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

profiles of trace elements and stable isotopes derived from giant long lived tridacna gigas bivalves potential applications in paleoclimate studies this study investigates the environmental and biological controls on trace element partitioning and stable isotope composition of modern giant long lived bivalves tridacna gigas with the aim to use these archives for paleoclimatic reconstructions firstly the intra shell variability is studied by measuring time equivalent profiles in the different shell layers characterised by different growth rates secondly the inter site variability is studied by comparing profiles derived from three modern specimens collected in sites across the indo pacific region characterised by different ranges of temperature and productivity these results show that 18o profiles are highly reproducible across the shell regardless of significantly different growth rates shell 18o is primarily controlled by water 18o and temperature comparison of intra shell mg ca profiles shows a clear and systematic partitioning where inner layer mg ca values are a least 2 3 times higher than outer layer and hinge areas inner layer mg ca shows seasonal oscillations but superimposed on an ontogenetic trend with increasing values and increasing amplitude mg ca oscillations with age the sr ca profiles do not show clear reproducible seasonal trends in the different shell zones it is concluded that mg ca and sr ca profiles appear to reflect a combination of biological and environmental controls that will need to be disentangled before using these proxies in paleoclimatic studies finally intra shell ba ca profiles are reproducible in great detail for all modern specimens studied inter site comparison shows that the amplitude and the timing of the ba ca peaks appear to reflect the timing and the amplitude of the chlorophyll peaks associated with phytoplankton blooms at each locality making this tracer a potential paleoproductivity indicator

atmospheric processes governing the changes in water isotopologues during enso events from model and satellite measurements enso el nino southern oscillation has profound effects on the global water cycle which can be examined at the process level by investigating the associated water isotopologues many isotope based studies are aimed at understanding enso variability in the tropics however focusing principally on near surface processes and isotopologue signals the goal of the present study is to investigate the atmospheric processes governing the changes in the isotopic composition of water vapor both near the surface and at midtroposphere in the pacific region during enso events using a combination of remote sensing data and model simulations for the lower atmosphere i e 1000 hpa our results show that rainout processes less rain reevaporation of falling droplets and increase of convective updrafts and diffusive exchange within the convective systems contribute to the isotope amount effect and isotopically deplete the water vapor during wet conditions in agreement with previous studies however we find that the enso associated isotopic signal in the midtroposphere i e 500 hpa diverges from the near surface response analysis suggests that transport of enriched water vapor from lower atmospheric layers through convective updrafts controls the enrichment of midtropospheric water vapor over the pacific ocean in the observations a strong positive correlation between the increase of convective precipitation and the isotopic composition of water vapor clearly points to such a mechanism r of 0 7 0 8 in the central pacific and 0 5 0 6 in the west pacific model results confirm this mechanisms though producing slightly lower correlation values with r values of 0 6 in the central pacific and 0 5 in the west pacific however the distinction between convective and stratiform precipitation remains a result of model dependent parameterization our analysis suggests that two issues should be investigated in more detail in further studies 1 the equilibrium and disequilibrium between rain droplets and surrounding vapor for convective and stratiform precipitation and 2 different convection schemes in the different isotopic general circulation models gcms describing the triggering of convection and uplift of lower layer air to higher layers ideally such a comparison of different isotopic gcms can provide us with an interesting benchmark test for the performance of the different convection schemes during enso and can help to disentangle the importance of the different processes contributing to the amount effect

strong biological controls on sr ca ratios in aragonitic marine bivalve shells 1 it is well known that skeletal remains of carbonate secreting organisms can provide a wealth of information about past environments sr ca ratios have been successfully used as a temperature proxy in corals and sclerosponges previous work on aragonitic bivalve shells has not been conclusive but suggests a major control of growth rate on sr ca ratios as many studies have used bivalve growth rates to determine temperature we tested if sr ca ratios could predict temperature through its relationship with growth rate shells from the two species of clams from the same family veneroidea studied here saxidomus giganteus and mercenaria mercenaria show vastly different seasonal sr ca profiles a strong relationship between average annual sr ca ratios and annual growth rate was found in s giganteus shells from both washington r2 0 87 and alaska r2 0 64 usa but not in m mercenaria shells from north carolina usa furthermore the sr ca growth rate relationship was also evident upon a more detailed inspection of subannual growth rates in s giganteus r2 0 73 although there were significant positive correlations between sr ca ratios and temperature in s giganteus shells the correlations were weak 0 09 r2 0 27 and thus sr ca ratios cannot be used as a reliable temperature proxy in these species of aragonitic bivalves it is clear from this study that sr ca ratios are not under thermodynamic control in either clam species since thermodynamics predict a negative correlation between sr ca ratios and temperature in aragonite this points toward dominance of biological processes in the regulation of sr2 this is also reflected by the largely differing sr ca partition coefficients dsr in these shells dsr 0 25 when compared to inorganic coral and sclerosponge studies dsr 1 all of which show a negative dependence of sr ca on temperature we suggest that caution be taken when using sr ca in any biogenic aragonite as a temperature proxy when the dsr greatly deviates from one as this indicates the dominance of biological controls on sr ca ratios

paleoclimate and location of the border between mediterranean climate region and the saharo arabian desert as revealed by speleothems from the northern negev desert israel speleothem bearing karstic caves of the northern negev desert southern israel provides an ideal site for reconstructing the paleoclimate and paleo location of the border between mediterranean climate region and the saharo arabian desert major periods of speleothem deposition representing humid periods were determined by high resolution 230 th u dating and corresponding studies of stableisotopecompositionwereusedtoidentifythesourceofrainfallduringhumidperiodsandthevegetationtype majorhumidintervals

vegetation evolution based hydrological climate history since lgm in southern south china sea abstract the reconstruction of vegetation evolution and climate changes at low latitudes since the last glacial maximum lgm remains incomplete in this study we reconstructed the palynological history of vegetation changes since the lgm using a sediment core collected from the slope in the southern south china sea scs the chronology of the core was based on eight ams14c dates and 85 stratigraphic samples were palynologically analyzed our results denote that the vegetation reconstructed during the lgm in the southern scs was characterized by a relatively high percentage of herb pollen and a modest decrease in the number of fern spores suggesting a temperature decline and humidity change in this region further the preservation of a rich diversity of pollen from the tropical lowland rainforest indicated that the rainforests might have covered large areas of the exposed sunda shelf during the lgm the dynamic concentration of the pinus pollen in the core which is a proxy for the east asian winter monsoon eawm satisfactorily matched the changes in the atlantic meridional overturning circulation and australian indonesian summer monsoon especially during the heinrich stadial 1 this suggests that the climate at the high latitudes of the northern hemisphere can drive the intertropical convergence zone itcz southwards based on the enhanced eawm the southward shifting itcz may change the hydrological climate of the equator and the southern hemisphere the pteridophyte spores which are good regional precipitation indicators were positively correlated with the warm pool convection and inversely related with the eawm possibly indicating the considerable impact of the high latitude climate in the northern hemisphere on precipitation in the tropical regions our results indicate that during the last deglaciation the tropical hydrological changes were relatively moderate when compared with the drastic change observed at high latitudes and were attributed to the regulation of the el nino southern oscillation like state our sequence of pollen and spores from the southern scs can be used to observe the detailed dynamics of climatic evolution in tropical regions the results of this study are essential to understand the complicated climate processes and the relation between high and low latitudes

millennial scale variations in western sierra nevada precipitation during the last glacial cycle mis 4 3 transition abstract dansgaard oeschger d o cycles had far reaching effects on northern hemisphere and tropical climate systems during the last glacial period yet the climatic response to d o cycles in western north america is controversial especially prior to 55 ka we document changes in precipitation along the western slope of the central sierra nevada during early marine oxygen isotope stages mis 3 and 4 55 67 ka from a u series dated speleothem record from mclean s cave the timing of our multi proxy geochemical dataset is coeval with d o interstadials 15 18 and stadials including heinrich event 6 the mclean s cave stalagmite indicates warmer and drier conditions during greenland interstadials giss 15 18 signified by elevated 18o 13c reflectance and trace element concentrations and less radiogenic 87sr 86sr our record extends evidence of a strong linkage between high latitude warming and reduced precipitation in western north america to early mis 3 and mis 4 this record shows that the linkage persists in diverse global climate states and documents the nature of the climatic response in central california to heinrich event 6

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

silicate versus carbonate weathering in the himalaya a comparison of the arun and seti river watersheds abstract we studied the water chemistry of two large and geologically differing himalayan watersheds in order to maximize the contrast between silicate versus carbonate weathering effects on river chemistry our previous research involved the seti river of westernmost nepal geologically typical of many rivers in nepal in draining mixed carbonate silicate lithologies including abundant carbonate rocks of the lesser himalayan sequence for comparison the arun river was chosen for study because south of the himalayan front it drains almost exclusively greater and lesser himalayan silicate rocks despite this dominance of silicate rocks carbonate weathering probably of metamorphic calcite in great himalayan paragneisses is clearly in evidence in many arun watersheds weathering of silicate rocks exposed all along the arun south of the range front has a small impact on mainstem river chemistry the mainstems of both the seti and arun systems are dominated by weathering of carbonate rocks although the contribution of silicate weathering is more visible in arun mainstem chemistry the carbonate weathering source to the arun mainstem is probably both limestone in the tethyan sequence widely exposed in northern headwaters of the system and metamorphic calcite within the greater himalayan sequence a number of small watersheds along the arun and seti appear to be carbonate free they probably provide the best constraints to date on the ca na and mg na ratios of waters draining himalayan silicate rocks two critical parameters for calculation of co 2 consumption by silicate weathering in the himalaya the observed ca na and mg na ratios would produce slightly higher estimates of silicate weathering fluxes than previous studies the geologic contrasts between the seti and the arun produce large differences in the 87 sr 86 sr ratio of each mainstem unlike the major element chemistry the seti mainstem displays much higher 87 sr 86 sr ratios than the arun mainstem the opposite of the expected relationship since radiogenic silicate rocks of the greater and lesser himalaya are so widely exposed along the arun 87 sr 86 sr ratios of the arun mainstem never exceed 0 734 and show little downstream change as the mainstem passes through silicate rocks of the greater and lesser himalaya 87 sr 86 sr ratios of the seti mainstem increase sharply from 0 725 to 0 785 when the river enters the belt of metacarbonate rocks of the northern lesser himalayan sequence a pattern also displayed by other himalayan rivers such as the kali gandaki and bhotse khola metacarbonate rocks including those of the lesser himalaya are a major source of radiogenic sr in modern himalayan rivers and probably have been key players in elevating marine 87 sr 86 sr ratios since the early miocene

micro x ray fluorescence μxrf line scanning on cretaceous rudist bivalves a new method for reproducible trace element profiles in bivalve calcite the reconstruction of palaeoclimate on a sub annual scale requires the measurement of chemical proxies in fossil material at a high spatial resolution while various methods for trace element analysis on the micrometre scale are available they are usually destructive to the sample or not widely accessible this study evaluates the performance of a table top micro x ray fluorescence scanner in obtaining reproducible trace element profiles on bivalve calcite standard calibration and repeatability tests demonstrate the robustness of results obtained with this new generation micro x ray fluorescence device that uses a comparatively high excitation energy of 30 w results show that elemental abundances measured using this fast readily accessible and non destructive analytical setup are reproducible on the g g level and therefore suitable for the analysis of the abundance of commonly studied elements in bivalve calcite for example sr mn and fe spectra obtained in this study show considerable improvement in terms of signal to noise ratio compared to earlier table top xrf studies reliability of the measurements is tested using a conservative detection and quantification limit count rates of ca are used to check for point measurements disturbed by irregularities on the sample surface furthermore the method allows semi quantitative two dimensional element mapping which is a convenient tool for the detection of diagenetic alteration in fossil samples the method reveals records of sr ca fe ca and mn ca ratios in a late campanian vaccinites vesiculosus shell with sr ca ratios showing a trend opposite to mn ca and fe ca resulting trace element records are discussed in terms of seasonal cyclicity in the late cretaceous and diagenetic alteration of the fossil shell this article is protected by copyright all rights reserved

holocene and eemian climatic optima in the korean peninsula based on textural and carbon isotopic records from the stalagmite of the daeya cave south korea abstract textural and stable isotopic records from the absolute dated stalagmite of the daeya cave dy 1 provide new insights into the climatic evolution of the korean peninsula during the holocene and eemian climatic optima the stalagmite yielded ages of 8572 227 to 5907 158 and 1 23 456 535 to 1 19 837 1089 years which coincide with the holocene and eemian climatic optima respectively the stalagmite s 13 c record closely resembles previously reported chinese speleothem 18 o data thus it can be suggested that textural and geochemical results of the dy 1 reflect east asian monsoon intensity which is forced by summer insolation patterns in the northern hemisphere lighter carbon isotopic compositions well developed fibrous calcite crystals and their relatively faster growth rate in the stalagmite sample are interpreted to reflect the warmest and wettest climate conditions of the holocene and eemian interglacials both climatic optima took place when insolation was decreasing from its maximum level temperature in greenland was highest and sea level approached its maximum level these climatic optima also coincide with decreasing antarctic temperatures compared the dy 1 data to other proxies it is suggested that the holocene and eemian climatic optima developed through a balance among boreal insolation monsoon intensity and sea level also continental ice volume which are the main climatic forcing factors in the northern hemisphere these trends also follow the bi polar seesaw mechanism as previously described

start of the last interglacial period at 135 ka evidence from a high alpine speleothem a detailed study of growth periods of a flowstone from spannagel cave in the zillertal alps austria at 2500 m above sea level a site highly sensitive to climate changes offers unprecedented new insights into pleistocene climate change in central europe flowstone sample spa 52 has a high u content to 116 ppm analyses of this sample reveal that episodes of calcite deposition started at 204 3 ka 135 1 2 ka and 122 ka suggesting that at these times the mean air temperature at this high alpine site was within 1 5 c of the present day condition the beginning of growth at 135 ka corresponds to the ending of the last glaciation and is concordant with a midpoint age for the penultimate deglaciation at 135 2 5 ka as deduced from the absolutely dated oxygen isotope curve in sediments from the bahamas as well as with recent coral evidence from barbados indicating a high sea level already by 135 8 0 8 ka this set of data supports evidence against northern hemisphere forcing of termination ii because the insolation maximum is at 127 ka

cyclic rapid warming on centennial scale revealed by a 2650 year stalagmite record of warm season temperature 1 a 2650 year bc665 ad1985 warm season mjja may june july august temperature reconstruction is derived from a correlation between thickness variations in annual layers of a stalagmite from shihua cave beijing china and instrumental meteorological records observations of soil co2 and drip water suggest that the temperature signal is amplified by the soil organism co2 system and recorded by the annual layer series our reconstruction reveals that centennial scale rapid warming occurred repeatedly following multicentenial cooling trends during the last millennia these results correlate with different records from the northern hemisphere indicating that the periodic alternation between cool and warm periods on a sub millennial scale had a sub hemispherical influence

the precession phase of the boreal summer monsoon as viewed from the eastern mediterranean odp site 968 the astronomical timescale of the eastern mediterranean plio pleistocene builds on tuning of sapropel layers to northern hemisphere summer insolation maxima a 3000 year precession lag has become instrumental in the tuning procedure as radiocarbon dating revealed that the midpoint of the youngest sapropel s1 in the early holocene occurred approximately 3000 years after the insolation maximum the origin of the time lag remains elusive however because sapropels are generally linked to maximum african monsoon intensities and transient climate modeling results indicate an in phase behavior of the african monsoon relative to precession forcing here we present new high resolution records of bulk sediment geochemistry and benthic foraminiferal oxygen isotopes from odp site 968 in the eastern mediterranean we show that the 3000 year precession time lag of the sapropel midpoints is consistent with 1 the global marine isotope chronology 2 maximum monsoonal precipitation conditions in the mediterranean region and china derived from radiometrically dated speleothem records and 3 maximum atmospheric methane concentrations in antarctica ice cores we show that the time lag relates to the occurrence of precession paced north atlantic cold events which systematically delayed the onset of strong boreal summer monsoon intensity our findings may also explain a non stationary behavior of the african monsoon over the past 3 million years due to more frequent and intensive cold events in the late pleistocene

oxygen and carbon isotope ratios of lampsilis cardium unionidae from two streams in agricultural watersheds of iowa usa abstract climate archives preserved as seasonal variation in oxygen and carbon isotope ratios 18o and 13c in unionid shells potentially provide records of pre instrumental environmental conditions in mid to high latitude continental regions this study measured 18o and 13c values of biogenic carbonate and 18owater to investigate the timing of growth line formation and to examine the utility of lampsilis cardium as an environmental archive we tested the hypotheses that 1 l cardium precipitates its shell in isotopic equilibrium with the environment during biomineralization and 2 growth lines form seasonally during winter months these questions were addressed by monitoring water chemistry by tagging l cardium to record growth and by combining sclerochronology and stable isotope geochemistry temperature and 18owater were measured fortnightly from september 2002 to july 2004 with a break in sampling from december 2003 to february 2004 in two iowa rivers boone river and buffalo creek these data were used to calculate expected 18o values to compare to measured shell values one hundred fifty four individuals were marked at the postero dorsal margin in september 2002 and june 2003 to monitor growth seven recaptured shells collected in july 2004 were analyzed for shell 18o and 13c across three growth lines including growth lines prior to the initial marking period from the growing edge toward the umbo comparison of shell 18o with expected values revealed precipitation of 18o in equilibrium with the ambient environment from early spring to early fall winter values were not recorded due to winter growth cessation change in temperature or reaching a threshold temperature appeared to control the onset and cessation of growth moreover the locations of seasonal growth lines corresponded to winter growth cessation allowing the assignment of calendar years to growth lines seasonal growth lines were distinguished from non seasonal disturbance lines by their seasonal location inferred from the 18o time series recorded in shell growth thus we can faithfully reconstruct ontogeny through time and environmental and climate conditions from mid to high latitudes using l cardium variation in 13cshell followed a more or less sinusoidal trend similar to the seasonal profiles of 18oshell suggesting that seasonal processes influenced the variation in carbon isotopes reduced amplitudes and more negative 13cshell values with increasing age suggest that kinetic and or metabolic isotope effects become important through ontogeny as observed in other bivalves the profiles of 13cshell potentially record local differences in landscape vegetation however specific factors influencing 13cshell are unknown and further study of water quality are required to fully assess the variation of 13cshell as an environmental proxy

a geochemical study on the specific distribution of barium in lake biwa japan the vertical distribution of alkaline earth elements aees was measured in a mesotrophic lake lake biwa of japan by comparing the distribution profiles of the elements it was noticed that the dissolved barium concentration markedly decreased in the bottom layer during the stagnation stage of the lake this characteristic distribution disappeared in the circulation stage but appeared repeatedly in the succeeding stagnation stage such periodic variation of the barium distribution profile contrasts with the result that other aees were uniformly distributed without regard to depth or stage of lake water circulation adsorption of aees onto synthetic hydrous manganese oxide hmo was examined in lake water the results suggest that the specific distribution of barium observed in lake biwa was caused by the selective adsorption of the element onto hmo which is naturally produced at the bottom of the lake

tectonic and sedimentary evolution of the korean peninsula a review and new view abstract this review focuses on the tectonics and sedimentation of major sedimentary basins and orogenic belts late proterozoic neogene in the korean peninsula the korean peninsula is part of the amuria plate and represents an important link between continental blocks of north and south china and the island arcs of japan the basement rocks exposed in the kyonggi and yongnam massifs consist of 2 7 to 1 1 ga high grade gneiss and schist these massifs are separated by the okchon fold belt which comprises metasedimentary rocks and bimodal meta volcanic rocks the stratigraphy of the okchon group is unclear at present the okchon basin was probably initiated as an intraplate rift prior to the late proterozoic the hwanggangri formation clast bearing phyllite most likely represents deposition by subaqueous debris flows in slope environments of an enclosed basin the stratigraphic relationship between the okchon group and the choson supergroup cambro ordovician of the taebaeksan basin is poorly constrained the choson supergroup unconformably overlies the yongnam massif and consists mainly of carbonate sequence that formed mostly in shallow marine and tidal environments reflecting numerous sea level fluctuations the sequence is disconformably overlain by siliciclastic sequence of pyongan supergroup carboniferous triassic which formed most likely in shallow marine deltaic and fluvial environments the imjingang belt is an east trending fold and thrust zone and consists of metasedimentary rocks and volcaniclastics devonian carboniferous underlain unconformably by proterozoic basement rocks late proterozoic amphibolites of oceanic affinity were metamorphosed at about 8 13 kbar and 630 740 c during the late permian to the early triassic the south vergent contraction and top down to the north normal faulting are suggestive of a suture belt between the north china block sino korea craton and the south china block yangtze craton an extension of sulu belt across the yellow sea entire peninsula experienced strong deformation and metamorphism during the suturing event namely songrim orogeny during this orogenic event the kyonggi massif and the okchon basin accreted to the yongnam massif and taebaeksan basin along the south korean tectonic line running northeast southwest a series of northward trending thrust formed along the boundary zone to the east kaktong and kongsuwon thrusts and others piggyback basins locally developed along the thrust faults forming the taedong group the crustal deformation resumed in the early to late jurassic daebo event under contractional setting dextral ductile shearing associated with thrusting and folding continued in the mid southern part of the peninsula it was due to orthogonal northwestward subduction of the izanagi plate under the asian continent the yongnam massif experienced continuous dextral offset along the honam shear zone in the early cretaceous the izanagi plate began to subduct northward and caused formation of strike slip basins in retroarc setting i e kyongsang basin in the southeastern part and a number of small scale basins in the mid southwestern part of the peninsula small scale alluvial fans and fluvial channel networks formed in the basin margin and were transitional to ephemeral lacustrine systems under semiarid to arid conditions extensive intrusion of granitoids occurred from triassic to early tertiary with a gap between 160 and 100 ma representing continental magmatic arc in the tertiary the southeastern margin of the korean peninsula experienced back arc opening pull apart basins formed in the miocene bounded by the yangsan and hupo faults the yonil group sedimentary fill of the pohang basin comprises more than 1 km thick siliciclastic sequence which represents deposition in fan delta systems on the hanging wall of the yangsan fault thick more than 10 km thick sediments in the ulleung basin margin were deformed in the late miocene due to the northward movement of kyushu block quarternary volcanic events in cheju island represent intraplate hot spots

timing and hydrological conditions of sapropel events in the eastern mediterranean as evident from speleothems soreq cave israel this paper explores the connection between the timing of sapropel events in the eastern mediterranean sea and the time of low 18o events in speleothems of the soreq cave israel a new well dated 18o and 13c profile of the soreq cave speleothems for the last 140 kyr reveals five prominent low 18o events dated at 124 to 119 kyr with the main peak at 122 kyr event v 108 to 100 kyr with peaks at 107 and 102 kyr event iv 85 to 79 kyr with peak at 80 kyr event iii 55 to 52 kyr with a peak at 54 kyr event ii and 8 5 to 7 kyr with peaks at 8 5 and 7 kyr event i these events are characteristic of period of enhanced rainfall in the eastern mediterranean area particularly so for events v and i where the marked decrease in 18o and the correspondingly marked increase in 13c indicate very wet conditions the chronology of the low 18o events v iv iii and i match the ages estimated for the formation of sapropels s5 s4 s3 and s1 which are also associated with high hydrological activity thus it is suggested that the low 18o events in the soreq cave speleothems constrain the maximum duration of the sapropel formation pollen data from the sapropel layers and the isotopic pattern of the speleothems indicate that sapropels s5 and s1 were deposited during very wet periods when there were major decrease in the sea surface salinity coupled with frost free winters and drought free summers sapropels s4 and s3 were formed during periods of increased precipitation but ones in which the general climate was mediterranean semi arid

antarctic link with east asian summer monsoon variability during the heinrich stadial bolling interstadial transition abstract previous research has shown a strong persistence for direct teleconnections between the east asian summer monsoon easm and high northern latitude climate variability during the last glacial and deglaciation in particular between monsoon weakening and a reduced atlantic meridional overturning circulation amoc however less attention has been paid to easm strengthening as the amoc was reinvigorated following peak northern hemisphere nh cooling moreover climate model simulations have suggested a strong role for antarctic meltwater discharge in modulating northward heat transport and hence nh warming yet the degree to which southern hemisphere sh climate anomalies impacted the asian monsoon region is still unclear here we present a new stalagmite oxygen isotope record from the easm affected region of central china which documents two prominent stages of increased 18 o depleted moisture delivery to the region through the transition from heinrich stadial 1 hs1 to the bolling allerod b a interstadial this is in general agreement with the other monsoonal records from both nh and sh mid to low latitudes through novel comparisons with a recent iceberg rafted debris ird record from the southern ocean we propose that the two stage easm intensification observed in our speleothem records were linked with two massive antarctic icesheet discharge aid events at 16 0 ka and 14 7 ka immediately following the peak hs1 stadial event notably the large increase in easm intensity at the beginning of the hs1 b a transition 16 ka is relatively muted in the nh higher latitudes and better aligns with the changes observed in the sh indicating the antarctic and southern ocean perturbations could have an active role in driving the initial easm strengthening at this time indeed antarctic freshwater input to the southern ocean during these aid events would have cooled the surrounding surface waters and caused an expansion of sea ice restricting the southern extent of the sh westerlies moreover increased meltwater flux during ird events would have freshened antarctic intermediate water leading to the increased formation of north atlantic deep water and enhanced north atlantic subsurface heat release and causing a strengthening of the amoc during the hs1 bolling transition the result of this sequence of events would have been warming in the north atlantic whilst at the same time cooling in the antarctic the ensuing interhemispheric temperature gradient would have acted to push the itcz northward weakening the australian indonesian summer monsoon aism whilst intensifying the easm

testing the effect of carbonate saturation on the sr ca of biogenic aragonite a case study from the river ehen cumbria uk it has been suggested that the incorporation of strontium into biogenic aragonite may be influenced by the degree of carbonate saturation in aquatic environments we measured the sr ca ratios of river water and the aragonitic shells of freshwater bivalves margaritifera margaritifera from two sites with different carbonate saturation states in the river ehen cumbria uk shell sr ca and river water sr ca are 0 1 mmol mol and 0 42 mmol mol lower respectively at the high carbonate saturation site however the distribution coefficients of strontium into aragonite kd are the same 0 28 at both sites these analyses show that sr uptake into aragonite bivalve shells is not affected by the degree of carbonate saturation of the water perhaps reflecting a strong biological control on trace element incorporation

reconstructing the history of fluid flow at cold seep sites from ba ca ratios in vesicomyid clam shells hydrogen sulfide discharge at cold seep sites is recorded as enrichment in the barium to calcium ba ca ratio in shells of vesicomyid clams collected live from cold seeps in monterey canyon and the cascadia margin a direct relationship between increased ba fluxes from cold seeps and ba incorporation into shells was established for the cascadia margin site for the monterey canyon site a 2 yr episode of high fluid flow centered on 1992 was inferred from coherent changes in the ba ca profiles of threecalyptogena kilmerishells comparison with precipitation and d 18 o data indicates that this high flow period may have been driven by an increase in rainfall after the 1988 1990 california drought high resolution records preserved in clam shells are shown to be useful in elucidating characteristics history and possible mechanisms driving fluid discharge at continental margin seeps thus establishing their potential use as paleotracers of fluid seepage events an extensive set of geophysical and geochemical measurements is currently available to document the flow and expulsion of fluids at transform and convergent margins it is now recognized that such fluid discharge has far reaching implications that include hydrocarbon prospecting benthic ecosystem structure and function and groundwater research moore 1999 at present we are unable to incorporate geochemical data from cold seeps to models quantifying their effects on marine geochemical budgets because we lack a clear understanding of the spatial and temporal variability of these systems and of the mechanisms responsible for the advective transport however vent macrofauna may afford such an opportunity by recording in their shells the immediate environment in which they grow and thereby allowing us to reconstruct the variability in fluid discharge rates vesicomyid clams live in association with sites of sulfide 1

paleohydrologic regimes in the southwestern great basin 0 3 2 my ago compared with other long records of gobal climate abstract nine distinct paleohydrologic regimes in the southwestern great basin over the last 3 2 my are recorded by the lacustrine deposits in km 3 a 930 m core from searles lake california these are characterized as being wet intermediate or dry like today excepting the present incomplete regime each lasted 0 12 to 0 76 my major regime changes 0 01 0 13 0 6 and 2 5 my ago appear to coincide with recognized changes in global ice sheet histories as represented by 18 o and other records from marine sediments but comparable changes 0 3 1 0 1 3 and 2 0 my ago do not appear to coincide closely with comparable perturbations in ice sheet histories however all regime boundaries during the last 1 75 my coincide closely in time with changes in sea surface temperatures in the tropical atlantic and many coincide with other deep sea and continental paleoclimatic boundaries the average duration of these paleohydrologic regimes was about 0 4 my standard deviation 0 2 my or less depending on assumptions and it is suggested that the regime boundaries reflect times of change in global sea surface temperatures possibly controlled in part by the earth s 413 000 yr orbital eccentricity cycle during the wettest and driest regimes in the searles lake area lake levels were not sufficiently affected by the 23 000 to 42 000 or 100 000 yr climate cycles related to high latitude ice sheet fluctuations to produce changes in the lacustrine sediment character during intermediate regimes however when lacustrine sedimentation in this area was more sensitive to climate the sediments in km 3 record lake fluctuations with average frequencies near those of the ice sheets this seems to indicate that the high latitude ice sheet fluctuations caused local climatic perturbations but did not dominate the hydrologic component of climate in this area other lacustrine deposits in the southwestern great basin of california and nevada have ages comparable in part to those of the wet to intermediate regimes indicated by km 3 and they may all be products of finite periods when lake expansion alluvial fan growth increased spring discharge and fluvial deposition were promoted in this area by widespread wet climates glacier expansion in the sierra nevada may also have been primarily an expression of and in phase with these wet regimes

middle holocene environmental change in central korea and its linkage to summer and winter monsoon changes to trace the surficial responses of lowlands to past climate change we investigated 13c in total organic carbon toc c n ratios magnetic susceptibility ms and silicon si intensity directly proportional to concentration in wetland sediments collected from the gimpo area of central korea covering 6600 4600 cal yr bp two organic layers with high toc negatively depleted 13ctoc values 27 to 29 low ms values and low si intensities were found at 6200 5900 and 5200 4800 cal yr bp respectively these middle holocene wet periods corresponded to relatively intensified summer monsoon and solar activity periods the intervening dry period 5900 5200 cal yr bp with high ms high si and low toc corresponded to an intensified dust activity interval and stronger winter monsoon this multi centennial climatic fluctuation of wet periods 6200 5900 cal yr bp and 5200 4800 cal yr bp and an intervening dry period 5900 5200 cal yr bp in central korea was more synchronous with climate change in the arid inner part of china than with that in south china suggesting possible strong high latitude driven climatic influences e g north atlantic cooling events during the middle holocene

textural and carbon isotopic evidence of monsoonal changes recorded in a composite type speleothem from korea since mis 5a abstract textural and stable isotopic records of a composite type speleothem from gwaneum cave in the eastern part of the korean peninsula show prominent paleoenvironmental changes since mis marine oxygen isotope stage 5a based on 230 th 234 u dating the speleothem experienced growth from 90 9 6 5 ka to 1 2 0 5 ka with several hiatuses four growth phases a b c and d are recognized based on speleothem type and texture very irregular and laterally discontinuous growth laminae in phases b and c indicate that the cave coralloids grew over the stalagmite phase a when the supply of dripping water became limited variations within the 13 c time series of phase a are interpreted as responses to millennial scale fluctuations of the east asian monsoon intensity during mis 5a the monsoonal interpretation is based on the idea that 13 c values reflect the isotopic composition of soil derived co 2 which in turn should relate to monsoon driven changes in terrestrial productivity above the cave during the mis 5a our reconstruction reveals that the significant monsoonal changes on the korean peninsula occurred in conjunction with changes in sea level and or oceanic circulations during the transition period from mis 5a to mis 4

rainfall and hydrological controls on speleothem geochemistry during climatic events droughts and typhoons an example from seopdong cave republic of korea abstract a five year old 20 cm long soda straw sd 1 was analyzed geochemically to delineate the relationship between the geochemical record and climatic behavior the growing tip of the soda straw was marked on july 18 1999 and the sample was collected on july 16 2004 thus the growth period of this speleothem is well constrained during the five years the soda straw grew about 20 cm a mean growth rate of about 4 cm year fast growth rate of this speleothem enabled not only to understand seasonal variations of geochemical data but also to compare these data directly with outside climatic variations near the cave 210 pb ex excess or unsupported 210 pb results suggest that the overall pattern of 210 pb ex changes as well as the frequency and relative intensity of their peaks show a strikingly similar pattern to that of the amounts of precipitation in the study area this suggests that 210 pb ex was transported into the cave with infiltrating rainwater mostly during rainy summers because 210 pb ex is a particle reactive element controlling detailed growth rates by the 210 pb ex fluctuations it can be noticed that 18 o compositions vary very little in spite of significant droughts and typhoon events whereas 13 c values clearly display impacts of a severe drought from 2000 to 2001 the sr ca ba ca u ca and mn ca ratios coincide with the 13 c trends and show anomalies during the drought period these coeval trends strongly indicate that hydraulic factors in vadose zone that were directly controlled by the amount of rainfall influenced on the geochemical imprints of the sd 1 this study illustrates the behavior of an atmospheric radionuclide 210 pb ex the o and c stable isotopes and trace elements in calcite speleothems and furthermore implies that they can be used to detect short term climatic behavior including climatic extreme events as well as the long term climatic fluctuations in the past

orbital and millennial antarctic climate variability over the past 800 000 years a high resolution deuterium profile is now available along the entire european project for ice coring in antarctica dome c ice core extending this climate record back to marine isotope stage 20 2 800 000 years ago experiments performed with an atmospheric general circulation model including water isotopes support its temperature interpretation we assessed the general correspondence between dansgaard oeschger events and their smoothed antarctic counterparts for this dome c record which reveals the presence of such features with similar amplitudes during previous glacial periods we suggest that the interplay between obliquity and precession accounts for the variable intensity of interglacial periods in ice core records

biological and water chemistry controls on sr ca ba ca mg ca and δ18o profiles in freshwater pearl mussel hyriopsis sp abstract we investigated oxygen isotope and sr ca ba ca and mg ca ratios in shells of a commercially cultured freshwater pearl mussel hyriopsis sp unionidae and ambient water the first order fluctuations of oxygen isotope ratios of the outer shell layer along the maximum growth axis recorded the mussels annual growth from 2002 to 2007 clear annual sr ca cycles suggest that sr was incorporated into the shells at a high rate during warm seasons all three examined shells showed a clear decrease in annual average sr ca with age inter and intra annual trends suggest that sr incorporation was higher during periods of faster growth the ba concentration and the ba ca ratio of ambient water showed neither an annual periodicity nor a seasonal trend in contrast to the findings of an inorganic aragonite precipitation experiment ba ca was positively correlated with ambient temperature in addition ba ca and sr ca ratios were positively correlated with each other these results suggest that not thermodynamic equilibrium partitioning but the shell growth rate controls ba incorporation into hyriopsis shells the mg ca profiles of the three shells suggest that complex factors control the incorporation of mg into shell aragonite water temperature and annual growth rates did not significantly influence mg incorporation and substantial interspecimen differences suggested that physicochemical factors do not exert any systematic control on mg ca ratios in hyriopsis instead the mg content of shell aragonite might reflect biological contamination with organic material or adsorption phenomena during crystal precipitation rather than regulated substitution into the aragonite crystal lattice our results suggest that trace element profiles in aragonitic bivalve shells could be interpreted as the result of strong biological controls over riding environmental influences on trace element incorporation

sr mg ratios of modern marine calcite empirical indicators of ocean chemistry and precipitation rate holocene biotic and abiotic marine calcite have a similar range of mg contents 0 to 22 and 4 to 21 mol mgco3 respectively yet biotic calcite has sr2 concentrations that are consistently 1250 ppm higher than those of abiotic calcite as in laboratory experiments a positive linear relation is observed between dsr and calcite mg content this produces two distinct linear trends on a plot of sr2 vs mg2 concentrations principal axes of variation for both trends have similar slopes yet distinctly different sr2 concentration intercepts biotic y 0 024x 1298 r2 0 70 abiotic y 0 027x 47 r2 0 77 the similar slopes of these trends reflect the constancy of mgca and srca ratios of modern seawater equations describing the dependence of dsr on calcite mg content are derived from both trends biotic dsr 3 16 x 10t 6 ppm mg 0 169 abiotic dsr 3 52 x 10 6 ppm mg 0 0062 characterization of sr mg trends for holocene materials allows comparison with analogous trends from ancient samples to estimate relative changes in seawater mgca and srca ratios the relatively high sr contents of biotic calcite result from rapid precipitation rates associated with shell accretion in marine organisms calcites precipitated from seawater in laboratory experiments have dsr values that are similar to those of biotic marine calcite suggesting that both precipitate at approximately the same rate our estimates of surface area normalized precipitation rates in planktonic and benthonic foraminifera are comparable to those of seeded ph stat experiments we conclude that the dsr values for biotic and experimental marine calcite are kinetically controlled whereas the lower precipitation rates of abiotic marine calcite yield dsr values that approximate equilibrium conditions experimentally derived equations describing the relation between dsr and calcite precipitation rate indicate that the offset in sr content between biotic and abiotic calcite is the result of abiotic precipitation rates that are two to five orders of magnitude lower than those of biotic precipitates however observations of naturally occurring marine cements suggest that the five order of magnitude offset best represents natural system processes

holocene and pleistocene pluvial periods in yemen southern arabia arabia is an important potential pathway for the dispersal of homo sapiens out of africa yet because of its arid to hyper arid climate humans could only migrate across southern arabia during pluvial periods when environmental conditions were favorable however knowledge on the timing of arabian pluvial periods prior to the holocene is mainly based on a single and possibly incomplete speleothem record from hoti cave in northern oman additional terrestrial records from the arabian peninsula are needed to confirm the hoti cave record here we present a new speleothem record from mukalla cave in southern yemen the mukalla cave and hoti cave records clearly reveal that speleothems growth occurred solely during peak interglacial periods corresponding to marine isotope stages mis 1 early to mid holocene 5 1 5 3 5 5 eemian 7 1 7 5 and 9 of these humid periods highest precipitation occurred during mis 5 5 and lowest during early to middle holocene

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

and ratios in skeletal calcite of mytilus trossulus covariation with metabolic rate salinity and carbon isotopic composition of seawater minor element and isotopic compositions of marine bivalve calcite are frequently used as proxy records of seawater temperature and salinity although molluscan calcite is secreted at or near oxygen isotope equilibrium the influence of metabolic activity i e vital effects on skeletal srca ratios and 13c values is not well known we present measurements of skeletal chemistry from a consecutive samples milled in chronological order from the organism s final year of growth and b adjacent samples within three separate growth bands of the marine mussel mytilus trossulus to investigate chemical disequilibrium effects among different parts of the shell seawater temperature and salinity were monitored for one year at squirrel cove british columbia at the end of the year a young rapidly growing mussel mussel a and an old slowly growing mussel mussel b were harvested from this site growth bands within the shells were sampled to provide a chronological record of shell carbonate chemistry results from consecutive samples show 1 a significantly higher average srca ratio in mussel a than that in mussel b and 2 13c values that correlate well with salinity in mussel a but not in mussel b results from time equivalent adjacent samples show 1 higher srca and 13c values near the ventral margin than at time equivalent regions on lateral margins of the shell and 2 little or no variation in 18o values these observations suggest that skeletal chemistry srca and 13c is primarily controlled by rate of mantle metabolic activity and secondarily modified by variation in seawater salinity because metabolic activity in the mantle at the site of carbonate precipitation varies with shell curvature the composition of calcite secreted along lateral margins is influenced to a greater extent by metabolic activity than calcite secreted coevally at the central margin of the shell hence the chemistry of calcite secreted at the ventral margin is precipitated in near equilibrium with seawater and allows accurate estimation of seawater srca ratios and carbon isotopic composition in contrast shell precipitation along lateral margins is dominantly controlled by metabolic activity and calcite chemistry is not in equilibrium with ambient seawater in this context we present a biomineralization model where variations in skeletal srca and 13c values are explained in the context of mantle metabolic activity and seawater salinity

dating of late pleistocene interglacial and interstadial periods in the united kingdom from speleothem growth frequency abstract the growth of speleothems is indicative of interglacial and interstadial conditions in the united kingdom since their growth is dependent on two factors first the occurrence of significant diffuse groundwater recharge and second the biogenic production of carbon dioxide in the soil both are dependent on temperature and water availability the growth frequency of speleothems is examined using a cumulative distributed error frequency method applied to 341 uncontaminated uranium series age determinations the curves derived are shown to be statistically stable and the ages of the peaks are interpreted as the best estimates of the ages of interglacial and interstadial periods ten such periods are recognized during the interval 220 000 to 20 000 yr b p considerably more than are currently recognized in the uk pollen and coleoptera based quaternary stratigraphy correlations between the speleothem growth frequency peaks and last interglacial ipswichian sites can be made but correlations with last glacial devensian interstadial sites are limited because of the paucity of dates the speleothem growth frequency record provides a well dated terrestrial chronology for the past 140 000 yr b p which directly reflects regional palaeoclimatic conditions in britain and should prove very useful in unravelling the complex stratigraphy of the devensian and ipswichian stages

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

mid latitude interhemispheric hydrologic seesaw over the past 550 000 years an interhemispheric hydrologic seesaw in which latitudinal migrations of the intertropical convergence zone itcz produce simultaneous wetting increased precipitation in one hemisphere and drying in the other has been discovered in some tropical and subtropical regions for instance chinese and brazilian subtropical speleothem cave formations such as stalactites and stalagmites records show opposite trends in time series of oxygen isotopes a proxy for precipitation variability at millennial to orbital timescales suggesting that hydrologic cycles were antiphased in the northerly versus southerly subtropics this tropical to subtropical hydrologic phenomenon is likely to be an initial and important climatic response to orbital forcing the impacts of such an interhemispheric hydrologic seesaw on higher latitude regions and the global climate system however are unknown here we show that the antiphasing seen in the tropical records is also present in both hemispheres of the mid latitude western pacific ocean our results are based on a new 550 000 year record of the growth frequency of speleothems from the korean peninsula which we compare to southern hemisphere equivalents the korean data are discontinuous and derived from 24 separate speleothems but still allow the identification of periods of peak speleothem growth and thus precipitation the clear hemispheric antiphasing indicates that the sphere of influence of the interhemispheric hydrologic seesaw over the past 550 000 years extended at least to the mid latitudes such as northeast asia and that orbital timescale itcz shifts can have serious effects on temperate climate systems furthermore our result implies that insolation driven itcz dynamics may provoke water vapour and vegetation feedbacks in northern mid latitude regions and could have regulated global climate conditions throughout the late quaternary ice age cycles

response of heterogeneous rainfall variability in east asia to hadley circulation reorganization during the late quaternary abstract the quaternary east asian summer rainfall evolution reconstructed with the chinese speleothem 18o records shows the consistency throughout the region of east asia and has long been considered equivalent to the monsoon intensity its variation and teleconnection with global climate were usually interpreted by the meridional shift of the intertropical convergence zone itcz however many other proxy records climate simulations and meteorological observations suggest the inconsistent rainfall patterns in the different regions of east asia on multi timescales such spatial heterogeneity in quaternary east asian summer rainfall indicates that the hydroclimate in this region is not fully paced by the migration of the itcz here we report a sediment record of rainfall evolution during the last 400 ka in the northern east china sea and this record in combination with a transient climate model simulation indicates an out of phase relationship between rainfall over middle southeastern east asia and northern and southwestern east asia on the precession band with high boreal summer insolation corresponding to the increased rainfall intensity in the northern and southwestern east asia however decreased rainfall intensity in the middle east asia we attribute this regional heterogeneity in east asian rainfall to the reorganization of the hadley circulation including shifts in the ascending branch itcz and descending branch subtropical westerly jet in response to changes in the hemispheric meridional temperature gradient our results highlight the crucial role of the hadley circulation in the east asian hydroclimate and have important implications for future climate projections

minor and trace elements in sclerosponge ceratoporella nicholsoni biogenic aragonite near the inorganic endmember abstract the trace and minor element composition have been investigated in the accretionary skeletons of two specimens of the caribbean sclerosponge species ceratoporella nicholsoni one from tongue of the ocean bahamas toto and the other from pear tree bottom jamaica ptb both sclerosponges were analyzed at high resolution using laser ablation icp ms la icp ms and verified using wet chemical methods icp oes the shallow ptb sclerosponge 25 m was analyzed for a short temperature calibrated record of trace and minor elements while the toto sclerosponge 146 m was analyzed for a century long record from subsurface waters the resulting ba ca mg ca pb ca and u ca ratios were compared with sr ca ratios which have been shown to reliably record seasonal scale temperature change in sclerosponges close to equilibrium precipitation of inorganic aragonite sclerosponge aragonite incorporates minor and trace elements according to general mineralogic constraints with less vital effects than other calcium carbonate secreting organisms this is perhaps most obvious in the behavior of mg ca ratios which show an inverse correlation to temperature unlike any other calcite or aragonite organism despite having mg concentrations 1 mmol mol within published estimates of equilibrium aragonite ratios of mg ca and ba ca show a strong positive correlation despite large differences in ionic radii and u ca values 3 15 mol mol are 2 5 higher in sclerosponge aragonite than in aragonite from corals supporting earlier work ratios of u ca show an insignificant correlation with temperature dependent sr ca ratios r 2 0 05 supporting existing theories that temperature signals recorded by u ca ratios can be convolved with ph co 3 2 and phosphate signals differences between sclerosponge aragonite and other calcium carbonate arising from siliceous spicule contamination are unlikely because of the small mole percent of silicon in the aragonite small differences between the two sclerosponges were noticed in pb ca and sr ca because of the average ages of the sampled material and average temperatures of the ambient environment respectively anomalies between la icp ms and icp oes were noticed in measurements of ba ca and pb ca due to standardization differences for la icp ms ba ca and measurements close to the instrument detection limits of pb icp oes

stable isotope stratigraphy of a late last interglacial speleothem from rana northern norway abstract a stalagmite from rana northern norway dated by the tims uranium series technique yields records of stable oxygen and carbon isotopes covering the period from late marine oxygen isotope substages mis 5e to 5a that is 123 350 to 73 300 yr ago rapid growth 46 m yr between 123 350 and 119 500 yr ago reflects climatic conditions favorable for speleothem growth this period is characterized by century to millennial scale oscillations in both stable isotope records where both the absolute values and the isotope ranges are similar to holocene and older samples from the region from 119 500 to 107 700 yr ago speleothem growth was slow 0 7 m yr and between 107 700 and 73 300 yr ago growth is barely noticeable 0 07 m yr during the period of slow growth the stable isotope records show an overall enrichment trend the transition between rapid and slow growth rate occurring sometime between 119 500 and 107 700 yr ago is believed to reflect the termination of interglacial climate in this region the absence of detritus and corrosion features in the slowly deposited calcite suggests that the valley outside the cave remained sufficiently ice free for speleothem growth to occur until at least 73 300 yr ago

high resolution climate simulation of the last glacial maximum the climate of the last glacial maximum lgm is simulated with a high resolution atmospheric general circulation model the ncar ccm3 at spectral truncation of t170 corresponding to a grid cell size of roughly 75 km the purpose of the study is to assess whether there are significant benefits from the higher resolution simulation compared to the lower resolution simulation associated with the role of topography the lgm simulations were forced with modified climap sea ice distribution and sea surface temperatures sst reduced by 1 c ice sheet topography reduced co2 and 21 000 bp orbital parameters the high resolution model captures modern climate reasonably well in particular the distribution of heavy precipitation in the tropical pacific for the ice age case surface temperature simulated by the high resolution model agrees better with those of proxy estimates than does the low resolution model despite the fact that tropical ssts were only 2 1 c less than the control run there are many lowland tropical land areas 4 6 c colder than present comparison of t170 model results with the best constrained proxy temperature estimates noble gas concentrations in groundwater now yield no significant differences between model and observations there are also significant upland temperature changes in the best resolved tropical mountain belt the andes we provisionally attribute this result in part as resulting from decreased lateral mixing between ocean and land in a model with more model grid cells a longstanding model data discrepancy therefore appears to be resolved without invoking any unusual model physics the response of the asian summer monsoon can also be more clearly linked to local geography in the high resolution model than in the low resolution model this distinction should enable more confident validation of climate proxy data with the high resolution model elsewhere an inferred salinity increase in the subtropical north atlantic may have significant implications for ocean circulation changes during the lgm a large part of the amazon and congo basins are simulated to be substantially drier in the ice age consistent with many but not all paleo data these results suggest that there are considerable benefits derived from high resolution model regarding regional climate responses and that observationalists can now compare their results with models that resolve geography at a resolution comparable to that which the proxy data represent

high resolution record of northern hemisphere climate extending into the last interglacial period high resolution record of northern hemisphere climate extending into the last interglacial period

seasonal stable isotope variations of the modern amazonian freshwater bivalve anodontites trapesialis in a floodplain lake of the amazon river near the city of iquitos northeastern peru a one year monitoring experiment was conducted during which water samples and living bivalves anodontites trapesialis were collected with the aim to investigate seasonal 18o variation in and fractionation between bivalve aragonite and host water both host water and molluscan growth increments show more than 8 seasonal variation in 18o in the floodplain lake under study the 18o variation of the water is controlled by contrasting dry and wet season evaporation precipitation regimes molluscan 18o appears to be in equilibrium with the host water although an approximately 4 0 offset occurs 13c records of water and bivalves are in good agreement suggesting that both 18o and 13c of the shells of freshwater bivalve a trapesialis are good recorders of palaeo environmental conditions the 13c of dissolved inorganic carbon dic is governed by plant growth and or by changes in aquatic chemistry affecting the dic pool

modelling karst vadose zone hydrology and its relevance for paleoclimate reconstruction abstract understanding past climatic changes allows us to better understand how our planet will evolve in the future one important source of information on paleoclimate is the analysis of speleothems that develop in karst caves and conduits due to the dissolution and precipitation of calcite however there are many uncertainties in paleoclimatic reconstruction with speleothems one of them being hydrological variability up to now only few studies have considered the impact of hydrological variability on speleothem formation and composition this review paper will provide an introduction to hydrological processes that have the potential to affect speleothem composition and the hydrological modelling approaches that are able to account for them it presents the current state of knowledge on paleoclimatic reconstruction using speleothems and shows that many important flow and transport processes have not yet been included in the interpretation of these archives mostly due to a lack of field information to parametrize them possible directions of future research efforts therefore include a better exploration of karst vadose zone processes and new approaches to incorporate this information into simulation models finally we foresee the exciting advances in reconstructing paleohydrology using karst hydrology models combined with speleothem growth rate and geochemical composition to understand how past climate changes affected the hydrological cycle and water availability

500 ka precipitation record from southeastern australia evidence for interglacial relative aridity 230 th 234 u dating of speleothems from southeastern australia documents changes in effective precipitation over the past 500 k y at a temporal resolution not previously achieved results show that the highest effective precipitation for the southeastern interior of australia occurred during stadials and cool interstadials of the past four glacial cycles interglacials and warm interstadials as well as glacial maxima are comparatively arid we suggest that lower regional temperatures over the continent and changes in atmospheric circulation stronger walker circulation produced the observed periods of increased effective precipitation

reconstruction of the northeast asian monsoon climate history for the past 400 years based on textural carbon and oxygen isotope record of a stalagmite from yongcheon lava tube cave jeju island korea abstract paleoclimatic changes over the past 400 years were investigated based on textural and geochemical characteristics of the yc 2 stalagmite which grew in yongcheon cave lava tube cave on jeju island korea the stalagmite is about 68 mm long and annual growth laminae are distinctively identified the age of the stalagmite was mainly determined by counting annual growth laminae supplemented by other radiometric dating methods and it is estimated that the stalagmite grew at least for ca 242 years including the hiatus this hiatus is located at about 15 mm from the base and is present in the form of one thick brown growth lamina which was formed when the stalagmite stopped to grow texturally the stalagmite can be divided into two phases fluid inclusion poor compact columnar calcite phase a and fluid inclusion rich sparse columnar calcite phase b this textural division is intimately related to the spacing of growth laminae that is phase a is characterized by narrower spacing of growth laminae phase a with narrow spaced growth laminae indicates the slower growth rate due to lower amount of rainfall when northeast asian summer monsoon intensity was relatively lower based on high resolution carbon isotope trend the stalagmite can be divided into three stages stages i ii and iii the relatively more positive carbon isotopic compositions of the stage i 13 c 3 3 0 4 pdb in the lower part indicate that it grew during the little ice age lia under cold and dry climate with less vegetation the stage ii is a transitional period from cold and dry to warm and wet climate with a continuous decrease in carbon isotope values from 0 6 to 9 6 in 13 c this stage shows the gradual weakening of the lia climate carbon isotope trend also suggests that the lia interval was terminated near middle 1870 s around korean peninsula relatively low carbon isotopic compositions during stage iii 13 c 11 0 8 0 in the upper part should indicate that climate was changed to the warm and wet current warm period warming since 1960 can also be recognized complete coincidence between textural data internal calcite texture and growth laminae spacing and high resolution carbon isotope compositions strongly suggests that past climate changes such as monsoonal variations in northeast asia have been clearly recorded in the stalagmite in yongcheon cave

the long lived mollusc arctica islandica a new paleoceanographic tool for the reconstruction of bottom temperatures for the continental shelves of the northern north atlantic ocean the carbonate shell of the bivalve arctica islandica has been recognized for more than a decade as a potentially important marine geochemical biorecorder owing to this species great longevity 200 years and wide geographic distribution throughout the northern north atlantic ocean a region vital to global climate and ocean circulation however until now this potential has not been realized owing to the difficulty of precisely sampling the shell of this slow growing species using newly available automated microsampling techniques combined with micromass stable isotope mass spectrometry a stable oxygen isotope record 1956 1957 and 1961 1970 has been obtained from a live captured 38 year old a islandica specimen collected near the former position of the nantucket shoals lightship 41 n 69 w the shell s 18o signal is compared with an expected signal derived from ambient bottom temperature and salinity data recorded at the lightship for the same period the results show that a islandica s 18o record 1 is in phase with its growth banding confirming the annual periodicity of this species growth bands 2 is in oxygen isotopic equilibrium with the ambient seawater 3 shows a consistent shell growth shutdown temperature of 6 c which translates into an 8 month may december shell growth period at this location and 4 records the ambient bottom temperature with a precision of 1 2 c these results add important information on the life history of this commercially important shellfish species and demonstrate that a islandica shells can be used to reconstruct inter and intra annual records of the continental shelf bottom temperature

millennial scale asian monsoon variability during mis 9 revealed by a high resolution stalagmite δ18o record in luoshui cave central china abstract a 67 yr resolution 18o profile of a230th dated stalagmite from luoshui cave central china is presented to refine the asian summer monsoon asm history from 336 to 290 kyr bp the sub stages of marine isotope stage 9 mis 9 are clearly reflected in the luoshui 18o record in line with changes in the northern hemisphere summer insolation nhsi the concurrency of eight weak monsoon intervals wmis between 320 and 290 kyr bp and shifts in the atlantic oceanic circulation suggest that monsoon weakening was forced by northern high latitude climate oscillations with north south shifts in the intertropical convergence zone itcz spectrum analyses show a cyclic change of 1 4 kyr between 320 and 290 kyr bp similar to the dansgaard oeschger cycles during the last glacial period this suggests a relatively unstable monsoon state when the northern ice volume reached intermediate levels the detrended 18o agrees well with the 13c record on the millennial to sub millennial scales suggesting a coupling of monsoon climate and cave environment after removal of the summer insolation signal at 65 n the residual luoshui 18o record is highly similar to orbital and millennial scale temperature changes in antarctica in an anti phased fashion revealing the significant influence of southern hemispheric climates on asm intensity the absence of counterparts of the two wmis between 315 and 310 kyr bp in antarctica however indicates a complicated teleconnection

the use of oxygen isotope variation in shells of estuarine mollusks as a quantitative record of seasonal and annual colorado river discharge abstract we describe a new method for the calculation of river flow that uses the oxygen isotope composition of bivalve mollusk shells that grew in the river water seawater mixing zone of the colorado river estuary sclerochronological techniques are used to identify tidally induced fortnight scale bundles of daily growth increments within shell cross sections these fortnightly markers are used to establish a chronology for samples taken for 18 o analysis a composite seasonal 18 o profile derived from five shells that grew in the absence of river water flow is used as a baseline against which profiles of river influenced shells are compared because this comparison is between matched fortnights within a year the temperature of shell growth is likely to be very similar the difference in 18 o between the river influenced shell and the no flow composite shell therefore represents the change in the 18 o of the water due to the presence of river water in the mixing zone the river water end member is also determined within a fortnightly context so that the change in the 18 o of mixing zone water can be used to calculate the relative proportions of seawater and fresh water the fresh water end member is calculated from the 18 o of bivalves alive prior to the emplacement of dams and water diversions on the colorado river the marine end member is based on direct measurements of the 18 o of northern gulf of california water during times of no colorado river flow the system has been calibrated to absolute flow amounts using recent releases of known volume and rate

variable winter moisture in the southwestern united states linked to rapid glacial climate shifts the last glacial period was characterized by large rapid climate fluctuations an analysis of a speleothem from new mexico shows that the coldest conditions over greenland coincide with increased winter precipitation in the southwestern united states which can be attributed to a southward displacement of the polar jet stream and the north american storm track

large variations of oxygen isotopes in precipitation over south central tibet during marine isotope stage 5 oxygen isotope 18 o records of two stalagmites from tianmen cave on the south central tibetan plateau grew during much of marine isotope stage 5 the tianmen record the fi rst cave record from the tibetan plateau characterizes a precipitation 18 o history larger in amplitude but similar in structure to asian monsoon records from the adjacent regions providing essential evidence that the asian monsoon system including the east asian and indian monsoon subsystems responds largely to changes in northern hemisphere summer insolation extremely low 18 o values during marine isotope stages 5a 5c and 5e suggest that precipitation rather than temperature was a major factor controlling 18 o in precipitation on orbital time scales in the south central tibetan plateau the tianmen record may help in the interpretation of regional ice core 18 o records the large range of orbital scale shifts in meteoric 18 o 9 raises important considerations related to reconstructing the uplift history of the plateau

tracking rainfall in the northern mediterranean borderlands during sapropel deposition the role of mid latitude precipitation in the hydrological forcing leading to the deposition of sapropels in the mediterranean sea remains unclear the new gdec 4 2 borehole east corsica margin northern tyrrhenian sea provides the first precisely dated evidence for enhanced rainfall in the western mediterranean during warm intervals of interglacial periods over the last 547 kyr comparison of gdec 4 2 proxy records with pollen sequences and speleothems from the central and eastern mediterranean reveals that these pluvial events were regional in character and occurred probably in response to the intensification of the mediterranean storm track along the northern mediterranean borderlands in autumn winter our dataset suggests that the timing of maxima of the mediterranean autumn winter storm track precipitation coincide with that of the north african summer monsoon and sapropel deposition besides highlighting a close coupling between mid and low latitude hydrological changes our findings suggest that during warm intervals of interglacial periods the reduced sea surface water salinities together with the high flux of nutrient and organic matter produced by the monsoonal nile and wadi systems floods were maintained throughout the winter by the mediterranean rainfall this provides an important additional constraint on the hydrological perturbation causing sapropel formation

seasonal stable isotope evidence for a strong asian monsoon throughout the past 10 7 m y o of wet season rainfall was signi cantly morenegative 29 5 smow prior to 7 5 ma than after 26 5 smow if this change is attributable to a lessening of the amounteffect in rainfall this agrees with oral and soil geochemical datathat indicate increasing aridity beginning at 7 5 ma keywords tibetan plateau monsoon stable isotopes paleohydrology seasonality introductionthe tibetan plateau is the engine that drives the modern asianmonsoon by generating a high altitude region of low pressure in thesummer as the plateau heats and a region of high pressure in the winteras the plateau cools hastenrath 1991 during the summer warm airrises from the plateau pulling moist air off the ocean across the indiansubcontinent and into the highlands this results in heavy summer rain fall on the subcontinent the opposite occurs in the winter resultingin cold dry air spilling off the plateau and effectively excluding rainfrom the subcontinent thus the presence of a strong wet season dry season alternation implies the presence of a plateau broad and highenough to drive the monsoon the timing of the uplift of the plateau remains a matter of con siderable debate because there are few direct indicators of paleotopog raphy in the geologic record consequently past workers in tibet re lying on indirect indicators of uplift have proposed dates ranging from40 to 3 4 ma on the basis of initiation of potassic volcanism chunget al 1998 turner et al 1993 or extension on the plateau harrisonet al 1995 coleman and hodges 1995 changes in marine sedimen tation rates burbank et al 1993 sediment types rea et al 1998 or biota nigrini and caulet 1992 kroon et al 1991 and changesin stable carbon isotope and palynological patterns on the indian sub continent quade et al 1989 chen 1981 although different areasof the plateau may have risen at different times many workers haveinferred rapid simultaneous uplift of large areas of the plateau at 7 8ma by a process such as lithospheric delamination molnar et al 1993 this inference was based on the following approximately coevalphenomena a major change in plant communities of the indian sub continent quade et al 1989 and shifts in marine upwelling patternsthat are linked to an intense monsoon kroon et al 1991 althoughthere is strong evidence for signi cant climate change at 7 8 ma it isunclear whether this is the onset of the monsoon the oral transitionseems to have been a global rather than local phenomenon cerling etal 1997 and monsoonally driven upwelling may have already beenpresent by 10 12 ma nigrini and caulet 1992 kroon et al 1991 because there is an intimate association between the intense sea sonality of the modern monsoon and a high tibetan plateau and be cause evaporation can be unambiguously recognized in the d

natural attrition and growth frequency variations of stalagmites in southwest sulawesi over the past 530 000 years previous studies have analysed the age distributions of stalagmites harvested from multiple caves and inferred important palaeoclimate changes that explain stalagmite growth phases however stalagmites may grow over tens of thousands of years thus they are irreplaceable the value of speleothems to science must be weighed against their potential and current aesthetic and cultural value in this study we show that some palaeoclimate information can be extracted from a cave system without the removal of stalagmites our case study is based on basal u th dates for 77 individual stalagmites from thirteen caves located in and around bantimurung bulusaraung national park southwest sulawesi indonesia the stalagmites grew during discrete intervals within the last 530 000 years and an analysis of their age distribution shows a first order exponential decrease in the number of older stalagmites surviving to the present day further this exponential relationship is observed in stalagmite populations around the world and is therefore likely to be a general cave phenomenon superimposed on the first order exponential age distribution in southwest sulawesi are positive anomalies in stalagmite growth frequency at 425 400 385 370 345 335 330 315 160 155 75 70 and 10 5 ka which are typically coincident with wet periods on borneo to explain this distribution we present a simple model of stalagmite growth and attrition a first order trend is controlled by processes intrinsic to karst systems that govern the natural attrition of stalagmites these processes are nearly constant over time and result in the observed exponential relationship of stalagmite basal ages second order variation is controlled by changes in the rate of stalagmite generation caused by fluctuating climates which is a well known concept in the speleothem literature removal of the exponential baseline allows for better assessment of relative peak heights and basic palaeoclimate information to be inferred importantly the first and second order growth frequency variations can be characterised using basal stalagmite ages only without the removal of stalagmites thereby helping reduce the impact of scientific sampling on the cave environment

vertebrate burrows in late pleistocene paleosols at korean palaeolithic sites and their significance as a stratigraphic marker abstract a vertebrate burrow bearing layer of late pleistocene age is commonly found at many paleolithic archaeological sites in korea the burrows are straight to slightly curved in horizontal plan view and gently inclined in lateral sectional view they are interpreted as having been produced by rodent like mammals based on their size and architecture the significance of such burrow bearing layers as a characteristic stratigraphic marker unit is demonstrated by high burrow abundance consistent stratigraphic position lack of stratigraphic recurrence at these sites and widespread geographic extent three dating methods tephrochronology radiocarbon and osl dating were used to infer the age of these burrow bearing layers the dating results indicate that they were formed between ca 40 000 and 25 000 yr mis 3 2 and this suggests that this layer can be used as a stratigraphic time marker in late pleistocene paleosol sequences for this region

environmental influences on speleothem growth in southwestern oregon during the last 380 000 years the growth of carbonate formations in caves speleothems is sensitive to changes in environmental conditions at the surface temperature precipitation and vegetation and can provide useful paleoclimatic and paleoenvironmental information we use 73 230th dates from speleothems collected from a cave in southwestern oregon usa to constrain speleothem growth for the past 380 000 years most speleothem growth occurred during interglacial periods whereas little growth occurred during glacial intervals to evaluate potential environmental controls on speleothem growth we use two new modeling approaches i a one dimensional thermal advection diffusion model to estimate cave temperatures during the last glacial cycle and ii a regional climate model simulation for the last glacial maximum 21 000 years before present that assesses a range of potential controls on speleothem growth under peak glacial conditions the two models are mutually consistent in indicating that permafrost formation did not influence speleothem growth during glacial periods instead the regional climate model simulation combined with proxy data suggest that the influence of the laurentide and cordilleran ice sheets on atmospheric circulation induced substantial changes in water balance in the pacific northwest and affected speleothem growth at our location the overall drier conditions during glacial intervals and associated periods of frozen topsoil at times of maximum surface runoff likely induced drastic changes in cave recharge and limited speleothem growth this mechanism could have affected speleothem growth in other mid latitude caves without requiring the presence of permafrost

abrupt millennial scale changes in intensity of southern hemisphere westerly winds during marine isotope stages 2 4 the strength of mid southern latitude westerly atmospheric circulation plays an important role in global climate due to a lack of long continuous high resolution paleoclimate archives from mid southern latitudes it remains unclear what factors control changes in its intensity and how past changes affected the climates of landmasses in their path here we show growth rate and stable isotope 18 o 13 c profiles from a south island new zealand stalagmite hw3 that permit centennial scale investigation of southern hemisphere westerly paleointensity between 73 and 11 ka correlation between hw3 growth rate and isotope profiles suggests sensitivity to changes in annual precipitation a factor controlled by westerly intensity low growth rates and relatively enriched isotope ratios define long term trends in hw3 supporting existing evidence that weaker westerlies predominated during the last glacial period abrupt millennial scale events occur frequently such that the hw3 record resembles greenland ice core stable isotope profiles furthermore nearly synchronous timing of nine prominent wet and cool intervals with heinrich events supports studies showing that increased westerly intensity is closely linked to north atlantic cooling as well as heinrich events the hw3 profiles also show an antarctic cold reversal like event during deglaciation advocating for a bipolar seesaw of global climate at that time

moisture evolution in central asia since 26 ka insights from a kyrgyz loess section western tian shan abstract central asia ca is located in the hinterland of the eurasian continent and faces an extreme risk of continued aridification under the current global warming trend to predict future climate change in ca paleoclimate studies provide essential references however the mechanisms underlying climate changes in ca remain relatively poorly known here we investigate moisture variations in ca as recorded in a 6 m loess section in the western tian shan kyrgyzstan which has accumulated since 26 ka based on the radiometric ams 14c dating we reconstructed the evolution of the wind regime and moisture conditions in the western tian shan with a modified grain size index gsim and a new l proxy l while the frequency dependent magnetic susceptibility fd redness a and yellowness b did not provide reliable paleoclimatic indicators due to weak pedogenesis and other controlling factors the gsim records demonstrated a precipitation maximum in summer before 15 ka shifting to a maximum in spring after 15 ka probably associated with large scale modulation of the latitudinal climatic zones and atmospheric circulation in response to retreat of the northern hemisphere ice sheets based on the l records we place emphases on the important role of temperature modulated evaporation in moisture evolution across ca however this has only influenced moisture evolution in spring and summer with little effect on winter moisture conditions moreover the l records may also indicate that atmospheric humidity can partly affect the long term effective moisture variations

paleoenvironmental changes in northern mongolia during the last deglaciation revealed by trace element records in ostracods from lake hovsgol ostracods possess bivalve carapaces composed of low mg calcite which can be preserved in a variety of sedimentary environments they are a useful paleoenvironmental indicator in particular for non marine environments although previous studies of lake baikal and lake hovsgol have provided some evidence of large scale paleoenvironmental changes in central asia during the late pleistocene trace element records in ostracods from these two lakes which may reveal the detailed limnological processes have not yet been reported in this study we analyzed stable isotopes and trace elements in ostracods in three gravity core sediments recovered from lake hovsgol northern mongolia to reconstruct the long term limnological histories of the lake radiocarbon dating results indicated that ostracod bearing core sediments were deposited from 14 5 to 21 5 ka which corresponds to the early stage of the last deglaciation including the last glacial maximum lgm the mg ca and sr ca ratios from two species of ostracods c lacustris and l inopinata ranged from 4 to 25 and 3 5 mmol mol respectively with distinct and consistent decreasing trends the changes in the mg ca and sr ca ratios indicate that the salinity of the lake water decreased substantially at the initial transition from the last glacial to the current interglacial period which was mainly due to the ice melting and introducing fresh water into the lake changes in the fe ca and u ca ratios were interpreted as water circulation changes in the bottom of the lake after the lgm the fe ca and u ca ratios gradually increased indicating that inflowing cold water induced stronger water circulation and subsequently a higher dissolved oxygen content in the bottom water of the lake the mn ca ratio had the opposite trend to the u ca and fe ca ratios which suggests that it was affected by the weathering intensity in the area around lake hovsgol the stable isotopic results for c lacustris support our paleoenvironmental interpretations in the region on the basis of trace elements as a result ostracod geochemical records from lake hovsgol northern mongolia provide new insights into paleoenvironmental changes in central asia during the onset of the last deglaciation

millennial scale trends in west pacific warm pool hydrology since the last glacial maximum models and palaeoclimate data suggest that the tropical pacific climate system plays a key part in the mechanisms underlying orbital scale and abrupt climate change atmospheric convection over the western tropical pacific is a major source of heat and moisture to extratropical regions and may therefore influence the global climate response to a variety of forcing factors the response of tropical pacific convection to changes in global climate boundary conditions abrupt climate changes and radiative forcing remains uncertain however here we present three absolutely dated oxygen isotope records from stalagmites in northern borneo that reflect changes in west pacific warm pool hydrology over the past 27 000 years our results suggest that convection over the western tropical pacific weakened 18 000 20 000 years ago as tropical pacific and antarctic temperatures began to rise during the early stages of deglaciation convective activity as inferred from oxygen isotopes reached a minimum during heinrich event 1 ref 10 when the atlantic meridional overturning circulation was weak pointing to feedbacks between the strength of the overturning circulation and tropical pacific hydrology there is no evidence of the younger dryas event in the stalagmite records however suggesting that different mechanisms operated during these two abrupt deglacial climate events during the holocene epoch convective activity appears to track changes in spring and autumn insolation highlighting the sensitivity of tropical pacific convection to external radiative forcing together these findings demonstrate that the tropical pacific hydrological cycle is sensitive to high latitude climate processes in both hemispheres as well as to external radiative forcing and that it may have a central role in abrupt climate change events

northwest european palaeoclimate as indicated by growth frequency variations of secondary calcite deposits a compilationn for the northwest of europe of over 500 uranium series speleothen and travertine dates is presented using a cumulative distributed error frequency approach these secondary carbonate deposits require both significant groundwater supply and a biogenic soil carbon dioxide source for their growth during glacial periods soil co2 production is inhibited and the water supply is ice locked therefore growth is slowed significantly if not stopped thus deposits can be used on a chronological basis to give a signal of glacial and non glacial periods however sensitivity to the groundwater supply modifies this signal with growth also limited in times of high aridity the palaeoclimatic signal is thus complex the compilation presented is used both as a chronology for comparison with the orbitally tuned marine oxygen isotope record and as a palaeoclimatic indicator attention is focused on two periods of the last glacial interglacial cycle where the record provides a significantly different palaeoclimatic record to other terrestrial and oceanic records these are the isotope stages 5 4 transition for which a relatively low cumulative growth frequency indicates an earlier increase in aridity than observed elsewhere and isotope stage 3 the pleniglacial where both statistically significant high 49 62 ka and low 22 35 44 46 ka levels of growth are observed and can be used to constrain the timing of many of the interstadial events within this period

high resolution geochemical investigation of the bivalve shells glycymeris sp from shell mounds in jeju island korea late holocene paleoclimatic implications related to east asian monsoon climate abstract recent and shell mound bivalves glycymeris sp were collected from two sites sangmori and udo jeju island to investigate paleoceanographic conditions using high resolution stable isotope and trace element data the radiocarbon ages are about 3210 50 and 4210 60 bp for the sangmori and udo shell mounds respectively both oxygen and carbon isotopic compositions of the shell mound bivalve shells show clear seasonal cycles with depleted values during summer and the coeval trend which indicates that they were controlled by freshwater input similar ranges of both isotopes indicate that shallow seawater conditions near the sangmori and udo shell mounds are more or less similar however more negative oxygen and carbon isotope values of the shell mound bivalves than the recent counterpart suggest that surface seawater salinity near jeju island was lower due to the increase in changjiang river discharge mg contents of the recent bivalve reflect surface seawater temperature changes whereas sr and ba contents were controlled by nutrient concentrations directly influenced by changjiang river discharge geochemical data of the recent and shell mound bivalves may imply higher precipitation more intense east asian summer monsoon activity at 3 2 and 4 2 ka under the influence of the terminal stage of holocene climatic optimum in south china or may reflect smaller fluctuating peaks during its decline

benthic foraminifer record of environmental changes in the yellow sea hwanghae during the last 15 000 years latest quaternary benthic foraminifer census counts in four cores from the yellow sea hwanghae were analyzed to decipher paleoenvironmental changes in this area since the last glacial maximum principal component analyses of samples from two cores in the central yellow sea indicate that the faunal variation in these cores re ects a sequence of distinct assemblages divided by sharp boundaries the shifts between individual biofacies correspond to changes in geochemical and lithological composition of the sediments and stable isotope ratios of foraminiferal shells and most can be correlated between cores the major faunal transition at a clear increase in bottom water salinity occurred between 8 47 and 6 63 ka and may indicate the establishment of modern type circulation in the yellow sea the inferred threshold size of the yellow sea basin for the establishment of such circulation seems to be rather close to its present day extent faunal shifts at 10 6 and 4 67 ka probably re ect changes in the intensity of river runo associated sediment and organic carbon delivery and bottom water oxygenation changes in benthic foraminifer faunas between 12 9 and 11 75 ka may signal the younger dryas climatic oscillation in the yellow sea the lateglacial marine transgression reached the central part of the yellow sea around 15 09 ka possibly an uplift of the central and eastern yellow sea area during the late holocene can explain the discrepancy between the timing of the transgression in the yellow sea and the global sea level curve 2000 published by elsevier science ltd all rights reserved

mg ca sr ca and stable isotopes in modern and holocene protothaca staminea shells from a northern california coastal upwelling region this study explores the potential of intertidal protothaca staminea shells as high resolution geochemical archives of environmental change in a coastal upwelling region mg ca and sr ca ratios were analyzed by excimer laser ablation inductively coupled plasma mass spectrometry la icp ms at sub weekly temporal resolution in shells growing 1 mm per month growth patterns of a modern p staminea shell from humboldt bay california collected in december 1999 made it possible to infer a lifespan from 1993 to 1998 growth hiatuses in the shell may have excluded records of extreme events mg ca ratios appeared to be partly controlled by water temperature the correlation coefficient between temperature and mg ca was r 0 71 in one of four growth increments significant year to year differences in the sensitivity of mg ca to temperature in p staminea could not be explained however sr ca ratios appeared to be more closely related to shell growth rate oxygen isotopes measured at 2 week temporal resolution in the same shell did not show a clear relation to local temperature in summer possibly because temperatures were higher and less variable at the king salmon mudflat where the shell was collected than in the main channel of humboldt bay where water properties were monitored negative shell 13c values 0 5 marked spring and summer coastal upwelling events the mg contents of p staminea midden shells dated to 3 ka and 9 ka were significantly lower than in the modern shell this may have resulted from degradation of a mg rich shell organic matrix and precluded quantitative interpretation of the older high resolution records elevated 13c values in the 3 ka shell suggested that the individual grew in highly productive or stratified environment such as a shallow coastal embayment or lagoon

interhemispheric ice sheet synchronicity during the last glacial maximum the timing of the last maximum extent of the antarctic ice sheets relative to those in the northern hemisphere remains poorly understood we develop a chronology for the weddell sea sector of the east antarctic ice sheet that combined with ages from other antarctic ice sheet sectors indicates that the advance to and retreat from their maximum extent was within dating uncertainties synchronous with most sectors of northern hemisphere ice sheets surface climate forcing of antarctic mass balance would probably cause an opposite response whereby a warming climate would increase accumulation but not surface melting our new data support teleconnections involving sea level forcing from northern hemisphere ice sheets and changes in north atlantic deep water formation and attendant heat flux to antarctic grounding lines to synchronize the hemispheric ice sheets

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

bouldery slope landforms on mt biseul korea and implications for paleoclimate and slope evolution identification of bouldery landforms in mountains and correctly understanding their formative processes play an important role in reconstructing the geomorphic history of a region we propose that blocks were liberated by frost cracking and wedging of cliff walls during the last glacial period however we further suggest and test four hypotheses comprising different scenarios for preconditioning by chemical weathering and subsequent block transport using terrain analysis characterization of boulders and 10 be exposure dating frost shattering from the backing cliff produced the boulders since the beginning of the last glacial period 80 ka and gelifluction transported them downslope throughout the last glacial period their activity then entered a dormant phase at the beginning of the holocene distribution patterns of exposure ages of tors and block streams are similar to those of previous studies implying that bouldery landscapes in the southern korean peninsula were likely to be formed by similar processes under periglacial conditions the timing of active periods in transport of block streams corresponds well with the cold periods identified in regional and global climate proxy records interestingly the activity of block streams in the study area reached a maximum during marine oxygen isotope stage 3 to 2 when the growth rate of nearby speleothems was lowest

indian summer monsoon variations and competing influences between hemispheres since 35 ka recorded in tengchongqinghai lake southwestern china abstract the southwestern yunnan province of china which is located at the southeastern margin of the tibetan plateau and close to bay of bengal is significantly influenced by the indian summer monsoon ism in this study we reconstruct proxies for the ism from 35 to 1 ka through detailed analysis of grain size distribution geochemical composition and environmental magnetism from a 7 96 m sediment core from tengchongqinghai lake yunnan province china globally recognized abrupt climatic events including heinrich events 0 3 h0 h3 and the bolling allerod b a warm period are identified in most of our proxies and the long term trend is consistent with other published records such as stalagmite oxygen isotopes 18o from sangxing cave northern hemisphere nh temperature which is influenced by nh solar insolation is commonly suggested to play a dominant role in controlling the ism a comparison of our record with the 18o variations of ice cores from greenland and antarctica a sea surface temperature sst record from the bay of bengal and summer solar insolation at 25 n latitude demonstrates that the general pattern of ism change does follow variations in summer insolation however the ism lags summer insolation by thousands of years while the ism fluctuations are highly correlated with nh temperature on shorter timescales centennial millennial the gradually weakened ism from 22 5 ka until the last glacial maximum lgm indicates a close relationship with the rise of southern hemisphere sh temperature and the relatively cold background of the sh our record expands on the findings of ism records from heqing paleolake basin in southwestern china and the arabian sea sediments suggesting that the nh and sh have a competitive influence on ism by controlling the cross equatorial pressure gradient this relationship means that when nh temperatures are relatively high it has a stronger influence on the ism than sh influences in contrast when the sh temperature is relatively low it has a dominant influence on ism in addition we speculate that the change of sh temperature not only influences the cross equatorial pressure gradient directly but also likely modulates the circulation system of ocean energy by influencing the atlantic meridional overturning circulation amoc

speleothems travertines and paleoclimates abstract age data for about 660 speleothems and about 140 spring deposited travertines were collected including many unpublished results these data were plotted as histograms and also as error weighted frequency curves on a 350 000 yr scale these plots clearly show periods of increased speleothem travertine growth as well as times of cessation the periods of most frequent speleothem growth were between approximately 130 000 and 90 000 yr ago and since about 15 000 yr ago such periods before 150 000 yr ago however cannot be yet recognized because of a lack of sufficient data and the associated uncertainties of dates in this age range a comparison with the oxygen isotope record of deep sea core v28 238 shows a clear relationship indicating that terrestrial calcite formation is controlled by paleoclimatic fluctuations the evident climatic stimulation of quaternary calcite formation is readily explained geochemically and is substantiated by the obvious difference in speleothem travertine growth as a function of geographic position

holocene changes in flooding frequency in south korea and their linkage to centennial to millennial scale el nino southern oscillation activity to trace past changes in flooding frequency we investigated fluvial sediments in the middle reach of the nakdong river south korea sediments with larger grain size lower total organic carbon percentage and depleted 13 c values in the recovered sediment cores were interpreted as periods of more frequent flooding patterns of decreased long term flooding frequency and vegetation changes during the early to late holocene were similar to the decreasing regional summer monsoon intensity multicentennial frequent flooding periods in the study area 2900 3400 cal yr bp 3600 3900 cal yr bp 4600 5300 cal yr bp and 5800 6400 cal yr bp corresponded to stronger el nino southern oscillation enso activity periods based on previous studies showing that high frequency tropical typhoon driven coastal inundation along the western coast of japan during the middle to late holocene was coupled with stronger enso activity it is likely that the observed centennial to millennial scale flood frequency change in south korea was influenced mainly by changes in the genesis and tracks of tropical typhoons at centennial to millennial time scales this suggests that the centennial to millennial scale hydrologic changes in east asia were linked to the remote atmospheric oceanic circulation changes represented by an enso like pattern

increasing australian indonesian monsoon rainfall linked to early holocene sea level rise the australian indonesian summer monsoon affects rainfall variability across the indo pacific region reconstructions of monsoon strength from stalagmites show that precipitation increased from 11 000 to 7 000 years ago as rising global sea level caused the flooding of the indonesian continental shelf the australian indonesian summer monsoon affects rainfall variability and hence terrestrial productivity in the densely populated tropical indo pacific region it has been proposed that the main control of summer monsoon precipitation on millennial timescales is local insolation1 2 3 but unravelling the mechanisms that have influenced monsoon variability and teleconnections has proven difficult owing to the lack of high resolution records of past monsoon behaviour here we present a precisely dated reconstruction of monsoon rainfall over the past 12 000 years based on oxygen isotope measurements from two stalagmites collected in southeast indonesia we show that the summer monsoon precipitation increased during the younger dryas cooling event when atlantic meridional overturning circulation was relatively weak4 monsoon precipitation intensified even more rapidly from 11 000 to 7 000 years ago when the indonesian continental shelf was flooded by global sea level rise5 6 7 we suggest that the intensification during the younger dryas cooling was caused by enhanced winter monsoon outflow from asia and a related southward migration of the intertropical convergence zone8 however the early holocene intensification of monsoon precipitation was driven by sea level rise which increased the supply of moisture to the indonesian archipelago

climate in sundaland and asian monsoon variability during the last deglaciation abstract the lack of semi quantitative paleo data from mainland southeast asia especially from the emergent sundaland creates a marked difficulty in following the past asian monsoon variability the published pollen records from the adjacent sites to the sundaland were selected in this study and evaluated for the relationship between taxa and plant functional types pfts and subsequently between pfts and biome to eventually reconstruct the semi quantitative temporal temperature and precipitation profile in order to comprehend the asian monsoon modification between 18 5 and 11 ka bp the derived pollen based temperature and precipitation records were further analyzed together with other selected speleothem records from the asian monsoon region with reference to the greenland and antarctic ice cores the warmer temperature in the southern hemisphere caused a southward shift of the mean position of the intertropical convergent zone itcz and weakened the summer monsoon in the asian monsoon region between 18 5 and 15 ka bp the northern hemisphere temperature played an important role in the asian monsoon modification between 15 and 13 5 ka bp where the warmer northern hemisphere conditions strengthened the summer monsoon intensity in the asian monsoon region and moved the mean position of the itcz to the north however the opposing precipitation pattern between the east and the west indian ocean suggested the potential influence of the walker circulation on the sundaland climate from 13 5 to 11 ka bp

sequence of events from the onset to the demise of the last interglacial evaluating strengths and limitations of chronologies used in climatic archives the last interglacial lig represents an invaluable case study to investigate the response of components of the earth system to global warming however the scarcity of absolute age constraints in most archives leads to extensive use of various stratigraphic alignments to different reference chronologies this feature sets limitations to the accuracy of the stratigraphic assignment of the climatic sequence of events across the globe during the lig here we review the strengths and limitations of the methods that are commonly used to date or develop chronologies in various climatic archives for the time span 140 100 ka encompassing the penultimate deglaciation the lig and the glacial inception climatic hypotheses underlying record alignment strategies and the interpretation of tracers are explicitly described quantitative estimates of the associated absolute and relative age uncertainties are provided recommendations are subsequently formulated on how best to define absolute and relative chronologies future climato stratigraphic alignments should provide 1 a clear statement of climate hypotheses involved 2 a detailed understanding of environmental parameters controlling selected tracers and 3 a careful evaluation of the synchronicity of aligned paleoclimatic records we underscore the need to 1 systematically report quantitative estimates of relative and absolute age uncertainties 2 assess the coherence of chronologies when comparing different records and 3 integrate these uncertainties in paleoclimatic interpretations and comparisons with climate simulations finally we provide a sequence of major climatic events with associated age uncertainties for the period 140 105 ka which should serve as a new benchmark to disentangle mechanisms of the earth system s response to orbital forcing and evaluate transient climate simulations

geochemical provenance of sediments from the northern east china sea document a gradual migration of the asian monsoon belt over the past 400 000 years abstract the reconstruction of the long term evolution of the east asian monsoon remains controversial in this study we aim to give a new outlook on this evolution by studying a 400 kyr long sediment record u1429 from the northern east china sea recovered during iodp expedition 346 neodymium isotopic ratios and rare earth element concentrations of different grain size fractions reveal significant provenance changes of the sediments in the east china sea between east asian continental sources mainly yellow river and sediment contributions from the japanese archipelago these provenance changes are interpreted as the direct impact of sea level changes due to the reorganization of east asian river mouth locations and ocean circulation on the east china sea shelf and latitudinal shifts of the intertropical convergence zone itcz from the interior of asia to the western north pacific ocean our data reveal the dominance of winter and summer monsoons during glacial and interglacial periods respectively except for glacial mis 6d 150 180 ka during which unexpected summer monsoon dominated conditions prevailed finally our data suggests a possible strengthening of the interglacial summer monsoon rainfalls over the east asian continent and japan throughout the past 400 kyr and between mis 11 and mis 5 in particular this could result from a gradual northward migration of the itcz

timing duration and transitions of the last interglacial asian monsoon thorium 230 ages and oxygen isotope ratios of stalagmites from dongge cave china characterize the asian monsoon and low latitude precipitation over the past 160 000 years numerous abrupt changes in 18o 16o values result from changes in tropical and subtropical precipitation driven by insolation and millennial scale circulation shifts the last interglacial monsoon lasted 9 7 1 1 thousand years beginning with an abrupt less than 200 years drop in 18o 16o values 129 3 0 9 thousand years ago and ending with an abrupt less than 300 years rise in 18o 16o values 119 6 0 6 thousand years ago the start coincides with insolation rise and measures of full interglacial conditions indicating that insolation triggered the final rise to full interglacial conditions

orbital scale nonlinear response of east asian summer monsoon to its potential driving forces in the late quaternary we conducted a statistical study to characterize the nonlinear response of the east asian summer monsoon easm to its potential forcing factors over the last 260 ka on orbital timescales we find that both variation in solar insolation and global ice volume were responsible for the nonlinear forcing of orbital scale monsoonal variations accounting for 80 of the total variance specifically easm records with dominated precession variance exhibit a more sensitive response to changes in solar insolation during intervals of enhanced monsoon strength but are less sensitive during intervals of reduced monsoon strength in the case of global ice volume with 100 ka variance this difference is not one of sensitivity but rather a difference in baseline conditions such as the relative areas of land and sea which affected the land sea thermal gradient we therefore suggest that easm records with dominated precession variance recorded the signal of a shift in the location of the inter tropical convergence zone and the associated changes in the incidence of torrential rainfall while for proxies with dominated 100 ka variance it recorded changes in the land sea thermal gradient via its effects on non torrential precipitation

age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr