increase in the rate of ocean ventilation which caused the atmospheric 14 c 12 c ratio to fall the record of sea level rise also shows that globally averaged rates of melting were relatively high at the beginning of the yd thus these measurements satisfy one of the conditions required by the hypothesis that the diversion of meltwater from the mississippi to the st lawrence river triggered the yd event

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

new insights on chinese cave δ18o records and their paleoclimatic significance abstract in the last two decades stalagmite oxygen isotope 18o records have been widely used to study the evolution of the paleomonsoon nevertheless interpreting cave 18o records in eastern monsoonal china as an indicator of east asian summer monsoon easm rainfall has been intensively debated this study provides new insights into chinese cave 18o records and their paleoclimatic significance based on recent research progress the following points are highlighted 1 chinese cave 18o records do not reflect changes in summer rainfall throughout the whole of eastern monsoonal china which is evident by comparing monitored summer rainfall amount in eastern china and an integrated chinese cave 18osyn proxy 2 chinese cave 18o records can document millennial scale easm events due to the sensitive response to large scale atmospheric circulation changes 3 during the early holocene before 7 ka a decoupled relationship between chinese cave 18o records and easm rainfall as represented by precipitation in north china is attributed to the reduction of rainfall in north china due to the influence of remnant melting ice sheets in the northern high latitude region 4 when the ice sheet boundary conditions were stable and ice sheets were small after 7 ka there is an indirect correlation between the chinese cave 18o and rainfall changes in north china 5 the first continuous speleothem 18o record spanning the entire holocene is synthesized for the core region of the indian summer monsoon ism domain comparison of this integrated ism proxy with chinese cave 18o records reveals that in china cave 18o is primarily a signal of changes in the tropical monsoon and related large scale circulation the coupled relationship between rainfall in north china and tropical monsoon ism rainfall is attributed to the response of downstream circulation to changes in circulation upstream while their decoupled relationship is due to the possible effects of northern high latitude ice sheets on reducing rainfall in north china 6 due to the imprecise definition of monsoon intensity we suggest that cave 18o can be used as an easm proxy if monsoon intensity is defined by changes in atmospheric circulation

an isotopic and modelling study of flow paths and storage in quaternary calcarenite sw australia implications for speleothem paleoclimate records abstract we investigated the distinctive shallow sub surface hydrology of the southwest western australia swwa dune calcarenite using observed rainfall and rainfall 18 o soil moisture cave drip rate and dripwater 18 o over a six year period august 2005 march 2012 a lumped parameter hydrological model is developed to describe water fluxes and drip 18 o comparison of observed data and model output allow us to assess the critical non climatic karst hydrological processes that modify the precipitation 18 o signal and discuss the implications for speleothem paleoclimate records from this cave and those with a similar karst setting our findings include evidence of multiple reservoirs characterised by distinct 18 o values and recharge responses low and high flow sites dripwaters exhibit 18 o variations in wet versus dry years at low flow sites receiving diffuse seepage from the epikarst with an attenuated isotopic composition that approximates mean rainfall recharge from high magnitude rain events is stored in a secondary reservoir which is associated with high flow dripwater that is 1 lower than our monitored low flow sites 18 o one drip site is characterised by mixed flow behaviour and exhibits a non linear threshold response after the cessation of drainage from a secondary reservoir following a record dry year 2006 additionally our results yield a better understanding of the vadose zone hydrology and dripwater characteristics in quaternary age dune limestones we show that flow to our monitored sites is dominated by diffuse flow with inferred transit times of less than one year diffuse flow appears to follow vertical preferential paths through the limestone reflecting differences in permeability and deep recharge into the host rock

rising waters new geoarchaeological evidence of inundation and early agriculture from former settlement sites on the southern yangtze delta china new pollen phytolith charcoal and diatom data from 14c ams dated sediments from three clusters of former occupation sites on the southern yangtze delta liangzhu majiabang and chuodun reveal

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

a high resolution absolute dated holocene and deglacial asian monsoon record from dongge cave china abstract we present a continuous record of the asian monsoon over the last 16 ka from 18o measurements of stalagmite calcite over 900 oxygen isotopic measurements providing information on shifts in monsoon precipitation are combined with a chronology from 45 precise 230th dates 18o and therefore asian monsoon intensity generally follows changes in insolation although changes in 18o are generally accommodated in abrupt shifts in contrast to smoothly varying insolation indicating that threshold effects may be important 18o decreased dramatically 3 at the start of the holocene 11 5 ka and remained low for 6 ka four positive 18o events centered at 11225 97 yr bp 1 05 10880 117 yr bp 1 15 9165 75 yr bp 1 4 and a double event centered at 8260 64 yr bp 1 1 and 8080 74 yr bp 1 0 punctuated this period of high monsoon intensity all four events correlate within error with climate changes in greenland ice cores thus the relationship between the asian monsoon and the north atlantic observed during the glacial period appears to continue into the early holocene in addition three of the four events correlate within error with outburst events from lake agassiz the decline of monsoon intensity in the mid late holocene is characterized by an abrupt positive shift in 18o which occurs at 3550 59 yr bp 1 1 in 100 yr in addition the holocene is punctuated by numerous centennial and multi decadal scale events amplitudes 0 5 to 1 up to half the amplitude of the glacial interstadial events seen in the last glacial period thus holocene centennial and multi decadal scale monsoon variability is significant although not as large as glacial millennial scale variability the monsoon shows a strong connection with northern south american hydrological changes related by changes in itcz position spectral analysis of the 18o record shows significant peaks at solar periodicities of 208 yr and 86 yr suggesting variation is influenced by solar forcing however there are numerous other significant peaks including peaks at el nino frequencies observed for high resolution portions of the record between 8110 and 8250 yr which suggest that changes in oceanic and atmospheric circulation patterns in addition to those forced by solar changes are important in controlling holocene monsoon climate in addition for this high resolution portion we observe a distinctive biennial oscillation of the asian monsoon which has been associated with the tropospheric biennial oscillation tbo

pollen record of the mid to late holocene centennial climate change on the east coast of south korea and its influential factors abstract to understand historical climate change in western pacific coastal areas a sediment core soj 2 from the stable sedimentary environment of the songjiho lagoon on the east coast of south korea was obtained for centennial resolution palynological analysis the ages of the soj 2 core is well controlled by carbon 14 dating with high resolution accelerator mass spectrometry ams and the results indicated a general warm to cold climate trend from the mid holocene to the present which can be divided into two different stages a warmer stage between 6842 and 1297 cal yr bp and a colder stage from 1297 cal yr bp to the present with fluctuations during these stages the climate was wetter from 6842 to 6227 cal yr bp and 4520 to 1297 cal yr bp and was drier from 6227 to 4520 cal yr bp the climate changed to cold and dry during the period from 1297 425 cal yr bp the impact of human activity on the climate began at approximately 1297 cal yr bp and became pronounced starting in 425 cal yr bp the general cooling trend may represent a response to decreasing solar insolation however the relative dryness or wetness of the climate may have been co determined by westerlies and the east asian summer monsoon easm the climate had a teleconnection with the north atlantic region resulting from changes in solar activity nevertheless ei nino southern oscillation enso activity played an important role in impacting the easm changes in western pacific coastal areas

absence of cooling in new zealand and the adjacent ocean during the younger dryas chronozone as the climate warmed at the end of the last glacial period a rapid reversal in temperature the younger dryas yd event briefly returned much of the north atlantic region to near full glacial conditions the event was associated with climate reversals in many other areas of the northern hemisphere and also with warming over and near antarctica however the expression of the yd in the mid to low latitudes of the southern hemisphere and the southwest pacific region in particular is much more controversial here we show that the waiho loop advance of the franz josef glacier in new zealand was not a yd event as previously thought and that the adjacent ocean warmed throughout the yd

inverse phase oscillations between the east asian and indian ocean summer monsoons during the last 12 000 years and paleo el nino abstract the inverse phase variations between the east asian and indian ocean summer monsoons on the interannual timescale result from the el nino southern oscillation activity in the tropical pacific which potentially provides a new way for studying paleo enso here we reconstruct a 12 000 yr proxy record for the east asian summer monsoon from 13 c time series of the plant cellulose of the hani peat bog in the northeastern china the comparison of it with the peat proxy record of the indian ocean summer monsoon suggests that the el nino conditions are coincident with strong east asian summer monsoons weak indian summer monsoons and drift ice events in the north atlantic at both orbital and millennial time scales the orbital scale inverse phase relationships between the monsoons indicate the occurrence of a long term enso like pattern confirming the sensitivity of the monsoon systems associated with enso to insolation forcing the nine inverse phase variations on the millennial time scales may suggest the nine el nino like patterns superimposing the long term enso like pattern the inverse phase variations between the monsoons also show close correspondence to the drift ice events at high northern latitudes in every case when the abrupt ice rafted debris events occurred in the north atlantic the inverse phase relationship established and the el nino like pattern occurred in the tropical pacific correspondingly the discussions on the influence of ocean thermohaline circulation on these global linkages have been made

holocene forcing of the indian monsoon recorded in a stalagmite from southern oman a high resolution oxygen isotope record from a thorium uranium dated stalagmite from southern oman reflects variations in the amount of monsoon precipitation for the periods from 10 3 to 2 7 and 1 4 to 0 4 thousand years before the present ky b p between 10 3 and 8 ky b p decadal to centennial variations in monsoon precipitation are in phase with temperature fluctuations recorded in greenland ice cores indicating that early holocene monsoon intensity is largely controlled by glacial boundary conditions after approximately 8 ky b p monsoon precipitation decreases gradually in response to changing northern hemisphere summer solar insolation with decadal to multidecadal variations in monsoon precipitation being linked to solar activity

holocene variability of the east asian summer monsoon from chinese cave records a re assessment oxygen isotope records from stalagmites in caves in southern china interpreted as proxy rainfall records reflecting the intensity of the east asian summer monsoon indicate gradual monsoon weakening for the last 9000 years as also documented for the indian monsoon coupled with high precision dating the speleothem proxy records have been used to test monsoon links with orbital forcing solar changes iceberg discharges in the north atlantic ocean currents and atmospheric methane however these benchmark cave records do not match other published dated e asian proxy rainfall record specifically here independently calibrated rainfall records from loess palaeosol magnetic properties and cave oxygen isotope intercomparisons which show variable e asian monsoon intensity through the entire holocene the strong correlation of the cave records with the extraregional indian monsoon record yet their mismatch with these other dated chinese rainfall records might be reconciled if the speleothem isotope variations reflect not changes in holocene rainfall amount but in rainfall source declining holocene influence of isotopically lighter indian monsoon sourced moisture over china would have resulted in increasing proportions of isotopically heavier rainfall sourced from the more oceanic e asian monsoon individual speleothems may thus regionally record holocene changes in indian monsoon intensity and isotopic influence conversely the other chinese proxy records described here reflect changes in rainfall amount and thus in e asian summer monsoon intensity for the holocene the e asian and the indian monsoon responses to orbital forcing are likely to have differed specifically due to e asian internal feedbacks and the seasonal contrasts between the two monsoon systems

tracking regional and global teleconnections recorded by western north american speleothem records abstract speleothem proxy records are useful for interrogating past climates in the low and mid latitudes given their ability to provide continuous high resolution and long lived records that can be dated with high precision several speleothem oxygen isotope records from western north america have recently been developed that highlight the importance of this archive in documenting past changes in atmospheric circulation taken individually these records hint at teleconnections between western north american hydroclimate and climate changes in the high northern latitudes and tropics however there has been no systematic investigation of global climate teleconnections to this region that draws upon the body of north american speleothem records as a whole here we review the dominant controls on precipitation oxygen isotopes across the region and conduct statistical comparisons and network visualizations of high resolution speleothem oxygen isotope records from western north america to investigate the regional response to pronounced climate changes of the last deglaciation and to determine the pattern of global teleconnections to this region we find that most western north american speleothem oxygen isotope records demonstrate a robust and consistent response to the events of the last deglaciation despite differing controls on the oxygen isotope ratio of precipitation across the region one record that receives a strong influence from the gulf of mexico exhibits a contrasting pattern in oxygen isotopes relative to most of the other records which are dominated by westerly storms generated in the pacific during the studied interval major shifts in western north american speleothem records appear broadly synchronous at least within the uncertainty of age models we also find strong statistical linkages between western north american speleothem records and speleothem records of asian monsoon variability and other records from regions directly influenced by movement of the intertropical convergence zone demonstrating that nearly synchronous changes in atmospheric circulation measurably altered precipitation dynamics in these regions during the last deglaciation further multi proxy investigations are needed to determine how such changes in atmospheric circulation recorded by speleothem oxygen isotope ratios influenced precipitation amounts in drought prone western north america

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

spatial and temporal variability in the stable isotope systematics of modern precipitation in china implications for paleoclimate reconstructions the stable isotopic composition of materials such as glacial ice tree rings lake sediments and speleothems from low to mid latitudes contains information about past changes in temperature t and precipitation amount p however the transfer functions which link 18op to changes in t or p d 18op dt and d 18op dp can exhibit significant temporal and spatial variability in these regions in areas affected by the southeast asian monsoon past variations in 18o and d of precipitation have been attributed to variations in monsoon intensity storm tracks and or variations in temperature proper interpretation of past 18op variations here requires an understanding of these complicated stable isotope systematics since temperature and precipitation are positively correlated in china and have opposite effects on 18op it is necessary to determine which of these effects is dominant for a specific region in order to perform even qualitative paleoclimate reconstructions here we evaluate the value of the transfer functions in modern precipitation to more accurately interpret the paleorecord the strength of these transfer functions in china is investigated using multiple regression analysis of data from 10 sites within the global network for isotopes in precipitation gnip 18op is modeled as a function of both temperature and precipitation the magnitude and signs of the transfer functions at any given site are closely related to the degree of summer monsoon influence 18op values at sites with intense summer monsoon precipitation are more dependent on the amount of precipitation than on temperature and therefore exhibit more negative values in the summer in contrast 18op values at sites that are unaffected by summer monsoon precipitation exhibit strong relationships between 18op and temperature the sites that are near the northern limit of the summer monsoon exhibit dependence on both temperature and amount of precipitation comparison with simple linear models 18op as a function of t or p and a geographic model 18op as a function of latitude and altitude shows that the multiple regression model is more successful at reproducing 18op values at sites that are strongly influenced by the summer monsoon the fact that the transfer function values are highly spatially variable and closely related to the degree of summer monsoon influence suggests that these values may also vary temporally since the southeast asian monsoon intensity is known to exhibit large variations on a number of timescales annual to glacial interglacial and the magnitude and sign of the transfer functions is related to monsoon intensity we suggest that as monsoon intensity changes the magnitude and possibly even the sign of the transfer functions may vary therefore quantitative paleoclimate reconstructions based on 18op variations may not be valid