evolution of the indian summer monsoon and terrestrial vegetation in the bengal region during the past 18 ka the indian summer monsoon ism is a major global climatic phenomenon long term precipitation proxy records of the ism however are often fragmented and discontinuous impeding an estimation of the magnitude of precipitation variability from the last glacial to the present to improve our understanding of past ism variability we provide a continuous reconstructed record of precipitation and continental vegetation changes from the lower ganges brahmaputra meghna catchment and the indo burman ranges over the last 18 000 years 18 ka the records derive from a marine sediment core from the northern bay of bengal nbob and are complemented by numerical model results of spatial moisture transport and precipitation distribution over the bengal region the isotopic composition of terrestrial plant waxes dd and d13c of n alkanes are compared to results from an isotope enabled general atmospheric circulation model isocam for selected time slices pre industrial mid holocene and heinrich stadial 1 comparison of proxy and model results indicate that past changes in the dd of precipitation and plant waxes were mainly driven by the amount effect and strongly influenced by ism rainfall maximum precipitation is detected for the early holocene climatic optimum ehco 10 5 6 ka bp whereas minimum precipitation occurred during the heinrich stadial 1 hs1 16 9 15 4 ka bp the isocam model results support the hypothesis of a constant moisture source i e the nbob throughout the study period relative to the pre industrial period the model reconstructions show 20 more rain during the mid holocene 6 ka bp and 20 less rain during the heinrich stadial 1 hs1 respectively a shift from c4 plant dominated ecosystems during the glacial to subsequent c3 c4 mixed ones during the interglacial took place vegetation changes were predominantly driven by precipitation variability as evidenced by the significant correlation between the dd and d13c alkane records when compared to other records across the ism domain precipitation and vegetation changes inferred from our records and the numerical model results provide evidence for a coherent regional variability of the ism from the last glacial to the present

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

stable isotope record and its palaeoenvironmental interpretation for a late middle pleistocene speleothem from victoria fossil cave naracoorte south australia abstract a speleothem from victoria fossil cave south australia provides a continuous stable isotope record from 185 to 157 ka oxygen isotope analysis indicates that at commencement of deposition mean annual temperatures were much lower than at present and that between 178 and 162 ka regional surface temperatures were similar to today such high temperatures during an interstadial are surprising but may be attributable to increased continentality due to low sealevels carbon isotope analysis indicates the presence of an active vegetation cover dominated by c3 plants during the interstadial while a sparse vegetation dominated by c4 grasses appears to have been dominant during full glacial conditions variations in moisture availability and vegetation productivity are probably closely related to stages in the precessional cycle

rapid changes of glacial climate simulated in a coupled climate model abrupt changes in climate termed dansgaard oeschger and heinrich events have punctuated the last glacial period approximately 100 10 kyr ago but not the holocene the past 10 kyr here we use an intermediate complexity climate model to investigate the stability of glacial climate and we find that only one mode of atlantic ocean circulation is stable a cold mode with deep water formation in the atlantic ocean south of iceland however a warm circulation mode similar to the present day atlantic ocean is only marginally unstable and temporary transitions to this warm mode can easily be triggered this leads to abrupt warm events in the model which share many characteristics of the observed dansgaard oeschger events for a large freshwater input such as a large release of icebergs the model s deep water formation is temporarily switched off causing no strong cooling in greenland but warming in antarctica as is observed for heinrich events our stability analysis provides an explanation why glacial climate is much more variable than holocene climate

climatic and local effects on stalagmite δ13c values at lianhua cave china abstract carbon isotopes in speleothems may serve as indicators of vegetative change climatic conditions and karst processes in many recent studies of chinese stalagmites however carbon isotopes have often been neglected or underutilized in interpreting paleoenvironments here we present a continuous decadal scale 13 c record 819 measurements of the mid to late holocene from a precisely dated 10 230 th dates aragonite stalagmite from lianhua cave hunan province china compared to coeval stalagmites from other chinese caves the average 13 c value 3 6 of stalagmite a1 is higher by 2 7 variations in the 13 c values 0 1 to 6 0 reflect changes in both vegetative productivity and inorganic processes which respond to climatic processes the 13 c record of stalagmite a1 can be subdivided into three intervals 1 warm humid stage 6 6 to 3 8 ka 2 transitional stage 3 8 to 1 6 ka and 3 cool arid stage 1 6 ka to present comparisons with other stalagmite and paleoclimatic records demonstrate that these intervals are generally consistent with changes in regional vegetation and climatic conditions

a high resolution record of holocene climate change in speleothem calcite from cold water cave northeast iowa high precision uranium thorium mass spectrometric chronology and 18o 13c isotopic analysis of speleothem calcite from cold water cave in northeast iowa have been used to chart mid holocene climate change significant shifts in 18o and 13c isotopic values coincide with well documented holocene vegetation changes temperature estimates based on 18o 16o ratios suggest that the climate warmed rapidly by about 3 c at 5900 years before present and then cooled by 4 c at 3600 years before present initiation of a gradual increase in 13c at 5900 years before present suggests that turnover of the forest soil biomass was slow and that equilibrium with prairie vegetation was not attained by 3600 years before present

on the resource evaluation of marine gas hydrate deposits using seafloor compliance methods summary methane hydrates are solid non stochiometric mixtures of water and the gas methane they occur worldwide in sediment beneath the seafloor and estimates of the total mass available there exceed 1016 kg since each volume of hydrate can yield up to 164 volumes of gas off shore methane hydrate is recognized as a very important natural energy resource the depth extent and stability of the hydrate zone are governed by the phase diagram for mixtures of methane and hydrate determined by ambient pressures and temperatures in sea depths greater than about 300 m the pressure is high enough and the temperature low enough for hydrate to occur at the seafloor the fraction of hydrate in the sediment usually increases with depth the base of the hydrate zone is a phase boundary between solid hydrate and free gas and water its depth is determined principally by the value of the geothermal gradient and stands out on seismic sections as a bright reflection the diffuse upper boundary is not as well marked so that the total mass of hydrate cannot be determined by seismic measurements alone ocean surface gravity waves induce a low frequency horizontally propagating pressure field which deforms the seafloor the displacement of the seafloor depends on the oceanic crustal density and elastic parameters particularly the shear properties seafloor compliance is the transfer function between seafloor deformation and pressure as a function of frequency compliance measurements made at specific frequencies are tuned to structure at specific depths methane hydrate like ice in permafrost changes the physical properties of the material in which it is found decreasing the density while increasing the compressional and especially the shear velocities we apply the method of crawford webb hildebrand 1991 and show how the addition of compliance data which is particularly sensitive to changes in shear velocity can aid in the evaluation of the resource two exploration scenarios are investigated through numerical modelling in the first a very simple example illustrates some of the fundamental characteristics of the compliance response most of the properties of the section including the probable regional thickness of the hydrate zone 200 m are assumed known from seismic surveys and spot drilling the amount of hydrate in the available pore space is the only free parameter hydrate content expressed as a percentage may be determined to about 2 given compliance measurements with per cent error the rule holds over the complete range of anticipated hydrate content values in the second less information is assumed available a priori the complementary compliance survey is required to find both the thickness and the hydrate content in hydrate zones about 200 m thick beneath the seafloor which contain up to 20 and 40 per cent hydrate in the available pore space respectively a linear eigen function analysis reveals that for these two models the total mass of hydrate the product of hydrate content and thickness may be estimated to an accuracy of about 2 81 and 1 83 per cent respectively given compliance measurements with an accuracy of per cent

the δ18o and δ13c records in an aragonite stalagmite from furong cave chongqing china a 2000 year record of monsoonal climate abstract a 7 cm long aragonite stalagmite fr0510 1 from furong cave chongqing was dated by 210pb and 230th methods revealing a 2000 year record of climate history under the influence of the east asian monsoon the fr0510 1 record resembles dongge cave da record on 10 100 year scales but quite different from the wanxiang cave wx42b record indicating that while stalagmite 18o record represents local regional moisture change spatial variability of the monsoonal rainfall over eastern china must take into account during the past 2000 years climate in chongqing was relatively wet in the intervals of 50 bc ad 250 ad 1150 1450 and ad 1600 1950 and relatively dry during the periods of ad 250 1150 and ad 1450 1600 dry conditions were prevailing over the medieval warm period whereas wet climates were dominant during the most time of the little ice age in chongqing area

century scale climatic oscillations during the last glacial maximum revealed by stalagmite isotopic records from longfugong cave china the isotopic records of two 230th dated stalagmites from longfugong cave mt shennongjia central china reveal a highly resolved asian summer monsoon asm history from 29 5 to 14 5 ka bp the two 18o records are consistent with other chinese cave 18o records suggesting that our new records are of regional significance due to the reservoir mixing of seepage water in the epikarst system the stalagmite 18o signals in this cave are more severely muted than those in other caves here we observed that the amplitude of the 13c variability is approximately twice that of the 18o signal and can be used as a sensitive proxy of east asian monsoon climates first the two stalagmite 13c records are consistent with each other on decadal to centennial timescales second there are high correlation coefficients between the 13c and 18o signals over shorter timescales third from 25 2 to 19 6 ka bp six peaks in the 13c records were identified and are coincident with corresponding warming events in the greenland ice core 18o records suggesting that strong coupling occurred between the high and low latitude northern climates on centennial timescales therefore we propose that atmospheric transmission mechanisms probably played an important role in linking the asm and greenland climates on short timescales a shift in westerly winds associated with variability in the extent of temperature in the north atlantic likely influenced changes in hydrological and thermal conditions at the cave site leading to changes in vegetation cover and soil co2 concentrations above the cave therefore the calcite 13c records probably had faster and more sensitive responses to rapid climate shifts compared with their related 18o records

the gisp2 δ18o climate record of the past 16 500 years and the role of the sun ocean and volcanoes measured 18o 16o ratios from the greenland ice sheet project 2 gisp2 ice core extending back to 16 500 cal yr b p provide a continuous record of climate change since the last glaciation high resolution annual 18o 16o results were obtained for most of the current millennium a d 818 1985 and record the medieval warm period the little ice age and a distinct 11 yr 18o 16o cycle volcanic aerosols depress central greenland annual temperature 1 5 c maximally and annual 18o 16o for about 4 yr after each major eruptive event on a bidecadal to millennial time scale the contribution of solar variability to holocene greenlandic temperature change is 0 4 c the role of thermohaline circulation change on climate problematic during the holocene is more distinct for the 16 500 10 000 cal yr b p interval analogous to 14c age calibration terminology we express time in calibrated cal yr b p a d 1950 0 cal yr b p the oldest dryas bolling older dryas allerod younger dryas sequence appears in great detail bidecadal variance in 18o 16o but not necessarily in temperature is enhanced during the last phase of lateglacial time and the younger dryas interval suggesting switches of air mass transport between jet stream branches the branched system is nearly instantaneously replaced at the beginning of the bolling and holocene at 14 670 and 11 650 cal yr b p respectively by an atmospheric circulation system in which 18o 16o and annual accumulation initially track each other closely thermodynamic considerations of the accumulation rate temperature relationship can be used to evaluate the 18 o 16o temperature relationship the gisp2 ice layer count years of major gisp2 climate transitions also support the use of coral 14c ages for age calibration

ice age terminations 230th dated oxygen isotope records of stalagmites from sanbao cave china characterize asian monsoon am precipitation through the ends of the third and fourthmost recent ice ages as a result am records for the past four glacial terminations can now be precisely correlated with those from ice cores and marine sediments establishing the timing and sequence of major events in all four cases observations are consistent with a classic northern hemisphere summer insolation intensity trigger for an initial retreat of northern ice sheets meltwater and icebergs entering the north atlantic alter oceanic and atmospheric circulation and associated fluxes of heat and carbon causing increases in atmospheric co2 and antarctic temperatures that drive the termination in the southern hemisphere increasing co2 and summer insolation drive recession of northern ice sheets with probable positive feedbacks between sea level and co2

cathodoluminescence microscopy of myrmekite rim wartlike and isolated myrmekite are the three types of myrmekite that occur in the rubidoux mountain leucogranite combined cathodoluminescence scanning electron microscopy and electron microprobe investigations suggest that myrmekite is the product of k feldspar and plagioclase replacement clusters of optically continuous quartz vermicules are interconnected exhibiting a dendroid shape the surrounding myrmekitic plagioclase is chemically undistinguishable from the host bluish luminescing plagioclase with a mean composition of ab 0 81 an 0 18 kf 0 01 only the fractured cores of some plagioclase grains which display yellowish luminescence represent a plagioclase with a higher an content an 0 59 ab 0 39 kf 0 2 petrographic evidence shows that myrmekite is a complex reaction where the main phase formed prior to exsolution of albite from k feldspar and crystallization of albitic rims the formation of myrmekite is therefore a reaction occurring during late stage magmatic crystallization

cyclic changes of asian monsoon intensity during the early mid holocene from annually laminated stalagmites central china abstract climate during the early holocene was highly variable due to the complex interplay of external and internal forcing mechanisms the relative importance for them on the asian monsoon am evolution yet remains to be resolved here we present two to six yr resolution oxygen isotope 18o records of five stalagmites four of which are annually laminated from qingtian cave central china revealing detailed am variability between 10 9 and 6 1 ka bp over the contemporaneous periods the 18o records agree well with each other at multi decadal to centennial timescales when pieced together with the previously published isotopic data from the same cave the final 18o record reveals detailed am variability from the last deglaciation to the mid holocene consistent with other cave records the most striking feature of the 18o record is the recurrence of centennial scale oscillations especially during the annually counted period 8 8 6 1 ka bp cross wavelet analyses between the 18o record and solar proxies show strong coherence at 200 yr cycle suggesting that solar output was actively involved as a primary contributor the am depression at 8 2 ka bp is indistinguishable in amplitude and pattern from a series of weak am events after 8 ka bp we speculate that these centennial scale am changes might be regulated by the positive feedbacks of oceanic atmospheric interactions to the solar activity under the condition of the retreat of continental ice sheets

solar forced dansgaard oeschger events 1 it has been suggested that the strong climatic changes during the last ice age the so called dansgaard oeschger d o events could have been prompted by solar activity changes this hypothesis is based on the apparent cyclic occurrence of the d o events and the solar influence on climate during the holocene on similar time scales we test this hypothesis by comparing the 10be and 18o records from the grip ice core a superimposed epoch analysis allows us to reduce the noise in the data and to extract estimates of solar activity changes in connection to the d o events this comparison does not provide convincing evidence for a persistent solar influence on these strong climatic oscillations during the last ice age

high resolution stalagmite δ18o records of asian monsoon changes in central and southern china spanning the mis 3 2 transition abstract high resolution oxygen isotope records of three stalagmites from sanbao central china wulu southern china and dashibao southern china caves based on 876 oxygen isotope measurements and 25 precise 230 th dates provide a detailed asian monsoon am history from 32 5 to 20 8 ka b p spanning the shift between marine isotope stages 3 and 2 the calcite 18 o records although geographically widespread about 1000 km between them including the previously reported hulu record are similar in timing shape and amplitude these observations support the idea that changes in speleothem 18 o largely represent variations of precipitation isotopic composition associated with large scale summer monsoon circulation over a large portion of china these profiles show four centennial to millennial scale strong summer monsoon events analogous in timing and structure to greenland interstadials 5 through 3 gis 5 3 chronology of the events refines the hulu record and broadly supports the ngrip gicc05 timescale five weak monsoon events are identified at 31 2 30 1 28 1 25 7 and 24 2 ka b p all of which correspond to stadial events in greenland the 30 1 and 24 2 ka events correlate with heinrich stadials 3 and 2 furthermore these events correlate to warm episodes in antarctic ice cores indicating that the climatic response to north atlantic cooling is similar in china and in antarctica but in an opposite sense these observations are consistent with the bi polar seesaw hypothesis the strong coupling between am circulation and climate at both high latitudes at the centennial scale indicates that atmospheric circulation changes are important in transmitting abrupt climate signals globally

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

palaeo climate reconstruction from stable isotope variations in speleothems a review abstract speleothems are now regarded as valuable archives of climatic conditions on the continents offering a number of advantages relative to other continental climate proxy recorders such as lake sediments and peat cores they are ideal materials for precise u series dating yielding ages in calendar years thereby circumventing the radiocarbon calibration problems associated with most other continental records stable isotope studies in speleothems have shifted away from attempting to provide palaeo temperature reconstructions to the attainable goal of providing precise estimates for the timing and duration of major o isotope defined climatic events characterised by high signal to noise ratios e g glacial interglacial transitions dansgaard oeschger oscillations the 8200 year event unlike the marine records speleothem data sets are not tuned and their independent chronology offers opportunities to critically assess leads and lags in the climate system that in turn can provide important insights into forcing and feedback mechanisms improved procedures for the extraction and measurement of stable isotope ratios in fluid inclusions trapped in speleothems are likely to provide in the near future a much enhanced basis for the quantitative interpretation of o isotope ratios in speleothem calcite the latter developments open up once again the tantalising prospect of palaeo temperature estimates but more importantly perhaps provide a direct test for a new generation of general circulation models whose hydrological cycles will incorporate the water isotopes the literature is reviewed briefly to provide for the reader a sense of the current state of the art and to provide some pointers for future research directions

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

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

a high resolution absolute dated 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

uranium series chronology and environmental applications of speleothems an increasing number of scientists recognize the value of speleothems1 as often extremely well preserved archives of information about past climate vegetation hydrology sea level nuclide migration water rock interaction landscape evolution tectonics and human action well constrained data are required to document past changes reconstruct past patterns and predict future responses of the earth system at a wide range of spatial and temporal scales speleothems are particularly useful in this regard because they can be found in many locations of the globe sampled at high resolution and reliably dated using high precision uranium series techniques speleothems are bodies of mineral material formed in caves as the result of chemical precipitation from groundwater flowing or dripping in a cave most speleothems are composed of calcite formed by slow degassing of co2 from supersaturated groundwater but aragonite and gypsum forms are also common particularly near cave entrances where evaporative effects are important a host of different speleothem types decorate the walls ceilings and floors of caves and their mineralogy and morphology is a function of fluid flow and chemistry of waters feeding a particular location as well as the ambient conditions temperature chemistry light in the air or water filled void subaerial forms include the familiar stalagmites stalactites draperies flowstones subaqueous forms include rimstone pools rafts mammillary calcite wall coatings and dog tooth spar for an extensive review of the types of speleothem that have been observed see hill and forti 1997 speleothems are used in a multitude of ways to explore past environmental conditions perhaps the most fundamental of which is their very presence or absence deposition of speleothems relies on sufficient water supply and soil co2 to enable dissolution and transport of reactants in the vadose zone to underlying caves in arid or glacial times conditions may not have been favorable for speleothem formation

the eastern mediterranean paleoclimate as a reflection of regional events soreq cave israel the climate of the eastern mediterranean region of the last 60 ky was determined by a high resolution study of the oxygen and carbon isotopic composition 1500 measurement pairs of speleothems from the soreq cave israel with chronology provided by 53 precise 230 th 234 u tims ages the high precision of the speleothem tims ages permits us to determine the timing of regional climatic events in the eastern mediterranean region and to see if they correlate with global events during the period from 60 to 17 ky the 18 o and 13 c values were generally 2 2 5 higher than during the period from 17 ky to present this is consistent with the climatic transition from glacial to interglacial within the 60 to 17 ky period the soreq cave stable isotope profile includes four cold peaks at 46 35 25 and 19 ky and 2 warm peaks at 54 and 36 ky in addition the period 17 ky has two more cold peaks at 16 5 and from 13 2 to 11 4 ky the ages of four of the six cold peaks correlate well with the ages of three heinrich events h1 h2 h5 and with the age of the younger dryas however the other two heinrich events are not reflected in the soreq cave record several other isotope peaks which appear during the last 7 ky are contemporaneous with regional climatic events in the middle east and north africa in addition to the drop in 18 o and 13 c observed between the last glacial and the holocene sharp simultaneous drops in 234 u 238 u 0 ratios sr concentrations and in 87 sr 86 sr are also observed suggesting that the latter are climate related these variations are interpreted in terms of major changes in the temperature the mean annual rainfall and its isotopic composition the isotopic composition of the mediterranean vapor source the soil moisture conditions and in the mixing proportions of sources with different 87 sr 86 sr ratios sea spray dust particles and dolomitic host rock

asynchronous variation in the east asian winter monsoon during the holocene the east asian winter monsoon eawm is one of the most active components of the global climate system climate anomalies associated with the eawm differ between extratropical and tropical regions due to the eawm s meridional extent spatial differences in the eawm variability on centennial and millennial time scales during the holocene have not been well understood this study describes holocene spatiotemporal features of the eawm based on comparisons of proxy records and climate simulations the analysis specifically compared four proxy records located throughout china to assess the eawm s spatial variability during the holocene these records indicate a stronger eawm during the early holocene than that during the late holocene the eawm also shows a rapid asynchronous decline from northwestern to southeastern china the eawm declined in northwestern china from 10 to 7 5 ka b p whereas the decline did not occur in southern china and the eastern tibetan plateau until 6 4 5 ka b p coupled equilibrium and transient simulations of climate evolution during the holocene indicate that the decline of the eawm from 10 to 7 5 ka b p was probably caused by melting of northern hemisphere nh ice sheets and enhanced atlantic meridional overturning circulation amoc the decline of the eawm from 6 to 4 5 ka b p over the eastern tibetan plateau and southern china is related to an abrupt increase in sea surface temperatures ssts of the tropical western indian ocean we therefore argue that the regional shift in eawm intensity was probably related to a distinguishing response to high latitude nh ice sheets and amoc and low latitude tropical ssts forcings

modelling stalagmite growth and δ13c as a function of drip interval and temperature abstract growth and stable isotope composition of stalagmites are affected by climate changes to understand the underlying mechanisms we developed a time dependent multi box model that describes stalagmite growth and stable isotope fractionation of carbon under disequilibrium conditions the model takes variations of the drip interval temperature and the amount of mixing between the impinging drops and the solution on top of the stalagmite into account which allows to quantify the influence of these parameters to calculate the variations of 13c the multi box model was calibrated by comparison with an existing growth model the results show that drip interval temperature and the mixing coefficient do have a significant influence on 13c however considering the higher natural variability of the drip interval this parameter might have the largest influence

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